Chromium (VI) handbook

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CHROMIUM(VI) HANDBOOK

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CHROMIUM(VI) HANDBOOK Written by

Independent Environmental Technical Evaluation Group (IETEG) Edited by

Jacques Guertin James A. Jacobs Cynthia P. Avakian

CRC PR E S S Boca Raton London New York Washington, D.C.

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Library of Congress Cataloging-in-Publication Data Chromium(VI) Handbook/ [written by Independent Environmental Technical Evaluation Group (IETEG)]; edited by James A. Jacobs, Jacques Guertin, Cynthia Avakian. p. cm. Includes bibliographical references and index. ISBN 1-56670-608-4 (alk. paper) 1. Chromium–Environmental aspects. I. Jacobs, James A. (James Alan), 1956- II. Guertin, Jacques. III. Avakian, Cynthia. IV. Independent Environmental Technical Evaluation Group. TD196.C53C49 2004 628.5’2–dc22 2004054445

This book contains information obtained from authentic and highly regarded sources. Reprinted material is quoted with permission, and sources are indicated. A wide variety of references are listed. Reasonable efforts have been made to publish reliable data and information, but the author and the publisher cannot assume responsibility for the validity of all materials or for the consequences of their use. Neither this book nor any part may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, microfilming, and recording, or by any information storage or retrieval system, without prior permission in writing from the publisher. All rights reserved. Authorization to photocopy items for internal or personal use, or the personal or internal use of specific clients, may be granted by CRC Press provided that $1.50 per page photocopied is paid directly to Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923 USA. The fee code for users of the Transactional Reporting Service is ISBN 1-56670-608-4/05/$0.00+$1.50. The fee is subject to change without notice. For organizations that have been granted a photocopy license by the CCC, a separate system of payment has been arranged. The consent of CRC Press does not extend to copying for general distribution, for promotion, for creating new works, or for resale. Specific permission must be obtained in writing from CRC Press for such copying. Direct all inquiries to CRC Press 2000 N.W. Corporate Blvd., Boca Raton, Florida 33431. Trademark Notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation, without intent to infringe.

Visit the CRC Press Web site at www.crcpress.com © 2005 by CRC Press No claim to original U.S. Government works International Standard Book Number 1-56670-608-4 Library of Congress Card Number 2004054445 Printed in the United States of America 1 2 3 4 5 6 7 8 9 0 Printed on acid-free paper

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Preface

The purpose of this book is to evaluate the history and characteristics of chromium(VI) in the environment, in industry, and in society. The book was created by the Independent Environmental Technical Evaluation Group (IETEG), a volunteer research organization located in Northern California. It was created in 1997 to present objective scientific and engineering information about controversial environmental issues as a foundation for rational discussion and policy development. The IETEG’s first project was MTBE: Effects on Soil and Groundwater Resources (CRC Press, 2000). Chromium(VI) has been a controversial contaminant for a variety of reasons. This project was started in early 2001 to objectively evaluate the Cr(VI) issues. The IETEG’s membership is multidisciplinary, including geologists, engineers, toxicologists, lawyers, regulators, and others working for environmental consulting and contracting companies, environmental equipment and product manufacturers, water companies, law firms, and academia. These environmental professionals are specialists in the assessment and remediation of soil, groundwater, and air, the complexities of environmental compliance, legal and regulatory issues, and the design of wastewater processing equipment. Given the level of misinformation on Cr(VI), this book was compiled to help facilitate a rational approach to the assessment and remediation of Cr(VI) contamination in the environment. The IETEG hopes that the book will contribute to maintaining the quality of our drinking water supplies contaminated by Cr(VI), the settlement and resolution of legal issues relating to Cr(VI), and the development of regulatory policies designed on scientifically based information.

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Contributors

David Abbott, R.G., C.H.G., earned his B.S. in geology from the University of Puget Sound, Tacoma, Washington and has conducted graduate studies in paleomagnetism and geophysics at Western Washington University. Since 1974, Mr. Abbott has worked as a consultant in groundwater resources. He serves on the board of the Groundwater Resources Association and has been a branch officer since 1992. Mr. Abbott is also a director of the California Council of Geoscience Organizations, where he is currently secretary. Cynthia Avakian, R.E.A., is a senior project scientist at Hydro-Environmental Technologies, Inc., Alameda, California. She earned her B.A. in mathematics from University of California, Berkeley in 1979. She has more than 20 years of professional experience with over 13 years in conducting environmental investigations. Rula A. Deeb, Ph.D., is a senior environmental engineer and bioremediation specialist at Malcolm Pirnie, Inc., Emeryville, California. Dr. Deeb received her Ph.D. from University of California, Berkeley in civil and environmental engineering in 1997. Her expertise includes water and waste-water treatment and hazardous waste remediation with an emphasis on bioremediation. Since joining Malcolm Pirnie over 3 years ago, Dr. Deeb has been involved in directing most in situ bioremediation projects in the firm and is an active member of Malcolm Pirnie’s in situ technology team. Prior to joining Malcolm Pirnie, Dr. Deeb developed and implemented research programs at U.C. Berkeley in collaboration with scientists and engineers at other universities, consulting firms, and the U.S. Air Force on the in situ bioremediation of sites contaminated with gasoline aromatics and fuel oxygenates. Her research has been recognized with awards from the National Science Foundation, U.S. Environmental Protection Agency, Water Environment Federation, American Society of Civil Engineers, American Society for Microbiology, American Association of University Women, Air and Waste Management Association, and the American Chemical Society. Following teaching assignments at Berkeley and Stanford, Dr. Deeb was selected as a National Science Foundation Engineering Education Scholar for excellence in engineering education. She has prepared over 25 peer-reviewed technical publications and has made over 50 presentations to technical audiences. She currently teaches two bioremediation courses for the U.C. Berkeley Extension Program for Continuing Education. Jacques Guertin, Ph.D., is a toxicologist, chemist, and teacher of all sciences. Dr. Guertin earned a Ph.D. in chemistry from McGill University, Montréal, and has more than 25 years experience in environmental science. He holds 5 U.S.

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patents and is author of more than 70 technical publications. He specializes in toxicology, health–ecological risk assessment, computer hardware and software, and is an expert in sampling and chemical analysis and materials science. He has worked at Bell Telephone Laboratories, the Electric Power Research Institute, and several environmental consulting firms. Dr. Guertin has his own environmental consulting business in Newark, California and teaches environmental science, risk assessment, forensic science, chemistry, and materials science at University of California and University of Wisconsin Extension. He also teaches advanced placement (AP) chemistry, physics, earth science, and astronomy to high school seniors, and teaches college chemistry. Elisabeth L. Hawley, M.S., is a project engineer at Malcolm Pirnie, Inc., Emeryville, California, where she works on environmental restoration projects involving site characterization and remediation. She has also collaborated on applied research projects involving unregulated contaminants and contaminants of emerging concern, including N-nitrosodimethylamine (NDMA) and methyl tertiary-butyl ether (MTBE). She earned an M.S. in civil and environmental engineering and a B.S. in environmental engineering science from University of California, Berkeley. As a graduate student working at Ernest Orlando Lawrence Berkeley National Laboratory, she researched environmental tobacco smoke sorption in the indoor environment. James A. Jacobs, R.G., C.H.G., is chief hydrogeologist with Environmental BioSystems, Inc., Jacobs has over 25 years of experience specializing in in situ remediation delivery methods. He received his B.A. in geology and English from Franklin and Marshall College, Lancaster, Pennsylvania, and an M.A. in geology from the University of Texas at Austin. He is registered as a geologist in several states. Jacobs has served as an expert witness on various cases and provided litigation support. He has written over 50 technical journal articles or chapters in several books. He has made over 15 technical presentations at technical conferences or workshops. He is a director of the Groundwater Resources Association of California and the California Council of Geoscience Organizations, where he was a past president and co-founder. He is the president of the California section of the American Institute of Professional Geologists and a director of two local community services districts. Jacobs was awarded two Fulbright Senior Specialist grants in environmental engineering. Michael C. Kavanaugh, Ph.D., P.E., DEE, is vice president and manager of Northern California operations for Malcolm Pirnie, Inc., Emeryville, California, Dr. Kavanaugh is a registered chemical engineer in California, Utah, and Michigan, and a diplomate (DEE) of the American Academy of Environmental Engineers. He is also a consulting professor of environmental engineering at Stanford University. He earned a Ph.D. in civil and environmental engineering from University of California, Berkeley, and B.S. and M.S. degrees in chemical engineering from Stanford and Berkeley, respectively.

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Dr. Kavanaugh has over 25 years of experience in environmental engineering consulting practice, with expertise in hazardous waste management, soil and groundwater remediation, process engineering, industrial waste treatment, technology evaluations, strategic environmental management, compliance and due diligence auditing, water quality, water and wastewater treatment, and water reuse. He also has expertise on issues related to the fate, transport, and treatment of MTBE and other fuel oxygenates in water. Dr. Kavanaugh has extensive litigation experience, and has served as an expert witness in his areas of practice on numerous cases. He has also served as an independent technical expert on both mediation and arbitration panels. He has co-authored over 40 technical papers and reports covering a diverse range of environmental subjects, and has edited two books. Dr. Kavanaugh has also given over 75 technical presentations at technical conferences, specialty workshops, universities, and public meetings, and has testified before Congressional and California legislative committees on environmental issues. William E. Motzer, Ph.D., R.G., is a senior geochemist with Todd Engineers in Emeryville, California. Dr. Motzer has more than 24 years of experience as a professional geologist and more than 16 years of experience in conducting surface, subsurface, environmental, and forensic geochemical investigations. He is a California registered geologist, registered in six other states, and holds a doctorate from the University of Idaho in geology. Dr. Motzer specializes in forensic geochemistry and the geochemistry of groundwater contaminants; specifically arsenic, chromium(VI), perchlorate, and NDMA. He has taught applied environmental geochemistry and the geology and geochemistry of hazardous waste disposal courses at the University of California, Berkeley Extension and conducted workshops in forensic geochemistry for both University of California, Berkeley Extension and the University of Wisconsin, Madison Extension. He was a contributor to MTBE:Effects on Soil and Groundwater Resources (Lewis Publishers, CRC Press 2000), is currently on the editorial board of the Journal of Environmental Forensics, and is a technical advisory member for the San Francisco branch of the Ground Water Resources Association of California. Frederick T. Stanin, M.S., is a senior hydrogeologist, project manager, and supervisor with Malcolm Pirnie, Inc. in Emeryville, California. He has 24 years of professional experience in industry and consulting. He has experience in site investigation with a particular focus on soil and groundwater contamination and its transport and fate, evaluation of and implementation of remedial alternatives, and strategic environmental management. Stanin also has experience providing technical and other support to litigation projects. He has planned, implemented, and managed environmental projects for government and private sector clients at RCRA, CERCLA, and LUFT sites. He has also conducted numerous studies for oil and gas exploration and development. Stanin is a registered geologist, certified

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hydrogeologist, and certified engineering geologist in the state of California. He earned B.A. and M.S. degrees in geology from the University of Tennessee. Martin G. Steinpress, R,G., C.H.G., earned a B.S. in geology from University of California, Santa Barbara, and an M.S. in geology from the University of New Mexico, with postgraduate work in hydrogeology. He is a chief hydrogeologist and National Groundwater Resources Service leader at in Brown and Caldwell, Walnut Creek, California. He is a California and Arizona registered geologist and California certified hydrogeologist with 25 years experience in geology and hydrogeology. He works with municipal, agricultural, state, and federal agencies to manage groundwater investigations and groundwater resources and conjunctive use projects, and has provided technical leadership on numerous groundwater resources projects in California and the western United States. He was project manager and project hydrogeologist for the Presidio of San Francisco case study of chromium(VI) in groundwater. He is also the director of the Groundwater Resources Association of California (GRA) and was an organizer of GRA’s Symposium on Hexavalent Chromium in Groundwater in January, 2001. Stephen M. Testa, R.G., earned his B.S. and M.S. in Geology from California State University at Northridge. He has over 25 years of experience as a geological consultant and currently serves as president of Testa Environmental Corporation in Mokelumne Hill, California. He has taught at California State University at Fullerton and the University of Southern California. Testa is the author of several books including Restoration of Contaminated Aquifers–Petroleum Hydrocarbons and Organic Compounds (with Duane Winegardner), Geological Aspects of Hazardous Waste Management, and The Reuse and Recycling of Contaminated Soil, and is the author of more than 130 papers and abstracts. He is past editor-in-chief of the peer-reviewed journal Environmental Geosciences, past national president of the American Institute of Professional Geologists, and is currently president-elect of the American Geological Institute. Tod I. Zuckerman, Esq., is an attorney in San Francisco who specializes in environmental law. He is currently the publisher and editor of the U.S. Insurance Law Report and the lead author of Environmental Insurance Litigation: Law and Practice, a two-volume treatise (West Group) and the editor of Environmental Insurance Practice Forms, a two-volume book (West Group). Zuckerman is a graduate of University of California Hastings Law School and is an adjunct professor at Lincoln Law School in San Jose.

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Table of Contents

1.

Overview of Chromium(VI) in the Environment: Background and History ................................................................ 1 James A. Jacobs and Stephen M. Testa

2.

Chemistry, Geochemistry, and Geology of Chromium and Chromium Compounds ................................ 23 William E. Motzer

3.

Naturally Occurring Chromium(VI) in Groundwater .............. 93 Martin G. Steinpress, Tarrah D. Henrie, Veronica Simion, Chet Auckly, and Jeannette V. Weber

4.

Sources of Chromium Contamination in Soil and Groundwater ........................................................... 143 Stephen M. Testa

5.

The Transport and Fate of Chromium(VI) in the Environment ..................................................................... 165 Frederick T. Stanin

6.

Toxicity and Health Effects of Chromium (All Oxidation States)................................................................. 215 Jacques Guertin

7.

Chromium Sampling and Analysis .......................................... 235 James A. Jacobs, William E. Motzer, David W. Abbott, and Jacques Guertin

8.

Treatment Technologies for Chromium(VI)............................. 275 Elisabeth L. Hawley, Rula A. Deeb, Michael C. Kavanaugh, and James A. Jacobs

9.

Bench Tests .................................................................................. 311 Jim E. Szecsody, John S. Fruchter, Vince R. Vermeul, Mark D. Williams, Brooks J. Devary, Angus McGrath, Daniel Oberle, David Schroder, John McInnes, Chris Maxwell, Sarah Middleton Williams, Craig S. Criddle, and Michael J. Dybas

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10. Case Studies ............................................................................... 357 James A. Jacobs, J.M.V. Rouse, Stephen M. Testa, Ralph O. Howard, Jr., David Bohan, David Wierzbicki, Jason Peery, Anna Willett, Steve Koenigsberg, John F. Horst, Suthan S. Suthersan, Lucas A. Hellerich, Matthew A. Panciera, Gregory M. Dobbs, Nikolaos P. Nikolaidis, and Barth F. Smets

11. Chromium(VI) Waste Stream Processing ................................. 465 Andrew Hyatt, James A. Hart, Stephen Brown, Mark Simon, Nicolas Latuzt, James A. Jacobs, and Jacques Guertin

12. Chromium: Policy and Regulations.......................................... 491 Elisabeth L. Hawley and James A. Jacobs

13. Chromium(VI) as the Basis for a Toxic Tort: A Legal Perspective ........................................................... 523 Tod I. Zuckerman

14. The Future; Emerging Mitigation and Remediation Technologies ................................................. 565 Stephen M. Testa, James F. Begley, James A. Jacobs, and Jacques Guertin

Appendix A ...................................................................................... 575 Appendix B ...................................................................................... 583 Appendix C ...................................................................................... 637 Appendix D ...................................................................................... 691 Appendix E ....................................................................................... 697 Appendix F ....................................................................................... 751 Appendix G ...................................................................................... 755 Index .................................................................................................. 761

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1 Overview of Chromium(VI) in the Environment: Background and History

James A. Jacobs and Stephen M. Testa

CONTENTS 1.1 Purpose............................................................................................................2 1.2 Introduction to the Chromium(VI) Problem.............................................3 1.2.1 Exposure Pathways...........................................................................3 1.2.2 Physical and Chemical Characteristics..........................................4 1.2.3 Analytical Methods...........................................................................5 1.2.4 Remediation Overview ....................................................................6 1.2.5 Regulatory Concentrations ..............................................................6 1.2.6 Health..................................................................................................7 1.3 Historical Perspective ...................................................................................7 1.4 Origin and Properties .................................................................................14 1.5 Production and Use of Chromium ...........................................................14 1.5.1 Chromium Production Methods...................................................14 1.5.2 World Production ............................................................................15 1.5.3 Resources ..........................................................................................15 1.5.4 Consumption....................................................................................15 1.5.5 Economics.........................................................................................16 1.5.6 Chromium Substitutes....................................................................16 1.5.7 Uses ...................................................................................................16 1.5.7.1 Paint ....................................................................................17 1.5.7.2 Stainless Steel ....................................................................17 1.5.7.3 Furnace Linings.................................................................17 1.5.7.4 Tanning and Dying Processes.........................................17 1.5.7.5 Photography ......................................................................17 1.5.7.6 Specialized Steels ..............................................................18 1.5.8 Chromium Processing and Alloys................................................18 1.5.9 Chromium Isolation........................................................................19

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1.6

Potential Adverse Environmental Effects from Use and Disposal of Chromium ...............................................................19 Bibliography ........................................................................................... 20

1.1

Purpose

Chromium (Cr) is one of the world’s most strategic and critical materials having a wide range of uses in the metals and chemical industries. Alloys containing Cr enhance metal resistance to impact, corrosion, and oxidation. In addition, Cr is used primarily in stainless steel and noniron alloy production for plating metals, development of pigments, leather processing, and production of catalysts, surface treatments, and in refractories. Cr occurs in various oxidation states, of which chromium(VI) [Cr(VI)] is a suspected carcinogen and a potential soil, surface water, and groundwater contaminant. Cr(VI) may also occur in the natural environment, but human-caused Cr(VI) contamination has recently been the focus of much scientific discussion, regulatory concern, and legal posturing. Owing to the many industrial uses of Cr(VI) with an active industrial base, California and other urbanized states have sites with significant Cr(VI) contamination. Drinking water supply wells and water sources are affected by Cr(VI). Common to many Cr(VI) sites are the questions that continue to arise regarding the safety of the drinking water supply. As with most environmental challenges, questions of science compete with emotional and political responses and financial interests. There is still uncertainty regarding what daily dose of Cr(VI) is considered toxic and what ingestion concentration of Cr(VI) is acceptable. To define the current state of technical knowledge of Cr(VI), the Groundwater Resources Association of California (www.grac.org) presented a Cr(VI) symposium in Glendale, California on January 25, 2001. At this symposium, national experts discussed the science, regulatory policies, and legal issues associated with this controversial pollutant. Based on disagreement on even the most basic of scientific points, such as safe levels of Cr(VI) to consume, it became apparent that Cr(VI) is a topic of both great importance and widespread debate. The Independent Environmental Technical Evaluation Group (IETEG), a volunteer research organization located in Point Richmond, California, was created in 1997 to objectively review scientific and engineering information concerning controversial environmental issues. The IETEG’s first project was MTBE: Effects on Soil and Groundwater Resources, a CRC Press book published in 2000. The next (and current) project was started in early 2001 to objectively evaluate Cr(VI) issues. The IETEG group is multidisciplinary and includes geologists, engineers, toxicologists, lawyers, regulators, and others performing environmental consulting, contracting, environmental equipment, design and

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manufacturing. Others work for, water purveyors, law firms, regulatory agencies and academia. Some of these environmental professionals are specialists in the assessment and cleanup of soil, groundwater, and air. The authors work on environmental compliance, legal and regulatory issues, or the design of water treatment equipment. Given the level of misinformation on Cr(VI), this book was prepared to help facilitate a rational approach to protect the quality of drinking water supplies that may contain Cr(VI).

1.2

Introduction to the Chromium(VI) Problem

Each contaminant has a unique set of characteristics and issues that must be evaluated to proceed with more detailed remediation efforts or developing public policy. These factors include persistence in groundwater, taste and odor thresholds, health risk, transport and fate, current laboratory analytical methods and detection limits, groundwater remediation, and regulatory issues. For Cr(VI), each of these factors will be evaluated in more detail below and in this handbook’s chapters.

1.2.1

Exposure Pathways

For some, a significant health concern is the possible adverse effects of human ingestion of Cr(VI) in drinking contaminated groundwater or surface water. This exposure risk is still being debated within the scientific community. Dermal contact through bathing or washing in Cr(VI)-contaminated water is another exposure pathway. A common form of Cr(VI) is a chromate, a compound containing the chromate ion, CrO42–, such as potassium chromate K2CrO4. CrO42– can enter the bloodstream through breaks in the skin. CrO42– blood poisoning occurs when CrO42– destroys red corpuscles. Inhalation is also an important human exposure pathway; however, it is less likely to be associated with exposure to Cr(VI)-contaminated soils and groundwater and more likely associated with industrial processes such as welding, cutting, heating of Cr alloys, and work-related practices which create Cr(VI) fumes and airborne dust. Even dental technologists are at risk of Cr(VI) inhalation disorders (pheumoconiosis) from breathing dust from chromium-cobult-molybdenum (Cr-CoIno) based dental constructions (Selden et al., 1995). Local exhaust ventilation can significantly reduce the inhalation hazard. Inhaling mists while showering with Cr(VI) contaminated water is also a common exposure pathway. For dermal exposure, chromated copper arsenate (CCA) pressure-treated lumber is ubiquitous in residential areas. This green-colored pressuretreated lumber is used for building residential decks, picnic tables, swing sets, and other play structures. Since January 1, 2004, the United States Environmental Protection Agency (USEPA) has banned the use of CCAtreated lumber for new residential use. The exception for residential use

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Chromium(VI) Handbook

will be permanent wood foundations. The USEPA is not banning the use of millions of CCA-treated wood products already in backyards and parks, however more affluent communities and school & districts have already removed CCA-treated play structures. CCA-treated wood is still be available for industrial and agricultural uses. With low pH rain or fruit juice (orange juice and lemon juice), the Cr can be leached off the wood surface. For those concerned about this possibility, coating that play set or picnic table with an appropriate penetrating oil every two years will minimize the potential for leaching and adverse dermal contact (Morrison, 2004). 1.2.2

Physical and Chemical Characteristics

Chromium is rarely found as a free metal in nature. A clean surface of Cr metal reacts strongly with the atmospheric oxygen (Kohl, 1967). However, the reaction stops quickly owing to the formation of a strong, dense, and nonporous Cr(III) oxide (Cr2O3) surface layer, which is estimated to be one to three formula units thick. Chromium oxide passivates the metal from any further reaction with oxygen. This is why Cr does not corrode and why it retains its metallic sheen. Chromium(III) oxide is among the ten most abundant compounds in the Earth’s crust. Cr, a solid at room temperature, generally reacts with halogen gases (such as fluorine) at temperatures of 400°C and pressures of 200 atm to 300 atm. Cr also reacts with the other halogen gases such as chlorine, bromine, and iodine to form a variety of brightly colored compounds. Cr metal dissolves in dilute hydrochloric acid and sulfuric acid. Cr does not appear to react with nitric acid, most likely owing to passivation by surface chromium oxides. Many of the Cr compounds are toxic. Chromium is one of the chief ingredients in mineral and metallic colors, being responsible for the color of some gem stones. Among the gem stones colored by Cr are emeralds, ruby, alexandrite, chrome garnet, and some sapphires. Chromium’s physical and chemical characteristics remained largely a laboratory curiosity for about hundred years from 1800 to 1900. Small amounts were used to harden steel alloys and its numerous compounds were used in many different industries. A rapid increase in Cr use occurred between 1915 and 1930, when Cr became a leading industrial metal, along with iron (Fe), copper (Cu), aluminum (Al), tin (Sn), lead (Pb), and nickel (Ni). The reason for the long delay between its discovery date and industrial use was its high resistance to heat and chemicals. Extracting Cr from its ores by early methods was costly and difficult. Cr’s useful properties such as brittleness, toughness, and resistance to corrosion made it difficult to work with. Cr’s brittleness is probably caused by oxide impurities. With a variety of characteristics and uses, Cr(VI) has entered subsurface soil, surface water, and groundwater. Sampling in California and other states has shown that Cr(VI) can exist as CrO42– and dichromate (Cr2O72–) in groundwater. The oxidation number of Cr in groundwater is governed by

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pH and Eh. Cr(VI) can exist naturally in groundwater that has been unaffected by local industrial activity. At least one hypothesis indicates that naturally occurring fluoride forms a soluble complex with Cr(III)-bearing minerals, after which the dissolved Cr(III) comes in contact with manganese(IV) dioxide (MnO2)containing aquifer material, causing oxidation to Cr(VI). Cr(VI) in groundwater can be reduced to Cr(III) at low pH and under reducing conditions. Cr(VI) is rapidly reduced to usually insoluble Cr(III) when Fe(II) or manganese(II) [Mn(II)] occur in reduced groundwater. There have been several examples of this immobilization phenomenon, both in industrial situations in the U.S. and at a Cr chemicals plant in Poland. Recent work on isotopic ratios of Cr(VI) may prove useful in evaluating the source or distance traveled and whether Cr(VI) is natural or anthropogenic in origin. Cr(III) is a stable oxidation state and slowly reacts to form complexes. Because of its low kinetic energy potential, Cr(III) is not a strong oxidizer and it appears that the stomach’s acidity is enough to keep the Cr in the Cr(III) state. Cr(VI) is not as stable as Cr(III) because it is a strong oxidizing agent, is fast reacting, and likely forms complexes. As with many toxic substances, exposure to metals by inhalation poses the greatest risk. However, for Cr(VI) to be inhaled, a person must be exposed to Cr fumes or airborne dust in industrial processes such as cutting or welding Cr metals or to Cr(VI) in airborne dust or water droplets. Some scientists suggest that Cr(VI) can cause cancer even when inhaled as an aerosol by showering in Cr(VI)-contaminated water. Disagreements still exist over the safe limits of Cr(VI) ingested as drinking water. There remains a debate by experts about the absorption potential that Cr(VI) might have in the stomach’s acid environment. There does not appear to be a perceptible odor or taste that Cr in any form imparts to drinking water. 1.2.3

Analytical Methods

The investigation of a groundwater resource impacted with Cr(VI) requires analysis of groundwater for both Cr(VI) and total Cr. Total Cr can be detected by atomic absorption (AA) spectroscopy and other instrumental methods. Cr(III) and Cr(VI) can be detected by ion chromatography. Cr(VI) can also be detected by titration with a standard mixture of Na2S2O4 and I2 (American Public Health Association, 1989). Analytical methods used include the USEPA method for drinking water, EPA 218.6. The equivalent method for wastewater (used for contaminated groundwater as well) is SW 7196A or SW 7199. Method SW 7199 is the more sensitive method, with a low detection limit of 0.02 µg/L [or parts per billion (ppb)] of Cr(VI). This method uses ion chromatography to estimate Cr(VI). Total Cr is analyzed using inductively coupled plasmamass spectroscopy (ICP–MS) using methods SW 6010 or SW 6020. While analyzing for Cr, it is important to account for interferences from sulfide (S2–), vanadium (V), Mo, and organic carbon to ensure the accuracy of analytical data (Winter, 2004).

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6 1.2.4

Chromium(VI) Handbook Remediation Overview

For in situ remediation of soil and groundwater, a variety of geochemical fixation or anaerobic biological treatment methods have been designed which make use of Cr’s ability to change the oxidation state of the oxidized, toxic, and highly mobile nature of Cr(VI) and convert it into the more stable, nontoxic, and immobile Cr(III). Cr(III) ultimately precipitates out as Cr(III) hydroxide [Cr(OH)3]. In these technologies, Cr is generally not removed from the environment, but becomes less toxic and immobile. Many treatment methods use sulfur-based reductants; anaerobic biodegradation enhancements use carbon-sources such as lactic acid, molasses, cheese whey, or corn syrup. Permeable reactive barriers use elemental iron [Fe(0)] technologies to create a reducing environment. These in situ technologies use period redox (or Eh) reactions with either biological or chemical processes to reduce Cr(VI) to Cr(III). A variety of technologies (known as pump and treat) are used in the extraction and treatment of surface water or groundwater. Once on the surface, water containing Cr(VI) can be reduced by Fe(II) compounds followed by several procedures including alkaline precipitation, ion exchange with regenerant treatment, or disposal. Electrochemical reduction is another method used where Cr(VI) reduction is followed by alkaline precipitation in which Fe(II) forms electrochemically, instead of being added as a purchased chemical; acidic reduction of the Cr at pH < 3.0 with sulfur dioxide, sodium sulfite, sodium bisulfite, or sodium metabisulfite completes the conversion to Cr(III). If reduction with a sulfite compound is used, there is a greater potential for incomplete conversion of Cr(VI) to Cr(III). Consequently, these reactions must be monitored carefully to ensure complete conversion to Cr(III). 1.2.5

Regulatory Concentrations

Chromium is listed as number 16 in the Agency for Toxic Substances and Disease Registry, Priority List of Hazardous Substances (ATSDR, 199a). Cr(VI) has been found in at least 304 of the 1,591 current or former USEPA National Priority List Superfund Sites (ATSDR, 2000). Neither the federal or state governments limits Cr(VI) concentration in water, but both regulate total Cr. The USEPA Drinking Water Maximum Contaminant Level (MCL) for total Cr is 100 µg/L. California limits total Cr in drinking water to 50 µg/L. Total Cr for contaminated site generic soil screening levels is 390 mg/kg for ingestion, 270 mg/kg for inhalation, and 2.0 mg/kg for migration to groundwater (USEPA, 1996). The California Office of Environmental Health Hazard Assessment (OEHHA) initially recommended a public health goal (PHG) of 2.5 µg/L for total Cr and 0.02 µg/L for Cr(VI). The OEHHA has since rescinded the PHG and the state is working to establish a Cr(VI) MCL (California Department of Health Services, 2002). For airborne Cr(VI), the U.S. Department of Labor, Occupational Safety and Health Administration (OSHA), regulates worker’s exposure to Cr(VI) and other toxic compounds. OSHA exposure limits for Cr compounds vary with potential work activities.

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7

Health

Although the elemental Cr and Cr(VI) can have adverse human health effects, normal mammalian metabolism requires minute amounts of Cr as an essential trace element. In addition to insulin, Cr is responsible for reducing blood glucose levels and is used to control certain cases of diabetes. Cr has also been used to reduce blood cholesterol by lowering the concentration of the unhealthy, low-density lipoproteins (LDL) in the blood. Cr is supplied in a variety of foods such as broccoli, Brewer’s yeast, liver, cheese, whole grain breads, and cereals. Some claims have been made that Cr aids in muscle development. Chromium picolinate, a highly soluble form of Cr, is used in dietary supplements for body builders. Cr(III) is an essential nutrient that helps the body use sugar protein, and fut. The minimum human raily Cr requirement for optimal health is unknown, but a daily in gestion of 50 µg/L to 200 50 µg/L is estimated to be safe and adequate according to the ASTDR (1989).

1.3

Historical Perspective

The history of Cr began over 200 years ago. Four Siberian Beresof gold mines had been worked for gold, copper, silver, and lead since 1752. In 1761, Johann Gottlob Lehmann obtained samples of an orange-red mineral that he termed “Siberian red lead,” while visiting the Beresof mines located on the eastern slopes of the Ural Mountains. Upon his return to St. Petersburg in 1766, analysis showed that the samples contained lead “mineralized with a selenitic spar and Fe particles.” This mineral turned out to be crocoisite or crocoite, a lead chromate (PbCrO4) (Figure 1.1). Lehmann described the mineral in a letter to the well known naturalist, Georges-Louis Leclerc comte de Buffon (1707 to 1788). Lehmann also observed that the mineral produced an emeraldgreen solution when dissolved in hydrochloric acid (HCl). Lehmann died the following year when a retort containing arsenic burst upon heating. In 1770, Peter Simon Pallas also visited the Beresof mines and noted: a very remarkable red lead mineral which has never been found in any other mine. When pulverized, it gives a handsome yellow guhr which could be used in miniature painting … .

In spite of its rarity and difficulty in obtaining samples from the Beresof mines, the use of Siberian red lead as a paint pigment was mined both as a collector’s item and for the painting industry as a paint pigment. A bright yellow made from crocoite rapidly became a fashionable color for carriages of the nobility in both France and England. As a boy in Normandy, Louis-Nicholas Vauquelin (1763 to 1829) was fascinated with chemistry and mineral specimens. His father was a farm laborer who provided for his son’s education. Progressing through school

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FIGURE 1.1 Lead chromate mineral, Crocoite, from Beresou, Russia.

rapidly, at the age of 14 he became a dishwasher and assistant in an apothecary. He eventually went to Paris with a letter of introduction and worked for several apothecary shops. One pharmacy was owned by his cousin, Antoine-François comte de Fourcroy (1755 to 1809). Upon hearing of Vauquelin’s interest in chemistry, Fourcroy hired his younger cousin as his assistant. Vauquelin continued to learn physics, chemistry, and philosophy while assisting Fourcroy with chemistry and teaching Fourcroy’s students. With the onset of the French Revolution, Vauquelin left Paris in 1793, served as a pharmacist in a military hospital, and then returned to teach chemistry at the Central School of Public Works which later became the École Polytechnique. In 1797, Vauquelin, a professor of chemistry and assaying at the School of Mines in Paris, received samples of the crocoite ore. Vauquelin noted the beauty and scarcity of this Cr ore (Figure 1.2). He noted its value equal to that of gold, and in an attempt to address several contradictory chemical analyses, he set out to determine the correct chemical composition of crocoite. Vauquelin boiled one part of pulverized crocoite with two parts of standard potash (K2CO3), which resulted in a yellow-colored solution. The solution formed a red precipitate with a mercury salt and a yellow precipitate with lead. Adding HCl turned the solution green. In 1798, he was able to precipitate lead with HCl, dried the green solid, and then heated it for 0.5 h in a charcoal crucible with charcoal dust. The charcoal was used as a reducing agent. Upon cooling, he observed a mass of metallic needles with a mass of about half of that of the original. He thus discovered through subsequent analysis via heating Cr2O3 with charcoal that crocoite was combined with an oxide of an unknown metal. Noting the many colors produced by the compounds, Fourcroy and Abbé

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FIGURE 1.2 Chromium ore.

René-Just Haüy (1743 to 1822) suggested the name Cr from the Greek word χρωµα (chroma) meaning color, reflecting the brilliant hues of reds, yellows, and greens of its compounds. With further research, Vauquelin analyzed an emerald from Peru and discovered that the lustrous green color was related to trace amounts of Cr. Vauquelin went on to determine that the red color of rubies was also related to trace amounts of Cr. Vauquelin later became an inspector of mines and professor of assaying at the School of Mines (Figure 1.3). In 1798, the German chemists Louwitz and Klaproth (the latter along with Vauquelin and Fourcroy were the top chemists of their times) shortly thereafter independently identified Cr in rocks located further north of the Beresof mines as a major component of the heavy black mineral later named chromite (FeCr2O4). In 1799, another German chemist Tassaert identified the same mineral from a small deposit in the Var region of southeastern France. This mineral was to be identified as Cr–Fe spinel and now known as chromite.

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FIGURE 1.3 Vauquelin isolated Cr in 1798 by charcoal reduction of the oxide.

Chromium is found in various minerals. However, FeCr2O4 is the sole source of Cr used commercially. From 1797 until 1827, FeCr2O4 was primarily produced for chemical use and was derived from the Ural Mountains of Russia, the principal source for world supply at this time. About 1808, the supply of Cr from the Ural Mountains greatly supported a growing paint industry and resulted in a Cr chemical factory being set up in Manchester, England. Russia did not dominate the market for long, however. With the discovery of FeCr2O4 in Maryland in 1827, followed by subsequent discoveries in Pennsylvania and Virginia, the U.S. became the principal supplier for what would be considered a limited world demand (Morning et al., 1980). In 1808 or 1810, an English gardener named Henfrey discovered what he thought was Cr ore in some black rocks on or near the summer estate of Jesse Tyson in the Bare Hills situated northwest of Baltimore, Maryland (Abbott, 1965). These rocks, were shown to Isaac Tyson who confirmed their identification, and subsequent analysis showed them to be rich in Cr(III) ore (Figure 1.4). With financial assistance from his father, Isaac Tyson went into the business of shipping Cr to England for the manufacturing of paint. Recognizing the association of FeCr2O4 with serpentine deposits, Tyson discovered and acquired control of other Cr deposits. In 1827, Tyson tried to make Cr compounds but failed to establish a commercial process. Isaac Tyson, Jr. (1792 to 1861) was considered one of the best “practical chemists,” and his main success was in establishing the Cr chemicals

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FIGURE 1.4 Twin sisters dunite Cr(III) ore.

industry in America (Gould, 1985). Along with Howard Sims, a member of the Philadelphia Academy of Natural Sciences, Tyson established a plant in Baltimore, Maryland, which was incorporated in 1823 and by 1833 became known as the Baltimore Chemical Company. In 1827, Tyson was granted a patent for making copperas (iron sulfate). Besides exporting FeCr2O4, Tyson also attempted to manufacture chrome yellow and other chrome colors. Encountering technical difficulties and a highly competitive market, Tyson turned to the increasing demand for the manufacturing of Cr2O72–. Between 1828 and 1850, the Baltimore Chemical Company supplied most of the Cr ore consumed by the world, with the remainder being supplied from serpentine deposits and platinum washings in the Urals. Tyson eventually succeeded in developing a commercially viable process for the manufacturing of Cr compounds in 1845. He applied to Yale for a technical expert, and William Phipps Blake (1829 to 1910) was sent. This was a historic step since Blake was a young chemistry student at the newly established Sheffield Scientific School. Blake would become the first professional chemist to be employed in industry in the U.S. (Abbott, 1965). Blake eventually graduated from Sheffield Scientific School where he served as assistant professor at New York College. In 1853, Blake accepted the position

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FIGURE 1.5 Blake provided technical expertise regarding Cr. Blake became renowned as a mineralogist, geologist, and mining engineer.

of geologist and mineralogist for the Williamson party of the Pacific Railroad Survey. On that survey, Blake was to ascertain a practical railroad route from the Mississippi River to the Pacific Ocean, notably in southern California (Testa et al., 2002). Blake went on to a prestigious career as a mineralogist, geologist, and mining engineer and eventually served as the third territorial geologist of Arizona (Dill, 1991) (Figure 1.5). Blake also developed an early version of a decimal book classification system, which was later copied in large part by the American librarian Melville Louis Kossuth Dewey (1851 to 1931). When Tyson died in 1861, the Baltimore Chrome Works was left to two of his sons; in 1902 it was acquired by the Kalion Chemical Company of Philadelphia and in 1906 acquired by the Henry Bower Chemical and Manufacturing Company, which merged with Mutual Chemical Company. Later, Allied Chemical and Dye Company acquired Mutual Chemical Company in 1954. Tyson’s monopoly on the world’s FeCr2O4 ore industry continued until 1850, when exports began to decline. Reflecting newly discovered FeCr2O4 deposits near Bursa in Turkey in 1848, and with the depletion of the deposits in Maryland around 1860, relatively large Turkish deposits were developed in 1860. Since the 1860s, production of FeCr2O4 ore has been primarily in the Eastern Hemisphere from over 20 countries, with only a few with large reserves. FeCr2O4 ore was discovered in California in 1873, and from 1886 until 1893 California was the only state to produce this commodity; however, 2000 to

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4000 metric tons of ore from Turkey was annually imported to the U.S., most of it being manufactured in Baltimore, Maryland (Glenn, 1893). Mining of FeCr2O4 ore commenced in India and Southern Africa around 1906. Although paint pigments remained the main application, other applications were being found. Kochin introduced the use of potassium dichromate (K2Cr2O7) as a mordant in the dyeing industry in 1820. Commercial use of Cr salts was introduced in leather tanning in 1884. First used as a refractory in France in 1879, its actual use started in Britain in 1886. The first patent for the use of Cr in steel was issued in 1865. However, large-scale use of Cr had to wait until development of the aluminothermic method in the early 1900s and when the electric arc furnace could smelt FeCr2O4 into the master alloy, ferrochromium. Although Cr provided brilliance and shine, its true importance came with the development of stainless steel, because it is Cr that makes the steel shiny and stainless. Stainless steels were developed from the initial work of Brearly and Sheffield in 1913. Stainless steels containing 12% or more Cr, together with Fe and Ni, titanium (Ti), or Mn (commonly with 18% Cr, 8% Ni, 74% Fe) are extensively used in fabricating vessels for corrosive fluids and in a wide range of industrial and domestic appliances. New or less costly corrosion-resistant steels, such as type 304 or 3 CR 12, are finding increasing application in mining and construction. In the 1920s, the process of electroplating was developed. Electroplating utilizes an electric current to bond Cr atoms with atoms of the original surface, creating a bond between the metals so strong that it will remain intact even when subjected to extreme force. Electroplating soon thereafter became a standard requirement for engine and machinery parts subjected to high loads, corrosion, and wear from friction. During the 1940s, plating production was important during the war effort with the production of hard chrome, a process that puts new life into many types of engine components. The first engine cylinders were restored using electroplated hard Cr during this period. During the 1960s and 1970s, new federal engine emission standards generated improvements to reduce the amount of lube oil consumed by diesel fuels. New finishing techniques were thus developed and applied to engines for the rail, gas transmission, marine, and stationary power industries. Primary developments during the 1980s pertained to more specialized finishes to reduce oil consumption, resistance to abrasion, ring seating, and controlled percent of load bearing surface and porosity.

1.4

Origin and Properties

Chromium metal is shiny and silvery in color, as well as hard and brittle. It has a high melting point (1857.0°C) and boiling point (2672.0°C). Oxidation states from –2 to +6 are known, however, the most stable oxidation state is +3.

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The natural isotopes for Cr are 50Cr (4.3%), 52Cr (83.8%), 53Cr (9.6%), and Cr (2.4%). The abundance of Cr in the universe and on Earth varies considerably. Cr is found in the universe at 15 parts per million (ppm) by mass, in the sun at 20 ppm, and in carbonaceous meteorites at 3.1 parts per thousand by mass. Crustal rocks on the earth contain an average of 140 ppm of Cr, seawater contains 0.6 ppb, stream water has 1 ppb, and humans have 30 ppb Cr by mass. Chromite, also called iron(II)-Cr(III) oxide (FeCr2O4), is the principal ore of Cr. FeCr2O4 is a weakly magnetic, Fe-black, brownish black to silvery white metal. FeCr2O4 is of igneous origin and forms in peridotite of plutonic rocks. FeCr2O4 occurs exclusively in mafic and ultramafic rocks as a crystal accumulated in the early stages of magmatic crystallization. FeCr2O4 has also been identified in serpentinites, which may be developed through hydrothermal alteration of a peridotite. Uvarovite, the Cr garnet, is commonly associated in the field with FeCr2O4. The Moh’s hardness of FeCr2O4 is 5.5 and the specific gravity is 4.3 to 5.0 and because of these physical characteristics of FeCr2O4, the metal is occasionally concentrated in placer deposits. 54

1.5

Production and Use of Chromium

The primary uses of Cr relate to the production of nonferrous alloys, ornamental plating of metal, and creation of green-colored glass. Prior to the development of hard rigid plastics, automobile fenders and hubcaps were frequently chrome-plated from the 1920s through the 1980s. The aircraft industry used Cr for anodizing aluminum. Cr has been used as a catalyst for particular chemical reactions. Oxidizing agents such as K2Cr2O7, and other Cr2O72– compounds, are used in quantitative analysis.

1.5.1

Chromium Production Methods

Chromite is the most commercially useful of the Cr ores. Cr is produced in two forms: ferrochrome and Cr metal produced by the reduction of Cr2O3. Ferrochrome is produced by the reduction of FeCr2O4 with coke in an electric arc furnace. Using ferrosilicon instead of coke as the reductant can produce a low-carbon ferrochrome. This is a popular Fe-Cr alloy used directly as an additive to produce stainless and hard Cr-steels. The reduction of chrome ochre (Cr2O3) produces Cr metal. This is obtained by oxidation of FeCr2O4 (by air) in molten alkali to yield sodium chromate (Na2CrO4), which is leached out with water, precipitated, and then reduced to the Cr(III) oxide using carbon. The oxide can be reduced by aluminum in the aluminothermic process: Cr2O3 + 2A1→ 2Cr + A12O3

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The chrome oxide can also be reduced using silicon: 2Cr2O3 + 3Si→ 4Cr + 3SiO2 Chrome ochre (Cr2O3) can be dissolved in sulfuric acid (H2SO4) to yield the common electrolyte solution used in the production of decorative and protective Cr plating. Sodium chromate (Na2CrO4) produced in the isolation of Cr is itself the basis for the manufacture of all industrially produced Cr chemicals. 1.5.2

World Production

Chromite world mine production was estimated at a gross mass of 13 million metric tons in 2002 (Papp, 2003). Cr ore is mined in over 20 countries, but 81% of the production is concentrated in four countries: South Africa accounts for 49% of the world total and 32% of the world total is accounted for by Kazakhstan, India, and to a lesser extent, Turkey. FeCr2O4 ore is found in Brazil and Cuba, the only countries in FeCr2O4 production in the Western Hemisphere. The largest U.S. Cr resource is in the Stillwater Complex in Montana. The U.S. base is estimated to be about 7 million metric tons (Papp, 2003). 1.5.3

Resources

Approximately 95% of the worldwide Cr resources are concentrated in southern South Africa. According to the U.S. Geological Survey (USGS), worldwide resources exceed 12 billion metric tons of shipping-grade FeCr2O4, enough to meet demand for centuries (Papp, 2003). Remaining resources are located in the Independent States (former USSR), the Philippines, and selected other countries. 1.5.4

Consumption

In 1998, ferrochrome accounted for approximately 85% of FeCr2O4 consumption. Remaining FeCr2O4 consumption includes Cr chemicals at 8%, foundry applications for 5%, and refractories for 2%. About 12% of the world Cr production is consumed by the U.S., in the form of FeCr2O4 ore, Cr ferroalloys, Cr metal, and Cr chemicals (Papp, 2003).

1.5.5

Economics

Prices for the ferrochrome industry are highly cyclic and have been unstable in recent years. During the most recent price reductions for Cr at $0.77/kg to $1.10/kg for high-carbon, charge grade ferrochromium, integrated producers consolidated and expansions were accomplished through process improvements. The largest market for Cr metal is in superalloys for aircraft and industrial gas turbines. At this time, production capacity for Cr metal exceeds

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demand and when prices exceed the benchmark of US $5,000 per metric ton, low-cost producers from the Independent States in central Asia and China increase production to meet Western market demands (Roskill Co., 2002). According to the USGS, Cr contained in recycled stainless steel scrap accounted for 37% of the apparent consumption in 2002 (Papp, 2003). 1.5.6

Chromium Substitutes

According to the USGS, FeCr2O4 ore has no substitute in the production of ferrochromium, Cr chemicals, or FeCr2O4 refractories. Cr has no substitutes in stainless steels, which is the largest use for FeCr2O4 or in superalloys. 1.5.7

Uses

Chromium is a strategic metal of the twentieth century but it is also used in dozens of industrial processes (Table 1.1) creating thousands of consumer products. Cr is used in the manufacturing of stainless steel, numerous alloys, Cr plating, pigments, catalysts, dye, tanning, wood impregnation, refractory bricks, magnetic tapes, and more. Until the early 1900s, FeCr2O4 was used mainly in the manufacturing of chemicals. In the early 1900s, FeCr2O4 became widely used in the manufacturing of metallurgical and refractory products, notably in stainless steels and basic refractory bricks (Morning et al., 1980). Refractory bricks and shapes formed of Cr are useful owing to the high melting temperature of Cr, moderate thermal expansion, and the general stability of the Cr crystalline structure. Cr steels have no substitute when TABLE 1.1 Chromium Use Antifouling pigments Antiknock compounds Alloy manufacturing Catalysts Ceramics Corrosion inhibitors Dental constructions Drilling muds Electroplating (decorative finishes, hard-wearing surfaces) Electronics Emulsion hardeners Flexible printing Fungicides Gas absorbers Harden steel (armor plating, armor piercing projectiles)

High-temperature batteries Human joint replacement pzrts (hip) Magnetic tape Metal finishing Metal primers Mordants Phosphate coatings Photosensitization Pyrotechnics Refractories Tanning Textile preservatives Textile printing and dyeing Wash primers Wood preservatives

Source: Modified after Stern, R. M., 1982, Biological and Environmental Aspects of Chromium, Langard, S., Ed., Elsevier, New York.

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combined high-temperature rigidity and resistance to tarnish and abrasion are required as in the case of roller bearings or in the aerospace and machine tool industries. 1.5.7.1 Paint Chromium compounds are used in paint pigments. Chromates of barium (Ba), lead (Pb), and zinc (Zn) give us the pigments of lemon Cr, Cr yellow, Cr red, Cr orange, zinc yellow, and zinc green. Cr green is used in the making of green glass. Cr chemicals enhance the colors of fabrics and are used to achieve the brightly colored Cr-based paints for automobiles and buildings. 1.5.7.2 Stainless Steel As an alloy, Cr has been referred to as the “guardian metal.” With as little as 10% Cr, an alloy made with steel or Fe protects these materials from corrosion, yielding the stainless steel and rustless Fe which are common household items, such as stainless steel knives, ball bearings, watch cases, and chrome front and rear vehicle bumpers. The ball bearings of chrome steel have been subject to more than 1,000,000 lb/in.2 or 6.895 × 109 Pa (N/m2). 1.5.7.3 Furnace Linings Chromium plating has replaced Ni-plating owing to Cr’s superior hardness and resistance to chemical action. Heat-resistant Cr oxides are used for hightemperature applications, such as the bricks used in lining furnaces. 1.5.7.4 Tanning and Dying Processes Chromium alum and chromic acid are used in the tanning and dyeing processes. 1.5.7.5 Photography When K2Cr2O7 is mixed with water and the solution is dried and exposed to light, it becomes solid again. This property is applied to the manufacture of waterproof glues and in photography and photoengravings. Photochemicals containing Cr2O72– compounds are toxic. 1.5.7.6 Specialized Steels Characterized as bright, hard, and tarnish resistant, these attributes have enhanced various ferroalloys. Most importantly, Cr-based steels support modern industry. The shift from paints and electroplating industries to Crhardened and corrosion-resistant steels occurred concurrent with evolving metallurgical technology with the introduction of more energy- and costeffective processes that could utilize low-grade ores.

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Chromium(VI) Handbook Chromium Processing and Alloys

About 13 million metric tons of Cr was produced annually in 2002 (Papp, 2003). Historically, about 60% to 70% of Cr ores are used in alloys (Stern, 1982). These alloys include stainless steel, which contains Fe, Cr, and Ni in varying proportions to fulfill final product requirements. Alloy steels contain about 10% to 26% Cr. Cr alloys have a moderate electrical resistivity and are used for heating elements. Cr has also been used for its catalytic properties. Cr is brittle at low temperatures. Substances such as Ni, Mn, and small amounts of Mo, tungsten (W), or palladium (Pd) are added to Cr to enhance various physical properties of the alloys. Cr can be highly polished and is resistant to attack by continued oxidation, leading to its use in alloys that are resistant to corrosion. Cr also increases hardness and resistance to mechanical wear. Refractory brick manufacturing utilizes about 15% of the Cr ore used for lining furnaces and kilns. About 15% is used in the chemical industries. Cr(III), referred to as chrome alum, is used for tanning leather, pigments, and wood preservatives [sodium dichromate (Na2Cr2O7)]. About 4% is used as chromic acid and used for electroplating or as an oxidant. Chromium is used as a corrosion-resistant decorative plating agent. It is also used as a pigment to give glass an emerald color. Both the green in emeralds and the red in rubies are credited to trace amounts of Cr oxides in the crystal lattice structure. PbCrO4 as chrome yellow is used as a pigment in yellow paint. K2Cr2O7, a form of Cr, has been used in the leather production business as a tanning agent. Chromates are compounds used in the textile industry as a mordant. Products that contain Cr(VI) include paints, pigments, inks, fungicides, and wood preservatives. Since FeCr2O4 has a high melting point, moderate thermal expansion, and a relatively stable crystalline structure, it has been used in the refractory industry for forming bricks and shapes. Cr in superalloys is used to improve heat flow and increases resistance to wear and corrosion. Cr hard-facing alloys increase hardness while resisting wear. In a specialized medical use, since Cr is a hard transition metal, it is amalgamated with Ti to make human replacement joints (hips) in the U.S. and Great Britain. Some dentists use Cr-based dental composites. Cr(VI) has been used in paint pigments, chrome plating, and other manufacturing processes such as leather tanning. Cr(VI) is also used by the aircraft and other industries for anodizing aluminum. The refractory industry uses FeCr2O4 for forming bricks and shapes. Because FeCr2O4 has a high melting point, moderate thermal expansion, and stable crystalline structure, it is used in the refractory industries.

1.5.9

Chromium Isolation

Starting with commercially available FeCr2O4, if this ore is oxidized by air in molten alkali, sodium chromate (Na2CrO4) is created wherein the Cr has been oxidized to, Cr(VI). Reducing the Cr(VI) in sodium chromate produces Cr(III)

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oxide or Cr2O3 wherein the Cr is in the Cr(III) form. The main Cr(III) species include Cr3+ and Cr2O3. Cr(III) exists in a moderately oxidizing or reducing environment. Cr(VI) species include CrO42– and Cr2O72–. Cr(VI) exists in an alkaline, strongly oxidizing environment. The reduction of Cr(III) oxide takes place by the extraction of water, precipitation, and the reduction of the Cr with carbon. The oxide is reduced further with silicon or aluminum to form Cr metal for the industrial processes. There are other ways of isolating and producing Cr metal; an example is electroplating, which requires the dissolution of Cr(III) oxide (Cr2O3) in sulfur acid to produce an electrolyte that is used for Cr electroplating. Consequently, plating shops are typical sources of Cr(VI) leaks, spills, and acid contamination in the soil and shallow groundwater. Chromium has been in the industrial environment in large supplies for well over a century. Based on the numerous and varied uses and industrial settings, Cr’s potential for contaminating soil and groundwater resources and for worker exposure is large.

1.6

Potential Adverse Environmental Effects from Use and Disposal of Chromium

Because of its toxic nature, Cr creates numerous environmental problems in waste products, mine wastes, and postmanufacturing slag piles. Cr waste products are inevitably formed during the numerous industrial processes using Cr. The electroplating and manufacturing industries use high volumes of Cr in their processes. Waste products from these processes normally contain Cr(VI) compounds, such as chromic acid and other oxidizing Cr(VI) cleaners. Cr(VI) comprises most of the wastes; a smaller amount of reduced Cr(III) and Cr as a solid metal are also produced. Management of waste products from industrial processes is always problematic and is associated with poor housekeeping. Therefore, Cr(VI) is commonly spilled or leaked into the environment as a contaminant, frequently with other associated wastes, ultimately moving into the soil and groundwater. (see Table 1.2). *The characteristics of Cr(VI) in the subsurface make assessment and remediation of Cr(VI)-contaminated sites challenging. Cr(VI)-contaminated sites are difficult to delineate vertically and laterally, and may be complicated by naturally occurring Cr(VI) that has not been characterized. Environmental professionals should be employed to assess and remediate Cr(VI)-contaminated soil and groundwater resources. The environmental consulting industry in conjunction with the regulatory agencies, including the USEPA, must continue to establish reliable, accurate analytical methods * Prevention efforts provide the greatest value in reducing Cr(VI) exposure risks and cleanup costs.

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Chromium(VI) Handbook TABLE 1.2 Chromium Releases (kg) to Water and Land, 1987 to 1993 Water

Land

1,304,557

89,303,549

Top Ten States* Texas North Carolina Indiana Ohio Utah Arkansas Kentucky Pennsylvania Georgia Idaho

46,302 19,741 38,814 23,510 794 1,043 116 49,963 308,316 41,617

29,166,860 25,046,030 7,237,472 3,773,707 2,638,554 1,602,088 1,130,134 1,060,456 637,160 637,238

Major Industries* Industrial organics Steelworks, blast furnace Electrometallury Copper smelting, refining Nonferrous smelting Inorganic pigments Pulp mills

1,484 276,317 15,091 794 1,043 40,243 447,151

54,752,143 7,547,269 4,897,404 2,638,554 1,602,088 624,007 101,695

Overall Total

Notes: * Water/Land totals only include facilities with releases greater than a certain amount . . . usually 450 kg to 4,540 kg.

for Cr(VI). The environmental industry must develop and optimize effective ex situ treatment systems for Cr(VI) in groundwater, especially in areas where trace concentrations exist. Environmental regulatory agencies must evaluate health risks posed by low Cr(VI) concentrations and establish background concentrations for groundwater (accompanied by health effect studies) before implementing new regulations.

Bibliography Abbott, C.M., 1965, Isaac Tyson Jr., Pioneer mining engineer and metallurgist, Maryland Historical Magazine, March, pp. 15–25. Agency for Toxic Substances and Disease Registry (ATSDR), 1999a, Priority List of Hazardous Substances, Division of Toxicology, U.S. Department of Health and Human Services. Agency for Toxic Substances and Disease Registry (ATSDR), 1999b, ToxFAQs, Division of Toxicology, U.S. Department of Health and Human Services.

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Overview of Chromium(VI) in the Environment

21

Agency for Toxic Substances and Disease Registry (ATSDR), 2000, Toxicological Profile for Chromium, Division of Toxicology, U.S. Department of Health and Human Services. American Public Health Association, 1989, Standard Methods for the Examination of Water and Wastewater, 17th ed., Washington, DC. California Department of Health Services, 2002, http://www.dhs.ca.gov/ps/ ddwem/chemicals/Chromium6/Cr+6index.htm_ Dill, Jr., D.B., 1991, William Phipps Blake-Yankee Gentleman and Pioneer Geologist of the Far West, J. Ariz. Hist., Winter, 385–412. Glenn, W., 1893, Chrome: In Maryland, its Resources, Industries and Institutions, prepared for the Board of World’s Fair, Chicago, IL, Mannigers, Baltimore, MD, pp. 120–122. Gould, R.F., 1985, Eminent chemists of Maryland, Maryland Historical Magazine, Vol. 80, No. 1, Spring, pp. 19–21. Hartung, W.H., 1939, Early Chemistry in Maryland, Baltimore, Vol. 32, No. 6, pp. 42–44. Jacobs, J., Foreman, T., Mavis, J., and Gopalan, R., Groundwater, Hexavalent Chromium White Paper, Groundwater Resources Association of California (in press). Kohl, W.H., 1967, Handbook of Materials and Techniques for Vacuum Devices, Reinhold Publishing, New York, p. 161. Morning, J.L., Matthews, N.A., and Peterson, E.C., 1980, Chromium: In Mineral Facts and Problems, 1980 ed., U.S. Bureau of Mines, Bulletin 671, pp. 167–182. Morrison, D.S., 2004, Pressure Treated Wood: The Next Generation, Fine Homebuilding, The Tauton Press, Newtown, CT, No. 160, pp. 82–85. Papp, J.F., 2003, U.S. Geological Survey (USGS) Minerals Commodity Summaries, http://minerals.er.U.S.G.S.gov/minerals/pubs/commodity/chromium/ Roskill Company, 2002, Chromium World Market Overview, company brochure, www.roskill.co.uk/chrome.html. Selden, A.I., Bornberger-Dankvardt, S.I., Winstrom, L.E., and Bodin, L.S., 1995, Exposure to cobult-chromium dust and lung disorders in dental technicians, Thorax, 50, 7, pp. 769–772. Stern, R.M., 1982, Biological and Environmental Aspects of Chromium, Langard, S., Ed., Elsevier, New York. Stowe, C.W., 1987, Evolution of Chromium Ore Fields, Van Nostrand Reinhold, New York, 340 p. Testa, S.M., Whitney, J.D., and Blake, W.P., 2002, Conflicts in relation to California geology and the fate of the first California geological survey, Earth Sci. Hist., 21, 1, 46–76. U.S. Environmental Protection Agency (USEPA), 1996, Soil Screening Guidance, Technical Background Document, OSWER, EPA/540/R-95/128. U.S. Environmental Protection Agency (USEPA), 1996a Report: Recent developments for in situ treatment of metals-contaminated soils, Office of Solid Waste and Emergency Response, draft. U.S. Environmental Protection Agency (USEPA), 2004, Consumer Fact Sheet on: Chromium, http://www.epa.gov/safewater/contaminants/dw_containts/chromium.html. Winter, M., 2004, Web Elements: History of Chromium, http://www.webelements.com/ webelements/scholar/elements/chromium/history.html. See http://www.amm.com/ref/chrom.HTM. See http://www.acornusers.org/education/HNC-Web/Theory.html. See http://www.ccaresearch.ort/tag12/present/CR.

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2 Chemistry, Geochemistry, and Geology of Chromium and Chromium Compounds

William E. Motzer

CONTENTS 2.1 Chromium Chemistry .................................................................................24 2.1.1 Background ......................................................................................24 2.1.2 Elemental/Metallic Chromium Characteristics .........................25 2.1.3 Ionic Radii ........................................................................................28 2.1.4 Oxidation States...............................................................................28 2.1.5 Stable and Radioactive Isotopes ...................................................29 2.1.6 Characteristics of Chromium Compounds .................................33 2.2 Natural Chromium Concentrations..........................................................33 2.2.1 Mantle ...............................................................................................46 2.2.2 Chromium Minerals........................................................................46 2.2.3 Chromium Ore Deposits................................................................46 2.2.3.1 Stratiform Mafic–Ultramafic Chromite Deposits.........64 2.2.3.2 Podiform- or Alpine-Type Chromite Deposits ............65 2.2.4 Crude Oil, Tars and Pitch, Asphalts, and Coal ..........................65 2.2.5 Rock ...................................................................................................66 2.2.6 Soil .....................................................................................................66 2.2.7 Precipitation (Rain Water) and Surface Water ...........................68 2.2.8 Groundwater....................................................................................69 2.2.9 Sea Water ..........................................................................................69 2.2.10 Air ......................................................................................................69 2.2.11 Biogeochemical Cycling .................................................................70 2.3 Chromium Geochemistry ...........................................................................72 2.3.1 Chromium(III) Geochemistry........................................................72 2.3.2 Chromium(VI) Geochemistry........................................................73 2.3.3 Chromium Reaction Rates (Kinetics)...........................................75 2.4 Chromium Distribution in Primary Environments ...............................76 2.4.1 Possible Sources of Natural Chromium(VI) in Rocks...............76 2.4.2 Known Sources of Natural Chromium(VI) in Rocks ................79 1-5667-0608-4/05/$0.00+$1.50 © 2005 by CRC Press LLC

23

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Chromium(VI) Handbook

2.5

Chromium Distribution In Secondary Environments ...........................80 2.5.1 Known Natural Chromium(VI) Occurrences in Surface Water and Groundwater ................................................................80 2.6 Forensic Geochemistry................................................................................82 2.6.1 Soil .....................................................................................................82 2.6.2 Groundwater....................................................................................82 2.6.3 Air ......................................................................................................83 Acknowledgments ................................................................................................84 Bibliography ........................................................................................... 84

2.1 2.1.1

Chromium Chemistry Background

In 1797, the French chemist Nicholas-Louis Vauquelin hypothesized that chromium (Cr) was a separate and distinct element. He had isolated the oxide of this element from a Siberian mineral known as crocoite (PbCrO4). In 1798, Vauquelin successfully isolated metallic Cr by heating chromic oxide (Cr2O3) with charcoal (a chemical reduction). He then named the new element after the Greek word χρωµα (chro^ ma), pronounced khrma, for color because it produced chemical compounds with distinct and unique colors. Vauquelin also analyzed a Peruvian emerald, determining that its green color was owing to the presence of Cr. About two years after Cr’s discovery, Tassaert, a German chemist, determined that Cr was present in an ore that we now know as chromite, FeCr2O4 (Greenwood and Earnshaw, 1998; ChemGlobe, 2000; Papp, 2000; Winter, 2002). Since its discovery, Cr has become a very important industrial metal because of its many applications in ferrous (cast iron and stainless steel) and in nonferrous (aluminum, copper, and nickel) alloy metal fabrication, and in the chemical industry (metal finishing, plating, corrosion control, pigments and tanning compounds, and wood preservatives) (Papp, 2000). Cr compounds are used in a wide variety of industrial and manufacturing applications including steel alloy fabrication, where they enhance corrosion and heat resistance in other metals, and in plated product fabrication where they are used for metal decoration or increased wear resistance. They are also used in nonferrous alloy metal fabrication to impart special qualities to the alloys; in production and processing of insoluble salts, as chemical intermediates; in the textile industry for dyeing, silk treating, printing, and moth proofing wool; in the leather industry for tanning; in the manufacture of green varnishes, inks, paints, and glazes; as catalysts for halogenation, alkylation, and catalytic cracking of hydrocarbons; as fuel and propellant additives; and in ceramics (Spectrum Laboratories, 1998).

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25

While Cr in its Cr(III) form is not considered a toxic element and is a required diet nutrient with recommended daily adult dosages ranging from 0.5 to 2 mg/day (required for glucose metabolism). In its Cr(VI) form, it does have toxic effects (see Guertin, Section 6, this volume). Acute exposure to Cr(VI)-laden dust results in skin rashes, ulcers, sores, and eczema in occupational workers. In humans, Cr(VI) exposure caused marked irritation of the respiratory tract and ulceration and perforation of the nasal septum in workers in the chromate producing and -using industries. Ingestion of 1.0 g to 5.0 g of Cr(VI) as chromate (CrO42−) results in severe acute gastrointestinal disorders, hemorrhagic diathesis, and convulsions. Death may occur following cardiovascular shock. Doses in animals of Cr(VI) greater than 10 mg/kg body mass mainly affect the gastrointestinal tract, kidneys, and hematopic system (IPCS, 1988). Cr(VI) causes cancerous tumors in mice by inhalation and is considered a possible human carcinogen by this route because workers engaged in the production of CrO42− salts and pigments experience an increased risk of developing bronchial carcinomas. However, ingestion of Cr(VI) has not been observed to cause cancer because it is believed that Cr(VI) is reduced to Cr(III) in the gastrointestinal tract (IPCS, 1988; WHO, 1988 and 1996; Smith and Huyck, 1999; CDHS, 2003). The understanding of Cr chemistry and geochemistry is therefore important in developing remediation systems that can deal with industrial-caused pollution (see Chapter 8). This chapter is a review of the characteristics of Cr in the natural environment; its concentration within the Earth’s crust, atmosphere, and biosphere; and its geochemistry. 2.1.2

Elemental/Metallic Chromium Characteristics

Chromium (atomic number 24) is a transition element occurring in Group 6B of the periodic table. General elemental Cr characteristics are summarized in Tables 2.1a to 2.1d. Cr has a ground state electron configuration of 1s22s22p6 3s23p64s13d5 (Table 2.2). In the periodic table, transition elements (all metals) (Groups 1B to 8B) occur between the main group elements (Groups 1A to 2A and Groups 3A to 7A and the inert gases—Group 8A) (Drew, 1972; Timberlake, 2003). The atoms of transition elements have electrons filling d subshells consisting of five d orbitals. The transition elements are noteworthy because five d orbitals: 1. Form alloys with one another and the main group metals. 2. Commonly are colorless lustrous metals with high melting and boiling points. The transition metals vary in abundance in the continental crust from iron, which is common at 5.63% to scandium which is rare at 22 (parts per million) ppm (Ronov and Yaroshevsky, 1972). 3. Have high melting points and densities because the electrons in the d orbitals, bind atoms together in the crystal lattice.

7.23 0.250 Cubic body centered 7.19

Atomic volume (cm3/mol)

Bond length: Cr–Cr (nm) Crystal structure

Electrical

Ionization Potential (eV): First Second Third

Electronegativity: Pauling Absolute (eV) Electrical resistivity (Ωm) (at 20 °C)

Electrical conductivity (Ωm)−1 (at 20 °C)

1/ Fills of subshell 2 Effective nuclear charges

e in shell 1,2,3,4 Electron binding energies Oxidation states (Table 2.4) Successive ionization Energies e– configuration –

Properties

6.7666 16.50 30.96

1.66 3.72 1.25 × 10−7

8.00 × 106

3d5 Table 2.1c

2,8,13,1 Table 2.1b −2 to +6 Table 2.1d {Ar}4s13d5

24

52

Cr

Heat of fusion J/g Specific heat capacity J/(g ⋅ K) (at 27 °C) Thermal conductivity W/(m ⋅ K) (at 27 °C)

Melting point

Boiling point Heat of vaporization (kJ/g)

Thermal

(most abundant isotope: 83.789%)

ChemGlobe (2000); ChemPros (2000); Winter: WebElements (2001); Handbook of Chemistry and Physics (1996).

8.5 1,120 1,060

Hardness: Mineral: Mohs (no units) Brinell (MN/m2) Vickers (MN/m2)

Sources:

279 115 160

Elastic Properties: Young’s modulus (GPa) Rigidity modulus (GPa) Bulk modulus (GPa)

Symbol Z A = mass number = number of protons + number of neutrons z = atomic number = number of protons

A

93.7

2,180 °C; 1,907 °C; 2,180 K 6.25 0.451

2,671 °C; 2,944 K 6,622

26

Density (g/cm3 at 20 °C)

0.185 0.118 0.062

Atomic radius (nm) Covalent radius (nm) Ionic radius (nm)

Physical

Atomic no. 24 Atomic mass 51.9961 Group no. 6B Group name Transition metals Period no. (shell) 4 Block (subshell) d Chemical Registry CAS no. 7440-47-3

Periodic Table

Elemental Chromium Properties

TABLE 2.1A

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27

Chemistry, Geochemistry, and Geology of Chromium TABLE 2.1B Chromium Electron Binding Energies Label

Orbital

eV

K LI LII LIII MI MII MIII

1s 2s 2p 1/2 2p 1/2 3s 3p 1/2 3p 3/2

5,989 696 583.8 574.1 74.1 42.2 42.2

TABLE 2.1C Chromium Effective Nuclear Charges Orbital

Zeff

Orbital

1s 2s 3s 4s 5s 6s 7s

23.41 16.98 12.37 5.13 — — —

— 2p 3p 4p 5p 6p —

Zeff

Orbital

Zeff

Orbital

20.08 11.47 — — — —

— — 3d 4d 5d — —

— — 9.76 — — — —

— — — 4f — — —

TABLE 2.1D Chromium Ionization Energies Ionization State +

Cr to Cr Cr+ to Cr2+ Cr2+ to Cr3+ Cr3+ to Cr4+ Cr4+ to Cr5+ 0

kJ/mol 652.7 1,592 2,987 4,740 6,640

Ionization State 5+

Cr Cr6+ Cr7+ Cr8+ Cr9+

to to to to to

6+

Cr Cr7+ Cr8+ Cr9+ Cr10+

kJ/mol 8,738 15,550 17,830 20,220 23,580

Note: Values in bold involve the removal of outer shell electron(4s’); for references see Table 2.1A.

4. Form compounds that are commonly brightly colored [e.g., Cr(III) chloride is violet]. This occurs because lower energy electrons move from a lower energy electrons move formula lower energy d orbital to higher energy d orbitals resulting in energy being taken in. When these electrons return to their original position, they release specific energies producing light of specific colors. 5. Like the main group metals, they form salts. However, where the main group salts will have cations that balance anions [e.g., halite or sodium chloride (NaCl) when dissolved in water forms an ionic solution of Na+ + Cl−], transition metals are more likely to form

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Chromium(VI) Handbook

TABLE 2.2 Electronic Configuration of Elements in Period 4 Subshell

Atomic No.

Element Name

1s

2s

2p

3s

3p

3d

4s

4p

4d

4f

21 22 23 24 25 26 27 28 29 30

Sc Ti V Cr Mn Fe Co Ni Cu Zn

2 2 2 2 2 2 2 2 2 2

2 2 2 2 2 2 2 2 2 2

6 6 6 6 6 6 6 6 6 6

2 2 2 2 2 2 2 2 2 2

6 6 6 6 6 6 6 6 6 6

1 2 3 5 5 6 7 8 10 10

2 2 2 1 2 2 2 2 1 2

— — — — — — — — — —

— — — — — — — — — —

— — — — — — — — — —

Note: By energy 4s fills before the 3d as in Cr = 1s22s22p63s23p64s13d5; for references see Table 2.1A.

complex ions or polyatomic ions with varying predominantly negative change [e.g., Cd(OH)42− and CrO42−] (Royal Society of Chemistry, 2000). At ambient temperatures (20 °C to 25 °C), metallic Cr has a silvery color is very hard, brittle *, corrosion resistant, and capable of taking a high polish (ChemGlobe, 2000). Heavy metals are those with densities greater than 5 g/cm3 at ambient temperature; Cr can also be considered as both a heavy metal and trace element. (de Haan and Bolt, 1979). In many cases, in the natural environment (such as in soils, rocks), Cr can also be considered as a trace element in that a trace element is defined as any chemical element that has a solid phase mass concentration less than 100 ppm (Sposito, 1989). 2.1.3

Ionic Radii

The radius of the neutral Cr atom is 0.130 nm (Chang, 1994); chromium ionic radii vary from 0.04 nm in Cr(VI) to 0.094 nm in Cr(II). Radii variations depend on coordination type, chemical form, and spin (Winter, 2001; Table 2.3). Ionic radii are important in determining ionic substitution for various Cr compounds/mixtures.

2.1.4

Oxidation States

Oxidation states in the transition metals are important in that transition metal ions that have charges greater than +3 cannot exist in aqueous solution. * Chromium metal’s reported brittleness in most of the literature may be caused by oxidized impurities. Pure Cr metal is extremely susceptible to combining with atmospheric oxygen. Therefore, it is almost impossible to have pure Cr in an oxygen-containing atmosphere (see Kohl, 1967).

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29

Chemistry, Geochemistry, and Geology of Chromium TABLE 2.3 Chromium Ionic Radii Oxidation State

Coordination Typea

Species

Cr(IV) Cr(V) Cr(VI) Cr(II) Cr(II) Cr(III) Cr(IV) Cr(V) Cr(VI) Cr(V)

4 4 4 6 6 6 6 6 8

Tetrahedral Tetrahedral Tetrahedral Octahedral Octahedral Octahedral Octahedral Octahedral Octahedral

a

Spin

Low High Low Low Low Low

Radius (nm) 0.055 0.0485 0.040 0.087 0.094 0.0755 0.069 0.063 0.058 0.071

Coordination type refers to covalent bonding.

Source:

Winter: WebElements (2001).

Cr oxidation states range from −4 to +6 (Table 2.4). The different oxidation states are important in determining what Cr compounds form in the environment (Smith, 1972). Oxidation states −2, −1, 0, and +1 primarily occur in synthetic organic-chromium compounds such as the chromium carbonyls, chromium bipyridine, carbonyl nitrosyls, and organometallic complexes (Kotz et al., 2000; Luis, 2001). Only three oxidation states are found in nature; these are: 1. Cr(0) which occurs in metallic or native Cr 2. Cr(III) which occurs in chromic compounds (usually Cr3+) 3. Cr(VI) which occurs in CrO42− and Cr2O72− compounds Chromium(0) is rarely found in the natural environment, although many references indicate that it does not occur. However, native Cr occurs as metallic inclusions in cryptocrystalline diamonds (carbonado) from kimberlite pipes in the Siberian Yakutia diamond deposits of Russia (Gorshkov et al., 1996). Native Cr also has been found in vein deposits from Sichuan, China (Guisewite, 2001), in meteorites such as the Agpalilik meteorite fragment from Cape York, Greenland, and as metal alloys in placer deposits (see Table 2.8). Chromium(III) occurs as insoluble chromium(III) oxide (Cr2O3) and chromium(III) hydroxide [Cr(OH)3]; it also occurs as soluble chromium(III) hydroxide cations: CrOH2+ and Cr(OH)2+. Cr(VI) generally occurs as soluble Cr2O72− and CrO42− anions. 2.1.5

Stable and Radioactive Isotopes

Currently, there are 26 known Cr isotopes (Table 2.5), of which four are stable (nonradioactive), naturally occurring isotopes (ChemGlobe, 2000; Winter, 2001;

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30

Chromium(VI) Handbook TABLE 2.4 Chromium Oxidation States Example Compound

Oxidation State

Name

−2

Sodium chromium(−II) carbonyl

Na2[Cr(CO)5]

−1

Sodium chromium(−I) carbonyl

Na2[Cr2(CO)10]

0

Chromium(0) (elemental, metal) Chromium(0) carbonyl

Cr0 Cr(CO)6

+1

Chromium bipyrydil (=L)

[Cr(L)3]

+2

Chromium(II) Chromium(II) Chromium(II) Chromium(II)

CrO CrF2 CrCl2 CrS

+3

Chromium(III) Chromium(III) Chromium(III) Chromium(III)

+4

Chromium(IV) oxide Chromium(IV) fluoride

CrO2 CrF4

+5

Barium chromate Chromium pentafluoride

Ba3(CrO4)2 CrF5

+6

Barium chromate Chromate anion Sodium dichromate Dichromate anion

BaCrO4 CrO42− Na2Cr2O7 Cr2O72−

oxide fluoride chloride sulfide oxide fluoride chloride hydroxide

Formula

Cr2O3 CrF3 CrCl3 Cr(OH)3

Note: Oxidation states in bold are those commonly found in minerals and compounds in the natural environment. Source:

Modified from USEPA (1984); Marques et al. (1999).

LBNL, 2002). These include 50Cr, 52Cr, 53Cr, and 54Cr; their naturally occurring abundances are 4.345%, 83.789%, 9.509%, and 2.465%, respectively (Winter, 2001). Stable Cr isotopes are known to fractionate (Table 2.5), that is, when one isotope is preferentially enriched over another relative to a known standard, which represents its natural abundance (see footnote in Section 3.6). There are several environmental and geologic controlling processes in stable isotopic fractionation; these may include (1) isotopic exchange reactions, (2) evaporation and condensation, (3) melting and crystallization of rocks, (4) adsorption and desorption, (5) mass dependent diffusion, (6) temperature, (7) ultrafiltration in water-rock reactions, and (8) the preference for some biological organisms in concentrating lighter over heavier isotopes (Hurst, 1991). By experimental methods, Ottonello (2002) has identified Cr fractionation under various conditions.

Artificial Artificial Artificial Artificial Artificial 4.345

83.789 9.509 2.465 Artificial Artificial Artificial Artificial Artificial

44.97911

45.96836 46.962905 47.954033 48.951338 49.9460464

50.944768 51.9405098 52.9406513 53.9388825 54.940842 55.940643 56.94344 57.94412 58.949

Cr

Cr Cr 48Cr 49Cr 50Cr

Cr Cr 53Cr 54Cr 55Cr 56Cr 57Cr 58Cr 59Cr

52

51

47

46

45

7/2– 0+ 3/2– 0+ 3/2– 0+ 3/2–, 5/2–, 7/2– 0+ —

0+ 3/2– 0+ 5/2– 0+ −0.934 — –0.47454 — — — — 0.0834 —

— — — 0.476 —

—

—

0+

Artificial 7/2–

— — — —

— (3/2+) (3/2+) —

Artificial Artificial Artificial Artificial

— Cr 43.98556 Cr 43Cr: meta state 43Cr: meta state: 0.000 MeV 44Cr 43.98556

43

42

Atomic Mass (amu) Nuclear Spin (I)

Isotope

Nuclear Magnetic Moment (µn/µN)

Natural Abundance (isotope %)

Chromium Nuclide (Isotope) Properties

TABLE 2.5

51V NA NA NA 55Mn 56Mn 57Mn 58Mn 59Mn

ε + β+ ε ε + β+ ε + β+ ε ε ε ε NA NA NA β– β– β– β– β–

0.05 s 0.26 s 0.51 s 21.56 h 42.3 min Rel. Stable: 1.8 1017 yr 27.7025 d Stable Stable Stable 3.497 min 5.94 min 21.1 s 7.0 s 0.74 s

Ti V 44Ti 45V 46V 47V 48V 49V 50Ti

ε+p

0.53 s

44

43

0.753 NA NA NA 2.603 1.617 5.090 3.970 7.700

8.500 10.310 10.850 12.460 7.603 7.451 1.659 2.631 —

— 15.890 15.700 11.930 — V 39Sc 41Sc

— ε ε+α ε+p

— 0.21 s 0.21 s 0.21 s 43

Decay Energy (MeV)

Decays to

Mode of Decay

Half Life (t1/2)

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Chemistry, Geochemistry, and Geology of Chromium 31

Cr Cr 62Cr 63Cr 64Cr 65Cr 66Cr 67Cr

59.95 60.954 — — — 64.97 — — Artificial Artificial Artificial Artificial Artificial Artificial Artificial Artificial

0+ (5/2–) 0+ (1/2–) 0+ (1/2−) 0+ (1/2–) — — — — — — — — 0.57 s 0.270 s 0.190 s 0.190 s 0.110 s — — —

β– β– β– β– β– β– (?) β– β– Mn Mn — — — — — —

61

60

5.900 8.800 — — — — — —

Sources:

Winter: WebElements (2001); Marques et al. (1999); Barbalace et al. (2001); Lawrence Berkeley National Laboratories (2002).

Note: Isotopes in bold are stable nonradioactive isotopes. ε = electron capture; α = alpha emission β– = beta emission; β+ = positron emission; p = proton emission. µn/µN = magnetic moment in nuclear magnetrons. NA = not applicable. s = seconds, min = minutes, h = hours, d = days, yr = years. Dash (—) indicates no available data. Values in parenthesis are tentative.

61

60

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33

Radioactive isotopes of Cr have been artificially produced. Most have very short half-lives (t1/2). For example, Table 2.5 shows that the t1/2 for isotopes from 42Cr to 47Cr and from 57Cr to 64Cr are much less than 1 s. Chromium isotope studies have been important in determining the age of solids (planetesimals) first formed in the solar nebula (Carlson and Lugmair, 2000) and in investigations of the solar wind (Kitts et al., 2002). Stable isotope fractionation may be important for forensic geochemical investigations (see Section 2.6).

2.1.6

Characteristics of Chromium Compounds

Chromium can be combined with various nonmetals (oxygen, fluorine, chlorine, etc.) and polyatomic anions (such as nitrate, sulfate, etc.), forming relatively stable, soluble and insoluble compounds (Table 2.6). More common are Cr(III) compounds such as chromium tribromide (insoluble), chromium nitrate (soluble), chromic hydroxide (insoluble), and chromic oxide (insoluble). In the chemical production industry, most chromium chemicals are produced from sodium dichromate, which is the principal feedstock. Chemicals made from sodium dichromate include chromic acid, Cr(III) oxide, and potassium dichromate (Papp, 2000). Most Cr compounds are brightly colored and these colors are reflected in synonyms for their respective compounds. For example, basic chromium sulfate is known as chrome tan, Cr(III) oxide is known as chrome green, barium chromate is known as baryta yellow or lemon chrome, basic lead chromate is known as chrome orange and chrome red, calcium chromate is known as calcium chrome yellow, and lead chromate is also known as chrome green. All Cr compounds are considerably denser than water with specific gravities ranging from 1.77 (for hydrated chromium sulfate) to 6.10 [for chromium(II) selenide] (Dean, 1992; ChemIDplus, 2001; Chemfinder, 2001). Therefore, saturated and very concentrated Cr compound solutions would tend to sink through the groundwater column.

2.2

Natural Chromium Concentrations

As with other elements in the periodic table, Cr concentrations in natural substances are quite variable. Cr preferentially concentrates in various rocks throughout the Earth’s crust with concentrations dependent on the rock’s origin and source (Table 2.7). Cr concentrations are also quite variable in secondary geochemical environments, particularly in soils, sediments, and stream and lake water. Concentrations may significantly vary because of anthropogenic influences and inputs, largely from smelting of Cr ore and the burning of fossil fuels such as coal and petroleum products.

Chromium(III) bromide hexahydrate Chromium(III) boride

Chromium(IV) boride

Chromium(IV) boride Chromium(II) bromide; chromium dibromide

(IV)boride

boride (II)bromide

285.226

Cr(C2H3O2)3

73.618

12006-79-0 12007-16-8 12007-38-4 10049-25-9

CrB CrB2 Cr5B3 CrBr2

292.414 211.804

62.807

10031-25-1

Cr(H2O)6Br3 399.799

6.10 4.236

5.22

6.1

7.11 7.04 4.68

CrSb Cr2As CrBr3 21679-31-2 12254-85-2 10031-25-1

1.72

1.79 1.79

Density (water = 1)

[CH3COCHC (CH3)O]3Cr CrNH4(SO4) · 12H2O 349.324 178.914 291.708

229.1295

Cr(C2H3O2)3 · 12H2O 1066-30-4

1066-30-4

170.10 188.101

Molar Mass (g/mol)

17593-70-3 628-52-4

Cr(C2H3O2)2 C4H8CrO5; Cr(C2H3O2)2 · H2O

Formula

CAS Number

1,900 842

2,200

2,100

1,130

1,110–1,220

94

216

Melting Point (°C)

340

Physical Description

Soluble

Soluble in hot H2O Soluble

Soluble

Insoluble

Soluble

White monoclinic crystals; forms blue aqueous solution

Purple powder or reddish-violet crystals Green powder or deep violet crystals Hexagonal crystals Tetrahedral crystals Dark green hexagonal crystals Violet hydroscopic crystals Refractory, orthorhombic crystals Refractory solid; hexagonal crystals

Blue needles

Reddish- brown powder; red monoclinic crystals Slightly Soluble Grayish--green powder or violet plates

Soluble

Aqueous Boiling Solubility at Point (°C) 20 °C (mg/L)

34

(III) bromide hexahydrate boride

Chromium(II) acetate Chromium(II) acetate; Chromium(II) acetate monohydrate (III)acetate Chromium(III) acetate; chromic acetate; Chromium(III) acetate Chromium(III) acetate (III)acetate hexahydrate hexahydrate acetylacetonate Chromium(III) acetylacetonate ammonium Chromium(III) ammonium sulfate sulfate ·12 hydrate antimonide Chromium(III) antimonide arsenide Chromium(III) arsenide bromide Chromium(III) bromide

(II)acetate (II) acetate hydrate

Chromium:

Compound

Names and Synonyms

TABLE 2.6 Physicochemical Properties of Some Chromium Compounds

L1608_C02.fm Page 34 Tuesday, November 9, 2004 9:23 AM

Chromium(VI) Handbook

Chromium(IV) bromide Chromium(III) bromide hexahydrate Chromium carbide

chromium carbide Chromium carbonyl; chromium hexacarbonyl Chromium(II) carbonate; chromus carbonate Chromium(II) chloride; chromus chloride

(IV)bromide (III)bromide hexahydrate carbide

carbide carbonyl

Chromium(III) chloride

Chromium(IV) chloride

Chromium(II) chloride octahydrate Cobalt chromite

Copper(II) chromite

(III)chloride

(IV)chloride

(II)chloride octahydrate (II)cobalt

(II)chromite

(II)chloride

carbonate

Chromium(III) bromide

(III)bromide

Compound

Names and Synonyms

12012−35−0 12105-81-6 13007-92-6

Cr3C2 Cr23 C6 Cr(CO)6

158.355

193.807

10025-73-7

15597-88-3 13931-94-7 13455-25-9 12018-10-9

CrCl4 Cr(H2O)4Cl2 · 4H2O CoCr2O4 CuCr2O4

(a) CrCl3 (b) CrCl3 · 6H2O

231.536

226.923

267.023

122.902

CrCl2

5.4

0.0085 (gas)

(a) 2.76 (b) 2.870

2.878

2.75

1.77

6.65

180.010

220.058

—

4.680

Density (water = 1)

371.612 266.445

291.708

Molar Mass (g/mol)

10049-05-5

CrCO3

23098-84-2 10060-12-5

10031-25-1

CrBr4 CrBr3 · 6H2O

CrBr3

Formula

CAS Number

TABLE 2.6 Physicochemical Properties of Some Chromium Compounds (Continued)

5.14

dec: 51

1,150

815–824

dec: 110–130

1,890–1,895

—

812; 1130 (?)

Melting Point (°C)

dec: >600

1,300

1,120

120

3,800

—

Physical Description

Insoluble

Insoluble

Chemistry, Geochemistry, and Geology of Chromium (Continued)

Bluish-green cubic crystals Grayish-black tetrahedral crystals

Olive green or dark Insoluble; Soluble in hot green solid H2O — Gas Soluble Violet crystals; hydroscopic Insoluble Gray, orthorhombic crystals may be unstable White crystalline solid Insoluble <1,000 Slightly soluble Grayish-blue amorphous powder Very soluble Lustrous white needles or fused fibrous mass; hydroscopic Insoluble in Reddish-violet cold H2O; crystalline solid; slightly hydroscopic soluble in hot H2O Stable at high temperatures Soluble

Aqueous Boiling Solubility at Point (°C) 20 °C (mg/L)

L1608_C02.fm Page 35 Tuesday, November 9, 2004 9:23 AM

35

305.805 432.71 559.614 223.835 238.0107

1308-14-1 13478-28-9 13569-75-0 23518-77-6 1308-31-2 13548-38-4

Cr(OH)3 · 3H2O CrI2

Chromium(III) iodide

Chromium(IV) iodide Iron(II) chromite Chromic(III) nitrate Chromium(III) nitrate

(III)iodide

(IV)iodide (II)iron (III)nitrate CrI4 FeCr2O4 Cr(NO3)3

CrI3

103.0179

1308-14-1

Cr(OH)3 157.063

295.15

Cr(CHO2)3 · 6H2O

Hydrated chromium(III) formate Chromic hydroxide; chromium(III) hydroxide Chromium(III) hydroxide trihydrate Chromium(II) iodide

(III)formate 6-water (III)hydroxide

5.0

5.300

5.100–5.32

2.9

3.8 2.2

3.790

Density (water = 1)

60

dec: 500

868

dec: >100

dec: −100

34

277

1,404

894

Melting Point (°C)

500

1,100

117

400

1,300

Physical Description

Bluish-green powder

Green crystals Green hexagonal crystals Green to violet crystalline solid Red orthorhombic to crimson crystalline solid Yellow crystalline solid; stable at low temperatures

Very soluble

(Continued)

Black cubic crystals Green, hydroscopic powder

Reddish-brown crystalline solid Slightly soluble Dark green crystalline solid

Soluble

Insoluble

Insoluble

Soluble

Soluble

Insoluble Soluble

Slightly soluble Blue-green monoclinic crystals; anhydrous

Aqueous Boiling Solubility at Point (°C) 20 °C (mg/L)

36

(III)hydroxide trihydrate (II)iodide

165.987

13843-28-2

CrF6

Chromium(IV) fluoride

(VI)fluoride

146.988

14884-42-5

CrF5

Chromium(V) fluoride

(V)fluoride

127.990

10049-11-3

CrF4

89.9928

108.991 163.037

10049-10-2

Molar Mass (g/mol)

7788-97-8 16671-27-5

(III)fluoride (III)fluoride trihydrate (IV)fluoride

CrF2

Formula

CAS Number

CrF3 CrF3 · 3H2O

Chromium(II) fluoride; chromium difluoride; chromus fluoride Chromium(III) fluoride Chromium(III) fluoride trihydrate Chromium(IV) fluoride

(II)fluoride

Compound

Names and Synonyms

TABLE 2.6 Physicochemical Properties of Some Chromium Compounds (Continued)

L1608_C02.fm Page 36 Tuesday, November 9, 2004 9:23 AM

Chromium(VI) Handbook

(III)phosphate

perchlorate 7789-04-0

13537-21-8 146.967

99.9942

1333-82-0

Chromic trioxide; CrO3 chromium anhydride Chromium(VI) oxide Cr(ClO4)3 Chromic perchlorate; chromium(III) perchlorate Chromic(III) phosphate CrPO4

12018-34-7 12018-01-8

Cr3O4 CrO2

(VI)oxide

219.968 83.9948

1308-38-9 151.9902

158.031

117.999

12053-27-9 814-90-4

66.003

400.148

24094-93-7

7789-02-8

Molar Mass (g/mol)

Cr2O3

CrC2O4· H2O

Chromium oxide Chromium(IV) oxide; chromium dioxide

Chromous oxalate monohydrate; chromium(II) oxalate monohydrate Chromia; chromic oxide; chromium(III) oxide; chromium sesquioxide; green cinnabar

(II)(III)oxide (IV)oxide

(III)oxide

oxalate

nitride

(III)nitride

Hydrated chromium(III) Cr(NO3)3 · 9H2O nitrate; chromium nitrate nonahydrate CrN Chromium(III) nitride; chromium mononitride Cr2N Chromium nitride

(III)nitrate 9-water

Formula

Names and Synonyms

Compound

CAS Number

Physicochemical Properties of Some Chromium Compounds (Continued)

TABLE 2.6

4.6

2.700

6.1 4.89

5.21

2.468

6.8

5.9

1.80

Density (water = 1)

>1800

dec: 400 (approximate; loses O2) 190; 195; 197

2,330; 2,435; 2,450

1650

dec: 1080

66.3 (dec: 100)

Melting Point (°C)

Insoluble

Insoluble

Insoluble

dec: ~250 617,000

~3,000; 4,000

Soluble

2,080,000

Aqueous Boiling Solubility at Point (°C) 20 °C (mg/L)

Chemistry, Geochemistry, and Geology of Chromium (Continued)

Blue orthorhombic crystals

Dark green, amorphous powder forming hexagonal crystals upon heating; hydroscopic Cubic crystals Brownish black acicular crystalline (tetragonal) solid Dark red orthorhombic crystalline (flakes or powder) solid; hydroscopic

Hexagonal crystals; CrN exists Yellowish-green crystalline powder

Greenish black to purple rhombic (monoclinic) crystals Gray crystalline solid

Physical Description

L1608_C02.fm Page 37 Tuesday, November 9, 2004 9:23 AM

37

chromium(II) sulfate pentahydrate Hydrated chromium(II) sulfate sulfate 12-water chromium(II) sulfate, 12-hydrate; (III)sulfide Chromium(III) sulfide; dichromium trisulfide

sulfate pentahydrate sulfate 7-water 608.3472

10101-53-8 12018-22-3

CrSO4 · 12H2O Cr2S3

200.190

274.17

238.136

130.956 184.074 108.167 392.183

499.405

CrSO4 · 7H2O

13825-66-0

CrSO4 · 5H2O

7788-99-0

CrK(SO4)2 · 12H2O

12053-13-3 12018-36-9 12018-09-6 10101-53-8

26342-61-0 10141-00-1

CrP CrK(SO4)2

CrSe Cr3Si CrSi2 Cr2(SO4)3

82.970

84359-31-9

CrPO4 · 6H2O

3.8

6.100 6.4 4.91 3.1

1.826

5.25 1.813

2.121

~1,500 1,770 1,490

89

Insoluble

229,000

Soluble

Insoluble

220,000

Soluble

Insoluble

Insoluble

2.12@14 °C

Aqueous Boiling Solubility at Point (°C) 20 °C (mg/L) Insoluble

dec: >500

Melting Point (°C)

2.15

Density (water = 1)

(Continued)

Brown to black crystalline solid

Peach-colored solid

Hexagonal crystals Cubic crystals Gray hexagonal crystals Reddish-brown hexagonal crystals Blue crystals

Purple to violet-black cubic crystals

Orthorhombic crystals Dark violet-red crystals

Violet crystals

Green crystals

Bluish-green powder

Physical Description

38

(II)selenide silicide silicide (III)sulfate

255.059

7789-04-0

CrPO4 · 4H2O

Chromium(III) phosphate tetrahydrate Chromium(III) phosphate hexahydrate Chromium(III) phosphide Potassium chromium(III) sulfate Chrome alum; chrome alum (dodecahydrate); potassium Chromium(III) sulfate potassium bisulfate 12-water chromium(II) selenide chromium silicide chromium silicide chromium(III) sulfate

210.021

84359-31-9

CrPO4 · 3.5H2O

chromium(III) phosphate hemiheptahydrate

(III)phosphate hemiheptahydrate (III)phosphate hydrate (III)phosphate hexahydrate phosphide potassium sulfate (III)potassium sulfate dodecahydrate

Formula

Names and Synonyms

Molar Mass (g/mol)

Compound

CAS Number

Physicochemical Properties of Some Chromium Compounds (Continued)

TABLE 2.6

L1608_C02.fm Page 38 Tuesday, November 9, 2004 9:23 AM

Chromium(VI) Handbook

24613-89-6

Cr2(CrO4)3

copper copper

cobalt CuCrO4 CuCrO4 · 2CuO · 2H2O

CoCrO4

174.927 179.540

24613-38-5 13548-42-0

192.102

13765-19-0

CaCrO4 · 2H2O

Calcium chromate dihydrate Chromic acid; chromium(III) chromate Cobaltous chromate: basic cobalt(II) chromate Copper(II) chromate Cupric chromate basic

calcium dihydrate chromic

156.0736

13765-19-0

CaCrO4

Calcium chromium oxide; calcium; chromate

calcium

228.405

14312-00-06

CdCrO4

Cadmium chromate

cadmium

253.3236

BaCrO4

104294-40-3

152.0702

486.79 233.38

643.968

7788-98-9

12053-39-3 12018-19-8

Molar Mass (g/mol)

12345-14-1

Ba3(CrO4)2

(NH4)2Cr2O4

Cr(C18H35O2)3 Cr2Te3 ZnCr2O4

Formula

barium(Cr(VI)) Barium chromate

barium(Cr(V))

ammonium

Ammonium chromium oxide; ammonium chromate Barium chromate

Chromium stearate Chromium(III) telluride Zinc chromite

stearate (III)telluride zinc

Chromate:

Names and Synonyms

Compound

CAS Number

Physicochemical Properties of Some Chromium Compounds (Continued)

TABLE 2.6

–4.0

2.50

2.89

4.5

4.50

5.25

7.0 5.29

Density (water = 1)

185

95–100 ~1,300

Melting Point (°C)

Greenish-black hexagonal crystals Yellow, orthorhombic crystals Yellow, orthorhombic crystals Bright yellow powder

Yellow crystals

Dark green powder Hexagonal crystals Green cubic crystals

Physical Description

Chemistry, Geochemistry, and Geology of Chromium (Continued)

Slightly soluble: <100 @ 22 °C Slightly soluble Yellow, orthorhombic crystals Trial dromic acid is H2CrO4 Soluble Black to brown crystals or yellow powder Soluble Reddish-brown crystals Light chocolate brown powder

Insoluble

Insoluble

Soluble

Soluble

Aqueous Boiling Solubility at Point (°C) 20 °C (mg/L)

L1608_C02.fm Page 39 Tuesday, November 9, 2004 9:23 AM

39

Chromate of soda; sodium Na2CrO4 chromate SrCrO4 Strontium chromate

sodium

zinc Basic zinc chromate zinc hydroxide Zinc hydroxide chromate zinc potassium Potassium zinc chromate hydroxide

potassium

Potassium chromate

Mercury(II) chromate Silver chromate

(II)mercury silver

ZnCrO4

K2CrO4

HgCrO4 Ag2CrO4

203.6136

7789-06-2

13530-65-9 15930-94-6 11103-86-9

7789-00-6

161.97314

7775-11-3

316.58 331.730

165.906

546.4

459.671 323.1936

Molar Mass (g/mol)

2.739

3.9

2.72

6.06 5.625

2.15

6.123

Density (water = 1)

971–975

dec

792

dec on heating

dec: 75

844

Melting Point (°C)

Physical Description

Yellow crystalline, deliquescent powder Yellow orthorhombic crystals Brick red powder

<1,000

(Continued)

Greenish-yellow solid

Red monoclinic crystals Brownish-red monoclinic crystals Slightly soluble Yellow orthorhombic crystals Soluble Yellow monoclinic crystals Very soluble Yellow orthorhombic crystals Solid

Soluble Insoluble

Insoluble

Very soluble

Soluble

Insoluble yellow powder Insoluble: <100 Yellowish-orange monoclinic crystals or orange-brown powder Insoluble Red powder

Aqueous Boiling Solubility at Point (°C) 20 °C (mg/L)

40

strontium

7789-01-7

Li2CrO4 · 2H2O

Lithium chromate dihydrate Mercury(I) chromate

lithium dihydrate mercury 13444-75-2 7784-01-2

14307-35-8

Li2CrO4

Lithium chromate

Hg2CrO4

18454-12-1

PbCrO4 · PbO

Lead(II) chromate oxide

10294-52-7 7758-97-6

(II)chromate (VI)oxide lithium

Iron(III) chromate Fe2(CrO4)3 Lead(II) chromate; chrome PbCrO4 yellow

iron lead

Formula

Names and Synonyms

Compound

CAS Number

Physicochemical Properties of Some Chromium Compounds (Continued)

TABLE 2.6

L1608_C02.fm Page 40 Tuesday, November 9, 2004 9:23 AM

Chromium(VI) Handbook

Chromium oxyfluoride

fluoride

Calcium dichromate trihydrate Iron(III) dichromate Copper(II) dichromate dihydrate Lithium dichromate

Lithium dichromate dihydrate

Mercury(II) dichromate; mercuric dichromate; mercuric bichromate

calcium trihydrate (III)iron (II)dichromate dihydrate lithium

lithium dihydrate

mercury

barium dihydrate calcium

Ammonium dichromate; dichromic acid Barium dichromate dihydrate Calcium bichromate

ammonium

Dichromates/Bichromates:

Chromium oxychloride

Names and Synonyms

chloride

Chromyl:

Compound

256.0678

14307-33-6 14307-33-6 10294-53-8 13675-47-3 13843-81-7 10022-48-7

7789-19-8

CaCr2O7 CaCr2O7 · 3H2O Fe2(Cr2O7)3 CuCr2O7 σ ·2H2O Li2Cr2O7 Li2Cr2O7 · 2H2O

HgCr2O7

416.58

265.901

759.654 315.565

310.112

389.346

10031-16-0

BaCr2O7· 2H2O

252.0644

154.90

7788-09-5

14977-61-8

Molar Mass (g/mol)

(NH4)2Cr2O7

CrF2O3

CrO2Cl2

Formula

CAS Number

Physicochemical Properties of Some Chromium Compounds (Continued)

TABLE 2.6

2.34

2.34 @ 30°C

2.286

2.37

2.136

2.15

1.9145

Density (water = 1)

dec: 130

130

dec

170

sub at 29.6

–96.5

Melting Point (°C)

116–117

Physical Description

Insoluble

Very soluble

Soluble

Soluble Very soluble

Very soluble

Reacts with water Soluble

310,000

(Continued)

Reddish-brown solid Reddish-brown triclinic crystals Yellowish-red crystalline powder Yellowish-red hydroscopic crystals Heavy red crystalline powder

Reddish orange crystals

Brownish-red crystals

Brownish-red needles

Bright orange crystals

reacts with H2O dark red, toxic, fuming liquid black crystals; polymerizes on exposure to light

Aqueous Boiling Solubility at Point (°C) 20 °C (mg/L)

L1608_C02.fm Page 41 Tuesday, November 9, 2004 9:23 AM

Chemistry, Geochemistry, and Geology of Chromium 41

Potassium dichromate; bichromate of potash Silver dichromate Disodium dichromate; +sodium dichromate Sodium chromate tetrahydrate Zinc bichromate

potassium

Source:

Note:

7778-50-9 7784-02-3 10588-01-9 10034-82-9 14018-95-2

K2Cr2O7 Ag2Cr2O7 Na2Cr2O7 Na2Cr2O7 · 4H2O ZnCr2O7

Formula

281.3778

234.035

431.724 261.96734

294.1678

Molar Mass (g/mol)

4.770 3.57

2.676

Density (water = 1)

dec

356.7

398

Melting Point (°C)

400

500

Dean (1992); ChemIDplus (2001); Chemfinder (2001).

Very soluble

Soluble Very soluble

49,000

Aqueous Boiling Solubility at Point (°C) 20 °C (mg/L)

g/mol = grams per mole; mg/L = milligrams per liter; °C = degrees Celsius; dec = decomposes; sub = sublimes.

sodium tetrahydrate zinc

silver sodium

Names and Synonyms

Compound

CAS Number

Physicochemical Properties of Some Chromium Compounds (Continued)

TABLE 2.6

Bright orangish-red triclinic crystals Reddish crystals Red hydroscopic crystals Yellow hydroscopic crystals

Physical Description

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42 Chromium(VI) Handbook

L1608_C02.fm Page 43 Tuesday, November 9, 2004 9:23 AM

43

Chemistry, Geochemistry, and Geology of Chromium TABLE 2.7 Total Chromium Concentration in Natural Substances Parameter

Reported Units

Average

Universe (Stars) Solar system

ppm 15 Relative to 5.13 × 105 H = 1 × 1012 Sun ppm 20 Carbonaceous meteorites mg/kg — Mantle mass percent Crust mg/kg 100 Igneous rocks: mg/kg 117 Ultramafic mg/kg 2,000 Mafic (basalts) mg/kg 220 Felsic (granites) mg/kg 20 Sedimentary rocks: Limestone Sandstone Shale Black shale Sediments: Deep sea clay Shallow water River suspended Stream bed (U.S.A.) Soil: World U.S.A. California Coal Petroleum Asphalt Plant (ash) Water: Ground Ocean North Sea Atlantic (surface) Atlantic (deep) Pacific (surface) Pacific (deep) River (total)b River (dissolved) Great Lakes (U.S.A/ Canada) Central Canada (surface water)

mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg

10 35 90, 120 90, 100 72 90 60 100 64a

Range

Enrichment Factor (EF)

— —

— —

— — 0.41–0.43 — — — 40–600 2–100

— — — — 1.17 20.0 2.20 0.20

References (21) (17) (21) (21) (3) (10) (22) (4) (14) (4) (14) (4) (14) (4) (14)

<1–120 34–90 30–590 26–1000 — — — — <1.0–700

0.10 0.35 0.9–1.20 0.9–1.0 — 0.90 0.60 1.00 0.64

(4) (14) (4) (14) (14) (4) (13) (14) (5) (5) (5) (5) (17)

— 1–2000 4–32 250 (max) 10.7 (max) 6.0 (max)

2.00 0.54 0.15 0.15

(1) (6) (14) (7) (11) (13) (2) (1)

mg/kg mg/kg mg/kg ppm ppm ppm ppm

200 54 15.4 15 0.09–3.15

µg/L µg/L

— 0.05–0.3

0.04–20 0.156–0.26

— —

µg/L ppb ppb ppb ppb µg/L µg/L µg/L

— 0.18 0.23 0.15 0.25 0.5b — 1.0

0.7 — — — — — 0.02–0.3 0.2–19

— — — — — — —

µg/L

—

0.2–44

—

—

9

(14) (8) (15) (19) (22) (16) (15) (17) (15) (17) (15) (17) (15) (17) (5) (16) (8) (8) (16) (Continued)

L1608_C02.fm Page 44 Tuesday, November 9, 2004 9:23 AM

44

Chromium(VI) Handbook

TABLE 2.7 Total Chromium Concentration in Natural Substances (Continued) Parameter Atlantic Region–Canada Antarctic Lakesc Precipitation Air: Arctic U.S.A. California (2000) Canada (5 remote areas) Netherlands Indoor (tobacco smoke) Human tissue: Blood Bone Liver Muscle Food: Milk and dairy products Meat Cereal Potatoes Fruits Sugars Intake from food and water Total intake from air, water, and food in U.K. Total intake from air, water, and food in Netherlands a b c

Reported Units

Average

Range

Enrichment Factor (EF)

µg/L µg/L µg/L

— — —

0.2–24 <0.6–30 0.2–1.0

— —

pg/m3 ng/m3 ng/m3 ng/m3 ng/m3 ng/m3 ng/m3 mg/kg

— <300 4.9 0.13

50–70 10–50 1–40 0.1–1.2 0.25–0.32 2–5 — —

— — — —

— ~1,000 30

— — —

References (8) (16) (16)

(16) (8) (16) (17) (20) (8) (16) (16)

mg/dL ppm ppm ppm µg/kg

— — — —

0.006–0.11 0.1–0.33 0.02–3.3 0.024–0.84 <10–1300

— — — — —

(17) (17) (17) (17) (16)

mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg µg/d

0.06 0.07 0.17 0.05 0.06 0.34 52–943

— — — — — — —

— — — — — — —

(8) (8) (8) (8) (8) (8) (16)

76–106

—

(16)

50–200

—

(16)

µg/d µg/d

100

Median concentration. Background concentration. Concentration increases with depth.

Note:

EF = average materials concentration/average crustal concentration.

Sources: 1. Hawkes and Webb (1962); 2. Krejci-Graf (1972); 3. Henderson (1982); 4. Thornton (1983); 5. Salomons and Förstner (1984); 6. Shacklette and Boerngen (1984); 7. Pettygrove and Asano (1985); 8. Canadian Environmental Health Directorate (1986); 9. Hem (1989); 10. Sposito (1989); 11. Finkelman (1993); 12. Manning and Gize (1993); 13. Leventhall (1993); 14. Allard (1995); 15. Donat and Bruland (1995); 16. WHO (1996); 17. Emsley (1999); 18. Rice (1999); 19. California Air Resources Board (2001a); 20. California Air Resources Board (2001b); 21. Winter: WebElements (2001); 22. Firestone (2002).

L1608_C02.fm Page 45 Tuesday, November 9, 2004 9:23 AM

Chemistry, Geochemistry, and Geology of Chromium

45

Efforts have been made to define what is meant by the terms “natural,” “normal,” and “background” and why such distinctions are important. Fergusson (1990) notes the following: An important reason for knowing the natural concentrations of the heavy elements is that they provide a true reference point for estimating the extent of pollution from the elements. This is of particular importance when assessing the toxicity of the elements. Natural concentrations allow contemporary concentrations to be seen in perspective, i.e., whether they are excessive or not.

Element concentrations currently found in the biosphere are often called normal, which may be misinterpreted for natural. Fergusson notes that the term “typical” is more applicable to contemporary trace element concentrations. As for natural element concentrations, distinctions must be made between: 1. Ancient concentrations as determined in prehistoric human remains such as bone, teeth, and hair recovered from skeletal and mummified remains. True prehuman background concentrations in natural materials may also be found in deep ice, sediment and peat cores, and in deep ocean waters as opposed to surface sea water which has been contaminated by human inputs (e.g., streams, rivers, and the atmosphere). 2. Remote places that include the Arctic, Antarctic, Greenland, midocean water, and in mountainous or alpine areas such as the Himalaya Mountains of Tibet. These areas have had little effect on humans, although with increasing atmospheric pollution even remote areas can be significantly affected. 3. Mineralized areas where element concentrations are higher than the surrounding region. Such element concentrations often surround known ore deposits or areas having undergone element enrichment from hydrothermal (hot spring) activity. The difference in mineralized areas from natural background is often called “threshold concentrations” (Hawkes and Webb, 1962). The determination of natural background or threshold concentrations of metals in surface water in mineralized areas has become a significant problem because many formerly mined areas have been designated as Superfund sites resulting from metals contamination produced by waste rock dumps and tailings at mines and smelter sites. Therefore, understanding background concentrations derived from mineralized areas becomes important in distinguishing natural threshold background concentrations from mined areas (Runnels et al., 1992). 4. Rural settings, that is, those areas away from urban environments. However, some rural areas such as farms may have element concentrations that have been influenced by the use of fertilizers and pesticides.

L1608_C02.fm Page 46 Tuesday, November 9, 2004 9:23 AM

46

Chromium(VI) Handbook 5. Urban areas, such as those within cities, which generally have element concentrations higher than natural background. This is particularly true of surface soils in parks, greenbelts, and alongside roads and highways that are affected by vehicles using and burning petroleum products and fuels (lubricating oil, gasoline, and diesel). 6. Industrial areas and zones where element concentrations may be considerably above those found in the other settings but still below regulatory agency concentrations which might be considered toxic to humans.

For a detailed explanation of the above, the reader is referred to Fergusson (1990, Chapter 6, pp. 166–176). 2.2.1

Mantle

In the Earth’s mantle, Cr occurring as Cr2O3 may range in concentrations from 0.41% to 0.55% depending on the model used (Henderson, 1982). That Cr originated in the upper mantle has been fairly well established in the study of podiform chromites, which are believed to have almost exclusively originated in the upper mantle or in crust–mantle transition that occurs in suprasubduction zones (Li et al., 2002). 2.2.2

Chromium Minerals

The International Minerals Association (IMA) recognized, as of mid-2002, the existence of 82 Cr minerals occurring in the natural environment (Table 2.8a); most are rather rare with some minerals unique to one mineral locality or deposit. Several Cr minerals are unique to meteorites. The major Cr ore mineral is chromite, a magnesium–iron–chromium–aluminum oxide, [(Mg,Fe2+)(Al,Cr,Fe3+)2O4] in which the chromic oxide content varies from approximately 15% to 65% owing to isomorphous substitution of Cr for Fe or Al. Cr concentrations in chromite generally average 46.46% (Sposito, 1989; Darrie, 2001; Barthelmy, 2002). Of the 82 known Cr minerals, 23 (approximately 30%) are Cr(VI)-bearing minerals; these are in the Dana mineral classes of anhydrous chromates; compound chromates; compound phosphates; compound borates; compound iodates, hydroxides, and oxides; and multiple oxides. Many Cr minerals are quite colorful (Table 2.8b); for example, uvarovite (a Cr-bearing garnet) is bright green and crocoite (an anhydrous chromate) forms bright-reddish orange acicular crystals. Mineral collectors covet such Cr minerals. 2.2.3

Chromium Ore Deposits

Chromite ore is not currently commercially mined in the United States, Canada, or Mexico. In the Western Hemisphere it is mined only in Brazil and Cuba. U.S. mining ceased in 1961, when the United States Defense Production Act

15.90

Mg6Cr2(CO3)(OH)16⋅ 4(H2O) Ca6(Cr, Al)2(SO4)3 (OH)12 ⋅26 (H2O) Cr3+O(OH)

Cr3S4

CrN (Ti, Cr, Fe)[O2x(OH)x]

Pb5(VO4)2(CrO4)2 (H2O) NaCrS2

Barbertonite

Bentorite

Bracewellite

Brezinaite

Calsbergite

Carmichaelite

Cassendanneite

Caswellsilverite 37.38

6.86

15.81

78.78

54.88

61.17

6.03

1.29

Cr Conc. (%)

Ba(Ti, V3+, Cr3+)8O16

Formula

Ankangite

Mineral Name

Sulfides—including selenides and tellurides

Compound phosphates

Multiple oxides with Nb, Ta, and Ti

Hydroxides and oxides containing hydroxyl Sulfides — including selenides and tellurides Native elements

Carbonates— hydroxyl or halogen Hydrated sulfates

Multiple oxides

Mineral Class

2.9.17.1

43.3.2.2

8.7.13.1

1.1.20.1

2.10.2.2

6.1.1.5

31.10.2.2

16b.6.1.2

7.9.4.2

No.

Dana Classification

Chromium Minerals: Chemical Formula, Classification, and Localities

TABLE 2.8A

Agpalilik fragment, Cape York meteorite, Greenland Garnet Ridge Ultramafic Diatreme, Colorado Plateau, AZ Beresov, Sverdlovsk (Ekaterinburg), Ural Mountains, Russia Norton County meteorite, KS

Tucson Meteorite, Pima County, AZ

Ankang County Shaanxi province, China Kaapsche Hoop, Barberton, Transvaal, Republic of South Africa Hatrurim Formation, Dead Sea, Israel Merume River, Kamakusa, Mararuni district, Guyana

Type Locality/Localities

(Continued)

Microscopic inclusions in mantle-derived pyrobe garnet. Associated with embreyite.

Environment/Remarks

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Chemistry, Geochemistry, and Geology of Chromium 47

11.04 46.46

NaMg3(Cr, Fe3+)6(BO)3 3Si6O18(OH)4 Fe3Cr1−x (x = 0.6) Fe2+Cr2O4

Cr (K, Ba)(Cr, Al)2[AlSi3 O10](OH, F)2

Chromdravite

Chromite (chrome iron ore; chromic iron)

Chromium Chromphyllite

Chromferide

KCrMg[Si4O10](OH)2

Chromceladonite

Native elements Micas—muscovite subgroup

Multiple oxides

Cycosilicates: tourmalines Native elements

Mica group

Anhydrous chromates Oxide minerals

Mineral Class

1.1.12.1 71.2.21.11

7.2.3.3

1.1.12.2

61.3e.1.11

71.2.2a.15

Found in metasomatizedhydrothermally altered U-V deposits. Crdominant analog 1 of aluminoceladonite. Formerly IMA 1999-024.

Environment/Remarks

(Continued)

Onega depression, Karelia, Russia Kumak region, Ural Mountains, Russia Stillwater, MT; Bastide de la Primary ore of chromium; Carrade, Gassin, Var, France occurs in granites and other igneous rocks; occurs in placer deposits. Sichuan (Szechuan), China Pereval marble quarry; Kaper Slyudyanka complex, pit Pokhabikha River Valley, Siberia, Russia: CrSouthern Lake Baikal region, enriched layers in quartzSiberia, Russia diopside-bearing rocks.

Jerusalem-Jericho Highway, Jordan Jialu mine, Luonan, Shaanxu province, China Srednyaya Padma U-V deposit, Southern Karelia, Russia

35.3.2.1 4.0.0.0

Type Locality/Localities

No.

Dana Classification

(Continued)

48

100.00 Trace

20.99

12.33

1.36

Bi16CrO27

Chrombismite

33.32

Cr Conc. (%)

CaCrO4

Formula

Chromatite

Mineral Name

Chromium Minerals: Chemical Formula, Classification, and Localities

TABLE 2.8A

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Chromium(VI) Handbook

(Co, Ni, Fe2+)(Cr, Al)2O4 PbCrO4

Fe2+Cr2S4

Hg2+Hg2+3Cr+6O5S2

Ca2(IO3)2(CrO4) (Fe2+, Mg)(Cr, Fe3+)2O4

Bi24Cr8O57(OH)6 (H2O)3

Hg2+3CrO4S2

Cocroite

Daubreelite

Deanesmithite

Dietzeite

Donathite

Dukeite

Edoylerite

Formula

Cochromite

Mineral Name

6.65

6.40

23.65

9.52

4.34

36.10

16.09

trace

Cr Conc. (%)

(Continued)

Anhydrous chromates

Hydroxides and oxides containing hydroxyl

Oxide minerals

Compound iodates

Sulfides — including selenides and tellurides Anhydrous chromates

Anhydrous chromates

Multiple oxides— spinel group

Mineral Class

35.4.4.1

6.4.12.1

4.0.0.0

23.1.1.1

35.4.3.1

2.10.1.11

35.3.1.1

7.2.3.5

No.

Dana Classification

Chromium Minerals: Chemical Formula, Classification, and Localities

TABLE 2.8A

Clear Creek mercury mine, New Idria district, San Benito County, CA

Lavra da Posse, San Jose de Brejauba, Conceicao do Mato Dentro County, Brazil

Clear Creek mercury mine, New Idria district, San Benito Country, CA Lautaro, Atacama Desert, Antofagasta, Chile Hestmandö Island, Norway

Bolsonde Mapimi meteorite, Mexico

Bon Accord nickel deposit, Barberton, Transvaal, Republic of South Africa Adelaide Mine, Dundas, Tasmania

Type Locality/Localities

(Continued)

Mixture of two spinels: one cubic and one tetragonal Found on a museum specimen of pucherite at Duke University, Durham, NC

Secondary Cr mineral in oxidized Pb veins infiltrated by Cr-bearing fluids

Environment/Remarks

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Chemistry, Geochemistry, and Geology of Chromium 49

Cr2O3 Cr3Fe1−x (x = 0.6) Cu(Cr1.5Sb0.5)S4

(Pb, Cu)3[(Cr, As)O4]2 (OH) Na6CaMg(IO3)6 (CrO4)2· 12(H2O)

Eskolaite Ferchromide

Florensovite

Fornacite

Cr3+O(OH)

Cr3+O(OH)

Ba(Cr, S)O4

Guyanaite

Hashemite 15.70

61.17

61.17

6.12

6.93

23.59

68.42 87.47

7.05

Cr Conc. (%)

Hydroxides and oxides containing hydroxyl Hydroxides and oxides containing hydroxyl Anhydrous chromates

Sulfides—including selenides and tellurides Compound phosphates Compound iodates

Simple oxides Native elements

Compound phosphates

Mineral Class

35.3.3.1

6.1.2.3

6.1.5.1

23.1.2.3

43.4.3.2

2.10.1.14

Lisdan-Siwaga Fault, Hashem region, Amman, Jordan

Merume River, Kamakusa, Mararuni district, Guyana

Merume River, Kamakusa, Mararuni district, Guyana

Oficina Chacabuco, Chile

Cumbria, England; Berezov, Ekaterinburg (Sverdlovsk), Ural Mountains., Russia Outokumpu, Karelia, Finland Kumak region, Ural Mountains, Russia Slyudyanka complex, Lake Baikal region, Zabaikalye (Transbaikal) Siberia, Russia El Khun mine, Anarak, Iran

43.4.3.1

4.3.1.3 1.1.12.3

Type Locality/Localities

No.

Dana Classification

(Continued)

(Continued)

Orthorhombic— dipyramidal

Arid climate mineral associated with Chilean nitrate caliche deposits. Coexists with halite, nitratine, and niter Trigonal—hexagonal scalenohedral

Environment/Remarks

50

Grimaldiite

Georgeericksenite

Pb5(CrO4)2(PO4)2 · H2O

Formula

Embreyite

Mineral Name

Chromium Minerals: Chemical Formula, Classification, and Localities

TABLE 2.8A

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Chromium(VI) Handbook

(Fe, Cr)1+x(Ti, Fe)2S4

Pb10Zn(CrO4)6 (SiO4)2F2 (Ce, REE,Ca)4 (Mg, Fe2+)(Mg, Fe3+)2 (Ti, Nb)2 Si4O22 Ca0.2(H2O)2CrS2

Heideite

Hemihedrite

IMA 1998-029

PbCr3+2(CO3)2(OH)4 H2O Mg6Cr2(OH)16C12 · 4H2O K3Na4Mg(CrO4)B24O39 (OH)⋅12(H2O)

IMA1999-034

IMA 2000-042

Iquiqueite

IMA 1999-018

Ba[Ti3Cr4Fe4Mg]O19

Formula

Hawthorinite

Mineral Name

3.55

15.64

20.10

32.46

6.26

10.21

3.55

19.99

Cr Conc. (%)

(Continued)

Sulfides — including selenides and tellurides Carbonates — hydroxyl or halogen Carbonates — hydroxyl or halogen Compound borates

Sorosilicates

Compound chromates

Sulfides — including selenides and tellurides

Multiple oxides

Mineral Class

27.1.8.1

16b.6.2.5

16b.2.1.4

32.46

56.2.8.7

36.1.1.2

2.10.2.3

7.4.1.3

No.

Dana Classification

Chromium Minerals: Chemical Formula, Classification, and Localities

TABLE 2.8A

Zapiga, Iquique, Tarapacá province, Chile

Florence Pb-Ag mine, Whickenburg, Maricopa County, AZ

Bultfontein, Kimberley, Republic of South Africa Bustee meteorite, Gorakhpur, Basti district, Uttar Pradesh, India

Type Locality/Localities

(Continued)

Cr analog of dundasite

Close to schollhornite.

Cr analog of chevkinite — (Ce) structure

Environment/Remarks

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Chemistry, Geochemistry, and Geology of Chromium 51

ZnCr2S4

Mg3Cr2(SiO4)3 NaCr3+Si2O6 NaMg2CrSi3O10

(Ba, Sr)(Ti, Cr, Fe, Mg)21O38 K2Cr2O7

Kalininite

Knorringite

Kosmochlor

Krinovite

Lindsleyite 35.35

17.69

14.14

22.89

22.95

34.94

67.41

10.22

Cr Conc. (%)

Multiple oxides with Nb,Ta, and Ti Anhydrous chromates

Nesosilicates — garnet group Inosilicates (clinopyroxenes) Inosilicates (aenigmatites)

Sulfides — including selenides and tellurides

Compound chromates Native elements

Mineral Class

35.2.1.1

8.5.1.8

69.2.1a.4

51.4.3a.4

65.1.3c.4

2.10.1.13

1.1.16.3

36.1.1.1

No.

Dana Classification

(Continued)

Toluca meteorite, Xiquipilco, Mexico Canyon Diablo meteorite, Meteor Crater, Coconino County AZ DeBeers mine, Kimberly, Republic of South Africa Oficina Maria Elena, Topcopilla and Oficina Rosario, Iquiquw Pampa, Tarapacá, Chile

Slyudyanka deposit, South Baikal, Zabaikalye (Transbaikal), Siberia, Russia Kao kimberlite pipe, Lesotho

Is River, Isovky District, middle Urals, Russia

Sebarz mine, Anarak, Iran

Type Locality/Localities

(Continued)

Subhedral grains in graphite nodules in octahedrites Found in kimberlites and peridotite nodules Atacama Desert, Chile

Cr analog of haxonite; found in Au-Pt placers along the Is River.

Environment/Remarks

52

Lopezite

Isovite

Pb10Cu(CrO4)6(SiO4)2 (F, OH)2 (Cr, Fe)23C6

Formula

Iranite

Mineral Name

Chromium Minerals: Chemical Formula, Classification, and Localities

TABLE 2.8A

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Chromium(VI) Handbook

Pb3Cu(CrO4)(SiO3) (OH)4 ⋅2H2O MgCr2O4 (Mn, Fe2+)(Cr, V)2O4

(K, Ca, Sr)(Ti, CrFe, Mg)21O38 CuCrO2 Pb2Cu[(As, P)O4][Mo, Cr)O4](OH) (Mg, Cr, Fe2+)2(Ti, Zr)5 O12

Macquartite

Magnesiochromite

Manganochromite

Mathiasite

Mcconnellite

Molybdofornacite

Mongshanite

6.81

(Ca, Ce)(Ti, Fe3+, Cr, Mg)21O38

Loveringite

5.24

1.32

35.24

18.54

43.80

54.08

5.30

Cr Conc. (%)

Formula

Mineral Name

(Continued)

Compound phosphates Multiple oxides

Multiple oxides

Multiple oxides with Nb, Ta, and Ti

Compound chromates Multiple oxides— spinel group Multiple oxides— spinel group

Multiple oxides with Nb, Ta, and Ti

Mineral Class

7.11.11.1

43.4.3.3

7.1.1.2

8.5.1.7

7.2.3.2

7.2.3.1

36.1.2.1

8.5.1.2

No.

Dana Classification

Chromium Minerals: Chemical Formula, Classification, and Localities

TABLE 2.8A

Yimenguan area (?), Shandong, China

Jimberlana intrusion, Norseman, Western Australia, Australia Mammoth mine, Tiger, Pinal County, AZ Schwarzenberg, Silesia, Germany Nairne deposit, Brukunga, Adelaide, South Australia, Australia Jagersfontein diamond mine, Orange Free State, Republic of South Africa Merume River, Kamakusa, Mararuni district, Guyana Tsumeb, Namibia

Type Locality/Localities

(Continued)

Considered a “doubtful” species. Physical properties are similar to ilmenite (ilm); found as inclusions in ilm. Not an IMA approved name.

Occurs in kimberlite

Synonym: chrompicotite

Encrusts dioptase

Synonym: chrompicotite

Environment/Remarks

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Chemistry, Geochemistry, and Geology of Chromium 53

(Mg, Ni)11(Fe3+, Cr)3 (SO4, CO3)3.5(OH)24 ⋅ 11H2O Na(V3+,Cr3+)Si2O6

(Ni, Co, Fe2+)(Cr, Fe3+, Al)2O4 (Cr3+, V3+)2Ti3O9

PbCr3+(CO3)2 (OH)4 ⋅H2O

Pb2(CrO4)O

(Fe2+, Mg,Ni)(Cr, Al)2 (SO4)4 ⋅22H2O BaTi6Cr2O16(H2O)

Mountkeithite

Nichromite

Olkhonskite

Petterite

Phoenicochroite

Redingtonite

Redledgeite

Natalyite

Formula

Mineral Name

12.96

8.49

Multiple oxides

Hydrated acid and sulfates

Anhydrous chromates

Carbonates — hydroxyl or halogen

Multiple oxides with Nb, Ta, and Ti

Multiple oxides — spinel group

Inosilicates (clinopyroxenes)

Compound sulfates

Mineral Class

7.9.5.2

29.7.3.6

35.1.2.1

16b.2.1

8.4.1.2

7.2.3.4

65.1.3c.5

32.4.3.1

No.

Dana Classification

(Continued)

Red Ledge mine south of Washington, Nevada County, CA

Mt. Keith Ni deposit, 400 km north-northwest of Kalgooolie, Australia Slyudyanka complex, Lake Baikal region, Zabaikalye (Transbaikal) Siberia, Russia Bon Accord nickel deposit, Transvaal, Republic of South Africa Western shore of Lake Baikal, 4.5 km south of Olkhon Island, Russia Red Lead mine, ZeehanDundas mining field, northwestern Tasmania, Australia Berezov, Ekaterinburg (Sverdlovsk), Ural Mountains, Russia Redington mine, Knoxville, Napa County, CA

Type Locality/Localities

(Continued)

Hg exhalative and sandstone-hosted U-V deposits

Found in oxidized zone Cr-analog of dundasite Formerly IMA 1999-034

Occurs in quartz-bearing schists

Occurs in bleached serpentinite

Environment/Remarks

54

9.52

20.10

19.94

30.65

5.74

3.34

Cr Conc. (%)

Chromium Minerals: Chemical Formula, Classification, and Localities

TABLE 2.8A

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Chromium(VI) Handbook

Ca2(Mg,Al)(Cr,Al)2 (SiO4)(Si2O7)(OH)2 · H2O Mg6Cr2(OH)16(CO3)· 4H2O K2CrO4 Cr3C2 Ca3Cr2(SiO4)3 Pb2Cu(CrO4)(PO4) (OH)

Shuiskite

Tarapacaite

Tongbaite

Uvarovite

Vauquelinite

Stichtite

36.87

Na0.3CrS2⋅ H2O

Schollhornite

7.37

20.78

86.66

26.78

15.90

Trace

2.01

Pb11CrO6

Santanaite

41.15

Cr Conc. (%)

(Cr,Al)6SiO11 ·5H2O (?)

Formula

Rilandite

Mineral Name

(Continued)

Nesosilicates — garnet group Compound phosphates

Carbonates — hydroxyl or halogen Anhydrous chromates Native elements

Anhydrous chromates Sulfides — including selenides and tellurides Sorosilicates

Multiple oxides

Mineral Class

43.4.3.1

51.4.3b.3

1.1.17.1

35.1.1.1

16b.6.2.2

58.2.2.9

2.9.17.2

35.4.1.1

7.11.14.1

No.

Dana Classification

Chromium Minerals: Chemical Formula, Classification, and Localities

TABLE 2.8A

Berezov, Ekaterinberg (Sverdlovsk), Ural Mountains, Russia

Adelaide mine, Stichtite Hill, Dundas, Tasmania, Australia Santa Ana mine, Caracoles, Sierra Gorda, Chile Liu Zhuang, Tonbai County, Henan, China Bissersk, Saransk, Mordovskaya, Russia

Riland carnotite claims 20 km ENE of Meeker, Coal Creek, CO Santa Ana mine, Caracoles, Sierra Gorda, Chile Enstatite achondrite meteorite, Norton County, KS Bisersk deposit, Ural Mountains, Russia

Type Locality/Localities

(Continued)

Metamorphosed chromite deposits

Atacama Desert, Chile

Alteration product of serpentine

Weathering product of caswellsilverite

Sandstone-hosted U-V deposits

Environment/Remarks

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Chemistry, Geochemistry, and Geology of Chromium 55

Ca0.3(Cr3+,Mg,Fe3+)2 (Si,Al)4O10(OH)2 · 4H2O (Mn3+,Fe2+)(V3+,Cr3+)2 O4 Hg+4Hg2+CrO6

Volkonskoite

(Cu,Zn,Fe,Al,Cr) ZnCr2O4

Zhanghengite

Zincochromite

Source:

44.56

4.28

29.19

3.17

9.47

11.73

13.12

Cr Conc. (%)

Multiple oxides — spinel group

Native elements

Oxyhalides and hydroxyhalides Multiple oxides

Multiple oxides — spinel group Anhydrous chromates

Clays — smectite group

Mineral Class

7.2.3.6

1.1.6.2

7.4.1.2

10.6.3.1

35.4.2.1

7.2.4.1

71.3.1a.4

No.

Dana Classification

(Continued)

Stäta, Doverstop, Bergslagen, Sweden Clear Creek mercury mine, New Idria district, San Benito County, CA Mammoth mine, Tiger, Pinal County AZ Yimengshan area, Shandong, China Xiaoyanzhuang, Boxian Co., Anhui, China Onega depression, Karelia, Russia

Mount Efimyatsk, Ural Mountains, Russia

Type Locality/Localities

Hurlbut (1963); Martin and Blackburn (1999 and 2001); Perroud (2001); Webmineral (2002).

Minerals in bold type are Cr(VI) minerals.

K(Cr,Ti,FeMg)12O19

Yimengite

Note:

Pb6CrCl6(O,OH)8

Yedlinite

Wattersite

Vuorelainenite

Formula

Mineral Name

Chromium Minerals: Chemical Formula, Classification, and Localities

TABLE 2.8A

Oxidized zone of exhalative Hg deposits

Synonyms: Volchonskoite and Wolchonskoite

Environment/Remarks

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Chemistry, Geochemistry, and Geology of Chromium 56

Chrombismite

Chromatite

Caswellsilverite

Cassendanneite

Carmichaelite

Calsbergite

Brezinaite

Bracewellite

Bentorite

Barbertonite

Ankangite

Mineral Name

Trigonalhexagonal scalenohedral Tetragonalditetragonal dipyramidal Tetragonal

Orthorhombicdipyramidal Isometrichexoctahedral Monoclinicprismatic Monoclinicprismatic

Tetragonaldipyramidal Hexagonaldihexagonal dipyramidal Hexagonaldihexagonal dipyramidal Orthorhombicdipyramidal

Crystal System

none

none

—

—

none

—

—

—

[1010]-perfect

[001]-perfect

none

Cleavage

Brown; orange; yellow

Lemon yellow

Yellowish-gray

Reddish-orange

Cinnamon to black

Darkreddish-brown; reddish-brown; black Brownish-gray to gray Gray

Violet; light violet

Violet; pink; pink violet

Black

Color

Chromium Minerals: Crystallography and Physical Properties

TABLE 2.8B

9.8

3.142

3.21

—

—

5.9

4.12

4.45–4.48 (av = 4.46)

2.025

2.1

4.44

Density (S.G.)

Translucent

Opaque

Translucent to opaque —

Opaque

Opaque

Translucent to opaque

Transparent

Transparent to translucent

Opaque

Diaphaneity

—

—

—

—

—

—

—

Habit

—

—

Microscopic crystals; platy: sheets —

Physical Properties

3.0–3.5

—

1.2

3.5

6.0

7.0

3.5–4.5

5.5−6.5

2.0

1.5−2.0

6.5

Mohs Hardness

Grayishblack White

Streak

Adamantine

—

Metallic

Resinous: greasy

Metallic

Metallic

Metallic: dull

Adamantine; metallic

Chemistry, Geochemistry, and Geology of Chromium (Continued)

Brownishyellow

—

—

Yellowishorange

—

—

—

Dark brown

Vitreous: glassy Violet

Vitreous: adamantine Pearly

Luster

L1608_C02.fm Page 57 Tuesday, November 9, 2004 9:23 AM

57

Donathite

Dietzeite

Deanesmithite

Isometrichexoctahedral Triclinicpinacoidal Monoclinicprismatic Tetragonalditetragonal dipyramidal None

[100]-indistinct

Good

[110]-distinct [001]-indistinct [100]-indistinct —

Indistinct

[001]-perfect

Black

Golden yellow

Orange-red

Black

Yellow; orangishred; reddish-orange

Black

Emerald green

White

Black or brownishblack

None

—

Grayish-white

Emerald-green to dark green Greenish-black or dark green

Color

None

Indistinct

—

Cleavage

5.0

3.617

—

3.81

5.9–6.1 (av = 6)

5.22

2.88

7.2

4.5–5.09 (av = 4.79)

—

3.4

—

Density (S.G.)

—

Transparent

Transparent

Opaque

Translucent

Opaque

Transparent

Opaque

Opaque

Opaque

Translucent to opaque

Transparent

Diaphaneity

—

—

—

—

Crystalline: acicular

—

Platy: sheets

—

6.5–7.0

3.5

4.5–5.0

4.5–5.0

2.5–3.0

7.0

—

Brown

—

Greenishgray

—

Streak

Brownishblack —

Yellowishorange

Metallic

(Continued)

Blackishbrown

Vitreous: glassy Light yellow

Adamantine

Metallic

Adamantine

Vitreous: glassy Whitishgreen Metallic Green

Metallic

4.0 3.0

Metallic

Metallic

4.0

—

5.5

Vitreous: resinous

Vitreous: dull

Luster

7.0–7.4

—

Mohs Hardness

—

—

Habit

Massive granular

Physical Properties

58

Daubreelite

Monoclinicspheroidal Chromdravite Trigonalditrigonal pyramidal Chromferide Isometrichexoctahedral Chromite Isometric(Chrome iron ore; hexoctahedral chromic iron) Chromium Isometrichexoctahedral Chromphyllite Monoclinicprismatic Cochromite Isometrichexoctahedral Cocroite Mmonoclinicprismatic

Chromceladonite

Mineral Name

Crystal System

Chromium Minerals: Crystallography and Physical Properties (Continued)

TABLE 2.8B

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Chromium(VI) Handbook

Hashemite

Guyanaite

Grimaldiite

Georgeericksenite

Fornacite

Florensovite

Ferchromide

Eskolaite

Embreyite

Edoylerite

Dukeite

Mineral Name

Orthorhombicdipyramidal

Trigonalditrigonal pyramidal Monoclinicprismatic Monoclinicprismatic Trigonalhexagonal scalenohedral Isometrichexocatahedral Isometrichexoctahedral Monoclinicprismatic Monoclinicprismatic Trigonalhexagonal scalenohedral Orthorhombicdipyramidal

Crystal System

Good

—

—

None

None

None

None

None

None

Good

—

Cleavage

Grayish-brown; golden brown; reddish-brown Brown; greenishbrown; yellow brown; light yellow brown; dark greenish-brown

Green; yellow; olive brown Pale yellow; bright lemon yellow Dark red or reddishbrown

Black

Grayish-white

Black

Greenish-yellow; orange Orange

Yellow; yellowishbrown

Color

4.59

4.53

4.11

3.035

6.27

—

—

5.18

6.45

—

—

Density (S.G.)

Chromium Minerals: Crystallography and Physical Properties (Continued)

TABLE 2.8B

Transparent to translucent

—

Transparent to translucent Opaque

Transparent

Opaque

Opaque

Transparent to opaque Transparent to translucent Opaque

Transparent

Diaphaneity

—

—

—

—

—

—

—

Habit

—

—

Prismatic crystals —

Physical Properties

3.5

—

3.5–4.5

3.0–4.0

2.0–3.0

5.0

6.5

8.0–8.5

3.5

—

—

Mohs Hardness

Black

Gray

—

Yellow

—

—

Streak

Adamantine

—

Metallic

Chemistry, Geochemistry, and Geology of Chromium (Continued)

Brownishwhite

Brown

Red

Greenishyellow Vitreous: glassy Pale yellow

Adamantine: metallic Adamantine

Metallic

Metallic

Earthy: dull

Resinous

—

Luster

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59

Isometrichexoctahedral Isometrichexoctahedral Isometrichexoctahedral Monoclinicprismatic

Isovite

Kosmochlor

Knorringite

Kalininite

—

None

—

—

[0001]-perfect; [0110]-indistinct —

—

— —

—

—

None

None

Cleavage

Bright green

Blue green; green

Black

Brownish-yellow; yellow; honey brown Iron gray

Yellow

Coal black Pale gray; pinkishviolet Magenta; purple

Orange; brown; black Black

Steel gray

Black

Color

—

3.756

—

—

5.8

2.05

—

— —

—

6.42

4.1

6.0–6.5

Density (S.G.)

Transparent to translucent Transparent to translucent

Opaque

Opaque

—

Transparent

Transparent

Opaque to translucent Opaque Translucent

—

Opaque

—

Diaphaneity

—

—

—

— —

—

—

—

—

Habit

—

—

—

Granular

Physical Properties

6.0–7.0

6.0–7.0

5.0

8.0

3.0

2.0

—

— —

—

3.0

3.5–4.5

—

Mohs Hardness

—

—

Streak

—

— —

—

—

—

(Continued)

Vitreous: glassy Light green

Vitreous: glassy

Adamantine

Metallic

Vitreous: glassy Yellowishwhite Vitreous: glassy Yellow

Vitreous: glassy

Submetallic Pearly

Resinous

Vitreous: glassy Saffron

Metallic

Metallic

Luster

60

Iranite

Iquiqueite

Trigonalhexagonal scalenohedral Trigonalditrigonal Triclinic-pedial

Hexagonaldihexagonal dipyramidal Monoclinicprismatic Triclinicpinacoidal Monoclinicprismatic Trigonal Orthorhombic

IMA 2000-042

IMA 1999-018 IMA 1999-034

IMA 1998-029

Hemihedrite

Heideite

Hawthorinite

Mineral Name

Crystal System

Chromium Minerals: Crystallography and Physical Properties (Continued)

TABLE 2.8B

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Chromium(VI) Handbook

Triclinicpinacoidal Trigonalrhombohedral Triclinicpinacoidal [010]-perfect; [100]-distinct; [001]-distinct None

None

None

Cleavage

Monoclinicprismatic [110]-distinct

Opaque Opaque —

— Opaque —

4.86 4.6 5.49

6.66 — 2.12

Grayish-black Black Dark red

Light green Black White or light pink

Transparent

Opaque

4.2

Black

3.55

—

5.49

Orange

Yellowish-green; light green

Opaque

Transparent

Subtranslucent to opaque Opaque

4.41

2.69

4.63

3.38

Diaphaneity Habit

5.0–6.0 2.0

— Flakes: flat thin crystals —

7.0

2.0–3.0

—

7.5

Vitreous: silky

Metallic Pearly

Adamantine

Metallic

Metallic

Metallic

Metallic

5.5

Metallic

—

—

(Continued)

Green

— White

Gray

—

Dark gray

Grayishblack Light orange

Vitreous: glassy Light yellow

Adamantine

5.5

Streak

Subadamantine Greenishwhite Metallic Gray

Luster

3.5

7.5

2.5

7.5

6.0–7.0

Mohs Hardness

—

—

—

—

Euhedral crystals —

—

Microscopic crystals Microscopic crystals —

Physical Properties

Black

Orange red; red

Dark green; emerald green Black

Color

Density (S.G.)

61

Natalyite

Trigonalrhombohedral [100]-good Monoclinicprismatic MagnesioIsometricNone chromite hexoctahedral Mangano-chromite Isometric— hexoctahedral Mathiasite TrigonalNone rhombohedral Mcconnellite Trigonal— hexagonal scalendohedral Molybdofornacite MonoclincNone prismatic Mongshanite Hexagonal — Mountkeithite Hexagonal [0001]-perfect

Loveringite (Chrompicotite) Macquartite

Lopezite

Lindsleyite

Krinovite

Mineral Name

Crystal System

Chromium Minerals: Crystallography and Physical Properties (Continued)

TABLE 2.8B

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Chromium(VI) Handbook

Tetragonaldipyramidal Unknown

Hexagonaltrapezohedral Trigonalditrigonal pyramidal Monoclinicprismatic Trigonalhexagonal scalenohedral Orthorhombicdipyramidal

Redledgeite

Santanaite

Tarapacaite

Stichtite

[001]-distinct; [010]-distinct

[0001]-perfect

[001]-perfect

[0001]-perfect

[0001]-perfect

—

Good

—

—

None —

Indistinct

Cleavage

Light yellow

Lilac; light violet pink

Dark brown

Gray

Straw yellow

Yellow green; black Black

White; light violet

Black Pale gray; pinkish violet Dark red

Black

Color

2.74

2.2

3.24

2.7

9.155

Opaque

3.72

1.761

7.01

4.48 —

5.24

Density (S.G.)

Transparent

Translucent to transparent

—

Opaque

—

Opaque

Opaque

Transparent

Translucent

Opaque Translucent

Opaque

Diaphaneity —

Habit

Encrustations nodular; micaceous —

—

Microscopic crystals

—

Platy: sheets

Fibrous crystals —

—

Platy: sheets —

Physical Properties

—

1.5–2.0

6.0

1.5–2.0

4.0

2.0–3.0

6.7

2.0

2.5

8.0 —

6.0–6.5

Mohs Hardness

—

Grayishwhite Grayishbrown —

Yellow orange White

Greenishgray Black —

Streak

—

(Continued)

—

Greenishbrown Vitreous: glassy Pale violet blue

—

Metallic

—

Resinous

Adamantine

Adamantine: resinous Silky

Metallic Pearly

Metallic

Luster

62

Shuiskite

Schollhornite

Rilandite

Redingtonite

Monoclinicprismatic Monoclinic

Isometrichexoctahedral Monoclinic Orthorhombic

Phoenicochroite

Olkhonskite Petterite

Nichromite

Mineral Name

Crystal System

Chromium Minerals: Crystallography and Physical Properties (Continued)

TABLE 2.8B

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Chromium(VI) Handbook

Note:

—

—

[0001]-perfect

[1120]-distinct

None

—

[?]-perfect

Indistinct

None

Cleavage

Brownish-black

None

Black

Brownish-gray; grayish-black Bronze; reddishbrown; black Red violet

Brown; brownishgreen; brownish black; green; black Yellow; olive green; green

Green

Color

—

—

4.34

5.85

8.91

4.64

2.0–2.5 (av = 2.25)

6.0

3.4–3.8

Density (S.G.)

Translucent to opaque

Golden yellow

Opaque to translucent Transparent to translucent Opaque

Opaque

Subopaque

Transparent to translucent Transparent to translucent

Diaphaneity Habit

—

—

—

Crystalline: encrustations —

—

Crystalline: fine lamellar Reniform: mammillarybotryoidal —

Physical Properties

5.8

3.5

4.0

2.5

4.5

6.5

1.5–2.0

2.5–3.0

6.5–7.0

Mohs Hardness

Streak

—

Blue green

Brownish

Submetallic

Metallic

Metallic

—

Bronze

Brown

Dark brick red Vitreous: glassy White

Submetallic

Metallic

Resinous

Adamantine: resinous

Vitreous: glassy White

Luster

Blackburn and Dennen (1997); Marlin (1999); Mandarino (2001); Martin and Blackburn (2001); Perroud (2001); Barthelmy (2002).

Isometrichexoctahedral Monoclinicprismatic Trigonalrhombohedral Hexagonaldihexagonal dipyramidal Isometrichexoctahedral Isometrichexoctahedral

monoclinicprismatic

Isometrichexoctahedral Monoclinicprismatic

Crystal System

av = average; S.G. = Specific gravity; IMA = International Mineral Names Association.

Sources:

Zincochromite

Zhanghengite

Yimengite

Yedlinite

Wattersite

Volkonskoite (Volchonskoite, Wolchonskoite) Vuorelaincnite

Vauquelinite

Tongbaite Uvarovite

Mineral Name

(Continued)

TABLE 2.8B

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Chemistry, Geochemistry, and Geology of Chromium 63

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64

Chromium(VI) Handbook

was phased out, which had subsidized many chromite mines. The United States currently has known chromite deposits in California, Maryland, Montana, North Carolina, Oregon, Pennsylvania, Texas, Washington, and Wyoming, but the ore’s low Cr content makes these deposits uneconomical for mining. There are essentially three grades of chromite ore: (1) chemicalgrade, which averages 28.6% Cr; (2) metallurgical grade, which also averages 28.6% Cr; and (3) refractory grade, which averages 23.9% Cr. In 2001, chromite ore and Cr ferroalloys and metal were imported from the Republic of South Africa (48%), Kazakhstan (16%), Russia (9%), Turkey (9%), Zimbabwe (9%), and other nations (9%). Current world resources exceed 11 billion tons of shipping-grade chromite (USEPA, 1984; Papp, 2002). In 2001, 22% of Cr metal was recycled mostly in the form of stainless steel scrap. In 2002, 63% of Cr ores were imported, primarily from South Africa, Kazakhstan, Zimbabwe, Turkey, and Russia (McCartan et al., 2003). Primary chromite deposits only exist in certain types of ultramafic or closely related anorthositic rocks, of which there are two main types: (1) the statiform or layered intrusion and (2) the pod shaped (podiform) type (Thayer, 1973). The main ore mineral is chromite [(Mg, Fe2+) (Cr, Al, Fe3+)2O4], which has a variable composition. The Cr2O3 content of most chromite ore ranges from about 15% to 64%; however, in mixtures of chromite and other silicate minerals, Cr2O3 contents range from 7% to 55% (Thayer, 1973; Lipin and Page, 1982). Thicknesses of ore grade zones vary from 0.5 m to 10 m. These deposits are described in the following sections. 2.2.3.1 Stratiform Mafic–Ultramafic Chromite Deposits These deposits are also known as Cr-platinum (Pt) mafic–ultramafic complexes. They occur as igneous plutons intruded into tectonically stable portions of the crust or craton during the Achaean period (Precambrian) more than 1.9 billion years ago. The elongated character of many of these complexes suggests possible intrusion during crustal rifting. As the magma cooled, it crystallized with different minerals crystallizing sequentially at different rates. Minerals thus preferentially settled out by the process known as magmatic segregation (Bates and Jackson, 1987), producing a layered igneous complex. Such layered complexes generally cover thousands of km2. Layering has resulted in more felsic (less dense) rock types in the upper portion of the complex and ultramafic (more dense) rocks near the bottom. However, the complexes’ overall composition is that of a gabbro. Secondary alteration in the form of serpentinization may occur in olivine-rich wall rocks (Hughes, 1982; Hatch et al., 1972; Lipin and Page, 1982). The stratiform mafic–ultramafic association includes world-class chromite deposits, which also produce significant amounts of Pt group metals (PGMs); two examples are: 1. The Precambrian Stillwater Complex in Montana, which was originally intruded as a sill. This basic layered intrusion composed of approximately 15 repetitious layers of hartzburgites, chromatite,

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Chemistry, Geochemistry, and Geology of Chromium

65

olivine chromatite, and bronzitite is exposed only over a 48.28 km length because it is bounded by faults at either end. The complexes’ thickness has been measured from 4,876.8 m to 5,486.4 m. Thirteen chromatite zones have been recognized but only one zone has been mined. PGMs and disseminated nickel–copper sulfide minerals also occur within the chromite ore zones (Ridge, 1972; Lipin and Page, 1982; Page 1992a). 2. The Bushveld Igneous Complex of the Republic of South Africa which covers an area that averages 280 km long by 160 km wide (with the greatest width approximately 400 km) and a thickness of 9 km centered on the town of Rustenburg in the Transvaal State. The Bushveld complex contains cumulus ferrogabbro to diorite, which has vanadium–titanium magnetite layers. Chromite layers occur in cumulate hartzburgite, dunite, and pyroxinite. The ores contain varying amounts of the minerals chromite, ilmenite, magnetite, pyrrhotite, pentlandite, chalcopyrite, and PGMs. Chromite ore thicknesses increase in basal depressions within the layers (Page, 1992b). Ore reserves may be several billion metric tons. 2.2.3.2 Podiform- or Alpine-Type Chromite Deposits Podiform-type deposits occur as podlike masses in the ultramafic portions of ophiolite complexes. Local rock types include highly deformed dunite and hartzburgite, which may be locally serpentinized. The deposits generally are highly deformed, having formed throughout the Phanerozoic in the lower part of the oceanic lithosphere along spreading plate boundaries. They can be divided into minor podiform chromites, most of which are found in California and Oregon, and major podiform chromite, occurring mostly in Iran, Turkey, and Cuba (Singer and Page, 1992; Singer et al., 1992; Ash, 1996). Ore mineralogy generally consists of chromite with possible ferrichromite, magnetites, and PGMs (ruthenium, osmium, and iridium) (Albers, 1992). Minor podiform deposits range from about 0.16 metric tons to 10,000 metric tons with a median of about 100 metric tons. Ore grades range from 10% to 56% Cr2O3 with a median grade of 44% Cr2O3. Major podiform deposits range from about 500 metric tons to 2.0 million metric tons with a median of about 2,000 metric tons. Ore grades range from 22% to 56% Cr2O3 with a median grade of 46% Cr2O3 (Singer and Page, 1992; Singer et al., 1992). 2.2.4

Crude Oil, Tars and Pitch, Asphalts, and Coal

Crude oils (Table 2.9) contain many different, mostly metallic, elements; cobalt (Co), chromium (Cr), copper (Cu), molybdenum (Mo), nickel (Ni), lead (Pb), vanadium (V), and zinc (Zn) are commonly found. Ni and V are generally enriched with respect to most other elements. Crude oils are poorly enriched with six valence group metals: Cr, Mo, W, and uranium (U). The ratio of V/Cr is generally equal to or greater than 10 in most crude oils (Krejci-Graf, 1972).

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Chromium(VI) Handbook

TABLE 2.9 Chromium Concentrations in Some Crude Oils, Tars and Pitch, Asphalts, and Coal Organic Material

Location Western Canada Basin Saudi Arabia

Crude oil

Tars and pitch

Central European Mollase Basin, Germany Italy Gösting II, Austria N.E. Caucasus, Russia (13 samples) Urals, Russia (27 samples) Messel, Germany Kohtla, Estonia Kohtla, Estonia Matitza, Romania Selenia, Albania United States (7,847 samples)

Asphalts

Coal

Cr Concentration (ppm) Average Maximum Average Maximum Average Maximum

0.05 1.68 0.65 1.18 0.11 0.45

Average Maximum Range

3.15 10.7 30–70

Average

100

Average

100

Average

80

Range Range Range

70–350 35–70 70–350

Range Average Maximum

35–70 15 250

Reference

Manning and Gize (1993)

Krejei-Graf (1972)

Finkelman (1993)

Coal contains more than 50% carbonaceous material with the remainder occurring as clay minerals, discrete mineral grains, and organically bound associated elements. Seventy-nine such elements have been detected in coal. Cr may be associated with the clays; the average Cr concentration for U.S. coals is 15 mg/kg (Finkelman, 1993). Airborne fly ash and bottom ash from coal-fired power plants have a typical Cr concentration of 900 mg/kg and 152 mg/kg, respectively (EPRI, 1983).

2.2.5

Rock

Elemental Cr concentrations in crustal rocks range from 20 mg/kg in felsic igneous rocks such as granites (Table 2.10) to more than 2,000 mg/kg in ultramafic igneous rocks (and their metamorphosed equivalents). The crustal average (CA) is reported at approximately 100 mg/kg. The CA is the basis for

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67

Chemistry, Geochemistry, and Geology of Chromium TABLE 2.10 Total Cr Concentrations in 1.0 km

Rock Type

Average Density (g/cm3)

3

Metric tons/km3 (mg/km3)

of the Crust for Different Rock Types Average Cr Concentration (mg/kg = g/Mg)

g-Cr/km3

Metric TonsCr/km3

Igneous: Granite Granodiorite Quartz diorite Diorite Gabbro Peridotite Dunite Pyroxenite

2.667 2.716 2.806 2.700 2.976 3.324 3.277 3.231

2.667 2.716 2.806 2.700 2.976 3.324 3.277 3.231

109 109 109 109 109 109 109 109

20 20 20 20 2,000 2,000 2,000 2,000

5.33 × 1010 5.43 × 1010 5.61 × 1010 5.40 × 1010 5.952 × 1012 6.648 × 1012 6.554 × 1012 6.462 × 1012

5.33 × 104 5.43 × 104 5.61 × 104 5.40 ×104 5.952 × 106 6.648 × 106 6.554 × 106 6.462 × 106

Volcanic: Basalt

2.965

2.965 × 109

220

6.523 × 1011

6.523 × 105

Sedimentary: Limestone

2.400

2.400 × 109 2.300 × 109 2.600 × 109

10

2.40 × 1010

2.40 × 104

Shale Sandstone

2.300 2.600

35 100

8.05 × 1010 2.6 × 1011

8.05 × 104 2.6 × 105

Notes: Source:

× × × × × × × ×

1 km3 = 1015 cm3; 1 Mg = 106 g Daly et al. (1966).

defining the Cr enrichment factor (EF) in rocks and soils, which ranges from 2 for felsic rock types, primarily granites, to 20 for ultramafic rocks. Cr(III) is also a trace element constituent of igneous rocks, probably occurring as separate phase minerals such as chromite, chromium-bearing magnetite, and/or ilmentite. It ranges from 100 mg/kg in amphiboles, pyroxenes (where it is actually dispersed in augite), biotite, magnetite, and olivine to 1.0 mg/kg in plagioclase and potassium feldspars (Hughes, 1982; Bricker and Jones, 1995). Therefore, the largest source of Cr in minerals in the crustal rocks is in the rock-forming minerals (Table 2.11). Black shales (also known as metalliferous shales) form in anoxic (anaerobic) environments in fresh, brackish, marine, or hypersaline water. Black shales are enriched in arsenic (As), Cu, Cr, Mo, Ni, and U in concentrations ranging from n × 101 mg/kg to n × 102 mg/kg (where n = 1 to > 9). Metals such as V and Zn are further enriched to concentrations ranging to n × 103 mg/kg. These metals generally are not visible with the naked eye or ordinary light microscopy because they do not occur as discrete mineral phases; rather, they are microscopically dispersed in organic matter, clay, or sulfides. Cr concentrations in black shale (Table 2.12) range from about 20 mg/kg to 3,000 mg/kg generally

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68

Chromium(VI) Handbook TABLE 2.11 Cr Concentration in Rock-Forming Minerals in a Typical Granite

Mineral Quartz Feldspar Biotite Magnetite Total

Average Mineral Fraction (%)

Cr Concentration in Mineral (mg/kg)

35.0 60.0 4.0 1.0 100.0

Trace (approx. ~0.1) 10 100 100

Total Cr Concentration in Rock mg/kg 0.035 6.0 4.0 1.0 11.035

% 0.32 54.37 36.35 9.06 100.10

TABLE 2.12 Chromium Concentrations for Various Shales Shale Type

Cr Concentration (ppm)

Average shale Average black shale Atlantic (Cretaceous) Green River Formation, WY (Eocene) Black Sea (layer C) Appalachian (Devonian) Condar, Australia Alum (Cambrian) Mecca Quarry, PA New Albany (Devonian) Falling Run /Henryville Associated phosphates

90 100–111 200 40 150 60 55 94 400 70 100 20

Source:

Leventhal (1993).

averaging 100 mg/kg to 111 mg/kg (Holland, 1979; Thornton, 1983; Leventhal, 1993; Quinby-Hunt et al., 1997). 2.2.6

Soil

Cr(III) coprecipitates with secondary soil clay minerals such as illites and smectites (Sposito, 1983). For residual soils, Cr concentrations generally reflect underlying bedrock concentrations; however, under tropical weathering conditions, Cr in soil may be considerably enriched over bedrock, particularly in the B horizon (Hawkes and Webb, 1962; Mattigod and Page, 1983 and Table 2.7). Worldwide Cr concentrations in soil average about 200 mg/kg. Scottish surficial soils range from 5.0 mg/kg to 3,000 mg/kg. In Canada, background Cr concentrations (from 173 soil samples) range from 10 mg/kg to 100 mg/ kg with an average of 43 mg/kg (CCME, 1996). U.S. soils range from 1.0 mg/ kg to 2,000 mg/kg, averaging 54 mg/kg (Shacklette and Boerngen, 1984). Nine samples of California residual soils had Cr concentrations ranging from 4.0 mg/kg to 32 mg/kg, averaging 15.4 mg/kg (Pettygrove and Asano, 1985).

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Chemistry, Geochemistry, and Geology of Chromium 2.2.7

69

Precipitation (Rain Water) and Surface Water

The average chromium concentration in rain water ranges from 0.2 µg/L to 1.0 µg/L (Keiber and Heiz, 1992). Surface fresh water has total chromium ranging from approximately 0.5 µg/L to 2.0 µg/L with dissolved chromium ranging from approximately 0.02 µg/L to 0.3 µg/L. Chromium in remote areas, such as Antarctic lakes, ranges from less than 0.6 µg/L to 30 µg/L with concentrations increasing with depth. Canadian surface waters range from 0.2 µg/L to 44 µg/L. Surface water concentrations in industrialized regions range from 1.0 µg/L to 10 µg/L. U.S. surface water concentrations range to 84 µg/L (WHO, 1996). Cr(VI) may be the dominant dissolved form in surface waters, particularly in oxygenated environments (CCME, 1996). 2.2.8

Groundwater

Background chromium groundwater concentrations generally follow the media that it occurs in. Most chromium concentrations are low, averaging less than 1.0 µg/L (WHO, 1996). Typical ranges are from 0.02 µg/L to 6.0 µg/L with a median concentration of 0.2 µg/L (Allard, 1995). 2.2.9

Sea Water

Chromium in ocean or seawater averages about 0.3 µg/L with Cr probably occurring as Cr(OH)4−and CrO42−. These species have an average residence time of 6,000 years (Henderson, 1982; Firestone, 2002). However, concentration variations occur in different oceans and seas. In the North Sea, a Cr concentration of 0.17 µg/L was detected (WHO, 1996). Chromium concentrations also vary with depth: in the North Pacific, Cr concentrations range from 0.156 µg/L at the surface to 0.26 µg/L in deeper waters. In the North Atlantic, Cr ranges from 0.182 µg/L at the surface to 0.234 µg/L in deeper water (Donat and Bruland, 1995).

2.2.10

Air

In remote areas, Cr ambient air concentrations (Table 2.7) are relatively low: in Arctic air, concentrations range from 0.005 to 0.07 ng/m3. In the Canadian Arctic, air samples collected in the early 1980s had chromium concentrations at 0.26 ng/m3 (CCME, 1996). Most nonindustrialized areas have Cr air concentrations below 10 ng/m3. In the United States, average Cr concentrations are generally less than 300 ng/m3 with median concentrations less than 20 ng/m3 (WHO, 1996). In California, the California Air Resources Board (CARB) routinely measures atmospheric Cr [including Cr(VI)]. In 1986, CARB estimated that the ambient Cr population-weighted annual concentration ranged from 8.9 ng/m3 to 17.8 ng/m3. They also estimated that Cr(VI) comprised 3% to 8% of the reported

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Chromium(VI) Handbook TABLE 2.13 Chromium Natural Atmospheric World Emissions Kilometric Tons per Year Median Percent Range

Source Wind-borne soil particles Sea salt spray Volcanoes Wild forest fires Biogenic: total Continental particulates Continental volatiles Marine Total Source:

27 0.07 15 0.09 1.11 1.0 0.05 0.06 43.27

62.40 0.16 34.67 0.21 2.57 2.31 0.12 0.14 100.01

3.6– 50 0.03–1.4 0.81– 29 0–0.18 0.1–2.22 0.1–2.0 0–0.10 0–0.12 4.5–83

Papp (1994).

ambient Cr in air; this occurred in the form of respirable particles with a median diameter of approximately 1.5 µm to 1.9 µm. Ambient Cr concentrations derived from soil particles are believed to be primarily composed of Cr(III) compounds. In the Regensburg area in the Federal Republic of Germany, Nusko and Heumann (1997) found that the surface layers of forest soils had a Cr(III)/Cr(VI) ratio of 1.47 as opposed to Cr(III)/ Cr(VI) in aerosol particles that ranged from 0.27 to 0.35. This suggested that Cr(III) predominates in organic-rich soil and that oxidation of Cr(III) to Cr(VI) occurs in the atmosphere. Cr(III) concentrations in aerosol particles (measured in three seasons from August 1994 to September 1995) ranged from 0.05 ng/m3 to 36 ng/m3, and Cr(VI) concentrations in aerosol particles (for samples analyzed for the same period) ranged from 0.16 ng/m3 to 1.22 ng/m3. Worldwide, most Cr atmospheric source emissions are from wind-borne soil particles (62.4%) and volcanoes (34.67%) with the remaining emissions from sea salt spray, forest fires, and biogenic sources (Papp, 1994 and Table 2.13). Atmospheric persistence or residence time is estimated at an experimental half-life (t1/2) of 13 h with total residence time estimated at less than 14 d. Cr is removed from the atmosphere by dry and wet (rain out) deposition with most Cr deposition occurring through wet deposition although Cr particles less than 5.0 µm diameter may remain airborne for extended periods, allowing extended transport over large distances by wind (CCME, 1996; CARB, 2002).

2.2.11

Biogeochemical Cycling

The determination of the natural biogeochemical cycling of Cr becomes somewhat difficult because of the large input of anthropogenic chromium, which has considerably perturbed the natural cycle. This is also typical in the natural biogeochemical cycling of other metals such as Al, Fe, Cu, Zn, and Pb in which atmospheric emissions from mining, smelting, and the burning of fossil fuels

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Chemistry, Geochemistry, and Geology of Chromium

have substantially increased atmospheric, surface water, sediment, soil, plant and animal tissue concentrations (Schlesinger, 1991). Dobrovolsky (1994) noted that most of the Cr total metal mass turnover (calculated in millions of metric tons per year) occurs in stream loss to the oceans of suspended sediment input from streams and rivers. The amount of suspended load transported by this process is 2.460 million metric tons per year (Table 2.14b). This probably is correct in that most of the Cr metal mass, some 278,000 million metric tons, is concentrated in granites in the continental crust and another 132,000 million metric tons is concentrated in sediments either overlying the granite crust or laying on the ocean floor. Recycling of this material is by subduction and reintroduction by magmatic activity (plutonic and volcanic) back into the crust. This occurs only over a wide geologic time scale. TABLE 2.14A Chromium Concentrations in Continental Vegetation Annual Growth Parameter

Cr Concentration (mg/kg)

Ash Dry Phytomass Live Phytomass Source:

35 1.8 0.7

Dobrovolsky (1994).

TABLE 2.14B Land Surface Chromium Fluxes Metal Mass Turnover (Metric Tons/year)

Parameter World biological cycle on land Stream loss: In solution In suspension Continental dust loss Transport from ocean to land Oceanic photosynthetic organisms biological cycling Source:

3.09 × 105 4.1 × 104 2.460 × 106 1.9 × 105 Minor 1.6 × 105

Dobrovolsky (1994).

TABLE 2.14C Chromium Mass Distribution in the Biosphere Parameter Land vegetation Oceans (dissolved) Sedimentary Granites in continental crust Source:

Dobrovolsky (1994).

Metals Mass (Metric Tons) 4.5 × 106 274 × 108 1.32 × 1011 2.78 × 1011

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2.3 2.3.1

Chromium(VI) Handbook

Chromium Geochemistry Cr(III) Geochemistry

In its Cr(III) form, the Cr3+ has an ionic radius of 0.064 nm and it readily substitutes in crystal lattices for Fe3+, which has an ionic radius of 0.060 nm and Al3+, with an ionic radius of 0.050 nm (Smith, 1972). Iron oxides and clays in soil and saturated zone alluvium therefore readily sorb Cr(III). Under standard conditions (at 25°C and 0.987 atm), in the Cr-O-H system (Figure 2.1), the Cr(III) stability zone occurs over a wide Eh and pH field under both reducing to oxidizing and acid to alkaline conditions. Cr(III) generally forms insoluble Cr(III) oxide (Cr2O3), from approximately pH 5.0 to 13.5 and from an approximate Eh ranging from +0.8 V to −0.75 V (volts). At slightly less than pH 5.0, Cr2O3 dissolves to form soluble Cr hydroxide (CrOH2+). At a pH of approximately greater than 13.5 and an Eh ranging from +0.05 V to −0.8 V, soluble Cr(III) anion (CrO2−) forms (Brookins, 1987). In aqueous environments under low Eh conditions, the main Cr(III) species are the Cr(III) cations (Cr3+) and CrOH2+ (Richard and Bourg, 1991). Under standard conditions, in the Cr−H2O−O system, the Cr(III) stability zone also occurs over a wide Eh and pH field under both reducing to oxidizing and acid to alkaline conditions. Cr(III) generally forms soluble Cr3+ from about pH 0 to about pH 8 and at an Eh from approximately −0.4 V to −1.2 V at the upper stability line. At a pH greater than 4 to about pH 7.5, Cr3+ dissolves to form soluble Cr(III) hydroxide cations: CrOH2+ and Cr(OH)2+. At a pH of approximately 8.0, insoluble and amorphous Cr(OH)3 forms, although small quantities of Cr(III) may be solubilized within this stability zone. At extreme pH and reducing conditions (above pH 12.0 and below Eh 0.0), soluble Cr(III) hydroxide anions [Cr(OH)4−] form (Hem, 1977). In aqueous environments under low Eh conditions, the main Cr(III) species are the Cr(III) cations Cr3+ and Cr(OH)2+ (Richard and Bourg, 1991). In the Cr−H2O−O system (Figure 2.2), under standard conditions (predominant in groundwater), the governing reactions are: Cr3+ + H2O ↔ CrOH2+ + H+

(2.1)

CrOH2+ + H2O ↔Cr(OH)2+ + H+

(2.2)

Cr(OH)2+ + H2O ↔ Cr(OH)3 + H+

(2.3)

Cr(OH)3 + H2O ↔ Cr(OH)4− + H+

(2.4)

Note: H3O+ is more accurate entity than H+ in aqueous systems Therefore, soluble Cr cations and anions are produced from insoluble Cr(III) hydroxide. However, under most natural groundwater conditions, Cr(III) is relatively insoluble and rarely occurs above concentrations exceeding the drinking water maximum contaminant level (MCL) of 50 ppb (Calder, 1988).

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Chemistry, Geochemistry, and Geology of Chromium 1.2 SYSTEM

PO

=0

2

1.0

Cr–O–H 25 °C, 0.987 atm

.98

7a

tm

HCrO4–

0.8

0.6 CrOH2+

CrO42– 10 –6

10 –4

Eh (V)

0.4

0.2

Cr2O3

0.0

PH

–0.2

2

=0

CrO2–

.98

7a

tm

–0.4

–0.6

–0.8 0

2

4

6

8

10

12

14

pH FIGURE 2.1 Eh-pH diagram for the Cr−O−H system. Eh values in volts (V). (Diagram from Brookins, D.G., 1987, With permission.)

2.3.2

Cr(VI) Geochemistry

Under standard conditions, in the Cr−H2O−O system (Figure 2.2), the Cr(VI) stability zone or field occurs over a much narrower range than the Cr(III) stability field. Cr(VI) species primarily occur under oxidizing (Eh >0) and alkaline conditions (pH >6.0). In this field, Cr(VI) generally forms soluble chromate (CrO42−) anions from approximately pH 6.0 to 14.0 and at an Eh from approximately −0.1 V to +0.9 V. At slightly less than pH 5.0, Cr2O3 dissolves to form soluble CrOH2+ (Brookins, 1987).

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Chromium(VI) Handbook 1.2

1.0

Dichromate Cr2O72– 0.6 Cr3+

OXIDIZING

0.8

0.2

Chromate CrO42–

Cr(OH)2+

Cr(OH)2+

Eh (volts)

0.4

0

Cr(OH)3 (am) Insoluble Hydroxide Cr(OH)–4

REDUCING

–0.2

–0.4

5 mg/L Dissolved Cr 0.5 mg/L Dissolved Cr –0.6 WATER REDUCED

5 mg/L Dissolved Cr

–0.8 0

2

4

6

8

10

12

14

pH FIGURE 2.2 Eh-pH diagram for the chromium–oxygen–water system. Eh values in volts (V). (Diagram modified from Hem, 1989.)

In aqueous environments, under oxidizing conditions, Cr(VI) is extensively hydrolyzed; therefore, it is present as an anion, generally forming CrO42− and hydrogen chromate (HCrO4−) anions (Calder, 1988; Richard and Bourg, 1991). According to Calder (1988), in the Cr−O−H2O and under standard conditions, the reaction that occurs is: HCrO4− ↔CrO42− + H+

(2.5)

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75

Cr(VI) substitutes for S(VI) because their ionic radii are similar: Cr(VI) anions have ionic radii between 0.0325 nm and 0.052 nm and S(VI) anions have ionic radii between 0.029 nm to 0.034 nm (Robertson, 1976). This becomes important because sulfate (SO42−) anions can replace CrO42− and Cr2O72− anions. In soils and aqueous environments, Cr(III) adsorption by Mn oxides is the first step toward its oxidation to Cr(VI) by Mn oxides. These typically accumulate on the surface of Fe oxides and clay minerals (Bartlett and James, 1979). Mn(III) and Mn(IV) oxyhydroxides and Mn(IV) oxides (such as the mineral pyrolusite) oxidize Cr(III) to Cr(VI); oxidation rates tend to be higher with increasing pH (Eary and Rai, 1986; Hug et al., 1997). Fendorf and Zasoski (1992) noted the following overall reaction: 2Cr3+ + 3δ-MnO2 + 2H2O → HCrO4− + 3Mn2+ + 2H+

(2.6)

A similar equation for this reaction was determined from experiments by Palmer and Puls (1994). Soil organic matter quickly adsorbs and reduces Cr(VI) to Cr(III). It generally remains mobile only if its concentration exceeds the adsorbing and reducing capacity of the soil (Bartlett and Kimble, 1979). Organic compounds also reduce Cr(VI) to Cr(III). Richard and Bourg (1991) noted that simple amino, humic, and fulvic acids produce intermediate Cr(V) that changes to Cr(III) within a few days. Cr(VI) reduction can also occur from reaction with Fe(II). This generally involves a three-step process (Sedlak and Chan, 1997):

2.3.3

Fe2+ + Cr(VI) → Fe3+ + Cr(V)

(2.7)

Fe2+ + Cr(V) → Fe3+ + Cr(IV)

(2.8)

Fe2+ + Cr(IV)+ → Fe3+ + Cr(III)

(2.9)

Chromium Reaction Rates (Kinetics)

Chromium reaction rates or kinetics (how fast a reaction will occur), from Cr(III) to Cr(VI) by oxidation and back to Cr(III) by reduction, have been extensively studied in the laboratory (Lin, 2000). As we have seen, Cr(III) can oxidize to Cr(VI) generally under the catalytic influence of Mn(IV) oxides. Eary and Rai (1986) noted that aqueous Cr(III) oxidation was not caused by surface catalyzed reactions but by direct reactions of β -MnO2. Kinetic experiments by Saleh et al. (1989) in lake water, sediment, and soil indicated that reaction rates for the oxidation of Cr(III) to Cr(VI) are relatively slow with t1/2 ranging from 0.58 year to 37.2 year. Reaction rates for the reduction of Cr(VI) to Cr(III) tend to be very rapid with t1/2 ranging from instantaneous to 53 d under anaerobic or reducing conditions. For aerobic conditions, the t1/2 was measured from 15 min to 21.5 d.

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2.4 2.4.1

Chromium(VI) Handbook

Chromium Distribution in Primary Environments Possible Sources of Natural Cr(VI) in Rocks

In the California Coast Ranges, the Franciscan complex contains ultramafic rocks that host chromite ore deposits. Davis (1966) described these deposits as magmatic segregations of FeCr2O4 in peridotite and peridotite altered to serpentinite. Cr minerals in these rocks, however, remain largely unaltered, mostly occurring in the form of the mineral chromatite (FeCr2O3). Other Crbearing minerals include eskolaite (Cr2O3) and the Cr-bearing spinel minerals include rutile, ilmenite, and magnetite; these are also contained within other silicate minerals such as the hornblendes and pyroxenes. Many ultramafic rock types contain significant amounts of Cr. Matzat and Shiraki (1974) reported that dunite, peridotite, pyroxentite, and serpentinite carry Cr concentrations to a maximum of 2,400 mg/kg. Soils and sediments derived from these rocks also contain Cr. Scott (1995) noted from the analysis of 158 soil samples, collected from 25 locations in Sunnyvale and Mountain View (California), that the average Cr concentration was 51.28 mg/kg with a range from 30.5 mg/kg to 72.0 mg/kg. Serpentinized and altered ultramafic rocks have been described in the literature; these include the New Idria serpentinite body in San Benito County, which covers an approximate 124.3 km2 area along the ridge of the Diablo Range (Figure 2.3). About 18.1 km2 of the unit is located within the Arroyo Pasajero’s Los Gatos Creek drainage basin. The serpentinite body contains an asbestos deposit of highly sheared and fractured, soft, friable, and powdery serpentinite containing blocks and fragments of harder rocks. The altered matrix includes plates and flakes of chrysotile, antigortite, magnesite, brucite, and talc. Asbestos, (FeCr2O4) and mercury (Hg) ore have been mined from this portion of the upper Los Gatos Creek drainage area (Jones, 1988). However, much of the Cr contained in these minerals probably is Cr(III), although Cr(VI)-bearing minerals may occur due to hydrothermal alteration of the source rocks (see the following paragraph; the Chapter 3.1; Steinpress, 2001). The possible geochemical processes that transform Cr(III) to Cr(VI) include deuteric and hydrothermal alteration of the country rock containing Cr and Cr-bearing minerals. Hydrothermal alteration of ultramafic rocks, including serpentinite, could mobilize relatively insoluble Cr(III) minerals by altering them into different mineral species. Numerous exhalative mercury–gold (Hg–Au) deposits, with associated carbonate–silicate alteration (producing a quartz, opal, and a carbonate-rich rock), occur throughout the California Coast Ranges. Examples include the Sulphur Bank mine in Lake County, the New Almaden mine in Santa Clara County, and the New Idria mining district in San Benito County, California (Figure 2.4). Hg–Au deposits occur mostly in serpentinite associated with Franciscan complex and associated ultramafic rocks. These deposits were

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Chemistry, Geochemistry, and Geology of Chromium San Francisco

580

101

99

San Jose

5

P i c i f a c

Santa Cruz

Monterey Bay

101 99

Monterey O a n c e

LEGEND

New Idria 5

- ultramafic rock 101

Modified from: Churchil and Hill, 2000.

FIGURE 2.3 Ultramafic rock bodies in the central Coast Range of northwest-central California.

formed by hot spring systems, from alkaline sulfide solutions at relatively low temperature and shallow depths, remnants of which are still present. [In the central and southern Coast Ranges, four hot springs with water temperatures 16.7 °C to 48.9 °C are listed on the San Jose 1:250,000 scale map sheet. The Santa Cruz 1:250,000 scale map sheet lists 12 hot springs with water temperatures ranging from 23.9 °C to 62.2 °C (Jennings, 1985).] Widespread alteration of country rock is in the vicinity of these hot-spring systems, with advanced argillic alteration occurring in adjacent volcanic rocks at the McLaughlin Hg–Au deposit in Lake County. That hydrothermal alteration has transformed Cr oxide minerals is evidenced by the presence of redingtonite (a hydrous chromium sulfate) at the Manhattan mine in the Knoxville mining district of Lake County, California (Davis, 1966; Albers, 1981; Vredenburgh, 1982; Peters, 1991; King and Rytuba, 1999). The geochemical process of transforming Cr(III) to Cr(VI) in soil, sediments, and groundwater also would include oxidation by Mn (IV) oxide (MnO2), and Franciscan complex rocks in the California Coast Ranges host numerous Mn mineral deposits. These occur as thin elliptical chert bodies containing the Mn minerals psilomelane, pyrolusite, rhodochrosite, hausmannite, and braunite. Such mineral assemblages occur in 70% of Mn

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Chromium(VI) Handbook

- Rocks younger than Coast Range thrust

- Rocks of Great Valley sequence lying above Coast Range thrust

- Eugeosynclinal (Franciscan) rocks lying beneath Coast Range thrust

- Older, generally metamorphosed rocks and late Mesozoic granltic rocks

Sulphur Bank RA SIER

AT GRE

T

AS

CO

Sacramanto

NE

San Francisco

VA DA

LL

IC

VA

CIF

PA EY

New Almaden LEGEND

New Idria

- Mercury - gold deposit - Less productive mercury deposit

Modified from: Bailey et al., 1973.

N EA C O

- Coast Range thrust - Major strike slip fault or fault zone

ES G AN R

Contact (Dashed where inferred, dotted where concealed, hachures on overthrust side)

Santa Barbara

FIGURE 2.4 Location of Hg-Au.

deposits (Albers, 1981; Mosier and Page, 1988). In groundwater, Mn(IV) oxide occurs in the same Eh and pH ranges as the CrO42− and Cr2O72− anions (Figure 2.5). Insoluble MnO2 coating sediments in the saturated zone may oxidize Cr(III) to Cr(VI).

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Chemistry, Geochemistry, and Geology of Chromium

1.2 Mn–O–H 25°C, 0.987 atm

SYSTEM

1.0

PO

2

=0

.98

7a

tm

0.8

0.6

Eh (V)

0.4

MnO2 Mn 2+

Mn

0.2

O

0.0 Mn3O4 –0.2

PH

2

=0

.98

7a

–0.6

Mn(OH)3–

Mn(OH)2

tm

–0.4

–0.8 0

2

4

6

8

10

12

14

pH FIGURE 2.5 Eh-pH diagram for the system Mn–O–H. Eh values in volts (V). (Diagram from Brookins, 1987, with permission.)

2.4.2

Known Sources of Natural Cr(VI) in Rocks

As of 2002, there were at least 24 known Cr(VI) minerals (Barthelmy, 2002); these occur as: 1. Cr(VI)-bearing minerals that are formed in the oxidized zones of lead (Pb) deposits, generally as the mineral crocoite (PbCrO4). In the

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80

Chromium(VI) Handbook United States, crocoite occurs in the Vulture mining district of Arizona (Hurlbut, 1963). Hemihedrite [Pb10Zn(CrO4)6(SiO4)2F2] occurs at the Florence Pb-Ag mine near Whickenburg, in Maricopa County, Arizona; deanesmithite (Hg2+Hg32+CrO5S2) and edoylerite (Hg32+CrO4S2) occur at the Clear Creek mercury mine in the New Idria mining district, in the Diablo range of San Benito County, California (Perroud, 2001; Barthelmy, 2002). 2. Cr(VI) minerals in nitrate-rich evaporite deposits in arid or desert environments such as the Chilean nitrate deposits in the Atacama Desert. Chromate minerals are largely confined to iodine-bearing nitrate deposits where the annual precipitation is very low (approximately 50 mm per year). The ores consist of caliche-containing sodium nitrate (NaNO3), lautarite [Ca(IO3)2], other iodates, and dietzeite [Ca2(IO3)2(CrO4)] (Williams-Stroud, 1991; Barthelmy, 2002). The Peru-Chile Desert, which includes the Atacama Desert, forms one of a series of apparently long-lived, west coastal-type, subtropical deserts such as those found in Australia and the Namib Desert of Africa. These are also known as hyperarid deserts and they may have begun forming as much as 14 million years ago. The Peru-Chile Desert is between 10° and 30° south latitude and 70° and 80° west longitude. The Atacama Desert is centered at approximately 25° south latitude and 70° west longitude (Hartley and Chong, 2002). Similar climatic conditions may have occurred in the recent geologic past (Cenozoic) in the Mojave Desert of California and Arizona. 3. Sheared, altered, and serpentinized ultramafic rocks, such as the Franciscan complex, containing Cr(III) minerals. Steinpress (2001; Chapter 3.1, this volume) reported the presence of 0.06 mg/kg to 0.46 mg/kg Cr(VI) in serpentinite. However, no specific mineral identification was made and the actual Cr(VI) mineral assemblages are not known.

2.5 2.5.1

Chromium Distribution In Secondary Environments Known Natural Cr(VI) Occurrences in Surface Water and Groundwater

In surface water, Cr(III) generally is the predominant Cr entity; however, Cr(VI) has been reported in oxygenated fresh water lakes and estuaries. Kaczynski and Kleber (1993) noted natural Cr(VI) maximum concentrations of 0.026 µg/L in Masonboron Inlet, North Carolina. In the Paradise Valley, north of Phoenix, Arizona, groundwater collected from wells with the pH approaching 9.0 contained 100 µg/L to 200 µg/L Cr(VI) (Robertson, 1976; Hem, 1989). Robertson believed that hydrolysis of

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Chromium(VI) Handbook

feldspars and common mafic minerals, such as augite and biotite comprising the alluvium, caused alkaline groundwater conditions in the middle of the valley. This coupled with calcite produced highly alkaline conditions. In addition, there was an absence of Fe(II), organic matter, and reducing organisms, which allowed the groundwater to retain its oxidizing and alkaline character, transforming Cr(III) into Cr(VI). Godgul and Sahu (1995) noted that in the Sukinda chromite belt of Orissa, India, serpentinization and magnesium ion releases during deuteric alteration of ultramafic rocks (peridotites) and associated extensive oxidation (laterization) created alkaline (high pH) pore water. This resulted in the production of Cr(VI) detected in stream, well, and quarry water. Cr(VI) concentrations ranged from 58 µg/L to 64 µg/L in stream water, not detected (ND) to 17 µg/L in well water, and ND to 1,791 µg/L in quarry water. These waters had relatively high total Mn concentrations (7,230 ppb to 1,541,000 ppb) and relatively low total iron (ND to 12,950 µg/L) concentrations. In the Presidio in San Francisco, Cr(VI) was present in background-oxidized groundwater with high pH’s, up gradient from any known contamination, with concentrations ranging from 52 µg/L to 98 µg/L (Steinpress, 2001; Chapter 3.1, this volume). Possible natural background concentrations of Cr(VI) occur in groundwater near Davis, California with concentrations ranging from 1.0 µg/L to 180 µg/L. It is believed that the overall regional Cr(VI) distribution in groundwater is random and therefore a natural condition (Davis, 1995). In studies by the U.S. Geological Survey (USGS), Cr(VI) has been found in western Mojave Desert, California groundwater (Ball and Izbicki, 2002). The USGS evaluated Cr(VI) in water sources from public water supplies, domestic and observation wells in alluvial aquifers. Total Cr concentrations ranged from 0.8 µg/L (the detection limit) to 60 µg/L; almost all of the total Cr was Cr(VI). In 2001, routine sampling of water wells in the Soquel Creek Water District (SCWD) south of Santa Cruz, California determined that Cr(VI) occurred in groundwater within the Aromas Red Sands (Aromas) aquifer at concentrations ranging from 6 µg/L to 38 µg/L. While these concentrations were below the MCL for total chromium of 50 µg/L, concerns about public health impacts from Cr(VI) in drinking water had been raised during public meetings. Todd Engineers (2002) conducted a focused Cr(VI) groundwater study to determine whether the detected Cr(VI) was from anthropogenic (man-made) releases or from naturally occurring Cr in the Aromas Red Sands Formation. The study found abundant evidence confirming that naturally occurring Cr-bearing minerals found in the Aromas Red Sands Formation were the possible sources of the Cr(VI) detected in the Aromas aquifer. Environmental conditions in Aromas aquifer water favor Cr(VI) production from dissolved Cr(III) because the Aromas aquifer waters are well oxygenated, generally have alkaline pH (greater than 7.0), and sediments are predominantly quartz-rich and low in Fe(II) and aluminum oxides. No anthropogenic sources of Cr(VI) were identified in the inventory of possible contaminating activities in areas surrounding public water supply wells.

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2.6

Chromium(VI) Handbook

Forensic Geochemistry

Bates and Jackson (1987) define forensic geology as “The application of the Earth Sciences to the law,” and Stout et al. (1998) define environmental forensics as “… the systematic investigation of a contaminated site(s) or events(s) that has impacted the environment which focuses on defensibly allocating liability for the contamination.” Forensic geochemistry is the application of geochemical principles in the natural environment to the law. Therefore, forensic geochemical investigations require chemical and isotopic analysis of physical materials such as air, water, soil, and sediment. For metals, this usually involves the analysis of their stable isotopes and at times their radioactive isotopes. For example, Hurst et al. (1996) and Hurst (2002) have successfully used stable Pb isotopes to identify gasoline release sources and even provided an age for these releases. A complete explanation of environmental forensic and forensic geochemical techniques is beyond the scope of this section and the reader is referred to recent texts by Morrison (2000) and Murphy and Morrison (2002). 2.6.1

Soil

Very few forensic geochemical investigations involving Cr(VI) from contaminated sites are cited in recent literature. This is largely because such forensic investigations are rather new. Recent experimental work by Prokisch et al. (2000) in soil showed that anthropogenic Cr could be distinguished from geological chromium by analysis of yttrium (Y) and total Cr; the results are plotted on an Y – Cr diagram (Figure 2.6). From experimental data, they found that soil collected and analyzed from noncontaminated areas (geologic Cr) had very close Cr–Y linear correlation. However, for areas contaminated by anthropogenic Cr the Cr–Y values were scattered. 2.6.2

Groundwater

Ellis et al. (2001) reported the first measurements of Cr isotope fractionation of 53Cr and 52Cr during Cr(VI) reduction to Cr(III). Their study showed that dissolved Cr(VI) from groundwater at three contaminated sites that had delta (δ )‡ 53Cr values ranging from 1.1 per mil to 5.8 per mil (1.1‰ to 5.8‰). This ‡ By established convention isotopic ratios are defined as delta (δ) values. The δ value in per mil (‰) can be obtained by the equation: δ(isotope) =([R(sample) −R(standard)]/R(standard))−1 × 1,000, where: δ (isotope) = values in per thousand (‰) or per mil and R(sample) = the mass ratio of the first and second isotope such as 53Cr/52Cr, and R(standard) = the ratio of the isotopes used in international or other standards; a commonly used standard for 53Cr/52Cr is the National Institute of Standards (NIST) 979 Cr standard. A δ value with a positive (+) sign corresponds to an increase of the first isotope (eg., 53Cr) with respect to the standard. A minus (–) sign indicates a decrease in a sample with respect to the standard. Standards have been established by the International Atomic Energy Agency (IAEA) and the NIST (Coplan et al., 1996).

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Chemistry, Geochemistry, and Geology of Chromium

83

60

anthropogenic chromium Cr (ppm)

40

geogenic chromium

20

Prokisch and others (2000) 0 7

10

13

Y (ppm)

FIGURE 2.6 Plot of total Cr versus yttrium (Y) for soils containing Cr from anthropogenic and geologic (geogenic) sources. (Diagram modified from Prokisch et al., 2000, with permission.)

indicated that reduction of Cr(VI) had occurred because the δ 53Cr values from plating bath solutions showed little or no fractionation for plating operations ranging up to five years of use. In a similar Cr isotope study, completed in the western Mojave Desert of California, Ball et al. (2001) noted that stable Cr isotopes could be used to determine the reduction of Cr(VI) to Cr(III) in a lower aquifer; they found that 53Cr was enriched in groundwater relative to 52Cr. This suggested that the Cr(VI) was from a natural source because anthropogenic sources of Cr typically have δ 53Cr values very near zero.

2.6.3

Air

As described in Section 2.2.10, Nusko and Heumann (1997) found that the Cr(III)/Cr(VI) ratio in dust from soil erosion ranged from 0.27 to 0.35, whereas the same ratio in the atmosphere aerosol particles was much higher, ranging from 0.39 to 0.63, indicating oxidation of Cr(III) to Cr(VI) in the atmosphere. They also found that the soil surface layer at the forest’s edge which was high in organic material had a Cr(III)/Cr(VI) ratio of 1.47, indicating that Cr(VI) was preferentially reduced by the soil organic matter. Therefore, stable Cr isotopes may be used to determine the source(s) of Cr(VI) in atmosphere aerosol particles.

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Acknowledgments The author appreciates the editorial comments and suggestions made by David W. Abbott, R.G., C.H.G., senior geologist with Todd Engineers; Cynthia P. Avakian, senior project manager with Hydro-Environmental Technologies, Inc.; and Dr. Jacques Guertin, consulting environmental scientist. Alain E. Boutefeu, graphics coordinator/technician with Todd Engineers, created and placed section figures into the required format.

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3 Naturally Occurring Chromium(VI) in Groundwater

CONTENTS 3.1 Naturally Occurring Chromium(VI) in Groundwater, including the Presidio of San Francisco Case Study ...............................................94 Martin G. Steinpress 3.1.1 Introduction......................................................................................94 3.1.2 Examples of Naturally Occurring Chromium(VI) in Groundwater ...............................................................................95 3.1.2.1 Arid Alluvial Basins in the Southwest United States......................................................................96 3.1.2.2 Natural Brines ...................................................................96 3.1.2.3 Chromite Ore Bodies........................................................97 3.1.2.4 Serpentinite Ultramatic Terrains ....................................97 3.1.3 The Erin Brockovich Effect: Hollywood and the Scientific Process...............................................................98 3.1.4 Presidio in San Francisco Case Study........................................100 3.1.4.1 Executive Summary........................................................100 3.1.4.2 Introduction .....................................................................103 3.1.4.2.1 Site Background ............................................104 3.1.4.2.2 Previous Investigations................................104 3.1.4.2.3 Potential Sources of Chromium(VI) ..........104 3.1.4.2.4 Approach for Presidio Investigation .........104 3.1.4.2.5 Objectives .......................................................106 3.1.4.3 Geology, Hydrogeology, and Geochemistry ..............106 3.1.4.3.1 Regional Geology .........................................106 3.1.4.3.2 Presidio Hydrogeology................................108 3.1.4.3.3 Groundwater Geochemistry in Upland Areas............................................108 3.1.4.3.4 Chromium Geochemistry............................108 3.1.4.4 Investigative Methods.................................................... 110 3.1.4.4.1 Field Methods ............................................... 110 3.1.4.4.2 Bedrock and Groundwat Analytical Methods ...................................... 113 3.1.4.4.3 Analytical Laboratories................................ 116 1-5667-0608-4/05/$0.00+$1.50 © 2005 by CRC Press LLC

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Chromium(VI) Handbook 3.1.4.5 Leaching Test Procedures .............................................. 117 3.1.4.6 Analytical Results ........................................................... 118 3.1.4.6.1 Bedrock Results............................................. 119 3.1.4.6.2 Groundwater Results ...................................120 3.1.4.6.3 Leaching Test Results...................................122 3.1.4.6.4 Discussion of Results ...................................129 3.1.4.6.5 Conclusions ...................................................133 Acknowledgments .....................................................................................134 Bibliography ...............................................................................................134 Chromium(VI) Concentrations in Drinking Water Wells and the Effects of Chlorination ...............................................................137 Tarrah D. Henrie, Veronica Simion, Chet Auckly, and Jeannette V. Weber 3.2.1 Introduction....................................................................................138 3.2.2 Methods and Materials ................................................................138 3.2.3 Results and Discussion.................................................................138 Bibliography ...............................................................................................141

3.1

Naturally Occurring Chromium(VI) in Groundwater, Including the Presidio of San Francisco Case Study

Martin G. Steinpress 3.1.1

Introduction

Chromium(VI) [Cr(VI)] in groundwater has generally been assumed to be anthropogenic (manmade) contamination, since it is used in a number of industrial applications, including electroplating, tanning, industrial water cooling, paper pulp production, and petroleum refining (Chapter 1). Chromium(III) [Cr(III)], the most common form of chromium (Cr) in the natural environment, is highly insoluble and relatively immobile. However, Cr(VI) minerals have been found in nature (Chapter 2), and the ability of manganese(IV) oxide (MnO2) to oxidize Cr(III) to Cr(VI) is well known (Bartlett and James, 1979; Eary and Rai, 1987; Fendorf and Zasoski, 1992). The number of occurrences of Cr(VI) is growing, particularly with statewide Cr(VI) sampling program with lower detection limits mandated for water suppliers by the California Department of Health Services (DHS) because of increasing health concerns. This chapter grew out of the hypothesis that widespread Cr(VI) in groundwater at the Presidio of San Francisco (Figure 3.1.1) was geogenic (naturally occurring) as opposed to anthropogenic. The results of the subsequent investigation and Technical Memorandum (TM), “Hexavalent Chromium in Serpentinite Bedrock and Groundwater in Upland Areas” (Montgomery Watson, 1999b; Steinpress, 1998), are summarized in the case study in Section 3.1.4.

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FIGURE 3.1.1 The Presidio in San Francisco, looking south across the Golden Gate Bridge.

The study culminated in the acknowledgment by the California Department of Toxic Substances Control (DTSC) that “it appears that Cr(VI) occurs naturally in serpentinite bedrock and in water from some monitoring wells, including background locations screened in that bedrock” (DTSC, 2000). During the course of the investigation, other examples of naturally occurring Cr(VI) in groundwater were identified and are also reviewed in this chapter. The impacts of the movie “Erin Brockovich” in the year 2000 are also considered in this chapter. Naturally occurring Cr(VI) can have as much effect on drinking water supplies as anthropogenic contamination, but remediation of background concentration are generally not feasible and there is not a responsible party to fund cleanup. This leaves water suppliers and the public in a quandary as to how to address the issue. 3.1.2

Examples of Naturally Occurring Chromium(VI) in Groundwater

Naturally occurring Cr(VI) in groundwater has been identified in the following geologic environments to date: • • • •

Arid alluvial basins in the Southwest U.S. Chromite ore bodies Saline brines in evaporate basins Serpentinite ultramafic terrains

Investigations of Cr(VI) in groundwater should also consider high tensile, low alloy (HTLA) steel well screens and casing, which have been in general use for many years (type 304 stainless steel is 18% Cr) (Roscoe Moss, 2003).

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3.1.2.1 Arid Alluvial Basins in the Southwest United States Chromium(VI) of natural origin has been found in the groundwater of numerous alluvial basins in Arizona and adjacent parts of California, New Mexico, and Nevada. This region includes portions of the Mojave Desert and Basin and Range Province. The first documentation of naturally occurring Cr(VI) in groundwater was in Paradise Valley, Maricopa County, Arizona, where a U.S. Geological Survey study revealed concentrations up to 220 mg/L. Cr(VI) concentrations are greater than 50 mg/L over 103.6 km2 area (Robertson, 1975; 1991). The basin consists of Tertiary and Quaternary alluvium, and there is a direct correlation between Cr(VI) concentration and the particle size of the alluvium (the fine-grained portion of the aquifer has the highest concentrations). The Cr(VI) is apparently present throughout the vertical extent of the aquifer. Eh and pH measurements of the groundwater indicated alkaline and oxidizing conditions, with many pH measurements in the 8 to 9 range. A direct relationship was also found between the pH and Cr(VI) concentrations. Analyses of drill cuttings did not detect any chromate (CrO42−) minerals or ions in a test well, including the minor sulfate SO42− minerals that were present. A subsequent broader study that included a total of 436 samples in Arizona and adjacent parts of California, Nevada, and New Mexico indicated a mean Cr(VI) concentration of 10.3 mg/L, standard deviation of 30.7, and a range of 0 mg/L to 300 mg/L (Robertson, 1991). Silicate hydrolysis of volcanic ash and tuffs in the fine-grained alluvial deposits combined with low CO2 content was found to be responsible for the elevated pH and the oxidation of Cr(III) to Cr(VI). The absence of iron(II) (Fe(II)), organic matter, or mafic minerals in the aquifer allows the water to retain its oxidizing and alkaline character. Basins in which groundwater has a longer residence time have higher Cr(VI) concentrations (concentrations are inversely correlated with recharge rates) (Robertson, 1991). More recently, naturally occurring Cr(VI) has been detected in water supplies in several alluvial basins as a result of greater scrutiny inspired by the film “Erin Brockovich.” In the remote Cadiz Valley in the Mojave Desert of southeastern California at the location of a proposed water storage project between Metropolitan Water District of Southern California (MWD) and Cadiz, Inc., concentrations of 15 ppb to 26 ppb (parts per billion) are present in native groundwater (MWD and Bureau of Land Management, 2001). U.S. Geological Survey sampling of selected public supply, domestic, and observation wells underlying uncontaminated areas of the western Mojave Desert detected total dissolved Cr from less than the 0.8 ppb detection limit to 60 ppb, and almost all of the Cr was Cr(VI) (Ball, 2002). In the eastern San Fernando Valley of Southern California, Cr(VI) is present at background concentrations of up to 0.01 mg/L upgradient of known sources in the vicinity of the Burbank Airport of volatile organic compounds (VOCs) and metals contamination (Nagel, 1999). 3.1.2.2 Natural Brines Both surface and subsurface natural brines found in saline lakes in closed basins in the western United States have been found to have high pH

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conditions (8.9 to 10.1) (Truesdall and Jones, 1969), which are favorable for Cr(VI). Cr(VI) minerals are well documented in evaporite deposits derived from brines in the Atacama Desert, Chile (Eriksen, 1983). Cr concentrations in the natural brines are reported to range from 0.01 mg/kg to 1 mg/kg. Although not specified, such Cr concentrations at a high pH are most likely Cr(VI). 3.1.2.3 Chromite Ore Bodies A combined field and laboratory study of chromite (FeCr2O4) bearing oxidized serpentinite rocks in India indicated the possibility of Cr mobilization from FeCr2O4 ores to water bodies (Godgul and Sahu, 1995). The authors observed that serpentinization is an intensely oxidizing process that creates alkaline pore waters that would promote oxidation of Cr(III). The study suggested that mining practices enhance the rate and intensity of Cr mobilization (Godgul and Sahu, 1995), although acidic conditions from mine wastes would tend to reduce Cr. Organic matter and iron-rich laterite deposits also tend to reduce any released Cr(VI). 3.1.2.4 Serpentinite Ultramafic Terrains Chromium(VI) has also been detected in groundwater associated with serpentine terrains consisting of ultramafic rocks that do not contain known FeCr2O4 ore bodies. Widespread Cr(VI) concentrations in groundwater detected in over 50% of the water supply wells downgradient of serpentinite terrains in Dixon, Willows, Livermore, South San Francisco, and other California locations support the interpretation that Cr(VI) is naturally occurring (Henrie et al., 2002; and this book). Background Cr(VI) in groundwater has been reported at three locations in California: • Lawrence Livermore National Laboratory • Vicinity of University of California (UC) Davis • Presidio of San Francisco At Lawrence Livermore National Laboratory, experiments have been conducted to remove Cr(VI) from groundwater using anion-exchange resin. Even though Cr(VI) is believed to be naturally occurring, the concentrations of tens to hundreds of ppb still exceed the discharge standards for the groundwater treated to remove VOCs (Torres, 1995). Leaching experiments are continuing to determine how Cr(VI) is being generated from soils (Ridley, 2002). Cr(VI) in groundwater has also been documented in the vicinity of U.C. Davis in the Sacramento Valley (Chung et al., 2001). Concentrations up to 0.2 mg/L have been reported from monitoring wells screened in alluvial deposits allegedly contaminated by laboratory waste. However, Cr(VI) is also present in off-site control wells and shallow upgradient wells. A study tested the inherent ability of the MnO2-rich soils from drill cuttings to produce Cr(VI) from native Cr(III).

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All of the samples generated Cr(VI) with concentrations in the extracts ranging from 0.02 mg/L to 0.1 mg/L, which is not statistically different from the concentrations in the background wells. The study concluded that hazardous concentrations of Cr(VI) can be generated in the unsaturated zone and transferred to groundwater by a natural geogenic process, i.e., oxidation of native Cr(VI) by native Mn oxides. It also suggested that other areas in the Sacramento and San Joaquin valleys with similar alluvium might also have naturally occurring Cr(VI) in groundwater (Chung et al., 2001). At the Presidio of San Francisco, Cr(VI) became a contaminant of concern in the remedial investigation of past U.S. Army activities. Cr(VI) is often attributed to anthropogenic sources, since it is used in a number of industrial applications. However, numerous detections of Cr(VI) in several areas of the Presidio where no anthropogenic sources existed led to the development of an alternative hypothesis that Cr(VI) in groundwater could be naturally occurring. The case study included at the end of this chapter indicates that Cr(VI) is present in trace amounts in the serpentinite bedrock and can be leached from serpentinite, as demonstrated by leaching tests of drill cuttings. In addition, Cr(VI) concentrations in new background wells located in pristine background areas are higher than in existing downgradient wells. The results of the study led to the development of a conceptual model in which the source of Cr(VI) in the groundwater is the serpentinite bedrock that underlies upland areas of the Presidio, which was acknowledged by DTSC (Steinpress et al., 1998; Montgomery Watson, 1999a; DTSC, 2000).

3.1.3

The Erin Brockovich Effect: Hollywood and the Scientific Process

In 1999, the movie Erin Brockovich was released, which focused on a legal case involving a cluster of cancers associated with groundwater contamination from a Pacific Gas and Electric (PG&E) site in Hinkley, California. The movie thrust the issue of Cr(VI) in drinking water into the public and political spotlight almost overnight. As a result, the high level of public concern both overwhelmed and undermined the relatively slow-paced processes of scientific investigation and regulatory evaluation. However, the concern also had the beneficial effect of spurring the California legislature to direct and provide funding for regulators to speed up decisions related to the current total Cr maximum contaminant level (MCL) and to consider a new MCL for Cr(VI). The Groundwater Resources Association of California (GRA) held a symposium in Southern California on Cr(VI) in groundwater to bring the thencurrent state of scientific knowledge and some common sense to the epicenter of the controversy (GRA, 2001). The eastern San Fernando Valley, which includes one of the largest chlorinated solvent Superfund sites in the country,

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had suddenly received intense local and national media attention on Cr(VI) concerns when Erin Brockovich hit theaters. GRA’s symposium included national and state experts who presented on all facets of this complex issue, including geochemical characteristics and distribution; risk, toxicology, and testing; social, political, and legal issues; and regulatory approach and remediation. Chromium commonly occurs as nontoxic, relatively immobile Cr(III). Until recently, toxic Cr(VI) was generally assumed to be a contaminant (anthropogenic) from industrial sites such as Cr plating facilities and cooling towers. But Cr’s chemistry is complex, and it is increasingly being recognized that Cr(VI) also occurs naturally (geogenic). However, the investigation, peer review, and publication of such occurrences are by necessity a methodical and time-consuming process. The movie, increasing public alarm, and uncertainties with respect to Cr(VI)’s toxicity and occurrence combined to create a blockbuster environmental and scientific challenge. While the issue was of national interest, California drinking water regulators were propelled into the limelight and were forced to sort through the risk dilemma with a dearth of directly applicable toxicological and water quality data. The development and refinement of a drinking water standard for a specific compound is a painstaking process that typically takes several years. The process begins with a risk assessment to develop a risk-based health goal. The United States Environmental Protection Agency (USEPA) does not consider Cr(VI) to be a carcinogen by the ingestion route. The USEPA MCL (which also considers the technical and economic feasibility of attaining a prescribed level) of 0.1 mg/L for total Cr is therefore considered protective. On the other hand, California Environmental Protection Agency’s (Cal/ EPA’s) Office of Environmental Health Hazard Assessment (OEHHA) completed an analysis of the data and considered Cr(VI) a carcinogen by ingestion. In February 1999, that risk hypothesis led to the calculation of a health protective level (PHL) for Cr(VI) of 0.0002 mg/L and a public health goal (PHG) of 0.0025 mg/L for total Cr. This result led the DHS to reevaluate the existing MCL of 0.05 mg/L for total Cr and consider a new MCL for Cr(VI). The PHGs are intended to be strictly advisory and are based solely on health considerations, whereas MCLs are legally enforceable drinking water standards. However, DHS must also evaluate the technical and economic feasibility for water systems when it is reevaluating an existing MCL or establishing a new MCL. When Erin Brockovich premiered, the scientific process already underway to evaluate the chromium MCL in light of the new PHG was short-circuited. In the movie, the Cr(VI) is contamination and a deep-pocket corporation was identified as the responsible party. In a typical Hollywood plot, “good” triumphs over “evil,” and a hefty financial settlement compensates the plaintiffs. While there was some education of the public with respect to groundwater contamination, science largely took a back seat to the showy legal wrangling (as in the movie A Civil Action).

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In reality, many water suppliers, such as in the Southern California cities of Glendale and Burbank, were caught between concerned members of the public that wanted cleanup to the lowest available regulatory standard or advisory concentration at any cost, and the technical and economic realities of pumping and treating huge quantities of contaminated groundwater. Unfortunately, the PHG was been taken out of context by the media, in part owing to difficulties in conveying the distinction between PHGs and MCLs. As a consequence, the PHG become a de facto action concentration. Meanwhile, Cr(VI) testing resulting from the emergency directive from DHS (and also proactive interests) showed that Cr(VI) is popping up in numerous groundwater basins (including some “pristine” environments) in California. State and federal regulators faced challenging decisions that demand scientific methods and common sense, and deep pockets will not be available to fund cleanup of naturally occurring Cr(VI). Sometimes Hollywood and real life converge and have a mutually reinforcing, long-lasting effect (e.g., The China Syndrome and Three Mile Island). Although the controversy over Cr(VI) taxed the scientific and regulatory processes, the Erin Brockovich effect ultimately led to a better-informed public and resulted in a flurry of legislative activity and funding for groundwater protection. This accelerated our scientific understanding of the occurrence and distribution of Cr, the development of realistic regulatory standards (MCLs), and more effective remedial technologies. We can only hope that the scientific and regulatory communities can stay ahead of the screenwriters and be better prepared for the media and public response when the next contaminant du jour hits the big screen. Subsequent to the release of the editorial views expressed above in Groundwater (Steinpress and Ward, 2001), the California legislature directed DHS to establish a primary drinking water standard for Cr(VI) by January 1, 2004, and to establish a secondary drinking water standard for Cr(VI) by July 1, 2003 (Senate Bill 351, signed by the governor on October, 7, 2001). An OEHHA review committee found no basis in either the epidemiological or animal data published in the literature for concluding that ingested Cr(VI) is a carcinogen, citing the previously used study to be flawed. As a result of finding no evidence of Cr(VI) being a carcinogen by ingestion, OEHHA withdrew the PHG of 0.0025 mg/L for total Cr on November 9, 2001.

3.1.4

Presidio of San Francisco Case Study

3.1.4.1 Executive Summary During the U.S. Army’s Main Installation Remedial Investigation (RI) of the Presidio (Figure 3.1.2), Cr(VI) was detected in groundwater samples from numerous monitoring wells. Owing to its toxicity, the presence of Cr(VI) became a significant risk assessment issue in the RI and the Main Installation Feasibility Study (FS). This case study summarizes the results of a study conducted to assess if Cr(VI) in groundwater at the Presidio of San Francisco could be attributed to natural sources.

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0

305

610

meter

FIGURE 3.1.2 General location map.

Chromium(VI) is often attributed to anthropogenic sources, since it is used in a number of industrial applications. However, numerous detections of Cr(VI) in several areas of the Presidio where no anthropogenic sources existed led to the development of an alternative hypothesis that Cr(VI) in groundwater could be naturally occurring (Figure 3.1.3). This hypothesis was based on the following: • Cr(VI) was reported in Presidio waste manifests; however, the Presidio was primarily an Army training and debarkation point with limited industrial operations (Dames and Moore, 1997a).

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VIEW TO SOUTHWEST Precipitation Uplands Bedrock Locations UBR01 and UBR02 Inspiration Point Serpentinite Barrens

Not to Scale

FIGURE 3.1.3 Presidio conceptual hydrogeologic model.

• Cr(VI) has been documented to occur naturally in several other California groundwater basins associated with serpentinite (Torres, 1995; Robertson, 1991; Henrie et al., 2002). • Extensive areas of the Presidio are underlain by Cr-rich serpentinite bedrock (Schlocker, 1974). • Groundwater sampling and analyses confirmed that Cr(VI) was present upgradient as well as downgradient of several sites (USEPA, 1996; Montgomery Watson, 1998). As a result, the Presidio stakeholders (Army, regulatory agencies, Presidio Trust, National Park Service, and others) agreed to explore and develop multiple lines of evidence to address the issue of whether Cr(VI) in Presidio groundwater could be naturally occurring. Three undisturbed background locations were selected for obtaining groundwater and serpentinite bedrock samples for use in a Cr(VI) leaching study. The current study was designed with the objective of developing the following three lines of evidence: 1. Background Bedrock Chemistry: Assesses Cr(VI) concentrations in bedrock samples collected at the three background drilling locations.

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2. Background Groundwater Geochemistry: Assesses Cr(VI) concentrations and water chemistry in monitoring wells at the three drilling locations. 3. Leaching Tests: Evaluate whether Cr(VI) can be generated through oxidation of Cr(III) or leached from serpentinite bedrock through a series of laboratory leaching tests. Serpentinite bedrock and groundwater samples were collected and the leaching tests were performed to address the above objectives. The results of the current study found the following: 1. Cr(VI) was detected at concentrations of 0.06 mg/kg and 0.46 mg/kg in the serpentinite bedrock composites from two of the boreholes. 2. Cr(VI) was detected at concentrations of 0.0521 mg/L to 0.0983 mg/L in groundwater samples from the three new background wells screened in serpentinite. 3. Cr(VI) was detected in the leaching test containing serpentinite bedrock and distilled water. The leaching tests performed under exaggerated conditions also yielded Cr(VI) and varying water chemistry parameters in the leachate over the 28-d test period. These results indicate that Cr(VI) is present in trace amounts in the serpentinite bedrock and can be leached from serpentinite. In addition, Cr(VI) concentrations in the new background wells are higher than in existing downgradient wells, and the concentration of Cr(VI) in groundwater is a result of various complex and competing reactions. The above results led to the conclusion that a source of Cr(VI) in the groundwater is the serpentinite bedrock that underlies upland areas of the Presidio. Previous studies have demonstrated that complex competing factors influence Cr(VI) concentrations in the environment (Bartlett, 1991). Geochemical data from the Presidio indicate an overall trend from oxidizing conditions in the upland areas to reducing conditions beneath Crissy Field. In summary, the groundwater geochemistry of the upland areas favors Cr(VI) chemical stability, whereas Crissy Field conditions favor Cr(VI) immobilization and/or reduction to Cr(III). The results of this investigation have potential implications for future uses of Presidio groundwater as a potential drinking water supply. Any evaluation of the potential beneficial uses of groundwater or Cr(VI) mitigation must consider that there is a continual natural source of Cr(VI) from serpentinite bedrock and serpentinite-derived soils or sediments. Because Cr(VI) concentrations vary across the Presidio, any groundwater mitigation/management plan should be location-specific to address the natural sources of Cr(VI) in groundwater. 3.1.4.2 Introduction Cr(VI) has been detected in both bedrock and groundwater samples in previous investigations at the Presidio. This document summarizes the results

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of a study (Montgomery Watson, 1999b) conducted to assess if Cr(VI) in the groundwater of the upland areas of the Presidio is naturally occurring. 3.1.4.2.1 Site Background The Presidio is located in the city of San Francisco at the northern tip of the San Francisco Peninsula and is bounded by San Francisco Bay on the north and the Pacific Ocean on the west (Figure 3.1.2). The topography ranges from rolling upland hills (approximately 122 m above sea level) to coastal beaches along the Pacific Ocean and the San Francisco Bay. The Presidio was occupied by the U.S. Army in 1848 and has served as a training, mobilization, and embarkation point during the Spanish American War and both World Wars, a medical debarkation center, and has provided coastal defense for the San Francisco Bay area. In 1994, the Presidio was transferred to the National Park Service (NPS) to become part of the Golden Gate National Recreation Area (Earth Tech, 1995). The Presidio Trust, established by the U.S. Congress in 1996, manages the park in partnership with the NPS. 3.1.4.2.2 Previous Investigations During the U.S. Army’s Main Installation RI of the Presidio (Dames and Moore, 1997a), Cr(VI) was detected in groundwater samples collected from numerous monitoring wells. Owing to its toxicity, it became a significant risk assessment issue in the Presidio RI and Feasibility Study (FS) (Dames and Moore, 1997a,1997b). Subsequent sampling and analyses also detected Cr(VI) in groundwater and bedrock samples throughout the Presidio (Table 3.1.1) (Steinpress et al., 1998). 3.1.4.2.3 Potential Sources of Chromium(VI) Chromium(VI) is often attributed to anthropogenic sources, since it is used in a number of industrial applications (including electroplating, tanning, industrial water cooling, paper pulp production, and petroleum refining [EPRI, 1988]). However, the Presidio was primarily an Army training and debarkation point with limited industrial operations (Dames and Moore, 1997a). The limited industrial operations at the Presidio primarily included maintenance and repair of motor vehicles and aircraft. Industrial activities that include the use of Cr were not reported as past activities (Dames and Moore, 1997a), although Cr(VI) has been reported in Presidio waste manifests. Chromium(VI) has been reported to occur naturally in several environments (Robertson, 1975, 1991; Bartlett, 1991; James, 1996; Nagel, 1999), including areas associated with serpentinite (Torres, 1995; Godgul and Sahu, 1995). Cr-rich serpentinite bedrock and serpentine-derived soils underlie extensive areas of the Presidio, including the upland areas. 3.1.4.2.4 Approach for Presidio Investigation Several previous investigations have detected Cr(VI) in Presidio bedrock, soil, and groundwater (Table 3.1.1). Based on these results, the approach for the current Cr(VI) investigation at the Presidio was developed in a series of

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TABLE 3.1.1 Previous Cr(VI) Investigations Investigation/Site Main Installation RI

Presidio sites

Crissy Field and Inspiration Point

Cr(VI) in Groundwater Technical Memorandum Building 1349 area

Tennessee Hollow

Presidio Golf Course Clubhouse Excavation

Results

Reference

Cr(VI) detected in groundwater upgradient of several sites as well as in background bedrock samples Cr(VI) detected in groundwater at Landfill 1, Battery Howe Wagner, Building 215 area, and El Polin Spring; the samples were requested by NPS and analyzed by USEPA’s National Enforcement Investigation Center (NEIC) Soil samples, requested by NPS, contained detections of total chromium (3,300 mg/kg to 3,900 mg/kg) and total nickel (1,930 mg/kg to 2,300 mg/kg); Cr(VI) was not detected at a reporting limit of 21 mg/kg. Confirmed presence of Cr(VI) in groundwater upgradient and downgradient of four upland sites (i.e., Landfills 1 and 2, Battery Howe Wagner, and Building 215 area) Cr(VI) detected at two of the three monitoring wells, including an upgradient well partially screened in serpentinite Cr(VI) detected in three of four piezometer wells installed by NPS as part of the Wetlands FS Cr(VI) detected in all three serpentinite bedrock samples

Dames and Moore, 1997a USEPA, 1996

USEPA, 1997

Montgomery Watson, 1998

Montgomery Watson, 1999b Montgomery Watson, 1999b Montgomery Watson, 1999b

joint technical meetings (Montgomery Watson, 1999b). This working group included representatives from the following regulatory agencies and stakeholders: • • • • • •

U.S. Army and U.S. Army Corp of Engineers (USACE) Department of Toxic Substance Control (DTSC) U.S. Environmental Protection Agency (USEPA) Presidio Trust National Park Service Restoration Advisory Board (RAB)

The objectives of the meetings were to: • Develop an approach to assess if Cr(VI) could be naturally occurring. • Select the undisturbed background locations for the field investigation. • Design the experimental conditions for a laboratory leaching study.

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This effort resulted in an agreement by the working group that multiple lines of evidence pursued in the current study were necessary in order to assess if Cr(VI) is naturally occurring. In addition, the group selected and agreed upon the field program, leaching tests, and work schedule outlined in the Final Work Plan (Montgomery Watson, 1999a). The three drilling locations selected were in Tennessee Hollow, upgradient of Fill Site 1 and Landfill 2 and any other known anthropogenic sources of Cr (Figure 3.1.3). 3.1.4.2.5 Objectives The objective of this study was to evaluate whether Cr(VI) in upland groundwater originates from serpentinite bedrock through the following lines of evidence: 1. Background Bedrock Chemistry: Measures Cr(VI) concentrations in bedrock samples collected at the three drilling locations. 2. Background Groundwater Geochemistry: Measures Cr(VI) and dissolved metals concentrations, as well as water chemistry parameters in the monitoring wells installed at the three drilling locations. 3. Leaching Tests: To evaluate if Cr(VI) can be leached from serpentinite bedrock and/or generated through the oxidation of Cr(III) to Cr(VI) through a series of laboratory leaching tests. The bedrock and groundwater analyses were performed to provide data on upgradient Cr(VI) concentrations and groundwater geochemistry. The leaching tests assess the relative influence of several chemical conditions and reactions that may be important to the chemically complex process of generating Cr(VI) in groundwater. 3.1.4.3 Geology, Hydrogeology, and Geochemistry The following section summarizes the geology, hydrogeology, and groundwater geochemistry of the Presidio upland area. A summary of the Cr geochemistry is also included in this section. 3.1.4.3.1 Regional Geology The bedrock beneath the San Francisco peninsula is composed of ocean-floor ultramafic basalts (magnesium (Mg)- and iron (Fe)-rich volcanic rocks) and sediments that were stacked against and beneath the North American continent as a result of subduction. This ancient complex terrain of subducted rocks, called the Franciscan Complex, has been deformed, heated, altered (i.e., physical and/or chemical composition of the rock changed), and mixed as it was crushed at the continental margin. This Mesozoic bedrock is overlain with Quaternary sediments that include dune sands, slope debris, bay mud, and artificial fill (Figure 3.1.4). The Franciscan Complex that underlies most of the Presidio includes large areas of the metamorphosed form of ultramafic rock known as serpentinite,

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Golden Gate Fort Point

Fort Mason Yerba Buena l.

Baker Beach Telegraph Hill Land’s End Cliff House

Hunter’s Point Merced Formation

Bayshore

San Bruno Fault

0

LEGEND Artificial Fill

Strike-Slip Fault

Holocene Dune Sand

Structural Boundary Between Franciscan Blocks (Approximate) Lithologic Contact

Colma Foundation Merced Formation Franciscan Bedrock (Roman Numerals Denote Structural Blocks)

1

2

3

SCALE IN Km

MONTGOMERY WATSON PRESIDIO OF SAN FRANCISCO GENERALIZED GEOLOGY OF THE SAN FRANCISCO PENINSULA

Source: Modified from Wahrhaftig, 1989.

FIGURE 3.1.4 Generalized geology of the San Francisco peninsula.

shown in Figure 3.1.4. The geology of the Franciscan Complex has been summarized in several documents [Schlocker, 1974; Wahrhaftig, 1989; the Basewide Groundwater Monitoring Plan (BGMP) (Montgomery Watson, 1996); Main Installation RI (Dames and Moore, 1997a); and Steinpress, 1998]. Ultramafic rocks contain FeCr2O4, Fe-Mg oxides, and silicates. Ultramafic rocks typically contain 1,000 mg/kg to 3,400 mg/kg Cr (Faust and Aly, 1981),

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and bedrock developed from serpentinite bedrock also have inherently high concentrations of chromium (Kabata-Pendias and Pendias, 1984). During the Main Installation RI, the USEPA detected high concentrations of Cr, nickel, and other metals in bedrock associated with Presidio serpentinite (Dames and Moore, 1997a; USEPA, 1996). As a result, the serpentinite in the geologic environment was considered a source of “metals” found in the Presidio groundwater. 3.1.4.3.2 Presidio Hydrogeology The Presidio has two hydrogeologic environments: • Upland areas • Crissy Field area The upland areas are underlain by dune and marine sands resting on the Franciscan Complex bedrock. Groundwater in the upland areas generally occurs in a shallow water-bearing zone in Quaternary sediments and has a northward regional flow direction toward San Francisco Bay beneath most of the Presidio. The low-lying areas around Crissy Field consist of interbedded estuarine sands and bay muds. Groundwater below Crissy Field encompasses the transition zone between groundwater recharged from the upland areas and a tidally influenced seawater intrusion zone. The hydrogeology in these two areas is discussed in detail in the Main Installation RI (Dames and Moore, 1997a), the Fuel Products Action Level Development Report (FPALDR) (Montgomery Watson, 1995), the Basewide Groundwater Monitoring Plan (BGMP) (Montgomery Watson, 1996), and subsequent summary publications (Steinpress, 1997; Steinpress et al., 1999). Table 3.1.2 includes a summary of the hydrogeologic units that overlie the Franciscan Complex bedrock in the Presidio upland areas, the focus of this investigation. 3.1.4.3.3 Groundwater Geochemistry in Upland Areas The groundwater chemistry of the upland areas is mostly magnesium hydrogen carbonate (Mg(HCO3)2)-type, reflecting contact with the magnesium-rich serpentinite bedrock (Montgomery Watson, 1996). Several of the wells also have sodium chloride-type groundwater, indicative of marine sedimentary units within the Franciscan complex. 3.1.4.3.4 Chromium Geochemistry Historical Oxidation-reduction potential (Eh) and pH measurements indicate that the upland area is generally an oxidizing environment with near neutral pH values (Dames and Moore, 1997a; Montgomery Watson, 1998). For Cr, the reduced oxidation state [Cr(III)] typically occurs in low to neutral pH (pH<7 to pH=7) and low Eh (reducing) conditions. Cr(VI) is the dominant oxidation state in alkaline (pH>7) and oxidizing (high Eh values) environments.

Source:

Quaternary interglacial periods Quaternary glacial periods

Historical (<150 year)

Pleistocene

Pleistocene and Recent

Age

Clean sand in west to silty sand in east

Silt, clay, and peat

Debris and silty sandy gravel

Well sorted (poorly graded) fine- to medium-grained unconsolidated sand Silty to conglomeratic sand, well bedded to cross bedded

Lithology

Commercial and military development Lagoon, intertidal mud flat, and marshes Dominantly tidal channels, beach, dune, and alluvial

Shallow marine

Eolian (windblown)

Depositional Environments

Dominant in subsurface in west

Dominant in subsurface in east

Thickest in former lagoon channels

Tennessee Hollow and Lobos Creek

Very extensive

Location (Figure A-2)

Modified from Montgomery Watson, 1996; Steinpress, 1997; and Montgomery Watson, 1998a.

Estuarine sand deposits and alluvium

Fine-grained estuarine deposits

Crissy Field area Artificial fill

Colma formation

Upland area Dune sands

Area/Unit

Hydrogeologic Units, Presidio of San Francisco

TABLE 3.1.2

Lenticular; 0.3 m to 3 m in west; up to 7.6 m to 15 m in east Variable, depending on depth to bedrock

Averages 0.61 m to 1.2 m

Om to over 24.4 m

Variable

Approximate Thickness

High

Low

Generally high, but variable

High (sands) to low (silt and clay)

High

Estimated Hydraulic Conductivity

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The concentration of Cr(VI) in groundwater is a function of several complex competing factors including: • Rates of dissolution of Cr from the bedrock, either as Cr(III) or Cr(VI), or both • Oxidation of Cr(III) to Cr(VI) • Reduction of Cr(VI) to Cr(III) • Sorption of Cr(III) to clay or organics • Precipitation of Cr(III) or Cr(VI) • Groundwater flow path The two Cr oxidation states have very different mobilities in the environment owing to differing solubility and adsorption characteristics. Cr(III) [e.g., Cr(OH)3] tends to be immobile because it is a cation that is sorbed to negatively charged surfaces in the bedrock or aquifer material (Calder, 1988; McLean and Bledsoe, 1992). Cr(VI) is an oxyanion (e.g., HCrO4– or CrO42–) and is more mobile in groundwater because of higher solubility and low adsorption to aquifer materials (Calder, 1988). Two of the constituents known to oxidize Cr(III) to Cr(VI) in laboratory studies are dissolved oxygen (O2) and Mn oxides (Eary and Rai, 1987). Cr(VI) can be reduced to Cr(III) in the presence of Fe(II), organic matter, and/or dissolved sulfides (S2−) as groundwater enters a reducing and/or oxygenpoor zone (Calder, 1988). 3.1.4.4 Investigative Methods This section describes the field methods, bedrock and groundwater sample analytical methods, and the leaching test procedures used in this investigation. 3.1.4.4.1 Field Methods Field activities were conducted as proposed in the Final Work Plan (Montgomery Watson, 1999a). The methods are summarized below and a detailed description is provided in the TM (Montgomery Watson, 1999b). 3.1.4.4.1.1 Drilling, Core Extraction, and Lithologic Logging — Three drilling locations upgradient of potential contaminant sources (e.g., landfills) in the Tennessee Hollow drainage area were chosen for this investigation by the stakeholders (Figure 3.1.3). Permits from the NPS and the Underground Alert Service (USA) were obtained before mobilizing to the drilling locations. Drilling began on February 22, 1999 using a hollow stem auger (Figure 3.1.5). Continuous bedrock core samples were collected, logged, and photographed by the site geologist (Figure 3.1.6). The core was removed from the liners and then placed in core boxes for temporary storage and future reference (Figure 3.1.7). The collected core was reviewed by the site geologist, project manager, and project chemist to select well screen intervals and the most appropriate sampling intervals for the leaching test study. Boring logs and well construction diagrams are included in the TM (Montgomery Watson, 1999b).

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Naturally Occurring Chromium(VI) in Groundwater

FIGURE 3.1.5 Hollow stem auger drilling at UBR01.

FIGURE 3.1.6 Undisturbed bedrock sample in core barrel at UBR02.

111

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FIGURE 3.1.7 Boxed serpentinite core at UBR02.

To minimize disturbance to the bedrock sample and preserve its innate chemical composition throughout the collection and handling activities, the samples were placed in double polyethylene bags, stored on ice, and transported under chain of custody to the analytical laboratory where they were stored at 4 ± 2 °C. 3.1.4.4.1.2 Groundwater Monitoring Well Construction, Development, and Sampling — Following completion of each borehole, the deep monitoring wells were installed in the borehole and the shallow wells were installed in the immediate vicinity of the borehole. The bedrock borings at upland locations UBR01 and UBR02 were drilled in or near outcrops of serpentinite bedrock and encountered groundwater in fractured serpentinite bedrock. The boring at UBR03 was drilled in Quaternary dune sands and encountered sandy clay to sands of the Quaternary Colma Formation at 6.858 m below ground surface (bgs). The five wells constructed at three locations are summarized in Table 3.1.3. Monitoring wells UBR01GW01, UBR02GW01, and UBR02GW02 were initially sampled on March 4, 1999 after being developed using only a bailer and centrifugal pump to provide rapid data necessary for the leaching test setup. Because the pH and Eh measurements taken during development

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Naturally Occurring Chromium(VI) in Groundwater TABLE 3.1.3 Upland Bedrock Monitoring Wells Location UBR01 UBR02

UBR03

Well Name

Screened Interval (m)

UBR01GW01 UBR02GW01

13.72 to 16.76 10.06 to 14.63

UBR02GW02

7.32 to 8.84

UBR03GW01 UBR03GW02

15.24 to 19.81 9.45 to 10.97

Rationale Screened in serpentinite fracture zone Screened in deep fracture zone in serpentinite Screened in shallow fracture zone in serpentinite Screened in deep Colma Formation Screened in Colma Formation above low permeability sandy clay

were different than those of other groundwater monitoring wells in the upland areas, the wells were redeveloped between March 16–18, 1999 using protocols specified in the BGMP (Montgomery Watson, 1996). The monitoring wells were sampled during March 22–23, 1999 according to protocols specified in the BGMP (Montgomery Watson, 1996), which include purging a minimum of three well volumes and sampling with a bailer equipped with a bottom-emptying device. Samples for the analyses of dissolved metals [including Cr(VI)] were filtered in the field using a 0.45 µm in-line filter. Monitoring well development and purge logs are presented in the TM (Montgomery Watson, 1999b). 3.1.4.4.2 Bedrock and Groundwater Analytical Methods The analytical methods are described in the approved Final Work Plan (Montgomery Watson, 1999a) and summarized below. 3.1.4.4.2.1 Bedrock Samples — The bedrock core from each of the borings was composited based on their similarity in mineralogy and degree of weathering to produce one composite sample for each boring. The sample depths used for the three bedrock composites were as follows: • UBR01: 11.125 m, 12.192 m, 13.411 m, and 14.326 m BGS • UBR02: 6.706 m, 8.382 m, and 9.754 m BGS • UBR03: 20.726 m and 21.336 m BGS To generate the composite samples, individual bedrock samples from the continuous cores from the three locations were each crushed and homogenized using a riffle splitter (Figure 3.1.8). After homogenization, the samples were passed through a 4 mm sieve (Figure 3.1.9). The three bedrock composite samples were analyzed for the parameters identified in Table 3.1.4.

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FIGURE 3.1.8 Homogenization of bedrock sample using a riffle splitter.

FIGURE 3.1.9 Sieving a bedrock composite sample using a 4 mm sieve.

Chromium(VI) Handbook

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Naturally Occurring Chromium(VI) in Groundwater TABLE 3.1.4 Laboratory Analyses for Bedrock Samples Parameter Cr(VI) Cr(VI) Total Metalsa Total Organic Carbon Total Organic Carbon Quick Oxidation Test Easily Reducible Manganese Percent Moisture pH Eh

Analytical Method

Laboratory

7199/DI Extraction 7196A/3060A 6010B Modified 9060 Walkley-Black Bartlett and James, 1979 Gambrell, 1996 D2216 — —

Quanterra Prima Quanterra Quanterra Prima Prima Prima Quanterra Prima Prima

a Al, Ag, As, Ba, Be, Ca, Cd, Cr, Co, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, Sb, Se, Si, Ti, Tl, V, and Zn.

TABLE 3.1.5 Individual Bedrock Samples Depth of Sample (m BGS)

Distinctive Feature

UBR01

10.36

Strong black staining

UBR01

7.32

UBR02

14.33

UBR02

14.63

UBR03

10.06

Slightly weathered serpentinite Strong iron-oxide staining White calcite deposits Slight black staining

Drilling Location

a

Analyses Cr(VI), easily reducible Mn, and quick oxidation test Cr(VI), easily reducible Mn, and quick oxidation test Cr(VI) and total metalsa Total metalsa Cr(VI) and easily reducible Mn

Al, Ag, As, Ba, Be, Ca, Cd, Cr, Co, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, Sb, Se, Si, Ti, Tl, V, and Zn.

The quick oxidation test is a qualitative measure of the samples’ capacity to oxidize soluble Cr(III) to Cr(VI). The easily reducible Mn test is an aggressive method for measuring the amount of reducible Mn oxide compounds in the bedrock that may be available to oxidize Cr(III) to Cr(VI). Detailed descriptions of the analytical methods are included in the TM (Montgomery Watson, 1999b). Several individual bedrock samples were also collected at discrete intervals throughout the bedrock core. These samples were collected based on distinct features observed in the bedrock. Table 3.1.5 lists the individual bedrock samples, their distinct features, and the analyses performed.

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Chromium(VI) Handbook TABLE 3.1.6 Laboratory Analyses for Groundwater and Leachate Samples Parameter Dissolved metalsa Cr(VI) Alkalinity pH Chloride Fluoride Nitrate/nitrite Sulfate Total dissolved solids

Analytical Method 6010B 7199 310.1 9040 300.0 340.2 353.2 300.0 160.1

a

Al, Ag, As, Ba, Be, Ca, Cd, Cr, Co, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, Sb, Se, Si, Ti, Tl, V, and Zn. Note: All laboratory analyses were performed by Quanterra Environmental Services.

3.1.4.4.2.2 Groundwater Samples — Groundwater samples were analyzed for the parameters identified in Table 3.1.6. Reporting concentration limits for all analytical methods are presented in the TM (Montgomery Watson, 1999b). Field measurements were also conducted for the groundwater samples using a Yellow Springs Instruments (YSI) multimeter equipped with an inline flow-through cell. These measurements include: • • • • • • •

Dissolved oxygen Eh pH Turbidity Specific conductance Temperature Salinity

The field measurement data can be found in the groundwater purge logs in the TM (Montgomery Watson, 1999b). 3.1.4.4.3 Analytical Laboratories The laboratory analyses of the groundwater and leachate samples were performed by Quanterra Environmental Services, an analytical laboratory validated by the USACE Missouri River District and certified by the State of California to perform the requested analyses. The leaching tests and selected analyses associated with the bedrock samples were performed by Prima Environmental, a treatability laboratory in Sacramento, California.

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Naturally Occurring Chromium(VI) in Groundwater TABLE 3.1.7 Leaching Test Conditions Test No.

Leaching Solution

1 2

a b c

Bedrock

Other Additions

125 mL of DI water 125 mL of groundwater sample UBR01GW01

None 25 g

None None

3

125 mL of DI water

25 g

None

4

125 mL of 5% H2O2a

25 g

None

5

125 mL of DI water

25 g

6

125 mL of 2 m mol/L CrCl3c

25 g

2.5 g (29 m mol) of MnO2b None

Rationale Blank To monitor if Cr(VI) can be leached or oxidized from bedrock with the site groundwater To monitor if Cr(VI) can be leached or oxidized independent of groundwater chemistry To enhance Cr(III) oxidation to Cr(VI) by adding a strong oxidant To enhance Cr(III) oxidation to Cr(VI) by adding an oxidant To determine if the solubility of Cr(III) is the limiting factor in the oxidation of Cr(III) to Cr(VI)

Prepared by diluting 333 mL of 30% H2O2 to 2 L with DI water. JT Baker, “Baker Analyzed” MnO2 powder. Prepared by dissolving 1.067 g CrCl3 • 6H2O in 2 L of DI water.

3.1.4.5 Leaching Test Procedures Based on the analytical results described in Section 3.1.4.4.2 for the three bedrock composite samples, composite UBR01 was selected for use in the leaching tests. The sample was crushed to increase the surface area of the bedrock in order to increase the chemical reaction rates and reduce the time of the tests. The leaching tests consisted of six batch tests conducted in duplicate, using a series of 14 bottles per test (Table 3.1.7). Test 1 was a blank and contained deionized (DI) water only. Groundwater collected from monitoring well UBR01GW01 was used as the leaching solution in Test 2 of the leaching test. Owing to the already elevated Cr(VI) concentration (0.0654 mg/L) in UBR01GW01, DI water was used in Test 3 and the exaggerated tests (e.g., Tests 4, 5, and 6) to allow any increases in Cr(VI) concentrations during the 28-d test period to be distinguished. As described in the Final Work Plan (Montgomery Watson, 1999a), Tests 4, 5, and 6 were performed under intentionally exaggerated conditions [i.e., excess concentrations of oxidants or soluble Cr(III)] to provide information on the time scale and limiting factors that may influence the oxidation of Cr(III) to Cr(VI) and its release into the groundwater. Hydrogen peroxide (H2O2), MnO2, and chromium(III) chloride (CrCl3) were added to the bottles in

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FIGURE 3.1.10 Leaching test bottle setup on shaker table.

Tests 4, 5, and 6, respectively, to achieve these different exaggerated conditions, as described in detail in the TM (Montgomery Watson, 1999b). The bottles containing the leaching mixture were continuously agitated on a shaker table (Figure 3.1.10). The leaching tests were performed over a 28 d period and sampled at 1 h, 4 h, 24 h, 7 d, 14 d, 21 d, and 28 d. At each sampling interval, two duplicate bottles from each of the test conditions were removed from the shaker table and sacrificed for analyses. The leachate was filtered and analyzed for the following parameters: • • • •

Selected dissolved metals (Cr, Fe, Mg, Mn, Ni) Cr(VI) pH Eh

At the 1 h and 28 d sampling intervals, the leachates were also analyzed for the complete suite of dissolved metals (Table 3.1.6), and the leached UBR01 bedrock composite was analyzed for Cr(VI), easily reducible Mn, and the quick oxidation test. 3.1.4.6 Analytical Results Samples collected for this Cr(VI) study were analyzed for a variety of parameters (listed above) to assess if Cr(VI) could be leached and/or generated from the serpentinite bedrock. These analytical results are described in the following

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Naturally Occurring Chromium(VI) in Groundwater TABLE 3.1.8 Bedrock Composite Analytical Results Analytical Parameters Cr(VI) by alkaline digestion (mg/kg) Cr (mg/kg) Mn (mg/kg) Quick oxidation test (mg/kg) Total organic carbon (mg/kg) Easily reduced Mn (mg/kg) pH Eh (mV)a a

Bedrock Composite ID UBR01 UBR02 UBR03 0.064 1,160 595 1.60 329 136 8.85 454

0.463 371 671 1.01 452 102 8.00 421

0.231 83.5 216 <0.08 897 15 8.44 441

Eh values are corrected for reference electrode and temperature.

three subsections. A discussion of the overall trends demonstrated by the analytical data is presented in Section 5.0. 3.1.4.6.1 Bedrock Results Key Points can be summarized as follows: • Cr(VI) detected in serpentinite bedrock. • Bedrock has the intrinsic ability to oxidize Cr(III) to Cr(VI). • Bedrock extracts are slightly alkaline and exhibit oxidizing conditions. All three of the serpentinite bedrock composites (UBR01, UBR02, and UBR03) contained detectable quantities of Cr(VI) as analyzed by the alkaline digestion method (Table 3.1.8). These results confirm bedrock Cr(VI) in the Presidio Golf Course excavation samples and RI (Dames and Moore, 1997a). Two of the bedrock composites, UBR01 and UBR02, also demonstrated the ability to oxidize dissolved Cr(III) to Cr(VI) (as seen in the quick oxidation test results). These results suggest that Cr(VI) could be generated from the serpentinite bedrock if soluble Cr(III) is present. The Eh and pH values for the three bedrock composites indicate alkaline (pH above 8) and oxidizing (large positive Eh values) conditions. There were also relatively low concentrations of reducing agents, such as total organic carbon. Bedrock composite UBR01 was used in the leaching tests due to relatively lower concentrations of extracted Cr(VI) and higher dissolved Cr, quick oxidation test and easily reducible Mn results than in the other two bedrock composites. Before the start of the leaching tests, the UBR01 bedrock composite was reanalyzed for Cr(VI), easily reducible Mn, and the quick oxidation test to

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Chromium(VI) Handbook TABLE 3.1.9 Ubr01 Bedrock Composite Analyses Analytical Parameters

UBR01 (Analysis on 3/1/99)

UBR01 (Reanalysis on 3/15/99)

0.064 1.60 136

0.127 1.67 137

Cr(VI) by alkaline digestion (mg/kg) Quick oxidation test (mg/kg) Easily reducible Mn (mg/kg)

TABLE 3.1.10 Individual Bedrock Sample Results Drilling Location

Depth of Sample (ft BGS)

UBR01

24

UBR01

34

UBR02 UBR03

47 33

Analysis

Result (mg/kg)

Cr(VI) Easily reducible manganese Quick oxidation test Cr(VI) Easily reducible manganese Quick oxidation test Cr(VI) Cr(VI) Easily reducible manganese

0.540 601 3.90 0.602 1,235 13.21 0.0104 0.0264 891

confirm that the composition of the bedrock had not changed between the initial analyses and the leaching test setup (Table 3.1.9). The original and reanalyzed results showed that the chemical composition of the bedrock composite did not change significantly before the beginning of the leaching test. Because Cr(VI), by alkaline digestion results, is very close to the reporting concentration limit (0.05 mg/kg), the difference between these results is not considered significant. Several individual bedrock samples were also collected at discrete intervals from the bedrock core based on distinctive features. The most notable result is that Cr(VI) was detected in the samples (Table 3.1.10). 3.1.4.6.2 Groundwater Results Key Points can be summarized as follows: • Cr(VI) detected in groundwater from all three monitoring wells screened in serpentinite bedrock. • Groundwater from monitoring wells screened in serpentinite bedrock showed slightly alkaline and oxidizing conditions. Monitoring wells UBR01GW01, UBR02GW01, and UBR02GW02 were initially sampled on March 4, 1999 after being developed with only a bailer

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and centrifugal pump. Because the pH and Eh measurements were different from groundwater in most other upland areas, the wells were redeveloped using a surge block and submersible pump to purge additional sediment and groundwater as per the BGMP (Montgomery Watson, 1996). The wells were resampled on March 22, 1999 and yielded Eh values more typical of the upland areas, but the pH values remained relatively high (Table 3.1.11). The original low Eh measurements were unexplained but are considered artifacts of the well installation. The monitoring wells at UBR03 were not sampled on March 4, 1999 owing to high turbidity that could interfere with the analyses. The analytical results for dissolved metals and general water chemistry parameters (i.e., alkalinity, anions, and total dissolved solids) were consistent between the two sampling events. Cr(VI) was detected in four out of the five monitoring wells installed at the background locations (Table 3.1.12). Wells screened in the serpentinite bedrock (UBR01GW01, UBR02GW01, and UBR02GW02) contained higher Cr(VI) concentrations than monitoring wells screened in the Colma Formation (UBR03GW01 and UBR03GW02). The Cr(VI) concentrations from all five wells strongly correlated (R2 = 0.99) with the dissolved Cr concentrations (Figure 3.1.11), showing that the Cr TABLE 3.1.11 Summary of Groundwater pH and Eh

Sample ID

Collected 3/4/99 pH Eha (mV)

Collected 3/22/99 and 3/23/99 pH Eha (mV)

UBR01GW01 UBR02GW01 UBR02GW02 UBR03GW01 UBR03GW02

8.32 9.14 8.33 NS NS

8.31 9.18 8.36 7.53 6.62

a

–24 –15 –33 NS NS

423 348 308 464 422

Eh values are corrected for reference electrode and temperature.

Note:

NS = not sampled.

TABLE 3.1.12 Groundwater Analytical Results

Analytical Parameter

UBR01 GW01

UBR02 GW01

Cr(VI) (mg/L) Dissolved Cr (mg/L) Dissolved Mn (mg/L) pH Eh (mV)a

0.0654 0.066 0.013 8.31 423

0.0521 0.049 <0.015 9.18 348

a

Monitoring Wells UBR02 UBR03G GW02 W01 0.0983 0.100 0.010 8.36 308

<0.00050 <0.010 0.280 7.53 464

Eh values are corrected for reference electrode and temperature.

UBR03 GW02 0.00064 <0.010 0.059 6.62 422

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Dissolved Cr (µg/L)

100

50

0 0

25

50 Cr(VI) (µg/L)

75

100

FIGURE 3.1.11 Correlation between Cr(VI) and dissolved Cr.

was predominantly Cr(VI). Monitoring wells from locations UBR01 and UBR02 also have slightly alkaline (pH>7) and oxidizing conditions (large positive Eh values). Groundwater samples collected from wells at location UBR03 had pH values that were closer to neutral as well as higher concentrations of dissolved Mn, indicating different groundwater chemistry. The geochemistry of groundwater samples from monitoring wells at UBR01 and UBR03 are similar to the Mg(HCO3)2 patterns seen in other upland area wells. Monitoring wells at UBR02 have higher concentrations of sodium (Na) and chloride (Cl−), a pattern more typical of groundwater associated with marine sedimentary units within the Franciscan Complex. High pH values associated with groundwater from the three upland bedrock wells are consistent with those typically found in serpentinite terrains (Kruckeberg, 1985). 3.1.4.6.3 Leaching Test Results Key Points can be summarized as follows: • Cr(VI) detected in Test 3 (DI water + bedrock composite) indicates that Cr(VI) can be leached from the bedrock. • Cr(VI) concentrations in bedrock and groundwater are a result of competing reactions (i.e., dissolution and precipitation). • Presence of oxidants and soluble Cr(III) is important in the complex chemical reactions governing Cr(VI) generation. The leaching tests consisted of six different test conditions, performed in duplicate, analyzed over the 28-d test period (Table 3.1.13). Results are presented as averages of the two duplicates for each of the test conditions in the following sections. Groundwater collected from monitoring well UBR01GW01 was used as the leaching solution in Test 2 of the leaching

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Naturally Occurring Chromium(VI) in Groundwater TABLE 3.1.13 Leaching Test Conditions Test No.

Leaching Solution

1 2

a b c

Bedrock

Other Additions

None 25 g

None None

3 4 5

125 mL of DI water 125 mL of groundwater sample UBR01GW01 125 mL of DI water 125 mL of 5% H2O2a 125 mL of DI water

25 g 25 g 25 g

6

125 mL of 2 mmol/L CrClc3

25 g

None None 2.5 g (29 mmole) of MnO2b None

Prepared by diluting 333 mL of 30% H2O2 to 2 L with DI water. JT Baker, “Baker Analyzed” manganese dioxide powder. Prepared by dissolving 1.067 g CrCl3 • 6H2O in 2 L of DI water.

test. Due to the Cr(VI) concentration (0.0654 mg/L) present in UBR01GW01, a leaching solution of DI water was used in the exaggerated tests (i.e., Tests 4, 5, and 6) in order to distinguish any increases in Cr(VI) concentrations during the 28 d test period. 3.1.4.6.3.1 Test 1: DI Water — Test 1 served as a blank control to monitor for the possible contamination sources from the DI water or during the analyses of the leaching test. This test condition contained DI water only (no bedrock composite). Dissolved metals and Cr(VI) were not detected above reporting limits during the leaching test, indicating that the DI water did not contribute to Cr(VI) concentrations in the leaching tests. 3.1.4.6.3.2 Test 2: Groundwater + Bedrock — Leaching Test 2 consisted of a combination of site groundwater [with an initial Cr(VI) concentration of 0.0654 mg/L] and bedrock samples from location UBR01. The objective of this test was to evaluate whether the groundwater affects the leaching or oxidation of Cr(VI) from the bedrock. The results show that Cr(VI) concentrations declined during the test period and the leachate contained a final Cr(VI) concentration of 0.0052 mg/L. This overall decrease in the leachate Cr(VI) concentration coincided with an increase in the Cr(VI) concentration in the remaining leached bedrock (Figure 3.1.12). The leached bedrock also demonstrated an overall decrease in the ability to oxidize Cr(III) to Cr(VI), as shown in the quick oxidation test results (Table 3.1.14). The inverse relationship between Cr(VI) concentrations in the leachate and the leached bedrock suggests that precipitation and dissolution are the likely controls on the Cr(VI) concentrations in the bedrock and groundwater. This could be owing in part to the increased surface area of the bedrock matrix providing additional active sites for sorption of Cr(VI). Other studies have

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80

0.3

60

0.2

40 0.1

20 0

0 1 Hour

Leached Bedrock (mg/kg)

Leachate (µg/L)

Chromium(VI) Handbook

28 Days

Cr(VI) in Leachate

Cr(VI) in Leached Bedrock

Sampling Interval FIGURE 3.1.12 Test 2 Cr(VI) concentrations.

TABLE 3.1.14 Leached Bedrock Analytical Results for Test 2 Analytical Parameter Cr(VI) by alkaline digestion (mg/kg) Quick oxidation test (mg/kg)

Sampling Interval 1h 28 d 0.09 1.32

0.238 0.24

also shown that increased Cr(VI) soil concentrations inhibit Cr(III) oxidation (Fendorf and Zasoski, 1992). 3.1.4.6.3.3 Test 3: DI Water + Bedrock — Test 3 consisted of DI water combined with the bedrock composite. The objective of this test was to evaluate if Cr(VI) could be leached from the bedrock by a leaching solution of DI water. The results indicate that Cr(VI) was leached from the bedrock, as shown by Cr(VI) concentrations in the leachate (0.00125 mg/L to 0.0054 mg/L) during the 28-d test period. The leachate Cr(VI) concentration peaked at 0.0054 mg/L at day 14 and then decreased to 0.00125 mg/L by day 28 (Figure 3.1.13). Over the test period, there was a slight increase in the leached bedrock Cr(VI) concentration (Table 3.1.15), indicating that the Cr(VI) precipitated out of solution and sorbed to the bedrock. The Cr(VI) concentrations in the leachate and leached bedrock were close to the reporting concentration limits (0.0005 mg/L and 0.05 mg/kg, respectively). Owing to the analytical uncertainties at concentrations close to the reporting concentration limits, it is not possible to assess whether these differences are significant. The quick oxidation test results decreased over the 28 d testing period. This suggests that as Cr(VI) was adsorbed onto the bedrock, it may have blocked sites on the bedrock that would have been available to oxidize the soluble Cr(III) added as part of the quick oxidation test.

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Naturally Occurring Chromium(VI) in Groundwater 6 Cr(VI) (µg/L)

5 4 3 2 1 0 1 hour

24 hours

14 days

28 days

Sampling Interval FIGURE 3.1.13 Test 3 leachate Cr(VI) concentrations.

TABLE 3.1.15 Leached Bedrock Analytical Results for Test 3 Sampling Interval 1h 28 d

Analytical Parameter Cr(VI) by alkaline digestion (mg/kg) Quick oxidation test (mg/kg)

0.093 1.66

0.155 0.89

Cr(VI) (µg/L)

600 500 400 300 200 100 0 1

4

24

7

14

hour hours hours days days

21

28

days

days

Sampling Interval FIGURE 3.1.14 Test 4 leachate Cr(VI) concentrations.

3.1.4.6.3.4 Test 4: DI Water + Bedrock + Hydrogen Peroxide — Test 4 consisted of the addition of the oxidant H2O2 in a mixture of DI water and the bedrock composite. This test was performed to evaluate if Cr(III) in the bedrock could be oxidized to Cr(VI) by adding H2O2. The results of Test 4 showed increased Cr(VI) concentrations in the leachate (Figure 3.1.14) relative to Test 3 (DI water and bedrock) concentrations. The initial high Cr(VI) concentration was followed by a decrease that stabilized

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Cr(VI) (mg/kg)

1

0

0.3

1 Hour

28 Days

Quick Oxidation Test (mg/kg)

0.6

2

Cr(VI)

Quick Oxidation Test

0

Sampling Interval

Cr(VI) (µg/L)

FIGURE 3.1.15 Test 4 Cr(VI) and quick oxidation test results.

6 5 4 3 2 1 0

Test 3 Test 5

1 hour

1 day

14 days

28 days

Sampling Interval FIGURE 3.1.16 Tests 3 and 5 leachate Cr(VI) concentrations.

at approximately 0.140 mg/L. These concentrations were much higher than the results of Test 3 (Figure 3.1.13), indicating that more Cr(VI) may be generated if suitable oxidizing agents are available. Cr(VI) concentrations and the quick oxidation test results also decreased in the leached bedrock (Figure 3.1.15). It has been previously noted that the addition of H2O2 can act as an oxidant or reductant under different geochemical conditions (James, 1999). 3.1.4.6.3.5 Test 5: DI Water + Bedrock + Manganese Dioxide — Test 5 consisted of MnO2 added to a mixture of DI water and bedrock. The objective of Test 5 was to evaluate if Cr(III) in the bedrock can be oxidized to Cr(VI) by MnO2, since MnO2 is known to oxidize Cr(III) to Cr(VI) (Fendorf and Zasoski, 1992). The test results (Figure 3.1.16) did not indicate a significant increase in leachate Cr(VI) concentrations compared to Test 3 (DI water and bedrock). However, the Test 5 Cr(VI) concentrations did not decrease over the last sampling intervals, as was seen in Test 3. A summary of dissolved metals [Cr(VI), Cr, and Mn] for this leaching test are presented in Table 3.1.16.

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Naturally Occurring Chromium(VI) in Groundwater TABLE 3.1.16 Test 5—dissolved Metals in Leachate Analytical Parameter Cr (mg/L) Cr(VI) (mg/L) Mn (mg/L)

1h

4h

0.018 0.0049 <0.015

0.0069 0.0046 <0.015

Sampling Interval 24 h 7d 14 d 0.00525 0.0051 <0.015

0.0082 0.00465 <0.015

0.0074 0.00515 <0.015

21 d

28 d

0.0204 0.057 <0.015

0.0067 0.0052 <0.015

14000

Mn (mg/kg)

12000 10000 8000 6000 4000 2000 0 1 hour

28 days

Sampling Interval FIGURE 3.1.17 Test 5 easily reducible Mn in leached bedrock.

It was expected that the dissolved Mn concentration in the leachate would have increased with the addition of MnO2 because Mn oxides are reduced to Mn(II) as Cr(III) is oxidized to Cr(VI). However, the dissolved Mn(II) concentration in the leachate remained below the reporting concentration limit throughout the 28-day test period (Table 3.16). The concentration of easily reducible Mn in the leached bedrock increased (Figure 3.1.17), but Cr(VI) and dissolved Mn concentrations in the leachate did not. This indicates that the easily reducible Mn test overestimates the amount of Mn oxides readily available for oxidizing Cr(III) to Cr(VI). This test could measure other forms of Mn that are insoluble but do not reduce to Mn(II) in the presence of Cr(III). In addition, a laboratory reagent grade form of MnO2, which is crystalline and not very soluble, was used for this test. In retrospect, a freshly precipitated form of MnO2 may have been more conducive for the oxidation of Cr(III) to Cr(VI). 3.1.4.6.3.6 Test 6: DI Water + Bedrock + Chromium Chloride — Test 6 consisted of adding soluble Cr(III) [in the form of CrCl3] to a mixture of DI water and bedrock. The objective of Test 6 was to evaluate if the bedrock could oxidize soluble Cr(III) to Cr(VI), similar to the quick oxidation test. This test

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Chromium(VI) Handbook TABLE 3.1.17 Test 6 Crcl3 Solution Dissolved Cr (mg/L) Cr(VI) (mg/L) pH

87.200 0.222 3.6

TABLE 3.1.18 Test 6—Cr(VI) in Leachate Analytical Parameter Cr(VI) (mg/L) a

1h

4h

1900a

0.137

Sampling Interval 24 h 7d 14 d

21 d

28 d

0.091

0.180

0.138

0.154

0.257

Qualified data; potentially biased.

is valuable in assessing not only the possible oxidation of Cr(III) to Cr(VI) but also the stability of Cr(VI). The CrCl3 solution that was added in this test contained some Cr(VI) (Table 3.1.17), which may have contributed to the Cr(VI) concentration measured in the leachate as described below. The 1 h sampling interval Cr(VI) data were qualified as potentially biased owing to the discrepancy between the duplicate samples. This data point may not truly represent an increased Cr(VI) concentration. Since the Cr(VI) concentrations from the remaining six sampling intervals (Table 3.1.18) were less than or very similar to the Cr(VI) concentration in the CrCl3 solution, it is inconclusive as to whether the Cr(VI) in the leachate was oxidized from Cr(III) or was an artifact of the Cr(VI) concentration of the CrCl3 solution. The leachate pH values for Test 6 were lower than the other leachate tests, most likely due to the addition of the CrCl3 solution. The lower pH could have caused metals (e.g., Mn) to become more soluble, explaining the initial increase in dissolved Mn (Figure 3.1.18) compared to Mn concentrations in Test 3 (DI water and bedrock). The leached bedrock lost some of its ability to oxidize soluble Cr(III) (e.g., quick oxidation test results) and showed decreased Cr(VI) concentrations over the 28-day testing period (Figure 3.1.19). 3.1.4.6.3.7 Data Quality — The analytical results were reviewed and validated according to EPA Functional Guidelines (USEPA, 1994a, 1994b) and the Chemical Data Acquisition Plan/Field Sampling Plan (Montgomery Watson, 1994). All analytical data met data quality objectives and are considered usable. The leaching tests were performed in duplicate (two samples per sampling interval per test condition). Relative percent differences (RPDs) between the sample and its associated duplicate outside the acceptance limit (40%) were

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Naturally Occurring Chromium(VI) in Groundwater 600

Mn (µg/L)

500 400 300 200 100 0 1

24

14

28

hour

hours

days

days

Sampling Interval

20

1.2

15

0.9

10

0.6

5

0

0.3

1 Hour

28 Days

Quick Oxidation Test (mg/kg)

Cr(VI) (mg/kg)

FIGURE 3.1.18 Test 6 dissolved Mn in leachate.

Cr(VI)

Quick OxidationTest

0

Sampling Interval FIGURE 3.1.19 Test 6 Cr(VI) and quick oxidation test results.

qualified to indicate a potential bias. Table 3.1.19 lists the percentage of samples considered comparable with their associate duplicates. 3.1.4.6.4 Discussion of Results This section discusses the groundwater analytical results in the Presidio upland areas and associated geochemical trends.

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Chromium(VI) Handbook TABLE 3.1.19 Sample and Duplicate Comparison Analytical Parameters

Number of Analyses

Number of RPDs <40%

Percent Acceptable

84 84 84 84 84 84 84 84 20 20 20

79 84 84 78 84 79 84 84 18 20 19

94 100 100 93 100 94 100 100 90 100 95

Dissolved Cr Dissolved Fe Dissolved Mg Dissolved Mn Dissolved Ni Cr(VI) pH Eh Cr(VI) by alkaline digestion Easily reducible Mn Quick oxidation test

+800 UBR03GW02 (0.64) Cr(VI) HWGW05 (<0.5) 1349MW02 (43) LF02GW04 (0.72) 1349MW03 (69) HWGW01 (122) UBR01GW01 (65.4)

+600

+400 Eh (mV)

HWGW04 (7.4) UBR03GW01 (<0.5)

UBR02GW01 (52.1)

LF07GW02 (<0.5) +200 LF02GW10 (<0.5) UBR02GW02 (98.3)

0

937GW12 (<0.5) Cr(III)

−200 6

7

8

9 pH

10

11

12

FIGURE 3.1.20 Eh-pH Diagram including Cr(VI) concentrations in groundwater.

3.1.4.6.4.1 Groundwater Analytical Results in Upland Areas — The groundwater analytical results from the new background wells in Tennessee Hollow and other existing monitoring wells screened in serpentinite at Presidio RI sites are plotted on the Eh-pH diagram in Figure 3.1.20 using the field

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Eh (i.e., Eh = ORP measurement + 200 mV as per the YSI instruction manual) and pH measurements. Eh-pH diagrams are used to illustrate geochemical conditions, namely the chemical equilibrium and speciation of multivalent elements (e.g., Cr) under a range of pH and Eh conditions. The methods used to construct the Eh-pH diagrams are described in the TM (Montgomery Watson, 1999b). The concentration of Cr(VI) detected in each of the wells is shown in parenthesis next to the well identification number. Samples collected from the new background wells screened in serpentinite at locations UBR01 and UBR02 are near or in the Cr(VI) stability field (shown in yellow), indicating that Cr(VI) is stable in the high pH and Eh environments present at these locations. The pH values of the background wells from locations UBR01 and UBR02 were significantly higher than the neutral (pH 7) values typical of previous investigations at the Presidio. It appears that the high pH in groundwater samples from the three upland wells (e.g., pH 8.5 to 9.3) is associated with the serpentinite bedrock in the upland areas, in contrast to downgradient areas overlain by Quaternary sedimentary units. This pH data are consistent with high pH values (up to 11.8) observed in other serpentinite terrains (Kruckeberg, 1985). Samples collected from the UBR03 wells screened in Colma Formation sediments fall within the same general pH and Eh range typical of most other Presidio upland monitoring wells, including those screened in serpentinite, which have Cr(VI) concentrations from <0.0005 mg/L to 0.122 mg/L (Table 3.1.20). This suggests that pH and Eh alone are not the only factors in producing conditions conducive to Cr(VI) generation. Rather, there are other constituents and chemical reactions in both the groundwater and the bedrock that are controlling the valence state and concentration of Cr. Dissolution/ precipitation reactions, availability and form of oxidants and reductants, and the buffering capacity of the bedrock also affect the concentration and oxidation state of Cr in the groundwater.

TABLE 3.1.20 Cr(VI) Concentration in Monitoring Wells Screened in Serpentinite Monitoring Well ID UBR01GW01 UBR02GW01 UBR02GW02 LF02GW02 LF02GW04 HWGW01 HWGW04 HWGW05 1349MW02 1349MW03

Cr(VI) Concentration (mg/L) 0.0654 0.0521 0.0983 <0.0005 0.00072 0.122 0.0074 <0.0005 0.043 0.069

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VIEW TO SOUTH

Inspiration Point Serpentinite Barrens

Fracture Zones

Notes: Concentration of Cr(VI) by ion chromatography in µg/L. LF01 and LF02 results from January 1998. UBR results from March 22, 1998. Not To Scale

MONTGOMERY WATSON PRESIDIO OF SAN FRANCISCO UPLAND AREA CONCEPTUAL MODEL AND Cr(VI) DISTRIBUTION

FIGURE 3.1.21 Upland area conceptual model and Cr(VI) distribution.

The groundwater sample results for Cr(VI) from the five new background wells are shown in Figure 3.1.21. All of the samples collected from the new background wells screened in serpentinite (e.g., UBR01 and UBR02 wells) had detectable concentrations of Cr(VI), indicating that Cr(VI) is apparently originating from the serpentinite bedrock. This is further supported by the fact that Cr(VI) has been detected in several other monitoring wells screened in the serpentinite bedrock at the Presidio (Table 3.1.20). The two monitoring wells in which Cr(VI) was not detected (LF02GW02 and HWGW05) had detections of dissolved iron. Since dissolved iron [Fe(II)] is a known reductant of Cr(VI), it would be expected that Cr(VI) would not be present in the groundwater. The results also indicate a strong correlation (R2 = 0.98) between the dissolved Cr and Cr(VI) concentrations in the groundwater from wells screened in serpentinite. This strong correlation between Cr(VI) and dissolved Cr demonstrates that virtually all of the chromium in groundwater from these wells is in the hexavalent state. 3.1.4.6.4.2 Geochemical Trends in Tennessee Hollow — Several trends are apparent when viewing Cr(VI), Eh, and pH in a regional perspective. Groundwater analytical results from the new background wells screened in

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serpentinite have higher Cr(VI) concentrations than those found downgradient in the Fill Site 1 and Landfill 2 areas (Figure 3.1.21). The groundwater flows from the upland areas towards Crissy Field with generally decreasing Cr(VI) concentrations (Figure 3.1.3). This pattern is consistent with Cr(VI) being leached and/or oxidized from the serpentinite bedrock, which remains stable in the upland areas due to the highly oxidizing environment (i.e., high pH and Eh). As groundwater flows north through Crissy Field toward the San Francisco Bay, it encounters the organic-rich, reducing sediments (including bay muds) which provide conditions suitable for reducing Cr(VI) to Cr(III) [i.e., low dissolved oxygen and the presence of dissolved Fe(II)] (Abu-Saba and Flegal, 1996). There is an overall northward decrease in Cr(VI) concentrations and pH values from the new upland bedrock wells (UBR01 and UBR02) through Fill Site 1 and Landfill 2, Tennessee Hollow (TH), the Building 215 area, and finally to Crissy Field. Eh measurements typically vary more at the Presidio because of the variability of oxidation/reduction couples, and do not show as clear a trend as pH. However, low dissolved oxygen and high dissolved iron associated with the organic-rich bay muds beneath Crissy Field indicate conditions unfavorable for the occurrence of Cr(VI) (Montgomery Watson, 1998). 3.1.4.6.5 Conclusions The Presidio investigation developed and assessed multiple lines of evidence to determine if Cr(VI) in the Presidio’s groundwater could be attributed to natural sources. Bedrock and groundwater samples were collected at three background locations and used in a laboratory leaching study for this investigation. The three undisturbed drilling locations near the head of the Tennessee Hollow watershed were selected by a stakeholder committee that included technical experts and other representatives of the Army, USACE, Presidio Trust, NPS, DTSC, USEPA, and the RAB. The bedrock and groundwater samples were analyzed to evaluate background bedrock chemistry and groundwater geochemistry. The leaching tests assessed whether Cr(VI) could be leached from the serpentinite bedrock or generated through the oxidation of Cr(III). The results of the bedrock, groundwater, and leaching test analyses indicate the following: • Cr(VI) is present in trace amounts in the natural geologic environment (i.e., serpentine bedrock). • Cr(VI) concentrations in groundwater from the new monitoring wells screened in the serpentinite bedrock were higher than existing downgradient wells. • Cr(VI) is generated or leached from the serpentinite bedrock by various complex chemical reactions. These results support the conclusion that the serpentinite bedrock is a source of Cr(VI) detected in upland groundwaters. The elevated pH and

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positive Eh of the groundwater from the new background wells screened in serpentinite bedrock indicate that geochemical conditions are favorable for the presence of Cr(VI) in groundwater. Cr(VI) in groundwater from wells downgradient in Tennessee Hollow indicates that it persists in the oxidized conditions of the upland water table aquifer. Geochemical data demonstrate a change from oxidizing conditions in the upland areas to reducing conditions further downgradient in the Crissy Field area. The groundwater geochemistry of the Presidio upland areas favors Cr(VI) stability, whereas the groundwater geochemistry in the Crissy Field area favors Cr(VI) immobilization and/or reduction of Cr(VI) to Cr(III). The results of this investigation also have potential implications for future groundwater use at the Presidio and similar environments. Any evaluation of groundwater use or Cr(VI) mitigation must consider that there is a continual natural source of Cr(VI) from the serpentinite bedrock and serpentinitederived soils and sediment, so traditional remediation is inappropriate. This investigation culminated in the acknowledgment by the California Department of Toxic Substances Control (DTSC) that “it appears that Cr(VI) occurs naturally in serpentinite bedrock and in water from some monitoring wells, including background locations screened in that bedrock” (DTSC, 2000). Coincidentally, the Presidio Trust assumed responsibility for environmental remediation of the Presidio from the U.S. Army at the conclusion of the study.

Acknowledgments The technical memorandum “Hexavalent Chromium in Serpentinite Bedrock and Groundwater in Upland Areas” (Montgomery Watson, 1999b) was prepared by Montgomery Watson (now MWH) under the direction of the Presidio of San Francisco Base Realignment and Closure (BRAC) Environmental Coordinator, David M. Wilkins. The following project staff with Montgomery Watson (unless otherwise noted) provided technical leadership, review, and other contributions: Bruce Handel (technical manager, USACE); Roger C. Henderson, P.E. (technical lead, USACE); Jessica Hardy (technical reviewer, USACE); Melih Ozbilgin, Ph.D. (program manager); Martin Steinpress, R.G., C.H.G. (project manager and hydrogeologist); Marla L. Miller (project chemist); Leslie R. Typrin, M.S. (project environmental scientist); Technical Advisory Committee comprised Gregory E. Little, R.G., John S. Porcella, P.E., Jim V. Rouse, R.G., and William R. Mabey, Ph.D; Laboratory Leach Tests were conducted at PRIMA Environmental (Sacramento, CA).

Bibliography Abu-Saba, K.E. and Flegal, R., 1996, Chromium in the San Francisco Bay Estuary: A Study of Cycling, Speciation, and Anthropogenic Inputs, Technical Completion Report, UCAL-WRC-W-833, University of California Resources Center, Berkeley, 66 p.

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Ball, J.W., 2002, Occurrence of Hexavalent Chromium in Ground Water in the Western Part of the Mojave Desert, California, Geological Society of America Denver Annual Meeting, Paper No. 197–2. Bartlett, R.J., 1991, Chromium cycling in soils and water: links, gaps, and methods, Environ. Health Perspect., 92, 17–24. Bartlett, R. and James, B., 1979, Behavior of chromium in soils: III oxidation, J. Environ. Qual., 8, 1, 31–35. Calder, L.M., 1988, Chromium contamination in groundwater, in Nriogen, J.O. and Nieboel, E., Eds., Chromium in the Natural and Human Environments, Vol. 20, John Wiley and Sons, New York, pp. 215–229. Chung, J., Burau, R.G., and Zasoski, R.J., 2001, Chromate generation by chromate depleted subsurface materials, Water, Air, Soil Pollut., 128, 407–417. Dames and Moore, 1997a, Final Remedial Investigation Report, Presidio Main Installation, Presidio of San Francisco, California, Report prepared for the U.S. Army Environmental Center (USAEC). Dames and Moore, 1997b, Final Feasibility Study Report, Presidio Main Installation, Presidio of San Francisco, California, Report prepared for USAEC. Department of Toxic Substances Control (DTSC), 2000, Letter from Henry Chui, P.E., Office of Military Facilities, to Ms. Sharron Reackhof, Presidio Trust, 2 p. Earth Tech, Inc. (Earth Tech), 1995, Base Realignment and Closure (BRAC) Cleanup Plan, Presidio of San Francisco, California, Report prepared for USAEC, version 2 (final). Eary, L.E. and Rai, P., 1987, Kinetics of chromium(III) oxidation to chromium(VI) by reaction with manganese and dioxides, Environ. Sci. Technol., American Chemical Society 21, 1187–1193. Electric Power Research Institute (EPRI), 1988, Chromium Reactions in Geologic Materials, Report prepared by Battelle, Pacific Northwest Laboratories for EPRI, Palo Alto, California, EPRI EA–5741, Interim Report. Eriksen, G.E., 1983, The Chilean nitrate deposits, Am. Sci., 71, 366–374. Faust, S.D. and Aly, M.A., 1981, Chemistry of Natural Waters, Ann Arbor Science, Ann Arbor, MI. Fendorf, S.E. and Zasoski, R.J., 1992, Chromium(III) oxidation by δ-MnO2, part 1, characterization, Environ. Sci. Technol., American Chemical Society 26, 1, 79–85. Garrells, R.M. and Christ, C.L., 1965, Solutions, Minerals, and Equilibria, Harper, New York. Godgul, G. and Sahu, K.C., 1995, Chromium contamination from chromite mine, Environ. Geol., Springer Verlag 25, 4, 251–257. Groundwater Resources Association of California, 2001, Symposium on Hexavalent Chromium in Groundwater, Glendale, CA, http://www.grac.org/hex_binders.html. Henrie, T.D., Simion, V., Auckly, C., and Weber, J.V., 2002, Chromium 6+ Concentrations in Drinking Water Wells and the Effects of Chlorination, Poster Presentation, Spring 2002 Conference of the CA-NV American Water Works Association section. James, B. R., 1996, The challenge of remediating chromium-contaminated soil, Environ. Sci. Technol., American Chemical Society 30, 6, 248–251. James, Bruce. R., 1999, of University of Maryland, personal communication. Kabata-Pendias, A. and Pendias, H., 1984, Trace Elements in Soils and Plants, 2nd ed., CRC Press, Boca Raton, FL. Kruckeberg, A.R., 1985, California Serpentines: Flora, Vegetation, Geology, Soils, and Management Problems, University of California Press, Berkeley. McLean, J.E. and Bledsoe, B.E., 1992, Behavior of Metals in Soil, Groundwater Issue, U.S. Environmental Protection Agency (USEPA), Robert S. Kerr, Environmental Research Laboratory, EPA/540/S-92/018, Ada, OK, 25 p.

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Montgomery Watson, 1994, Chemical Data Acquisition Plan/Field Sampling Plan (CDAP/FSP), Investigation of Various Underground Storage Tanks Sites, Presidio of San Francisco, California, Report prepared for the USACE, Sacramento District, Sacramento, CA. Montgomery Watson, 1995, Fuel Products Action Level Development Report (FPALDR), Presidio of San Francisco, California, Report prepared for the USACE, Sacramento District, Sacramento, CA. Montgomery Watson, 1996, Draft Basewide Groundwater Monitoring Plan (BGMP), Presidio of San Francisco, California, Report prepared for the USACE, Sacramento District, Sacramento, CA. Montgomery Watson, 1998, Technical Memorandum: Hexavalent Chromium in Groundwater, Presidio of San Francisco, California, Report prepared for the USACE, Sacramento District, Sacramento, CA. Montgomery Watson, 1999a, Final Letter Work Plan for Hexavalent Chromium Investigation in Upland Areas, Presidio of San Francisco, California, Report prepared for the USACE, Sacramento District, Sacramento, CA. Montgomery Watson, 1999b, Technical Memorandum: Hexavalent Chromium in Serpentinite Bedrock and Groundwater in Upland Areas, Report prepared for the USACE, Sacramento District, Sacramento, CA. Metropolitan Water District of Southern California (MWD) and Bureau of Land Management, 2001, Cadiz Groundwater Storage and Dry-Year Supply Program, Final EIR/EIS response to Comments. Nagel, R., 1999, personal communication. Ridley, M., 2002, personal communication. Robertson, F.N., 1975, Hexavalent chromium in the groundwater in Paradise Valley, Arizona, Groundwater, 13, 516–527. Robertson, F.N., 1991, Geochemistry of Grand Water in Alluvial Basins of Arizona and Adjacent Parts of Nevada, New Mexico, and California, U.S. Geological Survey Professional Paper 1406-C, 89 p. Roscoe Moss Company, 2003, A guide to water well casing and screen selection, http://www.roscoemoss.com. Schlocker, J., 1974, Geology of the San Francisco North Quadrangle, California, U.S. Geological Survey Professional Paper 782, Washington, DC, 109 p. Steinpress, M.G. and Ward, A.C., 2001, The scientific process and Hollywood: the case of hexavalent chromium in groundwater, guest editorial in Ground Water (AGWSE Journal), 39, 3, 321 p. Steinpress, M.G., Miller, M., Ozbilgin, M., Henderson, R., and Handel, B., 1999, Hydrostratigraphic controls on groundwater geochemistry and remediation at the Presidio of San Francisco, Cordilleran Section Centennial Meeting, Berkeley, CA. June 2–4, Geological Society of America, Abstract with Programs, pp. A to 98. Steinpress, M.G., 1998, Transformation of the Presidio of San Francisco: hydrogeology and environmental restoration, in Jacobs, J.A. and Bertucci, P.F., Eds., Hydrogeology of the Northern San Francisco Bay Area Field Trip Guidebook, Groundwater Resources Association of California, Seventh Annual Meeting. Steinpress, M.G., Miller, M., Little, G., Ozbilgin, M., Mabey, R.V., Henderson, R., Handel, B., and Wilkins, D., 1998, Hexavalent chromium in groundwater at the Presidio of San Francisco: anthropogenic or naturally occurring? Seventh Annual Meeting on California Groundwater Effective and Efficient Usage for the Year 2000 and Beyond, October 22 and 23, 1998, California Groundwater Resources Association, Walnut Creek, 23 p.

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Steinpress, M.G., 1997, Geology and hydrogeology of the Presidio, in Barnes, N.L., Ed., Hydrogeology and Environmental Restoration at the Presidio of San Francisco, Association of Engineering Geologists San Francisco Section Spring Field Trip. Torres, R.A., 1995, Removing Hexavalent Chromium from Subsurface Waters with Anion-Exchange Resin, Lawrence Livermore National Laboratory, UCRL-ID114369, 12 p. Truesdall, A.H. and Jones, B.F., 1969, Ion association in natural brines, Chem. Geol., 4, 51–62. U.S. Environmental Protection Agency (USEPA), 1994a, Contract Laboratory Program (CLP) National Functional Guidelines for Organic Data Review, EPA 540/R-94/012. U.S. Environmental Protection Agency (USEPA), 1994b, Contract Laboratory Program (CLP) National Guidelines for Inorganic Data Review, EPA 540/R-94/012. U.S. Environmental Protection Agency (USEPA), 1996, Analytical Results—Hexavalent Chromium Results for Samples from Presidio Army Base, San Francisco, California, National Enforcement Investigations Center (NEIC) Project Q53. U.S. Environmental Protection Agency (USEPA), 1997, Analytical Results—Elemental Constituent Results for Soil Samples from Presidio Army Base, San Francisco, California, National Enforcement Investigations Center (NEIC) Project Q53. Wahrhaftig, C., 1989, Geology of San Francisco and vicinity, American Geophysical Union Field Trip Guidebook, T105, 69 p.

3.2

Cr(VI) Concentrations in Drinking Water Wells and the Effects of Chlorination

Tarrah D. Henrie, Veronica Simion, Chet Auckly, and Jeannette V. Weber ABSTRACT The California Water Service Company (Cal Water) conducted a one-year study on the occurrence of chromium(VI) [Cr(VI)] in groundwater and the effects of chlorination on speciation. Owing to recent health concerns raised by the media and the public, the California Department of Health Services instituted a statewide Cr(VI) study. The State requires monitoring Cr(VI) concentrations in the water from wells, where total chromium (Cr) concentrations have previously been above 0.0025 mg/L. Cr(VI) was found in the northern portion of the Central Valley and in the Bay Area. The majority of total Cr was Cr(VI) and not chromium(III) [Cr(III)] as previously thought by public health professionals. Cr(III) is much less soluble than the chromate anion (CrO42–), so this finding is not surprising. There was little difference in Cr(VI) concentration in chlorinated and unchlorinated water. It was not confirmed whether the Cr was from anthropogenic sources or naturally occurring.

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138 3.2.1

Chromium(VI) Handbook Introduction

The California Water Service Company owns and operates 25 districts and provides drinking water in over 70 communities. Many of these districts use groundwater only, others use surface water only, and some are served by a combination of ground water and surface water. During the first year of this study, the districts were prioritized according to Cr concentration and only sources with more than 0.0025 mg/L of Cr were sampled during 2001. Over 500 samples were collected from more than 80 groundwater wells throughout California. Total Cr is made up of Cr in primarily two oxidation states: Cr(III) and Cr(VI). While most Cr(III) compounds are insoluble at pH 5 and Eh>0.8 V, and are of low toxicity, Cr(VI) is more soluble and carcinogenic when inhaled. Cr(VI) has received much media attention, because the California Public Health Goal (PHG, 0.0002 mg/L) is lower than the California maximum contaminant level (MCL, 0.05 mg/L). The PHG is set by the California Environmental Protection Agency, which is a nonenforceable concentration below which there is no expected health effect. The MCL is the enforceable concentration limit for a contaminant 3.2.2

Methods and Materials

Samples were collected from 76 wells before and after chlorination. Two rounds of sampling were performed with a gap of six months. Until 2001, the Cr concentration detection limit for reporting (DLR) was 0.001 mg/L. Because our internal detection limit had in the past been as low as 0.001 mg/L, we were able to use these data to classify the wells as less than 0.0025 mg/L or greater than 0.002 mg/L. Total chromium was analyzed by Cal Water’s in-house certified laboratory in San Jose, California, by EPA method 200.8. BSK Analytical Laboratory in Fresno, California, analyzed Cr(VI) by EPA method 218.6. In order to observe the 24 h hold-time for Cr(VI), the samples were collected after 11:00 a.m. and shipped with blue ice, overnight, to BSK. The samples were analyzed in the morning when received. 3.2.3

Results and Discussion

Table 3.2.1 lists the districts that receive groundwater along with the number of active wells and the range of total Cr concentration. The DLR for the Cr data shown is 0.010 mg/L. Based on our lower internal detection limit, wells were classified as below a concentration of 0.0025 mg/L or above it. Bakersfield, King City, and Oroville (all California) did not have any wells that contained more than 0.0025 mg/L of total Cr, and thus were not sampled during 2001. In other districts more than 50% of the wells had detectable Cr [Dixon, Willows, Livermore, and South San Francisco (all California)]. The results from all of the districts were grouped in order to draw meaningful conclusions on a statewide basis. Figure 3.2.1 shows a linear correlation

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Naturally Occurring Chromium(VI) in Groundwater

35 30

Cr(VI) (µg/L)

25 20 15 10 5 0 0

5

10

15

20

25

30

35

Total Cr (µg/L)

Total Cr versus Cr(VI) y = 0.818x – 0.90 r2 = 0.83 95% Confidence Interval

FIGURE 3.2.1 Total Cr versus Cr(VI) in 12 California communities.

between total Cr and Cr(VI). Although the correlation coefficient is only 0.83, the graph does demonstrate that the concentration of Cr(VI) can be reasonably estimated from the total chromium concentration. Note that the slope of the line is 0.818, which indicates a higher proportion of Cr(VI) than previously thought. The amount of Cr(VI) ranged between no detection up to 100%. Based on a single investigation, in 1999, the Office of Environmental Health and Hazard Assessment (OEHHA) estimated that Cr(VI) comprised about 7% of the total Cr (DHS, 2001). Chromium(III) is not very soluble under normal groundwater conditions, because insoluble solid Cr(OH)3 and Cr2O3 form even under slightly acidic conditions (Rai et al., 1987). In aerobic aquifers, with alkaline pH, Cr(VI) is more common (Evanko and Dzombak, 1997). Figure 3.2.2 shows Cr concentrations in chlorinated and unchlorinated water. A linear regression fits the data well and yields a correlation coefficient of 0.95. The slope of the line is 0.99, demonstrating that Cr(VI) concentrations are essentially unchanged by chlorination. Though there was no expectation that total Cr concentration would change with chlorination, it was plotted for reference, and is similar to the Cr(VI) data. The oxidation state of chromium can be changed through several redox reactions. Cr(VI) can be transformed under anaerobic conditions to Cr(III) by reaction with iron(II) (Fe2+), sulfide (S2–), and organic matter (Batchelor et al., 1998). The reduction

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140

Total Cr (µg/L) in chlorinated water

Chromium(VI) Handbook 30 25 20 15 10 5 0 0

10 20 30 Chromium (µg/L) in unchlorinated water

Total Cr Cr(VI)

FIGURE 3.2.2 Chromium in chlorinated and unchlorinated water in 12 California communities.

reaction with Fe(II) is fast in water, but not quite as fast as in soil environments (Batchelor et al.,1998). Cr(III) can be converted to Cr(VI) by reaction with Mn oxides and hydroxides (Bartlett and James, 1979). Cr(III) can also be oxidized to Cr(VI) by O2. The oxidation reaction of Cr(III) by O2, shown in Equation 3.2.1, is very slow (Kent, 2001). This reaction is pH dependent, forming Cr(III) at low pH. 4Cr3+ + 3O2 + 10H2O ↔ 4CrO42− + 20H+

(3.2.1)

The Department of Health Services required that the samples be taken from each source twice, with a gap of six months. The data would establish whether or not Cr(VI) concentrations vary seasonally. Figure 3.2.3 shows data from the first quarter plotted against data from the third quarter at the same location. Interestingly, Cr(VI) concentrations do not appear to vary (the slope is 1.02), however, total Cr concentrations may vary seasonally; they were slightly higher in the third quarter. Chromium can be naturally occurring or it can be the result of anthropogenic activities. High concentrations of naturally occurring Cr in groundwater have been found near Baltimore, Maryland and are probably the result of serpentine parent material, which often contains some Cr. Serpentine [Mg3Si2O5(OH)4] is the state mineral of California and can be found in the Coast Range as well as in the Sierra Nevada (Alt and Hyndman, 1995).

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Naturally Occurring Chromium(VI) in Groundwater 35

Total Cr (µg/L) Third Quarter

30 25 20 15 10 5 0 0

5

10 15 20 Cr (µg/L) First Quarter

25

30

Total Cr in unchlorinated water Cr(VI) in unchlorinated water Total Cr y = 1.24x – 0.026 r2 = 0.94 Cr(VI) y = 1.02x – 0.02 r2 = 0.95

FIGURE 3.2.3 Chromium in the first and third quarter in 12 California communities.

Bibliography Alt, D.D. and Hyndman, D.W., 1995, Roadside Geology of Northern California, Mountain Press, Missoula, MT. Batchelor, B., Schlautman, M., Hwang, I., and Wang, R., 1998, Kinetics of Chromium(VI) Reduction by Ferrous Iron, Amarillo National Resource Center for Plutonium Report ANRCP-1998-13. Bartlett, R. and James, B., 1979, Behavior of chromium in soils: III oxidation, J. Environ. Qual., 8, 31–35. California Department of Health Services (DHS), 2001, Hexavalent chromium [chromium-6] in drinking water, http://www.dhs.ca.gov/org/ps/ddwem/ chemicals/chromium6/cr+6index.htm. Evanko, C.R. and Dzombak, D.A., 1997, Remediation of Metals—Contaminated Soils and Groundwater. Groundwater Remediation Technologies Analysis Center Technology Evaluation Report TE-97-01. Kent, D.B., 2001, Processes Influencing the Distribution, Fate, and Transport of Chromium in Ground Water, Groundwater Resources Association of California Hexavalent Chromium in Groundwater Seminar. Rai, D., Sass, B.M., and Moore D.A., 1987, Chromium(III) hydrolysis constants and solubility of chromium(III) hydroxide, Inorg. Chem., 26, 345–349.

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4 Sources of Chromium Contamination in Soil and Groundwater

Stephen M. Testa

CONTENTS 4.1 Introduction ............................................................................................... 143 4.1.1 The Chromium Cycle .................................................................. 147 4.1.1.1 Natural Occurrence of Chromium in Soil and Rock.......................................................................... 150 4.1.1.2 Natural Occurrence of Chromium in Surface and Groundwater .......................................................... 152 4.1.1.3 Natural Sources of Chromium in the Atmosphere ......................................................... 152 4.1.2 Anthropogenic Sources of Chromium...................................... 152 4.1.2.1 Anthropogenic Chromium in Soil .............................. 157 4.1.2.2 Agricultural Materials................................................... 158 4.1.2.3 Sewage Sludges.............................................................. 159 4.1.2.4 Coal and Fly Ash Disposal........................................... 159 4.1.2.5 Mining and Smelter Wastes ......................................... 160 4.1.2.6 Roadside Soils ................................................................ 160 4.1.2.7 Anthropogenic Chromium in Water........................... 160 4.1.2.8 Anthropogenic Chromium in the Atmosphere ........ 161 Bibliography ........................................................................................ 162

4.1

Introduction

Chromium (Cr) occurs naturally at high concentration in ultramafic rocks, and is a common contaminant in surface water and groundwater (Bartlett and James, 1988). The ubiquitous occurrence of Cr in surface water and groundwater reflects 1-5667-0608-4/05/$0.00+$1.50 © 2005 by CRC Press LLC

143

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Chromium(VI) Handbook TABLE 4.1.1 Uses of Chromium Form

Uses

Cr(O)

Stainless steel production Alloy production Metal and alloy manufacturing

Cr(III)

Metal and alloy manufacturing Brick lining Chrome plating Leather tanning Textiles Copying machine toner

Cr(VI)

Chrome plating Leather tanning Textiles Copying machine toner

its use as an important industrial metal and in a variety of diverse products and processes (Table 4.1.1). Characterized as a lustrous, silver-gray metal, Cr rarely occurs in the Earth’s crust as the element (or metal) but almost only in compound form or as ions in water. The chief commercial source of Cr is chromite (FeCr2O4), with Cr being mined as a primary product. The main uses for Cr are metallurgical (67%), refractories (18%), and chemical (15%). Metallurgical uses include a wide range of alloys such as iron (Fe), nickel (Ni), and cobalt (Co). The more important alloys and approximate Cr concentration in the most important alloys are shown in Table 4.1.2. More specialized Cr alloys include stellite using tungsten (W), molybdenum (Mo), and Co yielding high-speed tool steel. In 2002, the U.S. consumed about 14% of the world chromite ore production, reflecting about $317 million in material value. This included various forms of imported materials such as chromite ore, Cr chemicals, Cr ferroalloys, and TABLE 4.1.2 Important Common Cr Alloys Alloy Low Cr steel Low Cr iron Medium Cr steel Stainless irons Stainless steel Super stainless steel Cr–Ni–Fe alloys Electrical resistance alloys Cr–Co alloys

Cr Concentration (%) 0.5–5 0.2–4 3–12 12–15 12–18 12–30 14–30 8–20 20–35

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Cr metal. Consumption of Cr ferroalloys, and metal was predominantly used for the production of stainless and heat-resistance steel and superalloys, respectively. Chromite ore is not mined in the U.S., Canada, or Mexico. Production in the western Hemisphere is only in Brazil and Cuba. Most of the Brazilian production is consumed there. Cuba’s production of Cr is small. The largest U.S. Cr resource is in the Stillwater Complex in Montana (Papp, 2003). About 95% of Cr resources are geographically concentrated in South Africa. Between 1998 and 2001, imported sources of chromite in descending order in total volume are derived from South Africa (50%), Kazakhstan (20%), Zimbabwe (9%), Turkey (7%), Russia (6%), and others (8%). South Africa accounts for more than 50% of the world production and has been the major supplier of chromite ore and ferrochromium to the western industrialized nations. World resources of Cr exceed 10.9 billion metric tons of shipping grade chromite. This includes shipping-grade chromite, sufficient to meet the Cr demand for centuries. Reserves and reserve bases are concentrated in Kazakhstan and Southern Africa. Thousands of Cr(III) compounds exhibit a wide range of colors, structures, and chemical properties. The physical and chemical properties of Cr are presented in Table 4.1.3. Some of the physical properties for some of the more important Cr compounds are listed in Table 4.1.4. However, Cr(VI) compounds are produced industrially essentially by heating Cr (III) compounds in the presence of mineral bases such as soda ash and atmospheric oxygen (O2). Cr is released to the environment primarily from electroplating and leather tanning operations, pigment manufacturing and applications, textile manufacturing, and disposal of Cr-containing wastes. Cr can enter the atmosphere as a result of fossil fuel burning, steel production, stainless steel welding, and

TABLE 4.1.3 Physical and Chemical Properties of Chromium Atomic number Atomic mass Atomic radius (pm) Main oxidation state(s) Ionic radius (pm) Electronegativity (Pauling) Density (g/cm3) Melting/boiling point (°C) Isotopes Acid/base of oxide State (at 27°C, 1 atm.) Metallic character Element group(s) Affinity

24 51.996 185 +2, +3, +6 87–94 (+2), 75.5 (+3), 55–69 (+4), 48.5–71 (+5), 40–58 (+6) 1.66 7.19 1,907/2,671 4 stable + 17 unstable Strong acid Solid metal Transition element, group 6B Lithophile

Source:

Lewis, 1992.

3.80 6.3 2.35

4.36 2.88

211.84 122.92

White, monoclinic crystals White, deliquescent crystals Greenish, shiny crystals Orange-yellow powder Red to orange monoclinic crystals 90.01 323.19 261.98

4.49 1.76 3.86 5.2 1.91

Density g/cm3

255.36 158.38 109.01 152.02 154.90

Molecular Mass

Heavy yellow powder Violet hexagonal crystals Dark green needles Green hexagonal crystals Dark red fuming liquid

Color

894 844 356.7

842 824

— 1,152 1,000 ~2,435 −96.5

Melting Point (°C)

— Decomposes —

— —

— Dissociates above 1,300 Sublimes at 1,100 ~3,000 115.7

Boiling Point (°C)

146

CrF2 Chromium(II) fluoride CAS 10049-10-2 PbCrO4b Lead(II) chromate CAS 7758-97-6 Na2Cr2O7 Sodium dichromate CAS 10588-01-9

BaCrO4 Barium chromate CAS 10294-40-3 CrCl3 Chromium(III) chloride CAS 10025-73-7 CrF3 Chromium(III) fluoride CAS 7788-97-8 Cr2O3 Chromium(III) oxide CAS 1308-38-9 CrO2Cl2 Chromium(VI) oxychloride CAS 14977-61-8 CrBr2 Chromium(II) bromide CAS 10049-25-9 CrCl2 Chromium(II) chloride CAS 10049-05-5

Molecular Formula, Substance Name, and CAS Registry No.

Properties of Certain Chromium Compounds

TABLE 4.1.4

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Cr manufacturing, whereas, emissions to water and soil can result from industrial processes such as electroplating, tanning, water treatment, or disposal of coal ash (USEPA 1995a and 1995b). The first instances of groundwater contamination were associated with Cr plating activities during World War II. The resulting groundwater plumes were reported to have migrated many kilometers over the past 50 years. (Rouse, 1997). Commonly associated with chrome plating, Cr(VI) in water solution is converted through electroplating (decorative chrome plating) to the bright metallic Cr coating observed on plastic or metal products such as car bumpers or shower heads and a host of consumer and industrial products. It is also used to apply a hard smooth surface to machine parts such as crankshafts and printer rollers. This process is known as “hard” Cr plating. Chromic acid (H2CrO4) anodizing is another industrial metal finishing process which incorporates Cr(VI). Substitutes for Cr are limited owing to cost, performance, or customer appeal (Crowson, 1982). For example, metals such as Ni and vanadium (V) can be substituted in alloy steels, whereas, zinc (Zn), cadmium (Cd), and Ni can be used in lieu of Cr for some industrial plating. Titanium has viability in chemical processing equipment. Magnesite and zircon have viability for some refractory products. For coating purposes, cadmium yellow is an alternative pigment. Technological potential includes new processes that would allow high-Fe Cr to be utilized in the production of high-carbon ferrochromium. Ore production is essentially highly concentrated by large state interests in Russia and Turkey. In South Africa, three companies control about 70% of the output, whereas, in the Republic of the Philippines, two companies control production (Crowson, 1982). There is a trend in the steel industry towards lower grade ferro chromium and production near mines. Although the industry as a whole is affected by problems related to the overall steel industry, strategic value may be of importance in the future.

4.1.1

The Chromium Cycle

Naturally occurring and anthropogenic Cr can occur in various environmental media including surface and groundwater, seawater, soil and sediments, rocks and air. Cr concentrations in various environmental media are presented in Table 4.1.5. The Cr Cycle (Figure 4.1.1) consists of the chemical processes associated with Cr which occur in the environment. This cycle is a fundamental part of the decision-making process in determining an appropriate treatment strategy. Elemental Cr, Cr(0), is rarely found in nature. It is produced principally from the mineral chromite. Cr can occur in any oxidation state from –2 to +6. The most common forms are elemental Cr, Cr(0), chromium(III), Cr(III), and chromium(VI), Cr(VI). Elemental Cr is chiefly used in the production of stainless steel and other alloys. Cr(III) is the most common form and is an essential human nutrient, promoting the action of insulin in the body tissues so that the body can use sugar protein. Also, Cr(III) in oxide form is used as brick lining for high temperature industrial furnaces in the manufacturing of metals, alloys,

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Chromium(VI) Handbook TABLE 4.1.5 Chromium Concentrations in the Earth’s Crusts and Rocks Material Bulk continental crust Upper continental crust Ultramafic rock Ocean ridge basalt Gabbro, basalt Granite, granodiorite Sandstone Greywacke Shale, schist Limestone Coal Typical minerals Chromite (FeCr2O4), crocoite (PbCrO4) Possible host minerals Pyroxenes, amphiboles, micas, garnets, spinels Mass (kg) in Continental crust Oceans Plants

Cr Concentration (mg/kg) 126/102/185 35/35 2,300 300 250 10 35 88 100 5 20

2.97 × 1018 3.97 × 1011 2.67 × 109

and compounds. Cr(VI) along with Cr(III) is used for chrome plating, manufacturing of dyes and pigments, leather tanning, textiles, toner for copying machines, and antifouling in cooling towers. In groundwater and soils Cr exists in two major oxidation states: the oxidized Cr(VI) and the less oxidized Cr(III). Whereas under common environmental conditions of pH and Eh, Cr(III) compounds are sparingly soluble in water, Cr(VI) compounds are quite soluble. The resulting Cr(VI) solutions are powerful oxidizing agents under acidic conditions, but less so under basic conditions. For example, H2CrO4 is often used in chemical labs to clean glassware by oxidizing organic residues. Thus, Cr(VI) is much more toxic and mobile in groundwater than the relatively immobile Cr(III). Depending on the concentration and acidity, Cr(VI) can exist either as chromate ion (CrO42–) or dichromate ion (Cr2O72–). The common dissolved Cr entities of Cr(VI) are the hydrogen chromate ion (HCrO4–), CrO42–, and Cr2O72– (McLean and Bledsoe, 1992; Palmer and Puls, 1994; Powell et al., 1995). Which entity will dominate in a particular environment depends upon the specific conditions, for example, pH, Eh, total concentration of Cr, and the overall aqueous chemistry. At pH>6.5, CrO42– dominates (Palmer and Puls, 1994). At pH < 6.5, HCrO4– dominates at low concentrations (<0.03 mol/L), but at concentrations greater than 0.001 mol/L, HCrO4– ions begin to change to Cr2O72– which becomes the dominant entity at concentrations greater than 0.03 mol/L (Palmer and Puls, 1994). HCrO4–

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Sources of Chromium Contamination in Soil and Groundwater

atmO 2

MnO2 Cr-citrate (soluble & mobile)

Mn

Cr(VI) Release From Facility

2+

Excess Cr(VI) Remains in Environment

. ox

Cit rat e

red.

−

as HCrO4

Citric Acid 3Fe(II)

H,

Or

)+ R OO

ga

red.

H

2(Mn3+ROOH)

ni

cs ,O

th e

r Li

gan

ds

Cr3+

. red

(Anion Exchange with Release fro PO43−, SO42−) m s

l oi

−O

Cr(III) + 3Fe(III)

Cr(VI)

ox.

Cr(III) Soil Adsoprtion, Precipitates & Polymers Mn 2+ +M n(IV

Uptake in Biosphere

so

il f i x a ti o n OH R CO ox. 2 H2O OH O R

(Anion Exchange with CI−, NO3−) SUN

O

Derived from Bartlett, 1991 ox. = oxidation red. = reduction FIGURE 4.1.1 Histogram showing “metals” most commonly present in all matrices at Superfund sites (USEPA, 1996).

imparts a yellow color to the water while Cr2O72– imparts an orange color. pH = − log [H3O+] In aqueous solution, Cr(III) dominates as soluble Cr3+ at pH<3. As pH increases, Cr(III) hydrolyzes to CrOH2+, Cr(OH)2+, Cr(OH)3, and Cr(OH)4– (Rai et al., 1987). In slightly acidic to alkaline conditions, Cr(III) can precipitate as amorphous Cr(OH)3 which can subsequently crystallize to Cr(OH)3 H2O (Palmer and Puls, 1994). Cr(III) can also precipitate as a solid in the presence of Fe(III). For most subsurface conditions, the equilibrium concentration of Cr(III) in solution between pH 5 and 12 is less than 10–6 mol/L (<50 ppb) which is less than the maximum concentration limit (MCL) of about 10–5 mol/L (Palmer and Puls, 1994, based on Rai et al., 1987 and Sass and Rai, 1987). The mobility

⋅

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of Cr(VI) is generally high, and in the subsurface depends upon pH, free Fe oxides, and total Mn, the latter two factors retarding Cr(VI) mobility, while pH is inversely proportional to mobility (Korte et al., 1976; Bartlett, 1991; Palmer and Wittbrodt, 1991). On the other hand, soil properties, cation exchange capacity, surface area, and clay content have no significant influence on Cr(VI) mobility—unlike most other metals. The mobility of Cr(III) is generally low. Cr(III) is readily sorbed by most soils. However, the presence of organic ligands can solubilize Cr(III), and the oxidation of Cr(III) to Cr(VI) can even be facilitated by organic matter (Bartlett, 1991). Because of its anionic nature (as polyatomic ions such as CrO42–, HCrO4–, Cr2O72–), Cr(VI) sorption in soils is limited to positively charged surface exchange sites, the number of which decrease with increasing pH. Fe and aluminum oxide (Al2O3) surfaces will adsorb CrO42– at acidic and neutral pH (McLean and Bledsoe, 1992). Stollenwerk and Grove (1985) concluded that the adsorption of Cr(VI) by groundwater alluvium was owing to the Fe oxides and hydroxides. The adsorbed Cr(VI) was, however, easily desorbed into uncontaminated groundwater, indicating nonspecific adsorption. The presence of CrO42– and nitrate (NO3–) had little effect on Cr(VI) adsorption, whereas sulfate (SO42–) and phosphate (PO43–) inhibited adsorption. Zachara et al. (1987) and Zachara and (1989) found that SO42– and dissolved inorganic carbon (C) inhibited CrO42– adsorption by amorphous Fe oxyhydroxide[FeO(OH)] and soil. However, the presence of SO42–, enhanced Cr(VI) adsorption to kaolinite (Zachara et al., 1988). Rai et al., (1988) suggested that BaCrO4(s) may form in soils at Cr contaminated waste sites. No other Cr(VI) precipitates have been observed at pH 1 to 9 (Griffin and Shimp, 1978). 4.1.1.1 Natural Occurrence of Chromium in Soil and Rock Chromium typically occurs in countries that have little use for it, whereas, most of the large industrial countries are deficient in it. Theoretically, Chromite is composed of 68% Cr2O3 (the oxide contains 68.4% Cr) and 32% FeO; however, Cr2O3 may be replaced by Al2O3, Fe2O3, MgO, CaO, and SiO2, reducing the Cr concentration to as little as about 40%. Commercial ores usually have a Cr concentration of at least 45%, with a Cr/Fe ratio greater than 2.5/1 for metallurgical Cr. Most Cr ores are not adaptable to various concentration processes, thus, are marketed as lump FeCr2O4 following hand sorting or rough concentration. The ore is mainly marketed as ferrochromium that is produced via smelting in an electric furnace utilizing fluxes and C. Primary Cr deposits are associated with magnesium (Mg) and Ni in ultrabasic rocks, or closely related anorthosite rocks. With rare exceptions, Chromite is found in peridotites, anorthosites, and other similar ultramafic rocks. Almost all Cr deposits are formed via magmatic segregations in ultrabasic rocks, occurring as masses, lenses, and disseminations. During cooling of magma, chromite forms either by early crystal settling or later gravitational liquid accumulation. Chromite deposits occur in two basic forms: stratiform (or layered) and pod-shaped. About 98% of the deposits are stratiform in

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nature. The Stillwater Complex in Montana and Bushveld Igneous Complex in South Africa are examples of large-scale stratiform deposits. Certain deposits found in mountainous regions such as the Appalachians, Urals, and belts rimming the Pacific Ocean are examples of pod-shaped deposits. Pod-shaped deposits form via liquid injection under conditions of differential pressures. Other Chromite deposit examples include the Great Dyke in Rhodesia, and other well-known deposits in parts of Russia, Turkey, and Canada. Smaller but high quality deposits also occur in Cuba, Pakistan, India, Yugoslavia, Greece, Brazil, and New Caledonia. Cr-bearing rocks may have Cr concentration up to about 1,000 ppm to 3,000 ppm, whereas, gabbros and granite contain Cr at only about 200 ppm and 5 ppm, respectively. Secondary deposits of Cr can develop as heavy minerals accumulations in placer and beach deposits (i.e., black sand). Under favorable tropical or subtropical conditions, lateritic soils may develop containing as much as 50% Fe and 2% to 4% Cr. Such reddish-colored soils result from the leaching of magnesium silicates from FeCr2O4-bearing ultramafic rocks. Cr concentration in refractory ores mined in Cuba is about 33% to 43%. The Republic of the Philippines produces ore with 46% to 50% Cr. In the U.S., relatively small deposits have been mined mainly in California, Oregon, Maryland, North Carolina, and Alaska. Elemental Cr is a solid metal at room temperature. However, Cr is rarely found as a free metal in the environment. Chromite has a Mohs hardness index of 5.5. Chromite occurs in igneous rocks and to a lesser extent in sedimentary and metamorphic rocks (Table 4.1.5). Host minerals include pyroxenes, amphiboles, micas, garnets, and spinels. Peridotite can become metamorphosed through hydrothermal alteration into serpentinite. As such, chromite commonly occurs within these rock bodies as euhedral crystals commonly forming high concentrated zones of chromite within the serpentinites. Uvarovite is a green colored Cr garnet and is frequently associated with the chromite ore. Chromdravite is a Cr-bearing mineral of the tourmaline group. Chrome diopside is a bright-green variety of the mineral diopside (Cr2O3) which contains a small amount of elemental Cr. Picotite is a Cr-bearing spinel. A cherty-like rock called chrome-chert is a chromite peridotite formed by the replacement of the silicate minerals by silica (SiO2). Chromite has been found in placer deposits within certain sedimentary ore bodies. Chrome ochre is a bright-green chromiferous clay containing 2% to 10.5% Cr2O3. Chromite ore, one of the main sources of elemental Cr, can take on a high gloss polish, is generally hard, lustrous, and has a steel gray color. Another less common but economical Cr ore is crocoite, also called lead(II) chromate (PbCrO4). Crocoite is a bright orange-red color mineral with a vitreous luster. Owing to the presence of lead (Pb), the mineral has a Mohs hardness index of only 2.5 to 3.0. The mineral has a specific gravity of 5.9 to 6.1. The fracture of crocoite is conchoidal. It forms as a secondary Pb mineral in the zone of alteration in massive hydrothermal replacement deposits. Although crocoite is considered a rare mineral, the element Cr was first extracted from this Cr mineral. In crustal rocks, Cr concentration is estimated to be 140 ppm. However, carbonaceous meteorites have Cr concentrations estimated to be 3,100 ppm.

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Cr forms a variety of compounds such as fluorides (CrF2, CrF3, CrF4, CrF5, CrF6), chlorides (CrCl2, CrCl3, CrCl4), bromides (CrBr2, CrBr3, CrBr4), iodides (CrI2, CrI3, CrI4), oxides (CrO2, CrO3, Cr2O3, Cr3O4), sulfides (Cr2S3), selenides (CrSe), nitrides (CrN), and tellurides (Cr2Te3). In a oceanic crust, continental crust collision (also called an island arc orogenic belt), lenses, or pods of chromite or nickel(II) sulfide (NiS) occur within the harzburgite or dunite part of the ophiolite sequence. The ophiolite sequence is part of the oceanic crust that has been thrust up into the outer arc (Smith, 1981). Economic chromite deposits occur in Cuba and in the Philippine island arc, which also contain NiS ores. In continent–continent collisions, Cr ores have been found in flysch deposits. The mafic portion of the Bushveld Complex in South Africa represents the largest layered intrusion in the world. It also contains the largest platinum (Pt) and Cr reserves in the world. Chromite seams vary in thickness to a maximum of approximately 1.8 m. Some of the FeCr2O4 seams have extended to more than 200 km. 4.1.1.2 Natural Occurrence of Chromium in Surface and Groundwater In natural water systems, Cr geochemically behaves in a unique manner. Cr(III) is the most common form of naturally occurring Cr. Cr(III) is largely immobile however, with natural waters containing only trace amounts unless the pH is extremely low. However, Cr can occur as Cr(VI) and persists in polyatomic anionic form as CrO42– under strong oxidizing conditions. Natural chromates are rare. (Table 4.1.6). 4.1.1.3 Natural Sources of Chromium in the Atmosphere Natural releases of Cr into the atmosphere arise from windblown sand, volcanic activity, forest fires, meteoric dust, and sea salt spray or particles, although only windblown sand and volcanic activities are of importance with regard to Cr (Table 4.1.7). Worldwide fallout of Cr to soil is estimated to be on the order of 4.6 × 10 3 metric ton/y and 3.4 × 104 metric ton/y (Schmidt and Andren, 1980). Bulk deposition of Cr is less than 0.2 kg/km2/y in remote areas, and 0.5 kg/km2/y to 5 kg/km2/y in rural areas, and generally more than 10 kg/km2/y in urban areas. 4.1.2

Anthropogenic Sources of Chromium

The most common “metals” (usually not as the element) found at U.S. Superfund sites occur in the following order of frequency: Pb, Cr, As, Zn, Cd, Copper (Cu), and mercury (Hg) (USEPA, 1996 and 2000). In 1986, the USEPA established the National Priority List (NPL) presenting approximately 1,000 sites of which about 40% reported “metals” problems. Of these, the most often cited ‘‘metals,” in descending number of sites, are Pb, Cr, As, Zn, Cd, Cu, and Hg (Figure 4.1). Of the Superfund sites that contain elevated concentrations of these contaminants, 306 sites contain Cr as a major source

Median 80* — Min Max — Medium Till C horizon Finland <0.063 mm total

Medium Soil World <2 mm total Agricultural soil–Ap horizon Canada <2 mm total (INAA) 57 10 510 Laterite (25 ±15 cm) Australia 0.45–2 mm total

0.00029 <0.0002 0.00576

Lake water unfiltered (mg/L)

(Continued)

Concentrations in soils and sediments (mg/kg) Urban soil (0–2 Forest soil Forest soil Topsoil Agricultural Agricultural Forest soil Till – Humus –B horizon –C horizon C horizon cm) Soil–Bottom (0–15 cm) soil–Top Norway Trondheim <2 (50–75 cm) England & (0–25 cm) Norway Norway Finland mm aqua regia <2 mm Wales Finland <2 mm Finland <2 mm <2 mm <2 mm <0.063 7N HNO3 7N HNO3 aqua regia <2 mm aqua aqua regia 7N HNO3 mm aqua regia regia 3 69.3 39.3 24.5 19.1 29.8 26.2 27.9 <1 7.9 — 0.2 <5 <5 <2 2.1 199 838 104 86 — 188.6 840 388 Overbank Organic Overbank Stream sediment Stream Stream sediment stream sediment sediment Southern sediment Norway Norway Harz, Scotland Austria sediment <0.063 <0.063 mm Germany <0.10 mm <0.18 mm Finland mm total <0.063 mm total (DCES) “total” <2 mm 7N HNO3 conc. (XRF) total (ICP–AES) (XRF) HNO3 ICP–AES

Concentrations in media sampled for the Kola Project (mg/kg) C horizon C horizon C horizon B horizon Medium Moss Humus <2 mm Humus <2 mm Topsoil (0–5 cm) B horizon <2 mm <2 mm conc. HNO3 conc. HNO3 <2 mm <2 mm NH4C2H3O2 <2 mm total <2mm aqua aqua regia total (XRF) total total (INAA) regia (INAA) (XRF) 28.2 — Median 35.2 0.07 53 2.91 99 — 0.6 Min 2.2 11 — 3.8 <0.02 <5 0.39 <0.2 — Max 471 910 — 413 670 2.96 109 14.4 —

Chromium Concentratons in Various Environmental Media

TABLE 4.1.6

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0.000212* — — Stream water Harz, Germany unfiltered ICP–MS

Concentrations in waters (mg/L) Stream water Stream water Stream water World Nova Scotia, Finland <0.45 Canada µm ICP–MS <0.45 µm ICP–MS 0.0007* 0.0001 0.0005 <0.0001 — <0.0002# 0.0011 — 0.00161^ Lake water Ground Norway water unfiltered Southern ICP–MS Norway unfiltered ICP–MS (Continued)

Lake water unfiltered (mg/L)

154

0.0003* — — Stream water Eastern India <0.2 µm ICP–MS

Median 0.0003* — Min — Max Medium Stream water Romania unfiltered ICP–MS

80.5 <3 4,500

Ocean water North Pacific

Estimated mean 2nd percentile 98th percentile

60 — —

Concentrations in media sampled for the Kola Project (mg/kg) C horizon C horizon C horizon B horizon Humus Topsoil (0–5 cm) B horizon <2 mm <2 mm <2 mm <2 mm <2 mm total <2 mm aqua <2 mm aqua regia total (XRF) total total NH4C2H3O2 (INAA) regia (INAA) (XRF) 24 76 69 161 64 31.3 2.6 2 20 <5 — 10.9# 4,48 11,400 3,176 4,484 245 84.2^

Medium Ocean water Ocean water World (2) World (1)

^

#

*

Median Min Max

Medium Moss Humus conc. HNO3 <2 mm conc. HNO3

Chromium Concentratons in Various Environmental Media (Continued)

TABLE 4.1.6

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0.000113 0.00005 0.179

0.0055 0.00344 0.0207

0.00023 <0.00001 0.00059

Concentrations in plants (mg/kg) Spruce bark Lichen Dandelion Canada Northwest Europe ashed total Territories oven-dried oven-dried total (INAA) (INAA) total (INAA)

Air World, polluted 40 1 300

0.00022 0.00009 0.00033

Concentrations in air (ng/m3) and yearly deposition (kg/km2/year) Bulk Throughfall Bulk Bulk deposition deposition deposition deposition Kola, polluted Kola, remote West Germany West Germany — 0.216* 0.6 5.24* — 0.61 — — — 2.3 — —

0.001145 0.00032 0.00131

<0.0002 <0.0002 0.00031

0.00047 0.00025 0.00095

0.0097 0.004,9 0.0588

0.00032 <0.00001 0.0027

Concentrations in media sampled for the Kola Project (mg/kg) C horizon C horizon C horizon B horizon Humus Topsoil (0–5 cm) B horizon <2 mm <2 mm <2 mm <2 mm <2 mm total <2 mm aqua <2 mm aqua regia total (XRF) total total (XRF) NH4C2H3O2 (INAA) regia (INAA) <0.0001 0.00054 0.00041 <0.0001 <0.0001 <0.00001 0.00485 0.00586 0.0071

Medium Moss Moss Crustose Norway Germany conc. lichen conc. HNO3 HNO3 + H2O2 Germany conc. HNO3 (1995) (1990)

* Estimated value

Medium Air World, remote Median 0.6 / 0.5 Min 0.005 Max 0.7

<0.0002 <0.0002 <0.0002

Estimated mean 2nd percentile 98th percentile

Median Min max

^

#

*

Median Min Max

Medium Moss Humus conc. HNO3 <2 mm conc. HNO3

Chromium Concentratons in Various Environmental Media (Continued)

TABLE 4.1.6

(Continued)

Lake water unfiltered (mg/L)

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Mean Geometric mean

0.9 <0.4 30

Human urine Lombardy, Italy 0.00061 0.00004 0.0051

Human serum Lombardy, Italy 0.00017 0.00004 0.0006

1.393 0.05 29

= 30.0 g

= 60.0 g

For example, 1 equivalent of CO32− = molar mass/charge

equivalent mass = g of ion that produces 1 mol of electrial charge

equivalent = g substance/equivalent mass

Concentrations in human fluids (mg/L)

Concentrations in media sampled for the Kola Project (mg/kg) C horizon C horizon B horizon Humus Topsoil (0–5 cm) B horizon <2 mm <2 mm <2 mm <2 mm total <2 mm aqua <2 mm aqua regia total total NH4C2H3O2 (INAA) regia (XRF) (XRF) 1.6* 0.35# 33 31 4 — — 16 250 — — 167 C horizon <2 mm total (INAA)

Lake water unfiltered (mg/L)

156

= gequivalents/ L of solution

N=normality

Medium Human blood Lombard, Italy Mean 0.00023 Min 0.00009 Max 0.00075

#

*

Median Min Max

Medium Moss Humus conc. HNO3 <2 mm conc. HNO3

Chromium Concentratons in Various Environmental Media (Continued)

TABLE 4.1.6

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TABLE 4.1.7 Estimated Chromium Emissions to the Atmospherea Source

Cr Emissions (metric tons/year)

Anthropogenic sourcesb Coal combustion Oil combustion Steel and iron Refuse incineration Municipal Sewage sludge Cement production Subtotal Average

0.089–0.89 0.14–0.41 0.81–1.61 6.66–48.63 27.65 (36%)

Natural sources Soil suspension Volcanoes Subtotal Total

45.36c 3.54c 48.9 (64%) 76.55

2.65–17.81 0.41–2.15 2.58–25.76

Note: a Modified after McGrath and Smith (1990). b Derived from Nriagu and Pacyna (1988). c Derived from Schmidt and Andren (1980).

of contamination. For Cr, sources of contamination include airborne sources (stack or duct emissions of air, gas, or vapor streams, and fugitive emissions such as dust from storage areas or waste piles), process solid wastes and sludges (from industrial processes), contaminated soils, and direct Cr contamination in groundwater. The use of “heavy metals” in waterborne wood preserving solutions has increased over time. In fact, as of 1995 the use of heavy metals has exceeded all other processes combined (AWPI, 1996). The most widely used wood preserving formulation is Cu-Cr arsenate (AsO43–). Thus, nearly all wood preserving plants 20 years or older have reported soil and groundwater contamination of varying degrees. Of these, about 71 are listed as CERCLA NPL sites. And, at least 678 additional sites are known for wood preserving operations currently or in the past (USEPA, 1997). The most significant contaminant associated with Cu–Cr–AsO43– is Cr(VI). 4.1.2.1 Anthropogenic Chromium in Soil Soil and under certain conditions groundwater can become contaminated with Cr and other metals by: • Direct infiltration of leachate from landfill disposal of solid wastes, sewage, or sewage sludge

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158

Chromium(VI) Handbook TABLE 4.1.8 Chromium Concentration in Fertilizers, Limestone and Animal Manure Material Fertilizers Nitrogen Phosphorus Potassium Mixed compounds Limestone Animal Wastes Cattle manure Poultry manure Pig waste Farmyard manure Cow manure

Cr Concentration (mg/kg)

trace–50 trace–1000 trace–1000 trace–900 trace–300 20–31 6 14 12 56

Modified after McGrath and Smith (1990).

• Leachate from mining wastes • Seepage from industrial lagoons • Spills and leaks from industrial metal processing or wood preserving facilities, and other industrial operations 4.1.2.2 Agricultural Materials Chromium in food is mainly in the Cr(III) form and can be found in such products as brewer’s yeast, calf liver, cheese, and wheat germ. The total annual input of Cr into soils has been estimated to be between 4.35 × 105 metric tons and 1.18 × 106 metric tons (Nriagu and Pacyna, 1988). From an agricultural perspective, Cr concentration in fertilizers, limestone, and animal manure is of interest (Table 4.1.8). The amount of Cr is greater in fertilizers with phosphates (McGrath and Smith, 1990). The National Research Council of Canada (1976) has reported Cr in phosphate fertilizers of approximately 30 mg/kg to 3,000 mg/kg. Although the amount of Cr entering the soil via phosphate fertilizers is uncertain, it is likely to exist as Cr(III). The amount of Cr utilized in phosphates and limestone (the latter being used to adjust soil acidity conditions) is greater than what exists in native soils. Published values of Cr in limestone vary significantly ranging from 1 mg/kg to 120 mg/kg, averaging 10 mg/kg. Animal manure contains little Cr. Chromic acid (H2CrO4) is registered in California as a fungicide and insecticide. It is used for wood and lumber protection treatments and also used to treat lumber used for pilings. Sodium dichromate (Na2Cr2O7) is registered as an insecticide used to prevent termite damage to wood products.

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4.1.2.3 Sewage Sludges Chromium derived in influent from natural, domestic, or industrial sources can concentrate in the organic resowing at sewage treatment facilities. Nearly 100% of Cr(III) can be removed from wastewater sludge depending on the process and age of the sludge. However, only 26% to 48% of Cr(VI) has been removed (Sterritt et al., 1981). Nonindustrial sources contributed about 48% of Cr in the influent to 12 sewage works in New York, New York (Klein et al., 1974). Cr-containing effluents can be released via metal plating, anodizing, ink manufacture, dyes, pigments, glass, ceramics, glues, tanning, wood preservatives, textiles, and corrosion inhibitors in cooling water (McGrath and Smith, 1990). Both Cr(III) and Cr(IV) may occur in wastewaters derived from these sources. Past practice, notably with plating operations, was to dispose off Cr-wastewater into dry wells. Also, it is not surprising that Cr(VI) is predominant in plating wastes. Such wastewater currently is either treated on site to reduce the Cr concentrations or at sewage treatment works. The Cr(VI) is thus reduced by organic matter and the resultant sludge exhibits Cr(III) type compounds (Grove and Ellis, 1980). Although little evidence suggests significant downward migration of “metals,” including Cr in the subsurface, laboratory studies suggest that such limitations may not apply in all cases (Christensen, 1984). At least 80% of Cr applied to soil in a long-term study was accounted for within the cultivated layer after 45 years (McGrath and Lane, 1989).

4.1.2.4 Coal and Fly Ash Disposal The largest amount of Cr applied directly to the land surface is by the disposal of trapped and bottom fly ash (Table 4.1.9; Nriagu and Pacyna, 1988). The disposal of large quantities of this ash on soil can result in elevated Cr concentrations relative to natural background levels, notably around coal-fired power plants. However, little Cr appears to be taken up by vegetation (Furr et al., 1976).

TABLE 4.1.9 Chromium Concentration in Coal and Fly Ash Material Concentration (mg/kg)

Cr

Coal Fly asha Bituminous Sub-bituminous Lignite

15 152 172 50 43

Source: From Adriano et al., 1980. a Fly ash means trapped and bottom ash (not airbombs fly ash).

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4.1.2.5 Mining and Smelter Wastes Although mining operations occur throughout the U.S., most of the mining for metals is situated in the western region of the country. In the U.S., the metals which constitute a significant domestic presence are Fe, Cu, Pb, Zn, gold (Au), and silver (Ag). No significant Cr mining operations are performed in the U.S. Despite this, Cr is noted as one of the contaminants of concern at some mine sites such as the Clear Creek/Central City site in Colorado, and the Eagle Mine, located in Gilman, Colorado (USEPA, 1995b). However, internationally, Cr production has increased tenfold during the period from about 1930 to 1980 (Stowe, 1987). In fact, since 1900, Cr production has doubled each decade. By 1984, production had reached 10.16 million metric tons. The major producers include New Caledonia, Turkey, Zimbabwe, Russia, and South Africa, with each having held the position of the leading producer. Since the 1960s and 1970s, Albania and Brazil have emerged as important producers. The current trend for producing countries is towards the processing of FeCr2O4 ore for export as ferrochromium alloys. Emissions of Cr from chromate smelters can result in large increases of Cr in soil. A large quantity of CrO42– waste in the form of Cr(VI) from the Croal Valley in northern England was reported to be intensely phytotoxic (Breeze, 1973). 4.1.2.6 Roadside Soils Sources of Cr that affect roadside soils include Cr derived from the wear of Cr-containing asbestos brake linings in vehicles and aerosols produced from Cr catalysts used in emission reduction systems for treating exhaust fumes. 4.1.2.7 Anthropogenic Chromium in Water In seawater, Cr is estimated to be at a concentration of 0.6 ppb. Surface water Cr concentrations are estimated as 1 ppb. Often, immobilization occurs by precipitation into solid phases as a result of changes in the pH or oxidation state (Eh). The adjustment of pH is often easier, but a change in oxidation state is usually more permanent, especially in the subsurface environment, because of the extremely large activation energies associated with many redox reactions. Also, changes in pH accompanied by fixation in an immobile phase often affect the mobility but not the toxicity of a “metal”. On the other hand, changes in oxidation state usually affect both the mobility and the toxicity. As an example, Pb, Zn, and Cd do not change oxidation states in the environment and are not considered redox-sensitive (oxidation–reduction sensitive). Therefore, changes in pH and the stability of specific phases are usually the strategies used to immobilize these metals in the subsurface. On the other hand, Cr normally exists as the relatively immobile Cr(III) under reducing conditions and the highly mobile and toxic Cr(VI) under oxidizing conditions. Therefore, redox manipulation is the preferred method of immobilizing Cr. Cr(VI) can be reduced to Cr(III) by several means and Cr(III) will not easily reoxidize to Cr(VI). The degree of Cr immobilization and the

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success of the proposed in-place treatments, depend upon the general chemical processes that act on all systems in the subsurface. These processes include complex formation, surface sorption, and precipitation. 4.1.2.8 Anthropogenic Chromium in the Atmosphere The largest total quantities of Cr released to the atmosphere are as suspended particles derived from metallurgical and chemical manufacturing industries and combustion of natural gas, oil, and coal. Other sources of Cr emissions in the environment can be derived from various consumer products, industrial wastes, and the working environment such as cement-producing plants, and exhaust emissions from catalytic converters. In a 1973 national survey, ferrochrome production was the most important with an estimated 11,213 metric tons/year, even after control of air pollution. The production of refractory brick products was also noted as an important source releasing 1,478.7 metric tons/year to the atmosphere, followed closely by the combustion of coal which released 1,418.8 metric tons/year with steel production releasing 471.7 metric tons/year. However, a more recent study conducted over a decade later concluded that the Fe and steel industry is the largest anthropogenic source of Cr emissions worldwide (Nriagu and Pacyna, 1988). Chromium also occurs naturally as a trace component in most crude oils, and can be found in residual and distillate oils. Cr(III) is known to be emitted from oil combustion, sewer sludge incineration, cement production, municipal waste incinerators, and refractories. In California, Cr(VI) emissions are primarily from Cr plating. Cr electroplating operations are conventionally conducted in baths containing chromic acid (H2CrO4). During the plating process, bubbles of gas are emitted through the surface of the bath. These bubbles carry entrained Cr(VI) into the air. Firebrick lining of glass furnaces is another source of Cr(VI) emissions. Lead(II) chromate (PbCrO4), a pigment used in yellow paint (i.e., for traffic lane demarcation), makes up a minor source of Cr(VI) emissions. Emissions from point and area sources in the Great Lake region were determined for the calendar year 1999 (http://www.great-lakes.net). Point sources dominated the emission of the top five metals compounds, accounting for more than 97.8% of the total regional emissions. In this inventory, 41.4% of Cr emissions were attributed to primary metal industries. Based on data generated around 1997 under the California Air Toxics “Hot Spots” Program, the total emissions of Cr(VI) and Cr compounds derived from stationary sources are estimated to be at least 2900 kg/year and 4,100 kg/year, respectively. The primary stationary sources of Cr compounds in California are lumber and wood products manufacturers, stone, clay and glass production, and petroleum refining. Reported Cr(VI) emissions from stationary sources in California include electrical services, aircraft and parts manufacturing, and steam and air conditioning supply services. Cr(VI) compounds such as Na2Cr2O7 and PbCrO4, once used in California as an additive to cooling tower water to control corrosion in the towers and associated heat exchangers, were prohibited in 1989.

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Bibliography Adriano, D.C., Page, A.L., Elseewi, A.A., Chang, A.C., and Strughan, I., 1980, Journal of Environmental Quality, 9, 333–344. (AWPI) American Word Preservers Institute 1996, The 1995 Wood Preserving Industry Production Statistical Report, September. Bartlett, R.J., 1991, Chromium cycling in soils and water: links, gaps and methods, Environmental Health Perspective, 92, 17–24. Bartlett, B.R. and James, B.R., 1988, Chromium in the Natural and Human Environments, Nriagu J.O. and Niebor E., Eds., Wiley, New York, pp. 267–304. Breeze, V.G, 1973, Journal of Applied Ecology, 10, 513. Christensen, T.H., 1984, Air and Soil Pollution, 44, 43–56. Crowson, P., 1982, Minerals Handbook, 1982–83, Van Nostrand Reinhold, New York, p. 248. Evanko, C.R. and Dzombak, D.A., 2000, Remediation of metals-contaminated soils and groundwater, in Lehr J., Ed., McGraw Hill Standard Handbook of Environmental Science, Health and Technology, New York, pp. 14.100–14.134. Furr, A.K., Kelly, W.C., Bache, C.A., Guttenmann, W.H., and Lisk, D.J., 1976, Journal of Agriculture and Food Chemistry 24, 885–888. Griffin, R.A. and Shimp, N.F., 1978, Attenuation of Pollutants in Municipal Landfill Leachate by Clay Minerals, EPA-6000/2-78-157. Grove, J.H. and Ellis, B.G., 1980, Soil Science Society of America Journal, 44, 238–242. Klein, L.A., Lang, M., Nash, N., and Kirscher, S.L., 1974, Journal of Water Pollution and Control Federation, 46, 2653–2662. Korte, N.E., Skopp, W.H., Fuller, W.H., Niebla, E.E., and Aleshii, B.A., 1976, Trace element movement in soils: influence of soil physical and chemical properties, Soil Science, 122, 350–359. Lewis, R.J., 1992, Sax’s Dangerous Properties of Industrial Materials, Eighth Edition,Volume II, Van Nostrand Reinhold, New York. McGrath, S.P. and Lane, P.W., 1989, Environmental Pollution, 60, 236–256. McGrath, S.P. and Smith, S., 1990, Chromium and Nickel, in Alloway B.J., Ed., Heavy Metals in Soils, Blackie and Sons, London, pp. 125–146. McLean, J.E. and Bledsoe, B.E., 1992, Behavior of metals in soils: ground water issue, Environmental Protection Agency, EPA/540/S-92/018, 25. Merck & Company 1989, The Merck Index, An Encylopedia of Chemicals, Drugs and Biologicals. Eleventh Edition, Whitehorse, New Jersey. National Research Council of Canada, 1976, Effects of Chromium in the Canadian Environment: NRCC/CNRC, Ottawa, Canada. Nriagu, J.O. and Pacyna, J.M., 1988, v. 333, pp. 134–139. Palmer, C.D. and Puls, R.W., 1994, Natural attentuation of hexavalent chromium in groundwater and soils: ground water issue, Environmental Protection Agency, EPA/540/S-94/505, 13. Palmer, C.D. and Wittbrodt, P.R., 1991, Processes affecting the remediation of chromium-contaminated sites, Environmental Health Perspective, 92, 25–40. Papp, J.F., 2003, Mineral Commodity Summaries (Chromium), U.S. Geological Survey, January 2003. Powell, R.M., Puls, S.K., Hightower, S.K., and Sabatini, D.A., 1995, Coupled iron corrosion and chromate reduction: mechanism for subsurface remediation, Environmental Science and Technology, 29, 1913–1922.

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Rai, D., Sass, B.M., and Moore, D.A., 1987, Chromium(III) hydrolysis constants and solubility of chromium(III) hydroxide, Inorganic Chemistry, 26, 345–349. Reimann, C. and de Caritat, P., 1998, Chemicals Elements in the Environment, Factsheets for the Geochemist and Environmental Scientist, Springer-Verlag, New York, pp. 96–99. Rose, J.V., 1997 Natural and Enhanced Attenation of CCA Components in Soil and Groundwater; in 93rd Annual Meeting of the American Wood-Preservers Association, April 27–29, 1997. Sass, B.M. and Rai, D., 1987, Solubility of amorphous chromium(III)-iron(III) hydroxide solid solutions, Inorganic Chemistry, 26, 2228–2232. Schmidt, J.A. and Andren, A.W., 1980, in Nriagu, J.O., Ed., Nickel in the Environment, John Wiley and Sons, New York, Chap. 6. Smith, D.G., 1981, The Cambridge Encyclopedia of Earth Sciences, Smith D.G., Ed., Cambridge University Press, New York, p. 236. Sterritt, R.M., Brown, M.J., and Lester, J.N., 1981, Environmental Pollution Series, A 24, 313–323. Stollenwerk, K.G. and Grove, D.B., 1985, Adsorption and desorption of hexavalent chromium in an alluvial aquifer near Telluride, Colorado, Journal of Environmental Quality, 14, 150–155. Stowe, C.W., 1987, The mineral chromite, in Stowe, C.W., Ed., Evolution of Chromium Ore Fields, Van Nostrand Reinhold, New York, NY, pp. 1–22. U.S. Environmental Protection Agency, 1995a, Contaminants and Remedial Options at Selected Metal-Contaminated Sites, U.S. Environmental Protection Agency, Office Research and Development, Washington, DC, Report 540/R-95-512. U.S. Environmental Protection Agency, 1995b, EPA Office of Compliance Sector Notebook Project—Profile of the Metal Mining Industry, U.S. Environmental Protection Agency Office of Enforcement and Compliance Assurance, EPA/310-R-95-008, 123 p. U.S. Environmental Protection Agency, 1996, Report: Recent Developments for In Situ Treatment of Metals-Contaminated Soils, U.S. Environmental Protection Agency, Office of Solid Waste and Emergency Response, draft, Washington, D.C. U.S. Environmental Protection Agency, 1997, Permeable Reactive Subsurface Barriers for the Interception and Remediation of Chlorinated Hydrocarbon and Chromium(VI) Plumes in Ground Water, USEPA Remedial Technology Fact Sheet, EPA/600/F–97/008. U.S. Environmental Protection Agency, 2000, In Situ Treatment of Soil and Groundwater Contaminated with Chromium, Technical Resource Guide, U.S. Environmental Protection Agency, Office Research and Development, Washington, D.C., Report EPA 625/R–00/005. Zachara, J.M., Ainsworth, C.C., Cowan, C.E., and Resch, C.T., 1989, Adsorption of chromate by subsurface soil horizons, Soil Science Society of America Journal, 53, 418–428. Zachara, J.M., Cowan, C.E., Schmidt, R.L., and Ainsworth, C.C., 1988, Chromate adsorption on kaolinite, Clay Mineralogy, 36, 317–326. Zachara, J.M., Girvin, D.C., Schmidt, R.L., and Resch, C.T., 1987, Chromate adsorption on amorphous iron oxyhydroxide in presence of major ground water ions, Environmental Science Technology, 21, 589–594.

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5 The Transport and Fate of Chromium(VI) in the Environment

Frederick T. Stanin

CONTENTS Introduction..........................................................................................................167 5.1 The Presence of Chromium in the Environment .................................168 5.1.1 Anthropogenic Sources ................................................................168 5.1.2 Natural Sources .............................................................................169 5.2 Geochemistry of Chromium ....................................................................169 5.2.1 Cr(III)...............................................................................................170 5.2.2 Cr(VI)...............................................................................................171 5.3 Oxidation-Reduction of Chromium........................................................172 5.3.1 Review of Oxidation-Reduction Reactions ...............................172 5.3.2 General Redox Behavior of Chromium in the Environment .......................................................................173 5.3.3 Oxidation of Chromium...............................................................174 5.3.3.1 Oxidation of Cr(III) to Cr(VI) by Dissolved Oxygen and Manganese Dioxides ...............................174 5.3.3.2 Oxidation of Cr(III) to Cr(VI) by H2O2 .......................176 5.3.4 Reduction of Cr(VI) to Cr(III) .....................................................176 5.3.4.1 General..............................................................................176 5.3.4.2 Fe(II) (Dissolved Fe(II) and Fe(II)-Containing Minerals)...........................................................................177 5.3.4.3 Reduced Sulfur................................................................179 5.3.4.4 Organic Matter ................................................................179 5.3.4.5 Cu(I) ..................................................................................179 5.3.4.6 Hydrogen Peroxide(H2O2).............................................180 5.4 Precipitation/Dissolution Reactions of Chromium .............................180 5.5 Sorption and Desorption Reactions of Chromium ..............................181 5.5.1 General Discussion of Sorption ..................................................181 5.5.2 Sorption of Chromium .................................................................182

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5.5.2.1 Sorption of Cr(III) ...........................................................182 5.5.2.2 Sorption of Cr(VI) ...........................................................183 5.6 General Transport and Fate of Chromium in Environmental Media...........................................................................184 5.6.1 Chromium in the Atmosphere....................................................184 5.6.2 Chromium in Aquatic Environments ........................................186 5.6.2.1 Surface Waters .................................................................186 5.6.2.2 Groundwater ...................................................................188 5.6.2.3 Plumes of Chromium in Groundwater:Case Studies ..............................................................................190 5.6.2.3.1 Nassau County, New York..........................190 5.6.2.3.2 Telluride, Colorado.......................................190 5.6.2.3.3 Wood Treatment Plant, Southwestern Michigan ........................................................191 5.6.2.3.4 Northern France, Industrial Waste Landfill.............................191 5.6.3 Chromium in Soil..........................................................................192 5.6.3.1 Overview of Metals in Soil ...........................................192 5.6.3.2 Behavior of Chromium in Soil......................................195 5.6.3.2.1 Sorption of Cr(III) and Cr(VI) ....................196 5.6.3.2.2 Reduction of Cr(VI) and Oxidation of Cr(III) .........................................................197 5.6.4 The Uptake and Transformation of Chromium by Biota.......198 5.7 Utilizing Natural Environmental Processes as a Remedy for Soil and Groundwater Contaminated with Chromium ...............199 5.7.1 Natural Reductants in the Aquifer.............................................200 5.7.2 The Amount of Cr(VI) and Other Reactive Constituents Do Not Exceed the Reductive Capacity of the Aquifer .........201 5.7.2.1 Mass of Cr(VI) .................................................................201 5.7.2.2 Mass of Cr(III) .................................................................202 5.7.2.3 Reduction Capacity of the Aquifer ..............................202 5.7.2.4 Oxidation Capacity of the Aquifer ..............................203 5.7.3 The Rate of Chromium(VI) Reduction to the Target Concentration Compared to the Rate of Transport of Chromium(VI) from Source to Point of Compliance..............204 5.7.3.1 Rates of Oxidation and Reduction...............................204 5.7.3.2 Estimating Reduction from Monitoring Well Data ..........................................................................205 5.7.3.3 Monitoring Reduction via Stable Isotopes of Chromium ...................................................205 Bibliography ......................................................................................... 207

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Introduction The knowledge of the transport and fate of contaminants in the subsurface environment is essential to achieving environmental restoration objectives. Unfortunately, gaining and using this knowledge can be difficult because of problems and limitations involving complex hydrogeology, hydrochemistry, and microbiology, or by economical restraints. This chapter discusses the most important physical, chemical, and biological parameters to understanding the transport and fate of Cr(VI), and chromium(Cr) in general, and how these parameters can be measured and utilized in environmental restoration projects. These discussions are drawn from several sources, as referenced. The assessment of the transport and fate of any contaminant in the environment generally consists of site characterization, risk assessment, and remediation, which are the three main phases of environmental restoration programs. Conventional approaches to site characterization may not adequately define the need to obtain enough detailed information about natural processes affecting the transport behavior and the ultimate fate of contaminants. The use of state-of-the-art site characterizations, although more costly to implement than more conventional means, may ultimately result in significant savings because of improved technical effectiveness and efficiency of site cleanup. Also, proper site characterization methods can aid risk management decisions (risk assessments) in determining if remediation is even necessary and/or to what extent, and choosing the proper cleanup technologies if remediation is needed. A sound conceptual site model (CSM) is absolutely necessary for transport and fate assessments. An adequate CSM incorporates information on geologic, hydrologic, chemical, and biological processes to produce an effective contaminant transport evaluation. The practical use of risk assessments and remedial technologies is highly dependent on site-specific knowledge of these processes. Therefore, the processes that govern the subsurface behavior and treatability of contaminants must be understood. This is particularly true for Cr(VI). This chapter discusses the transport and fate of Cr(VI) as well as other forms of Cr in the environment, most notably Cr(III). These forms or species of Cr are inexorably linked by many environmental transport and fate processes. First presented is an overview of the presence of Cr in the environment and its general geochemistry. The most important transport and fate processes are discussed, namely oxidation-reduction (redox), precipitationdissolution, and sorption-desorption. Then, the general aspects of the transport and fate of Cr in the atmosphere, aquatic environments (surface waters and groundwater), and soil, including the uptake and transformation of Cr(VI) by biota, are summarized. The chapter concludes with a discussion of how natural attenuation processes can be implemented as a remedy for sites contaminated by Cr(VI).

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The Presence of Chromium in the Environment

Chromium contamination of soil and groundwater is a significant problem worldwide. The extent of this problem is owing primarily to its use in numerous industrial processes (i.e., metal plating and alloying, leather tanning, wood treatment, etc.), but also its natural presence in rocks enriched in Cr (i.e., ultramafic rocks such as serpentinite). Compared to the results of contamination of soil and groundwater by industrial practices, the naturally-occurring concentrations of Cr in soil and groundwater are relatively low. However, relatively high concentrations of naturally-occurring dissolved Cr have been observed, usually associated with the very soluble Chromates (CrO42-) (Robertson, 1975). Thus, both anthropogenic (manmade) and natural sources of Cr can lead to locally elevated concentrations in soils and waters. The presence of Cr in the environment is discussed by several authors (Davis and Olsen, 1995; Kimbrough et al., 1999; Richard and Bourg, 1991; Kotas and Stasicka, 2000). Their presentations are briefly summarized below. Chapter 4 gives additional information on naturally-occurring Cr(VI) in groundwater.

5.1.1

Anthropogenic Sources

Chromium is used in several industries, including metallurgy (steel, ferroand nonferrous alloys), refractory (chrome and chrome-magnesite), and chemical manufacturing (pigments, electroplating, tanning and other), involving numerous commercial processes including electroplating, leather tanning, pulp production, milling, mining (ore refining), and wood preservation. The industrial use of Cr generally begins with the mining of chromite (a naturally-occurring ore), usually as iron(II) chromite (FeO•Cr2O3 or FeCr2O4) (Hartford, 1983). Then, the ore is either oxidized or reduced during industrial processing. Sodium chromate (Na2CrO4) has usually been produced by the oxidation of chromite. Sodium carbonate (Na2CO3), calcium oxide (CaO), and calcium chromate (CaCrO4) are produced as byproducts. In turn, several substances are derived from Na2CrO4, including dichromates (Na2Cr2O7 or K2Cr2O7), Cr(VI) oxide (CrO3), chromic acid (H2CrO4), and other oxides of Cr (e.g., K2CrO4), including Cr pigments (barium, calcium, lead, strontium, and zinc chromate). Also, FeCr2O4 ore can be reduced by a variety of methods using aluminum, silicon, or carbon as reducing agents (Hathway, 1989). Materials from this reduction are used for producing Cr alloys and chrome alum (NH4Cr(SO4)2 • 12H2O). Most of the Cr consumed by industry in the U.S. is for the production of metal alloys, mainly wrought-stainless and heat-resisting steels (Hartford, 1983). Cr as part of an Fe alloy is insoluble with a zero oxidation state and therefore is not a form of Cr having an environmental concern. However, Cr can be oxidized and leached from stainless steel into a water-soluble form (Kimbrough et al., 1999).

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Chromium from anthropogenic sources can be released to soils and sediments indirectly by atmospheric deposition, but releases are more commonly from dumping of Cr-bearing liquid or solid wastes such as chromate (CrO42-) byproducts (“muds”), ferrochromium slag, or Cr plating wastes. Such wastes can contain any combination of Cr(III) or Cr(VI) with various solubilities. The nature and behavior of various forms of Cr found in wastewaters can be quite variable. The presence, form and concentration of Cr in discharged effluents depends mainly on the Cr compounds utilized in the industrial process, on the pH, and on the presence of other organic and inorganic processing wastes. Chemicals containing Cr(VI) are principally used for metal plating (which use Chromic acid H2CrO4), as dyes, paint pigments, and leather tanning (Hartford, 1983). Cr platers involve the use of H2Cr2O7 to plate Cr onto pieces of other metals. Thus, Cr(VI) will dominate in wastewater from the metallurgical industry, metal finishing industry (Cr hard plating), refractory industry and production or application of pigments (chromate color pigments and corrosion inhibition pigments). Cr(III) will be found mainly in wastewaters of the tannery, textile (printing, dying) and decorative plating industries. However, there are exceptions to these generalities owing to several factors. For example, in tannery wastewater where Cr(III) is the most expected form, the redox reactions occurring in sludge can increase the concentration of Cr(VI). Such transformations are also common in the subsurface, such as oxidation, reduction, sorption, precipitation, and dissolution, which are all discussed later in this chapter. 5.1.2

Natural Sources

As previously mentioned, Cr occurs naturally in the environment, most notably in its most concentrated forms as an ore mineral. Cr also occurs naturally as a component of soils (Schacklette and Boerngen, 1984), usually as chromite, a relatively insoluble soil mineral (Schmidt, 1984). The main source of such Cr in natural soils is the weathering of their parent materials. The average amount of this element in various kinds of soils ranges from 0.02 m◊mol/g to 58 m◊mol/ g (Richard and Bourg, 1991; Coleman, 1988). The Cr concentration will be influenced by the composition of the parent rock. Granite, carbonates (CO32-) and sandy sediments present the lowest Cr content whereas shales, river suspended matter, and soils typically exhibit highest concentrations. Highest Cr contents tend to be associated with finest grain size soils (Robertson, 1975) and sediments (Salomons and DeGroot, 1978). Thus, the natural concentration of Cr in the environment varies greatly (Cary, 1982).

5.2

Geochemistry of Chromium

Chromium can exist in several chemical forms with oxidation numbers ranging from –2 to +6. However, in the environment, Cr commonly exists in only two stable oxidation states, Cr(VI) and Cr(III), which have greatly different

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toxicity and transport characteristics. Cr speciation in the environment, particularly in groundwater, is affected primarily by Eh (oxidizing or reducing conditions) and pH (acidic or alkaline conditions). In general, Cr(VI) predominates under oxidizing conditions, and Cr(III) predominates under more reducing conditions. These two different forms of Cr are quite different in their properties: charge, physiochemical characteristics, mobility in the environment, chemical and biochemical behavior, bioavailability, and toxicity. Most notably, Cr(III) is considered to be a trace element essential for the proper functioning of living organisms, whereas Cr(VI) may exert toxic effects on biological systems. Also, Cr(VI) compounds are generally more soluble, mobile, and bioavailable in the environment compared with Cr(III) compounds. And, as previously mentioned, the more toxic and mobile Cr(VI) predominates in oxidizing environments, while the less toxic and immobile Cr(III) is restricted to reducing environments. Therefore, it is quite important to distinguish these forms of Cr rather than discussing this element as “total Cr.” The geochemistry of these forms are briefly discussed below. A more comprehensive discussion of the geochemistry of Cr and Cr compounds is presented in Chapter 2.

5.2.1

Chromium(III)

In aqueous systems, soluble Cr(III) can be present as Cr3+, Cr(OH)2+, Cr(OH)2+, and Cr(OH)4–. Additionally, the precipitated phase Cr(OH)3 predominates between pH 6 and pH 12 (Rai et al., 1987). Under slightly acidic to alkaline conditions, and if Fe(III) is present, Cr(III) can precipitate as an amorphous mixed hydroxide CrxFe1–x(OH)3 (Eary and Rai, 1988). Amorphous Cr(OH)3 can crystallize as Cr(OH)3 • 3H2O or Cr2O3 (eskolaite) under different conditions (Palmer and Puls, 1994). With high redox potential, Cr(VI) predominates with a much higher solubility (Loyaux-Lawniczak et al., 2001). In a reducing environment, and in the absence of Fe, Cr(III) precipitates readily to form Cr(OH)3 (Rai et al., 1987). In relatively low Eh aqueous environments, the main Cr(III) Constituents are Cr3+,Cr(OH)2+,Cr(OH)2+ Cr(OH)3 and Cr(OH)4- (Rai et al., 1986, 1987). The Cr3+ species is prevalent only at pH lower than about 4. With increasing pH, hydrolysis of Cr3+ yields Cr(OH)2+ and Cr(OH)2+ (generally present in groundwater at a pH of 6 to 8 but also in some acidic waters), and Cr(OH)3 and Cr(OH)4– (generally in alkaline groundwater) (Rai et al., 1987). Polymeric species such as Cr2(OH)24+, Cr3(OH)45+ and Cr4(OH)66+ are never significant in natural systems (Rai et al., 1986, 1987). Cr(III) readily forms complexes with a variety of ligands: hydroxyl (OH-), sulfate (SO42-), ammonium (NH4+), cyanide (CN-) and sulphocyanide (SCN-), fluoride (F-) and chloride (Cl-)(to a lesser extent), and natural and synthetic organic ligands (Richard and Bourg, 1991). Only one Cr(III) compound, Cr2O3, is an oxide, so the role of oxygen is central to the redox process for Cr (Kimbrough et al., 1999).

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Solubility can significantly limit the concentration of Cr(III) in groundwater at a pH above 4. The low solubility of the Cr(III) solid phases, Cr2O3 and Cr(OH)3 (Hem, 1977), is likely the major reason why Cr(III) generally makes up a small percentage of the total Cr concentration in natural or contaminated groundwaters. Cr(III) tends to be essentially immobile in most groundwaters because of its low solubility (Calder, 1988).

5.2.2

Cr(VI)

Chromium(VI) exists in the environment as part of several compounds, Cr(VI) is present in solution as monomeric forms: H2CrO4, HCrO4– (hydrogen chromate), CrO42–, and CrO3 (chromium(III) oxide), or as Cr2O72– (dichromate) (Palmer and Puls, 1994). Under oxidizing conditions, aqueous Cr is present in a Cr(VI) anionic form, HCrO4– or CrO42–, depending on the pH (CrO42– at a higher pH) (Richard and Bourg, 1991). Within the normal pH range in natural waters (i.e., 6 to 8), the CrO42–, HCrO4– and Cr2O72– ions are the forms expected. At relatively high Cr(VI) concentrations, the Cr2O72– ion predominates in acidic environments (Richard and Bourg, 1991). It should be noted here that the term Cr(VI) is somewhat of a misnomer. This is because Cr(VI) is not present in the environment as a free cation, Cr6+, (whereas Cr(III) does exist in the environment as Cr3+ as previously mentioned). In fact, as all Cr(VI) species are oxides, they act like a –2 anion (ion2–) rather than a Cr(VI) cation (Kimbrough et al., 1999). The relative concentration of the various Cr(VI) species depends on the pH and the total Cr(VI) concentration (Palmer and Puls, 1994). For example, significant concentrations of H2CrO4 only occur under the extreme condition of pH around 1. Above a pH of about 6, CrO42– generally dominates (Davis and Olsen, 1995). Below pH of about 6, HCrO4– dominates when the Cr(VI) concentrations are relatively low, but Cr2O72– becomes more significant as Cr(VI) concentrations increase, or it may even dominate when the total Cr(VI) concentrations are relatively high (Palmer and Puls, 1994). These constitute many of Cr(VI) compounds which are quite soluble and thus mobile in the environment (Kotas and Stasicka, 2000). These species differ in their solubility and in their tendency to be sorbed by soil or aquifer materials (Calder, 1988). There are no significant solubility constraints on the concentrations of Cr(VI) in groundwater. CrO42– and Cr2O72– are water soluble at all pH. However, CrO42- can exist as an insoluble salt of a variety of divalent cations, such as Ba2+, Sr2+, Pb2+, Zn2+, and Cu2+, and these salts have a wide range of solubilities. The rates of precipitation/dissolution reactions between CrO42-, Cr2O72- anions, and these cations vary greatly and are pH dependent. An understanding of the dissolution reactions is particularly important for assessing the environmental effects of Cr because Cr(VI) often enters the environment by dissolution of CrO42- salts (e.g., SrCrO4) (Rai et al., 1987).

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Oxidation-Reduction of Chromium

Chromium in the environment is altered by redox reactions, changing its physical and chemical properties. To understand these changes, it is worthwhile to review the basics of oxidation and reduction.

5.3.1

Review of Oxidation-Reduction (redox) Reactions

Oxidation-reduction reactions involve the transfer of electrons. In redox reactions, some components (charged/uncharged atoms) lose electrons and some components gain electrons from this transfer. The process of removing electrons from a component (loss of electrons) is called oxidation and results in a more positive oxidation number. After oxidation has occurred, the component is said to have been oxidized. The process of adding electrons to an atom (gain of electrons) is called reduction, and results in a more negative oxidation number. After reduction has occurred, the component is said to have been reduced. The component which gains electrons in an redox reaction is called the oxidizing agent, whereas the component which loses electrons is the reducing agent. Owing to the conservation of mass, and also the conservation of electrons and oxidation numbers, electrons lost by the oxidized component are gained by the oxidizing agent. Therefore, oxidation is always accompanied by reduction, and the oxidation and reduction always takes place to an equal degree. For this reason, reference is usually made to combined redox reactions rather than separate oxidation or reduction reactions. It is sometimes useful to consider the oxidation reaction and reduction reaction separately as “1/2 reactions”. The potential for an electron transfer is best measured by the redox potential (Eh), which is sometimes expressed as the redox intensity factor (pe), the negative log of the electron activity (ae), pe = - log (ae)

(5.1)

Also, Eh = (pe)(2.3RT/F) = 0.059 pe where R = gas constant T = temperature F = Faraday constant essentially the ratio of electron donors (oxidizing agents) to electron acceptors (reducing agents) (Kimbrough et al., 1999).

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General Redox Behavior of Chromium in the Environment

The oxidation and reduction of Cr in the environment is discussed by several authors, including Kimbrough et al. (1999), Richard and Bourg (1991), and Calder (1988). Their presentations are summarized below, followed by separate, more detailed discussions of Cr oxidation and reduction. The distribution between Cr(III) and Cr(VI) in the environment, including aquatic environments such as groundwater, will be regulated by redox reactions and redox conditions (Richard and Bourg, 1991). To understand the distribution of Cr(III) and Cr(VI), Eh-pH diagrams for Cr in aqueous environments are usually employed, such as the one discussed earlier in Chapter 3. The redox transformation of Cr(III) to Cr(VI), the oxidation of Cr(III), or the reduction of Cr(VI) to Cr(III), requires another redox couple (of oxidizing/ reducing agent) which accepts or gives the necessary electrons. In natural aquatic environments, the significant redox couples (reducing agents/oxidation agents) are (Richard and Bourg, 1991): • • • • • •

H2O/O2 (aq) Mn(II)/Mn(IV) NO2/NO3 Fe(II)/Fe(III) S2–/SO42– CH4/CO2

In the case where O2 is the oxidizing agent, oxidation of Cr requires donation of electrons to oxygen, while reduction of oxygen requires the accepting of electrons from Cr. For a given Cr compound, the redox reactions involving other chemical agents (i.e., oxidizing and reducing agents) are governed by the agents’ capacity for donating or accepting electrons. Several oxidation and reduction reactions of Cr with common environmental agents are given in several sources, including Kimbrough et al. (1999). Oxidation Example: Cr(III) Æ Cr(VI) 2Cr2O3 + 3O2 Æ 4CrO3

(5.2) (5.3)

The concentration of these oxidizing and reducing agents affects the oxidation-reduction of Cr. Many oxidizing agents are known to oxidize Cr(III) to Cr(VI), but only a few of them are found in the environment (i.e., groundwater) in sufficient concentration to do so. On the other hand, the many reducing agents for Cr(VI) reduction to Cr(III) are typically found at sufficient concentrations. For example, ozone (O3) can theoretically oxidize Cr(III) to CrO42- (a reaction with Eh = 0.87 V), but the concentration of O3 in the environment is usually insufficient (it is relatively unstable) to accomplish this oxidation (Grohse et al., 1988). However, the reduction of Cr(VI) by

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Fe(II), even though less favored thermodynamically (a reaction with Eh only 0.56, V) is feasible because Fe concentrations are generally sufficient in the environment (Rai et al., 1989). At lower pH, CrO42- exist as chromic acid (H2CrO4) and hydrogen chromate (HCrO4–). When the concentration of CrO42– is high, CrO42- are transformed to dichromate (H2Cr2O7 or HCr2O7–), which are strong oxidizing agents and are thus rapidly reduced in the presence of reducing agents at low pH or high Eh. At high pH and lower Eh, CrO42-, a poor oxidizing agent, is prevalent. Cr(VI) can be transported great distances in groundwater owing in part to its high solubility, whence it may be transformed by reduction to, and precipitated as, Cr(III) if the transported Cr(VI) enters an area with relatively low Eh. Cr(VI) can be reduced readily to Cr(III) in the presence of organic matter, especially where pH is low (Bartlett and Kimble, 1976; Bloomfield and Pruden, 1980). Cr(VI) can also be reduced by Fe(II) and dissolved sulfides (Schroeder and Lee, 1975). Cr(III) generally is not transported great distances by groundwater because of its low solubility. However, Cr(III) can be transformed to the more soluble Cr(VI) if the redox conditions along the transport pathway change from reducing to oxidizing. Under natural conditions, Cr(III) has been found to be oxidized to Cr(VI) by Mn (Schroeder and Lee, 1975; Bartlett and James, 1979). In the laboratory, Cr(III) can exist as highly soluble organic complexes, particularly under low pH conditions (Bartlett and Kimble, 1976; James and Bartlett, 1983). Therefore, if Cr(III) is in a complexed form, it could be present at much higher concentrations in groundwater than if it is uncomplexed. However, the existence of Cr(III) complexes has not been documented under field conditions. 5.3.3

Oxidation of Chromium

There are several sources of oxygen for the oxidation of Cr. In the environment, water is the most important source; MnO2, O3, hydrogen peroxide (H2O2), and lead(IV) oxide (PbO2) are other notable sources of oxygen (Kimbrough et al., 1999). Oxidation of Cr involving these sources requires the presence of water, thus water chemistry is important to the understanding of Cr oxidation. Generally, high values of Eh in water correspond to strongly oxidizing conditions. A summary of Cr(III) oxidation via dissolved oxygen, MnO2, and H2O2 are discussed below, based on papers by Kotas and Stasicka (2000); Loyaux-Lawniczak et al. (2001); Palmer and Puls (1994); Davis and Olsen (1995); and Richard and Bourg (1991). 5.3.3.1

Oxidation of Cr(III) to Cr(VI) by Dissolved Oxygen and Manganese Dioxides The redox potential of the Cr(VI)/Cr(III) couple is high enough so that only a few oxidants are present in natural systems capable of oxidizing

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Cr(III) to Cr(VI). Only dissolved oxygen and MnO2 are known to oxidize Cr(III) to Cr(VI) (Eary and Rai, 1987) and MnO2 is the more common oxidant; oxidation of Cr(III) by dissolved oxygen without any mediate species has been reported to be negligible (Schroeder and Lee, 1975; Eary and Rai, 1987), whereas mediation by Mn oxides has been found to be the effective oxidation pathway in environmental systems (Schroeder and Lee, 1975; Bartlett and James, 1979; Nakayama et al., 1981; Saleh et al., 1989; Johnson and Xyla, 1991). Dissolved oxygen can oxidize Cr(III) into Cr(VI), (Rai et al., 1986; Schroeder and Lee, 1975; Eary and Rai, 1987; Nakayama et al., 1981) but laboratory studies indicate that this can be relatively slow requiring several months (Palmer and Wittbrodt, 1990), especially in slightly acidic to basic environments (Eary and Rai, 1987). Such slow kinetics enable Cr(III) to be involved in other reactions (sorption or precipitation) that are much faster. Therefore, the oxidation of Cr(III) in the environment by dissolved oxygen is unlikely. Manganese oxides are likely to be responsible for most Cr(III) oxidation in aquatic environments. Fendorf and Zasoski (1992) suggest that CrOH2+ is the reactive species in this Cr(III) oxidation. Bartlett and James (1979) observed a correlation between the amount of Cr(III) oxidized by soils and the amount of reduced Mn in soils, thereby suggesting the oxidation of Cr(III) is the result of interaction with MnO2, which has been verified by laboratory studies. Experimental results indicate that the oxidation follows the reaction (Palmer and Puls, 1994): 2CrOH2+ + 3d - MnO2 Æ 2HCrO4- + 3Mn2+

(5.4)

Manganese oxides are present in the subsurface as grain coatings, deposits in cracks or fractures, or as finely disseminated grains; sometimes this presence is a result of bacterial activities. The mechanisms for the reaction with MnO2 occurring at the Mn oxide surfaces (by adsorption of Cr(III) on active surface sites) are very complex and not yet fully understood (Eary and Rai, 1987; Fendorf and Zasoski, 1992). The Cr(III) oxidation rate is likely related to the amount and surface area of Mn oxides (Schroeder and Lee, 1975; Eary and Rai, 1987), and lab studies indicate this rate to be initially rapid, but then slowing down significantly. Also, there is an increase in the rate and amount of Cr(III) oxidation as pH decreases, and the surface area to solution volume increases. Richard and Bourg (1991) explain that the oxidation of Cr(III) by MnO2 is likely to occur as a result of three sequential steps (Rai et al., 1986; Schroeder and Lee, 1975; Bartlett and James, 1979; Eary and Rai, 1987; Amacher and Baker, 1982). First, the Cr(III) would be sorbed onto MnO2 surface sites. Then, the Cr(III) would be oxidized to Cr(VI) by Mn(IV) on the surface sites, however, all the Mn(IV) reaction sites are probably not accessible to Cr(III) (Rai et al., 1986; Amacher and Baker, 1982). Finally, the reaction products,

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Cr(VI) and Mn(II), would be desorbed. Richard and Bourg (1991) give theoretical stoichiometries that have been suggested for this oxidation: 2Cr3+ + 3d -◊MnO2(s) + 2H2O = 2HCrO4- + 3Mn2+ + 2 H+ (Amacher and Baker, 1982)

(5.5)

and Cr(OH)2+ + 3d -◊MnO2(s) + 3H2O = HCrO4- + 3MnOOH(s)+ 3H+ (Eary and Rai, 1987) (5.6) The solid MnOOH(s) would dissolve later into Mn2+ (aqueous) into aqueous Mn2+ afterwards. 5.3.3.2

Oxidation of Cr(III) to Cr(VI) by H2O2

In an attempt to mobilize Cr(III) by oxidizing it to Cr(VI), H2O2 was applied to groundwater in laboratory studies by Davis and Olsen (1995). Also, Pettine et al. (2002) have studied the oxidation of Cr(III) with H2O2 in basic solutions (Pettine and Millero, 1990 and 1991). They found that H2O2 controls the rate of oxidation of Cr(III) in surface waters.

5.3.4 5.3.4.1

Reduction of Cr(VI) to Cr(III) General

Cr(VI) is a strong oxidant and therefore can be reduced in the presence of electron donors. The most common forms of Cr dissolved in natural waters, within the environmentally normal range of pH, are CrO42–, HCrO4– and Cr2O72– ions, (Kotas and Stasicka, 2000) which form many of the Cr(VI) compounds that can be quite readily reduced to Cr(III) forms in the presence of electron donors like organic matter and inorganic compounds in their reduced state, many of which are quite common in soil, water, and the atmosphere (Stollenwerk and Grove, 1985). The major factors in this reduction to Cr(III) are dissolved Fe(II), minerals with Fe(II), sulfides (reduced sulfur), and organic matter (Kotas and Stasicka, 2000; Palmer and Puls, 1994; Wielinga et al., 2001). Studies of reaction kinetics by Fendorf et al. (2001) indicate that Fe(II) and dissolved sulfides will probably dominate the reduction of CrO42- (Wielinga et al., 2001). Loyaux-Lawniczak et al. (2001) report that photoreduction is another pathway to reduce Cr(VI) in the environment (Kieber and Heiz, 1992; Hug et al., 1997), but this mechanism is probably only important in the atmosphere or in upper surface waters. Much of the information of Cr(VI) reduction is based on laboratory studies, and many are referenced herein. However, it should always be noted that the application of these experimental observations to field situations remains dubious. Cr(VI) can be reduced by biological and chemical (abiotic) processes. It is difficult to determine which processes are responsible for the reduction of

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metal contaminants. However, it is probable that the reaction rates will determine the reduction process and its specific pathway. By comparing reduction rates involving Fe(II) and sulfides with those reported for direct microbial reduction, the chemical reduction of CrO42- by Fe(II) is more than 100 times faster than the observed biological reduction rate, thus chemical reduction of Cr(VI) will probably be the main process for CrO42- reduction when either Fe(II) or sulfides are present, and these are present in the environment under anaerobic conditions (Wielinga et al., 2001). Yet, both aerobic and anaerobic reduction by microbes have been observed, the latter being more common (Palmer and Puls, 1994). The specific mechanisms for Cr(VI) reduction by these microbes is not well known, but the CrO42- may actually be used as an electron acceptor for cell metabolism (Palmer and Puls, 1994). The major factors in the reduction of Cr(VI) to Cr(III), namely dissolved Fe(II), minerals with Fe(II), sulfides (reduced sulfur), and organic matter, are discussed below, based on papers by Pettine et al. (2002); Palmer and Puls (1994); Wielinga et al. (2001); and Richard and Bourg (1991). The roles of copper and H2O2 are also discussed. 5.3.4.2 Iron(II) (Dissolved Fe(II) and Fe(II)-Containing Minerals) Iron(II) is a major factor in the reduction of Cr(VI) to Cr(III) — experimental results of Davis and Olsen, 1995 from column tests were consistent with other published observations (Schroeder and Lee, 1975) that found Cr(VI) to be reduced to Cr(III) by Fe(II). Dissolved Fe(II) ions in environmental waters can be generated by the discharges of some industrial wastes, but also can result from the weathering of Fe(II)-containing minerals. Numerous minerals in geologic materials contain Fe(II) for Cr(VI) reduction, including silicates, oxides, or sulfides (Palmer and Puls, 1994): • Silicates: Olivine, pyroxenes (augite and hedenbergite), amphiboles (hornblende, cummingtonite, and grunerite), micas (biotite, phlogopite, and glauconite), chlorites, and clays (the smectite nontronite) • Oxides: Magnetite, ilmenite, and hematite • Sulfides: Pyrite (FeS2), in which both the iron(II) and the sulfide are active in reducing Cr(VI) Cr(VI) reduction via Fe(II) in silicate minerals (e.g., biotite in solution rather than at the mineral surface) was reported by Eary and Rai. (1989). This is described by Palmer and Puls (1994) as a rather complex process. The presence of Fe3+ increases the reduction rate, and the Fe3+ is reduced at the mineral surface. The Fe in the crystal structure is oxidized, K+ is released to solution, and Cr(VI) in solution is then reduced by the Fe2+. The Fe3+ resulting from this reduction reaction is then sorbed to the surface of the biotite where it is again reduced to Fe2+. Palmer and Puls (1994) state that Cr(VI) reduction in the presence of Fe oxides has been observed in several experiments (Eary and Rai, 1989; White

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and Hochella, 1989). In the case of hematite, the reduction is suggested to occur in solution after the FeO component has dissolved. The reduction of Cr(VI) via Fe(II) in pyrite is described in work by Lancy (1966), who suggested that pyrite could be used for treating spent cooling waters that contain Cr(VI) as a corrosion inhibitor, because reduction of Cr(VI) occurs at the pyrite surface rather than in solution. This reduction was described as occurring even in slightly alkaline solutions; however, the pyrite had to be continuously abraded to remove surface coatings. Batch testing reported by Blowes and Ptacek (1992) involving pyrite both in the presence and in the absence of calcite showed faster removal of Cr(VI) with no calcite. Also, Loyaux-Lawniczak, et al. (2001) demonstrated that Fe(II)-Fe(III) hydroxysalt green rusts can reduce Cr(VI); ferrihydrite is the Cr(III)-bearing solid phase that is formed from this reduction. Under neutral to alkaline pH conditions, Fe(II) controls the reduction of Cr(VI) in natural anaerobic systems (Pettine et al., 1998), while at acidic pH other reductants may be more efficient than Fe(II). The involvement of Fe(II) in Cr(VI) reduction, where the Fe(II) (as FeO) comes from hematite or biotite, can be expressed as follows (Richard and Bourg, 1991): [3FeO] + 6H+ + Cr(VI)(aq) = Cr(III)(aq) + 3Fe(III)(aq) + 3H2O

(5.7)

This can be a relatively rapid reaction from the standpoint of environmental situations; laboratory studies report this reaction being complete in less than 5 min (Eary and Rai, 1988). In acidic waters, the end products of this reaction are Fe(III) and Cr(III) (Stollenwerk and Grove, 1985), whereas under neutral to alkaline conditions, Cr(OH)3 is probably the end product because of the very low solubility of Fe(OH)3 (Rai et al., 1988). In groundwaters of pH more than 4, Cr(III) precipitates with the Fe(III) in a solid solution with the general composition CrxFe1–x(OH)3 (Eary and Rai, 1988; Rai et al., 1988; Sass and Rai, 1987). Wielinga et al. (2001) reported that the Cr(VI) reduction via Fe(II) (or sulfide) depends on microbial activity. A diverse and widely distributed group of bacteria are able to couple the oxidation of organic compounds or H2 to the reduction of Fe hydroxides (Lovely, 1993; Coates et al., 1996). Thus, in many environments where Fe reduction is the predominant terminal electric accepting process (TEAP) in microbial respiration, the indirect reduction of Cr(VI) (CrO42-) via reaction with a respiratory byproduct is likely a dominant reductive pathway as shown below (Wielinga et al., 2001): 3C3H5O3- + 12Fe(OH)3 Æ 3C2H3O2- + 12Fe2+ + 3HCO3- + 8H2O + 21OH-

2+

-

+

3Fe + HCrO4 + 8H2O Æ 3Fe(OH)3 + Cr(OH)3 + 5H

(5.8) (5.9)

This reduction of Cr(VI) (CrO42-) is via a coupled, two-step, biotic-abiotic reaction pathway in which Fe(II) produced during iron respiration catalyzes the reduction of Cr(VI). Thus, attenuation of CrO42- in saturated, subsurface

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environments may be in large part attributable to Fe reduction. In addition, the capacity for soils to reduce and immobilize Cr(VI) could be dramatically underestimated if this biotic-abiotic process is not considered. Wielinga et al. (2001) emphasize that the implications of these reactions is important—the primary terminal electron acceptor is continually regenerated. Fe(II) produced in the first reaction listed (Equation 5.6) is cycled back to Fe(III) in the second listed reaction (5.7) thereby acting as an electron shuttle (a catalytic role) between the bacteria and Cr. Thus, a significant amount of Cr(VI) could potentially be reduced even with little available Fe. With the rapid cycling of Fe(II) back to Fe(III), evidence such as high pore water Fe(II) concentrations in pore water could be hidden. 5.3.4.3 Reduced Sulfur Reduced sulfur such as S, S2-, H2S, S2O32- can be a major factor in the reduction of Cr(VI) to Cr(III). Although most sulfides (S2-) are not soluble, some dissolved S(II) ions can be present in the environment owing to processes including the discharge of industrial wastes, the decomposition of organic matter, and SO42- reduction (a common process in the biodegradation of chlorinated solvent chemicals). Laboratory studies have reported that the reduction of Cr(VI) involving sulfides is initially rapid, slows down in a few minutes, but reaches completion after one day (Schroeder and Lee, 1975). The rates of reduction of Cr(VI) with H2S have been studied by Pettine et al. (1994) and Pettine et al. (1998).

5.3.4.4 Organic Matter Organic matter is an important reductant in soils. Much of the organic matter (i.e., organic carbon) in soil is present as humic and fulvic acids. Organic matter, important in the reduction of Cr(VI), is also present as simple amino-acids (Schroeder and Lee, 1975). The reduction of Cr(VI) by soil humic and fulvic acids has been demonstrated by several researchers as referenced in Palmer and Puls (1994). This reduction, with an intermediate Cr(V) species, is favored by acidic conditions (Bloomfield and Pruden, 1980; Stollenwerk and Grove, 1985; Cary et al., 1977; Grove and Ellis, 1980). The rate of reduction of Cr(VI) decreases with increasing pH, increases with the increasing initial Cr(VI) concentration, and increases as the concentration of soil humic substance increases (Palmer and Puls, 1994). At a very low pH, laboratory studies indicate that the half-life for Cr(VI) reduction with humic acids is approximately three days, whereas several days are required within the pH range of 4 to 7 (Eckert et al., 1990). 5.3.4.5 Copper(I) Reduced copper [Cu(I)] may also play a role in the reduction of Cr(VI) to Cr(III), discussed by Pettine et al. (2002) especially in atmospheric and

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surface waters with low pH and low ionic strength (Abu-Saba et al., 2000). The reduction of Cr(VI) with Cu(I) has been produced in the laboratory by radiolysis experiments in dilute solutions in the presence of Cr(II).

5.3.4.6

Hydrogen Peroxide (H2O2)

The role of H2O2 in the reduction of Cr(VI) is discussed by Pettine et al. (2002) who describe H2O2 as an oxidant of Cr(III) at pH > 7.5, a reductant at lower pH, and its strength as a reductant being greatly increased at low pH. In acid wastes receiving freshwater, and in atmospheric aqueous media with pH ranging from about 1 to 5, the reduction of Cr(VI) with H2O2 is thermodynamically possible (Seigneur and Constantinou, 1995), and has been used in treatment processes for removing Cr(VI) from wastewaters (Eary and Rai, 1988). In the latter, the reduction of Cr(VI) with H2O2 includes a preliminary conversion of Cr(VI) to Cr(III) and its subsequent precipitation.

5.4

Precipitation/Dissolution Reactions of Chromium

In addition to oxidation-reduction (redox) mechanisms for Cr(VI) reduction as discussed above, Cr can undergo precipitation dissolution reactions (Bodek et al., 1988), which are governed by the solubility of the Cr compound and the kinetics of the dissolution. Kimbrough et al. (1999) list and discuss these reactions. Most Cr(III) species that are water-soluble do not occur naturally and are unstable in the environment. The principle Cr(III) reaction in water is the formation of Cr hydroxides of varying solubilities. The precipitation of Cr(III) as the mixed Fe-Cr hydroxide (Cr,Fe)(OH)3, discussed previously, enhances the precipitation of Cr(III) in waters with neutral pH levels. The kinetics of this reaction is rather rapid, making it an important solubility controlling compound (Sass and Rai, 1987). The Cr(VI) ions, CrO42– and Cr2O72– are water soluble at all pHs. However, CrO42- can exist as the insoluble salt of a variety of divalent cations, such as Ba2+, Sr2+, Pb2+, Zn2+, and Cu2+. The rates of precipitation/dissolution reactions between CrO42-, Cr2O72-, and these cations vary greatly and are pH dependent. An understanding of the dissolution reactions is particularly important for environmental assessments because Cr(VI) often enters the environment by dissolution of such chromate salts. Dissolution of somewhat soluble chromate salts (e.g., SrCrO4) is particularly important because they provide a continual source of CrO42- anions.

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181

Sorption and Desorption Reactions of Chromium General Discussion of Sorption

McLean and Bledsoe (1992) and Calder (1988) give general discussions of sorption, which are summarized here. It is first important to define and distinguish some important terms, which are used interchangeably, properly and improperly, in the literature. The general term sorption actually comprises two processes: (1) adsorption, the process by which a solute clings to a solid surface; and (2) absorption, the process by which the solute diffuses into a porous solid and clings to interior surfaces. Sorption is important in the transport and fate of a constituent. An equilibrium distribution coefficient (Kd) is used in the estimation of the retardation of a constituent’s migration in groundwater. As with redox and precipitation reactions, sorption reactions are highly influenced by the complex environmental conditions inherent in the subsurface. Therefore, general assumptions about sorption cannot be made. Such variables as pH, surface area, density of active sites, among others, influence sorption equilibrium (Kimbrough et al., 1999). Sorption studies also can are used to evaluate the effect that changing a soil solution parameter, (e.g., adjustment of pH, ionic strength, addition of competing cations, or addition of inorganic or organic ligands) has on the retention of a constituent by the aquifer matrix. Laboratory studies generate sorption isotherms, which describe equilibrium conditions of sorption. These isotherms are the relationship between the amount of constituent sorbed and the equilibrium concentration of the constituent. If the isotherm is linear, a single coefficient (Kd) can be defined to describe sorption. For metals, such as Cr, the relationship is seldom linear. Soil processes are never at equilibrium; soil systems are dynamic and are thus constantly changing. Therefore, other equations with two or more coefficients must be used. Nonlinear sorption behavior of metals in soil are usually expressed by the Langmuir and the Freundlich equations, even though sorption of metals by soils violates many of the assumptions associated with these equations. For nonlinear sorption, groundwater transportation equations must be solved iteratively using a concentration-dependent retardation factor because the retardation of the contaminant will vary with time owing to changing solution concentrations as the plume of contaminated groundwater passes a particular portion of the aquifer segment. This makes comparisons and predictions more difficult than for the linear adsorption model. Equilibrium studies predict whether a reaction will occur but give no indication of the time necessary for the reaction to take place. Therefore, kinetic studies have been performed to establish the proper time interval for use in equilibrium sorption/desorption studies. Many mathematical transport models now allow a kinetic term for sorption.

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Adsorption occurs because dissolved ionic species are attracted to mineral surfaces that have a net electrical charge due to imperfections or substitutions in the crystal lattice or chemical dissociation reactions at the particle surface. This electrical charge varies with pH. The importance of sorption to the transport and fate of constituents in groundwater is that it retards the advance of the contaminant with respect to the groundwater velocity, and can also reduce the contaminant concentration. However, sorption is reversible, meaning that sorbed contaminants can be released back into the aqueous medium, causing an increase in concentrations after periods of decreasing concentrations. Davis and Olsen (1995) showed that in laboratory experiments with columns containing predominantly Cr(III) that were not augmented by additives, less than 2.5% of the total Cr was leached, while in soil bearing primarily Cr(VI), over 80% of total Cr was leached; Cr(VI) readily dissolved or desorbed from contaminated soils, while Cr(III) occurred in a predominantly nonleachable form. 5.5.2

Sorption of Chromium

Several papers, notably Calder (1988); Richard and Bourg (1991); and Davis and Olsen (1995) give detailed discussion of the sorption of the different forms of Cr in the subsurface. Their work is discussed below. Also, Calder (1988) gives examples of Cr(III) and Cr(VI) partitioning ratios (e.g., Kd) that can be used to describe the sorption of Cr and describes the effect of different values pH and Cr concentrations on sorption. 5.5.2.1 Sorption of Cr(III) Cr(III) is rapidly, strongly and specifically sorbed in soil by Fe and Mn oxides, clay minerals, and sand (Bartlett and Kimble, 1976; Schroeder and Lee, 1975; Korte et al., 1976; Griffin et al., 1977; Rai et al., 1984; Dreiss, 1986). According to experimental data, this sorption is rapid, with about 90% of Cr being sorbed by clay minerals and Fe oxides in 24 h. Furthermore, the sorption of Cr(III) increases with increasing pH (Griffin et al., 1977; Rai et al., 1984) (as the clay surfaces become more negatively charged) and increasing organic matter content of soils (Paya Perez et al., 1988); whereas the adsorption of Cr(III) decreases when other inorganic cations or dissolved organic ligands are present. Partitioning ratios (Kd) for Cr(III) have been estimated to be very high. Cr(III) sorption is nonlinear, however, so the Kd sorption model cannot be used for assessing retardation except for a particular concentration. If these partitioning ratios were equivalent to Kd’s, retardation factors of 500 to 6,100 could be estimated, indicating the relative immobility of Cr(III) due to sorption at a pH of around 4. Above this pH, Cr(III) would also be relatively immobile because of its low solubility. It is probable that Cr(III) mobility would be enhanced by the formation of complexes owing to their decreased sorption or increased solubility compared with the uncomplexed form of Cr(III).

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5.5.2.2 Sorption of Cr(VI) The ions, HCrO4– and CrO42–, can be sorbed by Mn, Al, and Fe oxides and hydroxides (positively charged surfaces), clay minerals and natural solids and colloids (Rai et al., 1986; James and Bartlett, 1983; Stollenwerk and Grove, 1985; Rai et al., 1988; Griffin et al., 1977; MacNaughton, 1975; Davis and Leckie, 1980; Music et al., 1986; Zachara et al., 1987). These substances commonly coat aquifer materials (Stumm and Morgan, 1981). Amorphous Fe is the adsorbate found at the highest concentrations in most aquifer materials. The batch experiments of James and Bartlett (1983) confirm that Fe hydroxides strongly sorb to Cr(VI). Batch sorption data from experiments on Cr(VI) conducted by Davis and Olsen, 1995 conformed best to a Freundlich isotherm, but Langmuirean behavior at a neutral pH, and a decreasing Kd of Cr(VI) with increasing concentration, has been reported (Griffin et al., 1977), probably owing to competitive inhibition for surface sites at higher Cr concentrations. Davis and Olsen, 1995 note that their observed linear sorption is probably owing to the lower range of Cr concentrations used in their experiments. This sorption is pH dependent (Richard and Bourg, 1991). At dilute concentrations, adsorption of Cr(VI) increases as pH decreases, no matter what the sorbent (Rai et al., 1986; Bartlett and James, 1979; Rai et al., 1988; Griffin et al., 1977; Rai et al., 1984; Davis and Leckie, 1980; Zachara et al., 1987). This suggests that Cr(VI) sorption is favored on sorbents which are positively charged at low to neutral pH. Interestingly, compared to clay, sandy material has a greater preponderance of positively charged surfaces over the pH 5 to 7.5 range, resulting in a greater affinity for CrO42– and thus a higher Kd of Cr(VI) on sand than for clay. Lower pH values result in higher Kd values, based on published Cr(VI) sorption data for sandy soils compared with soils containing kaolinite and montmorillonite clays. Sorption of Cr(VI) by clays, soils, and natural aquifer materials is low to moderate in pH ranges common to groundwater. Sorption of Cr(VI) characteristically decreases with increasing pH due to the decrease in positive surface charge of the sorbing medium. Furthermore, Cr(VI) sorption has been found to be nonlinear (Stollenwerk and Grove, 1985; Griffin et al., 1977), fitting the Langmuir adsorption model. Similar to the discussion of Cr(III) previously, if Cr(VI) adsorption were linear, the calculated partitioning ratios would correspond to retardation factors of 2.5 to 329 (much lower than those calculated for Cr(III)), indicating that Cr(VI) mobility at pH 7 could range from high to low—lower below a pH of 7 and higher above a pH of 7 (and above a pH of 8.5, Cr(VI) would be entirely unretarded). Competing anions have a drastic effect on Cr(VI) sorption, with the effect being variable, depending on dissolved concentrations of the competing anion and CrO42–, on their relative affinities for the solid surface, and on surface site concentration (Rai et al., 1986). The competitive sorption of Cr(VI) with cations and anions has been investigated by much research (Rai et al., 1986; Stollenwerk and Grove, 1985; Rai et al., 1988; Rai et al., 1984; Music et al., 1986;

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Zachara et al., 1987; Benjamin and Bloom, 1981). The electrostatic sorption of anions is enhanced by cation sorption (owing to enhanced positive surface charge). Also, CrO42- either increase or has no effect on the sorption of heavy metals (Cd2+, Co2+, Zn2+) ie., metals with density greater than 5g/cm3; competition for surface sites is relatively minor (Benjamin and Bloom, 1981). Additionally, sorption of CrO42- in the presence of a mixture of ions is lower than in two-solution systems, particularly when hydrogen silicate ion (H2SiO42–) is present. The effect appears to be additive (Rai et al., 1986; Zachara et al., 1987). Richard and Bourg (1991) note that the kinetics of Cr(VI) sorption are not well documented. The sorption of CrO42- on soils apparently follows a twostep reaction rate (Amacher et al., 1988). Also, sorption of Cr(VI) does not seem totally reversible. Amacher et al. (1986) attributed this lack of reversibility to reduction of Cr(VI) to Cr(III), possibly by organic matter from the soil they studied.

5.6

General Transport and Fate of Chromium in Environmental Media

Kimbrough et al. (1999) discuss a generalized intermedia transport scheme for environmental Cr. Cr is directly emitted from industrial activity either into the air, into water systems (e.g., streams, sewers, lakes, etc.), or to the ground. Airborne Cr eventually settles out into soil or water. In a given parcel of soil, there can be a mixture of Cr(VI) and Cr(III), both naturally occurring and anthropogenic. Cr(VI), but not Cr(III), can be leached out of the soil and enter groundwater, which in turn can become part of an aquifer and also migrate to surface waters. As Cr(VI) is leached from the soil, the remaining Cr(III) can slowly oxidize to Cr(VI) to reestablish the equilibrium of the soil (Bartlett, 1991). In surface waters, Cr(VI) can migrate in the dissolved form, while both Cr(III) and Cr(VI) can migrate while being bound with dissolved organic carbon (DOC) or suspended particles. And, Cr can migrate from the aqueous phase to sediments from a dissolved state or with DOC or particles. In the sediment, dissolved Cr(VI) can be immobilized if it enters a stable anaerobic portion, but Cr(VI) in aerobic sediments can be redissolved. The following are discussions of each of these environmental compartments included in the general transport and fate of Cr in environmental. Presented are discussions of Cr in the atmosphere, aquatic environments (surface waters and groundwater), and soil, and the uptake of Cr by biota. 5.6.1

Chromium in the Atmosphere

Kotas and Stasicka (2000) and Kimbrough et al. (1999) give detailed discussions of the behavior of Cr in the atmosphere, and their work is summarized

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here. The majority of Cr in the atmosphere (approximately 60% to 70%) is owing to anthropogenic sources. Cr from natural sources accounts for the remaining amounts (Seigneur and Constantinou, 1995). Human activities that can product Cr in the atmosphere include metallurgical industries, refractory brick production, electroplating, combustion of fuels, the production of Cr chemicals (i.e., CrO42- and Cr2O72-, pigments, Chromium (VI) oxide (CrO3), Cr salts), the cement industry, production of phosphoric acid (H3PO4) in thermal processes, and combustion of refuse and sludges (Nriagu, 1988). Natural sources of Cr include volcanic eruptions, erosion of soils and rocks, airborne sea salt particles, and smoke from forest wildfires (Pacyna and Nriagu, 1988). Average atmospheric concentrations of Cr range from 1 ng/m3 in rural areas to 10 ng/m3 in polluted urban areas (Nriagu, 1988). The atmosphere has become a major pathway for long-range transfer of Cr to different ecosystems (Nriagu, 1988; Spokes and Jickells, 1995). Atmospheric Cr-containing particles are transported over varying distances by the wind, before they fall or are washed out from the air onto land and water surfaces, and the distance of transport depends on meteorological factors, topography, and vegetation (Nriagu, 1988; Spokes and Jickells, 1995). Wet precipitation and dry fallout of Cr from the atmosphere is greatly affected by particle size; the Cr oxidation state is less important. The atmospheric transport and fate of Cr largely occurs in the liquid phase and solids phases (i.e., droplets and particles) or, more generally, aerosols instead of as a gas (Seigneur and Constantinou, 1995). The size of the particles is important not only to the transport of Cr in the atmosphere, but to health effects as well. Only particles with diameters less than 10 mm are respirable; their retention in the lungs can pose a carcinogenic risk (Friess, 1989). Chromium in aerosols is generally removed from the atmosphere by both dry deposition and wet deposition. In dry deposition, the particles settle and are captured by the soil or surface waters via gravitational sedimentation, impaction, or interception. Wet deposition is the process where aerosol particles are actively entrained or scavenged by atmospheric moisture, such as rain, snow, fog, or dew. Cr can also be introduced, or reintroduced, into the atmosphere via wind resuspension of Cr-containing soil particles. The two stable oxidation states of Cr in the atmosphere are Cr(III) and Cr(VI). Atmospheric particles do not contribute to the chemical reactions that control the occurrence and ratio between Cr(III) and Cr(VI). Instead, precipitation, complex formation, and oxidation reactions influence the abundance and ratio of Cr(III) and Cr(VI). Computer simulations by Seigneur and Constantinou (1995) have led to the conclusion that typical atmospheric conditions favor the Cr(VI) reduction to Cr(III). This is the likely case because of the presence and concentrations of reducing agents in the air (i.e., V2+, Fe2+, H2S, HSO3–, NO2–, and organic materials) as well as the acidity of the atmosphere. Cr(VI) can be reduced rapidly in the atmosphere based on theoretical (Seigneur and Constantinou, 1995) and experimental (Grohse et al., 1988) studies. Estimates of atmospheric half-life for Cr(VI) reduction to Cr(III) range from 16 h (Grohse et al., 1988) to 4.8 days.

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The few materials capable of oxidizing Cr(III) to Cr(VI) in the atmosphere, such as ozone, occur in concentrations too low to produce measurable conversions in the atmosphere.

5.6.2

Chromium in Aquatic Environments

5.6.2.1 Surface Waters Kotas and Stasicka (2000) and Kimbrough et al. (1999) give detailed discussions of the behavior of Cr in surface aquatic environments, and their work is summarized here. Cr in natural waters originates from natural sources or from manmade pollution. Natural sources include the weathering of rock constituents, wet precipitation and dry fallout from the atmosphere, and run-off from the terrestrial systems. Manmade pollution sources to waters (mostly surface waters such as rivers) include the discharge of industrial wastewaters (i.e., from the metallurgical, electroplating, tanning, and dying industries), from sanitary landfill leaching, and from water cooling towers (Nriagu, 1988). The number and type of Cr species present in effluents depend on the character of the industrial processes using chromium. In natural waters, Cr exists in its two stable oxidation states, Cr(III) and Cr(VI). The presence and ratio between these two forms depend on various processes, which include chemical and photochemical redox transformation, precipitation/dissolution reactions, and adsorption/desorption reactions. Simplistically, Cr(III) should be the only form present in anaerobic or subanaerobic conditions, whereas in aerobic aqueous environments, Cr(VI) should be the only form present. However, the presence of Cr(III) and Cr(VI) is also dependent on the pH of the water. Under neutral to basic conditions, Cr(III) will tend to precipitate out, while under acid conditions, Cr(III) will tend to solubilize. While Cr(VI) ions (i.e., CrO42- and Cr2O72-) are extremely water soluble at all pHs, they can precipitate with a number of divalent cations. In waters of intermediate pH values, the Cr(III)/Cr(VI) ratio is largely dependent on the concentration of oxygen. In contrast to the atmosphere, many aqueous environments do contain oxidizing agents, such as MnO2 and Mn3+ in sufficiently high concentrations to produce measurable yields of Cr(VI). In oxygenated surface waters, not only are pH and oxygen concentration important, but the nature and concentrations of reducing agents, oxidation mediators, and complexing agents play important roles. These factors seem to be responsible for the occurrence of significant Cr(III) quantities in many oxygenated surface waters (Kieber and Heiz, 1992; Cranston and Murray, 1978 and 1980; Pettine et al., 1991). At times, Cr(III) can be the predominant Cr component in oxygenated waters (Chuecas and Riley, 1966). Several mechanisms for this might include Cr(VI) reduction via Fe(II), Cr(VI) reduction via H2O2, and dissolved organic matter. Other reducing agents might include H2S, S, NH4+, and V2+ (Eary and Rai, 1988; Bodek et al., 1988). The photochemical

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generation of Cr(III) has also been suggested (Kieber and Heiz, 1992; Kaczynski and Kieber, 1993). Both Cr(III) and Cr(VI) have been shown to bind with naturally occurring dissolved organic carbon (DOC). Organically bound Cr(III) can stay in solution at higher pH than unbound Cr(III) (Palmer and Wittbrodt, 1991) and organically bound Cr can also sorb to and desorb from the organic portion of suspended and settled sediments. Therefore, Cr migrates as either dissolved ions or as attached to particles, or both. The effect of sunlight can be important in surface water chemistry. The oxidation and reduction of Cr are affected by sunlight (Kaczynski and Kieber, 1994). Sunlight appears to degrade organically bound Cr, and this process releases inorganic Cr. Also, sunlight acts indirectly by assisting the reduction of iron, which also results in the formation of H2O2 (Kieber and Heiz, 1992; Beaubien et al., 1994) affecting the oxidation state of chromium. Additionally, sunlight aids the oxidation of Mn (Bartlett, 1991), also affecting the oxidation state of Cr. Chromium transport and fate in surface waters can be discussed by using three subsystems: rivers, lakes, and oceans. The transport pathways are controlled by specific conditions prevailing in each of these subsystems, including temperature, depth, degree of mixing, oxidation conditions, and amount or organic matter. Cr as a component of suspended particles is the most important transport mechanism in rivers. Dissolved Cr in river water decreases during its passage through turbid coastal environments. Lakes generally have relatively high levels of biologic activity and high ratios of sediment-to-water surface area, which greatly influence transport of metals. The high level of organic matter creates the medium for reduction and the formation of complexes, favoring the reduction of Cr(VI) to Cr(III), which is afterwards rapidly precipitated or sorbed onto the sediment minerals. And, Cr in sediments can be remobilized into the surrounding pore water via oxidation or solubilization of Cr(III) sediments. The most complex transport pathways of Cr are in seasonally anaerobic lakes (Beaubien et al., 1994; Achterberg et al., 1997) where deep basinal water in the summer months becomes anaerobic owing to the coupling of high biological activity and thermal stratification. Therefore, depth and season heavily influence the concentration and speciation of Cr. Dissolved Cr usually decreases in the summer months, and the areas dominated by Cr(VI) versus Cr(III) become more segregated to surface and deep layers, respectively. This distribution of Cr is consistent with what would be expected from seasonal increases in temperature, a decrease in pH, and the oxygen content in the basinal water. The aerobic regime favors Cr(VI), and Cr(III) is favored in anaerobic areas. Chromium generally enters oceans via rivers and from atmospheric fallout. Atmospheric inputs result in more homogeneous distribution of Cr in the ocean water compared with river inputs; the latter are the subject of eustarine removal processes and ocean circulation patterns Spokes and Jickells, 1995). It has been proposed that Cr sources to the oceans are mostly as particles (suspended solids from river and aerosols). In ocean waters,

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dissolved and precipitated Cr exist together in equilibrium. Dissolved Cr is generally removed from the aqueous phase and incorporated into biologic material (i.e., siliceous and carbonaceous skeletons) and by adsorption onto sediment particles. This removal occurs both in the water column and at the sediment–water interface, resulting in deep and bottom–water enrichment of dissolved Cr. Except in estuaries, Cr concentrations in seawater are dominated by chromates, probably due to the generally oxidizing conditions in the ocean and low suspended concentration of particles. Reduction of Cr(VI) occurs in anaerobic basins and the oxygen-free zones, where increased Cr removal may be due to Cr(III) adsorption onto bottom sediments (Smith et al., 1995). Cr cycling in the water column occurs in response to nutrient biogeochemistry. When Cr scavenged by particles is deposited on the ocean floor, diagenetic processes can lead to remobilization of Cr either as CrO42- or as organic Cr(III) complexes. The remobilization of Cr(III) from sediment can also occur by its oxidation, carried out mostly by MnO2. 5.6.2.2 Groundwater Richard and Bourg (1991) and Calder (1988) give detailed discussions of the behavior of Cr in groundwater environments, and their work is summarized here. The mobility of Cr in groundwater depends on its solubility and its tendency to be sorbed by soil or aquifer materials. These factors, in turn, depend on the groundwater chemistry and the characteristics of soil or aquifer material in contact with the Cr-containing groundwater. Otherwise, much of the basic considerations discussed for surface waters also apply for the understanding of the transport and fate of Cr in groundwater. Large plumes of Cr-contaminated groundwater in shallow aquifers have been well documented (Stollenwerk and Grove, 1985; Deutsch, 1972; French et al., 1985; Perlmutter and Lieber, 1970; Wiley, 1983). Sources of this contamination can be the same as those listed for surface waters. Such plumes in sand and gravel aquifers have been reported to reach lengths of up to 1,300 m (Perlmutter and Lieber, 1970). The contamination in many of the plumes have been serious enough to necessitate the abandonment of local groundwater supplies. Groundwater contamination by Cr can be extensive in permeable aquifers (i.e., sand and gravel and fractured rock aquifers) because groundwater velocities in these materials are relatively high (i.e., about 0.1 m and 5 m per day, respectively). On the other hand, groundwater velocities in aquifers of much lower permeability (i.e., clayey materials) tend to be low, perhaps on the order of a few centimeters or less per year. Thus, Cr-contaminated groundwater in these settings cannot extend far from the source of the Cr. Cr(III) tends to be relatively immobile in most groundwater because of the precipitation of Cr(III) compounds of low-solubility (e.g., Cr(OH)3(s), FeCr2O4(s), (Fe1–x, Crx)(OH)3 (solid solution)) in neutral to alkaline pH range (i.e., above pH 4). This results in low Cr(III) dissolved concentrations. Also,

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in neutral to slightly acidic conditions (i.e., especially below pH 4), Cr(III) is removed from solution by sorption. Calder (1988) reported that sorption of Cr(III) increases with increasing pH. Furthermore, it has been speculated that Cr(III) may be mobile in groundwater if it is in a complexed form, although this has not been documented in the field. Precipitation and sorption can be inhibited by complex formation with dissolved ligands such as natural organic matter (Gerritsee et al., 1982). Cr(VI) tends to be moderately to highly mobile in most shallow groundwater aquifers. This tends to be owing to two major factors: (1) the lack of solubility constraints; and, (2) the low to moderate sorption of Cr(VI) anionic form in neutral to alkaline waters. In soils or sediments with high content of Fe and Mn oxides conditions, Cr(VI) should be removed by sorption processes (Rai et al., 1986; Eary and Rai, 1987; Stollenwerk and Grove, 1985; Rai et al., 1988; Cary et al., 1977). But sorption is significantly depressed by competing background anions (Rai et al., 1988) so that Cr(VI) can expected to be highly mobile. In alkaline environments, sorption is not strong enough to keep Cr(VI) from migrating through soil or sediments. Cr(VI) sorption generally increases with decreasing pH, so sorption of Cr(VI) can be very significant in neutral to acidic groundwater. As previously discussed, Cr(VI) sorption can be strongly nonlinear, such that sorption decreases with increasing Cr(VI) concentration. Also, sorption also appears to be rate-dependent, so the kinetics of the sorption process would very important, especially in high-velocity groundwater regimes. Also, Cr(VI) reduced to Cr(III) with subsequent precipitation and sorption is believed to control the mobility of Cr(VI) (Rai et al., 1988): Cr(VI) reduction to Cr(III), which is afterwards rapidly precipitated or sorbed. In Fe(II)-rich and dissolved organic matter-rich environments, the reduction of Cr(VI) is more likely to occur and the resulting aqueous Cr(III) concentration will be controlled by the solubility of Cr(III). In such cases, Cr(VI) should not migrate significantly. The impact of water chemistry on the presence and movement of Cr in groundwater was demonstrated in field experiments involving injections of 100 mmol/L of Cr(VI) into various zones of a gravel aquifer (Kent et al., 1989). Some Cr disappeared from the aqueous phase in the anaerobic part of the aquifer due to reduction to the less soluble Cr(III) form. Cr(VI) (CrO42-) generally migrated at about the same rate as groundwater flow, except in areas with low pH and low concentrations of anions, where it was retarded owing to competition with these forms for sorption sites. The relationship of Cr and Mn is particularly interesting in the transport and fate of Cr in groundwater. Cr and Mn form a pair of chemical elements with contrasting tendencies (Murray et al., 1983). Under oxidizing conditions, Cr(VI) is soluble as CrO42– while Mn(IV) is scavenged as MnO2(s). Under reducing conditions, Cr(III) is removed from solution as Cr(OH)3(s) while Mn(II) is soluble as Mn2+. These contrasting tendencies for the solubility of Cr and Mn have been observed in shallow groundwater of the western San Joaquin Valley in California (Deverel and Millard, 1988). In the alluvial-fan geologic zone, dissolved Cr concentrations are high, whereas

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dissolved Mn is low. However, in the basin-trough zone, Cr concentration is low and Mn concentration is high. 5.6.2.3 Plumes of Chromium in Groundwater : Case Studies There are a number of documented cases of Cr plumes in groundwater. The following are accounts of major occurrences of Cr in groundwater as summarized by Calder (1988) and Loyaux-Lawniczak et al. (2001). 5.6.2.3.1 Nassau County, New York The best known and the first major published case study in North America of Cr in water supply wells was in Nassau County, Long Island (Lieber et al., 1964). A number of investigators have studied the site, and this case demonstrates the types of uncertainties that complicate predictions of Cr migration in groundwater. The source of Cr was an aircraft plant that used Cr solutions for anodizing and plating metals. The site is located on a very permeable sand and gravel aquifer with groundwater velocities estimated to be approximately 0.15 m/d to 0.5 m/d (Perlmutter and Lieber, 1970). The estimated length and width of the plume was 1,300 m by 300 m, with a maximum Cr concentration in groundwater of 40 mg/L. The groundwater pH was 4.6 to 6.2 which is the range where Cr(VI) could be significantly sorbed by the aquifer materials. Calder (1988) promotes three hypotheses that can account for the apparent retardation of the Cr plume: 1. Greater sorption as a result of the lowering of the Cr concentration owing to remediation efforts (i.e., concentration–dependence of chromium sorption) 2. The slow reduction of Cr(VI) to Cr(III), with subsequent precipitation of Cr(III), particularly in deeper groundwater 3. Slow kinetics of the sorption process in the more permeable portions of the aquifer, such that chemical equilibrium, and therefore maximum sorption, would not occur until the aquifer had been exposed to Cr-containing groundwater over a long period of time 5.6.2.3.2 Telluride, Colorado This is the site of a heavy metal mining and milling operation near Telluride, Colorado (Grove and Stollenwerk, 1985). The source of Cr was a tailings pond which, since 1977, apparently discharged Cr-containing wastes into the groundwater system. Water in the tailing pond had chromium concentrations of 8.8 mg/L (Stollenwerk and Grove, 1985). The USGS initiated a study of the site in October 1978, providing an excellent opportunity for comparison of field observations with laboratory experiments and computer simulation (Stollenwerk and Grove, 1985). The shallow aquifer was gravel and sand alluvium, and the estimated groundwater velocities were

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approximately 5 m/d. In 1979, a Cr plume at least 520 m long was observed, with a maximum Cr concentration of 2.7 mg/L (Grove and Stollenwerk, 1985). The groundwater pH was approximately 6.8 (Stollenwerk and Grove, 1985). Laboratory and field investigations determined that the Cr was retarded by a factor of 10 relative to the groundwater velocity. Even with such an appreciable retardation rate, the high groundwater velocity resulted in a relatively mobile Cr plume. 5.6.2.3.3 Wood Treatment Plant, Southwestern Michigan An incidence of groundwater contamination by Cr from a wood treatment plant was reported in southwest Michigan in 1980 (French et al., 1985). The wood was treated with a 2% aqueous solution containing 47.5% CrO3, 34% arsenic (V) oxide (As2Os), and 18.5% copper oxide. Effluent from a sump pit was discharged to the ground adjacent to the treatment building until 1980. An effluent sample from the pit contained 1,600 mg/L chromium, of which 1,500 mg/L was Cr(VI). The site is located on a permeable outwash plain consisting of gravelly sands with up to 17% silt and clay-sized particles. The water table was at a depth of about 8 m. The groundwater had a moderately alkaline pH of up to 8.4, and groundwater velocities were estimated at approximately 0.15 m/d. The highest Cr concentration in the plume was 6.58 mg/L, and Cr was detected in the facility’s supply well as high as 2.5 mg/L. The Cr plume, defined by total Cr concentrations above 50 parts per billion (ppb), extended approximately 600 m from the discharge area, with a width of approximately 200 m and a vertical thickness of 20 m. The length of the plume was found to be consistent with estimated groundwater velocities, suggesting that Cr was essentially unretarded. It was assumed that the Cr was almost entirely Cr(VI). A purge well-spray irrigation system was established to restore the aquifer to drinking water standards. 5.6.2.3.4 Industrial Waste Landfill, Northern France The site, an industrial waste landfill located in northern France, was operational from 1905 to 1982, producing materials including Cr2O72-, H2CrO4, sulfuric acid (H2SO4), and phosphates (PO43-). Chromite and pyrite (FeS2) were the main primary minerals used at the facility, and Cr mineral processing wastes were collected in a slag heap, which was covered in 1990 by a geomembrane to limit runoff. The groundwater table is normally located at 2 m depth, with an annual fluctuation of 1 m, within the infill. The water table aquifer, in a silt layer, is well separated from deeper aquifers by a green clay unit. The hydraulic conductivity was estimated to be about 7 ¥ 10–7 m/s. The Cr concentrations in the source area were about 210 mg/L, with the migrating plume extending approximately 160 m downgradient. The plume does not extend to the downgradient boundary of the site 375 m away. The Fe(II) distribution in groundwater is quite variable. It is virtually absent in the major area of the Cr plume, then the Fe(II) concentration abruptly increases near the downgradient end of the

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Cr plume (1,680 mg/L). Concentrations of total copper (Cr), cadmium (Cd), zinc (Zn), and SO42- show a similar distribution to Fe(II). The pH values in the groundwater are mostly neutral (6.5 to 7.3) in the major portion of the plume, becoming more acidic (approximately 4) at the downgradient portion of the Cr plume, possibly owing to the oxidation of pyrite that was used in massive amounts in this area of the site. Loyaux-Lawniczak et al. (2001) explain the distribution of metals in groundwater by postulating that Cr(VI) (produced by leaching of the ore residue slag heap) migrates in groundwater flow and then enters into a reducing zone (with Fe(II) present), where the Cr(VI) is reduced by Fe(II). It has been widely accepted that the kinetics of this reaction in solution is fast, and that with excess Fe(II), all of the Cr(VI) is reduced. Cr(III) is especially immobilized in the clay fraction of the soil; analyses of this clay fraction revealed that montmorillonite flakes are the Cr-bearing mineralogical phase. In summary, Cr(VI) migration in groundwater is retarded horizontally by a redox mechanism involving CrO42- and Fe2+ or Fe(II)-bearing minerals, and vertically by a thick green clay unit. 5.6.3

Chromium in Soil

The discussion of Cr behavior in soil presented here is preceeded by an overview of the presence and behavior of metals in soil. The discussion specific to the behavior of Cr in soil includes a general overview followed by discussions of the sorption, oxidation, and reduction of Cr. 5.6.3.1 Overview of Metals in Soil McLean and Bledsoe (1992) present an overview of metals in soil, and their work is discussed below. Metals are found in soil within one or more soil “pools”: 1. 2. 3. 4. 5. 6. 7.

Dissolved in the soil solution Occupying exchange sites on inorganic soil constituents Specifically sorbed on inorganic soil constituents Associated with insoluble soil organic matter Precipitated as pure or mixed solids Present in the structure of secondary minerals Present in the structure of primary minerals

“Metals” exist in soil solution as either free (uncomplexed) metal ions (e.g., Cr3+), or in soluble complexes with inorganic or organic ligands, or associated with mobile inorganic and organic colloidal material. A complex is a molecular unit where a central metal ion is bonded by a number of associated atoms or molecules ( e.g., Cr(OH)4–), and these associated atoms

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or molecules are termed ligands (i.e., OH– is a ligand). Metals will form soluble complexes with inorganic ligands such as SO42–, Cl–, OH–, PO43–, NO3–, and CO32–. Soluble complexes with organic ligands are not as well defined. The free metal ion is generally the most bioavailable and toxic form of the metal. With complex formation, the resulting metal species may be positively or negatively charged or be electrically neutral. The presence of a complex of a metal in the soil solution can significantly affect the migration of metals through the soil relative to the free metal ion. In addition to dissolved metal complexes, metals also may associate with mobile colloidal particles (size of 0.01 mm to 10 mm). Colloidal particles include Fe and Mn oxides, clay minerals, and organic matter. These surfaces have a high capacity for metal sorption. The extent of migration of metals from the ground surface into and through the subsurface depends on the retention capacity of the soil is exceeded, and it is directly related to the solution and surface chemistry of the soil and to the specific properties of the metal and associated waste matrix. The mechanisms for retention of metals in soil include sorption and precipitation. Retention of cationic metals is related to soil properties such as pH, redox potential, surface area, cation exchange capacity, organic matter content, clay content, Fe and Mn oxide content, and carbonate content. Anionic metal retention has been correlated with pH, Fe and Mn oxide content, and Eh. Consideration must also be given to the type of metal, its concentration, the presence of competing ions and complexing ligands, and the pH and redox potential of the soil-waste matrix. Also, the migration of metals can depend on the type of wastes that may be associated with the metal. Therefore, because of the differing varieties of soils, and the many different forms of metals themselves and the wastes containing them, evaluating the extent of metal retention by a soil is site specific, soil specific, and waste specific. Precipitation and sorption are the main metal retention mechanisms in soil. Precipitation is where metals precipitate to form a solid (3-dimensional) phase in soils, which might be a pure solid or a solid solution (e.g., (FexCr1–x)(OH)3); the latter forms when various elements co-precipitate. Sorption of metals is the accumulation of ions at the solid phase–aqueous phase interface. Sorption of metals in the soil matrix often involves organic matter, clay minerals, Fe and Mn oxides and hydroxides, carbonates, and amorphous aluminosilicates. Binding of metals to organic matter ranges from weak forces of attraction to formation of strong chemical bonds. Soil organic matter can be the main source of soil cation exchange capacity. Organic matter content generally decreases with depth in soil, so that the mineral (inorganic) constituents of soil will become a more important surface for sorption with increasing depth. There have been numerous studies of the adsorptive properties of clay minerals, in particular montmorillonite and kaolinite, and Fe and Mn manganese oxides. Griffin and Shimp (1978) found the relative mobility of 9 metals through montmorillonite and kaolinite to be: Cr(VI) > Se > As(III) > As(V) > Cd > Zn > Pb > Cu > Cr(III). Also, Fe and Mn oxides are the principal soil surface that control the mobility of metals in soils and water (Jenne,1968). In arid soils,

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carbonate minerals may immobilize metals by providing sorbing and nucleating surface (Santillan-Medrano and Jurinak, 1975; Cavallaro and McBride, 1978; McBride, 1980; Jurinak and Bauer, 1956; McBride and Bouldin, 1984; Dudley et al., 1988, 1991). Generally, the sorption capacity for anions (some metals form anionic contaminants) is lower than the cation sorption capacity of soils. The sorption capacity (both exchange and specific sorption) of a soil is determined by the number and kind of sites available. Sorption process are affected by various soil factors (i.e., pH, Eh, clay, soil organic matter, oxides, and calcium carbonate (CaCO3) content), by the form of the metal added to the soil, and by the solvent introduced along with the metal. Therefore, interactions of these influences on sorption may increase or decrease the migration of metals in soil. Although the principles affecting sorption and precipitation are similar for cationic and anionic metals, the following is a list with a brief description of factors affecting the behavior of cationic metals in soils. Competing cations: Trace cationic and anionic metals are preferentially sorbed over the major cations (Na+, Ca2+, Mg2+) and major anions (SO42–, NO3–). However, when the specific sorption sites become saturated, exchange reactions dominate and competition for these sites with soil major ions becomes important. Complex formation: Metal cations form complexes with inorganic and organic ligands, whereby the ligand forms a coordinate bond with the metal atom. The resulting association has a lower positive charge than the free metal ion (and might even be uncharged or negatively charged). The effect of complex formation on sorption is dependent on the type and amount of metal present, and type and amount of ligands present, soil surface properties, soil solution composition, pH, and redox. The presence of complexing ligands may either increase metal retention or greatly increase metal mobility. Data from the literature that do not consider the presence of complexing ligands at the site, both organic and inorganic, may lead to significant error in estimating metal mobility. pH: The pH of the soil system is a very important parameter, directly influencing sorption/desorption, precipitation/dissolution, complex formation, and oxidation–reduction reactions. The pH affects several mechanisms of metal retention of soils both directly and indirectly. Sorption increases with pH for all cationic metals, but retention does not significantly increase until the pH gets above 7. As true for all oxyanions (i.e., Cr(VI) as Cr2O72-), sorption decreases with pH. The pH dependence of sorption reactions of cationic metals is owing in part to the preferential sorption of the hydrolyzed metal entity in comparison to the free metal ion. Many sorption sites in soils are pH dependent (i.e., Fe and Mn oxides, organic matter, carbonates, and the edges of clay minerals). As the pH decreases, the number of negative sites for cation sorption diminishes while the number of sites for anion sorption increases. Also, as the pH becomes more acidic, metal cations also face competition for available permanent charged sites by Al3+ and H+. Hydrous oxides of Fe and Mn play a principle role in the retention of metals in soils

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(Jenne, 1960). Solubility of Fe and Mn oxides is also pH-related. Below pH 6, the oxides of Fe and Mn dissolve, releasing sorbed metal ions to solution (Essen and El Bassam, 1981). In soils with significant levels of dissolved organic matter, increasing soil pH may actually mobilize metal owing to complex formation. A word of caution is warranted here, however. The complexity of the soil-waste system (several types of surfaces and solution compositions) may render generalizations just given to be not true. For example, cationic metal mobility can actually increase with increasing pH owing to the formation of metal complexes with dissolved organic matter. Oxidation-Reduction: Many metals have more than one oxidation state, and are directly affected by changes in the oxidation-reduction (redox) potential of the soil. Redox reactions can greatly affect contaminant transport, in slightly acidic to alkaline environments. In general, oxidizing conditions favor retention of metals in soils, while reducing conditions contribute to accelerated migration. 5.6.3.2 Behavior of Chromium in Soil Kimbrough et al. (1999); Kotas and Stasicka (2000); and McLean and Bledsoe (1992) present overviews of the behavior of Cr in soil, and their work is summarized here. More details concerning the chemistry of Cr in soils and sediments are provided in review articles by Cary (1982); and Richard and Bourg (1991). Chromium commonly exists in two oxidation states in soils, Cr(III) and Cr(VI). Forms of Cr(VI) in soils are as hydrogen chromate ion (HCrO4– predominant at pH < 6.5 or CrO42– predominant at pH 6.5), and as dichromate (Cr2O72–) predominant at higher concentrations and at pH 2 to 6. Cr2O72is more toxic to humans than CrO42-. In neutral-to-alkaline soils, Cr(VI) is mostly soluble (e.g., Na2CrO4) but also in moderately-to-sparingly soluble chromates (e.g., CaCrO4, BaCrO4, PbCrO4) (Bartlett and Kimble, 1976; James, 1996). In more acidic soils (pH < 6), HCrO4– becomes a dominant form. CrO42– and HCrO4– are the most mobile forms of Cr in soils. They can be taken up by plants and easily leached out into the deeper soil layers causing groundwater and surface water pollution (Calder, 1988; James and Bartlett, 1984; Handa, 1988). Some minor amounts of Cr(VI) are bound in soils. This binding depends on the mineralogical composition and pH of the soil. The CrO42– ion can be sorbed by goethite, FeO(OH), aluminum oxides and other soil colloids with a positively charged surface (Richard and Bourg, 1991; James and Bartlett, 1983 and 1988). HCrO4–, which occurs in more acidic soils, may also be held in soils, or remain soluble (James and Bartlett, 1983). Reviews of the processes that control the fate of Cr in soil and the effect these processes have on remediation are given in Bartlett (1991) and Palmer and Wittbrodt (1991). In a study of the relative mobilities of 11 different trace metals for a wide range of soils, Korte et al. (1976) found that clayey soil, containing free Fe and Mn oxides, significantly retarded Cr(VI) migration. Cr(VI) was the only

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“metal” that was highly mobile in alkaline soils. The study also showed that free Fe oxides, total Mn, and soil pH influenced Cr(VI) immobilization, whereas soil properties such as cation exchange capacity, surface area, and percent clay had no significant influence on Cr(VI) mobility. Chromium in soils is naturally present mostly as insoluble Cr(OH)3 or as Cr(III) sorbed to soil components, which prevents leaching into the groundwater or its uptake by plants (Bartlett and Kimble, 1976). The dominant Cr form depends strongly on pH; in acidic soils (pH<4) it is Cr(H2O)63+, whereas at pH < 5.5 it is its hydrolysis products, mainly soluble CrOH2+ (Ritchie and Sposito, 1995); both these forms are easily sorbed by clays. The process is intensified by an increase in pH, which can be interpreted in part due to an increase of negative charge on the clays. Here humic acids contain donor groups forming stable Cr(III) complexes. The Cr(III) sorption to humic acids renders it insoluble, immobile, and unreactive; this process is the most effective within the pH range of 2.7 to 4.5 (James, 1996). In contrast, mobile compounds such as citric acid (H3C4H5O7) and fulvic acid, form soluble Cr(III) complexes which control its oxidation to Cr(VI) in soils (Bartlett and Kimble, 1976; Bartlett and James, 1979; James and Bartlett, 1983; James, 1996; Wittbrodt and Palmer, 1995). Both reduction of Cr(VI) to Cr(III) and the sorption of Cr(VI) can occur in soil, even simultaneously. Therefore, this causes a problem in assigning one mechanism of observed attenuation of Cr(VI) in the subsurface (Bartlett, 1991). The following are discussions of each of these mechanisms. 5.6.3.2.1 Sorption of Cr(III) and Cr(VI) Cr(VI) is an anion, and its association with soil surfaces is thus limited to positively charged exchange sites, which decrease in number with increasing soil pH. Therefore, sorption of Cr(VI) decreases with increasing soil pH. Iron and aluminum oxide (Al2O3) surfaces will adsorb CrO42– at acidic and neutral pH (Davis and Leckie, 1980; Zachara et al., 1987; Ainsworth et al., 1989). The sorption of Cr(VI) in groundwater by alluvium aquifer materials has been found to be owing to the Fe oxides and hydroxides coating the alluvial particles (Stollenwerk and Grove, 1985). But the sorbed Cr(VI) was desorbed by adding uncontaminated groundwater, indicating nonspecific sorption of Cr(VI). The presence of chloride (Cl-) and NO3- have little effect on Cr(VI) sorption, whereas SO42- and PO43- tend to inhibit sorption (Stollenwerk and Grove, 1985). Chromates can be sorbed by Fe, Al oxides, amorphous Al, hydroxides, organic complexes, and other soil components, which may protect Cr(VI) from reduction (Bartlett, 1991; Bartlett and James, 1988). Also, Cr(III) materials can be sorbed onto silicacious components. In the aqueous phase of soils, Cr(III) that is not sorbed by the solid phase would generally hydrolyze to the hydroxide and precipitate. CrO42- would be far less likely to precipitate and so would be expected to be more mobile. In this situation precipitation reactions are closely tied to oxidation and reduction reactions. In anaerobic

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sediments, oxidation is unlikely to take place and chromium(III) hydroxide [Cr(OH)3] could be immobilized as long as the sediments are physically stable (Eary and Rai, 1989). Soil pH determines both the speciation of Cr(VI) and the charge characteristic of the surface with which it reacts (James and Bartlett, 1983). Above pH 6.4, HCrO4– dissociates to CrO42– as the dominant form of Cr(VI) and the charge characteristic of the surface with which it reacts (James and Bartlett, 1983), and the CrO42– may in turn be sorbed. Sorption of chromates can be a reversible process suggested by leaching of Cr(VI) from soils (Baron et al., 1996). However, such reversibility depends on the chemistry of the leachate and of the soil or sediment. 5.6.3.2.2 Reduction of Cr(VI) and Oxidation of Cr(III) Oxidation and reduction reactions can convert Cr(III) to Cr(VI) and vice versa (Bartlett and Kimble, 1976; Bartlett and James, 1979; James and Bartlett, 1983; James and Bartlett, 1988; Wittbrodt and Palmer, 1995; James, 1994; Powell et al., 1995; Deng and Stone, 1996). These processes depend on pH, oxygen concentration, presence of appropriate reducers and mediators acting as ligands or catalysts. Mobile forms for Cr(VI) (HCrO4– and CrO42–) can be reduced by different reducers such as Fe(II) or S2–. It has been thought that Cr(VI) can be reduced to Cr(III) under normal soil pH and redox conditions. However, Bloomfield and Pruden (1980) reinvestigated earlier claims that Cr(VI) is readily reduced to Cr(III) under such normal soil conditions, and they found that the analytical methods used in previous investigations (Bartlett and Kimble, 1976) were unreliable because the soil extracts probably contained organic matter capable of reducing Cr(VI). They also found that the reduction of Cr(VI) in soil of normal pH was not particularly rapid under aerobic conditions. The reduction of CrO42- by Fe(II), V2+, reduced sulfur, and organic materials is well demonstrated (Cary, 1982), and the kinetics of Cr(VI) reduction has been reported to follow a simple first-order reaction kinetics (Amacher and Baker, 1982; Bartlett and James, 1988). Soil organic matter has been identified as the important electron donor (i.e., the principal reducing agent) in this reaction (Bartlett and Kimble, 1976; Bloomfield and Pruden, 1980), and the reduction of Cr(VI) in the presence of organic matter proceeds at a slow rate at normal levels of pH and temperatures found in the environment (Bartlett and Kimble, 1976; James and Bartlett, 1983). This relatively slow rate of Cr(VI) reduction increases with decreasing soil pH (Bloomfield and Pruden, 1980; Cary et al., 1977). In the absence of soil organic matter, Fe(II)containing minerals reduce Cr(VI), however, tests have shown that this reduction occurs in subsurface soil with a low pH (<5) (Eary and Rai, 1991). Reduction by Fe(II) is more favorable under anaerobic conditions since oxygen can oxidize the Fe(II) (Fendorf and Li, 1996). However, high concentrations of Cr(VI) may quickly exhaust the available reducing capacity of the soil, and excess Cr(VI) may persist for years in soils (Baron et al., 1996). In general, it has been noted that CrO42- is relatively stable and mobile in

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soils that are sandy or have low organic content (Cary, 1982; Bloomfield and Pruden, 1980; Frissel et al., 1975). Under conditions prevalent in some soils, Cr(III) can be oxidized (Bartlett and James, 1979). Only a few oxidants present in soils and sediments (i.e., dissolved oxygen and MnO2) are capable of oxidizing Cr(III) to Cr(IV). The oxidation of Cr(III) by MnO2 (which serves as an electron acceptor) has been shown to occur in soils (Eary and Rai, 1987; Johnson and Xyla, 1991; Fendorf and Zasoski, 1992), and aerobic sediments, but not in anaerobic sediments. Oxidation of Cr(III) by dissolved oxygen has been found to be insignificant (Rai et al., 1989) when compared with MnO2, which is the most likely oxidant of Cr(III) in soils. Thus, if soluble Cr(III) is added to an “average” soil, a portion of the soluble Cr(III) will become immediately oxidized by MnO2 to Cr(VI) (Cary, 1982). The rest of the Cr(III) may remain reduced for long periods of time, even in the presence of electron-accepting manganese oxides, perhaps because soluble Cr(III) can form complexes with low-molecular mass organic molecules and then be oxidized where redox conditions are optimal. Added organic matter also may facilitate oxidation of Cr(III) to Cr(VI). This has implications to remediation strategies. The addition of organic residues potentially as a remediation strategy for Cr(VI)-contaminated soils containing high levels of oxidized Mn may result in the formulation of unstable Mn(III) organic complexes that not only temporarily prevent Cr(III) oxidation but also promote the desired reduction of Cr(VI) (Bartlett and James, 1988). 5.6.4

The Uptake and Transformation of Chromium by Biota

Kotas and Stasicka (2000) and Kimbrough et al. (1999) present overviews of the uptake and transformation of Cr by biota, and their work is summarized here. Cr can be taken up by biota from the air, water, and soil. Most studies in this realm do not distinguish between the oxidation states of Cr. However, it is known that the Cr(VI) form is more available for living organisms than Cr(III), and the uptake of Cr(VI) by biota is a main role in the removal of Cr(V) from water and soil systems. The following discussion of the role of biota in the transport and fate of Cr is presented for bacteria, plants, aquatic animals, and terrestrial animals. Microorganisms accumulate Cr (Coleman, 1988) and reduce Cr(VI) to Cr(III) (Campos et al., 1995; DeLeo and Ehrlich, 1994). Although high levels of Cr(VI) are toxic to microorganisms (Bartlett, 1991), Cr is important to yeast metabolism (Coleman, 1988; Anderson et al., 1977). However, there is not much evidence in the literature of bioaccumulation of Cr as Cr(VI) in bacteria, since most studies report Cr bioaccumulation in terms of total Cr. There are conflicting views concerning the uptake and translocation of Cr(VI) in plants. Also, whether Cr is an essential element in plants has been debated in the literature. The World Health Organization says it is unknown whether Cr is an essential nutrient for all plants, yet all plants contain the element. On the other hand, Richard and Bourg (1991) suggested that Cr(III) is an

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essential nutrient in plant metabolism (amino and nucleic acid synthesis). The literature on Cr bioaccumulation in aquatic animals (e.g., finned fish) suggests that Cr(VI) is not expected to accumulate and increase in the aquatic food chain. And, there is no indication of biomagnification of Cr within the terrestrial animal food chain (soil-plant-animal) (Clay, 1992; ATSDR, 1992).

5.7

Utilizing Natural Environmental Processes as a Remedy for Soil and Groundwater Contaminated with Chromium

Natural attenuation is a term that describes the naturally-occurring environmental processes that act without human intervention to reduce the mass, toxicity, mobility, volume, or concentration of contaminants. These processes can be grouped into two classes, destructive and nondestructive processes. Destructive processes include biotransformation and abiotic chemical reactions. Nondestructive processes include sorption (sorption and absorption), dispersion, dilution from recharge, and volatilization. Natural attenuation is sometimes referred to by several other names, such as intrinsic remediation, intrinsic bioremediation, natural restoration, or passive bioremediation. For the purposes of this chapter, the term natural attenuation will be used, because some of the synonyms used such as intrinsic bioremediation actually refer to only one of many processes responsible for natural attenuation. The implementation of natural attenuation processes as a remedy for soil and groundwater contamination is termed Monitored Natural Attenuation (MNA). The United States Environmental Protection Agency (USEPA) has stated its position on the use of MNA for the remediation of contaminated soil and groundwater in their Final OSWER Directive “Use of Monitored Natural Attenuation at Superfund, RCRA Corrective Action, and Underground Storage Tank Sites” (OSWER Directive Number 9200.4–17P), dated April 21, 1999. The USEPA defines MNA as the reliance on natural attenuation processes (within the context of a carefully controlled and monitored clean-up approach) to achieve site-specific remediation objectives within a time frame that is reasonable compared to that offered by other more active methods. MNA is generally not seen as a viable stand-alone remedy, but is more commonly viewed as a possible component of an overall remedial strategy for a contaminated site. Nonetheless, MNA is increasing being viewed as a viable alternative for the management of contaminated sites in the U.S. and other countries. Palmer and Puls (1994) present an outline of how the natural attenuation of Cr(VI) in the environment, especially in groundwater, can be evaluated and how MNA can be implemented as a remedy for contamination. Their work is summarized here. Also Ellis et al. (2002) and Blowes (2002) give summaries of the use of stable isotopes of Cr as an evaluation methodology for the implementation of MNA, and their work is also summarized herein.

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Minerals containing reduced forms of Fe and S are abundant in many aquifers, and these minerals reduce Cr(VI) to Cr(III) and promote the precipitation of insoluble solids such as Cr(OH)3. Also, organic carbon-rich materials can also reduce Cr(VI). In aquifers where reduced sediments are abundant and the concentrations of Cr(VI) are low, the attenuation capacity of the aquifer may be sufficient to prevent chromium migration. This mechanism of the natural attenuation of Cr(VI) could be used as a remedial strategy. The appropriateness of MNA depends on the groundwater flow system, the rate of Cr migration, and the ability of the aquifer materials to reduce Cr(VI). It can be difficult, however, to distinguish measured CrO42decreases caused by attenuation reactions from those caused by mixing or dispersion (a dilution effect) in the aquifer. However, for such a strategy to be adopted by a regulatory agency, the likelihood that natural attenuation is likely to occur under the specific conditions at the site being investigated will most likely have to be demonstrated. There is no single test that can tell us if natural attenuation of Cr(VI) will occur at a particular site. Several tests are briefly described which have been utilized to address the factors affecting Cr(VI) transport in the subsurface and describe how the results can be utilized in determining the potential for the natural attenuation of Cr(VI) in the subsurface. Such a demonstration will likely comprise at least the following three items: 1. There are natural reductants in the aquifer 2. The amount of Cr(VI) and other reactive constituents do not exceed the reductive capacity of the aquifer 3. The rate of Cr(VI) reduction to the target concentration is greater than the rate of transport of Cr(VI) from source to point of compliance Some of these criteria are relatively simple while others require additional tests and interpretation. Each are discussed below. 5.7.1

Natural Reductants in the Aquifer

In principle, the natural attenuation of Cr(VI) in the subsurface is feasible as a result of interaction with naturally existing reductants. There are several natural reductants that can transform Cr(VI) to Cr(III). Potential reductants of Cr(VI) include • • • •

Aqueous species Sorbed ions Mineral constituents Organic matter

During the migration of a Cr(VI) plume in groundwater, there is little mixing of the waters containing the reducing agents and the Cr(VI). What

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mixing does occur will be driven by molecular diffusion at the front or edges of the plume, and diffusion from lower permeability lenses containing relatively immobile water. Thus, reductants that are primarily dissolved in groundwater such as Fe2+ are not going to be important in reducing Cr(VI). The mixing of reductants and Cr(VI) is instead going to occur primarily through the interactions of the Cr(VI) plume and the immobile soil matrix. Such interactions include • Desorption of reductants such as Fe2+ from mineral surfaces • Direct and indirect surface redox reactions between Cr(VI) and the mineral surfaces • Reduction by soil organic matter The presence of Cr(III) may indicate either active reduction in the soil or neutralization of acidic waters containing Cr(III) with subsequent precipitation of chromium hydroxides. Therefore, specific reductants in the aquifer should be identified, and this can be fairly straightforward. Reductants (such as pyrite, FeS2) can be readily identifiable by visual characteristics or by standard petrographic techniques (i.e., powder x-ray diffraction (XRD), scanning electron microscopy (SEM), polarized light microscopy (PLM)). Also, testing for organic carbon can provide a measure of the amount of carbon available for reduction of Cr(VI). Knowledge of the specific reductant within the aquifer can be useful in determining the time scale for the reduction of Cr(VI). This is discussed later. Based on literature studies, soils containing Fe sulfides or organic matter are more likely to reduce Cr(VI) on the time scales of interest than soils containing iron(II) silicates.

5.7.2

The Amount of Cr(VI) and Other Reactive Constituents Do Not Exceed the Reductive Capacity of the Aquifer

Studies demonstrate that groundwater contributes less than 1% of the oxidation capacities (equivalents of Cr oxidized per gram of soil) and reduction capacities (equivalents of Cr reduced per gram of soil) of aquifer systems while the soil matrix contributes the remaining fraction (Barcelona and Helm, 1991). Thus, any discussion of Cr(VI) reduction or Cr(III) oxidation in the subsurface must focus on the soil matrix. Several soil tests can be useful in determining the mass of Cr(VI) and Cr(III) and also the reduction and oxidation capacities of the aquifer materials. 5.7.2.1 Mass of Cr(VI) It must be demonstrated that the amount of Cr(VI) in the aquifer does not exceed the capacity of the soil for reducing Cr(VI) to Cr(III). Therefore, an important step in evaluating the potential for natural attenuation is to

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determine the mass of Cr(VI) in the aquifer. Aqueous samples are most often obtained from monitoring wells, or water can separated from the soil matrix either by centrifugation or by squeezing. The pH of the water should be measured to determine if it is within the proper range (5.5 to 12) to insure the Cr(III) concentrations are less than 1 m mol/L (0.05 mg/L). Cr(VI) associated with the soil matrix may be sorbed to mineral surfaces (particularly Fe oxides) or precipitated as chromate minerals. There is no accurate method for determining each of these fractions of Cr(VI); but, sequential extractions have been used, where an initial water extraction serves to remove remaining pore water and dissolve highly soluble Cr minerals present in the soil or that may have precipitated due to evaporation during sample handling. Then, a phosphate extraction is used as a measure of the “exchangeable” CrO42- in the soil (Bartlett and James, 1988); the water is separated from the slurry and Cr(VI) is measured by the DPC Method (Bartlett and Kimble, 1976; Bartlett and James, 1988). The increase in the CrO42concentrations is the amount of “exchangeable” CrO42-. The phosphate removes CrO42- by both directly competing for the sorption sites in the soil and indirectly (in some cases) by increasing the pH. Palmer and Puls (1994) report that at many sites, the total Cr(VI) associated with the soil matrix is the sum of BaCrO4 and the phosphate-extractable Cr(VI). This sum is then added to the aqueous Cr(VI) to get the total concentration of Cr(VI) in the soil (total Cr(VI). 5.7.2.2 Mass of Cr(III) The presence of Cr(III) in the soil may demonstrate that Cr(VI) reduction is occurring. Thus, the mass of Cr(III) in the soil could provide a measure of the amount of reduction that has occurred. The total amount of Cr(III) present in the soil is the sum of the mass in solution as well as mass associated with the solid phase. Total Cr in solution can be determined by atomic absorption spectroscopy (AAS) or inductively coupled plasma spectroscopy (ICP). When total Cr is statistically greater that Cr(VI), Cr(III) can be simply determined by difference. 5.7.2.3 Reduction Capacity of the Aquifer For the natural attenuation of Cr(VI) to be demonstrated, the soil must possess sufficient reducing capacity (RC) to reduce all the Cr(VI) in the source area. Thus, the total mass of Cr(VI) from the source (MO) must be less than the total mass of Cr(VI) (MTOT) that can be reduced by the aquifer material between the source and a point of compliance where XC is distance between them. Where A is the cross-sectional area of the plume normal to the direction of groundwater flow, and rb is the dry bulk density of the aquifer, this requirement can be expressed as M O < M TOT = XA rb R C

(5.8)

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As the distance XC increases, the mass of Cr(VI) that can be reduced also increases. A key difficulty in applying this criterion is in providing a reasonable estimate of the total mass of Cr(VI) in the source area (MO). The total Cr(VI) reducing capacity can be obtained using the classical Walkley-Black method for determining soil organic carbon (Bartlett and James, 1988; Walkley and Black, 1934). Although this method has its limitations (Nelson and Sommers, 1982), it is a direct measure of how much Cr(VI) can be reduced by a soil at extreme acid conditions. Variations on this method have been described (Barcelona and Helm, 1991; Nelson and Sommers, 1982). The extreme conditions of pH and temperature used in the total Cr(VI) reducing capacity test may yield a greater reducing capacity than would be available under most environmental conditions. The “available reducing capacity” test of Bartlett and James (1988) is designed to determine the reducing capacity at pH values more likely to be encountered in the field. However in long-term reduction tests at near neutral pH, reduction has been observed to be occurring after 250 days. Such long-term reduction tests are not practical at most waste sites. 5.7.2.4 Oxidation Capacity of the Aquifer As part of a geochemical cycle, both oxidation and reduction of Cr are occurring simultaneously within the subsurface. As the Cr(III) is oxidized to Cr(VI) by MnO2 in the soil, Cr(VI) can be reduced to Cr(III) by some reductant such as soil organic carbon or pyrite. Ultimately, a steady state situation will be reached where the rate of loss of Cr(VI) via reduction is balanced by the rate of production by the oxidation of Cr(III). Under certain conditions, oxidation of Cr(III) may be favored over the reduction of Cr(VI). For example, soil containing Cr(III) formed by the reduction of Cr(VI) may become a source of Cr(VI). Therefore, a potential limitation to the use of natural attenuation of Cr(VI) as a remedial option is the oxidation of the Cr(III) to Cr(VI) by oxidants such as MnO2. If the oxidizing capacity of the soil is greater than the reduction capacity, then as the Cr is cycled in the soil, the reductants could be exhausted, the Cr(III) could oxidized, and ultimately, Cr(VI) could be mobilized in the soil. It is therefore important to determine the capacity of the aquifer to oxidize Cr(III). Bartlett and James (1979, 1988) suggest a simple test for the amount of Cr(III) that can be oxidized by a soil. Barcelona and Helm (1991) give a method to measure the oxidation capacity of soils. Each of these methods has some problems. If the sole Cr(III) oxidation mechanism is by Mn oxides, then using extraction methods specifically designed for this purpose may be useful (Chao, 1972; Gambrell and Patrick, 1982). Fendorf and Zasoski (1992) suggest that CrOH2+ is the reactive species in the oxidation of Cr(III) by MnO2. The key point to consider when considering natural attenuation in soils that contain both a reductant and MnO2 is that as long as the supply of reductant and MnO2 have not been

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significantly depleted, (the HCrO4– concentration) does not converge to zero with increasing residence time within the aquifer as one would expect for a first-order reaction that only considers reduction of Cr(VI). Rather, HCrO4– converges to some steady-state concentration that is >0 that may or may not be higher the MCL. This steady-state concentration increases with a preference of oxidation over reduction and it varies with pH.

5.7.3

The Rate of Chromium(VI) Reduction to the Target Concentration Compared to the Rate of Transport of Chromium(VI) from Source to Point of Compliance

In principle, if the rate equations are correct and all of the parameters are known, one could calculate the steady-state Cr(VI) concentration and determine if natural attenuation could achieve compliance goals. The major limitation to this approach is the lack of information about the rate of oxidation and reduction of Cr under conditions likely to be encountered by plumes emanating from Cr sources. Without better information about these rate processes under a wider range of conditions with respect to pH, the use of the natural attenuation option for contaminated soils will continue to be a highly debated issue.

5.7.3.1 Rates of Oxidation and Reduction If natural attenuation is to be a viable option, the time for the reduction reaction to decrease the concentration from its initial concentration (CO) to some target concentration (CS), such as a drinking water standard (i.e., MCL), should be less than the residence time of the contaminated water in the portion of the aquifer between the source of the Cr(VI) and the point of compliance. Difficulties in utilizing this criterion as mentioned above arise in applying the appropriate rate equation and obtaining the pertinent rate coefficients. Rates can be obtained from the technical literature, but one must use reduction rates based on materials that are most likely controlling the Cr(VI) reduction at the site under evaluation. In addition, because the rates are concentration-dependent, and are related to the specific reductant and the pH level, it is important to obtain rate coefficients that were acquired under conditions similar to the site. As far as reductants are concerned, literature studies indicate soils containing Fe sulfides or organic matter are more likely to reduce Cr(VI) on the time scales of interest than soils containing Fe(II) silicates. One method of obtaining the net rate of reduction is through tests on uncontaminated soils (background soil) at the site that are similar to those through within the contaminant plume. Cr(VI) can be added to the background soil in the laboratory and the Cr(VI) concentrations monitored over time. The reaction vessels must exclude light to prevent photoreduction reactions and the slurry must have the same pH as the contaminant plume.

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A key limitation to such experiments is that they require several months to a year to complete. 5.7.3.2 Estimating Reduction from Monitoring Well Data In principle, Cr(VI) reduction can be estimated from the decrease in the mass of Cr(VI) in the aquifer (Henderson, 1994). The key difficulty in such an approach is to estimate the mass of Cr(VI) using aqueous concentrations. The total mass of Cr(VI) in the aquifer is the sum of the mass that is in solution, the mass that is sorbed to the aquifer matrix, and the mass that is precipitated within the aquifer. The mass of Cr(VI) in solution (Maq) is obtained by integrating the Cr(VI) concentrations over the volume of the contaminated aquifer, Maq = qv CV

(5.9)

where V is the volume of aquifer containing a plume with a Cr(VI) concentration of C (and qv represents the porosity). The mass of Cr(VI) sorbed to the soil matrix (Mads) can be computed from an sorption isotherm. There is no unique amount of Cr(VI) precipitate for a given Cr(VI) concentration. Therefore, it is impossible to estimate mass of this fraction of Cr(VI) in the subsurface using only the measured concentrations in monitoring wells. Thus, natural attenuation of Cr(VI) from mass balances using monitoring well data can only be used when it can be reasonably demonstrated the Cr(VI) precipitates cannot form within the aquifer. Even when it is demonstrated that the formation of precipitates within the aquifer is unlikely, there are inherent problems with any monitoring system, creating uncertainties in the estimated mass of Cr(VI) during a sampling round. 5.7.3.3 Monitoring Reduction via Stable Isotopes of Chromium Variations in the isotopic ratios of some reactive elements are sensitive indicators of chemical processes that occur in natural systems. For example, the 34S/32S ratio in dissolved SO 2- increases when bacteria reduce SO 2- to 4 4 sulfide (S2-). Reduction reactions tend to enrich products in the isotopes with the lower mass number (number of protons + number of neutrons) because they preferentially react (Hoefs, 1987), and the residual reactants become progressively enriched in the heavier isotopes with the higher mass number as reduction proceeds (Boettcher et al., 1990; Thode and Monster, 1965; and Johnson et al., 1999). Ellis et al. (2002) now show that the 53Cr/52Cr ratio also changes during reduction of Cr(VI) to Cr(III). They show that abiotic reduction of Cr(VI) resulting from reaction with the mineral magnetite, estuarine sediments, and freshwater sediments leads to a consistent 53Cr/52Cr shift. This observation indicates that 53Cr/52Cr ratios increase systematically with progressive Cr(VI) reduction in groundwater.

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The measurement of Cr isotope ratios provides a new tool for evaluating the extent and rate of the natural attenuation of CrO42-. Relative to conventional methods, Blowes (2002) states that the use of isotopes has two advantages: (1) each 53Cr/52Cr determination provides a measure of the amount of reduction that has already occurred, and there is thus no need to see whether Cr(VI) mass decreases over time; and (2) the measurement of reduction integrates spatially over a flow path, whereas analyses of aquifer solids give information on a much smaller spatial scale. 53Cr/52Cr measurements can also help to evaluate in situ approaches of remediation, which have been developed for site where natural attenuation is insufficient to prevent CrO42- migration (i.e., permeable reactive barriers, injection of chemical reactants to reduce CrO42-, and injection of a reductant to react with the aquifer materials to form reduced minerals in the aquifer). The new finding by Ellis et al. (2002) that 53Cr/52Cr ratios reveal the extent of abiotic reduction suggests that 53Cr/52Cr measurements can assist in the evaluation of the effectiveness of all these approaches to CrO42- reduction in groundwater. Chromium has four stable isotopes of mass number 50 (4.35%), 52 (83.8%), 53 (9.50%), and 54 (2.37%) (Rotaru and Birck, 1992; Handbook of Chemistry and Physics, 1996). Ellis et al. (2002) measured Cr isotope fractionation during reduction of Cr(VI) by slurries of magnetite and two sediment samples. Because magnetite is a likely reducing agent in some aquifer sediments (Anderson et al., 1994), the magnetite experiment provided a simple analog for a natural aquifer. In these experiments at pH 6 to 7, sorption of Cr(VI) was negligible. As reduction proceeded and the Cr(VI) concentrations decreased, d 53 Cr (defined in Chapter 2) values of the remaining unreduced Cr(VI) increased, indicating preferential reduction of the isotopes with lower mass number. These experiments showed that reduction of Cr(VI) results in Cr stable-isotope fractionation. To estimate initial isotopic compositions of the contaminants, Ellis et al. (2002) measured d 53Cr values in samples of plating baths in active use at different sites, the chromic acid (H2CrO4) supply used to make up plating baths, laboratory Cr reagents, and basaltic rock standards. All of these samples yielded d 53Cr values close to 0%. Therefore, Ellis et al. (2002) suggested that Cr released as plating waste generally has an initial d 53Cr value slightly greater than zero. If so, detection of Cr(VI) reduction in groundwater systems would be relatively simple, as the initial d 53Cr value would be known and groundwater values greater than that would directly indicate the extent of reduction. If, on the other hand, plating wastes have variable d 53Cr values, then it may be possible to distinguish different contamination sources via their d 53Cr values. In studies of groundwater contamination sites, Ellis et al. (2002) showed that all of the groundwater Cr(VI) analyses indicated enrichment in the isotope with higher mass number relative to the plating baths, and Cr(VI) reduction had preferentially removed isotopes with lower mass numbers from the groundwater. The variation in d 53Cr values at each of the sites suggested that reduction of Cr(VI) was occurring and had progressed to different degrees in

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different parts of the contaminant plumes. The highest d 53Cr values were found in samples with lowest Cr(VI) concentration at (the sites studied). This result was to be expected because the fringe areas of the contaminant plumes likely would have greater degrees of reduction than the plume cores, where Cr concentrations are high and the reducing power of the aquifer materials had been depleted. Stable Cr isotope ratios can thus serve as indicators of the extent of Cr(VI) reduction in groundwater. Cr(VI) reduction by bacteria or reducing agents other than those studied by Ellis et al. (2002) could induce greater or lesser isotopic fractionation than (they) observed. Processes other than reduction (i.e., sorption, precipitation, and uptake by plants and algae) could also be responsible for removing Cr from solution (James and Bartlett, 1983, 1984, and 1988). If such processes and/or Cr(III) oxidation also induce isotopic fractionation, this could complicate the interpretation of d 53Cr measurements. However, as with S and Se isotopes (Johnson et al., 1999), it could be expected that the dominant cause of Cr isotope fractionation is reduction.

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Barcelona, M.J. and Helm, T.J., 1991, Oxidation-reduction capacities of aquifer solids, Environ. Sci. Technol., vol. 25, pp. 1565–1572. Baron, D. Palmer, C.D., and Stanley, J.T., 1996, Identification of two iron-chromate precipitates in a Cr(VI)-contaminated soil, Environ. Sci. Technol., vol. 30, pp. 964–968. Bartlett, R.J. and James, B., 1979, Behavior of chromium in soils: III: Oxidation, J. Environ. Qual., vol. 8, pp. 31–35. Bartlett, R.J. and James, B.R., 1988, Mobility and bioavailability of chromium in soils, in Chromium in the Natural and Human Environments, Nriagu, J.O. and Nieboer, E., Eds., John Wiley and Sons, New York, pp. 267–304. Bartlett, R.J. and Kimble, J.M., 1976, Behavior of chromium in soils, I. Trivalent forms, II. Hexavalent forms, J. Environ. Qual., vol. 5, pp. 379–386. Bartlett, R.J., 1991, Chromium cycling in soils and water: links, gaps and methods, Environ. Health Prespective, vol. 92, pp. 17–24. Beaubien, S., Nriagu, J., Blowes, D., and Lawson, G., 1994, Chromium speciation and distribution in the Great Lakes, Environ. Sci. Technol., vol. 28, pp. 730–738. Benjamin, M.M. and Bloom, N.S., 1981, Effect of strong binding of anionic adsorbates on adsorption of trace metals on amorphous iron oxyhydroxide, in Adsorption from Aqueous Solution, Tewari, P.H., Ed., Plenum Press, New York, pp. 41–60. Bloomfield, C. and Pruden, G., 1980, The behavior of Cr(VI) in soil under aerobic and anaerobic conditions, Environ. Pollut. (Series A), vol. 23, pp. 103–114. Blowes, D.W. and Ptacek, C.J., 1992, Geochemical remediation of groundwater by permeable reactive walls: removal of chromate by reaction with iron-bearing solids, Proc. Subsurface Restoration Conference, June 21–24, 1992, Dallas, TX, pp. 214–216. Blowes, D., 2002, Tracking hexavalent Cr in groundwater, Science, vol. 295. Bodek, I., Lyman, W.J., Reehl, W.F., and Rosenblatt, D.H., 1988, Environmental Inorganic Chemistry Properties, Processes and Estimation Methods, Bodek, I. Ed., Pergamon Press, New York. Boettcher, J., Strebel, O., Voerkelius, S., and Schmidt, H.L., 1990, J. Hydrol., vol. 114, pp. 413. Calder, L.M., 1988, Chromium contamination of groundwater, in Chromium in the Natural and Human Environments, Nriagu, J.O. and Nieboer, E., Eds., John Wiley and Sons, New York, pp. 215–231. Campos, J., Martinez-Pacheco, M., and Cervantes, C., 1995, Hexavalent-chromium reduction by chromate-resistant Bacillus sp. strain, Antione von Leeuwenhoek, vol. 68, pp. 203–208. Cary, E.E., Allaway, W.H., and Olson, O.E., 1977, Control of chromium concentration in food plants, II. Chemistry of chromium in soils and its availability to plants, J. Agric. Food Chem., vol. 25, pp. 305–309. Cary, E.E., Ed., 1982, Chromium in Air, Soil, and Natural Waters, Elsevier Biomedical, New York, pp. 49–63. Cavallaro, N. and McBride, M.B., 1978, Copper and cadmium adsorption characteristics of selected acid and calcareous soils, Soil Sci. Soc. Am. J., vol. 42, pp. 550–556. Chao, T.T., 1972, Selective dissolution of manganese oxides from soils and sediments with acidified hydroxylamine hydrochloride, Soil Sci. Amer. Proc., vol. 36, pp. 764–768. Chuecas, D.L. and Riley, J.P., 1966, The spectrophotometric determination of chromium in sea water, Analyt. Chim. Acta, vol. 35, pp. 240–246.

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Clay, R.E., 1992, Multimedia Environmental Distribution of Gaseous, Dissolved and particle-Bound Pollutant, M.S. thesis, Chemical Engineering Department, University of California, Los Angeles. Coates, J.D., Phillips, E.J.P., Lonergan, D.J., Jenter, H., and Lovely, D.R., 1996, Appl. Environ. Microbiol., vol. 62, pp. 1531. Coleman, R.N., 1988, Chromium toxicity: effects on microorganisms with special reference to the soil matrix, in Chromium in the Natural and Human Environments, Nriagu, J.O. and Nieboer, E., Eds., John Wiley and Sons, New York, pp. 335–368. Cranston, R.E. and Murray, J.W., 1980, Chromium species in the Columbia River estuary, Limnol. Oceanogr., vol. 25, pp. 1104–1122. Cranston, R.E. and Murray, J.W., 1978, Determination of chromium species in natural waters, Analyt. Chim. Acta, vol. 99, pp. 275–282. Davis, A. and Olsen, R.L., 1995, The geochemistry of chromium migration and remediation in the subsurface, Ground Water, vol. 33, pp. 759–768. Davis, J.A. and Leckie, J.O., 1980, Surface ionization and complexation at the oxide/water interface: III. Adsorption of anions, J. Colloid Interface Sci., vol. 74, pp. 32–43. DeLeo, P.C. and Ehrlich, H.L., 1994, Reduction of hexavalent chromium by pseudomonas fluorescens LB300 in batch and continuous cultures, Appl. Microbiol. Biotechnol., vol. 40, pp. 756–759. Deng, B. and Stone, A.T., 1996, Surface-catalyzed chromium(VI) reduction: the TiO2-Cr(VI)-mandelic acid system, Environ. Sci. Technol., vol. 30, pp. 463–472. Deutsch, M., 1972, Incidents of chromium contamination of groundwaters in Michigan, in Water Quality in a Stressed Environment, Pettyjohn, W.A., Ed., Burgess Publishing, Minneapolis, MN, pp. 149–159. Deverel, S.J. and Millard, S.P., 1988, Distribution and mobility of selenium and other trace elements in shallow groundwater of the Western San Joaquin Valley, California, Envir. Sci. Technol., vol. 22, pp. 697–702. Dreiss, S.J., 1986, Chromium migration through sludge treated soils, Ground Water, vol. 24, pp. 312–321. Dudley, L.M., McLean, J.E., Furst, T.H., and Jurinak, J.J., 1991, Sorption of Cd and Cu from an acid mine waste extract by two calcareous soils: column studies, Soil Sci., vol. 151, pp. 121–135. Dudley, L.M., McLean, J.E., Sims, R.C., and Jurinak, J.J., 1988, Sorption of copper and cadmium from the water-soluble fraction of an acid mine waste by two calcareous soils, Soil Sci., vol. 145, pp. 207–214. Eary, L.E. and Rai, D., 1991, Chromate reduction by subsurface soils under acidic conditions, Soil Sci. Soc. Am. J., vol. 55, pp. 676–683. Eary, L.E. and Rai, D., 1988, Chromate removal from aqueous wastes by reduction with ferrous iron, Environ. Sci. Technol., vol. 22, pp. 972–977. Eary, L.E. and Rai, D., 1987, Kinetics of chromium (III) oxidation to chromium(VI) by reaction with manganese dioxide, Environ. Sci. Technol., vol. 21, pp. 1187–1193. Eary, L.E. and Rai, D., 1989, Kinetics of chromate reduction by ferrous ions derived from hematite and biotite at 25∞C, Am. J. Sci., vol. 289, pp. 180–213. Eckert, J.M., Stewart, J.J., Waite, T.D., Szymezek, R., and Williams, K.L., 1990, Anal. Chim. Acta, vol. 236, pp. 357–362. Ellis, A.S., Johnson, T.M., and Bullen, T.D., 2002, Chromium isotopes and the fate of hexavalent chromium in the environment, Science, vol. 295, pp. 2060–2062. Essen, J. and El Bassam, N., 1981, On the movility of cadmium under aerobic soil conditions, Environ. Pollut. Ser. A., pp. 15–31.

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Fendorf, S., Wielinga, B.W., and Hansel, C.M., 2001, Int. Geol., vol. 42, pp. 691. Fendorf, S.E. and Li, G., 1996, Kinetics of chromate reduction by ferrous iron, Environ. Sci. Technol., vol. 30, pp. 1614–1617. Fendorf, S.E. and Zasoski, R.J., 1992, Chromium(III) oxidation by d-MnO2, 1. Characterization, Environ. Sci. Technol., vol. 26, pp. 79–85. French, W.B., Gallagher, M., Passero, R.N., and Straw, W.T., 1985, Hydrogeologic investigation for remedial action related to a chromium–arsenic–copper discharge to soil and groundwater, in Innovations in Water and Wastewater Fields, Glysson E.A., Swan D.E., and Way, E.J., Eds., Ann Arbor Press, Ann Arbor, MI, pp. 209–229. Friess, S.L., 1989, Carcinogenic risk assessment criteria associated with inhalation of airborne particulates containing chromium(VI/III), Sci. Tot. Environ., vol. 86, pp. 109–112. Frissel, M.J., Poelstra, P., and Reisinger, P., 1975, The Behavior of Chromium in Aquatic and Terrestrial Food Chains: EUR 5375e, Boite postale 1003, Luxembourg, pp. 27–42. Gambrell, R.P. and Patrick, W.H., 1982, Manganese, in Methods of Soil Analysis, Part 2, Chemical and Microbiological Properties, Page, A.L., Ed., 2nd ed., Agronomy No. 9, Part 2, American Society of Agronomy, Soil Science Society of America, Madison, WI, pp. 313–322. Gerritsee, R.G., Vriesema, R., Dalenberg, J.W., and DeRoos, H.P., 1982, Effect of sewage sludge on trace element mobility in soils, J. Environ. Qual., vol. 11, pp. 359–364. Griffin, R.A. and Shimp, N.F., 1978, Attenuation of pollutants in municipal landfill leachate by clay minerals, EPA/600/2–78/157, U.S. Environmental Protection Agency, Washington, DC. Griffin, R.A., Au, H.K., and Frost, R.R., 1977, Effect of pH on adsorption of chromium from landfill leachate by clay minerals, J. Environ. Sci. Hlth. Ser. A., vol. 12, pp. 431–449. Grohse, P.M., Gutknecht, W.F., Hodson, L., and Wilson, B.M., 1988, The fate of hexavalent chromium in the atmosphere: Research Triangle Institute Report on CARB Contract #A6–096–32, Report Number ARB/R–89/379, California Air Resources Board, Sacramento, CA. Grove, D.B. and Stollenwerk, K.G., 1985, Modeling the rate-controlled sorption of hexavalent chromium, Water Resources Res., vol. 21, pp. 1703–1709. Grove, J.H. and Ellis, B.G., 1980, Extractable chromium as related to soil pH and applied chromium, Soil Sci. Soc. Am. J., vol. 44, pp. 238–242. Handa, B.K., 1988, Occurrence and distribution of chromium in natural waters of India, in Chromium in Natural and Human Environments, Nriagu, J.O. and Nieboer, E., Eds., Wiley Interscience, New York, pp. 189–215. Hartford, W., 1983 Chromium chemicals, in Kirk-Othmer Encyclopaedia of Chemical Technology, Grayson, M., Ed., 3rd ed., vol. 6, Wiley-Interscience, New York, pp. 83–120. Hathway, J.A., 1989, Role of epidemiologic studies in evaluating the carcinogenicity of chromium compounds, Sci. Total Environ., vol. 86, pp. 169–179. Hem, J.D., 1977, Reactions of metal ions at surfaces of hydrous iron oxide, Geochim. Cosmochim. Acta, vol. 41, pp. 527–538. Henderson, T., 1994, Geochemical reduction of hexavalent chromium in the Trinity Sand, Ground Water, vol. 32, pp. 477–486. Hoefs, J., 1987, Stable Isotope Geochemistry, 3rd ed., Springer-Verlag, New York.

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Hug, S.J., Laubscher, H.U., and James, B.R., 1997, Environ. Sci. Technol., vol. 31, pp. 160–170. James, B.R. and Bartlett, R.J., 1983, Behavior of chromium in soils: V. Fate of organically complexed Cr(III) added to soil; VI. Interaction between oxidation-reduction and organic complexation; VII. Adsorption and reduction of hexavalent forms, J. Environ. Qual., vol. 12, pp. 169–181. James, B.R. and Bartlett, R.J., 1988, Mobility and bioavailability of chromium in soil, in Chromium in Natural and Human Environments, Nriagu, J.O. and Nieboer, E., Eds., Wiley Interscience, New York, pp. 265–305. James, B.R. and Bartlett, R.J., 1984, Plant–soil interactions of chromium, J. Environ. Qual., vol. 13, pp. 67–70. James, B.R., 1994, Hexavalent chromium solubility and reduction in alkaline soils enriched with chromite ore processing residue, J. Environ. Qual., vol. 23, pp. 227–233. James, B.R., 1996, The challenge of remediation chromium-contaminated soil, Environ. Sci. Technol., vol. 30, pp. 248–251. Jenne, 1968, Control of Mn, Fe, Co, Ni, Cu, and Zn concentrations in soils and water—the dominant role of hydrous manganese and iron oxides, Adv. Chem., vol. 7, pp. 337–387. Johnson, C.A. and Xyla, A.G., 1991, The oxidation of chromium(III) to chromium(VI) on the surface of manganite (Gamma-MnOOH), Geochim. Cosmochim. Acta, vol. 55, pp. 2861–2866. Johnson, T.M., Herbel, M.J., Bullen, T.D., and Zawislanski, P.T., 1999, Geochim. Cosmochim. Acta, vol. 63, pp. 2775. Jurinak, J.J. and Bauer, N., 1956, Thermodymanics of zinc adsorption on calcite, colomite and magnesite-type minerals, Soil Sci. Soc. Am. Proc., vol. 20, pp. 466–471. Kaczynski, S.E. and Kieber, R.J., 1993, Aqueous trivalent chromium photoproduction in natural waters, Environ. Sci. Technol., vol. 27, pp. 1572–1576. Kaczynski, S.E. and Kieber, R.J., 1994, Hydrophobic C18 bound organic complexes of chromium and their potential impact on the geochemistry of chromium in natural waters, Environ. Sci. Technol., vol. 28, pp. 799–804. Kent, D.B., Davis, J.A., Maest, A.S., and Rea, B.A., 1989, Field and laboratory studies of transport of reactive solutes in groundwater, in Proc. 6th Int. Conf. Water–Rock Interaction, Miles, D.L., Ed., Miles, Balkema, Rotterdam, Netherlands, pp. 381–383. Kieber, R.J. and Heiz, G.R., 1992, Indirect photoreduction of aqueous chromium (VI), Environ. Sci. Technol., vol. 26, pp. 307–312. Kimbrough, D.E., Cohen, Y., Winer, A.M., Creelman, L., and Mabuni, C., 1999, A critical assessment of chromium in the environment, in Crit. Rev. Environ. Sci. Technol. vol. 29, pp. 1–46. Korte, N.E., Skopp, J., Fuller, W.H., Niebla, E.E., and Aleshii, B.A., 1976, Trace element movement in soils: influence of soil physical and chemical properties, Soil Sci., vol. 122, pp. 350–359. Kotas, J. and Stasicka, Z., 2000, Chromium occurrence in the environment and methods of its speciation, Environ. Poll., vol. 107, pp. 263–283. Lancy, L.E., 1966, Treatment of spent cooling waters, U.S. Patent No. 3,294,960. Lide, D.R., Ed., Handbook of Chemistry and Physics, 1996, 77th ed., CRC Press, Boca Raton, FL. Lieber, M., Perlmutter, N.M., and Frauenthal, H.L., 1964, Cadmium and hexavalent chromium in Nassau County ground water, J. AWWA, vol. 56, pp. 739–747.

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Lovely, D.R., 1993, Annu. Rev. Microbiol., vol. 47, p. 263. Loyaux-Lawniczak, S., Lecomte, P., Ehrhardt, J., 2001, Behavior of hexavalent chromium in a polluted groundwater: redox processes and immobilization in soils, Environ. Sci. Technol., vol. 35, pp. 1350–1357. MacNaughton, M.G., 1975, Adsorption of chromium(VI) at the oxide–water interface, Interim Report: Envir. Chem. Div., Environics Directorate, Air Force Civil Eng. Center, Tyndal AFB, FL. McBride, M.B. and Bouldin, D.R., 1984, Long-term reactions of copper(II) in a contaminated calcareous soil, Soil Sci. Soc. Am. J., vol. 48, pp. 56–59. McBride, M.B., 1980, Chemisorption of Cd2+ on calcite surfaces, Soil Sci. Soc. Am. J., vol. 44, pp. 26–28. McLean, J.E. and Bledsoe, B.E., 1992, Behavior of metals in soils, EPA/540/S-92/018. Murray, J.W., Spell, B., and Paul, B., 1983, The contrasting geochemistry of manganese and chromium in the Eastern Tropical Pacific Ocean, in Trace Metals in Seawater, Wong, C.S., Boyle, E., Bruland, K., Burton, J.D., and Goldberg E.D., Eds., Plenum Press, New York, pp. 643–670. Music, S., Ristic, M., and Tonkovic, M., 1986, Sorption of chromium(VI) on hydrous iron oxides, Z. Wass. Abwass. Forsch., vol. 19, pp. 186–196. Nakayama, E., Kuwamoto, T., Tsurubo, S., Tokoro, H., and Fujinaga, T., 1981, Chemical speciation of chromium in sea water 1. Effect of naturally occurring organic materials on the complex formation of chromium(III), Analyt. Chim. Acta, vol. 130, pp. 289–294. Nelson, D.W. and Sommers, L.E., 1982, Total carbon, organic carbon, and organic matter, in Methods of Soil Analysis, Part Two, Dinauer R.C., Ed., American Society of Agronomy, Inc. and Soil Science Society of America, Inc., Madison, WI, pp. 539–580. Nriagu, J.O., 1988, Historical perspectives; and, Production and uses of chromium, in Chromium in the Natural and Human Environments, Nriagu, J.O. and Nieboer, E., Eds., John Wiley and Sons, New York, vol. 20, pp. 1–20 and pp. 81–104. Pacyna, J.M. and Nriagu, J.O., 1988, Atmospheric emissions of chromium from natural and anthropogenic sources, in Chromium in Natural and Human Environments, Nriagu, J.O. and Nieboer, E., Eds., Wiley Interscience, New York, pp. 105–125. Palmer, C.D. and Wittbrodt, P.R., 1990, Geochemical characterization of the United Chrome Products Site, Final Report, in Stage 2 Deep Aquifer Drilling Technical Report, United Chrome Products Site, Corvallis, Oregon, CH2M Hill, Corvallis, OR. Palmer, C.D. and Wittbrodt, P.R., 1991, Processes affecting the remediation of chromium-contaminated sites, Environ. Health Perspectives, vol. 92, pp. 25–40. Palmer, C.D. and Puls, R.W., 1994, Natural attenuation of hexavalent chromium in groundwater and soils, Ground Water, EPA/540/S–94/505. Paya Perez, A.B., Gotz, L., Kephalopoulos, S.D., and Bignoli, G., 1988, Sorption of chromium species on soil, in Heavy Metals in the Hydrocycle, Astruc, M. and Lester, J.N., Eds., Selper, London, pp. 59–66. Perlmutter, N.M. and Lieber, M., 1970, Dispersal of plating wastes and sewage contamination in ground water and surface water, South Farmingdale–Massapequa Area, Nassau County, New York, U.S.G.S. Water Supply Paper 1879-G. Pettine, M. and Millero, F.J., 1990, Limnol. Oceanogr., vol. 35, pp. 730–736. Pettine, M. and Millero, F.J., 1991, Mar. Chem., vol. 34, pp. 29–46. Pettine, M., Campanella, L., Millero, F.J., 2002, Reduction of hexavalent chromium by H2O2 in acidic solutions, Environ. Sci. Technol., vol. 36, n. 5.

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Pettine, M., D’Ottone, L., Campanella, L., Millero, F.J., and Passino, R., 1998, The reduction of chromium(VI) by iron(II) in aqueous solutions, Geochim. Cosmochim. Acta, vol. 62, pp. 1509–1519. Pettine, M., Millero, F.J., and La Noce, T., 1991, Chromium(III) interactions in seawater through its oxidation kinetics, Mar. Chem., vol. 34, pp. 29–46. Pettine, M., Millero, F.J., and Passino, R., 1994, Mar. Chem., vol. 46, pp. 335–344. Powell, R.M., Puls, R.W., Hightower, S.K., and Sabatini, D.A., 1995, Coupled iron corrosion and chromate reduction: mechanism for subsurface remediation, Environ. Sci. Technol., vol. 29, pp. 1913–1922. Rai, D., Eary, L.E., and Zachara, J.M., 1989, Environmental chemistry of chromium, Sci. Tot. Environ., vol. 86, pp. 15–23. Rai, D., Sass, B.M., Moore, D.A., 1987, Chromium (III) hydrolysis constants and solubility of chromium (III) hydroxide, Inorg. Chem., vol. 26, pp. 345–349. Rai, D., Zachara, J.M., Eary, L.E., Ainsworth, C.C., Amonette, J.E., Cowan, C.E., Szelmeczka, R.W., Resch, C.T., Schmidt, R.L., Girvin, D.C., and Smith, S.C., 1988, Chromium reactions in geological materials, Interim Report, Electric Power Research Institute (EPRI) EA-5741, EPRI, Palo Alto, CA. Rai, D., Zachara, J.M., Eary, L.E., Girvin, D.C., Moore, D.A., Resch, C.T., Sass, B.M., and Schmidt, R.L., 1986, Geochemical behavior of chromium species, Interim Report Electric Power Research Institute (EPRI) EA EA–4544, EPRI, Palo Alto, CA. Rai, D., Zachara, J.M., Schwab, A.P., Schmidt, R.L., Girvin, D.C., and Rogers, J.E., 1984, Chemical attenuation rates, coefficients, and constants in leachate migration, Vol. 1, A critical review, Final Report Electric Power Research Institute (EPRI) EA EA-3356, EPRI, Palo Alto, CA. Richard, F.C. and Bourg, A.C.M., 1991, Aqueous geochemistry of chromium: a review, Wat. Res., vol. 25, pp. 807–816. Ritchie, G.S.P. and Sposito, G., 1995, Speciation in soil, in Chemical Speciation in the Environment Ure, A.M. and Davidson, C.M., Eds., Blackie Academic and Professional, Glasgow, Scotland, pp. 201–233. Robertson, F.N., 1975, Hexavalent chromium in the groundwater in the Paradise Valley, Arizona, Ground Water, vol. 13, pp. 516–527. Rotaru, M., Birck, J.L., and Allegre, C.J., 1992, Nature, vol. 358, pp. 465. Saleh, F.Y., Parkerton, T.F., Lewis, R.V., Huang, J.H., and Dickson, K.L., 1989, Kinetics of chromium transformation in the environment, Sci. Tot. Environ., vol. 86, pp. 25–41. Salomons, W. and DeGroot, A.J., 1978, Pollution history of trace metals in sediments, as affected by the Rhine River, in Environmental Biogeochemistry, Krumbein, W.E., Ed., Ann Arbor Science, Ann Arbor, MI, pp. 149–162. Santillan-Medrano, J. and Jurinak, J.J., 1975, The chemistry of lead and cadmium in soils: solid phase formation, Soil Sci. Am. Proc., vol. 29, pp. 851–856. Sass, B.M. and Rai, D., 1987, Volubility of amorphous chromium(III)-Iron(III) hydroxide solid solutions, Inorg. Chem., vol. 26, pp. 2228–2232. Schacklette, H.T. and Boerngen, J.G., 1984, Element concentration in soils and other surficial materials, U.S. Geol. Surv. Prof. Paper 1710, Washington, D.C. Schmidt, R.L., 1984, Thermodynamic properties and environmental chemistry of chromium, U.S. Dept. Energy, DE-AC06-76RLD-1830, Washington, D.C. Schroeder, D.C. and Lee, G.F., 1975, Potential transformation of chromium in natural waters, Water Air Soil Pollut., vol. 4, pp. 355–365. Seigneur, C. and Constantinou, E., 1995, Environ. Sci. Technol., vol. 29, pp. 222–231.

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Smith, L.A., Means, J.L., Chen, A., Alleman, B., Chapman, Ch.C., Tixier, J.S., Brauning, S.E., Gavaskar, A.R., and Royer, M.D., 1995, Remedial options for metalscontaminated sites, Contaminant Fate and Migration, CRC Press, Boca Raton, FL, pp. 17–34, chap. 3. Spokes, L.J. and Jickells, T.D., 1995, Speciation of metals in the atmosphere, in Chemical Speciation in the Environment, Ure, A.M. and Davidson, C.M., Eds., Blackie Academic and Professional, Glasgow, Scotland, pp. 137–168. Stollenwerk, K.G. and Grove, D.B., 1985, Adsorption and desorption of hexavalent chromium in an alluvial aquifer near Telluride, Colorado, J. Environ. Qual., vol. 14, pp. 150–155. Stumm, W. and Morgan, J.J., 1981, Aquatic Chemistry, John Wiley and Sons, New York. Thode, H.G. and Monster, J., 1965, in Fluids in Subsurface Environments—a Symposium, American Association of Petroleum Geologists, Tulsa, OK, pp. 367–377. Walkley, A. and Black, L.A., 1934, An examination of the Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method, Soil Sci., vol. 37, pp. 29–38. White, A.F. and Hochella, M.F., 1989, Electron transfer mechanisms associated with the surface oxidation and dissolution of magnetite and ilmenite, Proc. 6th Internat. Sympos. On Water–Rock Interaction, pp. 765–768. Wielinga, B., Mizuba, M., Hansel, C., and Fendorf, S., 2001, Iron promoted reduction of chromate by dissimilatory iron-reducing bacteria, Environ. Sci. Technol., vol. 35, n. 3. Wiley, K.G., 1983, Hydrogeological investigation examining the identification and cleanup of chromium contaminated groundwater in Richland Township, Kalamazoo County, Michigan. M.S. thesis, Wright State University. Wittbrodt, P.R. and Palmer, C.D., 1995, Reduction of Cr(VI) in the presence of excess soil fulvic acid, Environ. Sci. Technol., vol. 29, pp. 255–263. Zachara, J.M., Girvin, D.C., Schmidt, R.L., and Resch, C.T., 1987, Chromate adsorption on amorphous iron oxyhydroxide in presence of major ground water ions, Environ. Sci. Technol., vol. 21, pp. 589–594.

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6 Toxicity and Health Effects of Chromium (All Oxidation States)

Jacques Guertin

CONTENTS 6.1 Introduction ................................................................................................216 6.2 Toxicology ...................................................................................................217 6.2.1 Ingestion .........................................................................................217 6.2.2 Dermal Contact..............................................................................219 6.2.3 Inhalation........................................................................................219 6.3 Cancer Effects .............................................................................................220 6.3.1 Inhalation........................................................................................220 6.3.2 Ingestion .........................................................................................220 6.3.3 Dermal.............................................................................................220 6.4 Noncancer Effects ......................................................................................221 6.4.1 Inhalation........................................................................................221 6.4.1.1 Death.................................................................................221 6.4.1.2 Systemic Effects...............................................................221 6.4.1.3 Immunological and Lymphoreticular.......................... 222 6.4.1.4 Neurological ....................................................................222 6.4.1.5 Reproductive....................................................................222 6.4.1.6 Developmental ................................................................223 6.4.1.7 Genotoxic..........................................................................223 6.4.2 Ingestion .........................................................................................223 6.4.2.1 Death.................................................................................223 6.4.2.2 Systemic............................................................................223 6.4.2.3 Immunological and Lymphoreticular.......................... 223 6.4.2.4 Neurological ....................................................................224 6.4.2.5 Reproductive....................................................................224 6.4.2.6 Developmental ................................................................224 6.4.2.7 Genotoxic..........................................................................224 6.4.3 Dermal.............................................................................................225 6.5 Ecological Effects .......................................................................................225 1-5667-0608-4/05/$0.00+$1.50 © 2005 by CRC Press LLC

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6.6 6.7 6.8

Evaluation of Studies and Data Gaps ...................................................226 Key Issues .................................................................................................. 226 Human Health Risk Calculations .......................................................... 226 6.8.1 General Procedure........................................................................ 227 6.8.2 Calculation of Exposure Concentration for Specified Incremental Risk (Child) ............................................................. 229 6.8.3 Calculation of Inhalation CPF (Adult) ......................................230 Bibliography ........................................................................................ 230

6.1

Introduction

Chromium (Cr) is considered an essential nutrient and a health hazard. How is this possible? The answer is that Cr exists in more than one oxidation state. Specifically, Cr in oxidation state +6, written as Cr(VI), is considered harmful even in small intake quantity (dose) whereas Cr in oxidation state +3, written as Cr(III), is considered essential for good health in moderate intake. The health effects or nutritional benefits of Cr in other oxidation states are unknown although there are regulatory limits for the metal, Cr(0) or Cr0, and Cr(II) along with those for Cr(III) and Cr(VI). For example, the federal maximum concentration level (MCL) for total Cr in drinking water is 100 µg/L (USEPA, 1999), the California MCL is 50 µg/L (Calder, 1988), and the National Institute for Occupational Health and Safety (NIOSH) recommends an exposure limit for Cr(VI) of 1 µg/m3 and an exposure limit for Cr(0), Cr(II), and Cr(III) of 500 µg/m3 for a 10-hour workday, 40-hour week (NIOSH, 1999). The concentration of Cr occurring naturally in the Earth’s normal mineral soil ranges from about 1 mg/kg to 2000 mg/kg in the United States (Shacklette and Boemgen, 1984) with a mean of 200 mg/kg worldwide (Hawkes and Webb, 1962; Motzer, Chapter 2, Table 2.7). In conterminous United State soils, Cr concentration ranges from 1 mg/kg to 2,000 mg/kg with a mean of 37 mg/ kg and most of this Cr is Cr(III) (Shacklette and Boerngen, 1984; ATSDR, 2000). Human activity further contributes to Cr in the environment (air, surface water, groundwater, soil). The greatest anthropogenic sources of Cr(VI) emissions are: (1) Cr plating, (2) chemical manufacturing of Cr, and (3) evaporative cooling towers (ATSDR, 2000). While combustion of coal and oil also release large quantities of Cr (1,700 metric tons per year), only approximately 0.2% of this is Cr(VI) (ATSDR, 2000). Approximately 35% of Cr released from all anthropogenic sources is Cr(VI). However, the ratio of Cr(III)/Cr(VI) in the natural environment varies considerably, from perhaps 0.3 to 1.5, depending on oxidation/reduction and acid/base conditions (Motzer, 2003, Chapter 2, Section 2.6.3). Cr metal or elemental chromium, Cr(0), rarely occurs naturally (Gorshkov et al., 1996; Guisewite, 2001; Chapter 2, Section 2.1.4) and Cr(II)

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is unstable in the environment, readily oxidizing to Cr(III). Only small quantities of Cr(II) are used in industry. Thus, most exposures to Cr in the environment will be to Cr(III) and not to Cr(VI), the toxic constituent of total Cr. Occupational exposure to Cr(VI) is the most likely potential for adverse health effects.

6.2

Toxicology

For any substance to have an adverse health effect, there must first be an exposure to that substance and then it must enter the body (conceptualized in Figure 6.1). The common exposure routes or intake modes are: • Ingestion (eating/drinking) • Dermal contact (skin penetration) • Inhalation (breathing) Health effects are categorized as carcinogenic (causing cancer) and noncarcinogenic including the following three different exposure durations that result in adverse health effects: • Acute (14 days or less) • Intermediate (15 to 364 days) • Chronic (365 days or more) Although the United States Environmental Protection Agency (USEPA) considers Cr(VI) to be a cancer agent by inhalation only, this chapter discusses all three main intake modes and includes Cr(III) as well as Cr(VI). Examples of numerical calculations of human health risk from exposure to Cr(VI) are in Section 6.8, “Human Health Risk Calculations”.

6.2.1

Ingestion

The common ingestion intake pathways are food consumption, drinking water, and ingestion of contaminated soil (mostly by children). Other possible ingestion intake pathways such as swallowing contaminated water while swimming or showering are less likely and not considered. Of the total Cr ingested, only about 2% to 3% is absorbed by the gut (gastrointestinal tract)—inferred from the quantity released in the urine. Gastric juices rapidly reduce Cr(VI) to Cr(III)! And, Cr(III) in small quantities is an essential nutrient (see end of references, Candlish, 2000). The reduction

RECEPTOR

Groundwater Transport

Enclosed Space Accumulation

Atmospheric Dispersion

NA

Return

Print Sheet

NA

Commercial

NA

Commercial

Commercial

Indoor Air: Commercial

NA

Receptors Off-site1

Outdoor Air: Commercial

Res./Constr.

On-site

Commands and Options

Surface Water Swimming, Fish Consumption, Aquatic Life

Groundwater Potable Water Ingestion

Air Inhalation of Vapor and/or Particulates

Soil Dermal Contact and Ingestion

Exposure Media

Help

Swimming Fishing Aquatic Life

Surf. Water

NA

Residential

NA

Off-site2

Job ID: CHROMIUM(VI) Handbook Date: 15-Feb-04

FIGURE 6.1 Exposure–route pathway. Flowchart for transport of toxic matter from source to receptor. With Permission from Groundwater Sciences Inc. (1999) RBCA Tool Kit for Chemical Releases.

TRANSPORT

Leaching

Volatilization

Wind Erosion

Transport Mechanisms

Site Name: Figure 1 Location: Section 6 Compl. By:

218

SOURCE

Affected Groundwater

Affected Subsurface Soils

Affected Surficial Soils

Source Media

Exposure Pathway Flowchart

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process appears to be 100% complete so that no Cr(VI) can be detected in the gastrointestinal tract or in the blood after ingestion of Cr(VI). This is the reason why Cr(VI) is not considered to be a health hazard by ingestion (IRIS, 1998a; IRIS, 1998b; ATSDR, 2000; Khitrov, 2001; Flegal et al., 2001). Currently, California regulators are reviewing this mechanism of conversion of Cr(VI) to Cr(III) (Flegal et al., 2001).

6.2.2

Dermal Contact

Nonoccupational dermal contact, a less common mode of exposure, can occur through swimming, bathing, showering, and contact with contaminated soil. Workers in the Cr industry (plating and chemical manufacturing) are likely to experience some degree of dermal exposure to Cr(VI) whether by settling of contaminated dust on the skin or by contact of the skin with liquids containing Cr(VI). Because Cr(VI) compounds are generally much more soluble in water than Cr(III) compounds, Cr(VI) will penetrate the skin 10,000 times faster than Cr(III) will, 5 × 10–11 cm/s versus 5 × 10–7 cm/s, respectively (Spruit and van Neer 1966; ATSDR, 2000). However, if skin lesions are present, the rate of penetration of Cr(VI) and Cr(III) are nearly identical. Here, it appears that Cr(VI) is reduced to Cr(III) by the blood prior to absorption (Corbett et al., 1997; ATSDR, 2000) — essentially the same reduction as occurs when ingesting Cr(VI).

6.2.3

Inhalation

Airborne Cr occurs as particles or dissolved in rain water. Owing to its very low equilibrium vapor pressure, Cr as a gas is rarely encountered. Inhalation of Cr (dust, fumes, aerosol) is the important intake mode. The inhalation health effects of Cr(VI) are clearly different than that of Cr(III). For example, inhaling Cr(VI) as chromium(VI) oxide (CrO3) causes nasal damage whereas there is no irritation from inhalation of Cr(III). Moreover, Cr(VI), because of its greater aqueous solubility, is absorbed more readily from the lungs than Cr(III) is. For example, Cr(VI) transferred to the blood from particles in the lung was at least three times more than that of Cr(III) transferred to the blood (Suzuki et al., 1984; ATSDR, 2000). But, Cr(III) is absorbed from the lungs more than expected based on its aqueous solubility alone. One explanation is the possibility of Cr(III) forming soluble complexes. Although 53% to 85% of the Cr(VI) is cleared by the lungs by absorption into the blood or by mucous in the pharynx, 15% to 47% of the Cr(VI) remains in the lung (Baetjer et al., 1959; ATSDR, 2000). This may be the main contributor to Cr(VI)’s toxicity, especially cancer.

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Cancer Effects

As discussed earlier, current evidence indicates that Cr(VI) is a cancer agent only by inhalation. The USEPA has assigned a Group A inhalation cancer classification (definite human carcinogen) and derived an inhalation unit risk of 0.012 µg/m3, equivalent to a cancer potency factor of 42 (mg/(kg body mass)/d)–1. And, the International Agency for Research on Cancer (IARC) has assigned a Group 1 inhalation cancer classification (definite human carcinogen). Chronic inhalation studies on mice exposed to airborne Cr(VI) suggest that Cr(VI) is an animal carcinogen (Nettesheim et al., 1971; ATSDR, 2000). The mice developed lung tumors from exposure to 4.3 mg/m3 of Cr(VI). However, a number of chronic animal studies showed no carcinogenic effects in rats, rabbits, or guinea pigs exposed to 1.6 mg/m3 of Cr(VI) (Baetjer et al., 1959; Steffee and Baetjer 1965; ATSDR, 2000). Thus, cancer effects on animals seem to depend on the type of animal.

6.3.1

Inhalation

Studies of chromate (CrO42−) production workers, exposed to Cr (mainly Cr(VI)), have shown a significant association with cancer from inhalation. Also, studies of workers in Cr plating, who were exposed to Cr(VI), indicate that Cr(VI) is a carcinogen by inhalation. Studies of workers exposed to Cr(III) indicate that Cr(III) has no adverse health effects (ATSDR, 2000).

6.3.2

Ingestion

When adjusted for lung cancer, the mortality rate for a population living in a polluted area (China) near Cr smelting operations does not appear to be significantly different than the mortality rate for the whole province (Zhang and Li, 1997; ATSDR, 2000). Also, three generations (880 days) of mice given a Cr(VI) dose of 9 mg/(kg body mass)/d in their drinking water showed no carcinogenic effects (ATSDR, 2000). Similarly, there was no evidence of carcinogenicity in rats fed a Cr(III) dose of 2,040 mg/(kg body mass)/d for 5 d/week for 2 years (Ivankovic and Preussmann, 1975; ATSDR, 2000).

6.3.3

Dermal

No information exists regarding cancer in humans or animals from dermal exposure to chromium. However, some Cr(VI) compounds are caustic/corrosive and may burn the skin. This could increase the absorption of Cr(VI) and result in some adverse health effects (not likely cancer because of the chemical reduction mechanism mentioned earlier).

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Noncancer Effects

The main noncancer effects from exposure to any potentially toxic matter are usually categorized as follows: • • • • • • •

Death Systemic Immunological and lymphoreticular Neurological Reproductive Developmental Genotoxic

The degree of adverse effect usually depends on the duration of exposure: acute (≤14 days), intermediate (15 to 364 days), and chronic (≥365 days). Also, it is useful to consider adverse effects that result in permanent damage more or less independent of exposure duration and those that disappear some time after the exposure stops.

6.4.1

Inhalation

The estimated equilibrium vapor pressure of elemental Cr (metal) at 25 °C is 1.6 × 10−59 mmHg (Handbook Physics and Chemistry, 1996) — essentially zero. Elemental Cr is so nonvolatile that no significant evaporation occurs until a temperature of at least 1,600 °C is reached, where the equilibrium vapor pressure is about 1 mmHg. Elemental Cr boils at 2,672 °C (equilibrium vapor pressure of 760 mmHg). Thus, exposure to Cr gas is most unlikely. However, Cr compounds can easily become airborne as small particles (solid or liquid droplets) and these particles may be inhaled with possible adverse health effects. 6.4.1.1 Death There are no data regarding death after acute inhalation of Cr or Cr compounds. 6.4.1.2 Systemic Effects The respiratory tract in humans is the major target of inhalation exposure to Cr compounds. Inhalation of Cr(VI) can produce asthma and nasal septum ulcers and even nasal septum perforations. It is likely that no significant adverse nasal effects nor lung function effects will occur if acute exposure concentrations of Cr(VI) are less than 0.001 mg/m3 (ATSDR, 2000). However,

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an intermediate exposure to Cr(VI) concentration of 0.000005 mg/m3 has been calculated as a minimal risk level (MRL). If Cr concentrations are high (e.g., 0.01 mg/m3), inhalation by breathing through the mouth (common for industrial workers) can result in stomach ulcers. A single study indicates that inhalation exposure to Cr(IV) (as CrO2) does not have significant adverse effect on the blood system (Lee et al., 1989; ATSDR, 2000). For example, there were no changes in the blood system of rats exposed to 15.5 mg/m3 of Cr(IV) — an extremely high concentration in air. There is little evidence of any adverse effects to the renal (kidney) system from inhalation of Cr(VI). For example, even though stainless steel welders had Cr(VI) concentrations in their urine that were higher than the norm, the welders did not have any adverse renal function (Littorin et al., 1984; Verschoor et al., 1988; ATSDR, 2000). 6.4.1.3 Immunological and Lymphoreticular Concentrations of some lymphocyte subpopulations were reduced in a group of workers exposed to Cr(VI) dust in a plastics factory. No effects to serum Cr concentrations or to serum immunoglobulins IgA, IgG, and IgM were observed (Boscolo et al., 1997; ATSDR, 2000). However, it was difficult to interpret these results owing to simultaneous exposure to other chemicals. Commonly, exposure to a Cr(VI) concentration of 0.05 mg/m3 did produce a greater number of macrophages and macrophage activity (Glaser et al., 1985; ATSDR, 2000). But, this also occurs from exposure to any nuisance dust. The lowest observed adverse effect level (LOAEL) for immunological effects in rats is a Cr(VI) concentration of 0.36 mg/m3 (Cohen et al., 1998; ATSDR, 2000). 6.4.1.4 Neurological In a Cr plating factory, workers exposed to high concentrations of Cr(VI) fumes owing to very poor working conditions, suffered from dizziness, headache, and weakness (Liberman 1941; ATSDR, 2000). No data were found regarding neurological effects in humans or animals from exposure to Cr(III) nor in animals exposed to Cr(VI). And, no histopathological lesions were observed in the brain, spinal cord, or nerve tissue of rats exposed to a Cr(VI) concentration of 15.5 mg/m3 for 2 years (Lee et al., 1989; ATSDR, 2000). No neurological tests were done. 6.4.1.5 Reproductive The evidence for pregnancy and childbirth problems from exposure to Cr(VI) is not strong. The quality of the few available studies on humans is poor. Rats exposed to a Cr(VI) concentration of 0.2 mg/m3 for three generations showed no reproductive effects (Glaser et al., 1984; ATSDR, 2000). Thus, it is not possible to draw any conclusions regarding reproductive effects from exposure to Cr (ATSDR, 2000).

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6.4.1.6 Developmental No information was available regarding developmental effects in humans from inhalation exposure to Cr in any form. And, there was no developmental effects in rats exposed to a Cr(VI) concentration of 0.2 mg/m3 for three generations (Glaser et al., 1984; ATSDR, 2000). There are no data regarding adverse effects to the human or animal muscle or skeleton system from inhalation of Cr or Cr compounds (ATSDR, 2000). 6.4.1.7 Genotoxic Workers exposed to a dichromate (Cr2O72–) concentration of approximately 0.03 mg/m3 did not show any significant deoxyribonucleic acid (DNA) molecular breaks or hydroxylation of deoxyguanosine in lymphocytes (Gao et al., 1994; ATSDR, 2000). Nevertheless, inhalation of Cr in various forms may cause chromosome effects in humans, suggesting a potential for cancer because interactions with DNA has been linked to the mechanism for carcinogenicity.

6.4.2 6.4.2.1

Ingestion Death

It is clear that ingestion of Cr(VI) may cause sickness and ultimately death. For example, a man died from gastrointestinal bleeding 1 month after ingesting only 4.1 mg/(kg body mass) of Cr(VI) as chromic acid, H2CrO4 (Saryan and Reedy, 1988; ATSDR, 2000). Ingesting a higher dose, 29 mg Cr(VI)/(kg body mass), as potassium dichromate, K2Cr2O7, killed a 17-yearold male. Acute oral (ingestion) lethal dose 50 (LD50) for rats ingesting Cr(III) or Cr(VI) varied depending on the Cr compound and the sex of the rat. For ingestion of Cr(VI), the lowest (most severe) observed LD50 was approximately 16.0 mg/(kg body mass) in female rats (ATSDR, 2000) and approximately 24.5 mg/(kg body mass) in male rats (Gad et al., 1986). 6.4.2.2 Systemic Ingestion of high concentrations of Cr(VI), for example, 29 mg/(kg body mass), often results in lung function and blood system problems; death may be the result of pulmonary or cardiac arrest. However, such effects have not been reported for ingestion of nonlethal quantities of Cr(VI). Ingestion of Cr(VI) often produces gastrointestinal burns and hemorrhage, liver damage, and kidney damage that may lead to death. Other symptoms are diarrhea, ulcers, abdominal pain, indigestion, and vomiting (ATSDR, 2000). 6.4.2.3 Immunological and Lymphoreticular Except for some skin problems, there are no reported effects on the immune system from human exposure to Cr in any form (ATSDR, 2000). Studies on

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rats suggest that some Cr-induced sensitization may result from ingesting Cr(VI) (Snyder and Valle 1991; ATSDR, 2000). 6.4.2.4 Neurological There are no dependable data regarding neurological effects in humans after ingestion of Cr(VI) (Kaufman et al., 1970; ATSDR, 2000). Rats ingesting a Cr(VI) dose of 98 mg/(kg body mass)/d for 28 days had reduced motor activity and balance (Diaz-Mayans et al., 1986; ATSDR, 2000). A large ingestion Cr(III) dose of 2,040 mg/(kg body mass)/d, did not result in any abnormalities to the brain or nervous system of the exposed rats (Ivankovic and Preussman 1975; ATSDR, 2000). 6.4.2.5

Reproductive

No information is available regarding reproductive effects in humans after ingestion of Cr in any form (ATSDR, 2000). In laboratory animals, ingestion of Cr(VI) can reduce sperm count (Zahid et al., 1990; ATSDR, 2000). A decrease in sperm count and fertility occurred in mice ingesting a Cr(VI) dose of 15.2 mg/(kg body mass)/d as K2Cr2O7 for 7 weeks (Zahib et al., 1990; ATSDR, 2000); a decrease in fertility occurred in mice ingesting a Cr(VI) dose of 6 mg/(kg body mass)/d as K2Cr2O7 for 12 weeks (Elbetieha and Al-Hamood 1997; ATSDR 2000). However, rats fed a Cr(III) dose of 1,806 mg/(kg body mass)/d for 60 days (but only 5 d/week) before gestation and during the gestation period had normal fertility and litter size (Ivankovic and Preussman 1975; ATSDR, 2000). This is consistent with the premise that Cr(III) is not toxic but that Cr(VI) can be toxic. 6.4.2.6

Developmental

There are no reports on developmental effects in humans after ingestion of Cr in any form (ATSDR, 2000). A number of animal studies indicate that ingestion of Cr(VI) hinders the development of rats and mice. For example, pregnant mice ingesting a Cr(VI) dose of 57 mg/(kg body mass)/d as K2Cr2O7 during gestation showed embryo lethal effects, gross abnormalities, and decreased fetal mass (Trivedi et al., 1989; ATSDR, 2000). In a more recent study, before mating, female rats ingesting a Cr(VI) dose of approximately 85 mg/(kg body mass)/d for 3 months had reduced maternal mass gain, reduced fetal mass, and reduced bone formation in fetuses (Kanojia et al., 1998; ATSDR, 2000). 6.4.2.7

Genotoxic

No studies were found on genotoxic effects in humans after ingestion of Cr in any form (ATSDR, 2000). Male mice ingesting a Cr(VI) dose of 20 mg/(kg body mass) for 1 day showed significant aberrations of chromosomes in cells (Sarkar et al., 1993; ATSDR, 2000). However, rats drinking water containing

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approximately 10 mg/L Cr(VI) as K2Cr2O7 for 48 hours showed no unscheduled DNA synthesis in hepatocytes, although an increase in DNAprotein crosslinking occurred in their livers (Coogan et al., 1991; ATSDR, 2000).

6.4.3

Dermal

Cr(VI) compounds such as CrO3 (and the corresponding chromic acid, H2CrO4), K2Cr2O7, K2CrO4, Na2Cr2O7, and Na2CrO4 are very corrosive and can severely burn the skin. Such burns make it easier for Cr(VI) to be absorbed through the skin with the potential for causing systemic toxicity. The dermal LD50 for rabbits was approximately a Cr(VI) dose of 500 mg/(kg body mass) as sodium chromate, Na2CrO4. Prior to death, symptoms were dermal necrosis, eschar (scab) formation, diarrhea, dermal edema, and erythema (excessive redness) (Gad et al., 1986; ATSDR, 2000). Reports of systemic, cardiovascular, gastrointestinal, and renal effects from dermal exposure to Cr(VI) are mostly of poor quality and old — reports from the 1920s to 1930s (ATSDR, 2000).

6.5

Ecological Effects

Because carcinogenic effects are not generally significant for ecological systems, Cr(VI) need not be considered separately. Therefore, total Cr can be used to estimate ecological effects. Chromium does accumulate in aquatic biota (NAS, 1974; Havas and Hutchison, 1987; Jackson, 1988) with a typical bioconcentration factor (defined as the ratio of concentration in dry tissue to concentration in water) range of 100 to 1,000 (CCREM 1987). Bioaccumulation occurs in vegetation roots but not in the above-ground portion of vegetation (Cary, 1982; Petruzzeli et al., 1987; WHO, 1988; ATSDR, 2000). Also, Cr does not biomagnify in aquatic or terrestrial food chains (Mance, 1987; Outridge and Scheuhammer, 1993; ATSDR, 2000). In most organisms, Cr(VI) is reduced to Cr(III), the form that is commonly found in proteins, enzymes, and nucleotides (Nieboer and Jusys, 1988). Also, it appears that Cr(III) is an essential trace element not just in humans but in all mammals (Katz and Salem, 1994). Thus, exposure to low concentrations of Cr in any form is unlikely to cause significant adverse effects to ecological species. Additional information for evaluating ecological effects of any chemical can be found in USEPA 1989a, USEPA 1989b, USEPA 1992, USEPA 1993, USEPA 1994.

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Evaluation of Studies and Data Gaps

Data are insufficient for derivation of acute inhalation or ingestion MRL for Cr(VI) (ATSDR, 2000). Moreover, there are no data on synergistic or antagonistic effects. In addition, dermal studies would be useful to determine possible target organs in humans other than the skin. Finally, the reduction of Cr(VI) to Cr(III) in the human body needs to be examined sufficiently to confirm where in the body it occurs and where it does not.

6.7

Key Issues

Clearly, the key to estimating degree of toxicity of Cr(VI) to humans is the effectiveness of the reduction process of Cr(VI) to Cr(III) within the human body. In the gut, the process seems to be 100%. This suggests that ingested Cr(VI) is not toxic. Consistent with this, the California Environmental Protection Agency’s (Cal/EPA’s) Office of Environmental Health Hazard Assessment (OEHHA) has withdrawn its Public Health Goal (PHG) of 2.5 µg/L for chromium in drinking water. A Cr(VI) PHG is being developed by OEHHA and should be available by the time this book is published. Further, there is likely to be a threshold concentration for any adverse effects from inhalation of Cr(VI). Inhalation of low concentrations of Cr(VI), such as <0.01 mg/m3, did not cause any lung cancers among exposed industrial workers (Pastides et al., 1991, 1994; ATSDR, 2000). The effect of smoking of workers exposed to airborne Cr(VI) is unclear.

6.8

Human Health Risk Calculations

Human health risk assessment provides an estimate of the probability of an adverse effect as a result of exposure to one or more toxic substances. Adverse effects are directly related to a substance’s intrinsic toxicity and the substance’s rate of intake into the body. The method of estimating risk must usually follow USEPA Risk Assessment Guidelines (RAGS) (USEPA 1989c) or other regulatory-approved methods such as risk-based-corrective-action (RBCA) (ASTM, 2002). A frequent goal of risk assessments is to estimate how much cleanup (i.e., residual concentration of contaminant) will be protective of human health. In this handbook, the focus is mainly on Cr(VI). Exposure to Cr(VI) compounds is considered to pose a cancer risk as well as a noncancer risk.

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The risk assessment tries to answer what the risk is from an intake (by inhalation, ingestion, dermal) of a specified quantity of Cr(VI) over a specified time interval.

6.8.1

General Procedure

The example calculations for the human health risk assessment are based on experimental animal (rat/mouse) carcinogenic effects. The risk of an adverse health effect from exposure to a toxic substance can be estimated by applying the following relationship: Risk ∝ (toxicity of substance)(quantity taken into the body) The overall process for assessing human health risk from exposure to a toxic compound consists of the following components: 1. Identification of substance of concern 2. Exposure and toxicity assessment 3. Risk calculation/estimate: incremental cancer risk = (CPF)(intake rate) where,

CPF = Cancer Potency Factor, (mg/(kg body mass)/d)–1 Intake rate = Quantity of contaminant taken in per unit time, mg/(kg body mass)/d

The CPF is a regulatory value (i.e., it usually must be used in risk assessments that must be approved by a regulatory agency). It is usually derived from tests on experimental animals and assumes that there is an adverse effect at all doses, that is, that there is no threshold for harm. To be conservative, the CPF is defined as the slope of the linear portion of the upper 95% confidence interval of the dose–response curve (Figure 6.2). An incremental cancer risk of less than 1 in 1 million (less than 1.0 × 10 −6) is almost always considered acceptable. Incremental noncancer risk from exposure to one substance by one intake route (inhalation, ingestion, or dermal sorption) can be estimated by the following relationship: For ingestion or dermal sorption, Hazard Quotient = (intake rate)/(RfD) For inhalation, Hazard Quotient = (intake rate)/(RfC)

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probability of cancer RESPONSE

upper 95% confidence interval

lower 95% confidence interval

DOSE FIGURE 6.2 Conceptual dose–response relationship. Choosing the maximum likelihood function (i.e., the lower dose giving greater response corresponding to the upper 95% confidence interval) to calculate slope (of the linear portion of plot), the cancer potency factor, is the most conservative approach.

where, RfD = Reference Dose in mg/(kg body mass)/d RfC = Reference Concentration in mg/(kg body mass)/d A hazard quotient of no more than 1.0 indicates that the intake of a contaminant would result in no significant adverse effects. The generic equation for calculating intake rate is, Intake rate = [(Cim)(IRm)(FIm)(ABSF)(EF)(ED)]/[(BM)(AT)] where, Cim = Concentration of contaminant i in medium m in contact with body IRm = Intake rate of exposure medium m FIm = Fraction of intake medium m that has contaminant i ABSF= Absorption factor, fraction of i absorbed (biologically available) by the body EF = Exposure frequency, days per year (d/year) ED = Exposure duration, year BM = Body mass (kg)

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AT = Averaging time (period over which exposure is averaged) = ED(365 d/year) for noncancer = (70 year)(365 d/year) for cancer

6.8.2

Calculation of Exposure Concentration for Specified Incremental Risk (Child)

The calculation for the exposure concentration, for inhalation of Cr(VI) in air, that results in an estimated cancer risk of 1 in 1 million is shown below: 1.0 × 10–6 = {42 (mg/(kg body mass)/d)–1}{intake rate} where intake rate, = {(Cim, µg/m3)(10–3 mg/µg)(10 m3/d)(350 d/y)(6 y)}/ {(15 [kg body mass])(70 y)(365 d/y)} = (Cim, µg/m3)(5.479 × 10–5)(m3/µg)(mg/[kg body mass]/d) Cim = (1.0 × 10–6)/[(42)(5.479 × 10–5)] = 4.3 × 10–4 µg/m3 (2.0 × 10–7 ppmv) This result is very strict when compared with (1) the National Institute of Occupational Safety and Health (NIOSH) Recommended Exposure Limit (REL) 8-h Time Weighted Average (TWA) limit of 1.0 µg/m3 and (2) the USEPA RfC of 0.1 µg/m3 (IRIS, 2000 for Cr(VI)). The calculation for the exposure concentration, for ingestion of Cr(VI) in water, for a hazard quotient of 1 is shown below: 1 = (intake rate)/(RfD) = (intake rate)/(0.003 mg/(kg body mass)/d) where intake rate, = {(Cim, µg/L)(10−3 mg/µg)(1 L/d)(350 d/year)(6 year)}/ {(15 (kg body mass))(6 year)(365 d/year)} = (Cim, µg/L)(6.3927 × 10−5 (L/µg)(mg/(kg body mass)/d) Cim = 1(0.003 mg/(kg body mass)/d)/ {6.3927 × 10–5 (L/µg)(mg/(kg body mass)/d)} ≈ 47 ppb) = 47 µg/L (≈

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Thus, a child drinking Cr(VI)-contaminated water at concentrations no greater than 47 µg/L is unlikely to experience any adverse noncancer effects. This calculated Cr(VI) concentration for a Hazard Quotient equal to 1 is based on a safety factor of 1,000.

6.8.3

Calculation of Inhalation CPF (Adult)

The calculation of the inhalation cancer potency factor is based on a minimum risk level (MRL) of 0.005 µg/m3. The following is a calculation of inhalation CPF based on a 1 in 1 million (1.0 × 10–6) incremental cancer risk: 1.0 × 10–6 = {CPF, (mg/(kg body mass)/d)–1}{intake rate} Adult (70 year of exposure) intake rate = {(Cim, µg/m3)(10–3 mg/µg)(20 m3/d)(350 d/year)(30 year)}/ {(70 (kg body mass))(70 year)(365 d/year)} = (Cim, µg/m3)(1.174 × 10–4 m3/µg)(mg/(kg body mass)/d) = (0.005 µg/m3)(1.174 × 10–4 m3/µg)(mg/(kg body mass)/d) = 5.87 × 10–7 mg/(kg body mass)/d Inhalation CPF = (1.0 × 10–6)/(5.87 × 10–7 mg/(kg body mass)/d) = 1.7 (mg/(kg body mass)/d)–1 The calculated CPF is about 25 times smaller than the USEPA or Cal EPA inhalation CPF of 42 (mg/(kg body mass)/d)–1.

Bibliography Agency for Toxic Substances and Disease Registry (ATSDR), 2000, Toxicological Profile for Chromium, U.S. Department of Health and Human Services, Public Health Service, ATSDR, September 2000. ASTM 2002, Emergency Standard Guide for Risk-Based Corrective Action Applied at Petroleum Release Sites, American Society for Testing and Materials. Baetjer, A.M., Lowney, J.F., Steffee, H., et al., 1959, Effects of chromium on incidence of lung tumors in mice and rats, Archives of Industrial Health, 20, 124–135.

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Boscolo, P., Di Gioacchino, M., Bavazzano, P., et al., 1997, Effects of chromium on lymphocyte subsets and immunoglobulins from normal population and exposed workers, Life Science, 60, 16, 1319–1325. Calder, L.M., 1988, Chromium contamination of groundwater, in chromium in the natural and human environments, Nriagu, J.O. and Nieboer, E., Eds., Vol. 20, in Wiley Series in Advances in Environmental Science and Technology, John Wiley and Sons, New York, pp. 215–229. Canadian Council of Resource and Environment Ministers (CCREM), 1987, Canadian water quality guidelines, The Task Force on Water Quality Guidelines of the Canadian Council of Resource and Environment Ministers, Ottawa, Ontario. Cary, E.E., 1982, Chromium in air, soil, and natural waters, Topics in Environmental Health 5, Biological and Environmental Aspects of Chromium, Elsevier Biomedical Press, New York, pp. 49–64. Cohen, M.D., Zelikoff, J.T., Chen, L.C., et al., 1998, Immunotoxicologic effects of inhaled chromium: role of particle solubility and co-exposure to ozone, Toxicological Applied Pharmacology, 152, 30–40. Coogan, T., Motz, J., Snyder, C., et al., 1991, Differential DNA-protein crosslinking in lymphocytes and liver following chronic drinking water exposure of rats to potassium chromate, Toxicological Applied Pharmacology, 109, 60–72. Corbett, G.E., Finley, B.L., Paustenbach, D.J., et al., 1997, Systemic uptake of chromium in human volunteers following dermal contact with hexavalent chromium (22 mg/l), Journal of Exposure Analysis and Environment Epidemiology, 7, 2, 179–189. Diaz-Mayans, J., Laborda, R., and Numez, A., 1986, Hexavalent chromium effects on motor activity and some metabolic aspects of wistar albino rats, Comparative Biochemistry and Physiology, 83C, 1, 191–195. Elbetieha, A. and Al-Hamood, M.H., 1997, Long-term exposure of male and female mice to trivalent and hexavalent chromium compounds: effect on fertility, Toxicology, 116, 39–47. Flegal, R., Last, J., McConnell, E., Schenker, M., and Witschi, H., 2001, Scientific review of toxicological and human health issues related to the development of a public health goal for chromium(VI), Report prepared for the Chromate toxicity Review Committee, p. 6. Gad, S.C., Powers, W.J., Dunn, B.J., et al., 1986, Acute toxicity of four chromate salts, Serrone D.M., Ed., Chromium Symposium 1986: An Update, Industrial Health Foundation Inc., Pittsburgh, PA, pp. 43–58. Gao, M., Levy, L.S., Faux, S.P., et al., 1994, Use of molecular epidemiological techniques in a pilot study on workers exposed to chromium, Occupational Environmental Medicine, 51, 663–668. Glaser, U., Hochrainer, D. Kloppel, H., et al., 1984, Inhalation studies with wistar rats and pathophysiological effects of chromium, Report to Umweltbundesamt, D-1 UFOPLAN FTE 10606007/2, Berlin 156 (German) (Cited in WHO, 1988). Glaser, U., Hochrainer, D., Kloppel, H., et al., 1985, Low level chromium(VI) inhalation effects on alveolar macrophages and immune functions in wistar rats, Archives of Toxicology, 57, 250–256. Gorshkov, A.I., Tikov, S.V., Bershov, L.V., and Marfunin, A.S., 1996, The first finds of native cr, ni, and Fe in carbonato from the diamond deposits of yakutia, Geochemistry International, 33, 59–63. Guisewite, A, 2001, Mineral collection images, http://www-2.cscmu.edu/~adg/adgpeimages.html, 5 p. Handbook of Chemistry and Physics, 1996, 77th ed., CRC Press, New York, pp. 4–124.

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Havas, H.E. and Hutchinson, T.C., 1987, Aquatic macrophytes as biomonitors and macronutrients in acidic and alkaline ponds at the Smoking Hills, Canada, in International Conference on Heavy Metals in the Environments, Lindberg, S.E. and Hutchinson, T.C. Eds., Vol. II, CEP Consultants Ltd., Edinburgh, Scotland, pp. 430–432. Hawkes, H.E. and Webb, J.S., 1962, Geochemistry in Mineral Exploration, Harper and Row, New York, 415 p. Integrated Risk Information System (IRIS), 1998a, Toxicological Review of Hexavalent Chromium, in support of summary information on the IRIS: USEPA, pp. 6, 47. Integrated Risk Information System (IRIS), 1998b, Chromium(VI), Integrated Risk Information System (IRIS), CASRN 18540-29-9, pp. 13–15. Ivankovic, S. and Preussmann, R., 1975, Absence of toxic and carcinogenic effects after administration of high doses of chromic oxide pigment in subacute and long-term feeding experiments in rats, Food Cosmetic Toxicology, 13, 347–351. Jackson, M.B., 1988, The dominant attached filamentous algae of Lake Huron: Field ecology and biomonitoring potential during 1980, Hydrobiology, 163, 149–171. Kanojia, R.K., Junaid, M., and Murthy, R.C., 1998, Embryo and fetotoxicity of hexavalent chromium: a long-term study, Toxicology Letters, 95, 165–172. Katz, S.A. and Salem, H., 1994, The Biological and Environmental Chemistry of Chromium, VCH Publishers, New York. Kaufman, D.B., DiNicola, W., and McIntosh, R., 1970, Acute potassium dichromate poisoning: treated by peritoneal dialysis, American Journal of Diseases of Children, 119, 374–376. Khitrov, G. and Jaeger, R., 2001, Chromium Toxicity, The Ronald O. Perlman Department of Dermatology, Department of Toxicology NYU Grad School of Arts and Science, http://www.nyu.edu/classes/jaeger/chromium_toxicity.htm (accessed August 2001). Lee, K.P., Ulrich, C.E., Geil, R.G., et al., 1989, Inhalation toxicity of chromium dioxide dust to rats after two years exposure, Science Total Environment, 86, 83–108. Liberman, H., 1941, Chrome ulcerations of the nose and throat, New England Journal Medicine, 225, 132–133. Littorin, M., Welinder, H., and Hultberg, B., 1984, Kidney function in stainless steel welders, International Archives of Occupational Environmental Health, 53, 279–282. Mance, G., 1987, Pollution Threat of Heavy Metals in Aquatic Environment, Elsevier Applied Sciences, New York, p. 372. National Academy of Sciences (NAS), 1974, Chromium, National Academy Press, Washington, DC, p. 155. National Institute for Occupational Safety and Health (NIOSH), 1999, Online Pocket Guide to Chemical Hazards, NIOSH, http://www.cdc.gov/niosh/npg/npg.html. Nettesheim, P., Hanna, M.G., Jr., Doherty, D.G., et al., 1971, Effects of calcium chromate dust, influenza virus, and 100 R whole-body x-radiation on lung tumor incidence in mice, Journal National Cancer Institute, 47, 5, 1129–1144. Nieboer, E. and Jusys, A.A., 1988, Biologic chemistry of chromium, in Chromium in the Natural and Human Environments, Nriagu, J.O. and Nieboer, E., Eds., John Wiley and Sons, New York, pp. 21–27. Office of Environmental Health Hazard Assessment (OEHHA), 2001, Public Health Goal (PHG) of 2.5 mg/L for Cr(VI) in Drinking Water is Withdrawn, http:// www. oehha.ca.gov/public_info/press/nochromphg.html, pp. 1–2.

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Outridge, P.M. and Scheuhammer, A.M., 1993, Bioaccumulation and toxicology of chromium: implications for wild life, Review Environmental Contamination Toxicology, 130, 31–77. Pastides, H., Austin, R., Lemeshow, S., et al., 1991, An epidemiologic study of Occidental Chemical Corporation’s Castle Hayne chromate production facility, Occupational Epidemiology Unit, University of Massachusetts School of Public Health. Pastides, H., Austin, R., Lemeshow, S., et al., 1994, A retrospective-cohort study of occupational exposure to hexavalent chromium, American Journal Industrial Medicine, 25, 663–675. Petruzzeli, G., Lubrano, L., Cervelli, S., 1987, Heavy metal uptake by wheat seedlings grown in fly ash-amended soils, Water Air Soil Pollution, 32, 389–395. Risk-Based Corrective Action (RBCA), 1999, Guide to risk-based corrective action (RBCA) applied at petroleum release sites, American Society for Testing and Materials, Standard on Assessment and Remediation of Petroleum Release Sites, Publication E1739. Software (version 1.3b) from Groundwater Services Inc., Houston, TX, 2003. Sarkar, D., Sharma, A., and Talukder, G., 1993, Differential protection of chlorophyllin against clastogenic effects of chromium and chlordane in mouse bone marrow in vivo, Mutation Research, 301, 33–38. Saryan, L.A. and Reedy, M., 1988, Chromium determination in a case of chromic acid ingestion, Journal of Analytical Toxicology, 12, 162–164. Shacklette, H.T. and Boerngen, J.G., 1984, Element concentrations in soils and other surficial materials of the conterminous united states, U.S. Geological Survey Professional Paper 1270, U.S. Government Printing Office, Washington, DC, p. 105. Snyder, C.A. and Valle, C.D., 1991, Immune function assays as indicators of chromate exposure, Environmental Health Prospect, 92, 83–86. Spruit, D. and van Neer F.C.J., 1966, Penetration of Cr(III) and Cr(VI), Dermatologica, 132, 179–182. Steffe, C.H. and Baetjer, A.M., 1965, Histological effects of chromate chemicals, Archives of Environmental Health, 11, 66–75. Suzuki, Y., Homma, K., and Minami, M., et al., 1984, Distribution of chromium in rats exposed to hexavalent chromium and trivalent chromium aerosols, Industrial Health, 22, 261–267. Trivedi, B., Saxena, D.K., Murthy, R.C., et al., 1989, Embryotoxicity and fetotoxicity of orally administered hexavalent chromium in mice, Reproductive Toxicology, 3, 275–278. U.S. Environmental Protection Agency (USEPA) 1989a, Ecological assessment of hazardous waste sites: a field and laboratory reference, EPA/600/3-89/013, National Technical Information Service (NTIS), PB89-205967. U.S. Environmental Protection Agency (USEPA) 1989b, Risk assessment guidance for superfund, volume 2, environmental evaluation manual, Interim Final, EPA/ 540/1-89/001. National Technical Information Service (NTIS), PB90-155599. U.S. Environmental Protection Agency (USEPA) 1989c, Risk assessment guidance for superfund. volume 1, human health evaluation manual, Part A: EPA/540/ 1-89/002, National Technical Information Service (NTIS), PB-155581. U.S. Environmental Protection Agency (USEPA) 1992, Framework for ecological risk assessment, Risk Assessment Forum, EPA/630/R-92/001. U.S. Environmental Protection Agency (USEPA) 1993, Wildlife exposure factors handbook, EPA/600/R-93/187A, National Technical Information Service (NTIS), PB94-174778.

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U.S. Environmental Protection Agency (USEPA) 1994, Ecological Risk Assessment Issue Papers, EPA/630/R-94/009. U.S. Environmental Protection Agency (USEPA) 1999, Code of Federal Regulations, 40 CFR 141.32. Verschoor, M.A., Bragt, P.C., Herber, R.F.M., et al., 1988, Renal function of chromeplating workers and welders, Institute Archives of Occupational Environmental Health, 60, 67–70. World Health Organization (WHO) 1988, Environmental Health Criteria 61, Chromium, Geneva, WHO 197. Zahid, Z.R., Al-Hakkak, Z.S., Kadhim, A.H.H., et al., 1990, Comparative effects of trivalent and hexavalent chromium on spermatogenesis of the mouse, Toxicological Environmental Chemistry, 25, 131–136. Zhang, J. and Li, X., 1997, Cancer mortality in a chinese population exposed to hexavalent chromium in water, Journal of Occupational Environmental Medicine, 39, 4, 315–319.

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7 Chromium Sampling and Analysis*

James A. Jacobs, William E. Motzer, David W. Abbott, and Jacques Guertin

CONTENTS 7.1 Sampling Methods.....................................................................................236 7.1.1 Overview of Soil and Groundwater Sampling .........................................................................................239 7.2 Conventional Drilling Techniques ..........................................................239 7.2.1 Hollow-Stem Auger ......................................................................240 7.2.2 Cable Tool Drilling........................................................................242 7.2.3 Rotary Drilling...............................................................................243 7.2.4 Wire Line Coring...........................................................................244 7.2.5 Monitoring Well Installation .......................................................244 7.3 Other Drilling Methods ............................................................................246 7.3.1 Horizontal Drilling........................................................................246 7.3.2 Direct Push Technology (DPT) Probe Rigs ..................................................................................................247 7.3.2.1 DPT Probe Soil Sampling ..............................................247 7.3.2.2 DPT Probe Water Sampling ..........................................248 7.3.2.3 DPT Probe Vapor Sampling ..........................................248 7.3.2.4 DPT Well Points ..............................................................249 7.3.3 Cone Penetration Testing (CPT) .................................................249 7.3.3.1 CPT Soil Sampling..........................................................249 7.3.3.2 CPT Water Sampling ......................................................250 7.3.4 Sensor Probes .................................................................................250 7.3.5 Soil Conductivity or Resistivity..................................................250 7.3.6 Pore Pressure..................................................................................250 7.3.7 Soil Texture.....................................................................................251 7.4 Direct Sensing of Contaminants..............................................................251 7.4.1 In Situ Screening of Heavy Metals .............................................251 7.4.2 X-Ray Fluorescence .......................................................................251 * Editor’s note: Along with the SI unit, we have included non-SI unit in parenthesis because the non-SI unit is commonly used in environmental sampling and measurement.

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7.4.3 Laser-Induced Breakdown Spectroscopy ..................................252 7.4.4 Colorimetric Indicators ............................................................... 252 7.4.5 Laser-Induced Fluorescence Spectroscopy................................253 7.4.6 Membrane Interface Probe ..........................................................253 7.5 Sampling Procedures and Field Data Recording .................................253 7.5.1 Equipment Decontamination ......................................................254 7.5.2 Instrument Calibration and Maintenance .................................254 7.5.3 Sample Control ..............................................................................254 7.5.3.1 Sample Labels..................................................................254 7.5.3.2 Chain of Custody Request for Analysis......................255 7.5.3.3 Sample Preparation, Packaging, and Handling ........255 7.5.3.4 Sample Delivery to Laboratory ....................................255 7.5.4 Soil Sampling Protocol .................................................................256 7.5.4.1 Prior to Drilling Activities.............................................256 7.5.4.2 Manual Sampling Methods...........................................256 7.5.4.3 Pedologic and Lithologic Descriptions .......................256 7.5.4.4 Soil Sample Quality Control .........................................257 7.6 Water Sampling..........................................................................................257 7.6.1 Well Development Protocol.........................................................257 7.6.2 Groundwater Monitoring Protocol ............................................258 7.6.3 Groundwater Samples Collected from Wells ...........................258 7.6.4 Turbidity .........................................................................................259 7.6.5 Quality Control of Groundwater Samples................................260 7.6.5.1 Duplicates.........................................................................261 7.6.5.2 Field Blanks .....................................................................261 7.7 Chemical Analysis .................................................................................... 261 7.7.1 Atomic Absorption Spectroscopy (AAS)...................................261 7.7.2 Graphite Furnace Atomic Absorption (GFAA) ........................267 7.7.3 Atomic Emission Spectroscopy (AES) .......................................268 7.7.4 Inductively Coupled Plasma (ICP) ............................................269 7.7.5 Ion Chromatography (IC) .................................................... 270 7.7.6 Mass Spectrometry (MS) ..............................................................270 7.7.7 X-Ray Fluorescence (XRF) Spectroscopy.............................. 271 Acknowledgments.................................................................................. 271 Bibliography ......................................................................................... 271

7.1

Sampling Methods

Sources of Cr(VI) contamination in soil and groundwater include, but are not limited to, steel and pulp mills, Cr plating facilities, power plants, leather tanning facilities, dye operations, discharge of Cr containing corrosion inhibitors, and erosion of natural ore deposits or mine waste. Cr-related compounds

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Name

Parameters

I

Preliminary site assessment

II

Media (soil, water, air, bulk materials) investigation

III

Corrective action plan implementation and remedial action (remediation) Verification monitoring

Initial site visit/examination; generally does not include sampling Surface and subsurface investigation; collection of appropriate media; collection of empirical chemical Implementation of site investigation to remediate surface/subsurface contamination to appropriate regulatory levels, which is a risk assessment

IV

Additional media collection

from tailings piles at mines or liquids or solid wastes from industrial processes that might leak or spill from containments, tanks, ditches, pipes, or ponds create the need to sample soil and groundwater. Typical of most sites, subsurface environmental evaluations of this type generally consist of four phases of work commonly known as Phase I through Phase IV Environmental Site Assessments (ESA) (Table 7.1). The generalized four phases reflect the process required to take a property potentially contaminated with Cr(VI) from assessment phase (Phase I) through the final monitoring and site closure phase (Phase IV). The phases generally proceed in order starting with Phase I. Some sites where soil or groundwater contamination is already suspected or documented might start with Phase II in the case of known leak or confirmed Cr(VI) in a water well, or in the case of visually stained surface soils or discolored or dead vegetation in the proximity of a suspected spill or leak of Cr(VI) related substances. A Phase I ESA is a set of noninvasive techniques to acquire information from site inspection and to obtain data generated and supplied by others. A Phase I ESA involves a site inspection, the development of the history of the property, and review of data supplied by regulators, environmental lists and building permit databases, owners, tenants, and so on. Techniques include interviews of knowledgeable persons, review of historical aerial photography, and examination of published and unpublished maps. Phase I includes the collection, sorting, and tabulation of all relevant existing geologic, hydrologic, and hydrogeologic information. Noninvasive data may be collected on a property using surface geophysical methods to locate buried pits or drums that might contain Cr(VI) waste products. A Phase I ESA may coincide with the transfer of property ownership and may be part of environmental due diligence. A Phase II ESA generally involves a subsurface investigation through field data collection that normally is invasive and is designed to evaluate the sitespecific geologic and hydrogeologic conditions by collecting soil and groundwater samples for Cr analysis. A variety of different techniques and equipment are currently available for assessing the subsurface. Environmental subsurface

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Chromium(VI) Handbook TABLE 7.2 Purpose of Groundwater Monitoring Wells Parameter Define Monitor Provide

Determine Estimate Develop Assist Evaluate Source:

Explanation Vertical and aerial extent of groundwater contamination Target chemical concentrations over time Measurement for detecting the contaminant plume front unexpected changes in plume size or direction of flow data base for groundwater modeling Aquifer characteristics (such as permeability, transmissivity, etc.) Extent of interaquifer movement of contaminants Effects of the remedial measures Rate of contaminant plume movement Data base for designing remedial measures In performing the remedial work (provide hydraulic control and contaminant removal) Aquifer during regular sampling events over the yearly hydrologic cycle

Modified after Sisk (1981).

investigation tools range in size, cost, and operating complexity from hand augers and hand-operated drive samplers to hollow-stem augers, direct push technology (DPT), and various drilling rigs. Borings are drilled for geologic, hydrogeologic, and lithologic characterization. Cr(VI) samples may be collected using special techniques for field screening and physical testing. Selected soil or groundwater samples are then submitted to a certified or accredited analytical laboratory for chemical analysis. As part of a Phase II ESA, groundwater monitoring wells may be installed. Several Phase II ESA subsurface investigations might be required prior to completing the Phase II process and fully characterizing vertical and horizontal extent of Cr(VI) soil and groundwater contamination. A Phase III ESA generally involves some type of corrective action; this is the remediation portion of an environmental project. This phase involves designing and implementing the corrective action plan or remediation of soil and/or groundwater. A corrective action plan, remedial option evaluations, and feasibility with remedial design are typically submitted to a regulatory agency for approval prior to commencement of the work. A Phase III ESA may be accompanied by a human health risk assessment, which is used to determine soil and groundwater cleanup concentrations. Commencement of the cleanup actions then occurs with construction of a remedial system. A Phase IV ESA occurs after remediation has been completed. In many cases, the regulatory agency in charge, requires at least one year of quarterly groundwater monitoring to verify that the major Cr(VI) contamination source has been appropriately treated or removed. This phase generally includes proper abandonment of existing groundwater monitoring wells after obtaining site closure.

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Overview of Soil and Groundwater Sampling

Different drilling and groundwater sampling techniques have been developed and are used for evaluating the presence of Cr(VI) in soil and groundwater. Factors to determine the appropriate drilling technique relate to accessibility, duration and cost of project, soil, sediment and rock or sample type (undisturbed or disturbed), and sample integrity (discrete or composite). Conventional drilling methods in unconsolidated alluvial deposits for environmental investigations generally use hollow-stem auger and rotary drilling techniques, and occasionally, cable-tool drilling. For consolidated or semiconsolidated deposits, continuous wire-line, rock coring, and rotary drilling techniques are commonly used. A brief description of groundwater monitoring well installation is included in this section. More detail regarding drilling techniques is provided in Campbell and Lehr (1973), Driscoll (1986), Roscoe Moss (1990), Aller et al. (1989), Barden (1992), and U.S. Department of Interior, Bureau of Reclamation (1981). Other drilling methods used mostly for reconnaissance fieldwork include horizontal drilling and DPT. DPT probe rigs and cone penetrometer testing (CPT) rigs can be used to sample soil, soil vapor, and water. In addition, sensor probes have been developed for DPT rigs, which can determine physical parameters, contaminants such as petroleum hydrocarbons, chlorinated solvents, and some trace ions, including Cr-containing ions. More detailed information on DPT sampling is in Geoprobe (2003), Jacobs et al. (2000), and Jacobs (2000). Direct sensing of soils and groundwater using sensor probes can be found in Kram et al. (2000).

7.2

Conventional Drilling Techniques

There are six basic well-drilling systems with various methodologies: (1) cable tool drilling—cased and open hole; (2) direct rotary drilling—air, air with casing hammer or variant, air with down hole hammer, and mud; (3) reverse mud rotary drilling; (4) auger drilling, both solid- and hollow-stem; (5) core drilling, and (6) DPT/CPT methods. The water well industry (domestic, exploration, agriculture, and municipal) has typically used cable tool and direct/reverse rotary systems, while the environmental industry has used either DPT/CPT methods for reconnaissance level investigations or hollow-stem auger methods for installation of permanent monitoring wells. The distinct difference in drilling methods dramatically affects the construction, design, and development of the well. For example, the size of the environmental monitoring wells usually range from 5.1 cm to 10.2 cm (2- to 4-inch) diameter; in contrast, the water well industry uses anywhere from 10.2 cm to 50.8 cm (4- to 20-inch) diameter casing, typically greater than 15.2 cm (6-inch) diameter. These diameter differences restrict the use of some development tools and impact the effectiveness of well development. Experience has shown

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that when most 5.1 cm (2-inch) diameter monitoring wells are sampled, water quality is characterized as very turbid and muddy because monitoring wells generally are not properly or fully developed after installation. Water quality measurements (especially for Cr(VI)) from monitoring wells that are not developed do not represent the aquifer’s actual water quality. Another notable difference between the water well and environmental industry is the use of steel casing, in the former, and polyvinyl chloride (PVC) casing and screen materials in the latter. Because of the superior strength of steel versus weaker PVC casing and screen, more rigorous and harsh development methods can be utilized. With steel casing, effective removal of mud slurries, wall cakes, drilling additives, fluids, and fine-grained material near the well screen/filter pack/borehole interface can be accomplished. The effectiveness of well development is directly proportional to the amount of energy applied to the interface. PVC casing and screens will break at lower applied energies than steel casing, resulting in poorly developed monitoring wells. Not only is the applied development energy important but also how that energy is effectively transferred to the screen/filter pack/ borehole interface. The percent open area of the intake (well screen) is directly related to efficient transfer of the development energy to the interface. For example, a PVC slotted pipe may have an 8% open area, whereas a PVC or steel wirewrap screen has a 50% open area. Most of the applied energy in slotted pipe interacts with the inside surface of the casing rather than the well screen/filter pack/borehole interface. Typically, PVC wirewrap screens are not used because of the significantly lower strength in comparison to either PVC slotted pipe or steel screens. The larger open area provides for a more interactive area in the well with the aquifer. 7.2.1

Hollow-Stem Auger

Hollow-stem continuous flight auger drilling is commonly used for soil sampling to depths of tens of feet, depending on drilling conditions. Hollow-stem auger rigs work well with a variety of unconsolidated soil and alluvial lithologies, including clays, silts, sands, and small-size gravels. However, this technology is not designed to penetrate or sample bedrock or geologic materials greater than small-sized gravel or hardpan. Hollow-stem augers consist of a series of continuous, interconnected hollow auger flights, usually 1.5 m to 3.0 m (5- to 10-feet) in length. Hollow-stem auger operates on the principle of a cork (Archemedes) screw. Typical hollow-stem augers for use in environmental investigation have inside diameters (ID) of 10.8 cm to 26.0 cm (4.25 to 10.25 inches) to construct 5.1 cm to 10.2 cm (2- and 4-inch) diameter monitoring wells. Hollow-stem flight augers are hydraulically pressed downward and rotated to start drilling. Soil cuttings are rotated up the outside of the continuous flight in the borehole annulus, which results in smearing of silts and clays and drilled materials along the borehole wall. A center rod with plug and pilot bit are mounted at the bottom. The plug is designed to keep soil from entering the mouth of the lead auger while drilling. Upon reaching the sampling depth, the center rod string with plug and pilot bit attached is removed from the mouth of the auger and replaced by a soil sampler.

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FIGURE 7.1 Hollow stem auger drilling rig, Richmond, California. (Todd Engineers, 1989.)

Soil sampling is achieved by passing a smaller diameter drill rod into the hollow-stem auger with a soil sampler attached at the bottom. The soil sampler is lowered into the borehole through the hollow stem of the auger and sampling or coring is started. The sampler is typically either a thinwall or modified split-barrel sampler with thin walled sample liners. For Cr sampling, polyethylene terephthalate glycol (PETG), PVC, or teflon liners are recommended. For nonmetal analysis, including petroleum or chlorinated solvents, brass or stainless steel liners can be used. Samples can be continuously retrieved, although for environmental investigations, soil samples are typically collected at 1.5 m (5.0-foot) intervals, or at significant changes in soil pedology or alluvium lithology. In addition, soil samples are usually collected at intervals of obvious contamination in order to develop a complete soil contamination profile.

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For environmental investigations, the most popular split-barrel samplers are 6.35 cm to 7.62 cm (2.5- or 3-inch) outside diameter (OD) samplers. The standard split-barrel sampler has its interior honed or otherwise machined to accept brass or stainless steel liners or rings. Three sample tubes each 15 cm (6-inches) in length, which can be removed from the sampler for capping and shipment to the laboratory, line the split-barrel sampler. Reloading the sampler with liners allows continued sampler use. Typically, the upper 15 cm (6-inch) sample tube is used for lithologic description and physical testing (i.e., permeability and sieve analysis). The middle sample tube is used for field-screening for constituents of concern, and the bottom sample tube is used to send to a chemical laboratory for analysis. If Cr(VI) waste had been mixed or associated with a petroleum hydrocarbon or chlorinated solvent, the middle tube might be screened with an organic vapor meter to detect volatile organic compounds. The sampler is driven into the soil at the desired sampling interval ahead of the auger bit by using a 63.5 kg (140-pound) hammer falling freely for 76 cm (30 inches). Boreholes are either grouted using a tremie pipe or converted into a monitoring well. Soil or drill cuttings are not used to backfill borings due to the potential for cross contamination.

7.2.2

Cable Tool Drilling

Cable tool drilling techniques can be used for Cr(VI) investigations. Cable tool drilling is the oldest drilling technique available and is not often used in environmental investigations. Cable tool rigs, called percussion rigs, operate by repeatedly lifting and dropping into the borehole a heavy string of drilling tools attached to a cable, crushing larger cobbles and rocks into smaller fragments creating a mud slurry. During cable tool drilling, the hole is continuously cased with steel. A drive shoe is attached to the bottom of the casing to prevent damage to the casing and to cut the borehole sides. A drive collar is used to protect the casing at the surface during driving operations. Cable tool drilling can also be accomplished without casing, which is known as openhole drilling. The tool string is attached to the cable by means of a rope socket, which is suspended through a pulley from the mast of the drill rig, through the pitman or spudder arm, to the cable storage drum. Drive clamps are attached to the drill string to advance the casing. The process of driving the casing downward about 0.61 m to 1.5 m (2 to 5 feet,) is followed by periodically bailing slurry and broken rocks from the bottom of the borehole. During cable tool drilling, in permeable and loose materials, the casing may fall on its own weight. Water generally is required to create a slurry at the bottom of the borehole in the unsaturated zone. Because the casing is advanced, soil or unconsolidated alluvium and groundwater samples can be collected during drilling. To open the casing to the water-bearing zone, the cable tool drilled well can be completed with telescope wirewrap screens by the pull-back method or downhole pipe perforators may also be used.

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FIGURE 7.2 Cable tool drilling rig, Riverside County, California. (Todd Engineers, 2002.)

7.2.3

Rotary Drilling

Rotary drilling techniques can be used for Cr(VI) investigations, especially appropriate in Cr mining areas where the bedrock is near or at the surface or landfills located in semi-consolidated to consolidated sedimentary rock. Rotary drilling techniques include direct mud rotary, direct air rotary, direct air rotary with a casing driver, direct air rotary with downhole hammer, and reverse dual tube rotary circulation. Direct mud rotary drilling uses prepared water-based drilling fluids (usually bentonite), which is pumped down the drill stem through the bit at the end of the drill rods. Drilling fluids and

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cuttings are circulated up the outside annular space back to the surface. Fluid at the surface is routed via a pipe or ditch to a sedimentation tank or pit, then to a suction pit where it is recirculated back through the drill rods. Air rotary drilling is similar to that of direct mud rotary, except that air is used as a circulation medium instead of water and the air is not recirculated. Although air lifts the cuttings from the hole, small quantities of water or foaming surfactants (not recommended) are sometimes used to facilitate cutting removal. In unconsolidated deposits, air rotary can be used with or without a casing. Simultaneous drilling and drive casing is needed when large quantities of groundwater are encountered. In reverse circulation, the circulating medium (mud) is pumped downward between the outer bore hole and inner drill pipe, out through the drill bit, then up the inside of the drill pipe. Air can be used in reverse rotary only in the unsaturated zone. Rotary drilling techniques are typically not used in subsurface environmental investigations due to poor sampling capabilities. However, site characterization can be significantly enhanced using downhole geophysical instruments providing a better understanding of the hydrogeologic framework. Sample integrity may be questionable because added water or mud may chemically react with the formation water and cuttings. With mud rotary, the mud filter cake that develops along the borehole wall may adversely affect adjacent formation permeabilities, similar to the smearing of clays during hollow-stem auger drilling. With air rotary, dispersion of potentially hazardous and toxic particles in the air during drilling may be a concern, especially with Cr(VI). 7.2.4

Wire Line Coring

Wire line coring produces cylindrically shaped cores. A modified rotary rig is used in conjunction with water, drilling mud, or air. This method has been used in mining areas containing Cr, where bedrock is at or near the surface. The core diameter varies depending on bit size, manufacturer specifications, or standards supplied by the Diamond Core Drill Manufacturers Association. Core sizes generally range from about 1.9 cm (0.75-inches) to greater than 15 cm (6-inches). Cutting occurs by drill bits located at the end of a rotating barrel or tube. The barrel gradually slides down into the annular opening. The core is then separated from the rest of the formation mass and the barrel containing the core is retrieved. 7.2.5

Monitoring Well Installation

The purpose of monitoring well network in a Cr(VI) contaminant investigation is to evaluate the hydrogeologic framework, which indicates groundwater movement, degradation of groundwater quality from Cr(VI), and to accomplish specific study objects. A work plan and drilling permit application are frequently submitted to and approved by the lead regulatory agency prior to well installation. The borehole for a monitoring or extraction well is frequently

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FIGURE 7.3 Reverse mud rotary drilling rig, Livermore, California. (Todd Engineers, 1999.)

drilled using a truck-mounted, continuous flight, hollow-stem auger drill rig. According to many regulatory agency guidelines, boreholes for monitoring wells are usually a minimum of 5 cm to 10 cm (2.0 to 4.0 inches) larger than the outside diameter of the well casing (DWR, 1981, 1990). Hollow-stem augers provide minimal interruption of drilling while permitting soil sampling at the desired intervals. Licensed drillers should install all wells. Well materials for monitoring and extraction wells must be chemically compatible with the potential contaminants (Barcelona et al., 1983). Casing, both blank and screen sections, can be constructed of fiberglass-reinforced plastic, mild steel, galvanized iron, stainless steel, concrete, or thermoplastic which include PVC, acrylonitrile butadiene styrene (ABS), and styrene rubber (SR). Based on cost, availability, and chemical compatibility, the most common casings and screens used for shallow drilling projects in

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environmental investigations are made of PVC. Deeper wells are typically constructed of either thicker gauge PVC or mild steel. For hollow-stem auger drilling, the auger will remain in the borehole while the well casing is set, to prevent caving. The well is cased with blank and factory-slotted, threaded schedule 40 PVC pipe. The slotted PVC casing is placed from the bottom of the borehole to the top of the aquifer. The blank casing extends from the top of the slotted casing to approximately ground surface. The slots can range from 0.0254 cm to 0.635 cm (0.01- to 0.25-inches) wide to 3.8 cm (1.5 inches) long (10 to 250 slot), with approximately 42 slots per linear foot. Slot sizes are determined by a grain size sieve analysis. A threaded PVC cap is fastened to the bottom of the casing. Centering devices may be fastened to the casing to assure even distribution of filter pack and grout within the borehole annulus. Well screens and casings are typically steam cleaned regardless of composition prior to installation to insure that no machine oils or other chemicals are on the casing surfaces. After setting the casing within the auger, filter pack is poured into the annulus to fill from the bottom of the boring to above the exposed interval. The auger is withdrawn as filter pack is poured into the annulus between the auger and casing, being careful to ensure that 0.61 m to 0.91 m (2 or 3 feet) of filter material is always in the auger. 0.3 m to 0.6 m (One to two feet) of bentonite pellets are then placed above the filter pack, and then hydrated with deionized water. Bentonite pellets are placed to prevent the grout and surface contaminants from reaching the filter material. Neat Portland cement, a common grout for sealing environmental wells, contains approximately 5% bentonite powder. The grout is tremied into the annular space from the top of the bentonite plug to the surface. Approved grout mixtures and grouting techniques may vary depending on local conditions and regulations. A lockable PVC cap is typically placed on the wellhead. A traffic-rated flush-mounted steel cover is installed around a wellhead located in traffic areas. A steel pipe monument is usually set over a wellhead in landscaped areas. The flush-mounted cover box or pipe monument contacts the grout. Grout fills the space between the monument and the sides of the borehole. The monument and grout surface seal is set at or above grade so that drainage is away from the monument. The monument lid is clearly marked “Monitoring Well” with the well number.

7.3 7.3.1

Other Drilling Methods Horizontal Drilling

Horizontal or lateral radial wells have been used by the water supply well and oil industry for decades. In map view, horizontal water wells emanate from a center hub well, which is generally 2.4 m to 3.7 m (8- to 12 feet) in diameter. Most applications are where the area of concern, such as a contaminant plume,

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is inaccessible owing to above-ground structures. Horizontal wells are also used where thin water-bearing zones prevent traditional vertical extraction wells from efficiently pumping groundwater. Horizontal wells can have a larger area of influence compared to vertical wells. These advantages make horizontal wells attractive as groundwater aeration (sparging), vapor recovery, pump-and-treat, and injection wells. Horizontal wells can also be used for pressure- or jet-grouting a permanent barrier under and around an affected area, bioremediation by use for delivery of microbes, nutrients, and oxygen into the affected area, or as a French drain and landfill leachate collection system. Cleaning and rehabilitation of clogged or inefficient horizontal wells is expensive and limits their use to one-time construction. 7.3.2

Direct Push Technology (DPT) Probe Rigs

DPT probe rigs, also called drive point sampling rigs, collect soil, vapor, or water by driving samplers into the subsurface without the rotary action associated with the more conventional hollow-stem auger rigs. DPT works well with a variety of unconsolidated sediments, including clays, silts, and sands; however, this technology is not designed to penetrate or sample coarse-grained formations or bedrock. Small DPT probes were first developed in the late 1980s and placed on pick-up trucks and vans. DPT rigs generally push the rods from the back of the truck. A percussion hammer may be added to such probe units to enhance the depth penetration. Truck-mounted DPT probe rigs, are typically hydraulically powered. The percussion/probing equipment pushes rods connected to small-diameter 2.0 cm to 7.6 cm (0.8 to 3.0 inch) samplers. Refer to geoprobe 2003 for more information. DPT sampling relies on dry impact methods to push or hammer boring and sampling tools into the subsurface for preliminary or reconnaissance environmental assessments. This technology does not require drilling fluids or water during operation. DPT equipment produces soil samples but generally does not produce large volumes of soil cuttings or other drilling derived wastes, associated with the hollow-stem auger drilling. 7.3.2.1 DPT Probe Soil Sampling Coring starts at the ground surface with an open-tube soil sampler. Soil samples are commonly collected in 0.61 m to 1.5 m (2- to 5-foot) long clear plastic (PETG, PVC, or butyrate) liners contained within an outer sampler. Plastic liners are easily cut with a knife and are transparent for easy soil and sediment identification and logging. After removal from the sampler, the soil liner container is immediately capped on both ends with teflon and/or plastic end caps. Samples are labeled, placed in individual transparent plastic sampling bags, appropriately cooled, and shipped to a federal or state accredited or certified analytical laboratory. Various DPT soil samplers have been designed and manufactured by numerous companies. The main sampler types used in DPT projects include

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FIGURE 7.4 Direct air rotary drilling rig, Minden, Nevada. (Todd Engineers, 2000.)

split-spoon samplers, open-tube samplers, piston samplers, and dual tube samplers. Split-spoon sampler consists of the sample barrel, which can be split in two along the length of the sampler to expose soil liners. The split-spoon sampler without sample liners is useful for lithologic logging where soil samples will not be collected for chemical analysis. 7.3.2.2 DPT Probe Water Sampling Various types of sealed samplers are available for DPT groundwater sampling. Many DPT probe water samplers use a retractable or expendable drive point. After driving to the zone of interest, the outer casing is raised from the borehole, exposing the underlying well screen. For a nondiscrete groundwater sample, the outer casing contains open-slots. The open-slotted tool is driven from ground surface into the water table. Groundwater is collected using an inner tubing or smaller diameter bailer inserted into the center of the openslotted water sampler. Water samples collected from this method cannot be compared to samples collected at a later date without drilling a new DPT. 7.3.2.3 DPT Probe Vapor Sampling Only if Cr(VI) is associated with volatile organic compounds (VOCs), such as chlorinated solvents or petroleum hydrocarbons, will soil vapor sampling

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be a method that might add value to the Cr(VI) subsurface investigation. As the soil vapor probe is being driven into the subsurface, vapor samples can be continuously pumped to the surface in vapor compatible tubing for analysis through conventional field analyzers, such as a photoionization detector with flame ionization detector PID–FID and gas chromatographs. Vapor samples may also be collected in Tedlar bags, steel canisters (Summa), or evacuated glass jars for transport to an analytical laboratory. 7.3.2.4 DPT Well Points Groundwater and vapor monitoring probes, implants, mini-wells, sparge points, well points or piezometers can be installed with DPT rigs. Well points ranging from approximately 1.27 cm to 10.2 cm (0.5- to 4-inches) in diameter can be installed using DPT methods. Generally, DPT installed well points are constructed without a filter pack. A sand pack enhances screened intervals, and probes can be designed and installed with a premade filter pack. The annulus of the well point is generally sealed with bentonite and cement.

7.3.3

Cone Penetration Testing (CPT)

Cone Penetration Testing (CPT) equipment, a form of DPT, has been used manually since the 1920s in Europe. This early CPT equipment did perform direct sensing of soil properties for engineering studies; however, manual methods and tedious calculations made widespread use impractical. In the 1970s, companies like Fugro Geosciences, Inc. (1999) developed automated and computerized CPT rigs for geotechnical uses. Truck-mounted CPT rigs were designed for sampling and performing direct sensing to depths of 61 m to 76 m (200 to 250 ft). These probes have been used extensively in the construction industry to obtain geotechnical data. Within the past 10 years, CPT rigs have been used more frequently for environmental applications. 7.3.3.1 CPT Soil Sampling Many soil sample collection options exist for CPT rigs, each depending on the specific medium to be sampled. Many of the CPT soil samplers resemble hollow-stem split-spoon cutting tools. Typically, a push rod with a closed tip (piston sampler) is advanced to a depth just above the desired sampling depth. The cutting tip of a CPT soil sampler is generally opened using a spring-loaded hinge system inside the sampling string. Once the hinge is triggered, the open cutting tube is advanced to the desired depth, filling the cylindrical sample chamber with soil. The former tip is retracted during soil sampling collection. This technique tends to work best in dry soil with low gravel percentages. In some over-pressured sandy environments beneath the water table, sample collection can be difficult. If relatively finer-grained material is located below the sand of interest, it is sometimes useful to space the sampling interval so that the finer material forms a plug at the bottom of the push stroke.

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7.3.3.2 CPT Water Sampling Groundwater samplers typically work by either pumping or mass displacement. The ConeSipper  water sampler consists of a screened lower chamber and an upper collection chamber. Two small-diameter teflon tubes connect the upper collection chamber to a control panel in the truck. The truck ballast and hydraulic rams are used to push the sampler to a predetermined depth. While the probe is being advanced, nitrogen gas under relatively high pressure, is supplied to the collection chamber via the pressure/vacuum teflon tube to purge the collection chamber and prevent groundwater from entering the chamber before the probe reaches the desired depth. Once the desired depth is reached, the pressurized nitrogen is shut off, excess nitrogen pressure is removed from the 100 mL upper collection chamber, and the chamber fills with groundwater. Finally, nitrogen gas under relatively low pressure is supplied to the collection chamber to gently displace the water and slowly push the water to the surface through the small-diameter teflon sampling tube. Sample collection times range from 20 min to 2 h, depending on the soil type adjacent to the sampling port. The groundwater samples are placed directly into 40 mL volatile organic analysis (VOA) containers.

7.3.4

Sensor Probes

Typical CPT rigs hydraulically push a small diameter instrumented probe and steel support rods into soils. Conventional probes used with the hydraulic ram systems are equipped with transducers for measuring point penetration resistance and sleeve friction. An empirical relationship between these physical strength measurements and soil types is used to derive soil classification logs for the layers penetrated. The most common sensors consist of load cells on the cone tip and sleeve (Robertson and Campanella, 1983a, 1983b; Robertson, 1990).

7.3.5

Soil Conductivity or Resistivity

Conductivity tools can be used to determine soil type. These systems are based on the observation that fine-grained materials will conduct electricity better than coarse-grained materials. Soil conductivity or resistivity logging produces a real time display of conductivity or resistivity. The probe is useful in detecting changes in subsurface lithology. Conductivity or resistivity logging can have vertical resolution of 2.54 cm to 10.2 cm (1- to 4-inch) clay layers that may influence plume migration.

7.3.6

Pore Pressure

Piezocone pore pressure probes are equipped with transducers for determining pore pressure. Piezocones tend to yield better soil type data and resolution than the probes that rely only on tip resistance and sleeve friction, since they

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yield point measurements and do not rely as much on averaging based on properties within the vicinity of the sensors. Piezocone soil classification data are only valid in saturated soils, since a positive pore pressure is required to obtain a reading on the pressure transducer. Many of the newer probes consist of both systems, allowing for continuous profiling throughout the unsaturated zone and saturated regions including perched zones. 7.3.7

Soil Texture

New sensors based on real time video imaging have been developed for determining soil texture. While the video resolution is exceptional, the images can sometimes be difficult to use for determining soil classification in the saturated zone, since pore fluids can yield complex images. Research is underway to refine the images to determine pore fluid saturation levels, relative permeability, moisture content, and hydraulic conductivity. 7.4

Direct Sensing Of Contaminants

For contaminant investigations, sensor probes have been developed to detect and delineate zones containing heavy metals (Cr, As, Cu, Pb, Hg and Ag), light nonaqueous phase liquids (LNAPLs), polycyclic aromatic hydrocarbons (PAHs), petroleum oils and lubricants (POLs), dense nonaqueous phase liquids (DNAPLs), light and heavy metals, explosives, and radionuclides. 7.4.1

In Situ Screening of Heavy Metals

The Tri-Services (U.S. Army, Navy, and Air Force) provided research, development, and a technology demonstration program to perform in situ screening of heavy metals, including Cr. As part of the site characterization and analysis penetrometer system (SCAPS), sensors have been developed to detect, delineate, and monitor sites with a variety of contaminants. Two in situ detection techniques for evaluating Cr and other metals have been developed. The x-ray fluorescence (XRF) based sensor systems originally developed for in situ measurement of petroleum hydrocarbons in soils have now been adapted for metals (USEPA, 1999). Another technology is the laser-induced breakdown spectroscopy (LIBS) technique, a sensor probe method to evaluate in situ concentrations of Cr(VI) and other metals. More detailed information is available in Lieberman (1998), Lieberman and Knowles (1998), and Lieberman et al. (1990, 1991, and 1997).

7.4.2

X-Ray Fluorescence

Field portable x-ray fluorescence (XRF) analyzers are nondestructive and are used to monitor concentrations of Cr, as well as other metals. The XRF analyzers are available in two forms: a portable above-ground tool and

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down-hole sensor probe. The above-ground analyzer is used for screening soil cores and is generally less expensive to own and operate. A sophisticated down-hole XRF spectroscopy sensor probe is used to screen in situ concentrations of metals while boring. The down-hole probe is pushed into the subsurface by CPT rigs. Wires transfer the data to the surface to be analyzed by the above-ground spectrometer. The XRF analyzer can detect metals at less than 100 parts per million (ppm). The depth constraint on the XRF sensor probe is the depth limitation of the CPT rig. A special operators permit or license is required to operate portable XRF devices. In addition to other heavy metals, XRF also provides rapid, real-time concentrations of nonmetallic toxic elements, and radioactive metals. XRF works by providing a source of x-rays to bombard a soil sample, exciting the elements (detect only atomic number >10), such as Cr or other element in the soil sample. The bombardment by the x-rays excites the atoms present to emit x-rays that are characteristic of that particular element. The field portable XRF analyzers can be operated in situ using a sensor probe, or on the surface. The x-ray source may vary, depending on the analysis that is required. For more information, see Kram et al. (2000), Elam (1998), and Elam et al. (1998).

7.4.3

Laser-Induced Breakdown Spectroscopy

Laser-induced breakdown spectroscopy (LIBS) provides for rapid, in the field analysis of heavy metals, including Cr, in soils. In the fiber optic LIBS method, sample atomization and excitation of the metallic elements in the soil is provided directly by a laser spark on the sensor probe. Focusing pulses of laser light on the soil produce the spark. The plasma spark is emitted briefly, and the wavelength of the emitted light (the constituent colors), is indicative of the elements present in the soil. The brightness or intensity of the emitted light at a specific wavelength, which is associated with a particular elemental metal, indicates the concentration of the specific metal, such as Cr. The spectrometer splits this emitted light into its constituent colors. A computer then analyzes the colors. Little or no sample preparation time is required using the LIBS technology. The complete spectrum can be obtained during one single laser shot, allowing for rapid analysis. The down-hole lasers for LIBS weigh less than 0.9 Kg (2 pounds). Theriault et al. (1998), and Kram and Lory (1998), Kram et al. (2000) describe the LIBS technology in more detail.

7.4.4

Colorimetric Indicators

Field portable analysis is available for a variety of organic and inorganic contaminants, including Cr. Colorimetric indicators use a chemical buffer that produces various colors, which quantitatively or qualitatively identify chemical contaminants.

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For example, Cr(VI) can be analyzed at concentrations in parts per billion (ppb) to ppm using well established colorimetric laboratory methods. Field determinations of colorimetric results are cumbersome, having significant analytical error and therefore should only be used on a reconnaissance level. The concentration of the chromium is related to the intensity and hue of the color of the reaction products. Calibration of these types of instruments is important to accurate results.

7.4.5

Laser-Induced Fluorescence Spectroscopy

Laser-induced fluorescence (LIF) was developed by the U.S. Army Engineers Waterways Experiment Station CPT development program to identify various chemicals in the subsurface using a CPT probe. Although LIF does not identify Cr, it does identify wavelengths of petroleum hydrocarbons and other organic chemicals that might be associated with Cr in the subsurface. Kram and Lory (1998) describe details of other LIF systems and similar sensing technologies.

7.4.6

Membrane Interface Probe

Although the membrane interface probe (MIP) detects only VOCs and not metals, Cr is sometimes associated with waste products containing VOCs. The MIP uses a thin film fluorocarbon polymer membrane in direct contact with the soil. This membrane is typically heated to a temperature of 100 °C to 120 °C. This thin film membrane is attached to a stainless steel screen, which serves as a rigid support for the fluorocarbon polymer. A clean carrier gas, such as nitrogen, helium, or clean air is used to carry the VOCs in the soil to the surface and into the gas detector, such as the PID/FID. As the probe is pushed into the soil, VOCs in the subsurface contact the heated surface of the MIP polymer membrane. Upon contact, a certain quantity of the VOCs will absorb into the polymer membrane. Once absorbed into the membrane, VOC molecules move by diffusion across the membrane to regions where their concentration is lowest (Geoprobe, 2003).

7.5

Sampling Procedures and Field Data Recording

All information pertinent to field investigations is typically kept on daily field logs and other field documents. Boring logs, water sampling data sheets and chain-of-custody forms comprise the field documents in which all pertinent information about borehole samples and groundwater samples are recorded.

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7.5.1

Equipment Decontamination

Prior to arriving at a sampling site, all sampling equipment should be cleaned with phosphate-free detergent, and double rinsed with deionized water. This procedure should also be carried out on site prior to, between, and after sampling. Hollow-stem auger drilling equipment should be steam cleaned prior to arriving on site, and between uses. The decontamination water is contained and disposed off in an approved manner.

7.5.2

Instrument Calibration and Maintenance

The following field equipment is frequently used during the environmental site during sample collection. Calibration procedures and frequency are listed in the manufacturer’s guidebooks. • • • •

Organic vapor meter (OVM) to measure soil vapors Photoionization detector (PID) to measure soil vapors Water level sounder to measure water depth and total depth of well Oil–water interface probe to measure water depth, free-product thickness and depth of well • pH/temperature/conductivity meter for water samples

7.5.3

Sample Control

Proper identification, preparation, packaging, handling, shipping and storage of samples obtained in the field is the responsibility of field personnel. Samples must be readily identifiable and should be as representative as possible of in situ conditions.

7.5.3.1 Sample Labels Each sample container is labeled at the time of collection. The label is attached to the individual sample containers. The labels should contain the following minimum information: • • • • •

Project name and number Date and time of collection Name of collector Sample number Location of sample collection (i.e., boring and depth, or well number) • Preservation or special handling employed

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7.5.3.2 Chain of Custody Request for Analysis A chain-of-custody form for each sample and container is used to track possession of the samples from the time they were collected in the field until the time they are submitted to and analyzed in the laboratory. The chain-ofcustody form will contain the following minimum information: • • • • • •

Project name and number Name and signature of collector Date and time of sample collection Number of containers in a sample set Description of sample and container(s) Name and signatures of persons who are involved in the chain-ofcustody • Inclusive dates and times of possession • Type of analysis requested If a sample is known to have a high chemical concentration, field personnel should make a note on the chain of custody so that appropriate dilutions may be made in the laboratory.

7.5.3.3 Sample Preparation, Packaging, and Handling For Cr sampling, PETG, PVC or teflon sample liners are recommended. Brass or stainless steel liners are not suggested for Cr sampling due to the potential for Cr alloys in the metal sample liners. For nonmetal analysis, including petroleum or chlorinated solvents, brass or stainless steel liners can be used. The tube ends are covered with teflon tape and plastic end caps, labeled, and sealed in plastic bags. Groundwater samples are placed in laboratory supplied containers, which are compatible with the requested analysis. For Cr and other metal analysis, plastic bottles rather than glass are recommended because metals may be sorbed to glass. Samples are placed into a cooler, generally with bagged ice. For nonmetals analyses, glass bottles are wrapped in padding (i.e., bubble wrap or foam) to prevent breakage.

7.5.3.4 Sample Delivery to Laboratory Environmental samples are delivered to a state certified laboratory under chain-of-custody procedures, usually within 48 h of sampling. Samples are generally maintained, in a cooler, at 4 °C for transport/shipping to the laboratory. Containers are sealed with security tape to assure the sample integrity during transport and/or shipping. A chain of custody should always accompany transported and delivered samples.

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Chromium(VI) Handbook Soil Sampling Protocol

Soil samples should be collected in accordance with local, state, and federal regulations and/or guidelines. Standard U.S. Environmental Protection Agency (USEPA) methodologies for sampling and analysis are routinely used for environmental projects. Soil cuttings and excess sampling materials should be properly stored and labeled on site in approved United Nations (UN)-designated containers pending off site disposal. 7.5.4.1 Prior to Drilling Activities An underground utility locating service should be contacted between 2 days and 2 weeks prior to drilling. In northern California and Nevada, the public service utility provider is known as Underground Service Alert (USA); in southern California it is known as Dig-Alert. Other areas of the U.S. have similar public service providers. Generally, an 800 telephone number may be found via the Internet or in the local Yellow Pages phone book. These public service providers will contact local utilities (gas and electric, water, sewer, and telecommunications), which will identify and mark buried utilities around and on the property if free access to the property is available. The exact boring locations must be marked, generally with white paint, by the project scientist, geologist, or engineer based on a prepared and approved work plan. The locating service also provides a unique number that will be used by individual utility companies to identify the property. This identification number is generally active for 28 to 30 days. Private locating services may be required for properties where there is no free access. 7.5.4.2 Manual Sampling Methods Undisturbed samples are obtained using a slide hammer and core sampler with a single sampling cup at the end. Hand-held slide hammers, typically weighing 5.44 kg to 13.6 kg (12 to 30 pounds), are dropped approximately 0.30 m to 0.61 m (12 to 24 inch) onto the steel extension rods. The soil sampler with retaining sample liner is connected to the leading edge of the extension rods. Some soil sampling systems have foot pedals attached to the rods allowing the operator to step down to push the manual sampler into the ground. Sampling depth can be increased using small hand-held augers to drill down to the target depth. Specialized augers have been developed for sand, mud, and boggy soils. Benefits for the manual sampling method are minimal setup time, low costs, and minimum disturbance of the site. The depth of sampling is the limiting factor for the manual sampling method. 7.5.4.3 Pedologic and Lithologic Descriptions Soils and unconsolidated deposits are commonly described according to American Society for Testing Materials (ASTM) Method D 2488-84 and the Unified Soil Classification System (USCS) for physical description and

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identification of soils. Other soils identification systems include the Burmister Soil Identification System (BSIS) for unconsolidated deposits, which are commonly used, with the USCS. Other soil description systems include the Comprehensive Soil Classification System (CSCS) developed by the U.S. Department of Agriculture. The CSCS describes soils as to agricultural productivity potential and best agricultural land use. A complete geologic description rather than engineering soil descriptions (ASTM and USCS) of the subsurface materials can provide information on the depositional geologic environment and yield to a better understanding of the site’s geologic framework. The ASTM Soil Classification Flow Chart and the USCS are generally accepted soil description methods used in the engineering and environmental fields. Descriptions for moisture, density, strength, and plasticity are made using ASTM guidelines (ASTM, 1984). However, these descriptions are all geotechnical properties related to the structural aspects and load bearing capacity of the soil and not to the hydrogeologic properties of the soil. For consolidated deposits (including igneous, metamorphic, and sedimentary rocks) the samples should be described using standard rock classifications. Color is described by comparing the soil sample with a Munsell Rock Color Chart (Munsell, 1988) The soil is described when moist or wet. Each soil stratum is identified in the order given by: color, soil type, classification symbol, Munsell color designation, consistency or relative density, moisture, structure, and modifying information such as grain size, particle shape, cementation, and stratification. 7.5.4.4 Soil Sample Quality Control Soil sample quality control may involve collection of duplicate samples. These are collected because small variations in soil pedology and alluvial lithology occurring in unconsolidated deposits within several Cm may lead to significant differences in analytical concentrations. Duplicate soil samples should be collected as close as possible to the original sample, in the same soil horizon, lithologic zone, or sampling interval. The recommended minimum for duplicate soil samples is 5% (1 in 20) of total collected samples.

7.6 7.6.1

Water Sampling Well Development Protocol

Wells are developed to remove residual drilling mud and fluids from the well bore, and to improve well performance by removing any fine material in the filter pack that can pass from the native soil or sediment into the well. Well development techniques include pumping, bailing, swabbing, surging,

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jetting, airlifting, and adding chemical agents. In most cases, surging and pumping is satisfactory. Development water is inspected for product sheen, odors, or sediments. Approximately 3 to 5 wetted casing volumes are removed during development. The well is considered fully developed when consistent pH, temperature, and conductivity readings (within 10%) indicate characteristic groundwater for the aquifer. If the aquifer is slow to recharge, development will continue until the well is pumped dry. Slow recharge to the well likely means that the well is not fully developed and the development process should continue with more rigorous methods and possibly chemicals (i.e., dispersants and flocculants); alternatively, the well may not have been properly designed or the permeability of the water-bearing zone is too small. Effective development procedures and activities are key to acquiring a representative groundwater sample especially for Cr(VI). Wells should be developed until the water is sand- and turbidity-free. Turbidity has a significant impact on the reliability and interpretation of minor ion results. Cross contamination of wells from pumps is avoided by using proper decontamination procedures. All development water is stored in UN rated or approved 20g L (55-gallon) drums, covered with lids, and labeled with the well number(s) and date of first accumulation. The development water is stored on site pending laboratory analysis, after which the water is disposed off properly.

7.6.2

Groundwater Monitoring Protocol

Monitoring of depth to water and free product for petroleum hydrocarbons, also called free-phase, separate-phase, floating product, or light non-aqueous phase liquid [LNAPL] thickness within wells at the site is conducted using a water level sounding device or an interface probe. For consistency, all measurements are taken from a reference point on the wellhead at the survey mark. Total depth of well is also measured. To reduce the potential for cross contamination between wells, the monitoring is performed in the order from the least to the most contaminated, if known. Wells containing free product are monitored last. The water level sounders are decontaminated between wells. Water level data collected from the wells are used to develop a water table contour map for the site.

7.6.3

Groundwater Samples Collected from Wells

If free product is detected, a product sample is sometimes collected for source identification. Where several chemical analyses are to be performed for a given well, individual samples are collected in order of decreasing volatility. Purging will proceed from the least to the most contaminated well, if known or indicated by field evidence. Samples are collected using a disposable polyethylene bailer with a bottom siphon and nylon cord. The

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groundwater in the bailer is inspected for free product. Samples are transferred to clean laboratory supplied containers. Sample filtration and sample preservation are the most common forms of sample pretreatment done in the field at the time of sampling (Herzog et al., 1991)

7.6.4

Turbidity

Turbidity is the state, condition, or quality of opaqueness or reduced clarity of a fluid, owing to the presence of suspended matter (Bates and Jackson, 1987) and is the measure of the ability of suspended material to disturb or diminish the penetration of light through a fluid. Turbidity refers to the presence of suspended solids and organic matter in water that results in reduced clarity and is measured in nephelometric turbidity units (NTU). Unlike surface water, which often contains suspended solids and colloidal or soluble organic matter, groundwater is rarely turbid (Driscoll, 1986). Turbidity is not to be confused with color, which usually results from leaching of organic debris (Hem, 1989). A water sample can have color and no turbidity. Turbidity represents not only an aesthetic problem (graphically depicted in the blockbuster movie “Back to the Future 3” by Marty McFly), but is associated with apparent excessive concentrations of metals such as iron, manganese, and, in particular, trace ions (aluminum, antimony, arsenic, barium, beryllium, cadmium, chromium, copper, lead, mercury, nickel, selenium, silver, thallium, and zinc). Excessive metal concentrations can be caused by the combined and indistinguishable analytical measurements of un-dissolved and dissolved trace ion fractions in the liquid. Accordingly, elevated turbidity levels may be accompanied with elevated trace ion concentrations, even if samples are filtered prior to laboratory analysis. Adding a turbid water sample to acid-charged container to preserve metal ion concentrations will dissolve a portion of the suspended sediment or colloidal metals resulting in overestimation of the true metal concentration in groundwater. Therefore, sample acidification should not be performed for turbid water samples. Rather the sample should be field filtered or immediately transported to the analytical laboratory. Recommended primary federal and state drinking water goals for turbidity concentrations are less than 1 NTU. A secondary standard of 0.5 NTU is based on the level at which the human eye can detect turbidity (Roscoe Moss, 1990). Turbidity in monitoring, observation, or production well water can result from many causes relating to the installation, drilling, construction, development, completion, operation, sampling methods, and maintenance of the well and may include, among others: 1. Incomplete well development is probably the most common reason for elevated turbidity. 2. Inappropriate well screen and aperture size design specifically because of low open area intake devices such as PVC horizontal or vertical slot screens.

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Chromium(VI) Handbook 3. Incorrect filter pack design and screen location caused by inadequate characterization of the aquifer grain size and poor formation sample collection. 4. Nonlaminar or turbulent near-well groundwater flow due to over pumping. 5. Excessive pumping water levels causing cascading water. 6. Improper pump design causing excessive well pumpage. 7. Ineffective foot valves on pumps resulting in inconsequential well development.

However, elevated turbidity levels can also be related to ineffective subsurface filtration of induced surface water to the well, or an inadequate sanitary seal with subsequent vertical leakage of water along the side of the casing. Effective surface water infiltration to a well is related to the lineal distance between the surface water body and the well intake plus the aquifer grain size and sorting. For example, the closer the well intake is to surface water, the more likely it is that natural subsurface filtration of groundwater will be minimal. Furthermore, clean gravels (gravels with unfilled voids) do not have the filtering capacity of bimodal medium- to coarse-grained sands and gravels. However, it is relatively rare to find such clean gravels in the geologic environment. In most cases, elevated turbidity levels can be attributed to the design, operation, and maintenance of the well. Wells with machine-made or mills knife perforations usually do not produce turbid-free or sand-free groundwater, in contrast to properly designed and placed wirewrap well screens. Perforations or screens placed opposite or directly underlying fine-grained aquifer or nonaquifer materials may result in persistent and elevated turbidity as the fine-grained materials are removed from around the well. Such mining can result in the collapse of overlying fine-grained materials. Excessive well yields or over-pumping not only increase well inefficiencies and shorten well life expectancies, but increase near-well entrance velocities so that fine-grained material can be continuously mobilized and pumped out of the well. This can result in collapse of the framework of the aquifer and increased turbidity levels. Finally, if well development has been incomplete, elevated turbidity may result from the displacement of fine-grained material adjacent to the well screen or perforations.

7.6.5

Quality Control of Groundwater Samples

A quality control program independent from the laboratory’s program is maintained. This program includes the submittal of duplicates, field blanks, and travel blanks to the laboratory. Spiked samples are not supplied from the field; the analytical laboratory provides these. Quality control samples are packaged and sealed in the same manner as the other samples.

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261

7.6.5.1 Duplicates A duplicate sample is collected for either 5% (1 in 20) of the samples or one per sampling round, whichever is greater. A duplicate sample is submitted to the laboratory for the same analyses as the original sample; it is acquired by filling separate containers from the same well bailer as the actual sample. The bailer’s contents are evenly divided between the actual and duplicate samples, to insure duplication. The duplicate sample is labeled so as it is not identified as a duplicate either on the sample container or on the chain of custody. 7.6.5.2 Field Blanks Field blanks are prepared for either 5% (1 in 20) of the samples or one per sampling set, whichever is greater. The field blank is submitted to the laboratory for the same analyses as the rest of the sampling set. The field blank is acquired by dispensing deionized water into the sampling bailer and then to sample containers in the same manner as groundwater samples. Field blanks are assigned an independent sample number.

7.7

Chemical Analysis

Chemical analysis for Cr is dependent on different analytical instruments, which have different instrumental detection limits. Some of these are briefly described below; more detailed descriptions are in Kebbekus and Mitra (1998), Harris (2000), and PerkinElmer (2000). Commonly used analytical methods are summarized in Table 7.3.

7.7.1

Atomic Absorption Spectroscopy (AAS)

AAS requires that a sample be atomized or broken into individual atoms; it uses light absorption to measure gas-phase atom concentrations. In AAS, a ground state atom absorbs energy in the form of light with a specific wavelength. As the number of atoms of the element is increased, the amount of light energy also increases. This relationship can be used to determine the amount of light present in an unknown substance versus a standard in which the quantity of the element is known. In AAS, the unknown is introduced into the instrument in aerosol form. It is vaporized by applying energy from an air-acetylene or nitrous oxide–acetylene flame. The flame burner head is aligned so that a light beam from an element-specific lamp passes through the flame where the light beam is absorbed. A detector measures the resultant wavelength intensity.

EPA 29 NonMercury Metals

EPA 0061/ 7199

EPA 306

Cr(total)

Cr(VI)

Cr(total)

Used for

Metals To determine emissions of emissions particles from stationary from stationary sources sources. Metals To determine emissions of emissions from particles from stationary stationary sources sources. Cr(VI) Determine Cr(VI) emissions emissions from from hazardous waste stationary incinerators, municipal waste sources incinerators, municipal waste combustors, and sludge incinerators. May also be used for Cr(total) Cr including Emissions from decorative Cr(VI) from and hard Cr electroplating stationary facilities, Cr anodizing sources operations, and continuous Cr plating operations at Fe and steel facilities

Name

ICP–PCR

ICP–GFAA

ICP—using EPA method 6010B or ICP—MS by method 6020 ICP— using EPA method 6010B or ICP–MS by method 6020 IC–PCR, similar to methods 306 and 306A

Instrument Type

6 months

—

60 days

µg/m3

ng/dscm

µg/L

2.5

8.0

5.0

14 days

6 months

Holding Timesa

µg/m3

Units

2.5

Detect. Limit

EPA SW-846

EPA 40CFR, Part 60– Appendix A

EPA 40CFR Part 60– Appendix A

Refrigeration not EPA 40CFR, required Part 63 4 °C

—

None

None

Method Preservativesa Documentation

262

Cr(VI)

EPA 29 Metals with Mercury

Cr(total)

Air:

Analytical Form of Chromium Method No.

Summary of Chromium Analytical Methods

TABLE 7.3

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EPA IO-3.3

NIOSH 7200

NIOSH 7024

NIOSH 7300

Cr(total)

Cr(total)

Cr(total)

EPA 306A

Cr(total)

Cr(VI)

Cr(total) Chromium Less expensive method than including EPA 306 Emissions from chromium(VI) decorative and hard Cr from stationary electroplating facilities, Cr sources (Mason anodizing operations, and Jar Method) continuous Cr plating operations at iron and steel facilities Metals in heavy Method applies to ambient urban/ aerosols for fine particle (<2.5 industrial µm diameter) samplers, dichotomous samplers, versatile air pollution samplers (VAPS) and PM10 samplers Metals in heavy urban/ industrial Metals in suburban areas Metals in suburban areas Metals in pristine area Metals in clean room manufacturing Chromium and For particles with concentrations in the compounds (as Cr) by AAb range of 0.05 mg/m3 to 2.5 mg/m3 For particles ranging from 0.05 Compounds (as Cr) by AA to 2.5 mg/m3 Elements by ICP 500 L air sample with digestion by HNO3/HClO4 ICP–AES

AAS

AAS

XRF spectroscopy

ICP–PCR

ICP or GFAA

µg/L

—

— —

µg

µg µg

0.06 1.0

—

14 days

60 days

0.06

0.0006

0.0011

0.0014

0.002

0.0027

0.0039 µg/cm3

5.0

—

—

—

—

(Continued)

NIOSH issue 2, August 15, 1994 NIOSH issue 2, August 15, 1994

NIOSH issue 2, August 15, 1994

EPA 625/R-96/ 010A

Refrigeration not EPA 40CFR, required Part 63 4 °C

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Chromium Sampling and Analysis 263

OSHA ID125G

Cr(total)

EPA 200.7

EPA 200.8

EPA 218.6

EPA 6010B

Cr(total)

Cr(total)

Cr(VI)

Cr(total)

Water:

OSHA ID-121

Cr(total)

Oxidation Analytical Method No. State Used for Instrument Type

Metals and trace Determination of dissolved elements by elements in groundwater, ICP–AES surface water, and drinking water. Also used for determination of total recoverable element concentrations in wastewater, sludges, and soil samples Trace elements Analysis of dissolved trace by ICP–MS elements in groundwater, surface water, and drinking water. Also used for total recoverable elements in waste-waters, sludges, and soil samples Determines Cr(VI) in drinking Cr(VI) in drinking water water using IC–PDC Analysis of trace elements in Elements by ICP–AES aqueous matrices ICP–AES

IC–PDC

Preserve within 2 HNO3 to weeks of pH < 2 collection; 6 months holding time for analysis

24 hours; cool to none 4°C 6 months HNO3 to pH < 2

µg/L

µg/L µg/L

0.9

0.2 4.7

HNO3 to pH < 2

—

Preserve within 2 weeks of collection; 6 months holding time for analysis

—

µg

1.3

—

µg/L

—

µg/mL

0.04

SW-846

EPA/600/ R-94-111

EPA/600/ R-94-111

OSHA-125G

OSHA ID-121

Method Preservativesa Documentation

4.0

Holding Timesa

Units

Detect. Limit

264

ICP–MS

ICP–AES

AAS or ES Metals and Determine the amount of metalloid specific metals and metallaoid particles by AA particles in workplace atmosphere using wipe methods for 100 cm2 Metals and Collection and subsequent ICAP–AES metalloid analysis of airborne metal and particles by metalloid particles ICAP–AES

Name

TABLE 7.3 Summary of Chromium Analytical Methods (Continued)

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Chromium(VI) Handbook

EPA 7196A water

Cr(VI)

TCLP water

EPA 6010B

EPA 6020

EPA 7196A solids

Cr(total

Cr(total)

Cr(total)

Cr(VI)

Solids:

EPA 6020

Cr(total)

Cr(VI) by colorimetry

ICP–MS

ICP–MS

ICP or GFAA 200 methods for metals

Determination of trace ICP–AES elements in solid matrices including soil, organic material, and industrial wastes Analysis of element in different ICP–MS matrices including soil, other solids, and industrial waste Determine concentration of Spectrophotometer dissolven Cr(VI) in EP/TCLP characteristic extracts and groundwater. Can be used to determine domestic and industrial wastes if no interfering substances are present

Toxicity Determine the mobility of Characteristics organic and inorganic Leaching analytes in liquid, solid, Procedure and multiphase wastes. (TCLP) Technique is followed by standard analytical methods

ICP–MS Elements by ICP Analysis of elements in an aqueous matrix Cr(VI) by Determine concentration of Spectrophotometer colorimetry dissolvent Cr(VI) in EP/TCLP characteristic extracts and groundwater. Can be used to determine domestic and industrial wastes providing no interfering substances are present 24 hours prior to analysis or extracts.

µg/L

—

6 months 24 hours prior to 4 °C analysis or extracts

mg/kg

µg/kg µg/L

0.5

50

SW-846

SW-846,

—

(Continued)

SW-846

SW-846

None prior to SW-846 extraction; refrigeration unless this causes irreversible change to waste — SW-846

HNO3 to pH < 2 4 °C

mg/L 6 months for metals from TCLP to extraction

6 months

µg/L

5.0

50

0.02

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Chromium Sampling and Analysis 265

TCLP solids

Cr(total)

Used for Instrument Type

Determines Cr(VI) in drinking IC–PDC Determines Cr(VI) in–soil water using IC–PDC using IC–PDC Toxicity ICP or GFAA 200 Determine the mobility of Characteristics organic and inorganic methods for Leaching metals analytes in liquid, solid, and Procedure multiphase wastes. Technique is followed by standard (TCLP) analytical methods

Name

Units mg/kg

mg/L

Detect. Limit 0.5 5.0 6 months for metals from TCLP to extraction

—

Holding Timesa

None prior to extraction; refrigeration unless this causes irreversible change to waste

—

SW-846

Method Preservativesa Documentation

266

Source: NIOSH (1994), USEPA (1999), Zymax (2001) AAS = Atomic Absorption Spectroscopy AES = Atomic Emission Spectroscopy GFAA = Graphite Furnace Atomic Absorption ICP = Inductively Coupled Plasma IC–PCR = Ion Chromatography – Post-Column Reactor ICAP = Inductively Coupled Argon Plasma MS = Mass Spectrometry XRF = X-ray Fluorescence Spectroscopy

Holding times and sample preservations are for total Cr and Cr(VI) only. For methods where multi-elements are analyzed, different metals may have different holding times and sample preservation requirements. Check method documentation. bElemental analysis for total Cr not compound specific. However, Cr(VI) can be sampled on a PVC filter and may be determined by a colorimetric analysis using NIOSH Methods 7600/7604.

a

Notes:

EPA 7199

Cr(VI)

Oxidation Analytical Method No. State

Summary of Chromium Analytical Methods (Continued)

TABLE 7.3

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ABSORPTION

+ e−

n=1 n=2 n=3

e− EMISSION

+ n=1 n=2 n=3

FIGURE 7.5 Principle of emission spectroscopy (ES). Atoms in sample are energized (flame, discharge, plasma). An electron in an atom absorbs the energy by moving from a lower energy shell or “orbit” (e.g., n = 1) to a higher energy shell (e.g., n = 3)—the absorption process. This energized (“excited”) state is not stable and the electron quickly releases its gained energy by moving from n = 3 to n = 2 (as shown) or to n = 1 (not shown)—the emission process. This released energy is a specific amount (a specific wavelength) characteristic of the type of atom (of the element).

7.7.2

Graphite Furnace Atomic Absorption (GFAA)

Graphite furnace atomic absorption is an improvement on AAS because in AAS only a small fraction of the sample reaches the flame, causing the atomized sample to rapidly pass through the light path. To improve on the AAS analytical method, electrothermal vaporization using a graphite furnace is required. With GFAA, an electrically heated graphite tube replaces the flame used in AAS and the sample is introduced directly into the tube. The tube is then heated to remove solvents and major matrix components; the remaining sample is then atomized. Because all of the analyte is atomized and the atoms are retained in the tube, thus sensitivity and detection limits are improved.

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anode cathode prism slit

hollow-cathode lamp

slit wavelength detector

burner/flame FIGURE 7.6 Flame atomic absorption (FAA) spectroscopy and principle of atomic absorption spectroscopy (AAS). Light of specific wavelengths from an element-specific hollow-cathode lamp passes through the flame of the gaseous atomized sample. In the sample flame, the element that is the same as in the hollow-cathode lamp absorbs the light from the lamp. The transmitted light is separated into its wavelengths by a prism or grating and the measured intensity is inversely related to the concentration of the element.

7.7.3

Atomic Emission Spectroscopy (AES)

AES uses quantitative measurements of optical emissions of excited atoms to determine an analytes concentration. Atoms in a solution are aspirated and excited into an unstable energy state by vaporization and subsequent atomizing by a flame, a discharge, or a plasma. This excitation provides enough energy so that the unstable atoms emit light as they ultimately decay energy levels. An AES instrument is very similar to that used for AAS except that no primary light source is used in AES. inert gas anode

sample

cathode graphite furnace hollow-cathode lamp

prism slit slit wavelength detector

FIGURE 7.7 Graphite furnace (nonflame) atomic absorption (GFAA) Spectroscopy. Same as for Figure 7.6 except that the sample is not burned in a flame. Instead, a graphite furnace heats the sample, converting it to an atomized gas. Typically, an inert gas such as argon flows across the sample and through the furnace. The residence time of atoms in the furnace (0.1 s) is about 500 times longer than in the flame of FAA, allowing improved atomization of compounds. GFAA usually has a detection limit at least 10 times lower than that of FAA.

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Chromium Sampling and Analysis argon

plasma

plasma argon + sample

emitted light

emitted light

induction coil argon

argon + sample

FIGURE 7.8 Plasma torch for inductively-coupled plasma (ICP) spectroscopy. A high-frequency alternating current in a copper coil strongly heats argon, producing thermal electrons that ionizes the gas forming a plasma. An aerosol consisting of argon gas and sample particle mixture is introduced into the plasma torch where the sample is atomized and energized. This results in the emission of element-specific energies or wavelengths.

7.7.4

Inductively Coupled Plasma (ICP)

Inductively Coupled Plasma (ICP) commonly uses an argon plasma that can reach temperatures as high as (9,727 °C) but generally ranges between 5,227 °C and 7,727 °C. At these temperatures, complete element atomization occurs, reducing interference effects commonly seen in flame AAS. The plasma is formed by a stream of argon gas passing between two quartz tubes with a radio frequency power at 27 MHz applied to a coil and an column

stationary phase

mobile phase mixture of ions

separated ions

FIGURE 7.9 Conceptual diagram showing the principle of ion chromatography (IC). A mixture of ions in a mobile phase (solvent) flows into a column (tube) containing a stationary phase (e.g., a resin). The difference in affinity of different ions toward the station phase compared to the affinity toward the mobile phase results in a different rate of movement for different ions through the column. Thus, the different eluted ions are separated.

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oscillating magnetic field. The sample is introduced with an ultrasonic nebulizer after which it is directed onto a piezoelectric crystal. 7.7.5

Ion Chromatography (IC)

Ion Chromatography (IC) requires the separation of ions in a sample. For ions with less than 500 atomic mass units (amu), an ion exchange resin is used in which the ionic species is retained. The exchange of ions can be for both cations and anions. A conductivity detector measures the electrical conductivity of the eluting mobile phase. IC has the ability to distinguish not only between anions and cations but it can also be used to determine species having different oxidation states. 7.7.6

Mass Spectrometry (MS)

A mass spectrometer is similar to the monochromator in an AAS or ICP emission system where the atoms or molecules of a substance are ionized, accelerated by an electric field, and then separated according to their mass. Rather than separating light according to its wavelength, the MS separates ions according to their mass-to-charge ratio. This instrument is often coupled with an ICP allowing for multi-element capabilities at much lower detection limits than ICP alone or GFAA. MS can also be used in measuring elemental isotope concentrations and ratios. sample

sample changed to gas

ionization

acceleration of ions

mass analyzer and detector

vacuum system

FIGURE 7.10 Principle of mass spectrometry (MS). MS requires that samples be in the gas phase and all operations are in vacuum (pressure less than 10–6 mmHg). Solid or liquid samples are converted to gas, and the gas is ionized. Charged plates (or rods) accelerate the ions in a specific direction (e.g., in a tube), the less massive ions moving more rapidly and arriving at a detector before the more massive ions do. Thus, components of the sample are separated my mass (more accurately, by mass/charge, m/e). The ion “current” is a measure of quantity of ions and relates to the concentration of the components in the sample.

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271

X-Ray Fluorescence (XRF) Spectroscopy

Fluorescence is the generation of secondary radiation from an atom. The principle of x-ray fluorescence (XRF) is similar to that shown in Figure 7.5, whereby the atoms of an energized sample give off specific x-rays that are characteristic of the element. Although the method is able to rapidly analyze nearly all elements simultaneously and is nondestructive, XRF is not commonly used for trace element analysis because it is at least 100 times less sensitive than ES, FAA, GFAA, ICP, or MS.

Acknowledgments Geoprobe is a Registered Trademark of Kejr Engineering, Inc. and ConeSipper is a registered trademark of Vertek Division of Applied Research Associates.

Bibliography Aller, L., Bennett, T.W., Hackett, G., Peity, R.J., Lehr, J.H., Sedoris, M., and Nielson, D.H., 1989, Handbook of Suggested Practices for the Design and Installation of Ground-Water Monitoring Wells, National Water Well Association, Dublin, OH, p. 398. American Society for Testing Materials (ASTM), 1984, Standard Practice for Description and Identification of Soils (Visual-Manual Procedure), Method D, pp. 2488–2484. Barcelona, M.J., Gibb, J.P., and Miller, R.A., 1983, A Guide to the Selection of Materials for Monitoring Well Construction and Ground-Water Sampling, Illinois State Water Survey (ISWS), Champaign, IL, ISWS Contract Report 327, p. 68. Barden, C.L., 1992, Australian Drilling Manual, Australian Drilling Industry Training Committee, New South Wales, Australia, p. 554. Bates, R.L. and Jackson, J.A., Eds., 1987, Glossary of Geology, American Geological Institute, Alexandria, VA, p. 788. California Department of Water Resources (DWR), 1981, California Well Standards, DWR Bulletin DWR, Sacramento, CA, pp. 74–81. California Department of Water Resources (DWR), 1990, California Well Standards, DWR Bulletin DWR, Sacramento, CA, pp. 74–90. Campbell, M.D. and Lehr, J.H., 1973, Water Well Technology, National Water Well Association, McGraw-Hill Book Company, New York, p. 681. Driscoll, F.G. Ed., 1986, Groundwater and Wells, Johnson Division, St. Paul, MN, p. 1089. Elam, W.T., 1998, Unit 3B.3, in Current Protocols in Field Analytical Chemistry, LopezAvila, V., et al., Eds., John Wiley and Sons, New York. Elam, W.T., Adams, J.W., Hudson, K.R., McDonald, B., and Gilfrich, J.V., 1998a, Subsurface measurement of soil heavy-metal concentrations with SCAPS

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x-ray fluorescence (XRF) metals sensor, Field Analytical Chemistry and Technology, 2, 97–102. Geoprobe Systems (Geoprobe), 2003, Tools Catalog, Kejr Engineering Inc., Salina, KS, Vol. 6. Harris, D.C., 2000, Quantitative Chemical Analysis, W.H. Freeman and Company, New York, p. 899. Hem, J.D., 1989 Study and Interpretation of the Chemical Characteristics of Natural Water, 3rd ed., U.S. Geological Survey Water Supply Paper 2254, U.S. Government Printing Office, Washington, DC, p. 263. Herzog, B., Pennino, J., and Nielson, G., 1991, Groundwater Sampling in, Practical Handbook of Groundwater Monitoring, Nelson, D.M., Ed., Lewis Publishers, Boca Raton, FL, pp. 449–499. Jacobs, J., 2000, Monitoring well construction and sampling techniques, in Standard Handbook of Environmental Science, Health, and Technology, Lehr, J., Ed., McGraw Hill, New York, pp. 11.46–11.68. Jacobs, J., Kram, M.L., and Lieberman, S., 2000, Direct push technology sampling methods, in Standard Handbook of Environmental Science, Health, and Technology, Lehr, J., Ed., McGraw Hill, New York, pp. 11.151–11.163. Kebbekus, B.B. and Mitra, S., 1998, Environmental Chemical Analysis, Blackie Academic and Professional, New York, p. 330. Kram, M.L. and Lory, E., 1998, Use of SCAPS Suite of Tools to Rapidly Delineate a Large MTBE Plume, Conference Proceedings for the Annual Meeting of the Environmental and Engineering Geophysical Society, March 22–26, 1998, Chicago, IL, pp. 85–99. Kram, M.L, Lieberman, S., and Jacobs, J., 2000, Direct sensing of soils and groundwater, in Standard Handbook of Environmental Science, Health, and Technology, Lehr, J., Ed., McGraw Hill, New York, pp. 11.124–11.150. Lieberman, S.H., 1998, Direct-push, fluorescence-based sensor systems for in situ measurement of petroleum hydrocarbons in soils, Field Analytical Chemistry and Technology, 2, 63–73. Lieberman, S.H. and Knowles, D.S., 1998, Cone penetrometer deployable in-situ video microscope for characterizing sub-surface soil properties, Field Analytical Chemistry and Technology, 2, 127–132. Lieberman, S.H., Inman, S.M., Theriault, G.A., Cooper, S.S., Malone, P.G., and Lurk, P.W., 1990, Fiber optic-based chemical sensors for in situ measurement of metals and aromatic organic compounds, in Seawater and Soil Systems, SPIE, vol. 1269, pp. 175–184. Lieberman, S.H., Inman, S.M., Theriault, G.A., Cooper, S.S., Malone, P.G., Olsen, R.S., and Lurk, P.W., 1991, Rapid, subsurface, in situ field screening of petroleum hydrocarbon contamination using laser-induced fluorescence over optical fibers, in Second International Symposium on Field Screening Methods for Hazardous Wastes and Toxic Chemicals, Air and Waste Management Association, Pittsburgh, PA, pp. 57–63. Lieberman, S.H., Knowles, D.S., Stang, P.M., Kertesz, J., and Mendez, D., 1997, Cone penetrometer deployed in situ video microscope for characterizing subsurface soil properties, in Field Analytical Methods for Hazardous Wastes and Toxic Chemicals, Air and Waste Management Association, Pittsburgh, PA, pp. 579–587. Munsell, K.S., 1988, Munsell Soil Color Charts, Munsell Color, Baltimore, MD.

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PerkinElmer, 2000, Guide to Atomic Spectroscopy Techniques and Applications, PerkinElmer Instruments, Norwalk, CT, 37 p. Robertson, P.K., 1990, Soil classification using the cone penetration test, Canadian Geotechnical Journal, 27, 151–158. Robertson, P.K. and Campanella, R.G., 1983a, Interpretation of cone penetration test, Part I: Sand, Canadian Geotechnical Journal, 20, 718–733. Robertson, P.K. and Campanella, R.G., 1983b, Interpretation of cone penetration tests, Part II: Clay, Canadian Geotechnical Journal, 20, 734–745. Roscoe M., 1990, Handbook of Groundwater Development, John Wiley and Sons, New York, p. 493. Sisk, S.J., 1981, NEIC Manual for Groundwater/Subsurface Investigations at Hazardous Waste Sites, EPA-330/9–81–002, U.S. Environmental Protection Agency, Denver, CO. Theriault, G.A., Bodensteiner, S., and Lieberman, S.H., 1998, A real-time fiber-optic probe for the in situ delination of metals in soils, Field Analytical Chemistry and Technology, 2, 117–125. U.S. Environmental Protection Agency (USEPA), 1999, Compendium Method IO-3.3: Determination of Metals in Ambient Particulate Matter Using X-Ray Fluorescence (XRF) Spectroscopy, EPA/625/R–96/010a, Center of Environmental Research Information, Office of Research and Development USEPA, Cincinatti, OH. U.S. Department of Interior, Bureau of Reclamation, 1981, Groundwater Manual, A Water Resources Technical Publication, John Wiley and Sons, New York, 480 p. Zymax Environmental Technology, Inc. (Zymax), 2001, Hex Chrome Analysis by EPA Method 218.6 and 7199, Zymax, San Luis Obispo, CA, 2 p., http:// www.zymax. com/hexchrome.asp.

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8 Treatment Technologies for Chromium(VI)

Elisabeth L. Hawley, Rula A. Deeb, Michael C. Kavanaugh, and James A. Jacobs

CONTENTS 8.1 Treatment Concepts.................................................................................. 276 8.1.1 Introduction: Chemistry of Chromium .....................................276 8.1.2 Chemical Transformations ...........................................................278 8.1.2.1 Oxidation–Reduction......................................................278 8.1.2.2 Sorption ............................................................................279 8.1.2.3 Precipitation.....................................................................280 8.1.3 Biological Transformations ..........................................................281 8.1.4 Physical Remediation Processes .................................................282 8.2 Classification of Treatment Technologies...............................................282 8.2.1 Reduction of Toxicity....................................................................282 8.2.2 Destruction and Removal ............................................................283 8.2.3 Containment...................................................................................283 8.3 Toxicity Reduction Methods ....................................................................283 8.3.1 Chemical Reduction......................................................................284 8.3.2 Microbial Reduction......................................................................285 8.3.3 Phytoremediation ..........................................................................288 8.4 Removal Technologies ..............................................................................290 8.4.1 Ex Situ Technologies .....................................................................290 8.4.1.1 Ion Exchange ...................................................................290 8.4.1.2 Granular Activated Carbon...........................................291 8.4.1.3 Adsorbents .......................................................................292 8.4.1.4 Membrane Filtration.......................................................292 8.4.1.5 Soil Washing and Separation Technologies................294 8.4.2 In Situ Technologies ......................................................................295 8.4.2.1 In Situ Soil Flushing .......................................................295 8.4.2.2 Electrokinetics..................................................................296

1-5667-0608-4/05/$0.00+$1.50 © 2005 by CRC Press LLC

275

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8.5

Containment Technologies .......................................................................297 8.5.1 Barrier Technologies .....................................................................297 8.5.1.1 Low-Permeability Passive Physical Barriers ..............298 8.5.1.2 Permeable Chemical Barriers........................................301 8.5.2 Vitrification.....................................................................................303 8.5.3 Solidification/Stabilization ..........................................................303 8.6 Combining Multiple Approaches to Remediate Chromium..............304 Bibliography ......................................................................................... 305

8.1

Treatment Concepts

The success of many different treatment technologies in remediating chromium(VI), Cr(VI), contamination has been demonstrated. However, most of these technologies require knowledge of site-specific conditions, flexibility in remediation design and creativity in optimization strategies, not adherence to a step-by-step recipe approach. Since the biogeochemical properties of Cr and the associated soil matrix can affect the removal efficiency of many treatment strategies, an understanding of these properties is essential for choosing an effective treatment method. Once the properties of Cr and the associated soil are understood and the behavior of Cr in the subsurface and treatment environments can be predicted, remedial alternatives for Cr(VI) can be addressed. The approach employed in this chapter is to first summarize the different forms of Cr present in the environment as a function of environmental conditions. The form of the Cr determines toxicity, mobility, and treatment strategy applicability. Next, a summary of common chemical processes (reduction/oxidation, adsorption/desorption and precipitation/dissolution), biological processes (reduction/oxidation) and physical processes utilized in treatment technologies will be presented. Finally, treatment technologies will be organized into three different categories: toxicity reduction methods, removal treatments, and containment technologies and discussed in more detail. 8.1.1

Introduction: Chemistry of Chromium

The properties of Cr are highly dependent on the molecular structure of the Cr compound, particularly on the oxidation state (or oxidation number) of the Cr. Cr is an element that exists primarily in two different oxidation states, hexavalent and trivalent. These oxidation states are symbolized as Cr(VI) and Cr(III), respectively. Except for the rarely-found, elemental Cr with an oxidation number of zero, Cr(0), other oxidation states of Cr are unstable and therefore, are not found in the natural environment. The oxidation state of the Cr has a significant affect on the transport and fate of Cr and on the type and cost of treatment required to reduce Cr concentrations less than regulatory health-based standards.

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Chromium(VI) is far more mobile than Cr(III) and more difficult to remove from water. It is also the toxic form of Cr, approximately 10 to 100 times more toxic than Cr(III) by the acute oral route, presumably owing to the stronger oxidizing potential and membrane transport of Cr(VI) (Katz and Salem, 1992). The EPA classifies Cr(VI) as a known human carcinogen via inhalation, but classify Cr(III) as not known to cause cancer. The most common Cr(VI) forms are chromate (CrO42–), and hydrogen chromate (HCrO4–) also called bichromate. The relative amount of these two species depends on pH. Dichromate (Cr2O72–) can also occur. The equilibrium concentration of dissolved Cr(III) in natural waters is small compared to Cr(VI) concentration (Richard and Bourg, 1991). In water, Cr(III) is mostly in the free-ion form Cr3+, although these ions associate with hydroxide OH– ions in a pH-dependent manner, forming Cr(OH)2+ , Cr(OH)2+, Cr(OH)3, and Cr(OH)4– (Rai et al., 1987). The solid precipitate Cr(OH)3(s) will equilibrate with these dissolved species. Cr3+ will also form complexes with organic and inorganic ligands such as SO42–, NH4+, and CN–. These are the major Cr species found in aqueous solutions. At pH<6 and Eh>0.6 V, HCrO4– can also be dissolved in water. In rocks and soil, Cr is a common trace mineral, found as amorphous Fe(III), Cr(III) hydroxides, eskolaite (Cr2O3(s)), and chromite (FeCr2O4(s)), all Cr(III) forms. There is a wide natural variation in Cr concentrations in soils and rocks. Shales, suspended river material, and soils with fine grain sizes have the highest concentrations, whereas granite, carbonates, and largegrained (sandy) sediments have the lowest concentrations (Richard and Bourg, 1991). Typically, natural background Cr concentrations are dwarfed by anthropogenic contamination. Dissolved concentrations of total Cr in groundwater from natural processes are typically below 10 µg/L (Richard and Bourg, 1991). In contaminated areas, Cr(VI) concentrations are commonly 300 to 500 µg/L (CRWQCB, 2000; Maxwell, 1997) and have been reported to reach 14 g/L (Palmer and Wittbrodt, 1991). A yellow color is imparted to the water at about 1 mg/L Cr(VI) (Palmer and Wittbrodt, 1991). The federal regulatory standard for total Cr in drinking water is 100 µg/L; the World Health Organization (WHO) and state of California have adopted a standard of 50 µg/L. The equilibrium distribution of the Cr between the two oxidation states is controlled by redox environment (either oxidizing, which most easily characterized by dissolved oxygen concentrations greater than 2 mg/L, or reducing, characterized by the absence of oxygen). For Eh/pH diagrams, see Figure 2.1 and Figure 2.2 (Chapter 2). Oxidation kinetics depend on a variety of factors and make the actual ratio of Cr(VI)/Cr(III) more complicated. Kinetics are a function of biogeochemical conditions, including pH, redox, and nutrient levels that govern microbial activity. Cr(VI) is converted to the less toxic and much less mobile form of Cr(III) by reduction reactions. The corresponding oxidation of Cr(III) to Cr(VI) also occurs, particularly in the presence of MnO2 and bacteria (Richard and Bourg, 1991). However, the kinetics are slow.

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Cr(III) Precipitation

Cr(VI) Sorption Cr Cr(VI) (VI)

Cr(III) Cr(III) Sorption

Oxidation (e– acceptor) (MnO2 /Bacteria) FIGURE 8.1 Reactions for Cr(VI) and Cr(III).

Common reactions that occur in the subsurface are summarized in Figure 8.1. Each of these processes will be explained in more detail, as the preferential enhancement of one or more of these processes is often the basis for remediation strategies. The processes include oxidation/reduction reactions, adsorption/ desorption, and precipitation/dissolution. These chemical processes can be biologically mediated — either directly through metabolic processes or indirectly as microorganisms change their geochemical environment. 8.1.2

Chemical Transformations

8.1.2.1 Oxidation–Reduction Some of the most common remediation strategies utilize oxidation–reduction reactions, converting Cr(VI) to Cr(III). An electron donor that commonly drives this reaction is Fe(II) which is either artificially supplied or is present from the natural weathering of iron oxides. Elemental Fe (Fe(0)), Mn(II), S2–, CH4, and reduced organics such as humic acids, fulvic acids, and amino acids can also be used as electron donors (Palmer and Wittbrodt, 1991). If conditions do not favor Cr(VI) reduction, the opposite can occur. Cr(III) can be oxidized to Cr(VI). Mn(III, IV) hydroxides and oxides are the primary oxidizers present in the subsurface (Palmer and Wittbrodt, 1991). The mechanism of this surface reaction is still a topic of research. Palmer and Wittbrodt (1991) found that the oxidation rate of Cr(III) by MnO2 increased proportionately with the surface area to volume ratio and with decreasing pH. In the same study, they found that oxygen (O2) did not play a major role in the oxidation process. The reduction of Cr(VI) to Cr(III) may influence the redox and pH of the subsurface. The new conditions could favor the precipitation of Cr(III). Examples of reactions that generate alkalinity or acidity are shown in Equation 8.1 to Equation 8.3 (James et al., 1997). 2Fe + 2CrO42– + H2O + 4H+ → 2Fe(OH)3 + Cr2O3

(8.1)

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Equation 8.1 illustrates the potential increase in pH associated with the formation of Cr(III) using Fe(0). Under moderate pH conditions, mixed Cr(III)-Fe (III) oxides and Cr(OH)3 (s) will form, increasing the redox reaction by Le Chatelier’s Principle as they precipitate. When Fe(II) is used as the electron donor, acidity is generated, as shown in Equation 8.2. Soil pH may decrease considerably, depending on the soil buffering capacity. 6Fe2+ + 2CrO42– + 13H2O → 6Fe(OH)3 + Cr2O3 + 8H+

(8.2)

Equation 8.3 shows an example of an organic compound, hydroquinone, oxidized to quinone, with the generation of alkalinity. The newly formed Cr(III) can complex with organics, so Cr(III) does not build up and reoxidize to Cr(VI). 3C6H6O2 + 2CrO42– + 4H+ → 3C6H4O2 + Cr2O3 + 5H2O

(8.3)

One important question is the stability of the Cr(III) that forms during redox reactions. Forms of Cr(III) that are inert to reoxidation are desirable. Research has shown that 15% of freshly precipitated Cr(III) was reoxidized by manganese oxides (James et al., 1997). Aged precipitates were not as likely to undergo oxidation. The mobility of the Cr(III) is another relevant question. James et al. (1997) found that Cr(III) could be chelated by soluble organics and remobilized. 8.1.2.2 Sorption Sorption processes for Cr can also be used in treatment strategies. However, Cr(III) is the primary form of Cr that is retained by sorption. The kinetics of Cr(III) sorption is rapid in clays, sands, and soil containing Fe and Mn oxides. For example, in one laboratory study, about 90% of Cr(III) added to clay minerals and iron oxides was adsorbed within 24 h (Richard and Bourg, 1991). Cr(III) behaves like a positively charged ion (such as Cr3+) when adsorbing onto surfaces. As pH increases, surfaces are deprotonated, increasing the attraction between Cr(III) and the surface. Sorption is therefore enhanced as pH increases. If soil has a high organic content, sorption is also enhanced, as more sites are present for sorption to occur. Although Cr(VI) is usually mobile in groundwater, it can sorb, under some conditions, as indicated in Figure 8.2. However, Cr(VI) behaves like an anion (such as CrO42– and HCrO4–), so sorption of Cr(VI) decreases with increasing pH. At low pH values, surfaces will be neutral or positively charged, leading to charge attraction. In addition, the ratio of HCrO4– to CrO42– is a function of pH. Richard and Bourg (1991) studied this relationship between pH and percent sorption of Cr(III) and Cr(VI) on Fe2O3 surfaces. However, sorption of Cr(VI) becomes less important as the concentration of competing anions sorbed to solid surfaces increases. In groundwater, therefore, adsorption of Cr(VI) is usually negligible (Richard and Bourg, 1991). Sorption processes are used indirectly to remediate Cr(VI); Cr(VI) is reduced to Cr(III), which can

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CONCENTRATION OF DISSOLVED HYDROXIDE OR SULFIDE (mg/L)

Pb(OH)2 Cr(OH)3 Zn(OH)2 AgOH Cu(OH)2 Ni(OH)2 Cd(OH)2

ZnS NiS CdS PbS

CuS 1

2

3

4

5

6

7

Ag2S 8

9 10 11 12 13 14

pH FIGURE 8.2 Solubility of hydroxides and sulfides as a function of pH.

precipitate or adsorb to soil. The effectiveness of this strategy depends on the sorption characteristics of the soil, including the clay content, iron oxide, and aluminum oxide (Al2O3) content, and the amount of organic matter present. Iskandar (2001), and Evanko and Dzombak (1997) provide an overview on metals remediation of soil and groundwater. 8.1.2.3 Precipitation Equilibration between solid and dissolved forms of Cr is a third physical– chemical interaction that is used in treatment processes. Precipitation of Cr(III) occurs as Cr(OH)3(s), FeCr2O4(s), or FexCry(OH)3(s) (Richard and Bourg, 1991). The solubility of Cr(III) governs its migration. Precipitation/ dissolution is a function of pH, complexation by organic matter, and the presence of other ions. As pH increases, OH– concentration increases and more Cr precipitates. Organics can complex with dissolved Cr, making removal by precipitation or adsorption difficult. The precipitation of Cr(III)

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is useful for increasing Cr(VI) to Cr(III) reaction rates, by Le Chatelier’s Principle. Natural precipitation of Cr(VI) is not a major removal mechanism. CaCrO4 was observed to precipitate naturally during summer months at a hazardous waste site (Palmers et al., 1990). Based on laboratory studies, BaCrO4 and Cr/Al coprecipitates were suggested to occur at other sites (Palmer et al., 1990; Palmer and Wittbrodt, 1991). Plating tank sludge at the first site contained PbCrO4, PbCrO4 H2O, and K2CrO4. However, the solids are highly soluble and are not a significant removal mechanism for Cr(VI). These three processes (redox reactions, sorption, and precipitation) are the underlying basis of both chemical and biological treatment processes used to influence the balance between Cr(III) and Cr(VI).

⋅

8.1.3

Biological Transformations

Microorganisms often carry out enzymatic redox reactions as part of their metabolic processes. Cr(VI) can also be reduced nonmetabolically by reactions that occur on bacterial surfaces (Fein et al., 2002). This has been postulated by Fein et al. (2002) as the dominant pathway for reduction in natural geologic settings. A third mechanism for Cr reduction involves intra-cellular precipitation (Cervantes et al., 2001). However, most studies have focused on the first mechanism, where Cr is reduced metabolically in the presence of large amounts of electron donors. Chemical reducing compounds used to stimulate biological reduction include molasses, lactic acid, and proprietary formulations such as Hydrogen Release Compound (HRC), and cheese whey. Bacteria can enzymatically reduce Cr(VI) by both aerobic and anaerobic pathways. However, other nonbiological Cr reduction pathways compete with the biological pathways. Under anaerobic conditions, biological reduction is slow so abiotic reduction by Fe(II) or hydrogen sulfide (H2S) is expected to dominate. Microbial reduction only becomes kinetically important in aerobic environments (Fendorf et al., 2001). Oxygen concentrations in the system are the primary factor influencing reduction rate, followed by pH and geochemical conditions. The role of microorganisms in Cr reduction is still being defined through research. Topics of interest include the role of bacterial surfaces in Cr reduction, new tools for monitoring transformations such as infrared spectromicroscopy (FTIR Beamline) (Holman et al., 1999) and coupled biological/chemical reduction processes. Phytoremediation is the engineered use of plants in the environmental remediation process. Phytoremediation is also a cutting-edge topic in research. There are six basic subsets of phytoremediation: phytoaccumulation (also called phytoextraction or hyperaccumulation), phytodegradation (also called phytotransformation), phytovolatilization, phytostabilization, rhizodegradation (also called phytostimulation or plant-assisted bioremediation), and rhizofiltration (also called contaminant uptake). Plants can take up Cr into

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their roots and aboveground tissues, storing it as Cr(III). When harvested, Cr is removed from the system. Plants can also stabilize Cr contamination in the soil, by one or several mechanisms, converting it to Cr(III). 8.1.4

Physical Remediation Processes

Chemical and biochemical processes render Cr(VI) unavailable by converting it to the less toxic and less mobile Cr(III) form. Physical processes separate Cr(VI) from the contaminated media (such as soil excavation and groundwater extraction), capture the extracted Cr (using ion exchange resins or granular activated carbon (GAC)), or isolate the contamination (using physical barriers around in situ contaminants or liners in landfills). Principles behind physical treatment concepts vary with the particular approach used. The basics and description of each technology are explained in Section 8.4 and Section 8.5.

8.2

Classification of Treatment Technologies

Taking a risk-based approach to the health problems associated with Cr(VI) inhalation/ingestion will provide a framework for classifying the numerous remediation strategies that have been developed and used to date.

8.2.1

Reduction of Toxicity

The carcinogenic effects of Cr on humans and ecological species remove can be expressed as the product of exposure and the inherent toxicity of the compound. One method of alleviating health impacts of Cr is toxicity reduction. Cr that is ingested in a chemical form that is biologically unavailable will theoretically be harmless, as long as transformations do not occur within the body to render it toxic. A major category of remediation technologies aims to decrease the toxicity of Cr(VI) by reducing Cr(VI) to Cr(III). This can occur naturally or by manipulating environmental conditions to stimulate selective biological activity (including bacteria, yeast, algae, and plants) or geochemical processes (Haq and Shakoori, 1998). Reduction can also occur when chemicals are added to directly reduce the Cr, such as ferrate or Fe filings. All other remediation strategies target the second component of the health impact equation, intake rate. Intake rate, expressed in mg/(kg body mass)/d can be expressed mathematically in the following way: Intake Rate = (concentration)(exposure frequency) (exposure duration)/((body mass)(lifetime))

(8.4)

where concentration is typically in mg/L, exposure frequency in L/days, exposure duration in days, body mass in kg body mass, and lifetime in days.

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Body mass and lifetime cannot be changed to reduce exposure. Exposure duration or frequency may be decreased by institutional controls — for example, prohibiting ingestion of groundwater or site access in soil contaminated areas. Thus, in order to reduce intake rate, remediation must focus on decreasing concentration in soil or groundwater. 8.2.2

Destruction and Removal

To decrease total Cr concentrations, several approaches are used. Destruction technologies are not practical for Cr, since it is an element. The energy to change the atomic nucleus of Cr to a different element would be enormous. Simple removal technologies include conventional methods such as excavation and off-site disposal of soil or pump-and-treat of groundwater. However, soil may require further treatment before it is disposed off and groundwater extraction must be followed by ex situ treatment. Other technologies involve separation of Cr from soil into a wastewater stream by soil washing, soil flushing or solvent extraction, concentration of Cr into a smaller waste volume or area using electrokinetics or phytoextraction, or the removal of Cr from groundwater by membrane technology (ultrafiltration, nanofiltration, reverse osmosis), ion exchange, or granular activated carbon. 8.2.3

Containment

Other technologies focus on preventing the spread of contamination into larger areas. These containment technologies include stabilization or solidification, biostabilization, phytostabilization, precipitation, encapsulation, and vitrification of soil. Slurry walls and other physical barriers are used for groundwater containment. Passive in situ remediation can be achieved by permeable reactive barriers, and hydraulic containment can be attained through pump-and-treat (this process may be enhanced by addition of surfactants). Containment technologies focus on either isolating the contaminants (in the case of in situ slurry walls) or immobilizing them. Passive remediation may occur as groundwater leaves the containment zone, as in the case of permeable reactive barriers. However, no attempt is made to decrease concentrations of Cr(VI) within the containment zone. In summary, remediation technologies focus on either decreasing toxicity (reducing Cr(VI) to Cr(III)), removing Cr from soil/groundwater, or confining the Cr to a certain area.

8.3

Toxicity Reduction Methods

Treatment systems based on the Cr(VI) reduction can be biological or abiotic, and is often a combination of these two.

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The term chemical reduction refers to abiotic in situ or ex situ reduction with an electron donor such as S, Fe(II) or Fe(0). The newly formed Cr(III) then precipitates out of solution. This approach achieves both a reduction in Cr toxicity and removal of the Cr from aqueous solution. Chemical reduction includes naturally occurring reduction by soil oxides and natural organic material. Engineered chemical reduction technologies involve the addition or in situ injection of an electron donor such as H2s (Thornton and Amonette, 1999), sodium dithionite (Na2S2O4) (Fruchter et al., 2000), sodium metabisulfite (NaHSO3), calcium metabisulfite (CaHSO3), FeSO4, calcium polysulfide (CaS5) (Jacobs et al., 2001), Fe(II) (Seaman et al., 1999), Fe(0) (Ponder et al., 2000), or tin(II) chloride (SnCl2). The pH is adjusted to optimize electrostatic surface interactions between Cr(VI) anionic species and the electron donor. Alternatively, for high Cr(VI) concentrations such as those encountered in industrial waste streams, pH is increased so that Cr(III) will form S2– and/or OH– precipitates. Metal sulfides are far less soluble than metal hydroxides. Except for alkali–metal sulfides, metal sulfides are relatively insoluble over the pH range of most naturally occurring groundwater (pH 5 to 9). Laboratory and pilot studies with different electron donors have demonstrated that there is a high potential of successful removal during in situ reduction. Actual results depend on the details; Powell et al. (1995) reported that different forms of Fe metal influence reduction kinetics. Impure, partially oxidized Fe was the most effective, with no reduction occurring when pure Fe(0) was used (Powell et al., 1995). This was explained by the hypothesis that Fe(0) does not have the materials needed to initiate the redox (corrosion) process to Fe(II). Surface area of the Fe is another factor that affects redox kinetics. Ponder et al. (2000) reported that reduction was 21 times greater for equal moles of Fe present when Fe nanoparticles (10 nm to 30 nm in diameter) were used instead of commercial Fe filings. H2S has been demonstrated to reduce Cr, either by adding H2S(g) to the soil in situ, or by stimulating sulfate (SO42–) reducers in the subsurface. Recently, field testing has shown that Na2S2O4 successfully reduces CrO42–. During demonstration and treatability testing at the DOE Hanford Site, Washington, sodium dithionate (Na2S2O6) was injected into an unconfined aquifer (USDOE, 2000). Chromate concentrations decreased from 900 µg/L to nondetect (<8 µg/L). Monitoring indicated that the treatment zone remained anoxic after 2 years and that chromate remained nondetected. Since no pumping and aboveground treatment is required, operation and maintenance costs are low. The DOE Hanford site cost analysis indicated that in situ chemical reduction could save 60% relative to pump-and-treat system over 10 years of treatment (USDOE, 2000). Further testing with Na2S2O4 at the Frontier Hard Chrome Superfund Site in Vancouver, Washington showed that CrO42– concentrations could be reduced from 4,500 µg/L to nondetect (<20 µg/L) (Vermeul et al., 2002).

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Ex situ chemical reduction of Cr(VI) is well established, so extensive laboratory and pilot scale testing is not necessary, prior to full-scale implementation. Extraction and ex situ chemical reduction is frequently a component of selected treatment remedies at Superfund sites (USEPA 1989a and 1986b). However, chemical costs are high and the system must include filtration or sedimentation. In addition, these systems are not cost effective for low concentrations of Cr(VI) in the wastewater. In situ chemical reduction is highly dependent on the existing site-specific physical and chemical conditions, including pH, permeability, lithology, water depth, concentrations of metals in water and soil, and alkalinity. Site data can be used to design and perform a series of simple bench-scale tests, followed by pilot scale tests in small areas of the site to verify treatability. After a successful in situ pilot scale test, a full-scale remediation may be performed. For in situ commercial applications, delivery is one of the key factors in successful remediation, since the treatment chemicals must fully contact and react with the Cr(VI). There are several methods of delivering chemicals into the subsurface. If screened correctly and located beneficially for the injection of treatment chemicals, existing wells or trenches can be useful for chemical delivery. A more precise method of delivering liquid chemicals to the subsurface uses high-pressure injection technology, also called jetting. There are two main methods of jetting: one uses a direct push drilling technology method where chemicals are sprayed into the subsurface through specially designed steel injection rods, typically 25 mm to 50 mm in diameter. The rods are pushed into the subsurface using the probe rig. One method is to push the rods to the target depth and inject chemicals up to 41 atm (4.2 × 105 Kgforce/m2) as the rods are retracted from the borehole. The other method uses a 6.35 mm to 12.7 mm outer diameter lance system for the delivery of treatment chemicals (Jacobs, 2001). Hand-held jetting lances operate at tip pressures up to 340 atm (3.5 × 106 Kgforce/m2) and allow accessibility in limited access areas such as underneath railways and buildings, around tanks, pipelines and subsurface utilities. Chemical compatibility of the injection equipment components and safety procedures become critical with the injection of strong chemicals. In low permeability soil, permeability enhancement can be performed in the subsurface prior to chemical injection. Higher injection tip pressures on the lance or injection probe rods are used to induce hydrofracturing in low permeability sediments, allowing for additional movement of the treatment chemicals into the target zone. 8.3.2

Microbial Reduction

As described in Section 8.1, microorganisms can catalyze redox reactions by a combination of several mechanisms, including enzymatic extracellular reduction, nonmetabolic reduction by bacterial surfaces and intracellular reduction

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FIGURE 8.3 Injection of liquids using RIP® lance equipment.

and precipitation. Microorganisms capable of reducing Cr(VI) to Cr(III) include bacteria (Psuedomonas, Micrococcus, Escherichia, Enterobacter, Bacillus, Aeromonas, Achromobacter, and Desulfomamaculum) (McLean and Beveridge, 1999), algae (Cervantes et al., 2001), yeasts, and fungi. External reduction reactions that are biologically mediated still require the presence of an external electron donor, such as Fe, Mn, or oxidized organic matter. The process is the same as chemical reduction, but is biologically mediated and is thus kinetically advantageous to nonbiological reactions, particularly under aerobic conditions. Alternatively, sulfur-reducing bacteria are stimulated to produce H2S, which serves as the reductant. Recent work by Fein et al. (2002) has shown that bacterial surfaces can also catalyze Cr reduction. Both eukaryotic and prokaryotic cells can actively transport Cr(VI) across their cell membrane. In yeasts, Cr(VI) may enter via the permease system, a nonspecific method of ion transport for anions such as phosphate (PO43–) and SO42– (Cervantes et al., 2001). Cr is toxic to yeast because it inhibits SO42– uptake. Differences in the retention of Cr(VI) by algae have been studied and reported. Green algae retain more Cr than red or brown algae (Cervantes

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FIGURE 8.4A Injection of liquids using a high pressure probe delivery method.

et al., 2001). In general, cells do not take up Cr(III) because it is not watersoluble is Cr(OH)3. Laboratory studies have quantified the impact of various factors affecting the rate of microbial reduction, including dissolved oxygen and organic carbon concentrations, pH and mass loading rates of Cr. Although biological reduction can be either aerobic or anaerobic, reduction reactions are sensitive to oxygen concentrations. Under anaerobic conditions, both abiotic and biotic reduction mechanisms are competitive. Over time, pH may increase owing to the mineralization of organic matter to CO2, which increases HCO3– concentration, or owing to an acid-consuming redox reaction. Optimal Cr(VI)

FIGURE 8.4B Shows high pressure liquid injection using probe rigs.

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loading rates have been determined by varying the influent concentration or dilution factor. Results are case specific as environmental conditions determine which mechanisms will dominate in the system. Bioremediation strategies used for Cr(VI) remediation include monitored natural attenuation (MNA), biostimulation, and bioaugmentation. MNA is frequently evaluated at sites as a baseline remedial option and has been implemented at Superfund sites such as the Quality Plating Superfund Site, Missouri (USEPA, 1995). During biostimulation, also known as enhanced bioremediation, oxygen and/or nutrients are injected to stimulate indigenous microorganisms. This was chosen as part of the final treatment technology for a chrome electroplating facility in Kansas in 1999 (Ace Services Superfund Site) (USEPA, 1999). The plan involved recirculating water amended by a carbon source through the contaminated area to stimulate bacterial activity. In situ bioremediation was intended to reduce source concentrations of Cr(VI) and thus reduce pump-and-treat timeframe for the site. Bioaugmentation refers to the injection and maintenance of cultured microorganisms into the subsurface. Bioaugmentation may not be necessary since a number of indigenous Cr(VI)-degrading cultures are present in the environment, and in some cases are superior Cr(VI)-reducers, as they have been acclimated to the site conditions (McLean and Beveridge, 1999). 8.3.3

Phytoremediation

Like biological and chemical reduction, phytoremediation is a multi-faceted approach towards Cr remediation. Plants contain the Cr by converting it to the less mobile Cr(III) (phytostabilization) and simultaneously reduce its toxicity. In addition, phytoremediation can be a removal technology, if Cr is sequestered in plant tissue and the plants are harvested (phytoextraction and rhizofiltration). For simplicity, all three mechanisms of phytoremediation are classified primarily as toxicity reduction methods and are discussed here. All three techniques are currently in the lab scale or pilot scale of development (USEPA, 1997). Phytoaccumulation, one of the most common forms of Cr(VI) phytoremediation, consists of the uptake of the Cr from the soil to the plant roots and ultimately into the above-ground parts of the plants. Some plants can accumulate very large amounts of a specific “metal,” such as Cr. The plant Leptospermum scoparium was found to contain soluble Cr in the leaf tissue as the trioxalatochromium(III) ion (Cr(Cr2O4)3)3–. The function of the chromium-organic acid complex was to reduce the toxicity of the Cr. Phytostabilization is perhaps the least advanced technology of the three currently in development. This method is sometimes viewed as a temporary measure until phytoextraction is further developed (USEPA, 1997). Plant and other biological secretions can stabilize Cr in the root zone. These can change pH or complex the Cr as Cr(III). In addition, plant roots minimize erosion and the migration of contaminated sediment. Phytostabilization is most useful for low concentration contamination or large polluted areas, when conventional

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chemical–physical methods are most expensive. Phytostabilization can be combined with best management practices such as amendments of phosphorus lime, or organic matter to enhance immobilization and avoid leaching. Several varieties of grasses are commercially available for phytostabilization of copper (Cu), lead (Pb) and zinc (Zn), but none for Cr (USEPA, 1997). Trees and other high-biomass crops can be used for phytostabilization, since harvest is not performed. Phytostabilization using poplar trees is currently a topic of research (USEPA, 1997). Metal accumulating plants are undesirable for phytostabilization, owing to the risk of generating hazardous plant waste and/or passing Cr along in the food chain. Experimental data on phytostabilization in mining and industrial slag disposal sites has been reported by Hse in 1996 working on plantations of Populus spp (Hse, 1996). More research has been conducted on phytoextraction and rhizofiltration of Cr. Cr reductases have not yet been identified in plants (Cervantes et al., 2001). Some research suggests that Cr is taken up as organic material/Cr complexes. Complexation with organics was identified as facilitating Cr availability to plants in lab-scale experiments (Cervantes et al., 2001). The sulfate transport system is apparently involved as it is for bacteria. In most experiments, Cr(VI) is preferentially taken up over Cr(III). Roots take up 10 to 100 times more Cr than shoots and other tissues. Much research has been done on the toxic effects of Cr(VI) on plants. Cr(III) is relatively nontoxic. The reason that Cr(VI) is toxic is that it generates free OH radicals as it is broken down to Cr(III). The energetic OH radicals can mutate DNA and lead to other toxic effects. Cr(VI) causes plant growth reduction owing to root damage (Salunkhe et al., 1998). Rhizofiltration refers to the uptake of Cr from wastewater by plant roots. Terrestrial plants with long fibrous roots and high surface areas are typically used because sorption onto the surface of roots provides an additional uptake mechanism. However, in some studies, only live roots were able to remove metals from solution (Dushenkov et al., 1995). Indian mustard seedlings grown in aerated water accumulated Cr(VI) by a factor of 100 to 250 times the concentration in water (Salt et al., 1997). Indian mustard has been used in other studies, including phytoextraction at an Ohio metal plating facility (Rock and Beckman, 1998) and lab-scale work differentiating between “metal” uptake efficiencies among various mustard species. B. juncea and B. nigra had the highest “metal“-accumulating ability and Cr had the highest extraction coefficient (followed by cadmium (Cd), nickel (Ni), Zn, and Cu) (Kumar et al., 1995). The wetland plant duckweed was also studied for phytoaccumulation of various metals (Zayed et al., 1998). Other lab studies have focused on alfalfa (Medicago sativa) (Gardea-Torresdey et al., 1998) and its ability to bind Cr from aqueous solution. Alfalfa shoots took up 7.7 mg Cr(III) per g of biomass and zero Cr(VI) from biomass. Selected aquatic plants have the ability to tolerate Cr. Water hyacinth (Eichhornia crassipes) can accumulate Cr as Cr(III) in high concentrations (6 mg/g dry mass) was observed in the plant’s roots when it was growing in only 10 ppm Cr(VI) (Cervantes et al., 2001). Herniaria hirusta was also found to be a

⋅

⋅

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Cr accumulator (Cervantes et al., 2001). Sulfur-loving plants such as cauliflower, kale and cabbage showed huge concentrations of Cr accumulation (160 mg/kg to 135 mg/kg in roots, 1.6 mg/kg to 2.0 mg/kg in shoots) (Cervantes et al., 2001) with Brassica spp. accumulating the most. The sulfur transport system may be responsible for the high uptake ability of these species. Considerable work remains in the development of phytoremediation technologies. The mechanism(s) for uptake are not yet clear. Neither are the effects of organic matter and other soil amendments on uptake efficiency, possibly owing to the uncertainty associated with the mechanisms of uptake and/or precipitation.

8.4 8.4.1

Removal Technologies Ex Situ Technologies

Following excavation, soil contaminated with Cr can be transported offsite to landfill. Owing to high costs of transport and landfill space, it may also be treated on site. Most ex situ technologies are appropriate for removing Cr from liquid waste streams following groundwater extraction. Some have also been applied to highly concentrated wastes generated by Cr industries (tanneries, metal-plating shops, and wood treatment facilities). Ex situ treatment techniques that capture and remove total Cr from waste soils, sludges, sediments, and liquids are discussed in this section. 8.4.1.1 Ion Exchange Ion exchange is a physical process in which an ion with a high affinity for the resin material of the ion exchange column replaces an ion with a lower affinity that was previously bound to the column resin. As water flows through, dissolved Cr(VI) ions bind to the resin and displace the previously bound ions (usually Cl– or OH– ions). The resins used for Cr sequestration are typically either a naturally occurring inorganic zeolite or a synthetic weak base or strong base anion exchanger resin. Once the resins have accumulated Cr on enough exchange sites that breakthrough surpasses a threshold value, they must be regenerated. Ion exchange resins are capable of reducing Cr(VI) concentrations to less than the detection limit. Resins are typically most effective at low pH values, because Cr(VI) will be present as HCrO4– and Cr2O72–, not as CrO42–. The ratio of ion exchange sites to Cr ions sequestered is then 1/1. When CrO42– is present, two ion exchange sites are used to sequester each Cr ion. Competition by other anions (namely SO42–, nitrate (NO3–), and Cl–) is not a problem in most applications, since Cr has a higher affinity for all polymeric anion exchangers. Increasing the ratio of competing ion concentration to Cr concentration may appreciably change the Cr selectivity (U.S. Filter Recovery

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Services, Inc., 2001). Breakthrough is gradual and is governed by equilibrium between the resin and the aqueous phase (U.S. Filter Recovery Services, Inc., 2001). Regeneration is typically accomplished using NaOH and alkaline brine. Cr(VI) in the regeneration effluent is either disposed of in concentrated form or is recovered for reuse. Bench-scale treatability tests are typically conducted at sites prior to the implementation of full-scale remedial activities. Variables include the type of resin that is most efficient for removal under the expected loading rate, the ion selectivity of Cr over SO42− and NO3−, the capacity of the system (time until breakthrough), and finally the possibility of organic fouling, which may also affect the duration of operation before regeneration. Bench-scale tests at the FMC-Fresno site in Fresno, CA , on six different commercially available ion-exchange media showed that ion exchange resins may not perform at the manufacturer’s stated loading capacity. (U.S. Filter Recovery Services, Inc., 2001). Ion exchange is commercially available for removing Cr from aqueous waste streams. The technology has been used at several Cr-contaminated Superfund Sites (USEPA, 2000c and 1986a). Ion exchange systems such as Ion Exchange Recovery of Cr (IERECHROM) have been developed to recover Cr(III) for future use, which is economically attractive for industrial facilities with concentrated Cr(III) waste streams (Petruzzelli et al., 1995). 8.4.1.2 Granular Activated Carbon Granular activated carbon (GAC) is a well-established technology for removing organics from water supplies and has been demonstrated to remove heavy metals as well, including Cr. GAC has an extremely high internal surface area, on the order of 1,000 m2/g. Cr(III) adsorbs only weakly to GAC and passes through the carbon. Cr(VI) is removed by two different mechanisms: electrostatic adsorption to GAC surfaces and reduction to Cr(III). Adsorption of Cr(VI) is a strong function of pH, owing to electrostatic surface interactions. Quantitative results vary with the type of GAC, because different types of GAC have different point of zero net charge (pznc) values (Corpapcioglu and Huang, 1987). The adsorption capacity of Calgon filtrasorb 400 GAC was shown to peak between pH 5 to 6 (Huang and Wu, 1977). Although CrO42–, HCrO4–, and Cr2O72– are all adsorbed, HCrO4– is the most easily adsorbed species. Coconut-fibre pith-based GAC (pznc = 7.5) achieved optimal removal at pH 2 (Manju and Anirudhan, 1997). Grinding GAC particles did not change Cr(VI) adsorption owing to the relatively small change in GAC internal surface area (Huang and Wu, 1977). However, GAC is not commonly considered/implemented at Cr-contaminated sites, owing to practical considerations. As explained in the Record of Decision for Coast Wood Preserving Superfund Site, Cr adsorption by GAC is a strong function of pH and would require chemical addition as a pretreatment to lower pH (USEPA, 1989a). During on-site GAC regeneration, adsorbed Cr would be released as Cr(VI), creating a second waste stream that would require treatment. On the other hand, Kysor Industrial Corp. Superfund Site used GAC as the primary remediation technology for Cr(VI)

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contamination. Spent GAC was transported to landfill instead of being regenerated (USEPA, 1989b). 8.4.1.3 Adsorbents Alternative sorbents have been proposed for removing Cr(VI), in order to save money and/or recycle waste material. Materials tested so far have ranged from used automobile tires to seaweed. Results have demonstrated that removal can be equivalent or superior to that of ion exchange resins (Bailey et al., 1999). Researchers have tested living and dead biosorbents, including bacteria, yeasts, milled peat, microalgae, fungi, and seaweed. Other natural materials tested include clays, peat moss, and plant litter. Low cost sorbents are not regenerated, but are disposed off as soon as significant breakthrough occurs. A summary of the adsorptive capacities of alternative sorbent materials is provided in Table 8.1, in terms of mg Cr(VI) sorbed per gram of sorbent (adapted from Bailey et al., 1999). Values in Table 8.1 are not meant to represent maximum adsorptive capacity of the materials, but the range of adsorptive capacities possible under the experimental conditions. Since adsorption is an equilibrium process, the mass of Cr(VI) sorbed to the surface depends on both the concentration of Cr(VI) in the aqueous phase and the affinity of the sorbent for the Cr. This in turn depends on the types of chemical attractions between the sorbent and the Cr (such as ionic bonding, electrostatic attraction, and hydrogen bonding), which can vary with pH and the presence/absence of competing molecules. For example, GAC may have a maximum adsorptive capacity of 500 mg/g (Fendorf et al., 2001), yet only remove 65 mg/g at saturation (Henshaw Associates, Inc., 1998). Adsorption isotherm data are also available for a variety of alternative adsorbents. (Bailey et al., 1999). Pretreatment for different natural and waste materials has also been tested, in attempts to improve adsorption performance. Chitosan, for example, is a deacetylated derivative of chitin. Free amino groups are exposed during deacetylation and serve as adsorption sites. To decrease the solubility of chitosan, loose crosslinking reactions can be performed. Different forms of chitosan (beads or powder) have also been created and tested for adsorption properties. Crosslinking has also been used for seaweed to decrease swelling inside adsorption columns. Waste materials such as tires and sawdust were pyrolyzed prior to testing. Costs of materials increase with the amount of pretreatment that is necessary yet may result in greater cost savings in the end, owing to higher sorption capacity.

8.4.1.4 Membrane Filtration Semipermeable membrane filters are used in water treatment to filter soluble compound anions and cations from water, including HCrO4– and CrO42–. The flux of water through the membrane is proportional to the pressure that is applied. The flux of solute (Cr) can be related to the flux of

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TABLE 8.1 Summary of Reported Adsorption Capacities for Cr(VI) Class

Sorbent Material

Chitosan Clay

Chitosan Wollastonite–fly ash mixture Tailored bentonite Bentonite

Clay Clay

27.3 0.271

Coconut fiber pith Leaf mould

Sharma and Forster, 1994

Green algae

Roy et al., 1993

162.23

Rice hulls

Roy et al., 1993

164.31

Peat Irish sphagnum peat moss

Tummavuori and Aho, 1980 Sharma and Forster, 1993 and 1995 Orhan and Büyükgüngör, 1993 Orhan and Büyükgüngör, 1993 Orhan and Büyükgüngör, 1993 Orhan and Büyükgüngör, 1993 Orhan and Büyükgüngör, 1993 Bryant et al., 1992; Dikshit, 1989; Zarraa, 1995 Santiago et al., 1992

Tannin-rich

Walnut shell

Tannin-rich

Exhausted coffee

Tannin-rich

Nut shell

Tannin-rich

Waste tea

Tannin-rich

Turkish coffee

Tannin-rich

Sawdust

Zeolite

EHDDMA-amended zeolite CETYL-amended zeolite Pyrolyzed tires

Source:

Masri et al., 1974 Panday et al., 1984

Adsorption Capacity (mg/g)

Cadena et al., 1990 Khan et al., 1995; Cadena et al., 1990 Manju and Anirudham, 1997

Coconutfiber Dead biomass Dead biomass Dead biomass Peat moss Peat moss

Zeolite Pyrolyzed tires Pyrolyzed sawdust Carbon

Source

57 0.512, 55 50 43

43.9 119; 43.9 1.33 1.42 1.47 1.55 1.63 10.1, 16.05, 4.44 0.42

Santiago et al., 1992 Hamadi et al., 2001

0.65 25.62–29.93

Pyrolyzed sawdust

Hamadi et al., 2001

20.09–24.65

Commercial F400 GAC

Hamadi et al., 2001

19.13–26.25

Adapted from Bailey et al. (1999).

water, the concentration of Cr and other empirically derived membrane parameters. Membrane filtration systems are categorized by pore size. From largest to smallest pore size, these include microfiltration, ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO). Although RO membranes can achieve the highest effluent water purity, they must operate at higher pressure. For this reason, nanofiltration has attracted increasing attention. Hafiane et al. (2000) tested a thin film charged surface (TFCS) nanofiltration membrane for Cr(VI) removal and found that results were promising (Hafiane

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et al., 2000). Owing to the negative surface charge of the membrane, Cr and other anions are repelled by the membrane surface. As ionic strength of the water increases, this effect is shielded and Cr removal decreases. As expected, Cr removal improves with increasing pH (membrane surfaces are deprotonated, increasing electrostatic repulsion, and Cr charge increases as CrO42– forms). The rejection rate of Cr(VI) (equivalent to the removal rate) can be expressed as the following: Rejection rate = σ (1 – F)/(1 – σF)

(8.5)

where rejection rate is dimensionless (no unit), σ is the reflection coefficient and corresponds to the maximum rejection at an infinite volume flux, and F is defined by the following: F = e(1 – σ)Jv / P

(8.6)

where e = 2,718... (base of natural logarithum) Here Jv is the flux of water through the membrane, with units of volume per membrane area per time, and P is an empirical parameter, known as the solute permeability, also with units of volume per membrane area per time. Hafiane et al. (2000) determined the empirical σ and P parameters for different ionic strength and pH values, allowing Cr rejection efficiency to be predicted once ionic strength and pH are known. Cr(VI) ions are too small to be removed by microfiltration or ultrafiltration membranes, unless pretreatment is performed to complex the Cr(VI) by larger molecules. Hexadecylpyridine chloride has been used in the past, followed by ultrafiltration through membrane with 17.5% of greater polymer content. Approximately 98% of the Cr(VI) was removed with this system (Bohdziewicz, 2000). Microfiltration has been used for removing Cr(III) precipitates from industrial wastewaters (Visvanathan et al., 1989). 8.4.1.5 Soil Washing and Separation Technologies Soil washing is used to chemically or physically separate Cr-contaminated soil from other soils prior to disposal. Physical separation based on size or lithology can be performed using a variety of screens, rotary scrubbers, grizzlyshakers, and settling tanks, technologies adapted from mineral processing. For example, if the Cr(VI) is primarily associated with the clay-rich fraction of a soil, sands and gravels can be separated from the clays physically. Contamination will then be concentrated in a smaller volume prior to subsequent treatment or disposal. Chemical treatment typically involves the addition of an acid, oxidant, surfactant, or a chelating agent to the soil slurry to increase the amount of Cr in the aqueous phase. Alternatively, the soil can be sprayed with water or a leaching solvent applied under high pressures to chemically leach Cr out of the soil. Soil washing solvents include commercially available chelating agents, surfactants, and acids. Leachability of Cr(VI) increases with the pH

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of the washing solution. Owing to the need for subsequent wastewater treatment, soil washing is not commonly used for environmental remediation. Cr has been extracted from radioactive processing wastes to help decrease the volume of high-concentration radioactive solids (Sylvester et al., 2001). Hot water washing of Cr slag (a mixture of ore processing residual and soil) has been used to recover Cr in the form of Cr(VI) for further industrial use (Ososkov and Bozzelli, 1994). After soil washing, the Cr(VI) wastewater can be further concentrated using ion-exchange resins. High removal rates (95% to 99%) of Cr(VI) from the waste ore have been reported (Ososkov and Bozzelli, 1994). Passive soil washing technologies, including heap-leaching methods have been applied for environmental remediation. 8.4.2

In Situ Technologies

In situ technologies are an attractive alternative to ex situ remediation technologies, since excavation and/or pumping costs are eliminated. The in situ removal technologies discussed in this section remove total Cr in the subsurface. Technologies include soil flushing, electrokinetics, and solvent extraction. 8.4.2.1 In Situ Soil Flushing In situ soil flushing is the extraction of Cr from the unsaturated zone using water or another solvent. It involves injection or infiltration of water through the unsaturated zone, which raises the water table into the contaminated area, and then extraction, followed by treatment and reinjection of the water. Soil flushing is analogous to soil washing, but the phase transfer of Cr occurs in the subsurface. Since Cr(VI) is soluble in water, it is easily removed with the water. The depth of the water table and the initial and final target concentrations of Cr remaining in the subsurface determine the practicality of soil flushing. Surfactants have been used to enhance soil flushing. Two characteristics of a desirable surfactant are a high ratio of surfactant CrO42– extraction to water extraction of CrO42– and a high resistance of the surfactant to subsurface losses (sorption and precipitation). Nivas et al. (1996) tested different surfactants to enhance pump-and-treat operations, and found that extraction effiency increased with surfactant concentration below the critical micelle concentration (CMC), and was fairly constant at doses above the CMC (Nivas et al., 1996). Adding a complexing agent, diphenyl carbazide (DPC), increased total Cr removal 9.3 to 12.0 times with respect to deionized water. The most effective surfactant tested was Dowfax 8390 (Nivas et al., 1996). This information was applied to ongoing pump-and-treat system at the U.S. Coast Guard Support Center, Elizabeth City, N.C. A Superfund Site using in situ soil flushing is the United Chrome Products Superfund Site in Corvallis, Oregon. Cr concentrations in the soil are as high as 60,000 mg/kg and 19,000 mg/L in groundwater (USEPA, 2000b). The approach since 1985 has been to flush the subsurface with water so that the water-soluble Cr(VI) goes into the aqueous phase and is extracted. Infiltration

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basins and trenches are used to deliver water to the contaminated soils. A groundwater extraction network is used to remove the chromium-contaminated water and recharge treated water. Soil flushing has been the most successful in coarse soils of relatively high hydraulic conductivity. Cr(VI) concentrations in the water extracted by the well network decreased from 5,000 mg/L to 50 mg/L over 2.5 years. Average concentrations in the groundwater plume decreased from 1,923 mg/L to 207 mg/L after flushing with 15 million liters (1.5 pore volumes). Concentrations have not yet stabilized at asymptotic limits, indicating that additional Cr(VI) removal can be expected (USEPA, 2000b). Recently, soil with concentrations greater than 6,000 mg/kg were excavated in order to shorten the time for remediation. 8.4.2.2 Electrokinetics Electrokinetic remediation applies low concentrations of voltage (50 V to 150 V) across contaminated soil in order to mobilize Cr(VI) anions. The Cr(VI) contaminants will concentrate around the anode in aqueous phase. Less soluble Cr(III) may build up near the cathode. Electrokinetics is typically applied in situ, with the electrodes placed directly in the ground to depths of 3 m to 5 m. In most cases, groundwater is extracted at each electrode and treated above ground. During ex situ electrokinetics, electrodes are installed on both sides of the contaminated soil or slurry. Factors that improve electrokinetic performance include a low cation exchange capacity, high soil moisture but not saturated conditions, low salinity, low conductivity, and a high fraction of exchangeable or soluble Cr concentrations. Reddy et al. (2001) tested electrokinetic removal of Cr(VI), Cr(III), Ni(II) and Cd(II) in two different soil types: clay (kaolin) and glacial till. The exchangeable and soluble fraction of Cr(VI) migrated towards the anode in both cases, but Cr(III), Ni(II) and Cd(II) migration depended on the amount of exchangeable and soluble metal present. In glacial till, this soluble fraction of Cr(VI) was negligible. In kaolin, migration was observed. Conductive pore fluids can be injected into the subsurface to enhance the electrokinetic process and make up for a lack of soil moisture in the unsaturated zone. Flushing the system with water can help counteract extreme changes in local pH as H3O+ and OH– ions migrate in opposite directions. Extreme local pH can change the solubility and speciation of the contaminants. Hybrids of the electrokinetic process include the Electro-KleanTM process, available through Electrokinetics, Inc. of Baton Rouge, LA (Electrokinetics, 1994), ElectroChemical Geo Oxidation (ECGO), patented by ManTech International Corporation, Germany, Electrochemical Ion Exchange (EIX), ElectrosorbTM, and the LasagnaTM Process, developed by Monsanto, DuPont, and General Electric (USDOE, 1996). In situ electrokinetics was applied at the Naval Air Weapons Station, Point Mugu, CA in a field demonstration in 1998 (USEPA, 2000a). Both Cr and Cd were present and ranged from “nondetect” to 25,100 mg/kg and 1,810 mg/kg,

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respectively. Soil was characterized as 85% sand, 7% gravel, 6% silt, and 1% clay. Electrokinetic extraction was found to be much slower than originally expected, although current densities were lower than those used in benchscale studies. After 22 weeks of operation, the pH front was just beginning to appear. Factors retarding performance were investigated for the rest of the study period. In general, the technology is still being developed and is not ready to be implemented at the full-scale until site-specific bench and pilot testing has been conducted.

8.5

Containment Technologies

Containment technologies are used to either physically stop the spreading of groundwater plumes or to chemically immobilize contaminants in a nonexchangeable, insoluble form. Most containment technologies are performed in situ, with the exception of soil vitrification prior to landfill disposal. Groundwater containment technologies involve the construction of a physical, chemical, or hydraulic barrier that isolates the contaminated zone, either directing impacted water through a treatment zone or stopping its migration. Soil contaminants are either physically isolated by a barrier or chemically treated to tightly bind and immobilize contaminants onto the soil.

8.5.1

Barrier Technologies

One advantage of physical barriers is the wide range of contaminants that can be contained and isolated, including Cr(VI). Physical barriers are constructed of low permeability materials such as grout, slurries, or sheet piling. Even in the best cases, however, a small amount of vertical or horizontal leakage is likely to occur. For this reason, chemical and hydraulic barriers have been developed as alternatives. Hydraulic control is maintained by an upgradient extraction system and must be accompanied by ex situ treatment. Hydraulic control is commonly employed as an interim corrective action measure to stop plume migration while site characterization and remedial technology evaluation are being conducted. Chemical barriers can be passive or reactive. Both are designed to let water pass through the barrier zone while the contaminant is immobilized. Passive barriers need little or no maintenance to chemically immobilize contaminants, yet are not always an option for a site. Reactive barriers are maintained by chemical addition and/ or contaminant extraction. Barrier technologies work only if the groundwater gradient is consistent and unlikely to change over time. Costly mistakes can be made using containment technologies in locations where the groundwater table has large seasonal fluctuations or the groundwater gradient is shallow or inconsistent.

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8.5.1.1 Low-Permeability Passive Physical Barriers Physical barriers are passive technologies; after installation, monitoring is the only maintenance that is required. Barrier materials include bentonite, grout, sheet piling, and synthetic materials such as polyethylene. The most common barrier configuration is a continuous trench or wall. Horizontal barriers are also used to stop vertical migration; the most commonly used barrier is a surface cap. Groundwater levels can mound upgradient of the barrier. In some cases, shallow trenches are used to collect and channel the ponding water. In places where groundwater mounding is extreme, groundwater can be pumped and treated. A slurry cutoff trench/wall is constructed using backhoes or excavators by digging a narrow vertical trench, typically 0.6 m to 1 m wide, and as deep as 11 m to 15 m. The trench is then backfilled with a bentonite-water slurry, stabilizing the walls of the trench and preventing it from collapsing. The slurry penetrates into the nearby soils and seals the formation (USEPA, 1991). Common slurry mixtures include soil/bentonite (SB) and cement/bentonite (CB). Hydraulic conductivity values of well-constructed SB and CB walls are approximately 10–8 cm/s and 10–6 cm/s, respectively (USEPA, 1985). One concern with slurry cut-off technology is the compatibility of the trench backfill material with the site geochemistry. Acids, bases, salt solutions, and some organic chemicals can desiccate slurry wells, possibly leading to cracking.

Backfill Mixing Area

Trench Spoils

Area of Active Excavation

Emplaced Backfill Unexcavated Soil

Aquiclude

FIGURE 8.5 Soil/bentonite slurry cutoff trench installation. (USEPA, 1988.)

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Groundwater Flow Slurry Wall

Wastes

Extraction Wells

FIGURE 8.6 Plan view of circumferential wall placement. (USEPA, 1988.)

Compatibility testing may be required to investigate the stability of the wall under site-specific conditions. A second concern with slurry wall technology is the potential for leakage underneath the wall. For this reason, slurry walls are often combined with hydraulic control systems that maintain a positive vertical gradient. Slurry cut-off trenches/walls can be installed downgradient of a source to prevent further migration of Cr, upgradient of a source area to divert clean groundwater around a source, or circumferentially around a source, in conjunction with capping, to isolate the contaminated soils and groundwater. Slurry walls and capping have been used to isolate contamination at the Gilson Road Superfund Site, NH (Weston, 1989). A downgradient slurry wall was installed at the Rocky Mountain Arsenal, Denver, CO (CSU, 1988). Alternative materials used for trench/well construction include sheet piling and grout. Sheet pile walls are constructed by driving interlocking steel sheet sections into the ground with pile drivers (USEPA, 1991). Joints can be sealed with hydrated clay or tremie-grouted with clay or neat cement. Sheet piling is faster to install than slurry walls; however, it is difficult to install in rocky soils or in areas with shallow bedrock. It is only economical to install sheet piling to depths of approximately 6 m to 9 m. Grout curtains are formed by injecting liquid grout into soil rock under pressure to reduce the permeability of unconsolidated soil. Particulate grout, also called suspension grout, is a suspension of solid materials—cement, clay, bentonite, or some combination of these. Particulate grouts have large particle size and are only suitable for highly porous sediments and soils. Chemical grouts, on the other hand, consist of silica and alumina-based solutions that gel and harden or polymers that initiate polymerization reactions and harden. The viscosity of chemical grouts is initially low, so it can

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Drain Slurry Wall Waste Groundwater Flow Drain

FIGURE 8.7 Plan view of upgradient wall placement with drain. (USEPA, 1988.)

be pumped into fine-grained soils. To prevent migration of groundwater from under the grout curtain, grouting must extend into low permeability clay or bedrock. Grout curtain materials must be compatible with site subsurface conditions and contaminants. Grout injection points of the curtain can be arranged in three rows. Primary holes form a double line of touching columns. The third line of injections is designed to fill any gaps in the primary injection columns. Holes are typically spaced 1 m to 1.5 m apart. Recently, synthetic high-density polyethylene (HDPE) barriers have been installed for groundwater containment. Specialized trenching machines have been designed to trench and continuously install polyethylene barriers, minimizing the number of seams. HDPE membranes are formulated to resist Secondary Grout Column

Primary Grout Pipe

Basic Cell Secondary Grout Pipe Primary Grout Column FIGURE 8.8 Typical grout curtain layout. (USEPA, 1991.)

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USE OF VERTICAL LINEAR SYSTEM FOR CONTAINMENT AND CAPTURE OF FLOATING CONTAMINANTS

FLOATING CONTAMINANTS

HDPE VERTICAL MEMBRANE CUTOFF WALL “POLYWALL”

HORIZONTAL WELL

NATIVE SOIL BACKFILL OR BENTONITE SLURRY

CEMENT GROUT

CLAY LAYER

FIGURE 8.9 Cross-section of a polyethylene barrier system. (CSU, 1988.)

degradation by sunlight and most contaminants. Sheets are joined together with interlocking waterproof joints. Polyethylene barriers are used to depths of approximately 9 m. The main limitation is the potential for groundwater and contaminants to leak past the barrier. A polyethylene barrier was used in conjunction with free-product (unchanged contaminant from source) recovery and hydraulic control to prevent migration of groundwater contaminants into the Little River in Star Lake, NY. The barrier extends along the riverbank for 400 m and is approximately 5 m deep (Horizontal Technologies, Inc., 1999). 8.5.1.2 Permeable Chemical Barriers Permeable barriers do not impede the flow of groundwater, just the mobility of the contaminant. Barrier material is used to filter, reduce and precipitate Cr(VI), decreasing its toxicity and mobility. Passive systems can be used at

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Zone of remediated groundwater

Chemical plume

Chemical source

Groundwater flow direction

Caisson containing treatment material Zone of remediated groundwater

Chemical plume

Chemical source Groundwater flow direction

FIGURE 8.10 Permeable treatment wall-caissons or large-diameter borings filled with treatment material placed across the path of the Cr plume. (CSU, 1988.)

sites where groundwater flow is slow and contamination is dilute. Types of permeable barriers discussed here include permeable treatment walls and remediation injection technologies. Permeable treatment walls are made of a reactive medium such as Fe(0), Fe2O3, iron sulfide, CaS, or bone char phosphate, all reducing agents for Cr(VI). Alternatively, sorbents such as zeolites, GAC or reactive polymers may be used. When designing a permeable in situ treatment system, five main factors must be examined in detail. These include groundwater characteristics (velocity, flux through the barrier and vertical gradients), stratigraphy (depths and thickness of units, degree of fracturing and channeling), hydrochemistry (contaminant distribution and water chemistry) depositional environment (mineralogy, total organic carbon), and microbiology (GRA, 1999). Several variables affect the overall reduction rate of Cr(VI) by an Fe barrier. The pH is naturally decreased as Cr(VI) is reduced by Fe(II). Low pH may inhibit Cr(III) precipitation. If the pH is increased by the addition of base, and the system is aerobic, Fe(II) will be preferentially oxidized by O2, owing to faster oxidation kinetics at higher pH values. Therefore, detailed bench tests with pH controls and site-specific geochemical conditions is appropriate prior to installing a barrier system. The most common emplacement technique is the conventional trenchand-fill method. In this method, sheet piles, or shoring may be required to keep the trench open while backfilling with treatment materials. Rapid, one-pass trenching machines can excavate and lay the treatment material using a conveyer belt on the trenching machine. No sheet piles or shoring is required in this method. Alternatively, a caisson (canister) can hold the reactive treatment material. Groundwater can flow horizontally through screened sections of the caisson(s), or vertically through the caisson (Warner et al., 1998). When designing the treatment zone, the length of the flow path must correspond to the residence time required within the treatment media. Nonuniform groundwater flow may lead to channeling and higher groundwater velocity zones (Gallinatti and Warner , 1994), resulting in preferential flow paths and less than optimal residence times. The width of the treatment wall or gate must take into account the desired changeout period of the treatment media.

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The funnel and gate barrier design is a hybrid technology of physical barriers that funnel contaminated groundwater through a series of permeable treatment zones (gates). Originally designed by the University of Waterloo, most treatment zones are less than 12 m to 15 m deep. Deeper treatment systems to 21 m to 30 m are possible with more specialized installation equipment. A funnel and gate barrier system was constructed in Sunnyvale, CA to treat solvents in 1994 (Yamane et al., 1995). Preliminary results of a Fe(0) barrier for Cr(VI) at the U.S. Coast Guard Support Center, Elizabeth City, NC indicate that the test barrier has reduced CrO42− in groundwater to less than detection limits (Wilson, 1995). 8.5.2

Vitrification

In situ vitrification (ISV) is accomplished by placed an array of electrodes into the soil and sending an electric current through the soil until it melts, sealing the metals in a glassy mixture. Resistance heating melts the soil. The melt grows outward since the molten soil usually provides additional conductance for the supplied current. An array of four electrodes can treat up to 907 metric tons of contaminated soil to depths of 6 m, at a typical treatment rate of 2.721 metric tons to 5.442 metric tons/h. Larger areas are treated by fusing together multiple individual vitrification zones (Evanko and Dzombak, 1997). ISV is best for areas in which removal of contamination is not possible owing to depth or other physical constraints. Local energy costs are a major consideration for vitrification projects. If the soils are too dry, soil temperature and conductivity enhancements such as flaked graphite or ground glass particles must be placed around the electrodes to provide the initial flow path for the electric current. The first full scale ISV application treated sediments contaminated with metals (Cr, As, Hg, Pb) as well as pesticides and dioxins at the Parsons Chemical/ETM Enterprises Superfund site in Grand Ledge, Michigan. The ISV program required eight separate melt events over a period of 10 days to 20 days for each melt event. A hood was employed to capture volatiles. The treatment was successful, meeting TCLP limits for all the metals in the treated waste (Evanko and Dzombak, 1997). The only commercial ISV technology is offered by Geosafe Corporation. Owing to high costs of ISV, it remains a rarely used technology at Superfund and other hazardous waste sites. Another drawback of ISV is the remaining solidified block of glassy soil—making it not suitable for common tasks such as growing crops. 8.5.3

Solidification/Stabilization

Solidification refers to treatment that solidifies Cr into an immobile mixture with an additive, such as cement. Stabilization, also known as fixation, refers to the formation of an insoluble Cr compound. In addition, the permeability of the area containing the stabilized contamination is lowered, resulting in groundwater flow around the area rather than through it.

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The main concern with stabilization and solidification technologies is longterm stability of Cr. Sometimes Cr(VI) can leach out of the system into groundwater over time or with a change in environmental conditions in the field (e.g., precipitation). Reducing Cr(VI) with S2– prior to solidification/stabilization reduces the chances of remobilization of Cr(VI). Allan and Kukacka (1995) found that stabilization with slag-modified cement grout did not leach as much Cr as lime or Portland cement grout. Leachability decreased as slag content increased. Solidification/stabilization is an option at sites with shallow contamination (maximum depth 2 m to 5 m). A final cost estimate for this technology should take into account the cost of pretreatment chemicals, solidification/stabilization reagents, equipment, labor, local energy rates, testing, and monitoring costs. Solidification and/or stabilization is well established, with over 200 Superfund sites choosing it as a component of soil remediation. Solidification/ stabilization is considered to be the best available technology for Cr remediation in nonwastewater, along with reduction (Evanko and Dzombak, 1997).

8.6

Combining Multiple Approaches to Remediate Chromium

Although it is convenient to group remediation technologies into categories based on their principal mechanism of minimizing exposure to Cr(VI), most remediation strategies combine multiple technologies and mechanisms. For example, toxicity reduction occurs when Cr(VI) is reduced to Cr(III). However, this will also result in containment since Cr(III) will usually sorb or precipitate as a solid. Phytoremediation is a broad term that encompasses all three remediation strategies. Plants take up Cr, removing it permanently from the soil once they are harvested. Plants can also be used to stabilize contamination via reduction that occurs at the roots and subsequent precipitation or adsorption. Finally, this process converts Cr(VI) to Cr(III), reducing the Cr toxicity (Fein et al., 2002). Some remediation strategies employ a variety of different mechanisms owing to the complex nature of biological, geological and chemical processes and interactions. Scientists are just beginning to understand the mechanisms that contribute to remediation. For example, constructed wetlands are emerging as a way to reduce contaminants in a low-tech, natural setting. In a wetland, Cr(VI) will be reduced to Cr(III) and sorb to the soil, or be taken up by plants, algae, or bacteria. Cr may associate with organics or soil particles, and undergo colloidal transport. More hybrid technologies are emerging, as advantages of each technology and the collaborative mechanisms under environmental conditions become apparent. For example, electrokinetics is being employed to enhance biological reduction in the LasagnaTM process. Reversing the polarity of the electrodes periodically leads to contaminant migration back and forth through the bioactive zone. New technologies that synthesize multiple treatment approaches will only continue to emerge in the future.

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Bibliography Allan, M.L. and Kukacka, L.E., 1995, Blast furnace slag-modified grouts for in situ stabilization of Cr-contaminated soil, Waste Management 15, 3, 193–202. Bailey, S.E., Olin, T.J., Bricka, R.M., and Adrian, D.D., 1999, A review of potentially low-cost sorbents for heavy metals, Water Resources, 33, 11, 2469–2479. Bohdziewicz, J., 2000, Removal of Cr ions (VI) from underground water in the hybrid complexation-ultrafiltration process, Desalination, 129, 227–235. Bryant, P.S., Petersen, J.N., Lee, J.M., and Brouns, T.M., 1992, Sorption of heavy metals by untreated red fir sawdust, Applied Biochemistry Biotechnology 34–35, 777–788. Cadena, F., Rizvi, R., and Peters, R.W., 1990, Feasibility studies for the removal of heavy metals from solution using tailored bentonite, in Hazardous and Industrial Wastes, Proceedings of the Twenty-Second Mid-Atlantic Industrial Waste Conference, Drexel University, pp. 77–94. California Regional Water Quality Control Board (CRWQCB), 2000, Waste discharge requirements for in situ pilot-study for the chemical reduction of Cr, Order No. R1–2000–54. Cervantes, C., Campos-Garcia, J., Devars, S., Gutierrez-Corona, F., Loza-Tavera, H., Torres-Guzman, J.C., and Moreno-Sanchez, R., 2001, Interactions of Cr with microorganisms and plants, FEMS Microbiology Reviews, 25, 335–347. Colorado State University (CSU), 1988, Digital operation management model of the north boundary system at the Rocky Mountain Arsenal near Denver, Colorado, Technical report No. 16, Department of Civil Engineering. Corpapcioglu, M.O. and Huang, C.P., 1987, The adsorption of heavy metals onto hydrous activated carbon, Water Resources, 21, 9, 1031–1044. Dikshit, V.P., 1989, Removal of Cr(VI) by adsorption using sawdust, National Academy of Science & Letters, 12, 12, 419–421. Dushenkov, V., Kumar, P.B.A.N., Motto, H., and Raskin, I., 1995, Rhizofiltration: the use of plants to remove heavy metals from aqueous streams, Environment Science and Technology, 29, 5, 1239. Electrokinetics, Inc., 1994, Electro-Klean electrokinetic soil processing, SITE technology profile-demonstration program. Evanko, C.R. and Dzombak, D.A., 1997, Remediation of metals-contaminated groundwater, groundwater Remediation Technologies Analysis Center, Technology evaluation report TE–97–01. Fein, J.B., Kemner, K., Fowle, D.A., Cahill, J., Boyanov, M., and Bunker, B., 2002, Nonmetabolic reduction of Cr(VI) by bacterial surfaces under nutrient-absent conditions, Geomicrobiology Journal, 19, 3, 369–382. Fendorf, S., Wielinga, B.W., and Hansel, C.M., 2001, Reduction of Cr in surface and subsurface environments, contributions of biological and abiological processes, Eleventh Annual V. M. Goldschmidt Conference. Fruchter, J.S., Cole, C.R., Williams, M.D., Vermeul, V.R., Amonette, J.E., Szecsody, J.E., Istok, J.D., and Humphrey, M.D., 2000, Creation of a subsurface permeable treatment barrier using in situ redox manipulation, Groundwater Monitoring and Remediation Review. Gallinatti, J.D. and Warner, S.D., 1994, Hydraulic design considerations for permeable in situ groundwater treatment wells, Ground Water 32, 5, 851.

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Gardea-Torresdey, J.L., Gonzalez, J.H., Tiemann, K.J., Rodriguez, O., and Gamez, G., 1998, Phytofiltration of hazardous cadmium, chromium, lead and zinc ions by biomass of medicago sativa (alfalfa), Journal of Hazardous Materials, 57, 1–3, 29. Groundwater Resources Association (GRA), 1999, Design and implementation of permeable reactive barriers for groundwater treatment, San Francisco CA. Hafiane, A., Lemordant, D., and Dhahbi, M., 2000, Removal of Cr(VI) by nanofiltration, Desalination, 130, 305–312. Hamadi, N.K., Chen, X.D., Farid, M.M., and Lu, M.G.Q., 2001, Adsorption kinetics for the removal of Cr(VI) from aqueous solution by adsorbents derived from used tyres and sawdust, Chemical Engineering Journal, 84, 95–105. Haq, R.U. and Shakoori, A.R., 1998, Short Communication, Microbiological treatment of industrial wastes containing toxic Cr involving successive use of bacteria, yeast and algae, World Journal of Microbiology and Biotechnology, 14, 583–585. Henshaw Associates, Inc., 1998, Pilot-scale GAC treatment study results, Former Remco Hydraulics Facility, Draft memorandum to Mr. John Farr, Ph.D., P.E. from Michael Harrison, P.E. Holman, H.Y.N., Perry, D.L., Martin, M.C., Lamble, G., McKinney, W.R., and HunterCevera. J.C., 1999, Real-time characterization of biogeochemical reduction of Cr(VI) on basalt surfaces by SR-FTIR imaging, Geomicrobiology Journal, 16, 4, 307–323. Horizontal Technologies, Inc., 1999, Case studies and technical information, Matlacha, FL. Hse, W., 1996, metals soil pollution and treatment by hybrid poplar trees, University of Iowa, M.S. thesis, Iowa City. Huang, C.P. and Wu, M.H., 1977, The removal of Cr(VI) from dilute aqueous solution by activated carbon, Water Research, 11, 673–679. Iskandar, I.K., Ed., 2001, Environmental Restoration of Metals-Contaminated Soils, CRC Press/Lewis Publishers, Boca Raton, FL, p. 304. Jacobs, J., Hardison, R.L., and Rouse, J.V., 2001, In situ remediation of heavy metals using sulfur-based treatment technologies, Hydrovisions, 10, 2, 1–4. Jacobs, J., 2001, In situ Liquid Delivery Systems for Chemical Oxidation, Bioremediation and Metals Stabilization, Association for Environmental Health and Sciences, 11th Annual West Coast Conference. on Contaminated Soils, Sediments and Water, San Diego, California, Abstracts. James, B.R., Petura, J.C., Vitale, R.J., and Mussoline, G.R., 1997, Oxidation-reduction chemistry of Cr: relevance to the regulation and remediation of chromatecontaminated soils, Journal of Soil Contamination, 6, 6, 569–580. Katz, S.A. and Salem, H., 1992, The toxicology of Cr with respect to speciation: a review, Journal Applied Toxicology, 13, 217–224. Khan, S.A., Riaz-ur-Rehman, A., and Khan, M.A., 1995, Adsorption of Cr(III), Cr(VI) and silver (I) on bentonite, Waste Management, 155, 4, 271–282. Kumar, P.B.A.N., Dushenkov, V., Motto, H., and Raskin, I., 1995, Phytoextraction: the use of plants to remove heavy metals from soils, Environmental Science and Technology, 29, 5, 1232–1237. Manju, G.N. and Anirudhan, T.S., 1997, Use of coconut fibre pith-based pseudoactivated carbon for Cr(VI) removal, Indian Journal of Environmental Health, 39, 4, 289–298. Masri, M.S., Reuter, F.W., and Friedman, M., 1974, Binding of metal cations by natural substances, Journal of Applied Polymer Science, 18, 675–681.

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Maxwell, C.R., 1997, Investigation and remediation of Cr and nitrate groundwater contamination: case study for an industrial facility, Journal of Soil Contamination, 6, 6, 733–749. McLean, J.S. and Beveridge, T.J., 1999, Chromate removal from contaminated groundwater using indigenous bacteria, in Bioremediation of Metals and Inorganic Compounds, Fifth International In Situ and On-Site Bioremediation Symposium, San Diego, CA, Battelle Press. Nivas, B.R., Sabatini, D.A., Shiau, B. J., and Harwell, J.H., 1996, Surfactant enhanced remediation of subsurface Cr contamination, Water Resources, 30, 3, 511–520. Orhan, Y. and Büyükgüngör, H., 1993, The removal of heavy metals by using agricultural wastes, Water Science Technology, 28, 2, 247–255. Ososkov, V. and Bozzelli, J.W., 1994, Removal of Cr(VI) from Cr contaminated sites by washing with hot water, Hazardous Waste and Hazardous Materials, 11, 4, 511–517. Palmer, C.D. and Wittbrodt, P.R., 1991, Processes affecting the remediation of Crcontaminated sites, Environmental Health Perspectives, 92, 25–40. Palmer, C.D., Wittbrodt, P.R., and Fish, W. 1990, Cr mineral phases at a highly contaminated hard-chrome plating site (abstract). EOS Newsletter of the American Geophysical Union, 71, 36, 1068. Panday, K.K., Prasad, F., and Singh, V.N., 1984, Removal of Cr(VI) from aqueous solutions by adsorption on fly ash – Wollastonite, Journal of Chemical Technology and Biotechnology, 34A, 367–374. Petruzzelli, D., Passino, R., and Tiravanti, G., 1995, Ion exchange process for Cr removal and recovery from tannery wastes, Industrial & Engineering Chemistry Research 34, 2612–2617. Ponder, S.M., Darab, J.G., and Mallouk, T.E., 2000, Remediation of Cr(VI) and Pb(II) aqueous solutions using supported, nanoscale zero-valent iron, Environmental Science and Technology, 34, 12, 2564–2569. Powell, R., Puls, R.W., Hightower, S.K., and Sabatini, D.A, 1995, Coupled iron corrosion and chromate reduction: mechanisms for subsurface remediation, Environmental Science and Technology, 29, 8, 1913–1922. Rai, E., Sass, B.M., and Moore, D.A., 1987, Cr(III) hydrolysis constants and solubility of Cr(III) hydroxide, Inorganic Chemistry, 26, 345–349. Reddy, K.R., Xu, C.Y., and Chinthamreddy, S., 2001, Assessment of electrokinetic removal of heavy metals from soils by sequential extraction analysis, Journal of Hazardous Materials, B84, 279–296. Richard, F.C. and Bourg, A.C.M., 1991, Aqueous geochemistry of chromiun: a review, Water Resources, 25, 7, 807–816. Rock, S. and Beckman, S., 1998, Phytoremediation field demonstrations in the U.S. EPA SITE program, [abstract only], in In Situ and On-Site Bioremediation, Vol. 3, Battelle Press, Columbus, OH. Roy, D., Greenlaw, P.N., and Shane, B.S., 1993, Adsorption of heavy metals by green algae and ground rice hulls: Journal of Environmental Science and Health, A28, 1, 37–50. Salt, D.E., Pickering, I.J., Prince, R.C., Gleba, D., Dushenov, S., Smith, R.D., and Raskin, I., 1997, Metal accumulation by aquacultured seedlings of Indian mustard, Environmental Science and Technology, 31, 1636–9. Salunkhe, P.B., Dhakephalkar, P.K., and Paknikar, K.M., 1998, Bioremediation of Cr(VI) in soil microcosms, Biotechnology Letters, 20, 8, 749–751.

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Santiago, I., Worland, V.P., Cazares-Rivera E., and Cadena, R., 1992, Adsorption of Cr(VI) onto tailored zeolites, 47th Purowing Industrial Waste Conference Proceedings, Lewis Publishers, Chelsea, MI, pp. 669–710. Seaman, J.C., Bertsch, P.M., and Schwallie, L., 1999, In situ Cr(VI) reduction within coarse-textured, oxide-coated soil and aquifer systems using Fe(II) solutions, Environmental Science and Technology, 33, 6, 938–944. Sharma, D.C. and Forster, C.F., 1993, Removal of Cr(VI) using sphagnum moss peat, Water Resources, 27, 7, 1201–1208. Sharma, D.C. and Forster, C.F., 1994, The treatment of Cr wastewaters using the sorptive potential of leaf mould, Bioresource Technology, 49, 31–40. Sharma, D.C. and Forster, C.F., 1995, Continuous adsorption and desorption of Cr ions by sphagnum moss peat, Process Biochemistry, 30, 4, 293–8. Sylvester, P., Rutherford, L.A. Jr., Gonzalez-Martin, A., and Kim, J., 2001, Ferrate treatment for removing Cr from high-concentration radioactive tank waste, Environmental Science and Technology, 35, 1, 216–221. Thornton, E.C. and Amonette, J.E., 1999, Hydrogen sulfide gas treatment of Cr(VI)contaminated sediment samples from a plating-waste disposal site—implications for in situ remediation, Environmental Science and Technology, 33, 22, 4096–4101. Tummavuori, J. and Aho, M., 1980, On the ion-exchange properties of peat, part II: on the adsorption of alkali, earth alkali, aluminum (III), Cr(III), iron (III), silver, mercury (II) and ammonium ions to the peat, Suo, 31, 2–3, 45–51. U.S. Department of Energy (USDOE), 1996, LasagnaTM soil remediation, Innovative Technology Summary Report, Office of Environmental Management, Office of Science and Technology. U.S. Department of Energy (USDOE), 2000, In situ redox manipulation, Innovative Technology Summary Report DOE/EM-0499, Office of Environmental Management, Office of Science and Technology. U.S. Environmental Protection Agency (USEPA), 1985, Modeling remedial actions at uncontrolled hazardous waste sites, Washington DC, EPA/540/2–85/001. U.S. Environmental Protection Agency (USEPA), 1986a, Record of Decision for Novaco Industries, Temperance, MI, EPA ID MID084566900. U.S. Environmental Protection Agency (USEPA), 1986b, Record of Decision for United Chrome Products, Inc., Corvallis, OR, EPA ID ORD009043001. U.S. Environmental Protection Agency (USEPA), 1988 from Figures 8.5–8.7. U.S. Environmental Protection Agency (USEPA), 1989a, Record of Decision for Coast Wood Preserving, Ukiah, CA, EPA ID CAD063015887. U.S. Environmental Protection Agency (USEPA), 1989b, Record of Decision for the Kysor Industrial Corp. Superfund Site, Cadillac, MI, EPA ID MID043681840. U.S. Environmental Protection Agency (USEPA), 1991, Stabilization technologies for RCRA corrective actions handbook, Office of Research and Development, Washington DC, EPA/625/6–91/026. U.S. Environmental Protection Agency (USEPA), 1995, Record of Decision for Quality Plating, Sikeston, MO, EPA ID MOD980860555. U.S. Environmental Protection Agency (USEPA), 1997, Recent developments for in situ treatment of metal contaminated soils, Office of Solid Waste and Emergency Response. U.S. Environmental Protection Agency (USEPA), 1999, Record of Decision for Ace Services, Colby, KS, EPA ID KSD046746731.

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U.S. Environmental Protection Agency (USEPA), 2000a, Electrokinetics at Site 5, Naval Air Weapons Station, Point Mugu, CA, Cost and Performance Report. U.S. Environmental Protection Agency (USEPA), 2000b, In situ treatment of soil and groundwater contaminated with Cr, technical Resource Guide, Office of Research and Development, Washington, DC, EPA/625/R–00/005, October, in review of Sturges, S.G. Jr., McBeth, P. Jr., and Pratt, R.C., Performance of soil flushing and ground-water extraction at the United Chrome Superfund Site, Journal of Hazardous Materials 29, 59–78, 1992. U.S. Environmental Protection Agency (USEPA), 2000c, Record of Decision for Boomsnub/Airco, Vancouver, WA, EPA ID WAD009624453. U.S. Filter Recovery Services, Inc., 2001, The removal of Cr from groundwater using ion exchange, Locus Technologies Project #98–002, FMC–Fresno Site, prepared for Locus Technologies, Inc. Vermeul, Vince, R., Williams, Mark D., Szecsody, Jim E., Fruchter, and John S., 2002, In situ redox manipulation pilot field test: remedial design support for ISRM barrier deployment, Frontier Hard Chrome Superfund Site, Vancouver, WA. Visvanathan, C., Aim, R.B., and Vigneswaran, S., 1989, Application of cross-flow electro-microfiltration in Cr wastewater treatment, Desalination, 71, 265–276. Warner, S.D., Yamane, C.L., Galinatti, J.D., and Hankins, D.A., 1998, Considerations for monitoring permeable groundwater treatment walls, Journal of Environmental Engineering, pp. 524–529. Weston Inc., 1989, Remedial program evaluation, Gilson Road Site, Nashua, NH, Prepared for New Hampshire Department of Environmental Service (NHDES). Wilson, E.K., 1995, Zerovalent metals provide possible solution to groundwater problems, Chemical and Engineering News, 73, 27, 19–22. Yamane, C.L., Warner, S.D., Gallinatti, J.D., Szerdy, F.S., Delfino, T.A., Hankins, D.A., and Vogan, J.L., 1995, Installation of a subsurface groundwater treatment wall composed of granular zero-valent iron, American Chemical Society 209th National Meeting, 35, 1, 792–795. Zarraa, M.A., 1995, A study on the removal of Cr(VI) from waste solutions by adsorption on to sawdust in stirred vessels, Adsorption Science and Technology, 12, 2, 129–138. Zayed, A., Gowthaman, S., and Terry, N., 1998, Phytoaccumulation of trace elements by wetland plants: I. Duckweed, Journal of Environmental Quality, 27, 3, 715–717.

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9 Bench Tests

CONTENTS 9.1 In Situ Reduction of Aquifer Sediments to Create a Permeable Reactive Barrier to Remediate Chromate (CrO42−): Bench-Scale Tests to Determine Barrier Longevity...................................................................312 Jim E. Szecsody, John S. Fruchter, Vince R. Vermeul, Mark D. Williams, and Brooks J. Devary 9.1.1 Introduction....................................................................................313 9.1.2 Geochemical Reactions of In Situ Chromate (CrO42−) Remediation ...................................................................................314 9.1.2.1 Fe Reduction Mechanism ..............................................315 9.1.2.2 Sediment Oxidation and CrO42− Immobilization .......317 9.1.2.2.1 Chromium Reduction/Precipitation .........317 9.1.2.2.2 Chromium Immobilization and pH ..........320 9.1.2.2.3 Chromium Reduction Rate .........................320 9.1.2.2.4 Chromium Sorption .....................................321 9.1.2.2.5 Cr Mobility upon Oxidation.......................321 9.1.3 Experimental Methods .................................................................322 9.1.3.1 Sediments and Fe Phase Measurements.....................322 9.1.3.2 Sediment Reduction by S2O42− in Column Systems.........................................................323 9.1.3.3 Sediment Oxidation in Columns..................................324 9.1.4 Results and Discussion.................................................................325 9.1.4.1 Fe Phase Changes during Reduction ..........................325 9.1.4.2 Superfund Site Physical Properties..............................326 9.1.4.3 Superfund Site Sediment Reduction ...........................327 9.1.4.4 Superfund Site Sediment Oxidation and Chromate (CrO42−) Barrier Longevity.............................................328 9.1.4.5 Field Scale Considerations of Chromate (CrO42−) Barrier Longevity.............................................329 9.1.5 Conclusions ....................................................................................332 Bibliography ...............................................................................................332 9.2 Bench Scale Evaluation of Ex Situ and In Situ Chromium(VI) Remedial Methods.....................................................................................335 Angus McGrath, Daniel Oberle, David Schroder, John McInnes and Chris Maxwell 1-5667-0608-4/05/$0.00+$1.50 © 2005 by CRC Press LLC

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9.3

9.1

Introduction....................................................................................335 Chromium Geochemistry ............................................................335 Aqueous Treatment Reagents .....................................................336 Solid Treatment Reagent ..............................................................339 Reductant Stoichiometry and Reaction Kinetics......................340 Reductant Treatment and Solids Generation............................341 Soil Reductant Demand ...............................................................341 Test Results.....................................................................................342 9.2.8.1 Analysis of Particles (Results) ......................................343 9.2.8.2 Soil Reductant Demand Results...................................345 9.2.8.3 Reactive Permeable Barrier ...........................................346 9.2.9 Conclusions ....................................................................................346 Bibliography ...............................................................................................348 Assessing the Potential for Biological Chromium(VI) Reduction in an Aquifer Contaminated with Mixed Wastes ................................348 Sarah Middleton Williams, Craig S. Criddle, and Michael J. Dybas 9.3.1 Introduction....................................................................................348 9.3.2 Materials and Methods ................................................................349 9.3.2.1 Microcosms ......................................................................349 9.3.2.2 Enrichment Culture ........................................................350 9.3.2.3 Analytical Methods ........................................................350 9.3.3 Results and Discussion.................................................................350 9.3.3.1 Simultaneous Cr(VI) and NO3− Reduction in Schoolcraft Microcosms ............................................350 9.3.3.2 Cr(VI) Reduction during Denitrification in Schoolcraft Enrichments ...........................................352 9.3.3.3 Cr(III) Solubilization.......................................................352 9.3.4 Conclusions ....................................................................................355 Acknowledgments .....................................................................................356 Bibliography ...............................................................................................356

In Situ Reduction of Aquifer Sediments to Create a Permeable Reactive Barrier to Remediate Chromate (CrO 42−): Bench-Scale Tests to Determine Barrier Longevity

Jim E. Szecsody, John S. Fruchter, Vince R. Vermeul, Mark D. Williams, and Brooks J. Devary Laboratory experiments showed that chemical reduction yielded a redox capacity (0.26% iron(II)) that falls within the range of values observed in sediments analyzed from sites where field-scale deployment of the in situ redox manipulation

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technology is currently in progress or being considered (0.1% Hanford 100D area, 0.24% Ft Lewis, 0.4% Moffett Federal Airfield). There was relatively little spatial variability in reducible iron (Fe) content between the three aquifer units. This mass of reducible Fe represents a sufficient quantity for a treatment zone emplaced to remain anoxic for 430 pore volumes, which would be expected to last 10 of years, depending on aquifer flow rates and the concentration of oxidizing species in the groundwater. The geochemical analysis also indicated relatively low spatial variability in reducible Fe content although some depth dependent variability was indicated. Variation in the CrO42− concentration and flow rates between the A1 and A2 aquifer units indicated the necessity for greater reduction in the A2 aquifer unit, in order that both aquifer units prevent offsite CrO42− migration for the same amount of time. Results from these laboratory analyses of sediment core samples are used in conjunction with: (1) site specific geologic information obtained during installation of monitoring wells; (2) results from hydraulic tests conducted at the site; (3) electromagnetic borehole flow meter testing results; (4) results from a conservative tracer injection test; and (5) results of a series of S2O42− injection simulations of the field site, to develop a S2O42− injection strategy for deployment of the ISRM technology at sites to prevent offsite CrO42− migration. 9.1.1

Introduction

Groundwater remediation using permeable reactive barriers or wells (McNab et al., 2000) offers a significant economic advantage of in situ treatment while relying on chemical technologies proven in industrial settings (Eary and Rai, 1988). Reactive barriers for reduction of metals and dechlorination of organic solvents are being implemented using primarily elemental Fe (Fe(0)) (Devlin and Muller, 1999; Waybrant et al., 1998), Fe-Cr (Appleton, 1996), and by reduction of natural sediments (Fruchter et al., 2000). Permeable reactive Fe barriers become less reactive over time, partially owing to changes in the surface chemistry and electron transfer mechanism (Seaman et al., 1999). The elemental Fe surface may act as a catalyst, a semiconductor, or provide the necessary surface coordination for the electron transfer reactions (Scherer et al., 1999; Wehrli, 1992). The electron donor may be Fe(0) (Hung and Hoffman, 1998), in which case the buildup of Fe(II) oxyhydroxides that occurs (Farrell et al., 2000) would dramatically decrease reduction efficiency. The association of CrO42− reduction with Fe(II) on Fe(0) surfaces (Blowes et al., 1997; Pratt et al., 1997) may indicate the Fe(II) phase is acting as an electron transfer species. The Fe(II) phases on the Fe(0) surface (Genin et al., 1998) are also electron donors, which may partially explain the increased reduction efficiency for “aged” Fe(0). While CrO42− can be reduced by aqueous Fe(II), the abiotic dechlorination of trichloroethene (TCE) requires Fe(II) as an electron donor and the presence of an Fe oxide or elemental Fe surface (Balko and Tratnyek, 1998), implying specific surface conditions are required for electron transfer.

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Although permeable Fe(0) barriers have significant electron donor capacity, some of the loss in barrier reactivity (Sivavec et al., 1996) is caused by physical and other secondary effects. The presence of reducible compounds such as nitrate (NO3−) in the groundwater have been shown to reduce barrier efficiency (Farrell et al., 2000; Gu et al., 1999) by competing for electrons with the contaminant of interest. The passivation of the Fe surfaces, however, is related to how strongly Fe oxide and mixed-metal oxides are complexed with existing aqueous ions and attach to surfaces, blocking further reduction (Farrell et al., 2000). CrO42− reduction will form insoluble Cr(III) and Cr(III)/Fe(II) precipitates (Pratt et al., 1997; Loyaux-Lawniczak et al., 2000) that clog surfaces, permanently reducing the Fe(0) donor capacity. The impact of these physical processes may be less on reduced natural sediments since precipitates would be more spread out with the low Fe content of reduced natural sediments. Iron oxides are ubiquitous in the subsurface environment, and because they can be chemically and biologically reduced, may represent an efficient means to create in situ redox reactive barrier at great depth. The S2O42− chemical treatment dissolves and reduces amorphous and some crystalline Fe(III) oxides, producing mainly one or more Fe(II) species. The longevity of a reduced sediment barrier is dependent on the mass of reduced species and rate of inflow of dissolved oxygen and other contaminants such as CrO42−, TCE, NO3−, uranium (U) (Szecsody et al., 2001). In relatively uncontaminated aquifers, dissolved oxygen in water is the dominant oxidant. This study describes laboratory-scale investigations of the chemical and physical processes that occur during chemical reduction of natural sediments for the purpose of providing the geochemical information needed to design a pilot-scale in situ redox manipulation (ISRM, U.S. patent #5,783,088) injection at the several CrO42−-contaminated sites. These data will also be used during any required refinements to the design for full-scale deployment of the technology and as an initial estimate of barrier longevity. The specific objectives of this study are: (1) determine the average reducible Fe content of sediments in the barrier zone at the site and (2) assess the spatial variability of the reducible Fe content. In addition to these primary objectives, several sediment physical properties will be measured. Results from these experiments will be used in conjunction with other geologic, geochemical, and hydraulic characterization data to develop the design for a field-scale injection. 9.1.2

Geochemical Reactions of In Situ Chromate (CrO42−) Remediation

The in situ geochemical reduction technology being tested on sediments in this study is based on the immobilization of CrO42− by a permeable reactive barrier containing reduced sediment. The geochemical reduction of CrO42−, Cr(VI) to Cr(III) occurs by Fe(II), which is created by the ISRM process within the reduced treatment zone. The reduced sediment zone is created by the injection of an aqueous reductant, Na2S2O4, through a standard groundwater well. The longevity of the reduced zone depends on the oxidation of the

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Fe(II) by CrO42− and other electron acceptors, such as dissolved oxygen, during the natural advection of groundwater through the treatment zone. 9.1.2.1 Fe Reduction Mechanism The ISRM technology utilizes existing Fe in aquifer sediment that is chemically treated with a reductant (Na2S2O4 buffered at high pH) for a short time into the contaminated sediment (typically 24 h to 60 h ) to reduce Fe(III)-oxides present in the sediment to adsorbed or structural Fe(II) phases. This reduction process of aquifer sediments result in the groundwater redox conditions becoming reducing and the disappearance of dissolved oxygen in water. Reduced Fe phases in sediment by this chemical treatment may behave similarly as permeable elemental Fe walls for some reactions such as TCE dechlorination (Szecsody et al., 2000; Vermeul et al., 2000) and CrO42− reduction (Fruchter et al., 2000). Elemental Fe/mixed metal barriers also rely on the oxidation of iron(II) (adsorbed or Fe(II) minerals such as green rust; Genin et al., 1998) to Fe(III) as the electron donor for remediation of chlorinated aliphatic contaminants (Balko and Tratnyek, 1998; Johnson et al., 1998) or reduction of metals such as CrO42− (Blowes et al., 1997; Burge and Hug, 1997), and not the oxidation of Fe(0). While aqueous Fe(II) can reduce CrO42− (Eary and Rai, 1988), adsorbed or structural Fe(II) on an Fe(III)-oxide, clay surface, or elemental Fe surface is necessary for dechlorination reactions, although the role of the surface is not clearly understood. The S2O42− chemical treatment dissolves and reduces amorphous and some crystalline Fe(III) oxides. The reduced Fe(II) created by the S2O42− chemical treatment appears to be present in several different Fe(II) phases: adsorbed Fe(II), FeCO3 (siderite), and iron(II) sulfide (FeS) although adsorbed Fe(II) appears to be the dominant Fe(II) phase. There may be other, unidentified Fe(II) mineral phases produced. Although more than one Fe(III) phase is likely reduced in a natural sediment, it can be useful to determine how simple a chemical model is needed to generally describe the observations. Below is a net ionic reaction/mechanism that describes a single phase of Fe that is reduced by Na2S2O4. (Here, Na+ is a “spectator” ion and SO2− is an ion radical—unstable.) ← 2SO2⋅− S2O42− →

(9.1.1)

← Fe2+ + SO32− + 2H+ SO2⋅− + Fe3+ + H2O →

(9.1.2)

Laboratory measurements show that the forward rate is a function of the S2O42− concentration and the square of the reducible Fe concentration (rate is overall a third-order function of concentration; Figure 9.1.1). The aqueous Fe(II) produced has a high affinity for surfaces, so is quickly adsorbed. Therefore, Fe(II) mobility in mid- to high pH, low ionic strength groundwater is extremely limited, and Fe is not expected to leach from sediments during the S2O42− treatment. Aqueous Fe measurements in previous studies have shown <1% Fe leaching even after 600 pore volumes of groundwater through a sediment column. Corresponding

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Dithionite (mol/L)

0.045 third-order model

0.040 0.035 0.030

first-order model

0.025 0.020 0

2

4

6

8

10

time (h) (a)

0

1

2

pore volume 3

4

5

Fe(II) /Fetotal

0.05

dithionite data

0.8

0.04

model

0.6

0.03 fraction reduced iron

0.4

0.02

0.2

0.01

dithionite (mol/L)

1.0

0

0.0 0

4

8

12

16

20

24

time (h) (b) FIGURE 9.1.1 Rate of sediment reduction as shown by batch dithionite consumption by sediment (a) and dithionite consumption during 1-D transport. Lines are first- or third-order reaction rate simulations.

solid Fe measurements of sediments used in these columns showed 4% to 10% loss of Fe. Fe mobility is somewhat higher during the actual S2O42− injection, as a high ionic strength solution of other cations (~0.3 mol/L in this case) compete for the same adsorption sites as Fe2+, so cause some Fe2+ desorption. Previous experimental transport studies with S2O42− injection into sediments have shown 0 to 12% Fe loss after 40 pore volumes of S2O42− treatment. Experimental evidence from previous studies with Hanford sediments have shown that two S2O42− parallel reduction reactions are needed to describe Fe oxidation data (i.e., a oxidized and a fraction more slowly oxidized, next section). This may be the result of the reduction of two or more major Fe(III) phases, such as the production of adsorbed Fe(II) and siderite. If the number of slowly reducing sites is small and the mass of Fe is far in excess of the S2O42− (Equation 9.1.1 and Equation 9.1.2) can be reduced to a first-order reaction in

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which Fe3+ remains constant. Another reaction occurs in the system, which describes the disproportionation of S2O42− in contact with sediment: ← S2O32− + 2HSO3− 2S2O42− + H2O →

(9.1.3)

accounts for the mass loss of S2O42− that cannot be used for Fe reduction. Previous studies have shown that this reaction has a half-life of ~27 h (basaltic sediments). The consequence of this reaction is to limit how slowly S2O42− can be reacted with (i.e., injected into) sediment in the field. If S2O42− is injected too slowly, a significant amount of the mass is lost to disproportionation. Although Fe(III) phases are the most significant phase that reacts with S2O42−, other mineral phases present in natural sediments may also be reduced, and utilize some of the S2O42−. Previous studies have shown that some Mn reduction occurs as a result of the S2O42− treatment of Hanford sediment, although reduced Mn(II) phases were only 3% to 4% relative to reduced Fe phases. 9.1.2.2

Sediment Oxidation and CrO42− Immobilization

9.1.2.2.1 Chromium Reduction/Precipitation The oxidation of the adsorbed and structural Fe(II) in the sediments of the permeable redox barrier occurs naturally by the inflow of dissolved oxygen through the barrier, but can additionally be oxidized by contaminants that may be present such as CrO42−, dissolved O2, NO3−, U, pertechnetate (TcO4−), or TCE other electron acceptors. If redox equilibrium completely defined the mechanism (i.e., no effects from activation energies or surface catalysis) and contaminants are present in equal molar concentrations, they would be reduced in the following order: CrO42− > dissolved O2 > NO3− > U > TcO4− > TCE In most aquifers, dissolved oxygen in water is the dominant oxidant of reduced Fe, as contaminants are generally present in lower molar concentrations relative to dissolved oxygen. The oxidation of reduced Fe in pure mineral phases is described by the following reactions first by dissolved oxygen, then with other contaminants. Fe(II) species that are known to exist in the S2O42−-reduced sediments include adsorbed Fe(II) and siderite (FeCO3). A single mole of electrons is consumed as a mole of these species are oxidized: ←Fe3++e− Fe2+ →

Eh=−0.771V

← Fe(OH)3(s) + 2H+ + HCO3− + e− FeCO3(s) + 3H2O →

(9.1.4) (9.1.5)

The use of dissolved oxygen as an oxidant is generally divided into two electron sequences, which combined: ← H2O O2 + 4H+ + 4e− →

Eh = +1.23 V

(9.1.6)

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show that four moles of electrons are needed per mole of O2 consumed. The rate of this reaction (Equation 9.1.6) has generally been observed to be firstorder at fixed pH and the rate increases 100 fold for a unit increase in pH. Experimental evidence during Fe oxidation experiments indicates that two differing reduced Fe entities are present (adsorbed Fe(II) and siderite). Combining the two Fe oxidation half-reactions with oxygen reduction: ← 4Fe3+ + H2O 4Fe2+ + O2 + 4H+ →

Eh = −1.85 V

(9.1.7)

← 4Fe3+ + 4CO32− + 2H2O 4FeCO3(s) + O2 + 4H+ →

(9.1.8)

yield 4 moles of Fe(II) are oxidized and 4 moles of electrons transferred per mole of O2 consumed. At oxygen-saturated conditions (8.4 mg/L O2, 1 atm, 25 °C),

0 1.0 1.0

100 200

O22 O

0.8 0.8

oxygen saturation

100

pore pore volume volumes 300 200

400

300500

600400

2400200

250 3200

v = 0.11 cm/h 1.9 cm/h

0.6 0.6 0.4 0.4 0.2 0.2 0.0 0.0 ––0.2 0.2 0

50 800

100 1600 time time(h) (h)

150

(b) (a)

reducedsaturation fraction or oxygen oxygen saturation

00 1.0 1.0 0.8 0.8

100 50

150 400

500 200

600

v = 23 cm/h v = 1.9 cm/h

OO2 2

0.6 0.6 0.4 0.4

pore pore volume volumes 100300 200

model

Fe(II)/[Fe(II) + Fe(III)]

dissolved oxygen

0.2 0.2 0.0 0.0

data

––0.2 0.2 00

50

50 100 time (h) (h) time

150 100

200

150 250

(c) (b)

FIGURE 9.1.2 Oxidation of dithionite-reduced sediment by dissolved O2 in 1-D column experiments with differing velocities resulting in different contact times: a) 60 h, b) 1.9 h, and c) 0.2 h. Oxidation simulated with a model that considers fast and slow oxidation by dissolved oxygen as shown in (c) for dissolved oxygen and fraction of reduced iron. The Eh of the effluent solution during sediment oxidation (d, same experiment as b) also illustrates partial oxidation of a fraction of the surface sites transport. Lines are first- or third-order reaction simulations.

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50

reduced fraction or oxygen saturation

1.0 0.6

150

200

v = 23 cm/h

O2

0.8

100

model

0.4

Fe(II)/[Fe(II) + Fe(III)]

dissolved oxygen

0.2

data

0.0 –0.2 0

50

100

150

time (h)

(c) pore volume 0

100

200

300

400

500

600

v = 1.9 cm/h

Eh 0 Eh (mV)

200

oxygen-free water std

–200

oxygen-saturated water = +400 mV

–400 dithionite injection solution –600 0

50

100

150

200

250

time (h)

(d)

FIGURE 9.1.2 (Continued)

1.05 µmol/L Fe(II) is consumed. Experimental evidence indicates that the oxygenation of Fe(II) in solutions (pH >5) is generally found to be first-order with respect to Fe(II) and O2 concentration and second-order with respect to OH−. The rate of oxidation of aqueous Fe2+ by oxygen at pH 8 is a few minutes (Eary and Rai, 1988; Buerge and Hug, 1997). In contrast, the oxidation rate (as a halflife) observed in natural sediments (surface Fe(II) phases mainly adsorbed Fe(II) and Fe(II)CO3) was found to be 0.3 h to 1.1 h (Figure 9.1.2). Oxidation of sediments is best described with the majority (~80%) of the sites being quickly oxidized (half-life ~10 min) and a second smaller fraction of sites that are slowly oxidized (half-life = 1.1 h), as illustrated in Figure 9.1.2. It is hypothesized that the quickly oxidizing iron(II) are adsorbed Fe(II) and the slowly oxidizing Fe(II) may be siderite, based on both this modeling and Fe extraction data described in the results section. Hydrogen chromate present as a contaminant in groundwater will also oxidize Fe(II) ← Cr3+ + 4H2O HCrO4− + 7H+ + 3e− →

(9.1.9)

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with 3 moles of electrons consumed per mole of CrO42− reduced. Cr3+ readily precipitates and is extremely difficult to oxidize under natural conditions, so remains permanently immobilized in the aquifer. Cr(VI) species that exist under highly oxidizing conditions are rapidly reduced to Cr(III) species (rate described below). Over much of the pH range of natural waters, a Cr(OH)3 precipitate should form, with the small amount of aqueous Cr(III). An Fe-reducing or sulfur-reducing environment (biologically or abiologically created) exhibits an order of magnitude or more less solubility, because when Cr(III) is precipitated as a mixed (Cr,Fe)(OH)3 precipitate, it has lower solubility. This effect was demonstrated in a series of mixed solubility experiments, where a lower fraction of Cr in the precipitate has much lower solubility than pure Cr(OH)3 (Sass and Rai, 1987). The ratio of Cr/Fe in precipitates has also been quantified (Eary and Rai, 1988; Loyaux-Lawniczak et al., 2000; Patterson and Fendorf, 1997). 9.1.2.2.2 Chromium Immobilization and pH While the three example sites provided where the ISRM technology has been previously demonstrated cover the pH range from 6.5 to 8.3, evidence exists that aquifers at a pH as low as 4.1 will also reduce and form Cr(III) precipitates that remain immobile. Under highly acidic conditions, CrOH2+ and other aqueous Cr(III) species should form, so reduction does not result in precipitates. For a pure laboratory system containing only Cr(VI), these mobile Cr(III) species form at a pH <4.3. As described above, the mixed (Cr,Fe) hydroxides that form have lower solubilities, so sediments with Fe reducing conditions typically have a large excess of Fe(II) relative to the CrO42−. For example, the Superfund site with 10 ppm CrO42− has 2,500 times more Fe(II) (46.1 µmol/g reducible Fe), which demonstrates why precipitates will typically contain a small Cr fraction. In a weathered shale (Jardine et al., 1999), natural Fe(II) present in the sediment at pH 4.6 results in significant CrO42− reduction and permanent immobilization, based on long-term (10 month) 1-D column laboratory transport studies. At a landfill in northern France, Fe(II) in green clay at pH 4.1 has also resulted in the reduction and precipitation of Cr(VI) species (Loyaux et al., 2001). In contrast, at a pH of 3.0, Cr(III) remained in aqueous solution in an aquifer (Seaman et al., 1999), possibly owing to acetate (C2H3O2−) or SO42− complexation. Reduction and precipitation of Cr(VI) has also been demonstrated in the laboratory with amorphous Fe sulfide from pH 5 to pH 8 (Patterson and Fendorf, 1997), with mackinawite (FeS) at pH 5 (Boursiquot et al., 2002), and with hydrogen sulfide (H2S) from pH 6.5 to pH 10 (Kim et al., 2001). At sites such with sufficient organic matter, sufficient reducing conditions can exist in specific localized zones (lignite deposits, for example, Murphy et al., 1992) that could reduce Cr(VI). 9.1.2.2.3 Chromium Reduction Rate The rate of Cr(VI) reduction by Fe(II) has been extensively studied in a variety of geochemical conditions. For a pH 4.4 to 7.2, the Cr(VI) reduction

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rate decreases from seconds at pH 7 to about three orders of magnitude less at pH 4.4 (Buerge and Hug, 1997). At a pH >10, and at lower pH in solutions containing significant phosphate (PO43−), CrO42− is less efficiently reduced by Fe(II) (Eary and Rai, 1988). In a field system, both Fe(II) and organic matter appear to influence the rate of Cr(VI) reduction, and a faster rate was observed with lower pH in one case (Anderson et al., 1994). The rate of Cr(VI) reduction by H2S increases significantly with decreasing pH between pH 6.5 and pH 10, potentially owing to the dependence of the reduction on the concentration of H2S (Kim et al., 2001). Data describing the rate of Cr(VI) reduction by iron sulfide materials are limited. 9.1.2.2.4 Chromium Sorption At neutral and alkaline pH, CrO42− moves nearly unretarded in aquifers (Fruchter et al., 2000), whereas under acidic conditions, considerable CrO42− sorption has been observed (Zachara et al., 1987; Jardine et al., 1999; Seaman et al., 1999). At a pH of 4.6 in a weathered shale, nonlinear sorption with an affinity parameter of 15.6 was observed (S (sorbed mass) = 15.6C0.61, where C = aqueous CrO42− mass). This sorption increased four fold with the addition of natural organic matter (i.e., S = 65C0.39), indicating in this case, it appears that sorption was dominated by organic matter. Interestingly, this same sediment also exhibited some reduction of CrO42−, which did not change with the addition of organic matter. Two sediments from the Savannah River site (pH 5.3 and pH 5.52) exhibited some sorption, but apparently not related to natural organic matter (NOM). At high NOM (0.76 g/100 g), little sorption was observed (Kd = 0.1 cm3/g), whereas at low NOM (0.02 g/100 g), moderate sorption was observed (Kd = 1.5 cm3/g; Seaman et al., 1999). 9.1.2.2.5 Cr Mobility upon Oxidation While the precipitation of (Fe,Cr)(OH)3 as the result of the remediation process might reduce the availability of Fe2+ for further reactions, this process is insignificant. Over the barrier lifetime, CrO42− is reduced and precipitated as the Fe2+ species are slowly oxidized by mainly dissolved oxygen and some by CrO42−. As demonstrated in a long term column experiment (Figure 9.1.3, Szecsody et al., 1999), the (Fe,Cr)(OH)3 remains immobile even in fully oxic systems for >1,800 pore volumes, so there is a potential for coatings of precipitated minerals forming and remaining in the barrier zone. However, at the anticipated maximum CrO42− concentration of 5 mg/L (based on the treatment goal for the selected source term remediation alternative), this effect will not be large enough to significantly effect the physical or geochemical properties or significantly alter the function of the barrier. For example, based on a previous analysis of this effect for sediments, if CrO42− were present at 200 mg/L and the barrier had sufficient redox capacity to last 170 pore volumes, only 1% of the pore space would be occupied with Cr(OH)3 precipitated over the life of the barrier.

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9.1.3

Experimental Methods

9.1.3.1 Sediments and Fe Phase Measurements Batch and column experiments were conducted to quantify the reductive dissolution of Fe phases on natural sediments with S2O42−. The two silty gravel sediments (glacial) are from a confined aquifer (18.3 m depth) in Tacoma, Washington, the silty sand (estuarine) is from a confined aquifer (19.8 m depth) in Palo Alto, California, and the sandy gravel (fluvial) is from an unconfined aquifer (29.0 depth) on the Hanford Site in Eastern Washington. The subsurface sediments are treated with a reductant solution which consisted of laboratory grade 0.001 to 0.1 mol/L Na2S2O4 (synonym: sodium hydrosulfite; CAS 777514-6), 0.001 to 0.4 mol/L K2CO3, and 0.0001 mol/L to 0.01 mol/L KHCO3. The carbonate (CO32−) was four times and the hydrogen carbonate (HCO3−) 0.4 times the dithionite (S2O42−) concentration, so that the pH does not decrease during reduction. The reaction of S2O42− with sediment generates 4 moles of H+ (Equation 9.1.1 and Equation 9.1.2) and with 4 moles of K2CO3 (relative to S2O42−), the pH will remain relatively constant to prevent Fe mobilization at low pH. Fe extractions conducted on untreated and S2O42−-treated sediments (Table 9.1.1) in an anaerobic chamber consisted of: (1) 1 mol/L CaCl2 (Fe(II) ion exchangeable); (2) 0.5 mol/L HCl (Heron et al., 1994a); (3) hydroxyl amine chloride [NH3 OH]Cl (Chao and Zhao, 1983); (4) ammonium oxalate ((NH4)2C2O4); (5)Ti-EDTA (Heron et al., 1994b); (6) S2O42−-citrate-hydrogen carbonate (DCB); and (7) 5 mol/L HCl. Aqueous Fe(II) and Fe(III) from extractions was quantified by ferrozine (Gibbs, 1976). The FeCO3/FeS was defined by the 0.5 mol/L HCl minus the 1 mol/L CaCl2 extraction. Amorphous and poorly crystalline Fe(III) oxides were defined by the ammonium oxalate ((NH4)2C2O4) and [NH3OH]Cl extractions, and crystalline Fe(III) oxides were defined by the

pore volume

Cr(VI) species (ppm)

0 3.0

400

800

1200

1600

Cr(VI) species influent

2.0 v = 4.6 cm/h Hanford Fm. sediment

1.0

Cr(VI) species effluent 0.0 0

1000

2000

3000

4000

time (h) FIGURE 9.1.3 Permanent CrO42− immobilization of a reduced sediment column (0 to 800 pore volumes) that is being oxidized for 1,800 pore volumes. The mass of chromate reduced/precipitated in the first 800 pore volumes (43 mg) remained immobilized during the next 1,000 pore volumes of water in the oxic sediment column (800 to 1,800 pore volumes).

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DCB minus the NH2OH, HCl extraction (Heron et al., 1994a). Total Fe(II) and Fe(III) oxides and carbonates were defined by the 5 mol/L HCl extraction. Ethylene glycol monoethyl ether (EGME) was used to measure total surface area on untreated and reduced sediments. The sediment dry bulk density and porosity were measured on the intact cores (i.e., whole sediment properties) as well as the <4 mm sieved fraction used in reduction/oxidation experiments, as described below. As cores were unpacked, the wet mass, dry mass, and core volume were used to calculate the dry bulk density and porosity. Both porosities were needed to relate the geochemical results of laboratory experiment to the field scale sediment. The entire sediment size fraction was not used in laboratory experiments because large cobbles exhibit essentially no geochemical control (i.e., the surface area of gravels are extremely small relative to clays), and experiments of this scale would not be practical. Sediment oxidation experiments (described below) for 1,200 pore volumes would take considerable time with a column containing the full sediment size fraction, so the <4 mm size fraction was used. The sediment size fractions were determined by ASTM sieve analysis and additionally by hydrometer analysis to accurately determine the clay fraction. 9.1.3.2

Sediment Reduction by S2O42− in Column Systems

Sediment reduction studies conducted in 1-D columns consisted of injecting the S2O42− solution at a steady rate into a sediment column and measuring the concentration of S2O42− over time in the effluent for 120 h to 160 h. The flux rate was chosen to achieve specific residence times of the S2O42− solution in the column (2 h to 4 h) relative to the reduction rate (~5 h to ~7 h). The dry bulk density and porosity of the column was calculated from the dry and saturated column weight and column volume. The volumetric flow rate was calculated from the effluent volume and elapsed time. The electrical conductivity of the column effluent provided a second (dynamic) measure of the porosity, and was measured using a flow-through electrode and automatic data logging. While these experiments can provide data of the mass of reduced Fe in the sediments, the method is more complex and less accurate than oxidizing sediments with dissolved oxygen (described below). The S2O42− concentration in the effluent was measured once per hour using an automated fluid measurement and control system (U.S. Patent 6,438,501; Figure 9.1.4). These measurements were taken with an HPLC injection valve with 15 µL to 52 µL loop that isolated a specified volume of the effluent. The contents of the loop were mixed with 5 mL to 10 mL of oxygen-free water, then injected into a UV-detector and absorbance measured at 315 nm. The sample injection took 2 min to flow the complete sample through the detector, and the absorbance over a 1 min interval was averaged for a single S2O42− concentration measurement. A triple-wash between injections prevented sample overlap. These fluid operations were controlled from one computer and the S2O42−concentration logged on a second computer. The concentration

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FIGURE 9.1.4 Sediment column oxidation system with automated calibration of oxygen electrodes.

of the S2O42− influent was measured with the same automated system by manually bypassing the column at approximately 24 h intervals over the multi-day experiments. The fraction of reduced Fe was calculated from S2O42− breakthrough curves by determining the total mass loss (i.e., S2O42− mass injected minus S2O42− in the effluent) and the mass of S2O42− lost to disproportionation. The remaining S2O42− mass loss was used for Fe reduction. This S2O42− breakthrough analysis assumes that S2O42− has reached a steady state mass loss owing to disproportionation and that all of the Fe has been reduced. The rate of Fe reduction is also calculated from the steady state S2O42− concentration during initial breakthrough (i.e., before the Fe is all reduced). 9.1.3.3 Sediment Oxidation in Columns Sediment oxidation studies were also conducted in 1-D columns to determine the rate at which the S2O42−-reduced sediments are oxidized and to measure of the mass of reduced Fe (i.e., capacity). These experiments consisted of injecting oxygen-saturated (8.4 mg/L) water at a steady rate (typically 2 pore volumes per hour) into a reduced sediment column and measuring the concentration of dissolved oxygen over time in the effluent for 300 h to 800 h. A series of in-line micro-electrodes were used to monitor geochemical changes during oxidation and included dissolved oxygen (1 or 2 electrodes), pH, and

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electrical conductivity. Electrode measurements were continuously monitored, averaged, and data logged at 2 min to 5 min intervals using an automated fluid measurement and control system. Two-point calibration was conducted on the in-line oxygen electrodes at 4 h to 8 h intervals (oxygenfree and oxygen-saturated solution for oxygen) using the automated system. Electrode data from calibrations were also data logged. The mass of reduced Fe that was oxidized was calculated from the mass of oxygen consumed.

9.1.4

Results and Discussion

9.1.4.1 Fe Phase Changes during Reduction Solid Fe phase extractions measured on unaltered, reduced, and reduced/ oxidized sediments showed that the S2O42− treatment dissolved and reduced a fraction of the Fe oxides present and possibly Fe in clays (Table 9.1.1). The Na2S2O4/K2CO3 treatment was expected to mobilize less Fe(II) than the S2O42− -citrate-hydrogen carbonate extraction (Heron et al., 1994a), since Fe species are not solubilized by the citrate. Structural Fe in smectite clays can be reduced by S2O42− (Stucki et al., 1984). The untreated silty gravel had a total of 625 µmol/g Fe oxides and carbonates, of which 90% were Fe(III) oxides (#1, Table 9.1.1). Differing extractions indicated 14% amorphous Fe(III) oxides, 16% crystalline Fe(III) oxides, and 8% Fe(II) phases. The unidentified 60% were Fe(III) phases, some of which may be associated with clays. The sediment was then reduced for 96 h with a large excess of S2O42− relative to Fe. Reduction decreased amorphous Fe(III) oxides by 40 µmol/g, showed no apparent decrease in crystalline Fe(III) oxides, and there was a 70 µmol/g to 155 µmol/g increase in ion exchangeable (adsorbed) Fe(II) and a 20 µmol/g to 40 µmol/g increase in siderite/FeS. In other words, up to 25% of the Fe(III) oxides were reduced by the treatment and adsorbed Fe(II) from clays may have contributed a significant amount. Reduction resulted in an increase in surface area by EGME (untreated = 31 m2/g, reduced 43 m2/g), likely caused by removal of some Fe oxides from clay surfaces. Oxidation of this sediment in a column by oxygen-saturated water (300 to 600 pore volumes) resulted in the disappearance of the ion exchangeable Fe(II), some decrease in siderite/FeS, and an increase in amorphous (20 µmol/g to 40 µmol/g) and crystalline (40 µmol/g) Fe(III) oxides. The total “redox capacity” of this reduced sediment (i.e., total O2 consumption) was 159 µmol/g; roughly equivalent to the adsorbed Fe(II). This implied nearly all the redox reactivity is related to adsorbed Fe(II) and contribution of reduced structural Fe in smectite clays was small. A silty gravel sample from the same aquifer (#2) with less total Fe (149 µmol/g) showed similar Fe phase changes during reduction and oxidation. Iron phase changes were measured on two other sediments from alternate environments that have a different distribution of crystalline and amorphous Fe oxides. A silty sand from a coastal aquifer had a total of 674 µmol/g Fe for the sediment (Table 9.1.1), which was 42% crystalline

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Fe(III) oxides, 28% amorphous Fe(III) oxides, and 9% Fe(II) phases (21% unaccounted for Fe(III) phases). Reduction resulted in a 50% decrease in both the amorphous and crystalline Fe(III) oxides (~100 µmol/g), with a corresponding increase in ion exchangeable Fe(II), again indicating the contribution of reduced Fe in clays may be minor. The 5 mol/L HCl extraction (total Fe(III) + Fe(II)) analyzed for Fe and Mn by inductively-coupled plasma spectroscopy–mass spectrometry (ICP–MS) (Heron, 1994b) showed that only 3.7% of the reduced phases were Mn. Oxidation of this reduced silty sand resulted in the disappearance of the 100 µmol/g adsorbed Fe(II), an apparent increase in siderite/FeS (30 µmol/g), and a 60 µmol/g increase in amorphous Fe(III) and 20 µmol/g to 40 µmol/g increase in crystalline Fe(III) oxides. The siderite/ FeS extraction may reflect the fact that siderite is forming or may be much slower to oxidize than ion exchangeable Fe(II). The sandy gravel sediment had a small amount of total Fe (14.4 µmol/g), which when reduced and oxidized showed a similar increase in siderite/FeS, as well as some increase in the amorphous Fe(III) oxides. Therefore, the reduction treatment of aquifer sediments from different environments resulted in the dissolution/reduction of a small fraction (15 to 25%) of the amorphous and crystalline Fe(III) oxides, with the dominant product observed being adsorbed Fe(II) and up to 20% siderite/FeS, and likely minor contribution of structurally reduced Fe in clays. The FeS formation in columns was minimal compared with that observed in batch systems. Since the aqueous solution in batch reductions are not removed as in columns, the persistence of the high ionic strength solution preventing Fe(II) adsorption and available sulfur may lead to the increased FeS. 9.1.4.2 Superfund Site Physical Properties During installation of injection and monitoring wells at the Superfund pilot test site, 16 sediment core samples were collected for laboratory analysis (Table 9.1.2). The three units within the A zone aquifer, in descending order, have been assigned the hydrostratigraphic designation of A1, A2, and A3. A generalized hydrogeologic description of the ISRM pilot test site consist of a silty clay upper confining layer to a depth of ~6.7 m, the A1 unit from ~6.7 m to ~8.2 m, the A2 unit from ~6.7 m to ~10.7 m, and the A3 unit from ~10.7 m to ~12.2 m ground surface. The A/B aquitard was encountered at a depth of ~12.2 m. Sediment particle size analysis indicates that the three hydrostratigraphic units within the A zone are sandy gravels containing some silt and very little clay. More specifically, all samples contained less than 7% silt and clay, and all samples contained less than 2% clay. A representative sample of the injection well sediment (Figure 9.1.1) contains 1.7% clay. The porosity for all sediments averaged 17.5%, and the dry bulk density averaged 1.95 g/cm3. The sieve analysis was used to calculate the saturated hydraulic conductivity of the sediment using Hazen’s formula, based on the 10% size fraction. These calculated values were compared with calculated conductivities obtained

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from hydraulic tests conducted in pilot test site monitoring wells, which showed the same general trends. 9.1.4.3 Superfund Site Sediment Reduction A series of seven column reductions followed by column oxidation experiments conducted with the sediment showed that there was sufficient Fe(III) that could be reduced by a sodium S2O42− injection. Reduction experiments consisted of the injection of 0.08 mol/L Na2S2O4 with 0.32 mol/L K2CO3. In three of the seven experiments the influent S2O42− concentration was recorded daily and the effluent concentration was automatically analyzed once per hour over the 5-day to 8-day experiments. In one experiment (Figure 9.1.5), the S2O42− concentration is low for the first 25 h, as it is completely consumed by Fe reduction. Over the next 100 h, the S2O42− concentration slowly increases, approaching the injection concentration (large squares) by 120 h. Simulations of this data indicate that the average reduction rate of the silty gravel is 5.3 ± 0.7 h half-life at 25 °C. Therefore, roughly 5 half-lives (24 to 30 h) of S2O42−-sediment contact time is needed to reduce most of the accessible Fe oxides. In laboratory experiments, sediments were reduced from 5 days to 8 days to achieve as much reduction as could occur. Sediment reduction experiments were conducted at temperatures from 2 °C to 42 °C to provide an understanding of how the sediment reduction and S2O42− disproportionation rates vary with temperature. Both the Fe reduction (2.27 times increase per 10 °C) and disproportionation (3.04 times increase per 10 °C) rates increased with temperature, as expected. At the Superfund site aquifer temperature (14 °C), the S2O42− reduction rate is slower (12 h halflife), so residence times for field scale injections were chosen to be up to 84 h

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from the start of the injection to the end of the residence phase before SO42− withdrawal to insure sufficient time for S2O42− to react with sediments. 9.1.4.4

Superfund Site Sediment Oxidation and Chromate (CrO42−) Barrier Longevity

The sediment oxidation experiments showed that the average mass of reducible Fe in the Superfund site sediments is 46.1 ± 18.8 µmol/g (0.26% reducible Fe, Table 9.1.2). Locations that contained a higher proportion of finer grained sediments had a greater mass of reducible Fe, but in general the spatial variability was low. These column oxidation experiments simulate what will naturally occur in the field (i.e., oxidizing species in groundwater flow through the reduced sediment under natural gradient conditions). The experiments are conducted until most of the reduced Fe has been oxidized, as evidenced by the oxygen concentrations in the effluent being 80% or more of saturation (oxygen saturated water is injected in these experiments). The automated laboratory experiments contain one or two oxygen electrodes, which are continuously monitoring the oxygen concentration of the effluent and recalibrated automatically every 8 h. This calibration data (not shown for most data sets) are used to calculate the oxygen-free and oxygen-saturated lines (Figure 9.1.6). The water was injected at a rate to achieve roughly 20 min of sediment-dissolved oxygen contact time (i.e., 20-min residence time), so over the course of 400 h, approximately 1,200 pore volumes of oxygensaturated water was injected. The shape of the oxygen breakthrough curve (Figure 9.1.5) shows a slow decrease in oxygen consumption, which levels out at approximately 75% of

Injection Well - Column Oxidation pore volume

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time (h) FIGURE 9.1.6 Oxidation of reduced superfund sediment in a column with oxygen-saturated water.

400

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saturation. Even by 1,200 pore volumes, the oxygen levels had only reached 83% of saturation. The interpretation of this breakthrough curve shape is there are at least two different Fe(II) species on the surface. Adsorbed Fe(II) (Fe(OH)2 or FeOH+) (as determined by Fe extraction analysis in other studies) is quickly oxidized, and may represent the majority of the reduced Fe in the sediment. A second species, siderite (FeCO3) may be present in minor (<20%) levels, and is slowly oxidized. Relative to the total mass of Fe in the sediment, the Na2S2O4 reduced a small fraction of the Fe oxides. Previous studies have shown that ∼20% of amorphous and crystalline Fe oxides are reduced by S2O42−. 9.1.4.5

Field Scale Considerations of Chromate (CrO42−) Barrier Longevity

In the previous section, the average S2O42−-reducible Fe content of the Superfund site aquifer sediments was 46.1 ± 18.8 µmol/g (0.26% reducible Fe), which is equivalent to 430 pore volumes of oxygen-saturated water, determined from the ratio of available electron donor (i.e., redox capacity of the sediment) per unit volume relative to the electron acceptors per unit volume (O2, CrO42−). The mass of electron donor (i.e., Fe(II) and other reduced transition metals) can be calculated per unit volume of water (i.e., pore space) in packed porous media as follows. Electron donor: Moles of electrons per cm3 liquid from the Fe(II): (74.1 µmol Fe2+/g)(1 µmol e−/µmol Fe2+)(1.49 g sediment/cm3) (cm3/0.447 cm3 liquid)(mol/106 µmol) = 2.470 × 10−4 mol e−/cm3 liquid #2 . . . with laboratory bulk density and porosity (74.1 µmol Fe2+/g)(1 µmol e−/µmol Fe2+)(2.3 g sediment/cm3) (cm3/0.16 cm3 liquid)(mol/106 µmol) = 1.065 × 10−3 mol e−/cm3 liquid #2 . . . with field bulk density and porosity Assumptions: • Total sediment average reducible Fe content • This maximum reduced capacity was uniformly achieved in the field • No oxygen diffusion from the unsaturated (vadose) zone • Field scale dry bulk density (2.3 g/cm3) and porosity (0.16) are the same as the lab

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Electron acceptor: Moles of electrons per cm3 liquid from dissolved oxygen and other redoxreactive species (CrO42−, TCE, RDX, NO3−. . .): (8.4 mg/L saturated O2)(g/1000 mg)(mol O2/32 g)(1/1000 mL) (4 mol e−/mol O2) = 1.050 × 10−6 mol e−/cm3 (4.0 mg/L HCrO4−)(g/1000 mg)(mol CrO42−/117 g)(1/1000 mL) (3 mol e−/mol CrO42−) = 1.022 × 10−7 mol e−/cm3 Oxygen-saturated field conditions (the Superfund site averages 3.0 mg/L, so the barrier would last considerably longer than this calculation) are assumed. Finally, the relative longevity of the barrier (in dimensionless “pore volumes”) can be calculated by the ratio of available electron donor (Fe(II)) to unit volume of aqueous oxidants that flow through the barrier: . . . electron donors/electron acceptors = number of pore volumes barrier will last Total electron donors/acceptors: Scenario 1 2.5 mg/L O2 and 4.0 mg/L HCrO4− total electron donors/acceptors: (7.57 × 10−4)/(3.125 × 10−7 + 1.022 × 10−7) = 1,825 pore volumes (calculated longevity scenario 1) Scenario 2 2.5 mg/L O2 and 55.0 mg/L HCrO4− total electron donors/acceptors: (7.57 × 10−4)/(3.125 × 10−7 + 1.405 × 10−6) = 441 pore volumes (calculated longevity scenario 2) To determine the actual longevity in years, the average groundwater flow rate through that aquifer zone needs to be calculated. This can be decades for natural hydraulic gradients, but can be considerably shorter if the reduced zone is near a pumping well gallery. An estimated longevity in years, based on a groundwater flow rate (0.61 m/d) and an average reduced sediment barrier diameter of 9.14 m is calculated as follows. Longevity in years: Assume: averaged velocity = 0.61 m/d and barrier width = 9.14 m (9.14 m)(d/0.61 m)(1,825 pore volume)(year/365.25 d) = 75 years . . . scenario 1 (9.14 m)(d/0.61 m)(441 pore volume)(year/365.25 d) = 18 years . . . scenario 2

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The above calculations assume a single, homogeneously reduced aquifer unit. At this (and many) field sites, multiple aquifer units are present with differing flow rates, Fe content, and oxidant concentration. In addition, field scale reduction of aquifer sediments is spatially dependent. While similar calculations can be made to approximate these differing characteristics, to fully account for the oxidation of the barrier with spatial considerations, 3-D simulations are needed. At this Superfund site, the A1 aquifer unit contains high CrO42− concentrations (averaging 20 mg/L) and the A2 unit contains low CrO42− (0.5 mg/L). Dissolved oxygen is the same in both units (3 mg/L), but the flow rate in the A2 unit is 10 times greater than the A1 unit. Given the relative electron acceptor concentrations and flow considerations, the A2 aquifer unit dominates the needed redox capacity, mainly to remove dissolved oxygen (only 3.3% of the A2 unit redox capacity is used to remove CrO42−, as opposed to 42% in the A1 unit). Therefore, the field-scale injection strategy is to reduce the A2 unit to a greater extent than the A1 unit in order that both units prevent offsite CrO42− migration for the same amount of time. An example of the full-scale implementation of this in situ redox manipulation barrier technology (Figure 9.1.7) is at the U.S. Department of Energy Hanford site in eastern Washington State. A CrO42− plume with a maximum

Columbia River

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45 37

157 11

FIGURE 9.1.7 In situ redox manipulation barrier at the U.S. DOE Hanford site in eastern Washington (Fruchter et al., 2000). The chromate plume is migrating north, The 701 m wide permeable reactive barrier is effectively preventing migration to the Columbia River. The treated aquifer zone is at a 24.4 m to 30.5 m depth, and was installed by injection of the aqueous reductant (dithionite) through a series of 65 wells.

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concentration of 1,100 ppb is migrating northward toward the Columbia river. Groundwater infiltrates into the river and because salmon redds are in the river bank sediments, they can be affected by groundwater contaminants. A series of 65 wells in a staggered array were installed to a depth of 30.5 m to treat the 24.4 m to 30.5 m deep aquifer with sodium S2O42− to form this 701 m wide permeable redox barrier, which took several years to complete. The contour plot of CrO42− concentration shows that the barrier is preventing any CrO42− from migrating (zero contour at the barrier). This redox barrier is expected to last about 20 years and can be reinjected if additional longevity is required. 9.1.5

Conclusions

Laboratory sediment experiments were conducted to determine physical and geochemical properties needed to develop a design for implementation of the in situ redox manipulation (ISRM) technology for CrO42− remediation at four sites. During installation of injection and monitoring wells at the superfund site pilot test site, 16 sediment core samples were collected for this laboratory analysis. Experiments showed that chemical reduction yielded a redox capacity for this Superfund site (0.26% Fe(II)) that falls within the range of values observed in sediments analyzed from sites where field-scale deployment of the ISRM technology is currently in progress or being considered (0.1% Hanford 100D area, 0.24% Fort Lewis, 0.4% Moffett Federal Airfield, 0.36% Aerojet). This mass of reducible Fe represents a sufficient quantity for a treatment zone emplaced at Superfund site to remain anoxic for hundreds of pore volumes, which would be expected to last tens of years, depending on aquifer flow rates and the concentration of oxidizing species in the groundwater. The geochemical analysis also indicated relatively low spatial variability in reducible Fe content although some depth dependent variability was indicated. Variation in the CrO42− concentration and flow rates between the A1 and A2 aquifer units indicated the necessity for greater reduction in the A2 aquifer unit, in order that both aquifer units prevent offsite CrO42− migration for the same amount of time.

Bibliography Amonette, J., 2000, Iron Redox Chemistry of Clays and Oxides, Environmental Applications, in Fitch, A. Ed., Electrochemistry of Clays, CMS Workshop Lectures, Clay Minerals Society, Aurora, Co, in review. Anderson, L.D., Kent, D.B., and Davis, J.A., 1994, Batch experiments characterizing the reduction of Cr(VI) using suboxic material from a mildly reducing sand and gravel aquifer, Environmental Science and Technology, 28, 1, 178–185. Appleton, E.L., 1996, A Nickel-Iron wall against contaminated ground water, Environmental Science and Technology, 30, 12, 536A–539A. Balko, B. and Tratnyek, P., 1998, Photoeffects on the reduction of carbon tetrachloride by zero-valent iron, Journal of Physical Chemistry, 102, 8, 1459–1465.

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Blowes, D., Ptacek, C., and Jambor, J., 1997, In situ Remediation of Cr(VI) contaminated groundwater using permeable reactive walls: laboratory studies, Environmental Science and Technology, 31, 12, 3348–3357. Boursiquot, S., Mullet, M., and Ehhrhardt, J., 2002, XPS Study of the reaction of chromium (VI) with mackinawite (FeS), Surface and Interface Analysis, 34, 293–297. Buerge, I.J. and Hug, S.J., 1997, Kinetics and pH dependence of chromium(VI) reduction by iron(II), Environmental Science and Technology, 31, 5, 1426–1432. Chao, T.T. and Zhou, L., 1983, Extraction techniques for selective dissolution of amorphous Iron oxides from soils and sediments, Soil Science Society of America, Journal, 47, 225–232. Chilakapati, A., Williams, M., Yabusaki, S., Cole, C., and Szecsody, J., 2000. Optimal design of an in situ Fe(II) barrier: transport limited reoxidation, Environmental Science and Technology, in press. Devlin, J.F. and Muller, D., 1999, Field and laboratory studies of carbon tetrachloride transformation in a sandy aquifer under sulfate reducing conditions, Environmental Science and Technology, 33, 7, 1021–1027. Eary, L. and Rai, D., 1988, Chromate removal from aqueous wastes by reduction with ferrous ion, Environmental Science and Technology, 22, 972–977. Farrell, J., Kason, M., Melitas, N., and Li, T., 2000, Investigation of the long-term performance of zero-valent iron for reductive dechlorination of trichloroethylene, Environmental Science and Technology, 34, 3, 514–521. Fruchter, J., Cole, C., Williams, M., Vermeul, V., Amonette, J., Szecsody, J., Istok, J., and Humphrey, M., 2000, Creation of a subsurface permeable treatment barrier using in situ redox manipulation, Ground-Water Monitoring Review, 66–77. Genin, J.R., Mayer, G., and Fried, C., 1998, Thermodynamic equilibria in aqueous suspensions of synthetic and natural Fe(II)-Fe(III) green rusts: occurance of the mineral in hydromorphic soils, Environmental Science and Technology, 32, 8, 1058–1068. Gibbs, C.R., 1976, Characterization and application of ferrozine iron reagent as a ferrous iron indicator, Analytical Chemistry, 48, 8, 1197–1200. Gu, B., Hue, C., and Zhao, T., 1999, Biogeochemical dynamics in zero-valent iron columns: implications for permeable reactive barriers, Environmental Science and Technology, 33, 13, 2170-2177. Heron, G., Christensen, T.H., and Tjell, J.C., 1994a, Oxidation capacity of aquifer sediments, Environmental Science and Technology, 28, 153–159. Heron, G., Crouzet, C., Bourg, A.C., and Christensen, T.H., 1994b, Speciation of Fe(II) and Fe(III) in contaminated aquifer sediments using chemical extraction techniques, Environmental Science and Technology, 28, 1698–1705. Hung, H. and Hoffman, M.R. 1998, Environmental Science and Technology, 32, 3011–3016. Jardine, P.M., Fendorf, S.E., Mayes, M.A., Larsen, I.L., Brooks, S.C., and Bailey, W.B., 1999, Fate and transport of hexavalent chromium in undisturbed heterogeneous soil, Environmental Science and Technology, 33, 17, 2939–2944. Johnson, T., Fish, W., Gorby, Y., and Tratnyek, P., 1998, Degradation of carbon tetrachloride: complexation effects on the oxide surface, Journal of Contaminant Hydrology, 29, 379–398. Kim, C., Deng, B., Thornton, E., and Xu, H., 2001, Chromium (VI) reduction by hydrogen sulfide in aqueous media: stoichiometry and kinetics, Environmental Science and Technology, 35, 2219–2225.

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Loyaux-Lawniczak, S., Lecomte, P., and Ehrhardt, J., 2001, Behavior of hexavalent chromium in a polluted groundwater: redox processes and immobilization in soils, Environmental Science and Technology, 35, 7, 1350–1357. Loyaux-Lawniczak, S., Refait, P., Ehrhardt, J.J., Lacomte, P., and Genin, J.R., 2000, Trapping of Cr by formation of ferrihydrite during the reduction of chromate ions by Fe(II)-Fe(III) hydroxysalt green rusts, Environmental Science and Technology, 34, 3, 438–443. Mayer, K., Blowes, D., and Frind, E., 2000, Reactive transport modeling of an in situ reactive barrier for the treatment of hexavalent chromium and TCE in groundwater, Water Resources Research, in press. McNab Jr., W.W., Ruiz, R., and Reinhard, M., 2000, In situ destruction of chlorinated hydrocarbons in groundwater using catalytic reductive dehalogenation in a reactive well: testing and operational experiences, Environmental Science and Technology, 34, 1, 149–153. Murphy, E., Schramke, J., Fredrickson, J., Bedsoe, H., Francis, A., Sklarew, D., and Linehan, J., 1992, Infuence of microbial activity and sedimentary organic carbon on the isotope geochemistry of the middendorf aquifer, Water Resources Research, 28, 3, 723–740. Patterson, R.R. and Fendorf, S., 1997, Reduction of hexavalent chromium by amorphous iron sulfide, Environmental Science and Technology, 31, 2039–2044. Pratt, A., Blowes, D., and Placek, C., 1997, Products of chromate reduction on proposed subsurface remediation material, Environmental Science and Technology, 31, 9, 2492–2498. Sass, B.M. and Rai, D., 1986, Solubility of amorphous chromium(III)-iron(III) hydroxide solid solutions, Inorganic Chemistry, 26, 14, 2228–2232. Scherer, M.M., Balko, B.A., and Tratnyek, P.G., 1999, The role of oxides in reduction reactions at the metal-water interface, in ACS Symposium Series, Sparks D.L., and Grundl, T., Eds., 715, 1–22. Seaman, J.C., Bertsch, P.M., and Schwallie, L., 1999, In situ Cr(VI) reduction within coarse-textured, oxide-coated soil and aquifer systems using Fe(II) solutions, Environmental Science and Technology, 33, 6, 938–944. Sivavec, T., Mackenzie, P., Horney, D., and Baghel, S., 1996, Zero-Valent Iron and TCE Degradation, General Electric Research and Development Center, Schenectady, NY. Stucki, J.W., Golden, D.C., and Roth, C.B., 1984, Preparation and handling of dithionite-reduced smectite suspensions, Clays and Clay Minerals, 32, 3, 191–197. Szecsody, Jim E., Fruchter, Jonathan S., Vermeul, Vince R., and Williams, Mark D., 1999, Results of Bench-Scale Studies for In Situ Redox Manipulation of Subsurface Sediments at the Frontier Hard Chrome Site, Vancouver, Washington, PNNL letter report. Szecsody, J., Chilakapati, A., Zachara, J., Jardine, P., and Ferrency, A., 1998, Importance of flow and particle-scale heterogeneity on CoII/IIIEDTA reactive transport, Journal of Hydrology, 209, 112–136. Szecsody, J., Williams, M., Fruchter, J., Vermeul, V., and Evans, J., 2000, Influence of sediment reduction on TCE degradation, remediation of chlorinated and recalcitrant compounds, in Chemical Oxidation and Reactive Barriers, Wickramanayake, G., Ed., pp. 369–376. Szecsody, J., Williams, M., Fruchter, J., and Vermeul, V., 2001, In situ Reduction of aquifer sediments for remediation: 1. Iron reduction mechanism, Environmental Science and Technology (in press).

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Vermeul, V., Williams, M., Evans, J. Szecsody, J., Bjornstad, B., and Liikala, T., 2000, In situ redox manipulation proof-of-principle test at the Fort Lewis Logistics Center: final report, Pacific Northwest National Laboratory PNNL-13357, Richland, WA. Waybrant, K.R., Blowes, D.W., and Ptacek, C.J., 1998, Selection of reactive mixtures for use in permeable reactive walls for treatment of mine drainage, Environmental Science and Technology, 32, 13, 1972–1979. Wehrli, B., 1992, Redox Reactions of metal oxides at mineral surface, in Aquatic Chemical Kinetics, Stumm W., Ed., John Wiley and Sons, New York, pp. 311–337. Zachara, J., Girvin, D., Schmidt, R., and Resch, C., 1987, Chromate adsorption on amorphous iron oxyhydroxide in the presence of major groundwater ions, Environmental Science and Technology, 21, 589–594.

9.2

Bench Scale Evaluation of Ex Situ and In Situ Cr(VI) Remedial Methods

Angus McGrath, Daniel Oberle, David Schroder, John McInnes and Chris Maxwell 9.2.1

Introduction

Selection of an in situ or ex situ remediation method for Cr(VI) requires understanding how the effectiveness of the remedial method will be affected by the geochemistry, lithology, and hydrogeology of the site. Just because a remedial method has been effective at numerous Cr(VI) impacted sites, does not necessarily mean that the method will function effectively at every site. Many factors can influence the effectiveness of a treatment, but the most important is the oxidation state of an aquifer and/or soils because the main remedial methods involve chemical reduction of Cr(VI) to Cr(III) and subsequent precipitation of the latter. Aerobic soils with high concentrations of Mn(IV) oxide (MnO2) can lead to the reoxidation of Cr(III) to Cr(VI) or a high soil reductant demand (the tendency of a soil to consume or react with reducing agents). The following paper describes the chemicals commonly used in Cr(VI) reduction and the results of bench scale testing of these reducing agents in neutral groundwater and soil. The purpose of the bench scale tests was to evaluate the dosing requirements, reaction kinetics, and precipitate loading of the different treatments. 9.2.2

Chromium Geochemistry

Chromium is found in the environment mainly in two oxidation states, Cr(III) and Cr(VI). Cr in the environment is typically reduced as Cr(III), and at ambient soil pH of 5 to 8, Cr(III) forms a hydroxide (Cr(OH)3) solid that is insoluble in water within that pH range. Cr(VI) usually originates from anthropogenic sources, but can be formed from Cr(III) in the environment

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by reaction with MnO2 (Bartlett, 1991). Cr(VI) in water may exist as either the CrO42− anion or the dichromate anion (Cr2O72−). Cr2O72− is the predominant anion at high concentrations when the pH of the water is between 4 and 6. CrO42− is predominant at pH values above 6 and/or in dilute solutions. At pH values less than 4 or at low concentrations, CrO42− converts back into CrO42−, creating chromic acid (H2CrO4). H2CrO4 is an unstable, fast-reacting, and powerful oxidizing agent. Therefore, Cr(VI) reactions are typically performed at low pH owing to the substantially increased reaction kinetics. For remedial methods, low pH treatment is frequently used in abovegroundwater treatment applications because the increased reaction kinetics allow for reduced retention times, which in turn allow for the use of smaller reaction vessels with lower capital costs and greater reaction efficiencies. However, low pH treatment may be uneconomical or infeasible for in situ applications because the natural buffer capacity of the soil may quickly consume the acid, and the acid may result in the dissolution of undesirable metals such as aluminum, Fe, and regulated heavy metals. In addition, ex situ pH manipulation with alkaline groundwater and high flow systems may prove to be too costly. Therefore, for most in situ and many ex situ applications treatment is conducted at neutral pH. Such treatment involves longer retention times and potentially increasing chemical dosages in order to drive the reactions to completion. The following studies were conducted to evaluate different reagents for in situ and ex situ treatment of Cr(VI). The purpose of the testing was to evaluate potential reductants, reduction reaction kinetics, chemical dosage requirements, precipitate mass, and precipitate properties (particle size, etc.). The goal of the testing was to identify the fastest reacting reagent with the greatest reducing potential and the lowest precipitate yield. Testing also included a slurried Fe-Si material, considered as an alternative to elemental Fe that could be injected or placed into the subsurface to form a reductive–reactive barrier. 9.2.3

Aqueous Treatment Reagents

Several experiments were conducted with reducing agents to test their ability to reduce dissolved Cr(VI) in order to identify the most reactive and effective reagent. Further tests were then run to evaluate the mass of precipitate formed and the properties of the precipitate. An additional test was conducted to evaluate the soil reductant demand associated with in situ groundwater treatment. The aqueous reagents selected for the study were: • • • • •

Calcium polysulfide (CaS5) Sodium thiosulfate (Na2S2O3) Sodium hydrogen sulfite (NaHSO3) Sodium dithionite (Na2S2O4) Iron(II) sulfate (FeSO4)

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The five aqueous reagents selected for testing are consistent with U.S. Environmental Protection Agency (USEPA) recommendations (USEPA, 2000). Calcium polysulfide (CaS5 or CaSx) is a NSF International (NSF) approved reagent for drinking water treatment. It is a nontoxic reagent that oxidizes under aerobic conditions to form calcium, SO42− and elemental sulfur. Calcium polysulfide has been recently used more frequently as a reducing agent for Cr(VI) owing to its ability to reduce Cr(VI) to Cr(III) without the need for acidification. Sulfur atoms have the ability to catenate into linear chains of sulfur atoms to create a polysulfide salt when reacted with a metal. When sulfur(S) is reacted with calcium(Ca) metal, a calcium polysulfide salt is formed that contains anywhere from 2 (CaS2) to 7 (CaS7) S atoms per Ca atom. The average amount of S is 4 to 5 S atoms per Ca atom. When the polysulfide anion S52− reacts with Cr(VI) in the groundwater, the sulfide is converted from a −2 oxidation state to zero oxidation state, thus releasing 2 moles of electrons for each mole of polysulfide anion reacted. The CaS5 reduction reaction with CrO42− is shown below, assuming that the average polysulfide salt contains 5 S atoms per each Ca atom. S52− has a stoichiometric requirement with Cr(VI) of 3 to 2, Polysulfide to Cr(VI). S52− reacts with Cr(VI) and does not form significant precipitate. However, there may be concern in specific cases because of the low mass yield of precipitate after reaction that the total Cr concentration may not be effectively treated with S52−. Total Cr concentrations after treatment were evaluated in this study to determine if this was a significant issue. The redox reaction shows that 3 moles of CaS5 are required to reduce two moles of Cr(VI). This is equivalent to 5.77 mg/L calcium polysulfide to reduce each 1 mg/L of Cr(VI) dissolved in the groundwater. The reaction for calcium polysulfide with CrO42− is as follows: Reduction:

10H+ + 2CrO42− + 6e− → 2Cr(OH)3 + 2H2O

(9.2.1)

Oxidation:

3CaS5 → 3Ca2+ + 15S + 6e−

(9.2.2)

10H+ + 2CrO42− + 3CaS5 → 2Cr(OH)3 + 3Ca2+ + 2H2O + 15S

(9.2.3)

Sodium dithionite (Na2S2O4) is an effective reagent for in situ treatment of Cr(VI). It has been tested extensively by the Department of Energy’s (DOE) Pacific Northwest National Laboratory (PNNL), because it decomposes into naturally occurring nontoxic byproducts that stimulate the reduction of Cr(VI) and do not destroy water quality down gradient. The S2O42− reacts with metal entities such as Fe(III) and Mn(IV) in a typical soil reducing them to Fe(II) and Mn(II). The reduced Fe is formed in solution and within the solid matrix of the soil. The reduced metal entities in the solid matrix of the soil form a reservoir that can continue to reduce influent Cr(VI) from Cr(VI) to Cr(III), which is insoluble at ambient pH and has a lower toxicity than Cr(VI). The Fe will precipitate with the Cr(III) forming a solid that is insoluble

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even at low pH (<2). One of the problems associated with Na2S2O4 is that the reaction of the S2O42− decreases the pH, consuming the buffering capacity of the soil. At low pH S2O42− decomposes without reacting with Cr(VI) or Fe (III) and Mn. The stoichiometric requirement of S2O42− for CrO42− is 3 to 2, but reaction kinetics and side reactions can significantly alter the reaction. Reduction:

16H+ + 2CrO42− + 6e− → 2Cr3+ + 8H2O

(9.2.4)

Oxidation:

3S2O42− + 6H2O → 12H+ + 6SO32− + 6e−

(9.2.5)

4H+ + 2CrO42− + 3S2O42− → 2Cr3+ + 6SO32− + 2H2O

(9.2.6)

Sodium thiosulfate (Na2S2O3) is another common NSF approved water treatment chemical that is used to reduce Cr(VI) to Cr(III). In the thiosulfate (S2O32−) reaction, the S atom is converted from a +2 oxidation state to a +2 1/2 oxidation state when S 2O 32− reacts to form the tetrathionate anion (S4O62−). One mole of electrons are released for each mole of S2O32− that is consumed during the reaction. The redox reaction shows that 3 moles of Na2S2O3 are required to reduce 1 mole of Cr(VI). This is equivalent to 9.12 mg/L Na2S2O3 to reduce 1 mg/L of Cr(VI) dissolved in the groundwater. The reaction of Na2S2O3 with CrO42− proceeds similar to Cr2O72−: Reduction:

8H+ + CrO42− + 3e− → Cr3+ + 4H2O

(9.2.7)

6S2O32− → 3S4O62− + 6e−

(9.2.8)

16H+ + 2CrO42− + 6S2O32− → 2Cr3+ + 3S4O62− + 8H2O

(9.2.9)

Oxidation:

Sodium hydrogen sulfite (NaHSO3) is also an NSF approved reagent and the most commonly used treatment chemical for Cr(VI) in industrial water treatment applications. In the hydrogen sulfite (HSO3−) reaction, the sulfur atom is converted from a +4 oxidation state to a +6 oxidation state, thus releasing 2 electrons for the redox reaction. The redox reaction shows that three moles of NaHSO3 are required to reduce two moles of Cr(VI). This is equivalent to a 3 mg/L NaHSO3 demand for 1 mg/L of Cr(VI) dissolved in the groundwater. The reaction of NaHSO3 with the CrO42− ion proceeds in a similar manner: Reduction:

16H+ + 2CrO42− + 6e− → 2Cr3+ + 8H2O

(9.2.10)

Oxidation:

3HSO3− + 3H2O → 9H+ + 3SO42− + 6e−

(9.2.11)

7H+ + CrO42− + HSO3− → 2Cr3+ + 3SO42− + 5H2O

(9.2.12)

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Iron(II) sulfate (FeSO4) is also a NSF-approved reagent for drinking water treatment. It is a nontoxic reagent that forms iron(III) sulfate (Fe2(SO4)3) upon oxidation. All of the Fe(III) precipitates with Cr(III). One drawback of the reagent is that the high stoichiometric requirement for treatment of Cr(VI) of 3 to 1, (Fe(II) to Cr(VI)) also increases the yield of precipitate. The fast reaction and precipitation of Fe(II) and Cr reaction byproducts effectively transform Cr(VI) and remove total Cr from solution. The kinetics of FeSO4 treatment of CrO42− have been evaluated extensively by Fendorf and Li (1996). They have observed that the rate is highest at pH 8, and above pH 8, oxygen competition for CrO42− reduces the observed rate. The anticipated limitation of Fe(II) is that it forms excessive amounts of precipitate that limit its applicability in groundwater treatment because of the problems with waste generation. Iron(III) hydroxides generated from the treatment have been shown to have toxicity characteristic leaching procedure (TCLP) concentrations of approximately 60 mg/L in some treatment systems, which will classify the waste as hazardous. Further stabilization can limit this problem. The reaction of CrO42− with Fe(II) is as follows: Reduction:

8H+ + CrO42− + 3e− → Cr3+ + 4H2O

(9.2.13)

Oxidation:

3Fe2+ → 3Fe3+ + 3e−

(9.2.14)

8H+ + 3Fe2+ + CrO42− → 3Fe3+ + Cr3+ + 4H2O

(9.2.15)

or → (CrxFe1−x)(OH)3(s) where 0 ≤ x ≥ 1

9.2.4

Solid Treatment Reagent

One solid reagent, Fe impregnated silica (SiO2) sand, was tested for its effectiveness as a permeable reactive barrier. The material is intended as a substitute for elemental Fe in reactive barriers. It is an Fe-impregnated SiO2 sand created by placing SiO2 sand in contact with molten ductile Fe, allowing the Fe to cool, and then removing the sand from the Fe. This process creates a SiO2 sand containing approximately 2% Fe by mass with a sponge-type surface when viewed under an electron microscope. The Fe contains around 3% silicon (Si), which helps it to resist atmospheric corrosion. Column studies flushing 1,000 pore volumes of groundwater containing 400 mg/L CaCO3 hardness through the material revealed that the material did not loose its reactivity. The main benefit of the material is the cost since the material costs only 25% as much as elemental Fe. The reaction for the SiO2 sand Fe is the same as that for elemental Fe, in which the chromium reacts with Fe(II) generated on the Fe-SiO2 surface, forming the same products as described in the above referenced FeSO4

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reaction. In traditional elemental Fe barriers, the Fe surface can become fouled by iron(III) hydroxides formed on the Fe surface, limiting its effectiveness for treatment. The sponge-type surface of the Fe has a much higher surface area, reducing the impact of fouling and creating more reactive sites. The Si limits the access to individual reactive sites, but limited reaction prevents the Fe from reacting rapidly and depleting the reducing capacity of the reactive barrier prematurely.

9.2.5

Reductant Stoichiometry and Reaction Kinetics

The reaction stoichiometry and kinetics were tested using increasing concentrations of the reducing agents and set reaction periods. Bench-scale reactions were conducted using four 29.6 mL, glass sample containers. Subsets of each reagent were prepared by adding two and three times the reductant stoichiometric requirement. Control samples were prepared by adding site groundwater to a clean container in order to account for changes in Cr(VI) concentration over time. All of the sample sets were allowed to react for one hour, while being mixed in a tumbler rotating at a speed of 18 revolutions per minute. After one hour, one sample was removed from each of the 10 test groups and 1% mass/volume NaOH was added by micropipette to raise the pH to 10.5. The samples were then stirred and allowed to sit for 15 min. Following this neutralization period, samples were passed through a 0.45 µm filter and the liquid placed into a 120 mL sample container with nitric acid (HNO3) preservation. Each sample was shipped to Merit Laboratory, Inc. in East Lansing, Michigan for total Cr analysis by USEPA Methods 3015A (sample digestion) and 200.8 (analysis). The total chromium analysis results represent the amount of Cr(VI) in solution after reaction, since the insoluble, Cr(III) is removed by the filtration step, assuming no other Cr oxidation state is present. The remaining samples were left in the tumbler for continued testing activities. The sample collection procedures detailed above were repeated following reaction time frames of 2 h and 3 h. Based on the results of the preliminary testing, the best performing treatment reagent was selected for further verification testing of the reaction kinetics. Test samples of the composite groundwater were prepared and over-dosed with reductant to ensure complete reduction of Cr(VI). The information gained by this testing was combined with the previous results to identify an optimal reagent concentration that provided sufficient reduction of Cr(VI) in solution and a representative reaction time frame for kinetics confirmation. Testing was conducted using 120 mL samples of the composite groundwater and the previously identified volume of treatment reagent. Samples were sent to Merit Laboratories, Inc. for off-site analysis of Cr(VI) following reaction

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periods of 1.0 h, 1.5 h, 2.0 h, and 2.5 h. Sample collection at each time interval followed earlier procedures, with the representative sample adjusted to pH 10.5 using 1% mass/volume NaOH to stop the chemical reaction.

9.2.6

Reductant Treatment and Solids Generation

Bench-scale testing activities were focused on the evaluation of the reducing agents NaHSO3, Na2S2O4, Na2S2O3, FeSO4, and CaS5. These compounds were selected owing to the theoretical reaction kinetics and the minimal colloidalrange solids generated as by-products (with the exception of FeSO4) of the reduction process. The first phase of testing was designed to verify the reaction kinetics and identify the optimal reactant under the given sitespecific conditions. Once the best treatment chemical was determined, the second phase of testing was used to evaluate solids production and potential concerns for pore-space fouling during in situ applications. Testing was conducted by preparing three samples that were subsequently sent to Particle Technology Labs, Ltd. in Downers Grove, Illinois for Elzone particle size analysis. The test was conducted by filling three beakers with 1000 ml of a composite groundwater sample. The three samples were treated as follows: 1. An untreated groundwater sample containing 4.3 mg/L Cr(VI) 2. A groundwater sample treated with 43 mg/L CaS5 3. A groundwater sample treated with 43 mg/L CaS5 and pH adjusted to 6.5 after treatment Following preparation of the three tests, the samples were allowed to react over a 24 h period prior to shipment for particle size analyses. Total precipitate generation per treatment reagent was conducted for FeSO4 and CaS5. Precipitate mass was measured on 2 L samples of groundwater treated with three times the CaS5 and FeSO4 stoichiometric requirement respectively for a 0.30 mg/L Cr(VI) concentration.

9.2.7

Soil Reductant Demand

Once the appropriate reducing agent was identified and optimal reaction kinetics determined for the Cr(VI) impacted groundwater, site-specific characteristics and parameters were evaluated. Since the process was also considered for application to the subsurface, the potential physical and geochemical limitations of a successful remedial program were evaluated. Examination of the soil samples collected from a test boring identified subsurface zones of relatively higher permeability at depths of 13.1 m and 24.8 m below ground surface. The samples were characteristic of silty sand and fell within the identified upper and lower aquifer units where the groundwater

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samples used in the test were collected. Representative samples of these two soil intervals were used during the third phase of bench-scale testing, designed to determine the soil reductant demand of the proposed treatment reagent. The two test samples were prepared by combining 80 g of soil with 80 mL of distilled water in a 500 mL sample container equipped with a screw-top lid. The optimal dose of reducing agent identified in the previous phases was applied to the soil/water mixtures. Each sample was shaken for 5 min to ensure proper mixing and then the oxidation-reduction potential (ORP or Eh) of the test samples was monitored. For purposes of determining when the reducing agent was no longer reacting with the soil, a negative Eh measurement was considered indicative of the presence of excess treatment chemical. The validity of this method was confirmed by iodine titration prior to testing. Following the initial Eh monitoring, the sample containers were placed in a tumbler rotating at a speed of 18 revolutions per minute. After 3 h of mixing the samples were removed and the Eh recorded. If the measurement was positive, the batch addition of reducing agent was repeated and the samples were placed back into the tumbler. If the results were negative, the sample mixing continued without further chemical addition. This procedure was repeated until the Eh measurements remained negative for a period of 24 h. The total volume of reductive chemical required to achieve and maintain the negative Eh reading was recorded and the total mass added to the soil/water matrix calculated. When Eh readings confirmed that the soil reductant demand was exceeded, 10 ml of water were collected from each test sample and titrated using a 0.01% mass/volume solution of iodine to determine the concentration of unspent reducing agent present in the water. The mass of unspent reductant was subtracted from the total mass added to the soil/water matrix to provide the soil demand for the 80 g sample. Values were calculated for both subsurface intervals and expressed in terms of milligrams reducing agent/kilogram soil. Once the reductant soil demand was determined, the soil/water sample matrices were spiked with a known volume of 5% mass/volume potassium chromate (K2CrO4) solution. The samples were then placed in the tumbler and mixed at a speed of 18 revolutions per minute for a 24 h period. Following the mixing period, the soil was allowed to settle and the water was then passed through a 0.45 µm filter. The filtrate was placed in a container and shipped to Merit Laboratories, Inc. for Cr(VI) analysis using EPA Method 218.4. The results of these sample analyses were used to evaluate the ability of the residual reducing agent to address continued chromium impacts.

9.2.8

Test Results

The results of the 3 h reaction test are presented in Table 9.2.1 and Table 9.2.2 for only CaS5 and FeSO4. The 3 h reaction test showed that NaHSO3 and

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TABLE 9.2.1 Calcium Polysulfide and Ferrous Sulfate Treatment Effectiveness Total Chromium CaS5

FeSO4

Dosing level

Initial mg/L

Final mg/L

Initial mg/L

Final mg/L

1 × Stoichiometric 2 × Stoichiometric 3 × Stoichiometric

0.39 0.39 0.39

0.026 <0.010 <0.010

0.39 0.39 0.39

0.018 <0.010 <0.010

Na2S2O3 provided no reduction of Cr(VI) at neutral pH values, despite increasing reagent dosages. CaS5 reduced Cr(VI) with an efficiency ranging from 11.6 to 100% reduction at dosages ranging from 1 to 3 times the stoichiometric requirement. The data also indicated that reductive reactions with calcium polysulfide appear complete after 2 h of reaction, since no further reduction was observed in the samples at 3 h. FeSO4 reaction is complete within 1 h for Cr(VI) reduction, but the settling kinetics for total chromium removal require longer settling times. NaHSO3 and S2O32− did not react effectively even at much higher treatment concentrations at neutral pH. Na2S2O4 was observed to be effective at 80 times the stoichiometric concentration with reaction within 24 h. The testing confirmed that 100% reduction of Cr(VI) can be achieved at a dosage ratio of 9 mg/L of CaS5 to 1 mg/L of Cr(VI) dissolved in the groundwater, which is 1.56 times the stoichiometric requirement. The reaction kinetics for the 9 to 1 ratio sample is presented in Table 9.2.3. 9.2.8.1 Analysis of Particles (Results) The geometric mean particle size on a population basis for the untreated water was determined to be 0.694 µm with a standard deviation of 1.326 µm. On a mass basis, the geometric mean was 1.089 µm with a standard deviation of 2.019 µm. The total mass of suspended solids in the water was 22 mg/L. Suspended particles in this size range are very difficult to remove from water by gravity separation and filtration methods.

TABLE 9.2.2 Calcium Polysulfide Treatment Concentrations CaS5 Concentration (mg/L)

Cr Reduction(%)

42 63 83

100 100 100

Ratio of CaSs/Cr(VI) 9.0 13.5 18.0

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TABLE 9.2.3 Cr(VI) Kinetic Testing Results Reaction 1.1.1.1 Time (hours)

CaS5 Concentration (mg/L)

Post-Treatment Cr (mg/l)

Cr Reduction (%)

0 1 1.5 2 2.5 2.5

0 43 43 43 43 43

4.3 0.516 0.215 0.095 0.093a 0.332b

0 88 95 97.8 97.8 92.3

a

Filtered at 0.45 µm.

b

Decant water only, no filtering.

The addition of CaS5 to the water produced a coagulation effect that increased the geometric mean particle size on a population basis to 1.823 µm with a standard deviation of 1.388 µm. On a mass basis, the geometric mean increased to 2.645 µm with a standard deviation of 1.488 µm. This shows that the particle size of the suspended solids was substantially increased, thus facilitating suspended solids removal. The total mass of suspended solids in the treated water was 48 mg/L after the CaS5 reaction. Additional testing showed that the suspended solids concentration increased to 200 mg/L when the pH was adjusted to 10.5 using 170 mg/L NaOH. This sample was not analyzed for mean particle size. Rapid settling and good clarification was observed in the water sample that was pH adjusted to 10.5. The decant water of this sample contained 20 mg/L suspended solids. Calcium carbonate (CaCO3) makes up a significant portion of the solids that precipitate during CaS5 treatment. This is owing to a disruption in the CO32− equilibrium caused by increased pH in the water. To test the effect of CaCO3 on the coagulation, one of the groundwater samples was pH adjusted to 6.5 following CaS5 treatment to evaluate whether lower pH would reduce the concentration of colloidal CaCO3 particles. The pH adjustment resulted in a geometric mean particle size based on a population basis of 1.904 µm with a standard deviation of 1.623 µm. However, on a mass basis the geometric mean was 5.088 µm with a standard deviation of 1.662 µm. The total mass of suspended solids in the treated water was 28 mg/L after pH adjustment. The quantity of sulfuric acid required to reduce the pH to 6.5 was 215 mg/L. This high acid demand indicates that pH adjustment is not a feasible remedial approach. In less alkaline water from a second site, CaS5 treatment resulted in precipitate formation at a concentration of less than 2.5 mg/L with a Cr(VI) concentration of 0.39 mg/L and a dosing concentration of 2 times the stoichiometric requirement. FeSO4 treatment by comparison resulted in the formation of 3.7 times the amount of solid, or 9.25 mg/L at a dosing of 2 times the stoichiometric requirement for a 0.39 mg/L Cr(VI) solution versus 1 mg/L in the original precipitation study described above.

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5 Chromium Concentration (mg/L)

4.5 4 3.5 3 2.5 –K = 2.0/h 2 1.5 1 0.5 0 0.1

1

10

Time (hours) FIGURE 9.2.1 Pseudo-first order reaction for CaS5.

Although the decreasing dosage requirement of CaS5 as a function of concentration indicates second-order kinetics, the data showed a poor correlation to second-order kinetics when evaluated graphically. Instead, a pseudo-first-order reaction was found to provide the best correlation with the data, showing that reduction occurred at a pseudo-first-order reaction rate constant of 2.0 h−1. The trend line does not conform to a linear regression, but it provides a good approximation of the rate constant as shown in Figure 9.2.1. 9.2.8.2 Soil Reductant Demand Results Permeable sand samples were evaluated to determine the amount of reducing agent the soils would consume if chromium reduction were performed in situ. Titrations were performed on the soil samples over a period of 10 days to monitor both long-term and short-term geochemical reactions. During the titrations, the 80 g shallow soil sample consumed 145 mL of 0.01 mol/L CaS5 solution before an Eh less than −100 mV was sustained for 24 h. The remaining water in the sample was then back-titrated with a 0.01% iodine solution to determine the amount of reductant in the water not consumed by the soil. The soil reductant demand was calculated by subtracting the unconsumed reactant from the total reductant added to the sample. The results showed that the shallow soil had a reductant demand of 3,440 mg of CaS5 per kg of soil. The same tests were repeated on the deep soil sample. 128 mL of 0.01 mol/L CaS5 solution was added to an 80 g soil sample in order to sustain an Eh less

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Chromium(VI) Handbook TABLE 9.2.4 Secondary Cr(VI) Reduction Results Sample I.D.

Theoretical Cr(VI) Concentration (mg/L)

Actual Cr(VI) Concentration (mg/L)

Relative Percent Difference (%)

43 81.5

101 91.4

114 102

12 11

than −100 mV. The remaining water was back-titrated with a 0.01% iodine solution to determine the fraction of reductant not consumed by the soils. The soil reductant demand for the deep soil calculated to be 2,780 mg of CaS5 per kg of soil. Suspected MnO2 nodules were identified in soil cores. In order to test the soil cores for MnO2, the identified MnO2 nodules were dissolved in 0.1 mol/L oxalic acid (H2C2O4). Release of CO2 and dissipation of brown/black were indicative of MnO2. The high soil reductant nodules demand was attributed to the MnO2 nodules. Although the soils consumed between 2,780 mg to 3,440 mg of CaS5 per kg of soil, some of the reductant reacted demand may be useful in treating Cr(VI). Fe and other minerals in the soil may be reduced by the CaS5, and these reduced minerals can later serve as reductants to reduce Cr(VI) to the trivalent state. Therefore, 1.87 mL of 5% K2CrO4 were added to the soil sample collected from 13.1 m, and 1.65 mL of 5% K2CrO4 were added to the soil sample collected from 24.8 m. The soil samples were placed into a tumbler for a period of 3 days so CrO42− could react with the treated soils. Following the reaction period, water from each sample was removed, filtered, and sent to Merit Laboratories for Cr(VI) analysis. The results showed no decrease in Cr(VI) concentrations that could be attributed to the secondary reducing reactions (see Table 9.2.4). 9.2.8.3 Reactive Permeable Barrier The batch test results indicate that the Fe-impregnated SiO2 sand was effective at reducing 100% of the reacted Cr(VI) in less than 24 h. The data, shown below in Figure 9.2.2, were linear on a semilog plot correlating to a regression line with an R-squared of 0.952. The pseudo-first-order reaction rate constant was not modeled, but would be anticipated to fall in the K = 0.2 h− to 0.3 h−1 range. The kinetics indicated that a Fe-impregnated SiO2 sand could operate effectively in slow and fast flowing aquifers.

9.2.9

Conclusions

The following conclusions were derived from the treatability study: • NaHSO3 and Na2S2O3 did not reduce Cr(VI) at neutral pH at the concentrations tested in this study.

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Concentration (mg/L)

7 6 y = –0.9375ln(x) + 3.3282 5 R2 = 0.952

4 3 2 1 0 0.01

0.1

1

10

100

Hours FIGURE 9.2.2 Reaction kinetics for Fe impregnated silica sand batch experiments.

• Na2S2O4 reduced Cr(VI) at neutral pH, but at 40 to 80 times the stoichiometric requirement. • FeSO4 reduced Cr(VI) at 2 and 3 times the stoichiometric requirement at the fastest rate tested, but generated 3.7 times the mass of precipitate generated by CaS5. • CaS5 reduced Cr(VI) at 1.56 the stoichiometric demand or from 7 to 9 mg/L of CaS5 per each mg/L of Cr(VI). • The reduction rate for Cr(VI) by CaS5 is best modeled using a pseudo-first-order reaction rate constant of 2.0 h−1 although the fit is based on a linear approximation of a nonlinear function. • CaS5 treatment coagulated suspended solids, and precipitated them from solution effectively. Rapid settling times with good clarification was observed at a pH of 10.5, although raising the pH was not required to get effective precipitation. The NaOH demand to increase the pH to 10.5 was 170 mg/L. • Reducing the pH of the water after CaS5 treatment increased the particle size and also improved settling of solids. However, traces of H2S gas were noted during pH adjustment. The sulfuric acid (H2SO4) demand to lower the treatment water pH to 6.5 was 215 mg/L. • The site-specific soil reducing demand ranged from 2,780 mg to 3,440 mg of CaS5 per kg of soil. Therefore, approximately 98% of the injected CaS5 in an in situ application would be used to create a reductive environment in the soils, and the remaining 2% would be used to reduce Cr(VI) in the groundwater. The high reductant demand was attributed to MnO2 nodules.

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Chromium(VI) Handbook • Fe impregnated SiO2 sand reduced Cr(VI) effectively within 24 h, and the SiO2-impregnated Fe was stable during column studies after 1,000 pore volumes indicating that the Fe will not undergo rapid auto-oxidation. Reaction kinetics were fast indicating that this material could be used in varriers under slow and fast flowing aquifer conditions.

Bibliography Bartlett, R.J. 1991, Chromium cycling in soils and water: links, gaps, and methods, Environmental Health Perspectives, 92, 17–24. Fendorf, S. and Li, 1996, Kinetics of Ferrous Iron Chromate Reduction by Green Rusts. U.S. Environmental Protection Agency (USEPA), 2000, In Situ Treatment of Soil and Groundwater Contaminated with Chromium.

9.3

Assessing the Potential for Biological Cr(VI) Reduction in an Aquifer Contaminated with Mixed Wastes

Sarah Middleton Williams, Craig S. Criddle, and Michael J. Dybas 9.3.1

Introduction

Owing to its widespread industrial use, Cr(VI) is often found in contaminated groundwater. In order to achieve concentrations of Cr less than the U.S. Environmental Protection Agency (USEPA) maximum contaminant level (MCL) for total soluble Cr (100 µg/l), remediation strategies focus on the reduction of Cr(VI) to insoluble Cr(III) forms, which are relatively stable and nontoxic at moderate concentration. The only compounds able to oxidize Cr(III) at any appreciable rate are Mn oxides (Eary and Rai, 1987). Bioremediation may be effective for the removal of Cr(VI) from groundwater, as many aerobic and anaerobic microorganisms reduce Cr(VI) to Cr(III) while utilizing a wide range of electron donors (Bopp and Ehrlich, 1988; Ishibashi et al., 1990; Shen and Wang, 1993; Rege et al., 1997; Tebo and Obraztsova, 1998; Francis et al., 2000; Myers et al., 2000). The potential for a bioremediation scheme to remove Cr(VI) was investigated for an aquifer contaminated with mixed wastes in Schoolcraft, MI. In addition to high concentrations of NO3−, SO42−, and chlorinated solvents, the contaminated area contains Cr(VI) contamination from a wood finishing operation in the range of 0.5 mg/L to 2.5 mg/L. There are both abiological and biological mechanisms for Cr(VI) reduction in a subsurface environment. Naturally occurring abiologic reductants of

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Cr(VI) include Fe(II) compounds, sulfur(II) compounds such as thiosulfate ion (S2O32−), and organic matter and reduction can occur with or without a surface-catalyst. Microorganisms can reduce Cr(VI) directly, via a respiratory or cometablic pathway or indirectly, via production of Fe(II) or sulfide by Fe(III) and SO42−-reducing bacteria [dissimilatory iron-reducing bacteria (DIRB) or sulfate reducing bacteria (SRB)] respectively. Understanding the mechanism of Cr(VI) reduction in an aquifer will determine which metabolic group of organisms to stimulate. In a mixed waste setting, the success of bioremediation may also hinge upon understanding the sequence in which electron acceptors are reduced. Bacteria often preferentially utilize more energetically-favorable electron acceptors. For example, in the presence of NO3−, reduction of Mn(IV), S2O32−, and Fe(III) in Shewanella putrefaciens 200 was inhibited, indicating that NO3− was the preferred electron acceptor for anaerobic respiration (DiChristina, 1992). Nitrate could pose a potential problem in Cr(VI) remediation in two ways. If indirect reduction of Cr(VI) (by DIRB or SRB) were to be the dominant mechanism of Cr(VI) reduction, then these bacteria should be stimulated. NO3− often inhibits DIRB or SRB, thus a 2-step treatment scheme may be needed, where NO3− is removed first. If direct reduction of Cr(VI) were to dominate, then NO3− could potentially inhibit Cr(VI) reduction since Cr(VI) and NO3− have similar redox potentials. Viamajala et al., (2002a) recently reported Cr(VI) reduction during denitrification in shewanella oneidensis MR-1. However, they found that NO3− and nitrite (NO2−) inhibited specific rates of Cr(VI) reduction in stationary phase cells (Viamajala et al., 2002b). This work examines whether indigenous microorganisms in School craft aquifer material can reduce Cr(VI) and whether NO3− and Cr(VI) reduction simultaneously occur. Successful removal of Cr(VI) hinges upon the formation and stability of Cr(III) precipitates. The USEPA MCL for Cr is measured in terms of total soluble Cr, including both soluble Cr(VI) and insoluble Cr(III). At the pH of most groundwater, Cr(III) formed from Cr(VI) reduction will precipitate as insoluble Cr(III) hydroxides (Jardine et al., 1999). However, Cr(III) is known to complex with organic ligands (Nieboer and Jusys, 1988). In this work, we also determine whether various electron donors, which could serve as potential ligands, influence Cr(III) solubility. 9.3.2

Materials and Methods

9.3.2.1 Microcosms Microcosms to test simultaneous nitrate and Cr(VI) reduction consisted of sediment from a comingled region of Schoolcraft Plumes F and G and anaerobic Schoolcraft groundwater amended with NH4Cl, KH2PO4, trace metals, and vitamins in 250 mL serum bottles. Lactate (C3H5O3−) was employed as the carbon and energy source and added to 0.01 mol/L from an autoclaved 1 mol/L sodium lactate stock. Microcosms were assembled

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in a Coy anaerobic chamber under an atmosphere of 10% hydrogen/nitrogen, sealed with butyl rubber stoppers and crimped. CrO42− was added as electron acceptor in the form of K2CrO4 (99.9%, Sigma) from an anaerobic 500 mg/L stock solution. Samples were withdrawn in the anaerobic chamber, filtered with a 0.2 µm filter and stored at −20 °C until analysis. All stock solutions were stored in serum bottles with a nitrogen headspace and kept in an anaerobic chamber. Microcosms prepared for Cr(III) solubilization experiments used a synthetic groundwater medium and varying electron denors. 9.3.2.2 Enrichment Culture An enrichment culture was started using Schoolcraft sediment and an anaerobic synthetic Schoolcraft groundwater medium. Lactate was employed as the carbon and energy source and added to 0.01 mol/L from an autoclaved 1 mol/L anaerobic sodium lactate stock. NO3− was added to approximately 0.005 mol/L from a 2 mol/L anaerobic stock solution. SO42− and other electron acceptors (other than Cr(VI)) were excluded from the medium. The culture was successively transferred to new medium approximately every 3 weeks over a 9 month period prior to these experiments. For the experiments described here, 1 mL of the enrichment culture was used to inoculate 20 mL of anaerobic synthetic groundwater medium (described above) in 25-mL serum test tubes prepared in an anaerobic chamber. Samples were periodically removed and analyzed for soluble Cr(VI), NO3−, and NO2−. 9.3.2.3 Analytical Methods Soluble Cr(VI) was determined colorimetrically using 1,5-diphenyl-carbazide in a sulfuric acid solution (pH 2) (Sandell, 1959). Samples were filtered with 0.2 µm filters prior to analysis. Absorbance was measured at 540 nm using a Uvikon XL Spectrophotometer (Bio-Tek Instruments). Total soluble Cr was measured using a TJA IRIS Advantage/1000 Radial ICAP Spectrometer with a solid state CID Detector. NO3− and NO2− were measured using ion chromatography with a LC 20 ion chromatograph (Dionex, Sunnyvale) equipped with CD 25 detector and an IonPac AS11-HC (4 mm) column (Dionex) using a NaOH buffer (0.025 mol/L NaOH) at a flow rate of 1.5 mL/min. 9.3.3

Results and Discussion

Simultaneous Cr(VI) and NO3− Reduction in Schoolcraft Sediment Microcosms The first question we explored was whether biological Cr(VI) reduction would occur in Schoolcraft aquifer material using the native microflora. If indigenous microorganisms capable of reducing Cr(VI) were not present, then other remediation approaches would have to be considered, such as bioaugmentation with a known Cr(VI)-reducer. As shown in Figure 9.3.1A, slightly more than 0.0001 mol/L Cr(VI) (6 mg/L) was completely reduced in microcosms containing Schoolcraft aquifer material and groundwater within 5 days. At the end

9.3.3.1

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200 2−

500

150 3 −

200

50

(µmol/L)

Cv

2−

300

100

−

400

NO

NO3 / SO4

Soluble Cr(VI) (µmol/L)

SO4

100 0

0 0

1

2

3

4

5

Days FIGURE 9.3.1A Microcosms with Schoolcraft aquifer material and groundwater simultaneously reduced Cr(VI) and NO3. Values are the average of duplicates and error bars represent the range. = Soluble Cr(VI), = NO3− , = SO42− _ _ _ USEPA MCL.

of the experiment, total soluble Cr hovered just above the USEPA MCL of 0.000002 mol/L (100 µg/L), indicating that a small amount of the Cr(III) did not precipitate as the insoluble hydroxide, but remained in a soluble form. This will be discussed in a subsequent section. No Cr(VI) reduction occurred in heatkilled (pasteurized) controls, indicating that biological activity is needed for Cr(VI) reduction to occur (Figure 9.3.1.B).

Soluble Cr (µmol/L)

150

100

50

0 0

1

2

3

4

5

6

7

8

9

10

Days FIGURE 9.3.1B Pasteurized microcosms did not show any Cr(VI) reduction, indicating that biological activity is needed for Cr(VI) reduction. Values are the average of duplicates and error bars represent the range. = Total soluble Cr.

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Figure 9.3.1A shows that NO3− and Cr(VI) were simultaneously reduced and that little SO42− reduction occurred over the course of the experiment. These findings have several implications for the bioremediation of at the Schoolcraft site First, it is clear that simple biostimulation can achieve the desired outcome. If NO3− had an inhibitory effect on Cr(VI) reduction, NO3− removal would have to precede Cr(VI) reduction, or organisms capable of simultaneous NO3− and Cr(VI) reduction would have to be added. Second, Cr(VI) reduction was not dependent upon SO42−-reduction. This is also advantageous, as SO42− reduction is often inhibited by NO3−. One hypothesis is that NO3−-reducing organisms in the aquifer material were able to reduce Cr(VI) cometabolically. As described below, enrichment experiments supported this hypothesis. However, it is also possible that indigenous Fe-reducing bacteria reduced Fe(III) to Fe(II), which in turn reduced Cr(VI). 9.3.3.2

Cr(VI) Reduction during Denitrification in Schoolcraft Enrichments To determine whether NO3−-reducing bacteria could reduce Cr(VI), batch studies were performed in synthetic groundwater using enrichment cultures. The enrichments were inoculated with Schoolcraft sediment, grown on lactate and NO3−, and successively transferred into fresh media over a 9-month period. The enrichment culture was used to inoculate test tubes with anaerobic synthetic groundwater spiked with 0.01 mol/L lactate, 0.005 mol/L NO3−, and approximately 2.5 mg/L (0.00005 mol/L) or 10 mg/L (0.0002 mol/L) of Cr(VI). As shown in Figure 9.3.2A and Figure 9.3.2B, Cr(VI) and NO3− were 6 5 3 4

−

NO3 /NO2 (mmol/L)

3

2

2 1

−

Cr(VI) Concentration (mg/L)

4

1 0

0 0

1

2

3

4

5

6

7

8

9

Days FIGURE 9.3.2A Schoolcraft enrichment cultures simultaneously reduced Cr(VI) and NO3− at initial Cr(VI) concentrations of 2 mg/L (9.3.2A) and 11 mg/L. Autoclaved and no-cell controls showed little Cr(VI) disappearance (data not shown). = Soluble Cr(VI), = NO3− NO2−.

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8

4

6

3

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2

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1

−

12

NO3 /NO2 (mmol/L)

0

−

Cr(VI) Concentration (mg/L)

Bench Tests

0 0

10

20

30

40

Days FIGURE 9.3.2B Autoclaved and no-cell controls showed little Cr(VI) disappearance (data not shown). Values are the average of duplicates and error bars represent the range. = Soluble Cr(VI), = NO3− NO2−.

simultaneously reduced at both low and high concentrations of Cr(VI). In enrichment cultures that were cultivated with Cr(VI) as the only electron acceptor, the Cr(VI) reduction rate was very slow and sometimes negligible (data not shown). In abiotic and autoclaved controls, minimal Cr(VI) reduction occurred (data not shown). The enrichment culture experiments showed that there are in fact indigenous microorganisms in present that are capable of simultaneously reducing NO3− and Cr(VI). This supports the conclusion that NO3−-reducing organisms play a significant role in the reduction of Cr(VI) in the Schoolcraft aquifer material.

9.3.3.3 Cr(III) Solubilization It has long been known that Cr(III) forms complexes with organic acid anions (Hamm et al., 1958). Total soluble chromium was measured at the end of microcosm experiments described in 9.3.3.1 in order to probe for the presence of soluble Cr(III). Soluble Cr(III) is commonly computed as the difference between total soluble Cr and total soluble Cr(VI). As shown in Figure 9.3.1A, the total soluble Cr at the end of the experiment was slightly above the MCL. This finding led to another set of experiments to determine the effect of electron donor on soluble Cr(III) concentrations. When lactate was used as electron donor at 0.001 mol/L, both Cr(VI) and total soluble Cr approached zero by the end of the experiment, indicating minimal soluble Cr(III) (Figure 9.3.3A). Through the course of the experiment, some soluble Cr(III) seemed to be formed but precipitated out by day 4. However, when 0.01 mol/L lactate was used, the final soluble Cr concentration was 530 µg/L, well above the USEPA MCL (Figure 9.3.3B). Some Cr(III) remained soluble, presumably as a complex to

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1 mmol/L Lactate 500

Total Cr 400

3 −

0 0

0

11

0

200

S Cr ol. (III ) Sol. Cr(VI)

100

MCL 22

3 Days Days

3

4

4

(µmol/L)

1

Cv

Total Sol. 50 Cr

2−

300

100 2

−

Insoluble Cr

3

NO

NO3 / SO4

Cr (mg/L) Soluble Cr(VI) (µmol/L)

2−

SO4

4 150

0

5

5

FIGURE 9.3.3A Electron donor affects the amount of Cr(III) that remains soluble following reduction of Cr(VI) to Cr(III) in microcosms containing Schoolcraft aquifer material. Soluble Cr(III) is the difference between total soluble Cr and soluble Cr(VI). Microcosms with lactate at 1 mmol/L showed little Cr(III) left in soluble form. Values are the average of duplicates and error bars represent the range. = Soluble Cr(VI), = total soluble Cr, – = total Cr _ _ _ USEPA MCL.

lactate. As expected, this trend was most obvious when citrate (C6H5O73−) was used as electron donor (Figure 9.3.3C), as it is known that citrate forms a complex with Cr(III) (James and Bartlett, 1983). In the case of citrate, the total soluble Cr concentrations were considerably greater the amount of Cr(VI) that was added to the microcosm. This is presumably owing to residual Cr in the 6 10 mmol/L Lactate

Total Cr 5 Sol. Cr(III)

Cr (mg/L) (mg/L) Cr

4

Insoluble Cr

3 Total Soluble Cr

Sol. Cr(VI)

2 1

MCL 0

0

1

2

3

4

5

Days FIGURE 9.3.3B Microcosms with lactate at 10 mM showed the final soluble Cr(III) to be above the USEPA MCL for total soluble Cr of 100 µg/L. = Soluble Cr(VI), = total soluble Cr, – = total Cr _ _ _ USEPA MCL.

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8 1 mmal/L Citrate 7

Cr (mg/L)

6 5 Sol. Cr(III)

4

Total Soluble Cr 3 2 MCL

Sol. Cr(VI)

1 0 0

1

2

3

4

5

Days FIGURE 9.3.3C Citrate caused the majority of Cr(III) to remain in soluble form throughout the experiment (9.3.3C). Values are the average of duplicates and error bars represent the range. = Soluble Cr(VI), = total soluble Cr, – = total Cr _ _ _ USEPA MCL.

sediment. Acetate at 0.001 mol/L and 0.01 mol/L, as well as palmitic acid (CH3 (CH2)14COOH) beads (a source of slow release hydrogen) showed little soluble Cr(III) formation throughout the duration of the experiment (data not shown). These observations are important for bioremediation of Cr(VI) because the USEPA MCL is measured in terms of total soluble Cr, including both soluble Cr(VI) and Cr(III). In addition, it should be noted that bioremediation strategies based on the addition of large amount of fermentable organic carbon, such as molasses or vegetable oil, are likely to produce organic acids such as lactic acid (CH3 CHOH COOH) that can potentially chelate and solubilize Cr(III).

9.3.4

Conclusions

Many electron acceptors are present in contaminated systems and often vary spatially and with time. Although NO3− has a half-reaction reduction potential that is comparable to Cr(VI), Schoolcraft organisms are able to reduce Cr(VI) while reducing NO3−. That native microflora from Plume G can reduce Cr(VI) in environments containing NO3− bodes well for bioremediation of Cr(VI) at the site. Building up denitrifying biomass that is able to reduce Cr(VI) has potential to be an effective remediation strategy. Cr(VI) reduction can occur without decreasing the redox potential to levels needed to support DIRB or SRB, which may require large amounts of electron donor that could potentially solubilize Cr(III). A pilot scale bioremediation scheme is currently operating at the Schoolcraft site to remove both chlorinated solvents and Cr(VI) using a biocurtain.

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Acknowledgments This work was supported by the Michigan Department of Environmental Quality. Partial support for S.M.W. was provided by the National Science Foundation Graduate Fellowship. We would like to thank Haekyung Kim and Elizabeth Kerrin for their experimental help.

Bibliography Bopp, L.H. and Ehrlich, H.L., 1988, Chromate resistance and reduction in pseudomonas fluorescens strain LB300, Arch. Microbiol., 150, 426–431. DiChristina, T.J., 1992, The effects of nitrate and nitrite on dissimilatory iron reduction in shewanella putrefaciens 200, J. Bacteriol., 174, 1891–1896. Eary, L.E. and Rai, D., 1987, Kinetics of Cr(III) oxidation to Cr(VI) by reaction with manganese dioxide, Environ. Sci. Technol., 21, 1187–1193. Francis, C.A., Obraztsova, A.Y., and Tebo, B.M., 2000, Dissimilatory metal reduction by the facultative anaerobe pantoea agglomerans SP1, Appl. Environ. Microbiol., 66, 543–548. Hamm, R.E., Johnson, R.L., Perlcins, R.H., and Davis, R.E., 1958, Complex ions of chromium, VIII. Mechanism of reaction with organic acid anions with Chromium(III), J. Am. Chem. Soc. 80: 4469–4471. Ishibashi Y., Cervantes C., and Silver S., 1990, Chromium reduction in pseudomonas putida, Appl. Environ. Microbiol., 56, 2268–2270. Jardine, P.M., Fendorf, S.E., Mayes, M.A., Larsen, I.L., Brooks, S.C., and Bailey, 1999, Fate and transport of hexavalent chromium in undisturbed heterogeneous soil, Environ. Sci. Technol., 33, 2939–2944. Myers, C.R., Carstens, B.P., Antholine, W.E., and Myers, J.M. 2000, Chromium (VI) reductase activity is associated with the cytoplasmic membrane of anaerobically grown shewanella putrefaciens MR-1. J. Appl. Microbiol., 88, 98–106. Nieboer, E. and Jusys, A.A., 1988, Biologic chemistry of chromium, in Chromium in the Natural and Human Environments, Nriagu, J.O. and Nieboer, E., Ed., John Wiley and Sons, pp. 31–33. Rege, M.A., Petersen, J.N., Johnstone, D.L., Turick, C.E., Yonge, D.R., and Apel, W.A., 1997, Bacterial reduction of hexavalent chromium by enterobacter cloacae strain HO1 grown on sucrose, Biotechnol. Lett., 19, 691–694. Sandell, E.B., 1959, Colorimetric Determination of Traces of Metals, Interscience Publishers, New York, 260 p. Shen, H. and Wang, Y., 1993, Characterization of enzymatic reduction of hexavalent chromium by escherichia coli ATCC 33456, Appl. Environ. Microbiol., 59, 3771–3777. Tebo, B.M. and Obraztsova A.Y., 1998, Sulfate-reducing bacterium grows with Cr(VI), U(VI), Mn(IV), and Fe(III) as electron acceptors, FEMS Microbiol. Lett., 162, 193–198. Viamajala, S., Peyton B.M., Apel, W.A., and Petersen, J.N., 2002a, Chromate reduction in shewanella oneidensis MR-1 is an inducible process associated with anaerobic growth, Biotechnol. Prog., 18, 290–295. Viamajala, S., Peyton, B.M., Apel, W.A., and Petersen, J.N., 2002b, Chromate/nitrite interactions in shewanella oneidensis MR-1: evidence for multiple hexavalent chromium Cr(VI) reduction mechanisms dependent on physiological growth conditions, Biotechnol. Bioeng., 78, 770–777.

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10 Case Studies

CONTENTS 10.1 Overview of In Situ Remediation Case Studies..................................362 James A. Jacobs and J.M.V. Rouse 10.1.1 Introduction to Geochemical Fixation and Chromium(VI) Reduction..................................................362 10.1.2 Brief Overview of Remediation Methods ..............................364 10.1.2.1 Conventional Methods..............................................364 10.1.2.2 Less Conventional Methods.....................................364 10.1.3 Recommended Technologies ....................................................365 10.1.3.1 Geochemical Fixation ................................................365 10.1.3.1.1 Chemistry ................................................367 10.1.3.1.2 Reducing Agents ....................................367 10.1.3.1.3 Reducing Agent ......................................369 10.1.3.1.4 Reducing Agent ......................................369 10.1.3.2 Geochemical Fixation Concerns ..............................369 10.1.4 Other Technologies.....................................................................369 10.1.4.1 Permeable Reactive Barriers (PRBS) .......................369 10.1.4.2 Chromium Reduction Using Reactive Media .......371 10.1.4.3 Brief PRB Case Study ................................................371 Bibliography..............................................................................................372 10.2 Frontier Hard Chrome, Vancouver, Washington ................................373 Stephen M. Testa 10.2.1 Introduction.................................................................................373 10.2.2 Site Location and History .........................................................373 10.2.3 Regulatory Overview.................................................................374 10.2.4 Site Characterization..................................................................374 10.2.5 Remedial Investigation..............................................................375 10.2.6 Remedial Performance ..............................................................375 10.2.7 Conclusion ...................................................................................376 Bibliography..............................................................................................376 10.3 United Chrome Products, Inc., Corvallis, Oregon..............................376 Stephen M. Testa 10.3.1 Introduction.................................................................................376 10.3.2 Site Location and History .........................................................377 1-5667-0608-4/05/$0.00+$1.50 © 2005 by CRC Press LLC

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10.3.3 Regulatory Overview.................................................................377 10.3.4 Site Characterization..................................................................378 10.3.5 Remedial Investigation..............................................................378 10.3.6 Remedial Performance ..............................................................379 10.3.7 Conclusion ...................................................................................380 Bibliography ..............................................................................................380 10.4 Former Wood Treating Plant, Windsor, Northern California ...........381 James A. Jacobs 10.4.1 Introduction.................................................................................381 10.4.2 Site Location and History .........................................................381 10.4.2.1 Site Setting...................................................................381 10.4.2.2 Historical Land Use ...................................................381 10.4.2.3 Recent Site Activities .................................................382 10.4.3 Regulatory Overview.................................................................382 10.4.3.1 Regulatory Agencies..................................................382 10.4.3.1.1 Timeline of Regulatory Activities ........382 10.4.3.2 Cleanup Standards.....................................................383 10.4.4 Site Characterization..................................................................383 10.4.4.1 Site Geology ................................................................383 10.4.4.2 Site Hydrology ...........................................................383 10.4.4.3 Field Sampling Activities..........................................383 10.4.5 Remedial Investigation..............................................................383 10.4.5.1 Remedial Alternatives Evaluation...........................383 10.4.5.2 Pilot Study Results.....................................................384 10.4.5.3 Selected Remedial Alternative .................................386 10.4.6 Remedial Performance ..............................................................386 10.4.6.1 Treatment Program ....................................................386 10.4.6.2 Performance Results ..................................................386 10.4.7 Conclusions .................................................................................387 Bibliography..............................................................................................387 10.5 Valley Wood Preserving Plant, Turlock, California............................388 James A. Jacobs 10.5.1 Introduction.................................................................................388 10.5.2 Site Location and History .........................................................388 10.5.2.1 Site Setting...................................................................388 10.5.2.2 Historical Land Use ...................................................389 10.5.2.3 Recent Site Activities .................................................389 10.5.3 Regulatory Overview.................................................................390 10.5.3.1 Regulatory Agencies..................................................390 10.5.3.2 Timeline of Regulatory Activities............................390 10.5.3.3 Cleanup Standards.....................................................390 10.5.4 Site Characterization..................................................................391 10.5.4.1 Site Geology ................................................................391 10.5.4.2 Site Hydrology ...........................................................391 10.5.4.3 Field Sampling Activities..........................................391

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10.5.5 Remedial Investigation..............................................................391 10.5.5.1 Remedial Alternatives Evaluation...........................391 10.5.5.2 Pilot Study Results.................................................... 391 10.5.5.3 Reducing Agent Selected ..........................................393 10.5.5.4 Selected Remedial Alternative .................................393 10.5.6 Remedial Performance ..............................................................393 10.5.6.1 Treatment Plan............................................................393 10.5.6.2 Performance Results ..................................................393 10.5.7 Conclusions .................................................................................395 Bibliography ..............................................................................................395 10.6 Townsend Saw Chain Company, Pontiac, Richland County, South Carolina ..........................................................................................396 James A. Jacobs and Ralph O. Howard, Jr. 10.6.1 Introduction.................................................................................396 10.6.2 Site Location and History .........................................................396 10.6.2.1 Site Setting...................................................................396 10.6.2.2 Historical Land Use ...................................................396 10.6.2.3 Recent Site Activities .................................................399 10.6.3 Regulatory Overview.................................................................400 10.6.3.1 Regulatory Agencies .................................................400 10.6.3.2 Timeline of Regulatory Activities............................400 10.6.3.3 Regulatory Standards ................................................404 10.6.3.3.1 Cleanup Standards.................................404 10.6.4 Site Characterization..................................................................404 10.6.4.1 Site Geology ................................................................404 10.6.4.2 Site Hydrology ...........................................................405 10.6.4.3 Field Sampling Activities..........................................405 10.6.4.4 Remedial Alternatives Evaluation (FS) ..................405 10.6.4.5 Selected Remedial Alternative .................................405 10.6.4.6 Pilot Study Results.....................................................406 10.6.5 Remedial Performance ..............................................................406 10.6.5.1 Performance Results ..................................................407 10.6.6 Conclusions .................................................................................409 Bibliography ..............................................................................................409 10.7 Former Paper Mill, Delaware River, East Coast .................................409 James A. Jacobs 10.7.1 Introduction.................................................................................409 10.7.2 Site Location and History .........................................................409 10.7.2.1 Site Setting...................................................................409 10.7.2.2 Historical Land Use ...................................................410 10.7.2.3 Recent Site Activities .................................................410 10.7.3 Regulatory Overview.................................................................410 10.7.3.1 Cleanup Standards.....................................................410 10.7.4 Site Characterization..................................................................410 10.7.4.1 Site Hydrology ...........................................................410

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10.7.5 Remedial Investigation..............................................................410 10.7.5.1 Review of Remedial Options ...................................410 10.7.5.2 Selected Remedial Alternative ................................. 411 10.7.6 Remedial Performance .............................................................. 411 10.7.6.1 Treatment Train .......................................................... 411 10.7.6.2 Performance Results .................................................. 411 10.7.7 Conclusions ................................................................................. 411 Bibliography ............................................................................................ 411 10.8 Wood Treating Facility, South Australia...............................................412 James A. Jacobs 10.8.1 Introduction.................................................................................412 10.8.2 Site Location and History .........................................................412 10.8.2.1 Site Setting...................................................................412 10.8.2.2 Historical Land Use ...................................................412 10.8.2.3 Recent Site Activities .................................................412 10.8.3 Regulatory Overview.................................................................412 10.8.3.1 Regulatory Agencies..................................................412 10.8.3.2 Timeline of Regulatory Activities............................412 10.8.3.3 Cleanup Standards.....................................................413 10.8.4 Site Characterization..................................................................413 10.8.4.1 Site Geology and Hydrogeology .............................413 10.8.4.2 Field Sampling Activities..........................................413 10.8.5 Remedial Investigation..............................................................413 10.8.5.1 Remedial Evaluation .................................................413 10.8.5.2 Selected Remedial Alternative .................................413 10.8.6 Remedial Performance ..............................................................413 10.8.6.1 Treatment Program ....................................................413 10.8.6.2 Performance Results ..................................................414 10.8.7 Conclusions .................................................................................414 Bibliography .............................................................................................414 10.9 Coast Wood Preserving Plant, Ukiah, California ...............................415 James A. Jacobs 10.9.1 Introduction.................................................................................415 10.9.2 Site Location and History .........................................................415 10.9.2.1 Site Setting...................................................................415 10.9.2.2 Historical Land Use ...................................................415 10.9.2.3 Recent Site Activities .................................................415 10.9.3 Regulatory Overview.................................................................416 10.9.3.1 Regulatory Agencies..................................................416 10.9.3.2 Timeline of Regulatory Activities............................416 10.9.3.3 Cleanup Standards.....................................................417 10.9.4 Site Characterization..................................................................418 10.9.4.1 Site Geology ................................................................418 10.9.4.2 Site Hydrology ...........................................................418 10.9.4.3 Field Sampling Activities..........................................418 10.9.5 Remedial Investigation..............................................................418

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10.9.5.1 Remedial Alternatives Evaluation...........................418 10.9.5.2. Pilot Study Results.....................................................418 10.9.5.3 Selected Remedial Alternative .................................419 10.9.6 Remedial Performance ..............................................................419 10.9.6.1 Treatment Train ..........................................................419 10.9.6.2 Performance Results ..................................................419 10.9.7 Conclusions .................................................................................419 Bibliography..............................................................................................420 10.10 Industrial Facility, Grand Rapids, Michigan .......................................420 David Bohan, David Wierzbicki, Jason Peery, Anna Willett, and Steve Koenigsberg 10.10.1 Introduction ...............................................................................420 10.10.2 Site Location and History........................................................421 10.10.2.1 Site Setting ...............................................................421 10.10.2.2 Historical Land Use................................................421 10.10.2.3 Recent Site Activities..............................................422 10.10.3 Regulatory Overview ...............................................................422 10.10.3.1 Regulatory Agencies .............................................422 10.10.3.2 Timeline of Regulatory Activities ........................422 10.10.3.3 Cleanup Standards .................................................422 10.10.4 Site Characterization ................................................................422 10.10.4.1 Site Geology.............................................................422 10.10.4.2 Site Hydrology ........................................................423 10.10.4.3 Field Sampling Activities ......................................423 10.10.5 Remedial Investigation ............................................................425 10.10.5.1 Remedial Alternatives Investigation ...................425 10.10.5.2 Pilot Study Results .................................................425 10.10.6 Remedial Performance .............................................................425 10.10.6.1 Treatment Train .......................................................425 10.10.6.2 Performance Results...............................................426 10.10.7 Conclusions................................................................................426 Bibliography .............................................................................................427 10.11 Remediation of Cr(VI) Using Engineered Anaerobic In Situ Reactive Zones ............................................................................427 John F. Horst and Suthan S. Suthersan 10.11.1 Introduction ...............................................................................427 10.11.2 Design Considerations .............................................................429 10.11.2.1 Hydrogeology..........................................................429 10.11.2.2 Groundwater Chemistry .......................................430 10.11.2.3 System Layout.........................................................430 10.11.2.4 Baseline Definition..................................................431 10.11.2.5 Carbon Donors........................................................431 10.11.3 Bio-Geo-Chemical Behavior of Chromium...........................431 10.11.4 Contaminant Removal Mechanisms......................................433 10.11.5 Regulatory Issues......................................................................433 10.11.6 Case Study 1: Western United States ....................................434

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10.11.7 Case Study 2: Southwestern United States ..........................436 10.11.8 Case Study 3: Eastern United States......................................437 Bibliography ..............................................................................................439 10.12 Attenuation of a Mixed Chromium and Chlorinated Ethene Groundwater Plume in Estuarine-Influenced Glaciated Sediments...................................................................................................440 Lucas A. Hellerich, Matthew A. Panciera, Gregory M. Dobbs, Nikolaos P. Nikolaidis, and Barth F. Smets 10.12.1 Introduction ...............................................................................440 10.12.2 Methodology..............................................................................441 10.12.2.1 Site Description .......................................................441 10.12.2.2 Field and Analytical Techniques ..........................442 10.12.2.3 Assessment Methodology .....................................442 10.12.3 Results and Discussion ............................................................444 10.12.3.1 Plume Characteristics and Geochemistry...........444 10.12.3.2 Geological Character ..............................................448 10.12.4 Attenuation Processes ..............................................................449 10.12.4.1 Partitioning and Mass Fluxes ...............................449 10.12.4.2 Reduction and Biotransformation........................455 10.12.4.3 Competition for Reduction Power and Sorption Interactions ..............................................457 10.12.5 Conclusions and Engineering Implications..........................460 Acknowledgments ...................................................................................461 Bibliography ................................................................................ 461

10.1 Overview of In Situ Remediation Case Studies

James A. Jacobs and J. M. V. Rouse The case studies contained in this section represent a variety of technologies from sites primarily throughout the U.S. The case studies have been compiled from publicaly available documents for the purposes of this handbook. The IETEG and editors of this handbook gratefully acknowledge the original referenced authors of the included case studies and encourage readers to contact them for further details. 10.1.1

Introduction to Geochemical Fixation and Chromium(VI) Reduction

There are several approaches to treatment of chromium(VI) (Cr(VI)) in soil and groundwater, including isolation, immobilization, toxicity reduction, physical separation, and extraction (USEPA, 2002). For cleanup goals for total and leachable Cr, various analytical procedures are used (Table 10.1.1). Since there are

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Cr (total)

Total chromium goals (mg/kg) Background (mean) Background (range) Superfund site goals Theoretical minimum total Cr to ensure TCLP leachate < threshold (i.e., TCLP × 20) California TTLC

Soil or solids (mg/kg) 100 1 to 1,000 6.7 to 375.0 100

Leachable chromium (µg/L) TCLP threshold for RCRA waste by SW 846, Method 1311 Extraction procedure toxicity test by EP Tox, Method 1310 California soluble threshold limit concentration (STLC) for RCRA waste MCL Superfund site goals Synthetic precipitate leachate procedure by Method 1312 Multiple extraction procedure by Method 1320

Cr (µg/L) 5,000

500

5,000 5,000 100 50 No specified level listed for Cr and no example cases identified No specified level listed for Cr and no example cases identified

SW = solid waste, EP = extraction procedure, TTLC = total threshold limit concentration, TCLP = toxicity characteristic leaching procedure, MCL = maximum contaminant level. Source:

USEPA, 2002.

numerous methods and regulatory goals, it is important to identify the Cr target concentrations for each site (total or leachable) early in the remediation planning process. In addition, individual site conditions vary significantly and greatly influence remediation effectiveness, so the technologies selected must match the closure goals in order to have a successful outcome. In uncontaminated groundwater, Cr concentrations varies widely, however, for most natural waters, Cr concentrations is less than 0.05 mg/L, the concentrations recommended for drinking water by the Commission of European Communities (CEC), the World Health Organization (WHO), and the U.S. Environmental Protection Agency (USEPA). By comparison, the Superfund site goal for groundwater is 0.05 mg/L and the maximum contaminant level MCL is 0.1 mg/L. Chromium is the second most common contaminant at 306 out of approximately 1,000 Superfund sites. Lead (Pb) is the most common contaminant in 460 Superfund sites (USEPA, 2002). Cr(VI) exists in solution as the anions, hydrogen chromate (HCrO4−), chromate (CrO42−), and dichromate (Cr2O72−), and may be present in soil as secondary chromate minerals such as calcium or barium chromate (CaCr4 or BaCrO4) or, Cr(VI) commonly is present as dissolved Cr in soil when the

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sample is dried and analyzed for Cr(VI) concentraton. As Cr(VI) decreases in concentration, it becomes more difficult to remove any additional Cr(VI). 10.1.2

Brief Overview of Remediation Methods

10.1.2.1 Conventional Methods Conventional approaches to ex situ remediation include excavation and disposal of the contaminated soil. Case studies are not necessary in this type of remediation, since the problem has only been moved from the source property to another, the landfill. Ex situ electrokinetics of Cr contaminated soil is another, less common ex situ method, wherein the “metals” are pulled to the cathode. The soil moisture content must be near saturation to allow for electromigration of the “metal” ions. Various acids, such as acetic (HCrH3O2) or citric (H3C6H5O7) can be used for the electrolyte solution to enhance the migration of the metals ions to the cathodes. For conventional groundwater remediation of Cr, “pump and treat” methods have been used for decades with varying degrees of success. “Pump and treat” is effective at controlling hydraulic movement, but mass removal tends to be difficult with this technology. A chemical enhancement of “pump and treat” system may add a reducing agent to the remedial process. The reducing agent is useful to overcome the tailing effect and reduce the overall time required for the in situ “pump and treat” remedial process. The three main remediation zones are (1) the source zone (area of high Cr concentration), whereby the concentrated Cr compound is leaked into the ground and down through the unsaturated zone to the top of the groundwater table, (2) the concentrated zone, the main and highest part of the dissolved Cr groundwater plume is the zone where “pump and treat” technology helps to maintain hydraulic control of the area, and (3) the zone outside the concentrated zone, the dilute zone, which contains lower concentrations (Figure 10.1.1). This zone is less likely to be successfully remediated with a “pump and treat” system, as concentrations are fairly low and significant mass reduction is unlikely in a short period of time. The geochemical zones are described in Rouse (1997), Rouse and others (1996) and Sabatini and others (1997). 10.1.2.2 Less Conventional Methods For in situ remediation of Cr(VI), many methods use chemical reduction or fixation. The goal of chemical reduction or fixation of Cr(VI) is to reduce it to the more thermodynamically stable Cr(III), which will precipitate or adhere to aquifer solids. There are primarily four main technologies or approaches: 1. 2. 3. 4.

Geochemical fixation Permeable reactive barriers (PRBs) Reactive zones Natural attenuation

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Water Table

Source Zone

Co

nce n Zo trate ne d Dilute Zone

Aquifer Aquitard

FIGURE 10.1.1 Conceptual model of geochemical zones in Cr contaminant plume. (Derived from Rouse et al. 1996 and Sabatini et al. 1997.)

In addition to the above mentioned methods, there are several other methods available for in situ Cr remediation: 1. Soil flushing and enhanced extraction 2. Electrokinetics 3. Biological processes: • Bioreduction • Bioaccumulation • Biomineralization • Bioprecipitation • Phytoremediation 10.1.3

Recommended Technologies

Site characterization should include numerous soil borings with groundwater samples to fully characterize the vertical and lateral extent of the Cr contamination. Several parameters should be evaluated, including total organic carbon (TOC), dissolved organic carbon (DOC), particulate organic carbon (POC), cation exchange capacity (CEC), and alkalinity. A summary of the recommended geochemical analysis was developed by the USEPA (2002) to be a guide of the analytical methods for understanding Cr remediation (Table 10.1.2). Additional methods can be added. 10.1.3.1 Geochemical Fixation Geochemical fixation reduces Cr(VI) in groundwater and contaminated soil to the thermodynamically stable Cr(III). The reduced Cr is geochemically

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TABLE 10.1.2 Recommended Geochemical Analysis Sample Type Site characterization

Analyte TOC (water) TOC (soil) DOC (water) POC Soil pH Groundwater pH Alkalinity (water) CEC Total Cr(VI) reducing capacity of soil Total manganese (Mn) (soil)

Groundwater preand post-treatment

Total Cr

Cr(VI)

Soil pre- and post-treatment

Cr(III) Total Cr

Cr(VI) Cr(III) Available Cr(III) to be mobilized Soil post-treatment (Leachate)

Source:

Cr(III)

Method EPA 415.1 or 415.2 SW-846 modified 9060 0.45 µm filter, then EPA 415.1 or 415.2 TOC minus DOC SW-846 9045C (use distilled water) EPA 150.1 EPA 310.1/SM2320B EPA 908.1 Walkley-Black Method Digest: SW-846 3050B, 3051, or 3052 Analysis: SW-846 7460, 6010B, or 6020 0.45 µm filter, Digest: SW-846 3020A Analysis: SW-846 7191–orDigest: SW-846 3005A Analysis: SW-846 6010B or 6020 0.45 µm filter, Analysis: SW-846 7196A Total Cr – Cr(VI) Digest: SW-846 3050B, 3051, or 3052 Analysis: SW-846 7090, 6010B or 6020 Digest: SW-846 3060A Analysis: SW-846 7196A Total Cr – Cr(VI) Prep: K2H – citrate extract (Bartlett, 1991) Analysis: SW-846 7196A Leachate: Cal. Title 22 Waste Extraction Test (WET) Digest: SW-846, 3010A Analysis: SW-846 7090, 6010B, or 6020 -orDigest: SW-846 3020A Analysis: SW-846 7191

USEPA, 2002.

fixed onto aquifer solids (USEPA, 2002). Some methods use “pump and treat” systems where the water is treated on the surface and reinjected with a reducing agent (Figure 10.1.2). Other delivery methods use trenches, filter galleries, wells,

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Prior Contamination Source

Unsaturated Zone

In Situ Cr(III) Fixation In Situ Cr(III) Fixation

Contaminated Groundwater

Original Water Table

Treatment Plant

Pumping Water Table

Cr(VI) Contaminated Groundwater

Reductant Treated Water

Advancing Front of Reductant Treated Water

Aquifer Aquitard Source: Rouse, 1997

FIGURE 10.1.2 Schematic of in situ Chromium remediation process.

and injection ports to introduce the reducing agent into the subsurface. The two keys to successful remediation are: 1. Selection of the appropriate reagent, considering the site geochemical conditions, and 2. Selection of the appropriate delivery system, considering site geohydrological conditions (Rouse and others, 1996), Rouse (1994) 10.1.3.1.1 Chemistry Various reducing agents are available, and the more common ones include metabisulfite (S2O52−), hydrogen sulfite (HSO3−), iron(II) sulfate (FeSO4), and calcium polysulfide (CaS5). The reactions are described below: 10.1.3.1.2 Reducing Agents Metabisulfite (S2O52−), Hydrogen Sulfite (HSO3−) S2O52− + H2O → 2HSO3−

(10.1.1)

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Natural Reduction

Fe(II) (Aqueous) Mn(III) Organic Acid Complexes Soil Organic Matter

Sodium MetaBisulfite

Chemical Reduction

Cr(III)

Inorganic (i.e. iron) Coprecipitate and Insoluble Humic Acid Complexes

Cr(OH)3 (Amorphous Pure Solid)

Cr 3+

Hydrolysis

Cr(OH)+2

CrOH2+

Cation Exchange on Fine Grained Soil Adsorption

FIXATION

FIGURE 10.1.3 Chart of Cr reduction and fixation (USEPA, 2002).

And, in the presence of excess HSO3−, Cr(VI) is reduced (Palmer and Wittbrodt, 1991): 6H+ + 2HCrO4− + 4HSO3− (excess) → 2Cr3+ + 2SO42− + S2O62− + 6H2O (10.1.2) In the presence of excess Cr(VI), the reduction to Cr(III) by HSO3− is performed by the following reaction (Palmer and Wittbrodt, 1991): 5H+ + 2HCrO4− (excess) + 3HSO3− → 2Cr3+ + 3SO42− + 5H2O Fixation is shown in Figure 10.1.3 (USEPA, 2002).

(10.1.3)

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10.1.3.1.3 Reducing Agent Iron(II) Sulfate (FeSO4) Dissolved Cr(VI) can be precipitated as Cr(OH)3 by injecting FeSO4 (Suthersan, 2002) Acidic conditions 14H+ + 6Fe2+ + Cr2O72− → 6Fe3+ + 2Cr3+ + 7H2O

(10.1.4)

Neutral or alkaline conditions 3Fe2+ + CrO42− + 4H2O → 3Fe3+ + Cr3+ + 8OH−

(10.1.5)

Both Cr(III) and Fe(III) ions are highly insoluble under natural groundwater conditions, and these ions precipitate out as hydroxides as follows (Suthersan, 2002): Fe3+ + 3OH− → Fe(OH)3(s)

(10.1.6)

Cr3+ + 3OH− → Cr(OH)3(s)

(10.1.7)

10.1.3.1.4 Reducing Agent Calcium Polysulfide (CaS5) 10H+ + 2CrO42− + 3CaS5(s) → 3Ca2+ + 2Cr(OH)3(s) + 15S(s) + 2H2O (10.1.8) 10.1.3.2 Geochemical Fixation Concerns The reducing agents must be in contact with the Cr(VI). Consequently, aquifer heterogeneities and low permeability sediments require injection spacing closer together than high permeability sediments. Although unlikely, the reduced Cr(III) potentially could reoxidize to Cr(VI) under certain conditions, such as in the presence of manganese(IV) oxide (MnO2); field evidence of this reoxidation has not been observed (USEPA, 2002). Reducing agents containing iron (Fe), such as FeSO4, could result in precipitation of the Fe and cause clogging near the injection locations. Excess reducing agents or reducing agent byproducts must be monitored so as not to create new groundwater contamination. The complicated Cr interactions are described in the Chromium Cycle (USEPA, 2002) and Bantlett (1991) as shown —? in Chapter 4, Figure 4.1.1. 10.1.4

Other Technologies

10.1.4.1 Permeable Reactive Barriers (PRBS) PRBs provide in situ groundwater treatment for a variety of chemicals and metals. This passive treatment technology functions on a reasonably constant groundwater flow direction to move the contaminated groundwater through a treatment zone. These technologies work best in shallower aquifers (generally less than 12.2 m). Two basic designs used for PRBs include the funnel-and-gate

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Treated Water

Treated Water

Contaminated Water

Contaminated Water Groundwater Flow

Groundwater Flow

Source: USEPA, 1997a FIGURE 10.1.4 PRBs: Funnel-and-gate on the left, continuous trench on the right (USEPA, 1997).

and the continuous trench method. For an overview of installation methods for PRBs, refer to O’Hannesin (1999). Successful site characterization is necessary to install a PRB that will work. Vertical and lateral plume location, groundwater gradient, groundwater flow direction, contaminant concentrations, seasonal hydrologic variability, confining layers, fracturing, aqueous geochemistry, lithologic variations, site history, contaminant attenuation over time and distance are key factors to evaluate when designing a PRB remedial system. In order to keep the groundwater flowing toward the treatment zone, metal or plastic shoring or sheeting can be used to create a funnel to move the water to the treatment system, also called the gate. In low permeable sediments, such as silts and clays, PRBs can be designed using a trench system across the plume and placing treatment media in the trench. This approach allows for physical contact between the targeted contaminant and the treatment media. The funnel-and-gate uses an impermeable funnel, typically consisting of an impermeable material such as interlocking steel or plastic sheet pilings or slurry walls. The purpose of the funnel is to direct the flow of contaminated groundwater into the treatment zone, also called the gate. Bypass can occur if groundwater flow directions change outside the funnel capture zone. The treatment zone can be emplaced using sheet pile excavation boxes, bucket auger holes, or other methods. Vibrating beam technology has been used for years for installing thin impermeable slurry walls. A large I-beam is driven into the ground and as the beam is vibrated out, the treatment media and bioslurry is pumped into the formation, filling the void created by the beam. Deep soil mixing using large auger machines can also be used to emplace treatment media. Jettting and azimuth controlled vertical hydrofracturing have been used to inject fine-grained treatment media into the aquifer. Jetting uses high pressure at the tip to drive the tool to the total depth and then the treatment media is injected as the tool is withdrawn. Azimuth controlled vertical hydraulic fracturing technology for deeper treatment zones allows for deep fractures in closely spaced wells (4.6 m to 6.1 m on center) to depths exceeding 30.48 m. Various gels or treatment

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media can be injected under high pressure into the aquifer, creating a somewhat continuous band of fracture filled treatment surfaces (O’Hannesin, 1999). 10.1.4.2 Chromium Reduction Using Reactive Media PRB typically uses elemental Fe (Fe(0)) to treat Cr(VI) contaminated groundwater. Cr(VI) as chromate (CrO42−) is reduced by elemental Fe. The elemental Fe donates the extra electrons necessary to reduce the CrO42− and in the process becomes oxidized to Fe(II) or Fe(III). Cr(III) in the presence of Fe, will precipitate from solution as a mixed Cr–Fe hydroxide solid, which has lower solution equilibrium activity than pure solid-phase hydroxide (USEPA, 2002). The reaction is shown as: Cr(VI) + Fe(II) → Cr(III) + Fe(II)/Fe(III)

(10.1.8)

This reaction works if pH <10 and for phosphate (PO43−) concentrations less than 0.0001 mol/L. For pH >10, the oxidation rate of the Fe(II) by dissolved oxygen is greater than the rate of oxidation of Fe(II) by CrO42− (Walker, 1999). The majority of the PRB remedial designs use granular elemental Fe filings that are easily available in course particle sizes and are inexpensive (USEPA, 2002). Another method of treatment is using ceramic foam having high surface concentrations with elemental Fe contents of 92% to 94% and high specific surface areas exceeding 5 m2/g. These blocks of foam can be handled easily and lowered into a well or cased gate area. Zeolites have large specific surface areas, high adsorption capacities, high cation exchange capacities, good hydraulic characteristics, and are relatively low in cost (Bowman et al., 1999). Zeolites can be treated with cationic surfactants or even elemental Fe to change their surface chemistry and improve their affinity for sorption of oxymetal ions such as CrO42−. Another developing technology that is being considered for Cr(VI) reduction is electrokinetics, wherein a series of electrodes is placed in the Cr(VI) contaminated area and 50A to 150A of direct current is applied to the electrodes, on 3.05 m to 6.10 m centers. An electrolyte solution or processing fluid not only maintains the pH at the anode and cathode, it helps solubilize and move the Cr(VI) contaminants. Cr is removed from the system by electroplating the metal at the cathodes or by being pumped out in the process fluid. For more information on electrokinetics, see Loo (2000), Jacobs and Loo (1994), and USEPA (1996). 10.1.4.3 Brief PRB Case Study Elizabeth City, North Carolina PRB: A need for Cr remediation at the U.S. Coast Guard (USCG) facility in Elizabeth City was prompted by 30 years of operations at a Cr plating shop. A significant release of chromic acid (H2CrO4) beneath the shop was discovered. The installation of the PRB involved two phases: the pilot scale and full scale remediation (USEPA, 1997). After a series of pilot tests and bench tests, the optimal mixture of granular Fe to treat both Cr(VI) and trichloroethene (TCE) was developed. Both Cr(VI) and TCE

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exceeded the MCLs of 5 and 10 mg/L, respectively. Groundwater contained in excess of 28 mg/L Cr(VI) near the Cr plating shop, the source of the Cr(VI). The full-scale PRB consisted entirely of elemental Fe filings. The PRB was 46.0 m in length, 5.5 m in depth and 0.6 m in width. The PRB was installed in less than 8 h using a continuous trenching technique. Total costs for the PRBs, site assessment, design, construction, materials and preliminary and supervision was about $1 million, including $350,000 for the installation of the granular Fe PRB (EPA, 2002). The cleanup goal was 0.05 mg/L Cr(VI) and the results of monitoring in November 1996 indicate that all the Cr(VI) was removed from the groundwater within the first 0.1524 m of the PRB. TCE also decreased by more than 95%. No Cr or Cr(VI) has been detected above MCLs downgradient of the PRB in either multilevel sampling ports or in the downgradient monitoring wells. The pH increased from a background of ~6.5 to ~9.75 in the PRB. The groundwater returned to background pH within 2 m downgradient of the PRB. The oxidation–reduction potential (Eh) showed a sharp decline from +100 mV to +500 mV in background to low values of –400 mV to –600 mV within the PRB. Alkalinity decreased from background concentrations of 40 mg/L to 100 mg/L as background, typically calcium carbonate (CaCO3), to less than 10 mg/L within the PRB (USEPA, 1999). In sum, significant reduction of Cr(VI) and TCE occurred at the Elizabeth City site using a passive elemental Fe treatment system.

Bibliography Bartlett, R.J., 1991, Chromium cycling in soils and water: links, gaps, and methods, Environmental Health Perspectives, 92, 17–24. Bowman, R.S., Zhaohui, L., Roy, S.J., Burt, T., Johnson, T.L., and Johnson, R.L., 1999, Surface-altered Zeolites as Permeable Barriers for In Situ Treatment of Contaminated Groundwater, Phase II Topical Report for the U.S. Department of Energy, Pittsburgh, PA. Jacobs, J. and Loo, W., 1994, DPT technology opens new remediation avenues, ECON Magazine, 36–37. Loo, W.W., 2000, Electrokinetic treatment of hazardous wastes, in Standard Encyclopedia of Environmental Science and Technology, Lehr, J., Ed., McGraw Hill, New York, Chapter 14.7; pp. 14.69–14.84. O’Hannesin, S., 1999, An Overview of Installation Methods for PRBs, Presentation for the USEPA Conference on Abiotic In Situ Technologies for Groundwater Remediation, Dallas, TX. Palmer, C.D. and Wittbrodt, P.R., 1991, Processes affecting the remediation of chromiumcontaminated sites, Environmental Health Perspectives, 92, 25–40. Rouse, J.V., 1994, In Site of Dissolved chromate-ION contamination of Groundwater: Paper presented at 87th Meeting of the Air and Waste Management Association, June. Rouse, J.V., Leahy, M.C., and Brown, R.A., 1996, A geochemical way to keep metals at bay, Environmental Engineering World, Mant June.

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Rouse, J.V., 1997, Natural and Enhanced Attenuation of CCA Components in Soil and Groundwater, Paper presentation for the 93rd Annual Meeting of the American Wood Preservers Association. Sabatini, D.A., Knox, R.C., Tucker, E.E., and Puls, R.W., 1997, Innovative Measures for Subsurface Chromium Remediation: Source Zone, Concentrated Plume, and Dilute Plume, USEPA, Environmental Research Brief. EPA/600/S-97/005. Suthersan, S.S., 2002, Natural and Enhanced Remediation Systems, Lewis Publishers, Boca Raton, FL, p. 419. U.S. Environmental Protection Agency (USEPA), 1997, Permeable reactive subsurface barriers for the interception and remediation of chlorinated hydrocarbon and chromium(VI) plumes in groundwater, USEPA Remedial Technology Fact Sheet, EPA/600/F-97/008. U.S. Environmental Protection Agency (USEPA), 1999, An In Situ Permeable Reductive Barrier for the Treatment of Hexavalent Chromium and Trichloro-ethylene in Groundwater: Vol 2, performance monitoring EPA/600/R-99/095b. September. U.S. Environmental Protection Agency (USEPA), 2000, In Situ Treatment of Soil and Groundwater Contaminated with Chromium, EPA/625/R-00/005, p. 84. Walker, W., 1999, Chromium Reduction/Fixation at the Townsend Saw Chain Site, presented for the USEPA Conference on Abiotic In Situ Technologies for Groundwater Remediation, Dallas, TX.

10.2 Frontier Hard Chrome, Vancouver, Washington

Stephen M. Testa 10.2.1

Introduction

The Frontier Hard Chrome (FHC) site is located in the city of Vancouver in the state of Washington, approximately 0.8 km north of the Columbia River. Situated on about 2,000 m2 (0.2 hectares), Cr plating operations occurred for about 25 years between 1958 and 1982. FHC operated the facility between 1970 and 1982. As part of the operation, process waste waters containing Cr(VI) was discharged directly to an on-site dry well.

10.2.2

Site Location and History

The FHC Cr plating operations occurred for about 25 years between 1958 and 1982. Pioneer Plating operated the facility from 1958 to 1970. FHC operated the facility between 1970 and 1982. Both operators discharges Cr plating wastes to the sanitary sewer system until 1975 when the city determined that wastewater from the site was upsetting the operation of its new secondary treatment system, FHC was directed by the city and Washington State Department of Ecology (DOE) to cease discharge to the sewer system until a treatment system was installed to remove the Cr waste. Thus, FHC

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began discharge of process waste waters containing Cr(VI) directly to an onsite dry well. Areal groundwater is used for drinking water for the City of Vancouver; two well fields used since 1955 are situated within 1.6 km of the site. 10.2.3

Regulatory Overview

In 1982, the site was found to be in violation of Washington State Dangerous Waste Regulations for disposal of hazardous waste. This violation reflected detection of Cr concentrations greater than twice the state groundwater cleanup standard of 0.05 mg/L in groundwater retrieved from an industrial well located 0.8 km southwest of the site. The Frontier Hard Chrome operations went out of business shortly thereafter. By December 1982 the site was being considered for inclusion on the National Priority List (NPL) under CERCLA and was added to the list in September 1983. In December 1987, the U.S. Environmental Protection Agency (USEPA) issued a record of decision (ROD) calling for removal, stabilization, and replacement of 5,658 m3 of contaminated soil, or all soils with concentrations of total Cr greater than 550 mg/kg, the latter based on a site-specific leachate test for protection of groundwater. The remediation of groundwater would be evaluated by a separate ROD. In October 1994, the Washington State DOE conducted an interim removal action of Cr contaminated soil on the site. Approximately 122 m3 of contaminated soil were removed allowing for redevelopment of the property. (USEPA, 1997). In May 2000, USEPA finalized the Focused Feasibility Study that identified and evaluated several new and innovative technologies. (USEPA, 2000). 10.2.4

Site Characterization

Located 0.8 km north of the Columbia River in Clark County, Washington, the site is situated in the river’s flood plain. These alluvial deposits consisting of unconsolidated silt, sand, and gravel range from a few meters to more than 30.48 m in thickness. A veneer of fill ranging in depth to about 5.79 m below ground surface underlies the site. The Troutdale formation underlies river channel and flood plain deposits. This formation is Pliocene in age and typically consists of semiconsolidated clay, silt, sand, and gravel deposits. Depth to the top of the Troutdale formation is on the order of 30.48 m to 36.58 m below ground surface. Nearly all domestic supplies, most industrial and municipal supplies, and more than half the irrigation supplies are obtained from groundwater resources. Most wells in the Vancouver area obtain groundwater from recent alluvial and Pleistocene alluvial deposits. Surface soil concentration of Cr(VI) ranged up to 42 mg/L. Subsurface concentrations for total Cr and Cr(VI) ranged up to 31,800 mg/kg and 7506 mg/kg, respectively.

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The remedial action master plan (CH2M Hill, 1983) incorporated conduct of an existing well inventory, sampling and analyses, gauging of water concentrations, installation of groundwater monitoring wells with subsequent sampling and analysis, sampling and analysis of onsite soil and surface water; and development of remedial investigation and feasibility study workplans. Initial subsurface on-site and off-site studies commenced in 1985. Seven cluster wells were initially installed (i.e., wells screened at two different depth intervals), with subsequent field hydraulic conductivity tests, gauging and sampling, and sampling of water from nearby fire hydrants. Groundwater samples were obtained and field determination of Cr concentration in groundwater was obtained with depth during drilling. The December 1987 ROD called for removal, stabilization, and replacement of 5,658 m3 of soil.

10.2.6

Remedial Performance

Evaluation of proposed remedial strategies by USEPA after issuance of the RODs revealed the soils remedy to be ineffective. Groundwater monitoring conducted after issuance of the ROD indicated the dissolved groundwater Cr(VI) plume was decreasing in size as hydraulically downgradient industrial supply wells located at FMC were taken off-line. USEPA issued separate RODs for the soils/source control operable unit (1987) and the groundwater operable unit (1988). Subsequent evaluation found the soils remedy to be ineffective. Subsequent evaluation of the groundwater monitoring program suggested that conventional “pump and treat” may not be the most appropriate strategy. A final ROD Amendment was issued in August 2001, identifying in situ treatment of soils and groundwater as the selected remedy. The selected remedial strategy combines the use of two innovative In situ treatment applications: (1) In situ Redox Manipulation (ISRM) for treatment and containment of hot spot groundwater; and (2) auger/injection of reducing agents for the treatment of source area soils and hot spot groundwater. A bench test was performed by Szecsody et al. (2002) to determine physical and geochemical properties needed to develop a design for the implementation of an ISRM remedial strategy. Sixteen sediment core samples were collected for subsequent laboratory testing during drilling and installation of injection and monitoring wells. Additional site specific hydrogeologic data and vertical contaminant distribution was assessed, and hydraulic testing and electromagnetic borehole flow meter testing were performed. In addition, sediment reduction studies via conduct of a laboratory tracer injection test to develop a dithionite (S2O42−) injection scheme based on a suite of reactive transport design analysis simulations was also conducted.

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In August 2001, a final ROD Amendment was issued by EPA identifying in situ treatment of soils and groundwater as the selected remedy. The selected remedial strategy was to combine the use of two innovative in situ treatment applications: (1) ISRM for treatment and containment of hot spot groundwater, and (2) auger/injection of reducing agents for the treatment of source area soils and hot spot groundwater. In October 2001, the USEPA initiated the remedial design of the selected remedial strategy with a completion target for the final remedial design of December 2002. Completion of demolition of structures was targeted for June 2002. Certain elements of the final remedial design remain to be completed. These include performing a refined bench test scale test to assess variability of soils, and conducting a pilot injection test for ISRM to determine the zone of influence which was completed in October 2002. Further refine remedial action cost estimates were also to be completed by November 1, 2002, with final design for these elements completed by December 31, 2002.

Bibliography CH2M Hill, 1983, Remedial Action Master Plan, Frontier Hard Chrome, Inc., Vancouver, Washington, Report No. 01-OV27.0. Szecsody, J.E., DeVary, B.J., Vermeul, V.R., Williams, M.D., and Fruchter, J.S., 2002, In Situ Redox Manipulation Bench-Scale Tests: Remedial Design Support for In Situ Redox Manipulation (ISRM) Barrier Deployment, Frontier Hard Chrome Superfund Site, Vancouver, WA, Pacific Northwest National Laboratory Report. United States Environmental Protection Agency (USEPA), 1997, Recent Developments for In Situ Treatment of Metal Contaminated Soils. United States Environmental Protection Agency (USEPA), 2000, In Situ Treatment of Soil and Groundwater Contaminated with Chromium.

10.3 United Chrome Products, Inc., Corvallis, Oregon

Stephen M. Testa 10.3.1

Introduction

The United Chrome Products, Inc. (UCP) site is a former Cr-plating facility situated on approximately 10,000 m3 (1 hectare) in the city of Corvallis, Oregon. From 1960 through 1977, an unknown quantity of Cr plating wastewater was discharged into a dry well resulting in significant soil and groundwater contamination and adversely affecting drinking water

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resources. In situ flushing employing several innovative approaches was the primary technology used for removal of significant amounts of Cr from soil and groundwater. On-site groundwater treatment utilized chemical reduction and precipitation to successfully remove Cr from the extracted groundwater prior to discharge. As of late 2002, EPA continues to evaluate the overall effectiveness of the remediation program. More information can be obtained from USEPA (1997, 2000a, 2002a and 2002b). 10.3.2

Site Location and History

The UPC site is a former Cr-plating facility situated at 2000 Airport Road, 4.83 km south of the city of Corvallis, Oregon, and within the Airport Industrial Research Park development. The property was leased to the operator by the city of Corvallis. Industrial electroplating was conducted at the site from 1956 to 1985. During this period, leakage of Cr plating waste from above-ground tanks and an unknown quantity of Cr plating waste was disposed off into an adjacent on-site dry well. The dry well was used to dispose off floor drippings, washings, and product rinsate collected in a sump within the building. The liquids were reportedly neutralized with sodium hydroxide (NaOH) and/or soda ash (Na2CO3) prior to disposal. The dry well was situated about 9.14 m east of a north-south oriented drainage ditch which was bisected by a manmade east-west oriented drainage channel north of the facility which discharges to other creeks and eventually to the West Fork of the Booneville Slough and Willamette River. The indoor plating tanks also leaked plating solution directly to subsurface soils. Groundwater, surface water, sediments, and on-site soils were contaminated with Cr. Two city wells were located approximately 914.4 m northeast of the site, although Corvallis was not using these wells. However, about 42,000 people live within 4.83 km of the site, with the closest residence situated approximately 274.3 m northeast of the facility. Corvallis obtained some of its water from the Willamette River, which formerly received drainage from ditches and surface water from the site until cleanup measures were implemented. 10.3.3

Regulatory Overview

Initial subsurface investigations were performed by Ecology and Environment under contract to the U.S. Environmental Protection Agency (USEPA) in 1983 and 1984. After determining that the site posed a significant threat to human health and the environment, the site was placed in the USEPA’s National Priority List (NPL). Extensive cleanup commenced in 1987. These efforts included the removal of contaminated debris and contaminated soils, installation of a groundwater extraction and treatment system, and rerouting a drainage ditch to prevent contaminated water from entering the local surface water drainage network. A final strategy for the site was selected in September 1986, and subsequently implemented in 1988. Estimated cost for the selected remedial strategy was

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$1,580,000, with an annual operation and maintenance cost on the order of $261,000. Under a legal agreement between the USEPA and the City of Corvallis, the city commenced management of cleanup efforts in 1988. In 2000, further investigations revealed two additional hot spots and subsequently removed about 1.77 × 106 kg of soil. This was disposed at a permitted hazardous waste landfill. A consent decree signed between the city and the USEPA legally requires Corvallis to perform cleanup actions and continue with the groundwater extraction and treatment programs until cleanup Cr concentration goals are met. Corvallis is also evaluating offsite sediments to assure that wildlife and vegetation are not being adversely affected. 10.3.4

Site Characterization

The site is situated on a broad alluvial plain in the central portion of the Willamette Valley and is virtually level. This portion of the valley is characterized by extensively developed soil profiles, seasonal perched water, and poor surface drainage with a large amount of rainfall diverted to surface waters rather than recharge to groundwater. Unconsolidated deposits of clay, silt, sand, and gravel comprising the older alluvium of Pleistocene or Holocene age underlie the site. Total Cr concentrations in soil ranged as high as 60,000 mg/kg, with concentrations in groundwater ranging up to 19,000 mg/L. The dissolved Cr plume was found to extend over 3.22 km off-site in surface water, and over 2.41 km off-site in sediments. Groundwater is encountered under shallow unconfined piezometric conditions within relatively low permeability soils (i.e., silt and clay). This strata also serves as a confining layer that overlies predominantly sand and gravel and is referred to as the deeper water-bearing zone or aquifer. Shallow wells extended to a depth of about 4.57 m, whereas, the deeper wells extended to a depth of about 9.14 m below round surface (i.e., about 1.52 m below the bottom of the confining layer). Chromium(III) was encountered at relatively high concentrations in shallow soils. Cr(III) is characterized by relatively low solubility, and as one would expect, was only a minor contaminant in groundwater estimated solubility of G(OH)3 is 0.0013 mg/L (Guertin, 2004, Chapter 10.11.5). Conversely, Cr(VI), was also encountered in high concentrations in shallow soils, but owing to its characteristic high solubility in water, was also encountered in high concentrations in shallow soils, within the soil comprising the confining layer and in groundwater. 10.3.5

Remedial Investigation

Early emergency efforts commenced in 1985 and included removal by the USEPA of about 30,282.4 L of Cr-contaminated groundwater and 4,989.52 kg of hazardous waste from the site for off-site disposal. The final strategy

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employed an unique full-scale soil flushing design. The system was designed to treat both shallow and deep water-bearing systems, and flushing of the confining clay strata via deep aquifer injection wells in conjunction with the upper zone extraction wells to create upward vertical gradients (USEPA, 1997). The strategy included the installation of a groundwater extraction and treatment system and demolition of buildings. Approximately 15 shallow wells (4.57 m to 6.10 m in depth) were installed that screened the upper unconfined water-bearing zone, and five deeper wells (10.67 m to 12.19 m in depth) screened within the lower confined production aquifer. A 23 well-extraction network was installed within the shallow water-bearing zone and an injection and groundwater extraction network was installed in the deeper gravel aquifer. On-site groundwater treatment utilized chemical reduction and precipitation to remove Cr from the extracted groundwater prior to discharge to nearby Muddy Creek or to the Corvallis wastewater treatment facility. Three methods of infiltration were employed via installation of infiltration basins, infiltration trench, and injection wells (McPhillips et al., 1991). Two above-ground infiltration or percolation basins with open bottoms were constructed in the area of the former dry well and former plating tank area to flush contaminated soil above the shallow unconfined piezometric surface. About 3.175 × 105 kg of contaminated soil was excavated during construction of these basins and subsequently disposed off at a permitted land disposal facility. These basins delivered water to the upper zone at an average rate of about 28,768.3 L/d and 11,355.9 L/d for Basin Nos. 1 and 2, respectively. These rates decreased to about 50% or less during the winter months relative to summer. The infiltration trench was constructed about 22 months after remedial efforts commenced. About 30.48 m in length and 2.44 m in depth, the trench was positioned to increase discharge rates of the extraction wells along the longitudinal axis of the plume during the dry summer months. A water level at 1.22 m below grade was maintained. Infiltration rates averaged 9,463.25 L/d. The third attempt at groundwater recharge was water injection into the deep water-bearing zone through two wells. The objective of injection into the deeper zone was to reverse the downward vertical gradient present between the upper unconfined and deeper confined water-bearing zones (McKinley et al., 1992). Culverts were also installed in the adjacent open drainage ditch in order to isolate the surface drainage system from the inflow of contaminated surface water and groundwater from the site. 10.3.6

Remedial Performance

In situ flushing was the primary technology used for removal of significant amounts of Cr from soil and groundwater. Implementation of a pumping strategy achieved hydraulic containment of the dissolved Cr(VI) plume. Cr(VI) concentrations decreased from a maximum measured concentration greater than 5000 mg/L to approximately 50 mg/L during the first 2.5 years

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of operation via water flushing. The average Cr concentration derived from multiple measurements in the groundwater plume decreased from 1,923 mg/L to 207 mg/L after flushing the first 1.5 pore volumes (approximately 9.84 × 106 L for 1 pore volume). This removal rate was expected to continue for the first few pore volumes of treatment until Cr(VI) removal began to tail off to asymptotic concentrations (Sturges et al., 1992). 10.3.7

Conclusion

During late 2002 to early 2003, the USEPA plans to embark on its third 5year review since installation of the groundwater and extraction system in 1988. The objectives of this review is to assess the overall effectiveness of cleanup efforts at the site and aid in development of a transition plan for discontinuing USEPA’s involvement after cleanup goals are met. The USEPA plans to continue with its 5-year review process until contamination concentrations are low enough to allow for unlimited and unrestricted use of the property. As of November 2002, about 14,515 kg of Cr and 115.45 × 106 L of contaminated groundwater have been extracted and subsequently treated. If all proceeds in a favorable manner, cleanup goals should be met around 2004. About 54.43 kg of Cr and 177.91 × 106 L of groundwater have been extracted from the deep aquifer. Thus, all but 3 of the 23 upper zone groundwater extraction wells have met cleanup goals, and all but 2 of the lower extraction wells have met cleanup goals. Major portions of the groundwater treatment system have since been decommissioned. In addition, the on-site treatment plant removed and 39 extraction and monitoring wells have also been decommissioned. In 1986, the USEPA’s Record of Decision (ROD) initially set forth a cleanup goal of 0.05 mg/L (0.05 ppm), the Federal drinking water standard for Cr at the time. The current federal drinking water standard for Cr is 0.1 mg/ L. In addition, certain site conditions have also changed, for example, the Airport Industrial Research Park development no longer relies on a private well, but rather utilizes public water and sewer utilities as of 1988. Outstanding issues relating to achieving cleanup is determination of how and where groundwater cleanup goals need to be met, whether cleanup goals should be revised, whether using average site-wide Cr concentration of well-by-well concentrations to assess success, among others.

Bibliography McKinley, S.W. et al., 1992, Cleaning up chromium, Civil Engineering, pp. 69–71. McPhillips, L.C. et al., 1991, Case History: Effective Groundwater Remediation at the United Chrome Superfund Site, 84th Annual Meeting and Exhibition of the Air and Waste Management Association, Vancouver, British Columbia.

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Sturges, S.G., Jr., McBeth, P., and Grove, D.B., 1992, Performance of soil flushing and groundwater extraction at the United Chrome Superfund Site, Journal of Hazardous Materials, 29, 59–78. United States Environmental Protection Agency (USEPA), 1997, Recent Developments for In Situ Treatment of Metal Contaminated Soils. United States Environmental Protection Agency (USEPA), 2000, In Situ Treatment of Soil and Groundwater Contaminated with Chromium. United States Environmental Protection Agency (USEPA), 2002a, Superfund Fact Sheet, United Chrome Products, Inc., September. United States Environmental Protection Agency (USEPA), 2002b, Superfund Fact Sheet, United Chrome Products, Inc., November.

10.4 Former Wood Treating Plant, Windsor, Northern California

James A. Jacobs 10.4.1

Introduction

The site was one of the first wood treatment facilities to use an in situ injection of geochemical fixation chemicals for Cr(VI) remediation in the groundwater.

10.4.2

Site Location and History

10.4.2.1 Site Setting The former wood treatment plant in Windsor in Sonoma County in northern California used acidic copper(II) chromate (ACC, CuCrO4) as a wood preservative. The preserved wood was primarily used in the construction of cooling towers. The former wood treatment plant operated from 1965 to 1984. Chromated copper arsenate (CCA) was used for only one specific treatment project in 1966. The wood treatment facility covered several hectares. Chromated copper arsenate is a mixture of the following compounds: • Arsenic(V) oxide As2O5 • Chromium(VI) oxide CrO3 • Copper(II) oxide CuO 10.4.2.2 Historical Land Use The former wood preserving plant used CCA as a wood-preserving compound to treat wood used in the construction of cooling towers. Operations

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were from 1965 to 1984. Almost 20 years of wood preserving activities created significant toxic “metals” contamination on the site. Most of the chemical transportation, storage, and handling practices developed at this wood facility predated federal or state requirements or regulations. The cumulative drippings or spillage of the CuCrO4 solution resulted in Cr(VI) contamination of the shallow soil. Copper (Cu), a significant element in CuCrO4, was also detected at high concentrations in the soil. High arsenic (As) concentrations were detected in only a few localized soils samples, presumably related to the overwhelming use of CuCrO4 over As-rich CCA wood preservative. Shallow groundwater was contaminated by only Cr(VI). 10.4.2.3 Recent Site Activities Starting in 1992, the former wood treatment facility operated a groundwater extraction and above ground electrochemical water treatment system. Groundwater extraction was problematic owing to the low permeability of the aquifer sediments. The site had been subjected to more than 10 years of conventional “pump and treat” remediation, with little affect on the Cr(VI) contamination. The “pump and treat” groundwater system did provide limited hydraulic control and plume stability. However, significant Cr(VI) was still observed in the unsaturated/vadose zone in the spill source area even after years of “pump and treat” activities, indicating that the highly soluble Cr(VI) had not leached out of the unsaturated zone and into the groundwater. Lysimeters were installed to measure dissolved Cr in unsaturated zone pore moisture, which was detected at concentrations exceeding 2,000 mg/L. The purpose of the in situ geochemical fixation was to accelerate remediation by reducing the soluble Cr(VI) to Cr(III) and precipitate the Cr as chromium(III) hydroxide (Cr(OH)3). Implementation of the in situ geochemical fixation occurred in the summer of 1997. One further applications of the reducing agent, calcium polysufide (CaS5) was performed based on the presence of dissolved Cr in localized areas. Currently the site is being monitored.

10.4.3

Regulatory Overview

10.4.3.1 Regulatory Agencies The lead California regulatory agency, the Department of Toxic Substances Control (DTSC), has been giving oversight to the subject property. The site is within the North Coast Regional Board, Region 1, of the Regional Water Quality Control Board (RWQCB) and Mendocino County Environmental Health Department. 10.4.3.1.1 Timeline of Regulatory Activities 1965 to 1984 Former wood treating plant used copper (II) chromate CuCrO4 for wood treatment

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1966 One specific CCA wood treatment event occurred 1992 Groundwater extraction and above ground electrochemical treatment began 1997 Regulatory approval and implementation of reducing agent injection over 8,000 m2 (0.8 hectares) 1998 Additional injection event at localized area

10.4.3.2 Cleanup Standards The regulatory-established cleanup level for dissolved Cr in groundwater was set at the State of California Maximum Contaminant Level (MCL) for drinking water of 0.05 mg/L (Montgomery Watson, 2000).

10.4.4

Site Characterization

10.4.4.1 Site Geology Quaternary sediments consisting of low permeability clays and silts with occasional sands characterize the shallow geology. 10.4.4.2 Site Hydrology Groundwater is shallow at less than 1.52 m to 4.57 m below ground surface. Groundwater extraction rates were limited owing to the heterogeneous nature of the sediments and the relatively low permeability of the shallow water bearing zones. The groundwater treatment did provide hydraulic control of the plume of dissolved Cr; significant residual Cr(VI) was detected in the unsaturated zone of the main source area (Montgomery Watson, 2000). 10.4.4.3 Field Sampling Activities A variety of groundwater monitoring wells having both soil and groundwater samples were available on this site. In addition, lysimeters were installed to measure dissolved Cr in the unsaturated zone pore moisture. Groundwater concentrations of Cr(VI) were detected up to 200 mg/L. 10.4.5

Remedial Investigation

10.4.5.1 Remedial Alternatives Evaluation “Pump and treat” for the groundwater was evaluated. Concentrations of the dissolved Cr in the unsaturated zone exceeded 2,000 mg/L using the lysimeters. Based on these soil concentrations, mass removal rates and groundwater extraction limitations in an area of low permeability and low groundwater

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flow, calculations by the consultant suggested that the remediation life cycle could easily be projected to the 15 year to 20 year time frame to meet the cleanup concentrations. In addition, owing to regulatory and local sanitary treatment plant requirements, the only discharge for the treated water would be through reinjection back into the shallow aquifer. Since the shallow water bearing zone is a low permeability, low flow aquifer, reinjection of large amounts of treated water would be problematic. 10.4.5.2 Pilot Study Results “Pump and treat” evaluations using aquifer tests, lithologic and geologic study of the boring logs and sediments, as well as the history of poor performance of the water reinjection wells provided the rationale for the concept of an in situ direct injection of the treatment chemicals into the subsurface. In addition, shallow infiltration trenches were excavated across the main source area to introduce the reducing agent in batches to the highly contaminated source soils. The application of treatment chemical in the trenches occurred prior to the onset of the annual rainy season in northern California, from November to March. The rainwater infiltration into the trenches was effective in distributing the treatment chemical throughout the contaminated source area. Owing to the low permeability in the aquifer, the ability to recover the Cr-contaminated groundwater was reduced significantly. Field tests of Fe(II) ion injection further reduced the already low permeability on the site, owing to Fe precipitation and clogging of the soil pore spaces. Owing to these concerns, a sulfur-based reducing agent, CaS5, was selected for the pilot-scale field program that occurred in the summer of 1997. Because groundwater extraction and reinjection was not feasible on this site, the CaS5 was injected under high pressure using a direct push technology (DPT) probe rig. The reducing agents were introduced using approximately 1.38 × 106 Pa (200 lb/in.2) maximum pressure. Hydrofracturing across the plume was initiated at higher pressures. The program was enhanced by a process of reducing agent infiltration in the unsaturated zone of the source area. For Cr(VI) groundwater-contaminated areas, the reducing agent was injected into the shallow aquifer using a direct push probe rig to hydraulically drive custom threaded, 19 mm diameter steel pipes into the contaminated areas. A grid pattern was designed with injection ports placed on a 6.10 m spacing. In addition, staggered rows of injection ports perpendicular to the groundwater flow direction were designed to ensure the best lateral coverage and dispersion of the treatment chemical. The reducing agent was injected using specialized and proprietary pumping equipment at approximately 1.38 × 106 Pa (200 lb/in.2) to further improve the treatment chemical distribution in the subsurface. The CaS5 was pumped under pressure through a DPT probe rig (Figure 10.4.1).

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FIGURE 10.4.1 Injection of reducing agent using a DPT probe rig.

The injection ports with expendable metal tips, were driven to about 4.57 m below grade. The point was knocked out of the bottom of the injection rod, and the rods were retracted about 1.52 m from the bottom of the borehole, exposing 1.52 m of sediments. The CaS5 is 29% concentration in a 208.19 L drum. It was pumped into the injection rods, followed by 946.33 L of water. Up to 1,135.6 L of liquid was pumped into the injection ports at a rate of about 75.71 L/min. A total of 114 injection ports were constructed in 10 days.

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The steel injection rods were installed and left in the subsurface for additional injections. Field evidence indicated that the radius of influence of the injection ports exceeded a 3.05 m radius.

10.4.5.3 Selected Remedial Alternative Based on successful results in the pilot scale study, and after a thorough evaluation of remedial options, the direct injection of the reducing agent and continued groundwater monitoring was selected as the remedial alternative.

10.4.6

Remedial Performance

10.4.6.1 Treatment Program Originally, the treatment train approach was to have the groundwater “pump and treat” system controlling hydraulic gradient and the direct injection of the reducing agent to decrease Cr(VI) concentrations.

10.4.6.2 Performance Results Concentrations of Cr(VI) before the injections ranged from 8 mg/L to 16 mg/L, from summer, 1993 to spring, 1997. Groundwater concentrations ranged from a low of 28.96 m above mean sea level during the dry summer period of July 3, 1994, to a high of 31.39 m above mean sea level during the wet winter period in January 2, 1995. Prior to injections, there was a direct correlation between high water concentrations and high Cr(VI) concentrations (Figure 10.4.2).

Reductant Injection

25 20 15 10 5

1/ 2/ 93 7/ 3/ 93 1/ 2/ 94 7/ 3/ 94 1/ 2/ 95 7/ 3/ 95 1/ 2/ 96 7/ 2/ 96 1/ 1/ 97 7/ 2/ 97 1/ 1/ 98 7/ 2/ 98 1/ 1/ 99

0

31.7 31.4 31.1 30.8 30.5 30.2 29.9 29.6 29.3 29.0 28.7

Elevation (m_msl)

Concentration (mg/L)

30

Time Cr(VI) concentration

Water Level

FIGURE 10.4.2 Chart of Cr concentration over time plotted with water levels (Thomasser and Rouse, 1999).

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The reducing agent was injected in early summer, 1997, when the average concentrations of Cr(VI) was 8 mg/L. Pore moisture samples from the lysimeters indicated an order of magnitude reduction in Cr(VI) concentrations over the first 24 months after the introduction of the reducing agent into the infiltration trenches. Additional Cr(VI) concentration reduction was observed after the direct injection event. A trend of declining contaminant concentrations in shallow groundwater was noted for more than 18 months after the initial injection event. This declining concentration trend continues to date. The Cr(VI) concentrations and water concentrations over time (see Figure 10.4.2) illustrates the average results of monitoring and sampling performed on the site. Prior to the direct injection of the reducing agent, there was a direct correlation between shallow groundwater concentrations and the Cr(VI) concentrations. That correlation appears to have disappeared after the one period of direct injection that occurred in the spring of 1997 (Montgomery Watson, 2000). Areas of localized elevated concentrations of Cr(VI) may still exist, and an additional injection event was performed in 1999.

10.4.7

Conclusions

The results of this case study indicate that the reaction-half life of the reducing agent is several months. Much of the reducing agent delivery used a DPT probe rig with a high pressure pump, rather than more conventional wells or filter galleries. The results show that the reducing agent, CaS5 , was successful in significantly reducing the Cr(VI) concentration at the site over a period of 18 months.

Acknowledgments The author appreciates the technical review of the case study by Jim V. Rouse of Montgomery Watson Horza.

Bibliography Thomasser, R. and Rouse, J.V., 1999, In Situ Remediation of Chromium Contamination of Soil and Groundwater, paper presented at the American Wood Preservers Association, Conference of Assessment and Remediation of Soil and Ground Water Contamination of Wood Treating Sites. Montgomery Watson, 2000, In Situ Remediation of Chromium Contamination of Soil and Groundwater, p. 8. U.S. Environmental Protection Agency (USEPA), 2000, In Situ Treatment of Soil and Groundwater Contaminated with Chromium, EPA/625/R-00/005, p. 84.

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10.5 Valley Wood Preserving Plant, Turlock, California

James A. Jacobs 10.5.1

Introduction

The site is a former wood treatment facility in Turlock, California and is listed as a federal Superfund site. Site remediation technologies to treat the Cr(VI) included groundwater “pump and treat” that had been used for 10 years prior to any commencement of any in situ remediation. The groundwater “pump and treat” system was effective in maintaining hydraulic control, however, reduction of the Cr(VI) concentrations in the groundwater was not occurring. In addition, off-site migration was observed. 10.5.2

Site Location and History

10.5.2.1 Site Setting The Valley Wood Preserving site was a former wood processing plant on 5.8 × 104 m2 (5.8 hectares). The site was in operation from 1973 until the Stanislaus County Environmental Health Department (SCEHD) revoked the company’s license in 1979. Valley Wood Preserving used an aqueous chromated copper arsenate (CCA) solution to pressure treat lumber. The solution was mixed in an above ground tank near the site boundary and was stored in three adjacent above ground tanks. Well water was piped into the mixing tanks, and after the treatment cycle, the CCA solution was drained into sumps and was pumped back into the mixing tank for reuse. From 1973 to 1975, the area around the treatment cylinders and storage tanks was unpaved. An asphalt cap exists currently where the treated wood was originally stored on bare ground and allowed to drip-dry in the open air. Additional asphalt covers were added form 1975 to 1978 as treated wood production increased. In 1979, the Regional Water Quality Control Board (RWQCB) identified Cr and arsenic (As) in an on-site storage pond, monitoring wells and on-site and off-site soils (USEPA, 2003). Chromated copper arsenate” is a mixture of the following compounds: • Arsenic(V) oxide As2O5 • Chromium(VI) oxide CrO3 • Copper(II) oxide CuO During the operations of the plant, as much as 2,721.6 kg of Cr(VI) are estimated to have been released into the subsurface through chemical spills, leaking tanks, improper on-site disposal practices, and chemical drippings from the treated lumber onto unpaved and paved areas (Figure 10.5.1).

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FIGURE 10.5.1 Valley Wood Preserving facility in Turlock. The large tanks were used for water storage and mixing tanks. Areas to the right of the tanks were used for air drying wood on unlined soil. Some of these areas were excavated.

10.5.2.2 Historical Land Use The land use in the area is predominantly agricultural and one residence is located on the property. Turlock is an agricultural community in the Central Valley of California. In this setting where surface water resources are minimal, groundwater resources are used extensively. Approximately 34,000 people live within 4.83 km of the site and the city of Turlock uses municipal wells to serve 26,200 people within this area. The municipal wells draw water from an aquifer that underlies the site. The company provided an alternate water supply to affected residents and businesses. 10.5.2.3 Recent Site Activities After closing the site, the company excavated and disposed off approximately 1,147 m3 of Cr and As contaminated soil. From 1979 to 1983, approximately 2.6497 × 108 L of Cr-contaminated groundwater were extracted and treated using an electrochemical process. The treated water was then discharged to paved depressions that were used as evaporation basins. Off-site water is not being used currently as a water supply because an alternate

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supply was brought in. Groundwater monitoring is continuing to verify groundwater concentrations and Cr(VI) plume extent. The site is fenced off and access is controlled to prevent public exposure to contaminated soil.

10.5.3

Regulatory Overview

10.5.3.1 Regulatory Agencies The USEPA is the lead regulatory agency. The California Department of Toxic Substances Control (DTSC), has also been involved in the project. Other regulatory agencies in the area include the California RWQCB, Region 5, and SCEHD. 10.5.3.2 Timeline of Regulatory Activities The following timetable was developed based on regulatory information (USEPA, 2002; DTSC, 2000). 1979: RWQCB inspection and noted noncompliance with the water discharge requirement WDR-79-176. 1982: Facility was identified through the Stanislaus County phone book. The county environmental agency worked on enforcement for site remediation. Company was out of business, and cleanup was in progress. Site referred to RWQCB for enforcement action. 1987: Site screening performed. 1990: An alternate domestic water supply from deeper wells was provided to residents adversely affected by the Cr(VI) plume. A groundwater extraction and soil excavation project was started as in interim remediation measure. Contaminants include Cr(VI), As, and Cu. 1995: A cost recovery settlement agreement was reached with the responsible parties. 1996: Design of pilot groundwater in situ treatment after years of “pump and treat” operations failed to significantly reduce Cr(VI) concentrations in groundwater. 1997: to 2002 Continued groundwater monitoring, operations and maintenance. 1998: to 1999 In situ injection treatment using a sulfur-based reducing agent, metabisulfite (S2O52−)/hydrogen sulfite (HSO3−), was performed. 10.5.3.3 Cleanup Standards The regulatory-established cleanup concentration for dissolved Cr in groundwater was set at the State of California Maximum Contaminant Level (MCL) for drinking water of 0.05 mg/L.

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Site Characterization

10.5.4.1 Site Geology Quaternary sediments consisting of low permeability clays and silts with occasional sands characterize the shallow geology. 10.5.4.2 Site Hydrology The site is underlain by a shallow, unconfined aquifer extending to 18.29 m below ground surface. A deeper confined aquifer from 24.38 m to 42.67 m exists on-site, with a locally continuous 6.10 m to 24.38 m thick clay bed known as the E-clay aquitard. The 312.36 m wide plume extends approximately 304.8 m from the site toward the southwest. It reaches the bottom of the shallow unconfined aquifer (USEPA, 2003). 10.5.4.3 Field Sampling Activities A variety of groundwater monitoring wells having both soil and groundwater samples were available on this site. Cr concentrations were noted as high as 3,100 mg/kg in on-site and off-site soils. Shallow groundwater contained Cr at a concentration as high as 178 mg/L. The shallow groundwater also contained As and Cu. 10.5.5

Remedial Investigation

10.5.5.1 Remedial Alternatives Evaluation “Pump and treat” for the groundwater had pumped about 3.407 × 107 L and removed 1,360.1 kg of Cr(VI) over a period of several years. Seven years of conventional pump and treat technology did not significantly reduce Cr(VI) concentrations or plume size. Concentrations of the dissolved Cr, in the groundwater exceeded drinking water standards. Based on mass removal rates and groundwater extraction characteristics, a 10-year remediation life cycle was projected for this site to achieve the regulatory concentration for site closure (Brown et al., 1998). Another treatment program was suggested for reducing the dissolved Cr in groundwater. 10.5.5.2 Pilot Study Results A laboratory bench-scale test using a parallel column to evaluate various reducing agents on Cr(VI). Three paired-column tests were performed with actual Cr-contaminated aquifer material from the site. The aquifer material was placed in each packed column. For each paired column, one column was flushed with demineralized water to simulate groundwater extraction. The other column was flushed with a mild reducing agent solution designed to reduce the Cr(VI). After 4 to 6 pore volumes, the reducing agent-treated groundwater achieved effluent concentrations less than the 0.10 mg/L federal drinking water standard (Table 10.5.1). After 14 to 17 pore volumes,

Rouse, 1994.

270 65 38 19 15 — — — 210 17 6.8 0.05 — 0.06 — —

Reductant Solution 2,800 220 18 10.5 — 1.35 — 0.22

Soil C Demineralized Water 2,800 120 1.05 0.01 — 0.02 — —

Reductant Solution

1,700 120 23 4.1 — 0.49 0.19 —

Soil D Demineralized Water

1,700 34 0.62 0.02 — <0.01 — —

Reductant Solution

392

Source:

1 2 3 6 9 10 14 17

Pore Volume

Soil A Demineralized Water

Total Chromium Concentrations (mg/L) of Paired-Column Effluent for Valley Wood Preserving Site in Turlock, CA

TABLE 10.5.1

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columns flushed with only demineralized water exceeded the federal drinking water standard (Rouse, 1994). The pilot study involved removing a measured quantity of water from a Cr-contaminated well from onsite and treating it with the appropriate reducing agent above ground in containers. The liquids were then reintroduced into the well. Samples were then collected from the well to measure the effect of the added chemical reducing agent. The pilot scale test was successful in reducing Cr(VI) concentrations in groundwater.

10.5.5.3 Reducing Agent Selected Based on the results of the pilot study, a sulfur based reductant, CaS5, used as reducing agent (Rouse, 2004).

10.5.5.4 Selected Remedial Alternative Based on successful results in the pilot scale study and after a thorough evaluation of remedial options, the direct injection of CaS5 and continued groundwater monitoring was selected as the remedial alternative.

10.5.6

Remedial Performance

10.5.6.1 Treatment Plan In situ treatment using metabisulfite (S2O52−) occurred at the site from February 1998 through October 1999. According to published reports, total plume size and mass of dissolved Cr in groundwater was reduced by 98% (Thomasser and Rouse, 1999; Thomasser, 1999). The Cr(VI) isoconcentration maps of January 1998 (Figure 10.5.2) and November 1999 (Figure 10.5.3) illustrate the plume and concentration reductions. The reductions occurred in less than 2 years.

10.5.6.2 Performance Results Monitoring data shown in the June 2000 status report indicate that 26 of 31 wells met the 0.05 mg/L cleanup standard for Cr(VI). The other 5 wells were only slightly above 0.05 mg/L (USEPA, 2002). Results from monitoring in the second gunter of 2004 (MWH, June, 2004) show that only two wells, at a single location, exceed the clearing goal. Groundwater extraction without injection of additional reducing agent has continued (Thomasser, (1999, 2000)). Site closure will be obtained when the selected recovery wells reach cleanup concentration for Cr and As. Recent monitoring data indicate that sulfate (SO42−) concentrations in many monitoring wells have increased higher than the drinking water standard of 250 mg/L as a result of the injection of the S2O52−/HSO3−. Manganese

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D PON

N 76 m

0

SCALE

POND

1.0

?

?

?

0.01

0.10

1.0 LEGEND PROPERTY LINE 0.10 Cr(VI) mg/L ?

FIGURE 10.5.2 Plot of Cr(VI) contaminant plume in January 1998 before in situ treatment at the Valley Wood Preserving, Inc. facility in Turlock, California (Thomasser and Rouse, 1999). Concentrations of Cr(VI) are mg/L.

POND

0.05 0.10

POND

N 76 m

0

?

?

SCALE

0.10

0.05

??

LEGEND 0.10

0.06

PROPERTY LINE 0.06 Cr(VI) mg/L ?

0.05

FIGURE 10.5.3 Plot of Cr(VI) contaminant plume in November 1999 after in situ treatment at the Valley Wood Preserving, Inc. facility in Turlock, California (Thomasser and Rouse, 1999). Concentrations of Cr (VI) are mg/L.

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(Mn) concentrations exceed the drinking water standard of 0.05 mg/L in a few locations (Lau, 2000). The SO42− and Mn concentrations are being monitored. 10.5.7

Conclusions

The results of this remediation project indicate the plume size and mass of dissolved Cr(VI) was reduced 98% in less than 2 years of in situ treatment using an injection of S2O52−/HSO3−. Acknowledgments The author thanks Jim V. Rouse of Montgenary-Watson-Harza for reviewing this article.

Bibliography Brown, A.B., M.C. Leahy, and R.Z. Pyrih, 1998, In Situ Remediation of Metals Comes of Age, in Remediation/Summer 1998, John Wiley and Sons. California Department of Toxic Substances Control (DTSC), 2000, Site Cleanup—Site Mitigation and Brownfields Reuse Program Database; Valley Wood Preserving, Inc. ID#50240001; http://www/dtsc.ca.gov/databaseCalsites/CALP001.CFM, IDNUM+50240001 Lau, M., 2000, Personal communication by telephone on August 10, 2000 with the USEPA Region IX RPM for the Valley Wood Preserving, Inc., Ukiah, California, NPL, Superfund. Montgenary-Watson, Harza (M-W-H), 2000 June, 2004 Quartery Groundent Sampling Event. Rouse, J.V., 1994, In Situ Remediation of Dissolved Chromate-Ion Contamination of Groundwater, Paper presented for the 87th annual meeting of the Air and Waste Management Association. Rouse, J.V., 2004, Personal communication. Thomasser, R.M., 1999, Pilot Study Groundwater Monitoring Results, Quarterly Status Report to the USEPA, Region IX, July 14. Thomasser, R.M., 2000, Remedial Program and Monitoring Results, Combined Fourth Quarter and Annual Report for 1999, January 15. Thomasser, R.M. and Rouse, J.V., 1999, In Situ Remediation of Chromium Contamination of Soil and Groundwater, Paper presented for the American Wood Preservers Association, May, 1999 Conference on Assessment and Remediation of Soil and Groundwater Contamination at Wood Treating Sites. U.S. Environmental Protection Agency (USEPA), 2000, In Situ Treatment of Soil and Groundwater Contaminated with Chromium, EPA/625/R-00/005, October 2000, p. 84. U.S. Environmental Protection Agency (USEPA), 2002, NPL Narrative for Coast Wood Preserving, Ukiah, California, NPL, Superfund, p. 2. http://www.epa.gov/ superfund/sites/npl/nar907.htm

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10.6 Townsend Saw Chain Company, Pontiac, Richland County, South Carolina

James A. Jacobs and Ralph O. Howard, Jr. 10.6.1

Introduction

The site is located along the north side of Interstate Highway 20 at the South Carolina (SC) Road 53 exit, Spears Creek Church Road, near Pontiac, South Carolina. The site is located approximately 16.09 km northeast of Columbia, South Carolina.

10.6.2

Site Location and History

10.6.2.1 Site Setting The site was originally part of a 40.5 × 104 m2 (40.5 hectare) parcel that was purchased by the Dictaphone Corporation in 1964. The Dictaphone Corporation constructed a small manufacturing facility to assemble selected lines of the company’s office recording equipment. Details of their operations are unavailable. Two permits were issued by the state and indicate that the wastewater generated during on-site manufacturing activities contained low concentrations of Cr as chromate (CrO42−), cyanide (CN−), zinc (Zn2+), as well as residues from acid and alkali cleaning operations. The state of South Carolina permitted the facility from June 1966 to June 1971. Dictaphone later became part of Pitney Bowes. The site was purchased in June 1971 by the Townsend Saw Chain Company, which began manufacturing operations on the site in July 1972. From that time until the plant closed in 2001, the facility (known as the “Townsend Saw Chain Company,” and later as Sabre-Textron and Homelite, owned by Textron Inc.) manufactured and assembled saw chains for chain saws. Processes included metal punch pressing, metal plating with Cr, heat treatment with a quench bath, dipping in a rust preventative bath, and metal parts cleaning and finishing. The wastewater generated during the manufacturing process of saw chains included Cr, cadmium (Cd), CN−, nitrite (NO2−) and nitrate (NO3−) salts, and several volatile organic compounds (VOCs). 10.6.2.2 Historical Land Use Between 1966 to 1981, both Dictaphone and Townsend Saw Chain Company released Cr containing waste rinse waters produced during the manufacturing operations into the ground surface in a low lying wastewater pond area adjacent to the facility on the north side. These discharges, which occurred over 15 years, are the source of the Cr groundwater contamination. In 1982, the South Carolina Department of Health and Environmental

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Control (SCDHEC) investigated the situation and cited Textron for violations of the established wastewater treatment regulations and the Federal Safe Drinking Water Act of 1974 (SDWA). Chromium(III) nitrate Cr(NO3)3, VOCs, and “metal” ions were detected above the Maximum Contaminant Level (MCL) onsite and offsite. Under a 1982 Consent Order, a groundwater “pump and treat” system was installed. The system included 5 extraction wells, chemical treatment tanks, and a spray irrigation field for disposal of the treated water. The system operated from 1982 until 1995 and was monitored by the SCDHEC under an industrial wastewater permit. After treatment to the then applicable South Carolina groundwater quality standard for Cr of 0.050 mg/L, groundwater was then discharged to a spray field (USEPA, 1999). After 1995, the system was augmented by the addition of 3 additional wells bringing the total well pumping network to 8 wells, and the system was operated until April 2002 as part of the site’s Remedial Action (groundwater cleanup). Under the 1993 Interim Record of Decision and 1996 Final Record of Decision (ROD), the purpose of the system was described as containment of the plume. A series of assessments was performed in the early 1990s. The results verified that the plume of Cr contaminated groundwater extended offsite to the northeast over 213.36 m beyond SC Road 53, the property line. The facility is shown on the aerial photograph (Figure 10.6.1). As of 1996, the plume measured approximately 457.2 m in length, and formed an elongate oval trending southwest to

0

FIGURE 10.6.1 Aerial photograph of site, circa 1979.

100 M

0

100 yd

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LEGEND DENOTES >200 mg/kg DENOTES>10 mg/kg DENOTES >1 mg/kg DENOTES PRE– SECOR WELLS

SCALE (APPROXIMATE) 0

53 m 106 m

MW–30 sm MW–31 s PZ–2 s

MW–1 sm

P2–3 si MW–33 s MW–33 i

MW–28 sm

MW–29 s PL–4 si MW–27 s

MW–32 s MW–26 s

MW–21s

MW–19 sm

MW–25 s

MW– 6 sm MW–7 si

ND SE WN AIN TO CH W A S

ING RK PA LOT

APPROXIMATE EXTENT OF Cr(VI) GROUND WATER PLUME MW–22 sm

FIGURE 10.6.2 Chromium groundwater plume as of 1996 (area exceeding USEPA MCL of 0.1 mg/L).

northeast (Figure 10.6.2). The plume is also discharging into an unnamed tributary of a nearby creek, through an off-site seep. The main contaminant is Cr(VI); VOC concentrations have rarely exceeded 0.05 mg/L in any wells. Chromium-contaminated soils were found in the former wastewater ponds area, an hourglass-shaped low-lying area adjacent to the facility. Contamination was generally limited to the uppermost 0.15 m below ground surface. The shallow soil appeared to be binding up the Cr(III), which is much less mobile and much less toxic than Cr(VI). Two “hot spots” associated with an old leach field close to the low-lying area were excavated in

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1995, comprising about 68,000 kg of soil contaminated with Cr, lead (Pb), and other heavy metals (elements with density >5 g/cm3). Treatment of the remaining soils in the former wastewater ponds area has been determined not to be necessary (see “Regulatory Standards” below). 10.6.2.3 Recent Site Activities Since the remedial design began in 1996, the main focus of the groundwater cleanup has been the development and implementation of an in situ chemical-reduction treatment process (SECOR, 1996). In 1999, the site work transitioned into remedial action (RA). The treatment uses iron(II) sulfate (FeSO4) in a chemical reducing agent solution that, once in contact with groundwater, converts Cr(VI) into a relatively inert and harmless chromium(III) hydroxide (Cr(OH)3), which can safely remain bound up on subsurface soil particles. Remedial injection ports (injection wells) on 12.19 m centers are used to place the FeSO4 into the groundwater. The remedial injection port lines are approximately 30.48 m apart and are perpendicular to the groundwater flow direction. Approximately 150 remedial injection ports were installed. The view looking northwest across the site shows injection line 3 (Figure 10.6.3). A closer view of the remedial injection ports is shown in Figure 10.6.4. A close up of a remedial injection port is shown in Figure 10.6.5. In April 2002, USEPA and SCDHEC approved the shut down of the “pump and treat” system. As of March 2002 more than 263.08 kg of Cr had been removed from affected groundwater by this system.

FIGURE 10.6.3 View across southwest (upgradient) end of plume showing injection lines.

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FIGURE 10.6.4 Closer view of remedial injection ports.

10.6.3

Regulatory Overview

10.6.3.1 Regulatory Agencies Site activities since 1991 have been under Superfund, and the lead regulatory agency is the USEPA, Region IV. The SCDHEC, under state wastewater authority, maintained oversight of response activities from 1982 through 1991. The state continues to play an active role as the support agency under Superfund. 10.6.3.2 Timeline of Regulatory Activities The following timetable was developed based on USEPA information: 1982 to 1995: A 5-well “pump and treat” system was operational during this period, consisting of 2 pumping wells on the site property and 3 wells along the northeast property boundary (SC Road 53). The original objective (under a state permit) was full cleanup of the plume; later however, the 1993 Interim Action recognized that only hydraulic control and containment of the Cr(VI) containing groundwater plume would be achieved (see below). In 1995, the “pump and treat” system was expanded through the addition of 2 new wells. From 1995 to 2002, the system provided leading end containment of the groundwater plume while the in situ treatment has been implemented.

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FIGURE 10.6.5 Close-up view of injection part with flex hoses, quick disconnects, flow reducer (on the line), and an analog pressure valve (top of part).

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Chromium(VI) Handbook 1985: SCDHEC performed a preliminary assessment/site inspection (PA/SI), which revealed elevated concentrations of Cr, pb, cadmium (Cd), arsenic (As), CN−, nickel (Ni) and 4 VOCs in groundwater at the site. Elevated concentrations of Cr, Pb, Cd, and As were found in the sediments within the wastewater pond area. A stream water sample collected across Spears Creek Church Road north of the site detected elevated concentrations of Cr and four VOCs. 1987: USEPA ranked the site using the hazard ranking system (HRS). Owing to the potential for off-site migration, and the use of groundwater for public supply wells serving a large local population, the site was assigned an HRS score of 35.94. June 1988: The site was proposed for listing on the National Priorities List (NPL). February 1990: The site was finalized on the NPL, placing it into the national Superfund program. 1991 to 1993: A remedial investigation (RI, Phase I, and Phase II) was performed at the site, as a potentially responsible party-lead project under EPA and SCDHEC oversight. Cr(VI) was the main Contaminant of Concern (COC) and the groundwater plume was shown to be migrating off-site. The USEPA-prepared baseline risk assessment, prepared for the RI/FS, concluded that the site presented potential risks to on-site and off-site water well users, as well as potential risks to on-site workers from Cr(VI), Pb, As, and Cd in surface soils. December 1993: USEPA issued an Interim ROD which called for construction and operation of the previously state-approved “pump and treat” system, with some expansions and modifications. The objective of the “pump and treat” system was to provide hydraulic control and containment of the plume, while the final remedy was developed. 1994 to 1995: A feasibility study (FS) was conducted that included a pilot scale demonstration of in situ Cr reduction using a chemical reducing agent. Two “hot spot” areas of soil were excavated and additional delineation of the extent of on-site surface soil contamination was performed. Full operations of the updated and expanded groundwater “pump and treat” system began in late 1995. USEPA and SCDHEC approved a modification to the risk assessment that showed there was no risk to site workers from soil exposure, but that contaminated soil could adversely affect site groundwater quality. December 1996: The USEPA issued a final ROD for the site. The main components included soil treatment, groundwater remediation, and site monitoring. The soil treatment was viewed as source control and included excavation and removal of the uppermost

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highly contaminated soil, and treatment of the surficial soil through in situ chemical treatment. The groundwater remediation included in situ chemical treatment of the Cr-contaminated groundwater and the continued operations of the interim action “pump and treat” system. A small-scale sediment removal action at the offsite Spring/ Seep area, which was the head of a tributary, was included in the remedy but was to be performed upon completion of the groundwater cleanup, to avoid recontamination of sediment. Monitoring included continued quarterly sampling and analysis of onsite and offsite groundwater samples (in accordance with a state permit in effect since the 1980s), and periodic sampling of treated onsite soils. 1997–1999: Remedial Design (RD) work for the in situ treatment was completed, which progressed from bench scale and field pilot studies, through actual well line injections along lines 2 and 3. An additional extraction (pumping) well was added to the “pump and treat” system, bringing the total number of pumping wells to 8. September 1999: The RD phase of work was completed in September 1999, and the site work transitioned into RA. Development of the in situ treatment technique was conducted in successive stages, working from upgradient areas (near line 1) toward downgradient and off-site areas (towards the unnamed off-site tributary). For monitoring purposes the areas between injection port lines were designated “cells.” The design and RA have been conducted using an “observational approach” that consists of making, at each step, continual changes or improvements to the process based on conclusions from earlier steps. Likewise, during the RA, Interim Remedial Action Reports are being submitted sequentially in order to document successful treatment of all affected groundwater, as well as the approved changes or improvements to the process. July 2001: USEPA issued an Explanation of Significant Difference (ESD) for the site. The ESD provided for a significant change to the remedy selected in the 1996 ROD concerning contaminated site soils. The 1996 ROD stated that at least three small areas of contaminated surface soil in the large grassy portion of the site property, north of the main plant building, posed unacceptable risks for contaminating site groundwater (but not to workers or residents.) These areas were to be tested for treatment using the in situ treatment. Or, if this proved unsuccessful, the soils were to be excavated and removed to an USEPA-approved hazardous waste landfill. The ROD indicated that a cleanup standard of 16 mg/kg would be used. With this ESD, and based on additional onsite work conducted during 1998 to 2000, the USEPA revised the numerical cleanup standard for soils to 144 mg/kg total Cr. The effect of the change was that no additional surface soil (beyond that removed in 1994 to 1995, small-scale spot removals) needed to be treated or excavated.

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10.6.3.3 Regulatory Standards 10.6.3.3.1 Cleanup Standards The regulatory-established cleanup level (USEPA, 1999) for dissolved Cr and other constituents in groundwater and soil is shown in the table below: The original remediation goals were developed in December 1996 and based on the anticipated continued use of the on-site facility with potential residential development in the surrounding adjacent off-site area. As noted above, a modification to the remedy issued in July 2001 (see above) established a revised soil cleanup goal of 144 mg/kg for Cr(VI). At this remedial goal, there were no surface soils requiring treatment or removal. 10.6.4

Site Characterization

10.6.4.1 Site Geology Quaternary sediments consisting of sands and low permeability clays and silts overlying Upper Cretaceous sediments of the coastal plain. A clay-rich aquitard, “Unit II,” was found in the RI to be fairly continuous throughout TABLE 10.6.1 Dissolved Chromium and Other Constituents in Groundwater and Soil Medium

Contaminant

Original Remediation Goal

Surface soil Cr(VI) 16 mg/kg .................................................................................................................................. Surface water Total Cr 0.040 mg/L Groundwater Total Cr 0.100 mg/L (Cd) 0.005 mg/L (CN−) 0.200 mg/L (Pb) 0.015 mg/L 10.0 mg/L (NO3−) Vanadium (V) 0.110 mg/L 1,1-dichloroethene 0.007 mg/L (1,1-DCE) Trichloroethene (TCE) 0.005 mg/L Tetrachloroethene (PCE) 0.005 mg/L

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the site at between 15.24 m and 21.34 m below ground surface. The uppermost predominantly-sand unit, “Unit I,” is the affected aquifer. 10.6.4.2 Site Hydrology Groundwater is generally shallow, ranging from 4.57 m to 7.62 m below ground. There are a few perched zones (clays) where groundwater occurs at shallower depths. 10.6.4.3 Field Sampling Activities During the long history of characterization activities (primarily 1985 to 1995), more than 50 groundwater monitoring wells had been installed on-site and hundreds of soil and groundwater samples collected. The RI eventually demonstrated that the area of contaminated groundwater was approximately 457.2 m in length and that it was discharging into an unnamed tributary of a nearby creek. Maximum groundwater Cr(VI) contamination, downgradient of the former wastewater pond areas, reached concentrations of approximately 4 mg/L. During the RD and RA, test kits have been used extensively to screen preinjection samples along the injection lines, with laboratory backup for quality assurance purposes. 10.6.4.4 Remedial Alternatives Evaluation (FS) In 1993, as an interim remedial action for groundwater, conventional “pump and treat” methodology was designed and implemented. The interim action “pump and treat” system, comprising 8 (later 9) pumping wells, began operations in December 1995 and operated until April 2002. As of March 2002 more than 263.1 kg of Cr had been removed from affected groundwater by this system. Rates of water extraction varied somewhat, but as an example, an average of 9.46 × 106 L/month of Cr-contaminated water were collected and treated between July and September 2001. As part of the main site FS, bench scale treatability testing of a new and innovative in situ chemical treatment process for groundwater and soil was conducted during late April to early May 1995 (“Demonstration Study”, Appendix D, Site Feasibility Study, 1996). The in situ process uses a chemical reducing agent, FeSO4 , injected into wells arranged along lines. The solution moves ahead of the plume as a reaction front. The Demonstration Study showed that the reduction of Cr(VI) concentrations in both soil and groundwater occurred. It stated also that additional treating would be needed to determine design parameters before full scale remediation. 10.6.4.5 Selected Remedial Alternative Based on these successful tests, and after a thorough evaluation of this and other remedial options, the 1996 ROD selected the following site remedy: (1) in situ chemical treatment for soil and groundwater, (2) continued operation of the “pump and treat” system, (3) continued groundwater monitoring, and

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(4) after completion of the groundwater cleanup, performing a small-scale sediment removal action in a certain portion of the off-site tributary which receives site-originated groundwater. For Cr-contaminated soil, the more conventional excavate and remove process was evaluated in addition to in situ treatment. 10.6.4.6 Pilot Study Results Work planning for the remedial design phase began in May 1997. Bench tests were performed proceeding to a pilot-scale treating project. Pilot studies using an existing spray field piping network and soaker hoses with FeSO4, a chemical reducing agent, showed average Cr(VI) reductions of 84% for saturated soils and 61% for drier, unsaturated soils. Maximum reductions were noted up to 97%. Pretreatment of surface soils ranged from 39 mg/kg to 1,500 mg/kg, while the posttreatment concentrations were 17 mg/kg to 680 mg/kg. Soil samples below the surface, at 0.46 m to 0.61 m below ground surface showed reductions in Cr(VI) from 7.9 mg/kg to 3.2 mg/kg. As noted above, treatment of soils was eventually determined not to be necessary. The first groundwater pilot treatment during RD showed reductions of concentrations of Cr(VI) as high as 0.38 mg/L prior to treatment, effectively decreased to 0.04 mg/L after treatment. A second pilot test was performed, and Cr(VI) was treated to less than the remediation goals. Approximately 3.05 m of vertical dispersion occurred in the wells. The pH of the treatment solution was reduced from approximately 3.0 to 2.5 to overcome the buffering capacity of the aquifer. Areas of high buffering capacity were recognized as requiring additional preacidification treatment. When the treatment reagent of FeSO4 is buffered, the Fe precipitates near the injection ports, causing backpressure within the injection ports and clogging the aquifer. Therefore, most injections after 1998 included preacidification as a preinjection step. The chemical treatment typically creates high Fe(II) concentrations (150 mg/L to 250 mg/L), high sulfate (SO42−) concentrations (700 mg/L), and low a pH. In addition to the Fe fouling described above, clogging of the aquifer from the formation of a solid, Fe-Cr hydroxide complex also can occur near injection ports. The SO42− is expected to attenuate naturally to concentrations less than 250 mg/L, the national secondary drinking water standard for SO42−. Owing to these characteristics of the aquifer during treatment, monitoring the capture of treated water and any excess FeSO4 reagent is important to prevent any offsite contamination. 10.6.5

Remedial Performance

During remedial design pilot testing in 1997 and 1998, the starting assumptions were that minimum 6.10 m spacing for injection wells would effectively provide lateral dispersion of the FeSO4. A 12.19 m spacing was ultimately used. Data collected over one month of monitoring indicated that effective treatment occurred at a distance of at least 11.28 m downgradient of the

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injection line. With additional reducing agent injected, an effective treatment at a 30.48 m distance was indicated. Eventually, from 1997 up through 2002, about 150 remedial injection ports (arrayed in 12 lines) were installed, 7 onsite and 5 offsite. Good lateral dispersion of the treatment chemical in the aquifer was achieved. After significant modeling and reviewing of the data, the potential for reoxidation of the Cr(III) at this site appears to be minimal.

10.6.5.1 Performance Results As noted above, in situ treatment is only being used for groundwater. Over the course of RD and RA, a series of lines of wells, approximately 30.48 m apart and perpendicular to the direction of groundwater plume movement were installed. The area downgradient of each line was considered a “cell,” and each contains 5 wells for monitoring, although many cells have additional pre-1997 monitor wells that are also used. The 5 wells are positioned 7.62 m, 15.24 m, and 22.86 m downgradient. Before injection of the reducing agent, an acidic water solution was injected to increase the acidity (lower the pH) of the groundwater. The reducing solution, FeSO4, is then pumped into the wells at a fixed rate. The treatment chemicals move downgradient as a reaction front, ahead of the plume. The total Cr concentration in the groundwater usually initially increases, as Cr is desorbed from the soil and available in the groundwater. A strong reaction occurs when the Cr(VI) is reduced into Cr(III), ultimately precipitating out as Cr(OH)3. When the Fe and SO42− present in the solution appear in the 15.24 m downgradientmonitoring wells, pumping is stopped and monitoring starts. A trend of declining contaminant concentrations in shallow groundwater in the treated cells has been seen since the start of injections in September 1998. (Officially, the RA began in October 1999 but three cells had already been treated and did not require retreatment.) This declining concentration trend continues to date. The remaining “hot spots” of highly concentrated soluble Cr are shown on the concentration contour map (Figure 10.6.6) of total Cr in groundwater as of November 2002. The offsite area to the northeast is the focus of current efforts. The map clearly illustrates that for most of the on-site groundwater, treatment has reduced total Cr from the soluble, mobile phase into a less soluble phase, such that most of the groundwater is less than 0.100 mg/L, the maximum concentration level (MCL) and the groundwater standard. The reduction of Cr concentrations in groundwater is a well documented trend for this site. A continuation of this trend is expected to ultimately lead to attainment of the MCL site-wide. The consultant for the Potentially Responsible Party, MACTEC, has estimated the assessment and remediation costs through mid-1999 to be about $2.5 million to $3 million. Total anticipated costs for the remediation to achieve site closure will likely bring the site total to $4 million to $5 million.

2.0

Line 2

1.5 1.0

MW-29 Line 3

0.5

Line 5

0.0

ar's Cre Line 7

MW-90

MW-89

MW-88

PZ-02

Line 6

Spe

Line 4

0.1

rch

hu ek C MW-93

MW-103 MW-110

MW-111

Line 10

MW-102

MW-101

Line 8 MW-38

Line 9

-96 MW

d

Roa

EW-14 EW-12 MW-117 Line 11 MW-118 EW-10 MW-112 MW-116 15 -1 MW MW-52

EW-9

EW-13

MW-54

MW-48

Scale 1 cm = ~ 10.8 m

MACTEC E & C, Inc

MW-53

MW-3

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

MW-94 MW-109 MW-35A EW-6 MW-100 MW-34A MW-114 Line 1 MW-104 Line 1C MW-91 TW-16 MW-70 Line 1A MW-76 MW-78 MW-79 TW-18 MW-17A MW-87 MW-108 MW-02A TW-9 MW-01A MW-113 Line 12 EW-7 M MW-71 MW-95 W MW-21MW-60 MW-80 MW-03A -5 MW-99 MW-77 6 MW-92 MW-105 TW-20 MW-66 MW-86 MW-72 MW-63 MW-107 MW-55 IMW-04 MW-64 MW-81 MW-59 MW-106 IMW-05 IMW-03 MW-67 MW-73 TW-4 TW-13 MW-25 MW-98 EW-8 MW-85 MW-82 MW-62 IMW-01B MW-65 MW-68 TW-12 MW-83 IMW-02B MW-1 MW-74 MW-84 IMW-02 MW-75 Line 1B MW-69 MW-97

2.5

408

FIGURE 10.6.6 Total Cr Concentration, November 2002, Townsend Saw Chain Site, Pontiac, SC.

26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0

3.0

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Conclusions

The results of the groundwater treatment based on the in situ injection of FeSO4 have been encouraging, with more than 2/3 of the affected groundwater plume now showing less than the MCL for Cr(VI). The overall size of the Cr(VI) plume exceeding 0.100 mg/L (the MCL) is steadily being reduced.

Bibliography Harding Lawson Associates, 1999, Draft Final Remedial Design Report for the Townsend Saw Chain Site, Pontiac, SC, USEPA, Region IV, September. Harding Lawson Associates, 2000, Preliminary Injection Monitoring Results and Revisions to the Final Remedial Design Report the Townsend Saw Chain Site, Pontiac, SC, July 27. Harding Lawson Associates-ESE, 2001, Preliminary Total Chromium Concentration Map, Townsend Saw Chain Company Site, Pontiac, Richland County, SC. SECOR International, Inc., 1996, Feasibility Study, Townsend Saw Chain Site, Pontiac, SC, August. U.S. Environmental Protection Agency (USEPA), 1999, Preliminary Close Out Report, Townsend Saw Chain Company Site, Pontiac, Richland County, SC, September. U.S. Environmental Protection Agency (USEPA), 2000, In Situ Treatment of Soil and Groundwater Contaminated with Chromium, Technical Reference Guide, EPA/625/R-00/005; October. U.S. Environmental Protection Agency (USEPA), 2001, Remedial Action Update and Explanation of Significant Differences, Townsend Saw Chain Company Site, Pontiac, Richland County, SC. U.S. Environmental Protection Agency (USEPA), 2004, NPL Site Narrative For Townsend Saw Chain Co. Site, Pontiac, South Carolina. URL: http://www_epa. gov/region4/waste/npl/nplsc/towsawsc.htm

10.7 Former Paper Mill, Delaware River, East Coast

James A. Jacobs 10.7.1

Introduction

The site was the first commercial in situ application of the iron (Fe) reduction process for treating Cr(VI) in soils and groundwater. 10.7.2

Site Location and History

10.7.2.1 Site Setting The subject property is located on the Delaware River and the site of a former paper mill.

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10.7.2.2 Historical Land Use The former paper mill used Cr-based materials on the property.

10.7.2.3 Recent Site Activities The former paper mill facility contained Cr(VI) at concentrations of 85 mg/L in the shallow perched aquifer (USEPA, 2000).

10.7.3 10.7.3.1

Regulatory Overview Cleanup Standards

The regulatory-established cleanup level for dissolved Cr in groundwater was set less than 0.05 mg/L, the drinking water standard.

10.7.4

Site Characterization

10.7.4.1 Site Hydrology Chromium(VI) was concentrated in the soils and shallow perched aquifers.

10.7.5

Remedial Investigation

10.7.5.1 Review of Remedial Options A conventional groundwater extraction system was evaluated with the potential for treatment of the extracted groundwater and reinjection. Had this remedial alternative been selected, treatment sludge generated during treatment would have required disposal. Various bench tests were performed prior to selecting the Fe reduction process. The Fe reduction process uses a FeSO4 solution as the reducing agent for the treatment of Cr(VI) contaminated soils and groundwater. Chemistry relating to Fe and Cr reactions was examined as part of the evaluation of the various remedial options. Cr(VI) exists as chromate (CrO42−), under neutral or alkaline conditions and dichromate (Cr2O72−) under acidic conditions, and both species of Cr react with Fe(II). Both the Cr(III) and Fe(III) ions are highly insoluble under natural conditions of groundwater (generally neutral or slightly alkaline or acidic conditions). The addition of an iron(II) sulfate FeSO4 solution in the reactive zone can create acidic conditions, and consequently the zone downgradient of the FeSO4 injection zone may require the injection with soda ash (Na2CO3) or caustic soda (NaOH) to bring pH back to the neutral conditions (Sutherson, 2002). A concern with FeSO4-based reducing agents may result in Fe precipitation and clogging of aquifer and unsaturated zone pore spaces.

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10.7.5.2 Selected Remedial Alternative After a thorough evaluation of remedial options, the direct injection of the reducing agent and continued groundwater monitoring was selected as the remedial alternative. 10.7.6

Remedial Performance

10.7.6.1 Treatment Train The treatment included using the in situ application of Fe reduction process for fixation of the Cr(VI). The reducing agent, a solution of FeSO4 was used for the treatment of soils. For perched groundwater treatment of Cr(VI), the contractor applied acidified iron(II) sulfate heptahydrate (FeSO4 ⋅ 7H2O) using a combination of infiltration galleries, additional well points and wells, and a vertical trellis network of conduits for delivery of the treatment liquids. No groundwater was extracted during this treatment process.

10.7.6.2 Performance Results Concentrations of Cr(VI) before the injections was 85 mg/L. After treating the subsurface soils and groundwater with the Fe reduction process, concentrations across the site were reduced to 0.05 mg/L. Continued monitoring for 4 years was performed to verify and confirm the reduction of the Cr(VI) to concentrations less than 0.05 mg/L, the drinking water standard (Brown, 1998). The total cost of the project was $250,000. That amount was equal to the cost of the alternative “pump and treat” equipment. An additional cost savings over the more conventional “pump and treat” method was noted and no sludges or wastes were generated during the treatment process that required disposal (Brown et al., 1998). 10.7.7

Conclusions

The first commercial in situ application of the FeSO4 solution successfully treated the Cr(VI) in soil and groundwater to a total Cr concentration equal to 0.05 mg/L, the drinking water standard.

Bibliography Brown, A.B., Leahy, M.C., and Pyrih, R.Z., 1998, In Situ Remediation of Metals Comes of Age, in Remediation/Summer 1998, John Wiley and Sons, New York. Suthersan, S.S., 2002, Natural and Enhanced Remediation Systems, Lewis Publishers, Boca Raton, FL, p. 419. U.S. Environmental Protection Agency, 2000, In Situ Treatment of Soil and Groundwater Contaminated with Chromium, EPA/625/R-00/005, October 2000, p. 84.

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10.8 Wood Treating Facility, South Australia

James A. Jacobs 10.8.1

Introduction

The South Australian site is underlain by cavernous limestone and is located approximately 1 km upgradient from the water supply of a city of 25,000 (Thomasser and Rouse, 1999).

10.8.2

Site Location and History

10.8.2.1 Site Setting The South Australian site is the location of a chromated copper arsenate (CCA) wood-treating facility. Past industrial and wood-treating activities on the site have resulted in the release of Cr into the unsaturated zone and shallow groundwater. Chromated copper arsenate is a mixture of the following compounds: • Arsenic(V) oxide

As2O5

• Chromium(VI) oxide CrO3 • Copper(II) oxide CuO 10.8.2.2 Historical Land Use The South Australian plant used CCA as a wood preserving compound. 10.8.2.3 Recent Site Activities The purpose of the in situ geochemical fixation using a sulfur-based reducing agent was to accelerate remediation by reducing the soluble Cr(VI) to Cr(III). 10.8.3

Regulatory Overview

10.8.3.1 Regulatory Agencies The present owner petitioned the South Australian government to install and operate in in situ geochemical fixation system in the cavernous limestone network. 10.8.3.2 Timeline of Regulatory Activities Given the proximity of the water supply well to a city, regulatory approval moved quickly.

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10.8.3.3 Cleanup Standards The regulatory-established cleanup concentration for this site for dissolved Cr(VI) in groundwater was set at 0.05 mg/L (Rouse, 1999).

10.8.4

Site Characterization

10.8.4.1 Site Geology and Hydrogeology The site is underlain by cavernous limestone deposits. Shallow groundwater occurs on the site. 10.8.4.2 Field Sampling Activities Unavailable.

10.8.5

Remedial Investigation

10.8.5.1 Remedial Evaluation “Pump and treat” methods have proven not to be effective for reducing Cr(VI) at groundwater contaminant reduction. After obtaining soil and groundwater data, an in situ groundwater fixation designed the system, including a series of recovery wells along the axis of the contamination plume. 10.8.5.2 Selected Remedial Alternative Based on successful results of the various geologic and geochemical studies, and an evaluation of remedial options, the direct injection of the reducing agent and continued groundwater monitoring was selected as the remedial alternative.

10.8.6

Remedial Performance

10.8.6.1 Treatment Program The remedial system included a series of recovery wells along the axis of the Cr(VI) plume. Pneumatic pumps were used to extract the water to a central waste treatment facility where a sulfur-based reducing agent is added, followed by in-line mixing and the start of the reducing agent reactions (Thomasser and Rouse, 1999). Then the reducing agent-dosed water was placed into a reaction tank, where the Cr(VI) was reduced to Cr(III), which ultimately precipitated out as chromium(III) hydroxide (Cr(OH)3) sludge. Water was then pumped to a series of remedial injection wells around the edge of the plume where the reducing agent-water solution was injected into the subsurface. Subsequent to decommissioning of the timber treating plant, an infiltration gallery was also constructed, to treat contamination of the unsaturated zone.

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10.8.6.2 Performance Results In less than 12 months of operation, the mass of dissolved Cr has been reduced by 55%. About 15% of the remediation is estimated to have occurred in the surface treatment tanks and the remaining 85% of the remediation occurred in the subsurface (Thomasser and Rouse, 1999). The system has been updated to allow for unsaturated zone remediation by using infiltration pits to allow for the percolation of reducing agent-water solution into the subsurface. Monitoring is performed using a network of pressure/ vacuum lysimeters in the unsaturated zone and groundwater monitoring wells in the saturated zone. One lysimeter located in the treatment cylinder sump contained 58 mg/L before the commencement of percolation of the reducing agent-water solution. Within 2 weeks, the Cr concentration decreased to less than 0.01 mg/L Samples from a well near the infiltration pit increased from a prior Cr concentration of 3.8 mg/L to a high of 120 mg/L as reducing agent-water solution desorbed Cr and remobilized it temporarily. This sample then decreased to less than 0.01 mg/L within 10 weeks of starting the percolation process in the unsaturated zone (Thomasser and Rouse, 1999). The site has since been certified as remediated by the South Australian EPA.

10.8.7

Conclusions

The results of this case study indicate that in less than 1 year of operation, 55% of the plume mass was reduced using a sulfur-based treatment. The site was completely remediated within two years of plant closure and decommissioning, and initiation of infiltration to address residual contamination in the unsaturated zone.

Acknowledgments The author appreciates the technical review of this article by Jim V. Rouse.

Bibliography Rouse, J.V., 1999, Monitoring Data and Results, Draft Remediation System Progress Report, South Australia. Thomasser, R.M. and Rouse, J.V., 1999, In Situ Remediation of Chromium Contamination of Soil and Groundwater, Paper presented for the American Wood Preservers Association, May, 1999, Conference on Assessment and Remediation of Soil and Groundwater Contamination at Wood Treating Sites. U.S. Environmental Protection Agency (USEPA), 2000, In Situ Treatment of Soil and Groundwater Contaminated with Chromium, EPA/625/R-00/005, October 2000, p. 84.

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10.9 Coast Wood Preserving Plant, Ukiah, California

James A. Jacobs 10.9.1

Introduction

The site is an active wood treatment facility in Ukiah. Site remediation technologies to treat the Cr(VI) ranged from groundwater “pump and treat”, capping, and slurry wall emplacement. After spending a large amount of time and financial resources on various technologies, which did not provide significant results toward site closure, in situ geochemical fixation was proposed and implemented. 10.9.2

Site Location and History

10.9.2.1 Site Setting Coast Wood Preserving is an active wood treatment facility on a 30, 000 m2 (3 hectare) site south of Ukiah, in Mendocino County in northern California. The plant is located off of Highway 101, approximately 4.83 km south of the main business district of Ukiah at the intersection of Plant Road and Taylor Drive. The town of Ukiah has 13,300 people and there are two duplexes, two bunkhouses, and six motel units located within 0.8 km of the site. 10.9.2.2 Historical Land Use Since 1971, the Coast Wood Preserving facility has used a solution of sodium dichromate (Na2Cr2O7), copper(II) sulfate (CuSO4), and arsenic acid (H3AsO4) as chromated copper arsenate (CCA) to pressure treat and preserve a variety of wood products. According to the lead California regulatory agency, the Department of Toxic Substances Control (DTSC), over the years of wood preserving activities, the cumulative drippings or spillage of the CCA solution resulted in soil and groundwater contamination of Cr, and soil contamination of arsenic (As) and copper (Cu). In addition, according to the EPA (2002), the leakage is result of past handling and storage practices. Chromated copper arsenate” is a mixture of the following compounds: • Arsenic(V) oxide As2O5 • Chromium(VI) oxide CrO3 • Copper(II) oxide CuO 10.9.2.3 Recent Site Activities The source of the Cr and As soil contamination remains and will be removed when the facility closes. Until that time, Coast Wood Preserving has funded a

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trust account to implement the final cleanup at that time. The site has been paved, as a method of capping of rain and surface water from intruding into the highest concentrations of Cr and As. A slurry wall and extraction wells have been installed to intercept Cr-contaminated groundwater. The original remedial action plan (RAP) was approved in December 1989. An amendment to the RAP was approved in 1999 to allow for implementing an in situ geochemical fixation as an enhancement to the existing groundwater “pump and treat” system. The purpose of the in situ geochemical fixation was to accelerate remediation by reducing the soluble Cr(VI) to Cr(III). Implementation of the in situ geochemical fixation occurred in 1999. Further applications of the reducing agent, calcium polysufide (CaS5), have been performed based on the presence of dissolved Cr in localized areas. According to DTSC records, a one-year evaluation of the in situ geochemical fixation and the second five-year review completed in May 2001 concluded that the in situ reduction process was effective and recommended that the groundwater extraction and treatment system be turned off. Four programs of direct-push reductant injection have been performed to date. Most recent monitoring results show that only 5 of the 29 monitoring wells exceed the cleanup goal for a Cr. A program of removal of accessible contaminated soil was conducted while the plant remained in operation, and further declines in contamination are anticipated (MWH, April 15, 2004). Currently the site is being monitored. Localized groundwater hot spots may be observed. Additional in situ geochemical fixation injections may occur based on the groundwater monitoring data. 10.9.3

Regulatory Overview

10.9.3.1 Regulatory Agencies The lead California regulatory agency, the DTSC, has been giving oversight to the subject property. Other regulatory agencies in the area include the North Coast, Region 1, of the Regional Water Quality Control Board (RWQCB) and Mendocino County Environmental Health Department. 10.9.3.2 Timeline of Regulatory Activities The following timetable was developed based on regulatory information (USEPA, 2002; DTSC, 2002). 1981: North Coast RWQCB issued an order requiring Coast Wood Preserving to establish measures to stop the release of toxic waste. Later that year, Coast Wood Preserving was referred to the RWQCB for violation of that order. 1983: The site was finalized and listed on the USEPA National Priorities List (NPL) in the Superfund Program. 1983 to 1989: In 1983, pumping and treatment of ‘‘metals” contaminated groundwater was performed under USEPA oversight. Over the next few years, a slurry wall and interceptor trench to prevent

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off-site migration of contaminated groundwater was also built. A groundwater extraction well was installed on the site to pump the contaminated groundwater and an injection well was used to inject treated water downgradient from the site. Coast Wood Preserving performed grading and constructed berms to prevent surface runoff from the main operations area. A cap was constructed by paving over contaminated soils to prevent water infiltration and leaching was constructed. Some contaminated soils were fixed using cement. Future deed restrictions will be required prior to any closure agreement. The “pump and treat” system for groundwater cleanup has been implemented, and the system will continue until the established cleanup goals are met. 1989: DTSC approved the Final Remedial Action Plan (RAP). The RAP included groundwater extraction, electrochemical treatment of the extracted groundwater or reuse of the groundwater in the wood treating process. A surface water run-off management plan was prepared and groundwater monitoring was implemented. 1990: A paved surface cap was installed and a sump was constructed. The groundwater pump and treat system was upgraded. 1994: The DTSC obtained a cost recovery settlement with the potential responsible parties through the summer of 1994. The primary responsible party was Coast Wood Preserving, Inc. 1999: DTSC approved a RAP amendment that made a provision for in situ geochemical fixation to accelerate the remediation of Cr(VI) in the groundwater. California Environmental Quality Act (CEQA) reports including negative declarations were submitted to the DTSC. The Remedial Design for implementing the amended RAP for in situ geochemical fixation was approved by the DTSC. The geochemical fixation using the reducing agent, Calcium Polysulfide (CaS5), was implemented. 2000: The 1999 Annual Report for the site showed a general decrease in the concentrations of dissolved Cr in the shallow groundwater had occurred from the implementation of the in situ geochemical fixation remediation. 2001: DTSC approved the second five-year review and one-year evaluation on in situ geochemical fixation. The five-year review concluded that the remedial actions were protective of human health and the environment. 10.9.3.3 Cleanup Standards The regulatory-established cleanup level for total dissolved Cr in groundwater was set at 0.05 mg/L, the State of California Maximum Contaminant Level (MCL) for drinking water.

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Chromium(VI) Handbook Site Characterization

10.9.4.1 Site Geology Quaternary sediments consisting of low permeability clays and silts with occasional sands characterize the shallow geology. 10.9.4.2 Site Hydrology Groundwater is shallow, at less than 3.05 m to 6.10 m below ground surface. Groundwater extraction rates were limited owing to low permeability. The groundwater treatment did provide hydraulic control of the plume of dissolved Cr. However, significant residual Cr(VI) was detected in the unsaturated zone of the main source area. Portions of two streams drain the property at a point 0.8 km upstream from where they meet the Russian River, a major waterway in northern California. The Russian River supplies municipal, domestic, and agricultural water to a variety of towns downstream of the site. The site is a groundwater recharge zone, even though shallow groundwater production is limited in the low-permeability clays and silts. Domestic, agricultural, and industrial uses rely on the local groundwater. Owing to the sensitive nature of groundwater resources and the high mobility of Cr(VI), the site is listed on the NPL. 10.9.4.3 Field Sampling Activities A variety of groundwater monitoring wells having both soil and groundwater samples were available on this site.

10.9.5

Remedial Investigation

10.9.5.1 Remedial Alternatives Evaluation “Pump and treat” for the groundwater was evaluated. Concentrations of the dissolved Cr, in the unsaturated zone exceeded drinking water standards. Based on mass removal rates and groundwater extraction characteristics, a 15-year to 20-year remediation life cycle was projected for this site to achieve the regulatory levels for site closure. In addition, owing to regulatory and local sanitary treatment plant requirements, the only discharge for the treated water would be through reinjection back into the shallow aquifer. Since the shallow water bearing zones is a low permeability, low flow aquifer, reinjection of large amounts of treated water would be problematic. 10.9.5.2 Pilot-Study Results “Pump and treat” evaluations using aquifer tests, lithologic, and geologic study of the boring logs and sediments, as well as the history of poor performance of the water reinjection wells provided the rationale for the concept of an in situ direct injection of the treatment chemicals into the subsurface. In addition,

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shallow infiltration trenches were excavated across the main source area to introduce the reducing agent in batches to the highly contaminated source soils. The application of treatment chemical in the trenches occurred prior to the onset of the annual rainy season in Northern California, which typically starts in November or December. The rainwater infiltration into the trenches was effective in distributing the treatment chemical throughout the contaminated source area. The reducing agent, CaS5, was selected as the chemical that would reduce the Cr(VI) to Cr(III), which would precipitate out as Cr(OH)3. 10.9.5.3 Selected Remedial Alternative Based on successful results in the pilot scale study, and after a thorough evaluation of remedial options, the direct injection of the reducing agent and continued groundwater monitoring was selected as the remedial alternative.

10.9.6

Remedial Performance

10.9.6.1 Treatment Train Originally, the treatment train approach was to have the groundwater “pump and treat” system controlling hydraulic gradient and the direct injection of the reducing agent to lower Cr(VI) concentrations. 10.9.6.2 Performance Results Concentrations of Cr(VI) were considerably greater than 0.05 mg/L, the State of California MCL for drinking water. In only five of 29 monitoring wells during January, 2004 sampling, with the maximum concentration in a well immediately adjacent to a tank farm holding timber-treating reagents. The shallow most groundwater depth ranged from 3.05 m to 6.10 m below ground surface. The reducing agent was injected using direct push technology (DPT) probe rigs in September 1999. A trend of declining contaminant concentrations in shallow groundwater was noted after the initial injection event and this declining concentration trend continues to date. For more detailed information, see Thomasser and Rouse, (1999), Thomasser (2000), and MontgrneryWatson-Harza, (2004).

10.9.7

Conclusions

The results of this remediation project indicate that the reaction time of the reducing agent is almost immediate upon contact between the reductant and the Cr(VI). Reducing agent last in the environment and continue to be effective years after the introduction into the subsurface. A one-year evaluation of the in situ geochemical fixation and the second five-year review completed in May 2001 concluded that the in situ process was effective. The groundwater extraction and treatment system was recommended to be turned off. Currently the

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site is being monitored and additional geochemical fixation injections may occur based on groundwater monitoring results (DTSC, 2002). Acknowledgments The author appreciates the technical review of this article by Jim V. Rouse.

Bibliography California Department of Toxic Substances Control (DTSC), 2002, Site Cleanup–Site Mitigation and Brownfields Reuse Program Database, Coast Wood Preserving, ID# 23240013, http://www/dtsc.ca.gov/databaseCalsites/CALP001.CFM,IDNUM+23240013. Montgrnery-Watson-Harza (MWH), April 5, 2004 Coast Wood Preserving Site, Ukiah, CA, First Quarter 2004 Groundwater Monitoring Report. Thomasser, R.M., 2000, Remedial Program and Monitoring Results, Combined Fourth Quarter and Annual Report for 1999. Thomasser, R.M. and Rouse, J.V., 1999, In Situ Remediation of Chromium Contamination of Soil and Groundwater, paper presented for the American Wood Preservers Association, Conference on Assessment and Remediation of Soil and Groundwater Contamination at Wood Treating Sites. U.S. Environmental Protection Agency (USEPA), 2000, In Situ Treatment of Soil and Groundwater Contaminated with Chromium, EPA/625/R-00/005, p. 84. U.S. Environmental Protection Agency (USEPA), 2002, NPL Narrative for Coast Wood Preserving, Ukiah, California, NPL, Superfund, p. 2. http://www.epa.gov/ superfund/sites/npl/nar907.htm

10.10 Industrial Facility, Grand Rapids, Michigan

David Bohan, David Wierzbicki, Jason Peery, Anna Willett, and Steve Koenigsberg 10.10.1

Introduction

Cr(VI) was found in high mg/L (ppm) concentrations at an industrial site in Grand Rapids, Michigan Wierzbicki et al., 2003. A large-scale pilot study was conducted to assess the effectiveness of Hydrogen Release Compound (HRC® ), manufactured by Regenesis, San Clemente, CA, for remediation of high concentrations of Cr(VI) in groundwater. HRC, a polylactate polymer, slowly releases lactic acid (CH3CHOH CODH) in the aquifer, which is used by native microorganisms as an electron donor, fermentation substrate for hydrogen production, and carbon source for growth.

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These processes reduce the redox potential (Eh) of the system (Wiedemeier et al., 1999). Under the reducing conditions created by HRC, the driving force for the reduction of Cr(VI) to Cr(III), is increased. For example, with suitable electron donors like the lactic acid and hydrogen that are produced from HRC, common microorganisms will reduce Fe(III) and sulfate (SO42−) to Fe(II) and sulfide (S2−), which in turn rapidly chemically reduce Cr(VI) to Cr(III) (Knox et al., 2001). Additionally, some microorganisms can also use lactate (C3H5O3−) and hydrogen from HRC to directly reduce Cr(VI) to Cr(III) (Wang, 2001). The HRC produces lactic acid and hydrogen. The reaction for the Cr(VI) reduction, after the hydrogen has been produced by the HRC process is: 5H+ + CrO42− + 3e− → Cr(OH)3(s) + H2O

(10.10.1)

Relative to Cr(VI), Cr(III) is immobile in the subsurface. Cr(III), precipitates as insoluble Cr(OH)3 and sorbs strongly to Fe and manganese (Mn) minerals. Cr(III), especially Cr(OH)3, is stable as a solid in groundwater having typical conditions of pH >5 and an Eh <+ 400 mV (Deutsch, 1997). 10.10.2

Site Location and History

10.10.2.1 Site Setting The site is located in an older, urban industrial and residential setting, 3.22 km southeast of downtown Grand Rapids, Michigan (Figure 10.10.1). 10.10.2.2 Historical Land Use The central area of the site is lined with industrial facilities and surrounded by residential property. Three companies in the area are suspected users of Cr(VI) for cleaning and/or plating processes and have had historical discharges and losses of Cr-bearing wastes to the ground. The HRC pilot study

Sparta Rookford

Green Bay Appleton Oshkosh

Coopersville 96

Sheboygan Saginaw Waukesha

Milwaukee Vyoming Racine Lansing Pontiac Kenosha St. Clair Shores Waukegan Detroit Rockford Taylor Evanston Kalamazoo Des Plaines Chicago 75 Oak Lawn South Bend Toledo Gary Hammond Lorain 55 Fort Wayne 65 69 57

Walker Allendale

Janesville

FIGURE 10.10.1 Site location.

Grandville Jenison Hudsonville 196 and

Comstock Park 37 Grand Rapids East Grand Rapids Wyoming Kentwood 6 Cutlerville

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is located near a Cr-plating company, where a Cr(VI) source has been identified under the still active building. The Silver Creek Drain, an 3.35 m by 2.44 m enclosed storm drain, bisects the site. 10.10.2.3 Recent Site Activities In 1989, the city of Grand Rapids detected Cr concentrations of 21.4 mg/L during routine water quality monitoring of the Silver Creek Drain. The contamination was traced back to a storm sewer near the site, where discolored groundwater, laterally leaking through cracks into the sewer, was videotaped. In 1993, an initial state funded remedial investigation identified the source of the Cr(VI). Investigations conducted in 1997 and 2000 determined the extent of soil and groundwater contamination and evaluated remedial alternatives. Pretreatment sampling of monitoring wells was conducted in 2001. 10.10.3

Regulatory Overview

10.10.3.1 Regulatory Agencies The responsible regulatory agency is the Michigan Department of Environmental Quality, Remediation and Redevelopment Division Grand Rapids Office. 10.10.3.2

Timeline of Regulatory Activities

1989: Cr detected in Silver Creek Drain 1993: Remedial investigation conducted to identify the source 2000: Extent of soil and groundwater contamination identified and remedial alternatives evaluated November 2001: Pretreatment sampling of monitoring wells December 2001: HRC applied onsite via 60 vertical direct push injections December 2002: Review and reporting of pilot-study results 10.10.3.3 Cleanup Standards The terms for acceptance of HRC for full-scale Cr(VI) remediation at the Berkey Street site were based on the successful pilot-study reduction of Cr(VI) concentrations to 10% of the baseline concentration in MW-17S. The Cr(VI) baseline concentration for MW-17S was 40 mg/L. Therefore, the cleanup goal is 4 mg/L of Cr(VI) in MW-17S. 10.10.4

Site Characterization

10.10.4.1 Site Geology The soils at the site consist of approximately 19.81 m of sand overlying clay. A sieve analysis performed in 1993 classified the soils as fine to medium grained and well sorted sand.

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10.10.4.2 Site Hydrology The water table begins approximately 7.62 m below ground surface (bgs). The hydraulic conductivity values range from between 0.91 m/d to 13.07 m/d. The horizontal hydraulic gradient is calculated to be (0.0014 m)/ (0.3048 m). The average groundwater flow rate is on the order of 0.24 m/d in a southwest direction. 10.10.4.3 Field Sampling Activities Monthly sampling was performed at MW-9, MW-14, MW-17S, MW-17D, MW-23, MW-24, and MW-25 for an 11-month period (Figure 10.10.2). Included in the sampling events were tests for metals and other geochemical data (Table 10.10.1).

MW-14

ENUE

RESIDENTIAL

BLAINE AV

ALLEY

HARD CHROME PLATING Co.

PARKING

MW-25 MW-16 (DATA MISSING)

MW-24

MW-17S MW-17D SB-ET-02 SB-ET-01 WELL

RETAINING WALL

LIGHT POLE MW-23 COTTAGE GROVE STREET MANHOLE (COLUMN) 120′

FIGURE 10.10.2 Site map.

MW-9

MW-17S % reduced MW-25 % reduced MW-24 % reduced MW-17D % reduced MW-9 % reduced MW-23 % reduced

Well ID

0.013

2/11/02 Day 70 6.7 83% 0.62 98% 0.21 81% 0.59 32% <0.005 100% <0.005 100%

1/14/02 Day 42 26 35% 21.222 21% 0.257 77% 0.838 4% 0.022 21% <0.005 100% 9 78% 0.164 99% <0.005 100% 0.86 1% <0.005 100% 0.011 15%

3/11/02 Day 98 2.96 93% 0.064 100% <0.005 100% 0.401 54% <0.005 100% 0.009 31%

4/9/02 Day 128 8.1 80% 0.073 100% <0.005 100% 0.35 60% <0.005 100% <0.005 100%

5/6/02 Day 156 18 55% 5.9 78% <0.005 100% 0.348 60% <0.005 100% <0.005 100%

6/3/02 Day 182

Total Cr(VI) Concentration (mg/L)

15 63% 6.2 77% 1.1 0% 0.41 53% <0.005 100% <0.005 100%

7/2/02 Day 211

17 58% 26 4% 0.049 96% 0.52 40% <0.005 100% <0.005 100%

8/5/02 Day 245

1.6 96% 4.2 84% 0.22 80% 0.73 16% <0.005 100% 0.009 31%

12/17/02 Day 379

424

0.028

0.87

1.1

27

40

11/13/01 Day 22

Monitoring Data

TABLE 10.10.1

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Remedial Investigation

10.10.5.1 Remedial Alternatives Investigation A request for proposals was sent out to three companies offering technologies to reduce Cr(VI) in groundwater. Envirologic was the only company to bid on the project and was awarded a contract for the pilot-study. 10.10.5.2 Pilot Study Results As mentioned in Section 10.10.3.3, the cleanup goal for the pilot study is to reduce Cr(VI) concentrations to less than 4 mg/L in MW-7S. As shown in Table 10.10.1, this cleanup objective was accomplished within 128 days of HRC treatment. 10.10.6

Remedial Performance

BLAINE AVEN

UE

10.10.6.1 Treatment Train A total of 43.35 kg of HRC was injected at each of 60 locations via direct push methods (Figure 10.10.3). A constant rate of injection was used to ensure

GP–10 <5

ALLEY

HARD CHROME PLATING Co. PARKING |24,000| GP–2 GP–7

MW–16

|210| |24,000| GP–5

MANHOLE

GP–4 |106,000| UTILITY POLE GP–6

VAS –9A

(210)- dissolved Cr(VI) (µg/L) 7.62 m below grade (water table surface) HRC application point

FIGURE 10.10.3 Sitemap of HRC treatment.

GP–3 RETAINING WALL |140,000| GP–9 GP–8 <5 |2,400|

|34,000| APPROXIMATE SEWER LOCATION COTTAGE GROVE STREET

MW–9

monitor well

VAS–17

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50,000 40,000 30,000 20,000 10,000 0 0

42

70

98

128 156 182 211 245 379 Time (Days)

FIGURE 10.10.4 Total Cr(VI) concentrations at MW-17S.

an application rate of 7.45 kg of HRC per vertical meter throughout the treatment zone. The HRC injection targeted the upper 6.10 m of the aquifer. 10.10.6.2 Performance Results In the most contaminated well in the pilot study area, MW-17S, total Cr(VI) was reduced from a baseline level of 40 mg/L to 3 mg/L at day 128 after HRC injection, meeting the 90% reduction goal (Table 10.10.1 and Figure 10.10.4). At day 182 after injection, the concentration rebounded to 18 mg/L. Nonetheless, monitoring on day 379 after injection, revealed a Cr(VI) concentration of 1.6 mg/L, marking a 96% total reduction. Similar results were recorded for other monitoring wells (results not shown). The typical longevity of HRC is 6 months to 18 months, depending on the HRC application loading, the microbial substrate demand in the aquifer, and the groundwater velocity. Low HRC application loading, high substrate demand, and high groundwater velocity decrease HRC’s longevity. In this case, it appears that the HRC application is still providing sufficient amounts of substrate needed to satisfy chemical and microbial demands. HRC’s role in Cr(VI) reduction during the pilot study is clearly indicated when preinjection data (from a period 5 years prior to injection) are compared to postinjection data. Using a first order rate analysis (rate = rate constant × concentration), the preinjection rate constant was 0.0008 d−1, while after injection the rate constant varied from 0.004 d−1 to 0.02 d−1. The rate constants for the postinjection period are larger than that prior to injection, showing that HRC directly increased the rate of Cr(VI) removal, despite the effects of rebound. 10.10.7

Conclusions

The Berkey Street pilot study showed reduction of aqueous Cr(VI) concentrations. Although some rebound did occur in some of the groundwater monitoring wells, the overall reductions ranged from 31% to 100% in the wells in the pilot study area over the period of 379 days. The largest decline,

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in MW-17S was from a pretreatment concentration of 40 mg/L to 1.6 mg/L, a reduction of 96%. The fulfillment of the 90% reduction requirement for the pilot study was met. A full-scale remedial approach will likely occur at the site in the future.

Bibliography Deutsch, W.J., 1997, Groundwater Geochemistry, Lewis Publishers, New York. Knox, A.S., Seaman, J.C., Mench, M.J., and Vangronsveld, J., 2001, Remediation of metal- and radionuclides-contaminated soils by in situ stabilization techniques, in Environmental Restoration of Metals-Contaminated Soils, Lewis Publishers, New York, Chap. 6. Regenesis Website, www.regenesis.com Wang, Y.T., 2001, Microbial Reduction of Chromate, in Environmental Microbe–Metal Interaction, Lovley, D.R. Ed., ASM Press, Washington, DC. Wiedemeier, T.H., Rifai, H.S., Newell, C.J., and Wilson, J.T., 1999, Natural Attenuation of Fuels and Chlorinated Solvents in the Subsurface, John Wiley and Sons, New York. Wierzbicki, D., Bohan, D., Mullin, S., Willett, A., and Peery, J., 2003, Hexavalent Chromium Reduction and Immobilization Using Hydrogen Release Compound, in The Seventh International Symposium, In Situ and On-Site Bioremediation Conference, Battelle Press, Columbus, OH.

10.11 Remediation of Cr(VI) Using Engineered Anaerobic In Situ Reactive Zones

John F. Horst and Suthan S. Suthersan 10.11.1

Introduction

Over the past 10 years, significant advances have been made in the use of engineered anaerobic in situ reactive zones (IRZs) for groundwater remediation. This technology provides a highly effective, yet economical way to remediate a wide variety of recalcitrant groundwater contaminants in all but the most complex geologic settings. It is probably best known for treating chlorinated solvents and Cr(VI). The concept of engineered anaerobic IRZs is based on the manipulation of the subsurface environment to create reducing conditions. The zone where these conditions are established can be used to intercept inorganic contaminants and permanently immobilize them. To create the reducing conditions, an easily degradable source of organic carbon is typically delivered to the targeted portion of the contaminated aquifer where naturally occurring bacteria begin to metabolize it. As a result of their increased activity, the microbes

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utilize dissolved oxygen for respiration at a rate greater than it can be recharged naturally, creating an anaerobic environment. In the presence of excess organic carbon and following depletion of dissolved oxygen, the bacteria begin to utilize alternative electron acceptors to support respiration, creating even more strongly reducing conditions. The successful design of an anaerobic IRZ requires an understanding of how the selected source of organic carbon will move in the subsurface environment and how it will modify the bio geo chemistry to support the reactions required to effect remediation. Thus, the major challenge is to design an engineered system around these processes, while taking into consideration wide variations and heterogeneous conditions encountered in the field. An alternative to the placement of expensive, slow-release sources of organic carbon in the subsurface is the periodic injection of inexpensive, easily degradable, food-grade sources of organic carbon. The nature of such sources and the active delivery techniques ensure immediate distribution of the organic carbon in the target zone, allowing microbial populations to flourish in a relatively short time frame. This is sustained and propagated through additional injections, natural dispersion, and advective groundwater transport. Adjustment of the injection frequency and carbon loading allows creation of the optimal environment to support the desired reactions at rates sufficient to meet remedial goals. Figure 10.11.1

FIGURE 10.11.1 Injection of carbon donor into subsurface.

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shows the manual injection of a food-grade molasses solution to create an engineered anaerobic IRZ. The Co-author (Suthersan) of this chapter installed the first engineered anaerobic IRZ for the precipitation and remediation of Cr in 1993 (Suthersan, 1998), and has since employed the technology at numerous other sites across the country. The following sections touch on the process/design considerations that must be accounted for in the application of engineered anaerobic IRZs, followed by the bio-geo-chemistry, physical removal mechanisms, and regulatory considerations associated with the in situ immobilization of Cr. Several case studies are provided at the end of the chapter. 10.11.2

Design Considerations

Any in situ technology is applied, de facto, out of sight. The understanding used to select, design, and apply the technology is based on limited data. The accuracy of the data we have describing the environment is a function of when, how, where, and often, and why the data were collected. As a result, it is important to use layers of useful information to define the subsurface and the conditions in which we must apply an in situ technology. Equally as important is to collect relevant corroborating data after a specific technology is selected in order to insure the proper application of that technology. Among the most critical design considerations for engineered anaerobic IRZs are hydrogeology, groundwater chemistry, and the contaminant characteristics. These design considerations help define the remedy implementation, including the system layout, type of injection points, frequency of injections, solution strength, and the maintenance and monitoring of the process. The following discussions provide further insight into the need to understand hydrogeology and groundwater chemistry. This is followed by brief discussions of system layout considerations, the need for proper baseline characterization, and the selection of a carbon donor. The next section covers the biogeochemical behavior of Cr. The injection of the carbon donor is shown in Figure 10.11.11. 10.11.2.1 Hydrogeology It is important to obtain specific hydrogeologic data in order to properly apply engineered anaerobic IRZs. The type of geology and the lithology of the subsurface are critical to the design and placement of the injection points. While a complicated lithology can constrain the design, in most cases it will not completely eliminate the technology as an option. By properly positioning injection well screen intervals to target specific zones, the technology can be effectively applied in most environments. Understanding the complexity and defining the lithologic variability as it relates to the groundwater contamination is an important first step. The depth to, and thickness of, the contaminated zone are also important considerations. In general, the deeper the contaminant remediation the greater the cost. The saturated thickness can also have a profound influence on cost, since there are practical limits on the maximum screened interval that can effectively be used in an injection well.

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A formation’s permeability is also important in that it affects the ability of a single injection point to serve as an effective reagent delivery mechanism. The higher the permeability the easier it is to deliver the reagent into the subsurface. As the permeability decreases, the effort required for injection increases. Similarly, secondary permeability features, hydraulic gradients, groundwater seepage velocity, and flow direction can all impact the effectiveness of injections and the speed with which the injected carbon source will spread. Low velocity systems typically require lower feed rates owing to the lower groundwater flux. Finally the chemical characteristics of the aquifer matrix are also important. The mineralogy can affect the desired remediation chemistry and the adsorptive capacity of the soil, as can the fraction of organic carbon. The characteristics of the aquifer matrix can also affect the ability of the formation to buffer fluctuations in pH. While microbial populations can endure a wide range of pH, ideally a pH close to neutral is the most conducive to healthy, diverse microbial populations. 10.11.2.2 Groundwater Chemistry Understanding the conditions present in the groundwater will make the application of engineered anaerobic IRZs more likely to succeed. This includes contaminant concentrations and distribution, the presence of necessary electron acceptors to support microbial respiration, and ambient geochemical conditions that may need to be accounted for during remedy implementation. Understanding of these issues allows the designer to optimize the processes required to remediate the target compounds.

10.11.2.3 System Layout Engineered anaerobic IRZs can be applied in a number of different configurations and using a variety of approaches. The variety and combinations used are limited only by the variety of potential scenarios that may be encountered in the field and the ingenuity of the practitioner. For the purposes of this discussion, two basic layouts will be discussed, (1) barriers and (2) wide-area treatment. These basic layouts can be used separately or can be combined to suit the needs of the remediation. Barriers consist of a series of injection points oriented in a line perpendicular to the groundwater flow direction. These can be positioned at a critical boundary for remediation or at regular intervals along the length of a plume. In most cases this layout is less expensive to deploy than wide-area layouts because the density of injection points is relatively low. Wide-area layouts target a large portion of the contaminated groundwater. Typically the injection points will be evenly spaced on a grid throughout the target zone. This method enhances the speed and completeness of the remediation, but there are significant cost implications. This type of well layout works best for small, shallow groundwater plumes.

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10.11.2.4 Baseline Definition It is critical that baseline conditions be established prior to initiating an active treatment program. Baseline conditions help establish a scale against which success can be measured. At a minimum, a complete suite of biogeochemical parameters and the target contaminant(s) should be measured from wells in the upgradient, contaminated, and down-gradient areas of the site. During application of the IRZ, field parameters such as oxidation-reduction potential (ORP or Eh), dissolved oxygen (DO), temperature and pH should be closely monitored along with 2-electron or 3-electron acceptor species, total organic carbon, and treatment end-products, if applicable. 10.11.2.5 Carbon Donors As previously discussed, the goal of supplying excess organic carbon is to create a reactive zone in the subsurface that is sustained, easily maintained, inexpensive, and appropriate to the target compounds. As such, molasses has been successfully applied for the treatment of heavy metals such as Cr. Unlike costly slow-release specialty products, molasses is injected in a water solution and moves readily with groundwater. As a result, organic carbon can be effectively delivered across a wide area from fewer injection points. Molasses is readily degraded, thus leading to the rapid formation of anaerobic conditions. However, the use of too much molasses can lead to fermentation and reduction of pH. Other sources of soluble organic carbon include methyl alcohol (CH3OH), ethyl alcohol (C 2 H 5 OH), sucrose (table sugar, C 12 H 22 O 11 ), cellulose ((C6H10O5)n), edible oils, and proprietary blends. The selection of the substrate is driven by the unit cost of the available soluble organic matter and the ease with which the material can be delivered to the subsurface. Many reagents are being selected from the wide variety of food-grade organic carbon sources (molasses, sucrose, and cooking oils for example). The reagent selection process is often driven by how comfortable the regulatory agency is with the material and the variety and depth of practical applications available for a particular substrate. 10.11.3

Bio Geo Chemical Behavior of Chromium

In the environment, Cr is typically found as Cr(III) or Cr(VI). Cr groundwater contamination nearly always involves the more toxic and mobile Cr(VI), which is used in a number of commercial processes including electroplating, leather tanning, pigment manufacturing, textile manufacturing, pulp production, ore refining, and wood preservation. Cr(VI) typically exists as one of the following: • Chromic acid: H2CrO4 (pH <0.9) • Chromate: CrO42− (pH >6.4) • Hydrogen chromate: HCrO4− (pH 0.9 to 6.4, concentration <1000 mg/L) • Dichromate: Cr2O72− (pH 0.9 to 6.4, concentration >1000 mg/L)

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All of the above Cr(VI) entities are soluble. In contrast, Cr(III) is much less toxic, much less mobile, and precipitates out of solution much more readily. Within an engineered anaerobic IRZ, the reduction of Cr(VI) to Cr(III) can be achieved through three mechanisms: 1. Direct microbial reduction, with Cr(VI) serving as a terminal electron acceptor for microorganisms such as Bacillus Subtilis (Melhorn et al., 1993) 2. Extra-cellular reaction with by-products of Fe and sulfate(SO42−) reduction, such as Fe(II) and hydrogen sulfide (H2S) (Palmer and Puls, 1994) 3. Abiotic reduction in the presence of reduced mineral species and the acids of soil organic matter such as humic and fulvic acids (USEPA, 2000) The primary end product of reducing Cr(VI) to Cr(III) is Cr(OH)3, a precipitate that forms readily under alkaline to moderately acidic conditions (pH 5 to 12). Cr(OH)3 precipitate has an extremely low solubility product (Ksp = 6.7 × 10−31) (DeFilippi, 1994) with an aqueous solubility reportedly less than 0.05 mg/L (Palmer and Puls, 1994) and is likely much less than that (see calculation in box below; Jacques Querlin, editor this volume). This precipitate can form as a pure solid-solution, or can coprecipitate with other metals such as Fe. Contrary to the numerous natural mechanisms that can cause the reduction of Cr(VI) to Cr(III), there very few natural mechanisms that can oxidize Cr(III) back to Cr(VI). The only natural mechanism of consequence is the unlikely possibility for a reaction between Cr(III) and manganese(IV) oxide (MnO2) present in the soil matrix (Eary and Rai, 1987). However, even this mechanism can be simultaneously countered by natural reduction processes (USEPA, 2000).

10.11.4

Contaminant Removal Mechanisms

Metal precipitates having particle size larger than 2 µm resulting from an engineered anaerobic IRZ, will typically be immobilized in the aquifer matrix through deposition/sedimentation in the aquifer (Vance, 1994b). Colloidal precipitates (particles with a size range of 0.001 µm to 1 µm) can be immobilized mechanically or through adsorptive mechanisms. Mechanical removal of such particles involves straining, a process by which particles are trapped in smaller pore spaces as they traverse the aquifer matrix (Vance, 1994b). Immobilization of colloidal particles less than 0.1 µm in size will more often occur through adsorptive mechanisms rather than mechanical. The adsorptive capacity of the aquifer matrix can be affected by its geologic composition, the ionic strength of the groundwater, the nature of

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Calculation of Aqueous Solubility of Cr(OH)3 based on Ksp ← Cr3+(aq) + 3OH−(aq) Cr(OH)3(s) → Ksp = [Cr3+][OH−]3 = 6.7 × 10−31 Let c = Cr3+ concentration, i.e., [Cr3+] in mol/L Before equilibrium, [Cr3+] = 0 [OH−] = 0 At equilibrium, [Cr3+] = c [OH−] = 3c Ksp = c(3c)3 = 27c4 = 6.7 × 10−31 c = ((6.7 × 10−31)/27)1/4 = 1.2551 × 10−8 mol/L Formula mass of Cr(OH)3 = 103.018 amu Molar mass of Cr(OH)3 = 103.018 g/mol c = (1.2551 × 10−8 mol/L)(103.018 g/mol) = 1.293 × 10−6 g/L [Cr3+] = 1.3 × 10−6 g/L = 0.0013 mg/L Thus, the solubility of Cr(OH)3 is 0.0013 mg/L. rounded of value

the suspended colloids, and the groundwater flow characteristics. In aquifer systems with high Fe concentrations, amorphous hydrous iron(III) oxides can act as an amphoteric ion exchange media. The Fe present in 0.765 m3 of typical soil is capable of adsorbing from 0.23 kg to 0.91 kg of ‘‘metals” as cations or metallic complexes (Vance, 1994a).

10.11.5

Regulatory Issues

In an application involving metals precipitation and subsequent immobilization in the aquifer matrix, one question often raised relates to the potential soil concentrations following precipitation. Two key facts to keep in mind are that groundwater makes up a relatively small portion of the total aquifer

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matrix and soil concentration standards for metals are typically in the 100s or even 1,000s of ppm. This disparity provides a major advantage for achieving remediation objectives through in situ precipitation. Consider 1 m3 of soil below the water table . . . . Assuming a total porosity of 30% and a dry density of 1,850 kg/m3, the 1 m3 of soil will contain approximately 1,850 kg of soil and 300 L of groundwater. If we conservatively assume that the dissolved Cr(VI) concentration within the cube is 50 mg/L, the pore water within the 1 m3 of soil contains approximately 30,000 mg of Cr(VI). If all of the Cr(VI) is reduced to Cr(III) and immobilized within the soil matrix of the cube, the concentration of the Cr(III) in the soil would be approximately 16 mg/kg (30,000 mg/1,850 kg). This is an entire order of magnitude less than 100 mg/kg, the current total Cr standard in soil. This example makes the advantages of in situ Cr precipitation very clear.

10.11.6

Case Study 1: Western United States

Full-scale treatment of groundwater was successfully completed at an industrial facility on the west coast using an engineered anaerobic IRZ developed through active injection of a dilute food-grade carbon source. Historic manufacturing operations at the facility involved metal plating from 1952 until 1995. As a result, the shallow aquifer beneath the site was contaminated with Cr(VI) and chlorinated solvents to a total depth of 7.3 m. The contaminated aquifer was comprised of interbedded clays and silts, with a depth to water ranging between 1.2 m to 2.4 m, and a horizontal groundwater seepage velocity averaging approximately 18.3 m/year. Figure 10.11.2 depicts the facility layout and groundwater plume orientation. A 6-month pilot study was first completed to evaluate the success of the technology at the site. The anaerobic IRZ was established through the injection of a dilute molasses (residual sugars from preparation of refined table sugar) solution through reusable injection points (Figure 10.11.3). Based on the success of the pilot test, a full-scale implementation of the technique was initiated. The full-scale system involved the installation of 91 small-diameter reusable injection points. Owing to the very slow groundwater velocity, the initial injection event was followed by only one more event 12 months later. As depicted in the chart on Figure 10.11.4, by the end of the full-scale application (24 months), Cr(VI) concentrations had been reduced from nearly 80 mg/L to 20 mg/L Total Cr concentrations were reduced from the same maximum to approximately 0.8 mg/L. The disparity between total and Cr(VI) concentrations was attributed to the time delay involved with the immobilization mechanisms for smaller (colloidal) precipitates. The overall project cost was approximately $400,000. This represented a significant savings over the cost of installing and operating a “pump and treat” system, the original remedy prescribed for the site.

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Note: MW–6 is located 91.4 m west southwest on Park Avenue

MW–1

MW–4 MW–16 Cr(VI) & HVOC Plumes

HORTON STREET

MW–10 Former TCE Degreasing Area

FORMER DRIVEPOINT INJECTION WELL MW–13

MW–17

Cr(VI) Plume

Former Chromium Waste-Storage Area

MW–14

MW–5 MW–9

MW–13 MW–3B

FIGURE 10.11.2 Facility layout and groundwater plume orientation.

FIGURE 10.11.3 Connecting the tubing containing dilute molasses solution to reusable injection point. Note pressure gauge.

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80,000

Concentration (µg/L)

70,000 60,000

Total Chromium

50,000

Cr(VI)

40,000 30,000 20,000 10,000 0 0

5

10

15

20

25

30

35

40

Time (months) Pilot Study

Full -Scale Remedation

FIGURE 10.11.4 Concentration of Cr(VI) overtime.

10.11.7

Case Study 2: Southwestern United States

Another full-scale application of engineered anaerobic IRZ technology was successfully launched to address Cr(VI) in shallow groundwater beneath a Cr-plating facility in the southwestern United States. The contaminated aquifer is heterogeneous, comprised of fine-grained sand lenses about 1 m thick to thin sandy seams interbedded with low permeability clays. The average depth to water is approximately 3.05 m, with a very slow horizontal groundwater seepage velocity (less than 6.10 m/year). The dissolved Cr(VI) plume extends approximately 365.76 m downgradient of the source area and covers approximately 48,000 m2(4.8 hectares). Treatment began with the injection of nearly 75,706 L of a carbohydrate solution consisting of food-grade molasses and potable water. The solution was injected into approximately 370 small-diameter reuseable injection points distributed on 6.10 to 12.19 m spacing across the lateral extent of the plume. An average of 189.27 L of solution was delivered at each injection point under pressures ranging from 1.38 × 104 Pa to 6.89 × 104 Pa (2 lb/in.2 to 10 lb/in.2). The same injection program was repeated two more times at roughly 12-month intervals. During the most recent injection event, a foodgrade Fe(II) organic complex was added to the carbohydrate solution. Because the mineralogy of the aquifer matrix was found to be limited in bioavailable Fe, the Fe(II) complex was added to enhance reduction of the Cr(VI) through abiotic reactions previously mentioned. As shown in the chart on Figure 10.11.5, prior to initiation of the remedial actions the average concentration of Cr(VI) identified in the four key monitoring points within the plume was approximately 50 mg/L, with similar

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Case Studies Engineered Anaerobic IRZ Technology Average: MP–1, 2, 3, and 4 60000

50000 Concentration (µg/L)

Total Chromium Cr(VI)

40000

30000

20000

10000

0 0

5

10

15

20 25 Time (months)

30

35

40

45

FIGURE 10.11.5 Cr(total) and Cr(VI) concentration in four monitoring wells over 42 months.

concentrations of total Cr. After 42 months of treatment, the average concentration of Cr(VI) and total Cr had decreased over 80% to approximately 7 mg/L. 10.11.8

Case Study 3: Eastern United States

This site was a 11.3 hectare Superfund site used for aircraft manufacturing. The primary targets for remediation were overlapping plumes of Cr(VI), cadmium (Cd), and chlorinated solvents. The contaminated aquifer consisted of shallow silts and sands extending to a total depth of approximately 7.32 m. The Record of Decision (ROD) called for a remedy consisting of a “pump and treat” system to contain and control off-site migration of contaminated groundwater, and institutional controls to limit future property use to those activities compatible with site conditions. A 6-month pilot test program was completed to demonstrate the effectiveness of engineered anaerobic IRZ technology. Owing to the success of the pilot test, the ROD was rewritten to include engineered anaerobic IRZ for metals precipitation. Immediately following the pilot, a 16-month full-scale technology application was initiated. The full scale system consisted of 20 5.08-cm diameter injection wells completed in the unconsolidated sandy-silt overburden. The automated injection system shown on Figure 10.11.6 was installed and a dilute solution of molasses and water was injected once a day. Groundwater monitoring conducted during the remedial action indicated that in the area of highest initial concentrations, Cr concentrations dropped

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FIGURE 10.11.6 Automated injection system.

from approximately 3 mg/L to less than 0.05 mg/L. In fact, the overall extent of the Cr plume shrank to approximately 1/4 its original size within 18 months of start-up, with the peak remaining concentrations very localized at slightly greater than 0.5 mg/L. The baseline configuration of the Cr plume and plume configuration following 18-months of treatment are depicted on Figure 10.11.7 and Figure 10.11.8, respectively.

TREET

Injection Well Monitoring Well

01

<0.

5.5 00.

1.0

EET

STR

1.5

VER

OLI

1.0

HIGH S

Treatment Building FIGURE 10.11.7 Baseline of Cr(VI) plume.

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TREET HIGH S IW–19 SPARE 19

IW–16

GM–2 (<0.010)

IW–11

GM–8 (<0.010)

IW–10 GM–3 (0.01)

GM–5 (<0.010) IW–5

IW–9

EET ST R

IW–12

GM–1 (<0.010)

VER

IW–13

IW–15

Injection and Monitoring Wells

O LI

SPARE 14 IW–14 MW–46 (<0.010)

MW–3R IW–2D (<0.040) IW–2S IW–20 IWMP–2B 2 3 0.0 IWMP–1B GM–3 0.500 CM–4 (0.313) (0.052) IW–18 IW–17

TH WALL

IW–1D 1S IW–4 IW–3 IW– IW–18 IW–8 MMW–1 (<1.0) PRW–10 PRW–8 IWMP–1A IWMP–3A(<0.010) PRW–9 (<0.010) (<0.010) MW–4 (0.061) Treatment Building IW–7 IW–6 PRW–7 (<0.010)

FIGURE 10.11.8 Cr(VI) plume after 18 months of IPZ treatment.

The cost to implement the reactive zone and operate it for a little less than 3 years was approximately $400,000 including capital, operations, maintenance, and monitoring. This system replaced a “pump and treat” system that had an estimated present worth cost of over $4,000,000. The cost for the “pump and treat” system included capital and operation and maintenance for a period of 20 years.

Bibliography DeFilippi, L., 1994, Bioremediation of hexavalent chromium in water, soil, and slag using sulfate reducing bacteria, in Remediation of Hazardous Waste Contaminated Soils, Wise, D. and Trantolo, D., Eds., Marcel Dekker, New York. Eary, L. and Rai, D., 1987, Kinetics of Chromium (III) oxidation to Chromium (VI) by reaction with manganese dioxides, in Environmental Science and Technology, 21:12, 1187–1193. Melhorn, R.J., Buchanan, B.B., and Leighton, T., 1993, Bacterial chromate reduction and product characterization, in Emerging Technology for Bioremediation of Metals, Means, J.L. and Hinchee, R.E., Eds., Lewis Publishers, Boca Raton, FL. Palmer, C. and Puls, R., 1994, Natural Affenuation of Hexavalent Chromium in Groundwater and Soils, USEPA, Office of Research and Development, Office of Solid Waste and Emergency Response, EDA/540/S-94/505. Suthersan, S.S., 1998, Engineered In Situ Anaerobic Reactive Zones, U.S. Patent Number 6,143,177, September.

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U.S. Environmental Protection Agency (USEPA), 2000, In Situ Treatment of Soil and Groundwater Contaminated with Chromium, Technical Resource Guide, EPA 625/R-00/005. Vance, D.B., 1994a, Iron: the environmental impact of a universal element, The National Environmental Journal, May/June. Vance, D.B., 1994b, Particulate transport in groundwater: I; colloids, The National Environmental Journal, November/December.

10.12 Attenuation of a Mixed Chromium and Chlorinated Ethene Groundwater Plume in Estuarine-Influenced Glaciated Sediments

Lucas A. Hellerich, Matthew A. Panciera, Gregory M. Dobbs, Nikolaos P. Nikolaidis, and Barth F. Smets 10.12.1 Introduction Chromium(VI) is a widespread contaminant, typically having been released to the environment as a result of metal plating operations and other industrial activities (Palmer and Puls 1994). Similarly, chlorinated organic solvents such as tetrachloroethene (PCE) and trichloroethene (TCE) have been used extensively in industrial and commercial activities and are commonly found at contaminated groundwater sites (Wiedemeier et al., 1998). The U.S. Environmental Protection Agency (USEPA) has reported that mixed Cr and chlorinated ethene groundwater plumes are common in the U.S. (Wiedemeier et al., 1998) owing to spatial proximity of their past and present uses in industrial processes and from contaminant spills resulting from these industrial processes. The USEPA has recently accepted Monitored Natural Attenuation (MNA) as an alternative to active remediation for appropriate cases of chlorinated solvent contamination (Wiedemeier et al., 1998). The USEPA protocol identifies that natural attenuation of chlorinated solvents is a viable part of the remediation of chlorinated ethene contamination if the capability of physical, chemical, and biological processes exists within a groundwater aquifer to effectively reduce PCE and TCE to innocuous species or concentrations less than specified regulatory limits. The protocol details the methodology for collecting data and analyzing the natural attenuation processes at a site. In contrast, no official protocol has been adopted for assessing the natural attenuation of Cr(VI). However, a set of conditions that must be present at a site to demonstrate the viability of natural attenuation of Cr(VI) has been proposed by Palmer and Puls (1994). The conditions are as follows:

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441

• There are natural reductants present in the aquifer • The quantity of Cr(VI) and other reactive constituents does not exceed the capacity of the aquifer to reduce them • The time scale required to achieve the reduction of Cr(VI) to the target concentration is less than the time scale for the transport of the aqueous Cr(VI) from source area to point of compliance • The Cr(III) will remain immobile, and there is no net oxidation of Cr(III) to Cr(VI) In addition, the USEPA’s Science Advisory Board (SAB) on MNA recommended that the analysis of attenuation of mixed wastes must consider the effect of one waste on the other (USEPA 2001), that is, synergism and antagonism. Potential interactions between the mixed wastes can alter the geochemical behavior of individual contaminants when present as a mixed waste. The objective of this work is to describe and quantify the attenuation behavior of a mixed Cr and chlorinated ethene plume in glacial sediments. The mixed waste is transported through and attenuated within an estuarine influenced aquifer of varying redox character and organic carbon content. In addition, potential interactions between the comingled wastes are examined.

10.12.2

Methodology

10.12.2.1 Site Description The investigation was conducted at a site located in southwestern Connecticut with a mixed chlorinated ethene and Cr(VI) waste in a spatially varying redox environment. This site has two distinct geologic environments: (1) a sandy aquifer; and (2) a brackish estuarine-influenced organic-rich wetland environment overlying a sandy aquifer. Groundwater (and the partially comingled contaminant Cr(VI) plume and chlorinated ethene plume) flows from the source (approximate depth of 6 m below ground surface) underlying a manufacturing facility, through the sandy aquifer (approximate depth of 5 m below ground surface) and then into the organic-rich/organic-poor wetland/sandy (fraction of organic carbon [Foc] and redox gradients) aquifer environment (approximate depth of 0 m to 1.5 m below ground surface) with a regional groundwater velocity of 0.03 m/d. The groundwater then discharges into a tidally influenced river directly down-gradient of the wetland. The groundwater flow direction was determined from hydraulic head measurements in groundwater monitoring wells at the site and an unpublished groundwater model of the site. TCE concentrations range from <0.01 mg/L (“nondetect”) at the plume boundary to greater than 100 mg/L at the plume source. Cr(VI) concentrations range from <0.01 mg/L (“nondetect”) at the plume boundary to >10 mg/L at the plume source.

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10.12.2.2 Field and Analytical Techniques The investigation utilized direct push technology (GeoprobeTM) to perform continuous aqueous sampling and geochemical parameter measurement, and the collection of soil samples over depths as great as 21 m below ground surface. The probing was performed along a groundwater flowline from the contamination source to a river acting as the receptor. The probing locations included in this work are named Points A, B, and C and are located approximately 120 m, 270 m, and 360 m downgradient of the contaminant source, respectively. These points were selected from a larger number of sampling locations, performed in the investigation as more detailed analyses were performed at these locations using more discrete sampling intervals. The river is located approximately 50 m down-gradient of Point C. Aqueous samples were collected using low flow sampling procedures (USEPA 1996) with a peristaltic pump and a stainless steel tip with screened ports located at the end of the GeoprobeTM drive rods. Pumping rates were maintained at less than 100 mL/min and groundwater was passed through a flow-through water quality cell. Samples were collected when ambient groundwater quality parameters (temperature, pH, dissolved oxygen (DO), oxidation-reduction potential (ORP or Eh), conductivity, and turbidity) stabilized to ±5% change for three consecutive measurements obtained at 10 min intervals. Measurements were performed using Orion 250A (pH, Eh, and conductivity), Orion 810 (DO), and Hach turbidity meters with temperature compensation. Eh was measured using a platinum redox electrode corrected to a Ag/AgCl reference and calibrated against a Zoebel solution. All water samples were filtered with 0.45 µm nylon in-line filters, collected in 40 mL glass VOA vials, purged with nitrogen (N2) gas, and capped with zero head space. Samples collected for total metals analysis, with the exception of Cr(VI), were preserved in the field with 1% (volume/ volume) concentrated nitric acid (HNO3). Soil cores were obtained using the Geoprobe macrocore sampler. Once soil cores (in acetate liners) were extruded from the Geoprobe tooling, soil cores were held in a N2 purged vessel to preserve the redox conditions of the soil. Soil cores were dissected and homogenized in a N2 purged glovebox within 48 h of completion of the field investigation. Soil samples were then sealed and stored at 4 °C in airtight amber glass jars. 10.12.2.3 Assessment Methodology Total organic and inorganic constituent concentrations were obtained for aqueous and soil samples using standard methods and USEPA protocols (Standard Methods 2320, 3120 B, 3500-Cr B, 3500-Fe B, 4110, 4500-CO2 C, 4500-S2−-D, 4500-SO32−-B, 4500-SO42−-E [APHA, AWWA, WEF 1998a, 1998b, 1998c, 1998d, 1998e, 1998f, 1998g, 1998h, 1998i]); USEPA Methods 3005A, 3050B, 5035A, 8260B [USEPA 2000a, 2000b, 2000d, 2000e]). Total dissolved and soil-bound Cr was determined using an acid digestion (USEPA Methods 3005A and 3050A, respectively [USEPA 2000a; USEPA 2000b]) followed

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by analysis using inductively coupled plasma (ICP). Cr(VI) was determined using the diphenylcarbazide method and a UV–VIS spectrophotometer at 540 nm. Foc in soil samples was measured using a CHN analyzer. The soil samples were ground to a fine powder followed by 2 M HCl treatment to remove carbonate (CO32−). The samples were then dried at 50 °C prior to analysis using the CHN analyzer. Cr(VI) extractions (USEPA 3060A [USEPA 2000c]), sequential chemical extractions (SCA) (Asikainen and Nikolaidis, 1994), and redox capacity analyses (RCA) (Barcelona and Holm, 1991) were performed to assess contaminant fate and geochemical conditions of the aquifer sediments. Redox capacities (Barcelona and Holm, 1991) were determined for soil and aqueous phases. Aqueous reduction capacity was determined by calculating the sum of the contributions to the reduction capacity by Fe(II), total organic carbon, and manganese(II). Soil reduction capacity was determined by calculating the sum of the contributions to the reduction capacity by Fe(II) and total organic carbon. Soil oxidation capacity was determined by calculating the sum of the contributions to the oxidation capacity by iron(III), total organic carbon, and manganese(IV). The apparent partitioning coefficients, reduction rates, and fluxes of chlorinated ethenes and Cr(VI) as a function of the plume length were calculated. Apparent partitioning coefficients (Kd) were calculated as the concentration on the soil (Csoil) divided by the aqueous concentration (Caq). The apparent partitioning coefficient for the chlorinated ethenes were compared to calculated partitioning coefficients (Kd = Foc × Koc) for quality assurance, where Foc is the fraction of soil organic carbon and Koc is the distribution coefficient for soil organic matter (Schwarzenbach et al., 1993). First-order transformation rate constants were determined from concentration profiles along the plume length for the inorganic and organic compounds using a normalized concentration profile data set and the Buscheck and Alcantar (Buscheck and Alcantar, 1995) method. The Buscheck and Alcantar method allows for the calculation of the first-order decay rate for a steady state one-dimensional plume with the following equation:

λ=

2   k  VC   + α 1 2   − 1  x  4α x    Vx   

(10.12.1)

Where λ = First-order biological rate constant VC = Retarded contaminant velocity in the x-direction αx = Dispersivity k/Vx = Slope of line formed by making a ln-linear plot of contaminant concentration versus distance down-gradient along flow path Fluxes were calculated as follows: F = (Caq)(Vx/Kd)

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Where F = Flux of Cr(VI) or chlorinated ethene Caq = Aqueous concentration of Cr(VI) or chlorinated ethene Vx = Groundwater flow velocity Kd = Apparent partitioning coefficient of contaminant 10.12.3

Results and Discussion

10.12.3.1 Plume Characteristics and Geochemistry The chlorinated ethenes and Cr concentrations varied as a function of depth and distance along the plume (Table 10.12.1 and Figure 10.12.1). Both plumes have migrated into the wetland region down-gradient of the source (Figure 10.12.1). Samples were only obtained at depths from 8 m to 11 m below ground surface (bgs) at point A (nearest the source). Historically, the highest concentrations have been found at this depth and the focus at point A in this investigation was to characterize the highest concentration closest to the contaminant source. Closest to the source and over a depth of 10 m to 11 m bgs (point A), PCE, TCE, and cis-1,2-dichloroethene (cis-1,2-DCE) concentrations ranged from 0.19 mg/L to 0.23 mg/L, 0.62 mg/L to 1.206 mg/L, and ND to 0.111 mg/L, respectively. Total chlorinated ethene concentrations decreased at point B (highest concentrations of approximately 1.5 mg/L) and point C (highest concentrations of approximately 1.2 mg/L) over similar depths. However, the ratio of less chlorinated ethenes (i.e., cis-1,2-DCE) to total chlorinated ethenes and the concentration of TCE and cis-1,2-DCE increased as a function of distance along the plume’s length (Table 10.12.1 and Figure 10.12.1). Closest to the source and over a depth range of 10 to 11 m below ground surface (point A), total Cr and Cr(VI) concentrations ranged from 1.136 mg/L to 2.36 mg/L and 0.538 mg/L to 1.575 mg/L, respectively. Total Cr was predominantly in the form of Cr(VI) close to the source. Total Cr will be in the form of Cr(VI) (and not Cr(III)) under the oxidizing conditions observed at this location (Table 10.12.1). In addition, Cr(VI) is much more mobile than Cr(III) and the aqueous Cr content will be more detectable under oxidizing conditions. Conversely, Cr is much less mobile under reducing conditions. The relative mobility of Cr(VI) and Cr(III) is true under typical groundwater conditions at near-neutral pH, but at a low pH or in the presence of certain ions, this condition may be reversed. Both total Cr and Cr(VI) concentrations decreased at point B (highest concentrations of approximately 0.277 mg/L (total Cr) and 0.235 mg/L (Cr(VI)), respectively) and C (highest average total Cr concentrations of 0.059 mg/L over similar depths. The Cr concentrations, and their respective depth ranges suggest that A, B, and C most likely lie along the same flow-line down-gradient of the Cr source. As indicated by maximum concentrations, the Cr plume appears to sink slightly along the plume’s length from point A to point B, and then rises from point B to point C (discharge to a river). Finally, the maximum total Cr and Cr(VI) concentrations at point C were 0.05 mg/L and 0.01 mg/L, respectively.

8.5 9.8 11

1.5 3.0 5.5 6.1 6.7 8.5 10.7 12.2 15.2 18.3

3.0 4.6 6.1 7.6 8.5 9.1 10.7 12.8 15.2 18.3

A

B

C

0.538 0.825 1.575

0.010 ND ND ND ND 0.125 0.195 0.235 0.205 0.085

ND 0.020 0.035 0.085 ND ND ND 0.005 0.005 ND

0.010 0.010 0.010

0.630 1.020 2.830 2.450 0.015 ND ND ND 0.010 0.005

9.850 1.100 1.435 1.460 12.350 6.150 0.010 0.005 0.010 0.015 ND ND ND ND ND ND ND 0.059 0.051 ND

0.011 ND ND ND ND 0.158 0.224 0.270 0.277 0.123

1.136 1.574 2.360

NC NC NC NC NC NC NC 0.08 0.10 NC

0.91 NC NC NC NC 0.79 0.87 0.87 0.74 0.69

0.47 0.52 0.67

335 100 90 265 270 165 40 36 34 30

8.0 1.0 2.0 0.5 31 36 34 33 32 32

26 28 25

0.020 7.975 9.463 7.625 0.089 0.024 0.000 0.000 0.007 0.001

8.025 2.050 0.133 0.006 0.001 0.001 0.001 0.001 0.003 0.003

0.003 0.008 0.002

2.8 28.0 37.6 24.8 4.0 2.8 3.6 3.2 6.0 4.8

25.8 8.0 4.8 25.2 6.4 3.2 4.0 3.2 4.8 2.8

6.4 4.8 NA

159.7 138.3 115.7 125.2 130.1 78.4 17.3 6.8 6.2 25.9

73.0 42.6 23.1 11.1 4.8 4.2 4.2 4.1 7.4 8.6

2.7 2.6 3.3

2.3 4.6 11.3 6.1 3.1 22 268 19 28 6.1

2 1.8 7.8 1.5 5.5 8.1 6.4 2.5 1.7 6.2

1.8 1.7 1.3

5,080 5,190 5,110 7,950 1,790 4,970 1,239 460 486 1,492

4,950 3,770 2,300 801 432 534 522 517 774 781

327 317 371

0.41 0.38 0.32 0.35 0.34 0.23 0.16 0.21 0.21 0.13

0.25 0.20 0.22 0.16 0.09 0.14 0.16 0.25 0.31 0.30

0.07 0.07 0.07

ND 0.255 0.216 0.190 ND ND ND ND ND ND

ND ND ND ND ND ND ND ND ND ND

0.001 ND ND

291.0 340.6 319.8 26.2 30.2 185.4 95.0 1.0 7.0 6.2

323.2 233.6 172.0 91.6 18.4 6.0 15.2 19.6 14.8 19.6

39.2 45.2 39.2

Aqueous parameters Cr Depth Fe(II) Cr(VI) (tot) Cr(VI) SO42− NO3 − SO32– S2– Turbidity Conductivity Cl− CO32– PO43– Point (m bgs) (mg/L) (mg/L) (mg/L) Cr(tot) (mg/L) (mg/L) (mg/L) (mmol/L) (NTU) (mS) (mmol/L) (mmol/L) (mg/L)

Soil and Aqueous Chemical Parameters

TABLE 10.12.1

NA 0.7 24.2 47.3 59.8 12.9 11.4 NA NA NA

NA NA 34.4 6.9 4.4 5.0 7.5 4.1 8.8 NA

3.4 19.5 NA

GSF% <0.150 mm

NA 85.5 99.9 99.6 98.0 45.8 49.5 NA NA NA

NA NA 77.4 65.0 34.1 32.3 40.0 76.2 82.2 NA

94.6 100.0 NA

NA 0.90 1.37 1.28 1.51 1.82 1.84 NA NA NA

NA 0.84 1.37 1.74 2.02 1.96 1.80 1.87 1.61 NA

1.56 1.42 1.42

NA 1.70 0.39 0.48 0.22 0.34 0.44 NA NA NA

NA 8.08 0.38 0.07 0.11 0.13 0.29 0.08 0.09 NA

0.08 0.05 0.15

Foc %

(Continued)

NA 40.3 44.8 47.7 36.7 26.6 27.7 NA NA NA

NA 44.0 43.6 26.0 32.6 17.3 26.1 22.6 35.3 NA

32.7 39.2 38.2

GSF% pbdry Porosity % <2 mm (g/cm3)

Soil parameters

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1.5 3.0 5.5 6.1 6.7 8.5 10.7 12.2 15.2 18.3 3.0 4.6 6.1 7.6 8.5 9.1 10.7 12.8 15.2 18.3

B

TCE (mg/L) 620 724 1,206 ND ND ND 10 23 1,569 1,168 308 300 256 ND ND ND ND 283 7 871 1,229 1,232 960

PCE (mg/L)

190 189 230

ND ND ND ND 11 515 440 211 207 178 ND ND ND ND 42 ND 180 264 306 143 ND ND 287 2,339 ND 45 33 13 70 89 ND ND ND ND 158 679 236 67 52 279

111 62 ND ND ND 3.0 24.7 0.2 15.6 11.9 3.8 4.3 4.0 ND ND ND ND 4.1 7.2 10.2 11.7 11.8 11.2

7.1 7.3 10.6 NC NC 0 0 0.28 0.20 0.22 0.34 0.29 0.27 NC NC NC NC 0.06 0 0.11 0.14 0.16 0.08

0.16 0.16 0.13 NC NC 0 0.003 0.72 0.77 0.75 0.63 0.54 0.49 NC NC NC NC 0.53 0.01 0.65 0.80 0.80 0.66

0.67 0.76 0.87 NC NC 1.00 0.997 0 0.03 0.03 0.04 0.17 0.24 NC NC NC NC 0.41 0.99 0.24 0.06 0.05 0.26

0.17 0.09 0 1.76 0.48 0.53 1.65 0.80 0.41 0.55 1.73 1.63 1.68 0.69 0.52 0.63 0.50 0.40 0.63 0.61 0.39 0.35 0.49

1.02 0.45 0.39

cis-1, 2PCE/ TCE/ DCE/CE cis-1, 2- CE CE(tot) CE(tot) (tot) DCE (tot) (mM/ (mM/ (mM/ DO (mg/L) mM mM) mM) mM) (mg/L)

–232.6 –208.1 –87.6 210.3 51.6 –1.0 155.3 111.8 122.1 –19.9 33.3 –262.3 –274.1 –265.8 –119.4 –15.3 105.2 –122.1 –161.7 –156.3

235.9 248.1 253.1 –33.6 –9.1 111.4 409.3 250.6 198.0 354.3 310.8 321.1 179.1 232.3 –63.3 –75.1 –66.8 79.6 183.7 304.2 76.9 37.3 42.7

434.9 447.1 452.1 NA 158.5 242.7 159.2 53.1 37.9 35.6 245.0 46.3 51.6 267.4 337.1 348.1 322.0 310.2 205.2 67.5 46.6 42.9 98.2

55.7 54.2 49.3

Eh Alk. (Ag/ (mg/L AgCl) Eh as (mV) (mV) CaCO3)

6.58 6.34 6.69 6.59 6.31 6.58 6.54 6.56 6.43 6.02 6.03 6.05 6.03 6.01 5.95 6.15 6.05 6.10 6.09 6.05

6.27 6.43 6.31

pH

18.6 14.5 15.2 12.1 9.2 14.2 20.1 16.8 14.2 11.5 17.5 15.1 13.6 10.9 7.7 16.3 16.8 15.2 12.3 10.2

12.2 10.9 11.4 NA NA 33.89 10.68 11.39 8.49 14.34 14.82 15.77 NA NA 35.44 30.4 30.7 19.4 9.7 13.9 NA NA NA

16.2 16.9 15.6

Moisture Temp Content (ºC) %

NA 90.4 62.1 22.7 21.5 7.9 3.1 5.3 4.2 NA NA 20.0 18.7 22.6 4.4 10.9 1.4 NA NA NA

9.1 10.3 3.4

Cr(VI) µg/g Wet Soil

NA 17.2 14.0 13.2 12.1 15.2 13.7 9.4 10.4 NA NA 12.2 7.2 12.3 14.7 23.2 18.6 NA NA NA

8.1 7.0 14.1

Cr µg/g Wet Soil

NA NA NA NA 14.5 NA 7.2 8.6 71.3 NA NA 29.6 60.4 31.2 42.5 41.9 58.4 NA NA NA

559.6 419.3 444.4

PCE ng/g Wet Soil

NA NA NA NA 12.2 NA NA NA 79.2 NA NA NA 43.7 NA NA 36.1 NA NA NA NA

352.5 291.5 304.6

TCE ng/g Wet Soil

446

Notes: GSF = grain size fraction NA = not analyzed NC = not calculated ND = not detected Ms = milli Siemen

8.5 9.8 11

Depth (m bgs)

A

Point

(Continued)

TABLE 10.12.1

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Chromium speciation at Point A (mg/L)

VOC Concentrations at Point A

10 PCE TCE cis-1,2-DCE

15 20 0

500 1000 1500 2000 2500

Depth (m)

Depth (m)

5

Concentration (µg/L)

5

Chromium speciation at Point B (mg/L)

10

0.0 0.5 1.0 1.5 2.0 2.5 0 PCE TCE cis-1,2-DCE

15 20

0

500 1000 1500 2000 2500

Depth (m)

Depth (m)

15 20

VOC Concentrations at Point B

Concentration (µg/L)

PCE TCE cis-1,2-DCE

20 0

500 1000 1500 2000 2500 Concentration (µg/L)

10 15

0.0 0.5 1.0 1.5 2.0 2.5 0 Depth (m)

15

Cr Cr(VI)

Chromium speciation at Point C (mg/L)

VOC Concentrations at Point C

10

5

20

5 Depth (m)

0.0 0.5 1.0 1.5 2.0 2.5 0 Cr 5 Cr(VI) 10

5

Cr Cr(VI)

10 15 20

FIGURE 10.12.1 Chromium (mg/L) and chlorinated ethene (µg/L) concentrations as a function of depth and distance along the aquifer groundwater flowline.

Contaminant concentrations decrease from physical, chemical, and biological processes. Cr is sorbed to the soils or is reduced to Cr(III) and precipitated out of solution as Cr(OH)3. Sorption is only significant in under-saturated systems. At near-neutral pH values, the solubility of Cr(OH)3 is much less than Cr(VI). Cr concentrations decrease and the ratio of Cr(VI)/Cr(total) decreases as a function of distance. Chlorinated ethenes are sorbed to the sediments and total chlorinated ethene mass decreases as a function of distance down-gradient of the source. In addition, the increasing fraction of chlorinated ethenes as cis-1,2-DCE indicate that reductive dechlorination of PCE and TCE is attenuating the chlorinated ethene plume. There may also be a chromatographic effect (different Koc values) for chlorinated ethenes. However, this chromatographic effect may only be significant for plumes that are relatively recent. The aqueous geochemistry of the mixed contaminant plume is variable along the length of the plume (Table 10.12.1). Conditions at point A are

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slightly oxidizing with positive Eh values and detectable dissolved oxygen (DO) concentrations. The groundwater becomes more reducing as a function of distance. DO concentrations decrease and Eh decrease from approximately +250 mV (point A at 11 m in depth) to approximately –122 mV (point C at 13 m in depth). Eh values also vary widely as a function of depth within the wetland region (point B and point C). Aqueous Fe(II), a strong naturally occurring reductant, increased as a function of distance and organic carbon content, from concentrations of 0.01 mg/L (point A at 13 m in depth) to 12.35 mg/L (point C at 9 m in depth). There are sharp redox gradients with respect to depth (Table 10.12.1). Generally, shallower depths were more reducing (EH < 0), correlating to Foc. As depth increased, the groundwater shifted to less reducing or more oxidizing conditions. These redox gradients may have effects on the speciation of Cr, a redox sensitive constituent, or on the transformation of chlorinated ethenes in groundwater. Geochemical character varied with respect to other parameters. The pH decreased slightly with distance from the source; however, all of the values are near-neutral. As expected, alkalinity and conductivity values increased as a function of increasing proximity to the salt-rich estuarine river downgradient of the contaminant source areas. The Soil Oxidation Capacity (Soil OXC), Soil Reduction Capacity (Soil RDC), and Aqueous Reduction Capacity (Aqueous RDC) were determined using the method of Barcelona and Holm (1991) (Table 10.12.2 and Figure 10.12.2). Aqueous RDC successively increased by factors of 10 from points A to B to C, owing to higher aqueous concentrations of organic matter and Fe(II) (Table 10.12.1). A much greater influence on the aquifer’s Eh is suggested by the sediment’s increased reducing capacities. Soil OXCs also increased from points A to B, but appeared to stabilize from B to C. However, Soil RDC remained approximately 1.5 to 10 times greater than Soil OXC at point A and point B, and this ratio increased to 3 to 10 times at point C. This method illustrates the potential for the reductive capacity of the soils. However, kinetic considerations must be given to the quantity of reductants desorbing from the soils into the aqueous phase and the rate at which individual reductants are able to reduce constituents. For example, soil organic carbon has been shown to rapidly reduce Cr(VI) to Cr(III) (Bartlett and Kimble, 1976). 10.12.3.2 Geological Character The aquifer is geologically complex. At point A, the aquifer is comprised of fine to coarse sands over the sampled depths. The geology is more variable over the depth profile within the wetland regions (point B and point C). There are fine to medium sands at greater depths, with a layer of fine to coarse gravel at an approximate depth of 10.7 m below ground surface observed in point B. From this gravel layer, the geological character transitions back to fine and medium sands to an approximate depth of 4.9 m to 5.5 m bgs. As the profile decreases in depth, the aquifer sediments

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Case Studies TABLE 10.12.2 Soil and Aqueous Phase Reduction and Oxidation Capacities Point

Depth (m bgs)

Soil Oxidation Capacity (meq/g)

Soil Reduction Capacity (meq/g)

Aqueous Reduction Capacity (meq/L)

A

9.1 10.4 11.6

0.094 0.078 0.162

0.252 0.159 0.471

0.002 0.002 0.003

B

4.3 5.5 6.7 7.9 9.1 10.4 11.6 15.2

2.471 0.246 0.229 0.201 0.207 0.268 0.149 0.102

25.270 1.173 0.229 0.350 0.408 0.910 0.250 0.297

0.041 0.072 0.061 0.168 0.090 0.027 0.001 0.001

C

4.3 5.5 6.7 7.9 9.1 10.4

0.573 0.232 0.270 0.228 0.300 0.333

5.317 1.220 1.502 0.688 1.065 1.376

0.229 0.108 0.047 0.238 0.121 0.030

Notes:

meq = milliequivalent

transition to increasingly organic-rich soils, resulting in peat at shallower depths near the ground surface in the wetland. Physical properties of the aquifer sediments are similar in complexity (Table 10.12.1). Porosity varies from 17.3% to 44%, and is a function of the variable dry bulk density (ρbulk,dry) (0.84 g/cm3 to 2.02 g/cm3). In addition, grain size fraction (GSF), described as percent of the soil mass with GSF <0.150 mm and GSF <2 mm, indicated that some sediments (point A at 9 to 11 m bgs, point B at 6 m and 12 m to 15 m bgs, point C at 4.6 m to 6 m bgs were homogeneous (<25 % <0.150 mm and >75 % <2 mm), while other sediments (point at C 5.5 m bgs) were heterogeneous (>25 % <0.150 mm and <75 % <2 mm). Foc varied from 0.08% for sandy soil to 8.08% in organicrich soils (Table 10.12.1). 10.12.4

Attenuation Processes

10.12.4.1 Partitioning and Mass Fluxes Sorption of Cr is highly dependent on its speciation. Sorption reactions may also either be equilibrium or kinetic depending on the time scales of interest. Cr(III) is rapidly and strongly adsorbed by Fe and manganese oxides, and silicate minerals and is also subject to strong binding with functional groups in organic matter (Richard and Bourg, 1991). Chromate

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Soil OXC Soil RDC Aqueous RDC

8 12

Depth (m)

4 Point A

16 0.0001

0.001

0.01

0.1

1

8 12

0.0001

0.001

0.01

0.1

1

10

Depth (m)

4 Point B

16 100 4 8 12

0.0001

0.001

0.01

0.1

1

Depth (m)

Point C

16 10

Soil Oxidation Capacity or Reduction Capacity (meq/g) and Aqueous Reduction Capacity (meq/L) FIGURE 10.12.2 Soil oxidation and reduction and aqueous reduction capacities as a function of depth and distance along the aquifer groundwater flowline.

adsorption is controlled by aqueous pH and mineral surfaces that have exposed inorganic hydroxyl groups (– OH) having a positive charge at a pH less than the soil’s pH (zero point of charge). Fe oxides, aluminum oxides, kaolinite, and to a lesser extent montmorillonite, are naturally occurring minerals capable of adsorbing Cr(VI) (Richard and Bourg 1991). Cr(VI) may undergo reduction and precipitation at soil surfaces and/or diffusion into soil pore spaces and subsequent reduction inside the pore spaces; and nonequilibrium desorption can follow thereafter (Nikolaidis et al., 1994 and 1999). The degree of sorption of chlorinated ethenes in the subsurface is a function of the physical and chemical properties of the dissolved contaminants, the solids, and the aqueous solution (Wiedemeier et al., 1998). In the hydrophobic sorption model, partitioning between the aqueous dissolved phase and the organic fraction of the soil is thought to be the mechanism for

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sorption (Schwarzenbach et al., 1993). For nonionic compounds (PCE and TCE), such sorption is perhaps least pronounced in materials with significant swelling clay content, and with low Foc-soils, where mineral surfaces act as the dominant sorption mechanism. The long-term persistence of volatile chlorinated hydrocarbons observed in recent field studies of aquifer systems has been attributed to slow desorption (Pignatello 1990). The variability of aqueous geochemistry does not have much effect on the sorption behavior of nonionic organic compounds (Schwarzenbach et al., 1993). An important mechanism for contaminant attenuation at the site is partitioning to the sediments. Apparent partition coefficients (Kd) were determined for Cr(VI) and chlorinated ethenes (Table 10.12.3) by measuring the sorbed and aqueous concentrations at specific depth intervals (Table 10.12.1). Partition coefficients were predicted for the chlorinated ethenes utilizing linear free energy relationships (Schwarzenbach et al., 1993) and the measured Foc in the sediments. Apparent partitioning coefficients for Cr(VI) varied from 2 mL/g to 1,002 mL/g (Table 10.12.3). The Kd were generally correlated to the Foc and concentration of Cr(VI) in the aqueous phase. The higher organic fractions and higher aqueous concentrations yielded higher and lower Kd values, respectively. The negative correlation between Kd and Cr(VI) concentrations are anticipated for adsorption reactions (Palmer and Fish 1997). However, there is a positive correlation of Kd with organic matter. Organics contribute to the reduction, and subsequent stronger apparent partitioning, of Cr(VI) to sediments and the formation of Cr(III)-organic complexes and Cr(III) precipitates. Generally, apparent partitioning coefficients of Cr(VI) (and total Cr) with the sediments increased as a function of distance from the plume source. Sorption of Cr is only important in systems that are undersaturated with respect to known precipitates. Cr(III) concentrations are approximately 0.5 mg/L at point A and up to 0.05 mg/L at point B and point C. These concentrations exceed the aqueous solubility of amorphous Cr(III) at nearneutral pH values. There was likely some sorption of Cr to mineral surfaces, however, precipitation as Cr(OH)3 is probably a greater sink. To this end, apparent partitioning is significantly affected by precipitation of Cr. Total Cr was sequentially extracted (Asikainen and Nikolaidis, 1994) with successively stronger extractants to elucidate how Cr partitioned to the sediments (Table 10.12.4). The fractions in order of weakest binding to strongest binding fractions are: (1) exchangeable, extracted with 0.05 M KH2PO4/ 0.05 M K2HPO4 at pH 7.2; (2) organic bound, extracted with 0.1 M sodium pyrophosphate (NaP4O7); (3) iron oxide bound, extracted with 0.1 mol/L hydroxylamine hydrochloride ([NH3OH]Cl); and (4) residual, extracted with hydrofluoric acid (HF). Cr fractions (extracted concentration ± standard deviation) in the “exchangeable phase” were similar for all sediment samples (4.9 ± 0.4 µg/g for all samples), indicating similar weak sorption character along the flow path. In addition, the operationally defined “organic bound”, “Fe and manganese oxide bound”, and “residual fractions” were 8.3 ± 1.2 µg/g, 0.5 ± 0.2 µg/g, and 21.5 ± 11.7 µg/g, respectively. The total extracted (sum

0.08 0.05 0.15 8.08 0.38 0.07 0.07 0.11 0.29 0.08 0.09 0.09 9.61 3.40 0.21 1.70 0.39 0.39

8.5 9.8 11.0

3.0 5.5 6.1 6.7 8.5 10.7 12.2 15.2 18.3

3.0 4.6 6.1 7.6 8.5 9.1

A

B

C 4.47 1.03 1.26 0.58 0.89 1.16

21 21 0.99 0.18 0.29 0.34 0.76 0.21 0.24

0.21 0.13 0.39

0.17

1.28 0.00 0.02 0.04 0.34

2.95 2.22 1.93

1.82 0.42 0.51 0.24 0.36 0.47

8.65 8.65 0.40 0.07 0.12 0.14 0.31 0.09 0.10

0.09 0.05 0.16

0.00

0.00

0 0.52 0.00 0.00 0.00 0.26

0.57 0.40 0.25

0.83 0.19 0.24 0.11 0.17 0.22

3.96 0.18 0.03 0.05 0.06 0.14 0.04 0.04 0.04

0.04 0.02 0.07

0.05 0.17 0.40

0.9 3.9 18.4 11.3 5.2

40 83 871

TCE cis-1, 2-DCE Cr(VI) Predicted Observed Predicted

52

48 1610 1217 303 806 642

739 973 571

PCE

747 15

24 156 8,556 5,829 917 1,902 1,537

3931 5472 5549

TCE

711 2,602

320 163 104 563 716

1217 19,970

919 568

160 323

151 2,473 18 937 640 118 302 275

526 640 548

Total ethenes cis-1, 2-DCE flux as C

Contaminant Fluxes (mg/m2/year)

452

1,002 533 265 265 265 265

172 172 172 172 172 63 16 23 20

17 12 2

PCE Cr(VI) Foc Point Depth M bgs (%) Observed Predicted Observed

Apparent (Observed) and Predicted Partitioning -Kd (mL/g)

Contaminant Partitioning and Mass Fluxes within the Aquifer

TABLE 10.12.3

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0.48 0.48 0.48 0.48 265 265 265 265 1.16 1.16 1.16 1.16 1.40

0.47 0.47 0.47 0.47 0.00 0.22 0.22 0.22 0.22 0.02 0.02

179 261 303 142 1,877 2,651 2,656 2,071 904 257 200 1,069

296 293 289 331

Notes: (1) Bolded Foc values are assumed. (2) Bolded Cr(VI) values are assumed from Kd at 8.5 m (point C) or at 6.1 m (point B). (3) Depths where soil Foc was not measured in point C (owing to no sample collected) used chlorinated ethene (CE) Kd given at 9.1 m depth. (4) Flux measured as the product of concentration and groundwater velocity. Retardation is not used; the existing groundwater concentration is used. (5) Flux data gaps indicate that either Cr, Cr(VI), PCE, or TCE were not detected in the aqueous phase. (6) Predicted PCE and TCE Kds are based on Linear Free Energy Relationships (Swartzenbach et al., 1993) and the measured Foc in the soil. (7) Total ethene flux represents sum of detectable CEs. (8) Observed Kd values for cis-1, 2-DCE were not able to be determined.

10.7 12.8 15.2 18.3

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TABLE 10.12.4 Sequential Chemical Extraction Results

Point A

B

C

Depth (M bgs)

Exchangeable Fraction Cr (ug/g)

Organic Bound Fraction Cr (ug/g)

Iron oxide Bound Fraction Cr (ug/g)

Residual Fraction Cr (ug/g)

Total Extractable (Sum) Cr (ug/g)

9.1 10.4 11.6 4.3

4.6 5.7 5.8 5.3

9.1 8.3 9.5 8.5

0.9 0.5 0.9 0.4

7.4 8.7 21.1 38.8

22.0 23.3 37.3 53.1

5.5 6.7 7.9 9.1 10.4 11.6 15.2

4.9 4.9 4.8 5.0 4.8 5.1 4.4

10.9 8.2 8.4 8.1 8.0 7.6 7.1

0.3 0.6 0.8 0.7 0.7 0.8 0.5

46.0 22.3 8.0 15.1 10.6 14.0 15.1

62.1 36.0 22.0 28.9 24.1 27.5 27.1

4.3 5.5 6.7 8.5 9.1 10.4

4.5 4.8 4.8 4.9 4.8 4.7

7.0 6.5 6.6 9.5 9.1 7.8

0.3 0.3 0.3 0.2 0.5 0.6

21.2 16.8 21.4 29.0 40.7 28.8

33.1 28.5 33.1 43.6 55.1 42.0

of the 4 fractions) Cr was 35.2 ± 12.2 µg/g. The low standard deviations of Cr concentrations exhibited by these fractions also suggest that the sorption character is similar along the flowpath. A high standard deviation might indicate heterogeneity in soil composition (i.e., sorption character). Chromium is slightly more tightly bound to the B and C sediments, with a higher residual fraction, indicating that Cr is becoming slightly more tightly bound to the soils, or Cr(III) precipitating out of solution, as a function of distance from the source. However, the total accumulation in the “Fe and manganese oxide bound” and “residual” fractions is low (approximately similar to background Cr concentrations observed in industrial areas of Connecticut), indicating that the Cr has not had ample opportunity to diffuse into the soil matrix, or become more tightly bound to the soil matrix. Cr concentrations in the residual fraction increase with increasing contact time (Nikolaidis et al., 1994 and 1999). As Cr is transported down-gradient, it may have the opportunity to strengthen its bonds to the sediments in the form of Cr(III), as Cr(VI) is reduced to Cr(III) in the more reducing environments. Cr(III) precipitation may also enhance the increasing apparent bonding strength. Predicted partition coefficients for chlorinated ethenes varied from 0.13 mL/g to 21.25 mL/g, 0.05 mL/g to 8.65 mL/g, and 0.02 mL/g to 3.96 mL/g, for PCE, TCE, and cis-1,2-DCE, respectively (Table 10.12.3). The chlorinated ethene Kd values were directly correlated to the Foc in the solid phase. The higher Foc and higher aqueous concentrations yielded higher and lower Kd

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values, respectively. Apparent partition coefficients of chlorinated ethenes with the sediments increased as a function of distance from the source owing to increasing fraction of organic carbon. Where both aqueous and solid phase chlorinated ethene concentrations were observed, the observed values correlated well with several of the predicted values. However, for other samples there were significant differences between the observed and predicted chlorinated ethene partitioning values. These differences may be attributed to volatilization of sorbed VOCs during sample collection and storage or to analytical error in the measurement of the fraction or soil organic matter. Linear free energy relationships also contain some uncertainty, which may be propagated throughout the prediction of Kd (Schwarzenbach et al., 1993). In addition, the presence of higher ionic strengths as a function of plume distance (owing to the estuarine environment) may have affected the chlorinated ethene partitioning values (Schwarzenbach et al., 1993). Fluxes of aqueous Cr(VI) and CE (Table 10.12.3) were calculated as a function of distance along the length of the plume using the average groundwater velocity, the partitioning coefficients, and aqueous concentrations. Fluxes of Cr(VI) varied from 0.02 mg/m2/year farthest from the source to 870 mg/m2/year closest to the source. Fluxes of chlorinated ethenes farthest and closest to the source at a depth range of approximately 8.5 m to 12.2 m below ground surface varied from 179 mg/m2/year to 1,610 mg/m2/year, 971 mg/m2/year to 8,556 mg/m2/year, and 104 mg/m2/year to 2,602 mg/ m2/year, for PCE, TCE, and cis-1,2-DCE, respectively. The decrease in fluxes as a function of plume length is linearly related to the increasing effect from attenuation processes. The reason for this is the flux calculation is directly related to the aqueous phase concentrations and inversely related to the apparent partition coefficient. The aqueous phase concentrations decrease as a function of distance. The apparent partition coefficient increases as a function of distance away from the source. The flux will be zero at the front of the plume. 10.12.4.2 Reduction and Biotransformation Redox potential (Eh) and pH control the speciation of Cr in aquatic systems (Palmer and Wittbrodt, 1991; Richard and Bourg, 1991). Under typical environmental conditions, Cr exists as Cr(III) and as the more mobile and toxic Cr(VI) (Richard and Bourg, 1991). Under oxidizing conditions, Cr(VI) predominates. Cr(VI), as chromate (CrO42−) is preferentially adsorbed to surface bound oxide groups and avoids significant complexation with other ligands. Under reducing conditions, Cr(III) predominates. Cr(III) forms complexes with – OH, sulfate (SO42−), phosphate (PO43−), ammonium (NH4+), cyanide (CN−), and surface-bound and aqueous phase organic ligands (Richard and Bourg, 1991). The distribution between Cr(III) and Cr(VI) in natural systems is regulated by redox reactions. Organic matter, ferrous ions, and reduced sulfur compounds have the potential for reducing Cr(VI) (Richard and Bourg, 1991). Microbial consortia from both contaminated and uncontaminated

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sediments have been observed to reduce Cr(VI) to Cr(III), also resulting in immobilization of Cr as Cr(III) (Wang and Shen, 1995). Although there are many possibilities for the reduction of Cr(VI) to Cr(III), oxidation of Cr(III) to Cr(VI) requires either oxygen or manganese oxides (Palmer and Wittbrodt, 1991). Chlorinated ethenes undergo abiotic and biotic transformations in groundwater systems. Abiotic transformations of PCE and TCE are usually not as significant as microbial transformations, but in many cases, they provide significant degradation routes (Vogel et al., 1987). Microbial transformations of chlorinated ethenes occur in both aerobic and anaerobic environments. PCE and TCE undergo reductive dechlorination under various anaerobic conditions, with various electron donors and carbon sources (Bouwer 1994; Semprini et al., 1995). In general, the reductive dechlorination of chlorinated ethenes occurs as sequential dechlorination from PCE to TCE to dichloroethene to vinyl chloride to ethene if sufficient quantities of electron donors are available. The most common forms of dichloroethene formed as a result of biotransformation of TCE in natural systems are as follows in decreasing order: cis-1,2-DCE, trans-1,2-DCE, and 1,1-DCE. The predominant processes for attenuation of contaminants at the site at point B and point C are likely abiotic and biotic reduction for Cr(VI) and chlorinated ethenes, respectively. The presence of cis-1,2-DCE (Figure 10.12.1 and Table 10.12.1), a common product of the reductive dechlorination of PCE and TCE suggests that reductive dechlorination of PCE and TCE is occurring at the site. Panciera (2001) performed microcosm studies that provided strong evidence that biotransformation of chlorinated ethenes is the likely mechanism of reduction of chlorinated ethenes in site sediments, through the observed production of cis-1,2-DCE in microcosms utilizing similar anaerobic conditions observed at the site. Trans-1,2-DCE and 1,1-DCE may also be produced via biotransformation processes, however, cis-1,2-DCE is the most common transformation intermediate observed (Bouwer 1994). Trans-1,2-DCE and 1,1-DCE were not observed at significant concentrations in this work. Similarly, evidence for reduction of Cr(VI) as a dominant process is present at the site. Geochemical conditions become more reducing as a function of plume length. In addition, the transition from Cr(VI) to Cr(III) as a function of plume length indicate that as Cr(VI) from the source is transported away from the source, it undergoes reduction. Solid and aqueous phase reduction capacities and soil oxidation capacities were calculated (Figure 10.12.2 and Table 10.12.2). There is a significant quantity of reducing power farther away from the contaminant source at point B and point C. The aquifer sediments in this region are characterized as having higher Foc than the sandy sediments upgradient. The organic carbon acts as the primary source of electrons. Average first-order reduction rates for Cr(VI) and CEs, based on data over the length of the plume, varied over two orders of magnitude. Cr(VI) had a

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rate constant of 0.0006 year−1 while the chlorinated ethenes had values of 0.020 year−1 (PCE), 0.046 year−1 (TCE), and 0.050 (cis-1,2,-DCE) year−1. The chlorinated ethenes may appear to reduce at a higher rate compared to Cr(VI), however the retardation coefficient for Cr(VI), R, is approximately 60 times greater than the R for PCE. If the first order rate of Cr(VI) was multiplied by its retardation coefficient, the resulting first order rate would be of the same order of magnitude to the first order rate of the chlorinated ethenes. These reduction rates are primarily representative of reduction rather than sorption owing to the relatively insignificant increase in sorbed concentrations as a function of plume length. 10.12.4.3 Competition for Reduction Power and Sorption Interactions The SAB report on Natural Attenuation (USEPA 2001) states that possible interactions of contaminants in a mixed waste must be considered in an MNA evaluation. These interactions may influence the fate and transport of one or more of the contaminants. Since both Cr(VI) and chlorinated ethenes can undergo reduction in a shallow aquifer system, competition for reducing power was considered in this work. The aqueous RDC minus the sum of the electron demands yields a surplus or deficit of reducing power in the aqueous phase (Table 10.12.5). The potential for competition exists where a deficit exists. This assumes that the reductants used in calculating the RDC may be utilized to reduce both Cr(VI) and chlorinated ethenes in this aquifer. The electron demand required for both the reduction of aqueous Cr(VI) to Cr(III) and chlorinated ethenes to ethene, and the available aqueous RDC were calculated. Deficits and surpluses of reducing power were noted in samples with low and high organic carbon sediments, respectively. An average (over the entire depth profile) deficit of –105 µeq/L was calculated for point A (average Foc = 0.093%). A trend of increasing reducing power as a function of distance along the contaminant plume was exhibited with average surpluses of 14 µeq/L and 98 µeq/L at point B (average Foc = 1.15%) and point C (average Foc = 0.595%), respectively. A higher average aqueous concentration of Fe(II) of 3.2 mg/L at point C compared to 0.70 mg/L at point B resulted in a positive trend of reducing power surplus in a downward trend of Foc. This analysis indicates that the aquifer has the ability to reduce both compound classes and that competition for reducing power will be decreased as a function of distance down-gradient of the aquifer. This analysis is performed on the available aqueous reductant concentrations and does not consider the regenerative capacity (kinetics) of the aquifer sediments to desorb additional reductants. In addition, only the potential for competition is assessed and not the extent to which compound class may out compete the other for reducing power. Finally, the migration of the higher concentrations of Cr(VI) (approximately 2 mg/L) and chlorinated ethenes from point A towards the

31.0 47.6 90.9 0.6 0.0 0.0 0.0 0.0 7.2 11.3 13.6 11.8 4.9 0.0 1.2 2.0 4.9 0.0

10.3 15.9 30.3 0.2 0.0 0.0 0.0 0.0 2.4 3.8 4.5 3.9 1.6 0.0 0.4 0.7 1.6 0.0

Depth (m bgs)

8.5 9.8 11

1.5 3.0 5.5 6.1 6.7 8.5 10.7 12.2 15.2 18.3

3.0 4.6 6.1 7.6 8.5

A

B

C

Location

Cr(VI) ED (µeq/L)

Cr(VI) Conc. (µM)

0 0 0 0 2

0 0 0 0 1 25 21 10 10 9

9.1 9 11

PCE ED (µeq/L)

0.0 0.0 0.0 0.0 2.2

0.0 0.0 0.0 0.1 0.2 11.9 8.9 2.3 2.3 1.9

4.7 5.5 9.2

TCE Conc. (µM)

0 0 0 0 13

0 0 0 0 1 72 53 14 14 12

28 33 55

TCE ED (µeq/L)

0.0 0.0 0.0 0.0 1.6

0.0 0.0 3.0 24.4 0.0 0.5 0.3 0.1 0.7 0.9

1.2 0.6 0.0

cis-1, 2-DCE ED (µM)

0 0 0 0 7

0 0 12 97 0 2 1 1 3 4

5 3 0

cis-1, 2-DCE ED (µeq/L)

2 2 3 89 41 72 61 168 90 27 1 1 1 373 229 108 47 238

0.0 0.0 12.0 97.9 1.6 98.2 75.8 24.7 26.6 24.0 0.0 0.0 0.0 0.0 21.5

Aqueous RDC (µeq/L)

42.1 44.7 66.1

Total CE ED (µeq/L)

373 227 106 42 216

88 41 60 –37 166 –16 –60 –37 –37 –27

–71 –90 –154

Surplus or Deficit of Reducing Power (µeq/L)

Available Reducing Power

458

0.0 0.0 0.0 0.0 0.3

0.0 0.0 0.0 0.0 0.1 3.1 2.6 1.3 1.2 1.1

1.1 1.1 1.4

PCE Conc. (µM)

Aqueous Electron Demand and Reducing Power

TABLE 10.12.5

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0.0 0.0 0.1 0.1 0.0 0.0 0.0 0.3 0.3 0.0 0.0 1.1 1.6 1.8 0.9 0 9 13 15 7 0.1 6.6 9.3 9.4 7.3 0 40 56 56 44

7.1 2.5 0.7 0.5 2.9

28 10 3 2 12 28.6 58.2 71.6 73.1 62.3 121 30 13 10 136 92 –28 –59 –64 74

(1) Conc. = Concentration (2) ND was replaced with the value of zero to simplify spreadsheet calculations. (3) Electron demand (ED) is calculated for each species by multiplying the molar concentration by the number of electrons required to reduce the species to either Cr(III) or to ethene. For example: Cr(VI) reduction requires 3 electrons per mole and PCE reduction requires 8 electrons per mole. µm = µmol/L µeq = micro equivalent CE = chlonnated ehene

Notes:

9.1 10.7 12.8 15.2 18.3

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down-gradient receptor (point C) as up-gradient reductants are depleted with respect to time has to be compared to the available Soil RDC along the flowpath. The average Soil RDC of 1 meq/g is much greater than the demand for reducing power of the 2 mg/L Cr(VI). However, the interaction between the Soil RDC and the dissolved phase Cr(VI) is unknown. Additional experiments are currently being performed to quantify the rate of Cr(VI) transport versus the rate of reduction.

10.12.5

Conclusions and Engineering Implications

Several important conclusions can be drawn from the analysis in this work. 1. There are sharp redox gradients. Rates of contaminant transformation vary across these gradients. 2. There is active retardation of Cr. The accumulation of Cr by soils appears to be stratified with depth, with layers of high concentrations (172 mg/kg to 1002 mg/kg) and lower concentrations (2 mg/kg to 17 mg/kg). This variability is likely owing to the stratified nature of soil organic matter within the wetland. Precipitation of Cr as Cr(OH)3 is significant as an attenuation process. 3. There is active reduction of Cr(VI) and chlorinated ethenes. Chlorinated ethenes are transformed at a higher rate than Cr(VI). The presence of cis-1,2-DCE and the absence of trans-1,2-DCE suggest that biotransformation of chlorinated ethenes is responsible for the higher rate of reduction. 4. There is the potential of competition for reducing power. Deficits in available reducing capacity suggest that there may be competition. However, the kinetics of reduction and RDC replenishment from the soils relative to contaminant transport must be quantified and incorporated into a reactive transport model to determine if there is indeed competition for reducing power and the extent that both contaminant classes may be decreased in concentration. 5. Attenuation processes in this groundwater aquifer have the potential to reduce contaminant concentrations at point C (close to the receptor) less than the applicable standards regulatory limits over time. Cr(VI) is already less than the Connecticut Remediation Standards Regulations (CTRSR) Groundwater Protection Criteria of 0.05 mg/L and the Surface Water Protection Criteria of 0.11 mg/L at point C. Total Cr concentrations decrease and the ratio of Cr(VI)/Cr(total) decreases as a function of distance. However, the chlorinated ethenes are above applicable standards. The presence of active biotransformation processes suggest that if source control is implemented, the PCE, TCE, and cis-1,2-DCE will be further decreased at point C.

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Acknowledgments This manuscript was greatly improved through the comments of two anonymous reviewers. The authors would like to thank Gary Ulatowski, Debra Lent, and Susan Beres of the Environmental Research Institute at the University of Connecticut for assistance with field activities and laboratory analytical work. This material is partially based upon work supported by the National Science Foundation under Grant No. 9702361.

Bibliography APHA, AWWA, WEF, 1998a, Method 2320 alkalinity B, titration method, in Standard Methods for the Examination of Water and Wastewater, Clesceri, L.S., Greenberg, A.E., and Eaton, A.D., Eds., APHA, 20th ed., 2–27. APHA, AWWA, WEF, 1998b, Method 3120 metals by plasma emission B, inductively coupled plasma (ICP) method, in Standard Methods for the Examination of Water and Wastewater, Clesceri, L.S., Greenberg, A.E., and Eaton, A.D., Eds., APHA, 20th ed., 3–38. APHA, AWWA, WEF, 1998c, Method 3500-Cr Chromium B, colorimetric method, in Standard Methods for the Examination of Water and Wastewater, Clesceri, L.S., Greenberg, A.E., and Eaton, A.D., Eds., APHA, 20th ed., 3–66. APHA, AWWA, WEF, 1998d, Method 3500-Fe Iron B, phenanthroline method, in Standard Methods for the Examination of Water and Wastewater, Clesceri, L.S., Greenberg, A.E., and Eaton, A.D., Eds., APHA, 20th ed., 3–76. APHA, AWWA, WEF, 1998e, Method 4110 determination of anions by ion chromatography B, ion chromatography with chemical suppression of eluent conductivity, in Standard Methods for the Examination of Water and Wastewater, Clesceri, L.S., Greenberg, A.E., and Eaton, A.D., APHA, 20th ed., Eds., 4–2. APHA, AWWA, WEF, 1998f, Method 4500-CO2 carbon dioxide C, titrimetric method for free carbon dioxide, in Standard Methods for the Examination of Water and Wastewater, Clesceri, L.S., Greenberg, A.E., and Eaton, A.D., Eds., APHA, 20th ed., 4–31. APHA, AWWA, WEF, 1998g, Method 4500-S2− Sulfide D, Methylene Blue Method, in Standard Methods for the Examination of Water and Wastewater, Clesceri, L.S., Greenberg, A.E., and Eaton, A.D., Eds., APHA, 20th ed., 4–165. APHA, AWWA, WEF, 1998h, Method 4500-SO32− sulfite B, iodometric method, in Standard Methods for the Examination of Water and Wastewater, Clesceri, L.S., Greenberg, A.E., and Eaton, A.D., Eds., APHA, 20th ed., 4–173. APHA, AWWA, WEF, 1998i, Method 4500-SO42− sulfate E, turbidimetric method, in Standard Methods for the Examination of Water and Wastewater, Clesceri, L.S., Greenberg, A.E., and Eaton, A.D., Eds., APHA, 20th ed., 4–178. Asikainen, J.M. and Nikolaidis, N.P., 1994, Sequential extraction of chromium from contaminated aquifer sediments, Ground Water Monitoring and Remediation, 14, 2, 185–191. Barcelona, M.J. and Holm, T.R, 1991, Oxidation-reduction capacities of aquifer solids, Environmental Science and Technology, 25, 9, 1565–1572. Bartlett, R.J. and Kimble, J.M., 1976, Behavior of chromium in soil: II, hexavalent forms, Journal of Environmental Quality, 5, 4, 383–386.

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Bouwer, E.J, 1994, Bioremediation of chlorinated solvents using alternate electron acceptors, in Handbook of Bioremediation, Norris, R.D., Hinchee, R.E., Brown, R., McCarty, P.L., Semprini, L., Wilson, J.T., Kambell, D.H., Reinhard, M., Bouwer, E.J., Borden, R.C., Vogel, T.M., Thomas, J.M., and Ward, C.H., Eds., Lewis Publishers, Boca Raton, FL, pp. 149–175. Buscheck, T.E. and Alcantar, C.M., 1995, Regression techniques and analytical solutions to demonstrate intrinsic bioremediation, in Proceedings of the 1995 Battelle International Conference on In Situ and On-Site Bioreclamation, San Diego, CA. Nikolaidis, N.P., Hellerich, L.A., and Lackovic, J.A., 1999, Methodology for sitespecific, mobility-based cleanup standards for heavy metals in Glaciated Soils, Environmental Science and Technology, 33, 17, 2910–2916. Nikolaidis, N.P., Robbins, G.A., Scherer, M., McAninch, B., Binkhorst, G., Asikainen, J.M., and Suib, S., 1994, Vertical distribution and partitioning of chromium contamination in a glacio-fluvial aquifer, Ground Water Monitoring and Remediation, 14, 3, 150–159. Palmer, C.D. and Fish, W., 1997, Chemically enhanced removal of metals from the subsurface, in Subsurface Restoration, Ward, C.H., Cherry, J.A., and Scalf, M.R., Eds., Ann Arbor Press, Chelsea, MI, pp. 217–230. Palmer, C.D. and Puls, R.W., 1994, Natural attenuation of hexavalent chromium in ground water and soils, United States Environmental Protection Agency Ground Water Issue, EPA/540/S-94/505. Palmer, C.D. and Wittbrodt, P.R., 1991, Processes affecting the remediation of chromium-contaminated sites, Environmental Health Perspectives, NIH Publication, 92, 25–40. Panciera, M.P, 2001, Biostimulation of chlorinated ethene reduction in near-estuarine soils through carbon addition, M.S. thesis, Environmental Engineering Program, University of Connecticut, Storrs, CT. Pignatello, J.J., 1990, Slowly reversible sorption of aliphatic halocarbons in soils. I. Formation of residual fractions, Environmental Toxicology and Chemistry, 9, 1107–1115. Richard, F.C. and Bourg, A.C.M., 1991, Aqueous geochemistry of chromium: a review, Water Research, 25, 807–816. Schwarzenbach, R.P., Gschwend, P.M., and Imboden, D.M., 1993, Environmental organic chemistry, John Wiley and Sons, New York. Semprini, L., Kitanidis, P.K., Kampbell, D.H., and Wilson, J.T., 1995, Anaerobic transformation of chlorinated aliphatic hydrocarbons in a sand aquifer based on spatial chemical distributions, Water Resources Research, 31 4, 1051–1062. United States Environmental Protection Agency (USEPA), 1996, Low stress (low flow) purging and sampling Procedure for the collection of ground water samples from monitoring Wells, SOP#: GW 0001, July 30, 1996. United States Environmental Protection Agency (USEPA), 2000a, Method 3005A: Acid Digestion of Waters for Total Recoverable or Dissolved Metals for Analysis by FLAA or ICP Spectroscopy, in SW-846 Test Methods for Evaluating Solid Wastes Physical/Chemical Methods, Office of Solid Waste. United States Environmental Protection Agency (USEPA), 2000b, Method 3050B: Acid Digestion of Sediments, Sludges, and Soils, in SW-846 Test Methods for Evaluating Solid Wastes Physical/Chemical Methods, Office of Solid Waste. United States Environmental Protection Agency (USEPA), 2000c, Method 3060A: Alkaline Digestion for Hexavalent Chromium, in SW-846 Test Methods for Evaluating Solid Wastes Physical/Chemical Methods, Office of Solid Waste.

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United States Environmental Protection Agency, 2000d, Method 5035: Closed-System Purge-and-Trap and Extraction for Volatile Organics in Soil and Waste Samples, in SW-846 Test Methods for Evaluating Solid Wastes Physical/Chemical Methods, Office of Solid Waste. United States Environmental Protection Agency (USEPA), 2000e, Method 8260B: Volatile Organic Compounds by Gas Chromatography/Mass Spectrometry (GC/ MS), in SW-846 Test Methods for Evaluating Solid Wastes Physical/Chemical Methods, Office of Solid Waste, USEPA, May 2001, Monitored Natural Attenuation: USEPA Research Program — An EPA Science Advisory Board Review, EPASAB-EEC-01-004. Vogel, T.M. Criddle, C.S., and McCarty, P.L., 1987, Transformation of halogenated aliphatic compounds, Environmental Science and Technology, 21 8, 722–736. Wang, Y.T. and Shen, H., 1995, Bacterial reduction of hexavalent chromium, Journal of Industrial Microbiology, 14, 159–163. Wiedemeier, T.H., Swanson, M.A., Moutoux, D.E., Gordon, E.K., Wilson, J.T., Wilson, B.H., Kampbell, D.H., Haas, P.E., Miller, R.N., Hansen, J.E., and Chapelle, F.H., 1998, Technical protocol for evaluating natural attenuation of chlorinated solvents in Ground Water, United States Environmental Protection Agency, EPA/ 600/R-98/128.

Reprinted from Groundwater Monitoring and Remediation, v. 23, n. 3, Summer 2003, pp. 74–84, with permission of the National Groundwater Association, copyright 2003.

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11 Chromium(VI) Waste Stream Processing

CONTENTS 11.1 Chromium(VI) Waste Stream Processing in Oahu, Hawaii .............466 Andrew Hyatt and James A. Hart 11.2 Chromium Plating, Using the Zero Discharge and Chemical Recovery Approach at a Manufacturing Facility in Massachusetts ..........................................................................................470 Stephen Brown and Mark Simon 11.2.1 Introduction .................................................................................470 11.2.2 Process Considerations ..............................................................471 11.2.3 Cleaning and Plating System Configuration .........................474 11.2.3.1 Plating Pretreatment...................................................474 11.2.3.2 Metal Plating Process .................................................474 11.2.4 Treatment System Description..................................................474 11.2.4.1 Treatment System Design ..........................................474 11.2.4.2 Waste Treatment Tank Farm......................................474 11.2.4.3 Ultra-Filter System......................................................475 11.2.4.4 Ion Exchange System .................................................475 11.2.4.5 Cast Flash Distillation Systems ................................476 11.2.5 Results and Conclusions............................................................476 11.3 Treatment for Chromium(VI) Containing Waste Waters Using Electrocoagulation and Electrooxidation ...................................477 Nicolas Latuzt, James A. Jacobs, and Jacques Guertin 11.3.1 Introduction....................................................................................477 11.3.2 Theoretical Foundations of the Electrocoagulation and Electrooxidation.....................................................................478 11.3.2.1 Electrocoagulation ..........................................................478 11.3.2.2 Electrooxidation ..............................................................480 11.3.3 Removal of Cr(VI) in Wastestreams...........................................481 11.3.3.1 Removal of Cr(VI) by Flocculation and Reverse Osmosis .....................................................481 11.3.3.1.1 Reducing Agents for Cr(VI)........................482 11.3.3.2 Removal of Cr(VI) by Means of the Technologies of Electrocoagulation and Electrooxidation.......................................................483 1-5667-0608-4/05/$0.00+$1.50 © 2005 by CRC Press LLC

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11.3.3.2.1 Particulars of the Operation of an Electrocoagulation Plant, Installed in a Metal Plating Facility ...........................483 11.3.4 Case Study......................................................................................486 11.3.4.1 Generation of Sludges....................................................487 11.3.5 Summary of the Operation of the System...............................487 11.3.5.1 Iron Electrodes.................................................................488 11.3.5.2 Details of the Equipment Considered in the Plant of Electrocoagulation Treatment ........................488 Bibliography ......................................................................................... 489

11.1

Cr(VI) Waste Stream Processing in Oahu, Hawaii

Andrew Hyatt and James A. Hart Kalaeloa Partners Power Plant, on the island of Oahu, Hawaii, produces electric power using Bunker C fuel oil in boilers (HRSG Units) to generate steam to power turbine electricity generators. The HRSG units become coated with soot from the burners which require bimonthly cleaning. The cleaning procedure utilizes a 90 min, 1,135.5 L min flush of the HRSG units, creating a 94,625 L waste stream. The waste stream contains 16 mg/L Cr(VI), 4,900 mg/L of iron, 25 mg/L lead, 5 mg/L mercury, several hundred mg/L hydrocarbons, and up to several percent solids. The facility has a deep well injection permit to discard the treated wastewater. RGF Environmental Group designed a treatment system which reduces the contaminants to discharge requirements. The system treats the wastewater using a chemical process which first reduces the Cr(VI) to Cr(III), then encapsulates the solids and metals in a bentonite/polymer mixture, called Quick Floc (QF). The system consists of two 47,312.5 L cone bottom tanks that accept the wash water and two 47,312.5 L storage tanks, where the treated water is stored pre-disposal testing. In between is the treatment system, consisting of a Cr(VI) reduction process and an encapsulation system. This fully automated process treats the wash water in 2,271 L batches by taking the wash water from the cone bottom storage tanks into the Cr(VI) reduction process, called CR-1. Because of the large amount of solids present in the waste stream, a dilution is necessary to ensure proper encapsulation of the contaminants, and to reduce the load on the unit. The dilution process is automated, using for dilution the water from the previously treated water, so fresh water is not added. When the process initiated, CR-1 will simultaneously fill with wash water and dilution water. The system initiates a mixer and begins the process to reduce Cr(VI) to Cr(III). Cr removal from waste waters is easily accomplished via hydroxide precipitation as Cr(OH)3. However, the Cr must be as Cr(III). The other, more soluble form

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is Cr(VI). This +6 oxidation state is commonly found in metal plating shop wastewaters. To properly remove Cr, it is first necessary to convert Cr from the +6 oxidation state to the +3 oxidation state. Conversion occurs via chemical reduction, using iron(II), or sodium sulfite, (Na2SO3), sodium metabisulfite/sodium pyrosulfide (Na2S2O5), or sulfur dioxide (SO2), a weak reducing agent—especially under acidic conditions. These compounds are termed “reducing agents.” The process requires pH adjustment at the beginning and end of the process. The chemistry involved is simple, thiosulfate ion (S2O32−) acts as the electron donor (reducing agent) and Cr(VI) as the electron acceptor (oxidizing agent). The general, partial reactions involved are (using Na2S2O5): Reduction: Potential: Cr2O72− + 14H+ + 6e− → 2Cr3+ + 7H2O + 1.33 V

(11.1.1)

Cr(VI) + 3e− → Cr3+ + 1.10 V

(11.1.2)

2S2O32− → S4O62− + 2e− − 0.09 V

(11.1.3)

Equation 11.1.1 shows the importance of maintaining the pH at 2, providing a proton rich environment. Equation 11.1.3 shows S2O32− as the electron donor. Equation 11.1.1 has positive potential, indicating the reaction will proceed as written. In Equation 11.1.2, Cr(IV) acts like Cr6+ (a nonoxidant ion) for charge volume in the equation. Its reduction potential is 1.10 V, indicting the reaction will proceed as written. Equation 11.1.3 shows the reaction will not proceed, in the absence of other driving forces. In this instance, the driving force is the +1.33 V potential provided in Equation 11.1.1, and the reaction proceeds quickly. Equation 11.1.3 shows that 2 electrons (e−) are donated, indicating that 3 moles of S2O32−will be required for each mole of Cr(VI) reduced. Reaction progress is monitored via an Eh meter, however, the Eh value will vary from waste stream to waste stream. You will need to develop a site-specific value to monitor. Color can also be used as an indicator, as the solution will change from yellow to green. At this point, Cr(III) precipitation is completed with addition of base. The chart following shows the amphoteric nature of some metals. Amphoteric means the formula unit can act as an acid or a base, depending on chemical conditions. It is this property that will dictate the correct pH to perform the precipitation, in that there is a “well,” or low spot, in the solubility curve. The chart shows that pH 9 is the optimal operating condition for precipitation. Once Cr(VI) has been reduced, the wash water is then transferred to the encapsulation process. The ESP-600 unit will mix the solution and adjust the pH to the desired value, precipitate the ‘‘metals”. Once the pH is at the desired value, the system will then add of QF Floc a dry, granular, a combination bentonite/polymer floc, to the wash water. The QF mixture has properties that will capture and absorb the contaminants in the waste stream and

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Ag 10.0

Concentration of Dissolved “Metals”, mg/L

Zn

1.0 Pb

0.1

Cr 0.01

Cd 0.001 Ni

Fe(III)

Fe(II)

Cu 0.0001

6

7

8

9

10

11

12

pH FIGURE 11.1.1 Solubility of hydroxides (as a function of pH).

remove them so the water can be disposed. The polymers are long chain molecules that, when added to water, uncoil as they absorb the water. The chains adhere to the solids in the stream, coagulating them into a mass. Bentonite is structured in millions of platelets stacked together, similar to pages of a closed book. The bentonite has hydrophilic properties, and when added to the solution will absorb water, causing the clay platelets to separate and the bentonite to expand some 16 times its original size, generating a negative potential between the platelets. It is this potential that absorbs the now coagulated mass between the platelets, locking them into the bentonite. This bond will not be reversed and when the sludge generated dries, the constituents are bound indefinitely.

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TABLE 11.1 Kalaeloa Cogeneration Plant Wastestream Reductions Constituent Total suspended solids Total oil and grease T/R Aluminum Chromium Copper Lead Zinc Mercury

Pretreatment mg/L 7,800 mg/L 10 mg/L 0.210 9.5 25 0.6 94 0.005

Posttreatment mg/L 198 mg/L 1.90 mg/L ND ND 0.0157 0.108 0.836 ND

ND= not detected

The ESP-600 is designed to properly mix the QF mixture, allowing for maximum exposure to the stream. Once the mixing phase is complete, the system will allow the generated sludge to settle to the Esp-600 cone tank bottom. The cleaned water in the upper portion of the system is first drained through 50-µm filter paper, stretched across an indexing filter table. Next, the sludge is drained onto the filter table until the tank is emptied. The cleaned water is directed to the treated water tanks. The sludge is incrementally advanced along the extension filter table, allowing further drying before being transferred into a lined dumpster for final disposal. Finally, the system performs a fresh water rinse of the process tank before receiving

FIGURE 11.1.2 Hawaii ESP equipment.

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the next contaminated batch from CR-1. The batching process is repeated until the entire 94,625 L has been processed. The stored, treated water is tested for “metals”, solids, hydrocarbons, and pH prior to disposal. The sludge must also pass the Toxicity Characteristic Leaching Procedure (TCLP) test. The ESP 600 system, with the CR-1 Chromium(VI) Reduction Process, has provided consistent results, allowing for Kalaeloa Partners to dispose of the treated waste water into a deep well, with the sludge disposed to a nonhazardous landfill. Table 11.1 shows the reduction and TCLP results.

11.2 Chromium Plating, Using the Zero Discharge and Chemical Recovery Approach at a Manufacturing Facility in Massachusetts

Stephen Brown and Mark Simon 11.2.1

Introduction

Columbia Manufacturing is a Westfield, Massachusetts-based manufacturing facility that produces a high quality line of tubular steel school furniture. Columbia began manufacturing bicycles in 1877 and expanded its operations in 1953 to include steel school furniture. Over the last 50 years the demand for school equipment outstripped Columbia’s production rate. The firm explored easier and faster surface treatment methods such as painting and baked coatings for the tubular desk frames, but the market demanded uniform Cr finishes for both esthetic and durability reasons. The facility was using more than 567,750 L/d of potable water in the Cr(VI) over Ni-plating process. The resulting plating wastewater from the Cr plating process was treated with a conventional hydroxide precipitation system and discharged to the local publicly owned treatment works (POTW). Columbia was required to maintain and hold a Massachusetts Department of Environmental Protection (DEP) wastewater permit, which incorporated standard discharge limit requirements for metals and wet chemical parameters. Settled solids from the existing wastewater treatment plant (WWTP) were treated by a plate and frame filter press and hauled off as F007 waste. In order to be competitive in the furniture market, increase furniture production, decrease city water use, and meet the looming U.S. Environmental Protection Agency (USEPA) metal products and machinery (MP&M) wastewater regulations, Columbia changed its plating and wastewater operations. The “Clean Sheet of Paper Approach” was utilized which involved the removal of the old plating line, refurbishing the process area, refining the plating rack design, and decommissioning the precipitation based wastewater system. Columbia only considered environmentally sound technologies that

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T1

T3

T2

T4

T5

T6

Alkaline Soak Alkaline Rinses Acidic Clean

471

T7

T8

T9

T10

T11

Acidic Rinses Electro Alkaline Rinses Acid Clean Dip

T12

DI Rinse

DI = dejonizes (water) FIGURE 11.2.1 Cleaning tank design.

would greatly increase the furniture production rate, allow for potable water and plating chemistry recovery, and completely eliminate the requirement for a DEP wastewater permit. A new high speed, automated Napco plating line and a “state-of-the-art” CASTion resource recovery system would replace the old wastewater and plating treatment trains. The new integrated system would allow for purifying and recycling water from the rinse baths, recovering expensive Cr and Ni chemistry, effective management of acid/cleaner wastes, and sludge volume minimization.

11.2.2

Process Considerations

Tubular steel is used to fabricate the bases and desk supports for the furniture. The tube stock is coated with oils, dirt, smut, and metal oxides. The tubing is bent, welded, and brazed prior to the plating process. The completed frames are then cleaned using alkaline soak cleaners, cathodic acid, electro-clean, and an acid activator. The large surface area of the tubing presents some special plating challenges. Radial surfaces require more controlled direct current (DC) throwing power because of current losses or current build up on curved areas of the piece. An improved rack system needed to be developed to optimize Ni and Cr deposition and ensure a final brilliant luster. The tubular geometry also retains more plating solution; therefore, dragout of Ni and Cr solutions becomes problematic. The speed of the process line, coupled with the excessive drag out rate, were primary design considerations for the wastewater recovery system. The processes are shown in Figure 11.2.1 to Figure 11.2.7.

T13 Nickel Plating

T 14

T 15 Drag Out

HS = high speed rinses FIGURE 11.2.2 Electroplating line.

T 16

T 17

Nickel Rinses

T 18

T 19

Chrome Plating

Drag Out

T 20

T 21

Chrome Rinses

T 22

T 23

HS Rinses

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Cr Concentrate Tank

U L T R A F I L T E R

Flash Distillation Systems Cr CAST FDA 18,927 L/d

CAST FDA 7,571 L/d Ni Rinses

CAST FDA 7,571 L/d Cr Rinses

Ni Filter Press Ni Concentrate Tank

Tank 1

Tank 2

Activated Carbon System

Tank 3

IX, Cationic/Anionic Beds System # 1

FIGURE 11.2.3 Zero Liquid Discharge treatment/recovery system.

FIGURE 11.2.4 Photo of the ultra.

Tank 4

Tank 5

IX, Cationic/Anionic Beds System # 2

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FIGURE 11.2.5 Photo of the ion exchange.

FIGURE 11.2.6 Photo of the 7,571 L/d CAST flash.

473

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FIGURE 11.2.7 CAST process flow diagram.

11.2.3

Cleaning and Plating System Configuration

11.2.3.1 Plating Pretreatment 11.2.3.2 Metal Plating Process 11.2.4 Treatment System Description The major components of the Zero Liquid Discharge System (ZLD) are as follows: 1. One Ultra-filter configured with an olio-phobic membrane for the rejection of oil and solids from the metal cleaning rinses. 2. Granular activated carbon to remove organic compounds and residual organically based cleaners. 3. Duplex Ion Exchange System that treats all rinse waters with the exception of the plating rinses which are delivered to the two 7,571 L/d CASTion. flash distillation systems outlined below. 4. Two 7,571 L/d CAST flash distillation systems receiving Ni and Cr plating rinse waters for subsequent concentration and reuse. 5. One 18,927 L/d CAST flash distillation system treating the Electrocleaner rinse water and the combined regeneration streams from the Ion Exchange System. The distillates from all three flash distillation systems are delivered to the Ion Exchange System before being reused as high quality rinse water. 11.2.4.1 11.2.4.2

Treatment System Design Waste Treatment Tank Farm

Tank 1 accepts Electro-Cleaning rinse water and the Ultra-filter reject. This combined stream is delivered to 18,927 L/d flash distillation system.

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Tank 2 accepts intermittent dumps of acid solutions. The recovered material is returned to the processing line. Tank 3 accepts rinse water from the fast plating rinses, Ultra-filter filtrate, and distillates from the three flash distillation systems. Tank 3 serves as the primary feed tank to the IX treatment system. Tank 4 stores the deionized (DI) water produced by the ion exchange system. Tank 5 is used as a redundant storage vessel. Provides excess holding capacity when necessary. The Ni and Cr concentrate holding tanks store the concentrated plating solutions from the two, 7,571 L/d distillation units. The chemical recovery process involves evaporating the segregated plating rinse waters within a reduced pressure environment. As water vapor is removed via the flash evaporation process, the Cr and Ni concentrations increase proportionally. Once the Ni content in the concentration tank reaches that of the actual Niplating bath, the chemistry is reintroduced. The same process occurs in the Cr concentration tank. The Cr content is monitored in the concentrate tank until reaching 337 g/L. The reclaimed Cr chemistry is further purified using a porous pot system prior to reintroduction to the Cr-plating tank. 11.2.4.3

Ultra-Filter System

The combined cleaning rinses from the alkaline and acidic cleaners are the primary feed for the Ultra-filter system. The alkaline and acid streams are titrated to reduce the incoming pH, thereby protecting the Ultra-filter membranes from damage owing to excessive alkalinity. The olio-phobic membrane is designed to reject suspended and emulsified oils as well as total suspended solids. Water and dissolved ionic species permeate through the membrane and the separated oils and solids are discharged in the reject waste. The rejected oils and solids are sent to Tank 1 for interim holding. Tank 1 then feeds the 18,927 L/d flash distillation system. The resulting distillate is fed to Tank 3, which is then delivered to the Ion Exchange System for final polish before reuse in the rinse baths. 11.2.4.4 Ion Exchange System The primary Ion Exchange (IX) System was developed to treat distillates, filtrates, and the high-speed plating rinses. A second duplex IX system is brought online when the primary IX system is in the regeneration mode. Prefiltration prior to the IX system is essential and is accomplished using activated carbon to guard the cationic and anionic resins from organic fowling and blinding. Conductivity and resistivity measurements are used as a feed back loop to initiate the regeneration cycles. Regeneration is countercurrent in regard to the process feed and utilizes hydrochloric acid to regenerate the cationic resin and

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sodium hydroxide (NaoH) to regenerate the anionic resin. The regeneration wastes are titrated in Tank 1 which produces a concentrated brine solution with a total dissolved solids (TDS) of 30,000 parts per million (ppm). The brine solution in Tank 1 is then pumped to the 18,927 L/d flash distillation system; and the deionized (DI) water is sent to Tank 4 for storage. Ultraviolet (UV) disinfection is the final stage in the DI water make-up process. UV light passes through the DI water for the destruction of heterotrophic, standard plate count, and coliform bacteria prior to reuse in the rinse baths. 11.2.4.5 CAST Flash Distillation Systems Columbia has two CAST 7,571 L/d and one CAST 18,927 L/d flash distillation systems. The principle of operation involves heating the process stream exterior to the distillation column and spraying the heated feed back into the vessel, which is maintained at high vacuum. A percentage of the heated spray flashes into water vapor and rises through a series of baffle plates. The baffle plates allow for the separation of small quantities of contaminant vapor from the pure water vapor by means of a torturous vapor path. Contaminant vapor losses energy within the baffle channels and falls back into the liquid spray zone. The separated water vapor moves through the baffles and is condensed back into liquid using a plate and frame heat exchanger/condenser. Vacuum is supplied using a jet pump connected to the outlet of the condenser. The circulation of clean distillate through the jet pump by means of a multistage pump eliminates the need for a conventional vacuum pump, therefore, no air emissions. The bottoms from the distillation process are recirculated to the corresponding concentration tank. The concentration tank essentially becomes an extension of the distillation vessel, and allows for simple isolation of the recovered chemistry. The 7,571 L/d systems process the Ni and Cr plating rinses and serves as the primary chemical recovery system. Tank 3 receives the distillates from all three distillation systems, all combined rinse waters and filtrate from the Ultra-filter. All of the resulting distillates are the sent to the ion exchange system to achieve a DI water quality of approximately 1 mega-ohm (1 MΩ resistivity. The resulting concentrated brine from the 18,927 L/d system is sent to the secondary treatment works where it is dosed with a proprietary flocculant/metal precipitant combination. The salts in the brine concentrate begin to precipitate from solution owing to supersaturation prior to filter pressing. Chemical demands for the flocculant and carbamate metal precipitant are therefore reduced significantly. 11.2.5

Results and Conclusions

Columbia’s innovative approach to water and process chemical recovery has led to the following achievements: 1. All wastewater is recovered as DI water and recycled to the rinse baths. 2. 98% of all Ni plating chemistry is recovered and reused.

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3. 98% of all chromic acid (H2CrO4) plating chemistry is recovered and reused. 271.8 kg of chromium(VI) oxide (CrO3) are recovered and reused per week. 4. The process has no discharges to the air or the municipal sewer system. 5. Massachusetts DEP has exempted Columbia from air and wastewater discharge permits. 6. Columbia has cut back on its potable water use and wastewater discharge by 492,050 L/d. 7. Columbia is exempt from Resource Conservation and Recovery Act (RCRA) hazardous waste treatment, storage, and disposal permits. 8. The metals content of the manifested filter cake has been significantly reduced. 9. Reduction in chemical precipitant demand for the dewatering of solids. 10. Production rate for the steel school furniture more than tripled while keeping waste production to an absolute minimum. 11. The resource recovery system was designed to close-loop the entire plating operation. The system has proven to be reliable and cost effective. 12. Columbia’s client base insisted on purchasing products from companies that practicing “green” manufacturing. Clients are pleased with the environmentally friendly technologies used to fabricate the furniture line. 13. The success of the new plating line and the CASTion resource recovery system won Columbia the Governor of Massachusetts “Green Seal” award for environmental stewardship.

11.3 Treatment for Chromium(VI) Containing Waste Waters Using Electrocoagulation and Electrooxidation

Nicolas Latuzt, James A. Jacobs, and Jacques Guertin 11.3.1

Introduction

Clotting and chemical flocculation, are the most traditional methods for treating chromium(VI) (Cr(VI)) in waste waters. These conventional wastewater treatment methods typically use iron(III) chloride (FeCl3) or aluminum sulfate (Al2(SO4)3), as clotting agents and polymers. Several main industries produce large quantities of waste water containing Cr(VI) wastes: mining,

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steel, metal plating, and petroleum refining. These processes require such large uses of the clotting and flocculation agents that regulatory limits of the treatment chemicals can be greater than the maximum regulatory acceptable concentrations. For this reason, treatment alternatives using electrocoagulation and electrooxidation have been developed. These processes reduce the Cr(VI) in a more efficient way and at less cost than traditional treatment systems. More traditional methods require physiochemical treatment plants and storage of chemical products for the continued operation.

11.3.2

Theoretical Foundations of Electrocoagulation and Electrooxidation

11.3.2.1 Electrocoagulation The process of electrocoagulation is defined as using an electrical current in the waste water to destabilize the suspended, emulsified or dissolved chemicals in an electrolytic solution. The electrical current provides the electromotive force to drive the numerous complex chemical reactions that breakdown the wastes, converting soluble and toxic metals such as Cr(VI) to the less toxic solid (chromium(III) hydroxide, (Cr(OH)3) that precipitates out of the waste-water solution. Electrocoagulation uses an anode–cathode process. Electrocoagulation, electroflocculation, and electropurification all refer to water treatment technologies, which use electrical energy to cause the release of dissolved ‘‘metals” such as Cr(VI) from the aqueous waste stream. Although not popular in the U.S., electrocoagulation has been used in Europe, South America, and Russia since the 1970s where the technology has been used to treat waste water from metal finishing and metal processing facilities. The process itself is simple. The electrocoagulation system is an anode– cathode process. It consists of a pipe, electrodes, a pump, a DC power supply, and appropriate tanks. However, the reactions that take place are rather complex. The electrocoagulation systems must be designed to optimize more than 20 variables and transfer the electrical energy to the wastewater effectively (Joffe and Knieper, 2000). As the Cr(VI) in waste water moves through the electrical field, the forces of ionization, electrolysis, hydrolysis, free-radical formation, and magnetism alter the physical and chemical properties of both the water and the dissolved Cr. In a matter of minutes, the water-contaminant mixture separates into three layers: (1) an organic-rich floating layer on the water; (2) a Cr-rich sludge which settles by gravity to the bottom of the tank; and (3) noncontaminated water in the middle that can be extracted using pumps and separators. The treated water is clear, noncontaminated, odorless, and reusable. Double layer compression is achieved electrically by producing ions at the anode during oxidation. Electrocoagulation charge neutralization occurs when the electron flow through the waste water reduces the surface charges. This contributes to agglomerations of the Cr waste particles. Bridging and

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waste water

479

treated water

+ −

anode

cathode

FIGURE 11.3.1 Electrocoagulation cell.

entrapment occurs when the flocculated metals create a sludge layer that traps the colloids that have not complexed. In the course of the electrolytic process, the cations are produced at the anode and enter into solution, reacting further forming metallic oxides and precipitating into their respective hydroxides. The electrochemical reactions resulting from the electrolytic process depends on the pH of the solution and the nature of the waste products. (Figure 11.3.1) The reactions depend on the acidity of the treatment solution: Reactions: Anode:

Fe(s) → Fe3+(aq) + 3e−

(11.3.1)

Anode:

2H2O → 4H+(aq) + O2(g) + 4e−

(11.3.2)

Cathode:

2H2O + 2e− → H2(g) + 2OH− (aq)

(11.3.3)

Overall:

2Fe(s) + 10H2O → 2Fe(OH)3 (4) + 7H2(g) + 2O2(g)

(11.3.4)

In the complex electrocoagulation process, the electrolysis generates oxidation–reduction (redox) reactions at the anodes and cathodes respectively, in addition to other reactions. The external electric power is applied alternately to the anodes and cathodes, providing the electromotive force to initiate the chemical reactions. Inside the electrocoagulation cell, the anodes and cathodes consist of parallel plates constructed of various metals such as iron (Fe) and aluminum(Al), which are selected to optimize the Cr(VI) removal process. Metal ions from the electrode plates are sacrificed into the waste-stream solution. Over time, the process slowly wears the metal surfaces of the plates away. The metal ions, which are released from the sacrificial electrodes, tend to form metal oxides. These oxides are attracted electromechanically to the Cr(VI) in the wastestream solution, which has been destabilized through the electrocoagulation

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process. There is a color change during the process, changing the yelloworange Cr(VI) in solution to green as it is reduced to Cr(III). 11.3.2.2 Electrooxidation Chromium(VI) waste streams often contain organic matter. Electrooxidation oxidizes soluble organic matter in the waste stream through the generation of hydroxyl radicals (OH•). The end product of the reaction is complete degradation of the organic matter to CO2 and H2O and other inorganic compounds. The hydroxyl radical (OH•) has greater potential for oxidation than most other oxidizers. The oxidizing power of OH• is greater than that of atomic oxygen O2 and ozone O3 and is only a little less than that permangate (Mn O4− ), chlorine(Cl2), and fluorine (Fl2), the most powerful oxidizer known. OH• is formed from hydrogen peroxide (H2O2) with a combination of either Fenton’s chemistry (which has an Fe(II) catalyst), or with O3 and/or ultraviolet (UV) light as a catalyst. In some cases, ultrasound is added to the process to enhance the reactions (Siegrist et al., 2001). OH• works best and has the longest reaction time at a pH of 3 to 4. (Table 11.3.1) R + H2O2 → RO2 + 2H+ + 2e−

(11.3.5)

where R = organic matter The process of OH• attacking the organic matter and quickly degrading it to CO2 and H2O, is known as “mineralization.” (Figure 11.3.2) TABLE 11.3.1 Oxidation Potentials Oxidant

Oxidation Potential (V)

Oxidizing Topower Relative Chlorine

Equivalent “Weight” (g)

3.03 2.80 2.42 2.07 1.78 1.70 1.68 1.57 — — — — 1.49 1.45 1.36 1.09 0.54

2.23 2.06 1.78 1.52 1.31 1.25 1.24 1.15 — — — — 1.10 1.07 1.00 0.80 0.39

— — 7.983 23.995 17.100 — 52.662 67.449 225.889 74.435 71.078 113.806 to134.853 — — 35.471 — —

Fluorine Hydroxyl radical Atomic oxygen Ozone Hydrogen peroxide Perhydroxyl radical Permanganate Chlorine dioxide Sodium chlorite Sodium hypochlorite Calcium hypochlorite Persulfates Hypochlorous acid Hypoiodous acid Chlorine Bromine Iodine Source:

Siegrist et al., 2001.

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O2−.

Energy

Photoreduction

O2 UV conduction − e band

Cr(VI)

Cr(III)

Hg2+

Hg0

Eg

TiO2

mixing valence band

OH.+ Organics

+

OH.+H−

H2O

CO2 +H2O

Photooxidation

FIGURE 11.3.2 “Mineralization”: organic matter is converted to CO2 and H2O.

The oxidation reactions of using OH• with the associated catalysts produces a series of chain reactions. These chain reactions are mainly photocatalytic radiation to wavelengths (λ = hν) of 240 nm to 340 nm. 11.3.3

Removal of Cr(VI) in Wastestreams

11.3.3.1 Removal of Cr(VI) by Flocculation and Reverse Osmosis Alum flocculant treatment has been used to remove dissolved ‘‘metals’’. The process starts with an injection of the liquid flocculant alum into the wastestream lines. When added to the waste water, the alum forms nontoxic precipitates of aluminum hydroxide (Al(OH)3) and aluminum phosphate (AlPO4). These precipitates combine with the Cr(VI) causing the contaminant to be rapidly removed from the waste water. Reductions of 50% to 90% for heavy metals are documented. This method generates a large quantity of sludge in the process and requires a large supply of clean water to backflush the self-cleaning filters associated with this process. Another approach is reverse osmosis (RO), a filtering process that uses semipermeable membranes, pressure differentials, and concentration gradients of waster water as part of the treatment process. Normal osmosis occurs when pure water moves across the membrane from the side with less concentration of contaminant to the side with greater concentration of contaminant. An example of the process includes a semipermeable membrane with pure water on one side and a concentrated aqueous solution of Cr(VI) on

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the other side. If normal (not reverse) osmosis occurs, the fresh water will cross the membrane to dilute the concentrated Cr(VI) solution. In reverse osmosis, pressure is exerted on the side with the concentrated Cr(VI) solution to force the pure water molecules in the concentrated Cr(VI) solution across the semiperemeable membrane to the fresh water side (overcoming the hindrance effect at the membrane). This dewatering process leaves behind the Cr(VI) ions on the one side of the RO filter. RO is used in commercial water filtration and purification and is a commonly used method to desalinate sea water. In order to treat high volumes of waste streams with Cr(VI) however, large RO systems must be used. RO requires significant capital costs of the RO membranes, high energy for pumping of the liquids under high pressures, and significant operational and maintenance costs. 11.3.3.1.1 Reducing Agents for Cr(VI) Reduction of Cr(VI) using an acidic reducing agent is commonly used. These reactions are highly pH dependent. Iron(II) sulfate (FeSO4) reacts quite fast with Cr(VI) and works at a pH of 5 to 6. FeSO4 is a one-electron reducing agent and will require that 3 moles of FeSO4 reacts with 1 mole of Cr(VI). At high concentrations of Cr(VI), large volumes of Cr-containing sludge will be produced. Sodium metabisulfite (Na2S2O5) works best at pH of ≤5. The closer the pH is to 5, the slower the reaction is between S2O5 2− with Cr(VI). Chromium(VI) can also be reduced using sodium hydrogen sulfite (NaHSO3) at a pH range of 8 to 9. However, NaHSO3 is flammable and may spontaneously ignite in moist air or upon contact with water. Contact with water forms sulfurous acid (H2SO3). The decomposition compounds include toxic “sulfur” fumes such as sulfur dioxide (SO2). Sulfur dioxide can act as an acidic reducing agent, however its fumes are toxic, corrosive, and odorous. For human health and safety concerns, caution must be used when working with SO2. Chemical formulas of acidic reducing agents: 1. 2. 3. 4.

Iron(II) sulfate . . . FeSO4 Sodium metabisulfite . . . Na2S2O5 Sulfur dioxide . . . SO2 Sodium hydrogen sulfite . . .NaHSO3

The reduction of the Cr(VI) corresponds to the oxidation of Fe2+ to Fe3+, while the Na2S2O5 and the SO2 are oxidized to form sulfates (SO42−). The oxidation of the reagent produces the reduction of the Cr(VI) to Cr(III) which precipitates out as Cr(OH)3. The general reaction occurs in two steps: 2H2CrO4 + 3SO2 → 3H2OCr2(SO4)3 + 5H2O Cr2(SO4)3 + 3Ca(OH)2 → 2Cr(OH)3 + 3CaSO4

(11.3.6) (11.3.7a)

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Or, 2Cr3+ + 6OH− → 2Cr(OH)3

(11.3.7b)

In the first equation, the SO2 in water (H2O) is added to the Cr(VI) waste stream. As an alternative to the SO2 , Fe2+ as FeSO4 could also be used. In that case, Fe2+ is oxidized to Fe3+ while the Cr(VI) is reduced to Cr(III). This is a quick reaction at a low pH 3, which can be aided by adding sulfuric acid (H2SO4). The main disadvantage of this technological route is that Fe2+ will form iron(III) hydroxide (Fe(OH)3) which is also insoluble. The Fe(OH)3 will be added to the sludge under the subsequent alkaline conditions that allow the Cr(III) to precipitate. The chemistry requires that this redox reaction use Fe(II) at 2.5 times the active mass of Cr(VI). With Na2S2O5 or with SO2, the reaction takes place starting from H2SO3 produced in a water solution. For the precipitation of the Cr(III) in the mixing tank, the pH should increase to 8 or higher, with calcium hydroxide (Ca(OH)2) or sodium hydroxide (NaOH), to form Cr(OH)3. The clarified water that leaves for the main tanks will be able to pass through a filtration stage, for final discharge. The Cr-containing sludge is removed and is later sent to be dehydrated by using a filter press or other method. 11.3.3.2

Removal of Chromium(VI) by Means of the Technologies of Electrocoagulation and Electrooxidation Electroplating companies and tanneries, among others, have concentrations of Cr(VI) between 20 mg/L and 60 mg/L in their waste waters. The pH of the aqueous waste stream is typically between 4 and 5. It is possible to reduce Cr(VI) to Cr(III), at pH 3 to 5 without making pH adjustments before sending the waste stream into the electrocoagulation cell consisting of Fe and Al electrodes. (Figure 11.3.3 and Figure 11.3.4) 11.3.3.2.1

Particulars of the Operation of an Electrocoagulation Plant, Installed in a Metals Plating Facility The waste water that comes from the metals plating and finishing process has a daily flow of 120 m3/day (31,703 gal/day), with an average concentration of 48 mg/L Cr(VI). (Table 11.3.2) The waste water is moved into the electrocoagulation cell at a constant flow of 5 m3/h (or 1,321 gal/h). The wastewater moves through the iron electrode area in the electrocoagulation cell and requires a 30 s residence time. The current and voltage that it is applied to the 11 electrodes are controlled automatically using a transformer producing a constant 500A and a constant 20 V, with automatic polarity change. A logical control system and sensor are used to control water conductivity, keeping a constant current through the pH adjustment process. The pH adjustment is a critical engineering control issue. The constantly changing pH and resistivity of the wastewater is sensed and adjusted as it enters the cell.

15

1

16

14 11

4

12

13

5

6

8

INSOLUBLE ELECTRODE

9

TREATMENT PLANT ELECTROCOAGULATION AND ELECTROOXIDATION

NT UE ER FL AT EF N W EA CL

7

10

484

FIGURE 11.3.3 Electrocoagulation and electrooxidation process/facility.

6-HYDROGEN PEROXIDE TANK (OPTIONAL) 7-OZONE EQUIPMENT 8-ULTRAVIOLET LIGHT 9-ELECTROOXIDATION CELL 10-FOAM 11-SAND FILTER 12-CARTRIDGE FILTER 13-ACTIVATED CARBON FILTER 14-RECTIFIER (DIRECT CURRENT, DC) 15-SLUDGE 16-RETROWASH 17-ULTRASOUND EQUIPMENT

3-CLARIFIER OR DISSOLVED AIR FLOTATION (DAF) WA INFL ST UE 4-POLYMER TANK E W NT AT 5-FRACTIONATOR TANK ER OR CONTACT TANK

1-ELECTROCOAGULATION CELL 2-MIXING

DETAIL:

ELECTRODE IRON/ALUMINUM

2

3

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ELECTRODE

14

15

SLUDGE

SLUDGE DEHYDRATED

1

2 3

6

10

7

8

16

9

17

ELECTRODE

INSOLUBLE

EFFLUENT

13

FLOW DIAGRAM TREATMENT PLANT ELECTROCOAGULATION AND ELECTROOXIDATION

11

12

ELECTROOXIDATION SYSTEM

485

FIGURE 11.3.4 Flow diagram for the electrocoagulation and electrooxidation facility.

INFLUENT

(IRON/ALUMINUM)

4

ELECTROCOAGULATION SYSTEM

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Chromium(VI) Handbook TABLE 11.3.2 Composition of Waste Water from Metals Plating and Finishing Process Parameter

Symbol

Unit

Concentration (average)

Chromium(VI) Chromium(III) Iron Zinc Nickel Total suspended solids pH

Cr(VI) Cr(III) Fe Zn Ni TSS pH

ppm ppm ppm ppm ppm ppm ppm

48 2 24 21 117 118 4–5

With the application of the electrical current and the voltage differential, it is possible to change the oxidation state and to reduce Cr(VI) to Cr(III) by means of the redox reactions that happen inside of the trays. The waste water is then accumulated in the equilization mixing basin having submergible impellers (capacity of 20 m3). 11.3.4

Case Study

The case study is from a metal plating and finishing facility in Chile. The pH of the waste water was only adjusted with the applied current and the OH− that are obtained from the electrolysis process of the water. NaOH or Ca(OH)2 was not used in the process. Once the water leaves the electrocoagulation cell with a pH between 8.0 and 8.5, it then moves into to the mixture basin, with a residence time between 10 min and 15 min. During this time there is gentle mechanical agitation using a mixing blade moving at around 105 revolutions per minute (rpm). The mixing blade is used for improving the coagulation/flocculation of the hydroxides and oxides formed in the electrocoagulation cell and to increase the size and consistency among these chemical constituents. The coagulation/flocculation occurs in the mixture basin. The process is favored by the elimination of oxygen and hydrogen molecules generated in the electrocoagulation cell. In some cases a flocculant might be used to enhance the physical separation of the solids and liquids using either sedimentation or flotation. If added, the flocculants are used in low concentration of 0.5% power/volume. Then, the contaminants in the water agglomerate or flocculate (precipitate) in the tank. At this point the waste water leaves the mixture basin and goes into the sedimentation or settling basin where the separation of the two phases takes place. The organic matter rises to the top of the sedimentation basin, while the sludges move to the bottom of the sedimentation basin, with the clarified water in between. The sludges are removed from the bottom of the basin and dehydrated to reduce volume and mass. The clarified water that leaves the sedimentation basin, is passed through a transfer or contact basin, from

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TABLE 11.3.3 Composition of Treated Water Parameter

Symbol

Chromium(VI) Chromium(III) Iron Zinc Nickel Total suspended solids

Cr(VI) Cr(III) Fe Zn Ni TSS

Input values ppm

Output values ppm

% Efficiency

<0.96 <0.05 <0.64 <0.42 <0.34 <2.36

48 2 24 21 117 118

98 98 98 98 98 98

where it is pumped into a filtration process composed of several filters. The filters consist of sand, cartridge and activated carbon installed in series. Finally, the highly purified treated water leaves the sequential installed filters, is accumulated in a transfer basin, and recycled into the facility. This process reuses the water, significantly reducing water use at the plant and waste flow to the sanitary treatment plant. 11.3.4.1 Generation of Sludges Less sludge is produced using electrocoagulation compared to conventional chemistry treatment systems. The sludge from the accumulation sludge basin is automatically pumped back into the mixture basin. This allows an increase in the concentration of iron(III) hydroxide (Fe(OH)3) into the mixture basin, improving the coagulation/flocculation, in the sedimentation stage. The extra Fe(OH)3 in the electrocoagulation cell, creates a savings of about 10% and 20% in energy use. The sludges produced in the sediment basin consist of 1% to 2% in solids (98% to 99% water). There is 0.015 m3 and 0.025 m3 of sludge production for every m3 of treated water. This process is not considered for the treatment and dehydrated of sludges, which are carried out using a conventional system such as a filter press. 11.3.5

Summary of the Operation of the System

• Concentration of the critical parameters (input and output) for a design flow of 5 m3/h (120 m3/day) (Table 11.3.3) • Operating cost (Table 11.3.4) TABLE 11.3.4 Operating Energy Cost for Electrocoagulation and Electrooxidation System Detail

Consumption

Consumption

Value

Cost

Energy

2.5 kwh

960 kwh/month

0.04 US$/kwh Cost total month

39 US$/month 39

Energy relationship: 0.5 kwh/m3 or 0.013US $/m3

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Chromium(VI) Handbook TABLE 11.3.5 Total Operating Cost (Energy + Electrode) for Electrocoagulation and Electrooxidation System Parameter

Cost US$/month

Energy Electrodes Total month US$

39 55 94

The total operating cost is: 0.02 US$/m3 of waste water

11.3.5.1

Iron Electrodes

The electrocoagulation cell uses 11 sacrificial Fe electrodes, which should be replaced 2 times per year. Each one of the electrodes has a cost of US$30. The monthly estimated cost of the 11 iron electrodes is (11 × US$30 × 2)/12 = US$55/month. Waste water treatment related to the Fe electrodes is 0.04 kg/m3 or 0.019 US$/m3 of water treated. • Monthly operating costs (Table 11.3.5)

11.3.5.2

Details of the Equipment Considered in the Plant of Electrocoagulation Treatment (2) Impelers pumps to the electrocoagulation cell (one stand by) (1) Submersible shaker, for equalization basin (1) Flow meter in-line (1) Conductivity sensor with dosage pump of salt (optional) (1) Conductivity sensor and controller (1) pH sensor and controller with dosage pump of base (NaOH) (optional) (1) Electrocoagulation cell in high-density reinforced plastic (11)Iron electrodes (1) Transformer continuous with a power of 500 A and 20 V (with automatic polarity change) (1) Mechanical mixer on-line (1) Mixture basin made in FRP (Glass Fiber reinforced) of 1 m3, with mechanical mixer (1) Sedimentator kind lamella in steel to the carbon (1) Electromechanical valve for the retirement of sludges from sedimentator lamella (1) Air compressor

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(1) Contact and transfer basin of 5 m3 (1) Sand filter with motor-pump (1) Activated coal filter (optional) (1) Electric control panel (Gl) Piping (pipes in PVC), fitting, spread electric Relationship of (investment cost/m3 of treated water) is considered: US$170/m3 to US$190/m3, using the electrocoagulation process.

Bibliography Joffe, L. and Kneiper, L., 2000, Electrocoagulation, Industrial Wastewater, p. 5. Siegrist, R.L., Urynowicz, M.A., West, O.R., Crimi, M.L., and Lowe, K.S., 2001, Principles and Practices of In Situ Chemical Oxidation Using Permanganate, Battelle Memorial Institute, Columbus, Ohio, p. 348.

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12 Chromium Policy and Regulations

CONTENTS 12.1 U.S. Chromium Policies and Regulations ............................................492 Elisabeth L. Hawley and James A. Jacobs 12.1.1 Industrial History of Chromium .............................................492 12.1.2 Waste Regulations ......................................................................493 12.1.3 Air Regulations...........................................................................494 12.1.4 Drinking Water Regulations .....................................................494 12.1.4.1 Recent Developments in California Policy ............496 12.1.5 Setting Drinking Water Standards: The Regulatory Process .............................................................499 12.1.6 Review and Revision of Drinking Water Standards ............500 12.1.7 Regulatory Implications of Drinking Water Standards .......501 12.1.8 Beyond Regulations ...................................................................501 12.1.9 Case Study: Glendale, California.............................................502 12.1.10 Other Contaminated Regions...................................................503 Bibliography..............................................................................................503 12.2 Worldwide Chromium Regulations ......................................................504 James A. Jacobs 12.2.1 Overview of Chromium Regulatory Agencies......................505 12.2.1.1 European Union .........................................................505 12.2.1.2 Japan.............................................................................505 12.2.1.3 South Africa ................................................................506 12.2.1.4 United States...............................................................506 12.2.2 Air Quality...................................................................................507 12.2.3 Water Quality ..............................................................................507 12.2.4 Soil Quality..................................................................................507 12.2.5 Waste Disposal............................................................................507 12.2.6 Work Place Exposure ................................................................. 511 12.2.6.1 Labeling of Packages and Containers .................... 511 12.2.6.1.1 European Union ..................................... 511 12.2.6.1.2 United States...........................................513 12.2.6.2 Material Safety Data Sheets (MSDS).......................514 12.2.6.2.1 European Union .....................................514 12.2.6.2.2 United States...........................................514 1-5667-0608-4/05/$0.00+$1.50 © 2005 by CRC Press LLC

491

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Chromium(VI) Handbook 12.2.6.3 Induction and Training of Employees....................515 12.2.6.4 Environmental Control and Monitoring ................515 12.2.6.4.1 European Union .....................................516 12.2.6.4.2 Japan ........................................................517 12.2.6.4.3 South Africa ............................................518 12.2.6.4.4 United States...........................................518 12.2.6.5 Chemical Management .............................................518 12.2.7 Product Stewardship..................................................................519 12.2.8 Tools..............................................................................................520 12.2.8.1 Life Cycle Inventory/Life Cycle Assessment (LCI/LCA)...................................................................520 12.2.9 International Standards Organization (ISO) ..........................520 12.2.10 Ecolabeling ..................................................................................520 Bibliography ................................................................................ 521

12.1 U.S. Chromium Policies and Regulations

Elisabeth L. Hawley and James A. Jacobs 12.1.1

Industrial History of Chromium

Chromium (Cr) is an elemental metal that is used for a variety of industrial purposes, including metal plating, wood treatment, paint production, leather tanning, and corrosion inhibition in cooling towers. A brief summary of historical uses of Cr for industrial purposes is included here. A more detailed description can be found by referencing the International Chromium Development Association (ICDA, 2001). The modern era of metal surface finishing began with the invention of electrolytic solutions and the galvanic dipping cells in the early 1800s. By the middle of the 19th century, (Cr), silver (Ag), gold (Au), copper (Cu), and brass (Cu/Zn alloy) plating was commercially performed. The first plating efforts were focused on decorations, jewelry, lamps, and hardware. Large metal parts were manufactured using an electroplating method called electroforming. With the variety of mechanical devices and the generation of electrical generators produced in late 1800s, electroplating became even more widespread. Metal machine components, hardware, and automotive parts were protected from the elements and harsh conditions by Cr plating. Owing to the hardness and surface sealing qualities, Cr plating provided corrosion-enhanced properties, and enhanced appearance. The aircraft industry in World Wars I and II further developed and refined the Cr plating industry by adding such processes as anodizing, conversion coating, Cr plating, bronze (Cu/Sn) alloy plating, nickel (Ni) plating, chemical milling,

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and phosphate (PO43−) treating, along with numerous other plating processes. Plating equipment originally consisted of manually operated wooden process dip tanks. The process evolved into automated equipment, capable of processing thousands of kilograms per hour of parts (ICDA, 2001). The war years of 1940 to 1945 created a need for military use of metals. Metals rationing was commonplace and there was a general lack of plated luxury and metal-containing household items at this time. With the conclusion of World War II, plating of household and luxury items increased greatly. During the 1950s, Cr plating was found in building materials, furniture, fixtures, car bumpers, radios, and other consumer goods. New processes were developed for Cr surfacing such as electro-painting, electro-less plating, electro-polishing, vacuum metalizing, mechanical plating, electrostatic painting, electrolytic painting, and powder coating (ICDA, 2001).

12.1.2

Waste Regulations

Before the formation of the U.S. Environmental Protection Agency (USEPA) in 1970, the Cr plating industry was not subject to Federal environmental regulations. Instead, Cr plating regulations were enforced in selected areas of the U.S. with local ordinance. For example, in 1969, the Chicago Metropolitan Sanitary District passed a law regulating the discharge of concentrated chemicals, including Cr and Cr wastes from the finishing process, to the sewer system and to surface waters. In 1970 the USEPA was formed, creating regulations for industrial dischargers to the surface waters of the U.S. under the Water Pollution Control Act (WPCA; Public Law 92-500). By 1977, Congress had given the USEPA power to regulate sewer discharges under the Clean Water Act (CWA; Public Law 95-217). Under the direction of Congress, USEPA passed regulations limiting mass and concentrations of pollutants that could be present in wastewater discharged by industries. The USEPA also studied and provided technical information on technologies that could be employed to comply with the new regulations. The EPA regulated Cr discharges by requiring the installation of pretreatment systems. These pretreatment systems were designed to remove heavy metals based on expected flowrate. In addition, the 1976 Resource Conservation and Recovery Act (RCRA) required the Cr plating and manufacturing industry to treat and dispose off wastes generated from surface finishing operations and pretreatment systems in an environmentally sound and appropriate manner. RCRA required generators to estimate waste volumes and record acquisition, discharge, sales etc. in their inventories. In response to the increased cost of waste handling and disposal, the Cr plating and manufacturing industry responded by developing alternate processes that generated less waste or less toxic waste. Pretreatment systems were developed that recycled/recovered Cr or employed water conservation. With the 1980 Comprehensive Environmental Response, Compensation and Liability Act (CERCLA), more regulations and financial responsibilities were

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placed on chromium generators, transporters and disposers. The Superfund Amendments and Reauthorization Act of 1986 (SARA) provided more funds for cleanup of the most polluted properties in the nation, 306 of which contained Cr as a major contaminant (USEPA, 1996).

12.1.3

Air Regulations

Like the first wastewater regulations, the first air quality regulations under the 1963 Clean Air Act (CAA) required metal industries to remove Cr dust from air exhaust streams with technology controls. The USEPA uses broad categories for specific industries, rather than numerical emission standards, and defines a maximum achievable control technology (MACT) standard for each industry. MACT standards are based on performance of technologies installed in similar facilities. In 1970, the Occupational Safety and Health Act (OSHA, Public Law 91-596) set up two new Federal agencies designed to monitor and protect workers from injury and illnesses. Both agencies developed numerical criteria for airborne Cr concentrations. The Office of Safety and Health Administration (OSHA) published legally binding standards known as Permissible Exposure Limits (PELs). The National Institute of Occupational Safety and Health (NIOSH) independently evaluated and published risk-based guidelines for workers. The Office of Safety and Health Administration set the PEL ceiling for Cr(VI) compounds at 100 µg/m3 measured as CrO3. Concentrations of Cr(II) and Cr(III) salts are regulated at 500 µg/m3 as an 8 h time-weighted average (TWA). Cr metals and insoluble salts are regulated at 1,000 µg/m3 8 h TWA (NIOSH, 2004). The National Institute of Occupational Safety and Health recommended that exposure to Cr(VI) compounds should be limited to 1 µg/m3 10 h TWA, and that Cr metal, Cr(II), and Cr(III) compounds be limited to 500 µg/m3 10-h TWA. NIOSH considers all Cr(VI) compounds potentially carcinogenic based on current evidence (NIOSH, 2004). A summary of air quality regulations is shown in Table 12.1.1. The Agency for Toxic Substances and Disease Registry (ATSDR) issued a Public Health Statement on Chromium in 1989 (ATSDR, 1989).

12.1.4

Drinking Water Regulations

Federal involvement in establishing public drinking water regulations began with the Public Health Service Act (PHSA) in 1912. Under this act, drinking water supplies used by interstate buses, trains, airplanes, and ships were subject to water quality guidelines, which focused primarily on preventing microbial diseases. The PHSA established guidelines for all public water supplies, but did not have enforcement power beyond the realm of interstate carriers. The first guideline was developed in 1914, limiting coliform bacteria to a count of 2 per 100 mL. In 1925, 1946, and 1962, standards were added

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TABLE 12.1.1 Air Quality Regulations and Guidelines for Chromium Description Workplace Insoluble Cr(VI) compounds, TWA Water-soluble Cr(VI) compounds, TWA Cr metal and Cr(III) compounds, TWA Chromic acid (H2CrO4) and all Cr(VI) salts, 10 h TWA Elemental Cr/Cr metal and Cr(II) and Cr(III) salts, 10 h TWA Chromic acid (H2CrO4) and chromates (CrO42–), PEL ceiling level Cr(II) and Cr(III) salts, 8 h TWA PEL Elemental Cr/Cr metal and insoluble salts, 8 h TWA PEL General Hazardous air pollutant Cancer potency factor/unit risk for inhalation

Concentration (µg/m3)

Guideline

Agency

10 50 500 1

Advisory Advisory Advisory Advisory

ACGIH ACGIH ACGIH NIOSH

500

Advisory

NIOSH

100 as CrO3

Regulatory

OSHA

500 1,000

Regulatory Regulatory

OSHA OSHA

NA 0.012

Regulatory Regulatory

USEPA USEPA

Source: Adapted from Toxicological Profile for Chromium (ATSDR, 2000). ACGIH = American Conference of Governmental Industrial Hygienists ATSDR = Agency for Toxic Substances and Disease Registry NA = Not applicable NIOSH = National Institute for Occupational Safety and Health OSHA = Occupational Safety Health Administration PEL = Permissible Exposure Limit; highest level of Cr in air to which a worker may be exposed averaged over an 8 h day, unless otherwise noted (10 h day) TWA = Time weighted average for a normal workday and a 40 h workweek to which nearly all workers may be repeatedly exposed USEPA = U.S. Environmental Protection Agency

for inorganics and dissolved solids, followed by synthetic detergents, radioactivity, and more inorganics. By 1962, 28 substances were regulated (National Research Council, 1999). Chromium was first included in drinking water regulations in 1942, when the PHSA specified that Cr salts could not be used for drinking water treatment. Cr was known to damage people’s health, including their skin (chromic acid, H2CrO4, is corrosive), nasal tissue, respiratory tract, eyes, and kidneys (Akatsuka and Fairhall, 1934; Bloomfield and Blum, 1928; Blair, 1928; Carter, 1929; Hunter and Roberts, 1932; Lieberman, 1941). It was also linked to lung cancer (Shimkin and Leiter, 1940). This knowledge was mostly gained from occupational exposure studies, in addition to accounts of accidental ingestion. In 1974, the PHSA was revised to become the Safe Drinking Water Act (SDWA), enforceable for all public water supplies on the basis of the federal government’s duty to protect human health. States that wanted to maintain

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primary control of environmental activities were given the option to establish a state EPA that would meet or exceed requirements passed by the USEPA. Many states set up a state EPA department and adopted the PHSA guidelines (last revised in 1962) as water quality standards. A total of 22 contaminants were regulated under the SDWA, including 1 microbial standard and 21 chemical compounds. The standard for total Cr was set at 50 µg/L. The USEPA chose to regulate total Cr rather than Cr(VI) because Cr can be converted from Cr(III) to Cr(VI), making an analytical determination of Cr(VI) susceptible to underestimating actual health risks. The 1974 SDWA also specified the process for developing water quality standards, introducing the terms Maximum Contaminant Level Goal (MCLG) and Maximum Contaminant Level (MCL). The MCLG is the concentration of contaminant at which no adverse health effects are expected. This concentration is determined from a synthesis of available epidemiological and toxicological research and appropriate safety factors. The MCL is then determined for each contaminant after taking into account practical considerations associated with drinking water treatment. The MCLG is a goal; the MCL is a regulatory standard. The MCL may be higher than the MCLG owing to an inability to detect the compound at MCLG levels, or to technical and/or economic limitations to meeting MCLGs with available treatment technology. In the case of Cr, the MCL was equal to the MCLG. Seventeen years later, in 1991, the USEPA replaced the interim MCL/MCLG of 50 µg/L with a final standard of 100 µg/L, based on the reasoning that Cr(VI) was not carcinogenic via oral ingestion, as was originally assumed, making the interim standard overly conservative. State EPA departments did not follow the federal lead in revising their Cr MCLs, possibly owing in part to the political implications of raising an environmental water quality standard (DHS, 2004). In 1996, when the World Health Organization (WHO) developed drinking water standards, it adopted the more conservative standard of 50 µg/L total Cr (WHO, 1996). Currently, the USEPA MCL for total Cr in public drinking water supplies is 100 µg/L (USEPA, 2004). Individual states may set stricter standards and most states regulate either total Cr or Cr(VI) at 50 µg/L (ASTDR, 2000). Recently, the drinking water standards for Cr have been more closely examined. The assumptions used in determining the Cr standard have been questioned, particularly in California, which is in the process of revising the state’s Cr regulations. Cr exposure by ingestion and dermal sorption are shown in Figures 12.1.2 and 12.1.3, respectively. 12.1.4.1 Recent Developments in California Policy In 1996, Congress passed amendments to the SDWA. In the state of California, these amendments included legislation to develop risk-based standards for drinking water contaminants that were protective of human health. The new standards, known as Public Health Goals (PHGs), are similar to MCLG values but have more implications for California public water system operations.

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While MCLGs are typically zero for carcinogens, PHGs correspond to a onein-a-million (10–6) cancer risk. Under the 1996 SDWA Amendment, California’s Office of Environmental Hazard and Health Assessment (OEHHA) was responsible for determining PHGs. OEHHA is a California government department that develops health guidance. In February 1999, OEHHA published a startlingly low PHG of 2.5 µg/L total Cr (OEHHA, 1999). OEHHA assumed that Cr(VI) should be considered carcinogenic by ingestion. Using results from a mouse study (Borneff et al., 1968), an acceptable concentration of 0.2 µg/L Cr(VI) in drinking water was calculated. Assuming that 7.2% of total Cr was Cr(VI), the acceptable amount of total Cr would then be 2.5 µg/L. Combined with concurrent public interest in Cr spawned by the movie Erin Brockovich, public concern mounted over OEHHA’s recommendation. Numerous bills were introduced in the State Congress to fund occurrence studies, investigate the difference between the federal and state findings, and to amend the discrepancy. The federal MCLG of 50 µ g/L was questioned, as was the validity of its principal assumption—that Cr(VI) was not carcinogenic if orally ingested. California faced two choices: (1) revise the OEHHA public health goal; or (2) revise the state MCL. In March 1999, the California EPA Department of Health Services (DHS) gave notice that it would be evaluating the MCL for total Cr to determine if the standard should be revised. DHS also announced its intention to identify Cr(VI) as an unregulated chemical for which monitoring in public water systems is required. In October 2000, the Association of California Water Agencies publicly announced that they would cooperate with DHS in collecting new information in support of a revised state MCL for Cr. They recognized the potential for the state to require occurrence monitoring for Cr(VI), in order to assess the cost of meeting a stricter MCL standard. DHS began certifying laboratories to perform Cr(VI) analyses. In January 2001, Cr(VI) had been added to the list of unregulated chemicals that required monitoring in all vulnerable drinking water sources. However, in March 2001, DHS asked the University of California (UC) to convene an expert panel (Chromate Toxicity Review Panel) to assess OEHHA’s assumptions. DHS essentially asked OEHHA to revise the PHG, although technically they asked OEHHA to develop a Cr(VI)-specific PHG. The UC committee report concluded that OEHHA’s assumption of Cr(VI) carcinogenicity via ingestion was not scientifically based, owing to flaws in the 1968 Borneff study (Chromate Toxicity Review Committee, 2001). In November 2001, OEHHA withdrew the PHG and began the process of developing a Cr(VI)-specific PHG. DHS will use the new PHG to develop a Cr(VI)-specific MCL by January 2004, in accordance with state bill SB351. If the new PHG is drastically less than the current MCLG, California’s work could impact federal Cr regulations and that of other states. A summary of drinking water regulations is shown in Table 12.1.2.

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Chromium(VI) Handbook TABLE 12.1.2 Drinking Water Quality Regulations and Guidelines for Chromium Description Cr(VI) Total Cr MCL Total Cr MCLG Total Cr in groundwater Water quality criteria Freshwater Saltwater Water and organism Organism only Health advisories for total Cr 10 kg child, 1 day 10 kg child, 10 days 10 kg child, longer term 70 kg adult, longer term 70 kg adult, lifetime 70 kg adult, drinking water equivalent level Bottled water limit for Cr Cr drinking water standards Alabama Alaska Arizona California Colorado Connecticut Delaware Florida Georgia Hawaii Idaho Illinois Iowa Kansas Kentucky Maine Maryland Massachusetts Minnesota Mississippi Montana Missouri Nebraska New Hampshire New Jersey New Mexico New York North Carolina North Dakota Ohio Oklahoma Oregon Puerto Rico Rhode Island

Concentration (µg/L)

Agency

Standard

50 100 100 50

WHO USEPA USEPA USEPA

Advisory Regulatory Advisory Regulatory

11 50 NA NA

USEPA

Regulatory

100 100 200 800 100 200

USEPA

Advisory

100

FDA

Regulatory

100 100 100 50 100 50 50 50 50 100 100 50 50 50 50 100 50 50 100 50 50 50 50 50 100 50 50 50 50 50 50 50 50 50

States

Regulatory Regulatory

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TABLE 12.1.2 Drinking Water Quality Regulations and Guidelines for Chromium (Continued) Description South Carolina Tennessee Texas Utah Vermont Virginia Washington West Virginia Wisconsin

Concentration (µg/l)

Agency

Standard

100 50 50 50 50 50 50 50 50

Adapted from Toxicological Profile for Chromium (ATSDR, 2000). ATSDR = Agency for Toxic Substances and Disease Registry FDA = Food and Drug Administration MCL = Maximum Contaminant Level MCLG = Maximum Contaminant Level Goal NA = Not Applicable TWA = Time weighted average for a normal workday and a 40 h workweek to which nearly all workers may be repeatedly exposed WHO = World Health Organization USEPA = U.S. Environmental Protection Agency

12.1.5

Setting Drinking Water Standards: The Regulatory Process

As apparent from drinking water standards summarized in Table 12.1.2, different regulatory agencies have set different regulations for chromium, raising some questions: • What is the current process for setting the federal MCLG? • What process will California follow when setting the state MCL? • In the meantime, and for the rest of the country, how were the current standards set? • Where did the concentrations 50 and 100 µg/L originate, since they are the basis for regulatory action? These questions will be addressed in this section. The MCLG value for carcinogens is set at zero. For noncarcinogens, a threshold value is assumed. After the typical threshold is defined, the acceptable 10–6 cancer risk is taken into account. So is the sensitivity of others (sick people, elderly people, pregnant women, and young children), and possible synergistic effects between that contaminant and others. The federal process of adopting new MCLs is essentially the same as that of California. California Health and Safety Code § 116365(a) requires DHS to establish a contaminant MCL at a level as close to PHGs as is technically and economically feasible. The PHG for total Cr or Cr(VI) is the contaminant’s concentration in drinking water that does not pose any significant risk to health, derived from a human health risk assessment.

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As part of the MCL development process, DHS evaluates the technical and economic feasibility of regulating Cr(VI). Technical feasibility includes an evaluation of commercial laboratories’ ability to analyze for and detect total Cr, Cr(VI), and Cr(III) in drinking water, the costs of monitoring, and the costs of treatment required to remove Cr(VI). DHS must consider the cost of complying with new MCLs. To determine the technical and economic feasibility, DHS typically: • • • • • • • •

•

Receives the Cr(VI) PHG from OEHHA Selects possible draft Cr(VI) MCL concentrations for evaluation Evaluates occurrence data Evaluates available analytical methods and estimate monitoring costs at various draft MCL concentrations Estimates population exposures at various draft MCL concentrations of Cr or Cr(VI) Identifies best available technologies (BAT) for Cr(VI) treatment Estimates treatment costs at the possible draft MCL concentrations Reviews the costs and associated health benefits (health risk reductions) that result from Cr(VI) treatment at the possible draft MCL concentrations Selects an MCL for proposal from the possible draft MCL concentrations considered above

The MCL is then put into place. It is subject to periodic review and/or revision, as described in the following section. 12.1.6

Review and Revision of Drinking Water Standards

The process for reviewing and revising drinking water standards and guidance is a combination of science and policy. While the underlying assumptions are based on science, margins of safety are added to make the value protective. The process costs time and money, and is slow. The primary question answered during review is as follows. Assuming future work has been done since the date of the previous MCL, does the work indicate that a lower or higher standard is appropriate, or does it corroborate the original value? To answer this question for Cr or any other drinking water contaminant of concern, the 1996 SDWA Amendments set up a process for reviewing EPA drinking water standards. The USEPA must review information on existing contaminants (68 chemical contaminants) every 6 years and decide which ones need to be revised (USEPA, 2002). The USEPA looks for new information on the following: • Health effects • Chemical analysis methods

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• Treatment technologies • Occurrence or exposure estimates • Economics Similarly, the state of California is in the process of reviewing MCLs in response to PHGs. The process is similar to the USEPA’s. If the PHG is lower than the current MCL, DHS looks for any changes in available health effects data, analytical methods, technology, occurrence, etc. As soon as OEHHA completes the Cr(VI) PHG analysis, DHS will begin this process (DHS, 2004).

12.1.7

Regulatory Implications of Drinking Water Standards

The implications of a standard or guidance value for total Cr or Cr(VI) or for any other contaminant are far-reaching in terms of both human health consequences and financial obligations. Water treatment plants may need to add to the treatment process. Water currently used for groundwater recharge may require treatment to meet the new regulatory levels. Industrial facilities may be required to meet stricter pretreatment requirements. Cleanup requirements at groundwater remediation sites may also change, requiring treatment systems to operate for longer periods of time and cover a larger plume area. 12.1.8

Beyond Regulations

While many compound regulations are based on the concept of a threshold value below which no adverse effects are anticipated, this is merely a best guess that is dependent on the detection levels of today’s scientific practice. In the movie Erin Brockovich, litigation centered around Cr(VI) contamination in Hinkley, CA, the lead attorney for the plaintiffs discusses the possibilities of risk beyond today’s scientific knowledge with the following statement: In Hinkley, the [chromium] levels went all the way to 24 parts per million. It’s fairly easy to prove that can kill you. What we don’t know is what [2 ppb] over 50 years will do . . . There isn’t anybody in this world who can give a prediction. All we can do is give a very educated guess. Edward Masry, Toxic Tort Specialist (Chromium Research Council, 2004)

This problem is often legally and scientifically gray when concentrations are approximately equal to the regulatory standard. Water providers may argue that no adverse health effects are associated with Cr concentrations below regulatory action levels or guidelines. However, toxicologists must scale up from mice and other small rodents to humans and correlate exposure concentrations and disease at low concentrations. Rodent lifespan, concentration dose, metabolic

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rate, mechanisms of carcinogenesis, synergistic effects and accumulation rates vary considerably between rodents and humans. Therefore, the results from animal cancer tests are not necessarily a good predictor of cancer risk to humans at the usually low concentrations of human exposures. Beyond these issues lies the fact that defining an “acceptable risk” to humans, wildlife, or the environment is not a scientific question. Water providers are wary of the legal traps associated with serving water to the public in the face of uncertain regulations. Cities are taking initiative to provide themselves with an additional factor of safety to address legal, political and potential health concerns, as illustrated by the case study of Glendale, a suburb of Los Angeles, California.

12.1.9

Case Study: Glendale, California

The San Fernando Valley groundwater basin serves as a drinking water source for the Los Angeles (LA) metropolitan area, the unincorporated area of La Crescenta and the cities of Glendale, Burbank, San Fernando, and La Canada-Flintridge. In 1998, Cr(VI) was detected in shallow and deep potable supply wells in the San Fernando Valley. While concentrations were below the state MCL of 50 µg/L, approximately 35% of samples exceeded OEHHA’s draft PHG of 2.5 µg/L (Chromium Research Council, 2004). The ratio of Cr(VI) to total Cr ranged between 61 to 99% (Regional Water Quality Control Board (RWQCB), 2000). After notifying USEPA and the State RWQCB, an interagency task force was set up to evaluate the problem. Approximately 250 potential sources were located with the help of the RWQCB (RWQCB, 2000). While concentrations were within the range of naturally high background levels seen in other areas, the industrial history of the San Fernando Valley has led regulators to consider the contamination anthropogenic (RWQCB, 2000). By 1980, chlorinated solvents used at defense-related facilities from the 1940s to the 1970s were detected in the San Fernando Valley aquifer operated as a water source for the city of Glendale. By the mid 1980s, the city stopped pumping water from approximately 20 groundwater production wells and began importing all of its water. In 1987, the USEPA and LA Department of Water and Power entered a cooperative agreement which required pumping the supply wells, treating the water to remove VOCs, and delivering water to the public. The water treatment plant was installed in the early 1990s. As part of a 1993 USEPA agreement, the city of Glendale agreed to deliver the treated water to the public. The treated water met all federal, state and local drinking water requirements. At this time, Cr was not determined to be a problem in the area. When Cr was detected in the treated water, Glendale water managers and city council agreed not to serve the water containing total Cr and Cr(VI) to Glendale water customers. Although the treated water was less than regulatory VOC levels, the city of Glendale was concerned about the newly discovered

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Cr in the treated water and wanted to voluntarily comply with the new public health goal of 2.5 µg/L for total Cr. Well water from the Glendale treatment plant measured as high as 17 µg/L Cr(VI). Instead, the treated water was discharged into the concrete-lined Los Angeles River against the opposition of the USEPA and the LA Metropolitan Water District. In subsequent litigation, Glendale was forced to take the treated water or be fined up to $10,000 per day for noncompliance with the 1993 USEPA agreement. A plan was developed in 2001 and was agreed upon by the city of Glendale, the USEPA and the Los Angeles Metropolitan Water District. The plan allowed for water drawn from the underlying groundwater aquifer to be blended with clean water from the LA Metropolitan Water District resulting in a blended Cr(VI) concentration less than 1 µg/L delivered to Glendale water consumers. In return, Glendale spends about $800,000 per month for water treatment. Eventually, Glendale plans to spend $6 million to $9 million on a new treatment plant to remove Cr(VI) and volatile organic compounds (RWQCB, 2000).

12.1.10

Other Contaminated Regions

Cr(VI) has been found in many areas of California, mostly at defense-related businesses, aircraft manufacturing and industrial plating facilities. Northern California locations of Cr(VI) impacted groundwater include Daly City, Davis, Brentwood, and Los Banos. Southern California Cr(VI) sites include Los Angeles, Arcadia, San Marino, Compton, Redondo Beach, Pomona, La Verne, Long Beach, Industry, Hawthorne, and South Gate (RWQCB, 2000). Under a voluntary State Cost Recovery Program administered by the Los Angeles RWQCB, many of these sites are being actively assessed and remediated.

Bibliography ATSDR, 1989, Chromium Public Health Statement archived at http://www.cla.sc.edu/ geog/hrl’/sc trap/tox fags/chromium.htm ATSDR, 2000, Toxicological profile for chromium, Agency for Toxic Substances Disease Registry, Public Health Service, U.S. Department of Health and Human Services. Akatsuka, K and Fairhall, L.T., 1934, The toxicology of chromium, J. Ind. Hyg., 16, 128. Blair, J., 1928, Chrome ulcers, report on twelve cases, J. Am. Med. Assoc., 90, 1927–1928. Bloomfield, J.J. and Blum, W., 1928, Health hazards in chromium plating, Public Health Report, 43, 2330–2351. Borneff, I., Engerlhardt, K., Griem, W., Kunte, H., and Reichert, J., 1968, Carcinogenic substances in water and soil. XXII, Mouse drinking study with 3,4-benzpyrene and potassium chromate, Arch. Hyg., 152, 45–53. (German). California Department of Health Services (DHS), 2004, Chromium-6 in drinking water: regulation and monitoring update, http://www.dhs.ca.gov/ps/ddwem/ chemicals/Chromium6/Cr+6index.htm

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California Regional Water Quality Control Board (RWQCB), 2000, Special board meeting on chromium contamination, California Regional Water Quality Control Board, Los Angeles Region, Glendale, CA, November 13. Carter, W.W., 1929, The effect of chromium poisoning on the nose and throat: the report of a case, Med. J. Rec., 130, 125–127. Chromium Research Council, 2004, Cr-Cleanup, Local efficiency and nationwide utility protection, http://www.cr-cleanup.com Hunter, W.C. and Roberts, J.M., 1932, Experimental study of the effects of potassium bichromate on the monkey’s kidney, Am. J. Pathol., 9, 133–147. International Chromium Development Association (ICDA), 2001, Health safety and environment guidelines for chromium, International Chromium Development Association, December, pp. 19–38. Lieberman, H., 1941, Chrome ulcerations of the nose and throat, New Engl. J. Med., 225, 132–133. National Institute of Occupational Safety and Health (NIOSH), 2004, 1988 OSHA PEL project documentation. http://www.cdc.gov/niosh/pel88/pelstart.html. National Research Council, 1999, Identifying Future Drinking Water Contaminants, National Academy Press, Washington, DC, p. 22–32. Office of Environmental Hazard and Health Assessment (OEHHA), 1999, Public health goal for chromium in drinking water, February. Shimkin, M.B. and Leiter, J., 1940, Induced pulmonary tumors in mice III: The role of chronic irritation in the production of pulmonary tumors in strain A mice, J. Natl. Cancer Inst., 1, 241–254. U.S. Environmental Protection Agency (USEPA), 2002, Fact sheet: Announcement of the results of EPA’s review of existing drinking water standards and request for public comment, EPA 815-F-02-002. U.S. Environmental Protection Agency (USEPA), 2004, List of drinking water contaminants and MCLs, U.S. Environmental Protection Agency, Office of Ground Water and Drinking Water http://www.epa.gov/safewater/mcl.html#mcls. World Health Organization (WHO), 1996, Health criteria and other supporting information, in Guidelines for Drinking-Water Quality, 2nd ed., 2, 940–949.

12.2 Worldwide Chromium Regulations

James A. Jacobs Worldwide Figure 12.1.3: Cr(VI) exposure (dermal sorption) Cr regulations are meant to protect health, safety, and the environment. Cr regulations from the European Union (EU) (including France, Italy, U.K., and Germany), Japan, South Africa, and the U.S. are listed for air, dust, wastewater, drinking water, soil, and waste. Most of this information was compiled from the Health Safety and Environment Guidelines for Chromium and is used

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with permission from the International Chromium Development Association (pp. 19–38; December, 2001).

12.2.1

Overview of Chromium Regulatory Agencies

12.2.1.1 European Union Three directorates within the EU deal with Cr-related hazards. • Directorates General (DG) XI is responsible for environment, nuclear safety and civil defense issues with classification, labeling and packaging of dangerous substances. • Directorates General (DG) V is responsible for employment, industrial relations, and social affairs deals with occupational health and safety including setting occupational exposure limits (OEL). • Directorates General (DG) III is responsible for industrial affairs deals with the extension of the dangerous substances regulations to all dangerous preparations. These directorates enact decisions through EU directives or regulations, which either lay down legally binding requirements or set out minimum standards for which authorities within member states may set more demanding limits. National authorities may also impose additional acts or regulations. Several EU directives deal with the pollution of water, namely 76/464/ EEC concerning the “Discharge of Dangerous Substances into the Aquatic Environment.” Cr appears in the “Grey List” of 20 metals. A water framework directive is being formulated based on the requirements of the above directive, the ESR Directive 793/93/EEC and the IPPC Directive 96/61/EC. 12.2.1.2 Japan The Japanese Society for Occupational Exposure Limits (JSOH) recommends OELs as reference values for preventing adverse health effects on workers. In addition, Cr is strictly regulated through legal controls by the following: • • • •

Industrial Safety and Health Law (workplace) Poisonous and Deleterious Substances Control Law (workplace) Wastes Disposal and Public Cleansing Law (wastes) Water Pollution Control Law (water purity)

The first three are under the jurisdiction of the Ministry of Health, Labor, and Welfare. The Water Pollution Control Law is administered by the Ministry of the Environment.

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12.2.1.3 South Africa At present all work-related matters fall under two government departments: the Department of Mineral and Energy Affairs and the Department of Manpower. The Department of Mineral and Energy Affairs specifies: • Health surveillance: regular medical examination and chest X-rays • Pollutant levels in the workplace: airborne contamination— American Conference of Governmental Industrial Hygienists (ACGIH) • Threshold Limit Values (TLVs) for occupational exposure limits The Department of Manpower is responsible for administering the hazardous chemical substances regulations which are similar to U.K. regulations. The primary focus is on medical surveillance, including biological monitoring, and exposure to gases and airborne particles.

12.2.1.4

United States

In the U.S., there are several government groups responsible for setting regulations to protect workers and the general public. There are also government departments that develop recommendations or guidelines: • Occupational Safety and Health Administration (OSHA) (workplace, regulatory) • National Institute for Occupational Safety and Health (NIOSH) (workplace, advisory) • American Conference of Governmental Industrial Hygienists (ACGIH) • US Environmental Protection Agency (USEPA) (general public, regulatory) • Agency for Toxic Substances and Disease Registry (ATSDR) of the U.S. Dept. of Health and Human Services, Public Health Serv. (Toxicological Profiles) OSHA publishes a hazard communication standard to ensure that all hazards of produced or imported substances are assessed and that the information is passed on to employers and employees. These rules deal with the labeling aspects, the preparation of Material Safety Data Sheets (MSDSs) and the training of employees. OSHA also publishes Permissible Exposure Limits (PELs) for airborne exposure to chemical compounds. Acting under the authority of the Occupational Safety and Health Act of 1970 (Public Law 91-596), NIOSH develops and periodically revises recommendations or limits of exposure to potentially hazardous substances or conditions

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in the workplace. NIOSH also recommends appropriate preventive measures designed to reduce or eliminate adverse health effects of these hazards. To formulate these recommendations, NIOSH evaluates available medical, biological, engineering, chemical, trade, and other information relevant to the potential hazard. These recommendations are then published, and transmitted to OSHA for use in promulgating legal standards. American Conference of Governmental Industrial Hygienists classifies, processes and recommends threshold limit values (TLVs) for use as guidelines. USEPA generates and enforces all aspects of environmental regulation.

12.2.2

Air Quality

Table 12.2.1 and Table 12.2.2 give specific air and dust emission limits for releases to the environment in countries for which information is available. Regulations are subject to review and changes; therefore it is essential to confirm with local, national, or regional authorities before using the value listed in the tables.

12.2.3

Water Quality

Chromium substances that are of particular concern in water include: • Suspended particles containing Cr • Dissolved total Cr • Dissolved hexavalent Cr(VI) These can be measured or monitored points of discharge or points of seepage. Generally water quality regulations consider both instantaneous concentrations (mass per liter) and flux (mass per time). Regulations for wastewater and drinking water from different countries are listed in Table 12.2.3 and Table 12.2.4 for reference.

12.2.4

Soil Quality

Table 12.2.5 lists soil regulations for selected countries.

12.2.5

Waste Disposal

Table 12.2.6 contains regulations regarding solid and liquid waste disposal. In Japan, ferrochromium slag with the Water-Leaching Test Value (as stipulated by law) of less than 1.5 Cr(VI) mg/L must be dumped into a “controlled final disposal site” when it is categorized as an industrial waste.

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TABLE 12.2.1 Ambient Air Regulations for Chromium Cr(VI) Compounds

Country

Cr(VI) as strontium chromate (SrCrO4) Cr(VI) as strontium chromate (SrCrO4) Cr(VI) as calcium chromate (CaCrO4) Cr(VI) as chromic acid (H2CrO4) and chromate (CrO42–) Cr(VI) Insoluble Cr(VI) compounds Cr(VI) as lead(II) chromate (PbCrO4) Cr(VI) as chromic acid (H2CrO4) Cr(VI) as chromate (CrO42–) Cr(VI) as chromic acid (H2CrO4) and chromate (CrO42–) Cr(VI) as lead(II) chromate (PbCrO4) Cr(VI) as chromate (CrO42–) Cr(VI) as chromic acid (H2CrO4) Cr(VI) compounds Cr(VI) compounds Cr(VI) compounds Cr(VI) compounds Cr(VI) as chromic acid (H2CrO4) Cr(VI) compounds Elemental Cr/Cr metal and Cr(III) compounds Cr(VI) compounds Cr(VI) compounds Cr(VI) short-term exposure limit (stel) value Cr(VI) compounds Maximum Exposure Limit (MEL) Soluble Cr(VI) as zinc chromate (Zn CrO4) Cr as chromite ore processing Zinc Chromate (ZnCrO4) Cr(VI) compounds (except insolubles) Cr(VI) compounds in welding fumes from MMA arc welding with coated electrodes Cr(VI) compounds Zinc chromate (ZnCrO4) Cr(VI) compounds (except insolubles) Cr(VI) compounds in welding fumes from MMA arc welding with coated electrodes Cr(VI) short-term exposure limit (stel) value Chromic acid (H2CrO4) and chromates as CrO3

Denmark U.S. U.S. Denmark

France U.S.

Elemental Cr and Cr(III) Compounds Cr as powder/soluble Cr(II) and Cr(III) salts Cr(III) compounds (OES) Cr, Cr(II), and Cr(III) compounds Cr, Cr(II), and Cr(III) compounds Cr(III) compounds

Denmark U.K. European Union Finland South Africa

Kazakhstan U.S. U.S. Iceland Iceland Norway Norway Sweden Sweden Germany European Union Finland France France Germany Iceland Japan South Africa Sweden U.K.

Standard (mg/m3) 0.0005 0.0005 0.001 0.005 0.01 0.01 0.01 0.02 0.02 0.02 0.02 0.02 0.02 0.025 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.5

U.S. U.S. Germany Germany Germany

0.05 0.05 0.05 as Cr 0.05 as Cr 0.05 as Cr

Germany Germany Germany Germany

0.1 0.1 as CrO3 0.1 as CrO3 0.1 as CrO3 0.1 0.1

0.5 0.05 0.5 0.5 0.5

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TABLE 12.2.1 Ambient Air Regulations for Chromium (Continued) Cr(VI) Compounds

Country

Standard (mg/m3)

Cr(III) compounds Occupational Exposure Standard (OES) Cr(II) and Cr(III) compounds Elemental Cr/Cr metal Elemental Cr/Cr metal, Cr(II), and (III) Elemental Cr/Cr metal Elemental Cr/Cr metal/inorganic Elemental Cr/Cr metal Elemental Cr/Cr metal and Cr(III) Cr metal

U.K.

0.5

U.S. France Norway South Africa Sweden U.K. U.S. U.S.

0.5 0.5 0.5 0.5 0.5 0.5 0.5 1.0

Other Total Cr ACGIH values, USA ACGIH values, USA ACGIH threshold limit values (TLVs)

Kazakhstan Italy Spain U.S.

1.0 NA NA NA

Source:

Adapted from ICDA, 2001.

TABLE 12.2.2 Other Air Regulations for Chromium Chromium Source Cr(VI) Chromates of Ca, Cr(III), Sr and Zn, and Zn-K as Cr Total metals-atmospheric pollution by industrial plants Cr(VI) as Cr Total Cr Total metals if total mass flow is >25 g/h Chromates of Ca, Cr(III), Sr and Zn if total mass flow is >5 kg/h Cr(III) as Cr Inhalable dust containing chromates of Ca, Cr(III), Sr and Zn if total mass flow is >5g/h Total dust Total dust if total mass flow is >1 kg/h Total dust stack emission limit Total dust if total mass flow is >0.5 kg/h Total dust if total mass flow is <1 kg/h

Country Kazakhstan U.K. European Union U.K. Kazakhstan Francea Germany U.K. Germany U.K. France South Africa Germany France

Source: Adapted from ICDA, 2001. a Metals include Sb, Cr, Co, Cu, Sn, Mn, Ni, Pb, V, and Zn

Standard (mg/m3) 0.0017 0.5 <1 1 4–4.8 5 5 5 1 20 40 40 50 100

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TABLE 12.2.3 Wastewater Regulations Scenario

Country

Cr(VI) Cr(VI) for freshwater – continuous (maximum) Cr(VI) for leather industry Cr(VI) for salt water – continuous (maximum) Cr(VI) if total mass flow is >1 g/day Cr(VI) for metal or chemical industry Cr(III) 4-day avg – continuous (maximum) Total Cr if total mass flow is 5 g/day Total Cr max for metal or chemical industry Cr(VI) public water systems Total Cr Total Cr max for leather industry Total Cr in public water system Range for estuary and coastal water, based on water hardness, receptors salmonid and cyprinid Source:

Kazakhstan U.S. Germany U.S. France Germany U.S. France Germany Japan South Africa Germany Japan U.K.

Standard (mg/L) 0.005 – 0.03 0.01 (0.015) 0.05 0.05 (1.1) 0.1 0.1 0.18 (0.55) 0.5 0.5 0.5 0.5 1 2 5–250

Adapted from ICDA, 2001.

TABLE 12.2.4 Drinking Water Regulation Compound Total Cr Total Cr Cr(VI) Total Cr Total Cr Total Cr

Country Kazakhstan Germany Japan United Kingdom South Africa U.S.

Standard (mg/L) 0.0031 0.05 0.05 0.05 0.1 0.1

Adapted from ICDA, 2001.

TABLE 12.2.5 Soil Regulations Scenario

Country

Cr(VI) Threshold trigger for total Cr Threshold value for total Cr, varies with soil type Draft soil screening level for total Cr, based on inhalation Provisional guidelines for total Cr, gardens and allotments Draft soil screening level for total Cr, based on ingestion Total Cr Provisional guidelines for total Cr, residential without gardens, parks, open spaces, etc. Provisional guidelines for total Cr, commercial and industrial areas Source:

Adapted from ICDA, 2001.

Kazakhstan U.K. Germany U.S. U.K. U.S. Kazakhstan U.K. U.K.

Standard (mg/kg) 0.558 25 30–100 140 150 390 400 1.000 3,800

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TABLE 12.2.6 Waste Leachate Disposal Regulations Scenario Landfill disposal Cr(VI) Landfill disposal Cr(VI) Ocean disposal Cr(VI) Landfill disposal total Cra Wastewater disposal

Country

Standard (mg/L)

Germany Japan Japan U.S. U.S.

0.5 0.5 1.5 5.0 2.77

Source: Adapted from ICDA, 2001. a TCLP = Toxicity Characteristic Leaching Procedure

The same slag, however, can be used as civil engineering material for land reclamation or road construction. In South Africa, a process authorization approach is being developed for landfills in terms of the Environmental Conservation Act (No 73 of 1989). Draft guidelines for the authorization of landfill site have been prepared under the auspices of the Department of Water Affairs (DWAF, 1993). The DWAF guidelines require that the developer of a site submits various reports detailing the geology and hydrology of the site, the results of an environmental impact assessment, the methods of operation and the closure of the landfill and a water quality monitoring program. 12.2.6

Work Place Exposure

Full information regarding health hazards related to chemical agents including metallurgical products or processes should be passed on to the employees concerned. The following are the three main routes of workplace information.

12.2.6.1

Labeling of Packages and Containers

12.2.6.1.1 European Union Substances and preparations may be classified as hazardous for supply or transport purposes. While there are many similarities between the two systems, they are separate from each other and must be dealt with separately. The first step in all cases is to classify the material. Where it is not hazardous for supply or transport, there are no special requirements for packaging, labeling or documentation. Where it is classified as hazardous, certain national and international regulations will apply. The decision on classification rests with the supplier, and must be based on good scientific data. 12.2.6.1.1.1 Supply — In the European Union, directives have created national regulations that include lists that specify the hazard classification for a large number of substances.

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Where a substance is classified, the listed Risk (R) and Safety (S) phrases must be used on all labels and safety data sheets without alteration. The label must also meet stringent requirements regarding content, hazard pictograms/symbols, size, position, method of attachment, and language(s). Where a substance is not listed, the manufacturer must use available data within strict rules to self classify the product correctly, that is, to assign the appropriate risk and safety phrases if it is hazardous or alternatively to classify it as not hazardous for supply purposes. 12.2.6.1.1.2 Transport — If the above classification process has concluded that the product is hazardous for transport purposes, then a series of international regulations will apply depending on the method(s) of transport to be used. These regulations were created initially as a series of model regulations by the UN (known as the Orange Book, or the UN Recommendations on the Transport of Dangerous Goods). They are updated every 2 years and are then translated into a series of modal regulations for the different modes of transport. These are: • International Maritime Dangerous Goods Code (IMDG Code): A set of legally enforceable international regulations for the transport of dangerous goods by sea. • International Cargo Aircraft Only (ICAO) Technical Instructions: These are legally enforceable regulations covering the transport of dangerous goods by air. These result in the publication of the IATA Dangerous Goods Regulations which in themselves are not legally enforceable as it is an industry publication. However, it is based on ICAO and is preferred by most users as it is more user friendly. • European Agreement concerning the International Carriage of Dangerous Goods by Road (ADR)/Regulation concerning International Carriage of Dangerous Goods by Rail (RID)/ European Provisions concerning the International Carriage of Dangerous Goods by Inland Waterways (ADN): These are regulations set up by agreement within Europe for the transport of dangerous goods by road, rail and inland waterways respectively. They are derived from the UN recommendations. Similar regulations exist outside Europe, with corresponding national regulations for each mode of transport, for example, Code of Federal Regulations (CFR) in the U.S. In each case, they specify packaging, labeling, documentation requirements, and signed declarations to ensure: • Use of the correct type of approved tested and UN marked packaging

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• Use of the correct type, and proper fitting of, approved diamond descriptor hazard labels to the packages and, if traveling by sea, also the container • Allocation and display of the correct Proper Shipping Name and UN number for the labeled material • Proper marking of the vehicle transporting the goods • Proper training to all relevant members of staff including special provisions for training vehicle drivers • Provision of documentation and emergency information for use by the driver and emergency services in the event of an accident in transit The regulations for supply and transport are quite specific and very extensive, such that a detailed description cannot be provided here. The reader is referred to the international regulations above, and their own national regulations for the various modes of transport for more detail. A key point to remember however, is that the regulations for all modes of transport to be used must be fully complied with, so that where a given mode has a special requirement, this must be met along with other requirements for other transport modes in use. 12.2.6.1.1.3 Hazardous Waste — There are extensive rules governing the consigning and disposal of hazardous wastes in most countries derived from international treaties. The transport rules will also apply where these materials are classified for transport purposes. 12.2.6.1.1.4 Alloys: A Special Case — A decision in the European Union has resulted in alloys being recognized as a special case within the Dangerous Preparations Directive. This means that inappropriate classification by the use of the current rules for preparations on alloys, which are not simple physical mixtures, can be avoided. The responsibility for this however, rests with the supplier who must provide a body of evidence to prove the case for nonclassification of their alloy. 12.2.6.1.2 United States All Cr-containing substances and mixtures must be labeled as hazardous. Massive alloys are also considered as mixtures and as such have to be labeled. Cr(VI) should contain a cancer hazard warning. Under OSHA Hazard Communication Standard (HCS), the manufacturer, importer or distributor shall ensure that each container of hazardous substances and mixtures is labeled, tagged, or marked with the following information: • Identity of the hazardous substance • Appropriate hazard warning • Name and address of the substance manufacturer, importer, or other responsible party

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12.2.6.2 Material Safety Data Sheets (MSDS) These documents are of prime importance for exporters, importers, and users of Cr-containing products. They are compulsory in some, but not all, countries. 12.2.6.2.1 European Union Directives 91/155/EC, 93/112/EC and 2001/58/EC lay out the MSDS format which must contain information under the following obligatory headings: • Identification of the substance/preparation and of the company • Composition (information on ingredients) • • • • • • • • • • • • • •

Hazards identification First aid measures Firefighting measures Accidental release measures Handling and storage Exposure controls/personal protection Physical and chemical properties Stability and reactivity Toxicological information Ecological information Disposal considerations Transport information Regulatory information Other information

MSDS are adhered to by the EAA (European Economic Area) countries. 12.2.6.2.2 United States The MSDS is of prime importance in the OSHA HCS. The most important rules can be summarized as follows: • Chemical manufacturers and importers (and this includes the metallurgical industries) shall obtain or develop a MSDS for each hazardous chemical they produce or import • Users will have an MSDS for each hazardous chemical they use • Under the HCS, the definition of the label and MSDS (see below) must be the result of an assessment made by the manufacturer, importer, or distributor, based on literature or other toxicological data. This decision is said to be ‘‘performance orientated.”A written assessment must be kept available

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Each MSDS will contain the following information: • Identity of the product (either single substance or compound) • Physical and chemical characteristics of the hazardous chemical • Physical hazards linked with the hazardous chemical: fire, explosion, reactivity • Health hazards linked with the hazardous chemical: symptoms linked with exposure to the said substance and to the other substances, which may be emitted during processing • Primary routes of exposure • The OSHA PEL or the ACGIH TLV • Whether the hazardous chemical is listed in the National Toxicology Program (NTP) Annual Report on Carcinogens or has been found to be a potential carcinogen in the International Agency for Research on Cancer (IARC) monographs or by OSHA • Any generally applicable precautions for safe handling and use which are known to the chemical manufacturer, importer or employer preparing the MSDS, including appropriate hygienic practices, protective measures during repair and maintenance of contaminated equipment and procedures for clean-up of spills and leaks • Any applicable control measures, which are known to the manufacturer, importer, or user preparing the MSDS such as engineering controls, work practice, or personal protective equipment • Emergency and first-aid procedures • Date of preparation of the MSDS or the latest modification • Name, address, and telephone number of the manufacturer, importer, user 12.2.6.3 Induction and Training of Employees Training of workers exposed to hazardous chemicals is obligatory in the U.S. (Hazard Communication Standard), in the EU (Directive 90/394/EEC) and most other countries. NOTE: The geographical regions or countries referenced above represent those areas with the strictest regulations in place. They can be used as guidelines with possible adaptation to the local regulatory trends or provisions. In addition, reference to the International Labor Organization (ILO) Convention No 170 and Recommendation No 177, published in June 1990 and entitled “Safety in the Use of Chemicals at Work” is also recommended.

12.2.6.4 Environmental Control and Monitoring Effective control and monitoring of all emissions to air, water, and land is essential. Wastes deserve special mention because of the potential for these to be moved from one region to another.

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The materials may include: • Recyclable metallic scrap • Slags or resiowings resulting from the manufacture of ferrochromium and stainless steel or chemicals • Filter dust resulting from the production of ferrochromium and stainless steel (including used filter bags) • Sludges from dust abatements • Metal finishing effluents, slurries, or wet cakes • Used CCA treated wood • Used packaging (bags, drums, etc.) that contained Cr chemicals • Cr-containing refractories • Tanning process solid and liquid wastes • End of life articles On an international basis, the UNEP “Basel Convention” of 22 March 1989 on transboundary movements of hazardous wastes and their disposal was implemented in May 1992. The OECD Decision of 30 March 1992 on the control of transfrontier movements of wastes destined for recovery operations classifies recyclable waste in three lists (green, amber, and red) according to the degree of risk–the red list imposes the strictest procedures. The lists are permanently under revision. (Refer to OECD Monograph No 34 “Monitoring and Control of Transfrontier Movements of Hazardous Wastes–Updated July 1993”). For the European Union, refer to the Council Regulation No 259/93 of 1 February 1993 on the “Supervision and Control of Shipments of Waste Within, Into and Out of the European Community”. This text is also based on three categories and became applicable as of May 1994. Under these regulations, it is obligatory for the contracting parties to declare such operations to all concerned authorities, expedition and destination and countries of transit. 12.2.6.4.1 European Union The Integrated Pollution Prevention and Control (IPPC) Regulations (96/ 61/EC) set out requirements for industries to apply Best Available Techniques (BAT) to control emissions to all environmental media (air, water, and land). These Regulations are supported by Best Reference Technology (BREF) notes for various industrial sectors and by other regulations or directives which apply to air, water, and waste classification, landfill, and incineration. 12.2.6.4.1.1 Air — Framework Directives 84/360/EEC and 89/369/EEC deal with atmospheric pollution from industrial plants and municipal waste

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incineration plants respectively and 96/62/EC with air quality, Annex 1 of which lists five agents for priority attention including three metals namely arsenic (As), cadmium (Cd), and nickel (Ni). 12.2.6.4.1.2 Water — Directive 76/464/EEC refers to the “Discharge of Dangerous Substances into the Aquatic Environment” and Cr appears in the “Grey List” of 20 metals. A water framework directive is being formulated based on the requirements of the above directive, the Existing Substances Regulation (ESR), 793/93/EEC and the IPPC Directive 96/61/EC. The Drinking Water Directive 98/83/EC lists limits for several metals. 12.2.6.4.1.3 Waste — The Directives 78/319/EEC (The Hazardous Waste Directive) amended by Council Decision 2001/118/CE, 91/689 EEC, and 94/ 31/EC along with Commission Decision 94/904/EC provide detailed lists of wastes and a systematic basis for classification of wastes consistent with the principles used for classifying products and preparations. The Landfill Directive (1999/31/EC) sets out criteria for preparation, operation, monitoring, and closure of landfill sites according to the type or class of waste deposited. 12.2.6.4.2 Japan 12.2.6.4.2.1 Air — The purposes of the Air Pollution Control Law are, firstly, to protect public health and preserve the living environment with respect to air pollution by controlling emissions of soot, smoke, and particles from factories and other business establishments. Secondly, to control emissions of particulates when buildings are being demolished. Thirdly, to promote various measures limiting the emission of hazardous air pollutants and by setting maximum permissible limits for automobile exhaust gases, etc. 12.2.6.4.2.2 Water — Under the Basic Environment Law, Environmental Quality Standards (EQS) for water pollutants are target levels for water quality to be achieved and maintained in public water. These standards are established to achieve two important goals: (1) to protect human health; and (2) conservation of the living environment. Cr(VI) is included in a list of EQS values for 26 substances for the protection of human health. An EQS for groundwater pollution was also established in 1997. For the living environment, EQS values have been established for Biochemical Oxygen Demand (BOD), COD, Dissolved Oxygen (DO), and other parameters. EQS values for nitrogen (N) and phosphorus (P) were established to prevent eutrophication of lakes and coastal waters. 12.2.6.4.2.3 Waste — The purpose of the Wastes Disposal and Public Cleansing Law is to preserve the living environment and improve public health through restriction of waste discharge, the control of appropriate sorting, storage, collection, transportation, recycling, and disposal of wastes, and the conservation of a clean living environment.

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12.2.6.4.2.4 Soil — Once soil is contaminated, the impacts last for a long time. Therefore environmental quality standards are presently defined based on the Basic Environmental Law for 27 items including Cr(VI). These EQS values are standards against which compliance is desirable for protecting human health and conserving the living environment and are reviewed according to accumulated scientific data on an as necessary basis. The soil EQS stipulates standards considering water quality including purification of groundwater and the farmland standard aims to conserve the production of food. These two standards are used to judge whether soil is contaminated or not and give targets for designing measures to protect against pollution. 12.2.6.4.3 South Africa The stack emission limit is generally 40 mg/m3 for total dust, but is subject to revision with the appropriate authorities. 12.2.6.4.4 United States “Maximum Achievable Control Technology” (MACT)-based rules are being developed for major and area Cr emission sources on an industry by industry basis. In most cases, different standards will be determined for Cr(III) and Cr(VI). These regulations are based on the “CAA of 1990”, which identifies “Chromium Compounds” in its listing of hazardous air pollutants. Sources not covered under MACT standards will be regulated at levels set by state agencies. 12.2.6.5 Chemical Management In an effort to improve the control and management of the widespread use of industrial chemicals, the OECD embarked upon a structured risk assessment review process for all chemicals. This was set out in the Existing Substances Regulation 793/93/EC (ESR), under which producers or importers were required to submit Standardized Information Data Sets (SIDS) on a scheduled basis. As a result of that process a group of five Cr(VI) products is undergoing a risk assessment review leading to further classification and risk reduction measures. Because of slow progress on ESR, the International Council of Chemicals Associations (ICCA) launched a voluntary initiative under which industry was encouraged to submit hazard data dossiers for its products. In February 2001, the EU published a White Paper Strategy for a Future Chemicals Policy containing the following key elements: • Making industry responsible for safety • Extending the responsibility along the supply chain

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• Authorization of substances of very high concern • Subscription of hazardous chemicals Alongside these, a series of end of life directives is emerging in the EU covering vehicles (ELV) Electrical and Electronic Equipment (WEED) and building materials and another on restriction of hazardous substances. Both ELV and WEED mention Cr(VI): restriction under ELV, ban under WEED. Under the precautionary principle on the one hand and sustainable development on the other, collectively these activities mean the following for industries: • Comprehensive characterization of products and their uses to enable human and environmental risk assessments to be made • Replacement of hazardous by less hazardous substances • Best practice benchmarking to international standards • Waste minimization, recycling of waste, and end of life articles In other words, Product Stewardship and Life Cycle Inventory/Assessment. 12.2.7

Product Stewardship

Under this regime, companies take visible responsibility for ensuring that best practice considerations apply to their products throughout the product life cycle. This includes addressing all of the features listed in Section 3 and Section 5 above. • Provide comprehensive information regarding products via communications such as MSDS. This is particularly important for hazardous products and where identified uses of an otherwise nonhazardous product can result in the generation of hazardous products, for example, stainless steel and the formation of Cr(VI) in stainless steel welding fumes. • Discourage inappropriate use(s) of products. • Work in an open and transparent way with customers and regulators as appropriate to resolve issues of concern relating to products and their uses. This may include advice on engineering standards, best practice standards for occupational exposure reduction and environmental controls, workforce education and training, waste minimization/recycling, and end-of-life solutions in line with Sustainable Development.

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12.2.8

Tools

12.2.8.1 Life Cycle Inventory/ Life Cycle Assessment (LCI/LCA) Life Cycle Inventory is essentially a technique for accounting and evaluating all of the inputs and outputs throughout the life cycle of a product under ISO Standard 14040. LCA assembles the above data for different players in the same industry enabling best practice benchmark values to be identified and it can also be used to compare alternative products that might be available for the same end use and gives: • To the producers, a set of benchmark data to support or defend current and future business decisions particularly where there are alternatives • To regulatory or other bodies, a set of current best practice data that can be used to formulate or influence regulations 12.2.9 International Standards Organization (ISO) Since 1993, several ISO standards have been developed and those relevant to the context of the guidelines are: Environmental management systems Environmental auditing Environmental labeling Environmental performance evaluation Life cycle assessment Occupational health and safety Management systems

ISO ISO ISO ISO ISO

14001, 14002, 14004 14010–14012, 14015 14020–14025 14031 14040–14043

ISO 18001, 18002

Members are strongly encouraged to set up and practice health, safety and environmental management systems that include all of the features set out above and to seek corresponding ISO accreditation. The ISO Standards relate all of the inputs and outputs throughout the life cycle. The various inputs and outputs include: product, wastes (air, soil, water), end of life, transport, raw material, energy, and processes.

12.2.10

Ecolabeling

Ecolabeling is a tool to enable producers to indicate the environmental aspects of a product or service. It may take the form of statements, symbols, or graphics on product or package labels, product literature, technical bulletins, etc. An environmental aspect is an element of an organization’s activities, products, or services, which can interact with the environment.

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Ecolabeling forms part of the ISO 14000 series of environmental management standards: • ISO 14020 Basic principles • ISO 14021 Self-declaration environmental claims: terms and definitions • ISO 14022 Self-declaration environmental claim: environmental labeling symbols • ISO 14023 Self-declaration environmental claims: testing and verification methodologies • ISO 14024 Environmental labeling type 1: guiding principles and procedures • ISO 14025 Environmental labeling type 111: guiding principles and procedures 38

Bibliography International Chromium Development Association (ICDA), 2001, Health Safety and Environment Guidelines for Chromium, International Chromium Development Association, December, pp. 19–3.

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13 Chromium(VI) as the Basis for a Toxic Tort: A Legal Perspective

Tod I. Zuckerman

CONTENTS 13.1 Introduction...............................................................................................524 13.2 The Legal Standards for Chromium(VI): Regulatory Background ...............................................................................................525 13.2.1 Exposure to Cr(VI) .....................................................................525 13.2.2 Regulation of Cr(VI) in Drinking Water.................................526 13.3 Plaintiffs’ Various Theories of Liability in Toxic Tort Cases.............527 13.3.1 Strict Liability..............................................................................528 13.3.2 Trespass ........................................................................................529 13.3.3 Waste ............................................................................................530 13.3.4 Nuisance ......................................................................................530 13.3.5 Damages for Nuisance and Trespass ......................................532 13.3.6 Negligence ...................................................................................533 13.3.7 Special Detail that Toxic Tort Plaintiffs Must Allege ...........534 13.4 Expert Witness Testimony Re: Causation ............................................534 13.4.1 Background on Expert Witness Evidence ..............................534 13.4.2 Special Rules Regarding Scientific Evidence .........................535 13.4.3 Other Examples of How Trial Courts Apply Daubert.........537 13.4.4 The Hanford Litigation: Expert Testimony in a Cr(VI) Case ..........................................................................538 13.4.4.1 Background .................................................................538 13.4.4.2 How the Court Treated the Experts’ Testimony ....................................................................539 13.4.4.2.1 The Testimony.........................................539 13.4.4.2.2 The Trial Court’s Rejection of the Testimony .....................................540 13.5 Damages Available for Toxic Torts........................................................541 13.5.1 What are Damages? ...................................................................541

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13.5.2 Theories of Damages in Toxic Tort Personal Injuries Cases ..............................................................................542 13.5.2.1 The Three Basic Types of Toxic Physical Injuries: Acute, Latent, and Subclinical..................542 13.5.2.2 Medical Monitoring ...................................................543 13.5.2.2.1 Background .............................................543 13.5.2.2.2 Under Federal Law ................................543 13.5.2.2.3 Under Common Law.............................544 13.5.2.2.4 Defenses to Medical Monitoring Claims.......................................................546 13.5.2.2.5 If Courts Opt for Medical Monitoring, They Usually Opt for Supervised Funds, Not Lump Sums .......................547 13.5.2.2.6 Emotional Distress and Cancerphobia ..........................................547 13.5.2.2.7 Increased Risk of Cancer.......................549 13.5.3 Theories of Damages in Toxic Tort Property Damage Cases.............................................................................550 13.6 Survey of Cr(VI) Published (and Otherwise Notable) Cases...........................................................................................................551 13.6.1 Case No. 1....................................................................................551 13.6.2 Case No. 2....................................................................................551 13.6.3 Case No. 3....................................................................................552 13.6.4 Case No. 4....................................................................................552 13.6.5 Case No. 5....................................................................................552 13.6.6 Case No. 6....................................................................................553 13.6.7 Case No. 7....................................................................................553 13.6.8 Case No. 8....................................................................................554 13.6.9 Case No. 9....................................................................................554 Endnotes................................................................................................ 554

13.1 Introduction This chapter concerns how the courts have treated chromium(VI) (Cr(VI)), as the basis of toxic tort. However, to gain such an understanding, one must first understand the basics of how our legal system handles toxic torts, since Cr(VI) is just one entry in a very long list of contaminants that have contributed to the development of toxic tort law.1 Thus, this chapter will primarily serve as a primer for nonattorneys and nascent attorneys on toxic tort litigation, with special emphasis on Cr(VI). We will also discuss how the nation’s public health officials view Cr(VI), as the regulatory community’s treatment of Cr(VI) serves as a backdrop for toxic tort litigation based on Cr(VI).

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13.2 The Legal Standards for Chromium(VI): Regulatory Background 13.2.1

Exposure to Cr(VI)

Exposure to Cr(VI) and its compounds can occur in the following workplace processes: • • • • • • • • • • • • • • • •

Photography and photoengraving Laboratories Textile dying Drilling mud Water treatment Chemical manufacturing Timber treatment of wood, wood preservatives containing Cr Glass, clay, and stoneware production (pigments containing Cr) Mining of chromite (FeCr2O4) Production of stainless steels Electroplating (decroplating, i.e., hard plating against corrosion) Welding, thermocutting, grounding of stainless steels Aluminum anodizing Manufacturing of cars, locomotives, ships, machines Manufacturing of electrotechnical equipment Manufacturing of instruments in fine mechanical equipment 2

Many people are exposed to Cr(VI) in many different occupations. Federal and state agency studies (among many others) have stated that the risk for workers exposed to Cr(VI) is quite high for lung cancer 3 and other less deadly diseases. For this reason, in addition to the danger to the general public if Cr(VI) it enters the public water supply, Cr(VI) has received the attention of the nation’s public health officials (see discussion below). Also, public health/environmental advocates and labor unions have, for the last several years, been campaigning litigation to force the U.S. Occupational Safety and Health Administration (OSHA) to better protect workers against Cr(VI). In 2002, they succeeded in challenging OSHA’s refusal to revise its standards for protecting workers from Cr(VI). In Public Citizen Health Research Group v. Chao, the United States Court of Appeals (Third Circuit) ruled as follows: • OSHA’s delay in adopting a new standard for workplace exposure to Cr(VI) was excessive, warranting an order compelling OSHA to act

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Chromium(VI) Handbook • OSHA had no valid scientific or policy based justification for the delay • OSHA had not adopted a new standard nine years after admitting that its existing standard of 100 µg/m3 was inadequate • OSHA had missed 10 self-imposed deadlines for adopting such a standard and had demoted the rulemaking from a “high priority” to a “long term action” with a timetable “to be determined”.

The Third Circuit ordered that OSHA issue a proposed standard for Cr(VI) no later than October 4, 2004 and a final rule no later than January 18, 2006. California has a stricter standard than that of the federal government. For example, CAL/OSHA’s present permissible exposure limit (PEL) for watersoluble and certain water-insoluble Cr(VI) compounds is 0.05 milligram of chromium/meter3 of air (0.05 mg/m3). California allows exposure to be greater than the PEL at times, but only if it is less than the PEL at other times, so that the average exposure for any 8 h work shift is no greater than the PEL. Many scientists, however, believe that even California’s PEL does not adequately protect workers against the danger of lung cancer and thus, they recommend even a more stringent tolerance for Cr(VI).4

13.2.2

Regulation of Cr(VI) in Drinking Water

Regarding drinking water, in the U.S., Cr(VI) is regulated under the federal maximum contaminant level (MCL) for total Cr in drinking water, 100 parts per billion (ppb) or 100 micrograms per liter (µg/L), unless the particular state’s standard is stricter. For example, in California the state MCL for total chromium is 50 ppb. Perhaps no other state has devoted as much study to Cr(VI) as California. Not surprisingly, no state has had a more lively debate on the proper regulation of Cr(VI) than California. Under California Health and Safety Code Section 116365.5, the State of California Department of Health Services (DHS) must adopt an MCL for Cr(VI) by January 1, 2004. Health and Safety Code Section 116365(a) requires the DHS, while placing primary emphasis on the protection of public health, to establish a contaminant’s MCL on a level as close as technically and economically feasible to its public health goal (PHG). A PHG is the contaminant’s concentration in drinking water that does not pose any significant risk to health, derived from a human health risk assessment. (PHGs are also commonly defined as concentrations of drinking water contaminants at which adverse health effects are not expected to occur from lifetime of exposure). In 2001, the DHS added Cr(VI) to its list of unregulated chemicals requiring monitoring. The monitoring data have enabled the DHS to determine the extent to which Cr(VI) exists within drinking water supplies, and at what concentrations. This information is necessary for the DHS to evaluate the costs of treating drinking water containing Cr(VI). As part of its MCL

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process, the DHS has evaluated the technical and economic feasibility of regulating Cr(VI). Technical feasibility includes an evaluation of commercial laboratories’s abilities to analyze and detect Cr(VI) in drinking water, the cost of monitoring, and the cost of treatment required to remove Cr(VI). (Cost must be considered whenever MCLs are adopted.) A Cr(VI) PHG is not yet available, again, in large part owing to the ongoing debate over determining an optimum drinking water standard and as to whether Cr(VI) is a carcinogen by ingestion. As stated, a scientific panel of experts, the Chromate Toxicity Review Committee (the Committee), convened by the University of California has recently (2001) reviewed the health effects of Cr(VI) in drinking water and has forwarded its report to the California Environmental Protection Agency’s Office of Environmental Health Hazard Assessment (OEHHA). The Committee was formed at OEHHA’s request to provide help identifying an optimum drinking water level, or PHG, for Cr(VI) in drinking water. The Committee concluded there was “no basis in either the epidemiological or animal data published in the literature for concluding that ingested Cr(VI) is a carcinogen”. The Committee emphasized that there was no compelling scientific evidence to make a case for or against more restrictive regulation of Cr(VI). For this reason, the Committee recommended that the state of California perform a major study on Cr(VI). The OEHHA accepted this recommendation, and has already begun a 5-year study to develop the nation’s first PHG for Cr(VI). The Committee agrees that until the study is complete, California should continue to consider its current drinking water standard (MCL) of 50 µg/L (50 ppb) for “total” chromium (consisting of Cr(VI) and the much less toxic form of the metal, Cr(III)) to be protective of public health. Lastly, not surprisingly, the Committee has received both praise and criticism (even condemnation) for its work. Usually, this praise or criticism comes from expected sources. For example, defense counsel has commended the Committee, while environmental activists have lambasted it.5

13.3 Plaintiffs’ Various Theories of Liability in Toxic Tort Cases The most prevalent (injury to persons or property) causes of action for pollution are negligence, nuisance, trespass, and strict liability. These common law theories provide a number of remedies without the procedural and burden of proof hurdles that environmental statutes frequently pose.6 For example, the common law plaintiff 7 can recover compensatory and punitive damages, not just pollution cleanup costs, which is the only available remedy under certain environmental statutes.

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13.3.1

Strict Liability

Strict liability is liability without fault. The beginning of the strict liability theory is rooted in the nonnatural uses of land principle promulgated in the seminal English case, Rylands v. Fletcher.8 The Rylands rule “allows for the imposition of liability for damages proximately caused by the defendant’s dangerous, nonnatural use of land regardless of the standard of care defendants utilized in conducting that activity”.9 Courts have applied the strict liability standard when the defendant’s activities have been abnormally dangerous or extremely hazardous. According to noted torts commentators, “the judicial rationalization seems to be that one who conducts highly dangerous activities should prepare in advance to bare the financial burden of harm proximately caused to others by such an activity”.10 Two sections of the Restatement (Second) of Torts11 explain how the strict liability rule applies to damages resulting from certain activities. Section 519 states: 1. Someone who carries on an abnormally dangerous activity is subject to liability for harm to person, land, or chattels of another resulting from any activity, although that person has exercised the utmost care to prevent the harm. 2. This strict liability is limited to the kind of harm, the possibility of which makes the activity abnormally dangerous.12 Also, under Restatement (Second) of Torts, Section 520, the following factors help to determine what constitutes an abnormally dangerous activity: • The existence of a high degree of risk of some harm to the person, land or chattels of others • Likelihood that the harm that results from it will be great • Inability to eliminate the risk by the exercise of reasonable care • Extent to which the activity is not a matter of common usage • Inappropriateness of the activity to a place where it is carried on • The extent to which its value to the community is outweighed by its dangerous attributes13 Plaintiffs prefer strict liability causes of action because they do not need to prove negligence, frequently a hurdle that is too difficult for plaintiffs to negotiate. However, plaintiffs still must prove foreseeability (strict liability does not apply to activities, which, when conducted, were commonplace)14 and causation — they must prove that the conduct subject to strict liability caused the alleged injury. In the late 1970s and 1980s, a trend developed toward adopting strict liability principles in environmental cases. “The decision to impose strict

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liability for environmental torts typically is motivated by recognition of the risk associated with toxic substances, and by a policy judgement that the burden of those risks should be expressly shifted from environmental tort plaintiffs and internalized as a cost of the defendant’s operations”.15 Many states have upheld strict liability claims in environmental cases involving toxic waste storage, disposal, and handling. For example, in Colorado a federal district judge held: “The widespread use of gasoline in no way diminishes its inherently dangerous character. Those who store and dispense gasoline for profit, and who attempt to increase that profit by locating their filling stations at incidental storage facilities in or near residential areas, should be held liable for harm resulting to persons or property from gasoline stored at or leaking from those stations”.16 A Massachusetts federal district court made the same basic ruling.17 Also, in Maryland, a party who placed a large underground gasoline tank in close proximity to a residence and water well was strictly liable.18 The court reasoned that such action involved a high degree of risk of some harm, was not a matter of common usage, and was an activity inappropriate to the residential neighborhood where it occurred.19 Also, Missouri implies strict liability to claims based on radiation damage,20 while New Jersey applies strict liability to claims based on a defendant’s processing, handling, and disposal of radiation.21 In North Dakota, the absence of negligence is not a defense to a claim for crop losses based on a defendant’s placement of wastewater lagoons on property adjacent to a plaintiff’s property.22 Rhode Island follows this rule as well.23 In Mississippi “plaintiff may recover damages by physical invasion of his property on a simple showing that the defendant was responsible for the physical invasion”.24 Moreover, a plaintiff can “recover damages to land caused by physical invasion of the plaintiff’s land by an agency put in motion by the defendant, even if the defendant, has not been negligent”.25 On the other hand, some states invalidate strict liability for many environmental torts. A Louisiana court has held that the dumping of toxic waste in industrial disposal wells is not abnormally dangerous.26 A Virginia court held likewise27 that gas station operations do not qualify as an abnormally dangerous activity that gives rise to strict liability. 13.3.2

Trespass

Restatement (Second) of Torts establishes that: One is subject to liability to another for trespass irrespective of whether the person thereby causes harm to any legally protected interest of the other, if the person intentionally (a) enters land in the possession of the other or causes a thing or a third person to do so; or (b) remains on the land; or (c) fails to remove from the land a thing which the person is under a duty to remove.28

Further, the Restatement provides: (1) a trespass may be committed by the continued presence on the land or structure, chattel, or other things which the

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actor has tortiously placed there, whether or not the defendant has the ability to remove it; (2) a trespass may be committed by the continued presence of the land of a structured, chattel or other thing which the defendant’s predecessor in legal interest therein has tortiously placed there, if the defendant, having acquired his legal interest in the thing with knowledge of such tortious conduct or having thereafter learned of it, fails to remove the thing.29 Trespass is slightly different from nuisance (discussed below) in certain ways. First, nuisance concerns the use and enjoyment of land, whereas trespass focuses on the possessory interest of land, hence the use of the word “entry” and “invasion”. An action in trespass for failure to remove polluting materials is based on a defendant’s intentional conduct. The interference of toxins on the plaintiff’s possessory interest in land can (and frequently does) constitute a trespass. Martin v. Reynolds Metals Co.,30 a 1964 Oregon Supreme Court case, was one of the earliest decisions that recognized such a toxic trespass. In Martin, the court ruled that fluoride compounds migrating from defendant’s facility onto plaintiff’s land constituted a trespass, and awarded damages to plaintiff for the reduction in his land’s grazing value. In so ruling, the court held it was immaterial that the fluoride was invisible to the human eye, and that, generally, there is no size requirement (i.e., the trespassing object can be invisible) for the tort of trespass. Instead, the court focused on the potential damage caused by the fluoride. Lastly, in recent years “toxic trespass” has often been referred to as “chemical trespass”—the terms are synonymous.31 13.3.3

Waste

Black’s Law Dictionary defines waste as follows: Action or inaction by a possessor of land causing unreasonable injury to the holders of other estates in the same land. An abuse or destructive use of property by one in rightful possession. Spoil or destruction, done or permitted to lands, houses, gardens, trees, or other corporeal hereditaments, by the tenant thereof, to the prejudice of the heir or of him in reversion or remainder. A destruction or material alteration or deterioration of the freehold, or the improvements forming a material part thereof, by any person rightfully in possession, but who has not the fee title or full estate. . . 32

As Black’s Law Dictionary establishes, “the primary distinction between ‘waste’ and ‘trespass’ is that in waste the entry is done by one rightfully in possession”. Thus, this cause of action can be used only against former owners and tenants.33 13.3.4

Nuisance

The common law recognizes two different causes action under rubric of nuisance: public nuisance and private nuisance. Public nuisance is common

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defined as an unreasonable interference with a right common to the general public. Circumstances that may sustain a holding that interference with a public right is unreasonable include the following: 1. Whether the conduct involves a significant interference with the public health, the public safety, the public peace, the public comfort, or the public convenience 2. Whether the conduct is proscribed by a statute, ordinance, or administrative regulation 3. Whether the conduct is of continuing nature or has produced a permanent or long-lasting effect that the (defendant) knows (or has reason to know) has significant effect upon the public right34 For examples of public nuisance cases based on toxic tort claims, see Village of Wilsonville v. SCA Services, Inc.35 and United States v. Hooker Chemicals and Plastics Corp.36 In the village of Wilsonville, local government officials sued for a court order to shut down and clean up a hazardous waste landfill which, in their view, endangered their community’s health and welfare.37 In Hooker Chemicals, the state of New York and the federal government sued a chemical company which disposed off wastes in New York’s Love Canal to recover costs incurred in preventing further migration of waste, to relocate families, and for other actions taken in response to the waste. The state of New York successfully moved for summary judgement, obtaining a determination that defendant was liable as a matter of law for the creation of a public nuisance at the Love Canal, as well as for the cleanup costs it incurred at the site.38 A private nuisance is defined as a “nontrespassory invasion of another’s interest in the private use and enjoyment of land”.39 This invasion must result in an injury that is both “substantial and unreasonable” to plaintiff’s use and enjoyment of land.40 “Substantial” obviously means significant: a slight inconvenience or annoyance is not actionable. An unreasonableness claim “requires the finders of fact to evaluate . . . the severity of the harm relative to its social value or utility”.41 Moreover, evidence concerning the degree of a defendant’s interference in the use and enjoyment of the plaintiff’s land and the reasonableness of the interference in the context of wider community interests controls the amount of damages recoverable, once liability is established.42 Private nuisance necessarily involves interference with use and enjoyment of land; a public nuisance does not.43 For example, groundwater pollution is a public nuisance as well as a private nuisance “if the polluted water under property comes into direct contact with and harms the owner or his property”.44 A toxic tort plaintiff may sue simultaneously for both public nuisance and private nuisance if (1) there is an interference with the public’s right, and (2) plaintiff has sustained special injuries as a result of defendant’s conduct.

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As for ex-owners and ex-occupiers, courts are split on the issue of whether a subsequent owner/occupier may sue a former owner/occupier for polluting his own property. As of June 2003, California is the only state that permits such claims. For example, see Newhall Land Farming Co. v. Superior Court,45 where the court held that the landowner could sue the prior owners of the land for nuisance, resulting from the contamination of soil and groundwater that occurred while defendants were operating a SAS processing plant on the property. But, see the following toxic tort cases, where courts refused to permit nuisance actions by property owners against previous owners: Rosenblatt v. Exxon Co. U.S.,46 and Drovin v. Ridge Lumber, Inc.47

13.3.5

Damages for Nuisance and Trespass

There are many similarities between nuisance and trespass in environmental cases. For example, in a hazardous waste cases the typical “measure of damages for trespass and nuisance (public and private) cases involving ‘permanent’ (or indefinite) (injury) is the diminished market value of the property, plus consequential losses for the loss of use of the land, or for from discomfort or annoyance to the possessor”.48 In contrast, “damages from ‘temporary’ entry, that is, injury that is remediable, typically include compensation for the cost of remediation or repair to the property or the property’s diminished rental or use value during the period in which the injury persists, plus consequential damages”.49 Sometimes torts recur and, thus, give rise to several claims. These types of claims are “continuing torts”. Groundwater pollution is a good example. Without steps to halt or spread, pollutants in groundwater will migrate vertically and laterally because of events that occurred many years ago. Because states have statutes of limitation for nuisance and trespass that range from 1 year to 10 years, labeling a nuisance or trespass as either permanent or continual can make or break a plaintiff’s case. If a nuisance or trespass is considered permanent, the plaintiff has only one cause of action, and only one opportunity to recover. Thus, if the statutes of limitations runs, the plaintiff can take no action, since successive actions are not permitted for permanent torts. However, if the trespass or nuisance is deemed continuing, “successive actions (are) maintained for the damages occurring from time to time”.50 When a continuing or recurring injury result from a continuing trespass or nuisance, a cause of action for the original wrong arises when the wrong is committed, and separate and successive causes of action for consequential damages arises when they are sustained. Accordingly, as long as the cause of injury exists and the damages continue to occur, a plaintiff may recover for damages that accrue after the statutory period for the original wrong, while a cause of action based solely on the original wrong may be barred.51 In theory the difference between a continuing nuisance or trespass and or a permanent nuisance or trespass lies in the “ability of man to abate the

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nuisance”.52 If the nuisance recurs frequently or is constant, then the nuisance or trespass is continuing.53 If the nuisance or trespass cannot be abated, then it is permanent.54 In this regard, the Arizona Supreme Court held that: If a nuisance is of such nature that although the thing itself may continue, yet its injury to another may be abated by human agency, and the owner or perpetrator of the nuisance fails to abate it, the nuisance is a continuing one, and one action does not exhaust the remedies of the party injured. If, however, the thing is of such character that it cannot be maintained without continuing to be, in the legal sense, a nuisance, it is permanent in its nature, and the rights of the injured party are exhausted by one action.55

13.3.6

Negligence

The elements of a cause of action for negligence are: 1. A duty recognized by law, requiring a person to conform to a certain standard of conduct, for the protection of others against unreasonable risk 2. A breach of the duty to conform to the required standard 3. A reasonably close causal connection between the conduct and the resulting injury (proximate cause or legal cause) 4. Actual loss or damage resulting to the interest of another56 Many courts have upheld environmental liability claims based upon negligence. For example, see Sterling v. Velsico Chemical Corp.,57 a class action against a chemical corporation for property damage and personal injuries brought by residents who lived near the chemical corporation’s waste burial site. The court ruled for plaintiffs and awarded compensatory damages of over $5 million and punitive damages of $7.5 million.58 In its specific finding of negligence, the court listed 21 specific instances of actionable negligence.59 Also, there is a type of negligence known as “negligence per se”. Under a limited number of circumstances, statutes or ordinances describe the level of conduct of a person held to a negligence pro se, or negligence as a matter of law, standard.60 To hold a defendant negligent for violating a statute or ordinance, a plaintiff must prove that his injuries “were of a kind that the statute or ordinance was enacted to prevent harm. Further, (the plaintiff) must show that the statute or ordinance prescribes or proscribes specific conduct and that the conduct at issue proximately caused the alleged harm”.61 Under the majority rule, this requirement encompasses all risk or harms that are a reasonably foreseeable result of a statutory violation.62 Since environmental statues and regulations are prophylactic and are designed to protect the health, safety, and welfare of the general public were specific groups likely to come into direct or indirect contact with hazardous substances, negligence pro se is a frequent cause of action in environmental liability cases.

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13.3.7

Special Detail That Toxic Tort Plaintiffs Must Allege

In a toxic tort personal injury lawsuit, the plaintiffs must allege specific facts detailing how the conduct caused the injury. In California, for example, a toxic tort plaintiff must set forth in the complaint the following allegations (this is representative of the rest of the country): 1. That a person was exposed to each of the toxic materials claimed to have caused a specific illness; (an allegation that the person was exposed to “most or perhaps all” of the substances listed is inadequate) 2. Each product or toxic waste that allegedly caused the injury must be identified (it is not enough to allege that the toxins in a defendants’s product or waste caused it) 3. As a result of the exposure, the toxins entered the person’s body 4. The person suffers from a specific illness, and each toxin that entered the person’s body was substantial factor in bringing about, prolonging, or aggravating that illness (except in a case governed by the principle of liability based on market share for uniform product)63

13.4 Expert Witness Testimony Re: Causation 13.4.1

Background on Expert Witness Evidence

A toxic tort plaintiff always must retain expert witnesses to establish causation. Failure to produce such expert evidence means certain failure, almost always in the form of a summary judgement for the defendant(s).64 Expert testimony is the opinion of a witness who has special skill, information, or knowledge concerning an issue that is under consideration by the judge or jury (the trier of fact). His expertise may have been gained through academic study, observation, investigation, or experience.65 The trial judge should not allow an expert witness to testify (to give his opinion) unless the jurors, owing to their lack of knowledge or experience, are incapable of making their own conclusions from the facts presented at trial: experts are not permitted to testify on matters of common knowledge.66 An expert must be properly qualified to testify and will be examined and cross-examined to establish evidence (or lack of evidence) about qualifications.67 An expert witness’ opinion should be based on the facts in evidence — not on other’s opinions — but it may be (and often is) based on facts related to the expert witness by other witnesses. Also, expert witness evidence — just as all evidence — should not be admitted (heard by the jury) unless it is both

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relevant and material. Evidence is relevant if it helps to prove or disprove a disputed fact and thus, aid the resolution of the inquiry. The relationship between the fact offered and the fact in dispute is called “relevancy” — when an expert witness offers to prove a fact/render an opinion, the expert is saying there is a logical relationship between the fact offered/opinion rendered and the fact in dispute. Evidence is material if it is sufficiently important to influence the trial’s result. The trial judge determines materiality and relevance. If the judge believes the fact (or opinion) has little materiality, though relevant, the judge can exclude it as immaterial.68 (In federal courts and some state courts, the definition of “relevance” includes materiality — see, for example, Federal Rules of Evidence, Rule 401, which states: “‘Relevant evidence means evidence having any tendency to make the existence of any fact that is of consequence to the determination of the action more probable or less probable than it would be without the evidence”.)

13.4.2

Special Rules Regarding Scientific Evidence69

For expert witness testimony on causation, the proponent (either plaintiff or defendant) of the proposed testimony must show not only that it is relevant and material, but also reliable. Before 1993 almost all federal courts, and many state courts, applied the “general acceptance” rule of a 1923 case, Frye v. United States.70 Under this standard, the proponent of expert scientific evidence must satisfy the following three-pronged test: • The technique used was sufficiently reliable that it has earned general acceptance in its scientific community or field • The witness testifying to the substantial reliability of the scientific method is qualified as an expert to give an opinion on the subject • The correct scientific procedures were used71 In 1993, in Daubert v. Merrell Dow Pharmaceuticals, Inc.,72 the United States Supreme Court ruled that the Frey rule set forth above was at odds with the Federal Rules of Evidence, Rule 702, which reads: If scientific, technical, or other specialized knowledge will assist the trier of fact to understand the evidence or to determine a fact in issue, a witness qualified as an expert by knowledge, skill, experience, training, or education, may testify thereto in the form of an opinion or otherwise, if (1) the testimony is based upon sufficient facts or data, (2) the testimony is the product of reliable principles and methods, and (3) the witness has applied the principles and methods reliably to the facts of the case.

The trial court has a legal duty to scrutinize an expert’s causation theory. Since 1993, the United State Supreme has ruled three times that trial courts

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must exercise a gatekeeper role to exclude weak (unreliable) science. Daubert,73 Supra; General Electric Co. v. Joiner,74 and Kumho Tire Company, LTD v. Carmichael.75 Each time the Supreme Court has amplified the federal trial court’s duty under Fed. R. Evid. 702 to exclude unreliable expert testimony. Also, many state’s supreme courts have endorsed the same (or very similar) roles for their trial courts under their respective state evidence codes. The 1993 Daubert decision sets forth the trial court’s task in reviewing scientific causation testimony. In Daubert, the plaintiff had eight experts who were prepared to testify, based on their scientific knowledge, that use of the drug Bendectin during pregnancy caused birth defects. The district court (again, the name for trial courts in the federal court system), ruled that the experts’s testimony linking the drug to birth defects was inadmissible because the opinions were not based on epidemiological studies, and, therefore, the science did not meet the “general acceptance” test of Frye v. United States. The Supreme Court remanded the case, and instructed the lower court to consider the experts’s testimony under new “Daubert” factors. To assist the trial judge in making a proper assessment, Daubert established a four prong test for reliability. Although not exclusive, these “Daubert factors” are the primary tests for the admission of scientific evidence: 1. Whether the theory underlying the opinion is generally accepted within the relevant scientific community 2. Whether the theory has been published and positively peerreviewed 3. Whether the expert’s technique or theory can be or has been tested—whether the expert’s theory can be challenged in some way, or whether it is instead simply a subjective, conclusory approach that cannot reasonably be assessed for reliability 4. The known or potential rate of error in the expert’s analysis76 Thus, though “general acceptance” still is a factor for the federal trial court to consider, it is not a threshold requirement, as the test under Rule 702 is more flexible. To make certain that the trial courts fulfill this “gatekeeper” function, the Supreme Court imposed the burden of proving admissibility squarely on the proponent of the scientific evidence.77 The Daubert criteria must be proven by “objective, independent validation of the expert’s methodology”.78 Thereafter, the U.S. Supreme Court, in its 1997 Joiner decision, expanded the trial court’s gatekeeper function. In Joiner, the Court stated the trial court must also determine that the expert’s conclusions rationally flow from the expert’s methodology. In Joiner, the district court, applying Daubert, excluded plaintiff’s expert, who had sought to testify that plaintiff’s exposure to polychlorinated biphenyl (PCB) caused his lung cancer. The expert had declared that his testimony was supported by an animal study and human epidemiology studies. On

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appeal to the Eleventh Circuit, the court reversed — it held that the federal rules of evidence preferred admissibility. However, the U.S. Supreme Court reversed, and held that the district court’s ruling should have been entitled to “deference” under the abuse of discretion standard. Concerning the animal studies, the court stated that the “infant mice” in the studies had massive doses of PCBs, but the plaintiff was an adult human with a much smaller exposure. Also, the court emphasized that the type of cancer that the mice developed was not the small cell carcinomas of plaintiff’s lung cancer. And, as respects the plaintiff’s complaint that the trial judge excluded the expert testimony based on the expert’s conclusions, not his methodology, the court ruled “conclusions and methodology are not entirely distinct from one another. Trained experts commonly extrapolate from existing data. But nothing in either Daubert or the federal rules of evidence requires a district court to admit opinion evidence which is connected to existing data only by the ipse dixit of the expert. A court may conclude that there is simply too great an analytical gap between the data and the opinion preferred”.79 Daubert provides a framework for excluding bad science to prevent the jury from being misled into believing that there is liability when none exists. Sutera v. Perrier Group of America AM.80 “Daubert established the duty of the trial judge to play the role of gatekeeper, ensuring that the fact-finding process does not become distorted by . . . ‘junk’ science”, Whiting v. Boston Edison Company:81 The trial court’s duty to exclude unproven and misleading scientific evidence is “especially sensitive in cases ‘where the plaintiffs claim that exposure to toxic substances caused their injuries, (because a) jury blindly accepts an expert’s opinion that conforms with their underlining fears of toxic substances without carefully considering or examining the basis for that opinion’” (quoting O’Conner v. Commonwealth Edison Company82).

13.4.3

Other Examples of How Trial Courts Apply Daubert

There are many cases, which have excluded scientific evidence proffered in support of toxic tort claims because it fails one or more prongs of the Daubert test. A good example is the Eighth Circuit’s decision in Wright v. Willamette Industries Inc.83 In Wright, the defendant owned a fiberboard manufacturing plant that was 1.6 km from the plaintiff’s home, and did not dispute that its plant emitted wood fiber particles containing formaldehyde. The defendant also conceded the formaldehyde emissions exceeded industry and state standards, and did not contradict plaintiff’s evidence that emission from the plant fell like “snow” on the plaintiff’s property (fibers from the plant were found in the plaintiff’s air conditioner). Finally, emissions from the plant were found in the plaintiff’s urine and sputum. The family’s treating physician testified the family’s symptoms—sore throats, headaches, water eyes, runny noses, dizziness, and shortness of breath—were probably related to their exposure to plant emission.84

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Nevertheless, the Eighth Circuit ruled that the plaintiffs had not produced enough evidence to submit their claim to the jury. The court explained that the plaintiffs’ failed to prove what amount of such fibers would pose a risk of harm to human beings.85 The Willamette Court held that the treating physician’s opinion “was simply speculation” and should have been excluded under Daubert, since it was not based on knowledge of the level of plaintiffs’ exposure to formaldehyde containing the wood fibers.86 The same result should occur when the expert’s conclusions about causation are based on studies involving chemicals not at issue in the litigation. For example, in Lopez v. Wyeth-Ayerst Laboratories, Inc.,87 the court determined that plaintiff’s expert relied on swine flue studies regarding flue vaccine at issue—this, ruled the court, was inherently unreliable. Thus, the court granted defendant’s motion in limine88 (“at the outset”) barring the expert’s testimony, and, at the same time, granted defendant summary judgement. Likewise, see Lust v. Merrill Dow Pharmaceuticals, Inc.,89 where the district court granted the defendant’s motion in limine to bar the plaintiff’s expert testimony because no human epidemiological or animal studies had linked the particular drug with the particular condition at issue and because the expert’s own article had not been peer-reviewed. The Ninth Circuit affirmed, and held: “When a scientist claims to rely on a method practiced by most scientists, yet presents conclusions that are shared by no other scientist, the District Court should be wary that the method has not been faithfully applied. . . . [T]he District Court can exclude the opinion if the expert fails to identify and defend the reasons that his conclusions are anomalous”. See also, Police Assn. of New Orleans v. City of New Orleans,90 where the court affirmed the district court’s decision to bar plaintiff’s expert testimony that vapors caused plaintiff’s illnesses since the expert did not follow correct toxicological methodology. Probably, the most illuminating case concerning how a court is apt to treat expert testimony regarding Cr(VI) exposure is the Hanford Litigation, which we discuss immediately below.

13.4.4

The Hanford Litigation:91 Expert Testimony in a Cr(VI) Case

13.4.4.1 Background The Hanford litigation was a consolidation of separate lawsuits filed by various groups of plaintiffs starting in 1990. The approximately 3,000 plaintiffs in this consolidated litigation alleged that they had suffered personal injury, or would suffer future injury as result of exposure to radioactive and nonradioactive emissions (principally, Cr(VI) emissions) from the Hanford Nuclear Reservation located in southeastern, Washington. They sought damages for present injuries including thyroid cancer, nonneoplastic thyroid diseases, and various nonthyroid cancers. They also sought damages based on future injuries. Under contract with the United States Department of Energy (DOE) and its predecessors, the defendants (E.I. Dupont De Munors Co., General

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Electric Company, UNC Nuclear Industries, Atlantic Ritchfield Company, and Rockwell International Corporation) operated the Hanford Nuclear Reservation at various times from 1943 to 1987. For most of that period, the Hanford facility’s function was to produce plutonium (Pu) for use in nuclear weapons. In addition to plutonium-239 (Pu-239 or 239Pu), other radionuclides were created during (Pu) production. The consolidated litigation was divided in phases. Phase I dealt with both plaintiffs’ and defendants’ written discovery. In Phase II the parties focused on causation, through preparation of expert witness reports and the conducting of expert witness discovery. Phase II became know as the “Generic” causation phase. Defendants’ summary judgement motions followed the completion of Phase II. After resolution of these motions, the remaining claims were to proceed into Phase III, which would have covered individual causation discovery, liability, and other remaining issues. Since the court considered causation to be the key issue, it opted to decide causation issues before addressing liability issues (i.e., breach of duty). The defendants’ summary judgement motion sought dismissal of a majority of the plaintiffs’ claims on the grounds that their alleged health conditions could not be linked to the Hanford emissions. In pertinent part, plaintiffs made claims for gastrointestinal (GI) cancer based on exposure to Cr(VI). Hanford’s original eight nuclear reactors were cooled by filtered, chemically treated water from the Columbia River which then was held for a period in retention basins, and then returned to the Columbia River. To prevent or reduce corrosion of reactor piping during the cooling process, Hanford’s operators sometimes added sodium dichromate (Na2Cr2O7) to the river water before it entered the reactor. Na2Cr2O7 contains Cr(VI). Thus, when the cooling water was returned to the river, it contained Cr(VI).

13.4.4.2 How the Court Treated the Experts’ Testimony 13.4.4.2.1 The Testimony Plaintiffs’ case for damages caused by Cr(VI) was based on two expert reports, one by Dale Hattis, Ph.D (a geneticist), and one by Sydney A. Katz, Ph.D (a chemist). Katz concluded that the amount of Cr(VI) discharged into the river, “represents a long-term hazard to public health and environmental quality.” Plaintiffs’ counsel asked Katz to comment about possible “synergistic” effects caused by the Cr(VI) with other substances discharged into the river, including radioactive Pu. In a letter addressed to plaintiffs’ counsel, Katz reported that he found no information on multifactorial cancer risk for exposure to Cr and Pu, or to exposure to Cr and arsenic (As), and similarly, was unable to find any information on studies connecting Cr exposure and radiogenic carcinoma. However, Katz stated that plaintiffs’ counsel were “probably correct” that “radiation insult coupled with chemical insult could well increase the cancer risk”.

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As for Dr. Hattis, he analyzed the population risk associated with ingestion of Cr(VI) by first defining his assumed exposed population, then by estimating population dose, and then by selecting risk coefficient (risk of GI cancer preunitive dose), and finally multiplying his risk coefficient by the population dose that generates an estimated number of cancers. The combination of his report was a table which provided a “plausible range of cancer cases from drinking water ingestion of Cr(VI) ranging from less than 1 case in a million to over 10 cases in a million.” 13.4.4.2.2 The Trial Court’s Rejection of the Testimony The trial court found that both Hattis’s and Katz’s proposed testimony were irrelevant to plaintiffs’ causation burden of proof. First, as respects Hattis, the court stated that because Hattis did not “opine the Cr(VI) doses from Columbia River ‘more than doubled’ the risk of gastrointestinal (GI) cancer”, his analysis had to be disregarded. The court explained: “Plaintiffs’ burden of proof at this stage of the proceedings is to show the dosage of which it is more likely than not Cr(VI) exposure causes GI cancer (or any other health effects).” Consequently, as Dr. Hattis proposed testimony did not so show, the court excluded it. Second, turning to Dr. Katz, the court held that his “proposed testimony (did) not address chromium concentration at the concentrations alleged to exist in the Columbia River and (did) not attempt to tie those concentrations to any health effects. Furthermore, in his risk analysis, Hattis places no reliance on Katz. Indeed Hattis does not even mention Katz’s report.” The court continued: Katz’s report is wholly irrelevant, not only for the proposition that, ingested Cr(VI) is “more likely” to be the cause of any health effect, but also for the proposition that it is “capable of causing” any particular health effect in humans. Having Dr. Katz testify in general about the biological and the environmental chemistry of Cr is no assistance whatsoever to a jury in determining whether Cr(VI) is “capable of causing” certain health effects, or more improbably, whether it is “more likely than not” a cause of certain health effects.

The court also rejected the Katz and Hattis proposed testimony on reliability grounds. First, as respects Hattis, the court the noted that Hattis’s risk coefficients were generated only for purposes of the litigation, and there was no showing whatsoever that before the litigation, or outside the litigation, Hattis conducted any independent research on Cr(VI) and its effects on humans, especially via ingestion. Also the court emphasized that Hattis’s risk coefficients and the methodology he used to produce them, had not been peer reviewed or published, the two principal ways for evidence to satisfy Daubert’s reliability prong. Moreover, the court held that there was no showing of the scientific community’s “general acceptance” that the ingestion of Cr(VI) is “capable of causing”

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cancer in humans. The court noted that a California Environmental Protection Agency (Cal EPA) committee’s recommendation that Cr(VI) be considered carcinogenic “hardly amounts to a general acceptance.” This recommendation has not even been adopted by the Cal EPA. “The court also emphasized that the Agency for Toxic Substances and Disease Registry (ATSDR) has not classified ingested Cr(VI) as carcinogenic, nor has the U.S. Environmental Protection Agency (USEPA) or the International Agency for Research on Cancer (IARC)”. Thus, the court held that when these factors are considered, along with Hattis’s “methodological shortcomings,” it left the court no choice but to find Hattis’s analysis, including his risk coefficients, unreliable for the proposition that ingested Cr(VI) is capable of causing GI cancer in humans, or that ingested Cr(VI) is a “more likely than not” cause of any of the plaintiffs’ GI cancers. As respects Katz, the court held that to the extent his report purported to opine ingested Cr(VI) was capable of causing certain health effects in humans, it was “scientifically unreliable”. The court noted that the plaintiffs had not produced any risk assessment concerning noncarcinogenic toxicity, and that Katz did not discuss risk. The court concluded that the plaintiffs’ produced no evidence from which a jury could reasonably infer that it was more likely than not that any of the plaintiffs’ noncarcinogenic toxicity was owing to Cr(VI) exposure from the Columbia River. Thus, the court struck the Katz and Hattis report on Daubert grounds and granted summary judgement for the defendants in all plaintiffs’ health effect claims which were based on alleged exposure to Cr(VI) emissions to the Columbia River.

13.5 Damages Available for Toxic Torts 92 13.5.1

What Are Damages?

“Damages” is the money that a court will award a plaintiff in a lawsuit to compensate for a loss or injury that the plaintiff sustained because of the defendant’s wrongful conduct. Damages should not be confused with costs, which are the expenses of the lawsuit that a judge (sometimes) orders a losing party to pay, or with the verdict which is the jury’s final decision, after all of the evidence from both sides has been presented. Damages are based on the principles of just compensation, indemnity, or reparation for loss or injury. The purpose of awarding damages is to assist the injured party regain, as much as possible, her position/condition before the injury. There are several types of damages. Special damages are those which were caused by the injury and include medical and hospital bills, ambulance charges, loss of wages, property repair or replacement costs, or loss of money due on a contract.93 General damages are damages for which no exact monetary sum can be calculated. They include pain and suffering, future medical problems and the crippling effect of an injury, loss of ability to perform various

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actions, shortening of life span, mental anguish, loss of companionship, loss of reputation (in a libel suit, for example), humiliation from scars, loss of anticipated business, and other harm. They are distinguished from special damages (discussed above), which, again, are for specific costs, and from punitive damages (discussed below). Future Damages are those damages the plaintiff is entitled to recover “for all the detriment certain to result in the future”. Also, because of the fundamental principle that damages should be compensatory only, future damages are reduced to present value.94 Punitive (also known as “exemplary”) damages is money that the judge or jury awards to the plaintiff over and above what will compensate the plaintiff for injuries and/or property loss. Those damages are awarded only when the defendant acted in a malicious or violent, or oppressive, or fraudulent, or wanton, or grossly, reckless way in causing the special and general damages to the plaintiff. Occasionally, punitive damages can be greater than the actual (special and general) damages. “The primary purposes of punitive damages are to punish wrongdoers and to deter the commission of wrongful acts”.95 Lastly, speculative damages are not permitted. For example, a standard California personal injury jury instruction reads as follows: Do not (award a party) (include) speculative damages, which means compensation for future loss or harm which, although possible, is conjectural or not reasonably certain. However, (if you determine that a party is entitled to recover,) you should compensate a party for loss or harm caused by the injury in question which is reasonably certain to be suffered in the future.96

13.5.2 13.5.2.1

Theories of Damages in Toxic Tort Personal Injuries Cases

The Three Basic Types of Toxic Physical Injuries: Acute, Latent, and Subclinical Acute injuries in toxic tort case are physical injuries that occur immediately from exposure to toxics. Latent toxic tort injuries are physical injuries that do not follow immediately, but, instead, possibly may not manifest themselves until many years (even decades) after the event that caused the exposure to the toxic matter. For example, cancer may not develop until 40 years after exposure to a carcinogen. A trial expert once testified as follows regarding latent injuries: “If you picture one cell of thousands, of millions, in the body that is being exposed, you may get a switch turned on. That’s the biological damage, injury, insult, whatever term you wish to use, that occurs on exposure. It may be actually seen in terms of 20 years from now when a cancer becomes evident, or it may never be seen”.97 Subclinical toxic tort injuries concern chromosomal or other cellular injuries resulting from toxic exposure. The same trial expert testified on these types of injuries: “Something occurs, we (scientists) believe, with the genetic material in the cell to start the process, and along the way other things affect that cell, flip more switches, make it ultimately become a cancer cell and ultimately manifest as a physical cancer”.98

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13.5.2.2 Medical Monitoring 13.5.2.2.1 Background Toxic tort plaintiffs often claim that the defendants should pay for medical monitoring (also known as ‘‘medical surveillance”) for the remainder of plaintiffs’ lives to check: (1) whether any diseases have manifested; and (2) that certain early preventative measures are taken. Medical monitoring damages are sought in the form of either a lump sum payment equal to the present value of the anticipated expense, or a court-monitored health program that the defendants finance. Medical monitoring, of course, is not limited to toxic tort cases; it has been available for years in accident cases (cars, airplanes, etc.), but the term medical monitoring usually was not used. Instead, the traditional term “future medical expenses” (also known as “future meds”) was understood to cover the monitoring expenses that necessarily resulted from increased susceptibility to future injury because of the accident.99 In the 1980s, the term “medical monitoring” became associated with toxic tort suits, where workers, or neighbors of polluted plants or landfills were exposed to carcinogens with lengthy latency periods. 13.5.2.2.2 Under Federal Law If plaintiffs make the medical monitoring claim under federal law, they usually cite to a federal statute, the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), also, commonly known as “Superfund,” which Congress enacted in 1980. CERCLA authorizes two types of responses to releases or threatened releases of hazardous substances that may endanger public health or the environment: (1) short-term removals, where actions may be taken to address releases or threatened releases requiring prompt response; and (2) long-term remedial actions that permanently reduce the dangers of releases or threats of releases of hazardous substances that are serious but not immediately life threatening. CERCLA defines “response” to include “removal”, and defines removal as “any action necessary . . . to monitor, assess, and evaluate a release”. Plaintiffs argue that these provisions give them the right to seek recovery for medical monitoring costs. However, the overwhelming majority of federal courts have held that CERCLA does not create a right to medical monitoring costs. See, for example the following cases: Durfey v. E.I. DuPont De Nemours Co.;100 (medical monitoring costs are not response costs under CERCLA); Price v. U.S. Navy;101 (the context in which the ‘monitoring’ and ‘health and welfare’ language appears is directed at containing and cleaning up hazardous substance releases. . . . The specific examples in §960123 are all designed to prevent and mitigate damage to public health by preventing contact between the spreading contaminants and the public. Monitoring long-term health has nothing to do with preventing such contact); Daigle v. Shell Oil Company;102 (a review of CERCLA’s legislative history “confirm[s] the obvious implication that Congress, intentionally deleted all personal rights to recovery of medical expenses from CERCLA”); Redland Soccer Club, Inc. v. Department of Army;103

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(The statutory definition of response is ‘remove, removal, remedy, and remedial action’ . . . 42 U.S.C. §9601(25). The definitions of remove, removal, remedy, and remedial action uniformly refer to acts involving cleanup of hazardous sites or assessment of environmental damage at those sites. There is no indication that Congress meant to include health risk assessment in the category of response costs). Woodman v. U.S.;104 (“The Court finds that future medical monitoring expenses are not CERCLA response costs”.); Ambrogi v. Gould, Inc.105; ([T]raditional remedies of state tort actions are available to an aggrieved individual. Since a statute should be construed in harmony with the sphere of legal remedies available, Congress surely did not intend to create an overlap between traditional state tort claims and a “new” CERCLA federal toxic tort action. Thus, the purpose of the Act, that is, the removal of hazardous waste from the environment, would seemingly preclude recovery of response costs). As for the courts which have concluded that medical monitoring costs are recoverable under CERCLA, see the following cases: Williams v. Allied Automotive;106 (Costs of future medical monitoring may be recovered and consistent with response costs, if plaintiffs prove that such costs are necessary and consistent with the National Contingency Plan).; Brewer v. Ravan;107 (“CERCLA’s legislative history clearly indicates that medical expenses incurred in the treatment of personal injuries or disease caused by an unlawful release or discharge of hazardous substances are not recoverable . . . . To the extent that plaintiffs seek to recover the cost of medical testing and screening conducted to assess the effect of the release or discharge on public health to identify potential public health problems presented by the release, however, they present a considerable claim under CERCLA; Adams v. Republic Steel Corporation;108 (“Under [CERCLA], a party may recover ‘response costs,’ which have been stated to include such costs as medical testing”.…These costs must be part of a “cleanup” or response to a hazardous waste problem, however, and a private right of action for damages only is not available under the Act); Pinole Point Properties, Inc. v. Bethlehem Steel Corp.109; Jones v. Inmont Corp.110; (Damages for medical testing appear to meet the definition of “removal” expressed in CERCLA). Besides CERCLA, another federal law, the Price-Anderson Act,111 is sometimes used as a basis for medical monitoring claims. The Price-Anderson Act, which became law in 1957, was designed to ensure that sufficient monies would be available to pay the public’s liability claims for personal injury and property damage in the event of a catastrophic nuclear accident. Although medical monitoring costs are recoverable for bodily injury, sickness, or disease resulting from nuclear incidents, they are not recoverable for purely emotional distress. 13.5.2.2.3 Under Common Law As respects common law claims, both federal and state courts have traditionally ruled that medical surveillance costs are not allowed unless there is

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accompanying physical harm. See Schweitzer v. Consolidated Rail Corp.112; (If mere exposure to asbestos were sufficient to give rise to a Federal Employers Liability Act (FELA) cause of action, countless seemingly healthy railroad workers who might never manifest injury, would have tort claims cognizable in federal court. It is obvious that proof of damages in such cases would be highly speculative, likely resulting in windfalls for those who never take ill and insufficient compensation for those who do. Requiring manifest injury as a necessary element of an asbestos-related tort action avoids these problems and best serves the underlying purpose of tort law: the compensation of victims who have suffered. Therefore, we hold that, as a matter of law, F.E.L.A. actions for asbestos-related injury do not exist before manifestation of injury); Ball v. Joy Mfg. Co.113; (Under West Virginia’s worker’s compensation statute, a mere exposure to toxic chemicals is not a compensable injury. Instead, employees must also show that “exposure is causally linked to a disease they presently suffer”). Other courts however, have ruled medical surveillance costs are recoverable without current physical harm. See, for example, Simmons v. Pacor, Inc.114; Redland Soccer Club, Inc. v. Department of the Army;115 Hansen v. Mountain Fuel Supply Co.116; Burns v. Jaquays Mining Corp.117; and Ayers v. Jackson Township.118 These courts allow for medical surveillance claims, and rationalize that such claims are not speculative since the jury issue is simply whether the plaintiff needs medical surveillance. (In contrast, increased risk of cancer claims is unduly speculative since the courts are forced to anticipate the probability of future injury.) In jurisdictions which allow for recovery of medical monitoring costs without proof of physical harm, a toxic tort plaintiff still must prove the following elements: 1. Plaintiff was exposed, in greater than normal background levels, to a proven hazardous substance 2. The exposure was owing to defendant’s actions 3. As approximate result of this exposure, plaintiff suffers a “significantly” increased or “greater than average” risk of contracting a serious latent disease 4. That increase risk makes periodic diagnostic medical examination reasonably necessary under contemporary scientific principles 5. Monitoring and testing procedures exist for the early detection and treatment of the disease 6. The prescribed monitoring regime is different from that normally recommended in the absence of exposure119 Jurisdictions which permit medical monitoring costs recovery usually do so in the asbestos context (but, as discussed below, occasionally in other contexts, too). These courts emphasize there is ample scientific evidence that

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asbestos fibers lodge in the lungs causing immediate injury to the lungs and later asbestosis and other dreaded diseases. See, for example, the Pennsylvania Supreme Court decision, Simmons v. Pacor, Inc.,120 where the plaintiffs had developed asymptomatic pleural thickening as a result of their occupational exposure to asbestos and sought damages for increased risk and fear of cancer. The court held that damages for increased risk and fear of cancer were too speculative to be recoverable where cancer was not present. Because the plaintiffs had not developed cancer, the court did not permit them to recover for their increased risk and fear of cancer. However, the court adopted a rule of law allowing plaintiffs with asbestos-related asymptomatic pleural thickening to recover for medical monitoring. Later, the Pennsylvania Supreme Court Redland Soccer Club, Inc. v. Department of the Army121 expanded on its Simmons decision by explicitly ruling that it found “no reason to limit common law medical monitoring claims to asbestos-related injuries”. In Redland, a soccer club sued the U.S. Department of Army and Department of Defense under Pennsylvania’s Hazardous Sites Cleanup Act, alleging that defendants disposal of hazardous wastes at the site caused them harm. The club, inter alia, sought a medical monitoring trust fund. The court sided with the plaintiffs, and held that medical monitoring trust fund is a valid response cost under the statute, and that the elements of the claim for medical monitoring under the statute are the same as elements of a common-law claim for medical monitoring. In contrast to asbestos, there is no scientifically accepted evidence connecting trace concentrations of Cr(VI) (or for that matter, volatile organic compounds) to related long-term diseases. One federal court explained the differences as follows: It is a medically and scientifically accepted fact that the exposure to asbestos particles can cause asbestosis and other more serious human health effects, such as mesothelioma, that is, lung cancer. Here, however, plaintiffs admit that it is not a medically or scientifically accepted fact that the exposure to these chemicals (viz., PCB) can cause any adverse human health affects other than chloracne, a benign reversible skin condition which none of the plaintiffs claim to suffer.122

Although this case concerned PCB, the same rationale would apply to numerous other hazardous substances, such as Cr(VI). 13.5.2.2.4 Defenses to Medical Monitoring Claims There are a number of possible defenses for medical monitoring claims. Two of the best articles123 on medical monitoring have listed the defenses, almost identically as follows: • Plaintiffs allege exposure to concentrations that are less than concentrations of safe exposure that have been established by the government (“maximum allowable concentrations”)124

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• The medical monitoring is not “reasonable or necessary”125 • The surveillance claim is another way of presenting the increased risk of disease claim, which, as discussed above, courts usually reject126 • The claimant seeks routine physicals that the general public should have anyway127 • Monitoring for diseases that are not treatable has no beneficial purpose128 • “Monitoring can increase health risks because of the possibility of false positives” that could result in “unnecessary invasive procedures with accompanying risk, or false negatives that could cause patients to ignore symptoms”, permitting disease processes to continue and worsen129 • Statutes of limitation130 13.5.2.2.5 If Courts Opt for Medical Monitoring, They Usually Opt for Supervised Funds, Not Lump Sums Courts that permit medical monitoring costs usually favor court, supervised funds, and not lump sum payments.131 The New Jersey Supreme Court discussed the advantages of the trust fund approach as follows: In our view, the use of a court-supervised fund to administer medical– surveillance payments in mass exposure cases … is a highly appropriate exercise of the Court’s equitable powers … Such a mechanism offers significant advantages over a lump-sum verdict.… [A] fund would serve to limit the liability of defendants to the amount of expenses actually incurred. A lump-sum verdict attempts to estimate future expenses, but cannot predict the amounts that actually will be expended for medical purposes. Although conventional damages awards do not restrict plaintiffs in the use of money paid as compensatory damages, mass-exposure toxic-tort cases involve public interests not present in conventional tort litigation. The public health interest is served by a fund mechanism that encourages regular medical monitoring for victims of toxic exposure.… Although there may be administrative and procedural questions in the establishment and operation of such a fund, we encourage its use by trial courts in managing mass-exposure cases.… [M]edical-surveillance damages will be paid only to compensate for medical examinations and tests actually administered, and will encourage plaintiffs to safeguard their health by not allowing them the option of spending the money for other purposes.132

13.5.2.2.6 Emotional Distress and Cancerphobia Many states allow a toxic tort plaintiff to seek damages for fear of contracting a disease (usually cancer) by permitting such a plaintiff to sue for negligent

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or intentional infliction of emotional distress. This is a cutting edge issue, and not all courts see eye to eye, as we discuss immediately below. As respects the cause of action for negligent infliction of emotional distress, a majority of courts have held a physical injury of some sort is required, or else plaintiff is not entitled to recover for emotional injury. For example, in Metro-North Commuter R. Co. v. Buckley133 the U.S. Supreme Court held that a toxic tort plaintiff who was disease-free and symptom-free could not recover for negligent infliction of emotional distress of fear of cancer under the Federal Employers Liability Act. Held the court: “[A] simple (though extensive) contact with a carcinogenic substance does not … offer much help in separating valid from invalid emotional distress claims”.134 The court drew a distinction between stand-alone emotional distress claims, and emotional distress claims prompted by physical injury. The court noted that for the latter claims common-law courts “do permit a plaintiff who suffers from a disease to recover for related negligently caused emotional distress …”.135 When a plaintiff suffers from a disease, the court added, common-law courts have made a “special effort” to recognize accompanying emotional distress claims, “perhaps from a desire to make a physically injured victim whole or because the parties are likely to be in court in any event”.136 One of the reasons some courts refuse to allow toxic tort plaintiffs without physical injuries to sue for negligent infliction of emotional distress (fear of cancer) concerns the “separate disease rule”, which is an exception to the general rule that causes of action must not be split. That is, under our system of civil procedure, an entire claim cannot be divided and made the basis of several lawsuits. There are two reasons for this general rule against splitting: (1) The defendant should be protected against vexatious litigation; and (2) it is against public policy to permit litigants to consume the courts’ time by relitigating matters already judicially determined, or by asserting claims which properly should have been settled in some prior action.137 A majority of states have adopted the separate disease rule—the Pennsylvania Supreme Court justified this exception to the general rule against “splitting” as follows: Damages for fear of cancer are speculative. The awarding of such damages would lead to inequitable results since those who never contract cancer would obtain damages even through the disease never came into fruition. . . . In any case, Appellants are not left without a remedy for their mental anguish. (Pennsylvania case law) permits an action to be commenced if cancer develops. It is in this action that Appellants can assert their emotional distress or mental anguish claims. To allow the asbestos plaintiff in a noncancer claim to recover for any part of the damages relating to cancer, including the fear of contracting cancer, erodes the integrity of any purpose behind the (separate) disease rule.138

As indicated above, if a toxic tort plaintiff can demonstrate some present physical effect, courts will allow such a plaintiff to prosecute an action for negligent (or intentional) infliction of emotional distress. For example, see

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the 2003 U.S. Supreme Court (fear of cancer) decision in Norfolk and Western Railway Co. v. Ayers,139 where the court held that mental anguish damages resulting from the fear of developing cancer may be recovered under the FELA by a railroad worker suffering from asbestosis (but not cancer) caused by work-related exposure to asbestos. (FELA is the Federal Employees Liability Act, which Congress enacted in 1908 to provide benefits for railroad workers who sustain injuries in the course of their employment). The Court did, however, qualify this ruling with one important reservation: the plaintiffs must prove that their alleged fear is genuine and serious. 13.5.2.2.7 Increased Risk of Cancer As stated, plaintiffs can only recover for injuries that have occurred or are certain to occur. This requirement is met by proving that the injury is “reasonably certain” to occur. Thus, if plaintiffs can show that they are reasonably certain to contract cancer in the future, they can be compensated for that cancer, albeit they have not yet contracted that disease. However, the state of scientific knowledge is such that experts are usually unable to testify persuasively that plaintiff is “reasonably certain” to contract cancer. Thus, plaintiffs are precluded from recovering from cancer that they have not yet contracted. “To avoid this result, plaintiffs often use a fallback position. They seek recovery for the increased risk, which they claim is a present injury. Under this theory, plaintiffs allege they have a much greater risk of contracting cancer than they would otherwise and seek compensation for this condition.”140 The majority of states that have addressed this type of claim have denied it. See, for example, Sterling v. Velsicol Chemical Corp.141 (“[T]he mere increased risk of a future disease or condition resulting from an initial injury is not compensable”); Ayers v. Jackson,142 (plaintiffs — county residents exposed to contaminated well water, not permitted to collect damages for prospective consequences, as plaintiffs’ experts unable to prove that it was reasonably certain they suffered excessive risk); Haggerty v. Al-Marine Services, Inc.143 (Plaintiff was accidentally drenched with chemicals containing known carcinogens, and sued for damages including compensation for the increased risk that they would develop cancer as a result of the exposure. The court ruled that since the plaintiff did not charge with sufficient medical certainty that the plaintiff would develop cancer, the plaintiff did not state a valid claim.) However, a minority of states have carved out an exception to the general rule against claims for increase risk of cancer. These states have allowed claims “for increased risk of future disease if the increased risk is caused by present physical injury. If such a showing is made, increased risk may be compensable regardless of the likelihood of the injury occurring”.144 Brafford v. Susquhanna Corp.145 (“Here, because of the high levels of radiation to which plaintiffs were exposed, the experts are able to conclude with a reasonable degree of medical probability both that there has been chromosomal damage and that such

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damage was caused by the radiation”); Cudone v. Gehret146 (Patent sued physician, on “increased risk” theory, for his failure to diagnose her breast cancer at earlier date, before it had metastasized to the rest of her body—court held patient could recover under this theory.)

13.5.3

Theories of Damages in Toxic Tort Property Damage Cases

The remedy for damages to real property is the amount which will compensate for all of the detriment that the defendant proximately caused. Under this rule, a plaintiff can seek recovery for 100% of the property loss that she suffered as a result of the defendant’s contamination of her property.147 Property damage caused by chemical contamination can be divided into two categories: physical and economic. As respects physical damage, generally, recoverable damages are limited to the diminution in value or cost of repair, whichever is less.148 However, in exceptional circumstances the cost of restoration maybe recoverable even if such costs are greater than the diminution in value. For example, see Davey Compressor Co. v. City of Delray Beach, a Florida case.149 In Davey, the city sued the firm which had polluted (with tetrachloroethene (C2Cl4)) the city’s groundwater supply, alleging liability. The jury awarded the city $5.6 million for estimated future response costs, and $3,097,488 for past damages. Although the court acknowledged that, generally, restoration costs should be restricted to the value of the property, it ruled that there are exceptions to the rule: in the case before it, the court ruled that the city “must be compensated for the restoration of the groundwater to a quality fit for human consumption, even if the cost of such restoration exceeds the value of the real estate on which the wells are located”.150 The court explained that the city’s ultimate goal to obtain an equivalent supply of water from another well field was speculative, and more costly, and thus the exception to the rule was justified. As respects economic damages, in the last 20 years there have been many cases in which plaintiffs have asked for “stigma” damages—these costs are to compensate plaintiffs for the past, present, or future presence of environmental contamination on their property, or the close proximity of their property to a contaminated site. This stigma may remain even after the land is cleaned up and plaintiffs may be compensated for this.151 Plaintiffs maintain this “stigma” reduces the marketability of their property. Such stigma claims are being made not only by individual plaintiffs, but also by class action plaintiffs, the latter seek to certify property damage classes based on stigma allegedly caused by widespread contamination. If plaintiffs are permitted to pursue stigma claims, the trial court needs to determine the existence and extent of any diminution in value. Appraisers are frequently called to testify on their valuation of the alleged stigma. These appraisers generally use comparable recent sales of similar properties, and then testify on whether the properties at issue have diminished in value

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because of the contamination. Also, sometimes appraisers employ a “multiple regression” analysis, under which they supposedly determine whether there was a systematic effect of the contamination in property values. This method focuses on isolating the contamination’s effect from the effect of other factors that may also have a negative influence on property value.152

13.6 Survey of Cr(VI) Published (and Otherwise Notable) Cases 13.6.1

Case No. 1

The Hinkley, California/PG&E Litigation The most famous case of Cr(VI) involved Erin Brockovich, the real life paralegal, who became the inspiration for the movie named for her, starring Julia Roberts. The case pitted residents of Hinkley, California (in California’s Central Valley) against Pacific Gas and Electric Company (PG&E). The residents in 1996 won a $333 million settlement from PG&E because (1) the grant utility company’s underground tanks leaked Cr(VI) into the town’s drinking water supply, and (2) it had disposed off Cr(VI)-laced water in unlined ponds, (i.e., mere holes in the ground) since 1950 — this, too, got into the drinking water. PG&E decided to settle after the first 39 Hinkley residents won in arbitration. Since the movie, there has been much written about the merits of this litigation. Critics of “junk science” say plaintiffs never proved that drinking water with Cr(VI) in it (1) causes cancer, (2) that the residents’ exposure to Cr(VI) made them sick, or (3) that these above-average numbers of residents were sick from drinking Cr(VI). Of course, these charges engendered angry responses from Ms. Brockovich and the attorneys who represented the Hinkley plaintiffs. The most famous of such exchanges is the one initiated by popular science and technology reporter Michael Fumento. In the pages of the Wall Street Journal and elsewhere, the two sides have made their respective cases. (A Google search in September 2003 shows 465 entries for “Fumento” and “Erin.”) 13.6.2

Case No. 2

U.S. v. Power Engineering Company 303F3d 1232 (10 Cir. 2002) USEPA sued the owners and operators of the metal finishing facility, seeking financial assurances for past and ongoing improper disposal of hazardous waste. The District Court granted summary judgment in favor of USEPA, and, on appeal, the Tenth Circuit affirmed. They held that as USEPA had the authority to seek assurances in tandem with state enforcement officials, the suit was not barred by res judicata. This litigation stemmed from a Colorado

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Department of Public Health and Environment finding of a discharge of Cr(VI) into the Platte River, and subsequent inspections of the Power Engineering Plant, which revealed the Cr(VI) discharge.

13.6.3

Case No. 3

Power Engineering Company v. Royal Insurance Company of America 105 Supp 2d 1196 (D. Colo. 2000). In this insurance coverage action (which resulted from the case discussed above), the insured, sought a declaratory judgement that its commercial general liability (CGL) insurer had a duty to defend and indemnify it against state and federal actions to compel environmental cleanup. Again, this lawsuit stemmed from a Colorado Department of Public Health and Environment order to the insured to clean up pollution that its plant caused, including discharges of Cr(VI) into the Platte River.

13.6.4

Case No. 4

Interfaith Community Organization v. Honeywell International, Inc. 188F Supp 2d 486 (D. N.J. 2002). A nonprofit community organization and its members sued the successorin-interest of a chemical manufacturer and current owners of a former manufacturing site, which was contaminated with Cr(VI), under the Resource Conversation and Recovery Act (RCRA), seeking declaratory and injunctive relief.

13.6.5

Case No. 5

U.S. v. Northrop Grumman Corporation 2002 W.L. 1796979 (N.D. Tex.) This case was brought by the U.S. ex rel.[153] on behalf of Steven G. Coppock, the plaintiff, who had worked for Northrop for several years as an engineer in its Naval Weapons Industrial Reserve Plant, a multi-acre production and waste treatment complex in Dallas, Texas that was built for the production of military aircraft. Since September 1988, Northrop directly or indirectly leased that facility from its owner, the U.S. Department of the Navy, using the complex mainly for production of military aircraft for the U.S. Department of Defense (DOD). Northrop was also contractually permitted to operate the facility to complete commercial aircraft contracts, if such use did not exceed 25% of its time, and did not interfere with the DOD production contracts. Coppock charged that Northrop knowingly mishandled the plant’s waste, allowing it to enter the environment untreated, and, thus, polluted the public drinking water by routinely discharging improperly treated waste into the public drinking water system, exceeding acceptable limits for Cr(VI) and other toxic chemicals. Additionally, by failure to maintain the facility,

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Coppock alleged that Northrop polluted not only its facility but the surrounding environs with Cr(VI). Coppock filed a False Claims Act claim, and state law claims for common law fraud and breach of contract.

13.6.6

Case No. 6

Hildago v. Chrome Crankshaft Co. 2002 W.L. 1797271 Residents living near a plant brought a toxic tort action against the chromium plating company and its Illinois parent corporation. The causes of action were for: 1. 2. 3. 4. 5. 6. 7.

Negligence Wrongful death Negligence per se Absolute liability for ultra hazardous activity Misrepresentation and fraudulent concealment Intentional affliction of emotional distress Violation of California Business and Professions Code Section 170000 et sec.

The complaint charged that the parent and subsidiary companies were alter egos of each other, and that the two companies failed to store or clean up hazardous substances, violated regulations by accidentally releasing large quantities of Cr(VI) into the environment, and concealed the spills by failing to apprise the appropriate governmental agencies. The complaint also alleged that the two companies’ conduct and operation of the sites at issue resulted in contamination of the surrounding communities’ air, soil, groundwater, and environment with hazardous and/or toxic substances, which threatened human health through ingestion, inhalation, and dermal contact. The plaintiffs charged they, and their children, had suffered personal injuries, increased risk of future health problems, and death as a result of their exposure to the release of hazardous substances from the site through sources such as drinking water, groundwater, soil, and air contaminants.

13.6.7

Case No. 7

Public Citizen Health Research Group v. Chao 314 F.3d. 143 (3rd Circuit 2002) A petition was filed to review the Occupational Safety and Health Administration’s (OSHA) failure to adopt new workplace exposure limit for Cr(VI). The court of appeals held that: (1) OSHA’s 9-year delay in adopting a new standard was excessive; (2) the delay was not justified by scientific uncertainty or OSHA’s competing policy priority; and (3) OSHA would be required to propose a new standard within a timetable determined by judicial mediation.

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Chromium(VI) Handbook Case No. 8

In Re: Pacific Gas and Electric Company 279 B.R. 561(2) (N.D. Cal. 2002) Personal injury claimants brought a motion to lift the automatic stay and to have the court abstain from hearing their claims. The bankruptcy court held that: (1) the bankruptcy judge, not the district judge, could and should make the decision regarding whether to abstain; (2) the bankruptcy court determined that the district court would abstain from deciding 1,250 personal injury claims; and (3) a cause existed to lift the automatic stay. The claims belong to approximately 1,250 individuals which alleged personal injury and wrongful death from exposure to Cr(VI) from facilities owned or operated by the debtor, PG&E. The claimants were plaintiffs in various lawsuits in various California superior courts. 13.6.9

Case No. 9

1325 “G” Street Associates, LP v. Rockwood Pigments NA, Inc. 235 F.Supp. 2d. 458 (2000) A landowner sued a potentially responsible party (PRP) seeking response costs and contribution under CERCLA. One of the contaminants at issue was Cr(VI).

Endnotes 1. A partial list of the contaminants that have prompted tort litigation include the following: 1,1,1-trichloroethane, 1,2-dichloroethane, 1,2-dichloropropane, acetaldehyde, acetone, acetonitrile, adhesives, asbestos, benzene, cellusolve, cyclohexane, “dioxin”, ethylene copolymer, formaldehyde, glycol ethers, herbicides, Cr(VI), hydrochloric acid, landfill/toxic tort exposure, lead paint, methyl alcohol, dichloromethane, n-butyl alcohol, nickel, organophosphates, PCB discharges, tetrachloroethene (“perchloroethylene”), pesticides, petroleum spills, photo resist chemicals, polystyrene, propylene, propylene oxide, sodium hypochlorite, solder flux, styrene, trichloroethene, toluene, urea-formaldehyde foam insulation, vinyl chloride, xylenes, and zinc. 2. International Programme on Chemical Safety (IPCS) Chemical Safety Training Modules, Part VII Metals (available on the Internet, at http.//www.itcilo.it/ english/actrav/telearn/osh/Kemi/ctm7.htm) 3. See, for example, U.S. Dept. of Labor, Occupational Safety and Health Administration Fact Sheet, entitled “Occupational Exposure to Cr(VI) (CrVI)” (available on the Internet at http://www.osha.gov): Health risks associated with occupational exposure to CrVI. Epidemiologic studies of workers exposed to Cr(VI) have consistently shown a positive correlation between exposure to Cr(VI) and excess lung cancer. See, e.g., Machle and Gregorius (1948, Ex. 7-2); U.S. Public Health Service/Gafafer (1953, Ex. 7-3); Baetjer (1950, Ex. 7-6); Hayes et al. (1979, Ex. 7-15); Braver

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(1985, Ex. 7-17); Mancuso (1975, Ex. 18-3; 1997 Exs. 23, 24); and Gibb et al. (2000, Ex. 25). The International Agency for Research on Cancer (IARC) (Ex. 18-1) and the U.S. Environmental Protection Agency (USEPA) (Ex. 19-1) have classified Cr(VI) as a human carcinogen based on excess lung cancers found in workers involved in chromate production, chromate pigment production, and a plating. The American Conference for Governmental Hygienists (ACGIH) classifies water-insoluble and water-soluble Cr(VI) compounds, zinc chromate, and strontium chromate as class A1 (confirmed human) carcinogens. (2002, ACGIH, TLVs® and BEIs®, Threshold Limit Values for Chemical Substances and Physical Agents and Biological Exposure Indices). Occupational exposure to Cr(VI) has also been associated with noncancer health effects of the skin, such as dermatoses and Cr holes; and problems of the respiratory system including nasal septum irritation and perforation. 4. The Paper, Allied-Industrial, Chemical and Energy Workers International Union (PACE), along with public watchdog groups, have filed a series of lawsuits to force government agencies to decrease the PEL for Cr(VI). 5. Compare “Chromium Cancer and Causation: Has a Death-Blow Been Dealt to Chromium Cases in California?”, Daniel L. Martens, 16-SPG Nat. Resources and Env’t 264 (2002) with the Feb. 28, 2003 “Comments Prepared for the California State Senate Health and Social Services Committee’s Investigative Hearing on Potential Misconduct of the Chromate Toxicity Review Committee,” by Alise Cappel, Research Director, Center for Environmental Health, Oakland, CA (available on the Internet, at http://www.cehea.org/AMCCComments.doc) Mr. Martens, a prominent Los Angeles defense counsel, wrote, in pertinent part: “The Review Committee’s recent report will present a significant obstacle for plaintiffs attempting to meet this burden (the burden of proving causation) in chromium cases where the plaintiff’s claimed ailment is cancer”. . . Experts contending that ingestion of Cr(VI) can cause cancer will find it more difficult to criticize or discount the Review Committee’s findings. Furthermore, it likely will not suffice for an expert merely to ignore the committee’s report and, like the ‘scientist’ in Erin Brockovich, simply proclaim that Cr(VI) is ‘highly carcinogenic’ when ingested in water. Trial courts are obligated to require adequate foundation for an expert’s opinion, and to prohibit the admission of opinions based on unsupported theory or untenable conclusions. (c.t. omit.) As the California Supreme Court has explained: “Like a house built on sand, the expert’s opinion is no better than the facts on which it is based”. (c.t. omit.) It may be that the Review Committee’s analysis and report leave nothing but sand on which a plaintiff’s expert may attempt to ‘build his house’ in future chromium cases”. In stark contrast to Mr. Martens’ positive response, Ms. Cappel said the following about the Commission: I would like to discuss two things: (1) what really happened with the Chromate Committee; and (2) how the Chromate Committee’s report will continue to pose a threat to Californians until it is officially withdrawn.

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Chromium(VI) Handbook I have been investigating the operations of this panel for the past year and a half and this is what I have learned: In 1999 OEHHA followed their mandate and determined that Crd(VI) in drinking water posed a legitimate threat in public health. Polluting industries, companies responsible for releasing Cr(VI) into the environment, and a few compromised public officials decided they wanted to overturn OEHHA’s stance on chromate carcinogenicity. So they created the “Blue Ribbon” Chromate Committee. They used political influence and through the Chromate Committee they attempted to silence OEHHA. Unfortunately, they were effective. The Chromate Committee’s report was used as the basis for withdrawing OEHHA’s 1999 Public Health Goal on total chromium—a decision benefiting PG&E and other industries facing contamination cleanup costs, yet harmful to the health of Californians and the safety of our drinking water. I am encouraged that Senator Ortiz has begun this investigation, yet after the opening testimony this morning, one thing is absolutely clear: The report that the Chromate Committee produced has been hopelessly tainted and cannot be relied upon as sound science. The University of California must immediately withdraw the report. The Secretary of California EPA and the Director of OEHHA must publicly reject it. Unfortunately, the Chromate Committee’s conclusions have already tainted other California risk assessments. The Committee’s Report has served as the basis for the San Fernando Basin Risk Assessment and OEHHA’s recently finished Public Health Goal for Cr(VI). Both of these assessments have been compromised and must be immediately withdrawn. Once withdrawn, OEHHA should commence new risk assessments that are not influenced, in any way, by the conclusions of the Chromate Committee. The public deserves to have risk assessments conducted by scientists we can trust. As long as the Chromate Committee’s Report remains intact, the possibility exists that physicians and other public health officials will be influenced by its conclusions. Furthermore, if allowed to stand, this report will discourage future research into the human health effects of Cr(VI) exposure via the oral route. Furthermore, to insure that something like this does not happen again, the California State Legislature should mandate that science conducted on behalf

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of California citizens, with our tax dollars, is done with public participation, in a balanced and transparent manner. . . . 6. For a more detailed discussion of this subject, see the following articles: Zuckerman, Motzer, Leonard and Soloman, “Transferring Contaminated Real Property”. 35 Real Property, Probate and Trust Journal, 305 at 323-347, Summer 2000; James L. Pray, “Civil Environmental Liability in Iowa”, available on the Internet (http://members.aol.com/IowaLegal/torthtm.htm). 7. By this term, we refer to a plaintiff who bases his allegations on legal principles developed in the decisions of courts, which establish precedents. In the U.S., the law of torts is based on common law, though frequently, states have enacted statutes which have modified or replaced certain parts of the common law. 8. 3 H and C 774, 159 Eng. Rep. 737 (1865), rev’d, L.R. 1 Exch. Ch. 265 (1866), aff’d. L.R. 3 H.L. 330 (1868). An abridged version is contained in Sterling v. Velsico Chem. Corp., 647 F. Supp. 303, 311-313 (N.D. Tenn. 1986). 9. 647F. Supp. At 312 10. Clarence Morris and C. Robert Morris Jr., Morris on Torts 231, 2d ed., 1980. 11. The Restatements of Law is a series of books that set forth the law in a special subject area, i.e., the Restatement of the Law of Torts, that are written by legal scholars. These books state the authors’ opinions on (1) what the law is, and (2) how it is changing. 12. Restatement (Second) of Torts § 519 (1977). 13. Id. At § 520. 14. Perez v. Southern Pac. Transp. Co. 180 Ariz. 187, 883 P.2d 424, 426 (1993) (“It is clear first of all, that unless a statute requires it, strict liability will never be found unless the defendant is aware of the abnormally dangerous activity, and has voluntarily engaged in or permitted it”). 15. Cook and Davis, The Law of Hazardous Waste § 17 D11 [5] [a] (1991). 16. City of Northglenn v. Chevron USA, Inc. 519 F. Supp. 515 (D. Colo. 1981). 17. Wellesley Hills Reality Trust v. Mobil Oil Corp. 747 F. Supp. 43(D.Mass. 1990) 18. Yommer v. McKenzie, 255 Md. 220, 257 A.2d 138 (1969). 19. Id. 20. Bennett v. Malline Krodt, Inc. 679 S.W.2d 854 (Mo. Et. App. 1985). 21. T and E Indust, Inc. v. Safety Light Corp. 123 N.V. 371, 587 A.2d 1249 (1991), and Prospect Indust. Corp. v. Singer Co. 283 N.J. Super 394, 569 A.2d 908 (1989) (PCBs). 22. Kroff v. American Crystal Sugar Co. 80 N.W. 2d 313 (N.D. 1986). 23. Wood v. Picillo, 433 A. 2d 1244, 1249 (R.I. 1982) (holding proof of negligence not required in toxic waste seepage claim). 24. Phillips v. Amoco Prod. Co. 468 So.2d 72 (Miss. 1985). 25. Donald v. Amoco Prod. Co. 735 So.2d 161 (Miss. 1999), see also Madison v. Vintage Petr. Inc. 114 F.3d 514 (5th Cir. 1997) (holding that state courts can find that production and disposal of naturally occurring radioactive material (NORM) waste supports strict liability). 26. Ewell v. Petro Processors of Louisiana, Inc. 364 So. 2d 604 (LA. Et. App. 1978). 27. Arlington Forest Assocs. V. Exxon, 774 F. Supp. 387 (E.D. Va. 1991), see also Hudson v. Peavey Oil Co. 279 Or.3, 566 P.2d 175, 177 (1977). 28. Restatement (Second) Torts, § 162 (1965). 29. Id. § 161. 30. 221 Or. 86, 89, 342 P.2d. 790, 792, Cert.den., 362, U.S. 918 (1959).

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31. See, for example, Burlington Northern Santa Fe v. Phillips Petroleum 164 F. Supp. 2d 1272 (N.D. Okla. 2001). 32. Black’s Law Dictionary 1589, 6th ed., 1990. 33. Id. at 1590. See also Smith v. Cap Concrete. 787 Cal. Rptr. 308 (Ct. App. 1982) (discussing waste as a cause of action). 34. Restatement (Second) of Torts § 821B (1964). 35. 426 N.E.2d 824 (Ill. 1981) 36. 722 F. Supp. 960 (N.D.N.Y. 1989) 37. 426 N.E.2d at 826 38. 722 F. Supp. at 960 39. Walker Drug Co. v. La Sal Oil Co. 972 P.2d 1238, 1243 (Utah 1998). 40. Id. at 1245. 41. Id. 42. Id. 43. See Restatement (Second) of Torts § 821B, cmt. H (1964). 44. Anderson v. N.R. Grace and Co., 628 F. Supp. 1219, 1233 (. Mass. 1986). This case was the subject of the famous book and movie, “A Civil Action”. 45. 19 Cal.App. 4th, 334, 23 Cal.Rptr. 2d 377 (1993). 46. 335 Md. 58, 642 A.2d. 180 (1994). 47. 209 A.D.2d. 957, 619 N.Y.S. 2d. 433, 435 (App. Div. 1994). 48. Walker Drug, 972 P.2d at 1246 (quoting L. Neal Ellis, Jr. and Charles D. Cuse, Toxic Tort and Hazardous Substance Litigation § 6-5(a) (1995), See also Rudd, 982 F. Supp. At 372-73 (providing a good discussion of damages in nuisance cases). 49. Walker Drug Co., 972 P.2d. at 1246. 50. City of Phoenix v. Johnson, 75 P.2d. 30 (1938). 51. For a discussion of this tonic, see Kafka v. Bozio, 218 P. 753 (Cal. 1923). Although Kafka was decided 80 years ago, its explanation of continuing trespass specifically, and continuing torts generally, is among the best that we have found. 52. City of Phoenix, 75 P.2d. at 35. 53. See id. 54. See id. 55. Id. 56. W. Page Keeton, et al., Prosser and Keeton On The Law of Torts Section 30 at 130, 5th ed. 1984. 57. 647 F. Supp. 303, (W.D. Tenn. 1986). 58. See id. At 307-308. 59. See id. At 316. 60. See Restatement (Second) of Torts Sections 285-286. 61. Discussion of negligence per se in the context of the Federal Motor Carrier Safety Regulations — available on the Internet at http://www.i-r.com/ tortslaw/negligen.htm. See also James L. Pray, “Civil Environmental Liability In Iowa”, Iowa Environmental Law Series (1996), available on Internet at http://members.aol.com./IowaLegal/torthtm.htm (“The doctrine of negligence per se is limited to safety codes that have the force of law either by statute, regulation, or ordinance”.) 62. What constitutes due care under the circumstances is ordinarily a question of fact for the jury in each case. “But the proper conduct of a reasonable person under particular situations may become settled by judicial decision or by prescribed by statute or ordinance. Conduct less than this standard is negligence

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63. 64.

65.

66.

67.

68.

69.

559

per se, or negligence as a matter of law. And, if the evidence establishes that the plaintiff’s or defendant’s violation of the statute or ordinance proximately caused the injury and no excuse or justification for violation is shown by the evidence, responsibility may be fixed upon the violator without other proof of failure to exercise due cause”. Satterlee v. Orange Glenn Sch. Dist., 1777 P.2d. 279 (1997). See also Davis v. Marathon Oil Co., 356 N.E., 2d. 93 (1976). Cottle v. Superior Court (Oxnard Shores Co.) (1992) 3 Cal. App. 4th 1367, 1384, 5 Cal. Rptr., 2d 882, 892; Aburn v. General Elect. Co. (9th Cir. 1993) 3 F 3d 329. Summary judgement (in some states “summary disposition”) is a court order that says no factual issues remain to be tried, and therefore the plaintiff’s allegations can be decided without a trial. A summary judgement is based on a motion (a formal written request made to a judge for an order) by one of the parties that asserts that all necessary factual issues are either settled or so clearly one-sided that a trial is unnecessary. See, for example, California Evidence Code § 720: “A person is qualified to testify as an expert if that person has special knowledge, skill, experience, training, or education sufficient to qualify that person as an expert on the subject to which that person’s testimony relates”. Also, see Mann v. Cracchiolo (1985) 38 C.3d 18, 37-38, 210 CR 762, 773 (where an expert witness has shown sufficient knowledge, the question of degree of knowledge goes more to the weight of the evidence than its admissibility). See, for example, the following California cases: People v. McDonald (1984) 3 C.3d 351, 367, 208 CR 236, 247; People v. Roberts (1997) 55 CA 4th 1073, 1078, 65 CR 2d 17, 19 (The jury need not be wholly ignorant of the subject matter of the opinion. Instead, expert testimony is admissible whenever it would “assist” the jury). In federal courts, and many state courts, the trial judge has the duty to preliminarily determine whether proffered expert testimony satisfies basic admissibility standards. These admissibility standards are codified in Federal Rules of Evidence, Rule 702: “If scientific, technical, or other specialized knowledge will assist the trier of fact to understand the evidence or to determine a fact in issue, a witness qualified as an expert by knowledge, skill, experience, training, or education may testify thereto in the form of an opinion or otherwise, if (1) the testimony is based upon sufficient facts or data, (2) the testimony is the product of reliable principles and methods, and (3) the witness has applied the principles and methods reliably to the facts of the case”. In some state court systems (such as California), the trial judge does not have an obligation to make a preliminary finding concerning the proffered testimony. Instead, the opposing party must first raise an objection, then, and only then, will the trial court determine the basic foundational facts required for admissibility of expert opinion testimony. See, for example, Calif. Evidence Code § 405; Miller v. Los Angeles County Flood Control Dist. (1973) 8 Cal. 3d 689, 701, 106 Cal. Rptr. 1,8. See, for example, Indiana Code § 34-1-14-12: “A witness who is an expert in any art, science, trade, profession, or mystery may be compelled to appear and testify in any court . . . to an opinion, as such expert, in relation to any matter, whenever such opinion is material evidence relevant to an issue before a court or jury. . . .” For a good background on this subject, see the following article: (1) Nachman Brautbar, M.D. “Chemicals and Cancer: Establishing Causation Through Medical Toxicology” (available on the Internet at http://www.environmentaldiseases.com/article_chemicals_and_cancer.html. Dr. Brautbar describes/defines

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70. 71.

72. 73. 74. 75. 76. 77. 78.

79. 80. 81. 82. 83. 84. 85. 86. 87. 88. 89. 90. 91.

92.

93. 94. 95.

Chromium(VI) Handbook causation, the role of epidemiological studies, and scientific criteria for establishing causation (application of animal studies to human cancers, chemicals proven to be carcinogenic in human studies, material safety data sheets and regulatory agencies, level of exposure, medical and forensic application of regulatory levels, and an expert’s checklist to prove causation). 293 F.1013 (D.C. Cir. 1923). See Frey v. U.S. supra and People v. Kelly (1976) 17 C. 3d 24, 30, 130 C.R. 144. (The California Supreme Court refused to adopt the Daubert standard—discussed below—and ruled that the Frey formulation should remain a prerequiste for the admission of expert scientific testimony in California state courts). 509 U.S. 579, 125 L.Ed. 2d 469, 113 S.Ct. 2786. 509 U.S. 579 (1993). 522 U.S. 136 (1997). 526 U.S. 137 (1999). Id., 509 U.S. at 591-94. Id., 509 U.S. at 592 n.10. Daubert v. Merrill Dow Pharmaceuticals, Inc., 143 F. 3d 1311, 1316 (1995) (“Daubert II”) (self-serving assertions by expert that his conclusions were derived by “scientific method” are insufficient). 118 S.Ct. at 519. 986 F. Supp. 655, 660 (D. Mass. 1997) 891 F. Supp 12, 24 (D. Mass 1995). 807 F. Supp. 1376, 1391(C.D. Ill. 1992), aff’d, 13 F. 3rd 1090 (7 Circuit 1994). 91 F.3rd 1105 (1996). Id at 1108-09. Id. at 1106. Id. at 1108. (9th Cir. 1998) 159 F. 3d 905. A motion in limine (limine, Latin for “threshold”, is a motion made at the start of a trial requesting that the trial court exclude certain evidence from trial). (9th Cir. 1996) 89 F.3d 594. (5th Cir. 1996) 100 F.3d 1150, 1159. 292 F.3d 1124 (9th Cir. 2002). This opinion seemingly concerned only the plaintiffs who made exposure to radioactive emission (not Cr(VI) exposure, but as of August 2003, it seems that the breath of this opinion, which reversed the trial court’s summary judgement for defendants is being contested, as plaintiffs appear to assert that the reversal also applies to plaintiffs who allegedly suffered from Cr(VI) only. For nonlawyers, we suggest purchasing Real Life Dictionary of the Law by Gerald N. Hill and Kathleen Thompson Hill. Many of our definitions of legal terms come from this source. 15 Cal. Forms of Pleading and Practice Annotated, Ch. 17, at 12-12.1. Id. Id. at 38. H. Punitive damages are available in at least 47 of the 50 states. See also the Model Punitive Damages Act put forth by the Chicago based National Conference of Commissioners on Uniform State Laws (NCCUSL). (The NCCUSL, created in 1891, is “an organization comprised of more than 300 attorneys, judges, and law professors, appointed by the states as well as the District of Columbia, Puerto Rico, and the U.S. Virgin Islands, to draft proposals for uniform and model laws on subjects where uniformity is desirable

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96. 97.

98. 99.

100. 101. 102. 103. 104. 105. 106. 107. 108. 109. 110. 111.

112. 113. 114. 115. 116. 117. 118. 119.

120. 121. 122. 123.

561

and practicable, and work toward their enactment in legislatures”. See the NCCUSL’s web site, at www.nccusl.org). BAJI 14.60. Ayers v. Township of Jackson, 525 A. 2d 287, 303 n.8 (N.J. 1987) Testimony of Dr. Joseph Highland, plaintiffs’ toxicology expert—plaintiffs sued the township arising from contamination of water by toxic pollutants leaking into an aquifer from the township’s landfill. Id. For a good discussion of what plaintiff needs to prove in order to obtain “future meds”, see Flahavan, Rea and Kelly, California Practice Guide: Personal Injury (2003). At § 3:60. In California (as in other states), the plaintiff must establish the following: (1) The reasonable value of each of the expected future medical charges; (2) that the future medical care, services or supplies are reasonably certain to be needed and given in treatment of the injury; and (3) that the condition requiring the future medical care is causally connected to the injuries inflicted by the defendant. 59F3d 121, 125 (9th Cir. 1995) 39F3d 1011, 1016-17 (9th Cir. 1994) 972F2nd 1527, 1536 (10th Cir. 1992) 801F Supp 1432, 1438 (M.D. PA 1992) 764F Supp 1467, 1469 (M.D. Fla. 1991) 750F Supp 1233, 1244 (PA 1990) 704F Supp 782 (N. Ohio 1988) 680F Supp. 1176, 1179-1180 (Tenn. 1988) 621F Supp 370, 376 (W.D. Tenn. 1995) 596F Supp (N.D. Cal 1984) 584F Supp 12 1425 (S.D. Ohio 1984) In re Berg Litig. (9th Cir. 2002) 293 F.3d 1127, 1132-1133. Durfey v. E.I. DuPont De Nemours and Co. (9th Cir. 1995) 59 F.3d 121, 126. The Price-Anderson Act is codified at 42 USC § 2011 et seq. 758F2d 936, 942 (3rd Cir. 1985) 755F Supp 1344 (S.D. W. VA. 1990); 958F2d 36 (4th Cir. 1991) 543 PA. 664, 674A. 2d 232 (1996) 548 PA. 1781, 696A. 2d 137 (1997) 858 P.2d 970 (U.T. 1993) 156 Ariz. 375, 752 P.2d 28 (App. 1987) N.J. 557, 525A2d 287 (1987) See, for example, Hansen v. Mountain Fuel Supply Co. 858 P.2d 970 at 979-980 (1993). Also, see Ostrager and McLaughlin, “Class Actions and Mass Torts”, at p. 61. Available on the Internet. 543 P.A. 664, 674 A.2d 232 (1996) 548 P.A. 178, 696 A.3d 137 (1997) Ball v. Joy Mfg. Co. 755F Supp 1344, 1366 (S.D. W. VA 1990), aff’d 958F2d 36 (4th Cir. 1991) See Scott P. DeVries and Patrick J. Richard, “Traditional and Novel Theories of Liability and Damages in Toxic Tort Actions” (2000) and Barry R. Ostrager and Joseph M. McLaughlin, “Class Actions and Mass Torts” (Undated, but apparently written in 2001). Both articles are available on the Internet. See also David T. Person, “Recent Developments in Medical Monitoring Claims in Mass Tort Litigation”, (Undated), also available on the Internet. Lastly, see Schwartz,

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124.

125.

126. 127.

128. 129. 130.

131.

132. 133. 134. 135. 136. 137. 138.

139. 140. 141. 142. 143. 144. 145. 146. 147.

Chromium(VI) Handbook Behrens, Burton and Groninger, “Medical Monitoring—Should Tort Law Say Yes, 34 Wake Forest Law Review 1057–1081 (1999) (The authors conclude that because of the complexities and important public policy concerns “inherent in allowing such awards, decisions about whether to permit medical monitoring should be made by legislatures and not by courts”.). See, Scott P. DeVries and Patrick J. Richard, “Traditional and Novel Theories of Liability and Damages in Toxic Tort Actions”. Available on the Internet, p. 24–27. Id. Abuan v. General Elec. Co. 3F 3d 329, 334 (9th Cir. 1993); In re Paoli R.R. Yard PCB Litigation (Paoli II) 35 F.3d 717, 787 (3d Cir. 1994) (Plaintiff must suffer from “a significantly increased risk of contracting a serious latent disease”). DeVries and Richard, supra. Id. The court was not impressed by one of plaintiff’s experts, who testified that “medical monitoring is justified at any level of risk” and that medical monitoring of the population at large would be a “good idea”. DeVries and Richard, supra. DeVries and Richard, supra. See, Barnes v. The American Tobacco Company, Inc. 984 F. Supp. 842 (E.D.P.A. 1997), and In re Burbank Environmental Litigation 42 F. Supp. 2d 976 (1998). See also Ostrager and McLaughlin, “Class Actions and Mass Torts”, at p. 88. Available on the Internet. See, for example, Hansen v. Mountain Fuel Supply Co., 858 P.2d 970 (Ut. 1993); Ayers v. Township of Jackson, 106 N.J. 557, 525 A.2d. 287 (1987); and Burns v. Jaquays Mining Corp., 156 Ariz. 375, 752 P.2d 28 (App. 1987). Ayers, 525 A.2d at 314. 521 U.S. 424, 117, S.Ct. 2113, 1382 Ed.2d. 560 (1997). Id. at 434, 1175 Ct. 2113. 521 U.S., at 432, 117 S.Ct. 2113. Id. at 436, 117 S.Ct. 2113. Wulfien v. Dolton (1994) 24 Cal.2d. 891, 894, 151 P.2d. 840, 846. Simmons v. Pacor, Inc., 543 Pa. 644, 677-678, 674 A.2d. 232, 238-239 (1996). See also Rogers v. R.J. Reynolds Tobacco Co. 557 N.E.2d. 045, 1056 (Ind.App. 1990) (plaintiff, a widow whose husband died of cigarette smoking, not entitled to recover for emotional distress because she had no physical injury), and In Hawaii Fed’l Asbestos Cases 734 F.Supp. 1563 (D.Hawaii 1990) (Plaintiffs could not recover for mental anguish-fear of cancer-because there was no compensable harm underlying the emotional distress.) 155 L.Ed.2d. 261, 123 S.Ct. 1210 (2003). DeVries and Richard, supra, at p. 14. 855F2d 1188, 1204 (6th Cir. 1988). 189 N.J. Supra. 561, 461A2d 184 (1983). 788F2d 315, 319 (5th Cir. 1986), recon.den., 797 F.2d 256 (5th Cir. 1956) (en banc). DeVries and Richard at p.15 586F Supp 14, 17 (Colo. 1984) 821 F. Supp. 266 (D. Del. 1993) Generally, “[a] person whose property is taken, damaged, or destroyed by the negligent or wrongful act or omission of another is entitled to compensation for the damage sustained in such a sum as will restore the person as nearly as possible to the person’s former position”. 36 N.Y. Jur.2d. Damages § 72; Cashin v. New Rochelle, 256 N.Y. 190 (1931). “[T]he proper measure of damages for

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149. 150. 151.

152.

153.

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permanent injury to real property is the lesser of the decline in market value and the cost of restoration. Jenkins v. Etlanger 55 N.Y. S.2d. 35, 39, 447 N.Y. S.2d. 696, 698 (1982)”. In environmental contamination cases, plaintiffs can recover “damages for diminution in the fair market value of their real property allegedly caused by contamination from hazardous substances”. This is usually referred to as the “restoration rule.” United States Steel Corp. v. Benefield, 352 So. 2d. 892 (Fla. 2d. DCA 1977), cert. den., 364 So. 2d. 881 (Fla. 1978). Benefield concerned 26 acres of a 750 acre land tract that the defendant damaged by removing phosphate minerals which had been deposited on the land as a by-product of a mining operation. As the land was originally bought for $466 per acre, and repair of the 26 acres would cost $13,084 per acre, the court held that the restoration cost should not be awarded if it was more than the diminution in market value. Id. Accordingly, the court held that the diminution in value was the appropriate measure of damages. 639 So.2d. 595 (Fl. 1994). Id. at 596. Nashua Corp. v. Norton Company, 1997 U.S. Dist. LEXIS (N.D.N.Y. 1997); In Re Paoli Railroad Yard PCB Litigation, 35 F.3d. 717 (3d Cir. 1994); Scribner v. Summers, 138 F.3d. 471 (2d. Cir. 1998); Criscuola v. Power Auth. of State of New York, 81 N.Y. 2d. 649, 602 N.Y.S. 2d. 588 (1993). See Paul Pederson, “Contaminated property appraisals: a practical guide to minimizing liability, available on the Internet”. Though written by a Canadian appraiser for a Canadian audience, its 95% applicable to the U.S. See also Mundy and Associates: “Stigma and Value”, available on the Internet. ex rel. is the abbreviation for the Latin term ex relatione, meaning “upon being related” or “upon information”, used in the title of a lawsuit by the United States Department of Justice (or by a state Attorney General) on behalf of the government, on the instigation of a private person, who needs the state to enforce his rights and the public’s rights.

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14 The Future; Emerging Mitigation and Remediation Technologies

CONTENTS 14.1 Emerging Mitigation and Remediation Technologies........................565 Stephen M. Testa, James F. Begley, and James A. Jacobs 14.1.1 Process Description ...................................................................567 14.1.2 Key Design Criteria ...................................................................568 14.1.3 Photoreduction of Chromium(VI)...........................................569 14.1.4 Pollution Prevention Trends ....................................................570 Bibliography ..............................................................................................572 14.2 Conclusions ...............................................................................................573 James A. Jacobs and Jacques Guertin

14.1 Emerging Mitigation and Remediation Technologies

Stephen M. Testa, James F. Begley, and James A. Jacobs Some of the emerging technologies for the mitigation and remediation of Cr(VI) include microbial strategies for in situ and on-site bioremediation strategies and use in permeable reactive barriers. Discovery of microorganisms capable of reducing Cr(VI) to Cr(III) have significant potential in development of in situ or on-site bioremediation strategies. In 1977, the first reported bacterial strains, Pseudomonas, were isolated from chromate(CrO42−)contaminated sewage sludge by Russian scientists N.A. Romanenko and V. Korenkov. Since 1977, several other CrO42− reducing strains have been reported, including other strains of Pseudomous as well as strains of Achromobacter, Aeromonas, Bacillus, Desulfomamaculum, Enterobacter, Escherichia, and Micrococus species (Gvozdyak et al., 1986; Horitsu et al., 1987; Bopp et al., 1983; Wang et al., 1989; and Fude et al., 1994). 1-5667-0608-4/05/$0.00+$1.50 © 2005 by CRC Press LLC

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An indigenous bacterium capable of reducing and immobilizing Cr to an insoluble Cr(III) precipitate on its surface, thus removing Cr(VI) from solution, has been isolated at a wood-preserving site located in Acton, Ontario (McLean and Phipps, 1999). The operation utilized a copper–arsenate–chromate solution to preserve the wood, which resulted in soil and groundwater contamination. A yet unidentified Gram-negative strain, tolerant to high concentrations of Cr(VI) [up to about 500 milligrams per liter (mg/L)], and possibly Cu and As (up to about 40 mg/L), has been noted. McLean and Phipps (1999) state that the high tolerance ensures that unpredicted release of adsorbed ‘‘metals” will not inhibit the reduction reaction. Laboratory studies showed the bacterium exhibited a broad range of reduction efficiency under minimal nutrient conditions at temperatures between 4 °C and 37 °C, pH 4 to pH 9, and under aerobic and anaerobic conditions. The exact mechanism by which the indigenous microorganism reduces aqueous Cr(VI) to Cr(III) remains uncertain; a combination of biochemical and surface-mediated reactions have been implicated in the process. In the consideration of permeable reactive barriers in the deep subsurface, metabolic capabilities of dissimilatory metal-reducing bacteria (DMRB) have shown merit (Gerlach et al., 1999). These capabilities have the potential to create zones of reduced indigenous metals (i.e., Fe(II)) in the path of a groundwater contaminant plume, thus forming redox-reactive barriers. Essentially, starved cells of Shewanella alga BrY were resuscitated with artificially associated Fe(II), which in turn almost instantaneously reduced Cr(VI) to Cr(III), the Cr(III) precipitating onto the sand media. In batch and column studies, the microbially-generated surface-associated Fe(II), produced from indigenous Fe(III), has been shown to reduce Cr(VI) to Cr(III), resulting in the precipitation of Cr(III) on existing surfaces, forming stable end products, and eliminating Cr(VI) from the water phase. In organic carbon-poor subsurface environments, sucrose-amended, yeast extract-amended, and lactate-amended systems were observed to be effective for the microbial reduction of Cr(VI) (Hong and Sewell, 1999). Depending on the supply of the electron donor (i.e., lactate), a reduction sequence of nitrate(NO3−), Cr(VI) and sulfate(SO42−) was observed. Acetate (C2H3O2−) and benzoate (C6H5COO−)-amended systems were found not to be as effective as electron donors, allowing for only 34.5% and 13.7% removal of Cr(VI) versus 100% removal utilizing sucrose stable sugar(C12H22O11), lactate(C3H5O3−), and yeast extract-amended systems. Use of the bacterium Pseudomonas Putida ATCC17484 was deemed successful for the biodegradation of naphthalene with the presence of Cr(VI) (Ghoshal et al., 2001). The presence of Cr(VI) however inhibited bacterial growth and reduced the biodegradation rate of the naphthalene(C10H8). Complete reduction of Cr(VI) was achieved at concentrations up to 6.3 mg/L. In another study, a bench-scale treatability study was performed to evaluate the feasibility of in situ bioremediation of perchlorate (ClO4−) and Cr(VI) (Perlmutter, 2001). Two media (sand and gravel), and four electron donors (acetate, molasses, composted manure, and concentrated fruit juice) were considered. Acetate and molasses were found to be acceptable electron donors. It was determined that

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acetate may be required to initiate the treatment system, but molasses would be used as the long-term electron donor. It was further noted that the Cr(VI) concentrations used in this study (up to 8.0 mg/L) did not inhibit ClO4− reduction (originally set at 1,500 mg/L) and was routinely reduced to below less than its analytical detection limit during the study. Another emerging technology is an enhanced anaerobic treatment of Cr(VI) contaminated groundwater using biostimulation of indigenous soil bacteria by adding an alkane(CnH2n+2) gas. An alkane gas, such as propane(C3H8) is used as a growth substrate to promote conditions leading to the reduction the Cr(VI). With this approach, the added substrate serves as both the electron donor and primary growth substrate for the bacteria. Cr(VI) is potentially the final electron acceptor in the process. Cr(VI) is known to be reduced both aerobically and anaerobically in different bacterial systems (Suthersan, 2002). While consuming C3H8, the microbes use up the oxygen and create the geochemical conditions necessary for the reduction of Cr(VI). Microbial transformation of Cr(VI) varies with the oxidation state. In groundwater, the predominant form of Cr is the oxidized form, Cr(VI), present as chromate (CrO42−) and dichromate (Cr2O72−) ions (Suthersan, 2002). Cr(VI) is the oxidized, toxic, and mobile version and Cr(III) is less toxic and less mobile. Cr(III) precipitates as a Cr(III) hydroxide [Cr(OH)3] at groundwater pH of 4.5 to pH 10.5, within the range of most naturally occurring groundwaters. A variety of aerobic and anaerobic microbes enzymatically reduce Cr(VI) to Cr(III), but the details of the process are not well understood (Suthersan, 2002). There are several hypotheses to explain these reduction reactions, including the following:

Process

Description

Detoxification Cometabolism Respiration Indirect reduction Chemical reduction

14.1.1

Move Cr away from the cells Fortuitous enzymatic reactions Use of Cr(VI) as a respirator electron acceptor Microbes reduce Cr(VI) by producing sulfide(S2−), Fe(II), and reduced organic compounds The Cr(VI) is reduced as the aerobic environment is changed using chemicals that react with oxygen. As the oxygen is used up the environment changes into a reducing environment, without the aid of microbes. In the reduced environment, the Cr(VI) is converted into Cr(III), and ultimately precipitates out as chrome hydroxide.

Process Description

Treatment by direct infusion of an alkane gas through a gas infusion emitter into a monitoring well is a straightforward process to treat Cr(VI). The iSOC unit introduces sparge-free gases into the saturated zone. No mounding of groundwater occurs with this in situ method (Figure 14.1.1).

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Chromium(VI) Handbook Gas Infusion Tool (iSOC) Process Diagram iTiiSOC Control Panel P2 iSOC Pressure Gauge Low Flow Gas Flowmeter Flowmeter Bypass Line Bypass Line Button Valve Polyflow Gas Line toiSOC

Gas Inlet Pressure Gauge P1 Gas Flow Control Adjustment Valve

iSOC Gas Outlet Panel Connection

Gas Inlet Panel Connection

Gas Regulator

Gas Cylinder Valve

Well Maximum Water Depth (iSOC Head)

Groundwater

iSOC Gas Cylinder

FIGURE 14.1.1 Gas infusion technology process diagram. (Archibald, 2001.)

The iSOC gas emitter tool consists of a microporous, hollow-fiber membrane enclosed in a stainless-steel casing that is lowered into a 50.8 mm diameter well. The source of the propane is a portable gas cylinder. The gas cylinder contains a two-stage, low-flow gas regulator and is attached to a control box and flow meter with 6.35 mm diameter polyethylene tubing. The iSOC tool is also connected to the control box and flow meter with 6.35 mm diameter tubing. This gas infusion system runs on the pressure in the gas cylinder; there are no moving parts in the system and no power is required. The iSOC gas infusion tool is placed in the 50.8 mm diameter treatment well, provides an inherently large surface area that allows for alkane gas delivery by direct contact with groundwater and ultra efficient mass transfer by direct infusion. C3H8, a somewhat soluble gas in water, can dissolve to 66 ppm with a minimum of 1.5 m of water in the well, and up to 175 ppm with 15 m of water column in a well. The treatment area established by direct infusion can be designed as a grid to treat Cr(VI) source areas and/or as a treatment curtain or fence of treatment wells to cut off Cr(VI) plume migration by creating reducing conditions. The radius of influence for 50.8 mm diameter wells being supplied with C3H8 is approximately 3 m to 5 m. 14.1.2

Key Design Criteria

To achieve supersaturated conditions, C3H8 is infused at a standard rate of 15 cm3/min, promoting the growth of soil bacteria. A concentration of

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FIGURE 14.1.2 Photo of regulator adjustment, control panel in background.

66 mg/L of propane can be achieved in groundwater with a water column of 1.5 m in a well above the iSOC unit. Spacing of iSOC injection wells are typically 6 m to 9 m to apart, depending on lithologies. Performance monitoring wells should be placed within the center of the groundwater plume and at cross-gradient locations to assess the area of influence. In addition, based on consistent groundwater flow direction data, the downgradient sampling points should continue to be evaluated because changes within the plume occur over several months. Monitoring parameters should include at a minimum, oxidation-reduction potential (ORP/Eh, field), dissolved oxygen (field), iron(total (Fe2+)) nitrate(NO3− lab) sulfate(SO42− lab) dissolved propane (lab), pH (field), and the target contaminant concentrations (lab). Changes in plume characteristics, as well as reduction in Cr(VI) concentration occur slowly in anaerobic systems over a period of several months to several years. Obtaining equilibrium with C3H8 in an aquifer is likely to take 3 to 6 months or more.

14.1.3

Photoreduction of Cr(VI)

Medical researchers have found that Cr(VI) in the form of potassium dichromate (K2Cr2O7) can be photoreduced to Cr(III) in aqueous solutions

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FIGURE 14.1.3 Photo of gas infusion tool (iSOC) being placed into well.

containing glycerol (C3H8O3). The photoreduction of Cr(VI) occurred after irradiation with either UVA (320 – 400 nm) or a wide spectrum light source. A lower spectrum UVB (290 – 320 nm) light source did not work at photoreducing the Cr(VI). The photoreduction of Cr(VI) was noted to be pHdependant and did not occur in dilute solutions of sodium hydroxide (NaOH). In the acidified solutions, the photoreduction of Cr(VI) occurred at elevated rates and at lower concentrations of glycerol. This reaction is apparently dependent on the unsubstituted alcohol groups of glycerol since alpha-phosphoglycerol or beta-phosphoglycerol did not support the photoreduction of Cr(VI) (Yurkow et al., 2000).

14.1.4

Pollution Prevention Trends

A systematic approach to pollution prevention can go far in identifying and reducing adverse environmental effects. Pollution prevention from a manufacturing perspective can include material substitution, process improvement, product change or redesign, or a combination or these strategies. Material substitution is essentially the use of different materials that are deemed less toxic or nontoxic. Replacement of Cr with non-Cr bearing raw

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materials or replacement of equipment that does not require Cr is a clear example of material substitution. Paint waste can be eliminated as a hazardous waste stream via the removal of lead (Pb) and Cr from most paint formulations. Paint sludge is now recycled into building materials such as quarry tile, asphalt, mastic, and binder. Process improvement allows for the reduction or elimination of the need to use Cr. This can be accomplished by increasing the operating efficiency of certain equipment or process, development of stringent maintenance programs, and formulation of training programs to reduce the risk of waste generation. With the prevalent use of Cr(VI) in plating operations, improvement in the type of bath used presents a good example of how a slight modification in equipment can significantly reduce the amount of Cr required and waste generated. A technique of porous pot bathing has been used to extend the bath life, thereby reducing the discharge of pollutants, and reducing the amount of Cr needed for the plating operation. During the plating process, concentrations of iron(Fe) and other cationic impurities build up in a Cr(VI) bath to the extent that the plating becomes unacceptable. If the bath is contained in a porous pot where a semipermeable membrane separates cathode from anode and power is applied, the (Fe) and other contaminant metal ions pass through the membrane. These ions accumulate in the cathode chamber from which they are periodically removed for subsequent disposal. CrO42− ion remains in the anode compartment as part of the solution and can be returned to the plating tank for reuse. Approximately 80% of the available power supplied to a Cr(VI) bath generates hydrogen gas (H2) during decorative and functional plating applications. The gas produces a mist of fine water particles with entrained Cr(VI), thereby creating a potential inhalation hazard to workers and increased costs for waste-water treatment to reduce Cr(VI) to Cr(III). However, with certain plating operations, notably decorative plating, the use of Cr(III) has proven successful in eliminating the need for misting and subsequent wastewater treatment. Furthermore, the use of Cr(III) allows for improved adherence, throw and coverage, and higher rack densities, with lower volumes of sludge produced during the process. Plating coatings are typically limited to less than 0.00254 mm since thicker coatings are prone to cracking and spalling; thus, the use of Cr(III) is usually unsuitable for hard chrome coatings which can be 0.508 mm or more in thickness. Product change or redesign in some cases may eliminate Cr from the manufacturing process altogether (www.epa.state.oh.us/opp/mfrm.txt). For example, colorants, adhesives, and dispersions used for the plastics industry, typically using lead chromate(PbCrO4) pigments, may be replaced with organic compounds. In another example, an aluminum(Al) extruding facility in Ohio was able to remove Cr(VI) by (a) changing from an alkaline cleaner to a dispersion cleaner that was Cr-free, (b) substituting an iron phosphate conversion coating in the pretreatment process for the previous Cr(VI) process, (c) removal of Cr(VI) from the paint line by changing to a powder coating,

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and (d) removal of Cr(VI) from the anodizing line by implementing a totally non-Cr conversion coating process.

Bibliography Archibald, J., 2001, In Situ Remediation of MTBE: TBA, and BTEX Using ISOC and Pure Oxygen, National Groundwater Association American Petrolium Institute Conference, Abstracts, Nov. 16. Bopp, L.H., Chakrabarty, A.M., and Ehrlich, H.L., 1983, Chromate resistance plasmid in Pseudomonas fluorescens, Journal of Bacteriology, 155, 1105–1109. Fude, L., Harris, B., Urrutia, M.M., and Beveridge, T.J., 1994, Reduction of Cr(VI) by a consortium of sulfate-reducing bacteria, Applied Environmental Microbiology, 60, 1525–1531. Gerlach, R., Cunningham, A. and Caccavo, Jr., F., 1999, Chromium elimination with microbially reduced iron-redox-reactive biobarriers, in Bioremediation of Metals and Inorganic compounds, Leeson A. and Alleman, B.C., Eds., Battelle Press, Columbus, OH, Vol. 5, No. 4, pp. 13–18. Ghoshal, S., Al-Hakak, A., and Hawari, J., 2001, Naphthalene degradation and concurrent Cr(VI) reduction by Pseudomonas putida ATCC17484, in Bioremediation of Inorganic Compounds, Leeson, A., Peyton, B., Means, J., and Magar V.S. Eds., Battelle Press, Columbus, OH, Vol. 6, No. 9, pp. 139–146. Gvozdyak, P.I., Mogilevich, N.F., Ryl’skii, A.F., and Grishchenko, N.I., 1986, Reduction of hexavalent chromium by collection strains of bacteria, Mikrobiologiya, 55, 962–965. Hong, J. and Sewell, G.W., 1999, Organic electron donors for the microbial Cr(VI) reduction, in Bioremediation of Metals and Inorganic Compounds, Leeson A., and Alleman, B.C., Eds., Battelle Press, Columbus, OH, Vol. 5, No. 4, pp. 135–140. Horitsu, H., Futo, S., Miyazawa, Y., Ogai, S., and Kawai, K., 1987, Enzymatic reduction of hexavalent chromium by hexavalent chromium-tolerant Pseudomonas ambigua G-1, Agricultural and Biological Chemistry, 51, 9, 2417–2420. McLean, J.S. and Phipps, D., 1999, Chromate removal from contaminated groundwater using indigenous bacteria, in Bioremediation of Metals and Inorganic Compounds, Leeson, A., and Alleman, B.C., Eds., Battelle Press, Columbus, OH, Vol. 5, No. 4, pp. 121–126. Perlmutter, M.W., 2001, In situ biotreatment of perchlorate and chromium in groundwater, in Bioremediation of Inorganic Compounds, Leeson, A., Peyton, B., Means, J., and Magar, V.S. Eds., Battelle Press, Columbus, OH, Vol. 6, No. 9, pp. 315–322. Suthersan, S.S., 2002, Natural and Enhanced Remediation Systems, CRC Press, Lewis Publishers, Boca Raton, FL, p. 419. Wang, P.C., Mori, T., Komori, K., Sasatsu, M., Toda, K., and Ohtake, H., 1989, Isolation and characterization of an Enterobacter cloacae strain that reduces hexavalent chromium under anaerobic conditions, Applied Microbiology and Biotechnology, 55, 1665–1669. Yurkow, E.J., Hong, J., Min, S., Wang, S., Cerven, D.R., and DeGeorge, G.L., 2000, Glycerol-Mediated Photoreduction of Hexavalent Chromium, presented by MB Research Laboratories, at the SOT Meeting, Philadelphia, PA. (Abstracts.)

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14.2 Conclusions

James A. Jacobs and Jacques Guertin Chromium (Cr) occurs naturally in the environment in three oxidation states, +3, +6, and rarely, 0. These oxidation states are named chromium(III) (Cr(III)), chromium(VI) (Cr(VI)), and elemental chromium/chromium(0) (Cr(0)), respectively. Owing to its unique properties, Cr is a strategic element in industry. It is important to handle Cr safely regardless of its oxidation state, especially Cr(VI). Although some properties of Cr were known 200 years ago, it has only been during the last 50 years that the toxic nature of Cr(VI) became known and the Cr(VI) form of Cr was measured in the environment. Because Cr(VI) is very soluble in water under most environmental conditions (whereas Cr(III) is not usually soluble in water), it can be transported in groundwater thousands of meters from its source. And since the mid 1970s, numerous industrial facilities and landfills have contaminated the groundwater with Cr(VI) at concentrations greater than the U.S. Environmental Protection Agency (USEPA) and California drinking water standards of 0.1 mg/L (0.1 ppm) and 0.05 mg/L (0.05 ppm), respectively. Chromium(VI) will continue to be used by industry. Fortunately, the processing of waste water has improved so that insignificant or no release of Cr(VI) should occur. Worker exposure to elemental Cr and Cr(VI) from operations that produce airborne particles or fumes such as welding, grinding, cutting, machining, and heating must be minimized. There are many ongoing studies regarding the exposure of Cr to humans and its toxicity. Experimental evidence suggests that Cr(VI) is most toxic when inhaled and that it is reduced to essentially nontoxic Cr(III) when ingested. Cr(III) at low concentration is a necessary human nutrient. There are effective remedial methods for cleaning up Cr-contaminated soil and groundwater to minimize exposure to Cr. These mainly use chemical or biological processes that reduce Cr(VI) to Cr(III) (usually to the insoluble Cr(OH)3), thus achieving a reduction in toxicity and Cr mobility. In order to determine the effectiveness of remediation and to more accurately estimate the health risk from any remaining contamination, better chemical analysis methods for the speciation of Cr in the environment or industrial settings (i.e., to measure the concentration of Cr(III), Cr(VI), and Cr(0)) are needed.

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Index

A Acetate, physicochemical properties, 34 Acetate hexahydrate, physicochemical properties, 34 Acetate hydrate, physicochemical properties, 34 Acetylacetonate, physicochemical properties, 34 Adsorbents, use of in remediation, 292 Afghanistan chromite production, 662 chromium production, 664 Agencies regulating chromium, 505–507 Agency for Toxic Substances and Disease Registry, 6 Agricultural materials, chromium in, 158 Air, 69–70 chromium concentration in, 44 forensic geochemistry, 83 quality regulations, 494, 507 Albania chromite ore production, 658 chromite production, 662 chromium production, 664 ferrochromium production, 660, 663 Allied Chemical and Dye Company, 12 Alloy manufacturing, chromium use in, 16 Alloys, in chromium processing, 18 Alpine-type chromite deposits, 65 Aluminum, wastestream reductions, 469 Ammonium, physicochemical properties, 39, 41 Ammonium sulfate, physicochemical properties, 34 Anaerobic in situ reactive zones, engineered, remediation of chromium using, 427–440 baseline definition, 431 bio geo chemical behavior of chromium, 431–432 case study, 427–440 contaminant removal mechanisms, 432–433

design considerations, 429–431 Eastern United States, 437–439 groundwater chemistry, 430 hydrogeology, 429–430 regulatory issues, 433–434 Southwestern United States, 436–437 system layout, 430 Western United States, 434–436 Analytical laboratories, naturally occurring chromium, 116–117 Analytical methods, 5–6 Animal wastes, chromium concentration in, 158 Ankangite chemical formula, classification, 47 crystallography, 57 Antarctic Lakes, chromium concentration in, 44 Anthropogenic chromium in soil, 157–158 Anthropogenic sources of chromium, 152–161, 168–169 Antifouling pigments, chromium use in, 16 Antiknock compounds, chromium use in, 16 Antimonide, physicochemical properties, 34 Aqueous treatment reagents, ex situ, in situ chromium remedial methods, bench scale, 336–339 Aquifer contaminated with mixed wastes, biological chromium reduction, bench test, 348–356 analytical methods, 350 chromium solubilization, 353–355 denitrification, in schoolcraft enrichments, 352–353 enrichment culture, 350 microcosms, 349–350 schoolcraft sediment microcosms, 350–352 Aquifer sediments, in situ reduction of, for creation of permeable reactive barrier to remediate chromate, barrier longevity determination, bench test, 312–334

761

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762 Aquifers natural reductants in, 200–201 oxidation capacity of, 203–204 Arctic, chromium concentration in, 44 Argentina, chromium annual production, 664 Arid alluvial basins, Southwest United States, 96 Arkansas, chromium releases to water, land, 20 Armor plating, chromium use in, 16 Arsenide, physicochemical properties, 34 Asphalt, chromium concentration in, 43, 66 Atlantic Ocean, chromium concentration in, 43 Atmosphere. See also Air anthropogenic chromium in, 161 chromium in, 184–186 natural sources of chromium in, 152 Atomic absorption spectroscopy, 261–267 Atomic emission spectroscopy, 268–269 Atomic oxygen, oxidation potential, 480 Australia chromite ore production, 658 chromite production, 662 chromium production, 664 production/trade, 666 wood treating facility, case study, 412–414 Austria, chromium annual production, 664

B Baltimore Chemical Company, 11 Baltimore Chrome Works, 12 Bangladesh, chromium annual production, 664 Barbertonite chemical formula, classification, 47 crystallography, 57 Barium, physicochemical properties, 39 Barium dihydrate, physicochemical properties, 41 Barriers longevity determination, in situ reduction of aquifer sediments for creation of permeable reactive barrier to remediate chromate, bench test, 312–334 reactive, permeable, 369–371 technologies, 297–303 life cycle inventory/life cycle assessment, 520 permeable chemical barriers, 301–303 Basalt, chromium concentration in, 43, 67 Bazil, exports of ferrochromium, 654 Bedrock analytical methods, 113–116

Chromium(VI) Handbook Belgium chromium production, 664 production/trade, 666 Bench scale, ex situ, in situ chromium remedial methods, 335–348 Bench test, 311–356 barrier longevity determination, in situ reduction of aquifer sediments for creation of permeable reactive barrier to remediate chromate, 312–334 biological chromium reduction, aquifer contaminated with mixed wastes, 348–356 ex situ, in situ chromium remedial methods, bench scale, 335–348 Bentorite chemical formula, classification, 47 crystallography, 57 Bichromates, physicochemical properties of, 41–42 Biogeochemical cycling, 70–71 Biological chromium reduction, aquifer contaminated with mixed wastes, bench test, 348–356 analytical methods, 350 chromium solubilization, 353–355 denitrification, in schoolcraft enrichments, 352–353 enrichment culture, 350 microcosms, 349–350 schoolcraft sediment microcosms, 350–352 Biological transformations, 281–282 Biota, uptake, transformation of chromium by, 198–199 Biotite, chromium concentrations in, 68 Biotransformation, 455–457 Black shale, chromium concentration in, 43 Blake, William Phipps, 11–12 Blast furnaces, 20 Blood, chromium concentration in, 44 Bone, chromium concentration in, 44 Boride, physicochemical properties, 34 Bracewellite chemical formula, classification, 47 crystallography, 57 Brazil chromite ore production, 658 chromite production, 662 chromium production, 664 ferrochromium production, 660, 663 production/trade, 66–667 Brezinaite chemical formula, classification, 47 crystallography, 57

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Index Brines, natural, 96–97 Brockovich, Erin, 98, 692–696. See also Erin Brockovich movie Bromide, physicochemical properties, 34, 35 Bromide hexahydrate, physicochemical properties, 34, 35 Bromine, oxidation potential, 480 Burma chromite production, 662 chromium production, 664

C Cadmium, physicochemical properties, 39 Calcium, physicochemical properties, 39, 41 Calcium dihydrate, physicochemical properties, 39 Calcium hypochlorite, oxidation potential, 480 Calcium trihydrate, physicochemical properties, 41 California chromium concentration in, 43, 44 Glendale, policy/regulations, case study, 502–503 Office of Environment Health Hazard Assessment, 6 policy, recent developments in, 496–498 Turlock, Valley Wood Preserving Plant, case study, 388–395 Ukiah, Coast Wood Preserving Plant, case study, 415–420 Windsor, former wood treating plant, case study, 381–387 Calsbergite chemical formula, classification, 47 crystallography, 57 Canada chromium concentration in, 43, 44, 66 chromium production, 664 exports of chromite ore, 653 exports of ferrochromium, 654 production/trade, 667 Cancer, risk of, damages for, 549–550 Cancer effects of chromium, 220 dermal effects, 220 ingestion, 220 inhalation, 220 Cancer phobia, emotional distress and, 547–549 Carbide, physicochemical properties, 35 Carbonaceous meteorites, chromium concentration in, 43 Carbonate, physicochemical properties, 35 Carbonyl, physicochemical properties, 35

763 Carmichaelite chemical formula, classification, 47 crystallography, 57 Case studies, 357–464 anaerobic in situ reactive zones, engineered, remediation of chromium using, 427–440 Australia, wood treating facility, 412–414 California Turlock, Valley Wood Preserving Plant, 388–395 Ukiah, Coast Wood Preserving Plant, 415–420 Windsor, former wood treating plant, 381–387 chromium, chlorinated ethene groundwater plume, in estuarine influenced glaciated sediments, attenuation of, 440–460 East Coast, Delaware River, former paper mill, 409–411 Michigan, Grand Rapids, industrial facility, 420–427 Oregon, Corvallis, United Chrome Products, Inc., 376–381 South Carolina, Richland County, Townsend Saw Chain Company, 396–409 Washington, Vancouver, Frontier Hard Chrome, 373–376 Cassendanneite chemical formula, classification, 47 crystallography, 57 CAST flash distillation systems, plating, zero discharge, chemical recovery approach, manufacturing facility, 476 Caswellsilverite chemical formula, classification, 47 crystallography, 57 Catalysts, chromium use in, 16 Cattle manure, chromium concentration in, 158 Central European Mollase basin, Germany, chromium concentration in, 66 Ceramics, chromium use in, 16 Cereal, chromium concentration in, 44 Chain of custody request for analysis, 255 Characteristics, chromium compounds, 33 Chemical analysis, 261–271 atomic absorption spectroscopy, 261–267 atomic emission spectroscopy, 268–269 graphite furnace atomic absorption, 267–268 inductively coupled plasma, 269–270 ion chromatography, 270

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764 mass spectrometry, 270 x-ray fluorescence spectroscopy, 271 Chemical barriers, permeable, 301–303 Chemical characteristics, 4–5 Chemical formula, classification, 47–56 Chemical management, regulations/policy, 518–519 Chemical recovery approach, plating, zero discharge, manufacturing facility in Massachusetts, 470–477 CAST flash distillation systems, 476 cleaning, plating system configuration, 474 ion exchange, 475–476 metal plating process, 474 plating pretreatment, 474 tank farm, waste treatment, 474–475 treatment system description, 474–476 ultra-filter system, 475 Chemical toxicity reduction, 284–285 Chemical transformations, 278–281 Chemistry of chromium, 23–92, 276–278 China chromite ore production, 658 chromite production, 662 chromium production, 664 exports of ferrochromium, 654 ferrochromium production, 660, 663 production/trade, 667–668 Chloride, physicochemical properties, 35, 41 Chloride octahydrate, physicochemical properties, 35 Chlorinated ethene groundwater plume, chromium, in estuarine influenced glaciated sediments, attenuation of, case study, 440–460 Chlorination, effects of, naturally occurring chromium, 137–141 Chlorine, oxidation potential, 480 Chlorine dioxide, oxidation potential, 480 Chromate physicochemical properties, 39–40 remediation, aquifer sediments, in situ reduction of for creation of permeable reactive barrier, barrier longevity determination bench test, 312–334 Chromate oxide, physicochemical properties, 40 Chromatite chemical formula, classification, 48 crystallography, 57 Chrombismite chemical formula, classification, 48 crystallography, 57

Chromium(VI) Handbook Chromceladonite chemical formula, classification, 48 crystallography, 58 Chromdravite chemical formula, classification, 48 crystallography, 58 Chrome plating. See also Chrome products occupational exposures in chromic acid mist, control of, 616 exposures, 611–612 health effects, 611–617 oxidation states, toxicology and, 612–613 Chrome products Frontier Hard Chrome, Vancouver, Washington, case study, 373–376 regulatory overview, 374 remedial investigation, 375 remedial performance, 375 site characterization, 374 site location, history, 373–374 United Chrome Products, Inc., Corvallis, Oregon, case study, 376–381 regulatory overview, 377–378 remedial investigation, 378–379 remedial performance, 379–380 site characterization, 378 site location, history, 377 Chromferide chemical formula, classification, 48 crystallography, 58 Chromite, 675 chemical formula, classification, 48 crystallography, 58 exports for consumption of, by country, 653 imports of, time-value relations for, 647 ore bodies, 97 physicochemical properties, 35 production, by country, 662 Chromium. See under specific aspect of Chromium oxide, international chemical safety cards, 715–717, 747–749 Chromphyllite chemical formula, classification, 48 crystallography, 58 Chrompicotite, crystallography, 61 Chromyl, physicochemical properties, 41 Classification of treatment technologies, 282–283 containment, 283 destruction and removal, 283 reduction of toxicity, 282–283 Clay, deep sea, chromium concentration in, 43

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Index Coal, chromium concentration in, 43, 66 Coal disposal, chromium in, 159 Coast Wood Preserving Plant, Ukiah, California, case study, 415–420 Cobalt, physicochemical properties, 39 Cochromite chemical formula, classification, 49 crystallography, 58 Cocroite chemical formula, classification, 49 crystallography, 58 Colorimetric indicators, 252–253 Combining multiple approaches to remediate chromium, 304 Common units, definition of, 575–576 Competing cations, 194 Complex formation, 194 Conductivity, soil, 250 Cone penetration testing, 249–250 sensor probes, 250 soil sampling, 249 water sampling, 250 Consumption of chromium, 15, 647–648. See also under specific area apparent, defined, 633 in United States, 645 Containers, labeling, policy, regulations, 511–513 Containment technologies, 283, 297–304, 752 barrier technologies, 297–303 life cycle inventory/life cycle assessment, 520 permeable chemical barriers, 301–303 solidification/stabilization, 303–304 vitrification, 303 Contaminants direct sensing of, 251–253 colorimetric indicators, 252–253 laser-induced breakdown spectroscopy, 252 laser-induced fluorescence spectroscopy, 253 membrane interface probe, 253 in situ screening of heavy metals, 251 x-ray fluorescence, 251–252 utilizing natural environmental processes, 199–207 Contaminated Superfund sites, 751–754 containment technologies, 752 electrokinetics, 754 in situ soil flushing, 754 in situ solidification, 753 in situ stabilization, 753 in situ vitrification, 753 soil washing, 753

765 solidification, 752 stabilization, 752 Conventional drilling techniques, 239–246 Conversions, International System of Units, 577–581 Copper physicochemical properties, 39 reduction of chromium, 179–180 smelting, 20 wastestream reductions, 469 Corrosion inhibitors, chromium use in, 16 Cow manure, chromium concentration in, 158 CPT. See Cone penetration testing Croatia ferrochromium production, 660, 663 production/trade, 668 Crocoisite, 7 Crocoite, 7 Crude oil, 65–66 chromium concentration in, 66 Crystallography, chromium, 57–63 Cuba chromite production, 662 chromium production, 664 Cycle, chromium, 147–152 Czech Republic, chromium annual production, 664

D Dairy products, chromium concentration in, 44 Damages, legal, 541–551 cancer, risk of, 549–550 defined, 541–542 medical monitoring suits, 543–550 defenses to, 546–647 property damage cases, 550–551 theories of, 542–550 toxic physical injuries, 542 Daubert case, legal application of, 537–538 Daubreelite chemical formula, classification, 49 crystallography, 58 Deanesmithite chemical formula, classification, 49 crystallography, 58 Death from ingestion of chromium, 223 from inhalation of chromium, 221 Decontamination of equipment, 254 Decorative finishes, chromium use in, 16 Delaware River, former paper mill, case study, 409–411

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766 Delivery of sample to laboratory, 255 Denitrification, in schoolcraft enrichments, 352–353 Dental constructions, chromium use in, 16 Depletion allowance, 681 Dermal contact, toxicology, chromium, 219, 225 Desorption reactions of chromium, 181–184 Developmental effects from ingestion of chromium, 224 from inhalation of chromium, 223 Dewey, Melville Louis Kossuth, 12 Dichromate, physicochemical properties, 41–42 Dichromate dihydrate, physicochemical properties, 41 Dietzeite chemical formula, classification, 49 crystallography, 58 Diorite, chromium concentration in, 67 Direct push technology probe rigs, 247–249 soil sampling, 247–248 vapor sampling, 248–249 water sampling, 248 well points, 249 Direct sensing of contaminants, 251–253 colorimetric indicators, 252–253 laser-induced breakdown spectroscopy, 252 laser-induced fluorescence spectroscopy, 253 membrane interface probe, 253 in situ screening of heavy metals, 251 x-ray fluorescence, 251–252 Dissipative use, defined, 634 Dissolution reactions of chromium, 180 Dissolved oxygen, manganese dioxides, oxidation of chromium to chromium, 174–176 Distribution in primary environments, 76–80 Domestic production, use, 681 Donathite chemical formula, classification, 49 crystallography, 58 DPT probe rigs. See Direct push technology probe rigs Drilling methods, 246–251 cone penetration testing, 249–250 sensor probes, 250 soil sampling, 249 water sampling, 250 conventional, 239–246 cable tool drilling, 242–243 hollow-stem auger, 240–242 monitoring well installation, 244–246

Chromium(VI) Handbook rotary drilling, 243–244 wire line coring, 244 direct push technology probe rigs, 247–249 soil sampling, 247–248 vapor sampling, 248–249 water sampling, 248 well points, 249 horizontal drilling, 246–247 pore pressure, 250–251 soil conductivity or resistivity, 250 soil texture, 251 Drilling muds, chromium use in, 16 Drinking water regulatory implications of, 501 regulatory process, 499–500 review, revision of, 500–501 standards/regulations, 494–498, 526–527 Drinking Water Maximum Contaminant Level, 6 Dukeite chemical formula, classification, 49 crystallography, 59 Dunite, chromium concentration in, 67 Duplicates, in groundwater sample quality control, 261

E Eastern United States, anaerobic in situ reactive zones, engineered, remediation of chromium using, 437–439 Ecolabeling, 520–521 Ecological effects of chromium, 225 data gaps, evaluation of, 226 exposure concentration, incremental risk, calculation of, 229–230 health risk calculations, 226–230 inhalation, calculation of, 230 studies, evaluation of, 226 Economic issues, 15–16 Edoylerite chemical formula, classification, 49 crystallography, 59 Egypt, chromium annual production, 664 Electrocoagulation, for chromium containing waste waters using, 477–489 case study, 486–487 equipment in plant, 488–489 flocculation, removal of chromium by, 481–483 iron electrodes, 488 sludge generation, 487 system operation, 487–489 Electrokinetics, 296–297, 754

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Index Electrometallury, 20 Electronics, chromium use in, 16 Electrooxidation, 483–496 for chromium containing waste waters using, 477–489 case study, 486–487 equipment in plant, 488–489 flocculation, removal of chromium by, 481–483 iron electrodes, 488 sludge generation, 487 system operation, 487–489 theoretical foundations of, 478–481 Electroplating, chromium use in, 16 Elemental/metallic chromium characteristics, 25–28 Elementis Chromium LP, 643 Embreyite chemical formula, classification, 50 crystallography, 59 Emotional distress, cancer phobia and, 547–549 Employees, induction, training of, 515 Emulsion hardeners, chromium use in, 16 Engineered anaerobic in situ reactive zones, remediation of chromium using, case study, 427–440 Environment transport, fate of chromium in environment, 165–214 geochemistry, 169–171 natural environmental processes, for soil, groundwater contaminated with chromium, 199–207 oxidation-reduction of chromium, 172–180 reactions, 172 precipitation/dissolution reactions, 180 presence of chromium in environment, 168–169 sorption, desorption reactions, 181–184 Environmental effects, 19–20, 644–647 monitoring, regulations/policy, 515–518 Environmental Protection Agency Drinking Water Maximum Contaminant Level, 6 National Priority List Superfund Sites, 6 Equipment decontamination, 254 Eramet Marietta Inc., 643 Erin Brockovich movie, comments on, 691–692 Eskolaite chemical formula, classification, 50 crystallography, 59 European Union, regulations/policy, 511–517, 665

767 Ex situ remedial methods. See also under specific method adsorbents, 292 aqueous treatment reagents, 336–339 bench scale, 335–348 chromium geochemistry, 335–336 granular activated carbon, 291–292 ion exchange, 290–291 membrane filtration, 292–294 particles, analysis of, 343–345 reactive permeable barrier, 346 reductant treatment, 341–342, 345–346 removal technologies, 290–295 soil washing, separation technologies, 294–295 solid treatment reagent, 339–340 stoichiometry, reaction kinetics, 340–341 test results, 342–346 Expert witness testimony, 534–541 background, 534–535 Daubert, application of, 537–538 expert testimony, court treatment of, 539–541 Hanford litigation, 538–541 scientific evidence, rules regarding, 535–537 trial court’s rejection of testimony, 540–541 Exports of chromium materials, by type, 650–652 for consumption of chromite ore, by country, 653 for consumption of ferrochromium, by country, 654–655 Exposure concentration, incremental risk, calculation of, 229–230 Exposure pathways, 3–4, 218

F Farmyard manure, chromium concentration in, 158 Fate of chromium in environment, environment transport, 165–214 geochemistry, 169–171 natural environmental processes, for soil, groundwater contaminated with chromium, 199–207 oxidation-reduction of chromium, 172–180 reactions, 172 precipitation/dissolution reactions, 180 presence of chromium in environment, 168–169 sorption, desorption reactions, 181–184 Feldspar, chromium concentrations in, 68

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768 Ferchromide chemical formula, classification, 50 crystallography, 59 Ferrochromium, 676 chromium production capacity, 664 exports for consumption of, by country, 654–655 imports of, time-value relations for, 647 producers of, 660–661 world production, by country, 663 Fertilizers, chromium concentration in, 158 Field blanks, groundwater sample quality control, 261 Field data recording, 253–257 chain of custody request for analysis, 255 delivery of sample to laboratory, 255 drilling activities, prior to, 256 equipment decontamination, 254 instrument calibration, maintenance, 254 labels for sample, 254 lithologic descriptions, 256–257 manual sampling methods, 256 pedologic descriptions, 256–257 protocol, soil sampling, 256–257 quality control, soil sample, 257 sample control, 254–255 sample preparation, packaging, handling, 255 Finland chromite ore production, 658 chromite production, 662 chromium production, 664 ferrochromium production, 660, 663 production/trade, 668 Fixation reactions in wood preservation industry, 596 Flexible printing, chromium use in, 16 Florensovite chemical formula, classification, 50 crystallography, 59 Fluoride, physicochemical properties, 36, 41 Fluoride trihydrate, physicochemical properties, 36 Fluorine, oxidation potential, 480 Fly ash disposal, chromium in, 159 Food, chromium concentration in, 44 Foreign trade, 648–649. See also individual country Forensic geochemistry, 82–83 air, 83 groundwater, 82–83 soil, 82 Formate 6-water, physicochemical properties, 36 Fornacite

Chromium(VI) Handbook chemical formula, classification, 50 crystallography, 59 France chromium production, 664 exports of ferrochromium, 654 production/trade, 668 Frontier Hard Chrome, Vancouver, Washington, case study, 373–376 Fruits, chromium concentration in, 44 Fungicides, chromium use in, 16 Future developments, 565–574

G Gabbro, chromium concentration in, 67 Gas absorbers, chromium use in, 16 General redox behavior of chromium in environment, 173–174 Genotoxic effects from ingestion of chromium, 224–225 from inhalation of chromium, 223 Geochemical fixation, 362–369 Geochemistry of chromium, 23–92, 106–110, 169–171 Geology chromium, chromium compounds, 23–92 naturally occurring chromium, 106–110 Georgeericksenite chemical formula, classification, 50 crystallography, 59 Georgia, chromium releases to water, land, 20 Germany chromium production, 664 exports of chromite ore, 653 exports of ferrochromium, 654 ferrochromium production, 661, 663 production/trade, 668 GFAA. See Graphite furnace atomic absorption Gosting II, Austria, chromium concentration in, 66 Government programs, 639–643 Government stockpiles of chromium, 681–684 year-end inventories, 646 Granite chromium concentration in, 43, 67 rock-forming minerals in, 68 Granodiorite, chromium concentration in, 67 Granular activated carbon, 291–292 Graphite furnace atomic absorption, 267–268 Great Lakes, chromium concentration in, 43 Greece chromite production, 662 chromium production, 664

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Index Grimaldiite chemical formula, classification, 50 crystallography, 59 Groundwater, 69, 188–190 agricultural materials, 158 analytical methods, 113–116 anthropogenic chromium, 160–161 arid alluvial basins, Southwest United States, 96 brines, natural, 96–97 chromite ore bodies, 97 chromium cycle, 147–152 coal, 159 contamination, 143–164 examples, 95–98 fly ash disposal, 159 forensic geochemistry, 82–83 geochemistry, 106–110 geology, 106–110 hydrogeology, 106–110 investigative methods, 110–117 leaching test procedures, 117–118 mining, 160 monitoring protocol, 258 natural chromium occurrences in, 80–81, 93–142, 152 plumes in, case studies, 190–192 Presidio of San Francisco case study, 94–137 sampling, 239 duplicates, 261 field blanks, 261 quality control, 260–261 from wells, 258–259 serpentinite ultramafic terrains, 97–98 sewage sludges, 159 smelter wastes, 160 sources of chromium, anthropogenic, 152–161 utilizing natural environmental processes, 199–207 wells, 137–141 Guyanaite chemical formula, classification, 50 crystallography, 59

H Handling of sample, 255 Hanford litigation, 538–541 Hard-wearing surfaces, chromium use in, 16 Harden steel, chromium use in, 16 Hashemite chemical formula, classification, 50 crystallography, 59

769 Hawaii, Oahu, waste stream processing, 366–470 Hawthorinite chemical formula, classification, 51 crystallography, 60 Health effects of chromium, 7, 215–234, 644–649 cancer effects, 220 dermal effects, 220 ingestion, 220 inhalation, 220 dermal effects of chromium, 225 ingestion, 223–225 death, 223 developmental effects, 224 genotoxic effects, 224–225 immunological, lymphoreticular effects, 223–224 neurological effects, 224 reproduction effects, 224 inhalation, 221–223 death, 221 developmental effects, 223 genotoxic effects, 223 immunological, lymphoreticular effects, 222 neurological effects, 222 reproduction effects, 222 systemic effects, 221–222 risk calculations, 226–230 Heavy metals. See under specific metal in situ screening, 251 Heideite chemical formula, classification, 51 crystallography, 60 Hemihedrite chemical formula, classification, 51 crystallography, 60 Henry Bower Chemical and Manufacturing Company, 12 Hide, transformation into leather, 585–590 advantages of chromium tanned leather, 586 clean technologies, development of, 590 consumer, effects on, 589–590 environment, effects on, 587 health risks, tanning workers, 587 tanning, 585–586 High-temperature batteries, chromium use in, 16 Hip replacement parts, chromium use in, 16 History of chromium use, 7–13, 492–493 Home scrap, defined, 634 Horizontal drilling, 246–247

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770 Human joint replacement parts, chromium use in, 16 Human tissue, chromium concentration in, 44 Hydrogen peroxide oxidation potential, 480 reduction of chromium, 180 Hydrogeology, naturally occurring chromium, 106–110 Hydroxide, physicochemical properties, 36 Hydroxide trihydrate, physicochemical properties, 36 Hydroxyl radical, oxidation potential, 480 Hypochlorous acid, oxidation potential, 480 Hypoiodous acid, oxidation potential, 480

I ICP. See Inductively coupled plasma Idaho, chromium releases to water, land, 20 Igneous rock, chromium concentration in, 43 Immobilization, chromium, 320 Immunological effects from ingestion of chromium, 223–224 from inhalation of chromium, 222 Importation of chromium sources, 681 time-value relations, 647 by type, 656–657 In situ remedial methods, 295–297. See also under specific method aqueous treatment reagents, 336–339 aquifer sediment reduction, 312–334 bench scale, 335–348 chromium geochemistry, 335–336 electrokinetics, 296–297 particles, analysis of, 343–345 reactive permeable barrier, 346 reductant technology, 341–342, 345–346 screening, heavy metals, 251 soil flushing, 295–296, 754 solid treatment reagent, 339–340 solidification of contaminated sites, 753 solids generation, reductant technology, 341 stabilization of contaminated sites, 753 stoichiometry, reaction kinetics, 340–341 test results, 342–346 vitrification of contaminated sites, 753 India chromite ore production, 658 chromite production, 662

Chromium(VI) Handbook chromium production, 664 ferrochromium production, 660, 661, 663 production/trade, 668–669 Indiana, chromium releases to water, land, 20 Indonesia chromite ore production, 658 chromite production, 662 chromium production, 664 Inductively coupled plasma, 269–270 Industrial facility, Grand Rapids, Michigan, case study, 420–427 cleanup standards, 422 field sampling activities, 423–424 historical land use, 421–422 pilot study results, 425 regulatory activities, timeline, 422 regulatory agencies, 422 regulatory overview, 422–424 remedial alternatives evaluation, 425 remedial investigation, 425 remedial performance, 425–426 site characterization, 422 site geology, 422 site hydrology, 423 site location, history, 421–422 site setting, 421 Industrial history of chromium, 492–493 Industrial organics, 20 Industrial waste landfill, northern France, 191–192 Industry structure, 649 Ingestion of chromium, 223–225 death, 223 developmental effects, 224 genotoxic effects, 224–225 immunological effects, 223–224 lymphoreticular effects, 223–224 neurological effects, 224 reproduction effects, 224 toxicology, 217–219 Inhalation of chromium, 221–223 calculation of, 230 death, 221 developmental effects, 223 genotoxic effects, 223 immunological effects, 222 lymphoreticular effects, 222 neurological effects, 222 reproduction effects, 222 systemic effects, 221–222 toxicology, chromium, 219 Inorganic pigments, 20 Instrument calibration, 254 maintenance, 254

L1608_Index.fm Page 771 Friday, October 29, 2004 4:58 PM

Index International chemical safety cards, 703–704 chromium, 703–704 chromium oxide, 715–717, 747–749 zinc chromate, 735–737 International Standards Organization, 520 regulations/policy, 520 International System of Units, conversions, 577–581 Iodide, physicochemical properties, 36 Iodine, oxidation potential, 480 Ion chromatography, 270 Ion exchange, 290–291 Ionic radii, 28 Iquiqueite chemical formula, classification, 51 crystallography, 60 Iran chromite ore production, 658 chromite production, 662 chromium production, 664 ferrochromium production, 660, 663 Iranite chemical formula, classification, 52 crystallography, 60 Iron physicochemical properties, 36, 40, 41 reduction of chromium, 177–179 in treated water, 487 in waste water from metal planting, 486 ISO. See International Standards Organization Isolation of chromium, 18–19 Isotopes, 29–33 monitoring reduction via, 205–207 Isovite chemical formula, classification, 52 crystallography, 60 Italy chromium concentration in, 66 chromium production, 664 ferrochromium production, 663 production/trade, 669

J Japan agencies regulating chromium, 505 chromium production, 664 exports of ferrochromium, 654 ferrochromium production, 660, 663 production/trade, 670 JMC (USA) Inc., 643

771 K Kalaeloa Cogeneration Plant wastestream reductions, 469 in Oahu, Hawaii, 469 Kalininite chemical formula, classification, 52 crystallography, 60 Kazakhstan chromite ore production, 658 chromite production, 662 chromium production, 664 exports of ferrochromium, 654 ferrochromium production, 660, 663 production/trade, 670 Kentucky, chromium releases to water, land, 20 Knorringite chemical formula, classification, 52 crystallography, 60 Kohtla, Estonia, chromium concentration in, 66 Korea, Republic of, chromium annual production, 664 Kosmochlor chemical formula, classification, 52 crystallography, 60 Krinovite chemical formula, classification, 52 crystallography, 61

L Labeling packages, containers, regulations/policy, 511–513 for sample, 254 Laboratory, delivery of sample to, 255 Laser-induced breakdown spectroscopy, 252 Laser-induced fluorescence spectroscopy, 253 LCI/LCA. See Life cycle inventory/life cycle assessment Leaching test procedures, naturally occurring chromium, 117–118 Lead physicochemical properties, 40 wastestream reductions, 469 Leather, transformation of hide into, 585–590 advantages of chromium tanned leather, 586 clean technologies, development of, 590 consumer, effects on, 589–590 environment, effects on, 587 health risks, tanning workers, 587 tanning, 585–586

L1608_Index.fm Page 772 Friday, October 29, 2004 4:58 PM

772 Legal cases, survey of, 551–554 Legal standards, 525–527 Legislation, 639–643 Lehmann, Johann Gottlob, 7 Liability, theories of, 527–534 detail alleged, 534 negligence, 533 nuisance, 530–532 damages for, 532–533 strict liability, 528–529 trespass, 529–530 damages for, 532–533 waste, 530 Life cycle inventory/life cycle assessment, in barrier technology, 520 Limestone, chromium concentration in, 43, 67, 158 Lindsleyite chemical formula, classification, 52 crystallography, 61 Lithium, physicochemical properties, 40, 41 Lithium dihydrate, physicochemical properties, 40, 41 Lithologic descriptions, sample, 256–257 Litigation, 523–564 causation, 534–541 damages, 541–551 cancer, risk of, 549–550 defined, 541–542 medical monitoring cases, 543–550 property damage cases, 550–551 theories of, 542–550 toxic physical injuries, 542 details alleged, 534 expert witness testimony, 534–541 background, 534–535 court treatment of, 539–541 Daubert, application of, 537–538 Hanford litigation, 538–541 scientific evidence, rules regarding, 535–537 trial court’s rejection of testimony, 540–541 legal standards, 525–527 negligence, 533 nuisance, 530–532 damages, 532–533 regulatory background, 525–527 strict liability, 528–529 survey of published cases, 551–554 theories of liability, 527–534 trespass, 529–530 damages, 532–533 waste, 530 Liver, chromium concentration in, 44

Chromium(VI) Handbook Lopezite chemical formula, classification, 52 crystallography, 61 Loveringite chemical formula, classification, 53 crystallography, 61 Lymphoreticular effects from ingestion of chromium, 223–224 from inhalation of chromium, 222

M Macedonia chromite production, 662 chromium production, 664 Macquartite chemical formula, classification, 53 crystallography, 61 Madagascar chromite ore production, 658 chromite production, 662 chromium production, 664 Magnesiochromite chemical formula, classification, 53 crystallography, 61 Magnetic tape, chromium use in, 16 Magnetite, chromium concentrations in, 68 Manganese dioxides, oxidation of chromium to chromium, 174–176 Mangano-chromite, crystallography, 61 Manganochromite, chemical formula, classification, 53 Manual sampling methods, 256 Manure, chromium concentration in, 158 Mass spectrometry, 270 Massachusetts, manufacturing facility in, chemical recovery approach, plating, zero discharge, 470–477 Material safety data sheets, 514–515 chromic acid, 727–735 accidental release measures, 730 acute effects, 728–729 chronic effects, 728 disposal considerations, 733–734 ecological information, 733 exposure controls/personal protection, 731 eye, 728 fire fighting measures, 729–730 first aid measures, 729 handling, 730–731 hazards identification emergency overview, 727–729 ingestion, 728 ingredients, 727

L1608_Index.fm Page 773 Friday, October 29, 2004 4:58 PM

Index inhalation, 728 material safety data sheet, 727 physical, chemical properties, 731–732 product, company identification, 727 reactivity, 732 regulatory information, 734–735 signs, symptoms, 728 stability, 732 storage, 730–731 toxicological information, 732–733 transport information, 734 chromic oxide, 705–710 accidental release measures, fire, 706–707 chemical properties, 707 disposal considerations, 708–709 ecological information, 708 exposure controls/personal protection, 707 fire fighting measures, 706–707 first aid measures, 706 flammable properties, 706 handling, 707 hazards identification, 705–706 ingredients, 705 physical properties, 707 product, company identification, 705 reactivity, 707–708 regulatory information, 70 stability, 707–708 storage, 707 toxicological information, 708 transport information, 709 chromium, 700–703, 738–747 accidental release measures, 741 aggravation of preexisting conditions, 740 chronic exposure, 740 composition/information on ingredients, 738 disposal considerations, 744 ecological information, 744 emergency, first aid procedures, 701 emergency overview, 738–739 explosion, 741 explosion hazards data, 700–701 exposure controls/personal protection, 742–742 eye contact, 739, 740 eye protection, 743 fire, 740–741 fire extinguishing media, 741 fire fighting measures, 740–741 first aid measures, 740 handling, storage, 741–742

773 hazardous ingredients, 700 hazards identification, 738 health hazard information, 701 ingestion, 739, 740 inhalation, 739, 740 label first aid, 746–747 label precautions, 746 personal respirators, 742 physical, chemical properties, 743 physical data, 700 potential health effects, 739 precautions, 702–703 product identification, 700, 738 reactivity data, 702 regulatory information, 745–746 skin contact, 739, 740 skin protection, 743 special information, 741 special protection information, 702 spill, leak procedures, 702 stability, reactivity, 743 toxicological information, 744 transport information, 744–745 ventilation system, 742 chromium sulfate N-hydrate, 710–713 emergency/first aid procedure, 711 general information, 710 material release/spill, 712–713 physical/chemical characteristics, 711 chromium trioxide, 719–727 accidental release measures, 722 carcinogenicity, 720 chronic effects, 720 company identification, 719 disposal considerations, 725 ecological information, 724–725 exposure controls/personal protection, 722–723 fire fighting measures, 721–722 first aid measures, 721 handling, storage, 722 hazards identification, 719–720 ingestion, 720 ingredients, 719 physical, chemical properties, 723 potential health effects, 720–721 product identification, 719 regulatory information, 725–726 signs, symptoms, 720 stability and reactivity, 723 toxicological information, 724 transport information, 725 tris(2,4-pentanedionato)chromium(III), 713–715

L1608_Index.fm Page 774 Friday, October 29, 2004 4:58 PM

774 Mathiasite chemical formula, classification, 53 crystallography, 61 Matitza, Romania, chromium concentration in, 66 Mcconnellite chemical formula, classification, 53 crystallography, 61 Meat, chromium concentration in, 44 Medical monitoring claims damages, 543–550 defenses to, 546–647 Membrane filtration, 292–294 Membrane interface probe, 253 Mercury physicochemical properties, 40, 41 wastestream reductions, 469 Messel, Germany, chromium concentration in, 66 Metal finishing, chromium use in, 16 Metal planting, waste water from, 486 Metal primers, chromium use in, 16 Metallic chromium characteristics, 25–28 Metals in soil, 192–195 Mexico, exports of ferrochromium, 654 Michigan, Grand Rapids, industrial facility, case study, 420–427 Microbial toxicity reduction, 285–288 Milk, chromium concentration in, 44 Mine production, 684 Mineral processing, industrial applications, 673–674 Mining wastes, chromium in, 160 Mitigation technologies, emerging, 565–574 Mixed chromium, chlorinated ethene groundwater plume in estuarine influenced glaciated sediments, attenuation of, 440–460 assessment methodology, 442–444 attenuation processes, 449–460 field, analytical techniques, 442 geological character, 448–449 methodology, 441–444 partitioning, mass fluxes, 449–455 plume characteristics, geochemistry, 444–448 reduction power, sorption interactions, competition for, 457–460 site description, 441 Mixed wastes, aquifer contaminated with, biological chromium reduction, bench test, 348–356 analytical methods, 350 chromium solubilization, 353–355

Chromium(VI) Handbook denitrification, in schoolcraft enrichments, 352–353 enrichment culture, 350 microcosms, 349–350 schoolcraft sediment microcosms, 350–352 Molybdofornacite chemical formula, classification, 53 crystallography, 61 Mongshanite chemical formula, classification, 53 crystallography, 61 Mordants, chromium use in, 16 Mountkeithite chemical formula, classification, 54 crystallography, 61 MSDS. See Material safety data sheets Muscle, chromium concentration in, 44 Mutual Chemical Company, 12

N Nassau County, New York, 190 Natalyite chemical formula, classification, 54 crystallography, 61 Natural chromium concentrations, 33–72 air, 69–70 asphalts, 65–66 biogeochemical cycling, 70–71 chromium minerals, 46 chromium ore deposits, 46–65 podiform-type chromite deposits, 65 stratiform mafic-ultramafic chromite deposits, 64–65 coal, 65–66 crude oil, 65–66 groundwater, 69, 152 mantle, 46 pitch, 65–66 precipitation, 69 rock, 66–68, 150–152 sea water, 69 soil, 68 surface water, 69, 152 tars, 65–66 Natural reductants in aquifer, 200–201 Natural sources chromium in environment, 169 in groundwater, 93–142 chlorination, effects of, 137–141 Natural sources of chromium in atmosphere, 152 Natural substances, chromium concentration in, 43–44

L1608_Index.fm Page 775 Friday, October 29, 2004 4:58 PM

Index N.E. Caucasus, Russia, chromium concentration in, 66 Netherlands, chromium concentration in, 44 Neurological effects from ingestion of chromium, 224 from inhalation of chromium, 222 New scrap, defined, 634 Nichromite chemical formula, classification, 54 crystallography, 62 Nickel in treated water, 487 in waste water from metal planting, 483 Nitrate, physicochemical properties, 36 Nitrate 9-water, physicochemical properties, 37 Nitride, physicochemical properties, 37 Nitrogen, chromium concentration in, 158 Nonferrous smelting, 20 North Carolina, chromium releases to water, land, 20 North Sea, chromium concentration in, 43 Norway chromium production, 664 ferrochromium production, 660, 663 production/trade, 670 Nutrition, 644–649. See also Health

O Occidental Chemical Corp., 643 Occupational exposures in chrome plating. See also under specific industrial activity chromic acid mist, control of, 616 exposures, 611–612 health effects, 611–617 oxidation states, toxicology and, 612–613 prevention, 616 Ocean, chromium concentration in, 43 OEHHA. See California, Office of Environment Health Hazard Assessment Ohio, chromium releases to water, land, 20 Old scrap, defined, 634 Olkhonskite chemical formula, classification, 54 crystallography, 62 Oman chromite ore production, 658 chromite production, 662 chromium production, 664 Ore deposits, chromium, 46–65 podiform-type chromite deposits, 65

775 stratiform mafic-ultramafic chromite deposits, 64–65 Oregon, Corvallis, United Chrome Products, Inc., case study, 376–381 Organic matter, reduction of chromium, 179 OSHA Oxalate, physicochemical properties, 37 Oxidation of chromium, 174. See also Oxidation-reduction of chromium dissolved oxygen, manganese dioxides, oxidation of chromium to chromium, 174–176 H/d2/DO/d2/D, oxidation of chromium to chromium by, 176 reduction, rates of, 204–205 Oxidation-reduction of chromium, 172–180, 195, 278–279 general redox behavior of chromium in environment, 173–174 oxidation of chromium, 174 dissolved oxygen, manganese dioxides, oxidation of chromium to chromium, 174–176 H/d2/DO/d2/D, oxidation of chromium to chromium by, 176 reactions, 172 reduction of chromium, 176–180 copper, 179–180 hydrogen peroxide, 180 iron, 177–179 organic matter, 179 reduced sulfur, 179 Oxidation states, 28–29 Oxides, 177 physicochemical properties of, 37 Ozone, oxidation potential, 480

P Pacific Gas & Electric Company, litigation against, 691–696. See also Erin Brockovich movie Pacific Ocean, chromium concentration in, 43 Packaging policy, regulations, 511–513 of sample, 255 Pakistan chromite production, 662 chromium production, 664 Pallas, Peter Simon, 7 Paper mill, Delaware River, case study, 409–411 cleanup standards, 410 historical land use, 410

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776 regulatory overview, 410 remedial alternative, 411 remedial investigation, 410–411 remedial options, review of, 410 remedial performance, 411 site characterization, 410 site hydrology, 410 site location, history, 409–410 site setting, 409 Pedologic descriptions, sample, 256–257 Pennsylvania, chromium releases to water, land, 20 Perchlorate, physicochemical properties, 37 Perhydroxyl radical, oxidation potential, 480 Peridotite, chromium concentration in, 67 Permanganate, oxidation potential, 480 Permeable chemical barriers, 301–303 Permeable reactive barriers, 369–371 Persulfates, oxidation potential, 480 Petroleum, chromium concentration in, 43 Petterite chemical formula, classification, 54 crystallography, 62 Philippines chromite ore production, 658 chromite production, 662 chromium production, 664 exports of chromite ore, 653 Phoenicochroite chemical formula, classification, 54 crystallography, 62 Phosphate, physicochemical properties, 37 Phosphate coatings, chromium use in, 16 Phosphate hemiheptahydrate, physicochemical properties, 38 Phosphate hexahydrate, physicochemical properties, 38 Phosphate hydrate, physicochemical properties, 38 Phosphide, physicochemical properties, 38 Phosphorus, chromium concentration in, 158 Photoreduction of chromium, 569–570 Photosensitization, chromium use in, 16 Physical characteristics of chromium, 4–5 Physicochemical properties of chromium, 34–39 Phytoremediation, 288–290 Pig waste, chromium concentration in, 158 Planet Earth, chromium concentration in, 43 Plating. See also Chrome occupational exposures chromic acid mist, control of, 616 exposures, 611–612 health effects, 611–617

Chromium(VI) Handbook oxidation states, toxicology and, 612–613 pretreatment, plating, zero discharge, chemical recovery approach, manufacturing facility, 474 zero discharge, chemical recovery approach, manufacturing facility in Massachusetts, 470–477 CAST flash distillation systems, 476 cleaning, plating system configuration, 474 ion exchange, 475–476 metal plating process, 474 plating pretreatment, 474 tank farm, waste treatment, 474–475 treatment system description, 474–476 ultra-filter system, 475 Plumes in groundwater, case studies, 190–192 Poland chromium production, 664 ferrochromium production, 663 Policy issues, 491–522 agencies regulating chromium, 505–507 Japan, 505 South Africa, 506 United States, 506–507 air quality, 494, 507 California, Glendale, case study, 502–503 California policy, recent developments, 496–498 chemical management, 518–519 drinking water standards, 494–498 regulatory implications of, 501 regulatory process, 499–500 review, revision of, 500–501 ecolabeling, 520–521 employees, induction, training of, 515 environmental control, monitoring, 515–518 European Union, 505, 511–517 industrial history, chromium, 492–493 International Standards Organization, 520 labeling, packages, containers, 511–513 material safety data sheets, 514–515 product stewardship, 519 soil quality, 507 tools, 520 United States chromium policies, regulations, 492–504 waste disposal, 507–511 waste regulations, 493–494 water quality, 507 work place exposure, 511–519 worldwide chromium regulations, 504–521

L1608_Index.fm Page 777 Friday, October 29, 2004 4:58 PM

Index Pollution prevention trends, 570–572. See also Remediation Pore pressure, 250–251 Potassium chromium concentration in, 158 physicochemical properties, 40, 42 Potassium sulfate, physicochemical properties, 38 Potassium sulfate dodecahydrate, physicochemical properties, 38 Potatoes, chromium concentration in, 44 Poultry manure, chromium concentration in, 158 Precipitation, 69, 280–281 chromium concentration in, 44 reactions of chromium, 180 Preparation of samples, 255 Presidio of San Francisco case study, 94–137 hydrogeology, 108 investigation, approach for, 104–106 Price quotations, 648 chromium materials, 648 Primary production, defined, 635 Priority List of Hazardous Substances, 6 Probes membrane interface, 253 sensor, 250 Procedures for sampling/field data recording, 253–257 chain of custody request for analysis, 255 delivery of sample to laboratory, 255 drilling activities, prior to, 256 equipment decontamination, 254 instrument calibration, maintenance, 254 labels for sample, 254 manual sampling methods, 256 pedologic, lithologic descriptions, 256–257 protocol, soil sampling, 256–257 quality control, soil sample, 257 sample control, 254–255 sample preparation, packaging, handling, 255 Process of electroplating development of, 13 Producers, world chromite ore, 658–659 Producers of chromium products, United States, by industry, 643 Product stewardship, regulations/policy, 519 Production of chromium, 14–15, 643–644 Projectiles, armor piercing, chromium use in, 16 Property damage cases, 550–551 Protocol for soil sampling, 256–257 Pulp mills, 20 Pyrotechnics, chromium use in, 16 Pyroxenite, chromium concentration in, 67

777 Q Quality control groundwater sample, 260–261 duplicates, 261 field blanks, 261 soil sample, 257 Quartz, chromium concentrations in, 68 Quartz diorite, chromium concentration in, 67

R Radioactive isotopes, 29–33 Reaction rates, chromium, 75 Reactive barriers, permeable, 369–371 Reactive media, chromium reduction using, 371 Recording of field data, 253–257 chain of custody request for analysis, 255 delivery of sample to laboratory, 255 drilling activities, prior to, 256 equipment decontamination, 254 instrument calibration, maintenance, 254 labels for sample, 254 manual sampling methods, 256 pedologic descriptions, 256–257 protocol, soil sampling, 256–257 quality control, soil sample, 257 sample control, 254–255 sample preparation, packaging, handling, 255 Recycling of chromium, 618–632, 681 disposition, 629–630 dissipated materials, 623–624 fabrication, 632 infrastructure, chromium-containing scrap, 630–631 new scrap, 627–629 old scrap generated, 624–627 old scrap recycling efficiency, 630 scrap metals, processing of, 631–632 smelting/refining, 631 sources, chromium-containing scrap, 622–629 statistics, 621–622 Recycling rate, defined, 635 Redingtonite chemical formula, classification, 54 crystallography, 62 Redledgeite chemical formula, classification, 54 crystallography, 62

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778 Redox behavior of chromium in environment, reduction of chromium, 173–174 Reduced sulfur, reduction of chromium, 179 Reducing agents, 367–368, 369, 482–483 Reductants in aquifers, natural, 200–201 Reduction of toxicity, 176–180, 282–283, 455–457. See also Remediation Reduction rate, chromium, 320–321 Refractories chromium in, 16, 604–609 current applications, 605–606 properties of, 606 special refractories, 606–607 waste management, 607–608 National Refractories and Minerals Corp., 643 Regulations, 491–522, 525–527 agencies regulating chromium, 505–507 air quality, 494, 507 California, Glendale, case study, 502–503 California policy, recent developments, 496–498 chemical management, 518–519 drinking water, 494–498 regulatory implications of, 501 regulatory process, 499–500 review, revision of, 500–501 ecolabeling, 520–521 employees, induction, training of, 515 environmental control, monitoring, 515–518 European Union, 505, 511–517 industrial history, chromium, 492–493 International Standards Organization, 520 Japan, 505 labeling, packages, containers, 511–513 material safety data sheets, 514–515 product stewardship, 519 soil quality, 507 South Africa, 506 tools, 520 United States, 506–507 U.S, 492–504 waste disposal, 507–511 waste regulations, 493–494 water quality, 507 work place exposure, 511–519 worldwide chromium regulations, 504–521 Regulatory activities, timeline of, 382–383 Regulatory concentrations, exposure to chromium, 6 Remediation methods, 6, 282. See also Removal technologies; Toxicity reduction methods

Chromium(VI) Handbook emerging, 565–574 overview of, 364–365 Removal technologies, 290–297 ex situ technologies, 290–295 (See also Ex situ remedial methods) in situ technologies, 295–297 (See also in situ remedial methods) Reproduction effects from ingestion of chromium, 224 from inhalation of chromium, 222 Resistivity, soil, 250 Reverse osmosis, removal of chromium by, 481–483 Rilandite chemical formula, classification, 55 crystallography, 62 Rivers, chromium concentration in, 43 Roadside soils, chromium in, 160 Rock, 66–68 chromium concentration in, 43 natural occurrence of chromium in, 150–152 sources of natural chromium in, 76–80 Romania, ferrochromium production, 663 Russia chromite ore production, 659 chromite production, 662 chromium production, 664 exports of ferrochromium, 654 ferrochromium production, 660, 663 production/trade, 670

S Sampling direct sensing of contaminants, 251–253 drilling techniques, 246–251 conventional, 239–246 field data recording, 253–257 methods, 236–239 procedures, 253–257 water sampling, 257–261 San Francisco, Presidio of, case study, 94–137 investigation, approach for, 104–106 Sandstone, chromium concentration in, 43, 67 Santanaite chemical formula, classification, 55 crystallography, 62 Saudi Arabia, chromium concentration in, 66 Saw chain company, Townsend Saw Chain Company, Pontiac, Richland County, South Carolina, case study, 396–409

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Index field sampling activities, 405 historical land use, 396–399 pilot study results, 406 regulatory activities, timeline, 400–404 regulatory agencies, 400 regulatory overview, 400–404 regulatory standards, 404 remedial alternative, 405–406 remedial alternatives evaluation, 405 remedial performance, 406–408 site characterization, 404–406 site geology, 404–405 site hydrology, 405 site location, history, 396–399 site setting, 396 Schollhornite chemical formula, classification, 55 crystallography, 62 Schoolcraft sediment microcosms, biological chromium reduction, bench test, 350–352 Scientific evidence, legal rules regarding use in court, 535–537 Secondary environments, chromium distribution in, 80–81 Secondary production, defined, 635 Sediment, chromium concentration in, 43 Sedimentary rock, chromium concentration in, 43 Selenia, Albania, chromium concentration in, 66 Selenide, physicochemical properties, 38 Sensing of contaminants, direct, 251–253 colorimetric indicators, 252–253 laser-induced breakdown spectroscopy, 252 laser-induced fluorescence spectroscopy, 253 membrane interface probe, 253 in situ screening of heavy metals, 251 x-ray fluorescence, 251–252 Sensor probes, 250. See also Probes Separation technologies, 294–295 Serpentinite ultramafic terrains, 97–98 Sewage sludges, chromium in, 159 Shale, chromium concentration in, 43, 67 Shuiskite chemical formula, classification, 55 crystallography, 62 Siberian Beresof gold mines, 7 “Siberian red lead” usage of term, 7 Silicates, 177 Silicide, physicochemical properties, 38 Silver, physicochemical properties, 40, 42 Sims, Howard, 11

779 Slovakia chromium production, 664 ferrochromium production, 660, 663 Slovenia chromium production, 664 ferrochromium production, 660, 663 Smelter wastes, chromium in, 160 Sodium, physicochemical properties, 40, 42 Sodium chlorite, oxidation potential, 480 Sodium hypochlorite, oxidation potential, 480 Soil conductivity resistivity, 250 Soil contamination, 68, 192–198 agricultural materials, 158 anthropogenic, 152–161 atmosphere, anthropogenic chromium in, 161 behavior of, 195–198 chromium cycle, 147–152 coal disposal, 159 concentration of, 43 conductivity, 250 resistivity, 250 contamination, 143–164 fly ash disposal, 159 forensic geochemistry, 82 metals in, 192–195 mining, 160 natural environmental processes, contamination with chromium utilizing, 199–207 resistivity, 250 roadside soils, 160 rock, natural occurrence of chromium in, 150–152 sewage sludges, 159 smelter wastes, 160 texture, 251 water, anthropogenic chromium in, 160–161 Soil flushing, of contaminated sites, 295–296, 754 Soil quality, regulations/policy, 507 Soil sampling, 239 cone penetration testing, 249 direct push technology probe, 247–248 Soil texture, 251 Soil washing, 294–295, 753 Solar system, chromium concentration in, 43 Solidification of contaminated sites, 303–304, 752, 753 Solids generation, reductant treatment, 341 Sorption of chromium, 182, 279–280 reactions, 181–184

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780 South Africa, 518 agencies regulating chromium, 506 chromite ore production, 658, 659 chromite production, 662 chromium production, 664 exports of chromite ore, 653 exports of ferrochromium, 654 ferrochromium production, 660, 663 production/trade, 671–673 South Carolina, Richland County, Townsend Saw Chain Company, case study, 396–409 Southwest United States anaerobic in situ reactive zones, engineered, remediation of chromium using, 436–437 arid alluvial basins, 96 Spain chromium production, 664 ferrochromium production, 663 Stabilization of contaminated sites, 303–304, 752, 753 Stable isotopes, 29–33 monitoring reduction via, 205–207 Stainless steel, 676 chromium production capacity, 664 Stars, chromium concentration in, 43 Stearate, physicochemical properties, 39 Steelworks, 20 Stichtite chemical formula, classification, 55 crystallography, 62 Stocks of chromium products, United States, 645 Stream beds, chromium concentration in, 43 Strontium, physicochemical properties, 40 Substitutes, 16, 685 Sudan chromite ore production, 658 chromite production, 662 chromium production, 664 Sugars, chromium concentration in, 44 Sulfate, physicochemical properties, 38 Sulfate 7-water, physicochemical properties, 38 Sulfate 12-water, physicochemical properties, 38 Sulfate pentahydrate, physicochemical properties, 38 Sulfides, 177 physicochemical properties, 38 Sulfur, reduced, reduction of chromium, 179 Sun, chromium concentration in, 43 Superalloys, defined, 635

Chromium(VI) Handbook Superfund sites chromium contaminated, 751–754 containment technologies, 752 electrokinetics, 754 in situ soil flushing, 754 in situ solidification, 753 in situ stabilization, 753 in situ vitrification, 753 soil washing, 753 solidification, 752 stabilization, 752 Environmental Protection Agency National Priority List, 6 Surface water, 186–188 natural chromium occurrences in, 80–81, 152 Survey of legal cases, 551–554 Suspended solids, in treated water, 487 Sweden chromium production, 664 exports of ferrochromium, 654 ferrochromium production, 661, 663 production/trade, 673 Systemic effects, from inhalation of chromium, 221–222

T Taiwan, chromium annual production, 664 Tank farm, waste treatment, plating, zero discharge, chemical recovery approach, manufacturing facility, 474–475 Tanning of leather, 585–590 advantages of chromium tanned leather, 586 chromium use in, 16 clean technologies, development of, 590 consumer, effects on, 589–590 environment, effects on, 587 health risks, tanning workers, 587 Tarapacaite chemical formula, classification, 55 crystallography, 62 Tars, chromium concentration in, 66 Telluride, Colorado, 190–191 Telluride, physicochemical properties of, 39 Testimony of expert witness, 534–541 background, 534–535 Daubert, application of, 537–538 expert testimony, court treatment of, 539–541 Hanford litigation, 538–541

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Index scientific evidence, rules regarding, 535–537 trial court’s rejection of, 540–541 Tetrahydrate, sodium, physicochemical properties, 42 Texas, chromium releases to water, land, 20 Textile preservatives, chromium use in, 16 Textile printing, dyeing, chromium use in, 16 Theories of legal liability, 527–534 detail alleged, 534 negligence, 533 nuisance, 530–532 damages for, 532–533 strict liability, 528–529 trespass, 529–530 damages for, 532–533 waste, 530 Timber preservation industry, 593–599 fixation reactions, 596 formulations, examples of, 594 future developments, 598–599 historical development, 593–594 role of chromium compounds in, 594–595 Timeline, regulatory activities, 382–383 Tobacco smoke, chromium concentration in, 44 Tongbaite chemical formula, classification, 55 crystallography, 63 Tools, regulations/policy, 520 Tort litigation, 523–564 damages, 541–551 cancer, risk of, 549–550 defined, 541–542 medical monitoring case, 543–550 property damage case, 550–551 theories of, 542–550 toxic physical injuries, 542 expert witness testimony, 534–541 background, 534–535 Daubert, application of, 537–538 expert testimony, court treatment of, 539–541 Hanford litigation, 538–541 scientific evidence, rules regarding, 535–537 trial court’s rejection of testimony, 540–541 legal standards, 525–527 regulatory background, 525–527 survey of cases, 551–554 survey of published cases, 551–554 theories of liability, 527–534 detail alleged, 534 negligence, 533 nuisance, 530–532

781 nuisance damages, 532–533 strict liability, 528–529 trespass, 529–530 trespass damages, 532–533 waste, 530 Townsend Saw Chain Company, Richland County, South Carolina, case study, 396–409 Toxic physical injuries, damages, 542 Toxicity reduction methods, 283–290. See also under specific method chemical reduction, 284–285 microbial reduction, 285–288 phytoremediation, 288–290 Toxicology of chromium, 217–219. See also Health effects dermal contact, 219 exposure-route pathway, 218 ingestion, 217–219 inhalation, 219 Transport, environment, fate of chromium, 165–214 geochemistry, 169–171 natural environmental processes, for soil, groundwater contaminated with chromium, 199–207 oxidation-reduction of chromium, 172–180 reactions, 172 precipitation/dissolution reactions, 180 presence of chromium in environment, 168–169 sorption, desorption reactions, 181–184 Treatment technologies, 275–310. See also under specific technology classification of, 282–283 containment technologies, 297–304 multiple approaches, combining, for remediation, 304 removal technologies, 290–297 toxicity reduction methods, 283–290 Trespass, damages for, 532–533 Trial court, rejection of expert testimony, 540–541 Turbidity, 259–260 Turkey chromite ore production, 659 chromite production, 662 chromium production, 664 exports of chromite ore, 653 ferrochromium production, 661, 663 production/trade, 673 Tyson, Isaac, 10–12

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782 U Ukraine, chromium annual production, 664 Ultra-filter system, plating, zero discharge, chemical recovery approach, manufacturing facility, 475 United Arab Emirates chromite ore production, 659 chromite production, 662 chromium production, 664 United Chrome Products, Inc., Corvallis, Oregon, case study, 376–381 United Kingdom chromium production, 664 exports of ferrochromium, 654 production/trade, 673 United States agencies regulating chromium, 506–507 chromium concentration in, 43, 44, 66 chromium policies, regulations, 492–504 chromium production, 664 Department of Labor, Occupational Safety and Health Administration, 6 Environmental Protection Agency Drinking Water Maximum Contaminant Level, 6 National Priority List Superfund Sites, 6 ferrochromium production, 661, 663 Units, common, definition of, 575–576 Uptake, transformation of chromium by biota, 198–199 Ural Mountains, 7 Urals, Russia, chromium concentration in, 66 Uses of chromium, 16–17 dying processes, 17 furnace linings, 17 paint, 17 photography, 17 stainless steel, 17 tanning, 17 Utah, chromium releases to water, land, 20 Uvarovite chemical formula, classification, 55 crystallography, 63

V Valley Wood Preserving Plant, Turlock, California, case study, 388–395 Vapor sampling, direct push technology probe, 248–249 Vauquelin, Louis-Nicholas, 7–8

Chromium(VI) Handbook Vauquelinite chemical formula, classification, 55 crystallography, 63 Vietnam chromite production, 662 chromium production, 664 Vitrification of contaminated sites, 303, 753 Volkonskoite chemical formula, classification, 56 crystallography, 63 Vuorelainenite chemical formula, classification, 56 crystallography, 63

W Wash primers, chromium use in, 16 Washington, Vancouver, Frontier Hard Chrome, case study, 373–376 Waste management. See also under specific technology electrocoagulation, electrooxidation, for chromium containing waste waters using, 477–489 case study, 486–487 equipment in plant, 488–489 flocculation, removal of chromium by, 481–483 iron electrodes, 488 sludge generation, 487 system operation, 487–489 Kalaeloa Cogeneration Plant wastestream reductions, 469 Oahu, Hawaii, 366–470 plating, zero discharge, chemical recovery approach, manufacturing facility in Massachusetts, 470–477 CAST flash distillation systems, 476 cleaning, plating system configuration, 474 ion exchange, 475–476 metal plating process, 474 plating pretreatment, 474 tank farm, waste treatment, 474–475 treatment system description, 474–476 ultra-filter system, 475 refractories, 607–608 regulations/policy, 493–494, 507–511 stream processing, 465–490 Water. See also Aquifers anthropogenic chromium in, 160–161 chromium concentration in, 43–44, 186–192 Water quality, regulations/policy, 507

L1608_Index.fm Page 783 Friday, October 29, 2004 4:58 PM

Index Water sampling, 257–261 cone penetration testing, 250 direct push technology probe, 248 groundwater monitoring protocol, 258 groundwater sample quality control, 260–261 duplicates, 261 field blanks, 261 groundwater samples collected from wells, 258–259 turbidity, 259–260 well development protocol, 257–258 Wattersite chemical formula, classification, 56 crystallography, 63 Wells data, estimating reduction from monitoring, 205 development protocol, 257–258 groundwater samples collected from, 258–259 naturally occurring chromium, 137–141 points, direct push technology, 249 Western United States, anaerobic in situ reactive zones, engineered, remediation of chromium using, 434–436 Witness, expert, testimony of, 534–541 background, 534–535 Daubert, application of, 537–538 expert testimony, court treatment of, 539–541 Hanford litigation, 538–541 scientific evidence, rules regarding, 535–537 trial court’s rejection of testimony, 540–541 Wood preservation industry, 16, 593–599. See also Wood treating facility Coast Wood Preserving Plant, Ukiah, California, case study, 415–420 cleanup standards, 417 field sampling activities, 418 historical land use, 415 pilot study results, 418–419 regulatory activities, timeline, 416–417 regulatory agencies, 416 remedial alternative, 419 remedial alternatives evaluation, 418 remedial investigation, 418–419 remedial performance, 419 site characterization, 418 site geology, 418 site hydrology, 418

783 site location, history, 415–416 site setting, 415 fixation reactions, 596 formulations, examples of, 594 future developments, 598–599 historical development, 593–594 role of chromium compounds in, 594–595 Valley Wood Preserving Plant, Turlock, California, case study, 388–395 cleanup standards, 390 field sampling activities, 391 historical land use, 389 pilot study results, 391–393 reducing agent selected, 393 regulatory activities, timeline, 390 regulatory agencies, 390 regulatory overview, 390 remedial alternative, 393 remedial alternatives evaluation, 391 remedial investigation, 391–393 remedial performance, 393–395 site characterization, 391 site geology, 391 site hydrology, 391 site location, history, 388–390 site setting, 388–389 Wood treating facility, 191 Australia, case study, 412–414 cleanup standards, 413 field sampling activities, 413 historical land use, 412 regulatory activities, timeline, 412 regulatory agencies, 412 regulatory overview, 412–413 remedial alternative, 413 remedial alternatives evaluation, 413 remedial investigation, 413 remedial performance, 413–414 site characterization, 413 site geology, 413 site location, history, 412 site setting, 412 Northern California, case study, 381–387 cleanup standards, 383 field sampling activities, 383 historical land use, 381–382 pilot study results, 384–386 regulatory agencies, 382–383 regulatory overview, 382–383 remedial alternative, 386 remedial alternatives evaluation, 383–384 remedial investigation, 383–386 remedial performance, 386–387 site characterization, 383

L1608_Index.fm Page 784 Friday, October 29, 2004 4:58 PM

784 site geology, 383 site hydrology, 383 site location, history, 381–382 site setting, 381 Work place exposure, regulations/policy, 511–519 World production of chromium, 15. See also under specific country Worldwide chromium regulations, 504–521

X X-ray fluorescence spectroscopy, 251–252, 271 XRF spectroscopy. See X-ray fluorescence spectroscopy

Y Yedlinite chemical formula, classification, 56 crystallography, 63 Yimengite chemical formula, classification, 56 crystallography, 63

Z Zero discharge, chemical recovery approach, plating, manufacturing facility in Massachusetts, 470–477 CAST flash distillation systems, 476

Chromium(VI) Handbook cleaning, plating system configuration, 474 ion exchange, 475–476 metal plating process, 474 plating pretreatment, 474 tank farm, waste treatment, 474–475 treatment system description, 474–476 ultra-filter system, 475 Zhanghengite chemical formula, classification, 56 crystallography, 63 Zimbabwe chromite ore production, 659 chromite production, 662 chromium production, 664 exports of ferrochromium, 654 ferrochromium production, 661, 663 production/trade, 673 Zinc physicochemical properties, 39, 40, 42 in treated water, 487 in waste water from metal planting, 486 wastestream reductions, 469 Zinc chromate, international chemical safety cards, 735–737 Zinc hydroxide, physicochemical properties, 40 Zinc potassium, physicochemical properties, 40 Zincochromite chemical formula, classification, 56 crystallography, 63

L1608_Appendix-A Page 575 Tuesday, November 2, 2004 6:55 PM

Appendix A

CONTENTS A.1 Definition of Common Units ..................................................................575 Jacques Guertin A.2 Conversions (Metric–English Units) International System of Units (SI)..................................................................................577 Jacques Guertin Bibliography ........................................................................................................581

A.1 Definition of Common Units

Jacques Guertin

Mass kg g mg mg ng lb mol

kilogram gram milligram microgram nanogram pound mole

Distance m km cm mm mm nm

meter kilometer centimeter millimeter micrometer nanometer

number of particles = number of atoms in 12 g of 12C (6.022 ¥ 1023)

(Continued)

1-5667-0608-4/05/$0.00+$1.50 © 2005 by CRC Press LLC

575

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Chromium(VI) Handbook

Volume m3 cm3 mm3 L gal

(meter)3 (centimeter)3 (millimeter)3 liter gallon

Concentration mg/kg

milligram/kilogram

mg/g

microgram/gram

mg/kg mg/L mg/L %

microgram/kilogram milligram/liter microgram/liter percent

M N

molarity normality (not currently used much)

part-per-million . . . by mass (ppm) part-per-million . . . by mass (ppm) part-per-billion (ppb) . . . by mass part-per-million (ppm) (approximate) part-per-billion (ppb) (approximate) part-per-hundred . . . by mass (must be stated if by volume) mol/L eq/L . . . equivalent/liter eq = equivalent mass . . . gram = formula mass/(H+)n = formula mass/(OH-)n

n=

(number of H + or OH - produced) source molecule

Pressure Pa mmHg lbf/in.2 atm kgf/m2

pascal millimeter of mercury poundf/(inch)2 atmosphere kilogramf/(meter)2

psi

Density g/cm3

gram/(centimeter)3

temperature needed for accuracy

Time s min hour day

second minute h d

Other pH Eh

∞C Kd mg/kg/d

log [H3O+] redox potential (volt [V]) degree Celsius partition coefficient (mL/g) milligram (kilogram body mass)/day

. . . gram . . .gram

. . . f = force

measure of acidity measure of oxidizing/reducing power

dose in toxicology

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577

Appendix A

A.2 Conversions (Metric–English Units) International System of Units (SI)

Jacques Guertin

From Area millimeter2 (m2) centimeter2 (cm2)

inch2 (in.2)

foot2 (ft2)

yard2 (yd2)

meter2 (m2)

acre

hectare (ha) kilometer2 (km2)

mile2 (mi2)

To centimeter2 (cm2) inch2 (in.2) millimeter2 (m2) meter2 (m2) inch2 (in.2) foot2 (ft2) millimeter2 (mm2) centimeter2 (cm2) meter2 (m2) foot2 (ft2) meter2 (m2) hectare (ha) inch2 (in.2) acre meter2 (m2) hectare (ha) foot2 (ft2) acre foot2 (ft2) yard2 (yd2) acre hectare (ha) meter2 (m2) foot2 (ft2) hectare (ha) meter2 (m2) acre meter2 (m2) hectare (ha) foot2 (ft2) acre mile2 (mi2) meter2 (m2) kilometer2 (km2) foot2 (ft2) acre hectare (ha)

Multiply by 1 ¥ 10–2 . . . exact 1.550003 ¥ 10–3 1 ¥ 102 . . . exact 1 ¥ 10–4 . . . exact 1.550003 ¥ 10–1 1.07639 ¥ 10–3 6.4516 ¥ 102 . . . exact 6.4516 . . . exact 6.4516 ¥ 10–4 . . . exact 6.9444 ¥ 10–3 . . . exact 9.290304 ¥ 10–2 . . . exact 9.290304 ¥ 10–6 . . . exact 1.44 ¥ 102 . . . exact 2.29568 ¥ 10–3 8.3612736 ¥ 10–1 . . . exact 8.3612736 ¥ 10–5 . . . exact 9 . . . exact 2.0661 ¥ 10–4 1.076391 ¥ 101 1.19599004631 2.471 ¥ 10–4 1 ¥ 10–4 . . . exact 4.046873 ¥ 103 4.3560178 ¥ 104 4.046873 ¥ 10–1 1 ¥ 104 . . . exact 2.471044 1 ¥ 106 . . . exact 1 ¥ 102 . . . exact 1.076391 ¥ 107 2.471044 ¥ 102 3.86102 ¥ 10–1 2.589988 ¥ 106 2.589988 2.787840 ¥ 107 . . . exact 6.399974 ¥ 102 2.589988 ¥ 102 (Continued)

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578

Chromium(VI) Handbook

From Pressure/Stress (force/area) poundf/inch2 (lb/in.2)

atmosphere (atm) water head, meter (m-head)a

water head, foot (ft-head)

pascal (Pa)

kilogram, force/meter2 (kgf/m2) bar atmosphere (atm)

Length meter (m)

To

Multiply by

pascal (Pa) water head, meter (m-head) millimeter of mercury (mmHg) water head, foot (ft-head) poundf/foot2 (lbf/ft2) atmosphere (atm) poundf/inch2 (lbf/in.2) pascal (Pa) millimeter of mercury (mmHg) water head, foot (ft-head) poundf/inch2 (lbf/in.2) poundf/ft2 (lbf/ft2) pascal (Pa) water head, meter (m-head) millimeter of mercury (mmHg) mercury head, foot (ft-head) poundf/inch2 (lbf/in.2) poundf/foot2 (lbf/ft2) newton/meter2 (N/m2) millimeter of mercury (mmHg) water head, meter (m-head) poundf/inch2 (lbf/in.2) poundf/foot2 (lbf/ft2) atmosphere (atm) pascal (Pa) millimeter of mercury (mmHg) poundf/inch2 (lbf/in.2) pascal (Pa) pascal (Pa) millimeter of mercury (mmHg) poundf/inch2 (lbf/in.2) water head, foot (ft-head)

6.894757 ¥ 103 7.030901 ¥ 10–1 5.171493 ¥ 101 2.306726 1.44 ¥ 102 . . . exact 6.8046 ¥ 10–2 1.4696 ¥ 101 9.806363 ¥ 103 7.35538 ¥ 101 3.28084 1.422293 2.048102 ¥ 102 2.988979 ¥ 103 3.048 ¥ 10–1 . . . exact 2.241919 ¥ 101 7.38 ¥ 10–2 4.33515 ¥ 10–1 6.242614 ¥ 101 1. . . exact 7.500638 ¥ 10–3 1.01975 ¥ 10–4 1.45038 ¥ 10–4 2.0885435 ¥ 10–2 9.86923 ¥ 10–6 9.806588 7.35557 ¥ 10–2 1.42233 ¥ 10–3 1 ¥ 105 . . . exact 1.01325 ¥ 105 7.6 ¥ 102 . . . exact 1.4696 ¥ 101 3.38995 ¥ 101

attometer (am) femtometer (fm) picometer (pm) nanometer (nm) micrometer (mm) millimeter (mm) centimeter (cm) kilometer (km) megameter (Mm) gigameter (Gm) terameter (Tm) petameter (Pm) exameter (Em) ångström (Å) mil inch (in.) foot (ft)

1 ¥ 1018 . . . exact 1 ¥ 1015 . . . exact 1 ¥ 1012 . . . exact 1 ¥ 109 . . . exact 1 ¥ 106 . . . exact 1 ¥ 103 . . . exact 1 ¥ 102 . . . exact 1 ¥ 10–3 . . . exact 1 ¥ 10–6 . . . exact 1 ¥ 10–9 . . . exact 1 ¥ 10–12 . . . exact 1 ¥ 10–15 . . . exact 1 ¥ 10–18 . . . exact 1 ¥ 1010 . . . exact 3.937007874 ¥ 104 3.937007874 ¥ 101 3.2808399

L1608_Appendix-A Page 579 Tuesday, November 2, 2004 6:55 PM

579

Appendix A

From

mile (mi)

Mass gram (g)

slug ton ("short" ton) Mass/Volume (density) gram/centimeter3 (g/cm3)

ounce/gallon (oz/gal) pound/yard3 (lb/yd3) pound/gallon (lb/gal) "short" ton/yard3 (tonshort/yd3) slug/foot3 (slug/ft3) Velocity meter/second (m/s)

mile/hour (mi/h)

Viscosity centipoise (cP)

centistokes (cSt)

To

Multiply by

yard (yd) mile (mi) meter (m) inch (in.) foot (ft) yard (yd)

1.0936133 6.2137119 ¥ 10–4 1.609344 ¥ 103 . . . exact 6.336 ¥ 104 . . . exact 5.28 ¥ 103 . . . exact 1.76 ¥ 103 . . . exact

kilogram (kg) ounce (oz)b pound (lb)b metric ton (tonne) ton ("short" ton) slug gram (g) pound (lb)b pound (lb)b

1 ¥ 10–3 . . . exact 3.5273962 ¥ 10–2 2.2046226 ¥ 10–3 1 ¥ 10–6 . . . exact 1.1023113 ¥ 10–6 6.8521780 ¥ 10–5 1.45939 ¥ 104 3.21740421 ¥ 101 2 ¥ 103 . . . exact

kilogram/meter3 (kg/m3) gram/meter3 (g/m3) pound/foot3 (lb/ft3) pound/yard3 (lb/yd3) pound/gallon (lb/gal) gram/liter (g/L) pound/foot3 (lb/ft3) gram/centimeter3 (g/cm3) slug/foot3 (slug/ft3) gram/meter3 (g/m3)

1 ¥ 103 . . . exact 1 ¥ 106 . . . exact 6.24279606 ¥ 101 1.685555 ¥ 103 8.34540437 7.489145 3.7037037037037037. . . ¥ 10–2 1.198264 ¥ 10–1 2.325017 ¥ 10–1 1.18655284 ¥ 106

gram/meter3 (g/m3) gram/centimeter3 (g/cm3)

5.153788 ¥ 105 5.153788 ¥ 10–1

meter/hour (m/h) kilometer/hour (km/h) mile/hour (mi/h) foot/second (ft/s) meter/second (m/s) kilometer/hour (km/h) foot/second (ft/s)

3.6 ¥ 103 . . . exact 3.6. . . exact 2.23694 3.28084 4.4704 ¥ 10–1. . . exact 1.690934. . . exact 1.466666666666666666. . .

poise (P) pascal-second (Pa-s) poundf-second/foot2 (lbf-s/ft2) poundf-hour/foot2 (lbf-h/ft2) stoke foot2/second (ft2/s) meter2/second (m2/s)

1 ¥ 10–2 . . . exact 1 ¥ 10–3 . . . exact 2.08854 ¥ 10–5 7.51876 ¥ 10–2 1 ¥ 10–2 . . . exact 1.076391 ¥ 10–5 1 ¥ 10–6 . . . exact (Continued)

L1608_Appendix-A Page 580 Tuesday, November 2, 2004 6:55 PM

580

Chromium(VI) Handbook

From rhe pascal-second (Pa-s) Volume meter3 (m)

centimeter3 (cm3) gallon (gal)

liter (L)c foot3 (ft3)

mile3 (mi3) yard3 (yd3) acre-foot (acre-ft)

kilometer3 (km3) Transmissivity: volume/cross-sectional area foot3/(foot-day) (ft3/(ft-d))

gallon/(foot-day) (gal/(ft-d)) Hydraulic Conductivity (permeability): volume/ (area-time) foot3/(foot2-day) (ft3/(ft2-d))

To –1

Multiply by –1

1

(pascal-second) (Pa-s) newton-second/meter2 (N-s/m2) poise (P)

1 ¥ 10 . . . exact 1. . . exact 1 ¥ 101 . . . exact

liter (L)c centimeter3 (cm3) millimeter3 (mm3) inch3 (in.3) foot3 (ft3) yard3 (yd3) ounce, fluid (fl oz) gallon (gal) milliliter (mL)c ounce, fluid (fl oz) liter (L) meter3 (m3) foot3 (ft3) ounce, fluid (fl oz) gallon (gal) yard3 (yd) inch3 (in.3) liter (L) meter3 (m3) gallon (gal) mile3 (mi3) acre-foot (acre-ft) acre-foot (acre-ft) foot3 (ft3) meter3 (m3) meter3 (m3) foot3 (ft3) gallon (gal) mile3 (mi3)

1 ¥ 103 . . . almost exact 1 ¥ 106 . . . exact 1 ¥ 109 . . . exact 6.102374 ¥ 104 3.53146667 ¥ 101 1.30795062 3.3814 ¥ 104 2.6417205 ¥ 102 1. . . almost exact 1.28 ¥ 102 . . . exact 3.785411784 3.785411784 ¥ 10–3 1.336806 ¥ 10–1 3.3814 ¥ 101 2.6417205 ¥ 10–1 3.7037037037037037. . . ¥ 10–2 1.728 ¥ 103 . . . exact 2.83168466 ¥ 101 2.83168466 ¥ 10–2 7.480517 6.79357278 ¥ 10–12 2.29567473 ¥ 10–5 3.37919 ¥ 106 2.7 ¥ 101 . . . exact 7.64554858 ¥ 10–1 1.2334818 ¥ 103 4.356017806 ¥ 104 3.258514 ¥ 105 2.399127586 ¥ 10–1

meter3/(meter-day) (m3/(m-d)) liter/(meter-day) (L/(m-d)) gallon/(foot-day) (gal/(ft-d)) meter3/(meter-day) (m3/(m-d)) foot3/(foot-day) (ft3/(ft-d))

9.2903065 ¥ 10–2 9.2903065 ¥ 101 7.48052 1.2419 ¥ 10–2 1.336805 ¥ 10–1

meter3/(meter2-day)(m3/(m2-d)) liter/(meter2-day) (L/(m2-d)) foot3/(foot2-minute) (ft3/(ft2-d)) gallon/(foot2-day) (gal/(ft2-d)) inch3/(inch2-hour) (in.3/(in.2-h))

3.048 ¥ 10–1. . . exact 3.048 ¥ 102. . . exact 6.944 ¥ 10–4. . . exact 7.48052 5 ¥ 10–1. . . exact

L1608_Appendix-A Page 581 Tuesday, November 2, 2004 6:55 PM

581

Appendix A

From 2

gallon/(foot -day) (gal/(ft2-d)) Volume/ Time meter3/day (m3/d) foot3/second (ft3/s)

gallon/minute (gal/min)

acre-foot/day (acre-ft/d)

To 3

2

Multiply by 3

2

meter /(meter -day) (m /(m -d)) liter/(meter2-day) (L/(m2-d)) foot3/(foot2-minute) (ft3/(ft2-d))

4.07458 ¥ 10–2 4.07458 ¥ 101 1.336805 ¥ 10–1

meter3/second (m3/s) foot3/second (ft3/s) liter/second (L/s) meter3/second (m3/s) gallon/minute (gal/min) acre-foot/second (acre-ft/s) foot3/minute (ft3/min) liter/second (L/s) meter3/second (m3/s) foot3/second (ft3/s) acre-foot/day (acre-ft/d) meter3/second (m3/s) foot3/second (ft3/s)

1.1574074074 ¥ 10–5 5.0416872 ¥ 10–1 2.83168466 ¥ 101 2.831685 ¥ 10–2 4.4883117 ¥ 102 1.983463 6 ¥ 101 . . . exact 6.30902 ¥ 10–2 6.30902 ¥ 10–5 2.22801 ¥ 10–3 4.419174 ¥ 10–3 1.42765 ¥ 10–2 5.0416872 ¥ 10–1

a

water-head is for 3.98 ∞C (liquid water’s maximum density) avoirdupois (avdp) c Liter is defined as volume occupied by 1 kg water at 3.98 ∞C. This is 1,000.027 cm3 because the maximum density of water at 3.98 ∞C is 0.999973 g/cm3 (not 1 g/cm3). However, for most calculations, assuming that 1 cm3 = 1 mL is accurate enough. Note that since density = mass/ volume, the density of water at 3.98 ∞C is 1 kg/L or 1 g/mL, exactly. b

Bibliography Handbook of Chemistry and Physics, 77th ed., CRC Press, Boca Raton, 1996. National Institute of Standards and Technology (NIST), Special Publication 811, Guide for the Use of the International System of Units (SI), 1995. National Institute of Standards and Technology (NIST), Special Publication 300 (SP 300), The International System of Units (SI), 2001. Guide to the Use of the Metric System [SI Version], U.S. Metric Association (USMA), Inc., Northridge, CA, 15th ed., 2002.

L1608_Appendix-A Page 582 Tuesday, November 2, 2004 6:55 PM

L1608_Appendix-B Page 583 Monday, November 8, 2004 8:04 AM

Appendix B CONTENTS B.1 Chromium and the Leather Tanning Industry .....................................585 Vincent Van den Bossche, Gérard Gavend, Marie-Joèlle Brun, and Antero Aitio B.1.1 Introduction....................................................................................585 B.1.2 Transformation of Hide into Leather.........................................585 B.1.2.1 Tanning ............................................................................585 B.1.2.2 Advantages and Applications of Chromium Tanned Leather...............................................................586 B.1.2.3 Health Risks for Tanning Workers..............................587 B.1.2.4 Effects on the Environment..........................................587 B.1.2.4.1 Water ..............................................................587 B.1.2.4.2 Soil..................................................................588 B.1.2.4.3 Ground Life and Microorganisms ............589 B.1.2.4.4 Vegetables and Animals..............................589 B.1.2.5 Effects on the Consumer...............................................589 B.1.2.6 Development of Clean Technologies ..........................590 B.1.3 Conclusion......................................................................................590 Bibliography ...............................................................................................590 B.2 Chromium and the Timber Preservation Industry ..............................593 Richard Murphy B.2.1 Introduction....................................................................................593 B.2.1.1 Historical Development and Current Status.............593 B.2.1.2 Functional Role of Chromium Compounds in Wood Preservatives...................................................594 B.2.1.3 Chromium in CCA Preservatives................................595 B.2.1.3.1 Safety and Environmental Effects of CCA Preservatives ..................................597 B.2.1.4 The Future .......................................................................598 B.2.2 Conclusions ....................................................................................599 Bibliography ...............................................................................................599 B.3 Chromium in Refractories........................................................................604 Mariano Velez B.3.1 Introduction....................................................................................604 1-5667-0608-4/05/$0.00+$1.50 © 2005 by CRC Press LLC

583

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584

Chromium(VI) Handbook

B.3.1.1 Current Applications .....................................................605 B.3.1.1.1 Copper Metallurgy ......................................605 B.3.1.1.2 Aluminum Metallurgy................................605 B.3.1.1.3 Steel Making .................................................606 B.3.1.1.4 Cement Kilns ................................................606 B.3.1.1.5 Glass Melting................................................606 B.3.1.2 Special Refractories........................................................606 B.3.1.3 Chromium(VI) Compounds in Refractories ..............606 B.3.1.4 Refractory Waste Management....................................608 B.3.2 Conclusion......................................................................................608 Bibliography ...............................................................................................609 B.4 Health Effects of Occupational Exposures in Chrome Plating .......... 611 Antero Aitio B.4.1 Introduction.................................................................................... 611 B.4.1.1 Exposures ........................................................................ 611 B.4.1.2 Toxicology of Chromium with Different Oxidation States .............................................................612 B.4.1.2.1 Elemental Chromium (Cr(0)) and Chromium(III) ......................................612 B.4.1.2.2 Chromium(VI) ..............................................612 B.4.1.3 Health Effects among Chromium Plating Workers ..............................................................613 B.4.1.3.1 Effects on Nasal Mucosa and Skin ...........613 B.4.1.3.2 Lung Cancer .................................................614 B.4.1.3.3 Carcinogenic Potency of H2CrO4 Mist .....615 B.4.1.3.4 Other Respiratory Diseases........................616 B.4.1.4 Prevention of Exposure and Control of Chromic Acid Mist....................................................616 B.4.2 Conclusions ....................................................................................616 Bibliography ...............................................................................................617 B.5 Chromium Recycling in the United States in 1998..............................618 John F. Papp B.5.1 Introduction....................................................................................619 B.5.2 Sources of Chromium-Containing Scrap...................................622 B.5.2.1 Dissipated Materials Not Available for Recycling ...624 B.5.2.2 Old Scrap Generated .....................................................625 B.5.2.3 New Scrap .......................................................................628 B.5.3 Disposition of Chromium-Containing Scrap............................629 B.5.4 Old Scrap Recycling Efficiency ...................................................630 B.5.5 Infrastructure of Chromium-Containing Scrap........................631 B.5.6 Processing of Scrap Metals ..........................................................632 B.5.6.1 Smelting/Refining..........................................................632 B.5.6.2 Fabrication.......................................................................632 B.5.7 Outlook and Summary.................................................................632 Bibliography ...............................................................................................633 Glossary.......................................................................................................634

L1608_Appendix-B Page 585 Monday, November 8, 2004 8:04 AM

Appendix B

585

B.1 Chromium and the Leather Tanning Industry

Vincent Van den Bossche, Gérard Gavend, Marie-Joèlle Brun, and Antero Aitio B.1.1

Introduction

Chromium(III) (Cr(III)) compounds are the most widely used tanning agent in the world for the transformation of hides and skins into leather. Cr tanned leather has been used for almost a century for the manufacture of consumer products such as clothing, gloves, footwear, furniture, automobile upholstery, as well as a variety of personal leather goods. The leather manufacturing process generates liquid and solid wastes containing Cr(III). This manufacturing activity and the resulting by-products prompt questions concerning their effect upon the environment and mankind. This article summarizes the current state of knowledge on this subject. B.1.2

Transformation of Hide into Leather

The use of leather goes back to prehistoric times. Archaeological evidence shows that the material was widely used in antiquity. The raw material is mammalian skin, which today is derived principally from animals which are butchered for the food industry, and to a lesser extent, skins from reptiles, fish and birds.1 The tannery operations consist of transforming the raw hide, a highly putrescible material, into leather, a stable product which can be conserved indefinitely and which has a significant commercial value. These operations follow a sequence of organized chemical reactions (using reactive products) and mechanical processes using specialized machinery. Among these, tanning is the fundamental stage which confers to leather its stability and essential characteristics. B.1.2.1 Tanning Tanning is the most important step in the production of leather and it is carried out in an aqueous environment with water in rotating drums.2 Its objective is to process the skins, which arrive from the abattoirs in a dried, Reprinted by permission: International Chromium Development Association 45 rue de Lisbonne, 75008 Paris, France. Tel: 33 01 40 76 06 89 Fax: 33 01 40 76 06 87  International Chromium Development Association December, 1997. http://www.chromium-asoc.com/publications/frame.html NOTE: Original publication has been updated by the Chromium(VI) Hanbook editors.

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salted state, to a condition which will facilitate the chemical operation of tanning. During this operation, collagen, the principal protein of the skin, will fix the tanning agent to its reactive sites, thus stopping the putrefaction phenomenon.3 The products which are capable of being fixed to skin to achieve tanning are many and varied. They can be classified into three groups: • Vegetable type tannins (mimosa, chestnut, quebracho) • Mineral tannins (chromium (Cr), iron (Fe), zirconium (Zr), in compound form) • Other organic tannins (formaldehyde (CH2O), synthetic tannins, fish oil, . . .) The most widely used today are Cr compounds. The process, which was invented at the turn of the century, uses Cr(III) hydrogen sulfate (Cr(HSO4)3) in powder form on skins which have been previously prepared following methods which were derived from work carried out in 1959.4 Regarding Cr tanning, only Cr(III) sulfate (Cr2(SO4)3) possesses tanning properties with respect to skin collagen. This tanning agent is produced from a natural product found in the form of chromite (FeCr2O4). To obtain good quality leather, it is necessary to use a quantity of Cr compounds representing 2% to 2.5% (calculated as Cr2O3) of the mass of skins to be tanned. This implies the use of 8% to 10% of commercial product containing on average 25% of Cr2O3.5 This procedure has thus replaced all the techniques based upon the use of chromium(VI) (Cr(VI)) which in the past necessitated the reduction to Cr(III) in the tannery before tanning. After tanning, the leather is stored for several days, allowing the consolidation of the Cr/collagen bonds. The resulting product can resist temperatures as high as 120 °C, while collagen is denatured at 50 ° C.6 In order to be transformed into a commercial product, the leather needs to be split and shaved to an even thickness, then superficially retanned with low quantities of tanning agents such as Cr, aluminum (Al) compounds or vegetable/synthetic tannins, dyed with coloring agents, then fat liquored with natural or synthetic fats in order to render the product flexible. After drying, it is embellished with a film of more or less pigmented products on its outer surface in order to attain the appearance and degree of protection required for its final use. The last stages are called leather finishing.7 B.1.2.2

Advantages and Applications of Chromium Tanned Leather

Chromium tanning is preferred because the process is quick, simple, reproducible, and is very cost effective. It yields a material with a high mechanical and thermal resistance and a pronounced capacity for dyeing, so that a wide range of colors in rich or pastel shades is possible. The collagen Cr bond is actually the strongest known today among the various alternatives, including vegetable and synthetic tannins. By virtue of their quality and mechanical characteristics, Cr-tanned leathers are well suited to a wide range of applications such as

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gloves, footwear, leather goods, luggage, and upholstery. Despite extensive investigation in laboratories around the world, no fully satisfactory alternative to Cr tanning has been found or is likely to be found in the foreseeable future. B.1.2.3

Health Risks for Tanning Workers

For many years the health risk associated with the use of Cr compounds in the tanning industry has been questioned. Unlike Cr(VI), Cr(III) compounds of the type used for tanning are less likely to penetrate and sensitize the skin.8 Due to the low risk of allergies owing to Cr(III),8 it was feared that leather dust could have an adverse effect on the nose, throat, and lungs. Dust is produced during several operations, notably by the buffing of the outer surface during finishing, which produces particles of which 50% have a diameter <5 µm.9 The International Agency for Research on Cancer (IARC) evaluated studies9,10 dealing with the incidence of nasal cancer in tannery workers and has not reported significant findings.11 The results of analyses carried out on air from tanneries,9 have revealed Cr(III) contents ranging from 5.5 µg/m3 to 8.0 µg/m3, which is far less than the French or American Conference of Government Industrial Hygienists (ACGIH) Time-Weighted Average (TWA) values, which are 0.5 mg/m3.12,13 From an epidemiological point of view, an American study14 related to a period from 1940 to 1982 in two tanneries in Minnesota and Wisconsin concerning 9,365 workers did not show higher death rates from nasal or lung cancer than those observed in the general population. A British study15 related to a period from 1939 to 1982 concerning 833 tannery workers, of which 573 were concerned with vegetable tanning and 260 with Cr tanning, did not reveal a higher incidence of death from cancer (of the stomach, large intestine, lung, rectum, or prostate) compared to the general population. IARC concluded in its monograph that the only study specific to tanning failed to reveal a statistically significant risk.9 B.1.2.4

Effects on the Environment

Chromium compounds which are not fixed to the collagen during the tanning process are discharged as effluents to the environment, notably to water and to the ground. B.1.2.4.1 Water It has been estimated that, with traditional tanning methods, from 4 kg to 9.5 kg of Cr (calculated as Cr2O3) per metric ton of skins are not chemically fixed during processing if it is not carried out with a suitable high exhaustion tanning system.16 Two thirds are rejected in the liquid effluent at the tanning stage.17 According to a Canadian scientific bibliography, in an aqueous medium of neutral pH, Cr(III) compounds form oxides, insoluble hydroxides, and insoluble phosphates, which bind themselves to solids in suspension. This is why soluble Cr(III) compounds are rapidly eliminated from surface water into sediment. This Cr complex is relatively stable and slightly biologically

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available.18 This aptitude for precipitation was confirmed in a study carried out in Costa Rica on a river polluted by several tanneries.19 Work was carried out by the Centre Technique Cuir Chaussure Maroquinerie (CTC) on activated sludge in an effluent treatment plant. Using the respirometry method, the purpose was to measure the toxicity of Cr. It was shown that while Cr is maintained in an insoluble form (pH ≥ 7, i.e. neutral or basic), its toxicity on activated sludge cannot be detected.20 Worldwide regulatory limits fixing the Cr(III) content of water which can be discharged into surface waters vary from 0.5 mg/L to 15 mg/L.21 Widely practiced efficient treatment of effluent combined with clean technologies (which we will mention later and which are increasingly being adopted by tanneries), enable tanners to comply with these strict regulations. To measure the effect of Cr(III) compounds, studies were carried out on living organisms in water. They showed that because of its low solubility (experimental condition: pH 7), Cr(III) did not prove toxic to bacteria, seaweed, or fish. Only daphnia (water flea) showed a marked sensitivity to concentrations in the order of 6 mg/L to 9 mg/L.20 B.1.2.4.2 Soil The manufacture of Cr-tanned leather also generates solid wastes or scrap resulting from mechanical operations of which the Cr(III) content (calculated as Cr2O3) is, on average, between 2% and 5.5%.22 In Europe, these are not listed as hazardous waste,23 and in the United States (U.S.) they are specifically exempt from federal hazardous waste regulations.24,25 The U.S. Environmental Protection Agency (USEPA) has conducted an extensive risk evaluation of Cr(III) in sludge used for agricultural land application and could find no adverse effect for any pathway of exposure.26 Therefore, Cr limits for land applied sludge have been eliminated.27,28 The Organization for Economic Cooperation and Development (OECD) considers that solid wastes produced by tanneries are to be included on the "green" list, which signifies that they only need to conform to commercial requirements with respect to their transboundary transport. On the other hand, leather dust and sludge are included on the "amber" list, which signifies that the tanner and recipient of the goods are required to inform their local or national environment administration concerning the commercial transaction.29 In the U.S., one publicly owned wastewater treatment plant receives 95% of its input from a tannery. Since 1977, it has been dumping on land sludge containing Cr(III) at a concentration of 34 g/kg. For the past 10 years, the town has been monitoring groundwater immediately below the landfill at down-gradient wells. It reported that the Cr-concentration in groundwater was less than the detection limit of 0.01 mg/L.30 When Cr-containing sludge is mixed with earth, the appearance of Cr(VI) could theoretically occur at oxidation–reduction (redox) potentials (Eh) typically found in well-aerated soils.31 However, in practice, the oxidation of Cr(III) to Cr(VI) does not occur in soil even under experimental conditions combining maximum aeration and high pH.32,33,34

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B.1.2.4.3 Ground Life and Microorganisms On microorganisms,35 the inhibitory effects of Cr(III) (concentrations up to 1,000 ppm) were noticed on short-term exposure but were no longer evident after a period of 6 weeks. However, 10,000 ppm of Cr(III) completely blocked nitrogen transformation. Earthworms could survive even with a Cr(III) concentration in their stomachs of 100 ppm.36 With higher concentrations, toxic effects were noticed: the individuals were less numerous and their size decreased. However, after extensive risk evaluation, the USEPA has established guidance cleanup for Cr(III) at land disposal sites of 78,000 mg/kg.37 This limit value is related to the most relevant pathway risk which, concerning Cr(III) and according to the USEPA, is ingestion of contaminated soil. Over this limit value, the site owner can be asked to perform a site-specific risk evaluation and even to clean up the site. Care should be taken to avoid high accumulation, which could produce harmful effects.

B.1.2.4.4 Vegetables and Animals Many studies have been carried out to determine the effect of Cr(III) compounds on different crops such as chicory, wheat, peas, tomatoes, fennel, etc., particularly with respect to the spreading of sludge onto agricultural ground.38–41 These studies concluded that Cr(III) compounds can be considered as nontoxic at concentrations no greater than 500 mg/kg.38 Once again care should be taken to avoid an accumulation of Cr(III) compounds in the soil. No toxic effect was detected on rats consuming water containing 25 mg/L of Cr(III) over a 6-month period.39

B.1.2.5

Effects on the Consumer

The consumer, the end-user of articles made from Cr-tanned leather, has a right to ask whether the use of such leather constitutes a health risk. As we have already indicated,8 unlike Cr(VI), Cr(III) compounds are only weakly allergenic. The question, however, is whether there is a risk of the appearance of Cr(VI) in leather articles. A French study has demonstrated that under specific conditions of humidity, ultraviolet (UV)-C light (the most energetic UV, "short wave", 280 nm to 10 nm), and pH, there is a possibility of transforming Cr(III) compounds into Cr(VI) compounds, which could migrate from the leather.40 The values of Cr(VI) found were in the order of "not detectable" to 17 mg/kg of dried degreased leather. As a precautionary measure, the German authorities require41 that Cr(VI) content which could be leached should be below the limits of detection and reproducibility of the analytical methods available to industry, that is to say of the order of 2 mg/kg to 3 mg/kg of leather.42 Furthermore, based on a similar precautionary principle, the European standard for safety gloves, EN 420,43 specifies a maximum limit for leachable Cr(VI) compounds as being 2 mg/kg of leather. However, research is still needed to

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better understand the transformation mechanism of Cr(III) to Cr(VI) in finished leather as well as the potential toxic effects to man at this very low range of values. B.1.2.6 Development of Clean Technologies The aforementioned studies did show some harmful effects on organisms living in the ground. Accumulation into the environment should therefore be avoided. Motivated by this objective and in order to economize chemicals and water, tanners have developed manufacturing methods whose aim is to reduce Cr emissions into the environment. These efforts are often based upon methods for the optimization of the use of Cr, through the exhaustion of tanning baths and the reuse of residual water, developed by research institutes and manufacturers of Cr compounds.44,45 The Cr exhaustion ratio in tanning floats, traditionally 70% to 80%, can attain 97% with the new processes.17 Effluent treatment plants are increasingly being installed throughout the world in order to purify liquid waste, often providing a common treatment service in highly concentrated tannery zones. In parallel, work is being carried out concerning the recovery of Cr(III) compounds from tanned waste and tannery sludge.46,47 B.1.3

Conclusion

Chromium(III) hydrogen sulfate (Cr(HSO4)3) remains an irreplaceable tanning agent owing to its ease of use and the quality that it confers to leather. Studies from 1997 conclude that Cr(III) tanned leather produces no toxic effect on the consumer. On the other hand, regarding fauna and flora, high accumulation in the environment is to be avoided. For this reason, tanners are concentrating their efforts on the application of clean technologies and processes for the recycling of effluent and solid waste containing Cr(III).

Bibliography 1. Jullien I., Prevot J., and Gavend G., 1989, La Peau Matière Première de la Tannerie Mégisserie, Lyon: CTC. 2. Jullien I., 1983, Le Travail de Rivière, Lyon: CTC. 3. Heidemann, E., 1997, Vergleich zwischen chrom und vegetabilgerbung, abgeleitet aus den bindepositionen am kollagen, Das Leder, 5, 99–104. 4. Spahrkäs, H. and Schmidt, H., Das Leder, 1959, 10, 145–147. 5. Jullien, I., 1981, Le tannage au Chrome, Lyon: CTC. 6. Heidemann, E., 1993, Fundamentals of Leather Manufacturing, Darmstadt: Eduard Roether KG.

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7. Jullien, I. and Gavend, G., 1990. Le Cuir, Origine et Fabrication (also in English), 4th ed., Lyon: CTC. 8. Baruthio, F., 1992. Toxic effects of chromium and its compounds, Biological Trace Element Research, 32, 145–153. 9. IARC monographs on the evaluation of the carcinogenic risk of chemicals to humans : wood, leather and some associated industries, 25, Lyon: International Agency for Research on Cancer (IARC), February 1981. 10. Langerwerf, J.S.A., Mutagenicity of Cr: Physico-chemical aspects of the genotoxicological behaviour of tri and hexavalent Cr compounds, International Symposium on Chemical and Toxicological Aspects of Environmental Quality, 23–25 November 1983. 11. Bernal, X., Borsa, J., Lopez, F., and Turuguet, D., Compuestos Químicos en la industria de curtidos y acabados: aproximación al problema en Catalunya, XXI International Union of Leather Technologists and Chemists Societies Congress, Barcelona, Spain, 25–29, September 1991. 12. Ministère français du travail, Valeurs admises indicatives des concentrations dans l’atmosphère des lieux de travail, Ciculaire du 19 Juillet 1982 modifiée par circ. n° 96–8, August 1996. 13. ACGIH, 1996, Threshold Limit Values (TLVs) for Chemical Substances and Physical Agents and Biological Exposure Indices (BEI), ACGIH, Cincinnati, Ohio, 1996. 14. Stern, F.B., Beaumont, J.J., Halperin, W.E., Murthy, L.I., Hills, B.W., and Fajen, J.M., 1987. Mortality of chrome leather tannery workers and chemical exposures in tanneries, Scand J. Work Environ. Health 13, 108–117. 15. Pippard, E.C., Acheson, E.D., and Winter, P.D., 1985. Mortality of tanners, British Journal of Industrial Medicine, 42, 285–287. 16. International Environment Commission (IUE), 1996, Typical pollution values related to conventional tannery processes, World Leather, V.9, 7, 13. 17. Luck, W. and Wehling B., Cr Tanning process with high exhaustion bath, Lecture at 33rd annual congress of Asociación Quimica Española de la Industria del Cuero, 30 April 1984. 18. Gouvernement du Canada, Loi Canadienne sur la protection de l’environnement; liste des substances d’intérêt prioritaire; rapport d’évaluation; le Cr et ses composés (also in English), ref. En40-215/39F, 1994. 19. Fuller, C.C., Davis, J.A., Lamothe, P.J., Fries, T.L., Fernandez, G., Vargas, J.A., and Murillo, M.M., 1990. Distribution and transport of sediment-bound metal contaminants in the Rio Grande de Tarcoles, Costa Rica, Wat. Res. V.24, 7, 805–812. 20. Carre, M.C., Vulliermet, A., and Vulliermet, B., 1983, Tannerie et Environnement (also in English), Lyon: CTC. 21. Buljan, J., 1996. Pollution limits for discharge of tannery effluents into water bodies and sewers, World Leather, 9, 7, 65–68. 22. Covington, A.D., 1985, Chromium in the leather industry, Chromium Review, 5, 2–9. 23. European Council Decision of 22 December 1994 (OJEC of 31 December 1994) and European Commission Decision of 20 December 1993 (OJEC of 7 January 1994). 24. Rutland, F.H., 1990, Tanneries and the environment, a look into the nineties, The Leather Manufacturer, 108, 5, 18–22. 25. Title 40, U.S. Code of Federal Regulations, Section 261.4 (b) (6).

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26. U.S. EPA, Technical support document for the surface disposal of severage sludge, November 1992. 27. U.S. Federal Register, vol 60, page 54764. 28. Rutland, F.H., 1996, An environmental renaissance, a review of development in the United States over the past year, World Leather, 9, 7, 10–12. 29. OECD, Le système de contrôle OCDE pour les mouvements transfrontières de déchets destinés à des opérations de valorisation. Manuel d’ApplicationMonographie sur l’Environnement nο. 96, Paris: OECD, 1995. 30. Davy, S., 1995, The leather industry fights back, Leather, 3, 37–40. 31. Shivas, S.A.J., 1979, The field disposal of tannery sludge, Journal of the American Leather Chemists Association, 74, 3, 70–81. 32. Bartlett, R.J. and Kimble J.M., 1976, Behaviour of chromium in soils. I. Trivalent forms, J. Environ. Qual., 5, 4, 379–383. 33. Lollar, R.M., 1982, Cr III or Cr VI: bases for delisting solid wastes containing trivalent chromium, The Leather Manufacturer, 100, 11, 16–22. 34. Blomfield, C., Pruden, G., 1980, The behaviour of chrome VI in soil under aerobic conditions, Environ. Pollut., 23, 2A., 103–114. 35. Shivas, S.A.J., 1978, The environmental effects of chromium in tannery effluents, Journal of the American Leather Chemists Association, 73, 8, 370–377. 36. Shivas, S.A.J, 1980, The effects of trivalent chromium from tannery wastes on earthworms, Journal of the American Leather Chemists Association, 75, 300–304. 37. U.S. EPA, Soil screening guidance : technical background document, report no. EPA/540/R-95/128, 1996. 38. Sykes, R.L., Corning, D.R. and Earl N.J., 1981, The effect of soil chromium III on the growth and chromium absorption of various plants, Journal of the American Leather Chemists Association, 76, 3, 102–125. 39. Katz, S.A., Salem, H., 1993. The toxicology of chromium with respect to its chemical speciation: a review, Journal of Applied Toxicology, 13, 217–224. 40. Martinetti, R., October 1994. Contribution à la labellisation “écoproduit” de cuirs tannés aux sels de Chrome: étude de la mobilité du Chrome”, thèse, LyonFrance: CTC, 27. 41. Nickolaus, G., May 1995. Does leather contain chromium (VI) ?, XXII International Union of Leather Technologists and Chemists Societies congress, Freidrichshafen-Germany, 15–20. 42. International Union of Leather Technologists and Chemists Societies, IUC18 standard: leather-determination of chromium (VI) content, September 1994. 43. Cen, E.N., 420 Protective gloves: general requirements, September 1994. 44. Gregori, J., Marsal, A., Manich, A.M., Cot J., Optimización del proceso de curtición al cromo: influencia del comportamiento de tres tipos de agentes complejantes, XXI International Union of Leather Technologists and Chemists Societies Congress, Barcelona, Spain, 25–29, September 1991. 45. Davis, M.H., Scroggie, J.G., Theory and practice of direct chrome liquor recycling, XVI International Union of Leather Technologists and Chemists Societies Congress, Versailles-France, 4–6 v. II, September 1979. 46. Taylor, M.M., Diefendorf, E.J., Thomson, C.J., Brown, E.M., Marmer, W.N., Cabeza i Fabra, L.F., 1996, Extraction of value-added byproducts from the treatment of chromium containing collagenous waste generated in the leather industry, Bol. Tec. AQEIC, 3, 124–150. 47. Harris, T., Practical experience in chromium recovery, World Leather, 1996, 9, 7, 29–32.

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B.2 Chromium and the Timber Preser vation Industry

Richard Murphy B.2.1

Introduction

Chromium compounds have been used in the formulation of water-borne wood preservatives for about a century. They function as essential chemical fixatives for the copper and other fungicidal and insecticidal components in the widely used chromated-copper preservatives, of which the best known example is CCA (copper–chromium–arsenic). Studies have shown that Cr in these preservatives has little or no direct action against decay fungi. However, stabilization of the other preservative components achieved through oxidation state reduction of Cr makes them resistant to leaching and provides the treated wood with long-term durability against fungal and insect attack, even in high risk environments. Recent research and development efforts have led to the introduction of controlled and accelerated fixation systems which provide CCA-treated timber products having very high degrees of fixation (>99%) of the chromium (Cr), copper (Cu) and arsenic (As) components. The development, functional role, safety, and environmental aspects of Crcontaining wood preservatives are summarized in this article. B.2.1.1 Historical Development and Current Status The first major application of Cr compounds in wood preservation took place in the early part of this century with the development of "Wolman" comopounds based on sodium fluoride (NaF) and dinitrophenol (C6H3OH(NO2)2) with sodium dichromate (Na2Cr2O7) or potassium dichromate (K2Cr2O7).1 This was followed in 1926 by the development of copper-chromate (CC) preservative by Gilbert Gunn of the Celcure Company. The CC preservative was a mixture of equal parts of K2Cr2O7 and copper sulfate which was dissolved in water to a concentration of about 10% mass/volume.1,2 This solution was then applied to dried timbers in large-scale impregnation cylinders using a combination of vacuum to remove air from the wood and hydraulic pressures of 8 bar (7.90 atm) to 12 bar (11.84 atm) to inject the preservative liquid deep into the wood. Although CC preservatives are effective against a wide

Reprinted by permission: International Chromium Development Association 45 rue de Lisbonne, 75008 Paris, France. Tel: 33 01 40 76 06 89 Fax: 33 01 40 76 06 87  International Chromium Development Association; November, 1998. http://www.chromium-asoc.com/publications/frame.html NOTE: Original publication has been updated by the Chromium(VI) Hanbook editors.

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TABLE B.2.1 Examples of CCA Wood Preservative Formulations Name Celcure A (BS Type I) Tanalith C (BS Type II) Boliden K33 NWPC type B AWPA type A AWPA type B AWPA type C

Country/ region

Cu

Composition Cr

As

UK

CuSO4 ⋅ 5H2O 33%

Na2Cr2O7 ⋅ 2H2O 41%

As2O3 ⋅ 2H2O 26%

UK

CuSO4 ⋅ 5H2O 35%

Na2Cr2O7 ⋅ 2H2O 45%

As2O3 ⋅ 2H2O 20%

Sweden

CuO 19.6%

CrO3 35.3%

As2O3 45.1%

USA USA USA

CuO 18.1% CuO 19.6% CuO 18.5%

CrO3 65.5% CrO3 35.3% CrO3 47.5%

As2O3 16.4% As2O3 45.1% As2O3 34.0%

range of wood destroying organisms, a number of Cu tolerant organisms are able to attack even well-treated wood. The most significant Cr based wood preservatives were invented in 1933 with the patent by Kamesam of a water-diluted CCA formulation which gave very good all-around fungal and termite resistance to the treated wood. This first CCA formulation was commercially marketed as "Ascu" and has led to the development of a range of formulations differing to a greater or lesser degree in the relative proportions of the main components and the source chemicals (see Table B.2.1). The CCA preservatives are applied to timber by the same methods as used for the CC systems. Since the late 1930s several variants have been evolved on the chromated copper formulations e.g., copper–chromium–boron (CCB), copper–chromium–fluoride (CCF), copper– chromium–phosphate (CCP), but the most widespread and commercially dominant system has been the CCA. CCA is now the market leader internationally with commercial metric tonnage of about 100,000 per year traded internationally (compared with about 15,000 metric ton per year for all other waterbornes, 1990 figures).3 The growth of markets for CCA preservatives has been dramatic over the last 25 years. CCA formulations are registered for use throughout the world including the European Union, USA, Australia, New Zealand, Canada, India, Brazil, South Africa, Malaysia, Indonesia, and Japan. B.2.1.2

Functional Role of Chromium Compounds in Wood Preservatives Chromium compounds fulfill two principal functions in wood preservatives: as a chemical "fixative" to prevent or reduce loss by leaching of other components of the preservative, and/or as an anti-corrosion agent. The first function can be regarded as the most significant and was the main reason for the incorporation of Na2Cr2O7 or K2Cr2O7 into preservatives such as CC, CCA, and "Wolman" NaF/C6H3OH(NO2)2 compounds in the 1920s and 1930s. Of these, the CCA and related preservatives will be considered in more detail below. The work of Brüning was the first to recognize that

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the addition of chromates (CrO42–) could impart leaching resistance to other metal compounds in the formulation (H. Brüning, 1912, British Patent 2972) and the ability to fix copper sulfate was then exploited by Gunn (G. Gunn 1926, British Patent 273007) in the Celcure Cu–Cr-based preservatives. In 1933 Kamesam (S. Kamesam, 1933, British Patent 404855) developed the first CCA formulation in which copper sulfate and arsenic(V) oxide (As2O5) are fixed by dichromate (Cr2O72–) after he had spent a period working with Falck in Germany where they developed the "Falkamesam" Cr–arsenate preservative.4,5 Other preservatives to make use of the fixing properties of chromates have been the "Boliden" compounds, chromated zinc chloride, and chromated mercury chloride in the 1930s and 1940s and the boron-fluorinechromium–arsenic (BFCA) diffusion treatment formulation in the 1950s and 1960s.1,6,7 The second function of imparting corrosion resistance was recognized early and was used by Wolman in 1913 to improve the corrosivity properties against iron and steel (in treating tanks and metal fastenings) of his NaF and C6H3OH(NO2)2 "Trioloth" preservative (often called "Wolman salts"). The content of CrO42– as either Na2Cr2O7 or K2Cr2O7 in these formulations was relatively low (NaF 85%, C6H3OH(NO2)2 10%, Na2Cr2O7 or K2Cr2O7 5%). In the 1920s, As compounds were added to Triolith to form a new preservative "Tanalith," and in the 1930s the CrO42– content of both preservatives was increased considerably to about 35% in recognition of its role not only as a corrosion inhibitor, but also as a fixative for the arsenic component. These high Cr and Cr/As formulations were identified respectively with a U or UA designation (e.g., Tanalith U, Trioloth UA). Chromates do not always improve the corrosion resistance of preservatives and have been reported to increase the corrosivity of zinc sulfate (ZnSO4) or zinc chloride (ZnCl2), whereas the corrosivity of copper sulfate and other components can be neutralized.1 It should be noted that Cr compounds have virtually no fungicidal (or insecticidal) activity in wood. This has been demonstrated clearly in work by Gray and Dickinson on the decay-inhibiting activity of various combinations of Cu, Cr, and As compounds in treated timber.8 B.2.1.3 Chromium in CCA Preservatives CCAs have fulfilled an essential role in providing durable, safe, treated timber products for nearly 50 years. In addition to providing added durability, they have only minimal effects on wood strength properties and are compatible with most metal fastenings, glues, and coatings for timber. CCA preservatives are sold only for professional application to timber, and the preservative is usually diluted with water at industrial wood treatment plants to give working solution strengths varying from about 2% mass/ volume to 5% mass/volume depending upon the type of wood to be treated and its intended use. In general, the amount of preservative formulation delivered to the wood varies between about 4 kg/m3 and 24 kg/m3 of wood and is termed the preservative "retention."

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TABLE B.2.2 General Scheme for CCA Fixation Reactions Reaction Initial-rapid(minutes) Main-hours/days

Long-term–weeks/ months

Source:

Description Cu , CrO4 adsorption to wood Cr(VI) reduction pH increase 2+

2–

Fluctuating pH

Products Cu /wood Cr(VI)/wood CrAsO4 Cu(OH)CuAsO4 CuCrO4 Cr2(OH)4CrO4 Cr(OH)3 Cr(VI)/wood complexes Cr(III)/wood complexes Cu(II)/wood complexes ? 2+

After Cooper et al. 13

Research and development efforts have focused on understanding the fundamental mechanisms of action of CCA (principally of the Cu and As components) against wood-destroying organisms, preservative treatment mechanics, the chemistry of "fixation" in wood, leaching behavior in different environments, and health and safety and environmental impact issues. The published literature is extensive, and useful texts and reviews have been presented by Nicholas,9 Wilkinson,2 Placket,10 Barnes,11 Anderson et al.,12 Cooper et al.,13 Gray,14 Eaton and Hale,15 Barnes and Murphy,16 Hillier et al.,17 Murphy and Dickinson.18 In addition to publication in the scientific literature, research on CCA and other wood preservatives has been reported to conferences of the International Research Group on Wood Preservation, which has provided a significant international forum for discussion since 1969. The fixation reactions begin when aqueous solutions of CCA preservative are injected into timber and may go on for some considerable time after the impregnation process is completed. A number of researchers, notably Wilson,19 Henry and Jerowski,20 Dahlgren and Hartford,21–27 Smith and Williams,28,29 Pizzi,30–35 and Ostmeyer et al.36,37 have studied the chemistry of reactions between CCA preservatives and wood and although several questions remain, a general scheme is available (Table B.2.2). The reactions can be divided into three phases according to their rapidity. Initially, there is a rapid (minutes) adsorption of Cr(VI) as CrO42– and Cu2+ to wood components which removes about 50% of the total Cr(VI) from the solution absorbed by the wood. This is followed by the principal reaction involving Cr which is a reduction of the free Cr(VI) to Cr(III) over a time period of several hours. This is accompanied by a rise in pH of the wood/preservative system and the formation of several low solubility compounds (CrAsO 4 , CuCrO 4 , Cu(OH)CuAsO4) involving the Cu and As components. It is unclear at present what happens to the initially adsorbed Cr(VI) but it is clear from Electron Paramagnetic Resonance (EPR) and other studies that this is eventually reduced to Cr(III), possibly after passage through intermediate Cr(V)

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and Cr(IV) steps which have been observed in treated wood.38,39 These reactions are followed by possible "long-term" reactions involving fluctuating pH and possible interconversions and additional reactions over several months,22 although reports of these reactions are limited. The importance of the fixation reactions is critical to the efficacy and acceptance of CCA preservatives. Fixation and the resistance to leaching of the Cu and As components is essential to guarantee long-term performance (e.g., decades) of the treated wood against fungal decay and insect and marine borer attack in environments ranging from house foundations to permanent soil contact to exposure in sea water. Completion of fixation also means that the Cr in treated wood is converted to the considerably less toxic Cr(III),40,41 which also has lower aquatic and soil ecotoxicity. Until recently most fixation of the preservative took place under ambient conditions at treatment plants, usually for periods of between 48 h and 72 h under various types of cover (e.g., roofing, tarpaulins, cover boards). However, while this has proved satisfactory in warmer climates, it is now known that fixation is highly temperature dependent and can take from 1 h to 10 h at 70 °C to give complete reduction of Cr(VI) to Cr(III), up to 30 h at 50 °C, and between 48 h and 100 h at 20 °C13,42,43 at moderate relative humidities. Since pioneering work by Peek and Willeitner on the use of accelerated fixation on freshly treated wood by elevated temperatures such as steaming, a number of commercial, controlled fixation systems have been developed.44–46 Several of these use conventional kiln drying chambers which are operated for the initial part of the cycle under conditions appropriate for high temperature fixation (e.g., high RH (low dry bulb/wet bulb depressions) maintained for several hours at 70 °C) prior to commencement of conventional drying schedules. Most recently, a novel process developed by the Forest Research Institute in New Zealand makes use of CCA solutions heated to about 70 °C (usually avoided to prevent sludging problems in conventional treatments) to treat Radiata pine by a multiple-phase pressure schedule (MPP) which delivers dry fixed treated wood at the end of the process.47,48 Controlled fixation systems now offer the ability to complete the CCA fixation reactions quickly at treatment plants and allow treated wood to meet increasingly stringent local and national regulations concerning occupational, public exposure and environmental contamination by components of all wood preservatives. B.2.1.3.1 Safety and Environmental Effects of CCA Preservatives Since the introduction of CCA and related preservatives, considerable improvements have been made in the industrial design of wood treating plants, delivery systems for the preservatives from manufacture to treatment sites, fixation of the treated wood as described above, and disposal of wastes and residues.49,50 There are very few reports of health and safety studies on workers exposed to Cr-containing wood and no reported excess of occupational illness due to the normal handling of CCA preservatives or treated wood.51,52 A study of CCA-exposed workers in Sweden and

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Norway concluded that, within the limited number of person-years under risk in the study, no increased risk of any cancer sites was indicated.53 A number of studies have been conducted on soils contaminated at wood treating plants through spillage and dripping from freshly treated wood.50 These have demonstrated the importance of good plant design including concrete drip pads and collection sumps, maintenance, and operational procedures to minimize environmental impacts. Additional factors influencing the potential for contamination include the soil type and oxidation state of the contaminants, particularly Cr and As.54 Studies using lysimeters to simulate aspects of spillages of preservatives are in progress at several laboratories.55, 56 Recent studies have demonstrated the possibilities for cleanup of CCA treatment sites at industrial scale.57,58 Recent research has also been concerned with establishing the potential for losses of CCA components during the service life of treated wood to the local environment. This work has often been done with laboratory-based water leaching systems or as soil depletion studies on small, treated wood stakes, and there are relatively few long-term field soil studies.59,60 The work of Cooper and Ung61 on CCA-treated poles and Hudson and Murphy62 on CCA-treated wood exposed in field soils for several years has established practical information on soil concentrations of CCA preservative components surrounding treated wood in service. These studies have generally shown steep gradients of concentration of Cu, As, and Cr compounds in soil surrounding CCA-treated wood in soil and little or no elevation of environmental concentrations of these elements beyond 100 mm to 250 mm distance from the treated wood. Cr shows the lowest level of leaching and dispersal into surrounding soil in all the studies conducted to date.61–65 Data such as these have been used by Hillier et al.66 in whole life-cycle assessments of the environmental impact of CCA treated wood. They concluded that the relatively low quantity of loss of CCA components to soil over a 40-year service life in soil of treated wood (increased concentration Cr, Cu, and As in soil of 1.6 mg/kg, 4.9 mg/kg, and 3.3 mg/kg, respectively, in 0.5 m3 soil affected) were insignificant in relation to regulatory concentrations. More important in relation to the LCA was the need to close the life cycle with environmentally benign means of post-service disposal of CCA treated timber and, encouragingly, several such routes are now available.67–69 B.2.1.4 The Future Despite the long and successful history of use of chromate-containing wood preservatives, a number of regulatory authorities are considering restrictions or bans on their use for certain products.70 In Sweden, a legislative ban on the use of As- and Cr-containing wood preservatives for above-ground timbers came into effect between 1992 and 1994 and led to immediate substitution with alternative formulations and a reduction of about 50% in the market size for CCA.71 Interestingly, CCA preservatives are still permitted for timber for export and for local heavy duty applications and they retained about a 35%

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market share in 1994. However, international pressure to reduce the consumption of CCA and related preservatives will remain because of the possible health and environmental effects. It should be stressed that this pressure is based only on possible effects and that the published evidence indicates that such preservatives have not caused either health or environmental problems when used in accordance with normal industry procedures. The wood preservation industry has developed alternative As- and Cr-free preservative systems, although it remains to be seen whether such treatments will provide the long-term performance, robust industrial handling properties, and economy of the chromated-copper wood preservatives such as CCA and CCB.

B.2.2

Conclusions

Chromium compounds have played an essential role in several wood preservative formulations, the most important of which have been the Cu–Cr–As (CCA) and Cu–Cr–B (CCB) types. These preservatives are currently the dominant international wood preservative systems. They have established an outstanding reputation for imparting long-term durability to treated timber. Systems are available to allow their safe handling and containment at industrial treatment sites and rapid and complete fixation of the components in freshly treated timber. Research on the environmental impact of CCA treated wood in service has indicated that they do not lead to significant local soil pollution. Methods for the reprocessing of CCA and other treated wood are being actively developed and their adoption in practice will close the life cycle for timber treated with chromated-copper preservatives.

Bibliography 1. van Groenou, H.B., Rischen, H.W.L., and van den Berge, J., 1951, Wood preservation during the last 50 years. A.W. Sijthoff’s Uitgeversmaatschappij N.V., Leiden, p. 318. 2. Wilkinson, J.G., 1979, Industrial Timber Preservation, Associated Business Press, London, p. 532. 3. Connell, M., 1991, Industrial wood preservatives: The history, development, uses, advantages and future trends, in: The Chemistry of Wood Preservation, Thompson R., Ed., Special Publication 38, The Royal Society of Chemistry, London, 16–33. 4. Falck, R. and Kamesam, S., 1931, Ein neues, allgemein Holzschutzmittel. Chemische Zeitschrift, 55, 837–838. 5. Popham, F.J. and Kamesam, S., 1932, A new wood preservative: the "falkamesam" process, Indian Forester, 58, 191–195. 6. Tamblyn, N., 1975, Treatment of building timbers by dip-diffusion, in: The economy and utilisation of timber in the tropics through wood preservation,

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7.

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11. 12.

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Chromium(VI) Handbook Proceedings of a Training Seminar, Forest Products Research Centre, Port Moresby, Papua New Guinea, p. 12. Levy, C.R., 1975, Application of dip diffusion in Papua New Guinea, in: The economy and utilisation of timber in the tropics through wood preservation, Proceedings of a Training Seminar, Forest Products Research Centre, Port Moresby, Papua New Guinea, p. 21. Gray, S.M. and Dickinson, D.J., 1987, Copper-based waterborne preservatives: the biological performance of wood treated with various formulations, International Research Group on Wood Preservation Document IRG/WP 3451. Nicholas, D.N., 1971, Wood deterioration and its prevention by preservative treatments, Preservatives and Preservative Systems, Vol. II. Syracuse Wood Science Series, 5, D.L. Nicholas, Ed., Syracuse University Press, NY. Placket, D.V., 1983, A discussion of current theories concerning CCA fixation, International Research Group on Wood Preservation Document IRG/WP 323883. Barnes, H.M., 1985, Trends in the wood-treating industry: State-of-the-art report, Forest Products Journal, 35, 3–22. Anderson, D.G., Cornfield, J.A., and Williams, G.R., 1991, Waterbased fixed preservatives, in: The Chemistry of Wood Preservation, Thompson R., Ed., Special Publication 38, The Royal Society of Chemistry, London, 101–116. Cooper, P.A., Alexander, D.L., and Ung, T., 1993, What is chemical fixation? in: Chromium-containing Waterborne Wood Preservatives: Fixation and Environmental Issues, Forest Products Society, Madison, 7–13. Gray, S.M., 1993, Chromated copper preservative systems—the performance of treated wood, in: Chromium-Containing Waterborne Wood Preservatives: Fixation and Environmental Issues, Forest Products Society, Madison, 14–22. Eaton, R.A. and Hale, M.D.C., 1993, Wood: Decay, Pests and Protection, Chapman and Hall, London. Barnes, H.M. and Murphy, R.J., 1995, Wood preservation: The classics and the new age, Forest Products Journal, 45, 16–26. Hillier, W., Murphy, R.J., Dickinson, D.J., and Bell, J.N.B., 1996, Life-Cycle Assessment of Treated Wood: A View from the Road, International Research Group on Wood Preservation Document IRG/WP 96-50078. Murphy, R.J. and Dickinson, D.J., 1997, Wood preservation research—What have we learnt and where are we going ? Journal of the Institute of Wood Science, 14, 147–153. Wilson, A., 1971, The effects of temperature, solution strength and timber species on the rate of fixation of a copper–chrome–arsenate wood preservative, Journal of the Institute of Wood Science, 5, 36–40. Henry, W.T. and Jeroski, E.B., 1967, Relationship of arsenic concentration to the leachability of chromated copper arsenate formulations, Proceedings of the American Wood Preserver’s Association Annual Meeting, 63, 187–196. Dahlgren, S.E., 1972, The course of fixation of Cu–Cr–As wood preservatives, Record of the Annual Convention of the British Wood Preserving Association, 109–128. Dahlgren, S.E., 1974, Kinetics and mechanism of fixation of Cu–Cr–As wood preservatives, Part IV: Conversion reactions during storage, Holzforschung, 28, 58–61.

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23. Dahlgren, S.E., 1975, Kinetics and mechanism of fixation of Cu–Cr–As wood preservatives, Part V: Effect of wood species and preservative composition on leaching during storage, Holzforschung, 29, 84–95. 24. Dahlgren, S.E., 1975, Kinetics and mechanism of fixation of Cu–Cr–As wood preservatives, Part VI: The length of the primary precipitation period, Holzforschung, 29, 130–133. 25. Dahlgren, S.E. and Hartford, W.H., 1972, Kinetics and mechanism of fixation of Cu–Cr–As wood preservatives, Part I: pH behaviour and general aspects of fixation, Holzforschung, 26, 62–69. 26. Dahlgren, S.E. and Hartford, W.H., 1972, Kinetics and mechanism of fixation of Cu–Cr–As wood preservatives, Part II: Fixation of Boliden K-33, Holzforschung, 26, 105–113. 27. Dahlgren, S.E. and Hartford, W.H., 1972, Kinetics and mechanism of fixation of Cu–Cr–As wood preservatives, Part III: Fixation of Tanalith C. Holzforschung, 26, 142–149. 28. Smith, D.N. and Williams, A.I., 1973, The effect of composition on the effectiveness and fixation of copper/chrome/arsenic and copper/chrome preservatives, Part I: Effectiveness, Wood Science and Technology, 7, 60–76. 29. Smith, D.N. and Williams, A.I., 1973, The effect of composition on the effectiveness and fixation of copper/chrome/arsenic and copper/chrome preservatives, Part II: Selective absorption and fixation, Wood Science and Technology, 7, 142–150. 30. Pizzi, A., 1981, The chemistry and kinetic behaviour of Cu–Cr–As/B wood preservatives, Part 1: Fixation of chromium on wood, Holzforschung und Holzverwertung, 33, 87–100. 31. Pizzi, A., 1982, The chemistry and kinetic behaviour of Cu–Cr–As/B wood preservatives, Part 2: Fixation of the Cu/Cr system on wood, Journal of Polymer Science, Polymer Chemistry Ed., 20, 707–724. 32. Pizzi, A., 1982, The chemistry and kinetic behaviour of Cu–Cr–As/B wood preservatives, Part 3: Fixation of a Cr/As system on wood. Journal of Polymer Science, Polymer Chemistry Ed., 20, 725–738. 33. Pizzi, A., The chemistry and kinetic behaviour of Cu–Cr–As/B wood preservatives, Part 4: Fixation of CCA to wood, Journal of Polymer Science, Polymer Chemistry Ed., 1982, 20, 739–764. 34. Pizzi, A., 1990, Chromium interactions in CCA/CCB wood preservatives, Part I: Interactions with wood carbohydrates, Holzforschung, 44, 373–380. 35. Pizzi, A., 1990, Chromium interactions in CCA/CCB wood preservatives, Part II: Interactions with lignin, Holzforschung, 44, 419–429. 36. Ostmeyer, J.G., Elder, T.J., Littrell, D.M., and Tatarchuk, B.J., 1988, Spectroscopic analysis of southern pine treated with chromated copper arsenate, I. X-ray photoelectron spectroscopy (XPS), Journal of Wood Chemistry and Technology, 8, 413–439. 37. Ostmeyer, J.G., Elder, T.J., and Winandy, J.E., 1989, Spectroscopic analysis of southern pine treated with chromated copper arsenate, II, Diffuse reflectance fourier transform infrared spectroscopy (DRIFT), Journal of Wood Chemistry and Technology, 9, 105–122. 38. Hughes, A.S., Murphy, R.J., Gibson, J.F., and Cornfield, J.A., 1994, Electron paramagnetic resonance (EPR) spectroscopic analysis of copper based preservatives in Pinus sylvestris, Holzforschung, 48, 91–98. 39. Ruddick, J.N.R., Yamamoto, K., and Herring. F.G., 1994, The influence of accelerated fixation on the stability of chromium (V) in CCA treated wood, Holzforschung, 49, 1–3.

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40. International Agency for Research on Cancer (IARC), 1990, IARC Monographs on the evaluation of carcinogenic risks to humans, Chromium, nickel and welding, vol. 49, Lyon, France, IARC. 41. O’Brien, P. and Kortenkamp, A., 1995, the chemistry underlying chromate toxicity, Trensition Metal Chemistry, 20 636–642. 42. Forsyth, P.G. and Morrell, J.J., 1990, Hexavalent chromium reduction in CCAtreated sawdust, Forest Products Journal, 40, 48–50. 43. Alexander, D.L., Ung, T., and Cooper, P.A., 1993, Effects of temperature and humidity on CCA-C fixation in pine sapwood, in: Chromium-Containing WaterBorne Wood Preservatives: Fixation and Environmental Issues, Forest Products Society, Madison, 32–35. 44. Peek, R.-D. and Willeitner, H., 1981, Accelerated fixation of chromate-containing wood preservatives by superheated steam, Part I: Effect of different heat treatments on the leaching of preservatives, 39, 495–502. 45. Peek, R.-D. and Willeitner, H., 1988, Fundamentals of steam fixation of chromated wood preservatives, International Research Group on Wood Preservation Document IRG/WP 3483. 46. Connell, M., Baldwin, B.J., and Smith, T., 1995, Controlled fixation technology, in: Proceedings of the 3rd International Wood Preservation Symposium—The Challenge-Safety and Environment, International Research Group on Wood Preservation Document IRG/WP 95-50040, 177–194. 47. Nasheri, K., Pendelbury, J., Drysdale, J., Pearson, H., and Hedley, M. 1997, The multi-phase pressure (MPP) process, One stage CCA treatment and accelerated fixation process, Part 1: The process as a new concept in preservative treatment, International Research Group on Wood Preservation Document IRG/WP 97– 40078. 48. Pendelbury, J., Drysdale, J., Nasheri, K., Pearson, H., and Hedley, M., 1997, The multi-phase pressure (MPP) process, One stage CCA treatment and accelerated fixation process, Part 2: Concept proved by repetitive pilot plant treatments, International Research Group on Wood Preservation Document IRG/WP 97–40079. 49. Anon, 1994, Environmental aspects of industrial wood preservation: A technical guide, Technical Report Series 20, United Nations Environment Programme (UNEP), Paris, p. 105. 50. Stalker, I.N. and Cornwell, P.B., 1975, Safe application of copper-chrome-arsenate preservatives, Record of the Annual Convention of the British Wood preserving Association, 3–34. 51. Konasewich, D.E. and Henning, F.A., 1988, Chromated copper arsenate wood preservation facilities: Recommendations for design and operation, Report EPS 2/WP/3, Conservation and Protection, Environment Canada, Ottawa, Canada, p. 81. 52. Arsenault, R.D., 1977, Health aspects of CCA wood preservatives—A review of arsenates and cancer, Record of the Annual Convention of the British Wood Preserving Association, 129–180. 53. Ohlson, C.-G., Andersen, A., Evans, F.G., Karlehagen, S., and Nilsson, K., 1995, Cancer incidence among CCA exposed workers in the wood preserving industry, in: Proceedings of the 3rd International Wood Preservation Symposium—The Challenge-Safety and Environment, International Research Group on Wood Preservation Document IRG/WP 95-50040, 147–149. 54. Bergholm, J., 1990, Studies on the mobility of arsenic, copper and chromium in CCA-contaminated soil, in: Proceedings of the 1st International Wood

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55.

56.

57.

58.

59. 60.

61. 62.

63.

64.

65.

66.

67.

603

Preservation Symposium—The Challenge—Safety and Environment, International Research Group on Wood Preservation Document IRG/WP 3571. Melcher, E. and Peek, R.-D., 1997, A comparison of the migration behaviour in soil of different waterborne wood preservatives and their leachates, International Research Group on Wood Preservation, Document IRG/WP 9750065. van Eetvelde, G., Hartman, R., Mwangi, J.M., Öztürk, H.S., and Stevens, M., 1998, Environmental fate of copper-based wood preservatives in different soil substrates, Part 2: Study of the metal sorption and migration potential under simulated rainfall, in: Proceedings of the 4th International Symposium—The Challenge Safety and Environment in Wood Preservation, International Research Group on Wood Preservation Document IRG/WP 9850101, 277–290. Rødsand, T., Hellum, K., and Lillemaehulm, H., 1998, Remediation of a site contaminated with creosote and CCA—a case study, in: Proceedings of the 4th International Symposium—The Challenge Safety and Environment in Wood Preservation, International Research Group on Wood Preservation, Document IRG/WP 98-50101, 127–134. Englöv, P., 1998, Remediation of a large CCA-impregnation plant, in: Proceedings of the 4th International Symposium—The Challenge Safety and Environment in Wood Preservation, International Research Group on Wood Preservation, Document IRG/WP 98-50101, 135–147. Cooper, P.A. and Ung, T., 1991, Leaching of CCA from treated wood: pH effects, Forest Products Journal, 41, 30–32. Cooper, P.A., 1994, Leaching of CCA: Is it a problem? in: Environmental Considerations in the Manufacture, Use and Disposal of Preservative-Treated Wood, Forest Products Society, Madison, 45–57. Cooper, P. and Ung, Y.T., 1997, Environmental impact of CCA poles in service, International Research Group on Wood Preservation, Document IRG/WP 97–50087. Hudson, N.J. and Murphy, R.J., 1997, Losses of CCA components and creosote from treated timber to soil, International Research Group on Wood Preservation Document IRG/WP 97-50098. De Groot, R.C., Popham, T.W., Gjovik, L.R., and Forehand, T., 1979, Distribution gradients of arsenic, copper, and chromium around preservative treated wooden stakes, Journal of Environmental Quality, 8, 39–41. Arsenault, R.D., 1975, CCA-treated wood foundations—A study of permanence, effectiveness, durability and environmental considerations, in: Proceedings of the American Wood Preservers’ Association, 71, 126–146. Ruddick, J.N.R., 1990, Wood preservation and the environment: A Canadian perspective, in: Proceedings of the 1st International Wood Preservation Symposium—The Challenge—Safety and Environment, International Research Group on Wood Preservation, Document IRG/WP 3581. Hillier, W., Murphy, R.J., Dickinson, D.J., and Bell, J.N.B., 1995, LCA examination of preservative treated timber products and alternatives; Initial results, in: Proceedings of the 3rd International Wood Preservation Symposium—The Challenge—Safety and Environment, International Research Group on Wood Preservation, Document IRG/WP 95-50040, 58–69. Cooper, P.A., 1994, Disposal of treated wood removed from service: The issues, in: Environmental Considerations in the Manufacture, Use and Disposal of Preservative-Treated Wood, Forest Products Society, Madison, 85–90.

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68. Nurmi, A. and Lindroos, L., 1993, Recycling of treated timber by copper smelter, International Research Group on Wood Preservation, Document IRG/WP 9350030. 69. Cooper, P.A., 1997, Management of used poles removed from service, in: Second Southeastern Pole Conference, Forest Products Society, Madison, 102–112. 70. Evans, F.G., 1998, Restrictions or environmental taxes as regulatory means—How will they influence the use of pressure treated wood? in: Proceedings of the 4th International Symposium—The Challenge—Safety and Environment in Wood Preservation, International Research Group on Wood Preservation, Document IRG/WP 98-50101, 372–376. 71. Jermer, J., Edlund, M.-L., and Nilsson, K., 1995, The implementation of restrictions on the use of arsenic and chromium based wood preservatives in Sweden, International Research Group on Wood Preservation, Document IRG/WP 9550062.

B.3 Chromium in Refractories

Mariano Velez B.3.1

Introduction

Refractory materials are chemical compounds that are used as structural materials forming insulation linings and/or as containment vessel in high temperature and corrosive environments in many industrial processes. The use of chromium (Cr) in refractories is second in importance to its metallurgical applications. The mineral chromite (FeCr2O4) is the only ore of Cr.1 About 15% of the total world chromite consumption is from the refractories industry.2 A typical analysis of a chromite suitable for refractory purpose is 38% to 48% chromium(III) oxide (Cr2O3), 12% to 24% aluminum oxide (Al2O3), 14% to 24% iron(III) oxide (Fe2O3), 14% to 18% magnesium oxide (MgO), and less than 10% silicon dioxide (SiO2). The usefulness of chromite as a refractory is based on its high melting point, 2,180 °C, moderate thermal expansion, neutral chemical behavior, and relatively high corrosion resistance. Chromite enhances thermal shock and slag resistance, volume stability, and mechanical strength. In contact with iron oxide, it forms a solid solution (a homogeneous crystalline phase Reprinted by permission: International Chromium Development Association 45 rue de Lisbonne, 75008 Paris, France. Tel: 33 01 40 76 06 89 Fax: 33 01 40 76 06 87  International Chromium Development Association 2000. http://www.chromium-asoc.com/publications/frame.html NOTE: Original publication has been updated by the Chromium(VI) Hanbook editors.

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composed of different minerals dissolved in one another) with iron oxide and expands considerably, causing the refractory to crumble (bursting). Adding MgO can prevent this problem.3 Chromium-based refractories4,5 are typically used in cement kilns, secondary steel refining furnaces, foundry sands, glass melting furnaces, and incinerators. In some cases alternative materials, such as magnesium-aluminum (MgAl) spinels, spinel-bonded magnesite, and high Al2O3 refractories—have replaced Cr-containing refractories. However, these materials do not always meet performance or cost requirements. B.3.1.1 Current Applications The iron (Fe) and steel industry consumes about 70% of the total tonnage of refractories produced globally. The cement and lime industry consume 7%, the ceramics industry 6%, the glass industry 3% to 4%, and the oil industry about 4%.6 Chromium refractory bricks of 100% Cr ore have been largely replaced by bricks composed of mixtures of chromite and added oxides (i.e., MgO) for greater refractoriness, volume stability, and resistance to spalling (cracking/rupturing of a refractory shape). A large quantity of Cr2O3 raw material is also being used in the production of refractories, either in the form of synthetic grain, such as MgCr2O4 and Cr2O3 or as additive.7 MgO-Cr brick can be severely affected by hydration during storage. The MgO (periclase) grains become superficially hydrated by the formation of a Mg(OH)2 (brucite) layer. Upon subsequent heating, the brucite layer decomposes, producing a loss of bond between the periclase grain and the matrix, severely decreasing the strength of the bricks.8 B.3.1.1.1 Copper Metallurgy Nearly all copper (Cu) producing furnaces have adopted refractory practices based on the use of MgO-Cr refractories.9 In converter furnaces, the lining of the furnace bottom and the tuyere zone (zone of greatest wear) is usually fused cast Mg–Cr or Cr–magnesite (MgCO3) brick. The prospective replacement of MgO–Cr by spinel MgO–Al2O3 spinel brick for Cu smelting, converting and refining is left undetermined at the time.10 B.3.1.1.2 Aluminum Metallurgy The Al industry uses Al2O3–Cr refractories with bricks having a Cr2O3 content ranging from 9.5% to 90%. The refractories are fired to develop a solidsolution bond, having a minimum of silicate bond phase. On the other hand, high Cr2O3 content refractories are being fused to obtain extremely dense refractories to be used in areas of high wear. The commercial products are highly resistant to the corrosive action of the variety of fluxes, slags, and glasses derived in the molten aluminum related processes.

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B.3.1.1.3 Steel Making Iron and steel plants are the major consumers of refractories, although new technological improvements have led to lower consumption.11 MgO–Cr refractories are commonly used in secondary steel-making plants because of their high resistance to a wide variety of slags and their stability at high temperatures. For instance, the reaction vessels in the argon–oxygen decarburization (AOD) process are lined with burned dolomite (CaMg(CO3)2), burned MgO or fused MgO–Cr refractories. B.3.1.1.4 Cement Kilns Several types of bricks are used in cement rotary kilns, and must have good mechanical behavior and high chemical stability. Magnesium oxide-spinel (MgO–MgAl2O4) refractories are mainly used for cement rotary kilns. In Japan, ultra high temperature fired MgO–Cr bricks are mostly applied in the burning zones of the kilns.12 B.3.1.1.5 Glass Melting Glass contact refractories are limited to compositions including Al2O3, Al2O3–SiO2, zirconium(VI) oxide (ZrO2), with or without Cr2O3 additions, and dense Cr2O3.13,14 High alkali borosilicate fiberglass (which is highly corrosive) is melted using fused Cr–AZS (Al2O3–ZrO2-SiO2 refractories) or fused Al2O3–Cr refractories. Low-alkali borosilicate glass is melted using dense sintered Cr2O3. Cr refractories (10% and 16% Cr2O3) offer high corrosion resistance to soda–lime glasses and are used as paving, sidewall and backup linings and increasingly in the foreheart/feeder components (mixing and cooling container for molten glass). Sintered Cr, Cr–magnesite, or magnesite–Cr is used in the bottom of the checkers, as well as on the structure surrounding the checkers and walls. During operation, the checkers develop minor amounts of soluble Cr(VI) on the surface.2 B.3.1.2 Special Refractories Chromium–borides, Cr–carbides, and Cr–silicides are relatively new high temperature materials intended for special applications15 (see Table B.3.1). Cr and boron compounds, because of their high melting point, have potential for structural applications, which require high temperature strength, chemical stability, and hardness and strength.19 B.3.1.3 Chromium(VI) Compounds in Refractories When Cr-based refractory materials are exposed to severe environments (high temperature, high pressure contact with different chemical species and phases), a possibility exists that toxic by-products or waste materials will form. Certain Cr compounds are classified as carcinogenic substances.20,21

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Appendix B TABLE B.3.1 Summary of Relevant Properties of Special Cr Compounds General Term

Compounds Identified

Cr-borides

Cr4B, Cr2B, Cr5B3, CrB, Cr3B, CrB2

Cr-carbides

Cr23C6, Cr7C3, Cr3C2

Cr-silicides

Cr3Si, Cr2Si, Cr5Si3, Cr3Si2, CrSi, CrSi2

Source:

Main Properties High melting point High electrical conductivity Resistant to chemical attack High melting point Very hard High melting point Hard and brittle Resistance to attack by acids

References 16, 17, 18.

Chromium(VI) compounds have been found at concentrations which exceed the United States Environmental Protection Agency (USEPA) limits when Cr-bearing materials are mixed with beta-calcium aluminate (βCa3Al2O6) cements (castable) at even relatively low temperatures.22,23 Environmentally hazardous chromium(VI) oxide (CrO3) forms in refractories along grain boundaries (narrow zone in ceramics or metals corresponding to the transition from one crystallographic orientation to another). As chromite comes into contact with alkali and alkaline earth oxides, the transition of Cr(III) into Cr(VI) in air is accelerated and occurs at notable rates.24 Hence, the content of alkali and calcium oxide (CaO) in Cr-containing refractories or materials coming into contact with them should be minimized. The Cr(VI) content, following the CaO–Cr2O3 phase diagram, increases with exposure to temperatures less than 1,022 °C and with an increase in CaO (from 0% to 42% CaO).25 The use of fused grains decreases the formation of Cr(VI). In the case of magnesite–Cr refractories, temperature, basicity (CaO/SiO2), and chromite phase size play important roles in Cr(VI) formation. The formation of Cr(VI) can be minimized by carefully controlling the amount of CaO in the refractory and by avoiding the use of a fine chromite phase during brick making. Today, there is a trend to try to substitute high-Cr brick refractories with other materials: Cu industry,9,10 steel industry,26,27 and cement industry.28 In the glass industry there has been the substitution of chromite refractories with other suitable materials (i.e., fused-cast AZS, dense zircon (ZrSiO4)). Some companies are taking back used Cr refractories from their customers and reprocessing them into new products.29 Another approach to reduce Cr in refractories has been the use of suitable coatings to improve the slagresistant behavior of MgO–Cr bricks.30 Still another practice is the use of fused-Cr magnesite, which is more expensive than its counterpart, sintered Cr-magnesite brick used in the steel industry. In this case, there has been an increase in refractory life as well as a lower consumption of refractory per ton of steel produced.

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B.3.1.4 Refractory Waste Management Most refractories are disposed as landfill.31 Recycling and waste management of refractories is extremely difficult since associated costs are difficult to quantify. For example, it is expensive to transport used refractories from users to recyclers. Also, since many recyclable, spent refractories are low value items, it is almost always cheaper to buy new raw materials than to use recycled materials. Only about 10% of total annual refractory production is recycled, even though successful recycling programs have existed for some time.32,33 Europe recycles a higher tonnage of refractories than the U.S., especially MgO–Cr from steel plants,34 while in Japan the used Cr bricks from cement kilns or glass furnaces are returned to the manufacturer.29 A preliminary research program35,36 has outlined a refractory recycling financial model that includes the major factors that impact the cost of management strategy. It quantifies the financial impact of tangible (i.e., loss of production owing to slow processes) and intangible (i.e., public relations, risk of major ecological liabilities) costs and benefits. A strong commitment by company management toward reducing waste refractory is required for successful recycling.37 Startup cost is the main reason companies are slow to recycle.38 A successful refractory recycling program includes several steps, of which sorting of the materials by type is the most critical. Upon sorting, there might be several sizing steps such as communication and final separation. In general, refractory waste minimization techniques currently include1 improved refractory materials that yield substantially longer vessel campaigns,2 zoning of refractory linings to yield consistent wear, and3 use of water-cooled panels in place of refractory materials.39 Refractory recycling from glass and steel furnaces has been presented as an economically and environmentally sound alternative to land filling. For instance, a method has been developed to recycle Cr-bearing refractories.40 The role of Cr2O3 in the corrosion resistance of Al2O3–Cr2O3 castables for waste-melting furnaces has also been discussed.41 B.3.2

Conclusion

Chrome-based refractories are being used in Portland cement rotary kilns, secondary steel refining furnaces and transfer ladles, specialty steel melting operations, foundry sands, glass manufacture (textile and fiberglass, throat areas of glass tanks), steel and glass reheat regenerators, Cu, nickel (Ni), and lead (Pb) smelters, utility boilers, coal gasification furnaces, and waste incinerators. Although alternative materials have been proposed to replace Cr-containing refractories, these substitutes do not always meet performance or cost requirements. What is the effect of Cr-based refractories on the environment? It is well agreed that soluble Cr(VI) is unwanted, however Cr-refractories continue to be produced by many countries throughout the world (Japan and China, for instance) and the U.S. The consensus is that if the refractories have been in contact at some moment with alkali materials then there is a strong

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possibility of Cr(VI) being formed. To sustain the already wide usage of Cr refractories in the steel, noniron, and glass industries further research (i.e., decision modeling,35 logistical and technological approaches9,10,39 needs to be conducted to either improve refractory compositions and/or treat the refractory wastes.

Bibliography 1. Klein, C. and Hurlbut, C.S., 1997, Manual of Mineralogy, 21st ed., John Wiley & Sons, Inc., pp. 389–390. 2. Kim, C., Kohler,A., Mulvaney, K., and Wagner, L., 1992, Chrome in Refractories, Ceramic Industry, 142(8), 57–61. 3. Technology of Monolithic Refractories (Plibrico Company), 1985, Toppan Printing Company, Japan, pp. 69. 4. ASTM Designation C-455-97: Standard Classification of Chrome Brick, Chrome–Magnesite Brick, Magnesite–Chrome Brick, and Magnesite Brick, Vol. 15.01, 1999, Annual Book of ASTM Standards. 5. ASTM Designation C-572: Methods for Chemical Analysis of Chrome-Containing Refractories and Chrome Ore, Vol. 3.06, 1999, Annual Book of ASTM Standards. 6. Mosser, J. and Karhut, G. 1999, Refractories at the Turn of the Century, in Proc. Unified International Technical Conference on Refractories (UNITECR 99), pp. XXV-XXX, Berlin, Germany. 7. Zong-Qi, G., Zeng-Fu, P., and Ning, C. 1996, Production and Properties of Cr 2O 3 Raw Material for Refractories, Industrial Ceramics, 16(3), 172–176. 8. Malarria, J.A., 1997, Degradation of Magnesite-Chrome Refractory Brick by Hydratation, Journal of the American Ceramic Society, 80(9), 2262–2268. 9. Schlesinger, M.E., Karakus, M., Crites, M.D., Somerville, M. A. and Sun, S. 1997. Chrome-Free Refractories for Copper Production Furnaces, in Proc. Unified International Technical Conference on Refractories (UNITECR 97), Vol. III, pp. 1703–1710, New Orleans, USA. 10. Crites, M.D., 1999, Chrome-Free Refractories for Copper Production, M. Sc. thesis, University of Missouri-Rolla, Ceramic Engineering Dept. 11. Semler, C.E., 1994, Overview of the U.S. Refractories Industry, Ceramic Industry, 144(2), 33–38. 12. Refractories Handbook, Chapter IV, Technical Association of Refractories of Japan, Tokyo, Japan, 1998. 13. Kondoh, K., Sakai, K., Ishino, T., and Abe, H., 1995, Mutual Interaction of the Development of Glass and Refractories Technology, in Proc. Unified International Technical Conference on Refractories (UNITECR 95), Vol. I, pp. 67–83, Kyoto, Japan. 14. McGarry, N., Monoroe, D.L., and Webber, R.A., 1991, New Thermal–shock resistant dense zircon and dense chromic oxide refractories, Ceramic Engineering and Science Proceedings, 12(3–4), 473–481. 15. Wang, Bu Qian, 1999, Chromium titanium carbide cermet cating for elevated temperature erosion protection in fluidized bed combustion boilers, Wear, 225(I), 502–509. 16. Encyclopedia of Inorganic Chemistry, Vol. 2, R.B. King, Ed., John Wiley & Sons, 1994.

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17. 2000 Materials Handbook, Ceramic Industry, 150(1), 67–69 (2000). 18. Kirk-Othmer Encyclopedia of Chemistry Technology, Chromium and Chromium Alloys, vol. 6, 4th Ed., John Wiley & Sons, 1993. 19. Lizumi, K., Kudaka, K., Maezawa, D., and Sasaki, T., 1999, Mechanochemical Synthesis of Chromium Borides, Nippon Seramikkusu Kyokai Gakujutsu Ronbunshi (Journal of the Ceramic Society of Japan), 107(1245), 491–493. 20. Katz, S.A. and Salem, H., 1994, The Biological and Environmental Chemistry of Chromium, VCH Publishers, New York. 21. International Agency for Research on Cancer (IARC), Monographs on the Evaluation of Carcinogenic Risks to Humans and their Supplements, Vol. 49 (Chromium Section), Last updated: 5 November 1997. http://193.51.164.11/htdocs/ monographs/Vol49/Chromium.html 22. Bray, D.J., 1985, Toxicity of chromium compounds formed in refractories, American Ceramic Society Bulletin, 64, 7, 1012–1016. 23. Marvin, C.G., 1993, Chrome-bearing hazardous waste, Am. Ceram. Soc. Bull., 72(6), 66–68. 24. Khoroshavin, L.B., Deryabin, V.A., Perepelitsyn, V.A., and Lapteva, T.N. 1993, Hexavalent Chromium in refractories, Ogneupory, No. 9, 7–10, Sept. 25. Lee, Y. and Nassaralla, C.L., 1997, Minimization of Hexavalent Chromium in Magnesite-Chrome Refractory, Met. & Mat. Trans. B —Process Metallurgy and Materials, Processing Science, 28(5), 855–859. 26. Obana, T., Tsuchinari, A., Shimizu, I., Nakamori, Y., Tokuchi, K., Ishihara, M., Sakakidani, K., and Shinagawa, H., 1999, Application of Chrome-Free Bricks to RH-Degasser Vessels, in Proc. Unified International Technical Conference on Refractories (UNITECR’99), pp. 269–271, Berlin, Germany. 27. Hiragushi, K., Mihashi, H., and Yamagushi, A., 1999, Hexavalent Chromium in used Magnesia Chrome Refractories and its Removal by Carbon Reduction, in Proc. Unified International Technical Conference on Refractories (UNITECR’99), pp. 257–262, Berlin, Germany. 28. Komatsu, H., Arai, M., and Ukawa, S. 1999, Current and Future Status of Chrome-Free Bricks for Rotary Cement Kilns, Taikabutsu Overseas (International Journal of the Technical Association of Refractories), 19, 4, 3–9. 29. Sheppard, L.M., 1999, Minimizing refractory waste, recycling and reusing refractory material, Ceram. Industry, 149(2), 39–46. 30. Deysarkar, S., Singh, M., Chaudhuri, J., Padhy, B.P., and Singh, D.K. 1999, A New Approach for the Design of Slag Resistant Mag-Chrome Bricks, in Proc. Unified International Technical Conference on Refractories (UNITECR’99), pp. 322–325, Berlin, Germany. 31. Bennett, J.P. and Maginnis, M.A., 1995, Recycling/disposal issue of refractories, Ceramic Engineering and Science Proceedings, 16(1), 127–141. 32. Bennett, J.P., Sikich, S.W., and Kwong, K.-S., 1995, Recycling and disposal of refractories, American Ceramic Society Bulletin, 74(12), 71–77. 33. Weber, R.A., 1995, Recycling at Corhart — A 30-year success story, Ceramic Engineering and Science Proceedings, 16(1), 214–219. 34. Kalpakli, Y., Gokmen, S., and Ozgen, S., 1999, Production of MagnesiteChromite Bricks by Regaining the Process Waste in the Basic Refractory Industry, in Proc. Unified International Technical Conference on the Refractories (UNITECR’99), pp. 73–75, Berlin Germany. 35. Nystrom, H.E. and Thompson, P.B., 1998, Refractory waste management financial decision model, Refractories Applications, 3(2), 5–6, June.

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36. Nystrom, H.E. and Kehr, W.R., 2000, Impediments to Refractory Recycling Decision-Making, to be published in Resources, Conservation and Recycling. 37. Bennett, J.P., Sikish, S.W., and Kwong, K.-S., 1997, Reusing spent refractory materials, Ceram. Industry, 147(11), 46–49. 38. Oxnard, R.T., 1997, The future of refractory materials recycling, Ceram. Industry, 147(2), 41–44. 39. Smith, J.D., Peaslee, K.D., Barnes, A.S., and Fang, H., 1997, An Economic, Logistic, and Technological Approach to Refractory Recycling, in the Proceedings Unified International Technical Conference on Refractories (UNITECR’97), Vol. II, p. 509–517, New Orleans. 40. Noga, J., 1994, Refractory recycling developments, Ceramic Engineering and Science Proceedings, 15(12), 73–77. 41. Miyaji, T., Sakamoto, S., and Kudo, E., 1999, The Role of Cr2O3 in Al2O3-Cr2O3 Castables for Waste Melting Furnace, Taikabutsu (Japanese Journal of the Technical Association of Refractories), 51(12), 656–657.

B.4 Health Effects of Occupational Exposures in Chrome Plating

Antero Aitio B.4.1

Introduction

Chromium (Cr) is an intriguing element. At low exposure concentrations, there are data that indicate that it is essential for health. At high exposure concentrations some forms of Cr are toxic, allergenic, and carcinogenic, while some forms of Cr seem to be practically innocuous. In the present review on the health effects of exposure to chromic acid (H2CrO4) mist in electroplating the main emphasis is on cancer findings, as this is an area where information which was rather limited has recently undergone a distinct improvement.22,25 B.4.1.1 Exposures Chromium plating is mainly done either to increase resistance to rust and corrosion or increase resistance to wear and tear (hard Cr plating) or for decoration and aesthetic reasons, in order to achieve a shiny surface (decorative Reprinted by permission: International Chromium Development Association 45 rue de Lisbonne, 75008 Paris, France. Tel: 33 01 40 76 06 89 Fax: 33 01 40 76 06 87  International Chromium Development Association (2001). http://www.chromium-asoc.com/publications/frame.html NOTE: Original publication has been updated by the Cr(VI) Hanbook editors.

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Cr plating). The surface thickness for the former is typically 10 µm to 1000 µm; for the latter, between 0.25 µm and 1.0 µm. Cr plating as an industry started in the 1920s, and several different applications have been developed. Although today techniques are available where Cr(III) is used, most of Cr plating is still done using H2CrO4. The main health concern is the H2CrO4 mist, which is formed when H2CrO4 is electrolyzed. The amount of H2CrO4 mist emission will depend on a number of process variables; particularly, the concentration of H2CrO4 in solution, the surface area of the articles treated, the current density, the length of time current is passed through the solution and the surface tension of the bath.6 In H2CrO4, Cr in Cr(VI) form is strongly irritating. B.4.1.2

Toxicology of Chromium with Different Oxidation States Chromium exists in several oxidation states, the most stable being Cr(III), Cr(VI), and elemental chromium (metal, Cr(0)). Cr in other oxidation states is apparently important mechanistically, but information on the toxicity of such compounds is practically nonexistent. B.4.1.2.1 Elemental Chromium (Cr(0)) and Chromium(III) The toxicity and fate of Cr in the body varies with its oxidation state. Cr(III) and elemental Cr seem relatively innocuous. Although several epidemiological studies have been carried out with the intention of uncovering even long-term effects owing to these forms of Cr, no study convincingly shows any health effects.5,15 Also, in experimental studies, notably on carcinogenicity in experimental animals as well on mutagenicity in vitro and in vivo systems, Cr(III) and Cr(0) are not active. B.4.1.2.2 Chromium(VI) Chromium(VI) is a potent sensitizer of the skin. It also induces sensitization of the respiratory tract (although the phenomenon is not very frequent), it induce mutations in vitro and in vivo and it causes cancer in experimental animals and in humans.4,5,8,10 Within the large group of Cr(VI) compounds, the physical–chemical characteristics show a wide variation. Notably, the water solubility of different Cr(VI) compounds and consequently their fate in the human body have distinct characteristics. Also, the carcinogenicity of different Cr(VI) compounds differ markedly. Strontium chromate (SrCrO4) is apparently more carcinogenic by far than any other Cr compound, and calcium chromate (CaCrO4) and zinc chromate (ZnCrO4) are also relatively potent. These chromates (CrO42–) are all relatively insoluble in water. Different lead chromates have been studied rather extensively and are apparently carcinogenic but with a low potency. Barium chromate (BaCrO4), which has not been equally

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well studied, shows no convincing evidence of carcinogenicity. Lead(II) chromate (PbCrO4) and BaCrO4 are practically insoluble in water. Of the readily water-soluble alkali chromates, evidence of carcinogenicity exists for chromium(VI) oxide (CrO3) and sodium dichromate (Na2Cr2O7). This evidence is limited, and the carcinogenic potency of these compounds in the experimental settings used is low. In epidemiological studies on cancer in humans, clearly and consistently elevated lung cancer risks have been observed in CrO42– production (exposure mainly to Cr(III) and water-soluble Cr(VI) compounds), in CrO42– pigment production (exposure mainly to water-soluble and water-insoluble chromates), and also in Cr plating using H2CrO4). B.4.1.3 Health Effects among Chromium Plating Workers B.4.1.3.1 Effects on Nasal Mucosa and Skin Exposure to H2CrO4 (like other Cr(VI) compounds) may induce nasal irritation, which in its extreme form may lead to nasal perforation.2,7,11,13,19 The information on exposure concentrations and durations that cause these different nasal problems is very scanty. Lindberg and Hedenstierna14 reported nasal irritation in Cr plating workers exposed to H2CrO4 mist at concentrations >1 µg/m3 and a high frequency of nasal perforations among workers exposed to peak H2CrO4 concentrations >20 µg/m3. Rather similar results were reported by Lin and co-workers.13 Scar formation was estimated to appear in the nasal septum at cumulative exposure of 0.4 mg/m3 to 1 mg/m3 months (i.e., exposure to, for example, 40 µg/m 3 to 100 µg/m3 for 10 months or 4 µg/m3 to 10 µg/m 3 for 100 months), while nasal septum perforations started to appear after an exposure of 1 mg/m 3 to 3 mg/m3 months. Although H2CrO4 is acutely irritating, it seems that the risk of nasal ulceration increases with the time of exposure.19 In the two British cohort studies,23,25 four cases of nasal cancer were reported among Cr plating workers. In one of the studies, where three cases were observed, this reached statistical significance. Because of these findings, and because of the known carcinogenicity of Cr(VI) compounds in general, possible precancerous lesions in the nasal mucosa have also been investigated among Cr plating workers. No increase in the frequency of micronuclei — as an indication of genotoxic action — was observed in exfoliated cells of the nose. In the same study, a positive finding was observed among workers exposed to ethylene oxide ((CH)2O).20 On the other hand, squamous cell metaplasia and cellular atypia were observed in cells brushed from the nasal mucosa.2 Chromic acid is irritating to the skin and induces skin ulceration, which may lead to "Cr holes" and scar formation.12,19,28 It has been proposed that H2CrO4 exposure leads to skin ulcers only when there is a pre-existing cut, abrasion, or other defect in the protective epidermis.28 Both sensitization and irritation may be behind a contact dermatitis in Cr plating workers. The latter mechanism seems to be involved more often.12

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B.4.1.3.2 Lung Cancer Suspicion of an increased risk of cancer among Cr plating workers was raised in a small study performed on decorative Cr plating workers in the United Kingdom (UK).27 Forty-nine lung cancer deaths were observed, while only 35 were expected. Based on studies published in the 1980s and earlier, the International Agency for Research on Cancer concluded in 1990 that there is sufficient evidence of carcinogenicity of Cr(VI) compounds as encountered in CrO42– production, CrO42– pigment production, and Cr plating industries. This conclusion was based mainly on five studies. The largest of these was a mortality analysis of the population investigated in the previously cited UK study.27 It reported23 a 1.5-fold mortality from lung cancer among chrome bath workers. No association was observed between lung cancer mortality and work with nickel (Ni) baths. In another study from the UK18, the mortality from lung cancer among Cr plating workers from Yorkshire was 1.4-fold in comparison to manual workers from other industries in the same geographic area. In a small Japanese study,16,26 an increased risk of lung cancer was observed among plating workers. When the cohort of plating workers was divided into Cr plating workers and other plating workers, the excess was larger among the Cr plating workers but did not reach statistical significance for either subgroup. In a study in the U.S., a doubling of lung cancer mortality was observed among workers in a die-casting facility that also performed Ni and Cr electroplating. However, the workers had also been exposed to Ni and polycyclic aromatic hydrocarbons (PAHs), both of which increase the risk of lung cancer.21 Finally, in a small cohort of Italian Cr plating workers, the risk of lung cancer was 3-fold over the expected and the lung cancer risk was only observed among hard Cr plating workers, whose exposure to H2CrO4 was higher than that of the decorative Cr plating workers.3 Two of the above studies have recently been updated, and form the most reliable basis for the assessment of the carcinogenicity of H2CrO4 mist in humans. They also give indications on the potency of this exposure in cancer induction.22,24,25 In the followup to the largest studied Cr plating workers cohort in England,22 the mortality experience of 2,689 men and women was investigated between the years 1946 and 1995. Altogether 69 lung cancer cases and 621 deaths from other causes were observed. In both women and men, lung cancer excess was observed among chromium bath workers but not among other chromiumexposed workers. The magnitude of the risk increased with the time of work at chrome baths, and was about 4-fold among those working longer than 5 years (relative risk, 3.88, 95% confidence interval (CI), 1.68 to 8.74). As in all studies on lung cancer, smoking is a potential confounding factor, especially since no information was available on the smoking habits of this cohort. However, the magnitude of the risk is such that it cannot be explained by smoking: risks greater than 1.5-fold cannot be attributed to smoking

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differences alone. In addition, the fact that the lung cancer risk was related to the duration of work at the chromium baths makes smoking a very unlikely factor for explaining the finding of increased cancer risk with chromate exposure. Another potential cause for the excess lung cancer could be exposure to Ni compounds, which have also been shown to cause lung and nasal cancer at exposure concentrations encountered in Ni refining.1,9 However, the mortality from lung cancer was not elevated for those plating workers in the studied factory, who had exposure to Ni but not to Cr.17 In a followup of the workers in 54 Cr plating plants in Yorkshire, UK,25 the lung cancer mortality between 1972 and 1997 was studied in reference to their working histories before 1972. For 85% of the members of this cohort, smoking habits were known; the results could thus be corrected for this potentially important confounding factor. However, the effect of smoking correction was very minor. The overall lung cancer risk among the chrome plating workers was 1.9-fold over the expected figures (SMR 185, 95% CI 141–238). B.4.1.3.3 Carcinogenic Potency of H2CrO4 Mist The information on how strong a carcinogen H2CrO4 mist is, is quite limited. Exposure has not generally been quantitatively assessed. Instead, surrogates such as time at work have been used. No laboratory animal studies are available where the exposure is qualitatively similar to Cr plating operations. Limited quantitative information on exposure to H2CrO4 was only available in the previously mentioned study carried out in a large Cr plating plant in England.22,24 Based on data collected by the company from the year 1973 onwards, the working concentrations of H2CrO4 mist exposure were "almost always less than 50 µg/m3 CrO3 (about 25 µg/m 3 Cr(VI))" and "earlier conditions were, in general, certainly worse." If it is assumed that all lung cancer risk in this cohort was owing to exposure to H2CrO4 mist, and that the working-time average exposure to Cr(VI) was 100 µg/m3, then it could be very roughly calculated that for 1,000 workers exposed to Cr(VI) for the duration of their working life to 50 µg/m 3 , there would be 310 excess lung cancer deaths. If, however, the true exposure to Cr(VI) in the studied cohort had been 1,000 µg/m3 (i.e., the exposures before 1973 had been very high indeed), the similarly calculated excess lung cancer number would be 40. Furthermore, on the assumption that, rather than all lung cancers being induced by H2CrO4, two-thirds of them were in fact induced by other factors such as smoking, the corresponding predicted number of lung cancer cases per 1,000 workers exposed to Cr(VI) for their working life to 50 µg/m3 would be 130 and 14.24 Thus, predicted cancer risk in the worst-case scenario is a catastrophe and even the lowest estimate means a significant increase in the lung cancer risk.

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B.4.1.3.4 Other Respiratory Diseases Some studies have reported an elevated occurrence of respiratory symptoms and of decreased pulmonary function among chrome plating workers.11,14,19 No clear-cut picture emerges from the mortality from nonmalignant respiratory diseases in the cohort studies (on lung cancer). Bronchial asthma is a rare disease after exposure to Cr(VI) compounds, and cases have been reported also among Cr plating workers.19 B.4.1.4 Prevention of Exposure and Control of Chromic Acid Mist The most effective prevention of exposure is replacement of Cr(VI) with Cr(III), which has been shown to be feasible in decorative Cr finishing. With tightening environmental and health requirements and improved technology, such substitution is now a very viable alternative. Safer Chromium Finishing (Metal Finishing Association, UK) provides further information.6 Where such a change to the process is not possible (i.e., leads to lower quality products) it is necessary to achieve adequate control of H2CrO4 mist by other means. With some operations the emission of H2CrO4 mist can be controlled by total enclosure of the process. Where this is not reasonably practicable, it is necessary to achieve adequate control by providing efficient exhaust ventilation and/or by treating the electrolyte (plating solution) with a mist suppressant to limit the emission of mist into the workplace atmosphere. Even when the process can be completely enclosed, extract ventilation should still be provided at the enclosure. The extraction should be sufficient to ensure that there is movement of air into the enclosure when any access points in the enclosure are opened for purposes of process control, thereby preventing emission of H2CrO4 mist into the workroom atmosphere. B.4.2

Conclusions

Workers in Cr electroplating where Cr(VI) as H2CrO4 is used are at risk of developing lung cancer. It is likely that there is also a low risk of nasal cancer. Chromium(VI) is genotoxic, and although it is not clear that this is the mechanism of carcinogenesis or the sole such mechanism, it is prudent to keep the exposure as low as is possible using best available technology. Exposure to H2CrO4 at concentrations that are in compliance with the prevailing occupational exposure standards for Cr(VI) in many countries, i.e. 50 µg/m3, are likely to carry a substantial, albeit unlikely, and epidemiologically detectable, lung cancer risk. Whether there is also a risk of other lung diseases is not clear. Exposure to H2CrO4 causes irritation, erosion, and ulceration of nasal mucosa. Serious irritation effects have been observed at an exposure concentration of approximately 10 µg/m3. Chromic acid exposure induces contact dermatitis and, especially when the skin has pre-existing mechanical trauma, chrome ulcer. In experimental

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animals H2CrO4 is a strong sensitizer, and Cr-induced respiratory and dermal sensitization has been infrequently reported among Cr plating workers. Where possible, Cr(III) rather than Cr(VI) should be used in electroplating. Where this is not technically viable, workers should be effectively protected against exposure, primarily using closed electroplating systems.

Bibliography 1. Anttila, A., Pukkala, E., Aitio, A., Rantanen, T., and Karjalainen, S., 1998, Update of cancer incidence among workers at a copper/nickel smelter and nickel refinery, Int. Arch. Occup. Environ. Health, 71:245–250. 2. Bolla, I., Gariboldi, L.M., Gabrielli, M., Baldo, D., Romanelli, A., Tuberti, E., and Magnani, F., 1990, Rinopatia da esposizione professionale a cromo nell'industria galvanica: aspetti citomorfologici, Med. Lav., 81:390–398. 3. Franchini, I., Magnani, F., and Mutti, A., 1983, Mortality experience among chromeplating workers, Scand. J. Work Environ. Health, 9:247–252. 4. Gibb, H.J., Lees, P.S., Pinsky, P.F., and Rooney, B.C., 2000, Clinical findings of irritation among chromium chemical production workers, Am. J. Ind. Med., 38(2):127–131. 5. Gibb, H.J., Lees, P.S., Pinsky, P.F., and Rooney, B.C., 2000, Lung cancer among workers in chromium chemical production, Am. J. Ind. Med., 38(2):115–126. 6. Safer Chromium Finishing, Metal Finishing Association, Birmingham, U.K. (1995). 7. Henning, F., 1972, Chromium plating, Ann. Occup. Hyg, 15:1993. 8. International Agency for Research on Cancer (IARC). Chromium and chromium compounds, In: IARC Monographs on the evaluation of carcinogenic risks to humans, Chromium, Nickel and Welding, Vol. 49, IARC, Lyon, France, 1990: 49–256. 9. International Agency for Research on Cancer (IARC), Nickel and nickel compounds, In: IARC Monographs on the evaluation of carcinogenic risks to humans, Chromium, Nickel and Welding. Vol. 49, IARC, Lyon, France, 1990:257–445. 10. International Programme on Chemical Safety (IPCS), Chromium, World Health Organization, Geneva, Switzerland, 1988 (Environmental Health Criteria; 61). 11. Kuo, H.-W., Lai, J.-S., and Lin, T.-I., 1997, Nasal septum lesions and lung function in workers exposed to chromic acid in electroplating factories, Int. Arch. Occup. Environ. Health, 70(4):272–276. 12. Lee, H.S. and Goh, C.L., 1988, Occupational dermatosis among chrome platers, Contact Dermatitis, 18(2):89–93. 13. Lin, S.C., Tai, C.C., Chan, C.C., and Wang, J.D., 1994, Nasal septum lesions caused by chromium exposure among chromium electroplating workers, Am. J. Ind. Med., 26(2):221–228. 14. Lindberg, E. and Hedenstierna, G., 1983, Chrome plating: symptoms, findings in the upper airways and effects on lung function, Arch. Environ. Health, 38:367–374. 15. Montanaro, F., Ceppi, M., Demers, P.A., Puntoni, R., and Bonassi, S., 1997, Mortality in a cohort of tannery workers, Occup. Environ. Med., 54(8):588–591. 16. Okubo, T. and Tsuchiya, K., 1979, Epidemiological study of chromium platers in Japan, BioI. Trace. Elem. Res., 1:35–44.

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17. Pang, D., Burges, D.C.L., and Sorahan, T., 1996, Mortality study of nickel platers with special reference to cancers of the stomach and lung, 1945–93. Occup. Environ. Med., 53(10):714–717. 18. Royle, H., Toxicity of chromic acid in the chromium plating industry, Environ. Res., 1975(a), 10:39–53. 19. Royle, H., Toxicity of chromic acid in the chromium plating industry, Environ. Res., 1975(b), 10:141–163. 20. Sarto, F., Tomanin, R., Giacomelli, L., Iannini, G., and Cupiraggi, A.R., 1990, The micronucleus assay in human exfoliated cells of the nose and mouth: application to occupational exposure to chromic acid and ethylene oxide, Mutat. Res., 244:345–351. 21. Silverstein, M., Mirer, F., Kotelchukj, D., Silverstein, B., and Bennett, M., 1981, Mortality among workers in a die-casting and electroplating plant, Scand. J. Work. Environ. Health, 7(Suppl. 4):156–165. 22. Sorahan, T., Burges, D.C., Hamilton, L., and Harrington, J.M., 1998, Lung cancer mortality in nickel/chromium platers, 1946–95. Occup. Environ. Med., 55(4): 236–242. 23. Sorahan, T., Burges, D.C.L., and Waterhouse, J.A.H., 1987, A mortality study of nickel/chromium platers, Br. J. Ind. Med., 44:250–258. 24. Sorahan, T., Hamilton, L., Gompertz, D., Levy, L.S., and Harrington, J.M., 1998, Quantitative assessments derived from occupational cancer epidemiology: a worked example, Ann. Occup. Hyg., 42:347–352. 25. Sorahan, T. and Harrington, J.M., 2000, Lung cancer in Yorkshire chrome platers, 1972–97., Occup. Environ. Med., 57(6):385–389 (http://oem.bmjjournals.com/ cgi/content/full/57/6/385; http://oem.bmjjournals.com/cgi/content/abstract/ 57/6/385). 26. Takahashi, K. and Okubo, T., 1990, A prospective cohort study of chromium plating workers in Japan, Arch. Environ. Health, 45:107–111. 27. Waterhouse, J.A.H., 1975, Cancer among chromium platers, Br. J. Cancer, 32:262. 28. Williams, N., 1997, Occupational skin ulceration in chrome platers, Occup. Med. Oxf, 47(5):309–310.

B.5 Chromium Recycling in the United States in 1998

John F. Papp ABSTRACT The purpose of this report is to illustrate the extent to which chromium was recycled in the United States in 1998 and to identify chromium-recycling trends. The major use of chromium was in the metallurgical industry to make stainless steel; substantially less chromium was used in the refractory and chemical industries. In this study, the only chromium recycling reported was that which was a part of stainless steel scrap reuse. In 1998, 20 percent of the U.S. apparent consumption of chromium was secondary (from recycling); the remaining 80 percent was based on net chromium commodity imports

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and stock adjustments. Chromite ore was not mined in the United States in 1998. In 1998, 75,300 metric tons (t) of chromium contained in old scrap was consumed in the United States; it was valued at $66.4 million. Old scrap generated contained 132,000 t of chromium. The old scrap recycling efficiency was 87 percent, and the recycling rate was 20 percent. About 18,000 t of chromium in old scrap was unrecovered. New scrap consumed contained 28,600 t of chromium, which yielded a new-to-old-scrap ratio of 28:72. U.S. chromium-bearing stainless steel scrap net exports were valued at $154 million and were estimated to have contained 41,000 t of chromium. B.5.1

Introduction

The chemical element chromium was discovered in 1797 by Nicolas-Louis Vauquelin, a professor of chemistry at the Paris École des Mines, which was one of the new European technical universities established to bring science education to the mining industry (Weeks and Leichester, 1968, p. 271–283). The mineral chromite, which consists primarily of chromium, aluminum, iron, magnesium, and oxygen, is a source of chromium. Chromite was first exploited for the production of pigments (Gray, 1988) and the manufacture of refractory materials. In the U.S. in 1998, the major use of chromium was in the metallurgical industry to make stainless steel; substantially less chromium was used in the refractory and chemical industries. The major chromium commodities are chromite ore, ferrochromium, and chromium chemicals, metal, and refractories. The major traded chromium commodity in the U.S. in 1998 was ferrochromium, which replaced chromite ore in 1983. Ferrochromium includes high-, medium-, and low-carbon ferrochromium; charge chrome is a type of high-carbon ferrochromium. Ferrochromium and ferrochromium silicon are chromium ferroalloys. More than half of the chromium consumed in the U.S. in 1998 was used in stainless steel; all grades of stainless steel contain appreciable amounts of chromium. To be used in stainless steel, chromite ore is first smelted into ferrochromium. Most ore is smelted near the chromite ore mine, but some is shipped to smelters near inexpensive electrical power sources or near stainless steel producers. Ferrochromium is mixed with iron to make stainless steel. The purpose of this report is to illustrate the extent to which chromium was recycled in the U.S. in 1998 (Figure B.5.1, Table B.5.1) and to identify chromiumrecycling trends. Most recycled chromium was part of stainless steel scrap, and smaller amounts were in superalloys. In this study, the only chromium recycling reported was that which was a part of stainless steel scrap reuse. For the purpose of computing chromium supply from trade, the traded chromium commodities include chromite ore, chromium ferroalloys and metal, and selected chromium chemicals and pigments. On the basis of trade statistics and stainless steel scrap receipts reported by U.S. stainless steel producers, 20% of the 1998 chromium apparent consumption was secondary (from recycling of stainless steel scrap); the remaining 80% was based on net

Old scrap unrecovered ....18.0

50.7 Old scrap exported ....50.7

18.0

Chromium products in reservoir, net change ...+355

619

Dissipative uses ....132

487 Chromium products to U.S. market ....619

73.0

Home scrap

Fabrication of stainless steel 522 products ....756

28.6

Net imports of semifabricated products ...126

New (prompt) scrap generated ....28.6

35.1

Exports

161 Imports

Exports of chromium materials: Chemicals ...................17.5 Ferroalloys ....................3.96 Metal .............................1.04 Total ........................22.5

FIGURE B.5.1 U.S. chromium materials flow in 1998. Values are in thousands of metric tons of contained chromium and have been rounded to three significant figures. In this study, the only chromium recycling reported was that which was a part of stainless steel scrap reuse.

28.6

75.3

75.3

9.69 Old scrap imported ...9.69

132

2.14 Old scrap Old scrap stock supply ...144 decrease ...2.14

132

Old scrap generated ........132

544

22.5

Distribution of Domestic Supply of Unwrought Primary and Secondary Chromium

620

New (prompt) scrap consumed ..................28.6

Old scrap consumed ..75.3

Home scrap

Domestic production 140 of chromium chemical, Government and industry ferrochromium, and ore stock changes ....62.4 62.4 refractory materials ...140

Net ore 77.7 imports ....77.7

Imports of chromium materials: Chemicals ...................9.07 263 Ferroalloys ..............245 Metal ...........................9.51 Total ....................263

Release of Government and industry stocks 37.2 of chromium ferroalloys and metal: Government ............35.5 Industry .....................1.76 Total ....................37.2

Domestic Supply of Unwrought Primary and Secondary Chromium

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Appendix B TABLE B.5.1 Salient Statistics for U.S. Chromium Scrap in 1998 (Values in Thousands of Metric Tons of Contained Chromium, Unless Otherwise Specified) Old scrap: Generated1 Consumed2 Value of old scrap consumed3 Recycling efficiency4 Supply5 Unrecovered6 New scrap consumed7 New-to-old-scrap ratio8 Recycling rate9 U.S. net exports of scrap10 Value of U.S. net exports of scrap11 1

2

3

4

5

6

7

8

9

132 75.3 $66.4 million 87% 144 18.0 28.6 28:72 20% 41.0 $154 million

Old scrap generated in 1998 is estimated to have been the chromium content of a fraction of the net stainless steel supply in 1968, as discussed in the text section "Old Scrap Generated." The chromium fraction of stainless steel is estimated at 0.170 (Papp, 1991, p. 20). The fraction of the 1968 supply reporting to old scrap in 1998 was 0.894. The net stainless steel supply was shipments plus imports minus exports of stainless steel mill products. Old scrap consumed is estimated to have been the chromium contained in stainless steel scrap receipts reported by consumers in 1998 less the sum of new scrap generated and scrap imports. Value is estimated to have been the annual average unit value of highcarbon ferrochromium in 1998 ($882/t of chromium or $497/t gross weight of high-carbon ferrochromium) applied to old scrap consumed. This value is used because stainless steel scrap and ferrochromium compete as sources of chromium for the production of stainless steel (Papp, 2000). Recycling efficiency is (old scrap consumed plus old scrap exported) divided by (old scrap generated plus old scrap imported plus any old scrap stock decrease or minus any old scrap stock increase). Old scrap supply is old scrap generated plus old scrap imported plus old scrap stock decrease. Old scrap unrecovered is old scrap supply minus old scrap consumed minus old scrap exported minus old scrap stock increase. New scrap (also called prompt industrial scrap) consumption is not reported. It is estimated to be the new scrap generated. See text for estimation procedure. New-to-old-scrap ratio is new scrap consumption compared with old scrap consumption, measured in weight and expressed in percentage of new plus old scrap consumption. Recycling rate is old plus new scrap consumed divided by apparent supply expressed as a percentage. Chromium apparent supply is primary domestic chromium production (from mining, which was nil for the U.S. in 1998) plus secondary domestic chromium production (from old plus new stainless steel scrap) plus imports minus exports plus adjustments for Government and industry stock changes. Old plus (Continued)

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10

11

new scrap consumed is estimated to be the chromium contained in stainless steel scrap receipts reported by Fenton (2000) and updated by Duane Johnson (U.S. Geological Survey, 2000, unpublished data). Chromium apparent supply used here is the same as that reported in the U.S. Geological Survey Mineral Commodity Summaries, where it is called apparent consumption (Papp, 1999). U.S. net exports of scrap are chromium contained in exports minus chromium contained in imports of stainless steel scrap. Value of U.S. net exports of scrap is the value of stainless steel scrap exports minus imports as reported by the U.S. Census Bureau on the basis of data collected by the U.S. Customs Service. Stainless steel scrap has value for reasons other than its chromium content.

chromium commodity imports and stock adjustments. Chromite ore was not mined in the U.S. in 1998 (Papp, 1999). On the basis of a different chromium material flow model, Gabler (1994, p. 18) estimated that in 1989, about 33% of chromium material potentially available for recycling was recycled and that the recycled material accounted for 23% of 1989 apparent consumption. Although the models differed for this study and Gabler’s, the percentages of apparent chromium consumption from recycling were similar for 1989 (23%) and 1998 (20%). In 1998, 75,300 metric tons (t) of chromium contained in old scrap was recycled in the U.S. it was valued at $66.4 million. Old scrap generated contained 132,000 t of chromium. The old scrap recycling efficiency was 87% percent, and the recycling rate was 20%. (See glossary for definitions.) About 18,000 t of chromium in old scrap was unrecovered. New scrap consumed contained 28,600 t of chromium, which yielded a new-to-old-scrap ratio of 28:72. The U.S. Census Bureau reported that U.S. chromium-bearing stainless steel scrap net exports were valued at $154 million in 1998 and were estimated to have contained 41,000 t of chromium. Trade data reported by the U.S. Census Bureau are based on data collected by the U.S. Customs Service. B.5.2

Sources of Chromium-Containing Scrap

Figure B.5.1 shows secondary chromium material supply, distribution, and recycling in the U.S. economy in 1998. Stainless steel scrap was the major source of recycled chromium and is the only type of scrap reported in Figure B.5.1. In the U.S. the average primary chromium supply distribution and usage trend in the metallurgical industry from 1983 through 1992, as measured by reported consumption, was stainless steel, 79% and increasing; alloy steel, 8% and decreasing; superalloys, 3% and increasing; and other uses, 10% (Papp, 1994, p. 68–70). Steel production classifications include alloy steel (except stainless), carbon steel, and stainless steel. U.S. steel production by these classes is, in descending

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order of magnitude of production as a percentage of total averaged from 1993 through 1998, carbon steel, 88.8%; alloy steel, 9.17%; and stainless steel, 2.06%. In 1998, U.S. carbon steel production was 88.0 million metric tons (88.0 Mt); alloy steel, 8.60 Mt; and stainless steel, 2.01 Mt. Relative to steel production, stainless steel production is small. In a world context, the U.S. accounted for 12.6% of world steel production and 15.2% of world stainless steel production on the basis of data from 1994 through 1998 (American Iron and Steel Institute, 1999; INCO Limited, 1999, p. 3). In 1998, U.S. stainless steel producers reported stainless steel scrap consumption of 1.04 Mt (Fenton, 2000, and updates by Duane Johnson, U.S. Geological Survey, 2000, unpublished data), or 51.8% of that year’s stainless steel production. Consumption consisted of receipts of new, old, and home scrap. The chromium fraction of stainless steel is estimated at 0.170 (Papp, 1991, p. 20). The 1.04 Mt of scrap was estimated to have contained about 177,000 t of chromium valued at $882/t and to have had a primary-chromium-material-equivalent value of $157 million. In 1998, reported receipts were 611,000 t of new and old stainless steel scrap, which were estimated to have contained 104,000 t of chromium. The difference between the chromium content of reported stainless steel scrap consumption and that of reported stainless steel scrap receipts was assumed to be equal to the chromium content of home scrap (73,000 t). Chromium is used in alloy, carbon, stainless, and tool steels; cast irons; chemicals; and superalloys. Chromite is used in refractories. The amount of chromium added to carbon and alloy steel is small, and chromium is included in only a few grades. Many grades of these alloys do not have any added chromium. As a result, when recycled, these alloys are not sought for their chromium content. Stainless and tool steels and superalloys are more valuable, contain greater amounts of chromium, and contain chromium more universally than do carbon or alloy steels. These materials are sought for recycling because of their high value, their high content of desirable elements (such as nickel, cobalt, molybdenum, and chromium), and their lack of undesirable, or tramp, elements. The carbon steel recycling rate is defined as carbon steel scrap consumption per carbon steel production on an annual basis. In the U.S. on average for 1994 through 1998, it exceeded the stainless steel recycling rate by about 15%. All grades of stainless steel contain chromium, whereas only a few grades of carbon steel contain chromium, and the quantities are small compared with those in stainless steel. Because of these circumstances, the amount of chromium contained in recycled carbon steel cannot be confidently estimated, and carbon steel recycling is not considered to contribute to chromium recycling in this study. In the U.S. on average for 1994 through 1998, alloy steel was recycled at less than one-sixth the rate of stainless steel. The alloy steel recycling rate was measured by comparing the ratio of alloy steel scrap consumption to alloy steel production with the ratio of stain-less steel scrap consumption to

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stainless steel production (AISI, 1995–99). The amount of alloy steel recycled was nearly 1 Mt in 1998. Only a few grades of alloy steel contain chromium, and the amounts are small compared with those in stainless steel. Because of these circumstances, the amount of chromium contained in recycled alloy steel cannot be confidently estimated, and alloy steel recycling is not considered to contribute to chromium recycling in this study. Although the production of superalloys is small compared to that of stainless steel, their high value makes recycling superalloys cost effective. Nevertheless, data were not available to estimate the contribution of superalloy recycling to chromium recycling in this study. B.5.2.1 Dissipated Materials Not Available for Recycling Dissipative uses do not result in new or old scrap generation in this model; they commonly involve dilution of the material or use in small volumes. Two broad categories of chromium products that are used dissipatively are chemicals and refractory materials; small amounts of chromium-containing steel can also be considered to be used dissipatively. For example, chromium is used in dyes and pigments that are subsequently incorporated in inks and paints. Because those inks and paints are used as thin coatings, the chromium becomes so diluted that recovery is uneconomic. Such materials leave the use cycle if incinerated or placed in a landfill. For the purpose of estimating the amount of dissipative use, chemical and refractory material production would be a good start except that such information is company confidential and, therefore, is not available for this calculation. Because imported chromite ore was used to make chromium chemicals, chromite-containing refractory materials, and chromium ferroalloys, net chromite ore imports can be used to estimate dissipative use. Inclusion of net trade in chromium chemicals and stock change of chromite ore to refine that estimate indicates that U.S. dissipative chromium use in 1998 was 132,000 t. Chromium ferroalloys are used to make the end-product iron and steel alloys discussed above. Some of that use is dissipative. The amount of chromite ore consumed in the U.S. in 1998 to make ferrochromium is the amount here-in assumed to have been used dissipatively in metallurgical applications. Although there is no quantitative information about dissipative use, the assumption seems reasonable. Because chromium ferroalloy and metal production data for 1998 were withheld, estimates made for 1997 are assumed to apply. Domestic ferrochromium production is estimated to have been reported domestic chromium ferroalloy and metal production less domestic chromium metal production. Chromium metal production in 1998 is estimated to have been 2,000 t, implying that 38,900 t of chromium contained in stainless steel was used dissipatively. That was 10.6% of chromium contained in the net stainless steel supply. The net stainless steel supply was material that entered the marketplace in products; it is calculated as stainless steel shipments plus net imports of

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stainless steel mill products. Applying this result to 1998 data indicates that 38,900 t of chromium contained in the 1998 net stain-less steel supply was used dissipatively in metallurgical applications, or about 11.4% of chromium contained in stainless steel production. Because chromium not used dissipatively becomes old scrap supply, the above assumption further implies that 88.6% of the net stainless steel supply in 1998 will become old scrap. B.5.2.2 Old Scrap Generated Old scrap generated was estimated to be the net stainless steel supply of 30 years before 1998 adjusted for trade and dissipative use. Stainless steel is used in virtually all industry sectors. Stainless steel is stronger, more durable, and more valuable than common grades of steel. The actual lifetime of stainless steel parts depends on the specific applications, but data are lacking on the distribution of stainless steel by end use, average product life by end use, and recovered fraction by product; therefore, old scrap generated was estimated on the basis of the past domestic net stainless steel supply. From 1994 through 1998, the U.S. was a net exporter of stainless steel. U.S. stainless steel ingot exports were in the range of 0.4% to 0.6% of domestic stainless steel production; semifinished stainless steel exports were 4% to 8% of that production. Stainless steel net exports in 1968 are assumed to have been balanced by stainless steel contained in net manufactured product imports. This leaves dissipative uses in 1968 to be accounted for. The same dissipative use pattern discussed above for 1997 is assumed to apply to 1968. Therefore, dissipative uses in 1968 were 10.6% of net stainless steel supply in 1968, leaving 89.4% of that supply potentially available for recycling. Thus, 89.4% of the 1968 net stainless steel supply is the input to old scrap generated in 1998. Stainless steel production in 1968 contained about 221,000 t of chromium. The net stainless steel supply (that is, stainless steel shipments plus imports minus exports) contained 148,000 t of chromium, of which 89.4% became the estimated amount of old scrap generated in 1998, 132,000 t of chromium. In mining terms, a "resource" is material available regardless of the economics of recovery, and a "reserve" is an economically recoverable resource — old scrap generated is a resource, and old scrap consumed is a reserve (U.S. Bureau of Mines and U.S. Geological Survey, 1980). This resource may or may not have been collected, sorted if collected, or traded if sorted. In effect, the scrap industry must undo what the wholesale and retail trade industries do —the wholesale and retail trade industries take goods concentrated at the point of production and distribute them to consumers, whereas the scrap industry takes distributed materials and concentrates them so that they can reenter the production process. Various factors affect material collection and recycling (Aylen and Albertson, 1995). The availability of obsolete stainless steel scrap is price sensitive. In other words, when the price of scrap goes up, so does the supply of obsolete stainless steel scrap. The reason for this is that scrap collectors and processors stock obsolete stainless steel scrap until it becomes profitable for

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them to handle, process, and ship that material. On the basis of the resource/ reserve analogy above, as price increases, resources become reserves. Old superalloy scrap is generated when parts made of superalloy material, such as jet engine parts, are replaced. Chemicals, such as plating and metal finishing baths, are processed to extend their useful life by removing contaminants. To the extent that this processing is recycling, it produces home scrap because such renewal is done within a plant. Refractory materials, such as chromite casting sand, are processed for reuse. To the extent that this processing is recycling, it produces home scrap because such reuse is done within a plant. Figure B.5.2 shows the supply of chromium by material to the U.S. economy and the use of that material by end-use market sector. Figure B.5.2A shows the distribution of chromite ore use by industry from 1978 to 1994; data are given individually for the chemical, metallurgical, and refractory industries from 1978 through 1985, but data are combined for the chemical and metallurgical industries from 1986 through 1994 to protect company proprietary data. After 1994, publication of chromite ore consumption by industry was discontinued to protect proprietary data. As shown in Figure B.5.2A, from 1978 through 1985, consumption of chromium from chromite ore by the chemical industry declined by 7%; consumption by the metallurgical industry dropped by half, to 65,200 t from 132,000 t; and consumption by the refractory industry decreased more than two-thirds, to 15,400 t from more than 53,800 t. Refractory industry consumption continued to drop until it reached less than 6,000 t in 1994, when reporting was discontinued. From 1979, a peak consumption year, to 1994, the chromium contained in the reported annual chromite ore consumption dropped to just more than 100,000 t from about 300,000 t. Chromite ore was being replaced by ferrochromium as the major source of chromium for the U.S. economy. Ferrochromium is used in the metallurgical industry, which is the major source and consumer of chromiumbearing scrap. Figure B.5.2B shows the relative importance of the two major commercial sources of chromium in the United States during the 20 years, 1978–1998. The figure shows that the dominant source of chromium for the U.S. economy shifted from chromite ore before 1981 to ferrochromium after 1983; for example, chromite ore supplied 61% of chromium contained in these imports in 1978, whereas ferrochromium supplied more than 67% of chromium in 1998. The major end use of chromium in the metallurgical industry is the manufacture of stainless steel. Figure B.5.2C shows the inferred distribution of chromium among major end-use market sectors, which are electrical and electronic equipment, fabricated metal products, industrial and commercial machinery, and transportation. Transportation and industrial and commercial machinery each accounted for more than 40% of the total; fabricated metal products and electrical and electronic equipment each accounted for under 10%.

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Appendix B 350 Contained Chromium, in Thousands of Metric Tons

A, U.S. consumption of chromite ore 300 250 200 150

Metallurgical

100 Chemical

Chemical and metallurgical

50 Refractory 0 1978 1980

1982

1984

1986

1988

1990

1992

1994

Year 700

B, Net U.S. imports for consumption

Contained Chromium, in Thousands of Metric Tons

600 500 400 300 Ferrochromium 200 100 Chromite ore 0 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998

Contained Stainless Steel, in Thousands of Metric Tons

Year 200 180 160 140

C, Inferred U.S. stainless steel consumption by market sector

Transportation

120 100 80 60 Industrial and commercial machinery 40 Electrical and electronic equipment Fabricated metal products 20 0 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 Year

FIGURE B.5.2 U.S. chromium source materials and consumption from 1978 through 1998. A, Reported U.S. consumption of chromite ore by the metallurgical, chemical, and refractory industries (data through 1994 only). B, Net U.S. imports for consumption by material. C, Inferred U.S. stainless steel consumption by market sector.

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Contained Chromium, in Thousands of Metric Tons

250 Stainless steel scrap 200 150

Consumption

100 Receipts

50 0 1978

1980

1982

1984

1986

1988

1990

1992

1994

1996

1998

Year FIGURE B.5.3 U.S. chromium recycling trend as indicated by reported consumption and receipts of stainless steel scrap from 1978 through 1998.

Figure B.5.3 shows reported consumption and receipts of stainless steel scrap from 1978 through 1998. Assuming that scrap receipts are new or old scrap, one may infer that scrap receipts shown in Figure B.5.3 came from the end-use manufacturing processes shown in Figure B.5.2C or from the products of those uses. If the difference between scrap receipts and scrap consumption in Figure B.5.3 is home scrap, then the source of that scrap is the primary metals industry market sector. The figure shows a trend of increasing importance of new and old scrap, as shown by the increasing amount of scrap receipts compared with scrap consumption, during the 20-year period. Scrap receipts accounted for less than 36.8% of consumption in 1978 compared with 58.7% in 1998. B.5.2.3 New Scrap New scrap results from steel fabrication processes. Stainless steel is either wrought or cast to make shapes, such as bars, plates, sheets, or strips, that are used to manufacture products. New scrap is valuable and is returned to the stainless steel producer through the supplier-purchaser channel or through scrap processors and dealers. New stainless steel scrap generation is proportional to stainless steel use. Reducing the amount of new scrap generated per unit of stainless steel production increases processing efficiency. The constancy of new scrap availability in the face of continued average production growth indicates that processing efficiency has increased coincident with and proportional to the growth in production. New scrap availability is not as price sensitive as old scrap availability because it is easier to collect, sort, and return new scrap; commonly, new scrap is returned under formal contract arrangements

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(Friedrich Terörde, ELG Haniel Group, U.S.A., 1997, written communication). New scrap may also be called prompt industrial scrap because it is generated when industry manufactures products that use stainless steel and is returned as it is generated; that is, promptly. Stainless steel production has been growing; from 1950 to 1996, the compounded annual growth for the major producing countries was 6.0% (INCO Limited, 1997, p. 6). Annual growth of stainless steel production for these countries from 1986 through 1996 ranged in magnitude from as little as 0.04% to more than 14%. For the secondary material flow model used in this report, new scrap generated was estimated on the basis of information from Austin van’t Wout (Capricorn BV, Holland, 1998, written communication) that 25% to 30% of scrap shipped by scrap suppliers to the stainless steel industry is new scrap. Thus, because scrap receipts were 58.7% of scrap consumption in 1998 and new scrap was 25% to 30% of scrap receipts (receipts by stainless steel producers being the same as shipments from scrap processors), new scrap was 14.7% to 17.6% of stainless steel scrap consumption, and the new-toold-scrap ratio was 28:72. In written communications in 1997, P.J. Probert (Hernic Ferrochrome, South Africa) and Josephine Ward (Reward Raw Materials, Inc., Carnegie, PA, U.S.A.) discussed secondary chromium consumption. Probert reported that stainless steel scrap typically provided 35% to 40% of the chromium required to produce stainless steel worldwide. For austenitic grades (those requiring nickel), scrap provided 45% to 50% of the required chromium units. Ward estimated the lifetime of stainless steel products to range from 15 to 20 years in the U.S. and stainless steel scrap to comprise 50% reclaimed (old scrap), 35% revert (home scrap), and 15% industrial (new scrap) in the U.S. This estimate suggests that 65% of scrap consumption is receipts. U.S. stainless steel receipts and consumption reported to the U.S. Geological Survey (USGS) indicate that receipts averaged 59% of stainless steel scrap consumption during 1994 through 1998. The new scrap percentage of net stainless steel scrap consumption inferred in this report from other sources is 16.2%. In a study of nickel that is more recent than the studies cited in the previous paragraph, Salamon (2000) reported the lifetime of stainless steel in buildings to be 70 years; industrial plants, 35 years; and consumer products, 5 to 25 years. Chemicals do not contribute to new scrap.

B.5.3

Disposition of Chromium-Containing Scrap

Scrap processors collect old and new scrap, segregate it by grade, and cut it to usable size. They commonly mix scrap to meet the chemical specifications of the stainless scrap consumers who use it as a feed material for their furnaces. The USGS monitors scrap consumption of the U.S. stainless steel industry. The industry reports scrap receipts and scrap consumption. Stainless steel scrap accounting procedures do not differentiate old from new scrap.

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In the model presented here, the difference between old scrap supply and old scrap consumed is taken as the sum of old scrap exported, old scrap going into stocks, and unrecovered old scrap. The rate of recovery of old scrap from the general economy by scrap dealers and processors is unknown. Old scrap generated is an estimated number. Old scrap consumed is estimated to be the difference between scrap receipts (a surveyed quantity) and new scrap consumed (an estimated quantity). Unrecovered old scrap is estimated by balancing old scrap supply inputs and outputs. In 1998, 1.04 Mt of stainless steel scrap was consumed to produce 2.01 Mt of stainless steel. In other words, the stainless steel industry consumed the equivalent of 51.8% of production in stainless steel scrap, an amount similar to the overall steel industry recycling performance of 58.4%, which is based on American Iron and Steel Institute (AISI) data averaged from 1994 through 1998 (AISI, 1999). Individual stainless steel producers reported scrap usage ranging from 0% to 80%. One company reported feed consisting of 20% in-house (home) scrap, 30% primary (previously unused) materials, and 50% secondary materials (new plus old scrap). By using reported stainless steel scrap receipts and consumption, secondary supply could be estimated as receipts, and in-house scrap could be estimated as consumption minus receipts; by using production to estimate feed, primary supply could be estimated as production minus scrap consumption. For the U.S. stainless steel industry, this process averaged from 1994 through 1998 yields the following stainless steel scrap types as percentages of stainless steel production: 22.2% in-house scrap; 46.1% primary materials, and 31.7% secondary materials. The U.S. Environmental Protection Agency (USEPA) reported the release and transfer of from 12,000 t to 42,000 t of chromium annually between 1987 and 1995 from the primary metals industry, which for chromium is the steel industry (Papp, 1994, p. 72; 1996; 1997, p. 182; 1998, p. 196). In 1991, industry started reporting recycling as part of transfers (USEPA, 1993, p. 6, 144, 162). As a result, transfers increased from about one-half of releases plus transfers to about three-fourths. One could conclude that in excess of one-half of the reported 40,000 t of transfers in 1991 were recycled. In the model used here, this material would be classified as either home or new (prompt) scrap. The above discussion of scrap disposition focuses on stainless steel scrap because it is accounted for separately from carbon steel, alloy steel, and superalloys. The chromium in stainless steel can reasonably be estimated, whereas the chromium in the other materials cannot, although brief discussions are provided above in the section, "Sources of Chromium-Containing Scrap." B.5.4

Old Scrap Recycling Efficiency

Old scrap recycling efficiency is defined as old scrap consumed plus old scrap exported as a percentage of old scrap generated plus old scrap

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imported plus old scrap stock released; it shows the relations among what is theoretically available for recycling, what is recovered, and what is not recovered. For U.S. chromium in 1998, old scrap recycling efficiency was 87%. As mentioned above in the section on "Old Scrap Generated," the availability of old stainless steel scrap is price sensitive. Therefore, the resource of old scrap is closely monitored and converted to commercial product when it is economically possible to do so. In an economic sense, old stainless steel scrap is being fully used consistent with the economic constraints placed upon its recycling by our economy.

B.5.5

Infrastructure of Chromium-Containing Scrap

Scrap collection takes different forms on the basis of the kind and quantity of scrap. For example, scrap generated in the manufacturing process (new scrap) has value because its composition, quality, and origin are known. One recycling expense is the cost of separating materials into usable groups. Manufacturers can avoid this cost by not mixing incompatible materials, then returning the material to the metal producer for reuse. Recycling obsolete products is more labor intensive than recycling new scrap because the products are a mixture of materials that need to be segregated. For some products, high-value materials are efficiently segregated from low-value ones. For example, automobile catalytic converters are housed in stainless steel cans. Because many automobiles are recycled, the cans are economically reclaimed and their material is reused. Although not all stainless steel in household products is recovered, much of the stainless steel in industrial products is. The stainless steel scrap industry includes suppliers of scrap to stainless steel producers and collectors of scrap who also sort material. Functions performed by these two groups—collecting, sorting, storing, and distributing—overlap. The scrap supplier takes on the responsibility for meeting the quality requirements of stainless steel producers. Scrap collectors are among their sources of scrap (Austin van’t Wout, 1998, written communication) The U.S. Harmonized Tariff System categorizes chromium metal import trade into waste and scrap and other; "other" includes wrought and unwrought chromium alloys. The system makes no such breakdown for chromium metal exports. Vastly more chromium is traded as part of stainless steel than is traded in chromium waste and scrap. In 1998, U.S. exports of chromium metal (including waste and scrap) were 1,038 t; in contrast, stainless steel scrap net exports (net exports are old scrap exported minus old scrap imported) of 241,000 t, gross mass, contained an estimated 41,000 t of chromium. Chromium contained in stainless steel scrap net exports was 23% of chromium contained in domestic stainless steel scrap consumption. Only stainless steel scrap is included in this report because it dominates the quantity of chromium recycled and because it is the material for which information is available.

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632 B.5.6

Chromium(VI) Handbook Processing of Scrap Metals

B.5.6.1 Smelting/Refining In the steel industry, smelting is the process of converting iron ore into iron. Chromium plays no role in this process. In the chromium industry, smelting is the process of converting chromite ore into ferrochromium. Steelmaking, in particular stainless steelmaking, is a refining process that involves combining iron and alloying elements to convert iron into steel. Steel is iron with carbon added. Chromium is one of the alloying elements added to iron to make stainless steel. The source of chromium could be ferrochromium or stainless steel scrap. Ferrochromium is the primary supply because it comes directly from mined materials, and stainless steel scrap is the secondary material because it is recycled material. Stainless steel scrap is mixed with ferrochromium and other feed materials, melted, and refined. Because primary and secondary materials are processed together in the stainless steelmaking process, secondary material metallurgical processing losses are the same as those of primary material. B.5.6.2 Fabrication Scrap generated in the fabrication industry may require processing before it is reusable. For example, only certain sized objects are permissible for materials handling and furnace feed. Large objects must be cut; small ones, agglomerated. Contaminants must be removed. Cutting operations require lubricants that may have to be cleaned off of the metal before it is reused. B.5.7

Outlook and Summary

Chromium is recycled as part of stainless steel recycling. Once it is reclaimed, stainless steel scrap is processed and sold to be used as a feed material in the stainless steel production process. The scrap is mixed with other feed materials, including primary materials, and is melted and refined. The U.S. stainless steel industry in 1998 produced stainless steel scrap in excess of its needs. With a chromium recycling rate of 20% and old scrap recycling efficiency of 87% as interpreted in this model, chromium recovery from obsolete material might be improved. Figures indicate that in 1998, 18,000 t of chromium could theoretically have been obtained from unrecovered old scrap. Although furnaces in industrialized countries (probably including the U.S.) produced stainless steel using as much as 80% scrap, the U.S. market did not absorb this additional material under 1997–1998 conditions of relatively strong demand. Price, of course, is a major inducement, and prices were relatively low in 1998. The 18,000 t is an estimate that could be off for several reasons—dissipative use could have been underestimated, old scrap supply could have been overestimated, or high-cost stocks may have built up in scrap yards.

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New scrap recycling efficiency is high relative to that of old scrap and likely cannot be improved significantly. Recycling of stainless steel in a wide variety of products, however, is the area where attention could be focused. Some believe that greater design for recycling would aid in this effort for a more sustainable environment. In 1998, the U.S. had net exports of stainless steel scrap containing 41,000 t of chromium that earned the U.S. $154 million. The U.S. stainless steel industry reported consuming 1.04 Mt of home, new, and old stainless steel scrap that was estimated to have contained about 177,000 t of chromium and to have had a primary-chromium-material-equivalent value of $157 million.

Bibliography American Iron and Steel Institute, 1968–99, Annual statistical report, American Iron and Steel Institute, Washington, DC. Aylen, J. and Albertson, K., 1995, Any old iron? The economics of scrap recycling, Manchester Statistical Society, Manchester, England, p. 14. Fenton, M.D., 2000, Iron and steel scrap: U.S. Geological Survey Minerals Yearbook 1998, 1, 40.1–40.19. (Also available online at http://minerals.usgs.gov/minerals/pubs/commodity/ iron_&_steel_scrap/360498.pdf.) Gabler, R.C., Jr., 1994, A chromium consumption and recycling flow model: U.S. Bureau of Mines Information Circular 9416, p. 40. Gray, Alan, 1988, Lead chrome pigments, in Properties and economics, Lewis, PA ed., Pigments Handbook, vol. 1, New York, Wiley-Interscience, p. 315–325. INCO Ltd., 1997, World stainless steel statistics (1997 ed.): Toronto, INCO Limited, p. 126. INCO Ltd., 1999, World stainless steel statistics (1999 ed.): Toronto, INCO Limited, p. 148. Papp, J.F., 1991, Chromium, nickel, and other alloying elements in U.S.-produced stainless and heat-resisting steel: U.S. Bureau of Mines Information Circular 9275, p. 41. Papp, J.F., 1994, Chromium life cycle study: U.S. Bureau of Mines Information Circular 9411, p. 94. Papp, J.F., 1996, Chromium: U.S. Bureau of Mines Minerals Year-book 1994, 1, 173–198. (Also available online at http://minerals.usgs.gov/minerals/pubs/ commodity/chromium/ 180494.pdf.) Papp, J.F., 1997, Chromium: U.S. Geological Survey Minerals Year-book 1995, 1, 169–195. (Also available online at http://minerals.usgs.gov/minerals/pubs/ commodity/chromium/ 180495.pdf.) Papp, J.F., 1998, Chromium: U.S. Geological Survey Minerals Year-book 1996, 1, 183–210. (Also available online at http://minerals.usgs.gov/minerals/pubs/ commodity/chromium/ 180496.pdf.) Papp, J.F., 1999, Chromium: U.S. Geological Survey Mineral Commodity Summaries 1999, p. 48–49. (Also available online at http://minerals.usgs.gov/minerals/ pubs/commodity/chromium/ 180399.pdf.)

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Papp, J.F., 2000, Chromium: U.S. Geological Survey Minerals Year-book 1998, 1, 17.1–17.32. (Also available online at http://minerals.usgs.gov/minerals/ pubs/commodity/chromium/ 180498.pdf.) Salamon, Mike, 2000, Nickel: Seminar on Billiton Nickel, London, March 24, 2000, Proceedings, CD-ROM. U.S. Bureau of Mines and U.S. Geological Survey, 1980, Principles of reserve/resource classification: U.S. Geological Survey Circular 831, p. 5. U.S. Environmental Protection Agency (USEPA), 1993, 1991 Toxics Release Inventory public data release: U.S. Environmental Protection Agency Report EPA 745–R–93–003, May, p. 364. Weeks, M.E. and Leichester, H.M., 1968, Discovery of the elements Easton, PA, Journal of Chemical Education, 7th ed., 896.

Glossary Apparent consumption. Primary domestic production plus secondary domestic production (old scrap) plus imports minus exports plus adjustments for Government and industry stock changes. For chromium, there is insufficient information about recycling to distinguish between new and old scrap consumption. Chromium apparent consumption is approximated by chromium apparent supply (see definition below) where new plus old scrap production is defined as stainless steel scrap receipts as reported in the U.S. Geological Survey’s Iron and Steel Scrap Survey (Fenton, 2000, and updates by Duane Johnson, 2000, unpublished data). Apparent supply. Apparent consumption calculated with secondary production equal to new plus old scrap; see apparent consumption. Dissipative use. A use in which a metal is dispersed or scattered, such as paints or fertilizer, making it exceptionally difficult and costly to recover the metal. Home scrap. Scrap generated as process scrap and consumed in the same plant where generated. New scrap. Scrap produced during the manufacture of metals and articles for both intermediate and ultimate consumption, including all defective finished or semifinished articles that must be reworked. Examples of new scrap are borings, castings, clippings, drosses, skims, and turnings. New scrap includes scrap generated at facilities that consume old scrap. Included as new scrap is prompt industrial scrap—scrap obtained from a facility separate from the recycling refiner, smelter, or processor. Excluded from new scrap is home scrap that is generated as process scrap and used in the same plant. New-to-old-scrap ratio. New scrap consumption compared with old scrap consumption, measured in mass and expressed in % of new plus old scrap consumed (e.g., 40:60).

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Appendix B

Old scrap. Scrap including (but not limited to) metal articles that have been discarded after serving a useful purpose. Typical examples of old scrap are electrical wiring, lead-acid batteries, silver from photographic materials, metals from shredded cars and appliances, used aluminum beverage cans, spent catalysts, and tool bits. This is also referred to as post-consumer scrap and may originate from industry or the general public. Expended or obsolete materials used dissipatively, such as paints and fertilizer, are not included. Old scrap generated. Metal content of products theoretically becoming obsolete in the U.S. in the year of consideration, excluding dissipative uses. Old scrap recycling efficiency. Amount of old scrap recovered and reused relative to the amount available to be recovered and reused. Defined as (consumption of old scrap (COS) plus exports of old scrap (OSE)) divided by (old scrap generated (OSG) plus imports of old scrap (OSI) plus a decrease in old scrap stocks (OSS) or minus an increase in old scrap stocks), measured in weight and expressed as a percentage: COS + OSE × 100 OSG + OSI decrease in OSS or − increase in OSS Old scrap supply. Old scrap generated plus old scrap imported plus old scrap stock decrease. Old scrap unrecovered. Old scrap supply minus old scrap consumed minus old scrap exported minus old scrap stock increase. Primary production. Chromium from ore. Because chromite ore was not mined in the U.S. in 1998, the primary domestic production term used in calculating apparent consumption is zero. Recycling. Reclamation of a metal in usable form from scrap or waste. This includes recovery as the refined metal or as alloys, mixtures, or compounds that are useful. Examples of reclamation are recovery of alloying metals (or other base metals) in steel, recovery of antimony in battery lead, recovery of copper in copper sulfate, and even the recovery of a metal where it is not desired but can be tolerated—such as tin from tinplate scrap that is incorporated in small quantities (and accepted) in some steels, only because the cost of removing it from tinplate scrap is too high and (or) tin stripping plants are too few. In all cases, what is consumed is the recoverable metal content of scrap. Recycling rate. Fraction of the metal apparent supply that is scrap on an annual basis. It is defined as (consumption of old scrap (COS) plus consumption of new scrap (CNS)) divided by apparent supply (AS), measured in weight and expressed as a percentage: COS + CNS × 100 AS

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Secondary production. Chromium from recycling of new plus old scrap. Superalloys. Alloys developed for high-temperature conditions where stresses (tensile, thermal, vibratory, and shock) are relatively high and where resistance to oxidation is required. Value. Unit value of primary metal applied to primary metal contained in scrap. For chromium, the primary metal is ferrochromium.

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Appendix C CONTENTS C.1 Chromium...................................................................................................638 John F. Papp C.1.1 Legislation and Government Programs ....................................639 C.1.2 Production ......................................................................................643 C.1.3 Health and Nutrition....................................................................644 C.1.3.1 Environment...................................................................644 C.1.3.2 Consumption..................................................................647 C.1.3.3 Stocks...............................................................................648 C.1.3.4 Prices ...............................................................................648 C.1.3.5 Foreign Trade .................................................................648 C.1.4 World Review ................................................................................649 C.1.4.1 Industry Structure.......................................................649 C.1.4.2 Capacity........................................................................649 C.1.4.3 Reserves........................................................................663 C.1.4.4 Production....................................................................665 C.1.4.5 European Union ..........................................................665 C.1.4.6 Australia .......................................................................666 C.1.4.7 Belgium.........................................................................666 C.1.4.8 Brazil .............................................................................666 C.1.4.9 Canada..........................................................................667 C.1.4.10 China.............................................................................667 C.1.4.11 Croatia...........................................................................668 C.1.4.12 Finland..........................................................................668 C.1.4.13 France............................................................................668 C.1.4.14 Germany.......................................................................668 C.1.4.15 India ..............................................................................668 C.1.4.16 Italy ...............................................................................669 C.1.4.17 Japan .............................................................................670 C.1.4.17 Kazakhstan...................................................................670 C.1.4.18 Norway.........................................................................670 C.1.4.19 Russia............................................................................670 C.1.4.20 South Africa .................................................................671 1-5667-0608-4/05/$0.00+$1.50 © 2005 by CRC Press LLC

637

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C.1.4.21 Sweden .........................................................................673 C.1.4.22 Turkey ...........................................................................673 C.1.4.23 United Kingdom .........................................................673 C.1.4.24 Zimbabwe ....................................................................673 C.1.5 Current Research and Technology .............................................673 C.1.5.1 Mineral Processing and Industrial Applications .....673 C.1.5.2 Technology .....................................................................674 C.1.5.3 Outlook ...........................................................................674 C.1.5.4 Chromite Ore .................................................................675 C.1.5.5 Chromium Chemicals...................................................675 C.1.5.6 Chromium Metal ...........................................................675 C.1.5.7 Ferrochromium ..............................................................676 C.1.5.8 Stainless Steel.................................................................676 Bibliography ...............................................................................................676 Internet Bibliography ................................................................................679 C.1.6 General Sources of Information..................................................680 C.1.6.1 U.S. Geological Survey Publications ...........................680 C.1.7 Other................................................................................................680 C.2 Chromium...................................................................................................681 C.2.1 Domestic Production and Use ....................................................681 C.2.2 Recycling.........................................................................................681 C.2.3 Import Sources (1999–2002).........................................................681 C.2.4 Depletion Allowance ....................................................................681 C.2.5 Government Stockpile ..................................................................681 C.2.6 Events, Trends, and Issues...........................................................684 C.2.7 World Mine Production, Reserves, and Reserve Base ............684 C.2.8 World Resources............................................................................684 C.2.9 Substitutes ......................................................................................685 C.3 Chromium Statistics ..................................................................................685 Thomas G. Goonan and John F. Papp

C.1 Chromium

John F. Papp* In 2002, the U.S. chromium supply (measured in contained chromium) was 139,000 metric tons (t) from recycled stainless steel scrap, 263,000 t from imports, and 705,000 t from Government and industry stocks. Supply distribution was 28,700 t to exports, 604,000 t to Government and industry stocks, and 483,000 t to apparent consumption. Chromium apparent consumption increased by 48.2% compared with that of 2001. * Domestic survey data and tables were prepared by Joseph M. Krisanda, statistical assistant, and the world production tables were prepared by Glenn J. Wallace, international data coordinator.

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639

The United States exported about 65,904 t, gross mass, of chromiumcontaining materials valued at about $67.6 million and imported about 512,512 t, gross mass, valued at about $256 million. Chromium has a wide range of uses in chemicals, metals, and refractory materials. Its use in iron, nonferrous alloys, and steel is for the purpose of enhancing hardenability or resistance to corrosion and oxidation; production of stainless steel and nonferrous alloys are two of its more important applications. Other applications are in alloy steel, catalysts, leather processing, pigments, plating of metals, refractories, and surface treatments. Chromium is an essential trace element for human health. Some chromium compounds, however, are acutely toxic, chronically toxic, and/or carcinogenic. The U.S. Environmental Protection Agency (USEPA) regulates chromium releases into the environment. The Occupational Safety and Health Administration (OSHA) regulates workplace exposure. Because the United States has no chromite ore reserves and a small reserve base, domestic supply has been a concern during every national military emergency since World War I. World chromite ore resources, mining capacity, and ferrochromium production capacity are concentrated in the Eastern Hemisphere. World chromite ore reserves are more than adequate to meet anticipated world demand. In recognition of the vulnerability of long supply routes during a military emergency, chromium was held in the National Defense Stockpile (NDS) in various forms, including chromite ore, chromium ferroalloys, and chromium metal. As a result of improved national security, stockpile goals have been reduced, and inventory is being sold. Material for recycling is the only domestic supply source of chromium. The U.S. Geological Survey (USGS) has conducted mineral-resource surveys of the United States to assess the potential for occurrences of chromium and other mineral resources. The National Aeronautics and Space Administration, the National Institute of Standards and Technology, the U.S. Department of Defense (DOD), and the U.S. Department of Energy conduct alternative materials research. C.1.1 Legislation and Government Programs The Defense National Stockpile Center (DNSC) disposed of chromium materials under its fiscal year (FY) 2002 (October 1, 2001, through September 30, 2002) Annual Materials Plan (AMP). The DNSC’s FY 2002 AMP (as revised in April) set maximum disposal goals for chromium materials at 136,000 t of chromium ferroalloys, 90,700 t of chemical-grade chromite ore (or remaining inventory), 90,700 t of metallurgical-grade chromite ore (or remaining inventory), 90,700 t of refractory-grade chromite ore, and 454 t of chromium metal. The Defense Logistics Agency (DLA) also developed its FY 2003 AMP, which set maximum disposal goals for chromium materials in FY 2003 the same as those of 2002, 136,000 t of chromium ferroalloys, 90,700 t of chemical-grade chromite ore (or remaining inventory), 90,700 t of metallurgical-grade chromite ore (or remaining inventory), 90,700 t of refractory-grade chromite

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ore, and 454 t of chromium metal. The DNSC reported the sale of 90,718 t of refractory-grade chromite ore, 13,518 t of high-carbon ferrochromium, 9,601 t of ferrochromium silicon, and 6,261 t of low-carbon ferrochromium in FY 2002 (Defense National Stockpile Center, 2002a, b; U.S. Department of Defense, 2002, p. 6, 9). The DNSC announced the sale of 90,700 t of refractory-grade chromite ore in January, exhausting the inventory; 10,900 t of low-carbon ferrochromium (6,260 t in February, 454 t and 1,814 t in August, 980 t in October, and 1,360 t in December); 6,940 t of ferrochromium silicon (3,080 t in February and 3,860 t in April); and 23,000 t of high-carbon ferrochromium (3,180 t and 9,072 t in August, 7,711 t in October, and 2,990 t in December) (Defense National Stockpile Center, 2002c–j). The USEPA announced in February that it reached a voluntary agreement with the treated-wood industry to discontinue the use of chromated copper arsenate (CCA) as a preservative treatment for wood that is to be used in a residential application (U.S. Environmental Protection Agency, 2002, 2002§*). The USEPA planned to ban such use in 2004 under the Federal Insecticide, Fungicide, and Rodenticide Act. The U.S. Department of Transportation reported the results of a study to estimate the economic impact of metallic corrosion to the U.S. economy and to identify national strategies to minimize that impact (Koch and others, 2002; U.S. Department of Transportation, Federal Highway Commission, 2002). Historical studies indicated that the cost of corrosion ranged from 1% to 5% of gross national product. The cost of corrosion to the United States in 1998 was estimated using two methods—by the cost of methods and services consumed as a result of corrosion and by the cost to industry sectors affected by corrosion. The direct cost of corrosion on the U.S. economy in 1998 was estimated to be $276 billion, or 3.1% of the gross domestic product in that year. The report recommended greater awareness of the problem. Increased emphasis on corrosion mitigation is likely to increase the use of stainless steel, a corrosion-resistant material. The U.S. Department of Labor regulates chromium in the workplace. The OSHA announced plans to go forward with proposed rulemaking on occupational exposure to chromium(VI) [Cr(VI)] based on a request in 1993 by the Oil, Chemical and Atomic Workers Union and Public Citizen Health Research Group petition to lower the exposure limit (U.S. Department of Labor Occupation Safety Health Administration, 2002). OSHA’s current permissible exposure limits (PELs) for chromic acid (H2CrO4) and chromates (CrO42−) are reported in table Z-2 (29 CFR §1910.1000), which specifies a ceiling limit of 100 µg/m3 of air for all forms of Cr(VI), measured as Cr(VI) and reported as chromium(VI) oxide (CrO3). The entry has remained unchanged since published in 1971. OSHA’s interpretation is that the PEL for Cr(VI) in general industry is a ceiling value of 100 µg/m3 of air, measured as Cr(VI) and reported as CrO3 , as it is published. In the construction *

References that include a section mark (§) are found in the Internet References Cited section.

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Appendix C TABLE C.1

Salient Chromium Statistics 1 (Metric tons of contained chromium unless otherwise specified) 1998 World production: Chromite ore, mine2 Ferrochromium, smelter3 Stainless steel4 U.S. supply: Components of U.S. supply: Domestic mines Secondary Imports: Chromite ore Chromium chemicals Chromium ferroalloys Chromium metal Stocks, January 1: Government Industry6

1999

4,120,000 2,710,000 2,790,000

r

r

4,300,000 2,850,000 2,970,000

2000 r

4,430,000 3,260,000 3,260,000

2001 r

r

2002

3,670,000 2,670,000 3,160,000

r

r

4,060,000 2,760,000 3,340,000

— 104,000

— 118,000

— 139,000

— 122,000

— 139,000

117,000 9,070 249,000 9,520

85,000 10,400 371,000 9,030

86,200 12,500 344,000 9,930

62,000 12,800 156,000 8,190

35,300 17,400 203,000 7,430

1,020,000 64,000

928,000 59,700

909,000 14,500

825,000 15,600

705,000 16,700

Total Distribution of U.S. supply: Exports: Chromite ore Chromium chemicals Chromium ferroalloys and metal Stocks, December 31: Government Industry6

1,570,000

1,580,000

1,520,000

1,200,000

1,120,000

39,900 17,500 5,000

37,200 17,300 5,790

44,600 16,400 25,400

20,000 13,200 9,840

928,000 59,700

909,000 54,500

825,000 15,600

816,000 16,700

Total Production, reported:7 Chromium ferroalloy and metal net production: Gross mass Chromium content Net shipments Consumption: Apparent Reported: Chromite ore and concentrates, gross mass Chromite ore percentage average Cr2O3 Chromium ferroalloys, gross mass8 Chromium ferroalloys, contained chromium8 Chromium metal, gross mass Stocks, December 31, gross mass: Government: Chromite ore Chromium ferroalloys Chromium metal Industry, producer9 Industry, consumer: Chromite ore10 Chromium ferroalloys11 Chromium metal Prices, average annual: Chromite ore, dollars per gross mass12 metric ton

1,050,000

1,020,000

927,000

875,000

W W W

W W W

W W W

W W W

524,000

558,000

589,000

326,000

269,000

W

W

W

45.4

45.0

44.8

45.0

345,000

398,000

384,000

195,000

220,000

215,000

4,670

4,690

4,980

5,880

885,000 974,000 7,720 W

820,000 973,000 7,720 W

636,000 919,000 7,550 W

636,000 906,000 7,430 W

159,000 17,300 195

130,000 24,900 245

W 26,400 191

W W 210

W 7,760 219

$68

$63

NA

NA

NA

r

r

r

e e e

5

7,360 10,500 10,800 604,000 8,340 641,000

W W W r

483,000 W 45.4

329,000

r

379,000

189,000

r

220,000 4,910

e, 5 e, 5 e, 5

204,000 763,000 7,220 W

5 5 5

(Continued)

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TABLE C.1 Salient Chromium Statistics 1 (Metric tons of contained chromium unless otherwise specified) (continued) 1998 Ferrochromium, dollars per chromium content13 pound Standard chromium do. metal, gross mass14 Vacuum chromium do. metal, gross mass14 Electrolytic chromium do. metal, gross mass15 Aluminothermic chromium metal, gross mass16 do. Value of trade:17 Exports thousands Imports do. Net exports18 do. Stainless steel, gross mass: Production19 Shipments20 Exports Imports Scrap: Receipts Consumption Exports Imports Value of trade: Exports thousands Imports do. Scrap exports do. Scrap imports do. Net exports18, 21 do.

1999

2000

2001

2002

$0.467

$0.366

$0.414

$0.324

$0.317

$4.73

$4.43

$4.43

$4.24

NA

$5.38

$5.38

$5.42

$5.43

NA

$4.50

$4.50

$4.50

$4.50

$4.50

$2.91

$2.50

$2.35

$2.08

$2.08

$102,000 $421,000

$92,500 $420,000

$110,000 $427,000

$89,400 $239,000

$67,600 $256,000

–$319,000

–$327,000

–$317,000

–$149,000

–$188,000

2,010,000 1,850,000 206,000 862,000

2,190,000 1,890,000 216,000 941,000

2,190,000 1,930,000 264,000 989,000

1,820,000 1,670,000 249,000 761,000

2,190,000 1,720,000 273,000 752,000

610,000 1,040,000 298,000 57,200

694,000 1,140,000 260,000 66,100

817,000 1,220,000 468,000 56,200

720,000 1,080,000 438,000 42,300

815,000 1,190,000 342,000 81,000

$622,000 $1,680,000 $176,000 $21,600

$628,000 $1,560,000 $151,000 $27,700

$782,000 $2,010,000 $310,000 $35,500

$752,000 $1,430,000 $270,000 $24,100

$742,000 $1,350,000 $252,000 $49,400

–$903,000

–$811,000

–$955,000

–$433,000

–$405,000

Estimated. rRevised. NA Not available. W Withheld to avoid disclosing company proprietary data. — Zero. Data are rounded to no more than three significant digits; may not add to totals shown. 2 Calculated assuming chromite ore to average 44% Cr O , which is 68.42% chromium. 2 3 3 Calculated assuming chromium content of ferrochromium to average 57%. 4 Calculated assuming chromium content of stainless steel to average 17%. 5 In September 2001, the Defense National Stockpile Center discontinued the accounting systems used to generate stocks by commodity reported in this table. Estimated stocks for 2001 and reported stocks before 2001 used the previous accounting systems. Reported stocks for 2002 used the current accounting systems. 6 Includes consumer stocks of chromium ferroalloys and metal and other chromium-containing materials. Also includes chromium chemical and refractory producer stocks of chromite ore before 2000. 7 Includes chromium ferroalloys and metal and other chromium materials in the United States. 8 Chromium ferroalloy and other chromium-containing materials excluding chromium metal. 9 Chromium ferroalloy and metal producer stocks of chromium ferroalloys and metal. 10 Chemical, chromium ferroalloy and metal, and refractory producer stocks of chromite ore. 11 Consumer stocks of chromium ferroalloys and metal and other chromium-containing materials. 12 Time-weighted average price of South African chromite ore, as reported in Platts Metals Week. 13 Time-weighted average price of imported high-carbon chromium that contains 50% to 55% chromium, as reported in Platts Metals Week. 14 Time-weighted average price of electrolytic chromium metal, as reported in American Metal Market, before 2002. 15 Time-weighted average price of domestically produced electrolytic chromium metal as reported by Ryan’s Notes. 16 Time-weighted average price of imported aluminothermic chromium metal as reported by Ryan’s Notes. 17 Includes chromite ore and chromium ferroalloys, metal, and chemicals. 18 Data indicate that imports are greater than exports. 19 Data on stainless steel production from American Iron and Steel Institute annual reports and quarterly production of stainless and heat-resisting raw steel. 20 Data on stainless steel shipments from American Iron and Steel Institute annual reports. 21 Includes stainless steel and stainless steel scrap. e

1

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Appendix C TABLE C.2 Principal U.S. Producers of Chromium Products in 2002, by Industry Industry and Company Metallurgical: Eramet Marietta Inc. JMC (USA) Inc. Refractory, National Refractories and Minerals Corp. Chemical: Elementis Chromium LP Occidental Chemical Corp.

URL Address

Plant

NA http://www.jmcusa.com http://www.nrmc.com

Marietta, OH. Research Triangle Park, NC Columbiana, OH

http://www.elementis.com http://www.oxychem.com

Corpus Christi, TX Castle Hayne, NC

NA: Not available.

industry, the PEL is also 100 µg/m3 as an 8-hour, time-weighted-average (29 CFR 1915.1000)

C.1.2 Production The major marketplace chromium materials are chromite ore and chromium chemicals, ferroalloys, and metal. In 2002, the United States produced chromium ferroalloys, metal, and chemicals, but no chromite ore. The United States is a major world producer of chromium metal and chemicals and of stainless steel. Chromite-containing refractory production decreased, and consolidation of the U.S. refractory industry in general continued. Domestic data for chromium materials are developed by the USGS by means of the monthly "Chromite Ores and Chromium Products" and "Consolidated Consumers" consumer surveys. North American Stainless (NAS) added a melt shop to its production facilities at Ghent, OH. NAS reported a stainless steel production capacity of 800,000 metric tons per year (t/year). With the addition of this melt shop, NAS joined AK-Steel, Allegheny Technologies, and J&L Specialty Steel as a major U.S. stainless steel producer (Platts Metals Week, 2002b). The NAS expansion was carried out against a background of consolidation in the steel industry (Platts Metals Week, 2002c). Stainless steel production accounts for about 2% of U.S. steel production. The rationalization of the U.S. chromium chemical industry has been completed. Since 1967, when five chromium chemical plants owned by four companies consumed chromite ore to produce sodium dichromate (Na2Cr2O7) in the United States, the number of such U.S. chromium chemical plants has been declining, while chromium chemical production has been slowly increasing. In 1986, the two currently producing chromium chemical plants became the last two such plants in the United States. Elementis Chromium LP (a subsidiary of Elementis plc of the United Kingdom) and Occidental Chemicals Corp. (OxyChem) (a subsidiary of Occidental Petroleum Company), operators of the two sodium-dichromate-producing plants in the

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United States, made an agreement whereby Elementis acquired OxyChem’s chromium chemical plant at Castle Haynes, NC, where Elementis continued to produce sodium dichromate and chromic acid. Elementis was to eliminate its production of those chromium chemicals at its Corpus Christi, TX, plant, leaving the Corpus Christi plant to produce downstream chromium chemical products. The Castle Haynes plant would then be left as the only sodiumdichromate-producing chemical plant in the United States (Elementis plc, 2002a,b).

C.1.3 Health and Nutrition Huvinen (2002) described the occupational exposure to chromium and its long-term health effects in stainless steel production. Workers involved in chromite ore mine, ferrochromium, and stainless steel production environments were studied. While production workers were exposed to chromium, the observed health effects were minimal. The author concluded that it is technically and economically possible to achieve low exposure levels in the stainless steel production chain with no adverse health effects.

C.1.3.1

Environment

James (2002) discussed the mobility and bioavailability of chromium in soils and natural waters. He found that the chromium(III) [Cr(III)] is less mobile, soluble, and toxic than Cr(VI). Cr(III) solubility is low and is dependent on pH. Soil contaminated with Cr(VI) can be cleaned up by converting the Cr(VI) to Cr(III). The conversion can be done using microorganisms or by manipulating the chemical environment. The oxidation state of chromium in natural waters and soils [Cr(III) and Cr(VI)] and the interconversion between the two are important factors in understanding the mobility, toxicity, bioavailability, and remediation of environments enriched with chromium-containing wastes. Chromium is a micronutrient that improves the efficiency of insulin in individuals with impaired glucose tolerance. The Institute of Medicine (IOM) reported on the dietary reference intake (DRI) values for chromium based on the diets of healthy Americans and Canadians. DRI values comprise recommended daily allowance (RDA), adequate intake (AI), tolerable upper intake level (UL), and estimated average requirement. Life stage and gender affect the DRI. The IOM found that there were inadequate data to set an RDA; however, they could set an AI based on the average unit chromium content of balanced diets and balanced diet intakes as reported by the Third National Health and Nutrition Examination Survey, 1988–1994. Data for chromium are not sufficient to develop a UL, the highest level of intake that is likely to pose no risk, suggesting the need for caution in consuming amounts greater than recommended intakes. Chromium chemical speciation (chromium in its various oxidation states and/or chemical form) and the route of exposure are important factors in chromium toxicity.

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Appendix C TABLE C.3 U.S. Reported Consumption and Stocks of Chromium Products

1

(Metric tons)

2001 Gross Mass Consumption by end use: Alloy uses: Iron alloys: Steel: Carbon steel High-strength low-alloy steel Stainless and heat-resisting steel Full alloy steel Electrical steel Tool steel Superalloys Other alloys2 Other uses not reported above Total Consumption by material: Low-carbon ferrochromium High-carbon ferrochromium Ferrochromium silicon Chromium metal Chromite ore Chromium-aluminum alloy Other chromium materials Total Consumer stocks: Low-carbon and high-carbon ferrochromium Ferrochromium silicon Chromium metal Chromite ore Chromium-aluminum alloy Other chromium materials Total

Chromium Content

9,980 12,700 255,000 17,200 W 5,640 10,400 21,100 W

r

335,000

r

35,600 253,000 38,200 5,880 1,020 682 612 335,000

2002

r

r

r

r r

r

5,910 7,790 146,000 10,300 W 3,390 8,130 12,000 W

r

195,000

r

23,600 151,000 14,000 5,880 332 383 252 195,000

r

r

r

r r

r

Gross Mass

Chromium Content

9,520 6,510 312,000 17,000 W 5,040 8,570 22,400 W

5,530 3,890 181,000 10,200 W 3,010 6,720 12,800 W

384,000

225,000

36,800 293,000 47,100 4,910 1,530 689 472

24,700 176,000 18,300 4,880 474 435 213

384,000

225,000

12,500

7,630

26,400

15,800

1,340 210 66 72 123

491 210 22 40 51

r

982 219 72 65 103

382 218 22 41 46

16,700

r

13,900

8,340

28,200

r

Revised. W Withheld to avoid disclosing company proprietary data; included in "Total." Data are rounded to no more than three significant digits; may not add to totals shown. 2 Includes cast irons, welding and alloy hard-facing rods and materials, wear- and corrosionresistant alloys, and aluminum, copper, magnetic, nickel, and other alloys. r

1

Inhaled, Cr(VI) is carcinogenic. Chromium in food appears universally as Cr(III) and is nontoxic (Institute of Medicine, 2001, p. 36, 197–223). Chromium is found in stainless steel welding fumes. The amount depends on the welding method and materials used. Cunat (2002) found that most arc welding processes create a fume containing predominantly Cr(III) and

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TABLE C.4 U.S. Government Stockpile Yearend Inventories and Change for ChromiumContaining Materials 1, 2 (Metric tons, gross mass) Material Chromite ore: Chemical Metallurgical Refractory Chromium ferroalloys: Ferrochromium-silicon High-carbon ferrochromium Low-carbon ferrochromium Chromium metal

January 1

2002 December 31

Change Quantity Percentage3

192,000 62,000 202,000

78,300 — 126,000

–114,000 –62,000 –75,800

–59 –100 –38

6,970 561,000 243,000 7,220

— 531,000 232,000 7,220

–6,970 –30,200 –11,500 —

–100 –5 –5 —

– Zero. 1 Data are rounded to no more than three significant digits. 2 In September 2001, the Defense National Stockpile Center discontinued the accounting systems used to generate stocks by commodity reported in this table. An alternate accounting system was adopted to report stocks by commodity. These Government stocks are reported by the Defense National Stockpile Center in Inventory of Stockpile Materials R-1, which reports uncommitted inventory. Uncommitted inventory is that inventory for which there is no sales contract. Committed inventory is that inventory for which there is a sales contract; however, the material has not yet been shipped. For chromium materials, the R-1 report includes chromium materials that (1) meet specifications and are held in excess of goal and (2) do not meet specifications and are held in excess of goal. The R-1 report excludes chromium materials that are committed and awaiting shipment. 3 Quantity change as a percentage of stocks on January 1, 2002. Source: Defense Logistics Agency, Defense National Stockpile Center.

Cr(VI) present in only small proportions; however, some arc welding processes did not generate significant amounts of chromium-containing fume. For those arc-welding processes for which chromium containing fume is generated, efficient fume extraction is possible. Antony and others (2001) investigated the recovery of chromium as sodium chromate (Na2CrO4) from chromite ore processing residue (COPR), a material that results from the production of sodium chromate by the roasting of soda ash (sodium carbonate, Na2CO3) with chromite ore. Typical chromium recovery by this process is 85%, leaving 15% in the residue. The authors investigated the kinetics of extracting chromium from COPR using the soda-ash roasting process under oxidizing conditions. They also examined the dissolution of Cr(III) from COPR through an acidic aqueous phase. They obtained a maximum recovery of chromium from COPR of 83%. Based on the demonstrated effectiveness of using iron to convert Cr(VI) to Cr(III), Singh and Singh (2001) employed ironcontaining industrial waste materials to treat Cr(VI)-containing waste materials. Singh and Singh found that sludge from the effluent treatment plant of a steel-tube-making plant and red mud discharged after reclamation of bauxite ore in the aluminum

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Appendix C TABLE C.5 Time-Value Relations for Imports of Chromite Ore, Ferrochromium, and Chromium Metal 1, 2 (Annual average value, dollars per metric ton) 2001 Material Chromite ore: Not more than 40% chromic oxide More than 40%, but less than 46% chromic oxide 46% or more chromic oxide Average3 Ferrochromium: Not more than 3% carbon: Not more than 0.5% carbon More than 0.5%, but not more than 3% carbon Average More than 3%, but not more than 4% carbon More than 4% carbon 3

Grand average3 Chromium metal

Contained Chromium 1,910

2002 Gross Mass

Contained Chromium

471

Gross Mass

833

195

232 182

67 58

431 r 176

132 58

187

61

191

60

2,180

1,490

1,550

1,030

993

622

950

586

2,050

1,390

1,410

921

1,500 579

1,020 335

(4) 546

(4) 326

709 —

415 6,170

646 —

390 5,770

r

Revised. — Not applicable. Based on customs value of chromium contained in imported material. 2 Data are rounded to no more than three significant digits; may not add to totals shown. 3 Mass-weighted average. 4 No imports of medium-carbon (more than 3%, but not more than 4% carbon) ferrochromium were reported in 2002. Source: U.S. Census Bureau. r

1

industry were effective at converting Cr(VI) to Cr(III) as measured by the toxicity characteristic leaching procedure (TCLP).

C.1.3.2

Consumption

The domestic chemical and refractory industries consumed chromite ore and concentrate in 2002. Chromium has a wide range of uses in the chemical, metallurgical, and refractory industries. The chemical industry consumed chromite for the manufacture of sodium dichromate, chromic acid, and other chromium chemicals and pigments. Sodium dichromate is the material from which a wide range of chromium chemicals is made. Chromite-containing refractory bricks were used to line metallurgical furnaces. Chromite sand was used as refractory sand in the casting industry. Ferrochromium was consumed to make chromium metal and special grades of ferrochromium. In the metallurgical industry, the principal use of chromium was in production of

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TABLE C.6 Price Quotations for Chromium Materials at Beginning and End of 2002 Material Cents per pound of chromium: High-carbon ferrochromium, imported:2 50% to 55% chromium 60% to 65% chromium Low-carbon ferrochromium, imported:2 0.05% carbon 0.10% carbon Cents per pound of product: Chromium metal, domestic: Electrolytic, standard3 Electrolytic, vacuum3 Electrolytic4 Chromium metal, imported: Aluminothermic4

January

December

Year average1

28.25–29.00 27.00–29.00

34.00–36.00 33.50–36.00

31.68 31.88

61–66 58–62

71–76 62–65

73 65

380–400 520–565 450

NA NA 450

NA NA 450

200–210

195–205

208

NA Not available. 1 Time-weighted average. 2 Platts Metals Week. 3 American Metal Market. 4 Ryan’s Notes.

stainless steel. Other important uses for chromium include the production of ferrous and nonferrous alloys. C.1.3.3 Stocks Consumer stocks of ferroalloys, metal, and other chromium materials contained 8,335 t of chromium at yearend 2002. At the 2002 annual rate of chromium consumption, these consumer stocks represented a 6-day supply of chromium. The DOD managed the National Defense Stockpile through the DLA. Government inventories declined because the DLA disposed of stocks. C.1.3.4 Prices Chromium materials are not openly traded. Purchase contracts are confidential information between buyer and seller; however, trade journals report composite prices based on interviews with buyers and sellers, and traders declare the value of materials they import or export. Thus, industry publications and U.S. trade statistics are sources of chromium material prices and values, respectively. C.1.3.5 Foreign Trade Chromium material exports from and imports to the United States included chromite ore and chromium chemicals, ferroalloys, metal, and pigments. In 2002, the value of foreign trade of these chromium materials was $68 million

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649

for exports and $226 million for imports. Compared with that of 2001, the value of exports dropped by 24%, while that of imports dropped by 7%. Compared with that of 2001, the gross mass of exports dropped by 40%, while that of imports dropped by 1.5%. C.1.4 World Review C.1.4.1 Industry Structure The chromium industry comprises chromite ore, chromium chemicals and metal, ferrochromium, stainless steel, and chromite refractory producers. Several trends are taking place simultaneously in the chromium industry. Chromite chemical production has been growing slowly, while the industry eliminates excess capacity, concentrating on production and growth in the surviving plants. Chromite refractory use has been declining; however, foundry use has been growing slowly. Chromite ore production is moving from independent producers to vertically integrated producers. In other words, chromite ore mines tend now to be owned and operated by ferrochromium or chromium chemical producers. This trend is associated with the migration of ferrochromium production capacity from stainless-steel-producing countries to chromite-ore-producing countries. While ferrochromium production capacity was rationalized in historically producing countries, which usually have been stainless-steel-producing countries, new furnaces or plants were constructed in chromite-ore-producing areas. The electrical power and production capacities of submerged-arc electric furnaces used to produce ferrochromium have been increasing. Production process improvements, such as agglomeration of chromite ore, preheating and prereduction of furnace feed, and closed furnace technology, have been retrofitted at major producer plants and are being incorporated into newly constructed plants. When ferrochromium plants started to be built, furnaces rated in the low kilovolt-ampere range were common. Furnaces built recently have an electrical capacity in the tens of megavoltamperes (MVA). Since the introduction of post-melting refining processes in the steel industry after 1960, there has been a shift in production from low-carbon ferrochromium to high-carbon ferrochromium. After years of ferrochromium production, slag stockpiles have built up. Recently developed processes efficiently recover ferrochromium from that slag. These processes have been or are being installed at plant sites. In South Africa, the major chromite-ore- and ferrochromium-producing country, two trends are emerging—ferrochromium plants are being developed in the western belt of the Bushveld Complex and ferrochromium production processes are being designed to accommodate chromite ore byproduct from platinum operations.

C.1.4.2 Capacity Rated capacity is defined as the maximum quantity of product that can be produced in a period of time at a normally sustainable long-term operating

Chromium metal waste and scrap, gross mass

Chromium metal other than unwrought powders and waste and scrap, gross mass Total chromium metal, gross mass

8112.22.0000

8112.29.0000

7202.49.0000

7202.41.0000

7202.41.0000

8112.21.0000

7,880,000

3,380,000

6,160

—

6,260

2,070,000

8,710,000

13,500,000

745,000

10,700

1,040,000 8,390,000

467,000

30,200

247,000

—

24,300,000

—

—

—

10,700

$6,680

—

—

—

1,040,000

61,000,000

2,640

—

7,140

7,450

4,490

449

2,510

—

$4,070

Value (thousands)

2002 Quantity (kilograms)

Canada (54%); Mexico (23%); Netherlands (11%); Belgium (3%); United Kingdom (3%); China (2%); Sweden (2%)

Switzerland (67%); Canada (20%); Mexico (11%); Brazil (2%)

Canada (54%); Japan (21%); Belgium (7%); Germany (7%); China (2%); Mexico (2%); Netherlands (1%); United Kingdom (1%) Austria (30%); Canada (26%); Japan (20%); Germany (14%); China (6%); Liechtenstein (2%); India (1%); Republic of Korea (1%) Japan (75%); Netherlands (15%); Peru (3%); Mexico (2%); Germany (1%); Singapore (1%)

Sweden (74%); Mexico (14%); Canada (11%)

Principal Destinations, 2002

650

Chromium ferroalloys: High-carbon ferrochromium, gross mass3 High-carbon ferrochromium, contained mass3 Low-carbon ferrochromium, gross mass4

Chromite ore and concentrate, gross mass Metal and alloys: Chromium metal including waste and scrap, gross mass Unwrought chromium powders, gross mass

2610.00.0000

8112.20.0000

Type

HTS2

Value (thousands)

2001 Quantity (kilograms)

U.S. Exports of Chr omium Materials, by T ype 1

TABLE C.7

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Chromium(VI) Handbook

Other

Chromium sulfates

Salts of oxometallic or peroxometallic acids: Zinc and lead chromate

2819.10.0000

2819.90.0000

2833.23.0000

2841.20.0000

Low-carbon ferrochromium, contained mass4 Ferrochromium-silicon, gross mass Ferrochromium-silicon, contained mass

Total ferroalloys: Gross mass Contained mass Chemicals, gross mass: Chromium oxides: Chromium(VI) oxide (CrO3)

7202.50.0000

7202.50.0000

7202.49.0000

158,000

13,100

416

200

10,300

26,600

10,700,000

2,730,000

12,500 —

—

92

—

16,400,000 8,800,000

26,600

85,500

5,400,000

125,000

93,400

2,410,000

8,380,000

15,900,000 10,100,000

97,000

281,000

1,250,000

389

365

7,660

15,700

10,100 —

—

290

Canada (79%); Taiwan (15%); Germany (2%); Mexico (2%) (Continued)

Canada (34%); Mexico (11%); Republic of Korea (8%); Brazil (6%); Taiwan (6%); Australia (5%); Germany (5%); New Zealand (5%); Japan (4%); Hong Kong (3%); China (2%); Indonesia (2%); Malaysia (2%); Thailand (2%); Singapore (1%) Canada (51%); United Kingdom (10%); Spain (8%); Japan (6%); Taiwan (6%); China (4%); Australia (3%); Republic of Korea (2%); Philippines (2%); Thailand (2%); Germany (1%); Singapore (1%) Canada (87%); Chile (6%); United Kingdom (3%); Colombia (2%); Hong Kong (1%)

Canada (89%); Hong Kong (5%); Germany (3%); Mexico (3%)

—

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Appendix C 651

Potassium dichromate Other chromates and dichromates; peroxochromates: Potassium dichromate

2841.40.0000 2841.50.0000

Pigments and preparations, gross mass

3206.20.0000

—

3,710

771,000

—

44 1,650

16,600

—

—

18,600 562,000

16,300,000

Value (thousands)

824,000

516,000

25,800

— —

12,600,000

7,650

1,750

46

— —

12,400

Value (thousands)

2002 Quantity (kilograms)

Republic of Korea (51%); Malaysia (15%); China (8%); Canada (7%); Mexico (4%); Netherlands (4%); Costa Rica (3%); Venezuela (3%); Saudi Arabia (2%) Canada (52%); Mexico (30%); China (2%); Switzerland (2%); Taiwan (2%); United Arab Emirates (2%); Singapore (1%)

Hong Kong (63%); Canada (32%); Finland (4%); Netherlands (1%)

Canada (41%); Thailand (22%); Mexico (15%); Peru (5%); Colombia (3%); Taiwan (3%); Hong Kong (2%); Republic of Korea (2%); Phillipines (2%); Brazil (1%)

Source: U.S. Census Bureau.

Principal Destinations, 2002

652

— Not applicable. 1 Data are rounded to no more than three significant digits; may not add to totals shown. Revised as of March 3, 2004. 2 Harmonized Tariff Schedule of the United States of America code. 3 More than 4% carbon. 4 Not more than 4% carbon.

2841.50.9000

Other chromates and dichromates; peroxochromates—Continued: Other

2841.50.0000

2841.50.1000

Sodium dichromate

Type

2841.30.0000

HTS2

Quantity (kilograms)

2001

U.S. Exports of Chr omium Materials, by T ype 1 (continued)

TABLE C.7

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Chromium(VI) Handbook

38 — 981 63 1,080

2002: Canada Germany Philippines South Africa Total 13 — 335 22 370

575 — — 575

Cr2O3 content (metric tons)

15 — 180 16 211

$751 — — 751

Value3 (thousands)

— — — 10,600 10,600

— 105r — 105r

Gross mass (metric tons)

— — — 4,470 4,470

— 47r — 47r

Cr2O3 content (metric tons)

— — — 710 710

— $14r — 14r

Value3 (thousands)

More than 40%, but less than 46% Cr2O3 (HTS2 2610.00.0040)

— 18 — 100,000 100,000

87 187,00r 306 187,000r

Gross mass (metric tons)

— 9 — 46,700 46,700

45 89,700r 168 89,900r

Cr2O3 content (metric tons)

— 5 — 5,800 5,810

$52 10,700r 70 10,800r

Value3 (thousands)

46% or more Cr2O3 (HTS2 2610.00.0060)

38 18 981 111,000 112,000

1,680 187,000 306 189,000

Gross mass (metric tons)

13 9 335 51,200 51,600

620 89,800 168 90,600

Cr2O3 content (metric tons)

Total

15 5 180 6,530 6,730

$803 10,700 70 11,600

Value3 (thousands)

Source: U.S. Census Bureau.

1

r

Revised. — Zero. Data are rounded to no more than three significant digits; may not add to totals shown. 2 Harmonized Tariff Schedule of the United States code. 3 Customs import value generally represents a value in the foreign country and therefore excludes U.S. import duties, freight, insurance, and other charges incurred in bringing the merchandise into the United States.

1,600 — — 1,600

2001: Canada South Africa Turkey Total

Country

Gross mass (metric tons)

Not more than 40% chromium(III) oxide (Cr2O3) (HTS2 2610.00.0020)

U.S. Imports for Consumption of Chr omite Or e, by Country 1

TABLE C.8

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Appendix C 653

11,800

—

—

—

17,200

72 —

28 —

25,700

40 5,100 919

38 —

$45 13 25 4 14,200 5,350

12 3 14 2 5,090 1,600 — 12 4,450 582

20 4 20 3 7,240 2,520 — 19 6,440 933

2,290

—

76 —

— — — — — — 500 — — 1,720

1,440

—

55 —

— — — — — — 345 — — 1,040

1,430

—

152 —

— — — — — — $275 — — 1,000

Value (thousands)

20

—

— —

— — — — — — — — 20 —

13

—

— —

— — — — — — — — 13 —

Chromium content (metric (metric tons) tons)

mass

Gross

20

—

— —

— — — — — — — — $20 —

Value (thousands)

More than 3% carbon, but not more than 4% carbon (HTS2 7202.49.1000)

236,000

37,200

38 20

— — 103 — — 20 61,400 — 20 138,000

(metric tons)

mass

Gross

137,000

22,400

28 14

— — 68 — — 14 42,100 — 14 72,100

Chromium content (metric tons)

79,200

14,900

78 20

— — $78 — — 42 21,100 — 12 42,900

Value (thousands)

More than 4% carbon (HTS2 7202.41.0000)

256,000

37,200

152 20

20 4 123 3 7,240 2,540 61,900 19 6,480 140,000

(metric tons)

mass

Gross

150,000

22,400

110 14

12 3 81 2 5,090 1,620 42,500 12 4,480 73,700

Chromium content (metric tons)

Total (all grades)

106,000

14,900

302 20

$45 13 103 4 14,200 5,390 21,400 40 5,140 44,900

Value (thousands)

654

Total

2001: Brazil Canada China France Germany Japan Kazakhstan Mexico Russia South Africa Sweden United Kingdom Zimbabwe

Country

mass

Chromium content (metric (metric tons) tons)

Gross

mass Value (thousands)

Gross

Chromium content (metric (metric tons) tons)

More than 0.5% carbon, but not more than 3% carbon (HTS2 7202.49.5010)

Not more than 0.5% carbon (HTS2 7202.49.5090)

U.S. Imports for Consumption of Ferr ochromium, by Country 1

TABLE C.9

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Chromium(VI) Handbook

25,600

India Japan Kazakhstan Russia Sout Africa Turkey Venezuela Zimbabwe

Total 17,000

65 3 2,920 — 726 1,820 8,420 2,820 189 — — 26,200

138 5 7,710 — 2,160 1,950 11,600 2,410 289 — — 8,040

— — — — — 1,960 991 5,090 — — — 4,960

— — — — — 1,360 695 2,900 — — — 4,710

— — — — — 1,370 884 2,450 — — — —

— — — — — — — — — — —

Source: U.S. Census Bureau. —Zero. 1 Data are rounded to no more than three significant digits; may not add to totals shown. 2 Harmonized Tariff Schedule of the United States code.

France Germany

98 4 4,180 — 1,040 2,600 12,300 5,040 261 — —

2002: China

—

— — — — — — — — — — — —

— — — — — — — — — — — 283,000

82 — 6,120 89 — 109,000 2,710 132,000 6,000 20 25,800 169,000

54 — 4,260 57 — 75,500 1,870 68,100 3,570 14 15,500 92,300

94 — 2,850 46 — 39,900 2,450 36,600 1,840 12 8,540 316,000

180 4 10,300 89 1,040 114,000 16,100 143,000 6,260 20 25,800 191,000

119 3 7,180 57 726 78,700 11,000 73,800 3,760 14 15,500

123,000

232 5 10,600 46 2,160 43,200 14,900 41,400 2,130 12 8,540

L1608_Appendix-C Page 655 Monday, November 8, 2004 9:31 AM

Appendix C 655

2819.90.0000

2819.10.0000

Other

Other than waste and scrap, gross mass Total Ferrochromium-silicon, gross mass Ferrochromium-silicon, contained mass Chemicals, gross mass: Chromium oxides and hydroxides: Chromium(VI) oxide (CrO3)

Metals and alloys: Chromium metal: Waste and scrap, gross mass Other than waste and scrap, gross mass Unwrought chromium powders, gross mass Waste and scrap, gross mass

Type

50,100 5,910

8,190,000 14,600,000

2,820,000

10,500,000

10,500

17,200

—

—

—

6,110,000

—

—

$154 49,900

—

—

41,000 r 8,150,000

Value (thousands)

r

2,860,000

16,500,000

12,000,000

7,430,000 28,900,000

6,570,000

83,300

776,000

— —

Quantity (kilograms)

2002

9,640

24,500

—

42,800 11,800

36,800

1,270

$4,820

— —

Value (thousands)

Turkey (42%); Kazakhstan (41%); China (5%); United Kingdom (4%); Italy (3%); South Africa (3%); Russia (2%) China (33%); Japan (26%); Germany (23%); United Kingdom (9%); Belgium (2%); Colombia (2%); Spain (2%); Hong Kong (1%); Poland (1%); Russia (1%)

Kazakhstan (98%); Zimbabwe (2%)

United Kingdom (48%); Russia (20%); Japan (16%); China (13%); Netherlands (2%) Russia (34%); Japan (27%); Germany (24%); Netherlands (10%); Republic of Korea (5%) Russia (28%); China (23%); France (24%); United Kingdom (18%); Kazakhstan (6%)

Principal Sources, 2002

656

7202.50.0000

7202.50.0000

8112.29.0000

8112.22.0000

8112.21.1000

8112.20.3000 8112.20.6000

HTS2

Quantity (kilograms)

2001

U.S. Imports for Consumption of Chr omium Materials, by T ype1

TABLE C.10

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Chromium(VI) Handbook

267,000

5,870,000

Other

Chromium carbide (Cr3C2)

Pigments and preparations based on chromium, gross mass: Chrome yellow

Molybdenum orange

Zinc yellow Other

2849.90.2000

3206.20.0010

3206.20.0020

3206.20.0030 3206.20.0050 98 4,100

5,050

16,300

2,900

—

—

7,760 322 291

224

151

— 1,220,000

1,300,000

6,610,000

261,000

241,000

189,000

18,800,000 — —

135,000

75,900

— 3,420

5,330

14,900

2,760

555

322

9,470 — —

395

90

France (57%); China (20%); Germany (10%); Italy (8%); Japan (2%); South Africa (1%)

Canada (59%); Republic of Korea (14%); Hungary (10%); Mexico (9%); China (4%); Colombia (3%); Germany (1%); Japan (1%) Canada (88%); Colombia (4%); United Kingdom (3%); Mexico (2%); Hungary (1%); Japan (1%)

United Kingdom (46%); Russia (42%); Kazakhstan (11%); India (1%) Republic of Korea (68%); Austria (8%); Italy (8%); Mexico (8%); United Kingdom (8%) Russia (43%); Japan (19%); Germany (14%); United Kingdom (12%); Canada (8%); France (4%)

Norway (39%); Republic of Korea (29%); Japan (24%); Colombia (8%) United Kingdom (99%); South Africa (1%)

United Kingdom (91%); Brazil (9%).

Appendix C

1

r

Revised. — Not applicable. — Zero. Data are rounded to no more than three significant digits; may not add to totals shown. Revised as of March 3, 2004. 2 Harmonized Tariff Schedule of the United States code.

Source: U.S. Census Bureau.

128,000 1,390,000

1,120,000

—

—

2841.50.9000

2841.50.1000

14,800,000 152,000 110,000

111,000

155,000

Sodium dichromate Potassium dichromate Other chromates and dichromates; peroxochromates: Potassium dichromate

Sulfates of chromium Salts of oxometallic or peroxometallic acids: Chromates of lead and zinc

2841.30.0000 2841.40.0000 2841.50.0000

2841.20.0000

2833.23.0000

L1608_Appendix-C Page 657 Monday, November 8, 2004 9:31 AM

657

Albkrom (Government owned) Consolidated Minerals Limited Pilbara Chromite Pty. Ltd. Cia. de Ferro Ligas da Bahia S.A. Mineracão Vila Nova Ltda. Magnesita S.A. Huazang Smelter Shashen Xizang Kangjinla Tibet Minerals Development Co., Ltd. Luobosa Mine Xinjiang Karamay Gold Mine Xinjiang Nonferrous Metals Industry Co. Outokumpu Oy Outokumpu Steel Oy Outokumpu Chrome Oy Ferro Alloys Corporation Ltd. Indian Metals and Ferro Alloys Ltd. Indian Charge Chrome Ltd. Misrilall Mines Ltd. Mysore Mineral Ltd. The Orissa Mining Corporation Ltd. The Tata Iron and Steel Co. Ltd. PT. Palabim Mining-PT. Bituminusa Faryab Mining Co. Donskoy Ore Dressing Complex Kraomita Malagasy Oman Chromite Company SAOG Benguet Corporation

Company

Sudan

South Africa—Continued

Country1

Company Bayer AG (Germany) Bayer (Pty.) Ltd. Rustenburg Chrome BHP-Billiton Plc. and Angol America Plc Samancor Lannex (Pty.) Ltd. Eastern Chrome Mines Steelpoort section Doornbasch section Montrose section Tweenfontein section Western Chrome Mines Millsell section Elandsdrift section Mooinooi section Elandskraal section Hernic Ferrochrome (Pty.) Ltd. Hernic Ferrochrome National Manganese Mines (Pty.) Ltd. Buffelsfontein Mine S.A. Chrome & Alloys Ltd. Horizon Mine Xstrata A.G. (United Kingdom) Xstrata S.A. Mining Division Kroondal section Thorncliffe section Vereeniging Refractories (Pty.) Ltd. Marico Chrome Corp. Ltd. Advanced Mining Works Co. Ltd.

658

Indonesia Iran Kazakhstan Madagascar Oman Philippines

India

Finland

China

Brazil

Albania Australia

Country1

TABLE C.11 Principal World Chromite Or e Producers, 2002

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Chromium(VI) Handbook

1

Zimbabwe

United Arab Emirates

Turkey

Other chromite-producing countries included Burma, Cuba, Pakistan, and Vietnam.

Russia South Africa

Heritage Resources & Mining Corporation. Krominco Inc. Velore Mining Corporation. Saranov Complex. Angovaal Ltd. Assmang Ltd. Dwarsrivier Chrome Assore Ltd. African Mining & Trust Co. Ltd. Rustenburg Minerals Development Co. (Pty.) Ltd. ASA Metals (Pty.) Ltd. Dilokong Chrome Bilfer Madencilik A.S. (Bilfer Mining Inc.) Dedeman Madencilik Sanayi ve Ticaret A.S. Eti Elektrometalurji A.S. General Management Hayri Ögelman Mining Co. Ltd. Türk Maadin Sirketi A.S. Derkek Raphael & Co. Derwent Mining Ltd. Maranatha Ferrochrome (Pvt.) Ltd. Amble Mining Co. Zimasco (Pvt.) Ltd. Zimbabwe Alloys Ltd.

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Appendix C 659

Company Darfo Albania Acesita S.A. Cia. de Ferro Ligas da Bahia S.A. Dandong Ferroalloy Plant Emei Ferroalloy (Group) Co. Ltd. Gansu Huazang Metallurgical Group Co. Ltd. Hanzhong Ferroalloy Works (Government owned) Hengshang Iron & Steel Hunan Ferroalloy (Government owned) Hunan Lengshuijiang Electrochemical Works Jiangyin Ferroalloy Factory (Government owned) Jilin Dongfeng Ferroalloy Works Jilin Ferroalloy Group Co. Ltd. Jilin Huinan Ferroally Works Jinzhou Ferroalloy (Group) Co. Ltd. Liaoyang Ferroalloy Group Corp Mengzang Ferroalloy Co. Ltd. Nanjing Ferroalloy Plant (Government owned) Ningjin Metal Smelting Co. Ltd. Northwest Ferroalloy Works Qinghai Datong Ferroalloy Works Qingzang Ferroalloy Co. Ltd. Quinhai Sanchuan Ferroalloy Co. Ltd. Taonan Ferroalloy Works Urad Zhongqi Ferrochrome Group Corp. Xibei Ferroalloy Works (Government owned) Zhejiang Hengshan Ferroalloy Works Dalmacija Ferro-Alloys Works Outokumpu Oy

Country

Slovakia Slovenia South Africa

Norway Russia

Kazakhstan

Japan

Iran

India-Continued

Company Sree Sarada Alloys Ltd. The Sileal Metallurgie Ltd. The Tata Iron and Steel Co. Ltd. VBC Ferro-Alloys Ltd. Faryab Mining Co. Abadan Ferroalloys Refinery. Nippon Denko Co., Ltd. NKK Corp. NKK Materials Co. Ltd. Showa Denko K.K. Shunan Denko K.K. Aksusky Ferroalloy Plant. Aktyubinsk Ferroalloy Plant. Elkem ASA.1 Chelyabinsk Electrometallurgical Integrated Plant. Klutchevsk Ferroalloy Plant. Metall Joint Venture. Serov Ferroalloys Plant. Oravske Ferozliatinarske Zavody. Tovarna Dusika Ruse-Metalurgija d.d. Anglovaal Mining Ltd. and Assore Ltd. Assmang Ltd. Machadodorp Works BHP-Billiton Plc. and Anglo American Corp. Plc. Samancor Ltd. Bathlako Ferrochrome Ferrometals Middelburg Ferrochrome Tubatse Ferrochrome

660

Croatia Finland

China

Albania Brazil

Country

TABLE C.12 Principal World Ferrochromium Pr oducers, 2002

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1

Ferrochromium production stopped in 2002.

Germany India

Outokumpu Steel Oy Outokumpu Chrome Oy Elektrowerk Weisweiler GmbH Andhra Ferro Alloys Limited Baroda Ferro-Alloys Deepak Ferro-Alloys Pvt. Ltd. Ferro-Alloys Corp. Ltd. Charge Chrome Plant Ferro-Alloys Unit GMR Vasavi Industries Ltd. IMFA Group Indian Metals and Ferro-Alloys Ltd. Indian Charge Chrome Ltd. India thermit Corp. Ltd. Industrial Development Corp. Ferro-Chrome Plant Ispat Alloys Ltd. Jalan Ispat Casting Ltd. Jindal Strips Ltd. Ferro Alloys Division Maithan Alloys Ltd. United States Zimbabwe

Sweden Turkey

Hernic Ferrochrome (Pty.) Ltd. Hernic Ferrochrome Xstrate A.G. (United Kingdom) Xstrate South Africa (Pty.) Ltd. Xstrata S.A. Chrome Division Rustenburg Works Wonderkop Works Lydenburg Works S.A. Chrome & Alloys S.A. Chrome A.S.A. Metals (Pty.) Ltd. Dilokong Ferrochrome Vargön Alloys AB. Eti Holdings. Eti Elektromatalurji. Eti Krom A.S. Eramet Marietta Inc. Maranatha Ferrochrome (Pvt.) Ltd. Zimasco (Pvt.) Ltd. Zimbabwe Alloys Ltd.

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Chromium(VI) Handbook

TABLE C.13 Chromite: World Production, by Country Country

1998

3

Afghanistan Albania5 Australia Brazil6 Burmae Chinae Cuba Finland Greece4 India Indonesia Iran Kazakhstan Macedonia Madagascar Oman Pakistan Philippines Russia South Africa Sudane Turkey United Arab Emiratese Vietnam Zimbabwe

4

Total

1999

3,409 102,189 80,000 537,426 r 4,059 7 220,000 r 46,000 498,075 4,432 1,311,310 4,700 211,555 1,602,700 5,000 104,300 28,684 77,500 53,871 150,000 6,480,000 30,500 1,404,470 76,886 7 59,000 605,405 13,700,000

r r

4,318 71,434 70,000 488,392 2,500 220,000 52,000 597,438 2,273 1,472,766 6,355 254,685 2,405,600 5,000 — 26,004 58,000 19,566 115,100 6,817,050 48,000 770,352 60,000 58,500 653,479 14,300,000

1, 2

(Metric tons, gross mass) 2000

r r r

r r

2001

2002

5,345 63,000 90,000 602,971 r 1,000 r 208,000 r 56,300 628,414 — 1,946,910 —r 153,000 2,606,600 5,000 e 118,750 15,110 r 119,490 26,361 r 92,000 6,622,000 r 28,500 545,725 30,000

5,682 129,700 11,800 408,549 r 1,000 r 182,000 r 50,000 r 575,126 — 1,677,924 —r 104,905 r 2,045,700 r 5,000 e 51,900 30,100 r 64,000 26,932 r 69,926 5,502,010 20,500 389,759 10,000

— 135,000 132,665 279,648 — 180,000 46,000 566,090 — 1,900,000 — 80,000 2,369,400 5,000 e 11,000 27,444 62,005 23,703 70,000 e 6,435,746 14,000 313,637 10,000

76,300 668,043

r

80,000 780,150

r

82,000 749,339

14,700,000

r

12,200,000

r

13,500,000

r

r

Estimated. Revised. — Zero. World totals and estimated data are rounded to no more than three significant digits; may not add to totals shown. 2 Table includes data available through June 25, 2003. 3 Figures for all countries represent marketable output unless otherwise noted. 4 Gross mass estimated assuming an average grade of 44% Cr O . 2 3 5 Direct shipping plus concentrate production. 6 Average Cr O content was as follows: 1998–99—39% (revised); 2000—42% (revised); 2 3 2001—42.6% (revised); and 2002—43% (estimated). 7 Reported figure. e

r

1

rate, based on the physical equipment of the plant and given acceptable routine operating procedures involving labor, energy, materials, and maintenance. Capacity includes both operating plants and plants temporarily closed that, in the judgement of the author, can be brought into production within a short period of time with minimum capital expenditure. Because not all countries or producers make information about production capacity available, historical chromium trade data have been used to estimate production capacity. Production capacity changes result from both facility changes and knowledge about facilities. Production capacities have been

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Appendix C TABLE C.14 Ferrochromium: World Production, by Country Country Albania Brazil3 Chinae Croatia Finland Germany India5 Iran Italy Japan3 Kazakhstan Norway Poland Romania Russia Slovakia Slovenia South Africa6 Spain Sweden Turkey United States7 Zimbabwe Total

1998 30,252 72,507 424,000 11,771 230,906 20,879 345,125 13,745 11,487 142,931 535,000 174,678 4,200 873 203,000 11,715 10,621 2,025,300 1,145 123,958 110,175 W 246,782 4,750,000

1999 28,120 90,784 400,000 — 256,290 16,960 312,140 13,680 — 119,777 731,563 159,714 — — 249,000 6,986 560 2,155,202 935 113,140 99,105 W 244,379 5,000,000

1, 2

(Metric tons, gross mass)

2000 12,500 r 142,522 450,000 15,753 260,605 r 21,600 376,693 11,505 — 130,074 799,762 153,500 — — 274,000 17,702 — 2,574,000 905 135,841 97,640 r W 246,324 5,720,000

2001 11,900 r 110,462 r 310,000 r 361 236,710 19,308 267,395 r 8,430 —e 111,167 761,900 82,600 —e —e 210,600 5,968 — 2,141,000 —e 109,198 50,735 W 243,584 r 4,680,000

2002e 22,800 169,658 400,000 — 248,181 20,018 311,927 15,000 — 91,937 835,800 61,100 — — 210,000 5,695 — 2,200,000 — 118,823 11,200 W 258,164 4,980,000

4

4 4 4

4 4

4

4

4

Estimated. rRevised. W Withheld to avoid disclosing company proprietary data; not included in “Total.” — Zero. 1 World totals, U.S. data, and estimated data are rounded to no more than three significant digits; may not add to totals shown. 2 Table includes data available through August 21, 2003. 3 Includes high- and low-carbon ferrochromium. 4 Reported figure. 5 Includes ferrochrome and charge chrome. 6 Includes high- and low-carbon ferrochromium and ferrochromiumsilicon. 7 Includes chromium metal, high- and low-carbon ferochromium, ferochromiumsilicon, and other chromium materials. e

rated for the chromite ore, chromium chemical, chromium metal, ferrochromium, and stainless steel industries. C.1.4.3 Reserves The United States has no chromite ore reserves. However, the United States has a reserve base and resources that could be exploited. The U.S. reserve base is estimated to be about 10 million metric tons (10 Mt) of chromium. World reserves are about 3.6 billion tons (3.6 Gt) of chromium and the world reserve base is about 7.5 Gt. More than 80% of world reserves and more than 70% of the world reserve base are in South Africa. The USGS

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TABLE C.15 World Chromium Annual Production Capacity of Chromite Ore, Ferrochromium, Chromium Metal, Chromium Chemicals, and Stainless Steel in 2002 1 (Thousand metric tons of contained chromium) Country

Ore

Afganistan Albania Argentina Australia Austria Bangladesh Belgium Brazil Burma Canada China Cuba Czech Republic Egypt Finland France Germany Greece India Indonesia Iran Italy Japan Kazakhstan Korea, Republic of Macedonia Madagascar Norway Oman Pakistan Philippines Poland Russia Slovakia Slovenia South Africa Spain Sudan Sweden Taiwan Turkey Ukraine United Arab Emirates

2 48 — 72 — — — 101 1 — 48 17 — — 189 — — 4 586 2 77 — — 903 — 2 42 — 9 36 26 — 46 — — 2,060 — 14 — — 466 — 23

FerroChromium — 22 — — — — — 109 — — 272 — — — 139 — 17 — 196 — 9 — 97 512 — — — 106 — — — — 180 10 — 1,470 — — 86 — 69 — —

3

Metal — — — — — — — — — — 6 — — — — 7 1 — (2) — — — 1 2 — — — — — — — — 16 — — — — — — — — — —

Chemicals — — 13 — — — — — — — 70 — — — — — — — 4 — 2 — 17 37 — — — — — 3 — — 31 — — 23 — — — — 17 — —

Stainless Steel — — — — 8 3 123 65 — 39 64 7 5 3 109 204 272 — 122 — — 221 672 — 269 — — — — — — — 38 — 12 92 204 — 138 231 54 33 — (Continued)

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Appendix C TABLE C.15 World Chromium Annual Production Capacity of Chromite Ore, Ferrochromium, Chromium Metal, Chromium Chemicals, and Stainless Steel in 2002 1 (Thousand metric tons of contained chromium) (continued) Country United Kingdom United States Vietnam Zimbabwe Total

Ore — — 16 214 5,000

FerroChromium — 20 — 221 3,530

Metal

Chemicals

Stainless Steel

7 3 — — 43

44 38 — — 299

92 374 — — 3,450

— Zero. 1 Data are rounded to no more than three significant digits; may not add to totals shown. 2 Less than 1/2 unit. 3 Ferrochromium production stopped in 2002.

reports reserves and reserve base information annually in Mineral Commodity Summaries. C.1.4.4 Production World chromite ore production in 2002 was about 13 Mt, of which about 90% was produced for the metallurgical industry; 1%, for the refractory industry; 6%, for the chemical industry; and 3%, for the foundry industry (International Chromium Development Association, 2003, p. 1). World ferrochromium production in 2002 was estimated to be about 5 Mt. World production of ferrochromium silicon is small compared with that of ferrochromium. Production of chromite ore, ferrochromium, and stainless steel all declined from 2000 to 2001, then increased from 2001 to 2002. In 2000, excess stocks resulted in major producers closing furnaces in an effort to bring production in balance with demand. The effect was mitigated by reduced stainless steel production, causing prices to decline. Prices weakened throughout 2001. The weakening of the South African rand (R) relative to the U.S. dollar further lowered prices. A strengthening rand decreased ferrochromium producer stocks, and strengthening demand resulting from increased stainless steel production caused the price of ferrochromium to increase in 2002, and furnaces were restarted. In addition to the countries listed, Spain and Taiwan produced stainless steel in 2002. C.1.4.5 European Union With major stainless-steel-producing plants in Belgium, Finland, France, Germany, Italy, Spain, Sweden, and the United Kingdom, the European Union accounted for about 50% of world stainless steel production.

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C.1.4.6 Australia Pilbara Chromite Pty. Ltd. (a division of Consolidated Minerals Limited) developed chromite ore reserves at its Coobina Chromite Project, about 80 kilometers (km) southeast of Newman, Western Australia. Reserves were estimated to exceed 1.6 Mt of chromite ore graded at 42% Cr2O3 to a depth of 30 meters (m). The chromite ore was found in 150 massive lenses. The chromite ore was mined by hydraulic excavator and transported by dump trucks. Pilbara stockpiles its chromite ore at Port Hedland, from where it is shipped. Consolidated started shipping chromite ore in February and planned to reach a production rate of 250,000 t/year by surface mining from 1.96 Mt of reserves measured to a depth of 30 m. Consolidated planned to increase production to 500,000 t/year and to develop a smelter to process its chromite ore (Consolidated Minerals, Ltd., 2003 §). C.1.4.7 Belgium UGINE & ALZ Belgium NV (a subsidiary of Arcelor) produced stainless steel at Genz.

CENTS PER POUND, CONTAINED CHROMIUM

C.1.4.8 Brazil Brazil produced chromite ore, ferrochromium, and stainless steel. In 2001, Brazil produced 409,000 t of chromite ore (42.6% Cr2O3), exported 78,500 t (38,400 t of Cr2O3-content), and imported 10,100 t (4,600 t of Cr2O3-content). Brazil produced chromium from a chromite ore reserve containing about Average weekly prices (cents per pound)1 50% to 55% chromium 60% to 65% chromium

50 45 40 35 30 25 50 45 40 35 30 25 0

10

20

30 WEEKS

1

Average weekly price shown against price range background. Source: Platts Metals Week

FIGURE C.1 U.S. imported high-carbon ferrochromium in 2002

40

50

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CENTS PER POUND, CONTAINED CHROMIUM

Appendix C

Average weekly prices (cents per pound)1 0.05% carbon 0.1% carbon

90 85 80 75 70 65 60 55 50 90 85 80 75 70 65 60 55 50 0

10

20

30

40

50

WEEKS 1 Average weekly price shown against price range background. Source: Platts Metals Week

FIGURE C.2 U.S. imported low-carbon ferrochromium in 2002

3 Mt of chromium. In 2001, Brazil produced 110,462 t of chromium ferroalloys, of which 97,100 t was high-carbon ferrochromium, 7,500 t was lowcarbon ferrochromium, and the remainder was ferrochromium-silicon. Brazil imported 7,173 t of ferrochromium and exported 144 t (Gonçalves, 2002 §). Based on production of chromite ore and trade of chromite ore and chromium ferroalloys, Brazilian chromium apparent consumption in 2001 was 113 t. Brazilian ferrochromium production in 2001 was limited by electrical power rationing that resulted from drought conditions. C.1.4.9 Canada Allican Resources planned to construct a low-carbon ferrochromium smelter in the Gaspé region of Québec. The plant was planned to have production capacity of 20,000 t/year, power rating of 30 megawatts (MW), and a cost of Can$100 million. Products planned included ferrochromium containing 0.015% carbon, 0.05% carbon, or 0.10% carbon (Ryan’s Notes, 2002). C.1.4.10 China China produced chromite ore, chromium chemicals, ferrochromium, and stainless steel. China’s chromite ore production was inadequate to meet domestic demand, so it imported ore. China reported its national chromium-material trade statistics for 2002. Chromite ore imports were 1,140,000 t in 2002 and 1,090,000 t in 2001.

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Ferrochromium exports were 51,951 t in 2002 and 89,656 t in 2001. Ferrochromium imports were 71,642 t in 2002 and 36,000 t in 2001. China did not report its chromite ore production; however, it was estimated to have been 113,000 t in 2002 and 113,000 t in 2001. Based on this reported trade and estimated production, apparent consumption of chromium was 390,000 t in 2002 and 326,000 t in 2001 (TEX Report, 2002a; Paxton, 2003). The Hunan Ferroalloys Group produced ferrochromium and chromium metal. Northwest Ferroalloys, Gansu Province, produced ferrochromium. C.1.4.11 Croatia The Government of Croatia sold the Dalmacija ferrochromium smelter. At one time, the smelter had ferrochromium production capacity of 100,000 t/year. It was not expected to produce any more ferrochromium. C.1.4.12 Finland Finland produced chromite ore, ferrochromium, and stainless steel. Avesta Plarit produced stainless steel, and AvestaPolarit Chrome produced chromite ore and ferrochromium as part of a vertically integrated company structure within Outokumpu Oy, which included an integrated mine-smelter-steel works in Kemi and Tornio, Finland. The Kemi Mine produced 566,000 t of chromite concentrate from 1.2 Mt of ore excavated in 2002 (575,100 t of chromite concentrate from 1.2 Mt of ore excavated in 2001). Production of chromite ore was from a proven reserve of 51 Mt of ore with an average grade of 25% Cr2O3. The Kemi Mine continued to develop underground chromite ore reserves. AvestaPolarit reported production of 248,000 t of ferrochromium in 2002 and 236,000 t in 2001. Outokumpu reported that electricity accounted for more than one-third of its variable ferrochromium production cost. In 2002, AvestaPolarit commissioned new stainless steel production capacity at its Tornio plant by adding a new melt shop. The company planned to increase its stainless steel melting capacity to 1.65 Mt of slabs by 2004 from 650,000 t of slabs in 2002. C.1.4.13 France France produced chromium metal and stainless steel. C.1.4.14 Germany Germany produced chromium metal, ferrochromium, and stainless steel. C.1.4.15 India India produced chromite ore, ferrochromium, stainless steel, and chromium chemicals. India reported that 20 mines produced 1,810,920 t of chromite ore

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in FY 2001–02 (April 2, 2001, through March 31, 2002) from a chromite ore recoverable reserve of 97.076 Mt (Indian Bureau of Mines, 2003 §). India reported that 20 mines produced 1,951,649 t of chromite ore from a recoverable reserve of 86.23 Mt, 97% of which was in Orissa, in FY 2000–01 compared with production of 1,737,985 t in FY 1999–2000. For FY 1999–2000, India reported chromite ore exports of 714,448 t and imports of 6,886 t as well as imports of 116 t of chromium metal and scrap. India reported that seven plants produced 315,002 t of ferrochromium (ferrochrome plus charge chrome) in FY 2000–01 compared with production of 273,665 t in 1999–2000 fiscal year. For FY 1999–2000, India reported ferrochromium exports of 85,316 t and imports of 73,000 t (Indian Bureau of Mines, 2002a,b). Based on the chromite ore production and chromite ore and ferrochromium trade, Indian apparent chromium consumption in FY 1999–2000 was 267,000 t compared with 220,000 t in FY 1998–99. Jindal Strips Ltd., a stainless steel and ferrochromium producer, planned to expand its stainless steel production capacity to 500,000 t/year by 2004. Part of the expansion included Jindal entering the chromite ore mining business (Platts Metals Week, 2002a). The Government of Orissa planned to develop the Tangarpada mines, 550 hectares in the Sukinda area containing 20 Mt of chromite ore reserves. Orissa selected Jindal Strips (89%) and Industrial Development Corp. of Orissa Ltd. (IDC) (11%) to develop the resources in a joint venture. The Government owned IDC and planned to privatize it. IDC operated a ferrochromium plant at Jajpur Road with high-carbon ferrochromium production capacity of 15,000 t/year and held mining rights for chromite ore at the Tailangi mines (Lobo, 2003). The IMFA Group reported that profitability returned to its subsidiary Indian Charge Chrome Ltd. (ICCL), which operated a charge chromium plant and captive powerplant (108 MW) at Choudwar, Orissa. ICCL built a large debt resulting from declining ferrochromium prices, the lack of dependable chromite ore supply, and a weakening rupee relative to the U.S. dollar, the currency in which it borrowed from banks. With the acquisition of a captive chromite ore supply and the price of ferrochromium increasing, ICCL planned to restructure its debt (IMFA Group, 2003 §). Orissa Mining Corp. (OMC) (wholly owned by the Government of Orissa) reported mining chromite ore from a reserve of 28.2 Mt from about 11 properties covering 5,800 hectares in the Jajpur District, Orissa. OMC operated the Bangur, Kaliapani, Kathal, and Sukrangi Mines, of which Kaliapani was the largest. OMC also operated a beneficiation plant at Kaliapani with output capacity of 84,000 t/year of chromite concentrate (Orissa Mining Corp., undated §).

C.1.4.16 Italy Acciai Speciali Terni produced stainless steel at Terni, Umbria.

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C.1.4.17 Japan Japan produced chromium chemicals, ferrochromium, and stainless steel. In 2002, Japan imported 727,385 t of highcarbon and 55,949 t of low-carbon ferrochromium; 354,928 t of chromite ore; 2,812 t of ferrochromium silicon; and 2,922 t of chromium metal. Japan produced 87,653 t of high-carbon and 4,380 t of low-carbon ferrochromium. Stainless steel production was 3.4517 Mt. Ferrochromium net imports represented 89% of market share. Japan exported 1,362 t of ferrochromium and 1.5245 Mt of stainless steel. Japan imported 131,411 t of stainless steel scrap and exported 121,584 t. Stainless steel net exports were 42% of stainless steel production (TEX Report, 2003a–i). Based on chromite ore, ferrochromium, chromium metal, and stainless steel scrap trade, chromium apparent consumption in Japan was 542,000 t in 2002. Nippon Denko Co., Ltd. produced ferrochromium at a plant in Toyama; NKK Materials (NKK), at a plant in Toyama; and Shunan Denko, at a plant in Shunan. All produced high-carbon ferrochromium; however, only NKK produced low-carbon ferrochromium. Showa Denko K.K. planned to dissolve Shunan Denko K.K. (a joint venture with Nisshin Steel Co., Ltd. and Tokuyama Corporation). The Shunan plant has supplied molten ferrochromium to Nisshin Steel since 1968. Nippon Denko planned to expand its chromium chemical business. Nippon Denko estimated the Japanese chromic acid consumption rate to have been 9,000 t/year, of which 6,000 t was consumed in plating products and 3,000 t was available for recycling. Of the 3,000 t available for recycling, only 500 t is currently being recovered and 2,500 t is disposed with post plating sludge. Nippon Denko currently handles about one-half of the recovered chromium and planned to address recovery of that which is available for recycling but not currently recovered (Watanabe, 2003§). C.1.4.17 Kazakhstan Kazakhstan produced chromite ore, chromium chemicals, chromium metal, and ferrochromium. C.1.4.18 Norway Elkem stopped production of ferrochromium at Rana and put the property up for sale. C.1.4.19 Russia Russia produced chromite ore, chromium chemicals, chromium metal, and ferrochromium. Polema Corp. planned to build a plant to produce chromium metal from chromic acid in Pervouralsk, Sverdlovsk region in cooperation with Russian Chrome 1915, a chromic acid producer in Pervouralsk. The plant was planned to be operational in 2003, with chromium metal production capacity of 1,000 t/year.

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C.1.4.20 South Africa South Africa produced chromite ore, chromium chemicals, ferrochromium, and stainless steel. The South African Minerals Bureau reported that, from a reserve base of 5,500 Mt of chromite ore in 2001, South Africa produced 5.502 Mt of chromite ore from which it produced 2.574 Mt of ferrochromium and other products. South Africa exported 931,000 t of chromite ore and 1.976 Mt of ferrochromium in 2001 (Armitage, 2002). Based on chromite ore production and chromite ore and ferrochromium trade, South African chromium apparent consumption was 512,000 t of contained chromium in 2000. The Minerals Bureau reported chromite ore production in 2002 of 6,435,746 t and sales of 5,951,480 t. Sales accounted for 82% of production, with domestic sales accounting for 89% of sales (South African Minerals Bureau, 2003). Based on chromite ore production and trade and ferrochromium trade, South African chromium apparent consumption was 289,000 t in 2001. The South African rand declined in value relative to the U.S. dollar to R8.5755 per $1.00 in December from R12.3772 per $1.00 in January (Pacific Exchange Rate Service, 2003 §). This change in exchange rate was partly responsible for the increased price of chromium materials. South Africa passed the Mineral and Petroleum Resources Development Act that required the empowerment of historically disadvantaged South Africans (HDSAs). The Act requires the South African mining industry to develop and implement business plans that address the government’s goal of 15% ownership in 5 years and 26% in 10 years by HDSAs. The plan had the support of the government, labor, and industry. Tata Iron and Steel Co., Ltd. (India) planned to build a ferrochromium plant at Richards Bay, a port city. Tata is a major chromite ore producer in India and produces ferrochromium there, too. Owing to the high cost of electricity in India, the cost of ferrochromium production in India exceeded that of South Africa. As a result, Tata elected to produce ferrochromium in South Africa using chromite ore from India. At a cost of $62 million, the company planned to build the plant using Outokumpu technology to produce ferrochromium from one closed furnace having production capacity of 120,000 t/year and electrical capacity of 57 MVA. Tata planned a second furnace to double production capacity. Construction was expected to begin in 2003; production, in 2005. Transvaal Ferrochrome proposed construction of a ferrochromium plant in association with Buffelsfontien Mine, which Transvaal Ferrochrome planned to acquire and develop as part of the project. Transvaal Ferrochrome planned to obtain financing through the Australian stock exchange in 2003. In 2002, Xstrata S.A. (Pty.) Ltd. (Xstrata) produced 2.929 Mt of chromite ore, run of mine, from a capacity of 4.44 million metric tons per year (4.44 Mt/ year) from three mines and 957,500 t of ferrochromium compared with 860,600 t of ferrochromium from a capacity of 1.3 Mt/year from four plants in 2001. Xstrata’s Kroondal Mine produced 1.33 Mt of chromite from a production capacity of 1.92 Mt/year, Waterval produced 453,000 t from a production

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capacity of 1.2 Mt/year, and Thorncliffe Mine produced 1.146 Mt from a production capacity of 1.32 Mt/year. Xstrata produced ferrochromium at plants in Lydenburg, Marikana, and Rustenburg. Xstrata reported chromite ore reserves of 52.106 Mt (Xstrata, 2002 §). Samancor Chrome [owned by BHP Billiton (60%) and Anglo American Corp. of S.A.( 40%)] produced 2.640 Mt of chromite ore and 892,000 t of ferrochromium in 2002 compared with 2.577 Mt of chromite ore and 799,000 t of ferrochromium in 2001 (BHP Billiton, 2003 §). Samancor reported proven plus probable chromite ore reserves of 20.7 Mt graded at 42.3% Cr2O3 (BHP Billiton, 2002 §). Hernic (Pty.) Ltd. produced chromite ore and ferrochromium at Brits, North-West Province. Hernic started production in 1996 with ferrochromium production capacity of 130,000 t/year from two 37-MVA semiclosed furnaces. Hernic doubled its production capacity in 1999 with the addition of a 54-MVA closed furnace, which pelletized and preheated the furnace feed. Hernic restructured ownership to 53% by Mitsubishi Corp. (Japan), 25% by Industrial Development Corp., 14% by ELG Haniel, and 8% by management. Hernic planned to increase production capacity by adding another closed furnace and a pelletizing/preheating plant (McCulloch, 2002). ASA Metals (Pty.) Ltd. produced chromite ore and ferrochromium at Burgersfort, North-West Province. ASA produced chromite ore at Dilokong Mine, which had a chromite ore production capacity of 400,000 t/year from a reserve of 40 Mt. ASA is owned 60% by East Asia Metal (China) and 40% by Limpopo Development and Enterprises. ASA started production in 1999 with one 33-MVA furnace capable of producing 55,000 t/year of ferrochromium that cost $20 million to construct. ASA planned to add a second 40-MVA furnace that would increase ferrochromium production capacity by 65,000 t/year at about the same cost (Claasen, 2003 §). Feralloys Limited (owned by Assmang Ltd.) produced chromite ore at Dwarsrivier and ferrochromium at Machadodorp. Feralloys commissioned a fourth furnace and associated pelletizing and preheating line designed by Outokumpu built at a cost of about $40 million. The new furnace has an electrical power capacity of 54 MVA and a ferrochromium production capacity of 175,000 t/year. The pelletizing operation is capable of turning out 350,000 t/year of pellets. The smelter is supplied chromite ore by the Dwarsrivier chromite ore mine in Mpumalanga Province about 140 km from the plant. The Dwarsrivier Mine had a reserve of 20 Mt and reserve base of 100 Mt. The mine was designed to produce 1 Mt/year, run of mine, which could be increased to 1.25 Mt/year. The mine started operation in 2000 as an opencast mine; however, as mining continues, surface mining will shift to underground. It was developed at a cost of R190 million (about $23 million). South African Chrome and Alloys Limited (SA Chrome) produced chromite ore and ferrochromium at Boshoek near Brits in North-West Province. The ferrochromium plant comprised two closed electric-arc furnaces with pelletizing and preheating process equipment and cost about $45 million

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to construct. The plant was built above 13.6 Mt of chromite ore reserves held by SA Chrome and adjacent to reserves held by the Bafokeng Nation, a coowner of SA Chrome. The Horizon Mine, which is 40 km from the plant, extracts chromite ore from the LG6 seam. The smelter uses a blend of LG6 and UG2 ore. Chromite ore recovered from platinum mining of the UG2 seam is available 8 km from the plant. The first furnace was started in June, the second, in July. The ownership structure of SA Chrome is as follows: Bafokeng Nation (35%), Industrial Development Corp. (24%), Bateman Titaco (5%), Outokumpu (3%), ThyssenKrupp Metallurgie GmbH (2%), and others (35%). The plant uses Outokumpu technology to pelletize, preheat, and smelt up to 520,000 t/year of chromite ore in two 54-MVA furnaces with ferrochromium production capacity of 235,000 t/year (Haase, 2002; Halwindi, 2002; Zhuwakinyu, 2002). Columbus Stainless produced stainless steel in Middelburg, Mpumalanga Province. Columbus planned to increase stainless steel production capacity to about 750,000 t/year from 350,000 t/year. C.1.4.21 Sweden Sweden produced ferrochromium and stainless steel. The Swedish Emergency Management Agency sold 6,529 t of ferrochromium that was held in the Swedish national stockpile. C.1.4.22 Turkey Turkey produced chromite ore, chromium chemicals, and ferrochromium. C.1.4.23 United Kingdom The United Kingdom produced chromium chemicals and metal and stainless steel. C.1.4.24 Zimbabwe Zimbabwe produced chromite ore and ferrochromium. Zimbabwe Alloys Mines Limited reported putting its mine on care-and-maintenance status.

C.1.5 Current Research and Technology C.1.5.1 Mineral Processing and Industrial Applications Industry conducts research to develop new, more efficient processes and to improve the efficiency of currently used processes. The Council for Mineral Technology (Mintek) of South Africa conducts Government-sponsored, commercially sponsored, and cosponsored research and development on chromite ore and ferrochromium.

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Researchers at Mintek reviewed the flotation of chromite and applied it to upgrading chromium-contaminated ilmenite (Hayes and others, 2001). The authors concluded that, owing to the similar response of chromite and ilmenite, it will be necessary to find a specific activator for chromite and a specific depressant for ilmenite to separate the two minerals. Reinke (2001) studied the reduction of chromite under conditions of controlled geometry and thermodynamics. Historical studies of chromite reduction used chromite ores, a material of variable grain sizes, shapes, and conditions. The author found reduction of chromite to be rate-limited by solid-state diffusion.

C.1.5.2 Technology Corrosion of metals results in a significant economic cost to society. (More information can be found in the "Legislation and Government Programs" section of this report). Stainless steel is called stainless because it does not corrode or stain perceptibly. The most common form of iron corrosion is rust. Stainless steel is an engineering alternative material to alloy steel that contains about 13% chromium and additions of other alloying elements. While resistant to rust and other forms of corrosion, common grades of stainless steel are susceptible to pitting corrosion in certain environments, namely wet salty environments. To counteract pitting corrosion, metallurgists increase chromium additions and add other alloying elements, such as molybdenum, and modify its processing, all of which increase cost. Ryan and others (2002) have identified the physical conditions that promote pitting corrosion as the reduction in chromium-to-iron ratio near manganese sulfide inclusions. Engineers may use this information as the basis for improving alloying or production technology that will result in the production of stainless steel with better material properties at a lower price. C.1.5.3 Outlook The outlook for chromium consumption in the United States and the rest of the world is about the same as that for stainless steel, which is the major end use for chromium worldwide. Thus, stainless steel industry performance largely determines chromium industry demand worldwide. (More information can be found in the "Current Research and Technology" section on stainless steel.) The trend to supply chromium in the form of ferrochromium by countries that mine chromite ore is expected to continue. With new efficient ferrochromium production facilities and excess capacity in chromite-ore-producing countries, ferrochromium capacity and production are expected to diminish in countries that produce ferrochromium but not chromite ore, and in countries with small, less efficient producers. Further vertical integration of the chromium industry is expected as chromite-ore-producing countries expand ferrochromium or stainless steel production capacity.

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C.1.5.4 Chromite Ore Chromite ore production capacity is in balance with average consumption. Consumption capacity by ferrochromium plants, however, exceeds production capacity, which can lead to short supply when demand surges, thus preventing ferrochromium producers from meeting surge demand. To improve chromite ore availability and to stabilize feed material price, ferrochromium producers invest in chromite-ore-producing mines. Indeed, most chromite ore is produced under vertically integrated mine-smelter or mine-plant ownership. C.1.5.5 Chromium Chemicals In 2002, major producing countries where large plants (capacity in excess of 100,000 t/year of sodium dichromate) operate included Kazakhstan, Russia, the United Kingdom, and the United States. Moderate-sized production facilities were located in China, Japan, Romania, South Africa, and Turkey. Small-scale local producers operated in China and India. CCA has been a popular wood treatment chemical in the United States. Globally, CCA was the second largest market for chromic acid, the major product of sodium dichromate, accounting for about 78,400 t of chromic acid in 2000. It was estimated that the United States accounted for about one-half of the CCA market, of which about three-quarters was used to treat wood used in residential applications. U.S. manufacturers of treated wood planned to phase out the use of CCA by voluntary agreement with the EPA. That change in use caused the U.S. chromium chemical industry to reorganize. Worldwide, about 1 Mt/year of chromite ore was consumed by the chemical industry to produce 692,000 t/year of sodium dichromate. Sodium dichromate has been converted to chromic acid at the rate of 224,000 t/year. Chromic acid has accounted for 32% of sodium dichromate demand; chromium sulfate, 30%; chromic oxide, 20%; and other chemicals, 18%. Chromic acid has been converted to CCA at the rate of 100,000 t/year. CCA has accounted for 35% of chromic acid demand; metal finishing, 50%; magnetic media, 5%; and other uses, 10% (Industrial Minerals, 2002). C.1.5.6 Chromium Metal Major chromium metal producers include Russia and the United States (by the electrolytic process) and China, France, Russia, and the United Kingdom (by the aluminothermic process). Chromium metal demand was estimated to be 19,500 t in 2002, down from about 21,000 t in 2001. Demand in 2003 was expected to decline. Chromium metal produced by aluminothermic reduction was estimated to have accounted for about 90% of production in 2002. Aluminothermically produced chromium metal accounted for 60% to 65% during the 1990s (TEX Report, 2002b; 2003j). New uses are developing for chromium metal. Buchanan (2002) estimated world production of chromium metal in 2001 to be 30,000 t, of which 17% to 25% was produced by the electrolytic process. In the electronics industry,

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chromium is used in the manufacture of hard disks, TV flat panel displays, and liquid crystal displays. C.1.5.7 Ferrochromium Ferrochromium production is electrical energy intensive. Charge-grade ferrochromium requires 2,900 kWh to 4,100 kWh of electrical energy per metric ton of product, with efficiency varying by ore grade, operating conditions, and production process. Thus, ferrochromium plant location reflects a cost balance between raw materials and electrical energy supply. De Wet (2002) reported chromium industry trends to include continued growth in stainless steel production at the average rate of 5% per year, increased ferrochromium industry transparency, and production sensitivity to price. He noted that, historically, the ferrochromium industry has increased production capacity in advance of real demand, thereby eroding price. He reported that, in 2001, chromite ore consumption was distributed among the metallurgical (82%), chemical (10%), and refractory and foundry industries (8%). Of the 82% consumed in the metallurgical industry, 75% was used in the production of stainless steel, with the remaining 25% in the production of alloy and carbon steel among other alloys. Jones (2002) reported ferrochromium price, supply, demand, balance, and capacity trends. Jones found that the price of ferrochromium entering 2002 was trending downward and was low compared with historical prices. He attributed the downward trend to producer inventory reduction and the depreciating value of the South African rand relative to the U.S. dollar. He identified stainless steel production as the major source of demand for ferrochromium. C.1.5.8 Stainless Steel Stainless steel demand is expected to grow in the long term. Short-term demand fluctuations can exceed longterm demand growth. Moll (2003) reported that stainless steel production grew at a rate of 6% per year from 1950 through 2002 and forecasted a growth rate of 5% per year to 2010. Moll’s review of planned or proposed projects suggested that 8 Mt to 15 Mt will be added to the current global stainless steel production capacity of 25 Mt by 2010.

Bibliography Antony, M.P., Tathavadkar, V.D., Calvert, C., and Jha, A., 2001, The soda-ash roasting of chromite ore processing residue for the reclamation of chromium, Metallurgical and Materials Transactions B, v. 32B, December, p. 987–995. Armitage, W.K., 2002, Chromium in South Africa’s minerals industry 2001/2002 (19th ed.): South Africa Department of Minerals and Energy, December, p. 108–112. Buchanan, Susan, 2002, Bell Metals’ quest for purity, Metal Bulletin Monthly, April, p. 56–57.

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Cunat, Pierre-Jean, 2002, Chromium in stainless steel welding fumes, The Chromium File, no. 9, April, 8 p. de Wet, John, 2002, Importance of value in the chrome industry, Metal Bulletin Southern African Ferro-alloys Conference, Sun City, South Africa, February 26–27, 2002, Presentation, [unpaginated]. Defense National Stockpile Center, 2002a, FY 2003 annual materials plan announced: Fort Belvoir, VA, Defense National Stockpile Center news release DNSC-03-2174, October 1, 2 p. Defense National Stockpile Center, 2002b, Revised FY 2002 annual materials plan: Fort Belvoir, VA, Defense National Stockpile Center news release DNSC-022117, May 6, 2 p. Defense National Stockpile Center, 2002c, Stockpile accepts chromite ore offer: Fort Belvoir, VA, Defense National Stockpile Center news release DNSC-02-2044, January 8, 1 p. Defense National Stockpile Center, 2002d, Stockpile accepts ferrochromium offer: Fort Belvoir, VA, Defense National Stockpile Center news release DNSC-022074, February 22, 1 p. Defense National Stockpile Center, 2002e, Stockpile accepts ferrochromium silicon offers: Fort Belvoir, VA, Defense National Stockpile Center news release DNSC-02-2077, February 28, 1 p. Defense National Stockpile Center, 2002f, Stockpile accepts ferrochromium silicon offer: Fort Belvoir, VA, Defense National Stockpile Center news release DNSC-02-2111, April 26, 1 p. Defense National Stockpile Center, 2002g, Stockpile announces ferrochromium sales for August 2002: Fort Belvoir, VA, Defense National Stockpile Center news release DNSC-02-2160, August 29, 1 p. Defense National Stockpile Center, 2002h, Stockpile announces ferrochromium sales for December 2002: Fort Belvoir, VA, Defense National Stockpile Center news release DNSC-02-2216, December 19, 1 p. Defense National Stockpile Center, 2002i, Stockpile announces ferrochromium sales for July 2002: Fort Belvoir, VA, Defense National Stockpile Center news release DNSC-02-2151, August 1, 1 p. Defense National Stockpile Center, 2002j, Stockpile announces ferrochromium sales for October 2002: Fort Belvoir, VA, Defense National Stockpile Center news release DNSC-02-2184, October 29, 1 p. Elementis plc, 2002a, Elementis announces restructure of chromium operations: Staines, United Kingdom, Elementis plc press information, November 14, 1 p. Elementis plc, 2002b, Elementis plc comments on CCA wood preservative: Staines, United Kingdom, Elementis plc press information, February 5, 1 p. Haase, Candice, 2002, Smelters, twin furnaces commissioned, Mining Weekly (South Africa), July 5–11, p. 18. Halwindi, Nkolola, 2002, Chrome smelter’s R550m furnaces near completion, Mining Weekly (South Africa), May 24–30, p. 18. Hayes, G.W., Bruckard, W.J., and Smith, L.K., 2001, Flotation of chromite—A review with applications to upgrading chromium-contaminated ilmenite, in International Heavy Minerals Conference, Fremantle, Australia, June 18–19, 2001, Proceedings: Carlton, Australia, Australasian Institute of Mining and Metallurgy, p. 137–142. Huvinen, Markku, 2002, Exposure to chromium and its long-term health effects in stainless steel production: Kuopio, Finland, Kuopio University Library, 212 p.

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Indian Bureau of Mines, 2002a, Chromite: Indian Bureau of Mines Minerals Yearbook 2001, p. 68–82. Indian Bureau of Mines, 2002b, Ferro-alloys: Indian Bureau of Mines Minerals Yearbook 2001, p. 158–180. Industrial Minerals, 2002, Timber treatment for the chop: Industrial Minerals, no. 416, May, p. 21–23. Institute of Medicine, 2001, Dietary intake references for vitamin A, vitamin K, arsenic, boron, chromium, copper iodine, iron, manganese, molybdenum, nickel, silicon, vanadium, and zinc: Washington, DC, National Academy Press, 773 p. International Chromium Development Association, 2003, Statistical bulletin—2003 edition: Paris, France, International Chromium Development Association, 2003, 45 p. James, B.R., 2002, Chemical transformations of chromium in soils relevance to mobility, bio-availability and remediation: The Chromium File, no. 8, February, 8 p. Jones, Andrew, 2002, A view on the chrome & stainless steel markets: Metal Bulletin Southern African Ferro-alloys Conference, Sun City, South Africa, February 26–27, Presentation, [unpaginated]. Koch, G.H., Brongers, M.P.H., Thompson, N.G., Virmani Y.P., and Payer, J.H., 2002, Corrosion cost and preventive strategies in the United States: National Technical Information Service report No. FHWA-RD-01-156, 773 p. Lobo, Gilbert, 2003, Orissa chrome ore sell-off is challenged, Metal Bulletin, no. 8750, February 20, p. 8. Moll, M.A., 2003, Status & outlook of the global stainless steel industry—Industry consolidation & focus on China: Institute of Scrap Recycling Industries Convention & Expo, April 12, 2003, Orlando, FL, Presentation, [unpaginated]. McCulloch, Russ, 2002, Mitsubishi secures South African charge chrome producer, Metal Bulletin, no. 8696, August 5, p. 7. Paxton, Robin, 2003, Chinese ferro-alloy exports rise despite domestic demand, Metal Bulletin, no. 8751, February 24, p. 7. Platts Metals Week, 2002a, India’s JSL eyes chrome mines: Platts Metals Week, v. 73, no. 50, December 16, p. 9. Platts Metals Week, 2002b, North American Stainless emerging as top scrap consumer, Platts Metals Week, v. 73, no. 44, November 4, p. 12. Platts Metals Week, 2002c, US steel industry saw major consolidation in 2002, Platts Metals Week, v. 73, no. 52, December 30, p. 2. Reinke, C., 2001, On the kinetics of chromite reduction: Radiation Effects and Defects in Solids, v. 156, p. 301–304. Ryan, M.P., Williams, D.E., Chater, R.J., Hutton, B.M., and McPhail, D.S., 2002, Why stainless steel corrodes, Nature, v. 415, no. 14, February 14, p. 770–774. Ryan’s Notes, 2002, First quarter ferrochrome price rollover likely, Ryan’s Notes, v. 8, no. 49, December 9, p. 2. Singh, I.B., and Singh, D.R., 2001, Hexavalent chromium removal using iron bearing industrial sludges, Indian Journal of Chemical Technology, v. 8, November, p. 487–495. South African Minerals Bureau, 2003, South African Minerals Bureau report: South African Minerals Bureau ME-P-014, March 7, [unpaginated]. TEX Report, 2002a, China’s imports of Mn-ore and Cr-ore in year 2002: TEX Report, v. 35, no. 8236, March 12, p. 5. TEX Report, 2002b, Demand for chromium metal in 2002 decreases: TEX Report, v. 34, no. 8170, November 27, p. 4.

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TEX Report, 2003a, Japan’s exports of stainless steel scrap in 2002 compared to 2001: TEX Report, v. 35, no. 8216, February 12, p. 7–8. TEX Report, 2003b, Japan’s ferro-alloys exports in Dec 2002: TEX Report, v. 35, no. 8213, February 6, p. 8. TEX Report, 2003c, Japan’s ferro-alloys imports in Dec 2002: TEX Report, v. 35, no. 8208, January 30, p. 7. TEX Report, 2003d, Japan’s imports of rare metals in December 2002: TEX Report, v. 35, no. 8239, March 17, p. 7. TEX Report, 2003e, Japan’s imports of raw material ores in Dec 2002: TEX Report, v. 35, no. 8210, January 3, p. 7. TEX Report, 2003f, Japan’s imports of stainless steel products in 2002 decreased: TEX Report, v. 35, no. 8216, February 12, p. 7. TEX Report, 2003g, Japan’s imports of stainless steel scrap by discharging port in 2002: TEX Report, v. 35, no. 8218, February 14, p. 4–5. TEX Report, 2003h, Output of stainless steel products in 2002 decreased by 1.3%: TEX Report, v. 35, no. 8219, February 17, p. 4–5. TEX Report, 2003i, Production of ferro-alloys in Japan in Dec 2002: TEX Report, v. 35, no. 8235, March 11, p. 12. TEX Report, 2003j, World composition of demand for Cr-Met in last 3 years: TEX Report, v. 35, no. 8264, April 22, p. 6. U.S. Department of Defense, 2002, Strategic and critical materials report to Congress—Operations under the Strategic and Critical Materials Stock Piling Act during the period October 2001 through September 2002: U.S. Department of Defense, February 12, 64 p. U.S. Department of Labor, Occupational Safety and Health Administration, 2002, Occupational exposure to hexavalent chromium [Cr(VI)]: Federal Register, v. 67, no. 163, August 22, p. 54389–54394. U.S. Department of Transportation, Federal Highway Commission, 2002, Corrosion costs and preventive strategies in the United States: National Technical Information Service report No. FHWA-RD-01-157, 17 p. U.S. Environmental Protection Agency, 2002, Notice of receipt of requests to cancel certain chromate copper arsenate (CCA) wood preservative products and amend to terminate certain uses of CCA products: Federal Register, v. 67, no. 36, February 22, p. 8244–8246. Zhuwakinyu, Martin, 2002, Countdown to new chrome mine and smelter begins, Mining Weekly (South Africa), March 29-April 4, p. 4.

Internet Bibliography BHP Billiton, 2002, Stability, growth, value, Annual Report accessed, April 24, 2003, via URL http://bhpbilliton.com. BHP Billiton, 2003 (March 31), BHP Billiton production report for the quarter ended 31 March 2003, News Release, accessed April 24, 2003, via URL http:// bhpbilliton.com. Classen, Larry, 2003 (February 5), Pyromet to build furnace for ASA Metals, Business Day (Johannesburg), accessed April 24, 2003, at URL http://allafrica.com/stories/200302050202.html.

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Consolidated Minerals, Ltd., 2003, Chromite operations, accessed March 19, 2003, at URL http://www.consminerals.com.au/chromite_operations/chromite.htm. Financial Express, The, 2002 (December 16), Be a little sympathetic, give us some consideration, says ICCL, accessed March 27, 2003, at URL http://www.imfagroup.com/news 2002_1.html. Gonçalves, Maria de Melo, 2002, Chromium, Mineral Summary 2002, accessed March 20, 2003, at URL http://www.dnpm.gov.br/dnpm_legis/sm2002.html. Indian Bureau of Mines, 2003 (February 14), Indian Bureau of Mines, accessed March 26, 2003, at URL http://ibm.nic.in. Orissa Mining Corp., [undated], Profile, accessed March 28, 2003, at URL http:// www.orissamining.com. Pacific Exchange Rate Service, 2003, Pacific Exchange Rate Service, Database Retrieval System, accessed April 12, 2003, at URL http://pacific.commerce.ubc.ca/xr/data.html. U.S. Environmental Protection Agency, 2002 (February 12), Whitman announces transition from consumer use of treated wood containing arsenic, accessed February 5, 2003, at URL http://www.epa.gov/epahome/headline_021202.htm. Watanabe, Hisaki, 2003 (February 28), 2003–2005 mid-term management plan, accessed April 30, 2003, via URL http://www.nippondenko.co.jp/english. Xstrata plc, 2002 (March 20), Competent person’s report for the chromium and vanadium assets held by Xstrata South Africa, accessed December 13, 2002, via URL http://www.xstrata.com/publications.php.

C.1.6 General Sources of Information C.1.6.1

U.S. Geological Survey Publications

Chromium. Ch. in Mineral Commodity Summaries, annual Chromium. Ch. in United States Mineral Resources, Professional Paper 820, 1973 Chromium. International Strategic Minerals Inventory Summary Report, Circular 930-B, 1984 Chromium. Mineral Industry Surveys, monthly.

C.1.7 Other American Iron and Steel Institute American Metal Market Annual Stainless Steel Statistics Chrome Market Spotlight Chromite. Ch. in Industrial Minerals and Rocks, 6th ed., Society for Mining, Metallurgy, and Exploration, inc., Donald Carr, ed., 1994 Chromium. Ch. in Mineral facts and problems, U.S. Bureau of Mines Bulletin 675, 1985 CRU Metal Monitor Economics of Chromium, The. Roskill Information Services Ferro-Alloy Directory and Databook. Metal Bulletin Ferro Alloys Manual. The TEX Report Ferrous Mineral Commodities Produced in the Republic of South Africa. South African Department of Mineral and Energy Affairs Directory D8

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International Chromium Development Association Mining Annual Review Nickel Outlook South Africa’s Minerals Industry. South Africa Minerals Bureau Stainless Steel Databook. Metal Bulletin Books Strategic and Critical Materials Report to the Congress. U.S. Department of Defense Welt-Bergbau Daten World Metal Statistics Yearbook World Mineral Statistics World Stainless Steel Statistics

C.2 Chromium (Data in thousand metric tons, gross mass, unless otherwise noted)

C.2.1 Domestic Production and Use In 2003, the United States consumed about 12% of world chromite ore production in various forms of imported materials, such as chromite ore, chromium chemicals, chromium ferroalloys, and chromium metal. Imported chromite was consumed by one chemical firm to produce chromium chemicals. Consumption of chromium ferroalloys and metal was predominantly for the production of stainless and heat-resisting steel and superalloys, respectively. The value of chromium material consumption was about $188 million. C.2.2 Recycling In 2003, chromium contained in purchased stainless steel scrap accounted for 26% of apparent consumption. C.2.3 Import Sources (1999–2002) Chromium contained in chromite ore and chromium ferroalloys and metal: South Africa, 48%; Kazakhstan, 23%; Zimbabwe, 9%; Turkey, 7%; Russia, 6%; and other, 7%. C.2.4 Depletion Allowance 22% (Domestic), 14% (Foreign). C.2.5 Government Stockpile The Defense Logistics Agency, U.S. Department of Defense, submitted the Annual Materials Plan for fiscal year (FY) 2004 in February 2003. Quantity

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Salient Statistics—United States1 Production, secondary Imports for consumption Exports Government stockpile releases Consumption: Reported2 (excludes secondary) Apparent3 (includes secondary) Price, chromite, yearend: South African, dollars per metric ton, South Africa Turkish, dollars per metric ton, Turkey Unit value, average annual import (dollars per metric ton): Chromite ore (gross mass) Ferrochromium (chromium content) Chromium metal (gross mass) Stocks, industry, yearend5 Net import reliance6 as a percentage of apparent consumption

1999

2000

2001

2002

2003e

118 476 60 19

139 453 86 85

122 239 38 9

139 263 29 119

129 344 16 37

298 558

206 589

196 332

225 500

224 492

63

63

NA4

NA4

NA4

145

141

NA4

NA4

NA4

62 732 6,267 54 79

64 797 5,976 16 67

61 709 6,116 17 63

60 646 5,770 8 68

45 704 5,550 10 74

Estimated. NA Not available. — Zero. Data in thousand metric tons of contained chromium, unless noted otherwise. 2 The year 1998 includes chromite ore; 1999 through 2003 exclude chromite ore. 3 Calculated demand for chromium is production + imports – exports + stock adjustment. 4 This price series was discontinued. 5 Includes producer and consumer stocks before 2000; consumer stocks after 1999. 6 Defined as imports – exports + adjustments for Government and industry stock changes. e

1

Tariff:7 Item Ore and concentrate Ferrochromium: Carbon over 4% Carbon over 3% Other: Carbon over 0.5% Other Chromium metal: Unwrought powder Waste and scrap Other Ferrosilicon Chromium 7

Number

Normal Trade Relations 12/31/03

2610.00.0000

Free.

7202.41.0000 7202.49.1000

1.9% ad val. 1.9% ad val.

7202.49.5010 7202.49.5090

3.1% ad val. 3.1% ad val.

8112.21.000 8112.22.000 8112.29.000 7202.50.000

3% ad val. Free. 3% ad val. 10% ad val.

In addition to the tariff items listed, certain imported chromium materials (see U.S. Code, chapter 26, sections 4661 and 4672) are subject to excise tax.

available for sale will be limited to sales authority or inventory. The Agency reported sales in FY 2003 of 6,810 tons of chemical-grade chromite ore, 51,800 tons of refractory-grade chromite ore, 45,300 tons of high-carbon ferrochromium, 12,000 tons of low-carbon ferrochromium, and 103 tons of chromium metal.

8

e

7.64 51.9 73.5 2.31 0.642 0.042

482 218 7.10

Committed Inventory

70.9 — 82.6

Uncommitted Inventory

Estimated. NA Not available – Zero. See Appendix B for definitions.

Chromite ore: Chemical-grade Metallurgical-grade Refractory-grade Ferrochromium: High-carbon Low-carbon Chromium metal

Material

Stockpile Status—9-30-038

90.7 90.7 90.7 136 — 0.454

482 218 7.10

Disposal Plan FY 2003

70.9 — 82.6

Authorized for Disposal

62.0 15.7 0.116

7.45 — 30.1

Disposals FY 2003

71.4% 71.4% 100%

28.6% 28.6% e23.9%

Average Chromium Content

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Mine production 2002 United States India Kazakhstan South Africa Other countries World total (rounded) 9

— 1,900 2,370 6,440 2,790 13,500

2003e — 1,900 2,400 6,500 3,000 14,000

Reserves9

Reserve base9

(shipping grade)10 — 25,000 290,000 100,000 390,000 810,000

7,000 57,000 470,000 200,000 1,100,000 1,800,000

See Appendix C for definitions. Shipping-grade chromite ore is deposit quantity and grade normalized to 45% Cr2O3.

10

C.2.6 Events, Trends, and Issues Rising cost of ferrochromium production and a strengthening South African rand, along with increased demand for ferrochromium and tightness in supply of stainless steel scrap, have caused the price of ferrochromium to reach historically high levels. Increased demand for ferrochromium resulted from increased world stainless steel production, the major end use for ferrochromium. World stainless steel production responded to world demand led by China. With strong economic growth, China’s importance as a consumer of raw materials has increased significantly. The high price of ferrochromium resulted in the reentry of China and India, two of the world’s higher cost ferrochromium producers, in that commodity’s export market. It also fueled ferrochromium production expansion in Kazakhstan and bolstered its interest in moving into stainless steel production. Kazakhstan is geographically well placed and endowed with mineral and energy resources to meet China’s growing demand for stainless steel. The high cost and tight supply of stainless steel scrap resulted from increasing production of stainless steel and the cost of nickel, which reached its highest level in at least 14 years despite increased nickel production. High chromium and nickel prices result in increasing stainless steel price, which may cause the use of less costly stainless steel grades, other metals, or nonmetallic materials. If stainless users shift to less costly stainless grades, nickel demand would fall without depressing chromium demand. If stainless consumers shift to other metals or materials, demand for both chromium and nickel would decrease. C.2.7 World Mine Production, Reserves, and Reserve Base The reserves and reserve base estimates have been revised from those previously published based on new information. C.2.8 World Resources World resources exceed 12 billion tons of shipping-grade chromite, sufficient to meet conceivable demand for centuries. About 95% of chromium resources

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is geographically concentrated in southern Africa. Reserves and reserve base are geographically concentrated in Kazakhstan and southern Africa. The largest U.S. chromium resource is in the Stillwater Complex in Montana.

C.2.9 Substitutes Chromium has no substitute in stainless steel, the largest end use, or in superalloys, the major strategic end use. Chromium-containing scrap can substitute for ferrochromium in metallurgical uses.

C.3 Chromium Statistics

Thomas G. Goonan and John F. Papp

5,580 6,510 12,600 7,280 7,680 17,100 13,700 13,300 8,910 12,700 12,300 12,000 17,400 20,800 25,700 25,100 51,300 36,400 57,400 21,200 49,300 26,200 28,700 40,800

5,540 6,390 12,500 7,230 7,640 17,100 13,700 13,200 8,800 12,500 12,200 12,000 17,300 20,700 25,500 24,100 36,500 22,700 31,500 19,600 48,500 26,100 28,600 40,700

1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 1920 1921 1922 1923 56 59 47 42 46 43 41 37 40 38 35 35 30 30 28 33 44 59 118 72 41 25 26 28

Unit Value (S/t)

1,100 1,200 890 760 840 780 750 650 730 690 610 610 510 494 457 532 658 752 1,270 679 333 227 252 267

16,500 27,900 26,400 29,500 36,600 44,500 49,700 34,700 20,700 33,300 33,600 25,100 38,000 45,500 48,500 57,400 87,000 81,300 96,500 52,900 53,200 41,400 43,300 63,500

World Production

686

44 116 99 47 39 7 34 91 113 188 64 38 63 80 186 1,030 14,800 13,800 25,900 1,600 787 89 112 71

Mass

Unit Value, Adjusted (985/t)

Apparent chromium Consumption

Chromium Secondary Primary Industry Government Chromite Ferroalloy Stocks and Metal Year Production Production Imports Exports Stocks Ore

Reported Consumption

[Metric tons (t), contained chr omium unless otherwise noted] Last modifi cation: January 13, 2003

TABLE C.3.1

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1924 1925 1926 1927 1928 1929 1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955

91 34 44 63 208 85 25 90 53 257 111 161 81 720 262 1,070 849 3,960 32,100 43,300 12,200 3,800 1,120 259 992 119 112 1,870 5,540 15,500 42,000 39,700

37,600 47,600 68,100 70,000 68,600 101,000 103,000 71,500 30,600 35,800 57,800 80,900 98,300 172,000 114,000 93,900 210,000 310,000 279,000 251,000 227,000 253,000 207,000 308,000 427,000 334,000 374,000 394,000 456,000 604,000 387,000 493,000 530 1,350 8,390 596 4,190 1,980 2,990 4,850 2,190 904 907 1,240 785 3,140 5,150

1,380 927 781 698 978

87,700 105,000 160,000 194,000 160,000 169,000 196,000 269,000 334,000 296,000

16,600 20,800 83,000 90,900 719,000 896,000 565,000 672,000 778,000 884,000 990,000 1,100,000 1,200,000 1,310,000 1,410,000 1,520,000 157,000 220,000 239,000 262,000 232,000 220,000 197,000 213,000 232,000 172,000 258,000 321,000 308,000 354,000 241,000 423,000 79,300 67,300 62,300 67,400 48,200 81,200 107,000 142,000 156,000 114,000 165,000

37,700 47,600 68,200 70,100 67,500 99,700 102,000 70,900 29,700 36,000 57,900 81,100 98,400 173,000 114,000 95,000 211,000 309,000 248,000 278,000 231,000 75,900 537,000 181,000 262,000 191,000 301,000 280,000 326,000 439,000 255,000 459,000 29 26 25 25 25 27 34 46 53 40 39 45 45 43 43 41 42 41 56 65 70 71 59 70 86 76 75 81 96 111 93 98 276 243 229 234 238 257 333 493 631 501 474 536 528 487 497 481 489 455 560 613 648 645 492 511 581 521 507 506 589 677 564 598

Appendix C (Continued)

90,200 95,300 112,000 124,000 140,000 197,000 173,000 127,000 101,000 123,000 183,000 241,000 317,000 392,000 362,000 347,000 457,000 509,000 637,000 542,000 411,000 318,000 352,000 521,000 644,000 650,000 720,000 823,000 963,000 1,130,000 924,000 1,040,000

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35,300 38,900 40,900 55,400 54,700 47,300 58,000 94,100 74,200 78,200 67,500 70,800 85,100 44,700 65,400 65,400 60,900 65,500

5,790 1,640 1,830 8,710 13,300 8,420 4,370 6,000 4,360 3,450 10,400 10,700 20,100 29,100 29,000 16,000 14,300 18,300 13,300 49,800 44,600 59,000 24,300 25,600 382,000 494,000 467,000 550,000 546,000 519,000 542,000 523,000 416,000 390,000 443,000 433,000 347,000 300,000 294,000 402,000 363,000 263,000 235,000 412,000 443,000 509,000 461,000 351,000 1,630,000 1,730,000 1,840,000 1,950,000 2,050,000 2,160,000 2,490,000 2,250,000 2,270,000 2,210,000 2,190,000 2,170,000 2,130,000 2,080,000 2,030,000 1,960,000 1,910,000 1,840,000 1,710,000 1,610,000 1,530,000 1,390,000 1,390,000 1,390,000 499,000 480,000 332,000 359,000 323,000 317,000 300,000 323,000 396,000 434,000 404,000 383,000 371,000 398,000 394,000 308,000 320,000 389,000 398,000 232,000 262,000 254,000 250,000 295,000

162,000 132,000 106,000 153,000 137,000 147,000 150,000 169,000 208,000 221,000 233,000 202,000 208,000 218,000 194,000 180,000 217,000 286,000 327,000 183,000 225,000 244,000 270,000 294,000 502,000 465,000 313,000 305,000 304,000 304,000 79,400 687,000 548,000 817,000 604,000 462,000 511,000 522,000 527,000 441,000 540,000 584,000 624,000 454,000 539,000 546,000 511,000 536,000

595,000 640,000 356,000 475,500 387,000 369,000 405,000 396,000 419,000 466,000 590,000 390,000 352,000 351,000 427,000 420,000 399,000 359,000 397,000 530,000 475,000 460,000 426,000 384,000

1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979

54,500 44,400 38,500 27,900 27,400 21,700

Mass 109 118 128 156 120 93 91 78 75 96 99 103 120 119 116 156 187 209 254 489 447 412 391 450

Unit Value (S/t)

653 686 723 872 659 508 492 415 395 497 497 502 563 528 487 628 729 767 840 1,480 1,280 1,110 978 1,010

Unit Value, Adjusted (985/t)

Apparent Chromium Consumption

Chromium Secondary Primary Industry Government Chromite Ferroalloy Stocks and Metal Year Production Production Imports Exports Stocks Ore

Reported Consumption

[Metric tons (t), contained chr omium unless otherwise noted] Last modifi cation: January 13, 2003 (Continued )

TABLE C.3.1

1,200,000 1,370,000 1,130,000 1,150,000 1,250,000 1,220,000 1,280,000 1,170,000 1,290,000 1,490,000 1,360,000 1,430,000 1,560,000 1,670,000 1,910,000 2,000,000 1,970,000 2,030,000 2,230,000 2,530,000 2,430,000 2,600,000 2,990,000 2,590,000

World Production

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688 Chromium(VI) Handbook

1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 59,100 66,000 62,000 75,900 81,400 86,100 85,100 99,000 124,000 97,300 101,000 96,100 102,000 92,000 99,000 112,000 98,000 120,000 104,000 118,000 139,000 122,000 421,000 463,000 214,000 211,000 323,000 304,000 363,000 322,000 449,000 380,000 346,000 310,000 324,000 330,000 273,000 415,000 362,000 350,000 384,000 476,000 453,000 239,000 29,900 33,200 11,300 12,000 34,400 40,200 38,700 10,600 15,500 27,200 16,300 18,200 17,900 20,900 33,200 26,700 51,000 30,300 62,400 60,300 86,300 43,000 249,000 261,000 195,000 171,000 128,000 122,000 119,000 123,000 161,000 156,000 141,000 134,000 133,000 118,000 118,000 110,000 107,000 99,600 83,100 84,400 46,300 48,800 1,290,000 1,290,000 1,290,000 1,290,000 1,250,000 1,260,000 1,270,000 1,240,000 1,220,000 1,260,000 1,270,000 1,250,000 1,280,000 1,210,000 1,170,000 1,120,000 1,070,000 1,020,000 929,000 910,000 825,000 816,000

233,000 209,000 135,000 83,400 136,000 143,000 107,000 141,000 160,000 163,000 120,000 115,000 116,000 109,000 104,000 105,000 87,200 108,000 83,600 229,000 230,000 143,000 208,000 210,000 188,000 191,000 231,000 243,000 214,000 226,000 208,000 218,000 218,000 206,000 193,000 190,000 225,000 192,000 217,000 220,000 196,000 631,000 483,000 331,000 299,000 446,000 351,000 397,000 438,000 553,000 415,000 433,000 413,000 378,000 485,000 387,000 553,000 464,000 494,000 528,000 551,000 589,000 325,000 668 679 608 779 779 722 675 750 1,070 1,170 1,090 1,140 1,060 907 961 1,330 995 1,350 1,080 859 904 1,020 1,320 1,220 1,030 1,280 1,220 1,090 1,000 1,080 1,470 1,540 1,350 1,360 1,230 1,020 1,060 1,430 1,030 1,370 1,080 840 856 942

2,830,000 2,550,000 2,390,000 2,540,000 2,950,000 3,180,000 3,530,000 3,450,000 3,870,000 4,320,000 3,950,000 4,060,000 3,420,000 3,080,000 3,090,000 4,530,000 3,660,000 4,330,000 4,460,000 4,750,000 4,680,000 3,970,000

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Appendix D

CONTENTS D.1 Comments on the Movie Erin Brockovich..............................................691 James A. Jacobs D.2 All about Erin ............................................................................................692 Walter Olson

D.1 Comments on the Movie Erin Brockovich

James A. Jacobs The movie Erin Brockovich, starring Julia Roberts and Albert Finney, was released in 2000 to an adoring public, critical acclaim, and over $125 million in sales. In a few months, the movie generated intense interest and national discussion among environmental professionals and nonprofessionals alike about chromium in water sources and the associated health issues. The technical issue of the movie was the quality of the water supply of Hinkley, California, a small desert town in San Bernardino County. In the Hinkley case, chromium(VI) (Cr(VI)) was used by Pacific Gas & Electric Company (PG&E) in cooling systems to prevent pipes from rusting. The runoff of Cr(VI) contaminated water on the PG&E property seeped into the ground and contaminated local water supplies. In the Hinkley case, approximately 36 claims were tried. The arbitration took about 24 months. At the end of the arbitration trial, PG&E settled the case and was required to compensate the plaintiffs $333 million, clean up the Cr(VI) contamination, and stop using Cr(VI) in their operations. Even after the settlement, scientific questions regarding Cr(VI) still exist. After reviewing the data from a purely scientific perspective, the personal illnesses supposedly attributed to the Cr(VI) exposure, and the descriptions of the actual Hinkley case, it is apparent that the causation of disease and 1-5667-0608-4/05/$0.00+$1.50 © 2005 by CRC Press LLC

691

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Cr(VI) exposure is not quite as simple as portrayed in the media or as determined by the arbitration results in the Hinkley case. There is still vigorous debate among the scientific community relating human dosage, toxicity, and disease to Cr(VI) exposure. Encouraged by the large settlement in the Hinkley case, more and more plaintiffs are lining up. Since the Hinkley case, more than 1,200 plaintiffs have filed a new lawsuit alleging that they too have a variety of illnesses that they suspect is related to Cr(VI) exposure. This time, the case is not just in Hinkley but also near PG&E's Kettleman Hills plant in Kings County, which pumps natural gas shipped from Texas to San Francisco. In addition to the much publicized Hinkley case, California has had numerous drinking water supply wells and water sources contaminated by Cr(VI) affecting the drinking water supplies to millions of people in the Glendale, California and surrounding Los Angeles area. Questions continue to arise regarding the safety of the drinking water supply. Currently, there is much uncertainty as to what daily dose of Cr(VI) is considered toxic and what quantity is acceptable to consume. The movie Erin Brockovich unfortunately shows the world through a simple, good versus evil lens. This view lacks a true understanding of the highly complex nature of Cr(VI) and the tenuous links between Cr(VI) exposure and specific human ailments and disease. Toxicologists will continue to debate the selection of a safe exposure concentration to Cr(VI) for the foreseeable future.

D.2 All about Erin

Walter Olson Heroine of screen and courtroom Erin Brockovich deserves a prize, all right. But not for what you think. It took a few months for the investigative journalists to overtake the Hollywood dream spinners, but by now it’s been pretty well established. What got left out of the blockbuster movie Erin Brockovich (now available at a video store near you) was in many ways juicier than what got put in. You’re probably familiar with the basic Erin story, as portrayed by the winsome Julia Roberts in a critically acclaimed performance. A spunky, foulmouthed single mother down on her luck, Erin gets herself hired with no experience for a routine job at a Los Angeles personal injury law firm. Soon Editors Note: Reprinted with permission, from October 2000 issue of Reason magazine. Copyright 2003 by Reason Foundation, 3415 S. Sepulveda Blvd. Suite 400, Los Angeles, CA 90034. www. reason.com. Also, the original document has been updated (minor style changes) by the Chromium(VI) Handbook editors.

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she stumbles into evidence that the townspeople of little Hinkley, California, are being poisoned by pollution in the water table originating with giant utility, Pacific Gas and Electric (PG&E), which runs a plant there. Brockovich begins doggedly accumulating evidence, convinces the lawyers in her firm they’ve got a case, and recruits townspeople to sue. Eventually, without admitting guilt, the utility coughs up an impressive $333 million settlement, a record for this kind of case. Not only did this result provide much-needed financial balm for both the townspeople and our heroine, but all the lawsuit organizing, as the writers at Oprah.com explain, assisted Brockovich in the task of "finding her true self." Although she had started out in life as a beauty pageant winner, winning the trust of the Hinkley townspeople "enabled Erin to grow and realize that inner beauty is most important." In fact, the challenge of working on the suit "allowed Erin to productively channel all of her pentup anger and frustration and realize her purpose in life: helping others." Litigation as a road to inner peace and helping others. It’s certainly an unusual story. After she spent years helping others, what more appropriate reward for Brockovich than to become the most famous environmental litigator in history, as by now she surely is? Though technically not a lawyer (her title at the California law firm of Masry & Vititoe is "research director"), she’s won more prizes and commendations than just about any regular lawyer you could name, including the Association of Trial Lawyers of America’s Champion of Justice Award, presented last July at its annual convention in Chicago; similar prizes from the California and Santa Clara County trial lawyer groups; commendations from the County of Los Angeles and the California Assembly; and the Court TV "Scales of Justice" Award. Clearly not unpleased at this nearly universal adulation, Brockovich has embarked on a career of touring the country to organize more toxic tort suits by communities in Pennsylvania, Idaho, and elsewhere. Just as all this personal growth and feistiness and indomitability were getting to be more than you could stand, along came critics who began sniping at the movie’s account of the Hinkley case. The first wave included such writers as Hudson Institute investigative science journalist Michael Fumento (a contributor to this [Reason] magazine), ABC 20/20 correspondent John Stossel, and New York Times science writer Gina Kolata. The headline above Kolata’s Times account sums up the main line of critique: "A Hit Movie Is Rated ‘F’ in Science." Few cases in this country of "disease clusters" linked to chemicals in groundwater have actually panned out upon investigation. Even the famous Woburn, Massachusetts, case dramatized in the book and movie A Civil Action (see "A Woburn FAQ," April 1999) left more questions than answers about whether a suspicious number of childhood leukemia cases had arisen from anything in the water supply. Only rigorous science can answer such questions as: Are people who drank water from a suspect source sicker than comparable populations elsewhere? If so, do they suffer from a particular, distinctive set of recurring symptoms

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(such as mercury-induced "Minimata disease" in 1950s Japan), or do they instead complain of a wide assortment of common ailments? Was the chemical exposure heavy, or something measured in parts per million or billion, only slightly above a threshold drawn to err on the side of extreme caution? And if the latter, are claims of injury from minor exposure consistent with what’s known to happen to workers or others who get exposed to much higher concentrations of the same substance? In the Hinkley case the alleged culprit was a pollutant called chromium(VI), (Cr(VI)). To judge by Fumento’s account, the problems with this theory were much the same as those commonly found in other toxic tort cases: The levels of contamination were orders of magnitude lower than those needed to induce health effects in experimental animals; the lawyers were seeking to blame the chromium for a wide assortment of ailments with no likely common origin; and science has not shown Cr(VI) to be a particularly lethal substance when ingested in trace quantities in drinking water. (When inhaled, as in welding fumes, Cr(VI) has been shown to cause cancer of the nose and lung, but very little can be inferred about the dangers of one route of exposure from the other.) Studies of persons known to have been exposed to waterborne Cr(VI) in Glasgow, Scotland, and elsewhere fail to confirm the Hinkley claims. Brockovich, to be sure, disputes most of this critique. She told journalist Kathleen Sharp (about whose Salon article we will have more to say in a moment) that she found "hundreds" of references in the scientific literature to a clear-cut pattern of toxicity from Cr(VI). But Sharon Wilbur, a toxicologist at the U.S. Department of Health and Human Services, told Sharp a very different story, namely that "Cr(VI) in water doesn’t harm humans. ‘It’s very unlikely that people could die from drinking Cr(VI) in the water, even over time,’ she said." Moreover, health studies found that the utility plant’s own workers, who were likely exposed to at least as much pollution as neighbors were, had a life expectancy exceeding the California average. If it had such good defenses, why did PG&E cough up $333 million to settle the case? Unlike most mass personal injury cases, the Hinkley matter was settled in private arbitration, which means we know less about how it was fought, and which arguments were raised, than we would had it proceeded in conventional litigation. But in her impressive investigation in Salon, Sharp unearths a few reasons why the utility might have ended up with such an unfavorable resolution of the case. One was that, if you credit allegations from the Brockovich side of the case and other sources, the first set of lawyers PG&E used may have engaged in misconduct, including privacy invasion by hired private investigators that would have caused a furor if proven. Additionally, it later developed that the two L.A. lawyers who teamed with Brockovich’s firm to handle the case, Thomas Girardi and Walter Lack, were on unusually friendly terms with some of the judges in the arbitration, who had joined the arbitration firm JAMS after retiring from the regular California bench. One judge had officiated at Girardi’s second

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695

wedding, another had flown in Girardi’s Gulfstream to attend the World Series, and so forth. Laurence Janssen, a partner in the L.A. office of the Washington law firm Steptoe & Johnson, told Sharp: "I became aware that I should absolutely stay away from JAMS or its retired judges when it came to any dealing with Tom Girardi …The common lore imparted to me was that it would be crazy to get in front of any JAMS arbitration with Girardi." Not long after the case was settled, generating $133 million in lawyers’ fees, Girardi and Lack just happened to invite the three Hinkley case arbitrators to join a week-long Mediterranean cruise for 90 guests, including 11 public and private judges, on a chartered ship. "One judge," reports Sharp, "called it ‘absolutely incredible’". A luxury yacht floated on azure waters; tuxedoed butlers balanced silver trays of free champagne; young bikini-clad ladies frolicked on the sun-splashed deck, according to retired Judge [William] Schoettler, who was a guest. "As another bare-chested judge remarked at the time: ‘This gives decadence a bad name.’" Naturally, this was all done for strictly educational purposes, under the aegis of a group Girardi and Lack ran called the Foundation for the Enrichment of the Law. Girardi told the Los Angeles Times that the trip included "an extensive professional program," which is supposed to make it OK under ethical rules, but Sharp reports that "retired judge Schoettler can’t recall anyone he knew actually attending a lecture." Eventually, the judges agreed to pay their expenses for the trip; the outcry over the cruise helped spur a California Supreme Court inquiry into the arbitration. Not a frame of this remarkable epilogue to the case, of course, made it into the movie Erin Brockovich. And the movie was equally misleading, it seems, in depicting a grateful Hinkley populace winning big. In the real world, many of the Hinkley clients feel they got the shaft from Brockovich’s firm of Masry & Vititoe, and are now proceeding to sue them. Specifically: • Of the $333 million settlement paid by PG&E, the lawyers kept a handsome 40% ($133 million) share, plus another $10 million to cover expenses. The clients say they were short on detail to back up the latter number. Worse, they say Masry, Brockovich, et al. held onto their money for 6 months after the settlement, a delay that appeared highly irregular to the experts Sharp checked with, while not paying interest or even returning their phone calls (the lawyers say the payments did include interest). Some with large awards also got steered toward certain financial advisers, among them Ed Masry’s son Louis. • When the payouts eventually came, many clients found the division of spoils mysterious, arbitrary, or worse. Divided among the 650 plaintiffs, the announced $196 million would provide about $300,000 per client. But an outside lawyer who interviewed 81 of the plaintiffs was told they received an average of $152,000, and Sharp reports that many long-term residents with presumably

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Chromium(VI) Handbook documented medical ailments got payments of $50,000 or $60,000. The allocation among clients was kept secret, which means they couldn’t get an accounting of who received what—must protect the privacy of the other plaintiffs, right? Moreover, writes Sharp, "there was no mention of the criteria, formula or method by which the money would be divided," other than a statement that the amounts would be based on clients’ medical records. Yet some residents say their medical records were never solicited. One elderly, ailing resident "blew up at one of the attorneys, who didn’t like his attitude," according to a fellow townsman, and "got a real bad deal," allotted in the end only $25,000. "Fairly or not," writes Sharp, "some residents say they saw a pattern in the distribution method. ‘If you were buddies with Ed and Erin, you got a lot of money,’ said [client Carol] Smith. ‘Otherwise, forget it.’" • Many clients (as well as members of the press) say they were unable to keep track of the case’s progress as it moved through arbitration. "We had no idea what was going on and weren’t allowed to watch," one plaintiff told Sharp. With help from the plaintiffs’ lawyers, Universal Studios, which made the movie, obtained a copy of the trial transcript–more than many of the actual plaintiffs in the case have yet managed to do.

When Sharp attempted to interview the lawyers on the Brockovich team, the resulting conversations were "short and explosive and terminated abruptly by the lawyers." And when an outside lawyer took an interest in the disgruntled clients’ case, Masry and fellow lawyers at once seized the offensive, suing him for allegedly slandering them and interfering with their business relationship with the clients; this slander suit was filed, then dropped two weeks later, then reinstated, then dropped again. So if you want to know how to win some of the most coveted prizes and accolades handed out by the American legal establishment, ask Erin Brockovich. She knows all about it.

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Appendix E CONTENTS E.1 Material Safety Data Sheet (MSDS) Chromium ...................................700 E.1.1 Product Identification.................................................................700 E.1.2 Hazardous Ingredients...............................................................700 E.1.3 Physical Data ...............................................................................700 E.1.4 Fire and Explosion Hazards Data ............................................700 E.1.5 Health Hazard Information ......................................................701 E.1.6 Emergency and First Aid Procedures......................................701 E.1.7 Reactivity Data ............................................................................702 E.1.8 Spill or Leak Procedures............................................................702 E.1.9 Special Protection Information .................................................702 E.1.10 Special Precautions .....................................................................702 E.2 International Chemical Safety Cards: Chromium................................703 E.3 Material Safety Data Sheet (MSDS) Chromic Oxide ...........................705 E.3.1 Product and Company Identification......................................705 E.3.2 Ingredients: Composition/Information ..................................705 E.3.3 Hazards Identification................................................................705 E.3.3.1 Emergency Overview .................................................705 E.3.3.2 Potential Health Effects..............................................705 E.3.4 First Aid Measures......................................................................706 E.3.5 Fire Fighting Measures ..............................................................706 E.3.5.1 Flammable Properties.................................................706 E.3.6 Accidental Release Measures....................................................706 E.3.7 Handling and Storage ................................................................707 E.3.8 Exposure Controls/Personal Protection .................................707 E.3.9 Physical and Chemical Properties ...........................................707 E.3.10 Stability and Reactivity..............................................................707 E.3.11 Toxicological Information..........................................................708 E.3.12 Ecological Information...............................................................708 E.3.13 Disposal Considerations ............................................................708 E.3.14 Transport Information................................................................709 E.3.15 Regulatory Information .............................................................709 E.3.16 Other Information.......................................................................709 1-5667-0608-4/05/$0.00+$1.50 © 2005 by CRC Press LLC

697

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E.4 Material Safety Data Sheet (MSDS) Chromium Sulfate N-Hydrate, 1630.........................................................................................710 E.4.1 Product Identification ...................................................................710 E.4.2 General Information .....................................................................710 E.4.3 Physical/Chemical Characteristics............................................. 711 E.4.4 Emergency/First Aid Procedure................................................. 711 E.4.5 Steps if Material Released/Spill .................................................712 E.5 Material Safety Data Sheet (MSDS) Tris(2,4-pentanedionato)chromium(III) ..................................................713 E.5.1 Product Information .....................................................................713 E.6 International Chemical Safety Card: Chromium Oxide......................715 E.7 International Chemical Safety Card: Chromium(VI) Oxide.............. 717 E.8 Material Safety Data Sheet (MSDS) Chromium Trioxide ...................719 E.8.1 Product and Company Identification......................................719 E.8.2 Ingredients: Composition/Information ..................................719 E.8.3 Hazards Identification................................................................719 E.8.3.1 Emergency Overview.................................................719 E.8.4 Potential Health Effects .............................................................720 E.8.4.1 Acute Effects ................................................................720 E.8.5 First Aid Measures......................................................................721 E.8.6 Fire Fighting Measures ..............................................................721 E.8.7 Accidental Release Measures....................................................722 E.8.8 Handling and Storage ................................................................722 E.8.9 Exposure Controls/Personal Protection .................................722 E.8.10 Physical and Chemical Properties ...........................................723 E.8.11 Stability and Reactivity..............................................................723 E.8.12 Toxicological Information..........................................................724 E.8.13 Ecological Information...............................................................724 E.8.14 Disposal Considerations ............................................................725 E.8.15 Transport Information................................................................725 E.8.16 Regulatory Information .............................................................725 E.8.17 Other Information.......................................................................726 E.9 Material Safety Data Sheet (MSDS) Chromium Trioxide, Chromic Acid .............................................................................................727 E.9.1 Product Information ...................................................................727 E.9.2 Product and Company Identification......................................727 E.9.3 Ingredients: Composition/information...................................727 E.9.4 Hazards Identification................................................................727 E.9.4.1 Emergency Overview.................................................727 E.9.4.2 Acute Effects ................................................................728 E.9.5 First Aid Measures......................................................................729 E.9.6 Fire Fighting Measures ..............................................................729 E.9.7 Accidental Release Measures....................................................730 E.9.8 Handling and Storage ................................................................730 E.9.9 Exposure Controls/Personal Protection .................................731 E.9.10 Physical and Chemical Properties ...........................................731

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699

E.9.11 Stability and Reactivity..............................................................732 E.9.12 Toxicological Information..........................................................732 E.9.13 Ecological Information...............................................................733 E.9.14 Disposal Considerations ............................................................733 E.9.15 Transport Information................................................................734 E.9.16 Regulatory Information .............................................................734 E.9.17 Other Information.......................................................................735 E.10 International Chemical Safety Card: Zinc Chromate ..........................735 E.11 Material Safety Data Sheet (MSDS) Chromium DILUT-IT® Analytical Conc. Std, 1g.Cr6+[sic] .....................................738 E.11.1 Product Identification ...............................................................738 E.11.1.1 General Information................................................738 E.11.2 Composition/Information on Ingredients ............................738 E.11.3 Hazards Identification ..............................................................738 E.11.3.1 Emergency Overview..............................................738 E.11.3.2 Potential Health Effects ..........................................739 E.11.3.3 Inhalation ..................................................................739 E.11.3.4 Ingestion....................................................................739 E.11.3.5 Skin Contact..............................................................739 E.11.3.6 Eye Contact...............................................................739 E.11.3.7 Chronic Exposure ....................................................740 E.11.3.8 Aggravation of Preexisting Conditions ...............740 E.11.4 First Aid Measures ....................................................................740 E.11.4.1 Inhalation ..................................................................740 E.11.4.2 Ingestion....................................................................740 E.11.4.3 Skin Contact..............................................................740 E.11.4.4 Eye Contact...............................................................740 E.11.5 Fire Fighting Measures.............................................................740 E.11.5.1 Fire .............................................................................740 E.11.5.2 Explosion...................................................................741 E.11.5.3 Fire Extinguishing Media.......................................741 E.11.5.4 Special Information .................................................741 E.11.6 Accidental Release Measures ..................................................741 E.11.7 Handling and Storage ..............................................................741 E.11.8 Exposure Controls/Personal Protection................................742 E.11.8.1 Ventilation System ...................................................742 E.11.8.2 Personal Respirators (NIOSH Approved) ...........742 E.11.8.3 Skin Protection .........................................................743 E.11.8.4 Eye Protection ..........................................................743 E.11.9 Physical and Chemical Properties..........................................743 E.11.10 Stability and Reactivity ............................................................743 E.11.11 Toxicological Information ........................................................744 E.11.12 Ecological Information .............................................................744 E11.12.1 Environmental Fate .................................................744 E.11.13 Disposal Considerations ..........................................................744 E.11.14 Transport Information ..............................................................744

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Chromium(VI) Handbook E.11.15 E.11.16

Regulatory Information............................................................745 Other Information .....................................................................746 E.11.16.1 Label Precautions ...................................................746 E.11.16.2 Label First Aid ........................................................746 E.12 International Chemical Safety Card: Chromium Oxide....................747

E.1 Material Safety Data Sheet (MSDS) Chromium * E.1.1

Product Identification

Trade Name: Synonym: Chemical Nature: Formula: CAS Number: Molecular Mass: E.1.2

Chromium Chromium Metal, Elemental Chromium Metallic Element Cr 7440-47-3 51.996

Hazardous Ingredients

Hazardous Components: Chromium Sec. 302: no Sec. 304: yes Sec. 313: yes

% 0 to 100%

OSHA/PEL 1 mg/m3

ACGIH/TLV 0.5 mg/m3

Hazardous Materials Information System (HMIS) Ratings: Health: 2 Flammability: 3 (as dust or powder) Reactivity: 0 Protective Equipment: F: glasses, gloves, apron, dust mask E.1.3

Physical Data

Boiling Point: Melting Point: Specific Gravity: Vapor Pressure: Vapor Density: % Volatiles: Appearance and Odor: Solubility in water: E.1.4

2,672 ° C 1,857 ° C 7.19 1 mmHg at 1,616 ° C No Data N/A Steel gray, lustrous metal, no odor Insoluble

Fire and Explosion Hazards Data

Flash Point (Method Used): N/A Autoignition Temp.: 400 ° C (powder) *

Editors have updated this "text" document.

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701

Flammable Limits: Upper: N/A Lower: N/A Extinguishing Media: Noncombustible except in powder form use water spray or fog, dry chemical extinguishing agents, carbon dioxide, dry sand. Special Fire Fighting Procedures: Wear NIOSH/MSHA approved self contained breathing apparatus (SCBA) and protective clothing. Fumes from fire are hazardous. Isolate runoff to prevent environmental pollution. Unusual Fire & Explosion: Ignites and is potentially explosive (as dust/ powder) in atmospheres of carbon dioxide (CO2). Chromium reacts violently or explosively when heated with ammonium nitrate (NH4NO3) and bromine pentafluoride (BrF5). It has an incandescent reaction with nitrogen oxide (NOX) or sulfur dioxide (SO2). Powders prepared by evaporation of mercury (Hg) form chromium amalgam may be pyrophoric.

E.1.5

Health Hazard Information

Effects of Exposure: Chromium(VI), a form of chromium, is a confirmed human carcinogen with experimental tumorigenic data. Also, chromium(VI) is a human poison by ingestion with adverse gastrointestinal effects. Acute Effects: Inhalation: May cause a red, dry throat. Ingestion: May cause gastrointestinal disorders. Skin: May cause abrasive irritation. Eye: May cause abrasive irritation. Chronic Effects: Inhalation: May cause histologic fibrosis of lungs, nasal and/or lung cancer. Ingestion: No chronic health effects recorded. Skin: No chronic health effects recorded. Eye: No chronic health effects recorded. Target Organs: May affect the respiratory system. Medical Conditions Generally Aggravated by Exposure: Pre-existing respiratory disorders, pulmonary functions and asthma. Carcinogenicity: NTP: Yes IARC: Yes OSHA: Yes

E.1.6

Emergency and First Aid Procedures

Inhalation: Remove victim to fresh air. Keep warm and quiet, give oxygen if breathing is difficult and seek medical attention. Ingestion: Give 1 to 2 glasses of milk or water and induce vomiting. Seek medical attention immediately. Never induce vomiting or give anything by mouth to an unconscious person. Skin: Remove contaminated clothing, brush material off skin, wash affected area with mild soap and water. Seek medical attention if symptoms persist. Eye: Flush with lukewarm water, lifting upper and lower eyelids for at least 15 minutes. Seek medical attention if symptoms persist.

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Chromium(VI) Handbook Reactivity Data

Stability: Stable Conditions to Avoid: Grinding, crushing, and melting may produce dust and fumes which may require control. Incompatibility (Material to Avoid): Powder incompatible with ammonium nitrate (NH4NO3), hydrogen peroxide (H2O2), nitric oxide/nitrogen monoxide (NO), potassium chlorate (KClO3), sulfur dioxide (SO2), mercury (Hg). Otherwise, avoid strong oxidizing agents, ammonium nitrite (NH4NO2), bromine pentafluoride (BrF5), and carbon dioxide (CO2). Hazardous Decomposition Products: Toxic chromium oxides fumes Hazardous Polymerization: Will not occur E.1.8

Spill or Leak Procedures

Steps to be Taken in Case Material is Released or Spilled: Wear appropriate respiratory and protective equipment specified in Section E.1.9, “Special Protection Information.” Isolate spill area, provide ventilation, and extinguish sources of ignition. Vacuum spill using a high-efficiency particulate absolute (HEPA) air filter and place in a closed container for proper disposal. Take care not to raise dust. Use nonsparking tools. Waste Disposal Method: Consult Local, State, and Federal Regulations for proper disposal procedures. E.1.9

Special Protection Information

Respiratory Protection (Specify Type): NIOSH/MSHA approved respirator for dusts and mists. Ventilation: Use local exhaust to maintain concentration at or less than PEL, TLV concentrations. Protective Gloves: Rubber gloves Eye Protection: Safety glasses Other Protective Equipment: Protective gear suitable to prevent contamination E.1.10

Special Precautions

Precautions to be Taken in Handling and Storage: Store in cool, dry area. Store in tightly sealed container. Protect against physical damage. Store away from acids and oxidizers. Wash thoroughly after handling. Precautionary Labeling: CAUTION! Do not swallow or inhale. Avoid contact with skin and eyes. Wash Thoroughly after handling. Keep container closed. Work Practices: Implement engineering and work practice controls to reduce and maintain concentration of exposure. Use good housekeeping and sanitation practices. Do not use tobacco or food in work area. Wash thoroughly before eating or smoking. Do not blow dust off clothing or

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skin with compressed air. Maintain eyewash capable of sustained flushing, safety drench shower and facilities for washing. The above information is accurate to the best of our knowledge. However, since data, safety standards, and government regulations are subject to change, and the conditions of handling and use or misuse are beyond our control, ESPI makes no warranty, either expressed or implied, with respect to the completeness or continuing accuracy of the information contained herein, and disclaims all liability for reliance thereon. Users should satisfy themselves that they have all current data relevant to their particular use. Issued by: S. Dierks Date: June 2002 Electronic Space Products International 1050 Benson Way Ashland OR 97520 Tel: (800) 638-2581 Fax: (541) 488-8313 e-mail: [email protected]

E.2 International Chemical Safety Cards: Chromium CHROMIUM

ICSC: 0029 CHROMIUM Chrome (powder) Cr (metal) Atomic mass: 52.0

CAS # 7440-47-3 RTECS # GB4200000 ICSC # 0029 Types of Hazard/ Exposure

Acute Hazards/ Symptoms

Fire

Combustible if in very fine powder, gives off irritating or toxic fumes (or gases) in a fire

No open flames if in powder form

Finely dispersed particles form explosive mixtures in air

Prevent deposition of dust; closed system, dust explosion-proof electrical equipment and lighting

Explosion

Exposure

Prevention

Prevent dispersion of dust; strict hygiene

First aid/fire Fighting In case of fire in the surroundings: all extinguishing agents allowed

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Inhalation

Cough

Skin

Redness

Local exhaust or breathing protection Protective gloves

Eyes

Redness

Face shield

Ingestion

Do not eat, drink, or smoke during work

Spillage disposal

Storage

Vacuum spilled material. Carefully collect remainder, then remove to safe place (extra personal protection: P2 filter respirator for harmful particles).

Fireproof. Separated from strong oxidants.

CHROMIUM I M P O R T A N T D A T A

Fresh air, rest Remove contaminated clothes; rinse skin with plenty of water or shower; refer for medical attention First rinse with plenty of water for several minutes (remove contact lenses if easily done), then take to a doctor Rinse mouth Packaging & labeling

ICSC: 0029 Physical State; Appearance: Steel Grey Lustrous Metal Physical Dangers: Dust explosion possible if in powder or granular form, mixed with air Chemical dangers: Reacts violently with strong oxidants such as hydrogen peroxide, (H2O2), causing fire and explosion hazard. Reacts with diluted hydrochloric (HCl) and sulfuric (H2SO4) acids. Incompatible with alkalis and alkali carbonates. Occupational exposure limits (OELs):

Routes of exposure: The substance can be absorbed into the body by inhalation of its aerosol and by ingestion. Inhalation risk: Evaporation at 20 °C is negligible; a harmful concentration of airborne particles can, however, be reached quickly when dispersed. Effects of short-term exposure: Effects of long-term or repeated exposure: Repeated or prolonged contact may cause skin sensitization.

TLV: ppm; 0.5 mg/m 3 (as TWA) (ACGIH 1994–1995). Physical properties Environmental data

Boiling point: 2,642 °C Melting point: 1,900 °C

Relative density (water = 1): 7.14 Solubility in water: none

Notes Explosive limits are unknown in literature. Depending on the degree of exposure, periodic medical examination is indicated.

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E.3 Material Safety Data Sheet (MSDS) Chromic Oxide * E.3.1

Product and Company Identification

Common name: Chemical name: Synonyms:

Chemical formula:

Chromic Oxide, Chromium(III) Oxide Metal Oxide G-4099, G-5099, G-6099, G-8599, G-112, G-120, M-100, GA-4090, GA-6090 ACCROX R, ACCROX S, ACCROX C, Chromium Oxide Metallurgical Cr2O3

Product CAS no:. Company: Address:

1308-38-9 Chromic Oxide RTECS: GB6475000 Elementis Chromium LP 3800 Buddy Lawrence Drive PO Box 9912 Corpus Christi, TX 78469 (361) 880-7725 FAX: (361) 866-1462 (361) 883-6421

City, state, zip: Phone: Emergency phone: E.3.2

Ingredients: Composition/Information

Ingredient Chromic Oxide Chromium (III) Oxide (Cr2O3)

E.3.3 E.3.3.1

Mass % > 98

PEL-OSHA 0.5 mg/m3 (CrIII Compounds)

TLV-ACGIH 0.5 mg/m3 (CrIII Compounds)

LD50/LC50 Route/Species No Data

Hazards Identification Emergency Overview

Odorless, nonflammable green powder which can cause skin, eye, and respiratory irritation. May have adverse effects if ingested. Long-term exposure may adversely affect the lungs. Avoid breathing dusts. E.3.3.2 Potential Health Effects Primary route(s) of entry: Inhalation, ingestion, skin and eye contact Eye: Contact with dusts may cause irritation or conjunctivitis. Skin: Contact may cause irritation and erythema. Repeated contact may cause dermatitis. *

Modern name is chromium(III) oxide.

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Ingestion: Ingestion may cause nausea, vomiting, and diarrhea. Inhalation: Inhalation of dusts may irritate the nose, throat and upper respiratory tract. Chronic: Long-term exposure may damage the lungs and respiratory tract. Target Organs: Respiratory system, eyes, skin. Medical Conditions Aggravated by Exposure: May exacerbate preexisting lung and skin conditions. Signs and Symptoms: Dermatitis, general eye, skin, and respiratory irritation. Carcinogenicity: IARC: no*, NTP: no, OSHA: no. E.3.4

First Aid Measures

Eye Contact: Flush eyes with large amounts of lukewarm water for 15 minutes. If irritation persists, seek medical attention. Skin Contact: Remove contaminated clothing and wash skin thoroughly with soap and water. If irritation persists, seek medical attention. Thoroughly clean contaminated clothes and shoes before reuse. Inhalation: Remove to fresh air. If breathing is difficult, administer oxygen. If breathing has stopped, give artificial respiration. Seek medical attention immediately. Other: Adverse effects are not anticipated. If substantial ingestion occurs, seek medical attention. E.3.5 E.3.5.1

Fire Fighting Measures Flammable Properties

HMIS Hazard Classification: Health: 1, Flammability: 0, Reactivity: 0 Flammable Limits: LEL: Not Applicable; UEL: Not Applicable Extinguishing Media: Use media appropriate for surrounding fire. Fire and Explosion Hazards: Fire conditions may produce small amounts of chromium(VI) and other oxidation products. Fire Fighting Equipment: Firefighters should wear a NIOSH/MSHA-approved full-facepiece self-contained breathing apparatus (SCBA) operated in positive pressure mode and full turn out gear or bunker gear. E.3.6

Accidental Release Measures

Isolate hazard area and deny entry to unauthorized and/or unprotected personnel. Cleanup personnel should wear appropriate protective equipment including respiratory protection as necessary. Carefully shovel or sweep * IARC considers chromium(III) compounds unclassifiable as to carcinogenicity to humans (Group 3).

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any spilled chromium(III) oxide into a clean, dry, closed container. Dike spilled liquid material with suitable inert sorbent (i.e., sand, soil, vermiculite) and place in clean, dry container for later recycle or disposal. E.3.7

Handling and Storage

Store away from incompatible materials. Keep containers closed when not in use. Wash hands thoroughly after handling, before leaving the work area, and before meals or breaks. Minimize dust creation. Remove any contaminated clothing and launder before re-use. Keep away from food. E.3.8

Exposure Controls/Personal Protection

Respiratory Protection: MSHA/NIOSH-Approved filter type dust respirator in accordance with the requirements of 29 CFR 1910.134. Skin Protection: Protective gloves should be worn to prevent skin contact. Eye Protection: Safety glasses or chemical safety goggles as necessary to prevent eye contact. Engineering Controls: Local exhaust ventilation for procedures which generate dust. Personnel Sampling: Air sampling for chromium(III): Mixed cellulose ester filter, 0.8 µm (NIOSH 7024). Other: Emergency eyewash stations and safety showers should be readily available. E.3.9

Physical and Chemical Properties

Appearance: Odor: Boiling point: Vapor pressure (mmHg): Vapor density (Air = 1): Solubility in water: Specific gravity (H2O = 1) Melting point: Evaporation rate (H2O = 1): pH: % Volatile: E.3.10

Green powder Odorless 4,000 ° C Not Applicable Not Applicable Insoluble 5.1 2,266 °C Not Applicable No Data Not Applicable

Stability and Reactivity

Stability: Stable under normal conditions and use. Incompatibility: Cr2O3 may react with molten alkali at high temperatures under oxidizing conditions. May react with lithium (Li), nitroalkanes

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Chromium(VI) Handbook

(CxHy(NO2)z), dirubidium acetylide [Rb2(RC C)2], oxygen difluoride (OF2) and other strong oxidizers. Reaction with chlorine trifluoride (ClF3) produces flame. Contact between glycerol (C3H8O3) and Cr2O3 may produce an explosion. Hazardous Decomposition Products: A small amount (less than 0.1% as Cr) may convert to chromium(VI) if this product is exposed to high temperatures. Hazardous Polymerization: Will not occur.

E.3.11

Toxicological Information

Chromium(III) has relatively low toxicity owing to poor cell membrane permeability and noncorrosivity. Ingestion: Cr2O3 has no established oral toxicity. Skin: Dermatitis has been reported in workers handling chromium(III) compounds. Eye: No data Inhalation: No data Chronic: Preliminary study of 300 workers exposed for 20–25 years to Cr(III) as Cr2O3 and chromium(III) sulfate Cr2(SO4)3 showed no differences from controls in respiratory illness and clinical or blood studies. Cr2O3 fed to rats in dosages up to 5% for 2 years produced no treatment related effects (NOEL). Subchronic: No data

E.3.12

Ecological Information

Fate: Generally Cr2O3 is removed from the atmosphere through wet and dry deposition. Cr2O3 particles <20 µm aerodynamic diameter may remain airborne for long periods and may be transported long distances. Cr2O3 is not expected to be transported from the troposphere to the stratosphere. Cr2O3 is expected to remain unchanged following release into soil. The predominant form of chromium in soil probably is as insoluble Cr2O3. Ecotoxicity: Bioaccumulation of chromium from soil to above ground parts of plants is unlikely. There is no indication of biomagnification of chromium along the terrestrial food chain (soil–plant–animal).

E.3.13

Disposal Considerations

Product does not exceed the RCRA extraction procedure limit of 5 ppm for total soluble chromium as shipped from the manufacturer. Wastes from this product may or may not be classified as a hazardous waste. Chemical processing of this product (particularly at high temperatures) can cause chemical reactions which produce substances which will exceed the RCRA limit. Wastes from this product should be tested to determine the proper waste

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709

Appendix E

classification. Incineration is not recommended as some Cr(III) may convert to the Cr(VI). Recycle, reclaim and dispose of in accordance with applicable local, state, and federal regulations. Dispose per 40 CFR Part 261 and 262.

E.3.14

Transport Information

DOT Classification: Not Classified E.3.15

Regulatory Information

OSHA Hazard Communication Rule, 29 CFR 1910.1200: Product is hazardous under criteria of this rule. SARA Hazard Category: This product has been reviewed according to the USEPA Hazard Categories promulgated under Sections 311 and 312 of the Superfund Amendment and Reauthorization Act of 1986 (SARA Title III) and is considered, under applicable definitions, to meet the following categories: Immediate Health Hazard; Delayed Health Hazard. SARA 313 Information: Cr2O3 is subject to the reporting requirements of Section 313 of Title III of the Superfund Amendments and Reauthorization Act of 1986 and 40 CFR Part 372 under the broad class of chromium compounds. Resource Conservation and Recovery Act (RCRA) 40 CFR 261 Subpart C: If this product becomes a waste, it may or may not be characterized as a hazardous waste (D007) as prescribed by the Resource Conservation and Recovery Act (RCRA) regulations. Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), 40 CFR Part 117, Part 304: Cr2O3 is a CERCLA hazardous substance included under the broad category of chromium compounds. No reportable quantity (RQ) has been listed for this broad class of compounds. Clean Air Act (CAA): Chromium is designated as a hazardous air pollutant under Section 112 of the CAA. California Proposition 65: Cr2O3 is covered under Proposition 65 for Cr(VI). Appropriate warnings should be given.

E.3.16 Key: ACGIH IARC NIOSH NTP

Other Information American Conference of Governmental Industrial Hygienists International Agency for Research on Cancer National Institute for Occupational Safety and Health National Toxicology Program

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710 MSHA OSHA TLV PEL

Chromium(VI) Handbook Mine Safety and Health Administration Occupational Safety and Health Administration Threshold Limit Value Permissible Exposure Limit

NOTE:

The information given above is believed to be accurate and was obtained from sources believed to be reliable. However, the information is provided without any representation or warranty, expressed or implied, with respect to its accuracy or completeness. It is the user’s responsibility to determine the suitability of this product and relevance of this information for their use. We do not assume liability resulting from the use, handling, storage and disposal of this product.

E.4 Material Safety Data Sheet (MSDS) Chromium Sulfate N-Hydrate, 1630 E.4.1

Product Identification

FSC: 6810 NIIN: 00N053537 Manufacturer’s CAGE: 70829 Part No. Indicator: A Part Number/Trade Name: CHROMIUM SULFATE N-HYDRATE, 1630 E.4.2

General Information

Company’s Name: GENERIC CHROMIUM MANUFACTURING CO. Company’s Address: 123 Main St., Littletown, NY 01234 USA Company’s Emerg Ph #: (800) CRINORM; (800) 424-9300(CHEMTREC) Company’s Info Ph #: (800) CHROMIUM Record No. For Safety Entry: 001 TOT Safety Entries This Stk#: 001 Date MSDS Prepared: 2000 Safety Data Review Date: 2001 MSDS Serial Number: BVQVN Ingredients/Identity Information Proprietary: no Ingredient: CHROMIUM(III) SULFATE (Cr2(SO4)3) (SARA III), 90% to 100% Ingredient Sequence Number: 01 NIOSH (RTECS) Number: GB7200000 CAS Number: 10101-53-8 OSHA PEL: 0.1 mg/m3 ACGIH TLV: 0.05 mg/m3

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Appendix E E.4.3

711

Physical/Chemical Characteristics

Appearance and Odor: GREEN OR VIOLET CRYSTALS WITH NO ODOR. Melting Point: N/A Vapor Density (Air = 1): N/A Specific Gravity: 1.80 (H2O = 1) Evaporation Rate and Ref: N/A Solubility in Water: Appreciable (>10%) Percent Volatiles by Volume: 0 Fire and Explosion Hazard Data Flash Point: N/A Extinguishing Media: use extinguishing media appropriate for surrounding fire Special Fire Fighting Procedure: use NIOSH/MSHA-approved SCBA (selfcontained breathing apparatus) and full protective equipment (FP N) Unusual Fire and Explosion Hazard: none specified by manufacturer Reactivity Data Stability: yes Condition to Avoid (Stability): heat Materials to Avoid: none specified by manufacturer Hazardous Decomposition Products: toxic gases produced: sulfur dioxide (SO2) Hazardous Polymerization Occur: no Conditions to Avoid (Polymerization): not relevant Health Hazard Data LD50-LC50 Mixture: none specified by manufacturer Route of Entry—Inhalation: yes Route of Entry—Skin: yes Route of Entry—Ingestion: no Health Hazard Acute and Chronic: contact with skin or eyes may cause irritation. inhalation of dust may cause irritation to upper respiratory tract Carcinogenicity—NTP: no Carcinogenicity—IARC: no Carcinogenicity—OSHA: no Explanation Carcinogenicity: not relevant Signs/Symptoms of Overexposure: see health hazards Medical Condition Aggravated by Exposure: none specified by manufacturer E.4.4

Emergency/First Aid Procedure

Inhalation: Remove to fresh air. support breathing (give oxygen/artificial respiration) (FP N). Ingestion: If conscious, immediately induce vomiting. Eyes: Immediately flush eyes with plenty of water for at least 15 minutes. Skin: Flush skin with water Precautions for Safe Handling and Use

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712 E.4.5

Chromium(VI) Handbook Steps if Material Released/Spill

Wear NIOSH/MSHA approved self-contained breathing apparatus and full protective clothing. With clean shovel, carefully place material into clean, dry container and cover; remove from area. Flush spill area with water Neutralizing Agent: none specified by manufacturer Waste Disposal Method: dispose in accordance with all applicable federal, state, and local environmental regulations. USEPA hazardous waste number: D007 (EP [Extraction Procedure] toxic waste) Precautions-Handling/Storing: keep container tightly closed. suitable for any general chemical storage Other Precautions: harmful if swallowed; causes irritation; avoid contact with eyes, skin, clothing Control Measures Respiratory Protection: none required where adequate ventilation conditions exist. if airborne concentration is high, use an appropriate NIOSH/MSHA approved respirator or dust mask Ventilation: use general or local exhaust ventilation to meet tlv requirements Protective Gloves: rubber gloves Eye Protection: safety glasses with sideshield Other Protective Equipment: uniform Work Hygienic Practices: wash thoroughly after handling Supplementary Safety & Health Data: none specified by manufacturer Transportation Data Disposal Data Label Data Label Required: yes Technical Review Date: 28 September 1994 Label Date: 23 September 1994 Label Status: G Common Name: chromium sulfate n-hydrate, 1630 Chronic Hazard: no Signal Word: Caution! Acute Health Hazard: Slight: X Contact Hazard: Slight: X Fire Hazard: None: X Reactivity Hazard: None: X Special Hazard Precautions: acute: contact with skin or eyes may cause irritation, inhalation of dust may cause irritation to upper respiratory tract; chronic: none listed by manufacturer Protect Eye: yes Protect Skin: yes Protect Respiratory: yes Label Name: J. T. Baker Inc. Label Street: 222 Red School Lane

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713

Appendix E Label Label Label Label Label

City: Phillipsburg State: New Jersey Zip Code: 08865 Country: United States Emergency Number: (201) 859-2151; (800) 424-9300(CHEMTREC)

E.5 Material Safety Data Sheet (MSDS) Tris(2,4-pentanedionato)chromium(III) E.5.1

Product Information

This product is a chemical substance and is intended to be used by persons having chemical knowledge and skill, at their own discretion and risk. IDENTITY: Cr(III)-AA Section I. Manufacturer’s Name: Address: Telephone Number for Information: Emergency Telephone Number: Data Prepared:

Generic Chromium Manufacturing Co. 123 Main St., Littletown, NY, 01234 USA (800) CRINFORM (800) CHROMIUM 1994

Section II. Identity Information Chemical Name: CAS Registry Number: OSHA standard-air: ACGIH TLV-TWA:

Tris(2,4-pentanedionato)chromium(III) 21679-31-2 TWA 1 mg(Cr)/m3 FEREAC 39,23540,74 0.5 mg(Cr)/m3 85INA8 5,139,86

Section III. Physical/Chemical Characteristics Melting Point: Boiling Point: Specific Gravity (Water = 1): Vapor Pressure: Vapor Density (Air = 1): Evaporation Rate (Butyl Acetate = 1): Solubility in Water: Appearance and Odor:

211 °C to 216 °C Not applicable Not applicable Not applicable Not applicable Not applicable Insoluble Reddish purple crystal

Section IV. Fire and Explosion Hazard Data Flash Point (Method Used): Flammable Limits: Extinguishing Media: Special Fire Fighting Procedures:

Not available Not available Carbon dioxide (CO2), dry chemical powder, foam, water Wear protective clothing, respirator, chemical safety goggles, rubber boots, and heavy rubber gloves

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714 Unusual Fire and Explosion Hazards: Section V. Reactivity Data Stability: Conditions to Avoid: Incompatibility (Materials to Avoid): Hazardous Decomposition/Byproducts:

Hazardous Polymerization: Conditions to Avoid: Section VI. Health Hazard Data Route(s) of Entry: Inhalation ? Skin ? Ingestion Health Hazards (Acute and Chronic):

Carcinogenicity: Chronic Effects: Medical Conditions Emergency, First Aid Procedures:

Chromium(VI) Handbook Fire may produce irritating or poisonous gases.

Stable Heat, sunlight, high temperature Strong oxidizing agents When decomposed it may emit toxic fumes of carbon monoxide (CO) and nontoxic CO2 (asphyxiation hazard) Will not occur Not applicable

Yes Yes Yes Harmful if inhaled or swallowed. May cause eye and skin irritation. Material is irritating to mucous membranes and upper respiratory tract. Listed in RTECS. RTECS No.GB7575000 Damage to the lungs. Generally Aggravated by Exposure : Not available In case of contact with eyes, immediately flush eyes with copious amounts of water for at least 15 minutes. In case of contact, immediately wash skin with soap and copious amounts of water. Assure adequate flushing of the eyes by separating the eyelids with fingers. If inhaled, remove to fresh air. If not breathing, give artificial respiration. If breathing is difficult, give oxygen. If ingested, wash out mouth with water. Call a physician. Wash contaminated clothing and shoes before reuse.

Section VII. Precautions for Safe Handling and Use Steps to be Taken in Case Material is Released or Spilled: Wear respirator, chemical safety goggles, rubber boots, and heavy rubber gloves. Sweep up, place in a bag and hold for waste disposal. Ventilate area and wash spill site after material pickup is complete. Avoid raising dust. Waste Disposal Method: The material should be dissolved in: (1) water, (2) acid solution, or (3) oxidized to a water-soluble state.

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715

Appendix E

Precipitate the material as a sulfide (S 2–), adjusting the pH of the solution to 7 to complete precipitation. Filter the insolubles and dispose of them in a hazardous-waste site. Destroy any excess sulfide with sodium hypochloride (NaClO). Precautions to be taken in Handling and Storing:

Other Precautions: Section VIII. Control Measures Respiratory Protection (Specify Type): Ventilation, Local Exhaust: Special: Mechanical (General): Other: Protective Gloves: Eye Protection: Other protective Clothing or Equipment: Work/Hygienic Practices:

Wear appropriate NIOSH/MSHAapproved respirator, chemical-safety goggles. Compatible chemical-resistant gloves, other protective clothing. Mechanical exhaust required. Safety shower and eye bath. Do not breathe dust. Do not get in eyes, on skin, or on clothing. Wash thoroughly after handling. Harmful solid. Keep tightly closed. Protect from metal. Store in a cool and dry place.

Necessary. Fume hood. NA Necessary NA Compatible chemical-resistant gloves. Chemical-safety goggles. Necessary Wash thoroughly after handling. Access to a safety shower and eye-wash. Do not permit eating, drinking, or smoking near material.

The above information is believed to be correct but does not purport to be all-inclusive and shall be used only as a guide. The manufacturer shall not be held liable for any damage resulting from handling or from contact with the above material.

E.6 International Chemical Safety Card: Chromium Oxide CHROMIUM(IV) OXIDE Chromium Dioxide, Chromium(IV) Oxide (Title updated by editors of this book) CrO2 Molecular mass: 84.00 ICSC # 1310 CAS # 12018-01-8 RTECS # GB6400000

ICSC: 1310

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716

Chromium(VI) Handbook

Types of Hazard/ Exposure

Acute Hazards/ Symptoms

First Aid/Fire Fighting

Prevention

Fire Explosion Exposure

Prevent Dispersion of Dust

Inhalation

Cough.

Skin

Redness.

Eyes

Local exhaust or breathing protection. Protective gloves.

Rinse and then wash skin with water and soap.

Safety spectacles.

Ingestion Spillage Disposal

Packaging & Labeling

Storage Vacuum spilled material. Sweep spilled substance into containers; if appropriate, moisten first to prevent dusting. (Extra personal protection: P2 filter respirator for harmful particles.)

R: S:

Prepared in the context of cooperation between the International Programme on Chemical Safety & the Commission of the European Communities (C) IPCS CEC 2002. No modifications to the International version have been made except to add the OSHA PELs, NIOSH RELs, and NIOSH IDLH values.

ICSC: 1310

I M

Physical State; Appearance: Brown-Black Powder

Routes Of Exposure: The substance can be absorbed into the body by inhalation.

Physical Dangers:

Inhalation Risk: Evaporation at 20 °C is negligible; a harmful concentration of airborne particles can, however, be reached quickly.

P O R

Chemical Dangers:

T A N T D A T A

Occupational Exposure Limits: TLV not established.

Effects Of Short-Term Exposure:

Effects of Long-Term or Repeated Exposure: Repeated or prolonged contact with skin may cause dermatitis. Lungs

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717

Appendix E

may be affected by repeated or prolonged exposure, resulting in fibrosis. Physical Properties

Decomposes below melting point: 250 °C to 500 °C Density: 4.9 g/cm3

Solubility in water: none

Environmental Data

E.7 International Safety Card: Chromium(VI) Oxide CHROMIUM(VI) OXIDE

ICSC: 1194

Chromic trioxide Chromic acid Chromic anhydride CAS # RTECS # UN ## EC #

1333-82-0 CrO3 GB6650000 Molecular mass: 100.01 1463 (anhydrous) 024-001-00-0

Types of Hazard / Exposure

Acute Hazards/ Symptoms

Fire

Not combustible but enhances combustion of other substances. Many reactions may cause fire or explosion.

Prevention No contact with combustible substances and reducing agents.

Explosion

Skin

Powder, water spray, foam, carbon dioxide (CO2).

In case of fire: keep drums, etc., cool by spraying with water.

Exposure

Inhalation

First Aid/Fire Fighting

Cough. Labored breathing. Shortness of breath. Sore throat. Wheezing. Redness. Skin burns. Pain.

Prevent dispersion of dust! Avoid all contact! Avoid inhalation of fine dust and mist. Ventilation (not if powder), local exhaust, or breathing protection. Protective gloves. Protective clothing.

In all cases consult a doctor! Fresh air, rest. Halfupright position. Artificial respiration if indicated. Refer for medical attention. Remove contaminated clothes. Rinse skin with plenty of water or shower.

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Chromium(VI) Handbook Eyes

Ingestion

Redness. Pain. Permanent loss of vision. Severe deep burns.

Safety spectacles, face shield, or eye protection in combination with breathing protection.

Abdominal cramps.

Do not eat, drink, or smoke during work. Wash hands before eating.

First rinse with plenty of water for several minutes (remove contact lenses if easily possible), then take to a doctor. Rinse mouth. Do NOT induce vomiting. Give plenty of water to drink. Refer for medical attention.

Spillage Disposal

Packaging & Labelling

Do NOT wash away into sewer. Sweep spilled substance into containers; if appropriate, moisten first to prevent dusting. Carefully collect remainder, then remove to safe place. Do NOT absorb in sawdust or other combustible absorbents. (Extra personal protection: complete protective clothing including self-contained breathing apparatus [SCBA]).

Do not transport with food and feedstuffs. EU Classification Symbol: O, T R: 49-8-25-35-43 S: 53-45 Note: E UN Classification UN Hazard Class: 5.1 UN Subsidiary Risks: 8 UN Pack Group: II

Emergency Response Transport Emergency Card: TEC (R)-866 NFPA Code: H3; F0; R1; OX CHROMIUM(VI) OXIDE Physical State; Appearance: Odorless, Dark Red Deliquescent Crystals, Flakes, or Granular Powder.

ICSC: 1194 IMPORTANT DATA Routes of Exposure: The substance can be absorbed into the body by inhalation and through the skin, and by ingestion.

Chemical Dangers: The substance decomposes above 250 °C to chromium(III) oxide (Cr2O3) and oxygen (O2) with increased fire hazard. The substance is a strong oxidant. Reacts violently with combustible substances and reducing agents causing fire and explosion hazard. In aqueous solution, is a strong acid which reacts with bases and is corrosive. OCCUPATIONAL EXPOSURE LIMITS: TLV (as Cr): 0.05 mg/m3 (ACGIH 1993–1994).

Inhalation Risk: Evaporation at 20 °C is negligible; a harmful concentration of airborne particles can, however, be reached quickly when dispersed, especially if powdered. Effects of Short-Term Exposure: The substance irritates the eyes, the skin and the respiratory tract. Effects of Long-Term or Repeated Exposure: Repeated or prolonged contact with skin may cause dermatitis and chrome ulcers. Repeated or prolonged contact may cause skin sensitization. Repeated or prolonged inhalation exposure may cause asthma-like reactions. See notes. The substance may have effects on the nasal septum, resulting in perforation. This substance is probably carcinogenic to humans.

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719

Appendix E

PHYSICAL PROPERTIES Decomposes below boiling point at 250 °C Melting point: 197 °C Relative density (water = 1): 2.70 Solubility in water: good ENVIRONMENTAL DATA This substance may be hazardous to the environment; special attention should be given to fish and crustacea. The substance may cause long-term effects in the aquatic environment. NOTES Rinse contaminated clothes (fire hazard) with plenty of water. ADDITIONAL INFORMATION LEGAL NOTICE

Neither the CEC nor the IPCS nor any person acting on behalf of the CEC or the IPCS is responsible for the use which might be made of this information

© IPCS, CEC 2001

E.8 Material Safety Data Sheet (MSDS) Chromium Trioxide * For the production of wood preservative pesticide formulations E.8.1

Product and Company †Identification

Common Name: Chemical Family: Synonyms: Chemical Formula: Product Cas No.: Company: Address: City, State, Zip: Phone: Emergency Phone:

E.8.2

Chromium Trioxide, chromic acid†, chromium(VI) oxide Metal oxide Chromic acid†, chromic anhydride CrO3 1333-82-0 Chromium Trioxide RTECS: GB6650000 Elementis Chromium LP 3800 Buddy Lawrence Drive PO Box 9912 Corpus Christi, TX 78469 (361) 880-7725 (361) 883-6421 FAX: (361) 866-1462

Ingredients: Composition/Information

Ingredient

Mass %

PEL-OSHA

TLV-ACGIH

Chromium Trioxide Chromium(VI) oxide (CrO3)

99

0.1 mg/m3 as CrO3 (ceiling)

0.05 mg/m3 as Cr (8 h TWA)

E.8.3

LD50/LC50 Route/Species LD50: 52 mg/kg oral/rat

Hazards Identification

E.8.3.1 Emergency Overview Odorless, dark red, nonflammable crystals which may be fatal via skin contact, inhalation, or ingestion. Modern name is chromium (VI) oxide. Oxidizer-use * †

Document has been updated by the editors. Actual chemical formula is H2CrO4.

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Chromium(VI) Handbook

and store away from incompatible materials. Corrosive—can cause severe burns to eyes, skin, and mucous membranes. Cancer hazard by inhalation–contains chromium(VI). May react explosively with organic materials to sustain fire. Avoid direct contact with this material. Do not eat, drink, or smoke in areas where chromic acid is being used or stored. Keep containers closed when not in use.

E.8.4

Potential Health Effects

Primary route(s) of entry: Skin and eye contact, inhalation, ingestion. Target organs: Eye, skin, kidneys, respiratory system, liver.

E.8.4.1 Acute Effects Signs and Symptoms: Chromic acid can damage the skin and mucous membranes. Chromic acid poisoning may cause vomiting, pain in the esophagus and stomach, and metallic taste. Circulatory collapse may follow with weak and rapid pulse, shallow respiration, and clammy skin. Early deaths are generally associated with shock. Late deaths are usually due to renal or hepatic failure. Eye: Contact can cause corrosive burns, corneal damage, and blindness. Direct contact may also cause severe damage including burns and blindness. Skin: Direct contact with chromic acid can cause sensitization, severe burns, and external ulcers, “Chrome Sores.” Chrome sores most commonly occur at breaks in the skin, nailroots, creases over knuckles, finger webs, backs of hands, and on forearms. Massive overexposure could lead to toxic quantities being absorbed through the skin causing systemic poisoning and/or kidney or liver damage. Ingestion: May be fatal if swallowed. Ingestion of chromic acid can be fatal due to corrosive burns as well as systemic effects. Chromic acid causes violent gastrointestinal irritation and vomiting. Systemic poisoning may follow ingestion with ensuing kidney and liver damage. Inhalation: Inhalation of dusts and mists can burn the mucous membranes, irritate the respiratory tract and/or cause bronchiospasms and mucous membrane ulceration. Repeated or prolonged inhalation may cause ulceration and perforation of the nasal septum. Chronic Effects: Repeated inhalation of chromic acid causes nasal perforation, skin ulceration, chronic rhinitis, pharyngitis, kidney and liver damage, inflammation of the larynx, changes in the blood and lung cancer. Transfer of chromic acid to the eyes from the fingers or droplets in the air can cause chronic conjunctival inflammation and occasionally a brown band in the cornea. Carcinogenicity: IARC: Yes (1) NTP: Yes (1) OSHA: No. IARC classifies chromium(VI) compounds as agents(s) which are carcinogenic to humans.

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Appendix E

721

NTP classifies chromium(VI) and certain chromium(VI) compounds as a group of substances which is known to be carcinogenic. Medical Conditions Aggravated by Exposure: Persons with skin, liver, kidney, and respiratory disorders may be more susceptible to the effects of chromates. Persons with known sensitization to chromic acid or chromates or with a history of asthma may be at increased risk from exposure (acute asthmatic attack). E.8.5

First Aid Measures

Eye Contact: Immediately hold eyes open and flush with a steady, gently stream of water for 15 minutes. Remove contact lenses, if present. Seek Immediate Medical Attention. Skin: Immediately flush affected area(s) with water for at least 15 minutes while removing contaminated clothing and shoes. Seek Medical Attention Immediately. Thoroughly clean contaminated clothing and shoes before reuse or discard. Inhalation: Remove to fresh air. If breathing is difficult, administer oxygen. If breathing has stopped, give artificial respiration. Seek medical attention immediately. Note to Physician: Continue to monitor for respiratory distress for 72 hours. Ingestion: Never give anything by mouth to an unconscious person. Do not induce vomiting. Give large quantities of water. If available, give several glasses of milk. If vomiting occurs spontaneously, keep airways clear and give more water. Seek medical attention immediately. Immediate administration of ascorbic acid (dissolved in water) by mouth or intravenously is recommended. (See Notes to Physician.) Note to Physician: Massive overexposure to chromic acid could lead to kidney failure and death. Death has been avoided in several such cases through the use of early renal dialysis. An effective treatment has been shown to be administration of ascorbic acid by mouth or intravenously. Skin ulcers may be treated by removal from exposure, daily cleansing and debridement, and application of antibiotic cream and dressing to prevent further exposure or contamination. E.8.6

Fire Fighting Measures

Flammable properties: Flammable limits: LEL: Not applicable UEL: Not applicable Hmis Hazard Classification: Health: 3 Flammability: 0 Reactivity: 1 Oxidizer Extinguishing Media: Product is nonflammable. Use media appropriate for surrounding fire. Fire and Explosion Hazards: Containers may explode when involved in fire. Chromic acid reacts strongly with materials which are readily oxidized. Reaction may be rapid enough to cause ignition. Combustion can be violent

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Chromium(VI) Handbook

with finely divided oxidizable substances. Oxidizing capability may also sustain a fire involving easily oxidizable material. Thermal decomposition may produce chromic oxide and oxygen. Fire Fighting Equipment: Firefighters should wear a NIOSH/MSHAapproved self-contained breathing apparatus in positive pressure mode and bunker gear. Additional chemical protective clothing may be necessary to prevent exposure. E.8.7

Accidental Release Measures

Spills should be cleaned immediately to prevent dispersion of airborne mists and dusts. Isolate hazard area and deny entry to unauthorized and/or unprotected personnel. Clean up personnel should wear appropriate protective equipment including respiratory protection as necessary (See Section 8). Any spill chromic acid should be placed in a separate clean dry closed container. Dike spilled liquid material with suitable inert sorbent (i.e., sand, soil, vermiculite) and place in a clean dry container for laterrecycle or disposal. Do not dry sweep. Clean spills using wet clean up methods (i.e., misting, etc.) or with a vacuum equipped with a High Efficiency Particulate Air (HEPA) filter. Run off water is corrosive and toxic. Dispose of small quantities through an approved Waste Contractor or reduce Cr(VI) to Cr(III) (See Section 13). Dispose of in accordance with all local, state, and federal regulations. E.8.8

Handling and Storage

Protect containers from physical damage and contamination. Store in cool, dry location away from ignition sources, combustible, organic, or other readily oxidizable materials. Do not eat, drink, or smoke in areas where chromic acid is being used or stored. Keep containers closed when not in use. Wash hands thoroughly after handling, before leaving the work area, and before meals or breaks. Wear appropriate personal protective equipment (See Section 8. Exposure controls/personal protection) to avoid contact with skin, eyes, and clothing. Wear respiratory protection where there is risk of exposure to this product. Remove any contaminated clothing and launder before reuse. Do not reuse empty containers. E.8.9

Exposure Controls/Personal Protection

Respiratory protection: MSHA/NIOSH—approved filter type dust respirator in accordance with the requirements of 29 CFR 1910.134. Skin protection: Impervious coveralls, gloves, and footwear or other fullbody protective clothing should be worn when the possibility of exposure exists. Eye protection: Safety glasses, close fitting chemical safety goggles are recommended when dust or mist is present.

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723

Appendix E

Engineering controls: Ventilation as necessary to control chromic acid levels to below acceptable exposure guidelines. Local exhaust ventilation with partial enclosure should be employed for processes likely to generate dust, fume or mist/spray. Emergency showers and quick drench eye wash stations should be in close proximity to work area. Personal sampling: Air sampling for Cr(VI): 5.0 µm polyvinyl chloride filter (OSHA ID 103). Other: Cover cuts, grazes or broken skin with impervious dressings to avoid contamination. Containers should be provided for work clothing discarded at the end of the shift or after a contamination incident. Contaminated clothing should be held in these containers until removed for disposal or decontamination. Non-impervious clothing which becomes contaminated should be immediately removed. Areas in which exposure may occur should be limited to authorized personnel. Workers who handle chromic acid should wash hands thoroughly with soap and water if skin becomes contaminated and before eating, smoking, or using toilet facilities.

E.8.10

Physical and Chemical Properties

Appearance: Odor: pH: Boiling point: Melting point: Vapor pressure: Vapor density: Bulk density: Solubility in water: Specific gravity: % Volatile by volume: Evaporation rate:

E.8.11

Dark red crystals None Approx. 1.0 for 1% aqueous solution Decomposes 196 °C Not applicable Not applicable 100 lbs/ft3 (1.6 g/cm3) 62.5% (20 °C) 2.70 (H2O = 1) Not applicable Not applicable

Stability and Reactivity

Stability: Stable under normal conditions and use. Keep away from incompatible materials. Incompatibilities: Readily oxidizes combustible, organic or other readily oxidizable materials (wood, paper, sulfur, aluminum, plastics, etc.). Corrosive to metals. Hazardous decomposition products: Thermal decomposition may produce chromic oxide and oxygen. Hazardous polymerization: Will not occur. Thermal decomposition: Decomposition begins at 196 °C.

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724 E.8.12

Chromium(VI) Handbook Toxicological Information

Acute Toxicity:

Oral LD50: Inhalation LC50: Dermal LD50:

(rat) (rat)

52 mg/kg (both sexes) 217 mg/m3 (4 h exposure-both sexes) (rabbit) 57 mg/kg (both sexes)

Ingestion: Human ingestion of 0.5 g of Cr(VI) has resulted in serious toxicity. Death has resulted from ingestion of 1 g to 8 g of Cr(VI) and survival has been reported following ingestion of 15 g (human). Skin: Chromic acid is toxic via skin absorption. Cr(VI) penetrates undamaged skin and reduces to Cr(III) which forms a skin allergen by combining with proteins or other skin components (human). Skin corrosion: Moistened material causes corrosion to the skin. Eye: Chromic acid injury is characterized by infiltration, vascularization, and opacification of the cornea. Inhalation: LC50: 217 mg/m3/4 h; rat Chronic: Epidemiological studies in the chromate production, chromate pigment and chromium plating industries indicate that long term exposure to dust and mist containing Cr(VI) compounds are associated with increased risk of respiratory tract cancer in humans. Specific soluble compounds of Cr(VI) that may reasonably be anticipated to be carcinogenic include calcium chromate, chromic acid, lead chromate, strontium chromate and zinc chromate (NTP, Seventh Annual Report on Carcinogens, pg. 46, 1994). Subchronic: No Data E.8.13

Ecological Information

ENVIRONMENTAL FATE: Cr(VI) may react with particles or pollutants to form Cr(III). Generally chromium is removed from the atmosphere through wet and dry deposition. The major stable form of Cr in seawater is Cr(VI). Chromium(VI) may remain unchanged or change slowly in many natural waters owing to the low concentration of reducing matter. The oxidizing ability of Cr(VI) in aqueous solution increases at lower pHs. Cr(VI) in water will eventually be reduced to Cr(III) by organic matter. The residence time of Cr in lake water has been estimated to be 4.6 to 18 years. Most Cr released into water will ultimately be deposited in the sediment as the hydroxide after being reduced to Cr(III). Chromium may be transported from soil through runoff and leaching of water and through aerosol formation. The organic matter present in soil is expected to reduce soluble chromate to insoluble Cr(III) oxide (Cr2O3).

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Appendix E

Ecotoxicity: This product is toxic to wildlife and aquatic invertebrates. Bioaccumulation of Cr from soil to above ground parts of plants is unlikely. There is no indication of biomagnification of Cr along the terrestrial food chain (soil-plant-animal ). Aquatic Toxicity: 96h LC50: Salmo gairdneri (rainbow trout) 69 mg/L as Cr 96h LC50: Pimephales promelas (fathead minnow) 37 mg/L as Cr E.8.14

Disposal Considerations

Do not discharge chromic acid into sewers or waterways. Do not incinerate or landfill. Reclaim if possible. If reclamation is not possible, reduce to Cr(III) by the methods described below or dispose of via an approved Waste Contractor to a licensed disposal site. 1. Slowly and carefully dissolve chromic acid in plenty of water. Solution can cause severe burns — handle carefully. 2. Mix with reducing agents (i.e., iron(II) sulfate) to reduce to Cr(III). 3. Precipitate Cr(III) as Cr(III) hydroxide (Cr(OH)3) by adjusting pH to 8.5 with sodium carbonate (Na2CO3). 4. Filter and dry precipitated Cr(III) hydroxide. Dispose of in accordance with local, state and federal regulations. Recycle, reclaim, and dispose of in accordance with applicable local, state, and federal regulations. Dispose per 40 CFR Part 261 and 262. E.8.15

Transport Information

DOT Classification: Name: Hazard Class/Division: Packing Group: Un Number: Label: E.8.16

Chromium trioxide, anhydrous, toxic (chromic acid) RQ 5.1 II 1463 Oxidizer, Corrosive, Toxic

Regulatory Information

OSHA HAZARD COMMUNICATION RULE, 29 CFR 1910.1200: Chromic acid is hazardous under criteria of this rule. Elementis Chromium: MSDS for chromium trioxide Sara hazard category: This product has been reviewed according to the EPA Hazard Categories promulgated under Sections 311 and 312 of the

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Superfund Amendment and Reauthorization Act of 1986 (SARA Title III) and is considered, under applicable definitions, to meet the following categories: Fire Hazard Acute Health Hazards Chronic Health Hazards Sara 313 Information: Chromic acid is subject to the reporting requirements of Section 313 of Title III of the Superfund Amendments and Reauthorization Act of 1986 and 40 CFR Part 372 under the broad class of Cr compounds. Comprehensive Environmental Response, Compensation, and Liability Act, 40 CFR Part 117, Part 304: Chromic acid is a CERCLA hazardous substance with a reportable quantity (RQ) of 10 pounds (4.5 kg). Releases in excess of this amount should be reported to the National Response Center, Washington, D.C. (1-800-424-8802). Resource Conservation and Recovery (RCRA) Act 40 CFR 261 SUBPART C: If this product becomes a waste, it may be characterized as a hazardous waste following testing as prescribed by the Resource Conservation and Recovery Act (RCRA) regulations for D007 wastes. Clean Air Act (CAA): Chromium is designated as a hazardous air pollutant under Section 112 of the CAA. California Proposition 65: Chromic Acid is covered under Proposition 65 for Cr(VI). Appropriate warnings should be given. Federal Insecticide, Fungicide and Rodenticide Act: 40 CFR PART 167 Chromic acid is designated as a pesticide under these regulations when used in the production of wood preservative pesticide formulations. The EPA approved FIFRA label is included as the last page of this MSDS. E.8.17 KEY: ACGIH IARC NIOSH NTP MSHA OSHA RTECS TLV PEL

Other Information American Conference of Governmental Industrial Hygienists International Agency for Research on Cancer National Institute for Occupational Safety and Health National Toxicology Program Mine Safety and Health Administration Occupational Safety and Health Administration Registry of Toxic Effects of Chemical Substances Threshold Limit Value Permissible Exposure Limit

The information given above is believed to be accurate and was obtained from sources believed to be reliable. However, the information is provided

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without any representation or warranty, expressed or implied, with respect to its accuracy or completeness. It is the users’ responsibility to determine the suitability of this product and relevance of this information for their use. We do not assume liability resulting from the use, handling, storage and disposal of this product.

E.9 Material Safety Data Sheet (MSDS) Chromium Trioxide, Chromic Acid * E.9.1

Product Information

Chromium trioxide for the production of wood preservative pesticide formulations. E.9.2

Product and Company Identification

Common Name:

Chromium Trioxide, Chromium(VI) Oxide, Chromic acid

Chemical Family: Synonyms:

Metal oxide Chromic acid, chromic anhydride+

Chemical Formula: Product CAS NO.: Rtecs: Company:

CrO3 1333-82-0 Chromium Trioxide GB6650000 GENERIC CHROMIUM MANUFACTURING CO. 123 Main St., Littletown, NY 01234 USA (800) CRINFORM (800) CHROMIUM

Address: Phone: Emergency Phone: E.9.3

Ingredients: Composition/information

LD50/LC50 Ingredient Mass % PEL-OSHA TLV-ACGIH Route/species Chromium Trioxide 990.1 mg/m3 as CrO3; 0.05 mg/m3 as Cr LD50: 52 mg/kg (ceiling) based on (8 h TWA) oral/rat

Editor’s Note: Chromic acid as CrO3 is a misnomer; chromic acid is H2CrO4. Hexavalent chromium is also wrong; the oxidation state of +6 is Cr(VI). (Also, editors have updated the original document.)

*

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E.9.4

Hazard Identification

E.9.4.1 Emergency Overview Odorless, dark red, nonflammable crystals which may be fatal via skin contact, inhalation, or ingestion. Oxidizer — use and store away from incompatible materials. Corrosive — can cause severe burns to eyes, skin, and mucous membranes. Cancer hazard by inhalation — contains Cr(VI). May react explosively with organic materials to sustain fire. Avoid direct contact with this material. Do not eat, drink, or smoke in areas where chromic acid is being used or stored. Keep containers closed when not in use. PRIMARY ROUTE(S) OF ENTRY: Skin and eye contact, inhalation, ingestion. TARGET ORGANS: Eye, skin, kidneys, respiratory system, liver. E.9.4.2 Acute Effects Signs and Symptoms: Chromic acid can damage the skin and mucous membranes. Chromic acid poisoning may cause vomiting, pain in the esophagus and stomach, and metallic taste. Circulatory collapse may follow with weak and rapid pulse, shallow respiration, and clammy skin. Early deaths are generally associated with shock. Late deaths are usually the result of renal or hepatic failure. Eye: Contact can cause corrosive burns, corneal damage, and blindness. Direct contact may also cause severe damage including burns and blindness. Skin: Direct contact with chromic acid can cause sensitization, severe burns, and external ulcers, “chromium sores.” Chromium sores most commonly occur at breaks in the skin, nailroots, creases over knuckles, finger webs, backs of hands, and on forearms. Massive overexposure could lead to toxic quantities being absorbed through the skin causing systemic poisoning and/or kidney or liver damage. Ingestion: May be fatal if swallowed. Ingestion of chromic acid can be fatal owing to corrosive burns as well as systemic effects. Chromic acid causes violent gastrointestinal irritation and vomiting. Systemic poisoning may follow ingestion with ensuing kidney and liver damage. Inhalation: Inhalation of dusts and mists can burn the mucous membranes, irritate the respiratory tract and/or cause bronchiospasms and mucous membrane ulceration. Repeated or prolonged inhalation may cause ulceration and perforation of the nasal septum. Chronic Effects: Repeated inhalation of chromic acid causes nasal perforation, skin ulceration, chronic rhinitis, pharyngitis, kidney and liver damage, inflammation of the larynx, changes in the blood, and lung cancer. Transfer of chromic acid to the eyes from the fingers or droplets in the air can cause chronic conjunctival inflammation and occasionally a brown band in the cornea. Carcinogenicity: IARC: yes (1) NTP: yes(1) OSHA: no

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IARC classifies Cr(VI) compounds as agents(s) which are carcinogenic to humans. NTP classifies Cr(VI) and certain Cr(VI) compounds as a group of substances which is known to be carcinogenic. Medical Conditions Aggravated by Exposure: Persons with skin, liver, kidney, and respiratory disorders may be more susceptible to the effects of chromates (CrO42–). Persons with known sensitization to chromic acid or chromates or with a history of asthma may be at increased risk from exposure (acute asthmatic attack). E.9.5

First Aid Measures

Eye Contact: Immediately hold eyes open and flush with a steady, gently stream of water for 15 minutes. Remove contact lenses, if present. Seek immediate medical attention. Skin: Immediately flush affected area(s) with water for at least 15 minutes while removing contaminated clothing and shoes. Seek medical attention immediately. Thoroughly clean contaminated clothing and shoes before reuse or discard. Inhalation: Remove to fresh air. If breathing is difficult, administer oxygen. If breathing has stopped, give artificial respiration. Seek medical attention immediately. Note to Physician: Continue to monitor for respiratory distress for 72 hours. Ingestion: Never give anything by mouth to an unconscious person. Do not induce vomiting. Give large quantities of water. If available, give several glasses of milk. If vomiting occurs spontaneously, keep airways clear and give more water. Seek medical attention immediately. Immediate administration of ascorbic acid (dissolved in water) by mouth or intravenously is recommended. (See Notes to Physician.) Note to Physician: Massive overexposure to chromic acid could lead to kidney failure and death. Death has been avoided in several such cases through the use of early renal dialysis. An effective treatment has been shown to be administration of ascorbic acid by mouth or intravenously. Skin ulcers may be treated by removal from exposure, daily cleansing and debridement, and application of antibiotic cream and dressing to prevent further exposure or contamination. E.9.6

Fire Fighting Measures

Flammable Properties: Flammable Limits: LEL: UEL: Hmis Hazard Classification: Extinguishing Media:

Not applicable Not applicable Not applicable Not applicable Health: 3; Flammability: 0 Reactivity: 1 Oxidizer Product is nonflammable. Use media appropriate for surrounding fire.

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Flammable Properties: Flammable Limits: LEL: Fire and Explosion Hazards:

Not applicable Not applicable Not applicable Containers May Explode When involved in fire. Chromic acid reacts strongly with materials which are readily oxidized. Reaction may be rapid enough to cause ignition. Combustion can be violent with finely divided oxidizable substances. Oxidizing capability may also sustain a fire involving easily oxidizable material. Thermal decomposition may produce chromium(III) oxide (Cr2O3) and oxygen (O2).

Fire Fighting Equipment:

Firefighters should wear a NIOSH/ MSHA-approved self-contained breathing apparatus (SCBA) in positive pressure mode and bunker gear. Additional chemical protective clothing may be necessary to prevent exposure.

E.9.7

Accidental Release Measures

Spills should be cleaned immediately to prevent dispersion of airborne mists and dusts. Isolate hazard area and deny entry to unauthorized and/or unprotected personnel. Cleanup personnel should wear appropriate protective equipment including respiratory protection as necessary (See Heading 8). Any spill chromic acid should be placed in a separate clean dry closed container. Dike spilled liquid material with suitable inert sorbent (i.e., sand, soil, vermiculite) and place in a clean dry container for later cycling or disposal. Do not dry sweep. Clean spills using wet cleanup methods (i.e., misting, etc.) or with a vacuum equipped with a High Efficiency Particulate Air (HEPA) filter. Runoff water is corrosive and toxic. Dispose of small quantities through an approved Waste Contractor or reduce Cr(VI) to Cr(III) (see Heading 13). Dispose of in accordance with all local, state, and federal regulations.

E.9.8

Handling and Storage

Protect containers from physical damage and contamination. Store in cool, dry location away from ignition sources, combustible, organic, or other

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readily oxidizable materials. Do not eat, drink, or smoke in areas where chromic acid is being used or stored. Keep containers closed when not in use. Wash hands thoroughly after handling, before leaving the work area, and before meals or breaks. Wear appropriate personal protective equipment (see Heading 8). Exposure controls/personal protection to avoid contact with skin, eyes, and clothing. Wear respiratory protection where there is risk of exposure to this product. Remove any contaminated clothing and launder before reuse. Do not reuse empty containers.

E.9.9

Exposure Controls/Personal Protection

Respiratory Protection: MSHA/NIOSH-approved filter type dust respirator in accordance with the requirements of 29 CFR 1910.134. Skin Protection: Impervious coveralls, gloves, and footwear or other fullbody protective clothing should be worn when the possibility of exposure exists. Eye Protection: Safety glasses, close fitting chemical safety goggles are recommended when dust or mist is present. Engineering Controls: Ventilation as necessary to control chromic acid levels to below acceptable exposure guidelines. Local exhaust ventilation with partial enclosure should be employed for processes likely to generate dust, fume or mist/spray. Emergency showers and quick drench eye wash stations should be in close proximity to work area. Personal Sampling: Air sampling for Cr(VI): 5.0 µm polyvinyl chloride filter (OSHA ID 103). Other: Cover cuts, grazes, or broken skin with impervious dressings to avoid contamination. Containers should be provided for work clothing discarded at the end of the shift or after a contamination incident. Contaminated clothing should be held in these containers until removed for disposal or decontamination. Nonimpervious clothing which becomes contaminated should be immediately removed. Areas in which exposure may occur should be limited to authorized personnel. Workers who handle chromic acid should wash hands thoroughly with soap and water if skin becomes contaminated and before eating, smoking, or using toilet facilities.

E.9.10

Physical and Chemical Properties

Appearance: Odor: PH: Boiling Point: Melting Point:

Dark red crystals None Approximately 1.0 for 1% aqueous solution Decomposes 196 ºC

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Vapor Pressure: Vapor Density: Bulk Density: Solubility In Water: Specific Gravity: % Volatile By Volume: Evaporation Rate: E.9.11

Not Applicable Not Applicable 1.6 g/cm3 (100 lbs/ft3) 62.5% (20 ºC) 2.70 (H2O = 1) Not Applicable Not Applicable

Stability and Reactivity

Stability: Stable under normal conditions and use. Keep away from incompatible materials. Incompatibilities: Readily oxidizes combustible, organic, or other readily oxidizable materials (wood, paper, sulfur, aluminum, plastics, etc.). Corrosive to metals. Hazardous Decomposition Products: Thermal decomposition may produce chromium(III) oxide (Cr2O3) and oxygen (O2). Hazardous Polymerization: Will not occur. Thermal Decomposition: Decomposition begins at 196 º C.

E.9.12

Toxicological Information

Acute Toxicity: Oral LD50: Inhalation LC50: Dermal LD50:

(rat) 52 mg/kg (both sexes) (rat) 217 mg/m3 (4 h exposure—both sexes) (rabbit) 57 mg/kg (both sexes)

Ingestion: Human ingestion of 0.5 g of Cr(VI) has resulted in serious toxicity. Death has resulted from ingestion of 1 g to 8 g of Cr(VI) and survival has been reported following ingestion of 15 g (human). Skin: Chromic acid is toxic via skin absorption. Cr(VI) penetrates undamaged skin and reduces to Cr(III) which forms a skin allergen by combining with proteins or other skin components (human). Skin Corrosion: Moistened material causes corrosion to the skin. Eye: Chromic acid injury is characterized by infiltration, vascularization, and opacification of the cornea. Inhalation: LC50: 217 mg/m3/4 h, rat Chronic: Epidemiological studies in the chromate production, chromate pigment and Cr plating industries indicate that long term exposure to dust and mist containing Cr(VI) compounds are associated with increased risk of respiratory tract cancer in humans. Specific soluble compounds of Cr(VI) that may reasonably be anticipated to be carcinogenic include calcium chromate (CaCrO4), chromic acid (H2CrO4), lead chromate (probably

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733

lead(II) as PbCrO4), strontium chromate (SrCrO4), and zinc chromate (ZnCrO4) (NTP, Seventh Annual Report on Carcinogens, p. 46, 1994). Subchronic: No Data

E.9.13

Ecological Information

Environmental Fate: Cr(VI) may react with airborne particles or pollutants to form Cr(III). Generally Cr is removed from the atmosphere through wet and dry deposition. The major stable form of Cr in seawater is Cr(VI). Cr(VI) may remain unchanged or change slowly in many natural waters owing to the low concentration of reducing matter. The oxidizing ability of Cr(VI) in aqueous solution increases at lower pHs. Cr(VI) in water will eventually be reduced to Cr(III) by organic matter. The residence time of Cr in lake water has been estimated to be 4.6 years to 18 years. After being reduced to Cr(III), most Cr released into water will ultimately be deposited in the sediment as chromium(III) hydroxide (Cr(OH)3). Chromium may be transported from soil through runoff and leaching of water and through aerosol formation. The organic matter present in soil is expected to reduce soluble chromate (CrO42–) to insoluble chromium(III) oxide (Cr2O3). Elementis Chromium: MSDS for chromium trioxide Ecotoxicity: This product is toxic to wildlife and aquatic invertebrates. Bioaccumulation of chromium from soil to above ground parts of plants is unlikely. There is no indication of biomagnification of Cr along the terrestrial food chain (soil–plant–animal). Aquatic Toxicity: 96 h LC50: Salmo gairdneri (rainbow trout) 69 mg/L as Cr 96 h LC50: Pimephales promelas (fathead minnow) 37 mg/L as Cr

E.9.14

Disposal Considerations

Do not discharge chromic acid into sewers or waterways. Do not incinerate or landfill. Reclaim if possible. If reclamation is not possible, reduce to trivalent Cr(III) by the methods described below or dispose of via an approved Waste Contractor to a licensed disposal site. 1. Slowly and carefully dissolve chromic acid in plenty of water. Solution can cause severe burns — handle carefully. 2. Mix with reducing agents (i.e., iron(II) sulfate (FeSO4)) to reduce to Cr(III) 3. Precipitate Cr(III) as chromium(III) hydroxide (Cr(OH)3) by adjusting pH to 8.5 with sodium carbonate (Na2CO3).

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Chromium(VI) Handbook 4. Filter and dry precipitated chromium(III) hydroxide. Dispose of in accordance with local, state, and federal regulations. Recycle, reclaim and dispose of in accordance with applicable local, state, and federal regulations. Dispose per 40 CFR Part 261 and 262.

E.9.15

Transport Information

DOT Classification: Name: Hazard Class/Division: Packing Group: UN Number: Label: E.9.16

Chromium trioxide, anhydrous, toxic (chromic acid) RQ 5.1 II 1463 Oxidizer, Corrosive, Toxic

Regulatory Information

OSHA hazard communication rule, 29 CFR 1910.1200: Chromic acid is hazardous under criteria of this rule. Elementis Chromium: MSDS for chromium trioxide SARA Hazard Category: This product has been reviewed according to the EPA Hazard Categories promulgated under Sections 311 and 312 of the Superfund Amendment and Reauthorization Act of 1986 (SARA Title III) and is considered, under applicable definitions, to meet the following categories: Fire Hazard Acute Health Hazards Chronic Health Hazards SARA 313 Information: Chromic acid is subject to the reporting requirements of Section 313 of Title III of the Superfund Amendments and Reauthorization Act of 1986 and 40 CFR Part 372 under the broad class of chromium compounds. Comprehensive Environmental Response, Compensation, and Liability ACT, 40 CFR Part 117, Part 304: Chromic acid is a CERCLA hazardous substance with a reportable quantity (RQ) of 10 pounds (4.5 kg). Releases in excess of this amount should be reported to the National Response Center, Washington, D.C., Tel.: (800) 424-8802. Resource Conservation and Recovery (RCRA) ACT 40 CFR 261 Subpart C: If this product becomes a waste, it may be characterized as a hazardous waste following testing as prescribed by the RCRA regulations for D007 wastes. Clean Air Act (CAA): Chromium is designated as a hazardous air pollutant under Section 112 of the CAA. California Proposition 65: Chromic Acid is covered under Proposition 65 for Cr(VI). Appropriate warnings should be given.

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Federal Insecticide, Fungicide and Rodenticide Act: 40 CFR PART 167 Chromic acid is designated as a pesticide under these regulations when used in the production of wood preservative pesticide formulations. The USEPA approved FIFRA label is included as the last page of this MSDS.

E.9.17 KEY: ACGIH: IARC: NIOSH:

Other Information American Conference of Governmental Industrial Hygienists International Agency for Research on Cancer National Institute for Occupational Safety and Health

Elementis Chromium: MSDS for Chromium Trioxide Revision Date: 07/16/01 MSHA: Mine Safety and Health Administration NTP: National Toxicology Program OSHA: Occupational Safety and Health Administration PEL: Permissible Exposure Limit RTECS: Registry of Toxic Effects of Chemical Substances TLV: Threshold Limit Value The information given above is believed to be accurate and was obtained from sources believed to be reliable. However, the information is provided without any representation or warranty, expressed or implied, with respect to its accuracy or completeness. It is the user’s responsibility to determine the suitability of this product and relevance of this information for their use. We do not assume liability resulting from the use, handling, storage, and disposal of this product.

E.10 International Chemical Safety Card: Zinc Chromate Zinc Chromate

ICSC: 0811 ZINC CHROMATE Chromium zinc oxide Zinc tetraoxychromate Chromic acid, zinc salt (1:1) ZnCrO4 Molecular mass: 181.4

CAS # 13530-65-9 RTECS # GB3290000 ICSC # 0811 EC # 024-007-00-3

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Types of Hazard/ Exposure Fire

Acute Hazards/ Symptoms Not combustible.

Explosion Exposure

Inhalation

Cough.

Skin

Prevention

In case of fire in the surroundings: all extinguishing agents allowed. Prevent dispersion of dust! avoid all contact! Local exhaust or breathing protection. Protective gloves. Protective clothing.

Eyes

Redness.

Safety goggles.

Ingestion

Abdominal pain. Diarrhea. Vomiting.

Do not eat, drink, or smoke during work.

Spillage Disposal Sweep spilled substance into containers. Dampen and sweep gently to avoid raising dust (extra personal protection: P3 filter respirator for toxic particles). I M P O R T A N T D A T A

First Aid/ Fire Fighting

Storage

Fresh air, rest.

Remove contaminated clothes. Rinse and then wash skin with water and soap. First rinse with plenty of water for several minutes (remove contact lenses if easily possible), then take to a doctor. Rinse mouth. Induce vomiting (Only in conscious persons!). Refer for medical attention. Packaging & Labeling

Well closed.

T symbol R: 45-22-43 S: 53-44 Note: AE

Physical State; Appearance: Odorless, Yellow Crystalline Powder.

Outes of Exposure: The substance can be absorbed into the body by inhalation of its aerosol and by ingestion.

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Chemical Dangers:

Occupational Exposure Limits (OELs): TLV (as Cr): ppm; 0.01 mg/m3 A1 (ACGIH 1992–1993).

Physical Properties Environmental Data

Relative density (water = 1): 3.4 This substance may be hazardous to the environment; special attention should be given to water organisms.

Inhalation Risk: Evaporation at 20 °C is negligible; a harmful concentration of airborne particles can, however, be reached quickly when dispersed. Effects of Short-Term Exposure: Inhalation of dust may cause irritation. Effects of Long-Term or Repeated Exposure: Repeated or prolonged contact with skin may cause dermatitis. Repeated or prolonged contact may cause skin sensitization. Repeated or prolonged inhalation exposure may cause asthma. Repeated or prolonged exposure may cause nasal ulceration. This substance is carcinogenic to humans. May cause genetic damage in humans. Solubility in water: none

Notes The term zinc chromate is also used to refer to a wide range of commercial zinc and zinc potassium chromates. Depending on the degree of exposure, periodic medical examination is indicated.

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E.11 Material Safety Data Sheet (MSDS) Chromium, DILUT-IT® Analytical Conc. Std, 1g.Cr6+[sic] E.11.1

Product Identification

Synonyms: CAS No.: Molecular Mass: Chemical Formula: Product Codes:

None Not applicable to mixtures. Not applicable to mixtures. K2Cr2O7 and H2SO4 in H2O 4765

E.11.1.1 General Information Company’s Name: Generic Chromium Manufacturing Co. Company’s Address: 123 Main St., Littletown, NY 01234 USA Company’s Emergency Ph #: (800) CRINORM; (800) 424-9300 (Chemtrec) Company’s Information Ph #: (800) CHROMIUM

E.11.2

Composition/Information on Ingredients

Ingredient Potassium Dichromate Sulfuric Acid Water

E.11.3

CAS #

Percent

Hazardous

7778-50-9

12% to 14%

Yes

7664-93-9 7732-18-5

1% to 3% 83% to 87%

Yes No

Hazards Identification

E.11.3.1 Emergency Overview Danger! Strong oxidizer. Contact with other material may cause fire. Corrosive. Causes severe burns to every area of contact. May be fatal if swallowed or contacted with skin. Harmful if inhaled. Vapor irritating to eyes and respiratory tract. Affects the respiratory system, liver, kidneys, eyes, skin, blood, and teeth. May cause allergic skin or respiratory reaction. Cancer hazard. Can cause cancer. Risk of cancer depends on duration and level of exposure. Health Rating: 4 — Extreme (Cancer Causing) Flammability Rating: 0 — None Reactivity Rating: 3 — Severe (Oxidizer) Contact Rating: 3 — Severe (Corrosive)

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739

Lab Protective Equip: • Goggles & Shield • Lab Coat & Apron • Vent hood; Proper gloves Storage Color Code: Yellow Stripe (Store Separately) E.11.3.2 Potential Health Effects The following hazards are for concentrated solutions. Hazards of less concentrated solutions may be reduced. Degree of hazard for reduced concentrations is not currently addressed in the available literature. This compound may produce allergic sensitization in some individuals. In such cases, even a small future exposure can cause symptoms. E.11.3.3 Inhalation Inhalation produces damaging effects on the mucous membranes and upper respiratory tract. May cause ulceration and perforation of the nasal septum. Symptoms may include irritation of the nose and throat, coughing, and labored breathing. May cause lung edema, a medical emergency. May produce pulmonary sensitization or allergic asthma. E.11.3.4 Ingestion Corrosive. Swallowing can cause severe burns of the mouth, throat, and stomach, leading to death. Can cause sore throat, vomiting, diarrhea. May cause abdominal pain, dizziness, intense thirst, shock and liver damage. May be followed by circulatory collapse or toxic nephritis. E.11.3.5 Skin Contact Corrosive. Symptoms of redness, pain, and severe burn can occur. Contact with broken skin may cause ulcers (“chrome sores”) and absorption, which may cause systemic poisoning, affecting kidney and liver functions. Circulatory collapse with clammy skin, weak and rapid pulse, shallow respirations, and scanty urine may follow skin contact or ingestion. Circulatory shock is often the immediate cause of death. May produce skin sensitization or allergic skin reactions.

E.11.3.6 Eye Contact Corrosive. Contact can cause blurred vision, redness, pain, and severe tissue burns. Can cause blindness.

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E.11.3.7 Chronic Exposure Long-term exposure to mist or vapors may cause damage to teeth. Chronic exposure to mists containing sulfuric acid is a cancer hazard. Chronic exposure may affect kidneys and liver. Certain, mainly water-soluble, chromium(VI) compounds (Cr(VI) compounds), have been determined to be human carcinogens. E.11.3.8 Aggravation of Preexisting Conditions Persons with pre-existing skin disorders, eye problems, impaired respiratory function, allergies or sensitization to chromic acid or chromates may be more susceptible to the effects of this material.

E.11.4

First Aid Measures

First aid procedures given apply to concentrated solutions. Exposures to dilute solutions may not require these extensive first aid procedures. E.11.4.1 Inhalation Remove to fresh air. If not breathing, give artificial respiration. If breathing is difficult, give oxygen. Get medical attention immediately. E.11.4.2 Ingestion If swallowed, DO NOT INDUCE VOMITING. Give large quantities of water. Never give anything by mouth to an unconscious person. Get medical attention immediately. E.11.4.3 Skin Contact Wipe off excess material from skin then immediately flush skin with plenty of water for at least 15 minutes while removing contaminated clothing and shoes. Get medical attention immediately. Wash clothing before reuse. Thoroughly clean shoes before reuse. E.11.4.4 Eye Contact Immediately flush eyes with plenty of water for at least 15 minutes, lifting lower and upper eyelids occasionally. Get medical attention immediately.

E.11.5

Fire Fighting Measures

E.11.5.1 Fire Not combustible, but concentrated material is a strong oxidizer and its heat of reaction with reducing agents or combustibles may cause ignition.

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Concentrated material is a strong dehydrating agent. Reacts with organic materials and may cause ignition of finely divided materials on contact. E.11.5.2 Explosion Contact of concentrated solutions with most metals causes formation of flammable and explosive hydrogen gas (H2). Contact with oxidizable substances may cause violent combustion. E.11.5.3 Fire Extinguishing Media Dry chemical, foam, or carbon dioxide (CO2). Concentrated solutions are water reactive. Water spray may be used to keep fire-exposed containers cool. E.11.5.4 Special Information In the event of a fire, wear full protective clothing and NIOSH-approved self-contained breathing apparatus (SCBA) with full facepiece operated in the pressure demand or other positive pressure mode.

E.11.6

Accidental Release Measures

Ventilate area of leak or spill. Wear appropriate personal protective equipment as specified in Heading 8. Isolate hazard area. Keep unnecessary and unprotected personnel from entering. Contain and recover liquid when possible. Neutralize with alkaline material (soda ash, lime), then absorb with an inert material (e.g., vermiculite, dry sand, earth), and place in a chemical waste container. Do not use combustible materials, such as saw dust. Do not flush to sewer! U.S. Regulations (CERCLA) require reporting spills and releases to soil, water and air in excess of reportable quantities. The toll free number for the U.S. Coast Guard National Response Center is (800) 424-8802. E.11.7

Handling and Storage

Store in a cool, dry, ventilated storage area with acid resistant floors and good drainage. Protect from physical damage. Keep out of direct sunlight and away from heat and incompatible materials. Do not wash out container and use it for other purposes. When diluting, always add the acid to water; never add water to the acid. Protect from freezing. When opening metal containers, use non-sparking tools because of the possibility of hydrogen gas (H2) being present. Wear special protective equipment (Heading 8) for maintenance break-in or where exposures may exceed established exposure levels. Wash hands, face, forearms and neck when exiting restricted areas. Shower, dispose of outer clothing, change to clean garments at the end of the day. Avoid cross-contamination of street clothes. Wash hands before eating and do not eat, drink, or smoke in workplace. Containers of this

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material may be hazardous when empty since they retain product residues (vapors, liquid); observe all warnings and precautions listed for the product. E.11.8

Exposure Controls/Personal Protection Airborne Exposure Limits:

OSHA Permissible Exposure Limit (PEL): Chromic acid (H2CrO4) and chromates (CrO42–), as CrO3 = 0.1 mg/m3 (ceiling) ACGIH Threshold Limit Value (TLV): For water-soluble Cr(VI) compounds, as Cr = 0.05 mg/m3 (TWA). A1 — a confirmed human carcinogen. For Sulfuric Acid: OSHA Permissible Exposure Limit (PEL)— 1 mg/m3 (TWA) ACGIH Threshold Limit Value (TLV)— 1 mg/m3 (TWA), 3 mg/m3 (STEL). A2 — a suspected human carcinogen for sulfuric acid contained in strong inorganic acid mists. E.11.8.1 Ventilation System A system of local and/or general exhaust is recommended to keep employee exposures below the Airborne Exposure Limits. Local exhaust ventilation is generally preferred because it can control the emissions of the contaminant at its source, preventing dispersion of it into the general work area. Please refer to the ACGIH document, Industrial Ventilation, A Manual of Recommended Practices, most recent edition, for details. E.11.8.2 Personal Respirators (NIOSH Approved) If the exposure limit is exceeded and engineering controls are not feasible, a full facepiece respirator with an acid gas cartridge and particulate filter (NIOSH type N100 filter) may be worn up to 50 times the exposure limit, or the maximum use concentration specified by the appropriate regulatory agency or respirator supplier, whichever is lowest. If oil particles (e.g., lubricants, cutting fluids, glycerine, etc.) are present, use a NIOSH type R or P particulate filter. For emergencies or instances where the exposure levels are not known, use a full-facepiece positive-pressure, air-supplied respirator. WARNING: Air purifying respirators do not protect workers in oxygendeficient atmospheres. Where respirators are required, you must have a written program covering the basic requirements in the OSHA respirator standard. These include training, fit testing, medical approval, cleaning, maintenance, cartridge change schedules, etc. See 29CFR1910.134 for details.

L1608_Appendix-E Page 743 Monday, November 8, 2004 8:32 AM

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Appendix E

E.11.8.3 Skin Protection Wear impervious protective clothing, including boots, gloves, lab coat, apron or coveralls, as appropriate, to prevent skin contact.

E.11.8.4 Eye Protection Use chemical safety goggles and/or a full face shield where splashing is possible. Maintain eye wash fountain and quick-drench facilities in work area.

E.11.9

Physical and Chemical Properties

Appearance: Odor: Solubility: Specific Gravity: pH: Volatiles by volume (21 °C/70 °F): Boiling Point: Melting Point: Vapor Density (Air = 1): Vapor Pressure (mmHg): Evaporation Rate (BuAc = 1): (BuAc = butyl acetate).

E.11.10

Clear, yellow–orange liquid. Odorless. Soluble in water. No information found. 0.7 (0.1 mol/L H2SO4 ) ≈ 85% No information found. No information found. Not applicable. Not applicable. No information found.

Stability and Reactivity

Stability: Stable under ordinary conditions of use and storage. Concentrated solutions react violently with water, spattering, and liberating heat. Hazardous Decomposition Products: Burning may produce chromium oxides, hydrogen, and sulfur oxides. Hazardous Polymerization: Will not occur. Incompatibilities: For potassium dichromate (K2Cr2O7): Reducing agents, acetone plus sulfuric acid, boron plus silicon, ethylene glycol, iron, hydrazine, and hydroxylamine. Any combustible, organic, or other readily oxidizable material (paper, wood, sulfur, aluminum, or plastics). For Sulfuric Acid: Water, potassium chlorate, potassium perchlorate, potassium permanganate, sodium, lithium, bases, organic material, halogens, metal acetylides, oxides and hydrides, metals (yields hydrogen gas), strong oxidizing and reducing agents and many other reactive substances. Conditions to Avoid: Heat and incompatibles.

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Chromium(VI) Handbook

E.11.11

Toxicological Information

Toxicological Data: te: Investigated as a tumorigen, mutagen, reproductive effector. For Sulfuric Acid: Oral rat LD50 2,140 mg/kg; Inhalation rat LC50 510 mg/m3/2 h; Investigated as a tumorigen, mutagen, reproductive effector. Carcinogenicity: Cancer Status: The International Agency for Research on Cancer (IARC) has classified “strong inorganic acid mists containing sulfuric acid” as a known human carcinogen, (IARC category 1). This classification applies only to mists containing sulfuric acid and not to sulfuric acid or sulfuric acid solutions. Cancer List Ingredient Potassium Dichromate Sulfuric Acid Water E.11.12

IARC Category

CAS #

Known

Anticipated

(7778-50-9)

Yes

No

1

(7664-93-9) (7732-18-5)

No No

No No

None None

Ecological Information

E11.12.1 Environmental Fate For Chromium: When released into the soil, this material may leach into groundwater. When released into water, this material is not expected to evaporate significantly. This material may bioaccumulate to some extent. When released into the air, this material may be removed from the atmosphere to a moderate extent by wet deposition. Environmental Toxicity: No information found. E.11.13

Disposal Considerations

Whatever cannot be saved for recovery or recycling should be managed in an appropriate and approved waste facility. Although not a listed RCRA hazardous waste, this material may exhibit one or more characteristics of a hazardous waste and require appropriate analysis to determine specific disposal requirements. Processing, use, or contamination of this product may change the waste management options. State and local disposal regulations may differ from federal disposal regulations. Dispose of container and unused contents in accordance with federal, state, and local requirements. E.11.14

Transport Information

Domestic (Land, DOT) Proper Shipping Name: Corrosive liquid, acidic, inorganic, n.o.s. (potassium dichromate, sulfuric acid)

L1608_Appendix-E Page 745 Monday, November 8, 2004 8:32 AM

745

Appendix E

Hazard Class: 8 UN/NA: UN3264 Packing Group: II Information reported for product/size: 1PK International (Water, I.M.O.) Proper Shipping Name: Corrosive liquid, acidic, inorganic, n.o.s. (potassium dichromate, sulfuric acid) Hazard Class: 8 UN/NA: UN3264 Packing Group: II Information reported for product/size: 1PK International (Air, I.C.A.O.) Proper Shipping Name: Corrosive liquid, acidic, inorganic, n.o.s. (potassium dichromate, sulfuric acid) Hazard Class: 8 UN/NA: UN3264 Packing Group: II Information reported for product/size: 1PK

E.11.15

Regulatory Information

Chemical Inventory Status—Part 1 Ingredient Potassium Dichromate (7778-50-9) Sulfuric Acid (7664-93-9) Water (7732-18-5) Chemical Inventory Status — Part 2

TSCA Yes Yes Yes

Canada Ingredient Korea Potassium Dichromate (7778-50-9) Yes Sulfuric Acid (7664-93-9) Yes Water (7732-18-5) Yes Federal, State & International Regulations —Part 1 -SARA 302Ingredient RQ Potassium Dichromate (7778-50-9) No Sulfuric Acid (7664-93-9) 1000 Water (7732-18-5) No Federal, State & International Regulations —Part 2 RCRAIngredient CERCLA

EC Yes Yes Yes

Japan Yes Yes Yes

Australia Yes Yes Yes

DSL Yes Yes Yes

NDSL No No No

Philadelphia Yes Yes Yes

TPQ No

SARA 313 List No

1000 No

Yes No

Chem. Catg. chromium compound No No

TSCA261.33

8(d)

L1608_Appendix-E Page 746 Monday, November 8, 2004 8:32 AM

746

Chromium(VI) Handbook

Chemical Inventory Status—Part 1 Ingredient TSCA EC Japan Australia Potassium Dichromate (7778-50-9) Yes Yes Yes Yes Potassium Dichromate (7778-50-9) 10 No No Sulfuric Acid (7664-93-9) 1000 No No Water (7732-18-5) No No No Chemical Weapons Convention: no TSCA 12(b): yes CDTA: No SARA 311/312: Acute: yes Chronic: yes Fire: yes Pressure: no Reactivity: no (Mixture/Liquid) Warning (Proposition 65): This product contains a chemical(s) known to the State of California to cause cancer. Australian HAZCHEM Code: None allocated. Poison Schedule: S6 WHMIS: This MSDS has been prepared according to the hazard criteria of the Controlled Products Regulations (CPR) and the MSDS contains all of the information required by the CPR.

E.11.16

Other Information

NFPA Ratings: Health: 3 Flammability: 0 Reactivity: 1 Other: Oxidizer Label Hazard Warning: Danger! Strong oxidizer. Contact with other material may cause fire. Corrosive. Causes severe burns to every area of contact. may be fatal if swallowed or contacted with skin. Harmful if inhaled. Vapor irritating to eyes and respiratory tract. Affects the respiratory system, liver, kidneys, eyes, skin, blood, and teeth. May cause allergic skin or respiratory reaction. Cancer hazard. Can cause cancer. Risk of cancer depends on duration and level of exposure. E.11.16.1 Label Precautions Keep from contact with clothing and other combustible materials. Store in a tightly closed container. Do not get in eyes, on skin, or on clothing. Do not breathe vapor or mist. Use only with adequate ventilation. Keep container closed. Wash thoroughly after handling. E.11.16.2 Label First Aid In case of contact, wipe off excess material from skin then immediately flush eyes or skin with plenty of water for at least 15 minutes while removing contaminated clothing and shoes. Wash clothing before reuse. If inhaled, remove to fresh air. If not breathing, give artificial respiration. If breathing

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747

Appendix E

is difficult, give oxygen. If swallowed, Do not induce vomiting. Give large quantities of water. Never give anything by mouth to an unconscious person. In all cases get medical attention immediately. Product Use: Laboratory Reagent. Revision Information: No Changes. Disclaimer: Generic Chromium Manufacturing Co. provides the information contained herein in good faith but makes no representation as to its comprehensiveness or accuracy. This document is intended only as a guide to the appropriate precautionary handling of the material by a properly trained person using this product. Individuals receiving the information must exercise their independent judgement in determining its appropriateness for a particular purpose.

E.12 International Chemical Safety Card: Chromium Oxide Chromium Oxide

ICSC: 1194 CHROMYL CHLORIDE Chromic oxychloride Dichlorodioxochromium Chromium dichloride dioxide CrO2Cl2 Molecular mass: 154.9

CAS # 14977-61-8 RTECS # GB5775000 ICSC # 0854 UN # 1758 EC # 024-005-00-2 Types of Hazard / Exposure Fire

Acute Hazards/ Symptoms Not combustible but enhances combustion of other substances. Many reactions may cause fire or explosion.

Prevention No contact with flammable substances.

Explosion

Exposure Inhalation

Avoid all contact! Cough. Labored breathing. Shortness of breath. Sore throat.

Ventilation, local exhaust, or breathing protection.

First Aid/fire Fighting Carbon dioxide. Special powder. No hydrous agents. No water. In case of fire in the surroundings: use no water unless protected against toxic gases. In case of fire: keep drums, etc., cool by spraying with water but No direct contact with water. In all cases consult a doctor! Fresh air, rest. Halfupright position. Artificial respiration if indicated. Refer for medical attention.

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Chromium(VI) Handbook

Skin

Redness. Skin burns. Pain. Blisters.

Protective gloves. Protective clothing.

Eyes

Redness. Pain. Severe deep burns.

Ingestion

Abdominal pain (further see Inhalation).

Face shield, or eye protection in combination with breathing protection. Do not eat, drink, or smoke during work.

Remove contaminated clothes. Rinse skin with plenty of water or shower. Refer for medical attention. First rinse with plenty of water for several minutes (remove contact lenses if easily possible), then take to a doctor. Rinse mouth. Do not induce vomiting. Refer for medical attention.

Spillage Disposal

Storage

Evacuate danger area! Ventilation. Collect leaking liquid in sealable containers. Absorb remaining liquid in sand or inert absorbent and remove to safe place. Do not wash away into sewer. Do not absorb in saw-dust or other combustible absorbents. Never direct water jet on liquid (extra personal protection: complete protective clothing including self-contained breathing apparatus).

Fireproof. Separate from combustible and reducing substances, food and feedstuffs. Cool. Dry. Keep in the dark. Keep in a well-ventilated room.

ICSC: 0854

I M P O R T A N T D A T A

Packaging & Labeling Airtight. Do not transport with food and feedstuffs. O symbol C symbol R: 8-35 S: 7/8-22-28 UN Hazard Class: 8 UN Packing Group: I

Prepared in the context of cooperation between the International Programme on Chemical Safety & the Commission of the European Communities © IPCS CEC 1993 Routes of Exposure: Physical State; Appearance: The substance can be absorbed Dark red fuming liquid, with into the body by inhalation of its pungent odor. vapor or aerosol and by ingestion. Inhalation Risk: Physical Dangers: A harmful contamination of the air can be reached very quickly on evaporation of this substance at CHEMICAL DANGERS: 20 °C. The substance decomposes violently on contact with water producing Effects of Short-term toxic and corrosive fumes Exposure: (hydrochloric acid (HCl), chlorine The substance is corrosive to the (Cl2), chromium(VI) oxide (CrO3), and chromium(III) chloride (CrCl3)). eyes, the skin and the respiratory The substance is a strong oxidant and tract. Corrosive on ingestion. reacts violently with combustible and Inhalation of the vapor may cause reducing materials. Reacts violently lung edema (see Notes). with water, nonmetal halides, nonmetal hydrides, ammonia (NH3) Effects of Long-Term and certain common solvents such as or Repeated Exposure: alcohol, ether, acetone, and Repeated or prolonged contact turpentine, causing fire and with skin may cause dermatitis. explosion hazard. Attacks many Repeated or prolonged inhalation metals in presence of water. exposure may cause asthma (see Incompatible with plastics. Can Notes). This substance is probably ignite combustible substances. carcinogenic to humans.

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749

Appendix E

Physical Properties

Environmental Data

Occupational Exposure Limits (OELs): TLV: 0.025 ppm; 0.16 mg/m3 (ACGIH 1991–1992). Boiling point: 117 °C Melting point: –96.5 °C Relative density (water = 1): 1.91

Solubility in water: reaction Vapor pressure, 2.67 kPa at 20 °C Relative vapor density (air = 1): 5.3 It is strongly advised not to let the chemical enter into the environment. Notes

Dissolves chromium trioxide, yielding a powerful oxidant. Reacts violently with fire extinguishing agents such as water. Depending on the degree of exposure, periodic medical examination is indicated. The symptoms of lung edema often do not become manifest until a few hours have passed and they are aggravated by physical effort. Rest and medical observation are therefore essential. Anyone who has shown symptoms of asthma owing to this substance should never again come into contact with this substance. Rinse contaminated clothes (fire hazard) with plenty of water. Transport Emergency Card: TEC (R)-80G10 NFPA Code: H3; F0; R1;

L1608_Appendix-E Page 750 Monday, November 8, 2004 8:32 AM

L1608_Appendix-F Page 751 Tuesday, November 9, 2004 9:48 AM

Appendix F Chromium Contaminated Superfund Sites

James A. Jacobs

CONTENTS F.1 Introduction ................................................................................................751 F.2 Containment Technologies .......................................................................752 F.3 Solidification/Stabilization ......................................................................752 F.4 Soil Washing ...............................................................................................753 F.5 In Situ Solidification/Stabilization..........................................................753 F.6 In Situ Vitrification ....................................................................................753 F.7 In Situ Soil Flushing ..................................................................................754 F.8 Electrokinetics.............................................................................................754 Bibliography ........................................................................................................754

F.1

Introduction

The most common heavy metals (i.e., metals having a density >5 g/cm3 at 20 °C) found at U.S. Superfund sites are in this order: lead (Pb), chromium (Cr), arsenic (As), zinc (Zn), cadmium (Cd), copper (Cu), and mercury (Hg) (USEPA, 1996c). Of the Superfund sites that contain an elevated concentration of metals, 306 sites contain Cr as a major source of contamination. Sources of Cr contamination include airborne sources (stack or duct emissions of air, gas, or vapor streams, and fugitive emissions such as dust from storage areas or waste piles), process solid wastes and sludges (from industrial processes), contaminated soils, and direct Cr contamination in groundwater. 1-5667-0608-4/05/$0.00+$1.50 © 2005 by CRC Press LLC

751

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Chromium(VI) Handbook

A summary of remedial measures for metal-contaminated soils and groundwater can be found in Evanko and Dzombak (2000). Based on USEPA studies (1996a, 1996b, 1996c), a variety of remediation options were tried for Cr as one of the major contaminants at the following sites:

F.2

Containment Technologies

Case 1: Industrial waste control in Alaska. The remediation method was a slurry wall containment technology with capping and French drain as secondary technologies. As of February 1996, the site was in operation. Other contaminants include As, Cd, and Pb. Case 2: Chemtronic facility in North Carolina. The remediation method was a capping containment technology. As of February 1996, the site had selected the technology, but was not yet in operation. Other contaminants include Pb. Case 3: Industriplex facility in Massachusetts. The remediation method was a capping containment technology. As of February 1996, the site was in operation. Other contaminants include As and Pb.

F.3

Solidification/Stabilization

Case 1: DeRewal Chemical facility in New Jersey. The remediation method was solidification. As of February 1996, the site had selected the technology, but was not yet in operation. Secondary technology is groundwater “pump and treat.” Other contaminants include Cd and Pb. Case 2: Roebling Steel facility in New Jersey. The remediation method was solidification/stabilization. As of February 1996, the site had selected the technology, but was not yet in operation. Secondary technology is capping. Other contaminants include As and Pb. Case 3: Waldick Aerospace facility in New Jersey. The remediation method was solidification/stabilization. As of February 1996, the site had completed the remediation. Secondary technology was off-site disposal. Other contaminants include Cd. Case 4: Alladin Plating facility in New Jersey. The remediation method was Stabilization. As of February 1996, the site had completed the remediation. Secondary technology is off-site disposal. No other contaminants were noted. Case 5: Bypass Highway 601 in North Carolina. The remediation method was solidification/stabilization. As of February 1996, the site had selected the technology, but was not yet in operation. Secondary technology is groundwater “pump and treat,” capping, grading, and revegetation. Other contaminants include Pb. Case 6: Independent Nail facility in South Carolina. The remediation method was solidification/stabilization. As of February 1996, the site had

L1608_Appendix-F Page 753 Tuesday, November 9, 2004 9:48 AM

Appendix F

753

completed the remediation. Secondary technology was capping. Other contaminants include Cd. Case 7: E.I. DuPont de Nemours in Iowa. The remediation method was solidification/stabilization. As of February 1996, the site had completed the remediation. Secondary technology was capping, grading, and revegetation. Other contaminants include Cd and Pb. Case 8: Frontier Hard Chrome in Washington. The remediation method was Stabilization. As of February 1996, the site had selected the technology, but was not yet in operation. No secondary technology was selected. No other contaminants were noted.

F.4

Soil Washing

Case 1: Ewan Property in New Jersey. The remediation method was water washing. As of February 1996, the site had selected the technology, but was not yet in operation. The secondary technology is solvent extraction to remove organics. Other contaminants include As, Cu, and Pb. Case 2: King of Prussia facility in New Jersey. The remediation method was water with potassium iodide (KI) solution additive. As of February 1996, the site had completed remediation. Secondary technology was sludge disposal. Other contaminants included silver (Ag) and Cu. Case 3: Zanesville Well Field in Ohio. The remediation method was water washing. As of February 1996, the site had selected the technology, but was not yet in operation. The secondary technology was on-site disposal of clean soil and soil vapor extraction (SVE) to remove organic compounds. Other contaminants include As, Hg, and Pb. Case 4: Twin Cities Army Ammunition Plant in Minnesota. The remediation method was acid leaching. As of February 1996, the site had completed remediation. The secondary technology was soil leaching. Other contaminants include Cd, Cu, Hg, and Pb. Case 5: Sacramento Army Depot in California. The remediation method was water washing. As of February 1996, the site had selected the technology, but was not yet in operation. The secondary technology was on-site disposal of clean soil and SVE to remove organic compounds. Other contaminants include As, Hg, and Pb.

F.5

In Situ Solidification/Stabilization

Case 1: General Electric Company facility in Florida. The remediation method was in situ solidification/stabilization. As of February 1996, the site had demonstrated the selected technology, but was not yet in operation. No secondary treatment was noted. Other contaminants include Pb, Cu, and Zn.

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754

F.6

Chromium(VI) Handbook

In Situ Vitrification

Case 1: Parsons Chemical facility in Michigan. The remediation method was in situ vitrification. As of February 1996, the site had completed remediation. No secondary treatment was noted. Other contaminants include As, Hg, and Pb.

F.7

In Situ Soil Flushing

Case 1: Lipari Landfill in Michigan. The remediation method was in situ soil flushing. As of February 1996, the site was in operation. Secondary treatment included slurry wall, cap, and excavation of wetlands. Other contaminants include Hg and Pb. Case 2: United Chrome Products facility in Oregon. The remediation method was in situ soil flushing with water. As of February 1996, the site was in operation. Secondary treatment included the consideration of electrokinetic and chemical reductant treatment. No other contaminants were noted.

F.8

Electrokinetics

Case 1: Undisclosed military base. The remediation method was electrochemical remediation. As of February 1996, the site had completed the remediation. No secondary treatments were noted. Other contaminants include Cd, Cu, nickel (Ni), Pb, and Zn.

Bibliography Evanko, C.R. and Dzombak, D.A., 2000, Remediation of metals — contaminated soils and groundwater, in Jay Lehr, Ed., Standard Handbook of Environmental Science, Health and Technology, McGraw-Hill, New York, pp. 14.100–14.134. U.S. Environmental Protection Agency (USEPA), 1996a, Completed North American Innovative Remediation Technology Demonstration Projects, EPA-542B-96-002, PB96-153-127, U.S. Environmental Protection Agency, Office of Solid Waste and Emergency Response, Washington, DC. U.S. Environmental Protection Agency (USEPA), 1996b, Report: Recent Developments for In Situ Treatment of Metals — Contaminated Soils, U.S. Environmental Protection Agency, Office of Solid Waste and Emergency Response, draft, Washington, DC. U.S. Environmental Protection Agency (USEPA), 1996c, Engineering Bulletin: Technology Alternatives for the Remediation of Soils Contaminated with Arsenic, Cadmium, Chromium, mercury, and Lead, U.S. Environmental Protection Agency, Office of Solid Waste and Emergency Response, Cincinnati, OH, draft.

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Appendix G Contributor Contact Information

1-5667-0608-4/05/$0.00+$1.50 © 2005 by CRC Press LLC

755

Author

Title

Frederick T. Stanin, R.G., C.E.G., C.HG.

Jacques Guertin, Ph.D. Toxicologist–Che mist–Teacher James A. Jacobs R.G., Chief C.HG. Hydrogeologist William E. Motzer, Senior Ph.D., R.G. Geochemist David W. Abbott, R.G., Senior Geologist C.HG. Jacques Guertin, Ph.D. Toxicologist–Che mist–Teacher Elisabeth L. Hawley Project Engineer

6

8

7

7

Address

Email Telephone

augerpro@sbcglob 415-381-5195 al.net

San Jose, CA 95112-4508

Emeryville, CA 2000 Powell Street, Suite 1180 94608-1832

19814 Jesus Maria Mokelumne Hill, Road CA 95245-9559

1720 North First Street

510-595-2120

510-595-2120

415-381-5195

510-793-8688

510-596-3060

209-754-1422

jacquesguertin@ju 510-793-8688 no.com 510-596-3060 ehawley@pirnie .com

jacquesguertin@ju no.com augerpro@sbcglob al.net bmotzer@toddeng ineers.com [email protected]

fstanin@pirnie .com

stesta@goldrush .com

[email protected] 408-367-8376 om

bmotzer@toddeng 510-595-2120 Emeryville, CA 2200 Powell Street, Suite 225 94608-1877 ineers.com 201 N. Civic Walnut Creek, CA msteinpress@brw 925-210-2408 Drive 94596 ncald.com

Newark, CA 94560-2034 707 View Point Environmental Mill Valley, CA Bio-Systems, Inc. Road 94941-3964 Todd Engineers Emeryville, CA 2200 Powell Street, Suite 225 94608-1877 Emeryville, CA Todd Engineers 2200 Powell Street, Suite 225 94608-1877 Newark, CA 94560-2034 Malcolm Pirnie, 2000 Powell Emeryville, CA Inc. Street, Suite 1180 94608-1832

Testa Environmental Corporation Malcolm Pirnie

City, State, Zip Mill Valley, CA 94941-3964

Fax

Web site

(Continued )

510-596-8855 www.pirnie .com

415-381-5816 www.ebsinfo .com 510-595-2112 www.toddengine ers.com 510-595-2112 www.toddengine ers.com 510-793-4056

510-793-4056

510-596-8855 www.pirnie .com

209-754-1422

408-367-8428

510-595-2112 www.toddengine ers.com 925-937-9026 www.brownandc aldwell. com

415-381-5816 www.ebsinfo.com

756

7

7

Senior Hydrogeologist/ Project Manager

President

5

4

Company 707 View Point Environmental Bio-Systems, Inc. Road

Senior Todd Engineers Geochemist Brown and Chief Caldwell Hydrogeologis, National Groundwater Resources Service Leader Water Quality California Water Project Manager Service Company

Chief Hydrogeologist

Tarrah D. Henrie, Veronica Simion, Chet Auckly, Jeannette V. Weber Stephen M. Testa

James A. Jacobs R.G., Stephen M. Testa C.HG. William E. Motzer, Ph.D., R.G. Martin G. Steinpress, R.G., C.HG.

3.2

3.1

2

1

Chapter

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Chromium(VI) Handbook

Stephen M. Testa

Stephen M. Testa

10.1

10.2

10.3

Michael J. Dybas

President

Chief Hydrogeologist Principal Geohydrologist President

Assistant professor

Department of Civil and Environmental Engineering, Michigan State University Environmental Bio-Systems, Inc. Montgomery Watson Harza Testa Environmental Corporation Testa Environmental Corporation

Malcolm Pirnie, Senior Inc. Environmental Engineer Bioremediation Specialist Michael C. Vice President, Malcolm Pirnie, Kavanaugh, Ph.D., National Science Inc. P.E. and Technology Leader James A. Jacobs R.G., Chief Environmental C.HG. Hydrogeologist Bio-Systems, Inc. Pacific Northwest Jim E. Szecsody, Ph.D., National R.G., John S. Fruchter, Laboratory Vince R. Vermeul, Mark D. Williams, Brooks J. Devary SECOR Angus McGrath, International Ph.D., Daniel Oberle, Incorporated David Schroder, John McInnes and Chris Maxwell Sarah Middleton Department of Williams and Craig Civil and S. Criddle Environmental Engineering, Stanford University

Rula A. Deeb, Ph.D.

James A. Jacobs R.G., C.HG. Jim V. Rouse

10.1

9.3

9.3

9.2

9.1

8

8

8

Lafayette, CA 94549-4321

925-299-9300

[email protected] .edu

517-355-2254

sarahsm@stanford 650-723-0315 .edu

amcgrath@secor .com

19814 Jesus Maria Mokelumne Hill, CA 95245-9559 Road

stesta@goldrush .com

209-754-1422

707 View Point Mill Valley, CA augerpro@sbcglob 415-381-5195 Road 94941-3964 al.net 1328 Northridge Golden, CO 80401 jim.rouse@mwhgl 303-526-5493 Court obal.com 209-754-1422 19814 Jesus Maria Mokelumne Hill, stesta@goldrush .com CA 95245-9559 Road

Stanford, CA Stanford 94305-4020 University, 380 Panama Mall, Terman Engineering Building, Room B-27 A-124 RCE East Lansing, MI 48824

57 Lafayette Circle

augerpro@sbcglob 415-381-5195 al.net jim.szecsody@pnl. 509-372-6080 gov

707 View Point Mill Valley, CA Road 94941-3964 P.O. Box 999, M.S. Richland, WA K3-61, Richland, 99352 WA 99352

510-596-3060

510-596-3060

mkavanaugh@pir nie.com

rdeeb@pirnie .com

2000 Powell Emeryville, CA Street, Suite 1180 94608-1832

2000 Powell Emeryville, CA Street, Suite 1180 94608-1832

209-754-1422

415-381-5816 www.ebsinfo .com 303-526-2795 www.mwhglobal. com 209-754-1422

517-355-0250

650-725-3162

925-299-9302 www.secor .com

415-381-5816 www.ebsinfo .com

510-596-8855 www.pirnie .com

510-596-8855 www.pirnie .com

L1608_Appendix-G Page 757 Tuesday, November 9, 2004 9:54 AM

Appendix G 757

10.12

10.12

Author

James A. Jacobs R.G., C.HG. James A. Jacobs R.G., C.HG. James A. Jacobs R.G., C.HG. David Bohan, David Wierzbicki, Jason Peery, Anna Willett, and Steve Koenigsberg John F. Horst, P.E.; Suthan S. Suthersan, P.E., Ph.D., Senior Vice President Lucas A. Hellerich, Ph.D., P.E. Matthew A. Panciera

James A. Jacobs R.G., C.HG. James A. Jacobs R.G., C.HG. James A. Jacobs R.G., C.HG. Ralph O. Howard, Jr., P.G.

Project Engineer

Project Engineer

Chief Hydrogeologist Chief Hydrogeologist Chief Hydrogeologist

Tighe and Bond

Metcalf & Eddy

ARCADIS Geraghty & Miller, Inc.

Newtown, PA 18940-1831

Mill Valley, CA 94941-3964 Mill Valley, CA 94941-3964 Mill Valley, CA 94941-3964 San Clemente, CA 92673-6244

860 North Main Wallingford, CT Street Extension 06492-2419 Middletown, CT 213 Court St., Suite 900 06457

6 Terry Drive, Suite 300

707 View Point Road 707 View Point Road 707 View Point Road 1011 Calle Sombra

Telephone

949-366-8001 ext. 114

415-381-5195

415-381-5195

415-381-5195

404-562-8829

415-381-5195

415-381-5195

415-381-5195

jhorst@arcadis267-685-1800 us.com ssuthersan@arca dis-us.com lucas.hellerich@m 203-269-7310 -e.com mapanciera@tighe 860-704-4760 bond.com

augerpro@sbcglob al.net augerpro@sbcglob al.net augerpro@sbcglob al.net awillett@regenesis .com

Email augerpro@sbcglob al.net augerpro@sbcglob al.net augerpro@sbcglob al.net howard.ralph@ep a.gov

City, State, Zip Mill Valley, CA 94941-3964 Mill Valley, CA 94941-3964 Mill Valley, CA 94941-3964 Atlanta, GA 30303

Address 707 View Point Road 707 View Point Road 707 View Point Road 61 Forsyth Street

Company Environmental Bio-Systems, Inc. Environmental Bio-Systems, Inc. Environmental Bio-Systems, Inc. U.S. Environmental Protection Agency, Region 4, Waste Management Division, Superfund Remedial and Site Evaluation Branch, Sam Nunn - Atlanta Federal Center Environmental Bio-Systems, Inc. Environmental Bio-Systems, Inc. Environmental Bio-Systems, Inc. Regensis

Title Chief Hydrogeologist Chief Hydrogeologist Chief Hydrogeologist Remedial Project Manager

Fax Web site

(Continued )

203-269-8788 www.m-e. com 860-704-4775 www.tighebond. com

267-685-1801 www.arcadisus.com

415-381-5816 www.ebsinfo .com 415-381-5816 www.ebsinfo .com 415-381-5816 www.ebsinfo .com 949-366-8090 www.regenesis .com

415-381-5816 www.ebsinfo .com 415-381-5816 www.ebsinfo .com 415-381-5816 www.ebsinfo .com 404-562-8788

758

10.11

10.10

10.9

10.8

10.7

10.6

10.6

10.5

10.4

Chapter

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Chromium(VI) Handbook

415-381-5816 www.ebsinfo.com

415-381-5195 augerpro@sbcglob al.net jacquesguertin@ju no.com nlatuz@ecosystem .cl ehawley@pirnie. com augerpro@sbcglob al.net augerpro@sbcglob al.net todzuckerman@sb cglobal.net

13

12.2

12.1

12.1

11.3

11.3

11.3

James A. Jacobs R.G., Chief C.HG. Hydrogeologist James A. Jacobs R.G., Chief C.HG. Hydrogeologist Tod I. Zuckerman, J.D. Publisher & Editor

413-589-7301 www.castion.com

413-589-1601

msimon@castion. com

290 Moody Street Ludlow, MA 01056-1244

Mill Valley, CA 94941-3964 Newark, CA 94560-2034 Ecosystem, S.A Diagonal Oriente Santiago, Chile 1381 Ñuñoa Emeryville, CA 2000 Powell Malcolm Pirnie, Street, Suite 1180 94608-1832 Inc. Mill Valley, CA 707 View Point Environmental 94941-3964 Bio-Systems, Inc. Road Mill Valley, CA 707 View Point Environmental 94941-3964 Bio-Systems, Inc. Road U. S. Insurance San Francisco, CA Law Report 707 View Point Environmental Bio-Systems, Inc. Road

ahyatt@ecequip. com

415-381-5195

415-381-5816 www.ebsinfo.com

415-381-5816 www.ebsinfo.com

415-381-5195

510-596-3060

(56) 2 225678 www. ecosystem.cl 510-596-8855 www.pirnie.com

510-793-4056

561-848-9454 www.rgf.com

772-283-2642 www.ecequip .com

(56) 2 2747622

510-793-8688

561-848-1826 ext. 13

772-283-2666

http:// www.engr.ucon n.edu/~bsmets/ smets.htm

CASTion Corporation

www.enveng.tuc. gr

Stephen Brown, Vice President and Mark Simon, Engineering Director, Philip Kemp, Director of Process and Technology James A. Jacobs R.G., Chief C.HG. Hydrogeologist Jacques Guertin, Ph.D. Toxicologist–Che mist–Teacher Nicholás Latuzt, P.E. Professional Engineer Elisabeth L. Hawley Project Engineer

+30-2821037847

11.2

+30-28210-37785

[email protected] (860) 486-2270 n.edu

nnikolai@mred. tuc.gr

[email protected]

1125 SW Tiburon Palm City, FL Way 34990

73100 Chania, Technical Crete, GREECE University of Crete, Polytechnioupol is Storrs, CT 06269261 Glenbrook 2037 Rd., UNIT-2037

3875 Fiscal Court West Palm Beach, FL 33404

11.1

10.12

RGF Environmental Group

[email protected] 860-610-7145 .com

James Hart, P.E.

East Hartford, CT 06108

11.1

411 Silver Lane

10.12

Gregory M. Dobbs

Senior Consulting United Technologies Scientist Research Center Hydrogeochemical Nikolaos P. Nikolaidis, Associate Engineering and Ph.D., P.E., QEP Professor Soil, Department of Environmental Engineering University of Barth F. Smets Associate Professor Connecticut, Department of Civil and Environmental Engineering Environmental Andrew Hyatt President Compliance Equipment

10.12

L1608_Appendix-G Page 759 Tuesday, November 9, 2004 9:54 AM

Appendix G 759

James A. Jacobs R.G., Chief C.HG. Hydrogeologist Jacques Guertin, Ph.D. Toxicologist–Che mist–Teacher Jacques Guertin, Ph.D. Toxicologist–Che mist–Teacher Environmental James A. Jacobs R.G., Chief C.HG. Hydrogeologist Bio-Systems, Inc. HydroCynthia P. Avakian Senior Project Scientist Environmental Technologies, Inc. Jacques Guertin, Ph.D. ToxicologistChemistTeacher Jacques Guertin, Ph.D. ToxicologistChemistTeacher CTC-Centre Vincent Van den Bossche, Gérard Technique Cuir Gavend and MarieChaussure Joèlle Brun Maroquinerie Antero Aitio, M.D., Chief Physician, Finnish Institute of Ph. D. Biomonitoring Occupational Laboratory Health, Department of Industrial Hygiene and Toxicology

B.1

Address City, State, Zip Mill Valley, CA 94941-3964 Plymouth, MA, 02360-2923

4, rue Hermann Frenkel

Email Telephone

415-381-5195

415-751-1800

415-381-5195

510-793-8688

510-793-8688

33 72 76 10 10

Jacquesguertin@ju 510-793-8688 no.com

jacquesguertin@ju 510-793-8688 no.com

augerpro@sbcglob al.net jacquesguertin@ju no.com jacquesguertin@ju no.com augerpro@sbcglob al.net cynthiaa@hydroen vironmental.com

[email protected] 209-754-1422 om

augerpro@sbcglob 415-381-5195 al.net jim.begley@isocinf 508-732-0121 o.com

F-69007 Lyon [email protected] Cedex 07, France

Newark, CA 94560-2034

Newark, CA 94560-2034

Mill Valley, CA 94941-3964 Newark, CA 94560-2034 Newark, CA 94560-2034 707 View Point Mill Valley, CA Road 94941-3964 San Francisco, CA 195 Second Avenue, Suite A 94118-1450

707 View Point Road

19814 Jesus Maria Mokelumne Hill, Road CA 95245-9559

707 View Point Road 24 Bay View Avenue

Fax Web site

33 72 76 10 00

510-793-4056

510-793-4056

(Continued )

415-751-1816 www.hydroenvir onmental.com

415-381-5816 www.ebsinfo.com

510-793-4056

510-793-4056

415-381-5816 www.ebsinfo.com

209-754-1422

508-732-0122 www.isocinfo .com

415-381-5816 www.ebsinfo.com

760

B.1

A.2

A.1

Editor

Editor

Editor

14.2

14.2

President

Stephen M. Testa

14.1

Company Environmental Bio-Systems, Inc. MT Environmental Restoration Testa Environmental Corporation Environmental Bio-Systems, Inc.

Title Chief Hydrogeologist

14.1

Author

James A. Jacobs R.G., C.HG. James F. Begley, LSP

14.1

Chapter

L1608_Appendix-G Page 760 Tuesday, November 9, 2004 9:54 AM

Chromium(VI) Handbook

Senior Fellow Chief Hydrogeologist

Antero Aitio, M.D., Ph.D.

John F. Papp

John F. Papp

John F. Papp

John F. Papp

Thomas G. Goonan

James A. Jacobs R.G., C.HG.

Walter Olson

James A. Jacobs R.G., C.HG.

B.4

B.5

C.1

C.2

C.3

C.3

D.1

D.2

F.1

Minerals and Materials Analysis Section Chief Hydrogeologist

Environmental 707 View Point Bio-Systems, Inc. Road

Manhattan Institute

Reston, VA 20192

Reston, VA 20192

Reston, VA 20192

[email protected]

[email protected]

[email protected]

(703)648-4963

(703)648-4963

(703) 648-4963

(703)648-4963

Mill Valley, CA 94941-3964

Mill Valley, CA 94941-3964

augerpro@sbcglob 415-381-5195 al.net

augerpro@sbcglob 415-381-5195 al.net

415-381-5816 www.ebsinfo.com

www.overlawyer ed.com

415-381-5816 www.ebsinfo.com

703-648-7757

703-648-7757

703-648-7757

703-648-7757

703-648-7757

[email protected]

1211 Geneva 27, Switzerland

[email protected]

[email protected]

Rolla, MO 654090330

Reston, VA 20192

[email protected] 44(0) 207 594 5389 44(0) 207 594 www.bio.ic.ac.uk 5390

London, England

Denver Federal Denver, CO 80225 [email protected] (303)236-8747 Center, M/S x228 750, Building 20

12201 Sunrise Valley Drive, MS 989

12201 Sunrise Valley Drive, MS 989

12201 Sunrise Valley Drive, MS 989

12201 Sunrise Valley Drive, MS 989

Environmental 707 View Point Bio-Systems, Inc. Road

U.S. Geological Survey

U.S. Geological Survey

U.S. Geological Survey

Minerals Information Team Minerals Information Team

U.S. Geological Survey

Imperial College of Science, Technology and Medicine Ceramic Engineering Department, University of Missouri-Rolla World Health Organization, International Programme on Chemical Safety U.S. Geological Survey

Minerals Information Team

Minerals Information Team

Mariano Velez, Ph.D.

B.3

Medical Officer

Richard Murphy, Ph. D.

B.2

L1608_Appendix-G Page 761 Tuesday, November 9, 2004 9:54 AM

Appendix G 761

L1608_Appendix-G Page 762 Tuesday, November 9, 2004 9:54 AM