Speciation of metals in water, sediment, and soil systems: proceedings of an international workshop, Sunne, October 15-16, 1986

Lecture Notes in Earth Sciences Edited by Somdev Bhattacharji, Gerald M. Friedman, Horst J. Neugebauer and Adolf Seilacher

11 Lars Landner (Ed.)

Speciation of Metals in Water, Sediment and Soil Systems Proceedings of an InternationalWorkshop, Sunne, October 15-16, 1986

Springer-Verlag Berlin Heidelberg NewYork London Paris Tokyo

Editor Dr. Lars Landner Swedish Environmental Research G r o u p G6tgatan 35, S- 11621 Stockholm, S w e d e n

ISBN 3-540-18071-0 Sprlnger-Verlag Berlin Heidelberg N e w York ISBN 0-387-18071-0 Sprlnger-Verlag N e w York Berlin Heidelberg

This work is subject to copyright All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, re-use of illustrations, recitation, broadcasting, reproductLon on microfilms or in other ways, and storage in data banks DuphcatJon of thts pubhcatton or parts thereof is only permitted under the provisions of the German Copyright Law of September 9, 1965, in its version of June 24, 1985, and a copyright fee must always be pa,d Violations fall under the presecutlen act of the German Copyright Law © Spnnger-Verlag Berlin Heidelberg 1987 Printed in Germany Printing and b~ndlng Druckhaus Beltz, Hemsbach/Bergstr 2132/3140-543210

PREFACE

It is to-day generally recognized by environmental

scientists that the parti-

cular behaviour of trace metals in the environment is determined by their specific physico-chemical duction,

forms rather than by their total concentration.

With the intro-

several years ago, of atomic absorption spectrometry at many laboratories

involved in environmental studies, a technique for simple, rapid and cheap determination of total metal concentrations

in environmental

samples became available.

As a consequence, there is a plethora of scientific papers and reports where metal concentrations in the environment are only reported as total concentrations. It appears that the simplicity of making accurate determinations of total metal contents in water,

sediment and biological samples has somewhat masked the need

for improved knowledge about the various forms of metals occurring in the environment as well as the bioavailahility of these forms. metal speciation become

obvious

In other words, the need for

in studies of metals in the environment does not seem to have to most

environmental

scientists

until

relatively

recently.

As

a matter of fact, it was only in the middle of the 1970s that the first systematic attempts were made to obtain information about the various metal species occurring in environmental samples. During the last ten years,

however, a revolutionary change of attitude towards

the importance of metal speciation has occurred and considerable research effort has been devoted by environmental biologically increasing

important effort

to

trace couple

scientists

metals the

to measuring the concentrations of

in surface

development

of

waters.

There

chemical

is currently

analytical

an

techniques

to process-related biological problems. Concurrently, a new focus is being imposed on ecological impact studies, merit

the most intensive

that of determining which active trace metal species

research

from the standpoint

of environmental

pertur-

bation. Current efforts are directed towards the development of chemical speciation schemes which can be related directly to measures of bioavailability (i). This resulted, and

considerable

growth

of

interest

during the last few years,

seminars

in the field of metal speciation

has

in the organisation of a number of workshops

dealing partly or exclusively with chemical

speciation.

The first

one in this new category of international scientific meetings seems to have been the NATO Workshop on "Trace Element Speciation in Surface Waters and Its Ecological Implications",

held in Nervi,

Italy,

in November 1981

(2).

Later,

the

Dahlem

IV

Conferences,

Berlin,

of

Speciation

Chemical

took up the same topic when a workshop on "The Importance in

Environmental

Processes"

was

organised

in September

1984 (3). It might be pertinent to mention in this context also the International Seminar on "Speciation, Separation and Recovery of Metals", held in 1986 (4). When the present workshop on "The Speciation of Metals in Water, Sediment and Soil

Systems"

was

organised

in Sunne,

Sweden,

in this field requires a multidisciplinary

it was recognised

that research

team approach. Therefore,

scientists

with many different backgrounds - engineers, physicists, hydrologists, geologists, analytical

chemists,

biologists

and

ecologists

- were

invited with the aim of

forcing them to find a common language and, as far as possible, a mutual understanding. The purpose of the workshop was to review and evaluate the recent scientific progress in the field of metal speciation and related subjects and to discuss, from

the

various

perspectives

of

the

participants,

priorities

for planning

of

future research and possible areas of common interest and cooperation. The programme of the workshop included critical reviews of the latest progress in the development of analytical in water,

methods

for separation and determination of various metal species

sediment and soil,

to be recommended,

a discussion

of why and when metal speciation

a review of the major environmental

is

factors influencing the

distribution and transformation of metal species, and a discussion of the implications of this approach to metal research for environmental planning and management. The

Sunne Workshop,

different

countries,

which was attended

by about

30 scientists

from several

started with presentations of five major background papers,

followed by a number of contributed papers. The integral text of all these contributions

is contained

in this volume.

During the second day of the workshop,

the

participants gathered in four separate Working Groups to discuss various scenarios wherein

speciation

of metals

adequate analytical techniques, studies, aspect

would be useful or necessary.

The development

of

both for routine work and for in-depth scientific

was discussed and future needs were considered.

A particularly fruitful

of these discussions was the close contact achieved between the analytical

chemists, who develop and run the analytical procedures,

and the biologists, who

make use of the analytical data so as to interpret the bioavailability and effects of metals in the environment. It became quite clear that a much closer cooperation between

the two sides is necessary - and possible - to further our knowledge on

the distribution and effects of metals in the environment.

REFERENCES I.

Leppard, G.G. Trace element speciation and the quality of surface waters: An introduction to the scope for research. In: ref. 2: I-i0.

2.

Leppard, G.G., Ed. Trace Element Speciation in Surface Waters and Its Ecological Implications. Proc. NATO Advanced Research Workshop, Nov. 2-4, 1981, Nervi, Italy, (New York: Plenum Press, 1983).

3.

Bernhard, M., F.E. Brinckman, and P.S. Sadler, Eds. The Importance of Chemical Speciation in Environmental Processes. Dahlem Conferences, September 2-7, 1984, Berlin. (Berlin: Springer Verlag, 1986).

4.

Patterson, J.W., Ed. Speciation, Separation and Recovery of Metals. of an International Seminar. (Chelsea: Lewis Publ., 1986).

Proc.

TABLE OF CONTENTS INTRODUCTION The Metal Conference in Athens, 1985: A Growing Interest in Metal Speciation; A Review Rudolf Reuther ............................................ SECTION

I: ANALYTICAL TECHNIQUES FOR SPECIATION OF METALS DETECTION AND ROLE OF MOBILE METAL SPECIES

Metal Speciation in Solid Wastes - Factors Affecting Mobility Ulrich FSrstner ........................................... Analytical Techniques in Speciation Studies Brit Salbu ................................................ Approaches to Metal Speciation Analysis in Natural Waters G.M.P. Morrison ........................................... Metal Fractionation by Dialysis - Problems and Possibilities Hans Borg ................................................. Trace Element Speciation in Natural Waters Using Hollow-Fiber Ultrafiltration E. Lydersen, H.E. Bj~rnstad, B. Salbu and A.C° Pappas ..... The Importance of Sorption Phenomena in Relation to Trace Element Speciation and Mobility B. Allard, K. H~kansson and S. Karlsson ................... SECTION 2: BIOLOGICAL

IMPLICATIONS

13 43 55 75

85

99

OF METAL SPECIATION

Testing the Bioavalaibility of Metals in Natural Waters Peter Pgrt ................................................ Case Studies on Metal Distribution and Uptake in Biota Olle Grahn and Lars H~kanson .............................. Effects of pH on the Uptake of Copper and Cadmium by Tubificid Worms (Oligocha'eta) in Two Different Types of Sediment Anders Broberg and Gunilla Lindgren ...................... Aluminium Impact on Freshwater Invertebrates at Low pH: A Review Jan Herrmann ..............................................

115 127

145 157

SECTION 3 Summary of Working Group Reports Lars Landner ..............................................

179

APPENDIX The Workshop

Participants

.......................................

189

Introduction

THE METAL CONFERENCE IN ATHENS, 1985 : A GROWING INTEREST IN METAL SPECIATION A REVIEW Rudolf Reuther Swedish Environmental Research Group Fryksta, S-665 O0 KIL

The 5th International Conference on Heavy Metals in the Environment, which took place in Athens

(Greece),

in September 1985, was called,

in advance, one of the

biggest scientific meetings in the field of environmental research held in Europe. Looking at the great number of authors (1112) and papers presented (433) from all over the world, the conference framework was indeed impressive. Its real importance for

our

future understanding of the environmental impact of heavy metals,

as a

basis for an effective health and environmental protection policy, has still to be eyaluated.

The aim of the present review is not to assess the importance of

the conference, but just to examine to what extent the papers presented were dealing with metal speciation. Furthermore, it will discuss the general approaches to metal speciation used in the middle of the 1980s, as well as the precise methods selected for separation and detection of various metal species. Almost one fourth of all papers published in the Conference Proceedings (2 volumes,

1337 pp) dealt with speciation of metals. Some of the papers were directed

to the determination of at least one analytically defined chemical form (e g tetraalkyllead), others used a more general approach, where groups of species were separated (e g low and high molecular weight compounds) (I). However,

the use of the term "species" still seems to cause some confusion:

generally it was used in a descriptive manner and not as a measurable

quantity

related to e g the "reactivity" of the metal in the environment. So far we may rely upon the definition suggested by the participants of the Dahlem Workshop on "The Importance of Chemical Speciation in Environmental Processes", where a "species" is

understood

as

the

"molecular

representation

of

a

specific

form

of

an

element" (2). An overview of the frequencies (x) of environmental samples and metals studied, as well as separation and detection methods applied in the work accounted for in the Conference proceedings, is presented in Table I.

Table I.

The frequency (x) of environmental matrices, metals, separation and detection methods used in speciation studies.

Enviranmentel Matrix

M e ta Is

o biologicalspecimens (24x) o freshwater(15x) o waste sallds (14x) o marine sediments (13x) o soil substrata (fOx) o atmosphericconstituents(9x) o marine water (4x) o freshwater sediments (4x) o waste water (Ix)

o Cu (37x) o Pb (34x)

whole mine

organisms: tailings,

substrates

AAS ASV XRD ICP radio tracer

o solvent extraction o Ion-exchangeand gel chromatography o gas chromatography o HPLCChromatography o chemicalextraction o Catecholvlolet, EDTA

o Cd (32x) o Zn (32x) o Fe (20x) o Ni (13x) o Cr (11x) o Hg (11x) o AI (Sx) o Sn ( 5 x )

and hatho phananthroLtne complexation,

o As (4x)

chem!calmodalllng,

o Ca, ~ , ~ , K, V, U, T1,

den~ity and magnetic separation, sorptton experiments

Si, Ti, Be

concern was

Detection Analysis

o mechanical (filtration, (9x) centrlfugatlon, seLvlng)

o Co (7x)

Most

SeparationMethods

24 x), dredged

water:

(fOx) (3x) (27x)

NAA

(3x)

ISE MS T~Js~ ZSR

(3x) (3x) (2x) (2x)

o M~ssbauer spectroscopy, I~R, PIX:, EDX; DPP, C3V, F.,DA, FPH, photoapectroscopy, thermograv i t y , magaetometry, derivative spectroscopy

dedicated to biological samples (e g cells, freshwater material:

samples

(15 x),

solid wastes

14 x), marine-estuarine

(I0 x) and airborne constituents

atmospheric

(8x) (13x)

9 x). However,

(39x) (7x) (5x) (5x) (3x)

(e g dust,

tissues,

organs,

(sewage sludge,

sediments

(13 x), soil

fly ash, aerosols, vapour,

no speciation studies among those presented in

the proceedings were dealing with colloidal systems.

Speciated metal s The heavy metals

copper

(37 x),

lead

(34 x),

cadmium (32 x) and zinc (32 x)

were most frequently subject to speciation procedures, both in laboratory and modelling studies (1,:475, ~:394") as well as in routine environmental monitoring (!:380, !:585,

~:34,

~:443,

~:454,

~:559).

The great interest in these metals was mostly

related to their toxic character and their wide-spread occurrence in many natural systems as a result

of releases

from a multitude

of human activities

(e g com-

bustion, ore smelting, metal plating). Speciation

studies

with iron (20 x) and manganese

to their oxidic-hydroxidic implications

(14 x), mainly with respect

forms, have been undertaken because of their well-known

in soil weathering and sedimentary processes.

both as mobile

scavengers

for trace metals

These metals might act

in solution and as an energy

source

for certain bacteria (e g Thiobacillus ferroxidans, see !:246, !:266). The *

speciation

of aluminium

(8 x) was generally attributed to its well estab-

see Conference Proceedings, vol.: page

lished toxic effects (as "labile" AI) in acidified soils and freshwaters (forest disease, fish kills; see !:700, ~:378, ~:443, ~:446). Among other heavy metals, the following have attracted relatively great interest in speciation studies: nickel (13 x: ~:98), mercury (ii x), chromium (II x: ~:350, ~:427),

cobalt (7 x: ~:381),

tin (5 x: ~:385, ~:466, ~:531, ~:537) and arsenic

(4 x: ~:7, ~:iO, ~:484). Some of these form organic derivatives, which may be more crucial and/or reactive in their biogeochemical behaviour (volatile, lipid-soluble, persistent) than the corresponding inorganic forms (e g methyl mercury: !:88, !:103, !:282, ~:59, ~:295, ~:513, methylarsenicals, arsenobetaine, organotin compounds). There was only one paper dealing with chromium (III) and chromium (VI) species (see ~:460).

No investigation has taken up the speciation of heavy metals like

bismuth and molybdenum or of metalloids such as selenium, antimony, germanium and tellurium. Earth and alkali metals, like calcium, magnesium, barium and potassium (!:263, ~:334)

played only a minor role in speciation studies. The same is true

for vanadium (!:478, ~:522), uranium (!:i13), thallium (!:286), silicium, titanium (~:375) and beryllium (~:454). Separation methods The most frequently used separation techniques for differentiation of the bulk concentration of metals into physico-chemically defined fractions were: l. Chemical extraction (27 x; see Table 2); 2. Ion-exchange/gel chromatography (13 x; see Table 3); 3. Filtration (!:113), centrifugation and sieving (!:174, ~:394, ~:519) procedures (9 x); 4. Selective solvent extraction (8 x: !:171, !:628, [:537). Sorption (~:394, ~:519), and complexation experiments with synthetic (e g EDTA treatment: !:475, ~:516, !:700),

solutions

or the Catechol Violet determination of AI:

separation with regard to density (!:375) and numeric chemical modelling

(i e calculating

stability and rate constants: ~:225, [:295) have been applied

only marginally. While chemical extraction of metals bound to sediment,

soil and solid waste,

both as single leaching steps and as modified sequential processing, was routinely employed

in order

to obtain "operationally defined metal phases" (3) or "solid

phases which contain metal species" (2), the use of gel filtration and permeation chromatography

offered

a means

for separating

organic,

metal-binding

fractions

of different molecular weight (e g amino acids, polypeptids, proteins, humic acids) from the labile, i e the free ionic or weakly eomplexed, metal species (see Tables 2 and 3). The latter separation method was also used in combination with gas chromatography (i0 x: !:82, ~:153, !:171) and high performance liquid chromatography (3 x: ~:313,

Table 2.

Chemical extraction techniques used for metal speciation.

¥ol./Deoe o 1 R NIi4AC, pH 4.8 1 R Ntl2OH.HC| I ffi Hli20H*HCI * 4 R flAc O,I R NatP207, pH 11 6 ffi I I C I

(OTA 0 . 0 1 R HCI 0 . 1 R HC1 1 R IIC1

o 0.1R

No-hydroxide t e t r i b o r a t e o pH 9.6 Ns-pyrophosphate, pH 9 . ? o x a l a t e b u f f e r , pH 3 . 0

!

m o r b i d / l o o s e l y bound |Fe-rlch concretions metals i spring eater Rn oxides | ( F e , Rn0 Zn, Ca, Rg, hydrous Fe oxides J K, $1) o r g a n i c a l l y bound m e t a l s v e i l ordered Fe o x i d e s

I / 263 / 266

m e t i l - h u l t c acid compl, urban sludge metals bound to humics (Rn, Zn, Cu)

l / 336

H

H

~

metal oxides e humlc complexes orgnno-mlneral colplexe

soil litter (Cd, Cu)

N

I / 342

amorphous/crystallized Fe and A1 oxyhydroxtdes

|

o NH2OH'HC1, a c i d H202~ a c i d

reducible fraction oxidizable fraction

I marine sediments (Fe0 Ca, Zn)

I / 348

o 255 HAC HF/equa r e g i s

n o n - d e d r l t s l phase d e t r i t a l phase

e a t . susp. p a r t . matter (Zn, Cu, Pbo Cd)

I / 380

o HAC NH2OH.HC1 NH~-oxalate b u f f .

exchangeable metals Rn oxides Fe oxides organic bound metals residual fraction

e a t u a r , sediment I / 384 (Re, Cu, Zn, Cd, Fe, Pb)

removal o f p h o s p h o r y l - , carboxyl-0 sulfhyd'ryland h y d r o x y l - g r o u p s o f membrane p r o t e i n

x / 47s cell vail struct. components i n savage sludge ( I n , Pb, Cr)

digest. o

EOTA

o 0.1R OTPA

CaC12

correlation be,vein hisevailabllIty and p l a n t uptake

o H20 NH4Ac dlthlonlte-citrate-b£carbonate b u f f e r HC1/HNO3

voter soluble exchangeable red. Fe phases

o 1R KNO3 0.5 R KF 0 . 1 R Na4P207 0 . 1 R Na2EDTA 6 M HNO3

exchangeable metals sorbed l e t a l s org. bound metals carbonate bound metals sulfides

0

HAC

eevage s l u d g e - s o i l (Zn, Cu, NL) I s S u e r . s i l t marsh eedLment (Fe, Rn,Zn, Cu, Cd, Pb)

I

/

I / 565

Insoluble fraction

leechab~llty/immoblllz a t l o n o f Zn, Cu and Pb

sewage sludge I / 582 (Cd, Cu, I n , NI, Pb)

s y n t h e t i c vastes I / 505 s i l i c a t e sources o f cement, s i l i c a t e f l y ash

o s= In I / 38~

T1

soils

o 1 R NH4Ao, pH ? acld digestion

exchangeable metals t o t a l metal conc.

sol1 (Re, NI, Be,

o 1 R MgC12, pH 7 flH~OH.HCI H2 2/HN03 HF/H£10~

eorhed phase letelllc coatings o r g a n i c hound phase c r y s t a l l i n e phase

sewage sludge (~u, Or, Zn)

o centrlfugatlon 1 R NH4Ac

pore v o t e r d i s s o l v e d phase marine sediment I I / 3 5 3 exchangeable metals | (Cd, Ag) | e a s i l y e x t r a c t a b l e phase| c o a s t a l susp.m. I//363 (- bloauallable) , I end sediment

o 0.5

N

HCI

484

II/ samples II/334 Cut Fel Pb, Zno Cd, Co, R0, Ca) II/350

28B

Table

3.

Ion-exchange and gel chromatography techniques used in speciation studies.

~qn-ex~hl_n_ge/ehelatlnQ resin

metal.______e2ecte__..!

kind of me_?ple

Cheles

Ion-exchangeable ~n

rlverlne

low m.w. Pb-binding

erythrocytee

Sephadex G-?5

vol,/paQa

water

I / 246

I / 313

proteins G-15 gel f i l t r a t i o n

chromat.

Pb species

lumen o f the small i n t e s t i n e of rats I / 423

Sephadex G-75

metallothloneln

(MT)

"Rlmulus g u t t a t u e " I I / 4?

l i k e Cu complexes, unbound Cu and Cu bound to excluded p r o t e i n OA[ 5ephsdex A-25

RT enriched Cu f r a c t i o n s grass "Oeachampsia I I / 52

(strong anion-exchanger)

ceapttosa"

Big-gel P-6O and Big-gel

Cu linked to low m.w.

P-30 (sequence of gel chro-

proteins, hlgh m.w. Cd

matography)

binding proteins

Sephadex G-T5

metalblndlng RT-llke

"Euglens" ( p h y t o f l a g e l l s t a ) I I / 55

larvae or "Mytilue

I ! / 5B

proteins of Hg, Znt Cd g a l l o p r o v l n c l e l l s "

Sephadex G-T5

In combination with. Ni- i n liver/kldney or B8 in p r o t e i n f r a c t i o n s

B i g - g e l P°60

I I / 98

rats

low and hlgh m . w . f r a c t - freshwater pulmonate ions ot Cu end Cd bind. "Physa acute a

Sephacryl S-3OO

proteins high m,w. f r a c t i o n s

HPLC chromatography

low m,w. proteins

I I /171

I

(< 20,000 O) 5ephadex G-~5 combined with

Cd-blndlng high m.w. com- freshwater bivalve

$-300 and S-400 gel f t l t r .

pounds

"Unl elongatulus Pf." I f / l ? ?

weak soluble Cu-com-

marine bay water

I I /249

surface f r e a h v | t e r

I t 1446

end d i a l y s i s processes Chelex-lOg and ABV

p l e x e s end e l e c t r o c h e m l a b i l e CU

Oowex 50W-X8

n o n - l a b i l e A1

(cation-exchange resin)

!:55)

attached to an atomic absorption or mass spectrometry detector, in order

to further isolate and quantitatively purify metal-binding organic compounds. For both chemical extraction and gel chromatography, there seems to be a distinct need for development of more advanced specification or refining methods. This might include improved purification of high molecular weight metal-binding proteins and non-metallothionein compounds by means of further developed gel chromatographic

sequences

(!:55, !:171),

studies of the correlation between metal accumulation

in organisms and sorption (~:397),

or combined application of spectroscopic and

X-ray devices (!:266, ~:585, ~:375, ~:466: infra-red-, nuclear magnetic resonance-, ultra violet-, mass spectrometry and X-ray diffractometry). Such approaches would provide additional information about structural and binding properties of the chromatographed and/or extracted organic and inorganic metal fractions. However, the low recovery of metal species from gel chromatographic methods precludes this separation mode for quantitative speciation. There was no study using metal fractionation by in situ dialysis. On the other hand, radioactive tracers have been used for toxicological assays of metal species (ll5mcd in !:llO; 203pb in !:424) and for sorption experiments (48V in ~:522).

Detection methods To determine the metal concentration in the fractionated samples, atomic absorption spectrometry (AAS), both in the flame, graphite furnace and hydride generation mode,

has proved to be effective due to its operational ease, high sensitivity

and the low detection limits (I0-I0 - 10-12 g) for most metals, even with a complex sample matrix (39 x). Electrochemical methods,

such as anodic

stripping voltammetry (I0 x: !:122,

~:384, ~:438), ion selective electrodes (3 x: ~:283, ~:372) or catodic stripping voltammetry (i x: ~:481), measuring the free and/or weakly complexed metal ions, have been used to a lesser extent. These have a high analytical sensitivity and low detection limits (10-6 - I0-I0 g), but are supposed to manipulate the species distribution in the sample solution during the deposition and stripping step. There

was

no

metal

determination

reported

using

potentiometric

stripping

analysis (PSA). One paper dealt with the correlation between the magnetic properties of fine solid particles and metal species, i e the correlation of adsorbed metals with the magnetic susceptibility of small particles (see !:363).

Preliminary conclusions Although we are still lacking a detailed and quantified knowledge of what is really happening when metal species become subjected to our fractionating and analytical "intervention", we may assume that they will adhere to the energetically most opportune reaction paths, as decisively anticipated by our experimental equipment and the designed methodology. Sampling, storage, preparation, separation and detection modes used can modify and consequently manipulate the original species of a metal and the species composition in the sample, e g by changing the species determining parameters (such as pH, temperature, light intensity, etc).

Nevertheless, the Metal Conference in Athens showed some good promises to overcome these operationally implied difficulties by the use of conserving sample treatment (sample handling in a glove-box with an inert atmosphere, immediate speciation after pretreatments) and by combining already existing methods which are sensitive, non-destructive

and applicable in situ/in vivo

(e g ion selective electrodes,

nuclear magnetic resonance (NMR), electron spectroscopy for chemical analysis (ESCA) or M~ssbauer spectroscopy: !:384, !:423, !:375, ~:466). Another aspect, related to the impact of metals on biota (essential, indifferent or toxic metal species), was almost completely neglected in the speciation studies presented at the Conference. This was the combination of epidemiological studies with monitoring of metal species, i e investigations of the occurrence of a certain metal species along with the detection of significant health anomalies or biological injuries. A more routine involvement of "reference material" (see the National Bureau of Standards, U.S.) and standardized speciation schemes (4, 5), e g "metal speciation handbooks", would help to intercalibrate and compare data from different study areas and environmental sites. An improved comparability between different studies would also facilitate a rapid implementation of effective remedial measures against metal pollution. In conclusion, there is a clear need to upgrade the Water and Soil Quality Standards for trace metals to a level where our present knowledge on chemical speciation of metals is taken into account, because the species distribution is crucial for our understanding of the biogeochemical cycling, the fate and the toxicity of metals.

References Io

International Conference on Heavy Metals in the Environment. Athens - September 1985. Vol. !:751 pp; Vol. ~:586 pp. CEP Consultants Ltd.

2.

Bernhard, M., F.E. Brinckman, and P.S. Sadler, Eds. The Importance of Chemical Speciation in Environmental Processes. Dahlem Conferences, September 2-7, 1984, Berlin. (Berlin: Springer Verlag, 1986).

3.

Tessier, A. and P.G.C. Campbell. Partitioning of Trace Metals in Sediments: Relationships with Bioavailability. Presented at the Internat. Workshop on "In-situ Sediment Contaminants", Aberystwyth, Wales, U.K., 28 pp. (1984).

4.

Hart, B.To and S.H.R. Davies. Estuarine coastal Mar. Sci. 12:353-374 (1981).

5.

Salomons, W. and U. FSrstner. Environ. Technol. Lett. !: 506-517 (1980).

Section 1 Analytical Techniques for Speciation of Metals Detection and Role of Mobile Metal Species

13

METAL

SPECIATION

IN

SOLID

WASTES

- FACTORS

AFFECTING

MOBILITY

Ulrich F~rstner Arbeitsbereich Umweltschutztechnik, Technische Universit~t Hamburg-Harburg P o s t f a c h 90 14 03, D-2100 Hamburg 90

Abstract The a v a i l a b i l i t y of trace metals for m e t a b o l i c processes is closely related to their chemical culate matter. e.g.,

species both in solution and in parti-

For the d i f f e r e n t i a t i o n of the solid metal

cation e x c h a n g e a b l e forms,

species -

carbonate phases,

reducible fractions,

associations with organic substances and sulfides,

and the inert "resi-

dual" fractions - chemical extraction sequences have been developed, which can be used for typical

(i) a s s e s s m e n t of sources by c h a r a c t e r i z a t i o n of

speciation patterns,

of metal pollutants,

(ii) estimation of biological a v a i l a b i l i t y

(iii) d i f f e r e n t i a t i o n of geochemical

(iv) e v a l u a t i o n of d i a g e n e t i c effects,

and

(v) e s t i m a t i o n on the poten-

tial r e m o b i l i z a t i o n of metals under changing e n v i r o n m e n t a l There is a tendency,

environments,

condition.

that elements introduced with solid waste material

are less stably bound than those in natural small p r o p o r t i o n s of these materials,

systems. Even at relative

therefore, m o b i l i z a t i o n

(and sub-

sequent transfer to biota) of p o t e n t i a l l y toxic elements by acidity, c o m p l e x i n g agents,

or redox changes, may be s i g n i f i c a n t l y increased.

INTRODUCTION

The general experience that the e n v i r o n m e n t a l b e h a v i o r and toxicity of an element can only be u n d e r s t o o d in terms of its actual molecular form led to the i n t r o d u c t i o n of the term "speciation", which is used in a vague manner both for the operational p r o c e d u r e for d e t e r m i ning typical metal

species in environmental

samples and for d e s c r i b i n g

the d i s t r i b u t i o n and t r a n s f o r m a t i o n of such species in various media [I, 21. The two major categories

in applied research are "analyte

14

species" and "matrix species"

[2]: During chemical analysis the species

present in a given volume will often be transformed into a single species for which the analytical

instrument is sensitive;

to different matrices change their reactivity,

species exposed

solubility, mobility as

well as their bioavailability and toxicity. Among the criteria to assess which element or elemental may be of major concern,

species

two questions deserve primary attention [3]:

Is the element mobile in geochemical processes because of either its volatility or its solubility in natural water, so that the effect of geochemical perturbations can propagate through the environment? What are the critical pathways by which the most toxic species of the element can reach the most sensitive organs? Characterizing mobility of a certain element species at the molecular, organelle and cellular level, with respect to its "bioavailability" and "toxicity", requires further insight into the interactions of different metals with complexing ligands at physiological concentrations. Problems of "speciation" genous systems,

e.g. in soils,

become particularly complex in heterosediments and aerosol particles;

thermo-

dynamic models may give suggestions as to the possible species to expect, but due to the important role of kinetically controlled processes in biogeochemistry,

the actual speciation is often different from what

can be expected [4]. In polluted

("stressed")

systems entropy increases

and there is a concomitant increase in instability in both the physical and biological

context

[5]: The greater the stress in the environment

the more difficulty in sample handling and storage prior to analysis. Many of the analytical

techniques are handicapped by disruptive pre-

paration techniques which may alter the chemical speciation of inorganic components or lead to loss of analyte before analysis, zing,

lyophilization,

catalyzed reactions,

evaporation,

oxidation,

reactions with the sample container,

before analysis with biologically active samples, statistically invalid sampling,

extraction

e.g. free-

changes in pH, light time delays

sample contamination,

in close to 100% yield; val-

idation of analytical methodology at least needs comparison authentic samples in the same matrix [ 5] . On the other hand, it is just the "stressed"

system, where action

is immediately needed and where for an assessment or prognosis of possible adverse effects the species and their transformations tants have to be evaluated.

of pollu-

The following questions have been raised

15

with respect to the m o b i l i t y and b i o a v a i l a b i l i t y o f metals in c o n t a m i n a t e d systems

p o t e n t i a l l y toxic

[6]:

{i) How reactive are the metals introduced w i t h solid m a t e r i a l s from a n t h r o p o g e n i c activities (hazardous waste, sewage sludge, a t m o s p h e r i c fallout) in c o m p a r i s o n to the natural compounds? (2) Are the i n t e r a c t i o n s of critical metals

between solution and solid phases c o m p a r a b l e for natural and c o n t a m i n a t e d systems?

(3) What are the factors and processes of r e m o b i l i z a t i o n to become p a r t i c u l a r l y effective, when either the solid inputs or the s o l i d / s o l u t i o n interactions lead to weaker bonding of certain metal species in contaminated compared to natural systems?

Once the impact of toxic elements or elemental m e a s u r e d or predicted by direct or indirect methods

species has been (e.g., bioassays),

a m a n a g e m e n t plan can be formulated which usually includes engineering activities [5].

Examples have been given for the treatment of solid

waste materials,

where valuable elements are sometimes enriched to the

extent of e c o n o m i c a l l y feasible recycling,

for acid mine effluents and

for m e r c u r y - p o l l u t e d sediments. A common aspect of most remedial m e a s ures in such highly p o l l u t e d e n v i r o n m e n t s is either to extract toxic species or to reduce their m o b i l i t i e s and transfer rates into b i o l o g i cal systems [5].

CYCLING

AND

MOBILITY

Chemical source,

e.g.

OF ELEMENTS

AND

ELEMENTAL

SPECIES

speciation of an element is at first affected by its

from natural weathering,

metal components,

industrial processing,

use of

leaching from garbage and solid waste dumps,

and human excretions.

animal

In the course of its terrestrial and aquatic cyc-

ling varying p h y s i c o - c h e m i c a l c o n d i t i o n s may s i g n i f i c a n t l y change an element's species d i s t r i b u t i o n and its b e h a v i o r in b i o g e o c h e m i c a l

pro-

cesses [7]. Release of p o t e n t i a l l y toxic elements into the e n v i r o n m e n t influences e c o s y s t e m s in global,

regional and local scales; these impacts

can be studied from d i f f e r e n t media,

such as soil, water and biota

(Table I). For a s s e s s i n g both the rates of input and historical evolution of a certain pollutant on a global and regional dated ice and sediment cores is p a r t i c u l a r l y useful

scale, analysis of [8, 9].

16

Table I.

P e r t u r b a t i o n of the geochemical cycles of selected metals by society (examples from [4]).

Scale of Perturbation global reg. local

Diagnostic Environments

Mobilizing Mechanisms

Critical Pathway

Pb

+

+

+

Ice, S e d i m e n t

Volatilization

Air, Food

A1

-

+

-

Water,

Soil

Solubilization

Water

Cr

-

-

+

Water,

Soil

Solubilization

Water

Hg

(-)

+

+

Fish,

Sediment

Alkylation

Food

Cd

(-)

+

+

Soil,

Sediment

Solub., Volat.

Food

Of the elements

(Air)

listed in Table 1 global p e r t u r b a t i o n s are most

d r a m a t i c a l l y seen for lead. Changes on a regional scale are t y p i c a l l y found for a l u m i n i u m m o b i l i z a t i o n in soils and waters of low buffer c a p a c i t y a f f e c t e d by acid p r e c i p i t a t i o n ;

despite i n s i g n i f i c a n t anthro-

pogenic inputs of A1 i n c r e a s e d s o l u b i l i t y will induce toxic effects on both terrestrial

and aquatic biota

examples of local significance; teristic differences,

[i0]. C h r o m i u m usually r e p r e s e n t s

here,

elemental

species exhibit charac-

in that the h e x a v a l e n t form is more toxic than

the t r i v a l e n t form. Other elements,

such as lead and m e r c u r y in Table

i, may be m o b i l i z e d by the biotic or abiotic formation of o r g a n o m e t a l lic compounds. A c c u m u l a t i o n of m e t h y l - H g in seafood, critical pathway of a metal

p r o b a b l y the m o s t

to humans [3]. For d e s c r i b i n g typical

fac-

tors e n h a n c i n g the m o b i l i t y of metals in both terrestrial and aquatic environments,

the element c a d m i u m was selected.

Sources and Critical P a t h w a y s of C a d m i u m in the E n v i r o n m e n t S u b s e q u e n t to the c a t a s t r o p h i c event of Itai-Itai disease in the Jintsu River area, w h i c h was caused by effluents from mine wastes, n u m e r o u s d e t a i l e d i n v e s t i g a t i o n s on soils and waters have been carried out in m a n y countries.

Strong c a d m i u m p o l l u t i o n in a q u a t i c systems

(without indications of acute toxic effects on humans, been r e c o r d e d in the Hudson R i v e r Estuary, b a t t e r y factory),

New York

the Hitachi area near Tokyo

from P a l e s t i n e Lake,

Indiana

however)

has

(nickel-cadmium

(braun tube factory),

(plating industry), S~rfjord/Norway and

17

Derwent Estuary/Tasmania River/FRG

and from the Neckar

(pigment factory [II] ).

Compared systems,

(smelter emissions)

to the relatively

few critical

sed uptake by plants is of world-wide situation

situations

is demonstrated

concern.

The aggravating

from the example of Switzerland

WP - Waste Water Purification SS - Sewage Sludge

WASTE WATER EFFLUENT

in aquatic

of cadmium in agricultural soils and its increa-

accumulation

[12]:

Cd [Tons/Year] :

• Sanitary Landfill for Refuse and Ash

I

0

]

Fluxes

[ ] Source

OSink

R

Figure

i.

Cadmium Input into Soil from Different Sources as Demonstrated from the Example of Switzerland [12].

It seems that the atmospheric inputs of cadmium have been increased approx, fossil

lO0-fold by anthropogenic

fuels,

activities

(including burning of

smelting of ores, waste incineration,

etc.); with these

cadmium levels the upper 30 cm of soil would increase within by 0.3 ppm Cd (natural

vely diffuse in character,

direct discharges

rials are playing a particularly (Figure I): According

critical

to rough estimates

both sewage sludge and municipal

compost would be continued,

from municipal waste mate-

role for soil contamination 1 t Cd/year

waste compost,

cadmium input via phosphate fertilizers. critical

is supplied

in addition

from

to the

If todays practice of using

it must be assumed that in 20-30 years a

level of 3 ppm Cd in soil would be surpassed,

hibit the production

170 years

level 0.01-i ppm). While such inputs are relati-

which will pro-

of food for human consumption.

Dissolved and Solid Fractions of Cadmium Mobility of an element in the terrestrial is reflected by the ratio of dissolved os are firstly influenced

and aquatic environment

and solid fractions;

by the respective

these rati-

inputs and subsequently

by

18

the interactions

taking place within the different

environmental

com-

partments: Direct emissions of cadmium into the environment rials are a p p r o x i m a t e l y objects,

pigments,

mining wastes, etc.)

IO-fold higher

phosphate

fertilizers,

smelting residues,

than from dissolved

inputs

from waste mate-

from solid materials sewage sludge,

batteries,

sewage treatment,

smelter effluents,

waste waters

works,

battery factories

and e l e c t r o p l a t i n g

plants;

(by which aerosols as soil particles

precipitation

or gaseous and plant

compounds

90% of bulk cadmium deposition, climatic

conditions

deposition deposited

rain water

depending

showed pHTvalues

upon the emission

soil constituents,

in West Germany,

between

increases

70% [17]; Mississippi

fractions

10% [18]). This

[21,

(Co, Ni, and Cu) in the Susque-

and July [19] have been interpreted

The situation

particles

are deposited

that

on the bottom relati-

Sorption vs. P r e c i p i t a t i o n

in rivers should be considered

and scientific

dial action - for dissolved between

as an

in the river water

22].

P r o c e s s e s of Solid Metal Speciation:

for practical

agents.

plankton are partially returned to the solution,

the allochthonous

vely unchanged

los-

of cadmium in

[20]. For lakes and oceans it is suggested

from decomposed

whereas

seepage

such as complexing

effect of decaying organic matter which is abundant during these periods

. While

[161.

River:

factors

of dissolved metals

hanna River during Dec./Jan.

metals

15

the

higher than in the less polluted

effect could be caused by m o b i l i z i n g Relative

sources,

where

3.9 and 4.4

there will be increasing

become more acid

are s i g n i f i c a n t l y

(Rhine River:

such

10% and

- upon pH [14]; the 90% wet

For rivers it seems that the dissolved systems

of dry deposition

of cadmium is generally adsorbed on organic

ses when the soil solutions

polluted waters

from steel

[13]).

are deposited on surfaces

for the situation

part of the wet d e p o s i t i o n

lead-zinc

has been observed between

and - in p a r t i c u l a r

is decribed

and inorganic

the percentage

leaves)

and

coal burning fly ash,

(from active and abandoned

mines,

For a t m o s p h e r i c

(plated

municipal

reasons.

or solid input?

the solid and dissolved

be d e s c r i b e d by a d i s t r i b u t i o n

in more detail both

Where is the more effective

Is there an equilibrium

phases of a certain element, coefficient

reme-

"KD"?

which can

19

Evaluation of the current literature

[23, 24] suggests that there

are many factors affecting the distribution of trace metals between solution and particulates

in aquatic systems:

chemical form of dissolved metal inputs both from natural and civilizational sources [25]; the type of interactive processes, i.e. either sorption/desorption- or precipitation/dissolution-controlled mechanisms [26]; concentration and composition of particulate matter, mainly with respect to surface-active phases [27] and grain siz~ distribution [28].

Many difficulties are associated with the discrimination of dissolved and particulate metal concentrations by filtration,

centrifuga-

tion, etc. A characteristic problem is the effect of colloidal metal species;

colloids seem to have been the "forgotten component in aquatic

systems"

[29], partly because

"few researchers have the facilities or

the inclination to investigate these substances" Two effects relevant for the behaviour of metals both in natural and polluted systems are still not satisfactory explained as yet: One relates to the competition between organic and oxidic adsorption processes,

the other is concerned with the discrimination between adsorp-

tion/desorption and precipitation/dissolution

processes:

With respect to the question of competition of various solid substrate constituents, radionuclides

it has been shown by experiments on sorption of

on reducing sediments

[30 ], that oxidation of samples led

to a significant increase in solid-liquid distribution coefficients, whatever the liquid/solid ratio used. This effect is ascribed to the involvement of ferric oxides which are generated in the solid phase and which lead to a displacement of the metal from the humic acid sink. It is suggested,

that at high pH, around 9, ferric oxides may be competi-

tive with humic acids for metal sorption and that this effect increases with pH [30]. The question of sorption versus precipitation has been discussed by Br~mmer et al. [31].

It has been suggested,

that although in soils,

especially in acid once, mainly adsorption-desorption

processes of

heavy metals combined with complexation processes of organic and inorganic ligands determine the composition of the soil solution,

a forma-

tion of definite heavy metal compounds is also possible under specific

20

conditions.

These conditions are relatively high content of the heavy

metal concerned,

a very low solubility of the metal compound,

a suffi-

cient amount of anions and cations needed for the formation of metal compounds and a low content of specific adsorption sites and also of substances

(like organic matter)

which may prevent the precipitation of

definite compounds. There is a typical temporal evolution of the sorption processes, i.e. for those processes,

which cannot be explained by a direct preci-

pitation of metals from solution;

four different types of evolution

(rapid or slower adsorption to nearly 1OO%; rapid or slow adsorption at a lower level) have been distinguished

from experiments using radio-

isotopes [32]. These processes are influenced by the hydrological chemical conditions;

sorption of cesium,

for example,

lowered in the presence of Ca- and Mg-ions.

For specific adsorption,

binding strength typically depends on adsorbend concentration, there exists a range of site-binding energies tion sites,

and

is typically

since

[33]: High-energy adsorp-

since they are fewer in number than lower energy sites,

become limiting first; as lower energy sites are gradually filled, overall binding constant decreases. organic substances,

the

Particularly in systems containing

a reduced reversibility of metal sorption has been

observed [34, 35]. In natural systems, for the individual

significant differences have been observed

elements,

which are contributing

particular with respect to the parameters

to the limitations of metal concentrations.

Data measured by Wollast [36] on River Meuse well correspond to calculated values for lead, copper and zinc, whereas for cadmium the measured concentrations

are approximately one order of magnitude

predicted from the stability of cadmium carbonate

Table 2: Limitation of dissolved metal concentrations Meuse at Tailfer [36].

Element

Lead

measured

(~g/L)

calculated

(~g/L)

in River

from compound:

6 ~g/L

3 ~g/L

Copper

16 ~g/L

14 zg/L

Cu2(CO3)(OH) 2

Zinc

39 ~g/L

20 ~g/L

ZnSiO 4

iO ~g/L

CdCO 3

Cadmium

0.8 ~g/L

lower than

(Table 2):

Pb3(CO3)2(OH) 2

21

Figure 2 presents in the River Rhine,

ing extremely polluted have taken place. the German/Dutch

the examples

of cadmium and mercury discharges

which at beginning

of 1970"s has been known as be-

in all respects.

In the d o w n s t r e a m border,

tons in 1971 to approx.

discharges

"wet years"

50 tons in 1983; mercury

is due to various

[38].

However,

factors,

of metals

a significant

in critical

at

from 250

is even more effecti[37].

such as high water flows in particularly

at the

portion of the reduction

should be affected by improvement of wastewater replacement

change

I0 tons during this period

and the effects of the economic crisis,

end of the 1970"s partial

considerable

of cadmium have decreased

vely reduced from I00 tons to approx. This development

Meanwhile,

sections of this river system,

treatment and by the

applications.

t/yr 7~ 7'3 7'5 7'7 7'9 8'1 83 , 7',1 7'3 7'5 7'7 7'9 8'1 a'3 80- \\\ Mercury \x Cadmium

t/yr 200. 150" 100-

40- ~

50.

20- ~

1971 73 75 77 79 81 83

1971 73 75 77 79 81 83

I-q Dissolved

Suspended Matter

Figure 2: Changes of metal load (dissolved and particulate) in the Rhine River at the Dutch-German border from 1971 to 1983 (after Malle [37]).

It is indicated mium occurred

from these data,

in the dissolved

tion of mercury concentrations At present, data

therefore,

(i.e. KD-factors

inadequate

phase,

that the major decrease whereas

- until

mainly took place in the solid phases.

it seems that calculations of solid/solution

to model natural

for cad-

1979 - the reduc-

conditions,

partition

using e q u i l i b r i u m coefficients)

because of operational

lems, complexity of interactive mechanisms

and,

in particular,

the lack of data on reaction kinetics of sorption/desorption

are probdue to

processes.

22

ASSESSMENT OF CRITICAL POOLS FOR REMOBILIZATION OF HEAVY METALS Solid surfaces play an important role in mediating the chemical behaviour of heavy metals; environmental environment

such experience was set in relation to

problems by Farmer & Linton

(via washout,

rainout,

[39]:

groundwater

"Accessibility to the leaching,

etc.) is governed by both metal surface accessibility face enrichment)

and metal surface solubility

lung fluids,

(extent of sur-

(surface speciation)".

Since adsorption of pollutants onto airborne and waterborne particles is a primary factor in determining the transport, vity, and potential

toxicity of these materials,

deposition,

analytical methods

should be related to the chemistry of the particle's the metal species highly enriched on the surface. three methodological

reacti-

surface and/or to

Basically there are

concepts for determining the distribution of an

element within or among small particles [40, 41]: Analysis of single particles by X-ray fluorescence using either a scanning electron microscope (SEM) or an electron microprobe Can identify differences in the matrix composition between individual particles. The total concentration of the element can be determined as a function of particle size. Other physical fractionation and preconcentration methods include density and magnetic separations. The surface of the particles can be studied directly by the use of electron microprobe X-ray emission spectrometry (EMP), electron spectroscopy for chemical analysis (ESCA), Auger electron spectroscopy (AES), and secondary ion-mass spectrometry. Depth-profile analysis determines the variation of chemical composition below the original surface. Solvent leaching - apart from the characterization of the reactivity of specific metals - can provide information on the behaviour of metal pollutants under typical environmental conditions. Common single reagent leachate tests, e . g . U . S . EPA, ASTM, IAEA, ICES, and German Water Chemistry Group (Deutsche Einheitsverfahren) use either distilled water or acetic acid. A large number of test procedures have been designed particularly for soil studies; these partly used organic chelators such as EDTA, DTPA, both as single extractants or in sequential procedures. A single step method of the U.S. EPA [42] designed for studies on the leachability of waste products consists of a mixture of sodium acetate, acetic acid, glycine, pyrogallol, and iron sulfate.

Application of Chemical Extraction Sequences In connection with the problems arising from the disposal of solid wates,

particularly of dredged materials,

extraction sequences

have been applied which are designed to differentiate between the exchangeable,

carbonatic,

reducible

(hydrous Fe/Mn oxides), oxidizable

23

(sulfides and organic phases)

and residual fractions

[43]. The undispu-

ted advantage of the present approach with respect to the estimation of long-term effects on metal mobilities

lies in the fact, that rearrange-

ments of specific solid "phases" can be evaluated prior to the actual remobilisation of certain proportions of the element into the dissolved phase. One of the more widely applied extraction sequence of Tessier and co-workers [44]

has been used to examine the different

"pools" of

Cd and Pb, and to estimate their reactivity in various types of metalrich particulates

(Figure 3).

With respect to the different substrates,

the extreme leachabili-

ty of both cadmium and lead in the urban particulate matter [45] and street dust [46]

is particularly relevant for subsequent interactions

with acid, complexing,

or salty solutions

(the high cation and chloride

concentration used in the exchange solution may reflect conditions

in

soils contaminated with de-icing salt.

0%

Atmospheric Particulates Cd Pb

Street Dust Cd Pb

Soil (Rural Road ) Cd Pb

Fresh S. Sludge Cd Pb

Incinerated Sludge Ash Cd Pb -

I

20%

100%

I

I

80%

I I

40%

-

60%

60%

-

40%

80% -

-

20%

/

100% Total 55 6730 /. 1500 1.4 256 (ppm) ~'] Exchange [/[/[/~ Reducible ~ O x i d i z a b l e +Carbonate Fraction Fraction

2

~

I10

II

2275

0%

Residual Fraction

Figure 3. Chemical Fractionation of Cadmium and Lead in Solid Waste Particles (Urban Particulate Matter Standard Reference Material (SRM 1648) [45]; street dust [46]; fresh sewage sludge [47]; incinerated sewage sludge ash [48]). Extractants (after [44], modified for [47]): (la) 1 M MgCl 2 (Exch.); (ib) 1 M sodium acetate (Carb); (2) 0.04 M hydroxylamine hydrochloride/25% acetic acid; (3) 0.02 M nitric acid/30% hydrogen peroxide at pH 2; (4) conc. nitric acid digestion.

Despite the relatively low concentration of cadium in the sewage sludge sample

(activated sludge; Landau/Pfalz

nificant shift to higher percentages

[47]),

there is a sig-

in the carbonate fraction, whereas

24

lead is t y p i c a l l y e n r i c h e d in the o r g a n i c / s u l f i d i c and residual The general e x p e r i e n c e that the

(anthropogenically)

forms.

more e n r i c h e d ele-

ments are also the more reactive ones seems to be valid only for waste material, w h i c h has not been treated by high t e m p e r a t u r e processes; this is e x e m p l i f i e d by the data from i n c i n e r a t e d sludge ash municipial

(Hamilton

incinerator), w h e r e the r e m a i n i n g metals are highly e n r i c h e d

but rather stably bound in the "residual ency of e m i s s i o n control,

however,

fraction"

[483. Better effici-

of stack gases from c o m b u s t i o n pro-

cesses will recycle higher p e r c e n t a g e s of a t m o s p h e r i c p a r t i c u l a t e matter into the residues to be deposited;

these m a t e r i a l s are e x p e c t e d to

contain higher fractions of l e a c h a b l e metals,

as shown in the first two

columns of Figure 3. In r e l a t i o n to the species d i s t r i b u t i o n in the soil example

(Fig-

ure 3 r e p r e s e n t s a m o d e r a t e l y p o l l u t e d soil near a rural road studied by H a r r i s o n et al. ric particulates,

E46]) the inputs of c a d m i u m and lead from atmosphestreet dust,

more labile forms and should, changes of the chemical

and fresh sewage sludge are bound in therefore, more easily be a f f e c t e d by

environment.

S u r f a c e - r e l a t e d studies on solid m a t e r i a l s have been p e r f o r m e d or are aimed for (a) a s s e s s m e n t of sources by c h a r a c t e r i z a t i o n of typical inputs There are as yet only few studies in this field. We have p e r f o r m e d a regional survey on the d i s t r i b u t i o n of t h a l l i u m in soils in an area, where two point sources were e f f e c t i v e [491: One was an abandoned lead-zinc mine, the other was the c h i m n e y of a cement factory w h i c h had used s u l f i d i c r o a s t i n g residues as additives to special cement. Results from leaching e x p e r i m e n t s w i t h a m m o n i u m acetate showed s t a t i s t i c a l l y highly s i g n i f i c a n t differences. In the mine area, the e x t r a c t a b l e p o r t i o n was in the range of 4%, whereas in the soils a f f e c t e d by the cement plant e m i s s i o n s approx. 18% could be extracted. The lower a b s o l u t e c o n c e n t r a t i o n s in the latter area were t h e r e f o r e m o r e available, leading also in some cases to increased c o n c e n t r a t i o n s of t h a l l i u m in plants.

(b) e s t i m a t i o n of b i o l o g i c a l a v a i l a b i l i t y of m e t a l p o l l u t a n t s Initial a p p l i c a t i o n s - about 30 years ago - have been p e r f o r m e d in soil science. There is a vast amount of literature [50], and the d i s c u s s i o n of this aspect is a b o u t the scope of this presentation. However, two recent d e v e l o p m e n t s shoud be mentioned. One is the c o m b i n a t i o n of chemical and b i o l o g i c a l tests (in such an e x p e r i m e n t Diks & A l l e n [51] found a high c o r r e l a t i o n between the uptake of copper and the amount of copper present in the m a n g a n e s e / e a s i l y r e d u c i b l e phase, and it is suggested, that the redox potential and

25

pH in the gut of the studied worm is such that manganese coatings are dissolved). Another is the application of body fluids, for example, for studying the effect of leaching of contaminants from airborne particles in the lung. It is suggested that biological chelators, possible cysteine and other serum proteins are important leaching agents, particularly to remove Zn, V, Cu, and Fe from fly ash particles in vivo [521. (c) d i f f e r e n t i a t i o n

of geochemical

environments

Diagenesis involves processes in the interstital water and gases, which are strongly affected by changes of redox conditions. The sequence of "redox titration" is comprising the major reactions "respiration", "manganese reduction", "nitrate reduction", "iron reduction" and "sulfate reduction" mediated by bacteria. In ancient sedimentary deposits, these zone can be identified from characteristic mineral assemblages [53] : The oxic environment contains oxyhydrates of Mn and Fe at low conten£s of organic matter (which is mostly degraded); the post-oxic environment is characterized by the presence of manganese carbonate, both oxides and carbonates of iron, and low organic matter as well. Under anoxic conditions two branches can be distinguished: In the marine milieu reduction of sulfate provides sufficient sulfide ions to form iron sulfide, whereas in the freshwater environment there is a tendency to form carbonate of iron, when the sulfide ions are consumed; the general tendency of diagenesis in anoxic freshwater sediments is the formation of methane. Sediments collected on four campaigns represent different early diagenetic environments according to the beforementioned classification [54]. Cadmium is associated in the oxic environment with reducible phases, carbonates and to some extent with exchangeable forms. Higher percentages of sulfides are found already in the post-oxic environment and in both anoxic milieus. These findings reflect the strong affinity of cadmium to the sulfidic phase, even in such environments, where the concentration of sulfide ions is limited.

(d) evaluation of d i a g e n e t i c effects The typical effects of the earliest stages of "diagenesis" (involving transformations of organic matter, "aging" of mineral components and formation of new equilibria between solid and dissolved species) have been demonstrated by Salomons [55] with respect to the behaviour of trace metals at the sediment/seawater interface. Desorption was studied by adding cadmium and zinc to suspended matter in river water~ after adsorbing periods of i, 3, 8, 24, and 60 days, NaCI was added to the suspension to increase the chloride concentration to 1.9% (approx. seawater composition). After an adsorption period of only one day, 24% of the adsorbed cadmium and 60% of the adsorbed zinc remains bound to the sediment; after 60 days 40% of the cadmium and 88% of the zinc bound to the sediment is not released after NaCI treatment. An extrapolation can be made to'geologic time scales by a comparison of the bonding intensity of stable metal isotopes and their unstable counterparts - the latter supplied from radioactive emissions of nuclear power and reprocessing plants. In Figure 4 the effects are shown of sequential leaching of a sediment sample from the lower RhSne River in France. The reducing agents hydroxylamine (pH 2) and oxalate buffer (pH 3) only extract 15% of the natural stable manganese while the artificial isotope Mn-54 from the reprocessing plant is mobilized at more than 80% by these treatments [56].

26

MOBILIZED

~I "Stable"Nn

50~

721 /,4

40%-

/'F

D

54 Nn

/,4 //q

/ r

30%20%10%-

Cation Exchange

Easily

H

Moderately

Reducible Fracfion

Organic Fraction

SEQUENTIAL EXTRACTION Figure 4: C o m p a r i s o n of Chemical E x t r a c t a b i l i t y of A r t i f i c i a l and Stable Isotopes of M a n g a n e s e from a Sediment Sample of the RhSne River [56].

E s t i m a t i o n of R e m o b i l i z a t i o n E f f e c t s u n d e r C h a n g i n g Conditions: P r o b l e m s w i t h Sample P r e t r e a t m e n t and Individual E x t r a c t a n t s

D e s p i t e of clear a d v a n t a g e s of a d i f f e r e n t i a t e d analysis over investigations of total

sample - sequential chemical e x t r a c t i o n is p r o b a b l y

the m o s t useful tool for p r e d i c t i n g l o n g - t e r m a d v e r s e e f f e c t s from contamined solid material

- it has become obvious that there are m a n y pro-

blems a s s o c i a t e d with these p r o c e d u r e s

[57]:

(a

R e a c t i o n s are not s e l e c t i v e and are i n f l u e n c e d by the d u r a t i o n of the e x p e r i m e n t and by the ratio of solid matter to volume of extractants. A too high solid content, together with an increased buffer c a p a c i t y may cause the system to overload; such an effect is reflected, for example, by changes of p H - v a l u e s in t i m e - d e p e n d e n t tests.

(b

Processes of r e a d s o r p t i o n and p r e c i p i t a t i o n have to be considered, p a r t i c u l a r l y during e x t r a c t i o n w i t h a m m o n i u m acetate.

(c

Most important: Labile phases could be t r a n s f o r m e d d u r i n g sample preparation, w h i c h can occur e s p e c i a l l y for samples from r e d u c i n g environments.

In this respect,

earlier w a r n i n g s have been m a d e by various authors,

not to forget changes of the sample m a t r i x during r e c o v e r y and treatm e n t of the material.

The first relates to the anoxic sediment mater-

ial, w h e r e changes are quite obvious:

"The i n t e g r i t y of the samples

must be m a i n t a i n e d t h r o u g h o u t m a n i p u l a t i o n and extraction"

[43, 58].

27

The second indicates, during treatment:

that even oxic m a t e r i a l s are not safe for changes

"No storage method c o m p l e t e l y preserves the initial

and physical c h a r a c t e r i s t i c s even of oxic sediments" these problems,

p a r t i c u l a r l y for anoxic sediments,

[591. A l t h o u g h

are well known since

m a n y years, we have clearly u n d e r e s t i m a t e d the effects for a long period.

It was realized, when we have been trying to separate iron

forms in dredged sediments. model calculations, iron carbonate.

Our results were totally d i f f e r e n t from the

which claimed for a very considerable percentage of

When we tried to produce artifical

iron carbonate,

we

failed as the o r i g i n a l l y white material was d i s i n t e g r a t i n g to form red iron oxide w i t h i n short time periods.

It became obvious,

that these

m a t e r i a l s were highly sensitive to aeration.

A simple but impressive experiment on the effect of oxidation in r e g u l a t i n g the chemical

form of cadmium and other trace metals has been

p e r f o r m e d on an anoxic sediment sample from Hamburg harbour;

the sample

was divided into four series under an argon flushed glove box in order to study the effect of various sample p r e t r e a t m e n t s including aeration and d e h y d r a t i o n on the chemical

forms of cadmium

(Figure 5 [60]):

A

M a n i p u l a t i o n s of the first series were all done under the inert a t m o s p h e r e to serve as a control.

B

The second series was treated by the E l u t r i a t e Test m o d i f i e d for air b u b b l i n g [61]. This test was initially designed by the U.S. Environmental P r o t e c t i o n A g e n c y to detect any short term release of chemical contaminants from polluted material during d r e d g i n g m a n i p u l a t i o n s and disposal. This test involves the m i x i n g of one volume of the harbour sludge with four volumes of the d r e d g i n g or disposal site w a t e r for a 30-min shaking period. If the soluble chemical c o n s t i t u e n t in the water exceeds 1.5 times the ambient c o n c e n t r a t i o n in the original water, special conditions will govern the remedial measures to be u n d e r t a k e n [62]. A study conducted on the factors influencing the results of the Elutriate Tests has shown that this test as o r i g i n a l l y developed cannot yield a reliable estimate of the potential release e s p e c i a l l y of Cd, since it did not define the conditions of m i x i n g to enable a well defined, r e p r o d u c i b l e oxygen status e x i s t i n g during the test period [61]. The result was that a m o d i f i e d E l u t r i a t e Test has been p r o p o s e d in w h i c h compressed air a g i t a t i o n is utilized during the m i x i n g period. The third subsample series was freeze dried, and the forth series was dried under air in a c o n v e c t i o n oven at 60°C.

S u b s e q u e n t to the p r e s e r v a t i o n and p r e t r e a t m e n t measures, the subsamples were extracted by a six-step sequential

respectively,

leaching tech-

28

nique

(modification of T e s s i e r s m e t h o d [44]).

The s i g n i f i c a n t diffe-

rences as shown in Figure 5 can be a s c r i b e d to the contact of the sediment with air and by d e h y d r a t i o n rather than to experimental artefacts such as i n h o m o g e n e i t y of the sediments or v a r i a t i o n s t r a c t i o n protocol. pended matter [63], individual

Indeed,

in the ex-

no d i f f e r e n c e s were o b t a i n e d for oxic sus-

and the sum of the metal

concentrations

in the

fractions of all four series of each sample agreed w i t h i n

10%.

[Z] 100 exchongeoble

ri!!ili

90

corbonotic

80

F--q

e,osiJv reaucdSle

70

F-/-/-/Z

60

mo e r t ly re~uc~e I

50

sulfid./org.

40

:

30 residuol

|

20 10 0

A

II B

C

i .... iii:ii

D

Figure 5: P a r t i t i o n of c a d m i u m in anoxic mud from Hamburg harbour in r e l a t i o n to the p r e t r e a t m e n t procedures: (A) Control e x t r a c t e d as r e c e i v e d under o x y g e n - f r e e conditions; (B) after t r e a t m e n t w i t h the E l u t r i a t e Test; (C) freezedried; and (D) o v e n - d r i e d (60°C) [60].

In the p r e t r e a t m e n t scheme, which was d e v e l o p e d from this experience, a n a e r o b i c d r e d g e d samples were taken i m m e d i a t e l y from the center of the material with a p o l y e t h y l e n e until the surface.

spoon,

filled into a p o l y e t h y l e n e bottle

I m m e d i a t e l y after a r r i v i n g at the laboratory,

sedi-

ments were inserted into a glove box p r e p a r e d w i t h an inert argon atmosphere.

Oxygen-free conditions

in the glove box were m a i n t a i n e d by pur-

ging c o n t i n o u s l y with argon under slight p o s i t i v e pressure.

Extractants

were d e a e r a t e d prior to the t r e a t m e n t procedure.

From the a p p l i c a t i o n of the various p r e t r e a t m e n t procedures,

typ-

ical b e h a v i o u r of cadmium in c o n t a m i n a t e d sediments can be e v a l u a t e d

29

[64 ]: Following the application of the elutriate test, the oxidizable sulfidic/organic

portion of Cd decreases drastically and is now found

in the easily reducible fraction.

Coprecipitation and adsorption of Cd

with the precipitated oxyhydrates may have removed the liberated metal from solution.

Freshly precipitated oxyhydrates are much more effective

in scavenging high concentration of trace metals because of greater reactive surface area than aged crystalline materials and oven-drying of the initially anoxic samples,

[65]. After freeze-

cadmium proportions

were found even in the most mobile operationally defined carbonatic and exchangeable fractions.

The high concentration of cadmium present in

these fractions may have a hazardous impact on water quality during dredging and disposal operations as well as upland disposal of these sediments

[66-68].

REMOBILIZATION

Solubility,

OF METALS

FROM

SOLID

WASTE

MATERIALS

mobility and bioavailability of particle-bound metals can

be increased by four major factors in terrestrial and aquatic environments:

lowering of pH; acidity imposes problems in all aspects of metal mobilization in the environment: toxicity of drinking water, growth and reproduction of aquatic organisms, increased leaching of nutrients from the soil and the ensuing reduction of soil fertility, increased availability and toxicity of metals, and the undesirable acceleration of mercury methylation in sediments [69]. On a regional scale, acid precipitation is probably the prime factor affecting metal mobility in surface waters; increasing occurrence of natural and synthetic complexing agents, which can form soluble metal complexes with trace metals that are otherwise adsorbed to solid matter; increasing salt concentrations, by the effect of competition on sorption sites on solid surfaces and by the formation of soluble chloro-complexes with some trace metals; and changing redox conditions, anoxic dredged materials.

e.g. after land deposition of polluted

Here, particular attention will be given to the effects of pH and redox changes in surface waters and soils: There are as yet only few data on the effect of acid precipitation on metal mobilization in groundwater.

It is expected that neutra-

lization of H+-ions in the unsaturated zone also leads to mobilization

30

of heavy metals that are d i s c h a r g e d into the g r o u n d w a t e r together with sulfate and nitrate ions [70]. In Swedish lakes a p r o n o u n c e d c o r r e l a t i o n was o b s e r v e d b e t w e e n d i s s o l v e d metal

levels and pH

(Figure 6 after Dickson [71]);

n o m e n o n is p r o b a b l y due to the c o m b i n e d effects of dissolved equilibria

(i) changing solid/-

in the a t m o s p h e r i c precipitation,

cesses on soils and rocks in the c a t c h m e n t area, water m o b i l i t y of metals and

this phe-

(2) w a s h o u t pro-

(3) e n h a n c i n g ground-

(4) by active r e m o b i l i z a t i o n from aquatic

sediments.

I

0.3

"0

0.2 •

l

•

~ \0")

5 4

-I

3

Q-

2?

0.1

0.05 ,,,=0.05 4.0

I

,, ,I,,,-,

I

5.0

6.0

7.0

8.0

= Figure 6.

O5 <015

I

4.0

5.0

pH

6.0 =

7.0

8.0

pH

D i s s o l v e d C o n c e n t r a t i o n s of C a d m i u m and Lead in 16 Lakes on the Swedish Coast with Similar D e p o s i t i o n but with D i f f e r e n t pH (after Dickson [71]).

At lower pH-values,

one can o b s e r v e a typical a n t a g o n i s t i c b e h a v i o u r

for c a d m i u m and iron under d i f f e r e n t r e d o x - c o n d i t i o n s .

An example of

solid w a s t e c o m p o s t in Figure 7a has been studied by Herms & BrOmmer ~ 2 ~ At pH 5, iron is m o s t m o b i l e at redox values b e l o w zero, and cone n t r a t i o n s in s o l u t i o n were up to 600 mg Fe/L; hand,

has h i g h e s t d i s s o l v e d c o n c e n t r a t i o n s

c o n d i t i o n s of +500 mV

. It seems,

cadmium,

- up to 1 mg

on the other Cd/L

-

at redox

that the study of such c o u p l e d cycles

will be p a r t i c u l a r l y p r o m i s i n g with respect to the interactions of large r e d o x - c o n t r o l l e d systems trace metals

such as cadmium,

R e l e a s e of trace metals,

like iron and m a n g a n e s e with critical m e r c u r y and arsenic.

p a r t i c u l a r l y of cadmium,

from anoxic sludges

has been r e p o r t e d from e s t u a r i e s and coastal m a r i n e zones [73]. experiments,

In

the m a j o r m o b i l i z a t i o n effects for c a d m i u m o c c u r r e d after

3-4 weeks t r e a t m e n t time.

Therefore,

it has been inferred that simple

31

pH5

Eh (mV)

.

pH7 ,

0,5 mg Cdtl

÷600" +400-

pH6

'

0,3

0,2

~/~"V//~"

Cd Fe

+200

2

J °t

"Z-O -200~

0

mgFell

560

10

20

30

~0

50 ~

t [days]

200 0

6

"

|

Figure 7. M e c h a n i s m s of Cadmium M o b i l i z a t i o n from Solid Waste Fig.

7a: S o l u b i l i t y of C a d m i u m and Iron in W a s t e Compost at D i f f e r e n t pH and Redox Conditons [72].

Fig. 7b: Effect of B a c t e r i a on C a d m i u m Release from Anoxic Sediment under S e a w a t e r Conditions [74].

cation exchange m e c h a n i s m s o b v i o u s l y have no importance addition of antibiotics

[741. In fact,

to the system on the 21st day resulted in an

interruption of the Cd release for a period similar to the initial phase

lag

(Figure 7b); it is suggested that bacterial a c t i v i t y can stimu-

late Cd r e m o b i l i z a t i o n by a complex system of substrate d e c o m p o s i t i o n [74 1.

M e c h a n i s m s such as o x i d a t i o n of organic and sulfidic m a t e r i a l s may explain the findings of Hunt & Smith [75] from e n c l o s u r e experiments in the N a r r a g a n s e t t Bay, where the a n t h r o p o g e n i c p r o p o r t i o n of c a d m i u m in m a r i n e sediments is r e l e a s e d to the water w i t h i n approx. three years time;

for the r e m o b i l i z a t i o n of copper and lead approx.

and 440 years is needed,

respectively,

40

a c c o r d i n g to these e x t r a p o l a -

tions. These data d e m o n s t r a t e the p r o b l e m a t i c effect of d i s p e r s i n g anoxic w a s t e m a t e r i a l s in e c o l o g i c a l l y productive, shore,

estuarine,

h i g h - e n e r g y near-

and inlet zones [67], and it has been e m p h a s i z e d by

Berman & Bartha [76],

that the "contaminated dredged spoils should be

prevented from w e a t h e r i n g and should be speedily e n t o m b e d in an anoxic s u l f i d e - r i c h environment". An example of oxidative r e m o b i l i z a t i o n of c a d m i u m and other heavy metals has been studied in a tidal f r e s h w a t e r flat in the upper Elbe estuary near Hamburg [77]. This m u d f l a t - diurnal tidal water fluctua-

32

SEO,.ENT

Eh

MILIEU

ZONES -

-

I

I

Cd spec

~ I~1 0

0

*200 .'4.00

,

50 i

Cdtot 100%

0

5 10 15 20 Cd [ppm] I

I

I

,|

4

oxic

8 post oxic

12

12

16

16

-

onoxJc

i

i

-200

0

i

i

20

20

2~

24

28 {cm}

2B

{cm)

Chemical I---"l exchangeable*carbonatic ~ forms L ~ reducible ~

Figure 8.

sulfidic/organic residual

Core S e d i m e n t s from the H e u c k e n l o c k Intertidal Flat in the Elbe near Hamburg [77]. Left: Sediment Milieu Z o n e s / E h - C o n d i t i o n s . Middle: Chemical Forms of Fe and Cd in Sediment. Right: Bulk Cd Distribution.

tions in the range of 3 m are a f f e c t i n g this p r o d u c t i v e site - is colon i a l i z e d by dense m o n o d o m i n a n t reed stands p r o v i d i n g an e f f e c t i v e trap for heavy metal m i u m contents

loaden s u s p e n d e d m a t t e r from upstreams.

in the rhizomes of the emerged m a c r o p h y t e s

E l e v a t e d cadindicate high

p r o p o r t i o n of b i o a v a i l a b l e Cd species in the root zone.

E x a m i n a t i o n of s e d i m e n t cores taken at this site showed d i s t i n c t p a t t e r n of redox potential and heavy metal

fractionation profiles

(Fig-

ure 8). Below a m a r k e d redox potential d i s c o n t i n u i t y the Fe fractionation p r o f i l e is c h a r a c t e r i z e d by i n c r e a s i n g N a - a c e t a t e e x t r a c t a b l e proportions,

w h i c h p r e s u m a b l y r e p r e s e n t s c a r b o n a t i c Fe(II)-forms.

t i c u l a t e c a d m i u m binding forms, invers to that of iron: While

on the other hand,

reveal a b e h a v i o u r

in the anoxic zone a p p r o x i m a t e l y

80% of Cd is found in the o x i d i z a b l e fraction,

The par-

60% to

high p e r c e n t a g e s of Na-

a c e t a t e e x t r a c t a b l e forms are found in the oxic and p o s t - o x i c zones of the sediment cores. The higher amounts of labile cadmium forms are a c c o m p a n i e d with a m a r k e d d e p l e t i o n in the total content of the toxic metal

compared to that in the anoxic sediment zone. C o m p a r i s o n of the

f r a c t i o n a t i o n patterns and total contents of other d i a g e n e t i c a l l y m o b i l e metal examples

less

indicates that a s i g n i f i c a n t p r o p o r t i o n of cad-

m i u m is leached from the surface sediment by a process of "oxidative pumping" by tidal water d r a i n i g e in this h i g h - e n e r g e t i c environment.

88

This could result in m i g r a t i o n of the r e m o b i l i z e d metal into either the deeper anoxic zone, where it can p r e c i p i t a t e again to contribute to the e n h a n c e d o x i d i z a b l e s u l f i d i c / o r g a n i c fraction,

or to the surface water,

from w h e r e it can be e x p o r t e d into the outer estuary.

It could,

ever, also c o n t r i b u t e to b i o a v a i l a b l e cadmium portions ted by the enhanced

how-

such as indica-

m a c r o p h y t e cadmium concentrations.

P r e d i c t i n g Potential Metal M o b i l i z a t i o n f r o m Solid S p e c i a t i o n Problems with metals which are d i s p e r s e d in the environment still exist both on a local and regional

scale. Large quantities of w a s t e m a t e r i a l s

on land and in aquatic systems represent l o n g - t e r m reservoirs for the release of metals p o t e n t i a l l y involving detrimental effects on the quality of both g r o u n d w a t e r and agricultural products.

A l t h o u g h the individual

"fraction" received from the chemical

leaching e x p e r i m e n t s rarely reflect specific metal

"phases",

but rather

are defined by the selection of the e x t r a c t i n g m e d i u m and by the experimental conditions

("operational phases"),

the elution m e d i u m is

designed to simulate certain - m o s t l y extreme - environmental tion,

condi-

such as the interaction with saline waters in estuaries or redu-

cing conditions during land disposal of sludge materials.

The overall

most s i g n i f i c a n t effects on the r e m o b i l i s a t i o n of heavy metals can be expected from acidification,

either from a t m o s p h e r i c emissions or from

o x i d a t i o n of sulfidic compounds in anoxic waste materials.

Experiments

on the long-term b e h a v i o u r of s l u d g e - i n d u c e d metals in agricultural soils should pose,

therefore,

and pH-conditions.

In addition,

to be studied,

p a r t i c u l a r a t t e n t i o n on changes of redoxthe effects of organic substances have

since the m o b i l i t y of released metals can be affected by

c o m p l e x a t i o n processes. Species d i f f e r e n t i a t i o n s can be used for the e s t i m a t i o n on the r e m o b i l i s a t i o n of metals under c h a n g i n g e n v i r o n m e n t a l conditions:

In the e s t u a r i n e e n v i r o n m e n t the "exchangeable fraction" might be a f f e c t e d in particular; however~ changes of pH and redox potential could also influence other easily e x t r a c t a b l e phases, e.g. carbonate and m a n g a n e s e oxides. The high p r o p o r t i o n of Cd in e x c h a n g e a b l e fractions of p o l l u t e d sediments is reflected in the typical mobilization effect of this element in the estuarine environment. Among the factors e n h a n c i n g metal m o b i l i t y a c i d i n t e r a c t i o n s - both from acid p r e c i p i t a t i o n and o x i d a t i o n of sulfide m i n e r a l s in mine wastes and dredged sediments - deserve particular a t t e n t i o n due to

34

the fact that ionic species predominates, which is readily available for biological uptake. Lowering of pH will affect, according to its strength, the "exchangeable", then the "easily reducible" and in case part of the "moderately reducible" fraction, the latter consisting of F e - o x y h y d r a t e s in less crystallized forms. In strongly reducing environments, e.g., in highly polluted sediments, the "moderately reducible fraction" can be affected too, especially when the iron is present in the form of "coatings". The effects on o r g a n i c a l l y bound metals are more complex; however it has been argued that this fraction is highly susceptible to environmental changes, e s p e c i a l l y during early diagenetic reactions, where recycling of m i n e r a l i z e d organic matter and pore fluid transfer processes are controlling the dynamics of pollutants and nutrients in solid waste materials. Estimations

on the long-term behaviour

ials should pose particular ditions.

For determining

term r e a r r a n g e m e n t originally

both effects

- we have m o d i f i e d

been used by Patrick

system from solutions. system are "pH",

simulating

the effect of time).

intensities

of contact between

using shakers,

Bioavailability

transport

applied

and "temperature"

sequence before

in the self(the latter for

The system can be applied for different solid materials

conditions

and solution,

e.g.

by

bags.

measure of the utilization E79~,

of an

and includes mechanisms

to a site of m e t a b o l i c / t o x i c active/toxic

form,

activity,

such as

biotrans-

retention/accumulation,

[80]°

With respect to the aqueous metal

or "speciation"

holds that the kinetics

species it has been suggested

ion form is the most available

compared to the particulate,

("equilibrium"

Chemi-

of Metals

that the "free" or aquo-metal organisms

which has

waste materials.

columns and dialysis

to a m e t a b o l i c a l l y

and excretion

The variables

is a quantitative

under specific

formation

scheme,

[78] and Herms and Brummer [721

and municipal

"redox"

flow-through

Predicting Bioavailability

absorption,

release and long-

and the released metals are recovered with an ion-

regulating

element

- short-term

are analysed with a six-step extraction

and after treatment exchanger

in solid waste mater-

an experimental

et al.

for the study of soil suspensions cal fractions

of metals

attention on changes of redox- and pH-con-

complexed,

hypothesis [ 81]). Another

of the dissociation

[82 ] - which can be determined

or chelated

forms

hypothesis

of trace metal

using a controlled

for

complexes

flow rate column

35

technique with cation exchange resin Chelex i00 toxicity of trace metal,

83

- may regulate the

since rapidly dissociating trace metal comple-

xes would constitute the bioavailable fraction of a given metal's total concentration [ 831 • It has been shown by Engel and Fowler [841 that mobilization of metals by increasing salinity or elevated contents of chelating agents does not necessarily lead to increased accumulation and toxic response of organisms.

Recent data of Florence & Stauber [85]

for Cu indicate that water-soluble city, whereas

ligands generally decrease the toxi-

lipid-soluble copper complexes were highly toxic.

The present state of knowledge on the interrelation between solid matter speciation and the quantitative extent of bioavailable element concentration is still unsatisfactory,

since the leachable fraction

does not necessarily correspond to the amount available to biota [861. In most cases information is lacking about the specific mechanism by which the organisms activity participate in the removal of nutrients from the solid substrate. redox changes,

Plant roots activities,

for example,

include

pH alterations and organic complexing processes.

tition exists between adsorption sites on the solid substrate

Compe-

(Fe/Mn-

oxides, organic matter) and selective mechanisms of metal uptake by the different organisms

[871.

Two possible ways for improving the correlation of data between the different solid substrates and the organisms could be: and

(i) Study of soil solution/interstitial

(or part of them) water chemistry

[88],

(ii) combination of chemical extraction and bioassay [ 891.

The application of various bioassays to assess the potential pollution arising from dredging activities,

as required by legislative mandate in

the U.S., has been reviewed by Engler [ 62] :

(i) Liquid-phase bioassay. Algae and zooplankton were found to respond adequately and may be used to assess stimulation or toxicity. An estimation of mixing and dilution factors that are expected to occur on disposal must be included in the experimental design to simulate field conditions. The mortality of organisms, rather than sublethal considerations, has to be chosen as the indicator of potential environmental effects. (ii) Solid-phase bioassay. The greatest potential for impact on benthic organisms generally lies with settleable or solid-phase material. When selecting organisms, one filter-feeding, one deposit-feeding and one burrowing species should be included [90~. Mortality is chosen as the interpretative endpoint because of its clear environmental significance.

36

(iii) Bioaccumulation. Because of long-term effects of bioaccumulation and the short-term nature of the laboratory bioassays (IO-day duration), field evaluation of bioaccumulation in site-specific aquatic organisms should be used wherever there has been a historic precedence of disposal at athe site in question. A valid conclusion regarding bioaccumulation is based on statistical significance (95% confidence level) differences in the body burden of specific constituents between organisms in the dump site and the same species living on uncontaminated sediments of similar sedimentologic characteristics. An integrated approach correlating bioassay data of a two-chamber exchange system to the results from a six-step chemical extraction sequence was designed by Ahlf [91]. With this system which separates an algal population

(or algal cell walls)

from suspended solids by a 0.45

fm membrane filter, variations of pH, salinity,

redox and effects of

complex~ng agents can be studied for their effects on both accumulation ah~toxicity.

OUTLOOK:

REMEDIAL

OPTIONS

Various remedial measures against excessive release of toxic metals into the environment may be considered,

giving priority to the techno-

logies applied near the source of pollution. persed,

If metals have been dis-

liming of soils and waters as well as mechanical

stabilization of solid waste such as

encapsulation,

and chemical

use of impermeable

base liners and surface covers could reduce fluxes and biological

avai-

lability of toxic metals [ 9 7 .

Generally,

maintenance of a pH of neutrality or slighly beyond

(by application of lime or limestone)

favors adsorption or precipita-

tion of soluble metals [93, 94]. For mercury contaminated sediments isolating from the waterbody by means of physical barriers, such as polymer film overlays,

blanket plugs of waste wool,

sand and gravel

overlays has been proposed [95-97]. Methods of controlling the problem of acidic mine drainage include thermodynamic measures oxygen and the maintenance of reducing conditions;

(elimination of

e.g. by application

of sewage sludge on the surface of the spoil heaps) and kinetic effects (e.g., changes of the bacterial propagation cycle [981). Control of tailing effluents includes seepage collection and handling,

and under-

water disposal [99]; there are many possibilities of applying physicochemical methods to effluent processing, other fields of metallurgy

as presently

(e.g., electroplating).

being applied in

37

The best strategy for disposing contaminated sediments is to isolate them in a permanently reducing environment [i00~, e.g. in capped mound deposits above the prevailing sea-floor or (capped) disposal subaqueous depressions;

in

from a geochemical view the marine sulfidic

environment is favourable due to the high stability of metal sulfides, particularly of mercury mercury),

(disproportionation of highly toxic monomethyl-

and more efficient degradation of organic matter [iO1].

Acklnowledgements The present review has been improved by discussions with many colleagues. In particular, I would like to thank Mr. Michael Kersten for his suggestions and for providing material on redox effects on metal speciation of sediments. The invitation by the Workshop Committee is gratefully appreciated.

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43

ANALYTICAL TECHNIQUES IN SPECIATION STUDIES B. Salbu, Department of Chemistry, University of Oslo, Blindern, 0315 Oslo 3.

ABSTRACT

Natural waters are dispersed multicomponent

systems where most

naturally occurring elements are present in micro or trace concentrations,

ranging from 1 mg/l to orders of magnitude below.

In addition trace elements,

especially multivalent metals may be

present in different physico-chemical charge and density.

forms varying in size,

They may be associated with forms ranging

from simple ions and molecules and via hydrolysis products and polymers form colloids,

pseudo-colloids and may be sorped or

incorporated in organic and inorganic material. other components

The presence of

in waters will also influence the distribution

pattern of the element in question as transformation processes OCCUr.

Due to the low concentrations of trace elements and the variety of components present in natural waters, favourable for speciation purposes.

combined techniques are most Species are therefore fracti-

onated according to physical and/or chemical properties f.inst. size and charge prior to their measurements.

Then analytical

methods having sufficiently low determination limits for the elements in question are required. The present paper will discuss requirements which should be met by techniques favourable for speciation studies of trace elements in natural waters.

44

INTRODUCTION For macrocomponents

the chemical behaviour in waters can be

derived from macrochemistry while in dilute solutions, which are negligible for macroconditioning, The reaction rates may f.inst,

become significant.

decrease as the probability of

effective collisions decreases.

Furthermore,

and mechanisms may change as other processes, phase boundaries

(e.g. sorption)

systems may become predominant.

phenomena

reaction directions such as chemistry at

and chemistry of colloidal These dilution concentration

phenomena are well known from radiochemistry

(1-3).

Trace

elements are therefore defined as elements present in a concentration range where these secondary reaction phenomena no longer can be neglected.

These reactions may become significant for a

10 -5 M solution corresponding to a concentration (ppm)

of 1 mg/l

for elements having a relative atomic weight of i00 (3).

Roughly,

1 ppm can be regarded as the lower limit for which

information from macrochemistry

is sufficient for describing

occurring phenomena.

Physico-chemical

states of trace elements.

In natural waters, metals,

most trace elements especially multivalent

can be present

As illustrated

in a variety of physico-chemical forms.

in Figure I, trace elements may be associated with

forms ranging from simple ions and molecules and via hydrolysis products and polymers form colloids and pseudo-colloids,

or be

sorped on and incorporated in suspended inorganic or organic particles

(4).

T h e dimentions given in the figure are only

tentative as the borderline between categories is difficult to establish because gradual transitions occur.

The kinetics and the

reversibility of the transition processes are, however, questions to be answered The categories

still

in the future.

indicated in Figure 1 comprise species behaving

chemically rather differently as neutral and charged species are not differenciated. in the water will

Furthermore, the presence of other components

influence the size distribution pattern for an

element of interest.

45

U] (D O~ IZ:

u

o

e~ 1

e-

e.

0

._o

e~

E

y_ e'-

r.,,.

~-~

(P

C

CL

ga o ° o

(P N

"0

(D

o ~ . _u

in

E

E '0

>- ¢ Jc - -

0

u o

o

---~

E ~

..¢:

.

E~

O(D O~

.c: O g

.,-I RD

E ¢-

~D •P (i}

h

E

E

8

(,0 (p

(Dc~ ,-~ (D (Du) U~ (i) (D O O ~0

>.

E%

e-

O0 Om

r 0 e~

O0

0

~o

8J

O (D 0

E 0

e~

E

r-

v.-

'~_

>, 0

E

-~E

C

.D

"'~

E

~00

O.

~. =_ E "5 z

r~

46

By sorption to sites offered by foreign surfaces,

the low

molecular fraction is usually reduced while f.inst, colloidal fraction increases.

the pseudo-

The presence of complexing agents

will often reduce the low molecular fraction while the polymeric fraction increases.

Various factors

(e.g.

ionic strength) may

influence the stability of colloids and aggregation/dispersion processes may result in an alteration of the distribution of species.

TOTAL CONCENTRATIONS

When total concentrations of trace elements to be determined, used,

in natural waters are

the analytical results may depend on the method

i.e. its capability to include all species,

culate/colloidal fraction,

in the analysis.

Based on acidified samples

(pH

also the parti-

i, HNO 3, 3 months),

scattered

results for total concentrations of AI, Fe, Mn and also Zn were obtained when using INAA, AAS and ICP (5). obtained, analysis.

Good agreement

was

however, when particles/colloids were removed prior to Furthermore,

the total concentrations f.inst,

for Mn

determined by ICP or AAS were equal to those in fractionated samples.

Thus,

a discrimination of particles/colloids

and asso-

ciated elements seems to take place when ICP and AAS are used.

Unless a full decomposition of particles/colloids

is obtained,

results will depend on the preanalysis handling procedure acid conservation,

time of storage).

the

(e.g.

Thus, acid conservation may

not be sufficient for decomposing particles retainable by filters.

This particle effect has been observed in waters of different composition and origin, material

is present.

being more pronounced if inorganic

Therefore,

discrepancies seen in literature

data concerning trace metals in natural waters when different methods are applied on acid conserved samples only, may at least partially be attributed to differences analysis.

in species included in the

47

FRACTIONATION

TECHNIQUES

Direct methods are not sufficiently

sensitive or selective

obtain information

species

heterogeneous

on trace element

systems as natural waters. properties

in multicomponent

Therefore,

techniques where samples are fractionated and/or chemical

to

combined

according to physical

prior to the analysis

itself,

are

required. It is quite obvious that

different

be interfaced with molecule, Within

inorganic

element or isotop specific

combined with element

esp. atomic absorption spectrometry inductively

coupled plasma spectrometry however,

combinations

spectrometry

(HPLC-MS)

of fractionation interesting

Especially,

when different

(e.g. size fractionation electrodialysis) chemical

Within organic

liquid chromatography-mass

the combination techniques

purposes. of GC-GFAAS Several

(6),

other

and detectors

are

for speciation purposes. fractionation

techniques

and charge fractionation

prior to analysis,

forms of trace elements

when the volume fractionated several different

(ICP).

(8) has been utilized.

potentially

tech-

specific detectors,

are used for speciation

compounds

(7)/HPLC-IPC

combinations

detectors.

such as gas chromatography-mass

(GC-MS) and high pressure

For organo-metallic

are combined

techniques

should be improved.

is large,

analytical methods

For studies of trace element species steps influencing

as in

information on physicoFurthermore,

it is most useful

to use

on each fraction to obtain

more data.

critical

can

(AAS) and atomic emission

spectrometry

HPLC-AAS

techniques

chemistry size and charge fractionation

niques are frequently

chemistry,

fractionation

analytical

in natural waters,

the

results are sampling,

handling of samples and the fractionation

techniques

applied.

48

Processes

influencing the physico-chemical forms of trace elements

takes place during storage of water samples. information on species actually present

In order to obtain

in a certain water system,

the fractionation should take place in situ or at least immediately/shortly after sampling. from disadvantages,

As all fractionation techniques suffer

methodological

effects must be controlled and

accounted for.

REQUIREMENTS Requirements which should be met by fractionation techniques for speciation purposes can be summarized as follows:

a)

Fractionation in situ or at the site is essential as storage effects are then avoided.

b)

The fractionation should be rapid in order to avoid the establishment of equilibria between species retained and to be separated during the fractionation (i.e. the production of species of interest during fractionation).

c)

Equipment surface area to sample volume ratio should be small in order to reduce sorption. However, conditioning with a sample aliquot minimizes this effect.

d)

The method should not be sensitive to clogging.

e)

Stability of colloids should not be disturbed aggregation).

f)

Aggregates present should not be disrupted by stirring of solutions.

g)

No reagents should be added.

h)

The contamination risk should be kept low (e.g. closed systems).

i)

Techniques providing large volume fractions are favourable as:

(e.g.

i) The determination limits of elements can be lowered by concentrating the samples from large volumes. 2) Further investigations methods, b i o t e s t s ) c a n

(e.g. different analytical be performed.

The degree of which the different most frequently used fractionation techniques meet these requirements and

2.

is indicated in Tables 1

49

,-1

X

-,-t t/l

X

I~

X

X

X

X

I~

~I

X

X

I~

~

X

Ix:

X

~

-~-~

A

,-.4 4.1

L) 1

X

t~ -PI X

I~

X

X

X

X

~I

~

X

X

X

X

X

X

X

X

X

X

X

X

X

.P = 0 .P 0 4J tQ

I~ .1-t

0

I~I

X

4J £: OJ

~2

OJ

-~-I t~

,-.4

X

50

Table

2.

R e q u i r e m e n t s for charge f r a c t i o n a t i o n techniques (x-acce)table)

Requirements:

I n exchanqe Membranes: Resins:

Rapid

X

In situ/at the site

X

Extractions:

X

I

Electrochemical methods ASV: Cent.pot.*) :

X

Insignificant sorption Insignificant clogging No aggregation

X

No stirring effect

X

X

X

X

(X)

X

X

x

x

(x)

(x)

x

X

X

No reagents added Closed system

X

X

Large volumes

X

X

filter effect

gel filter effect

Other effects or information needed

X

collodial particl~ atp~se interface. Distr~ut. coeff. needed, ~pendson ~n~ct time

Operationally *) C o n t r o l l e d

potential

defined

electrolysis

change of pH

X

depends on potential

depends on deposition time, stirring

51

Among size fractionation

techniques,

in situ dialysis

able being essentially a sampling technique

(9-11).

However,

low flow rate of water masses during growth season, membranes

occurs.

Furthermore,

episodic

changes

is favour-

in the water

quality may not be recognized

as the diffusion

In these cases large membrane

(hollow fiber) ultrafiltration

suitable as fract~onation (sampling and subsequent

is a slow process.

fractionation

in close systems).

sorption can be minimized

by conditioning

In addition,

large volumes for further

investigations

The benefit of large membrane

that different

Conventional

(hollow fiber)

low molecular weight species

from rate measurements

(4, ii). are obtain-

dialysis

is

can be distinguished

(4).

ultrafiltration

and gel-filtration

is

can be performed directly at the site

Furthermore, able.

at

clogging of

(cell),

conventional

dialysis

suffer from several disadvantages.

gical effects may seriously

influence on the distribution

and results obtained using these techniques,

(cell)

Methodolopattern

should be handled

with great care. Analytical

results obtained using charge fractionation

are operationally influenced

defined

(Table 2), and are to a certain extent

by the presence of polymers,

and particles.

Therefore,

techniques

colloids/pseudo-colloids

when size fractionation

prior to charge fractionation,

analytical

is applied

results are easier

to

interpret.

Among charge fractionation essentially

added may influence only be partial. experimental

species present,

Furthermore,

extraction and ASV are

techniques.

When ionic exchange

However,

reagents

and the fractionation

analytical

design esp. the experimental

(e.g. mixing time,

separation

techniques,

rapid fractionation

may

results depend on times involved

plating time). resins or chelating

is essentially

resins are used,

slow and distortion

tribution patterns may occur.

Using columns,

of original analytical

the disresults

52

depend f.inst,

of flow rates.

Furthermore,

the column may also

act as a gel-filtration resin while filtration through ionexchange membranes may be affected by clogging.

Thus,

retained

species cannot be interpreted as originally charged "free" ions only. RADIOACTIVE TRACERS

Chemically well defined radioactive tracers are also most useful for speciation purposes and for investigating microchemical cesses affecting substances

pro-

in "infinite dilute" solutions.

is due to the ease of detecting radiation;

This

i.e. the very high

sensitivity using radioactive tracers when compared to other techniques.

Within analytical chemistry,

the use of radioactive tracers repre-

sents a powerful tool for investigating the applicability of analytical procedures.

By adding chemically well defined radio-

active species to solutions,

chemical yields of individual species

at different fractionation steps or whole procedures can be determined. Tracer experiments can also reveal information on the distribution of traces between different exchange reactions) in heterogeneous

species in homogeneous systems

or between f.inst,

systems

(i.e.

solution and solid phases

(e.g. sorption processes).

Furthermore,

dynamic tracer studies can be utilized for investigation of microchemical processes affecting the physico-chemical forms of trace elements.

By combinding size and charge fractionation techniques,

the transformation of species can be followed and information on the reaction paths and kinetics involved can be obtained. mation on naturally occurring components

Infor-

influencing the chemistry

of trace elements can also be achieved if dynamic tracer experiments are performed using model solutions containing specific interferences as of naturally occurring colloids.

53

CONCLUSIONS

The presence of different physico-chemical in natural waters logical uptake.

influences the transport,

distribution and bio-

As most direct methods are not sufficiently

sensitive and selective,

combined techniques

nation and measurements must be applied. most

forms of trace elements

involving fractio-

In situ fractionation is

favourable as storage effects are avoided.

Several other requirements should also be met by techniques applicable for speciation purposes. gical effects are minimized, should be applied.

Thus,

techniques where methodolo-

controlled and can be accounted for,

Chemically well defined radioactive tracers

are useful tools for investigating methodological effects influencing analytical results and transformation processes affecting physico-chemical

forms of trace elements.

ACKNOWLEDGEMENT

The author will thank Professor A. C. Pappas, University of Oslo, for valuable discussions and the Norwegian Research Council for Science and the Humanities for grants provided.

REFERENCES I.

Starik, I.E. Principles of Radiochemistry, Akademy of Science, USSR. (Translation Series AEC-tr-6314, US Atom Energy Com., 1959).

2.

HaYssinsky, M. Nuclear Chemistry and its Application. (Mass., Palo Alto, Cal., London: Addison-Wesley Publ. Comp. Inc., Reading, 1964).

3.

Benes, P. and V. Majer. Trace Chemistry of Aqueous Solutions. (Amsterdam, Oxford, New York: Elsevier 1980).

4.

Salbu, B. Preconcentration and Fractionation Techniques in the Determination of Trace Elements in Natural Waters - Their Concentration and Physico-chemical Form. (Oslo: University of Oslo, 1984).

V

54

5.

Salbu, B., H.E. Bjernstad, N.S. Lindstr~m, E.M. Brevik, J.P. Ramb~k, J.O. Englund, K.F. Meyer, H. Hovind, P.E. Paus, B. Enger and E. Bjerkelund. Anal. Chim. Acta, 167:161 (1985).

6.

Segar,

7.

Manahan,

8.

Irgolic, K.J., R.A. Spectrochim. Acta.

9~

Benes,

D.A. S.E.

Anal.

Left.

and D.R.

7:89

Jones.

Stockton 38B:437

(1974). Anal.

Left.

6:745

(1973).

and D. Charkabarse. (1983).

¥

W

P. and E. Steinnes. Gjessing

War.

Res.

8:947

and E. Steinnes.

(1974).

I0.

Benes, P., E.T. (1976).

War.

Res.

10:711

ii.

Salbu, B., H.E. Bj~rnstad, N.S. Lindstr~m, E. Lydersen, E.M. Brevik, J.P. Ramb~k and P.E. Paus. Talanta 32, 9:907 (1985).

55 APPROACHES TO METAL SPECIATION ANALYSIS IN NATURAL WATERS G.M.P. Morrison Department of Sanitary Engineering, Chalmers University of Technology, S-412 96 G~teborg, Sweden

Abstract Approaches to the separation and i d e n t i f i c a t i o n of metal species in natural waters are discussed. Dissolved and colloidal metal species may be fractionated, on the basis of physicochemical characteristics,

by ion

exchange, u.v.

irradiation,

resin

adsorption,

solvent extraction or strong acid digestion. Size fractionation techniques include filtration,

centrifugation, d i a l y s i s , u l t r a f i l t r a t i o n and gel f i l t r a t i o n

chromato-

graphy. Suitable detection techniques, either before or after fractionation,

are

anodic stripping voltammetry, ion selective electrodes and atomic absorption. The bioavailable uptake rate of metal species may be determined by Dialysis with Receiving Resins. The separation of particulate associated metal species into fractions is best achieved by a series of sequential chemical extractions. Metals may be partitioned between the exchangeable fraction (which is considered to be that which is available primarily and immediately for biological uptake) the carbonate fraction,

the hydrous metal

oxide fraction and the organic/residual fraction. Additional

approaches to speciation analysis include mathematical models and the

product approach, as well as complexation capacity and conditional s t a b i l i t y constant determinations. Metal Speciation Analysis Metal speciation analysis involves the fractionation of total metal concentration by physico-chemical

methods (Florence 1986). The fractionation

of metal species

is

recognised as an essential step in the assessment of the potential biological uptake and t o x i c i t y of metals in a water sample. As a consequence total metal concentrations may soon be replaced in water quality standards by an assessment of the bioavailable metal fraction.

56

Metal Species in. Natural Waters Heavy metals in aqueous systems may occur as organic and inorganic complexes of varying sizes, or be associated with colloidal or particulate material of a heterogeneous nature (Stumm and Brauner 1975, Steinnes 1983). An important problem, which relates to most natural aquatic systems, is the d i f f i c u l t y of distinguishing between dissolved (0-0.8 rim), colloidal (0.8-400 rim) and particulate (>400 nm) species using conventional physical methods, such as f i l t r a t i o n . Dissolved metal species, particularly those that are free and weakly complexed are potentially available to organisms (Morrison et al.

1984a). In addition, certain

lipid soluble metal complexes, such as Cu xanthogenate, rapidly diffuse into biomembranes and are extremely toxic (Florence 1986). Separation of Metal Fractions in the Dissolved and Colloidal Phase Preliminary separation and instrumental techniques have been used to fractionate metals. Instruments which respond to certain metal species include Ion Selective Electrodes (ISE) and Differential Pulse Anodic Stripping Voltammetry (DPASV). Preliminary separation techniques include f i l t r a t i o n and ion exchange resins. The different approaches are complementary to each other providing a wide range of information on metal speciation.

DPASV is sufficiently sensitive, with a typical detection limit of about 10-9M, for the direct determination of heavy metals in natural waters (Florence 1982a). This analytical technique can distinguish between the eletrochemically available fraction, which may be toxic, and the bound or electrochemically inert fraction, which is less likely to demonstrate toxic properties. DPASV has commonly been applied to the primary distinction between "labile" and "bound" metals in filtered water samples (Chau and kum-Shue-Chan 1974, Duinker and Kramer 1977). The normal procedure for estimating the fraction of labile or electrochemically available metal involves a standard addition analysis of an untreated sample and is therefore dependent on the kinetics of the reactions controlling the assimilation of the metal spike (Whitfield and Turner 1979). However, Florence (1986) avoids metal spike complexation by calibrating using a blank solution containing standards. Labile metal, as defined by the experimental conditions, includes ionic as well as some weakly complexed metal. Bound metal is identifiable as the non-labile fraction

57 and is t y p i c a l l y associated with a variety of organic and inorganic colloidal mater i a l s (Batley and Florence 1976). Ion Selective Electrodes

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

Metal ISE respond only to the a c t i v i t y of the toxic free (hydrated) metal ion and have therefore attracted widespread interest (Florence and Batley 1980). The limiting factor for ISE is the non-linear response of the elctrode to metal a c t i v i t y below 10-6M, although measurements in the non-linear region can be made with proper calibration (Midgley 1981). I t is important to satisfy the experimental conditions so that only a Cu ion response is obtained, as the response can also be affected by the physical state of the electrode surface and the chemical environment within which the electrode is working (Frazer et al. 1983). Changes in pH and ionic strength can have a dramatic effect on the electrode response and i t is therefore necessary to take these into account when using ISE to monitor environmental samples.

Graphite Furnace Atomic Absorption is an automated sensitive technique suitable for measuring total metal concentrations (Astruc et al. 1981.) although i t can be used, in conjunction with a preliminary separation process, to provide information on metal speciation. Radojevic et al. (1986) have used Gas Chromatography/Atomic Absorption to determine tetraalkyllead and ionic alkyllead species simultaneously. Radiotracers Radiotracers can be added to a sample as a means of tracing the species which a heavy metal can form. Attempts to use ionic radiotracers have been hindered by the slow equilibration of the labelled ions with the non-ionic species of the heavy metal in the sample (Benes and Steinnes 1974). Radiotracers can also be used to investigate metal species uptake by l i v i n g organisms. The uptake and release of I09cd2+ by small fish-has been followed using whole body counting (John et al. 1986).

Ion exchange resins can be used to provide some indication of bioavailable metal, for example Chelex-100 is known to take up the free and weakly complexed metals in solution (Morrison et al. 1984a). Thiol resins may more closely resemble the uptake of metal ions by organisms; certainly more Cu is removed by this resin (Florence 1982b). Ion exchange separations have been used in speciation schemes to separate

58 cationic from anionic metal species (Ramamoorthy and Morgan 1983), although i t been stated that such separations probably have l i t t l e

has

biological relevance (Batley

1983). Chelex-lO0 Chelating Resin Chelex-lO0 has been successfully applied to seawater metal analysis (Riley and Taylor 1968, Florence and Batley 1976).

The resin

contains

an iminodiacetate chelating

group, but i t is mainly only the ionic form of the metal which is taken up due to the small pore diameter of the resin (1.5 to 3 nm). In addition weakly complexed metals may dissociate and p r e f e r e n t i a l l y associate with

the Chelex-lO0. The ionic

form

retained by the resin represents the more r e a d i l y bioavailable metal, w h i l s t the organically coated c o l l o i d a l p a r t i c l e s which are excluded are nevertheless considered to be p o t e n t i a l l y available f o r metal s o l u b i l i s a t i o n and transport (Morrison et a l . 1984a). A l t e r n a t i v e l y , Figura and McDuffie (1979) stated that the slow dissociation of metal complexes in solution, rather than molecular exclusion, is the cause of the incomplete retention by Chelex-lO0 of some trace metals in natural waters. Therefore column and batch techniques provide f o r d i f f e r e n t time scales of metal l a b i l i t y f o r Chelex-lO0. In the column technique metal ions are taken up as the water sample passes down the column at a known flow rate (Florence and Batley 1975, Montgomery and Santiago 1978). In the batch technique longer contact times, up to 16-24 hours, are employed enabling f u l l e q u i l i b r a t i o n of resin and sample metals to be reached (Hart and Davies 1977). The method has proved useful in i d e n t i f y i n g c o l l o i d a l associated metals on the basis that these are not k i n e t i c a l l y l a b i l e during the batch experiment (Figura and McDuffie 1980). In order to maintain stable pH conditions in the sample and to carry out the experiment over a wide range of pH values the Ca form of Chelex-lO0 is now preferred (Figura and McDuffie 1977) compared to the Na (Hart and Davies 1977) and H (Florence and Batley 1975) forms. Thiol Chelating Resins The presence in organisms of chelating sulphydryl groups has been shown to correlate with heavy metal t o x i c i t y (Fisher and Price 1981) and on t h i s basis the metal f r a c tion removed by the t h i o l group is considered to be a r e a l i s t i c estimate of bioavailable metal (Florence 1982b). The transportation of metals across a c e l l membrane is believed to be dependent on the l i p i d s o l u b i l i t y of metal Species. S i m i l a r i t i e s between metallothioneins and membrane c a r r i e r proteins (Cherian and Goyer 1978,

59 Kojima and K~gi 1978, Lerch 1980, Roesijaldi 1980) suggest that metals may be complexed and transported in association with sulphydryl groups. This process may be simulated using a thiol resin and i t has been reported that thiol material generally has a lower a f f i n i t y for Pb, Cd and Zn, but a higher a f f i n i t y for Cu, than Chelex-lO0 (Florence 1982b).

Chemical and physical methods have been used to decompose dissolved organic materials in natural waters. Some organic compounds are highly resistant and require extensive oxidation before the associated heavy metals are released. Ultra-Violet Irradiation The decomposition of organic compounds in natural waters by ultra-violet irradiation has been used to release organically associated heavy metals (Florence and Batley 1977, taxen and Harrison 1981a). The,sample, usually 150 to 200 ml, is introduced into quartz tubes and after the addition of a few drops of 30 % H202, is irradiated for four to eight hours with a medium pressure ultra-violet lamp of between 500 and 1000 W. The method has had most success in seawater analysis because, in freshwaters, Fe hydroxide is released from an organic colloidal coating and co-precipitates the heavy metals (Laxen and Harrison 1981b, Florence 1982a). Adsorption of Organics by Resins I t is possible to remove l i p i d soluble (highly toxic) metal organic complexes from water samples using a high surface area divinylbenzene resin (Florence 1982b). The analysis is carried out at pH 4.0 to prevent free metal ion adsorption to the resin. Following adsorption the metal organic complexes can be eluted with methanol and decomposed by wet acid oxidation or determined by the difference of total metal and soluble metal remaining after resin adsorption (Florence 1982b). Solvent Extraction Solvent extraction separates metal species on the basis of their polarity (Batley 1983) and may therefore represent those species that are l i p i d soluble (Florence 1983). A 9:1 hexane-butanol mixture has a similar dielectic constant to the cell membrane l i p i d bilayer (Batley 1983).

Oxidation by Concentrated Acids Organic material can be completely oxidised by the addition of suitable concentrated acids. The addition of concentrated n i t r i c and perchloric acids (9:1) followed by

60 warming and evaporation to dryness is usually sufficient to liberate a l l heavy metals (Morrison 1985). The remaining metal perchlorates are taken up in 1M HNO3. Decomposition of Organics by Ozonolysis The use of ozone to decompose organics in natural waters has been investigated (Laxen and Harrison 1981a) and shown to give an unexpected decrease in the levels of electrochemically available Pb, possibly due to the precipitation of Pb (IV). Filtration A single f i l t r a t i o n step, through a 0.4 ~m or 0.45 ~m f i l t e r is often employed as a preliminary separation

for

the dissolved and particulate phases. However, this

separation is complicated by the presence of colloids (Stumm and Brauner 1975). In addition low pressure f i l t r a t i o n is essential as rupture of l i v i n g cells may occur (Batley and Gardner 1977). taxen and Harrison (1981a) have introduced a speciation scheme using a series of f i v e nuclepore f i l t e r s ranging in pore size from 12 ~m to 0.015 ~m. Nuclepore f i l t e r s act as barrier, rather than depth, f i l t e r s allowing a very effective cut-off value and few adsorption losses (Sheldon 1972).

Centrifugation at 3000 rpm for 30 minutes has been used to separate particles smaller than 190 nm (Benes and Steinnes 1975) whilst centrifugation at 40 000 rpm for up to f i v e hours may remove humic substances (Buffle et al. 1978, Steinnes 1983). Centrifugation can be used as a rapid separation technique, although the dependence on both size and density makes an e f f i c i e n t comparison with other techniques d i f f i c u l t .

Q!~l_z!i~ Dialysis allows the separation of different groups of metal species on the basis of size (Buffle 1981). Typically ultra-pure water in a dialysis bag is allowed to equilibrate with the sample for 24 hours (Guy and Chakrabarti 1976). Under these conditions and with a pore size of one to f i v e nm (nominal molecular weight cut-off value ~ 1000) i t is found that free dissolved and low molecular weight metal species concentration inside and outside the dialysis bag are equal. An alternative approach is to place the bag in situ for I to 14 days until equilibrium is reached. However, over longer experimental time periods the membrane function may be affected as a result of the action of micro-organisms or coatings of organic and inorganic compounds (Salbu et al. 1985). Hart and Davies (1981) have incorporated a semi-continuous process into their speciation scheme in which a dialysis unit was coupled with a Chelex-lO0 column. This

61

system was found to reduce the time of e q u i l i b r a t i o n to f i v e hours. When d i a l y s i s is performed with

hollow fibres

the diffusion

equilibrium f o r

low molecular weight

species is reached within one hour (Salbu et a l . 1985). I t has been argued that the d i a l y s i s process may r e a l i s t i c a l l y represent bioavailable metal uptake, as i t is also a membrane transfer process. Cox et a l . (1984) found that d i a l y s i s with a cation exchange membrane gave s i m i l a r results to a sulphonate ion exchanger, but gave lower results

when compared to

uptake by Chelex-lO0 resin.

Dialysis could be combined with a receiving chelating resin to imitate the metal uptake process in a biological c e l l .

~!~!~!~_~_~£~i~i~_~i~ Metal b i o a v a i l a b i l i t y is determined by the type of metal species present and the transfer and uptake processes at the organism/environmental interface. Metals complexed with humic and f u l v i c materials are in a r e l a t i v e l y non-bioavailable form (Sedlacek et a l .

1983, Winner 1985) and therefore emphasis has been placed on the

free and weakly complexed metal species as being those forms which are most b i o a v a i l able (Florence 1983, Batley 1983, Turner 1984).

In addition certain organic l i p i d

soluble metal complexes, such as ethyl xanthogenate metal complexes (a common mineral f l o t a t i o n agent) and Cu 8-hydroxyquinolinate (a herbicide), are l i k e l y

to rapidly

penetrate a cell membrane and damage the cell contents (Florence 1983). The cell membrane i t s e l f and impregnated proteins.

is a complex b i l a y e r structure comprised of phospholipids Metal transport

include protein co-transport,

processes across and onto the membrane

direct lipid solubility,

surface protein binding and

aqueous pore passage. However is has been proposed that metal transport across the membrane may be dominated by d i f f u s i o n (Luoma ~983) which is supported by the correlation between metal concentration Darlington et a l . 1986).

and body size

in

aquatic

insects

(Smock 1983,

As a major direction of speciation studies is the analysis of metals by a process which imitates metal uptake by organisms, Dialysis with Receiving Resins has been developed as a simple chemical model (Morrison 1985).

In Dialysis with Receiving

Resins a receiver is encapsulated in a d i a l y s i s bag and placed, in s i t u , in the water of i n t e r e s t . A diffusion gradient is estabished as the metal concentration is maintained near zero inside the d i a l y s i s cell

by chelation to Chelex-lO0 resin.

transfer of metal into the model d i a l y s i s cell

The

is expressed in terms of a metal

uptake rate per unit membranbe surface area and is more meaningful

in terms of

bioavailable metal than a d i r e c t concentration measurement (Morrison 1986).

62

Ultrafiltration

Metal species size can be compared with typical cut-off values for ultrafilters. The Amicon PMlO f i l t e r has a pore size of 2.8 nm and should permit the separation of free metal ions and small organic and inorganic complexes resulting from trace metals associated with humic substances and colloidal species. Laxen and Harrison (1981a) incorporated this single u l t r a f i l t r a t i o n step in their f i l t r a t i o n based scheme. Dialysis may be preferred to ultrafiltration on the basis of cost, speed of analysis and efficiency of separation (de Mora and Harrison 1983). Hollow fibre u l t r a f i l t r a tion may also overcome many of the problems of conventional u l t r a f i l t r a t i o n (Salbu et al. 1985).

For polluted waters gel f i l t r a t i o n chromatography may be an alternative method for separating metal into molecular size fractions (Steinberg 1980). Sample or solute flow is retarded in relation to eluant on a column of porous polymeric beads. The large molecules elute f i r s t followed by a continuous size spectrum of molecules (de Mora and Harrison 1984). Preconcentration is often required as the small sample volume compared to eluant gives rise to high dilution factors and large blank values. Qualitative evidence of large humic complexes (<1500 molecular weight) has been shown for Pb in tap water (de Mora and Harrison 1983, 1984). However, the low metal recovery efficiencies from the gel of 6-50 % precluded the use of gel f i l t r a t i o n chromatography as a quantitative metal speciation method for tapwater samples. The Separation of Heavy Metal Fractions in Suspended Solids and Sediments Although the toxicity of the dissolved phase is higher because of its direct contact with organisms, the non-lithogenic fractions of suspended solids may subsequently release heavy metals into aqueous systems. The fractions studied must therefore reflect all heavy metal species which might have a direct effect on aquatic biota. The separation of sediment associated metal species into fractions is best achieved by a series of sequential extractions (Tessier et al. 1979). The extraction steps are not species-selective and repeated treatment often gives a further release of metals, especially in the reducible fractions. They can, however, provide valuable information on the mobility and availability of metals in suspended solids (Morrison et al. 1984a), soils, sediments and sludges (Lum and Edgar 1983).

63

The exchangeable f r a c t i o n is considered to be that which is available p r i m a r i l y and immediately for biological uptake (Morrison et a l . 1984a, Morrison et a l . 1984b). I t may include metals which are weakly attached to the surfaces of e i t h e r clays or hydrous Fe and Mn oxides or organic coatings. The addition of a high concentration of chloride or acetate provides a competing ligand for the heavy metals. Hence MgCI2 (Tessier et a l .

1979, Eisenreich et a l .

1980), BaCl2-triethanolamine (Forstner and

Patchineelam 1980) and NH4OAc (Salomons and Forstner 1980) have been proposed as extracting agents, usually at IM concentrations and at pH 7.0. The use of ammonium acetate as an extractant has been c r i t i c i s e d due to i t s tendency to attack carbonates (Tessier et a l . 1979). Carbonate Fraction Carbonates in sediments e x i s t as cements and coatings which co-precipitate with heavy metals. A lowering of pH, such as occurs with a c i d i f i e d rain, would dissolve carbonates and release the associated heavy metals. The most accepted extraction method is a sodium acetate/acetic acid (pH 5.0) treatment although some attack on metals weakly bound to hydrous Fe and Mn oxides may occur (Tessier et al.

1979).

Forstner and

Patchineelam (1980) claim that t h e i r acidic cation exchange method is very specific f o r carbonate associated metals.

Hydrous Fe and Mn oxides are thought to e x i s t as coatings on particulate surfaces (Davis and Leckie 1978). These coatings have a high capacity f o r metal adsorption (Gadde and l a i t i n e n 1974). In order to reduce this f r a c t i o n ( F e ( l l l )

to F e ( l l ) , Mn

(IV) to M n ( l l ) ) , several extractants have been proposed. D i t h i o n i t e / c i t r a t e (Salomons and Forstner 1980), hydroxylamine hydrochloride/acetic acid (Chao 1972, Tessier et a l . 1979) and O.3M HCl (Eisenreich et a l . 1980) a l l appear to have been used successfully. The metals in t h i s f r a c t i o n are more strongly bound than the exchangeable or carbonate f r a c t i o n and occur mainly as surface associated metals (Davis and leckie 1978) and co-precipitates

of hydrous metal oxides.

immediate biological

This f r a c t i o n

is

unlikely

to have any

impact, but may accumulate in r i v e r or estuarine sediments.

Subsequently the metals may be released into the water column when a s i g n i f i c a n t drop in pH occurs (Florence and Batley 1980).

84

Much of the organic fraction w i l l be particle coatings of plant derived organic material. Humic and fulvic acid associated metals can be successfully removed using 1M NaOH. However, the use of sodium hydroxide remobilises metals from phosphates and silicates (Forstner and Patchineelam 1980). Strong oxidising agents, such as O.4M Na4P207 (Eisenreich et al. 1980) may also attack the crystalline phase and so Tessier et al. (1979) decided on a compromise and used an extraction mixture of hydrogen peroxide and O.02M HNO3. However, metals released from organics by peroxide oxidation are readily adsorbed on clays (Eisenreich et al. 1980). The r e l a t i v e l y strong association of organically bound metals ensures that they are unlikely to be bioavailable. However, this fraction may act as an important transportation mechanism and sink for such metals as Pb and Cu, which have high s t a b i l i t y constants with organic compounds (Mantoura et al. 1979). Mathematical Models All the mathematical models presented to date are based on thermodynamic considerations only. I f the total concentrations and interactions of a l l the major components of the aqueous system are known and perfect equilibrium conditions prevail, then the concentration of each chemical species of a given element can be calculated. The values of the s t a b i l i t y constants and the corresponding dissolved and surface free ligand concentrations must be known. The uncertainty over many s t a b i l i t y constants, p a r t i c u l a r l y with organic ligands, makes a comparison with real

data d i f f i c u l t .

Another problem is the d i f f i c u l t y of considering a l l the ligands which may be a v a i l able in an aqueous sample to complex metals. In seawater organic ligands are generally present at low levels ( i mg/l) and are therefore thought to be relatively unimportant. This allows calculations on the basis of homogeneous chemical reactions and precipitations, particularly as open ocean water is so well mixed. Hence mathematical modelling of seawater has compared favourably with analytical work (Millero 1974, Whitfield 1975). In freshwaters two other important interactions must be taken into account: a) The adsorption of metals onto particulates (Jenne 1968, Davis and Leckie 1978) and interactions at the suspended solid/water interphase (Westall 1980, Hohl et al. 1980). b) The presence of organic material. Most of this material is largely uncharacterised, especially f u l v i c acids which form important complexes with heavy metals.

85 Organic compounds may be dissolved or present as surface coatings on particulate material

(Davis and Leckie 1978). In addition organic colloids should be taken

into consideration. A computer model, taking these factors into account would need to be backed up by a considerable amount of analytical data. Batley (1983) considers i t u n l i k e l y that one could ever account f o r the heterogeneous interaction of metal species with the mixed organic

and inorganic

colloidal

and p a r t i c u l a t e

phases which

represent a major

component of the t o t a l metal concentrations found in most natural systems. Hart and Davies (1981)

incorporated

data from a speciation

study,

together with

general

water q u a l i t y data, into a computer model. In this way computer calculations were used to assist in the i n t e r p r e t a t i o n , rather than prediction, of heavy metal speciation. The Product Approach Mixing experiments were introduced by Sholkovitz (1976) to determine the composition of removal products (flocculants) due to the mixing of f i l t e r e d r i v e r and sea waters at varying s a l i n i t i e s . The results of these experiments showed that rapid f l o c c u l a tion of Fe, Mn, AI, P, organic carbon and humic acids occurs in the estuarine environment. Most of the p r e c i p i t a t e is formed within one h a l f hour of mixing and is removed for analysis. A f u r t h e r 24 hours is required before enough p r e c i p i t a t e forms f o r a second determination. Further studies (Boyle et al. 1977, Sholkovitz et a l . 1978) demonstrated the important role of dissolved organic matter. The high molecular weight component of dissolved humic acids ( 0 . i um - 0.45 um f i l t e r e d ) , which constitutes a small f r a c t i o n of r i v e r dissolved organic material, is p r e f e r e n t i a l l y and rapidly flocculated during estuarine mixing. Apparent Heavy Metal Complexin 9 Capacities and Conditional S t a b i l i t y Constants A large proportion of heavy metals in natural waters are believed to e x i s t in complexed or chelated forms with therefore control

organic

ligands

(natural

or anthropogenic)

the geochemical transport and b i o a v a i l a b l i l i t y

which

of metals in the

aquatic environment (Van den Berg and Kramer 1979). Furthermore colloids may complex and transport trace metals in natural waters. Analysis of the complexation properties of these organic compounds is complicated by the i r r e g u l a r structure and wide range of components present. Experimental methods to investigate the complexing behaviour of organic fractions in natural waters involve a t i t r i m e t r i c

procedure in which the ligands are reacted with a suitable

66

metal ion until the end point, equivalent to the complexing capacity, is reached. A technique to detect remaining free metal is therefore required. Voltammetry is the most tested method (Shuman and Woodward 1973, 1977, Shuman and Cromer 1979) although i t may measure weakly complexed metals in addition to free metal ion. Potentiometry (Schnitzer and Kahn 1972), ISE (Buffle et al. 1977), solubilisation (Kunkel and Manahan 1973), bioassay (Davey et al. 1973, Gatcher et al. 1978, Gillespie and Vacarro 1978), dialysis (Sterrit and Lester 1984) and ion exchange (Van den Berg and Kramer 1979) are other available techniques. Complexation analysis is essentially a complexometric titration of metal ion against ligand and, as ligands are titrated sequentially, those with the highest stability constants are complexed f i r s t of all (Crosser and Allen 1977). Changes in the t i t r a tion slope (added metal versus measured free metal ion) are therefore related to the product of the concentration of the ligand times its conditional stability constant. The conditional stability constant can be calculated on the basis of formation of the complex (equation I).

["a aM + bE = Matb where a L M K'ML

K'M[= - ~

[L]b

(1)

and b depend on stoichiometry = Ligand = Metal = Stability Constant

The complexation capacity and conditional stability constant are calculated according to the method proposed by Ruzic (1982), as shown in equation (2). CF CF/CB :

(2) Ct + 1/K'ML" Ct

where C F = concentration of free metal CB concentration of bound metal

The straight line plot of CF/CB against CF gives a slope of I/C t and an intercept of I/K'M[.C L • Sterritt and tester (1984) have compared the conditional stability constants obtained for Cd, Pb and Cu with fulvic acid by using three different analytical techniques; ISE, dialysis and DPASV. The stability constants obtained by DPASVmeasurements were lower than for the other two methods, suggesting the existence of increased metal complex l a b i l i t y . However, the complexation capacity was similar for all methods. ISE detected both weak and strong complexes, while DPASVand dialysis were only sensitive

67 to stronger complexes. For stronger complexes a log K range of 4.7 to 7.0 was found, while weaker complexes gave a log K value of between 3.8 and 5.6 for a l l

three

metals. Weaker binding sites often show a much greater metal capacity for Cu and Cd than stronger binding sites ( S t e r r i t t and Lester 1984, S t e r r i t t and tester 1985).

Acknowledgements Financial support from the National Swedish Environmental Research Council is gratef u l l y acknowledged. This a r t i c l e is to a great extent based on the "Handbook for Metal Speciation in Natural Waters",

published i n t e r n a l l y by the Department of Sanitary Engineering,

Chalmers University of Technology, G~teborg, Sweden. Both Mike Revitt, Middlesex Polytechnic and B r i t Salbu, University of Oslo made extensive contributions to the handbook.

88

References Astruc, M., Lecomte, J., and Mericam, P. (1981). Environmental Technology Letters, 2, 1-8. Batley, G.E. (1983). In: Leppard, G.G. (ed.), Trace Element Speciation in Surface Water and its Ecological Implications, NATOConf. Ser., Vol. 6, 17-36, Plenum Press. Batley, G.E., and Florence, T.M. (1976). Analytical Letters, 9, 279-388. Batley, G.E., and Gardner, D. (1977). Water Research, 11, 745-756. Benes, P., and Steinnes, E. (1975). Water Research, 9, 741-749. Boyle, E.A., Edmond, J.A., and Sholkovitz, E.R. (1977). Geochimica Cosmochimica Acta, 41, 1313-1324. Buffle, J. (1981). Trends in Analytical Chemistry, i , 90-95. Buffle, J., Greter, F., and Haerdi, W. (1977). Analytical Chemistry, 49, 216-222. Buffle, J., Deladoey, P., and Haerdi, Wo (1978). Analytica Chimica Acta, 101, 339-357. Chao, T.T. (1972), Proceedings of the American Soil Science Society, 36, 764-768. Chau. Y.K. and Lum-Shue-Chan, K. (1974). Water Research, 8, 383-388. Cherian, M.G., and Goyer, R.A. (1978)o Life Science, 23, 1-10. Cox, J.A., Slonawski, K., Gatchell, Chemistry, 54, 650-653.

D.K., and Hiebert,

A.G. (1984). Analytical

Crosser, M.L., and Allen, H.E. (1977). Soil Science, 123, 176-181. Darlington, S.T., Gower, A.M., and Ebdon, L. (1986). Environmental Technology Letters, 7, 141-146. Davey, E.W., Morgan, M.J., and Erickson, S.J. (1973). Limnology and Oceanography, 18, 993-997. Davis, J.A., 1309-1315.

and Leckie, J.O.

(1978).

Environmental

Science and Technology,

12,

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De Mora, S.J., and Harrison, R.M. (1983). Water Research, 17, 723-733. De Mora, S.J., and Harrison, R.M. (1984). In: Environmental Contamination, 124-130, CEP Consultants Ltd, Edinburgh. Duinker, J.C., and Kramer, C.J.M. (1977). Marine Chemistry, 5, 207-228. Eisenreich, S.J., Hoffman, M.R., Rastetter, D., Yost, E., and Maier, W.J. (1980). In: Kavanaugh, M.C., and Leckie, J.O. (ed.), Particulates in Water, 136-176, ACS Symposium Series No. 189, Amer. Chem, Soc,, Washington D.C. Figura, P., and McDuffie, B. (1977). Analytical Chemistry, 49, 1950-1953. Figura, P., and McDuffie, B. (1979). Analytical Chemistry, 51, 120-125. Figura, P., and McDuffie, B. (1980). Analytical Chemistry, 52, 1433-1439. Fisher, N.S., and Price, G.J. (1981). Journal of Phycology, 17, 108-111. Florence, T.M. (1982a). Talanta, 29, 345-364. Florence, T.M. (1982b). Analytica Chimica Acta, 141, 73-94. Florence, T.M. (1983). Trends in Analytical Chemistry, 2, 162-166. Florence, T.M. (1986). Analyst, 111, 489-505. Florence, T.M., and Batley, G.E. (1976). Talanta, 22, 201-204. Florence, T.M., and Batley, G.E. (1976). Talanta, 23, 179-186. Florence, T.M., and Batley, G.E. (1977). Talanta, 24, 151-158. Florence, T.M., and Batley, G.E. (1980). Critical Reviews in Analytical Chemistry, 219-296. Forstner, U., and Patchineelam, S.R. (1980). In: Kavanaugh, M.C., and Leckie, J.O. (ed.), 177-183, Particulates in Water, ACS SymposiumSeries No. 189, Amer.Chem. Soc., Washington D.C. Frazer, J.W., Balaban, D.J., Brand, H.R., Robinson, G.A., and Lanning, S.M. (1983). Analytical Chemistry, 55, 855-861.

70 Gadde, F.F., and Laitinen, H.A. (1974). Analytical Chemistry, 46, 2022-2026. Gatcher, R., Davies, J.S., and Mares, A. (1978). Environmental Science and Technology, 12, 1416-1421. Gillespie, P.A., and Vaccaro, R.F. (1978). Limnology and Oceanography, 23, 253-548. Guy, R.D. and Chakrabarti, C.L. (1976). Chemistry in Canada, 54, 26-29. Hart, B.T., and Davies, S.H.R. (1977). Australian Journal of Marine and Freshwater Research, 28, 397-402. Hart, B.T., and Davies, S.H.R. (1981). Estuarine and Coastal Shelf Science, 12, 353-374. Hohl, H., Sigg, L., and Stumm, W. (1980). In: Kavanaugh, M.C., and Leckie, J.O. (ed.), Particulates in Water, 1-31, ACS Symposium Series No. 189, Amer. Chem. Soc., Washington D.C. Jenne, E.A. (1968). In: Baker R.A. (ed.), Trace Inorganics in Water, 337-387, ACS Symposium Series No. 73. Amer. Chem. Soc., Washington D.C. John, J., Gjessing, E.T., Grand, M., and Salbu, B. (1986). Proceedings Int. Humic Subst. Soc. Meeting, University of Oslo. Kojima, Y., and K~gi, J.H.R. (1978). TIBS, 90-93. Kunkel, R., and Manahan, S.E. (1973). Analytical Chemistry, 45, 1465-1468. Laxen, D.P.H., and Harrison, R.M. (1981a). Science of the Total Environment, 19, 59-82. Laxen, D.P.H., and Harrison, R.M. (1981b). Water Research, 15, 1053-1065. Lerch, K. (1980), Nature, 184, 368-370. Lum, K.R., and Edgar, D.G. (1983). Analyst, 108, 918-924. Luoma, S.N. (1983). Science of the Total Environment, 28, 1-22. Mantoura, R.F.C., Dickson, A., and Riley, J.P. (1978). Estuarine and Coastal Marine Science, 6, 387-408.

71 Midgley, D. (1981). Ion Selective Electrode Reviews, 3, 43-104. Millero, F.J. (1974). In: Goldberg, E.D. (ed.), The Sea, Vol. 5, Marine Chemistry, 3-81, Wiley-lnterscience, New York. Montgomery, J.R., and Santiago, R.J. (1978). Estuarine and Coastal Marine Science, 6, 111-116. Morrison, G.M.P. (1985). Ph.D. Thesis, Middlesex Polytechnic, U.K., 316 pp. Morrison, G.M.P. (1986). Environmental Technology Letters, in Press. Morrison, G.M.P., Revitt, D.M., E l l i s , J.B., Svensson, G., and Balm6r, P. (1984a). In: Balm~r et al. (ed.) Urban Storm Drainage, Department of Sanitary Engineering, Chalmers Tekniska H~gskola, Sweden, Volo 3, 989-1000. Morrison, G.M.P., Revitt, D.M., E l l i s , J.B., Svensson, G., and Balm~r, P. (1984b). In: Vernier, J.P. (ed.), Interactions between Sediments and Water, CEP Consultants Ltd., Edinburgh, 226-229. Radojevic, M., Allen, A., Rapsomanikis, S., and Harrison, R.M. (1986). Analytical Chemistry, 58, 658-661. Ramamoorthy, S., and Morgan, K. (1983). Regulatory Toxicology and Pharmacology, 3, 172-177. Riley, J.P., and Taylor, D. (1968). Analytica Chimica Acta, 40, 479-485. Roesijaldi, G. (1980). Marine Environmental Research, 4, 167-179. Ruzic, I. (1982). Analytica Chimica Acta, 140, 99-113. Saar, R.A., and Weber, J.H. 510A-517A.

(1982).

Environmental Science and Technology, 16,

Salbu, B., and Bj6rnstad, H.E., Lindstr~m, N.S., Lydersen, E., Brevik, E.M., Ramboek, J.P., and Paus, P.E. (1985). Talanta, 32, 907. Salomons, W., and Forstner, U, (1980). Environmental Technology Letters, 1, 506-517. Schnitzer, M., and Kahn, S.U. (1972). Humic Substances in the Environment, Dekker, New York.

72 Sedlacek, J., K~llqvist, T., and Gjessing, E. (1983). In: Christman, R.F., and Gjessing, E. (ed.), Aquatic and Terrestrial Humic Materials, 26, 495-516, Ann Arbor Science, Michigan. Sheldon, R.W. (1972). Limnology and Oceanography, 17, 494-498. Sholkovitz, E.R. (1976). Geochimica Cosmochimica Acta, 40, 831-845. Sholkovitz, E.R., Boyle, E.A., and Price, N.B. (1978). Earth and Planetary Science Letters, 40, 130-136. Shuman, M.S., and Cromer, J.L. (1979). Environmental Science and Technology, 13, 543-545. Shuman, M.S., and Woodward, G.P. (1973). Analytical Chemistry, 45, 2032-2035. Shuman, M.S., and Woodward, G.P. (1977). Environmental Science and Technology, 11, 809-813. Smock, L.A. (1983). Freshwater Biology, 13, 313-321. Steinberg, C. (1980). Water Research, 14, 1239-1250. Steinnes, E. (1983). In: Leppard, G.G. (ed.), Trace Element Speciation in Surface Waters, 37-47, NATOConf. Ser., Vol, 6., Plenum Press. Sterritt, R.M., and Lester, J.N. (1984). Water Research, 18, 1149-1153. Sterritt, R.M., and Lester, J.N. (1985). Water Research, 19, 315-321. Stumm, W., and Brauner, P.A. (1975). In: Riley, J.P., and Skirrow, G. (ed.), Chemical Oceanography, Vol. 1, 173-239, 2nd edition, Academic Press. Tessier, A., Campbell, P.G.C., and Bisson, M. (1979). Analytical 844-851.

Chemistry, 51,

Turner, D.R. (1984). In: Siegel, H. (ed.), Metal Ions in Biological Systems, Vol. 18, 137-164, Marcel Dekker, New York. Van den Berg, C.M.G., and Kramer, J.R. (1979). Analytica Chimica Acta, 106, 113-120. Westall, J. (1980). In: Kavanaugh, M.C., and Leckie, J.O. (ed.). Particulates Water, 33-44, ACS Symposium Series No. 189, Amer. Chem. Soc., Washington D.C.

in

73 Whitfield, M. (1975). In: Riley, J.P., and Skirrow, G. (ed.), Chemical Oceanography, Vol. 1, 44-162, 2nd edition, Academic Press, London, Whitfield, M., and Turner, D.R. (1979). In: Jenne, E.A. (ed.), Chemical Modelling in Aqueous Systems, 657-680, ACS Symposium Series No. 93, Amer. Chem. Soc., Washington D.C. Winner, R.W. (1985). Water Research, 19, 449-455.

75

METAL FRACTIONATION

BY DIALYSIS

- PROBLEMS

AND POSSIBILITIES.

Hans Borg The National

Environmental

Protection

Board

Trace Metal Laboratory Box 1302 S-171

25 SOLNA,

Sweden.

Abstract

Dialysis weight

is a convenient method

species

applications

to separate different molecular-

in natural waters

of dialysis methods

or other

The main advantage

of metal of dialysis

are:

- possible

to separate

- relatively - suitable

truly disolved

few contamination

aware of,

forms

from colloids

problems

for in situ measurement.

As with other fractionation

methods

there are some problems

- no definite

slow diffusion separation

organic

rate

between

inorganic

and low molecular-

forms

- changed pore size caused by microbial

attack and clogging with

organic matter.

Results

to be

for example:

- relatively

weight

Some

for the fractionation

forms in water have been reported. methods

solutions.

from different

acidified,

applications

of in situ dialysis

limed and metal polluted waters

are dicussed.

in

76

Introduction

The concentration of trace metals in unpolluted waters are mostly in the sub-microgram per litre level. Only elements like Fe, Mn, A1 and often Zn are frequently present in concentrations higher than one microgram per litre, while Cd for instance,

generally is found in

the range 0.005-0.05 ~g/l (1,2). Because of these low concentrations,

it is difficult even to perform sampling and

analysis of total concentrations techniques,

such as filtration,

accurately.

Most fractionation

ultrafiltration or centrifugation

increase the contamination problems during the procedure.

A

technique which is relatively free of these problems is dialysis, especially when performed in situ. Some applications of in situ dialysis

for the collection of dissolved metals in water have been

reported in the literature

(3,4,5,6,7,).

The method is also possible

to combine with chelating resin (8). In situ dialysis has also been used to culture fytoplankton for the evaluation of the effect of pollutants

(9).

Methods

The dialysis experiments were performed in lakes in the province of Sm~land,

in the Ava nature reserve south of Stockholm,

area in H~isingland,

in mountain brooks in Lofsdalen,

in the Delsbo H~rjedalen and

in lakes around Skellefte&, V~sterbotten in northern Sweden. The measurements were generally repeated two times a year (April and September)

during 1981 -1986.

The experiments were performed as described in references 6 and i0. The dialysis tubings were filled with ultra-pure

(Milli-Q) water and

allowed to equilibrate in the lake waters for 5 days. Samples for determination ot total metal concentrations

and other water chemical

77

parameters were collected at the start and at the end of the dialysisperiod.

The tubings were then brought to the laboratory in

bottles filled with the same water as they had been equilibrated in. The outside was cleaned,

the top of the tubing was cut off and the

content was pipetted into a polyethylen bottle. Ultra-pure conc. nitric acid was added for preservation

(2 ml/l).

All the steps in

the laboratory were performed in a class-100 clean bench. All storage bottles and other laboratory ware were acid cleaned as described in ref.

Ii.

The metal determinations were performed with flame AAS (Fe,Mn) or graphite furnace AAS (Zn,Cu,Pb,Cd,AI).

To increase the accuracy, the

determinations of Cd,Pb and Cu were made after a preconcentration of about ten times by freeze drying in the sample bottles.

Results

The results reported here are partly presented in previous reports which will be referred to in the text. The dialysis experiments performed in various lake waters have been able to show some general features of the elements: Iron occured to a great deal as particulate bound even in relatively acid waters. Generally, very clear waters

just a few percent was dialysable except in

(Fig.l, ref.12).

Manganese occured more in dialysable form, often to about 90 % . However,

the variation was very large depending on pH and especially

on the content of organic substances

(TOC)

(Figl.).

Lead was generally found as particulate especially at high humic content

(Fig.2). In more clear waters there was a larger fraction

that was dialysable and negatively correlated to pH (6,10).

78

TOEa5rag/( TOE":5mg/l I Fe • Mn

O

0

D~aLysabte me~a! frection ,%

•

I

.~ °° •

•o

o

•

.. ..

•

•e

%

•

••

•

m

,am

s0

" ":":" "" I • •

".'.."

•

..

"'"

mmmlm

• .. 2°}

mm

. ~'a.(e.

m

A i

;

o mm mm#m

°" mmm •

l

• (

TOC, mg/l

Fig.

i pH

i. Dialysable fraction of Fe and Mn in Swedish forest lakes plotted against pH and TOC. Error bars represent standard deviations of three to four measurements.

C a d m i u m and zinc existed mainly as dialysable, values.

especially at low pH

Even at pH 7 up to around 60% of cadmium was dialysable. No

correlation between dialysable fraction and the TOC concentration was found for zinc and cadmium

(6,10).

Dialysable copper showed a negative correlation with TOC but not with pH (6). Copper was mostly found in the colloidal fraction, which probably consists of humic substances

(i0).

Dialysable aluminium showed a negative correlation both to pH and TOC values

(6). At pH 5, about 70% of aluminium was dialysable in

clear water lakes

(TOC < 5 mg/l).

Arsenic occured to a relatively high degree in dialysable form (3060 %). In lakes with low TOC concentration around 90 % of arsenic was dialysable (I0).

79

100

= o

I

O0

50

|o

.Q

O0

m

0

~5

!

l

l

!

8

!

I

!

•

I

!

5

i

!

l

I

l

!

15

10 TOC , rng I[

Fig.

2. I n f l u e n c e of TOC on the d i a l y s a b l e f o r e s t lakes.

Pb f r a c t i o n

in S w e d i s h

Discussion

For s e p a r a t i o n

of d i s s o l v e d

technique

some a d v a n t a g e s

have

advantages

can be s u m m e r i z e d

- separates

truly dissolved

- relatively - practicly

losses

to c o m b i n e

- low c o s t c o m p a r e d

However,

as w i t h

some p r o b l e m s

in water,

over

the in situ d i a l y s i s

filtration

techniques.

The m a i n

as follows:

species

small c o n t a m i n a t i o n unlimited

- no a d s o r p t i o n - possible

metals

supply

problems

of m a t e r i a l

to d i a l y z e

at e q u i l i b r i u m with

chelating

resins

to u l t r a f i l t r a t i o n .

all other

to be aware

fractionation of.

techniques,

there

are a l s o

80 The diffusion

rate of elements through the membrane

In deionized water,

equilibrium

is rather slow.

is generally reach within 24 hours,

but in natural waters the diffusion

is slower,as

shown in Fig.3.

The

membrane used had a pore-size of 2.4 nm. Similar results were reported by Bene~ and 3teinnes for organic complexes ions. The relatively dialysis chemistry

(3) who found that the diffusion rate

like Fe-EDTA was slower than for inorganic slow diffusion

rate might cause problems when

is used in running waters with fast changes in water (12).

~oo

.oi--o

, -

/

I

/

.

.

.

.

Deionized wafer

/

/ 1 1

I

e~ o

5 i

~= 50

II I I I/

II II !1

J Fig.

/

i l li

I/

/

o~ /

/ /~ ,// // I

!

1

2

1

1

Humic lake wafer pH o,9

!

I

I

3 & S Dialysis lime, days

I

I

6

7

3. Percentage of dialysable Cu as a function of time. The filled symbols represent samples with additions of sulphate (I0 meq/l), chloride and bicarbonate (i meq/l). 2000 mwco membrane.

Donnan disequilibrium substantial

can occur if the organic anions make up a

fraction of the total equivalents

cited in ref.13).

of ions

Then it will be more inorganic

more cations outside then would normally occur. to calculations

by LaZerte

(Bull 1951,

anions inside and However,

(13) who applied a correction

according factor for

the Donnan effect when measuring dissolved AI, relatively high TOCvalues error.

(around i0 mg/l or more)

is required to cause any significant

81

Depending on the molecular-weight

cut-off of the membrane,

organic compounds will also penetrate. penetration

Fig.4 shows the organic

in lake waters with different TOC contents,

inside and outside the dialysis about 2000 and the dialysis

some

tubing.

measured

The membrane had a mwco of

time was 7 days. LaZerte

(13) reported

an organic penetration of 6-12 % even in a i000 mwco membrane

for a

dialysis time of 24 h. If these findings mean that organically complexed metal forms will be included in the dialysate unclear,

is still

but that might be expected as the low molecular-weight

organic fractions passing through the membrane,

probably to a gleat

deal consist of fulvic acids with strong ability to complex metal ions. One way to minimize the organically complexed the dialysis

forms is to keep

time as short as possible.

100

o

r._

5O o

:::: ii:ii{!

ililliilili

iiiii ~i!iii iiii I

5

Fig.

!

I

!

I

1

I

!

I

I

15

10 TOE, 0ufside,mgl[

4. Penetration of organic substances through a 2000 mwco membrane. In situ equilibration for 7 days.

Cellulose dialysis membranes growth.

Experiments

conditions

(+20°C),

provide

a good substrate

in marine environments a considerable

for epiphytic

have shown that at summer

bacterial population develops

82

after 3 days and that the membrane is degraded and collapses after 9 days. At winter

(+4°C) however,

the tubes remain strong and

transparent for at least the first 9 days after which biota develops, which after 17 days reach the same density as after 5-7 days in the summer

(14). The dialysis experiments discussed in this

report were generally performed when the water temperature was 10°C at the most and the dialysis time was limited to 5 days. It is not likely that epiphytic growth have had any substantial influence on the transport of ions through the membrane.

In spite of the potential sources of error discussed above it is still possible to use in situ dialysis for succesful fractionation of dissolved metal species in natural waters, on the condition that attention is given to the possible errors when interpreting the results.

Preliminary results of comparisons between dialysis and cationexchange separation have shown that in lake waters with low concentration of humus there was a good correlation between the dialysable and the labile inorganic Al-fraction. waters,

In more humic

the concentration of dialysable A1 was higher than the

labile inorganic AI, which would be expected as some organic complexes probably penetrate

the membrane.

Determinations of the complexing capacity of the waters by potentiometric titration with Cu-solution and Cu-ion selective electrode,

showed that generally more dialysable metals were found

in waters with lower complexing capacity,

i.e. lower TOC-levels

(I0). The findings discussed above point

to the condition that the

dialysable metal fraction is more closely connected to the bioavailable fraction than is the filterable the total concentration.

(0.4 ~m) fraction or

A good correlation between dialysable Cd

and biological uptake in mussels have been demonstrated.

Cu showed

83

another accumulation pattern than Cd with a certain treshold concentration accumulate

(around 0.2 ~g/1) where the mussels started to

(15).

The in situ dialysis experiments have demonstrated that, in general, Zn, Cd, As and Mn occur waters, occur

to a high degree in dissolved form in fresh

Cu in dissolved and colloidal form, while Pb, A1 and Fe mainly in the particulate fraction except in very acid lakes

with low TOC-concentration.

The results indicate that Cd, Zn, and As

generally would be more bioavailable in fresh waters than Cu, A1 and especially Pb.

References

Borg, H. Hydrobiologia !01:27-34

(1983

2.

Borg, H. Water Res.

3

Bene~, P. and E. Steinnes. Water Res.

4.

Bene~, P. Water res. 14:511-513

5

Hart, B.T. and S.H.R. Davies. Aust. J. Mar. Freshw. Res. 175-189

(in press) (1974)

(1980) 32:

(1981)

Borg, H. and P. Andersson. Verh. 22:

8:947-953

725-729

Internat. Verein. Limnol.

(1984)

Truitt, R.E. and J.H. Weber. Environ. Sci. Technol.

15: 1204-

1208 (1981) Morrison, G.M.P. Metal Speciation in Urban Runoff. Thesis. Middlesex Polytechnic U.K.

I0.

Ph.D.

316 pp (1985)

Powers,

C.D., R.G. Rowland and C.F. Wurster. Water Res.

991-994

(1976)

i0:

Borg, H. Metal species in lake waters in the R~nnsk~r area. The National Environmental Protection Board, report 3124, 16 pp (in Swedish)

ii.

(1986)

Borg, H., I. Gustavsson, G. Johansson and M. Bengtsson. Recommendations for sampling and analysis of trace metals in natural waters. The National Environmental Protection Board,report 1918, 40 pp (in Swedish)

(1984)

84

12.

Borg, H. Water,

13.

LaZerte,

14.

Vargo,

15.

del Castilho,

G.A.,

31:113-120 Salomons.

Air & Soil Pollut.

B.D. Can. J. Fish. Aquat. P.E. Hargraves

(in press) Sci. 4 1 : 7 6 6 - 7 7 6

and P. Johnson.

(1984)

Marine Biology

(1975) P., R.G° Gerritse,

In: C.J.M.

Comp!exation

J.M. Marguenie and W.

Kramer and J.C. Duinker,

Eds.,

of Trace Metals in Natural Waters.

Publ. The Hague

(1984) pp 445-448.

Nijhoff/Junk

85

TRACE E L E M E N T

SPECIATION

IN NATURAL W A T E R S

USING

HOLLOW-FIBER

ULTRAFILTRATION E. Lydersen,

H.E. Bj~rnstad,

Department of Chemistry, P.O.B. 1033, Blindern,

B. Salbu, A.C. Pappas University of Oslo

0315 Oslo 3, Norway

ABSTRACT In

natural

waters

physico/chemical

In

order

to

hollow-fiber are

made

trace

elements

present

in

obtain

information

on

the

size

main

inert

polymers

advantages

filtering

capacity,

problems.

with

Using

a

with

disc

filtering

hollow-fibers

are

with

clogging

minimal

peristaltic pump,

the field,

The

membranes

different nominal molecular weight

traditional

combined

into the molecular weight in

different

distribution pattern,

ultrafiltration technique is a useful tool.

of

performed

be

forms, varying in size, charge and density.

cut-off levels. Compared with the

may

techniques,

basically

the

and

the water is transported directly

discriminators.

Thus

fractionation

"in situ" fractionation.

to

degree

surfaces

sorption

on

the

internal

equipment

mass-balance approach. Applications of hollow-fibers and in laboratory studies are demonstrated

can

be

The system is closed,

contamination risks are minimized and it is possible of

high

sorption

in

determine natural

using

the a

waters

in this paper.

INTRODUCTION

In

general,

information biological must

be

total on

concentrations

interactions

availability. fractionated

properties

of

actual

with

of

trace

biota,

and/or

with

respect

elements.

to

the

The

chemical hollow

separation

smaller

of

the

give

pore-diameter

the

and/or

fiber

technique

membrane

limited

degree

In order to achieve such information,

technique is a mechanical/physical than

elements

of

samples physical

ultrafiltration where

are

fractionation takes place without addition of any reagents.

species

isolated. The

86

EQUIPMENT DESCRIPTION A

hollow

fiber

cartridge

consists of several fine cylindrical tubes,

each with a lumen diameter of 0.2 non-ionic produces

polymers. high

concentration

The

shear

high

forces

polarization,

or

at

(figure

the i).

membrane, The

mm.

The

matrix

is

inert,

flow through hollow fiber lumens

the

membrane

surface,

minimizing

clogging and sorption by rejected solutes.

As water flows through the fiber, penetrate

0.5

axial

it causes micro solutes and

salts

to

while rejected solutes are discharged as waste

filtering

pressure

is

generally

about

10-15

psi

(69-172 kPa).

mt sample

fil~'ate mf

it flow) mw

Figure i: The principal of hollow fiber fractionation

Different hollow different Dalton.

fiber

nominal

membranes

molecular

are

comercially

weight cut-offs

available,

having

in the range 3x103 to 106

In our laboratory we have systematically used membranes

of

all

cut-offs. In

Table

(ml/min) valid

1

cartridge

specification

for deionized distilled water listed

under

temperature

field

conditions

waters,

dramatically, turbidity

some

especially

waters,

either

as

which for

the 103

in

viscosity

reduces the

are listed

and

the 104

this

(i). Flow-rates table

are

not

increases

for

low

filtering Dalton

flow-rate

fibers.

High

due to prescence of organic and/or inorganic

87

components, extent

also

than

flow-rates

affect

the are

the

filtering

temperature. more

For

flow-rate,

106

and

affected

by

turbidity

Nominal Cut-off

Surface Area

Dalton

m2 ft 2

Number of Fibers

but

10 5

to

Dalton

a

lesser

fibers

the

than for the 104 and 103

Dalton fibers.

Cartridge Type

Deionizec I Recomme.ded Water Recirculatio. Flow-Rak Rate ml/min ee I/rain

| HIPI - 4 3 1,000"ii.03 H 1 P I O - 8 10,000e!.09 H1PIO - 2 0 10,000 .06 H1P100-20 100,000 .00 H1MP01-43 0.tlJm .03

.3 .9 .6 .6 .3

SS 1000 250 250 55

20-30 170-320 60-90 100 - t 4 0 800-1100

0.6-1.8 0.2-0.6 0 . 3 - 0.0 0 . 3 - 0.0 0.6-1.0

• " not available "e " transmembrane pressure)of 1Opsi ( 6 9 kPa) at room temp. lea. 20 °

Table i:

Some h o l l o w

I

fiber cartridge s p e c i f i c a t i o n s a c c o r d i n g to the

manufacturer

(i).

WASHING PROCEDURE

Before and after use, the h o l l o w fiber thorough the

washing

presented

procedure.

work

recommendation

are

given

by

addition,

a

the procedure,

in

c h e l a t i n g agent, order

After

cleaning,

the

water,

at least 15-20 I.

to

which

are

manufacturer

be p r e p a r e d with h i g h p u r i t y water In

have

to

undergo

a

In Figure 2 the c l e a n i n g solutions used in

listed the

cartridges

(e.g.

metals

should

accordance

deionized

like EDTA,

desorbe

cartridges

in

be

to

the

(i). These solutions should distilled

water).

should also be included in from

internal

rinsed

with

surfaces. high purity

MEMBRANE CUT-OFF MEASUREMENTS

In order to a c h i e v e i n f o r m a t i o n about membranes, species

e.g.

standard globular

solutions proteins,

pore-size

containing

distributions

chemically

carbohydrates

can

be

well used

of

the

defined (2,3).

88

I

Storage 40 in 0.1 % NaN3

............. t ............ 0.1 % LaboratoryDetergent i (Alconox, Sparkleen, etc.)

~

- H20-- 5 J

0.1 M Sodium Hydroxide

~

I

- H 2 0 - 51

I-2 M Sodium Choride

~

- - - - H 2 0 - 51

0.1M HydrochloricAcid (for removal of metal ions)

~

H20- 51

0.01 M.HNO3

~ Fi@ure 2: A r e c o m m e n d e d h o l l o w

H20~15-201

fiber w a s h i n g p r o c e d u r e

Figure 3 i l l u s t r a t e s the r e j e c t i o n s of Dalton

membrane

(HIP10-8)(4).

pore-size distribution.

}

A

different steep

curve

compounds indicates

by a

a

10 4

narrow

89

%

Z,

100!

HIPIO-~

Z 0 o...e I-U

uJ 5O UJ t~

t I I

10

/

1 ~°.... ~ ~'

,

,

, ~. . . . .

~'

,~

NOLECULAR Figure

3:

Rejection

characteristics

(cut-off:104

Dalton),

nominal

molecular

: PVPK-15 Albumin

CONTAMINATION

Working the

with

trace and

(Figure

2),

(10-15

I),

risks followed

using

sorption

and

mass-balance p =

where

the

milieu in

WEIGHT for

hollow

different average.

3 : Cyt.Crom

may

a

(Figure

C = 12 500

contamination seriously

= 5 0 0 0 mw,

2

mw

:

closed

system

conditioning

with

contamination fiber to

risks

degree

an o p e r a t i o n - q u a l i t y

mf + m w mt

the

and

4

mass

in i n f l o w i n g

mf = t o t a l

mass

in f i l t r a t e

m w = total

mass

in o u t f l o w i n g

external

washing

procedure

the

sample too.

technique,

itself One main is

be controlled.

factor

that From a

can be defined:

water water water

"In

minimizes

(i)

m t = total

from both

results.

are minimized

fractionation

a certain

problems

affect

by a thorough

can

varying

PROBLEMS

the

clogging

HIP10-8

with

1 : Inulin

Furthermore

calculation,

fiber

solutes

4).

hollow

,k Dalton

, ~', ,,,~_

(4).

concentrations,

internal

advantage

mw,

- SORPTION

internal

fractionation

contamination

weight

= 67 000 m w

- CLOGGING

external

situ"

= i0 0 0 0

using

.

(waste)

90 "1N SITU,,- fractionation

• pump

II111t

mf • sample mw

Figure 4:

S c h e m a t i c set-up of a h o l l o w fiber system under fractionation sampling

If p < i, there

is

a

loss,

"in situ"

(5).

either

due

to

sorption

into

internal

s u r f a c e s a n d / o r c l o g g i n g of the membrane.

If p > i, the water

is c o n t a m i n a t e d by internal sources.

If p = I, the f i l t r a t i o n is p r o b a b l y not a f f e c t e d by these effects.

eGSZn (It)

]oo,.

OSier(Ill) O iv

VS;Cr(Vl)

i

\

s'o

.

.

.

.

2~o

"

"

""

"

;

filtrate (ml) Figure 5:

Sorption hollow

of

Zn

fiber

(II),

Cr

(cut-off

(III)

and :

Cr (VI) on a H I P 1 0 - 8 10 4

Dalton)(6).

91

Information

about

sorption

effects

speciation

studies

of

artificial

spikes.

Radio-nuclides

(Figure 5). 65Zn sodiumcromate MBq/~q to

were

added

are

(III)

(0.5

deionized

pg/l

13%

respectively,

For

the

104

conditioning samples, above,

Dalton water

is

with

cartridge

effects Nepptjern

were

be

studied

in

natural

studied

(Table

2)(5). is

14

to

that

as

MBq/~g

about

means

i. However, species

sorbed. waters.

Cr) 5,

0,

7

a

total

in natural water other

than

used

Thus clogging and sorption Water

samples near

from

Oslo,

lake

Norway,

lakes were chosen b e c a u s e of their

same levels of total monomeric

difference

:

(VI)

: 65Zn = 8

(6). As shown in Figure

two small acid lakes These

51Cr

activity

the samples can be collected.

(HIP10-20)

preferentially

in

using

in these studies

and

is minimized

that

consume of about 10-15

and lake Lomstjern,

approximately main

may

useful spec.

there will be inorganic and organic that

obtained

(as cromate)

the sorption

indicating

often

chlorides

distilled water

250 ml filtrate,

and

connection with membranes,

very

as

Zn, 51Cr = 12 MBq/~g Cr and 51Cr

after about

The

in

elements,

(II) and 51Cr

ultrafiltered

were

trace

aluminium

the total organic carbon

(Ala)

and

(TOC) content

pH.

(Table

2).

NEPPTJERN

~20 o

LOMSTJERN

28 ~S/cm

30 ~S/cm

pH

5.0

5.1

Ala*

596 Hg/l

518 pg/l

TOC

1.7 mg/l

13.7 mg/l

* Total monomeric aluminium

Table 2:

Some p h y s i c a l / c h e m i c a l lake Lomstjern

According

to

the

parameters

from lake Nepptjern and

(5).

mass-balance

calculation

(i),

sorption/clogging

losses may be estimated.

ms% = (i - p) x i00 where

ms% = Internal

(ii)

mass loss/gain

and c o n t a m i n a t i o n

(%) due to sorption/clogging

92

Figure

6

is

based

d e t e r m i n a t i o n of Barnes/Driscoll

on

total method

these

monomeric

calculations. aluminium

In

(Ala)

this

is

work

the

on

the

based

(7,8).

NEPPTJERN

LOMSTJERN

ms%

m

I0-

10-

5-

0 ....

i ....

l ....

I'LI'I

500

....

; . . . . . .

1000 filtrate ml

I ....

I ....

I

.

.

.

.

11100 filtrate ml

500

-5

-5-

ms%

ms~

B

10-

10-

0

1 ....

'I 1000

I~

500

Iml.

0 U"l['"I

,-

...... " I '

'"

10100'i..o.om,

filtrate ml

-5

-5

Figure 6:

Mass sorbed (ms%) of total m o n o m e r i c a l u m i n i u m (Ala) under 104 and 105 D a l t o n filtration, based on the mass-balance calculation (ii), in lake N e p p t j e r n and lake Lomstjern. A : 10 5 Dalton fiber. B : 104 Dalton fiber.

For

fibers,

both

104

and

mass-balance calculations fiber

a

mean

net loss

in the low TOC lake, and in

net

loss

in

retention

(ms%)

content,

which

104

Dalton

these

105

Dalton

(HIP10-20,

gave r e a s o n a b l e results. (positive value) of about

HIP100-20),

In

the

is

small,

The

fibers,

Dalton

fiber

high

TOC

mean lake,

The h i g h e r higher

TOC

to cause a small s o r p t i o n / c l o g g i n g effect. U s i n g it

is

difficult

to

discover

sorption/clogging

effects in the h i g h TOC lake c o m p a r e d to the low TOC lake.

and

difference

but significant.

in the h i g h TOC lake is p r o b a b l y due to the seems

the

Dalton

(i ~ 1)% was o b s e r v e d

(8 • 4)% in the h i g h TOC lake. lakes

105

net loss was about respectively.

(I ~ 1)% and

Therefore

the

In

the

104

(0 ~ 3)% in the low sorption/clogging

losses of A1 a seem to be small and s c a r c e l y significant.

93

The

total

flow-rate through the fibers is the same for all fibers

300 ml/min) reduced

due to the

peristaltic

sorption/clogging

waste water

flow-rate,

in

pump-speed.

The

main

(ca.

reason

for

the 104 Dalton fibers is due to a higher

and a c o r r e s p o n d i n g r e d u c t i o n

in

the

flow-rate

of the filtrate.

During

104

Dalton fiber filtrations the waste water

leading to an important washing

effect

and 104 Dalton fibers. flow-rate washing

of

leads

that

effect

of

the

sorption/clogging,

in to

the

105

higher

and

tube

interior.

This

and m o s t l y affects the 103

Due to lower waste water

filtrate

effect

indicate

washing

minimizes

flow-rate is high,

flow-rate,

but

106 Dalton fibers,

sorption/clogging.

higher

a reduced

These

results

s o r p t i o n / c l o g g i n g effects seem to be minimal with h o l l o w

fiber f r a c t i o n a t i o n s c o m p a r e d to traditional

filtering techniques.

H O L L O W F I B E R F R A C T I O N A T I O N - SOME RESULTS

The h o l l o w catchment,

fiber f r a c t i o n a t i o n Astadalen,

200

was

carried

kilometers

patterns

zinc

from

A-E

here.

Two incident studies have b e e n carried

during

a

heavy

watersheds,

rain

period,

and

in

a

high

mountain

n o r t h - n o r t h e a s t of Oslo, N o r w a y

(12). Some results on d i s t r i b u t i o n different

out

for

(Figure

one

aluminium, 7)(12),

out,

at

one

iron

and

are p r e s e n t e d at

high

flow,

low flow, during a summer

s t a g n a t i o n period.

The pH, as an average for the whole catchment, flow,

but

during

was about 6 ~

1

at

low

h i g h flow a marked p H - d r o p of about 0.5 to 1 pH-unit

was observed.

As i l l u s t r a t e d

in Figure 7, a substantial

and

associated

zinc

is

fraction

of

aluminium,

with colloids, p s e u d o - c o l l o i d s

iron

and particles,

i.e. mw > 103 Dalton. The relative d i s t r i b u t i o n p a t t e r n s d e p e n d

on

origin

for the

of

spring site flow.

This

water,

seasonal v a r i a t i o n s etc. At all sites,

(A), the total spring

site

element

concentrations

(A) o r i g i n a t e s

d i l u t i o n effect p r o b a b l y due to h e a v y rainfall

most

studies,

interesting

results

from

increased

the

at

high

from a small ground water pool

and the d e c r e a s e in total element c o n c e n t r a t i o n s

The

except

this

is the o b s e r v e d changes in m o l e c u l a r

at

high

flow,

is

a

(12).

hollow weight

fiber f r a c t i o n a t i o n distribution.

On

94

the whole, at

there is a lot more low

high

molecular

weight

species

observed

flow than at low flow. This u n d e r l i n e s the importance of doing

f r a c t i o n a t i o n studies.

A! pg/I

%

A

B

C

D

E

A

B

C

D

A

B

C

D

E

A

B

C

D

0 E

~N

-g =

50.

E

pg/I

Zn pg/I

% [~

Mw;103Do"on 103LMwL_10~Dalton

A o

B

C

D

E

lOO ,~,Mw.~lOSDolton

,.a

•J l

50

A

Figure 7:

B

C

O

Mw ~OSO~ton

E

A

: Spring

B

: Brook S k v z l d r a

C

: Brook Grunnbekken

D

: Brook Hestbekken

E

: River ,~,sta

MwX 10/,Dolton

D i s t r i b u t i o n of Fe, A1 and Zn (% of total c o n c e n t r a t i o n s ) a c c o r d i n g to size

(hollow fiber filtration)

sites in the A s t a d a l e n c a t c h m e n t

(12).

at d i f f e r e n t

95

OTHER APPLICATIONS

In a d d i t i o n to "in situ" fractionation, many

other

applications,

8

(9).

hollow

unit

is

used,

high

rejected

by

molecular the

radio-nuclides, enter

the

compounds,

membrane.

metal ions

mixing

The

in

as

the

test

e.g.

in

In such

illustrated

the

colloids

has

mixing etc.,

in

and is chamber

completely

s o l u t i o n in the test chamber contains

etc.

chamber

These

and

O b s e r v i n g the d e c r e a s e in the species

system

This system has one mixing and one test chamber,

kept going by a p e r i s t a l t i c pump. The s o l u t i o n contains

fiber

as for instance a s s o c i a t i o n studies.

studies a c o n t i n u o u s d i a f i l t r a t i o n figure

the

can

low

molecular

weight

then

associate

with

concentration

chamber,

it

is

of

low

possible

c o m p l e x i n g rates and q u a n t i f y amounts complexed,

species colloids.

molecular to

weight

estimate

as i l l u s t r a t e d

in

some the

r e f e r e n c e s 9 and 13.

MOL EC ULA RWEIGHT DISCRIMINATOR

f MIXINGC HAMBER Figure 8:

S c h e m a t i c set-up of a h o l l o w fiber system under a s s o c i a t i o n studies

The

hollow

(9).

fiber system can also be used in d i f f u s i o n / d i a l y s i s

w h e r e b o t h d i f f u s i v e and c o n v e c t i v e membrane water,

(Figure

9)(10).

One

transport

chamber

and one a solution of c o m p o u n d s

Molecular dialysis

TESTC HAMBER

weight rates

molecular weight

is are

the

far

concerned

standards

and

most

take

place

studies

across

the

contains h i g h p u r i t y d i s t i l l e d of

unknown

important

(ii).

After

their

dialysis

weight of u n k n o w n species may be e s t i m a t e d

molecular

parameter

as

weights. far

as

h a v i n g s t a n d a r d i z e d known

(ii).

rates,

the

molecular

96

CONCLUSIONS

The main advantages with hollow fiber fractionation high

filtering

problems, equipment out

capacity

compared

to

combined

with

traditional

are

basically

the

minimal clogging and sorption

disc

filtering

techniques.

The

is easy to handle and the whole fractionation can be carried

in

a

closed

calculations, controlled

system

in

the

internal contamination,

(calculations

association-,

(i),

field.

Based

sorption/clogging

(ii)).

on

mass-balance

effects

can

be

It is also very easy to perform

diffusion/dialysis-studies

with

stable

elements

and

radio-active nuclides.

a) SAMPEL CHAMER b) MOLECULARWEIGHT DISCRIMINATOR c) DIALYZATE CHAMBER.

.I ¢ - - ~

I

, ~

Iii i ii1,, iiiii

o) Fi@ure 9:

Schematic

b)

c)

set-up of a hollow fiber system under diffusion/

dialysis studies

(i0).

ACKNOWLEDGEMENT The

authors

thank

the

Water Acidification Project

Norwegian Hydrological Committee, (SWAP) and the

for Science and the Humanities

(i)

Amicon

Corporation.

Pub.

Norwegian

Ogura,

Research

Council

for financial supports.

No. I-IIIB, Amicon Corp., Mass., U.S.A.

(1983).

(2)

the Surface

N. Marine Biology 24 : 305-312

(1974).

97

(3)

Buffle,

J.,

Delaoey,

Acta 24 : 339-357

(4)

Salbu,

B.

In

and

Doctoral

Fractionation Elements

P.

thesis.

Techniques

W.

Anal.

Chim.

Preconcentration

and

in the D e t e r m i n a t i o n of trace

in Natural Waters

physico-chemical

Haerdi,

(1978).

forms.

-

their

concentration

University

of

Oslo,

and

106-114

(1984).

(5)

Bjornstad,

H.E.,

T., Munitz,

I.P. and Voght,

Al-species

(6)

Salbu,

(7)

Barnes,

(8)

Driscoll, 267-283

(i0)

Salbu,

C.T.

Intern. J.

B.,

Bjornstad, Copper, Products

Activation

L.C.,

Environ.

Anal.

Chem.

16

:

B.,

Eds.,

Bjornstad,

in

H.E., J.P.

Astadalen,

S.E. Norway.

(In prep.).

Salbu,

Bjornstad,

B.,

B. Talanta

(1986,

in press).

Speciation

In : R.A.

of

Fission

the Environment.

Elsevier

A.

J.

Am.

Chem.

(1957).

from

A.C.

and

(1975).

King, T.P. and Stracher,

Hovin, H. and Rambaek,

(13)

N.S.

Publ., London, New York, p. i01 (1985).

79 3729-3737

Waters

Lindstrom, (1985).

H.E. and Pappas, A.C.

and

Salbu,

of

(In prep.).

15 : 177-191

Bulman and J.R.

Craig,

H.E.,

H.E. and Salbu,

AppI. Scient.

(12)

Bjornstad,

B., Sullivan,

Fractionation

(1984).

Bjornstad,

Soc.

Salbu, Size

E. Talanta 9 : 907-913

R.B. Chem. Geol.

(9)

(li)

E., R.

in A c i d i f i e d Fresh Waters.

B.,

Lydersen,

Lydersen,

Determination

a

Trace High

H.E.,

of

Bibow, J.O.,

Englund,

Elements Mountain

Lydersen,

Radionuclides

in

H.,

Fresh

Catchmentin

E. and Pappas,

Associated

with

C o l l o i d s in Natural Waters.

In : Proc.

Int.

Conf.

Level

Actinides

and

Long-Lived

Measurements

Radionuclides Lund, June 9-13

in

of

Biological and E n v i r o n m e n t a l

(1986,

in press).

Low

Samples,

99

THE IMPORTANCE OF SORPTION PHENOMENA IN RELATION TO TRACE ELEMENT SPECIATION AND MOBILITY

B. Allard, K. H~kansson and S. Karlsson Department of Water in Environment and Society LinkSping University, S-581 83 LinkSping, Sweden

INTRODUCTION

The transport of water in environmental

systems, e.g. surface waters and

groundwaters, can in principle be described in terms of advection and dispersion phenomena as well as diffusion. Constituents in the water, either in true solution or as suspended matter, can undergo chemical transformations or interact with solid phases present in the system and will therefore not generally be described by the same transport models as the water itself. Dissolved trace elments in particular are prone to participate in sorption processes and will in most cases be retarded in relation to the physical transport of the non-reacting water. Diffusion of trace components into micro fissures in water-exposed solid materials would in fact lead to a retention even in the absence of any specific sorption reaction.

The importance of sorption phenomena for the transport of dissolved micro components in e.g. environmental waters and the relation of these processes to chemi cal speciation are reviewed in this paper. Examples are given from a case study of metal releases from a mine waste deposit.

SORPTION PHENOMENA

The removal of dissolved trace elements from an aqueous phase is the result of several processes, notably adsorption reactions or precipitation. There are, however, no distinct borders between the various types of reactions, and the mechanisms for different sorption processes as well as precipitation/coprecipitation etc. can rarely be unambiguously characterized.

100

Adsorption processes

In general some idealized sorption mechanisms can be distinguished, as described below [I-4].

Physical adsorption is due to non-specific forces of attraction (van der Waals forces) involving the entire electron shells of the dissolved trace element and of the adsorbent. The process is rapid, reversible and not particularly dependent of temperature and the ionic strength of the solution (well below saturation of any solid trace element phase). The presence of complexing agents as well as pH of the aqueuous phase have a large influence on the process.

Electrostatic adsorption (ion exchange) is due to coulombic forces of attraction between charged solute species and the adsorbing phase.

The process is

usually rapid, largely reversible, somewhat dependent on temperature and strongly dependent on the composition of the solution as well as of the sorbent.

Specific ads0rption ' (chemisorption) is due to the action of chemical forces of attraction leading to surface bonds to specific sites on the solid phase. The process can be slow and partly irreversible. It is highly dependent on the composition of the solid surface as well as of the concentration of the solute, pH and temperature.

Chemical substitution (coprecipitation or solid solution) can be compared with adsorption reactions in the sense that the result of these processes ~ u l d

be a

removal of a trace constituent from the solution phase.

The various types of sorption are influenced by physical and chemical parameters of the system such as *

the hydrogen ion availability of the aqueous phase (defined by pH)

*

the presence of complexing agents in the aqueous phase

*

the free electron availability of the aqueuous phase (defined by Eh)

*

the trace element concentration

*

the ionic strength of the aqueous phase

*

the composition and surface properties (e.g. charge) of the solid phase

Thus, the sorption of a particular trace element on a solid surface is largely dependent on its chemical state, which is illustrated in Figure I. In principle, the interaction of every species in solution with every single different component of the solid phase can be described in terms of a chemical reaction with a formation constant.

101 MOx

--

Mn+

k

k'

M(OH)(n-1) k ~ l

M(OH)(n-1)

ML(n-l) ~

M(OH)2(n_2) k2

IK2 M(OH)2(n_2)

IK2 mk2(n.2) k_~

M(OH)n

Fi6ure I

~

M(OH)n(S), MLn(S) ~K,K' s s Mn+ ,,

•

m

I

m

k

n

I Kn M(OH)n

I K'n MLn

ML(n-l)

k' =

-~

•

m

•

•

Mk2(n_2)

ML n

Simplified schematic of speciation and sorption of metals in solution considering hydrolysis and the presence of a complexing ligand L (adsorbed species denoted by a bar)

The interaction between solute and sorbent (sorption-desorption) can either be described as an equilibrium situation or as a kinetic process. The interaction with inner surfaces (in micro fissures and between micro crystals etc.) in the solid sorbent phase would be diffusion controlled. Therefore, the sorption of dissolved matter on solids would often exhibit a fast initial phase (corresponding to the interac%ion with easily accessible outer surfaces), followed by a slow and partly irreversible process (corresponding to sorption within the solid matrix). Thus, true equilibrium would require long reaction times, unless the solid phase consists of very small particles with short distances for diffusion. A truly reversible reaction (desorption) can in principle never be expected, since diffusion into the matrix and sorption would continue even under conditions where desorption would prevail on the outer surfaces of the solid sorbent phase.

102

The distribution coefficient concept The sorption of a dissolved element on a solid can easily be experimentally determined and described e.g. in terms of concentrations in the two phases (solid and aqueous phases) under the particular condition of the measurements. The distribution coefficient (Kd) is defined as the ratio of concentrations, i.e. mass or activity of the element which is bound to the solids present divided by the corresponding amount remaining in the solution phase (units L3 M-I or L3 L-2). This is a convenient way of expressing the distribution of the element between the two phases, e.g. from analyses under controlled conditions observationsIt

or from field

should be recognized that Kd is a purely experimental parameter

which is highly dependent on the chemical and physical properties of the system and only defines the over-all distribution of the element regardless of chemical state or non-equlibriam conditions. Various sorption models utilizing more sophisticated expressions defining the sorption of a trace element has successfully been applied in simple well defined systems (isotherm models, mass action models, statistical models, double layer or surface complexation models, etc.).

Sorption behaviour of Cu, Zn, Cd and Pb The sorption of hydrolysable transition elements, e.g. the divalent metals Cu, Zn, Cd and Pb, onto hydrous oxide surfaces has been described according to a variety of models, e.g. *

the Gouy-Chapman-Stern-Graham

model (accounts for specific and electrostatic

adsorption), *

the adsorption-hydrolysis model (sorption related to the degree of hydrolysis)

*

the ion-solvent interaction model (considers coulombic, solvation and specific chemical interactions)

*

the ion exchange model (cations replacing protons)

*

the surface complexation model (hydrous oxide surface groups treated as complex forming species).

Also differences between the bulk solution and the surface or aqueous surface film of the solid could lead to: *

precipitation/coprecipitation surface compounds etc.).

(redox changes, formation of sparingly soluble

103

Regardless of the choice of model for the theoretical evaluation of the observed sorption behaviour the distribution of hydrolyzable metals between hydrous oxides and aqueous solutions is very strongly related to pH of the aqueous phase, as illustrated in Figure 2. Data in Figure 2 origin from laboratory experiments under well-defined controlled conditions (a single sorbent, constant solid/solution ratio; control of trace element concentration

and pH in an aqueous phase with a constant ionic

strength; controlled contact times, etc.). Under field conditions there will be variations with time and location of important parameters such as *

composition of the aqueous phase (presence of complexing agents, pH, salt con-

*

compositon of solid phases (presence of a heterogeneous stationary solid phase

*

hold-up times and flow conditions (various degree of equilibria; kinetic ef-

tent; mixing of surface waters, groundwater and precipitation)

as well as of suspended matter of various composition and particle sizes) fects due to mixing conditions, flow conditions, diffusion controlled sorption processes, precipitation, formation of large aggregates/coagulation as well as formation of colloidal phases).

I

I

I

I

I

100

50

Pb

-i t+

Figure 2

I 5

£u

I 6 pH

Zn

I ?

I 8

Adsorption of Cu, Zn, Cd and Pb on amorphous Fe203.H20 [ 5] (Total metal concentrations 5 x 10-5 M).

104 I SPECIESIN SOLUTION I (ORGANIC,INORGANIC; I MOLECULARCOLLOIDAL)I

Preci an tion/ di ssolp uittio

Sorption/ desorption

m

SOLD IPRECP IT IATES Sedimentation

I

Figure 3

II

SOLID PARTICULATE MATTER (ORGANIC,INORGANIC)

Sorpti on/desorption

1

SOLID STATIONARYPHASE

[Sedimentation i

Distribution of a trace element between solid phases and solution phase

The complicated multi-component multi-phase system encountered in nature is illustrated in Figure 3. Thus, the difficulties in explaining or predicting the quantitative distribution and transport properties of trace metals under environmental conditions are substantial, despite the large volume of data from sorption studies under ideal laboratory conditions.

FIELD C~SERVATIONS

The data presented below originate from field observations of the effluents from a sulfide mine waste deposit at Bersbo, some 250 km SSW of Stockholm in Sweden.

The Bersbo area Copper was mined at Bersbo as early as in the 14th century and continued until the early 20th century. A period of rational mining from 1765 to 1902, lead to a peak production during a few decades around 1860-1870. The host rock in the area

105

is granite, while the principal ore is chalcopyrite in association with pyrite. The pyrite also contains minor quantities of sphaelerite and galena. Tailings from the mining, mostly from the late 19th century, cover an area of approximately 0.2 km 2 and consist of waste materials with grain sizes from silt to rock (totally some 300 000 m3 in the area). The deposit area and one of the major drainages of leachates are illustrated in Figure 4. Hydraulic conductivities within the deposit have been estimated to be in the range of 10-3 m s-I. Thus, the material is readily exposed to precipitation. Weathering processes lead to an oxidation of the sulfides, generating an acidic leachate (ph ca 3) with high concentrations of sulfate (more than I g 1-I) and dissolved transition metals (particularly Fe, Mn, Zn, Cu, Cd, Pb; e.g. more than 0. I g 1-I of zinc).

Water has been sampled weekly and analyzed (pH, major anions and cations; Fe, Cu, Zn, Cd and Pb from the leachate) since early 1983. Detailed anlyses of the observed metal mobilities in the field are in progress. Efforts are made to model the quantitative out-flow of dissolved matter fom the deposit as well as the pHchanges in the down-stream river and lake system [6-11]. The data given below are parts of this study, selected to serve as a demonstration of the various processes indicated in Figure 3.

Metal adsorption on solid phases

The unpolluted water (location I, Figure 4) generally has a pH of 4.5-6 and low alkalinity (total carbonate < 10 ~

i-I ). Total salt content is in the range

50-100 mg 1-I inorganic constituents,

and organic material is usually in the

range 5-20 ~

i-I . The dominating anions are sulfate (25-50 mg 1-I ) and chloride

(5-15 mg i-I). The principal cations are calcium (5-12 mg I-I), sodium (5-15 mg i-I), magnesium (5-10 mg 1-1) and potassium (I-5 mg i-I).

The

in-flow of acidic leachates causes a drastic change in the composition,

particularly for pH and sulfate (3-3.5 and < 1500 mg 1 -I, respectively in the leachate). Down-stream, pH is gradually decreasing, due to mixing with unpolluted water as well as neutralization reactions. The sulfate concentration is gradually decreasing, see~Qingly as a function of pH according to [10]: log(S042-) = -0.3 pH - 1.2 (M)

106

LAKE (~ RISTEN( "

A

WATER DEVIDE

.......__..._

._~ ,

WEIR

l

TAILINGS~ 2 1 I

0

Figure 4

1 KM

The Bersbo area[6 ] (Numbers indicate water sampling locations}

107 Carbonate concentrations

are increasing,

roughly determined

by the equilibrium

with atmospheric carbondioxide: log (C032-) = 2 pH - 19.8

(M)

(pH

6.5)

log (C032-) = p H -

(M)

(pH

6.5)

The

total

13.3

concentrations

samples, 0 . 4 ~

of dissolved

trace

metals

(analyses

of filtered

polycarbonate filters) as a function of pH are given in Figure 5

(for the period May 1984 - August 1984). Calculated above

the

solubilities

observed

(considering

concentrations,

decrease in metal concentrations

I

-3

except

possibly

for

cadmium.

Thus,

I

I

I

\

\

I

"\ \

\

~ " ' ~ ~ ~ ~ \

\ \ ZnCO3ls)

-4 ~Cu(OH)2(s) -S

~-6

0

\\ \,~ '\\, ~

-

Cd

\

\\\

-

\

\

\\ \\ \ ",,PbCO3(s) -7

"~\

\P b

x ") TM

-8

-9

I

L,

I

I

I

I

5

6 pH

7

8

Figure 5 Observed metal concentrations (C, M) as a function of pHI 10] (Dashed lines indicate calculated solubilities for some possible solid phases).

the

as a function of pH would reflect sorption on

\ Zn

pH, S042- and C032-) are significantly

108

solids and the dilution down-stream the "location of the in-flow of leachate rather than precipitation of sparingly soluble metal compounds.

The dilution due to mixing of polluted and unpolluted water can be assessed from the sulfate balance m d e r

the assumption that the sulfate concentration is

constant and low in the unpolluted waters in comparison with the leachate. Thus, from the sulfate balance, a dilution factor can be estimated, and the fraction lost due to sorption processes can be calculated [10]:

F = (1+x)Q(Mcalc - Mobs)Mobs -I where x : the dilution factor, Q : water flow, Mcalc : calculated metal concentration assuming dilution only and Mob s = observed metal concentration. The function F is a distribution function describing the sorption onto solid sorbents in the stream (disregarding differences in mixing and contact times for various Q). The sorption of trace metals defined by the function F is illustrated in Figure 6. The observed sorption behaviour is in fair agreement with distribution functions obtained in laboratory studies [ 5 ] considering the heterogeneity in flowconditions, slow kinetics and the approximate estimate of the dilution.

I

I

I

I

I/.

c,, 0 o

Cu

-1

Zn, £d

-2 I

Figure 6

I

I

I

I

5

6 pH

7

8

Fraction of trace metals lost due to sorption processes; F as a function of pH [10].

109

The

fraction

of

the metals

that

(retained by filtration through 0 . 4 0 ~

I 100

are associated

with

particulate

matter

filter) is illustrated in Figure 7 [9].

I

-

~At Pb Cu

,,J

50

Zn

I

J

I

I

I

5

6 pH

7

8

Figure 7 Metal distribution between suspended matter (>0.40~) and solution as a function of pH [9].

Sorption mechanisms

Sorption on the solid suspended phase (or precipitation/coprecipitation)

is

the major mechanism for the removal of metals from the the aqueous phase. Calculations of theoretical solubilities, ass~ing the formation of hydroxides, carbonates, sulfates, hydroxycarbonates or hydroxysulfates under the present conditions show that al~m~inum and iron both reach saturation already at pH around 4 [11]. Possibly, also cadmium could reach saturation at high pH, as well as copper and lead (basic carbonates). The pH-dependence of the removal of Cu, Zn and Cd rather indicates a sorption on the fresh amorphous A1-Fe-hydroxy precipitate and a subsequent coprecipitation and occlusion as the mechanism for the removal. The suspended solid matter ( > 0 . 4 0 ~ ) 20 to almost 100% ass~ing

contains mainly aluminum and iron (from

hydroxides) with some additional silica (less than

5%). The remaining fraction (up to 76%) is organic [11].

110

The

solid

is largely

amorphous,

although

minor

quantities

of crystalline

matter (possibly iron hydroxide and basic lead carbonates as well as quartz) are indicated from X-ray powder diffraction data.

The suspended

solids were characterized

by a sequential leaching procedure

[12, 133 identifying the following metal fractions: *

Exchangeable and bound to carbonates and hydroxides

*

Bound to (hydrous) oxides

*

Bound to organics and sulfides

*

Residual.

Some results are given in Table I.

Table I

Sequential leaching of suspended solids (pH 6.51, oxygen saturation)

Exchangable/carbonates

Organic

Residual

Total

%

Oxides %

%

%

mg/g

AI

15

19

26

40

Fe

23

59

9

9

Cd

93

5

I

I

0.010

32 39

Cu

52

8

39

I

0.50

Pb

53

38

3

6

0.034

Zn

79

15

3

3

4.0

The exchangable fraction appears to be the most significant one for all elements, with lead also largely present in the organic fraction. Although solid (amorphous?) oxides are precipitating in the stream the heavier elements are only present as coprecipitates to a minor extent. Organic material in association with the solid surfaces are binding copper and lead. It is possible that this reaction limit the coprecipitation of these elements with the precipitating solid phases.

Sedimentation of suspended solid s The suspended solids are incorporated into the bottom sediments under periods with low water flow. Dissolved species can also contribute to the metal content in the sediments when pH is sufficiently high. Sediment cores were collected at

111

the same location as discussed previously and treated with the same leaching procedure as ~ms applied to the suspended solids. Some leaching data are given in Table II. Table II

Sequential leaching of sediments (0-10 cm; pH 7.0) Exchangable/carbonates

%

Oxides

Organic

Residual

Total

%

%

%

mg/g

A1

0.8

Fe

100

Cd

50%

30%

15%

5%

Cu

10%

I%

70%

10%

0.034 2.4

Pb

30%

10%

10%

45%

0.15

Zn

30%

25%

40%

5%

7. I

The exchangable fraction appears to be decreased in comparison with the suspended solids. Amorphous oxides are to a greater extent contributing to metal binding which might be attributed to variations in redox conditions. The increase in organic and mineral fractions are also liable to depend on transformations of suspended oxides for reasons mentioned above.

D~C~SI~

~D

~NCL~I~S

Sorption to precipitating solids can be the most important mechanism in controlling apparent solubility of Cd, Cu and Zn in undersaturated solutions. This process is highly dependent on pH in the system. Lead appears to be readily incorporated into more stable chemical forms either by coprecipitation or formation of solids not included in this discussion. Elemental distribution between different fractions in the solid sediments are different in comparison with the suspended solids. Elements are typically present in more "stable" associations in the sediments. Redistribution of settling particles from the aqueous phase leads to chemical changes.

The solute speciation appears to be more important for sorption than the composition of the solid itself. This is also apparent in the sediment but in this environment it is also of great importance to consider the stability of solids in

112

relation to important chemical parameters such as pH and redox conditions. The general schematic description in Figure 3 of the distribution of trace elements between the solution phase and solid phases (mobile or stationary) and the corresponding processes determining this distribution (complexation, sorption/desorption, precipitation/dissolution,

sedimentation) is well illustrated in the field

example. REFERENCES I. Benes, P. and V. Majer. Trace Chemistry of Aqueous Solutions

(Amsterdam:

Elsevier, 1980). 2. FSrstner, U. and W. Salomons. In: G.C. Leppard. Ed., Trace Element Speciation in Surface Waters and its Ecological Implications, pp. 245-273. (Burlington: National Water Research Inst., 1983). 3. Muller, A.B., Ed., Sorption. Modelling and Measurement for Nuclear Waste Disposal Studies. (Paris: OECD/NEA, 1983). 4. Solomons, W. and U. F~rstner. Metals in the Hydrocycle. (Berlin: Springer, 1984). 5. Benjamin, M.M. and J.O. Leckie. J. Colloid Interface Sci. 79:209-211 (1981). 6. Allard, B., S. BergstrSm, M. Brandt, S. Karlsson, U. Lohm and P. Sand~n. Nordic Hydrology (1987, in press). 7. Brandt, M., Bergstr~, S. and P. Sand~n. Nordic Hydrology (1987, in press). 8. Sand~n, P., S. Kar!sson and U. Lohm. Nordic Hydrology (1987, in press). 9. Karlsson, S., P. Sand~n and B. Allard. Nordic Hydrology (1987, in press). i0. Sand~n, P., S. Karlsson and B. Allard. Water Res. (1987, in press). 11. Karlsson, S., B. Allard and K. H~kansson. Geochim. Cosmochim. Acta (1987, in press). 12. Tessier, A., P.G.C. Campbell and M. Bisson. Anal. Chem. 51:844-851 (1979).

13. Slavek, J. and W.F. Pickering. Water, Air & Soil Poll. 28:151-162 (1986).

Section 2 Biological Implications of Metal Speciation

115

TESTING THE BIOAVAILABILITYOF METALSIN NATURALWATERS Peter P~rt Department of Zoophysiology, Uppsala university Box 560, S-751 22 Uppsala, Sweden Introduction Natural waters show a great diversity in their physical and chemical properties.

The various

mechanisms by which water quality controls the a v a i l a b i l i t y of

metals to aquatic organisms is therefore of parmount importance when we want to predict metal impacts in the aquatic environment. The basic question to answer i s ; what extent

to

does a measured water concentration of a metal relate to the amount

taken up by the organisms? The present a r t i c l e is an attempt to review some of methods that

have or

could

the

be used in measuring the biological a v a i l a b i l i t y of

metals. Two approaches can be distinguished. The f i r s t is methods that aim to

iden-

t i f y bioavailable forms or fractions of metals as a guide to the development of methods for chemical analysis of these enteties. The second is methods to

be used in

the evaluation of the actual b i o a v a i l a b i l i t y in the prevailing conditions in a natural water. The b i o a v a i l a b i l i t y of a chemical is varies

depending on trophic

level

a relative

strategy etc. Moreover i t depends on the form of polarity

concept.

The a v a i l a b i l i t y

of the organism, developmental stage, feeding occurence, size,

lipophilicity,

and charge of the molecules under consideration. However, ultimately the

b i o a v a i l a b i l i t y of a xenobiotic is determined by the physical and chemical properties

of

the

barries which the organisms expose to the environment. These barriers

exhibit various degrees of complexity in structure and function. They include partmental

com-

epithelial cell systems as well as simple structures like the u n i t memb-

rane that determines the morphological boundries of which xenobiotics

are

the

cell.

The mechanisms by

bound and transported through c e l l u l a r membranes is poorly

understood, although passage of membranes and binding to ligands are

two phenomena

fundamental in biological transfer and accumulation. So, the key physiological process when discussing metal b i o a v a i l a b i l i t y is the mechanism of uptake. I t is at this level that we have the sieve which determines a particular

if

metal form or fraction is available or not. Uptake is defined in the

OECD Guidelines for t o x i c i t y testing as "the process of sorbing a test compound into and/or onto the organism". The uptake rate is therefore the natural measure of bioav a i l a b i l i t y . To be considdered bioavailable, a metal species or form must be taken up with

a rate that later on w i l l result in a net accumulation of the element, i e

the uptake have to exceed exkretion and d i l u t i o n within the body due to growth.

116

Until now, direct measurements of uptake rates

is

not

commonly applied

in

b i o a v a i l a b i l i t y studies with metals. The reason is obvious - lack of reliable methods. Instead, b i o a v a i l a b i l i t y is evaluated from t o x i c i t y or bioconcentration

data.

Although these approaches have contributed with valuable information, i t must be kept in mind that response parameters are

indirect measures of

bioavailability.

Besides the uptake rate, they depend on factors such as binding, excretion, metabolism and toxic mechanism. Therefore, they do not permit straight

conclusions about

a v a i l a b i l i t y except in well defined and controlled experimental situations. So, i t is to be preferred in the future that b i o a v a i l a b i l i t y studies w i l l measurements of

include

direct

uptake rates across the borders which aquatic organisms expose to

the environment.

Figure 1. Longitudinal section of a g i l l filament from a freshwater adapted rainbow trout. 1 um section stained in toluidine blue. ~L~ g i l l filament secondary lamellae BS= blood space containing erythrocytes PC= p i l l a r cells with flanges lining the blood spaces EP= epithelium of f l a t epithelial cells joined by tight junctions CC= Chloride cells at lamellar bases BL= basal lamina L : lymphatic space

117

Physiology of the barriers

Aquatic organism, except unicellular alage, are covered with epithelia towards the external environment. The epithelium consists of epithelial cells in multiple

single

or

layers, with the cells joined by regions of apparent membrane fusion - the

t i g h t junctions. Substances penetrate the epithelium either by a trans-cellular route through the cells, or by a para-cellular route via the junctions. and properties

The thickness

of the epithelia varies between different parts of the organism and

further on between organisms. Generally, the thinnest epithelia respiratory organs ( g i l l s ) ,

are

found in

the

which are specialized and optimized for gas exchange

with the environment (large surface area, short diffusion

distances

between blood

and water). A representative example is the fish g i l l ( f i g . 1). In general the permeability properties of epithelia are similar

to

those of

cell membranes. The membrane consists of a bi-molecular layer of phospho-lipid molecules perpendiculary orientated to the plane of the membrane with their polar

parts

towards the surface and the non-polar parts inwards. Proteins tranversing the thickness of the membrane are embedded in the lipoid layer. These proteins act as comunicators between the i n t e r i e r and exterior of the cell by participating in the

trans-

location of ions and nutrients across the membrane. The mechanisms for heavy metal penetration through the epithelial cell membranes is basically unknown. However, the following have been suggested (1): 1. Diffusion in non-polar complexes through the lipoid regions of the membrane. 2. Penetration in ionic form by binding to carrier proteins in the membrane, "facil i t a t e d diffusion". 3. Endocytosis of particulate fractions. A vacuole is formed from the cell

membrane

around the particle. The whole package is engulfed by the cell and digested i n t racellularly (particulary important suspension feeders). 4. Metals complexed to nutrients (amino acids, carboxylic acids) by nutrient f i c carriers.

speci-

Water quality may affect the penetration rate of metals, e g b i o a v a i l a b i l i t y , by two fundamental processes. F i r s t l y , by modifying the chemical speciation of the metal in the water, hereby making i t either more or less available for mechanism. For

the

uptake

example, soluble ligands that binds the metal ion in the water w i l l

prohibit binding to any type of "carrier" in the membrane thus decreasing the uptake rate. However, depending on the nature of the ligand and the chemical properties

of

the metal complex formed - polar or non-polar - complexation could also increase the a v a i l a b i l i t y . The uptake rate of cadmium through fish g i l l s was shown to increase in the presence of xanthates, probably because of the formation of non-polar,

lipophi-

118

l i c metal-xanthate complexes (2). Secondly, water quality may change the a v a i l a b i l i ty by a biological mechanism by changing the properties of the epithelia. An example 2+ is the commonly observed antagonistic effect of Ca on metal accumulation and 2+ toxicity which most l i k l y is the result of Ca decreasingthe epithelial permeab i l i t y of the metals (3).

Methods to identify bioavailable forms

The following nomenclature for the chemical speciation of metals is used (4). Metal species refer

to

those enteties (ions, molecules, complexes) which can be

described in terms of well defined stoichiometry. Metal forms include both species and less well defined enteties ( e g metal associated with un-characterized organic material). Finally, metal fraction refers to groups of

forms resolved by -

and

thus operationally defined by - particular analytical techniques. Unicellular algae grown in culture have widly been used as monitors of cal

chemi-

speciation in metals (5,6,7,8,9,10,11). This approach has proven to be success-

f u l l although response parameters are used. Examples of proper bioavailability studies with algae are those of Guy and Ross Kean (12) and Florence et al.. (13). Both have used algal growth rate as a response parameter to investigate the a v a i l a b i l i t y of

copper in the presence of various natural and a r t i f i c i a l organic ligands. Growth

was evaluated from the number of cells or, better, chorophyll or ATP content. The assays include careful chemical speciation of the metal by f i l t r a t i o n , anodic-stripping voltametry, ion selective electrodes and binding to ion exchange resins

(Che-

lex-lO0). These measurements were combined with theoretical calculations of metal speciation from existing equilibria, and the

toxicity

of

various metal species,

forms and fractions could be compared. The results points on the free metal ion (Cu2+) as the principally available metal species while complexed metal generally was less available. However, they also found several exceptions where complexed metal proved to be toxic. Here a drawback of

using response parameters is illustrated. Although complexation increased metal

toxicity, i t does not necessarily mean an increased a v a i l a b i l i t y . The possibility of the metal complex being more toxic as such, than the free metal ion, has f i r s t to be investigated before conclusion about bioavailability can be made. A way to overcome this uncertainity is direct measurements of the uptake rates in the algae. I t is preferably done by using radioactive isotops, of

because analysis

radioactivity is much simpler than conventional analysis of stable elements. The

119

algal cells are exposed to the radioactive metal in the incubation medium. Cells are sampled at regular time intervals and the cell-associated radioactivity is measured. The exposure should ideally continue until an apparent "steady-state"

is

reached.

The i n i t i a l uptake rate is calculated from the accumulation curve by non-linear regression (14,15). The obvious advantage of this approach is the

b i o a v a i l a b i l i t y of

various

direct

concentration can be kept low - often at more environmentally tions

realistic

concentra-

than in t o x i c i t y tests - by the use of radionuclides with high specific acti-

v i t y . PossibTe toxic effects on the mechanisms which determines the in

measurements of

metal species or forms. Moreover, the total metal

the

cells

bioavailability

is herby also eliminated. Unfortunately, this approach has not sofar

been appreciated in b i o a v a i l a b i l i t y studies with algae, except in the study of Macka et a l . (16) where the uptake of mercury and cadmium in the microalgae Chlamydomonas ÷ reinhardi WT was investigated. Crustaceans grown in laboratory culture under controled generations

conditions

for

have also been used in b i o a v a i l a b i l i t y studies of metals (17,18,19,20,

21). Here again effect parametars such as survivial, reproductive success or content

many tissue

has been used in the evaluation. Particulary in the studies of Sunda et al.

(22), Poldoski ~3) and Borgman and Ralph ~4) a thourough chemical speciation

of

the metals (cadmium and copper) is combined with their t o x i c i t y or tissue concentrations. Metal speciation is based on measurements with ion selective electrodes

and

theoretical calculations. As found with the alagal tests, the free metal ions proved generally to be the most available species. Inorganic and organic complexation decreased metal a v a i l a b i l i t y . However, s i m i l a r i l y to the algae, increased a v a i l a b i l i t y was observed with certain organic ligands. material

(18),

Low molecular weight

sodiumdiethyldithiocarbamate

~3)

natural

organic

and ethylxanthogenate ~ 5) were

found to increase t o x i c i t y or tissue accumulation. The inclusion of radionuclides in these assays for calculation of i n i t i a l uptake rates and to avoid toxic

metal con-

centrations is to be recomended as discussed previosly. Direct measurements of the uptake rates across the epithelia of aquatic nisms is

measurements in intact animals appears to be unrealistic. parations

of

However, in

are

vitro

pre-

isolated organs or epithelia may be useful in this respect. One such

approach is the isolated perfused fish g i l l preparation (Figure 2). gills

orga-

a desirable future development of b i o a v a i l a b i l i t y studies. Unfortunately

Basically,

the

dissected from the fish body and the afferent and efferent blood vessels

are cannulated. The efferent cannula is connected to a perfusion pump delivering the perfusion medium, usually physiological saline containing

albumin or

dextran

as

plasma protein substitute. After passage of the g i l l s , the perfusion medium is collected from the efferent branchial vessels. The g i l l s are

submersed in

water

and

effectively irrigated during perfusion. This type of g i l l preparation allows direct measurements of uptake rates of substances from the water to the

perfusion

medium,

120

or vice vers from medium to the water (excretion). Until now i t has basically

been

used in studies of g i l l physiology (26), but i t appears also to have an applicabili~ ty in bioavailability studies.

PP

WK

TD

ME

:L

I

DA

PR

CP

Figure 2. Experimental set-up for perfusion of fish gills used in cadmium uptake experiments. PP= perfusion pump, replaces the heart CP= circulatory pump ventilating the gills C = circulating refrigerant from thermostat unit WK= pulse damper TD= pressure transducer for registration of perfus~on p~ssure ME= ion selective electrodes for measurement of NaT, Cd~T, pH VW= ventilatory water PR= perfusion medium DA= efferent perfusate collected from the dorsal aorta after passage of the gills

The uptake of cadmium in the perfused gill preparation from freshwater adapted rainbow trout (Salmo gairdneri) was investigated salinities

and pH's (3),

in

different water hardnesses,

in the presence of organic complexants (EDTAand citra-

te)(27) and diethylditiocarbamate,

ethyl- and isopropylxanthate ~ ) and in the

pre-

sence of detergents (NPIO-EO and LAS)(28). ~s found that Cd uptake basically was + a function of free Cdz in the water, that decreaseduptake, that Cd-citrate complexes to some extent were available and that the anionic tensid LAS facilitated Cd uptake. Moreover, the dithiocarbamate and the xanthates increased Cd uptake The method has also been used in studies of the availability of hexavalent chromium at two pH levels (29). One conclusions from these perfusion studies is that the chemical properties of the metal complexes are of bioavailability.

importance with

respect to

their

Three categories could be distinguished. The f i r s t comprises metal

complexes un-available to aquatic organisms type EDTA (ethylenediaminotetraacetic acid),

NTA (nitrilotriacetic acid) and DTPA ( diethylenetriaminopentaacetic acid).

121

The second includes complexes that are available to some extent, but the complexed metal

is s t i l l less available than the free metal ion. Within this groupe low mole-

cular weight fulvic acids, amino acids and carboxylic acids (citrate) are found. The third containes non-polar metal complexes with a higher availability than the

free

metal ion. Examples in this groupe are diethyldithiocarbamates and xanthates. An alternative method for measuring uptake rates across epithelia is the

"Us-

sing chamber technique" (30). The prerequisite is that the epithelial tissue can be mounted f l a t . Is is clamped between two chambers thus separating the

solutions

in

two environmental compartments.The metal, preferably as a radioactive nuclide, is added to one compartment andthe appearence in the opposite compartment is by regular

followed

sampling. This technique has mostly been used in studies of ion permea-

b i l i t y of various epithelia like thel frog skin, the toad urinary bladder, the gall bladder, the intestine of mammals~and fish and fish skin. I t has not until now been used in bioavailability studies, neither of organic xenobiotics or

of

metals, but

appears to have a potential in this kind of studies as well.

Methods for evaluating bioavailability under natural conditions

One approach to estimate the bioavailable concentration of metals under field conditions

is to use indicator organisms. The most frequently used are mussels (My-

t i l u s edulis) and Fucus sea-weeds. The c r i t i c a l

assumption in

using idicator

organisms is that they accumulate themetal in direct proportion to the environmental concentration. To what extent this criteria is f u l l f i l l e d is many times s t i l l question of

a

debate. Anyhow, Bryan (31) concludes that analysis of Fucus vesiculo-

sus probably gives a good indication on the~arage bioavailability of silver,

cad-

mium, copper, l e a d and zinc in waters modified by factors including inorganicand organic complexation, presence of metals.

particulate forms and competition from other

A method to estimate the bioavailable concentration of lead in

sediments is

presented by Luoma and Bryan (32). They found a good correlation between the Pb concentration in the deposit feeding bivalve Scrobicularia

plana and the

lead/iron

ratio in 1M hydrochloric acid extracts of sediment (Figure 3). Similarily, Langston (33) tried successfully the sameconcept on the arsenic content in the same animal but extended the studies to

also

include the polychaet Nereis and Fucus. The

conclusion is that Pb/Fe and As/Fe ratios in acid extracts of sediments is predictor Fucus.

of

a good

Pb and As bioavailability to the deposit feeder but not to Nereis and

122

iO00 f~ £~ 4J

o r~ o

5 g

O3

500

m CL

0 Ratio Pb/Fe

lO0 200 (ug/g / mg/g) in sediment

Figure 3. Correlation between concentrations of lead in soft tissues of Scrobicularia plana and ratio Pb/Fe extracted with 1N hydrochloric acid from seaiment (after ref. 32)

A promising approach to measure the bioavailablity of natural

metals to

fish

under

conditions is presented by Bendell-Young et a l . (34). They used the Cd con-

tent in the l i v e r and the growth rate of the fish to compare Cd b i o a v a i l a b i l i t y in 6 acidified lakes. The amount of Cd in the l i v e r was assumed to be a function

of

the

b i o a v a i l a b i l i t y and the weight of the fish: Cdliver = f ( b i o a v a i l a b i l i t y , weight) They measured the l i v e r Cd content, the weight.

age from examining the

scales

and the

From these measurements they could estimate the change in l i v e r Cd content

over time (dCd/dt)(mg Cd/year) and the absolute change in weight over time (dW/dt)(gram/year). Assuming that the b i o a v a i l a b i l i t y not is changing over the year, then the change in l i v e r Cd content over time to growth rate is a function

(Z)

of

bioavailability. dCd/dt / dW/dt = Z ( b i o a v a i l a b i l i t y , weight) A plot of dCd/dt / dW/dt versus W for the various fish populations w i l l

yield

straight lines, where differences in the slopes reflects differences in bioavailabil i t y (figure 4). Analysis of the slopes in figure 4 shows that of

Cd was essentially the same in four of the lakes.

the

bioavailability

In two lakes, marked with 1

and 2 in f i g . 4, the Cd a v a i l a b i l i t y was comparably reduced. Lake nr. 1 had the highest pH (pH=6.4) of the lakes investigated, while lake nr. 2 appeared to be unique among the lakes in that i t was a small, shallow and highly organic, acidic lake. The authors assume Cd to be less available in this lake because the metal organic material.

is

bound to

123

i2 iO 4J 13 3=

8

5 4 ~D

2 0 -2

0

200

400

800 weight

800 (g)

CO00 1200

Figure 4. Relative b i o a v a i l a b i l i t y factors. Lake nr. 1 has the highest pH of lakes (pH=6.4). Nr. 2 is acidic buy highly organic (after ref. 34).

As a conclusion, simple methods for measuring b i o a v a i l a b i l i t y which are versal

to

all

the

uni-

organisms w i l l certainly not be found. Rather, the solution to the

b i o a v a i l a b i l i t y problem l i e s in a basic understanding of

the

physiological,

bioc-

hemical, geochemical and ecological controls on the process. Such deepend understanding w i l l be the key to the future development of both chemical and biological

met-

hods to be used in metal speciation and b i o a v a i l a b i l i t y studies. The natural measure of b i o a v a i l a b i l i t y is the uptake rate. By the use of radionuclides, direct ments of

uptake rates

today used b i o a v a i l a b i l i t y studies. The perfused g i l l and similar rations,

measure-

could be made in those biotests with alga and crustaceans in

vitro

prepa-

which allow direct measuremets of uptake rates across the epithelia expo-

sed, may provide further information on the b i o a v a i l a b i l i t y of particular metal species, forms and fractions. For the f i e l d situation several are

methods, or

approaches

available. Among those, the recently presented one (Bendell-Young et al. 1986),

where l i v e r metal content is related to growth rate attention in the future.

appear promising and deserve

Acknowledgements

Financial support has been obtained from the National Swedish Environment Protection Board within the project areas Fish/Metals and ESTHER.

124

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3.

P~rt, P., O. Svanber9 and A. Kiessling. Water Res. 19:427-434 (1985).

4.

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5.

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Guy, R.D. and A. Ross Kean. Water Res. 14:891-899 (1980).

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Florence, T.M., 281-295 (1983)

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Borle, A.B. Cell Calcium2:187-196 (1981).

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Poldoski, J.E. Environm. Sci. Technol. 13:701-706 (1979).

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Borgmann, U. and K.M. Ralph. Water Res. 11:1697-1703 (1983).

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Ahsanullah, M. and T.M. Florence. Mar. Biol. 84:41-45 (1984).

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Environm. Safety

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127

CASE STUDIES ON M E T A L D I S T R I B U T I O N AND U P T A K E IN BIOTA

Olle Grahn and Lars H ~ k a n s o n Swedish Environmental Research Group

(SERG)

Fryksta 665 00 Kil Sweden Dept. of H y d r o l o g y ~ U n i v e r s i t y of Uppsala V Agatan 24 752 20 Uppsala

ABSTRACT

The aim of this paper

is to sum up some results on h e a v y metals from

Swedish studies on the linkage b e t w e e n metal contamination, sensitivity,

environmental

b i o l o g i c a l uptake and ecological effects.

Man's a c t i v i t y has caused a drastic increase of metal fluxes in the b i o s p h e r e by emissions

from industries and by b u r n i n g o ~ fossil

fuels.

The increased a c i d i f i c a t i o n of soils and w a t e r s has also a strong b e a r i n g on the d i s t r i b u t i o n and fate of metals and the m o b i l i z a t i o n of metals from soils.

The b i o a v a i l a b l e part of the metals present

in natural waters varies

w i t h i n a wide range due to several e n v i r o n m e n t a l

factors. M e t a l s are

taken up d i f f e r e n t l y by different test organisms.

In future e v a l u a t i o n s of d i f f e r e n t kinds of metal p o l l u t i o n in different types of aquatic environment,

it is n e c e s s a r y to make metal speciations

as a step to d e t e r m i n e w h i c h fractions are b i o a v a i l a b l e .

INTRODUCTION AND AIM

Numerous p a p e r s and reports have b e e n w r i t t e n on the transport, and e c o t o x i c o l o g i c a l aspects of metals in a q u a t i c systems. general surveys have b e e n given by, e.g.,

F~rstner and W i t t m a n

Salomons and F~rstner

(1984).

The aim of this paper

is to sum up some results

the linkage b e t w e e n metal contamination, b i o l o g i c a l uptake,

turnover

Excellent (1979) and

from S w e d i s h studies on

environmental

sensitivity,

e c o l o g i c a l effects and a s s e s s m e n t of h e a v y metals

128

in limnic environments, principle

interest.

and to c o n c e n t r a t e on some case studies of

For a more t h o r o u g h d i s c u s s i o n on the causal

r e l a t i o n s h i p s b e t w e e n dose, effects of metals, discuss methods, general,

deposition.

see H ~ k a n s o n

(1984a,

r e l i a b i l i t y of data,

principle

investigations

environmental

interest.

s e n s i t i v i t y and e c o l o g i c a l

1984b). Thus, h e r e we do not

etc., but will focus on results of

Most e x a m p l e s will be taken from

in areas a f f e c t e d by d i s c h a r g e s

We will not try to give a g e n e r a l

presuppositions

from mines and acid l i t e r a t u r e review. These

imply that the r e f e r e n c e list gives a d i s t o r t e d and poor

p i c t u r e of the most

important p u b l i c a t i o n s on metals in a q u a t i c systems.

Some metals like Fe, Mn, Cu,

Zn, Co and Mo, are essential

for life in the

p r o p e r c o n c e n t r a t i o n range. This range can be narrow. Other metals,

like

Hg, Cd and Pb are not e s s e n t i a l but are toxic to smaller or larger extents d e p e n d i n g on c o n c e n t r a t i o n and e n v i r o n m e n t a l conditions.

In this

p a p e r we will address some c o n d i t i o n s of i m p o r t a n c e for a q u a t i c ecosystems.

Man's a c t i v i t y has caused a drastic biosphere by emissions

increase of metal fluxes in the

from d i f f e r e n t types of industry,

smelters and iron- and steelworks.

e.g.,

mines,

E m i s s i o n s of a c i d i f y i n g c o m p o u n d s and

metals to air, water and soils b y b u r n i n g of fossil fuels h a v e also i n c r e a s e d s i g n i f i c a n t l y d u r i n g recent decades.

This has a strong b e a r i n g

on the d i s t r i b u t i o n and fate of metals and a l s o causes m o b i l i z a t i o n of metals

in the soils.

OLD SINS A N D N E W

In the area of G a r p e n b e r g

in central S w e d e n

(Fig. i) mining a c t i v i t i e s

h a v e b e e n g o i n g on since the M i d d l e Ages. T o d a y a r e a ~ i s one of the most m e t a l - c o n t a m i n a t e d areas p a r t l y b u i l t on wastes

in Sweden.

Roads and entire c o m m u n i t i e s are

from the mining.

Fig.

i l l u s t r a t i n g the sites of the p r e s e n t mines, d e p o s i t s and the lake

2 gives a location map locations of major older

(Gruvsj~n or M i n e lake in translation) w h i c h

r e c i e v e s a h e a v y load of m a n y metals.

The d i a g r a m in Fig. 2 d i f f e r e n t i a t e s b e t w e e n the metal fluxes of Cu, Pb, Zn and Cd from the following

sources:

- d i f f u s e sources a r o u n d the lake -

old d e p o s i t s

129

- present mines It should be noted that for Cu, Zn and Cd only a small percentage, total metal flux to Lake Gruvsj~n today emanates activity.

For Pb about 40% can be linked to present

(Lindestr~m and Qvarfort

of the

from the present mining industries

1985)

N~Lake Saxen1 / A. ~ Lake Gruvsj~n ~ ~ L Lake Asgarn

tot

River At r a n ~

Figure I: Location map of discussed

It is evident that significant Gruvsj~n.

amounts of metals are transported

This has caused high metal concentrations

and all types of investigated fish population however,

lakes and rivers.

organisms

and a reduced bottom

in the lake, which is oligotrophic.

which is located about 5 km downstream

which has a much higher

in water,

level of bioproduction

to Lake

sediments fauna and

In Lake Asgarn,

from Lake Gruvsj~n and due to nutrient

load the

130

c o n c e n t r a t i o n s of metals in b i o t a are s i g n i f i c a n t l y lower and no a p p a r e n t e c o l o g i c a l effects h a v e b e e n d o c u m e n t e d - in spite of the fact that the metal load also to this lake is very h i g h

Acidification

(Grahn and S a n g f o r s 1984).

is a well d o c u m e n t e d menace in many parts of S c a n d i n a v i a

and N o r t h America.

The spread and e c o l o g i c a l effect of m a n y metals are

h i g h l y r e l a t e d to the p H of the water. leakage of metals

It has b e e n d e m o n s t r a t e d that the

from soils increases s i g n i f i c a n t l y w i t h lower pH. A

clear example of this is g i v e n for Cd in Fig. 3. Note the marked peak b e l o w pH 5.

Present mine

[]

Present mine

[]

[] ke Gruvsj~n

50 10000~ 10 Cu

Pb

Zn

Cd

]

Diffuse sources around the lake

]

Old depots

]

Present mine

To lake Asgarn

k

Figure 2: L o c a t i o n map of the area a r o u n d Lake Gruvsj~n. E s t i m a t e d of metals (in kg) from M a y 1979 to A p r i l 1980.

fluxes

131

An i n v e s t i g a t i o n in d i f f e r e n t w a t e r s h e d s in S w e d e n where mean p H in the run-off water varied b e t w e e n 4.1 -5.0 also c l e a r l y d e m o n s t r a t e s that the transport of metals is much higher m o b i l i z a t i o n of, e.g.,

in areas w i t h low pH

(Fig. 4). The

Zn, Cd, A1 and Co is 5 - i0 times h i g h e r

in the

area with pH 4.1 in the run-off water than in the area with pH 5.0 (Grahn and Ros~n 1984).

Ue/L 3.0

2.5

2.0

<

,°

1.0

.:{ 0.5 .

o

°~-~°" ~ ~.

I

I

I

i

4

5

6

7

I

8

PH

Figure 3:

The r e l a t i o n s h i p b e t w e e n pH and Cd c o n c e n t r a t i o n s soil water.

in lake and

132

Zn g/ha and year 200 I 2 3 4 5

l i00 •

pH pH pH pH pH

4.1 4,2 4,4 4,8 5,0

) i)

-

i

F-~ F-] pH

0 1

2

4

3

.5

Al g/ha and year PO00 GO00 SO00 4000 3000 2000 1000 0

I

2

4

3

5

Co g/ha and year

Cd g/ha and year i.~

10

i

iF-q

f

J

J

o

~

1

Figure

4:

due

depend

on

as w e l l

Old mine

to sulfide the

deposits

areas

and

can

oxidation.

character

as t h e m e t a l

acidified

~-] 5

4

3

0

pH

1

M o b i l i z a t i o n o f m e t a l s in a r e a s drainage water (g/ha and year).

TO conclude: mainly

2

of t h e

dose.

leak

the mobilization

e.g.,

will

is n e g a t i v e l y

~--] ~-pH 4 5

pH

amounts

ecological

water,

mobilisation

3

different

significant

The potential

receiving

Metal

with

2

in t h e

of m e t a l s ,

damage

would

the trophic

also

take place

correlated

status in

t o t h e pH.

133

Lake

Area

Volume

(ha)

( M m ~3 )

Mean

(m)

Mean

depth

pH

Trophical

level

Gruvsj~n

141

4.2

3

7.0

Asgarn

183

3.7

2

6.7

Eutrophic

82

2.5

3

6.6

Mesotrophic

Saxen

Oligotrophic

3860

410

10.6

6.8

Mesotrophic

Orvattnet

72

6.0

8.4

4.9

Oligotrophic

Table

Background

V~sman

i:

Lake

data

Hg

on

lakes

wat

Cd

Pb

wat

sed

wat

sed

Gruvsj~n

-

1.5

5.6

25

Asgarn

-

1.6

1.6

Saxen

-

0.95

-

V~sman

-

2.35

-

Orvattnet

-

-

0.3

Table

Metals

2:

ug/l

THE NEED

Heavy

metals

on

Lake

12

Zn

wat

9100

20

sed

wat

sed

4800

3500

ll200

40

4

900

6

860

1200

10400

105

20

16100

150

4030

2400

35430

5.1

-

790

-

i00

3

2

210

2

28

and

surficial

sediment

-

1210

i0

of l a k e s

300

discussed

in

ds.

inhomogeneous

to m e t a l

waste

area

group

contamination

water

since

concentrations

and

from a mine,

1880

of m o s t

the

may vary

the p r e s e n t metals

are

sensitivity

of

within

a wide

range.

Saxberget.

Mining

has

industry found

starting

in w a t e r

and

been

in 1936. sediments

2).

V~sman,

smaller

a most

receives

in t h i s

Very high (Table

are

waters

Saxen

going

ug/g

Cu sed

FOR DIFFERENTIATION

receiving

Lake

in w a t e r

and

discussed.

which

amounts

Comparing in b i o t a ?

the

is l i n k e d

of m o s t

situation

to L a k e

of the

metals

in t h e s e

two

Saxen

via

a short

(Lindestr~m

lakes,

how

river,

receives

1984).

are

the m e t a l s

picked

up

134

We will

illustrate

plankton,

some central concepts with data on Zn and Cd in

perch muscle and p e r c h liver

is clear

(Fig. 5). From these diagrams

it

that:

- Zn is found in much higher

concentrations

than Cd in the test organisms.

- V e r y little Zn and Cd are found in fish muscle.

The Zn c o n c e n t r a t i o n s

are much lower in p l a n k t o n

Lake Saxen - but the Zn c o n c e n t r a t i o n

in Lake V~sman than in

in perch liver and muscle is

about the same in the two lakes.

-

The Cd c o n c e n t r a t i o n

is about the same in the p l a n k t o n

- but the Cd c o n c e n t r a t i o n

is much lower in p e r c h liver in Lake VEsman.

PLANKTON

PERCH LIVER

PERCH MUSCLE

200

50OO N

100

I .

!000

SAXEN

V~SMAN

PLANKTON

Jm

SAXEN

to

V~<SMAN

PERCH LIVER

SAXEN PERCH MUSCLE

o10 0.1

SAXEN

5:

V~,SMAN

SAXEN

V~SMAN

Zinc and cadmium in plankton, Lake Saxen and Lake V~sman.

C o n f u s i o n would prevail of metals.

V~.SMAN

03

20

Figure

in the two lakes

if we continue

The crucial q u e s t i o n

biologically

available

I

SAXEN

I

VASMAN

pike liver and perch muscle

to determine

in

total c o n c e n t r a t i o n s

is: How much of a given metal dose is

and can be picked up in the food chains?

t35

This is a most complex issue.

It is also important to note that different

metals are taken up d i f f e r e n t l y by d i f f e r e n t test organisms. illustrates,

-

-

for Zn and Cd, that:

different

test organisms

the

causing

range

often

more

Zn a n d Cd

than

(just

concentration exception the

react

long-term

3 orders

as m o s t

differently

and short-term

of magnitude

metals)

is n o t h i g h e r

from this general

form of methyl

later

Fig. 6

mercury

to one and effects

(for

(i.e.

in t h e p r e d a t o r

than

rule

metals"

which

same metal

Zn a n d Cd)

-

is

in c o n c e n t r a t i o n ;

do not biomagnify

for

the

"heavy

is l i p o p h i l i c .

the

in its p r e y ) . since

We will

H g is a n

Hg appears

return

in

to Hg

on.

E ©

1 08

O .C ~n

105

E 83

10 4

C O _J

4~ C © E -4 73 C~ GO

[0 c

o 3 4~ E 4~ o /z £]3

[

l!

10 3

10 2

C

It I

T

c o

1

10 1 f--t 4J c 0d u c o L~

T 1 I I 1

10 0

10-I .1.

Zn ~--~ Cd .....

10-2

Figure

6:

r

iE .~ b_

T ! I I I I .1.

T I 1 1 1.

C o n c e n t r a t i o n s o f Zn a n d C d y i e l d i n g s h o r t - t e r m a n d l o n g - t e r m e f f e c t s , a n d c o n c e n t r a t i o n s in w a t e r , lake s e d i m e n t s , a t t a c h e d a l g a e , b o t t o m fauna, f i s h m u s c l e a n d f i s h l i v e r ( f r o m H & k a n s o n a n d J a n s s o n , 1983).

136

One crude way to try to distinguish the biologically available dose from the total dose is to make a fractionation. (=speciation)

schemes exist

Many fractionation

(see, e.g., Chester and Hughes,

et al. 1979; Salomons and F~rstner,

1967; Tessier

1980).

M E T A L SPECIATION Most metals can appear in different chemical characteristics particles"

forms with different

and different affinities to various types of "carrier

(Fig. 7) existing in natural water systems

Fe/Mn-oxides,

carbonates,

(humic substances,

etc.). These "carrier particles"

may camouflage

the toxic properties and govern the spread in nature in a way that is often very difficult to foresee from laboratory tests.

Io.

1+Metalform ~

\ \

Complex CheLate

h~org:mic ~ ~

Soluble

Org:mic

P~rticulale~

~tolecule

Col{oh} Sorption Suspended

Mineral detritus

/ Clayminerals //j~ m, mic subs,a.ce "Carrier particles" ~ i~tug: enp Residual org;mics Hydroids Fe/~.lnoxides C~rbon:*,¢s

/

2. Presence or other substitutes . ~

Synergism Addition Anlagonism

Temperature

p}l

3. Waters y s t e m

Geographical position Geology of drainag¢ area Morpbometry of basin Hydrologicalconditions

Dis.~;otv~doxygen Light Transparency S~linity Alkalinity Trophic level Levelof bioproduction Reside,~¢etime

~edi.~a.ttn+pping

4. Biologicalsystem

Figure 7:

~

Age Size

Sex Foodsupply

Activity System of protection Adaptation o£ metals Ecologic{status

Factors affecting the toxicity of metals in aquatic systems. From Beijer et al. (1977) and H&kanson and Jansson (1983).

137

Fig. 8 exemplifies the distribution of various metal fractions in suspended matter and surficial sediments in the river system of the River ~tran (see Fig. 1 for geographical orientation). have been determined

-

Metals

(Landner & Grahn,

The following fractions

1975).

(Cd, Zn, Pb, Cu, Cr, Ni, Fe and Mn) adsorbed on particles.

This

may be called the easily exchangeable fraction.

-

Metals co-precipitated as hydroxides or carbonates on particles.

Metals

in this fraction are less available for biological uptake than metals in the first group.

o~ oo

~

Figure 8:

-

....

~ o oooo

[] Incrystallineparticulatematter

Various fractions of selected metals in sediments and suspended matter in the River ~tran, southern Sweden.

Metals incorporated in organic particles. by organisms

These metals may be picked up

feeding on organic matter or when the organic aggregates,

the "carrier particles",

are mineralized.

138

-

Metal in c r y s t a l l i n e p a r t i c u l a t e matter. M e t a l s in this fraction are the least b i o l o g i c a l l y a v a i l a b l e and may be called the inert fraction.

F r o m the figure we m a y note that:

- 50 to 80% of the Cd, Pb and Cu appear surficial

-

The e a s i l y e x c h a n g e a b l e for Cd w h e r e

The results

in the inert fraction in the

sediment and 50 to 80% of Pb and Cu in the s u s p e n d e d matter.

f r a c t i o n is small for most toxic metals,

except

25% - 50% b e l o n g s to the fraction.

from this water

system c o n c e r n i n g the a f f i l i a t i o n of the

various metals to the various

fractions cannot be a p p l i e d to other water

systems with d i f f e r e n t c h a r a c t e r i s t i c s s a l i n i t y or h u m i c content,

in terms of, e.g., pH, alkalinity,

since these e n v i r o n m e n t a l

affect the d i s t r i b u t i o n of the metals to the various

factors s t r o n g l y fractions.

ENVIRONMENTAL SENSITIVITY

The chemical,

limnological,

s e d i m e n t o l o g i c a l and h y d r o d y n a m i c a l

c h a r a c t e r s of the r e c e i v i n g waters metals

(Fig. 7). Subsequently,

i n f l u e n c e the spread and fate of

we will give one typical example of this.

The o b j e c t i v e of this p a r t i c u l a r

investigation

(Grahn and Sangfors,

was to study the seasonal v a r i a b i l i t y of s e l e c t e d perch,

z o o p l a n k t o n and water

contamination, be d i s c u s s e d

"heavy metals"

1984)

in

in four lakes w h i c h varied in metal

a c i d i t y and t r o p h i c status

(Tables 1 and 2). Results will

from two of these lakes:

- Lake Asgarn; h i g h metal pollution,

- Lake Orvattnet;

h i g h pH and h i g h b i o p r o d u c t i v i t y ;

low metal pollution,

a c i d i f i e d with pH "5, low

bioproductivity.

Fig.

9 shows Cd and Zn c o n c e n t r a t i o n s

1983 in these two lakes. Cd c o n c e n t r a t i o n s .

in water and p e r c h liver

from M a y

Zn c o n c e n t r a t i o n s are g e n e r a l l y much h i g h e r than

The most r e m a r k a b l e

is that the Cd c o n c e n t r a t i o n in

the water is about 6 times lower in the "unpolluted" c o n c e n t r a t i o n in fish liver is about 3 times higher.

lake, but the Cd

139

M~/KG

UG/L 0.5

[]

UNCONTAMINATED ACIDIFIEO LAKE

0.1

I [ ~ CONTAMINATED LAKE WITH'NEUTRAL PH

rLo WATER

500 Figure 9 :

Zinc and c a d m i u m concentrations

~

_ca

FISH LIVER

z~

in water and

20

p e r c h liver from Lake

10

A s g a r n and Lake Orvatt-

N~

1oo

net, May 1983. WATER

FISH LIVER

How can this occur? Once again we must seek the answer form of the metals and the e n v i r o n m e n t a l In the a c i d i f i e d and o l i g o t r o p h i c easily a v a i l a b l e

lake, more of the c a d m i u m is in the

form, and the b i o l o g i c a l d i l u t i o n is lower due to the

lower amount of suspended matter Thus,

in the a v a i l a b l e

factors that govern this form.

(plankton, humus substances,

etc.).

total analysis of metals may be a crude a p p r o a c h in a s s e s s m e n t s of

p o t e n t i a l b i o l o g i c a l risks.

MERCURY

About 40 000 p a p e r s h a v e b e e n p u b l i s h e d on m e r c u r y in the e n v i r o n m e n t (Andersson et al.,

1987). M e r c u r y may be r e g a r d e d as a special case among

the "heavy metals" due to its toxicity, b e c a u s e of its threat to man can be d e c l a r e d exceeds 1.0

(consuming fish w i t h h i g h Hg content). Lakes

"black-listed"

(mg Hg/kg)

a b i l i t y by b i o a c c u m u l a t e and

if the Hg content in fish (i kg pike)

in Sweden and 0.5 mg H g / k g in Canada. Most m e r c u r y

in fish appears in the form of methyl mercury,

The m e r c u r y content in fish (i kg pike) (H~kanson,

1980):

- the dose of Hg to the lake;

a most toxic variety.

depends on many factors,

e.g.,

140

- the a c i d i t y

of the water;

the

lower

level of the

lake;

the p H the h i g h e r

the Hg c o n t e n t

in

fish;

- the trophic lower

the Hg c o n t e n t

The r e l a t i o n s h i p

F(Hg)

the h i g h e r

the lake b i o p r o d u c t i v i t y ,

the

in fish.

between

these

= (4.8"iog(i

factors

m a y b e g i v e n b y the

+ Hg50/200))/((pH

- 2)*log

formula:

(BPI))

where

F(Hg)

the c o n t e n t

=

This

methyl

mercury

may be r e g a r d e d

in muscle

as a effect

in 1 kg pike

in mg/kg.

term or a b i o l o g i c a l

response

parameter.

Hg50

the areal

=

median

in ng/g ds).

pH

sensitivity

lake

A comparison empirical

r,

is 0.86

normated

for s e a s o n a l

From data g i v e n Hg c o n t e n t is I0%,

dose,

data

(H~kanson,

of a lake

fish data

(Table

in Table

If we add one lake

formula

from d i f f e r e n t and

if these

is a second

and a set of

the c o r r e l a t i o n

the p a i r - w i s e

4, H~kanson,

means

that

h o w much more of the v a r i a t i o n

different

data

Hg

are

in a d e f i n e d correlation

1984b).

how much of the v a r i a t i o n

from the dose alone.

for this p a r t i c u l a r

a small p a r t

sensitivity

lakes w i t h

empirical

(only fish caught

3, we can c a l c u l a t e

This

This

3).

Hg f l u c t u a t i o n s

r 2 = 0.i.

is an e x a m p l e

1984b).

from the g i v e n

in fish that can be e x p l a i n e d

i.e.

This

very good correlation;

the dose will o n l y e x p l a i n

value.

system.

and size variation,

is r = 0.9

(0 - 1 cm,

parameter.

in fish are c o m p a r e d

s e a s o n are compared) coefficient

index

(Table

sets of e m p i r i c a l

concentration

set,

model

d a t a has r e v e a l e d

coefficient,

If tWO

sensitivity

between

sediments

of a dose p a r a m e t e r .

parameter.

the b i o p r o d u c t i o n

=

of s u r f i c i a l

is one e x a m p l e

the mean p H of the water

=

BPI

Hg c o n t e n t

This

factor,

The answer

empirical

of the response,

data

the F(Hg)

the b i o p r o d u c t i o n ,

in Hg c o n t e n t

in

to the

in fish will be

141

explained? The answer

is about 26 %. If we a l s o account for pH, the

degree of e x p l a n a t i o n will i n c r e a s e d to 74 % (0.842"100).

This means that

the g i v e n formula explains about 74 % of the v a r i a b i l i t y in Hg content

in

fish. This is a very h i g h figure since the m a x i m u m degree of e x p l a n a t i o n that may be e x p e c t e d is 0.92 = 0.81 = 8 1 % . Environmcmal

Dose

parameter

W,

W:

parameter

Empiri~l

W~

D

£ =f(D, W=)

E =f(O. W))

E =f(D, Wr W~)

E-data

F(Hg) = f ( H g ~ pH) BPI = eonsl = 3,83

F(Hg) ~ f ( H g ~ BPI) pH ~ COast ~ 6.35

F(H 8) (rag kg'I)

F(Hg) (rag k ~ ? )

Atta (kn~

pH

BPI

Hg~g (ttg 8"t ds)

35~'2 2066 1856 91

7.2 7.1 7.6 7.3

2.9 3.1 2.9 5,0

730 160 80 260

1.I 0.4 0.2 053

1.6 0,55 0,35 0.55

1.3 0.5 0 25 0 45

II 07 045 0,5

6.6 7.1 6,9 7,0 7.2

4.0 4.9 5.2 5.1 4.0

340 2040 650 470 470

0.75 1.7 1.1 0.85 0.85

0.75 1,7 0.95 0.8 0.85

0,7 1,4 0.85 0.7 0.7

0.6 1.2 03 0.7 0.45

[.35 0.38 1.36 9.38 l.I~

5.1 5.5 3.9 5.0 6.0

3.4 3.8 3.5 3.0 3.4

300 280 220 220 160

I.] 0.9 0.70 0.70 0.55

0.03 0.7 0,65 0.6 035

1.2 0.9 0.75 0.70 0.55

L3 L] 09 0.7 0.5

0.31 0.23 1.07 0.42

4.8 5.9 5.3 5.7

5.3 2.5 3.1 3.9

300 290 250

1.2 0,0 0.0 0.8

0,85 13 0,8 0,65

1.3 L2 LI 0.75

15 t,0 0.9 0.7

6.35 0,07 -0.61 99*/. 62.8

3.83 0.86 -0.30 75*/, 91.0

416 438 0.31 75~, 90.4

0.05 0,35 0.62 99°/. 62.4

0.83 0,35 0.51 97.5~ 74,0

0.85 0.33 0.86 99~/* 26.0

0.84 0,33 1,00

Large L a k ~ V~rm[andssjfa Dalbosjdn V~tte~ Blacken (M~l~tren} River Kolb~ck~a L~kes Bysjdn Ovre Hilled Leran Sddra Barken

Stora Aspen

5.1 4.4 2.8 3O.5 5.9

F(H8),~, N v ~ t a n d Lake* L2-I.8 8 L0-L2 9 0.8-L0 7 0.6~3.0 15 0 4~).6 II Smilgnd/Halland Lakes L3-L7 5 1,0-1,2 3 0.8-1.0 9 0.6-0.8 10

260

m = 18

42f0 s.

I000.8

-0.03

Corr. sign. R~idual term ( a )

Not 99.9

.~"= mean vahm s v ~ standard deviation, • = cor~latlon c~fficient and R = the r~idual t e n

Table 3:

which is defined as I00(I -r~). Modified after HAkanson (1980b)

The r e l a t i o n s h i p b e t w e e n the effect parameter, the Hg content in pike, the dose parameter, the Hg content in surficial sediment, and three e n v i r o n m e n t a l p a r a m e t e r s - lake area, p H and b i o p r o d u c t i o n index (BPI). From H ~ k a n s o n (1984b). SarapM I

Weight

F(Hg)~

Weight

Lake

(k8)

(rag kg -t ws)

(kg)

Runa

2.48 0,84 1.15 L30 0,49 1,48 t.34 1.03 0.72 0.73 0,58 0.27

1.75 1.45 1.00 0.05 0.02 0£7 0.54 0.53 0.40 042 0.37 0.3 [ 0.27 0.22 0.21 0.19 0.18 0.18 0,17 0, t 7 0,16 0.15 0.I5 0.i ~ 0.004

2.35 0.77 LI0 1.24 0.43 i.30 1,30 1,02 0.78 038 0.63 0.25 0.84 0.44 1.57 034 0.42 1.03 2.45 0.04 0.25

Eskdklubb Mj6m S Bjfrk fj~rdea Eskdk[ubb

BMmhn Mjdrn glvka~led S Bjdrk0~rde~ Oresjan

Ashen Skikkisjdn Ljusne str0mmar

Labbas St Lulcvattact Sd~ik~jdn

Storvlndcln Hj~lmaren Ladtjojaure Roxeo Siijan Hj~lma~a V Riagsjdn Vombsjgn Vombsj~u i (N = 25)

0,$9

0,48 1,71 0.71 0,42 117 2.82 0.88 0.22 0.87 0,86 L00 0.89

0.46

0,42

0.82

0.0I 1.04 0,85

Sample 2 F(Hg}~ (rag kg "~ ws) 230 1,15 0.77 0.4 [ 0,9[ 0,55 0.94 0.45 0A2 030 0,36 040 0,16 0A6 1,37 0.27 033 0,[6 0.23 0.23 0.39 0.17 0.15 0.096 0. i 2 0.48 0,48

SCor~lati~ coefficient: • = 0.90 Residuat t e N : R = 100 (1 - r ~ ) = 18.2~

Table 4:

C o m p a r i s o n b e t w e e n two sets of empirical data on the Hg content in muscle in 1 kg pike, F(Hg)emp, from 25 lakes from d i f f e r e n t geographical, limnological and c o n t a m i n a t i o n a l e n v i r o n m e n t s in Sweden. These data have b e e n c o r r e c t e d for seasonal v a r i a b i l i t y (all fish were caught during O c t o b e r - N o v e m b e r 1966) and size (only fish of equal weight are compared). From H ~ k a n s o n (1984b).

142

In this c o n t e x t we w i l ! n o t

d i s c u s s p r e s u p p o s i t i o n s and l i m i t a t i o n s

c o n c e r n i n g the g i v e n formula and the results.

Instead we will assume that

the r e s u l t s c o u l d reflect the major factors g o v e r n i n g the Hg content in fish. The m a i n point h e r e is that the dose will o n l y account

for a

minor part of the r e s p o n s e and that it is v e r y important to account the e n v i r o n m e n t a l

for

s e n s i t i v i t y factors that r e g u l a t e the "road from dose

to response".

In this context we will also v e r y b r i e r y m e n t i o n a n t a g o n i s t i c effects and more s p e c i f i c a l l y how zinc p r o b a b l y m a y act a n t a g o n i s t i c a l l y towards mercury

(H&kanson and Uhrberg,

1981; L i n d e s t r ~ m and Grahn,

A b n o r m a l l y low Hg c o n c e n t r a t i o n s

1982).

in fish h a v e b e e n found in several lakes

h i g h l y p o l l u t e d with m e r c u r y and other metals.

The mean c o n c e n t r a t i o n in

1 kg p i k e in such lakes lies in the range from 0.15 down to 0.05 mg/kg, w h i c h is v e r y low indeed since the "natural" Hg content in fish from "unpolluted"

Fig.

lakes is seldom lower than about 0.2

i0 e x e m p l i f i e s results

for Zn and Hg from

(A) " u n c o n t a m i n a t e d "

lakes

(B) " u n c o n t a m i n a t e d "

lakes from middle Sweden.

(H~kanson 1984b)

:

from n o r t h e r n Sweden.

(C) lakes r e c e i v i n g waste water

[] []

from mines.

ZN ~° 104 H~

n=8Z :::ff~::::::~¢::<:%::

-×-×-×-x-×,'/~<

::::::::::::::::::::::: VAII:.I:/AI:A:

Q

Cl a.

A

B

C

I A

B

c

Figure i0: Zinc and m e r c u r y c o n c e n t r a t i o n s in surficial sediments and methyl m e r c u r y in muscle in pike from (A) " u n c o n t a m i n a t e d " n o r t h e r n S w e d i s h lakes, (B) "uncontaminated" middle Swedish lakes and (C) lakes r e c e i v i n g waste water from mines.

143

The sediment concentrations of several metals

(Cu, Pb, Cd, Zn and Hg) are

low in the lakes belonging to the (A)and (B) categories,

but the Hg

content in pike is much higher in these lakes than in the lakes belonging to the (C) category. This is a most interesting situation where pollution of one comparatively harmless metal,

Zn (or Se, see Bj~rnberg et al., 1987), which is

essential and does not biomagnify,

may act antagonistically towards a

very toxic metal, Hg.

REFERENCES

Andersson,

T., Nilsson, A., H~kanson,

L. (1987). Kvicksilver

i svenska

sj~ar (Mercury in Swedish lakes). Report SNV (preprint).

Beijer,

K., Bengtsson,

Westermark,

B-E., Jernel~v,

A., Laveskog,

A., Lithner,

T. (1977). Svenska vattenkvalitetskriterier

I, II (Swedish water quality criteria - metals).

G.,

- metaller.

Del

IVL Rapport B 398,

Stockholm.

Bj~rnberg,

A., H~kanson,

L., Lundbergh,

K. (1987). A theory on the

mechanisms regulating the bioavailability of mercury in natural waters. Manuscript.

Chester,

Dept. of Hydrology,

Univ of Uppsala.

R. and Hughes, M. J. (1967). A chemical technique for the

separation of ferromanganese minerals,

carbonate minerals and adsorbed

trace elements

Chem. Geol. 2

F~rstner,

U. and Wittman,

environment.

Grahn,

from pelagic sediments.

O. and Ros~n,

some acid watersheds Swedish).

G. T. W.

Springer - Verlag,

(1979). Metal pollution in the aquatic

Berlin.

K. (1984). Deposition and transport of metals in in southwestern,

middle and north Sweden.

Grahn, O. and Sangfors,

O. (1984). Temporal variation of heavy metals

(Cd, Pb, Cu, Zn) in perch,

zooplankton and water in four Swedish lakes

with different metal loads and trophic status. S 8401.

(In

Swed. Env. Prot. Bd. SNV report 1687.

(In Swedish).

SERG report

144

H~kanson,

L.

(1980). The q u a n t i t a t i v e

impact of pH, b i o p r o d u c t i o n and

H g - c o n t a m i n a t i o n on the H g - c o n t e n t of fish (pike). Env. Poll.,

H~Manson,

L. and Uhrberg,

R.

(1981).

Investigations

in the River

K o l b ~ c k s ~ n water

system. XIII M e t a l s in fish and sediments.

Swed.

Bd. SNV report 1408.

Env. Prot.

H~kanson,

L.

(1984a). Metals

K o l b ~ c k s ~ n water system,

H~kanson,

L.

(In Swedish).

from the River 101:3.

(1984b). A q u a t i c c o n t a m i n a t i o n and ecological risk - an

attempt to a c o n c e p t u a l

Landner,

in fish and sediments

Sweden. Arch. Hydrobiol.

18.

L. and Grahn,

framework. Water res. vol.

O.

in three swedish rivers.

18 no. 9.

(1975). O c c u r r e n c e and b e h a v i o r of h e a v y metals (In swedish).

Swe. Env. Prot. Bd. Final proj.

report.

Lindestr~m,

L. and Grahn,

O.

(1982). A n t a g o n i s t i c

some mine d r a i n a g e areas. A m b i o vol.

Lindestr~m,

L.

Lindestr~m,

L. and Qvarfort,

water

effects to m e r c u r y in

ii no. 6

(1984). U n p u b l i s h e d data. SERG.

U.

(1985). Metals

in soil water and surface

in the G a r p e n b e r g area - a study of the metal balance.

SERG report

S 8501.

Salomons,

W. and F~rstner,

sediments.

U.

(1980). T r a c e metal a n a l y s i s on p o l l u t e d

Part II: E v a l u a t i o n of e n v i r o n m e n t a l

impact. Environ Tech lett

1:506-517.

Salomons,

W. and F~rstner,

Heidelberg

Tessier,

U.

(1984). Metals

in the Hydrocycle.

P.G.C.

and Bisson, M.

(1979). S e q u e n t i a l

Springer

349 p.

A., Campbell,

extraction procedure Chem 51:844-851.

for the s p e c i a t i o n of p a r t i c u l a t e trace metals. Anal

145

EFFECTS

OF

pH

BY T U B I F I C I D TYPES

OF

Anders

THE

UPTAKE

OF

COPPER

(OLIGOCHAETA)

AND

IN TWO

CADMIUM

DIFFERENT

SEDIMENT

Broberg

Institute Box

ON

WORMS

557,

and

Gunilla

of L i m n o l o g y , S-751

Lindgren

University

22 U p p s a l a ,

of U p p s a l a

Sweden

ABSTRACT

The

uptake

of

and

7 was

and

an

The

sediments

Cu

sediment,

with

types

of

sediment

concentration

concentration

of

sediment

from

the

death

the

of

that

probably

Cu

or Cd

humic

added

are

skin

uptake

by

the

supply

of

food

and

worms and

analysed

also

be of

Fe,

in

to

all

to

Cu

pH

5,

6

humic

the

addition

and

Cd.

lake

water

5 resulted

in

an the

was

in

very

almost

a markedly

high

sediment

The

reasons

uptake

The

with

momentanous

eutrophic

decreased

pH-dependent

and

The

of m e t a l s .

sites.

of

Total

or Cd.

fractions.

with

uptake

of b i n d i n g due

Cu

fractions

resulted

adsorption,

the

for

(MgCI2) , pore

Mn,

experiments

surface

at

productive

Cd b e f o r e

in pE

a smaller

activity

or

labile

which

competition can

Ca,

metals

the

The

pH g a v e

decreasing

the

in

lake,

worms.

a lower

Cu

were

for

the

a low

with

a decrease

of

from

fraction

analysed

(Oligochaeta)

production.

incubation

were

worms

sediment

high

contaminated

after

water

increased

through

tubificid

adsorbed/exchangeable

overlaying

showed

by

using

lake

vere

which

In b o t h

Cd

investigated

eutrophic

animals,

and

directly

differences

variations

in

in

animals.

INTRODUCTION

The

effect

of h e a v y

concentration the

aquatic

chemical

of

the

metal

environment

form

ions

adsorbed

than

the

different

metals

of

on and

this

the m e t a l

on p a r t i c l e s

fraction

of

the

oxides

( I,

2

aquatic on

its

organisms

availability

availability

in w a t e r

and

are

more

metal

much bound

). T h e r e f o r e ,

depends

to

is

the

controlled

sediment. available organic

the

to

both

Free to

content

of,

In

the

metal living

for

the

biota.

by

material

on

or

ions

and

organisms to

example,

Fe

146

and

organics

in the

availability

The

uptake

pH.

Often

of

sediment

of a m e t a l

of m e t a l s lower

the m e t a l

by

showing

not

more

accumulate

unit

( 6 ). The

with

Cd and

Cu was

also

decreased

this

was

two

contents

metal

MATERIAL

AND

METHODS

from

the m o s t

tWO

The

One

of

the

lake

the

other,

fauna

in l a k e s

with

of pH

in m u s s e l s

Cd by types

aim was

see

fractions

in U p p l a n d ,

Funbosj~n,

) did one

a low pH

and

(Oligochaeta) at pH

nutrient was

the

Sweden,

5, 6 and level

of

the

sediment.

were

used

in

is a low p r o d u c t i v e

is a e u t r o p h i c

and

any

concentration

of

central

Tarml&ngen,

of

a pH-level

worms

if t h e r e

pH and

( pH 4.4

( 7 ) and

regarding

to

results

in e x p e r i m e n t s

of s e d i m e n t

or Cd,

as

uptake

(8).

tubificid

different

of Cu

lakes,

lakes

a lowering of Cd

by

in a c i d

by

such

increased

contradicted

by alga

available

lakes

experiments. whereas

Ca.

are

organisms

quite

uptake

of

the

by f a c t o r s

and

of p h o s p h o r u s

of Cu and

were

Mn and

between

two

Sediments

than

uptake

in two d i f f e r e n t

of Fe,

in

benthic

stimulated

sediments

correlation

that

the u p t a k e

investigated

7. The

for

affected

availability

findings

the a c c u m u l a t i o n

study

is a l s o

increased

metals

higher

In

the b i o t a

5 ). T h e s e

investigations

important

( 3 ).

pH m e a n s

( 4,

can be v e r y

lake

with

the

humic

high

production.

Contamination The

sediments

homogenized plus

distilled

water The

was

sediment

was

Each

shaken

others

with

dark

at

period

the

pH was

and

fresh

portions

sediment

heated

50°C

to s e t t l e

and

once

was

divided

H20).

were

at

added

into

water

water The

aerated

and

for

adjusted

portions.

24 h o u r s .

the m i x t u r e

again

the w a t e r

portions,

200 mg Cu

portions for

17 days. in o r d e r

During to get

and

one

the

placed

After

the the

was

(CUS04.5

were

5 days.

The stirred.

of w h i c h

1 of s e d i m e n t

containing

shaken

for

The

30 % tap w a t e r

and

three

per

different

intermittently

measured

) and h o m o g e n i z e d .

approximately

was

distilled

and

size

with

water

I00 ml d i s t i l l e d

(CdCi2.2.5 20°C

( 2 mm mesh supplied

(50/50)

and

allowed

I00 ml

period

different

was

sediment

with

or I00 mg Cd the

sieved

water

decanted

decanted. was

were

sediment

H20) in

this

aeration same

pH in

the

147

Experimental The

three

parts

and

sediment series was

procedure

sediment pH was and

of

in

times

with

of

were

and

a period

of

sediment

two

vessels

containing

The

worms

and

dry

the

last

were

Cd

starved

weights

were

sampling

each

The

worms

39

acid

lake

of

was

from

5,

each

of

an

tubificids.

The

and

days.

On

each

occasion

were

collected

24 h o u r s

kept

in

in

for

and

and

in

vessel

20-30

store

were

worms

sediment

distilled

3

and

experimental

samples

a sieve

Sediment

7 both

Each

water

aquarium

20°C

into

experimental

arranged.

at

Cu-contaminated

divided

6 and pH

lake

dark

with

for

further

to

and

50 ml came

species the

were

4 controls,

determined.

were

lake

sediment,

different in

each

sulphuric

For

of

incubated

during

control

with

including

worms.

5-6

from

water.

50 ml

tubificid

consisted series

adjusted lake

20 v e s s e l s ,

supplied

weighed

portions

from

and

(0.2

taken one

two

with

mm mesh

water

and

overlaying

4

size).

their

water

wet

from

analyses.

Analyses Sediment Mn,

Ca

and

and

water

Cu

or

content,

carbon

The

water

pore

sediment through or the

at

In

order

filtered

Mn,

Fe

The

worms

and

were

animals

solution

was

water I05 °C.

to

for

the

20 m i n u t e s .

the

the

) were

also

analysed

analysed

sediment The

and

adsorbed

centrifugation

for

I hour.

a 0.45 ~ m

content

on

for

for

Fe,

water

centrifuging

supernatant for

extracted

filtered

Ca,

Fe,

and

Mn

fraction with

centrifugation filter

wet

was

/ exchangeable was

After

by

analysed

membrane

foil

autoclaved

diluted

of

the

N were

(Carlo-Erba)

and

absorption

the

with

and for

to I0 ml

( Whatman

flame

concentrations,

from

obtain

weighed

filter

atomic

pm

30 ml

the

liquid

analysed

for

and

Cu

2 g of I phase Ca,

Cd.

were

C and

0.45

were

(0.45 ~ m )

7,

or

sediments

filter

through

Cu

glassfiber

at

rpm

pH

The

filter

nitrogen.

separated

after

MgCI2,

was

The

was

7500

residual

dried

Cd. and

a membrane

Cd.

mole/l

( membrane

with

GF/C

I05'C

distilled

in

was

determined

through of

the

oven.

metals Pye

24 h o u r s . H N O 3.

filtered

for

combustion

spectrophotometer

for

7 moles/l

water,

analysed

concentrations

a graphite

at

) and

sediment

obtained

dried

30 m i n u t e s

Cu

or

The The

through

a

Cd.

by d r y i n g

overnight

in a C H N - a n a l y s a t o r were

Unieam

SP

measured 192

or,

with at

a

low

148

RESULTS

Sediment-chemical I.

The

sediment

content

and

however, Lake

unusually

means

proportion Funbosj~n higher

Table

large

Funbosj~n

which

was

that

than

2.

the

two

lakes

Tarml~ngen

was

amounts

of o r g a n i c

material.

high

for

largely

the

this

of Ca,

type

affected

sediment

can be

material

in s e d i m e n t

from

Fe and Mn

was

of

by

clearly

The

The

which

I and

87.4 7.66 0.80 45.0 0.61 3.3 1.49

86.8 7.86 0.76 46.3 0.70 3.7 1.83

7

6

87.2 7.72 0.76 42.3 0.69 3.5 0.78

pH

7

86.6 7.86 0.76 50.2 0.80 3.9 0.83

The

from

seen

from

its

2).

sediments

pH

9 72 76 3 68 3 50

can be

in

lake,

sediment

Funbosj~n pH 5 pH 6

87.0 7.66 0.80 42.5 0.61 3.5 0.78

the

as g y t t j a .

the

from Lake

Tarml~ngen pH 5 pH 6

pH 7

96 22 1 28 0 0 5

96 22 1 31 0 I 5

5 0 88 8 30 0 45

Tarml~ngen pH 5 pH 6

pH

7

96.7 22.0 1.87 28.8 0.24 0.6 2.63

96.5 22.2 1.86 33.9 0.36 1.3 3.34

Characteristics of C d - c o n t a m i n a t e d sediments L a k e F u n b o s j D n and L a k e T a r m l ~ n g e n .

W a t e r c o n t e n t (%) C a r b o n (%) N i t r o g e n (%) iron ( m g / g dw) Manganese " Calcium " Cadmium "

sediment in

water

of N was,

characterized in

in T a b l e

high

higher

(Tables

FunbosjSn pH 5 pH

shown with

content

production

Tarml~ngen,

85 7 0 44 0 3 1

are

h~mic

sediment.

the

Characteristics of C u - c o n t a m i n a t e d F u n b o s ~ O n and Lake T a r m l ~ n g e n .

W a t e r c o n t e n t (%) C a r b o n (%) N i t r o g e n (%) Iron ( m g / g dw) Manganese " Calcium Copper "

Table

for

Lake

of i n o r g a n i c

contents

I.

characteristics from

5 1 88 5 24 6 45

96.6 21.7 1.83 31.5 0.28 0.8 5.61

from

96.6 22.6 1.89 31.3 0.26 0.8 3.05

149

Tables

3 and

overlaying

4

show

water,

sediment.

In

both

increased

fractions.

However,

the

concentrations water

and

of

sediment

types

a markedly

in

the

pore

with

of

sediments

of

from

sediments

from

Lake

Funbosj~n

at

a pH

pore

water

contents

of

Ca

experiments

with

sediment

from

the

Table

3.

Concentrations

the

concentration

water

and

of

certain

adsorbed/exchangeable

Water Cu

(ppb)

Ca

(ppm) (ppm)

Mn

(ppm)

Cu

Mn

and

Cu

of

and Lake

or

pH in

Cd

On

5 resulted

pH

in

7 was than

other

(Tables

water,

fraction

pore

in

in

of

3 analysed

the in

higher

in

hand,

considerably

Funbosj~n

Cd

to

at

the

were

or

all

Tarml&ngen

5. Mn

metals

sediment

in

Cu

fraction

the

higher

3 and

water

experiments

in

4).

and with

Tarml&ngen pH

6

pH

7

pH

5

pH

6

pH

7

phase

Fe

Pore

5

Fe,

metals

Lake

Funbosj~n pH

Ca,

a decrease

concentration the

experiments

of

adsorbed/exchangeable

(1430) 266

150

75

9000

1350

183

62

54

44

0.09 17.6

445 8

0.03

0.02

0.06

0.06

0.06

2.0

0.01

2.2

0.9

0.04

water (ppb) (~g/g

485 dw)

Ca

(ppm)

Fe

(ppm)

327 1.0

Mn

(ppm)

20.5

Adsorbed/exchangeable

115

2.1

0.5 510

50

7750

1800

360

0.3

81.5

18.3

7.2

-

59

30

-

0.36

-

0.36

1.8

-

7.3

-

2.6

1,2

-

fraction

Cu

(~g/g

dw)

120

Ca

(mg/g

dw)

Fe

(~g/g

dw)

20

I0

Mn

(~g/g

dw)

180

140

2.7

50 2.9

45 -

-

1355 1.7

1195 2.3

480 -

20

5

-

80

85

-

Cu.

150

Worms

added

to c o n t a m i n a t e d

immediately this

type

Funbosj~n metals 2), at

except

and

that

for

Cd

the

cases

owing

partly

days)

is not

Table

4.

taken

large

uncertainty high

into

lower

when

of

certain

adsorbed/exehangeable

Cu

from

metals

sediment

content

at pH

5 than

of

I and

7 than

at h i g h e r

pH

the d u p l i c a t e s ,

the a u t o c l a v e d

objects the

for

Lake

(Figures

larger

with

serie

5

in w a t e r ,

fraction

FunbosjSn

Water

in

available

from their

at p H

weighing

for

are

period

between

included

died

sample

very

low

at pH 5 (ii

consideration.

Concentrations

pH

increased

variations

value

uptake

sediment

of Cu was

was

particles

Tarml~ngen

incubation

The u p t a k e

were

abnormally

with

worms

the

the u p t a k e

sediment

to some

An

5

Cd

there

to

tubificid of

Lake

on m e t a l

experiments

length

at pH

from

no r e s u l t s

The

increased

p H and w i t h

In some

weights.

therefore

showed

with

lower

partly

and

of s e d i m e n t .

sediment

pore

water

and

in e x p e r i m e n t s

with

Tarml~ngen

pH 6

pH 7

pH

5

pH 6

pH 7

phase

Cd

(ppb)

1390

760

70

24600

10400

3000

Ca

(ppm)

453

337

107

73

44

15

Fe

(ppm)

Mn

(ppm)

0.12 20

0.03 6.9

>0.02 0.01

0.06

0.06

0.06

2.3

1.4

0.43

Pore w a t e r Cd

(ppb) (~g/g

Ca

IIi0 dw)

(ppm)

4.8 675

Fe

(ppm)

9.3

Mn

(ppm)

28.3

Adsorbed/exchangeable

(30) (0.I) 505 0.I0 10.8

180 0.8 337 0.6 12.8

42000

16800

9240

645

240

170

102

7

27

0.01

0.01

0.36

3.6

1.7

1.2

fraction 205

(~glg

dw)

Ca

(mg/g

dw)

1.0

I.i

Fe

(~g/g

dw)

i0

5

65

5

5

15

Mn

(~g/g

dw)

205

215

I00

90

90

80

3.6

70

50

Cd

4.2

5.4

1970

2165

1660 1.6

C~.

151

Confent (/ug/g dw) 2000

pH7

pHs

1000

pH6

Time t

I

t

0 2 Figure

t0

I

t

20

I

I

I

30

40

(days)

I. T h e e f f e c t s of pH on the u p t a k e of Cu by t u b i f i c i d w o r m s l i v i n g in c o n t a m i n a t e d s e d i m e n t from L a k e Funbosj~n.

Contenf (pg [d/g dw) 600

, pH7 o pH6 o pH5

300

100 TIME

t0 Figure

2.

20

30

40 (days)

The e f f e c t s of pH on the u p t a k e of Cd by t u b i f i c i d w o r m s l i v i n g in c o n t a m i n a t e d s e d i m e n t f r o m L a k e Funbosj~n,

152

DISCUSSION

The

two

sediments

Tarml~ngen

and

added

bound

(pH

were

7).

The

should, Coker

were

gyttja

to the

high

especially toxicity.

to,

), r e s u l t Cu,

were

Funbosj~n,

8 and

6 % for Cd

organic

in and

inorganic

part

in

A lowering

example,

for

the

are

the l o w e r

Cd in

sediments

the

overlaying

to

with

( ii

). The

groups,

resulted

labile

in a c c o r d a n c e

according

a relatively

the m e t a l s

3)

the low

mainly

to the

and h y d r o x i d e s ,

two

of the m e t a l s

can,

(Table

that

the m e t a l s

the

release

Sylva

of

and

in

Cu

be

has

water

may

in

the l a b i l e

in

increased

Funbosj~n.

contaminated

of Cu a n d

for

of r e a c t i v e of

&

low

than

might

carbonates

concentration

from Lake

with

respectively

Binding

Nriagu

Cd in p o r e

Tarml~ngen

i.e.,

Tarml&ngen

added,

in T a r m l ~ n g e n

explanation

Lake

contamination

( 9 ) and

the m e t a l complexes

proportion

small.

sediment,

sediment

+ H+ ~

increased

the

fractions water

results

& F~rstner

of Cu

( 12

in

(Tables

presented

concentration

to S a l o m o n s

and

by,

in

), be

3 and for

the

labile

a result

of

Cu 2+ + HX

of d i s s o l u t i o n (Cu,

The

Mn)O(OH)

contents

of s u b s t r a t e + K+ ~

relatively

oxidized

conditions.

(calculated

11.7

times

for

exchangeable same

was

high The

In s e d i m e n t s concentrations

were

FunbosjDn

but

example:

(Tables

3 and

4),

which

of o x y g e n

(not

lowering

to

a larger

and 2.7

of pH

in

the p o r e

Tarml~ngen and

on a less

f r o m Lake

low

for

+ E20.

concentrations

as a p e r c e n t a g e )

fractions,

found,

for b i n d i n g ,

Mn 2+ + Cu 2+ + e-

of Fe in w a t e r

reflects

Cu

from

the

The m e t a l s

from Lake

of Cu and

amount One

2).

exchange: CuX

or

organic

is q u i t e

fractions ion

4).

% at

& Suzuki

higher

total

that

of pH in the

increased This

sense

of the

concentrations

4).

the

I00

of

dy in Lake

I and

sediment

of m o s t

clearly

(Table

hydroxides,

reason

fractions

Tada

stable

in s e d i m e n t

the

carboxyls

be one

3 % of

material

reactivity

in

the p r o p o r t i o n s

fraction

and

55 and

example

in r e l a t i v e l y

(Tables

to a l m o s t

of o r g a n i c s

for

in c h a r a c t e r ,

Funbosj~n

in a b i n d i n g

In c o n t r a s t ,

exchangeable

different

sediments

content

according

( I0

quite in L a k e

3 times

pronounced

FunbosjDn

of Cu or Cd but

the

also

5 gave water

analysed)

than

respectively

(Table

decreased a very

for Cd

pH not

strong

7.5

only

of

and

in the 3).The

(Table

elevation

and

increase

fractions,

respectively,

level,

probably

4).

gave

higher

of the

153

contents

of Ca and

solubility and Mn

above

in s e d i m e n t

sediment smaller

all

of c a r b o n a t e s

from

from

Lake

increases

Mn,

Lake

these

implying

ions

Relatively

high

concentrations

extraction

with

MgCI2,

loosely This

bound

indicates

carbonates more

The

to the

and

stable

effect

Cd in

the

the

labile

fractions

TarmlAngen

(Tables

worms

very

they

died

survived

metal

3 and

soon

also

ion

lower

the l o w e r i n g

of pH gave

give

water

the

partly

in

the

( 14

addition

the m e t a l 3 and

considered

is o f t e n

with

to

as b e i n g

a function

sediment

to t h e s e

4).

of the metal.

concentration

Therefore

5 in c o n t a m i n a t e d

4).

Cu or Cd b o u n d

fraction

in

the

) (Tables

are

). The

high.

of

in

Fe

than

3 and

obtained

released

experiments

very

their

at a pH of

16

(Tables

fraction

which

organisms ( 15,

4) w a s

after

considerably

the a d s o r b e d

on a q u a t i c

of free

of Ca,

was

fractions,

than

contents

that

the p a r t i c l e s

extraction

toxic

on an i n c r e a s e d

). The

of Ca and Mn w e r e should

reducible

less

( 13

in the p o r e

of

that

of a m e t a l

concentration

which

surface

easy

and

depended

Tarml&ngen

Funbosj~n, of

which

and h y d r o x i d e s

the

of the of Cu or

from

Lake

tubificid

sediments,

sediment

from

whereas Lake

Funbosj~n.

The u p t a k e s sediment ought

degree

increased

in w h i c h

through

This

implies

the

competition Ca,

Mn

(Tables

the that

largest

amounts

( 18,

19,

20

to the

supply a lower

were

3 and 4).

surfaces

sites

Such

). This

where,

to and

is

in

7. The r e a s o n s

for

the d i f f e r e n t Possible

integument

sites

on

ways

and

particles

ways for

uptake

in a d e c r e a s e d through

between from

the

the m e t a l s

the

sediment

relations

between

is

the m e m b r a n e s uptake

skin.

of Cu or Cd at a l o w e r

inverse

owing

ligands

the w o r m s

of pH on

of o r g a n i c

directly

released

pH

).

pH results

accumulation

at pH 7 and

through

( 17

Funbosj~n

in o r g a n i s m s .

uptake

of m e t a l s

organisms

Lake

effects

of p r o t o n a t e d

and/or

the

2. A l o w e r

and i n o r g a n i c

of Cd at p H 6 and

the

adsorption,

of b i n d i n g

), w h i c h

to

in c o n t a m i n a t e d

1 and

accumulation

organic

from

probably

adsorption

smaller

from

incubated

in F i g u r e s

results

of Cu w a s

of m e t a l s by

worms

shown

can be a c c u m u l a t e d

surface

binding

as s u r f a c e for

are

ingestion

influenced

are

the m e t a l

the

the h i g h e s t

a metal

are

of

with

the u p t a k e

discrepancy

uptake

tubificid

to an i n c r e a s e d

availability

accumulated

The

Cd by

Funbosj~n

of d i s s o c i a t i o n

in a c c o r d a n c e

contrast,

this

Lake

to be c o r r e l a t e d

a higher

not

of Cu and

from

and at

( 21

).

of m e t a l s

Another

reason

pH is p r o b a b l y other

cations

the l o w e r i n g

salinity

and

(

of pH

uptake

154

of

metals

are

described

(23).

In p h a s e

there

was

an

which

can

partly,

thus

than of

in

Lake

site

The

or

Cd

in

metals. total

In

and

the

pH

rate

live

present

ingestion.

biomass

unpubl.).

Furthermore,

carbonates

enter

the

tubificid

and

and worms

environment.

smaller

uptake

experiments

Cd

the

by

of

is the

in

the

of

Other

and

used

is

with

organisms

( 25

).

The

accumulation

fractions

and

described

above,

different

ways.

indicates

that

metals

the

in

loosely starving this

amount

affected The

the

to in

was

largest

in

were

animals

among

the

other

at

the

length

of

included

pH

of

food

type

of

in

in

animals.

patterns

of

water

that of

the

metals was

the

sediment.

the for

The

hours

analysis

to

decrease

( 8

).

a

of

Cu

the

incubation

certain from

is

pH

7

that

in

the

important

was ( 26 the

the

total

metal pH,

as

biota

1 and source

Cu

released ) and

period

Llake

(Figs.

of

or

fractions

certain

uptake

their

of

uptake

Most

of

a neutral

cause

in

acid

). The

the

most

organisms 24

the

( 6

the

reason

at

in

exposed

between

of m e t a l

extent

compounds

from

sediments

correlations

of

pH

of m e t a l

a greater

they

to be

show

the

organisms

are

be i.e.,

( Broberg,

dissolved

taken

a lower

worms

to

things,

supposed

with

surfaces

distilled not

was

animals,

food, pH

of

the

must

uptake

These

the

in

in

the

of

uptake

at

of

are

by

found

of

sediments

of

bound

the

uptake

this

were

surface.

experiments

the

the

is

lowered

in

contents

metal

up

such

the

a lower

food,

the

level

for

at

the

change

in

ingestion

worms

sorbed them

result

a lower

that

lower

concentration

not

less

vital

activity

sediment

tubificid

did

Lake

content

differences

and

by m u s s e l s

Funbosj~n

from

a more

on

contaminated

taken

stress

the

Mn

and

its

means

be

increases to

feed

to be

with

by w h i c h ,

This metals

correlated sediment

the

pH

and

considerable

indicates

availability

7 the

can

Ca

anions,

sediment

differences

the

food

the

together metal

food.

but

regards

at

the

stress

of

large

of

at p H

of

complexes

therefore

and

ought

between

2),

As

in

was

which

), w h i c h

considerably

oxides

When

physiological ingestion

was

intestine

environment

no

supply

with

and

sediment

( 24

1 and

in

plankton

metals.

particles case

) and

corresponding

metals

ions

4),

binding

the

of m e t a l s

bacterial

to

in

the

bind

experiments

3 and

the

detritus

(Tables

of

of

of

pH,

( 22

concentrations

competing

complex

sediment

to v a r i a t i o n s

their

(Tables

effect

concentration

different due

of

worms

the

low

the

and

macrophytes increased

contents

the At

toxic

tubificid

the

uptake.

FunbosjDn

microorganisms Cu

in

concentration

competition

pronounced

e.g.

strongly

despite

the

the

for,

the

increase

depress

TarmlAngen

with

or

Cd

by

therefore metal

in

2) for

155

content.

Some

directly

through

the skin

or b y r e s p i r a t o r y

important

routes

of m e t a l

uptake

processes

are not

protons,

which

concentration and

4)

authors

and

( 18,

depressed

happens

) consider

by

pH.

in s o l u t i o n

of c o m p l e x a t i o n

for m e t a l

uptake

are

contents

of m e t a l s

in the

organisms

in

particulate clear

Funbosj~n.

metal

the

for

by c o m p a r i n g

fractions whereas

was

the

total

about

twice

the

Figs.

I and

2).

than

amounts

The

the

Cd b y

in

content

of Cu

in

7 these

which

or

at p H

lower

3

these

Highest

the

tuhificid

role

of f o o d

worms

the i m p o r t a n c e

the w o r m s

7 the

(Tables

is w h y

7 indicate

will

he

living of

quite

of Cd in the l a b i l e

concentration

corresponding

hand,

important.

Furthermore,

accumulation

Cu and Cd.

higher

the o t h e r

less

the m o s t

cations

considerably

at p H

of Cu and

f r o m Lake

to be

At a p H of

by other

higher,

probably

in the a c c u m u l a t i o n

sediment

On

was

of m e t a l s

activity

in o l i g o c h a e t a .

patterns

ingestion

the u p t a k e

competition

at a l o w e r

of m e t a l s

the d e g r e e

19

of Cu

sediment

(Tables

3 and 4),

and o r g a n i s m s

concentrations

of Cd

(pH 7) w e r e

(Tables

1 and

2 and

ACKNOWLEDGEMENTS

This

work

is a part

sediment-bound Environment

of the p r o j e c t

heavy metals"

Protection

"Bioavailability

supported

by

and

the N a t i o n a l

conversion

of

Swedish

Board.

REFERENCES

i.

F ~ r s t n e r , U . , a n d G.T.W. W i t t m a n . M e t a l p o l l u t i o n in the A q u a t i c E n v i r o n m e n t . ( B e r l i n H e i d e l b e r g : S p r i n g e r - V e r l a g , 2nd E d , 1 9 g l )

Z.

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3.

Luoma,S.N.,and (1979).

4.

S t o k e s , P . M . , a n d E.C. B a i l e y . the E n v i r o n m e n t , H e i d e l b e r g ,

In: pp.

5.

Heit,M. Athens,

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Bryan.

Proc. Int. Conf, 655-657(1985).

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Mar.

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Ass.

U.

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Andrew,R.W., (1977).

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157

A L U M I N I U M IMPACT ON F R E S H W A T E R I N V E R T E B R A T E S AT LOW pH: A R E V I E W

Jan H e r r m a n n D e p a r t m e n t of Animal Ecology, Ecology Building,

U n i v e r s i t y of Lund

S-223 62 LUND,

Sweden

Abstract

The

state

of

knowledge

on

aluminium

(AI)

impact

on

freshwater

i n v e r t e b r a t e s at low pH is reviewed. M a i n l y inorganic ions seem biologically

harmful.

Published

seem somewhat contradictory, of

"the

invertebrate

of

A1

to

streams

in

some

m a i n l y some " s u r f a c e - d e p e n d e n t " flies,

dixid

(isopods,

midges),

stoneflies),

but

the

be may

heterogeneity

as well as the m u l t i t u d e and c o m p l e x i t y

t h e r e b y also A1

has

descriptions

but this can be due to

group",

of o c c u r r i n g A1 species,

effect/mechanism

to

analysis

cases

species also

problems.

Addition

increased drift and death of

(chironomids, some

mayflies,

strictly

benthic

while other studies on a v a r i e t y of

dance animals

animals

do

not record any change in neither drift, m o r t a l i t y nor biomass.

In

laboratory

exposures

A1

has b e e n shown to cause raised m o r t a l i t y

for some d a p h n i d s and b l a c k f l y larvae at pH around animals

the

freshwater even

i n v e r t e b r a t e s were not affected. Moreover,

been

shown

daphnids,

otherwise

this

not

still

is

weak.

to

level

the

survival

Proofs

high

for

or

additions

of

nymph,

mechanical

A1

for by improved r e s p i r a t i o n Studies

A1

have

while

A1

on can

crayfish, lower

rate.

daphnids,

osmoregulatory

sublethal

and

effects

are

critically

bioavailability.

a

The

caused more

important discusses

A

A1

has

nymphs

and

reason

for

a

decreased

field-relevant

model

mayflies

mechanisms

also

at pH 4,

mayfly

suggests a

osmoregulation,

affect the ion b a l a n c e m a i n t a i n i n g

review

latter

indicating

impact. The lowered oxygen uptake is then

compensated

that

of

increased r e s p i r a t i o n in m a y f l y n y m p h s . T h i s

presented. indicate

the

"food chain a c c u m u l a t i o n " of A1 are

stress situation, p r o b a b l y due to impaired chemical

in

impaired by the low pH in itself.

clear. Very

improve

r e s p i r a t i o n rate in a d r a g o n f l y exposure

5;

effect was h o w e v e r m i t i g a t e d by humus. A v a r i e t y of other

for and

efficiency of

the

this

is

waterbugs and t h e r e b y

animals.

Such

should be studied further. The the

concepts

mortality

and

158

Introduction

Air p o l l u t i o n causes m a n y e n v i r o n m e n t a l problems, substances

are

among

to n e u t r a l i z e acids, is

an

increasing

the

accompanied

deposited

of a c i d i f i e d

by

(1-3),

declining

acid

In areas unable

soil and surface w a t e r s show d e c l i n i n g number

in Europe and N o r t h A m e r i c a been

and

most important p o l l u t a n t s .

pH.

There

lakes and r u n n i n g w a t e r c o u r s e s

and

acidification

has

numbers of b o t t o m l i v i n g

generally

invertebrates

(4-7). The pH levels of 4-5.5 also cause a rise of in

the

water,

probably

which seriously

more

observations

serious have

effects

focused

e s p e c i a l l y some insects, some

Crustaceans,

dissolved

impaires most just

the

above

attention

pH of

affected

in

increasing

the

of

(6, 11-12,

susceptibility 29-33,

the

benthic

35, 45). However,

but

also

role

of

A1

invertebrates the

by to

co-occurence

of

and h i g h levels of A1 o b s c u r e s the role of A1 per se for

the i n c r e a s e d s u s c e p t i b i l i t y of the animals. AI,

Such

a c i d i f i e d waters. The reason is

acidification

which

(8-10).

as m a y f l y nymphs and elmid beetles,

seem

attributed

acidity

5

(A1)

o f t e n with

the s c i e n t i s t s on that

the idea that this p o s s i b l y c o u l d be

high

aluminium

fish species,

under

certain

conditions,

Also

the

mechanisms

by

can act as a h a r m f u l agent are

largely unknown.

A l u m i n i u m is one of the most (over

8%).

Its

chemistry

sufficiently understood hydroxide

and

other

common and

of

the

earth's

A1

being

insoluble

as

aluminium

a r o u n d pH 6 but e a s i l y d i s s o l v e d at pH of

4-5, a v a r i e t y of A1 ions d o m i n a t e in acid n a t u r a l

waters.

different

or solids,

large

forms

-

molecules

accepted

that

inorganic

of

or

are

often

these

the

organic,

called organic

b o u n d to some large o r g a n i c molecules, relatively dominate

"harmless" at

low

(I0,

pH,

but

14-16). also

in

ions

"species". forms, e.g.

It

humus,

species)

i n o r g a n i c A1 monomeric

fraction.

these

small or generally

biologically

ions, A13+ o f t e n

aluminium

hydroxide,

(15).

some studies d e a l i n g w i t h the e c o l o g i c a l effects of

thereof should

is

are

A1 it is not clear w h e t h e r total A1 or some fraction of

All

i.e. w h e n A1 is complex

Of the inorganic

unsaturated

fluoride and sulfate c o m p l e x e s occur

Unfortunately,

crust

d y n a m i c s are c o m p l i c a t e d and far from

(e.g. 13). forms

elements

is be

(one

or

a

group

meant by a d e n o t e d value. At least the total determined,

Further,

preferentially

in some e x p e r i m e l t a l

limited

to

the

studies the denoted

159

A1 c o n c e n t r a t i o n s derived

from

dissolved

seem

the

to

refer

amount

of

concentration.

probably

a

nominal

is

unfortunate,

reactions,

especially

the

This

can

be

throughout an experiment, physical

processes.

overcome and

in

organic do

is

not the a c t u a l l y

as

becomes

what

many

cases

(hydroxide at

molecules.

Both

probably

lower

of

biological

less

the

by m e a s u r i n g the A1 c o n c e n t r a t i o n

adding

Otherwise,

to

latter,

"toxicity" of AI, which t h e r e b y p r o b a b l y importance.

i.e.

part of the A1 has p r e c i p i t a t e d

pH a r o u n d 5.5 - 6.0) or is c o m p l e x b o u n d these

values,

A1 added to the water,

This

substantial

to

A1

as

compensation

for

these

it could be r e c o m m e n d e d to report the

c o n c e n t r a t i o n value for the fraction of A1 that is r e a l l y dissolved.

In some a c i d i f i e d regions of Europe and N o r t h America, in

natural

A1

L -1 ,

surface

sometimes

unpublished).

Up

even

more

(12,

14,

17-20,

to i0 mg A1 L -I has b e e n reported

most of this is then p r o b a b l y complex b o u n d to humus

The aim

of

knowledge

this for

paper

is

to

present

and

invertebrates.

The i n t e n t i o n is then to put the effect

proposed

mecahnisms,

than A1 o c c u r e n c e descriptions. on

all

vertebrates. (8-9,

16,

A1

content

J.

Herrmann,

for bog lakes, but (21).

discuss

the

the impact of A1 at low pH on m a i n l y b e n t h i c

and

effects

the

waters can reach up to 1.0 mg inorganic m o n o m e r i c

types

of

emphasis

state

on

possible

including c o n n e c t e d problems,

Havas

(22) very

freshwater

recently

organisms,

algae

I n f o r m a t i o n on the effects of A1 on fish can be 22-27), w h i l e Ganrot

rather

reviewed

incl.

of

freshwater

found

A1 and in

(28) e v a l u a t e s A1 effects from medical

points of view.

Field studies

Field surveys of the o c c u r e n c e of benthic

fauna

abiotic

the

factors

do

usually

not

give

s e n s i t i v i t y of the animals to A1 explicitly. strong

correlation

of

A1 to acidity

and most

This

its

relation

useful data on the is

because

of

(cf. above and 6, 11-12,

to

either

of these studies do h o w e v e r hint at the

or

AI.

Some

p o s s i b i l i t y of A1 may affect waters,

thus

being

partly

the

animals

the

29-33),

and t h e r e f o r e less p o s s i b i l i t y acidity

relate

to

invertebrate p o p u l a t i o n s responsible

in

for

zooplankton

at

A1

acid

to

surface

for d e c l i n i n g species and/or

a b u n d a n c e n u m b e r s e.g. m a y f l y nymphs and elmid beetles. indicated

occurence

This

way

also

levels of 0.2 mg L -I (34), whereas

field data for rotifers g e n e r a l l y imply these animals to be rather

160

tolerant to A1

However, can

(22).

"outdoor" e x p e r i m e n t a t i o n in

give

pertinent

simulated

the

information.

conditions

Thus,

during

the

snowmelt b y t r e a t i n g a s e c o n d - o r d e r pH

down

to

film,

as

the

e g g - l a y i n g mayflies, were

found

dead.

production.

as well It

Especially

as

was

As

the

this case, however,

an

raised

role

of

higher

at

increase

(up to 3.8

(35) during

mg

water

surface that

the

L-l;

to

the

emerging and

feeding

A1

dance

caused

also i n d i c a t e d by a

interpretation

Hall and Likens A1

A1

drift

short-term

related

midges,

of

flies

a detrimental

pronounced

these

values

foam

results

is

in

in

this

(37) of

(36) lowered the stream pH, this

and

invertebrate

context

showed

m a y f l y nymphs,

pH d e p r e s s i o n s

drift,

is not clear.

that

A1

but

the

In other

field

addition

at

pH

5-5.5

c h i r o n o m i d s and d i x i d midges.

The authors then c o n c l u d e d that these i n v e r t e b r a t e s A1

co-workers

A1

animals

dixid

suggested

the

e x p e r i m e n t s Hall et al. caused

and

waters

u n c e r t a i n as to the specific role of AI.

earlier study, causing

specific

artificial

rise of the A1 c o n t e n t c o n c u r r e n t l y a l s o caused a

s u b s t a n t i a l d r o p in pH,

In

Hall

episodic

s t r e a m w i t h A1

hyponeustic

r e d u c t i o n of the surface tension,

also

and

4.8). T h e y then noted an i n c r e a s e d drift of i n v e r t e b r a t e s

with i n c r e a s i n g A1 c o n c e n t r a t i o n . surface

natural

are

sensitive

to

that by t h e m e s e l v e s are s u p p o s e d not

to be stressful.

O r m e r o d and c o - w o r k e r s stream,

one

was

an e l e v a t e d A1 content that

A1

caused

(38)

brought

treated

(0.35 mg inorganic

foam p r o d u c t i o n .

section was shown by the mayfly, values

for

Dixa

A l l a r d and M o r e a u mortality pH,

and

and

use

sewage

of

water

of

using

concentration

aluminium

Baetis rhodani,

artificial

of

a

They

also

but

found

from the A1

also

the

drift

streams,

noted

increased

alum and

can this

(0.4

mg

L -1)

did

lowered however

rise in these parameters.

sulfate plants

One r e a s o n is

of

c o m p l e x e s on the bottom, chironomids

L-l).

i n v e r t e b r a t e s due to an a r t i f i c i a l l y

treatment

e n v i r o n m e n t a l hazards. high

A1

from a r o u n d 6.5 to 4.0. A d d i n g also A1

in

sections

V e r y h i g h drift r e s p e n s e s

not cause any c o n s i s t e n t a d d i t i o n a l

Excessive

subsequent

the m a y f l y E p h e m e r e l l a i n c r e a s e d significantly.

(39),

drift

two

to pH 4.3, and the next part to pH 5.0 plus

(alum) to p r e c i p i t a t e p h o s p h o r u s has

also

been

shown

cause

that

at

pHs

result

in

dense floc layers of A1

can

exert

a

around

to

physical

neutrality

stress

(40). A n o t h e r reason is that the A1 p r e c i p i t a t i o n s can be

on

16t

activated from

to

about

aluminate 7

to

ions,

8-9

potentially

(41).

present"non-neutrality"

Even

context,

toxic to fish,

if

less

this

if pH rise

relevant

phenomenon

in

should

the

not

be

ignored. Mortality

experiments

A detrimental or

effect can exhibit

sublethal

effects,

as acute toxicity,

chronic

though of course no distinct

between these concepts.

Acute toxicity often implies

a

96

short

time,

often

h,

while

exposure during many days to weeks, animal

to

reach

its reproductive

to state that a chronic organisms

life

span

these expressions as

that

is

correspond

or

energy

(G.

Mackie,

should be

an

if

impact, the

consumption

of

preventing

e.g.

pers.

i/i0

comm.).

instead

by

a

death

is

of

on

of

studies

thereby be

a population

individuals

in

effects

excretion,

etc. They cause an

are

a

or

an

ultimately

more

serious

of some organism killed,

as

the

for (42).

drastic and simplified parameter

m o r t a l i t y experiments

susceptibility

might

is

"toxicity",

utilization,

animals,

an

the

In fact,

of

metabolism,

movements

This

pollutant number

a

as

resource the

reproduction.

considerable

appropriate

for

used

perception,

unefficient

latter might very well be compensated Even

example

stage. One p o s s i b l e d e l i m i n a t i o n

impacts on processes

and

impact

than if a

more

osmoregulation,

retarding growth ecological

for

within

appears after

what is mostly meant by the latter w o r d . S u b l e t h a l

condition,

increased

thus

mortality

toxicity

effect often continues

"mortality"

to adverse

respiration, impaired

chronic

toxicity,

limits can be put

can give a lot of useful

of

different

organisms.

of

sublethal

effects,

of a substance information

of

T h e r e b y data can hint at towards

which

mechanism

research always should aim.

That

A1

already

may four

cause

immobilisation

decades

ago,

interpretation

is

acidification

perspectives,

improverished to

the

uncertain

invertebrate

elevated

fish,

cause

without It

frequently

exposed

to

a

any

pH

has

later,

been

was

reported

information, from

suggested

elevated

levels of A1

mortality of benthic

experiments

variety of A1 values

would,

invertebrates. with

the

recent that

the

be

due

at pH around 4-5 could

this has been shown to be valid in different species,

manna

(e.g. 35, 45). Thus it is expected

in itself,

additional

Daphnia

(43-44).

commmunities

A1 levels

a low pH, detrimental

but

of

that at as

for

Certainly Daphnia

from 1 (realistic)

to 20

162

(very high level) reduce

A1

mg A1 L -I (34, 45-46).

toxicity

to Daphnia

Also,

Ca

has

been

shown

to

(47), but only at pH 6.5, where almost

all A1 is in solid form.

Burton and Allan that pH

A1

=

4.0

0.5

for

snail

stonefly

to

some

Nemoura extent

sp.

for

but not so for the caddis

Physella

heterostropha.

and

the

Survival

were

lethal also animals,

tested.

to

Further,

blackfly

raised

humic

larvae content

the

of

at

4.8

Asellus

Pycnopsyche

liba

and

the

better at pH 5 and A1 =

content of the

levels pH

mortality at

larva

Lepidostoma was

report

isopod

caddis

larva

0.25 mg A1 L -I, as well as with high organic mayflies

streams,

mg A1 L -I in most cases cause additional

the

intermedius, 9uttifer,

(48), using large outdoor artificial

0.2-0.5

water.

mg

(49).

No

A1 L -I seem

For

the

of the water counteracted

latter

the adverse

effect of AI. However, did

exposure

not

cause

Crustacea as

to A1 levels of 1 mg L -I, and at variotls any

Daphnia catawba,

the

insect

anthracinus Daphnia

substantially

D__t.manna and H o l o p e d i u m

larvae

(47, 50).

species

Chaoborus

The

species

decrease

p r o b a b l y due to biotic ion

or

A1

bivalves levels

toxicity

up

acidifying

to

fairly

mortality

(=mortality). orders

Mackie

magnitude

Neither

Three crayfish

below

did

the

showed

(G. Mackie,

sublethal

important. 5,

of

sensitive, out,

relationships (51)

pH

species,

than

cause

higher

than

amphipod any

as

6.5

well

the

two

reduction that

if

acute

mortality

H+ of at

found in most

Hyalella

azteca, increaed

However,

effects

in

this is more to

can

more or less affected by a

not seem a d d i t i o n a l l y

for the

Chironomus

consistently

unpublished).

detrimental

levels,

found that treatment

with inorganic A1 did not

at high A1 levels pointed

at

showed a significant

in numbers at low pH conditions,

lakes of Ontario.

generally author

two

that

and

The authors then concluded

interspecific

and gastropods

was

pH

effects

9ibberum,

punctipennis

exception

in some experiments

vitality with increases A1 levels. these

increased m o r t a l i t y

as

the

still pH

be just

influenced by an A1 water content

of 1-2 mg inorganic A1 L -I (52). In l a b o r a t o r y lotic

mayfly

experiments,

carried

nymphs were studied

well as acidity were controlled The

regimes

were

pH

4

and

out

by

myself,

the

survival

kept

at

different

levels

and 5, c o m b i n e d with A1 c o n c e n t r a t i o n s

0.5 and 2.0 mg inorganic A1 L -I.

of

for 2-3 weeks in set-ups where A1 as (53). of 0,

163

As anticipated, nymphs

was

taking

in

most

experiments

also

at

pH

4.

the detrimental

example

of

of

one

(53). Heptagenia

However,

seemed to mitigate

these

experiments

at

A1

mg

demonstrated

L -I. for

Leptophlebia

Further,

the

low

--o--

Also

pH,

seen

the

~

so

AI = 0 m g / L

effect

i.

This

2.0

than

way,

in early

was

clearly

danica

and

rh0dani,

whereas

very

in the more

the response was not clear. At

¢

pH

around

or even reversed,

=

AI = 0 . 5 m g / L

9o

p X = 4.0

thus

AI = 2 . 0 m g / L

pH = 4 . 8

8O

70 60

,--

~

40" ~o.

60 50

Z 3o 20

I

0

5

~0

~s

!

2o

0

2s

--

0

I

I

I

:

"1

s

~0

~5

2o

25

Day No. Figure i:

Day No.

M o r t a l i t y of nymphs of the mayfly Heptagenia sulphurea at different pH and A1 conditions. Responses are s i g n i f i c a n t l y different (p " 0.02) for both pH and A1 (for the latter at pH 4.0).

published

studies

seem

to

exist,

which demonstrate

survival at low pH, at least for some time, However,

recently

this

I

pattern

unpublished).

Further,

was (G.

informed

similar

impact of low pH per se, have animals,

(8-10,

55-57).

be

unpublished;

results,

the negative test

can

that insect

improved

by

AI.

that also other mayfly nymphs can

Raddum,

other eggs

at

An

too

;

show

Fig.

Baetis

this

effect of A1 was outlevelled

20' I0'

No

in

of A1

to the expected eTfect.

9o

"• .--

seemed

stress.

Ephemera

mayfly in

too 8o

The

sulphurea,

responded

H__t fusco~risea

beneficial

more according

~.

is

ion

the effect was less p r o n o u n c e d

Heptagenia

mar~inata.

to

acid-tolerant 5,

mayfly

fusco~risea

more p r o n o u n c e d

close to the nymphs emerging period.

sensitive

the

at pH around 4 the p r e s e n c e

effect of A1 was generelly

0.5

of

impact of h y d r o g e n

ameliorating summer,

mortality

s i g n i f i c a n t l y higher at pH 4 than it was at pH 5, thus not

into account any A1 impact

tolerant

the

as Daphnia magna

P.

Greenwood,

i.e. that A1 can ameliorate been

reached

with

a

few

(47, 54) and some fish and fish

164

The

mechanism

ion

permeability,

buffering

behind

this

changed

ability

of

larva

sodium

A1

i n d i c a t e d b y C o r r e a et.al caddis

effect might be reduced m e m b r a n e h y d r o g e n

(47, (59),

Limnephilus

and/or 54,

who

sp.

to

calcium

58).

fluxes,

Another

found

that

increase

or

the

possibility pH

4

caused

its n i t r o g e n

m e t a b o l i s m and loss, but also that this a d v e r s e effect was

was the

(= protein) reduced

by

a d d i t i o n of 0.3 mg A1 L -I.

It

has

sometimes

been

put

forward that A1 like e.g. o r g a n o c h l o r i n e

r e s i d u e s and m e r c u r y may a c c u m u l a t e in animals, storage

may

be

is

presently

prep.). A "food chain account

for

high

flycathchers. stoneflies

from

dealt

birds a

of

nearby

insects, Hall

exposed

up

to

Likens

(36)

as 4.9

A

few

1.3

mg

mg

provided

"aquatic insects" in

rate

of

laboratory

in

being,

and by

but

the

Andersson, Nyholm

in

(60)

to

in the b o n e m a r r o w and eggs of p i e d

A1

eating

a

a

freshly

emerged

a n a l y s e s i n d i c a t e d that the A1

g-i

L -I

value

w

(E.

been

clear

of

H+-treated

d

have

but the v a l i d i t y of this value is not

and

undefined

Even

time

suggested

reported

lake.

insects c o u l d c o n t a i n as much

the

(Herrmann

was

A1

were

for

with

transport"

levels

The

unpublished).

the

related to time and the animals level in the throphic

web. No g o o d p r o o f of this does exist phenomenon

and that

Nyholm,

reported

(cited

in

for 22).

0.84 mg A1 g-i f w for small

stream.

Mayflies

to 2.0 mg i n o r g a n i c A1 L -I c o n t a i n e d up to 0.6

mg A1 L -I d w (J. Herrmann,

unpublished).

noted

and m a c r o p h y t e s have been r e p o r t e d capable

that

benthic

of a c c u m u l a t i n g A1

algae

Further,

it

(63) found h i g h stream A1 content

dippers,

that

mainly

This

might

less frequently. provided

that

A1

can

feed

levels

of

maturity

of A1 in insects

a

caddisfly.

in animals kept under acid alkaline

water,

due

to

a

items

"true"

food

chain

for

the

birds,

effect,

or an effect or

just

a

relationships.

decreasing

Further,

conditions differences

c o n c l u d e d that e m e r g i n g caddis A1 to predators,

where

from acid w a t e r s are not universal.

(6) found the levels in

values

act as a t o x i c a n t to the dippers,

c o - v a r i a t i o n due to other c a u s e - e f f e c t

and S v e n s s o n

be

on caddis and m a y f l y larvae, b r e e d

indicate

due to the a b s e n c e of p r o p e r p r e y

High

also

(22, 61-62).

O r m e r o d and c o - w o r k e r s birds

can

with

increasing

Otto

degree

the A1 c o n c e n t r a t i o n was lower that in

larvae could

in

those

from

solubility. not

The

substantially

as leaving most A1 b e h i n d in the exuviae.

sl:ightly authors convey

165

Respiration

At

low

studies

pH,

hydroxide

high

osmoregulation causes

gill

leading

inorganic

precipitation -

on

to

levels

in

mechanical

blockage

hyperventilation,

but

have

invertebrates

However,

been

very

then

few

studies

due

to

Herrman that

limited extent, (67).

One

transport

to

(I0, 64-65).

oxygen

for

exist

elevated

suffocation

was

and

respiratory

Andersson

and

was

shown

could counteract

days,

measured.

A1

(cf.

9).

for

The

The

animals

basic

exposure

that mechanical

region

measured

in

of

which

South

this

way.

The

fusco~risea

to elevated A1 was

these

species occurring

A1

to

restricted was

to

most

responses less

of

caddis larvae

of

pronounced,

level at pH 6.8

Further,

2).

pH

affect

4.0

and

increase

the

less

affected

in

(66). The heavily

by

AI,

H__t. sulphurea

and

in

accordance for

as H~. with

Interesting respiration.

sp.) to ph 4.0 and pH 4.0+_0.3

respiration,

compared

to

the

(59).

Herrmann

cause-effect

case

for oxygen

rate of the nymphs

also at more acid localities. (Limnephilus

to a

odonates

concentration

the effect of pH alone seemed less important

mg A1 L -I did in neither

(Fig.

is

rate

assumption

blockage

significant

raised

Sweden,

of

recent

this stress response.

showed

with

In

increase respiration,

naphtalene

and then "mask"

respiration

acidified

Exposures

same

changes

impact.

and then the oxygen consumption

mayfly species E. danica,

two

The

(66) related the r e s p i r a t i o n

any adverse condition would as

weight-specific

enough,

(8, i0,

to operate on some benthic

on

acidity

must be aware, however,

i0

This

transport,

Mayfly nymphs were exposed to 0, 0.5 and 2.0 mg A1 L -I at 4.8

impaired

just above pH 5.

expected

to some kind of stress on the animals was

waters cause A1

exposed to similar conditions.

invertebrates experiments

therefore

for later

25-26). All these effects seem most evident mechanisms

natural

of mucus - due

the gills of many fish species

lesions,

first

A1

and o v e r p r o d u c t i o n

and

relationship Its

Andersson model

(66)

presented

for A1 impact routes on

a

tentative

mayfly

nymphs

essence is that mucus and/or h y d r o x i d e s p h y s i c a l l y can

prevent

access to oxygen,

oxygen

over

the

epithelia

(not only on gills,

Compensation

for

this

attained

(hyperventilation),

hence is

causing

lowering

stress.

by This

the

uptake

efficiency

of

but most of the body).

increased response

respiration was

termed

rate the

166

"mechanical

impact

osmoregulation, membranes, route".

Also

a

Alternatively,

less

efficient

here

the

be

increased

energy

the

planktonic

a

for growth

for

caddisflies

larvae

impact

(59),

both

fits

cases,

and

the

(cf. 68),

reproduction.

Daphnia manna showed in chronic

0.3 and 0.7 mg A 1 L -1, respectively

respiration is a stress reaction due caddis

"chemical

impairments of 16

and

50%,

when

(46). The observations

that A1 leads to a higher respiration of mayflies change

impaired over the

demands or expenditures

crustacean

tests for three weeks reproductively to

the transport

impeded oxygen transport efficiency should be

in less energy being available

Actually, exposed

ion

for by an increased respiration rate. In

would

resulting

route". is

together with other toxic effects form

compensated result

that

(66),

but

with

no

with the idea that the increased to

affected

osmoregulation,

as

are known to withstand also highly brackish waters with

osmoregulatory problems.

Formation of aluminium hydroxides

Impaired osmoregulation and ion transport

1

1

Precipitation on epithelia

t

Other toxic effects

l

J

Mucus formation on epithelia

J

!

Mechanical impact route

Chemical impact route

1

1

Respiration prevented; lowered efficiency

t

Decreased oxygen transport efficiency

t,

1

Increased (compensator,/) respiration rate ("STRESS")

l Increased energy cost Less energy available for growth and reproduction

Figure 2:

A proposed model for the possible physiological impact routes for A1 effects on freshwater invertebrates at low pH conditions. From (61), with permission from D. Reidel Publishing Company.

167

Larvae

of

the

dragonfly

Somatochlora

q ingulata did however exhibit

s l i g h t l y d e c r e a s e d r e s p i r a t i o n rates with but

as

the

treatment

levels

were

increased

very high

i n t e r p r e t a t i o n of the data is uncertain.

No

with

exist,

relevant

co-workers also

levels

(70)

cadmium,

of

A1

seem

to

A1

levels

(69),

(10-30 mg A1 L-l),

other

respiration

but

the

study

Diaz-Mayans

and

found that increased e x p o s u r e to lead, to some extent likewise

caused

a

higher

respiration

rate

of

the

respiration

is

far

c r a y f i s h P r o c a m b a r u s clarkii.

Thus,

the way that A1 might

from

clear.

One

reason

affect

A1 on small, m a i n l y apneustic, reported

for

fish.

If

animals

thereby

more

the

problem

is

not

comparable

to

those

a "mirror" of general stress

as suggested,

it is rather

an

indirect

u n c e r t a i n p a r a m e t e r of the influence of AI, as also

suggested by Havas is

are

respiration

related to various mechanisms, and

invertebrate

for this might be that the direct effects of

(68). One important direct with

maintaining

the

effect,

internal

treated

ion

below,

b a l a n c e of the

animal.

O s m o r e ~ u l a t i o n studies

Cost and success for m o v e m e n t s of ions - simple or or

"unwanted",

other things, many

passive

or

active

organisms.

Generally,

impaired

inhibitions,

their

fish (8, 64,

71-72).

by

acidity

in the caddis according conditions the with

to

It is now

widely

accepted

less

Inhibition

invertebrates

that

in

many

suspected

larva P o t a m o p h y l a x c i n g u l a t u s under these

authors.

Astacus

astacus

effects

Exposure

to

by

natural

realistic

and P a c i f a s t a c u s

than

cases

in acid w a t e r s d e t r i m e n t a l effects Otto

There was h o w e v e r no indication of p h y s i o l o g i c a l

adverse of

Osmoregulatory

(8-9, 23, 73).

(up to 1 mg A1 L -1) reduced the h a e m o l y m p h

crayfish

for

cause and effect, have been studies e x t e n s i v e l y on

freshwater

(6).

among

conditions

(54-55).

of i n c r e a s i n g A1 levels on o s m o r e g u l a t i o n was Svensson

pH

o s m o r e g u l a t i o n b y freshwater o r g a n i s m s is high

these p r o b l e m s are also due to the impact of A1

for

essential

- over a cell m e m b r a n e are,

largely d e p e n d e n t on and a f f e c t e d by

considerably

Also

complex,

those

conditions, inorganic

A1

content

in

Na +

leniusculus,

reported

for

and

stress

although

fish

(74).

Ca ++ uptake at pH 5.5 was regarded m a i n l y due to the pH

itself, o n l y to a smaller extent a f f e c t e d by A1 thus causing an a d d i t i o n a l

stress

(55).

(up to 1

mg

A1

L-l),

168

By

using

the

22Na

isotope,

Havas

and

Likens

a f f e c t s b o t h influx and o u t f l u x of sodium in D_% higher

there

was

However,

so that the net

at

pH

net

loss

result

of

was

an

sodium,

although

reduced.

The

(47, 53)(cf.

resulting

effect

decrease

at

4.5. The authors Na

content

of

temporary,

may

pH

A mg

sodium

of

be a r e a s o n a b l e

AI,

also

observed

these fluxes

(54) was found c o n s i s t e n t with

6.5,

no

mortality.

cause

a

c h a n g e at p H 5.0, but an i n c r e a s e at p H an

Recently

inverse it

relationship

was

between

also found that A1 can

cause a d e c l i n e of the Na content of m a y f l y nymphs at b o t h pH 4.8

and

reduction

Thus a d d i t i o n of A1 was r e p o r t e d to

(54) also r e p o r t e d

and

5

the section on mortality).

the o b s e r v e d Na contents. Na

pH

increased

This

e x p l a n a t i o n for the o b s e r v e d b e n e f i c i a l effects of by others

At

4.5 the influx did not change much w h e n A1 was

added, w h e r e a s o u t f l u x was s u b s t a n t i a l l y the

manna.

a p r o n o u n c e d r e d u c t i o n of the influx but o n l y small

changes in outflux, loss.

(54) showed that A1

4.0

and

(76).

pronounced A1

L -1 ,

a

demonstrated Na-flux

from

of

very

for

to c o m p e n s a t e levels

reduction

high

the

the

in Na influx at increased A1 levels level)

hemipteran

tissue

at

pH

3

waterbug

and

4

C0rixa

has

also

punctata

been

(21).

A

c o m p a r t m e n t to the h a e m o l y m p h was suggested

for this. The net result w o u l d be s l i g h t l y

the

(up to 50

haemolymph

during

increased

the 20 h long experiment,

Na

and thus

less h a r m f u l to the animal.

P o t e n t i a l l y a d v e r s e effects of A1 on o s m o r e g u l a t i o n by

the

observation

Al-specific

that

s t a i n i n g of

chironomids

(M.

Havas,

mediate the t r a n s p o r t balance the anal Herrman,

processes. region

A1

addition

anal

of

of

in

unpublished). cations,

mayflies,

phantom

These

hence

supported

the

midges

(77)

and

s t r u c t u r e s are known to

being

stainings

but

also

at low pH can cause increased

papillae

Al-indicating

is

vital

have

meaning

to

the

salt

a l s o b e e n found in is

not

clear

(J.

unpublished).

C 0 n c l u d i n 9 remarks

It

is

perhaps

not

so strange that the results of the r e l a t i v e l y few

studies that exist r e g a r d i n g are

somewhat

contradictory,

A1 as

impact the

affect the s o l u b i l i t y and s p e c i a t i o n

on

freshwater

concentration of

AI.

Hence

invertebrates

of H + do largely the

patterns

of

169

occurence chemistry reason

of

the different

forms become quite complicated,

is still p a r t l y under is

that

the

group

debate of

(see

e.g.

invertebrates

13,

of

and the A1

24).

course

Another is

quite

heterogeneous. To detect detrimental generally adverse

not

effects of

possible

factors

Nevertheless,

are

field

or

and

freshwater

it is important

laboraotry

changed

hint in

pressure.

at

is

the

concurrently.

possible physical

Generally

to stress that

experiments

invertebrates

as a variety of p o t e n t i a l l y

and

might

as changes

predation

impact research, types

on

interrelated studies

effects on invertebrates, resources

A1

in field surveys,

"need"

in

indirect habitat,

all

field

A1 food

environmental

studies

eachother,

of

thus

all being

complementary. Mortality as

effects of A1 on freshwater

serious

concluded might

as

in

anticipated

the

actually

Nevertheless,

reason

section,

be more important

is

type

organism.

of

exposure

The

on time.

A

does

about the biological indicated

research

substance

low pH.

Thus,

its

given

are in

surface

might

or

on

the

however

just

pass

and

word

As

levels

bioavailability.

therefore

not

potential in

that

taken

be incorporated

throug

habits,

the

as attained say

the

by

into the

organism,

developmental

necessarily

up

all

but also

stage

and

from e.g. a whole

truth

or real a c t i v i t y of a substance.

this review, studies

essential future

is,

type and amount of the substance,

feedings

of

both mortality and respiration osmoregulatory

for the interpretation

studies

freshwaters

may

crucial process to study suggested t o affected,

effects

than those that kill sDme organisms.

measure of bioavailability,

earlier

suggest

invertebrates acidified

sublethal

can be, or even really

the affinity,

organism,

dialysis bag,

As

be

that this concept often implies the amount and type of

o r g a n i s m without any harm, depending

to

there is p r o b a b l y a need of both types of approach.

a substance that p o t e n t i a l l y an

do not seem

from the knowledge on fish (cf. above).

mortality

A c a u t i o n a r y note could also be The

invertebrates

of

how

affect be

increased these

effects A1

levels

aquatic animals,

osmoregulation;

as well as how this affects the animals.

on

of impact of A1 at

how

~t

in a is

170

Acknowledgements Valuable

comments

were

kindly

given by prof. P. Brink a,d Drs. K.G.

Andersson and B.S. Svensson.

References

i.

Drablos,

D. and Tollan, A.

Acid Precip.,

383 pp.

Eds.

Proc.

Int.

(Oslo-Aas:SNSF-Project,

Conf.

Haines,

T.A. Trans. Am. Fish. Soc. i i 0 : 6 6 9 - 7 0 7

3.

Wright,

R.F. Water Quality Bulletin 8 : 1 3 7 - 1 4 3

4.

Burton,

T.M.,

Stanford,

R.M.

5.

-

and

Allan,

~ffects

on

209-235.

(Ann Arbor: Ann Arbor Sci. Publ.,

Singer,

R.

In:

Ecological Publ.,

F.M.

Systems,

D'Itri, pp.

(1981) (1983)

J.W.

329-363.

(Ann

Arbor:

Ann

Okland, J. and Okland,

K.A. Experientia 42, 471-486

8.

Muniz,

I.P. and Leivestad,

Proc.

Int.

Conf.

SNSF-project,

Scio

Ecol.

Int.

Conf.

(1983) (1986).

H. In: D. Drablos and A.

Tollan,

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of acid stress in

(1987, in press)

(1986)

Section 3

179

SUMMARY OF WORKING GROUP REPORTS Lars Landner Swedish Environmental Research Group GStgatan 35, S-I16 21 Stockholm

INTRODUCTION During the second day of the "Workshop on the Speciation of Metals in Water, Sediment and Soil Systems", four separate Working Groups discussed different aspects of metal speciation in relation to diff@rent situations of metal discharge and metal contamination of the environment. Three Working Groups addressed the following three situations: i)

Metal speciation in relation to current wastewater discharges and atmospheric emissions from mining operations and metal processing (chairman:

Professor

Bert Allard, LinkSping). 2)

Metal speciation in relation to the dumping of solid waste, sewage sludge, dredging and other related activities (chairman: Professor Ulrich F~rstner, Hamburg).

3)

Metal

speciation in relation to the mobilisatJon of metals from existing

deposits in soil/sediments:

acid rain,

sulphide oxidation, etc (chairman:

Professor Lars H~kansson, Uppsala). The forth Working Group concentrated on analytical techniques and it was chaired by Dr. Brit Salbu, Oslo. Among the various questions addressed by the three first mentioned Working Groups were for example: -

why do we need information on metal speciation ?

- what environmental factors control the distribution of species ? -

how can information on metal speciation be used to draw conclusions on the bioavailability and toxicity of metals ?

- what analytical procedures can be recommended ? -

what research needs can be identified ? All four Working Groups prepared separate reports. However, since several over-

laps occurred between the conclusions from the different groups, the editor has tried to make a synthesis of the major conclusions from all four Working Groups. It is hoped that the following summary will give a correct account of at least the most important points expressed during the Working Group discussions and during the following plenary session. If not, only the editor is to blame. A complete list of participants of the Workshop is given in Appendix I.

180

THE NEED FOR METAL SPECIATION The release processing,

of metals

from various metal handling

activities

(mining,

metal

dumping of solid waste, etc) could lead to negative effects if these

metals are distributed to living organisms

to, are taken up into,

in the ecosystem.

- evaluate and quantify

are accumulated by and are toxic

It is therefore essential for society to:

potentially

harmful effects of certain metals in the

environment; - predict future effects due to the presence and/or extended releases of metals from anthropogenic sources; - design proper technical concepts for release control and deposition of metal wastes; - understand

basic processes in the ecosystem related to the distribution and

mobilisation of metals; - assess the chemical reactivity and transformations of critical species (bioavailable and toxic species); - identify

species

which

are

bioavailable

(and

possibly

toxic)

for

various

organisms. A

knowledge

physical

of metal

speciation

characterisation)

is

(including

required,

chemical

speciation

since the speciation

as well as

of the individual

metal has an influence on: -

metal mobility - metal distribution in space and time;

- transport chains in the ecosystem - biological uptake, mineralisation, - chemical

reactivity

-

effects

of environmental

parameters

and

etc;

changes

in

the environment on chemical processes; - bioavailability and impact/toxicity for various organisms. Since be

metal

performed

Therefore,

speciation

routinely

is a laborious

and expensive

undertaking,

it cannot

as a part of all studies of metals in the environment.

we have to develop some simple priorities regarding when metal speci-

ation should be Undertaken. An important

parameter,

to describe the major metal species in water, is the

partition coefficient, Kp, for metal in solution, Me(s), and particle-bound metal, Me(p): K

K

is a function P content of humus, normally

= Me(s) / Me(p). P of pH, temperature, redox potential,

alkalinity,

salinity and

Ca, Fe, Mn and A1 of the water. Most of these parameters are

analysed within water

quality monitoring programmes.

Improved knowledge

of how they influence Kp will aid in predicting major heavy metal speciation. It is also obvious

that metals are a quite heterogeneous group of elements with

respect to their release,

mobility and toxicity. Based on a set of simple criteria

18t

related

to the occurrence,

mobility

the natural concentrations,

(solution and sorption behaviour)

the release pattern,

the

and the toxicity of the metals,

the

following priority setting regarding which metals should be speciated in the first place could be useful: High priority group

Hg, Cd, As, A1

Medium priority group

Cr, Cu, Ni, Pb

Low priority group

Fe, Mn, Zn

FACTORS CONTROLLING THE DISTRIBUTION OF METAL SPECIES The waste categories considered by the Working Groups were airbourne particles, wastewater and solid waste (ash, process sludge,

tailings, high risk wastes) from

mining operations and metal processing, dredged material, sewage sludge and household wastes. Airbourne particles of two kinds would be expected: - primary

particles,

frequently of low water solubility (e g high temperature

fired oxides); - secondary particles: metals associated with a carrier matrix. Both types of particles will reach the terrestrial and the aquatic ecosystems, although the transport time and chemical state would be related to meteorological/ climatological

factors as well as chemical factors (solubility and redox reactions

in the air/precipitation system). Liquid wastes would primarily be fairly acidic aqueous solutions with metals in ionic forms, metal sludges originating from the neutralization of acidic process solutions

(e g mixtures

of metal hydroxides

and calcium sulphate)

or deposits

of precipitated dust and slag. The here mentioned solid wastes as well as dredged material,

mine tailings, sewage sludge, etc are generally characterized by means

of various tests for prediction of the long and short term fate of metals. Currently used characterisation methods or tests are: elutriate test, acid leachate test,

chelator

saturation

test,

leachate test, phase

cation exchange

characterisation

soil test,

(sequential

buffer capacity,

leaching)

base

before and after

stabilisation and bioassays. However, analysis and identification of metal species and of their bioavailability

normally

start

when

the wastes have reached the ecosystem,

which would

determine (or modify) the chemical state of the metals, in principle independently of the source. The environment

can be looked upon as a system of compartments

in relation

to metal speciation and metal transformation: *

Aqueous

solutions - metal species in true solution

(ions,

organic and in-

182

organic complexes). * Non-stationary particulate and colloidal matter - true metal (hydroxides) or pseudo-colloids (organic or inorganic carriers). * Stationary solid systems - soil materials, sediments, etc. * Organisms and detritus (dead biological material).

colloids

The speciation and distribution of a metal in and between these compartments are illustrated in Figure 1. Chemical parameters that govern metal speciatio n are: i. Redox potential (oxidation state) 2. pH (degree of hydrolysis, precipitation, sorption behaviour) 3. Complexing agents (OH-, CO~-,- pO3-4' SO~-, organics such as humic and fulvic acids) 4. Salinity, concentrations of competing elements 5. Temperature 6. Residence time These factors are also significantly inter-related. The sorption of species in solution would primarily depend on the degree of metal complexation (hydrolysis, complexes with inorganic or organic ligands) and properties of exposed solid surfaces (charge, presence of compl~xing groups, etc). Thus, also the distribution between solid surfaces and the solution phase can be described in terms of metal speciation (exchangeable metals, oxide-bound metals, organic-bound metals, co-precipitates, mineralised metals).

(sorption)

Species in solution (org.,inorg.)

(precipitati°n)I

----

particulate matter (org. or inorg.)

(sedimentation)

I

Solid precipitate

Solid

.......

f

(sedimentation

Solid stationary phase

Figure i. Distribution of species between solid and solution phases.

183

BIOAVAILABILITY AND TOXICITY To be considered

bioavailable

a metal species must have a measurable uptake

rate, resulting in bioaccumulation or a toxic response within the organism. Metal species

presently

recognized

as bioavailable

are low molecular weight species,

mainly "free" and/or weakly bound ions but also small size molecules and complexes. The ultimate

goal of chemical metal speciation is to identify and describe bio-

available

species

transform

other

(size,

charge,

species and to identify processes.

ligands,

physico-chemical

forms

etc),

to identify the processes which

(reservoir

-

colloids,

the factors (pH, redox potential,

etc)

into

such

etc) that invoke such

It should also be held in mind that the bioavailability

of a metal

could be enhanced by the presence of organophilic ligands. It is important that biological

to remember

that bioavailability

is a relative concept and

uptake and toxic~impact of individual metals must be related to

biological factors such as: - type of organism -

developmental stage and sex

- activity patterns - feeding strategy,

etc.

More research is needed to establish good correlations between metal species and their bioavailability to different organisms.

ANALYTICAL TECHNIQUES Routine analytical procedures - water Most countries have routine procedures for water sampling and water analysis. In these standard procedures, metal analysis in general is based on either atomic absorption

spectrometry

(AAS)

or inductively

coupled plasma emission

(ICP).

In

addition, some laboratories have standard procedures for filtration (0.45 um filter), centrifugation, or for the use of ion-exchange resins or extraction agents. In order to obtain information

on low molecular

weight species, dialysis in

situ is recommended as a standard routine technique. This dialysis technique reduces the influence of colloids which affect results obtained, filtration,

ion-exchange

to be specified

and extraction

procedures.

for example,

This standard

from

procedure has

in an informative manual. The laboratories using this procedure

should also carry out inter-calibration tests.

Routine analytical procedures - sediments and soils For

routine

analysis,

the total metal concentration

is usually analysed

by

184

strong acid digestion followed by atomic absorption determination. In

order to obtain information

components

present

on the association

in soils/sediments,

of metals with different

a three step sequential extraction scheme

is recommended. The three fractions to be determined are: I. Exchangeable

fraction

-

based

on

extraction

with

magnesium

chloride

or

ammonium acetate at pH 7.0. 2. Metals associated with the carbonate and hydrous metal oxide fraction - based on extraction with acidic hydroxylamine/hydrochloride. 3. Metals

associated

with

organics

and

mineral

lattice

- based on digestion

with strong acid/oxidation. This scheme provides information on surface adsorbed metal species (fraction i), the effect of reduced

pH and redox potential

(fraction 2), and the inert metal

species (fraction 3). Direct methods

(analysis)

are usually

species as the concentrations

not informative

with respect

to metal

in natural waters are low and numerous compounds

are present and may interfere with analytical signals. At present, combined techniques, i e different fractionation techniques interfaced with different detectors, where species are fractionated and then analysed with respect to total metal concentrations in different obtained fractions, are preferred for speciation purposes.

Procedures used in current research A variety

of

techniques

have

been

used and further

developed

at different

research institutes. Metal species in water solutions can be fractionated according to, for example, size, charge, solubility, density, volatility and polarity. These different

fractionation

techniques

can

also

be

performed

sequentially.

These

techniques are then interfaced with detectors giving information on the concentrations of metals and other elements (multielement methods) or information regarding structures (organic ligands) and isotopic composition.

Along with the development

of a useful combination, work is also conducted in order to simplify the techniques for routine analytical purposes.

RESEARCH NEEDS It was concluded that basic research related to the speciation, biological towards

uptake

and

effects

a basic understanding

of metals in the environment of the mechanisms

distribution,

should be directed

behind the observed phenomena.

Important research needs can be recognised in the following areas:

185

i. Analytical methods for distinguishing various metal species: - methods fractionating species according to size and charge simultaneously - specific methods for lipid soluble metal species - methods to get information on the influence of colloids on metal species 2. Determination of the bioavailability: - for various elements/species - for various organisms - under different conditions - general properties of bioavailable metal species (cha~ge, size, complexation) 3. The role of natural

organics

in metal speciation,

transport and biological

uptake: - properties of humic substances (e g functional groups) - synergistic effects (increased bioavailability of toxic metals) - increased mobility - mobilising agents 4. Design of model systems that in a controlled way can simulate environmental systems and be used for the study of biological uptake - choice of conditions - choice of organisms -

use of fractionated natural waters in model ecosystem experiments

5. Development

of useful

standardised

biomonitoring

methods

and assessment

of

their limitations 6. Mathematical modelling to obtain a better understanding of sorption/desorption phenomena: - quantitative modelling - coupling of sorption and chemical speciation 7. Modelling of combined transport and chemical/biological reactions of dissolved metals: -

-

retardation of metals in various environments fixation/mineralisation of metals

8. Development

of

cheap

and

effective

technology

for metal demobilisation

to

be used in solid waste disposal 9. Preparation

of

an

informative

manual

for metal speciation in natural waters.

describing

a

standardized

procedure

Appendix

189

LIST OF THE PARTICIPANTS

OF THE "INTERNATIONAL WORKSHOP ON SPECIATION OF METALS

IN WATER, SEDIMENT AND SOIL SYSTEMS, HELD AT SUNNE, SWEDEN, SEPI~MEER 15-16, 1986

ALLARD BERT Department of Water, University of LinkSping, S-581 83 LINKOPING, Sweden AZCUE JOSE M.P. Laboratorio de Radioisotopas, Instituto de Biofisica, Universidade Federal de Rio de Janeiro, Ilha do Fundao, RIO DE JANEIRO, Brazil BJORNSTAD HELGE E.O. Department of Chemistry, University of Oslo, P.O.B. 1033, Blindern, N-0315 OSLO 3, Norway BORG HANS The National Environmental Protection Board, Trace Metal Laboratory, Box 1302 S-171 25 SOLNA, Sweden BROBERG ANDERS Institute of Limnology, University of Uppsala, Box 557, S-751 22 UPPSALA, Sweden FORSTNER ULRICH Arbeitsbereich Umweltschutztechnik, Technical University of Hamburg-Harburg, P.O. 90 14 03, D-2100 HAMBURG 90, Federal Republic of Germany GRAHN OLLE Swedish Environmental Research Group (SERG), Fryksta, S-665 00 KIL, Sweden GRANDE MAGNE Norwegian Institute for Water Research (NIVA), P.O. Box 333, Blindern, N-0314 OSLO 3, Norway GORANSSON TORBJORN Boliden Mineral AB, S-936 OO BOLIDEN, Sweden HERRMANN JAN Department of Animal Ecology, University of Lund, Ecology Building, S-223 62 LUND, Sweden HULTBERG HANS Swedish Institute for Water and Air Pollution Research (IVL), Box 5207, S-402 24 GOTEBORG, Sweden H~KANSSON LARS Department of Hydrology, University of Uppsala, V. ~gatan 24, S-752 20 UPPSALA, Sweden IVERSEN EIGIL Norwegian Institute for Water Research (NIVA), P.O. Box 333, Blindern, N-0314 OSL0 3, Norway LANDNER LARS Swedish Environmental Research Group (SERG), G~tgatan 35, S-I16 21 STOCKHOLM, Sweden LEHTINEN KARL-JOHAN Finnish Environmental Research Group (FERG), Torpv~gen 13-15 B7, SF-OII50 SODERKULLA, Finland LINDESTROM LENNART Swedish Environmental Research Group (SERG), Fryksta, S-665 OO KIL, Sweden

190

LYDERSEN E. Department of Chemistry, University of Oslo, P.O. Box 1033, Blindern, N-0315 OSLO 3, Norway MORRISON GREG Department of Sanitary Engineering, Chalmers University of Technology, S-412 96 GOTEBORG, Sweden PART PETER Department of Zoophysiology, University of Uppsala, Box 560, S-751 22 UPPSALA, Sweden RASMUSON ULRIKA Technical Department, The National Environmental Protection Board, Box 1302, S-171 25 SOLNA, Sweden REUTHER RUDOLF Swedish Environmental Research Group (SERG), Fryksta, S-665 00 KIL, Sweden ROSEMARIN ARNO AMBIO, Royal Swedish Academy of Sciences, Box 50005, S-I04 05 STOCKHOLM, Sweden SALBU BRIT Department of Chemistry, University of Oslo, P.O. Box 1033, Blindern, N-0315 OSLO 3, Norway SANGFORS OLOF Swedish Environmental Research Group (SERG), Fryksta, S-665 O0 KIL, Sweden SVEDBERG ROLF Boliden Metall AB, S-932 O0 SKELLEFTEHAMN; Sweden TIMM BIRGITTA Department of Research and Development, The National Environmental Protection Board, Box 1302, S-171 25 SOLNA, Sweden WALTERSON EVA Swedish Environmental Research Group (SERG), GStgatan 35, S-I16 21 STOCKHOLM, Sweden WESTLING OLLE Swedish Institute for Water and Air Pollution Research (IVL), Aneboda, S-360 30 LAMMHULT, Sweden ~NES KARL JAN Norwegian Institute for Water Research (NIVA), PoO. Box 333, Blindern, N-0314 OSLO 3, Norway.