Atmospheric Pollution: 15th: International Colloquium Proceedings (''Science of the Total Environment'')

ATMOSPHERIC POLLUTION 1982 Other volumes in this series 1 Atmospheric Pollution 1978 edited by M.M. Benarie 2 Air ...

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ATMOSPHERIC POLLUTION 1982

Other volumes in this series

1 Atmospheric Pollution 1978 edited by

M.M. Benarie

2 Air Pollution Reference Measurement Methods and Systems edited by T. Schneider, H.W. de Koning and L.J. Brasser 3 Biogeochemical Cycling of Mineral-Forming Elements edited by P.A. Trudinger and D.J. Swaine 4 Potential Industrial Carcinogens and Mutagens by L. Fishbein

5 Industrial Waste Management by S.E. Jsrgensen 6 Trade and Environment: A Theoretical Enquiry by H. Siebert, J. Eichberger, R. Gronych and R . Pethig 7 Field Worker Exposure during Pesticide Application edited by W.F. Tordoir and E.A.H. van Heemstra-Lequin

8 Atmospheric Pollution 1980 edited by M.M. Benarie 9 Energetics and Technology of Biological Elimination of Wastes edited by G. Milazzo 10 Bioengineering, Thermal Physiology and Comfort edited by K. Cena and J.A. Clark

11 Atmospheric Chemistry. Fundamental Aspects by E. M6sz6ros 12 Water Supply and Health edited by H. van Lelyveld and B.C.J. Zoeteman 13 Man under Vibration. Suffering and Protection edited by G. Bianchi, K.V. Frolov and A. Oledzki 14 Principles of Environmental Science and Technology by S.E. Jsrgensen and I . Johnsen 15 Disposal of Radioactive Wastes by Z . Dlouhq 16 Mankind and Energy edited by A. Blanc-Lapierre 17 Quality of Groundwater edited by W. van Duijvenbooden, P. Glasbergen and H. van Lelyveld

18 Education and Safe Handling in Pesticide Application edited by E.A.H. van HeemstraLequin and W.F. Tordoir 19 Physicochemical Methods for Water and Wastewater Treatment edited by L. Pawlowski

Studies in Environmental Science 20

ATM0sPHER IC POLLUTION 1982 Proceedings of the 15th International Colloquium, UNESCO Building, Paris, France, May 4-7,1982 Organised by the lnstitut National de Recherche Chimique Appliquie, Vert-le-Petit, France, in association with the Commission on Atmospheric Environment of the International Union of Pure and Applied Chemistry (IUPAC), the World Health Organization (WHO), the Gesellschaft fur Aerosolforschung (GAeF) and the Fraunhofer Gesellschaft (FhG) edited by

Michel M. Benarie

These papers have been published as a special issue of The Science of the Total Environment, Volume 23, 1982

ELSEVIER SCIENTIFIC PUBLISHING COMPANY Amsterdam - Oxford - New York 1982

E L S E V I E R S C I E N T I F I C P U B L I S H I N G COMPANY Molenwerf 1, P.O. B o x 21 1, 1000 A E Amsterdam, The Netherlands Distributors for the United States and Canada:

E L S E V I E R SCIENCE P U B L I S H I N G C O M P A N Y INC. 52, Vanderbilt Avenue N e w York. N.Y. 10017

ISBN 0-444-42083-5 (Vol. 2 0 ) ISBN 0-444-41696-X (Series)

0 Elsevier Scientific Publishing Company, 1982 A l l rights reserved. No p a r t of this publication m a y be reproduced, stored in a retrieval system or transmitted in any f o r m or by any means, electronic, mechanical, photocopying, recording or otherwise, w i t h o u t t h e prior w r i t t e n permission o f t h e publisher, Elsevier Scientific Publishing Company, P.O. B o x 330, 1000 A H Amsterdam, The Netherlands Printed in The Netherlands

V

PREFACE Why a c o l l o q u i u m ?

I n t h e s e t i m e s o f an i n f o r m a t i o n e x p l o s i o n , o f a

mushrooming number o f s c i e n t i f i c j o u r n a l s , and when we a r e a t t h e t h r e s h o l d o f e l e c t r o n i c p u b l i s h i n g , why g a t h e r p e o p l e t o g e t h e r , a t c o n s i d e r a b l e expense and

loss o f t i m e f o r them, s i m p l y so t h a t t h e y n a y l i s t e n t o o r a l p r e s e n t a t i o n s ? I can p u t f o r w a r d two reasons.

The f i r s t reason i s d e r i v e d f r o m my v i e w t h a t t h e purpose o f a l l s c i e n t i f i c communication i s i n t e r a c t i o n .

To i n t e r a c t means t o spread o n e ' s own ideas,

r e s u l t s , e t c . , as w i d e l y as p o s s i b l e

t o g a t h e r i n as many comments, c r i t i -

cisms, novel p o i n t s o f view and, perhaps, applause as p o s s i b l e .

I f a measure

o f t h e " s t r e n g t h o f i n t e r a c t i o n " can be o b t a i n e d f r o m t h e number o f r e f e r e n c e s t o work done and p u b l i s h e d , t h e n I can propose some c o n c l u s i o n s I have o b t a i n e d from examining a sample o f papers w i t h i n t h e f i e l d o f t h e atmospheric e n v i r o n ment.

I n any paper, on average, t h e papers most f r e q u e n t l y quoted a r e those of

t h e author himself, t h e so-called self-references.

Second i n frequency a r e

r e f e r e n c e s t o papers o r i g i n a t i n g f r o m t h e same l a b o r a t o r y , work group o r i n s t i t u t e as t h e a u t h o r .

Then f o l l o w , w i t h about t h e same frequency, r e f e r e n c e s

t o a u t h o r s who c o - p a r t i c i p a t e d w i t h i n t h e p r e v i o u s 10 y e a r s a t a c o l l o q u i u m o r o t h e r k i n d o f m e e t i n g and r e f e r e n c e s t o papers t h a t appeared i n t h e same j o u r n a l as t h e a u t h o r ' s paper i s p u b l i s h e d . Please do n o t s m i l e a t t h e frequency o f s e l f - r e f e r e n c e s .

They a r e n o t

Nobody i s n e a r e r t o t h e r e c e n t h i s t o r y o f a v e r y

evidence o f a u t h o r s ' v a n i t y .

s p e c i f i c t o p i c , t o a g i v e n t r a i n o f t h o u g h t s , t o t h e p a r t i c u l a r method o f i n v e s t i g a t i o n o f a s c i e n t i s t , than the author himself.

With t h i s i d e a i n mind,

i t i s c l e a r t h a t t h e above-mentioned o r d e r o f f r e q u e n c i e s o f r e f e r e n c e s , i . e .

s e l f , group, c o - p a r t i c i p a n t ,

same j o u r n a l , s i m p l y express t h e i n c r e a s i n g l y

l a r g e r s e t s o f s c i e n t i s t s who a r e i n v o l v e d w i t h , understand, and a r e i n t e r e s t e d i n , t h e work t h a t t h e a u t h o r i s c u r r e n t l y doing.

This order o f reference

f r e q u e n c i e s proves how e f f e c t i v e l y a c o l l o q u i u m enhances s c i e n t i f i c i n t e r a c t i o n . I n o u r s p e c i f i c s i t u a t i o n , when t h e Colloquium papers a r e a t t h e same t i m e a s p e c i a l volume o f The Science o f t h e T o t a l Environment, a well-known and w i d e l y a v a i l a b l e j o u r n a l i n t h e . f i e l d , t h e d i f f u s i v e i n t e r p e n e t r a t i o n o f ideas i s even more enhanced. The second reason why people come t o a c o l l o q u i u m i s so t h a t t h e y can f o l l o w o r t a k e p a r t i n t h e d i s c u s s i o n s , t h e remarks, and t h e q u e s t i o n s which f o l l o w each o r a l p r e s e n t a t i o n .

U n f o r t u n a t e l y , t h e p r e s e n t volume, f o r t h e

convenience o f t h e p a r t i c i p a n t s , had t o be ready a t t h e opening o f t h e Colloquium, and t h u s c o u l d n o t i n c l u d e t h e d i s c u s s i o n s h e l d d u r i n g t h e

Colloquium i t s e l f . Such discussions are nevertheless a very e s s e n t i a l component of any meeting. Every author l e f t the podium enriched with some suggestion o r , a t l e a s t , with t h e i m p l i c i t judgement of a p o l i t e b u t sparse applause not followed by any p e r t i n e n t question - perhaps because h i s work o r h i s manner of presentation f a i l e d t o arouse s u f f i c i e n t i n t e r e s t . No j o u r n a l , no r e f e r e e , no e d i t o r i a l committee i s able t o a c t as such a multiheaded, e f f e c t i v e , and quick j u r y . Vox populi, vox Dei. Why t h i s colloquium? My s t a r t i n g point i s once more t h e information explosion. Every year new s u b - s p e c i a l i t i e s and sub-sub-specialities a r e born. There a r e s p e c i f i c gatherings, not only f o r atmospheric modellers, b u t a l s o separately f o r urban, f o r meso-scale, f o r long-range, e t c . modellers. Every atmospheric p o l l u t a n t , whether i t be sulphur, nitrogen, p e s t i c i d e s , o r n i t r o samines, draws together i t s s p e c i a l i s t s somewhere. Aerosol science i s branching out i n t o a dozen t o p i c s , each one with i t s annual, or even more frequent, meeting . Ours i s a h o l i s t i c approach. The divergences r e s u l t i n g from growing s p e c i a l i z a t i o n require increased e f f o r t s i n synthesis. Our purpose i s t o draw together individual s c i e n t i s t s who a r e in danger of becoming c l o i s t e r e d within t h e i r narrowly limited f i e l d . We wish t o t r y a n d maintain l i n k s , develop a common language, s t r e s s points o f common i n t e r e s t , and f u r t h e r i n t e r a c t i o n among t h e ever-widening branches of atmospheric environmental science. New shoots nourish a t r e e , b u t they cannot support themselves in t h i n a i r without a sustaining stem. A t a time when science i s looking with more and more accuracy a t l e s s and l e s s , we must a l s o s u s t a i n t h e s p i r i t of t h e whole. To f u l l y understand t h e p a r t s of our subject we must occasionally t r y and look a t the whole in a s p i r i t of comprehensiveness. Such an approach i s the basis of the scope of The Science of the Total Environment. This h o l i s t i c tendency notwithstanding, we a r e always receptive t o new extensions. Since i t s beginnings, a i r pollution science has been urban-

industrial/temperate-zone o r i e n t a t e d .

The problems were the most acute and

t h e most perceptible in t h i s geographical context. Now, gradually, we a r e becoming increasingly aware t h a t a r i d and t r o p i c a l regions a l s o have t h e i r problems. We a r e almost t o t a l l y ignorant about wet-subtropical a i r chemistry. The t r o p i c a l agroindustry i s an enormous, d i f f u s e source of a i r p o l l u t a n t s . Last, b u t not l e a s t , t h e problems of d e s e r t a i r have barely been touched. Therefore, a s f i r s t point on our programme t h i s y e a r , we included a session dealing with the pollution problems of hot and d e s e r t regions, and we hope t o follow t h i s topic u p i n a f u t u r e Colloquium i n more depth. covered in t h e programme were:

The o t h e r topics

w - Atmospheric flow and dispersion; modeling.

-

Health e f f e c t s , i n d u s t r i a l hygiene and t h e control of a i r pollution in

industry. - Aerosols: t h e i r c h a r a c t e r i z a t i o n , techniques of measurement. - Aerosol physics.

-

Air chemistry; wet and dry deposition of p o l l u t a n t s . Field r e s u l t s ; monitoring and surveys. This volume contains t h e accepted papers selected from the 80 t h a t were submitted t o t h i s 15th International Colloquium held in t h e Palais des C0ngrS.s ( P o r t M a i l l o t ) i n P a r i s . The international character of the meeting i s evident from the o r i g i n o f the papers received. They were contributed by s c i e n t i s t s from 22 countries.

Michel

BENARIE

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CONTENTS

Preface .............................................................

V

POLLUTION PROBLEMS OF HOT AN0 DESERT REGIONS Air pollution i n t r o p i c a l areas E. Sanhueza, M. African0 and J . Romro

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

3

Trends i n ozone concentrations i n Jerusalem E . H . Steinberger .............................................

11

Background continental ozone l e v e l s i n the rural U.S. Southwest desert T.E. Hoffer, R.J. Farber and E.C. E l l i s ......................

17

Atmospheric contamination of archeological monuments i n t h e Agra Region ( I n d i a ) J.S. Sharrm and D . N . Sharma ..................................

31

Air monitoring program i n Saudi Arabia T. Husain and S.M. Khan ......................................

41

A study of physocochemical c h a r a c t e r i s t i c s of r e s p i r a b l e dust i n an Indian coal mine N.S. Rawat ..................................................

47

Contamination of s o i l s and plants by m r c u r y . a s influenced by t h e proximity o f i n d u s t r i e s i n Alexandria, Egypt I.H. Elsokkary ..............................................

55

Study of atmospheric p o l l u t i o n i n an urban zone deprived o f measurement systems, f o r purposes of l e g i s l a t i o n application t o t h e c i t y o f Tunis M.C. Robe and J . Carbonnelle ............................... 61 MODELING Atmspheric dynamics of NO, emission controls A . Eschenroeder .............................................

71

S i t e and season-speci f i c variations of the atmospheric p o l l u t a n t t r a n s p o r t and deposition on the local and regional s c a l e G. Neumann-Hauf and G. M a l b r i t t e r ...........................

91

Daily forecasting of a i r pollution p o t e n t i a l A. Joukoff and L.M. Malet ...................................

97

The forecasting method of a i r pollution peaks developed and used i n t h e Nord-Pas-de-Calais area P. Allender a n d J . M. Dejardin .............................

103

A

Turbulent d i f f u s i v i t i e s and deposition c o e f f i c i e n t s : application t o calm wind conditions P.J.H. B u i l t j e s ...............................................

107

Measurement o f turbulence p r o f i l e s i n t h e boundary l a y e r and observations o f atmospheric diffusion by smoke plumes emitted near t h e ground and i n a l t i t u d e D. Schneiter .................................................

119

A comparison o f numrical models f o r c a l c u l a t i n g dispersion from accidental releases of p o l l u t a n t s D.W. Pepper, R.E. Cooper and A.J. Baker ......................

127

Detection and impact prediction of hazardous substances released

t o the atmosphere E . E . P i c k e t t , R.G. Whiting and H . L . Kocchiu

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

141

Modeling p o l l u t a n t dispersion w i t h i n a tornadic thunderstorm D.W. Pepper ..................................................

151

The influence of the emission height on the meso-scale a n d longrange t r a n s p o r t o f reactive p o l l u t a n t s M. Benarie ...................................................

163

HEALTH EFFECTS

-

POLLUTION CONTROL

Mortality and a i r pollution -- lessons from s t a t i s t i c s F.W. L i p f e r t ..................................................

175

Opposite e f f e c t s o f inhaled cadmium microparticles on mouse suscept i b i l i t y t o an airborne b a c t e r i a l and airborne viral infection G . Bouley, C. Chaumard, A.-M. Quero, F. Girard and C. Boudene.. 185 Genetic f a c t o r s and acute carbon monoxide i n t o x i c a t i o n M. S t u p f e l , A. Perramn, V.-H. Demaria-Pesce, P . Merat, V. Gourlet and H . Thierry .....................................

189

Water analogue m d e l achieves optimal design o f furnace f l u e gas c o l l e c t i o n system J . Rigard and M. Milhe ........................................

197

Fluoride deposition through p r e c i p i t a t i o n and leaf l i t t e r i n a boreal f o r e s t i n the v i c i n i t y o f a phosphorous plant S.S. Sidhu ....................................................

205

Study of t h e working of a new multicell scrubber applied i n the f i g h t against pollution L. Perdreau, S . Djerid, C. Belin, A. Laurent and J.-C.Charpentier

215 AEROSOLS Application o f thermal analysis t o the characterization of organic aerosol p a r t i c l e s E . C . E l l i s and T. Novakov .....................................

227

On the problem o f measuring and analysis of chemically changed miner a l f i b e r s i n t h e environment and i n biological materials K.R. Spumy ................................................... 239

XI

Formation o f monodisperse l e a d a e r o s o l s and i d e n t i f i c a t i o n o f p a r t i c l e number c o n c e n t r a t i o n by i c e n u c l e a t i o n Y . Ueno, D.E. Rosner, Rosa G. de Pena and J.P. H e i c k l e n ........ 251 O p t i c a l o b s e r v a t i o n d u r i n g chemical r e a c t i o n s H . S t r a u b e l ....................................................

259

Comparison among s i x d i f f e r e n t i n s t r u m e n t s t o determine suspended p a r t i c u l a t e m a t t e r l e v e l s i n ambient a i r J.G. Kretzschmar and J . B. Pauwels

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

265

Some uses o f a d i l u t e r f o r a e r o s o l s J.-C. Guichard .................................................

273

F o r m t i o n and e v o l u t i o n o f s u l f a t e and n i t r a t e a e r o s o l s i n plumes C. Seigneur, P. Saxena and A. B e l l e Hudischewkyj ............... 283 Photography as a t e c h n i q u e f o r s t u d y i n g v i s u a l range T.E. H o f f e r , D.E. Schorran and R.J. F a r b e r

293

E x p e r i m e n t a l s t u d y o n t h e v i s i b i l i t y i n a b s o r b i n g media H. Horvath, J . G o r r a i z and C. Johnson

305

Changes i n l o c a l p l a n e t a r y albedo by a e r o s o l p a r t i c l e s H. Grass1 and M. Newiger

313

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

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

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

Laser t r a n s m i s s o m e t e r - - a d e s c r i p t i o n P.H. Lee, T.E. H o f f e r , D.E. Schorran, E . C . E l l i s and J.W. Moyer

.

B i p o l a r charge e q u i l i b r i u m f o r s p h e r i c a l a e r o s o l s ( minimum f l u x hypothesis ) C.S. L i u , S . Davisson and J.W. Gentry ..........................

321

337

SURVEYS and tXlNITORING

The t h i r d dimension i n t h e Los Angeles B a s i n R.J. Farber, A.A. Huang, L.D. Bregman, R.L. Mahoney,D.J. L.D. Hansen, D.L. B l u m n t h a l , W.S. K e i f e r and D.W. A l l a r d

Eatough,

............ 345

C h a r a c t e r i z a t i o n o f a l o c a l a e r o s o l on a r u r a l s i t e o f t h e Po V a l l e y S. F u z z i , M. M a r i o t t i and G. O r s i

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

361

Comparison o f r e g i o n a l and temporal t r a c e substance d i s t r i b u t i o n i n b u l k p r e c i p i t a t i o n and atmospheric d u s t W . Thomas ......................................................

369

The c h e m i s t r y o f p r e c i p i t a t i o n i n r e l a t i o n t o p r e c i p i t a t i o n t y p e J.A. Warburton

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

379

D a i l y measurements o f atmospheric s u l f a t e s i n P a r i s Y . Le M o u l l e c , F. Coviaux and B. F e s t y ..........................

387

S i z e , shape and e l e m e n t a l a s s o c i a t i o n s i n an urban a e r o s o l R. H a m i l t o n and G. Adie .........................................

393

Subject index Author index

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

403

404

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1

POLLUTION PROBLEMS OF HOT AND DESERT REGIONS

Some r e a d e r s w i l l f i n d t h i s s e c t i o n r a t h e r heterogeneous.

It i s .

T o p i c s such as network d e s i g n and v i s i b i l i t y , m o n i t o r i n g and c a r e o f monuments, problems i n c o a l m i n i n g and p l a n t c o n t a m i n a t i o n by mercury seem t o be enmes hed. The common t r a i t l i n k i n g a l l these t o p i c s t o g e t h e r i s c l i m a t e o r , more a c c u r a t e l y , t h e ambient temperature g o v e r n i n q t h e phenomena.

Some elements

o f c l i m a t e , such as wind o r t u r b u l e n c e , have always been seen as s t r o n g l y influencing a i r pollution.

Temperature was c o n s i d e r e d more o r l e s s o f

secondary importance and t h e d i s t i n c t i o n between temperate, a r c t i c a i r c h e m i s t r y was seldom e v e r made. a i r c h e m i s t r y " seems t o be n o n - e x i s t e n t .

tropical or

The s p e c i a l i t y o f " t r o n i c a l T h i s c h a p t e r i s perhaps a modest

beginning t o r e c t i f y t h i s s i t u a t i o n .

A f u r t h e r p o i n t t o be s t r e s s e d i s t h a t owing t o h i s t o r i c a l reasons, t h e d i s c u s s i o n o f which i s beyond o u r scope here, t h e socio-economic frame of r e s e a r c h i n many t r o p i c a l c o u n t r i e s i s q u i t e d i f f e r e n t f r o m t h a t p r e v a i l i n g i n t h e temperate and c o l d zones.

Social p r i o r i t i e s , a v a i l a b i l i t y o f

adequate manpower, t h e r e l a t i v e w e i g h t o f i n v e s t m e n t i n l a b o r a t o r y f a c i l i t i e s , t h e a v a i l a b l e budgets

...

and much more, a r e d i f f e r e n t .

T h e r e f o r e , t h e answers p r o v i d e d by some o f t h e papers w i t h i n t h i s s e c t i o n w i l l n o t be those which i n t e r e s t a l l r e a d e r s .

Some papers seek avenues

o f i n q u i r y r a t h e r than a p a r t i c u l a r destination.

But i n t h i s context, i t

i s o f t e n more i m p o r t a n t t o f o r m u l a t e t h e r i g h t k i n d o f q u e s t i o n than t o p r o v i d e t h e u l t i m a t e answer.

The p o i n t i s l e s s one o f s o p h i s t i c a t i o n ,

of t h e g e o g r a p h i c a l e x t e n s i o n o f t h e f i e l d o f e n q u i r y .

What has a l r e a d y

been accomplished i n N o r t h America and Europe, must s t i l l be done f o r about 2.10

than

9 people l i v i n g w i t h i n d i f f e r e n t c l i m a t i c b e l t s .

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3

A I R POLLUTION IN TROPICAL AREAS EUGENIO SANHUEZA, MABELL AFRICAN0 and JOHNNY ROMERO I.V.I.C.

Apartado 1827, C a r a c a s , Venezuela

ABSTRACT Air p o l l u t i o n problems i n t h r e e d i f f e r e n t t r o p i c a l a r e a s a r e p r e s e n t e d .

The

l e v e l s o f v a r i o u s atmospheric contaminants ( i . e . S O i ) i n d i c a t e t h a t t h e o p e r a t i o n o f a l a r g e petroleum r e f i n e r y a f f e c t s a s u b s t a n t i a l p o r t i o n o f t h e i s l a n d o f Curacao.

A s i g n i f i c a n t f r a c t i o n o f t h e suspended p a r t i c l e s i n Curacao a r e due t o

n o n - t r a d i t i o n a l open s o u r c e e m i s s i o n s a i d e d by t h e predominantly high w i n d s p e e d s . P a r t i c u l a t e e m i s s i o n s from t h e i n d u s t r i a l complex i n Guayana, Venezuela, n o t i c e a b l y a f f e c t t h e s o r r o u n d i n g savannah.

The c o n s t a n t d i r e c t i o n o f t h e Trade Winds i s an

i m p o r t a n t f a c t o r i n t h e high long-term a v e r a g e p a r t i c u l a t e l e v e l s down-wind o f t h e complex.

A s e r i o u s atmospheric c o n t a m i n a t i o n problem ( i . e . TSP) e x i s t s i n The

Valley o f Caracas.

The high e m i s s i o n , p r i n c i p a l l y due t o t h e c i r c u l a t i o n o f v e h i c l e s ,

exceed t h e a v e r a g e d i s p e r s i o n c a p a c i t y o f t h e atmosphere.

INTRODUCTION T r o p i c s i s a term t h a t has no w e l l - d e f i n e d meaning.

I t i s g e n e r a l l y agreed

t h a t t r o p i c a l a r e a s a r e l o c a t e d between t h e 23.5 degree p a r a l l e l s .

However, some

r e g i o n s w i t h t r o p i c a l c h a r a c t e r i s t i c s a r e found a t l a t i t u d e s g r e a t e r than 23.5", and some n o n - t r o p i c a l a r e a s a r e l o c a t e d c l o s e r t o t h e Equator. Nieuwolt ( r e f . 1 ) s u g g e s t s t h a t c e r t a i n c l i m a t i c c h a r a c t e r i s t i c s can be used t o e s t a b l i s h t h e boundaries o f t r o p i c a l a r e a s .

Some o f h i s c r i t e r i a a r e :

i) t h e absence o f a c o l d w i n t e r season

i i ) a l a r g e r diurnal f l u c t u a t i o n i n temperature than t h e y e a r l y variation i n the d a i l y mean t e m p e r a t u r e ( i n t h e m i d - l a t i t u d e s t h e i n v e r s e i s t r u e ) i i i ) s u f f i c i e n t r a i n f a l l t o support a g r i c u l t u r e without i r r i g a t i o n I t i s u s u a l l y c o n s i d e r e d improbable t h a t t h e a i r i n t r o p i c a l a r e a s can become p o l l u t e d t o harmful l e v e l s .

Petersen ( r e f . 2 ) estimated t h a t t h e a i r pollution

p o t e n t i a l ( i n a b i l i t y o f t h e atmosphere t o d i s p e r s e p o l l u t a n t s ) o f most t r o p i c a l r e g i o n s i s low.

The 1972 F l o r i d a S t a t e Air Implementation Plan s t a t e s "Because o f

t h e general p a t t e r n o f t e r r a i n and t h e t r a d e wind c i r c u l a t i o n , m e t e o r o l o g i c a l condit i o n s t h a t a g g r a v a t e a i r p o l l u t i o n do not o f t e n occur a t any p l a c e i n F l o r i d a " .

4 More r e c e n t l y Ng'ang'a ( r e f . 3 ) Concluded t h a t i n t r o p i c a l r e g i o n s " a i r p o l l u t i o n may not become such a s e r i o u s problem u n l e s s o r u n t i l t h e r a t e o f i n d u s t r i a l i z a t i o n

i s dramatically increased". There a r e however a number o f examples o f p o l l u t i o n problems i n t h e t r o p i c s . G e r r i s h ( r e f . 4 ) found t h a t atmospheric c o n d i t i o n s i n " t r o p i c a l " F l o r i d a could l e a d t o s e v e r e a i r p o l l u t i o n e p i s o d e s . NOx ( r e f . 5 ) and Pb ( r e f . 6 ) l e v e l s measured i n Caracas exceed t h e a i r q u a l i t y s t a n d a r d s e s t a b l i s h e d f o r v a r i o u s c o u n t r i e s . This paper d i s c u s s v a r i o u s c i r c u m s t a n c e s under which r e l a t i v e l y l a r g e t r o p i c a l a r e a s may e x p e r i e n c e a i r p o l l u t i o n problems.

THE ISLAND OF CURACAO Curacao i s a Caribbean i s l a n d l o c a t e d a t 12"North l a t i t u d e , 56 Km from t h e South American c o n t i n e n t . 3.2 and 1 2 . 1 Km.

The t o t a l a r e a i s 466.2 Km2.

The t e r r a i n i s r e l a t i v e l y f l a t with

The average annual m e t e o r o l o g i c a l c o n d i t i o n s (1947 t o 1978)

o n l y a few low h i l l s . are:

I t i s 6 1 . 2 Km l o n g , w i t h a width t h a t v a r i e s between

t e m p e r a t u r e 27.5"C, maximum t e m p e r a t u r e 30,8"C, minimum t e m p e r a t u r e 19.8"C,

r a i n 564.2 mm, w i n d d i r e c t i o n 90°, wind speed 7.2 m/s, and wind s t a b i l i t y 96.5%. I t i s i m p o r t a n t t o mention t h a t t h e d i f f e r e n c e between t h e monthly average temperat u r e o f t h e c o l d e s t and t h e warmest month i s o n l y 2.5"C. A t h r e e month d i a g n o s t i c s t u d y was undertaken t o make a p r e l i m i n a r y assessment

of the i s l a n d ' s a i r quality.

Principal sources include a l a r g e o i l r e f i n e r y i n

S h o t t e g a t Bay and a power p l a n t ( w i t h a sea water d e s a l i n i z a t i o n p l a n t ) .

Fig. 1 is

a p a r t i a l map o f Curacao t h a t shows the p o s i t i o n o f t h e s e s o u r c e s and of t h e f i v e monitoring s i t e s .

P i s c a d e r a i s a t o u r i s t complex w i t h beaches, Wishi i s a low-

income r e s i d e n t i a l a r e a , Buena V i s t a i s a r e s i d e n t i a l a r e a , Blauw i s p r e s e n t l y empty l a n d but i t has p o t e n t i a l f o r t o u r i s t i c o r r e s i d e n t i a l development, Soltuna i s an experimental A g r i c u l t u r a l S t a t i o n . wind r o s e f o r 1973.

Figure 1 a l s o i n c l u d e s a r e p r e s e n t a t i v e

Based on t h e wind i n f o r m a t i o n , v a l u e s measured i n Soltuna a r e

c o n s i d e r e d r e p r e s e n t a t i v e o f background l e v e l s . Almost a l l o f t h e i m p o r t a n t a i r q u a l i t y p a r a m e t e r s were monitored d u r i n g t h e diagnostic study.

The l e v e l o f t o t a l suspended p a r t i c l e s r e p r e s e n t s t h e g r e a t e s t

problem and w i l l be d i s c u s s e d i n d e t a i l , i n c l u d i n g t h e chemical c o m p o s i t i o n .

This

a s p e c t i s o f i n t e r e s t t o environmental s c i e n t i s t s because o f t h e p o t e n t i a l l y hazardous n a t u r e o f c e r t a i n components and because t h e ch,emical composition can be used t o i d e n t i f y s p e c i f i c s o u r c e s . The combustion o f r e s i d u a l f u e l c o n s t i t u t e s art i m p o r t a n t s o u r c e o f primary sulfate (ref.7,8).

Since both t h e r e f i n e r y and power p l a n t burn r e s i d u a l f u e l w i t h

2% o r more S, SO; w i l l be used t o e v a l u a t e i n d u s t r i a l e m i s s i o n s .

Atmospheric l e a d

l e v e l s w i l l be used t o e s t i m a t e t h e i n f l u e n c e o f v e h i c u l a r t r a f f i c and C1- f o r t h e sea s a l t c o n t r i b u t i o n .

5

F i g . 1.

P a r t i a l Map o f Curacao

T a b l e 1 summarizes t h e r e s u l t s o f t h e TSP measurements, t h e s i z e c h a r a c t e r i s t i c s and t h e SO;,

C l - and Pb c o n t e n t .

The SO; v a l u e s have been c o r r e c t e d f o r a r t i f a c t

f o r m a t i o n o f s u l f a t e i n t h e f i b e r g l a s s f i l t e r u s i n g t h e f o r m u l a p r o p o s e d by Coutant (ref.9). T a b l e 1 shows t h a t t h e c o n c e n t r a t i o n s o f TSP, SO; and l e a d a t t h e o t h e r f o u r s t a t i o n s are s i g n i f i c a n t l y higher than a t t h e reference s t a t i o n , Soltuna. l e v e l s o f TSP and SO;

a t Wishi a r e v e r y high.

The

The l e v e l s o f C1- a r e v e r y s i m i l a r

a t a l l f i v e s t a t i o n s , s h o w i n g t h e common sea s a l t s p r a y o r i g i n . The c a l c u l a t e d e n r i c h m e n t f a c t o r s (E.F.)

f o r s u l f a t e and Pb a r e :

P i s c a d e r a (201) > Blauw ( 1 2 6 ) > Buena V i s t a ( 1 0 3 ) > W i s h i ( 8 7 ) and

EFsoi : EFpb : W i s h i ( 4 . 2 ) > Buena V i s t a ( 2 . 0 5 ) > B l a u w ( 1 . 5 ) > P i s c a d e r a (1.4)

The E F ' s were c a l c u l a t e d u s i n g EF ( i ) = ( X / T S P ) i / ( X / T S P ) s o l t u n a Where X i s t h e c o n c e n t r a t i o n s o f SO; o r Pb and i i n d i c a t e s t h e m o n i t o r i n g s t a tion. Based o n t h e EF v a l u e s and t h e d a t a i n T a b l e 1, t h e f o l l o w i n g i n f e r e n c e s c a n be made:

6

Piscadera:

T h i s s t a t i o n has the lowest l e v e l s o f TSP, one of the highest absolute

values o f s u l f a t e s and the l a r g e s t E . F . f o r s u l f a t e s . small vehicular t r a f f i c influence.

The EF f o r lead i n d i c a t e s a

Considering t h e high incidence of s u l f a t e s

associated with small p a r t i c l e s (MMO < 1.Ovm)

i t can be concluded t h a t t h i s part of

the island i s s i g n i f i c a n t l y a f f e c t e d by t h e r e f i n e r y and power p l a n t emissions.

TABLE 1 Total Suspended P a r t i c l e s , SO%, C 1 - and Pb in t h e Curacao Air Site

na

Piscadera Wishi Buena Vista B1 auw Sol tuna

6 5 5 8 2

TSP

MMD

<2.5pm

vm

% ~ 7 5 54.5 58.7 47.3 61.5

~ 1 m 3

a)

60.1 163.7 68.8 68.6 28.6

<1.0

1.8 1.7 2.7 1.4

>7.0pm %

30.0

20.3 26.0 15 .O

so;

ci-

Pb

vg/m3 19.0 22.5 11.2 13.7 0.05

vg/m3 8.43 5.72 6.53 4.29 5.51

w/m3 0.054 0.44 0.089 0.065 0.018

number of samples

Wishi : This r e s i d e n t i a l and commercial area i s q u i t e influenced by vehicular t r a f f i c

as shown by t h e h i g h E F f o r lead.

The highest absolute values f o r s u l f a t e s were found here, demonstrating t h e influence o f the r e f i n e r y emissions. The extremely

h i g h TSP l e v e l s , coupled w i t h the l a r g e percentage o f l a r g e p a r t i c l e s i n d i c a t e t h a t

t h e r e must be a n additional source of p a r t i c l e s .

Lincoln and Rubin ( r e f . 1 0 ) suggest

t h a t most of the p a r t i c u l a t e matter associated with vehicular t r a f f i c i s due t o reentrainment o f road dust r a t h e r t h a n t o p a r t i c l e s emitted d i r e c t l y from the mobile source.

A l a r g e f r a c t i o n of t h e suspended p a r t i c l e s measured a t Wishi must have

been produced by the c i r c u l a t i o n of vehicles aided by the h i g h w i n d speeds observed on the island ( r e f . 1 1 ) . Buena Vista: t i a l area.

As expected, some vehicular t r a f f i c influence i s seen in t h i s residenThe r e f i n e r y plume c r o s s e s t h i s area very i n f r e q u e n t l y and the SO= 4

concentration i s t h e lowest of the four s t a t i o n s . Blauw:

The h i g h s u l f a t e E F i n d i c a t e s the influence of the r e f i n e r y emissions on

the TSP l e v e l s i n Blauw.

I t i s important t o note t h a t t h i s s t a t i o n i s more t h a n

5 Km downwind o f t h e r e f i n e r y .

The various unpaved roads in t h e v i c i n i t y of t h i s

s t a t i o n a r e probably the source o f the l a r g e p a r t i c l e s observed t h e r e (Table 1 ) . There a r e strong i n d i c a t i o n s t h a t the health damage formerly a t t r i b u t e d t o SO; i s caused by acid p a r t i c u l a t e s u l f a t e ( r e f . 1 2 ) .

Community health s t u d i e s (CHESS)

have demonstrated a s u b s t a n t i a l r e l a t i o n s h i p between some types of morbidity and s u l f a t e l e v e l s in t h e 8-12 pg/m3 range ( r e f . 1 3 ) . I n several places i n California w i t h low atmospheric d i s p e r s i o n , t h e l e v e l s o f SO;

5.7 a n d 21.8 pg/m3 ( r e f . 1 4 ) . was 7 . 2 ug/m3 ( r e f . 1 5 ) .

(1972-1973) varied between

In 1976 the average SO,= level f o r 43 Ontario s i t e s

In Caracas, a contaminated t r o p i c a l c i t y , the y e a r l y

average i n 1977 was 5.6 ug/m3 ( r e f . 1 6 ) .

7

Taking t h i s i n t o c o n s i d e r a t i o n , one can conclude t h a t a SO= contamination

4

problem e x i s t s i n p r a c t i c a l l y a l l t h e a r e a downwind o f t h e r e f i n e r y t o a d i s t a n c e o f g r e a t e r t h a n 5 Km.

I t i s l o g i c a l t o suppose t h a t o t h e r contaminants a r e

d i s t r i b u t e d i n t h e same manner.

The p r e s e n c e o f high wind s p e e d s i s u s u a l l y c o n s i d e r e d a f a v o r a b l e meteoroloHowever, a s i g n i f i c a n t f r a c t i o n

g i c a l f a c t o r i n a i r p o l l u t i o n problems ( r e f . 3 ) .

o f t h e suspended p a r t i c l e s i n t h e atmosphere i n Curacao a r e due t o n o n - t r a d i t i o n a l open s o u r c e e m i s s i o n s ( i . e . t r a v e l on paved and unpaved r o a d s , wind e r o s i o n ) aided by the predominantly h i g h w i n d s p e e d s .

Excluding from t h e a n a l y s i s t h e days with

r a i n and t h o s e i n which t h e predominantly wind d i r e c t i o n d e v i a t e d g r e a t l y from t h e normal a r e a s o n a b l e c o r r e l a t i o n between t h e TSP l e v e l s and t h e wind speed was observated. THE GUAYANA INDUSTRIAL COMPLEX

Ciudad Guayana i s a planned i n d u s t r i a l c i t y t h a t was founded i n 1961 t o s e r v e a s t h e urban nucleous o f an i n d u s t r i a l complex i n t h e s o u t h e a s t e r n p a r t o f Venezuela I t i n c l u d e s one o f t h e b i g g e s t s i n g l e i r o n - s t e a l p l a n t s i n t h e w o r l d , a v e r y l a r g e aluminum complex, f e r r o a l l o y p r o d u c t i o n p l a n t s , among o t h e r i n d u s t r i e s . The main e n e r g y s o u r c e f o r t h e i n d u s t r i a l complex i s an h y d r o e l e c t r i c p l a n t . The second most i m p o r t a n t form o f e n e r g y used i s n a t u r a l g a s .

As a r e s u l t , t h e

a t m o s p h e r i c e m i s s i o n s a s s o c i a t e d with e n e r g y use a r e r e l a t i v e l y low. a t m o s p h e r i c e m i s s i o n s g e n e r a t e d by t h e i n d u s t r i a

However, t h e

processes a r e s i g n i f i c a n t .

A

r e c e n t e m i t i o n i n v e n t o r y has found t h a t 3.4 t o n s o f p a r t i c u l a t e m a t t e r per hour a r e e m i t t e d from t h e numerous i n d u s t r i a l s t a c k s

r e f .17).

I t i s i m p o r t a n t t o p o i n t o u t t h a t t h e i n d u s t r a1 complex i s l o c a t e d downwind o f t h e Ciudad Guayana urban development. The plumes d i s p e r s e o v e r c u r r e n t l y undeveloped a r e a s t h a t a r e i m p o r t a n t t o t h e f u t u r e growth o f t h e r e g i o n ( e x p l o i t a t i o n o f t h e Orinoco Heavy O i l B e l t ) .

Mathematical d i s p e r s i o n models have been used t o

e s t i m a t e t h e c o n t a m i n a t i o n l e v e l s i n undeveloped a r e a a t t r i b u t e d t o t h e atmospheric e m i s s i o n s from t h e i n d u s t r i a l complex ( r e f . 1 8 ) . The c a l c u l a t i o n s i n d i c a t e t h a t d u r i n g t h e day, p a r t i c u l a t e l e v e l s h i g h e r t h a n 100 ug/m3 should o n l y e x i s t v e r y c l o s e t o t h e i n d u s t r i a l complex.

Neverthless,

d u r i n g t h e hours w i t h low i r r a d i a t i o n t h e l e v e l s e x a c t l y downwind, exceed 100 pg/m3 o v e r a l a r g e d i s t a n c e r e a c h i n g a maximum o f 400 pg/m3 1 4 Km from t h e s o u r c e s , which

i s m a i n t a i n e d t o a d i s t a n c e o f 23 Km.

Levels h i g h e r t h a n 150 pg/m3 a r e o b t a i n e d

o v e r a downwind width o f a p p r o x i m a t e l y 10 Km a t d i s t a n c e s o f 1 2 t o 19 Km. Ciudad Guayana i s l o c a t e d on a wide savannah. The Trade Winds dominate t h e w i n d patterns.

Around 90% o f t h e time t h e w i n d d i r e c t i o n f l u c t u a t e s between E and NE.

C o n s i d e r i n g t h a t t h e plume d i s p e r s e s p r e f e r e n t i a l l y o v e r t h e same a r e a and t h a t t h e n i g h t time d i s p e r s i o n ( r a d i a t i v e i n v e r s i o n ) i s low, i t i s l i k e l y t h a t t h e

8

annual T . S . P .

a v e r a g e s exceed t h a a i r q u a l i t y

standards i n relatively extensive

area.

TABLE 2 Suspended p a r t i c l e s and b e n z o ( a ) pyrene c o n c e n t r a t i o n s (pg/m3) i n downtown Caracas a s a f u n c t i o n o f p a r t i c l e s i z e a t two d i f f e r e n t h e i g h t s . Aerodynamic d i a m e t e r s um

Suspended P a r t i c l e s 56ma 5mb

>7.2 7.2 -3.0 3 . 0 -1.5 1 . 5 -0.95 0.95-0.49 ~0.49 TOTAL a)

average of 3 days;

b)

56ma

B(a)PC 5mb

21.6 18.0 7.3 5.5 6.2 36.6

10.9 15 .O 8.6 5.7 5.2 31.6

0.18 0.094 0.11 0.083 0.10 6.99

0.096 0.094 0.102 0.079 0.102 5.88

95.2

77.0

7.56

6.35

average of 6 days. c )

x

lo3.

THE CARACAS VALLEY Caracas i s l o c a t e d a t 10.30"N and 66.7"E a t an a l t i t u d e o f 996 m above sea l e v e l i n a v a l l e y sorrounded by mountains w i t h peaks a s high a s 2600 m . The p o p u l a t i o n There a r e i s a p p r o x i m a t e l y 2.5 m i l l i o n w i t h a c a r d e n s i t y o f %I000 vehicles/Km

.

v e r y few i n d u s t r i e s .

The a v e r a g e t e m p e r a t u r e r a n g e s from 18" t o 23°C.

Almost

e v e r y day, a t e m p e r a t u r e i n v e r s i o n forms i n t h e v a l l e y a t n i g h t and b r e a k s u p between 10 and 11 i n t h e morning. Previous p a p e r s have shown t h a t t h e p r i n c i p a l a i r p o l l u t i o n problems i n Caracas a r e r e l a t e d t o the a t m o s p h e r i c c o n c e n t r a t i o n o f primary p o l l u t a n t s ( r e f . 5 , 6 , 1 9 ) . Since t h e i n v e r s i o n b r e a k s u p b e f o r e noon a l l the s t e p s condusive t o t h e p r o d u c t i o n o f p r i n c i p a l components i n t h e c l a s s i c a l photochemical smog do n o t o c c u r . The r e p o r t e d l e v e l s o f TSP a r e r e l a t i v e l y h i g h .

The annual geometric mean f o r Since t h e formation

t h e sampled y e a r i n downtown Caracas was 95.7 ug/m3 ( r e f . 2 0 ) .

o f l a r g e amounts o f secondary p a r t i c l e s i s n o t p r o b a b l e , most o f t h e suspended p a r t i c l e s found were e m i t t e d t o t h e atmosphere (mainly by v e h i c u l a r c i r c u l a t i o n ) . I t i s o f i n t e r e s t t o i n v e s t i g a t e the s i z e d i s t r i b u t i o n o f t h e p a r t i c l e s .

Using a high volume c a s c a d e impactor t h e p a r t i c l e s i z e o f suspended p a r t i c u l a t e has been d e t e r m i n e a t two d i f f e r e n t h e i g h t s (5 and 56 m ) . The B(a)P c o n t e n t a l s o has been e v a l u a t e d .

Table 2 summarizes t h e r e s u l t s .

Ta bl e 2 shows t h a t s i m i l a r r e s u l t s a r e o b t a i n e d a t both h e i g h t s .

This i n d i c a t e s

t h a t t h e suspended p a r t i c l e l e v e l s based on a 24 hour c o l l e c t i o n p e r i o d a r e independent o f t h e sampling h e i g h t .

Hence i n Caracas t h e r e i s r a p i d t u r b u l e n t mixing

d u r i n g the p e r i o d o f most abundant e m i s s i o n ( t r a f f i c ) . The lognormal f u n c t i o n i s w i d e l y used t o r e p r e s e n t t h e size d i s t r i b u t i o n o f the p a r t i c l e s t h a t compose t h e a t m o s p h e r i c a e r o s o l s ( r e f . 2 1 ) . Figure 2 shows the r e s u l t s o f t h i s s t u d y p l o t t e d on a l o g p r o b a b i l i t y s c a l e .

The MMD's o b t a i n e d

9 compare w e l l w i t h t h o s e f o r o t h e r c i t i e s ( r e f . 2 1 ) . l i n e a r i t y f o r p a r t i c l e s g r e a t e r t h a n 3 . 0 pm.

There i s a marked l o s s o f

T h i s i m p l i e s t h a t i n Caracas t h e r e

i s a s i g n i f i c a n t source o f l a r g e p a r t i c l e s o t h e r t h a n combustion sources.

Most

p r o b a b l y t h e l a r g e p a r t i c l e s a r e e m i t t e d f r o m n o n - t r a d i t i o n a l open s o u r c e s such as t h e c i r c u l a t i o n o f v e h i c l e s o n d u s t - f i l l e d s t r e e t s and c o n s t r u c t i o n a c t i v i t i e s . I t i s i m p o s s i b l e t o c a l c u l a t e t h e MMD o f t h e p a r t i c l e s c o n t a i n i n g B ( a ) P s i n c e

93% o f t h e m were n o t s e p a r a t e d ( p a r t i c l e s <0.45 pm). i s <0.15pm.

We e s t i m a t e t h a t t h e MMD

The p r e s e n c e o f B ( a ) P i n t h e s m a l l e s t p a r t i c l e s c a n be e x p l a i n e d i f

t h e c o n t a m i n a n t s r e m a i n i n t h e Caracas a t m o s p h e r e o n l y a s h o r t t i m e and t h e maj o r i t y o f t h e B(a)P c o l l e c t e d i s associated w i t h r e c e n t l y e m i t t e d p a r t i c l e s .

The

MMD measured i n a s u b - u r b a n a r e a i n f l u e n c e d b y e m i s s i o n s i n Caracas was 0.44um. I t i s now c l e a r t h a t t h e i n f l u e n c e o f suspended p a r t i c l e s o n h e a l t h depends o n

t h e i r penetration i n t o the respiratory t r a c t .

The m o s t damaging f r a c t i o n s a r e

t h e i n h a l a b l e p a r t i c l e s ( < 15 p m ) and t h o s e c a p a b l e o f r e a c h i n g t h e l u n g s ( < 2 . 5 p m ) . A c c o r d i n g t o f i g u r e 2, a p p r o x i m a t e l y YO% o f t h e p a r t i c l e s i n Caracas a r e i n h a l a b l e and 65% c a n p e n e t r a t e i n t o t h e g a s - i n t e r c h a n g e a r e a . S i n c e t h e TSP a n n u a l a v e r a g e i n Caracas i s s u b s t a n t i a l l y g r e a t e r t h a n 75 1.1g/m3 ( r e f . 2 0 ) and a h i g h percentage o f these p a r t i c l e s a r e s u f f i c i e n t l y small t h a t t h e y p e n e t r a t e d e e p l y i n t o t h e r e s p i r a t o r y t r a c t , t h i s " t r o p i c a l " c i t y has a s e r i o u s a t m o s p h e r i c p o l l u t i o n p r o b l e m due t o p a r t i c l e s . SUMMARY AND CONCLUSIONS Three s i t u a t i o n s w i t h v e r y d i f f e r e n t c h a r a c t e r i s t i c s have been p r e s e n t e d . each one, pollution.

In

i t has been shown t h a t a t r o p i c a l a r e a c a n be s e r i o u s l y a f f e c t e d b y a i r

The p r e d o m i n a n t m e t e o r o l o g i c a l c o n d i t i o n s i n t h e t r o p i c s , g e n e r a l l y

c o n s i d e r e d t o be f a v o r a b l e f o r m i n i m i z i n g t h e i n f l u e n c e o f a i r p o l l u t i o n , c a s e s o n c i r c u m s t a n c e s may a c t u a l l y worsen t h e p r o b l e m .

i n some

Good d i s p e r s i o n c o n d i -

t i o n s p r e v a i l i n Caracas m o s t o f t h e day, however, t h e e m i s s i o n s exceed t h e d a i l y average d i s p e r s i o n capacity,

r e s u l t i n g i n h i g h atmospheric contamination l e v e l s .

ACKNOWLEDGEMENTS We w i s h t o t h a n k K a t h y H. O c t a v i o f o r u s e f u l d i s c u s s i o n .

R o l a n d M a r t ? and

Enigma G i j s b e r k h a f o r t h e i r f i e l d w o r k i n Curacao and Z y n n i a T o l l i n c h e f o r t h e preparation o f t h e manuscript. REFERENCES

1 S. N i e u w o l t , T r o p i c a l C l i m a t o l o g y , An I n t r o d u c t i o n t o t h e C l i m a t e s o f t h e Low L a t i t u d e s , John W i l e y and Sons, New York, 1977, p . 1 . 2 S . P e t e r s e n , B u l l . Amer. M e t e o r . SOC. 47(1966)950-963. 3 J.K. N g ' a n g ' a , Water, A i r and S o i l P o l l . , 1 3 ( 1 9 8 0 ) 2 7 - 3 4 . 4 H.P. G e r r i s h , Miami I n t e r a c t i o n , 4 ( 1 9 7 2 ) 2 1 - 2 4 . 5 E. Sanhueza and J. Romero, J. A i r P o l l . C o n t r o l Ass., 28(1978)157-158. 6 L. E s c a l o n a and E. Sanhueza, Atrnos. E n v i r o n . , 1 5 ( 1 9 8 1 ) 6 1 - 6 4 . 7 J.B. Homolya and C.R. F o r t u n e , Atmos. E n v i r o n . , 12(1978)2511-2514.

10 8 9 10 11 12 13 14 15 16 17

18 19 20

21

J . 8 . Homolya and S . Lambert, J . A i r P o l l . Control Ass., 31(1981)139-143. R.W. C o u t a n t , Environ. S c i . Technol ., 11(1977)673-878. D.R . L i n c l o l n and E.S. Rubin, J . Air P o l l . Control Ass., 30(1980)777-781. J.S. Evans, S.E. Spedden and D.W. Cooper, J . Air P o l l . Control A s s . , 3 1 ( 1981) 395 -397. P o s i t i o n Paper on R e g u l a t i o n o f Atmospheric S u l f a t e s , U.S. Environmental P r o t e c t i o n Agency, EPA-450/275-007, S e p t . 1975. A . P . A l t s h u l l e r , Environ. S c i . Technol ., 7(1973)709-712. B.R. Appel, E . L . Kothny, E . M . H o f f e r , G . M . Hidy and J . J . Wesolowski, Environ. Sci Technol . 12( 1978)418-425. K . C . Heidorn, J . Air P o l l . Control Ass., 28(1978)803-806. E . Sanhueza, C h . I s h i z a k i , M . Africano and R . Pefia, Atmos. Environ. 13 ( 1979) 1205- 1208. E . Sanhueza, A . Anselmi, J . Romero, K . H . Octavio and J.C. S i n c h e r , I n v e n t a r i o de Emisiones Atmosf6ricas Para e l Area de Proyecto D.S.M.A., Final Report, INTEVEP, Venezuela, 1980, 85pp. E. Sanhueza and K . H . O c t a v i o , Estimaci6n de 1 0 s N i v e l e s de Contaminantes en e l Area Ubicada a1 Sur del R i o Orinoco y Oeste del Complejo I n d u s t r i a l de Matanza, Technical Report, INTEVEP, Venezuela, 1981, 27pp. C h . I s h i z a k i , E. Sanhueza and J . Romero, Chemosphere, 6(1978)517-536. E. Sanhueza, Ch. I s h i z a k i and M. A f r i c a n o , Acta C i e n t i f . Venezolana, 30(1979) 425-427. R . E . Lee, J r . and S. Goranson, Environ. S c i . Technol., 10(1976)1022-1027.

.

10.0r

5.0c

E 4.0-

-a 3.0W I-

w 2.02 Q 1.5w

J

0 1.0l0:

2 0.80.4-

0.3I

10

Fig. 2 .

1

l

l

l

l

l

l

20 30 40 50 60 70 80

I

1

90 95 CUMULATIVE PERCENT MASS S PARTICLE DIAMETER

1

98

Downtown Caracas p a r t i c l e - s i z e d i s t r i b u t i o n c u r v e s .

11

TRENDS IN OZONE CONCLNTRATIONS IN JERUSALEM

STEINBERGER Dept. of Atmospheric Sciences, The Hebrew University, Jerusalem E.H.

ABSTRACT Ozone concentrations have been measured in Jerusalem since 1977 by a chemiluminescent ozone meter. During the l a s t f i v e years ozone l e v e l s have

increased considerably. In order t o t e s t whether t h i s increase r e f l e c t e d the growth i n t h e number of motor vehicles o r was caused by atmospheric conditions, t h e summer data of the l a s t f i v e years were analyzed. Ozone l e v e l s were characterized by the d a i l y one-hour maxima; the atmospheric f a c t o r s considered were temperature, i n s o l a t i o n and s t a b i l i t y . A multiple regression equation was computed and a c o r r e l a t i o n c o e f f i c i e n t r = 0.77 obtained. The yearly mean reduced ozone l e v e l s showed a d e f i n i t e trend, which r e f l e c t e d the corresponding trend i n t h e number of motor vehicles. INTRODUCTION One of t h e aims of a i r p o l l u t i o n monitoring is t h e detection of trends i n p o l l u t a n t concentrations. The p r a c t i c a l applications of such information can r e a d i l y be seen; f o r example i f the ambient concentration of a given pollutant seems t o be increasing, than t h e emission standards f o r t h a t p o l l u t a n t may have t o be reduced. However, trend a n a l y s i s of atmospheric variables over a period of years i s f a r from easy. The actual value of such an element i s usually determined by several f a c t o r s , which i n turn may vary, e i t h e r randomly, o r periodically with time. ( r e f . 1 ) . In order t o evaluate possible trends i n ozone concentrations, several variables have t o be considered. The ozone concentration a t a given time and place w i l l b e determined by the production, d e s t r u c t i o n and t r a n s p o r t processes. The necessary conditions f o r ozone production a r e adequate amounts of NO2, hydrocarbons and s o l a r r a d i a t i o n , while the main d i s t r u c t i o n process i s the reaction of ozone w i t h NO. Transport processes a r e determined by the prevailing atmospheric condit i o n s , such a s s t a b i l i t y , wind v e l o c i t y and others. The reacting molecular species a r e emitted i n t o the atmosphere mainly by motor vehicles. Their concentration will depend o n the number of sources, and

12

a l s o o n atmospheric f a c t o r s , such a s temperature. Solar r a d i a t i o n and temperature e x h i b i t diurnal and seasonal v a r i a t i o n s , a p a r t from random changes. The o t h e r r e l e v a n t f a c t o r s vary with time in a complex manner. I t follows t h e r e f o r e t h a t any changes in ozone concentration w i t h time have t o be examined in conjunction with these v a r i a b l e s , i n order t o determine whether these changes r e f l e c t corresponding v a r i a t i o n s of t h e relevant parameters o r i n d i c a t e real trends i n ozone concentrations. EXPERIMENTAL METHODS The concentration of ozone i n Jerusalem has been measured continuously s i n c e 1977; by means of a chemiluminescent ozone meter. The instrument was c a l i b r a t e d regularly and exhibited good s t a b i l i t y . Ozone concentrations were expressed as one-hour averages i n u n i t s of p a r t s per b i l l ion per volume (ppb). The r e s u l t s of t h e measurements were summarized i n terms of d a i l y average concentration, mean monthly diurnal v a r i a t i o n and the maximal one-hour concentration measured each day. I t was noticed t h a t during t h e period of f i v e years ozone l e v e l s increased, e s p e c i a l l y t h e maximal values. I t was t h e r e f o r e decided t o t e s t s t a t i s t i c a l l y whether t h i s change with time indicated a real trend o r could be accounted for by v a r i a t i o n s i n the relevant meteorological f a c t o r s . In order t o eliminate diurnal and seasonal cycles, both i n ozone values and meteorological parameters, t h e following procedure was adopted: Ozone concentrations were expressed by t h e i r d a i l y maximum value. Since the maximum level occurred i n almost a l l cases between 14-16 hours L.S.T., the diurnal v a r i a t i o n was minimized. Furthermore, only data obtained d u r i n g t h e summer months May-August were used, thereby reducing t h e influence of t h e seasonal cycle. The r e l e v a n t meteorological parameters considered were temperature, s o l a r r a d i a t i o n f l u x , atmospheric s t a b i l i t y and wind v e l o c i t y , The temperature and

wind v e l o c i t y values were measured a t the same time a s t h e ozone maxima occurred. Atmospheric s t a b i l i t y was defined as 1000/H, where H was t h e m i x i n g depth, Solar r a d i a t i o n f l u x ( i n meters), measured each day a t about 13 hours L.S.T. was expressed i n terms of t h e d a i l y t o t a l , i n order t o exclude diurnal v a r i a t i o n s and random u n c h a r a c t e r i s t i c f l u c t u a t i o n s within t h e hour o f measurement. Variance a n a l y s i s showed t h a t w i t h i n each year t h e average monthly values ( f o r May-August) of a l l the v a r i a b l e s were not s i g n i f i c a n t l y d i f f e r e n t , therefore y e a r l y averages could be computed and compared. A preliminary multiple-regression a n a l y s i s showed t h a t the influence of wind v e l o c i t y was n e g l i g i b l e , and therefore omitted from f u r t h e r analyses.

13

N

6oc

50C

+ I

N

I

I 6

rn

rloc Figure 1 .

1977

1978

1979

1980

1981

(a) Y e a r l y average ozone maxima ; ( b ) y e a r l y average n o r m a l i z e d ozone maxima (y), and v e h i c l e numbers, i n thousands,(N).

14

RESULTS

The mean y e a r l y values of ozone, temperature, i n s o l a t i o n and s t a b i l i t y parameters, and t h e numbers of days a r e given i n Table 1 . Var.

1977

1978

1979

1980

03 T

49.1

43.9

54.9

57.0

27.6

30.0

30.0

28.2

30.9

29.4

I

625.2

528.4

694.0

630.4

635.0

622.6

2.94

S

N

1.34

103

Table 1 .

2.34

95

92

2.94 97

1981 6.32

2.34 98

Fi ve-yr Mean 53.6

2.38 485

Yearly average values of ozone maxima, O3 i n ppb, temperature

T i n degrees c e n t r i g r a d e , i n s o l a t i o n I i n cal.cm-2 m i n . parameter S .

-1 and s t a b i l i t y

I t can be seen from Table 1. t h a t during the period of t h i s study t h e mean maximal ozone l e v e l s have, i n general, increased. There was no corresponding v a r i a t i o n i n the values of the meteorological parameters; except f o r 1978, when both I and S were minimal, no systematic change can be noticed and t h e small f l u c t u a t i o n s a r e not s t a t i s t i c a l l y s i g n i f i c a n t . A m u l t i p l e regression equation of the type ( 1 ) O3 = a + b [T - TA) + c (I - IA) + d + ( S - SA) was computed f o r a l l the data and a t o t a l c o r r e l a t i o n c o e f f i c i e n t r = 0.77 obtained. For each data s e t t h e dimensionless parameter y. r e f e r r e d t o a s "normalized" ozone level and defined as t h e r a t i o of the measured ozone value t o the value computed by eq. ( l ) , was calculated. Then t h e mean value of y f o r each year was obtained. The r e s u l t s a r e presented below. Year

1977

1978

1979

1980

1981

Five-year mean

Y

0.892

0.925

0.995

1.036

1.160

1.008

The general growth trend can c l e a r l y be seen here and the trend l i n e f i t t e d t o t h e data i n d i c a t e s a y e a r l y growth r a t e of about 6.5% i n ozone maxima. I t may be noted t h a t t h e low ozone values i n 1978 can, a t l e a s t p a r t i a l l y , be explained by the unusually low i n s o l a t i o n and s t a b i l i t y parameter values which prevailed then.

15

F i g u r e 2.

( a ) Y e a r l y average ozone maxima ( 0 ) vs. number o f v e h i c l e s i n thousands

3 (N) ; ( b ) y e a r l y average normalized ozone maxima vs. N .

16

In trying t o explain the reasons f o r the increase in ozone levels, which could not be attributed t o meteorological factors, the annual changes in source strengths may be examined. Since ozone precursors are emitted by motor vehicles, t h e i r yearly variations were obtained. Vehicle numbers were expressed i n terms of the total quantity i n Israel on the l a s t day of each calendar year, for the purpose of t h i s study for the following reason: I t has been shown ( r e f . 2 ) , t h a t the maximal ozone concentration in Jerusalem during the summer months was usually due t o transport from the coastal area, where more t h a n 60% of the total number o f vehicles i n the country are concentrated. Therefore i t can be assumed t h a t the variations i n the total number of vehicles r e f l e c t the corresponding changes in the coastal area, and in Jerusalem i t s e l f . Figure 1 . i l l u s t r a t e s the trends in vehicle numbers and the changes in the yearly average maximum ozone levels ( l a ) , and the normalized ozone levels, (16). I t should be mentioned, that a t the time of w r i t i n g the total number of vehicles f o r 1981 has n o t y e t been published and the number used here has been estimated both by extrapolating from the results of the l a s t seven years and from partial results supplied by the I s r a e l i Central S t a t i s t i c s Bureau. Finally, ozone values were plotted as a function of vehicle numbers. The r e s u l t s are shown i n Fig. 2 . , (a) and ( b ) . I t can be seen, t h a t the f i t i s much better f o r the normalized ozone concentrations, [Fig. 2 ( b ) ] , t h a n f o r the measured ozone levels [Fig. 2 ( a ) ] , demonstrating the influence of the meteorological parameters. DISCUSSION AND CONCLUSIONS I t has been shown t h a t during the p a s t f i v e years ozone levels have increased i n Jerusalem. The influence of several meteorological parameters (temperature, solar radiation, atmospheric s t a b i l i t y and wind speed) was examined. I t was found t h a t the f i r s t three variables influenced significantly the measured ozone levels, b u t wind speed was not a n important parameter. Although b o t h the Gaussian and the box models predict an inverse dependence of pollutant concentration on wind speed, experimental evidence suggests that during the summer months pollutant concentrations are not influenced by the wind speed, ( r e f . 3). The yearly averages of the normalized ozone levels showed a steady increase, o f about 6.5% per year. T h i s apparent trend could be explained by n o t i n g t h a t emission sources, a.e. the number of motor vehicles, have also increased d u r i n g t h i s time period REFERENCES 1 ) R.E. Munn, Environ, Monit. Assesment, (1981), 1 , 49-58 2 ) E.H. Steinberger, Atmospheric Pollution, (1980r, Elsevier, Amsterdam, Ed. M. Benarie 165-172 3) M.M. Benarie, :bid, 49-53

17

BACKGROUND CONTINENTAL OZONE LEVELS I N THE RURAL U.S.

SOUTHWEST DESERT

THOMAS E. HOFFER Desert R e s e a r c h I n s t i t u t e , Reno, Nevada (U.S.A.)

ROBERT J. FARBER and ELIZABETH C. ELLIS R e s e a r c h and Development, S o u t h e r n C a l i f o r n i a Edison Company, Rosemead, C a l i f o r n i a

(U. S.A. )

ABSTRACT From 1969 t h r o u g h

a i r q u a l i t y m o n i t o r i n g program,

1978 a n e x t e n s i v e ambient

i n c l u d i n g t h e measurement

of a t m o s p h e r i c c o n c e n t r a t i o n s of

ozone,

h a s been conUsing a Monitor

d u c t e d i n a r e m o t e s e c t i o n of t h e d e s e r t i n t h e s o u t h w e s t e r n U.S.

t h e s e l e v e l s were measured a t o p a small

Labs c h e m i l u m i n e s c e n t ozone i n s t r u m e n t ,

mountain 500 f e e t above t h e v a l l e y f l o o r of t h e Colorado R i v e r .

During t h e w i n t e r

months, when t h e p r e v a i l i n g low l e v e l w i n d s are n o r t h e r l y i n t h i s r u r a l c o n t i n e n t a l background l e v e l s of ozone are a t t a i n a b l e . ozone

data

base,

13 of

selected for analysis.

these

representative

high

ozone minimum o c c u r r i n g from 0800-1000

From t h i s c o n t i n u o u s

pressure

Results i n d i c a t e a very d i s t i n c t

river valley,

periods

diurnal

have

been

t r e n d w i t h an

h o u r s Mountain S t a n d a r d T i m e (MST) and a n

ozone maximum from 1600-1900 h o u r s MST.

Ozone c o n c e n t r a t i o n s r a n g e from a low of

19 ppb t o a h i g h of 4 4 ppb w i t h t h e d i u r n a l p a t t e r n e x h i b i t i n g marked r e p e a t a b i l i t y w i t h r e s p e c t t o t i m e of minima and maxima,

s e a s o n a l c h a n g e s and c o n c e n t r a t i o n

levels.

INTRODUCTION From 1969 t o t h e p r e s e n t a n e x t e n s i v e a i r q u a l i t y m o n i t o r i n g program, i n c l u d i n g t h e measurement o f a t m o s p h e r i c c o n c e n t r a t i o n s of been

conducted

in

the vicinity

of

l o c a t e d 30 miles n o r t h of N e e d l e s , known as t h e Mohave V a l l e y .

the

ozone and n i t r o g e n o x i d e s ,

1580 MW Mohave

coal-fired

has

power. p l a n t

C a l i f o r n i a n e a r t h e Colorado R i v e r ,

a region

The p r i m a r y o b j e c t i v e s of t h i s program are t o monitor

18 t h e a m b i e n t a i r q u a l i t y i n t h i s r e m o t e r u r a l d e s e r t environment and t o d e t e r m i n e t h e r e l a t i v e i m p a c t from t h e Mohave G e n e r a t i n g S t a t i o n (Ref.

1).

The g e o g r a p h i c a l

l o c a t i o n i n c o m b i n a t i o n w i t h t h e s y n o p t i c m e t e o r o l o g i c a l p a t t e r n s p r o v i d e a unique o p p o r t u n i t y to c o n t i n u o u s l y m o n i t o r c o n t i n e n t a l background l e v e l s of g e o g r a p h i c a l l o c a t i o n and s a m p l i n g c o n f i g u r a t i o n are shown i n Fig. l i n g sites are positioned

i n a north-south

alignment along

the

ozone.

1.

The

The samp-

Colorado

River

because t h e topographical channeling of t h e r i v e r v a l l e y produces n o r t h o r south winds a b o u t 90% of t h e time. Background o r n a t u r a l c o n c e n t r a t i o n s of

I n l i g h t of

studies. separate

t h e f e d e r a l EPA s t a n d a r d of

t h e background

s.(Ref.

Singh,

levels

21,

of

reported

ozone average

from

the

120 ppb,

it

several

is important t o

anthropogenic

contributions.

ozone c o n c e n t r a t i o n s a t remote

sites

and 48"N t o r a n g e from 20 t o 50 ppb w i t h e x c u r s i o n s above

between l a t i t u d e s 19'N

They found t h a t t h e predominant s o u r c e of t r o p o s p h e r i c ozone a r i s e s from

80 ppb.

stratospheric (Ref.

ozone have been t h e f o c u s of

injections.

4 ) reached

Derwent

sg.

Derwent

et

al.

(Ref.

3 ) and

Chatfield

and

s i m i l a r conclusions a t varying l o c a t i o n s throughout

(Ref.

Harrison

t h e world.

3 ) a l s o n o t e d s h o r t p e r i o d s of e l e v a t e d ozone a t 100 ppb.

Fig.

1.

Mohave V a l l e y m o n i t o r i n g s t a t i o n s .

19 AN A I R QUALITY SAMPLING PROGRAM I N THE MOHAVE VALLEY

I n s t r u m e n t a t i o n and C a l i b r a t i o n i t i s c r i t i c a l l y impor-

Because r u r a l ozone l e v e l s a r e i n t h e lower ppb range, t a n t t o have a n i n s t r u m e n t w i t h t h e p r e r e q u i s i t e

This

accuracy.

An

o u r a i r m o n i t o r i n g network i s t h e q u a l i t y a s s u r a n c e program.

i m p o r t a n t p a r t of

Ozone measurements were made u s i n g a Monitor analyzer.

s e n s i t i v i t y and

analyzer

has

been

Labs Model 8410A chemiluminescent

calibrated

monthly

against

1003-AH u l t r a v i o l e t ozone a n a l y z e r which i n t u r n i s t r a c e d

a

Dasibi

Model

back t o a s t a n d a r d

u l t r a v i o l e t ozone photometer o p e r a t e d by t h e C a l i f o r n i a Air Resources Board.

An

independent g r o u p h a s provided q u a l i t y a s s u r a n c e a u d i t s f o r t h e ozone measurements between t h e summer of 1977 t o t h e p r e s e n t . R e s u l t s of

s i x q u a r t e r l y a u d i t s of

s q u a r e s r e g r e s s i o n of y = 0 . 9 6 7 ~

t h e measured ozone r e s p o n s e show a l e a s t

-0.01

w i t h r 2 = 0.96 where r i s t h e c o r r e l a -

A t a 95% c o n f i d e n c e i n t e r v a l t h e s l o p e i s between 0.862

tion coefficient.

A r e a s o n a b l e upper

1.072.

+

limit

estimate of

the

error

associated with

and these

measurements i s between 10 t o 15%.

A p o t e n t i a l l y i m p o r t a n t parameter t o t h e ozone c y c l e i s t h e c o n c e n t r a t i o n l e v e l of n i t r o g e n o x i d e s .

T h i s measurement i s even more d i f f i c u l t t h a n t h a t f o r ozone

In t h i s study the

because of t h e p u r p o r t e d l y v e r y low r u r a l ppb l e v e l s of NO2.

measured NO2 c o n c e n t r a t i o n s were made u s i n g a new Columbia S c i e n t i f i c I n d u s t r i e s Model

1600 chemiluminescent

instrument.

This

analyzer

can

detect

NO2

levels

between 3 t o 5 ppb w i t h a n a c c u r a c y of 15 t o 20%.

Sampling P r o t o c o l and S y n o p t i c M e t e o r o l o g i c a l Regimes During t h e w i n t e r months f o r f a i r w e a t h e r p e r i o d s t h e P a c i f i c S u b t r o p i c a l High e x t e n d s i n t o t h e d e s e r t southwest.

T h i s t y p i c a l p a t t e r n (shown i n Fig.

2 a t the

500 mb l e v e l o r a b o u t 5.6 km) can p e r s i s t f o r s e v e r a l days a s t h e l o n g wave r i d g e p o s i t i o n becomes f i r m l y e s t a b l i s h e d o v e r t h i s p a r t of t h e w e s t e r n U.S.

The r e s u l t

i s c l e a r s k i e s , w i t h n o r t h e r l y winds a l o f t which o f t e n extend down t o t h e surface.

During t h i s

period

t h e Great

Basin

surface high

(Fig.

3 ) becomes w e l l

e s t a b l i s h e d o v e r t h e c o l d e r , h i g h e r desert p l a t e a u , g i v i n g rise t o predominantly n o r t h e r l y winds i n t h e Mohave Valley.

These a r e o f t e n l o c a l l y i n t e n s i f i e d i n t h i s

a r e a because of t h e t o p o g r a p h i c a l c h a n n e l i n g e f f e c t of t h e Colorado R i v e r Valley. When s u r f a c e g r a d i e n t s a r e l i g h t , o c c a s i o n a l l y l o c a l topography dominates, g i v i n g r i s e t o up-slope,

o r s o u t h e r l y b r e e z e s f o r a c o u p l e of hours i n t h e l a t e a f t e r n o o n

a t t h e t i m e of maximum h e a t i n g . i s f a r t o t h e n o r t h of

expected.

During t h i s p e r i o d (Fig.

2) t h e t r o p o s p h e r i c j e t

t h i s r e g i o n w i t h minimal s t r a t o s p h e r i c

ozone i n t r u s i o n s

A s t h e l o n g wave r i d g e p o s i t i o n s h i f t s s l o w l y e a s t w a r d , s o u t h e r l y winds

b o t h a l o f t and a t t h e s u r f a c e b e g i n t o i n c r e a s e i n f r e q u e n c y and speed wi.th t h e p o t e n t i a l f o r a d v e c t i o n of a d i f f e r e n t airmass.

20

Fig. 2. N a t i o n a l Weather S e r v i c e 500 mb (5.6 km) analysis 0500 MST, Nov. 5, 1976, showing s t r o n g l o n g wave h i g h p r e s s u r e r i d g e o v e r S o u t h w e s t e r n U.S.

Fig. 3. N a t i o n a l Weather S e r v i c e C h a r t a t 1100 MST, Feb. 8, 1979, d e p i c t i n g G r e a t Basin High o v e r S o u t h w e s t e r n U.S.

Fig. 4. N a t i o n a l Weather S e r v i c e 500 mb (5.6 km) a n a l y s i s 1700 MST, Dec. 6, 1978, depicting "Nevada Low" c o l d o u t b r e a k , and tropospheric jet stream a f f e c t i n g S o u t h w e s t e r n U.S.

21 Another s y n o p t i c p a t t e r n of i n t e r e s t i s shown i n Fig. is

just

beginning

to

build

into

t h e area w i t h

the tropospheric jet

4.

Here t h e 500 mb r i d g e

"Nevada Low"

still

giving

During t h i s p e r i o d t h e 500 mb h e i g h t s are low

c y c l o n i c flow t o t h e Mohave Valley. and

the

i s d i r e c t l y a f f e c t i n g t h e Mohave V a l l e y w i t h maximum Winds are c o n s i s t e n t l y n o r t h e r l y both on t h e

s t r a t o s p h e r i c i n t r u s i o n s possible.

s u r f a c e and a l o f t and t h e s k i e s are clear. These two g e n e r a l t y p e s of October and g r a d u a l l y end between 13" t o L8'C

p a t t e r n (Figs.

by l a t e A p r i l .

2-4)

g e n e r a l l y o c c u r beginning i n

Daytime maximum t e m p e r a t u r e s average

w i t h n i g h t t i m e minimums above f r e e z i n g .

Relative humidities

are low, g e n e r a l l y l e s s t h a n 20%. I n t h e p r e s e n c e of t h e s e h i g h p r e s s u r e r i d g e s , a v e r y r e g u l a r d i u r n a l i n v e r s i o n p a t t e r n occurs.

From e a r l y e v e n i n g u n t i l abour 1000-1200 MST h o u r s t h e f o l l o w i n g

morning, a w e l l developed surface-based d e p t h of

radiational inversion i s established to a

150 t o 300 m and a s t r e n g t h of

inversion i s dissipated,

5°C t o 10°C.

U s u a l l y by 1200 MST t h e

l e a v i n g a n e u t r a l s t a b i l i t y atmosphere w i t h w i n t e r t i m e

mixing d e p t h s t o a b o u t 600-YO0 m AGL. Given t h e above s y n o p t i c c o n s i d e r a t i o n s , D R I Mountain ( F i g .

1) w a s s e l e c t e d as

t h e s t u d y s i t e f o r ozone measurements and K a t h e r i n e Landing,

immediately t o t h e

n o r t h , was s e l e c t e d f o r measurements of

nitrogen oxides.

The e l e v a t i o n of

DRI

Mountain i s 400 m MSL o r 170 m above t h e g e n e r a t i n g s t a t i o n l o c a t e d 8 km t o t h e s o u t h and LOO m above t h e f l o o r of i s 2 5 0 m MSL.

The l o c a t i o n of

t h e Colorado R i v e r VaJfey.

K a t h e r i n e Landing

t h e s e s i t e s i s i d e a l f o r remote gaseous measure-

ments s i n c e t h e y are removed from even small l o c a l i z e d sources.

Any impact from

t h e p l a n t on t h e s e s i t e s i s e a s i l y d e t e c t e d by SO2 m o n i t o r s as t h e steam p l a n t is

t h e o n l y d e t e c t a b l e SO2

source

in

the area

(Ref.

1).

The NOx

K a t h e r i n e Landing a l s o s e r v e s a s a f u r t h e r check on p o t e n t i a l plant.

A s p r e v i o u s l y s t a t e d , p l a n t impact i s expected t o be minimal.

i m p o r t a n t c o n s i d e r a t i o n because of

monitor a t

i m p a c t s from t h e This i s an

t h e w e l l known O 3 d e p l e t i o n phenomenon asso-

c i a t e d w i t h t h e NO i n power p l a n t plumes. The l o c a t i o n of t h e s e s i t e s w i t h r e s p e c t t o l o n g range t r a n s p o r t of p o l l u t a n t s from l a r g e u r b a n c e n t e r s i s a l s o a n i m p o r t a n t c o n s i d e r a t i o n .

Normally, d u r i n g t h e

s e a s o n s from October t h r o u g h March t h e Mohave Valley i s removed from t h e p o s s i b l e i n f l u e n c e of l o n g range t r a n s p o r t f o r two r e a s o n s .

First,

t h e t r a j e c t o r y of t h e

airmass which a r r i v e s a t Mohave i s from t h e n o r t h e r l y q u a d r a n t and no l a r g e urban c e n t e r s a r e w i t h i n hundreds of m i l e s i n t h i s d i r e c t i o n . meteorological

and c h e m i c a l r e a s o n s ,

Second, f o r a v a r i e t y of

ozone f o r m a t i o n i s l i m i t e d

i n l a r g e urban

a r e a s d u r i n g t h e w i n t e r months and t h u s l o n g range t r a n s p o r t of t h i s p o l l u t a n t i s u s u a l l y a moot p o i n t . For

the

above

stated

reasons,

the

selection

of

DRI

Mountain

and

Katherine

Landing a s r e p r e s e n t a t i v e of remote d e s e r t l o c a t i o n s a t a l a t i t u d e of about 32'N

22 is valid.

During t h i s period,

observed

ozone and NO2

c o n c e n t r a t i o n s s h o u l d be

t y p i c a l of n a t u r a l o r background c o n t i n e n t a l l e v e l s .

RESULTS

Ozone d a t a from D R I Mountain were s e l e c t e d f o r s y n o p t i c p a t t e r n s as p r e v i o u s l y described i n Figs.

2-4

f o r the fall-winter-spring

O c t o b e r 1976 t o March 1979.

5-11 and T a b l e 1.

months d u r i n g t h e p e r i o d from

Data from t h e s e t h r e e y e a r s a r e p r e s e n t e d i n F i g s .

Examination o f t h i s d a t a b a s e i n d i c a t e s d e f i n i t e p a t t e r n s and

c o n s i s t e n t ozone c o n c e n t r a t i o n s f o r a v a r i e t y of s e a s o n a l and s y n o p t i c s i t u a t i o n s . Fig.

5

is

a

compilation

of

hourly

averaged

ozone

d i s c r e t e h i g h p r e s s u r e r i d g e p a t t e r n s f o r 1976-1977.

a r e b e s t d e s c r i b e d by F i g s .

2 and 3.

concentrations

for

five

These h i g h p r e s s u r e p e r i o d s

During t h e s e p e r i o d s ,

winds were n o r t h e r l y

t h e e n t i r e t i m e f o r t h e p e r i o d November 2-9 and n o r t h e r l y a b o u t 22 h o u r s a day f o r e a c h of

t h e o t h e r periods.

S o u t h e r l y w i n d s create a p o s s i b i l i t y of

plume impact on D R I Mountain and K a t h e r i n e Landing.

However,

power p l a n t

a t no t i m e d u r i n g

a n y of t h e s e r i d g e p e r i o d s was t h e plume d e t e c t e d a t D R I Mountain.

-

36-

OCT. 4-7 NOV. 2-9

---- FEE. 14-20 32 30 -

.__.._____... NOV. 16-19 -.-.- JAN. 13-18

34

-z

n n I0

a 4 It Y 0

z

0

0 Y

az

0

18

I

1

I

I

I

t

05

10

15

20

24

I

00

I

I

TIME OF DAY (MST)

Fig. 5. Hourly-averaged ozone c o n c e n t r a t i o n s f o r e a c h h i g h p r e s s u r e r i d g e p e r i o d from O c t . 1976 - March 1977.

Figs.

5 and 8 were c o n s t r u c t e d

curve representing t h e period period,

i n t h e f o l l o w i n g manner.

As a n example,

from November 2 t h r o u g h November 9,

the

a n e i g h t day

i s a c o n d e n s a t i o n of e i g h t d a t a p o i n t s a v e r a g e d t o make one h o u r l y a v e r -

aged d a t a p o i n t on t h i s c u r v e .

This condensing of t h e d a t a i s reasonable because

23 of t h e r e p e a t a b i l i t y and small v a r i a b i l i t y i n ozone l e v e l s a s a f u n c t i o n of of

day.

Fig.

6 i l l u s t r a t e s t h i s b e h a v i o r w i t h t h e November 2-9

i n t o h o u r l y a v e r a g e d p o i n t s f o r e a c h day.

time

c u r v e expanded

The ozone l e v e l s are n e a r l y i d e n t i c a l

f o r t h e same h o u r i n d e p e n d e n t o f t h e day.

5 i n d i c a t e s e a s i l y i d e n t i f i a b l e ozone p a t t e r n s indepen-

An e x a m i n a t i o n of Fig.

dent

of

the

particular

ridge

period

or

seasonal

t i m e of

year.

All

of

these

s e l e c t e d p e r i o d s a r e f o r c o n d i t i o n s where t h e t r o p o s p h e r i c j e t stream i s 1500 !a t o t h e n o r t h o f t h e area f o r a minimum of 60 hours. t h a n 60 h o u r s d u r a t i o n , no d i u r n a l p a t t e r n , ible.

6, i s discern-

5 i n d i c a t e s a v e r a g e h o u r l y minimum c o n c e n t r a t i o n s from 18 t o 24 ppb

Fig.

occurring

For t r a n s i t o r y r i d g e s of less

t y p i c a l l y shown i n Fig.

about

the

same t i m e e a c h day from 0900

to

1100 h o u r s MST.

Average

h o u r l y maximum c o n c e n t r a t i o n s r a n g e from 29 t o 35 ppb o c c u r r i n g between 1600 t o 1900 h o u r s MST. As

mentioned

previously,

period

from

S u r f a c e winds were n o r t h e r l y d u r i n g t h i s e n t i r e p e r i o d .

Fig.

6 shows

the

high

pressure

ridge

The

November 2-9,

1976.

diurnal trend

i s v e r y d i s t i n c t w i t h t h e same maximum and minimum c o n c e n t r a t i o n s

o c c u r r i n g a b o u t t h e same t i m e e a c h day.

Concentrations

r a n g e from 23 ppb t o a

maximum h o u r l y a v e r a g e o f 38 ppb.

40 -J

35 302520 -

I , , , , , , , ,

02/01

03/00 04/00 05/00

06/00 07/00 08/00

09/00 09/23

DATE/TIME (MST)

Fig. 6. Curve from Fig. 5 p l o t t e d f o r e a c h h o u r l y a v e r a g e f o r t h e h i g h p r e s s u r e r i d g e p e r i o d from Nov. 2 t o Nov. 10, 1976.

During t h e w i n t e r s e a s o n of (Fig.

1977 t o 1978 o n l y one w e l l - d e f i n e d

2) developed i n t h e S o u t h w e s t e r n U.S.

1978 (Fig.

7).

A s the short-lived

become n o r t h e r l y and

season, i s again seen f o r January 7,

period

T h i s o c c u r r e d from J a n u a r y 6 t o 11,

r i d g e b u i l d s i n t o t h e area,

t h e well-defined

ridge

diurnal pattern,

8 and 9.

t h e s u r f a c e winds

observed i n t h e p r e v i o u s

The maximum O3 o c c u r s d u r i n g t h e

l a t e a f t e r n o o n w h i l e minimum c o n c e n t r a t i o n s are i n t h e morning h o u r s .

By Janu-

a r y 1 0 t o 11, t h e upper r i d g e i s moving t o t h e e a s t , b e i n g r e p l a c e d by a t r o u g h

24

and i n c r e a s i n g s o u t h e r l y winds a t t h e s u r f a c e .

The d i u r n a l p a t t e r n of

with

O3

i t s d e f i n i t e maximum and minimum i s a l s o c h a n g i n g , b e i n g r e p l a c e d by more uniform h o u r l y ozone a v e r a g e s .

06/17

I

I

I I

07/00

08/00

I

I

11/00

11/08

I

1

I

09/00

10/00

DATE/TIME (MST)

Fig. 7. 1977.

Hourly averaged ozone c o n c e n t r a t i o n s f o r t h e p e r i o d Jan.

From t h e w i n t e r season of

1978 t o 1979,

r i d g e s of 60 hour minimum d u r a t i o n ( F i g s . between October and mid-February.

Fig.

seven w e l l - e s t a b l i s h e d

2-4)

6 t o Jan.

11,

high pressure

moved i n o v e r t h e Southwestern U.S.

8 i s an a v e r a g e of

e a c h of

these ridge

p e r i o d s , w i t h t h e e x c e p t i o n of t h e f i r s t h i g h p r e s s u r e r i d g e p e r i o d from October 1 t o 5.

The d a t a

could

have

normally occurred f o r a

been

plotted with

s o u t h e r l y winds e x c l u d e d , which

c o u p l e h o u r s e a c h day,

b u t were p l o t t e d

for

the

full

24-hour day because i n s i g n i f i c a n t d i f f e r e n c e s were d e t e c t e d . Comparison t o Fig.

5 i n d i c a t e s no s i g n i f i c a n t changes have o c c u r r e d i n ozone

p a t t e r n s i n t h e Mohave V a l l e y d u r i n g t h e 1976 t h r o u g h 1979 w i n t e r seasons. mum and minimum c o n c e n t r a t i o n s are comparable a s a r e t h e i r Fig.

9 i s a n expanded

p l o t of

a t y p i c a l period

t i m e of

Maxi-

occurrence.

from December 20 t o 27,

Examination of t h i s g r a p h i n d i c a t e s i t i s v e r y similar t o Fig.

1978.

6 with respect t o

maximum and minimum O 3 c o n c e n t r a t i o n s and t h e i r times of o c c u r r e n c e e a c h day. There were two anomalous p e r i o d s d u r i n g t h e 1978 t o 1979 w i n t e r season. f i r s t p e r i o d o c c u r r e d between October 1 t o 6, obvious f e a t u r e s are t h e "high" ozone l e v e l s . 81.4 ppb ( T a b l e 1 ) o c c u r r e d on October 1.

1978.

P o r t r a y e d i n Fig.

The

10, t h e

The maximum h o u r l y c o n c e n t r a t i o n of

However,

t h e time of o c c u r r e n c e f o r t h e

maximum and minimum and t h e r e l a t i v e d i f f e r e n c e between them i s similar t o o t h e r h i g h p r e s s u r e r i d g e s d e s c r i b e d by Fig.

9.

Another i n t e r e s t i n g phenomenon occurred

on October 3 when t h e ozone dropped s u b s t a n t i a l l y .

and

supplemental meteorological d a t a ,

a wind

shift

A s i n t e r p o l a t e d from Table 1 from s o u t h e r l y t o n o r t h e r l y

25 o c c u r r e d a b o u t i800 hours MST October 2, maximum of

15.3

km/hr

0700 h o u r s MST October

at

remained i n t o October 5 ,

i n c r e a s i n g i n i n t e n s i t y and r e a c h i n g a

3.

Although n o r t h e r l y winds

t h e y d e c r e a s e d c o n s i d e r a b l y i n speed w i t h t i m e .

Ozone

v a l u e s r e t u r n e d t o a “ h i g h ” l e v e l on October 4.

NOV. 3-8 - NOV. 28-30

--- DEC. 2-1 1 --- DEC. 20-26 ... .....

-

n

__---_ ‘.

DEC. 31-JAN. 2 FEE. 4-12

23

12 TIME OF DAY (MST)

Fig. 8. Hourly averaged ozone c o n c e n t r a t i o n s f o r e a c h h i g h p r e s s u r e r i d g e period from Nov. 1978 t o March 1979.

42 38

2 P

n

34

0 c a

30

i

IK

w z

26

V

z 0 u W z

a 0

22 I

1

1

l8 14

10 20/00

I

I

21/00 22/00

II

I

23/00

24/00

I

I

25/00 26/00

1

27/00

DATEITIME (MST)

Fig. 9. Hourly averaged ozone d a t a f o r a t y p i c a l h i g h p r e s s u r e r i d g e p e r i o d from Dec. 20 t o Dec. 27, 1978.

N

m

TABLE 1 Summary of Daily Maximum and Minimum Hourly Averaged Ozone Concentrations, Daily Maximum and Minimum Wind

Speed, Direction and Temperature at DRI Mtn.

for Selected

High Pressure Ridge Periods from

October 1976 to March 1979. MAX 03 (ppb)

DATE

TIME (MST)

MIN 03 (ppb)

MAX TIME (MST)

WIND (km/hr)

(")

TIME (MST)

MIN WIND (Whr)

34 9 343 45 40 30 36 44 46

16 16 05 02 13 14 13 01

1.8 1.5 4.7 0.7 0.4 2.2 3.0 0.9

16 05

DIR

17 17 17 20 17 18 19

la

26.2 22.8 24.2 21.8 22.2 23.5 22.3 23.0

10 09

9

37.1 35.1 32.7 37.9 37.5 33.7 37.7 34.7

07 10

10.6 12.0 11.9 8.1 5.6 6.8 10.5 10.2

1 2 3 4

81.4 74.1 50.8 72.6

15 17 16 16

40.2 43.9 39.2 33.7

08 05 03 09

9.4 5.9 15.3 6.0

213 186 31 21

oa

2 3 4 5 6 8 9 10 11

41.0 39.2 39.6 39.9 36.6 39.1 36.9 37.7 42.5

14 16 16 20 17 17 17 15 17

31.4 30.3 23.3 16.8 30.1 32.8 27.8 21.2 30.7

07 02 08 06 23 07 06 09

11.1 11.9 11.7 18.9 14.1 14.7 15.1 17.9 12.9

Dec. 31 Jan. 1 1979 2

40.0 37.5 37.0

ia

16

33.9 28.0 31.0

07 04 23

12.5 34.2 14.6

Nov. 1976

2 3 4 5 6

7

a Oct. 1978

Dec.

15

09

08

oa

oa

oa

MAX DIR

("1 68 107 34 16

TIME (MST)

TEMP

MIN TEMP

'c

"C

28.5

359 7 220

22 01 21 21 21 18 09 19

30.1 29.2 30.1 29.3 28.9 28.0 26.7

19.0 21.8 21.6 16.7 15.3 15.9 14.9 16.0

0.6 1.2 4.5

01

0. a

45 27 5 12 94

03 10 23 09

40.3 39.3 37.3 40.0

27.1 27.0 26.6 24.4

337 322 29 331 324 324 33 32 32

00 13 05 17 09 13 23 02 22

2.0 4.2 2.1 2.0 1.0 4.9 5.8 6.7 6.0

40 25 336 233 329 330 360 354 344

20 07 15 22 09 04 19 17

15.3 13.4 15.9 14.7 8.0 5.2 8.9 13.6 15.5

9.2 7.4 7.2 5.4 3.2 .5 1.9 5.3 8.4

332 330 355

15 14 13

4.9 6.5 9.2

20 30 356

23 05 02

11.1 5.0 6.9

4.5 2.9 1.3

220

la

27

z 0

t-

i Iz

W

Y0

0

W

z

! 20 01/00

03/00

02/00

,

I

i

04/00

05/00

06/00

DATE/TIME (MST)

Hourly averaged ozone c o n c e n t r a t i o n s f o r a h i g h p r e s s u r e r i d g e period Fig. 10. from Oct. 1 t o Oct. 6, 1978.

41-1

23 20

1

31/00

I

01/00

I

02/00

I

03/00

DATEITME (MST)

Fig. 11. Hourly a v e r a g e d ozone d a t a f o r a h i g h p r e s s u r e r i d g e period n o r t h e r l y winds from Dec. 31, 1978 t o Jan. 3 , 1979.

f o r strong

28 The o t h e r a t y p i c a l p e r i o d f o r t h e 1978-1979 s e a s o n i s shown i n Fig. p e r i o d December 3 1 t o J a n u a r y 3. increased

to

90 km/hr

and

night,

By t h e a f t e r n o o n o f J a n u a r y 1, wind s p e e d s had

continued

d e c r e a s i n g below 24 km/hr.

11 f o r t h e

strong

during

the

next

two

days,

seldom

The g r a p h i n d i c a t e s t h a t ozone l e v e l s d i d n o t d r o p a t

remaining q u i t e uniform throughout

the period.

Nevertheless,

O3 maximum

s t i l l o c c u r r e d d u r i n g t h e a f t e r n o o n h o u r s on e a c h of t h e t h r e e days. During t h e s e t h r e e w i n t e r s e a s o n s NO2 However,

only during

Mohave network

the

t h e CSI Model

of

measurements

o f NO2

1978-1979

been

d a t a have been c o l l e c t e d c o n c u r r e n t l y .

season,

because

1600 NOx

possible.

In

of

analyzers,

general,

the has

installation increased

remained

o r below t h e s e n s i t i v i t y l i m i t o f a b o u t 5 ppb f o r d a y s a t a time. higher

at

concentrations

periods,

Katherine

w i t h a maximum v a l u e o f

v a l u e s were a s s o c i a t e d w i t h

the

Landing

power

were

observed

50 ppb.

about

plant

plume.

However,

at

Occasionally

during

N e a r l y a l l of

the

sensitivity

still

levels

NO2

in

these

the

ridge

time

these

the data i n this

s e c t i o n have been c a r e f u l l y e d i t e d t o e x c l u d e any p o s s i b l e e f f e c t on O3 l e v e l s due

to

o n l y r a r e l y was

A s stated previously,

t h e plume.

t h e plume

travelling

n o r t h d u r i n g t h i s t i m e of y e a r .

CONCLUSIONS Ozone d a t a p r e s e n t e d three

winter

characterized

seasons

above

from

have

been

1976 i n t o

collected

1979

by p e r s i s t e n t h i g h p r e s s u r e

n o t e d from t h i s d a t a s e t .

A well-defined

for

in

t h e Mohave V a l l e y

typical

ridges.

meteorological

Several

during regimes

i m p l i c a t i o n s may be

d i u r n a l p a t t e r n i s observed w i t h average

h o u r l y maximum v a l u e s r a n g i n g between 29 and 4 4 ppb and minimum l e v e l s between 18 and 24 ppb.

T h i s r e m a r k a b l y p e r s i s t e n t p a t t e r n a p p e a r s t o be a n o u t g r o w t h of t h e Ozone maxima are observed

s t a b l e m e t e o r o l o g i c a l p a t t e r n s as a l r e a d y e x p l a i n e d .

i n t h e l a t e r a f t e r n o o n h o u r s when t h e m i x i n g d e p t h due t o s o l a r i n s o l a t i o n and mechanical

turbulence

is greatest.

These

ozone

concentrations

averaging about

40 ppb r e p r e s e n t n a t u r a l t r o p o s p h e r i c l e v e l s w i t h i n t h e boundary l a y e r . t h e a f t e r n o o n h o u r s ozone ground

by

this

i s continually being

mechanical

turbulence.

Ozone

replenished

and

carried

c o n c e n t r a t i o n s are

at

During to

the

a minimum

d u r i n g t h e e a r l y morning h o u r s b e c a u s e t h i s i s t h e t i m e of maximum s t a b i l i t y i n t h e boundary l a y e r .

Overnight,

as a r e s u l t of t h e s u r f a c e - b a s e d

r a d i a t i o n inver-

s i o n , ozone r e p l e n i s h m e n t from t h e t r o p o s p h e r e h a s c e a s e d a l l o w i n g s u r f a c e removal ozone mechanisms

t o deplete

t h e ozone

levels.

These

i n t e r p l a y between O3 and m e t e o r o l o g y are r e p e a t e d

basic

daily

processes

and

the

f o r a s long a s a high

pressure ridge persists. From t h e above r e s u l t s

several other conclusions

can

be

drawn.

The NOx-03

p h o t o c h e m i s t r y o b s e r v e d i n u r b a n areas a p p e a r s t o p l a y no o b v i o u s r o l e i n t h e s e

29 remote r u r a l a r e a s .

L e v e l s of

remain low,

NO2

f o r s e v e r a l days a t a time.

limit,

l e v e l s and,

i n addition,

O3

amount of s o l a r i n s o l a t i o n . r o l e of NO

l e s s t h a n t h e 5 ppb d e t e c t a b l e

There i s no measurable d i u r n a l t r e n d of NO

C o n c e n t r a t i o n s remain However,

the

same

regardless

2 the

of

l a b o r a t o r y work i s ongoing t o e v a l u a t e t h e

a t sub-ppb l e v e l s .

There i s f u r t h e r e v i d e n c e of t h i s d i u r n a l c y c l e coupled t o t h e meteorology a s s u g g e s t e d i n Fig.

11.

I n t h e p r e s e n c e o f h i g h winds,

t i v e l y h i g h a t n i g h t s i n c e no i n v e r s i o n i s formed.

ozone l e v e l s remain r e l a -

The atmosphere remains w e l l

mixed and t h e r e i s c o n t i n u a l r e p l e n i s h m e n t of O3 from t h e t r o p o s p h e r e throughout t h e 24 hour p e r i o d . The d a t a s e t p r e s e n t e d i n t h i s paper ( F i g s .

5 and 8 ) a l s o i n d i c a t e t h a t t h e r e

i s no d e t e c t a b l e s e a s o n a l e f f e c t on ozone c o n c e n t r a t i o n s , e i t h e r i n t h e maximum o r

minimum l e v e l s o r i n t h e d a i l y t i m e of o c c u r r e n c e of t h i s d i u r n a l c y c l e . more,

even when t h e t r o p o s p h e r i c j e t

Further-

stream i s a t a maximum o v e r t h e Southwest

r e g i o n , ozone l e v e l s do n o t i n c r e a s e .

Such w a s t h e c a s e f o r December 2-11,

1978

T h e r e f o r e , a l t h o u g h i t i s w e l l known t h a t t h e r e a r e s e a s o n a l v a r i a t i o n s

(Fig. 8).

in latitudinal

s t r a t o s p h e r i c ozone c o n c e n t r a t i o n s and

that

stratospheric intru-

s i o n s of ozone have been observed i n t h e f o l d i n g of t h e t r o p o p a u s e ( s e e Fig. t h e s e e f f e c t s do n o t seem t o p e n e t r a t e down below t h e t o p of

4),

t h e mixed l a y e r i n

t h e Mohave Valley. Another v e r y i n t e r e s t i n g f e a t u r e t o t h i s d a t a s e t i s shown i n Fig.

10.

This

p e r i o d of h i g h ozone l e v e l s r e s u l t e d from l o n g range t r a n s p o r t of ozone a n d / o r i t s p r e c u r s o r s i n t o t h e Mohave V a l l e y from t h e Los Angeles Basin.

During t h i s p e r i o d ,

t h e Los Angeles a r e a e x p e r i e n c e d ozone c o n c e n t r a t i o n s i n e x c e s s of 0.40 ppm i n t h e e a s t e r n p a r t of t h e B a s i n and t h e 24-hour from Los

Angeles

to

dropped s u b s t a n t i a l l y .

t h e Mohave Valley.

However,

on October

3

the

O3

levels

T h i s o c c u r r e d because t h e NE o r " o f f s h o r e " S a n t a Ana winds

i n c r e a s e d d u r i n g t h i s 24-hour Basin.

a v e r a g e wind t r a j e c t o r i e s were southwest

p e r i o d t o l i m i t l o n g range t r a n s p o r t from t h e L.A.

These o f f s h o r e o r n o r t h e r l y winds are t h e normal p a t t e r n d u r i n g t h e w i n t e r

months a s e x p l a i n e d p r e v i o u s l y (Fig.

3).

I n summary, ozone d a t a c o l l e c t e d a t a remote desert s i t e i n t h e Mohave Valley from 1976 t o 1979 i n d i c a t e s background ozone l e v e l s remain w e l l below t h e new EPA s t a n d a r d of 120 ppb.

D i u r n a l ozone l e v e l s are observed and a p p e a r t o be coupled

t o t h e s y n o p t i c m e t e o r o l o g i c a l p a t t e r n s w i t h d a i l y maximum O3 c o n c e n t r a t i o n s o f 40 ppb.

There a p p e a r s t o be no o b v i o u s r o l e

of

NO

in

the

p r o d u c t i o n of

0

3

and n o d e t e c t a b l e e f f e c t of s t r a t o s p h e r i c i n t r u s i o n on s u r f a c e ozone l e v e l s .

REFERENCES

1 R.J. F a r b e r , T.E. H o f f e r , P.M. F r a n s i o l i , J . G . Hudson and P.B. MacCready, J r . , Paper No. 78-70.9 p r e s e n t e d a t 71st Annual A i r P o l l u t i o n C o n t r o l A s s o c i a t i o n Meeting, Houston, J u n e 25-30, 1978.

30 2

3 4

Singh, - . F.L. Ludwig - and W.B. Johnson, Atm. Env., 12(1978)2185-2196. R.G. Derwent, A.E.J. Eggleton, M.L. Williams and C.A. B e l l , Atm. Env., 1273-1277. R. C h a t f i e l d and H. Harrison, J. Geophy. R e s . , 81(1976)421-423.

H.B.

12(1Y78)

31

ATMOSFHEHIC CONTAMINATlON OF ARCHAEOLOGICAL MONUMENTS IN THE AGRA REGION (INDIA) and D.N. SHARMA Post-graduate Studies and Research Deptt. of Chemistry St. John's College, Agra ( I N D I A )

J.S. SHARMA

ABSTRACT An analysis of water-soluble samples collected from marble and sandstone of monuments for different ions have been done, The combustion, manufacturing and other polluting operations existing within Agra area have been investigated. The measurements of flue gases amounting to 3.63 x l o 9 S.C.F. indicate atmospheric contamination and deterioration of archaeological monuments of Agra. It has been found that the principal sources of air contamination are the 325 iron foundries and 3 railway shunting yards located within 0.3 to 3.0 Km. of the main monuments. The topographical and micrometeorological conditions of the city have tended to favour and aggravate the concentration of effluents in the surrounding air of the monuments. The annual average existing level of SO2 ranges from 16 to 20 micrograms/rn 3 The seasonal distribution of SO2 and suspended particulate matter in the air at Taj Mahal, Red Fort and Sikandra have been discussed and illustrated. It has been observed that there is substantial sulphur dioxide contamination existing at Agra. The 2 maximum concentration of SO4and NO; amounting 0.46 and 0.38 respectively by weight percentage found existing at Red Fort cause efflorescences of sandstone.

.

INTRODUCTION Agra (Lat. 27O 10' N. and Long 78O 3' E.), the historical city of India, contains the glories of Indian architecture. Among the famous monuments which are on a scale of striking rnagnificance are Taj Mahal (1653 A.D.), Red Fort (1565 A.D.), Itmad-ud-Daula (1628 A.D.) Sikandra (1613 A.D.) and Fatehpur Sikri (1569 A.D.) (ref. 11, (Fig. 1 A ) . In this presentation an attempt has been made to study qualitatively and quantitatively the contamination of the atmosphere of Agra zone

32

Fig. 1 A ATION, MONUMENTS

FREQUENCY OF WIND DIRECTION AT AG RA MEAN ANNUAL

/

/n

CONDITION

n n

5 ~

2

n‘ 7

r r

rn

LOCATION OF MATHURA

REFERENCES

17803’~

ARCHAEOLOGICAL MONUMENT IRON FOUNDRIES ( L A R G E ) l e a c h dot represrnts 3 u n i t s l IRON FOUNDRIES (SMALL 1 (each dot represent 3 units1

-

@

NO. OF DAYS

A

RAILWAY SHUNTING YARD POWER

HOUSE

0 20 4 0 5 0

MEAN

n

m FIGURE IN CIRCLE DENOTES NUMBER OF

CALMS

VALUES

0 FATEHPUR

P

P

Fig. 1 B

MONTHLY ISOPLETHS

OF 2 4 - H O U R

0 E

SlKRl 20

4 0 KM l

‘25)

IN

AVERAGE

O F SO2

WINTER

LEVEL

- MEAN (1975-001

33

and i t s e f f e c t s on s l o w l y b u t s t e a d i l y decaying s t o n e s of t h e monuments by t a k i n g c h e m i c a l , m e t e o r o l o g i c a l , b i o c h e m i c a l and g e o g r a p h i c a l a s p e c t s i n t o consideration. PRINCIPAL SOURCES OF CONTAIfiIINATION The primary c o n t a m i n a n t s t h a t a f f e c t t h e monuments' marble and sands t o n e a r e s u l p h u r d i o x i d e , o x i d e s of n i t r o g e n and suspended ( d u s t ) p a r t i c u l a t e matter.

The p r i n c i p a l s o u r c e s of a i r p o l l u t i o n a t Agra a r e

i n d u s t r i e s p a r t i c u l a r l y i r o n f o u n d r i e s , g l a s s works, power p l a n t s , r a i l w a y s h u n t i n g y a r d s , a u t o m o b i l e v e h i c l e s and many l i m e - k i l n works. I r o n foundThere a r e a b o u t 175 l a r g e s c a l e i r o n f o u n d r i e s w i t h c u p o l a m e l t i n g o p e r a t i o n s and 150 s m a l l s c a l e f o u n d r i e s c a l l e d K o t h a l i e s producing more t h a n 200,000 t o n s of c a s t i r o n goods p e r y e a r , w i t h an annual c a s t i n g c a p a c i t y of 450,000 t o n s . The i r o n f o u n d r i e s a r e s i t u a t e d w i t h i n a b o u t 0.3 t o 3.0 Kms. w e s t , north-west

o r n o r t h of T a j Mahal, Red F o r t and Itmad-ud-Daula

(Fig. 1 ) .

The m a t e r i a l s c h a r g e d e v e r y month i n t h e s e f o u n d r i e s amount 5,450 t o n s of h a r d coke and 1,200 t o n s of l i m e s t o n e and 20,000 t o n s of p i g i r o n and s c r a p i r o n .

M e l t i n g i s done at150O0C i n f a u l t y combustion chambers

i n which a i r r e g u l a t i o n i s n o t m a i n t a i n e d .

lo8

e x h a u s t e d from c u p o l a f u r n a c e s 32.8 x

The amount of f l u e g a s e s S.C.F.

p e r month.

The s u l p h u r

d i o x i d e l i b e r a t e d h a s been e s t i m a t e d t o be 0.004% by volume and it i s r e l e a s e d a t v e r y low h e i g h t s of about 5 meters b e c a u s e no s t a c k h e i g h t s t a n d a r d s ( r e f s . 2-3)

a r e followed.

A d e t a i l e d discussion regarding

t h e s e have a l r e a d y been p u b l i s h e d by one of t h e a u t h o r s Sharma J.S.

et al.

(ref. 4).

&

The s t a c k e m i s s i o n s a r e accompanied by l a r g e amounts

of carbon, s i l i c o n , i r o n o x i d e , manganese, c a l c i u m s i l i c a t e , s u l p h u r and o t h e r m e t a l l i c and non m e t a l l i c compounds.

The p a r t i c l e s i z e of t h e

s o l i d s v a r i e s from sub-microscopic t o 1000 micron and t h e i r s p e c i f i c g r a v i t y r a n g e s between 1.30 and 7 . 5 0 r ( r e f .

5)

Railway s h u n t i n g v a r d s a n d power houses There a r e 3 r a i l w a y s h u n t i n g y a r d s i n c l u d i n g one of Yamuna % r i d g e s i t e d between T a j Mahal and Itmad-ud-Daula o f c o a l e v e r y day.

( F i g . 1 A ) u s e s 40 t o 50 t o n s

The two power p l a n t s e a c h w i t h c a p a c i t y of 1 0 MW

using11,OOO t o n s of c o a l are s i ' t u a t e d v e r y n e a r t o t h e monuments.

The

power p l a n t a d j a c e n t t o Red F o r t which was i n o p e r , a t i o n f o r l a s t 54 y e a r s h a s been c l o s e d i n t h e y e a r 1981.

34

G l a s s works 374 g l a s s works a r e working i n a i n d u s t r i a l town of F i r o z a b a d S i n c e t h e wind d i r e c t i o n i s g e n e r a l l y

s i t u a t e d 4 2 Kms. e a s t o f Agra. away from Agra most o f t h e t i m e ,

it may be assumed t h a t it i s u n l i k e l y

f o r t h e e f f l u e n t s from t h e smelters t o r e a c h Agra monument.

However,

p o t e n t i a l impact would a r i s e from t h e s u l p h u r d i o x i d e which i s c o n t i nuously b e i n g added t o t h e atmosphere of t h e Agra r e g i o n by t h e comb u s t i o n o f a l a r g e q u a n t i t y of c o a l . One c a n n o t deny t h e f a c t t h a t t h i s i s l i k e l y t o a f f e c t t h e monumentsin l o n g r u n . Motor v e h i c l e s , n a t u r a l g a s 2 n d f o s s i l f u e l 53,000 motor v e h i c l e s r e g i s t e r e d i n Agra a t p r e s e n t c o n t a m i n a t e t h e atmosphere by p r o d u c i n g o x i d e s of n i t r o g e n which a r e p o t e n t t o s t o n e as w e l l a s i n d i r e c t l y h e l p t o i n c r e a s e t h e S O 2 f o r m a t i o n by r e d u c i n g

r e a c t i o n (1) i n t h e atmosphere ( r e f . 6 ) . Burning of 5 1396.84 t o n s o f k e r o s e n e , p e t r o l , d i e s e l and 2.4 x 1 0 Kg. of l i q u i d

sulphur trioxide,

n a t u r a l g a s p e r month a l s o add s u l p h u r ( r e f . 7 ) c o n t e n t s (Table 1) t o t h e a i r of Agra.

P o t e n t i a l p o l l u t i o n t h r e a t from o i l r e f i n e r y A l a r g e o i l r e f i n e r y w i t h a c a p a c i t y of p r o c e s s i n g of s i x m i l l i o n

t o n s p e r annum i s b e i n g commissioned s h o r t l y ( A p r i l 1 9 8 2 ) n e a r Mathura a b o u t 30 Km. upwind north-west

of Agra.

The down stream l o c a t e d monu-

ments of Agra b e i n g d e f i n i t e l y i n t h e most v u l n e r a b l e zone of i n f l u e n c e of t h e r e f i n e r y have a g r e a t p o t e n t i a l p o l l u t i o n t h r e a t from t h e refinery.

T h i s r e f i n e r y alone i s expected t o e m i t 100 t o n s of carbon

monoxide, 60 t o n s o f s u l p h u r d i o x i d e , 50 t o n s of hydrocarbon, 4 t o n s o f o x i d e s o f n i t r o g e n , 3 t o n s of s u l p h u r t r i o x i d e ,

2 t o n e s of a c r o p o l i s ,

1 0 t o n s of p a r t i c u l a t e s and enormous amounts of carbon-dioxide

t h e atmosphere of Agra-Mathura

into

r e g i o n everyday ( r e f . 8 ) .

EXTENT OF CONTAMINATION I N THE A I R

The l e v e l of a n n u a l a v e r a g e s u l p h u r d i o x i d e a t Agra h a s been e s t i m a t e d a t 16 t o 20 micrograms/m3 by p a r a r o s a a n i l i n e method ( r e f . 9) and i t s s e a s o n a l c o n c e n t r a t i o n i s p l o t t e d i n t h e b a r g r a p h (Fig. 2 A ) .

24-hour

a v e r a g e l e v e l of t h e suspended p a r t i c u l a t e m a t t e r ( F i g . 2B) i n w i n t e r r a n g e s around 200 t o 400 rnicrograms/m3

whereas t h e summer v a l u e s are 3

found t o be i n t h e o r d e r of 300-500 micrograms/m

.

Fig. 2 A MEAN SULPHUR DIOXIDE LEVELS IN THE AIR AT AGRA 6

2 -HOUR

( 1975- 1980 AIR MONITORING

1500

SUSPENDED PARTICULATE c 2 4 -HOUR

700 W

- HOUR

-24

a

600

I

fa 500

n

I

n

n r l

MAXIMUM

A

i

TAJ MAHAL

B

:

RED FORT

6 2 4 - HOUR

AVERAGE

C

i

ITMAD-UD-DAULA

D

i:

SIKANDRA

n.I II

AVERAGE

n

u 0

In

i3oa

: 200 E u

100 0 I

N

T

E

R

(1975-1980 1 Fig. 26

e 400

W

I

STATIONS

-24-HOUR

MATTER IN THE AIR AT AGRA

MAXIMUM

1

MAXIMUM

S

U

APR _.. .,.

M

I M

MAY ......

E

' R

/I '

JUN.

L

nn

I

0

JUL. R

I

AUG.

A

I

N

I Y

SEP.

36

NET PRODUCTION OF SULPHUR IN THE CITY'S ATNOSPHEKE From literature it is known that hard coke, coal, pig iron, fossil fuel and natural gas contain varied amount of sulphur (ref. 10). By putting the values of sulphur present in the energy consumption of the city (Table 1) it is calculated that approximately 705.96 tons of sulphur is produced every month. TABLE 1 Total sulphur of the city Quantity charged per month (in tons)

Kinds of material

Hard coke and coal Pig and scrap iron Fossil fuels: (Kerosene petrol and diesel) Natural gas Total

Sulphur produced per month (in tons1

7,950.00

636.00

20,000.00

60.00

1,396.84

5.16

240.00

4.80

29,586.84

705.96

CHENICAL INVESTIGATION OF MARBLE AND SANDSTONE The formation of black spots and decay has been noticed on the marble of Taj, Itmad-ud-Daula and Tomb of Salim Chisti in their certain zones. Exfoliation, white efforescence on the detaching layers and black encrusted layers are common features noticed on sandstones of Red Fort and Taj. The samples of degraded materials collected from each of the monuments during Nov.-Dec. 81 were chemically examined. The measurements of ionic components of the samples have been carried out by flame photometry (ref. 1 1 ) and the results (Table 2) are as given below. All concentrations are mean values of 3 samples taken from each monument. TABLE 2 Composition of water-soluble samples from marble and sandstone Ions

Concentrations (weight % of samples) ~~~~~

~

Marble samples Taj ItmadMahal daula Na+

0.81

0.76

Tomb S.Ch.

Sandstone samples Taj Red SikanMahal Fort dra

Fateh. sikri

0.32

0.56

0.61

0.58

0.62

37 K+

0.78

Ca2+ Mg2+

6.40

7.42

3.54

0.05

0.06

0.28

0.54

0.01

0.01

0.58

0.58

NOS

1.23

1.81

0.92

sop-

0.04

-

-

0.51 0.02

0.01

0.50 0.04 0.01

0.28

0.38

0.25

0.24

0.38

0.46

0.41

0.38

0.48

0.51

-

TOPOGRAPHICAL AND METEOROLOGICAL CONDITIONS It may be ernphasised that not only the great mass of emission but also a combination of topographical, rnetecrological and land use conditions of Agra and its region contribute to air pollution by concentrating the pollutants in the atmosphere surrounding the monuments. Situation of Agra on the banks of large Yamuna river at a wide bend, its surrounding countryside of a featureless level plain devoid of natural vegetation and its location in the semi-arid southern part of the upper Ganga Plain of north India profoundly affect the micro climate of Agra and thus important f o r the assessment of air contamination. Wind pattern Meteorological data indicate that the most frequent prevailing wind direction is westerly, north-westerly or south-westerly (Fig. 1B) and In winter strongly stable most frequent wind speed is 4 Km/hr. conditions of the atmosphere are observed, calm conditions prevail 43 to 68% of the time (Table 3). The normal wind pattern during summer month is little more active than winter months. TABLE 3 Directional pattern of wind and relative humidity at Agra Season

Average % of wind direction (1976-80)

-

Re1ative Humidity

N

NE

E

SE

S

SW

W

NW

CALM

0830 h r s IST %

Winter (Oct-Feb)

3.4

4.2

3.2

6.6

1.4

8.8

12.4

15.4

44.6

62.6

Summer (Mar-Jun)

8.0

6.2

3.2

3.5

4.0 12.3

25.5

16.3

21.0

37.8

Rainy (Jul-Sep)

2.4

6.3

6.7

6.3.

2.6

14.0

12.4

26.3

76.7

23.0

38

There is a good evidence that the large city of Agra, particularly during summer season of high speed winds, acts to some extent like mound, blocking the passage of air. Onrushing air from the west or north-west tries to flow around rather than through it, what flows through is slowed down considerably by the roughness of the structural elements of the city. Consequently, the prevailing westerly winds are deflected towards south-east and wind speeds are reduced 15 to 35% This impedes dispersion of pollutants discharged by the city. Inversion of temperature and focr A low level inversion of temperature takes place in Agra zone during several nights in months of December, January and early February, when Agra region is a l s o under the zone of high pressure system. Vast cold stretch of sandy bed of Yamuna during night intensify the ground inversion. This inversion condition (ref.6-2) prevents vertical diffusion and dilution of the pollutants. Fog also takes place over the city and surrounding countryside. Heavy smog is frequent in the early nights over the eastern part of the city. The relative humidity of the atmosphere ranges from 75-80% (Table 3 1 in rainy season to 60-70% in winter season (Tab1e 3). DISCUSSION After diagnosis of the nature and extent of contamination of the atmosphere and deterioration of monuments, the mechanism of steady corrosion of marble and sandstone surfaces of the monuments is as below: 1 The upcoming pollutants in flue gases from low level stacks of central pollution zone go up vertically due to high temperature and low density of fluids and then move horizontally in the direction of the monuments located downward in the direction of prevailing winds. 2 During winter season, mostly a period of strongly stable air structure inversion of temperature and calm conditions with high relative humidity heavy particles remain suspended in the air near the ground normlly for 6 to 10 hours in night and early morning. This suspended mass, often smog, contains acidic emissions which is enough to contaminate the atmosphere and corrode the stones of the monuments, by means of oxides of sulphur (Fig. 2A) and nitrogen. 3 It is evident from the Fig. 2A that the sulphur dioxide concentration is found maximum during winter months. The monthly 24-hours average 3 The m a . 2-hr ranges from 20 micrograms/m3 30 micrograms/m

-

.

value of sulphur dioxide viz 100 to 200 micrograms/m3 confirms that

39

there is a significant source of pollution in the neighbourhood of Taj Mahal, Red Fort, Itrnad-ud-Daula. Possibly, the contaminants created by iron foundries signify the high SO2 values (2-hr. max.) of Red Fort (208 micrograms/rn 3), Itmad-ud-Daula (155 micrograms/m 3 ) and Taj Mahal (135 rnicrograms/rn 31. On the other hand, the low 2-hr. max. SO2 value of 55 micrograms/m3 of Sikandra - being situated (Fig. 1A) away upwind from the iron foundries' source of pollution is very low. The existing level of the annual average sulphur dioxide at Agra is estimated to range from 16 to 20 micrograms/m 3 It is causing substantialsulphur dioxide pollution at Agra which is alarming. Published literature on the subject suggest that to avoid corrosion of building stones the permissible level of sulphur dioxide should be approximately 10-1 5 micrograms/m3 for long term (annual concentration) With the aforesaid concentration of SO2 in presence of high relative humidity (about 75%) the air flowing towards the direction of the monuments affects the stone surfaces of the monuments in one of the two ways: (a) Firstly it forms sulphurous acid, then sulphuric acid which reacts with marble and sandstone and makes their surfaces corroded, rough and porous. (b) Dust particles and other acidic compounds accumulate over the stone surfaces for long time and later on become their part, thus starts slow and steady corrosion of these stones, reactions (2-3). The other factor responsible for yellow-greyish dusty inner surfaces of the roof of the arches of the Taj, inaccessible to rain is the Black spots accumulation of some gypsum and silica, reaction ( 4 ) . of some projecting parts of the nlonunients, both on marble and sandstone are also observed due to the presence of heterotrophic bacteria, fungi and blue green algae which are sulphur oxidising and reducing in nature. A great water-body of Yamuna river adjoining the Taj Mahal, Red Fort, Itmad-ud-Daula provides additional moisture to the surrounding air of the monuments even in summer season by evaporation of river water. Therefore, it is an additional factor to increase the rate of formation of sulphurous and nitrous acid, reactions (1-2-3) which has a most deletorious corrosive effect upon the marble and sandstone. The moisture accelerates the rusting of many iron bars used in the structure. The phenomenon has increased the corrosion rate of some stone surfaces by providing additional hydroxyl ion to the surfaces of the stones, reaction (6).

.

.

4

5

6

7

40

8 Efflorescences of sandstone surfaces at Agra Fort is attributed to 2the maximum amount of SO4 and NO; ions (Table 2 ) developed at the

monument and formation of gypsum, reaction s(4-7)

.

CHEMISTRY OF CONTAMINATION Reactions NOX Bacteria’

“3 SO2

+

2H2S03 NO

+

s02

-

H20

+

H SO

O2

_I__*

2 3 2H2S04

2N02

O2

2HN03 + NO + H20 H2S03 + CaC03 _ _ _ j CaS03 + H 2 0 iC02 CaS04 . 2H20 2CaS03 + O 2 + H20 CaS04 + 2H20 + C02 H SO + CaC03 2 4 4Fe + 2H2S04 + 2 0 2 + 4FeS04 + 2H20 2N02

-

4FeS04 +

CaC03

+

‘2

2No;

+

6H20

+

+ 4FeO.OH

2H+ j

Ca(N03)2

+ +

4H2S04 C02 4- H20

(7)

ACKNOWLEDGEMENTS We are pleased to acknowledge the gracious co-operation of personnel at National Environmental Engineering Research Institute, Nagpur and Air Pollution Lab., Archaeological Survey of India, Agra especially Shri A.S. Tiwari as well as the advice and help of Prof. M.P. Singh of I.I.T., New Delhi, Atmospheric Sciences Research Centre. REFERENCES 1 E.B. Joshi (Ed.),Gazetteerof Agra, Govt. of U.P. Pub. 1965, pp.21-74 505. 2 W.L. Lee and A.C. Stern, J. Air. Pollu. Contr. Asso..23(1973) 3 A.C. Stern (Ed.), Air Pollu. Vol. V, Aca. Press Lond. 1977, pp. 666. 4 J.S. Sharma, Proc. 1st Symp. Ind. Ccuncil of Chemists,Agra, India, 1981, ING 25. 5 Indust. Air Cont. Asso.Tech. Sub Commi. Geneva Report Dec. 16, 1948. 6 R.A. Papetti and P.R. Gilmore, Edeavour, 7(1971), pp. 107-14. 7 V.B. Guthrie (Ed.),Petro. Produ.Hand Book, 1st ed. McGraw. 1960,p.3 8 T. Shivaji Rao, Proc. Indian. Environ. SOC. 23-24 Oct. 1978. 9 Air Ciual. Crit. for Sulphur oxides, U.S. Deptt., Health Education and Welfare, Nat. Air Pollu.Contro1 Adm. A.P. 50. 10 H.Groppe. Amm.Chem.Soc.Symp. Sanfrancisco, Calif., Apri 13-18, 1958. ll A . I . Vogel, Quant. Inorg.Anal!+ 4th ed., Long. 1978, N.Y., pp. 814-24.

-

41

A I R M O N I T O R I N G NETWORK PROGFLUI I N SAUDI ARABIA

T. Husain and S.M. Khan Water and Environment D i v i s i o n , The Research I n s t i t u t e U n i v e r s i t y of Petroleum and M i n e r a l s , Dhahran, Saudi A r a b i a

ABSTRACT

The Kingdom of Saudi A r a b i a h a s i n i t i a t e d a program t o i n s t a l l a i r q u a l i t y n e t work s t a t i o n s t h r o u g h o u t t h e c o u n t r y i n o r d e r t o measure c o n c e n t r a t i o n of t h e ambient a i r p o l l u t a n t s . The s i t e s e l e c t i o n o f t h e s e s t a t i o n s i s an i m p o r t a n t o b j e c t i v e t o be accomplished and must b e done based on s c i e n t i f i c and r a t i o n a l work. T o accomplish t h i s o b j e c t i v e , a m o d i f i e d v e r s i o n of a t m o s p h e r i c t r a n s p o r t and d i s p e r s i o n model, known as a i r r e s o u r c e s l a b o r a t o r i e s - a t m o s p h e r i c t r a n s p o r t and d i s p e r s i o n (ARLATAD) model, i s used t o e v a l u a t e l o n g range t r a n s p o r t and d i f f u s i o n o f a i r p o l l u t a n t s from major p o l l u t i o n c a u s i n g s o u r c e s such as r e f i n e r i e s , open-air b u r n i n g of assoc i a t e d g a s e s of o i l f i e l d s and m a j o r i n d u s t r i e s . Hourly m e t e o r o l o g i c a l d a t a f o r a p e r i o d o f t h r e e y e a r s (from 1977 t o 1979) on wind s p e e d , wind d i r e c t i o n , p r e s s u r e , and t e m p e r a t u r e from 20 s y n o p t i c s t a t i o n s i n Saudi A r a b i a i s p r o c e s s e d and used a s model i n p u t . In a d d i t i o n t o t h e s e , meteorol o g i c a l d a t a from t h r e e u p p e r a i r s t a t i o n s i s a l s o p r o c e s s e d i n o r d e r t o determine b a s e and t o p o f c r i t i c a l i n v e r s i o n h e i g h t s . Various p o l l u t i o n c a u s i n g s o u r c e s a r e i d e n t i f i e d w i t h i n t h e s t u d y a r e a . A i r t r a j e c t o r i e s a r e drawn w i t h s o u r c e s as t h e o r i g i n s o f t h e t r a j e c t o r i e s and t h e d i s p e r s i o n c h a r a c t e r i s t i c s i s s t u d i e d w i t h d i s t a n c e and t i m e . Based on l o n g term m e t e o r o l o g i c a l r e c o r d s , t h e a d v e r s e l y a f f e c t e d zones a r e s t a t i s t i c a l l y i d e n t i f i e d for potential station s i t e s .

INTRODUCTION

The s p a t i a l and t e m p o r a l v a r i a t i o n s o f t h e p o l l u t a n t s i n t h e atmosphere caused by t h e e m i s s i o n s o u r c e s , which i s complex and dynamic i n n a t u r e , depend upon t h e m e t e o r o l o g i c a l and t o p o g r a p h i c a l c o n d i t i o n s .

In order t o characterize the variations

of t h e s e p o l l u t a n t s i n s p a c e and t i m e domains e i t h e r m o n i t o r i n g o r modeling o r combinations of t h e s e two are needed. A i r m o n i t o r i n g a l o n e i s e x p e n s i v e , t i m e consuming, and r e q u i r e s s k i l l e d manpower and s o p h i s t i c a t e d equipments. It is t h e r e f o r e n e c e s s a r y to develop s i m u l a t i o n models which must b e f l e x i b l e enough

42 t o d e t e r m i n e t h e p o l l u t i o n c o n c e n t r a t i o n w i t h t h e change i n t h e e m i s s i o n s o u r c e s and

v a r i e d m e t e o r o l o g i c a l c o n d i t i o n s . Such models can b r o a d l y b e c a t e g o r i z e d

i n t o m i c r o s c a l e and m e s o s c a l e models. The m i c r o s c a l e models are used t o e s t i m a t e p o l l u t i o n l e v e l s n e a r t h e s o u r c e w h i l e t h e l o n g range i m p a r t o f t h e s o u r c e c a u s i n g background c o n c e n t r a t . i o n i s e s t i m a t e d u s i n g m e s o s c a l e mode1.s. M i c r o s c a l e models are u s u a l l y developed f o r s o u r c e s such a s a u t o m o b i l e e x h a u s t e m i s s i o n b u t t h e mesoscale models a r e used f o r l a r g e p o i n t s o u r c e s such as p e t r o c h e m i c a l i n d u s t r i e s , r e f i n e r i e s and open a i r b u r n i n g of n a t u r a l g a s e s e t c . T h i s s t u d y i s p r i m a r i l y b a s e d on t h e concept o f m e s o s c a l e modeling.

OBJECTIVES Due t o r a p i d f u t u r e i n d u s t r i a l development i n Saudi Arabia ( r e f . 8 ) , i t i s becoming a n i n c r e a s i n g l y i m p o r t a n t i s s u e t o i n s t a l l a n optimum a i r m o n i t o r i n g network t o c o l l e c t d a t a on background l e v e l c o n c e n t r a t i o n . The main o b j e c t i v e o f t h i s s t u d y i s , t h e r e f o r e , t o i d e n t i f y l o c a t i o n s o f t h e optimum a i r m o n i t o r i n g s t a t i o n s f o r p r o p e r s p a t i a l r e s o l u t i o n o f background l e v e l c o n c e n t r a t i o n due t o t h e p o l l u t a n t s e m i t t i n g from l a r g e p o i n t s o u r c e s . To accomplish t h i s o b j e c t i v e , v a r i o u s t y p e s o f l o n g range t r a n s p o r t models a r e reviewed and a i r r e s o u r c e s l a b o r a t o r i e s t r a j e c t o r y model i s s e l e c t e d f o r t h i s s t u d y due t o i t s s i m p l i c i t y , f l e x i b i l i t y t o v a r i e d e n v i r o n m e n t a l c o n d i t i o n s , and a d a p t a b i l i t y t o o u r meteorol o g i c a l conditions.

A I R TRAJECTORY MODELS Smith and J e f f r y ( r e f . 7 ) c a r r i e d o u t t r a j e c t o r y c a l c u l a t i o n s by hand which i n v o l v e d e s t i m a t i n g winds from t h e m e t e o r o l o g i c a l c h a r t s . T h i s i s v e r y t i m e consuming methodology which cannot b e used where t h e l a r g e number o f t r a j e c t o r i e s

are needed t o b e drawn. Due t o a d v e n t of computer and e a s y a c c e s s i b i l i t y t o t h e m e t e o r o l o g i c a l i n f o r m a t i o n , computer programs have been developed t o c a l c u l a t e t r a j e c t o r i e s . Henrickson ( r e f . 3 ) proposed n u m e r i c a l f o r e c a s t model t o c a l c u l a t e i s o b a r i c t r a j e c t o r i e s . Nagel and C l a r k ( r e f . 5) computed t r a j e c t o r i e s on i s e n t r o p i c s u r f a c e s w h i l e Mesinger ( r e f . 4 ) used c o n s t a n t d e n s i t y s u r f a c e t o trace t h e p a t h of a b a l l o o n . Barnum and D i e r e k s ( r e f . 1 ) computed t h r e e d i m e n s i o n a l t r a j e c t o r i e s

t o d e t e r m i n e c l o u d , t e m p e r a t u r e , and m o i s t u r e f i e l d s a t s p e c i f i c p r e s s u r e l e v e l s . Reap ( r e f . 6 ) a l s o developed a t h r e e d i m e n s i o n a l t r a j e c t o r y model u s i n g f o r e c a s t e d h o r i z o n t a l wind f i e l d s and g e o s t r o p h i c wind f i e l d s o b t a i n e d from m u l t i l a y e r p r i m i t i v e e q u a t i o n model. A i r r e s o u r c e s l a b o r a t o r i e s t r a j e c t o r y model used f o r t h i s s t u d y which is developed by H e f f t e r e t a l . ( r e f . 2 ) h a s been v e r y p o p u l a r i n t h e p a s t . The c o n c u r r e n t 6-hourly m e t e o r o l o g i c a l o b s e r v a t i o n s on wind s p e e d ,

43 wind d i r e c t i o n i n a d d i t i o n t o t e m p e r a t u r e and p r e s s u r e p r o f i l e d a t a , a r e used as i n p u t t o t h i s model.

PROBLEM FORMULATION

A t r a j e c t o r y segment i s computed from t h e a v e r a g e wind i n t h e t r a n s p o r t l a y e r

a t each r e p o r t i n g s t a t i o n w i t h i n a chosen r a d i u s of t h e segment o r i g i n as f o l l o w s (ref. 2). n

c

i = l Di Ai

Si

S =

C Di Ai i=1

where,

S -

i s t h e t r a j e c t o r y segment d u r i n g t h e t i m e i n t e r v a l A t , c o n t r i b u t e d by In'

r e p o r t i n g s t a t i o n s f a l l i n g w i t h i n t h e r a d i u s R f r o n t h e segment

origin. S.-

i s t h e c o n t r i b u t i o n from s t a t i o n i e q u a l t o V.. A t where Vi

is t h e

a v e r a g e wind speed a t s t a t i o n i i n t h e t i m e increment At=3 h o u r s D.-

A.-

i s t h e d i s t a n c e weighing f a c t o r e q u a l t o 1/d2 where, d . i s t h e d i s t a n c e i' from i t h s t a t i o n t o t h e midpoint o f S i' i s t h e alignment weighing f a c t o r which i s a f u n c t i o n of D and e q u a l i 1-0.51 S i n . O i l where,@. is t h e a n g l e between S . and a l i n e from t h e

segment o r i g i n t o t h e s t a t i o n .

The t r a j e c t o r y computation i n t h i s model must have a t l e a s t two r e p o r t i n g s t a t i o n l o c a t i o n s w i t h i n t h e r a d i u s R o r one s t a t i o n l o c a t e d w i t h i n h a l f of t h e r a d i u s . For t h i s s t u d y r a d i u s , R , i s t a k e n as 300 km. I f t h e above c o n d i t i o n i s n o t f u l f i l l e d , t h e t r a j e c t o r y w i l l b e t e r m i n a t e d . The computer program i s designed t o a n a l y z e t h e wind d a t a from a l l s t a t i o n s w i t h i n t h e radius.. The wind vectors o f a l l r e p o r t i n g s t a t i o n s are d i v i d e d i n t o X & Y components. Each components g i v e s t r a j e c t o r y segment i n X & Y d i r e c t i o n by u s i n g

E q . 1 . The combined a f f e c t a t segment o r i g i n i s determined by f i r s t adding X and

Y components of t h e t r a j e c t o r y segments s e p a r a t e l y and t h e n computing t h e r e s u l t a n t v a l u e o f t h e s e components.

44 ANALYSIS

Six-hourly m e t e o r o l o g i c a l r e c o r d s f o r t h r e e y e a r s ( 1 9 7 6 - 7 8 ) on wind speed and d i r e c t i o n from a l l s y n o p t i c m e t e o r o l o g i c a l s t a t i o n s i n t h e Kingdom which a r e l i s t e d i n Table 1, were p r o c e s s e d . The l o c a t i o n s of t h e p o t e n t i a l p o l l u t i o n c a u s i n g s o u r c e s were t h e n i d e n t i f i e d as shown i n Table 2 . Using p r o c e s s e d s i x - h o u r l y m e t e o r o l o g i c a l d a t a , t h e t r a j e c t o r i e s s t a r t i n g from t h e s o u r c e o f p o l l u t i o n were c a l c u l a t e d . The c o o r d i n a t e s of t h e t r a j e c t o r i e s p a s s i n g from v a r i o u s g r i d s i n t h e s t u d y a r e a w e r e s t o r e d f o r frequency e s t i m a t i o n . Four t r a j e c t o r i e s p e r day from each s o u r c e were p l o t t e d . TABLE 1

M e t e o r o l o g i c a l s t a t i o n s i n Saudi A r a b i a ~~

S. No.

1

Station Identific a t i o n No.

16 17 18

356 357 36 1 362 37 3 375 394 400 405 4 16 430 438 4 39 477 4 80 495 49 8 569

19 20

5 70 572

2

3 4 5 6 7 8 9 10 11 12 13 14

15

*

Name of Station

Turaif Badana A l - Jou f Rafha Quaifsumah" Tabouk" Hail Al-Wajh" Gassim DhahranX Madina Riyadh" Y anb o Jeddah" Taif Sulayed Bisha KhamisMushait N ej r a n Gizan

Latitude (Degrees)

Longitude (Degrees)

E l e v a t i o n Above M. S . L . (Meters)

31.68 30.97 29.93 29.63 28.33 28.36 27.52 26.23 26.30 26.27 24.55 24.70 2 L . 12 21.50 21.48 20.47 19.97

38.67 40.98 40.20 43.48 46.12 36.58 41.73 36.43 43.97 50.17 39.72 46.73 38.05 39.20 40.53 45.67 42.67

824 537 559 440 356 76 9 944 19 745 21 6 32 608 6 11 1457 6 12 1161

18.30 17.60 16.87

42.80 44.42 42.58

205 7 1206 3

Upper A i r M e t e o r o l o g i c a l d a t a i s a l s o r e c o r d e d

I n o r d e r t o e s t i m a t e t h e e x t e n t by which t h e t r a j e c t o r i e s a r e p a s s i n g o v e r an a r e a , t h e c o n c e p t o f f r e q u e n c y d i s t r i b u t i o n i s u s e d . The s t u d y area i s d i v i d e d

i n t o g r i d s o f one d e g r e e l a t i t u d e by one d e g r e e

longitude.

Number of t r a j e c t o r i e s

a r e drawn f o r one complete c a l e n d e r y e a r ( 1 9 7 8 ) , u s i n g 6-hourly m e t e o r o l o g i c a l r e c o r d s . The p e r c e n t f r e q u e n c y o f o c c u r r e n c e of t r a j e c t o r i e s p a s s i n g through each g r i d are computed and t h e r e s u l t s are shown i n c o n t o u r forms. Based on one y e a r t r a j e c t o r y r e c o r d s , s t a r t i n g from each s o u r c e ( T a b l e 2)

, c o n t o u r maps of

p e r c e n t f r e q u e n c y of t r a j e c t o r y t r a v e r s e s are computed. The combined e f f e c t s of a l l m a j o r s o u r c e s , i n t h e form of r e l a t i v e f r e q u e n c y of Occurrence of

45

t h e t r a j e c t o r i e s p a s s i n g t h r o u g h v a r i o u s g r i d s a r e shown by c o n t o u r map ( F i g . 1).

TABLE 2 The m a j o r a i r p o l l u t i o n s o u r c e s w i t h i n t h e Kingdom o f Saudi Arabia

S . No.

1 2 3 4 5 6

L o c a t i o n o f Major Sources

Latitude (Degrees)

Safania o i l f i e l d Jubail Ghawar o i l f i e l d Riyadh Jeddah Y anb u

27.9 26.7 25.5 24.5 21.5 24.2

Longitude (Degrees)

48.8 49.8 49.5 46.5 39.2 38.3

Type o f S o u r c e s

N a t u r a l Gas F l a r e d Chemical I n d u s t r i e s N a t u r a l Gas F l a r e d Petroleum Refineries Petroleum Refineries Chemical I n d u s t r i e s

CONCLUSIONS The f o l l o w i n g c o n c l u s i o n s are drawn from t h i s s t u d y :

- A i r t r a j e c t o r y c o n c e p t i s a u s e f u l t o o l i n d e t e r m i n i n g t h e movements o f a i r p a r c e l c a r r y i n g t h e p o l l u t a n t s from l a r g e e m i s s i o n s o u r c e s .

- Computer drawn t r a j e c t o r i e s are e f f i c i e n t and r e l i a b l e s i n c e number o f m e t e o r o l o g i c a l f a c t o r s , i n a d d i t i o n t o wind s p e e d and d i r e c t i o n , c a n b e taken i n t o account.

- The a d v e r s e l y a f f e c t e d zones ( F i g . 1) as i n v e s t i g a t e d by u s i n g f r e q u e n c y d i s t r i b u t i o n o f t h e t r a j e c t o r i e s p a s s i n g t h r o u g h v a r i o u s g r i d s and o r i g i n a t i n g from number o f e m i s s i o n s o u r c e s , are t h e zones f o r p r e l i m i n a r y m o n i t o r i n g p u r p o s e s . The m a j o r c i t i e s f a l l i n g i n t h e s e zones are J u b a i l , Abqaiq, Dhahran, Riyadh and B i s h a . It i s t h e r e f o r e recommended t o i n s t a l l a i r m o n i t o r i n g s t a t i o n s i n t h e s e c i t i e s p r e f e r a b l y i n t h e down wind d i r e c t i o n o f t h e most p r e v a i l i n g wind which i s n o r t h - n o r t h - w e s t .

ACKNOWLEDGEMENTS The a u t h o r s a r e g r a t e f u l t o D i r e c t o r , Research I n s t i t u t e f o r h i s p e r m i s s i o n t o submit t h i s paper f o r t h e conference. REFERENCES

1 D . C . Barnum and J.W. D i e r e c k s , J o u r n a l o f A p p l i e d Meteorology, 8(1969)3-14. 2 J . L . H e f f t e r , A.D. T a y l o r and G . J . F e r b e r t , NOAA T e c h n i c a l Memo, Environmental Research L a b o r a t o r y , ARL-50( 1975). 3 A.B. H e n r i c k s o n , S e r i e M e t e o r o l o g i , Stockholm, 27(1971). 4 F. Mesinger, J o u r n a l o f Atmospheric S c i e n c e , 22(1971)479-492. 5 R.E. Nagle and J . R . C l a r k , Meteorology I n t e r n a t i o n a l I n c . , F i n a l R e p o r t , 1966, C o n t r a c t Cwb-11254. 6 R.M. Reap, J o u r n a l o f A p p l i e d Meteorology, 11(1972)1193-1202. 7 F.B. Smith and G.H. J e f f e r y , J o u r n a l o f t h e Atmospheric Environment, 9(1975)643-659. 8 T h i r d Development P l a n (1980-85), M i n i s t r y o f P l a n n i n g , Kingdom of S a u d i Arabia.

Fig. 1 . Contour map of Frequency D i s t r i b u t i o n of T r a j e c t o r y T r a v e r s e s due t o m u l t i p l e s o u r c e s

41

A

STUDY OF PHYSICOCHEMICAL CHARACTERISTICS OF RESPIRABLE DUST

I N AN

I N D I A N COAL M I N E

N. S. RAWAT

I n d i a n School of Mines, Dhanbad-826004,

INDIA

ABSTRACT

The r e s p i r a b l e coal d u s t samples w e r e c o l l e c t e d from t h e mine atmosp h e r e d u r i n g d r i l l i n g o f c o a l seams u s i n g ' H e x l e t ' apparatus. Sixteen d u s t samples were collected from each t h r e e d i f f e r e n t seams f o r invest i g a t i o n s . A f t e r d e s t r u c t i o n of t h e o r g a n i c matter by w e t o x i d a t i o n and f i l t e r i n g o f f t h e c l a y and s i l i c a , Fe, Ca, Mg, N a , K, Mn, Zn, Cu, C d and N i were determined d i r e c t l y in t h e r e s u l t i n g s o l u t i o n by atomic a b s o r p t i o n s p e c t r o p h o t o m e t r i c methods. The x-ray d i f f r a c t i o n s t u d i e s have shown t h e p r e s e n c e o f k a o l i n i t e , q u a r t z , p i r r s o n i t e , and beidel l i t e c l a y minerals i n t h e coal dust. The mass-size d i s t r i b u t i o n of t h e c o a l d u s t h a s been s t u d i e d by u s i n g micron p h o t o s i z e r . The r e s u l t s showed t h a t t h e d i s t r i b u t i o n are unimodal, asymmetric, and p o s i t i v e l y skew. Although t h e assumption of log-normality w a s u s e f u l i n i n t e r p r e t i n g t h e r e s u l t s , c l o s e r obsemat i o n s i n d i c a t e d t h a t t h e r e l a t i o n s h i p between t h e s i z e and weight of t h e p a r t i c l e s can be r e p r e s e n t e d by a second degree p a r a b o l i c equation 2 W = a + bS + CS , where W and S are weight and s i z e of t h e p a r t i c l e s and a, b and c are c o n s t a n t s . This e q u a t i o n h e l p s u s to c h a r a c t e r i s e t h e mass of t h e respirable p a r t i c l e s i f t h e s i z e is known. The s t u d i e s throw l i g h t on t h e n a t u r e and mode o f t r a c e elements found in I n d i a n Coal a s w e l l as on t h e c a u s e s of r e s p i r a t o r y d i s e a s e , pneumoconiosis, a f f e c t i n g t h e workers i n t h e mine environmental condition.

INTRODUCTION

Among d i f f e r e n t o p e r a t i o n s i n c o a l mines, d r i l l i n g i n c o a l seams f o r s h o t h o l e s f o r b l a s t i n g produces m a x i m u m q u a n t i t y of a i r b o r n e dust. Dust p a r t i c l e s less t h a n 1 micron s i z e t e n d to s t i c k t o g e t h e r on cont a c t due t o Brownian movement ( r e f . 1). The p a r t i c l e s g r e a t e r than

48

7 micron s i z e a r e removed through s e t t l i n g by g r a v i t y whereas p a r t i c l e s between 1-7 micron s i z e remain suspended i n a i r f o r a long t i m e . The 1-7 micron s i z e p a r t i c l e s are c a l l e d r e s p i r a b l e d u s t and a r e t h e cause of pneumoconiosis, a lung d i s e a s e ( r e f . 21, among t h e coal miners. I t is n o t p r e s e n t l y known whether only t h e c o a l dust, o r s p e c i f i c elements o r chemical compounds or s y n e r g i s t i c e f f e c t s of s e v e r a l compounds assoc i a t e d with r e s p i r a b l e d u s t is r e s ? o n s i b l e for t h e d i s e a s e . EXPERIMENTAL

The r e s p i r a b l e c o a l d u s t samples used f o r t h e study w e r e c o l l e c t e d by C a s e l l a ' s 'Hexlet' apparatus ( r e f . 3 ) , e s p e c i a l l y designed and f i t t e d with a h o r i z o n t a l e l u t r i a t o r t o c o l l e c t t h e r e s p i r a b l e d u s t f r a c t i o n simulating c l o s e l y t h e l u n g ' s r e t e n t i o n c o n d i t i o n s of t h e coal miners. Dust samples w e r e c o l l e c t e d immediately a f t e r d r i l l i n g a t t h e working s i t e from I, I1 and 111 seams. The w e t o x i d a t i o n procedure of E l l i n g t o n and Adams ( r e f . 4 ) w a s adopted to d e s t r o y t h e o r g a n i c m a t t e r i n c o a l d u s t and to b r i n g t h e c o n s t i t u e n t s to be determined i n t o s o l u t i o n using A R q u a l i t y chemicals. The u l t i m a t e s o l u t i o n was obtained a s 25 cm3 f i l t r a t e . By t a k i n g suit a b l e a l i q u o t p o r t i o n s of t h i s s o l u t i o n t h e v a r i o u s elements w e r e det e m i n e d with a Varian-Tech t r o n atomic absorption spect r o p hotome ter For d e t e c t i o n of c l a y minerals, a p a r t of t h e c o l l e c t e d d u s t samples was ashed a t 380% f o r 16 hrs. While the low temperature ashing does not cause decomposition of c l a y minerals, i t ensures complete oxidation of c o a l d u s t due to prolonged p e r i o d of heating. X-ray d i f f r a c t i o n powder p a t t e r n s of ashed samples were taken f o r i d e n t i f i c a t i o n of c l a y m i n e r a l s using Rich S i e f a r t Instrument ( n i c k e l - f i l t e r e d CuKotradiation with 35 KV and 20 mA c u r r e n t ) . The c l a y m i n e r a l s were i d e n t i f i e d by matching Id' v a l u e s with hS?M standard c a r d value. Mass and frequency s i z e measurement of t h e d u s t p a r t i c l e s w a s done by micron p h o t o s i z e r Instrument of S e i s h i n E n t e r p r i s e Co. Ltd., Japan. I t is based on t h e p r i n c i p l e of sedimentation and photo-extinction.

.

RESULTS AND DISCUSSION

The averaged r e s u l t s of a n a l y s i s of 16 r e s p i r a b l e c o a l d u s t samples from d i f f e r e n t seams a r e given i n Table 1. Each sample was analysed by atomic absorption spectrophotometer f o r f i v e minor elements (Fe, Ca, Mg, Na and K) and f i v e trace elements (Mn, Cu, Zn, C d and N i ) . A f t e r complete d i s s o l u t i o n of t h e sample t h e standard a d d i t i o n method desc r i b e d by Manning ( r e f . 5) was used t o determine t h e recovery of t h e

49

element. The absorbance d a t a showed no s t a t i s t i c a l d i f f e r e n c e s t h u s v e r i f y i n g t h a t there a r e no mutual i n t e r f e r e n c e s from e l e m e n t s t h a t a r e usually p r e s e n t i n coal dust. It w a s reported e a r l i e r (ref.6) t h a t t h e r e is a tendency f o r p o t e n t i a l l y more hazardous c o n s t i t u e n t s l i k e Cu, Cd, Zn and N i t o p r o g r e s s i v e l y c o n c e n t r a t e i n r e s p i r a b l e c o a l d u s t . The r e s u l t s of t h e s t u d i e s c a r r i e d o u t h e r e c o r r o b o r a t e t h o s e of t h e s t u d i e s r e l a t i n g t o US c o a l s ( r e f . 7) by d i f f e r e n t methods. TABLE 1

Average minor and t r a c e elements of r e s p i r a b l e c o a l mine d u s t Element

R e s p i r a b l e Coal Mine Dust (Minus 7 micron) I Seam XI Seam 111 Seam

Fe%

2.32 250 1 1490 650 886 89 145 38 26 20

Ca Na K

Mn Zn cu Cd N i

2.12 2580 1310 530 890 80 140 33 28 21

2.05 2612 1212 470 875 75 135 35 27 20 ~

A l l v a l u e s i n ppm u n l e s s o t h e r w i s e s t a t e d .

The r e s u l t s o f x-ray d i f f r a c t i o n a n a l y s i s of 15 c o a l d u s t samples from I, I1 and 111 seams (5 from each a s s e r i a l l y numbered i n Table 2) show t h a t t h e m i n e r a l c o n s t i t u e n t s a r e k a o l i n i t e , p i r r s o n i t e , beidel l i t e and q u a r t z . With t h e exception of h a r d e r q u a r t z , t h e s o f t and p l a t y c l a y m i n e r a l s are e n g u l f e d i n t o t h e p h a g o c y t i c c e l l s more e a s i l y under a given s t r e n g t h o f impact. These may a c t as c a t a l y s t s f o r pneumoconiosis. Frequency s i z e d i s t r i b u t i o n a n a l y s i s For each seam b e f o r e averaging, t h e 16 r e s u l t s , o b t a i n e d i n a l l s i z e ranges, were converted to p e r c e n t a g e s on weight b a s i s t o ensure t h e seamwfse frequency s i z e d i s t r i b u t i o n a t d i f f e r e n t l e v e l s , a s shown i n Table 3. The cummulative frequency o f p a r t i c l e diameter f o r i n d i v i d u a l as w e l l a s average l e v e l e x h i b i t s p o s i t i v e skewness for a l l t h e t h r e e sample sets and g i v e s r e a s o n a b l e approximation to s t r a i g h t l i n e when p l o t t e d on l o g - p r o b a b i l i t y p a p e r (Fig. 1) i n d i c a t i n g a log-normal d i s t r i b u t i o n . T h i s is i n agreement with t h e f i n d i n g s of Whitby e t a1 (ref. 8).

50

TABLE 2 I d e n t i f i c a t i o n of minerals i n r e s p i r a b l e coal d u s t No.

1 2 3 4 5 6

Intensity w M-

MS s M M

7 v v w

a

w

9

w

10 11

M

12 13 14 15

M M+ Me+

s S

'd' A.U. 3.346 2.283 2.62 4.58 5.150 4.924 4.240 3.340 2.554 1.982 1.375 3.568 1.452 7I160 4.331

Kaolinite

Luartz B e i d e l l i t e 3.34

2.284

2.282 2.60 4.45

2.55

2.48 1.987 1.375 3.57

Pirrsonite

4.26 3.34 2.458

5.10 4.92 4.29 2.60

1.450

7.15 4.35

4.45

TABLE 3

Frequency s i z e d i s t r i b u t i o n d a t a of r e s p i r a b l e p a r t i c u l a t e s a t each level

-

Seam

Depth from s u r f a c e l e v e l (m)

No.

of Samples

Averaqe wt. % i n s i z e (micron) 7-6

6-4

4-2

I I1 1x1

55 36 24

16 16 16

7.5 5.6 9.5

22.5 30.9 28.3

52.4 59.3 51.7

0.1

Fig. 1.

05 2 10 30 C U M M U L A T I V E '/OMASS<

50 70 90 PARTICLE SIZE

17.6 4.2 10.5

98

Composite mass-size d i s t r i b u t i o n of r e s p i r a b l e p a r t i c u l a t e s comprising t h r e e c o a l seams p l o t t e d on log-probability coordinates.

51

The mass median diameter (MMD), t h e r a t i o R, of t h i r d t o f i r s t obtained q u a r t i l e diameters and t h e geometric standard d e v i a t i o n s d g' from t h e s e l o g - p r o b a b i l i t y p l o t s of each seam a r e computed i n Table 4. TABLE 4 Variation of s i z e parameters of t h e r e s p i r a b l e d u s t p a r t i c l e s from d i f f e r e n t seams. ~~

Seam

Depth N o . of MMD Geometric (m) samples (micron) sn

75% s i z e (micron)

25% s i z e (micron)

Ratio

2.3

1.9 1.5 1.8

R

(U1

I I1 I11

55 36 24

16 16 16

3.2 3.6 3.5

1.6 1.3 1.5

4.4 4.5 4.7

2.9 2.6

I t i s e v i d e n t from T a b l e 4 t h a t t h e average m a s s median diameter

f o r a l l t h e t h r e e seams v a r i e s from 3.2 t o 3.6 microns whereas 25% of t h e r e s p i r a b l e p a r t i c l e s i s l e s s than 3 micron s i z e and t h e remaining 75% p a r t i c l e s i s around 4.5 micron s i z e . The averaged computed r e s u l t s of Table 3 show t h a t 10.8"A of t h e r e s p i r a b l e p a r t i c l e s a r e of minus two micron s i z e . Moreover, a consistency of mass median diameter, geometric standard d e v i a t i o n and t h e l a c k of any v i s i b l e t r e n d i n t h e percentage of mass having a diameter below 2 micron i n s i z e i n a l l t h e seams suggest t h a t within t h e l i m i t of experimental e r r o r t h e r e w a s no v a r i a t i o n i n d i s t r i b u t i o n of v a r i o u s s i z e f r a c t i o n s among the three seams. However, a s i s e v i d e n t from Table 4, t h e r e e x i s t s an Inverse c o r r e l a t i o n between t h e q u a r t i l e r a t i o and t h e mass median diameter ( r e f . 9). A comparison of Tables 3 and 4 r e v e a l s a t y p i c a l d u s t d i s t r i b u t i o n p a t t e r n of r e s p i r a b l e p a r t i c u l a t e s . As t h e q u a r t i l e r a t i o i n c r e a s e s the p a r t i c l e s i z e less than two micron (which i s most l i k e l y t o be r e t a i n e d i n lungs of exposed workers) a l s o increases. The r e s u l t s conform to t h e f i n d i n g s of Odgon e t a1 ( r e f . 10). A f i n a l e v a l u a t i o n t o c h a r a c t e r i s e t h e d i s t r i b u t i o n curve i s to f i n d a mathematical f u n c t i o n which f i t s them. Although Fig. 1 i s usef u l i n i n t e r p r e t i n g t h e c h a r a c t e r i s t i c s f o r comparative purposes and r e a d i l y g i v e s t h e cummulative percentage of t h e p a r t i c u l a t e s i n t h e v a r i o u s s i z e rangescovered, t h i s type of p l o t is, howetter, u n s u i t a b l e f o r r e g r e s s i o n purposes. The s i z e v e r s u s mass d i s t r i b u t i o n curve was found to f i t w e l l to a second degree p a r a b o l i c equation as shown i n Pig. 2 f o r I seam. S i m i l a r curves are o b t a i n e d f o r o t h e r seams also.

52

2

A B O L IC C U R V E

01

I

I

I

I

I

I

I

I

1

2

3

4

5

6

7

8

PARTICLE

SIZE

/l m

Fig. 2. IIDeg. Parabolic curve showing the r e l a t i o n between the s i z e and d i s t r i b u t i o n pattern of coal dust i n I seam.

The second degree parabolic equation €or the respirable dust p a r t i c l e s may be represented a s W = a

+ bS +

cS

2

where W and S represent weight and m e a n size of the p a r t i c l e

53

r e s p e c t i v e l y and a, b and c a r e constants. The t h r e e parameters a, b and c determine t h e percentage weight of t h e p a r t i c l e s i f t h e mean s i z e is known. The v a l u e s of a, b and c f o r F e s p i r a b l e p a r t i c u l a t e s f o r t h e t h r e e seams were determined by t h e p r i n c i p l e of l e a s t square regression, and a r e given i n Table 5. The observation is p a r t i c u l a r l y t r u e for c h a r a c t e r i s i n g t h e mass-size d i s t r i b u t i o n of r e s p i r a b l e p a r t i c u l a t e s analysed with micron p h o t o s i z e r model SKN 1000.

TABLE 5

Values of a, b and c f o r d i f f e r e n t seams Seams

a

b

I

3.34

10.48

-1.54

I1

-6.90

17.40

-2.39

I11

-2.55

12.94

-1.72

C

The s t u d i e s throw l i g h t on t h e presence of some minor and t r a c e elements, t h e n a t u r e of c l a y minerals and t h e r e l a t i o n s h i p of second degree p a r a b o l i c equation between m a s s and s i z e of t h e r e s p i r a b l e c o a l d u s t p a r t i c l e s i n an Indian mine.

ACKNOWLEDGEMENTS

The author expresses h i s thanks t o t h e members of h i s research group f o r t h e i r h e l p i n completing t h i s work. Special thanks a r e a l s o extended t o S h r i B N Sahoo f o r t e c h n i c a l a s s i s t a n c e .

REFERENCES

1

Lee, J.S. 6(1972) 593.

R.E.

Coldwall and G.S.

Morgan, Atmospheric Environ.,

54

2

3 4 5 6

R.P. Fairman, R.J. O'Brien, S. Sweeker, H.E. Amandur and E.P. Shoub, Arch. Environ. Health, 32 (1977) 211. B.M. Wright, B r i t . J. I n d u s t r . Med., ll(1954) 284. P. E l l i n g t o n and W.N. A d a m s , Fuel (London), 30(1951) 272. D.C. Manning, A t . Absorpt. N e w s l e t t . , 14(1975) 99. N.S. R a w a t , B.N. Sahoo and J.K. Sinha, Chemistry and I n d u s t r y ,

13 (1981) 470-471. D.J. Von Lehmdev, R.E. Jengens and R.E. Lee ( J r . ) , Anal. Chem., 46 (1974) 239-245. 8 K.T. Whitby, R.B. Husar and B.Y.H. Liu, I n d u s t r i a l Aerosols and Atmospheric Chemistry ( e d i t e d by G.N. Hidy) Academic, New York* (1971) 237. 9 J. Dodgon and W. Whittaker, Ann. Occup. Hyg., 16(1973) 373. 10 T.L. Odgon and A.M. Rickman, Ann. Occup. Hyg., 20(1977) 257.

7

55

OF SOILS AND PLANTS BY MERCURY AS INFLUENCED BY THE PROXIMITY TO

CONTAMINATION

INDUSTRIES I N ALEXANDRIA, EGYPT.

I.H.

ELSOKKARY

S o i l & Water S c i . Dept., F a c u l t y Of A g r i c u l t u r e , A l e x . , Univ., and Univ. of Alexa n d r i a Research C e n t e r (UNARC)

. Egypt.

ABSTRACT The amounts of t o t a l Hg i n t h e s o i l s and t h e e d i b l e p a r t s of seven v e g e t a b l e p l a n t c r o p s grown i n u n p o l l u t e d and p o l l u t e d s o i l s were s t u d i e d . The h i g h l y p o l l u t e d s o i l s c o n t a i n e d h i g h e r l e v e l s of Hg (495 ppb) t h a n t h o s e i n t h e u n p o l l u t e d (35 ppb).

The t o p s o i l w a s h i g h l y e n r i c h e d w i t h Hg t h a n t h e

s u b s o i l a s t h e r e s u l t of t h e d e p o s i t i o n of Hg p a r t i c u l a t e s produced from t h e industries. P l a n t s grown i n s o i l s n e a r i n d u s t r i e s c o n t a i n e d h i g h l e v e l s of Hg up to 362 ppb.

The amounts of Hg i n t h e p l a n t s p e c i e s which grown i n w i n t e r were h i g h e r

t h a n t h o s e grown i n summer.

INTRODUCTION E a r l i e r s t u d y showed g r e a t p o s s i b i l i t y f o r Hg accumulation i n t h e p l a n t s grown i n t h e s o i l s of A l e x a n d r i a d i s t r i c t due t o t h e i n c r e a s i n g s o u r c e s of c o n t a m i n a t i o n by Hg ( R e f . 3 ) .

The main s o u r c e s of Hg p o l l u t i o n i n t h a t a r e a a r e c h l o r i n e a l k a l i

i n d u s t r i e s , paper f a c t o r i e s , e l e c t r i c g e n e r a t i o n , o t h e r d i f f e r e n t t y p e s of indust r i e s and a g r i c u l t u r a l a c t i v i t i e s . The o b j e c t i v e of t h e p r e s e n t work w a s t o e v a l u a t e t h e magnitude of contamina t i o n of seven v e g e t a b l e p l a n t c r o p s grown i n s o i l s of s i x s i t e s i n A l e x a n d r i a d i s t r i c t by mercury.

MATERIALS AND METHODS S i x s i t e s i n t h e a g r i c u l t u r a l l a n d i n A l e x a n d r i a were s e l e c t e d t o r e p r e s e n t u n p o l l u t e d and p o l l u t e d zones ( F i g . 1 ) . (pH = 7 . 5

-

These s o i l s have and a l k a l i n e r e a c t i o n

8.11, low o r g a n i c m a t t e r ( 1 . 6 - 2 . 8 % ) , r e l a t i v e l y h i g h t o t a l c a r b o n a t e

( 2 - 4 % ) and s o i l t e x t u r e of c l a y loam.

56 S o i l s of s i t e No.1 are n o t s u b j e c t e d t o any s o u r c e s of p o l l u t i o n by Hg e x c e p t t h o s e from a g r i c u l t u r a l a c t i v i t i e s w h i l e s o i l s of s i t e s No. 2 , 3 , 4 , 5 and 6 a r e s u b j e c t e d t o v a r i o u s s o u r c e s of p o l l u t i o n from t h e s u r r o u n d i n g i n d u s t r i e s . Seven v e g e t a b l e p l a n t c r o p s ; l e t t u c e (Lactuca s a t i v a ) , cabbage ( B r a s s i c a o l e r a c e a v a r . c a p i t a t a ) , c a r r o t s (Dancus c a r o t a ) , p a r s l e y ( P e t r o s e l i n u m h o r t e n s e ) , pepper (Capsium f r u t e s c e n s ) , j e w ' s mallow (Corchorus o l i t o r i u s ) and r a d i s h (Raphanus s a t i v u s ) ; which a r e grown i n t h e s e s i t e s were c o l l e c t e d .

The e d i b l e p a r t s of t h e s e

p l a n t s were washed w i t h d i s t i l l e d water, d r i e d a t 35°C f o r 24 h o u r s , c r u s h e d by hand and s t o r e d f o r Hg a n a l y s i s . T o t a l Hg was d e t e r m i n e d by d i g e s t i n g t h e s o i l o r t h e p l a n t m a t e r i a l w i t h c o n c e n t r a t e d HN03 (Ref.4). spectrophotometer

Mercury was measured by f l a m e l e s s a t o m i c a b s o r p t i o n

.

F i g . 1- L o c a t i o n s of t h e c u l t i v a t e d s i t e s .

RESULTS AND DISCUSSION Mercury i n s o i l s :

T o t a l Hg i n t h e s u r f a c e s o i l l a y e r v a r i e d from 12-30 ppb

i n t h e u n p o l l u t e d s o i l s and from 60-495 ppb i n t h e p o l l u t e d s o i l s ( T a b l e 1 ) . T h i s p o i n t s o u t t o t h e o c c u r r e n c e of h i g h c o n t a m i n a t i o n o f t h e s e s o i l s by Hg due t o the increasing industrial a c t i v i t i e s i n that area. w e r e found i n s i t e s No. 4 , 5 and 6.

The h i g h e s t l e v e l s of p o l l u t i o n

The d a t a a l s o show a n accumulation of Hg i n

t h e t o p s o i l which i n d i c a t e s t h a t Hg t r a n s p o r t i n t h e s o i l p r o f i l e i s v e r y slow. T h i s i s due t o t h e low s o l u b i l i t y of H g - p a r t i c u l a t e s d e p o s i t e d on t h e s o i l a s t h e

57 of h i g h s o i l pH a n d / o r f o r m a t i o n o f low s o l u b l e Hg compounds.

F i g . 2 showes

t h e r e l a t i o n s h i p between s o i l d e p t h and t o t a l Hg i n six s o i l p r o f i l e s r e p r e s e n t i n g the six s i t e s . TABLE 1

V a r i a t i o n s i n t h e amounts o f t o t a l Hg (ppb) w i t h t h e s o i l d e p t h i n t h e s i x s i t e s .

Site No

Soil depth cm

Number of samp 1e s

Range

Average

1

0-15 15-30 30-60

7 7 7

12-30 12-35 10-25

25 20 20

2

0-15 15-30

60-75 58-80 35-48

68 66

44

197-235 80-105 44-67

205 95 56

0-15 15-30

296-345

30-60

80-99

315 185 89

7 7 7

285-415 170-265 60-96

355 200 80

7 7 7

310-495 150-285 60-100

385 200 85

30-60

3

4

5

0-15 15-30

7 7

30-60

7

0-15 15-30 30-60

6

0-15 15-30 30-60

Mercury i n p l a n t s :

160-218

The e d i b l e p a r t s o f v e g e t a b l e s grown in s o i l s of s i t e

No 1 c o n t a i n e d t h e l o w e s t l e v e l s of Hg w h i l e t h o s e grown i n s o i l s of s i t e s No 4 ,

5 and 6 c o n t a i n e d t h e h i g h e s t l e v e l s ( T a b l e s 2 and 3 ) .

The r e s u l t s a l s o show

v a r i a t i o n s i n Hg c o n t e n t s i n t h e l e a v e s of d i f f e r e n t p l a n t s p e c i e s grown i n t h e s a m e s i t e which a matter of m o r p h o l o g i c a l and g e n e t i c c h a r a c t e r i s t i c s of e a s h

p l a n t a s found w i t h l e t t u c e , r a d i s h , cabbage and p a r s l e y . The p l a n t s grown i n w i n t e r c o n t a i n e d h i g h Hg t h a n t h o s e grown i n summer (Table 2 ) .

T h i s c l e a r l y show t h e i n f l u e n c e o f s e a s o n a l v a r i a t i o n s on Hg c o n t e n t s

58

T o t a l s o i l Hg ppb

T o t a l s o i l Hg ppb 0

Soil depth cm

.

0

?

15

-

30

-

45

-

i

-

i

c

u

m

e

L

0 0 r -

1c

I

0 0 N

r

0 0 n .

0 0 3

0 0

0

0

,

60 *

S i t e No.1

I

S i t e No.2

75..

*

90

Soil depth cm

-

0-

.

:f soil depth cm

.

60

.

15

-

90

-

S i t e No.3

S i t e No.4

0.

15

.

45 30

Fig.2-

60

-

75

-

90

L

S i t e No.5

S i t e No.6

R e l a t i o n s h i p b e t w e e n s o i l d e p t h and t o t a l Hg (ppb) i n s i x s o i l p r o f i l e s representing t h e s i x sites.

59 TABLE 2

Mean v a l u e s of t o t a l Hg (ppb) i n t h e e d i b l e p a r t s of v e g e t a b l e p l a n t s grown i n s o i l s of t h e s i x s i t e s c o l l e c t e d i n J a n . and Aug. 1980 (Values between parent h e s i s d e n o t e s of t h e number of p l a n t samples).

Site No

Lettuce

Radish

Parsley

.

.

Jan.

Aug

20(11)

18(5)

Jan.

Aug

41(5)

30(3)

32(6)

90(7)

68(5)

45(4)

32(5)

38(4)

38(4)

3

115(6)

78(5)

118(8)

66(7)

46(6)

40(7)

4

282(7)

190(6)

212(6)

154(5)

115(3)

95(4)

5

291(5)

205(8)

200(6)

165(6)

118(5)

98(6)

6

345(6)

280(8)

287(5)

215(7)

125(7)

lOO(6)

Jan.

Aug.

1

38(6)

2

TABLE 3

Mean v a l u e s of t o t a l Hg (ppb) i n t h e e d i b l e p a r t s of v e g e t a b l e p l a n t s grown i n s o i l s of t h e s i x s i t e s ( v a l u e between p a r e n t h e s i s d e n o t e s t o t h e number of p l a n t samples).

i n t h e p l a n t s and g i v e a n i d e a about t h e e f f e c t i v e n e s s of atmospheric p r e c i p i t a t i o n , which i s h i g h e r i n w i n t e r t h a n i n summer. It i s c l e a r t h a t l e a v e s of t h e p l a n t s c o n t a i n e d u s u a l l y t h e h i g h e s t l e v e l s

of Hg.

I t i s obvious t h a t f r u i t s c o n t a i n t h e lowest l e v e l s w h i l e r o o t s could

accumulate r e l a t i v e l y moderate l e v e l s .

I n t h i s s t u d y , t h e amounts of Hg i n pepper

f r u i t d i d n o t i n c r e a s e , by t h e same r a t e a s occurred w i t h l e a v e s of o t h e r p l a n t s , by i n c r e a s i n g r a t e of p o l l u t i o n (Table 3 ) .

This could be expected w i t h such f r u i t s .

60 CONCLUSION The l e v e l s of Hg and t h e i r d i s t r i b u t i o n i n t h e s o i l p r o f i l e of t h e p o l l u t e d s i t e s show h i g h a c c u m u l a t i o n of Hg i n t h e t o p s o i l . polluted soils.

T h i s i s n o t found i n t h e un-

The d i f f e r e n c e between t h e amounts of Hg i n t h e t o p s o i l and t h e

s u b s o i l i n c r e a s e d w i t h i n c r e a s i n g r a t e of p o l l u t i o n .

This indicates t h a t t h e

f a l l o u t of p a r t i c u l a t e s on t h e s o i l from t h e i n d u s t r i e s i s t h e major s o u r c e of Hg.

The r a t e of c o n t a m i n a t i o n i s g e n e r a l l y r e l a t e d t o t h e magnitude and p r o x i m i t y

t o t h e s o u r c e of p o l l u t i o n .

Even i n d u s t r i a l a c t i v i t i e s n o t d i r e c t l y r e l a t e d t o

Hg c a n g i v e r i s e t o s u b s t a n t i a l r e l e a s e of t h i s m e t a l i n t h e environment. Comparing l e v e l s of Hg i n o u r p l a n t s w i t h t h o s e r e p o r t e d i n t h e l i t e r a t u r e , i t i s c l e a r t h a t t h e s t u d i e d p l a n t s c o n t a i n e d r e l a t i v e l y h i g h l e v e l s of Hg and

it i s h i g h l y p o l l u t e d (Ref. 1 and 2 ) . S i n c e most of t h e s e c u l t i v a t e d v e g e t a b l e s a r e of s h o r t growth p e r i o d and have s u r f a c e and s h o l l o w r o o t systems, Hg i n t h e s e p l a n t s w i l l be absorbed by t h e i r r o o t s and f o l i a r p a r t s .

A t t h e s e e n v i r o n m e n t a l c o n d i t i o n s , growing v e g e t a b l e s

a s l e t t u c e , r a d i s h , p a r s l e y , cabbage and j e w ' s mallow i n t h e s e s o i l s a r e n o t recommended.

ACKNOWLEDGEMENTS The a u t h o r w i s h e s t o e x p r e s s h i s t h a n k s t o P r o f . D r . A. El-Sadr;

d i r e c t o r of

UNARC, f o r t h e f a c i l i t i e s a v a i l a b l e and h i s encouragement d u r i n g c a r r i n g on t h a t

work.

REFERENCES

1- Bouquiaux, J. P r o c . of t h e I n t . Symp. on t h e problem o f c o n t a m i n a t i o n of man and h i s environment by mercury and cadmium. Luxembourg 3-5 J u l y 1973 CEC Luxemburg (1974) p 23. 2- E l s o k k a r y , I . H . and J-Lag, B e i t r a g e t r o p . L a n d w i r t s c h , Veterinarmed., 1 8 , J g (1980) 35-47. 3- E l s o k k a r y , I . H . S t u d i e s i n Environ. Sc. Vol. 8 , Atmos. P o l l . , M.N.Benarie (Ed.), P r o c . of t h e 1 4 t h I n t . Colloquium, P a r i s F r a n c e May 5-8 (1980) E l s e v i e r , pp 433-438. 4- Holak, W.B., J. Assoc. O f f . Anal. Chem. 55 (1972). 741-742.

61

STUDY OF ATMOSPHERIC POLLUTION I N AN URBAN ZONE DEPRIVED OF MEASUREMENT

SYSTEMS, FOR PURPOSES OF LEGISLATION APPLICATION TO THE C I T Y OF TUNIS

M.C.

ROBE and J. CARBONNELLE

Commissariat h 1 ' E n e r g i e Atomique, I n s t i t u t d e P r o t e c t i o n e t d e Silret6 N u c l g a i r e , DGpartement d e P r o t e c t i o n , S e r v i c e s Techniques d e P r o t e c t i o n , S e r v i c e d e P r o t e c t i o n Technique, C e n t r e d ' E t u d e s N u c l 6 a i r e s d e S a c l a y ,

91191 Gif-sur-Yvette

Cedex. F r a n c e .

ABSTRACT I n o r d e r t o l e g i s l a t e on and p r o v i d e a g a i n s t t h e a t m o s p h e r i c p o l l u t i o n s p e c i f i c t o a c o u n t r y i n a r e g i o n d e p r i v e d of measurement s y s t e m s , i t i s f i r s t n e c e s s a r y t o examine t h e f o l l o w i n g p o i n t s :

-

l o c a t i o n of c h i e f p o l l u t i o n s o u r c e s ,

- e m i s s i o n c h a r a c t e r i s t i c s of t h e main s o u r c e ,

-

e f f e c t s of t h e s o u r c e on t h e environment, p r e d i c t a b l e e f f e c t s of a p p l i e d l e g i s l a t i o n . I n t h e c i t y of T u n i s f o r example t h e road t r a f f i c was i d e n t i f i e d a s t h e major

s o u r c e of p o l l u t i o n . Ways t o c u t down t h e p o l l u t i o n l e v e l a r e proposed on t h e b a s i s o f d i f f e r e n t s h o r t - t e r m measurements

. Calculation

shows t h a t i f r u l e s s i m i l a r t o t h o s e l a i d

down i n F r a n c e were a p p l i e d and t h e t r a f f i c f l o w o r g a n i s e d t h e l e v e l s of c e r t a i n p o l l u t a n t s (CO, NOx) would b e s u b s t a n t i a l l y r e d u c e d .

INTRODUCTION

G e n e r a l l y s p e a k i n g t h e a n t i - p o l l u t i o n campaign i s guided by two p r i n c i p l e s :

- i d e n t i f i c a t i o n and l o c a t i o n of p o l l u t i o n a g e n t s and e m i t t e r s , - a c q u i s i t i o n of t h e t e c h n i c a l , s t a t u t o r y and c o n t r a c t u a l means t o m o n i t o r , r e d u c e and e l i m i n a t e p o l l u t a n t e m i s s i o n s i n t o t h e atmosphere.

A f i r s t p o s s i b i l i t y , c o n t i n g e n t on economic c o n d i t i o n s , i s t o s e t up a complex system of measurements a p p r o p r i a t e t o a long-term s t u d y . T h i s w i l l show up t h e i n f l u e n c e of a l l e x t e r n a l p a r a m e t e r s and a l l o w t h e e f f e c t s of l e g i s l a t i o n t o be monitored a f t e r w a r d s .

62 Otherwise i t i s p o s s i b l e w i t h p r e s e n t measurement f a c i l i t i e s t o o r g a n i s e short-term r u n s s u f f i c i e n t l y r e p r e s e n t a t i v e of t h e a c t u a l s i t u a t i o n so t h a t techn i c a l o r s t a t u t o r y a n t i - p o l l u t i o n s t e p s may be t a k e n . By t h e same means a l s o t h e eventual measurement system may be optimised f o r permanent monitoring of t h e reduced p o l l u t i o n l e v e l o b t a i n e d . An example i s given by t h e enquiry conducted i n t h e c i t y of Tunis, where no measurement system o r p o l l u t i o n d a t a were a v a i l a b l e except f o r a l i s t of i n d u s t r i a l f i r m s i n s t a l l e d on t h e s i t e .

EXPERIMENTS An enquiry of t h i s kind i s conducted i n f o u r s t a g e s :

- p o l l u t i o n survey, - study of t h e main source t h u s d e f i n e d ,

-

e f f e c t of t h e source on t h e environment, p o l l u t i o n r e d u c t i o n measures.

P o l l u t i o n survey A p r e l i m i n a r y survey i s c a r r i e d o u t t o determine t h e main cause of causes of

p o l l u t i o n . Although t h e time spent on t h i s survey i s l i m i t e d t h e maximum number of t y p i c a l l o c a l m e t e o r o l o g i c a l s i t u a t i o n s must be included. Mobile measurement systems a r e used, t o g e t h e r w i t h m e t e o r o l o g i c a l f a c i l i t i e s i f t h e r e l e v a n t d a t a a r e n o t a v a i l a b l e on t h e s p o t . A s f a r a s p o s s i b l e , according t o t h e meteorological d a t a of t h e s y n o p t i c g r i d a period r e p r e s e n t i n g t h e worst c o n d i t i o n s f o r pollut i o n i s chosen.

In t h e c a s e of Tunis (Figure 1 ) t h e major p o l l u t a n t c o n c e n t r a t i o n s (CO, NOx, SO2,

C H ) were mapped over a l l t h e b u i l t up a r e a and t h e main cause of p o l l u t i o n X Y

was determined by t h e u s e of a v e h i c l e c a r r y i n g a number of a n a l y s e r s . Meteorological d a t a were supplied by t h e s y n o p t i c g r i d on t h e one hand and by an a c o u s t i c probe on t h e o t h e r . F i g u r e 2 g i v e s an example of t h e c h a r t obtained f o r CO i n a given d i s p e r s i o n situation. An a n a l y s i s of t h e r e s u l t s showed t h a t a p a r t from a s t r o n g l o c a l e f f e c t of t h e i n d u s t r i a l zone, t h e major problem came a s a r u l e from t h e emissions of motor v e h i c l e s (Ref. 1 ) .

Study of t h e main source The c h i e f source being t h u s e s t a b l i s h e d i t s emission c h a r a c t e r i s t i c s must t h e n be determined. I n t h e c a s e of motor t r a f f i c t h e problem i s complicated by t h e f a c t t h a t t h e source c o n s i s t s of many small emissions, n o t n e c e s s a r i l y identical

.

63

Fig. 1

monoxyde de carbone

-Q 5 m g . n ~ - ~ )HHCC

%>lo

5 i 10 mg.rnm3 mg.m-3

I Fig. 2

I

\

1

64

I n T u n i s t h e t r a f f i c s i t u a t i o n i s q u i t e d i f f e r e n t from t h a t i n Western Europe. The C O , NOx,

SO2 and C H

c o n c e n t r a t i o n of e x h a u s t g a s e s were measured on about

X Y

200 v e h i c l e s . A check a g a i n s t e x i s t i n g c a r r e g i s t r a t i o n s t a t i s t i c s proved t h e sample t o be

r e p r e s e n t a t i v e of t h e normal t r a f f i c on t h e r o a d s .

3 x

2 h

Fig.

3

Fig. 4

F i g u r e 3 shows t h e sample d i s t r i b u t i o n f o r e x h a u s t CO c o n c e n t r a t i o n . Given t h e c h a r a c t e r i s t i c s of t h e v e h i c l e s i t i s p o s s i b l e t o c a l c u l a t e a n e m i s s i o n r a t e ( f i g u r e 4 ) , t h e n knowing t h e h o u r l y t r a f f i c f l o w a t a c e r t a i n p o i n t t o c a l c u l a t e t h e amount of p o l l u t a n t i n t r o d u c e d a t t h i s p o i n t .

E f f e c t s of t h e s o u r c e o n t h e environment The q u a n t i t y of p o l l u t a n t s e m i t t e d b e i n g known, t h e i r e f f e c t o n t h e environment may b e i n f e r r e d from a knowledge of t h e l o c a l d i f f u s i o n c o n d i t i o n s . T h i s however i m p l i e s a d e t a i l e d m i c r o m e t e o r o l o g i c a l s t u d y which c a n b e l o n g and c o s t l y . Another method i s t o measure t h e c o n c e n t r a t i o n s i n t h e environment under chosen m e t e o r o l o g i c a l c o n d i t i o n s (Ref. 2 ) . Two k i n d s of measurement were t h u s c a r r i e d o u t s i m u l t a n e o u s l y i n c e n t r a l Tunis :

- from a v e h i c l e c a r r y i n g a n a l y s e r s and t r a v e l l i n g a l o n g t h e t h o r o u g h f a r e s studies,

- from a f i x e d measurement s t a t i o n w i t h sampling p o i n t s a t d i f f e r e n t a l t i t u d e s , s e t up t e m p o r a r i l y a t a p o i n t on t h e p a t h of t h e v e h i c l e . T h i s m o b i l e system n o t o n l y c h a r t s t h e p o l l u t a n t c o n c e n t r a t i o n o v e r t h e p a t h t r a v e l l e d , b u t a l s o g i v e s o t h e r i n f o r m a t i o n such as t h e a v e r a g e t r a f f i c speed a t t h e t i m e of measurement o r t h e amount of p o l l u a n t i n h a l e d by a n o b s e r v e r f o l l o w i n g t h e same p a t h .

65

30

-a

25 28

\

p 15

v

c &10 5 0 -

N

m

*

l

n

c

o

h

m

Rverage veloclty (m/s) Fig. 5

F i g u r e 5 shows t h e i n f l u e n c e of t h e a v e r a g e t r a f f i c speed on t h e CO concentrat i o n i n a g i v e n t h o r o u g h f a r e . The f i x e d s t a t i o n s u p p l i e s d a t a on t h e p o l l u t a n t v a r i a t i o n and i t s v e r t i c a l c o n c e n t r a t i o n g r a d i e n t d u r i n g t h e day ( f i g u r e 6 ) , as w e l l a s t h e e f f e c t of t r a f f i c peaks (Ref. 2 ) . A s t a t i s t i c a l t r e a t m e n t r e v e a l s t h e i n f l u e n c e of e x t e r n a l p a r a m e t e r s :

-

t r a f f i c f l o w o n CO c o n c e n t r a t i o n ( f i g u r e 7 ) ,

-

t e m p e r a t u r e g r a d i e n t on v e r t i c a l CD p r a d i e n t .

#%

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

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

......... ......... c 0

t

2!

.4 0 U

.........l

;

8 .....................

...... ........ .......... ........ ; ................................. ! ! l f

! 4 $ 3 f f g f Traffic flow
-

.....

PARIS 19 TUNIS 19

Fig. 7

Fig. 8

P o l l u t i o n r e d u c t i o n measures Once t h e e m i s s i o n c o n d i t i o n s and e f f e c t s on t h e environment a r e known, i t i s p o s s i b l e t o draw up a n a n t i - p o l l u t i o n p l a n (Ref. 3 ) . I n t h e c a s e of T u n i s f o r example t h i s d i f f e r e n t a c t i o n were proposed :

a

-

S t a t u t o r y measures

A comparison of CO e m i s s i o n s from v e h i c l e s i n F r a n c e and i n T u n i s i a (Table 1 )

( f i g u r e 8) shows t h a t t h e a p p l i c a t i o n of French r e g u l a t i o n s (Table 1 )

(Ref. 4

and 5) would c u t down t h e d i s c h a r g e by n e a r l y 20 Z f o r a v e h i c l e of c y l i n d e r c a p a c i t y 1 200 cm3 t r a v e l l i n g a t a v e r a g e speed 20 km.h

-1

on a n u r b a n t h o r o u g h f a r e .

66

TABLE 1

CO C o n c e n t r a t i o n

* b

France

Number of v e h i c 1e s

*

Tunisia

< 5 %

53 %

38 Z

> 7 %

22 %

43 %

French norm : maximum CO c o n c e n t r a t i o n a t reduced speed 4 , 5 %.

-

T e c h n i c a l measures It i s shown t h a t t h e American CO norm

of 10 m g . ~ n - ~i n 8 h o u r s c a n b e r e s p e c t e d

by o r g a n i s i n g t h e t r a f f i c f l o w i n such away a s t o keep a n a v e r a g e speed of more than 5 m.s-'

i n c e r t a i n t h o r o u g h f a r e s , i . e . a n e x p e r i m e n t a l o u t p u t of 1500

v e h i c l e s a n h o u r . T h i s c o r r e s p o n d s t o a r e d u c t i o n of a b o u t 20 Z o n t h e t r a f f i c f l o w a t peak h o u r s f o r t h e r o a d c o n s i d e r e d .

CONCLUSION T h i s method of approach t o a complex problem, u s u a l l y s o l v e d by t h e compiling of many d a t a o v e r a l o n g p e r i o d , i s p a r t i c u l a r l y w e l l s u i t e d t o c o u n t r i e s where economic c o n s i d e r a t i o n s l i m i t t h e p o s s i b i l i t i e s o f a c t i o n i n t h e environmental f i e l d . It implies : a ) The m a s t e r y of m o b i l e o r e a s i l y p o r t a b l e measurement systems and t h e a c q u i s i t i o n of d a t a i n s i t u . b ) C a r e f u l f o r e t h o u g h t . S i n c e e x p e r i m e n t a l r u n s a r e s h o r t ( t w i c e 15 days i n t h e c a s e of T u n i s ) it i s i m p o r t a n t t h a t a s many u s e f u l m e t e o r o l o g i c a l s i t u a t i o n s as p o s s i b l e should b e e n c o u n t e r e d . T h i s may b e a c h i e v e d by c o n s u l t i n g t h e r e c o r d s of t h e m e t e o r o l o g i c a l s y n o p t i c g r i d , u s u a l l y a v a i l a b l e , and by c l o s e c o o p e r a t i o n

w i t h t h e a u t h o r i t i e s concerned. c ) A d e t a i l e d a n a l y s i s of t h e d a t a o b t a i n e d (computer p r o c e s s i n g ) . Given t h e s e p r e c a u t i o n s i t i s p o s s i b l e t o o b t a i n , q u i c k l y and a t minimum c o s t , enough i n f o r m a t i o n t o a l l o w :

-

s t a t u t o r y o r technical a n t i - p o l l u t i o n s t e p s t o be taken, t h e i n s t a l l a t i o n of a permanent m o n i t o r i n g system t o b e o p t i m i s e d .

ACKNOWLEDGEMENTS The measurements campaing i n t h e c i t y of T u n i s was f i n a n c e d i n t h e c o n t e x t of Franco-Tunisian agreements by t h e French Environment M i n i s t r y , and backed by t h e T u n i s i a n A g r i c u l t u r e M i n i s t r y and t h e T u n i s i a n N a t i o n a l M e t e o r o l o g i c a l Bureau

.

REFERENCES 1 J . D e l s e y , L a p o l l u t i o n due aux moyens d e t r a n s p o r t , Note d ' h f o r m a t i o n no 13.

I R T - CERNE - Mars 1979, 56. 2 H.W. G e o r g i i , E . Busch, E . Weber, I n v e s t i g a t i o n o f t h e temporal and s p a t i a l d i s t r i b u t i o n of t h e immission c o n c e n t r a t i o n of c a r b o n monoxyde i n F r a n k f u r t / Main, R e p o r t s of t h e I n s t i t u t e f o r Meteorology and Geophysics of t h e Univers i t y of F r a n k f u r t h i n , May 1967. 3 R . J . Larbey, Tendances dans l a r 6 d u c t i o n d e s 6 m i s s i o n s 1 l'dchappement d e s v o i t u r e s europdennes e t amGricaines, OP 7 9 / 1 . O c t e l S.A., P a r i s , J a n v i e r 1979. 4 P . J a r r a u l t , L i m i t a t i o n s d e s dmissions d e p o l l u a n t s e t q u a l i t 6 d e l ' a i r . V a l e u r s r d g l e m e n t a i r e s en v i g u e u r e n 1980 d a n s l e s p r i n c i p a u x pays i n d u s t r i e l s . Normes d e Q u a l i t 6 d ' A i r , Volume I , I n s t i t u t FranGais d e l ' E n e r g i e , no 66, 1980.

5 A i r q u a l i t y c r i t e r i a f o r c a r b o n monoxide, U.S. Department of H e a l t h . Education, and W e l f a r e , C h a p i t r e 8 , p. 1-57. C h a p i t r e 9, p . 1-20. March 1970.

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MODELING

More specialized meetings, such as the Worth A t l a n t i c Treaty Organization's Committee f o r Challenges of t h e Modern Society: Expert Panel on Air Pollution Modelling o r the American Meteorological S o c i e t y ' s Symposia on Turbulence, Diffusion and Air Pollution deal more with submodules of the models and aim r a t h e r a t t h e development of modeling as a t o o l . A . Eschenroeder points towards t h e use of such t o o l s - - chemical a n d dispersion modules -- i n s e t t i n g l i m i t s and designing s t r a t e g i e s f o r a i r q u a l i t y improvements. The paper of G . Neumann-Hauf and G. H a l b r i t t e r i s in t h e same extensive s p i r i t : modeling i s used t o assess t h e environmental impacts t o be expected, in t h i s case those of an expanded use of coal in the Federal Republic i n Germany. In both i n s t a n c e s , t h i s i s a f a r cry from modeling as an i n t e l l e c t u a l exercise.

The a i r pollution model serves t o

improve our standards of l i v i n g , health included, a t l e s s c o s t and l e s s liquid-fuel expenditure. Subsequent papers discuss more speci i c a s p e c t s , mostly representing t o p i c s of considerable present i n t e r e s t episode f o r e c a s t , calm wind conditions, problems of complex t e r r a i n transport.

accidental r e l e a s e s a n d mesoscale

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71

ATMOSPHERIC DYNAMICS OF NOx E M I S S I O N CONTROLS

ALAN ESCHENROEDER Arthur

D. L i t t l e , I n c . , Cambridge, Massachusetts, USA

ABSTRACT Fundamental p h y s i c a l and chemical processes i n f l u e n c i n g t h e e f f e c t i v e n e s s of o x i d e s o f n i t r o g e n (NOx) a i r p o l l u t i o n c o n t r o l s a r e surveyed i n t h i s paper. Phenomenological d e s c r i p t i o n s a r e t r e a t e d f o r some of t h e main f e a t u r e s analyzed i n r e c e n t r e s e a r c h work.

The p a r t i c i p a t i o n o f NOx as a p r e c u r s o r t o secondary

p o l l u t a n t s depends b o t h on t h e r a t e o f m i x i n g and t h e r a t e o f r e a c t i o n w i t h o t h e r atmospheric p r e c u r s o r r e a c t a n t s .

M i x i n g i n t h e l a r g e s c a l e may depend on plume

d i s p e r s i o n and i n t h e s m a l l s c a l e on cascading o f t u r b u l e n t c o n c e n t r a t i o n eddies down t o m o l e c u l a r s c a l e . n i t r i c o x i d e (NG),

A c c o r d i n g l y , r e a c t i o n s between t h e p r i m a r y e m i t t a n t ,

and ambient ozone

(0,) produce s h o r t - t e r m n i t r o g e n d i o x i d e

(NO2); whereas l o n g e r t e r m g e n e r a t i o n depends on o r g a n i c a l l y - d e r i v e d c h a i n c a r r i e r s t h a t o x i d i z e NO t o NO2.

These i n t e r a c t i o n s between emissions and t h e en-

v i r o n m e n t p l a y key r o l e s i n s e t t i n g l i m i t s on b o t h 0, and NO2-production t h r o u g h the a l t e r a t i o n o f emission r a t e s .

The paper concludes w i t h some b a s i c c r i t e r i a

t h a t must be addressed i n d e s i g n i n g s t r a t e g i e s f o r a i r q u a l i t y improvements t h r o u g h NOx emissions c o n t r o l .

INTRODUCTION Ba c kq r o und F o s s i l f u e l combustion i s t h e m a i n a n t h r o p o g e n i c o r i g i n o f o x i d e s o f n i t r o g e n e m i s s i o n s i n t o t h e atmosphere.

N i t r i c o x i d e i s t h e p r i n c i p a l compound e m i t t e d

d i r e c t l y by combustion sources; however, o u r main concern i s t h e chemical format i o n o f t h e secondary p o l l u t a n t s , n i t r o g e n d i o x i d e and ozone, i n areas o f potent i a l human exposure.

Because o f t h e q u a n t i t y generated and t h e widespread

p o t e n t i a l f o r adverse e f f e c t s on p u b l i c h e a l t h and w e l f a r e , NOx emissions and a s s o c i a t e d secondary p o l l u t a n t s have been t h e s u b j e c t o f s t a n d a r d - s e t t i n g and r u l e m a k i n g by e n v i r n n m e n t a l management a u t h o r i t i e s . T h i s paper t r a c e s t h e consequences o f changing NOx emissions t h r o u g h t h e i r t r a n s p o r t , d i s p e r s i o n , t r a n s f o r m a t i o n and f a t e i n t h e atmosphere.

Principal

72

e f f e c t s a r e t r e a t e d h e r e w i t h q u a n t i t a t i v e examples i l l u s t r a t i n g t h e i n t e r a c t i o n s governing these e f f e c t s .

The t h e o r e t i c a l and e x p e r i m e n t a l f o u n d a t i o n s o f

t h e examples a r e drawn f r o m t h e l i t e r a t u r e ; t h e r e f o r e , o n l y t h e h i g h l i g h t s l e a r n e d f r o m t h e r e s u l t s a r e d i s c u s s e d below.

The e x p e r i e n c e i n t h e USA i s

chosen t o p r o v i d e most o f t h e q u a n t i t a t i v e aspects o f t h e t r e a t m e n t because of i t s e x t e n s i v e documentation i n t h e p u b l i c domain.

Thus, o u r scope i s l i m i t e d t o

t h e emphasis o f a few s i g n i f i c a n t phenomena p u n c t u a t e d w i t h examples based on methods t h a t a r e comprehensively developed elsewhere. Receptor E f f e c t s B e f o r e we examine t h e consequences o f c o n t r o l e f f o r t s , i t i s i n s t r u c t i v e t o g e t some p e r s p e c t i v e r e g a r d i n g t h e i r p r i m a r y g o a l s : health.

t h e p r o t e c t i o n of p u b l i c

The q u a l i t a t i v e s i m i l a r i t y o f n i t r o g e n d i o x i d e h e a l t h e f f e c t s and those

o f ozone i s expressed e i t h e r as suspected i n c r e a s e s i n c h r o n i c pulmonary disease (e.g.,

emphysema o r b r o n c h i t i s ) o r i n c r e a s e s i n t h e d i s a b i l i t y due t o p r e e x i s t -

i n g c h r o n i c pulmonary d i s e a s e .

Acute e f f e c t s a t t r i b u t e d t o exposures t o these

p o l l u t a n t s a r e i n c r e a s e s i n r e s p i r a t i o n r a t e and decrease i n t i d a l volume.

Also,

i n c r e a s e d s u s c e p t i b i l i t y t o r e s p i r a t o r y i n f e c t i o n has been under i n v e s t i g a t i o n f o r b o t h O3 and NO2.

The l i t e r a t u r e on t h e s e h e a l t h e f f e c t s and t h e i r i n v e s t i -

g a t i o n i s summarized i n d e t a i l i n r e f s . 1, 2 and 3; t h e r e f o r e , f u r t h e r c i t a t i o n s w i l l n o t be made h e r e . C o n t r o l agencies s e t ambient g o a l s f o r a i r q u a l i t y a c c o r d i n g t o c r i t e r i a based on n o t i o n s o f dose-response b e h a v i o r o f t h e p o l l u t a n t s .

Because of funda-

m e n t a l s c i e n t i f i c and e t h i c a l problems, we c a n n o t know w i t h c e r t a i n t y t h e doseresponse c h a r a c t e r i s t i c s ; t h u s , s t a n d a r d - s e t t i n g must proceed on t h e b a s i s o f c o l l e c t i v e opinions o f experts.

S i n c e t h i s i s an accepted approach, i t seems

r e a s o n a b l e t o use a q u a n t i t a t i v e method based on c o l l e c t i v e judgments of doseresponse e f f e c t s .

T h i s has been d e v i s e d ( 4 ) u s i n g a D e l p h i s t u d y approach w i t h

a panel o f f o u r t e e n m e d i c a l e x p e r t s .

F i g . 1 shows t h e ranges o f dose-response

t h u s o b t a i n e d f o r n i t r o g e n d i o x i d e compared w i t h t h o s e f o r ozone (as a s u r r o g a t e f o r photochemical o x i d a n t ) .

The upper l i m i t o f each dose response area i s

e s t a b l i s h e d by i n c a p a c i t y l e v e l s w h i l e t h e l o w e r corresponds t o d i s c o m f o r t levels.

The reason t h a t t h e c h a r a c t e r i s t i c s f o r t h e two p o l l u t a n t s can be com-

p a r e d on t h e same p l o t i s t h a t i d e n t i c a l approaches a r e used f o r d e f i n i n g t h e c o n d i t i o n s o f i n c a p a c i t y and d i s c o m f o r t f o r b o t h p o l l u t a n t s f o r normal i n d i v i duals.

The d e f i n i t i o n used f o r i n c a p a c i t y i s :

"May p r e c i p i t a t e r e s p i r a t o r y and c a r d i a c problems, broncho-pneumonia." The d e f i n i t i o n used f o r d i s c o m f o r t i s : "Eye i r r i t a t i o n ; n o n - p r o d u c t i v e coughing, c h e s t t i g h t n e s s . "

A v e r y i m p o r t a n t c o n c l u s i o n t o b e drawn f r o m F i g . 1 i s t h a t n i t r o g e n d i o x i d e c o n c e n t r a t i o n s must be 5 t o 10 t i m e s t h o s e o f ozone t o produce t h e same e f f e c t .

73

T

T

I = Incapacity D = Discomfort

1 I

5

I 10

I

I

20

1 1 , I I I 40 50 70 80 90 Percent of Population Responding

95

3

F i g . 1. D e l p h i dose-response curves f o r normal a d u l t s exposed t o n i t r o g e n d i o x i d e and t o ozone ( 4 ) . D e s p i t e t h e l a r g e range o f v a l u e s between d i s c o m f o r t and d i s a b i l i t y , t h i s f i n d ing i s distinctly significant.

The U.S.

s t a n d a r d f o r n i t r o g e n d i o x i d e i s 0.05 ppm

on an annual b a s i s , b u t F i g . 1 i s f o r a c u t e e f f e c t s t h a t p e r s i s t f o r p e r i o d s measured i n hours.

The C a l i f o r n i a s t a n d a r d f o r one h o u r i s 0.25 ppm f o r n i t r o h o u r l y s t a n d a r d i s 0.12 ppm f o r ozone.

gen d i o x i d e and t h e U.S.

t h a t t h e former i s f a r more c o n s e r v a t i v e t h a n t h e l a t t e r .

I t would appear

lhese considerations

e s t a b l i s h t h e magnitude o f t h e g o a l s o f a c o n t r o l program f o r l i m i t i n g n i t r o g e n d i o x i d e and ozone by NO

X

emissions r e s t r i c t i o n s .

view of t h e o t h e r s i d e o f t h e problem: various source categories.

L e t us t u r n now t o an over-

t h e magnitude o f t h e emissions from

Emission Sources The U.S.

i n v e n t o r y of NOx emissions f o r e i g h t y e a r s d u r i n g t h e p a s t decade i s

summarized i n T a b l e I .

The p r o p o r t i o n s o f t h e e m i s s i o n problem a r e t h a t s t a -

t i o n a r y combustion i n c l u d i n g e l e c t r i c u t i l i t i e s , i n d u s t r i a l and space h e a t i n g , i s s t e a d i l y r e s p o n s i b l e f o r a p p r o x i m a t e l y 56% o f t h e emissions, w h i l e v e h i c u l a r sources a c c o u n t f o r 38 t o 40% o f t h e emissions.

Electric u t i l i t i e s contribute

a p p r o x i m a t e l y h a l f of t h e s t a t i o n a r y combustion source emissions on a n a t i o n a l basis.

R e l a t i v e l y l i t t l e i s c o n t r i b u t e d by t h e o t h e r t h r e e source c a t e g o r i e s .

TABLE 1

6 (10 M t / y r ) (Ref. 5

Oxides o f N i t r o g e n Emissions E s t i m a t e s f o r t h e U.S. S t a t iona ry

Industrial

Solid Total

1970 1971 1972 1973 1974 1975 1976 1977

7.9 8.7 9.0 8.6 8.6 9.4 9.2

11.3 11.9 12.3 12.1 11.5 12.4 13.0

0.6 0.7 0.7 0.7 0.7 0.7 0.7

0.2 0.2 0.2 0.2 0.1 0.1 0.1

0.2 0.1 0.1 0.1 0.2 0.1

19.6 20.2 21.6 22.3 21.7 21 .o 22.8 23.1

I t appears f r o m t h i s t a b l e as i f t h e main c o n t r o l i s s u e i s b a l a n c i n g s t r a t e g i e s between t r a n s p o r t a t i o n and s t a t i o n a r y f u e l combustion sources.

The growth w i t h

t i m e o f t h e f o r m e r averages f i f t y p e r c e n t h i g h e r t h a n t h a t o f t h e l a t t e r source category . Approach o f t h i s Paper With these perspectives i n mind f o r t h e receptor effects

and f o r t h e source

c o n t r i b u t i o n s , we w i l l focus on t h e atmospheric c o n n e c t i o n between t h e two f o r t h e remainder o f t h i s paper.

I n t h e n e x t s e c t i o n we examine t h e p h y s i c a l i n f l u -

ences o f t h e atmosphere on t h e NOx emissions as t h e y a r e t r a n s p o r t e d and mixed. F o l l o w i n g t h a t i s a s e c t i o n d i s c u s s i n g t h e chemical t r a n s f o r m a t i o n s t h a t f o r m pathways f o r NO2 and O3 p r o d u c t i o n and removal.

The c o u p l i n g o f t h e t u r b u l e n t

e n t r a i n m e n t w i t h t h e NOx-03 chemical c y c l e l e a d s us i n t o t h e s e c t i o n on l o c a l and r e g i o n a l i m p l i c a t i o n s o f NOx-control i n t h e South Coast A i r B a s i n o f California.

A b r i e f s e t o f c o n c l u d i n g remarks c l o s e s t h e paper.

ATMOSPHERIC PHYSICAL EFFECTS V e r t i c a l D i s p e r s i o n I n f l u e n c e s on Short-Term Impacts The s u r f a c e c o n c e n t r a t i o n d i s t r i b u t i o n of p o l l u t a n t s produced by NOx emiss i o n s i s e s t a b l i s h e d by t h e p a t t e r n o f sources and by m e t e o r o l o g i c a l processes. I n t h e p r e v i o u s s e c t i o n we n o t e d t h a t NO,

sources f e l l i n t o two p r i m a r y c a t e -

g o r i e s : t r a n s p o r t a t i o n and s t a t i o n a r y combustion.

L e t us examine by way o f a

highly s i m p l i f i e d a n a l y s i s t h e r e l a t i v e ground concentration contribution of uniformly deployed area sources ( t o model t r a n s p o r t a t i o n ) and an elevated source ( t o model combustion e m i t t e r s g e n e r i c a l l y ) . Selecting the South Coast Air Basin (SCAB) o f C a l i f o r n i a as a t e s t environment, we can c o n s t r u c t t h e a n a l y s i s based on r e a l i s t i c ranges of parameters. Since NOx emissions a r e precursors of b o t h NO2 and O3 formation, t h e i r morning concentrations along with those of organic gases a r e considered c r i t i c a l i n determining the secondary p o l l u t a n t l e v e l s . This meteorology a l s o simulates p e r s i s t e n t conditions on winter mornings when NO2 episodes occur. I n e i t h e r event i t c o n s t i t u t e s an extreme lower l i m i t of elevated source influence. (Following t h i s a n a l y s i s i s a treatment of an upper l i m i t c a s e . ) T h u s , we w i l l assume s t a b l e atmospheric conditions c h a r a c t e r i s t i c of a t h i c k surface based inversion i n the morning i n the SCAB.

Fig. 2 . Qe @

Xe xY u Y o

Z

Geometry of d i f f u s i o n source configuration Strength of source a t (O,O,H) Source f l u x over (q x 6 ) area Concentration a t ground due t o elevated source = Concentration a t ground due t o surface sources = = Horizontal d i f f u s i o n parameter = Vertical d i f f u s i o n parameter = =

Figure 2 i l l u s t r a t e s t h e geometry assumed. Elevated sources a r e aggregated a t a s i n g l e height and l a t e r i t w i l l be seen t h a t t h e i r horizontal dispersion parameter (T i s forced t o approach q / 2 as x 5 t o model t h e merging of multiple Y plumes a t some e l e v a t i o n within the broad f l a t urban plume. Neglecting chemistry we f i n d t h a t the s u r f a c e concentration a t the downwind edge of t h e rectangle ( x = 5 ; z = 0) i s approximated by -f

Mass p e r u n i t volume o f p o l l u t a n t e m i t t e d by ground-based sources D i s t a n c e s i n c o o r d i n a t e frame d e f i n e d i n F i g u r e 2 Mass e m i s s i o n r a t e p e r u n i t area f r o m surface-based sources assuming a u n i f o r m d i s t r i b u t i o n a t t h e average v a l u e Wind speed D i s p e r s i o n parameter Eq. ( 1 ) i s o b t a i n e d f o l l o w i n g t h e approach o f H o l z w o r t h ( 6 ) and Lucas ( 7 ) who assumed t h a t t h e s u r f a c e sources were approximated by a n a g g r e g a t i o n o f doubly

i n f i n i t e c r o s s w i n d l i n e sources. i n t e r e s t ; i . e . uz <<

0.

T h i s i s a good a p p r o x i m a t i o n f o r t h e case of

I f t h e ASME power law f o r m u l a s ( 8 ) a r e employed f o r t h e b where values o f a and b a r e em-

d i s p e r s i o n parameters uz t a k e s the f o r m o f ax

p i r i c a l l y d e t e r m i n e d f o r each s t a b i i i t y c l a s s . Using t h i s t o i n t e g r a t e t q . ( l ) , we o b t a i n

xg =

2Qg 5 uzu(l-b)

The c o r r e s p o n d i n g e x p r e s s i o n f o r t h e s u r f a c e c o n c e n t r a t i o n under t h e a x i s o f t h e e l e v a t e d s o u r c e plume i s ( 9 )

Now i f we d e f i n e t h e t o t a l mass e m i t t e d by ground-based sources as Q obtain Q

=

@gn 5.

we g’ We f i n d by s u b s t i t u t i o n o f t h i s r e l a t i o n s h i p i n t h e concen-

g t r a t i on e q u a t i o n s t h a t

(4) Z

Note t h a t t h e geometry and w i n d dependence vanishes e x c e p t for t h e argument of t h e e x p o n e n t i a l where H depends upon u and u z , upon 5 f o r any p a r t i c u l a r source configuration.

F i g u r e 3 shows t h e i n f l u e n c e c o e f f i c i e n t K as i t depends upon

plume h e i g h t H where

K i s d e f i n e d on t h e p l o t .

77

0.25

am

0.20

-

m x ‘a, 0.15

-

,a‘

a .I. I

-111 A’

Y +a,

‘G .- 0.10

-

Lc

a,

0 01

c

-2

0.05

-

Lc

-C 0

0.1

0.2 0.3 Plume Height - km

0.4

0.5

F i g . 3. Surface c o n c e n t r a t i o n i n f l u e n c e o f e l e v a t e d sources r e l a t i v e t o s u r f a c e based a r e a sources under s t a b l e c o n d i t i o n s ( b = 0 . 7 1 )

Examining E q . 4 and F i g . 3, we n o t e s e v e r a l s i g n i f i c a n t f e a t u r e s : The downwind d i s t a n c e and w i n d speed dependences a r e i m p l i c i t i n

ti and uz. A l l i n f l u e n c e curves appear t o approach maximum K v a l u e s between 20 and 25% r e g a r d l e s s of downwind d i s t a n c e . F o r t y p i c a l plume h e i g h t s , t h e i n f l u e n c e c o e f f i c i e n t i s more n e a r l y 10%. Thus, a t e x t r e m e l y l o w - l i d d e d i n v e r s i o n c o n d i t i o n s , t h e s u r f a c e c o n c e n t r a t i o n c o n t r i b u t i o n of e l e v a t e d sources r e l a t i v e t o t h a t o f surface-based a r e a sources i s o n l y 10 t o 20%.

L e t us now t u r n b r i e f l y t o t h e o t h e r extreme, t h a t o f c l o s e range plume i m pact.

The s c e n a r i o chosen h e r e i s an e l e v a t e d i n v e r s i o n base a t t h e a s y m p t o t i c

h e i g h t o f t h e plume.

T h i s c o n d i t i o n p r e c l u d e s upward p e n e t r a t i o n o f t h e i n v e r -

s i o n by t h e plume and c o n f i n e s d i s p e r s i o n t o downward f u m i g a t i o n .

I f we assume

( 9 ) t h a t t h e plume f i l l s t h e u n s t a b l e l a y e r u n d e r l y i n g t h e i n v e r s i o n l a y e r a t we f i n d t h e f o l l o w i n g

a downwind d i s t a n c e o f t w i c e t h a t where o z = 0.47H,

c h a r a c t e r i s t i c s f o r m i n i m i z i n g t h e d i s t a n c e f o r plume touchdown f o r t h e SCAB

78 e l e v a t e d sources : 6

I n v e r s i o n base e l e v a t i o n s between 600 and 800 m above an u n s t a b l e l a y e r .

0

Downwind d i s t a n c e s o f 6 t o 10 km.

Under t h e s e c o n d i t i o n s , e p i s o d e l e v e l NU2 c o n c e n t r a t i o n s a r e n o t a c h i e v e d because i n c i d e n t s o l a r energy s u f f i c i e n t t o s u p p o r t > 600 m u n s t a b l e l a y e r depths r a p i d l y d r i v e s t h e p h o t o c h e m i s t r y w e l l beyond t h e NO2 p e a k i n g phase.

A t down-

wind d i s t a n c e s o f 6 t o 10 km f r o m t h e s o u r c e under t h e s e u n s t a b l e c o n d i t i o n s , t h e l a t e r a l s p r e a d i n g o f t h e plume w i l l be l a r g e and

t i t r a t i o n o f ozone w i l l be t h e

p r i m a r y chemical s t e p o c c u r r i n g i n t h e a f f e c t e d environment (see t h e n e x t sect i o n f o r e x p l a n a t i o n s o f t h e chemical dynamics o f NO2-peaking and t i t r a t i o n by ozone). Weinstock, Chang and Norbeck ( 1 0 ) have i n v e s t i g a t e d t h e combined m i x i n g and p h o t o c h e m i s t r y i n an i n v e s t i g a t i o n o f t h e r e l a t i v e e f f e c t i v e n e s s o f v e h i c l e e m i s s i o n c o n t r o l and s t a t i o n a r y power p l a n t e m i s s i o n c o n t r o l .

They used a photo-

chemical d i f f u s i o n model w i t h c a r e f u l l y d e r i v e d m e t e o r o l o g i c a l d a t a and emissions i n p u t s d r i v i n g a n u m e r i c a l s o l u t i o n o f an a i r p a r c e l h i s t o r y .

The c o n c l u s i o n s

drawn above f o r e p i s o d e m e t e o r o l o g i c a l c o n d i t i o n s were s u p p o r t e d g e n e r a l l y by the findings o f r e f .

10.

I f t h e emissions o f , say, e l e c t r i c a l u t i l i t y sources were o n l y o n e - f i f t h o f

t h o s e o f t h e t r a n s p o r t a t i o n sources ( w h i c h t h e y were a p p r o x i m a t e l y i n t h e 1979 i n v e n t o r y ) , t h e i r s u r f a c e c o n c e n t r a t i o n c o n t r i b u t i o r k would b e i n t h e r a t i o o f o n l y 1:26 because o f t h e

%

20% i n f l u e n c e c o e f f i c i e n t f o r e l e v a t e d sources.

In a

s i m p l i f i e d example where t h e s e were t h e o n l y sources, a 50% r e d u c t i o n i n v e h i c l e emissions would reduce t h e s u r f a c e c o n c e n t r a t i o n b y 48%; whereas a 50% r e d u c t i o n i n power p l a n t emissions would reduce t h e s u r f a c e c o n c e n t r a t i o n by o n l y 1.9%. I f p r o p o r t i o n a l r o l l b a c k were used f o r each c l a s s o f s o u r c e i n t h e 1 : 5 emissions

r a t i o scenario,

t h e 50% emissions r e d u c t i o n s i n each s o u r c e c l a s s would y i e l d

e s t i m a t e d c o n c e n t r a t i o n decreases o f 42% and 8% r e s p e c t i v e l y .

Thus, a p p l i c a t i o n

o f p r o p o r t i o n a l r o l l b a c k would g i v e t h o s e r e s p o n s i b l e f o r v e h i c l e systems a b a s i s f o r c o m p l a i n t t h a t t h e i r already-mandated e x h a u s t c o n t r o l s a r e b e i n g undercounted; whereas t h o s e r e s p o n s i b l e f o r i n s t a l l i n g power p l a n t systems would have cause f o r c o m p l a i n t t h a t f u t u r e l a r g e emissions r e d u c t i o n s would n o t be c o s t e f f e c t i v e because o f a n o v e r e s t i m a t e o f t h e i r b e n e f i t s u s i n g r o l l b a c k .

Feedback

f r o m t h e s e two i n d u s t r i a l groups has r e s u l t e d i n p r o p o s i n g m o d i f i e d c o n t r o l system g o a l s f o r b o t h sources by F e d e r a l , s t a t e and r e g i o n a l a u t h o r i t i e s .

This

s h i f t i n p o l i c y a l s o tends t o be s u p p o r t e d by d i s p a r i t i e s between human h e a l t h tolerance levels o f

NO2 and O 3 i l l u s t r a t e d i n F i g . 1.

As we s h a l l see i n t h e

chemical s e c t i o n o f t h i s paper, a n e a r - f i e l d r e d u c t i o n i n NO2 f r e q u e n t l y r e p l a c e s t h e NO

2

w i t h O3 on a o n e - f o r - o n e b a s i s .

79 H o r i z o n t a l T r a n s p o r t I n f l u e n c e s on A n n u a l l y Averaged Impacts A l t h o u g h t h e most p r o m i n e n t l y d i s c u s s e d h e a l t h e f f e c t s o f NO2 a r e a c u t e ones due t o s h o r t - t e r m exposures, t h e N a t i o n a l Ambient A i r Q u a l i t y Standard f o r t h e U.S. i s an annual average. d a t a f o r NO2 ( r e f s . standard).

( D i f f i c u l t i e s i n a s s e s s i n g t o x i c o l o g i c a l and e p i d e m i o l o g i c a l

1, 2, 3 and 4) have d e l a y e d t h e a d o p t i o n o f a s h o r t - t e r n

I n response t o t h i s r e g u l a t o r y c l i m a t e , G u t f r e u n d and c o l l e a g u e s (11)

have developed and a p p l i e d a s e m i - e m p i r i c a l model t o p r o v i d e q u a n t i t a t i v e e s t i mates o f each m a i n e m i s s i o n s o u r c e c a t e g o r y t o t h e annual average NO2 c o n c e n t r a t i o n a t any s p e c i f i e d m o n i t o r i n g s t a t i o n .

l h e model approach, which emphasizes conser-

v a t i v e ( h i g h ) e s t i m a t e s of p r i n c i p a l e l e v a t e d s t a t i o n a r y c o n t r i b u t i o n s ,

i s in-

tended t o t r e a t : 0

complex f l o w f i e l d s such as t h o s e i n t h e SCAB

0

NOx l o s s t h r o u g h d e p o s i t i o n o r n i t r i c a c i d f o r m a t i o n

0

v a r i a t i o n i n mixing height

0

day-to-day c a r r y o v e r o f p o l l u t a n t s

I n c o n t r a s t t o t h e a n a l y s i s p r e s e n t e d above, t h i s model focuses on t h e h o r i z o n t a l t r a n s p o r t o f p o i n t s o u r c e e m i s s i o n s averaged o v e r many hours ( t h r e e y e a r s : 1974, 1975 and 1979).

I t assumes a l l NOx i s e m i t t e d and i s homogenously mixed f r o m t h e

s u r f a c e t o t h e m i x i n g h e i g h t ; i t f u r t h e r assumes t h a t a l l o f t h e NOx i n t h e gas phase i s NO2 a t a l l p o i n t s .

The combined s u r f a c e and n i t r i c a c i d loss pathways

a r e r e p r e s e n t e d b y a c o n s t a n t 7% p e r h o u r l o s s . These assumptions a r e embodied i n a n a i r p a r c e l t r a c k i n g program ( t h a t g i v e s t h e model i t s name: NOXTRAK) t h a t uses t h r e e h o u r l y averaged windspeeds t o c a l c u l a t e t r a j e c t o r i e s downwind f r o m each m a j o r ( r e f i n e r y o r power p l a n t ) s t a t i o n a r y p o i n t s o u r c e o f NOx u n t i l i t l e a v e s t h e b a s i n o r i t d i s s i p a t e s t h e NOx l e v e l below a c e r t a i n preset threshold.

T h i s i m a g i n a r y p a c k e t o f a i r has a h e i g h t equal t o

t h e m i x i n g h e i g h t , a w i d t h o f 10 km c e n t e r e d on each mass p o i n t on t h e t r a j e c t o r y and a l e n g t h e s t i m a t e d by t h e t i m e i n t e r v a l o f c o m p u t a t i o n ( 1 5 m i n u t e s ) d i v i d e d by t h e w i n d speed as t h e a i r passes o v e r t h e source.

D i r e c t i o n s and speeds t h a t

d e t e r m i n e t h e 15-minute v e c t o r s a r e i n t e r p o l a t e d among n e i g h b o r i n g m e t e o r o l o g i c a l stations.

The c o n c e n t r a t i o n i n t h e moving box i s t h e e m i s s i o n r a t e of t h e p o i n t

s o u r c e t i m e s t h e t i m e s p e n t o v e r t h e s o u r c e d i v i d e d by t h e box volume.

T h i s con-

c e n t r a t i o n i s i n f l u e n c e d o n l y by t h e l o s s processes c i t e d above d u r i n g t h e subsequent h i s t o r y o f i t s t r a v e l .

Any m o n i t o r i n g s t a t i o n t r a v e r s e d by i t s 10 km wide

swath i s counted as a " h i t " a t t h e c o n c e n t r a t i o n c u r r e n t l y i n t h e box.

The number

o f h i t s , each w e i g h t e d b y t h e c o n c e n t r a t i o n a r e counted f o r each s o u r c e - r e c e p t o r p a i r and t h e c o n t r i b u t i o n o f t h e p o i n t sources w i t h i n a c l a s s t o each s t a t i o n ' s annual average. A t t h i s p o i n t t h e t r a j e c t o r y m o d e l i n g i s complete, and t h e sum o f t h e p o i n t sources i s s u b t r a c t e d f r o m t h e observed annual average f o r t h e s t a t i o n o v e r t h e

80 corresponding time i n t e r v a l .

T h i s p r o c e d u r e i s t h e e m p i r i c a l p a r t o f t h e approach.

The remainder i s a p p o r t i o n e d i n t o m o b i l e sources and o t h e r sources u s i n g p u b l i s h e d emissions i n v e n t o r y and m e t e o r o l o g i c a l d a t a i n a m u l t i - s o u r c e Gaussian d i s p e r s i o n model w i t h a l l NOx assumed t o be

NO2. Thus, f r o m NOXTRAK t r a j e c t o r y a n a l y s i s , t h e

e l e c t r i c power and p e t r o l e u m i n d u s t r y c o n t r i b u t i o n s a r e determined s y n t h e t i c a l l y . From t h e measured v a l u e of t o t a l annual average and f r o m m o d e l - d e r i v e d a p p o r t i o n ilient t h e m o b i l e and o t h e r s o u r c e c o n t r i b u t i o n s a r e determined a n a l y t i c a l l y . F o r t h e y e a r s s t a t e d above, t h e c a l c u l a t i o n s (11) y i e l d v a l u e s o f t h e measure of e f f e c t i v e n e s s o f r e d u c t i o n s i n annual average NO

2 c o n c e n t r a t i o n s as a conse-

quence of r e d u c t i o n s i n emissions f r o m each d e s i g n a t e d s o u r c e c a t e g o r y . [his i s 3 s t a t e d as AX/AQ, o r t h e change i n c o n c e n t r a t i o n (ug/ni ) p e r u n i t change i n emissions (kg/s).

H i g h e r v a l u e s o f A X / A Q denote h i g h e r degrees of a s o u r c e t y p e ' s

i n f l u e n c e on p r o d u c i n g a c o n c e n t r a t i o n r e d u c t i o n t h r o u g h c o n t r o l o f t h e emissions o f t h a t source type.

T a b l e 2 d i s p l a y s t h e e f f e c t i v e n e s s of each o f t h e f o u r

s o u r c e t y p e s f o r each of t h e two m o n i t o r i n g s t a t i o n s b e l i e v e d t o pose t h e g r e a t e s t problems i n 1987. TABLE 2 C o n t r o l E f f e c t i v e n e s s ( A x / A Q ) ~by Source ype f o r Two M o n i t o r i n g S t a t i o n s i n t h e South Coast A i r B a s i n o f C a l i f o r n i a (pg/m ) + ( k g / s ) (Ref. 11)

!i

~~~~

Station Source Type M o b i l e Sources E l e c t r i c Power I n d u s t r y Petroleum I n d u s t r y Otherb

Burbank

Pasadena

14.0 2.5 1.0 10.5

13.5 2.0 2.0 8.5

aQ

a

A x 2 Annual average c o n c e n t r a t i o n change;

b

" O t h e r " i n c l u d e s r e s i d e n t i a l space h e a t i n g , r a i l w a y o p e r a t i o n s , d i e s e l c o n s t r u c t i o n equipment, i n d u s t r i a l b o i l e r s and j e t a i r c r a f t

5

E m i s s i o n change

S e v e r a l s i g n i f i c a n t c o n c l u s i o n s emerge t r o m T a b l e 2: 0

M o t o r v e h i c l e c o n t r o l s a r e many times more e f f e c t i v e as t h o s e on

0

The b a s i c p a t t e r n of p r o p o r t i o n a l i t y i s r e p i i c a t e d a t t h e two

r e f i n e r i e s and power p l a n t s i n r e d u c i n g t h e annual coverage. stations. Based on a n a l y s i s o f t h e s i x h i g h e s t s t a t i o n s , i t was concluded by G u t f r e u n d e t a1 ( 1 1 ) t h a t m o t o r v e h i c l e c o n t r o l s a r e i n t h e a r e a o f f o u r t i m e s h i g h e r on t h e A x / A Q s c a l e t h a n power p l a n t s and r e f i n e r i e s .

R e t u r n i n g t o o u r example a t t h e end o f t h e l a s t s u b s e c t i o n i n w h i c h i t was assumed t h a t e l e c t r i c u t i l i t y sources were h a l f of t h e motor v e h i c l e sources i n aggregate emissions, we can r e r u n t h e comparison between model r e s u l t s p r e s e n t e d h e r e and r o l l b a c k .

Using G u t f r e u n d ' s e s t i m a t e of f o u r f o r t h e e f f e c t i v e n e s s r a t i o ,

we f i n d t h a t 50% r e d u c t i o n o f t h e m o t o r v e h i c l e e m i s s i o n s a l o n e w o u l d improve t h e combined ( m o t o r v e h i c l e p l u s e l e c t r i c u t i l i t y ) c o n t r i b u t i o n by 47%; whereas a 50%

81 e l e c t r i c u t i l i t y emissions c u t would o n l y e f f e c t a 2.4% improvement i n t h e annual average c o n c e n t r a t i o n o f NO2.

W i t h p r o p o r t i o n a l 50% r o l l b a c k o f each source t y p e

i n t h e 1:5 e m i s s i o n s r a t i o we r e c a l l t h a t t h e e s t i m a t e s would have been 42% and 8% i n s t e a d o f 47% and 2.4% r e s p e c t i v e l y .

Again, t h i s i n d i c a t e s t h a t m o t o r v e h i c l e

c o n t r o l s i n p l a c e w i l l be more e f f e c t i v e t h a n p l a n n e d and t h a t proposed e l e v a t e d source c o n t r o l s w i l l b r i n g a b o u t l e s s c o n c e n t r a t i o n r e d u c t i o n t h a n t h e amount hoped f o r on t h e b a s i s o f l i n e a r r o l l b a c k . A l t h o u g h t h e s e d i s c u s s i o n s o f p h y s i c a l a t m o s p h e r i c dynamics o f NUx c o n t r o l a r e f a r f r o m e x h a u s t i v e , t h e y do s e r v e t o p o i n t o u t how modeling r e s u l t s can be used t o a i d i n decision-making.

I t i s g r a t i f y i n g t o note t h a t these a n a l y t i c a l

s t u d i e s t h a t a r e t i e d c l o s e l y t o o b s e r v a t i o n a l d a t a produce c o r r o b o r a t i v e r e s u l t s as t o t h e r e l a t i v e e f f e c t i v e n e s s o f d i f f e r e n t approaches t o NOx c o n t r o l .

L e t us

t u r n now t o t h e p r i m a r i l y chemical aspects o f t h e same problem.

ATMOSPHERIC CHEMICAL EFFECTS

-

The Ozone C y c l e and NOx S i n k s

Emissions o f NOx as t h e y undergo a t m o s p h e r i c processes a r e i n v o l v e d i n pathways l e a d i n g t o NO2 and O 3 formation; mates a r e p l o t t e d i n F i g . 1.

t h e p o l l u t a n t s whose h e a l t h e f f e c t s

esti-

The b e g i n n i n g s of t h e pathways and t h e u l t i m a t e

f a t e o f NOx a r e dominated b y i n o r g a n i c r e a c t i o n s whose r o l e s have been r a t h e r w e l l d e f i n e d (e.g.,

see r e f . 3 ) .

The p a r t i c i p a t i o n o f NO2 and NO i n t h e ozone c y c l e i s d e s c r i b e d b y t h e t h r e e r e a c t i o n steps: hv (290 - 430 nm) + NO2 + O(3P) + NO O (3 P ) + 0 2 + M + 0 3 + M

O3 + NO

+ NO2 + O2

rhe photon o r i g i n a t i n g f r o m u l t r a v i o l e t p o r t i o n s of s u n l i g h t d i s s o c i a t e s NO2 t o f o r m a ground s t a t e oxygen atom which r e a c t s r a p i d l y i n t h e second s t e p t o form ozone.

The ozone r e a c t s i n a c h a r a c t e r i s t i c t i m e o f l e s s t h a n a m i n u t e t o p r o -

duce NO2 and an oxygen m o l e c u l e .

T h i s system e f f e c t i v e l y c o l l a p s e s t o an

e q u i l i b r i u m between photons and NO2 d r i v i n g one way w i t h ozone and NO w o r k i n g i n opposition.

The b a l a n c e i n t h e atmosphere between NO and NO2 i s s e t up by

t h e p h o t o n f l u x and t h e ambient ozone. e m i t t e d , i t i s NO2 t h a t produces 03.

Note t h a t a l t h o u g h p r i m a r i l y NO i s I n t e r v e n i n g i n t h i s c y c l e i s an o r g a n i c a l l y -

s u p p o r t e d pathway f o r o x i d i z i n g NO t o NO2 i n p o l l u t e d atmospheres.

This

mechanism, w h i c h i s d i s c u s s e d i n t h e n e x t s u b s e c t i o n , t i p s t h e b a l a n c e of t h e q u a s i - e q u i l i b r i u m s e t up by (+02)

hv

+ NO2 2

NO + 03

82

toward t h e f o r m a t i o n of more NO2.

Emissions of NO i n i t i a l l y c o n t a c t i n g t h e a i r

g e n e r a t e NO2 r a p i d l y b y t h e t h i r d r e a c t i o n i n t h e s e t i n i t i a l l y i n t r o d u c e d . O t h e r branches o f ozone c y c l e a r e s e t up by

O3

NO2

f

-+

NO3

f

O2

w h i c h feeds NO3 + NO2 + N205 D i n i t r o g e n p e n t o x i d e can r e d i s s o c i a t e t o r e t u r n NO3 and NO2 t o t h e system. Where t h e r e i s a s m a l l c o n c e n t r a t i o n o f NO, such as i n r u r a l areas, t h e ozone p h o t o d i s s o c i a t i o n may be i m p o r t a n t v i a

O3 + hv ( 2 9 0

-

1 350 nm) -+ O2 + O ( D)

-

700 nm)

or

O3

h v (450

f

-+

O2 + O(3P)

T e r m i n a t i o n o f c h a i n s i n v o l v i n g NOx s p e c i e s o c c u r s as a r e s u l t o f s i n k r e actions.

Some o f t h e s e a r e

HO f NO + M N205 f H20

-+

HON02 + M 2 HON02

+.

HONO

+.

and

HO

NO

f

f

M

f

M

p r o d u c i n g n i t r i c a c i d and n i t r o u s a c i d r e s p e c t i v e l y . a t e t o r e t u r n h y d r o x y l (HO) r a d i c a l t o t h e system.

The l a t t e r can p h o t o d i s s o c i -

HO i s p r e s e n t i n p o l l u t e d

atmospheres due t o t h e o r g a n i c r e a c t i o n s and i n n o n p o l l u t e d atmospheres due t o

O(’D)

f

H20 -+ 2HO.

The a c i d - f o r m i n g r e a c t i o n s a r e e x t r e m e l y i m p o r t a n t as c h a i n

t e r m i n a t o r s i n s e t t i n g t h e r e a c t i v i t y l e v e l o f atmospheric m i x t u r e s ; hence, addi n g NOx t o a system i n h i b i t s i t s secondary p o l l u t a n t f o r m i n g p o t e n t i a l . The n e t r e s u l t s of t h e ozone c y c l e r e a c t i o n s and t h e s i n k r e a c t i o n s a r e t o c o n v e r t NO t o NO2 and t o remove t h e s e two s p e c i e s from t h e system r e s p e c t i v e l y . The R o l e o f NOx i n Secondary P o l l u t a n t F o r m a t i o n v i a t h e Organic C y c l e I n urban atmospheres t h e c o n v e r s i o n o f NO t o p r e d i c t e d by t h e r e a c t i o n s o u t l i n e d above.

NO2 goes w e l l beyond t h e amounts

T h i s o c c u r s because of t h e p a r t i c i -

p a t i o n o f o r g a n i c compounds and t h e i r oxygenated i n t e r m e d i a t e s o r p r o d u c t s .

The

o r g a n i c s a r e a t t a c k e d by HO r a d i c a l s t o f o r m a l k y l r a d i c a l s b y

OH + O r g a n i c

-+

Re

+ H20

The a l k y l r a d i c a l (R.),

w h i c h has a f r e e e l e c t r o n , q u i c k l y r e a c t s w i t h m o l e c u l a r

oxygen t o f o r m a l k y l p e r o x y l r a d i c a l s v i a M

+

R.

+ 02

+.

R02@+ M

w h i c h p r o v i d e an oxygen atom t o o x i d i z e NO t o NO2 i n t h e r e a c t i o n ROp t NO +. ROe t NO2

83

The a1 k o x y l RU produces h y d r o p e r o x y l r a d i c a

ROO + 02

-+

OHC + H02*

which regenerates

H02e

f

NU

-+

H02* v i a

OH by way of

OH + NO2.

T h i s i l l u s t r a t e s t h e p r o d u c t i o n of a t l e a s t two NO2 m o l e c u l e s f o r each OH- c y c l e . Because o f o r g a n i c c h a i n b r a n c h i n g , t h i s f a c t o r i s - t y p i c a l l y up a t v a l u e s greater than three. The r e s u l t s o f t h e s e r e a c t i o n s a r e t w o f o l d : ( 1 ) They produce NO2 f r o m NO from t h e oxygen a b s t r a c t i o n from R02*. ( 2 ) They a l l o w ozone t o b u i l d up more t h a n o t h e r w i s e by removing i t s r e a c t i o n p a r t n e r , NU, f r o m t h e system. Hence, t h e presence of o r g a n i c p r i m a r y p o l l u t a n t s enhances t h e r a t e of product i o n o f b o t h o f t h e secondary p o l l u t a n t s , NO2 and 0 3 . F o r p l a n n i n g purposes, an E m p i r i c a l K i n e t i c Model A n a l y s i s (EKMA) has been developed t o r e f l e c t t h e combined r o l e s o f NO, ozone ( 1 2 ) .

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

EKMA i s based on a k i n e t i c s model ( o r models) t o e s t i m a t e maximum

a f t e r n o o n ozone c o n c e n t r a t i o n as i t depends upon m o r n i n g ambient l e v e l s of nonmethane hydrocarbons (NMHC) and NOx.

I t i s e m p i r i c a l i n t h a t i t uses an ob-

s e r v e d ozone l e v e l and observed p r e c u r s o r r a t i o s (NMHC/NOx) t o l o c a t e an i n i t i a l p o i n t f o r beginning c o n t r o l s t r a t e g y c a l c u l a t i o n s . F i g u r e 4 shows one o f t h e e a r l y EKMAs based on a smog chamber d e r i v e d mechanism t h a t r e p r e s e n t s a t m o s p h e r i c o r g a n i c m i x t u r e s w i t h a s u r r o g a t e m i x t u r e o f propene and n-butane.

E n t e r i n g a t a g i v e n ozone p o i n t a l o n g an i s o p l e t h

d e f i n e d b y a r a y o f c o n s t a n t p r e c u r s o r r a t i o emanating f r o m t h e o r i g i n , we The

scale emissions according t o the precursor concentrations along the axis.

scaled-down c o o r d i n a t e s d e f i n e t h e c o n t r o l p o i n t on t h e diagram which defines a new ozone i s o p l e t h v a l u e . F o r o u r purposes i n t h i s paper, t h e diagram i s used t o i l l u s t r a t e q u a l i t a t i v e t r e n d s r a t h e r t h a n p r e d i c t s p e c i f i c v a l u e s as a r e needed i n s t r a t e g y p l a n n i n g exercises.

Indeed, t h e r e i s c u r r e n t l y a f o r m a l e f f o r t underway t o e v a l u a t e and

r e v i s e EKMA t e c h n o l o g y because of q u e s t i o n s t h a t have a r i s e n f r o m e v a l u a t i o n t e s t s and s p e c i a l a p p l i c a t i o n s .

The most p r o m i n e n t f e a t u r e o f t h e diagram i s

b e s t v i s u a l i z e d by i m a g i n i n g t h a t ozone c o n c e n t r a t i o n i s p l o t t e d o u t o f t h e page i n t h e t h i r d dimension.

A r i d g e i n t h i s ozone s u r f a c e r i s e s f r o m t h e

o r i g i n toward t h e upper r i g h t hand c o r n e r .

This i n d i c a t e s t h a t t h e r e i s a locus

of o p t i m a l p r e c u r s o r c o n c e n t r a t i o n combinations.

Above and t o t h e l e f t o f t h e

r i d g e , NOx decreases t e n d t o i n c r e a s e ozone; t h e r e i t appears as i f NMHC reduct i o n s a l o n e a r e t h e most d i r e c t anil e f f e c t i v e p a t h t o ozone r e d u c t i o n s . r i g h t and below t h e r i d g e ( a t h i g h NMHC/NOx

To t h e

r a t i o s ) , ozone l e v e l s a r e almost

t o t a l l y i n s e n s i t i v e t o NMHC changes w h i l e t h e y a r e d i r e c t l y r e l a t e d t o NO,

84

changes. direction.

Most areas a r e above t h e r i d g e and moving i n a d o m i n a n t l y l e f t w a r d The NOx c o n t r o l i m p l i c a t i o n s a r e o b v i o u s :

w h i l e NO2 l e v e l s may go

down, we a r e p a y i n g d i r e c t l y by t r a d i n g each NO2 f o r an 0 3 .

Considering the

h e a l t h i m p l i c a t i o n s shown i n F i g . 1, t h i s r e s u l t s s e v e r a l t i m e s t h e h e a l t h d e t r i m e n t i n O3 enhancement as t h e r e i s improvement caused by NO2 decreases.

NMHC. ppmC

F i g . 4. S e n s i t i v i t y o f maximum a f t e r n o o n ozone c o n c e n t r a t i o n s t o morning p r e c u r s o r l e v e l s measured upwind.

The C o m p e t i t i o n Between C h e m i s t r y and M i x i n g

As NOx i s e m i t t e d i n t h e a i r , t h e dominant s p e c i e s NO w i l l r e a c t r a p i d l y w i t h ambient 0 3 , u s u a l l y as r a p i d l y as i t i s i n t i m a t e l y mixed.

Concentration fluctua-

t i o n s h a v i n g a s c a l e t h e o r d e r of h a l f a plume w i d t h and a s s o c i a t e d f l u c t u a t i o n v e l o c i t i e s measured i n t e n t h s o f meters p e r second w i l l r e q u i r e s e v e r a l minutes t o a c h i e v e t h e d i s s i p a t i o n s c a l e where m o l e c u l a r m i x i n g t a k e s p l a c e .

T h i s con-

d i t i o n i s necessary f o r t h e r e a c t i o n of NO t o proceed w i t h O 3 e n t r a i n e d i n t h e plume from ambient a i r .

S i n c e t h e h a l f l i f e o f t h e NO + O 3 r e a c t i o n w i l l be

l e s s t h a n a m i n u t e a t ozone c o n c e n t r a t i o n s g r e a t e r t h a n 0.1 ppm, t h e a p p a r e n t r e a c t i o n r a t e w i l l b e c o n t r o l l e d by t h e m i x i n g r a t e . Thus,

i t i s a c o n s e r v a t i v e assumption when p r e d i c t i n g

NO2 l e v e l s t o use

plume-averaged c o n c e n t r a t i o n i n t h e chemical k i n e t i c s e q u a t i o n s as i f t h e s p e c i e s

85

a r e homogeneously mixed.

Indeed, t h i s assumption has been adopted i n t h e model

approaches r e v i e w e d i n t h e n e x t s e c t i o n .

To c o r r e c t f o r t h e m i x i n g i n t e r f e r e n c e

w i t h r e a c t i o n r a t e s r e q u i r e s t h e use of t u r b u l e n t t h e o r e t i c a l t r e a t m e n t s of t h e s t a t i s t i c s o f concentration f l u c t u a t i o n covariances.

The a d d i t i o n a l accuracy

o b t a i n e d by t h i s t y p e o f c o r r e c t i o n has n o t g e n e r a l l y been c o n s i d e r e d t o be w o r t h t h e a d d i t i o n a l computing e f f o r t r e q u i r e d .

Having r e v i e w e d t h e main p h y s i -

c a l and chemical f e a t u r e s o f NOx p o l l u t i o n i n t h e atmosphere, we w i l l b r i e f l y examine some examples o f c a l c u l a t i o n s of a i r q u a l i t y i n f l u e n c e s b r o u g h t a b o u t by hypothetical control strategies.

EXAMPLES OF NO,

CONTROL STRATEGY ANALYSES

*

A L o c a l S c a l e Example The a i r p o l l u t i o n c o n t r o l a u t h o r i t i e s have proposed r e g u l a t i o n s r e s t r i c t i n g values of NOx emissions f o r v a r i o u s c l a s s e s of sources i n an e f f o r t t o m i n i m i z e secondary p o l l u t a n t i m p a c t s i n t h e SCAB.

The example we w i l l examine h e r e con-

s i d e r s an i n d u s t r i a l g a s - f i r e d furnace t h a t i s a c a n d i d a t e f o r such c o n t r o l s . S i n c e h o u r l y ambient s t a n d a r d s f o r ozone a r e s e t by Federal a u t h o r i t i e s and f o r NO2 by s t a t e a u t h o r i t i e s , a u s e f u l s c e n a r i o t o examine i s t h e e f f e c t o f t h e p r o -

posed c o n t r o l s on nearby ambient a i r q u a l i t y . c o n d i t i o n s and NO,

T a b l e 3 summarizes t h e s t a c k

emissions w i t h and w i t h o u t t h e proposed c o n t r o l s .

TABLE 3 E m i s s i o n Source S p e c i f i c a t i o n s f o r Loca7 S c a l e Example Stack Height S t a c k Diameter Velocity Temperature Volume Flow NO, E m i s s i o n NO, E m i s s i o n

40 f t . 42 i n . 26 f p s 400°F 13,000 dscfm 65 I b / h r u n c o n t r o l l e d 41.7 l b / h r c o n t r o l l e d

I n o r d e r t o a n a l y z e t h e i m p a c t o f t h e s e two s o u r c e c o n f i g u r a t i o n s , p e r f o r m a t w o - s t e p c a l c u l a t i o n p r o c e d u r e f o r each.

we can

The f i r s t s t e p i s t o e s t i -

mate t h e ground l e v e l c o n c e n t r a t i o n p a t t e r n of a l l of t h e NOx e m i t t e d u s i n g a Gaussian plume model assuming s t a b l e e m i s s i o n and m e t e o r o l o g i c a l c o n d i t i o n s t h r o u g h o u t an h o u r .

The second s t e p i s t o p a r t i t i o n t h e NO,

i n t o NO and NO2

a c c o r d i n g t o a n assumption of p h o t o s t a t i o n a r y e q u i l i b r i u m among t h e f i r s t t h r e e r e a c t i o n steps s t a t e d i n the previous section.

The Gaussian model s e l e c t e d was

X

The a u t h o r i s i n d e b t e d t o F. Lurmann o f Environmental Research and Technology, I n c . f o r c r e a t i n g t h e URBANOX program and t o A. C o l e l l a o f A r t h u r D. L i t t l e , I n c . f o r a p p l y i n g i t a l o n g w i t h t h e I S C program t o produce t h e r e s u l t s i n t h i s subsection.

86

t h e I n d u s t r i a l Source Complex (ISC) program o p e r a t e d i n a s i m p l e mode f o r an uno b s t r u c t e d i s o l a t e d p o i n t source.

The NOx c o n c e n t r a t i o n p a t t e r n was t h e n i n p u t

t o a p h o t o s t a t i o n a r y s t a t e program c a l l e d URBANOX.

T h i s s o l v e s f o r l o c a l values

o f ozone, n i t r o g e n d i o x i d e and n i t r i c o x i d e u s i n g t h e NO,

i n p u t s along w i t h the

ambient ozone l e v e l and i n t e r n a l l y c a l c u l a t e d s u n l i g h t - i n d u c e d p h o t o d i s s o c i a t i o n t h a t depend on l o c a t i o n , t i m e and c l o u d cover.

T a b l e 4 summarizes t h e c o n d i t i o n s

d u r i n g a September 1979 p o l l u t i o n e p i s o d e t h a t were used i n t h e c a l c u l a t i o n . TABLE 4 M e t e o r o l o g i c a l C o n d i t i o n s f o r L o c a l S c a l e Example ~~

September 8, 1979 0.15 ppm 63 deg ees 2.4 ms2

Date Background Ozone Wind D i r e c t i o n Wind Speed S t a b i l i t y Class

f

Because we a r e c o n s i d e r i n g t h r e e p o l l u t a n t s and two c o n d i t i o n s , s i x i s o p l e t h maps c o u l d b e shown; however, o n l y one composite map i s necessary t o i l l u s t r a t e t h e main p o i n t o f t h e e x e r c i s e .

I t i s shown on F i g u r e 5 w h i c h shows t h e d i f -

f e r e n c e between ambient ozone l e v e l s w i t h and w i t h o u t c o n t r o l s .

B o t h cases

depress t h e ozone l e v e l s , b u t t h e one w i t h o u t c o n t r o l s depress them a p p r o x i m a t e l y one p a r t p e r hundred m i l l i o n ( o u t o f 12 o r 13 maximum) more t h a n t h e one with controls.

L i k e w i s e , t h e NO2 changes w i l l be t h e i n v e r s e o f t h e c o n d i t i o n s

shown i n F i g . 5 because o f t h e t i t r a t i o n r e a c t i o n , O 3 + NO, p r o d u c i n g one NO2 f o r each O3 i t consumes.

Here again, t h e t r a d e o f f i s o n e - f o r - o n e between NO2

r e d u c t i o n s and O 3 i n c r e a s e s .

\

OlnlnCe from Source = 1500m

Angle from North

Source

t.4 @

+I+

0

t.4 @

+.3

&

@-

t.2

0

t.1

All values are m pphm and a l i d li*S we 1.0 pphm intmals.

F i g . 5. Map o f [(ozone w i t h NOx c o n t r o l ) - (ozone w i t h o u t NOx c o n t r o l ) ] f o r a p o i n t s o u r c e i n t h e SCAB on September 8, 1979.

87

Regional S c a l e Examples D u r i n g 1981, t h e q u e s t i o n of p a c i n g t h e NOx c o n t r o l w i t h t h a t o f v o l a t i l e o r g a n i c compounds has been r a i s e d f o r t h e C a l i f o r n i a South Coast A i r B a s i n w i t h t h e r e s u l t t h a t s l o w i n g t h e r e s t r i c t i o n s on NOx would h a s t e n a t t a i n m e n t o f t h e ozone standard.

The f o l l o w i n g c i t a t i o n s r e p r e s e n t s t r o n g statements o f t h i s

principle. A photochemical d i f f u s i o n model was used by Chock e t a1 ( 1 3 ) t o s t u d y t h e i n f l u e n c e o f added o x i d e s o f n i t r o g e n c o n t r o l s on motor v e h i c l e s on p o l l u t a n t l e v e l s on smoggy days i n Southern C a l i f o r n i a .

The model was d e r i v e d from

l a b o r a t o r y c h e m i s t r y s t u d i e s and checked a g a i n s t carbon monoxide l e v e l s t o verify i t s diffusion logic.

The emissions were v a r i e d t o g e n e r a t e v a r i o u s

scenarios; namely, b a s e l i n e (1973) and f u t u r e c o n d i t i o n s w i t h and w i t h o u t 1983 C a l i f o r n i a NOx emissions c o n t r o l s .

The r e d u c t i o n o f v e h i c l e emissions w i t h non-

v e h i c u l a r emissions f i x e d a t 1973 v a l u e s reduced C O , NO, NO2, 0 3 , PAN and HN03 throughout t h e basin.

When n o n v e h i c u l a r emissions a r e h e l d f i x e d a t f u t u r e

c o n d i t i o n s , a decrease i n v e h i c l e NOx a c t u a l l y i n c r e a s e s t h e ozone and PAN a l o n g t h e whole t r a j e c t o r y w h i l e NO2 s t i l l decreases. exceeds t h e

The ozone i n c r e a s e g e n e r a l l y

NO2 decrease.

The consequences o f t h e s e f i n d i n g s f o r s t a t i o n a r y s o u r c e NOx c o n t r o l s a r e obvious:

i f NOx c o n t r o l on a s u r f a c e - b a s e d s o u r c e complex l e a d s t o i n c r e a s e d

ozone o v e r t h e whole e a s t e r n e x t e n t of t h e b a s i n , an e l e v a t e d s o u r c e c o n t r o l would e x e r t t h i s same q u a l i t a t i v e i n f l u e n c e o v e r an even l o n g e r range; however, t h e s i z e o f t h e e f f e c t w o u l d b e s m a l l e r f o r s t a t i o n a r y sources.

These c a l c u l a -

t i o n s were done a l o n g a t r a j e c t o r y e x t e n d i n g a l l t h e way t o R i v e r s i d e .

A s t u d y by I n n e s ( 1 4 ) approached t h e o b j e c t i v e o f examining t h e r o l e of NOx c o n t r o l s i n b o t h t h e r e c e n t p a s t ozone t r e n d s and on f u t u r e smog l e v e l s i n t h e

Los Angeles b a s i n .

A number of a p p r o x i m a t e k i n e t i c s c a l c u l a t i o n s were demon-

s t r a t e d t o e s t i m a t e r a t e s o f p h o t o o x i d a t i o n , peak ozone and i n f l u e n c e s of oxides o f n i t r o g e n c o n t r o l s .

I t was s t a t e d t h a t :

0

t i m e s f o r NO d e p l e t i o n and ozone o n s e t can be e s t i m a t e d a n a l y t i c a l l y .

0

r e a c t i v i t y o f v a r i o u s o r g a n i c p o l l u t a n t s can be expressed t h r o u g h a v a r i e t y o f c o e f f ic i e n t s .

0

t h e peak ozone method used by EPA t o r a n k hydrocarbons i s u n s a t i s factory .

0

f o r emissions o f p a r a f f i n s , peak ozone r i s e s m o n o t o n i c a l l y w i t h HC/NOx r a t i o , b u t goes t h r o u g h a maximum f o r o l e f i n s .

0

f o r l o n g ( 3 t o 6 h o u r s ) i r r a d i a t i o n s , t h e ozone l e v e l i s essent i a l l y p r o p o r t i o n a l t o HC/NOx r a t i o up t o a b o u t 10.

88 0

an 80% i n c r e a s e i n NOx/HC i n Los Angeles s h o u l d r e s u l t i n a t t a i n ment o f t h e 0.12 ppm ambient h o u r l y ozone s t a n d a r d s u g g e s t i n g a s t r a t e g y c o n s i s t i n g o f a " r e a s o n a b l e i n c r e a s e " i n NOx t o g e t h e r w i t h a decrease i n hydrocarbon emissions.

0

a decrease i n NOx emissions would be l i k e l y t o i n c r e a s e ozone

0

p r o p o r t i o n a t e decreases i n NO2 l e v e l s a r e n o t o b t a i n e d from NOx

l e v e l s f o r v a r i o u s m e t r o p o l i t a n c e n t e r s o t h e r t h a n Los Angeles. emissions c o n t r o l s . 0

c o n s i d e r i n g t h e t r a d e o f f o f NOz f o r ozone, t h e removal of ozone a t t h e expense o f h i g h e r NO2 i s b e n e f i c i a l because NOz t o x i c i t y i s o f t h e o r d e r o f 10% o f t h a t o f 0 3 .

T h i s paper, as t h e p r e v i o u s one, has c l e a r i m p l i c a t i o n s t h a t NOx r e d u c t i o n s a r e c o u n t e r p r o d u c t i v e w i t h r e s p e c t t o human h e a l t h e f f e c t s .

These r e s u l t s

demonstrate c l e a r l y t h a t r e g u l a t i o n o f l a r g e e l e v a t e d s t a t i o n a r y source o x i d e s o f n i t r o g e n emissions must be c a r e f u l l y paced i n r e l a t i o n s h i p t o hydrocarbon emission c o n t r o l s i f they a r e t o e x e r t a b e n e f i c i a l e f f e c t . An i n t e r e s t i n g comparison can be made between t h e I n n e s a n a l y s i s ( 1 4 ) and t h a t of EKMA ( 1 2 ) u s i n g t h e s t a n d a r d approach f o r t h e SCAB.

Ifwe t a k e t h e

d e r i v a t i v e o f t h e peak ozone l e v e l w i t h r e s p e c t t o p r e c u r s o r NOx c o n c e n t r a t i o n a t c o n s t a n t NMHC ( i . e . ,

- 0.097 f r o m EKMA and

d[03]/d[NOx]

-

a t NMHC = c o n s t ) , we o b t a i n a v a l u e of

0.12 f r o m I n n e s .

A l t h o u g h t h i s i s a 20% disagreement,

i t i s s u r p r i s i n g l y c l o s e c o n s i d e r i n g t h e g r e a t l y d i f f e r e n t k i n e t i c s approaches

employed by t h e two methods. Tesche, O l i v e r and Haney ( 1 5 ) summarized t h e r e s u l t s o f some 60 s e n s i t i v i t y s i m u l a t i o n s u s i n g a d e t a i l e d g r i d a i r s h e d model and assembled a s e t o f r e s u l t s t o i l l u s t r a t e t h e e f f e c t s o f d i f f e r e n t c o n t r o l s t r a t e g i e s on a g i v e n e m i s s i o n i n v e n t o r y (1979) i n t h e SCAB and t h e e f f e c t s o f a l r e a d y adopted c o n t r o l s w i t h t h e passage of t i m e (1974, 1979 and 1987).

E x t e n s i v e ozone i s o p l e t h maps were

presented t o r e p o r t the r e s u l t s o f the simulations. The c o n c l u s i o n s t h a t a r e drawn a r e as f o l l o w s : 0

The g r i d a i r s h e d model i s a c c u r a t e t o w i t h i n 26 p e r c e n t f o r h i g h

0

ozone l e v e l s d u r i n g t h e e p i s o d e chosen. P r e d i c t i o n s o f 1979 ozone a r e v e r y s i m i l a r t o those o f 1974 ozone.

0

The measures under t h e p r e s e n t A i r Q u a l i t y Management P l a n a r e n o t adequate t o a t t a i n t h e s t a n d a r d by 1987 f o r ozone; i n f a c t , t h e c o n t r o l s f a l l f a r s h o r t o f the goal.

0

The maximum h o u r l y O 3 c o n c e n t r a t i o n a t t h e w o r s t s t a t i o n (Upland) f o r t h e e p i s o d e c a l c u l a t e d f o r 1 / 3 s t a t i o n a r y s o u r c e and 2/3 m o t o r v e h i c l e s o u r c e c o n t r o l s show a b e t t e r r e d u c t i o n w i t h RHC c o n t r o l s o n l y (34.0 pphm t o 25.5 pphm) t h a n w i t h RHC + NOx c o n t r o l s (34.0 pphm t o 26.4 pphm).

89 A g i v e n f r a c t i o n a l r e d u c t i o n i n m o t o r v e h i c i e emissions i s more e f f e c t i v e i n c o n t r o l l i n g ozone t h a n t h a t same f r a c t i o n a l r e d u c t i o n i n s t a t i o n a r y source emissions. These s t u d i e s show t h a t t h e c o n t r o l of NOx emissions must be c a r e f u l l y phased w i t h t h a t o f o r g a n i c emissions t o h a s t e n t h e a t t a i n m e n t o f t h e 0,

J

standard.

More a t t e n t i o n seems t o have been devoted t o t h i s i s s u e t h a n t o t h e a t t a i n m e n t

o f t h e NO2 s t a n d a r d .

CONCLUDING REMARKS We have d e s c r i b e d t h e dominant p h y s i c a

NO,

i n t h e atmosphere.

and chemical processes t h a t a f f e c t

These i n v e s t i g a t i o n s p r o v i d e i n s i g h t s i n t o t h e key

i s s u e of c o n t r o l e f f e c t i v e n e s s ; namely, t h e mechanisms g o v e r n i n g s u r f a c e l e v e l c o n c e n t r a t i o n changes as t h e y a r e i n f l u e n c e d by emissions r a t e changes. The p h y s i c a l processes o f m i x i n g and t r a n s p o r t i n g s t a t i o n a r y e l e v a t e d p o i n t s o u r c e e m i s s i o n s i n f l u e n c e s t h e i r c o n t r o l e f f e c t s on ambient compared w i t h t h e e f f e c t s o f pervasive area source emissions.

F i r s t , t h e source e l e v a t i o n i t s e l f

can l o w e r t h e l e v e r a g e o f c o n t r o l l i n g l a r g e sources by as much as a f a c t o r o f f i v e f o r a wide range o f plume h e i g h t s and downwind d i s t a n c e s .

T h i s was demon-

s t r a t e d above by a s i m p l e d i s p e r s i o n c a l c u l a t i o n o f t h e f a t e of a n o n r e a c t i v e p o l l u t a n t e m i t t e d f r o m a s i n g l e e l e v a t e d p o i n t s o u r c e a t t h e upwind edge o f a u n i f o r m l y d i s t r i b u t e d a g g r e g a t i o n o f a r e a sources.

Because o f t h e need t o f i x

t h e c o o r d i n a t e system a l o n g a s i n g l e w i n d d i r e c t i o n f o r t h i s s c e n a r i o , i t is a p p r o p r i a t e f o r d e s c r i b i n g s h o r t - t e r m c o n d i t i o n s ( l e s s t h a n an h o u r ) o n l y . F o r l o n g - t e r m averages, l i k e a y e a r , a n o t h e r t e c h n i q u e i s needed, and r e s u l t s c i t e d f r o m t h e l i t e r a t u r e show c o n s e r v a t i v e l y n e g l e c t i n g v e r t i c a l d i s p e r s i o n o r chemical i n h i b i t i n g f a c t o r s t h a t s t a t i o n a r y p o i n t s o u r c e c o n t r o l s a r e o n l y a p p r o x i m a t e l y o n e - f o u r t h as e f f e c t i v e as surface-based area source c o n t r o l s . B o t h t h e s h o r t - and l o n g - t e r m r e s u l t s i m p l y changes f r o m t h e l i n e a r r o l l back o r p r o p o r t i o n a l m o d e l i n g r e s u l t s .

V e h i c l e NO,

c o n t r o l s a l r e a d y scheduled

t o t a k e e f f e c t w i l l b r i n g a b o u t g r e a t e r b e n e f i t s t h a n t h o s e expected from p r e v i o u s analyses, w h i l e t h e o p p o s i t e w i l l be t h e case w i t h t h e p l a n s t o reduce

NOx e m i s s i o n s f r o m l a r g e e l e v a t e d s t a t i o n a r y sources.

Adding t h e chemical

aspects o f NO t o NO2 c o n v e r s i o n and t h e f i n i t e m i x i n g r a t e s w i l l r e i n f o r c e t h i s conclusion. The chemical b e h a v i o r o f NOx e m i s s i o n e i t h e r reduces t h e ozone o r p a r t i c i pates i n i t s production.

The f o r m e r case occurs i n t h e immediate v i c i n i t y o f

a s o u r c e where NO r e a c t s w i t h ozone and i s t i t r a t e d t o form NO2.

The l a t t e r

t a k e s p l a c e i n c o m b i n a t i o n w i t h o r g a n i c compounds i n a c h a i n r e a c t i o n s u p p o r t e d by h y d r o x y l and o t h e r f r e e r a d i c a l s . the production

A l t h o u g h NOx compounds a r e r e a c t a n t s i n

of ozone, t h e i r dominance as a p r e c u r s o r t o t h i s process lowers

90

t h e e f f i c i e n c y w i t h w h i c h i t occurs.

T h i s i n t u r n slows t h e c o n v e r s i o n o f NO

t o NO2; t h u s , t h e f o r m a t i o n o f t h e secondary p o l l u t a n t made from NOx i s a c t u a l l y i n h i b i t e d by NOx-rich c o n d i t i o n s .

There i s an optimum m i x t u r e f o r ozone produc-

t i o n as i n d i c a t e d by t h e ozone r i d g e on t h e EKMA diagram. The c o m b i n a t i o n o f m i x i n g and r e a c t i o n processes i n m o d e l i n g c a l c u l a t i o n s o f

NOx e f f e c t s i n t h e SCAB shows t h a t n e a r - f i e l d ozone c o n c e n t r a t i o n s a r e depressed l e s s w i t h c o n t r o l s t h a n t h e y a r e w i t h o u t c o n t r o l s because o f d i f f e r i n g degrees o f effectiveness o f the t i t r a t i o n reaction. expected consequence o f NOx-control; f o r ozone g e n e r a t i o n , NO,

Regional s t u d i e s a l l e x h i b i t an

namely, a t NOx l e v e l s above t h e optimum

r e d u c t i o n s must be accompanied by hydrocarbon reduc-

t i o n s t o a v o i d r a i s i n g t h e ozone l e v e l .

These c o n s i d e r a t i o n s have and w i l l

temper o u r approaches t o t h e r e d u c t i o n of NOx f o r secondary p o l l u t a n t c o n t r o l ; e s p e c i a l l y i n l i g h t of t h e l a r g e r p o t e n t i a l h e a l t h t h r e a t posed by ozone i n comparison w i t h t h a t o f n i t r o g e n d i o x i d e . REFERENCES 1 2 3

4

5 6 7 8 9 10

11

12 13 14 15

N i t r o g e n Oxides, N a t i o n a l Academy o f Science, Washington, D.C., 1977 Oxides o f N i t r o g e n , E n v i r o n m e n t a l H e a l t h C r i t e r i a , World H e a l t h O r g a n i z a t i o n , Geneva, 1977. A i r Q u a l i t y C r i t e r i a f o r Oxides o f N i t r o g e n , U.S. Environmental P r o t e c t i o n Agency, Revised E x t e r n a l Review D r a f t , 1979. S. Leung, E. G o l d s t e i n and N. Dalkey, Human H e a l t h Damages f r o m M o b i l e Source A i r P o l l u t i o n , U.S. Environmental P r o t e c t i o n Agency R e p o r t EPA-600/5-78-016a, J u l y 1978. N a t i o n a l A i r Q u a l i t y , M o n i t o r i n g and Emissions Trends Report, U.S. E n v i r o n m e n t a l P r o t e c t i o n Agency R e p o r t EPA-450/2-78-052, December 1978. G.C. H o l z w o r t h , M i x i n g H e i g h t s , Wind Speeds, and P o t e n t i a l f o r Urban A i r P o l l u t i o n Throughout t h e Contiguous U n i t e d S t a t e s , Environmental P r o t e c t i o n Agency R e p o r t AP-101, January 1972. D.H. Lucas, The I n t e r n a t i o n a l J o u r n a l o f A i r P o l l u t i o n , 1 (1958)71-86. American S o c i e t y o f Mechanical Engineers, 1968: Recommended Guide f o r t h e P r e d i c t i o n o f t h e U i s p e r s i o n o f A i r b o r n e E f f l u e n t s , M. Smith ( e d . ) New York, New York. D.B. T u r n e r , Workbook o f Atmospheric D i s p e r s i o n E s t i m a t e s , U.S. Department o f H e a l t h , E d u c a t i o n and W e l f a r e , P u b l i c H e a l t h S e r v i c e . NAPCA. C i n c i n n a t i , Ohio, 1972. B. Weinstock, T.Y. Chang and J.M. Norbeck, The R e l a t i o n s h i p Between V e h i c l e NO, Emissions and A i r Q u a l i t y : An Update, Proceedings o f t h e Conference on A i r Q u a l i t y Trends i n t h e South Coast A i r Basin, C a l i f o r n i a I n s t i t u t e of Technology, February 1980. P.D. G u t f r e u n d , S.R. Hayes, W.R. O l i v e r , S.D. Reynolds, and P.M. Roth, Assessment o f NO, Emissions C o n t r o l Requirements i n t h e South Coast A i r B a s i n : A P r e l i m i n a r y R e p o r t f o r C o n s i d e r a t i o n i n P r e p a r i n g t h e AQMP, Systems A p p l i c a t i o n s , I n c . No. 81277, November 13, 1981. Uses, L i m i t a t i o n s and T e c h n i c a l B a s i s o f Procedures f o r Q u a n t i f y i n g Relat i o n s h i p s Between Photochemical O x i d a n t s and P r e c u r s o r s , U.S. Environmental P r o t e c t i o n Agency R e p o r t EPA-450/2-77-021a, 1977. D.D. Chock, A.M. Dunker, S. Kumar and G.S. Sloane, E f f e c t o f NOx Emission Rates on Smog F o r m a t i o n i n t h e C a l i f o r n i a South Coast A i r Basin, E n v i r o n m e n t a l Science and Technology, 15(1981)933-939. W.B. Innes, E f f e c t o f N i t r o g e n Oxide Emissions on Ozone L e v e l s i n Metrop o l it a n Regions, Environmental Science and Technology, 1 5 ( 1981 )904-912. T.W. Tesche, W.R. O l i v e r and J.L. Haney, S e n s i t i v i t y o f S A I A i r s h e d Model Ozone P r e d i c t i o n s t o Emission I n v e n t o r y P e r t u r b a t i o n s , Systems A p p l i c a t i o n s I n c o r p o r a t e d , R e p o r t 81225, September 1981.

91

S i t e and Season-specific V a r i a t i o n s o f t h e Atmospheric P o l l u t a n t Transport and D e p o s i t i o n on t h e Local and Regional Scale G . Neumann-Hauf,

Abteilung

fur

6 . Hal b r i t t e r

Angewandte Systemanalyse des Kernforschungszentrurns K a r l sruhe,

K a r l sruhe (F.R.G.)

ABSTRACT I n o r d e r t o assess and e v a l u a t e t h e environmental impacts o f an expanded use o f c o a l i n t h e Federal Republic o f Gennany s i t e and season-specific v a r i a t i o n s o f the atmospheric p o l l u t a n t t r a n s p o r t and d e p o s i t i o n were i n v e s t i g a t e d on a l o c a l and r e g i o n a l scale. The i m p o r t a n t m e t e o r o l o g i c a l parameters f o r 8 s e l e c t e d s i t e s were compared and area mean values o f t h e long-term d r y and wet d e p o s i t i o n f a c t o r s f o r a e r o s o l s were c a l c u l a t e d . While t h e r e were no d i s t i n c t d i f f e r e n c e s i n t h e area mean values around sources o f a h e i g h t o f 200 m i n t h e n o r t h e r n Gennan lowlands, h i g h e r d i f f e r e n c e s were found i n t h e southern p a r t o f t h e c o u n t r y v a r y i n g m a i n l y between 116 and 160 %, and sometimes even between 116 and 218 % w i t h r e s p e c t t o t h e n o r t h e r n German s i t e on t h e c o a s t . C a l c u l a t i o n s o f t h e t o t a l amount o f p o l l u t a n t s deposited between 44'-62'N,

lOoW

-

20°E demonstrated r e g i o n a l d i f f e r e n c e s

due t o t h e long-range t r a n s p o r t and d e p o s i t i o n o f p o l l u t a n t s e m i t t e d a t 2 German s i t e s i n t h e n o r t h e r n and southern p a r t o f t h e country, r e s p e c t i v e l y . Season-specific v a r i a t i o n s o f the p o l l u t a n t t r a n s p o r t and d e p o s i t i o n were i n v e s t i g a t e d f o r one selected s i t e i n southern Gennany. On the l o c a l and r e g i o n a l s c a l e values o f t h e d e p o s i t i o n f a c t o r s were h i g h e s t d u r i n g the summer period, e s p e c i a l l y f o r wet d e p o s i t i o n , w h i l e t h e r a t i o o f l o s s by wet d e p o s i t i o n t o l o s s by d r y d e p o s i t i o n i s h i g h e r i n w i n t e r than i n summer time. INTRODUCTION I n t h e c o n t e x t of assessing and e v a l u a t i n g t h e consequences o f an expanded use

o f coal i n t h e Federal Republic o f Germany t h e atmospheric t r a n s p o r t and deposit i o n o f p o l l u t a n t s e m i t t e d from h i g h stacks were i n v e s t i g a t e d f o r v a r i o u s s i t e s on t h e l o c a l and r e g i o n a l s c a l e w i t h r e f e r e n c e t o seasonal v a r i a t i o n s . The l a t t e r were considered w i t h regard t o t h e s p e c i a l importance o f summer time as growing p e r i o d f o r p l a n t s . I n o r d e r t o c a l c u l a t e t h e p o l l u t a n t exposure on t h e l o c a l scale s i t e s were s e l e c t e d where t h e m e t e o r o l o g i c a l c o n d i t i o n s were r e p r e s e n t a t i v e

for

l a r g e r areas. For the purpose o f comparison, i n a d d i t i o n a l s o s i t e s were consider-

92

ed where t h e m e t e o r o l o g i c a l c o n d i t i o n s a r e governed by t y p i c a l mesoscale phenomena. On t h e r e g i o n a l s c a l e , t h e long-range t r a n s p o r t and d e p o s i t i o n o f p o l l u t a n t s e m i t t e d a t two s i t e s i n n o r t h e r n and s o u t h e r n Germany, r e s p e c t i v e l y , were i n v e s t i g a t e d w i t h a view t o d i f f e r e n c e s i n t h e l o n g - r a n g e p o l l u t a n t d i s p e r s a l caused b y l a r g e - s c a l e v a r i a t i o n s i n t h e s y n o p t i c f l o w f i e l d . C a l c u l a t i o n s were performed f o r t h e emissions o f a e r o s o l s from s t a c k s o f a h e i g h t o f 200 m u s i n g a m o d i f i e d Gaussian-Plume model and t h e t r a j e c t o r y - p u f f model PESOS ( r e f . 1). SITE-SPECIFIC DIFFERENCES Four main c l i m a t i c p r o v i n c e s can be d e f i n e d f o r t h e area o f t h e Federal R e p u b l i c o f Germany: ( 1 ) t h e l o w l a n d s n o r t h o f t h e c e n t r a l h i g h l a n d s ; ( 2 ) t h e h i g h l a n d s ; ( 3 ) t h e n o r t h e r n A l p i n e f o r e l a n d and ( 4 ) t h e A l p s ( r e f . 2 ) . I n o r d e r t o d e s c r i b e

t h e atmospheric d i s p e r s i o n c o n d i t i o n s f o r 3 o f t h e 4 main c l i m a t i c p r o v i n c e s s t a t i s t i c s o f wind speed, a t m o s p h e r i c s t a b i l i t y , p r e c i p i t a t i o n and l o w - l e v e l i n v e r s i o n were analysed f o r Hannover, a s i t e i n t h e l o w l a n d s , Essen, a s i t e on t h e n o r t h w e s t e r n b o r d e r o f t h e l o w l a n d s , S t u t t g a r t - E c h t e r d i n g e n and Nurnberg, 2 s i t e s i n t h e h i g h l a n d s , and Miinchen i n t h e n o r t h e r n A l p i n e f o r e l a n d as w e l l as f o r 4 o t h e r s i t e s w i t h s p e c i a l l o c a l f e a t u r e s such as Emden, a n o r t h e r n German s i t e on t h e c o a s t o f t h e N o r t h Sea, F r e i b u r g , w i t h an u r b a n c l i m a t e c h a r a c t e r i z e d b y i t s l o c a t i o n a t t h e f o o t o f t h e western s l o p e o f t h e B l a c k F o r e s t , and K a r l s r u h e , s i t u a t e d i n t h e Upper Rhine V a l l e y and i n f l u e n c e d by t h e urban c l i m a t e . W h i l e t h e mean wind speed decreases form n o r t h t o south, t h e i n c i d e n c e o f calm s i t u a t i o n s i n c r e a s e s ( e s p e c i a l l y i n t h e c i t y o f F r e i b u r g up t o 30 9 ) as w e l l as t h e frequency o f s t a b l e and u n s t a b l e atmospheric c o n d i t i o n s and o f l o w - l e v e l

inversions. Preci-

p i t a t i o n i s s t r o n g l y i n f l u e n c e d by topography w i t h h i g h e s t v a l u e s a t F r e i h u r g . Beside t h e above mentioned d i f f e r e n c e s from n o r t h t o s o u t h i n c r e a s i n g c o n t i n e n t a l i t y i s a l s o found from west t o e a s t . TABLE 1 2 Long-term d e p o s i t i o n f a c t o r s f o r areas o f 20 x 20 km i n t h e s u r r o u n d i n g s o f s e l e c t e d s i t e s i n t h e Federal R e p u b l i c o f Germany.

Stati o n

F a c t o r (m-’)

P

1 Emden

1

R a t i o t o Emden

Dry D e p o s i t i o n

Essen Freiburg Hannover Karl sruhe Munch en Nu r nb e r g Stuttgart-

4.7 5.1 9.5 5.1 7.2 6.2 6.5

E-12 E-12 E-12 E-12 E-12 E-12 E-12

7.2

E-12 I

Wet D e p o s i t i o n

R a t i o t o Emden

in %

F a c t o r (m-’)

in %

100 108 202 108 152 132 139

4.5 4.8 9.8 3.7 6.2 7.2 5.2

E-12 E-12 E-12 E-12 E-12 E-12 E-12

100 107 218 82 138 160 116

152

6 . 4 E-12

142

93 For t h e above-mentioned s i t e s a r e a mean v a l u e s o f t h e l o n g - t e r m d r y and wet d e p o s i t i o n factors'

were c a l c u l a t e d from a 10 y e a r s ' f r e q u e n c y d i s t r i b u t i o n o f

m e t e o r o l o g i c a l parameters. The d i f f e r e n c e s f o r d r y and wet d e p o s i t i o n f a c t o r s were l e s s t h a n 10 o r 25 %, r e s p e c t i v e l y , among t h e n o r t h e r n s i t e s Emden, Essen, and Hannover, and up t o 20 o r 50 %, r e s p e c t i v e l y , f o r d r y and wet. d e p o s i t i o n f a c t o r s among t h e s o u t h e r n s i t e s , e x c e p t f o r F r e i b u r g ( s e e Tab. 1). F i g u r e s 1 and 2 g i v e t h e s p a t i a l d i s t r i b u t i o n s o f t h e t o t a l d e p o s i t i o n f a c t o r f o r t h e sources a t Hannover and S t u t t g a r t . The d i s t r i b u t i o n s a r e dominated by t h e frequency d i s t r i b u t i o n s o f t h e wind d i r e c t i o n w i t h h i g h e s t v a l u e s o f t h e t o t a l d e p o s i t i o n f a c t o r near S t u t t g a r t .

Fig. 1

Fig. 2

Annual mean o f t o t a l d e p o s i t i o n f a c t o r s (sum o f d r y and wet d e p o s i t i o n ) i n t h e s u r r o u n d i n g s o f s t a c k s o f a h e i g h t o f 200 m a t Hannover ( F i g . 1) and S t u t t g a r t (Fig. 2). However, a t a d i s t a n c e o f 100 km from t h e sources about 90 % o f t h e e m i t t e d mat e r i a l i s s t i l l a i r b o r n e . T h e r e f o r e , c a l c u l a t i o n s o f long-range t r a n s p o r t ( u p t o a b o u t 800 km away f r o m t h e sources) were performed f o r a n o r t h e r n and a southern German s i t e , r e s p e c t i v e l y ( s e e F i g . 3 and F i g . 4 ) . D i f f e r e n c e s i n t h e s p a t i a l d i s t r i b u t i o n o f d e p o s i t i o n f a c t o r s a r e expected because o f t h e l a r g e - s c a l e f l o w f i e l d o v e r t h e Federal R e p u b l i c o f Germany. While l o w p r e s s u r e systems pass o v e r t h e n o r t h w e s t e r n p a r t o f Germany t o t h e e a s t , t h e i n f l u e n c e o f h i g h p r e s s u r e c o n d i t i o n s -

+

The d e p o s i t j o n f a c t o r i s d e f i n e d as t h e i n t e g r a t e d amount of p o l l u t a n t s depos i t e d p e r m n o r m a l i z e d b y t h e source s t r e n g t h .

94

i s i n c r e a s i n g l y f e l t i n t h e s o u t h e r n p a r t o f t h e c o u n t r y . Regarding t h e annual mean v a l u e s o f d e p o s i t i o n f a c t o r s i n t h e y e a r 1973, t h e s e v a l u e s a r e h i g h e s t e a s t , south-east,

and s o u t h o f t h e sources a t Hannover and S t u t t g a r t . Areas w i t h h i g h

d e p o s i t i o n f a c t o r s a r e a p p r o x i m a t e l y t h e same s i z e f o r b o t h s i t e s . The b l o c k i n g o f t h e f l o w f i e l d i n f r o n t o f t h e A l p s i s shown by t h e i s o l i n e s o f t h e d e p o s i t i o n f a c t o r s approaching each o t h e r i n s o u t h e a s t e r l y and south-southe a s t e r l y d i r e c t i o n from t h e sources a t Hannover and S t u t t g a r t , r e s p e c t i v e l y .

Fig. 4

Fig. 3

A n p a l vean of t 8 t a l d e g o s i t i o n f a c t o r s (sum o f d r y and wet d e p o s i t i o n ) between 44 - 62 N and 10 W 2 0 E r e s u l t i n g from e m i s s i o n s a t Hannover ( F i g . 3 ) and S t u t t g a r t (Fig. 4).

-

S i g n i f i c a n t d i f f e r e n c e s a r e found between t h e r a t i o o f loss by wet d e p o s i t i o n t o l o s s b y d r y d e p o s i t i o n a t d i f f e r e n t d i s t a n c e s from t h e sources. While t h i s r a t i o i s i n c r e a s i n g w i t h i n c r e a s i n g d i s t a n c e from t h e s o u r c e a t Hannover, i t dec r e a s e s a t S t u t t g a r t ( s e e Tab. 2 ) . TABLE 2 R a t i o o f loss by wet d e p o s i t i o n t o loss by d r y d e p o s i t i o n Distance from source

100 km 200 km 400 km 750 km

Hannover summer 1.4 1.4 1.7 1.9

Hannover winter

Stuttgart summer

Stuttgart winter

2.1 2.1 2.3 2.6

2.5 2.5 2.4

2.9 2.8 2.4

-

-

95

SEASON-SPECIFIC VARIATIONS I n v e s t i g a t i o n s o f seasonal d i f f e r e n c e s i n atmospheric t r a n s p o r t and d e p o s i t i o n were c a r r i e d o u t f o r t h e s o u t h e r n s i t e a t S t u t t g a r t . D i f f e r e n t from t h e annual mean, t h e f r e q u e n c y o f s t a b l e and u n s t a b l e s i t u a t i o n s i n c r e a s e s by about 6 % and t h e w i n d speed i s reduced by 0.5 m s-'

i n summer. Also, 36 % o f t h e annual amount

o f p r e c i p i t a t i o n i s measured d u r i n g t h e 3 months i n summer. C a l c u l a t i o n s o f t h e a r e a mean v a l u e s g i v e a maximum f o r t h e t o t a l , and e s p e c i a l l y f o r t h e wet depos i t i o n f a c t o r d u r i n g summer (134 o r 179

X

o f t h e annual mean v a l u e s , r e s p . ) .

T h e r e f o r e , annual mean v a l u e s do n o t always l e a d t o a c o n s e r v a t i v e e s t i m a t e o f t h e p o l l u t a n t exposure leewards from a source.

Fig. 5

Fig. 6

Mean t o t a l d e p o s i t i o n f a c t o r s i n summer t i m e ( F i g . 5 ) and w i n t e r t i m e ( F i g . 6 ) o v e r Europe f r o m e m i s s i o n s a t S t u t t g a r t . Seasonal d i f f e r e n c e s between t h e 6 summer and t h e 6 w i n t e r months i n t h e y e a r 1973/74 were analysed w i t h r e g a r d t o l o n g - r a n g e t r a n s p o r t and d e p o s i t i o n (see F i g . 5 and F i g . 6 ) . The comparison o f f i g u r e s 5 and 6 shows t h a t t h e area o f dep o s i t i o n factors g r e a t e r than

m-'

i s s i g n i f i c a n t l y l a r g e r i n summer, reach-

i n g f a r t o t h e west, t h a n i n w i n t e r . The s p a t i a l d i s t r i b u t i o n o f annual means r e sembles t h a t o b t a i n e d f o r t h e summer p e r i o d ( s e e F i g . 4 and F i g . 5 ) . W h i l e i n summer t h e r a t i o o f l o s s by wet d e p o s i t i o n t o l o s s by d r y d e p o s i t i o n i s about 2 . 5 a t a d i s t a n c e o f 100 km from t h e source, t h i s r a t i o i n c r e a s e s i n w i n t e r t i m e (see Tab. Z ) , a l t h o u g h most o f t h e p r e c i p i t a t i o n i s measured i n summer t i m e .

96

CONCLUSIONS

In order t o a s s e s s and evaluate the environmental impacts of an expanded use of coal i n the Federal Republic of Gennany s i t e and season-specific v a r i a t i o n s of the atmospheric p o l l u t a n t t r a n s p o r t and deposition were investigated with a view t o estimating their influence on the t o t a l c o l l e c t i v e p o l l u t a n t exposure over Europe. As a r e s u l t i t should be kept in mind t h a t s i t e - s p e c i f i c d i f f e r e n c e s among selected s i t e s lead t o v a r i a t i o n s in t h e long-term area mean value of deposited a e r o s o l s of u p t o a f a c t o r of 2 on the local s c a l e with l a r g e r d i f f e r e n c e s on the regional s c a l e . The i n v e s t i g a t i o n s of season-specific v a r i a t i o n s showed t h a t the highest values of t o t a l deposition f a c t o r s around S t u t t g a r t a r e found during summer, i . e . during the growing period, t h i s being mainly due to wet deposition both on the local and regional s c a l e . However, the r a t i o of l o s s by wet deposition t o l o s s by dry depos i t i o n a t d i s t a n c e s between 100 and 400 km i s highest i n winter time, and always g r e a t e r than 1 . 0 .

ACKNOWLEDGEMENTS MESOS c a l c u l a t i o n s f o r the long-range p o l l u t a n t t r a n s p o r t were c a r r i e d out by Imperial College, London, and a r e published in agreement with Imperial College. REFERENCES H . M . ApSimon, J . Wrigley and A.J.H. Goddard, Estimating the Possible Transfront i e r Consequences of Accidental Releases; the MESOS Model f o r Long-Range Atmospheric Dispersal, Proc. C.E.C. Seminar - Radioactive Releases and Their Dispersion in the Atmosphere Following a Hypothetical Reactor Accident, Risb (Denmark), April 22 - 25, 1980. C . C . Wallen (Ed.). Climates of Central and Southern EuroDe, . - Vol. 6 , World Survey of C1 imatology, Eisevier, Amsterdam, 1977. H.M. ApSimon, J . Wrigley and A.J.H. Goddard, Research Contract Report, 1981, u n pu bl i shed. BMI (Bundesministerium des Innern) , A1 lgemeine Berechnungsgrundlage Fur d i e Strahlenexposition bei radioaktiven Ableitungen mit der Abluft oder in Oberflachengewlsser, Gemeinsames Ministerial b l a t t , 21 (1979). 6. H a l b r i t t e r , K . - R . Bri;utigam, F.-W. Fluck, E . LeRmann, G . Neumann-Hauf, Beitrag zu e i n e r vergleichenden llmwel tbelastungsanalyse am Beispiel der Strahlenexposition beim Einsatz von Kohle u n d Kernenergie zur Stromerzeugung, Kernforschungszentrum Karlsruhe, KfK 3266, 1982.

97

D A I L Y FORECASTING O F A I R POLLUTION POTENTIAL

A.

JOUKOFF and L.M.

MALET

Royal M e t e o r o l o g i c a l I n s t i t u t e . Uccle (Belgium)

ABSTRACT E x p e r i m e n t a l f o r e c a s t s p e r f o r m e d a t t h e Royal M e t e o r o l o g i c a l I n s t i t u t e o f B e l gium d u r i n g t h e w i n t e r s 1979-1980 and 1980-1981 a r e d e s c r i b e d and a n a l y s e d .

These

f o r e c a s t s are b a s e d on t h e e v a l u a t i o n o f an a i r p o l l u t i o n p o t e n t i a l i n d e x which u s e s t h r e e i m p o r t a n t m e t e o r o l o g i c a l p a r a m e t e r s : wind s p e e d , v e r t i c a l s t a b i l i t y and t e m p e r a t u r e . These m e t e o r o l o g i c a l f o r e c a s t s combine n u m e r i c a l f o r e c a s t s a t t h e 850 mbar lev e l with a semi-climatological air mass characteristics.

scheme g i v i n g a i r t e m p e r a t u r e s a s s o c i a t e d w i t h t h e

The m e t e o r o l o g i c a l i n d e x i s c o n v e r t e d i n t o p o t e n t i a l

a i r p o l l u t i o n l e v e l s by means o f a r e l a t i o n deduced from a l i n e a r r e g r e s s i o n u s i n g SO

measurements from t h e p r e v i o u s w i n t e r . The r e s u l t s o f t h e two s e a s o n s of 2 experimental f o r e c a s t s a r e very encouraging.

INTRODUCTION

The f i v e l a r g e s t urban a g g l o m e r a t i o n s o f Belgium (Antwerp, B r u s s e l s , C h a r l e r o i , Ghent and L i e g e ) are c o v e r e d by a m o n i t o r i n g network measuring a s w e l l a i r q u a l i t y a s meteorological parameters.

Every minute t h i s t e l e m e t e r e d network i s s u e s v a l u e s

o f t h e d i f f e r e n t p a r a m e t e r s measured by a l l s a m p l i n g s t a t i o n s t o a r e g i o n a l d a t a reduction c e n t r e (R.D.R.C.) R.D.R.C.'s

where h a l f - h o u r l y a v e r a g e s a r e computed.

send these half-hourly

(N.D.P.C.).

The N.D.P.C.

The f i v e

averages t o a n a t i o n a l dat a processing cent r e

i s d i v i d e d i n t o two p a r t s

:

t h e f i r s t one i s p l a c e d

a t the I n s t i t u t e o f Hygiene and Epidemiology o f t h e M i n i s t e r y of P u b l i c H e a l t h and t h e s e c o n d a t t h e Royal M e t e o r o l o g i c a l I n s t i t u t e .

One o f t h e p r i n c i p a l t a s k s

of the l a t t e r c o n s i s t s i n i s s u i n g d a i l y fo reca st s of t he a i r q u a l i t y p o t e n t i a l f o r the f i v e r e g i o n s and f o r the n e x t 24 h o u r s . and a n a l y s e d i n t h e p r e s e n t paper.

These f o r e c a s t s are d e s c r i b e d

They have been t r a n s m i t t e d t o the p u b l i c

h e a l t h a u t h o r i t i e s d u r i n g t h e w i n t e r p e r i o d s 1979-1980 and 1980-1981, b e r t o march.

They s t i l l must b e c o n s i d e r e d as e x p e r i m e n t a l .

from novem-

A i r quality potential

i s e v a l u a t e d b y a n a i r p o l l u t i o n p o t e n t i a l i n d e x b a s e d on m e t e o r o l o g i c a l p a r a meters o n l y .

98 THE METEOROLOGICAL A I R POLLUTION POTENTIAL I N D E X I n o r d e r t o a p p r e c i a t e t h e d i f f u s i v e c a p a c i t y o f t h e atmosphere and to e s t i mate t h e a i r p o l l u t i o n l e v e l , a m e t e o r o l o g i c a l a i r p o l l u t i o n p o t e n t i a l i n d e x (MPI) h a s been developped on t h e b a s i s o f a c e r t a i n number o f s t u d i e s ( r e f s . 1 - 5 ) .

It

combines t h r e e o f t h e most s i g n i f i c a n t m e t e o r o l o g i c a l p a r a m e t e r s which can b e f o r e c a s t e d on a r o u t i n e b a s i s w i t h a s u f f i c i e n t r e l i a b i l i t y .

The t h r e e p a r a m e t e r s

s e l e c t e d are :

2 4 h o u r s a v e r a g e t e m p e r a t u r e , T , which d e t e r m i n e s t h e s t r e n g t h o f d o m e s t i c heat i n g s o u r c e s , dominant i n urban a r e a s

;

2 4 h o u r s a v e r a g e wind s p e e d , v , which d e t e r m i n e s t h e h o r i z o n t a l t r a n s p o r t o f the a t m o s p h e r i c p o l l u t a n t s

:

v e r t i c a l s t a b i l i t y o f l o w a t m o s p h e r i c l a y e r s , which d e t e r m i n e s t h e h o r i z o n t a l and v e r t i c a l d i s p e r s i o n of the p o l l u t a n t s .

T h i s s t a b i l i t y i s c h a r a c t e r i z e d by

an i n d e x s i n p l a c e o f t h e p r e v i o u s l y u s e d mixjng h e i g h t ( r e f . 5 ) which i s rather d i f f i c u l t to predict.

T h i s i n d e x i s a f u n c t i o n o f t h e r a t i o between t h e

700-1000 mbar l a y e r t h i c k n e s s , H , and t h e t h i c k n e s s Hd f o r t h i s l a y e r c a l c u l a t e d according t o a dry a d i a b a t i c lapse rate f o r the s a m e sur f ace conditions.

The

index s used i n p r a c t i c e i s : H s =

d

lo--

9

n

The MPI h a s t h e f o l l o w i n g form

MPI

:

25 - T 1/2

Such a p u r e l y m e t e o r o l o g i c a l i n d e x does t a k e i n t o a c c o u n t t h e p o s s i b l e p o l l u t a n t a c c u m u l a t i o n and the p o s s i b l e a d v e c t i o n o f p o l l u t a n t s from one r e g i o n t o a n o t h e r . Thus i t r e p r e s e n t s t h e l o c a l p o t e n t i a l o f a i r p o l l u t i o n .

METEOROLOGICAL FORECASTING

M e t e o r o l o g i c a l f o r e c a s t i n g h a s been p e r f o r m e d on t h e b a s i s of m e t e o r o l o g i c a l maps as p r e d i c t e d u s i n g a m a t h e m a t i c a l model.

The use of one model o n l y may b e

dangerous due t o the f a c t t h a t no model i s p e r f e c t ; however i t g a r a n t e e s homogen e i t y as r e g a r d s t h e d e t e r m i n a t i o n of t h e i n i t i a l c o n d i t i o n s l e a d i n g t o t h e 2 4 , 48 and 72 h o u r s forecasts.

Our e x p e r i e n c e shows t h a t maps a t t h e 850 mbar l e v e l

are the most a d e q u a t e t o d e s c r i b e a i r p o l l u t i o n p o t e n t i a l e v o l u t i o n (more r e p r e s e n t a t i v e t h a n t h e 500 mbar l e v e l e . g . )

.

From t h e s e maps, one can r e a d 700-1000 mbar

l a y e r mean t e m p e r a t u r e and f u r t h e r d e r i v e s u r f a c e l e v e l maps g i v i n g p r e s s u r e g r a d i e n t s and wind d i r e c t i o n s o v e r Belgium. wind s p e e d s .

P r e s s u r e g r a d i e n t s are c o n v e r t e d i n t o

99 Wind d i r e c t i o n s are used t o e s t i m a t e extreme temperature by means o f a semic l i m a t o l o g i c a l method (based on r e f . 6) giving d a i l y extremes from the c a r a c t e r i s From these extremes, i t i s p o s s i b l e t o e v a l u a t e 24-hours

t i c s of the a i r mass. mean temperature. about 1 m . s - '

Due t o t h e s c a l e of t h e maps, reading accuracy i s l i m i t e d t o

f o r t h e wind speed and t o 5 degrees f o r t h e wind d i r e c t i o n i n most

This accuracy i s a s s o c i a t e d w i t h the reading only and does n o t take i n t o

cases.

account t h e f o r e c a s t f i t n e s s .

V e r t i c a l s t a b i l i t y index s i s evaluated from d i r e c t

reading of H (700-1000 mbar t h i c k n e s s ) and the f o r e c a s t e d values of s u r f a c e temper a t u r e and p r e s s u r e ( g i v i n g Hd)

.

During the second experimental f o r e c a s t i n g season, some improvements have been brought t o t h e method

:

r e v i s e d c l i m a t o l o g i c a l d a t a and a c o r r e c t i o n f o r cloudi-

ness in e v a l u a t i n g t h e temperature.

i n the N.D.P.C.

The f o r e c a s t i n g procedure has been implemented

computer t o f a c i l i t a t e the f o r e c a s t e r s work.

The o u t p u t gives i n t e r p o l a t e d values each 6 hours and an i n t e r a c t i v e procedure allows the f o r e c a s t e r s t o introduce c o r r e c t i o n s i n t h e temperature.

A f i r s t correc-

t i o n i s provided by t h e program from t h e comparison o f observed and c o e u t e d val u e s f o r 0 , 6 and 1 2 hours U . T . Forecasting r e s u l t s a r e summarized i n t a b l e 1, giving the number of successes ( t a k i n g a t o l e r a n c e i n t o a c c o u n t ) , underestimates and overestimates f o r each meteor o l o g i c a l parameters and t h e i r combination MPI

TABLE 1

Forecastina r e s u l t s ( % ) Parameter T V

S

MPI

:

meteorolocw

Tolerance

20

2 m.s

-1

0.1

5 (+)

Good a b a b a b a b

66 78 73 76 75 87 71 79

Over

LJuier

11 6 19 21 7 10 19 6

22 15 7 3 18 4 10 15

b : 1980-1981. a : 1979-1980 ; (+) 5 u n i t s MPI correspond t o about 2 ~ / i g . m - SO ~ /24h i n B r u s s e l s . 2 Except f o r the cases when t h e numerical f o r e c a s t i n g f a i l e d , t h e f o r e c a s t e d values followed r a t h e r w e l l t h e observed ones.

Fig.

1 gives t h e s c a t t e r p l o t of

t h e observed and f o r e c a s t e d values f o r t h e MPI d u r i n g t h e two considered w i n t e r s respectively.

100

WINTER 1979 - 1980

WINTER 1980- 1981

50

40

30

20

10 PMI 0

Fig.

1. S c a t t e r p l o t s o f o b s e r v e d (MF'I) vs f o r e c a s t e d (MPI (F)) v a l u e s of MPI

POTENTIAL A I R POLLUTION FORECASTING MPI v a l u e s c a n be c o n v e r t e d t o e x p e c t e d p o t e n t i a l a i r p o l l u t i o n l e v e l s i n -3 o f SO2 (24h mean) i n o r d e r t o g i v e a more e x p l i c i t p i c t u r e o f the s i t u a P9.m t i o n ; t h i s c a n e a s i l y b e used by p u b l i c h e a l t h a u t h o r i t i e s . During t h e f i r s t e x p e r i m e n t a l w i n t e r , this c o n v e r s i o n h a s been done s i m p l y by m u l t i p l y i n g t h e MPI by a f a c t o r d e t e r m i n e d f o r e a c h urban area from p r e v i o u s winter observations. During t h e s e c o n d w i n t e r , l i n e a r r e g r e s s i o n s b a s e d on o b s e r v a t i o n s performed d u r i n g t h e f i r s t w i n t e r have been u s e d .

Comparison between t h e f o r e c a s t e d p o t e n -

t i a l a i r p o l l u t i o n and o b s e r v e d SO2 c o n c e n t r a t i o n s i s summarized i n t a b l e 2 .

High p o l l u t i o n p e r i o d s have been f o r e c a s t e d w i t h s u c c e s s , however c o n c e n t r a t i o n s c a n n o t b e f o r e c a s t e d a c c u r a t e l y due t o t h e c o n c e p t i o n of t h e MF'I i t s e l f , as n e i t h e r a c c u m u l a t i o n n o r t r a n s p o r t a r e i n c l u d e d i n t h e method.

The p u r p o s e

o f t h i s method i s t o c h a r a c t e r i z e t h e d i f f u s i o n c o n d i t i o n s and o n l y those s o u r c e e f f e c t s which are due t o d o m e s t i c h e a t i n g .

101

TABLE 2

Forecasting r e s u l t s Urban area

(%)

concentrations Good ( + 2 0 % )

a b a b a b a b a b

Brussels Antwerp Liege Ghen t Charler o i

33 37 41 39 37 55 45 49 38 51

Over

( 4 2 ) (+) (46) (53) (43) (61) (70) (57) (46) (41) (54)

13 51 24 48 5 10 20 26 26 21

(28) (23) (21) (23) (18) (18) (16) (23) (33) (24)

Under

54 12 35 13 58 35 35 25 37 28

(31) (31) (26) (34) (20)

(12) (27) (31) (27) (33)

a : 1979-1980 , b : 1980-1981 ( + ) F i g u r e s between b r a c k e t s r e p o r t a p o s t e r i o r i f o r e c a s t i n g u s i n g f o r e c a s t e d MPI b u t a l i n e a r r e g r e s s i o n between o b s e r v a t i o n s f o r t h e same w i n t e r .

CONCLUSIONS The s i m p l e e s t i m a t i o n o f t h e p o t e n t i a l a i r p o l l u t i o n t h a t h a s been e x p e r i m e n t e d i n Belgium f o r two y e a r s p r o v e d t o be o p e r a t i o n a l f o r d a i l y f o r e c a s t i n g i n o r d e r

t o warn p u b l i c h e a l t h a u t h o r i t i e s a b o u t t h e p o s s i b l e d e t e r i o r a t i o n o f t h e a i r quality

2 4 o r 48 h o u r s i n advance.

The method of f o r e c a s t i n g t h e p o t e n t i a l a i r

p o l l u t i o n d e v e l o p p e d a t t h e Royal M e t e o r o l o g i c a l I n s t i t u t e o f Belgium and d a i l y u s e d d u r i n g two w i n t e r s h a s g i v e n e n c o u r a g i n g r e s u l t s .

When n u m e r i c a l f o r e c a s -

t i n g s w e r e correct, i . e . i n most o f t h e cases, MPI w a s g e n e r a l l y w e l l e s t i m a t e d . I t appears thus p o s s ib le

t o f o r e c a s t t h e d i f f u s i v e c a p a c i t y o f t h e atmosphere

and t o e s t i m a t e p o t e n t i a l a i r p o l l u t i o n from r o u t i n e s y n o p t i c f o r e c a s t i n g s a v a i l a b l e a t a weather o f f i c e .

SO

an i n d i c a t i o n o f t h e a i r q u a l i t y .

2

c o n c e n t r a t i o n s computed from t h e MPI g i v e I t i s t o b e n o t e d t h a t t h e MPI t a k e s only i n t o

a c c o u n t t h e d i s p e r s i o n c o n d i t i o n s and p o l l u t a n t p r o d u c t i o n due t o d o m e s t i c heat i n g sources.

Background p o l l u t i o n and i n d u s t r i a l s o u r c e s are i m p l i c i t e l y t a k e n

i n t o a c c o u n t by t h e c o n v e r s i o n method ; however t r a n s p o r t and a c c u m u l a t i o n o f p o l l u t a n t s are n o t i n c l u d e d i n t h i s scheme, p r i m a r i l y d e s i g n e d f o r urban areas. Even when p a r t i c u l a r y u n f a v o u r a b l e m e t e o r o l o g i c a l c o n d i t i o n s e x i s t , an a i r p o l l u t i o n e p i s o d e only occurs i f s o u r c e s t r e n g t h i s s u f f i c i e n t .

The MPI must be

c o n s i d e r e d as an i n d i c a t o r o f the a t m o s p h e r i c d i f f u s i o n c a p a b i l i t y and o f p o l l u t a n t p r o d u c t i o n due t o m e t e o r o l o g i c a l c o n d i t i o n s ( h e a t i n g d u r i n g very c o l d p e r i o d s ) . I t c o n s t i t u t e s a simple b u t e f f e c t i v e t o o l f o r d a i l y f o r e c a s t i n g o f t h e p o t e n -

t i a l air pollution.

102 REFERENCES 1 . B, B r i n g f e l t , Atmosph. E n v i r o n . , 5 (1971) 949-972. 2. D.M. Elsom a n d T . J . C h a n d l e r , Atmosph. E n v i r o n . , 12 (1978) 1543-1554. 3 . H . van Dop, A.P. van Ulden a n d W.R. R a a f f , S c i e n t i f i c r e p o r t , W.R. 75-4, K.N.M.I. (1975) D e B i l t . 4. M.E. B e r l y a n d , P r e s e n t T o p i c s i n a t m o s p h e r i c d i f f u s i o n a n d a i r p o l l u t i o n ( i n r u s s i a n ) , chap.12 (1975) L e n i n g r a d . 5. L.M. Malet a n d A. J o u k o f f , W.M.O. Symposium on boundary l a y e r p h y s i c s a p p l i e d n 0 5 1 0 ( 1 9 7 8 ) , 135-141. t o s p e c i f i c p r o b l e m s o f a i r p o l l u t i o n W.M.O. 6 . A . Bodeux, Approche d ' u n e esquisse c l i m a t o l o g i q u e d e s t y p e s d e temps e n B e l g i q u e , I.R.M., Publ. s e r i e A n o 2 ( 1 9 7 2 ) .

103

THE FORECASTING METHOD

OF A I R

POLLUTION PEAKS DEVELOPED AND USED I N THE NORD -

PAS-DE-CALAIS AREA

P. ALLENDER and J.M. D E J A R D I N Armines - Cen r e de D O U A I ( F r a n c e )

ABSTRACT An o r i g i n a

s t a t i s t i c a l method, based o n t h e use o f t h e d i s c r i m i n a t ng a n a l y -

s i s , has been d e v e l o p e d t o make p o s s i b l e t h e m u l t i v a r i a t e f o r e c a s t o f a i r p o l l u t i o n peaks i n t h e Nord - P a s - d e - C a l a i s a r e a . T h i s p a p e r p r e s e n t s t h e m a i n mathem a t i c a l c h a r a c t e r i s t i c s o f t h e method, and d e s c r i b e s how i t i s used i n t h e p r a c t i c e i n t h e a u t o m a t i c a i r p o l l u t i o n c o n t r o l n e t w o r k s o f t h e Nord

-

Pas-de-Calais

area.

INTRODUCTION The f o r e c a s t i n g o f p o l l u t i o n peaks r e q u i r e s t h e use o f a m u l t i v a r i a t e f o r e c a s t i n g method. I t i s now w e l l known t h a t mono v a r i a t e methods l i k e A R I M A schemes d o n ' t g i v e good r e s u l t s . The m u l t i v a r a t e method chosen h e r e i s based o n a p a r t i c u l a r use o f the discriminating analysis

THE METHOD L e t us c o n s i d e r a group o f o b j e c t s i n which a p a r t i a l c l a s s i f i c a t i o n a l r e a d y e x i s t s and l e t us suppose t h a t s e v e r a l p a r a m e t e r s have been measured on a l l o b j e c t s . The d i s c r i m i n a t i n g a n a l y s i s e n a b l e s t o a p p r e c i a t e i f t h e p a r t i a l c l a s s i f i c a t i o n i s w e l l r e p r e s e n t e d b y t h e knowledge o f t h e measures. I f i t i s so, t h e d i s c r i m i n a t i n g a n a l y s i s shows how t h e u n c l a s s i f i e d o b j e c t s may be c l a s s i f i e d by t h e u s e o f t h e i r measures. I n t h e c a s e o f a t w o g r o u p s c l a s s i f i c a t i o n ,

t h e method e n a b l e s t o o b t a i n

a l i n e a r f u n c t i o n o f parameters ( c a l l e d Fisher f u n c t i o n ) w i t h which t h e unclassif i e d o b j e c t s w i l l be a f f e c t e d t o one o r a n o t h e r g r o u p , d e p e n d i n g on t h e s i g n o f t h e function. The i d e a i s t o c o n s i d e r t i m e p e r i o d s ( 6 h o u r s f o r example) as o b j e c t s and t o assoc i a t e t o e a c h t i m e p e r i o d t h e v a l u e s o f m e t e o r o l o g i c a l p a r a m e t e r s w h i c h have been measured on t h e p r e v i o u s p e r i o d . The knowledge o f p o l l u t i o n v a l u e s e n a b l e s t o c l a s s i f y t h e p e r i o d s i n t w o g r o u p s : peak o f p o l l u t i o n " o r n o t " . I n t h e s e c o n d i t i o n s t h e d i s c r i m i n a t i n g a n a l y s i s d e s c r i b e d above becomes a s h o r t t e r m f o r e c a s t i n g t o o l .

104

The knowledge o f t h e F i s h e r f u n c t i o n and o f t h e m e t e o r o l o g i c a l p a r a m e t e r s a t t h e p e r i o d t n w i l l show wether t h e p e r i o d t n + 1 w i l l be p o l l u t e d o r n o t .

EVALUATION The method has been t e s t e d w i t h p e r i o d s o f twenty f o u r hours on t h e b a s i s o f o l d d a t a . AF and c l a s s i c a l meteorology o f t h e L I L L E network. A d i s c r i m i n a t i n g a n a l y s i s o f t h e y e a r 1977 gave t h e f o l l o w i n g F i s h e r f u n c t i o n ( p o l l u t i o n i f n e g a t i v e ) f ( j ) = 0,0010 T, + 0,351 v18 - 0,857 CD12 + 0,378 MM - 3,226 + K ( j + l )

Tm, V18, C012 a r e t h e maximum t e m p e r a t u r e , t h e wind speed a t 6 p.m. and the c o s i n e o f t h e wind d i r e c t i o n 0 p.m. measured f o r t h e day j-1 Y M M i s the "modified month" d e f i n i d a s f o l l o w s MM 1 2 3 4 5 6 7

o f which :

X

JAN

FEB

MAR

APR

DEC

NOV

JUN SEP

MAY OCT

JUL AUG

% K(j+l) = 0 , 8 i f j + l i s Saturday K ( j + l ) = 1 , 4 i f j + l i s sunday K(jt1) = 0 i n t h e o t h e r c a s e s

The s e l e c t i o n o f t h e d i f f e r e n t p a r a m e t e r s c a n n o t be j u s t i f i e d here ; a s r e s u l t s from v a r i o u s e x p e r i m e n t a t i o n s . T h i s f u n c t i o n , t e s t e d on t h e y e a r 1978, gave t h e f o lowing r e s u l t s : 24 hours average pol 1 u t i o n measured number o f days concerned

40

134

74

100

80

60

62

43

110

13

I

150

130

16

9

14

2

2

0

1

2

3

I

forecasting errors

1

error i m po r t a nce

2

4

4

13

4 I

2

1

1

0

The l i m i t o f t h e c l a s s i f i c a t i o n " p o l l u t e d " o r " n o t p o l l u t e d " has been chosen at 110~~glm3

-

t h e r e i s an e r r o r when a non p o l l u t e d day has been f o r e c a s t e d " p o l l u t e d "

( " f a l s e peak") o r r e v e r s l y ( " m i s s e d peak") - t h e e r r o r importance index o f f e r s a f o u r l e v e l s e x p r e s s i o n o f t h e importance

o f each f o r e c a s t i n g e r r o r .

As a c o n c l u s i o n , t h e o b t a i n e d r e s u l t s a r e a l r e a d y e x c e l l e n t , and w i l l be improved by t h e u s e o f a s m a l l e r p e r i o d ( t h e measurement p e r i o d i s 15 mn i n t h e automat i c new n e t w o r k ) , and o f new t y p e s o f p a r a m e t e r s ( l i k e micro m e t e o r o l o g i c a l d a t a f o r example) .

105

PRACTICAL USE

A t p r e s e n t , t h e Dunkerque n e t w o r k i s o p e r a t i n g as an " a l a r m " .

D u r i n g 1981,

22 a l a r m s e n a b l e d , by t h e u s e o f a p a r t i c u l a r f u e l i n t h e f o u r m o s t i m p o r t a n t i n d u s t r i e s d u r i n g a s h o r t w h i l e , t o r e d u c e g r e a t l y t h e peak l e v e l o f a i r p o l l u t i o n . The " t r i g g e r i n g " o f t h e a l a r m s i s g e n e r a l l y done i n t h r e e t i m e s :

1) a m e t e o r o l o g i c a l s t u d y has shown t h a t t h e knowledge o f s y n o p t i c a l w e a t h e r r e p o r t s p e r m i t s t o e l i m i n a t e a r o u n d 250 days a y e a r d u r i n g w h i c h t h e r e i s a b s o l u t e l y no peak p o l l u t i o n d a n g e r . 2) Regarding t h e o t h e r days, t h e F i s h e r f u n c t i o n proper t o t h e network i s i m p l a n t e d o n a m i c r o c o m p u t e r w h i c h i s t i e d t o t h e a u t o m a t i c n e t w o r k o n one s i d e and t o an a u t o m a t i c phone c a l l s y s t e m o n t h e o t h e r s i d e . As a r e s u l t , t e c h n i c i a n s may be c a l l e d d u r i n g t h e n i g h t and t h e d a y i f t h e F i s h e r f u n c t i o n becomes n e g a t i v e . 3) The t e c h n i c i a n s may t h e n use q u i c k l y a n i n t e r a c t i v e d i f f u s i o n model, a v a i l a b l e on another microcomputer, o r analyse t h e e v o l u t i o n o f t h e m e t e o r o l o g i c a l data before t r i g g e r i n g t h e alarm. F o r t h e y e a r 1981, t h e e f f i c i e n c y o f t h e w h o l e method has been e v a l u a t e d t o 85 %. I t seems t o be an e x c e l l e n t a p p r o a c h o f t h e o p t i m i s a t i o n o f r u n n i n g c o s t s ,

industrial

e n e r g e t i c c o s t s and a i r qua i t y .

CONCLUSION

A l a s t p o i n t has t o be u d e r l i n e d : i t r e f e r s t o t h e f a s c i n a t i n g d u a l i t y b e t ween t h e huge i n f o r m a t i c a l s y s t e m r e q u i r e d f o r t h e d e t e r m i n a t i o n o f t h e F i s h e r f u n c t i o n , and t h e u t m o s t s i m p l i c i t y o f i t s p r a c t i c a l u s e on a s m a l l m i c r o c o m p u t e r . T h i s i s an i m p o r t a n t a s p e c t o f t h e power o f t h e p r o p o s e d method. REFERENCES

1 P. A l l e n d e r , A p p o r t de 1 ' a n a l y s e d i s c r i m i n a n t e aux p r o b l e m e s de p r e v i s i o n a c o u r t t e r m e - A p p l i c a t i o n a l ' e l a b o r a t i o n d ' u n e p r o c e d u r e de p r e - a l e r t e s u r l e r e s e a u de c o n t r 6 l e de l a p o l l u t i o n a t m o s p h e r i q u e dans l a zone de Lille-Roubaix-Tourcoing, Armines, D o u a i , 1980. 2 P. A l l e n d e r , I m p l a n t a t i o n de 1 ' I n d e x d i s c r i m i n a n t d ' a l e r t e s u r m i c r o - o r d i n a t e u r , Armines, Douai 1981. 3 J.M. D e j a r d i n , J. Mahieu, J.P. Dondeyne, A p p o r t des p r e v i s i o n s m e t e o r o l o g i q u e s synoptiques 2 l a d e t e r m i n a t i o n d ' u n e a l e r t e en p o l l u t i o n atmospherique - A p p l i c a t i o n 2 l a zone d e Dunkerque, A r m i n e s , Douai 1981. 4 P. A l l e n d e r , J.M. D e j a r d i n , A p p l i c a t i o n du m o d s l e GCTSP a 1 ' e t u d e de l a d i f f u s i o n de p o l l u a n t s emis ti p a r t i r de s o u r c e s p o n c t u e l l e s , Armines, D o u a i , 1981.

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107

TURBULENT DIFFUSIVITIES AND DISPERSION COEFFICIENTS: APPLICATION TO CALM WIND CONDITIONS P.J.H. BUILTJES Netherlands Organization for Applied Scientific Research TNO, Fluid Dynamics Department. Apeldoorn, the Netherlands

ABSTRACT Based on theoretical considerations and experimental data some remarks have been made about the relationship between dispersion coefficients, u-parameters, and turbulent diffusivities, K-parameters. Special attention has been paid to the behaviour of these parameters at calm wind conditions and their use in existing calm wind dispersion models.

INTRODUCTION Dispersion processes in the atmosphere can be described by the diffusion equation or the gaussian plume model. For the dispersion from point sources the gaussian plume model is often used This model contains two dispersion coefficients, describing the width of the and vertical direction, uzIn gridmodels the diffusion equation is used. The terms of this equation

concentration distribution in the horizontal,.U

Y

describing the turbulent transport contain two turbulent diffusivities in the horizontal, K and vertical direction, KZ. Both sets of parameters give a

Y

representation of the turbulent transport. This leads to the question of the relationship between U- and K-parameters, from a theoretical as well as from a practical point of view. This relationship is of special importance in the case of calm wind conditions. The existing calm wind dispersion models are gaussian plume models and diffusion equation models. Consequently it is of importance to know the behaviour of U- and K-parameters at low windspeeds.

108

SOME THEORETICAL CONSIDERATIONS The diffusion equation describing the transport of a pollutant c can be given by

with the mean concentration of a pollutant c

U K

Y

KZ

the mean velocity in the x-direction the turbulent diffusivity of mass in the lateral direction y the turbulent diffusivity of mass in the vertical direction z

In eq. (1) it is assumed that the mean velocities in the y- and z-direction are small and the turbulent transport in the x-direction is small relative to the mean velocity transport. Furthermore it is assumed that the turbulent transport can be described by the gradient type transport, which leads to the use of the turbulent diffusivities. The gradient type transport model can only be viewed as a first approximation. By writing in analogy with the concept of molecular diffusivity Ky, KZ

CI

V L

(2)

with V an appropriate velocity scale and L an appropriate length scale it is clear that eq. (1) can in principle only describe the dispersion of a cloud with dimensions larger than L. However, in practice, as is also known from the theory of turbulent diffusion of momentum, this restriction will not be so severe.

In recent years attempts have been made to improve the gradient type transport concept. The second order closure modelling (ref. 1) and the use of the telegraph equation (ref. 2 , 3 , 4 ) tan be mentioned. These methods try to improve the strictly local character of the gradient type transport by incorporating the influence of a larger space and time domain on the turbulent transport. The different influences of different length scales is also incorporated in the spectral turbulent diffusivity concept (ref. 5 ) . In this paper, however, the discussion will be restricted to the gradient type transport. The gaussian plume model is an analytical solution of eq. (1) under the following conditions:

-

All parameters in eq. (1) are stationary The windfield is homogeneous

109

-

The turbulent diffusivities are only a function of the distance from the source

-

There is complete reflexion from the pollutant against the ground

The gaussian plume model can be written as

with Q

The emission from a source

H

the effective height of the source

u ,a the dispersion coefficients Y

Z

Under the above mentioned restrictions the relation between a- and K-parameters can be given by: U d

KY = -2 -d x

ay2 , K = -U -d ' a 2 z 2dx z

(4)

These relations show directly that it is impossible that both u- and K-parameters are independent of the mean velocity U. In the further discussion a distinction will be made between the horizontal and vertical direction.

THE HORIZONTAL TURBULENT TRANSPORT Because the turbulent transport in the horizontal direction can be viewed as transport in a homogeneous turbulent field, the statistical theory of Taylor can be applied:

2 d a

-

-& = 2 v2

oJt RL (t') dt'

(5)

sth: v2 the turbulent fluctuation in the y-direction

RL (t) the lagrangian auto-correlation for lateral turbulence. In general it is assumed that RL(t)

can be given by

wiCh IL the lagrangian integral time scale.

110

Integration of eq. (5) with eq. (6) leads to

which gives:

-

u = 2v2 Y

-

t = 2v2 I x/u for t >> L

This is the well-known result from Taylor's theory. For small travel times the spread of a plume is determined by the turbulent fluctuations and is proportional to t. For large travel times the larger eddies, represented by IL, play a major role and the spread is proportional to 't

(see for example ref. 6 , pg. 477).

A remark has to be made about travel time and travel distance. The values for 13 as given for example by Pasquill-Gifford, are given as a function of Y' x, the travel distance. However, from a theoretical point of view it is often desirable to use travel time. These two approaches can lead to some confu-

sion, as will be shown later. Because in the horizontal direction there is a homogeneous field eq. (4) can be applied which leads to

-

-

K = v2 t = v2 x/U Y

for t << IL

-

K = v2 IL Y

for t >> IL

This result shows that plume dispersion close to a source can only be described by the diffusion equation with a distanceltime-dependent K -value. Only for Y larger distancesltimes, in the so-called diffusion limit, a constant K -value Y is applicable. (For an unstable atmosphere with a value for IL of about 150 sec, K will only be constant after travel times of the order of 500 sec

Y

and more. This leads to a minimum gridsize which must be used in gridmodels with a constant K -valve.) Y In most Relatively few numerical values are given in the literature for K Y' gridmodels the value for K is set to zero, which leads to the neglection of

Y

turbulent transport across gridcell boundaries. In large scale models 4 (horizontal resolution 30-100 km) a value of K = 10 m2/s is used (ref. 7, 8 j , Y

111 in smaller-scale models (horizontal resolution 1-10 km) a value of K = 50 mZ/s

S

Y

is used (ref. 9 ) . Gifford (ref. 4) mentioned a value of about 10 m2/s for

'large-scale' diffusion. These different values indicate that K is a function Y of scale. No remark is made about a possible influence of the mean velocity on K Y'

This dependency on scale, that is to say on travel distanceltime and averaging time is also clear for the values for u In case of a fixed mean Y' wind direction, the horizontal spread will be determined by length scales from about to 103 meters which can be called boundary-layer turbulence (ref.

lo). This is the turbulence which on scale is generated in an atmospheric boundary layer windtunnel. Larger length scales will cause the so-called meandering of a plume. This meandering is often called relative diffusion, the spread due to boundary-layer turbulence absolute diffusion (ref. 11, 12). This phenomenon leads to the fact that the value of

(7 will be a function of Y the averaging time and will increase with increasing averaging time. The rate

of increase is determined by the turbulent spectrum (ref. 11, 13). Hanna (ref. 14) gives the following correction for the averaging tire, starting from the Pasquill-Gifford values with an averaging time of 3 minutes: a

u

(t)

Y

= u (t = 3 min) (t/3) Y

(11)

with: t

averaging time in minutes

a a

0 . 2 for t < 60 min

0.25-0.3 for t > 60 min

The discrepancy at t = 60 min indicates the accuracy of the methode. A l s o higher values for a can be found, up to 0.5 (ref. 15). The u -values given by Pasquill-Gifford can be written as:

Y

(7

Y

= A x

B

(12)

with B = 0.9 for all stability classes and A a function of the stability class, the surface roughness, and the averaging time, which is 3 min for the original values. In case information about turbulence levels is available, the

112 following expression can be used (ref. 14, 3):

u = u x s Y

with u

O

O

Y

(X/U IL)

the standard deviation of the horizontal winddirection fluctuations,

which is a function of the averaging time, the surface roughness, the height above the ground and the stability class. Several proposals for the function S have been made (ref. 14, 16, 171, which all show a weak dependence on x for small values of x, with a transition to a dependence on x-’ for large values of x. This dependency is in agreement with the expressions (8) and ( 9 ) . Gifford (ref. 4, see also ref. 3) gives the following expression for a point source

with values for K and IL related to large scales. Y Note that this equation is identical to eq. (7). Eq. (14) with the appropriate values for K and IL is claimed to give good Y results for traveltimes from 10 sec to 1 year. Also eq. (14) is in agreement with the limits for small and large values of t. A very simple expression is given by Heffter (18)

u

Y

(m) = 0 . 5 t (sec)

This expression cannot be valid for large traveltimes. For the determination of the values of u and K at low wind speeds it is Y Y necessary to know their dependency on the mean velocity. It can be assumed that the function S of eq. (13) is independent of the mean

velocity. Pasquill (ref. 19, pg. 82) gives a graph from observations at Porton which show for unstable conditions that u is constant down to 0 U = 2 m / s , with a linear increase with decreasing velocity to U = 1 m/s. For stable conditions u Consequently:

u Y

O(

F(x)/U

u a F(x) Y

@

decreases linearly with U from U = 8 m/s to 2 m / s .

for U < U+ for

u

> U+

113 with U+ about 2 m/s for unstable and 8 m/s for stable conditions. F(x) = x for small values of x and xh for large values of x. This result is also in agreement with measurements by Kristensen (ref. 121, which show that u is proportional to U-o'8 for U Y

5

10 m/s at stable conditions.

However, eq. (14) and (15) which are given in travel time indicate that 0 Y is proportional to U-l also at higher velocities, which especially for unstable conditions is incorrect. Consequently, it will be assumed that eq. (13), in combination with the above mentioned dependency on U, gives the correct behaviour of u Assuming that eq. ( 4 ) is still correct for low windY' speeds leads to the following behaviour of K . Y'

with G(x) = 1 €or large values of x , and G(x)

= x for small values of x.

This result shows that there is a distinct dependency on the mean velocity of K Y' THE VERTICAL TURBULENT TRANSPORT

In the case of vertical transport the statistical theory of Taylor can no longer be applied because of the inhomogeneity of the turbulent field. Consequently, also eq. ( 4 ) will be of limited value. Using the so-called similarity theory the following expression for a source close to the ground can be given (see for example ref. 2 0 ) .

with:

k

the von Karman constant

u

9

the wall shear stress velocity the stability function, $I = 1 for neutral conditions

L

the monin-obukov length

*

For a stationairy condition eq. (18) can be rewritten to:

* u = k

x 4 (z/L)

This equation shows a linear dependency on x .

114 A n analogous expression as eq. ( 1 3 ) can be given for uZ (ref. 3 ) :

with u the standard deviation of the vertical winddirection fluctuations, which will be a function of the surface roughness, the height above the ground and the stability class. It is important to note that above a certain averaging time u and consequently u will be independent of the averaging time. This upper averaging time is generally assumed to be 3-10 minutes. In ref. (16) an expression for Sz is given which is identical to S This Y' leads to a dependency of uz on x for small distances, and of 'x for large distances, in accordance with u Y' The original Pasquill-Gifford values can be represented by:

u = c x D with D = 0.9 for unstable and 0.7 for stable conditions. With the aid of the similarity theory also expressions can be given for KZ. Based on the experiments by Deardorff, Reynolds (ref. 9) gives the following algoritm for Kz. for neutral conditions

-

*

*)

*2

U

z < 0.45 f

F (z, u

KZ =

*

KZ = 0.01 m2/s

-

z > 0.45

U

with f the Coriolis parameter for stable conditions

*

K = k u z G

* , L, vg)

(z, u

with V the geostrophic wind

-

g

for unstable conditions

*

K = w zi H (z/zi)

(24)

*

*

with z i the inversion height, and w = u

(-

1

c)113

i'

115

In eq. (22)-(24) KZ is independent of x, which indicates that eq. (22)-(24) can only be used for not too small values of x. It should be noted that in this case eq. (4), which gives the relation between K and aZ is only of limited value, due to the inhomogeneity in the z-direction. The dependency of KZ and u on the mean velocity can be determined in the following way. In eq. (20) the function Sz is independent of U. From measurements quoted by Pasquill (ref. 14) it can be seen that at values of z < 100 m, 0 tends to be independent of U, also for low windspeeds. Consequently it can be concluded from eq. (20) that a is independent of U for all * values of U. The same result can be obtained from eq. (19) because u /U will be independent of U as long as the flow is aerodynamically rough. From eq. (22)-(24) it can be concluded that, assuming u /U is independent of

*

U and using the full expressions for the functions F, G and H (see ref. 9), as

a first-order approximation, K

is proportional to U for all conditions. Consequently, the following result is obtained for all values of U:

u independent of U

This dependency is in agreement with eq. (4).

MODELS FOR CALM WIND CONDITIONS Finally some remarks will be made concerning calm wind conditions. The amount of calm wind conditions will vary from place to place, and is of course highly dependent on the definition for calm wind condition. Often the lower detection limit of the anemometer used is taken as the determining factor, which of course again is highly dependent on the type of windmeter, maintenance, etc. For the Netherlands and Belgium it can be stated that conditions with

U < 0.5 m/s will occur at 1-3% of the total time (ref. 21, 22). About 50% of the calm wind situations takes place during stable conditions. This condition, in relation with low-level sources is most relevant in view of high concentration levels. The dispersion during calm wind conditions is a complicated phenomenon. The principal difficulty is whether (modifications of) the diffusion equation and the gaussian plume model give still valid descriptions of the dispersion process at low windspeed. The following discussion, however, will be restricted to the use of K- and a-parameters in existing models. There are

116

relatively few models that claim to be able to describe the dispersion of a pollutant during calm wind conditions. Berlyand (ref. 23) and Demuth (ref. 21) use the diffusion equation for this situation and obtain analytical solutions for the concentration field. The following expressions for the K-parameters are used:

K = K1 f l K

(2)

= K2 x f2 Y K = K zn 2

ref. (23)

(2)

1

ref. (21)

K r = K 2 rY zm

The description in ref. (21) is given in cylindrical coordinates. K linearly dependent on the travel distance (in case y = l ) , and K

is Y is independent

of the travel distance. This result is in agreement with eq. (17) and eq. (22)(24). However, no dependency on U is mentioned which is in contradiction with the results obtained in this paper. Yamartino (ref. 24) and Okamoto (ref. 25) use the gaussian puff model to describe the dispersion. The following expressions for the o-parameters are used, written in travel distance for comparison: b

u = ah (x/U) Y b u = av (x/U)

ref. (24)

with b = 0.9, and ah and a

V

to U0”

are constant f o r U < 6.2 m/s and are proportional

for higher windspeeds.

u = c1 x/u Y U“ = p x/u

ref. (25)

L.

In both applications u

Y

is about proportional to U

-1

at low windspeeds, which

is in agreement with eq. (16). However, in contradiction with the results obtained in this paper, also oz is proportional to U-’. The result that a

Y

(J

increases with decreasing windspeed at low values and

remains constant is supported by some dispersion measurements at low

windspeeds carried out by Sagendorf (ref. 26) and van der Hoven (ref. 27). Both mention the fact that a comparison between measurements and calculated concentrations with the use of the Pasquill-Gifford values of u

Y

and u

gives too

high calculated results. The agreement between measurements and calculations i s much improved in case u

Y

is increased proportionally to U

-1

and u2 remains

constant. CONCLUSIONS Clear relationships exist between

U-

and K-parameters, which should be kept

in mind when using the diffusion equation and the gaussian plume model for the same situation.

117

-

Below a critical velocity u and K are proportional to U-I. Y Y At higher velocities u is independent of U and K is proportional to U. Y Y For all velocities uZ is independent of U and K is proportional to U.

-

For practical applications the gaussian plume/puff model with the appropriate values for u and u2 seems the best model to describe the dispersion during Y calm wind conditions.

References: 1. W.S. Lewellen and M.E. Teske 'Second order closure modeling of diffusion in the atmospheric boundary layer' Bound. Lay. Met. 10, 69 (1976) 2.

3.

B.E.A. Fisher 'Physical theories of turbulent diffusion' Atm. Pollution, 71, Elsevier (1980) S.R. Hanna 'Application in Air Pollution Modelling' A short course on Atm. Turb. and Air Poll. Modelling, The Hague, (Sept. 1981)

4.

F.A. Gifford 'Horizontal diffusion in the atmosphere- A Lagrangian Dynamical Model' LA-8667-MS, Los Alamos Sc. Lab. (1981)

5.

R. Berkowicz and L.P. Prahm 'Generalization of K-theory for Turbulent

6.

Diffusion' J. of Appl. Met. 18, 3, 266 (1979) J.O. Hinze 'Turbulence' Mc.Graw Hill (1975)

7.

W.B. Johnson e.a. 'Long term regional pattern and transfrontier exchanges of airborne sulfur pollution in Europe' Atm. Env. 12, 511 (1978)

8.

M.K. Liu and D.R. Durran 'The development of a regional air pollution model and its application to the Northern Great Plains' EPA-908/1-77-001 (1977)

9.

S.D. Reynolds e.a. 'An introduction to the SAI-airshed model and its usage' EF 78-53R4 EF79-31 SAI-San Rafael, Cal. U.S.A. (1979)

10. F.B. Smith 'The character and importance of plume lateral spread

affecting the concentration downwind of isolated sourcesof hazardeous 11.

airborne material. Bound. Lay. Res. Branch, Met.-Off. Ref XI (1980?) C.M. Sheih 'On lateral dispersion coefficients as function of averaging

time' J. of Appl. Met. 19, 5, 557, (1980) 12. L. Kristensen e.a. 'Lateral dispersion of pollutants in a very stable atmosphere - the effect of meandering' Atm. Env. 15, 5, 837 (1981) 13. F.A. Gifford, R.D. Rowe, T. Mikkelsen 'Comments on lateral dispersion

coefficients as function of averaging time' J. of Appl. Met. 20, 213, 728, 731 (1981) 14.

S.D. Hanna 'AMS Workshop on stability classification schemes and sigma curves' Bull. Am. Met. SOC. vol 58, 12 (Dec. 1977) 15. D.J. Moore 'Calculation of groundlevel concentration for different sampling periodes and source locations' Atm. Poll. 51-60, Elsevier A'dam (1976)

118 16. R.R. Draxler 'Determination of atmospheric diffusion parameters' Atm. Env. 17.

10, 99 (1976) J.S. Irwin 'Estimating plume dispersion

-

a recommended generalized

scheme'. Fourth Sym. on Turb. Diff. and Air Poll. Am. Met. SOC. 62-69 (1979) 18. J.L. Heffter 'A regional-continental scale transport diffusion and

deposition model' NOAA Tech. Memo ERL-ARL-50 (1975) 19. F. Pasquill 'Atmospheric Diffusion', 2nd Ed. Ellis-Horwood (1974) 20.

21

F.T.M. Nieuwstadt and A.P. v.Ulden 'A numerical study on the vertical dispersion of passive contaminents from a continuous source in the atmospheric surface layer' Atm. Env. 12, 2119 (1978) C1. Demuth e.a. 'Analytical modelling of pollutant dispersion during calm wind conditions' Atm. Poll. 167-173, Elsevier A'dam (1978)

22

P.E.J. Vermeulen 'Persistency and calm wind conditions' (in Dutch) MT-TNO Ref.nr. 81-010569 (Sept. 1981)

23

M.G. Berlyand and G.I. Kurenbin 'Atmospheric Diffusion of impurities during a calm' Am. Inst. of Crop Ecology Survey of USSR. Air Poll. Lit.

Vol IV (1970) 24. R.J. Yamartino 'An air quality dispersion model applicable to calm wind conditions' 7th Int. Tech. Meeting on Air Poll. Modelling and its 25.

Applications, Airlie Virginia, 537, (Sept. 1976) S. Okamoto and K. Shiozawa 'Validation of an air pollution model for the Keihin Area' Atm. Env. 12, 2139 (1978)

26. J.F. Sagendorf and C.R. Dickson 'Diffusion under low windspeed inversion

conditions' NOAA Tech. Memo. ERL-ARL-52 (1974) 27. I. v.d.Hoven 'A survey of field measurements of atmospheric diffusion under low windspeed inversion conditions' Nucl. Safety, 17, 2, 223 (March 1976)

119

MEASUREMENT OF TURBULENCE PROFILES I N THE BOUNDARY LAYER AND OBSERVATIONS OF ATMOSPHERIC DIFFUSION BY SMOKE PLUMES EMITTED NEAR THE GROUND AND I N ALTITUDE D. S c h n e i t e r

Swiss M e t e o r o l o g i c a l I n s t i t u t e , A i r P o l l u t i o n S e c t i o n , CH 1530 Payerne A French v e r s i o n o f t h i s a r t i c l e i s a v a i l a b l e (Rapport de t r a v a i l de 1 ' I n s t i t u t S u i s s e de M 6 t @ o r o l o g i e , No. 108, Z u r i c h 1982).

ABSTRACT S t u d i e s o f t h e atmospheric d i s p e r s i o n o v e r complex t e r r a i n , w i t h t h e a i d o f smoke plumes, e n a b l e t h e d i r e c t o b s e r v a t i o n o f t h e m a r g i n a l d e n s i t y p r o b a b i l i t y o f t h e e m i t t e d p a r t i c l e s . Experiments n e a r t h e ground c o r r e l a t e t h e t u r b u l e n c e measurements a t 10 rn h e i g h t and plume p i c t u r e s ( p r o f i l e , e l e v a t i o n and p l a n ) t a k e n b y a network o f cine-cameras. Experiments i n a l t i t u d e c o r r e l a t e t h e t u r b u l e n c e p r o f i l e , measured b y a m i c r o a e r o l o g i c a l equipment and t h e development o f f i v e smoke plumes o f d i f f e r e n t c o l o r s , d i s t r i b u t e d e v e r y 25 m a l o n g t h e c a b l e o f a t e t h e r e d b a l l o o n . The g r a p h i c a l d a t a t r e a t m e n t and v i d e o e d i t i n g o f t h e f i l m s e n a b l e easy access t o t h e r e s u l t s . These measurements w i l l be used t o check t h e v a l i d i t y o f d i f f e r e n t assumptions proposed i n t h e s t o c h a s t i c modell i n g s (Gaussian o r non Gaussian) o f atmospheric d i s p e r s i o n .

INTRODUCTION The mean c o n c e n t r a t i o n a t p o i n t

?,

a t t i m e t, o f a p a s s i v e p o l l u t a n t , e m i t t e d

b y a c o n t i n u o u s p o i n t source o f i n t e n s i t y Q (number o f p a r t i c l e s p e r u n i t t i m e ) +

a t p o i n t rs, i s g i v e n b y t h e g e n e r a l e q u a t i o n ( r e f s . 10, 1 1 ) t p (F, t ;s, t ' ) d t ' c (?, t ) = Q

+ where p ( r , t i

1 +rs, t ' )

0 i s the p r o b a b i l i t y d e n s i t y t h a t a p a r t i c l e released a t

r s a t t i m e t ' w i l l be f o u n d a t

a t t i m e t. We assume t h a t v e r t i c a l a c c e l e r a t i o n s

due t o t e m p e r a t u r e d i f f e r e n c e s between plume and ambient a i r (buoyancy) a r e negl i g i b l e . I n t h i s case, t h e mean c o n c e n t r a t i o n

c(?, t )

i s only f u n c t i o n o f the

n a t u r a l d i s p e r s i o n c o n d i t i o n s o f t h e a i r . The p i c t u r e s o f t h e plumes, f o r i n s t a n c e

120

i n t h e v e r t i c a l d i r e c t i o n z, r e p r e s e n t t h e m a r g i n a l c o n c e n t r a t i o n f i e l d ( r e f . 17) -

c Z ( x, Y, t )

=

I c (x,

Y, z, t ) dz

0 The d i s t a n c e f r o m t h e camera t o t h e plume must b e s u f f i c i e n t t o m i n i m i z e p e r s p e c t i v e e f f e c t s . Outputs o f n u m e r i c a l models a b l e t o c a l c u l a t e t h e f i e l d

cz (x,

y, t )

can b e d i r e c t l y compared t o these p i c t u r e s . The d a t a o b t a i n e d w i t h smoke plumes experiments performed n e a r t h e ground and i n a l t i t u d e on t h e h i l l y s i t e o f Payerne (100 km f r o m Geneva) w i l l b e used t o v e r i f y s t o c h a s t i c models o f atmospheric d i s p e r s i o n o v e r complex t e r r a i n and by weak t o moderate winds.

SMOKE PLUME EXPERIMENTS NEAR THE GROUND

The t h r e e w i n d components, measured b y a t h r e e p r o p e l l e r s anemometer X Y Z ( F i g . l ) , mounted on a mast 10 m o v e r ground, a r e memorized e v e r y 5 s, d u r i n g 1 h o u r . Three smoke plumes a r e f i r e d s u c c e s s i v e l y , n e a r t o t h e anemometer. For e v e r y e x p e r i m e n t ( T a b l e 1 ) t h e camera l o c a t i o n s were d e t e r m i n e d t a k i n g i n acc o u n t t h e mean w i n d d i r e c t i o n and t h e sun p o s i t i o n . A p l a n view i s o b t a i n e d b y an a i r l i f t e d camera, p o i n t e d down, a t t a c h e d under a t e t h e r e d b a l l o o n , s t a b i l i z e d between 200 and 500 m above t h e ground. White markers on t h e ground a r e used t o s c a l e plume dimensions.

Fig. 1

X Y Z anemometer and smoke c a r t r i d g e 10 m above t h e ground

Fig. 2

Plume blown down showing a l o g a r i t h m i c wind p r o f i l e n e a r t h e ground

Clocks i n t h e f i e l d o f view o f t h e cine-cameras p r o v i d e s y n c h r o n i z a t i o n between t u r b u l e n c e measurements and p i c t u r e s . M i c r o a e r o l o g i c a l soundings ( r e f . 19) f o l l o w t h e v a r i a t i o n s i n temperature, h u m i d i t y , w i n d speed and d i r e c t i o n p r o f i l e s d u r i n g d i s p e r s i on o f smoke.

121

TABLE 1 Smoke experiments near the ground Smoke c a r t r i d g e

Cine cameras l o c a t i o n s

No

Date

Time

Duration

8 mm

1 2 3 4 5 6 7 8

3.3.78 3.3.78 3.3.78 8.3.78 8.3.78 9.3.78 9.3.78 9.3.73

14h59 '30" 15h 16 ' 30" 15h31'30" 9h26 '50" 10 h04 ' 50 " 16h42 ' 20" 16h52' 10" 17 hO 2 ' 30 "

1 ' 50" 3'30" 3 ' 10" 3'10" 3'10" 3'10" 3'10" 2 ' 30 "

LlOO LlOO LlOO F 75 F 75 F 75 L 75 L 75

9 10 11 12 13 14 15 16 17 18 19 20 21 23 24 25 26

11.3.80 11.3.80 11.3.80 12.3.80 12.3.80 12.3.80 12.3.80 12.3.80 12.3.80 17.3.80 17.3.80 17.3.80 18.3.80 18.3.80 18.3.80 18.3.80 18.3.80 18.3.80

15h20' 50" 15h38'25" 15h48' 30" 9 h 12 ' 25" 9 h 25 ' 30" 9 h 38 ' 2 7" 15h 10 ' 15" 15h26'17" 15 h 34 ' 35 " 14hl3'25" 14h24'05" 14h 3 5 ' 15 " 11h 10 ' 02" 11 h24'50" 1 1h40 ' 20" 14h25 ' 22" 14h34'12" 14h 43 ' 55 "

2 ' 50" 3'05" 3'18" 2 ' 50" 2 ' 50" 2 ' 5 8" 3'10" 3 ' 43" 2 ' 45" 2'55" 3'08" 3'00" 2'58" 2 ' 48" 3 ' 10" 3 ' 00"

2'21)"

G 50 G 50 G 50 G 50 G 50 GlOO KlOO KlOD K100 L 75 L 75 L 75 T 85 T 85 T 85 H150 H150 H150

27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43

3.4.81 3.4.81 6.4.81 6.4.81 6.4.81 7.4.81 7.4.81 7.4.81 7.4.81 7.4.81 7.4.81 8.4.81 8.4.81 8.4.81 8.4.81 8.4.81 8.4.81

14H17 ' 17" 14h42'53" 15h15 '00" 15h 30 ' 00" 15h45 ' 00" 14h15 '00" 14h26'00" 14h44'00" 16hl5 ' 00" 16h33 ' 45" 16h49 ' 20" 14h 15 ' 00" 14h30'00" 14h45 ' 00" 1 5 h l 4 ' 58" 15h25 ' 00'' 15h 39 ' 22"

2 ' 53" 8'03" 3'15" 9'15" 2 ' 50" 2 ' 45" 9 ' 36" 2 ' 45 " 2 ' 42" 1 0 ' 15" 2 ' 50" 3 ' 00" 9 ' 45" 3 ' 20" 2 ' 42" 9 ' 30" 2 ' 28"

S150 S150 ClOO ClOO c100 ClOO ClOO ClOD -ClOO c100 c100 ClOO ClOO ClOO ClOO ClOO

22

3 ' 23"

Weight

8 mm

8 mm

-300m 500m 500m 500m 500m 500m 500m 500m

---

-_ 500m 500m 500m 300m 500m 500m H150 H150 H150 H150 H150 H150 H150 H150 H150 H150 H150 H150 H150 H150 H150 H150 H150

L L L L F F L

50 50 50 75 75 75 75

--

L 75 T 85 T 85 T 85 P100 PlOO PlOO FlOO FlOO

--

B150 B150 -- BlOO -- B l O O -- B1OD -- B l O O - - B700 -- B l O O 200m B l O O 200111 B l O O zoom B l O O 200m B l O O -200m 200m B l O O -- B l O O -- B l O O -- B l O O

500m

500m

Measurements

Top o f 16mm X Y Z sounding

XYXYXYXYXYXYXYXYXYXYXYXYXYXYXYXYXYXYXYXYXYZ XYZ XYZ XYZ XYZ XYZ XYZ XYZ XYZ XYZ XYZ XYZ XYZ XY2 XYZ

_405111 399m 677m

--

709111 49 7m

--

435m 49 7m _508m 499m

--

505m 499m

__

508m 306m 290m 287m 31 4m 241111 495m 49 4m 49 7m 402111 246m 462111 802111 49 8m 501m 523111 507m 51 4m

i

\\

0

El

s

I I

=4

E

p

i Ln ,f

-i

v

-

ma, o m

m-

L

.r

L Q -

0

C

v)

m--

m

m

LL

.r

123 RESULTS A f t e r p a r t i a l c o r r e c t i o n o f n o n - l i n e a r i t i e s ( r e f s . 8 and 18), the 5 s wind components are f i l e d and analysed on graphs, traced b y computer. The curve obtained by a d d i t i o n o f h o r i z o n t a l components, i n a reverse chronological order (Fig. 4), can be compared w i t h the actual plume t r a j e c t o r y (Fig. 3 ) . The s e t of h o r i z o n t a l wind vectors (Fig. 5 ) c o l l e c t e d d u r i n g one hour i s presented i n chronological order, from l e f t t o r i g h t and up t o down. They reveal the organizat i o n o f small eddies ( l i f e time, some tens o f s ) and l a r g e eddies ( l i f e time, about f i f t e e n minutes). The same wind vector set, drawn from a comnon o r i g i n (Fig. 6 ) represents the s e c t o r i a l d i s t r i b u t i o n o f wind speeds and d i r e c t i o n s t h a t extend over n e a r l y a l l azimuts i n t h i s case.

SMOKE PLUME EXPERIMENTS I N ALTITUDE

Sensors o f the microaerologi c a l sounding system HOBILAB (pressure, temperature, humidity, wind d i r e c t i o n ) are supplemented by two p r o p e l l e r s having oblique axes (Fig. 7). These two c o v a r i a n t wind components a r e used t o c a l c u l a t e h o r i z o n t a l and v e r t i c a l speed a t every measurement l e v e l . Ascents and descents are performed successively. Measurements a r e made every 5 m, t o g i v e the f i n e s t r u c t u r e (Figs. 9 and 11) o f the boundary layer. F i v e smoke plumes o f d i f f e r e n t colors are d i s t r i b u t e d every 25 m along the cable o f a tethered balloon. They are f i r e d by r a d i o remote c o n t r o l . Two super 8 cine-cameras f i l m the plumes along v e r t i c a l (Fig. 8) and o b l i q u e axes. A 16 mm cine-camera, placed on a nearby h i l l , a t 800 m distance, gives a view along a h o r i z o n t a l a x i s (Figs. 10 and 12). An automatic camera equipped w i t h a fish-eye o b j e c t i v e , p o i n t e d up, takes s l i d e s every 3 s . These p i c t u r e s being i n p o l a r coordinates g i v e azimuts and e l e v a t i o n s o f the plumes o u t l i n e .

Fig. 7

MOBILAB sonde w i t h two p r o p e l l e r s f 300

Fig. B

F i v e airborne smoke fumes and two tethered balloons viewed from the ground, l o o k i n g v e r t i c a l l y up

124

TABLE 2 Smoke experiments i n a l t i t u d e No

Date

1 9.4.81 2 9.4.81 3 9.4.81 4 9.4.81 5 10.4.81 6 10.4.81 7 10.4.81 8 10.4.81 9 10.4.81

Time

10 h 39 00 " 1 l h40 ' 00" 1 4h5 3 ' 15" 15h41'30" 8h 46 ' 1 4" 9h 2 3 ' 00 " 9h 58 ' 42 " 1 1 h 1 4 ' 1 7" 1 1 h 35 ' 1 5 "

Duration

Number o f fumes

1'30" 1'25" 1'05" 1 ' 30"

Heights 50m t o 117111t o 43m t o 53m t o 113m to 56m t o 53m t o 35m t o 38m t o

1'21" 1'25" 1'18" 1 ' 28" 1'25"

150111 217111 118m 153m 188m 156111 153m 135m 138m

Top sounding aboveoftheground

--

-80 4m 992m 49 4m 496m 505m 505m 49 4m

RESULTS

These experiments revealed a c l e a r l y noticeable s t r a t i f i c a t i o n of the dispersion conditions i n the lower atmospheric boundary l a y e r ( 0 t o 200 m ) . A f i r s t case ( F i g s . 9 and 10) shows an important r o t a t i o n of the wind d i r e c t i o n between 20 m and 80 m. The nearly windless s h e e t (horizontal as well as v e r t i c a l components) between 80 rn and 100 m appears t o be an impassable obstacle t o passive p o l l u t a n t s . The second case (Fig. 11 and 1 2 ) , observed 2 hours l a t e r , i s more i n s t a b l e (-1,ZOC per 100 m between 36 m and 136

in).

The strong ascending and descending wind com-

ponents produce the mixing of the plumes, a t a s h o r t distance of the source p o i n t .

FINAL REMARKS The smoke f h e experiments c a r r i e d out during t h e l a s t few years c o n s t i t u t e a s u i t a b l e data base f o r the d i f f i c u l t study of the atmospheric dispersion over complex t e r r a i n . The c o l l e c t i o n of d a t a , photographs and films describes in d e t a i l t h e behaviour of passive plumes, by weak o r moderate winds. The a v a i l a b l e technological progress (automatic meteorological s t a t i o n , minicomputer, automatic cine cameras and video e d i t i n g of the f i l m s ) gives new p o s s i b i l i t i e s t o experiments previously c a r r i e d out ( r e f s . 2 , 4 , 5 , 12, 13, 15 and 16) t h a t proved the merits of the method. The numerical s t o c h a s t i c models simulate the Lagrangian dispersion o f the plumes, based on the Eulerian turbulence measurements near the ground and

i n a l t i t u d e . The experiments made in Payerne w i l l be used t o check the v a l i d i t y of the d i v e r s e hypotheses associated with the c a l c u l a t i o n of s t o c h a s t i c p a r t i c l e t r a j e c t o r i e s i nvol ved i n these models.

125

I

C"G1 Fig. 9

T360"J

[ms-']

[ms -'I

MOBILAB soundings, A p r i l 1 0 t h 1981, 9h13' t o 9h27'

trns -'I F i g . 11

MOBILAB soundings, A p r i l 1 0 t h 1981, l l h 1 4 ' t o l l h 2 5 '

t

April 10L-h81 F i g . 10

Smoke plumes observation

April 10 tb 81 Fig. 12

0924h

1115h

Smoke plumes observation

ACKNOWLEDGEMENTS T h i s work c o u l d n o t have been achieved w i t h o u t t h e e f f e c t i v e s u p p o r t o f D r . A. Junod, deputy d i r e c t o r o f t h e Swiss M e t e o r o l o g i c a l I n s t i t u t e , P. Jeannet,

c h i e f o f t h e A i r P o l l u t i o n S e c t i o n and h i s c o l l a b o r a t o r s . Flrs: A . B u r g d o r f e r ,

A. J u n o d - R i e t v e l d , F. Pahud, D. Spielmann; Messrs: A . A e p l i , H. Berger, Ph. T e r c i e r , A. Vernez, P. V i a t t e and P. W a s s e r f a l l e n . Graphs were drawn by Mrs. M. S c h n e i t e r . D r . P. Du P a s q u i e r h e l p e d e f f i c i e n t l y w i t h t h e E n g l i s h v e r s i o n .

126

REFERENCES F. Baatard e t S. Magnin - La mecanique a l e a t o i r e de Dedebant e t Philippe Wehrle B u l l e t i n technique de l a Suisse Romande No 4, 9 e t 12, Lausanne 1972 N . L . Byzova and E . K . Garger - Experimental study of d i f f u s i o n parameters with the a i d of smoke plumes - Izv. Atmos. and Ocean. Phys. 6(1970) 996-1006 R . R . Draxler - Some observations of the along-wind dispersion parameter - AMS, Fourth symposium on turbulence, d i f f u s i o n and a i r p o l l u t i o n , Reno, Nevada, Jan. 1979, 5-8 E . K . Garger and Lemann - Measurement of v e r t i c a l d i f f u s i o n parameter according t o smoke plume data - Izv. Atmos. and Ocean. Phys. 14(1978) 101-107 F.A. Gifford - Smoke as a q u a n t i t a t i v e atmospheric diffusion t r a c e r - J . Atmos. Env. 14(1980) 1119-1122 S.R. Hanna - Diurnal v a r i a t i o n of horizontal wind d i r e c t i o n f l u c t u a t i o n s i n complex t e r r a i n a t Geysers, California - Boundary-Layer Met. 21(1981) 207-213 S.R. Hanna - Lagrangian and Eulerian time-scale r e l a t i o n s i n t h e daytime boundary layer - J . Appl. Net. 20(1981) 242-249 T.W. Horst - Correction f o r response e r r o r s i n a three-component p r o p e l l e r anemometer - J . Appl. Met. 12(1973) 716-725 S.K. Kao, H . N . Lee and K.I. Smidy - Analysis of the topographical e f f e c t on turbulence and d i f f u s i o n i n the atmosphere's boundary layer - Boundary-Layer Met. 8(1975) 323-334 10 R . G . Lamb - ' A numerical simulation of dispersion from an elevated p o i n t source i n the convective planetary boundary layer - J . Atmos. Env. lZ(1978) 1297-1304 11 R.G. Lamb - Mathematical Drincioles of turbulence d i f f u s i o n modellinq A. Longhetto: Atmospheric' planetary boundary l a y e r physics, Elsevier; Amsterdam 1980. 173-210 12 T. Mikkelsen - Simulation of obscuration smoke d i f f u s i o n - Riso National Laboratory, Denmark, Jan. 1979, 73 p . 13 T. Mikkelsen, S.E. Larsen and I . Troen - Some puff modelling principles r e l e v a n t f o r dispersion c a l c u l a t i o n i n the atmosphere - Riso National Laboratory, Denmark, Sept. 1980, 29 p . 14 P.K. Misra - Determination of boundary-layer parameters using a v e r t i c a l Gill anemometer - Boundary-Layer Met. 17(1979) 93-100 15 C.J. Nappo - Atmospheric turbulence and d i f f u s i o n estimate derived from observation of a smoke plume - J . Atmos. Env. 15(1981) 541-547 16 C.J. Nappo - Relative and s i n g l e p a r t i c l e diffusion estimates determined from smoke plume photographs - AMS, Fourth symposium on turbulence, d i f f u s i o n and a i r p o l l u t i o n , Reno, Nevada, Jan. 1979, 46-47 1 7 A. Papoulis - P r o b a b i l i t y , random v a r i a b l e s , and s t o c h a s t i c processes McGraw-Hill, New-York, 1965, 583 p . 18 P.E. Ravussin and R.J. Hopkirk - A gust and turbulence sensor - Ecole polytechnique f e d e r a l e , Chaire de l a mecanique de l a turbulence, Groupe EPFL-ISM No 102, Lausanne 1979, 27p. 19 P. Wasserfallen and P . Du Pasquier - Systsme de sondage dans l a basse troposphere de 1 ' Ins t i t u t s u i s s e de meteorologic - OMM, No. 480, Proceedings (1977) 165-167 20 R.B. Wilson, G.E. S t a r t , C . R . Dickson and N . R . Ricks - Diffusion under low windspeed conditions near Oak Ridge, Tennessee - AMS, Third symposium on atmospheric turbulence, d i f f u s i o n , and a i r q u a l i t y , Raleigh, 1976, 269-276 21 0. Yokoyama - Measurements of wind f l u c t u a t i o n by a vane mounted on the captive balloon cable - J . Met. SOC. of Japan, 47(1969) 159-166

-

127

A COMPARISON bk NUMERICAL MODELS FOR CALCULATING DISPERSION FROM ACCIDENTAL RELEASES OF POLLUTANTS D. W. E.

PEPPER and R.

E. COOPER

I. du Pant de Nemours & Co.,

Savannah R i v e r L a b o r a t o r y , Aiken, SC, USA

A. J. BAKER U n i v e r s i t y o f Tennessee, K n o x v i l l e , TN, USA

ABSTRACT

A modular, data-based system approach has been developed t o f a c i l i t a t e comput a t i o n a l s i m u l a t i o n o f m u l t i - d i m e n s i o n a l p o l l u t a n t d i s p e r s i o n i n atmospheric, stream, e s t u a r y , and groundwater a p p l i c a t i o n s .

T h i s system i s used t o assess

e f f e c t s o f a c c i d e n t a l r e l e a s e s o f p o l l u t a n t s t o t h e environment.

Model s o p h i s t i -

c a t i o n ranges from s i m p l e s t a t i s t i c a l t o complex t h r e e - d i m e n s i o n a l numerical methods.

The system used s p e c i f i e s d e s i r e d degree o f model s o p h i s t i c a t i o n f r o m a

terminal.

The model used depends on t h e p a r t i c u l a r t y p e o f problem b e i n g solved,

and on a b a s i s o f m e r i t r e l a t e d t o computer c o s t .

The r e s u l t s o f p r e d i c t i o n f o r

s e v e r a l model problems a r e presented.

INTRODUCTION A c o n c e r t e d e f f o r t i s under way a t t h e Savannah R i v e r L a b o r a t o r y t o d e v e l o p and assess s t a t e - o f - t h e - a r t

d i s p e r s i o n models t o p r e d i c t p o l l u t a n t t r a n s p o r t .

P r i m a r y i n t e r e s t has focused on r e l e a s e s t o t h e atmosphere, w i t h a d d i t i o n a l e f f o r t a p p l i e d t o d e v e l o p i n g s o p h i s t i c a t e d stream and groundwater models.

Both

a n a l y t i c a l and m u l t i - d i m e n s i o n a l numerical models have been developed and e v a l u ated.

D i s p e r s i o n models c o n s i s t o f s e v e r a l Gaussian procedures, (puff/segmented

plume [ r e f .

l ] ) , s t a t i s t i c a l methods, and a s e t o f m u l t i - d i m e n s i o n a l codes which

n u m e r i c a l l y s o l v e t h e a d v e c t i o n - d i f f u s i o n s p e c i e s t r a n s p o r t equation. The p r i n c i p a l t o p i c o f t h i s paper i s t h e comparison o f performances o f t h e s e v e r a l mu1 t i - d i m e n s i o n a l

codes f o r s e v e r a l example problems.

The computer code

system i s based upon u s e r s e l e c t i o n o f one o f s i x d i f f e r e n t and t h e o r e t i c a l l y d i s t i n c t algorithms, i n c l u d i n g : element),

(1) chapeau f u n c t i o n ( i d e n t i c a l t o l i n e a r f i n i t e

( 2 ) method o f second moments, (3) p a r t i c l e - i n - c e l l

(PIC), (4) c u b i c

s p l i n e , ( 5 ) p s e u d o s p e c t r a l , and ( 6 ) q u a d r a t i c f i n i t e element, c o n v e n t i o n a l (2D)

128 and t i m e - s p l i t (1-3D).

Topography i s accounted f o r u s i n g elementary sheared

c o o r d i n a t e t r a n s f o r i n a t i o n s t o map t h e s o l u t i o n domain t o t h e u n i t cube, except i n t h e c o n v e n t i o n a l f i n i t e element method. The essence o f t h e c o m p u t a t i o n a l d a t a base management system (JEREMIAH) i s i l l u s t r a t e d i n Fig. 1.

The r e a l - t i m e wind f i e l d r e q u i r e d f o r t h e atmospheric

s i m u l a t i o n s i s c o m p u t a t i o n a l l y determined u s i n g d a t a measurements f r o m a system o f i n s t r u m e n t e d t o w e r s l o c a t e d a t t h e Savannah R i v e r P l a n t , f r o m t h e N a t i o n a l Weather S e r v i c e , and f r o m a c o u s t i c sounder data.

Mass c o n s i s t e n c y o f t h e

r e s u l t a n t t h r e e - d i m e n s i o n a l v e l o c i t y f i e l d i s ensured u s i n g v a r i a t i o n a l t e c h n i q u e s ( r e f . 2) t o t e m p o r a l l y a d j u s t t h e nodal d i s t r i b u t i o n s f o r t h e m u l t i - d i m e n s i o n a l codes.

Turbulence d i f f u s i o n parameters a r e o b t a i n e d f r o m

s t a n d a r d d e v i a t i o n o f t h e measured wind d i r e c t i o n f r o m t h e meteorology towers, o r are estimated w i t h s t a t i s t i c a l / e m p i r i c a l

methods.

The stream and e s t u a r y

c o m p u t a t i o n a l a l g o r i t h m s use t h e JEREMIAH system, and a r e based on c o n v e n t i o n a l f i n i t e element, a n a l y t i c a l , and s i m p l e f i n i t e d i f f e r e n c e methods.

Specific

i n p u t parameters t o t h e stream models a r e o b t a i n e d f r o m f i e l d experiments a t t h e Savannah R i v e r P l a n t .

A s e r i e s o f w e l l s have been d r i l l e d o v e r t h e

300-square-mile p l a n t s i t e t o measure w a t e r t a b l e head and h y d r a u l i c c o n d u c t i v i t y , f o r use i n t h e groundwater f l o w s i m u l a t i o n s u s i n g a second-moment code.

PRINTER COM AND OTHER GRAPHICS M V I C E S JOB DATA SET

F i g . 1. The JEREMIAH c o m p u t a t i o n a l system.

129

THEORETICAL MODELS A b r i e f d e s c r i p t i o n o f t h e v a r i o u s numerical a l g o r i t h m s serves t o h i g h l i g h t t h e i r d i s t i n c t i o n s . Gaussian p u f f / p l u m e models, a l s o r e s i d e n t i n JEREMIAH, a r e w e l l known, and w i l l n o t be d i s c u s s e d h e r e (see r e f . 1).

I n a l l instances, the

models a r e a p p l i e d t o t h e s o l u t i o n o f t h e e q u a t i o n g o v e r n i n g m u l t i - d i m e n s i o n a l t r a n s p o r t o f s p e c i e s Q ("x,t)

+ I n eq. ( l ) , Q i s t h e c o n c e n t r a t i o n (g/m3), U i s t h e v e c t o r a d v e c t i o n v e l o c i t y f i e l d , K i s t h e d i r e c t i o n a l l y dependent eddy d i f f u s i v i t y (m2/sec), s i n c l u d e s a l l source and/or s i n k terms ( d e p o s i t i o n , chemical r e a c t i o n s , e t c . ) , and t i s time.

"x

The s o l u t i o n domain i s t h e t h r e e - d i m e n s i o n a l space spanned by

and bounded by t h e topography, t h e m i x i n g h e i g h t , and a s u i t a b l e box

surrounding t h e release point.

z

=

x,y

0,H: =

The boundary c o n d i t i o n s f o r eq. (1) a r e

t ( Q ) = -kVQ.n = 0

0,N:

t(Q) =

-kVQ.n = 0 , f.n>O

DQ -

kVQ.n = UnQ, l.n
where n i s t h e u n i t v e c t o r normal t o t h e boundary,

H i s t h e l i d h e i g h t , and N i

t h e l a t e r a l domain e x t e n t .

A l l models except t h e pseudospectral and c o n v e n t i o n a l f i n i t e element employ f a c t i o n a l steps and t i m e s p l i t t i n g t o e c o n o m i c a l l y s o l v e eq. (1).

Hence, each

procedure c o n s i s t s o f a m u l t i p l i c a t i v e sequence o f a l g o r i t h m steps, each based upon t h e s o l u t i o n o f t h e one-dimensional

advection-diffusion equation,

The m u l t i - d i m e n s i o n a l c a p a b i l i t y i s produced by r e p e a t e d o p e r a t i o n s i n t h e other directions. The chapeau f u n c t i o n r e c u r s i o n r e l a t i o n ( r e f . 3) can be e s t a b l i s h e d u s i n g l i n e a r f i n i t e elements w i t h i n t h e G a l e r k i n weighted r e s i d u a l method ( r e f . 4). The chapeau f u n c t i o n r e c u r s i o n f o r m u l a f o r c o n s t a n t v e l o c i t y and d i f f u s i v i t y is

130

kX

- 2 [Qi+l AX

-

2Qi + Q i - l

1

+ si

= 0

In eq. (4), t h e superscript dot denotes the time d e r i v a t i v e , and U and AX are uniform constants. The generalized r e l a t i o n f o r v a r i a b l e velocity and d i s c r e t i z a t i o n i s given in r e f . 4. Cubic s p l i n e r e l a t i o n s , although derived d i f f e r e n t l y , look s i m i l a r t o the chapeau function r e l a t i o n s . Results in t h i s study a r e b a s i c a l l y i d e n t i c a l t o t h e chapeau function r e s u l t s . A more d e t a i l e d analysis i s discussed in ref. 5. The method of second moments i s a quasi-Lagrangian e x p l i c i t scheme which c a l c u l a t e s t h e zeroth, f i r s t , and second moments of t h e d i s t r i b u t i o n of Q within a c e l l volume ( r e f . 6 ) . By conserving t h e moments, t h e d i s t r i b u t i o n can be advected without numerical dispersion. The moments a r e defined by the r e l a t i o n s

Inclusion of t h e d i f f u s i o n part of eq. ( 3 ) i s handled using centered differencing (ref. 7). The P I C numerical method, used t o c a l c u l a t e multi-dimensional transport problems ( r e f . 8 ) , b a s i c a l l y divides t h e c a l c u l a t i o n a l sequence into Eulerian and Lagrangian steps. Following c a l c u l a t i o n of a pseudo-transport v e l o c i t y , a simple averaging technique i s used t o convert the concentration gradients a t four c e l l c e n t e r s t o match t h e pseudo-velocity a t a c e l l corner. P a r t i c l e s within each individual c e l l a r e then advected by t h e pseudo-velocity t o t h e new position, viz.

131 The f i n a l c o n c e n t r a t i o n a t t h e end o f t h e t i m e s t e p i s c a l c u l a t e d by c o u n t i n g t h e number o f p a r t i c l e s w i t h i n each c e l l volume. The c o n v e n t i o n a l f i n i t e element method u t i l i z e s b o t h l i n e a r and q u a d r a t i c i s o p a r a m e t r i c elements.

The model employed here i s based on t h e two-dimensional

model developed i n r e f . 9.

C o n v e n t i o n a l f i n i t e element methodology i s w e l l

r e c o g n i z e d and r e f e r e n c e d .

Because c o n v e n t i o n a l f i n i t e elements become cumber-

some i n three-dimensions,

o n l y two-dimensional t r a n s p o r t problems ( i .e.,

shallow

w a t e r e q u a t i o n s ) a r e analyzed. The t i m e - s p l i t q u a d r a t i c t e n s o r p r o d u c t f i n i t e element method i s a d i r e c t e x t e n s i o n o f t h e model developed i n r e f . 10.

When embodied u s i n g l i n e a r i n t e r p o -

l a t i o n on u n i f o r m g r i d s and c o n s t a n t v e l o c i t y , t h e chapeau r e c u r s i o n r e l a t i o n i s obtained. tion.

A s i m p l e r e c u r s i o n r e l a t i o n does n o t r e s u l t u s i n g q u a d r a t i c i n t e r p o l a -

Eq. (1) i s r e c a s t as t h e m a t r i x problem

R a t h e r t h a n e v a l u a t i n g t h e banded sparse m a t r i x [J],

the time-split algorithm

f a c t o r s [J] on t h r e e - d i m e n s i o n a l space as

where

x

s i g n i f i e s t h e t e n s o r m a t r i x product.

S i m i l a r l y , F i s e v a l u a t e d as t h e

a l g e b r a i c p r o d u c t o f t h e elementary one-dimensional

i n t e r p o l a t i o n s , i.e.,

The m u l t i - d i m e n s i o n a l problem s o l u t i o n i s t h e n completed by t h e elementary sequence

where

{O}

and

{o}

a r e intermediate solutions.

132

I n t h e pseudospectral procedure, t h e space d e r i v a t i v e s o f t h e a d v e c t i o n d i f f u s i o n e q u a t i o n a r e computed u s i n g t h e f i n i t e F o u r i e r t r a n s f o r m ( r e f . 11). The d e r i v a t i v e a t a g i v e n g r i d p o i n t i s g l o b a l s i n c e i t s v a l u e i s determined f r o m f u n c t i o n values o v e r t h e e n t i r e domain. components A ( k , t ) ,

The time-dependent F o u r i e r

i n two-dimensional s p e c t r a l space, a r e determined from

t h e g i v e n d i s t r i b u t i o n Q ( x , t ) as

N, and N, a r e t h e number o f mesh p o i n t s spanning t h e x and y c o o r d i n a t e d i r e c t i o n s , i = fl,and k i s t h e wave number. The d e r i v a t i v e s a r e e v a l u where

a t e d d i r e c t l y f r o m t h e F o u r i e r components, i.e.,

aQ(-k,t) = a xj

1ik,

k

v2C(-k,t) =

A(t(,t)

exp ( t k t x ) , j = 1, 2

J

1 -k2A(k,t)

exp ( i k . 9 )

k

u s i n g a F a s t F o u r i e r Transform a l g o r i t h m ( r e f . 12). a r e solved using t h e three-level

The t i m e d e r i v a t i v e terms

leap-frog algorithm.

USE CRITERIA AND RESULTS

A p r i m a r y r e q u i r e m e n t i s t o assess t h e f e a t u r e s and t h e l i m i t a t i o n s o f t h e v a r i o u s a l g o r i t h m s f o r s o l u t i o n o f eq. (l), such t h a t t h e u s e r can make a c o s t e f f e c t i v e choice.

The d i s t i n g u i s h i n g f e a t u r e o f t h r e e - d i m e n s i o n a l t r a n s p o r t

p r e d i c t i o n on t h e mesoscale i s t h e domain s i z e , t y p i c a l l y 80 km square by 10 km e l e v a t i o n ( o r l e s s ) .

I n JEREMIAH, t h e s t a n d a r d 3-D d i s c r e t i z a t i o n i s

33 x 33 x 10 km, p r o d u c i n g on t h e o r d e r o f l o 4 nodal dependent v a r i a b l e s , and 3 x Id, v e l o c i t i e s and nodal c o o r d i n a t e s .

The s t o r a g e r e q u i r e m e n t s f o r d i f f u s i o n

c o e f f i c i e n t s a r e t y p i c a l l y n o t c o n s e q u e n t i a l on t h i s scale.

I n most cases, t h e

source o f an a c c i d e n t a l r e l e a s e w i l l appear n o m i n a l l y as a p o i n t source on t h e mesoscale g r i d .

The r e q u i r e m e n t f o r coarse g r i d accuracy i s s e l f - a p p a r e n t .

B a s i c a l l y , some o f t h e methods more a c c u r a t e l y r e s o l v e t h e source d e s c r i p t i o n c l o s e i n , w h i l e o t h e r s a r e more s u i t a b l e f o r f a r f i e l d accuracy.

F o r example,

F i g . 2 summarizes t h e p r e d i c t i o n o f a p o i n t s o u r c e under p u r e one-dimensional c o n v e c t i o n , t h e c o r r e c t s o l u t i o n f o r which t r a n s p o r t o f t h e i n i t i a l d i s t r i b u t i o n downstream i s u n a l t e r e d .

The P I C , second moment, and pseudospectral a l g o r i t h m s

produce e x c e l l e n t r e s u l t s , w h i l e t h e chapeau and f i n i t e element a l g o r i t h m s a r e

133

100

a) Chapeau/ Cubic Spline

100

b) Finite Element

lo0li.*loo 100

d) Pseudospectral

100

100

i.

i.

I .

F i g . 2. One-dimensional a d v e c t i o n o f a s i n g l e c e l l .

l o 0 !

134 A l t e r n a t i v e l y ( r e f . 1 3 ) , i f t h e p o i n t r e l e a s e can be i n i e r p o -

very inaccurate.

l a t e d o v e r a few node p o i n t s , a l l b u t t h e second-moment method produce a c c e p t a b l e accuracy (Fig. 3). These t r e n d s e x t e n d t o m u l t i - d i m e n s i o n a l problems.

F o r example, Fig. 4

summarizes a l g o r i t h m s t e a d y - s t a t e p r e d i c t i o n s f o r a p l a n e area source ( c o n s t i t u t e d o f f o u r c e l l s e m i t t i n g a c o n s t a n t s t r e n g t h ) w i t h one-dimensional The a n a l y t i c a l l y e x a c t s o l u t i o n is

wind f i e l d and two-dimensional d i f f u s i o n . o b t a i n e d from t h e Gaussian plume model.

A l l b u t t h e P I C a l g o r i t h m , which g r o s s l y

u n d e r p r e d i c t s l a t e r a l spread (due t o use o f t o o few p a r t i c l e s ) , produce accepta b l e accuracy.

T a b l e 1 summarizes t h e computer c o s t aspects f o r t h i s t e s t case

e x e c u t i o n on a p e r - s t e p b a s i s .

The pseudospectral method is t h e l e a s t c o m p e t i t i v e

i n t h i s comparison t o t h e o t h e r methods.

The c o n v e n t i o n a l f i n i t e - e l e m e n t method

g e n e r a l l y r e q u i r e s n e a r l y an o r d e r o f magnitude more t i m e t h a n t h e t i m e - s p l i t method t o produce comparable accuracy. TABLE 1 Compari son o f CPU/time-step I B M 360/195 CPU seconds/step

Method Second moment Chapeau/cubic s p l i ne F i n i t e element (time s p l i t ) Pseudospect r a l Particle-in-cell

0.10 0.20 0.23 0.44 2.56

The t h r e e - d i m e n s i o n a l problem d e s c r i p t i o n s f o l l o w t h e s e same general c r i t e r i a . The Gaussian plume and moments a l g o r i t h m s a r e b e s t s u i t e d f o r n e a r - f i e l d p r e d i c tion.

The chapeau and q u a d r a t i c t i m e - s p l i t f i n i t e element a l g o r i t h m s appear

comparable i n c o s t e f f e c t i v e n e s s .

Fig. 5 summarizes t h e s o l u t i o n comparison i n

t h e h o r i z o n t a l p l a n e o f a t h r e e - d i m e n s i o n a l source, w i t h one-dimensional convect i o n and t h r e e - d i m e n s i o n a l d i f f u s i o n ( r e f .

14).

Fig. 6 is t h e t i m e - s p l i t f i n i t e

element s t e a d y - s t a t e s o l u t i o n f o r t h e c o n t i n u o u s p l a n e source e m i s s i o n encounteri n g an i s o l a t e d h i l l .

The added accuracy o f t h e q u a d r a t i c element a l g o r i t h m comes

a t t h e c o s t o f about 15% a d d i t i o n a l CPU i n t h e s e cases. CONCLUSIONS The JEREMIAH d a t a base management system i s a comprehensive computer s o f t w a r e system t o f a c i l i t a t e a c c u r a t e , r e a l - t i m e m u l t i - d i m e n s i o n a l p r e d i c t i o n o f a c c i d e n t a l r e l e a s e s i n t o t h e environment.

User s e l e c t i o n o f a l g o r i t h m s p e r m i t s

135

b) Finite Element

In-Cell

100

d) Pseudospectral

100

A

100

F i g . 3. One-dimensional a d v e c t i o n o f a Gaussian d i s t r i b u t i o n .

18

--_-

99

52

12

19

128

366

366

154

30

18

315

j15

15 4

30

27

130

339

339

130

145

338

JJ8

145

18

116

363

363

116

27

24

19

143

331

331

14

12

128

24

143

129

356

356

97

392

392

97

14

129

34

41

16 0

296

296

1 60

41

35

140

319

319

140

35

34

151

311

311

151

43

50

163

281

2 81

16 3

50

43

147

302

302

147

43

43

156

294

294

156

164

165

164

70

17

65 13

164

165

246

246

58

256

256

70

17

17

61

156

262

262

156

61

17

164

267

267

65

13

14

11

58

56

154

273

273

154

56

14

49

151

287

287

151

49

11

16

162

12

161

160

256 256

64

267

280

88

39

383

383

94

413

413

372

126

372

380 47

128

16

10

22

31

403

403

31

22

376 49 33

41 28

49 376

41

371 371

33

28

Values less t h a n 10 s u p p r e s s e d .

22

11

*

416

444

412 107

22 416

12 444

412

107

16

10

36

311

329

26

311

329

16

153

144

I53

36

26

39

161

299

299

144

357

88

19

161

133

377 115

429

134

16

28

*

155

319

319

15

357

115

28 155

144

342

342

377

88 429

P a r t i c l e - i n - C e 11*

380

128

47

Pseudospect r a l ( F o u r i e r )

88

15 126

144

94

64 3Y

tinitr ~~emrnt*

162

16

58

267

280

51

58 161

51 160

12

Fig. 4. Advection and d i f f u s i o n o f an area source.

404

395

135

99

404

395

135

52

Chapeau*

70

34

426

426

340

340

111

70

111

34

107

388

444

65

388

444

Second Moment

Are a S o u r c e

----I

107

65

u

U

*

Analytical Solution*

48

38

56

345

345

56

38

44

156

294

294

156

44

48

163

283

283

163

58

64

66

44

66

339

339

15

11

79 47

44

302

71

302

79

47

20

16

64

161

253

253

161

64

16

69

164

247

247

164

69

15

328

328

71

44

11

13

44

59 10

161

268

268

161

59

52

160

278

278

160

52

13

64

10

166

58

258

258

166

166

270

270

166

12

W 0)

w

137

t a i l o r i n g of a c o s t - e f f e c t i v e a n a l y s i s with t h e b a s i s of merit being the tradeoff between cost and accuracy. The system has been e f f e c t i v e l y used t o predict actual r e l e a s e s of p o l l u t a n t s in accident s i t u a t i o n s from t h e Savannah River P1 ant.

l

CHAPEAU

1

SOURCE

19

72

1131 111

79

65

55

47

I

40 31

30

15

14

3

4 1

FINITE ELEMENT

Fig. 5. Comparison of chapeau and f i n i t e element algorithm s o l u t i o n s f o r a threedimensional continuous s t e a d y - s t a t e source.

177

159

138

108

123

134

16

HILL

80

78

67

76

72

61

48

86

119

76

66

58

45

-3

4

30

59

81

80

71

58

46

38

28

-1

-1

4

10

21

29

28

24

20

17

13

1

3

4

4

4

4 1

Fig. 6 . Three-dimensional continuous s t e a d y - s t a t e r e l e a s e over i s o l a t e d h i l l (midplane view).

138

The a b i l i t y of t h e conventional f i n i t e element method t o model t r a n s p o r t within i r r e g u l a r domains i s well recognized, and i s p a r t i c u l a r l y e f f e c t i v e and easy t o implement in two dimensions. Fig. 7 shows a typical element mesh used in modeling dispersion in the Savannah River. Fig. 8 shows isotherms of heated e f f l u e n t from Four Mile Creek s p i l l i n g into t h e Savannah River.

The heated e f f l u e n t occurs from t h e discharge of heat from nuclear r e a c t o r s located within the Savannah River Plant s i t e . Diffusion c o e f f i c i e n t estimates and stream v e l o c i t i e s were obtained from in s i t u measurements. ACKNOWLEDGMENT

The information contained in t h i s a r t i c l e was developed during t h e course of work under Contract No. DE-AC09-76S0001 with t h e U.S. Department of Energy.

Fig. 7. Typical f i n i t e element representation o f a s e c t i o n o f t h e Savannah River (Savannah River Four Mile Creek Section).

139

I

FIG. 8. Isotherms downstream of Four Mile Creek.

140 REFERENCES

1 M.M. Pendergast, Model E v a l u a t i o n f o r T r a v e l D i s t a n c e s 30-140 km, American M e t e o r o l o g i c a l S o c i e t y F o u r t h Symposium on Turbulence, D i f f u s i o n , and A i r P o l l u t i o n , American M e t e o r o l o g i c a l S o c i e t y , Boston, MA, 1979. 2 Y. Sasaki, Some B a s i c Formalisms i n Numerical V a r i a t i o n a l A n a l y s i s , Mon. Weather Rev., 98( 1970)876. 3 P.E. Long and F.J. Hicks, Simple P r o p e r t i e s o f Chapeau F u n c t i o n s and T h e i r A p p l i c a t i o n t o t h e S o l u t i o n o f t h e A d v e c t i o n Equation, N a t i o n a l Oceanic and Atmospheric A d m i n i s t r a t i o n TDL O f f i c e Note No. 75-8, S i l v e r S p r i n g , MD, 1975, 23 PP. 4 D.W. Pepper and A.J. Baker, A Simple One-Dimensional F i n i t e Element A l g o r i t h m w i t h M u l t i - D i m e n s i o n a l C a p a b i l i t i e s , Num. Heat. Trans., 2(1979)81. 5 D.W. Pepper, C.D. Kern, and P.E. Long, M o d e l i n g t h e D i s p e r s i o n o f Atmospheric P o l l u t i o n Using Cubic S p l i n e s and Chapeau F u n c t i o n , Atmos. Environ., 13 (1979)223. 6 B.A. Egan and R. Mahoney, Jr., Numerical Modeling o f A d v e c t i o n and D i f f u s i o n o f Urban Area Source P o l l u t a n t s , J. Appl. Meteor., 2(1972)312. 7 D.W. Pepper and P.E. Long, A Comparison o f R e s u l t s Using Second-Order Moments W i t h and W i t h o u t Width C o r r e c t i o n t o Solve t h e A d v e c t i o n Equation, J. Appl. Meteor., 17(1978)228. 8 R.H. Sklarew, A.J. F a b r i c k , and J.E. Prager, A P a r t i c l e - I n - C e l l Method f o r Numerical S o l u t i o n o f t h e Atmospheric D i f f u s i o n Equation, and A p p l i c a t i o n t o A i r P o l l u t i o n Problems, Report No. 34R-844, Systems, Science, and Software, Inc., La J o l l a , CA, 1971. 9 F.L. Smith and C.A. B r e b b i a , F i n i t e Element S o l u t i o n o f Navier-Stokes E q u a t i o n f o r T r a n s i e n t Two-Dimensional I n c o m p r e s s i b l e Flow, J. Comp. Physics, 17(1975) 235. 10 A.J. Baker, M.O. Soliman, and D.W. Pepper, F i n i t e Elements i n Water Resources, 11, Pentech Press, London, 1978, p.4.53. 11 0. C h r i s t e n s e n , and L. P. Prahm, A Pseudospectral Model f o r D i s p e r s i o n o f Atmospheric P o l l u t a n t s , J. Appl. Meteor., 15(1976)1284. 12 J.W. Cooley and J.W. Tukey, An A l g o r i t h m f o r t h e Maching C a l c u l a t i o n o f Complex F o u r i e r S e r i e s , Math. Comp., 1 9 ( 1965)297. 13 R.E. Cooper, D.W. Pepper, and A.J. Baker, An I n v e s t i g a t i o n o f M u l t i Dimensional Computational Models f o r C a l c u l a t i n g P o l l u t a n t T r a n s p o r t , S o u t h e a s t e r n Conference f o r T h e o r e t i c a l and A p p l i e d Mechanics, Vol. 10, U n i v e r s i t y o f Tennessee, K n o x v i l l e , TN, 1980, p.397. 14 A.J. Baker, M.O. Soliman, and D.W. Pepper, Environmental Release P r e d i c t i o n w i t h a N o n c l a s s i c a l S p l i t F i n i t e Element A l g o r i t h m , American Meteorology S o c i e t y Second J o i n t Conference on A p p l i c a t i o n s o f A i r P o l l u t i o n Meteorology, 1980, p.438.

141

DETECTION AND IMPACT PREDICTION OF HAZARDOUS SUBSTANCES RELEASED TO THE ATMOSPHERE E.E.PICKETT,

R.G.

W H I T I N G and H . L .

KOCCHIU

F a c u l t y o f A p p l i e d S c i e n c e and E n g i n e e r i n g , U n i v e r s i t y o f T o r o n t o , T o r o n t o , Canada. M5S 1A4

ABSTRACT An emergency r e s u l t i n g from t h e e s c a p e o f a h a z a r d o u s s u b s t a n c e t o t h e atmosphere r e q u i r e s l o c a l a u t h o r i t i e s t o assess e x p o s u r e r i s k s t o s u r r o u n d i n g p o p u l a t i o n s . An i m p o r t a n t p a r t o f t h i s a s s e s s m e n t i n v o l v e s t h e a b i l i t y t o d e t e c t , t r a c k , and p r e d i c t t h e t r a j e c t o r y of t h e s u b s t a n c e a s i t moves s u b j e c t t o c h a n g i n g m e t e r o l o g i c a l conditions.

A s t r u c t u r e t o provide t h i s a b i l i t y i s developed i n t h i s paper.

An example s i m u l a t i n g t h e a p p l i c a t i o n o f t h e s e p r o c e d u r e s i s g i v e n .

INTRODUCTION

The o b j e c t i v e o f t h i s p a p e r i s t o d e s c r i b e a p r o c e d u r e f o r s e a r c h i n g f o r and 17redicting t h e t r a j e c t o r y of an a c c i d e n t l y r e l e a s e d hazardous Substance

that is

s u b j e c t t o atmospheric motions. With i n c r e a s i n g numbers of n u c l e a r power r e a c t o r s , c h e m i c a l p l a n t s t h a t m a n u f a c t u r e t o x i c and o t h e r w i s e h a z a r d o u s s u b s t a n c e s , and t h e t r a n s p o r t a t i o n and storage of these

s u b s t a n c e s o v e r w i d e r g e o g r a p h i c a l a r e a s , t h e p r o b a b i l i t y of

a c c i d e n t a l escape i n creas es .

Agencies r e s p o n s i b l e f o r emergency measures c o n c e r n i n g

t h e r e l e a s e o f h a z a r d o u s a i r b o r n e m a t e r i a l r e q u i r e c u r r e n t , a c c u r a t e , and w e l l i n t e g r a t e d i n f o r m a t i o n on which t o b a s e d e c i s i o n s r e g a r d i n g t h e p r o t e c t i o n o f t h e population.

It i s important,

therefore,

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

d e c i s i o n making a i d s t h a t o p e r a t e i n r e a l - t i m e and c a n c o n t r i b u t e t o r e d u c i n g t h e i m p a c t o f t h i s t y p e of emergency when i t a r i s e s . It i s assumed t h a t aovement o f a c l o u d o f t h e r e l e a s e d material o r t a r g e t , a s

i t w i l l b e r e f e r r e d t o , t a k e s p l a c e i n two d i m e n s i o n a l s p a c e . i n t h e i m p a c t o f t h e t a r g e t a t ground l e v e l .

W e are i n t e r e s t e d

A descripbion of the v e r t i c a l

t r a j e c t o r y c a n e a s i l y b e i n c o r p o r a t e d p r o v i d e d a n a d e q u a t e model e x i s t s t o do t h i s . The emphasis h e r e i s on how a model c a n b e i n t e g r a t e d w i t h a d a t a a c q u i s i t i o n and d e c i s i o n making s y s t e m r a t h e r t h a n i t s p a r t i c u l a r a d v a n t a g e s o r l i m i t a t i o n s w i t h r e s p e c t t o accuracy o f p red ict io n . A t r a j e c t o r y p r e d i c t i o n model i s u s e d t o d e s c r i b e t h e p o s i t i o n o f t h e t a r g e t

a s i t moves s u b j e c t t o a m b i e n t a t m o s p h e r i c m o t i o n s .

The model used h e r e , a l t h o u g h

s i m p l e i n c o n c e p t , i s e s p e c i a l l y c o n s t r u c t e d t o i n c o r p o r a t e d a t a from c u r r e n t

142 o b s e r v a t i o n s o f m e t e r o l o g i c a l v a r i a b l e s , p r e d i c t t h e e v o l u t i o n of targetposition o v e r t i m e and e v a l u a t e u n c . e r t a i n t i e s a s s o c i a t e d w i t h t a r g e t l o c a t i o n . I t i s assumed t h a t m o b i l e m o n i t o r i n g u n i t s a r e a v a i l a b l e and t h a t t h e y c a n

Since

be d i r e c t e d t o s p e c i f i c a r e a s f o r t h e purpose o f s e a r c h i n g f o r t h e t a r g e t .

t h e a r e a of p o s s i b l e t a r g e t l o c a t i o n w i l l b e l a r g e r e l a t i v e t o t h e a r e a t h a t c a n be e f f e c t i v e l y searched with a v a i l a b l e monitoring resources, an "optimal" search plan is specified f o r t h e current search i n t e r v a l .

The p l a n i s made o p t i m a l i n

t h e s e n s e o f a s s i g n i n g a v a i l a b l e s e a r c h e f f o r t i n t h e r e q u i r e d amount t o t h o s e a r e a s t h a t w i l l maximize t h e p r o b a b i l i t y o f t a r g e t d e t e c t i o n . The d e t e c t i o n f u n c t i o n u s e d r e l a t e s t h e p r o b a b i l i t y o f d e t e c t i n g t h e t a r g e t i n

a g i v e n a r e a o r c e l l t o t h e amount of s e a r c h e f f o r t expended i n t h e c e l l .

It

e x h i b i t s two i n t u i t i v e l y p l a u s i b l e f e a t u r e s ; f i r s t , t h e r e i s always a p o s i t i v e p r o b a b i l i t y t h a t t h e t a r g e t w i l l n o t b e found i n a c e l l even though i t was l o c a t e d t h e r e when t h e s e a r c h w a s p e r f o r m e d , and s e c o n d , t h e g r e a t e r t h e s e a r c h e f f o r t a s s i g n e d t o a c e l l , t h e s l o w e r t h e r a t e o f i n c r e a s e o f p r o b a b i l i t y of d e t e c t i o n . The p r o p e r t i e s o f t h e d e t e c t i o n f u n c t i o n r e v e a l t h a t p e r f o r m i n g a s e a r c h p l a n and n o t f i n d i n g t h e t a r g e t w i l l a l t e r t h e c o n d i t i o n a l p r o b a b i l i t i e s a s s o c i a t e d with the t a r g e t d i s t r i b u t i o n .

Thus, i n s e q u e n t i a l s e a r c h , t h e f a c t t h a t a s e a r c h

p l a n i n a g i v e n i n t e r v a l f a i l s t o d e t e c t t h e t a r g e t can p r o v i d e i m p o r t a n t t a r g e t l o c a t i o n information f o r search i n a subsequent i n t e r v a l .

This updating of t h e

t a r g e t d i s t r i b u t i o n a f t e r a n e g a t i v e s e a r c h p l a n h a s b e e n e x e c u t e d i s performed by means o f B a y e ' s f o r m u l a .

I t h a s b e e n shown i n Ref. 1 t h a t i n a l l cases o f

s e a r c h where p a s s i v e o b s e r v a t i o n s o f a t a r g e t a r e made t h a t B a y e ' s f o r m u l a p r o v i d e s a c o m p l e t e s o l u t i o n t o t h e u p d a t i n g problem. The a v a i l a b i l i t y of t h e p o s t e r i o r t a r g e t d i s t r i b u t i o n c o n d i t i o n e d by t h e most r e c e n t s e a r c h (assuming n e g a t i v e s e a r c h r e s u l t s ) p e r m i t s t h e " o p t i m a l " a s s i g n m e n t of s e a r c h e f f o r t i n t h e s u b s e q u e n t p e r i o d t o b e b a s e d on o u r " b e s t knowledge" o f target localization.

T h i s p o s t e r i o r t a r g e t d i s t r i b u t i o n when combined w i t h t h e

most r e c e n t o b s e r v a t i o n s o f m e t e r o l o g i c a l v a r i a b l e s p e r m i t t h e e s t i m a t i o n o f t a r g e t i m p a c t p r o b a b i l i t i e s on s u r r o u n d i n g areas of c o n c e r n .

DESCRIPTION OF TARGET POSITION The e v o l u t i o n o f t h e t a r g e t p o s i t i o n i s d e s c r i b e d by a s p a t i a l Markov p r o c e s s X(i,j,t)

such t h a t :

X(i,j,t)

=

"

...,MI

1 ' i f t a r g e t i s i n g r i d l o c a t i o n i , j a t t i m e t , where i , j ~ { l ,

0

otherwise

A t any t i m e t E { O ,

...,N}

that: pr[x(i,j,t)=ll = a(i,j,t)

a probability d i s t r i b u t i o n is assigned t o X ( i , ] , t )

such

143 Hence A

MxM

(t) = [a(i,j,t)lMxM is an MxM matrix which completely characterizes the

distribution of X at time t. MxM The initial distribution of X at time t=O is A (0). All elements of A(0) will be zero except for some element a(i*,j*,O)=l, which corresponds to the release point of the target. If X(i,j,t)=l is subject to position and associated uncertainty change, then for each location k,R define the function f as: Pr{X(k,R,t+l)=llX(i,j,t)=l}

3

f(i,j;k,k).

f is also a function of the wind vector w(t) at time t. in a subsequent section.

This dependence is explained

Hence,

Pr{X(k,R , t+l)=1} = a (k,Q,t+l) S f(i,j;k,R)a(i,j,t)

=

1 1

MxM MxM Let F (k,k) = Cf(i,j;k,Q)] be an MxM ma rix of

ransition probabilities then:

MxM a(k,Q,t+l) = tr(F (k,R) AT (t)) MxM

If A(t) is known and the F

(k,R) matrices (ML of them) are known then A(t+l)

can easily be produced. It remains to specify a suitable parametrization of the conditional transition probabilities, F(k,R), in terms of the observable meterological variables. It is assumed that the target is subject to advection over time.

There is

inherent uncertainty in relating observable wind patterns to advective motion.

Our

approach to the parameterization problem is to represent F(k,R) as the composite of two mappings:

Fl(k',Q'), a translation mapping representing advection, and

F2(k,R), a mapping which representes uncertainty in advective transport.

If we

define:

then the composite mapping is: a(k,R,t+l)

=

Z

Z f (k',k';k,R) al (k',R',t+l)

k' R '

The advection and advection uncertainty mappings F

1

and F

2

are discussed separately

in the next two sections.

THE ADVECTION MODEL Advection transport of the target due to wind is represented here via a simple translation mapping on the X-Y grid. we have, for fixed k',R'

E

{l, ...,MI.

Using the notation of the previous section,

144

1 if k'=i+Ax,!L'=j+Ay

fl(i,j;k',!L')=

where i,j E

0 otherwise {l, . . .,MI.

The displacements Ax,Ay are determined for each time period (t,t+l) as the integer parts of x(t+l), y(t+l) respectively, where:

for

t=O,l,..,N, where u(t+l) and v(t+l) are the mean observed East-West and

North-South wind velocity components over (t,t+l) and At is the interval length. The predicted values of the velocity components u(t+l), v(t+l) are assumed to be adequately described by a time varying lagged model of the form: u(t+l)

=

bll(t)u(t)

+

b13(t)u(t-l) + b15(t)u(t-2) + eu(t+l)

v(t+l) = bZ2(t)v(t) + bZ4(t)v(t-l) where e

and e

+

b

26

(t)v(t-2) + ev(t+l)

are normally distributed with zero mean and covariance matrix Q.

An autoregressive, but time invariant, model of this form has been used to predict local wind velocity components in Venice (Ref.2). A prediction of velocity components at time t+l is obtained from previously

observed values

r

I

means of the product:

r

0

u(t)

0

b2

v(t)

0

0

0

u(t-1)

0

0

0

0

v(t-1)

0

1

0

0

0

u(t-2)

0

0

1

0

0

11

O

b13

0

b22

0

1

0

0

0

1

0 0

O b

24

b15

-

v(t-2)

(3)

t

where i(t+l), and G(t+l) are the forecast values of u(t+l) and v(t+l) made at To obtain predictions for time t+2 at time t the previously predicted

time t.

values (at time t+l) must be substituted in the right-side of ( 3 ) .

Thus we can

write in matrix form the following recursion for obtaining wind velocity predictions i time periods beyond the observations obtained at time t: w(t+i)

=

B(t)w(t+i-l)

The variance of w(t+l)

=

B(t) P(t) BT(t) + Q(t) (4)

E P(t+l)

where P(t) is the covariance matrix of y(t).

Thus a measure of the uncertainty

associated with the w(t+i) can easily be calculated by means of P(t+i).

145 A recursive least squares algorithm is used to obtain the time varying parameters of the model (2). The advantages of this approach are that very little prior data are necessary, there is a small amount of computational burden at each step, and, of course, it permits tracking of time varying parameters.

Descriptions of

recursive least squares algorithms may be found in Ref. 3.

ADVECTION UNCERTAINTY AS the model (2) only approximates the behaviour of the wind vector over the

interval (t,t+l), there is inherent uncertainty in the values used for the displacements Ax,Ay in the advection model. If we assume that unbiased estimates of u(t) and v(t), with variances pll(t), (t) respectively, are available at time t, then the one step predictions f22 u(t+l) , v(t+l) have variances pll(t+l), ~ ~ ~ ( t as + lgiven ) by From (1), A

(4).

2 the estimates of Ax,Ay (assumed unbiased) have variances (At) pll(t+l) and 2 (At) ~ ~ ~ ( t respectively. + l ) By using these predictions we are incorporating

, E ) in the advection model. X Y errors are uncorrelated and normally distributed, then: additive error terms (say, E

f (k',i?';k,i?)2 Pr{X(k,R,t+l) 2 =

Pr{k-k'-i$'c

=

Assuming that these

llX(k',i?',t)=l}

X

which are easily computed normal probabilities.

Y

Si?-i?'+%)

These values, determined for

all k,i? and k',i?' provide the mapping F (k,i?)which represents the advection 2 uncertainty in the composite model, F ( k , i?) -

THE SEARCH PLAN Search is considered for a target which moves among a finite set of cells in discrete space.

A limited amount of search effort is available and is assigned

to fixed time intervals which correspond to the basic prediction period.

The

search is made optimal in the sense that effort is allocated to maximize the probability of target detection subject to the given constraint on effort. The search starts with the knowledge of the function a(i,j,t) which is the probability that the target occupies the cell i,j at time t.

During the search

interval there are available R(t)>O units of search effort that may be allocated to cells in arbitrary proportions. Let the number of units of effort allocated to cell i,j at the beginning of the interval be @(i,j,t).

If the search has the properties that characterize

a random search (Ref. l), thenthe probability of detection given that the target is in the cell during the interval can be expressed by the exponential detection function : d($ (i,j,t)1

=

1-exp (-a(i,j)$ (i,j ,t))

.

146 The v a l u e of a ( i , j ) r e f l e c t s t h e c o n d i t i o n s o f s < ? a r c h i n t h e c e l l .

The

p r o b a b i l i t y of t a r g e t d e t e c t i o n d u r i n g t h e t i m e i n t e r v a l u n d e r s e a r c h p l a n E (1,...,M} i s D ( ( $ ( i , j , t ) ) = a ( i , j , t ) (l-exp(-cx(i,j)$(i,j,t)). 1 J The o p t i m a l s e a r c h p l a n i s t o o b t a i n t h e $ ( i , j , t ) t h a t maximizes D ( $ ( i , j , t ) )

$ ( i , j , t ) for i , j

subject t o the constraints: $ ( i , j , t ) 2 0 and

C

$(i,j,t)

5R(t).

1 1 O p t i m i z a t i o n t e c h n i q u e s , b a s e d on Lagrange m u l t i p l i e r s t h a t do n o t r e q u i r e d i f f e r e n t i a b i l i t y a s s u m p t i o n s a r e g i v e n i n Ref. 4 .

I t i s shown t h e r e t h a t t h e

d e t e c t i o n f u n c t i o n must b e concave ( s u c h a s t h e e x p o n e n t i a l ) t o g u a r a n t e e t h a t maximizing a p o i n t w i s e

Lagrangian i s necessary f o r c o n s t r a i n e d o p t i m a l i t y .

BAYESIAN UPDATING Assume a s e a r c h h a s been p e r f o r m e d , w i t h t h e p r i o r t a r g e t d i s t r i b u t i o n g i v e n by a ( i , j , t ) , and t h e r e s u l t o f t h e s e a r c h i s n e g a t i v e .

Then f o r c e l l i , j , t h e

p r o b a b i l i t y t h a t t h e t a r g e t i s a c t u a l l y i n t h a t c e l l , c o n d i t i o n e d on t h e e v e n t t h a t t h e t a r g e t was n o t found i n t h e c e l l s s e a r c h e d i s : P r I t a r g e t i n c e l l i,j and n o t found t h e r e } = a'(i,j,t) P r I t a r g e t n o t found by s e a r c h } ~

The numerator i s o b t a i n e d from t h e p r o b a b i l i t y p r o d u c t : PrItarget i n cell i,jj.Pr{target

n o t found i n c e l l i , j l t a r g e t i n c e l l i , j } .

The second t e r m i n t h i s p r o d u c t i s s i m p l y 1 - P r I t a r g e t d e t e c t e d i n c e l l i,jltarget in cell i,j}.

This r a t i o i s j u s t B a y e ' s f o r m u l a and c a n be e x p r e s s e d

i n t e r m s of t h e d e t e c t i o n fu n cti o n as :

s used i n place of A ( t ) t o o b t a i n t h e p r i o r t a r g e t The m a t r i x [ a ' ( i , j , t j M XiM d i s t r i b u t i o n f o r t h e subsequent period ( A ( t t - 1 ) ) .

AN ILLUSTRATIVE EXAMPLE A s an i l l u s t r a t i o n o f t h es e procedures,

t h e r e l e a s e o f a t a r g e t i n t o a 10x10

g r i d w a s simulated f o r a period of four t i m e units.

The c h o i c e o f p a r a r r s t e r s

u s e d i n t h e a d v e c t i o n p o r t i o n o f t h e model r e s u l t e d i n t h e t a r g e t b e i n g t r a n s p o r t e d t h r o u g h t h e ( x , y ) l o c a t i o n s (l,l), ( 2 , 2 ) ,

(4,3),

( 3 , 5 ) and (5,5).

A symmetric p a t t e r n o f l o c a t i o n u n c e r t a i n t y w a s o b t a i n e d by i n c o r p o r a t i n g t h e

v a l u e o f 0 . 4 f o r t h e s t a n d a r d d e v i a t i o n of b o t h t h e x and y a d v e c t i v e d i s p l a c e m e n t disturbances.

Note t h a t t h i s c h o i c e r e s u l t s i n a v e r y s m a l l l i k e l i h o o d of

r e a l i z i n g d i s t u r b a n c e s o f more t h a n one g r i d e l e m e n t i n any d i r e c t i o n o v e r a single t i m e period. The t o t a l s e a r c h e f f o r t f o r e a c h t i m e p e r i o d w a s l i m i t e d t o 100 u n i t s .

TWO

147 s e a r c h s t r a t e g i e s w e r e employed; t h e f i r s t p e r m i t s any number o f c e l l s t o be s e a r c h e d , t h e second o n l y t w o . The r e s u l t s f o r t h e f o u r p e r i o d s a r e p r e s e n t e d i n F i g s . 1 (a-d) and 2 ( a - d ) , c o r r e s p o n d i n g t o t h e f i r s t and second s t r a t e g i e s , r e s p e c t i v e l y .

Each d i s p l a y

r e p r e s e n t s a s u b s e c t i o n o f t h e e n t i r e s p a t i a l g r i d , w i t h t h e x , y components d i s p l a y e d on t h e h o r i z o n t a l and v e r t i c a l a x e s , r e s p e c t i v e l y .

The u p p e r number

appearing i n a c e l l r e p r e s e n t s t h e p r o b a b i l i t y of t h e t a r g e t being i n t h a t c e l l , c o n d i t i o n e d on t h e n e g a t i v e s e a r c h o f t h e p r e c e e d i n g t i m e p e r i o d . d e n o t e d by

*,

The lower number,

gives t h e optimal search e f f o r t a l l o c a t e d t o t h a t c e l l during t h e

current t i m e period. The p a t t e r n o f c o n d i t i q n a l p r o b a b i l i t i e s r e v e a l s t h e combined e f f e c t o f t h e p r e v i o u s s e a r c h and a d v e c t i o n u n c e r t a i n t y o v e r t h e p a s t t i m e i n t e r v a l .

Search

e f f o r t i s a l l o c a t e d so a s t o e n s u r e as many c e l l s as p o s s i b l e a r e s e a r c h e d , w i t h t h e r e s t r i c t i o n t h a t i n t h e e v e n t o f a n e g a t i v e outcome, a l l c e l l s s e a r c h e d w i l l have e q u a l c o n d i t i o n a l l o c a t i o n p r o b a b i l i t i e s . Advection u n c e r t a i n t y a c t s t o ' s p r e a d ' t h e l o c a t i o n p r o b a b i l i t y mass from any one c e l l t o a d j a c e n t c e l l s . North-South

I n t h i s example, t h e s p r e a d o c c u r s e q u a l l y i n t h e

and E a s t - W e s t d i r e c t i o n s .

T h i s e x p l a i n s t h e symmetry i n t h e s e a r c h

patterns f o r the f i r s t search strategy (Fig. 1). The r e s t r i c t i o n t o two c e l l s i n t h e second s e a r c h s t r a t e g y r e s u l t s i n t h e asymmetric p a t t e r n s o f F i g . 2 .

Comparing F i g u r e s l ( d ) and 2 ( d ) , w e s e e t h a t t h e

f i r s t s t r a t e g y h a s r e d u c e d u n c e r t a i n t y i n t a r g e t l o c a t i o n so t h a t n o c e l l remains d i s t i n c t l y more p r o b a b l e . the monitoring u n i t s .

Note t h a t t h i s s t r a t e g y assumes u n r e s t r i c t e d m o b i l i t y of

The second s t r a g e g y , which a s s u m e d l i m i t e d m o n i t o r m o b i l i t y ,

h a s n o t been a b l e t o r e d u c e t h e number of

' m o r e p r o b a b l e ' c e l l s as e f f e c t i v e l y .

The c o n d i t i o n a l l o c a t i o n p r o b a b i l i t i e s , when combined w i t h t h e p r e d i c t i v e

a d v e c t i o n model, y i e l d t h e i m p a c t p r o b a b i l i t i e s f o r any c e l l s c o r r e s p o n d i n g t o a r e a s o f c o n c e r n o v e r th e f o r e c a s t horizon.

To i l l u s t r a t e t h i s , a n area o f c o n c e r n

was assumed t o b e l o c a t e d i n c e l l s ( 6 , 6 ) , (6,7), (7,151,

and (7,7). Using wind

v e l o c i t y p r e d i c t i o n s up t o f o u r h o u r s i n advance from t h e c u r r e n t s e a r c h p e r i o d , i m p a c t p r o b a b i l i t i e s were o b t a i n e d o v e r t h e s i m u l a t i o n h o r i z o n . i n T a b l e 1. TABLE 1 P r o b a b i l i t i e s o f t a r g e t i m p a c t on area o f c o n c e r n Search Period

P r o b a b i l i t y o f Impact Two C e l l S e a r c h U n r e s t r i c t e d Search

.018 .095

.lo8 .211

.018 -068 .071 -187

These are shown

mi

148

1 2

.04

3

4 5

2

3

4

.01

1 1

1

1.04 1.16

2

3

5

6

I1 1 1 I .04 I

*18

4 5

3 4

5 6

7

3

4

5

6

7

3 4 5 6

7

.02

.06

.07

.06

.02

.05

.07

.07

.07

.05

.02

.06

.07

.07

.02

-02

-05

-02

Fig. 1. Unrestricted Number of Cells Search

Fig.

2.

Two Cell Search

149 SUMMARY AND CONCLUSIONS A b a s i c systems s t r u c t u r e h a s been developed t o a i d i n t h e d e t e c t i o n , t r a c k i n g ,

and t r a j e c t o r y p r e d i c t i o n o f a h a z a r d o u s s u b s t a n c e s u b j e c t t o a t m o s p h e r i c t r a n s p o r t . A c t u a l a p p l i c a t i o n r e q u i r e s t h e a b i l i t y t o a c q u i r e and p r o c e s s o b s e r v a t i o n s i n r e a l

time.

To p r o v i d e t h i s c a p a b i l i t y would i n v o l v e t h e u s e o f a computer g r a p h i c s

d i s p l a y , d a t a e n t r y f a c i l i t i e s , and m o b i l e m o n i t o r i n g u n i t s w i t h two-way communications.

Although n o t s p e c i f i c a l l y d e a l t w i t h h e r e , t h e a b i l i t y t o p r e d i c t

t h e t r a j e c t o r i e s o f m u l t i p l e t a r g e t s would b e i m p o r t a n t i n an a p p l i c a t i o n . An example w a s p r e s e n t e d t o i l l u s t r a t e t h e u s e o f d a t a a c q u i s i t i o n , s e a r c h and p r e d i c t i o n components assuming two d i f f e r e n t t y p e s o f s e a r c h e f f o r t c o n s t r a i n t s on t h e m o n i t o r i n g equipment.

The example i l l u s t r a t e s t h e tendancy f o r s e a r c h e s

made w i t h no r e s t r i c t i o n s on m o n i t o r m o b i l i t y t o b e most e f f e c t i v e where e f f e c t i v e n e s s i s measured by t h e p r o b a b i l i t y o f t a r g e t d e t e c t i o n .

The p r o b a b i l i t i e s

a s s o c i a t e d w i t h t h e hazardous s u b s t a n c e c o n t a c t i n g populated a r e a s or o t h e r a r e a s o f c o n c e r n a r e o b t a i n e d by combining t h e p r e d i c t i v e a d v e c t i o n model w i t h t h e conditional target location probabilities.

REFERENCES 1 B.O.

Koopman, S e a r c h and S c r e e n i n g , Pergamon P r e s s , N e w York, 1980.

B o n i v e n t o , G. F r o n z a and A . T o n i e l l i , i n M. B e n a r i e ( E d . ) , S t u d i e s i n Environmental S c i e n c e , V o l u m e 8 , E l s e v i e r , Amsterdam, 1980, p p . 105-108.

2

C.

3

P.

4

L.D.

Eykhoff, System I d e n t i f i c a t i o n , Wiley, N e w York, 1974. S t o n e , Theory o f Optimal S e a r c h , Academic P r e s s , N e w York, 1975.

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151

MODELING POLLUTANT D I S P E R S I O N WITHIN A TORNADIC THUNDERSTORM D . W.

PEPPER

E. I. du Pont de Nemours & Co.,

Savannah R i v e r L a b o r a t o r y , Aiken, SC

29808

ABSTRACT A t h r e e - d i m e n s i o n a l n u m e r i c a l model has been developed t o c a l c u l a t e g r o u n d - l e v e l a i r c o n c e n t r a t i o n and d e p o s i t i o n o f p a r t i c l e s e n t r a i n e d i n a t o r n a d i c thunderstorm. The r o t a t i o n a l c h a r a c t e r i s t i c s o f t h e t o r n a d i c storm a r e w i t h i n t h e l a r g e r mesoscale f l o w o f t h e storm system and t r a n s p o r t e d w i t h t h e v o r t e x . c i e n t s a r e based on e m p i r i c a l v a l u e s .

Turbulence exchange c o e f f i -

The quasi-Lagrangian method o f moments i s used

t o model t h e t r a n s p o r t o f c o n c e n t r a t i o n w i t h i n a g r i d c e l l volume.

Results i n d i c a t e

t h a t u p d r a f t s and downdrafts, coupled w i t h scavenging o f p a r t i c l e s by p r e c i p i t a t i o n , account f o r most o f t h e m a t e r i a l b e i n g d e p o s i t e d c l o s e r t o t h e s i t e t h a n a n t i c i p a t e d . A p p r o x i m a t e l y 5% o f t h e p o l l u t a n t i s d i s p e r s e d i n t o t h e s t r a t o s p h e r e .

INTRODUCTION E x t e n s i v e r e s e a r c h has been undertaken a t t h e r e q u e s t o f t h e U.S.

Nuclear

R e g u l a t o r y Commission t o assess t h e r a d i o l o g i c a l consequences f r o m n a t u r a l phenomena occurring a t plutonium f a b r i c a t i o n f a c i l i t i e s .

T h i s r e p o r t d e s c r i b e s t h e s t u d y con-

cerned w i t h t h e m e t e o r o l o g i c a l d i s p e r s i o n o f p l u t o n i u m p a r t i c l e s i n a t o r n a d i c storm once t h e f a c i l i t y i s breached b y a t o r n a d o . The r i s k assessment and s i t e c h a r a c t e r i z a t i o n o f an e x i s t i n g n u c l e a r f a c i l i t y i n Pennsylvania, USA,

i s used as an example i n t h i s s t u d y .

Records o f extreme windstorms

and tornadoes f o r t h e P e n n s y l v a n i a area, along w i t h t h e storm c h a r a c t e r i s t i c s f o r a d e s i g n - b a s i s tornado, were o b t a i n e d f r o m F u j i t a ( r e f . 1). Three windspeeds a r e used t o r e p r e s e n t tornadoes t y p i c a l o f t h e area, as shown i n T a b l e 1: TABLE 1 Windspeed v a l u e s (m/sec) P r o b a b i l i t y per year Maxi mum t o t a l Trans1 a t io n a l Tangent ia1

125 25 100

96.5 19.2 77.3

7.2 x 67.0 13.4 53.6

152

The radius of the tornado i s assumed t o be 150 m with t h e vortex extending t o an a l t i tude of 1000 m.+

F u j i t a r e p o r t s t h a t numerous tornadoes with windspeeds corresponding t o these p r o b a b i l i t i e s have occurred in t h e Pennsylvania area ( r e f . I ) . Most smalland medium-sized tornadoes tend t o move in an east-northeast d i r e c t i o n , while large-sized tornadoes move in an east-southeast d i r e c t i o n . The model can be used f o r any location i f windspeed and d i r e c t i o n of t h e tornadic storm a r e available.

G O V E R N I N G EQUATIONS The model i s based on t h e solution of the three-dimensional time-dependent equation

f o r pollutant t r a n s p o r t :

where C i s the concentration, g/m3,

i s t h e vector velocity f i e l d , m/sec, K i s

the d i r e c t i o n a l l y dependent eddy di f f u s i vi t y (exchange c o e f f i c i e n t of diffusion , & / s e c ) , and S represents the sink term associated with p r e c i p i t a t i o n scavenging, The complexity of t h e flow f i e l d s associated with tornadic storms and t h e numerous s c a l e s of turbulence involved (which c h a r a c t e r i z e the diffusion processes)

g/d-sec.

do not permit simple solutions t o eq. (1). To accommodate t h e temporal and s p a t i a l v a r i a t i o n s of numerous meteorological parameters, including the e f f e c t s of wind shear and wet deposition, a numerical method i s used t o solve eq. (1). associated with eq. (1) a r e given as follows:

Boundary conditions

where H i s t h e height of the thunderstorm c e l l and a c t s a s a p a r t i a l l i d t o the concentration. The horizontal and l a t e r a l boundaries are incremented over a predetermined maximum distance. The i n i t i a l dispersion conditions a r e crucial t o the downwind dispersal p a t t e r n s following breach of the f a c i l i t y .

A u n i t source ( p u f f ) consisting of p a r t i c l e s with

diameters of < l o um i s assumed t o be picked u p by t h e tornado and l i f t e d i n t o t h e t;iunderstorm c e l l .

The puff i s subsequently dispersed by t h e dynamics of the

+T. T. F u j i t a , Personal Communication (1977).

153

t h u n d e r s t o r m c e l l (Jessup [ r e f . 21, Pasquill')

w i t h i n about 20 m i n u t e s .

The i n i t i a l

c o n c e n t r a t i o n p a t t e r n i s l i m i t e d t o t h e s i z e o f t h e t h u n d e r s t o r m c l o u d and i s skewed i n a log-normal d i s t r i b u t i o n w i t h maximum v a l u e s c e n t e r e d on t h e a x i s o f t h e tornado.

d

i s r e q u i r e d a t each t i m e - s t e p o f i n t e g r a t i o n .

U n f o r t u n a t e l y , t h e mesoscale

wind f i e l d o f a t o r n a d i c storm i s a d i f f i c u l t problem t o a c c u r a t e l y model.

Correct

c a l c u l a t i o n o f t h e t r a j e c t o r y o f t h e s t o r m and p o l l u t a n t d i s p e r s i o n p a t t e r n i s d i r e c t l y dependent upon t h e wind f i e l d s t r u c t u r e . To c r e a t e a p l a u s i b l e mesoscale wind f i e l d , a s u b j e c t i v e a n a l y s i s and i n t e r p o l a t i o n scheme was used t o generate a m a s s - c o n s i s t e n t t h r e e - d i m e n s i o n a l wind f i e l d ( r e f . 3 ) . The h o r i z o n t a l winds o u t s i d e t h e storm c e l l were assumed t o v a r y as f o l l o w s : u ( z , t ) = 2.2 zO.18 (m/sec);

u(z,t)

=

25.0 (m/sec) 19.2 (m/sec) 13.4 (m/sec)

u ( z , t ) = 1.25

i

z
1000

G

z
(3)

25.0 (m/sec) 19.2 (m/sec) 13.4 (m/sec)

The d i s t r i b u t i o n o f v e r t i c a l winds w i t h i n t h e t o r n a d i c storm c e l l i s shown i n F i g . 1.

The u p d r a f t and downdraft v e l o c i t i e s a r e a l l o w e d t o i n c r e a s e l o g a r i t h m i c a l l y

t o s p e c i f i c h e i g h t s w i t h i n t h e t h u n d e r s t o r m c e l l and t h e n decrease t o zero a t t h e t o p

o f t h e a n v i l , H.

The magnitude o f t h e v e r t i c a l windspeeds i s comparable t o observa-

t i o n s and measurements o f v e r t i c a l v e l o c i t i e s w i t h i n severe storms ( r e f s . 4, 5 ) .

A

more d e t a i l e d d e s c r i p t i o n o f t h e t o r n a d i c storm wind f i e l d i s g i v e n by Pepper ( r e f . 6 ) . A d v e c t i o n and d i f f u s i o n o f t h e h o r i z o n t a l d i s t r i b u t i o n o f t h e v e r t i c a l v e l o c i t y f i e l d enable t h e u p d r a f t and downdraft r e g i o n s o f t h e storm t o be propagated w i t h t h e t r a j e c t o r y o f t h e storm.

The r o t a t i o n a l c h a r a c t e r i s t i c s o f t h e h o r i z o n t a l wind f i e l d

w i t h i n t h e storm c e l l a r e s i m i l a r l y propagated w i t h t h e t r a j e c t o r y o f t h e storm.

The

r o l e o f t h e v e r t i c a l wind d i s t r i b u t i o n tends t o keep t h e p o l l u t a n t w e l l mixed througho u t t h e storm c e l l . To c a l c u l a t e eddy d i f f u s i v i t i e s under t h e s i m p l e s t o f c o n d i t i o n s i s a c l a s s i c a l problem.

Knowledge o f eddy d i f f u s i v i t y v a l u e s a s s o c i a t e d w i t h tornadoes and thunder-

storms i s e s s e n t i a l l y n o n e x i s t e n t .

W h i l e some experiments have been conducted on t h e

d i s t r i b u t i o n o f c h a f f i n thunderstorms, t h e d a t a a r e sparse, and t h e c h a f f are much l a r g e r i n s i z e than t h e plutonium p a r t i c l e s considered i n t h i s study.

Since p r e c i s e

f o r m u l a t i o n o f t h e d i f f u s i o n c o e f f i c i e n t s i s i n t r a c t a b l e , an e m p i r i c a l e q u a t i o n i s used.

The t u r b u l e n t d i f f u s i o n c o e f f i c i e n t s ( r e f s . 6-10) can be d e f i n e d by t h e general

equ a t i on 'F.

Pasqui 11, Personal Communication (1976)

154

t I

-

I I

1.000 m

+

lOOm

I I

-14 -12 -10 -8 -6

-4 -2

0

2

4

6

8

10 12 14

16

18

20

Vertical Velocity (m/sec)

FIG. 1. D i s t r i b u t i o n o f u p d r a f t and d o w n d r a f t v e l o c i t i e s w i t h h e i g h t i n t h e thunders torm.

where u i s t h e s t a n d a r d d e v i a t i o n o f t h e wind due t o t u r b u l e n c e (ux, uy, uZ) and has dimensions o f m2; K = K,,

Ky,

KZ; t i s t i m e .

eq. ( 4 ) i s a l t e r e d t o t h e e m p i r i c a l r e l a t i o n

K = - Azn u2 t

To s i m p l i f y t h e s o l u t i o n ,

155 where n :0.2, and A i s equal t o 0.10 (Kx, KY) and 0.6 ( K z ) .

TO account f o r t h e

v e r t i c a l v a r i a t i o n i n t u r b u l e n c e i n t e n s i t y , eq. ( 5 ) i s assumed t o be v a l i d f o r t <20 minutes.

To account f o r t h e decrease o f t u r b u l e n t i n t e n s i t y f o l l o w i n g decay o f t h e

t h u n d e r s t o r m ( t >20 minutes),

i

eq. ( 6 ) i s used i n l i e u o f eq. ( 5 )

Kx = D ( i t ) a / ( 2 t ) Ky = E ( z t ) a / ( 2 t ) K,

K

=

zo (Z/Z,)~

= F u*

where il i s t h e t r a n s l a t i o n a l v e l o c i t y o f t h e storm, t i s time, D = 0.004

(1-0.075 loq,,z),

E = 0.0075 (1-0.075

logl0z),

a = 7/4,

F = 0.41,

zo i s

6 = 0.45,

t h e s u r f a c e roughness, u* i s t h e f r i c t i o n v e l o c i t y d e f i n e d by u* = 1.2CgUg

-

(log,,Ro

1.8), w i t h Cg b e i n g t h e g e o s t r o p h i c drag c o e f f i c i e n t , Ug t h e geoand Ro = Ug/zof, where f i s t h e c o r i o l i s parameter.

s t r o p h i c wind,

The e m p i r i c a l

c o n s t a n t s appearing i n eq. ( 6 ) were o b t a i n e d f r o m Ragland and Dennis ( r e f . 7), and L e t t a u ( r e f . 11).

The e f f e c t o f topography i s n o t i n c l u d e d i n t h e a d v e c t i v e wind b u t i s i n t r o d u c e d t h r o u g h t h e d i f f u s i o n c o e f f i c i e n t s by t h e s u r f a c e

f i e l d analysis,'

roughness parameter, zo. To account f o r d e p o s i t i o n , t h e f l u x a t t h e ground i s expressed i n terms o f a d e p o s i t i o n v e l o c i t y , p ( C a l d e r [ r e f . 13]),

such t h a t

l i m [-F(z)] = p l i m [C(z)]

z+o

(7)

z-to

and

where vg i s t h e a c t u a l s e t t l i n g v e l o c i t y . t h e form

-

F =

(1-r) K

where 0 t o give Pc

a

<

r

<

~

az

~

By e x p r e s s i n g t h e f l u x a t t h e s u r f a c e i n

C

1 i s t h e r e f l e c t i o n c o e f f i c i e n t , eqs. ( 7 ) t h r o u g h ( 9 ) can be combined

ac

VgC + (Kz -)a z z = o

V a r y i n g t h e v a l u e o f r f r o m 0 t o 1 s i m u l a t e s t h e e f f e c t o f l o s s e s a t t h e s u r f a c e by deposition ( r e f . 14). Scavenging o f t h e p l u t o n i u m p a r t i c l e s o c c u r s b y r a i n o u t .

Based on t h e work o f

S l i n n ( r e f . 15), t h e s i n k t e r m i n eq. (1) i s w r i t t e n as 'Topographic e f f e c t s on p o l l u t a n t d i s p e r s i o n a r e d i s c u s s e d i n Pepper and Baker ( r e f . 3), and Reynolds e t a l . ( r e f . 12).

156

The removal r a t e ,

(J,

i s o b t a i n e d f r o m t h e r e l a t i o n ( f o r i n - c l o u d and below-cloud

scavenging)

where B i s an e m p i r i c a l c o n s t a n t , Jo i s t h e r a i n f a l l r a t e , R,

i s t h e mean d r o p l e t

s i z e , E i s t h e c o l l i s i o n e f f i c i e n c y ( 3 ) ,and a i s t h e r a d i u s o f t h e p a r t i c u l a t e . Eq. ( 1 2 ) approximates t h e removal r a t e o f c o n c e n t r a t i o n due t o r a i n d r o p s f a l l i n g t h r o u g h t h e t h u n d e r s t o r m c e l l . A water d r o p l e t - p a r t i c u l a t e c o l l i s i o n e f f i c i e n c y o f

100% i s used. mm/hr;

R a i n f a l l r a t e s near t h e c e n t e r o f a severe storm can v a r y above 100

however, such h i g h r a i n f a l l r a t e s a r e n o t c o n s t a n t and f l u c t u a t e i n l o c a t i o n .

A v a l u e of 20 mm/hr i s used as an ensemble average c h a r a c t e r i s t i c o f severe storms ( r e f . 2).

Since u p d r a f t s markedly reduce t h e d e p o s i t i o n due t o r a i n o u t , t h e removal

r a t e i s z e r o i n t h o s e r e g i o n s o f t h e storm where v e r t i c a l v e l o c i t i e s a r e p o s i t i v e . T h i s a l l o w s t h e r a i n f a l l t o o c c u r i n t h o s e r e g i o n s o f t h e storm c o r r e s p o n d i n g t o t h e r a i n s h a f t and d o w n d r a f t r e g i o n s observed i n a c t u a l storms. NUMERICAL MODEL The problems o f d i s p e r s i o n e r r o r and mesh r e f i n e m e n t a s s o c i a t e d w it h n u m e r i c a l methods a r e reduced by u s i n g a quasi-Lagrangian scheme w i t h an E u l e r i a n f i n i t e d i f f e r ence method.

The method o f f r a c t i o n a l s t e p s ( r e f . 16) i s used t o s p l i t t h e t h r e e -

d i m e n s i o n a l e q u a t i o n i n t o a Lagrangian a d v e c t i o n p a r t p l u s an E u l e r i a n d i f f u s i o n p a r t . The method o f second moments i s used t o m a i n t a i n s u b g r i d s c a l e r e s o l u t i o n o f t h e c o n c e n t r a t i o n (Egan and Mahoney [ r e f . 171, Pedersen and Prahm [ r e f . 181). The c o m p u t a t i o n a l domain c o n s i s t s o f 2640 c e l l s , 30 c e l l s i n t h e l o n g i t u d i n a l d i r e c t i o n , 11 c e l l s i n t h e l a t e r a l d i r e c t i o n , and 8 l e v e l s i n t h e v e r t i c a l d i r e c t i o n . Equal mesh spacing i s used i n t h e h o r i z o n t a l p l a n e w i t h Ax = Ay = 2000 m. v e r t i c a l mesh begins w i t h z,=O, Zk = Zk-l

f o l l o w e d by

z2

=

The

2 m, z 3 = 350 m, z,, = 1000 m, and

= ( H - z k ) / 4 where k = 5-8.

The h e i g h t o f t h e a n v i l , H, t h e ground i s s e t t o 1000 m.

i s s e t t o 15,000 m; t h e h e i g h t o f t h e c l o u d base above The t i m e s t e p increment, A t ,

ensures t h e s t a b i l i t y c r i t e r i a , X c OAt/As,

when

8

i s equal t o 30 sec.

This

and As correspond t o

components o f t h e v e l o c i t y v e c t o r and g r i d i n t e r v a l s .

The t r a n s l a t i o n a l v e l o c i t y o f

t h e c l o u d c e n t e r i s p r e s c r i b e d a c c o r d i n g t o t h e t r a n s l a t i o n a l speeds o f t h e tornado, g i v e n i n T a b l e 1.

A second-moment t e c h n i q u e i s a l s o used t o advect t h e u p d r a f t and

downdraft v e l o c i t y d i s t r i b u t i o n w i t h i n t h e storm c e l l .

The t e r m i n a l v e l o c i t y o f

p a r t i c l e s (10 p i s n e g l i g i b l e compared t o t h e u p d r a f t and d o w n d r a f t v e l o c i t i e s .

157 RESULTS Output f r o m t h e model c o n s i s t s o f c o n c e n t r a t i o n v a l u e s s p e c i f i e d w i t h i n i n d i v i d u a l c e l l volumes ( F i g s . 2 and 3 ) .

These v a l u e s a r e a p p r o p r i a t e l y a d j u s t e d w i t h i n each c e l l

volume t o correspond t o t h e s p a t i a l dimensions of t h e c e l l . Ground-level c e n t e r l i n e C / Q values a r e shown i n F i g . 4 f o r each s p e c i f i c t r a n s l a tional velocity.

The displacement o f c o n c e n t r a t i o n as a f u n c t i o n o f t r a n s l a t i o n a l

v e l o c i t y i s evident.

In a l l t h r e e cases, 90% o f t h e peak a i r c o n c e n t r a t i o n has

reached ground l e v e l w i t h i n one hour a f t e r i n i t i a l d i s p e r s i o n w i t h i n t h e c l o u d (20 minutes a f t e r u p t a k e o f t h e p o l l u t a n t ) .

The decrease o f C/Q values i s due t o t h e

d e p l e t i o n o f concentration from t h e cloud (excepting t h a t p a r t transported t o t h e a n v i l r e g i o n ) and t o n e a r l y complete d i f F u s i o n o f t h e c o n c e n t r a t i o n below c l o u d base.

I

X

a. Initial skewed log-normal distribution

158

3A '

Fig. 3 . Ground level a i r concentration in t h e x-y plane ( t = 40 minutes) ( r o t a t i o n a l ) winds [ v e l o c i t y vectors] represent tornadic storm).

3

Longitudinol Distance (X), km

Fig. 4. Maximum ground level c e n t e r l i n e a i r concentration from plant s i t e .

159 I s o p l e t h s o f a i r c o n c e n t r a t i o n a t ground l e v e l f o r t = 60 m i n u t e s a r e shown i n F i g . 5.

The i r r e g u l a r i t y i n t h e i s o p l e t h c o n t o u r i s due t o t h e a d v e c t i o n and d i f f u -

s i o n o f t h e u p d r a f t / d o w n d r a f t r e g i o n s o f t h e storm.

F i g . 5 shows t h a t as t h e t r a n s l a -

t i o n a l v e l o c i t y o f t h e storm increases, t h e l a t e r a l spread o f a i r c o n c e n t r a t i o n i s s t r e t c h e d downwind.

H i g h e r peak c o n c e n t r a t i o n v a l u e s appear l e s s d i s p l a c e d t o t h e

r i g h t f o r t h e t o r n a d i c s t o r m w i t h a t r a n s l a t i o n a l v e l o c i t y o f 13.4 m/sec t h a n w i t h t h e succeeding two v e l o c i t i e s .

However, once beyond t h e i n i t i a l peak c o n c e n t r a t i o n area,

downwind values o f g r o u n d - l e v e l a i r c o n c e n t r a t i o n a r e l e s s t h a n values o b t a i n e d f o r

U

= 19.2

and 25.0 mlsec.

T h i s i s t o be expected because t h e i n c r e a s e i n a d v e c t i o n

causes t h e peak c o n c e n t r a t i o n values t o be more d i s p l a c e d (and d i s t r i b u t e d ) i n t h e longitudinal direction.

I n t e s t cases r u n w i t h o u t t h e i n f l u e n c e o f u p d r a f t s and

d o w n d r a f t s (and scavenging), t h e a i r c o n c e n t r a t i o n e v e n t u a l l y reached ground a f t e r 6 h o u r s b u t was s e v e r a l o r d e r s o f magnitude l e s s i n value. t i r o u n d - l e v e l d e p o s i t i o n ( r 2 ) i s shown i n F i g . 6.

The d e p o s i t i o n p a t t e r n s c o n s i s t

o f r a i n d r o p s t h a t have scavenged p o l l u t a n t f r o m t h e storm c e l l .

As shown i n F i g . 2,

t h e e f f e c t o f a d v e c t i o n on a i r c o n c e n t r a t i o n i s a l s o e v i d e n t on g r o u n d - l e v e l deposition:

t h e h i g h e s t peak v a l u e s a r e o b t a i n e d when U = 13.4 m/sec w i t h t h e peak r e g i o n

being nearest t o t h e i n i t i a l dispersion p o i n t i n t h e cloud. CONCLUSIONS Based on t h e t e s t cases analyzed i n t h i s study, d e p o s i t i o n o f t h e p o l l u t a n t b e g i n s t o occur i m m e d i a t e l y a f t e r t h e i n i t i a l d i s p e r s i o n w i t h i n t h e storm c e l l .

The p r i m a r y

mechanisms f o r c o n c e n t r a t i o n r e a c h i n g t h e s u r f a c e comes f r o m t h e e f f e c t o f t h e d o w n d r a f t v e r t i c a l v e l o c i t y d i s t r i b u t i o n and wet d e p o s i t i o n .

I n a l l cases, 50% o f t h e

i n i t i a l concentration, excepting t h a t p o r t i o n l i f t e d i n t o t h e a n v i l region o f the cloud,

i s removed f r o m t h e c l o u d w i t h i n 15 m i n u t e s from t h e t i m e o f i n i t i a l d i s p e r s i o n

w i t h i n t h e storm.

The maximum g r o u n d - l e v e l c o n c e n t r a t i o n i n a l l cases occurs w i t h i n

35 m i n u t e s o f w o u n d - l e v e l i n j e c t i o n . Maximum c e n t e r l i n e a i r c o n c e n t r a t i o n values r e v e a l t h a t peak c o n c e n t r a t i o n a t t h e s u r f a c e occurs w i t h i n 15 km f r o m t h e p o i n t where t h e i n i t i a l d i s p e r s i o n w i t h i n t h e storm i s established.

The c o n c e n t r a t i o n i s e s s e n t i a l l y d e p l e t e d f r o m t h e lower and

m i d d l e l a y e r s o f t h e c l o u d w i t h i n 50 km o f t h e peak g r o u n d - l e v e l value. ACKNOWLEDGEMENT The i n f o r m a t i o n c o n t a i n e d i n t h i s a r t i c l e was developed d u r i n g t h e course o f work under C o n t r a c t No. DE-AC09-SR00001 w i t h t h e U.S.

Department o f Energy.

160

Y

t a. Translational velocity tornadic storm).

=

13.4 m/sec (rotational winds [velocity vectors] represent

................... ..........-......... .............. . . . . . . . . . . . ........................................ .......................... ..... -. . . . ......................... '15' .................................................................. ...........

r

.... -14 ..................... ................. - . .

.....

Y

t+'

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

............................................. X

b. Translational velocity = 19.2 m/sec.

.... -12

......

.....11 ....

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

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

Y

t

L

X

c. Translational velocity

=

25.0 m/sec.

Fig. 5. Ground level air concentration isolog plots (m-3) in the x-y plane (t minutes).

=

60

161

X'

a. Translational velocity = 13.4 rn/sec.

I

'

x

b. Translational velocity = 19.2 m/sec.

Fig. 6. Ground level deposition isolog p l o t s

( N - ~ )in

t h e x-y plane ( t = 60 minutes) :es).

162

REF E K E NC E S

1 T.T. F u j i t a , Review of Severe Weather Meteorology a t Babcock & Wilcox Company, Leechburg, Pennsylvania, Department of Geophysical Sciences, University of Chicago, January 31, 1977, 24 pp. 2 E.A. Jessup, Mon. Weather Rev., 100(1972)653. 3 D.W. Pepper and A.J. Baker, Computers and Fluids, 8(1980)371. 4 T.T. F u j i t a , Workbook of Tornadoes and High Winds f o r Engineering Applications, SMRP Research Paper 165, Department of Geophysical Sciences, University of Chicago, 1978, 142 pp. 5 K.A. Browning and R.J. Donaldson, J r . , J. Atmos. Sci., 20(1963)533. 6 D.W. Pepper, USDOE Report DP-1556, E. I. du Pont de Nemours & Co., Savannah River Laboratory, May 1981. 7 K.W. Ragland and R.L. Dennis, Atmos. Environ., 9(1974)175. 8 E.M. Agee, J. Atmos. Sci., 32(1975)642. 9 A.S. Frisch and R.G. Strauch, J. Appl. Meteorol., 15(1976). 10 P.H. Hildebrand, J. Appl. Meteor., 16(1977)493. 11 H.H. Lettau, Advances i n Geophysics, Vol. 6, Atmospheric Diffusion and Air Pollution, Academic Press, New York, 1959, p.241. 1 2 S.D. Reynolds, P.M. Roth, and J.H. Seinfeld, Atmos. Environ., 7(1973)1033. 13 K.L. Calder, The Numerical Solution of Atmospheric Diffusion Equation by F i n i t e Difference Methods, Dept. of Army Tech. Memo, 1968, p.130. 14 S.K. Kao, J. Atmos. Sci., 33(1976)157. 15 W.G. Slinn, USAEC Report BNWL-1950 ( P t . 3 ) , B a t t e l l e Northwest Laboratories, Richland, WA, 1975. 16 T.T. F u j i t a , Tornado Structure f o r Engineering Application with Design Basis Tornado Model (DBT-77), Department of Geophysical Sciences, University of Chicago, 1977, 111 pp. 1 7 B.A. Egan and J.R. Mahoney, J. Appl. Meteor., 11(1972)312. 18 0. Christensen and L.P. Prahm, J. Appl. Meteor., 15(1976)1284.

163

THE INFLUENCE OF THE EMISSION H E I G H T ON THE MESO-SCALE AND LONG-RANGE

TRANSPORT

OF REACTIVE POLLUTANTS

M.

BENARIE

12, rue de l ' y v e l i n e , 91220 Bretigny (France)

ABSTRACT A s e a r l y i n t h e second day a f t e r t h e emission t h e p o l l u t a n t

i s well mixed

r e g a r d l e s s of t h e emission h e i g h t , i t s mass balance i s independent of t h e emission h e i g h t . A l l d i f f e r e n t i a l , height-dependent d e p o s i t i o n occurs during t h e period immediately subsequent t o t h e emission and can be computed a s shown i n w i t h i n t h e paper.

INTRODUCTION The purpose of t h e p r e s e n t paper i s t o examine t h e i n f l u e n c e of t h e e f f e c t i v e emission h e i g h t ( = s t a c k h e i g h t

+

plume r i s e ) on t h e mesoscale and long-range

t r a n s p o r t of a c t i v e (chemically r e a c t i v e o r scavenged) p o l l u t a n t s . The s t a r t i n g p o i n t i s t h e m a t e r i a l balance of an a i r p a r c e l containing t h e plume. The same p r i n c i p l e of

" s u l f u r budgets" has been a p p l i e d t o SO2 ( r e f s . 1 and 2) t h i s work

a p p l i e s t h e budget i d e a t o i n v e s t i g a t e t h e e f f e c t of t h e emission h e i g h t on mesoscale t r a n s p o r t i n g e n e r a l and t h e consequences of t h e p e n e t r a t i o n of inversion l a y e r s i n p a r t i c u l a r . The p r i n c i p l e of any budget c a l c u l a t i o n i s t o i n v e s t i g a t e t h e f r a c t i o n

of t h e p o l l u t a n t e x t r a c t e d by t h e various mechanisms from t h e a i r p a r c e l during e a r l y s t e p s of t h e t r a n s p o r t p r o c e s s , and t o compute by d i f f e r e n c e t h e amount which remains a i r b o r n e a f t e r some given p e r i o d .

THE BUDGET FROM EMISSION TO FULL M I X I N G .

Two b a s i c s i t u a t i o n s must be d i s t i n g u i s h e d : t h e absence of an e l e v a t e d inversion when a well-mixed convective s i t u a t i o n dominates, and i n s t a n c e s when v e r t i c a l exchange i s hindered, slowed down o r even comes t o a s t o p . Well-mixed,

convective s i t u a t i o n s

S i t u a t i o n s i n which t h e mixed l a y e r r e a l l y deserves i t s name and becomes uniform, occur mainly during t h e d a y l i g h t hours with well-developed thermal turbulences. The time r e q u i r e d f o r uniform mixing t o be achieved, can be computed e i t h e r

164 in a rigorous way following ref. 3, or estimated in much simpler way fully adequate for our purpose, after ref. 4, as the distance, respectively wind velocity dependent time, when the value of the vertical dispersion coefficient for the prevailing stability conditions equals the height L of the mixed layer (or a conventional fraction, as L/1.25 thereof). As

an example

with L = 1000 m, moderate insolation and 4 m sec-' wind

:

velocity (Pasquill B stability class)

;

Uz

=

1000 m at 2.5 km from the source

which corresponds to a travel time of 625 sec

=

1 / 6 hour. Therefore, during the

day, a thorough mixing throughout the mixed layer may be assumed within less than the half-hour. Deposition losses from an emission at any height within the mixed layer occurring from sunrise until about one hour before sunset, can be-approximated in the following way

:

The rather complex process of "dry deposition", depending on surface resistance, surface roughness, wind velocity and turbulence, is described by a single quantity, the pollutant deposition velocity vd. Two very complete reviews of deposition velocities appeared recently

:

refs. 5 , 6 .

Designing by L the height of the mixed layer, the rate constant for dry deposition will be bl = vd/L. In presence of other simultaneous decay mechanism ( s ) , as e.g., rain scavenging with b2, we have to consider the sum of all decay constants

:

c

bi and at the end of the time t, the decaying air parcel will contain

mt = mo exp ( -tCbi)

(1)

of the initial pollutant mass mo. The deposition flux F cm-2sec-1 per unit area and unit time is F = vdc and g M = Fxy = xyvdc represents the total mass deposited in unit time within the area xy. Neglecting for the time being deposition losses, the mass within the box xyh is constant when x

+

Xk and y

+

yk through the effect of longitudinal (lateral)

dispersion. The concentration varies according to ckxkykh = const. Therefore, in first approximation, i.e., as far h may be considered constant, and Xk and yk are large enough to include all the diffusing material, the mass deposited per unit time is independent of the extent of the box. This way of reasoning allows to disregard lateral (or longitudinal) diffusion coefficients, plume meandering and the introduction of more or less arbitrary constants that take into account these phenomena. Therefore, the horizontal limits of the box will always be defined as boundaries of vanishing concentration. It is very important to stress that emission height did not enter into these considerations. An elevated plume satisfies the condition of uniform distribution within the mixed layer even earlier in convective situations than is the case with a ground level source.

165 So f a r f o r p a r t i c u l a t e s s u b j e c t only t o d e p o s i t i o n and dry ( = no r a i n ) s i t u a -

t i o n s . When r a i n ( o r snow) occurs, a washout c o e f f i c i e n t should be considered coupled with t h e average d u r a t i o n of t h e p r e c i p i t a t i o n ( s e e below). In t h e i n s tance of SO2, two more complications occur ; t h e r a t e of oxidation i n t o p a r t i c u l a t e s u l f a t e which, i f f i n e d e t a i l i s sought, may be broken down i n day (photochemically r a t e - l i m i t e d ) a n d n i g h t ( c a t a l y t i c a l l y r a t e - l i m i t e d ) processes. P a r t i c u l a t e s u l f a t e i s a l s o s u b j e c t o t dry and wet d e p o s i t i o n . Although f u r t h e r below we w i l l attempt some numerical computations f o r SO2, it i s q u e s t i o n a b l e i f a l l t h e s e mechanisms should be taken i n t o account i n d e t a i l , a s few of t h e r a t e const a n t s a r e r e l i a b l e enough. We probably g e t b e t t e r e s t i m a t e s by lumping s e v e r a l of t h e s e mechanisms t o g e t h e r .

MASS BALANCE OF THE WELL-MIXED

A I R PARCEL

A s convection f u l l y develops on t h e second day a f t e r t h e emission, t h e pollu-

t a n t becomes well-mixed. I n s t e a d of computing with a "two-box"

model s e q u e n t i a l l y , one f o r t l hours of

t h e day and t h e o t h e r f o r t 2 hours f o r t h e n i g h t a s t h i s has been done i n r e f . 1 , we d e f i n e and use a s i n g l e compound r a t e c o n s t a n t f o r a 24-hour p e r i o d a s t h e average of t h e day and n i g h t r a t e s

t Cbi 1

+

:

t2bn = B

+

t2

Thus a f t e r a 24-hour cycle t h e a i r p a r c e l w i l l contain

p a r t of t h e o r i g i n a l p o l l u t a n t m a s s . A f t e r k c y c l e s t h e remaining mass w i l l be

exp (-Bk)

(4)

Numerical c a l c u l a t i o n s follow i n Section 3.

NUMERICAL APPLICATIONS TO SO2 PLUMES

Emissions i n f u l l y convective s i t u a t i o n s The c o n s i d e r a t i o n s developed above a r e v a l i d ; one o r a t most t w o hours a f t e r emission i t s h e i g h t has no i n f l u e n c e anymore because t h e p o l l u t a n t i s well-mixed.

Formula (1) a p p l i e s f o r t h e t hours a f t e r sunset. Typical c o n s t a n t s

t o be used a r e i n Table 2 .

166 S t a b l e condition - decoupling of t h e s u r f a c e l a y e r . During t h e n i g h t , t h e p o l l u t e d box i s . d e c o u p l e d from t h e ground. This process may be described a s follows. The v e r t i c a l t u r b u l e n t f l u x becomes smaller than t h e d e p o s i t i o n v e l o c i t y and t h u s t h e v e r t i c a l d i f f u s i v e exchange alone i s r a t e determining. This pccurs when KZ

5

1 m2sec-l, t h a t means i n very s t a b l e atmospheric

c o n d i t i o n s . P r a c t i c a l l y , i t i s enough i f only a very t h i n l a y e r - a few centimeters t o a few meters - has t h i s s t a b l e s t r a t i f i c a t i o n . The upper l a y e r s are decoupled from t h e underlying s u r f a c e . This occurs q u i t e o f t e n by r a d i a t i o n i n v e r s i o n during a l a r g e p o r t i o n of t h e n i g h t hours provided t h e s t a b l e s t r a t i f i c a t i o n i s n o t p e r t u r b e d by winds.

We may c h a r a c t e r i z e t h i s s i t u a t i o n by a " n i g h t r a t e constant" bn which almost vanishes i n t h e above-described i d e a l c o n d i t i o n s ; otherwise it has some small value when compared t o t h e day r a t e . Experimental d i s t r i b u t i o n of convective and s t a b l e s i t u a t i o n s Beyond g e n e r a l i t i e s , such a s t h a t convective s i t u a t i o n s a r e more f r e q u e n t during

the day and poor exchange dominates d u r i n g t h e n i g h t , only experimental determinations of t h e atmospheric l a y e r i n g can g i v e f u r t h e r i n s i g h t i n what a c t u a l l y happens.This l a y e r i n g i s s t r o n g l y influenced by l o c a l c l i m a t e and geography. I t should be experimentally e s t a b l i s h e d f o r many s i t e s . To our p r e s e n t knowledge, one s i n g l e paper r e l a t e s about such measurements ; r e f . 7 . During summer about 1/3 of t h e s i t u a t i o n s a r e convective, and 1/6 of t h e time ground-based i n v e r s i o n s a r e t o be found. During t h e w i n t e r months, convective s i t u a t i o n s a r e less than 10% of t h e

t i m e and somewhat less than 10% a r e t h e ground-based i n v e r s i o n s . Therefore, i n summer 1/2 of t h e time, and i n winter 1/5 of t h e time t h e r e i s no emission h e i g h t e f f e c t on t h e mesoscale mass balance of a c t i v e p o l l u t a n t s .

The p e n e t r a t i o n of i n v e r s i o n s . In t h e presence of e l e v a t e d l a y e r i n g , r e f . 7 shows t h a t a s f a r a s Scotland i s concerned, t h a t e l e v a t e d l a y e r i n g can be observed with n e a r l y t h e same average frequency of 1/5 e i t h e r i n winter

o r i n summer. In

w i n t e r , t h e r e i s s c a r c e l y a d i u r n a l c y c l e t h a t i s q u i t e a s pronounced a s i n summer. During summer days, e l e v a t e d i n v e r s i o n s almost never occur, though they a r e frequent during t h e n i g h t . In r e f . 7 , t h e " p o t e n t i a l c o n t r i b u t i o n " of d i f f e r e n t s t a c k h e i g h t c a t e g o r i e s (category I :

2

150 m ; category I1 : 90-120 m , and category I11 : 50-85 m) t o

t h e ground l e v e l concentration h a s been c a l c u l a t e d . The p r e s e n t use of t h e s e r e s u l t s

w i l l be t h e complement : the frequency by which plumes emitted from t h e s e s t a c k

h e i g h t c a t e g o r i e s p e n e t r a t e i n v e r s i o n s and t h u s remain f o r a more o r less long time decoupled from t h e ground, The summer and winter seasons p r e s e n t d i s t i n c t i v e f e a t u r e s and t h e r e f o r e w i l l be discussed s e p a r a t e l y . From A p r i l u n t i l September, between 700 h and 1800 h l o c a l time, t h e emissions

167 always occur i n f u l l y convective s i t u a t i o n s . There i s no d i f f e r e n c e , t h e r e f o r e , a s f a r a s s t a c k h e i g h t i s concerned. The average frequency f o r p e n e t r a t i n g n i g h t i n v e r s i o n s (averaged from Fig.4, of r e f . 7 ) i s i n Table 1.

TABLE 1

Average inversion p e n e t r a t i o n percentage during t h e n i g h t , i n f u n c t i o n of stack h e i g h t , v a l i d f o r t h e Forth Valley, Scotland, a f t e r Maugham (1979).

Stack Height 50-85 m 90-120 m > 150 m

Summer

Winter

60 82 96

92

81 98

The frequency of n o t p e n e t r a t i n g through an i n v e r s i o n - t h a t i s , of afumigation s i t u a t i o n with t h e plume remaining below t h e i n v e r s i o n - i s obviously 100

-

( p e n e t r a t i o n frequency 8 ) . Thus, d u r i n g t h e n i g h t , i n d i f f e r e n t l y i f i n summer o r

> 150 m high s t a c k s w i l l fumigate about 4-5 times l e s s f r e q u e n t l y i n winter, than 90-120 m , and

10 times l e s s f r e q u e n t l y than 50-85 m s t a c k s .

We may conclude therefrom, t h a t i n t h e summer approximately h a l f t h e daytime short-range d e p o s i t i o n of p o l l u t a n t s w i l l n o t be influenced a t a l l by t h e emission h e i g h t . The p o l l u t a n t decay w i l l follow a unique exponential law ( s e e below) f o r any h e i g h t . During t h e n i g h t , t h e plumes l o c a t e d above t h e i n v e r s i o n s may be s u b j e c t t o r a i n scavenging, b u t they a r e decoupled from t h e ground and t h e r e f o r e not s u b j e c t t o dry d e p o s i t i o n . The events must be evaluated each with i t s respect i v e frequency. During t h e winter months (October-March) between 800 and 1600 hours, t h e r e i s a r e l a t i v e l y smooth r i s e u n t i l noon, afterwards t h e r e i s a f a l l i n t h e convective mixing, which a t any time and a t any s t a c k h e i g h t category does n o t a t t a i n t h e summer values. The noon peak values f o r t h e frequency of p e n e t r a t i o n a r e of 75% for

2

150 m s t a c k s ,

=

43% f o r 90-120 m and 50% f o r 50-85 m s t a c k s .

For t h e n i g h t , t h e p e n e t r a t i o n frequencies can be read from Table 1. Deposition and o t h e r l o s s e s u n t i l t h e morning t h a t follows t h e emission I f t h e emission - a t any h e i g h t - occurs a t a time when it i s decoupled from ground, d e p o s i t i o n l o s s e s may be neglected u n t l l

convectice mixing occurs. This

sets i n u s u a l l y a t t h e f i r s t subsequent morning. I f t h e emission occurs d u r i n g a convective s i t u a t i o n , t h e l o s s e s should be computed only f o r t h e time t h i s s i t u a t i o n l a s t s . I f a non-convective (ground o r low-based i n v e r s i o n ) follows, t h e d e p o s i t i o n during t h i s i n t e r v a l w i l l be n e g l i g i b l e u n t i l f u l l convection develops t h e n e x t morning.

-

168 TABLE 2

Constants f o r t h e SO2 decay. Mainly a f t e r Denison (1979) and Sehmel (1980)

Summer Mean Range Mixing h e i g h t L m

1200

Dry d e p o s i t i o n v e l o c i t y vd cm s-1 S O -SO

2

4 kS02 s - l

1.2 (Grass)

conversion

10-6

Winter Mean Range

1800-6000

700

400-1200

0.5-2.5

0.15 (snow)

0.05-1.5

3.10-7-3.10-6

10-6

3.10-'-3.

0.5

0.01-1.5

Scavenging c o e f f i c i e n t so2 s-1

10-5

Par ti c u l a t e d e p o s i t i o n v e l o c i t y ( a ) vso4 cm s-1

0.5

0.01-1.5

P a r t i c u l a t e scavenging c o e f f i c i e n t so4 s-1

10-4

2.10-5-30.

P r o b a b i l i t y of p r e c i p i t a t i o n ( b ) Pp

0.1

0.0-0.4

210-5-3010-4 0.2

0.1-0.8

( a ) S i z e dependent ( b ) C l i m a t i c average f o r Western Europe - o c e a n i c a l l y influenced climate. Large y e a r l y , monthly v a r i a t i o n s . The SO - t o - s u l f a t e conversion, and t h e scavenging and d e p o s i t i o n of s u l f a t e 2 i s a r a t h e r complex process. This s u b j e c t has been q u i t e thoroughly and c r i t i c a l l y reviewed r e c e n t l y i n r e f . 8 , t a k i n g i n t o c o n s i d e r a t i o n t h e experimental and t h e o r e t i c a l r e s u l t s of t h e l i t e r a t u r e . This r e f e r e n c e should be consulted f o r d e t a i l s . Considering r e a l i s t i c values f o r t h e long-range average of wet and dry p e r i o d s i n C e n t r a l Europe, r e f . 8 comes t o an o v e r a l l residence time of f o r SO2 t o Cbi = 1.75 10-5s-1. with L = 1000 m and vd

=

16 h

This f i g u r e i s an average f o r winter and summer,

0.8 c m s-1.

The p o r t i o n of s i n g l e removal processes i s

a follows : 9% homogenous SO7 oxidation 35% l i q u i d phase SO2 o x i d a t i o n 45% dry d e p o s i t i o n 11%wet d e p o s i t i o n About 50% of t h e emitted SO2 i s removed by dry d e p o s i t i o n (predominantly a s SO ) and 50% i s removed by t h e atmosphere by w e t d e p o s i t i o n a s s u l f a t e .

2

Ref. 9 , based on h i s own measurements a s w e l l a s on o t h e r s '

( f o r example r e f . 1 0 )

has shown t h a t most o x i d a t i o n occurs e a r l y i n t h e plume's l i f e and h a l f of t h e f i n a l s u l f a t e y i e l d i s obtained c l o s e t o t h e source. Therefore t h e c o n s t a n t Cbl =

1.75 10-5 w i l l only be used f o r t h e f i r s t 12 hours o r less of consecutive plume history. Table 3 p r e s e n t s a c a l c u l a t i o n of t h e s u l f u r budget of an a i r p a r c e l i n which

169

SO

2

has been emitted at the hour of the day as given by the first column.

TABLE 3 Yearly average of sulfur remaining in an air parcel - Central European conditions. Emission in convective situation

:

the source height does not enter into conside-

ration.

Time of emission

Sulfur remaining in the air parcel at 18-20 h.

8-10 10-12 12-14 14-16 16-18 18-20

0.54 0.61 0.69 0.78 0.88 1 .oo

The figures have been confirmed by numerous experiments, e.g., ref. 1 1 where further bibliography can be found. Emission under poor vertical exchange conditions Emissions near the ground. As radiation inversion develops in the proximity of the surface, stabilizing the nocturnal surface layer, a shallow mixing layer may develop caused by mechanical turbulence. The height of this nocturnal mixed layer depends on surface roughness and wind velocity. At very low wind speeds, the depth of the nocturnal mixed layer is essentially zero and may attain a few hundred meters for high wind speeds. Therefore a pollutant emitted near ground into this layer will be trapped and can be subject to removal - provided tdat sufficient vertical turbulence exists to transport material towards the ground. Beyond these qualitative considerations, begins the great area of quantitative ignorance. The lack of detailed knowledge notwithstanding, we may attempt a few calculations for two idealized limiting situations. One of these instances occurs when a low, impenetrable inversion barrier exists, but under which the shallow wind-induced -+ lOn~*s-~, which z c allows vd to remain rate determining. This situation is fairly frequent when

mixing layer still provides a vertical diffusion constant K

surface roughness is rather high, as in extended suburban regions with cottagetype houses isolated with 500-1000m2 gardens, and each one fenced and surrounded by shrubs and some tall trees. Quite frequently the mixed layer is limted to about 100 m in such surroundings, and capped by a strong inversion (unpublished results,

based on measurements in Strasbourg, France, Benarie (1975)

1. Applying results

from ref. 12 for stable atmosphere and grass in summer, vd = 0.5 cm snow in winter vd = 0.05 cm s-1, we have

S-l,

and for

bl = - =0 ' 5

5 10-5

summer

104

A further major incertitude arises regarding the conversion rate into sulfate

and the subsequent sulfate deposition. Most authors (ref.13) agree that night conversion rates are substantially lower than those found during the day.Refs.8 estimates are based on long term(year1y) averages. To use them for night conditions only would be an overestimate. Therefore, we roughly guess that in between figures, bl

=

7.5

s-l (summer) and bl

=

7.5

s-l (winter), would be

adequate. Considering that the thickness of the mixed layer which co-determines the results has already been a rather sweeping generalization with considerable possibility of error, there is no point in trying to obtain better estimates for the deposition rates, at the time being. If we use the most frequent heights for the inversion as found by ref. 7 - 175 m (see below) - the above bl values must approximately be halved. Anyway, the use of these figures is only to obtain an upper limit for night deposition losses from ground level sources (see Tables 4 and 5). The other limiting case would be when stability is so high that the last few decimeters represent an impenetrable barrier to diffusion. It is immaterial if the vertical extent of the polluted air layer is a few tens or several hundred meters. In this case, only a very thin layer next to the ground is subject to deposition - a few percent of the total mass at most. What we do not know with precision is the intensity

-

frequency distribution of such strong ground-based

inversions. Obviously this zero deposition rate is a lower limiting value. Stack emissions. We are guided here by Maugham's paper which can be used for a (locally valid) comparative computation. Table 1 shows the average night penetration frequencies for various stack heights. The method for computation has been obtained above

;

the constants -

with the exception of L - are in Table 2.

As the most frequent night inversion height, L = 175 m is assumed for summer and

winter alike based on Maugham's data. When conditions are stable, the minimum vd values are selected. It should be stressed that this way of reasoning assumes implicitly that vertical exchange below the inversion is still strong enough to let v be rate determining. We use the exponential deposition formula (1) d with dry deposition and scavenging rates for the fraction of time the plume is considered below inversion, and scavenging alone with penetrating plumes. Transformation rate into sulfate, and subsequent sulfate deposition are not being taken here into account due to three reasons. First, most authors (refs. 1 , 9 ) agree, that night oxidation rates are from small to negligible, below 0.5%

h-l. Second, the sulfate oxidation deposition rate is of importance for the absolute mass balance only, for the computation of the total amount of sulfur

171 remaining. As far as our special problem is concerned, that is the relative mass balance for various stack heights, any loss rate, and therefore the assumed zero loss rate, yields the same relative result. Finally, the assumed zero loss rate

leads to an upper limit estimation of the sulfur transported at distance. The time-weighted situations are taken from Table 1. A reminder of the numerical values is summarized in Table 4 , the results of computation in Table 5. Sulfur balance in the well-mixed parcel. The second day decay can be computed in the same way as the first well-mixed period. The computation and the constants to be used have already been discussed previously. From sunrise to sunset, the well-mixed air mass loses for about 10 hours sulfur, at the rate shown by Table 3 , i.e., about 0.54 part of the original budget remains, at evening. TABLE 4

Reminder of the night loss rates used for calculation in Table 5 A. For stacks

Vd

Summer dry depositions

; -=

L

scavenging Pp SO

2

=

0 . 5 cm s-1 17500 cm

=

0.1 h-l

0.1 10-5 s-1 = 3 . 6

Summer dry deposition + scavenging

h-1

0.1 h-l

Vd = 0 . 5 cm s-l Winter dry deposition L 17500 cm

= o.017

h-l

scavenging 0.2 10-5 s-1 = 7.2 10-3h-1 Winter dry deposition + scavenging

2.4 10-2h-1

B. For ground level sources.

Estimated upper limits. Summer

7 . 5 10-5 s-l = 0.27 h-1

Winter

7.5 10-6 s-1 = 0.027 h-l

TABLE 5 Average mass of SO2 remaining at sunrise in an air parcel. Stack emissions during the night - poor vertical exchange. Inversion penetration frequencies from Maugham (1979) i assumed average Western Europe Oceanic climate conditions. ~

Height of Emission m Time of emission 16-18 18-20 20- 2 2 22-24 24-02 02-04 04-06 06-08

Summer 50-85

90-120

.71 .I4 .78 .83 .89 .96

.85 .87 .89 .91 .94 .98

Winter h150 .94 .95 .96 .97 .98 .99

50-85 .86 -88 .89 .91 .93 .95 .97 .99

90-120 .88 .90 -91 .93 .94 .96 .97 .99

2150 .89 .91 -92 .94 .95 .96 .98 .99

172

As the assumptions for the mixed layer height are different for Table 5 and Table 3, the results are not directly comparable. During the night, the air parcel is decoupled from the ground and thus the dry deposition loss will be negligible, but rain scavenging has to be accounted for

9 hours of the summer night and for 13 hours of the winter night. On the

average, after one summer night it remains the 0.968 part (0.911 part of the winter night) of SO2 within the air parcel. Thus, after one cycle of 24 hours, the remaining SO2 represents 0.52 part in summer and 0.49 in winter - not significantly different in view of the incertitudes of the assumptions and constants. Subsequent days of transport will account on the average for the same rate of exponential decay. The third morning the air parcel will contain30.25 part of the original SO

mass

;

the fourth 0.12, and so on.

If the initial emission takes place in a convective situation, the time of the emission has to be accounted for taking the respective figure from Table 3 For instance, an air parcel containing a 12-14 hour emission, in summer, attains the evening with an 0.69 part of the inital SO2 mass

;

of that .968 remains on

next morning. Therefore .69 x 0.968 has to be mulitiplied by 0.50 for each subsequent 24 hours of transport. As the subsequent sulfur during transport days is insensitive as regards emission height, the differential deposition during the first 24 hours will account for the mass-balance at any transport distance.

REFERENCES 1 R.B. Husar, D.E. Patterson, Y.D. Husar, N.V. Gilliani and W.E. Wilson Jr., Atmos. Environm., 12 (1978)549-568. 2 J.N. de Wys, A.C. Hill and E. Robinson, Atmos. Environm., 12 (1978) 633-639. 3 R.J. Yamartino Jr., J. Air Pollut. Control Assoc., 27 (1977)467-468. 4 M.E. Smith and I.A. Singer, J. Appl. Meteor. 5 (1966)631-639. 5 T.A. McMahon and P.Y. Denison, Atmos. Environm., 13 (1979)571-585. 6 G.A. Sehmel, Atmos. Environm. 14 (1980)983-1011. 7 R.A. Maughan, Atmos. Environm., 13 (1979)1697-1706. 8 D. Moller, Atmos. Environm. 14 (1980)1067-1076. 9 J. Freiberg, Atmos. Environm., 12 (1978)339-347. 1 0 M.T. Dana, J.M. Hales and M.A. Wolf, J. Geophys. Res., 80 (1975)4119-4129. 11 H. Flyger, E. Levin, T.E. Lund, J. Fenger, E. Lyck and S.E. Vryning, Atmos. 12 D.M. Whelpdale and R.W. Shaw, Tellus 26 (1974)196-204. 13 Y. Forrest and L. Newman, Atmos. Environm., 11 (1977)517-520.

173

HEALTH

EFFECTS POLLUTION CONTROL

The reader should n o t be misled by the slimness of t h i s s e c t i o n .

The

number of pages or t h e amount of words i s not a measure of t h e significance of t h e opinions or of the s u b s t a n t i a l i t y of t h e r e s u l t s . Health e f f e c t s were and a r e considered as the main r a t i o n a l e behind a i r pollution research and abatement.

Dr. L i p f e r t draws our a t t e n t i o n here t o

~

t h e f a c t t h a t t h e measured a i r p o l l u t a n t s , more s p e c i f i c a l l y sulphur dioxide and suspended matter concentrations on non-episodic l e v e l s , did n o t display any demonstrable harm t o human h e a l t h . To avoid any misunderstanding, I emphasise t h a t t h e r e i s no a s s e r t i o n i n the sense t h a t health e f f e c t s do not occur, b u t merely a statement t h a t such e f f e c t s cannot c l e a r l y be proved with our present s t a t e of knowledge. I f s o , t h e money and e f f o r t spent on reducing emissions of sulphur dioxide i s counter-productive. Loosely coupled t o t h i s section a r e several technological papers about pol 1 u t a n t c o n t r o l .

This Page Intentionally Left Blank

175

MORTALITY AND A I R POLLUTION

-

LESSONS FROM STATISTICS

Frederick W. L i p f e r t Brookhaven National Laboratory, Upton, NY 11973

ABSTRACT

This paper reviews cross s e c t i o n a l s t u d i e s which attempt to l i n k p e r s i s t e n t geographic

differences i n mortality rates with a i r pollution.

Some e a r l y

s t u d i e s are mentioned and d e t a i l e d r e s u l t s are given f o r seven major contemp o r a r y studies, two o f which are s t i l l in the p u b l i c a t i o n process.

Differences

among t h e s t u d i e s are discussed with regard t o s t a t i s t i c a l techniques, i n the r e s u l t s over time (1959-19741, sults.

trends

and i n t e r p r e t a t i o n and use o f the r e -

The a n a l y s i s concludes t h a t t h e r e a r e f a r too many problems w i t h t h i s

technique t o a l l o w c a u s a l i t y t o be f i r m l y established,

and thus the r e s u l t s

should n o t be used f o r c o s t b e n e f i t o r p o l i c y analysis.

INTRODUCTION Since the beginning o f the environmental movement, a t t e n t i o n has focused on p r o t e c t i o n o f human h e a l t h .

The a i r p o l l u t i o n episodes o f t h e 1 9 5 0 ' s and

1 9 6 0 ' s provided dramatic evidence o f man's s u s c e p t i b i l i t y to p o l l u t e d a i r ,

although these e f f e c t s were l a r g e l y unnoticed a t the time.

I n general,

the

e a r l y attempts a t a n a l y s i s o f these episodes were crude and incapable o f determining

which

specific

pollutant

was

associated

m o r t a l i t y r a t e s , since a l l p o l l u t a n t s tend to show d u r i n g an episode.

with

the

increased

elevated concentrations

Subsequent s t u d i e s o f time-varying p o l l u t i o n and m o r t a l i t y

have employed s o p h i s t i c a t e d time-series a n a l y s i s methods, r e s u l t i n g i n g r e a t e r s t a t i s t i c a l power and more d e f i n i t i v e conclusions. relate

only

causality.

to

the

timing o f

death,

However,

and n o t n e c e s s a r i l y

these studies to

fundamental

I t has l o n g been assumed t h a t o n l y t h e f r a g i l e p o r t i o n o f t h e

p o p u l a t i o n i s a t r i s k from acute a i r p o l l u t i o n episodes,

and the degree o f

p r e m a t u r i t y o f death has never been s a t i s f a c t o r i l y determined.

Such studies,

even though they p r o v i d e q u a n t i t a t i v e r i s k f a c t o r s f o r acute exposures to s p e c i f i c p o l l u t a n t s , have n o t found f a v o r w i t h economists seeking dose-response f u n c t i o n s f o r use i n c o s t - b e n e f i t studies.

176

The cross-sectional approach, on the o t h e r hand, deals with geographic d i f f e r e n t i a l s which a r e assumed t o be s t a b l e in time, and t h u s i s intended t o r e l a t e t o chronic e f f e c t s , which should be a b e t t e r i n d i c a t o r of the basic s t a t e of health. Some cross-sectional studies have found r e l a t i v e l y l a r g e d i f f e r e n c e s i n mortality r a t e s associated w i t h a i r pollution. Various costb e n e f i t s t u d i e s have t h e n drawn on these findings, a l s o in p a r t because they have been c a s t in a form which i s convenient to use. For example, a recent OECD study ( r e f . 1) c i t e d the work of Lave and Seskin ( r e f . 2 ) in quantifying b e n e f i t s of sulphur oxides control. In so doing, OECD used a r e l a t i o n s h i p between t o t a l (crude) mortality r a t e and the minimum annual sulphate concentrat i o n , without regard to the cause of death, the age of the decedent, or the actual chronic exposure. However convenient, there a r e many flaws i n the cross-sectional studies in t h e l i t e r a t u r e and a l s o i n t h e way they have been used in policy-related studies. T h i s paper is intended to explore the f e a t u r e s and r e l i a b i l i t y of findings of the major cross-sectional s t u d i e s and t h e i r implications f o r policy. Some r e s u l t s from a new cross-sectional study based on 1970 mortality in U.S. metropolitan areas will a l s o be discussed.

REVIEW OF CROSS-SECTIONAL AIR POLLUTION-MORTALITY STUDIES The Early Studies The e a r l y s t u d i e s of geographic d i f f e r e n t i a l s were often qua1 i t a t i v e i n nature. Dust-fall s t a t i s t i c s were sometimes used as the measure of a i r pollut i o n ( r e f . 3 ) o r , in some c a s e s , s o l i d fuel usage r a t e s ( r e f . 4 ) . Most of these s t u d i e s focused on r e s p i r a t o r y - r e l a t e d causes of death, and some of them attempted to control f o r smoking habits. The most r e l i a b l e conclusion was t h a t there was an urban-rural g r a d i e n t i n m o r t a l i t y ( i n B r i t a i n ) f o r c e r t a i n causes of death, even accounting f o r smoking ( r e f . 5 ) . In the U.S., Winkelstein and h i s co-workers went a step f u r t h e r i n t h e i r analysis' of various causes of death in E r i e County ( B u f f a l o ) , New York ( r e f s . 6-9). They found a highly s i g n i f i c a n t association between t o t a l suspended p a r t i c u l a t e s (TSP) measured from J u l y 1961 t o January 1963 and t o t a l mortality from 1959-61, f o r white males and females. Such a r e l a t i o n s h i p was not found f o r s u l p h u r oxides, a1 though a r e l a t i v e l y crude measuring technique (lead sulphation candles) was used. The association w i t h p a r t i c u l a t e s was a l s o shown t o hold f o r stomach cancer, chronic r e s p i r a t o r y disease (males), and h e a r t Winkelstein's s t u d i e s did not control f o r d i s e a s e , b u t not f o r lung cancer. smoking and used only two broad age groups. However, Finch and Morris ( r e f . 10) reanalyzed t h e Winkelstein data using the actual ages of the decedents (obtained from death c e r t i f i c a t e s ) and e s s e n t i a l l y confirmed the e a r l i e r

findings.

A l a t e r paper by Winkelstein and Kantor ( r e f . 11) discounted the

p o s s i b i l i t y o f smoking h a b i t s as a confounding f a c t o r , and a l s o showed a r e l a t i o n s h i p between r e s p i r a t o r y symptoms and TSP f o r females.

I t i s important to

note t h a t the lowest mean TSP l e v e l i n t h i s study was 79pg/m3, s l i g h t l y above t h e U.S.

primary standard; t h e h i g h e s t annual mean was about 2 4 O p g l d .

Thus,

t h i s group o f s t u d i e s i s n o t u s e f u l w i t h regard t o questions concerning the presence o f n o - e f f e c t thresholds below the U.S. standard. Zeidberg and h i s colleagues conducted an extensive i n t r a - u r b a n cross-sectiona l study i n the N a s h v i l l e , TN area from 1949 t o 1960 ( r e f . 12). c o n t r o l l e d f o r age, race, sex, tion.

The study was

economic c l a s s , b u t n o t f o r smoking o r occupa-

For the middle c l a s s , an a s s o c i a t i o n was shown f o r females between var-

ious h e a r t disease c a t e g o r i e s and " s o i l i n g , " s i m i l a r t o " B r i t i s h smoke."

I n general,

an index o f p a r t i c u l a t e matter

t h i s a s s o c i a t i o n was n o t seen f o r

males ( p o s s i b l e confounding due to occupation o r smoking?), and was stronger f o r nonwhites than f o r whites. Contemporary Cross-sectional Studies The f o l l o w i n g t a b l e s describe seven more r e c e n t studies,

a l l o f A i c h used

mu1 t i p l e r e g r e s s i o n techniques i n a v a r i e t y o f d i f f e r e n t ways. coefficient*

The regression

r e l a t i n g changes i n m o r t a l i t y r a t e to changes i n ambient a i r

q u a l i t y i s t h e parameter d e s i r e d by the economist f o r use i n c o s t - b e n e f i t studies. able,

and,

However,

i n most s t u d i e s the c o e f f i c i e n t s tend to be h i g h l y v a r i -

i n any event,

a s t a t i s t i c a l l y s i g n i f i c a n t coefficient i s not a

guarantee o f causal i t y . Taken as a group, the seven s t u d i e s support the f o l l o w i n g conclusions: 0

There i s no one "model" o r group o f v a r i a b l e s t h a t uniquely "explains"

t h e U.S.

geographic d i s t r i b u t i o n o f m o r t a l i t y r a t e s ( h i g h e r i n t h e East and

South).

For age- o r d i s e a s e - s p e c i f i c r a t e s , t h i s problem i s more severe.

0

I n general,

as more n o n - p o l l u t i o n v a r i a b l e s are included, the s i g n i f i -

cance o f the p o l l u t i o n v a r i a b l e s drops. e f f e c t i n t h i s regard.

No one v a r i a b l e has an overwhelming

Since as a r u l e , the standard e r r o r s o f the p o l l u t i o n

v a r i a b l e s are n o t g r e a t l y i n f l a t e d when the models are expanded to i n c l u d e new ( n o n - p o l l u t i o n ) v a r i a b l e s , t h i s appears to be an instance o f p o l l u t i o n serving as a surrogate v a r i a b l e r a t h e r than a case o f m u l t i c o l l i n e a r i t y per se.

* I n d i s c u s s i n g these r e s u l t s , the term " s i g n i f i c a n t " r e f e r s to a regression c o e f f i c i e n t w i t h l e s s than 5% chance o f being zero.

178

Table 1 Synopses o f Contemporary Cross-Sectional

Studies

Lave and Seskin (Ref. 2 ) 1. 1 9 M M i Analyses 117 SMSA's, 1960 h 1961: Crude ( t o t a l ) , age-adjusted, by broad age M o r t a l i t y Data: group (0-14, 15-44, 45-64, 65+), by r a c e and sax. by cause o f death. A i r Q u a l i t y Data: 1957-61, c e n t r a l c j t y observations; min, mean, max TSP. SO; ( o n l y 58 v a l i d s i t e s f o r SOa).* Other Variables .%3 5 , .%nonwhite, .% w i t h incomes <$3000, p o p u l a t i o n density, log of B a s i c Model : SMSA population. Occupation, h o m heating, and c l i m a t e v a r i a b l e s ; s u i c i d e and venereal Variables i n Other d isea% rates. Models Tested: Findings: min SO: and mean TSP were s i g n i f i c a n t w i t h t h e b a s i c model, but o n l y ( 1 ) Total M o r t a l i t v : TSP was s i g n i f i c a n t w i t h occupation v a r i a b l e s and n e i t h e r was (crude o r a d j u i t e d ) s i g n i f i c a n t w i t h t h e home-heating f u e l model. S i g n i f i c a n t Associations By Age Group: mean TSF' : age 15-44, 45-64. 65+ ( b a s i c model, a l I causes) min : age 45-64, 65+ mean TSP : nonwhite &Race, Sex: m i n SO; : females By Cause o f death: mean TSP : TE a l l ages, b a s i c min : a l l cancers, dig. cancer, h e a r t disease model w i t h occupations mean TSP : TE, asthma : h e a r t disease min 4mean TSP : none w i t h home h e a t i n g fuel min SOi : h e a r t disease A.

'Results f o r min SO; a r e i n v a l i d s i n c e about h a l f t h e q u a r t e r l y composite samples r a t h e r than t h e minimum of a r t i f a c t r a i s e s t h e min SOZ value f o r those c i t i e s by about R 2 I s d r a m a t i c a l l y increased when occupational o r h e a t i n g w i t h both s e t s of a d d i t i o n a l v a r i a b l e s , bath p o l l u t a n t s negat ive.

2. 1%9 Analyses Mortality Data:

observations were t h e minimum o f 4 26 bi-weekly samples. T h i s sampling a f a c t o r o f 2. v a r i a b l e s were added t o Lasic model; l o s t s i g n i f i c a n c e and SOZ was o f t e n

1969 m o r t a l i t y f o r 112 SMSA's: crude, age-adjusted, by broad age groups (0-14. 15-44, 45-64, 65+), by r a c e and SEX. 1969 c e n t r a l c i t y observations; min, mean, max, SO; and TSP. same basic mcdel as 1960-61; I n t e r p o l a t e d p o p u l a t i o n and socioeconomic data; no a l t e r n a t i v e m d e l s except non-linear p o l l u t a n t s p e c i f Ications. S l q n l f i c a n t Associations

A i r Quality Data: Other Variables:

F I n d ings:

mean TS? both crude and age-adjusted mortal i t y min mean TSE : age 15-44, 65+ (except males) : 65+ min (3) By Race, Sex: mean T y : a l I race-sex groups min Sqi : nonwhite o n l y ( 4 ) Non-linear p o l l u t a n t s : mean TSP : mld-range values more important ( t o t a l mortality) mln 504 : h i g h values more important colents: The a i r q u a l i t y data used a r e more v a l i d than f o r 1960, but a l t e r n a t i v e m d e l s were not e x t e n s i v e l y t e s t e d w i t h t h i s data set, making it impossible t o evaiuate t h e e x t e n t of u n d e r s p e c i f i c a t i o n i n t h e same manner as w i t h t h e 1960 data.

(1)

Total Mortallty:

(2)

By Age Group:

8. Chappie and Lave Mortality Data:

A i r Qua1lty Data:

Mher Variables: F Indinqs: ( 1 ) Total Mortality:

-

(Ref.

13) 104 SMSA's f o r 1975 f o r t o t a l and "nontraumatic" deaths. Separate r e g r e s s i o n s f o r c i t i e s and counties. 1973-75 averages f o r min, mean, max S64, and TSP ( c e n t r a l c i t y observations). same basic model as Lave and Seskin, p l u s a l c o h o l and tobacco expenditure, education, income, occupation, diet, medical care var i a b I8s. With b a s i c model f o r t o t a l m r t a i l t y , mean TSP was n o t s i g n i f l c a n t , min SO= was more s i g n i f i c a n t than i n 1960 and 1969 d a t a sets; mean 5044 was more s i g n i f i c a n t than min SO;.

179

Table 1 ( c o n t ' d ) Synopses o f Contemporary Cross-Sectional 8.

(2)

Studies

Chapple and Lave cont. Changes t o P o l l u t i o n C o e f f i c i e n t s ' Smking Medlcal educ. diet care

E f f e c t s of other v a r i a b I es ( t o t a l mortality):

6 alcohol mean

505

mean TSP

+

-

-

nil

-

'nil

nil

OCC.

-

collents:

e4

The c o e f f i c i e n t s were w c h l a r g e r r e l a t i v e to t h e 1969 r e g r e s s i o n s which i s unexplained s i n c e t h e mean SO; v a l w has decreased. T h i s may be r e l a t e d t o t h e use o f intracensal p o p u l a t l o n data; e r r o r s c o u l d be associated w i t h p o l l u t i o n through s e l e c t i v e m i g r a t i o n away fran i n d u s t r i a l c i t i e s n o t r e f l e c t e d i n t h e p o p u l a t i o n estimates. Ad hoc s p e c i f i c a t i o n s were used throughout t h e study r a t h e r than searching f o r t h e best specification. The smoking v a r i a b l e was o f t e n n o n - s i g n i f i c a n t and negative. presumably due t o e r r o r s i n measurement ( s e l f - r e p o r t e d d o l l a r s a l e s f i g u r e s were used, by %SA, w i t h no c o r r e c t i o n s for p r i c e d i f f e r e n c e s per u n i t OT t a x d l f f e r e n c e s c r e a t i n g I n t e r - a r e a t r a n s f e r s ) . The repeated use of minimum mean, and maximum p o l l u t i o n v a r l a b l e s c r e a t e s confusion and has no physical mean 1 ng.

*+

i n d i c a t e s t h a t i n c l u d i n g t h e v a r i a b l e increased t h e c o e f f i c i e n t ;

-

i n d i c a t e s a decrease.

................................................................................................. C. Mendelsohn and Or& MCNIailty Data:

A i r Quality Data:

Other Variables:

F 1n d 1ngs:

(Ref. 14) E n t i r e US, grouped i n t o 404 county groups by race, sex. and broad age 1-4, 5-17, 18-24, 25-44, 45-64, 65+), f o r 1970 deaths by groups (0-1, iI I ness. Mlssing loca1974, a v a i l a b l e data f o r SOz, S.O ,; TSP. NOz. CO, t i o n s were f i l l e d by i n t e r p o l a t i o n . 4 e * . education*. r e l a t i v e Incane*, m a r i t a l * and f a m i l y status, populat l o n density, c l i m a t e , r e g i o n a l dummy v a r i a b l e , n e t mlgration, housing, unemployment. *These v a r i a b l e s were s u p p l i e d both f o r t h e e n t i r e county group as a whole and f o r i n d i v i d u a l age, race. sex c e l l s w i t h i n t h e group. was t h e most important p o l l u t i o n v a r i a b l e and was s i g n i f i c a n t f o r a i l ages above 18, w h i t e males and females. CO was s i g n i f i c a n t fran age 25 t o 64. male and female; o t h e r p o l l u t a n t s were o f t e n negative. Use o f (*I c e l I - s p e c i f i c v a r i a b l e s d i d n o t improve regressions. Family and m a r i t a l v a r l a b l e s were Important.

q. "5.

k t s : T h l s study i s to be canmended i n i t s search f o r a meaningful s p e c l f l c a t i o n , which u n f o r t u n a t e l y d i d n o t Include smoking, alcohol, or d i e t factors. It i s s e r i o u s l y flawed i n t h e use of t h e a l r q u a l i t y data, which were p o s t mortem and p o o r l y matched to t h e r m r t a i i t y data. E r r o r s due to i n t e r p o l a t i o n a r e p o t e n t i a l l y s e r i o u s ; a subset o f t h e county groups having v a l i d a i r q u a l i t y d a t a should have been analyzed separately. Note: t h e R2 values published i n t h i s paper have been found to be i n e r r o r ( t o o large) ( r e f 15).

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

0. Crocker. Crt a l Mortality Data: A i r Quallty Data: Other Varlables:

Findings:

(Ref.

16) 60 ( c e n t r a l ) c l t i e s for 1970, by cause of death. 1970 TSP, 1970 SOz, 1969 NO2. nonwhite, median age, education, cllmate, c i g a r e t t e sales, d i e t a r y v a r l a b l e s , p o p u l a t i o n per roam, physlclans per c a p i t a (used i n a 2-stage procedure). TSP : s i g n i f i c a n t f o r pneumonia 502 : s i g n i f i c a n t f o r e a r l y i n f a n t disease : n e a r l y s i g n i f i c a n t (negative) f o r h e a r t disease and e a r l y I n f a n t dlsease

4

c lgarette sales : s l g n l f i c a n t f o r t o t a l mortal i t y . disease, b i r t h defects, and cancer.

vascular

disease,

heart

Corsnts: Lack o f s i g n i f i c a n c e of a i r p o l l u t i o n v a r l a b l e s may be due i n p a r t t o s u b s t a n t i a l e r r o r s i n t h e d a t a base, I n c l u d i n g I n d l v l d u a i c i t i e s f o r TSP and SO2 and t h e e n t l r e s e t f o r NO ( i n v a l i d measurement method). Although t h i s r e l a t i v e l y crude measure of c l g a r e t t e m k l n g was 8 u n d to be s l g n i f l c a n t for m s t causes o f death ( i n c l u d i n g h e a r t disease and cancer), t h e 2-stage procedure whlch Incorporated m a k i n g I n a n e g a t i v e sense i n t h e axpresslon f o r medical care s i g n l f l c a n t l y reduces t h e magnltude o f t h e r e s u l t .

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

180

Table 1 ( c o n t ' d ) SvnoDses o f Contemmrarv Cross-Sectional S t u d i e s

E. L i p f e r t (Ref. Mortality Data:

A i r Qua1ity

17-19)

Data:

Other Variables:

Findinqs:

1969-71:

Up to 189 c e n t r a l c i t i e s , 1969-71, by 10 year age group (0-1. 2-44, 45-84 by 10's. 85+) and cause o f death. 1959 t o t a l m r t a i i t y f o r up t o 97 c i t i e s . Matched f o r 1969-71, f o r SIT^, TSP, SO2*, Fe, Mn, k P * . 1955-62 data used w i t h 1959 m o r t a l i t y . % 2 65, ;I nonwhite, % w i t h f a m i l y incomes below poverty, adjusted c i g a r e t t e sales, b i r t h r a t e , b u s i n g age, education, population, p o p u l a t i o n change, p o p u l a t i o n density. TSP: s i g n i f i c a n t f o r t o t a l m o r t a l i t y , iI lness deaths, h e a r t disease; n o t s i g n i f i c a n t by age group.

s%. SO;

1959:

: never ( p o s i t i v e l y ) s i g n i f i c a n t BaP : n o t s i g n i f i c a n t Fe, Ih : s i g n i f i c a n t f o r t o t a l m r t a i i t y , i n f a n t s , ages above 55, cancer, lung cancer, resp. disease, h e a r t disease. c igarelte sales : s i g n i f i c a n t for t o t a l m o r t a l i t y , a i l cancers, lung cancer, most age groups except 65-74. Only h was s i g n i f i c a n t .

w t s : T h i s study went to some lengths to use t h e best a v a i l a b l e a i r q u a l i t y data, b u t suffered from incomplete data sets for b P and for a g e - s p e c i f i c death rates. hb attempts were-made to disaggregate by SEX. Separate regressions f a c o u n t i e s and s t a t e s showed t h a t t h e SO4 c o e f f i c i e n t tended to Increase w i t h t h e s i z e of t h e geographic area, u s i n g c e n t r a l c i t y a i r q u a l i t y throughout. *Data n o t a v a i l a b l e for a i l locations,

r e q u i r i n g use of subsets.

................................................................................................ F. L i p f e r t (Ref. 2 0 ) M o r t a l i t y Data: A i r @fa1 ity Data:

Other Variables:

Findings:

l i l WSA's f o r 1970, by sex and age (<65, -%5). 1969 Sd'4 and TSP from Lave and Seskin ( w i t h e r r o r s c o r r e c t e d ) ; 1975 Ozone'; 1969-71 Fe, Mn. V a r i a b l e t h r e s h o l d s tested, adjustments made for migration. Lave and Seskln's basic m d e l p l u s d i e t , d r i n k i n g water quality.* a d j u s t e d c i g a r e t t e sales, m i g r a t i o n , % o t h e r nonwhite ( o r i e n t a l 1, home h e a t i n g fuels. S a m r e g r e s s i o n s performed with a p r i o r i values s p e c i f i e d f o r age, race, smoking. TSP : s i g n i f i c a n t f o r t o t a l m r t a i i t y , h i g h values tend to be more important; g e n e r a l l y n o t s i g n i f i c a n t f o r age 1p5. v a r i a b l e r e s u l t s f o r age 6 5 . s4, : g e n e r a l l y n o t s i g n i f i c a n t f o r t o t a l m o r t a l i t y or age <65; v a r i a b l e r e s u l t s f o r age F65. : u s u a l l y s i g n i f i c a n t f o r t o t a l mortal ity.females <65. Fe. Ih : o n l y s i g n i f i c a n t f o r males L65.

w,

orone

c Igarelte sales : s l g n l f i c a n t f o r t o t a l and male m r t a i i t y . d r i n k i n g water quality : s i g n i f i c a n t f o r t o t a l and male m r t a i i t y ; females 565. Caents: T h i s study confirms L i p f e r t ' s e a r l i e r ( c l t y ) r e s u l t s , suggests t h a t t h e manganese r e s u l t s f o r c i t i e s were a s u r r o g a t e for occupational e f f e c t s , and suggests t h e need for f u r t h e r s t u d i e s o f ozone and d r i n k i n g water qua1 i t y . 'Data

not a v a i l a b l e f o r a i I locations,

r e q u i r i n g use o f subsets.

As the geographic observational unit increases in size (from central c i t i e s to SMSA's, e t c ) , the sulphate coefficients tend to increase in magnitude and statistical significance when based on central c i t y air quality measurements. TSP coefficients, on the other hand, tend to decrease, as expected,

183

When sulphate is indicated to be significant, i t i s mainly associated with heart disease, n o t respiratory causes of death. No physiological hypothe s i s has been advanced f o r t h i s association, which was not found i n the early studies. Since there is abundant amonia present i n human airways for neutral i z a t i o n ( r e f . 211, even an acid aerosol would not likely behave differently than f i n e smoke particles i n the lung. T h i s tends to reinforce the suspicion t h a t the sulphate-mortal i t y associations indicated i n some studies are spurious. Note t h a t associations of cancer mortail i t y with pollution measurements of the same time period are also suspect because of the latency periods of most cancers 0 Studies of this type are generally incapable of establishing h e t h e r a threshold is present o r , alternatively, whether a pollutant has a linear e f f e c t a t a l l concentration levels. Since lifetime dose is the theoretically preferable variable, the response should be expressed i n terms of (concentration x years of exposure). The e a r l i e s t studies of chronic a i r pollution e f f e c t s in the U.S. had the v i r t u e of a relatively constant prior experience of a i r pollution levels. In many U.S. locations, natural gas began replacing coal f o r home heating i n the 1950's, w i t h a resulting drastic improvement i n ambient particulate levels. In the l a t e 1960's and early 1970's, clean a i r legislation began h a v i n g an e f f e c t on industrial and commercial pollution sources, such that SOx levels began t o improve i n many urban areas. Pollution changes related to mobile sources began i n the 1970's, b u t only carbon monoxide levels have shown much improvement. These improvements i n ambient a i r qua1 i t y mean t h a t studies based only on ca. 1970 data do n o t r e f l e c t the whole prior exposure history t h a t should r e l a t e to chronic health effects. I t is also useful to compare the behavior of the various regression coeffic i e n t s across time periods, i n order to formulate judgements regarding the evidence f o r causality. The Lave and Seskin model for SMSA's finds that the S O i c o e f f i c i e n t increases w i t h time (from 1960 t o 1969 to 19741, d u r i n g a period of generally improving a i r quality. Also, the S& coefficient i n creases i n magnitude as the size of the area surrounding the measuring s t a t i o n increases (from central c i t i e s to counties to SMSA's), as shown i n both L i p f e r t ' s work w i t h the 1969 data s e t s and some of the Chappie-Lave results. Both of these findings are counter-intuitive, a1 though i t could be argued that according t o conventional s t a t i s t i c a l tests, none of the coefficients are significantly different. However, these are not randomly drawn samples being tested here, b u t simply d i f f e r e n t mathematical treatments of essentially the same data set. Thus there i s a rationale to attempt to interpret the results o f these "numerical experiments"in a re1 ative context without rigorous regard f o r significance t e s t s , especially when rep1 icated i n several studies. 0

.

182 While the TSP c o e f f i c i e n t s decrease as the area surrounding the measuring s t a t i o n increases, as expected, the behavior o f these c o e f f i c i e n t s over time i s more puzzling.

Both L i p f e r t and Lave-Seskin found s u b s t a n t i a l l y l a r g e r TSP

c o e f f i c i e n t s ( f o r t o t a l m o r t a l i t y ) i n 1969-71 than i n 1959-60 ( L i p f e r t ' s 1959 c i t y c o e f f i c i e n t s were n o n - s i g n i f i c a n t ) , were s u b s t a n t i a l l y higher.

However,

even though the e a r l i e r TSP l e v e l s

they b o t h also showed t h a t t h e r e was

s l i g h t tendency f o r a b e t t e r r e g r e s s i o n when lagged a i r p o l l u t i o n v a r i a b l e s were used (measured some years previous to t h e m o r t a l i t y data).

Thus t h e

poorer r e s u l t s i n 1959-60 m i g h t be explained by the l a r g e changes i n TSP t h a t had occurred i n the mid-50's

and t h e f a c t t h a t same-year

s u r r o g a t e f o r long-term exposure. r e s u l t s o f Chappie and Lave.

TSP i s a poor

S i m i l a r reasoning appl i e s to the 1974

I f t h e proper TSP v a r i a b l e i s a lagged one o r a

long-term exposure average, then i t i s n o t s u r p r i s i n g t h a t 1974 TSP ( a p e r i o d o f much lower c o n c e n t r a t i o n s ) i s n o t associated w i t h 1974 m o r t a l i t y . A f u r t h e r problem area t h a t i s shown i n most o f the s t u d i e s i s the sensi-

t i v i t y o f t h e p o l l u t i o n c o e f f i c i e n t t o the model o r s p e c i f i c a t i o n employed. Sulphate c o e f f i c i e n t s are seen to depend on the presence o f other v a r i a b l e s i n t h e regression,

such as o t h e r a i r p o l l u t a n t s ,

l i f e s t y l e v a r i a b l e s such as smoking.

occupational

variables,

and

T h i s l a c k o f robustness leads t o the

s u s p i c i o n t h a t sulphate may be a c t i n g as a surrogate f o r some i l l - d e f i n e d c h a r a c t e r i s t i c s o f i n d u s t r i a l and urban populations, e s p e c i a l l y i n view o f the behavior o f t h e c o e f f i c i e n t s over t i m e and f o r d i f f e r i n g geographical areas. I n summary, the body o f cross-sectional

s t u d i e s suggest the f o l l o w i n g asso-

ciations with mortality: TSP

-

l i k e l y to be s i g n i f i c a n t o n l y a t h i g h concentrations;

lagged

a n a l y s i s should be used.

SO=, - l i k e l y a surrogate f o r i n d u s t r i a l i z a t i o n , u r b a n i z a t i o n e f f e c t s ; no p l a u s i b l e p h y s i o l o g i c a l hypothesis. Mn,Fe

-

probably surrogates f o r some occupational e f f e c t s associated w i t h heavy i n d u s t r y .

Ozone

-

c o n f l i c t i n g findings;

d e t a i l e d study hampered by r e s t r i c t i v e

data base. Concluding Discussion These cross-sectional

s t u d i e s are seen to p r e s e n t the policymaker w i t h some-

t h i n g o f a dilemma i n attempting to evaluate c h r o n i c a i r p o l l u t i o n e f f e c t s . The c o n f l i c t s include: 0

The e a r l y s t u d i e s f e a t u r e d h i g h p o l l u t i o n l e v e l s ( a t which a r e a l e f f e c t

i s more l i k e l y ) b u t crude measurement and a n a l y s i s techniques.

Even though we

may n o t be able to s a t i s f a c t o r i l y q u a n t i f y t h e i r f i n d i n g s , n e i t h e r can they be summarily discounted.

183 0 More recent s t u d i e s disagree on whether any p o l l u t a n t s a r e associated w i t h mortality and i f so, which species. Furthermore, threshold models cannot be re1 iably distinguished from 1 i n e a r , non-threshold models. 0 In the U.S., the population is becoming more mobile and pollution l e v e l s a r e decreasing w i t h time. This may i n d i c a t e t h a t the only hope f o r a definit i v e a n a l y s i s will involve e i t h e r s e l e c t e d non-migratory segments of the population, studied r e t r o s p e c t i v e l y over a long term, o r analyzing some of the older studies. W i t h regard t o c o s t - b e n e f i t a n a l y s i s , the use of response functions or c o e f f i c i e n t s from any of the cross-sectional s t u d i e s i s obviously fraught with g r e a t uncertainty. The reaction of most analysts to the d i v e r s i t y of r e s u l t s shown i n the t a b l e s has been to employ some s o r t of averaging technique i n order to e s t a b l i s h a "damage function" and its l i k e l y range of e r r o r . I t has been the aim of this paper t o show t h a t such a procedure should not be done without f u l l y considering in d e t a i l the conditions under which a s p e c i f i c c o e f f i c i e n t was generated and whether c a u s a l i t y r e a l l y has been established. I t has been shown t h a t regression c o e f f i c i e n t s f o r pollution are extremely s e n s i t i v e t o the model used, i.e., the o t h e r explanatory v a r i a b l e s in the s p e c i f i c a t i o n . Thus i t makes l i t t l e sense to average the c o e f f i c i e n t s from a sparse model (such a s Lave and Seskin) with those from a more complete s p e c i f i c a t i o n (such as L i p f e r t ) . Yet, t h i s is e s s e n t i a l l y what Morgan and his coworkers have done .(ref 27) and what the OECD study employed. Instead, a b e t t e r procedure is to decide a p r i o r i (on t h e o r e t i c a l grounds, i f necessary), on the required f e a t u r e s of a study and then to consider only those s t u d i e s which meet these c r i t e r i a . The appropriate range of e r r o r s f o r the c o e f f i c i e n t s i s then given by the s t a t i s t i c a l l i m i t s derived from the regression a n a l y s i s , plus any b i a s e s f o r the c o e f f i c i e n t per se which may be indicated by comparing studies. I f the a v a i l a b l e s t u d i e s f a i l t o meet these c r i t e r i a , the cost-benefit a n a l y s t i s faced w i t h the need to j u s t i f y c o s t s without considering chronic health b e n e f i t s a t a l l . He would then be assured t h a t any such b e n e f i t s t h a t were underestimated o r neglected would t i 1 t the balance f u r t h e r i n favor of the proposed control action.

Acknowledgments: T h i s was work performed under the auspices of the U.S. Department of Energy, c o n t r a c t no. DE-AC02-76CH00016. I thank Laine McCarthy and June Martino f o r cheerfully typing several versions of the manuscript. REFERENCES 1 Organization f o r Economic Cooperation and Development, The Costs and Benefits of Sulphur Oxides Control: A methodological Study, P a r i s , 1981. 2 L.B. Lave and E.P. Seskin, Air Pollution and Human Health, Johns Hopkins Press f o r Resources f o r the Future, 1978.

184

3 4 5

6

7 8 9 10

11 12 13 14 15 16

17 18 19 20

21 22

C.A. Mills and M. Mills-Porter, "Health Costs of Urban Air Pollution," Arch. Ind. Hygiene and Occ. Medicine 2(1948)614 P. Stocks, "Recent Epidemiological Studies of Lung Cancer Mortality, Cigar e t t e Smoking, and Air P o l l u t i o n , w i t h Discussion of a New Hypothesis of Causation", Br. J of Cancer ZO(1966) p . 595 See, f o r example, G. Dean, "Lung Cancer and Bronchitis i n Northern I r e l a n d , " B r i t i s h Medical Journal l(196611506, o r S.F. Buck and A.J. Wicken, "Models f o r Use i n Investigating the Risk of Mortality from Lung Cancer and Bronchitis," Applied S t a t i s t i c s 16(1967)185 , as referenced by Lave and Seskin ( 2 ) . W. Winkelstein, J r . , e t a l . , "The Relationship of Air Pollution and Economic S t a t u s t o Total Mortality and Selected Respiratory System Mortali t y in Men. I . Suspended P a r t i c u l a t e s , " Arch. Environ. Health 14(1967) 162-171. I b i d "11. Oxides of Sulfur," Arch. Environ. Health. 16(1968)401-5 S.M. Brown, S. Selvin, and W. Winkelstein, Jr., "The Association of Economic S t a t u s w i t h the Occurrence of Lung Cancer," Cancer 36(1975)19031911. W. Winkel stein, J r . and S. Kantor, "Stomach Cancer: P o s i t i v e Association w i t h Suspended P a r t i c u l a t e Air P o l l u t i o n , " Arch. Environ. Health 18(1969) 544-547. S.J. Finch and S.C. Morris, "Consistency of Reported Health Effects of Air Pollution ," Brookhaven National Laboratory, BNL-21808R (January 1977). W. Winkelstein, Jr. and S. Kantor, "Respiratory Symptoms and Air Pollution i n an Urban Population of the Northeastern United S t a t e s , " Arch. Environ. Heal t h 18(May 1969). L.D. Zeidberg, R.J.M. Horton, and E . Landau, "The Nashville Air Pollution Study: VI. Cardiovascular Disease Mortality in Relation t o Air Pollution," Arch. Environ Health 15(1967)225-235 M. Chappie and L. Lave, "The Health Effects of Air Pollution: A Reanalysis ,'I Journal of Urban Economics, forthcoming. R. Mendelsohn and G. Orcutt, "An Empirical Analysis of Air Pollution DoseResponse Curves," J . Env. Econ. and Management 6(1979)95-106. F.W. L i p f e r t , "Comment t o Robert Mendelsohn and Guy Orcutt Regarding: An Empirical Analysis of Air Pollution Dose Response Curves," submitted to J . Env. Econ. and Management. T.D. Crocker, W. Schulze, S-B. David, and A.V. Fneese, "Methods Development f o r Assessing Air Pollution Control Benefits, Vol I , Experiments i n the Economics of Air Pollution Epidemiology. EPA-600/5-79-001a (February 1979). F.W. L i p f e r t , " D i f f e r e n t i a l Mortality and the Efvironment: The Challenge of Mu1 t i c o l l i n e a r i t y i n Cross-Sectional S t u d i e s , Energy Systems and Pol icy 3 , 4(1980)367-400. F.W. L i p f e r t , " S t a t i s t i c a l Studies of Mortality and Air Pollution: Multiple Regression Analyses S t r a t i f i e d by Age Group," Science o f the Total Environment 15(1980 )103-122. F.W. L i p f e r t , " S t a t i s t i c a l Studies of Mortality and Air Pollution: Multiple Regression Analyses by Cause of Death," Science of the Total Environment 16(1980)165-183. F.W. L i p f e r t , "Air Pollution and Mortality: An SMSA-Based Analysis o f Additional Explanatory Variables," submitted t o J . Env. Econ. and Management (September 1981). T.V. Larson, D.S. Covert, R. Frank, and R.J. Charlson, "Ammoni; i n the Human Airways: Neutralization of Inspired Acid S u l f a t e Aerosols, Science 197(1977)121-3 M.G. Morgan, S.C. Morris, A.K. Meier, and D.L. Shenk, "A P r o b a b i l i s t i c Methodology f o r Estimating Air Pollution Health Effects from Coal-Fired Power P l a n t s , " Energy Systems and Pol i c y , 2(1978)287-309

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185

OPPOSITE EFFECTS OF INHALED CADMIUM MICROPARTICLES ON MOUSE SUSCEPTIBILITY TO AN AIRBORNE BACTERIAL AND AN AIRBORNE VIRAL INFECTION

G . BOULEY, C . CHAUMARD, A-M.

QUERO, F . GIRARD and C 1 . BOUDENE

L a b o r a t o i r e de Toxicologie-U 122 INSERM, and L a b o r a t o i r e de V i r o l o g i e , F a c u l t 6 de Pharmacie de 1 ' U n i v e r s i t C P a r i s - S u d , r u e J - B .

Clement, 92290 Chatenay-Malabry

(France)

ABSTRACT

An e x p e r i m e n t a l s t u d y on 489 mice i s r e p o r t e d . The t e s t a n i m a l s were submitted t o a s i n g l e 15-mn exposure t o atmosphere c o n t a i n i n g a b o u t 10 mg of cadmium microp a r t i c l e s (CdO) p e r m3 of a i r and t h e c o n t r o l s t o a n e q u i v a l e n t amount of aluminium m i c r o p a r t i c l e s (A1203). A t t h e 48th hour a f t e r e x p o s u r e s , t h e t e s t and cont r o l mice were s u b m i t t e d t o a b a c t e r i a l ( P a s t e u r e l l a m u l t o c i d a ) o r t o a v i r a l (Orthomyxovirus i n f l u e n z a e A) c h a l l e n g e , v i a t h e r e s p i r a t o r y r o u t e . The exposure t o cadmium s i g n i f i c a n t l y i n c r e a s e d t h e d e a t h - r a t e o f mice s u b m i t t e d t o t h e b a c t e r i a l challenge, but i t s i g n i f i c a n t l y decreased the death-rate following the v i r a l cha 1l e n g e .

INTRODUCTION The amounts of heavy m e t a l s i n t h e a i r of i n d u s t r i a l a r e a s i n c r e a s e s i n c e 1950 (ref.1).

I n p o l l u t e d atmospheres cadmium, one o f t h e most noxious of t h e s e heavy

m e t a l s f o r t h e r e s p i r a t o r y system, i s p r e s e n t mainly i n t h e form of p a r t i c l e s , e s p e c i a l l y of o x i d e (CdO) i n s o l u b l e i n w a t e r . We i n v e s t i g a t e d on t h e e f f e c t s of i n h a l e d cadmium m i c r o p a r t i c l e s on two e x p e r i m e n t a l a i r b o r n e i n f e c t i o n s of Mouse: p a s t e u r e l l o s i s and i n f l u e n z a .

MATERIAL AND METHODS A t o t a l of 489 s p e c i f i c pathogen f r e e mice w a s u s e d , 8 6 f o r b a c t e r i a l c h a l l e n g e

and 403 f o r v i r a l c h a l l e n g e . The body w e i g h t s of t e s t and c o n t r o l a n i m a l s d i d n o t s i g n i f i c a n t l y d i f f e r a t t h e b e g i n n i n g of e x p e r i m e n t s . The mice s u b m i t t e d t o m i c r o p a r t i c l e s i n h a l e d CdO o r A 1 0 ( m i c r o p a r t i c l e - c o n t r o l s ) i n a s i n g l e 15 mn2 3 e x p o s u r e ; t h e nose o f t h e a n i m a l s was t h e o n l y p a r t exposed t o t h e p o l l u t e d a t mospheres. The CdO and A1203 m i c r o p a r t i c l e s were g e n e r a t e d by two a p p a r a t u s b u i l t a c c o r d i n g t o Horstman e t a l ' s d e v i c e ( r e f . 2 ) :

d r o p l e t n u c l e i a e r o s o l i z e d from aqueous

186 s o l u t i o n s of cadmium a c e t a t e o r aluminium l a c t a t e ( i n e q u a l m o l a r i t i e s ) were pyrol y z e d a t 650°C. The p a r t i c l e s i z e w a s measured on electron-photomicrographies and a n a l y z e d a c c o r d i n g t o Raabe ( r e f . 3 ) : t h e count median d i a m e t e r (CMD) of CdO p a r t i c l e s was 0.33 prn and t h e g e o m e t r i c s t a n d a r d d e v i a t i o n of t h e d i s t r i b u t i o n 6

was g g i v i n g a mass median d i a m e t e r (MML)) of 1 . 7 9 p m ; t h e CMD of A 1 0 p a r t i c l e s 2 3 was 0 . 3 8 pm, w i t h 6 = 2 . 1 6 and MMD = 2 . 2 5 pin. The chemical d e t e r m i n a t i o n of p o l l u g t a n t l e v e l s i n a i r and i n t h e t r a c h e a - b r o n c h i a - l u n g a r e a ("lung") of mice was per2.12,

formed by a t o m i c a b s o r p t i o n s p e c t r o p h o t o m e t r y ; t h e cadmium amount i n a i r was 9.02

+ 1 . 9 7 mg of

Cd p e r m3 of a i r (mean

2

SD); t h e Cd l e v e l s i n t e s t mouse "lung"

1 . 1 8 p g p e r g of f r e s h "lung" immediatly a f t e r e x p o s u r e , and 3 . 0 6

was 5.52

2

0 . 3 7 p g two days l a t e r (immediatly b e f o r e i n f e c t i o u s c h a l l e n g e s ) ; t h e Cd l e v e l s i n c o n t r o l mice were 2 5 - f o l d lower than i n t e s t a n i m a l s . A i r b o r n e i n f e c t i o n s i n mice were provoked through i n h a l a t i o n of atmospheres c o n t a i n i n g b a c t e r i a l o r v i r a l a g e n t s d i s p e r s e d i n f i n e d r o p l e t s . These i n f e c t i o u s c h a l l e n g e s were performed a t t h e 48th hour a f t e r a s i n g l e s h o r t exposure t o microp a r t i c l e s . B a c t e r i a l i n f e c t i o n w a s provoked by one l e t h a l dose 50% (LD-50) of a P a s t e u r e l l a m u l t o c i d a s t r a i n ( L B 4203), u s i n g H e n d e r s o n ' s a p p a r a t u s ( r e f . 4 ) ; t h e t e c h n i c a l p r o c e d u r e was d e t a i l e d e l s e w h e r e ( r e f . 5 ) . V i r a l c h a l l e n g e used one LD-50 of a n Orthomyxovirus i n f l u e n z a e s t r a i n (APR 8 H N ) and was performed a c c o r d i n g 1 1 t o B r e d o n ' s p r o c e d u r e ( r e f . 6 ) . Animals were observed f o r 1 7 days and t h e d e a t h r a t e of mice was d e t e r m i n e d . The e x p e r i m e n t s were conducted i n random o r d e r and t h e m o r t a l i t y of c o n t r o l and t e s t a n i m a l s was compared by t h e P e a r s o n ' s c h i - s q u a r e test

2

(XI.

RESULTS Table 1 shows t h a t , i n o u r e x p e r i m e n t a l c o n d i t i o n s , cadmium a l o n e was n o t l e t h a l (group 1 ) ; however when cadmium m i c r o p a r t i c l e s were a s s o c i a t e d w i t h a i r b o r n e b a c t e r i a l i n f e c t i o n ( g r o u p 4 ) , t h e d e a t h - r a t e of mice i n c r e a s e d v e r y much i n comp a r i s o n t o t h e c o r r e s p o n d i n g r a t e of o n l y i n f e c t e d mice (group 2 ) . A 1 0 micropar2 3 t i c l e s d i d n o t s i g n i f i c a n t l y modify t h e i n f e c t i o u s m o r t a l i t y (group 3 ) . TABLE 1

E f f e c t s of i n h a l e d CdO m i c r o p a r t i c l e s on t h e d e a t h - r a t e o f mice exposed t o a n a i r borne b a c t e r i a l i n f e c t i o n ( P . m u l t o c i d a )

*

Mouse t r e a t m e n t : 1-0d0 a l o n e Dead/ t o t a l : (% m o r t a l i t y )

0120 (0%)

2-Infection alone

3-A1 0 + i n f e c t . 2 3

4-CdO+infect.

10/22 (45%)

9/22 (41%)

22/22 (100%)

187 Table 2 shows t h a t , c o n t r a r i l y t o what we observed w i t h p a s t e u r e l l o s i s ,

the

d e a t h - r a t e of mice i n f e c t e d by i n f l u e n z a a f t e r exposure t o CdO m i c r o p a r t i c l e s (group 3 ) was s i g n i f i c a n t l y lower than i n A1203 exposed a n i m a l s ( g r o u p 2 ) o r than i n v i r u s - c o n t r o l s (group 1). TABLE 2 E f f e c t s of i n h a l e d CdO m i c r o p a r t i c l e s on t h e d e a t h - r a t e of mice exposed t o an a i r borne v i r a l i n f e c t i o n (0. i n f l u e n z a e A ) Mouse t r e a t m e n t :

1-Infection alone

2-A1 0 + i n f e c t i o n 2 3

3-CdO+infection

551138

671 132 (51%)

25/133 (19%)

Dead/ t o t a l : (% m o r t a l i t y )

(40%)

Statistical

x1,2,3=30.239 2

(p=3xlO-');

xz ,3=29. 858

ana 1y s i s :

( ~ = l x l O - ;~ )

C o a r s e l y , Cd exposure i n c r e a s e d decreased

twice

twice

x:,,=

3.238 (p=0.072);

x 21,

=14.43 5

(p=5xlO-') t h e d e a t h - r a t e by p a s t e u r e l l o s i s and

t h e d e a t h - r a t e by i n f l u e n z a .

DISCUSSION The enhanced s u s c e p t i b i l i t y of mice t o a i r b o r n e p a s t e u r e l l o s i s ,

f o l l o w i n g expo-

s u r e t o cadmium, i s e a s i l y e x p l a i n e d by t h e noxious e f f e c t s of t h i s heavy metal on n a t u r a l and a c q u i r e d immunity, p a r t i c u l a r l y i n t h e r e s p i r a t o r y system. I n t h e c a s e of n a t u r a l r e s i s t a n c e ,

t h e d e f e n s e mechanisms of t h e lower r e s p i r a t o r y t r a c t , p r i n -

c i p a l l y t h e a l v e o l a r macrophages, a r e impaired ( r e f s . 7 - 8 ) ;

t h i s impairment pro-

vokes a s l o w e r c l e a r a n c e o f i n h a l e d b a c t e r i a , a f t e r exposure t o Cd*

( r e f . 9 ) and

t o m i c r o p a r t i c u l a t e Cd ( r e f . 10). I n s p e c i f i c immunity, Cd++ i m p a i r s t h e a n t i b o d y production (refs.11-12);

on t h e o t h e r hand, Cd++ i n h i b i t s i n v i t r o t h e plasma

membrane r e c e p t o r s of mononuclear c e l l s ( i n c l u d i n g macrophages) f o r IgG immunog l o b u l i n s ( r e f . 1 3 ) and t h i s e f f e c t which d i s t u r b s p h a g o c y t o s i s of i n f e c t i o u s bact e r i a , i s a l s o observed w i t h Cd m i c r o p a r t i c l e s , i n v i t r o and i n v i v o ( r e f . 1 4 ) . A f t e r c h r o n i c o r a l exposure t o s o l u b l e cadmium, a d e c r e a s e i n mouse d e a t h - r a t e f o l l o w i n g i n t r a p e r i t o n e a l i n o c u l a t i o n of e n c e p h a l o m y o c a r d i t i s v i r u s , was f i r s t r e p o r t e d by Exon e t a l . ( r e f . 1 5 ) . We c o r r o b o r a t e t h i s f a c t , u s i n g r e s p i r a t o r y e x p o s u r e t o m i c r o p a r t i c u l a t e cadmium and t o i n f l u e n z a v i r u s . We c a n n o t y e t e x p l a i n t h i s p a r a d o x i c a l e f f e c t , though w e a r e s t u d y i n g cadmium i n f l u e n c e on v i r a l r e p l i c a t i o n i n v i t r o and i n v i v o , on i n v i v o i n t e r f e r o n p r o d u c t i o n , and on a n t i b o d y and c e l l - m e d i a t e d immunity of Mouse.

ACKNOWLEDGMENTS T h i s work was s u p p o r t e d by a g r a n t of INSERM &

M i n i s t e r e de 1'Environnement

e t du Cadre de V i e (programme " A i r , Eau, Amiante e t SantB")

188 REFERENCES M . B r i a t , i n M.M. B e n a r i e ( E d . ) , Atmospheric P o l l u t i o n 1978, E l s e v i e r , Amsterdam, 1978,pp.225-228. S . Horstman, W. B e r t l e y , E . Larson and E. Bingham, Arch. Environ. H l t h , 26

(1973) 75-77. O.G. Raabe, i n C.L. S a n d e r s e t a l . ( E d s . ) , Pulmonary T x i c o l o g y of R e s p i r a b l e ? P a r t i c l e s , T e c h n i c a l I n f o r m a t i o n C e n t e r ( E d . ) , U.S.Dep of Energy, 198O,pp.l-28 D.W. Henderson, J . Hyg. Cambridge, 50 (1952) 53-69. E . Azoulay, G. Bouley and M-C. Blayo, J . T o x i c o l . Environ. H l t h , 7 (1981) 873-

882. M. Bredon, I n f l u e n c e de l a fumee de t a b a c s u r l a r e s i s t a n c e d e s s o u r i s 1 c e r t a i n e s m a l a d i e s v i r a l e s , These 3e Cycle U n i v e r s i t e P a r i s - S u d , 1980. J.A. Graham, D.E. Gardner, M.D. Waters and D.L. C o f f i n , I n f e c t . Immun.,11

(1975) 1278-1283. A . D u b r e u i l , G. Bouley and C 1 . Boudene ,Scand. j . work e n v i r o n and h e a l t h ,

5 (1979) 211-216. D . E . Gardner, F . J . M j l l e r , J . W . I l l i n g and J . M . K i r t z , B u l l . e u r o p . P h y s i o p a t h . r e s p . , l 3 (1977) 157-174. 10 G . Bouley, A . D u b r e u i l , N . Despaux and C 1 . B o u d h e , Scand. j . work e n v i r o n and h e a l t h , 3 (1977) 116-121. 11 R . H . J o n e s , R . L . W i l l i a m s and A.M. J o n e s , Proceed. S O C . exp. B i o l . Med., 137

(1971) 1231-1236. 12 L.D.

Koller, J.H.

Exon and J.G. Roan, Proceed. SOC. exp. B i o l . Med., 151 (1976)

339-342. 13 J . G . Hadley, D.E. Gardner, D.L. C o f f i n and D . B . Menzel, J. R e t i c u l o e n d o t h . SOC. 22 (1977) 417-425. 14 H . Vo P h i , G. Bouley and C 1 . Boudene, C . R . Acad. S c i . P a r i s , 293(1981)697-700. 15 J . H . Exon, L.D. K o l l e r and N . I s s a c s o n - K e r k l i e t , Arch. Environ. H l t h , 3 4 (1979) 469-475.

189

GENETIC FACTORS AND ACUTE CARBON MONOXIDE INTOXICATION

Victor-Hugo DEMARIA PESCE",

Maurice STUPFEL*, A r t h u r PERRAMON"", P h i l i p p e FlfRAT"",

Veronique GOURLET',

Huguette THIERRY"

" I n s t i t u t N a t i o n a l de l a Sante e t de l a tiecherche MGdicale (INSERM), Groupe de Recherches s u r l e s MScanismes Physiopathologiques des Nuisances de 1 ' Environnernetit, 44, Chemin de Ronde, 78110, Le Vesinet, France.

""Institut

N a t i o n a l de l a Recherche Agronomique (INN), L a b o r a t o i r e

de Gen6tique F a c t o r i e l l e ,

ABSTRACT. LD12:12

78350, Jouy en Josas, France.

(L = 0600-1800;

L = 100 l u x ) synchronized, 5-10

grouped sinall l a b o r a t o r y v e r t e b r a t e s , were d u r i n g p a r t o f t h e L p e r i o d (0900-1130) exposed t o an acute carbon monoxide i n t o x i c a t i o n , r e s a l t i n g i n an o v e r a l l 50 % m o r t a l i t y . I n t e r s p e c i f i c and i n t e r s t r a i n d i f f e r e n c e s were found i n outbred and i n b r e d mice (CEA, C57B1, OFl), outbred r a t s (Sprague-Dawley,

Wistar),

guinea-pigs,

c h i c k s (R+, R-),

and Japanese q u a i l s . I n t h i s l a s t b i r d species, a g e n e t i c s e l e c t i o n produced two genotypes, one s e n s i t i v e and one r e s i s t a n t t o a carbon monoxide acilte i n t o x i c a t i o n .

INTRODUCTION. Carbon monoxide i s s t i l l a h e a l t h hazard f o r homes, f i r e f i g h t e r s , i n d u s t r y workers which causes thousands o f death per y e a r (10, 2 3 ) , and i t i s a l s o a p o t e n t i a l r i s k f o r p a t i e n t s w i t h c a r d i o v a s c u l a r disease

(2, 25). I t i s m o s t l y b e l i e v e d , s i n c e

Claude BERNARD, t h a t carbon monoxide i n t o x i c a t i o n r e s u l t s from t h e

C3 f i x a t i o n on hemoglobin ( 5 ) , though t h e importance o f i t s e f f e c t s

190 on r e s p i r a t o r y enzymes ( 6 ) i s debated. Moreover t h e r o l e o f g e n e t i c f a c t o r s has been evidenced i n o t h e r r e s p i r a t o r y c h a l l e n g e s and p a r t i c u l a r l y i n a c u t e h y p o x i a (11, 13, 19), w h i c h i s u s u a l l y cons i d e r e d as t h e consequence o f an exposure t o h i g h c o n c e n t r a t i o n s o f carbon monoxide. I t i s t h i s a s p e c t o f g e n e t i c v a r i a t i o n s i n carbon monoxide t o x i c i t y t h a t we have e x p e r i m e n t a l l y i n v e s t i g a t e d (20, 2 1 ) . C o n s i d e r i n g t h e t o x i c i t y o f carbon monoxide,the

acute e f f e c t s

o f h i g h c o n c e n t r a t i o n s o f t h i s gas have t o be s t u d i e d on animal models w h i c h advantages and l i m i t s have been d i s c u s s e d elsewhere

(13). Two k i n d s o f e x p e r j m e n t a l processes were used t o i n v e s t i g a t e p o s s i b l e g e n e t i c d i f f e r e n c e s . The f i r s t one was t o t e s t t h e l e t h a l i t y o f an a c u t e CO t o x i c i t y i n d i f f e r e n t s p e c i e s and s e v e r a l s t r a i n s

o f small l a b o r a t o r y v e r t e b r a t e s . The second one was t o t r y t o s e l e c t , i n a same species, two s t r a i n s , one s e n s i t i v e and one r e s i s t a n t t o an a c u t e carbon monoxide i n t o x i c a t i o n . F o r t h i s l a s t e x p e r i m e n t a t i o n Japanese q u a i l s were chosen because i t i s p o s s i b l e , w i t h t h i s b i r d species, t o g e t a new g e n e r a t i o n w i t h i n s i x weeks. ANIMALS AND METHODS. C o n v e n t i o n a l a l b i n o g u i n e a - p i g s , o u t b r e d OF1,

i n b r e d CBA and

C57B1, SPF ( s p e c i f i c pathogen f r e e ) n i c e , o u t b r e d Sprague-Dawley and Wistar, SPF,rats were i s s u e d from t h e Breeding Research Center o f Les Oncins ( S a i n t Germaiti s u r l ' A r D r e s l e , 69210, France). Kt and R- young c h i c k e n s w h i c h had been s e l e c t e d f o r a h i g h and l o w a d u l t

feed e f f i c i e n c y , and Japanese q u a i l s which had been s e l e c t e d f o r r e s i s t a n c e t o carbon monoxide a c u t e t o x i c i t y came f r o m t h e F a c t o r i a l Genetics Laboratory o f INRA. The a n i m a l s were, a c c o r d i n g t o s p e c i e s , housed i n separated rooms, which were a i r c o n d i t i o n e d ( t e m p e r a t u r e 20-21°C; 50-60 % ) and LD12:12

liuinidity

( L = 0600-1800 h r ) l i g h t e d w i t h 100 l u x . A l l

a n i m a l s were randomly d i s t r i b u t e d , species, s t r a i n and sex b e i n g separated, i n w i r e mesh cages of 2 s i z e s . I n t h e s m a l l e s t ones, mice were 10-11 grouped; i n t h e l a r g e s t ones, r a t s , g u i n e a - p i g s , q u a i l s , c h i c k s were 5-7 grouped. A s y n t h e t i c f o o d a p p r o p r i a t e t o t h e v a r i o u s species, and t a p w a t e r , were p r o v i d e d ad l i b i t u m . F o r t h e a c u t e i n t o x i c a t i o n , t h e w i r e mesh cages c o n t a i n i n g t h e a n i m a l s were e n c l o s e d i n a l u c i t e p a r a l l e l e p i p e d chamber. A r n i x t u r e

191 of 5.0 % carbon monoxide, 2 1 % oxygen, and 74

X

n i t r o g e n (Compagnie

F r a n q a i s e des P r o d u i t s Oxygenes) was f l u s h e d t h r o u g h t h i s chamber a t a r a t e of 75-120 l i k e r s p e r hour. Soda l i m e ( P r o l a b o , a n e s t h e s i a g r a d e ) was p l a c e d i n t h e b o t t o m of t h e chamber t o m a i n t a i n a l o w c o n c e n t r a t i o n o f carbon d i o x i d e (0.05-0.30

% ) . The atmosphere o f

t h e chamber was analyzed f o r carbon monoxide, c a r b o n d i o x i d e

(ONERA i n f r a r e d a n a l y s e r s ) and f o r oxygen ( V i a l m o n i t o r ) concent r a t i o n s . Carbon monoxide f l u s h i n g was stopped and t h e chamber was opened when i t appeared t h a t about 50 % o f t h e enclosed a n i mals had ceased b r e a t h i n g . Continuous r e c o r d i n g (Maxant r e c o r d e r ) shows t h a t i n s i d e t h e chamber, d u r i n g t h e i n t o x i c a t i o n , t h e t e m p e r a t u r e and h u m i d i t y ranges i i e r e r e s p e c t i v e l y 19-22°C and 84-100 %; t h e l i g h t i n g was 100-120 l u x . Because o f c i r c a d i a n v a r i a t i o n s i n s e n s i t i v i t y t o carbon moriox i d e i n t o x i c a t i o n ( 1 5 ) , a l l e x p e r i m e n t s were begun a t t h e same tiitie o f t h e day (0910-0920). S t a t i s t i c a l d i f f e r e n c e s were t e s t e d by F i s h e r analysis,or

5 test,

variances

chi-square t e s t i n g .

RESULTC,. T a b l e 1 shows t h e r e s u l t s o f d i f f e r e n t e x p e r i m e n t s performed i n one s t r a i n o f g u i n e a - p i g s , 3 s t r a i n s o f mice, 2 s t r a i n s o f r a t s , 2 s t r a i n s o f c h i c k s and 2 ( s e l e c t e d f o r CO s u r v i v a l ) s t r a i n s o f q u a i l s . Species, s t r a i n , sex, age, number o f a n i m a l s and t h e i r body w e i g h t s , a r e shown i n columns 1-6 o f t h e t a b l e . I n column 7 i s t h e p r o d u c t o f t h e l e n g t h o f t h e carbon monoxide exposure ( i n m i n u t e s ) by t h e pC0 ( i n t o r r ) , which was achieved when t h e o v e r d l l 50 % s u r v i v a l was reached. I n column 8 a r e t h e s u r v i v a l percentages o f t h e a n i m a l s o f each s p e c i e s , s t r a i n , and sex. When s e v e r a l r e s u l t s were obtained, t h e a r i t h m e t i c mean i s f o l l o w e d by i t s s t a n d a r d d e v i a t i o n (mean f SD). I n t e r s p e c i e s comparisons, made by a c l a s s i f i c a t i o n a c c o r d i n g t o t h e l e n g t h o f i n t o x i c a t i o n m u l t i p l i e d by pC0, g i v e a c l a s s i f i c a t i o n r a n g i n g f r o m small t o g r e a t CO s e n s i t i v i t y : g u i n e a - p i g s c mice c r a t s = c h i c k s < q u a i l s . When c o n s i d e r i n g s t r a i n and sex d i f f e r e n c e s t h e f o l l o w i n g d a t a a r e obtained :

192

SURVIVAL TO AN OVERALL 50 % LETHAL CARBON MONOXIDE CHALLENGE OF DIFFERENT

T a b l e 1.

S P E C I E S AND S T R A I N S OF SMALL LABORATORY VERTEBRATES. ( m e a n ? SD; n u m b e r of e x p e r i m e n t s b e t w e e n brackets)

-. :

SPECIES

GUINEAPIGS

YICE

STRAIrNS

:

SEX

:

A N I M A L S AGE NUMBERS WEIGHTS days: (9)

:

: :

: :

Conventional

: :

1. F

:’ 47f7

.

I.

57 59

: 354 f 6 9

:

CBA

: :

M F

: :

: :

93 78

:

:

C57El

i

1.

103 101

:

45’4

: 368f60

:

:

: LENGTH OF EXP. :

:

x END PCO x torr)

; (min. I. 1494

103(2)

19f1 15f2 19f2 16’2

: :

:

285 f 6 ( 3 )

1

47.37 55.93

1

:

.

SURVIVAL

:

:

10.75 24.36 65.05 67.35

:

103 102

27f2 2122

: :

: :

58.25 84.31

: :

61 62

: 351214

: :

: :

9.84 68.33

: 349f12

:

:

:

60 60

: 207* 8

:

:

35.00 91.67

: :

158 174

: 140f14 : 151f20

: :

: :

58.23 71.26

: :

25.00 33.07

OF1

:

ivl F

: :

SpragueDawley

: :

M F

:

: :

Wistar

: 14 : F

:

:

:

: :

: :

I :

:

:

:

RATS

:

Ls+

M F

:

QUAILS

:

Ls-

:

: M : : F :

79f3

: :

: 222i10

:

:

:

56f9 : :

124 127

: 134?23 : 142?20

:

:

158 f 22(4)

:

95 t 31(9)

193 I n mice, CBA o f b o t h sexes a r e s t a t i s t i c a l l y ( P <

0.01) l e s s

r e s i s t a n t t h a n C57B1 and OF1. A s e x - r e l a t e d d i f f e r e n c e i s noted i n OF1 where s u r v i v a l i s s t a t i s t i c a l l y ( P

(58.25

X)

< 0.001)

t h a n i n females (84.31 % ).

I n rats,a sex-related difference (P b o t h s t r a i n s . I n each sex,Sprague-Dauleys P

l e s s i n males

< 0.001)

i s noticed i n

<

a r e s i g n i f i c a n t l y (0.01

0.001) l e s s r e s i s t a n t t h a n W i s t s r s .

R t c h i c k s are s i g n i f i c a n t l y (P

< 0.001)

l e s s r e s i s t a n t than

R- chicks.

I n Japanese q u a i l s a s i g n i f i c a n t ( P < 0.001) d i f f e r e n c e i s observed between t h e s e l e c t e d r e s i s t a n t L s t and t h e s e l e c t e d s e n s i t i v e Ls- s t r a i n . I n each of t h i s s t r a i n , males a r e s l i g h t l y

P

<

0.05)

l e s s r e s i s t a n t t h a n females.

DISCUSSION.

The a f o r e m e n t i o n e d d a t a c o n f i r m s t h e d i s c r e p a n c i e s i n carbon monoxide a c u t e t o x i c i t y a c c o r d i n g t o t h e chosen animal model (1, 4, 14, 24).

I n a d d i t i o n i t p r o v e s t h a t , i n a same species, d i f f e r e n c e s

a r e o b t a i n e d a c c o r d i n g t o s t r a i n and sex. Several p h y s i o l o g i c a l and b i o c h e m i c a l f a c t o r s a r e i n v o l v e d i n t o t h e s e reporceci g e n e t i c d i f f e r e n c e s .

A few c o n c e r n v e n t i l a t i o n and

d i f f u s i o n w h i c h d e t e r m i n e t h e i n t a k e o f t h e i n h a l e d CO, o t h e r s c o n cern cardiac output which takes care o f i t s d i s t r i b u t i o n . Both t h e s e r e s p i r a t o r y and c i r c u l a t o r y parameters a r e g r o s s l y r e l a t e d t o body w e i g h t s (8, 16). To e x p l a i n t h e s e i n t e r and i n t r a s p e c i e s d i s c r e p a n c i e s i n carbon monoxide t o x i c i t y one must a l s o c o n s i d e r d i f f e r e n c e s i n COHb k i n e t i c s (7, 9, 2 1 ) , i n n e u r o v e g e t a t i v e r e a c t i o n s (12), and even i n r e s p i r a t o r y c i r c a d i a n and u l t r a d i a n rhythms (17, 22) o f t h e v a r i o u s phenotypes. It c a n be conceived t h a t t h e g e n e t i c s e l e c t i o n performed i n q u a i l s has developed one o r a few o f t h e p h y s i o l o g i c a l o r biochemical mechanisms c o n s i d e r e d above and r e s p o n s i b l e f o r r e s i s t a n c e o r s e n s i t i v i t y t o t h e a c u t e carbon monoxide c h a l l e n g e . M o r e o v e r , i f c a r b o n monoxide i n t o x i c a t i o n m i g h t be c o n s i d e r e d as a k i n d o f hypoxia, i t c a n be h y p o t h e s i z e d t h a t t h e here r e p o r t e d CO g e n e t i c s u r v i v a l d i f f e r e n c e s a r e s i m i l a r t o t h o s e w h i c h have

been r e p o r t e d i n e x p e r i m e n t a l a c u t e h y p o x i c h y p o x i a (3, 11, 12, 13, 23), and which a r e w e l l known i n h i g h and l o w a l t i t u d e r e s i d e n t s o f Andes and Himalaya.

194

T h e r e f o r e t h e here evidenced g e n e t i c d i s c r e p a n c i e s , i n s e v e r a l v e r t e b r a t e s species, i n s u r v i v a l t o a n a c u t e CO c h a l l e n g e , p o i n t

o u t t h e p o s s i b i l i t i e s o f such g e n e t i c d i f f e r e n c e s i n t h e human species. These g e n e t i c d i f f e r e n c e s i n s e n s i t i v i t y t o carbon monoxide c o u l d be o f i n t e r e s t t o e x p l a i n human i n t e r i n d i v i d u a l d i s c r e p a n c i e s o f c a r d i a c p a t h o l o g i c a l s e n s i t i v i t y o f smokers and m o r t a l i t y i n a i r p o l l u t i o n a c u t e episodes.

.

AC KNOWL EDGEIlE NTS 1Je acknowledge w i t h g r a t i t u d e t h e s k i l l f u l t e c h n i c a l a s s i s t a n c e of C h r i s t i a n LEMERCERRE, Jean-Louis M O N V O I S I N , Gerard COQUERELLE, and t h e t a l e n t e d s e c r e t a r i a l a s s i s t a n c e o f M i r e i l l e PAUCHARD.

REFERE NCE S

1. ALEXANDROV, N.P. Choice o f e x p e r i m e n t a l a n i m a l s f o r e l a b o r a t i o n o f s t a n d a r d s f o r carbon monoxide ( i n R u s s i a n ) . Gig. i S a n i t . , 1973, 11, 92-95.

2. ARONOW, K.S. E f f e c t o f carbon monoxide on c a r d i o v a s c u l a r d i s e a s e . P r e v e n t . bled., 1979, 8, 271-278. 3. BARTELS, H., BARTELS, R . , RATHSCHLAG-SCHAEFER, A.N.,

ROBBEL, H., LUODERS, S. A c c l i m a t i z a t i o n o f newborn r a t s and g u i n e a - p i g s t o 3000 t o 5000 m s i m u l a t e d a1 ti t u d e . Resp. P l i y s i o l , 1979,

.

375-389.

36,

4. CAMERON, J. Age and s p e c i e s d i f f e r e n c e s among r o d e n t s i n r e s i s t a n c e t o CO asphyxia. J . C e l l . Comp. P h y s i o l . , 1941, 18, 379-383. 5. COBURN, R.F. Mechanisms o f carbon monoxide t o x i c i t y . Prev. Med.,

1979,

8,

310-322.

6. GOLDBAUM, L.R., RAllIREZ, R.G., ABSALON, K.B. What i s t h e mechanism o f c a r b o n monoxide t o x i c i t y ? A v i a t . Space Env. Med.,

1975,

46,

1289-1291.

7. HOLLAND, A.B. R e a c t i o n r a t e s o f carbon monoxide and hemoglobin. N . Y . Acad. Sci., 1970, 154-171.

174,

8. KLEINMAN, L . I . , RADFORD, E. J r . V e n t i l a t i o n s t a n d a r d s f o r small mammals. J . Appl. P l i y s i o l . , 1965, 20, 113-116. I

9. KLIMISCH, H.J., CHEVALIER, H.J., HARKE, H.P.,

DONTENWILL, W. Uptake o f carbon monoxide i n b l o o d o f m i n i a t u r e p i g s and o t h e r mammals. T o x i c o l o g y , M75, 3, 301-310.

195

10. LARENG, L., FABRE, M. Place a c t u e l l e du gaz de v i l l e dans l e s causes d ' i n t o x i c a t i o n s aigugs par l ' o x y d e de carbone. Nouvel. Presse Med., 1981, 10, 371-372.

11. MERAT, P., STUPFEL, M., COQUERELLE, G., PERRAMON, A. Sex-linked dwarf gene and c h i c k s u r v i v a l t o acute hypoxia. Ann. Genet. s e l . anim., 1978, 10, 525-531. 12. MORDELET-DAMBRINE, !I., STUPFEL, M. Comparison i n guinea-pigs and i n r a t s o f t h e e f f e c t s o f vagotomy and o f a t r o p i n e on r e s p i r a t o r y r e s i s t a n c e m o d i f i c a t i o n s induced by an acute carbon monoxide o r n i t r o g e n hypoxia. Comp. Biochem. P h y s i o l . , 1979, 63A, 555-559. 13. PERRAMOW, A., MERAT, P., STUPFEL, M., MOUTET, J.P., MAGNIER, 1.1. Mise en evidence, chez l a c a i l l e japonaise, de d i f f e r e n c e s genetiques l o r s de l a s u r v i e 2 l ' h y p o x i e . C.R. Ac. S c i . , 1976, D, 1313-1315.

283,

14. SPENCER, T.D. E f f e c t s o f carbon monoxide on man and canaries. Ann. Occup. Hyg., 1961, 5, 231-240. 15. STUPFEL, M., IZAGNIER, M., ROMARY, F. Rythme c i r c a d i e n de 1 ' a c t i o n de 1 'oxyde de carbone sur 1 '&mission du gaz carbonique du Rat en groupe. C.R. Ac. Sci., 1973, 276, D, 1009-1012. 16. STUPFEL, FI. Choix des modsles animaux pour l ' e t u d e des nuisances r e s p i r a t o i r e s . S c i . Techn. Anim. Lab., 1976, 45-51.

1,

17. STUPFEL, I!., DAVERGNE, E l . , PERRANON, A., LEMERCERRE, C., GDURL;ET, V. Sythmes u l t r a d i e n s ( 5 < S C 70 minutes) r e s p i r a t o i r e s (VO , VCD ) de q u a t r e p e t i t s vertEbrEs u t i l i s e s pour l a rechercge 289, D, 675-678. b i o t k d i c a l e . C . R . Ac. Sci., 1979, -

18. STUPFEL, M., MORDELET-DAMBRINE, M., VAUZELLE, A., PERRAiqON, A. Animal models and acute and long-term carbon monoxide i n t o x i c a t i o n . Prevent. Med. 1979, 8, 333-343. ¶

19. STUPFEL, I l . , PERRAMON, A., MERAT, P., FAURE, J.M., DEMARIA PESCE, V.H., MASSE, H. I n t e r and i n t r a s p e c i e s g e n e t i c d i f f e r e n c e s i n surv i v a l t o an acute hypoxic challenge i n mice, r a t s , q u a i l s and chickens. Comp. Biochem. P h y s i o l . , 1979, 648, 317-323. ~

20. STUPFEL, M., DEMARIA PESCE, V.H., PERROT, A . Phenotypic d i f f e r e n c e s i n s u r v i v a l t o an experimental acute carbon monoxide i n t o x i c a t i o n . Environ. Res., 1980, 21, 207-216. 21. STUPFEL, M., MORDELET-DAMBRINE, M., VAUZELLE, A . COHb f o r m a t i o n and a c u t e carbon monoxide i n t o x i c a t i o n i n a d u l t male r a t s 17, and guinea-pigs. B u l l . Europ. Physiopath. Resp., 1981, 43-51. 22. STUPFEL, M., PERRAMON, A., GOURLET, V., THIERRY, H., LEMERCERRE, C., DAVERGNE, M . , M O N V O I S I N , J.L., DA SILVA, J. L i g h t - d a r k and s o c i e t a l s y n c h r o n i s a t i o n o f r e s p i r a t o r y and motor a c t i v i t i e s i n l a b o r a t o r y mice, r a t s , guinea-pigs and q u a i l s . Comp. Biochem. 265-274. P h y s i o l . , 1981,

E,

196

23. T E R R I L L , J . B . , MONTGOMERY, K . R . , REINHARDT, C.F. Toxic gases from f i r e s . Science, 1978, 200, 1343-1347. 24. THEODORE, J . , O ' D O N N E L L , R . D . , BACK, K . V . Toxicological evaluation o f carbon monoxide i n humans and o t h e r mammalian species. J . Occup. Med., 1971, 13, 242-255. 25. Forum : Workshop on carbon monoxide and cardiovascular d i s e a s e . Prevent. Ned., 1979, 8, 261-406.

197

WATER ANALOGUE MODEL ACHIEVES OPTIMAL DESIGN OF FURNACE FLUE GAS COLLECTION SYSTEM J. RIGARD and M. MILHE

NEYRTEC, Grenoble Division of Alsthom-Atlantique, Le Pont-de-Claix (France).

ABSTRACT Arc furnaces used for melting and refining steel generate large amounts of smoke and dust that can cause severe pollution in and around the furnace building unless a satisfactory depollution system is provided. This paper discusses a water analogue model study conducted at Neyrtec's Research & Test Centre t o design an efficient

furnace-pollution collection

system

in which

the gas

flow to

be

processed was optimized. The study showed that this flow could be 25-30 per cent lower than the value recommended by dust collection plant suppliers on the basis of standard design procedures. A fullscale collection system based on the design developed with the model has just been completed. The fullscale system confirmed the excellence of the collection efficiencies and the validity of the model results

.

1. INTRODUCTION Arc furnaces for melting and refining steel cause considerable pollution within the furnace building unless suitable means are provided to eliminate the fumes and smoke produced. Also, as this pollution is ultimately discharged to atmosphere, considerable inconvenience or damage is likely to be caused in the exterior environment.

Current

legislation

concerned

with

waste

gases

and

airborne

particulates in work areas requires furnace operators to restrict the amounts rejected to atmosphere. This means that pollutants must be collected at source and then suitably processed. Air purification equipment is expensive and savings much greater than the cost of a comprehensive design study may be achieved by careful design of the plant. This, at any rate, was the case of the study reported here, which relates to a 30-ton arc furnace initially discharging all gaseous and airborne

particulate

waste

outside

the

furnace

building.

The

study

was

comprehensive in that it involved (a) measurements within the plant to assist in setting up a scale-model and in designing the filter system, ( b ) a full-fledged water

analogue

model

(WAM)

investigation,

and

(c)

implementation

of

the

model-optimized design in the furnace building. The initial factory measurements, described in the next section, related to gas velocities and temperatures and photographic records showing how certain factors affect the upward motion of the warm furnace gases. Also measured in the factory were the

R ISS

flow and size

198 distribution of the solid particulates emitted. The WAM tests we conducted - the principles and essential results of which form the basis of this paper

-

led to the

optimal design of airborne waste collection and purification system and indicated the optimum amount of solids-laden gas to be processed per hour. As will be seen, recent fullscale implementation of the design thrown up by the model bore out the validity of the design. For comparison purposes, solids removal efficiencies

-

on

which the final design considerably improves - were initially estimated by dust collection plant suppliers on the basis of standard design procedures in the absence of an auxiliary burner as : 95 per cent efficiency at a gas flow of 340 000 Nm3/h, 50 per cent at 200 000 Nm3/h and 20 per cent at 100 000 Nm3/h.

2. DESCRIPTION OF ORIGINAL, PLANT AND IN SITU MEASUREMENTS The 30-ton arc furnace investigated (Fig. 1) does not comprise a flue-gas outlet port (the so-called fourth port) t o collect the gases as soon a s they are produced. The flue gases and dust thus rise directly to the top of the building. Most of the gas and smoke is discharged to atmosphere through the opening in the roof but a significant proportion flows along the opening (Fig. 2 ) ,

cools down and returns to

the floor where pollution and worker discomfort occurs in various parts of the building. To counter this pollution process a flue-gas collection and filtration system was needed and this could only be installed at roof level owing to the presence of the overhead crane which moves continually above the furnace. The aim of the measurements taken within the furnace building was (a) to time and (b) to characterize the various stages making up the furnace operating cycle. Times were as follows : charging (11 min), melting (108 min, including 7 5 min in which

oxygen

was

admitted),

refining

miscellaneous other operations ( 2 7

min),

(40

min),

discharging

(4

min)

yielding a total cycle time of

and 190

minutes. The miscellaneous other operations, which include for example electrode adjustment, skimming and furnace repairs, were assigned either to the charging stage (eg furnace repairs) or to the melting and oxygenation stage (eg electrode adjustment, skimming, etc.). The velocity of the gas rising to the roof was measured by taking photographs at various relatively-short intervals. The rise velocity varied from 1.5 to 3.5 m/s with a mean value (eg during the melting stage) of about 2.5-3.0 m/s. Temperatures recorded in the rising column of warm gas at electrode level fluctuated between 150 and 200°C with occasional values as high a s 25OoC during the oxygen admission

stage.

The fluctuation in temperature reflected

the varying

composition of the gas column which comprised successive volumes of hot gas each followed by a volume of cooler entrained air. The temperature above the furnace by the overhead crane varied between about 5OoC and a peak of occurred during oxygen admission.

about 60°C which

199

F i g . 1. View of a r c f u r n a c e modelled F i g . 2. Smoke a t r o o f l e v e l

The s i z e of t h e d u s t p a r t i c l e s produced, knowledge of which w a s mainly needed t o d e s i g n t h e f i l t e r , w a s measured by a n a l y s i n g samples of a i r a t c r a n e l e v e l d u r i n g the

various

100-600 mg/m3

furnace

operating

depending

stages.

Particle

concentration

on t h e s t a g e i n t h e c y c l e ,

50-75

and

was

typically

per cent

of

the

easy

to

p a r t i c l e s sampled were smaller t h a n 2 u m . The measurements and

photographs

taken

showed t h a t

would n o t

it

d e s i g n a n e f f i c i e n t d u s t c o l l e c t i o n system u n l e s s a n in-depth

be

s t u d y of t h e d e t a i l e d

phenomena was u n d e r t a k e n . P o i n t s r e q u i r i n g p a r t i c u l a r s t u d y were shown t o be ( a ) the

b e h a v i o u r of

"rebound" e f f e c t ,

t h e hot

gas

in

the

roof

region

and

the

associated

kinetic

( b ) t h e e x t e n t t o which t h e overhead c r a n e a f f e c t s t h e upward

p a t h of t h e g a s e s r i s i n g from t h e f u r n a c e , eg d u r i n g t h e c h a r g i n g and d i s c h a r g i n g stages,

and

( c ) t h e f e a s i b i l i t y of u s i n g t h e r o o f

region a s a

b u f f e r volume to

smooth o u t t h e i n s t a n t a n e o u s f l u c t u a t i o n s i n t h e r a t e of f l o w of t h e p o l l u t a n t s .

3. DESIGN OF COLLECTING HOOD USING A WATER ANALOGUE MODEL

3.1 P r i n c i p l e of w a t e r model s i m u l a t i o n , model and t e s t s The s t u d y of t h e d i f f u s i o n of g a s e o u s and p a r t i c u l a t e p o l l u t i o n d i s c h a r g e d i n t o the

atmosphere

almost

always

involves

the

difference

in

density

between

the

p o l l u t a n t s and t h e s u r r o u n d i n g a i r o r between d i f f e r e n t r e g i o n s of t h e a i r i t s e l f . These d e n s i t y d i f f e r e n c e s may be due e i t h e r t o d i f f e r e n c e s i n t e m p e r a t u r e o r t o d i f f e r e n c e s i n t h e t y p e of gas.

I t h a s been shown t h a t s u c h d e n s i t y d i f f e r e n c e s and

t h e r e s u l t i n g d i s p e r s i o n of t h e p o l l u t a n t c l o u d may be s i m u l a t e d w i t h a n a i r model and a l s o w i t h a water model

(ref.

1,2,3).

200

Long experience of atmospheric diffusion phenomena has stressed the advantages of adopting the water-model approach, especially when density effects have to be modelled. In addition, the fact that the kinematic viscosity of water is 10

-

15

times smaller than that of air means that WAM simulation of Reynolds number turbulence effects can be achieved with smaller models than would be possible when using a wind tunnel. WAM simulation also lends itself extremely well not only to qualitative flow tracing and visualization of diffusion phenomena but also to the quantitative measurement of pollutant dilution rates along the path of plumes such as the warm gas emitted by the furnace in the present investigation.

In a WAM simulation, a flow of warm gas whose density differs from that of ambient air is modelled by an appropriate aqueous solution and the ambient air is modelled by pure water. To simplify the test procedure, the model may be turned upside down

so

that gravity forces are exerted upwards rather than downwards. In

this upside-down configuration, which we adopted here, rising flows of warm gas are simulated by denser-than-water aqueous solutions that are emitted downwards, as shown in Figure 3 . We used a denser-than-water salt solution to simulate the warm pollutant upflow from the furnace and we chose the initial salt concentration so that the ratio of the densities of the pollutants and air (simulated by water) was complied with. Use of salt meant that the concentration of the pollution throughout the diffusion process could readily be determined by conductivity measurements. Had the model not been turned upside down, the warm rising plume would have had to be modelled by a lighter-than-water alcohol solution whose concentration at various points within the model would have been far more

difficult

to measure.

The

arrangement used thus made it possible to characterize pollutant dilution factors by conductivity probes linked to signal amplifiers and chart recorders. Accurate modelling is possible by applying a number of scaling laws involving density and momentum scales, Froude-Richardson similarity and a sufficient Reynolds number. The Richardson number Ri representing the ratio of inertia forces to thermal and gravity forces must be the same on the model as at fullscale and may be written as : R i = !?-.gD P

7

, with

Ri model / Ri fullscale

=

1

(1)

in which : p

= specific gravity of ambient air (or of pure water simulating air on the

model); Ap

=

difference between densities of warm gas and ambient air (or between salt solution and pure water);

g D

-

=

acceleration due to gravity (9.81 m/s2

=

characteristic dimension of fullscale geometry (represented by d for the

same on model and at fullscale);

model)

V = characteristic fullscale velocity (represented by v for the model).

201

I

F i g . 3 . a ) The r e a l s i t u a t i o n . b) Schematic of upside-down model. c ) View of model t e s t .

F i g . 4 . V i e w s of model. a ) M e l t i n g and o x y g e n a t i o n s t a g e s . b ) c h a r g i n g and r e p a i r s . c ) Skimming a n s d i s c h a r g i n g .

Most model t e s t s a r e based on a r e l a t i v e d e n s i t y s c a l e of u n i t y , t h a t i s , t h e r a t i o A P / P i s t h e same on t h e model a s a t f u l l s c a l e . A s t h e s c a l e of o u r model w a s

1 / 3 3 , t h e s c a l e s of a l l t h e v a r i a b l e s of i n t e r e s t were as f o l l o w s : L i n e a r model scale............................ Density s c a l e

(

Ap

/

p model)

(4)

S c a l e of volume flow, from

A

/ ( Ap / p fullscale)

......... ................. ( Z ) , (5) .........

V e l o c i t y s c a l e , from (l), ( 2 ) , T i m e s c a l e , from ( 2 ) ,

d/D =

(3)

V/V

t/T

=Alp

q / Q =A5/’=

1/33

(2)

=

1

(3)

=

1/5.75

(4)

=

1/5.75

(5)

1/6250

(6)

=

The model was d e s i g n e d t o p e r m i t s i m u l a t i o n of t h e m e l t i n g c y c l e , i n c l u d i n g t h e c h a r g i n g and d i s c h a r g i n g s t a g e s ( F i g .

4 ) . The model of t h e f u r n a c e b u i l d i n g was

e n t i r e l y b u i l t of P l e x i g l a s s o t h a t t h e f l o w c h a r a c t e r i s t i c s c o u l d be photographed. The c o l l e c t o r hood comprised a n a d j u s t a b l e - f l o w

s u c t i o n system t o remove t h e

p o l l u t i o n from t h e model, which c o u l d a l s o r e p r e s e n t t h e overhead c r a n e between t h e hood

and

the furnace.

202 V a r i o u s hood d e s i g n s were t e s t e d . Hood w i d t h s ranged from 8 t o 1 4 m and l e n g t h s from 1 0 t o 24 m. P r e l i m i n a r y t e s t s showed t h a t w i d t h s less t h a n 10-12 m p r e v e n t e d some of t h e g a s from b e i n g sucked o u t of t h e b u i l d i n g .

The main t e s t s were run

w i t h hood d e s i g n s 14 m wide because t h i s w a s t h e w i d t h of t h e b u i l d i n g and i t made i t e a s i e r t o s u p p o r t and f i t t h e hood i n t o t h e r o o f .

T e s t s were r u n f o r e a c h hood d e s i g n and s t a g e i n t h e f u r n a c e o p e r a t i n g c y c l e t o d e t e r m i n e t h e minimum f l o w t h r o u g h t h e hood t h a t was needed t o c o l l e c t a l l t h e f u r n a c e g a s and

particulates.

The

tests a l s o i n d i c a t e d

c o l l e c t i o n system ( i e t h e r a t i o of

the

efficiency

of

the

p o l l u t a n t s e m i t t e d by t h e model f u r n a c e t o

p o l l u t a n t s c o l l e c t e d ) when t h e hood f l o w was l e s s t h a n t h e optimum flow. Knowing t h e f u r n a c e o p e r a t i n g c h a r a c t e r i s t i c s and t h e d u r a t i o n of e a c h s t a g e i n t h e c y c l e , i t was a l s o p o s s i b l e t o assess t h e o v e r a l l c o l l e c t i o n e f f i c i e n c y i n terms of hood

flow.

3.2 T y p i c a l t e s t r e s u l t s F i g u r e s 5 and 6 a r e t y p i c a l of t h e r e s u l t s o b t a i n e d f o r t h e o p t i m a l hood f l o w and t h e c o l l e c t i o n e f f i c i e n c i e s a t lower f l o w s . T a b l e 1 shows t h e o p t i m a l f l o w s required

by

three

hood

designs during

the

four

main

stages

of

the

furnace

operating cycle. 3 T a b l e 1. Optimal f l o w s t h r o u g h t h r e e hood d e s i g n s , 1 0 Nm3/h DESIGN 1

STAGE

DESIGN 2

DESIGN 3

Charging

350

200

225

Melting

120

120

150

Oxygenation

300

250

290

Discharging

300

200

275

Optimal f l o w

350

250

290

Amongst a l l t h e hood d e s i g n s t e s t e d , Design 2 ( l e n g t h a b o u t 16 m) was shown t o I t was l a r g e enough t o c o l l e c t t h e p o l l u t a n t s d u r i n g t h e

be t h e most e f f i c i e n t .

c h a r g i n g and d i s c h a r g i n g s t a g e s d e s p i t e t h e p r e s e n c e of t h e overhead c r a n e and i t r e s t r i c t e d t h e d i f f u s i o n of smoke and fumes i n t h e working areas of t h e b u i l d i n g . T a b l e 1 (Design 2 ) shows t h a t t h e minimum f l o w needed t o c o l l e c t a l l p o l l u t i o n w a s about 250 000 Nm3/h, necessary

being

e f f i c i e n c y of each

stage,

procedures. possible study.

by

35

per

Design 2 , and

t h e f l o w of cent

greater.

assessed

compares

this

340 000 Nm3/h Figure

s t u d y were

t h a t was o r i g i n a l l y thought

shows

the

overall

collection

by i n t e g r a t i n g t h e i n d i v i d u a l e f f i c i e n c i e s of with

the

C o n s i d e r i n g t h e h i g h c o s t of t h e WAM

6

curve plant

appreciable

-

estimated of

by

t h i s kind,

several

times

standard

design

t h e s a v i n g s made the

cost

of

the

203

0.4 0.2

F i g . 5. D e t e r m i n a t i o n of hood e f f i c i e n c y : a ) & b ) D i s p e r s a l of plume i n model. c ) T y p i c a l p l o t of c o l l e c t i o n e f f i c i e n c y E v s f l o w r a t e Q ( l o 3 Nm3/h) t h r o u g h hood.

E

t 120

250

me1t ing b, charging c, discharging d, oxygenation

Fig. 6 . Hood-collection e f f i c i e n c y tests f o r each furnace operating stage. a ) Model test d u r i n g oxygenation. b ) S t a g e e f f i c i e n c i e s . c ) Average model e f f i c i e n c y o v e r whole cycle(*)and e f f i c i e n c y i n i t i a l l y e s t i m a t e d by s u p p l i e r s (0).

4 . FULLSCALE IMPLEMENTATION A

fullscale

developed

c o l l e c t i o n hood

on t h e model and a

was

constructed i n

250 000 Nm3/h

accordance

extractor

fan was

with

t h e design

installed.

The

f u l l s c a l e b e h a v i o u r e x a c t l y r e f l e c t e d t h e model behaviour in a l l r e s p e c t s . F i g u r e s

9 - 1 2 show t h e hood i n p o s i t i o n i n t h e f u r n a c e b u i l d i n g and F i g u r e s 8 and 9 show t h e e f f i c i e n c y of t h e g a s c o l l e c t i o n p r o c e s s . The smoke and fumes g i v e n o f f by t h e f u r n a c e a r e now no l o n g e r d i s p e r s e d i n t h e b u i l d i n g b u t are e n t i r e l y c o l l e c t e d by t h e hood where t h e y p a s s t h r o u g h f i l t e r s a t t h e end of t h e b u i l d i n g b e f o r e being r e j e c t e d t o atmosphere. The c o s t of t h e i n s i t u measurements t o d e v e l o p t h e model and t h e c o s t of r u n n i n g t h e a c t u a l model t e s t s were small compared w i t h ( a ) t h e s a v i n g s i n i n i t i a l o u t l a y t o c o n s t r u c t t h e hood system, and ( b ) t h e r e d u c t i o n i n operating costs

achieved

by minimizing

the

gas

flow

through

the

system.

204

Today the collection plant is running efficiently and has solved the operator's worrying air pollution problem as economically as possible.

Fig. 7 and Fig. 9

-

8. Hood in the furnace building at roof level.

12. Smoke collected in hood.

REFERENCES

1. L.CAUDRON, P.L VIOLLET : M6thodes et moyens d'6tude des panaches d'effluents rejet6s dans l'atmosphgre - EDF no 4 - 1 9 7 5 . 2. VADOT : Etude de la pollution industrielle par l'emploi d'une analogie hydraulique - Nuisances et Environnement no 2 4 . 3 . VADOT : Etude des retombees de particules solides, sur modgle hydraulique - 13 8me Colloque sur les atmosphsres pollu6es - Avril 1978.

205

FLUORIDE DEPOSlTION T4ROIJGFT PRECIPITATION AND LEAF LITTER Ib! A BOREAL

FOREST IY TEE V I C I N I T Y OF A PHOSPHORUS PLANT S . S . SIPHU

EIewfoundland F o r e s t %?search Centre, Canadian F o r e s t r y S e r v i c e , E w i r o m e n t Canada, St. cJohn’s, ?levfoundland, Canada.

A J C 5X8

A-ESTHACT S e s u l t s of s h o r t term n o n i t o r i n g of f l u o r i d e ( F ) d e p o s i t i o n i n s o i l humus through p r e c i p i t a t i o n and l e a f l T t t e r i n a b o r e a l f o r e s t i n the v i c i n i t y of phosphorus p l a n t , a r e described i n t h i s paper.

P

Regressional r e l a t i o n s h i p s of

F-deposition by t h e tv:o pa~thwayst o t h e d i s t a n c e f r o n t h e emission source a r e

also presented. The concentrati.ons of f l u o r i d e i n l e a f l i t t e r of s e v e r a l s p e c i e s and prec i p i t a t i o n and P, Ca, l , : ~ ,S amd ‘\rai n p r e c i p i t a t i o n only, a r e summarized.

‘he

average P-concentrations ranged Crom 930 t o 17 ppm i n s e v e r e l y and l i g h t l y danaged a r e a s r e s p e c t i v e l y . were 0.36 t o < 0 . 0 1 pprn.

Corresponding F-concentrations i n p r e c i p i % a t i o r

Fluoride d e p o s i t i o n i n s o i l humus v i a p r e c i p i t a t , i o n

was a t l e a s t 5 t i c e s g r e a t e r than through l e a f l i t t e r . c i p i t a t i o n ranged f r o n damape r e s p e c t i v e l y . !:gF/’na/year

F-input through pre-

3.43 t,o 0.15 kg/ha/year i n a r e a s of severe t o l i g h t

F--

Corresponding values from l e a f l i - t t e r were 0.72 t o 0.010

.

Estimates of t o t a l and a v a i l a b l e amounts of f l u o r i d e i n t h e upper 4 cm of s o i l h m x s were 57.0 t o 1 . 2 0 kg/ha and 1.20 t o 0.24 kg/ha i n a r e a s of severe and l i g h t damage r e s p e c t i v e l y .

The excessive concentrations of f l u o r i d e i n

s o i l humus d i d not appear t o c o n t r i b u t e towards t h e F-accumulation i n f o l i a g e . INTRODUCTION

F l u o r i d e s ( F ) emitted i n t h e atmosphere e v e n t u a l l y f i n d t h e i r way t o t e r r e s t r i a l and a q u a t i c r e c e p t o r s e i t h e r by a c t i v e a b s o r p t i o n b y p l a n t s or by a d s o r p t i o n on s u r f a c e s and washdown by p r e c i p i t a t i o n .

Ares (Re:.

1 ) concluded

i n h i s work on t h e f l u o r i d e budget for a c o a s t a l f l u o r i d e emission source t h a t a major n o r t i o n of f l u o r i d e s absorbed a n d incorporated i n t o t h e s o i l follow the l e a f l i t t e r pathway.

However, very l i t - t l e i s understood of t h e f a t e of

f l u o r i d e s once t h e s e a r e deposited on t h e s o i l s u r f a c e . Present i n v e s t i y a t i o n s were a p a r t of an imgact study of a nhosphorus p l a n t

206 i n :jewfoundland, Canada (47°26'?J,53O17'W).

The e x t e n t o f F-damage and

p a t t e r n s and l e v e l s of F-accumulation i n f o l i a g e were r e p o r t e d e a r l i e r ( R e f s .

2,2,4). The F-concentrations i n a i r for t h e a r e a from 1976 t o 1980 were r e p o r t e d by Sidhu (Ref. 5 ) .

This paper d e s c r i b e s t h e r e s u l t s of s h o r t term

monitoring of F-deposition i n s o i l humus v i a p r e c i p i t a t i o n and l e a f l i t t e r i n a b o r e a l f o r e s t under t h e i n f l u e n c e of emissions from a phosphorus p l a n t . VETHODS

The study a r e a was t h e same a s described by Sidhu ( R e f s . 3 , 5 ) . o f t h e a r e a i s c l a s s i f i e d a s b o r e a l (B.3'0,

The f o r e s t

Avalon, Newfoundland; Ref. 3 ) with

Abies balsamea ( L . ) I f i l l . (balsam f i r ) and Picea mariana (Mill.) BSP ( b l a c k spruce) a s dominant s p e c i e s .

Betula p a p y r i f e r a Marsh. (white b i r c h ) and

L a r i x l a r i c i n a [ Du Roi ) Koch ( l a r c h ) form a minor component i n f o r e s t s t a n d s of t h e study a r e a .

D e t a i l s of c l i m a t i c c o n d i t i o n s , v e g e t a t i o n and i n d u s t r i a l

emissions were published e a r l i e r ( R e f s .

4,5).

F i e l d sampling o f p r e c i p i t a t i o n Based on previous knowledge of t h e p a t t e r n and e x t e n t of F-damage t o v e g e t a t i o n and F-concentrations i n t h e a i r ( R e f s . 2,4,5),p r e c i p i t a t i o n samplers were l o c a t e d a t v a r i o u s d i s t a n c e s along a NE-transect from t h e emission source ( F i g . 1).

Fig. 1. Map showing t h e sampling l o c a t i o n s f o r l e a f l i t t e r (1 t o 15), r a i n water (2,4,6,10,15),and snow water (2,4,15). (X) i s t h e source of emission; Zones I - I V a r e t h e F-damage zones, Zone-I being t h e most damaged and. Zone-Iv t h e l e a s t damaged a r e a .

207 Five r a i n sampling s t a t i o n s were e s t a b l i s h e d on September 1, 1977 a t various d i s t a n c e s from t h e emission source ( F i g . 1, l o c a t i o n s 2,4,6,10,15).

A t each

s t a t i o n , r a i n was c o l l e c t e d i n p l a s t i c c y l i n d e r housed within a standard copper r a i n gauge. coating. period.

The s u r f a c e of t h e r a i n gauge was sprayed with a p l a s t i c

Rain water was c o l l e c t e d on t h e morning following each 24 h r a i n There were 8 samples c o l l e c t e d a t each s t a t i o n during t h e 30 day

monitoring p e r i o d .

In t h e f i e l d , t h e volume a s well a s amount of r a i n f a l l

was recorded and r a i n water was s t o r e d i n p l a s t i c b o t t l e s a t 4OC u n t i l l a b o r a t o r y analyses were completed.

The winds were from S-SW 547 of t h e times

during t h e sampling period. Snow samples were c o l l e c t e d a t s t a t i o n

2,4 and 1 5 ( F i g . 1) using Nipher

Shielded snow gauges l i n e d with polyethylene p l a s t i c bags from 29 January t o 1 0 March 1978.

The amount of snow water equivalent was recorded a f t e r each

snowfall and snow water c o l l e c t e d f o r l a b o r a t o r y a n a l y s i s .

Seven samples

were c o l l e c t e d a t each s t a t i o n during t h e monitoring period.

The winds were

from S-SW 72% of t h e times during t h e sampling p e r i o d . F i e l d sampling of l e a f l i t t e r Leaf l i t t e r of dominant t r e e s and shrubs was sampled a t 1 5 s i t e s ( F i g . 1 ) ;

3 s i t e s i n each o f t h e f o u r damage zones and 3 from an a r e a with no v i s i b l e F-damage t o v e g e t a t i o n . survey ( R e f s . 2 , 4 ) .

The damage zones were e s t a b l i s h e d by an e a r l i e r

Leaf l i t t e r was c o l l e c t e d i n square t r a p s (0.5 m x 0.5 m )

w i t h 1 0 ern high wooden w a l l s and bottoms of f i n e nylon screening.

Three t r a p s

were i n s t a l l e d for each s p e c i e s a t each sampling s i t e on June 1, 1977 and opera t e d until November, 1977.

The s p e c i e s a r e l i s t e d i n Table 2 .

The l i t t e r

t r a p s were checked a t 2 week i n t e r v a l s from June t o October and a t monthly i n t e r v a l s for t h e r e s t of t h e p e r i o d .

The l i t t e r from each box was c o l l e c t e d

s e p a r a t e l y , s o r t e d f o r s p e c i e s , weighed and d r i e d a t 7OoC f o r a t l e a s t 72 h. The d r i e d samples were weighed and ground t o p a s s through 40 mesh s i e v e . The ground samples were analysed for t o t a l f l u o r i d e s using a p o t e n t i o m e t r i c method used e a r l i e r by Sidhu ( R e f . 3 , 6 ) . HESULTS AND DISCUSSION Fluoride d e p o s i t i o n through u r e c i D i t a t i o n The results of monitoring of r a i n and snow and t h e i r chemical a n a l y s i s a r e summarized i n Table 1. The average pH of t h e r a i n and snow water v a r i e d from 6 . 2 t o 6 . 4 , s u b s t a n t i a l l y h i g h e r t h a n t h e pH 5.6 expected f o r p r e c i p i t a t i o n from unpolluted a r e a s .

The concentrations of f l u o r i d e (F), phosphorus (P) and

calcium ( C a ) i n r a i n a s well a s snow water were d i r e c t l y r e l a t e d t o t h e d i s t a n c e from t h e emission source, being maximum c l o s e s t t o and minimum f a r t h e s t from t h e source ( T a b l e 1). For example, average F, P and Ca-concentrations i n r a i n water were r e s p e c t i v e l y 0.28, 0.50 and 0.91 ppm a t 1 . 4 km and < 0.01 and 0.26

TABLE 1

Average concentrations of fluoride [ F- J arid selected cations in rain and snow water r?ear a phosphorus plant,, Lone: Harbour, Newfoundland. VE

I. T o t a l precipitation

-

3istance from s o u r c e (h)

5.E

8.0

129.6*(8.4-29.5)+

116.3( 5.8-29.9)

142 .?( 5.6-38.6 )

96.5(3.1-19.8)

77.0(1.1-17.0)

6.?( 6.2-6.5) 6.4(6.2-6.5)

6.3c6.2-6.5 ) 6.3( b .2-6.4 )

1.4

Parameter

10.3

IF.?

for the

sampling period: rain (mm; 1 to 30 September 1977)

(a)

(b )

127.5(5.8-38.'7)110.5:7.1-33.2)

snow water equivalent (mi; 29 Jan. to 10 Mar.,

1978)

-

-

98.6( 2.3-44.7)

11. pH precicita:ion (a) r a i n

(b)

snor; waTer

111. F-concentration (ppm) (a) rai? water ( b ) snow water 2 ( c ) air (ugF/dm /? days, Ref. 5 ) IV. F-deposition :hrough precipitation ( a ) gF/ha/monitoring period (i) rain (gF/ha/30 days) ( ii ) sp.ow ( gF/ha/40 days)

0.28( 0.11-0.58) 0.36(0.11-1.04)

6.4(6.3-6.'I )

-

h .2(h.1-6.4 )

-

G.3( 6.2-6.j) 6.2(6.1-6.1)

0.0?(0.03-0.14)0.@6(0.02-0.13) 0.03(0.02-0.0b) < 8.01(N.D-0.02) 0.04(N.D-0.12) 0.02( ': . D-0 . 0Y )

155.7

'75 .O

37.8

317.6 ?Ol.3

71.3 3.6

59.8 5'7. 5

2.4

18.6

36.3

( estimate )

39.1, ( estimate )

0.42 0.40 ( estimate )

0.28 0.31 ( est,lmatej

<

11.0 l4.>

( b ) Av. gF/ha/mm ?f precipitation

(i) rain water (ii) snow water

2.61 1.10

0.64

0.43

0.10 0.15 Con'utd

,

-

Distance frov s o u r c e (h)

Parameter

1.4

5.8

( c)

3.4? x 103

0.64 x 10'

e s t i m a t e d gF/ha/year based on a v e r a g e o f 1200 nun of p r e c i p i t a t i o n ( R e f . 5)

8.0

18.7

10. j

0 . 3 5 x I03 \ estirnaLe)

3.49 x 103 (esximate )

<

u.15 x 103

V. C a t i o n c o n c e n t r a t i o n (rum) of g r e c i p i t a t i o n :

(a ) Phosphorus c\Ji d

--

. (9.

e m

1

r l 0

I

00

??

00

-id

d-i

00

mr-

M M

. . oo -. . -

0

I r - I

0 0

d

d

0

r-

-- --

r -.m.

1

00

. .

I

00

0 0

d

toa

d

. .

00

0 PJ M (U

0.30( 0.08-0.79) 0.22(0.06-0.81)

-

m

I

L n l

0:

0

?

0

d

M

0

N

m

I

0 *

0

d

r i

0

d

4,

0

1.72(0.60-4.2) -

P O

. .

I 1 Lnn

00

-2

00

i

. -i.

1

r

00

00

m

01

I n l

-

-

u'

0

I

3

v \ I

-f

C'

-

d

0

1 . U 0.63-4.3) -

0

a

.f

0

I

C

0

0

0

miu

-- --

1

M d oi u . 3.

I

00

0 0

66

an

. .

-v

-Id

iunl

0 CI

1

. .

Ma N N

0 0

. .

I

FC0 0

0 0

. .

m m

-Id

dv

0 0

1.21( 0.61-4 .O ) 1.28( 0.65-3.89)

0

0.2319.05-0.98 ) -

0 0

0 . Mr3.05-0.43 ) -

-,

0.2610.10-0.31.) 0.28(0.10-0.?7)

CI! -i

0.331 0.08-1.39)

-

0.66(0.3-1.35 ) -

-

0.iO( 0.05-0.21) 9.10(0.05-0.21)

ru

no\

M M . .

0 0

. .

I 1 M F

0 0

0 0

-LA

2. 2.

00

0.1?(3.05-0.29) -

--

m.r -.

1

. .

0 0

I

--u

. .

. .

. .

. .

=

@Jk

N.D.

k

Ldf)

'Values

+> a,

*Average

00

1.21(0.50-1.90) 1.31(0.41-3.48)

00

( e ) Sodium ( i ) r a i n water ( i i ) snow w a t e r

-Y

0.12(0.06-0.31) 0.18(0.07-0.10) 0.1710.07-0.33) 0.18(0.13-0.61) 0.12( 0.05-0.28) 0.17(0.10-0.60)

r-iu mc-

0.13(0.07-0.28) 0.12(0.07-0.26)

00

( d ) Magnesium ( i) r a i n w a t e r ( i i )snow w a t e r

F.N

3.14(0.03-0.38) 0.1.4(0.07-0.32)

Lcr-

0.1410.06-0.35) 0.13(0.05-0.29)

rid 1 1

( c ) Potassium ( i ) r a i n water ( i i ) snow water

00

0 . 4 3 ( 0.13-1.10 ) 0.42( 0.10-1.40)

NID ( N

0.91(0.32-1.89) 0.86(0.29-1.72) vv

(b) Calcium ( i ) r a i n water ( i t ) SROW w a t e r

TI& Dto

0.37(0.04-0.83) 0.20(0.02-0.46) 0.32(0.04-0.79) -

00

O.50( 0.05-1.41) 0.55( 0.05-1.52)

( i ) r a i n water ( i i ) snow w a t e r

2.2210.64-5.40) 2.3010.7-4.80)

o f 8 r a i n w a t e r samples and 7 snow water samples i n p a r e n t h e s e s a r e r a n g e of v a l u e s r e c o r d e d f o r the s a n p l e s

Not d e t e c t a b l e

209

210 ppm a t 18.7 km.

Ares (Ref. 1) r e p o r t e d much h i g h e r F-concentrations i n r a i n

water a s compared t o values l i s t e d above.

It i s estimated t h a t 2.61 gF/ha/mm

o f r a i n and 3.10 gF/ha/mm of snow water equivalent were deposited a t 1 . 4 km from t h e source.

The r a t e of F-deposition decreased with t h e i n c r e a s e d d i s t a n c e

from t h e source (Table 1 ) . Based on t h e a f o r e l i s t e d r a t e s of F-denosition p r e c i p i t a t i o n and 1200 mm of annual p r e c i p i t a t i o n , deposited a t 1.4 km from t h e emission.

.,l'o~gh

3.43 kg/ha/year were being

I n c o n t r a s t , F-deposition i n t h e a r e a

with no f l u o r i d e damage was < 0.15 kgF/ha/year ( F i g . 2, Table

3).

Unlike F, P and Ca c o n c e n t r a t i o n s of K , Mg and Na d i d not show any r e l a t i o n s h i p w i t h t h e d i s t a n c e from t h e emission source.

The increased i n p u t of P and

Ca i n t h e a c i d i c and n u t r i e n t poor s o i l s of t h e study a r e a may have a p o s i t i v e e f f e c t on t h e growth of v e g e t a t i o n where F - e f f e c t s were minimal. Fluoride d e p o s i t i o n through l e a f l i t t e r The average q u a n t i t y of l i t t e r f a l l , t h e F-concentrations i n f r e s h l y f a l l e n l e a f l i t t e r and estimated d e p o s i t i o n of f l u o r i d e t o s o i l humus v i a l e a f l i t t e r a r e presented i n Table 2.

The e s t i m a t e s of F-deposition v i a l e a f l i t t e r a r e

based on average l i t t e r f a l l and F-concentration of t h e l i t t e r of a l l s p e c i e s l i s t e d i n Table 2.

This method of e s t i m a t i n g F-input through l i t t e r was

adopted because v e g e t a t i o n below t h e dominant s t r a t u m d i d not appear t o cont r i b u t e t o F-input s i g n i f i c a n t l y .

The f l u o r i d e concentrations i n s p e c i e s of

t h e subdominant s t r a t a were t h e same a s f o r t h e unpolluted condition.

For

example, f l u o r i d e c o n c e n t r a t i o n s i n kalm5a l i t t e r under a balsam f i r overstorey was 1 2 t o 20 pprn a s compared t o > 1000 ppm i n l e a f l i t t e r of Kalmia growing i n open heathland.

The e s t i m a t e s of F-inputs through l e a f l i t t e r were conservative

a s any l i t t e r f a l l of evergreens o c c u r r i n g through w i n t e r was not included.

The

w i n t e r sampling was excluded because an e a r l i e r work by Damman concluded t h a t peak l i t t e r f a l l i n evergreens occurred during s p r i n g and f a l l (Ref. 7 ) . I n evergreen a s well a s deciduous s p e c i e s , t h e average amount of l e a f l i t t e r d i d not r e l a t e t o t h e s e v e r i t y of F-damage t o v e g e t a t i o n . with t h e s p e c i e s , s i t e c o n d i t i o n s and s i z e of t h e t r e e s .

Leaf l i t t e r v a r i e d I n case of evergreen

s p e c i e s , t h e l e a f l i t t e r c o n s t i t u t e d one t o t h r e e y e a r o l d f o l i a g e i n s e v e r e l y F-damaged a r e a s (Zones I and 11; F i g . 1 and Table 2 ) but s i x t o e i g h t year o l d i n a r e a s w i t h l i g h t o r no v i s i b l e F-damage.

Depending on t h e s p e c i e s , t h e

amount o f l e a f l i t t e r ranged from 204 kg/ha t o 1693 kg/ha (Table 2) and f l u o r i d e c o n c e n t r a t i o n s v a r i e d from 1085 ppm i n Zone-I t o 1 2 ppm o u t s i d e Zone-IV. On t h e average l e a f l i t t e r amounted t o 776, 590, 623, 864 and 717 kg/ha i n Zones I , 11, 111, I V and o u t s i d e Zone-IV r e s p e c t i v e l y w i t h corresponding Fc o n c e n t r a t i o n s of 930, 243, 118, 60 and 1 7 ppm.

A s a r e s u l t t h e F-input v i a

l e a f l i t t e r t o s o i l was q u i t e v a r i a b l e , 720 i n Zone-I t o 10 gF/ha/year a r e a s o u t s i d e Zone-IV (Table

3).

in

The r e l a t i o n s h i p of annual F-input v i a

211 'TABLE 2 l-verage f l u o r i d e (F-) c o n c e n t r a t i o n i n l e a f l i t t e r o f domicant f o r e s t , s p e c i e s and e s t i m a t e d c o n t r i b u t i o n t o soil f l u o r i d e s v i a l e a f l i t t e r i n f o u r F-damaged zones* and o u t s i d e F - v i s u a l damage a r e a .

Av. l e a f litter dry w t . (kg/ha)+

Species

(L. ) M i l l (Erilsam f i r ) Zone - I Zone - I1 Zone - I11 Zone - IV O u t s i d e 7,or.e - I V

Av . F-cone. (ppm, d r y wt.)

g F/ha/ kg l e a f l i t t e r

892 272 163 '7 5 18

0.89 0.27 0.16 0.07 0.02

405 649 556 1002

845

0.84

317 61

544

17

0.32 0.06 0.04 0.02

548

577 195 117

_L

Abi.i.7 balsamea

P i c e a m a r i a n a ( h i i l l . ) RSP (Black s p r u c e ) Zone - I Zone - I1 Zone - 111 Zone - IV @ u t s i d e Zone - IV

925

1104 864 645 1572

36

Larix l a r i c i n a (Du R o i ) Koch (Larch) Zone - I Zone - I1 Zone - 111 Zone - IV O u t s i d e Zone

511

-

IV

B e t u l a p a p y r i f e r a 14arsh. [White b i r c h ) Zone - I Zone - I1 Zone - I11 Zone - IV O u t s i d e Zone - IV

552 792 356

78 17

696

809

196 408

133 137

938 370

26 12

P i c e a g l a u c a (Moench) Voss [White spruce ) Zone - I Zone - I1 Zone - I11 Zone - IV O u t s i d e Zone - IV

496 662

A h u s c r i s p a ( A i t . ) Pursh. ( Green a l d e r ) Zone - I Zone - I1 Zone - I11 Zone - IV O u t s i d e Zone - IV

1264 929 1154 11'76 1691

0.58 0.19 0.12 0.08 0.02

0.81 0.33 0.14 0.03 0.01

0.15 0.02

1085 350

1.1

0.35 0.13 0.06 0.03

133 62 2L Cont'd

. ..

+

212 TABLE ?

-

Concluded

Spec i e s

Av. l e a f lizter d r y wt . (kg/ha)'

Av. F-cone. .~ g !
Sorbus americana b r s h . (American a s h ) Zone - I Zone - I1 Zone - I11 Zone - I V Outside Zone - I V

492

Kalmia a n g u s t i f o l i a L ( Sheep l a u r e l ) Zone - I Zone - I1 Zone - I11 Zone - IV Out s i d e Zone - I V

952 4 09

1.I 0.15

547 160

0.04 0.01.

Rubus i d a e u s L. (Lispberry) Zone - I Zone - I1 Zone - 111 Zone - I V Outside Zone - I V

644

-

3 80

909 189

16

-

Average of a l l s p e c i e s Zone - I Zone - I1 Zone - 111 Zone - I V Outside Zone - I V

0.02

-

-

-

75%

0.10

-

-

S p i r a e a l a t i f o l i a ( A i t . ) Borkh. 7Meadowsweet) Zone - I Zone - I1 500 Zone - I11 Zone - I V Outside Zone - IV ;.'yrica gal; 1,. (Sweetgale Zone - I Zone - 11 Zone - I11 Zone - I V Outside Zone - I V

0.91 0.19

0.23

-

-

204 -

0.10

-

0.20

550 776 580

910 243

623 864

118 60 17

71'7

*Damage zones based on an e a r l i e r s t u d y ( Ref. 1). 'Average of 9 samples from each damage zone. ( - ) s p e c i e s n o t p r e s e n t i n sample p l o t .

0.91 0.24 0.12 0.06

0.02

213 TASLF!

3

Estirriated t o t a l and a v a i l a b l e f l u o r i d e i n iipper 4 c m of s o i l humus and average F-input t h r o u g h p r e c i p i i a i i o r i and l e a f l i t t e r .

Damage zone

ZONE-I ZONE-II ZONE- II I ZONE- IV Unpolluted area**

Average f l u o r i d e ( F ) S o i l humus ( k g / h a i n 4 em s l i c e ) * Precipitation toial available kgF/ha/year 57.00 26.40 12.12

2.88 1.27 0.67 0.24

1.20 0.90

0.20

<

Leaf l i t - t e r kg/ha/year

3.43

0.720

0.64 0.49

0.140 0.070

0.15

0.010

0.15

0.00'7

*Based on 0 . 3 2 g/cm3 b u l k ' d e n s i t y o f humus. it*

Based on 710 kg o f l i t t e r / h a and F-cone. of 5 ppm i n l e a f l i t t e r .

@

LEAF LITTER RAIN WATER WATER

8. SNOW

Yr3.0e-o.osx,r1=o.~ Y=2.8-00(1~,~*=0.0~ Y = 2 26-0.Mx1r2= 0.87

F i g . 2 . R e l a t i o n s h i p between amount of f l u o r i d e d e p o s i t e d t h r o u g h r a i n and snow w a t e r , and l e a f l i t t e r and NE-distance from t h e e m i s s i o n s o u r c e .

l e a f l i t t e r t o d i s t a n c e from t h e e m i s s i o n i s i l l u s t r a t e d i n F i g . 2.

i s e s t i m a t e d t o b e 7 gF/ha/year

at

The i n p u t

an a v e r a g e l i t t e r f a l l o f 710 kg/ha/year

and 5 ppm F - c o n c e n t r a t i o n i n t h e i i t t e r .

The comparison of y e a r l y i n p u t v i a

214 p r e c i p i t a t i o n and l e a f li tt,er showed t h a t i n p u t through p r e c i p i t a t i o n i s 5 t i m e s t o 15 iirnes g r e a t e r t h a n t h a t v i a l e a f l i t t e r i n s e v e r e l y and l i g h t l y Fdamaged a r e a s r e s p e c t i v e l y .

The F-input, t o s o i l by p r e c i p i t a t i o n i s s t , i l l

more s i g n i f i c a n t t h a n F-input by l i t t e r i n u n p o l l u t e d a r e a s ( T a b l e

3).

The

f l u o r i d e s accumulated i n s o i l s of t h e study a r e a a t t h e r a t e of 7010, 3140, 1402, 37 gF/ha/year

1969 t o 1977.

i n Zones I , 11, Ill and I V r e s p e c t i v e l y f o r the p e r i o d

Although both t o t a l and a v a i l a b l e f l u o r i d e i n s o i l from F-

p o l l u t e d a r e a s i n c r e a s e d 50 times t h a t i n c o n t r o l s , it i s u n l i k e l y t h a t much

i s removed by r o o t a b s o r p t i o n and accumulated i n t o f o l i a g e of p l a n t s .

A com-

p a r i s o n of two y e a r s d a t a , d u r i n g one o f which t h e phosphorus p l a n t was nono o e r a t i v e , shows -t,his [ Table 4 ) .

During t h e non-operative y e a r , t h e c u r r e n t

y e a r ' s f o l i a g e accumulated f l u o r i d e not s i g n i f i c a n t l y g r e a t e r t h a n f o l i a g e

from c o n t r o l a r e a s .

The pathway of t h e l o s t f l u o r i d e from s o i l during t h e non-

Q p e r a t i o n n l p e r i o d i s n o t knovm.

TABLE

4

Concentralions o f f l u o r i d e i n s o i l and balsam f i r f o l i a g e during o p e r a t i o n a l and non-operational y e a r s .

Damage zone

In o p e r a t i o n F-concentration (ppm) soil foliage t o t a l available

I

475

I1 I11

220 101 52 10

IV Outside I V

Out of o p e r a t i o n F-concentration ( ppm) soil f o l i aEe t o t a l available

237

281

8

10

10 "

149

141

6

75

6

3

36

91 44

8 4

2

6

6

2 2

6 6 2

ACKNOWLEDGFMENTS S i n c e r e thanks a r e due t o M r . C . French f o r a s s i s t a n c e i n t h e f i e l d and

Mrs. D.J. Didharn f o r t y p i n g t h e manuscript.

REFERENCES J o r g e 0. P.res, J . A i r P o l l u t . Control Assoc. 28(1978) 344-349. S.S. Sidhu and B.A. Roberts, Environ. Canada, Can. For. S e r v . , Bi-Monthly Res. Notes, 32[ 1976)29-31. S.S.Sidhu, S t u d i e s i n Environ. S c i . Vol. 8 ( 1 9 8 0 ) 425-432, E l s e v i e r , Ams t e r d am. L. K . Thompson, S.S. Sidhu and B . A . Roberts, Environ. P o l l u t . 18 ( 1 9 7 9 )

2221-2234. S.S. Sidhu, Environ. Canada, Nfld. For. Res. Centre, I n f . Rep. N-X-203 (1981)l-55. S.S. Sidhu, Proc. 7 1 s t Ann. Meeting A i r P o l l u t . Control A ~ S G C . June 25-30, 1978, Houston, Texas, Paper No. 78-21.7, pp. 1-16. A.W.H. Damman, Ecol. ldonographs 4l(1971) 253-270.

215

STUDY OF THE WORKING OF A NEW MULTICELL SCRUBBER APPLIED IN THE FIGHT AGAINST AIR POLLUTION L. PERDREAU (*), S. DJERID ( * ) , C. BELIN (**), A. LAURENT (*) and J.C. CHARPENTIER (*) (*)

Laboratoire des Sciences du G h i e Chimique, CNRS-ENSIC, 1 , rue Grandville, 5 4 0 4 2 Nancy Cedex (France)

(**) Europoll, 2 rue Amorteaux, 78730 Saint Arnoult en Yvelines (France)

ABSTRACT The EUROPOLL multicell scrubber is a new gas-liquid contactor that may be use for the fight against the chemical and dust pollution of air. This contactor involves a regular package of elementary patterns called cells in which it is possible to transfer mass and/or heat between the gas and liquid phases. Indeed each cell comprises a convergent and a divergent the intersection of which constitutes the throat and thus leads to a good contact between the phases. From the hydrodynamic point of view, the scrubber is characterized by graphs of pressure losses and liquid holdup and by the domain of the flowrates leading to the working in satisfactory conditions. The capacity of the mass transfer of the contactor is presented in terms of 1;quid side and gas side mass transfer coefficients and of gas-liquid interfacial area. Finally the performances of the scrubber are compared with those of the other classical contactors employed to fight the air pollution. This is made with the use of a diagram plotting the mass transfer parameters versus the spent energy. INTRODUCTION The main classical absorbers and gas-liquid reactors are packed columns, plate columns, spray columns, bubble columns, mechanically stirred tanks, venturi and ejector reactors. Generally each one has its own specificity as concerns its application field and has its own flexibility of operation (ref. I).

For example, packed

columns are employed for the treatment of the gaseous effluents free of dust particles during an absorption with a rapid chemical reaction. Moreover turbulent jet reactors are well adapted for the washing of hot gases containing solid particles together with very rapid gas-liquid reactions. The aim of the present paper is to present the new EUROPOLL multicell scrubber, then to precise its hydrodynamica1 characteristics and its mass transfer performances and finally to define the limits of its potential use when compared with the other types of absorbers.

216 DESCRIPTION OF THE EQUIPMENT AND EXPERIMENTAL Description of the multicell contactor The multicell scrubber involves three main parts :

- an inferior hopper for the gas entrance and the recovering of the washing liquid, - a modular shell for gas washing the length and/or the height of which are variable by placing side to side and/or by packing identical elementary cells (Fig. la),

-

a cap for the gas exit and the entrance and distribution of the liquid. A classical elementary cell involves a

convergent and a divergent of rectangular section, the intersection of which forms the throat (Fig. Ib). The elementary cell investigated in the present study is defined by the angles of the convergent ( = 20 degrees) and the divergent

(2

20 degrees), the thick-

ness of the throat ( 1 0 mm), the wideness (80 mm), the length (80 mm) and the height ?

( 2 0 0 mm).

The contactor of the present study is Fig. la. Multicell scrubber

Fig. Ib. Elementary cell

constituted by a vertical package of elementary cells the number of which is comprised between I and 8.

Experimental apparatus A schematic description of the experimental apparatus is presented in figure 2.

The gas and the liquid phases flow counter-currently inside the absorber either with an initial trickling flow of the liquid phase or with an initial bubble flow of the gas phase. The liquid is distributed at the top of the package by a distributor having the shape of a cross and containing many holes. The gas is injected at the bottom of the apparatus by a fritted distributor. The range of the liquid and gas flowrates L and G are respectively 0.8xlO

-5

to

3

~ x I O -m3.s-' ~ and 0 to 0.01 m . s - ' . The scrubber is thus operating at range L/G comprised between 0.8 and 4 m3 of liquid per 1000 m3 of gas to be washed. The pressure l o s s in the equipment is measured with a U-tube water manometer at trickling flow operations and with two piezometric manometers at bubble flow operations ( a l s o sometimes called at flooded flow conditions). The amount of liquid held in the

apparatus is measured by weighting the liquid that leaves the apparatus after a rapid shut of the flows of the phases at the entrance and at the exit. Samples gathered in both phases before the entrance in the equipment and after the exit allow for the analysis of the gas solute concentration and of the liquid reactant concentration during the mass transfer study.

217

D

Fig. 2. Experimental apparatus. 1 . Liquid storage tank 6. Bottom of the scrubber 2. Centrifugal pump 7. Liquid rotameter 3. Liquid rotameter 8. Air compressor 4 . Multicell scrubber 9. Air rotameter 5. Gas-liquid demister 10. Gas solute rotameter

11.

Washing column

12. Gas sampling (in)

13. Gas sampling (out) 14. Liquid sampling (in) 15. Liquid sampling (out)

HYDRODYNAMICS

\

Operating zones 2:

When the equipment is initially working at

G (N m3.s-') A

m TRCKLW REGIME 0

BUBBLING REGIME

trickle flow (trickling regime), Boldo (ref. 2) and Djerid (ref. 3 ) have described the different flow regimes visually observed and have shown the

.\

existence of a discontinuity for the operation between the zones corresponding to a trickle flow or a surging flow of the liquid on the walls of the cells and the zone corresponding to a correct operation with a good mixture of both phases. This last zone is limited between the "picking-up" and TRICKLING FLOW

curves and the "flooding" curves in a L versus G

or

0.25 --.

plot.

BUBBLING FLOW

AIR-WATER AIR - WATER WSTEM n-5 I

1

1

1

2

3

When the equipment is initially working at bubble flow (bubbling regime), Perdreau (ref. 4 ) did .

i

Fig. 3. Operating zones of the multicell scrubber.

.

not observed the discontinuous picking-up phenome*non and led to the conclusion that the operating zone was only limited by the flooding curve.

218 The o p e r a t i n g zones of t h e s c r u b b e r working e i t h e r a t t r i c k l i n g regime o r a t b u b b l i n g regime a r e p r e s e n t e d i n f i g u r e 3 . It h a s t o b e u n d e r l i n e d t h a t t h e zone c o r r e s p o n d i n g t o a c o r r e c t o p e r a t i o n a t t r i c k l i n g regime i s i n c l u d e d i n t h e operat i n g zone a t b u b b l i n g regime. B e s i d e s , t h e f l o o d i n g c u r v e , which i s comnon f o r both o p e r a t i n g r e g i m e s , may b e p r e d i c t e d by a more g e n e r a l c o r r e l a t i o n c o n c e r n i n g t h e c o n t a c t o r s of t u b u l a r t y p e ( r e f . 5-6). P r e s s u r e drop The v a r i a t i o n s of t h e p r e s s u r e drop p e r u n i t l e n g t h AP/Z measured f o r t r i c k l i n g and b u b b l i n g f l o w regimes i n f u n c t i o n of t h e g a s and l i q u i d f l o w r a t e s a r e p r e s e n t e d i n f i g u r e 4a. T h i s p l o t confirms t h e l o c a t i o n of t h e f l o o d i n g zone f o r t h e same gas and l i q u i d f l o w r a t e s a t b o t h r e g i m e s . It should b e n o t e d t h a t t h e f l o o d i n g o c c u r s f o r a n a p p r o x i m a t i v e l y c o n s t a n t p r e s s u r e drop as i n t h e c a s e of packed columns ( r e f . 7 ) . A t t r i c k l i n g regime, f o r a g i v e n l i q u i d f l o w r a t e t h e p r e s s u r e drop f i r s t i n c r e a s e s

s l o w l y f o r t h e low gas f l o w r a t e s ( b e f o r e t h e picking-up p o i n t ) , t h e n p r e s e n t a jump a t t h e picking-up p o i n t and f i n a l l y i n c r e a s e s q u i c k l y up t o t h e f l o o d i n g p o i n t . For a c o n s t a n t gas f l o w r a t e i s a l l t h e more h i g h t h a t t h e l i q u i d f l o w r a t e i s h i g h . On t h e c o n t r a r y , a t b u b b l i n g regime, t h e p r e s s u r e drop d e c r e a s e s w i t h t h e gas flow-

r a t e f i r s t v e r y q u i c k l y , t h e n more s l o w l y up t o t h e f l o o d i n g . A l s o t h e p r e s s u r e drop

i s a l l t h e more weak t h a t t h e l i q u i d f l o w r a t e i s h i g h .

P(r) 100

AIR - WATER S T E M

AIR-WATER SYSTEM

.s-9 *G F i g . 4a.-4b.

V a r i a t i o n s of t h e p r e s s u r e drop ( 4 a ) and of t h e l i q u i d holdup (4b) v e r s u s gas and l i q u i d f l o w r a t e s .

219 L i q u i d holdup The v a r i a t i o n s of t h e t o t a l l i q u i d holdup r e p o r t e d t o t h e t o t a l empty volume of t h e s c r u b b e r i n f u n c t i o n of t h e g a s and l i q u i d f l o w r a t e s a r e r e p o r t e d i n f i g u r e 4b. The g e n e r a l t r e n d observed i n t h i s g r a p h i s i d e n t i c a l t o t h a t c o n c e r n i n g t h e p r e s s u r e drop. A t t r i c k l i n g regime, t h e e v o l u t i o n of t h e l i q u i d holdup a l s o p r e s e n t s a d i s c o n t i -

n u i t y a t t h e l e v e l of t h e picking-up p o i n t . The o r d e r of magnitude of t h e l i q u i d holdu p i s t h e same a t t h a t i n a packed column.

A t b u b b l i n g regime, t h e l i q u i d holdup i s g r e a t l y s u p e r i o r as compared w i t h t h e val u e s o b t a i n e d a t t r i c k l i n g regime. G e n e r a l l y t h e l i q u i d holdup d e c r e a s e s when t h e gas f l o w r a t e i n c r e a s e s and t h e i n f l u e n c e of t h e l i q u i d f l o w r a t e i s a l l t h e more marked t h a t t h i s l i q u i d f l o w r a t e i s h i g h and i s l o c a t e d n e a r t h e f l o o d i n g of t h e s c r u b b e r . MASS TRANSFER

The chemical t e c h n i q u e s f o r t h e e x p e r i m e n t a l d e t e r m i n a t i o n of t h e mass t r a n s f e r c o e f f i c i e n t s k S ( l i q u i d f i l m ) and k S (gas f i l m ) and of t h e i n t e r f a c i a l a r e a S (gasL G l i q u i d ) f o r a g a s - l i q u i d r e a c t o r by a b s o r p t i o n w i t h chemical r e a c t i o n have been reported in the l i t e r a t u r e (ref. I ) . A slow i r r e v e r s i b l e r e a c t i o n i s used f o r t h e measurement of k S , a f a s t pseudo m-th

L

o r d e r r e a c t i o n f o r S and an i n s t a n t a n e o u s s u r f a c e r e a c t i o n f o r t h e d e t e r m i n a t i o n of

kGS. The k i n e t i c s of each r e a c t i o n employed h a s been p r e v i o u s l y s t u d i e d i n a l a b o r a t o r y model of known i n t e r f a c i a l a r e a and c o n t a c t t i m e ( c y l i n d r i c a l w e t t e d w a l l column). These t e c h n i q u e s have been a p p l i e d i n t h e p r e s e n t equipment. L i q u i d phase c o e f f i c i e n t The l i q u i d mass t r a n s f e r c o e f f i c i e n t k S was determined by t h e a b s o r p t i o n of d i l u L t e carbon dioxyde (2 %) i n a i r i n t o aqueous p o t a s s i u m c a r b o n a t e and b i c a r b o n a t e b u f f e r s o l u t i o n s ( 0 . 6 M K 2 C 0 3 + 0 . 2 M HKCO ) i n t h e c o n d i t i o n s of a slow r e a c t i o n t o t a l l y 3 c o n t r o l l e d by t h e mass t r a n s f e r r e s i s t a n c e i n t h e l i q u i d phase. The v a r i a t i o n s o f t h e k S v a l u e s i n f u n c t i o n of t h e gas f l o w r a t e s f o r d i f f e r e n t L g i v e n l i q u i d f l o w r a t e s a r e p r e s e n t e d i n f i g u r e 5. A t t r i c k l i n g regime, k S i s simul-

L

t a n e o u s l y i n f l u e n c e d b o t h by L and G . A t b u b b l i n g regime, k S i n c r e a s e s w i t h t h e gas

L

f l o w r a t e and i s independent of t h e l i q u i d f l o w r a t e i f t h e a c c u r a c y of t h e measurements ( w i t h i n ? 10 %)

i s taken i n t o account. It has t o be noted t h a t t h e values

d e t e r m i n e d w i t h t h e b u b b l i n g regime a r e g r e a t l y s u p e r i o r . Gas phase c o e f f i c i e n t The g a s mass t r a n s f e r c o e f f i c i e n t k S was determined by a b s o r p t i o n of d i l u t e s u l G

phur dioxyde ( 2 % ) i n a i r i n t o aqueous s o l u t i o n of sodium hydroxyde ( I N )

i n t h e con-

d i t i o n s of an i n s t a n t a n e o u s s u r f a c e and i r r e v e r s i b l e r e a c t i o n t o t a l l y c o n t r o l l e d by t h e r e s i s t a n c e i n t h e g a s phase.

220

,lo4 k,S W . s - 9 4F 0'

A + -/

/*n,

5

0

/-

t 0

0.25

0.5

1O'G (Nm3.s-') a75 1F i g . 6. Gas-side mass t r a n s f e r i n the m u l t i c e l l scrubber

F i g . 5. L i q u i d - s i d e mass t r a n s f e r i n the multicell scrubber

S (m9

The v a r i a t i o n of t h e k S v a l u e s i n funcG t i o n of t h e gas f l o w r a t e s f o r d i f f e r e n t

1

1.2?

1.01

constant l i q u i d flowrates a r e reported in A

10SL(m3.r-1)OA33 25 1333

f i g u r e 6. A t t r i c k l i n g regime, k S i n c r e a G s e s w i t h b o t h L and G . A t b u b b l i n g regime,

4

i n t h e s t u d i e d zone, k S i s p r a c t i c a l l y a G

l i n e a r f u n c t i o n of t h e gas f l o w r a t e and i s independent of t h e l i q u i d f l o w r a t e . Interfacial area The i n t e r f a c i a l a r e a S w a s determined by the absorption with the rapid irreversible f a s t pseudo f i r s t o r d e r r e a c t i o n of d i l u t e carbon dioxyde ( 2 %)

i n a i r i n t o aqueous

s o l u t i o n of sodium hydroxyde ( 0 . 2 N ) .

0

a25

0.50

The v a r i a t i o n s of t h e S v a l u e s i n func-

0.75 1

1

t i o n o f L and G a r e r e p o r t e d i n f i g u r e 7 .

Fig. 7. Interfacial area in the multiceii I t i s observed t h a t S i n c r e a s e s w i t h both scrubber L and G i n t h e t r i c k l i n g and b u b b l i n g f l o w s . However a t b u b b l i n g regime, t h e i n t e r f a c i a l a r e a becomes independent of t h e l i q u i d f l o w r a t e when L i s h i g h e r t h a n 2 . 5 x 1 0 - ~m 3 . s - ' . regime i s a l s o b i g g e r t h a n w i t h t h e t r i c k l i n g regime.

The a r e a o b t a i n e d w i t h t h i s

221

COMPARISON OF THE PERFORMANCES OF THE MULTICELL SCRUBBER WITH OTHER ABSORBERS To tempt an exhaustive confrontation between the performances of the different ty-

pes of gas-liquid absorbers is very often a challenge due to the scatter of the literature results, of the various conditions of the tests and/or of the lack of the data necessary for this comparison. We are going to try to present now the performances of the EUROPOLL scrubber in a diagram with the plot - mass transfer parameter versus spent energy

-

in both trickling and flooding regimes and then to confront these per-

formances with those of other contactors when the literature data are available. k, S parameter

k

a(x )'I3

Perdreau determined the values of the

992

powers in the EUROPOLL scrubber necessary to obtain the values of the liquid side mass transfer k S reported in figure 5. L These are comprised between 1 to 2 watts for each cell in the trickling regime and between 1.5 and 4 watts for each cell in the bubbling regime (ref. 4 ) . It was also shown that for a constant dissipated power in each cell, the k S value at bubbling reL

gime is thrice as high as at trickling regime together with a liquid holdup ratio of ten. This leads to suggest the potential use of the EUROPOLL scrubber in the cases of gas-liquid absorptions followed by a 'slow

6

10-h-1

loo

10' <(VL

-'h p: 94)

Fig. 8. Dimensionless form of the volumetric liquid mass transfer coefficient for various contactors 1 . Stirred loop reactor 2. Stirred vessel (coalescing) 3. Stirred vessel (hollow stirrer) 4 . Injector 5. Stirred vessel (non coalescing) 6. Multicell scrubber

chemical reaction processes such as those encountered in the treatment of effluents with slow kinetics processes or in aerobic fermentations. Figure 8 presents in a dimensionless form the volumetric mass transfer coefficient k a as a function of the specific L power requirement and gives the location of the EUROPOLL scrubbcr among the conven-

tional reactors employed for oxidation (ref. 8). Comparing regions 1 , 5 and 6, it can be seen that the EUROPOLL scrubber achieves same mass transfer rates than the stirred vessel and the stirred loop reactor.

222 k,S

parameter

BUBBLING (n131

4

The comparison o f t h e k,S v a l u e s i n t h e " EUROPOLL s c r u b b e r shows t h a t t h e o p e r a t i o n a t t h e b u b b l i n g regime r e s u l t s i n g a s phase e f f i c i e n c i e s comprised between 99.6 % and 99.97 Z w h i l e t h e o p e r a t i o n a t t h e t r i c k l i n g regime r e s u l t s i n gas phase e f f i c i e n c i e s comprised between 8 3 and 93 %. The Number o f T r a n s f e r U n i t s i n t h e gas

PRP 25

DUAL FLOW TRAY

phase i s p l o t t e d a g a i n s t t h e energy d i s s i p a t e d p e r u n i t volume of t r e a t e d gas i n f i g u r e 9 . I t i s s e e n t h a t t h e performances of

TRICKLNG

t h e absorber s t r i c t l y vary with t h e dissipated energy f o r t h e studied gas-liquid

system

and whatever t h e flow regime. For a compari-

$ (k J. m3) 1

a1

I

I

I

I

I I l l 1

E

l

I

I

,

'

5 *

F i g . 9. Comparison between t h e a t t a i n a b l e number o f g a s mass t r a n s f e r u n i t s f o r d u a l flow t r a y , packed column and multicell scrubber.

son w i t h o t h e r a b s o r b e r s , t h e same diagram r e g r o u p s t h e d a t a o b t a i n e d w i t h t h e same g a s - l i q u i d s y s t e m i n a p l a t e column i n v o l v i n g 4 d u a l flow t r a y s ( d i a m e t e r : 0 . 5 m and d i s t a n c e between t h e t r a y s : 0.4 m) and i n a packed column ( h e i g h t : 1 m, packings a r e I i n c h and 2 i n c h e s p o l y p r o p y l e n P a l l

r i n g s ) , ( r e f . 9 ) . T h i s c o n f r o n t a t i o n shows t h e p o t e n t i a l u s e of t h e EUROPOLL s c r u b b e r f o r t h e t r e a t m e n t a t t r i c k l i n g flow regime of t h e gaseous e f f l u e n t s when an absorpt i o n with a rapid and/or instantaneous reaction i s required. S parameter

The comparison of t h e i n t e r f a c i a l a r e a i n t h e EUROPOLL equipment i n f u n c t i o n of t h e d i s s i p a t e d energy p e r u n i t volume of s c r u b b e r has been made by P e r d r e a u ( r e f . 4 ) . I t was o b s e r v e d t h a t a t t h e t r i c k l i n g regime, t h e o r d e r of magnitude was 2 -3 f o r a d i s s i p a t e d power comprised between I and I .5 kW.m while

a = 100-200 m .m-3

a t t h e b u b b l i n g regime, t h e i n t e r f a c i a l a r e a w a s comprised between -3 f o r a d i s s i p a t e d power comprised between 2 and 3 . 6 kW.m

m2.m-3

Moreover Nagel e t a l .

00 and 200

.

( r e f . 10) have proposed t h e u s e of a n o t h e r i n t e r e s t i n g

c h a r a c t e r i s t i c diagram p l o t t i n g t h e i n t e r f a c i a l a r e a c r e a t e d p e r un t v o l u m e t r i c gas f l o w r a t e i n f u n c t i o n of t h e energy s u p p l i e d p e r u n i t v o l u m e t r i c g a s f l o w r a t e , i n order t o d e f i n e a c r i t e r i o n f o r t h e c o n f r o n t a t i o n and t h e s e l e c t i o n of g a s - l i q u i d a b s o r b e r s . Using such a p l o t , f i g u r e 10 a l l o w s f o r a comparison t o be made between t h e performances of t h e EUROPOLL s c r u b b e r and o t h e r c o n t a c t o r s . T h i s working diagram shows t h a t t h e EUROPOLL s c r u b b e r i s o n l y s u i t a b l e f o r p r o d u c t i o n of a v e r a g e mass t r a n s f e r a r e a s , b u t a such diagram i s o n l y q u a l i t a t i v e l y v a l i d f o r t h e i n v e s t i g a t e d chemical system.

223

S/G(m2. s .m-?

CONCLUSION The present study shows that the

B . PIPE FLOW C . COUNTERCURRENT M E 0 COLUMN

EUROPOLL scrubber may be employed at trickling regime for the treatment of gaseous effluents containing eventually particles or dust in suspension and when a gas-liquid absorption accompanied by a rapid or an instantaneous chemical reaction occurs (abatement of SO2 , H2S, acidic aerosols...). It seems also

NH3,

that this equipment could be employed at bubbling regime for the treatment of gas effluents by liquids where a s l o w chemical reaction happens (absorption of

I

D - CELLULAR RUBBER (BUBBLING) E CELLULAR ?RIBBER (TWKLNG)

I

P/G (kJ.m-3

lfl .-

lo-'

Nitrogene oxides or oxygenation of loaded liquids) in trying in future to compare its performances with those of bubble columns.

10

Summarizing due to its flexibility de-

Fig. 10. Comparison of interfacial trans- pending its operating regime encountered, fer areas and specific power dissipathis new type of multicell contactor tions for any gas-liquid reactors. should allow to propose solutions adapted to the problems of the fight against the air pollution. NOTATIONS a

e g G kG kL L n NG P S

V

z B

pL TIL

AP

interfacial area per unit volume of reactor thickness of the throat gravitational acceleration volumetric gas flowrate gas mass transfer coefficient liquid mass transfer coefficient volumetric liquid flowrate number of elementary cells number of gas mass transfer units dissipated power total interfacial area total volume of reactor height of column total liquid holdup liquid density dynamic viscosity of liquid gas pressure drop

REFERENCES 1.

J.C. Charpentier, Mass transfer rates in gas-liquid absorbers and reactors, in Adv. Chem. Engng., Ed. T.B. Drew and T. Vermeulen, Vol. 1 1 , Academic Press, 1981, 1-133.

224

2.

P . Boldo, A . L a u r e n t , C . B e l i n and J . C .

C h a r p e n t i e r , La H o u i l l e Blanche, 6 / 7

( 1 9 7 9 ) 435. 3. 4. 5. 6.

S. L. T. T.

7. 8. 9. 10.

L. G. P. 0.

D j e r i d , DEA, Nancy ( 1 9 8 0 ) . P e r d r e a u , ThGse I N P L , ENSIC, Nancy ( 1 9 8 1 ) . Takahashi, Y . Akagi and K. F u j i t a , J. Chem. Eng. J a p a n , 1 ( 1 9 7 3 ) , 9 7 . Takahashi, Y. Akagi, K . F u j i t a and T . Kishimoto, J. Chem. Eng. J a p a n , 3

( 1 9 7 4 ) 223. M u s i l , C . P r o s t and P . Le G o f f , Chem. I n d . G h i e Chimique, 5 ( 1 9 6 8 ) 6 7 4 . K e i t e l and U. Onken, Ger. Chem. Eng. 4 ( 1 9 8 1 ) 250. KrEtzsch and M. Molzahn, Ger. Chem. Eng. 3 (1980) 257. Nagel, B . Hegner and H . KGrten, Chem. Ing. Techn. 50 ( 1 9 7 8 ) , 9 3 4 .

225

AEROSOLS

Aerosol science i s a branch of t h e study of the highly dispersed s t a t e o f matter and as such, exemplified by the work o f Tyndall, Raleigh,

Srnoluchovski, E i n s t e i n , Zsigrnondy and o t h e r s , antedates present day concern with pollution. Nonetheless, since s i l i c o s i s was pinpointed in S o u t h Africa a t the beginning o f t h i s century, airborne p a r t i c u l a t e matter has become a central t o p i c f o r those concerned with i n d u s t r i a l hygiene as well a s f o r a i r pollution s c i e n t i s t s . This section demonstrates, i f ever a demonstration were needed, t h a t aerosol science has m u l t i d i s c i p l i n a r y roots and polymorphous branches: basic aerosol physics, measuring techniques and devices, physics and, more p a r t i c u l a r l y , o p t i c s o f t h e atmosphere.

This Page Intentionally Left Blank

227

APPLICATION

THERMAL

OF

ANALYSIS

THE

TO

OF

CHARACTERIZATION

ORGANIC

AEROSOL

PARTICLES

ELIZABETH C. ELLIS R e s e a r c h a n d Development, S o u t h e r n C a l i f o r n i a Edison Company, Rosemead, C a l i f o r n i a

(U. S.A. ) TIHOMIR NOVAKOV* NM R e s e a r c h , Inc.,

Richmond, C a l i f o r n i a ( U . S . A . )

ABSTRACT A number

analyzed

of

by

Los Angeles

thermal

a e r o s o l samples,

(effluent

sample a t a p r e d e t e r m i n e d

gas)

c o l l e c t e d on

analysis.

quartz

The method

t e r m p e r a t u r e r a t e i n oxygen.

were

filters,

involves

heating

The e v o l v e d

gases

the

are

passed over a copper oxide c a t a l y s t t o a s s u r e t h e i r complete conversion t o carbon which i s d e t e c t e d by a n o n d i s p e r s i v e i n f r a r e d c a r b o n d i o x i d e a n a l y z e r .

dioxide, The

output

plot. to

the

of

the

analysis

a

is

thermogram,

i.e.,

a

C02

versus

temperature

The thermograms of a m b i e n t s a m p l e s show d i s t i n c t i v e p e a k s t h a t c o r r e s p o n d volatilization,

materials,

decomposition

and

s u c h as v o l a t i l e o r g a n i c s ,

combustion

of

higher molecular

different weight

carbonaceous

organic

species,

The f e a t u r e s of t h e thermograms a r e d i s t i n c t l y

elemental carbon, and carbonates.

d i f f e r e n t f o r a g e d a e r o s o l s t h a n f o r f r e s h source-dominated

Also, a t

particles.

t h e r e c e p t o r s i t e t h e r e are s u b s t a n t i a l d i f f e r e n c e s between daytime and n i g h t t i m e samples.

Based o n t h e s e r e s u l t s ,

a n e m p i r i c a l approach

to

by r e s u l t s on s o l v e n t t r e a t e d samples,

aided

differentiate

primary

and

secondary

organics

will

be

described.

INTRODUCTION

S t u d i e s of that sulfur-,

t h e a e r o s o l c o m p o s i t i o n of nitrogen-,

t h e Los Angeles

and carbon-containing

r e s p i r a b l e p a r t i c u l a t e mass (Ref. *Also a f f i l i a t e d w i t h Lawrence B e r k e l e y , C a l i f o r n i a (U.S.A.).

1).

a t m o s p h e r e have

shown

p a r t i c l e s a c c o u n t f o r most of t h e

The s u l f u r and n i t r o g e n p a r t i c l e s have been

Berkeley

Laboratory,

University

of

California,

228 shown t o be p r i m a r i l y v a r i o u s s u l f a t e and n i t r a t e compounds,

respectively,

but

v e r y l i t t l e i s y e t known a b o u t t h e s p e c i a t i o n of t h e c a r b o n - c o n t a i n i n g p a r t i c l e s . In

general,

t h e s e carbon

p a r t i c l e s would

consist

of

volatile

organics,

higher

m o l e c u l a r w e i g h t o r g a n i c s p e c i e s , e l e m e n t a l c a r b o n and c a r b o n a t e s .

I n a n e a r l i e r s t u d y i n Los Angeles, i t has been shown t h a t t h e o r g a n i c f r a c t i o n of t h e carbonaceous a e r o s o l can a c c o u n t f o r a s much as 30% t o 50% of t h e a e r o s o l

mass, e s p e c i a l l y on h i g h l y p o l l u t e d d a y s (Ref. 2 ) .

S i n c e t h e carbonaceous a e r o s o l

i s s u s p e c t e d t o have a l a r g e impact on human h e a l t h and i t o f t e n makes such a s i g n i f i c a n t c o n t r i b u t i o n t o t h e t o t a l r e s p i r a b l e p a r t i c u l a t e mass, i t i s important t o examine t h i s a e r o s o l f r a c t i o n i n more d e t a i l . have

applied

a

thermal-evolved

gas

analysis

With t h i s o b j e c t i v e i n mind, we technique

for

carbon

as

a

rapid

s c r e e n i n g p r o c e d u r e t o i d e n t i f y a e r o s o l samples f o r more i n - d e p t h o r g a n i c s p e c i a tion

analyses.

This

technique

could

a l s o provide

the

means

to

differentiate

between primary and s e c o n d a r y o r g a n i c s i n t h e Los Angeles a e r o s o l . Thermal a n a l y s i s methods such as Thermogravimetric A n a l y s i s (TGA), D i f f e r e n t i a l Scanning

Calorimetry

(DSC),

and

Effluent

Gas A n a l y s i s

a p p l i c a t i o n s f o r materials c h a r a c t e r i z a t i o n .

Out of

(EGA)

these,

have

found wide

TGA (Ref.

3 ) and EGA

(Refs. 4 - 5 ) have been a p p l i e d t o t h e c h a r a c t e r i z a t i o n of t h e carbon-, nitrogen-containing

s p e c i e s of

ambient and s o u r c e p a r t i c l e s .

In

sulfur-,

and

t h i s paper we

d e s c r i b e t h e a p p l i c a t i o n o f EGA t o t h e c h a r a c t e r i z a t i o n of t h e carbonaceous aeros o l p a r t i c l e s i n t h e S o u t h e r n C a l i f o r n i a A i r Basin. I n EGA t h e sample i s h e a t e d a t a p r e d e t e r m i n e d rate i n a n o x i d i z i n g o r n e u t r a l atmosphere.

The e v o l v e d g a s e s r e s u l t i n g from v o l a t i l i z a t i o n ,

sition

combustion

and

are

monitored

by

one

Depending on t h e purpose of

the analysis,

nitrogen.

carbonaceous

For

a n a l y s i s of

more

p y r o l y s i s , decompo-

gas-specific

detectors.

t h e carrier g a s i s u s u a l l y oxygen o r

materials

oxygen and t h e e v o l v e d g a s d e t e c t e d i s C02. a s s u r e complete c o n v e r s i o n of CO,

or

the

carrier gas

is u s u a l l y

An o x i d i z i n g c a t a l y s t i s used

to

hydrocarbons and o t h e r o r g a n i c vapors t o C02.

When a p p l i e d t o a e r o s o l samples t h e EGA can be used t o o b t a i n t h e t o t a l carbon, o r g a n i c c a r b o n , b l a c k carbon and c a r b o n a t e carbon. method, however,

The g r e a t e s t s t r e n g t h of

i s its "fingerprinting" capability.

(Cog

VS.

that

correspond t o v o l a t i l i z a t i o n ,

temperature

carbonaceous material.

plot)

c o n s i s t s of

distinct

o x i d a t i o n and

Namely,

peaks

the

t h e EGA thermogram

and/or

decomposition

groups of

the

of

peaks complex

I t h a s a l r e a d y been shown t h a t thermograms are d i f f e r e n t

f o r d i f f e r e n t s o u r c e s , and f o r ambient p a r t i c l e s c o l l e c t e d a t d i f f e r e n t l o c a t i o n s (Ref. 6 ) .

SAMPLING AND ANALYTICAL METHOD A e r o s o l samples were c o l l e c t e d a t two l o c a t i o n s i n t h e Los Angeles A i r Basin:

1.

Lennox,

near

the

Pacific

Coast,

primary e m i s s i o n p a r t i c l e s ; and

that

represents

a

site

dominated

by

229 2.

D u a r t e , l o c a t e d a b o u t 35 m i l e s i n l a n d t o t h e e a s t and downwind of metrop o l i t a n Los Angeles which i s impacted by b o t h primary and aged secondary particles.

High volume f i l t e r s a m p l e r s equipped w i t h cascade impactor p l a t e s t o r e s t r i c t t h e c o l l e c t e d p a r t i c l e s t o l e s s t h a n 3.5 each site.

( P a l l f l e x QASD). May,

micrometer d i a m e t e r were

The c o l l e c t i o n medium was acid-washed, P a r t i c u l a t e samples were

operated a t

prefired quartz fiber f i l t e r s

c o l l e c t e d between J u l y 25,

1980 and

1981 w i t h t h e b u l k c o l l e c t e d d u r i n g t h e summer smog p e r i o d of J u l y through The sampling p e r i o d w a s t y p i c a l l y f o r e i g h t h o u r s d u r a t i o n between

O c t o b e r , 1980.

noon and 8 : O O i n t h e evening.

On s i x days,

low volume t o t a l p a r t i c u l a t e samplers

f i t t e d w i t h 37 m i l l i m e t e r q u a r t z f i l t e r s were c o - l o c a t e d samplers.

The

low

volume

7:OO a.m. and 7:OO p.m.

sampler

two-hour

with

aerosol

t h e h i g h volume samples

t h e EGA a p p a r a t u s used i n t h e work i s shown i n

T h i s a p p a r a t u s i s s i m i l a r t o t h e one d e s c r i b e d by Dod e t a l .

The main components of grammed f u r n a c e .

between

f o r a d i u r n a l p r o f i l e of t h e carbonaceous a e r o s o l .

A s c h e m a t i c r e p r e s e n t a t i o n of

F i g u r e 1.

provided

(Ref.

5).

t h i s a p p a r a t u s a r e a q u a r t z tube and a temperature-pro-

The t u b e i s mounted a x i a l l y i n s i d e t h e f u r n a c e .

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

sample, c o l l e c t e d on a p r e f i r e d q u a r t z f i l t e r , is p l a c e d i n t h e q u a r t z t u b e so i t s s u r f a c e i s perpendicular t o t h e tube a x i s . oxygen. tube,

The tube i s c o n s t a n t l y s u p p l i e d w i t h

The e x c e s s oxygen e s c a p e s through a n a x i a l opening a t

w h i l e t h e remainder of

h e a t i n g p a s s through a n o n d i s p e r s i v e i n f r a r e d a n a l y z e r s t a n t flow.

t h e end of

(Beckman 215B) a t a con-

I n a d d i t i o n t o t h e v a r i a b l e t e m p e r a t u r e f u r n a c e , t h e a p p a r a t u s also

c o n t a i n s a c o n s t a n t t e m p e r a t u r e f u r n a c e , u s u a l l y k e p t a t about 800'C. of

g a s e s evolved

The purpose of

t h e c a t a l y s t i s t o e n s u r e t h a t carbon-containing

from t h e sample a r e c o m p l e t e l y c o n v e r t e d t o C02.

important a t

The segment

t e m p e r a t u r e f u r n a c e i s f i l l e d w i t h a copper

quartz tube i n s i d e the constant

oxide c a t a l y s t .

cially

the

t h e oxygen and o t h e r g a s e s evolved d u r i n g sample

T h i s i s espe-

r e l a t i v e l y low t e m p e r a t u r e s when complete o x i d a t i o n

t o C02

does n o t o c c u r .

- i

Ouartz Tube

/

'Light Guide

Temp Rcqmrned Furnace

Fig.

1.

~

~ Filter

~

I

~

Recorder

f

~

~

1

Schematic r e p r e s e n t a t i o n of EGA a p p a r a t u s used i n t h i s study.

r

;

~

~

230 The

actual

measurement

consists

f u n c t i o n of

t h e sample t e m p e r a t u r e .

of t h e

concentration

C02

of

monitoring

The r e s u l t i s a

temperature.

VS.

the

p r o p o r t i o n a l t o t h e carbon c o n t e n t of

"thermogram,"

area

The

t h e sample.

concentration

CC2

under

i.e.,

the

as

a

a plot

thermogram

is

The carbon c o n t e n t i s q u a n t i -

t a t e d w i t h a c a l i b r a t i o n g a s ( C 0 2 i n oxygen) and by measuring t h e g a s flow r a t e through

the

system.

calibration is

This

crosschecked

by

analyzing

samples of

known c a r b o n c o n t e n t . One

important

component

of

the

carbonaceous

aerosol

the

is

"graphitic"

" b l a c k " c a r b o n , which i s known t o cause t h e b l a c k o r g r e y c o l o r a t i o n of and p a r t i c u l a t e samples. corresponds

to

concentration,

this the

In order

carbon,

intensity

to

d e t e r m i n e which

simultaneously of

the

light

with beam

the

of

the

thermogram peaks

measurement

produced

by

monitored by a photodiode and d i s p l a y e d by t h e second pen of

or

ambient

a

of

He-Ne

the

C02

laser

is

the c h a r t recorder.

I n a c t u a l e x p e r i m e n t s t h e l i g h t p e n e t r a t i n g t h e f i l t e r i s c o l l e c t e d by a q u a r t z l i g h t g u i d e and f i l t e r e d by a narrow band i n t e r f e r e n c e f i l t e r t o e l i m i n a t e t h e e f f e c t of t h e glow of

the furnaces.

An e x a m i n a t i o n of

t h e C 0 2 and l i g h t i n t e n -

s i t y t r a c e s e n a b l e s t h e assignment of t h e peak o r peaks i n t h e thermograms c o r r e sponding t o t h e b l a c k c a r b o n because

they a p p e a r c o n c o m i t a n t l y w i t h t h e d e c r e a s e

i n sample a b s o r p t i v i t y .

RESULTS AND DISCUSSION

As

an

i l l u s t r a t i o n of

t h e EGA method,

Figure

ambient sample c o l l e c t e d a t Duarte on September 1 2 , p o r t i o n of

0

100

the

f i g u r e r e p r e s e n t s t h e COL vs.

200 ma 400 Temperature, t

500

2

shows 1Y80.

the

thermogram of

an

The t r a c e i n t h e lower

temperature p l o t ,

while

the

curve

600

Fig. L. An example of t h e EGA o u t p u t - thermogram of a sample c o l l e c t e d a t Duarte on September 1 2 , 1980. Four p r i n c i p a l f e a t u r e s of t h e thermogram are i n d i c a t e d by a , 0 , Y and C The 6 peak c o r r e s p o n d s t o t h e combustion of b l a c k ( e l e m e n t a l ) carbon. T h i s i s evidenced by t h e change i n l i g h t i n t e n s i t y from I t o I,.

.

231 i n t h e upper p a r t o f t h e f i g u r e shows t h e dependence of t h e l i g h t i n t e n s i t y penet r a t i n g t h e sample a s a f u n c t i o n of t h e sample temperature. The area under t h e C02-temperature

c u r v e i s p r o p o r t i o n a l t o t h e t o t a l combus-

t i b l e p a r t i c u l a t e c a r b o n l o a d i n g on t h e f i l t e r punch used f o r a n a l y s i s . measurement 2 cm2 o f t h e exposed f i l t e r were used.

In t h i s

The t o t a l carbon w a s d e t e r -

mined t o be 33.9 p e r cm2 of t h e f i l t e r , which c o r r e s p o n d s t o 32.2 ug/m3 of a i r .

18 ambient samples c o l l e c t -

I n o r d e r t o a s s e s s t h e q u a n t i t a t i v e a s p e c t s of EGA,

ed a t b o t h s i t e s and 9 blank q u a r t z f i l t e r s were a n a l y z e d by EGA by more c o n v e n t i o n a l combustion-volumetric

method by Global Geochemistry C o r p o r a t i o n

The samples used f o r a n a l y s i s were 1 ) as c o l l e c t e d on

of Canoga P a r k , C a l i f o r n i a .

q u a r t z f i l t e r s and 2 ) a f t e r s o n i c a t i o n i n s o l v e n t s . c a r b o n c o n c e n t r a t i o n s i n a wide range

c m 2 were used f o r a n a l y s i s .

from 2-8

and by a

US

from 0.24

These samples c o n t a i n e d t o t a l 2 Sample punches

t o 47 ug/cm

The mean v a l u e of

.

t o t a l carbon f o r a l l

samples as d e t e r m i n e d by t h e two methods d i f f e r s by o n l y 3%.

We conclude from

t h e s e r e s u l t s t h a t EGA i s a v a l i d method f o r d e t e r m i n i n g t o t a l p a r t i c u l a t e carbon. The g r e a t e s t s t r e n g t h o f t h e EGA method i s i t s a b i l i t y t o p r o v i d e a chemical f i n g e r p r i n t o f t h e carbonaceous m a t e r i a l and t o assess t h e c o n t r i b u t i o n of primary p a r t i c l e s t o t h e ambient a e r o s o l .

The remainder of

t h i s section discusses t h i s

t h e method and i t s a p p l i c a t i o n t o ambient p a r t i c l e s c o l l e c t e d a t t h e

a s p e c t of

D u a r t e and Lennox s i t e s . A thermogram of a n ambient sample, s u c h as t h e one shown i n F i g u r e 2 , e x h i b i t s c h a r a c t e r i s t i c f e a t u r e s i n t h e form of peaks o r groups of peaks. thermograms t h a t w e have examined show a low-temperature

as a

i n the

temperatures.

f i g u r e and t h r e e peaks The a

seen

only with

the

oxidation

correspond

Y

,

and 6

--

appearing a t higher

group o b s e r v e d between a p p r o x i m a t e l y 100°C and 23OOC c o r r e -

sponds t o t h e v o l a t i l i z a t i o n of apparent

-- p ,

In general the

group of peaks denoted

lower m o l e c u l a r weight o r g a n i c s .

post-oxidation to

C02.

Peaks

t o decomposition and

catalyst,

indicating

B and 7'

at

o x i d a t i o n of

T h i s group i s

volatilization

approximately 3OOOC

higher

without

and

m o l e c u l a r weight

375°C

species,

w h i l e t h e 6 peak a t a p p r o x i m a t e l y 450°C i s due t o t h e combustion of t h e e l e m e n t a l o r black p a r t i c u l a t e

carbon.

That

this

l a t t e r peak

does

correspond t o

black

c a r b o n i s e v i d e n t from t h e c o r r e s p o n d i n g change i n t h e l i g h t i n t e n s i t y t r a n s m i t t e d t h r o u g h t h e f i l t e r due t o t h e combustion of cles.

light-absorbing

b l a c k carbon p a r t i -

Based on a n a l y s i s of more t h a n 70 f i l t e r samples c o l l e c t e d i n 1980, we

found t h a t t h e p o s i t i o n of t h e 6 enables thermal a n a l y s i s measurements.

The Y

for

peak i s p r a c t i c a l l y c o n s t a n t a t 450 +15'C.

b l a c k c a r b o n t o be performed w i t h o u t

peak a p p e a r s a t 75 +lO°C

lower t h a n t h e

This

the o p t i c a l

6 peak f o r most

samples a n a l y z e d . To i l l u s t r a t e t h e v a r i e t y of s i t u a t i o n s o b s e r v e d a t t h e Duarte s i t e , F i g u r e 3 shows thermograms of f o u r 8-hour t o t a l carbon content,

(noon-8:OO

p.m.1

samples a r r a n g e d by i n c r e a s i n g

c o l l e c t e d on f o u r d i f f e r e n t days.

T o t a l carbon and black

232 carbon c o n c e n t r a t i o n s a r e i n d i c a t e d i n t h e f i g u r e . these

thermograms

the increase

is

r a t i o which g o e s w i t h a n i n c r e a s e i n t o t a l carbon. and t h e v o l a t i l e

a

The most n o t a b l e f e a t u r e of

Y peak i n t e n s i t y and t h e Y : 8

i n the

The b l a c k carbon c o n c e n t r a t i o n

group a l s o show an i n c r e a s e w i t h t o t a l carbon.

r e l a t i v e and a b s o l u t e Y

peak

However, t h e

peak i n t e n s i t y shows t h e most d r a m a t i c change from sample

t o sample. The thermograms of samples c o l l e c t e d on t h e same days and d u r i n g t h e same time i n t e r v a l s a t t h e Lennox s i t e a r e shown i n F i g u r e 4.

A number of f e a t u r e s of these

thermograms are d i s t i n c t l y d i f f e r e n t from t h o s e shown i n F i g u r e 3. Duarte samples where t h e Y

peak i s t h e most i n t e n s e ,

carbon peak i s most prominent.

I n contrast to

i n Lennox samples t h e black

A s t h e t o t a l carbon i n c r e a s e s ,

a l l components of

DUARTE. CA Y Oct 23.1980

July 29,1980

Aug 12, 1980

7

-r

I

l

l

400

200

4

1

601 Temperoture. “C

Fig. 3 . Thermograms of samples w i t h i n c r e a s i n g t o t a l carbon c o n t e n t c o l l e c t e d a t D u a r t e on f o u r d i f f e r e n t days.

LENNOX. CA Auq 12.1980

I

Fig.

4.

I O c t 23.1980

Julv 29. 1980

Sept 24.1980 %

230

400

600 Temperature, ‘C

Thermograms of f o u r c o r r e s p o n d i n g samples c o l l e c t e d a t Lennox.

233 the

Lennox

thermograms

increase

a p p r o x i m a t e l y by

same amount,

the

o v e r a l l a p p e a r a n c e of t h e thermograms e s s e n t i a l l y unchanged,

leaving

the

i n sharp contrast t o

t h e D u a r t e samples, where t h e changes in t h e a b s o l u t e and r e l a t i v e i n t e n s i t i e s o f components a s a f u n c t i o n of

t o t a l carbon c o n c e n t r a t i o n s are obvious.

Also,

both

t h e t o t a l c a r b o n and t h e b l a c k carbon a r e s y s t e m a t i c a l l y h i g h e r a t Duarte f o r a l l I t i s e v i d e n t from F i g u r e s 3 and 4 t h a t t h e d i f f e r e n c e s i n thermo-

days s t u d i e d .

gram f e a t u r e s are more pronounced among t h e Duarte t h a n t h e Lennox samples.

This

is t o be e x p e c t e d because t h e l a t t e r are from a source-dominated r e g i o n , and t h e s e s o u r c e s a r e n o t e x p e c t e d t o vary s i g n i f i c a n t l y from day t o day. During smog e p i s o d e s t o t a l p a r t i c u l a t e c a r b o n l o a d i n g s are h i g h e r d u r i n g t h e day

than during t h e night.

samples were

collected

An

midnight-8:00

a.m.

and

subsequent night-day p.m.

noon-8:OO

at

both

The r e s u l t s of EGA f o r September 4 , 1980 are shown i n F i g u r e s 5

sampling sites. and 6.

During s e v e r a l such e p i s o d e s ,

between

i n s p e c t i o n of

t h i s f i g u r e shows t h a t t h e t o t a l carbon c o n c e n t r a t i o n

d u r i n g t h e day a t D u a r t e was h i g h e r by a b o u t a f a c t o r of 2 . 5 t h a n t h e concentration during the night.

The

black

carbon,

however,

was

only

about

10% h i g h e r

I t i s o b v i o u s from F i g u r e 5 t h a t most of t h e i n c r e a s e i n carbon

d u r i n g t h e day.

Lennox Sept 4. 1980

J , 0

00

1

I

200

l

330

1

1

1

400

Temperoture.

"C

1

500

,

I

600

I

I00

1

1

I

200

I

300

1

1

400

I

I

500

1

\

I

600

Temperature, *C

F i g s . 5 and 6 . Thermograms of daytime and n i g h t t i m e samples c o l l e c t e d a t Duarte and Lennox on September 4 , 1980.

234 c o n c e n t r a t i o n was due t o s p e c i e s t h a t c o r r e s p o n d t o @

and Y

peaks.

The r e s u l t s

of EGA a n a l y s i s of samples c o l l e c t e d d u r i n g t h e same i n t e r v a l s a t Lennox are shown i n F i g u r e 6.

I n t h e s e samples t o t a l carbon and b l a c k carbon are h i g h e r by about

In c o n t r a s t t o t h e D u a r t e thermograms,

15% f o r t h e daytime sample. a p p e a r a n c e of

t h e Lennox thermograms

daytime and n i g h t t i m e samples.

did not

change

the overall

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

the

S i m i l a r d i f f e r e n c e s between daytime and n i g h t t i m e

samples a t Duarte and Lennox were observed on o t h e r days.

One such example is

shown i n F i g u r e s 7 and 8, where d a t a from sampling on October 9, 1980, are shown.

I n o r d e r t o f o l l o w t h e changes i n chemical composition of carbonaceous a e r o s o l s

a series of 2-hour

d u r i n g t h e day,

samples was c o l l e c t e d a t D u a r t e and Lennox.

The sampling spanned t h e i n t e r v a l from 7 : O O a.m. f i l t e r s were used w i t h o u t s i z e s e g r e g a t i o n .

t o 7 : O O p.m.

g u s t 13, 1980, a r e shown i n F i g u r e s 9 t h r o u g h 1 2 . b e r 24 ( F i g u r e 9 ) c l e a r l y d e m o n s t r a t e t h a t

Open-face

47-mm

R e s u l t s from September 24 and AuThe Duarte r e s u l t s from Septem-

t h e midday i n c r e a s e i n t o t a l carbon,

t y p i c a l of Los Angeles smog e p i s o d e s , i s due p r i m a r i l y t o t h e i n c r e a s e i n s p e c i e s corresponding t o

0 and

t i o n s d e s c r i b e d above,

Y

peaks i n thermograms.

t h e Lennox r e s u l t s

C o n s i s t e n t w i t h o t h e r observa-

show a much

less

pronounced

diurnal

variation. There are days when no

Such d i u r n a l b e h a v i o r , however, does n o t always occur.

Duorle OcI 9.1980

I

7

Lennox O c l 9 . 1980

s

I

s

A

A

NIGHT

I I I J l l ( l l l j j l I00

230 300 400 Tempernlure, F

500

600

NIGHT

, M L

I

L

I

100

I

I

D

200

I

300

8

I

400

I

I

m

i

I

600

Temperoture. *C

F i g s . 7 and 8. Daytime and n i g h t t i m e sample thermograms f o r D u a r t e and Lennox on October 9, 1980.

235 DUARTE Sept 24, 1980

0700- 0900

0900- 1100

AA 400

200

200

600

7

600

1700- I900

1500-1700

I

200

400

600

200 400 Temperoture, "C

200

600

400

600

Fig. 9. Thermograms of a series of two-hour samples c o l l e c t e d between 0700 and 1900 h o u r s a t Duarte on September 24, 1980. The dashed peak i n t h i s and t h e f o l l o w i n g f i g u r e s i s an e s t i m a t e o f t h e b l a c k carbon peak, l'

.

c l e a r d i u r n a l v a r i a t i o n s a r e observed. t h e r e s u l t s of a s e t of 2-hour

A s an example i n F i g u r e s 11 and 1 2 w e show

samples c o l l e c t e d on August

13,

1980.

No c l e a r

t r e n d s i n t h e thermogram f e a t u r e s were observed a t e i t h e r s i t e on t h a t day. o v e r a l l f e a t u r e s of

the

thermograms a s w e l l a s t h e

The

t o t a l carbon l o a d i n g s were

s i m i l a r t h r o u g h o u t t h e sampling p e r i o d a t b o t h Duarte and Lennox. An e x a m i n a t i o n of important

thermograms of a l l samples c o l l e c t e d i n

regularities.

sampling days.

Their

1980 r e v e a l s some

Lennox thermograms on t h e a v e r a g e are s i m i l a r principal

component i s

the

black

carbon

peak,

for a l l which

is

236

LENNOX Sept. 24, 1980

1300 - 1500

400

200

1700 - 1900

1500- 1700

Fig. 10. Thermograms September 2 4 , 1980.

600

of

200 403 T e m p e r a t u r e , "C

a s e r i e s of

trast,

200

400

samples c o l l e c t e d a t

two-hour

h i g h e r i n i n t e n s i t y t h a n t h e two o r g a n i c peaks, nighttime

603

0

and Y

samples a r e q u i t e s i m i l a r t o thermograms of

.

600

Lennox on

Thermograms of Duarte

Lennox samples.

In con-

t h e daytime (and e a r l y a f t e r n o o n samples i n a d i u r n a l sequence) of Duarte

show pronounced

0

and Y peaks, w i t h t h e Y

peak being t h e most i n t e n s e .

These r e g u l a r i t i e s can be used t o d e v i s e a procedure t o e m p i r i c a l l y determine t h e amounts of emissions;

primary and secondary o r g a n i c a e r o s o l material w i t h t h e primary

assuming t h a t

t h e Lennox a e r o s o l can be

s o u r c e emissons i n t h e b a s i n ,

c o n s t r u c t e d and used as a f i n g e r p r i n t o r s i g n a t u r e of ticles.

used

a n a v e r a g e thermogram of

as

representative

of

Lennox samples could be primary carbonaceous par-

J u s t i f i c a t i o n of t h i s a p p r o a c h i s c o r r o b o r a t e d by t h e f a c t t h a t n i g h t t i m e

D u a r t e thermograms are s i m i l a r t o t h o s e of Lennox.

T h i s would s u g g e s t t h a t d u r i n g

t h e n i g h t , under low wind c o n d i t i o n s , t h e p a r t i c l e s sampled are m o s t l y from l o c a l s o u r c e s and from aged a e r o s o l .

237

DUARTE Aug. 13, 1980

x

m

200

m

400

o

,

600

200

400

200

600

4oom

A 1500 a

1300-I500

200 Fig. 11. 1980.

1700- 1900

400

600

200 400 600 Temperature, "C

D i u r n a l sequence of two-hour

200

400

600

s a m p l e thermograms f o r D u a r t e on August 13,

LENNOX A u q 13, 1980

0900 - I100

Al AHA

0700-0900

m

400

200

600

1300-1500

400

600

1500- I700

200

400

600

400

600

1700-1900

I

200

Fig.

12.

400

600

200

400 600 Temperoture, "C

Diurnal sequence f o r Lennox on August 13, 1980.

200

238 Because t h e b l a c k carbon peak i s due o n l y t o primary e m i s s i o n s ,

t h e primary

thermogram s i g n a t u r e can be normalized t o t h e b l a c k carbon peak i n t h e thermograms of r e c e p t o r s i t e s s u c h as Duarte.

By t h i s procedure we c o u l d d e f i n e t h e secondary

o r g a n i c s a s t h e d i f f e r e n c e o b t a i n e d between t h e normalized primary s i g n a t u r e and Because t h i s d i f f e r e n c e i s due mainly t o t h e

t h e ambient thermogram. peaks,

a

simple determination

of

t h e Y : 6 peak

ratio

can be

used

0 to

and Y assess

whether a sample c o n t a i n s m o s t l y primary m a t e r i a l o r whether i t i s e n r i c h e d w i t h a secondary component.

CONCLUSIONS

The r e s u l t s d e s c r i b e d above i l l u s t r a t e t h e p o t e n t i a l of EGA f o r t h e c h a r a c t e r i zation

of

thermograms

carbonaceous can be

source-dominated

aerosol

used

particles.

t o provide

a

It

chemical

(Lennox) ambient p a r t i c l e s .

has

been

demonstrated

s i g n a t u r e of

aged

that

the

(Duarte)

and

The f i n d i n g s can be summarized a s

follows : o

The D u a r t e a e r o s o l samples produced thermograms t h a t a r e d i s t i n c t l y d i f -

o

The thermograms of daytime Duarte samples a r e d i f f e r e n t from t h o s e of t h e

o

The d i f f e r e n c e s between daytime and n i g h t t i m e samples a r e minimal a t t h e

o

D i u r n a l v a r i a t i o n s i n thermogram f e a t u r e s are pronounced

f e r e n t from c o r r e s p o n d i n g samples c o l l e c t e d a t Lennox.

n i g h t t i m e samples.

Lennox s i t e . a t Duarte when

t h e r e i s a s i g n i f i c a n t d i u r n a l v a r i a t i o n i n t o t a l p a r t i c u l a t e carbon. o o

D i u r n a l v a r i a t i o n i n thermogram f e a t u r e s i s much l e s s pronounced a t Lennox. D i f f e r e n c e s between samples c o l l e c t e d a t t h e two s i t e s and d u r i n g d i f f e r e n t times of day a r e p r i n c i p a l l y c o n f i n e d t o twa thermogram peaks,

@

and

Y , which p r o b a b l y c o r r e s p o n d t o t h e secondary o r g a n i c s p e c i e s .

REFERENCES

The C h a r a c t e r and O r i g i n of Smog A e r o s o l , e d i t e d by G.M. Hidy, P.K. M u e l l e r , D. G r o s j e a n , B.R. Appel and J. Wesolowski, John Wiley & Sons Ltd., New York, 1980. S.L. Heisler, R.C. Henry, P.K. M u e l l e r , G.M. Hidy and D. G r o s j e a n , Environm e n t a l Research and Technology, I n c . , Westlake V i l l a g e , C a l i f o r n i a , Document #P-A085-1, O c t o b e r , 1980. T. Meisel, "Thermal A n a l y s i s " i n A n a l y s i s of Airborne P a r t i c l e s by P h y s i c a l Methods, H. M a l i s s a , ed. p. 237, CRC-Press, Palm Beach, 1978. H. Malissa, H. Puxbaum and E. P e l l , "Zur s i m u l t a n e n relativkonduktometrischen K o h l e n s t o f f - und Schwetelbestimmung i n Stauben, F r e s e n i u s 2. a n a l . Chem., 282, lOY(1976); H. Puxbaum, I n t e r n . J. Environ. Anal. Chem., 10,1(1981). R.L. Dad, H. Rosen and T. Novakov, Lawrence Berkeley Report LBL-8696(1979). T. Novakov, "Microchemical C h a r a c t e r i z a t i o n of A e r o s o l s " i n Nature, A i m and Methods of Microchemistry, H. M a l i s s a , M. G r a s s e r b a u e r and R. B e l c h e r , e d s . , p. 141, Springer-Verlag, Wein-New York, 1981.

239

ON THE PROBLEM OF MEASURING AND ANALYSIS OF CHEMICALLY CHANGED MINERAL FIBERS IN THE ENVIRONMENT AND IN BIOLOGICAL MATEIZIALS K.R. Spurny Fraunhofer-Institut fur Toxikologie und Aerosolforschunq, 5948 Schmallenberg 1 1 - Grafschaft (G.F.R.)

ABSTRACT Chemical and physical microanalysis of asbestos and glass fibers obtained by environmental sampling (air, water), and from human and animal tissue have shown chemical and crystalline changes in these particles. Scanning electron microscopy, electron microprobe analysis and mass spectroscopic analysis were used in these investigations. Also chemical and physical changes of asbestos and glass fibers after application of different milling procedures were observed A partial or a total leakage could be assessed. The leakage of elements in fibers is of statistical nature. Some fibers rested chemically unchanged, in some fibers elements were partially leached and in some fibers the majority of metalic elements were leached.

INTRODUCTION It is well known that asbestos fibers (AF) as well as man-made mineral fibers (MMMF) of a defined size range (concerning fiber lengths as well as fiber diameter) - although mechanically stable and insoluble in water - are biologically rather active in producing fibrosis and/or cancer (ref. 1 ) . Publications (ref. 2-4) over the last 5 years have convincingly demontrated the primary importance of fiber geometry on the carcinogenic effect. However, this does not exclude chemical properties as well as chemical reactivity of such fibers to be of considerable pathogenetic importance (ref. 5 , 6 ) . Chemical instabilities of chrysotile

-

and of some amphiboles-

have been demontrated in acidic and alkaline solutions as wee1

240

as in living organisms by several researchers (ref. 2 , 3 ) . Also some chemical instabilities of glas fibers has been published recently (ref. 7). Chrysotile is also chemically unstable in different environments (air - corrosion and weathering, water leaching etc.) (ref. 8). We have tried in this investigations to prove the ability of some analytical procedures for determining such chemicals changes in fibers, and we have done some preliminary analyses of different types of AF and MMMF.

MATERIAL AND ANALYTICAL PROCEDURES UICC standard asbestos -chrysotile and crocidolite -and MMYF (glass fibers types JX and rock wool fibers) were used for these analytical investigations. halysis were carried out before and after leaching. Acids and bases, water, blood serum, animal tissues (rabbits, rats and hamsters), human lung tissue, weathering in atmospheric environment, etc., were used as leaching solutions and environments. Qualitative changes in the surface structure of AF and MMMF were observed by scanning electron microscopy (SEM). For the chemical analysis of bulk fibers and of single fibers, followinq methods were applied: SEM and microprobe analysis (EDXA), transmission electron microscopy (TEM) with EDXA and SAED (selected area electron diffraction analysis), x-ray fluorescence spectroscopy (XRF), x-ray diffraction, Auger-spectroscopy (ESCA) and mass spectroscopy (LAMMA) (ref. 9 , l O ) . qualitative changes in the surface structure of AF and MMMF could be observed from SEM and from gas adsorption studies (BET). The chemical and crystallographical changes of fibers in different environments (bulk samples) were studied by means of XRF- and x-ray diffraction methods.

ESCA were used for surficial fiber analysis and the other procedures (EDXA, SAED and LAMMA) were sensitive enough for the analysis and for studies of chemical changes in single individual fibers.

RESULTS AND DISCUSSIONS In inorganic and organic solutions as well as in tissue of living organism, partially also by weathering, chrysotile decomposes by removal MgO nad H 2 0 . A complete breakdown of the chrysotile

241

structure can appear after Mg-ions were fully leached. The remaining fiber fragments appear to be of colloidal nature. In agreement with the results of other publications (ref. 2 , 3 ) a significant chemical instability of chrysotile fibers in environmental samples, in acids and in living orqanism (human lung tissue and animal tissues of lung, spleen, liver, etc.) was found. Also by mechanical comminution, physical and chemical changes in single fibers were found. In some solutions magnesium was relatively quickly leached out, but leaching of iron and silicon ions were also observed. In strong acids, the entire (Mg0H)-sheets of chrysotile were stripped away leaving a silica skeleton. Analysis of single fibers in human lung tissue could be done using SEM

+ EDXA directly in the dried lung samples (Fiqure

1 and

2).

Fig. 1. Micrograph (SEX) of a broken asbestos fiber in the dried sample of the human lung tissue (alveolar region)

After low temperature ashing or after a "wet" dissolution of tissues in Na-hypochloride, analysis of single fibers can be also done by TEM + EDXA + SAED as well as by LAMMA (Figures 3 and 4). Bulk fiber analysis by XRF was also succesfully applied for the demonstration of fast chemical changes of chrysotile fibers in strong H C 1 solutions (Figure 5). In fig. 2 the analysis of a sinqle fiber in human lung tissue shows a complete leaching of M g after the long time exposition to biological liquids. Fig. 3 is an example of the analysis of a

242

single chrysotile fiber by means of TEM + E D X A + S A E D and of the morphological properties by single fibrills. LAMMA - spectra of

Fig. 2. Scanning electron micrograph of one asbestos fiber in the human tissue with its element spectrum (EDXA)

asbestos fibers are well reproducible (Figure 4) and characteristic for each type of asbestos. For instance, a clearcut differentiation between serpentines and amphiboles or also between crocidolite and

243

amosite is well possible. The LAMMA spectra can clearly discriminate different asbestos minerals on the basis of single fiber analysis. The method is also sensitive enough to indicate any changes in the chemical composition in single AF and MMMF.

Si

CU

Fe 3. TEM-microqraph of one sinqle chrysotile fibril of the caiacteristic tub;la; morphology with an-element spectrum (EDXA) and an electron diffraction pattern (SAED).

Fiq.

Results of analysis of 100 chrysotile fibers (human lung tissue) examined by LAMMA indicated that deqree of corrosion (leaching of Mq, Fe and Si) in sinqle fibers is statistically distributed in a

larger fiber population. While some fibers remained chemically unchanged, in the majority of fibers, only Si could be estimated. In some fibers a partially leachinq was observed. Analytical measurements have shown that the leaching was faster in thin fibers than in fibers with a diameter > 1.5 urn. In some favourable cases, where analytical profiling along an extended fiber was possible, LAMMA analysis revealed that the

244

Nq-leaching was rather nonhomogeneous along the fiber axis. Very similar results could be obtained also by the application

Fig. 4. LAMMA spectra (mass spectra) for positive ions obtained from standard UICC asbestos fibers

(+)

and negative

Fig. 5. Element spectra obtained by bukl analysis of chrysotile and crocidolite fibers.Virgine material ( 1 ) and after extraction in H C 1 solution (2).

245

Yi

: A BINDINC ENERGY. EV

PROBE 2 UTE ERHCILTEN DETRIL

183.5 EV IKORRIGIERTI

ISILIKRT, 5102 U.RC.1

02s

B 0

-225

-200

-175

-150

-125

-108

-75

-58

-2s

e

BIHDIHC EHERCY, EV

6. Analyses of small amounts of chrysotile fibers by ESCA: standard UICC chrysotile before (A) and after ( B ) extraction in HC1 solution. Differences in the element composition are evident.

Fig.

246

Fiq. 7. Scanninq electron microqraph of fine q l a s s fibers (type JM 104) used in animal experiments.

23

2a

LO

No

dl

Ca

15L

00 G

HH Sr

157

d Fiq. 8. LAMMA spectrum for positiv ions of one single fiber. The method is very sensitive (ppm and ppb range).

Pig. 9. SEM-micrographs and element spectra of single glass fibers: XRF analyses of original fibers ( I ) , EDXA analysis of single fibers ( 2 - 4 ) after an exposition (5 years) in rabbit lungs.

Fig. 10. XRF bulk analysis of glass and slag fibers: original probe ( 1 ) and after exposition in H C 1 solutions (2). The leaching effect is very evident.

248

of TEM + EDXA + SAED or also in some cases of SEM + EDXA. TEY can be used for the observation and analysis of very thin (fiber diameter < 0.1 urn) fibers, while the LAMMA-method is limited for fibers with a diameter of with a diameter

>

0.2 pm. Also SEM

+

EDXA is limited for fibers 0.2 urn. A fast extraction of Yg and other elements >

from chrysotile in acids can be also followed by XRF (Figure 5.: bulk analyses). Not only AF, but also PDDlF, primarily qlass fibers, can be changed chemically under different environmental conditions and after long residence in animal tissue. Our experimental results with glass fibers have shown that these inorganic fibers undergo similar chemical and physical changes as do chrysotile fibers. They are not resistant to basic solutions, they lose some elements (e. g. Na, K, Ca, Zn) upon exposure to acids and their surface becomes corroded. Changes of chemical composition have been found in glass fibers after 5 years deposition in animal tissue (instillation experiments done on rabbits). Analysis by LAMMA revealed that also in glass fibers a preferential leachinq of elements occur. But also the original chemical composition as well as the leaching of elements in glass fibers are inhomogeneous. Analyses done along the fiber axis demontrate that their chemical composition was different at different locations of the same fiber. Similarly, the chemical leaching of glass fibers was not constant for all fibers, but differed from one fiber to another. These conclusions are also documented by some examples of analyses done by LAMMA, SEM + EDXA and XRF (Figures 7-10.).

CONCLUSION Both AF and MYMF are chemically not inert when subjected to different environmental conditions or when measured in biological liquids. The proved analytical methods seem to be suitable for the analyses of fiber bulks as well as for the analyses of single fibers.

249

REFERENCES F. Pott, Staub-Reinhalt.Luft 38(1979)490-494. M.C. Jaurand, J. Bignon, P. Sgbastien and J. Goni, Environ.Res. 14(1977)245-251. 3 N. Kohyama, K. Kawai, S. Aita, M. Suzuki and H. Hayashi, Ind.Health (Japan)15 (1977)159-1 68. 4 A. Morgan, P. Davies, J.C. Wagner, G . Berry and A. Holmes, Brit.J.Exp.Pathol.58(1977)465-479 5 J. Harrington, A.G. Allison and D. Badami, Adv.Pharmacol.Chemother.12(1975)291-403. L.D. Palekar, C.M. Spooner and D.C. Coffin: Ann.N.Y.Acad.Sci.330 (1979)673-687 H. Tiesler, Glastechn.Ber.54(1981)136-143 and 369-381. K.R. Spurny, W. Stober, G . Weiss and H. Opiela, Atmos.Pollution 8 (1980)31 5-322 9 K.R. Spurny, J. Schormann and R . Kaufmann, Fresenius 2.Anal.Chem. 308(1981)274-279. 10 H. Malissa and J.W. Robinson, Analysis of Airborne Particles by Physical Methods. CRC Press 1nc.Palm Beach,FL,USA(1978) 1 2

This Page Intentionally Left Blank

251

FORMATION O F MONODISPERSE L E A D AEROSOLS AND IDENTIFICATION O F P A R T I C L E NUMBER CONCENTRATION BY I C E NUCLEATION

YASUO UENO* a n d DANIEL E . ROSNER D e p a r t m e n t of E n g i n e e r i n g a n d Applied S c i e n c e , Y a l e U n i v e r s i t y , 9 H i l l h o u s e Avenue, New Haven, Connecticut 06511, U . S. A. ROSA G . d e P E N A D e p a r t m e n t of M e t e o r o l o g y , T h e P e n n s y l v a n i a S t a t e U n i v e r s i t y , U n i v e r s i t y P a r k , P e n n s y l v a n i a 1 6 8 0 2 , U . S. A. JULIAN P. HEICKLEN D e p a r t m e n t of C h e m i s t r y a n d A e r o c e n t e r f o r E n v i r o n m e n t , 152 Davey L a b o r a t o r y , The Pennsylvania State University, U n i v e r s i t y P a r k , P e n n s y l v a n i a 16802, U. S. A.

ABSTRACT L e a d a e r o s o l s w e r e g e n e r a t e d t o i n v e s t i g a t e the conditions f o r the f o r m a t i o n of m o n o d i s p e r s e a e r o s o l s in n i t r o g e n s t r e a m . A e r o s o l s of high m o n o d i s p e r s i t y could b e o b t a i n e d by v a p o r i z i n g l e a d a t a t e m p e r a t u r e i n the r a n g e of 1000° t o 1150°C a n d by flowing n i t r o g e n at a r a t e of 1. 5 l l m i n . In o r d e r to p r o d u c e "lead iodide a e r o s o l s " p o r t i o n s of the l e a d a e r o s o l s w e r e conducted into a t e s t c h a m b e r i n which the a t m o s p h e r e of iodine vapor had previously been p r e p a r e d . T h i s m i x t u r e containing the a e r o s o l s with low c o n c e n t r a t i o n w a s m o d e r a t e l y s t i r r e d u n d e r d i f f e r e n t t e m p e r a t u r e s . "The l e a d iodide a e r o s o l s " w e r e s a m p l e d with a s y r i n g e to be i n j e c t e d T h e a e r o s o l s injected into a m o d i f i e d B i g g ' s t e s t d e v i c e f o r i c e nucleation. r a p i d l y changed into i c e c r y s t a l s , which could g r o w in s i z e . A s the n u m b e r of i c e c r y s t a l s could give t h a t of l e a d iodide a e r o s o l s , the r e a c t i v i t y of l e a d a e r o s o l s with iodine v a p o r w a s i n v e s t i g a t e d u n d e r v a r i o u s t e m p e r a t u r e s . An i n c r e a s e in t e m p e r a t u r e d u r i n g the a g e i n g of l e a d a e r o s o l s with iodine vapor promoted t h e i r reactivity.

INTRODUCTION F o r m a t i o n of h e a v y m e t a l a e r o s o l s ( l e a d e. g. ) with m o n o d i s p e r s e s i z e d i s t r i b u t i o n is of g r e a t i m p o r t a n c e to inhalation toxicology e x p e r i m e n t s or air pollutionlaerosol studies. In t h i s p a p e r , p h y s i c o - c h e m i c a l c o n s i d e r a t i o n i s given on the m e c h a n i s m of l e a d a e r o s o l f o r m a t i o n a n d t h e conditions f o r the f o r m a t i o n of m o n o d i s p e r s e a e r o s o l s a r e experimentally investigated. F u r t h e r e x p e r i m e n t s h a v e a l s o b e e n p e r f o r m e d o n the f o r m a t i o n of "lead iodide a e r o s o l s " b y u s i n g g a s - s o l i d i n t e r f a c e r e a c t i o n between iodine vapor 'KPresent a d d r e s s : D e p a r t m e n t of C h e m i s t r y , T e x a s A & M U n i v e r s i t y , C o l l e g e S t a t i o n , T e x a s 77840.

252

and lead a e r o s o l s obtained. The e x p e r i m e n t a l r e s u l t s of t h e i r reactivity u n d e r v a r i o u s t e m p e r a t u r e s a r e evaluated by a n ice nucleation method.

EXPERIMENTAL PROCEDURES L e a d a e r o s o l s w e r e g e n e r a t e d by a condensation method. The operating t e m p e r a t u r e s and flow r a t e s for a e r o s o l generation ranged f r o m 9500 to 1150°C and f r o m 1 . 0 l i m i n to 4 . 5 l / m i n , respectively. The a e r o s o l s w e r e collected with a n e l e c t r i c a l p r e c i p i t a t o r ( r e f . 1) and thoroughly washed away with a known amount of distilled w a t e r containing a s m a l l amount of n i t r i c acid. The amount of l e a d i n the washed solution was t i t r a t e d with EDTA. The mass concentration was calculated f r o m the a e r o s o l volume having passed through the e l e c t r i c a l p r e c i p i t a t o r and the t i t r a t e d amount of l e a d ( r e f . 2 ) . P a r t i c l e s i z e distribution was a l s o m e a s u r e d by sizing and counting l o t s of p a r t i c l e s in the photos taken by e l e c t r o n m i c r o s c o p e to d e t e r m i n e a v e r a g e particle size. P a r t i c l e number concentration could be known by calculating f r o m m a s s concentration and p a r t i c l e s i z e . "Lead iodide a e r o s o l s " w e r e obtained b y introducing a s m a l l amount of l e a d a e r o s o l s for 30 seconds into a t e s t c h a m b e r , in which the a t m o s p h e r e of iodine vapor had a l r e a d y been p r e p a r e d ( r e f . 3 ) . After lead a e r o s o l s r e a c t e d with iodine vapor under m o d e r a t e s t i r r i n g , s m a l l portions of the

2 \

0 ZE

15-

z

0

2

K I-

z

10-

z 0

0 u) u)

a

5-

FLOW RATE, L/MIN

Fig.

1. Influence of flow r a t e on m a s s concentration.

253 a e r o s o l s w e r e s a m p l e d f r o m t h e c h a m b e r to b e f u r t h e r d i l u t e d i n a n o t h e r c h a m b e r , t h e i n s i d e of w h i c h w a s u n i f o r m l y s t i r r e d . T h e f i n a l dilution f a c t o r i n e a c h e x p e r i m e n t w a s 1:12000 o r m o r e by u s i n g c l e a n n i t r o g e n . A small a m o u n t of t h e a e r o s o l s t h u s d i l u t e d w a s slowly i n j e c t e d into t h e In a d v a n c e , t h e m o d i f i e d B i g g ' s a p p a r a t u s which i s shown i n F i g . 5. a t m o s p h e r e of a cold c h a m b e r i n i t w a s m a i n t a i n e d at a t e m p e r a t u r e of -10. 5' o r -7OC by s t i r r i n g c o o l t a n t i n t h e o u t e r c e l l s ( e t h y l e n e g l y c o l t d r y The t e m p e r a t u r e s of t h e c e l l s a n d t h e c h a m b e r w e r e i c e o r ethyleneglycol). frequently examined, T h e t e m p e r a t u r e s of t h e c h a m b e r w e r e c h e c k e d a t t h r e e d i f f e r e n t p o i n t s i n h e i g h t (top, c e n t e r a n d b o t t o m ) . The temperature of t h e c h a m b e r w a s d e f i n e d a t the c e n t e r w h i c h is shown i n t h e f i g u r e . About o n e m i n u t e l a t e r a f t e r i n j e c t i n g t h e a e r o s o l s , t h e y u s u a l l y s e t t l e d down onto t h e c o l d s u r f a c e of a q u e o u s s u g a r solution. T h e a p p a r e n c e of t i n y i c e c r y s t a l s a s w e l l a s t h e i r g r o w t h i n s i z e could b e o b s e r v e d t h r o u g h a t r a n s p a r e n t t h i c k window f r o m t h e c e i l i n g .

R E S U L T S AND DISCUSSION T h e i n f l u e n c e s of the flow r a t e of n i t r o g e n s t r e a m o n mass c o n c e n t r a t i o n and M a s s c o n c e n t r a t i o n and p a r t i c l e o n p a r t i c l e s i z e a r e g i v e n i n F i g s . 1 a n d 2. s i z e v a r y w i t h t h e flow r a t e of n i t r o g e n a n d t h e t e m p e r a t u r e of l e a d v a p o r . Both of t h e m r e a c h a p e a k a t a c e r t a i n flow r a t e u n d e r a n y of t h e t e m p e r a t u r e s

%

5-0.20 IW

-5

n W

0152 t U

U

a

:W

0.10

>

U

FLOW RATE, L/MIN

Fig.

2. I n f l u e n c e of flow r a t e o n p a r t i c l e s i z e .

254

f r o m 950° to 115OoC, making a c o n t r a s t to the n u m b e r concentration passing through a t r o u g h ( F i g . 3 ) . In o r d e r to calculate the h e a t of evaporation f o r f u s e d l e a d f r o m t h e s e e x p e r i m e n t a l r e s u l t s , p r o p e r a s s u m p t i o n s w e r e m a d e and Clausius -Clapeyron's Equation was applied to e x p e r i m e n t a l data in both regions of slower flow r a t e s ( 1 . 0 and 1. 5 l / m i n ) and f a s t e r flow r a t e s ( 3 . 5 and 4. 5 l / m i n ) . Table 1 In f a c t , indicates the a v e r a g e values of heat of evaporation for fused lead. The values in the table do a l i t e r a t u r e shows the value of 47 k c a l / m o l e . not always m a k e a n a g r e e m e n t with this value a s a h e a t of evaporation. T h i s i s why the calculation was m a d e on b a s i s of the a s s u m p t i o n that the efficiency of t h e r m a l precipitation of the a e r o s o l s i s constant, r e g a r d l e s s of the t e m p e r a t u r e s of f u s e d lead. In f a c t , it m a y possibly be r e a s o n a b l e that the a e r o s o l m a s s concentration in the region of s l o w e r flow r a t e s cannot always be controlled by only t h e r m a l precipitation. The t e m p e r a t u r e s f o r nuclei formation w e r e calculated u n d e r the condition of s u p e r s a t u r a t i o n r a t i o of 5 o r 10. Table 2 shows the t e m p e r a t u r e s f o r A s we can e a s i l y observe from the a p p a r e n c e of the nuclei formation. p a r t i c l e s in the photo shown in Fig. the p a r t i c l e s look round. A S the

50001

s, 0

-

0

I

I

I

1

1000 500

.

-

2-

0 + a

U

I-

2

W

50 -

100

0 2 0

0 U

10-

m

5-

W

3z W

A

0 I-

a

d

10.5

FLOW R A T E , LIMIN

Fig.

3 . Influence of flow r a t e on p a r t i c l e n u m b e r concentration.

255 TABLE 1 A v e r a g e e v a p o r a t i o n heat of f u s e d l e a d f r o m e x p e r i m e n t a l d a t a Flow r a t e ( l / m i n )

H e a t of e v a p o r a t i o n ( k c a l / m o l e )

1.0 1. 5 3.5 4. 5

31. 3 25. 1 33.4 31. 1

TABLE 2 T e m p e r a t u r e s f o r n u c l e i f o r m a t i o n b y t h e s u p e r s a t u r a t i o n r a t i o s of 5 a n d 10 T e m p e r a t u r e (OC)

Supersaturation ratio

F o r lead vapor formation

1150

5 950

10 1150

10 950

F o r nuclei formation

1020

860

980

820

5

r).

Fig.

7. L e a d p a r t i c l e s i n n i t r o g e n ( a v e r a g e d i a m e t e r 0. 11

Fig.

8. A p p a r e n c e of i c e c r y s t a l s i n a modified B i g g ' s a p p a r a t u s .

256 melting point of l e a d i s 327OC, it may be suggested that the p a r t i c l e s w e r e actually in a liquid s t a t e while they w e r e s t i l l growing by mutual collision o r coagulation a f t e r fir s t p a r t i c l e formation. L e t us a s s u m e t h a t p a r t i c l e s i z e m a y be influenced by mutual collision while the a e r o s o l s a r e in a liquid s t a t e a t high t e m p e r a t u r e s , the following equation can ba obtained.

k: rl:

p:

71

:

K:

Boltzmann constant v i s c o s i t y coefficient of nitrogen gas vapor p r e s s u r e of fused l e a d a v e r a g e t e m p e r a t u r e while p a r t i c l e formation, coagulation and growth of p a r t i c l e s a r e undergoing constant

Assuming that nitrogen i s a n i d e a l g a s , the viscosity coefficient i s i n

4

5

5

4

4

F i g . 5. Modified Bigg's t e s t device f o r i c e nucleation. 1. T h e r m a l l y insultaing m a t e r i a l , 2. Ethyleneglycol and d r y i c e , 3. Ethyleneglycol, 4. S t i r r e r , 5. Thermocouple, 6. Inlet for t e s t a e r o s o l s , 7 . Aqueous s u g a r solution, 8 , T r a n s p a r e n t window.

257

- 112 The v a p o r p r e s s u r e of fused lead i s a l s o in proportion proportion to T . to the t e r m of exp (-AH/RT)!/' T h e s e t e r m s c a n be introduced into Eq. ( 1 -112 d 3 = K ' T

( e

- b H I R T 112

1

( 2 )

i s obtained and futher t r a n s f o r m e d .

E q . ( 3 ) c a n finally be derived.

In c a s e In ( K ' 'i: ' I 2 ) is constant, t h e r e m a y be a l i n e a r relationship between In d and 1/T. The slope of s t r a i g h t line can give the value of h e a t of evaporation. Applying Eq. ( 3 ) to e x p e r i m e n t a l r e s u l t s , a plot of In d against 1 / T should be l i n e a r and this i s found to bP actually the c a s e , a s i s shown i n F i g . 4. T h e s e plots a r e a l l s t r a i g h t lines p a r a l l e l with one another a s might be expected of Eq.( 3 1. The heat of evaporation f o r fused lead has been obtained a s the value of 47 k c a l / m o l e . T h e r e h a s been a good a g r e e m e n t between the values calculated f r o m e x p e r i m e n t a l data and the l i t e r a t u r e value with r e s p e c t to heat of evaporation f o r fused lead.

I

I

I

-4.

-4

I k t3 0 -5. J

- 5. 0 2.5

/'

0 3.5 0 4.5

"

7.0

.

/,

1

I

7.5

8.0

I/T,

10-4/0~

F i g . 4. P l o t of log d a g a i n s t 1 / T .

1.

258

Fig. 6 shows the influence of t e m p e r a t u r e and flow r a t e on a e r o s o l monodispersity. T h e n u m b e r s in the f i g u r e show the m o n o d i s p e r s i t y of l e a d aerosols. A e r o s o l s of high m o n o d i s p e r s i t y could be obtained by vaporizing l e a d a t a t e m p e r a t u r e i n the r a n g e of 1000° t o 115OOC and by flowing nitrogen s t r e a m a t a r a t e of 1. 5 l / m i n . A s s o m e e x p e r i m e n t s w e r e p e r f o r m e d on i c e nucleation by using r e a l l e a d iodide a e r o s o l s g e n e r a t e d f r o m fused l e a d iodide ( r e f . 41, this p r e s e n t e x p e r i m e n t i s c a r r i e d out by u s i n g two different l e a d a e r o s o l s : d = 0. I l p ( t e m p e r a t u r e 95OoC, flow r a t e 4. 5 l / m i n , m o n o d i s p e r s i t y 0. 31) and d = 0. 78,&(temperature 1000°C, flow r a t e 1. 5 l / m i n , m o n o d i s p e r s i t y 0. 17). As a r e s u l t , i t s e e m s t h a t the c o a r s e r l e a d a e r o s o l s r e a c t with iodine to produce l e a d iodide a e r o s o l s m o r e r e a d i l y than f i n e r ones. The reactivity i s T h e a p p a r e n t h e a t of activation a c c e l e r a t e d by the t e m p e r a t u r e of reaction. could a l s o be e s t i m a t e d . F u r t h e r d i s c u s s i o n will be d e m o s t r a t e d on the effect of r e a c t i o n t e m p e r a t u r e o n t h e r e a c t i v i t y of l e a d a e r o s o l s with iodine v a p o r and t h e i c e nucleation t e m p e r a t u r e s . F i g s . 7 and 8. show t h e photos of l e a d a e r o s o l s and i c e c r y s t a l s in the modified B i g g ' s a p p a r a t u s , r e s p e c t i v e l y .

1150

-

.

1100-

036

Y 10503

I-

4

.

a w

2w

1000-

+ 951

o;. "' ;o 1 0.27

1.0 1.5

25

35

4.5

FLOW RATE, L/MIN

Fig.

6. Influence of t e m p e r a t u r e and flow r a t e on a e r o s o l m o n o d i s p e r s i t y .

REFERENCES 1. Y . 2 Y. 3 Y. 4 Y.

Ueno Ueno Ueno, Ueno,

and I. Sano, Bull. C h e m . SOC.Japan, 44(1971) 908-911. and I. Sano, Bull. Chem. SOC.J a p a n , 45(1972) 975-980. Atmos. E n v i r o n . , lO(1976) 409-413. the 56th Colloid & I n t e r f a c e Sci. S y m p . , Virginia, in J u n e ,

1982.

259

OPTICAL OBSERVATIONS DURING CHDTICAL REACTIONS

H. STRAUBEL Vorderhindelang (G.F.R.

)

AE S TRACT Droplets or solids freely suspended in a three-plate-capacitor and illuminated by a laser beam yield a characteristic diffraction pattern. Assumed an exactly shaped sphere, this diffraction pattern consists in a system of concentric equidistant fringes of equal intensity. Each deviation from geometry or/and intensity in this system indicates a change of the refractive index n. This may be effected by impurities, by a mixture of two components, by an evaporating gradient, by crystalization of solutions or by chemical reactions. Using the electrical voltages connected with the capacitor and by optical evaluating the diffraction patterns, the whole running off can be investigated.

INTRODUCTION In the atmosphere chemical reactions occur between aerosol particles f.e. NaC1, NH C1, Pe 0 in presence of anthropogenic gases such as 4 2 3 C1, SO2, NOx and H2S. Due to these very diluted gases, the reactions run off in minutes to many hours. Therefore it is impossible to investigate such reactions with usual light scattering instruments, as their retention time is shorter (ca 1/100 s) than the time required for the chemical reaction. Besides this the particle is lost having passed the device. Possible reactions are known, however, they could not yet be observed on single particles at any state. Only integral measurement with a big number of particles was possible until now. In a three-plate-capacitor, described by the author previously, droplets or single solid particles can be freely suspended for more than 100 hours, undisturbed by boundaries except the surrounding air (ref. 1 ) Illuminated by a laser beam ( A = O , 6 3 2 8 / u m ) , radii of

.

260

the droplets can be calculated by the distance of the interference fringes, provided the droplet’s shape is exact spherical. The voltages a.c. and d.c., connected with the capacitor, work as a balance. Through it changes of mass are recorded at any time. To evaluate the optical data during the chemical reaction, the process under investigation must ~ n c elead to a spherical shape of the product. (ref. 2). Only in this state it is possible to calculate the radius r of the particle. By using the spheres data as starting point, now all changes during the process can be derived forward and backward at each time. If the specific weight of the sphere is unknown, it can be determined by two different voltages at the cahacitor (ref. 3 ) .

EXPERIMENTS 1). Disturbed ring system Droplets consisting of uniform substances as f.e. water, benzene, glycerine, yield as diffraction pattern a system of concentric, equidistant fringes, easy to evaluate. Fig. 1 shows the possible interferences between the beams 1 and 2 for a transparent sphere. The path difference between 1 and 2 is defined by equation (1) with the radius r and refractive index n: n A = 2r sin Y If the sphere is containing some small impurities (non transparent, monodisperse) the fringes become disturbed and dissimilar, dependent from number and size of these impurities. Fig. 2.

Fig. 1. Possible path difference between beams 1 and 2 for a transparent sphere.

Fig. 2. Disturbed fringes by small particles inside a sphere. Diameter 1 7 , l p .

261

The particles composition was 5% MoS2 ( d< l w ) in 95 % oil. For the particles inside the droplet Rayleigh-scattering can be assumed. The same phenomena will be observed if a frozen homogeneous sphere with a shrinked surface is illuminated by a laser beam. In this case essentially the reflected beam 2 of the surface is influenced.

2). Optical inhomogeneities By suspending a clear transparent droplet in the beam, another appearence can be seen. The fringes are very fine smoothened, however, a series of different diameter, thickness and intensity spreads out in radial direction, indicating a I1modulation1lof the whole system. Fig. 3. Such a phenomenon cannot be explained by Fig. 1, as the relation between reflected and permeating beam is only valid for a uniform refractive index n. This relation is also valid during evaporation o r condensation of the droplet (diminution o r growing). However, smallest deviations of n inside the sphere lead to optical inhomogeneities which appear in the diffraction pattern.,The droplet under research was a mixture of 80% oil with 20% benzene. As the vapour pressure of benzene is higher than that Fig. 3. Modulated interference of oil, the benzene evaporates fringes due to evaporation at the surface and effects a of one component in a mixture. radial gradient of the mixture Diameter 4 2 p . inside the sphere. (noil>nbenzene). This produces a modulation of the system. By evaporation o r condensation of one component of a mixture o r by a more or less concentration of a salt solution, the same phenomenon is developped. Generally, each change inside a particle will be visible as a change of refractive index n.

3).

Chemical reaction Chemical reactions lead always to changes of n. To irivestigate this relation, fixing salt (Na2S203 5 H20) was chosen. A dry crystal freely suspended in the capacitor, is dissolved by increasing relative

262

humidity (r.h.) of the surrounding air. Pig. 4a shows the dry crystal, 4b the initial water film on the crystal's surface. Gradually the crystal is dissolved, deviations in the ring diameters 4c indicate still undissolved small crystal particles (d< 1 w ) within the droplet (d = 2 9 , 3 6 m ) . Now injecting HC1-vapour in the capacitor leads to the reaction, Fig. 4d. The fringes of the diffraction pattern break open, 4e, forming a structure like llcellslt. We detect bright and dark spots, quickly traveling. New formed products NaCl and S are separated. Electrical control of the particle's weight shows that the whole portion of H2S03 5 H20 is expelled from the droplet, Fig. 5. At last a zone of preferred forward scattering appears in the middle of the pattern, and the contours of a NaC1-crystal emerges Fig. 4f During and after the reaction we see a strong turbidity of the NaC1-solution, due to the liberated S-molecules. After a few minutes, however, the pattern is cleared, as the S-molecules have formed greater agglomerates with smaller light scattering.

.

Fig. 4 a-f. Reaction between Na S 0 2 2 3 Compare Fig. 5 and 6

5 H20 + 2 HC1

263

/ i

L

:loo "

( H,O +SO,) .5H,O

(Y

8 0,

Fig. 5. Weight changes during the reaction

4). Fluid crystals Fluid crystals are organicsubstances with a temperature-dependent opacity, but without chemical change. They are used for displays, controled by temperature or electric fields (ref.$). The so called 0 Wf3BAtf substance is solid and turbid below 21 C, however, it becomes clear above 44 OC. In this interval the molecules have only degrees of freedom for translation and rotation. They arrange in domains of 105 molecules. Due to the walls between these regions, differences in refractive index n arise. Fig. 7a shows a droplet's ring system above 44 O C . Below this temperature there are confused regions and fringes of unequal distances in droplets with 2 0 0 . This may be due to the rotational sywnetric diameters d whirling of the molecules and simultaneous changes of refractive index n.

Fig. 7.

a

above 44

OC

b

between 21 and 44

OC

264

CONCLUSIONS The described method enables the observation of smallest optical deviations in solids o r fluids, freely suspended in electric fields. By two-beam-interference it is possible to differentiate between the properties of clear o r mixed fluid-droplets and of evaporating solutions.

x

tW3BAlf N-(p-Methoxy-bemyliden)-p-n-butylanilin

REFERENCES 1 H,Straubel, in Atmospheric Pollution 1978, Proceedings of the 13th International Colloquium, Paris, France, April 25-28, 1978, M.M.Benarie (Ed.), Studies in Environmental Science, Volume 1 Elsevier Scientific Publishing Company, Amsterdam 2

H.Straube1, in Atmospheric Pollution 1980, Proceedings of the 14 International Colloquium, Paris, France, May 5-8, 1980, M.M.Benarie (Ed.), Studies in Environmental Science, Volume 8 Elsevier Scientific Publishing Company, Amsterdam

3

H.Straube1, “Elektro-optische Messung von Aerosolen” Technisches Messen 48.Jahrgang 1981 Heft 6 tm 199-210 Verlag Oldenbourg, Miinchen

4. H.Kelker, “History of Liquid Crystals”, in: Molecular Crystals and Liquid Crystals, 1973, Vol. 21, pp. 1-48, Copyright 1973 Gordon and Breach Science Fublishers, Printed in Great Britain

265

COMPARISON BETWEEN S I X DIFFERENT INSTRUMENTS TO DETERMINE SUSPENDED PARTICULATE MATTER LEVELS IN AMBIENT AIR

J.G. KRETZSCS.MAR and J.B. PAUWELS

Studiccer.trum voor Kernenergie, B-2400 Mol, Belgium

ABSTRACT Over a period of six months simultaneous suspended particulate matter measurements with two different high volume samplers, two different low volume samplers, an automated dichotomous particulate system and an integrating Nephelometer were carried out at the same semi-rural monitoring site in the vicinity of the Nuclear Energy Research Centre, Mol, Belgium.

Except for the nephelometer all SPY-deter-

minations were done gravimetrically. The entire experiment was based on the comparison of daily averages. A reasonable to good correlation was found between the different instruments although the daily levels as well as the overall statistics of the SPM-situation over a period of six months showed large deviations.

For certain instruments the

deviations seemed to be systematic. The experiment will be repeated over another period of six months in order to control the present findings.

INTRODUCTION During the past years suspended particulate matter (SPM) levels in ambient air were determined with many different systems in a rather impressive number of short term projects or more permanent monitoring networks.

This paper reports the pre-

liminary results of the intercomparison under field conditions of six different systems used or in use under the previously mentioned conditions for the determination of SPM-levels in Belgium. comparison

The aims of the project are first of all the

of individual short-term (daily averages) measurements, simultaeously

obtained under field conditions with each of the systems, and secondly the analysis of the possible influence of the choice of a specific measuring system upon the evaluation of the actual SPM-situation when collectinq a sufficient number of individual measurements, and comparing some specific statistical parameters (means, percentiles or maxima) with the specifications of air quality guidelines, recommendations or standards.

266

DESCRIPTION OF THE MONITORING SITE AND SYSTEMS Figure 1 shows the semi-rural monitoring site in the vicinity of the Nuclear Energy Centre, Mol (SCK/CEN) with the following measuring systems

1 and 1'

:

:

two versions of the high volume LIB-Filterverfahren (LIB-HI1 and LIB-HI1' as described in ref. 1).

Fig. 1. Monitoring site (SCK/CEN, Mol) with different sampling systems.

2

:

the low-volume sequential sampler of the Instituut voor Hygiene en Epidemiologie, Brussel (IHE-LO, ref. 2).

3

:

the Beckman Dichotomous Particulate Sampler (DVI-LO, refs. 3-5). ment separates the collected dust in a fine and coarse fraction.

This instru-

267 The concentration corresponding to the sum of both fractions is used in the comparison with the other systems.

4 : a low-volume version of the LIB-Verfahren (LIB-LO). 5 :the SCK/CEN high volume sampler (SCK-HI, ref. 6).

6 :the MRI Integrating Nephelometer (NEPH, not represented on fig. 1 ) .

The main characteristics of the sampling systems for the gravimetric determination of the SPM-levels are summarized in Table 1.

done on conditioned filters (20 "C, 54 averages.

% RH).

All gravimetric determinations are Reported SPM-levels are daily

For the Nephelometer analogue recording was used.

TABLE 1 Main Characteristics of the sampling systems for gravimetric determination of SPM System

Fig. 1

filter

filtered volume/day

loaden surface LIB-HI1 LIB-HI 1 ' IHE-LO DVI-LO LIB-LO SCK-HI

450 500 15 24 80 550

m3 m3 m3 m3 m3 m3

Whatman 41, Whatman 41, Sartorius, Sartorius, Whatman 41, Whatman 41,

87 cm2 77 cm2 12,6 cm2 6,6 cm2 15 cm2 104 cm2

cellulose cellulose membrane 0,45 !Jm membrane 0,80 Um cellulose cellulose

1 1' 2 3 4 5

COMPARISON OF THE SIMULTANEOUS MEASUREMENTS Over a period of six months 77 simultaneous valid determinations of the SPMlevels were obtained. day-by-day LIB-LO.

Of the six systems three showed a very good agreement on a

base namely the SCK-HI, the LIB-HI (in bath versions 1 and 1') and the

The IHE-LO sampling system Predominantly followed the pattern of these

three systems although some prolonged deviations in both directions (lower or higher) were noted during the experiment.

The dichotomous virtual impactor (DVI-LO)

systematically gave lower levels than all the other instruments while the Nephelometer (NEPH) recorded the hiqhestpeak values.

Full details of the time series of

the simultaneous measurements are given in reference 7. The results of a linear regression analysis on the simultaneous measurements of each time two different systems are summarized in Table 2 (r cient, to the left of the diagonal

;

a/b

=

=

correlation coeffi-

coefficients of the equation y = a x + b ,

to the right), while Figure 2 gives the correspondinq scatter diagrams with respect to the SCK-HI sampler.

268

0 0 N

L

I

2 _J

R=O. 95 0

0

100

0

200

100

200

SCK-HI lug/rn31

SCK-HI ( ~ g / m ~ I

7

0

0

0

100

100

0

200

SCK-HI (ug/m31 0 0

0 0

N

N

I

u

0

I

200

SCK-HI h g / m 3 1

N=77 A=O. u B=2 R = O . 66

R=O. 86 0

0

1 0

100

SCK-HI

200 (4m31

0

100

200

SCK-HI [ ~ ~ g / m ~ 1

Fig. 2. Scatter diagrams of the simultaneous measurements with respect to the SCK-HI system.

269

TABLE 2 Correlation between the different measuring systems

SCK-HI LIB-HI 1 LIB-HI 1 ' LIn-Lo IHE-LO DVI-LO NEPH

SCK-HI

LIB-HI1

LIB-HI1'

LIB-LO

IHE-LO

DVI-LO

NEPH

-

0.9/10

0.94 0.95 0.94 0.71 0.66 0.86

-

1.0/-2 1.0,'-9

0.6/44 0.7/40 0.7/47

0.4/2 0.5/-3

-

1.0/1 1.1/-8 1.0/4

0.97

-

0.6/47

0.4/0

0.76 0.77

0.73 0.74 0.90

-

0.4/-11

0.96 0.97 0.71 0.71 0.89

0.92

0.67

-

1.4,'-24 1.6/-38 1.4/-17 1.4/-22 1.3,'-45 2.0/11

0.73

0.76

-

0.5/0

Table 2 and Figure 2 confirm the very good agreement between the SCK-HI, the LIB-HI'S and the LIB-LO samplers. The Nephelometer has a good correlation with these devices too but the regression equations confirm the tendacy of the Nephelometer for too hi.gh readinqs once the SPM-levels exceed a certain value. shows an acceptable correlation (r

=

The ME-LO

0 . 7 1 to 0 . 7 6 for n = 77) with the previous

systems. With respect to SCK and LIB the regression equations show a tendacy for overestimation of the lower SPM-levels measured in this test.

The SPM-levels given

by the dichotomous virtual impact are systematically too small over the entire SPMrange, and the correlation varies between 0.66 and 0.77.

COMPARISON OF THE GLOBAL STATISTICS Cumulative frequency distributions of the 77 simultaneously obtained daily averages are given on Figure 3 for each of the systems. The main statistical parameters are summarized in Table 3. in very good agreement.

As before the LIB'S and the SCK-HI sampler are

The IHE-LO device gives a significantly larger arithmetic

average, 87 1.1g/m3 against 6 1 to 6 7 ug/m3, and larger percentiles except above P90 where the SPM-levels are within the range of the LIB'S and the SCK-HI device. This results in a smaller u

9

( 1 . 4 against 1 . 6 to 1 . 8 ) for IHE-LO.

The Nephelo-

meter gives the inverse picture namely arithmetic average and lower percentiles (beneath P80) are comparable with the LIB'S and the SCK-HI but the higher percentiles, and consequently the geometric standard deviation,are larger ( u = 2 . 4 against 9

1 . 6 to 1 . 8 ) .

On the average the results of the dichotomous virtual impactor are a

factor 2 to 2 . 5 smaller than the corresponding results of the LIB-HI, the LIB-LO and the SCK-HI.

270

/ 1.;.

SC K - H,I,,, .. ..

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

. . ... ...

i..i..i...l..i..l.... .. .. .. .. .. .. I . ... .I ..

LIB-HI 1

200

100

i . .

GO 50 40

.?.H E.

.. .. . . . . . .. .. ...................... ... . ... . ... . . . . . . . . .... . . ... .. .. . . . . . . . .. .. ,............ . .......... .. ... .. . .. . .. . .. ... ... ..................... .. .. . .. ... .. . . .. .. .. . . . .... , .. . .. . ... . . ......... .. .. .. .. .. . . . . . .. .. . . . . . .. .. . . ., . .. . . ,. ..... ,. ...... .. .. ,........ .. .. .. .. .. ... ... .. . .. . .. . .. ... ... . . . . . . ;..: .: . : :.. : , . i . . I ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... . . . . . . .

' ?

30

20

:

. . .. . .. .. . . . . . .. ...; . ..

"E

100

GO

50

z

ti0 30

GO 50 UO

-

:lo 50 70 85 9598 PROBRBILITY . . . .

Fig. 3.

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

60 50

' 7

20

:

.

l

j

110 30 20

10

I

200

) . . _ ...........

. . . . . .

100

,.:.

i

.. ... .. ... . ... .. ,:

50 70 85 9598 PROBRBILITY

Cumulative Frequency Distributions.

.I 1 0 0

.....

.....

30 .. .. .. .. .. .. .. . . , . , . , .. ...................... . . . . . . .. ... ... ... ... ... ... ... ... ... ... ... ... ... .. .. .. .. .. .. .. .. .. .. .. .. .. .. . . . . . . . j

,

m~

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

UO

j

.

50 70 85 9598 PROBRBILITY

50

j

.

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

G O "e

"E

I

.

NEPH.?

.. .. . . . . . . . . . . .:..;..;.. . . . . .. . . .;. ..: .. .. .. :..;..: .. .. .. .. .. ... ... . .. . .. . .. . .. .. .. . . . . . . i. N. 4 7 3 i 1 .. .. .. .. . . . . . . . ... . . .... . . ... . . ... . . .. . . ... . . . . . . . . .. .. .. .. .. .. .. .. , ...... ,......, . . . . . . . . . . . . . . . . .

30

20

100

... ... ... ... ... ... ... ... .. .. .. . . . . . . . . :..:..: . :. :...:. . . .:. . . . ; ... ... . . . . . .. . . . . .. .. ... ... ... ... ... ... ... ... ... ... ... ... . .. . .. . .. .. ... ... ... ... ... ... ... ... .. .. . . . . . .. ..

DVI-LO

100

.

. , ,

i i

. . , ..... ............. .. .. .........., ............. .. .. .. .. .......................... .. .. .. .. .. .. .. .. ,. ........................... .. ... ... ... ... ... ... ... ......................... .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .,. ..,.... ,........ . , ........... . . . . .. .. .. ... ... ... ... ... ., ......................... . . . . . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . . . . . ;..:...;...:..;..: .. .. .. .. .. . . ... .; ... . i.. .. .. .. .. .. .. .. .. ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... .. .. .. .. .. .. .. .. . . . . . . .

.

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

PROBRBILITY

200

.

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

"!

50 70 85 9598

LO

. . . . -.. . ... .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . . . . . . .:,.:..;,..:.:..: . . . . . .. .. .. .. .. . . ... .; .... . .j.. . . . . . . . .

.

m10

10

50 70 85 9598 PROBRBILITY ,,

//

N s77

%... . . . . . . .

. . . . . . . .. .. .. . ... ... ... ... ... .. .~. . ... . ... . ... . ... . ... . ... 200 .. .. .. .. .. .. .. ..

200

:. N. =77 : I . . .. .. ..

.......................... .. . . . . . . . . . . .. .. .. .. .. .. .. .. . . . .. .. .. .. .. .. ........................ .. .. .. .. .. .. .. .. ... ... ... ... ... ... ... ... ......................... .. .. .. .. .. .. .. .. ... ... ... ... ... ... ... ... .. .. .. .. .. .. .. ..... .,. ....... . /................. . . . . . .. .. .. ... ... ... ... ... .. .. .. .. .. .. .. .. ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... . . . . . . .

L I.. B. . -. .L.9.. . . . .

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

20

10

' 7

. . . . . . . .:

.. .. .. .. . .:. ... .

:.

.. .. .. .

60 "E

. . . . . . . .. .. ... . . . . . . . . . .,.... ,. ....... , ..... ;. . . j . . . . . . . .. .. .. . . . . . . :. i .. . . !.. i . .. I . ... .I .. . . ..I 30 ... ... ... ... . .. . .. .. .. .. .. .. .. .. .. :,. :...:..;..: . . . .:. . . . .: 20 . .. .. .. .. .. .. ... ... ... ... ... ... ... ... ... ... ... ... ... ... . . . . . . . .. .. .. .. .. .. .. .. .. .. .. . . . . . : 10

uo

.. ..

.

50 70 85 9598 PROBRBILITY

271

TABLE 3 Global statistics of the 7 7 simultaneous daily averages System

m

P50

P60

P70

SCK-HI LIB-HI1 LIB-HII' LIB-LO IHE-LO DVI-LO NEPH

66 67 61 64 87 28 69

59 59 54 58 80 24 51

65 68 58 61 89 30 63

73 72 63 67 96 33 73

with

P80 77 78 72 77 110 37 83

P90 92 98 91 90 124 47 128

m

:

arithmetic average

P50...P98

:

percentiles

max .

:

maximum value

U

:

geometric standard deviation

9

P95

P98

max

0

125 132 137 140 141 73 214

164 148 149 158 155 80 221

180 162 172 171 164 87 227

1.6 1.6 1.8 1.6 1.4 2.0 2.4

g

based on P98 and P50

These ratios are even larger than the 1.2 and the 1.8 reported for two different sites in reference 8.

It's obvious that more detailed studies of the DVI are

needed.

CONCLUSIONS The first phase of an intercomparison under field conditions of several commonly used methods for the determination of SPM-levels in ambient air leads to the following preliminary conclusions. Simultaneously determined daily SPM-levels are systematically in excellent agreement for certain sampling systems while others show random or systematic deviations.

Correlations ranged from acceptable to excellent while linear regression

techniques confirmed functional differences over the entire measured concentration range or over parts of it. Taking into account that normally the main purpose of measuring SPM-levels is to make a statement with respect to air quality recommendations, guidelines or standards, the obtained data sets of 77 simultaneous daily averages were analized from this point of view too.

If the WHO-Guidelines of 60 to 90 ug/m3 for the year-

ly average, and 150 to 230 ug/m3 for the 98-percentile of the gravimetrically determined daily average SPM-levels (ref. 9) are taken as reference this leads to the following observations. One system (DVI) gave results significantly smaller than the reference levels (approx. a factor 2).

The statistics of all the other systems

were within the specified range for respectively the mean and the 98-percentile level.

The results of the LIB'S and SCK-HI were rather around the lower limit of

the specified ranges while IHE-LO was high for the mean, low for the 98-percentile and vice versa for NEPH.

212

ACKNOWLEDGMENT This research was carried out under contract with the Ministry of Public Health.

REFERENCES 1 VDI-Richtlinien, Messen der Massenkoncentration von Partikelen in der Aussenluft, VDI 2463, August 1974. 2 IHE, Jaarrapport 1980. IHE Meetnet Zware Metalen, Brussel, 1981. 3 B.W. Loo, J . M . Jaklevic and F.S. Gouldinq, in B.Y.M. Lin (Ed.), Fine Particles, Aerosol Generation, Measurement, Sampling and Analysis, Academic Press Inc. N.Y., 1976, pp. 311-350. 4 W. John, G.P. Reisahl and J. Wesolowski, PB 80-113731, NTIS, 1978. 5 H. van Duuren, Kema 6792-79, 1979. 6 J.G. Kretzschmar, I. Delespaul and Th. De Rijck, The Science of the Total Env., 14 (1980) 85-97. 7 SCK, Onderzoek naar de niveaus van de luchtverontreiniging door Zware Metalen in Belgie, Mol, 1981. 8 R.K. Stevens et al., Atm. Env., 1 2 (1978) 55-68. 9 WHO, Environmental Health Criteria 8, Geneva, 1979.

213

SOME USES OF A DILUTER FOR AEROSOLS J.C. GUICHARD I n s t i t u t N a t i o n a l de Recherche Chimique Appliquee

-

I R C H A - VERT-le-PETIT - ( F r a n c e )

AB ST RA CT To d i l u t e an a e r o s o l i s a u n i t o p e r a t i o n which i s m m a n d n n r e f r e q u e n t i n the everyday work o f a l a b o r a t o r y o f p h y s i c s o f a e r o s o l s . We proposed a s o l u t i o n and have been d e v e l o p i n g i t s i n c e 1966. The I R C H A d i l u t i o n system i s h e r e d e s c r i b e d , and i t s main c h a r a c t e r i s t i c s are g i v e n . P r e s e n t l y commercialized, i t has p r o v e d e f f i c i e n t i n v a r i e d a p p l i c a t i o n s - a choice o f which i s h e r e o r e s e n t e d .

INTRODUCTION

To d i l u t e an a e r o s o l i s a u n i t o p e r a t i o n o f p h y s i c e n g i n e e r i n g which r e q u i r e s t o be more c a r e f u l t h a n i n t h e case o f t h e simDle m i x i n g gas-gas. T h i s s p e c i f i c c h a r a c t e r of t h e p r o b l e m o f t h e d i l u t i o n o f an a e r o s o l was d e f i n e d i n t h e l a t e 1 9 5 0 ' s and t h e c o m m e r c i a l i z a t i o n o f t h e o p t i c a l c o u n t e r s o f p a r t i c l e s has l e d t o t h e s t u d y o f o r a t i c a l systems, o a r t i c u l a r l y a t t h e I R C H A . We d e s c r i b e d t h e f i r s t " d i l u t i o n system" i n

1966 ( 1 ) and o r e s e n t e d i t t o t h e general o u b l i c t h e same y e a r ( 2 ) . That i n s t r u m e n t has r a o i d l y become an e s s e n t i a l t o o l which i s mentioned i n q u i t e a number o f o u r p u b l i c a t i o n s , f o r i n s t a n c e i n ( 3 ) where we show how u s e f u l i t can be f o r t e s t i n g a i r

f i 1 t e r s . O t h e r teams have a l s o worked on such r e a l i s a t i o n s w i t h o u t always o u b l i s h i n g t h e i r r e s u l t s . The l a t e s t s t u d i e s seem t o be those o f F e l i x and h i s colleagues ( 4 ) . F o r many y e a r s t h e p r o d u c t development o f these d i l u t i o n systems has been n u r e l y e m p i r i c which l i m i t e d t h e i r d i f f u s i o n . But, i n 1976 we managed t o work c u t a semiq u a n t i t a t i v e t h e o r y w h i c h now enables us t o c a l c u l a t e these anparatus a c c o r d i n g t o each p a r t i c u l a r case. A system o f c o m m e r c i a l i z a t i o n has t h e n been s e t t l e d i n s a t i s f a c t o r y c o n d i t i o n s , t h e r e s u l t o f which was t o show us t h a t these d i l u t i o n systems had o t h e r a p p l i c a t i o n s t h a n t h e ones o r i g i n a l l y t h o u g h t o f , as we s h a l l see now.

P r i n c i p l e s o f t h e I R C H A d i l u t i o n ' systems and d i f f e r e n t types o f r e a l i s a t i o n P r i n c i p l e s . Because o f t h e l a r g e dynamic o f usual c o n c e n t r a t i o n s i n t h e f i e l d o f a e r o s o l ( l o 4 and beyond) t h e system must reach d i l u t i o n r a t i o s o f

and beyond,

which imposes t o d i l u t e a s m a l l q u a n t i t y o f a e r o s o l i n a l a r g e volume o f c l e a n a i r .

274

The p r i n c i p l e of resolution chosen c o n s i s t s i n making a progressive d i l u t i o n i n a t u r bulent medium i n a dynamic system ( s e e f i g u r e 1 ) . For t h a t we use a cone perforated with rings of blowing holes which are supplied with clean a i r . The aerosol i s s e n t t o the top of the cone and finds i t s ' way out by d i l u t i n g i t s e l f gradually. There e x i s t two types of apparatus whether the mean airflow velocity in the cone i s constant o r

n o t . I t i s the constant tyoe apparatus t h a t we s h a l l now study.

clean air

porous media FIGURE 1 : General schema of the d i l u t e r model A The p r i n c i p l e above mentioned must come i n t o operation in a p r a c t i c a l system answering a c e r t a i n number of c r i t e r i o n s which define the ideal d i l u t i o n . There are three c r i t e r i o n s : - the aerosol should be homogeneous i n concentration and p a r t i c l e s i z e d i s t r i b u t i o n a t the output.

-

the system should be " l i n e a r " t h a t i s t o say the concentrations of aerosol a t the

e n t r y Co and a t the way-out C should be linked by q c = c0 Q + q Q clean a i r flow '

q aerosol flow

c

dilution ratio

CO

Whatever be Q and q between the ooerational l i m i t s appropriate f o r each d i l u t e r . - The l o s s e s i n the cone, which a r e i n e v i t a b l e s i n c e we have t o go through a t u r b u l e n t phase, should be, as much as p o s s i b l e , reduced. The theory a t our disposal enables us t o cone e n t i r e l y with the f i r s t two problems B u t the losses cannot be q u a n t i t a t i v e l y delimited a p r i o r i . Experience showed us

275 which types o f c o n s t r u c t i o n c o u l d g i v e r a t i o s g o i n g beyond 10 %.So we know how t o a v o i d t h a t problem b u t , f a c e d w i t h a new c o n s t r u c t i o n f o r which we p r e c i s e l y want t o know t h a t r a t i o , we must r e s o r t t o a d i r e c t d e t e r m i n a t i o n through a s i m p l e enough experiment. E v e n t u a l l y , l e t us m e n t i o n t h a t , uo t o now, o u r systems have been used w i t h a continuous a e r o s o l f e e d i n g . We a r e D r e s e n t l y s t u d y i n g t h e i r r e a c t i o n under an impuls i o n a l f e e d i n g i n o t h e r words we a r e t r y i n g t o q u a n t i f y t h e d e f o r m a t i o n which a s h o r t a e r o s o l p u f f undergoes d u r i n g i t s d i l u t i o n . B u i l d i n g o f d i l u t i o n systems. The d i l u t i o n system i s e s s e n t i a l l y d e f i n e d by i t s i n t e r n a l cone ( t h e o u t p u t d u c t i s meant t o smooth down t h e t u r b u l e n t f l o w coming o u t from t h e cone). The b u i l d i n g parameters a r e t h e a n g l e o f t h e cone and i t s o u t p u t diameter, t h e number and p o s i t i o n o f t h e r i n g s o f b l o w i n g h o l e s , t h e number o f h o l e s i n a r i n g and t h e i r own d i a m e t e r s . I t f o l l o w s t h a t t h e number o f p o s s i b l e cones i s v e r y l a r g e , b u t t h e t h e o r y enables t o s e l e c t s o l u t i o n s which answer t h e c r i t e r i o n s above mentionned ( s e e p r i n c i p l e s ) . Faced w i t h a problem which we a r e asked t o s o l v e , we can t h u s propose an apparatus t h e p e r f e c t f u n c t i o n i n g o f which we can a s c e r t a i n , b u t we do n o t p r e t e n d t o d i s c o v e r a l l t h e p o s s i b l e s o l u t i o n s . Indeed we happened t o c r e a t e systems d i v e r g i n g f r o m t h e t h e o r e t i c a l s o l u t i o n b u t we had t o check t h e i r good f u n c t i o n i n g by r a t h e r c o s t l y experiments, f o l l o w i n a procedures t h e g e n e r a l l i n e o f which has a l r e a d y been mentioned i n ( 1 ) . Another i m p o r t a n t p o i n t i s t h e area s u r r o u n d i n g t h e cone and which c o n s t i t u t e s a plenum where t h e f l o w s h o u l d be s u f f i c i e n t l y u n i f o r m so as t o have t h e same f l o w i n g speed f o r each o f t h e h o l e s i n t h e cone. There a r e two main ways t o s o l v e t h e problem; t h e y a r e governed by t h e acceptance o r n o t o f a s t r a i g h t f o n v a r d e n t r y l e n g t h f o r t h e aerosol p i p e . I n model A ( f i g u r e 1) t h e c l e a n a i r i s blown t a n g e n t i a l l y i n t o a f i r s t compartment t h e n t h e f l o w i s s t a b i l i z e d by p a s s i n g t h r o u g h a porous l a y e r b e f o r e p e n e t r a t i n g i n t o t h e plenum s u r r o u n d i n g t h e cone. T h a t d i s p o s i t i o n which g i v e s D a r t i c u l a r l y cheap c o n s t r u c t i o n s n e c e s s i t a t e s t h a t t h e f i r s t compartment s h o u l d have a p i g e g o i n g across i t and l e a d i n g t h e a e r o s o l . T h i s s t r a i g h t f o r w a r d l e n g t h i s n o t a c c e p t a b l e f o r c e r t a i n problems, because o f t h e l o s s e s i t may provoke ( f o r i n s t a n c e an a e r o s o l o f s m a l l drops t o be d r i e d ) . We t h e n use model B ( f i g u r e 2 ) i n which t h e a i r i s i n t r o d u c e d i n t o a compartment s u r r o u n d i n g t h e o u t p u t p i p e b e f o r e i t be blown towards t h e cone t h r o u g h a f i n e g r i d o f d i f f u s i o n . T h a t s o l u t i o n which p e r m i t s t h e i n t r o d u c t i o n o f t h e a e r o s o l p r a c t i c a l l y a t t h e l e v e l o f t h e f i r s t b l o w i n g r i n g , gives apparatus much more c o s t l y and b u l k y .

276

clean air

FIGURE 2 : General schema of the d i l u t e r model B General c h a r a c t e r i s t i c s of d i l u t i o n systems. A f i r s t p r a c t i c a l apnroach consists i n

giving t h e i r dimensions. The smallest d i l u t i o n system which i s t h e o r e t i c a l l y possible to conceive i s 7 cm i n diameter a n d t r e a t s 100 l/mn and more of clean a i r . I t i s f e a s i b l e t h a t systems 5 cm i n diameter should function b u t t h e i r perfecting will have

t o be made through an experimental approach. Picture 1 shows asystma little 1-r

which i s of a model B type and whichis special i n t h a t i t was devised t o sample aerosols a t

high temperature. There are no t h e o r e t i c a l l i m i t s t o l a r g e s i z e s b u t we have never had the occasion t o check i t beyond 1 m in diameter. The l a r g e s t we a r e personally using i s 60 cm i n diameter and i t s t o t a l length i s 3 m . I t can be seen o n p i c t u r e 2 . There e x i s t , of course, a l l the intermediary s i z e s w i t h a model of output diameter measuring 20 cm which i s often requested by the laboratory o f ohysics of aerosols f o r i t covers most of t h e needs. The next parameter t o be considered i s the airflow through the d i l u t i o n system o r the mean airflow velocity a t the output. I n general the minimal airflow corresponds t o an output velocity i n f e r i o r t o 1 m/s ( t e c h n i c a l reasons). The maximum airflow i s limited t o the value which gives a pressure drop i n the cone o f 60 mm of water (pract i c a l reason); the corresponding output velocity i s then 8,5 times the minimal veloc i t y . This r a t i o 8,5 a l s o represents the dynamic of the flows currently used. The pressure drop o f the cone i s given by

2 = 0,1326 V P in which V i s , i n m/s, the output airflow velocity common t o every hole. A A

P

t h e pressure drop i n mm o f water

217

A more c o n v e n i e n t f o r m u l a i s = 0,1326 ( K Us)’ where Us i s , i n m/s, t h e a i r f l o w v e l o c i t y a t the P o u t p u t and K a c o n s t a n t c h a r a c t e r i s t i c o f t h e cone. T h a t c o n s t a n t , g i v e n w i t h each

h

system, i s always > 2,5 Another i m p o r t a n t c h a r a c t e r i s t i c i s t h e c a o a c i t y o f d i l u t i o n . F o r an o r d i n a r y system o p e r a t i n g a t a g i v e n a i r f l o w , t h e r e i s a maximum v a l u e o f t h e aerosol a i r f l o w which can be a d m i t t e d . T h i s v a l u e depends on t h e c o n s t r u c t i o n c h a r a c t e r i s t i c s ; i t can be a d e t e r m i n a n t element f o r c e r t a i n a p p l i c a t i o n s such as t h e p r o d u c t i o n o f d u s t l a d e n f l o w s . I n o t h e r i n s t a n c e s ( t o measure a e r o s o l s f o r i n s t a n c e ) i t can be

gnored.

F i g u r e 3 i l l u s t r a t e s t h i s p o i n t f o r systems 23 cm i n diameter designed f o r d i f e r e n t a p p l i c a t i o n s . On t h e c o n t r a r y t h e r e i s no i n f e r i o r l i m i t t o t h e a i r f l o w t o d i Ute;

dilution ratio x

lo-*

I/mn 100

1000

clean air flow

FIGURE 3 : Examples o f t h e maximum r a t i o f o r two d i l u t e r s o f t h e same d i a m e t e r (pi 23 cm)

however, i n t h e case o f an a e r o s o l , p r a c t i c a l l i m i t s can be found, f o r i f t h e a i r f l o w i s too low

t h e l o s s e s , i n t h e c a r r y i n g p i p e s , b e f o r e r e a c h i n g t h e d i l u t i o n system

become s i g n i f i c a n t . T h a t i s why t h e g e n e r a l r u l e i s t o work on as much aerosol as p o s s i b l e so as t o o b t a i n e v e n t u a l l y a qood p r e c i s i o n . T h i s leads t o use i m p o r t a n t a i r f l o w o f c l e a n a i r f e e d i n g s e r i a l l y disposed systems (we s h a l l see an example of

t h a t application t o medical n e b u l i z e r s ) . Finally another c h a r a c t e r i s t i c , with which we s h a l l deal b r i e f l y , concerns the l i m i t a t i o n s of the s i z e s of the p a r t i c l e s which can be t r e a t e d . A few common sense recommendations, which our experience taught us as w e l l , are here very useful t o know. The d i l u t i o n operation i t s e l f can function without problems f o r n a r t i c l e s of 100 u ( d e n s i t y 2 ) b u t losses with local concentration decreases can be the consequence of thc natural sedimentation o r of centrifugation e f f e c t s due t o the turbulence in the cone and i n the straightforward length a t the outout. I n a l l the cases, when the s i z e s are s u p e r i o r t o 10 p ( d e n s i t y l ) , i t i s b e t t e r t o work with systems equipped with a v e r t i c a l a x i s , which prevents l o s s e s i f we do not go beyond 20 p . Beyond t h a t p o i n t , according to the model of the d i l u t e r and i t s operating flow, we can come across problems which i t i s b e t t e r t o discover and quantify during an i n i t i a l study o f q u a l i f i c a t i o n from which t a b l e s of correction of t h e observed defects may be drawn. Examples of a p p l i c a t i o n of d i l u t i o n systems Measuring aerosols. A d i l u t i o n system i s an often indispensable i n t e r f a c e between the real aerosols, o r the ones made i n l a b o r a t o r i e s , and the various o p t i c a l counters (Royco, S a r t o r i u s e t c . . ) , b u t we a l s o happened t o use i t f o r l e s s recent instruments, such as the cascade impactor, when the smoke t o be studied was highly concentrated. I t would seem cheaper t o use small models b u t , as we already noticed, the d i l u t i o n c o e f f i c i e n t s sought being and below, we would then t r e a t small airflows of aerosols and losses would a l t e r the measuring accuracy. That i s why we generally recommend t o use d i l u t e r s 20 t o 23 cm i n diameters and operating around 1000 l/mn. There a r e , however, cases i n which high d i l u t i o n r a t i o s a r e sought and we have a permanent apparatus which c l e a r l y i l l u s t r a t e s t h i s point ( s e e p i c t u r e 2 ) . I t i s used t o study the clouds produced by medical nebulizers. (pneumatic nebulizers, u l t r a s o n i c nebulizers o r "spray cans") The i n i t i a l concentrations a r e usually of some millions of p a r t i c l e s per cm3 and they must be reduced t o r a t i o s i n f e r i o r t o 50/cm3 which n e c e s s i t a t e s d i l u t i o n s of 105 times and more. I n the i n s t a l l a t i o n presented, the nebulizer i s enclosed i n a t i g h t box i n t o which s t a i n l e s s s t e e l ( p = 10 cm) The whole of the droplets aerosol i s s e n t i n t o t h a t f i r s t s t a g e where i t i s mixed with 300 l/mn of hot a i r (temperature of 120°C) so a s t o dry i t up t o obtain a penetrates the e n t r y of a d i l u t i o n system model B made of

cloud of nuclei which will be the o b j e c t of the measuring. The output of the d i l u t e r i s p u t under pressure thanks t o a g r i d , so t h a t one p a r t of the airflow should be send towards a second stage (@=60cm)through an o r i f i c e p l a t e . This d i l u t e r operates around 10.000 l/mn and i s followed by a terminal level (@=23cm)i n which the airflow of clean a i r i s 1000 l/mn.

219

The r e a l i s a t i o n of dust laden flows. We had t h e occasion t o present such a n applic a t i o n a t the 1 2 t h colloquium of the I R C H A ( 5 ) . Since then the same basic principles have been applied t o the r e a l i s a t i o n of flows a t a g r e a t e r velocity ( 2 0 m/s) obtained i n i n s t a l l a t i o n s t h a t we f i t out when asked, according t o a common scheme. A fluidized bed aerosol generator of the " n u l d o u l i t " tyne model B sends a concentrated aerosol i n t o the e n t r y of a special d i l u t e r capable of operating a t a high airflow velocity. A t the output, the homogeneous phase obtained a t t a c k s a second f l u i d i z e d bed where the aerosol undergoes i f necessary a f u r t h e r disnersion and where the flow acquires turbulence c h a r a c t e r i s t i c s which can be regulated a t will ( f l a t velocity c h a r t , uniform turbulence r a t i o e t c . .) Another obvious application i s in the f i e l d of a i r - f i l t e r s t e s t i n g f a c i l i t y . The d i l u t e r , j o i n t l y operating with a f l u i d i z e d bed aerosol generator enables t o create an "entry s e c t i o n " which can be very e f f i c i e n t and whose reduced s i z e i f compared t o the straightforward lengths necessary t o have a c o r r e c t aerosol i n c l a s s i c a l i n s t a l l a t i o n s (ASHRAE t e s t , Na C1 t e s t e t c . . . ) T h a t disposition proves p a r t i c u l a r l y e f f i c i e n t when we want t o s e t u p a permanent i n s t a l l a t i o n enabling t o measure the f r a c tional e f f i c i e n c y of f i l t e r s and of f i l t e r i n g l a y e r s . Moreoverin the domaine of f i l t e r s , t h a t same technology enabled us t o find a good s o l u t i o n to the t r i c k y problem of t e s t i n g c a r t r i d g e f i l t e r s with c i r c u l a r l y opened s u c t i o n . I t i s well known t h a t we generally have t o deal with cylindrical nleated paper i n a housing where polluted a i r i s admitted t h r o u g h a c i r c u l a r s l o t opened near the top of the housing. The nroblem of t e s t i n g i s t o make the aerosol penetrate uniformly i n t o the s l o t , while avoiding as much as possible the deposits on the housing i t s e l f . We have b u i l t and studied a n i n s t a l l a t i o n accordinq t o the diagram in figure 4. The f i l t e r t o be t e s t e d i s s e t t l e d on the f l o o r of a c y l i n d r i c tank in which i s f i t t e d the outnut of a d i l u t i o n system which sends the t e s t aerosol uniformly dispersed i n a flow representing, on a n average, half of the one aspirated by the f i l t e r being t e s t e d . The complementary flow comes from the outside and goes t h r o u g h the ring s i t u a t e d between the two cylinders where i t i s transformed i n t o a p r o t e c t i v e flow meant t o minimize the dust l o s s e s . With t h a t system, the quantity of dust which penetrates i s exactly i d e n t i c a l i n a l l points of the a s p i r a t i n g s l o t and the deposits ( t h a t can be released i n suspension a t the end of the t e s t ) do n o t exceed 10 % of the q u a n t i t y s e n t . Applications i n the f i e l d of the mixinq of gases. The homogeneous mixing of two o r more gases can be done by methods well known in chemical engineering and practised i n apparatus which may be simpler than those here described. That i s why we did n o t think a t f i r s t t h a t our d i l u t e r s could have an onening in t h a t f i e l d and y e t they

280

dust .-c

.-- clean air

ambiant air

FIGURE 4 : Schema o f a f a c i l i t y t o t e s t c a r t r i d g e f i l t e r have n o t ceased t o develo? i n t h a t a p p l i c a t i o n . The reasons a r e many b u t v e r y o f t e n

i t i s t h e i r c h a r a c t e r i s t i c o f b e i n g a b l e t o make r a p i d l y , i n a reduced space, a p e r f e c t m i x i n g w h i c h i s p a r t i c u l a r l y a p p r e c i a t e d as p r o v e d by t h e two f o l l o w i n g examples The f a b r i c a t i o n o f g r e a t f l o w s o f gaz o n l y s l i g h t l y p o l l u t e d , f o r i n s t a n c e by t o x i c s , can be done almost c o r r e c t l y i n v e s s e l s which a r e expensive because o f t h e i r volume. The d i l u t i o n system i s a v e r s a t i l e and cheap s o l u t i o n . Thus, i t was p o s s i b l e t o m i x 50 cc/mn o f gas i n 15.000 l/mn o f c l e a n a i r , g i v i n g c o n c e n t r a t i o n s o f 3 ppm i n volume. The c l e a n i n g o f gases and noxious vapours by making them r e a c t w i t h a n o t h e r gas which t r a n s f o r m s them i n t o aerosol i s a o o s s i b i l i t y which arouses g r e a t i n t e r e s t . We have made a d e m o n s t r a t i o n i n t h e case o f t h e phosgen. I t i s a dangerous t o x i c which chemical i n d u s t r i e s r e j e c t , more and more f r e q u e n t l y , under t h e f o r m o f d i l u t e d e f f l u e n t s , which l i m i t s p u r i f y i n g e f f i c i e n c y and makes i t expensive t o use c l a s s i c a l systems such as t h e washers ( w i t h a l i m e s o l u t i o n t h e b e s t ones reach an e f f i c i e n c y o f 90 % on c o n d i t i o n o f t o l e r a t i n g 200 t o 300 mm o f w a t e r o f p r e s s u r e d r o p ) . B u t t h e phosphogene can r e a c t w i t h t h e ammoniac by g i v i n g an aerosol o f u r e a . Thus, f o r

281

e f f l u e n t s a t 650 ppm, i n t r o d u c e d i n t h e main c i r c u i t o f t h e d i l u t e r ( f l o w o f 2500 l / m ) a f l o w o f ammoniac o f 8 l/mn s e n t by t h e a e r o s o l c i r c u i t enables t o p u r i f y a t 95 % whereas t h e p r e s s u r e drop accepted w i t h t h e c i r c u i t o f e f f l u e n t s i s o f 40 mm o f w a t e r . Even i f t h e a e r o s o l produced must t h e n be stopped, t h i s means o f o u r i f i c a t i o n seems t o be cheaply c o m p e t i t i v e . L e t us m e n t i o n t h a t t h e c o m m e r c i a l i z a t i o n o f d i l u t e r s f o r t h a t t y p e o f a p p l i c a t i o n i s c a r r i e d o u t by EUROPOLL l t d ( 6 ) . Sampling h o t a e r o s o l s . The g r e a t m a j o r i t y o f t h e measuring apparatus f o r a e r o s o l s p a r t i c u l a r l y t h e most e l a b o r a t e ones, h a r d l y e v e r f u n c t i o n beyond 50 o r 6 0 " . I f we have t o s t u d y d u s t s u b m i t t e d t o h i g h temoeratures (400 t o 800°C),

t h e y have t o be

c o o l e d . The use o f an exchanoer i s a s o l u t i o n e n t a i l i n g heavy l o s s e s o f a e r o s o l , moreo v e r t h e a e r o s o l can a l s o be d e t e r i o r a t e s . Combining b o t h t h e c o o l i n g and t h e d i l u t i o n i n one o f o u r apparatus i s a s o l u t i o n w h i c h gave e x c e l l e n t r e s u l t s , f o r i n s t a n c e when we s t u d i e d t h e e x h a u s t fumes o f i n t e r n a l combustion e n g i n e s . I t was t h e d i l u t e r model B, i n s t a i n l e s s s t e e l , p r e s e n t e d i n p i c t u r e 2 which was used. A n o t i c e a b l e c h a r a c t e r i s t i c o f t h e method i s t h a t t h e f l o w o f h o t qas which e n t e r s i n t o t h e appar a t u s i s measured by a t h e r m i c method. F o r t h a t , thermocouples w i t h r e c o r d e r s a r e p l a c e d a t t h e e n t r y o f t h e h o t gas ( T 2 ) , a t t h e e n t r y o f t h e d i l u t i o n c i r c u i t ( T o ) and a t t h e o u t p u t o f t h e d i l u t e r (T1). I f we draw t h e e n t h a l o i c balance o f t h e system, t h e r e s u l t o b t a i n e d , i n a f i r s t a p n r o x i m a t i o n i n t h e case o f t h e a i r i s :

5

Q

=

1 ;

-

To

2_- T 1

With a d i l u t i o n r a t i o o f

lo-[,

= dilution ratio

w i t h gas a t 600°C, whereas c l e a n a i r i s a t 22°C t h e

r i s e i n temperature a t t h e o u t p u t i s 5,8"C. Thus equipped, t h e d i l u t e r i s v e r y c o n v e n i e n t f o sampling and measurinq h o t a e r o s o l s whether these be a t a s u f f i c i e n t o v e r p r e s s u r e o r whether we de-pressure t h e d i l u t e r by a s p i r a t i n g a t i t s o u t p u t . The examples o f a p p l i c a t i o n s above mentioned have been chosen among o t h e r s because t h e y a r e p a r t i c u l a r l y s i g n i f i c a n t . They show t h a t these d i l u t e r s c o n s t i t u t e an operat i o n a l s o l u t i o n f o r most o f t h e problems o f a e r o s o l d i l u t i o n and o f t h e f a b r i c a t i o n o f d u s t l a d e n f l o w s w h i c h can a r i s e i n t h e l a b o r a t o r y o r i n i n d u s t r y . REFERENCES 1 J.C. Guichard e t J.C. Ney, C o n s t r u c t i o n e t etude d'une chambre d d i l u t i o n pour a e r o s o l s . I R C H A , n o t e i n t e r i e u r e NO32 (1966) 2 J.C.

Guichard, Chambre

a

d i l u t i o n p o u r a e r o s o l s . Conference a l a s e s s i o n 1966 d

Munich de " A r b e i t k r e i s F u r Reine Riume" ( S t u g g a r t )

282

3 J.C. Guichard e t J . TGsio, Performance of a i r f i l t e r s f o r clean rooms. The t e s t f a c i l i t y of I R C H A . F i l t r a t i o n a n d se9aration Sent/Oct. 1370 n.577 B 585. 4 L.G. F e l i x , R . L . t l e r r i t t , J.D.Uc Cain e t J.W. Ragland, S a m l i n g a n d d i l u t i o n system design f o r measurement o f submicron o a r t i c l e s i z e and concentration i n stack emission a e r o s o l s . TSI q u a t e r l y Oct/Dec. 7 1 9 8 1 N O 4 D . 3 B 1 2 . 5 J . C . Guichard, A . Saint-Yrieix e t J.L. Magne, E h d e s oreliminaires a la construc

t i o n d'une cheminee d ' e s s a i . lZPme Colloque International orqanisi! par 1 ' I R C H A in Atmosoheric Pollution e d i t e d by PI. Benarie, 0 . 325 B 338. 6 EuroDoll, 2 Rue Amorteaux 78730 Saint-Arnoult-en-Yvelines - France

Picture 2

283

FORMATION AND EVOLUTION OF SULFATE AND N I T R A T E AEROSOLS I N PLUMES C h r i s t i a n Seigneur, Pradeep Saxena, and A. Be1 l e Hudischewskyj Systems A p p l i c a t i o n s , Inc.,

San R a f a e l , C a l i f o r n i a

94903

ABSTRACT A mathematical model i s p r e s e n t e d t h a t d e s c r i b e s t h e b e h a v i o r o f gaseous and a e r o s o l s p e c i e s i n plumes.

The processes r e p r e s e n t e d b y t h e model i n c l u d e

a d v e c t i v e t r a n s p o r t , t u r b u l e n t d i f f u s i o n , s u r f a c e d e p o s i t i o n , gas-phase c h e m i s t r y , a e r o s o l c o a g u l a t i o n and s e d i m e n t a t i o n , and gas-to-aerosol s i o n f o r b o t h n i t r a t e and s u l f a t e species.

conver-

The model p r e d i c t i o n s a r e compared

w i t h measurements o b t a i n e d i n t h r e e power p l a n t plumes having d i f f e r e n t environments.

INTRODUCTION The s t u d y o f secondary a e r o s o l f o r m a t i o n i n t h e atmosphere i s a s u b j e c t o f p a r t i c u l a r i n t e r e s t i n a i r p o l 1 u t i o n r e s e a r c h because secondary a e r o s o l s c o n t r i b u t e t o v i s i b i l i t y impairment, a c i d p r e c i p i t a t i o n , and p o s s i b l y a f f e c t human h e a l t h a d v e r s e l y .

Secondary a e r o s o l s a r e formed i n t h e atmosphere when

gaseous s p e c i e s e i t h e r n u c l e a t e t o form new a e r o s o l s o r condense on t h e surface o f e x i s t i n g aerosols.

Chemical s p e c i e s i n v o l v e d i n t h e s e gas-to-

a e r o s o l c o n v e r s i o n processes i n c l u d e s u l f a t e , n i t r a t e , and o r g a n i c species. The p r i m a r y p o l l u t a n t s e m i t t e d from power p l a n t s i n c l u d e SO2,

NO,

and p r i m a r y

a e r o s o l s ; s i n c e small amounts o f hydrocarbons a r e e m i t t e d , o r g a n i c a e r o s o l f o r m a t i o n i n power p l a n t plumes can be c o n s i d e r e d t o be n e g l i g i b l e .

In this

paper, we c o n s i d e r t h e f o r m a t i o n and e v o l u t i o n o f secondary s u l f a t e and n i t r a t e a e r o s o l s i n power p l a n t plumes. I n r e c e n t y e a r s , s e v e r a l e x p e r i m e n t a l programs have been undertaken t o s t u d y secondary s u l f a t e and n i t r a t e a e r o s o l f o r m a t i o n i n plumes.

Conversely,

t h e o r e t i c a l s t u d i e s have been conducted t o q u a n t i t a t i v e l y d e s c r i b e t h e processes i n v o l v e d i n aerosol f o r m a t i o n and dynamics and, u l t i m a t e l y , t o s i m u l a t e a e r o s o l b e h a v i o r i n t h e atmosphere.

To t h i s end, s e v e r a l mathematical models f o r s u l f a t e f o r m a t i o n have been developed ( r e f s . 1-2-3).

Comparisons o f model p r e d i c t i o n s w i t h a i r b o r n e

measurements performed i n power p l a n t plumes have shown s a t i s f a c t o r y agreement ( r e f s . 1-3).

N i t r a t e a e r o s o l c h e m i s t r y i n t h e atmosphere has a l s o been

s t u d i e d ( r e f s . 4-5-6-7).

However, t o o u r knowledge, t h e r e has been no a t t e m p t

t o model n i t r a t e aerosol f o r m a t i o n i n plumes.

Since t h e r e i s i n c r e a s i n g

e v i d e n c e o f i t s f o r m a t i o n i n power p l a n t plumes ( r e f s . 8 - 9 ) , i t i s c l e a r l y i m p o r t a n t t o i n c l u d e n i t r a t e aerosol dynamics i n t h e mathematical t r e a t m e n t o f plume a e r o s o l f o r m a t i o n . T h i s paper p r e s e n t s t h e e x t e n s i o n o f a s u l f a t e a e r o s o l plume model t o i n c l u d e n i t r a t e aerosol formation.

We f i r s t p r e s e n t a b r i e f d e s c r i p t i o n o f

t h e model and t h e c h e m i s t r y o f secondary aerosol f o r m a t i o n a t l o w humidities.

The f o l l o w i n g s e c t i o n d i s c u s s e s t h e model s i m u l a t i o n o f secondary

a e r o s o l f o r m a t i o n i n power p l a n t plumes f o r t y p i c a l cases i n v o l v i n g d i f f e r e n t background c h e m i s t r y and compares model s i m u l a t i o n s w i t h e x p e r i m e n t a l data. F i n a l l y , t h e s t u d y r e s u l t s a r e d i s c u s s e d i n terms o f model a p p l i c a t i o n s and o f a d d i t i o n a l work needed t o understand and s i m u l a t e atmospheric aerosol formation.

D E S C R I P T I O N OF THE MODEL

Formation o f s u l f a t e a e r o s o l s S u l f a t e a e r o s o l s a r e formed i n t h e atmosphere from t h e o x i d a t i o n o f SO2

on soot aerosol s u r f a c e s o r i n l i q u i d c o a t e d a e r o s o l s o r l i q u i d d r o p l e t s . A r e v i e w o f t h e v a r i o u s chemical pathways ( w h i c h can o c c u r i n t h e gas phase)

t h a t l e a d t o t h e f o r m a t i o n o f s u l f a t e s i n t h e atmosphere has been presented by B u r t o n e t a l . ( r e f . 10).

A f t e r a b r i e f o v e r v i e w o f t h e s e processes, we

address i n more d e t a i l t h o s e chemical processes o f i n t e r e s t t o t h e p r e s e n t study. The most i m p o r t a n t chemical pathways o f gas-phase o x i d a t i o n o f SO2 i n t h e

A

atmosphere i n v o l v e t h e r e a c t i o n o f SO2 w i t h OH, CH3O2, and H02 r a d i c a l s . r e v i e w o f t h e k i n e t i c d a t a a v a i l a b l e f o r t h e s e r e a c t i o n s suggests t h a t t h e

r e a c t i o n w i t h OH i s t h e most s i g n i f i c a n t gas-phase o x i d a t i o n pathway f o r SO2 ( r e f . 1 1 ) ; t h e r e f o r e , i n t h i s s t u d y , i t w i l l be t h e o n l y pathway c o n s i d e r e d ( r e f s . 3-12):

SO2

+

OH

----+

HS03

----+

H SO

2 4

k = 1320 ppm-' m i n - l

(11

285

Because t h e vapor p r e s s u r e o f H2SO4 i s low, i t w i l l condense i n t h e presence o f H20 ( r e f . 13).

Another g a s - t o - p a r t i c l e c o n v e r s i o n process f o r H2SO4

i n v o l v e s t h e r e a c t i o n o f H2SO4 w i t h NH3 t o form NH4HS04 and (NH4)2S04.

This

process i s b e l i e v e d t o p r e v a i l o v e r t h e f o r m a t i o n o f H2SO4 s o l u t i o n a e r o s o l s i n t h e t r o p o s p h e r e ( r e f s . 14-15-16).

The f o r m a t i o n o f ammonium s u l f a t e s i s

i n v e s t i g a t e d i n g r e a t e r d e t a i l a t t h e end o f t h i s s e c t i o n . The o x i d a t i o n o f SO2 a l s o o c c u r s on t h e s u r f a c e o f soot a e r o s o l s and i n t h e l i q u i d phase o f l i q u i d - c o a t e d a e r o s o l s o r l i q u i d d r o p l e t s .

The l i q u i d -

phase o x i d a t i o n processes i n c l u d e o x i d a t i o n by 02, 03, and H202, and o x i d a t i o n b y O 2 c a t a l y z e d by t r a n s i t i o n metal i o n s ( r e f . 10).

Liquid-phase o x i d a t i o n o f

SO2 has been i n c l u d e d i n aerosol plume models e i t h e r as a parameterized

process ( r e f . 3 ) o r as a m e c h a n i s t i c component ( r e f . 2 ) .

The model s i m u l a t i o n

p r e s e n t e d here i n v o l v e d cases w i t h l o w r e l a t i v e h u m i d i t i e s (below 60 p e r c e n t ) f o r which l i q u i d - p h a s e o x i d a t i o n o f SO2 i s u n i m p o r t a n t ( r e f .

17); therefore,

we c o n s i d e r o n l y gas-phase o x i d a t i o n o f SO2. An i m p o r t a n t component o f an aerosol model i s t h e g a s - t o - p a r t i c l e convers i o n process.

It d e t e r m i n e s t h e k i n e t i c s o f a e r o s o l f o r m a t i o n , as w e l l as t h e

chemical c o m p o s i t i o n o f t h e a e r o s o l s .

F i r s t l e t us c o n s i d e r t h e case o f H2SO4

and NH3 i n e q u i l i b r i u m w i t h a d r y a e r o s o l .

The f o l l o w i n g e q u i l i b r i u m

r e l a t i o n s h i p s hold:

“H31[H2SO41 NH3(g) + H2S04(g)=NH4HS04(s)

= 2.0

K1 =

“H31 NH3(g) + NHqHSO4(S)=(NH

) SO 4 ( S )

4 2

ppm2

(2)

x

K 2 = ___ - 3.8 x

Y

x

ppm

(3)

when ( 9 ) and ( s ) r e f e r t o t h e gas phase and s o l i d phase, r e s p e c t i v e l y , and K1 and K2 a r e t h e e q u i l i b r i u m constants.

The chemical c o m p o s i t i o n o f t h e aerosol i s charac-

t e r i z e d b y t h e mole f r a c t i o n s x and y o f NH4HS04 and (NH4)2S04, r e s p e c t i v e l y . We can c a l c u l a t e t h e c o m p o s i t i o n o f t h e a e r o s o l f o r a c l o s e d chemical system i f

t h e i n i t i a l gas-phase c o n c e n t r a t i o n s [NH31° and [H2SO4I0 a r e known. t i o n leads t o t h e f o l l o w i n g r e l a t i o n s h i p s :

Mass conserva-

286 x + y = l [ N H 3 I 0 = [NH31 + (2x + Y) M [H2S04]0

= CH2S041 + ( x + Y) M

where M i s t h e t o t a l c o n c e n t r a t i o n o f aerosol s u l f a t e and b i s u l f a t e . This system o f equations can be solved t o g i v e t h e e q u i l i b r i u m composition o f t h e aerosol f o r v a r i o u s gas-phase concentrations.

Several s i m u l a t i o n s were

performed f o r an i n i t i a l c o n c e n t r a t i o n o f H2SO4 o f 5 x c o n c e n t r a t i o n s o f NH3 r a n g i n g from 10-1 ppm t o

ppm.

ppm, and i n i t i a l The r e s u l t s showed t h a t

t h e mole f r a c t i o n y o f NH4HS04 was always l e s s than 0.01. Alternatively,

we can c a l c u l a t e t h e gas-phase c o n c e n t r a t i o n o f H2SO4 and NH3,

f o r which an a p p r e c i a b l e amount o f NH4HS04 w i l l be present. percent o f NH4HS04 and 90 percent o f (NH4)$04 t i o n s o f 3.4 x

lo-'

For instance,

ppm f o r NH3 and H2SO4, r e s p e c t i v e l y .

and 5.8 x

10

would r e q u i r e gas-phase concentraThe

s u l f u r i c a c i d c o n c e n t r a t i o n t h a t i s r e q u i r e d t o produce an appreciable amount o f ammonium b i s u l f a t e i s f a i r l y h i g h and such c o n c e n t r a t i o n s have n o t been observed i n t h e atmosphere, except p o s s i b l y i n t h e f l u e gases c l o s e t o t h e stack.

Thus,

i t i s safe t o assume t h a t i n atmospheric plumes, H2S04 and NH3 w i l l l e a d t o t h e

f o r m a t i o n o f (NH4)2S04,

and t h a t n e g l i g i b l e amounts o f NH4HS04 w i l l be formed.

I n t h i s model, we t h e r e f o r e assume t h a t H2SO4 condenses w i t h NH3 t o form (NH4)2S04,

which i s s o l i d a t r e l a t i v e h u m i d i t i e s below 80 percent.

Formation o f n i t r a t e a e r o s o l s N i t r i c a c i d and n i t r a t e are formed i n t h e atmosphere m a i n l y by t h e o x i d a t i o n

o f NO2.

The most i m p o r t a n t chemical pathways i n v o l v e d i n t h e f o r m a t i o n o f HNO3

a r e t h e gas-phase o x i d a t i o n o f NO2 by OH r a d i c a l s , which occurs d u r i n g t h e daytime, and t h e gas-phase o x i d a t i o n o f NO2 by NO3 r a d i c a l s t o form N2O5, which then r e a c t s on wetted aerosol surfaces t o heterogeneously form HNO3.

This second

process occurs m a i n l y a t n i g h t because d u r i n g t h e daytime NO3 i s r a p i d l y photolyzed t o NO2 and 0 ( r e f . 18).

Since t h e s i m u l a t i o n s t h a t were conducted

correspond t o daytime c o n d i t i o n s , t h i s chemical pathway i s unimportant and i s n o t considered i n t h e model; however, t h e model c o u l d e a s i l y t a k e i n t o account t h i s heterogeneous r e a c t i o n i f necessary. o x i d a t i o n o f NO2 b y

For t h e study simulations,

OH i s t h e main pathway t o HN03 formation.

therefore, the (Some n i t r i c a c i d

i s a l s o formed when HS04 r e a c t s w i t h NO2 t o form H2S04 and HNO3): NO2 + OH - - - - +

HN03

k = 1.4 x

lo4

ppm-' min-'

(7)

287

The s a t u r a t i o n vapor p r e s s u r e o f HN03 i s h i g h , so t h a t HN03 does n o t condense i n a p p r e c i a b l e amounts and remains m a i n l y i n t h e gas phase.

The main process

l e a d i n g t o t h e f o r m a t i o n o f i n o r g a n i c n i t r a t e a e r o s o l s i n daytime i s t h e r e a c t i o n o f NH3 w i t h HN03 a t r e l a t i v e h u m i d i t i e s below 62 p e r c e n t when t h e r e a c t i o n p r o d u c t NH4N03 is s o l i d . NH3(g) + HN03(g)=NH

4 NO 3 ( s )

(8)

The e q u i l i b r i u m parameters f o r t h i s two-phase e q u i l i b r i u m have been e v a l u a t e d u s i n g thermodynamic and e x p e r i m e n t a l d a t a ( r e f s . 6-7) and depend on t h e ambient temperature.

I n t h i s study, t h e f o l l o w i n g e q u i l i b r i u m parameter was chosen ( r e f .

6) :

K3 = [NH3][HN03]

= 70.68

-

--,--24090

-

6.04

in

T

m

(9)

where t h e t e m p e r a t u r e T i s expressed i n K, and K j i n ppm2. T h i s e q u i l i b r i u m between gaseous ammonia and n i t r i c a c i d and aerosol ammonium n i t r a t e constitutes the gas-to-particle f o r m a t i o n i n t h i s model.

c o n v e r s i o n process f o r aerosol n i t r a t e

U n l i k e t h e c o n v e r s i o n o f H2S04 t o aerosol s u l f a t e ,

which can be c o n s i d e r e d t o be i r r e v e r s i b l e i n a power p l a n t plume because o f t h e l o w vapor p r e s s u r e o f H2SO4, t h e f o r m a t i o n o f ammonium n i t r a t e i s a r e v e r s i b l e process; ammonium n i t r a t e w i l l decompose i n t o i t s p r e c u r s o r s i f t h e i r c o n c e n t r a t i o n p r o d u c t i s below t h e s a t u r a t i o n v a l u e g i v e n by Equation ( 9 ) . F o r m u l a t i o n o f t h e aerosol plume model The mathematical model t h a t has been developed t o d e s c r i b e t h e f o r m a t i o n o f s u l f a t e and n i t r a t e a e r o s o l s and t h e e v o l u t i o n o f t h e aerosol s i z e d i s t r i b u t i o n i n plumes i n c l u d e s t h r e e components: c h e m i s t r y , and a e r o s o l dynamics.

plume t r a n s p o r t and d i s p e r s i o n , gas-phase

These components have been d e s c r i b e d i n d e t a i l

elsewhere ( r e f . 3). The plume i s d e s c r i b e d i n a Lagrangian frame o f r e f e r e n c e .

It c o n s i s t s o f

s i x c o n t i g u o u s p u f f c e l l s t h a t a r e v e r t i c a l l y w e l l mixed and t h a t expand as t h e plume i s d i s p e r s e d by t h e atmospheric t u r b u l e n t eddies.

I n e r t species a r e

d i s p e r s e d a c c o r d i n g t o a Gaussian c o n c e n t r a t i o n d i s t r i b u t i o n , whereas t h e d i f f u s i o n o f c h e m i c a l l y r e a c t i n g s p e c i e s i s t r e a t e d by means o f a K-theory formulation.

The plume model t a k e s i n t o account t i m e - v a r y i n g wind speed, m i x i n g depth,

288

e n t r a i n m e n t o f gaseous chemical s p e c i e s and a e r o s o l s from t h e background i n t o t h e plume, and d e p o s i t i o n o f gases and a e r o s o l s on t h e ground ( r e f . 19). The gas-phase c h e m i s t r y mechanism uses t h e Carbon-Bond Mechanism developed by Whitten, K i l l u s , and Hog0 ( r e f . 20).

M o d i f i c a t i o n s t o t h e mechanism t o make i t

s u i t a b l e f o r plume c h e m i s t r y have been d i s c u s s e d by Seigneur ( r e f . 3 ) and t h e c h e m i s t r y o f ammonium s u l f a t e and ammonium n i t r a t e f o r m a t i o n has been d i s c u s s e d i n t h e previous sections.

The mechanisms c o n s i s t o f 7 5 r e a c t i o n s among 37

chemical species. The a e r o s o l dynamics component d e s c r i b e s t h e c o a g u l a t i o n o f a e r o s o l s , t h e gas-to-particle

c o n v e r s i o n processes t h a t govern t h e f o r m a t i o n o f ammonium

s u l f a t e and n i t r a t e , and t h e thermodynamic e q u i l i b r i u m between NH3, HN03, and NH4N03.

The aerosol s i z e d i s t r i b u t i o n i s r e p r e s e n t e d by a s e c t i o n a l d i s t r i b u t i o n

t h a t c o n s i s t s here o f 7 s e c t i o n s i n t h e a e r o s o l d i a m e t e r s i z e range o f 0.01 t o 2.15

@I. This

d i s t r i b u t i o n corresponds t o t h e a c c u m u l a t i o n mode where most o f

t h e secondary a e r o s o l mass i s formed.

L a r g e r aerosol s i z e s (coarse-mode

a e r o s o l s ) can a l s o be t r e a t e d by t h e model as i n e r t a e r o s o l s .

The e v o l u t i o n of

t h e a e r o s o l s i z e d i s t r i b u t i o n i s governed b y t h e s e c t i o n a l General Dynamic Equation t h a t i s presented elsewhere ( r e f s . 3-21). t o c o n d e n s a t i o n o f H2SO4 and HN03 as (NH4),S04

Condensational growth i s due

and NH4N03 monomers.

If the

c o n c e n t r a t i o n p r o d u c t o f NH3 and HNO3 i s below i t s s a t u r a t i o n value, NH4N03 decomposes and l e a v e s t h e a e r o s o l phase. The model i s a p p l i e d i n cases f o r which (NH4)$04 f o r r e l a t i v e h u m i d i t i e s below 62 p e r c e n t .

and NH4NO3 a r e s o l i d , i.e.,

It i s assumed t h a t (NH4)2S04 and

NH4N03 e x i s t as an e x t e r n a l m i x t u r e i n t h e a e r o s o l phase. MODEL APPLICATIONS The model s i m u l a t e d t h e f o r m a t i o n o f s u l f a t e and n i t r a t e a e r o s o l s i n power p l a n t plumes i n t h r e e d i f f e r e n t environments:

a c l e a n background w i t h l o w NH3

c o n c e n t r a t i o n s , a c l e a n background w i t h h i g h NH3 c o n c e n t r a t i o n s , and a p o l l u t e d background w i t h h i g h NH3 c o n c e n t r a t i o n s . Clean environment w i t h l o w NH2 c o n c e n t r a t i o n s The 1979 VISTTA f i e l d programs were conducted, i n p a r t , t o s t u d y t h e p h y s i c s , c h e m i s t r y , and o p t i c a l p r o p e r t i e s o f t h e plume o f t h e Navajo power p l a n t l o c a t e d i n n o r t h e r n A r i z o n a ( r e f . 22).

A t t h i s l o c a t i o n , t h e background a i r i s g e n e r a l l y

v e r y c l e a n , w i t h l o w NH3 c o n c e n t r a t i o n s ( r e f . 16).

The s i m u l a t i o n s o f plume

c h e m i s t r y , s u l f a t e a e r o s o l f o r m a t i o n , and t h e e v o l u t i o n o f t h e aerosol s i z e

289

d i s t r i b u t i o n on f o u r d i f f e r e n t days o f t h e VISTTA programs have been presented elsewhere ( r e f . 3).

The p o s s i b l e f o r m a t i o n o f a e r o s o l n i t r a t e was i n v e s t i g a t e d

w i t h t h i s model and

t appeared t h a t background NH3 c o n c e n t r a t i o n s and plume HN03

c o n c e n t r a t i o n s were t o o l o w t o l e a d t o t h e f o r m a t i o n o f NH4N03 a e r o s o l s .

This

f i n d i n g i s i n agreement w i t h t h e a i r b o r n e plume measurements, which showed l i t t l e f o r m a t i o n o f NH4N03 i n t h e plume.

These r e s u l t s a r e shown i n t a b l e 1.

I n two

cases o n l y - - 9 and 13 December 1979--the measured gas-phase c o n c e n t r a t i o n s o f NH3 and HN03 a r e above t h e s a t u r a t i o n v a l u e ; f o r one o f t h e cases--9 December--some n i t r a t e a e r o s o l was measured i n t h e plume. t h a t K3

>

[HN03][NH3].

I n a l l cases, t h e model p r e d i c t e d

The r e s u l t s o f t h e plume s i m u l a t i o n s a r e t h e r e f o r e

i d e n t i c a l t o t h o s e a l r e a d y presented.

The reader i s r e f e r r e d t o Seigneur ( r e f .

3 ) f o r a d e t a i l e d p r e s e n t a t i o n o f t h e comparison o f model p r e d i c t i o n s and measurements f o r s u l f a t e a e r o s o l c o n c e n t r a t i o n s and a e r o s o l s i z e d i s t r i b u t i o n s . TABLE 1 C o n c e n t r a t i o n Product o f NH3 and HN03 i n t h e Navajo power p l a n t plume

P1 ume S i m u l a t i o n

Measured

13 J u l y 1979, 58 km downwind 13 J u l y 1979, 88 km downwind 5 December 1979, 33 km downwind 5 December 1979, 80 km downwind 9 December 1979, 30 km downwind 13 December, 25 km downwind

2.1 2.8 5.4 5.9 8.3 5.0

10-5 x 10-5 x x loe8 x lom7 x

Predicted

(ppm‘)

4.7 1.1 2.0 5.3 1.3 2.0

3.0 5.0 4.2 7.3 2.3 4.0

10-6 10-5

x x x x

lom8

10-5 10-5

x x x x

Clean environment w i t h h i g h NH3 c o n c e n t r a t i o n s The K i n c a i d power p l a n t i n I l l i n o i s i s l o c a t e d i n an area where background NH3 c o n c e n t r a t i o n s a r e h i g h e r t h a n t h o s e i n n o r t h e r n Arizona.

The February 1981

VISTTA f i e l d program was conducted t o s t u d y t h e chemical and p h y s i c a l processes and t h e v i s u a l e f f e c t s o f t h e K i n c a i d power p l a n t plume ( r e f . 9).

On 25 February

1981, t h e Meteorology Research, Inc. a i r c r a f t performed one-hour sampling o r b i t s i n t h e plume a t 60 km downwind, and i n t h e background.

A plume s i m u l a t i o n was

performed w i t h t h i s model f o r a p u f f r e l e a s e d a t 1150 CST f r o m t h e stacks. a wind speed o f 6.25 m.sec-l,

t h i s p u f f t r a v e l e d 60 km i n 160 minutes, which

With

290 corresponds t o t h e a i r b o r n e measurement p e r i o d o f 1400-1500 CST.

I n p u t d a t a were

deduced from t h e VISTTA d a t a base and t y p i c a l v a l u e s were assumed f o r t h e background hydrocarbon c o n c e n t r a t i o n s . plume SO2 c o n c e n t r a t i o n s . t e m p e r a t u r e was 10°C.

Plume d i s p e r s i o n was determined from t h e

The r e l a t i v e h u m i d i t y was about 60 p e r c e n t and t h e

Measured and p r e d i c t e d c o n c e n t r a t i o n s o f secondary aero-

sols a r e p r e s e n t e d i n t a b l e 2, where plume excess c o n c e n t r a t i o n r e p r e s e n t s t h e plume c o n c e n t r a t i o n minus t h e background c o n c e n t r a t i o n .

The model u n d e r p r e d i c t s

t h e amount o f a e r o s o l s u l f a t e and n i t r a t e formed, p o s s i b l y because t h e background OH c o n c e n t r a t i o n s o r t h e plume t r a v e l t i m e a r e underestimated.

However, t h e

model p r e d i c t s w e l l t h e r e l a t i v e amounts o f s u l f a t e , n i t r a t e , and ammonium. TABLE 2 P r e d i c t e d and measured c o n c e n t r a t i o n i n t h e K i n c a i d power p l a n t plume

Chemical Species

Background C o n c e n t r a t i o n (Pg m-3) Measured

P1 ume Excess C o n c e n t r a t i o n (!4 m-31 Measured Predicted

so42-

2.26

2.22

0.39

NO3-

0.47

1.54

0.25

NH~+

1.06

1.19

0.22

Pol 1 u t e d environment The c h e m i s t r y and d i s p e r s i o n o f t h e common plume o f t h e Haynes steam p l a n t and t h e A l a m i t o s power p l a n t i n t h e Los Angeles b a s i n were s t u d i e d on s e v e r a l days i n t h e w i n t e r o f 1974 ( r e f s 2-3).

The plume model s i m u l a t e d t h e case s t u d y

o f 7 November 1974, f o r which g r o u n d - l e v e l measurements o f plume c o n c e n t r a t i o n s were conducted a t 18 km downwind between 1400 and 1500 PST. were o b t a i n e d from Richards e t a1 ( r e f .

23).

Model i n p u t d a t a

T y p i c a l v a l u e s were assumed f o r t h e

background c o n c e n t r a t i o n s o f gaseous s p e c i e s t h a t were n o t a v a i l a b l e .

Plume

d i s p e r s i o n was determined from t h e plume c o n c e n t r a t i o n of t h e i n e r t t r a c e r SF6. The wind speed was 5 m.sec-l, t e m p e r a t u r e was 23OC.

t h e r e l a t i v e h u m i d i t y was 34 p e r c e n t , and t h e

The p r e d i c t e d and measured s u l f a t e and n i t r a t e c o n c e n t r a -

t i o n s a r e compared i n t a b l e 3.

291

TABLE 3 P r e d i c t e d and measured c o n c e n t r a t i o n i n t h e HayneslAlamitos p l a n t s plume

Chemical Species

Background C o n c e n t r a t i o n (ug m-3) Mea s u red

P1 ume Excess C o n c e n t r a t i o n (ug m-3) Measured Predicted

so42-

3.0

+6.2

+2.8

NO3-

8.0

-3.3

-0.8

The s u l f u r i c a c i d e m i t t e d from t h e s t a c k s i s c o n v e r t e d t o (NH4)2S04 as i t r e a c t s w i t h t h e background NH3 e n t r a i n e d i n t o t h e plume.

The p r e d i c t e d concen-

t r a t i o n o f s u l f a t e i s l e s s t h a n t h e measured v a l u e ; t h i s d i s c r e p a n c y i s p o s s i b l y due t o u n c e r t a i n t i e s i n t h e measurements, s i n c e t h e model p r e d i c t i o n s correspond w e l l w i t h t h e t o t a l c o n v e r s i o n o f e m i t t e d H2SO4 t o (NH4)2S04, and s i n c e l i t t l e

SO2 o x i d a t i o n t o o k p l a c e i n t h e plume.

The d e p l e t i o n o f NH3 i n t h e plume due t o

(NH4)2S04 f o r m a t i o n l e a d s t o t h e displacement o f t h e NH3-HN03-NH4N03 e q u i l i brium.

Thus, NH4N03 decomposes i n t o NH3 and HNO3 i n t h e plume t o r e e s t a b l i s h t h e

equilibrium.

T h i s e f f e c t appears i n b o t h t h e measurements and t h e model p r e d i c -

tions. CONCLUSION

A model has been p r e s e n t e d t h a t d e s c r i b e s t h e f o r m a t i o n o f ammonium s u l f a t e and n i t r a t e a e r o s o l s and t h e e v o l u t i o n o f t h e aerosol d i s t r i b u t i o n i n plumes a t h u m i d i t i e s below 6 2 percent.

The model was a p p l i e d t o t h e s i m u l a t i o n o f aerosol

f o r m a t i o n i n power p l a n t plumes f o r t h r e e d i f f e r e n t t y p e s o f background e n v i r o n ments and appeared t o reproduce w e l l t h e p r i m a r y c h a r a c t e r i s t i c s o f aerosol plume c h e m i s t r y under v a r i o u s c o n d i t i o n s .

F u r t h e r work should be d i r e c t e d toward t h e

s t u d y o f a e r o s o l f o r m a t i o n a t h i g h r e l a t i v e h u m i d i t i e s f o r which t h e c h e m i s t r y o f t h e l i q u i d - c o a t e d a e r o s o l s must be t a k e n i n t o account. ACKNOWLEDGMENTS Thanks a r e due t o Dr. L. W. Richards f o r p r o v i d i n g v a l u a b l e i n f o r m a t i o n r e g a r d i n g t h e e x p e r i m e n t a l d a t a and t o C.

J. Lawson f o r e d i t o r i a l a s s i s t a n c e .

REFERENCES

1 M.W. E l t g r o t h and P.V. Hobbs, Atmos. Environ., 13(1979)953-975. 2 M. Basset, F. Gelbard and J.H. S e i n f e l d , Atmos. Environ., 15 ( 1981 ) 2395-2406. 3 C. Seigneur, Atmos. Environ., i n press. 4 A.E. Ore1 and J.H. S e i n f e l d , Environ. Sci. Techol., ll(1977)lOOO1007. 5 T.W. Peterson and J.H. S e i n f e l d , Am. I n s t . Chem. Eng. J., 25( 1979)831-838. 6 A.W. S t e l s o n , S.K. F r i e d l a n d e r and J.H. S e i n f e l d , Atmos. Environ.. 13 (1979)369-371. Doyle, E.C. Tuazon, R.A. Graham, T.M. Mischke, A.M. Wine and J.N. P i t t s , Jr., Atmos. Environ. Sci. Techno1 13(1979)1416-1419. 8 D.A. Hegg and P.V. Hobbs, Atmos. Environ., 13(1979)1715-1716. 9 L.W. R i c h a r d s , J.A. Anderson, D.L. Blumenthal, A.A. Brandt, S.Z. Hynek, J.A. McDonald, and N. Waters, Report 81-DV-1806, 1981 Meteorology Research, Inc., Santa Rosa, C a l i f o r n i a . 10 C.S. B u r t o n , M.K. L i u , P.M. Roth, C. Seigneur and G.Z. Whitten, Proc. 1 2 t h NATO/CCMS I n t . Techn. Meeting A i r P o l l u t i o n Modeling and I t s A p p l i c a t i o n s , Palo A l t o , C a l i f o r n i a , August 25-28, 1981. 11 R. A t k i n s o n and A. C. L l o y d , J. Phys. Chem. Ref. Data, lO(1981) i n press. 12 0.0. Davis, A.R. Ravishankara and S. F i s c h e r , Geophys. Res. L e t t . ,

7 G.J.

.,

6(1979)113-116. 13 J.I. R n i t r o and T. Vermeulen, Am. I n s t . Chem. Eng. J., 10(1969)740746. C a t t e l l , Atmos. Environ., 13( 1979)307-317. 14 W.D. S c o t t and F.C.R. 15 P.K. Dasgupta, Atmos. Environ., 14(1980)267. 16 L.W. R i c h a r d s , J.A. Anderson, D.L. Blumenthal, A.A. Brandt, J. A. 17

McDonald, N. Waters, E.S. Macias, and P.A. Bhardwaja, Atmos. Environ., 15(1981)2111-2134. P.H. McMurry, D.J. Rader and J.L. S t i t h , Atmos. Environ.,

15( 1981)2315-2328 18 L.W. R i c h a r d s , s u b m i t t e d t o Atmos. Environ., 1982. 19 D.A. Stewart and M.K. L i u , Atmos. Environ., 15(1981)2377-2394. 20 G.Z. W h i t t e n , J.P. K i l l u s and H. Hogo, Report EF79-129, Systems A p p l i c a t i o n s , Inc., San R a f a e l , C a l i f o r n i a , 1980. 21 F. Gelbard and J.H. S e i n f e l d , J. C o l l o i d I n t e r f . Sci., 78(1980)485501. 22 D.L. Blumenthal, L.W. Richards, E.S. Macias, R.W. Bergstrom, W.E. Wilson and P.S. Bhardwaja, Atmos. Environ., 15(1981)1955-1970. 23 L.W. Richards, E.L. Avol, and A. B. Marker, Report SC593-5 FRD, 1976, Rockwell I n t e r n a t i o n a l , A i r M o n i t o r i n g Center, Newbury Park, California.

293

PHOTOGRAPHY AS A TECHNIQUE FOR STUDYING VISUAL RANGE

T.E.

HOFFER, D.E.

SCHORRAN

Desert R e s e a r c h I n s t i t u t e , U n i v e r s i t y of Nevada System R. J. FARBER

S o u t h e r n C a l i f o r n i a E d i s o n Company

ABSTRACT

A t e c h n i q u e i s d e s c r i b e d t h a t u s e s b l a c k and w h i t e a n d c o l o r photography t o s t u d y v i s u a l r a n g e , a n d t h e e f f e c t s o f c l o u d s and h a z e on a s c e n e . w h i t e f i l m i s u s e d f o r q u a n t i t a t i v e measurement of v i s u a l r a n g e .

Black and

Film density

measurements are d i g i t i z e d u s i n g a f l y i n g s p o t s c a n n e r t o a s s u r e t h a t t h e meas u r e m e n t , a n a l y s i s a n d i n t e r p r e t a t i o n are r e p r o d u c i b l e and a c c u r a t e .

The p r o c e d u r e and a n example are

s i t y wedges a n d t h e n e g a t i v e s are d i g i t i z e d . presented.

Color f i l m is used t o q u a l i f y

The den-

t h e b l a c k a n d w h i t e measuremenw.

The t e c h n i q u e s a p p l i e d i n a n a l y s i s and some r e s u l t s of

t h e f i e l d measurement

program a r e p r e s e n t e d .

INTRODUCTION

Koscmeider ( r e f . y e a r s ago.

1) p u b l i s h e d a p i o n e e r i n g work on v i s i b i l i t y a l m o s t s i x t y

I n t h i s p a p e r , h e d e r i v e d t h e f u n d a m e n t a l r e l a t i o n s h i p between t h e

v i s u a l range,

contrast,

and t h e b a c k s c a t t e r i n g c o e f f i c i e n t ,

t h e p a r t i c l e number a n d s i z e .

a term r e l a t e d t o

U n t i l 1977, o b j e c t i v e r e p r o d u c i b l e measurement

t e c h n i q u e s f o r v i s u a l r a n g e a n d c o l o r c o n t r a s t were n o t mandated. t h e United

S t a t e s Congress

p a s s e d amendments t o

Under a new s e c t i o n of t h a t A c t ;

areas

was

to

be

protected.

In t h a t y e a r

t h e C l e a n A i r Act of

1970.

v i s i b i l i t y i n n a t i o n a l p a r k s and w i l d e r n e s s

The

act

also

specified

that

the

scientific

294

community was t o d e v e l o p methods of a c c u r a t e l y measuring v i s i b i l i t y . perception

s t u d i e s were s t a r t e d t o c o r r e l a t e i n s t r u m e n t measurements o f v i s u a l

range w i t h how p a r k v i s i t o r s p e r c e i v e v i s i b i l i t y . have

Recently,

tried

to

Furthermore,

these

studies

a s s e s s t h e r o l e of v i s i b i l i t y on a e s t h e t i c a p p r e c i a t i o n of t h e

wilderness. I n a recent experimental visibility

conditions

in

work,

hydrosols

have

demonstrated

p e r c e p t i o n of d e t a i l .

that

simulated

atmospheric

and showed t h a t t h e r e l a t i o n s h i p between

c l a r i t y and v i s u a l range i s n o t l i n e a r . (ref. 4 )

(ref. 2 )

Stankunas

A l l a r d and Tombach ( r e f . 3 )

color

the

is

dominant

and

parameter

These f a c t o r s must b e c o n s i d e r e d i n t h e

Malm i n the

measurement

of

v i s u a l range. Measurement

techniques

can

b e c l a s s i f i e d i n t o two broad c a t e g o r i e s ; t h o s e

t h a t m o n i t o r v i s u a l r a n g e a t a p o i n t and t h o s e t h a t i n t e g r a t e over a l o n g p a t h . Point source techniques include various nephelometers,

and

samplers

for

measurements

include

techniques.

Transmissometers,

measuring

transmissometers,

measure p a r a m e t e r s r e l a t e d t o techniques

types

integrate

of

particle

particle

sizing

counters,

absorption.

Long p a t h

telephotometers

nephelometers extinction.

and

and

photographic

p a r t i c l e s i z e counters a l l

Telephotometers

and

photographic

t h e v a r i a b l e s o f sun a n g l e and t h e s t a t e o f t h e sky i n t o

t h e measurement. A

photographic

simultaneously paper.

technique

exposed

black

for

assessing

and

white

visibility

that

makes

which

of

and c o l o r f i l m i s d e s c r i b e d i n t h i s

The t e c h n i q u e i n c o r p o r a t e s a q u a n t i t a t i v e a n a l y s e s o f b l a c k

negatives

use

and

white

y i e l d s v i s u a l r a n g e measurements and a q u a l i t a t i v e assessment

of c o l o r s l i d e s t o c a t e g o r i z e and q u a l i f y v i s u a l r a n g e measurements.

PHOTOGRAPHIC ASSESSMENT OF VISIBILITY The d e s e r t a r e a s o f t h e s o u t h w e s t e r n United S t a t e s are an i d e a l e v a l u a t i n g d i f f e r e n t methods of measuring v i s i b i l i t y . region

varies

from

locale

for

The v i s u a l r a n g e i n t h i s

i n e x c e s s o f 200 k i l o m e t e r s i n t h e w i n t e r t o l e s s t h a n 7 5

k i l o m e t e r s d u r i n g t h e summer.

The t o p o g r a p h i c r e l i e f

provides

many

mountain

295 targets

at

varying

distances.

Some

of

the

valleys

have

small

s e t t l e m e n t s , which can be t h e s o u r c e o f s p a t i a l inhomogenities i n

A

distribution.

the

urban aerosol

p a t h measurement w i l l b e s t r e p r e s e n t t h e v i s i b i l i t y i n

long

such a n environment. A f t e r c o n s i d e r i n g many f a c t o r s , photography measuring

technique

for

characterizing

was

visibility

selected in

as

our

primary

t h e r e g i o n 100 miles

southwest of t h e Grand Canyon.

. .

.

D t m i z a t i o n o f t h e Dhotonrabhic t e c h n i q u e The p h o t o g r a p h i c d e t e r m i n a t i o n of v i s u a l r a n g e and a t m o s p h e r i c

clarity

has

been o p t i m i z e d i n t h r e e ways. F i r s t , a b l a c k and w h i t e f i l m was chosen t h a t y i e l d s a l a r g e change i n f i l m density

for

a s m a l l change i n e x p o s u r e .

The v i s u a l r a n g e c a l c u l a t i o n s remain

t h e same a s d e s c r i b e d by S t e f f e n s ( r e f . 5 ) . Second, a f t e r development, t h e b l a c k and w h i t e n e g a t i v e s a r e d i g i t i z e d film

density.

This

minimizes

handling

o f t h e f i l m and e l i m i n a t e s o p e r a t o r

e r r o r i n p o s i t i o n i n g t h e n e g a t i v e on a manual d e n s i t o m e t e r . resolution

is

increased

because

than those permitted

using

densitometers.

resolution

The

the

for

In

addition,

the

t a r g e t areas a r e d i g i t i z e d t h a t a r e smaller apertures acheived

commonly

associated

with

manual

with t h i s technique i s g r e a t e r than

t h a t of t h e human e y e . T h i r d , s i m u l t a n e o u s l y exposed c o l o r s l i d e s o f t h e same v i s t a qualify

and

categorize

the

black

and

white

are

used

c o n t r a s t measurements.

p r o v i d e background i n f o r m a t i o n about sky and t a r g e t c o l o r a t i o n , c l o u d i n e s s

to

These and

shadow o r i e n t a t i o n .

Camera system A

range

two

camera

adjacent

i s l o c a t e d on t o p of a mountain peak i n t h e Newberry

system to

the

Lake

Mead

National

Recreation

Area.

t o p o g r a p h i c f e a t u r e s a t s e v e r a l azimuth a n g l e s a r e used f o r t a r g e t s . white

exposures

are

made

with

a

35

Discernible Black and

mm camera equipped w i t h a 600 mm l e n s

296 Color e x p o s u r e s a r e made w i t h a 35 mm camera equipped w i t h

system. lens.

Both

cameras

feature

automatic

exposure

control

100 mm

a

and f i l m advance.

Exposures a r e made i n t h e morning, a t midday, and d u r i n g t h e a f t e r n o o n .

.

Black and w h i t e f i l m

The b l a c k and w h i t e f i l m s e l e c t e d i s Kodak Linagraph

S h e l l b u r s t 2476.

A t y p i c a l exposure v e r s u s d e n s i t y p l o t i s shown i n

and

the

illustrates

large

change

s e n s i t i v i t y p e r m i t s t h e r e s o l u t i o n o f s m a l l changes i n v i s u a l r a n g e . r e p r e s e n t a t i v e o f Plus-X

film

.

1

i n d e n s i t y o b t a i n e d f o r a s m a l l change i n

The p l o t i s f o r f i l m exposed a t ASA 200 and developed n o r m a l l y .

exposure.

Color

Figure

A

The curve

f i l m i s a l s o shown f o r comparison.

The c o l o r f i l m i s Eastman 5 2 4 7 , a c o l o r n e g a t i v e f i l m t h a t i s

p r o c e s s e d commercially.

A c o l o r c h a r t i s photographed a t t h e b e g i n n i n g o f each

r o l l t o p r o v i d e f o r c o r r e c t i o n o f t h e f i l m p o s i t i v e by f i l t r a t i o n t o

the

true

c o l o r of t h e s c e n e .

Film d i g i t i z a t i o n We have developed t h e f o l l o w i n g t e c h n i q u e t o d e t e r m i n e t h e v i s u a l r a n g e from

the

black

and

white

photographs.

On

each r o l l o f f i l m a d e n s i t y wedge is

d i g i t i z e d u s i n g a s p o t s i z e o f 0 . 1 mm i n x by 0.4 mm i n y, measurement

parallel

t o the film breadth.

Where x

refers

to

t o t h e f i l m l e n g t h and y r e f e r s t o measurements p a r a l l e l Two s i d e by s i d e s c a n s are averaged f o r

precision.

The

s m a l l s p o t s are averaged over a s u i t a b l e increment i n x , u s u a l l y 20 v a l u e s , and tabulated

by

a

computer.

The d e n s i t y v a l u e s a s r e l a t e d t o exposure a r e t h e n

g r a p h e d , a s shown i n F i g u r e 1. I n p r a c t i c e t h e f i l m i s exposed so t h a t t h e d e n s i t y is i n t h e l i n e a r p o r t i o n of t h e c u r v e .

The exposure can t h e n b e d e t e r m i n e d from an e q u a t i o n of t h e form

297

Step Number 3.0

I

I

I

I

I

I

1

1

I

August 5, 1980 I

0

2.5

2 .a

c .-

u)

f

1.5

0

.-E -

LL.

I.a

-----

Plus X Film Linogroph Shellburst Film, Monuol Densitometer Linograph Shellburst Film, Digitized

--

0.5

/r

0

/' I

0.3

I

I

1

1

I

1

I

I

0.6

0.9

1.2

1.5

1.8

2.1

2.4

2.7

:

Log E

Fig. L Film characteristic curves for Linagraph Shellburst and Plus-X hlack and white f i l m s . D a t a from manually reduced densitometer measurements and digitized measure ments are shown f a a w e roll of Linagraph Shellburst. where d i s t h e f i l m

density,

m

is

the

slope

and

a

is

the

extrapolated

intercept. Photographs of each v i s t a a r e d i g i t i z e d w i t h a s p o t s i z e of 0 . 1 mm by 0.lmm. For

35

mm f i l m 360 v a l u e s would b e d i g i t i z e d p e r s c a n in t h e x d i r e c t i o n , and

240 in t h e y d i r e c t i o n .

can

be

averaged

The d e n s i t y v a l u e s o b t a i n e d w i t h t h i s s m a l l s p o t

over i n t e g r a l v a l u e s of x and y.

and y v a l u e s are a v e r a g e d .

(60,40).

This reduces t h e

matrix

size

In p r a c t i c e six a d j a c e n t x size

from

(360,240)

to

298

Coordinates

o f t h e t a r g e t and background a r e a s a r e d e t e r m i n e d by p r o j e c t i n g

t h e n e g a t i v e on a l i n e d s c r e e n .

These c o o r d i n a t e s are

used

as

inputs

to

a

program t h a t c a l c u l a t e s t h e v i s u a l r a n g e . In

routine

measurements,

t h e c o o r d i n a t e s o f t h e t a r g e t and an a r e a i n t h e

sky a d j a c e n t t o i t a r e used.

A f t e r t h e exposure i s

calculated,

the

contrast

between sky and t a r g e t i s found from t h e e x p r e s s i o n

(2)

C’E(tar)-E(back)/E(back) where

E(tar)

is

the

exposure

similar quantitity for calculated

using

a

the

a s s o c i a t e d w i t h t h e t a r g e t and E(back) i s t h e

background.

suitable

The

threshold

value

visual and

range

is

subsequently

an assumed v a l u e f o r t h e

inherent contrast of the t a r g e t . T h i s p r o c e d u r e p e r m i t s comparison o f any a r e a on t h e t a r g e t w i t h any element of t h e background, F i g u r e 2 shows an example; h e r e a s i n g l e area on t h e was

used

background.

to

calculate

four

visual

ranges.

Four

sky

The r e s u l t s o f t h e s e c a l c u l a t i o n s a r e p r e s e n t e d

target

a r e a s were used a s in

Table

1.

A

s i m i l a r c a l c u l a t i o n i s shown f o r two o t h e r t a r g e t s .

F i g . 2 . T a r g e t and sky a r e a s u t i l i z e d i n t h e c o n t r a s t d e t e r m i n a t i o n s o f v i s u a l r a n g e shown i n Table 1.

299 TABLE 1

V i s u a l r a n g e s from d i g i t i z e d n e g a t i v e s f o r t h r e e t a r g e t s u s i n g a r e a s of s k y f o r c o n t r a s t d e t e r m i n a t i o n . I n h e r e n t c o n t r a s t = -1.

four

different

Threshoid c o n t r a s t = 0 . 0 2 .

V i s u a l Range (Km)

Sky Area

Target 1

Target 2

Target 3

1

95

85

85

2

109

106

107

3

113

101

109

4

112

103

105

is

There

a

change i n t h e c a l c u l a t e d v i s u a l range f o r d i f f e r e n t sky a r e a s .

The c a l c u l a t i o n u s i n g t h e background a r e a c l o s e s t t o t h e peak (Area 1) in

all

cases,

a

lower

visual

range.

c o n s i s t e n t l y higher v i s u a l ranges. calculations

the

results

are

yields,

The o t h e r c o n t r a s t measurements g i v e

I f d i f f e r e n t t a r g e t a r e a s a r e used

similar.

The

technique

gives

in

the

reproducible

r e s u l t s , p a r t i c u l a r l y when t h e sky and t h e h o r i z o n are c l e a r . V i s u a l range i s a f u n c t i o n o f t h e practice,

this

quantity

inherent

assumption,

several

d i s t a n c e s o r e a c h view. dark

in

increases.

color

and

of

the

target.

i s g e n e r a l l y assumed and r a r e l y measured.

c a n g r e a t l y e f f e c t t h e computed v i s u a l r a n g e . by

contrast

I n o u r work, t o

In

I t s value

minimize

error

c o n t r a s t i n g measurements a r e made a t d i f f e r e n t t a r g e t

A s t h e t a r g e t approaches t h e v i s u a l r a n g e

it

appears

t h e j u s t i f i c a t i o n f o r assuming an i n h e r e n t c o n t r a s t o f -1

T h i s i s e s p e c i a l l y i m p o r t a n t i n t h e d e s e r t southwest where much

of

the terrain i s light i n color. To

reiterate,

these

calculations

are

for

a c l e a r hor zon and sky.

The

on

the

e f f e c t of f a c t o r s such as h o r i z o n b r i g h t n e s s , c l o u d i n e s s v i s u a l range i s n o t incorporated i n t o t h e c a l c u l a t i o n .

and

shadows

300 Color f i l m a n a l y s i s Color

photographs

provide

a medium f o r i n v e s t i g a t i n g how t h e v i s u a l range

a p p e a r s t o change w i t h d i f f e r i n g e n v i r o n m e n t a l this

subjective

measurement

from

a

conditions.

To

differentiate

measurement we have c a l l e d it

physical

V i s u a l a i r q u a l i t y i s dependent upon many a s p e c t s o f t h e

"visual a i r quality".

photographed s c e n e w i t h shadows, c l o u d s , haze and

sun

angle

being

the

most

important. Color

photographs

taken

during

s p r i n g of 1980 were a n a l y z e d . of

the

p e r i o d e x t e n d i n g from w i n t e r through

The p a r a m e t e r s o f p e r c e n t

cloudiness,

presence

shadows o r h a z e , and v i s u a l a i r q u a l i t y were t a b u l a t e d f o r m u l t i p l e t a r g e t s

on e a c h photograph.

The v i s u a l a i r q u a l i t y was

catagorized

for

each

target

according t o t h e following.

1.

C l e a r , no p e r c e p t i b l e h a z e .

2.

P e r c e p t i b l e haze b u t t h e f e a t u r e s a r e d i s t i n c t .

3. Moderate h a z e w i t h many d e t a i l s o b s c u r e d . Target o u t l i n e v i s i b l e . 4 . Dense h a z e , o u t l i n e i s b a r e l y d i s c e r n i b l e . Details a r e o b s c u r e d .

5. The

Target is obscured. t h i r d c a t e g o r y w a s s e l e c t e d a s a good estimate o f t h e d i s t a n c e t h a t c a n

be e a s i l y seen.

It i s not a q u a n t i t a t i v e value of t h e threshold of perception,

b u t i t s e r v e s a s an e s t i m a t o r much reported

at

airports.

This

will

in

the be

same

manner

that

visibility

is

referred t o as the qualitative visual

range. F i g u r e 3 shows t h e q u a l i t a t i v e v i s u a l r a n g e f o r t h i s p e r i o d . d i s c u s s e d , d e g r a d a t i o n o c c u r s as t h e summer a p p r o a c h s . air

quality

is

previously

In addition, the visual

b e t t e r i n t h e morning h o u r s b e f o r e t u r b u l e n c e h a s s t i r r e d t h e

s u r f a c e l a y e r , and l i f t e d it t o t h e h e i g h t o f t h e mountain a r e located.

As

where

the

cameras

0 z

y e ZZE

a. o

$&

0 0 0 0

a : ?

0

0

g d

0

a

4 a 4

?

8 a .

4 4

o o a

0 0

0

. a .a

0

a

t

0

0

d

gg 4

d a

oa

8

0 - 0

‘3

0

80

4

4 0

a 0

a :

a 80 a.

a

a

3

-8

-w N

-8

-R m

2

a

-“g N -

- 9

0

m (0

f N

0 N

m

-R

N

-8 -5

-i? -%I

=

- s Ir V a -9

301

302

CLEAR HORIZON

WHITE CLOUD DARK CLOUD ON HORIZON

Fig. 4. The frequency of occurrence of standard and non-standard horizon conditions during the winter 1980. The region 100 m&s southwest of the Grand Canyon is represented.

ON TARGET

Fig. 5. The frequency of Occurrence of shadow conditiom on visibility tat-gets during t h e w i n t e r of 1980. The r e g h 100 miles southwest of the Grand Canyon is represented.

Fig. 6. The frequency of occurrence of dlwdiness during the winter 1980. The region u)O miles southwest of the G r a d Canyon is represented.

303

Factors affecting visual a i r quality Allard

and

(ref. 6 )

Tombach

c o n d i t i o n s on v i s i b i l i t y .

have

summarized t h e e f f e c t s o f non-standard

Our d a t a b a s e h a s been s o r t e d

into

the

conditions

l i s t e d i n Table 2 .

TABLE 2 . Sort parameters Horizon Clear Horizon White Cloud Dark Cloud

The

Shadows No Shadows Topographic Shadows Cloud Shadows

frequency

Cloudiness < 5 Percent > 5 < 30 P e r c e n t > 3 0 < 60 P e r c e n t > 6 0 <90 P e r c e n t >90 P e r c e n t

of o c c u r r e n c e of h o r i z o n , shadow, and c l o u d i n e s s c o n d i t i o n s ,

5,

which i n f l u e n c e v i s i b i l i t y p e r c e p t i o n , a r e p r e s e n t e d as F i g u r e s 4 ,

The

maximum v a l u e cannot b e found by a s i m p l e s o r t because t h e s o r t p a r a m e t e r s

can

a

non-standard

6.

c o n d i t i o n s e x i s t f o r t y p e r c e n t of t h e t i m e .

As

minimum,

and

be inter-related.

The q u a l i t a t i v e a n a l y s i s of t h i s c o l o r f i l m p r o v i d e s a means

for

the

categorizing

c o n t r a s t measurements from t h e b l a c k and w h i t e f i l m and

a s s e s s i n g t h e c l a r i t y of t h e atmosphere.

SUMMARY I n t h i s paper measurements

we

from

have

presented

photographic

a

means

photometry

for

on

optimizing

black

and

visual

range

white film.

This

t e c h n i q u e i s a p p l i c a b l e w i t h s t a n d a r d a t m o s p h e r i c c o n d i t i o n s , i . e . , a c l e a r sky and t a r g e t s o f known i n h e r e n t c o n t r a s t .

The t e c h n i q u e a l s o

feature

path

of

integrating

over

a

long

comparable

D i g i t i z a t i o n o f t h e b l a c k and w h i t e f i l m l e n d s i t s e l f measurements. the future.

to

has

positive

t o t h e v i s u a l range. repeatable

The permanency of t h e medium p e r m i t s r e - a n a l y s i s

I n a d d i t i o n , t h e method i s i n e x p e n s i v e , h a s a

the

contrast

a t any t i m e i n

variable

field

of

view, and p r o v i d e s f o r r a p i d d a t a a n a l y s i s . Yet

visual

r a n g e may b e o n l y a p a r t o f what w e a r e a t t e m p t i n g t o q u a n t i f y .

A v i s i t o r t o a N a t i o n a l Park

or

Wilderness

Area

perceives

the

visual

air

304 quality or the scenic beauty of the setting. Visual range is one attribute of visual air quality. Other attributes are general amounts

of

clouds, haze,

measurement.

types

and

foreground features, and time of day. Eventually,

color photography may be used to objective criteria by

topography, the

transform

these

subjective qualities

into

relating color contrast measurements to an extinction

The semi-quantification of our calibrated color

photographs may

be an important first step in quantifying visual air quality and scenic beauty.

ACKNOWLEDGEMENT This

research was supported by Southern California Edison as a part of its

environmental research program.

REFERENCES

1 H. Atm.

Koschmieder, Theorie der 12(1924)33-53; 171-181.

horizontalen

sichtweite, Beitr. Phys. freien

2 Alexander R. Stankunas, An initial investigation of the relationship between visual acuity and haze, Proc. View on Visibility, November 1979, Denver, 70-77. 3 Douglas Allard and Ivar Tombach, Intercomparison of visibility measurement methods, Proc. View on Visibility, November 1979, Denver, 197-221.

4 William Malm, Considerations in the measurement of visibility, J. of the Air Pol. Control Assoc.

29(10)1042-1052.

5 Carsten Steffens, Measurement of visibility by photographic photometry, Industrial and Eng. Chem. 41(1949)2396-2399. 6 Douglas Allard and Ivar Tombach, The effects of non-standard visibility measurement, Atmos. Environ. , 10(1981)1847-1857.

conditions on

305

EXPERIMENTAL STUDY ON THE VISIBILITY I N ABSORBING MEDIA

H. HORVATH, J . GORRAIZ and C. JOHNSON I n s t i t u t fiir E x p e r i m e n t a l p h y s i k d e r U n i v e r s i t a t Wien, Vienna ( A u s t r i a )

ABSTRACT An a b s o r b i n g atmosphere has been s i m u l a t e d by means o f a m i x t u r e o f a hydrosol and a p a r t i c l e f r e e dye. T h i s model a l l o w s an easy d i s t i n c t i o n between a b s o r p t i o n and s c a t t e r i n g . F o r t h i s s i m u l a t e d atmosphere t h e i n f l u e n c e o f a b s o r p t i o n o f t h e medium on t h e v i s i b i l i t y o f b l a c k and g r e y o b j e c t s was determined. The luminance o f t h e h o r i z o n and o f d i f f e r e n t g r e y t a r g e t s a s w e l l as t h e v i s i b i l i t y o f t h e t a r g e t s has been measur e d w i t h i n c r e a s i n g a b s o r p t i o n under monochromatic i l l u m i n a t i o n . The v i s i b i l i t y o f b l a c k t a r g e t s depends o n l y on t h e t o t a l e x t i n c t i o n c o e f f i c i e n t . The v i s i b i l i t y o f non b l a c k t a r g e t s decreases w i t h i n c r e a s i n g a b s o r p t i o n , and depends n o t o n l y on t h e e x t i n c t i o n c o e f f i c i e n t b u t a l s o , t h r o u g h t h e i n h e r e n t c o n t r a s t o f t h e t a r g e t , on t h e e x i s t e n t a b s o r p t i o n . ivleasurements o f t h e i n h e r e n t c o n t r a s t o f t h e o b j e c t a t t h e e x i s t e n t a b s o r p t i o n a r e necesbary i n o r d e r t o d e t e r m i n e t h e v i s i b i l i t y o f non b l a c k o b j e c t s i n a b s o r b i n g media. The r e f l e c t i v i t y o f t h e ground a l s o i n f l u e n c e s t h e v i b i b i l i t y o f non b l a c k t a r g e t > , e s p e a i a l l y a t l o w c o n c e n t r a t i o n - t h e t a r g e t beeing m a i n l y i l l u m i n a t e d by d i r e c t s u n l i g h t

-

and f o r b r i g h t o b j e c t s . Even i f t h e standard v i s i -

b i l i t y can be k e p t c o n s t a n t (e.g. due t o a d d i t i o n a l a i r p o l l u t i o n c o n t r o l ) t h e v i s i b i l i t y o f non b l a c k t a r g e t s i s s m a l l e r ; i . e . t h e o p t i c a l q u a l i t y o f t h e atmosphere decreases w i t h i n c r e a s i n g a b b o r p t i o n . O n l y when t h e t a r g e t s a r e b r i g h t e r than t h e horizon, t h e i r v i s i b i l i t y w i l l increase w i t h increasing absorption. INTRODUCTION A l t h o u g h t h e c l a b s i c works a b o u t t h e v i s i b i l i t y t h e o r y ( M i d d l e t o n 1952, McCartney 1976, K e r k e r 1969) drew t h e a t t e n t i o n t o t h e i m p o r t a n t r o l e o f a b s o r p t i o n , i t was o f t e n u n d e r e s t i m a t e d o r n e g l e c t e d : The s i m p l e v i b i b i l i t y f o r m u l a o f Koschmieder (1924) - i n v e r s e r e l a t i o n between t h e v i s i b i l i t y o f an o b j e c t and t h e e x t i n c t i o n c o e f f i c i e n t o f t h e atmospheric a e r o s o l

-

i s applied, i n s p i t e o f i t s l i m i t i n g

absdmptionb ( H o r v a t h 1971a), l e a d i n g t o c o n s i d e r a b l e e r r o r s i n d e t e r m i n a t i o n o f v i b i b i l i t y , e s p e c i a l l y i f t h e s c a t t e r i n g c o e f f i c i e n t i t used i n s t e a d o f t h e e x t i n c t i o n c o e f f i c i e n t . The e a r l i e r paper o f Dessens (1944), d e a l i n g w i t h t h e e f f e c t s o f a b s o r p t i o n on v i s i b i l i t y , seems t o have been f o r g o t t e n f o r a l o n g time. However, i n h e a v i l y p o p u l a t e d and i n d u s t r i a l i s e d r e g i o n s , t h e c o n c e n t r a t i o n o f d i e b e l and o t h e r carboneceous a e r o s o l s

-

aerosols predominantly absorbing

306

1i g h t

r a t h e r than s c a t t e r i n g v i s i b l e

-

has c o n s t a n t l y grown. T h e r e f o r e nowadays

more and more a t t e n t i o n i s focused on t h e e f f e c t o f a b s o r p t i o n on v i s i b i l i t y , as i t i s shown by t h e r e c e n t l y p u b l i s h e d papers f r o m Faxvog & R o e s s l e r (1978,1980).

They p r e s e n t formulas f o r t h e v i s i b i l i t y o f b l a c k and o t h e r o b j e c t s viewed h o r i z o n t a l y t h r o u g h a e r o s o l s which may b o t h s c a t t e r and absorb l i g h t . L a b o r a t o r y e x p e r i m e n t s t o d e t e r m i n e t h e e f f e c t o f a b s o r p t i o n on t h e h o r i z o n t a l v i s i b i l i t y o f b l a c k t a r g e t s and f u r t h e r on t h e h o r i z o n t a l v i s i b i l i t y and c o n t r a s t o f g r e y t a r g e t s had n o t been performed. Therefore, a s t u d y i n a s i m u l a t e d atmosphere w i t h a s t r o n g l y and a weakly r e f l e c t i n g ground was made and w i l l be r e p o r t e d i n t h i s paper. T h e o r e t i c a l c o n s i d e r a t i o n s o f t h e v i s i b i l i t y o f b l a c k and g r e y o b j e c t s The b r i g h t n e s s c o n t r a s t o f an o b j e c t i s d e f i n e d a s : C = (B

-

Bh)/Bh

where 6 i s t h e b r i g h t n e s s o f t h e o b j e c t and Bh t h e b r i g h t n e s s o f t h e background o r h o r i z o n . The d i s t a n c e a t which t h e c o n t r a s t o f t h e o b j e c t a g a i n s t t h e h o r i z o n j u b t e q u a l s bhe observe& c o n t r a s t t h r e s h o l d

is

E

t h e v i s i b i l i t y V . Koschmieder's

t h e o r y (1924) g i v e s t h e f o l l o w i n g e q u a t i o n : E

= Co.exp(-bext.V)

where Co i s t h e c o n t r a s t a t d i s t a n c e x = 0, o r i n h e r e n t c o n t r a s t . is : 9 I n lCoO/bext

And t h u s t h e v i s i b i l i t y o f a g r e y o b j e c t V

V = (- I n / E l + 9 F o r a p e r f e c t l y b l a c k o b j e c t Co = -1, and t h e n t h e v i s i b i l i t y Vb i s t : Vb = - I n I E l / b e x t One c a n w r i t e t h e r a t i o o f v i s i b i l i t i e s o f g r e y and b l a c k o b j e c t s as: V /V = 1 g b Laboratory simulations

-

I n ICol/ln

/El

A s c a t t e r i n g h y d r o s o l , such as a m a s t i c h y d r o s o l , has s i m i l a r p r o p e r t i e s as a n

a t m o s p h e r i c a e r o s o l . These h y d r o s o l s a r e produced b y m i x i n g a s o l u t i o n o f m a s t i c i n e t h a n o l w i t h w a t e r and t h e y a r e v e r y s t a b l e . The p a r t i c l e s a r e p o l y d i s p e r s e and have a d i a m e t e r t h e same o r d e r o f magnitude as t h e wavelength o f l i g h t ( H o r v a t h & P r e s l e 1979). F o r t h e s i m u l a t i o n of a n a b s o r b i n g a e r o s o l a m i x t u r e o f m a s t i c h y d r o s o l and a dye w h i c h c o n t a i n s no p a r t i c l e s

-

being therefore responsible o n l y f o r absorption

-

was

used. T h i s a b s o r b i n g h y d r o s o l shows o p t i c a l p r o p e r t i e s s i m i l a r t o a b s o r b i n g atmospheric a e r o s o l s and a l l o w s a n easy d i s t i n c t i o n between a b s o r p t i o n and s c a t t e r i n g . As a b s o r b i h g m a t e r i a l two brands of b l a c k i n k and a w a t e r s o l u b l e b l a c k a n i l i n e dye were used. P r e l i m i n a r y measurements showed t h a t t h e s c a t t e r i n g c o e f f i c i e n t remains c o n s t a n t w i t h t h e a d d i t i o n o f dye and t h e e x t i n t i o n c o e f f i c i e n t b e i n g t h e sum o f t h e s c a t t e r i n g c o e f f i c i e n t w i t h t h e a b s o r p t i o n c o e f f i c i e n t o f t h e employed dye c o n c e n t r a t i o n .

307

The v i s i b i l i t y observations have been performed i n a container of approximately 1,5 x 0,s x 0,15 m 3 s i,z e , f i l l e d with hydrosol. The hydrosol was illuminated by means of 5 sodium lamps of 180 W each, giving a homogeneous illumination of approximately 11000 l x . The bottom of the hydrosol container was black anodized aluminium and simulated a weakly r e f l e c t i n g ground. To obtain a strongly r e f l e c t i n g ground t h i s bottom was covered with a white sheet. Experimental resul t s f o r black t a r g e t s The v i s i b i l i t y of black t a r g e t s was measured f o r a purely s c a t t e r i n g hydrosol and f o r increasingly absorbing hydrosols by two observers. Table 1 l i s t s the average v i s i b i l i t y of the two observers a s well a s the standard deviation ( l i s t e d in

(v)

p a r e n t h e s i s ) . ,Also included a r e t h e e x t i n c t i o n c o e f f i c i e n t s determined by means of the long path photometer and v i s i b i l i t i e s calculated from these e x t i n c t i o n c o e f f i c i e n t s a t two c o n t r a s t thresholds: the standard c o n t r a s t threshold of 0,02 and the mean of the measured c o n t r a s t thresholds of the two observers

I E ~=

0,015.

The v i s i b i l i t y c a l c u l a t e d from the mean of the measured c o n t r a s t threshold i s in good agreement with the average measured v i s i b i l i t y . On the o t h e r hand, the v i s i b i l i t y calculated from t h e standard c o n t r a s t threshold i s an average of l o % smaller than the measured v i s i b i l i t y , since both observers have c o n t r a s t thresholds l e s s than 0,02. V i s i b i l i t y i s inversely proportional t o the e x t i n c t i o n c o e f f i c i e n t , independent of t h e s i z e of the absorption c o e f f i c i e n t . Thus t h e v i s i b i l i t y of ideal black t a r g e t s i n absorbing media i s experimentally proven t o depend only on the t o t a l extinction coefficient.

TABLE 1 Measured and c a l c u l a t e d v i s i b i l i t i e s f o r black t a r g e t s Dye concentration ml/l Hydrosol 0 0,5 0,lO 0,15 0,20

Measured v i s i b i l i t y V cm 60,71 49,75 41,85 37,53 34,05

(2,58) (1,71) (2,23) (1,42) (1,14)

bexf

Calculated

Visibility

cm-

IE/

/EI

0,072 0,090 0,100 0,111 0,124

= 0,02

53,8 43,4 39,l 35,l 31,5

=

0,015

58,3 46,65 42 ,O 37,8 33,9

Experimental resul t s f o r grey t a r g e t s The v i s i b i l i t y was measured by t h r e e observers f o r a purely s c a t t e r i n g hydrosol and then f o r three increasing absorbing hydrosols. First a black t a r g e t B was used, followed by four d i s t i n c t . g r e y t a r g e t s ( G 1 was d a r k e s t and 64 l i g h t e s t ) and then t h e black repeated. The r e s u l t s a r e given

in

Table 2.

The measurements f o r the t a r g e t 64 contains an additional uncertainty since the observers could see t h e dark edges of the t a r g e t b e t t e r than the l i g h t face, t h u s

308

Neawrements o f t h e r a t i o o f t h e i l l u m i n a n c e of t h e h o r i z o n t o t h e i r r a d i a n c e o f the i n c i d e n t l i g h t w i t h i n c r e a s i n g a b s o r p t i o n . The p o i n t s xx

$*.. .W

'

r e p r e s e n t t h e measurements f o r a weakly r e f l e c -

20

2: 8 . Pa

t i n g ground, t h e p o i n t s ooo t h e measurement5 f o r

ra

a s t r o n g l y r e f l e c t i n g one. The continuous and

* 3.

broken l i n e s r e p r e s e n t t h e t h e o r e t i c a l values

OQ

5

L

b-

ABSORPTION COEFFICIENT / EXTINCTION COEFFICIENT

h o r i z o n t o t h e i n c i d e n t i r r a d i a n c e was conbidered instead o f the illuminance o f the h o r i z o n . The r e s u l t s a r e p l o t t e d i n f i g .

1 for

a s t r o n g l y and a weakly r e f l e c t i n g ground. These r e s u l t s show t h e i m p o r t a n t r o l e of t h e r e f l e c t i o n o f t h e ground. The r a t i o o f t h e i n h e r e n t b r i g h t n e s s o f the observed o b j e c t t o t h a t o f the h o r i z o n was measured f o r each s e t of g r e y t a r g e t s i n each h y d r o s o l . The r e s u l t s a r e r e p r e bented f o r b o t h weakly and s t r o n g l y r e f l e c t i n g ground i n f i g u r e 2. From t h i s f i g u r e one concludes t h a t t h e d i f f e r e n c e between t h e weakly and s t r o n g l y r e f l e c t i n g ground

i b

negligible.

From t h e measured r a t i o s Bo/Bh,

t h e i n h e r e n t c o n t r a s t o f t h e g r e y t a r g e t s was

c a l c u l a t e d a t t h e bame c o n d i t i o n s as f o r the measurements of t h e v i s i b i l i t y (see t a b l e 2 ) . The r a t i o s o f t h e v i s i b i l i t y o f t h e g r e y t a r g e t s t o t h a t o f a b l a c k t a r g e t wab t h e n determined u s i n g t h e t h e o r e t i c a l formula:

V /V = 1 - I n ICol/ln I E ~ 9 b Results, c a l c u l a t e d u s i n g t h e standard c o n t r a s t t h r e s h o l d and the mean c o n t r a s t t h r e L h o l d of t h e t h r e e observers

1 ~ =1 0,018 a r e

shown i n t a b l e 2 a l o n g w i t h t h e

d i r e c t meabured r a t i o s o f v i s i b i l i t i e s . The correspondence between t h e average measured r a t i o and t h a t c a l c u l a t e d u s i n g t h e mean c o n t r a s t t h r e s h o l d o f t h e obbervers

ib

v e r y good f o r t h e f i r s t t h r e e g r e y o b j e c t s .

309 F i g . 2:

. 9. W

Behaviour o f t h e r a t i o o f t h e i n h e r e n t b r i g h t ness o f t h e o b j e c t t o t h e b r i g h t n e s s o f t h e

- theoret ica I x x x grey 1 + + + o D o

grey2

bbb

grey 3

h o r i z o n w i t h i n c r e a s i n g a b s o r p t i o n . The L A &

symbols l e f t o f " g r e y " r e p r e s e n t t h e measurements f o r a weakly r e f l e c t i n g ground, t h e symbols r i g h t o f " g r e y " t h e measurements f o r a s t r o n g l y r e f l e c t i n g one.

I n t h e case o f t h e f o u r t h g r e y t a r g e t t h e d i s agreement i s most l i k e l y caused b y t h e exa g g e r a t e d v i s i b i l i t y o f t h e t a r g e t s due t o t h e i r d a r k e r edges. I

.

.

.

. . . . 0.4 0.6 A B S O R P T ION COEFFICIENT/ E X T lN C T lO N COEFFICI E N 1 0.2

Thus t h e p r e d i c t i o n o f t h e v i s i b i l i t y o f g r e y o b j e c t s i n a b s o r b i n g media f r o m t h e t o t a l e x t i n c t i o n c o e f f i c i e n t alone i s n o t s u f f i c i e n t .

The i n h e r e n t c o n t r a s t o f t h e observed o b j e c t s as a f u n c t i o n o f a b s o r p t i o n i s a l s o necessary. A p p l i c a t i o n t o t h e atmosphere and comparison w i t h o t h e r r e w l ts The v i s i b i l i t y o f p e r f e c t l y b l a c k o b j e c t s i n a b s o r b i n g media i s i n v e r s e l y p r o p o r t i o n a l t o t h e e x t i n c t i o n c o e f f i c i e n t , independent o f t h e s i z e o f t h e absorpt i o n c o e f f i c i e n t , a s i t was t h e o r e t i c l y f o r m u l a t e d b y Foaxvog & R o e s s l e r (1978). For non-perfectly black objects, appearing o f t e n i n nature, the e f f e c t o f a b s o r p t i o n must be i n c l u d e d . I n t h i s case t h e f i r s t f a c t o r t o be t a k e n i n t o c o n s i d e r a t i o n i s t h e i l l u m i n a n c e

o f t h e horizon (see f i g . 1 ) .

The t h e o r e t i c a l r e s u l t s f r o m Faxvog & R o e s s l e r (1980)

do n o t correspond w i t h t h e performed measurements, e s p e c i a l l y n o t f o r s t r o n g a b s o r p t i o n and f o r a s t r o n g l y r e f l e c t i n g ground. The a u t h o r 5 suggest t h a t p o s s i b l e 5ource5 o f e r r o r a r e t h e n o t - c o n s i d e r a t i o n o f t h e mu1 t i p l e scattering-mu1 t i p l e s c a t t e r i n g i s i m p o r t a n t i n o p t i c a l l y t h i c k media

-

and t h e n o t - c o n s i d e r a t i o n o f

t h e r e f l e c t i o n o f t h e ground, which i n f l u e n c e s t h e decrea5es o f t h e i l l u m i n a n c e o f t h e horizon w i t h increasing absorption. The second f a c t o r t o be t a k e n i n t o c o n s i d e r a t i o n

i 5

t h e i n h e r e n t b r i g h t n e s s of

t h e observed o b j e c t . The i n h e r e n t b r i g h t n e s s o f t h e o b j e c t i s n o t a c o n s t a n t l i k e i t was assumed by Faxvog & R o e s s l e r (1980) b u t depends on t h e i l l u m i n a t i o n r e c e i v e d

by t h e o b j e c t and t h e r e f o r e depend? on t h e a b s o r p t i o n o f t h e a e r o s o l and on t h e r e f l e c t i o n o f t h e ground. To d e t e r m i n e t h e v i s i b i l i t y , t h e d e c i s i v e f a c t o r i s however t h e r a t i o o f t h e i n h e r e n t brightness o f the t a r g e t t o the brightness o f the horizon. I n our

310

TABLE 2 deasured v i s i b i l i t i e s f o r g r e y t a r g e t s and measured and c a l c u l a t e d r a t i o s o f v i s i b i l i t i e s o f g r e y and b l a c k o b j e c t s w i t h i n c r e a s i n g a b s o r p t i o n ba/bext

Target

B Gi E2

0

G3 64 B

B B1

0,27

G2 G3 G4 B B G1

0,37

62 63 G4 B

0,47

B G1 G2 G3 G4 B

Visibility cm

46,40 45,oG 44.31 42,93 38,67 46,91

V/Vb

ICo

I

E

V/Vb = 0,018

(calculated) E

= 0,02

1 0,97 0,96 0,92 o ,83 1

1 0,89 0,85 0,75 0,46 1

1 0,97 0,96 0,93

1 0,97 0,96

0,81 1

o $0 1

1 0,86

1 0,96 0,945 o,90 0,72 1

0,96 0,94 o ,89 o ,71 1

0,92

1

32,04 30,88 29,69 28,60 25,49 31,95

(1,72) (1,45) (1,77) (1,81) (2,44) (1,53)

1 0,96 0,93 o,89 1

0,675 0,325 1

27,49 25,70 25,57 24,06 20,48 27,39

(1,07) (1,64) (1,44) (2,08) (1,62) (1,78)

1 0,94 0,93 0,87 0,75 1

1 0,83 0,78 0*,625 0,225 1

1 0,95 0,94 0,88 0,63 1

o $8 o ,62 1

24,56 22,56 22,16 20,84

(1,68) (1,26) (1,49) (0,96)

1 0,91 o,90 0,81

25,63

(2,94)

1

1 0,82 0,74 0,60 0,16 1

1 0,95 0,93 0,87 0,55 1

1 0,95 0,92 o ,87 0,53 1

--

-_

0,80

--

0,80

1 0,95 0,93

e x p e r i m e n t a l s e t u p t h e r e f l e c t i o n o f t h e ground had no e f f e c t on t h i s r a t i o ( s e e f i g . 2 ) : t h e e f f e c t o f t h e r e f l e c t i o n o f t h e ground on t h e i n h e r e n t b r i g h t n e s s o f t h e t a r g e t compensates t h a t on t h e b r i g h t n e s s o f t h e h o r i z o n . A l t h o u g h t h e two assumptions, used f o r t h e t h e o r e t i c a l f o r m u l a f r o m Faxvog & K o e s s l e r , c o u l d n o t be proven e x p e r i m e n t a l l y , t h e i r f i n a l formual r e p r e s e n t s a good a p p r o x i m a t i o n , a s shown i n f i g . 2. O n l y a t s t r o n g a b s o r p t i o n t h e t h e o r e t i c a l r e s u l t s i n c r e a s e f a s t e r t h a n t h e e x p e r i m e n t a l measurements. Because o f t h e l a c k o f a good t h e o r e t i c a l l y bahed formula, w h i c h c o u l d g i v e t h e v a r i a t i o n o f t h e i n h e r e n t c o n t m s t w i t h i n c r e a s i n g a b s o r p t i o n , i t i s necessary t o measure t h e r a t i o o f t h e i n h e r e n t brightness o f t h e t a r g e t t o the brightness o f the horizon a t t h e e x i s t e n t absorption i n order t o determine t h e v i s i b i l i t y o f non-perfectly black o b j e c t s i n absorbing media ( s e e t a b l e 3 ) .

311

Table 3 shows t h e v i s i b i l i t y o f b l a c k and g r e y t a r g e t s i n a non a b s o r b i n g atmosp h e r e a n atmosphere w i t h 25 % and 50 % o f t h e e x t i n c t i o n beeing due t o a b s o r p t i o n . We have assumed two p o s s i b l e p a r t i c l e c o n c e n t r a t i o n s , h i g h c o n c e n t r a t i o n mean5 l o w v i s i b i l i t i e s and t h u s a h i g h v e r t i c a l o p t i c a l d e n s i t y and t h e r e f o r e a l a r g e p o r t i o n o f d i f f u s e l i g h t i l l u m i n a t i n g the t a r g e t ( s i m i l a r t o our simulation e x p e r i m e n t s ) ; l o w c o n c e n t r a t i o n means h i g h v i s i b i l i t y and t h e t a r g e t beeing m a i n l y i l l u m i n a t e d by d i r e c t s u n l i g h t . The d i f f e r e n t shades o f g r e y would correspond t o c o n i f e r 5 w i t h t h e sun b e h i n d t h e t a r g e t ( G l ) , c o n i f e r s 90' c o n c r e t e a t 90'

f r o m t h e sun (GZ),

(G3), c o n c r e t e i l l u m i n a t e d b y t h e sun (G4). The v i s i b i l i t y o f t h e

b l a c k t a r g e t was n o r m a l i z e d t o 1. I n p u r e s c a t t e r i n g t h e v i s i b i l i t y o f t h e g r e y t a r g e t s a r e up t o 20 % l o w e r b o t h f o r s t r o n g and w e a k l y r e f l e c t i n g grounds. W i t h i n c r e a s i n g a b s o r p t i o n t h e v i s i b i l i t y o f a l l g r e y t a r g e t s decreases, f o r d a r k t a r g e t s t h e r e f l e c t a n c e o f t h e ground has a minimal i n f l u e n c e , e x c e p t f o r 50 % a b s o r p t i o n and l o w c o n c e n t r a t i o n , where t h e a d d i t i o n a l r e f l e c t i o n o f t h e ground has a marked i n f l u e n c e on t h e luminance o f t h e h o r i z o n . F o r t h e l i g h t e r t a r g e t s (G3, 54) t h e same i s t r u e ,

t h e i n c r e a s e i n v i s i b i l i t y f o r 64 a t 50 % a b s o r p t i o n

and l o w c o n c e n t r a t i o n i s caused b y t h e t a r g e t b e e i n g b r i g h t e r t h a n t h e h o r i z o n . TABLE 3 V i s i b i l i t y i n d i f f e r e n t a b s o r b i n g atmospheres w i t h a s t a n d a r d v i s i b i l i t y o f 1. Target

Pure s c a t t e .

25 % absorp. h i b h concen. weak. s t r o n g r e f l e c t i ng

weak. s t r o n g r e f l e c t i ng Black ~~

1

1 ~

~

25 % absorp. l o w concen. weak. s t r o n g r e f l e c t i ng

50 % absorp. h i g h concen. weak. s t r o n g r e f l e c t i ng

50 % absorp. l o w concen. weak. s t r o n g r e f 1ec t ing

1

1

1

1

1

1

1

1

~~

Grey 1

0,97

0,97

0,96

0,96

0,96

0,95

0,94

0,94

0,91

0,83

Grey 2

0,96

0,96

o,94

0,94

0,94

0,92

0,92

0,91

0,86

o,70

Grey 3

0,92

0,92

o,90

0,89

0,89

0,85

0,84

0,83

0,70

0,43

Grey 4

0,80

0,80

0,71

0,71

0,66

0,41

0,23

0,22

0,80

1,06

G e n e r a l l y one can say: An i n c r e a s e o f t h e a b s o r p t i o n o f t h e atmospheric a e r o s o l ( w i t h t h e e x t i n c t i o n c o e f f i c i e n t r e m a i n i n g c o n s t a n t ) does n o t change t h e v i s i b i l i t y

of b l a c k t a r g e t s . The v i s i b i l i t y o f nonblack t a r g e t s decreases w i t h i n c r e a s i n g a b u e r p t i o n , t h e decrease i s l a r g e r f o r atmospheres w i t h h i g h amounts o f d i f f u s e l i g h t and f o r s t r o n g l y r e f l e c t i n g ground. F o r t h e model c a l c u l a t i o n s o f t a b l e 3, t h e extreme cases, b o t h f o r t h e amount o f d i f f u s e l i g h t and t h e r e f l e c t i o n o f t h e ground have been chosen, so t h a t most o f t h e cases t o be expected w i l l l i e i n between.

312

snow f i e l d s ) w i l l be b e t t e r v i s i b l e i n a s t r o n g l y

O n l y v e r y b r i g h t t a r g e t s (e.g.

a b s o r b i n g atmosphere ( M i d d l e t o n 1952), because t h e p o s i t i v e i n t r i n s i c c o n t r a s t o f the t a r g e t r e l a t i v e t o the horizon increases, since the brightness o f the h o r i z o n decreabes due t o a b s o r o t i o n . REFERENCES Dessenb, H.,

1944, " R e l a t i o n e n t r e 1 ' a b s o r p t i o n p a r 1 'atmosphere e t l a v i s i -

b i l i t 6 " , C.R.

Acad. S c i . 218, pp. 685 - 687

and R o e s s l e r , D.M.,

Faxvog, F.R.,

1978, "Carbon a e r o s o l v i s i b i l i t y vs. p a r t i -

c l e s i z e d i s t r i b u t i o n " , A p p l . Optic. Horvath, H.,

A t m . Environment 4 , pp. 177

Horvath, H.,

17, pp. 2612-2616

1911 a, "On t h e a p p l i c a b i l i t y o f t h e Koschm:edcr b : s i h i i i t y and P r e s l e , G.,

-

formula",

134

1979, "Measuremenbof v i s i b i l i t i e s i n s i m u l a t e d

atmospheres ( h y d r o s o l s ) and a p p l i c a t i o n s t o r e a l atmospheres", Aero-

sols research a t the I n s t i t u t e f o r Experimental Physics o f the U n i v e r s i t y o f Vienna, P a r t I 1 K e r k e r , M.,

1969, "The s c a t t e r i n g o f 1 i g h t and o t h e r e l e c t r o m a g n e t i c r a d i a t i o n " ,

New York: Academic p r . 1924, " T h e o r i e d e r h o r i z o n t a l e n S i c h t w e i t e " , B e i t r . z . Phys.

Koschmieder, H.,

f r e i e n A t m . 12, pp. 33 - 53 and 1 7 1

-

181

1976, " O p t i c s o f t h e atmosphere",

McCartney, E.J., M i d d l e t o n , W.E.K.,

John Wiley, New York

1952 and 1963, " V i s i o n t h r o u g h t h e atmosphere", U n i v e r s i t y

o f T o r o n t o Press, Toronto R o e s s l e r , D.M.,

and Faxvog, F.R.,

1981, " V i s i b i l i t y i n a b s o r b i n g a e r o s o l s " ,

A t m . Environment 15, pp. 151

-

156

ACKNOWLEDGEMENT: T h i s work was s u p p o r t e d i n p a r t by a g r a n t o f t h e "Fonds z u r Forderung d e r w i s b e n s c h a f t l i c h e n Forschung i n U s t e r r e i c h " , g r a n t number 3453.

313

CHANGES OF LOCAL PLANETARY ALBEDO BY AEROSOL PARTICLES HARTMUT GRASSL, I n s t i t u t fur Meereskunde, Universitat of Kiel, F R G MADELEINE NEWIGER, Max-Planck-Institut fur Meteorologie, Hamburg, FRG

ABSTRACT T h e c l i m a t e p a r a m e t e r local p l a n e t a r y a l b e d o i s a f f e c t e d both in c l e a r a n d cloudy a r e a s by a e r o s o l particles. In b o t h cases t h e a l b e d o may i n c r e a s e or d e c r e a s e i f

turbidity

increases, i.e. t h e r e a r e a r e a s w h e r e a n additional pollution l e a d s t o a n energy gain o r loss. While t h e most i m p o r t a n t p a r a m e t e r s in c l e a r a r e a s a r e s u r f a c e albedo a n d t h e mass absorption c o e f f i c i e n t of t h e particles, aerosol p a r t i c l e c o n c e n t r a t i o n v i a t h e number of condensation nuclei a n d a g a i n absorption a r e t h e dominating f a c t o r s i n clouds. A reappraisal of known bulk formulae for c l e a r a r e a s points t o additional p a r a m e t e r s determining t h e crossover from h e a t i n g t o cooling. T h e most i m p o r t a n t additional p a r a m e t e r i s sun elevation, however, a e r o s o l o p t i c a l d e p t h also has to b e considered. T h e weakness of former e s t i m a t e s of cloud a l b e d o c h a n g e w i t h aerosol p a r t i c l e c h a r a c t e r i s t i c s i s demonstrated f o r broad cloud

drop s i z e distributions and for simultaneous c h a n g e s in p a r t i c l e number, size, a n d chemical composition. T h e t e r r e s t r i a l radiation does n o t c o m p e n s a t e f o r t h e partly d r a s t i c changes in t h e solar radiation in c l e a r a n d cloudy a r e a s , a g a i n pointing t o a s t r o n g influence of aerosol p a r t i c l e s o n local p l a n e t a r y albedo.

INTRODUCTION Minor c o n s t i t u e n t s of t h e a t m o s p h e r e c a n play a n important role for climate. If t h e s e 'climatic' minor c o n s t i t u e n t s a r e moreover influenced i n t h e i r c o n c e n t r a t i o n of distribution by human a c t i v i t i e s t h e y become especially important. A s long as many of t h e feedback loops of t h e n a t u r a l c l i m a t e system a r e poorly o r n o t at all understood, o u r c o n c e r n with global

man-made p e r t u r b a t i o n s of t h e c l i m a t e system h a s t o b e speculative, being justified only by potentially dangerous c l i m a t i c changes a n d by obvious regional perturbations, as for i n s t a n c e h e a t islands of c i t i e s a n d acid rain, B e s t , b u t still only p a r t l y understood of a l l t h e possible c l i m a t i c perturbations i s t h e consequence of t h e greenhouse effect of radiatively a c t i v e g a s e s like C O

.

N 0, C H T h e 2' 2 4 e s t i m a t i o n of t h e a e r o s o l p a r t i c l e influence, however, i s much m o r e complicated e v e n for c l e a r a r e a s of t h e a t m o s p h e r e s i n c e 1) t h e seasonal a n d local c o n c e n t r a t i o n , composition and s i z e of t h e p a r t i c l e s v a r i e s tremendously, 2) t h e i n c r e a s e of p a r t i c l e c o n c e n t r a t i o n i s questioned, a n d 3) e v e n t h e sign of t h e local e n e r g y budget c h a n g e equivalent to a change in local p l a n e t a r y a l b e d o is u n c e r t a i n (ref. 1) depending o n s u r f a c e albedo, absorption a n d

314 s c a t t e r i n g c h a r a c t e r i s t i c s of t h e particles.

-

Since aerosol p a r t i c l e s

besides c i r c u l a t i o n p a t t e r n s - d e t e r m i n e t h e microphysics of

clouds, and t h u s a r e responsible for p r e c i p i t a t i o n a n d t h e radiation budget of clouds, t h e r e is n o justification for a n omission of t h e a e r o s o l particles’ influence o n t h e e n e r g y budget i n cloudy areas. A s a c o n s e q u e n c e of t h e u n c e r t a i n t i e s mentioned, t h e following s e c t i o n s will f i r s t give a n assessment of t h e a c c u r a c y of a l r e a d y known bulk formulae f o r c l e a n a r e a s , will show t h e i m p o r t a n c e of t h e p a r t i c l e s for t h e r a d i a t i v e t r a n s f e r i n a n a t m o s p h e r e w i t h clouds, and will also d e p i c t p r e s e n t u n c e r t a i n t i e s in estimating cloud a l b e d o changes just by showing t h e number of a c t i v a t e d p a r t i c l e s f o r given c h a n g e s in number, size, composition and s u r f a c e tension. ALBEDO IN A CLOUDLESS ATMOSPHERE T w o a t t e m p t s h a v e been made (ref. 1, 2) t o d e s c r i b e t h e i n f l u e n c e of aerosol p a r t i c l e s o n t h e r a d i a t i o n budget in cloudless a t m o s p h e r e s by bulk formulae. R a d i a t i v e t r a n s f e r c a l c u l a t i o n s using t h e

6

-Eddington approximation have b e e n c a r r i e d o u t t o test t h e

validity of t h e s e bulk formulae. Comparisons w i t h socalled e x a c t calculations with t h e matrix o p e r a t o r method show a good a g r e e m e n t for i n t e g r a l f e a t u r e s as albedo. For i n s t a n c e t h e a l b e d o d i f f e r e n c e f o r t w o cloud types, a p u r e w a t e r cloud a n d a n aerosol contaminated cloud, a r e 0.1186

a n d 0.1152

6

for t h e matrix o p e r a t o r a n d t h e

-Eddington method

respectively. In a f i r s t s t e p ChGlek and Coackley (ref. I ) derived a relationship b e t w e e n t h e r a t i o absorption-to-backscattering a / b of a n aerosol a n d t h e s u r f a c e a l b e d o A

E (1 -- As)2T

a

S’

>

o

heating

=

o

equilibrium

<

o

cooling

(1)

This bulk formula i s independent of t h e o p t i c a l thickness a n d n e i t h e r t h e sun e l e v a t i o n nor t h e s p e c t r a l d e p e n d e n c e of a / b a n d s u r f a c e a l b e d o a r e considered. Fig. 1 demonstrates, t h a t t h i s simple relationship is n o t a b l e t o r e p r e s e n t t h e main f e a t u r e s of aerosol influence. T h e conditions f o r equilibrium following. Eq. 1 a r e compared t o our r e s u l t s f o r t w o aerosol s i z e distributions depending on sun elevation, o p t i c a l thickness, a n d complex index of refraction. Since o u r r e s u l t s include t h e i n t e g r a t i o n over t h e solar spectrum, t h e y have been allied t o t h e a p p r o p r i a t e v a l u e a / b at h = 0.55 pm,

t h e c e n t e r wavelength of t h e visible spectrum.

T h e v a r i a t i o n i n v a l u e s a / b is mainly d u e t o a c h a n g e i n t h e complex r e f r e c t i v e index, t h e p a r t i c l e s i z e distribution h a s a minor influence. For a t y p i c a l industrial a e r o s o l w i t h a complex index of r e f r a c t i o n

m=1.5-0.02,

as measured in Mainz (ref, 3), a n d a J u n g e s i z e

distribution t h e equilibrium may c h a n g e from s u r f a c e a l b e d o 0.26 t o 0.56 depending o n sun e l e v a t i o n a n d o p t i c a l thickness. Such a n aerosol l a y e r over a snow s u r f a c e will lead t o a h e a t i n g of t h e atmosphere. F o r d e s e r t s with a n albedo v a l u e of -0.3

t h e effect i s critically

d e p e n d e n t o n both sun e l e v a t i o n a n d o p t i c a l depth: f o r cos 0 = 0.7 a n o p t i c a l thicknes ‘I; = 0.1 will c a u s e a heating, w h e r e a s a n aerosol l a y e r w i t h ‘I; = 0.5 cools t h e sythem. T h e e f f e c t

315

10

1;ykky

1974 1

I1 - A S 1'

n b

10

size distributions ~ _ . Haze L iDelrrnendjlani Junge wlth r d

zenlth angles c o s 0

\

\

009 4 07 0 05 003 0Of

\

\

10

10

1

02

04

06

*'

AS

Fig. 1: Absorption-to-backscattering r a t i o a / b of a e r o s o l p a r t i c l e s as a function of c r i t i c a l s u r f a c e a l b e d o A R e s u l t s f o r a bulk formula by Ch$lek a n d C o a c k l e y (ref. 1) a r e compared t o r a d i a t i v e t r a d f e r c a l c u l a t i o n s f o r t w o aerosol s i z e distributions with optical thicknessZ = 0.1 (open symbols) and Z = 1.0 (dark symbols) and f i v e z e n i t h a n g l e s 0. T h e domain t o t h e r i g h t s i d e of t h e equilibrium c u r v e defines conditions w h e r e additional aerosol p a r t i c l e s d e c r e a s e t h e albedo of t h e system a n d t h e r e f o r e h e a t s it.

.

of t h e o p t i c a l t h i c k n e s s 1 is more pronounced for low sun elevations, as well as for low

values a / b

-

i n t h i s case c h a n g e s in aerosol o p t i c a l thickness led t o t h e same s h i f t of t h e

equilibrium point as sun elevation. In a follow-up p a p e r (ref. 2) t h e a u t h o r s of (ref. I ) included a d e p e n d e n c e o n sun elea n d angular d e p e n d e n t phase f u n c t i o n by introducing a b(p). For a sufficiently thin

vation

aerosol l a y e r t h e y derived:

>0

heating

Again n e i t h e r t h e s p e c t r a l d e p e n d e n c e of t h e r a t i o a/b(p) nor t h e variation of optical thickness is considered. Fig. 2 shows t h e resuIts of t h e bulk formula (Eq. 2) a n d o u r c a l c u l a t i o n s i n terms of a/b(p) a n d t h e c r i t i c a l s u r f a c e albedo As f o r f i v e values p = cos 0 from 0.1 t o 0.5 and t h e t w o "extremes" for a / b from Fig. 1. T h e formula (Eq. 2) o v e r e s t i m a t e s t h e dependence o n p;

316

-_

._

zenith angles cos0 0 09

07 05 a03 0

00’

Fig. 2: a/b(p) a s a function of t h e c r i t i c a l s u r f a c e a l b e d o A f o r f i v e d i f f e r e n t z e n i t h a n g l e s p = cos 8 using Eq. 2 (-----) for t w o d i f f e r e n t aerosol siz; distributions. Own calculations T 6 0.5). (-) a l s o show d e p e n d e n c e o n o p t i c a l d e p t h 1 (0.1 t h e d i f f e r e n c e s being l a r g e s t f o r low sun e l e v a t i o n a n d low values a/b. T h e question w e t h e r a n additional aerosol l a y e r c a u s e s cooling o r h e a t i n g of t h e atmosphere-earth system c a n obviously n o t b e a n s w e r e d by t h e formulae (1) o r (2). AEROSOL PARTICLES AND RADIATION PARAMETERS O F WATER CLOUDS

If a e r o s o l p a r t i c l e s a b s o r b solar radiation (mainly i n t h e visible spectrum a n d in ‘windows’ b e t w e e n w a t e r vapour bands in t h e n e a r infrared), t h e r e i s a high probability t h a t t h e o r d e r of magnitude of absorption i s k e p t a f t e r t h e incorporation i n t o cloud air. This should hold w h e t h e r t h e p a r t i c l e s have been used as a condensation nucleus, c a t c h e d by cloud d r o p l e t s o r only grown with r e l a t i v e humidity t o a size normally n o t called a cloud droplet. C a l c u l a t i o n s by o n e of t h e a u t h o r s (ref. 4) a n d a n experimental verification f o r a f e w c a s e s by And& et al. (ref. 5), w h e r e simultaneous samples of cloud w a t e r a n d t h e una c t i v a t e d component w e r e available have confirmed t h i s expectation. If only t h e number of aerosol p a r t i c l e s changes, however, t h e i r chemical composition and r e l a t i v e s i z e distribution does not, t h e number of cloud d r o p l e t s under a fixed circulation p a t t e r n , e q u i v a l e n t t o fixed s u p e r s a t u r a t i o n and liquid w a t e r c o n t e n t , should c h a n g e i n t h e s a m e direction. Then t h e following r e l a t i o n b e t w e e n condensation nuclei number C or optical depth

T and t h e number of aerosol p a r t i c l e

should e x i s t (ref. 6-8):

N under t w o d i f f e r e n t situations

317 c2

N2a

I -

(-)

-

c2

NI

t 2

N2R (--)

-5

N1

-=

a = 0.8 as measured by Warner a n d Twomey (ref. 9) for a s p e c i f i c case

(3)

13 -0.3 if using a= 0.8, assuming narrow d r o p l e t s i z e distribution a n d T = 2 . C * r-z with t; = mean s q u a r e radius a n d C* = condensation nuclei used above unit surface.

(4)

If t h e a e r o s o l p a r t i c l e s a r e not only increasing in number b u t a l s o have a higher mass

absorption c o e f f i c i e n t k , t h e resulting clouds following r e l a t i o n (3) have higher optical d e p t h a n d a b s o r b stronger. S i n c e increasing

T, e n h a n c e s a l b e d o a n d increasing k lowers

albedo, both e f f e c t s additionally depending o n 7; for t h e s t a n d a r d case, t h e r e should e x i s t a n optical depth extent

Tc with no a l b e d o c h a n g e (T "35

- 0.8 km at 0.2

for highly polluted c a s e 2, v e r t i c a l

gmm3 liquid w a t e r conten?). Thinner clouds become brighter, thicker

clouds darker. If t h e absorption c o e f f i c i e n t remains c o n s t a n t , a l l clouds in a n increasingly polluted a t m o s p h e r e r e f l e c t more solar radiation, leading t o a n energy loss for t h e atmosphere-earth

system. This discussion of cloud albedo c h a n g e w i t h aerosol p a r t i c l e

changes included a n albedo e n h a n c e m e n t d u e t o a f l a t t e n i n g of t h e s c a t t e r i n g o r phase function which a l w a y s accompanies a decreasing mean d r o p l e t size. T h e variations of absorption, r e f l e c t i o n and transmission i n t h e i n t e g r a t e d

solar spectrum (0.3-3.7

vm

wavelength) c a u s e d by v a r i a t i o n s of a n a l y t i c a l cloud d r o p l e t s i z e distributions within observed limits have been presented e l s e w h e r e (ref. 10). Before questionning r e l a t i o n (4),which may b e necessary f o r simultaneous changes in size, c h e m i s t r y a n d number of p a r t i c l e s , in t h e n e x t section, w e will answer t h e question: Does longwave r a d i a t i o n compensate t h e e f f e c t s of aerosol p a r t i c l e variations o n shortw a v e cloud p a r a m e t e r s ? Again using t h e matrix-operator method f o r r a d i a t i v e t r a n s f e r c a l c u l a t i o n s f o r a n azimutally a v e r a g e d , plane parallel a t m o s p h e r e a n d accounting f o r t h e inhomogeneous s o u r c e extension by Wiscombe (ref. 1 I), our answer is: t h e longwave radiation d o e s n o t c o m p e n s a t e t h e e f f e c t s in t h e s h o r t w a v e domain. In Fig. 3 t w o cloud transformations

covering

t h e conceivable r a n g e from maritime (typical d r o p l e t

size

distribution C 5 a f t e r Deirmendjian (ref. 12) to c o n t i n e n t a l ( C l ) a n d c o n t i n e n t a l to strongly polluted (C3) l e a d to nearly t h e same n e t flux d i f f e r e n c e

A Fnet

= Fnet (C5)

-

Fnet (C1)

i n t h e s h o r t w a v e domain. N o i n c r e a s e i n t h e mass absorption c o e f f i c i e n t k is included. Additional absorption

A Fn e t in t h e longwave p a r t a r e a t l e a s t o n e o r d e r of

i n t h e s t r o n g e r pollution case would lower b o t h curves. T h e

values i n c r e a s e w i t h sun elevation.

A Fnet

magnitude lower a n d f o r t h e C5-C1 transformation e v e n a d d t o t h e s h o r t w a v e effect T h e s e small

a Fnet

a r e caused by t w o competing mechanisms. By adding p a r t i c l e s T is

increased lifting t h e e m i t t i n g l a y e r t o lower t e m p e r a t u r e s , causing r e d u c e d emission. This would f a v o r a compensation. T h e single s c a t t e r i n g albedo, however, i s lowered at t h e same time, bringing cloud emission n e a r e r t o blackbody emission, t h e r e f o r e increasing emission t o space.

318

AFnet

200

i -

100 : 50 -

-

optical depth at 0.55pm 26(C1) mean liquid water content = 0.2 gm-3

20 -

---

c1 -c3 continental 3 highly polluted

-

10 :

C5-Cl

continent a1 ---------

maritime

521

3

K

1

LW

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 cos 0 fig. 3. Radiative n e t f l u x d i f f e r e n c e A F = F (C5) - F function of solar zenith angle; upper &%es f0"rt shortwa%?

'

- F (C3) as a and lower (constan"e$alues) for

(1) or Fnet(C1)

long wave radiation. These results apply t o high lying clouds as well. An influence of pollution for high clouds is, however, much more uncertain because pollution by aerosol particles is f i r s t of all a problem of t h e planetary boundary layer. Since t h e location, t h e type and t h e height of a cloud determine, whether a n increase in cloud cover causes a n energy loss or gain for t h e earth-atmosphere system (for details

see Hartmann and Short (ref. 13)), additional aerosol particles without strongly increasing absorption favor a still more dominating albedo e f f e c t and thus enhanced energy losses if cloud amount should increase. ACTIVATED PARTICLES FOR DIFFERENT AEROSOL POPULATIONS T h e foregoing discussion avoided a n explicit t r e a t m e n t of changes in chemical composition and s i z e distribution of aerosol particles. Also changes in liquid water c o n t e n t and maximum supersaturation, which

-

even at fixed circulation p a t t e r n s

particle characteristics, have been neglected.

-

would vary with

T h e following example shows possible

variations of t h e number of a c t i v a t e d particles as a consequence of varying aerosol

319 p a r t i c l e parameters. T h e equations used stem from Hanel (ref. 14) a n d t h e example shown should only give a n impression of t h e possible reactions. T h e p a r a m e t e r c h a n g e s in Fig. 4 a r e at t h e margin of applicability of t h e r e l a t i o n s used, s i n c e Hanel's assumption of only minor c h a n g e s i n liquid w a t e r c o n t e n t

-

if comparing basic a n d new state - a r e already

stressed. Variations i n s u r f a c e tension a n d w a t e r u p t a k e with r e l a t i v e humidity, resulting from c h a n g e s i n chemical composition a r e n o t shown explicitly in Fig. 4, because r e a c t i o n s t o a 10% i n c r e a s e in p a r t i c l e numbers (n /n =1.1) a r e equivalent t o a lowering of s u r f a c e 1

0

tension by 6% or a n i n c r e a s e of t h e exponential mass i n c r e a s e c o e f f i c i e n t by 6.6%. T h e exponent

y

i n t h e r e l a t i o n b e t w e e n t h e r a t i o of cloud d r o p l e t s a n d t h e r a t i o of aerosol

p a r t i c l e numbers CCN1/CCNo =(NI/No)Y

, which

i s t h e r e s u l t of a l l t h e influences,

t h e r e f o r e h a s t o b e known for d i f f e r e n t a e r e a s a n d aerosol types.

16

I

I

.-c 121

0

I I I I I I I I I I I 1

2

3

4

5

6

7

8

9

10.10-5

liquid water mass mixing ratio

Fig. 4. A c t i v a t e d p a r t i c l e s in p e r c e n t as a funFtion of liquid w a t e r mass mixing ratio. T h e s u p e r s a t u r a t i o n at t h e basic state is 5 . 10- ; c( a n d 0: a r e t h e exponents of t h e power l a w s i z e distributions within t h e 0.01-0.1 a n d t h e 0.1-6.0 pm p a r t i c l e s i z e range. N /N is t h e r e l a t i v e p a r t i c l e number, n /n - 1.1 IS equivalent t o a 10 p e r c e n t i n c r e a s e 1 0 inlpa?ticle numbers. DISCUSSION Aerosol p a r t i c l e s play a n i m p o r t a n t r o l e f o r s h o r t w a v e r a d i a t i v e t r a n s f e r both i n c l e a r a n d cloudy areas. T h e e r e a r e only t w o p a r a m e t e r s grossly determining t h e sign of t h e energy-budget variation. In c l e a r and cloudy a t m o s p h e r e s o n e of t h e s e main parameters is t h e imaginary p a r t of t h e r e f r a c t i v e index of p a r t i c l e s , while t h e second o n e is s u r f a c e a l b e d o i n c l e a r a r e a s a n d o p t i c a l thickness of clouds i n cloudy areas. High s u r f a c e albedo a n d mean v a l u e s of t h e imaginary p a r t f o r c o n t i n e n t a l aerosol p a r t i c l e s favor energy gain

320 of t h e a t m o p s h e r e - e a r t h system. On t h e o t h e r hand thin w a t e r clouds under conditions w i t h

m e a n imaginary p a r t f a v o r a n e n e r g y loss. T h e s e p a r t l y o v e r simplified s t a t e m e n t s h a v e t o be modified in b o t h areas. T h e crossover from e n e r g y loss t o e n e r g y g a i n i s a f u n c t i o n of solar z e n i t h a n g l e a n d o p t i c a l d e p t h of t h e a e r o s o l p a r t i c l e s too. T h e crossover in cloudy a r e a s may e v e n n o t b e found, if cloud d r o p l e t s i z e distributions o c c u r i n g b e f o r e a c h a n g e i n p a r t i c l e c h a r a c t e r i s t i c s a r e broad a n d c h a n g e s in p a r t i c l e number a r e accompanied by a n i n c r e a s e in s u r f a c e t e n s i o n or a v a r i a t i o n in t h e s l o p e of t h e a e r o s o l p a r t i c l e s i z e dist r i b u t i o n prior to cloud formation. T h e t h e r m a l i n f r a r e d c a n n o t at all c o m p e n s a t e t h e possible v a r i a t i o n s in t h e s o l a r spectrum. In c l e a r a r e a s t h e longwave o p t i c a l d e p t h t e

i s by a f a r l o w e r t h a n t

in t h e

s h o r t w a v e s p e c t r u m e v e n if only a c c o u n t i n g f o r t h e a b s o r p t i o n o p t i c a l depth. T h e cloud d r o p l e t s i z e v a r i a t i o n s c a u s e d by c h a n g e s in a e r o s o l p a r t i c l e number a n d s i z e as well as chemical composition, which s h i f t t h e e m i t t i n g l a y e r s upwards t o l o w e r t e m p e r a t u r e s if a r e d u c t i o n i n m e a n d r o p l e t s i z e should o c c u r , a r e a c c o m p a n i e d by a n i n c r e a s e i n single s c a t t e r i n g a l b e d o fully compensating for r e d u c e d emission a t l o w e r temperatures. T h e o v e r a l l e f f e c t of human a c t i v i t i e s c a n only b e a s s e s s e d if reliable v a l u e s of p a r t i c l e c o n c e n t r a t i o n depending on l a t i t u d e a n d h e i g h t f o r n a t u r a l a n d disturbed cases a r e available. We hope t h a t w e c a n give t h i s a s s e s s m e n t r e f e r i n g t o a two-dimensional global a e r o s o l t r a n s p o r t model which i s now t e s t e d by our group. ACKNOWLEDGEMENT This work i s mainly s u p p o r t e d by t h e Environmental P r o t e c t i o n Agency of t h e F R C under G r a n t 104 02 621 a n d t h e European Commission under G r a n t CL I-044-D(B). REFERENCES 1 P. Ch$lek a n d J.A. C o a c k l e y , S c i e n c e , 183 (19741, 75-77. 2 J.A. C o a c k l e y a n d P. ChGlek, J. Atm. Sci., 32 (1975), 409-418. 3 K. Fischer, Contr. Atm. Physics, 46 (1973), 89-100. 4 H. Grassl, Contr. Atm. Physics, 48 (1975), 199-210. 5 K. Andrg, R. Dlugi a n d G. S c h n a t z , J. Atm. Sci., 38 (1981), 141-155. 6 T.S. Twomey, in G A R P C l i m a t e Dynamics Sub-programme, R e p o r t of IOC-Study C o n f e r e n c e o n p a r a m e t e r i z a t i o n of e x t e n d e d cloudiness, Appendix E, WMO, G e n e v a , 1978. 7 H. Grassl, R e i h e A, H e f t 37, Hamburger Geophysik. Einzelschriften, 1978, pp., 136. 8 H. Grassl, i n W. Bach, J. P a n k r a t h a n d W.W. Kellogg (Eds.), Man's Impact o n c l i m a t e Elsevier, Amsterdam, 1979, 229-241. 9 3. Warner a n d T.S. Twomey, J. Atm. Sci., 25 (19671, 704-706. 10 H. Grassl, Idoj&&s, in press (1982). 11 W.J. Wiscombe, J. Quart. Spectrasc. Radiat. T r a n s f e r , 16 (1976), 477-489. 12 D. Deirmendjian, E l e c t r o m a g n e t i c s c a t t e r i n g on s p h e r i c a l polydispersion; Elsevier, Amsterdam (1969), 290 pp. 13 D.L. H a r t m a n n a n d D A . Short, J. Atrn. Sci., 37 (1980), 1233-1250. 14 G. Handel, Contrib. Atm. Physics, 54 (19811, 159-172.

321

LASER TRANSMISSOMETER --A DESCRIPTION P.H. LEE University of California at Santa Barbara T.E. HOFFER, D.E. SCHORRAN Desert Research Institute, University of Nevada System E.C. ELLIS AND J.W. MOYER Southern California Edison

ABSTRACT A

laser

atmospheric

transmissometer is

described

extinction measurements.

that

The

is

suitable

for

instrument design

long path

incorporates

several unique features which greatly enhance the signal to noise ratio of the system. These are apodization of controlled beam

aiming

and

the

output

automatic

beam

beam

by

conical

width measurement

intervals. The system is completely automated and

utilizes

scan, servo at

regular

a micro-computer

designed by the DRI for data acquistion and s e r v o control.

INTRODUCTION The

optical

transmission of a particular medium is defined as the ratio of

t.he initial intensity to the final intensity of light after the medium.

Clearly

it

has

traversed

this number will vary with the path length through the

medium as well as the characteristic extinction of the medium. For a uniEorm medium, the transmission, T, is given by the equation: T=exp(-kL)=I/Io

,

(1)

where L is the path length and k is the extinction coefficient. The extinction

322 coefficient is, in

turn, the

sum

of

the

absorption coefficient and

the

scattering coefficient. In

the

atmosphere, the transmission in the visible portion of the spectrum

is affected principally by scattering. As a consequence, the transmission is a weak function of color and any convenient wavelength

can be

for

used

such

measurements. We have conceived and built a transmissometer that uses a red He-Ne laser to measure

atmospheric

extinction over

long paths.

The instrument has several

unique design features which allow the accurate measurement of small changes in transmission.

INSTRUMENT ARCHITECTURE The instrument has two paths, one for the reference and one for the This

is

a

conventional way

to

eliminate

sample.

the errors due to changes in the

sensitivity of the detector or in the intensity of the source. We have tested the instrument over a sample length of about two In

practical

planned.

field

operation, path

These path

lengths

are

lengths as

singly

folded

kilometers.

long as ten kilometers are by

the use

of

a

remote

retroreflector that requires no input power. The

optical

plan

of

this

instrument

is

shown

in Figure 1.

With the

exception of the retroreflector array, all of the components are mounted single rigid plate. and

the

on

a

The data paths between the components on the optical table

other major electronic components associated with the transmissometer

are illustrated in Figure 2 . Some of the block names are abbreviated as listed in the following table.

323 TABLE 1

Abbreviations S SM RSFM CSM VSM HSM SCM IRET IREF DME

SOURCE SPLITTING MECHANISM REFERENCE SIGNAL FOCUSING MECHANISM CONICAL SCAN MECHANISM VERTICAL SERVO MECHANISM HORIZONTAL SERVO MECHANISM SIGNAL C O M B I N I N G MECHANISM RETURN SIGNAL INTENSITY REFERENCE SIGNAL INTENSITY DEMODULATING ELECTRONICS

The remainder o f t h i s s e c t i o n on i n s t r u m e n t a r c h i t e c t u r e w i l l

describe

the

f u n c t i o n and s t r u c t u r e o f t h e s e b l o c k s and components. helium neon l a s e r i s used a s t h e s i g n a l s o u r c e .

Laser--A has

an

output

operates in a

of 10 m i l l i w a t t s a t a wavelength o f 6 3 3 nanometers.

power single

The l a s e r s e l e c t e d

transverse

mode

with

a

Gaussian

intensity

It

profile.

Angular

d r i f t o r beam p o i n t i n g s t a b i l i t y i s l e s s t h a n 0.050 m i l l i r a d i a n s a f t e r

warmup.

The beam d i v e r g e n c e i s about one m i l l i r a d i a n .

The

output

is

light

plane polarized. Source

Splitting

Mechanism

(SSM)--A

p e r c e n t as i n t e n s e as t h e main beam polarizing

beam

splitter.

The

is

r e f e r e n c e s i g n a l i n i t i a l l y about t e n split

reference

off signal

a d j u s t e d by r o t a t i n g t h e l a s e r about i t s a x i s . turned

to

as semb 1y

.

be

parallel

L i g h t Chopper--The

to

the

main

beam

The

used

are

this

block

by

a

i n t e n s i t y can b e c o a r s e l y reference

beam

is

then

f o r e n t r y i n t o t h e l i g h t chopper

l i g h t chopper i s a c o m e r c i a l l y a v a i l a b l e component

u s e s a r o t a t i n g d i s c w i t h a x i a l l y spaced s l o t s . radii

inside

that

Two sets o f s l o t s a t d i f f e r e n t

t o modulate t h e main beam and t h e r e f e r e n c e beam a t d i f f e r e n t

frequencies. R e f e r e n c e S i g n a l Focusing Mechanism (RSFM)--In reference

this

block,

the

modulated

s i g n a l i s focused by a l e n s o n t o t h e end of a f i b r e o p t i c bundle.

In

a d d i t i o n , mounting space i s provided ahead o f t h e l e n s f o r f i l t e r s t h a t f u r t h e r attenuate the reference signal provided

strength.

by f i x e d a b s o r p t i o n f i l t e r s .

a rotatable polarizer.

Coarse

steps

in

attenuation

are

F i n e a t t e n u a t i o n c o n t r o l i s provided by

324

PRIMARY MIRROR RETROREFLECTOR HORIZONTAL SERVO WEDGE PRISMS

VERTICAL SERVO WEDGE PRISMS

I

I

\"/

/

/ LASER'

POLARIZING BEAMSPLITTER

CONICAL SCANNER WEDGE PRISMS

LASER TRANSMISSOMETER OPTICS LAYOUT

Fig. L Laser transmissometer optics layout.

--I RETURN -._/SIGNAL

--

/ PHOTOMULTIPLIER TUBE

RECEIVING TELESCOPE

&--

TRANSMITTED

'

t

LL W

a

n z a I-

ki I

1

II I CONICAL SCAN

-VOLTAGE CONTROL AMP

HORZ. ERROR

Fig. 2. I n f o r m a t i c m signal links between the c o m p n e n t s on the optical table and the peripheral electronics.

325 C o n i c a l Scan Mechanism (CSM)--This rotate

c o n t i n u o s l y a t f i v e Hz.

block contains

time-averaged

apodization

properties

of

wedges

scan

is

twofold:

results

It

that

beam

toward

the

this

in

a

retreoreflector.

a r e t h e most u n u s u a l f e a t u r e o f t h i s i n s t r u m e n t .

and implementation of

that

t h e o u t p u t beam and i t p r o v i d e s a r e t u r n s i g n a l

of

s u i t a b l y modulated f o r s e r v o - p o i n t i n g These

pair

T h i s r o t a t i o n r e s u l t s i n a conical scan of the

The purpose o f t h i s c o n i c a l

main beam.

a

conical

scan

are

described

in

The t h e o r y

detail

in

the

d e s c r i p t i o n o f t h e t r a n s m i s s o m e t e r f e a t u r e s below. a d j u s t a b l e m i r r o r is used for the initial alignment

Mirror--This

Alignment

of t h e t r a n s m i t t e d s i g n a l beam. V e r t i c a l and H o r i z o n t a l Servo Mechanism (VSM, HSM)--These driven

by

the

are

the

devices

o u t p u t o f t h e s e r v o e l e c t r o n i c s t o d i r e c t t h e main beam toward

the retroreflector.

The d e t a i l s o f t h e s e r v o p r i n c i p l e s a r e a l s o c o n t a i n e d

in

t h e s e c t i o n on f e a t u r e s . Output

Mirror--This

mirror

launches

the

main

beam o n t o t h e a x i s o f t h e

receiving telescope. R e t r o r e f l e c t o r Array--This measuring

path.

The

component i s s i t e d a t t h e f a r

end

of

a

folded

c u r r e n t l y used c o n s i s t s o f f i f t e e n 2 . 5 cm c o r n e r

array

cubes. R e c e i v i n g Telescope--A laser

light.

component

is

with

eyepiece

This

reflecting telescope

t e l e s c o p e i s used t o c o l l e c t and f o c u s t h e

the

a

reflected

commercially a v a i l a b l e 1 2 . 5 cm d i a m e t e r replaced

by

the

signal

combining

mechanism. S i g n a l Combining Mechanism (SCM)--Within signals

are

combined

and

t h i s b l o c k t h e r e t u r n and r e f e r e n c e

d i r e c t e d toward t h e p h o t o m u l t i p l i e r t u b e .

A small

f r a c t i o n o f t h e combined l i g h t i s d i r e c t e d toward an a u x i l i a r y e y e p i e c e t o h e l p i n aligning t h e instrument.

The remainder o f t h e l i g h t

is

passed

series of s t o p s , c o l l i m a t o r s and f i l t e r s t o t h e p h o t o m u l t i p l i e r t u b e .

through

a

Care h a s

been t a k e n i n t h e d e s i g n of t h i s s i g n a l combining b l o c k t o make s u r e t h a t t h r e e i m p o r t a n t c r i t e r i a are m e t : 1)

The

light

from

both

beams must f a l l on e x a c t l y t h e same a r e a of t h e

326 photocathode. 2 ) The combined beams must be c o l l i m a t e d when p a s s i n g through t h e p o l a r i z e r

and t h e narrow band p a s s f i l t e r .

3 ) The f i e l d and a p e r t u r e s t o p s must be o p t i m i z e d f o r f u l l

suppression

of

any s t r a y l i g h t . Photomultiplier tube i s used.

Tube--A

commercially

available

high gain photomultiplier

I t h a s an end-on c a t h o d e w i t h a h i g h quantum e f f i c i e n c y

wavelength o f t h e He-Ne

at

the

laser.

Chopper Frequency Control--A

commercially a v a i l a b l e motor speed c o n t r o l t h a t

p r o v i d e s a s t a b l e chopping f r e q u e n c y . S i g n a l C o n d i t i o n i n g Electronics--A

commercially a v a i l a b l e u n i t t h a t performs

t h e f o l l o w i n g f u n c t i o n s : a d j u s t s t h e s i g n a l g a i n ; demodulates and d i s c r i m i n a t e s t h e r e t u r n and r e f e r e n c e s i g n a l s ; and r a t i o s t h e r e t u r n s i g n a l t o t h e r e f e r e n c e signal. Servo

Control

Electronics--Interface c i r c u i t r y t h a t processes conical scan

p o s i t i o n s i g n a l s from t h e CSM and t r a n s m i s s i o n measurements i n t o e r r o r

signals

t h a t p r o v i d e beam p o s i t i o n i n f o r m a t i o n . Field

Data

A c q u i s i t i o n Computer--A CMOS computer used f o r d a t a a c q u i s i t i o n

and t h e c o n t r o l o f a l l t r a n s m i s s o m e t e r f u n c t i o n s . proper

control

strategy

to

drive

The

computer

develops

the

s t e p p e r m o t o r s i n t h e VSM and HSM through

i n t e r r o g a t i o n o f t h e e r r o r s i g n a l s from t h e s e r v o c o n t r o l e l e c t r o n i c s i n

order

t o minimize p o i n t i n g e r r o r .

UNIQUE FEATURES OF THE TRANSMISSOMETER Our

transmissometer

has

several

unique

features.

The most i m p o r t a n t o f

t h e s e i s t h e a p o d i z a t i o n o f t h e beam. The o t h e r f e a t u r e s o f importance are

beam

width

measurement

and

uniform

intensity.

A p o d i z a t i o n by c o n i c a l s c a n

A l a s e r beam t y p i c a l l y h a s a Gaussian d i s t r i b u t i o n as i t s i n t e n s i t y p r o f i l e .

327 Thus,

if

t h e i n t e n s i t y , I , i s p l o t t e d a g a i n s t d i s t a n c e from t h e c e n t e r of t h e

beam, y , t h a t f u n c t i o n t a k e s t h e form

I=Io exp(-by2)

(2)

where t h e c o n s t a n t 10 d e f i n e s t h e i n t e n s i t y on t h e beam a x i s , and t h e c o n s t a n t , The e x p r e s s i o n i s e x a c t b o t h c l o s e t o t h e l a s e r ( i n

b , d e f i n e s t h e beam w i d t h .

In

t h e n e a r f i e l d ) and f a r away from t h e l a s e r ( i n t h e f a r f i e l d ) . field,

the

near

c o n s t a n t , b , i s a l i n e a r measurement u s u a l l y g i v e n i n m i l l i m e t e r s .

the

I n t h e f a r f i e l d , t h e c o n s t a n t , b , i s an a n g u l a r measurement normally g i v e n

milliradians.

3

Figure

in

i l l u s t r a t e s t h e c o n t o u r s o f i n t e n s i t y through such a

beam. When such a beam i s a p o d i z e d , some d e l i b e r a t e s t e p s

this

Gaussian

intensity

distribution,

c o n s t a n t independent of p o s i t i o n i n

the

i.e.,

to

beam,

y.

are

make

taken the

That

to

flatten

intensity, I, a

constant

intensity

d i s t r i b u t i o n s h o u l d p r e v a i l f o r some u s e f u l d i s t a n c e away from t h e beam a x i s . If

symmetrical Gaussian beam i s r o t a t e d about i t s own a x i s , t h e r e i s , o f

a

c o u r s e , no change i n i t s however,

the

intensity

profile

anywhere

along

the

beam.

If,

beam i s scanned smoothly about a n o t h e r a x i s somewhat i n c l i n e d t o

i t s own, t h e peak i n t e n s i t y a t t h e c e n t e r of t h e o r i g i n a l laser beam w i l l t r a c e o u t a cone i n s p a c e .

This i s i l l u s t r a t e d i n Figure 4 .

a t a p o i n t , p, i n t h i s f i g u r e . It

be

will

maximum

when

Consider t h e

intensity

Here t h e i n t e n s i t y w i l l f l u c t u a t e p e r i o d i c a l l y .

t h e l a s e r p o i n t s c l o s e s t t o i t and minimum when i t

p o i n t s f a r t h e s t away. The time averaged v a l u e of t h e p e r i o d i c a l l y v a r y i n g i n t e n s i t y o f f

the

scan

a x i s ( a t p i n F i g u r e 4 ) can b e made n e a r l y e q u a l t o t h e i n t e n s i t y sensed on t h e axis.

By

properly

selecting

the

scanning angle.

I n o t h e r words, t h e t i m e

averaged beam p r o f i l e can be shaped t o be remarkably f l a t i n

the

vicinity

of

the distant target. A p l o t o f t h e t i m e averaged i n t e n s i t y as a f u n c t i o n of p o s i t i o n with r e s p e c t t o t h e c e n t r a l a x i s o f c o n i c a l s c a n t h r o u g h such an F i g u r e 5.

apodized beam

i s shown a s

328

Fig. 3. Contours of normalized intersity for a laser beam of G a d a n Shape. The contour interval equals 0 1 units. Beam axis is directed through the paper at the onqh. X and Y represent distances measured in meters perpendicular to this axis. The eras section typifies a certain 1;Lser beam at a distance of sL5 K m from the source.

SCAN ABOUT THE LASER / RETRO REFLECTOR AXIS

-,,

I

...’.,.

DIRECTION OF

EZ’. LASER

Fig. 4. Conical Scan with a laser beam of G a d a n shape.

%-:*

329

GAUSSIAN PROFILE BEAM

APODIZED BEAM PROFILE

0.7

/

t

/

\

\

a

/ ;,'

3 v)

APODIZED BEAM

'

10.3

\

I

i\

DISTANCE PERPENDICULAR TO CENTRAL AXIS OF CONICAL SCAN (meters)

Fig. 5. An apodized beam prof& at a distance of %L5 K m from the laser s)uTce. The normalized time averaged inte&ty is plotted as a function of distance as measured perpendicular to the conical scan axis. Averaging time is greater than 10 scan cycles. The half width of the profile is shown. A nori-amized Gaussian beam profile is shown as a dashed line fur comparison. BEAM AT START OF SCAN TO LEFT t = t 2

BEAM JUST COMPLETING SCAN TO RIGHT t = t

y--\ \

/ /

\

I

I

\

fi SCAN DlREC /

&AM JUST COMPLETING SCAN TO LEFT t = t 3

BEAM AT START OF SCAN TO RIGHT t = t ,

THE INPUT SIGNAL TO THE SERVO CONTROL ELECTRONICS vo ( t ) IS PROPORTIONAL TO THE RATIO OF THE RETURN SIGNAL INTENSITY IRET ( 1 ) AND THE REFERENCE SIGNAL INTENSITY IREF

Yo I t )

k 11

13

'2

i v t2 o(t)

-

[v,(t) 13

HORIZONTAL ERROR SIGNAL = I

2

Fig. 6. Scan of the retrorefkctor array for beam steering feedback. The integrated return signal received during the scan to the right of the retroreflectck- is electronically m the signal returned during the scan to the bft. This difference is subtracted m propor+ional to the beam aiming error in the horizontal plane.

330 Conical

scan

and

a p o d i z a t i o n have been p u t i n t o p r a c t i c e i n

t r a n s m i s s o m e t e r by mounting two matched wedge prisms i n t o a

In

the

mount,

one

prism

the laser

cylindrical

c a n be r o t a t e d w i t h r e s p e c t t o t h e o t h e r .

tube.

In t h i s

c o n f i g u r a t i o n , t h e wedges a r e a d j u s t a b l e f o r an optimum s c a n n i n g a n g l e and correct

apodization

conical scan

of

the

When t h e t u b e i s r o t a t e d about i t s a x i s , a

t h e beam.

and as a r e s u l t a p o d i z a t i o n o f t h e main beam.

OCCUKS

In a d d i t i o n t o a p o d i z a t i o n , t h i s c o n i c a l s c a n t e c h n i q u e p r o v i d e s a means pointing

the

laser

beam a t t h e r e t r o r e f l e c t o r .

of

Feedback s i g n a l s are d e r i v e d

from t h e p e r i o d i c a l l y v a r y i n g i n t e n s i t i e s o f t h e r e t u r n s i g n a l i n

conical

its

sweep.

C o n i c a l s c a n p o s i t i o n s i g n a l s from t h e CSM t i m e t h e i n p u t o f t h e r e t u r n

signal

intensity

into

a

pair

of

differential

amplifiers.

s u b t r a c t s t h e r e t u r n s i g n a l i n t e n s i t y a s t h e beam p a s s e s t o retroreflector

from

the retroreflector. return

signal

retroreflector. zero,

the

left

the

The o t h e r a m p l i f i e r i s used t o compute d i f f e r e n c e s i n

as

intensity

the

beam

the

p a s s e s o v e r t h e t o p and bottom o f t h e

This i s i l l u s t r a t e d i n Figure

6.

If

both

differences

are

I f t h e two d i f f e r e n c e s a r e

o t h e r t h a n z e r o , t h e s i g n s of t h e d i f f e r e n c e s i n d i c a t e t h e d i r e c t i o n the

of

t h e i n t e n s i t y r e t u r n e d as t h e beam p a s s e s t o t h e r i g h t o f

beam i s c e n t e r e d on t h e r e t r o r e f l e c t o r .

the

One a m p l i f i e r

in

which

beam i s o f f - t a r g e t ( r i g h t o r l e f t , up o r down) and t h e magnitudes i n d i c a t e

t h e d e g r e e of p o s i t i o n i n g e r r o r .

These e r r o r s i g n a l s a r e used t o c o n t r o l s e r v o

mechanisms which steer t h e beam i n t h e

horizontal

(left-right)

and

vertical

(up-down) p l a n e s , r e s p e c t i v e l y . Aiming

of t h e beam i s accomplished by t h e alignment o f matched p r i s m s as i t

p a s s e s through t h e h o r i z o n t a l and principle

involved

in

this

vertical

adjustment

mechanism, t h e beam p a s s e s through a p a i r opposite

directions.

s t e p p e r motor. change

The

amount

of

servo

mechanisms.

The

is i l l u s t r a t e d i n Figure 7 . of

wedges

that

are

physical

In each

rotatable

in

r o t a t i o n i s c o n t r o l l e d by a f i n e a n g l e

As t h e wedges r o i a t e , t h e magnitude of t h e beam d e f l e c t i o n

can

from a minimum o f z e r o t o a maximum o f t w i c e t h e d e v i a t i o n a n g l e of t h e

wedge prism.

-

331

MATCHED WEDGE PRISMS

U

u

SIDE VIEW OF STEERING WEDGES

FRONT AXES OF VIEW DEFLECTION OF PRISMS SHOWN

PRISMS ROTATED THROUGH ANGLE e

'I

Yl

VECTOR COMPONENTS OF DEFLECTION

Fig. 7. Beam steering with matched wedge prisms. A light beam incident to the p r k m s shown at the top experiences no net deflection. The right wedge cancels the deflection affected by the left wedge. If the wedges are corstrained to rotate o b t e to each other through an angle, as shown above, the net deflection is to the right This can be represented as the vector sum of A + B. V e r t i c a l components of deflection cancel, horizontal components add.

332 Beam w i d t h

The i n t e n s i t y of t h e r e f l e c t e d l i g h t c o l l e c t e d by t h e t e l e s c o p e i s dependent n o t o n l y on a b s o r p t i o n and

atmospheric

established.

medium

The

transmission

beam

spreading

we

periodic

have beam

selected

is

normalization

width measurements.

the

main

to

It i s i l l u s t r a t e d on F i g u r e 4

beam.

.

of

the

Beam w i d t h , i n t h i s

a p p l i c a t i o n , i s d e f i n e d as t h e h o r i z o n t a l width between h a l f of

due

and i t s c o n t r i b u t i o n t o changing t r a n s m i s s i o n must be

technique

through

on

also

but

T h i s beam d i s p e r s i o n i s an i n h e r e n t f e a t u r e c r e a t e d by

atmospheric turbulence. the

scattering

intensity

points

It can b e measured by a

c o n t r o l l e d d e f l e c t i o n o f t h e beam from i t s c e n t e r e d p o s i t i o n . I n p r a c t i c e , t h e wedges o f t h e h o r i z o n t a l s e r v o mechanism a r e

the

centered

position

in

one

from

d i r e c t i o n u n t i l the returned signal i n t e n s i t y

f a l l s t o one h a l f i t s i n i t i a l v a l u e . opposite

rotated

The

prisms

are

then

rotated

in

the

d i r e c t i o n past t h e center point t o the opposite half i n t e n s i t y point.

The wedges a r e t h e n r e t u r n e d t o calculated

from

the

central

position.

The

beam

width

is

t h e p u l s e count needed t o d r i v e t h e h o r i z o n t a l servomechanism

between t h e h a l f i n t e n s i t y p o i n t s and t h e i n i t i a l

alignment

position

of

the

h o r i z o n t a l s t e e r i n g prisms. A

subroutine

i n t h e f i e l d d a t a a c q u i s i t i o n computer i s a c t i v a t e d h o u r l y t o

i n t e r r u p t t h e t r a n s m i s s i o n measurement and make The

transmission

data

are

normalized

to

the

beam

width

measurement.

an a v e r a g e beam width d u r i n g d a t a

processing.

Uniform i n t e n s i t y A p o d i z a t i o n c r e a t e s a beam of uniform i n t e n s i t y when i n t e g r a t e d This

means

beams

sections.

time.

t h a t w i t h i n t h e beam volume, a l l p a r t i c l e s w i t h i d e n t i c a l p h y s i c a l

c h a r a c t e r i s i t i c s w i l l a b s o r b and s c a t t e r l i g h t t h e same. light

over

that

have

Gaussian

or

other

shape

to

This i s not

true

of

their intensity cross

333

This uniform

intensity

transmissometers and

feature

all

eliminates

a

common

deficiency of

laser

other long path transmissometers that do not use an

apodized beam.

ELECTRONIC FEATURES The electronic signals that carry information to and from the optical table They are also enumerated in Table 2 below.

are illustrated i n Figure 2 . TABLE 2

-..Electronic information signals to and from the optical table.

INPUT

OUTPUT

VERTICAL SERVO CONTROL HORIZONTAL SERVO CONTROL CHOPPER SPEED CONTROL

P.M.T. SIGNAL (1) CONICAL SCAN POSITION SIGNALS ( 2 ) CHOPPER SPEED FEEDBACK

(1) Combined return and reference signal. ( 2 ) The four position signals from the conical scan mechanism. A

schematic

illustration of the electronic components associated with the

transmissometer are components with

shown as

Figure

8.

The

interconnections of

the optical table are shown on Figure 2 .

from the optical table are the combined return and conical

scan

The signal outputs

reference

signals, four

position signals,and the chopped frequency, The combined signal

is intially discriminated by demodulating electronics which lock in on chopped

these

signals

at discrete frequencies. These signals are then electronically ratiod

to obtain the transmission, T.

This information is passed

on

to

the

servo

control electronics (SCE) and the computer. The

SCE

serves

as an electronic interface between the electro-optical and

electromechanical components located on computer.

the

optical

table

and

the

control

Four scan position signals from the (CSM) indicated the position of

the beam in its scan about the retroreflector. These signals are used to the

input

of

the

transmission signal

to

two

differential amplifiers.

Differences in the transmission signals computed during top and scans

are

integrated

to

develop

a beam

aiming

time

bottom

sector

error signal in the plane

334 v e r t i c a l t o the scan a x i s . and

left

S i m i l a r l y , d i f f e r e n c e s computed

during

the

right

s e c t o r s c a n s a r e i n t e g r a t e d t o develop a beam aiming e r r o r s i g n a l i n

the plane horizon tal t o t h e scan a x i s . CH0PPI NG

ELECTRONICS

lRET RATIOMETRIC AMPLIFIER

PHOTOMULTIPLIER TUBE

SCAN SIGNALS FROM CSM

ELECTRONICS VERTICAL ERROR

HORIZONERROR

FIELD DATA ACQUISITION COMPUTER CONTROLS BEAM AIMING

- 11

OUTPUTS TO CONTROL VSM AND HSM

ACCUMULATES DATA MEASURES BEAM WIDTH

F i g . 8. Block diagram of t h e major e l e c t r o n i c components a s s o c i a t e d w i t h transmissometer.

and h o r i z o n t a l e r r o r s i g n a l s g e n e r a t e d i n t h e SCE a r e fed i n t o t h e

Vertical computer.

the

The

interrogation

of

computer

generates

the error signals.

servo

control

signals

based

upon

These c o n t r o l s i g n a l s are t h e n o u t p u t t o

t h e a p p r o p r i a t e servomechanism.

SUMMARY We have developed and put i n t o features

that:

provide

for

practice continually

a

laser pointing

transmissometer the

laser

at

beam

r e t r o r e f l e c t o r , t h e r e b y e l i m i n a t i n g t h e e r r o r s a s s o c i a t e d w i t h changes beam

with

in

a the

d i r e c t i o n due t o r e f r a c t i v e index changes; p r o v i d e a means o f n o r m a l i z i n g

t h e t r a n s m i s s i o n d a t a t o minimize t h e e f f e c t s of atmospheric t u r b u l e n c e on d i s p e r s i o n o f t h e beam; and p r o v i d e a beam of uniform i n t e n s i t y .

the

335 Experiments

are

in progress

to compare the transmission measurement with

other instruments that measure extinction parameters. The transmissometer is designed to operate in a field folded

path

of

ten kilometers.

installation with

Field installation is facilitated by using a

passive retroreflector. All functions have been successfully controlled by computer during

the development

anticipated that

it

interventions, and

will that

a

operate

period. for

In

at

a

least

field a

a

installation it is

week

without

operator

the data will be accessed by telephone using remote

terminals that can be indefinitely far away.

ACKNOWLEDGEMENT The authors wish to acknowledge the project

possible.

assistance of

Clarence Fought who

designed

and

others who made

the

built all the analog

circuitry, Rick Brown who designed the CMOS computer and wrote all the software to control the transmissometer, and Malcolm Barr who machined all the parts for the instrument. The development of this transmissometer was supported by Southern California Edison as a part of its environmental research program.

This Page Intentionally Left Blank

337

BIPOLAR CHARGE EQUILIBRIUM FOR SPHERICAL AEROSOLS (MINIMUM FLUX HYPOTHESIS)

L i u , S. Davisson and J.W.

C.S.

Gentry*

Department o f Chemical E n g i n e e r i n g , " I n s t i t u t e f o r P h y s i c a l Science and Technology,

U n i v e r s i t y of Maryland, Cot l e g e Parh, Maryland 20742,

U.S.A.

ABSTRACT An a l g o r i t h m based on t h e "minimum f l u x h y p o t h e s i s " f o r d e t e r m i n i n g t h e r e l a t i v e charge d i s t r i b u t i o n o f s p h e r i c a l p a r t i c l e s has been developed. l a t i o n s were c a r r i e d o u t f o r b o t h equal and unequal

ion mobil i t i e s .

Ca cu-

The

a l g o r i t h m was used t o d e t e r m i n e e x p e r i m e n t a l c r i t e r i a f o r t h e p r o d u c t i o n o f monodisperse a e r o s o l s and f o r t h e i n t e r p r e t a t i o n of measurements w i t h u l t r a

I ne

aeroso I s.

I NTRODUCT I O N P a r t i c l e s w i t h d i a m e t e r s j e s s than 0.05 Llm ( u l t r a f i n e a e r o s o l s ) must be measured i n d i r e c t l y .

One such method i s based on The e l e c t r i c a l m o b i l i t y o f t h e

p a r t i c l e i n which o n l y t h e charged p a r t i c l e s a r e measured.

Such a measurement

r e q u i r e s an a c c u r a t e t h e o r y f o r d e t e r m i n i n g t h e r a t i o o f uncharged t o charged p a r t i c l e s as a f u n c t i o n o f p a r t i c l e size.

Presented i n t h i s paper i s a d e s c r i p t i o n

o f a method based on t h e mean charge h y p o t h e s i s ,

i t s use i n d e t e r m i n i n g experimental

c o n d i t i o n s f o r o b t a i n i n g m n o d i s p e r s e a e r o s o l s by e l e c t r o s t a t i c c l a s s i f i c a t i o n , and i t s appl i c a t i o n i n i n t e r p r e i a t i o n of experiments.

CALCULATION OF CHARGE DISTRIBUTION The charge d i s t r i b u t i o n i s c a l c u l a t e d on t h e b a s i s o f two assumptions:

I. (ref.

The i o n f l u x t o t h e p a r t i c l e s a r e g i v e n by t h e "minimum f l u x " c r i t e r i o n

I ,2).

The e l e c t r o s t a t i c p o t e n t i a l ,

a t a reduced r a d i u s ;=r/a

i n c l u d i n g the image term,

obtained from t h e s o l u t i o n o f :

where +o i s t h e d i m e n s i o n l e s s charge parameter

2.

i s evaluated

(E

2

/akT).

The charges a r e assumed t o be i n d e t a i l e d e q u i l ibrium.

That is,

338

where NJ i s t h e number o f p a r t i c l e s w i t h J charges and F ( J , k )

i s the flux o f a

p a r t i c l e w i t h J charges changing t o k charges. In o u r f i r s t simulations, symmetrical --a

i t was assumed t h a t t h e charge e q u i l i b r i u m was

d i r e c t consequence o f assuming t h a t p o s i t i v e and n e g a t i v e i o n s

have t h e same m b i I i t y . In F i g .

I , t h e p a r t i c l e r a d i u s i s p l o t t e d a s a function o f t h e normalized

number r a t i o NJ Exp ( J

2

$,)/No

IW

( t e m p e r a t u r e @ 30O0K) f o r 1-4 charges.

I 10

I

RATIO

2 10

NJ E X P (

3

10

4 10

J2 Po

NO

F i g . I . P a r t i c l e r a d i u s a s a f u n c t i o n o f normal i z e d number r a t i o f o r p a r t i c l e s w i t h J e l e m e n t a r y charges.

Were t h e Boltrmann charge d i s t r i b u t i o n appl i c a b i e , t h e normal i z e d r a t i o would be e x a c t l y one.

W i t h i n c r e a s i n g charge number and d e c r e a s i n g charge, t h e

d i s c r e p a n c y between t h e two t h e o r i e s increase. (ref.

New p a r t i a l l y e m p i r i c a l t h e o r i e s

3 , 4 , 5 ) a g r e e w i t h t h e d i r e c t i o n o f our t h e o r y which c o n t a i n s no a d j u s t a b l e

parameters b u t suggests t h a t t h e t r u e c h a r g i n g d e n s i t y I i e s between t h e two t h e o r i e s a1 though c l o s e r t o t h e "mean charge h y p o t h e s i s " .

A p o s s i b l e s o u r c e o f e r r o r I i e s i n t h e assumption t h a t p o s i t i v e and n e g a t i v e i o n s have t h e same m o b i l i t y - - a

c o n c l u s i o n n o t i n agreement w i t h c l o u d p h y s i c s

experiments o r w i t h t h e recent studies o f Porstendorfer.

Our approach has been

t o examine t h e e f f e c t o f asymmetric d i s t r i b u t i o n s by assuming t h e r a t i o o f p o s i t i v e t o n e g a t i v e ion mobil i t y .

339 EXPERIMENT SELECT I ON Recent e x p e r i m e n t s by Heyder and Madelaine suggested an o p p o s i t e c o n c l u s i o n t o t h a t found by P o r s t e n d o r f e r i n t h a t p a s s i n g a p o l y d i s p e r s e aerosol t h r o u g h a TSI e l e c t r o s t a t i c c l a s s i f i e r d i d n o t r e s u l t i n a monodisperse a e r o s o l .

In

r e t r o s p e c t , t h e i r r e s u l t s c o u l d be e x p l a i n e d i n t h a t t h e c l a s s i f i e r s e l e c t s p a r t i c l e s by t h e i r m b i l i t y r a t h e r t h a n by s i z e .

The somewhat h i g h e r experimental

v a l u e s f o r p a r t i c l e s w i t h two o r m r e charges c o u l d be e x p l a i n e d by t h e erroneous use o f t h e Boltzmann d i s t r i b u t i o n . However, t h e r m r e i n t e r e s t i n g q u e s t i o n is: on t h e i n i t i a l p a r t i c l e d i s t r i b u t i o n ( i . e .

can one s e t t h e a p r i o r i c r i t e r i a

mean s i z e and s t a n d a r d d e v i a t i o n )

necessary t o d e t e r m i n e a m n o d i s p e r s e d i s t r i b u t i o n ?

To answer t h i s question,

a

computer code was designed and t e s t e d c h a r a c t e r i z e d by parameters d e s c r i b i n g t h e i n l e t aerosol and parameters d e s c r i b i n g t h e l o c a t i o n and w i d t h o f t h e window i n A t y p i c a l r e s u l t i s shown i n F i g . 2.

t h e EAC.

1.0

- 0.04

-

u)

K

& W

B 0

w

w

K

-0.02

g

5

t, a

E -I

0

3

6

Fig. 2. S i m u l a t i o n o f EAC performance: f r a c t i o n o f o u t 1 i e r s and f r a c t i o n o f p a r t i c l e s recovered as a f u n c t i o n o f t h e d i f f e r e n c e i n mean d i a m e t e r s o f t h e d i s t r i b u t i o n and EAC.

The i n i t i a l s i z e d i s t r i b u t i o n i s l o g normal w i t h equal t o D I .

&

LnB=o=l .O and w i t h a mean

The s e l e c t e d d i a m e t e r o f p a r t i c l e s f r o m t h e EAC i s 0.075 pm w i t h

t h e r e l a t i v e range o f mobil i t i e s b e i n g 10 and 20%.

The f r a c t i o n o f t h e i n i t i a l

d i s t r i b u t i o n w i t h p a r t i c l e s i n t h e s p e c i f i e d m b i l i t y range ( i . e . l e a v i n g t h e EAC) i s d i s p l a y e d on t h e r i g h t h a n d s i d e .

the particles

On t h e l e f t h a n d side, t h e

340 f r a c t i o n of charged p a r t i c l e s w i t h more t h a n one c h a r g e i s d i s p l a y e d .

An optimum

e x p e r i m e n t a l d e s i g n would r e q u i r e t h a t t h e f r a c t i o n o f p a r t i c l e s l e a v i n g t h e EAA be as l a r g e as p o s s i b l e w i t h as few o u t l i e r s a s p o s s i b l e .

The s i m u l a t i o n s i n d i c a t e d t h a t as t h e p a r t i c l e s become l a r g e r , t o have a n a r r o w e r d i s t r i b u t i o n .

i t is necessary

B e s t r e s u l t s a r e o b t a i n e d when t h e c l a s s i f i e r

s i z e i s n e a r t h e maximum o f t h e d i s t r i b u t i o n .

When t h e mean d i a m e t e r o f t h e

d i s t r i b u t i o n i s l a r g e r t h a n t h e EAC d i a m e t e r , t h e number o f o u t l i e r s i n c r e a s e dramat i c a l I v.

APPL ICAT ION TO EXPERIMENTAL MEASUREMENTS One t e s t o f t h e method i s whether t h e s i z e d s t r i b u t on o f a t e s t a e r o s o l t h e same f o r d i f f e r e n t c l a s s i f i e r s ( i . e . pore sizes).

GCAF d f f us i o n b a t t e r i e s w i t h d i f f e r e n t

In t h e "apparent diatneter method" ( r e f .

o f a h y p o t h e t i c a l monodisperse aerosol

6

, the

diffusion coefficient

h a v i n g a t heo r e t c a l p e n e t r a t i o n equal t o

t h e e x p e r i m e n t a l p e n e t r a t i o n i s p l o t t e d as a f u n c t i o n o f p e n e t r a t i o n . curve,

can be determined unambiguously.

where N

From t h i s

t h e parameters o f a log norma I d i s t r i b u t ion d e s c r i b i n g t h e measurements

diffusion coefficient

and NJti,

is

(T)/NJ(c) and WJ(')

6*(Q)

S p e c i f i c a l l y , t h e "apparent v a l u e " o f t h e

f o r a f l o w r a t e Q would be q i v e n b y :

i s t h e number o f p a r t i c l e s o f mobi I i t y J per measured charge, a r e t h e measured charge b e f o r e and a f t e r t h e g l a s s f i l t e r .

F o r each s i z e o f f i l t e r , one would e x p e c t t h a t increasinq flow rate. I

theoretical r a t i o

6*(Q) would

increase w i t h

A1 I t h e p o i n t s should f a l l on t h e same c u r v e i f t h e

NJ(T)/NJ(c)

i s calculated correctly;

f o r t h e d i s t r i b u t i o n does

n o t change o n l y t h e e x p e r i m e n t a l v a l u e s W J ( I ) and

W,"'.

v a l u e s f o r a s i l v e r a e r o s o l generated a t 650

The s o l i d c u r v e r e p r e s e n t s a

OC.

c a l c u l a t e d d i s t r i b u t i o n based on parameters o f 0=1.3

F i g . 3 shows t y p i c a l

and D*=1.6 x 10-4(cm2/sec).

The t h r e e symbols r e p r e s e n t t h e d i f f e r e n t p o r e s i z e s o f t h e GCAF and f a l l on t h e same c u r v e as would be expected i f t h e number t o charge r a t i o were c o r r e c t . contrast,

In

were t h e Boltzmann charge d i s t r i b u t i o n used, a sequence o f t h r e e d i f f e r e n t

curves a r e obtained (Fig. 4.).

The c o n s i s t e n t t r e n d i n t h e d a t a a r e due t o t h e

f a c t t h a t w i t h t h i s d i s t r i b u t i o n , t h e Boltzmann charge d i s t r i b u t i o n c o n s i s t e n t l y o v e r e s t i m a t e s t h e number o f p a r t i c l e s w i t h a s t r o n g b i a s toward y i e l d i n g e s t i m a t e s o f t h e d i f f u s i o n c o e f f i c i e n t which a r e t o o l a r g e . w i t h t h e d a t a i n F i g . 4.

T h i s i s i n accord

For t h e 50 urn, most p a r t i c l e s p e n e t r a t e , and t h e

e x p e r i m e n t i s n o t skewed toward srnal l e r p a r t i c l e s where t h e number/charge r a t i o i s inaccurate.

Consequently,

agreement w i t h t h e o r y .

the calculated d i f f u s i o n c o e f f i c i e n t i s in

341

o 0

L A

-

lo 0

5 0.5

1 1.0

0.5

lo -5 0

PENETRATlON

10um FILTER 25um FILTER 5 0 p m FILTER SIMULATION

F i g . 3. Apparent d i f f u s i o n c o e f f i c i e n t (crn2/sec) a s a f u n c t i o n of p e n e t r a t i o n f r o m EM measurements u s i n g minimum flux criteria.

1.0

PENETRATION

F i g . 4. Apparent d i f f u s i o n c o e f f i c i e n t (cm2/sec) a s a f u n c t i o n o f p e n e t r a t i o n f r o m E A A measurements u s i n g Boltzmann charge d i s t r i b u t i o n .

B o t h Koj irna and Haaf have proposed a s e m i - e m p i r i c a l

charge d i s t r i b u t i o n

A p p r o x i m a t e l y 50 e x p e r i m e n t s

d i f f e r i n g f r o m t h e Boltzmann c h a r g e d i s t r i b u t i o n .

were a n a l y z e d w i t h t h e s i z e d i s t r i b u t i o n c a l c u l a t e d u s i n g t h e s e c h a r g e d i s t r i b u tions,

t h e "minimum charge" h y p o t h e s i s , and t h e B o l t z m n n d i s t r i b u t i o n .

"minimum f l u x " model and t h e t w o s e m i - e m p i r i c a l a e r o s o l s whose mean d i a m e t e r i s l e s s t h a n 0.02

methods agreed w i t h i n 5%.

urn,

The For

t h e d e p a r t u r e i n t h e mean

c a i c u l a t e d w i t h t h e b i t z r n a n n c h a r g e d i s t r i b u t i o n was 25% whereas f o r a e r o s o l s whose mean d i a m e t e r s were g r e a t e r t h a n 0.02 was w i t h i n 8%.

urn,

agreement armng a l l f o u r t h e o r i e s

These r e s u l t s a r e c o n s i s t e n t w i t h o t h e r e x p e r i m e n t s which show

t h e Boltzniann d i s t r i b u t i o n o v e r e s t i m a t e s t h e number/charge r a t i o f o r smal I p a r t i c l e s .

CONCLUSION The "minimum f l u x c r i t e r i a " has been used t o d e v e l o p a code f o r p r e d i c t i n g f r a c t i o n r e c o v e r y and t h e p e r c e n t a g e o f o u t 1 i e r s ( d e g r e e o f m o n o d i s p e r s i t y ) t o s i m u l a t e p e r f o r m a n c e o f an E l e c t r i c a l A e r o s o l C l a s s i f i e r . ments a r e c o n s i s t e n t w i t h t h e o r y .

E x p e r i m e n t a l rneasure-

342 ACKNOWLEDGEMENTS

T h e a u t h o r s would I i k e t o r e c o g n i z e t h e s u p p o r t o f t h e N a t i o n a l Science Foundat ion under Grant # CPE-80-1 1269-AOI and t h e S t a t e o f Mary1 and Department o f N a t u r a l Resources under G r a n t #

P 678004.

REFERENCES

I 2 3 4

5 6

J. Gentry, J. Aerosol Science, 3(1972)65-76. C. L. , L i u and J.W. Gentry, J. Aerosol Science, 15(1982). W. Haaf, J. Aerosol Science, I I (1979)201-212. H. Kojirna, Atomspheric Environment, 12( 1978)2363-2368. J P o r s t e n d o r f e r , Pr i v a t e Commun i c a t ion, G o t t ingen , I 9 8 1 Y.O. Park, W. King, J r . and J. Gentry, I&EC P r o d u c t R&D, 19(1980)151-157.

.

.

343

SURVEYS AND MONITORING

Surveys were, and remain, the mainstay of a i r pollution science.

Their

methodology may range from simple h i s t o r i c a l recording t o the most s o p h i s t i c a t e d i n t e r p r e t a t i o n s and presentations. They may cover many p o l l u t a n t s and s i t e s , o r deal with one s i n g l e t o p i c , e . g . , p a r t i c u l a t e matter. T h e above proves t h a t surveys s t i l l cannot be made by completing some printed form. I n t h i s section a t l e a s t no routine or y e a r l y record and r e p o r t - l i k e survey has been included. Each one has some s p e c i f i t y , i t s own approach, i t s own outlook o r i n t e r p r e t a t i o n .

This Page Intentionally Left Blank

345

THE THIRD DIMENSION IN THE LOS ANGELES BASIN

R.J.

FARBER, A.A. HUANG, L.D.

BREGMAN, and R.L. MAHONEY

Southern California Edison Company, Rosemead, California (U.S.A.) D.J. EATOUGH and L.D. HANSEN Brigham Young University, Provo, Utah (U.S.A.) D.L. BLUMENTHAL and W.S. KEIFER Meteorology Research, Inc., Altadena, California (U.S.A.) D.W. ALLARD Aerovironment, Inc., Pasadena, California (U.S.A.)

ABSTRACT Airborne measurements were made during the summer and early fall seasons of 1978-1980 to characterize the third dimension of the Los Angeles Basin during air

pollution days.

One to three aircraft were employed per flight day to measure the

vertical profile of meteorology and air quality continuously, and to collect aeros o l samples for the various chemical analyses across the Basin.

sis was placed in the nighttime measurements.

Particular empha-

This was done because relatively

little nighttime third dimension data are available to date, and because they are important in defining the initial conditions f o r the following photochemically active days.

It was found that the physical and chemical characteristics with-

in the two meteorological regimes, i.e., mixed and stable layers, are distinctively different.

The mixed layer is characterized by uniformly low O3 and rela-

tively high NOx at night, while the stable layer has stratified high O3 but low NO

.

Aerosol size distribution in the mixed layer is found to be tri-modal,

while that in the stable layer is nearly bi-modal.

Based on the collected data,

the nighttime sulfur, nitrate and ammonia chemistry is discussed. INTRODUCTION During the past three decades, several research groups using a variety of techniques have sampled the vertical distribution of pollutants and meteorological parameters in the Los Angeles Basin.

Vertical pollutant and meteorological profiles

have been obtained by blimp (Refs. 1, 21,

small aircraft (Refs. 3-5) and helicop-

346 ter

(Ref.

_ et _ al.

6).

The most e x t e n s i v e

(Ref. 5),

set o f measurements were made by Blumenthal

i n 1972 and 1973.

The t h i r d dimension i n t h e Los Angeles B a s i n i s t y p i c a l l y c h a r a c t e r i z e d d u r i n g t h e s p r i n g , summer and e a r l y f a l l months by a s t a b l y s t r a t i f i e d atmosphere w i t h a strong,

persistent

well-defined

temperature

inversion.

There

is

a

pronounced

boundary between t h e P a c i f i c Ocean marine mixed l a y e r and a d r y , w a r m , c a p p i n g s u b s i d e n c e l a y e r above.

stable or

Mixing h e i g h t s d u r i n g t h e a f t e r n o o n summer months

t y p i c a l l y r a n g e from a b o u t 500 t o 1500 f e e t above ground l e v e l (AGL) i n t h e c o a s t a l sections increasing

Basin. hours,

The

capping

t o 1500 t o 2500 f e e t AGL i n t h e i n l a n d

inversion,

typically

2000 f e e t

portions

t h i c k during

the

of

the

nighttime

i s formed by a c o m b i n a t i o n o f m e t e o r o l o g i c a l p r o c e s s e s s u c h as s u b s i d e n c e Above t h i s s t a b l e a i r mass,

and r a d i a t i o n .

t h e atmosphere i s c o n d i t i o n a l l y sta-

b l e , o f t e n t o 10,000 f e e t mean sea l e v e l (MSL). The above c i t e d r e s e a r c h programs have p r i m a r i l y f o c u s e d on summertime daytime and e p i s o d i c s t u d i e s ( 0 3 h o u r l y a v e r a g e d peaks

>350

s e a b r e e z e d r i v e n "smog f r o n t " a c r o s s t h e Basin.

ppb),

often following

the

With t h e advancement d u r i n g t h e

p a s t few y e a r s of measurement t e c h n i q u e s i n g e n e r a l and a i r b o r n e sampling methodology i n p a r t i c u l a r ,

an increased

understanding

of

m e t e o r o l o g i c a l and

chemical

p r o c e s s e s i s now f e a s i b l e . Realizing

this,

the

Research

and

Development

E d i s o n (SCE) h a s embarked upon a m u l t i - y e a r dimension i n t h e Los Angeles Basin.

group

of

Southern

California

r e s e a r c h program t o e x p l o r e t h e t h i r d

The e l e v a t e d plumes from s e v e r a l l a r g e power

p l a n t s l o c a t e d a l o n g t h e immediate c o a s t i n t h e Los Angeles B a s i n p e n e t r a t e i n t o the stable layer.

T h i s r e s e a r c h program i s e x p l o r i n g t h e l o c a t i o n ,

sembled w i t h a long-range three-dimensional

t r a n s p o r t pro-

A s u f f i c i e n t d a t a b a s e i s b e i n g as-

cesses a n d u l t i m a t e f a t e of t h e s e e f f l u e n t s .

g o a l of a p p r o p r i a t e l y modeling t h e B a s i n u s i n g complex

E u l e r i a n and Lagrangian g r i d models.

s i m u l a t i o n s are p l a n n e d b e c a u s e of

Where p o s s i b l e ,

multi-day

t h e p o t e n t i a l " c a r r y over" e f f e c t and p e r s i s -

t e n c e of " e p i s o d e " p e r i o d s i n t h e Los Angeles Basin.

A s a f i r s t s t e p toward r e a l i z a t i o n of t h i s modeling g o a l , a g e n e r a l understandi n g of

t h e t h i r d dimension i s n e c e s s a r y .

meteorological

questions,

including

T h i s p a p e r a d d r e s s e s some fundamental

transport

t r a n s p o r t of p o l l u t a n t s i n t o t h e s t a b l e l a y e r ;

processes

in

the

inversion;

the

d e c o u p l i n g of t h e mixed and s t a b l e

l a y e r s ; and t h e p o t e n t i a l i m p o r t a n c e of c a r r y o v e r from one day t o t h e n e x t . p h a s i s i n t h i s p a p e r i s p l a c e d on t y p i c a l summer and f a l l non-episode m e t e o r o l o g y f o r which few d a t a have been p r e v i o u s l y a v a i l a b l e .

Em-

nighttime

The c h e m i c a l and

p h y s i c a l t r a n s f o r m a t i o n of p o l l u t a n t s i n t h e B a s i n and t h e a e r o s o l s i z e d i s t r i b u t i o n s r e s u l t i n g from t h e s e p r i m a r y and s e c o n d a r y p r o c e s s e s are a l s o examined. DESCRIPTION OF RESEARCH PROGRAM, EXPERIMENTAL PROCEDURES AND DATA BASE During

t h e summer

s e a s o n s of

1978-1980

a i r b o r n e measurements

were

conducted

347 t h r o u g h o u t t h e Los Angeles Basin, e x t e n d i n g from t h e ocean e a s t w a r d t o t h e mountains.

Sampling d u r i n g t h e f i r s t two

w i t h two t h r e e - h o u r f l i g h t s and

s e a s o n s emphasized n i g h t t i m e measurements The emphasis i n 1980 s h i f t e d t o daybreak

f l i g h t s per night.

afternoon flights.

T h i s paper

will

d i s c u s s mainly

1978-1979

the

n i g h t t i m e measurements. T h i s r e s e a r c h program r e p r e s e n t s s e v e r a l advances i n b r e a d t h and q u a l i t y of data collected. of-the-art

Continuous p a r t i c l e s i z e measurements have been made u s i n g s t a t e -

a i r b o r n e techniques.

A i r b o r n e p a r t i c u l a t e l i d a r d a t a , c o l l e c t e d by an

i n d e p e n d e n t g r o u p , a r e a v a i l a b l e as w e l l as s i z e s p e c t r a of s t r a t u s c l o u d s u s i n g t h e K n o l l e n b e r g forward s c a t t e r i n g probe.

A t y p i c a l t h r e e - h o u r a i r b o r n e f l i g h t would c o n s i s t of s e v e r a l v e r t i c a l s p i r a l s from c l o s e t o t h e s u r f a c e t o 5000 f e e t MSL a t s t r a t e g i c a l l y s e l e c t e d p o i n t s a c r o s s t h e B a s i n and o v e r t h e ocean.

S p i r a l s were connected by t r a v e r s e s a t

a l t i t u d e i n e i t h e r t h e mixed o r s t a b l e l a y e r s .

Twenty- t o t h i r t y - m i n u t e

constant orbits i n

b o t h t h e mixed and s t a b l e l a y e r s were conducted n e a r t h e s p i r a l s t o c o l l e c t aero-

s o l s u s i n g a wide v a r i e t y of f i l t e r d e v i c e s . From one t o t h r e e a i r c r a f t c o l l e c t e d d a t a s i m u l t a n e o u s l y d u r i n g e a c h sampling period. (AV)

D i f f e r e n t t y p e s of small, i n s t r u m e n t e d a i r p l a n e s from AeroVironment,

and Meteorology Research,

Inc.

(MRI)

collected

airborne data.

Inc.

Additional

ground based m e t e o r o l o g i c a l and chemical d a t a were c o l l e c t e d s i m u l t a n e o u s l y by t h e N a t i o n a l Weather S e r v i c e and SCE r e s e a r c h s t a f f . B e e c h c r a f t Queen A i r .

MRI used e i t h e r a Cessna 206 o r

The Cessna 206 had a f u l l complement of c o n t i n u o u s meteoro-

l o g i c a l i n s t r u m e n t s i n c l u d i n g t e m p e r a t u r e and t u r b u l e n c e equipment and c o n t i n u o u s gas analyzers, elometer.

i n c l u d i n g 0 3 , NOx,

and

SO2 m o n i t o r s

plus

an

i n t e g r a t i n g neph-

The Queen A i r i n c l u d e d i d e n t i c a l gaseous and m e t e o r o l o g i c a l i n s t r u m e n t s

as were a b o a r d t h e Cessna,

p l u s a e r o s o l and f o g measuring d e v i c e s t o provide a

complete a r r a y of p a r t i c l e s i z i n g from n u c l e i t o d r o p l e t s .

These d e v i c e s i n c l u d e d

a n e l e c t r i c a l a e r o s o l a n a l y z e r , K n o l l e n b e r g a c t i v e and forward s c a t t e r i n g probes and a Royco o p t i c a l p a r t i c l e c o u n t e r .

The Queen A i r a l s o i n c l u d e d a Volker Mohnen

fog d r o p l e t c o l l e c t o r f o r s t r a t u s clouds.

For a d d i t i o n a l d e t a i l e d i n f o r m a t i o n ,

t h e Cessna 206 i s d e s c r i b e d i n Blumenthal e t a l . Richards

st. (Ref.

8).

(Ref.

7) and t h e Queen A i r i n

AeroVironment used a P i p e r Turbo Navajo and P i p e r Aztec

i n s t r u m e n t e d w i t h a s i m i l a r complement of m e t e o r o l o g i c a l and gaseous a n a l y z e r s . I n t e r p r e t a t i o n of t h e i n s t r u m e n t s '

r e s p o n s e s i n v o l v e d d a t a a d j u s t m e n t s based on

(1) s t a n d a r d c a l i b r a t i o n of a n a l y z e r r e s p o n s e t o r e f e r e n c e s t a n d a r d s , and ( 2 ) det e r m i n a t i o n of s p e c i a l d a t a c o r r e c t i o n s n e c e s s a r y t o a c c o u n t f o r e a c h a n a l y z e r ' s r e s p o n s e and l a g t i m e , pressure day.

(altitude).

and changes i n a n a l y z e r r e s p o n s e w i t h changes i n ambient Analyzer

c a l i b r a t i o n s were performed

before

every

flight

S p e c i a l c a l i b r a t i o n f a c t o r s were d e r i v e d s e p a r a t e l y and were a p p l i e d t o t h e

s t a n d a r d c a l i b r a t i o n f a c t o r s t o a l l o w computation of

meters a s f u n c t i o n s of t i m e and p o s i t i o n .

the

values for

a l l para-

A d d i t i o n a l d e t a i l s have been d e s c r i b e d

348 by B l u m e n t h a l s & .

(Ref.

7) and R i c h a r d s %&. (Ref. 8).

An a r r a y of f i l t e r s were deployed t o c o l l e c t p a r t i c u l a t e analyzed f o r s u l f a t e ,

nitrate,

chloride,

o t h e r c a t i o n s s u c h as l e a d and sodium.

organic sulfur I V species,

s a m p l e r (0.3 p pore f i l t e r ) o r sequen-

t i a l tandem two s t a g e s a m p l e r s ( 8 pm and 0.3

and a l s o on a c i d

p pore f i l t e r s )

washed P a l l f l e x q u a r t z f i l t e r s u s i n g a high-volume

sampler.

c l u d e d i o n chromatography

proton

(IC),

ammonium and

These samples were c o l l e c t e d on n u c l e p o r e

membrane f i l t e r s u s i n g e i t h e r a low-volume

s p e c t r o s c o p y (PIXE).

samples s u b s e q u e n t l y

calorimetry,

and

Aerosol analyses ininduced

x-ray

ct. (Ref.

c h e m i c a l a n a l y s i s t e c h n i q u e s are g i v e n i n Eatough

Gaseous hydrocarbon samples were a l s o c o l l e c t e d .

emission

Details on t h e

S t r a t u s f o g samples were a n a l y z e d u s i n g I C .

9).

P o l i s h e d s t a i n l e s s s t e e l can-

i s t e r s , s u p p l i e d by Washington S t a t e U n i v e r s i t y , were f i l l e d w i t h ambient samples and w i t h i n 48 h o u r s a n a l y z e d f o r s p e c i a t e d hydrocarbons versity

u s i n g g a s chromatography

necessary,

mass s p e c t r o s c o p y .

by Washington S t a t e Uni-

(GC) w i t h f l a m e i o n i z a t i o n d e t e c t i o n and when d a t a are a n e c e s s a r y

These s p e c i a t e d hydrocarbon

i n p u t f o r modeling a p h o t o c h e m i c a l l y a c t i v e atmosphere. Aircraft

f o r a wide v a r i e t y

have c o l l e c t e d d a t a

of

m e t e o r o l o g i c a l c o n d i t i o n s d u r i n g t h e p a s t t h r e e summers. done on b a d l y p o l l u t e d d a y s d u r i n g t h e "smoggy" s e a s o n .

i s severely

and f a l l months v e r t i c a l mixing B a s i n d u r i n g a n e n t i r e 24-hour

time.

period.

air quality

ambient

Sampling was t y p i c a l l y During t h e s p r i n g , summer

restricted

across

the

This condition persists

Los Angeles

f o r days a t a

The mixed l a y e r i s capped by a v e r y s t r o n g t e m p e r a t u r e i n v e r s i o n ,

degrees

i n magnitude.

With v e r y

light

winds

night

and

through

morning

several

hours

and

s t r o n g s o l a r i n s o l a t i o n , t h e Los Angeles B a s i n behaves as a c l a s s i c a l photochemic a l smog chamber.

Furthermore,

s t r a t u s c l o u d s o r marine m o i s t u r e

are normally

p r e s e n t to promote h e t e r o g e n e o u s aqueous d r o p l e t c h e m i s t r y .

A l l this results i n

summer d a y s c h a r a c t e r i z e d by c o m b i n a t i o n s of e l e v a t e d ozone,

a e r o s o l and s u l f a t e

and a e r o s o l l e v e l s .

l e v e l s and f a l l d a y s c h a r a c t e r i z e d by h i g h NO

AND

CHEMICAL

PHYSICAL

CHARACTERISTICS OF

GASES AND

AEROSOLS

IN

THE

VERTICAL

DIMENS I O N A i r b o r n e measurements were conducted f o r a v a r i e t y of ambient a i r q u a l i t y and meteorological conditions during the past

three years.

v e r t i c a l p r o f i l e o f t h e Los Angeles B a s i n a t n i g h t , d i f f e r e n c e s between t h e s t a b l e a n d mixed l a y e r s .

Figure 1 i l l u s t r a t e s the

showing t h e marked chemical

These f i g u r e s a l s o i l l u s t r a t e

t h e maximum mixing h e i g h t d u r i n g t h e p r e v i o u s daytime hours. completely eroded, uniform a c r o s s result, layer.

masses.

the

even i n t h e

i n l a n d areas.

t h e e n t i r e Basin,

stable

in

spite

of

The mixing intense

The i n v e r s i o n i s n o t height

solar

i s remarkably

insolation.

As a

a i r mass r e m a i n s m e t e o r o l o g i c a l l y d e c o u p l e d from t h e mixed

T h i s i s r e f l e c t e d i n c h e m i c a l and p h y s i c a l d i f f e r e n c e s between t h e two a i r

349

Fig. 1. Vertical profile of meteorological and air quality data collected by light aircraft over the L.A. Basin; (top) from 2007-2248 PST, August 2, 1978; and (bottom) from 2020-0258 PST, October 24-25, 1979.

350 Gases ___ polluted,

being

characterized

by

These ozone c o n c e n t r a t i o n s are months) and because o f multiple

thin

is surprisingly quite

i n F i g u r e 1, t h e i n v e r s i o n ( s t a b l e ) l a y e r

As depicted

elevated

often

ozone

i n excess

levels,

t h e s t a b l y s t r a t i f i e d n a t u r e of

horizontal

l a y e r s e x t e n d i n g westward

p a s t t h e c o a s t l i n e s e v e r a l miles o v e r t h e ocean.

but

200 ppb

of

low

values.

NOx

(during

the inversion,

from

the

summer

the

occur i n

mountains

to

Above t h e i n v e r s i o n l a y e r ,

out

O3

values decrease rapidly. By c o n t r a s t , t h e mixed l a y e r i s a f r e s h a i r mass and c o n t a i n s h i g h v a l u e s of NOx

and v e r y

the year NOx

03.

low v a l u e s of

toward

the

fall,

Higher v a l u e s

of

NOx

are

observed

c o i n c i d i n g w i t h d e c r e a s i n g mixing

later

heights.

in

Highest

v a l u e s are u s u a l l y o b s e r v e d from t h e E l Monte area westward t o t h e c o a s t .

S p a t i a l c o n c e n t r a t i o n s of NOx v a r y n i g h t l y depending on t h e sea-land culation pattern.

The r a t i o of NO t o NO

breeze c i r -

a l s o v a r i e s seasonally.

C o n c e n t r a t i o n s o f SO2 m o n i t o r e d by t h e a i r c r a f t were low a c r o s s t h e Basin i n E x c e p t i o n s are immediately downwind of p o i n t

b o t h t h e mixed and s t a b l e l a y e r s . sources

s u c h a s power

p l a n t s and

refineries.

Otherwise,

nighttime

SO2 v a l u e s

a r e t y p i c a l l y 10 t o 25 ppb i n t h e mixed l a y e r and 10 t o 15 ppb i n t h e i n v e r s i o n . Aerosols

A s outlined previously,

a i r b o r n e p a r t i c u l a t e f i l t e r samples were c o l l e c t e d i n

t h e Los Angeles B a s i n as p a r t of t h i s r e s e a r c h program. i z e d i n T a b l e 1 and F i g u r e 1.

less a e r o s o l t h a n does layer.

These r e s u l t s a r e summar-

These d a t a show t h a t a l t h o u g h t h e s t a b l e l a y e r has

t h e mixed

layer,

substantial aerosol

is i n t h e s t a b l e

I n t h i s section, the nighttime chemistry i s described.

Nighttime

sulfur

chemistry.

Table

1 shows

the

highest

c o n c e n t r a t i o n s of

p a r t i c u l a t e s u l f u r s p e c i e s t o be i n t h e i n l a n d p o r t i o n s of t h e B a s i n i n t h e mixed layer.

The c o n c e n t r a t i o n s found w i t h i n t h e i n v e r s i o n l a y e r , b o t h i n l a n d and a l o n g

t h e c o a s t , are comparable.

The l o w e s t c o n c e n t r a t i o n s are observed a l o n g t h e c o a s t

i n t h e mixed l a y e r , which i s r e a s o n a b l e c o n s i d e r i n g t h e s t r e n g t h of t h e sea b r e e z e d u r i n g t h e summer months.

T a b l e 1 a l s o shows t h a t ,

s u l f a t e i s i n t h e f i n e s i z e range

( l e s s t h a n 2.5

s u l f a t e c o n c e n t r a t i o n s d e t e r m i n e d by hi-volume

and low-volume

a r e i n good agreement a s i n d i c a t e d by t h e low-volume

are a t l e a s t two r e a s o n s f o r t h e c o m p a r a b i l i t y .

on t h e a v e r a g e , p~ p a r t i c l e

90% of

diameter).

the The

sampling t e c h n i q u e s

t o hi-volume

ratio.

There

First, particulate sulfate i n the

atmosphere i s thermodynamically s t a b l e because t h e s u l f a t e s a l t s have low vapor pressures (Ref.

10).

Second,

since there was little sulfate i n larger particles,

t h e d i f f e r e n c e i n c u t p o i n t s among t h e sampling systems d i d n o t markedly a f f e c t t h e measured s u l f a t e c o n c e n t r a t i o n s .

351 TABLE 1

Summary of a i r b o r n e nighttime a e r o s o l samples in the Los Angeles Basin i n 1979

Locallo"

*nversran Layer, CDOStale

On sampling n i g h t s following days with s t r a t u s a s f a r inland a s t h e E l Monte a r e a , s u l f a t e l e v e l s i n t h e mixed l a y e r a r e n e a r l y twice a s high a s those on the days without

stratus.

This r e s u l t

i s c o n s i s t e n t with previous work suggesting

that heterogeneous SO2 t o s u l f a t e conversion occurs more r a p i d l y i n the presence

of c o a s t a l moisture and higher r e l a t i v e humidities than do slower homogeneous conv e r s i o n processes (Refs. 11-13). Perhaps t h e most i n t r i g u i n g chemical r e s u l t i s the l a r g e f r a c t i o n of particul a t e s u l f u r bound t o organic compounds.

i s r e f e r r e d t o a s organic S(IV) c o n c e n t r a t i o n s of

organic

s p e c i e s (Ref.

S(IV)

Figure 1) have been observed.

This f r a c t i o n of the p a r t i c u l a t e s u l f u r 14).

a s high a s 6

The e x i s t i n g d a t a base shows

pg/m3 expressed a s

s u l f a t e (see

In general, organic S(1V) i s observed in the d r i e r

p o r t i o n s of t h e Basin, both i n l a n d and throughout t h e i n v e r s i o n from the coast t o inland areas.

Figure 2 shows t h a t a t times,

more than 50% of

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

s u l f u r is in t h e form of organic S(1V). Figure 2 i n d i c a t e s a very good c o r r e l a t i o n between organic and t o t a l particul a t e s u l f u r f o r days with warm a i r masses. open p o i n t s f o r a i r masses c o o l e r than 2 2 ° C .

Figure 2 a l s o includes data denoted by Excluding days when the average day-

time temperature of t h e a i r mass i s l e s s than 2 Z 0 C , obtained:

t h e following r e l a t i o n s h i p i s

352

A

Fig.

2.

R e l a t i o n s h i p between a i r b o r n e t o t a l f i n e p a r t i c u l a t e s u l f a t e and organic i n t h e L.A. Basin f o r s e v e r a l summer and f a l l days i n 1979. Solid data p o i n t s a r e f o r warmer a i r mass while open d a t a p o i n t s a r e f o r cooler a i r mass. The l a t t e r a r e not included i n the r e g r e s s i o n a n a l y s i s .

S(1V)

2-

+

[So4 ] = 1.10 [Org. S(IV)] where ground

all

concentrations a r e

level

of

inorganic

a l s o suggests t h a t i n warm,

in

SO-:

nanomoles/m in

the

3

17.7

.

Basin

Equation of

about

(1)

2

suggests pg/m

3

.

a

back-

Figure

dry a i r masses SO2 conversion t o inorganic

2

sulfate

and organic S(IV) occur a t similar r a t e s . These r e s u l t s a r e complicated by the f a c t

that

these data were

n i g h t when photochemical homogeneous processes were a t a minimum.

collected a t Furthermore, a

d i f f e r e n c e i n residence times and a i r mass age between the mixed and s t a b l e l a y e r s m u s t a l s o be considered.

Additional sampling and d a t a a n a l y s i s a r e needed t o un-

r a v e l t h e d i f f e r e n c e s between daytime and nighttime chemistry w i t h i n and between each l a y e r .

Nighttime n i t r a t e

chemistry.

Proper

sampling

of

nitrate

in

the

atmosphere

353 i n the data s c a t t e r n e s s shown i n Fig-

continues t o be a challenge a s r e f l e c t e d ure 3.

From t h e c o a s t

to the inland areas,

l e v e l s i n c r e a s e a s the dry a i r masses aged. tions

of

particulate

nitrate

to

occur

measured

fine particulate nitrate

The trend is f o r higher concentra-

toward

the

fall

months

as

NO2

values

increase.

100

fn

0 INVERSION A MIXED L A Y E R

W

-

c

a

0

U

n

60 -

W

5

LL

40

z 0"

z

E

2o A

0

I

0

A

20

I

I

I

,

,

I

40

60

80

100

120

140

[NO;] IN FINE PARTICLES

, nanomol/m3

Fig. 3. R e l a t i o n s h i p between the percent of t o t a l p a r t i c u l a t e n i t r a t e i n the f i n e S o l i d data mode ( < 2 . 5 pm Dp) and ambient c o n c e n t r a t i o n of f i n e p a r t i c l e n i t r a t e . p o i n t s a r e samples where evidence e x i s t s f o r gaseous HNO3. The percentage of p a r t i c u l a t e n i t r a t e in t h e fine size range i s d i r e c t l y proportional

t o the

fine

particle

concentration

as

shown i n Figure

3.

Figure

3

suggests t h a t the background p a r t i c u l a t e n i t r a t e is about 30% f i n e p a r t i c l e and

70% c o a r s e p a r t i c l e .

These concentrations

a r e derived from the regression

line

obtained i n Figure 3: % NO;

where

NO;

suggests

( f i n e s ) = 0.334 [NO;]

concentration that

is

t h e background

in

nanomoles/m

nitrate

+

fines

3

.

31.0

This

concentration

in

(2) regression

the

Basin

pg/m3 f o r t h e 2 . 5 pm p a r t i c l e diameter (Dp) range and about 2 . 3

relationship

is about

1.0

pg/m3 f o r the

2.5 pm Dp range. The d a t a obtained i n t h i s study lead t o believe t h a t f o r n i g h t s when s t r a t u s clouds a r e not p r e s e n t i n the mixed l a y e r inland and i n the inversion a substant i a l p o r t i o n of n i t r a t e might be i n the form of

gaseous HN03.

The i n t e r p r e t a -

t i o n of t h e i n l a n d and i n v e r s i o n p a r t i c u l a t e n i t r a t e concentrations is d i f f i c u l t

354 because

of

t h i s g a s e o u s HN03.

The

c o n s i d e r i n g c h a n g e s i n t h e C1volume and high-volume The

presence

of

presence

of

g a s e o u s HN03 was

concluded

by

p a r t i c l e s i z e d i s t r i b u t i o n and comparing t h e low-

sampling r e s u l t s .

should

g a s e o u s HN03

result

in

release

of

coarse

particle

C1- as g a s e o u s HC1 a c c o r d i n g t o t h e r e a c t i o n (Ref. 1 5 ) :

I t h a s been s u g g e s t e d by Moskowitz

(Ref.

16) t h a t t h i s r e a c t i o n is i m p o r t a n t i n

t h e p r o d u c t i o n of c o a r s e p a r t i c l e n i t r a t e i n t h e Basin.

Evidence t o s u p p o r t t h i s

c h e m i s t r y i s shown in F i g u r e 4 , which p l o t s t h e % C1% NO;

the

in

coarse

particles.

While

p a r t i c l e s l e s s t h a n and g r e a t e r t h a n 2.5

the

i n coarse particles versus

of

distribution

pm Dp i s r e l a t i v e l y

NO;

constant,

between t h e C1-

d a t a c a n be d i v i d e d i n t o two g r o u p s as denoted by t h e two c i r c l e s .

100

1

I

,/

v)

w

I _----_ -.

,

-

0 l-

\

A

/ I

80 -

0

\

\\

-0

,tiI

A

0

I I'

0

/'

A

0

-

',..-?--*.#' A /----A,

60 -

0

', i

o

\, O

a a a w v) a a

I

A'

40 -

z

\, 1 I

! I \\,

m

a

-

0 :

;

'\ A ,,' '\..e----.-.,'

20 -

-

-

OlNVERSlON

aQ

AMIXED LAYER 0 0

I

I

I

I

20

40

60

80

100

F i g . 4 . R e l a t i o n s h i p between p e r c e n t o f t o t a l c h l o r i d e in c o a r s e mode and p e r c e n t o f t o t a l n i t r a t e i n c o a r s e mode. S o l i d d a t a p o i n t s are samples from l o c a t i o n s of g r e a t e r photochemical a c t i v i t y .

The

samples having

the

majority

c o l l e c t e d i n t h e mixed l a y e r a t

c l e NO;

and

SO:-

levels

ures 2 and 3) a n d / o r

were

of

the

t h e coast. close

to

C1-

in

At

this

the

expected

t h e r e was no m e a s u r a b l e a c i d i t y

coarse

location

background i n the

particles

were

b o t h fine p a r t i levels

samples,

(Figso

that

355 gaseous HN03 c o n c e n t r a t i o n s would be u n i m p o r t a n t ( T a b l e 1). Table 1 s u g g e s t s t h a t i n t h e mixed l a y e r a t t h e c o a s t , c e n t r a t i o n i n t h e s i z e r a n g e of > 2 . 5

pm Dp i s a b o u t 1 pg/m

The samples having t h e m a j o r i t y of

t h e C1-

i n the

t h e background C13

con-

.

f i n e p a r t i c l e s were c o l -

i n t h e i n l a n d areas and from t h e s t a b l e l a y e r

l e c t e d from t h e mixed l a y e r

The s h i f t t o smaller p a r t i c l e C1-

the coast.

An examination of

in

i s c o r r e l a t e d w i t h g r e a t e r photo-

c h e m i c a l a c t i v i t y ( h i g h e r O3 and gaseous HNO ) as w e l l a s h i g h e r f i n e p a r t i c u 3 l a t e NO;, SO:a n d a c i d i t y and presumably r e s u l t s from d i s p l a c e m e n t of from c o a r s e p a r t i c l e s as shown i n E q u a t i o n ( 3 ) .

C1-

c a t e t h a t a b o u t one-half

i n l a n d mixed l a y e r samples by way of E q u a t i o n ( 3 ) . inland

coarse particle

levels

NO;

the experimental value

3.9

of

pg/m

of 3

about

4

of

t o form 2 pg/m3 of NO;.

The

the

pg/m3

from

of CI-

present

2

study

i s displaced i n the drier

1,

(Table

background

indicates

that

NO;

T h i s would l e a d t o p r e d i c t e d

pg/m

3

,

agrees w e l l

with

"mixed l a y e r ,

in-

which

row l a b e l l e d

l a n d , no i n l a n d low c l o u d s t h e p r e v i o u s day"). comes

The d a t a i n F i g u r e 4 i n d i -

t h i s c o a r s e p a r t i c l e C1-

of

T h i s p r e d i c t e d v a l u e of 4 pg/m and

elevated

the

displacement

particle

1 pg/m3

of

concentrations

NO;

3

can

o c c u r a t n i g h t n o t o n l y when t h e a i r mass was w a r m and d r y on t h e p r e v i o u s day ( T a b l e 1) b u t a l s o when t h e a i r mass was c o o l e r and m o i s t d u r i n g t h e n i g h t (Refs. 18).

17,

P e r h a p s NO2 i s c o n v e r t e d p h o t o c h e m i c a l l y d u r i n g t h e warmer,

d r i e r day-

t i m e h o u r s t o g a s e o u s HN03 and t h e n w i t h t h e o n s e t of c o o l e r n i g h t t i m e temperat u r e s and i n c r e a s i n g r e l a t i v e humidity to particulate nitrate.

t h e gaseous HN03 i s g r a d u a l l y converted

Thermodynamically, t h e f o r m a t i o n of

particulate nitrate

i s f a v o r e d by c o o l e r t e m p e r a t u r e s and h i g h e r r e l a t i v e h u m i d i t i e s (Ref.

A p r i n c i p a l a t m o s p h e r i c r o l e f o r ammonia is as a n e u t r a l -

Ammonia chemistrll. izer for

s u l f u r i c and n i t r i c a c i d .

i n t h e f i n e p a r t i c l e mode. i s bound

t o Na

The

Table

two

a c i d i t y of

columns

+

i n Table

the aerosol.

1 shows t h a t n e a r l y a l l t h e NH;

is

This again suggests t h a t the coarse p a r t i c l e n i t r a t e

t o some c a t i o n o t h e r t h a n NH4,

+.

19).

as d i s c u s s e d above,

and,

1 a d d r e s s t h e abundance of

+

the

NH4

concentration,

From examining t h e H+

age a e r o s o l a c i d i t y i s observed i n t h e i n l a n d samples.

most

ion

likely

and

the

t h e h i g h e s t aver-

However,

t h e h i g h e s t con-

c e n t r a t i o n s of a c i d i t y o c c u r i n samples c o l l e c t e d a t t h e c o a s t .

T h i s i s reason-

able

NH3

s i n c e most

inland aerosols.

NH;

was

in

sources The

t h e <2.5

of

NH3

are

further

size-fractionated pm

Dp

range.

inland

samples

generally

Generally,

particulate

NH;

calculated

from

s e v e r a l times h i g h e r t h a n t h a t from t h e high-volume

this

indicate

reasonable

s e r v e d between t h e h i g h volume and low volume samples. c o n c e n t r a t i o n of

and

neutralizes

90% of

the

was

ob-

agreement

However, i n some cases t h e the

low-volume

samples.

samples

was

T h i s d i f f e r e n c e may

356 a r i s e from h a n d l i n g p r o c e d u r e s which may l e a d t o t h e a b s o r p t i o n of

gaseous

NH3

by a c i d i c p a r t i c u l a t e s a f t e r sample c o l l e c t i o n . The the

mole

ratio

extent

to

+

(NO; NO;

which

+

s a l t s of

NH4

+.

H

or

ples collected i n

42SO4

and

When t h e r a t i o i s 1.0,

salts.

For

or

+

NH4.

The

layer

the suggestion If

that

t h o s e samples

background Equations

of

the

other

2

pg/m3 then

are c a l c u l a t e d t o be p r e s e n t as NH;

Aerosol s i z e d i s t r i b u t i o n .

the

or

1

Table

as

present

salts

cation

c o a s t are

reflects

+

NH4

exist.

strongly

and and

a

toward

occurs for

salts

SO:-

samples

neutralization

(Z)],

of and

other

along

SO:-

collected inland

SO:-

(1)

NH3

are

in

The

with

drier

value

gaseous

a i r masses

background

NO;

all

the

essentially

are

of

than

1.0

HN03

are

by

or

H'

supports H2S04.

corrected for

of 1.0 pg/m3 [see 2secondary SO4 and NO3

compounds.

F i g u r e s 5 and 6 p o r t r a y t y p i c a l s u r f a c e area and In

t h e volume d i s t r i b u t i o n s are t r i - m o d a l w i t h d i a m e t e r peaks cen-

t e r i n g a t a b o u t 0 . 2 pm, 0.5 p and 7 pm. show b i - m o d a l .

sam-

t h a t ca-

other

volume d i s t r i b u t i o n p l o t s f o r t h e a c c u m u l a t i o n and c o a r s e modes of a e r o s o l s . t h e mixed l a y e r ,

H+

or

influenced

The l a r g e c a l c u l a t e d r a t i o i n d i c a t e s

background

tendency

species

r a t i o s >1.O,

t h e mixed

with

H+)

t h e s u l f a t e and n i t r a t e can a l l be accounted f o r as

background s u l f a t e and n i t r a t e . tions associated

+

2S02-)/(NHi

By c o n t r a s t ,

t h e i n v e r s i o n volume p l o t s

No c o a r s e mode e x i s t s , w i t h a bi-modal

f i n e p a r t i c l e mode a t 0.2

and 0.5 p Dp. From p r e v i o u s s t u d i e s ( R e f s . 12, 21) t h e 0.2

p mode may be a s s i g n e d p r i m a r i l y

t o t h e o r g a n i c component and homogeneously formed s u l f a t e s and n i t r a t e s , w h i l e t h e

0.5

pm mode

c o n t a i n s h e t e r o g e n e o u s s u l f a t e and n i t r a t e .

have i n d i c a t e d a mass median d i a m e t e r (MMD)

whereas f o r o r g a n i c s t h e MMD i s smaller, but unknown.

on e x i s t i n g p a r t i c l e s and growth ceases a t 0.2 However,

close

Gas-to-particle

b e h a v i o r i n t h e B a s i n a l s o s u p p o r t s t h i s modal assignment.

hydrophobic p r o p e r t i e s .

These p r e v i o u s s t u d i e s

f o r s u l f a t e very

to

0.5

pm

conversion

The o r g a n i c s condense

t o 0.3 pm i n p a r t , because of t h e i r

t h e a c c u m u l a t i o n mode s u l f a t e and n i t r a t e can

condense o r form i n s t r a t u s l f o g d r o p l e t s and c o n t i n u e t o grow h y g r o s c o p i c a l l y i n t h e m o i s t marine environment t o a l a r g e r e q u i l i b r i u m s i z e of 0.5 t o 2 pm. The volume i n e a c h of

t h e s e modes i s a l s o c o n s i s t e n t w i t h t h e i r chemical as-

Assuming a d e n s i t y of

signment.

1.5 g/cm3 f o r t h e s e p a r t i c l e s , o r g a n i c a e r o s o l s

have a mass c o n c e n t r a t i o n v a r y i n g from a b o u t 35 t o 60 pg/m3 i n t h e mixed l a y e r , b u t c o n s i d e r a b l y less i n t h e s t a b l e l a y e r .

3 20 ug/m

.

S u l f a t e and n i t r a t e w i l l t o t a l about

These r e s u l t s are c o n s i s t e n t w i t h ACHEX e x p e r i m e n t s a s w e l l as w i t h

more r e c e n t work conducted by SCE which shows t h a t a c o n s i d e r a b l e amount of a c c u m u l a t i o n mode a e r o s o l i s i n t h e form of o r g a n i c s ( R e f s 15, 1 7 , a n a l y s i s of samples c o l l e c t e d i n d i c a t e t h a t

15% s u l f a t e ,

5-10% n i t r a t e ,

18).

the

Detailed

t h e a e r o s o l mass i s 30-40% o r g a n i c ,

5% ammonium, 25% t r a c e e l e m e n t s ,

and

30-35% unas-

5. R e p r e s e n t a t i v e d i f f e r e n t i a l s i z e d i s t r i b u t i o n p l o t s i n t h e mixed l a y e r o v e r S a n t a Monica ( a l o n g c o a s t ) a t 5 5 0 m MSL a t 0441 PST, O c t . 9, 1980: (a) volume d i s t r i b u t i o n ; a n d ( b ) s u r f a c e area d i s t r i b u t i o n .

Fig.

6. Representative d i f f e r e n t i a l s i z e d i s t r i b u t i o n p l o t s i n the inversion l a y e r o v e r S a n t a Monica ( a l o n g c o a s t ) a t 1280 m MSL a t 0448 PST, Oct. 9 , 1980: ( a ) volume d i s t r i b u t i o n ; a n d ( b ) s u r f a c e a r e a d i s t r i b u t i o n .

Fig.

358 b a s e d on

The u n a s s i g n e d p o r t i o n may b e water,

signed.

t h e e a r l i e r ACHEX work

( R e f s . 2 2 , 23). The d i f f e r e n c e s between t h e f i n e and c o a r s e modes once a g a i n p o i n t s t o t h e deThe 0.5

c o u p l e d n a t u r e between t h e mixed and s t a b l e l a y e r s .

p Dp h e t e r o g e n e o u s

s u l f a t e / n i t r a t e mode i s g r e a t l y d i m i n i s h e d i n t h e s t a b l e l a y e r .

First,

t h e rela-

t i v e h u m i d i t y of t h i s l a y e r i s low, u s u a l l y < 3 0 % so t h a t l i q u i d water i s n o t asT h e r e f o r e , t h e volume o f t h e s e a e r o s o l s c a n be re-

sociated with these aerosols. duced

by

one-third

l i k e l y t h e s e 0.5

compared

t o mixed

layer

pm Dp mode a e r o s o l s were

l a y e r a n d t r a n s p o r t e d upward

into

aerosols initially

the drier

(Ref.

22).

formed i n

inversion.

Second,

t h e m o i s t mixed

T h i s marked

r e l a t i v e h u m i d i t y may r e s u l t i n a h y s t e r i s t y p e s h r i n k i n g of

most

change

in

t h e a e r o s o l down t o

t h e u p p e r e n d o f t h e c o n d e n s a t i o n a l 0.2 pm Dp mode. The c o a r s e mode i s c h e m i c a l l y and p h y s i c a l l y q u i t e d i f f e r e n t from t h e accumul a t i o n modes.

The f i n e a n d c o a r s e modes b e i n g p h y s i c a l l y s e p a r a t e d o c c u r s b e c a u s e

c o n d e n s a t i o n p r o d u c e s f i n e p a r t i c l e s whereas m e c h a n i c a l p r o c e s s e s produce m o s t l y coarse p a r t i c l e s .

The e q u i l i b r i u m dynamics of f i n e p a r t i c l e s p r e v e n t t h e s e par-

t i c l e s from growing l a r g e r t h a n a b o u t 1 p.

Thus,

t h e c o a r s e mode i s a b s e n t i n

t h e s t a b l e l a y e r b e c a u s e t h e s o u r c e of t h e s e l a r g e r p a r t i c l e s i s a t t h e s u r f a c e a n d t h e s e t t l i n g v e l o c i t i e s of t h e s e p a r t i c l e s are t o o h i g h . s e t t l i n g v e l o c i t y o f a b o u t 1 cm/sec (Ref.

Given a c o a r s e mode

2 4 ) and c o n s i d e r i n g t h e l o n g r e s i d e n c e

times o f 2 4 h o u r s o r g r e a t e r i n t h e s t a b l e l a y e r ,

t h e e q u i l i b r i u m dynamics p o i n t s

t o no c o a r s e mode i n t h e s t a b l e l a y e r . The l a r g e s u r f a c e area a s s o c i a t e d w i t h t h e 0.2

p Dp peak s u g g e s t s t h a t most of

t h e new p a r t i c l e s a r e produced i n t h i s s i z e range.

Condensation occurs preferen-

t i a l l y on p a r t i c l e s h a v i n g t h e l a r g e s t s u r f a c e area. G e n e r a l l y , when t h e s u r f a c e area e x c e e d s 500 pm 2 / c m 3 , s u f f i c i e n t p a r t i c l e s e x i s t so t h a t c o n d e n s a t i o n o c c u r s on e x i s t i n g p a r t i c l e s .

Thus, o n e would e x p e c t t h e n u c l e a t i n mode ( s o u r c e s

s u c h a s t h e a u t o m o b i l e ) t o r a p i d l y d i s a p p e a r i n t o t h i s 0.2

pm Dp mode.

However,

i n t h e i n v e r s i o n , s u r f a c e area i s s u f f i c i e n t l y low t h a t p a r t i c l e growth dynamics o c c u r s p r i m a r i l y v i a t h e n u c l e a t i o n and c o n d e n s a t i o n r o u t e .

CONCLUSIONS AND FUTURE WORK The Los A n g e l e s B a s i n i s a complex e n v i r o n m e n t w i t h a n a r r a y o f m o b i l e and stat i o n a r y s o u r c e e m i s s i o n s s p r e a d o v e r a r a t h e r l a r g e g e o g r a p h i c a l area.

One o f t h e

most complex a n d l e a s t u n d e r s t o o d d i m e n s i o n s i n t h e Los Angeles B a s i n i s t h e v e r -

t i c a l p r o f i l e of a m b i e n t a i r c o n s t i t u e n t s . gram t o g a i n a n improved u n d e r s t a n d i n g of years'

a i r b o r n e d a t a base,

gases and a e r o s o l s .

A s p a r t o f a long-term t h i s dimension,

r e s e a r c h pro-

using an i n i t i a l three

t h i s p a p e r h a s examined t h e c h e m i s t r y and p h y s i c s o f

Because of t h e a c t i v e i n t e r p l a y o f t h e s e phenomena, t h e p a p e r

h a s t r e a t e d e a c h i n some d e t a i l . A d d i t i o n a l d a t a on t h e c h e m i s t r y a l o f t

i s needed

i n order

t o elucidate the

359 s p a t i a l d i s t r i b u t i o n of sulfur species.

c h e m i c a l compounds s u c h as s u l f a t e ,

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

Improved sampling t e c h n i q u e s a r e needed t o d i f f e r e n t i a t e between

p a r t i c u l a t e n i t r a t e and n i t r i c a c i d . ~ t a n dg a s - t o - p a r t i c l e

More e x p e r i m e n t a l d a t a are needed t o under-

t r a n s f o r m a t i o n s and i n what manner t h e s e t r a n s f o r m a t i o n s are

a f f e c t e d by t r a n s p o r t p r o c e s s e s .

P e r h a p s t h e g r e a t e s t gap i n o u r knowledge i s i n

t h e t r a n s p o r t p r o c e s s e s i n t h e v e r t i c a l dimension.

Much more d e t a i l e d v e r t i c a l

m e t e o r o l o g i c a l i n f o r m a t i o n i s needed t o c l a r i f y t h e " c a r r y over"

of

pollutants,

p a r t i c u l a r l y f o r a e r o s o l s a n d ozone

of

fall-winter

stagnation,

precursors.

During

periods

" c a r r y o v e r " may become i n c r e a s i n g l y i m p o r t a n t .

A d d i t i o n a l meteoro-

l o g i c a l and c h m e i c a l p r o f i l e s are needed t o t h e w e s t of t h e Los Angeles Basin o u t t o 50-100 miles o v e r t h e P a c i f i c Ocean.

Because of t h e d a i l y sea b r e e z e ,

a i r is

t r a n s p o r t e d from t h i s f a r e a s t w a r d o v e r t h e Los Angeles B a s i n p r a c t i c a l l y e v e r y day.

The i n t e r a c t i o n and t r a n s p o r t of p o l l u t a n t s w i t h s t r a t u s c l o u d s i s an a l m o s t

untouched s u b j e c t .

REFERENCES 1 M. N e i b u r g e r , N.A. R e n z e t t i , L.H. Rogers and R. T i c e , An Aerometric Survey of 1954--Interpretation of R e s u l t s , A i r t h e Los Angeles B a s i n , August-November, P o l l u t i o n F o u n d a t i o n R e p o r t No. 9, Los Angeles, 1955. Hidy, 3. Appel, R.J. C h a r l s o n , W.E. C l a r k , S.K. F r i e d l a n d e r , R. Giauque, 2 G.M. S . Heisler, P.K. M u e l l e r , R. R a g a i n i , L.W. R i c h a r d s , T.B. Smith, A. Waggoner, J.J. Wesolowski, K.T. Whitby and W. White, C h a r a c t e r i z a t i o n of A e r o s o l s i n C a l i f o r n i a (ACHEX), F i n a l Rep. t o C a l i f o r n i a A i r Resources Board, under C o n t r a c t 358, 1974. 3 J.G. E d i n g e r , J . of Meteor., 16(1959)219-226. 4 J.G. E d i n g e r , Environ. S c i . Technol., 7(1973)247-252. Smith, W.H. White, S . L . Marsh, D.S. Ensor, R.B. Husar, 5 D.L. Blumenthal, T.B. P.S. McMurry, S.L. Heisler and P. Owens, Three-Dimensional P o l l u t a n t G r a d i e n t Study--1972-1973 Program, Meteorology Research, Incorporated, Altadena, C a l i f o r n i a , R e p o r t No. MRI 74FR-1262, 1974. 6 J.G. C a l v e r t , Environ. S c i . Technol., 10(1976)248-256. 7 D.L. Blumenthal, J.A. Ogren and J.A. Anderson, Atmos. Environ., 12(1978)613-620. 8 L.W. R i c h a r d s , J.A. Anderson, D.L. Blumenthal, A.A. B r a n d t , J.A. McDonald, N. Waters, E.S. Macias a n d P.S. Bhardjawa, Atmos. Environ., 15(1981)2111-2134. 9 D.J. Eatough, N.L. Eatough, M.W. H i l l , N.F. Mangelson, J. Ryder, L.D. Hansen, R.G. Meisenheimer and J.W. F i s c h e r , Atmos. Environ., 13(1979)489-506. 10 W.D. S c o t t and F.C.R. C a t t e l l , Atmos. Environ., 13(1979)307-317. 11 G.R. Cass, Methods f o r S u l f a t e A i r Q u a l i t y Management w i t h A p p l i c a t i o n s t o Los A n g e l e s , Ph.D. T h e s i s , C a l i f o r n i a I n s t i t u t e of Technology, 1978. 12 R.E. Meyers and E.N. Z i e g l e r , Environ. S c i . Technol., 12:(1978)302-309. Eatough, T. Major, J. Ryder, M. H i l l , N.F. Mangelson, N.L. Eatough and 1 3 D.J. L.D. Hansen, Atmos. Environ., 12(1978)263-271. 14 D.L. Eatough, L.D. Hansen, M.L. Lee, and N.F. Mangelson, Measurement of S u l f u r (LV) and M e t h y l a t e d S u l f a t e S p e c i e s i n A e r o s o l s Produced by F o s s i l F u e l Burning Steam P l a n t s , F i n a l Report EPRI C o n t r a c t RP-1554-1, J a n u a r y , 1981. 1 5 J. F o r r e s t , R.L. Tanner, D. Spandau, T. D'Ohavio and L. Newman, Atmos. Environ., 14(1980)137-144. 16 A.H. Moskowitz, The D i s t r i b u t i o n of A e r o s o l N i t r a t e Compounds w i t h Respect t o P a r t i c l e S i z e , M.S. T h e s i s , C a l i f o r n i a I n s t i t u t e of Technology, 1977, p. 195. 1 7 E.C. E l l i s , R.J. F a r b e r , S.L. H e i s l e r , P.K. M u e l l e r , R.E. Henry and G.M. Hidy, C h a r a c t e r i z a t i o n o f Ambient S u l f a t e A e r o s o l s i n Los Angeles, 1 7 7 t h Meeting o f t h e American Chemical S o c i e t y , Honolulu, Hawaii, A p r i l , 1979.

360 18 S.L. Heisler, R.C. Henry, P.K. M u e l l e r , G.M. Hidy and D. G r o s j e a n , A e r o s o l B e h a v i o r P a t t e r n s i n t h e S o u t h C o a s t A i r B a s i n w i t h Emphasis on A i r b o r n e S u l f a t e , E n v i r o n m e n t a l R e s e a r c h a n d Technology, Inc., W e s t l a k e V i l l a g e C a l i f o r n i a , Document P-A085-1, 1980. 19 I. N. Tang, A t m o s . E n v i r o n . , 14(1980)819-828. 20 B.W. S t e l s o n , S.K. F r i e d l a n d e r and J.H. S e i n f e l d , Atmos. Environ., 13(1979) 369-37 1. 21 W.H. White a n d P.T. R o b e r t s , Atmos. Environ., 11(1977)803-812. 22 W.W. Ho, G.M. Hidy a n d R.M. Govan, J. Appl. Meteor., 4(1974)871-879. 23 K.T. Whitby a n d G.M. S v e r d r u p , i n G.M. Hidy (Ed.), The C h a r a c t e r and O r i g i n s of Smog Aerosols, California Aerosols: Their Physical and Chemical C h a r a c t e r i s t i c s , J o h n Wiley & Sons, New York, 1980, p. 484. 24 N.A. F u c h s , Mechanics of A e r o s o l s , Pergamon P r e s s , N e w York, 1964, p. 33.

361

CHARACTERIZATION OF A LOCAL AEROSOL ON A RURAL SITE OF THE PO VALLEY

*

**

S. FUZZ1 , M. MARIOTTI

*

*

and G . ORSI

**Istituto FISBAT - CNR, Bologna (Italy) Sezione Chimica, Laboratorio Provinciale Igiene e Prof ilassi, Bologna (Italy)

ABSTRACT A site was chosen in the Po Valley (Northern Italy) that could be considered representative of the whole eastern part of the Valley. High volume aerosol samples were collected during periods characterized by weak pressure gradients over the region, so that any influence by external sources, over the aerosol composition, could be reasonably excluded. The measured total concentration of airborne particles appears notably high in a rural atmosphere. The following aerosol characteristics were determined: a) concentration of water soluble and insoluble material; b) concentration of ether soluble organic material; c) chemical element balance. Synoptic and local meteorological data were also collected during the samplings. The results are discussed from the point of view of the contribution of various sources to the total particulate matter.

INTRODUCTION This work represents the first step of a study program on aerosol production, transformation and circulation in the Po Valley (Northern Italy). The topographic feature of the Po Valley determines particular cases of circulation analysed, as a first approach, by Tampieri et al. (ref. 1 ) . This ample valley is essentially flat, about 400 Km long, and has a maximum width of about 100 Km; it is surrounded by mountains to the north, west and south, whereas its eastern side faces the North Adriatic Sea (Fig. 1 ) . The eastern part of the Valley is an agricultural area with light industrial activities (except for a big localised plant in Ferrara) and homogeneous cultivations. High volume aerosol samples were collected in an equipped field near S. Pietro

362

Capofiume (see Fig. l ) , during periods characterized by weak pressure gradients at the mean sea level,

so

that valuable advection of material from outside the

Valley could be reasonably excluded.

4

on

UF A

Fig. 1. Map of the Po Valley. The shaded area refers to elevations greater than 500 m. The dots indicate some of the main cities in the Valley; the triangle indicates the sampling point S. Pietro Capofiume (SPC). This sample would thus represent the chemical composition of the local aerosol (of both natural and anthropogenic origin), and it is, in a first instance, assumed that the present data could be roughly consistent for the whole eastern part of the Po Valley. The knowledge of the composition of the locally produced particulate matter, related to different seasonal situations and agricultural activities, is the first step in the evaluation of transportation and transformation of the aerosol.

EXPERIMENTAL PART The measurements were carried out at ground level, with an high volume sampler. The sampling time was between 12 and 24 hours, at a constant rate of 46 SCFM. In addition to the synoptic data, provided by the Air Force Meteorological Service, continuous measurements were performed of local temperature and humidity, both at ground level and at a height of 50 m, whereas wind speed and direction were measured at a height of 12 m.

363 The samples were collected during two distinct periods in 1981. Period A, late summer (25 August - 1 September). This period was subsequent to a precipitation; under a synoptic situation of weak baric gradients near the ground the mean wind speed was 1.5 m/sec and the prevailing wind direction was west, southwest (70% of the cases). The period was characterized by vertical stability between the ground and 50 m and by strong temperature inversions during the night; the temperature ranged between a maximum mean value of 25 OC at noon and a minimum of 12 'C just before sunrise. The humidity was higher than 60% most of the time. Period B, fall (13

-

16 November). The samples were taken at the end of a stable

weather period just before a perturbation. The mean wind speed was 1.0 m/sec in the first part and 2.5 m/sec in the last part of this period. The prevailing wind direction was west, north-west (90% of the cases). There were also strong nighttime inversions and vertical stability situation. The temperature ranged between a mean maximum of 12 "C at 2.00 p.m. and a minimum value of -2 "C at 2.00 a.m.. The humidity was very low during a few central hours of the day (less than 4 0 % ) and near saturation most of the time: in one case there were a few hours of fog. The sampled glass fiber filters, after weighing, were divided into three parts. The first part was treated with water for one hour, in an ultrasonic tank, in order to extract the soluble part of the particulate. After filtration, the concentration + + 2+ + 2of Na , K , Ca , NH o f colorimetric methods 4' SO ,3-NO3 was determined by means 2+ and AAS (ref. 2 ) . C1 and PO were always absent, Mg concentration was negligible. 4 The second part of the filter was extracted in a Soxhlet apparatus, for 8 hours, with ether, in order to determine the ether soluble organic part (ref. 3 ) . No data are at present available on the composition of organic ether extractable fraction of the aerosol.

In the third part of the filter the total concentration of Fe, Mn and Pb was determined by AAS, after acid attack.

RESULTS AND DISCUSSION

Total suspended particulate matter Five samples were collected in period A, and four were collected in period B. The total suspended particulate matter concentration, as a function of time is presented in Fig. 2. The total suspended particulate matter concentration was increasing during period A, subsequent to a precipitation, and almost constant (after

a strong decrease in sample B2) in period B .

364

0

24

48

72 time

96 h

144

120

168

F i g . 2 . T o t a l suspended p a r t i c u l a t e m a t t e r f o r t h e d i f f e r e n t samplings. Samples A r e f e r t o t h e f i r s t p e r i o d , samples B t o t h e second; time z e r o i s considered t h e beginning of every p e r i o d . The f i g u r e shows t h a t , d u r i n g t h e s e p e r i o d s of atmospheric s t a b i l i t y , t h e t o t a l a e r o s o l load, i n t h i s r u r a l area, i s considerably high. Water s o l u b l e f r a c c i o n The p e r c e n t a g e of water s o l u b l e m a t e r i a l of t h e samples i s given i n t a b l e 1 TABLE 1 Water s o l u b l e f r a c t i o n of t h e samples Sample

A1

A2

A3

A4

A5

B1

B2

B3

B4

Z of s o l u b l e m a t e r i a l

68

71

46

49

ne

75

64

52

ne

ne = n o t e v a l u a t e d The s o l u b l e f r a c t i o n i s v a r i a b l e i n t h e d i f f e r e n t samples, b u t i t i s , on average, n o t a b l y h i g h a s a l s o p o i n t e d o u t by C o r r a d i n i e t a l . i n a p r e v i o u s work on t h e a e r o s o l i n t h e Po Valley ( r e f . 4 ) . The amount of hygroscopic p a r t i c u l a t e p l a y s an important r o l e i n t h e v i s i b i l i t y d e g r a d a t i o n by h a z e , q u i t e a common c o n d i t i o n i n t h i s a r e a . On t h e o t h e r hand, w i n t e r r a d i a t i o n f o g s occur i n t h e Po Valley w i t h a r a t h e r unique frequency and t h i c k n e s s .

365

The chemical composition of the soluble fraction of the aerosol is summarized in table 2 , in wich the mean concentrations are reported relative to both periods A and B. TABLE 2

Chemical composition of the water soluble fraction of the aerosol Constituent

3

Concentration (ug/m ) Period A

Period B

K+

0.7

1.2

+ Na ++

4.1

6.8

Ca

2.9

3.2

Mg++

nm

0.2

NHI

6.9

6.7

14.3

20.7

-

so-4

-

(increasing traces-10.dlf-ing 4 the pe 10 3+ Fe

Mn

++

nm

=

24.0

0.06

0.09

0.04

0.04

not measured

The first set of ions are undoubtedly of soil origin. In fact, there is no sea ++ salt in the samples (Cl absent) and the relatively high concentration of Ca accounts for a typical calcareous soil. The SO- concentration in period B is con4 sistent with the data reported by Corradini et al. (ref. 4 1 , who performed measu-

+

rements during the same period of the year; on the other hand the NH concentration 4 results, in comparison, to be about half. The correctness of the analysis of the water soluble fraction was assessed by both specific conductance and ion exchange methods (ref. 5 ) . A s a matter of fact the ionic composition of the samples was unbalanced, namely the cation equivalents were always in excess with respect to the anions. It can be suggested that carbonates from soil lime are the missing ions in the anion/cation balance. Adjusting the ionic balance with CO- the calculated and measured conductance of the water 3' extract agree within the limit of analytical error.

366 Organic p a r t i c u l a t e The organic content of t h e a e r o s o l can roughly be represented by t h e e t h e r soluble fraction: 3 period A 16.4 pg/m ;

period B 16.1 pg/m

3

.

It i s however necessary t o i n v e s t i g a t e t h e composition of t h e organic f r a c t i o n ,

i n order t o e v a l u a t e t h e sources and chemical processes involved i n i t s formation.

Trace metals Only few t r a c e metals were measured, namely Mn and Fe, both of s o i l o r i g i n , and Pb a s a t r a c e r of v e h i c u l a r p o l l u t i o n . The r e s u l t s a r e reported i n t a b l e 3 . TABLE 3

T o t a l c o n c e n t r a t i o n of t r a c e metals i n t h e samples Element

Fe Mn Pb

3 Concentration (pg/m ) Period A

Period B

0.52 0.04 0.15

0.75 0.06 0.38

Comparing t h e d a t a r e l a t i v e t o t h e t o t a l c o n c e n t r a t i o n of Mn and Fe (both import a n t a s c a t a l y s e r s of SO2 oxidation i n t h e l i q u i d phase) and t h e i r s o l u b l e f r a c t i o n ( t a b l e Z),

i t can be seen t h a t t h e former, although p r e s e n t a s only a t e n t h of the

Fe c o n c e n t r a t i o n , it i s almost completely water s o l u b l e , whereas t h e l a t t e r i s s o l u b l e only t o a small e x t e n t . The p a r t i c u l a t e v e h i c u l a r p o l l u t i o n , evaluated from t h e lead content of t h e samples ( r e f . 6 ) , does not account f o r more than 1 % of t h e t o t a l a e r o s o l .

P r i n c i p a l c o n s t i t u e n t s of t h e a e r o s o l Summarizing t h e r e s u l t s obtained from t h e f i l t e r s a n a l y s i s , it can be shown t h a t t h e r e l e v a n t p a r t of t h e l o c a l a e r o s o l , i n t h i s a r e a of t h e Po Valley, i s c o n s t i t u t e d by water s o l u b l e n i t r a t e and s u l f a t e , and by organic m a t e r i a l , which together account f o r 50-70% by weight of t h e t o t a l p a r t i c u l a t e . While n i t r a t e s and s u l f a t e s a r e u s u a l l y regarded a s secondary products o r i g i n a t e d by atmospheric r e a c t i o n s ( r e f . 7),

organic a e r o s o l s can be o r i g i n a t e d both by r e a c t i v e organic

367 v a p o r s ( n a t u r a l and a n t h r o p o g e n i c ) and by s o i l c o n t r i b u t i o n by f e r t i l i z e r s . The ammonium i s n o t s u f f i c i e n t , on a molar b a s i s , t o c o m p l e t e l y " n e u t r a l i z e " s u l f a t e and n i t r a t e i o n s . T h e r e f o r e o n l y a p a r t of n i t r a t e s and s u l f a t e s e x i s t i n t h e form of ammonium s a l t s ; t h o s e remaining a r e i n t h e form of c a l c i u m and sodium salts.

CONCLUSIONS

The r e s u l t s of t h e p r e s e n t work, a s p r e v i o u s l y o u t l i n e d , a r e o n l y a f i r s t approach t o t h e s t u d y of t h e a e r o s o l i n t h e Po V a l l e y ; t h e s e p r e l i m i n a r y d a t a , however, a l l o w f o r some c o n s i d e r a t i o n s on f u t u r e work: a ) s i z e f r a c t i o n a t e d samplings of t h e p a r t i c u l a t e a p p e a r t o b e u s e f u l , i n o r d e r t o i n v e s t i g a t e t h e s i z e d i s t r i b u t i o n of t h e v a r i o u s chemical compounds; b ) a complete a n a l y s i s of t h e o r g a n i c e x t r a c t from t h e f i l t e r s c o u l d a l l o w f o r t h e i d e n t i f i c a t i o n of t h e s o u r c e s of o r g a n i c compounds and t h e e v a l u a t i o n of t h e atmospheric processes involved i n t h e i r formation; and NO i n t h e atmosphere, d u r i n g t h e a e r o s o l X 2 c o l l e c t i o n , would h e l p t o e x p l a i n t h e c h a r a c t e r i s t i c s of n i t r a t e and s u l f a t e proc ) a c o n t i n u o u s r e c o r d i n g of SO

d u c t i o n under d i f f e r e n t a t m o s p h e r i c c o n d i t i o n s . Moreover, a s t u d y on t h e a e r o s o l c i r c u l a t i o n would o b v i o u s l y c a l l f o r a widespread network of sampling p o i n t s , equipped w i t h m i c r o m e t e o r o l o g i c a l i n s t r u m e n t a t i o n . A t p r e s e n t t h e c o l l e c t i o n of p a r t i c u l a t e i n t h e sampling p o i n t h e r e d e s c r i b e d i s s t i l l c a r r i e d o u t i n o r d e r t o o b t a i n b e t t e r i n f o r m a t i o n s on the l o c a l a e r o s o l ,

a t l e a s t on a y e a r l y b a s i s ; a i r c r a f t samplings a t d i f f e r e n t l e v e l s a r e a l s o under way, i n o r d e r t o measure t h e v e r t i c a l p r o f i l e s of t h e a e r o s o l s .

ACKNOWLEDGEMENTS We a r e i n d e b t e d t o D r . F. Tampieri, D r . F . T r o m b e t t i and P r o f . P. Lanza f o r t h e i r h e l p f u l comments.

REFERENCES 1 F . T a m p i e r i , F. T r o m b e t t i and C .

2 3

4 5

S c a r a n i , Geophys. A s t r o p h y s . F l u i d Dynamics, 17(1981)97-112. J . N . Galloway and G . E . L i k e n s , T e l l u s , 30(1978)71-82. G. K e t s e r i d i s , J . Hahn, R. J a e n i c k e and C . Junge, Atmos. Environ. 10(1976)603-610 C . C o r r a d i n i , M. Dalfiume and B. F a v a l e , J . A e r o s o l S c i . 8(1977)231-236. S t a n d a r d Methods f o r t h e Examination of Water and Wastewater, 1 2 t h edn.,

368

A.P.H.A., New York, 1965, pp. 36-40. 6 G.M. Hidy and P.K. Mueller, in G.M. Hidy, P . K . and J.J. Wesolowski (Eds.), The Character and and Sons, New York, 1980, pp. 17-52. 7 G.M. Hidy and C.S. Burton, in G.M. Hidy, P.K. and J.J. Wesolowski (Eds.), The Character and and Sons, New York, 1980, p p . 385-433.

Mueller, D. Grosjean, B.R. Appel Origin of Smog Aerosols, Wiley Mueller, D. Grosjean, B.R. Appel Origin of Smog Aerosols, Wiley

369

COMPARISON OF REGIONAL AND TEMPORAL TRACE SUBSTANCE DISTRIBUTION I N BULK PRECIPITATION AND ATMOSPHERIC DUST

W. THOMAS L e h r s t u h l fur H y d r o l o g i e d e r U n i v e r s i t a t B a y r e u t h (G.F.R.)

ABSTRACT Mean c o n c e n t r a t i o n v a l u e s o f PAH ( l . l Z - b e n z o p e r y l e n e , anthene),

3.4-benzopyrene,

fluor-

t r a c e m e t a l s (Zn, Pb, Cu, Fe) and y-BHC i n b u l k p r e c i p i t a t i o n and a t -

mospheric p a r t i c u l a t e m a t t e r f r o m 20 sampling s t a t i o n s i n B a v a r i a (G.F.R.)

were

used f o r a m u l t i v a r i a t e r e g i o n a l c l a s s i f i c a t i o n o f a i r p o l l u t i o n s i t e s . For t h i s purpose a c l u s t e r a n a l y s i s w i t h Ward's a l g o r i t h m was chosen. The r e s u l t s o f t h e c l u s t e r a n a l y s i s show a number o f p o l l u t i o n c l a s s e s w i t h d i s t i n c t t r a c e substance p a t t e r n s .

A f u r t h e r c h a r a c t e r i s a t i o n o f these p o l l u t i o n c l a s s e s c o u l d be reached by anal y s i s o f temporal t r a c e substance c o n c e n t r a t i o n s i n t h e atmosphere.

INTRODUCTION F o r t h e r e g i o n a l comparison o f sampling s t a t i o n s r e l a t i v e t o t h e i r atmospheric t r a c e substance c o n t e n t s o f t e n a c l a s s i f i c a t i o n i n t o remote, r u r a l , and urban s i t e s i s used. T h i s k i n d o f c l a s s i f i c a t i o n r e s u l t s f r o m measured p o l l u t i o n l e v e l s a s w e l l as t h e l o c a t i o n o f sampling s t a t i o n s . E s p e c i a l l y when a l a r g e r number o f parameters a r e used f o r f o r m i n g atmospheric p o l l u t i o n types, i t i s n o t easy t o d e c i d e t o w h i c h t y p e a s t a t i o n c a n be a t t a c h e d . T h e r e f o r e t h e r e s u l t s f r o m d i f f e r e n t i n v e s t i g a t i o n s o f t e n a r e n o t d i r e c t l y comp a r a b l e because o t h e r c l a s s i f i c a t i o n c r i t e r i a were used. T a b l e 1 shows a p a r t i a l l i s t w i t h t r a c e substance c o n c e n t r a t i o n v a l u e s from some p o l l u t i o n c l a s s e s . I t can be seen t h a t o n l y t r a c e

metal

- or

PAH-con-

t e n t s were measured a t e v e r y sampling s i t e so t h a t i t i s necessary t o combine t h e d a t a of d i f f e r e n t a u t h o r s t o c l a s s i f y p o l l u t i o n t y p e s . F u r t h e r , r e g i o n a l comparison o f p o l l u t i o n d a t a i s made more d i f f i c u l t when t h e c l a s s i f i c a t i o n i s done r e l a t i v e so s i n g l e o r mean v a l u e s a l o n e w i t h o u t showing t h e temporal d i s t r i b u t i o n p a t t e r n by means o f s t a n d a r d d e v i a t i o n o r o t h e r parameters.

370

TABLE 1 Comparison of some atmospheric t r a c e substance concentrations from d i f f e r e n t sampling s i t e s ( i n ng . m-3)

Sampling s i t e

Trace substance

(Reference)

Zn

remote s i t e s

rural s i t e s urban s i t e s

Pb

Cu

Fe

8.0

1.6 0.3

70 32

(1) 5.0

(2) (3) (4) (5) (6) (7) (8) (9) (10)

(7)

1.7

-

-

0.3-27 0.1-64 33-140 30-150

-

-

0.1-10 3.4-220 6-10 59-310

1.12-benzo- 3.4-benzo- f l u o r perylene pyrene anthene

0.1-2.4 0.1

-

0.3-0.8 2800 213 2800 145-298 499-518 18-25 1231-2467 4.4-10.5 -

-

-

-

0.1-2.4 0.1

-

-

0.1-6.3 0.3 0.8-5.3

-

0.7-1.7 0.8-29.5

The aim of t h i s i n v e s t i g a t i o n i s to present a c l a s s i f i c a t i o n method f o r sampling s t a t i o n s according t o t h e i r t r a c e substance concentrations ( i n t h i s case PAH, t r a c e metals and y-BHC i n bulk p r e c i p i t a t i o n and atmospheric d u s t p a r t i c l e s ) using mu1 t i v a r i a t e c l u s t e r i n g techniques. This kind of a n a l y s i s computes groups ( p o l l u t i o n c l a s s e s ) of sampling s t a t i o n s with similar atmospheric pollution leve l s , taking a l l parameters into consideration.

MATERIAL AND METHODS Sampling s t a t i o n s The l o c a t i o n of the 20 sampling s t a t i o n s i n Bavaria, G.F.R., i s shown in Fig. 1. The s t a t i o n s show a l a r g e regional variance with locations i n t h e northern and e a s t e r n paleozoic highlands (1, 2, 3, 4, 15), i n the meso- and neozoic lowlands (5-14, 16-18), as well as i n t h e Alps (19, 2 0 ) . The surrounding anthropogenic area ranges from woodland (2, 4, 6, 9, 14, 15, 19) and a g r i c u l t u r a l areas (8, 12, 13, 17) t o suburban l o c a t i o n s (1, 3, 5, 7, 16, 18). 2 Each s t a t i o n was equipped with t o t a l i s a t o r s (funnel = 855 cm ) f o r taking bulk p r e c i p i t a t i o n samples ( r e f . 11). Atmospheric p a r t i c u l a t e matter was sampled w i t h low-volume samplers ( r e f . 12) using c e l l u l o s e - n i t r a t e f i l t e r s (0.45 pm). This f i l t e r material was preferred because of low blancs e s p e c i a l l y f o r t r a c e metals. D u r i n g each sampling period 100-150 m 3 of a i r were f i l t e r e d .

371

F i g . 1. Sampling s t a t i o n s f o r b u l k p r e c i p i t a t i o n and atmospheric p a r t i c u l a t e m a t t e r i n B a v a r i a , G.F.R.

1 2 3 4 5 6 7

= Hof = = = =

= =

8 = 9 = 10 =

Hohenberg/Eger Arzberg Oc hsen ko p f /F ic h t e 1ge b . Bayreuth Veldensteiner F o r s t Nuremberg/zoological garden Schwabach-Kammerstein Claffheim Greding

11 12 13 14 15 16 17 18 19 20

= Kelheim

= Manching = Moosburg/Isar = Ebersberger F o r s t = Brotjacklriegel/Bayer.

Wald

= Munich = Grunwald = A1 t e n m a r k t / A l z = Grassau/Chiemsee = Bad R e i c h e n h a l l

Sampling p e r i o d s

A t a l l t h e s t a t i o n s samples of b u l k p r e c i p i t a t i o n and atmospheric p a r t i c l e s were t a k e n c o n t i n u o u s l y f r o m F e b r u a r y t o September 1980 w i t h a l l sample m a t e r i a l s b e i n g t a k e n t o t h e l a b o r a t o r y i n t h e same 3-week p e r i o d s . Mean c o n c e n t r a t i o n v a l ues f o r a l l t r a c e substances c o u l d t h e r e f o r e be computed f r o m t h e d a t a o f 13 sampl i n g p e r i o d s . Chemical a n a l y s i s P r e c i p i t a t i o n samples were t a k e n t o t h e l a b o r a t o r y u s i n g 2 1 g l a s s b o t t l e s

372

( f o r o r g a n i c t r a c e substance a n a l y s i s ) and 250 m l p o l y e t h y l e n e b o t t l e s ( f o r t r a c e metal a n a l y s i s ) .

PAH (1.12-benzoperylene,

3.4-benzopyrene,

f l u o r a n t h e n e ) were determined by

h i g h performance t h i n - l a y e r chromatography ( r e f . 12), y-BHC by gas-1 i q u i d c h r o matography u s i n g c a p i l l a r y columns ( r e f . 11). The a n a l y s i s o f t h e t r a c e m e t a l s Zn, Pb, and Cu was c a r r i e d o u t by a n o d i c - s t r i p p i n g voltammetry; Fe was analysed by AAS ( r e f . 11). F o r t r a c e substance a n a l y s i s o f atmospheric p a r t i c u l a t e m a t t e r t h e f i l t e r s were d i v i d e d i n t o two equal p a r t s . One p a r t was d i g e s t e d w i t h n i t r i c a c i d ( s u p r a pure grade) f o r t r a c e metal analysis, methane f o r PAH-analysis.

t h e o t h e r h a l f was e x t r a c t e d u s i n g d i c h l o r o -

B o t h methods a r e d e s c r i b e d i n d e t a i l i n r e f . 13.

C1 u s t e r a n a l y s i s C l u s t e r a n a l y s i s belongs t o t h e group o f mu1 t i v a r i a t e s t a t i s t i c a l methods and makes i t p o s s i b l e t o group measuring s t a t i o n s r e l a t i v e t o t h e i r d a t a on two o r more v a r i a b l e s , i n o u r case atmospheric p o l l u t a n t s . Grouping o f s t a t i o n s f o l l o w s two c r i t e r i a : 1) t o g e t m i n i m a l d i s t a n c e o f v a l u e s between s t a t i o n s w i t h i n a g r o u p and 2) t o g e t maximal d i s t a n c e o f v a l u e s between t h e groups. The measure used t o group s t a t i o n s i s c a l l e d t h e ' e r r o r i n d e x ' . A c c o r d i n g t o t h e purpose o f t h e i n v e s t i g a t i o n , i t i s i m p o r t a n t t o d e c i d e which e r r o r index i s r e l e v a n t ( r e f . 14). F o r t h i s i n v e s t i g a t i o n t h e e r r o r i n d e x f r o m Ward ( r e f . 1 5 ) w h i c h i s based on t h e a b s o l u t e d i s t a n c e s o f t h e measured v a l u e s ( e q u a t i o n 1) was used t o d e t e r m i n e atmospheric p o l l u t i o n c l a s s e s . n

with n

= number o f measured v a r i a b l e s

= data o f .th-group j J x . =~ d a t a o f k t h - g r o u p .

x.

The c l u s t e r a n a l y s i s was computed w i t h t h e program YGROUP ( r e f . 1 6 ) . To a v o i d mathematical b i a s t h e r e should be no h i g h c o r r e l a t i o n c o e f f i c i a n t s between t h e measured v a r i a b l es.

RESULTS Atmospheric p o l l u t i o n c l a s s e s

-

regional d i s t r i b u t i o n

P r i o r t o t h e c l u s t e r a n a l y s i s a c o r r e l a t i o n a n a l y s i s w i t h mean c o n c e n t r a t i o n v a l u e s o f a l l measured v a r i a b l e s and s t a t i o n s was c a r r i e d o u t . S i g n i f i c a n t c o r r e l a t i o n c o e f f i c i a n t s c o u l d o n l y be f o u n d between t h e t h r e e PAh-substances, each

373

o c c u r i n g i n b u l k p r e c i p i t a t i o n and a t m o s p h e r i c p a r t i c u l a t e m a t t e r . As p o i n t e d o u t b e f o r e , i n t e r c o r r e l a t i o n can i n f l u e n c e r e s u l t s , b u t comparison o f two computed c l u s t e r analyses, one w i t h a l l PAH-substances and one w i t h f l u o r anthene alone, showed t h a t t h e r e s u l t i n g p o l l u t i o n c l a s s e s were i n b o t h cases absolutly identical. Thus t h e r e s u l t s o f t h e p r e s e n t e d c l a s s i f i c a t i o n i n t e g r a t e t h e d a t a o f a l l 15 measured v a r i a b l e s ( T a b l e s 2a and 2b). The f i r s t p o l l u t i o n c l a s s , c o n s i s t i n g o f 8 s t a t i o n s , i s c h a r a c t e r i s e d by t h e l o w e s t mean c o n c e n t r a t i o n v a l u e s o f t r a c e m e t a l s and PAH, i n b o t h p r e c i p i t a t i o n and d u s t . T h i s g r o u p shows p a r t l y e l e v a t e d y-BHC ( L i n d a n e ) v a l u e s which r e s u l t from a g r i c u l t u r a l s t a t i o n s , as t h e c l a s s i n t e g r a t e s them w i t h f o r e s t e d s i t e s . Lower c o n c e n t r a t i o n s , comparable w i t h 'remote s i t e s ' , were n o t found a t t h e measuring stations. TABLE 2a

(x),

Atmospheric p o l l u t i o n c l a s s e s r e s u l t i n g f r o m c l u s t e r - a n a l y s i s - mean v a l u e s m i n i m a l and maximal v a l u e s o f t r a c e substance c o n c e n t r a t i o n s i n p a r t i c u l a t e m a t t e r Class

T r a c e substance

(Sampling s t a t i o n )

I (2,6,12,13,14, 17,19,20)

I 1 (4,15)

I 1 1 (1,3,5,9,11)

I V (8,10,18)

v

Zn

Pb

Cu

Fe

1.12-benzop e r y l ene

135 x m i n 102 x max 208

59 35 73

15 8 26

221 96 384

0.11 0.06 0.16

0.03 0:02 0'.07

0.55 0.30 1.01

57 55 59

23 16 30

199 150 247

0.10 0.10 0.10

0.03 0.03 0.03

0.59 0.38 0.79

107 63 191

30 15 49

361 196 518

0.19 0.16 0.24

0.05 0.02 0.11

0.72 0.44 1.29

151 80 x m i n 109 55 x max 194 115

15 10 18

208 187 224

0.13 0.13 0.14

0.04 0.03 0.04

0.62 0.59 0.66

x 222

116

18

282

0.22

0.20

3.11

x 294

295

45

527

0.17

0.08

1.23

x

x

259 x m i n 245 x max 272

x

243 x m i n 171 x max 329

x

(7)

V I (16) ( a l l v a l u e s i n ng

m

-3

3.4-benzo- f l u o r a n t h e n e pyrene

)

Two measuring s t a t i o n s ( 4 and 15) r e p r e s e n t p o l l u t i o n c l a s s 11. T h i s c l a s s i s d i s t i n g u i s h e d f r o m I because o f e l e v a t e d Z n - c o n c e n t r a t i o n s i n p r e c i p i t a t i o n and p a r t i c u l a t e m a t t e r , and PAH i n p r e c i p i t a t i o n . While P A H - p o l l u t i o n a t t h e s e s t a t i o n s , w h i c h b o t h l i e i n f u l l y f o r e s t e d a r e a s on t h e t o p o f mountain highlands, i s caused by a n e a r b y i n c i n e r a t o r a t s t a t i o n 4 (a T V - s t a t i o n ) ,

f o r t h e Zn-con-

374 t e n t a n o r i g i n f r o m s u b s o i l ( g r a n i t i c r o c k s a t b o t h s t a t i o n s ) can b e suspected. E s p e c i a l l y t h e Zn-content i n p r e c i p i t a t i o n t h a t i n t e g r a t e c o a r s e r d u s t p a r t i c l e s as d r y d e p o s i t s a r e e x t r a o r d i n a r i l y h i g h f o r a f o r e s t s t a t i o n . TABLE 2b

(x),

Atmospheric p o l l u t i o n c l a s s e s r e s u l t i n g from c l u s t e r - a n a l y s i s - mean v a l u e s m i n i m a l and maximal v a l u e s o f t r a c e substance c o n c e n t r a t i o n s i n b u l k p r e c i p i t a t i o n Class

T r a c e substance

(Sampling s t a t i o n )

I (2,6,12,13,14

Zn

-

Pb

Cu

Fe 1.12-benzoperylene

3.4-benzopyrene

f l u o r - y-HCH anthene

8.2 6.6 9.8

4.4 3.3 5.3

21.4 19.6 15.3 6.9 35.3 28.5

71 47 94

12.6 8.3 16.8

6.9 3.5 10.3

55.3 17.5 28.6 12.8 82.0 22.1

x min x max

64 19 10 178 41 13 4 82 86 25 17 356

14.7 9.8 21.5

5.9 3.O 8.0

39.2 11.5 17.7 6.9 64.4 16.1

x x min x max

54 22 49 17 63 25

4 101 3 98 6 103

13.4 12.3 15.1

9.6 7.5 12.9

32.2 27.4 25.0 19.6 38.4 34.8

v (7)

x

94 19

8 134

20.4

14.3

58.9 21.4

V I (16)

x

59 41 17 250

9.3

5.2

17,19,20)

x x rnin x max

39 13 28 9 59 16

x 132

I 1 (4,15)

13

x min 123 8 x max 140 17

x

I11 (1,3,5,9,11)

I V (8,10,18)

( t r a c e m e t a l s i n 1-19

*

6 84 3 61 9 151 6 4 8

1 - I ; o r g a n i c t r a c e substances i n ng

.

51.7

7.7

1-I)

T h i s a s p e c t o f geogenic p o l l u t i o n i s a l s o c o n f i r m e d by comparison w i t h p o l l u t i o n c l a s s 111. T h i s c l a s s c o n s i s t s o f measuring s t a t i o n s w i t h a n t h r o p o g e n i c i n f l u e n c e o f a t m o s p h e r i c t r a c e substance c o n c e n t r a t i o n s . The s t a t i o n s a r e s i t u a t e d n e x t t o small c i t i e s and c o u l d be c a l l e d suburban s i t e s . Here i n a d d i t i o n t o Zn a l s o t h e Pb, Cu, and Fe l e v e l s , as w e l l as PAH i n d u s t , a r e e l e v a t e d . P e s t i c i d e values a r e lower than i n a g r i c u l t u r a l areas. Class I V shows s i m i l a r t r a c e m e t a l and PAH d a t a a s 111 b u t i s separated from i t because o f h i g h e r y-BHC c o n c e n t r a t i o n s . How atmospheric t r a n s p o r t f r o m nearby a g r i c u l t u r a l areas o r p o l l u t i o n f r o m chemical i n d u s t r y , s t o r a g e e t c . causes t h e s e p e s t i c i d e l e v e l s should be t h e s u b j e c t o f f u r t h e r i n v e s t i g a t i o n s . The ' c l a s s e s ' V and V I each c o n s i s t o f one measuring s t a t i o n o n l y . W h i l e s t a t i o n 7 ( c l a s s V ) was l o c a t e d i n t h e z o o l o g i c a l garden o f t h e c i t y of Nuremberg, t h a t i s a suburban s i t e , s t a t i o n 16 ( c l a s s V I ) i s a downtown s t a t i o n . F o r c l a s s V i n d u s t r i a l i n f l u e n c e t o a t m o s p h e r i c q u a l i t y i s dominant whereas f o r V I t h e d i -

r e c t exposure t o c a r t r a f f i c i s c h a r a c t e r i s t i c .

375

A d i s c r i m i n a t i o n between t h e s e two urban p o l l u t i o n c l a s s e s was made by t h e PAH values (Table 2). The r e s u l t s o f c l u s t e r a n a l y s i s show t h a t t h e l a r g e number o f p o s s i b l e combin a t i o n s o f t r a c e substance v a r i a b l e s t o f o r m p o l l u t i o n c l a s s e s can be d e t e c t e d and grouped by t h i s method. I n a d d i t i o n t o a d i f f e r e n t i a t i o n between t r a c e metal and PAH p o l l u t i o n o f s i m i l a r s t a t i o n s , a c h a r a c t e r i s a t i o n by comparing s i n g l e substances o f t h e s e two groups o f p o l l u t a n t s i s a l s o p o s s i b l e . Furthermore, a p e s t i c i d e v a r i a b l e h e l p s t o d e t e c t t h e i n f l u e n c e o f a g r i c u l t u r e on a i r q u a l i t y . The c o m b i n a t i o n o f numerous i n f l u e n c i n g f a c t o r s t o a i r q u a l i t y cause r e l a t i v e l y h i g h v a r i a t i o n s o f data w i t h i n a c l u s t e r e d c l a s s . Temporal t r a c e substance d i s t r i b u t i o n o f some atmospheric p o l l u t i o n c l a s s e s Temporal v a r i a t i o n s of a t m o s p h e r i c t r a c e substance c o n c e n t r a t i o n s r e s u l t from a number o f v a r i a b l e s . I n a d d i t i o n t o emission-dependent parameters, as f o r examp l e i s known f o r PAH by h e a t i n g i n w i n t e r , m e t e o r o l o g i c a l parameters a l s o i n f l u ence i m m i s s i o n v a l u e s . F o r p o l l u t a n t v a l u e s i n b u l k p r e c i p i t a t i o n t h e amount o f r a i n , r a i n f a l l i n t e n s i t y and d r o p l e t s i z e s a r e i n f l u e n c i n g parameters. The d i s t r i b u t i o n between wet- and d r y f a l l i s i n a d d i t i o n t o o t h e r v a r i a b l e s dependent on t h e degree o f a n t h r o p o g e n i c p o l l u t i o n ( r e f . 11).

-10

--

50-

12

30-

10-

1

'

F

'

M

'

A

' M ' 1980

J

'

J

'

A

'

S

F i g . 2. Temporal d i s t r i b u t i o n o f Pb i n b u l k p r e c i p i t a t i o n ( i n ug measuring s t a t i o n s 7, 10 and 1 2 .

.

1-l)

-

One method o f d e t e c t i n g t h e temporal s t r u c t u r e o f data i s t h e comparison o f mean v a l u e s

(x) and s t a n d a r d d e v i a t i o n s

( s ) o f a d a t a s e t . Here o n l y few aspects

o f s - a n a l y s i s can be p o i n t e d o u t . Lowest s - v a l u e s o f t r a c e m e t a l s c o u l d be computed f o r Pb, i n b o t h p r e c i p i t a t i o n and p a r t i c u l a t e m a t t e r . A p a r t f r o m s t a t i o n s 10 and 18 w h i c h belong t o p o l l u t i o n c l a s s I V , t h e r e l a t i o n s between

1.80 and 2.83 (10 = 1.07; 18

x and s f o r

Pb ( b u l k p r e c i p i t a t i o n ) l i e between

1.25). As F i g . 2 i n d i c a t e s , t h e Pb d i s t r i b u t i o n from Jan. t o Sept. 1980 showed r e l a t i v e l y equal v a l u e s a t t h e s t a t i o n s 7 and 12. As mentioned b e f o r e , t h e Pb l e v e l s o f s t a t i o n 10 show h i g h e r temporal v a r i a t i o n . =

376 A t t h i s highway-near s t a t i o n t h e amount o f d r y d e p o s i t i o n and so t h e i n f l u e n c e

o f t h e amount o f p r e c i p i t a t i o n a r e h i g h e r .

1

-4

-...........1-.._ :

4 .O

I

V

I

\

\ I'\

2.0

..........

' 0

1980

F i g . 3. Tern o r a l d i s t r i b u t i o n o f f l u o r a n t h e n e i n atmospheric p a r t i c u l a t e m a t t e r ( i n ng * m-g) - measuring s t a t i o n s 4, 7 and 19.

- 1

-

- 8

50-

_J

'

F

'

M

'

A

' M J 1980

J

A

s

F i g . 4. Temporal d i s t r i b u t i o n o f y-BHC i n b u l k p r e c i p i t a t i o n ( i n ng

.

1-I)

Another t y p e o f temporal d i s t r i b u t i o n i s shown by f l u o r a n t h e n e ( F i g . 3 ) and t h e c h l o r i n a t e d p e s t i c i d e y-BHC ( F i g . 4). Here t h e e m i s s i o n - p e r i o d o c i t y dominates a t m o s p h e r i c t r a c e substance c o n c e n t r a t i o n s . PAH show h i g h e s t l e v e l s i n w i n t e r and

311 e a r l y s p r i n g caused by h e a t i n g a c t i v i t i e s w i t h d i f f e r e n t a b s o l u t e v a l u e s due t o t h e above-discussed p o l l u t i o n c l a s s e s . I n comparison, y-BHC l e v e l s i n t h e atmosphere a r e h i g h e s t i n s p r i n g and summer because o f a p p l i c a t i o n i n a g r i c u l t u r e and h i g h e r m o b i l i s a t i o n r a t e s f r o m s o i l and v e g e t a t i o n r e l a t i v e t o atmospheric temperatures. W h i l e PAH and y-BHC a t n e a r l y a l l s t a t i o n s show s i m i l a r temporal d i s t r i b u t i o n p a t t e r n s w i t h d i f f e r e n t absol U t e c o n c e n t r a t i o n v a l u e s r e l a t i v e t o t h e degree o f atmospheric p o l l u t i o n , f o r Zn ( F i g . 5) one can r e c o g n i z e d i f f e r e n t p o l l u t i o n t y pes. C i t y - n e a r s t a t i o n s (1 and 7 ) show h i g h e s t Z n - l e v e l s i n b u l k p r e c i p i t a t i o n i n l a t e w i n t e r which decrease r a p i d l y t o r e a c h minimum v a l u e s i n summer. I n c o n t r a s t a t s t a t i o n 4 ( p o l l u t i o n c l a s s 11) s i n g l e h i g h Zn-values were measured a t a l l seasons. A t t h i s s t a t i o n where h i g h Z n - p o l l u t i o n f r o m s u b s o i l was suggested t o cause atmospheric Zn-levels,

t h e h i g h e r w i n t e r c o n c e n t r a t i o n s f o r t h i s metal a r e super-

posed by m e t e o r o l o g i c a l parameters i n f l u e n c i n g s o i l p a r t i c l e u p t a k e i n t o t h e a t mos p h e r e .

F i g . 5. Temporal d i s t r i b u t i o n o f Zn i n b u l k p r e c i p i t a t i o n ( i n Fig measuring s t a t i o n s 1, 4 and 7

.

1-l)

-

CONCL US I O N S C l u s t e r a n a l y s i s has been shown t o be a u s e f u l method f o r a m u l t i v a r i a t e and o b j e c t i v e c l a s s i f i c a t i o n o f measuring s t a t i o n s due t o mean atmospheric t r a c e subs t a n c e c o n c e n t r a t i o n s . The r e s u l t s i n d i c a t e t h a t 20 s t a t i o n s can be grouped i n t o

6 p o l l u t i o n c l a s s e s . I n a d d i t i o n t o c l a s s e s w i t h d i f f e r e n t k i n d s o f anthropogenic emissions, Zn p o l l u t i o n f r o m s u b s o i l as w e l l as e l e v a t e d p e s t i c i d e l e v e l s a t r u r a l l o c a t i o n s c o u l d b e found.

318

As mean v a l u e s i n t e g r a t e r a t h e r l a r g e v a r i a t i o n s i n p o l l u t i o n d a t a w i t h i n t h e t i m e o f i n v e s t i g a t i o n , a c l a s s i f i c a t i o n s h o u l d a1 so i n c l u d e temporal t r a c e substance d i s t r i b u t i o n . Next t o p o l l u t a n t s w i t h n e a r l y e q u a l l y d i s t r i b u t e d values (as Pb f r o m t r a f f i c ) o t h e r s w i t h d i s t i n c t temporal d i s t r i b u t i o n s were found. PAH's show maximal a t m o s p h e r i c c o n c e n t r a t i o n s d u r i n g w i n t e r , y-BHC c o n t e n t i n b u l k p r e c i p i t a t i o n i n c r e a s e s d u r i n g summer. Thus, b o t h r e g i o n a l and temporal d i s t r i b u t i o n o f atmospheric t r a c e p o l l u t a n t s a r e necessary f o r a d i f f e r e n t i a t e d and complete c h a r a c t e r i s a t i o n o f measuring s t a tions.

ACKNOWLEDGMENTS The a u t h o r would l i k e t o t h a n k t h e ' B a y e r i s c h e s Landesamt f u r Umweltschutz' f o r f i n a n c i a l s u p p o r t o f t h e i n v e s t i g a t i o n , Miss M. Tyzenhouse f o r r e v i e w i n g and Mrs. E. Misch f o r t y p i n g t h e paper.

REFERENCES

1 A. Semb, D e p o s i t i o n o f t r a c e elements f r o m t h e atmosphere i n Norway, SNSF-proj e c t , FR 13/78, Oslo, 1978, p. 28. 2 N. Z. Heidam, Atmospheric Environment, 15 (1981) 1421-1427. 3 A. B j o r s e t h and G. Lunde, Atmospheric Environment, 13 (1979) 45-53. 4 J . M. Daisey, R. J . McCaffrey and R. A. G a l l a g h e r , Atmospheric Environment, 15 (1981) 1353-1363. 5 R. A. Duce, G. L . Hoffmann and W. H. Z o l l e r , Science, 187 (1975) 59-61. 6 P. A. Cawse, A s u r v e y o f atmospheric t r a c e elements i n t h e UK, AERE 7669, Her M a j e s t y ' s S t a t i o n e r y O f f . , London, 1974, p. 95. 7 G. Broddin, W. C a u t r e e l s and K. van Cauwenberqhe, Atmospheric Environment, 14 (1980) 895-910. 8 K. A. Rahn, Study o f n a t i o n a l a i r p o l l u t i o n by combustion. Progress R e p o r t I n s t . N u c l . Wet., Gent, 1972, D . 312. 9 H. A. Trindade, W. C. P f e i f f e r ; H. Condres and C . L. C o s t a - R i b e i r o , E n v i r o n mental Science and Technology, 15 (1981) 84-89. 10 M. Katz, T. Sahuma and A . Ho, Environmental Science and Technology, 12 (1978) 909-915. 11 W. Thomas, Deutsche Gewasserkundl i c h e M i t t e i l u n g e n , 25 (1981) 120-129. 12 R. Herrmann, Catena, 5 (1978) 165-175. 13 W . Thomas, B a y r e u t h e r G e o w i s s e n s c h a f t l i c h e A r b e i t e n , 3 (1981) p. 144. 14 W. Symader and W. Thomas, Catena, 5 (1978) 131-144. 15 J . H. Ward, J . Am. S t a t i s t . Ass., 58 (1963) 236-244. 16 D. Veldman, F o r t r a n Programming f o r t h e B e h a v i o r a l Sciences. H o l t , R i n e h a r t & Winston, New York, 1967, p. 406.

379

THE CHFMISTRY OF PRECIPITATION IN RELATION TO PRECIPITATION TYPE

J. A. WAF?.l3UMON

Amspheric Sciences Center, Desert Research Institute, Reno, Nevada (U.S.A.)

ABSTRACT

Collections have been made of several types of wet deposition and of aerosols in various particle size ranges. The chemical canposition of the precipitation changes significantly from one precipitation type to another. The forms of deposition, diffusionally-gram ice for exqle, canpared with accretionally-grown ice, appear to be important factors controlling the concentrations and ratios of the several elements which have k e n measured. The aerosol samples show significant changes in chemical carpsition with particle size, consistent with other observers' results. It is hypothesized that these changes in aerosol chemistry and those of the wet deposition are related, and that t h i s information, canbined with the theoretically supported processes of nucleation, Brownian capture, phoretic processes and impaction, provide a better insight to the physical processes involved in the r m v a l of chemical impurities fran the atmosphere. ~

~~~

~

SCIENTIFIC BACKGRWND The chemical carpsition of precipitation as it relates to precipitation grayth processes has not been extensively investigated. Takahashi (1963) has studied the romposition of snow in relation to ice crystal habit. His results showed that the elemental content of snow flakes varied with the crystal habit. The concentrations of Na, C1 and MI4 for example, were l m s t in colmar crystals, whereas the concentration of MI4 was greatest in denckitic types. Additionally, he found that the C1 and Na contents were greatest in graupel. His investigations also discussed possible origins of the chemical impurities by looking at elemental ratios and comparing them with crustal and sea water values. The interpretation of his results was ccmplicated by apparent contamination fran industrial pollutants. The implication of his results, however, appears to be that the predaninant ice g r m t h mechanism (diffusion and accretion) which vary in degree for the different crystal structures, are in saw way related to the differences in chemical capsition.

380

W e n t studies of dew chemistry also show that the deposition of chemical substances from the atmosphere by this fonn of precipitation is different f r m that due to rain at the sam location. BrimblecQnbe and Todd (1977) have provided results of measurments of the ptassium and sodium camposition of dew collected in England. They found that the potassium-sodium ratios are higher than those normally found in rain by a factor of 20, using values fran Junge (1963). This apparent potassium enrichment in dew has also been observed by Yaalon and Ganor (1968), who investigated the chemical canpsition of dew and dry fallout in Jerusalem, Israel. T h e enrichment factor for potassium was about three. Yaalon and Ganor also showed that the dew was richer in Ca, HC03 and SO4 than rainfall at the sane site. It was also found that the relative proportions of the salts in the dew showed. very little variation, and although the origins of the higher calcium and bicarbonate were able to be identified, the mechanisms by which dew can have greater enrichments than precipitation (when referenced to sodium) were not understood. It has been suggested that the fine dust particles may have acted as condensation nuclei for dew formation resulting in a disproportionally higher ccmpnent of these substances in the dew compared with rainfall. Since the chemical composition of wet depsition and that of the amspheric aerosol should be related, it is of interest to review briefly, the results of recent invetigations of aerosols of various origins and collected by cascade impaction methods so that chemical canpsition can be studied as a function of particle size. Duce, Woodcock and Wyers (1967) studied variations of ion ratios with size amng particles in ocean air in Hawaii. The I/C1 ratio increased with decrease in particle size. The Br/C1 ratio s h d a minimm at intenrediate particle sizes. They also found that these ratios were significantly greater than sea water values and that most of the iodine mass was on particles around 0.6 p m radius, whereas the chlorine and bromine masses maximized on particles of radii between 1.25 and 2.5pm. Barker and Zeitlin (1972) in Hawaii found that the aerosols were enriched in most metals relative to sodim, and to the metal to scdim ratio found i n sea water. Generally, enrichments were greatest on the snaller aerosols approaching Aitken size (
381

the other hand, was found to be enriched relative t o Fe w i t h increasing particle

s i z e , from a c r u s t a l value i n the m l l e s t particles t o about six times this value for particles >4pm diameter. Page, Elseewi and Straughan (1979) obtained r e s u l t s of a similar nature f o r the chemical camposition of fly-ash f r m a coal-fired power plant.

In a study of

the trace element ccenposition of the ash a s a function of particle s i z e they found t h a t the p r o p r t i o n s of P, Zn, I%,

Cu, N i , Cd, Pb, Na and S increased with de-

crease i n particle size, w h i l e Ca, Fe, Mg t o 141-1 remained relatively constant. Their r e s u l t s showed t h a t particulates emitted into the atmosphere by coal-fired power stations can be considerably enriched i n trace elements.

Once a i r b r n e ,

they are available t o be inmrporated into wet deposition. OBSERVATION PRGRW

AND IWI'HCKX~IKY

The Ross Ice Shelf, Antarctica, was chosen as the region f o r this study of atmospheric chemical processes because it is a large, f l a t expanse of i c e and snow approximately 800 Km i n width and extending up t o 800 Km f r m the i c e front t o the Transantarctic kBuntains along i t s southern bundary. void of orcgraphic features.

I t is essentially de-

Cyclonic storm systems originating i n the southern

oceans often m e i n across the Shelf, penetrating t o the muntains and beyond. These storms and other large scale a i r mass m t i o n s , carry aerosols, particulates and hydrmetexs inland, enabling them to precipitate onto the Shelf. The snowpack was intensively sampled i n p i t s of approximately 2 m depth a t three sites, 70 Km t o 470 Km frm the ocean. Workers used p l a s t i c coated paper cleanr m coveralls while sampling t o ensure that samples =re free of contamination. Sheets of f i n e mesh nylon net w e used t o c o l l e c t samples of f a l l i n g snow during storms, ard diffusionally-grown ice and hoar during periods of supercooled fog a t the same sites.

The nylon nets on which the precipitation w a s collected,

were cleaned by a series of leachings i n analytical grade solutions of n i t r i c acid, This treatToent was followed by several rinses and leachings in doublyd i s t i l l e d , deionized w a t e r . All the e q u i p e n t was then sealed i n polyethylene bags f o r transport t o the Antarctic.

All sample preparation and analyses were conducted in the c l e a n r m of the Elemental analyses were made using flameless atanic absorption techniques. Repeated blanks and matrix standards were used to establ i s h reference levels. Excellent consistency and statistical control over results

Desert Research Institute.

o c m e d by first conducting five analyses on each of four standards over the range of experimental values anticipated, follawed by the samples, the analyses The spectrophotaneter was

of which were repeated five times f o r each e l m t .

cycled through drying and analysis rrodes i n an exact t h i n g sequence to ensure reproducibility. !the analytical procedures produced concentration values with

382

uncertainties of 5 - 10%. Aerosol filter samples were analyzed by proton-excitation methods using a 2 &V van der Graaf generator. RESULTS Aerosol Chemical Catimsition This elemental enrichment has also k e n observed in aerosols by Warburton in the pristine environment of Antarctica. The chemistry of natural aerosols collected on Nuclepore filters of different pore sizes ( 0 . 2 u m and 0.08 pm) was investigated. Fe, Br and MI showed increased concentrations on the mailer particles whereas S, K, Ca, Sr and Pb showed decreases (see Table 1).

TABLE 1 Natural Aeroso1sI Antarctica ~ e a nass

El-t

0 . 2 u m Pore Size 2096

S K

ca

120 75

Fe Br Sr Pb

45 4 11

Mn

0

19

ng 0.08pm Pore Size 1586 56 42 66 70

2 6 3

'!"nesemeasurerents were made on the Ross Ice Shelf (latitude 8OoS) , where during the same period, fresh ice-phase precipitation was occurring from time to time. Three different types of ice-phase precipitation were collected; supercooled fog depositicm, fresh snadall, and the snow and firn constituting the upper layers acmlated snawpack. Eslhanced Dxiclnnent of Heavy bktals i n Fresh IcePhase Precipitation We define enriclrment by the factor: (X/R) Atnospheric (X/R) Sea where R = Na for marine elerrwts, and R = Fe for crustal elements; X(sea) is the mass of elerrent X in (sub-surface) sea water and X(atm0spheric) is the mass of the smne el-t in the sample d u m (rain,snow, aerosol, etc.); similar definitions hold for the crustal c v i s o n s . Table 2 shows the results obtained from the accumulated firn, and Table 3 the results of analyses of the fog deposition and the fresh snowfall. Firstly, in E

=

Table 3 w note in lines 3 and 4 that the E(Ag) values for fog deposition at C-7 and Bc sites are four and ten times greater respectively than those for the firn samples at the same locations, given in Table 2. This is not fully explained by changes in sodium.

383

TABLE 2 Silver :ar,ganeseand Iron Wichments in Accumulated Snowpack Location and Distance from open Sea Sea Water Crustal C-7 (70 Km) RIC (220 Ial) Bc (470 Km) F-9 (600 Km)

Mean

OBSERVED CYLCUTATIOIG da ppb ~ c ppb i Mn ppb

lo7 2.6~10 162 117 78 32

2x10-1 80 8~10-~ 1.5~101: 1.5xlg 8x10-

OBSERVED RATIOS Location and Distance Aq/Na Mn/N a Fe/Na from Open Sea Sea Water Mean crustal C-7 (70 Km) RTC (220 Km) Bc (470 Km) F-9 (600 Km)

Fe ppb

26 5.3~10-~ 7 10 2.8xlOI; 1.1~10-~ 3.2~10-~ 1.2~10-~ 4.1x10-3 1.7~10-~ 6.1~10 2.3xlO

CX'NLATED ENRICF h ) E(Mn) E ( Fe)

~

-

-

620

Secondly, the set of fresh snowfall samples collected at the J-9 site also show enhanced enrichrent factors ccnpared with those for firn samples collected at Ice Shelf sites at similar distances from the ice front. This is true for silver, mganese and iron when the enrichent factors are calculated on the basis of sea water cunparisons. The mean E(Mn) factor is 200 times the value in firn; the mean E(Ag) factor is 20 t h s the firn values; and the mean E(Fe) factor is 350 times greater than the firn value at the same location. The enhanced E(Ag) values are still evident when crustal camparisons are made. Thirdly, the concentrations of elements vary considerably as a function of sampling time during the precipitation event. The Na, Fe and Mn concentrations change i n similar ways from sample to sample, whereas the silver (Ag) concentrations tend to be more uniform throughout the precipitation period, suggesting that the origins of these e l m t s may be different or that they are distributed differently in the 1 absphere. We also note that the Mn/Fe ratio in the fresh snow samples remains fairly constant at h u t the crustal ratio, supporting the crustal origin. Hence it is appropriate to distinguish between origin and enrichment when discussing the chemical canpsition of t h i s fresh precipitation. As regards enri-t as a function of precipitation characteristics, an earlier paper by Warburton and Linkletter (1978) shailed that enrichment factors for potassium and magnesium of 2.4 and 1.2 respectively were found in the supercooled f q deposition. E'urther to t h i s , T a b l e 3 shows that silver i s enriched four to ten times in the fog depsition above the firn values, and an average of 20 times in the fresh snowfall h v e the firn values at similar locations. Same of this enhancement (a factor of 3.4) is accounted for by reduced mean sodim content

384 TABE 3

Bhanced Enrichment in Fresh ice-Phase Precipitation - Observed Concentrations Location and Distance frwi ice front and collection times Sea Water Mean Crustal Ice Shelf C-7 Site 70 Km (Fog Deposition) Ice Shelf Bc Site 470 Km (Fog Deposition) Ice Shelf J-9 Site 450 Km Fresh Snawfall Sample Collection Oh 8hl5m 8h45m 9h15m 9h45m 10h15m 10h45m llh15m llh45m 12h15m 12h50m

1 2 3 4 5 6 7 8 9 10 11 12

-

M ppb

Aq ppb

Fe ppb

2.6~10-~ :06

lo7

2x10-l 80

7 5.3~10

237

5.2~10-~

47

9.~ x I O - ~

Times

No.

lvlean

OBSERVED CONCENTRATIONS

Na ppb

13Nh

Values:

50 55 42 32 18 10 8

6 12 11 11 21 23

7 l ~ 1 0 - ~ 8.3~10-~ 85 55 5.4 17 39 5.0 8 36 0.4 7 13 6.0 3 19 4.0 8 9 5.0 3 10 4.5 3 5 12.5 3 25 2.2 29 12 3.0 16 12 4.2 7 2 5 ~ 1 0 - ~ 5.4~10-1 16

(23 ppb) With which the silver is canpared, but the remaining factor of six enhancenent is not able to be explained in this manner. The apparent enhancements in IQI and Fe in fresh precipitation under l o w wind velocity conditions are also not accounted for by changes in sodium, the man E ( M ) and E(Fe) values being sore 60 to 100 times greater respectively in the fresh precipitation, than in the f i m at similar locations. CONCLUSIONS We have seen that the ratios of the concentrations of chemical constituents of three different types of fresh wet deposition, one in the water phase, the other bm in the ice phase, have shown significant departures from the values of these ratios in rainfall or total accumulated snowpack. Based upon these limited studies it appears that the various forms of water depsition to the surface m k e differing contributions to the total chemical ramval process. The reasons for this are not well understood although there is good reason to believe that they may relate to aerosol particle size both from the viewpoint of varying chenical canpsition and varying efficiencies of the aerosol removal processes (nucleation, Brownian diffusion, phoretic effects and impaction).

385

TABLE 3 (continued)

Eslhanced Enriclnnent in Fresh Ice-Phase Precipitation - Calculated Enrichents cAUXLAmD E N R I C 2 " T S

Referenced to Na (sea water) mation and Distance frcm ice front and collection t h s

E(M)

E(A3)

E(F5)

xi04

x l ~

xl~

-

Sea Water Mean Crustal

Ice Shelf C-7 Site 70 Km (Fog Deposition) Ice Shelf Bc Site 470 Km (Fog Deposition) Ice Shelf J-9 Site 450 Km Fresh Snowfall Sample No.

1 2 3 4 5 6 7

a

9 10 11 12 Wan

Values:

Collection T h s Oh 8~5m 8h45m 9hl5m 9h45m 10hl5m 10h45m llh15m llh45m 12N5m 12h5Cm 13hlOm

-

Referenced to Fe Crustal E(Md

E(Ag)

x10

-

1 10

7 5 5 5 3

9 5

a

2 11 5 3 6

7 5 6 7 17 20 31 38 52 10 14 10 20

17 3

2 2 2 8 4 5 3

26 15 3 7

0.5 1.5 2.5 2.5

2.0 1.0 1.5 1.5 1.0 0.5 0.5 1.0 1.3

7 20 40 40 130 33 113 100 280 7 13 40 70

The diffusionally-grown s ~ l water l droplets of dew and supercooled fog depsition, both rely on Brownian capture and phoretic forces for particle capture which would tend to favor the smaller aerosol particles sizes and which, in general, exhibit chemical enriclnnent. Rainfall or accreted snowfall (graupel) muld terd to favor larger particle capture by nucleation and impaction by the larger raindrops and ice particles. This muld tend to de-emphasize the enrichm t manifestation in the wet depsition. We have not demonstrated an aerosolprecipitation chemistry relationship, merely suggested it, and further m r k is needed to help resolve these phenanenological questions. AcmmLEEm

This mrk was supported by the U.S. National Science Foundation under a grant frcm the Division of Polar Programs, &ich is gratefully acknowledged.

386

w-ims 1 R.A. Duce, A.H. Woodcock and J.L. Moyers, Variations of ion r a t i o s with s i z e amng particles i n tropical ocean a i r , Tellus, 1 9 (1967), 369-379. 2 T . Takahashi, Chemical corip?osition of snow relation t o crystal shapes, J. Met. SOC. Japan, 14, (1963) 6, 327. 3 P. Brimbleccknbe aid I . Y . '~wcl,Sdium and p t a s s i m i n dew. Atmos. h v i r o n . , 11 (1977) 649-650. 4 C.E. Junge, Air chemistry and radioactivity. Academic Press, New York (1963). 5 D.H. Yaalon and E. Gmor, Chemical composition of dew and dry fallout in Jerusalem, Israel. Nature, 217 (1968) , 1139-1140. 6 D.R. Barker and H. Zeitlin, Wtal-ion concentrations i n sea-surface microlayer and s i z e separated a m s p h e r i c aerosol samples i n Hawaii, J. Geophys. Res., 77, (1972), 27, 5076-5088. 7 D.L. Meinert and J.W. Winchester, Chemical relationships in North Atlantic aerosol, J. Geophys. Res. 82, (19771, 12, 1778-1782. 8 A.L. Page, A.E. Elseewi and I. Straughan, Physical and chemical properties of fly-ash from coal-fired power plants w i t h reference t o environmental impacts, Residue Reviews, 71, (1979) ,83-120. 9 J.A. Warburton and G.O. Linkletter, Atanspheric processes and the chemistry of snow on t h e Ross Ice Shelf, Antarctica. J. Glaciol. 20, (1978),149-162.

387

DAILY MEASUREMENTS OF ATMOSPHERIC SULFATES I N PARIS

Y . LE MOULLEC, F. COVIAUX, and B . FESTY

L a b o r a t o i r e d'HygiPne d e l a V i l l e de P a r i s , P a r i s (France)

ABSTRACT S u l f a t e c o n c e n t r a t i o n measurements were made from J u n e 1977 through March 1981 a t a sampling s i t e l o c a t e d i n t h e c e n t e r of P a r i s . The f i f t i e t h p e r c e n t i l e f o r s u l f a t e w a s a p p r o x i m a t e l y lOyg/m

3 and t h e mean v a l u e 12 yg/m 3

.

R e l a t i o n s h i p s of s u l f a t e s w i t h m e t e o r o l o g i c a l and chemical q u a n t i t i e s were s t u d i e d . C o r r e l a t i o n s w i t h SO2 and f i n e suspended p a r t i c u l a t e s were h i g h e r i n w i n t e r (October t o March i n c l u s i v e ) t h a n i n summer ( A p r i l t o September i n c l u s i v e ) . The h i g h e s t c o n c e n t r a t i o n s were o b s e r v e d e s p e c i a l l y in w i n t e r , when wind speed was l e s s t h a n 2 m / s a n d / o r f o g o r i m p o r t a n t morning haze o c c u r e d , b u t f o r t h e s e days SO /SO

4

2

r a t i o s were n o t h i g h e r t h a n f o r t h e o t h e r d a y s . On t h e o t h e r hand, i n

summer SO / S O 2 r a t i o s were abnormally s t r o n g f o r p r e f e r e n t i a l wind d i r e c t i o n s .

4

Measurements a t s u b u r b s sampling s i t e s proved

t h a t the s u l f a t e concentrations

were a t t h e same time v e r y homogeneous i n t h e P a r i s m e t r o p o l i t a n a e r o s o l ; a s t a t i o n exposed t o d i e s e l e x h a u s t d i d n o t show s i g n i f i c a n t i n c r e a s e i n s u l f a t e s .

INTRODUCTION

S u l f a t e s c o n s t i t u t e a l a r g e f r a c t i o n of f i n e a t m o s p h e r i c p a r t i c u l a t e m a t t e r (Ref. 1 ) ;

t h e y have been i m p l i c a t e d as l u n g i r r i t a n t s and i n a number of a d v e r s e

e c o l o g i c a l e f f e c t s . Among t h e more prominent a d v e r s e e f f e c t s a r e reduced v i s i b i l i t y (Ref. 2) and f r e s h w a t e r a c i d i f i c a t i o n . Atmospheric s u l f a t e s may b e a r e s u l t of l o c a l e m i s s i o n s , f o r m a t i o n i n t h e atmosphere by a v a r i e t y of homogeneous and h e t e r o g e n e o u s mechanisms, and t r a n s p o r t a t i o n from d i s t a n t SO2 s o u r c e s . The r e l a t i o n s h i p of SO4 t o S O 2 , and t o o t h e r m e t e o r o l o g i c a l and p o l l u t i o n v a r i a b l e s , was s t u d i e d i n v a r i o u s u r b a n a r e a s (Ref. 3-4-5)

; t h i s r e p o r t summarizes t h e f i n d i n g s

of a r e c e n t s t u d y of a t m o s p h e r i c w a t e r s o l u b l e s u l f a t e s i n t h e P a r i s a r e a .

SAMPLING SITE, SULFATE COLLECTION AND ANALYTICAL METHOD The p r i n c i p a l sampling s i t e was on t h e r o o f of t h e l a b o r a t o r y which was l o c a t e d i n t h e c e n t e r of P a r i s n e a r St-Jacques Tower. From June 1977 through March 1981

388 daily sulfate samples were collected on a 50 mm cellulose acetate filter (Sartorius

SM 11105, poke size 0.65 um) placed in a plastic filter holder. Air sampling was achieved with an Austen F65 DE pump ; mean 24 h sample volumes were of the order 3 of 3 5 m /day. The extraction procedure consisted of immersion in 8 ml of bidistilled water at 70°C for 2 h, and mecanic and ultrasonic vibrating for respectively 5 and 15 w . In the filtrate, passed through a cellulose nitrate filter (pore size 0.01 um), sulfates were determinated by the classical BaS04 turbidimetric procedure on an autoanalyser. In the same site, routine measurements were made of SO concentrations (by 2 (by spectrometry after sampling on impregnated filters), 2 black smoke (by reflectometry) and fine suspended particulates (by @-particle attestrong acidity method), NO

nuation method). All of these samples were changed at 3 p.m. each day. Meteorological data were supplied by the Montsouris observatory (for solar radiation) and by the St-Jacques Tower meteorological station for the other variables (precipitation, visibility, relative humidity, air temperature, wind speed and wind direction). It is important to note that wind direction in the center of Paris can be influenced by the urban constructions and by the Seine river.

RESULTS

Sulfate results From analyses of 1300 filters collected over these four years the monthly sulfate averages were given in table 1 . TABLE 1 3 Monthly average concentrations of sulfates in vg/m

April May June July August September October November December January February March

1977-78

1978-79

-

16.0 20.0

12.5 10.6 9.6 10.2 8.1 7.5 13.6 9.7 14.2 9.7

-

13.4 10.5 12.0 17.7 19.7 12.9 17.0 22.2 8.0

1979-80 11.5 I 1 .o 16.8

-

8.3

15.0 13.6 9.6 8.2 17.0 13.3 17.3

1980-81 15.2 14.8

6.6 10.4 7.4 8.5 7.5

11.4 9.7 9.8

16.6 5.0

The four-year average was 1 2 . 3 ug/m3. As with a number of atmospheric pollutants, sulfate concentrations had approximately a lognormal distribution. The median values 3 were slightly higher in summer than in winter (10.7 ug/m3 and 10.1 ug/m ) and in

389 c o n t r a s t t h e mean v a l u e s were s l i g h t l y h i g h e r i n w i n t e r t h a n i n summer (12.5 pg/m 3 3 and 12.1 ug/m ) . It appeared t h a t summer v a l u e s ( A p r i l t o September i n c l u s i v e ) were more grouped t h a t t h e w i n t e r v a l u e s (October t o March i n c l u s i v e ) ; t h e h i g h e s t 3 on 2.20.79 and 58 ug/m3 on 2.25.81 I .

v a l u e s o c c u r e d d u r i n g t h i s p e r i o d (68 ug/m

For b o t h s e a s o n s i t was n o t e d t h a t 90 % of t h e c o n c e n t r a t i o n s were c o n t a i n e d 3

between 3 and 30 ug/m

.

S u l f a t e c o n c e n t r a t i o n s f o r e a c h day of

t h e week d u r i n g t h e f o u r y e a r s were

averaged and showed a c y c l e which i n d i c a t e d t h e i n f l u e n c e o f t h e a n t h r o p o g e n i c a c t i v i t y . The l o w e s t v a l u e s were grouped d u r i n g t h e week erd (10.6 ug/m3 on Sunday, 3 1 1 . 7 ug/m on S a t u r d a y and 13.6 ug/m3 on Tuesday and Wednesday).

Relationshius with the other o o l l u t a n t s ~~

Table 1 showed t h a t a h i g h monthly a v e r a g e c o u l d o c c u r i n t h e summer ; t h e s e a s o n a l c y c l e was l e s s r e g u l a r t h a n t h e s t r o n g a c i d i t y c y c l e , however t h e corr e l a t i o n SO -SO remained s i g n i f i c a n t f o r p c O . 0 1 . 4 2 TABLE 2

C o r r e l a t i o n c o e f f i c i e n t s , r , f o r 843 d a t a (1977-1981) s04 1

s04 s02

s02

0.59 1

BS(a)

FSP(b)

0.62 0.80

0.81 0.73 0.78

1

BS

FSP

1

N02 0.29 0.34 0.47 0.33 1

NO2

( a ) Black Smoke

(b) F i n e Suspended P a r t i c u l a t e s

The b e s t c o r r e l a t i o n between t h e s e p o l l u t a n t s was observed between s u l f a t e s and f i n e suspended p a r t i c u l a t e s (FSP) e s t i m a t e d by t h e @ - p a r t i c l e a t t e n u a t i o n method ( t a b l e 2 ) . It i s n o t i c e d t h a t t h e s e two p o l l u t a n t s a r e n o t independant because s u l f a t e s c o n s t i t u t e

about 20 Z of t h e suspended p a r t i c u l a t e s weight.

F r a c t i o n s s e l e c t i v e s t u d y of t h e r e s u l t s , a c c o r d i n g t o month, s e a s o n o r t o d i f f e r e n t m e t e o r o l o g i c a l c o n d i t i o n s , showed t h a t t h i s c o r r e l a t i o n w a s s t i l l v e r y s i g n i f i c a n t . It was b e s t i n w i n t e r (r=0.86 ; n=455) t h a n i n summer (r=0.75 ; n=363). The f i g u r e 1 i l l u s t r a t e s t h i s r e s u l t d u r i n g t h e w i n t e r 1977-1978

390

30

2o

It

0

Fig. 1 . Correlation between daily concentrations in water soluble sulfates and daily concentrations in fine suspended particulates during winter 1 9 7 7 - 1 9 7 8 .

Relationships with the meteorological variables Sulfates, SO2, fine suspended particulates and meteorological variables were regressed with SO4 as dependent variable ; the formulation which yielded the most statistically significant ( r = 0 . 8 2 ) results was : [SO4] = 7.27 + 0 . 2 0

[ I FSP

- 0.096

3

Z HR

with SO and FSP i n ug/m 4

In comparison with SO /FSP correlation (r=0.81) i t appears that influence of 4

relative humidity was negligible. In the same way, statistical analysis showed that wind speed, air temperature, precipitation

and solar radiation could not explain

the variations of the daily sulfate concentrations. However table 3 proves that the highest concentrations were observed when low wind speed, and/or, fog occured without rain.

TABLE 3 3

Highest sulfate values (ug/m ) for each tropic year and associated meteorological factors. Date

udm ~

2.18.78 2.20.79 3.16.80 2.25.81

SO4

FSP 3

udm

3

wind dir. speed m/ s

visibility at 10 a.m

T°C

HR %

m

rain m

m

~~

192 218 96

-

36.0 68.0 45.0 58.5

ENE ENE NNE NNE

4.1 1.2 2.9 1.8

2500 1500 2800 3500

-1.5 1.6 4.0 1.8

78 83 82 65

0

0 0 0

391 Wind direction (divided into 16 directional sectors) was also a meteorological factor of great interest. Table 4 shorn

the average concentrations of S O 2 and

SO

for each wind direction during the four years. For these two pollutants the 4 lowest concentration appeared when the wind was blowing from the west (these

winds were predominant over Paris), the highest values occured when the wind blowed from the south-east (only in winter) or from the north-east. In winter S04/S0 ratios were about the same for all directions ; but in summer higher 2 ratios from the north-east were observed ; this might indicate sulfate transportation

from this direction. TABLE 4

3 SO and S O concentrations (in ug/m ) and SO /SO ratios averaged over all wind 4 2 4 2 directions during the four years.

WIND DIR.

SUMMER n

NNE NE ENE

29 39 38

E

13

ESE SE SSE

14 7 24 26 15 13 16 47 45 54 45 34

S

ssw sw wsw W WNW NW NNW N

WINTER

So4

SO2

S04/S02

n

SO4

SO2

15.4 15.2 17.5 12.0 12.2 12.5 11.9 11.8 7.4 7.5 7.8 7.3 8.7

33 48 56 47 52 64 62 61 25 20 20 23 34 51 60 59

0.46 0.32 0.32 0.26 0.24 0.19

15 27 54 22 21 22 78 46 49 50 45 53 53 42 28 17

22.7 18.5 20.8 16.1 15.0 18.8 16.1

147 132 142 129

10.1

14.0 14.2

0.19

0.19 0.30 0.38 0.39 0.32 0.26 0.20 0.23 0.24

11.0

9.0 6.1 5.7 7.0 7.0 8.3 9.2 14.7

S04/SQ2

110

212 172 115 92 64 60 79 92 102 106 129

0.15 0. I4

0.15 0.12 0.14 0.09 0.09 0.10 0.10 0.10

0.09 0.09 0.08 0.08 0.09 0.11 -

(n) number of occurrences

Results of the other samoline sites ~

~

From July 1978 through June 1979 sulfates were also collected on cellulose Whatman filter (W 4 0 ) at two other sites located in suburbs diametrically opposed : Blanc Mesnil 13 km north-east of Paris and Issy les Moulineaux 7 km westsouth-west of the center of Paris. This study did not indicate any important variations for daily sulfate concentrations in relation to the wind direction ; an influence from primary local sources of sulfates in Paris or in the near suburb 3 seemed therefore to be exclude. The mean values were slightly lower ( 1 2 pg/m ) than those noted in the center of Paris ( 1 4 pg/m3 during the same period). The correlation coefficients between the three sampling sites were higher than r=0.90 which showed that for sulEates evolutions were very closely linked.

392 Relationships with urban traffic Studies (Ref. 6) showed that diesel fuels contained sulfur which was mainly converted to sulfur dioxide upon combustion

; a portion of the sulfur was con-

verted to sulfate. It appeared of great interest to measure the concentration of sulfate in a sampling site located Porte d'Aubervilliers (about 5 km of the center of Paris), 5 m above ground level, in front of an exit of the periferical avenue, very used by trucks. From July 1978 through December 1979 aerosols and gas were collected to measure the sulfate (on cellulose Whatman W 40), the SO

the black smoke and

concentrations in the same conditions as in the center of Paris.

2

Table 5 shows

a significant increase of black smoke and also of SO2, a part

of which had to be attributed to the diesel exhaust

. In contrast sulfate concen-

trations did not increase. The comparative evolution of the daily concentrations between the four sampling stations still showed very high correlations ( 0 . 8 0 c r < 0 . 9 0 ; n= 139). These results seem

indicate that, near a great avenue, contribution of diesel

is negligible

in regard to the urban concentration in sulfates. TABLE 5 3

Six-month averages of SO4, SO2 and black smoke (BS) in the two sites (ug/m ) Sites Center of Paris Porte d'Aubervilliers

s04 14.1 14.2

s02

91 136

BS 35 124

CONCLUSION Results from these four years showed that sulfate concentrations could be correctly described by the fine suspended particulates concentrations estimated by @-particle attenuation method. Sulfate concentrations were in the same time

very

uniform in the Paris metropolitan aerosol. On the other hand, with the statistical method used in this study, variations of SO /SO ratios could not be explained by the meteorological data collected. 4

2

Transportation of primary sulfates was possible but not prwed. REFERENCES 1 J . Wagman, R.E. Lee and C.J. Axt, Atmos. Environ., I (1967) 479-489. 2 B.P. Leaderer, J. Air Pollut. Control Assoc., 28 (1978) 321-327. 3 M.J. Cooke and R.A. Wadden, J . Air Pollut. Control Assoc., 31 (1981) 1197-1199. 4 R.E. Meyers and E.N. Ziegler, Environ. Sci. Technol., 1 2 (1978) 302-308. 5 R.C. Henry and G.M. Hidy, Atmos. Environ., 13 (1979) 1581-1596. 6 T . J . Truex, W.R. Pierson and D.E. McKee, Environ. Sci. Technol., 14 (1980) 1118-1121. 7 A.P. Altshuller, Environ. Sci. Technol., 14 (1980) 1337-1348.

393

SIZE, SHAPE AND ELEMENTAL ASSOCIATIONS IN AN URBAN AEROSOL. R. HAMILTON and G. ADIE Urban Pollution Research Centre, Middlesex Polytechnic, London NW4 4 B T .

A BS TR A CT An analysis of 1 2 0 individual airborne particles for size, shape and elemental composition has provided information on elemental occurrence patterns not available trom published cascade impactor studies. Particles ot size greater than 3 k m were analysed by scanning electron microscopy and energy-dispersive X-ray spectrometry. Zinc and copper exhi bit similar occurrence patterns but lead i s appreciably different.

The levels of iron and titanium

i n the bulk aerosol are strongly attected by the existence of a small number of highly enriched particles.

The use of particle morphology i s discussed and the distinctive appearance

ot some zinc particulates i s described.

INTRODUCTION Investigations of the size spectrum of an urban aerosol (rets. 1,2,3)have shown that the volume distribution i s bimodal with a dominant mode formed by particulates ot diameter greater than 2 lLm, commonly known as coarse particles. These particles are inhalable (ref. 4) and have non-health ettects although these effects are generally considered to be less important with coarse particles than with tine particles (ret. 5). A knowledge of the composition of these particles i s important, both to assess their effects and also as a technique for pollution source identification.

In addition, airborne particulates contribute

t o and are enriched by street surtace sediments.

These sediments are known to be important

carriers of heavy metal pollution and also the main contributor to suspended solids i n urban runoff (ref. 6). The particulate parameters most trequently monitored are size and elemental composition. By sampling with a cascade impactor, the aerosol i s size fractionated and each fraction subjected t o multielemental analysis (refs. 7,8,9,10,11,12).

An alternative approach

i s to characterise the aerosol by summing the properties o t the individual particulates, using a scanning electron microscope (SEMI equipped with an energy-dispersive X-ray

394

spectrometer (EDS); a technique which has been used i n air pollution studies to examine pollution from specific sources (ret. 13,14).

This approach ofters three main advantages;

it has superior size resolution to that attainable from a cascade impactor, i t allows an

examination of elemental enrichment on individual particulates and it permits an analysis of particulate morphology.

The disadvantages are that it i s time-consuming and it cannot be

used for particles with diameter much less than 1,,,m because spreading of the electron beam i n the sample results i n a pear-shaped volume with effective diameter of the order ot

1pm from which the X-rays originate. EXPERIMENTAL PROCEDURE Samples were collected at the Middlesex Polytechnic site at Hendon, NW London. There are no major industrial pollution sources i n the immediate vacinity, though one motorway, the M1, and two main trunk roads, the A 1 and A 4 1 , are each 0.5 km away. were collected on 0.8 pm Nucleopore filter paper. with a graphite aerosol.

The samples

Before sampling, the tilters were coated

This procedure permitted the use of a thin second carbon coating

so details of surface texture were not obscured while at the same time charging was avoided.

The samples were located i n an

IS1

Super Ill SEM and a field of view of some 50 particulates

selected. A l l particulates of diameter greater than 3 pm were photographed and their emitted X-rays collected and analysed by Links EDS, using an automatic ZAF correction so that the sulphur K and lead M peaks could be separated.

In this way, each particulate

was recorded as an SEM photograph which could be analysed for size and morphology and a printout of percentage elemental composition.

A total of 120 particulates was analysed.

RESULTS

E I emental Composition To obtain reliable quantitative results from X-ray emission spectrometry, it i s highly desirable to ensure the sample surface i s highly polished and the standard has similar composition to the sample.

This i s not possible with samples of airborne particulates so

our values of elemental concentration are semi-quantitative. concerned with trends rather than absolute values. Reported elemental concentrations are given i n Table 1.

However, this study i s

395

TABLE 1 Elemental concentration (cg 9 - l or "/I of an urban aerosol Location Reference S Si Ca Al Fe Mg

Na K CI Ti Pb Zn

Toronto

Milwaukee

St. Louis

Nagoya

(7)

(9)

(3)

5.3 2.1 2.2 1.4 0.65 0.87 1.20 0.17 0.97 0.32

4.8 3.1 3.0 2.2 0.70 1.2

(8,10,11 averaged) 6.0 1.2 6.9 13 3.1 6.6 2.7 5 2.1 3.7

CU

Total suspended 100 particulates (approximate) (TSP),g m-3 aerosol fraction analysed. total

0.90 0.12 0.05 41

total

0.95 0.43 0.70 1.50 .13 .02

1.4

1.3 .55 1.1 .82 .ll

I02 60

total

4.1

73

coarse

coarse

Size dependence of elemental composition The bulk volume distribution showed the size dependence expected of coarse particulates. The distribution i s shown i n fig. 1.

-

Volume (arbi tary units)

-

-

7

4

Particle diameter (,m) Fig.1.

Volume distribution of total aerosol.

10

396

The size dependence of relative concentration was investigated for each element. A typical result i s shown i n fig.2,

1.5

1

n

Concentration (cg g-' )

I

i n which both mean value and standard deviation

IS

shown.

I

0.51

I

I

I

4 7 10 Fig. 2. Variation of concentration (cg.g-l) with particle size. Fig.2 shows the results for

Particle diameter (,m)

Al, but a l l other elements behaved simularly. The spread of

concentrations for each size i s such that the elemental concentration i n cg.g-'

i s eftectively

size independent. Accordingly, the elemental concentration i n ng m-3 w i l l show the same form ot size dependence as the bulk aerosol.

This explains the distribution reported tor

Si and A l i n the Nagoya aerosol (ref.31, for A l and Pb i n the Toronto aerosol (ref.7) and for Fe, A l and Ca i n the Birmingham aerosol (ret.12).

One result from the Birmingham

study i s clearly inconsistent with our general observation.

CI

That study showed a marked

peak i n the region 3-7 p,m. We can only speculate that this was due t o a localised

pollution source. Parti cu Iate enrichment The cascade impactor studies referred to earlier can only measure the amount of each element present i n each size range. It cannot describe if that amount i s produced by a small number of highly enriched particulates or by a large number of low enrichment particulates.

This information i s readily available from SEM/EDS analysis, and the

results are summarised i n Table 2.

397

Detected at level

'0-0.170 0.'1-0.3% 0.3-170 1.0-3.070 3.0-10.070 10-3070 30-100./6

d[Jet:d S Si Ca Al Fe M9 Na K

CI Ti Pb Zn cu

0 1 6 0 1 9 0 3 4 56 63 20 1

0 12 38 4 22 17 0 20 40 38 7 42 4

3 44 24 48 35 47 6 51 51 3 9 32 89

41 20 12 33 26 24 30 23 5 2 13 6 6

41 15 8 11

8 2 5 2 0 0

6 0 0

15 8 10 3 3 1

a

1 0 1 2

0 0

2 2 2 1 3 0 0 0 0 0 0 0 0

0 0 0 0 2 0 0 0 0 0 0 0 0

A s discussed earlier, these results are only semi-quantitative, but the trends show two points of particular interest.

The observed levels of some minor elements are high because of the occurrence of a small number of particles with anomolously high elemental concentrations.

This i s particularly

true of iron, observed at a concentration of 6070in one particulate, fig. 3(a), presumably a speck of rust.

This also occurred with titanium, tig. 3(b), i n this case the particulate

presumably originating trom road surface markings. With the toxic heavy metals Pb, Zn and Cu, different occurrence patterns were observed. Copper occurred on virtually every particle, Zn on most and Pb on only 37%. We observed that on the 44 Pb-bearing particles, 13 did not contain zinc and this accounted for 6270 of the zinc-free particles. We can offer no explanation for this eftect. However, the occurrence patterns are consistent with quoted mass median equivalent diameters (MMED), (ref.15).

Both Zn and Cu have a MMED of 1.3 *m, Pb has a MMED of 0.6 pm.

Particulate Morphology The use of morphology as a characteristic property, complementary to size and composition yet, like these other properties, capable of providing information on particle source i s a well-established technique i n sedimentology (ref. 16) but one which has found little application i n air pollution studies because airborne particulates are at least an order of magnitude smaller than most sediment grains. It has, however, been used to distinguish soil particles from flyash (ref.17) and also to distinguish the particle emissions from oil-fired from coal-fired power plants (ref. 18).

398

F i g . 3 a . A particulate containing 6076 F e .

F i g . 3b. A particulate containing 976 Ti.

399

Many airborne particles are an aggregate of individual particles and accordingly, our first step in quantifying morphology was a classification of 'degree of aggregation', as summarised i n Table 3.

Table 3 . Degree of aggregation i n an urban aerosol

% of particles (i)

3

single particle

(ii) one main particle with up t o 5 much smaller particles

23

(iii) one main particle with more than 5 much smaller particles

32

(iv)

two particles of approximately equal size

5

(v)

3 - 5 particles of approximately equal size

6

(vi)

aggregate of more than 5 submicron particulates

31

Sedimentologists normally describe the morphology of single particles by the concept of 'form' (ref.191, this description generally being provided by three more or less independent properties.

In descending order of magnitude, these are sphericity, roundness or angularity,

and surface texture. The smaller airborne particulates are normally characterised by descriptive terms.

The recommended terms for shape (ref. 20) are acicular, angular, crystalline,

dendritic, fibrous, granular, irregular, nodular and spherical.

Surface textures are

conveniently described (ref. 2 11 as cemented, cracked, cratered, dimpled, orange peel, porous, reticuled, smooth and valleyed.

The two particles i n figure 3 have very similar

shapes but the difterent surface textures reflect the different sources and confirms the separation by elemental composition.

The elemental composition of flyash and soil

particulates i s similar, and surface texture provides the main method for distinguishing these sources (ref. 17). The McCrone group have described the sphericity of a particle by classifying it according to i t s degree of elongation and/or flattening.

Using this system i n conjunction with a

roundness index, airborne non-aggregate particulates, i .e. those belonging to classes i-v of Table 3, can be classified by morphology and the results are given in Table 4.

400

A"

elongated, flattened flattened but not elongated

1

el ongated but not flattened not elongated not f I attened

17 0

770

170

11%

25%

170

6% 11%

I angu Iar Published photomicrographs (refs.21,22)

I

4%

16% II su brounded

11% Ill rounded

show mineral particulates normally occur in

groups Al, All, BI and BII. The large percentage of particulates i n our study which f e l l i n these groups i s yet another indication that soil and the road surface are the main contributors to coarse airborne particles. Metals which normally occur at trace levels are occasionally found highly enriched on individual particulates and i n these circumstances they frequently exhibit a characteristic morphology.

This has been reported for lead (refs. 23,241 and vanadium (ref. 15). An

aerosol sample collected by us above the roof of St.Bartholomews Medical College i n London EC1 contained zinc i n a very different occurrence pattern t o that shown in Table 2. In this case, Z n was observed at high concentrations i n irregular rods of 1pm diameter and

4 0 pm length (fig.4).

The difference in size, shape and elemental associations between

these zinc-enriched rods and the zinc-bearing particles i n our Hendon study i s a clear indication of the magnitude of the alterations i n zinc particle chemistry which occurs i n the air and on the road surface.

401

FUTURE APPLICATIONS OF SEM/EDS STUDIES. In addition to examining the particulate emissions from specific pollution sources, SEM/EDS offers a valuable technique for the study of situations with anomalous particulate pollution levels.

The values of size, shape and elemental composition for the urban aerosol

i n our study are consistent with the expected sources of airborne particles, namely soil, road surface wear and transport sources such as vehicle emissions and tyre wear. emissions contribute a small amount.

Industrial

Situations producing large spatial and temporal

variations of heavy metal levels i n aerosols and i n street dust have been reported (ret.25) but they are, as yet, poorly understood. Characterisation of the heavy metal bearing particles i n these situations, using SEM/EDS, provides invaluable information for identifying the pollution source. This technique w i l l prove increasingly popular with the development ot digital and computerised instrumentation for processing SEM and EDS data to give automatic particle analysis (rets. 26,271.

---- -

Fig.4.

Irregular rods highly enriched i n Zn.

402

REFERENCES 1 K. Willeke and K.T. Whitby, J. Air Pollut. Control Ass., 25(1975) 529-534. 2 A. Meszaros, Atmospheric Environment, II (1977) 1075-1081. 3 $. Kadowaki, Envir. Sci. Technol, 13(1979) 1130-1133. 4 R.E. Walter, Atmospheric Environment, 14(1980) 1115-1118. 5 J.P. Lodge, A.P. Waggoner, D. T. Klodt and C.N. Crain, Atmospheric Environment,

15(1981) 431-482. 6 J.B. Ellis, R. Hamilton and A.H. Roberts, Proc. Second Int. Conf. on Urban Storm Drainage, Illinois, June 15-19, 1981, Vol II, 184-190. 7 J.J. Paciga and R.E. Jervis, Envir. Sci. Technol, lO(1976) 1 1 2 4 - 1 1 2 8 . 8 J.W. Winchester, R.J. Ferek, D.R. Lawson, J.O. Pilotte, M.H. Thiemens and L.E. Wangen, Wat. A i r Soil Pollut., 12(1979) 431-440. 9 T.R. Stolzenburq and A.W. Andren, Wat. A i r Soil Pollut., 15(1981) 263-270. 1 0 D.J. Alpert and P.K. Hopke, Atmospheric Environment, 1 5 1 9 8 1 ) 675-681. 11 B.H. O’Connor and J.M. Jaklevic, Atmospheric Environment, 1 5 1 9 8 1 ) 1681-1690. 1 2 J.D. Butler and P. Crossley, Sci. Total Envir., 19(1981) 179-194. 13 M. Grasserbauer, i n H. Malissa (Ed.), Analysis of Airborne Particles by Physical Methods, CRC Press, Florida, 1978, p p . 1 2 5 - 1 7 8 . 1 4 S.J. Palenik, i n W.C. McCrone, J.G. Delly and S.J. Palenik (Eds.), The Particle Atlas, Edition Two, Ann Arbor, Michigan, 1979, Vol. V, pp. 1362-1368. 1 5 J.D. Butler, Air Pollution Chemistry, Academic Press, London, 1979. 16 P.A. Bull, Prog. Phys. Geog., 5(1981) 368-397. 1 7 M. Pitchford, R.G. Flocchini, R.G. Draftz, T.A. Cahill, L.L. Ashbaugh and R.A. Eldred, Atmospheric Environment, 15, (19811, 321-335. 1 8 R.J. Cheng, V.A. Mohnen, T.T. Shen, M. Current and J.B. Hudson, J.Air Pollut. Control Ass., 26(1976) 787-790. 1 9 W.B. Whalley, Jour. Sed. Petrology, 42(1972) 961-965. 2 0 British Standards Institution, BS 2955, 1958. 21 W. C. McCrone and J.G. Delly (Eds.), The Particle Atlas, Edition Two (6 volumes), Ann Arbor, Michigan, 1973-1979. 22 E.M. Hamilton and W.D. Jarvis, The Identification of Atmospheric Dust by Use of the Microscope, CEGB, London (1963). 23 W.R. Boggess and B.G. Wixson (Eds.), Lead i n the Environment, Castle House Publications (1979). 24 J.S.C. McKee, C. Lapointe and M.L.H. Wise, J. Environ. Sci. Health, A 1 5 ( 1 9 8 0 ) 1-23. 2 5 M.J. Duggan, Clean Air, l l ( 1 9 8 1 ) 87-89. 26 J. Pawley, P. Statham and T. Menzel, Proc. 1 0 t h Ann. SEM Symp., Chicago, Ill., (19771, 297-306. 27 P.J. Statham and M. Jones, Scanning, 3(1980) 168-171.

403

SUBJECT Page Aerosol ,charged 337 diluter for 273 elemental associations393 2 83 nitrate organi c 227 particles 3 13 rural 36 1 shape 39 3 size 39 3 spherical 337 sulfate 2 83 urban 39 3 Agra, India 31 Alexandria, Egypt 55 Archeological monuments 31 Bacteri a1 i n f e c t i o n 185 Boreal f o r e s t 205 Boundary 1 ayer 119 Cadmi um mi c r o p a r t i cles 185 Carbon monoxide 189 337 Charge, equi 1 i bri um bipolar 337 Chemical r e a c t i o n s , o p t i c a l observation o f 259 Chemistry 379 Coal mine ( I n d i a ) 47 Deposition , 1 ocal 91 regional s c a l e 91 s i t e and season spe ci f i c 91 17 Desert Di spe rsi on coe f f i ci en t 107 Dust, a t m s p h e r i c 369 respi rable 47 Egypt 55 Emission control 71 height 163 Fibers, mineral 2 39 i n the environment 239 i n biological material239 Flue gas, c o l l e c t i o n o f 197 Fluoride deposition 205 Forecast of pollution peaks 103 o f pollution potential 97 Gas c o l l e c t i o n ( f l u e ) 197 Genetic f a c t o r s 189 Ice nucleation 251 I mp a c t p r e d i c t i on 141 India 31,47 Instruments,comparison of 265 Jerusalem 11 L as e r t rans mi ssomet e r 32 1 Leaf l i t t e r 205 Lead aerosols,mnodisperse 251 61 Legi s 1a t i on Los Angeles Basin 345

INDEX Mercury 55 Minimum f l u x 337 12 7 Models, numerical water analogue 197 Mortal i t y 175 Mouse 185 Multicell scrubber 215 Network 41 Nitrogen oxides 71 Nord-Pas-de-Cal ais,France 103 Ozone 11 continental background 17 Paris , France 387 P a r t i c u l a t e matter 265 Peaks (pol 1 ution) 103 Phosphorous plant 205 P1 anetary albedo 313 P1 ants 55 P1 ume 283 Pollution potential 97 Po Valley, I t a l y 361 Precipitation 369,379 Releases , accidental 127 Rural 17 Saudi Arabia 41 55 Soi 1s Sulfates 387 S us cepti bl i t y ,t o i n fe c t i on 185 Thermal analysis 227 Thundersstormymodeling of 151 Trace substance d i s t r i b u t ion 369 Transmissometer, l a s e r 321 Transport, local 91 long range 163 meso-scale 163 of reactive pollutants 163 regional scale 91 s i t e and season speci f i c 91 Tropical area 3 Tunis, Tunisia 61 Turbulence profi l e s 119 Turbulent d i f f u s i v i t y 107 Urban 61 U. S . ,Southwest Desert 17 Viral i n f e c t i o n 185 Visi bi 1 i t y 305 Visual range 293 Water analogue model 197 Wind, calm 107

404

AUTHOR

Page 39 3 Adie, G. 3 Africano, M. Allard, D.W. 345 Allender, P . 103 127 Baker, A.J. 2 15 Belin, C . 163 Benarie, M. 345 Blumenthal, D . L . 185 Boudsne , C. 185 Bouley, G. 345 Bregman, L . D . B u i l t j e s , P.J.H. 107 61 Carbonnel l e , J . 215 Ch arpenti e r , J .C . 185 Chaumard, C . 127 Cooper, R.E. 387 Coviaux, F. 337 Davisson, S. 103 Dejardin, J.M. 189 Dema r i a-Pes ce , V. -H . 2 15 Djerid, S. 345 Eatough , D.J. 17,22 7,32 1 E l l i s , E.C. 55 Elsokkary, I . H . 71 Eschenroeder, A. 17,293,345 Farber, R.J. 387 Festy, B. 36 1 Fuzzi, S. 337 Gentry, J.W. 185 Girard, F. 30 5 Gorraiz, J . 189 Gourlet, V . Grassl, H . 313 273 Guichard, J.-C. 91 H a l b r i t t e r , G. 39 3 Hamilton, R. 34 5 Hansen, L.D. 25 1 Heiklen, J.P. 17,293,321 Hoffer, T.E. 30 5 Horvath, H. 345 Huang, A.A. 2 83 Hudischewskyj, Belle A. 41 Husain, T . 305 Johnson, C . 97 Joukoff, A. 345 Keifer, W.S. 41 Khan, S.M.

INDEX Kocchiu, H . L . Kretzschmar, J.G. Laurent, A. Lee, P.H. Le Moullec, Y . L i p f e r t , F.M. L i u , C.S. Mahoney, R.L. Malet, L.M. Mariotti, M. Msrat, P . Milhe, M. Moyer, J.W. Neumann-Hauf, G. Newiger, M. Novakov, T . Orsi, G. Pauwels, J.B. de Pena, Rosa G. Pepper, D.W. Perdreau, L . Perramon, A. Pi c k e t t , E .E . Quero, A.-M. Rawat, N . S . Rigard, J . Rob@, M.C. Romro , 3 . Rosner, D.E. Sanhueza, E . Saxena, P . Schneiter, D . Schorran, D.E. Seigneur, C. Sharma, D . N . Sharma , J .S . S i d h u , S.S. Spurny, K.R. S t e i nberger, E . H . S t r a u b e l , H. S t u p f e l , M. Thierry, H . Thomas, W . Ueno, Y. Warburton, J.A. Whiting, R . G .

14 1 265 2 15 32 1 387 175 337 345 97 36 1 189 197 32 1 91 313 227 36 1 265 251 127,151 215 189 14 1 185 47 197 61 3 251 3 283 119 293,321 283 31 31 205 239

11 259 189 189 369 251 379 141