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UBC Theses and Dissertations

Mobilization of selected trace metals in the aquatic environment (sediment to water column and benthic… Bindra, Kuldip Singh 1983

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MOBILIZATION OF SELECTED TRACE METALS IN THE AQUATIC ENVIRONMENT (Sediment to Water Column and Benthic Invertebrates) by KULDIP SINGH BINDRA .A.Sc., U.B.C. ( 1 9 7 4 ) ; M.A.Sc., Univ. of Toronto ( 1 9 7 6 ) A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in THE FACULTY OF GRADUATE STUDIES ( C i v i l Engineering) We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA © Kuldip Singh Bindra, 1 9 8 3 In presenting t h i s thesis i n p a r t i a l f u l f i l m e n t of the requirements f o r an advanced degree at the University of B r i t i s h Columbia, I agree that the Library s h a l l make i t f r e e l y a v a i l a b l e for reference and study. I further agree that permission for extensive copying of t h i s thesis for s c h o l a r l y purposes may be granted by the head of my department or by his or her representatives. I t i s understood that copying or p u b l i c a t i o n of t h i s thesis for f i n a n c i a l gain s h a l l not be allowed without my written permission. K u l d i p S. Bindra Department of C i v i l E n g i n e e r i n g The University of B r i t i s h Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3 Date ^IJP l±7. i i ABSTRACT Laboratory experiments were conducted to determine the processes a f f e c t i n g m o b i l i z a t i o n of t r a c e metals (Cu, Fe, Mn, Pb and Zn) across the sediment-water and sediment-benthic i n v e r t e b r a t e i n t e r f a c e s . The r e l e a s e of t r a c e metals from two contaminated w e l l - c h a r a c t e r i z e d sediments was s t u d i e d under q u i e s c e n t and a g i t a t e d c o n d i t i o n s . Trace metal r e l e a s e was s t u d i e d under d i f f e r e n t c o n d i t i o n s of s a l i n i t y (0-29.5 °/oo), oxygen ( a i r s a t u r a t e d and n i t r o g e n gas purged) and pH (5. 7, 10). Four groups of b e n t h i c i n v e r t e b r a t e s , namely the opossum shrimp, an amphipod, chironomids, and o l i g o c h a e t e s were exposed to the two sediments f o r periods up to s i x weeks. Organisms were ana l y z e d f o r Cu, Fe, Mn, Pb and Zn to determine whether accumulation occurred. Rapid a g i t a t i o n confirmed many of the o b s e r v a t i o n s made under long term (30 day) qui e s c e n t experiments. Under o x i c ( a i r saturated) freshwater c o n d i t i o n s c o n c e n t r a t i o n s of the more t o x i c metals (Cu, Pb and Zn) were l e s s than 10 X g / 1 . More Zn (27 y**g/l) was r e l e a s e d under s a l i n e c o n d i t i o n s . Iron and Mn were r e l e a s e d i n high c o n c e n t r a t i o n s under anoxic ( n i t r o g e n gas purged) c o n d i t i o n s . Extreme pH (5»10) r e s u l t e d i n very h i g h c o n c e n t r a t i o n s of a l l metals. Release at pH 10 was a t t r i b u t e d to d i s s o l u t i o n of humic substances which can bind the metals. V a r i a t i o n i n r e l e a s e i i i c ould not always be r e l a t e d to the sediment t r a c e metal geochemistry. The sediment or g a n i c content and p a r t i c l e s i z e were important i n determining t r a c e metal r e l e a s e . Microcosm s t u d i e s i n d i c a t e d t h a t t o t a l sediment t r a c e metals are not n e c e s s a r i l y i n d i c a t i v e of l e v e l s i n benthic i n v e r t e b r a t e s . The geochemistry of the t r a c e metals as w e l l as the p h y s i c o - c h e m i c a l c h a r a c t e r of the sediment i n f l u e n c e d b i o a v a i l a b i l i t y . Contaminated sediments were most t o x i c to the opossum shrimp. Chironomids showed the g r e a t e s t uptake of a l l t r a c e metals. O l i g o c h a e t e s appeared to have the best c a p a b i l i t y to m o b i l i z e and excrete t r a c e metals from t h e i r t i s s u e . TABLE OF CONTENTS Page LIST OF TABLES x LIST OF FIGURES x i i ACKNOWLEDGEMENTS. . x i v Chapter 1 : INTRODUCTION AND LITERATURE REVIEW........ 1 I. INTRODUCTION 1 A. General 1 B. O b j e c t i v e s 5 I I . LITERATURE REVIEW 6 A. M o b i l i z a t i o n of Sediment Trace Metals to Water 6 1 . E f f e c t of a g i t a t i o n 8 2 . E f f e c t of s a l i n i t y 1 2 3 . E f f e c t of redox changes ! 6 U. pH e f f e c t s 2 1 5 . E f f e c t of o r g a n i c coraplexing agents.... 2k 6 . E f f e c t of m i c r o b i a l a c t i v i t y 27 7. Summary 30 B. Accumulation of Sediment Trace Metals by Benthic I n v e r t e b r a t e s 30 1 . Copper (Cu) 31 2 . Iron (Fe) 39 3 . Lead (Pb) U i. Manganese (Mn) 4-8 5 . Zinc (Zn) 5 5 TABLE OF CONTENTS (Continued) Page 6. Summary 62 Chapter 2 : MATERIALS AND METHODS 65 I. MATERIALS AND METHODS FOR EXCHANGE BETWEEN SEDIMENTS AND WATER 65 A. Column Studies 66 1. Sampling 66 2. Construction of columns 67 3. Setup of columns, operation and sampling 67 B. E l u t r i a t e Studies 70 1. Sampling 70 2. Test procedure 72 3. Environmental conditions of e l u t r i a t e Test 72 IIV" MATERIALS AND METHODS FOR EXCHANGE BETWEEN SEDIMENTS AND BENTHIC INVERTEBRATES 73 A. Organisms for Exchange Experiments 73 B. Sediments and Water for the Experiments.. IL, C. Experimental Setup 74 I I I . ANALYTICAL PROCEDURES FOR EXCHANGE AT BOTH SEDIMENT-WATER AND SEDIMENT-INVERTEBRATE INTERFACE.76 A. Geochemical Partiti o n i n g of Sediments ... 76 1. General ... ....... 76 2. I n t e r s t i t i a l water (IW) 77 3- Exchangeable phase (EP) 77 4. E a s i l y reducible phase (ERP) 78 v i TABLE OF CONTENTS (Continued) Page 5. Organic and sulphur phase (OSP) 78 6. E a s i l y acid extractable phase (EAEP)... 7 9 7. Residue phase (RP) 79 8. Total trace metal analysis (Total) 80 B. Trace Metals i n Water 81 1. Digestion of e l u t r i a t e samples 81 2. Digestion of suspended solids 81 3. Preparation of reagents 82 4. Extraction procedure 82 C. Trace Metals i n Benthic Invertebrates and Algae 83 1. Dissolution of benthic invertebrates... 83 2. Dissolution of benthic algae 84 D. Atomic Absorption Spectrophotometry 84 E. Other A n a l y t i c a l Techniques 85 Chapter 3: RESULTS 89 I. TRACE METAL EXCHANGE BETWEEN SEDIMENTS AND WATER 89 A. Characteristics of the Sediments 89 1. Sediment trace metal geochemistry ... 89 2. Sediment p a r t i c l e size d i s t r i b u t i o n . 92 B. Dissolved Trace Metal Exchange i n Static Columns at Different Oxygen and S a l i n i t y Conditions 92 1. Copper (Cu) 92 2. Iron (Fe) 95 v i i TABLE OF CONTENTS (Continued) Page 3. Lead (Pb) 97 4 . Zinc (Zn) 97 5. Water q u a l i t y c o n d i t i o n s i n sediment microcosms 100 C. E f f e c t of pH on D i s s o l v e d Trace Metal Exchange 101 1. Copper (Cu) . 101 2. Iron (Fe) 101 3. Lead (Pb) 106 4 . Zinc (Zn) 106 5. Water q u a l i t y c o n d i t i o n s i n the v a r i a b l e pH sediment systems....,.,... 107 D. E f f e c t of pH on P a r t i c u l a t e and D i s s o l v e d Trace Metal Exchange 108 E. D i s s o l v e d Trace Metal Exchange i n A g i t a t e d Water-Sediment Systems ( E l u t r i a t e T e s t ) . I l l 1. E f f e c t s of oxygen and s a l i n i t y I l l 2. E f f e c t of pH 115 TRACE METAL EXCHANGE BETWEEN SEDIMENTS AND INVERTEBRATES 117 A. I n i t i a l Organism and Sediment Trace Metal L e v e l s . 117 B. Accumulation or Loss of Trace Metals i n the Benthic I n v e r t e b r a t e s 119 C. Rate of Uptake or Loss of Trace Metals by Benthic I n v e r t e b r a t e s 124 D. R e p r o d u c i b i l i t y of Trace Metal Determi-n a t i o n i n Organisms 127 v i i i TABLE OF CONTENTS (Continued) Page Chapter 4 ; DISCUSSION OF RESULTS ' 130 I. GEOCHEMICAL PHASES 130 A. I n t e r s t i t i a l Water (IW) . 130 B. Exchangeable Phase (EP) 131 C. E a s i l y Reducible Phase (ERP) 131 D. Organic and Sulphur Phase (OSP) 131 E. E a s i l y Acid E x t r a c t i b l e Phase (EAEP) ... 132 F. Residue Phase (RP) 132 G. Total Phase (Total) 133 I I . TRACE METAL EXCHANGE AT SEDIMENT-WATER INTERFACE 133 A. General .- 133 1. Static columns 133 2. E l u t r i a t e tests 134 B. Dissolved Trace Metal Exchange 135 1. Copper (Cu) 136 2. Iron (Fe) 142 3. Lead (Pb) 148 4. Manganese (Mn) 154 5. Zinc (Zn) 158 C. Particulate Trace Metal Exchange (pH Effects) I 6 4 I I I . TRACE METAL EXCHANGE AT THE SEDIMENT-INVERTEBRATE INTERFACE 167 i x TABLE OF CONTENTS (Continued) Page Chapter 5 : SUMMARY AND SIGNIFICANCE OF RESULTS AND RECOMMENDATIONS FOR FURTURE RESEARCH 176 I. SUMMARY 176 A. Trace Metal Exchange at the Sediment^Water Interface 177 B. Trace Metal Exchange at the Sediment-Invertebrate Interface 180 II . SIGNIFICANCE OF RESULTS . . 182 A. Impact of Trace Metal Contaminated Bottom Sediments on Water Quality 182 B. Impact of Trace Metal Contaminated Sediments on Benthic Invertebrates 186 II I . RECOMMENDATIONS FOR FUTURE STUDIES 187 A. Exchange at the Sediment-Water Interface .. 187 B. Exchange at the Sediment-Invertebrate Interface 188 REFERENCES 190 APPENDICES 213 Appendix A. Water Quality Conditions i n Sediment Microcosms 213 Appendix B. Ef f e c t of pH on Trace Metal Exchange . 220 Appendix C. Trace Metal Levels in Benthic Invertebrates ' 224-X LIST OF TABLES Table Page I. Relationship Between Bioconcentration Ratios of Copper i n Chironomids and Amount of Fines «0.25 mm) in the Sediment (data from Bindra and H a l l , 1977) . . 38 II. Relationship Between Iron in Chironomid Larvae and Amount of Very Coarse Sand in the Sediment (data from Bindra and H a l l , 1977, pp. 74,84,94,95) 42 I I I . Manganese Concentrations in Oligochaetes and Sediment Characteristics Which Appear to A f f e c t the Metal Levels in Organisms (data from Bindra and H a l l , 1977, Tables A3 and A4) 49 IV. C o e f f i c i e n t s of Linear Correlations (r) Between Manganese Levels in Oligochaetes and Their Habitat-Related Parameters (data from Bindra and H a l l , 1977, Table III of this thesis) 51 V. Bioconcentration Ratios of Zinc in Oligochaetes from Three Watersheds of the Lower Mainland of B r i t i s h Columbia (adapted from Bindra and H a l l , 1977, p. 40) 56 VI. Comparison of Bioconcentrations R a t i o s of Z i n c i n Chironomids from Two Watersheds, Lower Mainland, B r i t i s h Columbia (from Bindra and H a l l , 1977, p.40). 63 VII. Combination of Environmental Conditions Used in S t a t i c Column Studies 71 VIII. A n a l y t i c a l Settings for Atomic Absorption S p e c t r o -photometry 86 IX. Trace Metal D i s t r i b u t i o n in Sediments from the Brunette Basin Used in Sediment-Water Exchange Studies (December 23, 1977) 90 X. Trace Metal D i s t r i b u t i o n in Sediments from the Brunette Basin Used in Sediment-Water Exchange Studies ( A p r i l 19, 1978) 91 XI. P a r t i c l e Size D i s t r i b u t i o n of Sediments at Two Stations on S t i l l Creek (Brunette Basin) Sampled for Trace Metal Exchange Studies (Bindra and H a l l , 1977) 93 x i LIST OF TABLES (Continued) Table Page XII. Total Trace Metal Concentrations in Organisms and Sediments Used for Microcosms 118 X I I I . Trace Metal Bioaccumulation in Benthic Invertebrates 123 XIV. Average Uptake Rate of Trace M e t a l s by B e n t h i c -, ?/-I n v e r t e b r a t e s (0-28 days) XV. Reproducibility of Trace Metal Determinations in Oligochaetes from Replicate Microcosms Chambers 128 XVI. Percent V a r i a b i l i t y in Trace Metal Levels in Four Duplicate O l i g o c h a e t s Microcosms 1 2 9 A l . Water Quality in High Organic Sediment Microcosm Under Oxic Conditions 214 A2. Water Quality in High Organic Sediment Microcosm Under Anoxic Conditions 215 A3. Water Quality in Low Organic Sediment Microcosm Under Oxic Conditions 216 A4. Water Quality in Low Organic Sediment Microcosm Under Anoxic Conditions 217 A5. Water Quality in High Organic Sediment Microcosm 218 A6. Water Quality in Low Organic Sediment Microcosm at D i f f e r e n t pH's 219 B l . E f f e c t of pH 5 on Trace Metal Exchange in Sediment 2 2 1 22 B2. E f f e c t s of neutral pH (7) on Trace Metal Exchange in Sediment B3. E f f e c t of pH on Trace Metal Exchange in Sediment 223 C I . Trace M e t a l L e v e l s i n B e n t h i c I n v e r t e b r a t e s i n L a b o r a t o r y Microcosms • 2 2 ^ x i i LIST OF FIGURES (Continued) Figure Page 15. Exchange of Dissolved Trace Metals in the E l u t r i a t e Test at D i f f e r e n t pH's (Oxic , S a l i n i t y <1 °/oo)...-. H 6 16. Trace Metal Levels i n Organisms Over Microcosm Period 120 xiv ACKNOWLEDGEMENTS I would l i k e to express my deepest gratitude to my supervisor, Dr. K.J. H a l l for his encouragement and guidance during experimental work and preparation of this thesis and for f i n a n c i a l assistance from his research funds secured mainly through the Associate Committee on S c i e n t i f i c C r i t e r i a for Environmental Quality , National Research Council of Canada, Contract No. 032-1082-6073. A minor f i n a n c i a l input was made by his NSERC operating grant 67-8935. Also, I f e e l g r a t e f u l to Dr. W.K. Oldham for h i s advice and p a r t i c u l a r l y for his encouragement to j o i n the Ph.D. program in the C i v i l Engineering Department and for some f i n a n c i a l assistance from his research funds during an i n i t i a l period. Special thanks also go to Drs. A. Carter, K. Fletcher and D.S. Mavinic for their advice in interpretation of some experimental results. In addition, I would l i k e to thank a number of other people who contributed to the success of my research: Mrs. E. McDonald for providing laboratory f a c i l i t i e s in the Environmental Engineering Laboratory, Dept. of C i v i l Engineering. - I. Yesaki and S. Boyd provided assistance in c o l l e c t i n g and sorting oligochaetes and chironomids. Joan Sharp of the I n s t i t u t e of Oceanography kindly provided the amphipods. Tom Johnson, Dept. of Zoology provided the opossum shrimp. - I. Yesaki for his excellent work in drafting the figures. Dick Postgate, head of the C i v i l Engineering Workshop and his s t a f f for constructing plexiglass columns to exact specif i c a t i o n s . my wife Balbir for her understanding and for typing the text. many others at the University of B r i t i s h Columbia and elsewhere. 1 Chapter 1 INTRODUCTION AND LITERATURE REVIEW I. INTRODUCTION A. General E f f e c t i v e management of tra c e metal p o l l u t i o n i n the a q u a t i c environment r e q u i r e s a good knowledge of processes r e s p o n s i b l e f o r metal m o b i l i z a t i o n i n v a r i o u s components of the environment. The a q u a t i c environment can be considered as a three component system namely, the water column, sediments, and organisms. The water column s a l t content may vary from the h i g h l y s a l i n e marine system through b r a c k i s h e s t u a r i e s to the f r e s h water of most i n l a n d lakes and r i v e r s . The sediments can range from h i g h l y i n o r g a n i c sands and g r a v e l s to organic ooze o f t e n c h a r a c t e r i s t i c of h i g h l y p r o d u c t i v e systems. The organisms show a wide a r r a y of adaptation to the v a r i e t y of sediment and water c o n d i t i o n s that e x i s t i n the a q u a t i c environment. The system i s very dynamic with exchange r e a c t i o n s o c c u r r i n g between these three compartments. These exchange r e a c t i o n s are c o n t r o l l e d by a wide v a r i e t y of p h y s i c a l , chemical and b i o l o g i c a l processes. M o b i l i z a t i o n and m i g r a t i o n of t r a c e metals i s one set of complex processes t h a t can take place between the three components of the system ( F i g u r e 1 ) . Figure 1. Interactions Between Sediments, Water and Benthic Invertebrates. Source I.W. = Interstitial water 3 The term " t r a c e metals" may mean d i f f e r e n t t h i n g s to d i f f e r e n t people, but as used here the term r e f e r s to a number of metals which are u s u a l l y found i n t r a c e amounts i n the a q u a t i c environment. In t h i s study " t r a c e metals" should be c o n s i d e r e d synonymous to "heavy metals" which i n c l u d e most metals w i t h atomic number g r e a t e r than 20, but excludes a l k a l i metals, a l k a l i n e e a rths, l a n t h a n i d e s and a c t i n i d e s . The metals most commonly i n c l u d e d i n the category of heavy metals are s i l v e r (Ag), cadmium (Cd), chromium ( C r ) , copper (Cu), i r o n ( F e ) , mercury (Hg), manganese (Mn), n i c k e l ( N i ) , l e a d (Pb), antimony (Sb), t i n (Sn), t i t a n i u m ( T i ) and z i n c (Zn). Widespread use of metals i n modern i n d u s t r i a l i z e d and urbanized s o c i e t i e s i s c o n t r i b u t i n g to tr a c e metal d i s c h a r g e s to the a q u a t i c environment from a number of sources such as sewage d i s c h a r g e (with or without i n d u s t r i a l waste-waters), dumping of sludges, drainage and discharges from mining s i t e s , metal r e f i n i n g and f i n i s h i n g and numerous other i n d u s t r i a l o p e r a t i o n s , l e a c h a t e s from l a n d f i l l s and by n a t u r a l processes r e s u l t i n g i n washout from atmosphere and contami-nated s o i l s . The p o t e n t i a l dangers of u n c o n t r o l l e d p o l l u t i o n of our a q u a t i c environment by t r a c e metals were d r a m a t i c a l l y demonstrated by a mercury p o i s o n i n g which occurred d u r i n g 1960's i n Japan (Takeuchi, 1972). To prevent s i m i l a r events elsewhere and to minimize damage to aqu a t i c ecosystems, the di s c h a r g e of t r a c e metals must be c u r t a i l e d at the source. 4 However, d e s p i t e c o n s i d e r a b l e e f f o r t s at source c o n t r o l , d i s c h a r g e s are bound to continue because complete removal of p o l l u t a n t s from e f f l u e n t s i s t e c h n i c a l l y d i f f i c u l t and the c o s t e c o n o m i c a l l y p r o h i b i t i v e . T h erefore, to minimize the impact of t r a c e metal p o l l u t i o n , a b e t t e r understanding of t r a c e metal behavior i n the a q u a t i c environment i s e s s e n t i a l . Trace metals discharged to n a t u r a l waters are r e a d i l y removed from the water column and d e p o s i t e d i n s e d i -ments as a r e s u l t of low s o l u b i l i t y and s u r f i c i a l r e a c t i o n s w i t h suspended m a t e r i a l s . The r e s i d u a l water s o l u b l e compo-nent and the sedimentary d e p o s i t s may be taken up by a q u a t i c organisms. D i s s o l v e d f r a c t i o n s are considered p o t e n t i a l l y more hazardous because they may d i r e c t l y a f f e c t human w e l l - b e i n g as a r e s u l t of contamination of d r i n k i n g water s u p p l i e s and f i s h r e a r i n g waters. The sedimentary component may appear to warrant l i t t l e concern upon p r e l i m i n a r y c o n s i d e r a t i o n , but on c a r e f u l i n v e s t i g a t i o n t h i s component of the system may prove to be very important. F i r s t , t r a c e metals i n sediments are o f t e n a 1000 times more concentrated than i n water. Second, changes i n environmental c o n d i t i o n s can m o b i l i z e t r a c e metals i n sediments and make them more a v a i l a b l e f o r uptake by organisms. Some of the environmental f a c t o r s t h a t may a f f e c t r e l e a s e of t r a c e metals a s s o c i a t e d with sediments to water column are presence and type of complexing compounds, presence or absence of d i s s o l v e d oxygen, s a l i n i t y , pH, geochemical and p h y s i c a l c h a r a c t e r i s t i c s of sediments, and extent of a g i t a t i o n 5 i n both water and sediments. These f a c t o r s have been s t u d i e d both i n the l a b o r a t o r y and the f i e l d , but the r e s u l t s are not c o n c l u s i v e . S i m i l a r l y , a v a i l a b i l i t y of t r a c e metals to organisms may be a f f e c t e d by a number of f a c t o r s i n c l u d i n g p h y s i o l o g y of the organisms and c h a r a c t e r i s t i c s of sediments and water column. Although a myriad of s t u d i e s have been conducted on uptake of t r a c e metals from water, experiments conducted on m o b i l i z a t i o n from sediments are r a r e . B. O b j e c t i v e s The o b j e c t i v e of t h i s work was to study the t r a c e metal exchange ( 1 ) between the sediment and water components and ( 2 ) between the sediment and be n t h i c i n v e r t e b r a t e components of the a q u a t i c environments (Figure 1 ) . The work c o n s i s t e d of two d i s t i n c t p a r t s . In the f i r s t p a r t my o b j e c t i v e was to i n v e s t i g a t e the i n f l u e n c e of s a l i n i t y , oxygen, pH, and a g i t a t i o n on the exchange of s e l e c t e d t r a c e metals (Cu, Fe, Mn, Pb and Zn) between sediment and water. H i g h l y contaminated sediments with d i f f e r e n t o r g a n i c matter content 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 were used. The sediments were c h a r a c t e r i z e d f o r t r a c e metal geochemistry to determine the e f f e c t of the form of metals on exchange. The e f f e c t s of both q u i e s c e n t c o n d i t i o n s ( s t a t i c l a b o r a t o r y columns) and a g i t a t e d c o n d i t i o n s ( e l u t r i a t e t e s t ) were s t u d i e d . In the second p a r t , my o b j e c t i v e was to study the e f f e c t of organism type, sediment c h a r a c t e r i s t i c s and t r a c e 6 metal geochemistry on exchange of the same f i v e metals between sediment and benthic i n v e r t e b r a t e s . The s t u d i e s were conducted i n microcosms with two contaminated sediments with w e l l c h a r a c t e r i z e d p r o p e r t i e s and t r a c e metal geochemistry. I I . LITERATURE REVIEW In t h i s s e c t i o n i n v e s t i g a t i o n s c a r r i e d out by others on m o b i l i z a t i o n of t r a c e metals i n sediments to water column and bent h i c i n v e r t e b r a t e s are reviewed. Metal m o b i l i -z a t i o n to water on one hand, and the be n t h i c organisms, on the other hand, are reviewed s e p a r a t e l y . A. M o b i l i z a t i o n of Sediment Trace Metals to Water Trace metals e n t e r i n g n a t u r a l waters are r e a d i l y i n c o r p o r a t e d i n t o sediment d e p o s i t s . R e m o b i l i z a t i o n of t r a c e metals from sediments may occur under c e r t a i n environmental c o n d i t i o n s . Some of the c o n d i t i o n s g e n e r a l l y c o n s i d e r e d to f a v o r r e m o b i l i z a t i o n a r e : - a g i t a t i o n of sediment d e p o s i t s - i n c r e a s e i n s a l t content of water - changes i n redox p o t e n t i a l ( i n c r e a s e or decrease i n d i s s o l v e d oxygen l e v e l s ) - low pH - presence of org a n i c complexing agents - m i c r o b i a l a c t i o n . Sediment d e p o s i t s may be a g i t a t e d as a r e s u l t of such e n g i n e e r i n g o p e r a t i o n s as c o n s t r u c t i o n of docks, b r i d g e s and o u t f a l l s and dredging of n a v i g a t i o n a l channels, o f f - s h o r e o i l e x p l o r a t i o n , d i s p o s a l of dredged m a t e r i a l s and motion of ships i n shallow waters. Sediments t r a n s p o r t e d by r i v e r s before e n t e r i n g oceans pass through e s t u a r i e s where the s a l t content of the water successively increases from less than 1 °/oo (parts per thousand) i n the r i v e r to 36 °/oo i n the ocean. I n d u s t r i a l e f f l u e n t discharges containing high concentration of dissolved s o l i d s may increase s a l t content of low flow freshwater streams Redox potentials i n natural waters depend upon dissolved oxygen (D.O.) l e v e l s ; high D.O. levels i n d i c a t i n g high redox potentials and low D.O. levels low redox p o t e n t i a l s . Redox changes are often associated with turnover and s t r a t i -f i c a t i o n cycles of natural waters. Deep water sediments are often low i n redox potential; discharge of decomposable wastes may also depress redox po t e n t i a l . Low pH conditions are ch a r a c t e r i s t i c of streams i n areas affected by mining and ore concentration operations. Natural v a r i a t i o n of s o i l minerals can also a f f e c t pH l e v e l s i n natural waters. Accidental or deliberate discharge of a c i d i c as well as alkaline materials can upset the pH balance of natural waters. Increasing a c i d i t y of r a i n and snow which enter natural waters, due to emissions from i n d u s t r i a l sources may also depress pH of natural waters. Poorly buffered waters are p a r t i c u l a r l y susceptible to this stress. Complexing organic compounds may be leached from s o i l s , produced i n aquatic environments or discharged i n i n d u s t r i a l or domestic ef f l u e n t s . Humic-like substances produced i n s o i l s or i n aquatic environments by microbial action on dead organic matter of plant or animal o r i g i n are an example of naturally produced complexing organic compounds. NTA ( n i t r i l o t r i a c e t i c acid) used i n detergents as a substitute 8 f o r phosphates t y p i f i e s complexing organic compounds discharged i n i n d u s t r i a l and domestic effluents. Microbial a c t i v i t y can vary with changes i n a v a i l -a b i l i t y of food and energy sources. For example, environments receiving untreated organic wastes w i l l have a higher microbial a c t i v i t y than an unpolluted environment. 1. E f f e c t of a g i t a t i o n In the early 1970's over 300,000,000 cubic meters of sediments were dredged annually i n the U.S.A. Management of dredging and disposal operations to minimize the impact on the aquatic environment required knowledge of the release/uptake behavior of trace metals and other contaminants. As a r e s u l t a m u l t i m i l l i o n d o l l a r research program was launched under the Dredged Material Research Program (DMRP) of the U.S. Corps of Engineers (Engler, 1976). Under th i s program, Lee and Plumb (1974) reviewed the e x i s t i n g l i t e r a t u r e to predict the release of contaminants, including trace metals, and concluded that most trace metals could p o t e n t i a l l y be mobilized with disturbance of sediments. Wakeman (1977) observed that Cr, Ni, Pb, and Zn were released s i g n i f i c a n t l y during the period of a dredging and disposal operation. I t was not determined whether the metals were removed from the s o l i d matrix during these operations or were already i n solution i n pore water. To assess p o t e n t i a l environmental impact of disposal of dredged materials i n natural waters the U.S. Environmental Protection Agency (EPA) h i s t o r i c a l l y used dredged m a t e r i a l d i s p o s a l c r i t e r i a based on the bulk composition of the dredged sediments. Soon i t was r e a l i z e d t h a t such a c r i t e r i o n was m i s l e a d i n g because environmental impact depends upon only a p o r t i o n of the t o t a l t r a c e metals, the p o r t i o n which i s a v a i l a b l e to the organisms a f t e r l e a c h i n g from the sediments. Consequently U.S. EPA (1973a) and the U.S. Corps of Engineers (U.S. EPA, 1973b) j o i n t l y developed a l e a c h i n g t e s t under a g i t a t i o n c o n d i t i o n s . The t e s t was c a l l e d the E l u t r i a t e T e s t . Lee e t a l . (1975) evaluated the performance of the t e s t and recommended the use of the t e s t i n p r e d i c t i n g the m o b i l i z a t i o n of t r a c e metals and other contaminants due to r e s u s p e n s i o n as i t occurs i n h y d r a u l i c dredging o p e r a t i o n s . The t e s t c o n s i s t s of a g i t a t i n g a sediment water mixture with compressed a i r , i n a 1:20 r a t i o f o r 30 minutes. The a g i t a t e d mixture i s allowed to s e t t l e f o r one hour and the supernatant decanted, f i l t e r e d and analyzed f o r t r a c e metals to determine the i n c r e a s e or decrease i n c o n c e n t r a t i o n s due to r e s u s p e n s i o n . Using t h i s t e s t with marine and f r e s h -water sediments and the a s s o c i a t e d waters sampled from v a r i o u s g e o g r a p h i c a l l o c a t i o n s i n the U.S. , Lee et a l . ( l 9 7 5 ) found t h a t Mn i s s u b s t a n t i a l l y r e l e a s e d , Zn was taken up and there was g e n e r a l l y no change i n c o n c e n t r a t i o n s of Cu, Cd, Pb and Fe. Chen et a l . (1976) c a r r i e d out l a b o r a t o r y i n v e s t i g a t i o n s to study t r a c e metal m o b i l i z a t i o n d u r i n g a g i t a t i o n and d u r i n g r e d e p o s i t i o n of the sediments, thus s i m u l a t i n g both dredging and dredged m a t e r i a l d i s p o s a l 10 o p e r a t i o n s i n aq u a t i c environments. Water and sediment samples f o r t h e i r study were obtained from marine and f r e s h -water environments of the Southern C a l i f o r n i a a r e a . Sediment, samples of s i l t y - s a n d , s a n d y - s i l t and s i l t y - c l a y types were c h a r a c t e r i z e d f o r p a r t i c l e s i z e and geochemical f r a c t i o n s of t r a c e metals. A modified form of the geochemical e x t r a c t i o n scheme of Engler et a l . (1974) was used f o r geochemical a n a l y s i s of the sediments. Chen et a l . (1976) suspended sediment-water mixtures i n the r a t i o of 1:20 i n p l e x i g l a s s columns f o r 48 hours. Then, they allowed the mixtures to s e t t l e . Samples of water were obtained p e r i o d i c a l l y both under suspension and s e t t l e d c o n d i t i o n s and analyzed f o r t r a c e metals a f t e r f i l t r a t i o n . Under s e t t l e d c o n d i t i o n s experiments l a s t e d f o r as l o n g as 120 days. Under suspension c o n d i t i o n s no r e l e a s e of Ag, Cd and Hg was observed by Chen et a l . (1976). C o n c e n t r a t i o n s of Cr, Cu and Pb were i n c r e a s e d by f a c t o r s r a n g i n g from 3 to 10 over the background seawater l e v e l s . Release of Fe, Mn and Zn was even l a r g e r . Release of metals from freshwater sediments i n seawater was somewhat g r e a t e r than the r e l e a s e from the marine sediments. Since background l e v e l s of t r a c e metals i n seawater are g e n e r a l l y low and the c o n c e n t r a t i o n s of t r a c e metals i n seawater a f t e r r e l e a s e from sediments were s t i l l low, hence the short-term impact of dredging on water q u a l i t y was considered i n s i g n i f i c a n t . In the long-term (120 days) experiments of Chen et a l . (1976), a f t e r sediments were s e t t l e d , redox c o n d i t i o n s 11 were a c c u r a t e l y c o n t r o l l e d . Release of t r a c e metals i n these qu i e s c e n t experiments depended upon redox p o t e n t i a l . These r e s u l t s w i l l be d i s c u s s e d i n a d i f f e r e n t s e c t i o n of t h i s review. Windom (1975) reviewed the l i t e r a t u r e r e s u l t i n g from f i e l d s t u d i e s around dredging o p e r a t i o n s . His review i n d i c a t e d t h a t the impact of a g i t a t i o n of contaminated sediments on water q u a l i t y , p a r t i c u l a r l y with r e s p e c t to t r a c e metals.was minimal. However, the author warned t h a t under c e r t a i n c o n d i t i o n s the r e l e a s e could be s u b s t a n t i a l and s t a t e d t h a t more i n f o r m a t i o n i s r e q u i r e d to determine what might happen when s e v e r e l y contaminated sediments are dredged. Independent of the DMRP, Rohatgi and Chen (1975) a l s o c a r r i e d out l a b o r a t o r y experiments which i n d i c a t e d t h a t sediments contaminated with sewage a s s o c i a t e d s o l i d s c o u l d i n oxic seawater r e l e a s e t r a c e metals on a g i t a t i o n . Sewage s o l i d s were kept i n suspension i n seawater i n the presence of a i r f o r p e r i o d s up to 36 days. Release of Cd, Pb, Cu, N i , Zn and Fe was observed to take p l a c e i n two-steps, a r a p i d r e l e a s e f o l l o w e d by a slower long-term r e l e a s e . A s i m i l a r two -step r e l e a s e was a l s o observed f o r Hg when contaminated organic r i c h sediments were a g i t a t e d i n s i t u ( L i n d b e r g and H a r r i s s , 1977). In each case the r e l e a s e was a t t r i b u t e d to o x i d a t i o n of org a n i c s and subsequent r e l e a s e of the metal ions i n the process. Release of t r a c e metals from d i s t u r b e d sediments may depend upon a number of other f a c t o r s (Lu and Chen, 1977; Jones, 1978; F o r s t n e r and Wittmann, 1979). 12 2. E f f e c t of s a l i n i t y In r e c e n t years, growing concern has been expressed t h a t discharge of s a l t s i n i n d u s t r i a l e f f l u e n t s and s p r i n g r u n o f f from the highways and snow dumps to freshwater streams and lakes may desorb t o x i c t r a c e metals ( F e i c k et a l . , 1972; Hanes et a l . , 1970; U.S. EPA, 1971; S c o t t , 1980). Experiments where e x c e s s i v e amounts of sodium c h l o r i d e and calcium c h l o r i d e were shaken with freshwater sediments i n d i c a t e d t h a t s i g n i f i c a n t amounts of t r a c e metals l i k e Hg may be r e l e a s e d due to d e s o r p t i o n with s a l t s ( F e i c k et a l . , 1972). In these experiments Hg was more e a s i l y removed from sandy sediment than from the sediment high i n or g a n i c matter. S i m i l a r l y , Holmes et a l . (1974.) a g i t a t e d samples of sediment f o r 30 minutes i n 0.5M s o l u t i o n of NaCl. Subsequent a n a l y s i s of f i l t e r e d s o l u t i o n s showed a s u b s t a n t i a l r e l e a s e of Cd and Zn. The extent of metal r e l e a s e d i n s a l t s o l u t i o n was i n p r o p o r t i o n to the amount of the metal l e a c h a b l e from the sediment on a g i t a t i o n f o r 30 minutes i n a s o l u t i o n of IM hydroxylamine-hydrochloride and 25 percent (v/v) a c e t i c a c i d . The p o t e n t i a l of r e l e a s e of t r a c e metals bound to sediments i s g r e a t e r i n e s t u a r i n e environments where m i l l i o n s of tons of freshwater sediments t r a n s p o r t e d by r i v e r s are exposed to the s a l i n e environment. Although i t has been recog n i z e d t h a t a complex chemical environment such as an estuary cannot be simulated by simple l a b o r a t o r y experiments i n v o l v i n g homogenous r e a c t i o n k i n e t i c s (Turekian, 1977), u s e f u l 1 3 i n f o r m a t i o n about r e l e a s e of t r a c e metals from sediments on suspension i n seawater has been generated. As part of a major study conducted to estimate d i s s o l v e d t r a c e metal f l u x from r i v e r s to oceans, Kharkar et a l . (1968) c a r r i e d out a d s o r p t i o n - d e s o r p t i o n s t u d i e s i n v o l v i n g c l a y s , minerals and e i g h t metals (Ag, Sb, Cr, Rb, Cs, Se, Co and Mo). On the b a s i s of these experiments, the authors s t a t e d t h a t due to d e s o r p t i o n from suspended p a r t i c u l a t e s Co has an a d d i t i o n a l supply of about twice the d i s s o l v e d l o a d , while Ag and Se add only an a d d i t i o n a l 10 percent more, and Cr and Mo none. Wagemann et a l . (1977) leached suspended and bottom sediments obtained from the MacKenzie R i v e r , N.W.T., Canada, by m e c h a n i c a l l y suspending them i n Beaufort Seawater f o r pe r i o d s of 2 to 100 hours. No s i g n i f i c a n t r e l e a s e of Cd, Co, Cr, Pb and Zn from suspended sediment was measured. Iron and Mn were r e l e a s e d to a sm a l l but measurable e x t e n t . About 50 percent of the copper i n seawater was adsorbed by the suspended sediment. The e f f e c t of l e a c h i n g time was n e g l i g i b l e f o r Fe but the percent r e l e a s e of Mn s i g n i f i c a n t l y i n c r e a s e d with time. R a d i o a c t i v e i s o t o p e s of t r a c e metals are c h e m i c a l l y i d e n t i c a l to the n o n r a d i o a c t i v e atoms of the r e s p e c t i v e metals; t h e r e f o r e , i n v e s t i g a t i o n s c a r r i e d out with l a b e l l e d metals are e q u a l l y important. Johnson (1966) and Johnson et a l . (1967) observed t h a t although r a d i o i s o t o p e s Co, Zn and Mn i n the e f f l u e n t s from the Hanford, Washington, r e a c t o r were i n i o n i c 14 form, they were i n c o r p o r a t e d i n t o p a r t i c u l a t e s by the time they reached the Columbia R i v e r e s t u a r y . The authors r e a l i z e d t h a t on mixing with seawater the r a d i o a c t i v i t y could be r e l e a s e d a g a i n . Subsequent experiments confirmed the b e l i e f ; under experimental c o n d i t i o n s seawater r e l e a s e d some 4O percent of ^Mn, 5 to 15 percent of ^ C o and only 1 percent 65 or l e s s of Zn. In another study (Robertson et a l . , 1973) these r e s u l t s were s u b s t a n t i a t e d . In the above experiments only one to two hour l e a c h i n g times were allowed. To i n v e s t i g a t e the e f f e c t of l o n g e r l e a c h i n g time, C u t s h a l l et a l . (1973) and Evans and C u t s h a l l (1973) provided a l e a c h i n g time of up to 11 weeks. The percentage of n u c l i d e s leached was approximately the same, about 50 p e r c e n t f o r ^Mh and very l i t t l e of ^ Z n and ^ C o . P a t e l et a l . (1978) i n s i m i l a r . e x p e r i m e n t s observed 13Z. 137 t h a t the amount of Cs and Cs r e l e a s e d i n c r e a s e d l i n e a r l y w i t h s a l i n i t y . In an e s t u a r i n e s i t u a t i o n , d e s o r p t i o n due to i n c r e a s i n g s a l i n i t y i s j u s t one of many processes t a k i n g p l a c e s i m u l t a n e o u s l y (Turekian, 1971). At the r i v e r - e s t u a r y boundary the three main processes o c c u r r i n g are: (a) d e s o r p t i o n of adsorbed t r a c e metals on s u r f a c e s of r i v e r - b o r n e sediments due to competing c a t i o n s and the s t a b i l i z i n g e f f e c t of complexation with c h l o r i d e and other a n i o n i c species (Kharkar et a l . , 1968), (b) h y d r o l y s i s and c o a g u l a t i o n of t r a c e metals due to i n c r e a s i n g pH which tends to counterbalance the d e s o r p t i o n e f f e c t of s a l i n i t y (Turekian, 1971) and (c) the 15 i n c r e a s e d i o n i c s t r e n g t h at hig h s a l i n i t y induces a " s a l t i n g out" e f f e c t on the r i v e r t r a n s p o r t e d p a r t i c u l a t e s and those produced i n s i t u (Boyle et a l . , 1977; Edzwald et a l . , 1974-). At the estuary-bottom sediment i n t e r f a c e , p a r t i c u l a t e s c a r r y i n g t r a c e metals accumulate from the o v e r l y i n g water and , c o n v e r s e l y , p r e v i o u s l y accumulated t r a c e metals may be r e l e a s e d due to chemical and bi o c h e m i c a l r e a c t i o n s . H y d r a u l i c c i r c u l a t i o n due to t i d a l c y c l e s i s s t i l l another c o m p l i c a t i n g f a c t o r (Grieve and F l e t c h e r , 1977). Consequently, r e s u l t s of e s t u a r i n e surveys f o r t r a c e metals are q u i t e d i f f i c u l t to i n t e r p r e t . Holmes et a l . (1974)>during a t r a c e metal survey i n Corpus C h r i s t i Bay, Texas, found that Zn and Cd l e v e l s i n the sediments were anomalously high and changed s i g n i f i -c a n t l y between the summer and winter seasons. Acc o r d i n g to these authors, the metals were p r e c i p i t a t e d under stagnant r e d u c i n g c o n d i t i o n s i n summer and i n winter water c u r r e n t s i n c r e a s e d oxygen l e v e l s and as a r e s u l t t r a c e metals d e p o s i t e d under low oxygen l e v e l s were r e m o b i l i z e d due to d e s o r p t i o n and d i s s o l u t i o n of p r e c i p i t a t e s . A t r a c e metal survey i n the F r a s e r River e s t u a r y , B r i t i s h Columbia, i n d i c a t e d t h a t both d i s s o l v e d and suspended loads were i n c r e a s i n g i n the e s t u a r y (Grieve and F l e t c h e r , 1977). The r e s u l t s were e x p l a i n e d by a d s o r p t i o n and d e s o r p t i o n t a k i n g place s i m u l t a n e o u s l y . Upstream c i r c u l a t i o n of marine bottom sediments c o n t a i n i n g Zn provides the supply of the metal to c o r r e c t the apparent imbalance. Thomas and G r i l l (1977) a l s o observed i n c r e a s e s i n d i s s o l v e d l e v e l s f o r Cu and Zn i n the F r a s e r R i v e r e s t u a r y and a t t r i b u t e d them to d e s o r p t i o n at the r i v e r - e s t u a r y i n t e r f a c e . Graham et a l . (1976) i n v e s t i g a t e d Mn i n samples obtained from Narragansett Bay, Rhode I s l a n d and i t s surrounding r i v e r s . The r e s u l t s i n d i c a t e d that t o t a l Mn was approximately c o n s e r v a t i v e but p a r t i c u l a t e and d i s s o l v e d Mn were not. Manganese was d i s s o l v i n g from r i v e r i n e p a r t i c u l a t e s i n t i d a l reaches of the r i v e r a t low s a l i n i t i e s . In the Bay, d i s s o l v e d Mn was p r e c i p i t a t i n g , p r o b a b l y due to o x i d a t i o n a t the higher bay water pH. 3. E f f e c t of redox changes The o v e r a l l redox c o n d i t i o n of sediments has been shown to play an important r o l e i n c o n t r o l l i n g the chemical exchange r e a c t i o n s a f f e c t i n g t r a n s p o r t of t r a c e metals a c r o s s the sediment-water i n t e r f a c e . From a l i t e r a t u r e review Mortimer (1971) concluded t h a t as long as .bottom d i s s o l v e d oxygen c o n c e n t r a t i o n s i n the Great Lakes remain between 1-2 mg/1, chemical exchange from the sediment d e p o s i t s may exert a measurable but q u a n t i t a t i v e l y i n s i g n i f i c a n t e f f e c t on the chemistry of the water i n the l a k e s . In an e a r l i e r work (Mortimer, 1941 and 1942), he found t h a t as d i s s o l v e d oxygen l e v e l f e l l to a n a l y t i c a l zero, redox p o t e n t i a l i n the s u r f a c e l a y e r of the sediment as i n d i c a t e d by an e l e c t r o d e a l s o f e l l . These changes were accompanied by r e l e a s e of sediment t r a c e metals: f i r s t Mn, l a t e r Fe. In a d d i t i o n to 17 Mn and Fe r e l e a s e , l i b e r a t i o n of ammonia and s i l i c a t e was a l s o measured. A f u r t h e r decrease i n redox p o t e n t i a l r e s u l t e d i n m i c r o b i a l r e d u c t i o n of sulphate. P a t r i c k J r . et a l . (1973) i n v e s t i g a t e d the e f f e c t of redox p o t e n t i a l and pH c o n d i t i o n s on the s o l u b i l i t y of s t r e n g i t e , a mineral component of s o i l s and sediments. Suspensions of s o i l i n water c o n t a i n i n g s t r e n g i t e were incubated f o r 7 to 10 days at p r e c i s e l y c o n t r o l l e d d i f f e r e n t redox p o t e n t i a l 1 (+300 to -250 mV) and pH (5.0 to 8.0) c o n d i t i o n s . At the end of the i n c u b a t i o n p e r i o d s the suspensions were e x t r a c t e d with ammonium acetate s o l u t i o n s having the same pH and under the same redox s t a t e as the suspensions. A n a l y s i s of the e x t r a c t s i n d i c a t e d t h a t the g r e a t e s t r e l e a s e of Fe and phosphate occurs under c o n d i t i o n s of low o x i d a t i o n - r e d u c t i o n p o t e n t i a l i n combination with low pH. Experiments by Chen et a l . (1976) were d i s c u s s e d above. They i n v e s t i g a t e d "effects of a g i t a t i o n and redox c o n d i t i o n s on t r a c e metal r e l e a s e from geochemically and p h y s i c a l l y c h a r a c t e r i z e d sediments and showed t h a t redox c o n d i t i o n s of the water c o n t r o l ' t h e exchange r e a c t i o n s , and the geochemistry of sediments plays l i t t l e or no r o l e . In oxygen d e f i c i e n t c o n d i t i o n s they observed a g r e a t e r r e l e a s e of Fe and Mn. During t h e i r quiescent long-term experiments , 1. A l l redox p o t e n t i a l s r e p o r t e d i n t h i s t h e s i s are standard redox p o t e n t i a l s ( i . e . r e l a t i v e to hydrogen). This i s the standard p r a c t i c e i n the l i t e r a t u r e . 18 2 c o n c e n t r a t i o n s of these metals almost reached the ppm range under reducing c o n d i t i o n s . The e f f e c t of redox changes i n the water column on exchange from sediment was s t u d i e d by F i l l o s and Swanson (1974). Water purged with a i r or n i t r o g e n gas was g e n t l y passed over a l a y e r of r i v e r sediment. C o n c e n t r a t i o n s of n u t r i e n t s and Fe were measured i n the water. Iron and phosphate were s u b s t a n t i a l l y m o b i l i z e d from sediment when d i s s o l v e d oxygen c o n c e n t r a t i o n i n the water was zero (achieved by purging with n i t r o g e n g a s ) . Ir o n and Mn occur i n sediments as hydrous oxide c o a t i n g s on p a r t i c l e s (Gibbs, 1 9 7 3 ) . Oxides of Fe and Mn have long been recognized as scavengers of t r a c e metals (Jenne, 1 9 6 8 ; McKenzie, 1972). T e s s i e r et a l . (1980) conducted a geochemical p a r t i t i o n i n g study on sediments obtained from two Quebec r i v e r s and showed t h a t t r a c e metals o r i g i n a t i n g from anthropogenic sources were bound to Fe and Mn oxides. Under anoxic c o n d i t i o n s the Fe and Mn phase of sediments becomes unstable and a m o b i l i z a t i o n of a s s o c i a t e d t r a c e metals r e s u l t s (Morgan and Stumm, 1 9 6 4 ) . Environmental c o n d i t i o n s may change from anoxic to o x i c c o n d i t i o n s i n stagnant waters such as f j o r d s and l a k e s due to turnover during' s p r i n g and f a l l (Mortimer, 194-2; Hutchinson, 1957). D i s s o l v e d Fe and Mn s p e c i e s undergo o x i d a t i o n , h y d r o l y s i s and p o l y m e r i z a t i o n (Stumm and Morgan, • 2~! Par t s per m i l l i o n . Throughout t h i s t h e s i s 'ppm' when a p p l i e d to water i s synonymous to mg/1, but when used f o r s o l i d s (sediments or b i o t a ) the u n i t i s e q u i v a l e n t to mg/kg (or jU.g/g) on a dry weight b a s i s u n l e s s i n d i c a t e d otherwise. 1 9 1970; Stumra and Lee, I960) to form coatings on sediment p a r t i c l e s . These f r e s h l y formed coat i n g s have s t r o n g a f f i n i t y f o r other t r a c e metal c a t i o n s (Jenne, 1968; Means et a l . , 1978). Thus, the t r a c e metal r e l e a s e may be hindered or completely stopped i f redox c o n d i t i o n s change from anoxic to p a r t i a l l y or f u l l y o x i c c o n d i t i o n s . In the above d i s c u s s i o n the m o b i l i z a t i o n of t r a c e metals under the i n f l u e n c e of redox changes from sediments would appear to bear a simple r e l a t i o n s h i p to Fe and Mn c y c l e s i n the n a t u r a l environment. However, there are other components which undergo redox changes and i n the process a f f e c t m o b i l i z a t i o n of t r a c e metals. Under extremly r e d u c i n g c o n d i t i o n s , sulphate ions are m i c r o b i a l l y reduced to v a r i o u s s u l p h i d e s p e c i e s , H 2S, HS~, S 2~ ( B e l l a , 1972). In the presence of sulphides the p r e d i c t e d r e l e a s e of Fe, Mn and a s s o c i a t e d t r a c e metals may not be observed as metals r e a c t w i t h s u l p h i d e to form extremely low s o l u b i l i t y compounds (Thompson et a l . , 1975). Spencer and Brewer (1971) i n a t r a c e metal survey of the Black Sea observed that i n bottom waters Cu and Zn were depleted due to p r e c i p i t a t i o n as i n s o l u b l e s u l p h i d e s . However, Fe and Mn c o n c e n t r a t i o n s were higher i n the bottom anoxic water l a y e r than i n the o x i c upper l a y e r because s u l p h i d e s of the reduced forms of these metals are more s o l u b l e than the hydroxides and oxides of t h e i r o x i d i z e d forms. Sulphide d e p o s i t s of t r a c e metals are s t a b l e under anoxic c o n d i t i o n s and l e s s s o l u b l e s u l p h i d e s are more s t a b l e (Engler and P a t r i c k J r . , 1975). 20 Presence of organic compounds a l s o a f f e c t s the m o b i l i z a t i o n of t r a c e metals from sediments. Pore waters r i c h i n s u l p h i d e s o f t e n have been found to c o n t a i n t r a c e metal l e v e l s f a r higher than those that can be c a l c u l a t e d from metal sulphide s o l u b i l i t i e s ( P r e s l e y et a l . , 1 9 6 7 ; E l d e r f i e l d and Hepworth, 1 9 7 5 ; E l d e r f i e l d et a l . , 1 9 7 1 ) . The hig h c o n c e n t r a t i o n s were a t t r i b u t e d to for m a t i o n of s o l u b l e complexes with or g a n i c compounds. Also under o x i c c o n d i t i o n s organic compounds p l a y an important r o l e i n modifying s o l u b i l i t y e q u i l i b r i a of t r a c e metals. Rohatgi and Chen (1975) measured two stage r e l e a s e of t r a c e metals Cd, Cu, N i , Pb and Zn from sewage-related s o l i d s on suspension i n seawater under o x i c c o n d i t i o n s . The f i r s t r a p i d r e l e a s e was a t t r i b u t e d to o x i d a t i o n of r e a d i l y o x i d i z a b l e o r g a n i c matter and the second slow r e l e a s e to o x i d a t i o n of r e l a t i v e l y i n e r t organic matter. A s i m i l a r two-step r e l e a s e of Hg from organic r i c h sediments was observed by Lindberg and H a r r i s s ( 1 9 7 7 ) . S t r u c t u r a l l y complex, l a r g e molecular weight organic compounds c h a r a c t e r i s t i c of anoxic environments are r e p o r t e d to be a l t e r e d to s m a l l e r l e s s complex compounds with l e s s metal b i n d i n g capaci-ty as a s o i l or sediment i s o x i d i z e d (Stevenson and A r d a k a r n i , 1 9 7 2 ; P a t r i c k J r . and Mikkelsen, 1 9 7 1 ) . Thus, i t appears that under changing redox c o n d i t i o n s the f a t e of t r a c e metals i n the a q u a t i c environment i s determined by chemical i n t e r a c t i o n s of Fe, Mn, S and organic m a t e r i a l s . 21 4. pH e f f e c t s pH of n a t u r a l waters may vary c o n s i d e r a b l y ; pH val u e s f o r s u r f a c e waters may range from 0 to 11 (Krauskopf, 1967). High pH values i n s u r f a c e waters may be caused by n a t u r a l a l k a l i n e compounds from s o i l s i n the watershed or by d i s p o s a l of a l k a l i n e i n d u s t r i a l wastes, such as products c o n t a i n i n g c a u s t i c soda. Runoff from mining areas and a c i d i c d i s c h a r g e s from i n d u s t r i a l operations are among the common sources of a c i d i t y i n n a t u r a l waters. In r e c e n t y e a r s , a c i d r a i n has been r e c o g n i z e d as an important source of a c i d i t y of n a t u r a l waters. In Sweden alone, more than 5000 l a k e s have pH values below 5 (Babich et a l . , 1980). Changes i n pH can have an immense e f f e c t on s o l u b i l i t y of t r a c e metals i n water. A number of authors have c a r r i e d out t h e o r e t i c a l c a l c u l a t i o n s f o r s o l u b i l i t i e s of s e l e c t e d t r a c e metals (Mann and Deutscher, 1977; Hem,1972; Hem and Durum, 1973; Stumm and Lee,1960). According to s o l u b i l i t y - pH curves presented i n these r e f e r e n c e s ,trace metals are extremely s o l u b l e at pH = 1 or l e s s and i n most cases the s o l u b i l i t i e s r a p i d l y decrease as pH i n c r e a s e s towards n e u t r a l i t y . Most t r a c e metals have s o l u b i l i t y minima a t n e u t r a l to s l i g h t l y a l k a l i n e pH values. Under s t r o n g l y a l k a l i n e c o n d i t i o n s (pH 10) the s o l u b i l i t i e s i n c r e a s e a g a i n . T h i s i n f o r m a t i o n i s obtained from thermodynamic and k i n e t i c data f o r the t r a c e metals p u b l i s h e d i n the l i t e r a t u r e and assumes t h a t waters contain only a few s e l e c t e d a n i o n i c s p e c i e s such as carbonates, s u l p h a t e s , 22 c h l o r i d e s and hydroxides. In the n a t u r a l a q u a t i c environment, the presence of p a r t i c u l a t e and d i s s o l v e d matter of. complex nature may s i g n i f i c a n t l y a l t e r the s o l u b i l i t y - pH r e l a t i o n -s h i p s d e p i c t e d from t h e o r e t i c a l c a l c u l a t i o n s (Farrah and P i c k e r i n g , 1977; Hem, 1972; Payne and P i c k e r i n g , 1975; Bunzl, 1979; Gupta and H a r r i s o n , 1980). To o b t a i n more meaningful r e s u l t s a l i m i t e d number of l a b o r a t o r y s t u d i e s have been conducted using m a t e r i a l s obtained from the n a t u r a l environment. A b r i e f summary of these s t u d i e s f o l l o w s : Stokes and Szokalo (1977) set up l a b o r a t o r y experiments with sediments and water obtained from l a k e s i n the Sudbury area of O n t a r i o . The sediments were contaminated with Cu and Ni b e l i e v e d to be from the metal smelters o p e r a t i n g i n the area. The purpose of the experiments was to study the e f f e c t of d i s s o l v e d oxygen and m i c r o b i o l o g i c a l r e a c t i o n s on the r e l e a s e of Cu and Ni a s s o c i a t e d with the sediments. Sediment cores o v e r l a i d with a l a y e r of f i l t e r e d water were incubated i n g l a s s j a r s under o x i c , anoxic, ' l i v e ' , and ' s t e r i l e ' c o n d i t i o n s . The i n c u b a t i o n c o n d i t i o n s were e s t a b l i s h e d by g e n t l y b u b b l i n g a i r ( o x i c ) , s e a l i n g the g l a s s j a r s with 'saran wrap' ( a n o x i c ) , and a u t o c l a v i n g the sediments ( s t e r i l e ) . Oxic and anoxic systems with unautoclaved sediments represented ' l i v e ' c o n d i t i o n s . T h e i r r e s u l t s showed t h a t Cu and Ni r e l e a s e was s u b s t a n t i a l l y g r e a t e r under a e r o b i c ' l i v e ' c o n d i t i o n s as compared to t h a t under anaerobic ' l i v e ' or ' s t e r i l e ' 23 c o n d i t i o n s . I n each c a s e , the r e l e a s e o f the m e t a l s appeared t o be r e l a t e d t o drop i n pH. The drop i n pH and the r e l e a s e of metals was minimum under ' s t e r i l e ' a n a e r o b i c c o n d i t i o n s . Hence, d i s s o l v e d oxygen ( h i g h redox p o t e n t i a l ) and m i c r o b i o l o g i c a l a c t i v i t y seem t o f a v o u r r e l e a s e o f Cu and N i by l o w e r i n g pH o f the sediment - water systems. The a u t h o r s a t t r i b u t e d the g r e a t e s t pH drop under the l i v e a e r o b i c c o n d i t i o n s t o o x i d a t i o n of s u l p h u r and s u l p h i d e s i n the sediments t o s u l p h a t e . T h i s does not mean t h a t redox p o t e n t i a l change was overshadowed by a pH change but t h a t changes i n redox p o t e n t i a l c o u l d cause a pH change which was r e s p o n s i b l e f o r m e t a l r e l e a s e . O'Connor and Renn ( 1964) i n v e s t i g a t e d the e q u i l i b r i u m r e l a t i o n s h i p s between d i s s o l v e d Zn, suspended sediment and pH f o r f r e s h w a t e r systems. R e s u l t s of t h e i r l a b o r a t o r y s t u d i e s suggest t h a t the c o n c e n t r a t i o n of d i s s o l v e d Zn i n a n a t u r a l stream s h o u l d be i n v e r s e l y p r o p o r t i o n a l t o water pH and the l o g a r i t h m of suspended s o l i d s c o n c e n t r a t i o n . G a m b r e l l e t a l . (1980) c a r r i e d out a l a b o r a t o r y s tudy t o determine the e f f e c t of d i f f e r e n t pH and redox c o n d i t i o n s on c h e m i c a l a v a i l a b i l i t y of Hg, Pb and Zn. M o b i l e Bay sediments and s u r f a c e water m i x t u r e s were k e p t i n s u s p e n s i o n under p r e c i s e l y c o n t r o l l e d pH (5.0, 6.5 and 8.0) and redox c o n d i t i o n s (-150, +50, +250 and +500 mV) f o r p e r i o d s o f two weeks. A comparison o f t r a c e m e t a l l e v e l s i n sediments b e f o r e and a f t e r the two week p e r i o d i n d i c a t e d t h a t s u b s t a n t i a l amounts of Zn were r e l e a s e d t o water a t pH 5 and 24 o x i d i z i n g environmental c o n d i t i o n s (+50, +250 and +500 mV). The other two metals were not s i g n i f i c a n t l y r e l e a s e d , sugg e s t i n g t h a t t r a c e metal r e l e a s e may a l s o depend on the type of a metal. E f f e c t s of pH on t r a c e metal m o b i l i t y are more dramatic i n low pH n a t u r a l waters. A study of Adirondack Mountain Lakes (Galloway et a l . , 1976) showed t h a t t r a c e metals, A l , Fe, Mn and Zn were 10 times higher i n water of a l a k e with pH 4 . 7 than i n the water of another lake w i t h pH of 6.7. At the same time, the top l a y e r of the sediments i n the more a c i d i c l a k e was d e p l e t e d of t r a c e metals. Menon et a l . (1979) observed that Cd, Cu and Zn l e v e l s i n South Mosquito Lagoon near Kennedy Space Centre v a r i e d s e a s o n a l l y . Trace metal l e v e l s i n the water were h i g h d u r i n g the summer months when pH was low; a c i d i t y i n the water was considered at l e a s t p a r t i a l l y r e s p o n s i b l e f o r the r e l e a s e of t r a c e metals from the bottom sediments. Sanchez and Lee (1978) noted t h a t , i n the e p i l i m n i o n of Lake Minona, Wisconsin, d i s s o l v e d Cu l e v e l s were i n v e r s e l y r e l a t e d to pH. Increase i n d i s s o l v e d Cu a t low pH was a t t r i b u t e d to d i s s o l u t i o n of Cu carbonate d e p o s i t s i n the sediments of t h i s hardwater l a k e . 5. E f f e c t of o r g a n i c complexing agents Although o r g a n i c matter normally makes up only 2 to 3 percent of sediments and r a r e l y exceeds a maximum of 20 mg/l i n water, i t . p l a y s an extremely important r o l e i n processes a f f e c t i n g t r a c e metals i n the a q u a t i c environment. Humic 2 5 compounds as p r i n c i p a l constituents of organic matter are p a r t i c u l a r l y important. Mobilization of trace metals by organic substances may occur i n a number of ways: ( 1 ) Fe and Mn may be reduced to more soluble divalent forms (Hem, I 9 6 0 ; Rawson, 1 9 6 3 ) » (2) metal ions may form soluble co-ordinate complexes with organic compounds (Rashid and Leonard, 1 9 7 3 ; Baker, 1 9 7 8 ; Boxma, 1 9 7 6 ) , ( 3 ) the metal ions may mobilize by forming metallo-organic c o l l o i d s (Hutchinson, 1 9 5 7 ; Stumm and Morgan, 1 9 7 0 ) and (4.) trace metals bound to particulate organic matter may s o l u b i l i z e on break-down of the organics under oxic conditions to simple soluble compounds (Rohatgi and Chen, 1 9 7 5 ; and Lindberg and Harriss, 1 9 7 7 ) . Kee and Bloomfield ( I 9 6 I ) studied the mobilization of a number of trace metals (Cu, Zn, Co, Ni, Mn, Pb, Cr , T i , Ga and Mo) from th e i r oxides by decomposing plant materials. Some of the metals (Zn, Cu, Pb, Mn, Fe etc.) were considerably s o l u b i l i z e d . D i a l y s i s and p H - s t a b i l i t y tests suggested that the metals were i n true solution i n the form of organic complexes and free ions. Decomposition of plant material Was generally accompanied by a decrease i n pH; therefore, at least a part of s o l u b i l i z a t i o n was due to low pH. Brockamp ( 1 9 7 6 ) found that Fe and Mn were released from rocks and minerals by the action of organic acids ( s a l i c y l i c acid, c i t r i c acid, tannic acid and humic acid) which occur naturally i n s o i l s and sediments. 26 Although the above s t u d i e s i n d i c a t e t h a t n a t u r a l organic compounds can cause c o n s i d e r a b l e m o b i l i z a t i o n of t r a c e metals from contaminated sediments and s o i l s , d i s c harge of s y n t h e t i c complexing agents to the a q u a t i c environment v i a i n d u s t r i a l and domestic e f f l u e n t s may make the s i t u a t i o n worse Co n s i d e r a b l e r e s e a r c h e f f o r t has been made to i n v e s t i g a t e the environmental impact of NTA ( N i t r i l o t r i a c e t i c a c i d ) from i t s use i n d e t e r g e n t s . Gregor (1972) noted t h a t Pb th a t had accumulated i n sediments as a r e s u l t of automobile emissions, was r e l e a s e d i n t o water c o n t a i n i n g NTA a t c o n c e n t r a t i o n s of 2 and 20 mg/l. The r e l e a s e of Pb, a t the higher c o n c e n t r a t i o n of NTA, was 12 times the American P u b l i c H e a l t h S e r v i c e maximum al l o w a b l e l e v e l f o r d r i n k i n g water s u p p l i e s . S i m i l a r l y Z i t k o and Carson (1972) observed t h a t Zn, c u p r i c and f e r r i c i ons were r e l e a s e d from sediments by NTA even at c o n c e n t r a t i o n s as low as 1.0 mg/l. In experiments with d i f f e r e n t c o n c e n t r a t i o n s (0-100 mg/l), they observed t h a t the amount of r e l e a s e d metal ions i n c r e a s e d with i n c r e a s i n g c o n c e n t r a t i o n of NTA and l e v e l e d o f f above a c e r t a i n c o n c e n t r a t i o n . In a d d i t i o n , the r e l e a s e depended upon sediment type and hardness of the water used i n the study. The r e l e a s e was much gr e a t e r from the sediments obtained from the Tomogonops R i v e r than from those obtained from the M i r a m i c h i R i v e r . Increased water hardness appeared to suppress the r e l e a s e of the t r a c e metal ions somewhat. 27 Banat et a l . (1974) a l s o measured a high percent r e l e a s e f o r Cu and Cd and a s l i g h t r e l e a s e f o r Ni from sediments shaken i n water c o n t a i n i n g d i f f e r e n t c o n c e n t r a t i o n s of NTA (1-100 ppm). Sediment samples f o r t h i s study were obtained from the contaminated p a r t s of the r i v e r s Wupper ( T r i b u t a r y of Rhine) and E l s e n z ( T r i b u t a r y of Neckar). The r e l e a s e of Cu and Cd i n c r e a s e d with both i n c r e a s i n g NTA c o n c e n t r a t i o n and shaking time. As these s t u d i e s i n d i c a t e , there i s a l i t t l e doubt t h a t NTA once i n the a q u a t i c environment can m o b i l i z e t r a c e metals. However, at present a c o n s i d e r a b l e degree of c o n t r o v e r s y e x i s t s with r e s p e c t to the q u a n t i t i e s of NTA d i s c h a r g e d to the a q u a t i c environment and i t s s t a b i l i t y once d i s c h a r g e d , i . e . , i t s e f f e c t i v e c o n c e n t r a t i o n i n r e c e i v i n g waters (Stoveland et a l . , 1980: Shannon et a l . , 1974)-6. E f f e c t of m i c r o b i a l a c t i v i t y Three major processes are r e s p o n s i b l e f o r m o b i l i z a t i o n of t r a c e metals through b a c t e r i a l a c t i o n : (1) d e s t r u c t i o n of complex sedimentary organic matter to simple o r g a n i c compounds which form s o l u b l e c o - o r d i n a t i v e complexes with the metals, (2) changes i n redox p o t e n t i a l and pH of the sediment-water systems, and (3) b a c t e r i a l l e a c h i n g of metal 28 s u l p h i d e s . L i t e r a t u r e on the f i r s t two processes has a l r e a d y been d i s c u s s e d above, a review of the t h i r d process f o l l o w s . Although the knowledge that b a c t e r i a a t t a c k m i n e r a l s u l p h i d e s i s r e l a t i v e l y new, n a t u r a l l e a c h i n g has been o c c u r r i n g f o r c e n t u r i e s . Presence of Cu i n mine drainage was d e s c r i b e d as e a r l y as Roman times (B.C. Research pamphlet). I t was only i n 194-7 t h a t two American s c i e n t i s t s , Colmer and H i n k l e , showed t h a t a c i d and i r o n contained i n c o a l mine drainage are the r e s u l t of b a c t e r i a l a c t i o n on the i r o n s u l p h i d e i n the c o a l seams (B.C. Research pamphlet). As reviewed by F o r s t n e r and Wittmann (1979),a group of b a c t e r i a , known as T h i o b a c i l l i , i s capable of o x i d i z i n g s u l p h i d e to s u l p h a t e . The o x i d a t i o n process s u p p l i e s energy r e q u i r e d by the organisms f o r t h e i r chemoautotrophic growth. These b a c t e r i a g e n e r a l l y can t o l e r a t e a c i d i c c o n d i t i o n s ; f o r example, optimum pH f o r T h i o b a c i l l u s t h i o o x i d a n s i s approximately 2.0. O x i d a t i o n of s u l p h i d e to sulphate coupled with r e s u l t i n g low pH provides a mechanism f o r metal m o b i l i z a t i o n . B a c t e r i a l l e a c h i n g i s o f t e n the cause f o r high metal c o n c e n t r a t i o n s i n streams d r a i n i n g m i n e r a l i z e d areas. C o l l i n s (1973). i n a survey of a p a r t of the watershed of Connecticut R i v e r , found Cu c o n c e n t r a t i o n s as high as 27.8 mg/1. Corbett (1977) measured t r a c e metals i n streams i n a coal-mining area of West V i r g i n i a , and found t h a t c o n c e n t r a t i o n s of Fe, Zn, Cu and Cr v a r i e d from 0.7 to 650 mg/1. The Coeur d'Alene-Spokane River system i n Idaho was shown to c o n t a i n high l e v e l s of d i s s o l v e d t r a c e metals (Funk et a l . , 1977). Zinc c o n c e n t r a t i o n s o f t e n exceeded 1.0 mg/l. Numerous other examples of h i g h metal concentrations i n streams f l o w i n g through a m i n e r a l i z e d area may be c i t e d (Leland et a l . , 1 9 7 8 ) . Stokes and Szokalo (1977) s t u d i e d the r e l e a s e of t r a c e metals from sediments contaminated by p a r t i c u l a t e matter from s m e l t e r s i n the Sudbury area of O n t a r i o . Experiments were conducted under l i v e and s t e r i l e c o n d i t i o n s . R e s u l t s from these experiments showed that c o n s i d e r a b l y more Ni and Cu were r e l e a s e d from l i v e system than from the s t e r i l e system thus s u g g e s t i n g that b a c t e r i a l a c t i o n s t i m u l a t e d l e a c h i n g of t r a c e metals from the sediment. B a c t e r i a l a c t i o n may a l s o m o b i l i z e some t r a c e metals such as Hg by methylation (Wood et a l . , 1968). This may happen with some other metals as w e l l such as As, Pb and Se ( F o r s t n e r and Wittmann, 1979). S t i l l another mechanism f o r m o b i l i z a t i o n of t r a c e metals by b a c t e r i a i n sediments under anaerobic c o n d i t i o n s i s d e s c r i b e d by C l i n e and Upchurch (1973). A c c o r d i n g to these a u t h o r s , anaerobic b a c t e r i a l a c t i o n on o r g a n i c matter i n sediments produces gases such as CH^, CO^» H^ and HgS which w h i l e m i g r a t i n g upwards through sediment pores could t r a n s p o r t metals bound to the a s s o c i a t e d s u r f a c e a c t i v e organic_compounds. Szalay and S z i l a z i (1968) found t h a t by the above mechanism Se and As were m i g r a t i n g upward through the sediment to the water column. 30 7. Summary The above review c l e a r l y i n d i c a t e s t h a t environmental c o n d i t i o n s marked by t u r b u l e n c e , h i g h s a l i n i t y , low redox p o t e n t i a l , low pH, high c o n c e n t r a t i o n of d i s s o l v e d o r g a n i c compounds and b a c t e r i a l a c t i v i t y i n the presence of metal s u l p h i d e s fa v o r m o b i l i z a t i o n of t r a c e metals from sediments to water. However, because of the wide v a r i e t y of p o s s i b l e p h y s i c a l , chemical and b i o l o g i c a l c o n d i t i o n s i n the a q u a t i c environment and complexity of i n t e r a c t i o n s between components of sediment-water systems exchange of t r a c e metals at the sediment-water i n t e r f a c e i s not f u l l y understood. F a c t o r s such as geochemistry of sediment t r a c e metals and sediment c h a r a c t e r i s t i c s such as p a r t i c l e s i z e and organic matter content may a l s o i n f l u e n c e t r a c e metal m o b i l i z a t i o n p r o c e s s e s . B. Accumulation of Sediment Trace Metals by Benthic  I n v e r t e b r a t e s There i s a l a r g e body of l i t e r a t u r e d e a l i n g with uptake and t o x i c i t y of t r a c e metals i n s o l u t i o n f o r a v a r i e t y of a q u a t i c organisms, but very l i t t l e has been done on the a v a i l a b i l i t y of t r a c e metals i n sediments (Leland et a l . , 1978; Murphy J r . , 1981). Yet, when t r a c e metals enter the a q u a t i c environment they are very r a p i d l y adsorbed and/ or p r e c i p i t a t e d and become a component of the suspended p a r t i c u l a t e s and u l t i m a t e l y bottom sediments. The c o n c e n t r a t i o n s of t r a c e metals i n sediments are o f t e n a thousand f o l d g r e a t e r than values i n water. T h e r e f o r e , a l o g i c a l pathway of t r a c e metal accumulation i s through 31 organisms t h a t process l a r g e amounts of p a r t i c u l a t e m a t e r i a l or d w e l l i n or near the sediments. S e v e r a l s t u d i e s have been done r e l a t i n g t r a c e metals i n sediments and benthic i n v e r t e b r a t e s . The f o l l o w i n g review i s o rganised on the b a s i s of metal type and organism c l a s s i f i c a t i o n namely; worms, molluscs, a q u a t i c i n s e c t s and other organisms. 1. Copper (Cu) (a) Worms; The polychaete worm, Nereis  d i v e r s i c o l o r , seems to r e f l e c t the extent of Cu contamination of i t s environment and i s proposed by Bryan (1971) as a s u i t a b l e i n d i c a t o r organism s p e c i e s f o r metal contamination of sediments. Polychaetes sampled from two e s t u a r i n e sediments having Cu c o n c e n t r a t i o n of 407 and U9 ppm had Cu contents of 22 and 9 ppm r e s p e c t i v e l y . F u r t h e r work by Bryan and Hummerstone (1971) and Luoma and Bryan (no date) f u r t h e r supports t h i s view. Mathis and Cummings (1973) i n a t r a c e metal survey of water, sediments, f i s h , clams and worms from a freshwater system, noted t h a t the h i g h e s t c o n c e n t r a t i o n s of t r a c e metals were measured i n worms, and Cu i n these organisms was even g r e a t e r than i n the sediments. Luoma and Bryan (no date) observed that Cu i n N. d i v e r s i c o l o r was e q u a l l y r e l a t e d to t o t a l Cu and IN HC1 e x t r a c t a b l e Cu i n sediments. Chapman et a l . (1980) s t a t e d t h a t f l u c t u a t i n g l e v e l s of Cu i n o l i g o c h a e t e t u b i f i c i d s at two l o c a t i o n s i n the Fraser R i v e r , B.C. and elsewhere 32 ( B i n d r a and H a l l , 1977) r e f l e c t l o c a l d i f f e r e n c e s i n b i o l o g i c a l l y a v a i l a b l e metal. Worms i n g e s t l a r g e q u a n t i t i e s of sediments (Cammen, 1980) to o b t a i n food m a t e r i a l s . Observations of Luoma and Bryan (no date) suggest that Cu r e l e a s e d from i n g e s t e d sediments by stomach a c i d s i s r e a d i l y absorbed by the t i s s u e m a t e r i a l of the worms. However, the exact route of metal accumulation by t u b i f i c i d s has not been determined (Chapman et a l . , 1980). In a l a b o r a t o r y study, Ray et a l . (1981) noted t h a t Nereis v i r e n s was able to c o n t r o l the l e v e l s of Cu i n i t s t i s s u e when exposed to sediments c o n t a i n i n g 37.4 and 55.5 ppm of t o t a l Cu. In the study by Bryan (1974.) where a l a r g e accumulation of sediment Cu by Nerei s was observed, Cu l e v e l s i n the sediment were gr e a t e r by s e v e r a l orders of magnitude . i n d i c a t i n g t h a t p h y s i o l o g i c a l mechanisms c o n t r o l l i n g Cu l e v e l s i n the organism were probably overcome. Ash and Lee (1980) , however, b e l i e v e t h a t such d i f f e r e n c e s i n Cu uptake may be due to v a r i a t i o n s i n chemistry of the environment. . Some re c e n t s t u d i e s show that b a c t e r i a ( P a t r i c k and L o u t i t , 1976), algae (Laube et a l . , 1979) or both (Geesey, 1980) may m o b i l i z e Cu and other t r a c e metals from sediments to worms. Bryan and Hummerstone (1971) a l s o presented evidence t h a t a c o n s i d e r a b l e amount of Cu may come from a d s o r p t i o n of d i s s o l v e d metal i n i n t e r s t i t i a l water of sediments on to the body of the worms. 33 P r e l i m i n a r y r e s e a r c h which l e d to t h i s t h e s i s p r o j e c t i n d i c a t e d t h a t Cu i n the exchangeable and e a s i l y r e d u c i b l e phases was important i n r e g u l a t i n g the metal c o n c e n t r a t i o n s i n o l i g o c h a e t e worms and some other b e n t h i c organisms ( H a l l and B i n d r a , 1979)-(b) M o l l u s c s : M o l l u s c s are f i l t e r f e e d e r s or d e p o s i t f e e d e r s ; t h e r e f o r e , f o r food supply they depend upon i n g e s t i o n of sediment or suspended p a r t i c u l a t e matter. Trace metals a s s o c i a t e d with i n g e s t e d sediments may become i n c o r p o r a t e d i n the body t i s s u e of these organisms. Mussels c o l l e c t e d from waters c l o s e to major p o p u l a t i o n and i n d u s t r i a l c e n t r e s o f t e n c o n t a i n h i g h c o n c e n t r a t i o n s of Cu (Fowler et a l . , 1974; Fowler and O r e g i o n i , 1976; Anderson, 1977b; Popham et a l . , 1980). Fowler and O r e g i o n i (1976) a t t r i b u t e d the accumulation of Cu by mussels to t h e i r f e e d i n g h a b i t and t h e i r slow uptake and e x c r e t i o n mechanisms. However, Anderson (1977b) b e l i e v e s t h a t g r e a t e r accumulation i n the organisms i s due to t h e i r a b i l i t y to e x t r a c t metals from both water and sediments. Although the exact route of metal uptake by molluscs i s not known, there i s s u f f i c i e n t evidence t h a t the organisms accumulate t r a c e metals from sediments. Anderson (1977b) and Mathis and Cummings (1973) determined t r a c e metals, i n c l u d i n g Cu,in both sediments and clams. Copper l e v e l s i n the organisms c l o s e l y r e f l e c t e d the l e v e l s i n the sediments. 34 I n a l a b o r a t o r y s t u d y , Ray e t a l . (1981) exposed Macoma b a l t h i c a t o two sediments m o d e r a t e l y contaminated w i t h Cu f o r a p e r i o d o f 30 days. I n each case a s i g n i f i c a n t amount of the m e t a l was accumulated by the clam. I n f i e l d c o n d i t i o n s , however, the organism d i d not accumulate any Cu (Ray e t a l . , 1979a). These r e s u l t s i n d i c a t e t h a t f a c t o r s such as b i o c h e m i s t r y of the organism, p h y s i c o - c h e m i c a l n a t u r e o f the sediments or e n v i r o n m e n t a l c o n d i t i o n s l i k e t e m p e r a t u r e and s a l i n i t y of the o v e r l y i n g water may c o n t r o l the uptake r a t e s . P r i n g l e e t a l . (1968) from a l i t e r a t u r e r e v i e w c o n c l u d e t h a t m o l l u s c s appear t o accumulate t r a c e m e t a l s a t d i f f e r e n t r a t e s depending on the type and c o n c e n t r a t i o n s o f the m e t a l i n the environment, t e m p e r a t u r e , s p e c i e s and p h y s i o l o g i c a l a c t i v i t y of the a n i m a l . P h y s i o l o g i c a l c o n t r o l s of some m o l l u s c s p e c i e s i n r e g u l a t i n g e s s e n t i a l t r a c e m e t a l s l i k e Cu and Zn, however, have been shown t o be poor ( B r y a n , 1976). Luoma and Jenne (1975a, 1975b, 1976) have shown t h a t a c c u m u l a t i o n of t r a c e m e t a l s from sediments depends upon the n a t u r e of g e o c h e m i c a l p h a s e ( s ) t o which the m e t a l i s bound. Ray e t a l . (1981) found t h a t more Cu was accumulated from the sediment w h i c h c o n t a i n e d h i g h e r l e v e l s o f exchangeable and p r e c i p i t a t e d Cu as i n d i c a t e d by EDTA e x t r a c t i o n o f the sediments. Cooke e t a l . (1979) showed t h a t a v a i l a b i l i t y of t r a c e m e t a l s i n sediments t o e d i b l e c o c k l e s i s r e l a t e d t o the ease w i t h which a m e t a l desorbs 35 from the sediment. Larsen (1979) measured Cu l e v e l s i n hard clams, M e r c e n a r i a mercenaria, caught from two r i v e r s of the Lower Chesapeake Bay Region. The c o n c e n t r a t i o n s i n the clam v a r i e d s i g n i f i c a n t l y with the age of the organisms. Others (Romeril, 1979; Boyden, 1974) found a s i m i l a r age/metal r e l a t i o n s h i p f o r Cu i n hard clams. From a s t a t i s t i c a l analyses of f i e l d data obtained f o r 18 e s t u a r i e s , Luoma and Bryan (no date) c o r r e l a t e d metal accumulation by Nereis d i v e r s i c o l o r and S c r o b i c u l a r i a plana w i t h a l a r g e number of geochemical and p h y s i c a l f a c t o r s . Copper i n the clam was r e l a t e d to Ag i n the organism. Also h i g h Cu l e v e l s i n the clam were observed i n the areas where sediment Fe l e v e l s were low and oxygen l e v e l s were depressed. Clams with s h e l l s having black hydrogen s u l p h i d e s t a i n s were found to c o n t a i n the h i g h e s t l e v e l s of Cu. Oysters known to accumulate high c o n c e n t r a t i o n s of Cu appear to r e f l e c t l e v e l s i n the environment. G r e i g and Wenzloff (1978) t r a n s f e r r e d the American Oyster, C r o s s o s t r e a v i r g i n i c a , from the r e l a t i v e l y u n p o l l u t e d waters of North C a r o l i n a to seawater and contaminated mud obtained from M i l f o r d Harbour and placed them i n an aquarium i n the l a b o r a t o r y . A f t e r 22 weeks of exposure to contamination, the o y s t e r s accumulated s i g n i f i c a n t l e v e l s of Cu. In an e s t u a r i n e environment, c o n c e n t r a t i o n s of Cu i n o y s t e r s ranged from 4O ppm f o r u n p o l l u t e d areas to 600 ppm f o r p o l l u t e d areas (Watling and Watling, 1976). A y l i n g ' s 36 (1974) data, however, showed that at sediment concentrations of only 50 ppm, oyster tissue l e v e l s of Cu may range from 300 to 1300 ppm . Brooks and Rumsby (1965) found that oysters from a sediment containing 100 ppm Cu contained only 40 ppm of the metal. Evidently either a v a i l a b i l i t y of Cu i n the sediment was l i m i t i n g or some other controls involving environmental or phy s i o l o g i c a l mechanisms were operative. (c) Aquatic insects: Anderson (1977a) monitored trace metals including Cu i n a number of insects, but did not rel a t e the metal l e v e l s i n the organisms with those i n the sediments. Namminga and Wilhm (1977) studied the d i s t r i b u t i o n of some trace metals i n Skelton Creek, Oklahoma. Concentrations of Cu i n chironomids were 10 percent higher than those i n the sediments i n d i c a t i n g that these organisms can accumulate Cu from the sediments. Bindra and Hall (1977) found even greater accumulation of Cu by these organisms; i n f i e l d conditions bioconcentration r a t i o s ranged from 1.1 to 4«5. As evidenced by Table 1 (data from Bindra and Hall, 1977) the bioconcentration r a t i o s appear to be depressed by percent f i n e s (<0.25 mm) i n the sediments. (d) Other organisms: In a p o l l u t i o n study of the River Irwell, U.K., Eyres and Pugh-Thomas (1978) investigated the r e l a t i o n s h i p between levels of trace metals i n substrate materials and i n the tissues of Asellus  aquaticus L., a detritivorous water louse, and Erpobdella  octoculata (L.), a carnivorous water leech. The substrate 37 m a t e r i a l s were algae scraped from rocks c o l l e c t e d from the r i v e r bottom. At low s u b s t r a t e c o n c e n t r a t i o n s of Cu, the lou s e accumulated the metal by f a c t o r s of 2 to 3 above the s u b s t r a t e l e v e l s . However, the t i s s u e l e v e l s of Cu i n the l e e c h d i d not reach s u b s t r a t e l e v e l s , p o s s i b l y because of blockage of uptake or e x c r e t i o n of the metal by the animals. Copper l e v e l s i n t i s s u e of both species decreased as the c o n c e n t r a t i o n of the metal i n the s u b s t r a t e m a t e r i a l i n c r e a s e d , suggesting t h a t the animals' mechanisms to reduce metal l e v e l s i n the t i s s u e were more e f f i c i e n t at higher s u b s t r a t e l e v e l s . Copper l e v e l s i n mud-dwelling Corophium v o l u t a t o r ( C r u s t a c e a : Amphipoda) were 259 ppm at a c o a s t a l s i t e r e c e i v i n g contaminated freshwater drainage ( I c e l y and Nott, 1980). At another s i t e with normal concentrations of Cu, the l e v e l s of the metal i n the animals were only o n e - t h i r d those of the contaminated s i t e . Hence Cu at the contaminated s i t e was i n a r e a d i l y a v a i l a b l e form. A l s o , the i n v e s t i g a t o r s found t h a t accumulated Cu i n the mud-dweller was c o n c e n t r a t e d i n the e l e c t r o n - d e n s e g r a n u l a r matter i n the animal t i s s u e . Walker et a l . (1975) propose that t r a c e metals can be d e t o x i f i e d w i t h i n t i s s u e s of animals by i n c o r p o r a t i o n i n t o i n t r a c e l l u l a r g r a n u l e s . Examples of such i n c l u s i o n s i n b i o t a have been reviewed by Coombs and George (1978). U n l i k e Corophium v o l u t a t o r , the crustacean Crangon septemspinosa, a shrimp, f a i l e d to accumulate Cu on exposure to two contaminated sediments i n a l a b o r a t o r y 3 8 Table I : R e l a t i o n s h i p Between Bioconcentration Ratios of Copper i n Chironomids and Amount of Fines (•<().25 mm) i n the Sediment (data from Bindra and H a l l , 1977) B i o c o n c e n t r a t i o n Percent F i n e s ^ n Ratio-'- the Sediment 4.5 1.5 2.1 4.3 1.9 18.9 1.5 52.8 1.1 56.9 C o r r e l a t i o n C o e f f i c i e n t = -0.75 B i o c o n c e n t r a t i o n R a t i o = Cu i n chironomids/ t o t a l Cu i n sediments T h i s r a t i o i s e q u i v a l e n t to c o n c e n t r a t i o n f a c t o r (van Hook, 1974) when food item(s) of consumer species can be d e s c r i b e d . 1. From Table 7 of Bindra and H a l l , 1977. 2. From Table A4 of Bindra and H a l l , 1977 (Sum of p a r t i c l e s i z e f r a c t i o n s 4 and 5 ) . 39 environment over a 30 day p e r i o d (Ray et a l . , 1981). C o n s i s t e n t w i t h these r e s u l t s , the t i s s u e contents of Cu and some other metals remained v i r t u a l l y constant i n C. septemspinosa under f i e l d c o n d i t i o n s . Bryan (1968) a l s o presented data f o r a decapod species i n d i c a t i n g t h a t some crustaceans can r e g u l a t e e s s e n t i a l t r a c e metals l i k e Cu and Zn. 2. I r o n (Fe) (a) Worms: In a l a b o r a t o r y food c h a i n study u s i n g b a c t e r i a , t u b i f i c i d s and f i s h , t u b i f i c i d s c o ncentrated a number of t r a c e metals i n c l u d i n g Fe ( P a t r i c k and L o u t i t , 1976). Geesey (1980) demonstrated that worms i n g e s t b a c t e r i a adhering on to sediment p a r t i c l e s . These s t u d i e s suggest t h a t b a c t e r i a may f a c i l i t a t e passage of Fe from sediments to t u b i f i c i d worms. In p a r t i c u l a r , a v a i l a b i l i t y of Fe from sediments r i c h i n organic matter should be g r e a t e r because of higher b a c t e r i a l populations i n such sediments. Bindra and H a l l (1977) observed no r e l a t i o n between Fe l e v e l s i n a q u a t i c o l i g o c h a e t e s and organic content of sediments. Thus i t appears t h a t as with t e r r e s t r i a l o l i g o c h a e t e s , Fe i n the a q u a t i c o l i g o c h a e t e s i s r e g u l a t e d by e x c r e t i o n ( I r e l a n d , 1975). In a l a b o r a t o r y microcosm experiment with f i v e b e n t h i c animals c o l l e c t e d from bay areas of U.S. East Coast, the lowest Fe accumulation occurred i n a p o l y c h a e t e ( G u t h r i e et a l . , 1979). Since these animals are d e p o s i t feeders one would expect t i s s u e l e v e l s to r e f l e c t Fe i n the sediments. 40 Chapman et al.(1980) showed t h a t although Fe c o n c e n t r a t i o n s were more than 12500 ppm i n sediments the l e v e l s i n the organisms were only s l i g h t l y above 1000 ppm . These s t u d i e s p r o v i d e f u r t h e r evidence t h a t worms can r e g u l a t e Fe c o n c e n t r a t i o n s i n t h e i r t i s s u e . (b) M o l l u s c s : In a marine microcosm c o n s i s t i n g of b a r n a c l e s , crabs, o y s t e r s , clams and polychaete, clams contained Fe l e s s than only b a r n a c l e s (Guthrie et a l . , 1979). The mean c o n c e n t r a t i o n of Fe i n the clams, however, was only 1.37 percent of the mean c o n c e n t r a t i o n i n the sediments. Ir o n i n the h a r d s h e l l clam, Mercenaria mercenaria , c o l l e c t e d from waters of Southampton R i v e r , U.K., r e f l e c t e d the Fe l e v e l s i n sediments and the c o n c e n t r a t i o n s dropped along a t r a n s e c t to the sea. In a f i e l d study of t r a c e metals i n molluscs, P r i n g l e et a l . (1968) measured Fe l e v e l s i n s o f t s h e l l clams, Mya a r e n a r i a , r anging from 49.70 to 1710 ppm on a wet weight b a s i s . P r i n g l e et a l . a l s o measured Fe l e v e l s i n o y s t e r s obtained from the c o a s t a l waters of U.S. The concen-t r a t i o n s were: 31-238 ppm i n the organisms from the East Coast and 15 - 9 1 ppm i n those from the West Coast, on a wet weight b a s i s Iron has been shown to d e p o s i t i n mollusc s h e l l s as porphyrin-Fe complex (Brooks and Rumsby, 1965). (c) Aquatic i n s e c t s : Bindra and H a l l (1977) determined Fe l e v e l s i n chironomid l a r v a e c o l l e c t e d from two freshwater streams of the lower Mainland of B r i t i s h Columbia. A s s o c i a t e d sediments were c h a r a c t e r i z e d f o r geochemical and p h y s i c a l parameters. Iron l e v e l s i n the chironomid l a r v a e 41 appear to be related to the coarseness of the r i v e r bed (Table I I ) . (d) Other organisms: In a marine microcosm consisting of barnacles, crabs, oysters, clams and polychaetes, barnacles accumulated the most Fe and the mean concentration of Fe i n this organism was more than one order of magnitude greater than the mean concentrations f o r the other members of the microcosm (Guthrie et a l . , 1979). 3. Lead (Pb) (a) Worms: A number of studies have been conducted r e l a t i n g Pb l e v e l s i n worms and sediments. In a p o l l u t i o n survey of I l l i n o i s River, trace metal l e v e l s were measured i n water, sediments, f i s h e s , clams and worms (Mathis and Cummings, 1973). Bottom-dwelling worms and clams r e f l e c t e d the sediment Pb l e v e l s . H a l l and Bindra (1979) also found that i n a freshwater environment, Pb burdens of oligochaetes were related to t o t a l Pb i n the sediments. McNurney et a l . (1975) investigated d i s t r i b u t i o n of Pb i n the sediments and fauna of r u r a l and urban sections of a mid-western U.S. stream. Lead contents of many organisms were affected evidently by their contact with the bottom sediments. The most s t r i k i n g conclusion of th i s study, according to the authors, was that oligochaetes which burrow i n and ingest sediments had the highest l e v e l s of Pb. The concentrations varied widely between urban and r u r a l samples; high concentrations of Pb i n urban samples r e f l e c t e d contamination A2 Table II. Relationship Between Iron in Chironomid Larvae and Amount of Very Coarse Sand in the Sediment (data from Bindra and H a l l , 1977, pp. 74,84,94,95) Station Iron in Very Coarse Sand Chironomids in Sediment (ppm) (7o) Salmon River . at Roberts Road 54 0.3 Salmon River at Springbrook Road 348 0.4 Salmon River at 64th Avenue 678 9.1 Coglan Creek at Otter Road (Salmon River Watershed) 4550 12.5 S t i l l Creek at Grandview Highway (Brunette River Basin) 8790 23.9 Correlation C o e f f i c i e n t = 0.92 Very Coarse Sand i s 1-2 mm size 43 from e f f l u e n t d i s c h a r g e s . Data presented by Packer e t a l . (1980) appear to show the same trend i n Pb c o n c e n t r a t i o n s i n marina and sediments, although the authors r e p o r t t h a t c o r r e l a t i o n i n c o n c e n t r a t i o n s was s t a t i s t i c a l l y i n s i g n i f i c a n t Earthworms, - t e r r e s t r i a l counterparts of a q u a t i c o l i g o c h a e t e s , have a l s o been found to accumulate Pb from a c i d s o i l s contaminated by heavy metals (Gish and C h r i s t e n s e n , 1973; I r e l a n d , 1975; Van Hook, 1974; Ash and Lee, 1980). There i s ample evidence i n the l i t e r a t u r e t h a t b a c t e r i a may p l a y an important r o l e i n metal uptake by worms i n s o i l s and sediments. Aquatic o l i g o c h a e t e s feed on b a c t e r i a a d h e r i n g to sediment p a r t i c l e s (Geesey, 1980; L o u t i t et a l . , 1967) and i n the process accumulate t r a c e metals c o n c e n t r a t e d by b a c t e r i a from sediment s u b s t r a t e s ( L o u t i t et a l . , 1973). In a food chain study by P a t r i c k and L o u t i t (1976), o l i g o c h a e t e s were shown to accumulate Pb from i n g e s t i o n of b a c t e r i a grown i n metal contaminated media. Ray et a l . (1981) i n v e s t i g a t e d the e f f e c t of sediment type on accumulation of Pb by i n v e r t e b r a t e s . Nereis  v i r e n s accumulated Pb from only one of the two sediments to which the worms were exposed f o r 30 days i n a l a b o r a t o r y aquarium. The accumulation was observed from the sediment which was s l i g h t l y c o a r s e r , contained s l i g h t l y l e s s o rganic carbon and much higher c o n c e n t r a t i o n of t o t a l and EDTA-e x t r a c t a b l e Pb. u (b) M o l l u s c s : Accumulation of Pb by m o l l u s c s has been the su b j e c t of a number of s t u d i e s . In a mid-western U.S. r i v e r ,Pb i n clams r e f l e c t e d the l e v e l s i n the bottom sediments (Mathis and Cummings, 1973). Lu et a l . (1975) s t u d i e d the environmental f a t e and e f f e c t of Pb and Cd a s s o c i a t e d w i t h sewage sludge i n t e r r e s t r i a l / a q u a t i c i n t e r f a c e ecosystems. Sewage sludge contaminated by metals was a p p l i e d to model s o i l s d r a i n i n g i n t o model p o o l s . L i v e animals i n c l u d i n g a s n a i l (Physa) were p l a c e d i n the model pools and a n a l y z e d f o r Pb and Cd at the beginning and a t the end of the experiments. The r e s u l t s c l e a r l y i n d i c a t e d t h a t Pb and Cd added to s o i l s w i t h the sludge were t r a n s p o r t e d to the model pools from where the metals were being r e a d i l y p i c k e d up by the a n i m a l s . S n a i l s used i n t h i s study were a l s o found to accumulate Pb under f i e l d c o n d i t i o n s (Enk and Mathis, 1977). Anderson (1977b) determined Pb c o n c e n t r a t i o n s i n t i s s u e s of s i x sp e c i e s of freshwater clams. Lead l e v e l s i n t i s s u e r e f l e c t e d the concentrations i n the environment. Popham et a l . (1980) showed that the f i l t e r f eeder M y t i l u s e d u l i s i s an e x c e l l e n t i n d i c a t o r of Pb p o l l u t i o n ; c o n c e n t r a t i o n s i n the clam c o l l e c t e d from Burrard I n l e t , Vancouver, d e c l i n e d by two orders of magnitude to background l e v e l s only 30 m d i s t a n c e from a source of Pb p o l l u t i o n . In another study, Pb l e v e l s i n the P a c i f i c o y s t e r , C r o s s o s t r e a g i g a , c l o s e l y p a r a l l e l e d the Pb c o n c e n t r a t i o n s i n the sediments from which the animals were c o l l e c t e d ( A y l i n g , 1974). Geochemical form of Pb i n sediments may a f f e c t i t s 45 a v a i l a b i l i t y to benthic i n v e r t e b r a t e s . Data from a l a b o r a t o r y study by Ray et a l . (1981) shows t h a t e q u i l i b r i u m c o n c e n t r a t i o n s of Pb i n Macoma b a l t h i c a exposed to two sediments f o r a p e r i o d of 30 days were i n exact p r o p o r t i o n to the EDTA e x t r a c t a b l e Pb i n the sediments. Luoma and Bryan (1978) r e l a t e d Pb c o n c e n t r a t i o n s i n the d e p o s i t f e e d i n g b i v a l v e , S c r o b i c u l a r i a plana, c o l l e c t e d from v a r i o u s e s t u a r i e s i n Europe, with metal c o n c e n t r a t i o n s i n d i f f e r e n t chemical e x t r a c t s of sediments. The r e s u l t s i n d i c a t e d t h a t accumulation of Pb i n the clam was r e l a t e d to Fe/Pb r a t i o i n the IN HC1 a c i d e x t r a c t . B i n d r a and H a l l (1977) determined Pb i n M. b a l t h i c a and sediment samples c o l l e c t e d from mud f l a t s a long the j e t t y f o r the Iona Sewage Treatment P l a n t o u t f a l l i n Vancouver, B.C. The c o n c e n t r a t i o n s of Pb i n the i n v e r t e b r a t e s and sediment samples were 20 . 6 , 32.0 and 25.3 ppm and 62.4 , 55.2 and 43.7 ppm. r e s p e c t i v e l y . Based on the l i m i t e d data r e s u l t s do not agree with the c o n t r o l mechanism proposed by Luoma and Bryan (1978). This suggests t h a t b i o a v a i l a b i l i t y of Pb i n sediments i s a complex phenomena and d i f f e r e n t c o n t r o l s may be o p e r a t i n g i n d i f f e r e n t a r e a s , or with d i f f e r e n t s p e c i e s . (c) Aquatic i n s e c t s : A number of s t u d i e s have been c a r r i e d out to determine the e f f e c t of Pb p o l l u t i o n on a q u a t i c i n s e c t s . Anderson (1977a) analyzed 35 genera of a q u a t i c macroinvertebrates, i n c l u d i n g 15 s p e c i e s of i n s e c t s , c o l l e c t e d from the f i v e s t a t i o n s on the Fox R i v e r northwest 46 of Chicago. The s t a t i o n s were a f f e c t e d by urban and i n d u s t r i a l e f f l u e n t s or a g r i c u l t u r a l r u n o f f . The maximum Pb c o n c e n t r a t i o n of 39 ppm was measured i n the Mayfly nymph, Potamanus. More commonly monitored i n s e c t s , namely chironomid l a r v a e , had a Pb value of 30 ppm which i s more than 20 times the mean c o n c e n t r a t i o n r e p o r t e d f o r those animals c o l l e c t e d from the S k e l e t o n Creek.Oklahoma (Namminga and Wilhm, 1977). The wide d i f f e r e n c e probably was due to d i f f e r e n c e i n degree of p o l l u t i o n i n the two r i v e r s . B i n d r a and H a l l (1977) monitored Pb l e v e l s i n chironomids c o l l e c t e d from two watersheds, urban and r u r a l , of the Lower Mainland of B r i t i s h Columbia. Animals c o l l e c t e d from the urban watershed had a c o n c e n t r a t i o n r a t i o r e l a t i v e to sediments of 2.76 while those from the r u r a l watershed had the r a t i o s i n the low range of 0.07 to 0.34. The d i f f e r e n c e i n accumulation of Pb between the two watersheds probably was due to d i f f e r e n t forms of Pb i n the sediments. In the urban sediment 51 percent Pb was i n the exchangeable, o r g a n i c and sulphur and p r e c i p i t a t e phases as compared to o n l y 11 to 13 percent i n the r u r a l sediments. B i s s o n n e t t e et a l . (1975) a l s o measured c o n c e n t r a t i o n r a t i o s over a wide range of 0.07 to 5.45 f o r chironomids from f o u r lakes i n western Washington. A s i m i l a r e x p l a n a t i o n as i n the above study by B i n d r a and H a l l (1977) may be extended to these r e s u l t s . However, other f a c t o r s such as d i f f e r e n c e s i n c o n c e n t r a t i o n s of d i s s o l v e d Pb may a l s o e x p l a i n the v a r i a t i o n i n the observed c o n c e n t r a t i o n ratio's. 47 Nehring et a l . (1979) i n v e s t i g a t e d the r e l a t i v e a v a i l a b i l i t y of d i s s o l v e d and sediment d e p o s i t e d Pb to aq u a t i c i n s e c t s . I n s e c t s c o l l e c t e d from an u n p o l l u t e d freshwater stream were pl a c e d i n l a b o r a t o r y a q u a r i a c o n t a i n i n g e i t h e r d i s s o l v e d Pb or Pb bound to sediment s u b s t r a t e s . Subsamples of i n s e c t s were p e r i o d i c a l l y withdrawn and analyzed f o r Pb. Both d i s s o l v e d Pb and Pb i n the sediment s u b s t r a t e were e q u a l l y accumulated by the i n s e c t s . A f t e r 100 to 200 hours i n v e r t e b r a t e s were t r a n s f e r r e d to c l e a n environment where the t i s s u e Pb l e v e l s dropped s h a r p l y but appeared to s t a b i l i z e a t higher l e v e l s than the o r i g i n a l c o n c e n t r a t i o n s . (d) Other organisms: Eyres and Pugh-Thomas (1978) determined Pb, Zn and Cu c o n c e n t r a t i o n s i n sediment s u b s t r a t e m a t e r i a l s and two s p e c i e s of i n v e r t e b r a t e s : water l o u s e , A s e l l u s a q u a t i c u s L., and l e e c h , E r p o b d e l l a o c t o c u l a t a (L.) c o l l e c t e d from the h e a v i l y p o l l u t e d R i v e r I r w e l l , U.K. Lead c o n c e n t r a t i o n s i n sediments, lou s e and l e e c h were i n the ranges of 37 - 13905 ppm, t r a c e -595 ppm, and t r a c e -110.9 ppm r e s p e c t i v e l y . A comparison of c o n c e n t r a t i o n s i n su b s t r a t e and i n v e r t e b r a t e s i n d i c a t e d t h a t as Pb i n c r e a s e d i n s u b s t r a t e , t i s s u e l e v e l s of i n v e r t e b r a t e s a l s o i n c r e a s e d but at a lower r a t e which suggested t h a t e i t h e r some phy s i c o - c h e m i c a l mechanism i s b l o c k i n g passage of Pb to the animals or the animals are able to excrete the metal a c t i v e l y . Lead l e v e l s i n leeches c o l l e c t e d by Anderson (197 7a) from the Fox R i v e r near Chicago were q u i t e low ( 40 ppm) as us compared to concentrations r e p o r t e d by Eyres and Pugh-Thomas (1978). Four species of c r u s t a c e a n s , Orconectes, Procambrus, Cambrus and A s e l l u s from the Fox R i v e r had Pb l e v e l s ranging from 16 - 26 ppm and Pb i n the f i f t h c r u s t a c e a n , Gammarus, was below 4 ppm (Anderson, 1977a). 4 . Manganese (Mn) Since manganese i s r e l a t i v e l y l e s s t o x i c than Cu, Pb and Zn, fewer s t u d i e s have been conducted to i n v e s t i g a t e the e f f e c t of t h i s metal on i n v e r t e b r a t e s . (a) Worms: Bin d r a and H a l l (1977) i n a study of the mechanisms of sediment t r a c e metal uptake by b e n t h i c i n v e r t e b r a t e s , c o l l e c t e d a c o n s i d e r a b l e amount of geochemical and p h y s i c a l data f o r U d i f f e r e n t a q u a t i c environments i n the Lower Mainland of B r i t i s h Columbia. Oligochaete worms, however, were found only i n the sediments of two freshwater environments, Brunette Basin and Salmon R i v e r B a s i n . In the Brunette Basin, the extent of Mn uptake was r e l a t e d to Mn i n the e a s i l y r e d u c i b l e phase of the sediments (Bindra and H a l l , 1 9 7 7 ) . Combined data f o r the two watersheds, however, showed no r e l a t i o n s h i p between Mn i n o l i g o c h a e t e s and the geochemical phases of the metal i n sediments. Some other f a c t o r s appeared to be r e s p o n s i b l e f o r r e g u l a t i o n of Mn i n the o l i g o c h a e t e s . A r e l e v a n t p o r t i o n of the data from the study by Bindra and H a l l i s summarized i n Table I I I . L i n e a r 49 Table I I I : Manganese Concentrations i n Oligochaetes and Sediment C h a r a c t e r i s t i c s Which Appear to A f f e c t the Metal Levels i n Organisms (data from Bindra and H a l l , 1977, Tables A3 and H). Mn i n O l i g o - Bioconcent. Sediment C h a r a c t e r i s t i c s No. chaetes (ppm) Ratio Redox P o t e n t i a l - •_ (mV) Organic Carbon (7.) Sum of Fine Sand & S i l t and Clay (%) 1 Brunette R. (Capilano Lumber) 1670 3.21 +3 0.51 21.7 2 Brunette R. (Brunette Ave.) 691 1.36 -38 0.27 13.4 3 Brunette R. (North Road) 3130 4.99 +103 0.23 24.2 4 Stoney Creek (Beaverbrook) 612 1.33 +41 0.27 30.4 5 Stoney Creek (E. Broadway) 435 1.14 +15 0.39 46.0 6 Eagle Creek (Piper Ave.) 1100 0.87 - 7 15.9 90. 7 7 Eagle Creek (above Golf course) 384 0.72 -224 15.3 83.9 8 Deer Creek (Glencairon Dr.) 233 0.51 -340 2.1 44.2 9 S t i l l Creek (Lougheed Hwy.) 263 0.56 -434 1.73 61.8 10 S t i l l Creek (Douglas Rd.) 222 0.41 -401 6.04 78.1 11 S t i l l Creek (Wellingdon) 266 0.52 -329 3.86 91.2 12 S t i l l Creek (Gilmore Ave.) 1350 2.74 - 68 0.52 10. 9 S- 2 Salmon R. (McKinnon) 476 0.87 -441 0.91 91.4 S- 4 Salmon R. (Rawlison Cres.) 954 1.42 -164 1.23 35.7 S-14 Coglan Creek (Otter Road) 1140 2.09 - 19 0.43 18.9 S-16 Salmon R. (Otter Road) 523 0.69 -105 0.83 38.5 S-18 Salmon R. (Coglan Road) 909 1.07 -110 . 1-74 73.4 Bi o c o n c e n t r a t i o n Ratio = Mn i n o l i g o c h a e t e s / t o t a l Mn i n sediment S t a t i o n s 1 to 12 , Brunette Basin ; St a t i o n s S-2 to S-18, Salmon River 50 r e g r e s s i o n a n a l y s i s of the data (Table IV) i n d i c a t e s t h a t the most s i g n i f i c a n t c o r r e l a t i o n f o r Mn i n o l i g o c h a e t e s was with redox p o t e n t i a l of sediments and with percent f i n e m a t e r i a l i n the sediments when Mn i n o l i g o c h a e t e s was expressed as a b i o c o n c e n t r a t i o n r a t i o . Percent organic matter i n the sediments a l s o showed some c o r r e l a t i o n with Mn bio a c c u m u l a t i o n i n the worms. The r e l a t i o n s h i p between Mn i n o l i g o c h a e t e s and redox p o t e n t i a l i s f u r t h e r i l l u s t r a t e d i n F i g u r e 2. I t appears t h a t t h i s n o n l i n e a r f i t i s even more s i g n i f i c a n t than the l i n e a r f i t . R e sults of the study by Bi n d r a and H a l l seem to be c o n s i s t e n t with other l i t e r a t u r e f o r Mn i n marine worms. Chapman et a l . (1980) noted t h a t i n the F r a s e r R i v e r , B r i t i s h Columbia, Mn i n o l i g o c h a e t e s d i d not r e f l e c t t o t a l sediment l e v e l s . S i m i l a r l y , Packer et a l . (1980) and Bryan and Hummerstone (1977) observed t h a t Mn i n polychaete worms, A r e n i c o l a marina and Nereis d i v e r s i c o l o r , from c o a s t a l and e s t u a r i n e environments r e s p e c t i v e l y , bore no r e l a t i o n s h i p to Mn i n sediments. Manganese i n A r e n i c o l a marina was below sediment l e v e l s , on the average, by a f a c t o r of approximately 30 and the f a c t o r f o r Nereis d i v e r s i c o l o r was 45. E v i d e n t l y , v a r i a b l e s other than t o t a l Mn l e v e l s i n the sediments determine the metal uptake by worm s p e c i e s . S ince redox p o t e n t i a l s of mud d e p o s i t s of deep e s t u a r i e s and marine areas are u s u a l l y low, and i n l i g h t of the f i n d i n g s of B i n d r a and H a l l (1977)»it i s not s u r p r i s i n g t h a t Mn l e v e l s are 51 Table IV : Coefficients of Linear Correlations (r) Between Manganese Levels in Oligochaetes and Their Habitat-Related Parameters (data from Bindra and Ha l l , 1977, Table III of this thesis) Redox Potential (mV) Organic carbon in Sediment (%) Sum of Fine Sand & S i l t and Clay(%) Mn in Oligo-chaetes Bioconcent-ration Ratio 0.653 (n=17) 0.641 1 (n=17) •0.481 (n=15) •0.403 (n=15) 3 -0.394^ (n=17) -0.616 1 (n=17) 0.01 > P> 0.001 0.05 > P-^O.Ol 0.2 >P^0.1 52 Figure 2. Relationship Between Mn i n Oligochaetes and Redox Pot e n t i a l of Sediment (data from Bindra and H a l l , 1977). 0 1000 2000 3000 4000 Manganese in Oligochaetes (ppm) 53 depressed, i n the worms. P a t r i c k and L o u t i t (1976) showed t h a t b a c t e r i a may mediate t r a n s f e r of Mn from sediments to t u b i f i c i d s . Thus, i t would appear that the g r e a t e r uptake of Mn by o l i g o c h a e t e s under h i g h e r redox p o t e n t i a l observed by Bindra and H a l l (1977) and as shown i n F i g u r e 2 may have been due to g r e a t e r supply of Mn c o n t a i n i n g b a c t e r i a l mass under a e r o b i c (high redox) c o n d i t i o n s . (b) M o l l u s c s : Feeding h a b i t s of molluscs seem to a f f e c t the Mn l e v e l s i n the organisms. Res u l t s of s e v e r a l s t u d i e s suggest that d e p o s i t f e e d e r s have higher t i s s u e Mn l e v e l s than the f i l t e r f e e d e r s . A l s o , the l i t e r a t u r e i n d i c a t e s t h a t molluscs c o l l e c t e d from marine environments accumulated only a s m a l l f r a c t i o n of the t o t a l Mn i n the sediments. In a b i o m a g n i f i c a t i o n study by Guthrie et al.(1979) Mn l e v e l s i n o y s t e r s and clams from the Galveston area of Texas were 1.4 and 7.6 ppm, r e s p e c t i v e l y , while the sediment had a Mn c o n c e n t r a t i o n of H4 ppm. Bryan and Hummerstone (1977) a l s o observed a s i m i l a r Mn d i s t r i b u t i o n p a t t e r n . Manganese l e v e l s i n d e p o s i t feeder b i v a l v e s , S c r o b i c u l a r i a  plana and Macoma b a l t h i c a were approximately 1 . 5 - 3 times g r e a t e r than i n f i l t e r f e e d e r s , Cerastoderma edule and M y t i l u s e d u l i s . F i l t e r f eeders as w e l l as d e p o s i t f e e d e r s , however, accumulated only a s m a l l f r a c t i o n (0.034 - 0.10 ) of t o t a l Mn i n the sediments. D i f f e r e n c e s i n Mn accumulation due to f e e d i n g h a b i t s 54 are a l s o evident from the data presented by P r i n g l e et a l . (1968). Oysters ( C r a s s o s t r e a v i r g i n i c a and C. gigas) and s o f t s h e l l clams (Mercenaria mercenaria and Mya a r e n a r i a ) c o l l e c t e d from the U.S. East Coast and some from the West Coast contained average Mn l e v e l s of 4-3 ppm and 6.7 ppm r e s p e c t i v e l y . - The h i g h e r l e v e l s i n clams were pr o b a b l y due to t h e i r having g r e a t e r contact with the sediments and being d e p o s i t f e e d e r s . A d e p o s i t f e e d e r , Macoma b a l t h i c a , c o l l e c t e d from 3 s t a t i o n s i n the Sturgeon Bank area o f f the Iona Sewage Treatment P l a n t o u t f a l l , Vancouver, B r i t i s h Columbia had Mn l e v e l s up to 209 ppm (Bindra and H a l l , 1977). Freshwater Pelecypod molluscs (clams and mussels) are r e p o r t e d to have very high a f f i n i t y f o r Mn, Zn and A l (Forester,1980). A review by F o r e s t e r i n d i c a t e d t h a t Mn l e v e l s f o r freshwater mussels ranged from 500 - 3500 ppm. Although the accumulation was compared to water c o n c e n t r a t i o n s , Mn l e v e l s i n sediments were not r e p o r t e d . (c) Aquatic i n s e c t s : Bindra and H a l l (1977) presented data f o r Mn i n chironomid l a r v a e and sediments c o l l e c t e d from a s t a t i o n on an urban creek and 4 s t a t i o n s on a r u r a l r i v e r system. The b i o c o n c e n t r a t i o n r a t i o (organism/ sediment) f o r the urban s t a t i o n was 2.84 as compared to 0.034 - 0.171 f o r the r u r a l s t a t i o n s . These r e s u l t s suggest t h a t Mn from urban p o l l u t i o n i s r e a d i l y b i o a v a i l a b l e . B a r i c a et a l . (1973) found that s y n t h e t i c c h e l a t i n g agents r e l e a s e d sediment Mn and some other t r a c e metals to water but had no e f f e c t on uptake of Mn by chironomids. Thus 5 5 i t appears t h a t the i n s e c t s r e c e i v e Mn mainly from b e n t h i c food sources. (d) Other organisms: In a marine microcosm c o n s i s t i n g of ba r n a c l e s , crabs, o y s t e r s , clams and p o l y c h a e t e s , crabs contained the lowest l e v e l s of Mn (Gu t h r i e et a l . , 1 9 7 9 ) . Crabs appear to c o n t r o l Mn l e v e l s i n t i s s u e . A freshwater crustacean c r a y f i s h , growing i n a stream r e c e i v i n g mine t a i l i n g s a l s o had r e l a t i v e l y low l e v e l s of Mn as compared to tadpoles (Gale et a l . , 1973). Manganese l e v e l s i n tadp o l e s dropped r a p i d l y with d i s t a n c e from the t a i l i n g s pond, r e f l e c t i n g metal l e v e l s i n the environment. 5. Zi n c (Zn) (a) Worms: Resu l t s of s t u d i e s on Zn accumulation i n worms are o f t e n c o n t r a d i c t o r y . Dean (1974-) i n a l a b o r a t o r y 65 study u s i n g a r a d i o i s o t o p e of Zn, Zn, showed t h a t t u b i f i c i d worms do not accumulate Zn when i t i s bound to sediments whereas Zn i n s o l u t i o n may be r e a d i l y p i c k e d up by the worms. Yet, Ray et a l . (1979b) r e p o r t that Zn i n Nere i s v i r e n s remained constant when exposed to water c o n t a i n i n g 1.0 mg Zn/1. Guthr i e e t a l . (1979) a t t r i b u t e a high c o n c e n t r a t i o n of Zn i n polychaetes from a marine microcosm to i t s a b i l i t y to accumulate Zn from both sediment and water. B i n d r a and H a l l (1977) (Table V) and others (Bryan, 1976; Packer et al.,1980) presented data which show th a t under f i e l d c o n d i t i o n s Zn i n worms may accumulate many times above the sediment l e v e l s . Ray et a l . (1981) on the c o n t r a r y f a i l e d to observe any change i n c o n c e n t r a t i o n of Zn i n Nere i s v i r e n s exposed to 56 Table V : Bioconcentration Ratios of Zinc i n Oligochaetes from Three Watersheds of the Lower Mainland of B r i t i s h Columbia (adapted from Bindra and H a l l , 1977, p. 40) 1 Station No. Bioconcentration Ratio (organisms/sediment) 1 8.53 2 6.06 3 7.91 4 7.95 5 4.88 6 3.32 7 1.85 8 1.28 9 3.06 10 1.15 11 1.65 12 7.66 S- 2 2.86 S- 4 1.66 S-14 9.46 S-16 4.02 S-18 4.21 A 0.20 B 0.56 C 1.27 1. Three Watersheds: (a) Brunette River Basin - stations 1-12. (b) Salmon River Basin - stations S-2 to S-18. (c) Ladner Side Channel - stations A,B and C. 57 two contaminated sediments, i n l a b o r a t o r y a q u a r i a , f o r 30 days. Obviously, mechanisms f o r Zn accumulation i n the worms from t h e i r environment are q u i t e complex. In a number of f i e l d s t u d i e s (Bryan, 1976; Bryan and Hummerstone,1977; Ray et a l . , 1979a; Chapman et al.,1980) c o r r e l a t i o n between Zn i n sediments and Zn i n worms burrowing i n the sediments was found to be i n s i g n i f i c a n t . In these s t u d i e s , l a c k of r e l a t i o n s h i p between Zn i n sediments and organisms was a t t r i b u t e d to e i t h e r the a b i l i t y of organisms to c o n t r o l metals i n t h e i r t i s s u e (Bryan, 1976; Bryan and Hummerstone, 1977) or v a r i a b i l i t y i n a v a i l a b i l i t y of Zn i n the sediments (Chapman et a l . , 1980). H a l l and Bindra (1979) s t u d i e d the d i s t r i b u t i o n of t r a c e metals i n v a r i o u s geochemical phases of sediments and i n the burrowing o l i g o c h a e t e worms, c o l l e c t e d from v a r i o u s watersheds of the Lower Mainland of B r i t i s h Columbia. Sediments were c h a r a c t e r i z e d f o r a number of chemical and p h y s i c a l parameters such as pH, redox p o t e n t i a l , percent organic and i n o r g a n i c carbon, 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 . No s i n g l e parameter appeared to c o n t r o l Zn i n the worms. P a t r i c k and L o u t i t (1976) suggested t h a t Zn a s s o c i a t e d with a q u a t i c sediments may be concentrated by b a c t e r i a and passed on to t u b i f i c i d worms- which i n g e s t b a c t e r i a coated sediments f o r food (Geesey, 1980). Although many such mechanisms have been proposed, a c t u a l route of metal uptake by worms has not been determined (Chapman et a l . , 1980). 58 (b) M o l l u s c s : Freshwater clams and mussels are known to have a h i g h a f f i n i t y f o r Zn ( F o r e s t e r , 1980). Mathis and Cummings (1973) determined a number of t r a c e metals i n components of a freshwater ecosystem (sediments, water, worms, clams and f i s h e s ) . Maximum concentrations of Zn among the b i o t a o c c u r r e d i n clams and most c l o s e l y r e f l e c t e d sediment l e v e l s . Anderson (1977b) r e p o r t e d Zn c o n c e n t r a t i o n s i n s i x s p e c i e s of f r e s hwater clam and sediments c o l l e c t e d from the Fox R i v e r near Chicago. Zi n c l e v e l s i n clams were g r e a t e r than those f o r the sediments. D i s t r i b u t i o n of Zn i n v a r i o u s organs of two s p e c i e s of clam (Anodonta marginata and Lasmigona  complanata) i n d i c a t e d maximum co n c e n t r a t i o n s i n g i l l s and v i s c e r a s u g g e s t i n g t h a t Zn uptake i s mainly through food i n t a k e . Z i n c l e v e l s i n molluscs i n at l e a s t three e s t u a r i e s have been found to d e c l i n e with d i s t a n c e from the mouths of the e s t u a r i e s . Bryan and Hummerstone (1977) i n a t r a c e metal survey of the Looe Estuary, U.K., observed t h a t Zn c o n c e n t r a t i o n s i n most molluscan species and sediments dropped toward the sea. Larsen (1979) and Romeril (1979) a l s o found t h a t Zn l e v e l s i n the h a r d s h e l l clam, Mercenaria mercenaria, f e l l as s a l i n i t y i n c r e a s e d i n the James R i v e r and Southampton waters r e s p e c t i v e l y . S i m i l a r trends i n Zn c o n c e n t r a t i o n s have been measured f o r sediments (Romeril, 1979; Chapman et a l . , 1980). Popham et a l . (1980) showed t h a t mussels are q u i t e s e n s i t i v e to metal p o l l u t i o n i n the environment. 5 9 Zinc accumulation among molluscan s p e c i e s may v a r y due to d i f f e r e n c e s i n p h y s i o l o g i c a l metal requirements of the animals ( P r i n g l e et al.,1968). A t r a c e metal survey of s h e l l f i s h along the U.S. A t l a n t i c Coast and the P a c i f i c Coast (Washington State) found that Zn i n the organisms obtained from the A t l a n t i c Coast v a r i e d from approximately IO-4O ppm f o r h a r d s h e l l and s o f t s h e l l clams to values of I8O-4IOO ppm f o r the E a s t e r n o y s t e r . Zinc c o n c e n t r a t i o n s i n the P a c i f i c o y s t e r s were lower by a f a c t o r of 10. Z i n c c o n c e n t r a t i o n s i n the organisms a l s o depended on degree of p o l l u t i o n i n the c o a s t a l areas and water temperature. P a c i f i c o y s t e r s ( C r a s s o s t r e a giga) caught from 15 s t a t i o n s along the Tamar R i v e r , Tasmania, contained Zn l e v e l s i n p r o p o r t i o n to and exceeding those i n the sediments ( A y l i n g , 1974). This suggests that animal c o n t r o l s based on p h y s i o l o g i c a l needs may be overwhelmed i f c o n c e n t r a t i o n s i n the sediments are high enough. Results of a l a b o r a t o r y study by Ray et a l . (1981) support t h i s h y p o t h e s i s . The clam, Macoma b a l t h i c a , exposed to two sediments v a r y i n g w i d e l y i n Zn contamination accumulated Zn only from the sediment which contained very high l e v e l s of the metal. A l s o , i t has been shown that accumulation of t r a c e metals by b i v a l v e clams may depend upon the geochemical form of the metals (Luoma and Jenne, 1975a,b). Luoma and Jenne (1975b) s t u d i e d the uptake of r a d i o l a b e l l e d Ag, Cd, Co and Zn by the d e p o s i t f e e d i n g clam M. b a l t h i c a . They c o p r e c i p i -t a t e d the metals with amorphous Pb and Mn oxides and 60 s y n t h e t i c c a l c i t e or adsorbed them to b i o g e n i c carbonates or d e t r i t a l o r g a n i c s and then M. b a l t h i c a was allowed to feed on these m a t e r i a l s . At the end of the experiment , t i s s u e l e v e l s of metals i n the b i v a l v e were determined. The uptake of Zn was h i g h from b i o g e n i c carbonates, but very l i t t l e a ccumulation of the metal took place from Pb and Mn o x i d e s . Zin c bound to b i o g e n i c carbonate was r e a d i l y desorbed by seawater. Thus, the a b i l i t y of a clam to a s s i m i l a t e Zn was r e l a t e d to the weakness of bonding between Zn ions and the sediment p a r t i c l e s . Luoma and Jenne (1976) compared the l e a c h a b i l i t y of Zn ( a l s o Ag, Cd and Co) from model sediments and accumulation of the metal by M. b a l t h i c a . Accumulation of Zn by the clam from v a r i o u s sediments was best r e l a t e d to amount of metal e x t r a c t e d by IN ammonium a c e t a t e or IN sodium hydroxide p l u s EDTA. The amount of Zn removed from sediments by weak a c i d s (0.1N h y d r o c h l o r i c a c i d ; 25$ a c e t i c a c i d ) , r e d u c i n g agents (IN hydroxylamine h y d r o c h l o r i d e i n 0.01N n i t r i c a c i d ; sodium d i t h i o n i t e plus c i t r a t e ) or o x i d i z i n g agents {3% hydrogen peroxide plus c i t r a t e ) showed a poor r e l a t i o n to the metal accumulated by the clam. Luoma and Bryan (1979) i n v e s t i g a t e d a v a i l a b i l i t y of sediment-bound Zn to two species of clam (M. b a l t h i c a and S c r o b i c u l a r i a plana) under f i e l d c o n d i t i o n s . Sediments and organisms were c o l l e c t e d from two separate study areas. One study area was San F r a n c i s c o Bay where M. b a l t h i c a and sediments were sampled. The second study area was southwest 61 England i n which S. plana and sediments were c o l l e c t e d from 17 e s t u a r i e s . Z i n c c o n c e n t r a t i o n r a t i o s between the clams and sediments were regressed a g a i n s t Fe, Mn and Zn i n v a r i o u s chemical e x t r a c t s and sediment c h a r a c t e r i s t i c s such as orga n i c and i n o r g a n i c carbon content and combinations of these. The r e g r e s s i o n analyses i n d i c a t e d t h a t p h y s i o c h e m i c a l form of Zn i n the sediments a f f e c t e d the a v a i l a b i l i t y of the metal to the clam. S i g n i f i c a n t c o r r e l a t i o n was obtained between ammonium a c e t a t e s o l u b l e Zn i n sediments and Zn i n S c r o b i c u l a r i a . Other c o r r e l a t i o n s i n d i c a t e d t h a t the presence of h i g h l e v e l s of amorphous Fe and Mn oxides or humic substances i n sediments enhances a v a i l a b i l i t y of sediment-bound Zn to clam s p e c i e s . (c) Aquatic i n s e c t s : Namminga and Wilhm (1977) r e l a t e d t r a c e metal l e v e l s i n chironomids and sediments c o l l e c t e d from Skeleton Creek, Oklahoma. The mean concen-t r a t i o n o f Zn i n the organisms was 57 ppm, 3.6 times the mean c o n c e n t r a t i o n i n the sediments. Bindra and H a l l (1977) a l s o determined Zn l e v e l s i n chironomid l a r v a e c o l l e c t e d from the Brunette R i v e r and Salmon River basins i n the Lower Mainland of B r i t i s h Columbia. The metal l e v e l s i n the chironomids were compared to Zn con c e n t r a t i o n s i n v a r i o u s chemical e x t r a c t s of sediments and p h y s i c a l and chemical c h a r a c t e r -i s t i c s of sediments such as organic and i n o r g a n i c carbon, pH, redox p o t e n t i a l , p a r t i c l e s i z e f r a c t i o n s . No r e l a t i o n s h i p s were observed. B i o c o n c e n t r a t i o n r a t i o s between organisms and sediments d i f f e r e d c o n s i d e r a b l y between g r o s s l y p o l l u t e d 62 S t i l l Creek and only s l i g h t l y p o l l u t e d r u r a l Salmon R i v e r (Table VI) . (d) Other organisms: In a t r a c e metal study of R i v e r I r w e l l , U.K., Eyres and Pugh-Thomas (1978) found t h a t as s u b s t r a t e Zn l e v e l s i n c r e a s e d , t i s s u e l e v e l s i n A s e l l u s  a q u a t i c u s and E r p o b d e l l a o c t o c u l a t a decreased. The authors admitted although the exact mechanisms of t r a c e metal c o n t r o l i n the animals were not known, two p o s s i b i l i t i e s e x i s t e d : (1) the animals were able to block entry of the metal i n t o t h e i r bodies or (2) the metals e n t e r i n g the animal bodies were e f f e c t i v e l y removed through animal e x c r e t i o n s . S i m i l a r metal c o n t r o l s were a l s o o perative i n Crangon  septemponosa when i t f a i l e d to accumulate Zn from two contaminated sediments to which the shrimp 0 was exposed i n a l a b o r a t o r y f o r a p e r i o d of 30 days (Ray et a l . , 1981). 6. Summary Trace metal l e v e l s i n benthic organisms do not always r e f l e c t the c o n c e n t r a t i o n s i n sediments. This suggests t h a t other f a c t o r s h e l p r e g u l a t e organism t r a c e metal l e v e l s . Although the exact nature of these c o n t r o l s i s not known, much s p e c u l a t i o n e x i s t s . Among the suggested c o n t r o l s are the a b i l i t y of the organisms to block uptake or e f f e c t i v e l y excrete the metals e n t e r i n g the animal body, and l i m i t e d b i o a v a i l a b i l i t y of the t o t a l metal i n the sediments. The l a t t e r has been r e c o g n i z e d only r e c e n t l y . I t i s b e l i e v e d t h a t the geochemical form of the metal i n sediments may 63 Table VI : Comparison of Bioconcentration Ratios of Zi n c i n Chironomids from Two Watersheds, Lower Mainland, B r i t i s h Columbia (from Bindra and H a l l , 1977,p.40) Watershed Station Bioconcentration Comments Ratio S t i l l Creek Grandview Hwy. 8. 16 Urban Salmon River Springbrook Rd. 3. 76 Rural Salmon River 64th Avenue 3. 34 Rural Salmon River Coglan Creek at Otter Rd. 2. 95 Rural Salmon River Roberts Rd. 2. 48 Rural Bioconcentration sediment Ratio = Zn in chironomids/ t o t a l Zn i n determine i t s p o t e n t i a l a v a i l a b i l i t y . Not many s t u d i e s have been conducted to evaluate the r e l a t i o n s h i p between b i o l o g i c a l uptake and geochemistry of t r a c e metals. 65 Chapter 2 MATERIALS AND METHODS I. MATERIALS AND METHODS FOR EXCHANGE BETWEEN SEDIMENTS AND WATER Laboratory experiments were set up to determine the e f f e c t s of oxygen , pH, s a l i n i t y , sediment type ( p a r t i c l e s i z e and or g a n i c content) and a g i t a t i o n on the exchange of t r a c e metals between sediments and water. V e r t i c a l p l e x i -g l a s s c y l i n d e r s c o n t a i n i n g 5 cm of sediment under a 100 cm column of water were used to simulate n a t u r a l q u i e s c e n t c o n d i t i o n s f o r exchange. The v a r i a b l e s s t u d i e d i n these s t a t i c columns i n c l u d e d oxygen, pH, s a l i n i t y and sediment type. C o n c e n t r a t i o n s of t r a c e metals Cu, Fe, Pb, Zn and sometimes Mn were monitored i n the water column above the sediment f o r approximately 5 weeks or u n t i l e q u i l i b r i u m c o n d i t i o n s were e s t a b l i s h e d . E l u t r i a t e t e s t s (see P. 8) were performed to i n v e s t i g a t e the e f f e c t s of a g i t a t i o n i n combination with oxygen, pH, s a l i n i t y , and sediment type on t r a c e metal exchange. A l l column s t u d i e s and e l u t r i a t e t e s t s were performed on two sediments d i f f e r i n g i n p a r t i c l e s i z e and organ i c matter content. 66 A. Column S t u d i e s  1. Sampling (a) Sediment: Sediments f o r a l l exchange s t u d i e s were obtained from the two p r e v i o u s l y e s t a b l i s h e d s t a t i o n s i n S t i l l Creek (Bindra and H a l l , 1977), s t a t i o n No. 11 (at W i l l i n g d o n Avenue) and No. 12 (at Gilmore Avenue) i n the Brunette B a s i n i n Burnaby, B.C. The c r i t e r i o n f o r t h e i r s e l e c t i o n was t h a t sediments at both s t a t i o n s contained h i g h l e v e l s of exchangeable t r a c e metals and d i f f e r e d s i g n i f i -c a n t l y i n p a r t i c l e s i z e and o r g a n i c matter content. The sediment c o l l e c t e d at W i l l i n g d o n Avenue was mainly s i l t and c l a y and r e l a t i v e l y h i g h i n o r g a n i c matter content. In c o n t r a s t , the sediment c o l l e c t e d at Gilmore Avenue was coarse (sandy) and r e l a t i v e l y low i n o r g a n i c content. For column s t u d i e s the sediments were c o l l e c t e d on two o c c a s i o n s : (1) 23 Dec. 1977.(used i n o x i c , anoxic, s a l i n i t y columns and low organic-pH columns) (2) 19 A p r i l 1978 (used i n high organic-pH columns, a l s o used i n e l u t r i a t e t e s t s d e s c r i b e d l a t e r ) Approximately 20 l i t e r s of sediment were c o l l e c t e d on each o c c a s i o n with an aluminum pot. The sediments were immediately s i e v e d through a coarse (2 mm) p l a s t i c s i e v e to remove coarse m a t e r i a l s and p l a c e d i n p l a s t i c bags f l u s h e d with n i t r o g e n and t r a n s p o r t e d to the l a b o r a t o r y i n i c e d c o o l e r s . A small p o r t i o n of each sediment was used f o r geochemical f r a c t i o n a t i o n and f o r d e t e r m i n a t i o n of organic matter, p a r t i c l e s i z e and percent dry weight. The remaining sediments were p l a c e d i n p l a s t i c bags and s t o r e d f o r p e r i o d s up to 115 days i n a f r e e z e r u n t i l needed. Although s t o r i n g 67 of sediments even under f r e e z i n g c o n d i t i o n s can a f f e c t geo-chemical d i s t r i b u t i o n of metals, f o r comparison of r e s u l t s i t i s important t h a t a l l s i m i l a r experiments be performed with the same sediment. (b) Water: Freshwater f o r the column s t u d i e s was obtained a t the same S t i l l Creek s t a t i o n s as the sediments j u s t p r i o r to s e t t i n g up the columns. Seawater f o r s a l i n i t y -changes was obtained from the seawater tap a t the P a c i f i c Environmental I n s t i t u t e (PEI) i n West Vancouver which takes seawater s e v e r a l hundred meters o f f s h o r e and s e v e r a l meters deep. A l l water was c o l l e c t e d i n c l e a n p l a s t i c c o n t a i n e r s and s t o r e d at 4 °C u n t i l used. 2. C o n s t r u c t i o n of columns Four p l e x i g l a s s columns 122 cm high, 30.5 cm 0D and 29.2 cm ID with p l e x i g l a s s bottoms and tops were c o n s t r u c t e d i n the C i v i l E n g i n e e r i n g Workshop. A g l a s s tube with a gas d i s p e r s i o n tube at i t s lower end was suspended i n each column. The columns were f i t t e d with s e v e r a l sampling p o r t s covered with rubber cups f i l l e d with s i l i c o n s e a l a n t . Columns were supported on 45 cm wooden bases to f a c i l i t a t e sampling and c l e a n i n g of columns. A schematic of a column i s shown i n F i g u r e 3. Three s i m i l a r columns of smaller diameter (14 cm 0D) were used to study the e f f e c t of pH on t r a c e metal.dynamics. 3. Setup of columns, o p e r a t i o n and sampling Frozen sediment with a wet volume of approximately 3.5 l i t e r s was p l a c e d i n t o a column and immediately o v e r l a i n Figure 3. Sketch of a Column f6mm plastic tubing to source of compressed air or nitrogen gas ^vent hole plexiglass column 30.5 O.D. 29.3 I.D. wooden support -sampling port 15 cm 15 cm H-15 cm - L . 7 ; 5 cm 7.5 cm 122.0cm 45.8 cm E 1 A-clamp -rubber cup I ! j V—. _L 6 mm 9 mm 1 ! m | s 1 J V —silicon sealant * — 2.5 cm" column wall SAMPLING PORT 69 with_70 l i t e r s of freshwater u s i n g a siphon arrangement to give a sediment to water r a t i o of 1:20. Compressed a i r from the l a b o r a t o r y o u t l e t was connected to the g l a s s tubes and allowed to purge the water column with the d i s p e r s i o n head 10 cm above the sediment to prevent sediment r e s u s p e n s i o n . To generate anoxic c o n d i t i o n s , compressed n i t r o g e n gas, p a s s i n g through a p y r o g a l l o l and d e i o n i z e d water c l e a n i n g t r a i n , was used to r e p l a c e the a i r . For anoxic runs, freshwater was purged with n i t r o g e n before s i p h o n i n g i n t o the columns. A f t e r 24 hours e q u i l i b r a t i o n , sampling began through the lower p o r t u s i n g p l a s t i c s y r i n g e s to o b t a i n 250 ml of sample. The samples were f i l t e r e d through 0.4.5/*-™ membrane f i l t e r s 1 a c i d i f i e d and s t o r e d f o r subsequent a n a l y s i s . The f i l t e r s r e t a i n i n g suspended s o l i d s were s t o r e d i n c l e a n p e t r i d i s h e s p r i o r to d i g e s t i o n . Sampling continued f o r approximately 5 weeks or u n t i l e q u i l i b r i u m was reached. At t h i s time, the f i r s t s a l i n i t y change was made where h a l f of the freshwater was r e p l a c e d with seawater (~28 °/oo). Subsequent s a l i n i t y changes were made to a t t a i n values of 21 u/oo and 28 u / oo i n the columns. The three smaller p l e x i g l a s s columns were used to study pH e f f e c t s u s i n g one sediment f o r each experimental s e r i e s . These experiments were only operated under o x i c c o n d i t i o n s with compressed a i r and the same r a t i o 1:20 of sediment to water was employed. No s a l i n i t y changes were attempted i n the pH s e r i e s . The three pH values used were 1. Throughout t h i s work M i l l i p o r e - t y p e ( c e l l u l o s e a c e t a t e ) membrane f i l t e r s were used. The f i l t e r s were soaked i n 0.05M p h t h a l a t e b u f f e r (pH=3.6) f o r s e v e r a l hours and r i n s e d i n d e i o n i z e d water before u s i n g . 70 the n a t u r a l pH of approximately 7 and adjusted pH's of 5 and 10. The pH 5 b u f f e r (0.1M) was an acetate b u f f e r made by d i s s o l v i n g 86.59 g of sodium a c e t a t e and 25.64 ml of g l a c i a l a c e t i c a c i d i n 15 l i t e r s of S t i l l Creek water. The pH 10 b u f f e r was a carbonate b u f f e r (0.1M) made by d i s s o l v i n g • . 87.45 g of sodium carbonate and 50.70 g of sodium bicar b o n a t e i n 15 l i t e r s of S t i l l Creek water. The v a r i o u s combinations of oxygen, pH, s a l i n i t y and sediment employed i n the column s t u d i e s are summarized i n Table V I I . During a l l column s t u d i e s , i n a d d i t i o n to t r a c e metal a n a l y s e s , c o l o r , t u r b i d i t y and pH measurements were made p e r i o d i c a l l y u n t i l no s i g n i f i c a n t change was apparent. A l s o , water i n the columns before and a f t e r each change was analyzed f o r c o l o r , t u r b i d i t y , pH, r e s i d u e , on e v a p o r a t i o n , d i s s o l v e d i n o r g a n i c and d i s s o l v e d organic carbon, n i t r a t e n i t r o g e n , c h l o r i d e , s u l p h a t e , hardness, calcium, a l k a l i n i t y , a c i d i t y , c o n d u c t i v i t y and s a l i n i t y . A l l column s t u d i e s were conducted at room temperature (22-23 ° C ) . B. E l u t r i a t e S t u d i e s  1. Sampling (a) Sediments: The sediments c o l l e c t e d on 19 A p r i l 1978 f o r the column experiments were used i n these s t u d i e s . (b) Water: Laboratory tap water was used as the freshwater source a l l o w i n g at l e a s t 10 minutes to 71 Table VII : Combination of Sta t i c Column Environmental Studies Conditions Used in Experiment''" Oxygen Conditions pH S a l i n i t i e s (°/oo) 2 1 oxic J natural (~~7) 0, 14, 21, 28 2 anoxic 4 natural 7) 0, 14, 21, 28 3 oxic 5 0 4 oxic natural 7) 0 5 oxic 10 0 1. Each experiment was conducted o n l y once w i t h b oth t h e low o r g a n i c ( G i l r a o r e ) and h i g h o r g a n i c ( W i l l i n g d o n ) sediments, 2. S a l i n i t i e s were adjusted stepwise with a period of 5 weeks allowed for equilibrium. 3 . C o n t i n o u s d i s p e r s i o n of compressed a i r i n water column. 4 . C o n t i n u o u s p u r g i n g of water column w i t h o x y g e n - f r e e n i t r o g e n . 72 purge the p i p e s . Seawater was obtained from PEI as d i s c u s s e d e a r l i e r . Water was st o r e d a t - 4 °C but allowed to come to room temperature before the t e s t s . 2. Test procedure Wet sediment e q u i v a l e n t to 25 g dry weight was p l a c e d i n 1 l i t e r Erlenmeyer f l a s k s c o n t a i n i n g 4.75 ml of water ( i n c l u d i n g i n t e r s t i t i a l water). The f l a s k contents were a g i t a t e d f o r 30 minutes with compressed a i r or n i t r o g e n . A f t e r 1 hour of s e t t l i n g , 200 ml of supernatant was decanted i n t o a p l a s t i c c e n t r i f u g e tube and c e n t r i f u g e d f o r 30 minutes at 3000 rpm f o l l o w e d by f i l t r a t i o n through a 0 . ( 5 P membrane f i l t e r . The f i l t e r e d water samples were a c i d i f i e d and s t o r e d f o r subsequent a n a l y s i s . For t e s t s i n v o l v i n g anoxic c o n d i t i o n s , a n i t r o g e n atmosphere was maintained over the water u n t i l i t was f i l t e r e d and a c i d i f i e d . A blank of water with no sediment was c a r r i e d through the procedure to e l i m i n a t e some of the e r r o r s due to s o r p t i o n on to and d e s o r p t i o n from the apparatus. 3. Environmental c o n d i t i o n s of e l u t r i a t e t e s t E l u t r i a t e t e s t s were performed with compressed a i r ( o x i c ) and n i t r o g e n (anoxic c o n d i t i o n s ) on both low and high o r g a n i c content sediments a t s a l i n i t i e s of 0, 1, 4» 10 and 25 °/oo and at ambient pH and adjusted pH's of 5 and 10. A l l t e s t s were performed at room temperature (22-23 ° C ) . For each s e t of c o n d i t i o n s the t e s t was performed on t r i p l i c a t e samples and the r e s u l t s averaged. 73 I I . MATERIALS AND METHODS FOR EXCHANGE BETWEEN SEDIMENTS AND BENTHIC INVERTEBRATES A. Organisms f o r Exchange Experiments Four groups of organisms were c o l l e c t e d f o r the t r a c e metal exchange experiments. They i n c l u d e d an e s t u a r i n e amphipod (Anisogammarus c o n f e r v i c o l u s ) taken from a l a b o r a t o r y c u l t u r e maintained i n the I n s t i t u t e of Oceanography, U.B.C. The parent stock was c o l l e c t e d from the Squamish est u a r y a t the head of Howe Sound. The second organism, the opossum shrimp (Neomysis m e r c e d i s ) , was taken from a l a b o r a t o r y p o p u l a t i o n that had been c o l l e c t e d i n the main arm of the F r a s e r River near Woodward I s l a n d . O l igochaetes were c o l l e c t e d on May 31» 1978 i n the middle of contaminated Ladner s i d e c h a n n e l , which i s the main harbour area f o r Ladner, approximately 4O km from Vancouver, B.C. They were c o l l e c t e d w ith an Ekman dredge and s i e v e d from the sediment w i t h a 0.038 mm bucket s i e v e at the c o l l e c t i o n s i t e . Recent surveys have i n d i c a t e d T ubifex t u b i f e x and L i m n o d r i l u s h o f f m e i s t e r i are the dominant s p e c i e s at t h i s s t a t i o n ( H a l l and Y e s a k i , unpublished d a t a ) . Chironomids, predominantly Chironomous sp. and Cryptochironomous sp., were c o l l e c t e d on June 19, 1978 i n a marsh side channel a d j a c e n t to the Ladner sewage lagoon. Samples were taken with a hand scoop from the s i d e channel bank at low t i d e and s i e v e d with a 0.038 mm bucket s i e v e on s i t e . Both the o l i g o c h a e t e s and the chironomids were p l a c e d i n r i v e r water i n p l a s t i c buckets f o r t r a n s p o r t a t i o n to the l a b o r a t o r y . 74 B. Sediments and Water f o r the Experiments Two contaminated sediments were c o l l e c t e d on May 23, 1978 a t the same two s t a t i o n s of S t i l l Creek and u s i n g the same methods as d i s c u s s e d e a r l i e r f o r the sediment-water exchange. As before, W i l l i n g d o n Avenue sediment was f i n e and r e l a t i v e l y high i n organic matter content, and Gilmore Avenue sediment was r e l a t i v e l y coarse (sandy) and lower i n o r g a n i c matter. A sma l l p o r t i o n of the sediment was used f o r d e t e r m i n a t i o n of t o t a l t r a c e metals. A geo-chem i c a l d i s t r i b u t i o n of t r a c e metals i n sediments c o l l e c t e d e a r l i e r ( A p r i l 19, 1978) provided some i n f o r m a t i o n on the form of t r a c e metals i n the sediment. U n c h l o r i n a t e d freshwater from a w e l l at UBC was used to s e t up the sediment-invertebrates exchange experiments. The amphipods r e q u i r e d b r a c k i s h water c o n d i t i o n s . T h e r e f o r e , seawater c o l l e c t e d from Burrard I n l e t a t PEI with a s a l i n i t y of a p p r o x i m a t e l y 28 °/oo was d i l u t e d with w e l l water to give a b r a c k i s h water of 7 °/oo. C. Experimental Setup Trace metal exchange experiments with the amphipods, chironomids, and opossum shrimp were set up i n wide mouth 3.64 l i t e r (128 oz.) j a r s while the chambers f o r experiments with o l i g o c h a e t e s Were wide mouth 0.45 l i t e r (16 oz.) b o t t l e s . Sediment and water were placed i n the b o t t l e s i n a r a t i o of 1:8 . To each amphipod microcosm chamber, 5 g wet weight of the be n t h i c algae, Enteromorpha, 75 was added as a food s u b s t r a t e . The microcosm b o t t l e s were set up i n a P e r c e v a l l i n c u b a t o r a t 10 °C on a 12 hour l i g h t , 12 hour dark c y c l e . Compressed a i r was bubbled i n t o each chamber with care taken to prevent r e s u s p e n s i o n of the sediment. The microcosm chambers were allowed a t l e a s t 24-hours to come to e q u i l i b r i u m before any organisms were added.-Approximately 4-0 - 50 opossum shrimp, 100 amphipods and 1 g wet weight t o t a l masses of o l i g o c h a e t e s and chironomids were p l a c e d i n i n d i v i d u a l b o t t l e s f o r the microcosms. The numbers and masses were s e l e c t e d i n order to provide s u f f i c i e n t m a t e r i a l f o r t r a c e metal a n a l y s i s . At approximately one week i n t e r v a l s , organisms i n the two d i f f e r e n t sediment types were c o l l e c t e d f o r a n a l y s i s . Since the analyses r e q u i r e d r e l a t i v e l y l a r g e numbers of organisms, i t was onl y p o s s i b l e to make d u p l i c a t e analyses f o r some of the o l i g o c h a e t e microcosms. The opossum shrimp were c o l l e c t e d with a l a r g e bore p i p e t t e . Amphipods were hand p i c k e d with tweezers from the algae f o l l o w e d by s i e v i n g the sediment through a 0.035 mm s t a i n l e s s s t e e l T y l e r s i e v e . Both o l i g o c h a e t e s and chironomids were s i e v e d from the sediments with the 0.035 mm s i e v e , t r a n s f e r r e d to a white enamel t r a y and segregated from l a r g e d e t r i t u s p a r t i c l e s with tweezers. A l l organisms were r i n s e d with d i s t i l l e d water, placed i n aluminum dishes and d r i e d at 60 °C to constant weight. 76 I I I . ANALYTICAL PROCEDURES FOR EXCHANGE AT BOTH SEDIMENT-WATER AND SEDIMENT-INVERTEBRATE INTERFACES A. Geochemical P a r t i t i o n i n g of Sediments  1. General A l l glassware and p o l y e t h y l e n e b o t t l e s used f o r geochemical e x t r a c t i o n s and i n ge n e r a l h a n d l i n g and storage of samples were soaked i n 50 percent h y d r o c h l o r i c a c i d f o r s e v e r a l hours and then r i n s e d 4- - 5 times with d i s t i l l e d water. Glassware and p o l y e t h y l e n e were s t o r e d i n d i s t i l l e d water u n t i l used. A l l chemicals were reagent grade. The e x t r a c t i o n scheme used i n t h i s study was f i r s t proposed by E n g l e r et a l . (1974). Serne (1975) u t i l i z e d t h i s scheme to p a r t i t i o n t r a c e metals i n marine sediments. The method of E n g l e r et a l . was p r e f e r r e d to others s i n c e i t attempts to keep the sediment as c l o s e as p o s s i b l e to i n s i t u c o n d i t i o n s f o r the f i r s t three e x t r a c t i o n s . Drying, g r i n d i n g and exposure to atmospheric oxygen are avoided. The f i r s t three e x t r a c t i o n s , n a m e l y i n t e r s t i t i a l water, exchangeable phase, and e a s i l y r e d u c i b l e phase,are c a r r i e d out under a n i t r o g e n atmosphere i n a glove box. Two a n a l y t i c a l d i f f i c u l t i e s were encountered when attempts were made to use the proposed p a r t i t i o n i n g scheme. In the moderately r e d u c i b l e phase, the d i s s o l v e d s o l i d s were too high f o r atomic a b s o r p t i o n flame spectrophotometry and the chemicals used to e x t r a c t t h i s phase were g r o s s l y contaminated w i t h z i n c . Both of these d i f f i c u l t i e s were 77 avoided by u s i n g an a l t e r n a t i v e geochemical e x t r a c t i o n method which employed 0.3M h y d r o c h l o r i c a c i d r a t h e r than the c i t r a t e d i t h i o n i t e b u f f e r . Malo (1977) has shown that t h i s technique i s e q u a l l y s e l e c t i v e and somewhat more e f f e c t i v e than the c i t r a t e - d i t h i o n i t e e x t r a c t i o n . T h i s geochemical phase w i l l be r e f e r r e d to as the e a s i l y a c i d e x t r a c t a b l e phase (EAEP). 2 . I n t e r s t i t i a l water (IW) Well mixed sediment was t r a n s f e r r e d from the sampl b o t t l e to a c e n t r i f u g e tube with a l a r g e p l a s t i c s p a t u l a i n the glove box under a p o s i t i v e n i t r o g e n p r e s s u r e . Enough sediment was c e n t r i f u g e d at 3000 rpm f o r two hours to p r o v i d e a t l e a s t 150 ml of i n t e r s t i t i a l water (IW). The IW was 0.45 membrane f i l t e r e d , a c i d i f i e d to pH 1 and s t o r e d i n 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 . 3 . Exchangeable phase (EP) Preweighed c e n t r i f u g e tubes (250 ml) and aluminum d i s p o s a b l e evaporating dishes were placed i n the glove box c o n t a i n i n g the sample and s p a t u l a . A p o r t i o n of sediment c o n t a i n i n g about 20 g of dry m a t e r i a l was placed i n the c e n t r i f u g e tube and sealed with a screw cap. Another p o r t i o n of the sediment c o n t a i n i n g approximately 10 g dry m a t e r i a l was placed i n the e v a p o r a t i n g d i s h . Both a l i q u o t s were weighed and the sample i n the aluminum d i s h was d r i e d to constant weight at 103 °c to determine the moisture c o n t e n t . One hundred ml of deoxygenated 1.3M ammonium 78 a c e t a t e (pH=7) was t r a n s f e r r e d to each c e n t r i f u g e tube i n the glove box. The tubes were capped and shaken f o r 1 hour on a B u r r e l l w r i s t - a c t i o n shaker and then c e n t r i f u g e d . The supernatant was 0.4.5 A m membrane f i l t e r e d , a c i d i f i e d (pH=l) and s t o r e d i n p o l y e t h y l e n e b o t t l e s f o r subsequent a n a l y s i s . The e x t r a c t s a l s o c o n t a i n e d i n t e r s t i t i a l water so i t was necessary to c o r r e c t v a l u e s f o r the t r a c e metal content of the 1W. 4. E a s i l y r e d u c i b l e phase (ERP) The r e s i d u e from the EP was washed once with 50 ml of deoxygenated d i s t i l l e d water,, c e n t r i f u g e d a t 3000 rpm f o r 1 hour and the supernatant d i s c a r d e d . This was done o u t s i d e the glove box but under a stream of n i t r o g e n gas. A 3-4 g sub-sample (on a dry weight b a s i s ) of the washed sediment was t r a n s f e r r e d to a preweighed c e n t r i f u g e tube i n the glove box. An a d d i t i o n a l sub-sample was taken f o r moisture d e t e r m i n a t i o n . One hundred ml of deoxygenated O.IK hydroxylamine-hydrochloride, a d j u s t e d to pH 2 with n i t r i c a c i d , was added to the sample, shaken f o r 30 minutes on the B u r r e l l shaker and then c e n t r i f u g e d f o r 1 hour. The supernatant was f i l t e r e d through a 0.45 Am membrane f i l t e r and s t o r e d f o r a n a l y s i s . Since the r e s i d u a l components of sediment are not a f f e c t e d by atmospheric oxygen the subsequent e x t r a c t i o n s were conducted on the open l a b o r a t o r y bench. 5. Organic and sulphur phase (OSP) The sediment from the ERP was washed with 50 ml of d i s t i l l e d , d e i o n i z e d water i n e x a c t l y the same manner as 79 p r e v i o u s l y d e s c r i b e d f o r the ERP except i t was not p r o t e c t e d from the a i r . Tubes c o n t a i n i n g the washed r e s i d u e were p l a c e d i n a 90 - 95 °C waterbath and 30$ ^2°2 ' a c i d i f l e d to pH 2, was added i n small a l i q u o t s u n t i l no vi g o r o u s steaming was noted. M i n e r a l ions l i b e r a t e d by t h i s d i g e s t i o n were e x t r a c t e d with 100 ml of 1.0M ammonium a c e t a t e s o l u t i o n , a d j u s t e d to pH 2 with n i t r i c a c i d , by shaking on the B u r r e l l shaker f o r 1 hour f o l l o w e d by f i l t r a t i o n as p r e v i o u s l y d e s c r i b e d . 6. E a s i l y a c i d e x t r a c t a b l e phase (EAEP) The r e s i d u a l sediment was washed, 10 ml of 3N HC1 . added and immediately d i l u t e d to 100 ml with d i s t i l l e d water. The tubes were heated with p e r i o d i c shaking i n a 90 - 95 °C waterbath u n t i l temperature reached 80 °C and then continued f o r 30 minutes. The e x t r a c t was recovered by c e n t r i f u g a t i o n . The r e s i d u e was washed with 10 ml of d i s t i l l e d water and the washings combined with the a c i d e x t r a c t which was f i l t e r e d and s t o r e d f o r a n a l y s i s . 7. Residue phase (RP) A weighed sub-sample (approx. 0.5 g dry wt.) of the washed residue from the previous e x t r a c t i o n was d i g e s t e d on a sand bath at 180 °C with 10 ml of fuming n i t r i c a c i d and 10 ml of cone, h y d r o f l u o r i c a c i d i n a covered T e f l o n 2. Approximate strengths of the concentrated i n o r g a n i c a c i d s used i n the experimental work of t h i s t h e s i s were: HN0 3, 90$, 21M; HC1,36.5-38$, 12M; HF, 48-51$, 29M; and HC10., 70-72$, 9M. 4 80 beaker. Upon complete e v a p o r a t i o n , 5 ml of cone, p e r c h l o r i c a c i d was added and evaporation continued u n t i l dry a g a i n . T h i s was f o l l o w e d by s u c c e s s i v e 10 ml a d d i t i o n s of hydro-f l u o r i c a c i d and evaporation u n t i l the s i l i c a t e m i n e r a ls were d i g e s t e d . The r e s i d u e was d i s s o l v e d i n d i l u t e hydro-c h l o r i c a c i d and made to volume i n a 50 ml v o l u m e t r i c f l a s k with a 5% s o l u t i o n of 1:1 mixture of n i t r i c and h y d r o c h l o r i c cone, a c i d s . A separate sub-sample of sediment was taken f o r moisture d e t e r m i n a t i o n and a blank was c a r r i e d through the d i g e s t i o n procedure to account f o r a c i d i m p u r i t i e s . 8. T o t a l t r a c e metal a n a l y s i s ( T o t a l ) Sediment sub-samples used to determine moisture content f o r the exchangeable phase were f i n e l y ground i n an agate mortar and approximately 0.5 g p o r t i o n s t r a n s f e r r e d to T e f l o n beakers. The sediment was d i g e s t e d and brought to volume i n the same manner as the r e s i d u e phase except t h a t the p e r c h l o r i c a c i d was d i l u t e d with 5 ml of fuming n i t r i c a c i d as a s a f e t y measure. A l l these geochemical e x t r a c t s were analysed f o r Cu, Fe, Mn, Pb and Zn u s i n g the atomic a b s o r p t i o n 3 spectrophotometric method d e s c r i b e d l a t e r i n t h i s chapter. 3. . P r e c i s i o n checks were made i n a previous study (Bindra and H a l l , 1977) standard d e v i a t i o n were w i t h i n 10$ of the average values except f o r some geochemical phases c o n t a i n i n g low c o n c e n t r a t i o n s the d e v i a t i o n s were as h i g h as 25 p e r c e n t . 81 B. Trace Metals i n Water Water samples were analyzed by atomic a b s o r p t i o n flame spectrophotometry. A complexation-solvent e x t r a c t i o n procedure was used due to the low l e v e l s of metals i n the water (McQuaker, 1976). Two problems were encountered when attempts were made to use t h i s procedure on the e l u t r i a t e samples. The s o l v e n t formed a s t a b l e emulsion w i t h the water and the s m a l l volume of solvent t h a t separated from the emulsion appeared to give an enhanced s i g n a l . These problems were probably caused by e x t r a c t i o n of o i l s and greases from these p o l l u t e d sediments. To overcome these d i f f i c u l t i e s , water samples from e l u t r i a t e t e s t s were d i g e s t e d w i t h s t r o n g a c i d before s o l v e n t e x t r a c t i o n . 1. D i g e s t i o n of e l u t r i a t e samples The f i l t e r e d samples (100 ml) were t r a n s f e r r e d to 250 ml g l a s s beakers and 10 ml of fuming HNO^ + 10 ml of cone. HC1 were added. Samples were evaporated to reduce the contents to approximately 35 ml followed by d i l u t i o n to 100 ml with d e i o n i z e d water. A blank was run through the above procedure to account f o r any tra c e metals i n the a c i d s . 2. D i g e s t i o n of suspended s o l i d s Suspended s o l i d s on membrane f i l t e r s were t r a n s f e r r e d to 250 ml beakers and di g e s t e d i n fumehood a f t e r adding 2 ml of fuming HNO^ and 1 ml of cone. HCIO^. Samples were taken to dryness and then s o l u b i l i z e d with 3 ml of a 50$ s o l u t i o n of 1:1 , HNO^ : HC1 cone, a c i d s . A blank was a l s o run to c o r r e c t f o r contamination from membrane f i l t e r s and a c i d s K. To check p r e c i s i o n eight 100 ml aliquots of a water sample co l l e c t e d from S t i l l Creek were analysed for Cu, Pb and Zn by solvent extraction method. Mean concentrations and percent standard deviations for the 3 metals are: 15(3.1?). Cu! 11(4.6$),Pbj 29(3.-!%). Zn, 82 3. P r e p a r a t i o n of reagents The d i e t h y l d i t h i o c a r b a m a t e (DDC) s o l u t i o n was prepared by d i s s o l v i n g 20 g of NaDDC i n 380 ml of d e i o n i z e d water, 0.45 JLm membrane f i l t e r i n g and e x t r a c t i n g with s e v e r a l 20 ml a l i q u o t s of methyl i s o b u t y l ketone (MIBK) u n t i l the y e l l o w i s h c o l o r of the e x t r a c t disappeared. This s o l u t i o n was prepared f r e s h f o r each batch of samples. The b i p h t h a l a t e b u f f e r was prepared by d i s s o l v i n g 87.4 g of potassium b i p h t h a l a t e i n 900 ml of d e i o n i z e d water, f o l l o w e d by the a d d i t i o n of 12 ml of IN HC1 and d i l u t i n g to 1 l i t e r . The b u f f e r was e x t r a c t e d with 25 ml of 0.01$ s o l u t i o n of d i t h i z o n e i n MIBK followed by s e v e r a l 25 ml a l i q u o t s of MIBK u n t i l the green r e s i d u a l c o l o r of d i t h i z o n e was completely removed. A standard stock s o l u t i o n of Cu, Pb, Zn (25 mg/l) and Fe (50 mg/l) was prepared by d i l u t i n g 1000 ppm F i s h e r AA s o l u t i o n s of these elements with a 10% s o l u t i o n of 1:1, HNO^: HC1 cone, a c i d s . 4. E x t r a c t i o n procedure The standard stock s o l u t i o n was d i l u t e d with a c i d i f i e d water (4 ml cone. HNO^/l) to prepare standards of 1, 3, 5, 10, 20, 30, 50, 80 and 120 /tg/1 f o r Cu, Zn and Pb and twice the c o n c e n t r a t i o n f o r Fe. A l l standards and 100 ml p o r t i o n s of water samples were t r a n s f e r r e d to 250 ml beakers. Two ml of b i p h t h a l a t e b u f f e r was added and the pH adj u s t e d to 3.6 + 0.1 wit h NH OH or HC1. The standards and samples 83 were t r a n s f e r r e d to 250 ml v o l u m e t r i c f l a s k s to which 10 ml of DDC s o l u t i o n was added, f o l l o w e d by mixing, and standing f o r 30 minutes. S i x ml of MIBK was added to each f l a s k and shaken f o r 10 minutes on a mechanical shaker ( B u r r e l l W r i s t A c t i o n ) . The samples were allowed to stand f o r 10 minutes to separate the phases and then d e i o n i z e d water was added to b r i n g the MIBK l a y e r i n t o the neck of the f l a s k . Samples were a s p i r a t e d i n t o the spectrophotometer a f t e r s t a n d i n g f o r 20 minutes. C. Trace Metals i n Benthic Invertebrates and Algae B e n t h i c organisms and algae samples were analyzed f o r t r a c e metals by atomic a b s o r p t i o n spectrophotometery a f t e r d i s s o l u t i o n as f o l l o w s . 1. D i s s o l u t i o n of benthic i n v e r t e b r a t e s In t r a c e metal analyses of organisms, e r r o r due to gut content i s g e n e r a l l y overlooked ( F l e g a l and M a r t i n , 1977). The common p r a c t i c e i s to keep l i v e organisms f o r s e v e r a l hours i n c l e a n water to empty t h e i r guts. This procedure has been q u e s t i o n e d s i n c e organisms may s t i l l c o n t a i n s i g n i f i c a n t q u a n t i t i e s o f sediment a f t e r s e v e r a l hours of f a s t i n g . F u r t h e r , the procedure does not prevent organisms from r e i n g e s t i n g t h e i r f e c e s . . T h e r e f o r e , to e l i m i n a t e most of the gut e r r o r , organisms were d i g e s t e d over medium heat i n 100 ml Erlenmeyer f l a s k s by s e v e r a l a d d i t i o n s of 30% hydrogen p e r o x i d e . One ml of fuming n i t r i c a c i d was added f o l l o w e d by 15 ml of d i s t i l l e d water before the a c i d 84 completely evaporated. Undigested sediment from organisms' guts was removed by f i l t r a t i o n on preweighed 0.45 xmn membrane f i l t e r s . The membrane f i l t e r and the f i l t e r e d sediment were oven d r i e d to constant weight (103 ° C ) . The p r e v i o u s l y determined membrane weight was subtracted to o b t a i n gut sediment weight. . The f i l t e r s and sediments were t r a n s f e r r e d to t e f l o n beakers and d i g e s t e d s i m i l a r l y to the r e s i d u e phase. S o l u b i l i z e d m a t e r i a l was combined with the p r e v i o u s organism d i g e s t a t e i n an Erlenmeyer f l a s k . The combined s o l u t i o n was evaporated and brought to a f i n a l volume of 10.ml ( f o r 50 - 100 mg of organisms) or 5 ml ( f o r 25 - 50 mg of organisms). Trace metal content of organisms was c o r r e c t e d f o r gut content by u s i n g gut sediment weight and se p a r a t e l y determined t o t a l t r a c e metal c o n c e n t r a t i o n i n the sediments. 2. D i s s o l u t i o n of benthic algae A l g a l samples were cleaned with tap water and d i s t i l l e d water then oven d r i e d (70 °C). The dry m a t e r i a l was ground and weighed p o r t i o n s digested i n 50% H^Og f o l l o w e d by fuming n i t r i c a c i d . Samples were f i l t e r e d to remove any r e s i d u a l sediment and the f i l t r a t e d i l u t e d to 25 ml f o r t r a c e metal a n a l y s i s . D. Atomic A b s o r p t i o n Spectrophotometry A J a r r e l l - Ash Model 810 double channel atomic a b s o r p t i o n spectrophotometer was used to determine Cu, Fe, Mn, Pb and Zn i n the sediment e x t r a c t s , MIBK e x t r a c t s of 85 water samples, and i n the d i g e s t e d benthic organisms and a l g a e . C a l i b r a t i o n curves were prepared with d i l u t e d F i s h e r Standard AA S o l u t i o n s . Background c o r r e c t i o n s could be c o n v e n i e n t l y made by u s i n g both channels and s u b t r a c t i o n made by the instrument. The a n a l y t i c a l s e t t i n g s f o r each element are summarized i n Table V I I I . E. Other A n a l y t i c a l Techniques 1. Color True c o l o r i n water was measured with the F i s h e r S c i e n t i f i c H e l l i g e Aqua T e s t e r on f i l t e r e d samples. H i g h l y c o l o r e d samples were d i l u t e d to w i t h i n the range of the instrument (0 - 100 mg/l P t . ) . 2. T u r b i d i t y T u r b i d i t y measurements were made on v i g o r o u s l y a g i t a t e d water samples with a Hach Turbidimeter (Model 2100A). The instrument was c a l i b r a t e d with Nephlene standards p r o v i d e d with the instrument. R e s u l t s are expressed i n NTU (Nephlometric T u r b i d i t y U n i t s ) or as e q u i v a l e n t JTU (Jackson T u r b i d i t y U n i t s ) . 3^ pH A F i s h e r S c i e n t i f i c pH meter (Model 320) s t a n d a r d i z e d with b u f f e r s of pH 4, 7 and 10 was used to measure pH. 4. Residue Appropriate volumes of f i l t e r e d and u n f i l t e r e d 86 Table VIII : An a l y t i c a l Settings for Atomic Absorption Spectrophotometry 1 Element Absorbing Temp. S l i t Flame Wavelength Current Width Stoichiometry (A) W ) Cu 3247 7 5 Very s l i g h t l y reducing Fe 2483 8 3 Lean Mn 2795 2 2833/2170 10 4 Very s l i g h t l y reducing Pb 5 4 S l i g h t l y reducing Zn 2138 7.5 3 Lean 1. 2. used air/acetylene as oxidant/fuel mixture. 2833 A for samples high in dissolved s o l i d s . 87 water were d r i e d o vernight a t 103 °C i n preweighed aluminum d i s h e s . On c o o l i n g i n a d e s s i c a t o r , dishes were reweighed to determine t o t a l and d i s s o l v e d s o l i d s . 5. D i s s o l v e d carbon T o t a l carbon and i n o r g a n i c carbon were measured on f i l t e r e d samples with a Beckman T o t a l Carbon A n a l y z e r (Model 915). Organic carbon was determined by d i f f e r e n c e . Samples c o n t a i n i n g high l e v e l s of i n o r g a n i c carbon r e l a t i v e to o r g a n i c carbon were a c i d i f i e d with HC1 and purged b e f o r e measuring the organic carbon on the t o t a l carbon channel. 6. Hardness, calcium, a l k a l i n i t y and a c i d i t y These water q u a l i t y parameters were measured by standard techniques o u t l i n e d i n Standard Methods (APHA,AWWA and WPCF, 1975). The EDTA t i t r i m e t r i c method was used f o r hardness and calcium measurements. A c i d i t y samples were t i t r a t e d w i t h 0.1N NaOH to pH 8.3 . 7. N i t r a t e , c h l o r i d e and sulphate - These anions were a l s o q u a n t i t a t e d by Standard Methods techniques (APHA, AWWA and WPCF, 1975). N i t r a t e n i t r o g e n was measured by the UV ab s o r p t i o n techniques u s i n g a Pye Unicam SP8-100UV spectrophotometer. C h l o r i d e was t i t r a t e d u s i n g the mercuric n i t r a t e method and sulphate was determined by t u r b i d i m e t r y . 8. C o n d u c t i v i t y and s a l i n i t y A Radiometer C o n d u c t i v i t y Meter (Model COM3) 88 was used to measure c o n d u c t i v i t i e s of water samples. Water samples and 0.0100N KC1 s o l u t i o n were allowed to come to room temperature and then temperature and s p e c i f i c c o n d u c t i v i t y were measured. Knowing the s p e c i f i c conductance of 0.0100N KC1 as a f u n c t i o n of temperature allowed sample c o n d u c t i v i t i e s to be c o r r e c t e d to 25 ° C S a l i n i t y was determined from c h l o r i d e measurement by the f o l l o w i n g r e l a t i o n s h i p . S a l i n i t y ( °/oo ) = (1.80655) . (CI" g/1) 9. Weight l o s s on i g n i t i o n Weighed sediment samples d r i e d at 103 °C were p l a c e d i n preweighed c r u c i b l e s and combusted i n a muffle furnace at 600 °C f o r 3 hours. Weight l o s s r e p r e s e n t e d the o r g a n i c matter content of the sediment. 10. P a r t i c l e s i z e a n a l y s i s Sediment samples were d r i e d at 150 °C and d i s a g g r e g a t e d i n a l a r g e mortar. F i f t y to one hundred grams of disaggregated sediment were separated by shaking f o r 4 minutes on a nest of Standard Sieves made up of No. 18, 35, 60 and 230 which have mesh s i z e s of 1, 0.5, 0.25 and 0.063 mm r e s p e c t i v e l y . The f i v e s i z e f r a c t i o n s were l a b e l l e d from coarse to f i n e as (a) very coarse sand, (b) coarse sand, (c) medium sand, (d) f i n e and very f i n e sand, (e) s i l t and c l a y . 89 Chapter 3 RESULTS I. TRACE METAL EXCHANGE BETWEEN SEDIMENTS AND WATER A. C h a r a c t e r i s t i c s of the Sediments 1. Sediment t r a c e metal geochemistry The geochemical d i s t r i b u t i o n of the t r a c e metals, Cu, Fe, Mn, Pb and Zn i n the sediments used i n the column and e l u t r i a t e sediment-water exchange s t u d i e s i s presented i n Tables IX and X. The sediment d e s c r i b e d i n Table IX was c o l l e c t e d on Dec. 23, 1977 and used i n the oxic"'", anoxic, s a l i n i t y , and low organic - pH column s t u d i e s . The sediment d e s c r i b e d i n Table X was c o l l e c t e d on A p r i l 19, 1978 and was used f o r the high organic - pH column s t u d i e s and the e l u t r i a t e t e s t s . During the p e r i o d between c o l l e c t i o n of the two sediment samples there was an i n c r e a s e i n the t o t a l t r a c e metal l e v e l s i n sediments from both s t a t i o n s . The W i l l i n g d o n s t a t i o n showed the g r e a t e s t i n c r e a s e with the c o n c e n t r a t i o n s of t o t a l Cu, Pb and Zn i n c r e a s i n g by f a c t o r s of approximately 5, 7 and 2.5 r e s p e c t i v e l y . Sediment contamination d u r i n g t h i s p e r i o d r e s u l t e d i n a l a r g e i n c r e a s e i n most t r a c e metals 1. Terms 'o x i c ' and 'anoxic', when used to express e x p e r i -mental c o n d i t i o n s of sediment-water exchange s t u d i e s of t h i s t h e s i s , s i g n i f y : o x i c-continuous d i s p e r s i o n of compressed a i r , anoxic-continuous purging with oxygen-f r e e n i t r o g e n (see chapter 2). Table IX : Trace Metal D i s t r i b u t i o n i n Sediments from the Brunette Basin Used i n Sediment-Water Exchange Studies (December 23. 1977) 1. Trace Metal Station Sediment Geochemical Fract i o n IW EP ERP OSP EAEP Residue Sum Total Copper Gilmore 0. 02 0. ,08 2.98 47.0 9.52 9.08 68.7 66.1 Willingdon 0. 13 0. ,11 2.82 57.8 19.4 7.05 87.8 71.4 Iron Gilmore 0. 16 1, ,90 592 133 3460 15200 19400 19400 Willingdon 2. 21 3. ,81 777 1180 9280 20600 31800 31400 Lead Gilmore 0. 04 3. .81 35.2 62.1 35.0 37.8 174 171 Willingdon 0. 12 1. ,08 5.89 80.0 25.3 25.0 137 138 Manganese Gilmore 0. 58 31.1 41.9 6.74 34.3 432 547 441 Willingdon 6. 90 18.4 30.6 24.6 89.6 443 613 560 Zinc Gilmore 0. 38 1.61 23.2 27.4 21.8 34.8 109 101 Willingdon 0. 35 1.42 27.0 62.7 26.8 33.1 151 181 1. A l l values are in ppm ( jug/g) on oven dry (103°C) basis. Sediment used in oxic, anoxic, s a l i n i t y and low organic-pH column studies. 2. IW = i n t e r s t i t i a l water, EP = exchangeable phase, ERP » e a s i l y reducible phase , OSP = organic and sulphur bound phase , EAEP = e a s i l y acid extractable phase. Total determined independently. Weight loss on i g n i t i o n : Gilmore = 2.4%, Willingdon = 9.97% vO O Table X : Trace Metal D i s t r i b u t i o n i n Sediments from the Brunette Basin Used i n Sediment-Water Exchange Studies ( A p r i l 19.1978) 1. Trace Metal Station IW EP Sediment ERP 2 : Geochemical Fraction OSP EAEP Residue Sum T o t a l Copper Gilmore 0.01 0.13 17.2 67.8 11.4 11.8 108 125 Willingdon 0.06 0.13 28.9 208 32.8 12.8 283 328 Iron Gilmore 0.22 232 1520 443 3270 15700 21200 22600 Willingdon 42.6 66.6 2180 789 4870 19300 27200 26100 Lead Gilmore 0.04 4.8 120 56.4 24.7 26.2 232 253 Willingdon 0.09 32.3 555 304 96.3 44.5 1032 980 Manganese Gilmore 1.35 55.6 44.3 10.6 35.5 353 502 549 Willingdon 7.05 60.8 56.1 17.7 45.7 398 586 525 Zinc Gilmore 0.16 5.8 61.5 36.6 17.9 38.0 161 162 Willingdon 0.35 30.0 216 110 34.9 26.8 418 450 1. A l l values column and are in ppm ( jug/g) e l u t r i a t e studies. on oven dry (103 °C) basis. Sediment used for high organic--pH 2. IW = i n t e r s t i t i a l water, EP = exchangeable phase, ERP - e a s i l y reducible phase, OSP - organic and sulphur bound phase, EAEP = eas i l y acid extractable phase. T o t a l determined independently. Weight loss on i g n i t i o n : Gilmore = 2.67. , Willingdon = 6.76% 92 i n the exchangeable and e a s i l y r e d u c i b l e phases. There was a l s o a 30% decrease (9.97 - 6.67$ change) i n the o r g a n i c content of the W i l l i n g d o n sediment. 2. Sediment p a r t i c l e s i z e d i s t r i b u t i o n P a r t i c l e s i z e d i s t r i b u t i o n of sediments obtained from W i l l i n g d o n Avenue and Gilmore Avenue s t a t i o n s i n the S t i l l Creek area of the Brunette Basin i s presented i n Table XI. T h i s p a r t i c l e s i z e a n a l y s i s i s from a f i e l d survey of sediments c a r r i e d out e a r l i e r i n four d i f f e r e n t areas of the Lower Mainland of B r i t i s h Columbia(Bindra and H a l l , 1 9 7 7 ) . The a n a l y s e s i n d i c a t e t h a t h i g h o r g a n i c W i l l i n g d o n sediment i s f i n e and c o n s i s t s of f i n e to very f i n e sand (53%) and s i l t and c l a y (38.2$). In c o n t r a s t , Gilmore low organic sediment i s mostly (>87$) medium to coarse sand. B. D i s s o l v e d Trace Metal Exchange i n S t a t i c Columns  at D i f f e r e n t Oxygen and S a l i n i t y C o n d i t i o n s The c o n c e n t r a t i o n s of d i s s o l v e d t r a c e metals, Cu, Fe, Pb and Zn i n the columns c o n t a i n i n g the two sediments and s u b j e c t e d to d i f f e r e n t oxygen and s a l i n i t y c o n d i t i o n s are p r e s e n t e d i n F i g u r e s 4, 5, 6 and 7. 1. Copper (Cu) The i n i t i a l c o n c e n t r a t i o n s of d i s s o l v e d Cu very r a p i d l y dropped to values of l e s s than 10 M-g/1 f o r both sediments under both o x i c and anoxic c o n d i t i o n s ( F i g u r e 4). D i s s o l v e d Cu i n the low o r g a n i c sediment columns reached an 93 Table XI : P a r t i c l e Size D i s t r i b u t i o n of Sediments at Two Stations on S t i l l Creek (Brunette Basin) Sampled for Trace Metal Exchange Studies (Bindra and H a l l , 1977) Station No. Description P a r t i c l e Size Analysis (/<, 11 12 S t i l l Creek at Willingdon Ave. S t i l l Creek at Gilmore Ave. 0.2 1.2 7.4 53.0 38.2 2.0 33.5 53.7 8.0 2.9 1 = very coarse sand (2-1 :mm), 2 = coarse sand (1-0.5 mm), 3 = medium size sand (0.5-0.25 mm), 4 = fine and very fine sand (0.25-0.063 mm), 5 = s i l t and clay ( ^ 0.063 mm). Figure 4. Dissolved Copper i n Microcosms Under Oxic and Anoxic Conditions at Different S a l i n i t i e s . 95 e q u i l i b r i u m c o n c e n t r a t i o n which was twice as h i g h as values f o r the high o r g a n i c sediment even though the high organic sediment contained a s l i g h t l y higher t o t a l Cu c o n c e n t r a t i o n . A f t e r the f i r s t s a l i n i t y change, the d i s s o l v e d Cu i n the anoxic column dropped to l e s s than the d e t e c t i o n l e v e l and remained low throughout subsequent s a l i n i t y i n c r e a s e s . In the a e r o b i c system ( F i g u r e 4), d i s s o l v e d Cu i n c r e a s e d to approximately 10 Ug/1 i n the h i g h organic sediment d u r i n g the f i r s t s a l i n i t y i n c r e a s e (I4 .5 °/oo) but decreased to 1-2 XXg/1 upon subsequent s a l i n i t y changes. In the low organic o x i c column the d i s s o l v e d Cu d i d not i n c r e a s e to as h i g h of c o n c e n t r a t i o n as i n the h i g h o r g a n i c column d u r i n g i n i t i a l s a l i n i t y a d d i t i o n s but d u r i n g the f i n a l s a l i n i t y change i t e s t a b l i s h e d a higher e q u i l i b r i u m c o n c e n t r a t i o n of 5 Ag/1. 2. Iron (Fe) D i s s o l v e d Fe i n the o x i c system (Figure 5) reached an e q u i l i b r i u m c o n c e n t r a t i o n of approximately 70 Mg/l a f t e r 15 days. S a l i n i t y adjustments i n the o x i c columns caused d i s s o l v e d Fe c o n c e n t r a t i o n s to f a l l to l e s s than 10 M.g/1 f o r both high and low organic sediments. Under anoxic c o n d i t i o n s (Figure 5) the column c o n t a i n i n g the low organic sediment with the lower t o t a l Fe l e v e l (19,4-00 ppm) r e l e a s e d Fe i n t o s o l u t i o n r e a c h i n g values over 2 mg/l. A f t e r the f i r s t and second s a l i n i t y adjustments there was an i n i t i a l drop i n d i s s o l v e d Fe l e v e l s f o l l o w e d by a l a r g e r e l e a s e of Fe 96 Figure 5. Dissolved Iron i n Microcosms Under Oxic and Anoxic Conditions at Different S a l i n i t i e s . Time (days) 97 i n t o s o l u t i o n . When the s a l i n i t y was a d j u s t e d to f u l l seawater, Fe values dropped to the d e t e c t i o n l e v e l of 1 /eg/1 i n t h i s column. In the high o r g a n i c sediment system w i t h h i g h e r sediment Fe l e v e l s (31,400 ppm), the d i s s o l v e d Fe l e v e l s dropped to the d e t e c t i o n l e v e l a f t e r the f i r s t s a l i n i t y adjustment and remained low. 3. Lead (Pb) In the oxic columns, d i s s o l v e d Pb i n both the h i g h and low organic sediment systems showed a s i m i l a r p a t t e r n ( F i g u r e 6 ) . During the i n i t i a l e q u i l i b r i u m stage with freshwater there was an e q u i l i b r i u m l e v e l between 5 and 10 Mg/1 Pb. The f i r s t s a l i n i t y change removed the metal from s o l u t i o n but there was some r e l e a s e a f t e r 5 days from both sediments which s t a b i l i z e d a t 7 Jig/1. D i s s o l v e d Pb was removed i n the oxic systems a f t e r the second s a l i n i t y adjustment. In the anoxic system there was a gradual decrease i n d i s s o l v e d Pb i n freshwater ( F i g u r e 6 ) . Lead decreased to the d e t e c t i o n l e v e l a f t e r the f i r s t s a l i n i t y adjustment i n the anoxic system. 4. Zinc (Zn) Under oxic c o n d i t i o n s ( F i g u r e 7) there was an i n i t i a l removal of d i s s o l v e d Zn r e a c h i n g an e q u i l i b r i u m c o n c e n t r a t i o n between 3 and 5 Mg/1 a f t e r 12 days. The f i r s t s a l i n i t y i n c r e a s e caused r e l e a s e of Zn i n t o s o l u t i o n w i t h the low organic sediment system r e a c h i n g an e q u i l i b r i u m c o n c e n t r a t i o n of approximately 25/£g/l. The second s a l i n i t y Figure 6 . Dissolved Lead i n Microcosms Under Oxic and Anoxic Conditions at Different S a l i n i t i e s . S = 24.5 %o Oxic Conditions Low Organic Sediment High Organic Sediment 60 70 80 S * 29.4 %« 90 100 110 120 130 140 ISO 160 Anoxic Conditions S = 26.8 %o 60 70 80 90 100 110 120 130 140 150 160 Time (days) 1 — L 170 180 170 180 oo Figure 7. Dissolved Zinc i n Microcosms Under Oxic and Anoxic Conditions at Different S a l i n i t i e s . Time (doys) 100 change i n i t i a t e d a slow removal of Zn from s o l u t i o n with one spor a d i c i n c r e a s e a t t r i b u t a b l e to a n a l y t i c a l contamination. A f t e r the f i n a l s a l i n i t y change, there was a gradual r e l e a s e of Zn from both sediments which was s t i l l o c c u r r i n g a f t e r two months. In the anoxic system (Figure 7), Zn was g r a d u a l l y removed from s o l u t i o n over the 30 day freshwater p e r i o d . A f t e r the f i r s t s a l i n i t y change, Zn was r a p i d l y removed from s o l u t i o n and remained low throughout subsequent s a l i n i t y changes with some s p o r a d i c i n c r e a s e s a t t r i b u t e d to resuspension of p a r t i c l e s or a n a l y t i c a l e r r o r . 5. Water q u a l i t y c o n d i t i o n s i n sediment microcosms The water q u a l i t y c o n d i t i o n s i n the columns subjected to d i f f e r e n t oxygen c o n d i t i o n s and a s e r i e s of s a l i n i t y changes are presented i n Appendix A (Tables A l to A4) Both i n i t i a l and f i n a l water q u a l i t y c o n d i t i o n s are presented f o r each s a l i n i t y change. A f t e r the f i r s t seawater a d d i t i o n , the system was dominated by the q u a l i t y of the seawater which b u f f e r s any minor changes t h a t take plac e due to the exchange r e a c t i o n s with the sediment. There was a general i n c r e a s e i n the pH of a l l columns between each s a l i n i t y change which could be a t t r i b u t a b l e to purging of carbon d i o x i d e from the water. A l k a l i n i t y values showed a general decrease between each i n c r e m e n t a l s a l i n i t y change. However, under anoxic c o n d i t i o n s i n freshwater, there was an i n c r e a s e i n a l k a l i n i t y p r obably r e f l e c t i n g d i s s o l u t i o n of carbonates under the low redox c o n d i t i o n s . An i n c r e a s e i n d i s s o l v e d 101 s o l i d s (30 - 4 5 mg/1) i n the o x i c systems occurred f o r both sediments d u r i n g the freshwater i n c u b a t i o n p e r i o d . T h i s i n c r e a s e c o u l d not be accounted f o r by the water q u a l i t y parameters measured. Changes i n d i s s o l v e d s o l i d s i n the anoxic systems under freshwater c o n d i t i o n s were s m a l l e r and showed no c o n s i s t e n t p a t t e r n . C. E f f e c t of pH on D i s s o l v e d Trace Metal Exchange The e f f e c t of three pH's ( 5 , 7 and 10) on the exchange of d i s s o l v e d Cu, Fe, Pb and Zn i n o x i c columns c o n t a i n i n g both high and low organic sediments i s presented i n F i g u r e s 8, 9, 10 and 1 1 . 1. Copper (Cu) D i s s o l v e d Cu c o n c e n t r a t i o n s were much h i g h e r at low and h i g h pH's than at the ambient pH of 7 ( F i g u r e 8 ) . In the low organic sediment e q u i l i b r i u m c o n c e n t r a t i o n s of 40 and 80 Ug/l occurred i n the pH 5 and 10 systems r e s p e c t i v e l y . For the high organic sediment at low pH there was a r a p i d r e l e a s e of Cu with a g r a d u a l removal over a month p e r i o d . At high pH there was gradual r e l e a s e of Cu from t h i s sediment over the e n t i r e study p e r i o d . F i n a l c o n c e n t r a t i o n s of Cu i n the high organic sediments were approximately twice the l e v e l f o r the low o r g a n i c sediments i n the pH 5 and 10 systems. 2. Iron (Fe) D i s s o l v e d Fe c o n c e n t r a t i o n s were high e r i n the 102 ure 8. E f f e c t of pH on D i s s o l v e d Copper Exchange i n Microcosms (Oxic C o n d i t i o n s , Salinity«<l °/oo) 103 F i g u r e 9. E f f e c t of pH on D i s s o l v e d Iron Exchange i n Microcosms (Oxic C o n d i t i o n s , S a l i n i t y - < 1 °/oo). 16000 11500 11200°^. 19800 8000 6000 800 600 400 200 O — — O Low Organic Sediment • - • High Organic Sediment 10 15 20 25 pH = 10 30 _] 35 Time (days) 104 F i g u r e 10. E f f e c t of pH on D i s s o l v e d Lead Exchange i n Microcosms (Oxic C o n d i t i o n s , S a l i n i t y <1 °/oo). iooor 800h 6 0 0 400H 2 0 0 Low Organic Sediment High Organic Sediment pH=5 3s 10 15 20 25 " — — — h - m — — — 3 0 35 pH = 7 « 5 0 0 r 4 0 0 h 10 15 20 25 30 35 3 0 0 r - pH = 10 2 0 0 \ 100 JL 10 15 20 25 Time (days) 30 35 105 F i g u r e 11. E f f e c t of pH on D i s s o l v e d Zinc Exchange i n Microcosms (Oxic C o n d i t i o n s , S a l i n i t y K°/o.o) 3000 2500 2000 1500 „ 1000 3 s S. 500 Low Organic Sediment 1 High Organic Sediment pH = 5 .* ***** 10 15 20 25 Time (days) 106 low and h i g h pH systems when compared to the ambient (pH 7) system except d u r i n g the i n i t i a l i n c u b a t i o n p e r i o d ( F i g u r e 9 ) . The r e l e a s e of Fe i n the high pH system was very s i m i l a r to t h a t of Cu wit h the hig h organic sediment system r e a c h i n g twice the c o n c e n t r a t i o n l e v e l found i n the low organic sediment. In the pH 5 systejn (Figure 9) there was a r a p i d r e l e a s e of Fe from the h i g h organic sediment f o l l o w e d by a gradual decrease and f i n a l i n c r e a s e when the g r a d u a l l y r i s i n g pH was a d j u s t e d back to 5. The low organic, low pH system d i d not r e l e a s e Fe u n t i l a f t e r one week then c o n c e n t r a t i o n s i n c r e a s e d to l e v e l s found i n the high organic system ( 1 1 . 5 mg/l). 3. Lead (Pb) Release of Pb from the sediments showed a response s i m i l a r to Cu. The high and low pH systems showed a g r e a t e r r e l e a s e of Pb than the ambient pH 7 system (Figure 1 0 ) . The low o r g a n i c sediment system achieved a r a p i d e q u i l i b r i u m w i t h the v a l u e s of 50 and 200 /tg/1 f o r the pH 10 and 5 treatments. For the h i g h organic sediment at pH 10 there was a grad u a l r e l e a s e of Pb over the month i n c u b a t i o n p e r i o d . 4 . Zinc (Zn) S i m i l a r to the other t r a c e metals, there was g r e a t e r r e l e a s e from the high and low pH than a t ambient pH with a g r e a t e r r e l e a s e from the high organic sediment ( F i g u r e 11 ) . 107 5. Water q u a l i t y c o n d i t i o n s i n the v a r i a b l e pH  sediment systems The t h i r t e e n water q u a l i t y parameters measured i n each pH system f o r the two d i f f e r e n t sediments are summarized i n Appendix A (Tables A5 and A6). The water q u a l i t y measurements were made at the beginning and end of the experiment. In the pH 5 system the t o t a l o r g a n i c carbon content, a c i d i t y , and a l k a l i n i t y were hig h due to the a c e t a t e used to b u f f e r the pH at 5. In the high pH system the i n o r g a n i c carbon and a l k a l i n i t y values were hig h due to bicarbonate-carbonate b u f f e r used to keep the pH at 10. T h i s h i g h pH r e s u l t e d i n d i s s o l u t i o n of organic matter from the sediment as i n d i c a t e d by the great i n c r e a s e i n true c o l o r and t o t a l organic carbon. These organic compounds are probably 'humic-like' substances s i n c e they are very c o l o r e d and d i s s o l v e at high pH. In the low pH systems a gradual pH i n c r e a s e was t a k i n g place but d u r i n g the f i r s t experiment wi t h low organic sediment the i n c r e a s e was delayed and slower. The i n c r e a s e was probably a t t r i b u t a b l e to m i c r o b i a l breakdown of the acetate b u f f e r and the d e l a y and slower a c t i o n f o r the f i r s t run was due to l a g i n development of a s u f f i c i e n t a c t i v e p o p u l a t i o n of acetate consuming b a c t e r i a . A f t e r 27 days, the second, low pH high o r g a n i c sediment system was a d j u s t e d back to i n i t i a l pH l e v e l of 5. The h i g h n i t r a t e c o n c e n t r a t i o n was most l i k e l y due to i n t e r f e r e n c e of c o l o r i n the u l t r a v i o l e t a b s o r p t i o n technique used to 108 measure t h i s i o n . • D. E f f e c t of pH on P a r t i c u l a t e and D i s s o l v e d Trace  Metal Exchange In a d d i t i o n to monitoring the d i s s o l v e d t r a c e metals i n the pH microcosms, samples were p e r i o d i c a l l y a n a lyzed f o r p a r t i c u l a t e t r a c e metals. The d i s s o l v e d and p a r t i c u l a t e t r a c e metals i n the columns at pH 5, 7 and 10 c o n t a i n i n g high and low organic matter are presented i n Appendix B (Tables B l , B2 and B3). The r e s u l t s f o r the pH 5 column are a l s o presented i n Fi g u r e 12 to show the e f f e c t of upward d r i f t i n g pH on the t u r b i d i t y and p a r t i c u l a t e and d i s s o l v e d t r a c e metal exchange. The pH 7 and 10 columns had no s i g n i f i c a n t d r i f t i n pH over the d u r a t i o n of these experiments. 1. pH 5 In the low organic column, pH g r a d u a l l y i n c r e a s e d from 4.93 5.50 (Figure 12). T u r b i d i t y dropped q u i c k l y a f t e r the f i r s t day and began to in c r e a s e s l o w l y a f t e r day 26 when pH i n c r e a s e d beyond 5.10 . Beyond pH 5.10 the d i s s o l v e d Cu and Pb began to come out of s o l u t i o n . I r o n came out of s o l u t i o n above pH 5.3 whereas Zn was s t i l l d i s s o l v i n g at the f i n a l pH of 5-5 . P a r t i c u l a t e Cu, Fe, Pb and Zn were hig h a t the beginning of the experiment, c o i n c i d e n t with high t u r b i d i t y ( F i g u r e 12). P a r t i c u l a t e a s s o c i a t e d metals dropped to low 109 F i g u r e 12. D i s s o l v e d and Suspended P a r t i c u l a t e Trace Metals i n a Microcosm at pH 5 (Oxic, S <1 °/oo). HIGH ORGANIC SEDIMENT LOW ORGANIC SEDIMENT 1000 > eoo • * 600 • -1 _l 400 I - \ •o o J 200 X • \ o o Dissolved e » Particulate 110 v a l u e s a t the second day and remained low except p a r t i c u l a t e Fe and Pb which i n c r e a s e d a f t e r 30 days when pH went above 5.3 , a g a i n c o i n c i d e n t with a s l i g h t i n c r e a s e i n t u r b i d i t y . In the high organic columns a t pH 5, there was a much f a s t e r i n c r e a s e i n pH which was r e a d j u s t e d to pH 4.9 a f t e r 26 days (Figure 12). With the exce p t i o n of Zn, the d i s s o l v e d t r a c e metals g r a d u a l l y decreased u n t i l the pH was r e a d j u s t e d which r e l e a s e d more Fe and Pb i n t o s o l u t i o n . D i s s o l v e d Zn i n c r e a s e d c o n t i n u a l l y over the t e s t p e r i o d , as was the case with low organic sediments. P a r t i c u l a t e Fe, Pb and Zn f o l l o w e d t u r b i d i t y very c l o s e l y w i t h h i g h i n i t i a l values t h a t dropped very r a p i d l y , then s l o w l y i n c r e a s e d as pH i n c r e a s e d and dropped when the pH was r e a d j u s t e d back to 4.9 . 2. pH 7 In both sediments, there was an i n i t i a l r e l e a s e of d i s s o l v e d metals and p a r t i c u l a t e a s s o c i a t e d metals were h i g h (Table B2). Both d i s s o l v e d and p a r t i c u l a t e metals g r a d u a l l y decreased throughout the e q u i l i b r a t i o n p e r i o d . 3. pH 10 In both columns (Table B3) there was an i n i t i a l s u s pension of p a r t i c u l a t e a s s o c i a t e d t r a c e metals which g r a d u a l l y decreased as the columns came to e q u i l i b r i u m . In the h i g h o r g a n i c system the c o n c e n t r a t i o n s of d i s s o l v e d metals i n c r e a s e d towards the end of the experiment whereas i n the low org a n i c columns, d i s s o l v e d metals reached an 111. e q u i l i b r i u m c o n c e n t r a t i o n a f t e r approximately a week to 10 days. However, d u r i n g the f i f t h week, d i s s o l v e d Fe c o n c e n t r a t i o n s showed some i n c r e a s e i n the low organic system. 4. Comparison of d i f f e r e n t pH columns The f i n a l c o n c e n t r a t i o n s of d i s s o l v e d and p a r t i c u l a t e a s s o c i a t e d t r a c e metals at the d i f f e r e n t pH's a f t e r 34 days of e q u i l i b r a t i o n are summarized i n Figure 13. I t i s q u i t e e v i d e n t t h a t both the low and h i g h pH cause a grea t e r r e l e a s e of t r a c e metals from sediment than occurs at n e u t r a l pH. There are u s u a l l y higher t r a c e metal concentrations i n the d i s s o l v e d phase at these h i g h and low pH's. With the e x c e p t i o n of Fe, there was a much grea t e r r e l e a s e of t r a c e metals from the high organic sediment which had a higher t o t a l t r a c e metal c o n c e n t r a t i o n and higher l e v e l s i n the exchangeable and e a s i l y r e d u c i b l e geochemical phases. E. D i s s o l v e d Trace Metal Exchange i n A g i t a t e d Water- Sediment Systems ( E l u t r i a t e Test) 1. E f f e c t s of oxygen and s a l i n i t y The r e l e a s e and uptake of d i s s o l v e d Cu, Fe, Pb, Mn and Zn i n . a g i t a t e d systems under d i f f e r e n t oxygen (oxic and anox-i c , see f o o t n o t e P.89) a n d s a l i n i t y c o n d i t i o n s are summarized i n F i g u r e I4. Both the high and low organic sediments were e q u i l i b r a t e d under a l l c o n d i t i o n s . A g r e a t e r number of lower s a l i n i t y v a l u e s were used i n the e l u t r i a t e procedure s i n c e the column s t u d i e s i n d i c a t e d t h a t the i n t e r e s t i n g exchanges were t a k i n g p l a c e between 0 - 1 0 °/oo s a l i n i t y . The n e g a t i v e F i g u r e 13. F i n a l Concentrations of D i s s o l v e d and P a r t i c u l a t e Trace Metals i n Microcosms at Three D i f f e r e n t pH's (Oxic, S< 1 °/oo). 150 100 HIGH ORGANIC SEDIMENT Cu ^ 5 0 10 n 220 3 0 0 0 h 2000r-1000 8 0 0 r • Dissolved • Particulate o a 150 100 LOW ORGANIC SEDIMENT 5 0 Cu 3 0 0 0 10 J T b L 2000h lOOOh Fe 14000 8 0 0 6 0 0 4 0 0 2 0 0 10 Pb 150 100 5 0 Z n 460 10 I 113 F i g u r e I 4 . Exchange of D i s s o l v e d Trace Metals i n the E l u t r i a t e Test Under Oxic and Anoxic C o n d i t i o n s and D i f f e r e n t S a l i n i t i e s . OXIC 4 28 ANOXIC 16 20 24 28 120 80 40 0 40 8 12 16 20 24 28 0> o a> o T OJ JC o "o o o 100 801-1 601 Sf+MoH 20 0 (-)20l--r-Q-r-T 1 8 12 16 20 24 28 2000 i n 1000 c 0 o> (+) 0 5 0 (-) _1_ 8 12 16 20 24 28 100 80 60 40 20k o p - i 6 " 20' 2000 1000 12 16 20 24 28 8 12 16 20 24 28 3000r-2000 IOOO: (+) 0 (-) 1 4 8 12 16 20 24 28 3000 2000 1000 4 8 12 16 20 24 28 Salinity (%») • • high organic O — O low organic 114 (-) values on F i g u r e I4 r e f e r to uptake of d i s s o l v e d element by the sediment while p o s i t i v e (+) values i n d i c a t e r e l e a s e from the sediment. Copper was removed from s o l u t i o n by both the h i g h and low o r g a n i c sediments under both oxic and anoxic c o n d i t i o n s . The amount of Cu taken up by the sediment decreased as the s a l i n i t y i n c r e a s e d because the seawater had a lower Cu c o n c e n t r a t i o n and e f f e c t i v e l y d i l u t e d the Cu i n the f r e s h w a t e r . However, expressed on a percent removal b a s i s the e f f e c t of changing s a l i n i t y on Cu removal was n e g l i g i b l e . Under o x i c c o n d i t i o n s there was some r e l e a s e of Fe by the low organic sediment at low s a l i n i t i e s (O-4 ° / 0 0 ) whereas there was no Fe exchange from the high o r g a n i c sediment. Under anoxic c o n d i t i o n s Fe was r e l e a s e d from both the high and low organic sediments over a wide s a l i n i t y range. For the low organic sediment maximum r e l e a s e occurred at low s a l i n i t i e s . Lead was r e l e a s e d from the high organic sediment i n freshwater under both o x i c and anoxic c o n d i t i o n s . Increases i n s a l i n i t y caused a r a p i d removal of Pb from s o l u t i o n with values d e c r e a s i n g to the d e t e c t i o n l e v e l at 4 °/oo s a l i n i t y f o r both sediments under high and low redox c o n d i t i o n s . There was a r e l e a s e of Mn by both sediments under o x i c and anoxic c o n d i t i o n s . Release i n c r e a s e d with i n c r e a s i n g s a l i n i t y r e a c h i n g a p l a t e a u at 4 °/oo s a l i n i t y w ith a Mn c o n c e n t r a t i o n between 1500 - 2000 M.g/1. 115 C o n c e n t r a t i o n l e v e l s were s l i g h t l y higher f o r the low organic sediment even though the t o t a l Mn and geochemical d i s t r i b u t i o n i n the two sediments was s i m i l a r . Zinc was taken out of s o l u t i o n i n freshwater f o r both sediments under o x i c and anoxic c o n d i t i o n s . A s l i g h t i n c r e a s e i n s a l i n i t y (1 °/oo) caused Zn to be r e l e a s e d by the low organic sediment. As s a l i n i t y i n c r e a s e d i n the low organic sediment system, Zn was removed from s o l u t i o n . In the h i g h organic sediment t h e r e was a g r a d u a l i n c r e a s e i n the r e l e a s e of Zn as s a l i n i t y i n c r e a s e d both under o x i c and anoxic c o n d i t i o n s . 2. E f f e c t of pH The e f f e c t s of pH on the exchange of t r a c e metals i n sediments u s i n g the e l u t r i a t e t e s t are summarized i n F i g u r e 15. In g e n e r a l there was a g r e a t e r r e l e a s e of t r a c e metals at pH 5 and pH 10 than a t the n a t u r a l pH of 7. The e l u t r i a t e t e s t r e s u l t s compared f a v o r a b l y with the o b s e r v a t i o n s made with the s t a t i c columns. For Fe, Mn and Pb,.metal was r e l e a s e d i n t o s o l u t i o n f o r both the high and low o r g a n i c sediments a t a l l three pH's. The g r e a t e s t r e l e a s e occurred a t pH 5 f o r three metals. There was no c o n s i s t e n t trend f o r r e l e a s e of Fe, Mn and Pb from the high or low organic sediments i n s p i t e of the g r e a t e r c o n c e n t r a t i o n of most metals i n the high organic sediment. Both Cu and Zn were adsorbed to the sediments at F i g u r e 15. Exchange of D i s s o l v e d Trace Metals i n the E l u t r i a t e T e s t at D i f f e r e n t pH'.s (Oxic C o n d i t i o n s , S a l i n i t y <1 °/oo). Values along the v e r t i c a l axes are i n j«.g/l 30COr ^  F e 3000 r 5 M n 32707 • R§07 _ n B 2000- I 2000- I 1000- I | ~ f l 1000- I -LIrL 11 ill A JS. a- so I I201 1000 1000 300 200h lOOh lOOh High Organic Sediment | Low Organic Sediment Numbers above histogram indicate pH 117 pH 7. The r e l e a s e or uptake of Cu and Zn at pH 5 and 10 v a r i e d c o n s i d e r a b l y depending upon the character of the sediment. I I . TRACE METAL EXCHANGE BETWEEN SEDIMENTS AND INVERTEBRATES A. I n i t i a l Organism and Sediment Trace Metal L e v e l s The i n i t i a l c o n c e n t r a t i o n s of t o t a l t r a c e metals, Cu, Fe, Mn, Pb and Zn i n the organisms and sediments used i n the exchange experiments microcosms are presented i n Table X I I . The amphipods had very h i g h i n i t i a l l e v e l s of Cu and Pb r e f l e c t i n g p o l l u t e d c o n d i t i o n of the Squamish R i v e r e s t u a r y at the head of Howe Sound (Thompson, 1974-). S i m i l a r l y , o l i g o c h a e t e s c o l l e c t e d from a r e l a t i v e l y p o l l u t e d area (Ladner sidechannel) of the F r a s e r River ( H a l l , unpublished data) contained h i g h i n i t i a l c o n c e n t r a t i o n s of Pb and Zn. The opossum shrimp had the lowest l e v e l s of Fe, Pb and Zn. The lowest l e v e l s of Cu and Mn were observed i n chironomids and amphipods, r e s p e c t i v e l y . A l l t o t a l t r a c e metal l e v e l s were c o n s i d e r a b l y h i g h e r i n the W i l l i n g d o n Avenue high organic (approx. 7%) sediment than i n low o r g a n i c sediments (approx. 2.5%) c o l l e c t e d at Gilmore Avenue. A geochemical d i s t r i b u t i o n of these 5 metals i n sediments c o l l e c t e d from the same s t a t i o n s a few weeks e a r l i e r p r o v i d e s some in f o r m a t i o n on t h e i r p o t e n t i a l a v a i l a b i l i t y to benthic i n v e r t e b r a t e s (Table X). The high organic sediment contained much higher l e v e l s of t r a c e metals 118 Table X l l : T o t a l Trace Metal Concentrations i n Organisms and Sediments Used f o r Microcosms^". Sample Copper Iron Lead Manganese Zinc Comments AmDhipods 162 (Lab., UBC) Chironomids 23 (Ladner Sidechannel •near sewage lagoon) Oligochaetes 27 (Middle of Ladner sidechannel) Ooossum shrimp 27 (Lab. UBC) Gilmore sediment 129 W i l l i n g d o n sediment 356 Algae (Enteromorpha) 19 550 204 5320 35 7130 167 383 <8 18300 194 23500 1280 3380 . 7 23 83.1 Polluted 92 99 U 452 597 81 106 147 P o l l u t e d 6 4 . 9 108 526 Low organic matter (2.5?) High organic matter (6.8?) 32.5 1 . A l l values i n ppm (mg/kg) dry weight. 2 . Food substrate added to amphipod microcosms. 3. Trace Metal D i s t r i b u t i o n of Ladner Sidechannel Sediment from which Oligochaetes were c o l l e c t e d (Data from Bindra and H a l l , 1977) X r a c e Metal Concentration in Geochemical Fractions (ppm) A e t & 1 I W EP ERP OSP EAEP RESIDUE TOTAL (Independent Test) Copper <0.02 Iron 45 Lead <0.2 Hanganese 14 Zinc 0.02 0.6 "0.3 8.4 27 17 7 2070 685 10800 41900 *0.3 «= 3 6 7 23 28 8 4 2 178 432 0.3 5 9 33 68 49 43500 22 698 121 119 a s s o c i a t e d with o r g a n i c - s u l p h u r phase. A l s o , c o n s i d e r a b l y h i g h e r l e v e l s of Pb and Zn were a s s o c i a t e d with the exchangeable and e a s i l y r e d u c i b l e phases i n the hig h organic sediment. In both sediments, with the exception of Fe and Mn, only a s m a l l p o r t i o n of the t o t a l t r a c e metals was bound i n the r e s i d u a l phase. The low or g a n i c sediment (Gilmore) was very sandy with approximately 35$ of the m a t e r i a l l a r g e r than 0.5 mm and approximately 85$ l a r g e r than 0.25 mm while the hig h o r g a n i c sediment ( W i l l i n g d o n ) was much f i n e r with over 90$ of the m a t e r i a l i n the very f i n e sand (0.25 - 0.063 mm) and s i l t - c l a y ( < 0.063 mm) f r a c t i o n s . B. Accumulation or Loss of Trace Metals i n the Benthic I n v e r t e b r a t e s The changes i n co n c e n t r a t i o n s of t r a c e metals Cu, Fe, Pb, Mn and Zn i n the a q u a t i c organisms d u r i n g the exchange experiments are presented i n Appendix C (Table C l ) and F i g u r e 16. The opossum shrimp d i d not l i v e much beyond one week so t r a c e metal l e v e l s were only a v a i l a b l e f o r t h i s p e r i o d . Those i n the hig h organic sediment d i d not even s u r v i v e f o r one week. P o s s i b l y these organisms are more s u s c e p t i b l e to t r a c e metal p o l l u t i o n s i n c e they l i v e under a lower t r a c e metal s t r e s s as i n d i c a t e d by t h e i r i n i t i a l c o n c e n t r a t i o n s of Pb, Fe and Zn. In the low organic sediment, the c o n c e n t r a t i o n s of Cu, Fe, Pb and Mn i n the shrimp i n c r e a s e d by a f a c t o r of 3 to 4 during one week. 120 F i g u r e 16. Trace Metal L e v e l s i n Organisms Over Microcosm P e r i o d . JO ' 20 ' "30 ' «T 10 20 *• 30 1 40 10 20 30 ' «T Time (days) Amphipoda Chironomidae Oligochaeta range of r e p l i c a t e microcosm values 121 In amphipods, the l e v e l s of Fe and Mn i n c r e a s e d by a f a c t o r of U i n both sediment microcosms d u r i n g a f o u r week p e r i o d . The c o n c e n t r a t i o n s of Cu, Pb and Zn i n the amphipods d i d not show much change over the i n i t i a l l e v e l s . There does not appear to be much d i f f e r e n c e i n t r a c e metal exchange from the two d i f f e r e n t sediments with the p o s s i b l e e x c e p t i o n of Pb where organism l e v e l s decreased i n the low or g a n i c sediment while i n the high organic sediment the l e v e l s remained f a i r l y c onstant. The t r a c e metal c o n c e n t r a t i o n s i n the food s u b s t r a t e (Enteromorpha)(Table X I I ) , p r o v i d e d f o r the amphipods, was probably one of the f a c t o r s a f f e c t i n g t r a c e metal l e v e l s i n t h e i r t i s s u e s . The l e v e l s of Fe and Mn, which were the only two elements to show accumulation, were higher i n Enteromorpha than i n amphipods whereas l e v e l s of Cu, Pb and Zn, the elements t h a t d i d not accumulate i n the organisms examined, were lower i n Enteromorpha than i n the amphipods. The chironomids showed in c r e a s e s f o r a l l f i v e t r a c e metals i n the two sediments over the s i x week microcosm p e r i o d . There was no c o n s i s t e n t trend i n accumulation of t r a c e metals from the two d i f f e r e n t sediments. Both Cu and Mn had c o n s i s t e n t l y higher l e v e l s i n the organisms i n contact w i t h the low org a n i c sediments. Although there was c o n s i d e r a b l e v a r i a b i l i t y between Pb and Fe l e v e l s i n chironomids i n the two sediments, the f i n a l c o n c e n t r a t i o n s were twice as hi g h i n chironomids that were i n con t a c t with the h i g h o r g a n i c sediments. Zinc i s another metal f o r which the accumulation i n chironomids from the two sediments v a r i e d d u r i n g the p e r i o d of the experiment but u n l i k e Pb and Fe, the f i n a l c o n c e n t r a t i o n s of Zn i n the organisms c o l l e c t e d from the two microcosm sediments were s i m i l a r . In o l i g o c h a e t e s , the l e v e l s of a l l t r a c e metals dropped from i n i t i a l values d u r i n g the f i r s t week of the microcosm. T h i s was f o l l o w e d by a gen e r a l i n c r e a s e i n c o n c e n t r a t i o n s d u r i n g the second and t h i r d week of the microcosm with a f i n a l decrease at the t e r m i n a t i o n of the microcosm. Iron and Mn f o l l o w e d a s i m i l a r p a t t e r n i n o l i g o c h a e t e s . L e v e l s of both elements i n the o l i g o c h a e t e s i n the h i g h o r g a n i c sediment remained very low while there was a greater, attempt to re c o v e r to the i n i t i a l Fe and Mn l e v e l s i n the low org a n i c sediment. Lead c o n c e n t r a t i o n s i n o l i g o c h a e t e s i n the high organic sediment always remained above l e v e l s i n organisms present i n the low organic sediments although the f i n a l c o n c e n t r a t i o n was very c l o s e to the i n i t i a l l e v e l . The co n c e n t r a t i o n s of Cu and Zn i n the o l i g o c h a e t e s d i d not show any c o n s i s t e n t p a t t e r n t h a t c o u l d be a t t r i b u t e d to the sediment used i n the microcosm. C a l c u l a t i o n s of changes i n the c o n c e n t r a t i o n r a t i o s of metal i n organism / metal i n sediment, over the microcosm p e r i o d , help to normalize the v a r i a b i l i t y of the d i f f e r e n t i n i t i a l t r a c e metal l e v e l s i n the organism and pr o v i d e a good method to compare accumulation a b i l i t y among the d i f f e r e n t organisms f o r d i f f e r e n t metals (Table X I I I ) . 123 Table X I I I : Trace Metal Bio-accumulation in Benthic Invertebrates Bioaccumulation Ratio Trace Metal Organisms L I n i t i a l 1 H F i n a l L 2 H 3 Change L H Copper Amphipods 1.26 .46 1.30 .51 +.04 +.05 Chironomids .18 .06 .71 .12 + .53 + .06 Oligochaetes .20 .07 .21 .18 +.01 +.11 0. Shrimp .21 - .67 - +.46 -Iron Amphipods .03 .02 .21 .22 + .18 +.20 Chironomids .29 .23 .40 .32 + .11 +.09 Oligochaetes .39 .30 •31 .13 -.08 -.17 0. Shrimp .02 - .05 - +.03 Lead Amphipods 1.05 .16 .63 .17 -.42 + .01 Chironomids .18 .03 .62 .09 +.44 + .06 Oligochaetes .86 .13 .63 .35 -.23 +.22 0. Shrimp .02 .10 - + .08 - -Manganese Amphipods .05 .04 .94 .81 + .89 +.77 Chironomids .20 .15 .93 .25 +.73 + .10 Oligochaetes .22 .17 .31 .10 + .09 -.07 0. Shrimp .10 - .47 - +.37 -: Zinc Amphipods .77 .16 .93 .26 + .16 + .10 Chironomids .98 .20 1.68 .29 + .70 +.09 Oligochaetes 1.36 .28 1.81 .44 + .45 +.16 0. Shrimp .60 - .64 - +.04 -: 1. Ratio of i n i t i a l cone, in organism/cone, i n sediment. 2. Ratio of f i n a l cone, in organism/cone. in sediment a f t e r 1 month incubation. For Opossum shrimp time i n t e r v a l = 1 week. 3. Difference between i n i t i a l and f i n a l bioaccumulation r a t i o , (+) indicates r e l a t i v e increase over sediment concentration, (-) indicates r e l a t i v e decrease over sediment concentration. L = low organic sediment, H = high organic sediment. 124 The amphipods showed a p o s i t i v e accumulation f o r a l l metals except Pb i n the low organic sediments. The order of accumulation i n the amphipods f o r both sediment types was Mn<Fe <Zn<Cu<Pb. There was very l i t t l e v a r i a b i l i t y i n c o n c e n t r a t i o n r a t i o changes f o r the two d i f f e r e n t sediments suggesting that the t r a c e metals i n the Enteromorpha may have i n f l u e n c e d accumulation. Chironomids showed an i n c r e a s e i n c o n c e n t r a t i o n r a t i o s f o r a l l t r a c e metals. There was a much g r e a t e r i n c r e a s e i n the c o n c e n t r a t i o n r a t i o s of a l l metals i n the low or g a n i c sediment. With the e x c e p t i o n of Fe, changes i n the c o n c e n t r a t i o n r a t i o s were 7 to 8 times h i g h e r f o r the low org a n i c sediment than f o r the high organic sediment. Oligochaetes showed c o n s i d e r a b l e v a r i a b i l i t y i n t h e i r a b i l i t y to accumulate t r a c e metals. There was an i n c r e a s e i n accumulation r a t i o f o r Cu and Zn i n both sediments, whereas the r a t i o s f o r Fe decreased. Lead and Mn showed a v a r i a b l e change i n accumulation r a t i o depending upon the sediment. Opossum shrimp showed an i n c r e a s e i n the accumulation r a t i o f o r a l l metals i n the low o r g a n i c sediments. The l a r g e s t i n c r e a s e was f o r Cu and Mn with o n l y s m a l l changes f o r Fe, Pb and Zn. C. Rate of Uptake or Loss of Trace Metals by Ben t h i c  I n v e r t e b r a t e s The changes i n t r a c e metal l e v e l s i n the b e n t h i c i n v e r t e b r a t e s over the one and two week i n t e r v a l s spanning 125 a 28 day p e r i o d of the microcosms as shown i n Appendix C (Table C) were used to c a l c u l a t e the r a t e of uptake or l o s s of the metals i n the organisms f o r each time i n t e r v a l . The uptake r a t e s f o r i n d i v i d u a l i n t e r v a l s were used to o b t a i n average r a t e s over the 28 day p e r i o d . The averaged r e s u l t s expressed i n mg/kg dry weight/day are presented i n Table XIV with standard d e v i a t i o n s i n parentheses. The negative s i g n denotes a l o s s . The uptake r a t e c a l c u l a t i o n s were l i m i t e d to a 28 day p e r i o d although chironomid and o l i g o c h a e t e microcosms spanned a p e r i o d of 4-2 days. This was considered a p p r o p r i a t e f o r comparisons of uptake r e s u l t s between d i f f e r e n t s p e c i e s . Amphipods showed the hi g h e s t uptake r a t e s f o r Fe and Mn f o l l o w e d by chironomids and the amphipods had the s m a l l e s t of the r a t e s f o r Cu and Zn. These r e l a t i v e r a t e s were c o n s i s t e n t f o r both the hi g h and low organic sediments. The uptake r a t e s of Cu and Pb f o r amphipods i n contact with the low or g a n i c sediment were negative i n d i c a t i n g t h a t the metal was being l o s t by the organisms over the 28 day p e r i o d . With the e x c e p t i o n of Zn, chironomids showed a higher uptake r a t e i n the low org a n i c sediment. Chironomids had the h i g h e s t uptake r a t e s f o r Cu and Zn f o l l o w e d by o l i g o c h a e t e s i n c o n t a c t with both the low and the high organic sediments. Except f o r Mn from low organic sediments- the o l i g o c h a e t e s ' uptake r a t e s of Fe and Mn were negative i n d i c a t i n g that the metals were l o s t by the organism over the 28 day p e r i o d . The uptake r a t e of Mn by o l i g o c h a e t e s from the low organic sediment was p o s i t i v e but 126 Table XIV: Average Uptake Rate of Trace Metals by Benthic I n v e r t e b r a t e s 1 (0-28 days). Trace Metal Organism High Organic Sediment Average (S.D.) Low Organic Sediment Average (S.D.) Copper I r o n Lead Manganese Zi n c Amphipods Chironomids O l i g o c h a e t e s Amphipods Chironomids O l i g o c h a e t e s Amphipods Chironomids O l i g o c h a e t e s Amphipods Chironomids O l i g o c h a e t e s Amphipods Chironomids O l i g o c h a e t e s 0.33(3.9) 1.34 1.05(1.75) 143(150) 68 -212(767) 0.67(2.10) 5.37 8.59(16.73) 10.45(8.82) 1.79 -2.33(7.82) 2.09(3.06) 3.02 2.41(3.28) -0.033(3.8) 3.53 (5.29) 0.38 (3.26) 183 (254) 92 (133) -101 (937) -3.25 (1.84) 6.67 (18.4) -2.92 (20.6) 16.05 (15.93) 16.9 (25.1) 1.31 (11.14) 0.93 (3.78) 2.81 (0.72) 1.71 (5.66) Values expressed as mg/kg dry wt. of organism/day. Negative values i n d i c a t e a net l o s s of metal. S.D. = Standard D e v i a t i o n n = 3, except f o r chironomids i n high organic sediment microcosms f o r which n = 2 127 s m a l l e s t of the r a t e s f o r the three s p e c i e s examined. However, because of the l a r g e v a r i a b i l i t y i n uptake r a t e s as i n d i c a t e d by standard d e v i a t i o n s the d i f f e r e n c e s i n uptake r a t e s do not appear to be s i g n i f i c a n t . P u r e l y on the b a s i s of s t a t i s t i c s , i t i s p o s s i b l e to miss the importance of the r e s u l t s . As d e p i c t e d i n F i g u r e 16 the v a r i a t i o n i n uptake r a t e s between s u c c e s s i v e i n t e r v a l s r e f l e c t s dynamics of t r a c e metal uptake and c o n t r o l mechanisms. D. R e p r o d u c i b i l i t y of Trace Metal Determination i n  Organisms A n a l y s i s of o l i g o c h a e t e s from d u p l i c a t e microcosm chambers c o n t a i n i n g s i m i l a r sediments and harvested on the same day are presented i n Table XV. There was i n s u f f i c i e n t space and numbers of organisms to s e t up d u p l i c a t e s f o r each organism at each time i n t e r v a l . However, the f o u r d u p l i c a t e s e t s of o l i g o c h a e t e s provide some estimate of b i o l o g i c a l v a r i a b i l i t y and a n a l y t i c a l p r e c i s i o n . The percent v a r i a t i o n i n the two values of each r e p l i c a t e r e l a t i v e to t h e i r mean value i s summarized i n Table XVI. Manganese showed the g r e a t e s t v a r i a b i l i t y with an average of 24.8 percent between r e p l i c a t e s with a high value of 4I.2 percent. The average r e p r o d u c i b i l i t y of Fe, Pb and Zn was w i t h i n 8 - 1 1 percent of the mean, while Cu values had an average d i f f e r e n c e of 19 pe r c e n t . Table XV : Reproducibility of Trace Metal Determinations i n Oligochaetes from R e p l i c a t e Microcosm Chambers"^. S a m p } c n § . D a t l \ ? u ° 3 K S a y Copper Iron Lead Manganese Zinc and (Sediment) Chamber r r & June 14, 1978 (High Organic Sediment) July 12, 1978 (High Organic Sediment) June 28, 1978 (Low Organic Sediment) July 12, 1978 (Low Organic Sediment) 1 29.4 2310 2 39.1 2140 1 19.4 789 2 21.6 829 1 31.9 5200 2 37.1 5890 1 53.2 3490 2 67.0 3820 235 35.3 155 261 48.4 169 168 39.0 155 168 26.5 123 112 150 203 133 130 190 92.4 88.6 133 108 78.0 140 1. A l l values in ppm (mg/kg dry wt.). H Co 129 Table XVI : Percent V a r i a b i l i t y in Trace Metal Levels i n Four Duplicate Oligochaetes Microcosm. Trace Metal Percent V a r i a b i l i t y Average Range Cu 19.1 10.7 -• 28.3 Fe 8.4 7.6 -•12.3 Mn 24.8 12.7 -- 41.2 Pb 10.7 0.0 -- 17.7 Zn 10.8 5.1 -- 23.0 130 Chapter 4" DISCUSSION OF RESULTS I. GEOCHEMICAL PHASES I t has r e c e n t l y been recognized that to f u l l y assess impact of t r a c e metals on water q u a l i t y and a q u a t i c organisms, exact knowledge of the metals' a s s o c i a t i o n with v a r i o u s m i n e r a l phases of the sediments i s necessary (Kitano et a l . , 1980). The bulk chemical composition of sediments i s a poor i n d i c a t o r of environmental s i g n i f i c a n c e of t r a c e metals i n sediments (Serne, 1975). As a r e s u l t , a h a l f dozen d i f f e r e n t e x t r a c t i o n schemes have been developed ( T e s s i e r et a l . , 1979). A m o d i f i e d v e r s i o n of the scheme proposed by E n g l e r et a l . , (1974-) was chosen f o r t h i s study. This scheme i s designed to provide a r e a l i s t i c r e p r e s e n t a t i o n of a c t u a l t r a c e metal and mineral a s s o c i a t i o n s , f o r sediments are kept i n t h e i r o r i g i n a l p h y s i c a l and chemical s t a t e as much as p r a c t i c a l l y p o s s i b l e 1 . F o l l o w i n g i s a b r i e f d i s c u s s i o n of the v a r i o u s geochemical phases obtained by the e x t r a c t i o n scheme employed i n t h i s work. A. I n t e r s t i t i a l Water (IW) I n t e r s t i t i a l water i s water i n sediment pores which i s i n dynamic e q u i l i b r i u m with v a r i o u s mineral and organic components of the sediment. Trace metals i n i n t e r s t i t i a l  1. Since fresh sediments were used for geochemical extractions but frozen sediments f o r exchange experiments, the relationships between trace metal exchange and t h e i r geochemical d i s t r i b u t i o n as discussed i n this chapter should be viewed keeping i n .mind that geochemical d i s t r i b u t i o n of metals i n sediments can change i n freezing (Thomson et a l . 1980, Water, Air and S o i l P o l lution,Ij. , 215-233). 131 water may d i f f u s e to o v e r l y i n g water or may be r e l e a s e d d u r i n g dredging o p e r a t i o n s (Chen et a l . , 1976). The i n t e r -s t i t i a l f r a c t i o n of t r a c e metals may a l s o be accumulated by burrowing t u b i f i c i d worms (Guthrie et a l . , 1979). Chemistry of IW i n Saanich I n l e t , B r i t i s h Columbia,was i n v e s t i g a t e d by P r e s l e y et a l . ( 1 9 7 2 ) . B. Exchangeable Phase (EP) EP i s t h a t p o r t i o n of tra c e metals i n sediments which i s bound to sediment p a r t i c l e s u r f a c e s through a d s o r p t i o n from water. Exposure of sediments to s a l t waters as i t occurs at r i v e r - e s t u a r y i n t e r f a c e may r e s u l t i n r e l e a s e of the exchangeable phase of t r a c e metals by replacement a c t i o n of Na +, K +, C a 2 + , Mg 2 + ions (Kharkar et a l . , 1968). In the l a b o r a t o r y EP phase may be e x t r a c t e d with NH^OAC, or other s i m i l a r chemicals ( d i l u t e HC1, NaCl, MgCl^, e t c . ) . C. E a s i l y Reducible Phase (ERP) ERP e x t r a c t r e p r e s e n t s trace metals h e l d i n Mn oxides, some amorphous Fe oxides and carbonates. Under re d u c i n g c o n d i t i o n s t h i s phase of t r a c e metals may be r e l a t i v e l y e a s i l y m o b i l i z e d (Jenne, 1968; Leeper, 1972). Chao (1972) proposed a method f o r s e l e c t i v e i s o l a t i o n of t h i s phase of t r a c e metals from s o i l s and sediments. D. Organic and Sulphur Phase (OSP) Trace metals bound to organic compounds and s u l p h i d e s o x i d i z a b l e with hot a c i d i f i e d ^2®2 c o m P r i s e the 132 OSP phase. Under o x i d i z i n g c o n d i t i o n s , as may occur i n the case of d i s p o s a l of anoxic, contaminated dredged sediments on l a n d , the OSP phase may become un s t a b l e and be l e a c h e d out i n storm r u n o f f . Jackson (1958) recommended the use of hydrogen p e r o x i d e d i g e s t i o n f o r determining the c o n c e n t r a t i o n of s o i l OSP n u t r i e n t t r a c e metals. E. E a s i l y Acid E x t r a c t i b l e Phase (EAEP) Trace metals contained i n metamorphic c r y s t a l l i n e Fe oxides c o n s t i t u t e the EAEP phase. EAEP t r a c e metals may m o b i l i z e i n a p e r s i s t i n g anoxic environment or under a c i d i c c o n d i t i o n s . This phase of t r a c e metals i s r e l a t i v e l y more t i g h t l y h e l d i n sediments than the p r e v i o u s l y d i s c u s s e d phases. E n g l e r et al.(1974) proposed the use of a method f i r s t suggested/used by Holmgren (1967) f o r s o i l s . R e c e n t l y Malo (1977) recommended a new method which proved to be e q u a l l y e f f i c i e n t and s e l e c t i v e f o r i s o l a t i o n of i r o n oxide a s s o c i a t e d t r a c e metals but without p r e s e n t i n g some of the a n a l y t i c a l d i f f i c u l t i e s a s s o c i a t e d with the Holmgren's approach (see chapter 2). F. Residue Phase (RP) This phase re p r e s e n t s the f r a c t i o n of t r a c e metals t i g h t l y bound i n s i l i c a t e m i n e r a l s . Only a harsh chemical treatment such as d i g e s t i o n i n hot HF-HNO^ a c i d mixtures can f r e e t h i s f r a c t i o n of t r a c e metals from sediments. T h i s phase has been found to c o n t a i n the l a r g e s t f r a c t i o n of t r a c e 133 metals i n sediments (Serne, 1975) and the f r a c t i o n decreases where t r a c e metals i n sediments accumulate from anthropogenic s o u r c e s ( T e s s i e r et a l . , 1980). T h i s phase i s l e a s t important from an environmental p o i n t of view. G. T o t a l Phase ( T o t a l ) Determination of t o t a l c o n c e n t r a t i o n s r e q u i r e s a chemical d i g e s t i o n s i m i l a r to t h a t d i s c u s s e d f o r the r e s i d u e phase (RP). Only a f r a c t i o n of the t o t a l t r a c e metals may a f f e c t the aquatic environment; t h e r e f o r e , the importance of t o t a l t r a c e metal c o n c e n t r a t i o n s has been questioned (Gupta and Chen, 1975). I I . TRACE METAL EXCHANGE AT SEDIMENT-WATER INTERFACE A. General 1. S t a t i c columns The s t a t i c column l a b o r a t o r y t e s t s were used to simulate r e l a t i v e l y quiescent f i e l d c o n d i t i o n s i n which the t r a c e metals are present i n sediments where very l i t t l e r e s u s p e n s i o n occurs but where p o s s i b l e change i n o v e r l y i n g water chemistry could a f f e c t exchange r e a c t i o n s . Changes i n water chemistry could r e s u l t from s t r a t i f i c a t i o n with a s s o c i a t e d oxygen d e p l e t i o n and pH r e d u c t i o n that o f t e n occur i n eutrophic l a k e s , o r from t i d a l s a l t wedge p:enetration i n an estuary. S t a t i c column l a b o r a t o r y experiments have been conducted by other r e s e a r c h e r s to i n v e s t i g a t e sediment 134 exchange r e a c t i o n s under c o n d i t i o n s of minimum sediment d i s t u r b a n c e ( F i l l o s and Swanson, 1974; Stokes and Szokalo, 1977; Lu and Chen, 1977; Leudtke and Bender, 1979; Bothner et a l . , 1980). 2. E l u t r i a t e t e s t s The e l u t r i a t e t e s t simulated exchange r e a c t i o n s between sediment and water. These could occur under n a t u r a l c o n d i t i o n s where h i g h surface r u n o f f r e s u l t s i n sediment suspension. A l s o man-induced a c t i v i t i e s such as dredging, p i l e d r i v i n g and s h i p p i n g i n shallow channels can r e s u l t i n sediment d i s t u r b a n c e and resuspension which c o u l d a f f e c t metal exchange r e a c t i o n s (Windom, 1975; Lee and M a r i a n i , 1977; Chen e t a l . , 1976; Wakemann, 1977). P h y s i c a l d i s t u r -bance of sediments i s a w e l l documented phenomenon (Rhoads, 1963; Gordon, 1966; Jones and Bowser, 1978) which c o u l d a l s o imbalance the normal e q u i l i b r i u m s t a t e of the sediment-water i n t e r f a c e and thereby i n f l u e n c e t r a c e metal exchange (Robbins and Edington, 1975; A l l e r and Cochran, 1976; Schink and Guinasso, 1977; Leudtke and Bender, 1979). Trace metal exchange i n e l u t r i a t e t e s t s was d i f f e r e n t from exchange i n column t e s t s i n some ways. In e l u t r i a t e t e s t s , exchange was r a p i d i n the sense that sediment and water were exposed to each other e x t e n s i v e l y and immediately but s e v e r e l y hindered because of l a c k of time f o r chemical and b i o c h e m i c a l ( b a c t e r i a l ) r e a c t i o n s to approach an e q u i l i b r i u m s t a t e . In c o n t r a s t , although p h y s i c a l exchange 135 f o r columns was slow as i t depended upon d i f f u s i o n of water i n and out of the sediment l a y e r , sediment and water ( i n t e r s t i t i a l water) were i n contact f o r l o n g enough times to undergo d i a g e n e t i c r e a c t i o n s i n v o l v i n g t r a n s f e r of t r a c e metals. These d i f f e r e n c e s should be considered i n comparing exchange r e s u l t s between the e l u t r i a t e t e s t s and the column s t u d i e s . B. D i s s o l v e d Trace Metal Exchange I n i t i a l s et up of columns r e s u l t e d i n the r e l e a s e of d i s s o l v e d metals from resuspended sediments. However, va l u e s soon decreased r e a c h i n g e q u i l i b r i u m a f t e r 2 to 5 days. The i n i t i a l r e l e a s e of metals probably r e s u l t e d from i n t r o d u c t i o n of m e t a l - r i c h sediment pore water i n t o the water l a y e r . F i l l o s and Swanson (1974) a l s o r e p o r t e d h i g h i n i t i a l c o n c e n t r a t i o n s of Fe and phosphorus d u r i n g experiment i n i t i a t i o n , w h i c h they a t t r i b u t e d to disturbance of sediment. S i m i l a r l y h i g h i n i t i a l r e l e a s e of Mn was observed by Graham et a l . (1976) i n t h e i r i n s i t u chamber s t u d i e s i n Narr a g a n s e t t Bay. Graham et a l . a t t r i b u t e d the h i g h i n i t i a l r e l e a s e of Mn to i n t r o d u c t i o n of pore water as the sediment was d i s t u r b e d i n the chambers duri n g emplacement. T h e r e f o r e , the i n i t i a l r e l e a s e of metals from resuspension of sediments seems to be a common problem i n s e t t i n g up q u i e s c e n t systems even though extreme care i s e x e r c i s e d . R e s u l t s of d i s s o l v e d t r a c e metal exchange s t u d i e s c a r r i e d out i n column microcosms and u s i n g the e l u t r i a t e t e s t . 136 procedure are d i s c u s s e d below t a k i n g one metal a t a time. 1. Copper (Cu) In column s t u d i e s , d u r i n g freshwater e q u i l i b r i u m d i s s o l v e d Cu i n the low organic system under both o x i c and anoxic c o n d i t i o n s (see fo o t n o t e p. 89) reached e q u i l i b r i u m values of approximately twice those found i n the high organic system even though both sediments contained s i m i l a r t o t a l Cu and had a s i m i l a r geochemical d i s t r i b u t i o n o f Cu. The higher Mn, Fe and organic matter content of the W i l l i n g d o n sediment most l i k e l y l i m i t e d r e l e a s e of Cu i n t o s o l u t i o n . Means et a l . (1978) have shown t h a t oxides of Mn and Fe and organic matter have a d s o r p t i v e c a p a c i t i e s f o r t r a c e elements which could r e s u l t i n lower e q u i l i b r i u m c o n c e n t r a t i o n s i n o v e r l y i n g waters. A f i e l d study by Lopez and Lee (1977) i n d i c a t e d s i m i l a r p r o f i l e s of Cu, Fe and Mn i n Torch Lake, Michigan, sediments which supports the b e l i e f t h a t Fe and Mn may d e p o s i t Cu i n f r e s h w a t e r s . Sanchez and Lee (1978) observed lower values f o r d i s s o l v e d Cu i n Lake Monona, Wisconsin. Low Cu l e v e l s i n the h y p o l i m n e t i c anoxic l a y e r were a t t r i b u t e d to lower s o l u b i l i t y of Cu s u l p h i d e , but carbonate was b e l i e v e d to be c o n t r o l l i n g s o l u b i l i t y i n the aerobic e p i l i m n i o n l a y e r . In t h i s study i n o r g a n i c carbon i n sediments was low , so Cu carbonate probably was not r e g u l a t i n g s o l u b i l i t y . A l s o , p r o d u c t i o n of Cu carbonate during the experiment could not be s i g n i f i c a n t because constant purging by n i t r o g e n or a i r prevented accumulation 137 of carbon d i o x i d e ( K h a l i d et a l . , 1978). In the freshwater systems of t h i s study, the o r g a n i c carbon (8-19 mg/1) was probably more important i n r e g u l a t i n g d i s s o l v e d Cu l e v e l s through complexation and / or through i n f l u e n c e on a d s o r p t i o n -d e s o r p t i o n r e a c t i o n s . Payne and P i c k e r i n g (1975) have demonstrated t h a t l i g a n d s such as a c e t a t e and t a r t r a t e can g r e a t l y i n f l u e n c e the a d s o r p t i o n of Cu to c l a y . Presence of NTA-like l i g a n d s may a l s o c o n t r o l l e v e l s of Cu i n freshwater systems (Sanchez and Lee, 1973). The two types of sediments used i n the present study a l s o d i f f e r e d i n p a r t i c l e s i z e . Wolfberg et a l . (1980) b e l i e v e t h a t h i g h o r g a n i c s o i l s or c l a y e y s o i l s c ould remove Cu to a g r e a t e r extent than the sandy s o i l s . R e s u l t s of Lu and Chen (1977) confirm t h i s , b e l i e f i n t h a t Cu was more r e a d i l y r e l e a s e d from t h e i r sandy sediment than from t h e i r c l a y e y sediment. In freshwater e l u t r i a t e t e s t s , Cu was completely removed r e g a r d l e s s of o r g a n i c matter content, oxygen c o n d i t i o n s or Cu c o n c e n t r a t i o n s i n sediments. Since Cu i n s o l u t i o n i s exposed to l a r g e m i n e r a l s u r f a c e areas, the metal was r e a d i l y removed (O'Connor and Kester, 1975) and d i f f e r -ences i n geochemistry of the sediments or chemistry of water were superseded. In column s t u d i e s , d u r i n g the f i r s t s a l i n i t y adjustment i n the a e r o b i c system there was some r e l e a s e of Cu i n t o s o l u t i o n e s p e c i a l l y i n the high organic column. This i s a t t r i b u t e d to d e s o r p t i o n of Cu from the sediment 138 as i t has been observed i n the Rhine E s t u a r y (Groot et a l . , 1976) and i n the F r a s e r E s t u a r y (Thomas and G r i l l , 1977) ; i n the former case up to 80 percent Cu was r e l e a s e d as sediment was t r a n s p o r t e d through the e s t u a r y . In a c o a s t a l environment, Menon et a l . (1979) a l s o observed s i m i l a r Cu d e s o r p t i o n from sediments and the authors b e l i e v e t h a t c a t i o n s 2+ 2+ Ca and Mg i n the seawater were exchanged f o r Cu i o n s . A g r e a t e r r e l e a s e from the h i g h o r g a n i c sediment can be e x p l a i n e d by the r e s u l t s of Rohatgi and Chen (1975) where Cu among some other t r a c e metals was removed from sewage r e l a t e d o r g a n i c s o l i d s on suspension i n seawater i n the presence of d i s s o l v e d oxygen. The removal of the metals from the o r g a n i c s o l i d s was b e l i e v e d to have occ u r r e d due to o x i d a t i o n of o r g a n i c matter and simultaneous r e l e a s e of a s s o c i a t e d t r a c e metals. Free metal ions i n seawater are probably s t a b i l i z e d i n s o l u t i o n by formation of c o o r d i n a t e complexes with v a r i o u s - - 2- — 2-anions, OH , CI , C0^ , HCO^ and S0^ (Long and Angino, 1977) .The high organic sediment a l s o contained s l i g h t l y more Cu i n the OSP phase.Although the EAEP phase of the h i g h o r g a n i c sediment contained twice as much Cu as t h i s phase i n the low or g a n i c sediment because of g r e a t e r s t a b i l i t y of c r y s t a l l i n e i r o n oxide under aerobic c o n d i t i o n s , the g r e a t e r r e l e a s e of Cu from the high organic sediment could not be a t t r i b u t e d to. t h i s d i f f e r e n c e i n geochemistry of the metal. In e l u t r i a t e t e s t s , Cu was removed from s o l u t i o n under both o x i c and anoxic c o n d i t i o n s over a wide s a l i n i t y 139 range even though Cu c o n c e n t r a t i o n s i n the sediments used i n these t e s t s were s e v e r a l times greater than the c o n c e n t r a t i o n s f o r the sediments used i n the column s t u d i e s . A e r a t i o n of the sediment-water mixture over a 30 minute p e r i o d f o r the hig h organic sediment o b v i o u s l y was not s u f f i c i e n t to break down ( o x i d i z e ) o r g a n i c matter as observed by Rohatgi and Chen (1975) and Lindberg and H a r r i s s (1977). Removal of Cu from seawater by freshwater sediments i n e l u t r i a t e type t e s t s has been observed elsewhere (Wagemann et a l . , 1977; Gustafson, 1972; Lee et a l . , 1975). The removal was most l i k e l y due to a d s o r p t i o n of Cu on s u r f a c e s of sediment p a r t i c l e s . P r e c i p i t a t i o n of Cu could a l s o occur but through d i f f e r e n t mechanisms f o r oxi c and anoxic t e s t s . Lee et a l . (1975) showed t h a t under oxic c o n d i t i o n s d i s s o l v e d Fe from IW phase of sediment o x i d i z e s and p r e c i p i t a t e s and i n the process removes other t r a c e metals from s o l u t i o n . Under anoxic c o n d i t i o n s f o r m a t i o n of low s o l u b i l i t y Cu s u l p h i d e may r e s u l t i n removal of the metal (Okutoni and O k a i c h i , 1971). Oakley et a l . (1980) showed t h a t under anoxic c o n d i t i o n s Cu p r e f e r e n t i a l l y binds to Fe s u l p h i d e . Under o x i c c o n d i t i o n s at f u l l seawater s t r e n g t h (S=25-30 /oo) both i n q u i e s c e n t (column) and e l u t r i a t e s t u d i e s there was some r e l e a s e of Cu from both sediments. I t seems t h a t f o r c e s r e s p o n s i b l e f o r Cu removal as d i s c u s s e d p r e v i o u s l y were e v e n t u a l l y overcome by i n c r e a s i n g 2+ 2 + c o n c e n t r a t i o n s of exchange c a t i o n s Ca and Mg and complexing anions such as c h l o r i d e and hydroxide. In H O e l u t r i a t e t e s t s where s u r f a c e r e a c t i o n s of metal removal from s o l u t i o n can be more e f f e c t i v e , s l i g h t l y l e s s Cu was r e l e a s e d from the h i g h o r g a n i c f i n e sediment. In column s t u d i e s where exchange of water through sediment pores may c o n t r o l exchange r a t e s , g r e a t e r Cu r e l e a s e was measured from the co a r s e r low o r g a n i c sediment. In the pH s t u d i e s , both i n microcosms and e l u t r i a t e t e s t s , d i s s o l v e d Cu l e v e l s were g e n e r a l l y h i g h e r i n the h i g h (10) and low (5) pH systems than t h a t a t the n a t u r a l pH (approx. 7 ) . In the low pH systems, a c e t a t e was used as a b u f f e r which could a i d i n d e s o r p t i o n of Cu from the sediments (Payne and P i c k e r i n g , 1975) and keep i t i n s o l u t i o n as an a c e t a t e complex although metal s p e c i a t i o n was not determined. Under a c i d i c c o n d i t i o n s carbonates, oxides and hydroxide m i n e r a l phases of sediments r e a c t w i t h protons and d i s s o l v e i n water r e l e a s i n g the a s s o c i a t e d t r a c e metals i n the process. A number of geochemical phases namely EP, ERP, OSP and EAEP are u n s t a b l e under low pH c o n d i t i o n s and hence must have c o n t r i b u t e d to t r a c e metal r e l e a s e a t pH 5. Trace metal r e l e a s e under low pH c o n d i t i o n s has been measured by o t h e r s . Naumov et a l . (1972) measured d i s s o l v e d Cu c o n c e n t r a t i o n s i n the range of 26.6 - 153 mg/1 i n the ore waters of Cu - B i d e p o s i t s where pH ranged from 3.05 - 4.25.' Stokes and Szokalo (1977) a l s o observed t h a t r e l e a s e of Cu and Ni from sediments p l a c e d i n l a b o r a t o r y a q u a r i a was r e l a t e d to a decrease i n pH of the o v e r l y i n g water. 1U In the high pH systems, carbonate b u f f e r should c o n t r o l the d i s s o l v e d Cu at a low c o n c e n t r a t i o n as measured by Sanchez and Lee (1978) i n Lake Monona, Wi s c o n s i n . T h e o r e t i c a l c a l c u l a t i o n s of Z i r i n o and Yamamoto (1972) suggest that a t pH 10 Cu^H),, would be a dominant s p e c i e s and t h e r e f o r e c o n t r o l the s o l u b i l i t y of Cu. However, hig h pH a l s o s o l u b i l i z e d o r g a n i c s from the sediment (T0C=50 mg/l and color=500 mg/l P t . ) . These hu m i c - l i k e o r g a n i c substances have a high complexing c a p a c i t y f o r Cu and other t r a c e metals ( S c h n i t z e r and Skinner, 1967; Cheshire et a l . , 1977; Reuter and Perdue, 1977). Kunkel and Manahan (1973) d i s c u s s how c h e l a t i n g agents can s t a b i l i z e c u p r i c ions i n s o l u t i o n a t pH 10 by forming m u l t i l i g a n d c o o r d i n a t e complexes with the metal. R e s u l t s of a study by Bondarenko (1972) are p a r t i c u l a r l y i n t e r e s t i n g i n r e l a t i o n to the p r e s e n t study. Humic and f u l v i c a c i d s were used to d i s s o l v e Cu i n c o n c e n t r a -t i o n s up to 26.25 mg/l under a l k a l i n e c o n d i t i o n s . S o l u t i o n s at i n i t i a l pH values from 10 to 11 were u n s t a b l e over a p e r i o d of 510 days; both d i s s o l v e d Cu and pH values dropped over the 510 day p e r i o d . The c o n c e n t r a t i o n s of d i s s o l v e d Cu were s t i l l i n the 10 to 20 mg/l range. In the pH s t u d i e s , the high o r g a n i c sediment when subjected to low (5) and high (10) pH c o n d i t i o n s r e l e a s e d more Cu i n t o s o l u t i o n than d i d the low organic sediment. The g r e a t e r r e l e a s e from the h i g h organic sediment can be 142 a t t r i b u t e d to d i f f e r e n c e s i n Cu d i s t r i b u t i o n between the two sediments and t h e i r geochemical phases. The h i g h o r g a n i c sediments used i n the pH s t u d i e s were c o l l e c t e d from S t i l l Creek about 4 months a f t e r the low organic sediments (Table IX and X). During the i n t e r v e n i n g p e r i o d t r a c e metal (Cu, Pb and Zn) c o n c e n t r a t i o n s i n the sediments i n c r e a s e d . Therefore, Cu l e v e l s i n the high organic sediment were almost 5 times those i n the low o r g a n i c sediment. The presence of more Cu i n the high organic sediment c o u l d have r e s u l t e d i n a g r e a t e r r e l e a s e of the metal from t h i s sediment. Copper i n the ERP, EP and IW probably accounts f o r most of the r e l e a s e at low pH (Chester and Hughes, 1967). The three geochemical phases ERP, EP and IW of the high o r g a n i c sediment together contained 9 times more Cu than the t o t a l f o r the three phases i n the low organic sediment. At h i g h pH (10), d i s s o l u t i o n of o r g a n i c matter oc c u r r e d and s i n c e over 200 ppm Cu was bound to the OSP phase of t h i s sediment (Table X), high d i s s o l v e d Cu c o n c e n t r a t i o n s were o b t a i n e d . This Cu would be s t a b i l i z e d i n s o l u t i o n by a s s o c i a t i o n with h u m i c - l i k e substances as d i s c u s s e d p r e v i o u s l y . • 2. Iron (Fe) Iron i n the o x i c freshwater columns reached e q u i l i b r i u m c o n c e n t r a t i o n s of approximately 75/W-g/l. Koenings (1976) i n a study of Fe i n an acid-bog l a k e 143 c a l c u l a t e d t h a t d i s s o l v e d i r o n i n an oxygenated system at n e u t r a l to b a s i c pH should not exceed 17 jUg/1. Iron c o n c e n t r a t i o n s i n r i v e r s f a r exceed the c o n c e n t r a t i o n s c a l c u l a t e d from e q u i l i b r i u m r e l a t i o n s h i p s i n v o l v i n g i n o r g a n i c r e a c t i o n s (Stumm and Morgan, 1970; Jones et a l . , 1974). Co-occurrence of high c o n c e n t r a t i o n s of d i s s o l v e d Fe and o r g a n i c matter has been observed by many authors (Abdullah and Royale, 1972; Perdue et a l . , 1976; Moore et a l . , 1979)- Organic substances are b e l i e v e d to cause h i g h c o n c e n t r a t i o n s of Fe i n oxi c waters by e i t h e r forming c h e l a t e type of complexes with the metal ions (Perdue et a l . , 1976) or a d s o r p t i o n on i n o r g a n i c f e r r i c hydroxide c o l l o i d s (Hem and Cropper, 1959). Adsorption of organics enhances s t a b i l i t y of Fe c o l l o i d suspensions. Under the o x i c c o n d i t i o n s of the columns i n t h i s study probably the l a t t e r mechanism was predominant. The c o l l o i d p a r t i c l e s could r e a d i l y pass through the 0.45 U-ra s i z e membrane f i l t e r s used i n o b t a i n i n g samples f o r d i s s o l v e d metal analyses (Hem,1972). In o x i c e l u t r i a t e t e s t s a t near freshwater c o n d i t i o n s ( S a l i n i t y < 4 °/oo) there was some r e l e a s e of Fe e s p e c i a l l y from the low organic sediment. A g r e a t e r r e l e a s e of Fe from the low organic sediment may be a t t r i b u t e d to d e s o r p t i o n of i t s p o o r l y adsorbed abundant exchangeable phase (Table X ) . At h i g h e r s a l i n i t i e s , however, d e s o r p t i o n was accompanied by c o a g u l a t i o n of c o l l o i d a l Fe, the form i n which f i l t r a b l e Fe occurs a t s l i g h t l y a l k a l i n e pH v a l u e s . Edzwald 144 et a l . (1974) s t u d i e d the s t a b i l i t y of p a r t i c u l a t e suspensions i n e s t u a r i n e water of v a r y i n g s a l i n i t y (0-16 °/oo). S t a b i l i t y o f c o l l o i d s s h a r p l y drops i n the s a l i n i t y range of 2 to 4 °/oo. Iro n f l o c c u l a t i o n i n e s t u a r i e s has been s t u d i e d by Coonley et a l . (1971), Boyle et a l . (1977) and S h o l k o v i t z (1976). In column s t u d i e s , the f i r s t s a l i n i t y change, achieved by r e p l a c i n g h a l f the e x i s t i n g freshwater with seawater, r e s u l t e d i n a l a r g e s a l i n i t y i n c r e a s e from zero to I 4 . 5 °/oo. Under ox i c c o n d i t i o n s d i s s o l v e d Fe c o n c e n t r a t i o n s dropped below the 10 jug/l l e v e l . A s i n t h e e l u t r i a t e t e s t s , t h i s can be a t t r i b u t e d to c o a g u l a t i o n of f e r r i c hydroxide c o l l o i d s . Under anoxic c o n d i t i o n s there was a c o n s i d e r a b l e r e l e a s e of Fe from both sediments i n the e l u t r i a t e t e s t s and from the low org a n i c sediment i n the column s t u d i e s . Under anoxic c o n d i t i o n s , r e l e a s e of Fe from sediments has been observed i n other s t u d i e s . P a t r i c k et a l . (1973) found t h a t s t r e n g i t e (FePO. . 2H o0) incubated i n water under low redox 4 <• and low pH c o n d i t i o n s underwent maximum d i s s o l u t i o n . In a l a b o r a t o r y microcosm, F i l l o s and Swanson (1974) measured s i g n i f i c a n t r e l e a s e of Fe and phosphate when water above the sediment was made anoxic. Mortimer (1941) found t h a t Fe and Mn were not r e l e a s e d u n t i l d i s s o l v e d oxygen values dropped below 2 mg/1. In a l a b o r a t o r y study, Chen et a l . (1976) a l s o measured c o n s i d e r a b l e r e l e a s e of Fe (maximum 1.95 mg/1) from sediments to water adjusted to low redox c o n d i t i o n s by 145 p u r g i n g with n i t r o g e n gas. In e l u t r i a t e t e s t s Lee et a l . (1975) obtained i d e n t i c a l r e s u l t s . Under anoxic c o n d i t i o n s Fe c o n c e n t r a t i o n s i n the e l u t r i a t e were up to 7 mg/l whereas under o x i c c o n d i t i o n s the v a l u e s d i d not exceed the O.O48 mg/l l e v e l f o r the Corpus C h r i s t i Bay sediments. Under anoxic c o n d i t i o n s the ERP phase of sediments i s unstable and hence the most l i k e l y source of measured r e l e a s e of Fe under these c o n d i t i o n s . With r e s p e c t to Fe r e l e a s e under anoxic c o n d i t i o n s , the two sediments behaved d i f f e r e n t l y . In column s t u d i e s under anoxic c o n d i t i o n s Fe l e v e l s dropped to the d e t e c t i o n l e v e l (< 1 Mg/l) i n the high o r g a n i c sediment while as d i s c u s s e d above there was a s u b s t a n t i a l r e l e a s e of the metal from the low o r g a n i c sediment. The water q u a l i t y c o n d i t i o n s i n these two anoxic systems do not provide an e x p l a n a t i o n f o r the l a r g e d i f f e r e n c e s i n Fe r e l e a s e . Therefore, the geochemistry of Fe i n the sediment must be the important r e g u l a t i n g f a c t o r . I t appears t h a t the W i l l i n g d o n sediment with the higher organic content and f i n e r p a r t i c l e s i z e was able to prevent the r e l e a s e of Fe i n t o s o l u t i o n even though i t had a higher t o t a l Fe l e v e l and higher l e v e l s i n the more l a b i l e phases (EP and ERP). A l s o , the high organic sediment may have p r e c i p i t a t e d more Fe as. F e S , i n h i b i t i n g f u r t h e r r e l e a s e . Free s u l p h i d e s which are produced under anoxic c o n d i t i o n s i n the sediments r e a c t with the a v a i l a b l e Fe to form c h a r a c t e r i s t i c b l ack FeS d e p o s i t s (Berner, I969). Such H 6 d e p o s i t s are commonly observed i n reduced l a c u s t r i n e sediments (Jones and Bowser, 1978). In t h i s study, c o i n c i d e n t with the drop i n Fe l e v e l s i n the W i l l i n g d o n sediment under freshwater c o n d i t i o n s was the appearance of a black c o l o r c h a r a c t e r i s t i c of FeS on the s u r f a c e of the sediment. The b l a c k c o l o r of the sediment s u r f a c e f o r the high o r g a n i c microcosm system p e r s i s t e d throughout the subsequent s a l i n i t y changes. No such black c o l o r a t i o n of the low organic sediment was observed. In the e l u t r i a t e t e s t s , due to l a c k of s u f f i c i e n t time f o r p r o d u c t i o n of hydrogen s u l p h i d e , subsequent i n h i b i t i o n of Fe r e l e a s e was not p o s s i b l e . I r o n r e l e a s e d from the low o r g a n i c sediment was l e s s s t a b l e a t higher s a l i n i t i e s probably because there was l e s s d i s s o l v e d organic matter to s t a b i l i z e i t s c o l l o i d s i n water (Hem and Cropper, 1959). In the v a r i a b l e pH microcosms and e l u t r i a t e t e s t s , the g r e a t e s t Fe' r e l e a s e occurred at pH 5 which i s c o n s i s t e n t w i t h o b s e r v a t i o n s of P a t r i c k et a l . (1973). High r e l e a s e of Fe at pH 5 i s e a s i l y understandable because at such a low pH hydrous oxides of Fe and carbonates are unstable (Gupta and Chen, 1975; Chester and Hughes, 1967). At pH values of 6 or h i g h e r the s o l u b i l i t y of f e r r i c hydroxide should c o n t r o l Fe i n s o l u t i o n at very low l e v e l s (Koenings, 1976). Lewis (1977) s t u d i e d the e f f e c t of a c i d i c mine drainage on the 210 Pb c o n c e n t r a t i o n s i n the water of the West Branch of the 210 Susquehanna R i v e r (WBSR) ; he noted t h a t Pb, Fe and Mn H 7 were p r e c i p i t a t i n g out of s o l u t i o n as pH was r i s i n g from l e s s than 4 to 7 as a r e s u l t of a l k a l i n e d i s c h a r g e s downstream from the p o i n t of the mine drainage e n t r y . Release of Fe at high pH (10) systems was o b v i o u s l y a t t r i b u t a b l e to a s s o c i a t i o n with h u m i c - l i k e o r g a n i c compounds i n carbonate-bicarbonate b u f f e r (Shapiro, 1964). A c c o r d i n g to Shapiro (1964) m o b i l i z a t i o n of Fe at high pH and redox p o t e n t i a l i s due to formation of c h e l a t e type s o l u b l e complexes (Hutchinson, 1957; Stumm and Morgan, 1970). A l s o , Shapiro (1964) has shown t h a t Fe h o l d i n g c a p a c i t y of y e l l o w o r g a n i c a c i d s separated from aq u a t i c sediments was maximum at pH 10 i n the pH range of 5 to 11 t e s t e d . F e r r i c i r o n , which i s dominant under o x i c conditions,has been shown 2 + to form s t r o n g e r bonds with humic acids than Fe (Stumm and Lee, I960; S e n s i et a l . , 1977). In microcosm pH s t u d i e s , Fe r e l e a s e from the h i g h o r g a n i c sediment was g e n e r a l l y g r e a t e r than the Fe r e l e a s e from the low o r g a n i c sediment. Since water chemistry, due to the use of i d e n t i c a l b u f f e r systems, was s i m i l a r the d i f f e r e n c e s i n metal r e l e a s e can be only a t t r i b u t e d to d i f f e r e n c e s i n sediment geochemistry and p h y s i c a l charac-t e r i s t i c s . The high organic sediment used i n pH microcosms (Table X) contained s e v e r a l times more Fe i n IW, EP, ERP, OSP and EAEP phases than i n the same phases i n the low o r g a n i c sediment (Table IX). Hence i t i s not s u r p r i s i n g t h a t Fe r e l e a s e from the high organic W i l l i n g d o n sediment M 8 was g r e a t e r a t pH 5, 7 and 10. Low p e r m e a b i l i t y of t h i s f i n e sediment d e p o s i t was more than o f f s e t by g r e a t e r geochemical a v a i l a b i l i t y of the metal. A g r e a t e r r e l e a s e from the high organic sediment at pH 5 can be s i m i l a r l y e x p l a i n e d by a grea t e r amount of Fe i n geochemical phases (IW, ERP, OSP and EAEP) of the h i g h o r g a n i c sediment. In e l u t r i a t e t e s t s , a g r e a t e r r e l e a s e of Fe a t hi g h pH (10) from the low org a n i c Gilmore Avenue sediment c o n t a i n i n g lower OSP phase Fe l e v e l s (Table X) i s a s u r p r i s i n g r e s u l t . The s u b s t a n t i a l l y g r e a t e r EP phase Fe l e v e l s of the low organic sediment together with d i f f e r e n c e s i n p h y s i c a l c h a r a c t e r i s t i c s such as 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 d i f f e r e n c e s i n chemical nature of organic matter content may account f o r t h i s r e s u l t . 3. Lead (Pb) In microcosm s t u d i e s , d i s s o l v e d Pb r a p i d l y dropped to e q u i l i b r i u m c o n c e n t r a t i o n s of l e s s than 10 xx.g/1 i n both freshwater o x i c and anoxic systems. My data accord with those of Hem and Durum (1973). They p r e d i c t e d an e q u i l i b r i u m s o l u b i l i t y f o r Pb of 10 Akg/~L at pH of 8 with t o t a l c a rbonic -3 sp e c i e s of 10 M. According to Saar and Weber (1980) 149 c e r t a i n types of organic m a t e r i a l s may l i m i t the c o n c e n t r a t i o n of Pb ions by c o - p r e c i p i t a t i o n . C o n d i t i o n a l s t a b i l i t y c o n stants f o r r i v e r water humic a c i d s (WHA) determined by B u f f l e et a l . (1977) at near n e u t r a l pH values a r e : Pb-WHA, pH=6.7, - l o g ^ =6.0, Pb-WHA, pH=6.8, - l o g Pb-(WHA) 2 , pH=6.8, - l o g £ 2=10.4-. Based on data from B u f f l e et a l . and t h e i r own experiments ,Saar and Weber (1980) b e l i e v e t h a t Pb-WHA or Pb-(WHA)2 c o - p r e c i p i t a t i o n i n freshwater.where Pb c o n c e n t r a t i o n s seldom exceed 2.4 x 10 M and humic substance —6 —4 (MW=1000) c o n c e n t r a t i o n s t y p i c a l l y are 10 to 10 4M, i s not l i k e l y to occur. At low con c e n t r a t i o n s of Pb, a d s o r p t i o n i s more l i k e l y the mechanism of removal. Under freshwater c o n d i t i o n s a d s o r p t i o n was r a p i d by the high o r g a n i c sediment which had g r e a t e r exchange c a p a c i t y f o r Pb as i n d i c a t e d by the exchangeable amount of the metal present i n the sediment ( T a b l e s IX and X). This sediment a l s o contained h i g h e r e a s i l y r e d u c i b l e phase Fe p r e c i p i t a t e which i s known to scavenge t r a c e metals l i k e Pb by surface a c t i o n . The low or g a n i c sediment contained more ERP Mn; i t appears t h a t the h i g h e r ERP Mn i n the low organic sediment was not s u f f i c i e n t to o f f s e t the e f f e c t of great e r ERP Fe i n the high o r g a n i c sediment. Under s l i g h t l y s a l i n e c o n d i t i o n s i n e l u t r i a t e t e s t s and a f t e r the f i r s t s a l i n i t y change i n microcosms, Pb was r e l e a s e d from the sediments. Metals adsorbed by sediments under freshwater c o n d i t i o n s may be desorbed 150 under s a l i n e c o n d i t i o n s due to exchange r e a c t i o n s of Na +, 2 + 2 + Ca , and Mg c a t i o n s and complexing r e a c t i o n s of anions l i k e C l ~ and 0H~. D e s o r p t i o n of t r a c e metals from sediments i n s a l i n e waters has been observed by others (Kharkar et a l . , 1968; Troup and B r i c k e r , 1975; Ramamoorthy and Rust, 1978; R e v i t t and E l l i s , 1980). According to Biggins and H a r r i s o n (1980) Pb c o l l o i d s d e p o s i t e d from automobile exhaust may be resuspended i n water and pass through O.45 A m membrane f i l t e r s (Hem and Durum, 1973) and hence be measured as d i s s o l v e d Pb. Net e f f e c t of i n c r e a s i n g s a l i n i t y and pH may be removal of d i s s o l v e d Pb. A f t e r the second s a l i n i t y change i n microcosms (24.5 °/oo) and at s a l i n i t y of 4 °/oo i n e l u t r i a t e t e s t s , P b was removed to below d e t e c t i o n l e v e l s . As Edzwald et a l . (1974) have shown , i n c r e a s i n g s a l i n i t y was probably c o a g u l a t i n g Pb c o l l o i d s . Poor d e s o r p t i o n of Pb from sediments suspended i n s a l i n e waters has a l s o been observed elsewhere (Benninger e t a l . , 1975; Wagemann et a l . , 1977; S c o t t , 1980). The r e l e a s e of Pb measured i n o x i c s t a t i c columns at a s a l i n i t y of I4.5 °/oo was not observed i n e l u t r i a t e t e s t s Perhaps the k i n e t i c s of Pb d e s o r p t i o n and/or complexation are slow and a lo n g e r e q u i l i b r i u m time i s r e q u i r e d to b r i n g Pb i n t o s o l u t i o n . Four days were r e q u i r e d before Pb was measured i n the column a t I4.5 °/oo s a l i n i t y . S i m i l a r slow r e l e a s e was measured by Chen et a l . (1976) and K h a l i d et a l . (1978) i n t h e i r d e s o r p t i o n experiments under o x i c c o n d i t i o n s . 151 Lead a s s o c i a t e d with sewage s o l i d s was l e s s mobile under b r a c k i s h c o n d i t i o n s than some other metals (Rohatgi and Chen, 1975). Most Pb i n the sediments used i n the present study-was bound to OSP phase (Tables IX and X). In the e l u t r i a t e t e s t s more Pb was r e l e a s e d from the high organic sediment under s l i g h t l y s a l i n e c o n d i t i o n s . Since d e s o r p t i o n i s a s u r f a c e phenomenon, the f i n e r p a r t i c l e s i z e of the higher o r g a n i c sediment may have been a f a c t o r i n the higher r e l e a s e of Pb from t h i s sediment. Under anoxic c o n d i t i o n s Pb was not r e l e a s e d i n t o s o l u t i o n under d i f f e r e n t s a l i n i t y regimes. I d e n t i c a l r e s u l t s were obtained by Lu and Chen (1977); d i s s o l v e d Pb at the sediment-seawater i n t e r f a c e remained i n the sub ppb (Mg/1) range d u r i n g a 30 day p e r i o d . T h i s r e s u l t was independent of sediment type ( s i l t y - c l a y , s a n d y - s i l t or s i l t y - s a n d ) . Under r e d u c i n g c o n d i t i o n s , p a r t i c u l a r l y i n the l o n g - t e r m s t a t i c column experiments, s u l p h i d e p r e c i p i t a t i o n of metal i o n s probably i n h i b i t e d Pb r e l e a s e ( B e l l a , 1972; Hem and Durum, 1973; Engler and P a t r i c k , 1975). The ERP phase of the low organic sediment contained about 6 times more Pb than the corresponding phase of the high organic sediment (Table I X ) . Since Pb r e l e a s e was not measured from e i t h e r one of the two sediments, i t suggests that sulphide p r e c i p i t a t i o n overwhelmed any r e l e a s e of Pb from d i s s o l u t i o n of the ERP phase. In the v a r i a b l e pH s t u d i e s , high c o n c e n t r a t i o n s 152 of Pb were r e l e a s e d at the low (5) and the high (10) pH systems. R e s u l t s obtained from s t a t i c columns were confirmed by the e l u t r i a t e s t u d i e s . Geochemical f r a c t i o n s from IW to EAEP . c o n t a i n i n g over 80 percent of Pb (Tables IX and X),are u n s t a b l e under a c i d i c c o n d i t i o n s and tend to d i s s o l v e . Hence i t i s not s u r p r i s i n g t h a t maximum d i s s o l u t i o n o c c u r r e d a t the lowest pH ( 5 ) . At pH 5 h y d r o l y s i s of Pb i s a t a minimum (Hahne and Kroontje, 1973) and hence other s p e c i e s i n water such as o r g a n i c s and carbon d i o x i d e may be c o n t r o l l i n g the Pb c o n c e n t r a t i o n s . According to thermodynamic c a l c u l a t i o n s of Hem and Durum (1973) at a low c o n c e n t r a t i o n of c a r b o n i c s p e c i e s (10~"^M COg) > a t pH 5 Pb c o n c e n t r a t i o n i n water may r e a c h as h i g h as 1000 mg/l. Henderson et a l . (1979) l e a c h e d Pb from ceramics up to c o n c e n t r a t i o n s of over 100 mg/l depending upon the amount of Pb used i n g l a z i n g . The l e a c h i n g agent was a 5 percent s o l u t i o n of a c e t i c a c i d . P a t r i c k et a l . (1977) and Day et a l . (1979) a l s o measured c o n s i d e r a b l e r e l e a s e of Pb from sediments and s t r e e t dusts r e s p e c t i v e l y . Day et a l . (1979) argue t h a t a g r e a t e r s o l u b i l i t y of Pb a t low pH and o x i c c o n d i t i o n s i s not unreasonable because both carbonates and sulphates of the metal convert to s o l u b l e b i c a r b o n a t e s and b i s u l p h a t e s r e s p e c t i v e l y and adsorbed Pb i o n s exchange f o r abundant hydrogen i o n s . The most l i k e l y source of Pb i n the sediments was automobile exhaust ( H a l l et a l . , 1976) which i s emitted mainly i n carbonate (ERP) and sulphate (ERP) forms (Motto et a l . , 1970; Daines 153 et a l . , 1970; B i g g i n s and H a r r i s o n , 1980; present study, Tables IX and X). Concentrations of Pb at pH 5, however, were much lower than the value of 1000 mg/1 suggested by c a l c u l a t i o n s of Hem and Durum (1973). The maximum d i s s o l v e d Pb c o n c e n t r a t i o n of approximately 2.7 mg/1 was measured i n the e l u t r i a t e of the high organic sediment. Under q u i e s c e n t c o n d i t i o n s d i s s o l v e d Pb c o n c e n t r a t i o n s were lower probably because of poor contact between the a c i d i c o v e r l y i n g waters and the sediments. D i s c r e p a n c i e s between the t h e o r e t i c a l c a l c u l a t i o n s and the measured values may be accounted f o r by the presence of other s p e c i e s such as a c e t a t e i o n and n a t u r a l o r g a n i c compounds which were not taken i n t o c o n s i d e r -a t i o n by Hem and Durum (1973) i n t h e i r c a l c u l a t i o n s . Payne and P i c k e r i n g (1975) have shown t h a t the presence of o r g a n i c compounds may a f f e c t the a d s o r p t i o n / d e s o r p t i o n behavior of metal i o n s . A h i g h r e l e a s e of t r a c e metals at as low a pH as 5 i s a common o b s e r v a t i o n and a r e a d i l y acceptable r e s u l t , whereas a h i g h r e l e a s e at pH 10 i s a somewhat unexpected o b s e r v a t i o n , although s i m i l a r observations have been made elsewhere (MacPherson et a l . , 1958; Hakanson, 1974)• As d i s c u s s e d e a r l i e r f o r Cu and Fe, a high r e l e a s e of Pb and other t r a c e metals at pH 10 may be a t t r i b u t e d to d i s s o l u t i o n of h u m i c - l i k e substances c a r r y i n g the metal ions (Desai et a l . , 1972; Cooper and H a r r i s , 1974). A c o n s i d e r a b l e p o r t i o n of the t o t a l Pb i n the sediments was i n the organic and 154 sulphur phase (Tables IX and X ) . Both low pH (5) and h i g h pH (10) r e l e a s e of Pb from the W i l l i n g d o n sediment were c o n s i d e r a b l y g r e a t e r than r e l e a s e at n e u t r a l pH. This can be e a s i l y e x p l a i n e d by the d i f f e r e n c e s i n c o n c e n t r a t i o n s of Pb i n the geochemical f r a c t i o n s of the sediments (Tables IX and X). For s t a t i c column t e s t s the W i l l i n g d o n sediment c o n t a i n e d approximately 6 times more t o t a l Pb, 15 times more Pb i n EP and ERP ( r e a d i l y s o l u b l e at pH 5) and about 5 times more than i n OSP ( S o l u b l e a t pH 10) than Pb i n the c o r r e s p o n d i n g phases of the Gilmore sediment. These d i f f e r e n c e s f o r the e l u t r i a t e t e s t s , however, were c o n s i d e r a b l y l e s s (Table X). 4. Manganese (Mn) Manganese r e l e a s e d from sediments i n s t a t i c column t e s t s was not monitored. Release of t r a c e metals i n these t e s t s was g e n e r a l l y low: t h e r e f o r e , d e t e r m i n a t i o n of t h e i r c o n c e n t r a t i o n s by flame AA spectrophotometry r e q u i r e d p r e c o n c e n t r a t i o n by s o l v e n t e x t r a c t i o n . Trace metals Cu, Fe, Pb and Zn can be s i m u l t a n e o u s l y e x t r a c t e d but a separate e x t r a c t i o n run f o r Mn i s r e q u i r e d because of the poor s t a b i l i t y of i t s c h e l a t e complexes (McQuaker, 1976). To save time Mn was omitted from these t e s t s . The time saved was used to extend the scope of exchange s t u d i e s f o r Cu, Fe, Pb and Zn. The r e s u l t s f o r Fe from the s t a t i c column s t u d i e s may p r o v i d e some i n s i g h t s i n t o Mn behavior under s i m i l a r 155 c o n d i t i o n s . However, i n view of the l i t e r a t u r e d i s c u s s e d by-Hoffmann and E i s e n r e i c h (1981),one must use c a u t i o n i n p r o j e c t i n g r e s u l t s obtained f o r one of these elements to the o t h e r . Although r e a c t i o n s a f f e c t i n g the exchange of Fe and Mn from sediments to water are s i m i l a r i n nature, the v a r i a t i o n s a r i s e from d i f f e r e n c e s i n k i n e t i c s of the r e a c t i o n s and r e l a t i v e s t a b i l i t i e s of the r e a c t i o n products. In e l u t r i a t e t e s t s Mn was r e l e a s e d from both sediments and under o x i c and anoxic c o n d i t i o n s . The extent of r e l e a s e was independent of redox c o n d i t i o n s but i n c r e a s e d w i t h s a l i n i t y and became asymptotic above 4 °/oo. A l s o , r e l e a s e was s l i g h t l y g r e a t e r from the coarse, low o r g a n i c sediment. The d i f f e r e n c e i n r e l e a s e of Mn from the two sediments cannot be e x p l a i n e d by the geochemical v a r i a t i o n s between the sediments. Manganese i n a l l r e a d i l y a v a i l a b l e phases such as IW, EP, ERP e t c . i s lower i n the low o r g a n i c sediment (Table X). Although t o t a l Mn i s s l i g h t l y h igher i n low o r g a n i c sediment the d i f f e r e n c e does not seem to be s i g n i f i c a n t . The g r e a t e r r e l e a s e from the low organic sediment may be due to i t s coa r s e r p a r t i c l e s i z e and lower o r g a n i c content. S i m i l a r f i n d i n g s f o r Mn r e l e a s e have been made elsewhere. Chen et a l . (1976) s t u d i e d the r e l e a s e of Mn from sediments on suspension i n seawater.The r e s u l t s f o r a one-half hour suspension time i n d i c a t e t h a t Mn r e l e a s e was independent of redox c o n d i t i o n s and a sandy type sediment r e l e a s e d more 156 Mn than a c l a y e y type sediment. Lee et a l . (1975),in a study to a ssess the E l u t r i a t e Test f o r p r e d i c t i n g r e l e a s e of t r a c e metals d u r i n g dredging of contaminated sediments,noted t h a t r e l e a s e of Mn depended upon sediment type among other f a c t o r s but was independent of the t o t a l Mn l e v e l s i n the sediments. D e s o r p t i o n of Mn from sediments on suspension i n s a l t w a t e r has a l s o been i n v e s t i g a t e d by many others (Johnson et a l . , 1967; P i c e r et a l . , 1973; Wagemann, 1977), but these authors d i d not use the standard e l u t r i a t e procedure. R e s u l t s o f P i c e r et a l . (1973) and Evans et a l . (1977) are p a r t i c u l a r l y r e l e v a n t to t h i s study. P i c e r et a l . (1973) noted t h a t Mn was r e l e a s e d from limestone and a q u a t i c sediments on suspen-s i o n i n water as s a l i n i t y was in c r e a s e d from 0 - 1 8 °/oo ; above 18 °/oo the d i s t r i b u t i o n c o e f f i c i e n t of the metal between the s o l i d and aqueous phases remained c o n s t a n t . Evans et al."(1977) observed a s i m i l a r dependence on s a l i n i t y i n Newport River Estuary, North C a r o l i n a ; maximum l e v e l s of d i s s o l v e d Mn occurred between 4 and I4 °/oo s a l i n i t y . In t h i s study, the l e v e l s of Mn i n s o l u t i o n were much high e r than f o r other t r a c e metals with the e x c e p t i o n of Fe under anoxic and low pH c o n d i t i o n s . A r e c e n t review of the l i t e r a t u r e on p o t e n t i a l r e l e a s e of contaminants from sediments d u r i n g dredging and dredge d i s p o s a l o p e r a t i o n s concluded that Mn as w e l l as ammonia are the most r e a d i l y r e l e a s e d p o l l u t a n t s (Lee and M a r i a n i , 1977). Lee and M a r i a n i a l s o measured high r e l e a s e of Mn i n e l u t r i a t e t e s t s 157 on dredge m a t e r i a l s . For a sediment to water r a t i o of 5:1, a maximum Mn c o n c e n t r a t i o n of 6 mg/1 was measured. In v a r i a b l e pH e l u t r i a t e t e s t s a l a r g e Mn r e l e a s e was observed at pH 5 as was the case f o r Fe. Again t h i s was a t t r i b u t a b l e to s o l u t i o n of Mn oxides which u s u a l l y r e g u l a t e s o l u b i l i t y of Mn i n o x i c a q u a t i c systems. S u b s t a n t i a l amounts of Mn and Fe were leached with o r g a n i c a c i d s (pH 2, 4, 6) from rocks (Brockamp, 1976). At pH 5 a s l i g h t l y g r e a t e r r e l e a s e from the low organic sediment cannot be e x p l a i n e d by geochemical d i f f e r e n c e s ; t h e r e f o r e i t has to be a t t r i b u t e d to d i f f e r e n c e s i n p h y s i c a l c h a r a c t e r i s t i c s of the sediments. U n l i k e other t r a c e metals, minimum Mn r e l e a s e was measured at h i g h pH (10). T h i s i n d i c a t e s t h a t a s s o c i a -t i o n s of Mn with humic-like substances are weaker than f o r other t r a c e metals. This i s not s u r p r i s i n g s i n c e the geo-chemical d i s t r i b u t i o n of Mn (Table X) shows t h a t v e r y l i t t l e Mn i s bound to the OSP phase of the sediments. A l s o , data from S c h n i t z e r (1969) and I r v i n g and W i l l i a m s (1948) presented by Jones (1978) show t h a t the s t a b i l i t y of the 2 + Mn - F u l v i c a c i d complex ranked 11th among a dozen d i f f e r e n t m e t a l l i c i o n - f u l v i c a c i d complexes. The l o g a r i t h m s of the s t a b i l i t y constants of the f u l v i c a c id-metal complexes of 3 + s p e c i a l i n t e r e s t i n r e l a t i o n to t h i s study a r e : Fe = 9.4-0, C u 2 + =.8.69, P b 2 + = 6.13, F e 2 + = 5.77, Mn 2 + = 3.78, 2 + Zn =2.34, a l l a t pH = 5.0. A number of other authors 158 a l s o r e p o r t poor a s s o c i a t i o n of Mn with o r g a n i c s (Abdullah and Royale, 1972; Krom and S h o l k o v i t z , 1978; Moore e t a l . , 1979). Another, probably more l i k e l y , reason f o r the low v r e l e a s e of Mn at high pH (10) i s the o x i d a t i o n of any Mn(II) to ( h i g h l y i n s o l u b l e ) Mn(IV). The r a t e of o x i d a t i o n of M n ( l l ) i s h i g h l y dependent on c o n c e n t r a t i o n of hydroxide i o n (Stumm and Morgan, 1971). 5. Zinc (Zn) L i k e Pb, d i s s o l v e d Zn l e v e l s i n s t a t i c f r e s hwater o x i c and anoxic systems r a p i d l y dropped to e q u i l i b r i u m c o n c e n t r a t i o n s l e s s than 10 xxg/1. Durum et a l . ( 1 9 7 l ) a l s o r e p o r t e d Zn concentrations below 10 M.g/1, i n some U.S. r i v e r s . Chemical thermodynamic c a l c u l a t i o n s of Hem(l972), however, i n d i c a t e d c o n s i d e r a b l y higher l e v e l s of Zn. For example, i n pure water a t pH 8 the c a l c u l a t e d Zn c o n c e n t r a t i o n was 4OO jxg/1 and i n the presence of carbonate s p e c i e s (44O mg/l as CO^) the c o n c e n t r a t i o n was lowered to 25 Ag/1. The presence of s i l i c a t e ions was shown to f u r t h e r l i m i t the c o n c e n t r a t i o n of Zn by 1 to 2 orders of magnitude by form a t i o n of s p a r i n g l y s o l u b l e Zn^SiO^ ( w i l l e m i t e ) . At n a t u r a l l y o c c u r r i n g s i l i c a t e c o n c e n t r a t i o n s of about 6 mg/l, Zn c o n c e n t r a t i o n s of l e s s than 4O XLg/l may be a t t a i n e d . C o - p r e c i p i t a t i o n o f Zn with s i l i c a has been f u r t h e r i n v e s t i g a t e d by W i l l e y (1977). Hem (1972) a t t r i b u t e d low (undersaturated) measured c o n c e n t r a t i o n s of Zn and Cd i n r i v e r s to removal of metals from s o l u t i o n by such processes as a d s o r p t i o n . Means et a l . (1978) presented 159 i n f o r m a t i o n , which shows that oxides of Mn, Fe and o r g a n i c s may remove t r a c e metals from s o l u t i o n . O'Connor and Renn (1964.) showed t h a t the extent of a d s o r p t i o n of Zn may depend upon pH and the c o n c e n t r a t i o n of suspended sediments i n water. Freshwater sediments are b e l i e v e d to be e f f e c t i v e scavengers of t r a c e metals (Iskander and Keeney, 1974; Dreher et a l . , 1977; C h r i s t e n s e n and Chien, 1981). Z i n c adsorbed under freshwater c o n d i t i o n s may be desorbed under s a l i n e c o n d i t i o n s . A f t e r the f i r s t s a l i n i t y adjustment (14.5 °/oo) i n oxic s t a t i c column and under both , o x i c and anoxic c o n d i t i o n s i n e l u t r i a t e t e s t s , Zn was r e l e a s e d i n t o s o l u t i o n . S i m i l a r d e s o r p t i o n of t r a c e metals have been observed i n a number of other s t u d i e s ( B r a d f o r d , 1972; Troup and B r i c k e r , 1975; Thomas and G r i l l , 1977; Kharkar et a l . , 1968; Grieve and F l e t c h e r , 1977). Freshwater sediments e n t e r i n g a s a l i n e regime as i n an e s t u a r y are + 2 + 2 + exposed to c a t i o n s such as Na , Ca and Mg and anions C l ~ and OH" i n c o n c e n t r a t i o n s a thousand times or more those i n the f r e s h w a t e r s . Consequently, e q u i l i b r i u m between the d i s s o l v e d and adsorbed f r a c t i o n s of t r a c e metals i s upset 2+ 2+ and to a t t a i n a new e q u i l i b r i u m , Ca and Mg may r e p l a c e t r a c e metals i n sediments. F r e s h l y d i s l o d g e d metal ions may form c o o r d i n a t e complexes with abundant anions such as c h l o r i d e s and hydroxides (Stumm and Morgan, 1970). M C l ^ -and MCl^ ~ a r e the dominant c h l o r i d e complexes at c h l o r i d e c o n c e n t r a t i o n s of g r e a t e r than 3500 ppm (Hahne and K r o o n t j e , 160 1973); however, at the n e u t r a l and s l i g h t l y a l k a l i n e pH of a mixture of freshwater and seawater, M(0H) + c o u l d a l s o be important complexes because they g e n e r a l l y have h i g h e r f o r m a t i o n constants than the c h l o r i d e complexes (Long and Angino, 1977). Rohatgi and Chen (1975) a l s o observed the r e l e a s e of 60 percent of the Zn from Los Angeles R i v e r suspended sediments a f t e r r e a c h i n g e q u i l i b r i u m i n a 2:1 seawater-riverwater mixture. In another study a t a h i g h e r d i l u t i o n (10:1) the percent r e l e a s e was c o n s i d e r a b l y lower, 26 percent (Chen and Hendricks, 1974). These s t u d i e s c o n f i r m the importance of d e s o r p t i o n processes and c h l o r i d e complex form a t i o n i n r e g u l a t i n g the s o l u b i l i t y of some heavy metals under b r a c k i s h and marine water c o n d i t i o n s . In the anoxic s t a t i c columns, as i n the case of Pb, Zn was not r e l e a s e d i n t o s o l u t i o n under d i f f e r e n t s a l i n i t y regimes. I d e n t i c a l r e s u l t s were obtained by Lu and Chen (1977); under anoxic c o n d i t i o n s Zn c o n c e n t r a t i o n s remained i n the sub ppb range at the sediment-seawater i n t e r f a c e d u r i n g a 30 day p e r i o d f o r a l l three sediment types ( s i l t y -c l a y , s a n d y - s i l t , s i l t y - s a n d ) . The redox c o n d i t i o n s i n the water column were the c o n t r o l l i n g f a c t o r s f o r r e l e a s e and uptake of Zn. Under red u c i n g c o n d i t i o n s s u l p h i d e p r e c i p i -t a t e s r e g u l a t e the r e l e a s e of most heavy metals from sediments ( B e l l a , 1972; Holmes et a l . , 19745 Engler and P a t r i c k , 1975; Morel et a l . , 1975). Pohland et a l . (1981) recommend t h a t l a n d f i l l l e a c h a t e s should be pumped back i n t o anoxic l a y e r s 161 of l a n d f i l l t o remove t r a c e metals as s u l p h i d e p r e c i p i t a t e s . The r e l a t i v e l y h i g h c o n c e n t r a t i o n of Zn i n the OSP phase of the sediments r e f l e c t s the d e p o s i t i o n of Zn as sulphide under n a t u r a l c o n d i t i o n s . The anoxic c o n d i t i o n s i n e l u t r i a t e t e s t s f a i l e d to prevent r e l e a s e of Zn as occurred under s t a t i c c o n d i t i o n s due to i n s u f f i c i e n t time a v a i l a b l e f o r g e n e r a t i o n of reduced s u l p h i d e s p e c i e s . The a v a i l a b l e supply of s u l p h i d e s from the IW phase appears to have been p r e f e r e n t i a l l y p r e c i p i t a t e d with Cu and Pb which have lower su l p h i d e s o l u b i l i t y products of 8.5 x 1 0 " 4 5 and 3.4 x 1 0 ~ 2 8 as compared to 1.2 x 1 0 ~ 2 3 f o r Zn (CRC, 1971). In the v a r i a b l e pH systems, high c o n c e n t r a t i o n s of Zn were r e l e a s e d from the sediments at pH 5 and 10. As p r e v i o u s l y d i s c u s s e d , geochemical f r a c t i o n s EP and ERP are h i g h l y u n s t a b l e under low pH c o n d i t i o n s and hence are e a s i l y m o b i l i z e d i n t o s o l u t i o n under a c i d i c c o n d i t i o n s . S o l u b i l i t y curves presented by Hem (1972) show t h a t at pH 5 i n the absence of c o n t r o l s , Zn c o n c e n t r a t i o n may reach l e v e l s •> 1000 mg/1. The presence of v a r i o u s l i g a n d s , as i s o f t e n the case i n n a t u r a l systems, may l i m i t the c o n c e n t r a t i o n s to a c o n s i d e r a b l e e x t e n t . For example, i n the presence of 10 M c a r b o n i c s p e c i e s Zn s o l u b i l i t y i s reduced to 650 mg/1. The maximum measured c o n c e n t r a t i o n was 3.0 mg/l i n d i c a t i n g t h a t r e l e a s e was l i m i t e d by c o o r d i n a t e complexation with, v a r i o u s i n o r g a n i c l i g a n d s as d i s c u s s e d above. 162 Despite these c o n t r o l s , the measured c o n c e n t r a t i o n of Zn was s t i l l v e ry h i g h as compared to the commonly measured values i n n a t u r a l waters (Hem, 1972). High r e l e a s e of Zn at pH 5 was a l s o measured by P a t r i c k et a l . (1977). Data presented by these authors showed t h a t Mobile Bay sediments incubated at three pH values (5.0, 6.5 and 8.0) and f o u r redox p o t e n t i a l s (-150, +50, +250, +500 mV) r e l e a s e d maximum Zn c o n c e n t r a t i o n s a t pH 5 and a t redox p o t e n t i a l of +500 mV. T h i s confirms the r e s u l t s of the p r e s e n t study i n which o x i c c o n d i t i o n s at a pH of 5 had the h i g h e s t r e l e a s e . As f o r Cu, Pb and Fe, more Zn was measured i n s o l u t i o n a t pH 10 than a t the u n c o n t r o l l e d n e u t r a l pH(near 7 ) . The geochemical d i s t r i b u t i o n of Zn i n the sediments (Tables IX and X) shows t h a t s u b s t a n t i a l amounts of the metal were bound i n the OSP phase. According to the p r e v i o u s d i s c u s s i o n s on f u l v i c acid-metal s t a b i l i t y c onstants of the l a s t s e c t i o n ( f o r Mn), Zn i s expected to p o o r l y a s s o c i a t e w i t h the o r g a n i c s i n the sediments. However, the sediment o r g a n i c s are composed of a complex group of substances c a l l e d humic substances, and f u l v i c a c i d s c o n s t i t u t e only one component of t h i s group of substances. T h e r e f o r e , Zn a s s o c i a t i o n with the OSP phase , 163 as i n d i c a t e d by geochemical f r a c t i o n a t i o n , i s p o s s i b l e through bonding to c e r t a i n o r g a n i c compounds other than f u l v i c a c i d s . Sediment o r g a n i c s (humic substances) are known to p r e f e r e n t i a l l y d i s s o l v e at a l k a l i n e pH values (Cooper and H a r r i s , 1974)• Th e r e f o r e , i t i s l i k e l y t h a t the measured h i g h s o l u b i l i t y of Zn a t pH 10 was due to d i s s o l u t i o n of the sediment a s s o c i a t e d o r g a n i c complexes of the metal. Shapiro (1964) noted t h a t y e l l o w organic a c i d s s o l u b i l i z e d Zn at a l k a l i n e pH values where i t should p r e c i p i t a t e . Some of the high s o l u b i l i t y of Zn at pH 10 can be a t t r i b u t e d to i t s amphoteric nature. A c c o r d i n g to Hahne and Kroontje (1973) Zn, due to i t s amphoteric nature, can form s o l u b l e hydroxide complexes i n a l k a l i n e waters. Model c a l c u l a t i o n s by the authors i n d i c a t e d at pH 10, Zn(0H)2 ( n e g l e c t i n g water' molecules) has an i n t r i n s i c s o l u b i l i t y (molecular s o l u b i l i t y ) of 160 mg/l. However, the s o l u b i l i t y curves of Hem (1972) do not support t h i s concept because the maximum s o l u b i l i t y of Zn as i n d i c a t e d by the curves f o r pH 10 i s only 6.5 A g / l . T h e r e f o r e , i t i s not c l e a r to what extent the amphoteric nature of Zn could have c o n t r i b u t e d to the measured hi g h s o l u b i l i t y of the metal at pH 10. Both at pH 5 and pH 10 r e l e a s e of Zn was much gre a t e r from the high organic sediment. These d i f f e r e n c e s can be e x p l a i n e d by geochemical d i s t r i b u t i o n of Zn i n the r e l e v a n t phases of the two sediments. In s t a t i c t e s t s the EP and ERP phases,which r e a d i l y d i s s o l v e under a c i d i c c o n d i t i o n s , 164 had a wide d i f f e r e n c e i n Zn c o n c e n t r a t i o n s between the two sediments. The sum of Zn c o n c e n t r a t i o n s i n these two phases i n the h i g h organic sediment was almost 10 times g r e a t e r than the sum f o r the low organic sediment (Tables IX and X ) . In e l u t r i a t e t e s t s the sum of Zn l e v e l s i n EP and ERP phases i n the h i g h organic sediment was approximately 3«5 times the sum f o r the low organic sediment. Therefore, the higher r e l e a s e of Zn at pH 5 from the h i g h organic sediment was due to g r e a t e r a v a i l a b i l i t y of the metal from the h i g h o r g a n i c sediment. S i m i l a r l y , f o r the pH 10 t e s t s i t i s l i k e l y t h a t the g r e a t e r r e l e a s e of Zn from the high o r g a n i c sediment was due to there being more Zn i n the OSP phase of the high o r g a n i c sediment. C. P a r t i c u l a t e Trace Metal Exchange (pH E f f e c t s )  1. pH 5 P a r t i c u l a t e t r a c e metal l e v e l s g e n e r a l l y r e f l e c t e d the t u r b i d i t y l e v e l s thus i n d i c a t i n g that high p a r t i c u l a t e t r a c e metal l e v e l s were e i t h e r due to r e s u s p e n s i o n of bottom sediments or due to p r e c i p i t a t i o n of metals from s o l u t i o n . The i n i t i a l h igh c o n c e n t r a t i o n of p a r t i c u l a t e t r a c e metals were due to re-suspension of sediments during the setup of the c o l -umns. The l a t e r i n c r e a s e was r e l a t e d to f a i l u r e of pH (5) a c e t a t e b u f f e r , probably due to m i c r o b i a l breakdown of a c e t a t e i o n . In the high organic system the f a i l u r e s e t i n e a r l i e r because the column was resued a f t e r the low o r g a n i c sediment run. D e s p i t e a thorough clean u p , b a c t e r i a l contamination might have 165 remained, e s p e c i a l l y through the f r i t t e d g l a s s a e r a t i o n tube. As the pH rose due to f a i l u r e of the a c e t a t e b u f f e r , Cu and Pb were s u b s t a n t i a l l y removed from s o l u t i o n and r e l e a s e of Fe, and Zn appears to have been i n h i b i t e d . Smith (1973) has shown.that metal s o l u t i o n s may be u n s t a b l e even at pH values as low as 2. Sediments may readsorb e x t r a c t e d t r a c e metals under a c i d i c c o n d i t i o n s ; Cu and Pb a d s o r p t i o n has been shown to s t r o n g l y depend upon pH changes (Rendell et a l . , 1980). A c c o r d i n g to James and MacNaughton (1977), a d s o r p t i o n of metal ions occurs r a p i d l y over a narrow pH range which i s c h a r a c t e r i s t i c of the metal i o n s and t h e i r complexes. In the p r e s e n t study a s l i g h t i n c r e a s e i n pH (4.9->5.1) appeared to have c r e a t e d c o n d i t i o n s f a v o u r a b l e f o r r e a d s o r p t i o n of Cu and Pb. Iron a d s o r p t i o n s t a r t s a t pH 5.3 and Zn seems to be l e a s t a f f e c t e d w i t h i n the pH range of the experiments. The l o s s of Cu and Pb from s o l u t i o n was not completely r e f l e c t e d by a p a r a l l e l i n c r e a s e i n the suspended p a r t i c u l a t e t r a c e metal c o n c e n t r a t i o n s . This can be e x p l a i n e d by d e p o s i t i o n of t r a c e metals i n a s s o c i a t i o n with the s e t t l i n g p a r t i c u l a t e s . C o i n c i d e n t with the b u f f e r f a i l u r e (by b a c t e r i a l a c t i o n on a c e t a t e i o n ) , r u s t y c o l o r e d p a r t i c u -l a t e s formed i n the water column and some s e t t l e d to the s.ediment l a y e r . The b a c t e r i a a s s o c i a t e d with, the s e t t l i n g p a r t i c l e s probably p r o v i d e d an a d d i t i o n a l mechanism f o r Cu and Pb removal through a d s o r p t i o n on c e l l w a l l s . 166 P a r t i c u l a t e t r a c e metal l e v e l trends f o r both sediments were s i m i l a r except t h a t i n the hi g h o r g a n i c sediment, the in c r e a s e due to b u f f e r f a i l u r e o c c u r r e d e a r l i e r i n the run. 2. pH 7 In the pH 7 microcosms, p a r t i c u l a t e t r a c e metal l e v e l s were high i n i t i a l l y due to resuspension of sediments d u r i n g s e t up of columns. As the sediments d e p o s i t e d , p a r t i c u l a t e t r a c e metal l e v e l s remained low with the e x c e p t i o n o f some i n c r e a s e s which may be a t t r i b u t e d to res u s p e n s i o n of sediments or to a n a l y t i c a l contamination. P a r t i c u l a t e l e v e l s f o r the h i g h organic sediment were higher because i t contained h i g h e r l e v e l s of the metals. 3. pH 10 P a r t i c u l a t e t r a c e metal trends at pH 10 were s i m i l a r to those of the pH 7 experiments with two important d i f f e r e n c e s . F i r s t , p a r t i c u l a t e t r a c e metal l e v e l s dropped more s l o w l y , probably because the p a r t i c u l a t e s were s t a b i l i z e d by the o r g a n i c s r e l e a s e d under a l k a l i n e c o n d i t i o n s . Secondly, t r a c e metal l e v e l s were r e g u l a t e d by t r a c e metal-organic matter a s s o c i a t i o n s . For example, Fe and Pb are known to s t r o n g l y bind to organic humic matter; hence p a r t i c u l a t e l e v e l s f o r these metals were much higher than those f o r Zn. A l s o OSP l e v e l s of the metals i n the sediments seem to be r e f l e c t e d i n p a r t i c u l a t e t r a c e metals. R e s u l t s show t h a t Cu 167 p r e f e r e n t i a l l y binds to the d i s s o l v e d f r a c t i o n of organic humus. I I I . TRACE METAL EXCHANGE AT THE SEDIMENT-INVERTEBRATE INTERFACE The c o n c e n t r a t i o n s of a l l t r a c e metals were higher i n the h i g h o r g a n i c sediment. Copper, Pb and Zn a s s o c i a t e d with the OSP phase i n the high organic sediment were approximately as h i g h as the t o t a l metal l e v e l s i n the low organic sediment. Greater a s s o c i a t i o n with the OSP phase d i d not r e s u l t i n g r e a t e r accumulation of t r a c e metals i n the organisms a s s o c i a t e d with the high organic sediment. Copper i n the high organic sediment was almost three times the l e v e l found i n the low o r g a n i c sediment with two t h i r d s of i t bound to the OSP phase. However, chironomids accumulated higher l e v e l s of Cu from the low o r g a n i c sediment and there was very l i t t l e d i f f e r e n c e i n accumulation of Cu by amphipods or o l i g o c h a e t e s i n the two sediments. The r e f o r e , OSP-bound Cu does not appear r e a d i l y a v a i l a b l e to these i n v e r t e b r a t e s . Luoma and Jenne (1975a) found that 109 r a d i o a c t i v e cadmium, Cd, was not a v a i l a b l e to clams when i t was adsorbed to organic d e t r i t u s or Fe oxide coated with o r g a n i c s . S i m i l a r l y , Phelps (1979) observed that the Cd i s o t o p e bound to albumen was not taken up by the s o f t s h e l l clam, Mya a r e n a r i a , whereas the i s o t o p e adsorbed to bentonite c l a y was r e a d i l y absorbed. The low b i o a v a i l a b i l i t y of albumen-held Cd was a t t r i b u t e d to strong bonding between the 168 metal and the s u b s t r a t e . Bryan and Hummerstone (1977) i n a f i e l d survey noted t h a t Ag i n s u l p h i d e form from mining sources was not a v a i l a b l e to S c r o b i c u l a r i a plana, an e s t u a r i n e b i v a l v e m o l l u s c . Although the s i m i l a r i t y of b e h a v i o r of Cd and Ag to Cu as i n d i c a t e d i n these s t u d i e s may be o n l y c o i n c i d e n t a l , i t i s obvious t h a t the geochemical form of t r a c e metals i n s e d i -ments may determine accumulation. H a l l and B i n d r a (1979) i n a f i e l d study found t h a t Cu i n o l i g o c h a e t e s was r e l a t e d to concen-t r a t i o n s i n EP, ERP and OSP phases. In a d d i t i o n , Cu c o n c e n t r a -t i o n s i n the organisms depended upon the percentage of coarse sand (0.5 - 1 mm) i n the sediments. A h i g h percentage of s i l t and c l a y depressed Cu l e v e l s i n chironomids (Table 1 ) . S i m i l a r l y , i n the p r e s e n t l a b o r a t o r y study, p a r t i c l e s i z e seems to have p l a y e d an important r o l e . Luoma and Jenne (1976) a l s o found no c o r r e l a t i o n between t r a c e metal l e v e l s i n b i v a l v e s and metal c o n c e n t r a t i o n s i n the a c i d e x t r a c t a b l e and e a s i l y r e d u c i b l e f r a c t i o n s of the sediments. Uptake r a t e of sediment bound metals by i n v e r t e b r a t e s i s a l s o s p e c i es s p e c i f i c . Ray et a l . (1981) s t u d i e d the uptake of Cu, Pb and Zn from two contami-nated sediments by three i n v e r t e b r a t e s p e c i e s . The i n v e r t e -b r a t e s were exposed to the sediments f o r 30 day p e r i o d and metal c o n c e n t r a t i o n s i n the organisms were measured s e v e r a l times d u r i n g the 30 day p e r i o d . Crangon septemspinosa and Macoma b a l t h i c a accumulated Cu from both sediments but i n the t h i r d s p e c i e , Nereis v i r e n s , Cu l e v e l s at the end of 30 day p e r i o d dropped s l i g h t l y below the i n i t i a l l e v e l s . 169 The Fe l e v e l s were h i g h e r i n most organisms kept i n the low o r g a n i c sediment even.though i t had a s l i g h t l y -lower Fe c o n c e n t r a t i o n . However, there was f o u r times as much exchangeable (EP) Fe i n the low organic sediment which appears to be b i o l o g i c a l l y a v a i l a b l e . The higher l e v e l of d i s s o l v e d Fe i n the i n t e r s t i t i a l water (IW) of the h i g h o r g a n i c sediment d i d not a f f e c t accumulation i n d i c a t i n g t h a t d i r e c t a b s o r p t i o n of the d i s s o l v e d element was not o c c u r r i n g to any measurable extent. Removal of the exchangeable (EP) Fe from the sediment probably occurs by i n g e s t i o n and r e l e a s e i n the gut of the d e p o s i t f e e d e r s . Coarseness of the low organic sediment appears to be another f a c t o r f a v o r i n g g r e a t e r accumulation of Fe . Although t h i s c o n c l u s i o n i s not s t a t i s t i c a l l y sound (n=2) i t i s supported 2 by many (n=5) f i e l d data (Table I I ) . C h a r a c t e r i s t i c s of a d s o r p t i o n s i t e s on coarse sediments probably are such t h a t adsorbed Fe i s r e a d i l y a v a i l a b l e . In the present study, a l t h o u g h the uptake r a t e of Fe was high f o r the amphipods and chironomids, there was only a s m a l l i n c r e a s e i n t h e i r accumu-l a t i o n r a t i o d u r i n g the study p e r i o d , i n d i c a t i n g t h a t the organism can r e g u l a t e t i s s u e Fe l e v e l s to some extent. Higher Pb accumulation occurred i n amphipods and o l i g o c h a e t e s the high organic sediment microcosms. The l e v e l s 2. S i m i l a r l y , elsewhere i n t h i s t h e s i s c o n c l u s i o n s have been drawn from r e s u l t s f o r two sediments. R e p l i c a t i o n of experiments of t h i s study with a l a r g e number of sediment types would be d i f f i c u l t and very time consuming. 170 of Pb i n the EP, ERP and OSP phases of the high o r g a n i c s e d i -ment were 5 to 6 times the values i n the low o r g a n i c sediment, so i t i s d i f f i c u l t to r e l a t e accumulation to a s i n g l e geo-chemical f r a c t i o n . Previous r e s e a r c h i n d i c a t e d t h a t the best r e l a t i o n was between t o t a l Pb i n the sediment and accumulation f o r organisms c o l l e c t e d i n the f i e l d ( H a l l and B i n d r a , 1979). S i m i l a r r e l a t i o n s h i p s between Pb l e v e l s i n m a c r o i n v e r t e b r a t e s , A s e l l u s a q u a t i c u s L. and E r p o b d e l l a o c t o c u l a t a ( L ) , and t o t a l Pb l e v e l s i n the sediment s u b s t r a t e were found i n the R i v e r I r w e l l , U.K. (Eyres and Pugh-Thomas, 1978). Chapman et a l . (1980) a l s o observed t h a t i n the Fraser R i v e r e s t u a r y t o t a l Pb c o n c e n t r a t i o n s i n the sediments were r e f l e c t e d i n the o l i g o -chaetes. A l a b o r a t o r y uptake experiment s i m i l a r to the p r e s e n t study, i n d i c a t e d t h a t Pb accumulated by three s p e c i e s of marine i n v e r t e b r a t e s , over a 30 day p e r i o d , was g r e a t e r from a f i n e r sediment c o n t a i n i n g higher l e v e l s of t o t a l Pb (Ray et a l . , 1981). U n l i k e the p r e s e n t study, the f i n e r sediment contained lower c o n c e n t r a t i o n of o r g a n i c carbon; however, the d i f f e r e n c e i n percent o r g a n i c carbon between the two sediments was s m a l l . As i n the case of Cu, Pb uptake may be a f f e c t e d by Fe (Luoma and Bryan, 1978). S t a t i s t i c a l a n a l y s i s of f i e l d data obtained from 17 e s t u a r i e s i n England and France i n d i c a t e d t h a t the Pb/Fe r a t i o i n IN h y d r o c h l o r i c a c i d e x t r a c t s of s u r f a c e sediments i s r e l a t e d to the Pb l e v e l s i n the e s t u a r i n e b i v a l v e S c r o b i c u l a r i a p l a n a . In the present study, metals i n the non-residue f r a c t i o n s are approximately e q u i v a l e n t to metals 171 i n a IN h y d r o c h l o r i c a c i d e x t r a c t . This amounts to 2060 ppm Pb and 5500 ppm Fe f o r the low organic sediment and 987 ppm Pb and 7900 ppm Fe f o r the high organic sediment. T h e r e f o r e , the Pb/Fe r a t i o s are 0.0375 and 0.1249 f o r the low o r g a n i c and h i g h o r g a n i c sediments r e s p e c t i v e l y . This suggests t h a t Pb i n the h i g h o r g a n i c sediment could be 3 to 4 times more a v a i l a b l e than i n the low organic sediment. However, a number of other f a c t o r s such as p a r t i c l e s i z e , organic carbon and calcium carbonate l e v e l s may a l s o a f f e c t a v a i l a b i l i t y of t r a c e metals (Luoma and Bryan, 1978). Therefore, the Pb uptake by i n v e r t e -b r a t e s was not i n exact p r o p o r t i o n to the Pb/Fe r a t i o s (Table XIV). Manganese l e v e l s were higher i n a l l organisms from the microcosm c o n t a i n i n g the low organic sediment even though t h i s sediment contained 100 ppm l e s s of t o t a l Mn. No s p e c i f i c geochemical f r a c t i o n of Mn was at a much high e r l e v e l i n the low o r g a n i c sediments; t h e r e f o r e , the p h y s i c a l c h a r a c t e r ( f i n e r p a r t i c l e s i z e and higher organic l e v e l ) of the high o r g a n i c sediment p o s s i b l y makes the element l e s s a v a i l a b l e when the sediment i s i n g e s t e d . A f i e l d survey demonstrated a f a i r l y good r e l a t i o n s h i p between the ERP phase (Mn bound as oxides and carbonates) and bioaccumulation r a t i o s i n chironomids and o l i g o c h a e t e s ( F i g u r e 1, adapted from B i n d r a and H a l l , 1977). In t h i s l a b o r a t o r y study such a r e l a t i o n s h i p was not observed. A number of s t u d i e s (Packer e t a l . , 1980; 172 Bryan and Hummerstone, 1973; I r e l a n d , 1979) i n d i c a t e t h a t Mn l e v e l s are r e g u l a t e d by organisms. The f i n e p a r t i c l e s i z e and high organic content of the high o r g a n i c sediment probably a l s o i n h i b i t e d organism uptake of Mn (Table IV, data from Bindra and H a l l , 1977). Even though there was f i v e times the l e v e l of t o t a l Zn i n the hig h o r g a n i c sediment as w e l l as h i g h e r l e v e l s i n the c h e m i c a l l y more a v a i l a b l e phases (EP, ERP and OSP), there was a much l a r g e r change i n the b i o a c c u m u l a t i o n r a t i o i n the low org a n i c sediment,although the a c t u a l f i n a l c o n c e n t r a t i o n i n the organisms was very s i m i l a r to both sediments. H a l l and Bindra's (1979) study i n d i c a t e d t h a t Zn i n o l i g o c h a e t e s and chironomids i s n e g a t i v e l y r e l a t e d to Fe i n the EAEP phase of the sediments. The h i g h o r g a n i c sediment contained approximately 1.5 times more EAEP Fe than the low organic sediment, t h e r e f o r e , a v a i l a b i l i t y of Zn i n the high organic sediment could be suppressed by the h i g h e r Fe l e v e l s . In a l a b o r a t o r y study (Romeril, 1974-) s i m i l a r to the present one ,where uptake of ^ Z n from sediments to two s p e c i e s of o y s t e r s , C r o s s o s t r e a a n g u l a t a and Ostrea  edulus, was i n v e s t i g a t e d over a s i x week period, i t was demonstrated t h a t Co and Fe co u l d i n h i b i t the b i o l o g i c a l uptake r a t e of Zn. The l i m i t i n g e f f e c t of Fe and Co on uptake of Zn was a t t r i b u t e d to competition f o r s i t e s a t the p o i n t of uptake. Luoma and Bryan (1978) i n a f i e l d i n v e s t i g a t i o n noted t h a t a v a i l a b i l i t y of Zn i n a q u a t i c 173 sediments to two b i v a l v e s , Macoma b a l t h i c a and S c r o b i c u l a r i a  p l a n a , was n e g a t i v e l y a f f e c t e d by the t o t a l organic carbon content of the sediments. Ray et a l . (1981) observed t h a t uptake r a t e of Zn and some other t r a c e metals i n sediments was r e l a t e d to metal l e v e l s i n EDTA e x t r a c t of sediments (adsorbed, p r e c i p i t a t e d and complexed phases). In a d d i t i o n to the geochemical form of the t r a c e metal, i n t e r - e l e m e n t a l i n t e r a c t i o n s , and the p h y s i c a l chemical p r o p e r t i e s of the sediment , there are other important f a c t o r s which may r e g u l a t e the l e v e l s o f t r a c e metals i n an organism and i t s a b i l i t y to m o b i l i z e and e x c r e t e the element from t i s s u e . P o s s i b l y those organisms l i v i n g under hi g h t r a c e metal s t r e s s are induced to develop a more e f f i c i e n t system to e l i m i n a t e t r a c e metals. Eyres and Pugh-Thomas (1978) i n v e s t i g a t e d accumulation of Cu, Pb and Zn by a-freshwater lou s e ( A s e l l u s aquaticus L.) and a l e a c h ( E r p o b d e l l a o c t o c u l a t a L.) , and found lower l e v e l s of Cu and Zn i n organisms l i v i n g under higher environmental c o n c e n t r a t i o n s . They suggested a p o s s i b l e mechanism f o r e x c r e t i o n d e v e l o p i n g at hig h c o n c e n t r a t i o n s . Bryan (1976) a l s o r e p o r t e d that some s p e c i e s were able to excrete a h i g h e r p r o p o r t i o n of the t r a c e metal i n t a k e under contaminated c o n d i t i o n s and thereby r e g u l a t e the c o n c e n t r a t i o n i n the body a t a f a i r l y normal l e v e l . Recent r e s e a r c h (Brown, 1978) has shown t h a t a q u a t i c organisms l i v i n g under t r a c e metal s t r e s s can induce s y n t h e s i s of a t r a c e metal b i n d i n g p r o t e i n , 174 m e t a l l o t h i o n e i n , which may a i d i n e x c r e t i o n of t r a c e metals. I t appears t h a t some mechanism was working f o r the o l i g o c h a e t e s i n t h i s study s i n c e c o n c e n t r a t i o n s of a l l f i v e t r a c e metals decreased a f t e r one week, i n c r e a s e d to a peak value a t f o u r weeks and then showed a decrease d u r i n g the f i n a l week of the microcosm. A l s o , the f a c t t h a t some organisms showed lower l e v e l s of t r a c e metals when incubated i n the sediments w i t h higher t r a c e metals i n the more c h e m i c a l l y , and p o s s i b l y b i o l o g i c a l l y , a v a i l a b l e phases suggests p o s s i b l e i n d u c t i o n of some m o b i l i z a t i o n mechanism. S t i c k n e y et a l . (1975). however, b e l i e v e t h a t i f t r a c e metals reach a c e r t a i n h i g h l e v e l , homeostatic t r a c e metal e l i m i n a t i o n mechanisms may be overcome. The decrease i n the Fe and Mn c o n c e n t r a t i o n s i n the o l i g o c h a e t e s a f t e r one week from the time of t r a n s f e r to microcosms appears to have occurred at l e a s t p a r t l y due to t r a n s f e r to an environment r e l a t i v e l y l e s s p o l l u t e d w i t h Fe and Mn. Ladner Sidechannel sediments, from which the o l i g o -chaetes were c o l l e c t e d f o r microcosm s t u d i e s c o n t a i n e d twice as much Fe as i n the microcosm sediments. S i m i l a r l y Mn was hi g h e r i n the Ladner Sidechannel sediments than i n the micro-cosm sediments (Table X I I ) , but the d i f f e r e n c e was.mo-t-quite as l a r g e as f o r Fe. The exposure of o l i g o c h a e t e s to lower Fe and Mn c o n c e n t r a t i o n s i n the microcosms probably r e s u l t e d i n l o s s of these metals. The much higher l e v e l s of r e a d i l y a v a i l -a b l e EP phase Fe and Mn i n the microcosm sediments (Table X) prob a b l y r e s u l t e d i n subsequent i n c r e a s e i n the organisms. 175 M i c r o b i a l p o p u l a t i o n s i n a q u a t i c sediments may a l s o a f f e c t uptake r a t e s of metals by be n t h i c i n v e r t e b r a t e s ( P a t r i c k and L o u t i t , 1976). C a r t e r (1976) i n a study of uptake r a t e s ^ S r and ^"^Cs by o r i b a t i d mites collembolans Q C from s o i l and l i t t e r , n o t e d t h a t Sr body burdens of the mite over a 60 day p e r i o d depended on the i s o t o p e l e v e l s i n f u n g a l mycelia growing on contaminated l i t t e r . Geesey (1980) i n v e s t i g a t e d the d i s t r i b u t i o n of b a c t e r i a l p o p u l a t i o n s i n sediments and a s s o c i a t e d i n t e r s t i t i a l waters i n two watersheds of the Lower Mainland of B r i t i s h Columbia. He noted t h a t o n l y a small f r a c t i o n of the b a c t e r i a e x i s t e d as f r e e f l o a t i n g c e l l s and the m a j o r i t y was attached to f i b r o u s m a t e r i a l i n the sediments. P r e f e r e n t i a l i n g e s t i o n of f i b r o u s matter or e x c l u s i o n could a f f e c t metal uptake r a t e s by the i n v e r t e b r a t e s . In the present study although b a c t e r i a l p o p u l a t i o n dynamics were not monitored, i t i s p o s s i b l e t h a t the observed uptake or l o s s of metals by the amphipods r e f l e c t e d the accumulation or l o s s of metals from the s e d i -ments by microorganisms growing on the algae i n t r o d u c e d to the microcosms as food f o r the amphipods. From t h i s d i s c u s s i o n i t i s obvious t h a t the t r a c e metal uptake or l o s s processes are q u i t e complex and a number of f a c t o r s such as t r a c e metal geochemistry, sediment charac-t e r i s t i c s and b i o l o g y of the organisms can i n f l u e n c e the exchange r a t e s . A l a r g e v a r i a t i o n i n the t r a c e metal uptake r a t e s f o r d i f f e r e n t time i n t e r v a l s of the microcosm p e r i o d probably r e s u l t e d from d i f f e r e n t f a c t o r s g a i n i n g c o n t r o l of the exchange processes at d i f f e r e n t times. 176 Chapter 5 SUMMARY AND SIGNIFICANCE OF RESULTS AND RECOMMENDATIONS FOR FUTURE RESEARCH I. SUMMARY The r e s u l t s of t h i s l a b o r a t o r y study encompass a wide range of t r a c e metal i n t e r a c t i o n s which have s i g n i f i c a n t management i m p l i c a t i o n s i n the a q u a t i c e n v i r o n -ment. M o b i l i z a t i o n of t r a c e metals i n sediments to both water and bent h i c i n v e r t e b r a t e s was i n v e s t i g a t e d . The r e s u l t s of m o b i l i z a t i o n of t r a c e metals have been d i s c u s s e d w i t h r e f e r e n c e to tr a c e metal geochemistry i n sediments and sediment c h a r a c t e r i s t i c s such as organic matter content 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 . Experimental c o n d i t i o n s were kept as c l o s e as p r a c t i c a l l y p o s s i b l e to n a t u r a l l y o c c u r r i n g c o n d i t i o n s . Under 'normal pH' 1 and both oxic and anoxic 2 c o n d i t i o n s through v a r y i n g s a l i n i t i e s t r e l e a s e of the t o x i c t r a c e metals Cu and Pb from contaminated sediments was not e x c e s s i v e . Under the same c o n d i t i o n s , however, a s i g n i f i c a n t r e l e a s e of Zn was observed. P h y s i c a l c h a r a c t e r of sediments ( o r g a n i c matter 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 ) determined 1. 2. Between pH 6.5 and 8. For d e f i n i t i o n of 'o x i c ' and 'anoxic' c o n d i t i o n s see foo t n o t e on p. 89-177 the r e l e a s e p a t t e r n under the normal pH c o n d i t i o n s . Under some extreme environmental c o n d i t i o n s , however, very h i g h c o n c e n t r a t i o n s of t r a c e metals were measured. G e n e r a l l y , a h i g h r e l e a s e of a l l metals was observed at low pH (5) and h i g h pH (10). I r o n and Mn were s u b s t a n t i a l l y r e l e a s e d from contaminated sediments under anoxic c o n d i t i o n s . A g i t a t i o n of sediments i n a s a l i n e environment r e s u l t e d i n a very h i g h r e l e a s e of Mn under both o x i c and anoxic c o n d i t i o n s and the r e l e a s e was independent of s a l i n i t y above 8 °/oo. In microcosms, the concentrations of t o t a l t r a c e metals i n sediments provided an i n d i c a t i o n of the p o t e n t i a l f o r exchange wi t h be n t h i c i n v e r t e b r a t e s . The geochemical d i s t r i b u t i o n of the t r a c e metals as w e l l as the p h y s i c a l c h a r a c t e r of the sediments i n f l u e n c e d b i o a v a i l a b i l i t y . However, p o s s i b l e development of e x c r e t i o n mechanisms under h i g h t r a c e metal s t r e s s complicates i n t e r p r e t a t i o n of data on exchange mechanisms. More s p e c i f i c f i n d i n g s f o r exchange acr o s s the sediment-water and sediment-biota i n t e r f a c e s are o u t l i n e d below. A. Trace Metal Exchange at the Sediment-Water  I n t e r f a c e ( l ) Under o x i c freshwater c o n d i t i o n s i n the s t a t i c column t e s t s e q u i l i b r i u m concentrations of the more t o x i c t r a c e metals (Cu, Pb and Zn) were l e s s than 10 j W g / l f w i t h Fe c o n c e n t r a t i o n s l e s s than 100 pig/1 ,even with t o t a l c o n c e n t r a -178 t i o n s i n the sediments of s e v e r a l hundred ppm. There was no r e l a t i o n s h i p between the l e v e l of sediment contamination and exchange of t r a c e metals i n t o the water. Often the high o r g a n i c sediment with higher l e v e l s of t r a c e metals r e l e a s e d l e s s metal i n t o s o l u t i o n . The high organic content, f i n e p a r t i c l e s i z e and high Fe and Mn l e v e l s appear to have l i m i t e d r e l e a s e of t o x i c t r a c e metals. (2) I n i t i a l set up of columns r e s u l t e d i n a r e l e a s e of d i s s o l v e d t r a c e metals which i s i n agreement with o b s e r v a t i o n s r e p o r t e d by ot h e r s . S o l u t i o n from resuspended sediment seems to be a common problem i n s e t t i n g up q u i e s c e n t columns even though extreme care i s e x e r c i s e d . (3) U n l i k e quiescent column t e s t s , e l u t r i a t e t e s t s do not r e p r e s e n t e q u i l i b r i u m exchange c o n d i t i o n s . Despite t h i s , the r a p i d e l u t r i a t e t e s t s confirmed many of the ob s e r v a t i o n s made d u r i n g the l o n g term quiescent s t u d i e s . (4) In the o x i c system at low s a l i n i t i e s some Cu and Pb and high e r l e v e l s of Zn were r e l e a s e d i n t o s o l u t i o n . T h i s was a p p a r e n t l y a t t r i b u t a b l e to d e s o r p t i o n from Fe and Mn oxides and/or formation of c h l o r i d e complexes. A g r e a t e r r e l e a s e of Cu from the high organic sediment was a t t r i b u t e d to break down of Cu c h e l a t e s under oxic c o n d i t i o n s . Higher c o n c e n t r a t i o n s of Zn were r e l e a s e d at low s a l i n i t i e s from the low o r g a n i c sediment,even though i t had a lower Zn content than the high organic sediment. Apparently organic matter h e l p s to bind Zn t i g h t l y i n the sediment and i n h i b i t s 179 i t s r e l e a s e by d e s o r p t i o n and complexation processes. The geochemical d i f f e r e n c e s between the two sediments were not s i g n i f i c a n t enough to account f o r v a r i a t i o n s i n t r a c e metal r e l e a s e . (5) Some Fe was r e l e a s e d from the low o r g a n i c -sandy sediment at very low s a l i n i t i e s (4- °/oo); however, a t s a l i n i t i e s above 10 °/oo,Fe was r e a d i l y removed from s o l u t i o n by f l o c c u l a t i o n p r o c e s s e s . Manganese was r e l e a s e d from sediments to a maximum c o n c e n t r a t i o n over a wide s a l i n i t y range (4-26 °/oo) and the r e l e a s e was s l i g h t l y g r e a t e r from the low org a n i c sediment. The d i f f e r e n c e i n Mn r e l e a s e between the two sediments c o u l d not be ex p l a i n e d by d i f f e r -ences i n geochemical d i s t r i b u t i o n of the metal. T h e r e f o r e , i t probably can be a t t r i b u t e d to d i f f e r e n c e s i n sediment p a r t i c l e s i z e . (6) Under anoxic c o n d i t i o n s , Fe and Mn were r e l e a s e d i n r e l a t i v e l y high c o n c e n t r a t i o n s . Apparently s u l p h i d e p r e c i p i t a t i o n c o n t r o l s the s o l u b i l i t y of Cu, Pb and Zn under r e d u c i n g c o n d i t i o n s . In the anoxic s t a t i c columns, Fe r e l e a s e was much h i g h e r from the low org a n i c sediment, again demonstrating the strong b i n d i n g c a p a c i t y of the organic matter and a g r e a t e r s u l p h i d e p r e c i p i t a t i o n . Sulphide p r e c i p i t a t i o n i n the h i g h organic sediment was apparent from the c h a r a c t e r i s t i c FeS black c o l o r a t i o n of the sur f a c e l a y e r . (7) Low (5) and hig h (10) pH r e s u l t e d i n a higher 180 r e l e a s e of a l l t r a c e metals than occurred at n e u t r a l pH. Release a t h i g h pH was a t t r i b u t a b l e to s o l u t i o n of o r g a n i c bound metals (a component of the OSP phase) and s t a b i l i z a t i o n of metal s p e c i e s i n s o l u t i o n by a s s o c i a t i o n with h u m i c - l i k e substances. T h i s mechanism of t r a c e metal r e l e a s e a p p a r e n t l y overwhelmed the p r e c i p i t a t i o n mechanisms o p e r a t i n g under a l k a l i n e c o n d i t i o n s . For Zn, a p a r t of the high s o l u b i l i t y at h i g h pH probably was due to i t s amphoteric n a t u r e . Trace metal r e l e a s e at low pH was a t t r i b u t a b l e to d i s s o l u t i o n of Fe and Mn oxides and t h e i r a s s o c i a t e d t r a c e metals (EP ( d e s o r p t i o n ) and ERP phases). However, i n more c a l c a r e o u s sediments, s o l u t i o n of carbonate p r e c i p i t a t e s and t h e i r a s s o c i a t e d t r a c e metals would a l s o occur. B. Trace Metal Exchange at the Sediment-Invertebrate  I n t e r f a c e (1) Opossum shrimp were most s u s c e p t i b l e to the t o x i c i t y of the contaminated sediments; i n the more contaminated high organic sediment, m o r t a l i t y was 100 percent w i t h i n one week. (2) Chironomids showed the h i g h e s t uptake of a l l t r a c e metals over the study p e r i o d . Change i n b i o c o n c e n t r a t i o n r a t i o i n the low organic sediment was i n the range of +0.11 to +0.73 and f o r the high organic sediment the change was between +0.06 and +0.10. Thus f o r chironomids, h i g h o r g a n i c content of sediments appeared to suppress 181 uptake of a l l f i v e t r a c e metals. (3) R e s u l t s f o r o l i g o c h a e t e s were highly-v a r i a b l e , thus suggesting t h a t these organisms had a s i g n i f i c a n t c a p a c i t y to both m o b i l i z e and e x c r e t e t r a c e metals from t h e i r t i s s u e s . (4.) In amphipods, accumulation of Fe and Mn appeared to have r e s u l t e d from consumption of the algae Enteromorpha which was p r o v i d e d as food to t h i s organism. (5) High Cu l e v e l s i n sediment, e s p e c i a l l y when a s s o c i a t e d with the OSP component, are not r e a d i l y a v a i l a b l e to benthic organisms. Sediment p a r t i c l e s i z e appears to have played an important r o l e i n determining degree of Cu uptake by the organisms. (6) Iron and Mn accumulated to higher l e v e l s i n i n v e r t e b r a t e s kept i n low o r g a n i c sediment c o n t a i n i n g lower l e v e l s of Fe and Mn. Iron i n the exchangeable phase of the low organic sediment probably was r e s p o n s i b l e f o r h i g h e r l e v e l s i n the organisms. P h y s i c a l c h a r a c t e r i s t i c s such as coarse p a r t i c l e s i z e and low o r g a n i c content could be other p o s s i b l e causes f o r high uptake from the low o r g a n i c sediment. The p h y s i c a l c h a r a c t e r i s t i c s were app a r e n t l y p a r t i c u l a r l y important f o r h i g h e r uptake of Mn from the low o r g a n i c sediment, there being no l a r g e d i f f e r e n c e i n the geochemical d i s t r i b u t i o n of Mn i n the two sediments. (7) Amphipods and chironomids appeared to be c o n t r o l l i n g t h e i r uptake of Fe. Although the uptake r a t e of 182 t h i s metal was h i g h f o r these organisms there was only a s m a l l i n c r e a s e i n bioaccumulation r a t i o , w h i c h i n d i c a t e s t h a t the organisms can r e g u l a t e t i s s u e Fe l e v e l s to some e x t e n t . (8) A g r e a t e r accumulation of Pb i n amphipods and o l i g o c h a e t e s occurred i n the high organic sediment c o n t a i n i n g h i g h e r l e v e l s of Pb i n EP, ERP and OSP phases. I t was d i f f i c u l t to a t t r i b u t e accumulation to a s i n g l e geochemical phase. (9) Z i n c l e v e l s were higher i n the organisms i n the low o r g a n i c sediment, as was the case f o r Cu, Mn and Fe, even though the low o r g a n i c sediment had t o t a l Zn l e v e l s o n e - f i f t h of those i n the h i g h organic sediment. The h i g h e r o r g a n i c matter and Fe l e v e l s i n the high o r g a n i c sediment probably i n h i b i t e d uptake of Zn. I I . SIGNIFICANCE OF RESULTS A. Impact Of Trace Metal Contaminated Bottom Sediments  on Water Q u a l i t y Disturbance of bottom sediments ( p a r t i c u l a r l y i n freshwater systems) even under normal pH (6.5-8) and o x i c c o n d i t i o n s may r e s u l t i n high concentrations of d i s s o l v e d t r a c e metals. F o r t u n a t e l y , the high c o n c e n t r a t i o n s o l u t i o n s of t r a c e metals under normal pH and oxic c o n d i t i o n s are u n s t a b l e and r a p i d l y drop to low e q u i l i b r i u m l e v e l s ( l e s s than 10 A g / l ) . T h e r e f o r e , dredging of c i t y water supply r e s e r v o i r s may be p e r m i t t e d without endangering h e a l t h of the c i t i z e n s i f moderately h i g h d i s s o l v e d oxygen c o n d i t i o n s can 183 be maintained at the same time. When such dredging o p e r a t i o n s must be c a r r i e d out under anoxic c o n d i t i o n s . w a t e r from the r e s e r v o i r must be t r e a t e d f o r removal of Fe and Mn before d i s t r i b u t i o n f o r d r i n k i n g . Lower d i s s o l v e d t r a c e metal l e v e l s may be expected f o r waters u n d e r l a i n by o r g a n i c matter-r i c h f i n e sediments as compared to waters s t a n d i n g above coarse, low organic sediments with s i m i l a r l e v e l s of t r a c e metal contamination. In e s t u a r i e s under normal pH and o x i c c o n d i t i o n s , co n c e n t r a t i o n s of d i s s o l v e d Cu and Pb i n water o v e r l y i n g contaminated sediments would not become high enough to have an a c u t e l y t o x i c e f f e c t upon most a q u a t i c l i f e . The c o n c e n t r a t i o n of Zn under changing s a l i n i t y c o n d i t i o n s , however, may reach l e v e l s of some environmental concern. S p e c i a l care must be e x e r c i s e d when dredging contaminated sediments from e s t u a r i e s or harbours because a g i t a t i o n of sediments i n s a l i n e waters r e s u l t s i n e l e v a t e d c o n c e n t r a t i o n s of Mn and Zn i n the water column. In e l u t r i a t e t e s t s with seawater , Mn conc e n t r a t i o n s up to 2 mg/1 were measured. Such high c o n c e n t r a t i o n s of Mn c o u l d a d v e r s e l y a f f e c t some forms of a q u a t i c l i f e . Under the v a r i a b l e pH and o x i c c o n d i t i o n s a great e r r e l e a s e of d i s s o l v e d metals o c c u r r e d . The h i g h e s t values f o r a l l t r a c e metals o c c u r r e d at pH 5 f o r the hig h organic sediment. D i s s o l v e d l e v e l s of Cu, Fe, Pb and Zn reached values higher than 100, 10,000 , 1,000 and 1,000 /tg/1 184 r e s p e c t i v e l y i n the " s t a t i c " columns. S i m i l a r c o n c e n t r a t i o n s of these t r a c e metals may be expected to occur i n a system such as a l a k e , provided the l a k e sediments are s i m i l a r to those used i n t h i s study and p r o v i d e d there i s no renewal of the water column. These c o n c e n t r a t i o n s could have some adverse e f f e c t s on a q u a t i c b i o t a even with l i m i t e d exposure. However, . these extremely a c i d i c c o n d i t i o n s are o r d i n a r i l y not very l i k e l y to occur. But energy shortages i n the r e c e n t years are f o r c i n g the use of c o a l h i g h i n sulphur and n i t r o g e n elements which r e s u l t s i n emissions of l a r g e amounts of a c i d gases l i k e SC^ and NOg which wash out from the atmosphere as a c i d r a i n . To make things worse, i n s t a l l a t i o n of d e v i c e s by i n d u s t r i e s f o r recovery of a c i d gases has become cost p r o h i b i t i v e under the adverse economic c o n d i t i o n s . As a r e s u l t , the p r o b a b i l i t y of r e a c h i n g very low pH values i n l a k e s and s o i l s has i n c r e a s e d g r e a t l y . Hence the p o t e n t i a l of exposure of organisms and p l a n t s i n the a q u a t i c environment and crops i n the s o i l s to t r a c e metal contamination has c o n s i d e r a b l y i n c r e a s e d l a t e l y . The C o a s t a l Mountain areas of B r i t i s h Columbia, Nova S c o t i a and the Canadian S h i e l d of Ontario and Quebec, where a l k a l i n i t y i s too low to c o u n t e r a c t a c i d r a i n are more s e n s i t i v e areas i n Canada. A c c i d e n t a l a c i d s p i l l s may occur anywhere and thus r e l e a s e h i g h l e v e l s of t o x i c t r a c e metals. Release of high l e v e l s of t r a c e metals from contaminated sediments i s a l s o p o s s i b l e i f a l k a l i n e m a t e r i a l s l i k e NaOH or KOH are a c c i d e n t l y s p i l l e d i n t o n a t u r a l waters. 185 Trace metal r e l e a s e was high both a t very low (5) and very h i g h pH (10) c o n d i t i o n s . The p o t e n t i a l of t r a c e metal r e l e a s e a t high pH (10) i s g r e a t e r where sediments are r i c h i n o r g a n i c s . However, the p o t e n t i a l of n a t u r a l l y o c c u r r i n g h i g h pH c o n d i t i o n s i s r e l a t i v e l y l e s s severe because i n d u s t r i a l emissions are g e n e r a l l y a c i d i c . A g i t a t i o n c o n d i t i o n s such as those i n l a b o r a t o r y e l u t r i a t e t e s t s r e s u l t i n the r e l e a s e of h i g h e r c o n c e n t r a t i o n s of d i s s o l v e d metals than occur under q u i e s c e n t c o n d i t i o n s . Manganese under both o x i c and anoxic c o n d i t i o n s and Fe under anoxic c o n d i t i o n s are r e l e a s e d i n c o n c e n t r a t i o n s w e l l above 1 000 jUg/1 and could be p o t e n t i a l l y t o x i c . However, i t r e q u i r e s extreme pH c o n d i t i o n s to cause s i g n i f i c a n t r e l e a s e of more t o x i c elements such as Pb and Zn. Probably the p h y s i c a l d i s t u r b a n c e with r e s u l t a n t sediment suspension and h i g h t u r b i d i t y would have more acute t o x i c impacts on a q u a t i c organisms than would the t r a c e metal l e v e l s . The impact of long term exposure to lower l e v e l s of d i s s o l v e d t o x i c metals such as those observed i n t h i s study should not be overlooked. Uptake of elements such as Pb ; with an extremely long b i o l o g i c a l h a l f - l i f e , and the accumula-t i o n of t r a c e metals by d i r e c t a d s o r p t i o n or food chain c o n c e n t r a t i o n processes provide a mechanism whereby even low l e v e l s can prove to be d e t r i m e n t a l i f exposure times are l o n g . 186 B. Impact of Trace Metal Contaminated Sediments on  Benthic I n v e r t e b r a t e s R e s u l t s of t h i s study i n d i c a t e t h a t contamination of bottom sediments can be d i s a s t r o u s to some benthic s p e c i e s l i k e the opossum shrimp. I t s s u r v i v a l time i n the more contaminated high o r g a n i c sediment was l e s s than one week. Some organisms l i k e chironomids c o n s t i t u t e a major food source f o r freshwater and e s t u a r i n e f i s h and can accumulate t o x i c t r a c e metals from contaminated sediment s u b s t r a t e s . In the process, t o x i c elements may be m o b i l i z e d d i r e c t l y from sediments to food chains l i n k e d to human a q u a t i c food sources. Salmon f i n g e r l i n g s , on the way to the sea, stop at r i v e r mouths where they a c t i v e l y feed upon amphipods. Amphipods,as i n d i c a t e d by the r e s u l t s of t h i s study,may accumulate h i g h l e v e l s of Fe and Mn. Although these metals are r e l a t i v e l y l e s s t o x i c , a t very high t i s s u e l e v e l s they may a f f e c t metabolism of consumer f i s h e s . F o r t u n a t e l y , the demonstrated a b i l i t y of amphipods to excrete t o x i c elements Cu, Pb and Zn may p r o t e c t f i s h e r i e s from becoming contami-nated and u n f i t f o r human consumption. Oligochaete worms are considered t o l e r a n t to metal p o l l u t i o n . The r e s u l t s of t h i s study show that the t o l e r a n c e probably i s a r e s u l t of t h e i r a b i l i t y to c o n t r o l l e v e l s of t r a c e metals i n t h e i r t i s s u e . 187 I I I . RECOMMENDATIONS FOR FUTURE STUDIES A. Exchange at the Sediment-Water I n t e r f a c e R e s u l t s of t h i s study show t h a t both very low (5) and ve r y h i g h (10) pH values promote r e l e a s e o f d i s s o l v e d t r a c e metals from sediments. Release a t i n t e r m e d i a t e pH valu e s (6, 8 and 9) should be i n v e s t i g a t e d to determine the s e n s i t i v i t y of r e l e a s e to pH changes near the n e u t r a l v a l u e . The e f f e c t of humic substances should a l s o be exam-in e d by adding v a r y i n g amounts of these m a t e r i a l s i s o l a t e d from o r g a n i c r i c h sediments to t e s t columns and e l u t r i a t e mixtures. At the end of these experiments t e s t water should be analyzed f o r bound (complexed) and f r e e ( i o n i c ) metal s p e c i e s to determine the mechanisms of r e l e a s e and the nature of the r e l e a s e d metal s p e c i e s . The e l u t r i a t e t e s t s have shown t h a t r e l e a s e of t r a c e metals i s more s e n s i t i v e to s a l i n i t y changes i n the 1 to 10 u / oo range. In columns s a l i n i t y was changed from zero to above 14. °/oo i n one step. Column t e s t s should be repeated at s a l i n i t i e s of 1, 2, 4 and 10 °/oo to determine the e f f e c t s of changing s a l i n i t y on metal exchange. The e f f e c t of sediment p a r t i c l e s i z e d i f f e r e n c e s on t r a c e metal r e l e a s e should be f u r t h e r i n v e s t i g a t e d , to confirm the r e s u l t s of t h i s study. In a d d i t i o n , not a l l combinations of v a r i o u s environmental f a c t o r s have been used i n t h i s i n v e s t i g a t i o n to determine t h e i r e f f e c t on t r a c e metal exchange. For 188 example, e f f e c t of v a r i o u s pH c o n d i t i o n s under anoxic c o n d i t i o n s (low redox p o t e n t i a l s ) has not been i n v e s t i g a t e d i n these experiments. Therefore, i t i s recommended t h a t these experiments be f u r t h e r extended to i n c l u d e a d d i t i o n a l p o s s i b l e environmental c o n d i t i o n s . A l s o , experiments should be c a r r i e d out to study t r a c e metal exchange a t the sediment-water i n t e r f a c e u s i n g v a r i o u s d i l u t i o n s of wastewater c o n t a i n i n g heavy metals such as e f f l u e n t from a p l a t i n g shop. The experiments should s i mulate d i f f e r e n t pH, oxygen and s a l i n i t y c o n d i t i o n s . F i n a l l y , s i n c e the e f f e c t of the geochemical form of t r a c e metals i n the presence of other v a r i a b l e s could not be s e l e c t i v e l y r e l a t e d to exchange r a t e s , model sediments c o n s i s t i n g of i n d i v i d u a l geochemical phases (EP, ERP, OSP etc.) should be used to study t r a c e metal exchange under d i f f e r e n t environmental c o n d i t i o n s . Although such experiments would be e n v i r o n m e n t a l l y u n r e a l i s t i c , the r e s u l t s could provide u s e f u l i n s i g h t s i n t o the e f f e c t of v a r y i n g geochemical form on t r a c e metal exchange i n r e a l s i t u a t i o n s . B. Exchange at the Sediment-Invertebrate I n t e r f a c e To develop a much b e t t e r understanding of the i n f l u e n c e of t r a c e metal geochemistry and sediment p h y s i c a l p r o p e r t i e s on accumulation, a much l a r g e r range of sediments must be su b j e c t e d to s i m i l a r uptake s t u d i e s . Two widely d i f f e r e n t sediments d i d not provide the range of 189 t r a c e metal geochemical d i s t r i b u t i o n needed. By t a k i n g a h i g h l y contaminated sediment and making a s e r i e s of d i l u t i o n s with c l e a n sand and f i n e o r g a n i c matter, such as peat or f i n e sawdust, the i n f l u e n c e of some i n d i v i d u a l p h y s i c a l f a c t o r s on accumulation could be documented. I f a complete range of t r a c e metals i n the geochemical f r a c t i o n s cannot be found a p o s s i b l e a l t e r n a t i v e would be to spike sediments w i t h d i f f e r e n t forms of t r a c e metals and be c e r t a i n they p a r t i t i o n i n t o the d e s i r e d chemical phase p r i o r to studying a ccumulation. Most benthic i n v e r t e b r a t e s graze on the microorganisms a s s o c i a t e d with d e t r i t u s p a r t i c l e s . T h e r e f o r e , f u t u r e t r a c e metal accumulation r e s e a r c h should i n v o l v e some measure of m i c r o b i a l a c t i v i t y or biomass throughout the study p e r i o d . Since m o b i l i z a t i o n and e x c r e t i o n of t r a c e metals can complicate i n t e r p r e t a t i o n of accumulation r e s u l t s , the measurement of m e t a l l o t h i o n e i n l e v e l s or other m o b i l i z a t i o n pathways i n organisms may provide an estimate of the p o t e n t i a l of organisms to e l i m i n a t e t r a c e metals and adapt to a contaminated sediment environment. Some of these recommendations would i n v o l v e an ex t e n s i v e microcosm system and n e c e s s i t a t e c o l l e c t i o n and s o r t i n g of l a r g e numbers or organisms. Therefore, i t would r e q u i r e a c o n s i d e r a b l e investment i n t e c h n i c a l a s s i s t a n c e . 190 REFERENCES Abdullah, M.I. and Royale, L.G.. (1972). Heavy metal content of some r i v e r s and l a k e s i n Wales. Nature 238, 329-330. A l l e r , R.C. and Cochran, J.K. (1976). 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In: Chemistry of Marine Sediments, T.F. Yen (ed. ) , Ann Arbor Science P u b l i s h e r s Inc., 173-180. 212 Walker, G.f Rainbow, P.S., F o s t e r , P. and H o l l a n d , D.L. (1975). Zinc phosphate granules i n t i s s u e surrounding the midgut of the barnacle, Balanus b a l a n o i d e s . Marine B i o l o g y 33, 161-166. Wat l i n g , H.R. and Watling, R.J. (1976). Trace metals i n o y s t e r s from Knysna E s t u a r y . Marine P o l l u t i o n B u l l e t i n 7 , 45. W i l l e y , J.D. (1977). C o p r e c i p i t a t i o n of z i n c with s i l i c a i n seawater and i n d i s t i l l e d water. Marine Chemistry 5. , 267-290. Windom, H.L. (1975). Environmental aspects of dredging i n the c o a s t a l zone. In: C r i t i c a l Reviews i n Environmental C o n t r o l , C P . Straube (ed.) 6, 91-109-Wolfberg,. A., Kahanovich, Y., Avron, M. and Nissenbaum, A. (1980). Movement of heavy metals i n t o a shallow a q u i f e r by leakage from sewage o x i d a t i o n ponds. Water Research I4, 675-679-Wood, J.H., Rasen, C.J. and Kennedy, S.F. (1968). S y n t h e s i s of methyl mercury compounds by e x t r a c t s of a methanogenic bacterium. Nature 220, 173-Z i r i n o , A. and Yamamoto, J . (1972). A pH dependent model f o r the chemical s p e c i a t i o n of copper, z i n c , cadmium and l e a d i n seawater. Limnology and Oceanography 17, 661-671. Z i t k o , V. and Carson, W.V. (1972). Release of heavy metals from sediments by n i t r i l o t r i a c e t i c a c i d (NTA), Chemosphere 3, 113-118. 213 APPENDICES Appendix A. Water Quality Conditions in Sediment Microcosms. Table Al. Water Quality in High Organic Sediment Microcosm Under Oxic Conditions F r e s h Water 50* Seawater 75% Seawater Seawater Parameter I n i t i a l P i n a l I n i t i a l F i n a l I n i t i a l F i n a l I n i t i a l F i n a l S a l i n i t y (o/oo) 0.0 0.0 - 14.1 20.8 20.8 29 .4 28.9 C o n d u c t i v i t y (uS/cm ) 226 - - 2 3 . 2 x l 0 3 3 4 . 2 x l 0 3 33.3x103 4 5 . 2 x l 0 3 44.5x10 PH 7.0 7.8 7.9 7.98 7.95 8.02 7.82 8.08 True C o l o r (mg/lPt) 40 20 10 10 5 7 0 -T u r b i d i t y (JTU) 7 17 10 .6 .65 .2 0.7 0.1 T o t a l S o l i d s 170 175 15287 15400 23900 24900 34400 34 300 D i s s o l v e d S o l i d s 131 168 15284 14900 - - - • -A l k a l i n i t y (mg/1 CaCO 3 ) 80 71 86 88 104 79 102 93 A c i d i t y (mg/1CaCOj) 15.4 4.0 7.5 - - - - - ' Hardness(mg/1 CaCOj) 77 80 2780 2650 4030 3920 5450 5400 C a l c i u m 27 27 249 184 276 240 356 -T o t a l I n o r g a n i c Carbon 16 14 18 16 19 16 23 -T o t a l O r g a n i c Carbon 9 12 10 6 23 22 24 C h l o r i d e 17.4 17.8 8309 7780 11500 11500 16300 16000 N i t r a t e - N 1.75 1. 3d 1.03 1.65 1.20 .95 0.88 0.42 S u l p h a t e 17 11 1030 1030 1580 1850 2750 2560 1 a l l v a l u e s i n mg/1 u n l e s s s t a t e d d i f f e r e n t l y . The v a l u e s a r e r e s u l t s of i n d i v i d u a l measurements. 1 T a b l e A Z . W a t e r Q u a l i t y i n H i g h O r g a n i c S e d i m e n t M i c r o c o s m U n d e r A n o x i c C o n d i t i o n s -P a r a m e t e r F r e s h W a t e r I n i t i a l F i n a l 5 0 * S e a w a t e r I n i t i a l F i n a l 75% S e a w a t e r I n i t i a l F i n a l S e a w a t e r I n i t i a l F i n a l S a l i n i t y ( o / o o ) 0 0 1 4 . 8 1 4 . 3 2 2 . 0 2 1 . 8 2 6 . 8 2 7 . 3 C o n d u c t i v i t y U S / c m ) 1 3 5 1 9 5 2 4 . 4 x l 03 2 3 . 9 x l 0 3 3 5 . 1 x l 0 3 3 3 . 0 x l 0 3 3 9 . 8 x l 03 4 1 . 8 x l 0 3 p H 6 . 7 1 7 . 6 0 7 . 7 2 7 . 9 2 7 . 8 8 8 . 3 3 7 . 9 0 8 . 8 8 T r u e C o l o r ( m g / l P t ) 20 20 10 15 7 5 2 -T u r b i d i t y ( J T U ) 14 0 . 8 0 . 8 2 . 2 2 . 5 j 1 . 0 1 . 5 0 . 6 T o t a l S o l i d s 1 6 3 129 1 6 5 0 0 1 6 9 0 0 - - - -D i s s o l v e d S o l i d s 137 128 1 5 8 0 0 - 2 5 9 0 0 2 2 6 0 0 2 8 9 0 0 3 0 5 0 0 A l k a l i n i t y ( m g / l C a C 0 3 ) 4 0 65 91 76 9 0 75 97 90 A c i d i t y ( m g / l C a C 0 3 ) I S - - - - - ~ ~ H a r d n e s s ( m g / l C a C 0 3 ) 60 66 2 8 0 0 2 7 5 0 4 2 0 0 4 2 0 0 5 1 5 0 4 9 0 0 C a l c i u m 22 - 192 196 276 - - -T o t a l I n o r g a n i c 9 12 16 16 19 1 8 . 5 24 - • C a r b o n T o t a l O r g a n i c C a r b o n 8 6 6 . 3 4 1 . 2 1 . 2 4 . 0 . C h l o r i d e 13 8 2 2 0 7 9 1 0 1 2 2 0 0 1 1 7 0 0 1 4 3 0 0 1 5 1 0 0 N i t r a t e - N 1 . 3 7 0 . 4 7 0 . 5 2 0 . 4 8 0 . 7 5 0 . 4 0 0 . 6 9 0 . 3 8 S u l p h a t e 17 15 1 0 6 0 1 2 4 0 1 8 8 0 1 8 7 0 2 4 0 0 2 4 8 0 1 . A l l v a l u e s i n m g / l u n l e s s s t a t e d d i f f e r e n t l y . T h e v a l u e s a r e r e s u l t s o f i n d i v i d u a l m e a s u r e m e n t s . T a b l e A 3 . W a t e r Q u a l i t y i n Low O r g a n i c S e d i m e n t M i c r o c o s m U n d e r O x i c C o n d i t i o n s F r e s h W a t e r 50% S e a w a t e r 75% S e a w a t e r S e a w a t e r P a r a m e t e r I n i t i a l F i n a l I n i t i a l F i n a l I n i t i a l F i n a l I n i t i a l F i n a l S a l i n i t y ( o / o o ) 0 0 - 1 4 . 7 2 2 . 4 2 1 . 9 2 9 . 4 2 8 . 9 C o n d u c t i v i t y ( « S / c m ) 1 5 0 - - 2 4 . 6 x l 0 3 3 5 . 2 x l 0 3 3 4 . 9 x l 0 3 4 5 . 2 x l 0 3 4 4 . 6 x l 0 3 P H 7 . 4 5 7 . 7 2 - 7 . 9 8 7 . 9 3 8 . 1 2 7 . 8 2 8 . 0 9 T r u e C o l o r ( m g / l P t ) 10 10 5 10 5 7 0 -T u r b i d i t y ( J T U ) 27 1 . 4 2 . 5 0 . 5 0 . 5 0 . 2 0 . 7 0 . 1 T o t a l S o l i d s 1 5 3 1 4 9 1 5 2 7 4 1 6 6 0 0 2 4 8 0 0 2 5 9 0 0 3 4 4 0 0 3 2 5 0 0 D i s s o l v e d S o l i d s 9 9 . 1 144 1 5 2 7 2 1 6 1 0 0 2 3 8 0 0 . - - -A l k a l i n i t y ( m g / l C a C 0 3 ) 6 0 48 75 6 5 91 75 1 0 2 92 A c i d i t y ( m g / l C a C O j ) 1 . 5 2 . 0 6 - - . - - -H a r d n e s s ( m g / l C a C 0 3 ) 45 4 3 2 ? 6 1 2 7 8 0 4 1 0 0 4 1 5 0 5 4 5 0 5 5 0 0 C a l c i u m 14 17 244 2 4 0 284 2 5 0 3 5 6 -T o t a l I n o r g a n i c C a r b o n 15 6 14 11 16 13 23 -T o t a l O r g a n i c C a r b o n 19 12 21 13 4 4 1 -C h l o r i d e 17 18 8 3 0 9 8 1 4 0 1 2 4 0 0 1 2 1 0 0 1 6 3 0 0 1 6 0 0 0 N i t r a t e - N 1 . 3 1 1 . 28 1 . 0 2 1 . 5 0 1 . 1 8 1 . 0 7 0 . 8 8 0 . 5 0 S u l p h a t e 14 9 1 0 7 0 1 0 8 0 1 6 3 0 1 9 0 0 2 7 5 0 2 5 2 0 1 a l l v a l u e s i n m g / l u n l e s s s t a t e d d i f f e r e n t l y . T h e v a l u o s a r e r e s u l t s o f i n d i v i d u a l m e a s u r e m e n t s . Table A4.Water Quality in Low Organic Sediment Microcosm Under Anoxic Conditions Fresh Water 501 Seawater 75% Seawater Seawater Parameter Before After Before After Before A f t e r Before After S a l i n i t y (o/oo) 0 0 14.3 14.6 21.5 21.4 26.8 26.9 Conductivity U S / c m ) : 149 167 24.7xl0 3 '23.9xl03 34 .9xl0 3 32 .6xl0 3 39.8xl0 3 41.4x10 pH 7.08 7.98 7.75 8.35 7.98 7.87 8.08 8.10 True Color (mg/1 f t ) 10 50 50 20 9 6 2 -Turbidity (JTU) 27 2.5 1.6 7.0 9.5 13 2.6 0.2 Total Solids 135 - 16100 17300 - - - -Dissolved Solids 87.2 10 7 15500 - 26500 22900 29400 28800 A l k a l i n i t y 38 (mg/1 CaC03) 58 96 61 82 72 97 94 Acidity (mg/1 CaCOj) 1.5 - - - ~ ~ Hardness 53 (mg/1 CaC0 3) Calcium 18 56 19 2780 196 2650 192 4000 272 4000 5100 4900 Total Inorganic 8 Carbon 9 17 10 17 17.5 24 -Total Organic Carbon 6 7 5 7 4 2.5 1.2 4.5 Chloride 12 - 7920 8060 11900 11700 14600 14900 Nitrate - N 1.58 0 . 6 7 0.75 0.63 0.75 0.65 .61 .56 Sulphate 12 10 1060 1240 1780 1420 2180 2580 3 1. A l l v a l u e s i n mg/1 u n l e s s s t a t e d d i f f e r e n t l y . T h e v a l u e s a r e r e s u l t s o f i n d i v i d u a l m e a s u r e m e n t s . Table A5. Water Quality in High Organic Sediment Microcosm at Dif f e r e n t pH's Parameter pH -I n i t i a l • 5 Final pH = I n i t i a l 7 Fin a l pH = I n i t i a l 10 F i n a l Conductivity (MS/CTH) 3680 3930 203 284 11100 10900 pH 4.90 5.08 7.25 8.2.3 9.99 9.75 True Color (mg/l Pt) 10 25 7 15 10 500 Turbidity (JTU) 4.7 18 3.6 12 72 1.3 Dissolved Solids 3330 3970 - - 9000 8430 A l k a l i n i t y (mg/l CaC03) 1250 1600 66 121 7900 7500 Ac i d i t y (mg/l CaCOj) 1620 1010 - - -Hardness (mg/l CaCOj) - - 76 120 - -Total Inorganic Carbon 0 - 15 .5 - 1100 -Total Organic Carbon 1670 1750 2 7.5 0 48.5 Chloride 13.8 15.6 8.3 15.6 11.7 16.7 Nitrate - N 6.16 4.97 1.55 1.67 11.9 15.5 Sulphate 19.2 - 16.3 5.7 -1. A l l values i n mg/l unless s t a t e d d i f f e r e n t l y . The values are r e s u l t s of oo i n d i v i d u a l measurements. Table A6. Water Quality i n Low Organic Sediment Microcosm at Different pH*s Parameter pH = I n i t i a l 5 Final pH = I n i t i a l 7 Fin a l pH = I n i t i a l 10 Final Conductivity (*s/cm) 3340 3080 142 125 12 x 10 3 10.6 : pH 4.93 5.54 6.90 7.90 10.0 10.0 True Color ( m g / i P t ) 20 20 20 20 20 450 Turbidity (JTU) 6 30 5 0.6 23 1.4 Dissolved Solids 4300 3180 - - 12000 8190 A l k a l i n i t y (mg/1 CaC0 3) 950 1300 40 41 7710 7350 Ac i d i t y (mg/1 CaCOj) 1430 324 • - - - -Hardness (mg/1 CaCO^) 50 - 50 48 28 -Calcium 16 - 16 - 3.2 -Total Inorganic Carbon 0 0 8 11 1120 -Total Organic Carbon 1500 1350 4 2 3.0 48 Chloride 7.5 9.7 9.0 8.3 7.5 13.1 Nitrate - N 5.3 3.2 1.45 1.18 11.8 15.0 Sulphate 15.2 16.8 13.5 12.7 - -T~. A l l values i n mg/1 unless s t a t e d d i f f e r e n t l y . The values are r e s u l t s of i n d i v i d u a l measurements. Appendix B. E f f e c t of pH on Trace Metal Exchange T a b i c H I . E f f e c t o f pi I 5 on T r a c e M e t a l Exchange i n Sediment TIME COPPER IRON LEAD ZINC TURBIDITY pl l ( d a y s ) D P D. P D P D P UIQI ORGANi: (WILLINGDON) 0 38 7 138 610 76 7 25 3 5 4 .90 1 110 153 lf.OOO 9240 1000 650 1030 189 110 5 .03 2 142 51 11700 4440 1000 276 1100 67 52 5 .03 3 158 9 7560 2370 950 72 1200 13 13 -4 150 3 5900 1420 840 42 1250 4 7 -5 158 3 5200 960 790 37 1300 4 6 4 . 9 7 0 146 2 5200 830 780 29 1320 3 - -7 142 2 5300 840 660 34 1350 2 9 5 .06 10 128 3 6600 1580 560 58 1470 13 17 5.10 13 - 4 - 3090 - 96 - 7 - - • 26 85 5 8960 12500 260 146 1780 86 57 5.50 63 2 2710 22500 530 48 2400 28 23 4 . 9 3 LOW ORGANIC (GILMORE) 1 33 28 173 1420 200 47 . 28 28 73 4 . 9 3 3 41 7 119 590 227 17 35 7 22 4 . 9 3 8 41 6 330 400 253 8 54 6 18 4 . 8 5 .12 44 4 1220 286 287 7 160 5 15 4 . 9 0 19 45 3 2500 380 303 8 228 4 10 5 .11 26 36 2 10000 538 254 13 380 1 9 5.17 31 32 4 11500 960 212 15 440 2 15 5 .29 34 30 4 8800 4000 140 86 460 3 19 5.40 36 27 4 6800 6010 - 103 490 3 24 5 .50 F o o t n o t e : D = D i s s o l v e d , P = P a r t i c u l a t e . A l l v a l u e s i n u g / 1 t o t a l Table H2 . Effects of neutral, pll (7) on Trace Metal Exchange in Sediment. TIME COPPER 1 IRON LEAD ZINC TURBIDITY pll (days) D P D P D P D P HIGH ORGAN I1 (WILLINGDON) 0 30 7 272 410 6 4 27 4 4 7.25 1 12 332 440 15500 48 1390 24 484 120 7.78 2 11 105 146 3260 27 471 16 180 59 -3 11 53 102 2110 16 308 13 87 34 -4 12 10 58 570 14 88 10 21 8 8.15 6 11 8 74 510 12 44 7 14 - -7 11 6 148 625 10 30 6 13 7 -10 11 3 - 694 7 18 5 10 8 8.00 13 9 2 196 715 2 11 3 7 8 7.96 26 6 2 85 1170 1 7 4 44 21 8.20 34 5 2 20 185 1 5 5 - 6 8.22 40 5 5 24 1310 1 12 3 - - -LOW ORGANIC (GILMORE) 0 24 11 152 470 7 19 34 9 - -1 9 84 320 5050 18 159 16 88 113 -• 3 9 17 160 810 9 38 5 19 29 7.73 8 8 7 138 182 9 13 6 10 13 7.76 12 8 4 138 270 8 10 5 7 8 -19 12 3 - 128 - 8 4 2 3 -28 9 <1 78 12 8 <1 4 1 .6 -31 10 <1 64 6 9 <! 4 <1 .3 7.82 34 9 <1 66 6 8 <1 4 <1 .3 7.90 36 9 <1 46 10 4 <1 2 <1 .5 7.90 Footnote : D = Dissolved, P = Particulate. A l l values in yg/1 total metal • Table B3. Effect of pll 10 on Trace Metal Exchange in Sediment. TIME COPPER IRON LEAD ZINC TURBIDITY pll (days) D P D P D P D P HIGH ORGANI : (WILLINGTON) 0 30 15 220 732 4 23 10 43 72 9.99 1 72 182 392 6860 773 945 16 343 120 9.92 2 68 1.47 262 6850 704 858 18 282 89 3 68 5.1 456 1600 272 426 16 82 35 4 52 35 448 1050 194 362 14 43 13 S 58 24 - 470 192 178 16 28 8 6 72 21 . 444 350 230 130 16 23 -7 78 20 484 310 240 120 16 20 5 10 82 20 •618 280 320 118 24 20 4 13 92 14 740 320 322 117 26 21 3 26 150 14 910 248 450 104 45 36 3 34 220 • 9 1.020 290 450 99 55 29 2 LOW ORGANIC (G1IMORE) 0 29 11 200 580 16 23 7 38 -1 60 57 240 4790 50 199 16 103 56 2 77 18 300 1330 52 70 14 39 25 5 80 11 400 847 52 35 15 26 14 8 82 7 400 585 43 30 21 15 5 12 84 6 416 428 60 27 12 13 4 19 102 5 452 340 60 24 - 7 3 28 89 2 440 187 62 17 13 5 2 31 88 2 510 .170 62 16 14 4 2 1 34 90 4 576 160 56 17 12 5 2 j 36 92 3 552 168 59 14 13 4 1 Footnote: D = Dissolved, P = Particulate. A l l values in ug/1 total metal. 224 Appendix C. Trace Metal L e v e l s i n Benthic I n v e r t e b r a t e s . Table CI : Trace Metal Levels i n Kenthic Invertebrates i n Laboratory Microcosms Organism Sampling Copper Iron Lead Manganese Zinc I n t e r v a l 1 r (days) H L H L H L H L H L Amph ipods 0 162 550 204 22. 8 83.1 s 7 142 140 1230 3280 200 182 72.8 109 115 111 14 158 153 3080 3890 214 150 119 159 119 105 28 180 168 4030 4900 222 122 366 561 135 100 Chironomids 0 23 5320 35 .4 92. 1 106 5 - 61.3 - 6280 - 143 - 275 - 123 9 51.5 - 5760 - 153 - 101 - 168 -18 - 66.1 - 7290 - 116 - 301 - 156 28 42.1 91.7 7420 7340 110 121 150 422 152 181 42 68.1 124 19,100 7470 286 159 266 368 211 199 01 igochaetes 0 26.7 7130 167 99 .3 147 7 24.5 15.4 1270 1280 132 30.9 37.8 50.9 153 130 14 34.3* 35.4 2225* 4440 248* 87.5 41.8* 113 162* 169 28 . 64.4 34. 5* 3130 5575* 447 122.5* 58.4 140* 233 196.5* 42 20. 5* 60.1* 809* 3655* 168* 100.2* 30.3* 83.3* 139* 136.5* Opossum 0 - 27.4 - 383 - < 7.8 - 43.8 • - 64.9 Shr imp 7 - 86.1. - 930 - 19.8 - 213 - 69.2 1. A l l values represent t o t a l metal i n ppm (mg/kg) dry weight of organisms. H = High organic sediment, L = Low organic sediment * Average values for two sets of organisms sieved from separate microcosm containers. K.S. B i n d r a LIST OF PUBLICATIONS M u e l l e r , J.C. and K.S. B i n d r a (1975). R o t a t i n g Disk Looks Promising f o r P l a n t Wastes. O i l and Gas J o u r n a l , 66-68 January 13. Keays, J.L., K.S. Bindra, P.F. McDowell and J.V. Hatton (1977) S i n g l e - P o i n t Procedure f o r P F I - M i l l E v a l u a t i o n of Softwood K r a f t Pulps. Tappi 60(6) 81-83. Bindra, K.S. and K.J. H a l l (1977). Geochemical P a r t i t i o n i n g of Trace Metals i n Sediments and F a c t o r s A f f e c t i n g Bioaccumulation i n Benthic Organisms. Report prepared f o r NRC, Ottawa ( c o n t r a c t #032-1082/60.73), 59 pp. Bindra, K.S. and K.J. H a l l (1978). Bioaccumulation of S e l e c t e d Trace Metals by Benthic I n v e r t e b r a t e s i n Laboratory B i o a s s a y s . Report prepared f o r NRC, Ottawa ( c o n t r a c t #032-1082/6073), 25 pp. B i n d r a , K.S. and K.J. H a l l (1979). E f f e c t of P h y s i c a l and Chemical F a c t o r s i n Water and Sediments on the Release of S e l e c t e d Trace M e t a l s . Report prepared f o r NRC, Ottawa ( c o n t r a c t #032-1082/6073), 54 pp. H a l l , K.J. and K.S. B i n d r a (1979). Geochemistry of S e l e c t e d Metals i n Sediments and F a c t o r s A f f e c t i n g Organism C o n c e n t r a t i o n s . A paper presented a t the I n t e r n a t i o n a l Conference on Management and C o n t r o l of Heavy Metals i n the Environment, I m p e r i a l C o l l e g e , London, Sept. 1979. 

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