UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

The voltammetric determination of copper and lead in seawater : applications to Indian Arm and Burrard… Erickson, Paul Eric 1973

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Notice for Google Chrome users:
If you are having trouble viewing or searching the PDF with Google Chrome, please download it here instead.

Item Metadata

Download

Media
831-UBC_1973_A6_7 E75_2.pdf [ 3.7MB ]
Metadata
JSON: 831-1.0060223.json
JSON-LD: 831-1.0060223-ld.json
RDF/XML (Pretty): 831-1.0060223-rdf.xml
RDF/JSON: 831-1.0060223-rdf.json
Turtle: 831-1.0060223-turtle.txt
N-Triples: 831-1.0060223-rdf-ntriples.txt
Original Record: 831-1.0060223-source.json
Full Text
831-1.0060223-fulltext.txt
Citation
831-1.0060223.ris

Full Text

THE VOLTAMMETRIC DETERMINATION OF COPPER AND LEAD IN SEAWATER: APPLICATIONS TO INDIAN ARM AND BURRARD INLET PAUL ERIC ERICKSON B.Sc, York Univ e r s i t y , 1970 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n the Department of Chemistry and the I n s t i t u t e of Oceanography We accept t h i s thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA May, 1973 In p r e s e n t i n g t h i s t h e s i s 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 a t the U n i v e r s i t y o f B r i t i s h Columbia, I agree t h a t the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and study. I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e copying o f t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the Head of my Department or by h i s r e p r e s e n t a t i v e s . I t i s understood t h a t c o p y i n g or p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be allowed without my w r i t t e n p e r m i s s i o n . Department of C-^uu,/s.j^y^_ d^C£^A^g^/^fL^^j, The U n i v e r s i t y o f B r i t i s h Columbia Vancouver 8, Canada Date J/U^JL • , ABSTRACT An anodic s t r i p p i n g voltammetric technique was de-veloped for the simultaneous determination of Cu and Pb in seawater. Mercuric ion added to the sample i s plated out with the metals of i n t e r e s t onto a highly polished glassy carbon electrode. The thin mercury films obtained by t h i s procedure gave excellent r e s o l u t i o n and s e n s i t i v i t y although a non-linear response resulted i n the case of Cu, presumably as a r e s u l t of saturation of the mercury, at concentrations i n excess of 4 yg/1. The technique was applied to a short term study of the d i s t r i b u t i o n of Cu and Pb i n Indian Arm and Burrard I n l e t . Large fluctuations i n the concentrations of both metals were observed during the sampling period, July to October, 1972. Although dissolved Pb concentrations were lower than might be expected near a large urban area, there was, nevertheless, an o v e r a l l enrichment of the subsurface waters of the i n l e t s r e l a t i v e to Georgia S t r a i t by as much as an order of magnitude. Dissolved Cu concentrations were not, however, s i g n i f i c a n t l y higher than those reported for other B.C. coastal waters. Although study of metal speciation by the method employed here was limited by the excess of mercuric ions added to the samples and interferences from surface i i i a c t i v e agents, evidence was o b t a i n e d i n d i c a t i n g t h a t a p o r t i o n of Cu i n some B r i t i s h Columbia c o a s t a l seawater samples i s complexed w i t h d i s s o l v e d o r g a n i c matter. The experimental c o n d i t i o n s i n d i c a t e t h a t these complexes are e i t h e r i n e r t t o d i s p l a c e m e n t by m e r c u r i c i o n s or have a h i g h degree of s p e c i f i c i t y f o r Cu. i v TABLE OF CONTENTS Page ABSTRACT i i LIST OF TABLES v i LIST OF FIGURES v i i ACKNOWLEDGEMENTS i x 1. INTRODUCTION . . . . . 1 2. ANODIC STRIPPING ANALYSIS OF COPPER AND LEAD IN SEAWATER USING A MERCURY PLATED GLASSY CARBON ELECTRODE . . . 5 2.1 Introduction to the Technique . . . . . . . 5 2.2 Description of the Method 10 2.3 Experimental 11 2.4 Pr e c i s i o n 29 2.5 Comparison of the Response with Theory 31 2.6 Multiple Peaks 38 3. THE DISTRIBUTION OF COPPER AND LEAD IN INDIAN ARM AND BURRARD INLET . . . . . . . . . . . . . 40 3.1 Introduction . . . . . . . . . 40 3.2 Sampling Procedures . 43 3.3 Storage Methods . . . . . 44 3.4 A n a l y t i c a l Methods . . . . . 46 3.5 Intercomparison of Techniques 46 3.6 Experimental Observations 49 3.7 Discussion 50 3.8 Summary • 62 V Page 4. APPLICATION OF THE MERCURY PLATED GLASSY CARBON ELECTRODE TO THE STUDY OF COMPLEXED METAL IN SEAWATER 64 4.1 Summary 73 BIBLIOGRAPHY 7 4 APPENDIX 78 v i LIST OF TABLES Table Page I. RELATIONSHIP BETWEEN i AND THE MERCURY CONCENTRATION 24 I I . PRECISION OF Cu AND Pb DETERMINATIONS AS DETERMINED BY REPLICATE ANALYSES OF AN AGED, FILTERED SEAWATER SAMPLE 30 I I I . COMPARISON BETWEEN THE OBSERVED AND CALCULATED RESPONSE FOR Pb IN SEAWATER S O L U T I O N S 33 IV. COMPARISON BETWEEN THE OBSERVED AND CALCULATED RESPONSE FOR Cu IN SEAWATER SOLUTIONS 35 V. COMPARISON BETWEEN THE CONCENTRATION OF Cu IN SELECTED SEAWATER SAMPLES AS DETERMINED BY ASV AND BY ATOMIC ABSORPTION ANALYSIS WITH SOLVENT EXTRACTION PRECONCENTRATION . . 48 VI. SAMPLING IN INDIAN ARM AND BURRARD INLET 49 v i i LIST OF FIGURES Figure Page 2.1 A t y p i c a l ASV response curve for Cu and Pb i n a 0.5 M NaCl solution 6 2.2 D e t a i l diagram of the voltammetric c e l l . . . 12 2.3 C a l i b r a t i o n curves for Cu and Pb i n seawater 18 2.4 The v a r i a t i o n of i p with flow rate for Cu in a 0.5 M NaCl solution 20 2.5 The e f f e c t of the i n i t i a l s o l u t i o n temperature on the temperature change during s e r i a l analysis 20 2.6 The v a r i a t i o n of i with pH for Cu and Pb i n a r t i f i c i a l seawater 22 2.7 The v a r i a t i o n of ip with plate p o t e n t i a l for Cu and Pb i n 0.5 M NaCl and aged seawater 25 2.8 The v a r i a t i o n of the Cu peak p o t e n t i a l with i and chloride concentration . . . . . 37 3.1 Location of Burrard I n l e t and Indian Arm . . 41 3.2 Station l o c a t i o n maps and l o n g i t u d i n a l sections for Burrard I n l e t and Indian Arm 42 3.3 Storage e f f e c t s on the Cu content of sea-water samples stored i n 125 ml polypropylene containers 45 3.4 The Cu d i s t r i b u t i o n at stations Indian 2 and Burrard 4 during July, September and October, 1972 51 3.5 The Pb d i s t r i b u t i o n at stations Indian 2 and Burrard 4 during July, September and October, 1972 52 3.6 Variations i n s a l i n i t y with depth at s t a t i o n Burrard 4 during J u l y , September and October, 1972 54 v i i i Figure Page 3.7 Variations i n the Cu concentration i n the upper 50 m at stations Burrard 4, Burrard 2 and Indian 2 during July and September, 1972 55 3.8 Variations i n the Pb concentration i n the upper 50 m at stations Burrard 4, Burrard 2 and Indian 2 during July and September, 1972 56 3.9 Longitudinal p r o f i l e of dissolved oxygen i n Indian Arm on September 5, 1972 58 3.10 Longitudinal p r o f i l e of dissolved Cu i n Indian Arm on September 5, 1972 60 3.11 Longitudinal p r o f i l e of dissolved Pb i n Indian Arm on September 5, 197 2 60 4.1 The e f f e c t of g e l a t i n on the Cu s t r i p p i n g response as a function of plate p o t e n t i a l i n a 0.5 M. NaCl solut i o n 67 4.2 V a r i a t i o n of i p for Cu as a function of pH i n aged seawater before and a f t e r photo-oxidation . 72 4.3 E f f e c t of EDTA on the i for Cu i n a r t i f i c i a l seawater before and a f t e r photo-oxidation. . 72 AC KNOWLED GEMENTS I would l i k e to thank my s u p e r v i s o r , Dr. E. V. G r i l l f o r h i s guidance and encouragement d u r i n g each s t a g e . i n the p r e p a r a t i o n o f t h i s t h e s i s . I would a l s o l i k e t o thank Mr. F. A. Whitney f o r h i s a s s i s t a n c e i n metal a n a l y s e s and i n the c o l l e c t i o n of samples a t sea. Dr. J . S. Nadeau was most h e l p f u l i n p r o v i d i n g me w i t h samples of g l a s s y carbon and i n the p o l i s h i n g of g l a s s y carbon e l e c t r o d e s . 1 1. INTRODUCTION Trace metals play an important r o l e i n the biochem-i s t r y of the marine environment. Because many are required for the proper growth and s u r v i v a l of marine organisms and almost a l l are toxic at s u f f i c i e n t l y high concentrations, the trace metal content of natural waters i s one of the factors that must be considered i n assessing i t s environ-mental q u a l i t y . This study describes a method for determining two trace metals, Cu and Pb, i n seawater and examines the i r d i s t r i b u t i o n i n a near shore marine environment. Although the average concentration of Cu i n seawater i s normally only about 3 ug/1 [Goldberg, 1965], i t i s , nevertheless, an e s s e n t i a l micronutrient to a l l marine organisms. Many are affected by small f l u c t u a t i o n s i n i t s concentration and others, though i n s e n s i t i v e to the range of Cu concentrations normally encountered i n seawater, are adversely affected by abnormally high l e v e l s [Steemann Nielsen and Wium-Anderson, 1970; Erickson et a l . , 1970]. I t has been demonstrated that chelation of Cu by organic compounds a f f e c t s i t s b i o l o g i c a l a v a i l a b i l i t y , i n d i c a t i n g that i t i s not ju s t the amount of Cu present but al s o i t s chemical speciation that i s important [Barber and Ryther, 1969; Lewis et a l . , 1972]. ( 2 Though less frequently determined, the concentration of Pb observed i n seawater (0.02 - 0.3 ug/1) i s generally an order of magnitude lower than that of Cu. Lead apparently i s not an e s s e n t i a l micronutrient but i t i s toxic to most organisms at s u f f i c i e n t l y high l e v e l s . There have been indica t i o n s of an increase i n the Pb content of surface waters p a r t i c u l a r l y near urban areas where i t i s a common a i r pollutant [Bryce-Smith, 1971], suggesting a need for more extensive studies of the Pb d i s t r i b u t i o n i n the sea and e s p e c i a l l y i n near shore waters. Spencer and Brewer [197 0] have reviewed the d i f f e r e n t a n a l y t i c a l techniques that have been applied to the determin-ation of trace elements i n seawater. The most commonly used techniques, atomic absorption spectrophotometry and c o l o r -imetry, are not s u f f i c i e n t l y s e n s i t i v e for d i r e c t measure--7 ments at the l e v e l s (10 M or lower) at which trace metals occur i n seawater. As a r e s u l t , various time consuming preconcentration procedures that increase the p o s s i b i l i t y of contaminating the sample are required. Only a few techniques permit analysis of Cu and Pb at the concentrations at which they normally occur i n seawater without extensive preconcentration. Neutron a c t i v a t i o n , which requires access to a reactor f a c i l i t y [Schutz and Turekian, 1965] can be used for the d i r e c t determination of Cu; Pb, however, cannot be measured with-3 o u t p r e c o n c e n t r a t i o n . I s o t o p e d i l u t i o n p r o c e d u r e s a r e p e r h a p s t h e m o s t p r e c i s e o f t h o s e a v a i l a b l e a n d h a v e b e e n s u c c e s s f u l l y u s e d t o d e t e r m i n e Pb i n s e a w a t e r [Chow, 1968] . An e x t r a c t i o n s t e p i s r e q u i r e d b u t , s i n c e q u a n -t i t a t i v e r e c o v e r y o f t h e m e t a l i s n o t n e c e s s a r y , s a m p l e p r e p a r a t i o n i s c o n s i d e r a b l y s i m p l i f i e d . The r e q u i r e m e n t f o r a mass s p e c t r o m e t e r , h o w e v e r , l i m i t s t h e e x t e n s i v e u s e o f t h e t e c h n i q u e . A n o d i c s t r i p p i n g o r i n v e r s e v o l t a m m e t r y (ASV) i s t h e t e c h n i q u e w h i c h h a s b e e n a d o p t e d f o r u s e i n t h i s s t u d y . P r e c o n c e n t r a t i o n i s a c c o m p l i s h e d by p l a t i n g o u t t h e m e t a l s o f i n t e r e s t o n t o a n e l e c t r o d e i m m e r s e d i n a s m a l l v o l u m e o f s a m p l e . The c o n c e n t r a t i o n o f t h e m e t a l s i s d e t e r m i n e d b y t h e m a g n i t u d e o f t h e c u r r e n t when t h e m e t a l s a r e s u b -s e q u e n t l y r e o x i d i z e d . S i m u l t a n e o u s c o n c e n t r a t i o n a n d m e a s u r e m e n t o f b o t h Cu a n d Pb c a n be c a r r i e d o u t i n t h e same s a m p l e . I t i s t h e s i m p l e s t o f a v a i l a b l e t e c h n i q u e s i n t e r m s o f i n s t r u m e n t a t i o n a n d s a m p l e p r e p a r a t i o n a n d h a s t h e a d v a n t a g e o f b e i n g c a p a b l e o f u s e a t s e a . I n a d d i t i o n , s i n c e ASV i s s e n s i t i v e t o m e t a l i o n a c t i v i t i e s , i t o f f e r s t h e p o s s i b i l i t y o f p r o v i d i n g i n f o r m a t i o n a b o u t t h e i r s p e c i a t i o n . T h i s s t u d y d e s c r i b e s t h e d e v e l o p m e n t o f a n a n a l y t i c a l m e t h o d e m p l o y i n g ASV f o r t h e d e t e r m i n a t i o n o f Cu a n d P b i n s e a w a t e r a n d i t s a p p l i c a t i o n t o t h e s t u d y o f t h e d i s t r i b u t i o n a n d s p e c i a t i o n o f t h e s e m e t a l s i n 4 B u r r a r d I n l e t and I n d i a n Arm. Evidence was sought f o r a p o s s i b l e enrichment o f these metals i n t h i s system as compared to Georgia S t r a i t . Enrichment might be expected on the b a s i s o f the p r o x i m i t y of t h i s system to G r e a t e r Vancouver and the a s s o c i a t e d urban and i n d u s t r i a l i n p u t s . 5 2. ANODIC S T R I P P I N G A N A L Y S I S OF COPPER AND LEAD I N SEAWATER USING A MERCURY PLATED GLASSY CARBON ELECTRODE 2.1 I n t r o d u c t i o n t o t h e T e c h n i q u e A n o d i c s t r i p p i n g v o l t a m m e t r y (ASV) h a s become w i d e l y u s e d f o r t h e a n a l y s i s o f l o w l e v e l s o f many m e t a l s . A l -t h o u g h n o t y e t e x t e n s i v e l y a p p l i e d t o t h e d e t e r m i n a t i o n o f t r a c e m e t a l s i n s e a w a t e r , i t s u s e i s b e c o m i n g i n c r e a s i n g l y more common b e c a u s e o f i t s r e l a t i v e s i m p l i c i t y a nd g r e a t s e n s i t i v i t y . The i n c r e a s e d s e n s i t i v i t y o f ASV a s c o m p a r e d t o o t h e r v o l t a m m e t r i c t e c h n i q u e s i s o b t a i n e d t h r o u g h c o n c e n t r a t i n g t h e m e t a l o r m e t a l s o f i n t e r e s t i n o r o n a n e l e c t r o d e h e l d a t a r e d u c i n g p o t e n t i a l f o r a f i x e d p e r i o d o f t i m e . The c u r r e n t i s t h e n r e c o r d e d a s a f u n c t i o n o f t i m e Cpotential) a s t h e m e t a l i s o x i d a t i v e l y s t r i p p e d f r o m t h e e l e c t r o d e w i t h a r a p i d , l i n e a r l y v a r y i n g anodic p o t e n t i a l sweep. M e r c u r y i s t h e m o s t commonly u s e d e l e c t r o d e m a t e r i a l , t h o u g h s o l i d e l e c t r o d e s h a v e a l s o b e e n e m p l o y e d . A t y p i c a l response f o r C u a n d Pb i n 0.5 M N a C l o b t a i n e d i n t h i s s t u d y i s shown i n F i g u r e 2.1. The p e a k p o t e n t i a l i s c h a r a c t e r i s t i c o f a g i v e n i o n ( o r o x i d a t i o n p r o c e s s ) a n d t h e p e a k h e i g h t i s p r o p o r t i o n a l t o t h e c o n c e n t r a t i o n o f t h e i o n i n s o l u t i o n . S h a i n [1963] Cu 0.0 -.20 Ep -.50 POTENTIAL /volts vs Ag/AgCI reference \ V . electrode / F i g u r e 2.1 A t y p i c a l ASV response curve f o r Cu and Pb i n a 0.5 M NaCl s o l u t i o n 7 and Barendecht [1967] have reviewed the theory and procedures i n c o n s i d e r a b l e d e t a i l . In a p p l i c a t i o n s to the marine environment, the hang-i n g mercury drop e l e c t r o d e (HMDE) has been most f r e q u e n t l y used [Whitnack and S a s s e l i , 1969; Z i r i n o , 197 0; Macchi, 1965]. I t has the advantages o f s i m p l i c i t y o f o p e r a t i o n and p r e p a r a t i o n as w e l l as adequate s e n s i t i v i t y . Because of the r e l a t i v e l y l a r g e volume to s u r f a c e r a t i o , however, the r e i s a t a i l i n g e f f e c t , due t o the slow d i f f u s i o n o f the metal out of the drop, t h a t r e s u l t s i n poor r e s o l u t i o n and lowered s e n s i t i v i t y . T h i n f i l m mercury e l e c t r o d e s overcome many o f these problems by o p t i m i z i n g the s u r f a c e t o volume r a t i o . U n f o r t u n a t e l y , p r e p a r i n g t h i n f i l m e l e c t r o d e s u s i n g normal techniques i s q u i t e d i f f i c u l t and r e p r o d u c i b l e r e s u l t s are not e a s i l y a t t a i n e d . Matson e t a_l. [1965] developed a composite mercury-graphite e l e c t r o d e CCMGE) i n which mercury was p l a t e d out onto a wax impregnated g r a p h i t e r o d . A l t h o u g h the mercury was p r e s e n t as a l a r g e number of v e r y s m a l l d r o p l e t s , the s t r i p p i n g response of the e l e c t r o d e agreed q u i t e w e l l w i t h t h a t p r e d i c t e d f o r t h i n f i l m e l e c t r o d e s [De V r i e s and Van Dalen, 1964]. Matson [1968] and F i t z g e r a l d [1970] have both demonstrated the a p p l i c a b i l i t y and the advantages of t h i s e l e c t r o d e i n the study o f Cu, Pb, Cd and Zn i n seawater. Because o f 8 the small diameter of the mercury droplets (generally less than 10 urn), diffusion of metal out of the mercury is extremely rapid and excellent sensitivity and resolution are obtained. The electrode does have an inherent instability, however, which seems to be a result of the high porosity of graphite. As a result, the graphite must be periodically reimpregnated with wax. The mercury "film" needs frequent replating as it is subject to alteration and contamination with use. Oxidation of the mercury in air and absorption of organics have been suggested as possible causes of this deterioration [Hume and Carter, 1972]. Florence [1970] has recently introduced a new method of preparing a thin film mercury electrode. Using highly polished glassy carbon sealed into a glass tube, Florence developed a technique whereby a thin mercury film was plated onto the glassy carbon "in situ." Sufficient mercuric ion was added to the test solution and the mercury and metal of interest were plated out simultaneously. The electrode was cleaned between runs simply by wiping with a damp tissue, insuring a fresh film for each run. The films obtained in this manner were very thin (0.01 - 0.001 um) and gave excellent resolution and sensitivity. Because of the superior electrical qualities and very low porosity of glassy carbon, no instability was noted over a period 9 of s e v e r a l months. In a l a t e r p u b l i c a t i o n , F l o r e n c e [1972] demonstrated the a p p l i c a b i l i t y o f h i s method t o t r a c e metal d e t e r m i n a t i o n s i n seawater. The method of e l e c t r o d e p r e p a r a t i o n used i n t h i s study i s an a d a p t a t i o n o f F l o r e n c e ' s technique. In ASV, i t i s necessary to s t i r the s o l u t i o n d u r i n g the p l a t i n g step to decrease the t h i c k n e s s of the d i f f u s i o n l a y e r and i n c r e a s e the f l u x o f metal i o n s t o the e l e c t r o d e . Two approaches can be taken. In the f i r s t , which i n v o l v e s p l a t i n g o ut a l l the metal i n the s o l u t i o n , f l u c t u a t i o n s i n s t i r r i n g r a t e are unimportant. However, i n the more common and p r a c t i c a l approach i n which o n l y a s m a l l f r a c t i o n of the metal i s p l a t e d o u t, the s t i r r i n g must be done i n a r e p r o d u c i b l e manner to ensure a c o n s t a n t f l u x of e l e c t r o a c t i v e m a t e r i a l to the e l e c t r o d e . A c o n s i d e r a t i o n p a r t i c u l a r l y p e r t i n e n t to shi p b o a r d a n a l y s i s by the l a t t e r approach i s t h a t the method of s t i r r i n g must be i n s e n s i t i v e to the v i b r a t i o n and t i l t i n g i n h e r e n t i n work a t sea. Few methods s a t i s f y these c r i t e r i a . R o t a t i o n of the e l e c t r o d e , the technique employed by F l o r e n c e [1970] , produces a ve r y w e l l d e f i n e d and e f f i c i e n t c o n v e c t i o n p a t t e r n but i s too s e n s i t i v e to e x t e r n a l movement t o be s u i t a b l e f o r s hipboard a n a l y s i s . A stream of N 2 gas has been used i n almost a l l work w i t h the CMGE to p r o v i d e the nece s s a r y c o n v e c t i o n . T h i s method p r o v i d e s r e p r o d u c i b l e r e s u l t s , i s w e l l s u i t e d t o f i e l d s t u d i e s and minimizes the p o s s i b i l i t i e s o f c o n t a m i n a t i o n . T h e r e i s a l i m i t t o t h e f l o w r a t e s w h i c h c a n be u s e d , h o w e v e r , due t o t h e d a n g e r o f f r o t h i n g . A t t h e f l o w r a t e s n o r m a l l y u s e d i n s e a w a t e r , t h e c o n v e c t i o n s e t up i s n o t v e r y e f f i c i e n t a n d l o n g p l a t i n g t i m e s a r e g e n e r a l l y r e q u i r e d . An a l t e r n a t e m e t h o d , t h e one u s e d i n t h i s s t u d y , i n v o l v e s c i r c u l a t i o n o f t h e s a m p l e t h r o u g h a c l o s e d s y s t e m . T h i s a p p r o a c h h a s b e e n u s e d p r e v i o u s l y b y K o s t e r a n d A r i e l [ 1 9 7 1 ] , who f o u n d t h a t i t p r o v i d e d r e p r o d u c i b l e r e s u l t s o v e r a w i d e r a n g e o f f l o w r a t e s . C i r c u l a t i o n o f t h e s a m p l e t h r o u g h a c l o s e d s y s t e m was f o u n d i n t h e p r e s e n t s t u d y t o p r o v i d e a more e f f i c i e n t m i x i n g o f t h e s o l u t i o n t h a n t h a t o b t a i n e d b y g a s b u b b l i n g a n d t o b e e q u a l l y w e l l s u i t e d t o a n a l y s i s a t s e a . 2.2 D e s c r i p t i o n o f t h e M e t h o d B r i e f l y , t h e m e t h o d t h a t h a s b e e n d e v e l o p e d f o r u s e i n t h i s s t u d y i n v o l v e s t h e f o l l o w i n g b a s i c p r o c e d u r e . A s u f f i c i e n t amount o f a m e r c u r i c c h l o r i d e s o l u t i o n i s a d d e d t o t h e s e a w a t e r s a m p l e b e i n g a n a l y s e d t o g i v e a f i n a l -5 m e r c u r y c o n c e n t r a t i o n o f a p p r o x i m a t e l y 10 M ( r o u g h l y 1000 t i m e s t h e c o n c e n t r a t i o n o f t h e m e t a l s t o be d e t e r m i n e d ) . The s a m p l e i s t h e n pumped i n a c l o s e d s y s t e m t h r o u g h a c e l l w i t h g a s p u r g i n g f o r a s u f f i c i e n t l e n g t h o f t i m e t o a l l o w r e m o v a l o f o x y g e n a n d t e m p e r a t u r e e q u i l i b r a t i o n . N e x t , t h e p u r g i n g g a s i s p a s s e d o v e r t h e s o l u t i o n w h i l e 11 the metals a re p l a t e d out. When the p l a t i n g i s completed, the pump i s turned o f f and the s o l u t i o n a llowed to come to r e s t . The s t r i p p i n g step i s then accomplished by a p p l y -i n g a l i n e a r anodic p o t e n t i a l sweep and r e c o r d i n g the c u r r e n t as a f u n c t i o n of the a p p l i e d p o t e n t i a l . The Cu and Pb c o n c e n t r a t i o n s are c a l c u l a t e d a f t e r subsequent runs u s i n g the method of standard a d d i t i o n s . The e f f e c t s of the v a r i o u s e x p e r i m e n t a l parameters were e v a l u a t e d t o determine o p t i m a l o p e r a t i n g c o n d i t i o n s f o r seawater a n a l y s i s . 2.3 E x p e r i m e n t a l (A) Apparatus A Chemtrix model SSP-2A p o l a r o g r a p h i c a n a l y z e r equipped w i t h a storage o s c i l l o s c o p e was used i n a l l work. A d d i t i o n a l c a p a c i t o r s were added t o the sweep time c i r c u i t to a l l o w sweep r a t e s as low as 7.4 mv/sec. C u r r e n t v s . p o t e n t i a l scans were r e c o r d e d w i t h a Hewlett-Packard Model 7035B X-Y r e c o r d e r . The e l e c t r o l y s i s c e l l ( F i g u r e 2.2) was machined from a p o l y p r o p y l e n e r o d and had a u s e a b l e volume of approximately 50 ml. Threaded plugs were used t o p r o v i d e exchangeable c o n n e c t i o n s . The i n l e t and o u t l e t f i t t i n g s on the c e l l were connected through a t u b i n g pump which c i r c u l a t e d the sample i n such a way t h a t the s o l u t i o n e n t e r e d the c e l l F i g u r e 2.2 D e t a i l diagram o f the voltammetric c e l l 13 from the bottom. The 1/16" diameter opening i n the entrance plug constricted and accelerated the flow at t h i s point so that there was a j e t - l i k e inflow of solut i o n directed at the electrode surface. The glassy carbon electrode was centered d i r e c t l y above t h i s opening. A sp e c i a l c e l l constructed from Teflon was used for pH studies. I t was of si m i l a r design but had a useable volume of about 200 ml to allow for a thermometer and a glass pH electrode. A Cole-Parmer Masterflex tubing pump (head #7015) employing Tygon tubing (special formulation R#3603, 3/16" I.D. x 3/32" wall) was used for c i r c u l a t i n g the solution through the c e l l . Cylinder grade N 2 (Canadian L i q u i d Air) or a mixture of 99.2% N 2 and 0.8% CC>2 (Canadian L i q u i d Air) was used without p u r i f i c a t i o n for deaeration of the samples. P r i o r to bubbling through the c e l l , the gas was saturated with water by passage through a 0.5 M.NaCl s o l u t i o n . Glassy carbon electrodes were prepared by sealing wafers of 0.63 cm diameter glassy carbon (Beckwith Carbon Corp.) into a 30 cm length of Pyrex glass tubing with epoxy r e s i n . The glassy carbon was then polished metallo-graphically, the f i n a l p o l i s h using a 0.01 urn alumina s l u r r y . E l e c t r i c a l contact was made with a Pt or Cu wire dipping into s u f f i c i e n t Hg to cover the surface to a depth of a few c e n t i m e t r e s . I t was necessary to soak the e l e c t r o d e i n d i l u t e HC1 f o r s e v e r a l hours p r i o r to use to remove cont a m i n a t i o n p i c k e d up i n the p o l i s h i n g p r o c e s s . The p o t e n t i a l v a l u e s r e p o r t e d i n t h i s study are w i t h r e s p e c t to a Metrohm model EA 425 Ag/AgCl narrow taper r e f e r e n c e e l e c t r o d e ( s a t u r a t e d KC1 f i l l i n g s o l u t i o n , p o t e n t i a l -0.043 v o l t s v s . s a t u r a t e d c a l o m e l e l e c t r o d e a t 25° C ) . A c o i l e d P t . w i r e was used ,as the counter e l e c t r o d e . D i s t i l l e d water t h a t had been passed through a mixed bed i o n exchange column p r i o r to use was used i n the p r e p a r a t i o n of a l l standard s o l u t i o n s and to r i n s e the c e l l between samples. A s t o c k Cu s t a n d a r d s o l u t i o n was prepared from reagent grade CuSO^ • 5 ^ 0 to g i v e a f i n a l Cu c o n c e n t r a t i o n o f 100 mg/1. The Pb standard was prepared from reagent grade P b C ^ and had a f i n a l Pb c o n c e n t r a t i o n of 478 mg/1. A substandard of 0.10 mg/1 Cu and 0.096 mg/1 Pb was prepared f r e s h from the s t o c k -3 s o l u t i o n s p r i o r to a s e r i e s of a n a l y s e s . A 10 M s t a n d a r d mercury stock s o l u t i o n was prepared from reagent grade HgC^. Reagent grade HC1 was d i l u t e d to g i v e 2N and 6N s o l u t i o n s . A r t i f i c i a l seawater was prepared a c c o r d i n g to the r e c i p e of Lyman and Fleming [1940J w i t h the o m i s s i o n of S r C l 2 . The pH was e s t i m a t e d w i t h an O r i o n Model 8 01 pH meter and Corning 476022 g l a s s e l e c t r o d e . C o n t r o l of the pH a t v a l u e s a b o v e 4.8 was a c h i e v e d by u s i n g m i x t u r e s o f N 2 a n d C 0 2 . The u s e o f N 2 a l o n e s l o w l y i n c r e a s e d t h e pH o f s e a w a t e r s a m p l e s w h i l e a m i x t u r e o f 9 9 ; 2 % a n d 0.8% C 0 2 l o w e r e d t h e pH o f s e a w a t e r t o a p p r o x i m a t e l y 7.0. L o w e r pH's w e r e o b t a i n e d by m i x i n g N 2 w i t h a r e g u l a t e d f l o w o f p u r e C 0 2 ( C a n a d i a n L i q u i d A i r , m e d i c a l g r a d e ) . E q u i l i b r a -t i o n o f s e a w a t e r w i t h p u r e C 0 2 l o w e r e d t h e pH t o a p p r o x i m a t e l y 4.8. F u r t h e r d e c r e a s e i n t h e pH was o b t a i n e d b y a d d i n g 0.1 m l a l i q u o t s o f 2N o r 6N HC1. (B) I n v e s t i g a t i o n o f E x p e r i m e n t a l P a r a m e t e r s No m e a s u r e a b l e c h a n g e was d e t e c t e d i n t h e Cu o r P b c o n c e n t r a t i o n o f s o l u t i o n s l e f t i n t h e p o l y p r o p y l e n e c e l l f o r p e r i o d s o f up t o 1 h o u r , t h e maximum l e n g t h o f t i m e a s a m p l e m i g h t be i n t h e c e l l d u r i n g t h e c o u r s e o f a r o u t i n e a n a l y s i s . The T e f l o n c e l l g a v e no i n c r e a s e o v e r a p e r i o d o f 3 h o u r s . The b l a n k v a l u e s f o r t h e s t a n d a r d Hg s o l u t i o n a n d 6N HC1 u s e d i n a c i d i f i c a t i o n w e r e b e l o w d e t e c t i o n l i m i t s . New T y g o n t u b i n g i n t r o d u c e d s i g n i f i c a n t a m o u n t s o f Pb a n d e s p e c i a l l y C u i n t o t h e s a m p l e s e v e n i f r i n s e d r e p e a t e d l y w i t h d e i o n i z e d w a t e r . S e v e r a l r i n s e s w i t h EtOH a n d 1% HC1 p r o v e d e f f e c t i v e i n r e m o v i n g t h e c o n t a m i n a t i o n . T h e r e a r e s e v e r a l p o s s i b l e e f f e c t s t h a t m i g h t i n t e r -f e r e w i t h e i t h e r t h e d e p o s i t i o n a n d / o r d i s s o l u t i o n o f t h e m e t a l . S u r f a c e a c t i v e a g e n t s c a n b o t h d e c r e a s e t h e r a t e of deposition and a l t e r the subsequent s t r i p p i n g response. Although i t may be assumed that surface active agents are present i n most natural waters, repeated analysis of the same seawater solutions, normally gave reproducible r e s u l t s , i n d i c a t i n g that they do not s e r i o u s l y a f f e c t the p r e c i s i o n of the measurements. Interferences can also a r i s e from other metals being stripped out of Hg at si m i l a r potentials as Cu or Pb as well as from the formation of i n t e r m e t a l l i c compounds. Many i n t e r m e t a l l i c compounds are known to e x i s t [Barendecht, 1967] but the factors influencing t h e i r formation and subsequent electrochemical behaviour are s t i l l obscure. Formation i s enhanced by high metal concen-trat i o n s i n the amalgam [Kozlovsky and Zebreva, 1972] and ASV, p a r t i c u l a r l y with th i n Hg f i l m s , i s very suspect i n t h i s respect. Matson [1968] found that Ni and Zn form a compound which s t r i p s out of Hg at the same p o t e n t i a l as Cu. Since both Ni and Zn are present i n seawater at about the same concentration as Cu, a p o t e n t i a l such that neither metal w i l l be plated out (.i.e., more p o s i t i v e than -1.0 v\ should be used. Other i n t e r m e t a l l i c compounds may also e x i s t and, thus, the p o s s i b i l i t y of such i n t e r -ferences cannot be completely excluded. Baier [1971] demonstrated that Sn i s stripped from Hg in t o seawater at the same p o t e n t i a l as Pb. The extent of interference i s strongly pH dependent, being n e g l i g i b l e at pH's of less 17 than 5 but s i g n i f i c a n t a t a normal seawater pH i f the concen-t r a t i o n s of Sn and Pb are of the same magnitude. None of the metals normally found i n seawater i n t e r -f e r e w i t h the Cu response. The V i n t e r f e r e n c e i n the d e t e r m i n a t i o n o f Cu r e p o r t e d by Smith and Redmond [1971] was not observed i n t h i s study, even w i t h V c o n c e n t r a t i o n s an order of magnitude g r e a t e r than t h a t n o r m a l l y found i n seawater. 1. Peak Height ( i ) vs M e t a l C o n c e n t r a t i o n : p I t i s e s s e n t i a l when u s i n g the method of standard a d d i t i o n s f o r c a l i b r a t i o n t h a t t h e r e be a l i n e a r r e l a t i o n s h i p between the s t r i p p i n g c u r r e n t peak h e i g h t and the concen-t r a t i o n o f metal i n the s o l u t i o n . Such l i n e a r i t y was r e p e a t e d l y observed f o r Cu and Pb i n both 0.5 M NaCl and a c i d i f i e d seawater (Figure 2.3). The Pb peak h e i g h t was p r o p o r t i o n a l t o the Pb c o n c e n t r a t i o n throughout the range s t u d i e d (£5 ug/1). The Cu response was l i n e a r up to a c o n c e n t r a t i o n o f approximately 4 ug/1; above t h i s , however, the s l o p e o f the response curve decreased w i t h i n c r e a s i n g c o n c e n t r a t i o n . The s o l u b i l i t y o f Cu i n Hg i s r e p o r t e d as o n l y 0.002% a t 20°C [Stephen and Stephen, 1963]. Even t a k i n g i n t o account i n c r e a s e d s o l u b i l i t y w i t h i n c r e a s e d temperature, t h i s suggests t h a t the Hg f i l m w i l l be s u p e r s a t u r a t e d whenever the Cu c o n c e n t r a t i o n exceeds c a . 0.1 ug/1. The degree of s a t u r a t i o n may be the d e t e r m i n i n g f a c t o r i n the l i n e a r i t y of the Cu response. or To 20 [M] ug/l AFTER STANDARD ADDITION Experimental C o n d i t i o n s ; Aged seawater, pH 2.0. Plate time '6 minutes, Plate potential -0.9 v., Sweep rate 0.032 v/sec. gure 2.3 C a l i b r a t i o n curves f o r Cu and Pb i n seawater 19 2. i p vs Pumping Rate: Although ^ i n c r e a s e s w i t h i n c r e a s i n g pumping r a t e f o r both Cu and Pb (Figure 2.4), h i g h pumping speeds a l s o reduce t u b i n g l i f e . Pumping a t a speed which gave a flow r a t e of 180 ml/min, the t u b i n g c o u l d be used f o r more than 100 hours without apparent d e t e r i o r a t i o n ; above 600 ml/min there was n o t a b l e d e t e r i o r a t i o n a f t e r o n l y 20 hours of use. Pumping a l s o heats the s o l u t i o n and, as the r e d u c t i o n c u r r e n t of a metal i o n a t a s t a t i o n a r y p l a n a r e l e c t r o d e v a r i e s by approximately 1.2%/°C [Heyrovsky and Kuta, 1966], l a r g e temperature d i f f e r e n c e s between s u c c e s s i v e p l a t i n g s teps w i l l a p p r e c i a b l y a f f e c t the magnitude o f i p and the p r e c i s i o n and a c c u r a c y of measurements. In order t o extend t u b i n g l i f e w h i l e m a i n t a i n i n g adequate s e n s i t i v i t y and p r e c i s i o n , the sample was degassed a t a flow r a t e of 445 ml/min f o r 10 minutes and the flow then decreased to 18 0 ml/min d u r i n g the p l a t i n g p e r i o d . T h i s n o r m a l l y r e s u l t e d i n a temperature of between 30 and 34°C t h a t was maintained to w i t h i n about 1°C over the span o f s i x o r seven c o n s e c u t i v e p l a t i n g and s t r i p p i n g s t e p s . As shown i n F i g u r e 2.5, the temperature change over a s e r i e s of p l a t i n g and s t r i p p i n g steps depended on the i n i t i a l temperature and on the l e n g t h of the p l a t i n g p e r i o d . 20 Experimental Conditions; 0.5 M NaCl. 2.0 pg/\ Cu 2+, 6XH plate ti'me 5 minutes, plate poteriial - 0 . 9 v.. sweep rate 0.032 v/sec, pH ~ 4.8 . 20-3.0 5J0 FLOW RATE ml/minlO"2 F i g u r e 2.4 The v a r i a t i o n o f i w i t h f l o w r a t e f o r C u i n 0.5 M N a C l . ' p F i g u r e 2.5 The e f f e c t o f t h e i n i t i a l s o l u t i o n t e m p e r a t u r e o n t h e t e m p e r a t u r e c h a n g e d u r i n g s e r i a l a n a l y s i s 21 3. i p vs Sweep Rate: The i o f both Cu and Pb was found to be d i r e c t l y P x p r o p o r t i o n a l to the sweep r a t e throughout the range t e s t e d (7.4 - 50 mv/sec). However, the s l o p e of the b a s e l i n e c u r r e n t r e s u l t i n g from d i s c h a r g e of the e l e c t r i c a l double l a y e r about the e l e c t r o d e a l s o i n c r e a s e s w i t h i n c r e a s i n g scan r a t e , e x c l u d i n g the use o f v e r y f a s t scans. A sweep r a t e of 32 mv/sec was used f o r most o f the a n a l y s e s r e p o r t e d i n t h i s study. 4. i p vs P l a t i n g Time: The i p of both Cu and Pb was p r o p o r t i o n a l to the p l a t i n g time i n the range 3 to 15 minutes. I t was found t h a t under normal c o n d i t i o n s a p l a t i n g time of 8 minutes was adequate f o r the simultaneous d e t e r m i n a t i o n of Cu and Pb but t h a t longer p l a t i n g times were nec e s s a r y when metal c o n c e n t r a t i o n s were l e s s than 0.1 ug/1. 5. i vs pH: -p The magnitude of i p f o r both Cu and Pb i n seawater i s pH dependent, i n c r e a s i n g markedly as the pH i s lowered from 8 to approximately 5. In a r t i f i c i a l seawater, i t remains e s s e n t i a l l y c o n s t a n t below t h i s ( F igure 2.6). In n a t u r a l seawater, however, the Cu c u r r e n t sometimes i n c r e a s e d f u r t h e r a t pH's of l e s s than 5. Such anomalous behaviour i s d i s c u s s e d l a t e r i n S e c t i o n 4. In the a n a l y s i s / 22 4 Cu Experimental Conditions; Plate time 5 minutes, Plate potential -0.9v.. Sweep rate 0.032 v/sec., UV irradiated artificial sea water F i g u r e 2.6 The v a r i a t i o n o f i w i t h pH f o r Cu and Pb i n a r t i f i c i a l s e a w l t e r of seawater, decreasing the pH therefore increases s e n s i t i v -i t y and, since hydrogen ions w i l l tend to displace metals from l a b i l e complexes, possibly provides a better estimate of the t o t a l metal i n the sample. The use of a low pH also decreases the p o s s i b i l i t y of Sn i n t e r f e r i n g i n the Pb determination. 6. i vs Mercury Concentration: -P 1  The v a r i a t i o n of i for Pb and Cu with the mercury concentration of the sample i s given i n Table I. There i s a very abrupt decrease i n the i below a Hg concen-— 6 t r a t i o n of approximately 3 x 10 M. This agrees quite well with the r e s u l t s obtained by Florence [1970], who calculated that t h i s cut-off point corresponds to a Hg f i l m thickness o of only 4A or roughly a monolayer of Hg atoms. Calculations based on the s t r i p p i n g current for Hg obtained i n t h i s study give a si m i l a r r e s u l t . Florence [1970] suggested that t h i s was evidence that the Hg was present as a di s c r e t e f i l m and not a number of very small droplets. 7. ip vs P l a t i n g P o t e n t i a l : The v a r i a t i o n of i with the p l a t i n g p o t e n t i a l for Cu and Pb i n 0,5 M NaCl i s shown i n Figure 2.7. A steady state peak current i s reached at a p l a t i n g p o t e n t i a l between 300 and 400 mv cathodic to the peak p o t e n t i a l of the metal. In seawater, steady state values often were not obtained with p l a t i n g potentials as low as -1.2 v o l t s , 24 TABLE I RELATIONSHIP BETWEEN i AND THE MERCURY CONCENTRATION P 10 5 C H g 2 + ( m o l e s . l 1) ixp]Cu ... a C V p b /• \ b ( l p } P b n i l 0.25 0.00 1.1 0.1 0.50 0.20 1.5 0.2 2.50 0.70 5.20 0.4 4.60 1.10 5.80 0.9 4.75 1.20 6.21 c 2.0 5.00 1.40 6.87 5.0 5.30 1.50 7.42 d a 3 y g / l Cu and 0.5ug/l Pb i n 0.5 M NaCl, p l a t e time 6 minutes, p l a t e p o t e n t i a l -0.9 v o l t s , v = 0.032 v/sec from F l o r e n c e [1970] c -5 Hg c o n c e n t r a t i o n 1.0 x 10 M ci "5 Hg c o n c e n t r a t i o n 10.0 x 10 M 25 COPPER 0.5 M NaCI 0 -.2 -.4 -.6 -.8 -10 -1.2 PLATE POTENTIAL (volts vs Ag/AgCI reference electrode) A LEAD Experimental Conditions; 0.3 ug Pb2"/!, 0.5 M NaCI PLATE POTENTIAL (volts vs Ag/AgCI reference electrode) F i g u r e 2.7 The v a r i a t i o n o f i w i t h p l a t e p o t e n t i a l f o r Cu and Pb i n 0.5 M^NaCl and aged seawater even i n a c i d i f i e d samples. T h i s e f f e c t i s d i s c u s s e d i n terms of s p e c i a t i o n of the metals i n S e c t i o n 4. The use of p o t e n t i a l s more c a t h o d i c than -1.0 v o l t i n a c i d s o l u -t i o n s i s l i m i t e d by hydrogen i o n r e d u c t i o n and by the p o s s i b i l i t y of Ni-Zn i n t e r m e t a l l i c compound i n t e r f e r e n c e s i n the Cu response. A p l a t i n g p o t e n t i a l of -0.9 v o l t s was used i n a l l the a n a l y s e s r e p o r t e d i n t h i s study. (C) Standard Procedure The f o l l o w i n g i s the procedure which was f i n a l l y adopted f o r the a n a l y s i s of seawater samples: 1. The c e l l i s r i n s e d twice w i t h d e i o n i z e d water and then once w i t h the sample. The s u r f a c e of the g l a s s y carbon e l e c t r o d e i s t h o r o u g h l y wiped w i t h a damp t i s s u e , r i n s e d w i t h d e i o n i z e d water and then p l a c e d i n the c e l l . 2. An a l i q u o t o f the sample i s p i p e t e d i n t o the c e l l C35 - 45 m l ) . A f t e r adding 0.5 ml of s t a n d a r d 0.001 M H g C l 2 s o l u t i o n and 0.3 ml of 6 N HC1 (which lowers the pH of the sample to approximately 2), the s o l u t i o n i s pumped through the c e l l a t a r a t e of 445 ml/min f o r 10 minutes w h i l e b u b b l i n g N 2 through the sample. 3. A f t e r d e a e r a t i o n , the p u r g i n g gas i s passed over the s o l u t i o n and the pumping r a t e i s reduced to 180 ml/min. The p o t e n t i a l of the g l a s s y carbon e l e c t r o d e i s a d j u s t e d to -0.9 v o l t s vs the Ag/AgCI r e f e r e n c e e l e c t r o d e and the p l a t i n g step timed w i t h a s t o p -watch. A f t e r p l a t i n g f o r 5 minutes, the pump i s turned o f f and the s o l u t i o n a l l o w e d to e q u i l i b r a t e f o r 45 seconds. The p o t e n t i a l i s then swept a n o d i c a l l y a t a r a t e of 0.032 v / s e c , the c u r r e n t being r e c o r d e d as a f u n c t i o n of p o t e n t i a l on the X-Y r e c o r d e r . A f t e r the Cu peak has been r e c o r d e d , the r e c o r d e r i s switched to standby and the c u r r e n t f o l l o w e d on the o s c i l l o s c o p e u n t i l the Hg has been completely s t r i p p e d o f f . The c o n t a c t to the g l a s s y carbon e l e c t r o d e i s then removed. The g l a s s y carbon e l e c t r o d e i s removed from the c e l l and c l e a n e d as b e f o r e . T h i s f i r s t run g i v e s an e s t i m a t e of the c o n c e n t r a t i o n s of both Cu and Pb i n the sample and c o n d i t i o n s the e l e c t r o d e Cthe f i r s t run always d i f f e r s s l i g h t l y from subsequent ones). Steps 3, 4, 5 and 6 are repeated u s i n g longer p l a t i n g times i f n e c e s s a r y . A f t e r s a t i s f a c t o r y c o m p l e t i o n o f step 7, an a l i q u o t of the substandard s o l u t i o n i s added to the sample. A volume o f 0.2 ml o f the s o l u t i o n c o n t a i n i n g 0.1 mg Cu/1 and 0.096 mg Pb/1 proved adequate f o r most l e v e l s of the metals encountered i n t h i s work. 28 A f t e r adding the s p i k e , the s o l u t i o n i s purged w i t h N 2 a g a i n f o r 2 minutes, pumping the s o l u t i o n a t a r a t e of 18 0 ml/min to mix the added metal and remove 0 2 i n t r o d u c e d w i t h the s p i k e . 9. Steps 3 through 6 are then repeated, The concen-t r a t i o n o f the metals i n the o r i g i n a l s o l u t i o n i s then c a l c u l a t e d from the d i f f e r e n c e i n the peak h e i g h t s of the s p i k e d and unspiked samples a c c o r d i n g to the formula: C o = ( i V C )/(i„V = + VAi) 1 S S 2. s where C o i s the c o n c e n t r a t i o n of the unspiked sample i s the peak h e i g h t o f the metal i n the unspiked sample V s i s the volume of the s p i k e C s i s the c o n c e n t r a t i o n o f the s p i k e i 2 i s the h e i g h t of the peak i n the s p i k e d sample A i = C i 0 - i-A V i s the volume of the o r i g i n a l s o l u t i o n + c e l l dead volume + the volume o f the Hg s t a n d a r d and a c i d added to the sample. The c e l l c o n t a i n s a dead volume ( i . e . , a volume of s o l u t i o n remaining i n the c e l l and t u b i n g a f t e r d r a i n i n g ) . T h i s was found to be approximately 0.8 ml and was determined 29 p e r i o d i c a l l y . The dead volume i s added to the volume of sample added to o b t a i n the t o t a l volume of sample i n the c e l l . C o r r e c t i o n f o r the d i l u t i o n of the sample by a d d i t i o n s of Hg standard and a c i d was made t o o b t a i n the c o n c e n t r a t i o n i n the o r i g i n a l sample. The method of standard a d d i t i o n s i s v a l i d when the peak h e i g h t i s p r o p o r t i o n a l t o the metal c o n c e n t r a t i o n . Although t h i s i s not t r u e f o r Cu c o n c e n t r a t i o n s i n excess of 4 yg/1, the c o n c e n t r a t i o n s encountered i n t h i s study were always l e s s than t h i s and r a r e l y g r e a t e r than 1.5 yg/1. The use of a standard a d d i t i o n s technique i s advantageous i n t h a t r i g i d c o n t r o l of e x p e r i m e n t a l parameters i s not r e q u i r e d throughout a whole s e r i e s o f a n a l y s e s . 2.4 P r e c i s i o n P r e c i s i o n was determined by r e p l i c a t e a n a l y s e s of an aged, f i l t e r e d seawater sample t h a t had been c o l l e c t e d i n Georgia S t r a i t a t 100 m and s t o r e d i n a 5 g a l l o n Pyrex carboy a t ca 5°C. The r e s u l t s a r e g i v e n i n T a b l e I I . The stan d a r d d e v i a t i o n of the Pb d e t e r m i n a t i o n s corresponds to the approximate d e t e c t i o n l i m i t of the method and a l s o to the lower l i m i t o f Pb c o n c e n t r a t i o n s r e p o r t e d f o r seawater {Chow, 1968]. The c o n c e n t r a t i o n of both Cu and Pb i n t h i s sample r o u g h l y corresponds t o the average l e v e l s o f these metals encountered i n t h i s study. 30 TABLE I I PRECISION OF Cu AND Pb DETERMINATIONS AS DETERMINED BY REPLICATE ANALYSES aOF AN AGED, FILTERED SEAWATER SAMPLE Sub-Sample [Cu]ug/1 [Pb]ug/1 1 0.52 0.18 2 0.56 0.23 3 0.49 0.19 4 0.55 0.30 5 0.60 0.26 6 0.53 0.24 7 0.51 0.21 Mean 0.54 0.23 Standard 0.04 0.04 D e v i a t i o n R e l a t i v e 7% 17% Standard D e v i a t i o n 3 experimental parameters as d e s c r i b e d i n the standard p r o -cedure w i t h a p l a t e time of 7 minutes 31 2.5 Comparison of the Response with Theory De Vries and Van Dalen [1964, 1965] have developed a mathematical model for the current-potential curves obtained i n ASV with planar, t h i n - f i l m mercury electrodes. I t was assumed that equilibrium e x i s t s between the oxidized and reduced forms of the metal during the d i s s o l u t i o n step, that the electrode reaction i s r e v e r s i b l e and d i f f u s i o n controlled and that the concentration of the oxidized species i n the s o l u t i o n at the s t a r t of the anodic sweep i s homo-geneous. The r e s u l t i n g equations showing the e f f e c t of f i l m thickness and sweep rate on the current wave were i n excellent agreement with observed r e s u l t s . In a l a t e r p u b l i c a t i o n 11967], a generalized s o l u t i o n was given for the case of very thin films ( i . e . , less than 1 um which yielded the following expressions: P CD n l E p E J) = -1.43 + 29.58 log (H) (2) 75.53 (3) where i i s the peak current i n amperes P A n i s the number of electrons involved i n the reaction 2 i s the area of the electrode i n cm C i s the c o n c e n t r a t i o n o f the metal i n the Hg r f i l m (moles .1 ) L i s the t h i c k n e s s of the Hg f i l m i n cm v i s the sweep r a t e i n v o l t s / s e c Ep i s the p o t e n t i a l of the peak c u r r e n t i n mv . E 2~ i s the h a l f wave p o t e n t i a l f o r the e l e c t r o d e r e a c t i o n i n mv 2 H i s a d i m e n s i o n l e s s parameter = L cr/D^ a = (nF/RT) . v D i s the d i f f u s i o n c o e f f i c i e n t of the metal i n r Hg i n cm^/sec (F/R) = 8.02 x 1 0 4 deg. v o l t " 1 T i s the temperature i n °K b i s the width o f the peak a t h a l f the peak h e i g h t i n mv. As p r e d i c t e d by e q u a t i o n 1, the i of both Cu and Pb was found to be a l i n e a r f u n c t i o n o f the sweep r a t e over the range t e s t e d . Comparison o f the c a l c u l a t e d response u s i n g e quations 1, 2 and 3 and the observed Pb response i s g i v e n i n Table I I I . I t i s apparent t h a t t h e r e i s e x c e l l e n t agreement between the response c a l c u l a t e d f o r a two e l e c t r o n , d i f f u s i o n c o n t r o l l e d o x i d a t i o n and t h a t observed f o r the Pb o x i d a t i o n i n seawater. In seawater, c u p r i c i o n s undergo a two s t e p r e d u c t i o n [Odier and P l i c h o n , 1971]: TABLE III COMPARISON BETWEEN THE OBSERVED AND CALCULATED RESPONSE FOR Pb IN SEAWATER SOLUTIONS.a A SUBSCRIPT C REFERS TO A CALCULATED VALUE AND A SUBSCRIPT o REFERS TO AN OBSERVED VALUE b n C °M r t i 1 p c a i p o V c/ C V o CE ) p c CE ) p o <4>c 2. O 0.03 0.63 0.70 0.90 -.51 -.50 38 "40 0.05 1.14 1.20 0.95 -.51 -.50 38 ~40 0.08 1.71 1.80 0.95 -.51 -.50 38 ~40 0.15 3.25 3.25 1.00 -.51 -.50 38 ~40 a R e s u l t s for a c i d i f i e d seawater CpH = 2.0) with: L = 5 x 10"'cm; H = 2.4 x 10~ 8; E l = -0.40 v; v = 0.032 v/sec; T = 34°C Calculated from the area of the Pb and Hg st r i p p i n g peaks 34 Cu + 2C1 + e = C u C l 2 ETJ- > 0.0 v o CuCl~ + e = Cu + 2C1 0.20 v The observed s t r i p p i n g peak f o r Cu i n seawater should correspond to the r e v e r s e o f the second r e d u c t i o n . T a b l e IV, where the t h e o r e t i c a l response f o r a r e v e r s i b l e , d i f f u s i o n c o n t r o l l e d , one e l e c t r o n o x i d a t i o n i s compared w i t h t h a t e x p e r i m e n t a l l y observed, i n d i c a t e s t h a t the observed v a l u e of b^- i s v a r i a b l e , d e c r e a s i n g w i t h i n c r e a s i n g peak h e i g h t . A t h i g h v a l u e s of i , bi- approaches a l i m i t i n g p /. v a l u e approximately h a l f t h a t p r e d i c t e d , c l o s e l y c o rrespond-i n g w i t h the t h e o r e t i c a l v a l u e f o r a two e l e c t r o n o x i d a t i o n . In o r d e r to determine whether the o x i d a t i o n of Cu i n seawater i s i n f a c t a 2 step r e a c t i o n , s u f f i c i e n t Cu was added to a seawater sample to a l l o w o b s e r v a t i o n of the o x i d a t i o n wave when the metal was p l a t e d d i r e c t l y onto g l a s s y carbon i n the absence of Hg. Two s t r i p p i n g peaks were observed, the f i r s t c o r r e s p o n d i n g to t h a t observed i n the presence of Hg. The second peak, which presumably corresponds to the o x i d a t i o n of C u ( l ) to C u ( l l ) , o c c u r s a t a p o t e n t i a l t h a t i s masked by the o x i d a t i o n of Hg when Cu i s s t r i p p e d from an amalgam. 35 TABLE IV COMPARISON BETWEEN THE OBSERVED AND CALCULATED RESPONSE FOR Cu IN SEAWATER SOLUTIONS.a A SUBSCRIPT c REFERS TO A CALCULATED VALUE AND A SUBSCRIPT o TO AN OBSERVED VALUE b n C ° M r U ) P o t i ) J t i 1 p c p o (E \ P c (E ) P o <4>C 2. O 0.06 0.33 0.64 0.52 -.43 -.30 76 ""55 0.20 1.02 2.00 0.51 -.43 -.24 76 ""40 0.30 1.55 3.10 0.50 -.43 -.23 76 ~40 a -7 Results for a c i d i f i e d seawater (pH = 2.0) with: L = 5 x 10 cm^H = 1.2 x I0~*; £ 1 = _ Q 2 V Q l t s ; v = 0.032 v/sec; T = 1_ Calculated from the area of the Cu and Hg s t r i p p i n g peaks 36 The observed Cu peak p o t e n t i a l i s anodic to t h a t p r e d i c t e d by eq u a t i o n 2 f o r a one e l e c t r o n r e d u c t i o n . In a k i n e t i c a l l y c o n t r o l l e d r e d u c t i o n , the h a l f wave p o t e n t i a l i s s h i f t e d to a more anodic p o t e n t i a l than t h a t f o r the simple d i f f u s i o n c o n t r o l l e d case [Heyrovsky and Kuta, 1966] . Si n c e r e d u c t i o n to the cuprous o x i d a t i o n s t a t e o c c u r s i n the presence of s u f f i c i e n t complexing agent, the p o t e n t i a l of the o x i d a t i o n o f Cu(0) to Cu (I) i n seawater would be expected to depend on the c o n c e n t r a t i o n o f c h l o r i d e i o n s . The observed peak p o t e n t i a l i s i n f a c t observed to v a r y w i t h the c h l o r i d e i o n c o n c e n t r a t i o n , s h i f t i n g a n o d i c a l l y w i t h d e c r e a s i n g c h l o r i d e (Figure 2.8). In a d d i t i o n , the peak p o t e n t i a l s h i f t s a n o d i c a l l y w i t h i n c r e a s i n g Cu c o n c e n t r a t i o n (Figure 2.8). Both o b s e r v a t i o n s are c o n s i s -t e n t w i t h the h y p o t h e s i s t h a t d i f f u s i o n o f c h l o r i d e i o n s to the e l e c t r o d e has a r a t e l i m i t i n g e f f e c t on the o x i d a t i o n p r o c e s s . I f the o x i d a t i o n i s k i n e t i c a l l y c o n t r o l l e d , the equations d e r i v e d f o r a r e v e r s i b l e , d i f f u s i o n c o n t r o l l e d o x i d a t i o n would not be a p p l i c a b l e . T h i s would account f o r the l a c k of agreement between the observed and c a l c u l a t e d s t r i p p i n g response f o r Cu i n seawater. 37 Ep mv -300 -250 -200-^  -150 -100H -50 0.5 M NaCI "O- ^ 0.01 M NaCI 4 —i— 6 10 -1 12 pamps F i g u r e 2.8 The v a r i a t i o n of the Cu peak p o t e n t i a l w i t h i p and c h l o r i d e c o n c e n t r a t i o n 38 2 . 6 Multiple Peaks Occasionally, a doublet or a shoulder was observed in the stripping current for Cu instead of one distinct and sharp peak as expected. Both Matson [1968] and Fitzgerald [1970] reported similar behaviour for both Cu and Pb. Matson attributed the anomalous Cu response to deterioration of the electrode. Reimpregnating the graphite rod with wax was found in most cases to remedy the situation. Hume and Carter [1972] found that the appearance of a Pb doublet was also a function of the electrode surface. If a large portion of the graphite surface were left uncovered by the Hg, doublet peaks resulted from metal stripped from both the Hg and the graphite. The presence of more than one Cu peak or an unsymmetrical peak in the present work was found, in some cases, to be a function of the glassy carbon surface. If different electrodes were used in the same solution, one might give a doublet while the other would not. If the electrode that gave the doublet was then repolished, a single sharp peak was obtained. The surface may become pitted after repeated use due to electrochemical oxidation in the presence of O^, although there was no microscopically visible difference in the surface of a freshly polished electrode and one that had been in use for several months. In these cases, the surface film may consist of many Hg droplets, resulting in the stripping of metal that has been deposited both in Hg and directly onto glassy carbon, as suggested by Hume and Carter. The peak potential for the Pb stripping peak from glassy carbon was found to be identical to that from Hg, explaining why doublets were not observed in the Pb response even under circumstances where doublets were observed for Cu. In many instances, however, the presence of a dis-torted or doublet Cu peak was found to be independent of the electrode used. As noted before, the Hg appears to be supersaturated with respect to Cu increasing the like-lihood of intermetallic compound formation. The presence of an extra peak or a distorted peak in the Cu response may thus reflect the presence of an intermetallic compound oxidized at a potential similar to that of Cu or the oxidation of Cu which has not dissolved in Hg and is present either on the surface of the Hg or covered by a thin film of saturated Cu-Hg amalgam. Kozlovsky and Zebreva [1972] have attributed the appearance of a new peak in stripping analysis to the oxidation of intermetallic compounds which have accumulated on the surface of the electrode. 40 3. THE DISTRIBUTION OF COPPER AND LEAD I N I N D I A N ARM AND BURRARD INLET 3.1 I n t r o d u c t i o n B u r r a r d I n l e t a n d I n d i a n Arm c o m p r i s e a c o n t i n u o u s s y s t e m t h a t f o r m s t h e s o u t h e r n m o s t i n l e t o n t h e m a i n l a n d B r i t i s h C o l u m b i a c o a s t ( F i g u r e 3 . 1 ) . B u r r a r d I n l e t i s n a r r o w a n d r e l a t i v e l y s h a l l o w , h a v i n g a n a v e r a g e d e p t h o f l e s s t h a n 30 m i n s i d e t h e s i l l a t F i r s t N a r r o w s ( F i g u r e 3 . 2 ) . The l o w e r p o r t i o n o f t h e i n l e t s e r v e s a s t h e m a i n h a r b o u r f o r t h e c i t y o f V a n c o u v e r , w h i l e t h e e n t i r e i n l e t i s b o u n d e d b y t h e u r b a n a r e a s o f G r e a t e r V a n c o u v e r . I n c o n t r a s t , t h e s h o r e l i n e o f I n d i a n Arm i s v i r t u a l l y u n i n h a b i t e d . I n d i a n Arm e x t e n d s a p p r o x i m a t e l y 22 km due n o r t h i n t o t h e C o a s t M o u n t a i n s f r o m i t s c o n n e c t i o n w i t h B u r r a r d I n l e t ( F i g u r e 3 . 2 ) . I t h a s t h e p h y s i c a l f e a t u r e s common t o m o s t f j o r d s o n t h e B r i t i s h C o l u m b i a c o a s t ; a s h a l l o w s i l l n e a r t h e e n t r a n c e s e p a r a t e s a d e e p c e n t r a l b a s i n f r o m t h e a d j o i n i n g w a t e r s . The e n t r a n c e s i l l h a s a l i m i t i n g d e p t h o f 26 m a n d t h e c e n t r a l b a s i n , a v e r a g i n g o v e r 200 m i n d e p t h , h a s a maximum d e p t h o f 224 m. S e a s o n a l v a r i a -t i o n s i n w a t e r p r o p e r t i e s h a v e b e e n s t u d i e d b y G i l m a r t i n [ 1 962] who o b s e r v e d t h a t t h e r e i s a c h a r a c t e r i s t i c 41 42 () Station Number F i g u r e 3.2 S t a t i o n l o c a t i o n maps and l o n g i t u d i n a l s e c t i o n s f o r B u r r a r d I n l e t and I n d i a n Arm 43 estuarine type of two layer circulation with a thin layer of relatively brackish water flowing out of the system at the surface and, below this, a compensating inflow of denser, more saline water. The shallow approaches in Burrard Inlet restrict the free exchange of deep water between Indian Arm and Georgia Strait. 3.2 Sampling Procedures All sampling in Indian Arm and Burrard Inlet was carried out from the oceanographic research vessel C.S.S. Vector at the stations shown in Figure 3.2. Water samples were collected either with 1.2 litre polypropylene N.I.O. bottles or five litre PVC Nisken bottles. The water collected in the Nisken samplers was used only for intercomparison and storage tests. Temperature observations and the samples for dissolved metal, oxygen and salinity determinations were all taken from the same water sample. The dissolved oxygen and salinity samples were withdrawn immediately after collection and the remaining water then transferred to 5 00 ml poly-ethylene bottles until filtered. Filtration was carried out under reduced pressure through membrane filters (0.2 average pore diameter) which were soaked for 1/2 hour in a 1% HC1 solution and then rinsed several times with deionized water before use. The first 100 ml of filtrate was used 44 to r i n s e out the f i l t e r f l a s k and then d i s c a r d e d . Storage b o t t l e s f o r the metal samples and the glassware i n v o l v e d i n f i l t r a t i o n were c l e a n e d w i t h hot 6N HC1 p r i o r to a c r u i s e and then r i n s e d s e v e r a l times w i t h d e i o n i z e d water and once w i t h the sample p r i o r to use. 3.3 Storage Methods S i n c e i t was not always f e a s i b l e to a n a l y s e the metal samples immediately a f t e r c o l l e c t i o n , the e f f e c t of s t o r a g e was i n v e s t i g a t e d . Samples c o l l e c t e d w i t h a 5 l i t r e Nisken b o t t l e and f i l t e r e d as d e s c r i b e d i n the p r e v i o u s s e c t i o n were a n a l y s e d on board s h i p w i t h i n 3 hours of c o l l e c t i o n and the remaining sample s t o r e d i n d i f f e r e n t ways and a n a l y s e d a t v a r i o u s times a f t e r r e t u r n t o the l a b o r a t o r y . Changes observed i n the c o n c e n t r a t i o n s o f Cu and Pb as a f u n c t i o n o f time and method o f s t o r a g e are g i v e n i n F i g u r e 3.3. The concen-t r a t i o n o f both metals decreased s i g n i f i c a n t l y w i t h time i n u n a c i d i f i e d samples even when f r o z e n , presumably through a d s o r p t i o n onto the w a l l s o f the c o n t a i n e r . No l o s s was found i f the samples were a c i d i f i e d w i t h HC1 to a pH of approximately 2 and s t o r e d i n p o l y p r o p y l e n e b o t t l e s . Robertson [19 68] observed t h a t other t r a c e metals behave s i m i l a r i l y . A l l d a t a r e p o r t e d i n t h i s study were o b t a i n e d u s i n g 100 ml f i l t e r e d samples t h a t were a c i d i f i e d w i t h 0.5 ml o f 45 F i g u r e 3.3 Storage e f f e c t s on the Cu content o f seawater samples s t o r e d i n 125 ml p o l y p r o p y l e n e c o n t a i n e r s 46 6N HC1 and stored in 125 ml polypropylene bottles at approximately 5°C until analysed. 3.4 Analytical Methods 1. Dissolved Cu and Pb: Seawater samples were filtered and stored as described above and analysed for Cu and Pb by the standard procedure given in Section 2.3. Samples were generally analysed within 10 days of collection. 2. Dissolved Oxygen: Dissolved oxygen was determined on board ship by standard Winkler titration using the modified reagents described by Carrit and Carpenter [1966]. 3. Salinity: Salinity was estimated with an Auto-Lab Model 601 MK3 Inductive Salinometer (Extended Range Modeli . 3.5 Intercomparison of Techniques The chemical species in which Cu occurs in solution in seawater have not been definitely established and there is no assurance that different analytical procedures all measure the same forms of dissolved Cu. As a consequence, it may not always be meaningful to compare values obtained by different techniques. The voltammetric method developed in this study was compared to another method which is currently being employed 47 f o r the r o u t i n e a n a l y s i s of Cu and s e v e r a l o t h e r t r a c e metals i n seawater a t the U n i v e r s i t y of B r i t i s h Columbia. T h i s technique [E.V. G r i l l , u n published procedure] i n v o l v e s a s o l v e n t e x t r a c t i o n p r e c o n c e n t r a t i o n f o l l o w e d by atomic a b s o r p t i o n s p e c t r o p h o t o m e t r i c a n a l y s i s . The p r e c o n c e n t r a t i o n c o n s i s t s o f c h e l a t i n g the metals i n 2 l i t r e s of f i l t e r e d seawater w i t h d i e t h y l d i t h i o c a r b a m a t e (DDC) a t a pH of 6 and e x t r a c t i n g the sample 3 times w i t h isoamyl a c e t a t e ; the metals are then back e x t r a c t e d from the o r g a n i c phase i n t o a 20 ml aqueous phase w i t h a c i d i f i e d C l 2 water. The above o p e r a t i o n s are c a r r i e d o u t on board s h i p immediately a f t e r f i l t e r i n g . The a c i d i f i e d aqueous e x t r a c t , which i s s t o r e d i n a c i d r i n s e d p o l y p r o p y l e n e b o t t l e s and r e t u r n e d to the l a b , i s f u r t h e r c o n c e n t r a t e d p r i o r t o a n a l y s i s by r e f o r m a t i o n o f the metal d i e t h y l d i t h i o c a r b a m a t e s and e x t r a c t i o n i n t o 5 ml of methyl i s o b u t y l ketone CMIBK). Copper i s then determined by flame atomic a b s o r p t i o n measure-ment of the MIBK s o l u t i o n . On two separate o c c a s i o n s , water samples c o l l e c t e d a t a v a r i e t y of depths were f i l t e r e d and s e p a r a t e d i n t o 2 a l i q u o t s and then a n a l y s e d by the two d i f f e r e n t methods. The r e s u l t s are g i v e n i n T a b l e V. The f i r s t s e t was o b t a i n e d u s i n g samples t h a t were s t o r e d u n a c i d i f i e d i n 1 g a l l o n p o l y e t h y l e n e carboys a t 5°C and a n a l y s e d 5 days a f t e r c o l l e c t i o n . The second s e t was run on board s h i p immediately a f t e r f i l t r a t i o n . 48 TABLE V COMPARISON BETWEEN THE CONCENTRATION OF C u I N SELECTED SEA-WATER SAMPLES AS DETERMINED BY ASV AND BY ATOMIC ABSORPTION A N A L Y S I S WITH SOLVENT EXTRACTION PRECONCENTRATION. a I . W a t e r c o l l e c t e d O c t o b e r 12, 1972 a t s t a t i o n I n d i a n 2. D e p t h (ml [Cu] ug/1 , [ C u ] s o l v . e x t r . * l [ C u ] ASV 1 ASV S o l v e n t E x t r a c t i o n 10 0.60 0.55 0.92 20 0.57 0.53 0.93 50 0.60 0.53 0 .88 75 0.46 0.42 0.91 100 0.43 0.45 1.05 150 0.47 0.42 0.89 200 0.40 0.40 1.00 Mean R a t i o 0.94 I I . W a t e r c o l l e c t e d a n d a n a l y s e d O c t o b e r 24, 1972 a t s t a t i o n P a c i f i c 2 148° 00' N, 128° 00' W). D e p t h (m) [Cu] yg/1 , [Cu] s o l v . e x t r .» l [ C u ] ASV ' ASV S o l v e n t E x t r a c t i o n 10 0.36 0.37 1.03 50 0.24 0.24 1.00 500 0.24 0.22 0.92 1000 0.55 0.46 0.84 2000 0.36 0.33 0.92 2300 b 2.96 2 . 82 0.95 Mean R a t i o 0.94 a A n a l y s t , F.A. W h i t n e y ^ S a m p l e a p p a r e n t l y c o n t a m i n a t e d i n c o l l e c t i o n 49 The r e s u l t s o b t a i n e d by the two methods agree i n most cases to w i t h i n 10%, though the v a l u e s o b t a i n e d by ASV tend g e n e r a l l y to be s l i g h t l y h i g h e r than those o b t a i n e d by e x t r a c t i o n . T h i s c o u l d r e f l e c t a r e a l d i f f e r e n c e i n the amount o f metal measured by the two methods or an ana-l y t i c a l b i a s r e l a t e d to the p a r t i c u l a r t e c h n i q u e s and a n a l y s t s i n v o l v e d . S i n c e the t r u e v a l u e f o r the metal c o n t e n t of the samples i s not known, i t i s not p o s s i b l e to determine whether one o f the methods i s more a c c u r a t e than the o t h e r or whether e i t h e r measures the t o t a l d i s s o l v e d Cu. The c l o s e agreement does suggest though, t h a t both methods d e t e c t r o u g h l y the same forms of the metal i n n a t u r a l seawater. 3.6 E x p e r i m e n t a l O b s e r v a t i o n s S t a t i o n s i n the system were sampled t h r e e times i n the p e r i o d J u l y to October, 1972. T a b l e VI l i s t s the d a t e s , c r u i s e numbers and the s t a t i o n s sampled. The obser-v a t i o n s from these c r u i s e s are t a b u l a t e d i n the Appendix. TABLE VI SAMPLING IN INDIAN ARM AND BURRARD INLET C r u i s e Dates S t a t i o n s Sampled 72/29 72/35 72/39 72/41 J u l y 17, 1972 Sept. 5, 1972 Oct. 12, 1972 Oct. 25, 1972 I n d i a n 0,1,2,3: B u r r a r d 2,3,4 I n d i a n o , l , 2 , 3 : B u r r a r d 2,3,4 I n d i a n 1.5, 2, 3 B u r r a r d 4 50 The s t a t i o n a t B u r r a r d 4 was taken as a c o n t r o l , assuming the s u b s u r f a c e water a t t h i s s t a t i o n t o be t y p i c a l of G e o r g i a S t r a i t water and o f the s u b s u r f a c e water e n t e r -i n g B u r r a r d I n l e t and subsequently I n d i a n Arm. The lowest c o n c e n t r a t i o n s o f both metals were observed i n the s u b s u r f a c e waters a t B u r r a r d 4 d u r i n g J u l y and September, w h i l e the h i g h e s t l e v e l s were encountered i n the su b s u r f a c e waters o f the harbour and I n d i a n Arm d u r i n g the same p e r i o d . The c o n c e n t r a t i o n o f Cu a t the s t a t i o n s sampled ranged from 0.19 to 2.20 ug/1, a l t h o u g h v a l u e s were g e n e r a l l y l e s s than 1.0 ug/1 (Appendix). The range i n Pb c o n c e n t r a t i o n s was from l e s s than 0.05 to 0.8 3 ug/1 (Appendix). The d i s t r i b u t i o n s of Cu and Pb observed a t B u r r a r d 4 and I n d i a n 2 a r e compared i n F i g u r e s 3.4 and 3.5. I t i s apparent t h a t both metals tend t o have p a r a l l e l d i s t r i b u t i o n s a t each o f the s t a t i o n s . 3.7 D i s c u s s i o n The marked tendency f o r Cu and Pb to covary, both s p a t i a l l y and temporally, suggests t h a t t h e i r d i s t r i b u t i o n s a re g e n e r a l l y c o n t r o l l e d by s i m i l a r f a c t o r s . A l t h o u g h these may be o f a b i o l o g i c a l , c h e m i c a l o r p h y s i c a l n a t u r e , the most important f a c t o r i n a t l e a s t some cases appears t o be the g e n e r a l c i r c u l a t i o n of water i n the system. The i n c r e a s i n g s a l i n i t y i n the s u b s u r f a c e waters a t B u r r a r d 4 d u r i n g s u c c e s s i v e c r u i s e s ( F i g u r e 3.6) i n d i c a t e s OJuly a) INDIAN 2 O September AOctober b) BURRARD 4 F i g u r e 3.4 The Cu d i s t r i b u t i o n a t s t a t i o n s Indian.2 and Bur r a r d 4 d u r i n g J u l y , September and October, 1972 on F i g u r e 3.5 The Pb d i s t r i b u t i o n a t s t a t i o n s I n d i a n 2 and B u r r a r d 4 d u r i n g J u l y , September and October, 1972 an intrusion of more saline Juan de Fuca Strait water into the Strait of Georgia [Waldichuk, 1957]. A corresponding increase in the Cu and Pb concentrations at this station suggests that the intruding water had a higher metal content than that resident in Georgia Strait. This increase is particularly evident in the Cu distribution (Figure 3.4). However, the Cu concentrations did not exceed 0.8 0 yg/1 and are consistent with reported concentrations of less than 1.0 yg/1 in the North Pacific and in other British Columbia coastal waters [Tatomer, 1972 , E.V. Grill, personal communication]. The dissolved Pb concentrations of the subsurface water at Burrard 4 are generally less than 0.10 yg/1 and approach the lower limit of detection for the method. These values are only slightly higher than the Pb concen-trations of 0.02 - 0.04 yg/1 observed in the open ocean below 1000 m [Chow, 1968] and are in good agreement with the values observed by Baier [1971] at stations near the mouth of Georgia Strait. During July and September, there was an increase in the Cu and Pb content of the subsurface waters on passing from Georgia Strait into Burrard Inlet and Indian Arm and a reversal of,this trend at the surface (Figures 3.7 and 3.8), gradients which are also apparently closely related to general circulation patterns. The surface water in the F i g u r e 3.6 V a r i a t i o n s i n s a l i n i t y w i t h depth a t s t a t i o n B u r r a r d 4 d u r i n g J u l y , September and October, 1972 55 A July 17,1972 15-U)-•a1 .O. 05-00-25 i -A A"' 1 Burrard 4 1 Burrard 2 STATION 1 Indian 2 A September 5,1972 20 15-05 0.0 10m . *• Burrard 4 Burrard 2 STATION 1 Indian 2 F i g u r e 3.7 V a r i a t i o n s i n the Cu c o n c e n t r a t i o n i n the upper 50 m a t s t a t i o n s B u r r a r d 4, B u r r a r d 2 and I n d i a n 2 d u r i n g J u l y and September, 1972 56 OA-July 17.1972 04-•3" 02-00-25 m j < 0 m _ _ _ ^ - - - £ - ^ A-'' A- •• 50n 1 Burrard4 Burrard 2 STATION Indian 2 08-September 5.1972 06-\ 25m \ 10 m f 0.4-02--9 A- . .50 m -6 ao- — i Burrard 4 Burrard 2 STATION Indian 2 F i g u r e 3.8 V a r i a t i o n s i n the Pb c o n c e n t r a t i o n i n the upper 50 m a t s t a t i o n s B u r r a r d 4, B u r r a r d 2 and I n d i a n 2 d u r i n g J u l y and September, 1972 57 i n l e t s i s r e l a t i v e l y brackish, flowing outwards while the subsurface water i s more saline and moving towards the head of Indian Arm. When t h i s i s considered, there i s an increase i n the metal content for both the surface and subsurface water as i t flows through Burrard I n l e t where the greatest inputs might be expected. A p e r s i s t e n t feature of the d i s t r i b u t i o n s of both metals i n Indian Arm were maxima between 10 and 50 m (Figures 3.4 and 3.5). Intrusions of water from Burrard I n l e t into Indian Arm normally occur at depths of between 10 and 100 m and are often noticeable as tongues of highly oxygenated water extending from the mouth towards the head of the i n l e t [Gilmartin, 19 62]. Such an i n t r u s i o n i s evident i n the l o g i t u d i n a l p r o f i l e for dissolved oxygen during September (Figure 3.9). The net e f f e c t of these intrusions i s the addition of Burrard I n l e t water, usually at an intermediate depth. The dissolved metal maxima i n Indian Arm between 10 and 50 m correlates with the approximate depth of these intrusions, suggesting that Burrard I n l e t water i s the source of the dissolved metal maxima at these depths. As a r e s u l t of mixing and the entrainment of t h i s higher metal content water with water of lower metal content at the surface, a concentration gradient between the mouth and the head of the f j o r d at the depths of the intruding water would be expected. This gradient i s present between stations Indian 0 and 1 i n July and September but the maximum OXYGEN IN ml/1 F i g u r e 3.9 L o n g i t u d i n a l p r o f i l e of d i s s o l v e d oxygen i n I n d i a n Arm on September 5, 1972. The dots i n d i c a t e sample depths CO metal c o n c e n t r a t i o n s were observed a t I n d i a n 2 i n the middle of the i n l e t ( F i g u r e s 3.10 and 3.11). In the absence of a d d i t i o n a l d a t a , i t i s not p o s s i b l e to determine i f t h i s i s the r e s u l t of an e a r l i e r i n t r u s i o n or of other sources of the metals i n the system. Sources of water i n I n d i a n Arm other than t i d a l i n t r u s i o n s a r e the I n d i a n R i v e r e n t e r i n g a t the head of the f j o r d and, to a l e s s e r e x t e n t , the d i s c h a r g e o f the Buntzen power p l a n t d i r e c t l y a c r o s s from I n d i a n 2 on the e a s t e r n shore [ G i l m a r t i n , 1962]. S i n c e the d i s s o l v e d Cu and Pb c o n c e n t r a t i o n s of the s u r f a c e l a y e r are very low, the f r e s h waters d e r i v e d from these sources would appear to have a lower metal c o n t e n t than t h a t of the r e s i d e n t s a l i n e waters. Water i n t r o d u c e d a t these sources may, however, a l s o c o n t a i n metal t h a t i s a s s o c i a t e d w i t h p a r t i c u l a t e matter. I f metals were desorbed as t h i s m a t e r i a l s i n k s i n t o more s a l i n e water, a s u b s u r f a c e maxima o r i g i n a t i n g near the head or middle of the i n l e t might then be expected. Kharkar e t al_. [1968] have shown t h a t s i g n i f i c a n t d e s o r p t i o n of t r a c e metals from suspended m i n e r a l matter can occur w i t h i n c r e a s i n g s a l i n i t y . I t i s p a r t i c u l a r i l y e v i d e n t t h a t the metal d i s t r i -b u t i o n s are not c o n t r o l l e d s o l e l y by p h y s i c a l f a c t o r s when the deep water i n I n d i a n Arm i s c o n s i d e r e d . D e s p i t e the f a c t t h a t t h e r e was no apparent d i s p l a c e m e n t o f water i n I n d i a n Arm below 100 m d u r i n g the sampling p e r i o d , l a r g e f l u c t u a t i o n s i n metal c o n t e n t were observed s i m i l a r t o those 60 Figure 3.10 Longitudinal p r o f i l e of dissolved Cu i n Indian Arm on September 5, 1972. The dots indicate sample depths Figure 3.11 Longitudinal p r o f i l e of dissolved Pb i n Indian Arm on September 5, 1972. The dots indicate sample depths in the upper 100 m (Figures 3.4 and 3.5). An increase in the metal concentrations between July and September was followed by a significant decrease in October. Since these variations are apparently independent of inputs of higher or lower metal content water, the controlling mechanism must be either biological consumption or decay, or else solution or sorption reactions involving suspended particulate matter. The extent of the effects of biological processes are impossible to predict at present and those of sorption processes can vary with the concentration of adsorbate, pH, salinity and temperature as well as the physical characteristics of the adsorbents. The fact that suspended mineral and detrital organic materials readily adsorb trace metals such as Cu and Pb from seawater is, however, well documented [Krauskopf, 1956], The Pb concentrations observed in this system are lower than might be expected considering its proximity to a large urban area. Baier [1971] reported that Pb concen-trations in arid near San Francisco harbour are more than 2 ug/1 and that in Lake Washington (Seattle) they are as high as 6 ug/1. The dissolved Pb concentrations observed in the present study are well below these levels and are particularily low at the surface within Burrard Inlet and Indian Arm. The results of previous studies on marine systems have indicated that the dissolved Pb concentration 62 i n t h e s u r f a c e l a y e r v a r i e s i n v e r s e l y w i t h t h e d i s t a n c e f r o m a l a r g e u r b a n a r e a [Chow, 1 9 6 8 ; B a i e r , 1 9 7 1 ] . S u c h a r e l a t i o n s h i p d o e s n o t a p p e a r t o h o l d i n t h e p r e s e n t s y s t e m w h e r e t h e l o w e s t s u r f a c e d i s s o l v e d Pb c o n c e n t r a t i o n s w e r e o b s e r v e d i n t h e h a r b o u r a n d I n d i a n Arm. B a i e r [1971] i n d i c a t e d t h a t t h e p a r t i c u l a t e Pb c o n t e n t o f n e a r s h o f e w a t e r s c o u l d e x c e e d t h e d i s s o l v e d c o n t e n t . I f Pb i s i n t r o d u c e d a s a p a r t i c u l a t e a e r o s o l , t h e l o w d i s s o l v e d l e v e l s a t t h e s u r f a c e i n t h e h a r b o u r a n d I n d i a n A r m w o u l d i n d i c a t e t h a t t h e p a r t i c u l a t e m e t a l i s r e m o v e d f r o m t h e s u r f a c e l a y e r b e f o r e much o f t h e Pb d i s s o l v e s o r i s d e s o r b e d e i t h e r b y t h e g e n e r a l s u r f a c e f l o w t h a t c a r r i e d i t o u t i n t o G e o r g i a S t r a i t o r b y s i n k i n g i n t o t h e more s a l i n e s u b s u r f a c e w a t e r . I n a g r e e m e n t w i t h t h i s , t h e h i g h e s t Pb c o n c e n t r a t i o n s w e r e a t i n t e r m e d i a t e d e p t h s i n t h e h a r b o u r a n d I n d i a n A r m a n d h i g h e r P b c o n c e n t r a t i o n s w e r e o b s e r v e d i n t h e s u r f a c e l a y e r a t B u r r a r d 3 a n d 4 t h a n a t B u r r a r d 2 i n t h e h a r b o u r . 3.8 Summary A l t h o u g h l o c a l i z e d p o c k e t s o f C u e n r i c h e d w a t e r o c c u r r e d a t d i f f e r e n t t i m e s a n d l o c a t i o n s w i t h i n b o t h B u r r a r d I n l e t a n d I n d i a n A r m , t h e r e d o e s n o t a p p e a r t o b e a n o v e r a l l s i g n i f i c a n t e n r i c h m e n t o f C u i n t h i s s y s t e m a s c o m p a r e d t o G e o r g i a S t r a i t a n d o t h e r B r i t i s h C o l u m b i a c o a s t a l w a t e r s . The o b s e r v e d d i s t r i b u t i o n a p p e a r s , t o a l a r g e e x t e n t , t o b e r e g u l a t e d by the c i r c u l a t i o n w i t h i n the system but a d d i t i o n a l r e g u l a t o r y mechanisms can a l s o be i n f e r r e d from the l a r g e f l u c t u a t i o n s i n c o n c e n t r a t i o n observed i n I n d i a n Arm t h a t are a p p a r e n t l y independent of the c i r c u l a t i o n . S i m i l a r mechanisms appear to r e g u l a t e the d i s t r i b u t i o n o f d i s s o l v e d Pb. A l t h o u g h the s u b s u r f a c e waters i n the i n l e t s are e n r i c h e d i n d i s s o l v e d Pb by as much as an order of magnitude compared to Georgia S t r a i t , the d i s s o l v e d Pb c o n c e n t r a t i o n s are lower than those r e p o r t e d f o r marine waters near other urban l o c a l i t i e s . 64 4. A P P L I C A T I O N OF THE MERCURY PLATED GLASSY CARBON ELECTRODE TO THE STUDY OF COMPLEXED METAL I N SEAWATER T r a c e m e t a l s o c c u r i n s e a w a t e r i n a v a r i e t y o f f o r m s t h a t c a n b e d i f f e r e n t i a t e d o n t h e b a s i s o f t h e i r c h e m i c a l o r p h y s i c a l c h a r a c t e r i s t i c s . The s i m p l e s t scheme o f c l a s s i f i -c a t i o n i s one b a s e d o n p h y s i c a l s i z e i n w h i c h a n y m e t a l r e t a i n e d b y a f i n e p o r o s i t y membrane f i l t e r ( n o r m a l l y o n e w i t h a 0.45 urn a v e r a g e p o r e d i a m e t e r ) i s t e r m e d p a r t i c u l a t e . The p o r t i o n p a s s i n g t h r o u g h t h e f i l t e r i s a r b i t r a r i l y d e -f i n e d t o be d i s s o l v e d b u t may i n f a c t c o n s i s t o f m e t a l t h a t i s a c o n s t i t u e n t o f c o l l o i d a l s i z e d o r g a n i c o r i n o r g a n i c m a t e r i a l a s w e l l a s m o l e c u l a r o r i o n i c s p e c i e s t h a t a r e c o n v e n t i a l l y c o n s i d e r e d t o be i n t r u e s o l u t i o n . The m e t a l i n t r u e s o l u t i o n p o t e n t i a l l y c o n s i s t s o f s i m p l e h y d r a t e d c a t i o n s a n d o f c o m p l e x e s f o r m e d b y t h e c a t i o n w i t h i n o r g a n i c l i g a n d s , p a r t i c u l a r i l y m a j o r s e a w a t e r a n i o n s , a n d s i m p l e o r g a n i c s o l u t e s . The m e t h o d s c u r r e n t l y a v a i l a b l e f o r t h e a n a l y s i s o f t r a c e m e t a l s a t t h e l e v e l s p r e s e n t i n s e a w a t e r do n o t a l l o w one t o r e a d i l y d i f f e r e n t i a t e b e t w e e n t h e d i s s o l v e d s p e c i e s t h a t a r e p o t e n t i a l l y p r e s e n t . T h u s , t h e v a l u e s r e p o r t e d i n t h e l i t e r a t u r e a r e g e n e r a l l y f o r t h e t o t a l o r some u n d e f i n e d p o r t i o n o f t h e t o t a l d i s s o l v e d m e t a l c o n t e n t . B u t , a s 65 p o i n t e d out p r e v i o u s l y , s p e c i a t i o n o f a metal may be more important b i o l o g i c a l l y Cand chemically} than i t s t o t a l c o n c e n t r a t i o n . There have been a number of r e p o r t s c i t i n g evidence f o r a s s o c i a t i n g a f r a c t i o n of Cu i n seawater w i t h 3 i d i s s o l v e d o r g a n i c matter [a review i s g i v e n by S e i ^ e l , 197,0] but as y e t v e r y l i t t l e i s known about the e x t e n t of such i n t e r a c t i o n s and the whole q u e s t i o n of whether the metal i n s o l u t i o n i s complexed to a s i g n i f i c a n t e x t e n t w i t h o r g a n i c matter remains l a r g e l y one o f s p e c u l a t i o n . Both Matson [1968] and F i t z g e r a l d [1970] have attempted to examine t h i s q u e s t i o n by means of ASV. Matson observed a v a r i e t y of anomalies i n the behaviour of the composite mercury g r a p h i t e e l e c t r o d e d u r i n g the a n a l y s i s of seawater s o l u t i o n s t h a t he a t t r i b u t e d t o o r g a n i c or i n o r g a n i c complexing o f the m e t a l . Hume and C a r t e r [1972] observed s i m i l a r anomalies but found t h a t most were the r e s u l t o f changes i n the 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 e l e c t r o d e i t s e l f and concluded t h a t i t i s u n l i k e l y t h a t the technique p r o v i d e d any u s e f u l q u a n t i t a t i v e i n f o r m a t i o n about metal i o n s p e c i a t i o n i n n a t u r a l waters. Much of the problem, they found, o r i g i n a t e s i n the d i f f i c u l t y i n d i s t i n g u i s h i n g between the i n t e r f e r i n g e f f e c t s of s u r f a c e a c t i v e agents t h a t are adsorbed onto the e l e c t r o d e and the e f f e c t s produced by complexation of the m e t a l . F o r i n s t a n c e , Matson [1968] observed t h a t the r a t e of i n c r e a s e of the peak c u r r e n t w i t h p l a t i n g p o t e n t i a l f o r Cu was lower i n most seawater samples compared to 0.5 M NaCl. Matson a t t r i b u t e d t h i s t o complexation of the metal i o n . S i m i l a r r e s u l t s were o b t a i n e d i n the p r e s e n t study but i t was a l s o found t h a t the a d d i t i o n of s m a l l amounts of g e l a t i n to a 0.5 M NaCl s o l u t i o n produced a s u p p r e s s i n g e f f e c t on the Cu peak h e i g h t s i m i l a r to t h a t observed i n seawater (Pigure 4.1). Thus the a d s o r p t i o n of s u r f a c e a c t i v e m a t e r i a l c o u l d be the source o f the anomalous behaviour observed i n seawater. O x i d a t i v e d e s t r u c t i o n of the o r g a n i c matter i n s o l u t i o n would not d i f f e r e n t i a t e between the two p o s s i b i l i t i e s . Matson {1968] and F i t z g e r a l d [1970] a l s o observed t h a t the peak h e i g h t of the Cu s t r i p p i n g c u r r e n t was very s e n s i t i v e to changes i n pH. F i t z g e r a l d concluded t h a t s i n c e l o w e r i n g o f the pH and prolonged p h o t o - o x i d a t i o n of the sample both had a s i m i l a r e f f e c t on the measured Cu c o n c e n t r a t i o n , the i n c r e a s e i n the c u r r e n t as the pH i s lowered i s the r e s u l t o f the r e l e a s e of metal complexed by o r g a n i c compounds p r e s e n t i n the sample. S i m i l a r i l y , A l l e n e t a l . [1970] a t t r i b u t e d the i n c r e a s e i n the Pb s t r i p p i n g c u r r e n t when samples were a c i d i f i e d to the r e l e a s e of metal from l a b i l e o r g a n i c complexes. The v a r i a t i o n of the Cu and Pb s t r i p p i n g c u r r e n t observed i n the p r e s e n t study w i t h changing pH i n i r r a d i a t e d , a r t i f i c i a l seawater i s shown i n F i g u r e 2.6. Samples were i r r a d i a t e d w i t h an U l t r a V i o l e t Products Inc. PCQ 9G-1 o q u a r t z lamp ( r a d i a n t o u t p u t a t 2537 A; 2.5 watts) immersed 67 Experimental Conditions; 2 >jg Cu /1, plate time 6 minutes. PLATE POTENTIAL (volts vs Ag/AgCI reference electrode) F i g u r e 4.1 The e f f e c t o f g e l a t i n on the Cu s t r i p p i n g response as a f u n c t i o n o f p l a t i n g p o t e n t i a l i n 0.5 M NaCI s o l u t i o n 68 i n a Pyrex c y l i n d e r c o n t a i n i n g approximately 200 ml of sample. T h i s technique i s p r e f e r a b l e to wet o x i d a t i o n s i n c e no reagents are added t o the samples and the pH i s not a p p r e c i a b l y a l t e r e d . F i t z g e r a l d [1970] u s i n g the same lamp, found t h a t the r a t e of d e s t r u c t i o n o f the o r g a n i c matter f o l l o w e d f i r s t o r d e r k i n e t i c s . I r r a d i a t i o n of 70 ml samples f o r 4 hours d e s t r o y e d 75% of the o r g a n i c matter. In t h i s work, samples were i r r a d i a t e d f o r a minimum of 10 hours. No attempt was made to determine the e f f i c i e n c y of the procedure. A r t i f i c i a l seawater which had not been i r r a d i a t e d w i t h UV l i g h t , some n a t u r a l seawater samples, and a l l seawater samples a f t e r p r o longed p h o t o - o x i d a t i o n gave i d e n t i c a l responses. The amount of Hg p l a t e d onto the e l e c t r o d e was found to be independent o f the pH below a pH of 7, i n d i c a t i n g t h a t the observed v a r i a t i o n s i n the Cu and Pb s t r i p p i n g c u r r e n t s a r e not due to changes i n the Hg f i l m t h i c k n e s s . The i n c r e a s e i n the s t r i p p i n g c u r r e n t w i t h d e c r e a s i n g pH Cand, thus, i n the amount of metal r e a d i l y r e d u c i b l e a t the e l e c t r o d e ) must t h e r e f o r e r e f l e c t changes i n the degree of complexation of the metals by i n o r g a n i c l i g a n d s or an a l t e r a t i o n i n e l e c t r o d e s u r f a c e c h a r a c t e r i s t i c s . The l a t t e r p o s s i b i l i t y has been suggested by P e t e r s and C r u s e r [1965]. They proposed t h a t the decrease i n the r a t e o f r e d u c t i o n o f Cu a t a Pt e l e c t r o d e i n c h l o r i d e media a t n e u t r a l or b a s i c pH's was the r e s u l t o f c u p r i c 69 i o n s b e i ng p r e c i p i t a t e d as Cu (OH) 2 onto the e l e c t r o d e s u r f a c e , c a u s i n g an e f f e c t i v e decrease i n the s u r f a c e a r e a . A l o c a l excess of hydroxide w i l l e x i s t i n the r e a c t i o n l a y e r a d j a c e n t to the e l e c t r o d e as a r e s u l t o f the r e d u c t i o n o f r e s i d u a l oxygen i n the s o l u t i o n [Heyrovsky and Kuta, 1966]. P r e c i p i t a t i o n of Pb (OH) 2 i n t h i s r e a c t i o n l a y e r has a l s o been suggested f o r the decrease i n the p u l s e p o l a r o g r a p h i c Pb c u r r e n t i n u n b u f f e r e d or b a s i c s o l u t i o n s [Osteryoung and Osteryoung, 1972]. I f the r e d u c t i o n i n the s t r i p p i n g c u r r e n t were simply due to an a l t e r a t i o n o f the e f f e c t i v e s u r f a c e a r e a , the pH dependence of a l l metals might be expected t o be r o u g h l y the same s i n c e the d e p o s i t i o n o f a p r e c i p i t a t e (s) on the e l e c t r o d e s u r f a c e would have a s i m i l a r e f f e c t on the r e d u c t i o n or d i s s o l u t i o n o f a l l m e t a l s . While the pH dependence of Cu and Pb observed i n t h i s study i s v e r y s i m i l a r , the Cd and Zn responses r e p o r t e d l y d i f f e r from t h a t observed f o r Cu and Pb [ Z i r i n o , 1969, P i r o e t a l . , 1969]. F o r these metals, a steady s t a t e c u r r e n t i s appar-e n t l y reached when the pH i s lowered to approximately 7. Thus, the v a r i a t i o n s i n s t r i p p i n g c u r r e n t s w i t h pH must be, a t l e a s t i n p a r t , the r e s u l t o f changes i n the a c t i v i t i e s of i n d i v i d u a l metal i o n s . Z i r i n o and Yamamoto [1972] have suggested t h a t v a r i a t i o n s i n the s t r i p p i n g c u r r e n t w i t h pH are the r e s u l t of changes i n s p e c i a t i o n i n the s o l u t i o n as a whole; however, s p e c i a t i o n changes i n the b u l k s o l u t i o n 70 cannot be d i s t i n g u i s h e d e x p e r i m e n t a l l y from those o c c u r r i n g i n a t h i n d i f f u s i o n l a y e r a d j a c e n t to the e l e c t r o d e . P i r o e t a l . [1969] demonstrated t h a t the pH depen-dence of the ASV response f o r Zn c o u l d be markedly a l t e r e d by adding s e v e r a l d i f f e r e n t c h e l a t i n g agents to seawater samples. T h e i r r e s u l t s showed t h a t c h e l a t i o n r e q u i r e s the pH t o be lowered below t h a t i n the base e l e c t r o l y t e f o r the r e l e a s e o f a l l the Zn, as might be expected, and t h a t the l e v e l t o which the pH must be lowered i s a f u n c t i o n of the s t a b i l i t y of the c h e l a t e formed. The pH dependence of the Cu and Pb s t r i p p i n g response w i t h the mercury p l a t e d g l a s s y carbon e l e c t r o d e was i n v e s t i g a t e d i n t h i s l i g h t t o determine i t s a p p l i c a b i l i t y t o the d e t e c t i o n of o r g a n i c a l l y complexed metal i n sea water. The s t a b i l i t y c o n s t a n t s o f the o r g a n i c c h e l a t e s formed by the m e r c u r i c i o n are i n many cases of the same order of magnitude as those formed by Cu and Pb [ S i l l e n and M a r t e l l , 1964]. As a r e s u l t , m e r c u r i c i o n s , which were added i n l a r g e excess to the samples, c o u l d i n some cases compete f o r o r g a n i c l i g a n d s which no r m a l l y would be bound t o these m e t a l s . The p r e s e n t method has, t h e r e f o r e , o n l y l i m i t e d a p p l i c a t i o n , even t o a q u a l i t a t i v e study o f metal complex-a t i o n . Only n a t u r a l l y o c c u r r i n g complexes having a h i g h s p e c i f i c i t y f o r Cu or Pb or those i n which. Cu or Pb are k i n e t i c a l l y i n e r t to d i s p l a c e m e n t by m e r c u r i c but not hydrogen i o n s would be expected to p e r s i s t under these 71 conditions. Such complexes do apparently exist. Several seawater samples from Georgia Strait and Indian Arm were found to have a pH response differing from that of artificial seawater. In these cases, the Cu stripping current increased as the pH decreased to 5, as is characteris-tic of all seawater samples, but instead of remaining con-stant below this level, increased again as the pH was lowered further. An example is given in Figure 4.2. Piro's work [1969] had indicated that chelation by organics produced a similar effect on the Zn response. To determine whether the anomalous results in this case were due to chelation of Cu, the samples were analysed before and after irradiation for 10 hours with UV light. In all cases, after irradiation, the pH response returned to normal (i.e. to a response identical to that obtained with artificial seawater). While addition of small amounts of gelatin to artificial seawater did not alter the character of the pH response, an addition —6 of 10 M EDTA produced a shift analogous to that observed in the raw seawater samples in question. An artificial seawater sample spiked with 10 ^ M EDTA, after irradiation, gave no anomalous behaviour (Figure A.31. These results strongly suggest that the shift in the pH response observed in some seawater samples was the result of the partial complexing of Cu by naturally occurring dissolved organic solutes. 72 a. O. b Seawater - stored in glass carboy at 5°C O Without irradiation © After 12 hours irradiation Experimental Conditions; plate time 8 minutes, plate potential -0.9 v. sweep rate 0.032 vysec. - O - — O PH F i g u r e 4.2 V a r i a t i o n of i f o r Cu as a f u n c t i o n of pH i n aged seawater b e f o r e and a f t e r p h o t o - o x i d a t i o n 8-a © Artificial seawater „-6 O +10 M EDTA A +10 M EDTA after 10 hours irradiation Experimental Conditions) plate time 5 minutes plate potential -0.9 v sweep rate 0032 w/sec 5 6 PH F i g u r e 4.3 E f f e c t o f EDTA on the i p f o r Cu seawater b e f o r e and a f t e r photo-i n a r t i f i c i a l o x i d a t i o n 73 No s i m i l a r e f f e c t was observed i n the Pb pH response. Complexation of Pb i s perhaps l e s s l i k e l y to occur s i n c e Pb c o n c e n t r a t i o n s on a molar s c a l e are more than an o r d e r o f magnitude lower than those of Cu. However, i t i s a l s o p o s s i b l e t h a t Pb was c o m pletely d i s p l a c e d from any complexes by m e r c u r i c i o n s or e l s e t h a t changes i n the magnitude of the Pb s t r i p p i n g c u r r e n t were not l a r g e enough to be d i s c e r n -a b l e a t the low l e v e l s of Pb encountered i n most samples. 4.1 Summary Al t h o u g h i t i s not p o s s i b l e t o o b t a i n q u a n t i t a t i v e i n f o r m a t i o n on the s p e c i a t i o n of Cu or Pb i n seawater by the p r e s e n t t e c h n i q u e , c o r r e l a t i o n s between the s t r i p p i n g c u r r e n t and hydrogen i o n a c t i v i t y can f u r n i s h some q u a l i t a t i v e i n f o r m a t i o n as to the r e l a t i v e e x t e n t o f the a s s o c i a t i o n of these metals w i t h c e r t a i n types of o r g a n i c s o l u t e s . On the b a s i s o f the r e s u l t s o b t a i n e d i n t h i s study, Cu i n seawater a t a normal pH appears to be complexed i n some cases by d i s s o l v e d o r g a n i c matter. The l a r g e excess of m e r c u r i c i o n s p r e s e n t i n the samples suggests t h a t these complexing agents have a h i g h s p e c i f i c i t y f o r Cu. 74 BIBLIOGRAPHY Allen, H. E., W. R. Matson and K. H. Mancy (1970). Trace metal characterization in aquatic environments by anodic stripping voltammetry. J. Water Pollut. Contr. Fed., 42: 573-581. Baier, R. W. (1971). Lead distribution in coastal waters. Ph.D. Thesis, University of Washington, Seattle. Barber, R. T., and J. H. Ryther (1969). Organic chelators: factors affecting primary production in the Cromwell Current upwelling. J. Exp. Mar. Biol. Ecol., 3: 191-199. Barendecht, E. (1967). Stripping voltammetry, p. 53 to 109, In A. J. Bard (ed.) Electroanalytical Chemistry, volume 2. Dekker, New York. Bryce-Smith, D. (.1971) . Lead pollution - a growing hazard to public health. Chemistry in Britain, 7: 54-56. Carritt, D. E., and J. H. Carpenter (1966). Comparison and evaluation of currently employed modifications of the Winkler method for determining dissolved oxygen in sea water: a NASCO report. J. Mar. Res., 24: 286-318. Chow, T. J, (1968). Isotope analysis of sea water by mass spectrometry. J. Water Pollut. Contr. Fed,, 40: 399-411. De Vries,W. T., and E. Van Dalen (1964). Theory of anodic stripping voltammetry with, a plane, thin mercury-film electrode. J. Electroanal. Chem. Interfacial Electrochem., 8: 366-377. De Vries,W. T., and E. Van Dalen (1965). Exact treatment of anodic stripping voltammetry with a plane mercury-film electrode. J. Electroanal. Chem. Interfacial Electrochem., 9: 448-456. De Vries, W. T., and E. Van Dalen (1967). Linear potential sweep voltammetry at a plane mercury-film electrode. J. Electroanal. Chem. Interfacial Electrochem., 14: 315-327. 75 E r i c k s o n , S. F., N. L a c k e y a n d T. E. M a l o n e y ( 1 9 7 0 ) . A s c r e e n i n g t e c h n i q u e f o r e s t i m a t i n g c o p p e r t o x i c i t y t o e s t u a r i n e p h y t o p l a n k t o n , J . W a t e r P o l l u t . C o n t r . F e d . , 4 2 : R 2 7 0 - 2 7 8 . F i t z g e r a l d , W. F. ( 1 9 7 0 ) . A s t u d y o f c e r t a i n t r a c e m e t a l s i n s e a w a t e r u s i n g a n o d i c s t r i p p i n g v o l t a m m e t r y . Ph.D. T h e s i s , M a s s a c h u s e t t s I n s t i t u t e o f T e c h n o l o g y , C a m b r i d g e . F l o r e n c e , T. M. (.197 0) . A n o d i c s t r i p p i n g v o l t a m m e t r y w i t h a g l a s s y c a r b o n e l e c t r o d e m e r c u r y - p l a t e d " i n s i t u " . J . E l e c t r o a n a l . Chem. I n t e r f a c i a l E l e c t r o c h e m . , 27: 2 7 3 - 2 8 1 . F l o r e n c e , T. M. ( 1 9 7 2 ) . D e t e r m i n a t i o n o f t r a c e m e t a l s i n m a r i n e s a m p l e s b y a n o d i c s t r i p p i n g v o l t a m m e t r y . J . E l e c t r o a n a l . Chem. I n t e r f a c i a l E l e c t r o c h e m . , 3 5 : 2 3 7 - 2 4 5 . G i l m a r t i n , M. ( 1 9 6 2 ) . A n n u a l c y c l i c c h a n g e s i n t h e p h y s i c a l o c e a n o g r a p h y o f a B r i t i s h C o l u m b i a f j o r d , J . F i s h . R e s . B d . C a n a d a , 1 9 : 9 2 1 - 9 7 4 . G o l d b e r g , E. D. (.19651 . M i n o r e l e m e n t s i n s e a w a t e r , p . 163 t o 1 96. In. J . R. R i l e y a n d G. S k i r r o w (ed.) C h e m i c a l O c e a n o g r a p h y , v o l u m e 1. A c a d e m i c P r e s s , L o n d o n a n d New Y o r k . H e y r o v s k y , J . f a n d J . K u t a ( 1 9 6 6 ) . P r i n c i p l e s o f P o l a r o - g r a p h y . A c a d e m i c P r e s s , L o n d o n a n d New Y o r k . Hume, D. N., a n d J . N. C a r t e r ( 1 9 7 2 ) . C h a r a c t e r i s t i c s o f t h e m e r c u r y c o a t e d g r a p h i t e e l e c t r o d e i n a n o d i c s t r i p p i n g v o l t a m m e t r y : a p p l i c a t i o n t o t h e s t u d y o f t r a c e m e t a l s i n e n v i r o n m e n t a l w a t e r s a m p l e s . Chem. A n a l . ( W a r s a w ) , 17: 7 4 7 - 7 5 8 . K h a r k a r , D. P., K. K. T u r e k i a n a n d K. K. B e r t i n e ( 1 9 6 8 ) . S t r e a m s u p p l y o f d i s s o l v e d s i l v e r , m o l y b d e n u m , a n t i m o n y , s e l e n i u m , c h r o m i u m , c o b a l t , r u b i d i u m a n d c e s i u m t o t h e o c e a n s . G e o c h i m . C o s m o c h i m . A c t a , 32: 2 8 5 - 2 9 8 . K o z l o v s k y , M., a n d A. Z e b r e v a ( 1 9 7 2 ) . I n t e r m e t a l l i c compounds i n a m a lgams, p. 157 t o 1 9 4 . I n P. Zuman, L. M e i t e s a n d I . M. K o l t h o f f ( e d . ) , P r o g r e s s i n P o l a r o g r a p h y , v o l u m e 3. W i l e y I n t e r s c i e n c e , New Y o r k , 76 K o s t e r , G., a n d M. A r i e l ( 1 9 7 1 ) . E l e c t r o c h e m i c a l f l o w c e l l . J . E l e c t r o a n a l . c h e m . i n t e r f a c i a l E l e c t r o c h e m . , 3 3 : 3 3 9 - 3 4 9 . K r a u s k o p f , K. B. ( 1 9 5 6 ) . F a c t o r s c o n t r o l l i n g t h e c o n c e n -t r a t i o n s o f t h i r t e e n r a r e m e t a l s i n s e a w a t e r . G e o c h i m . C o smochim. A c t a , 9: 1-32. L e w i s , A. G.,P. H. W h i t f i e l d a n d A. R a m n a r i n e ( 1 9 7 2 ) . Some p a r t i c u l a t e a n d s o l u b l e a g e n t s a f f e c t i n g t h e r e l a t i o n s h i p b e t w e e n m e t a l t o x i c i t y a n d o r g a n i s m s s u r v i v a l i n t h e C a l a n o i d C o p e p o d E u c h a e t a J a p o n i c a . M a r . B i o l . , 17: 2 1 5 - 2 2 1 . Lyman, J . , a n d R. H. F l e m i n g ( 1 9 4 0 ) . C o m p o s i t i o n o f s e a -w a t e r . J . M a r , R e s . , 3: 1 3 4 - 1 4 6 . M a c c h i , G., ( 1 9 6 5 ) . The d e t e r m i n a t i o n o f i o n i c z i n c i n s e a w a t e r b y a n o d i c s t r i p p i n g v o l t a m m e t r y u s i n g o r d i n a r y c a p i l l a r y e l e c t r o d e s . J . E l e c t r o a n a l . Chem. I n t e r f a c i a l E l e c t r o c h e m . , 9: 2 9 0 - 2 9 8 . M a t s o n , W. R. ( 1 9 6 8 ) . T r a c e m e t a l s : e q u i l i b r i u m a n d k i n e t i c s o f t r a c e m e t a l c o m p l e x e s i n n a t u r a l m e d i a . Ph.D. T h e s i s , M a s s a c h u s e t t s I n s t i t u t e o f T e c h n o l o g y , C a m b r i d g e . M a t s o n , W. R., D. K. Roe a n d D. E. C a r r i t t ( 1 9 6 5 ) . C o m p o s i t e g r a p h i t e - m e r c u r y e l e c t r o d e f o r a n o d i c s t r i p p i n g v o l t a m m e t r y . A n a l . Chem. 37: 1 5 9 4 - 1 5 9 5 . O d i e r , M., a n d V. P l i c h o n ( 1 9 7 1 ) . L e c u i v r e e n s o l u t i o n d a n s l ' e a u de mer: f o r m e c h i m i q u e e t d o s a g e . A n a l . C h i m . A c t a , 5 5 : 2 0 9 - 2 2 0 . O s t e r y o u n g , J . G., a n d R. A. O s t e r y o u n g ( 1 9 7 2 ) . P u l s e p o l a r o g r a p h i c a n a l y s i s o f t o x i c h e a v y m e t a l s . A m e r i c a n L a b o r a t o r y , J u l y . P e t e r s , D. G., a n d S. A. C r u s e r ( 1 9 6 5 ) . C h r o n o p o t e n t i o m e t r y o f C u ( I ) a n d C u ( I I ) i n c h l o r i d e m e d i a . J . E l e c t r o -a n a l . Chem. I n t e r f a c i a l E l e c t r o c h e m . , 9: 2 7 - 4 0 . P i r o , A., M. V e r i z i a n d C. P a p u c c i ( 1 9 6 9 1 . L 1 i r a p o r t a n z e d e l l o s t a t o f i s i c o c h i m i c o d e g l i e l e m e n t i p e r l ' a c c u m u l o n e g l i o r g a n i s m i m a r i n i . I . L o s t a t o c h i m i c o - f i s i c o d e l l o z i n c o i n a c q u a d i m a r e . P u b b l . S t a z . Z o o l . N a p o l i , s u p p l e m e n t 37: 2 9 8 - 3 1 0 . R o b e r t s o n , D. E. ( 1 9 6 8 ) . The a d s o r p t i o n o f t r a c e m e t a l s i n s e a w a t e r o n v a r i o u s c o n t a i n e r s u r f a c e s . A n a l . C h i m . A c t a , 42: 5 3 3 - 5 3 6 . 77 S c h u t z , D. F., a n d K. K. T u r e k i a n ( 1 9 6 5 ) . The i n v e s t i g a -t i o n o f t h e g e o g r a p h i c a l a n d v e r t i c a l d i s t r i b u t i o n o f s e v e r a l t r a c e m e t a l s i n s e a w a t e r u s i n g n e u t r o n a c t i v a t i o n a n a l y s i s . G e o c h i m . C o s m o c h i m . A c t a , 29: 2 5 9 - 3 1 3 . S e i g e l , A. ( 1 9 7 1 ) . M e t a l o r g a n i c i n t e r a c t i o n s i n t h e m a r i n e e n v i r o n m e n t , p. 265 t o 289. I n S. J . F a u s t a n d J . V. H u n t e r (ed.) O r g a n i c compounds i n A q u a t i c  E n v i r o n m e n t s . D e k k e r , New Y o r k . S h a i n , I . ( 1 9 6 3 ) . S t r i p p i n g a n a l y s i s , p. 2533 t o 2 5 6 8. I n I . M. K o l t h o f f a n d P. D. E l v i n g (ed.) T r e a t i s e o n  A n a l y t i c a l C h e m i s t r y , v o l u m e 4, p a r t 1. P e r g a m o n P r e s s , L o n d o n . S i l l e n , L. G., a n d A. E. M a r t e l l ( 1 9 6 4 ) . S t a b i l i t y c o n s t a n t s o f m e t a l i o n c o m p l e x e s . S p e c . P u b l . n o . 1 7 , T h e C h e m i c a l S o c i e t y , L o n d o n . S m i t h , J . D., a n d J . D. Redmond ( 1 9 7 1 ) . A n o d i c s t r i p p i n g v o l t a m m e t r y a p p l i e d t o t r a c e m e t a l s i n s e a w a t e r . J . E l e c t r o a n a l . Chem. I n t e r f a c i a l E l e c t r o c h e m . , 33: 1 6 9 - 1 7 5 . S t e e m a n n N i e l s e n , E., a n d S. W i u m - A n d e r s o n ( 1 9 7 0 ) . C o p p e r i o n s a s p o i s o n i n t h e s e a a n d i n f r e s h w a t e r . M a r . B i o l . , 6: 9 3 - 9 7 . S t e p h e n , H., a n d T. S t e p h e n (ed.) ( 1 9 6 3 ) . S o l u b i l i t i e s o f  I n o r g a n i c a n d O r g a n i c Compounds, v o l u m e 1, p a r t 1. P e r g a m o n P r e s s , L o n d o n . T a t o m e r , C. J . ( 1 9 7 2 ) . C o p p e r i n s e a w a t e r i n t h e S e a t t l e Tacoma a r e a a n d i n two C a n a d i a n i n l e t s . M a s t e r ' s t h e s i s , U n i v e r s i t y o f W a s h i n g t o n , S e a t t l e . W a l d i c h u k , M. ( 1 9 5 7 ) . P h y s i c a l o c e a n o g r a p h y o f t h e S t r a i t o f G e o r g i a , B r i t i s h C o l u m b i a . J . F i s h . R e s . B d . C a n a d a , 14: 3 2 1 - 4 8 6 . W h i t n a c k , G. C , a n d R. S a s s e l i ( 1 9 6 9 ) . A p p l i c a t i o n o f a n o d i c s t r i p p i n g v o l t a m m e t r y t o t h e d e t e r m i n a t i o n o f some t r a c e m e t a l s i n s e a w a t e r . A n a l . C h i m . A c t a , 47: 2 6 7 - 2 7 4 . Z i r i n o , A. R. ( 1 9 7 0 ) . V o l t a m m e t r i c m e a s u r e m e n t , s p e c i a t i o n a n d d i s t r i b u t i o n o f Zn i n o c e a n w a t e r . Ph.D. T h e s i s , U n i v e r s i t y o f W a s h i n g t o n , S e a t t l e . Z i r i n o , A. R., a n d S. Yamamoto ( 1 9 7 2 ) . A pH d e p e n d e n t m o d e l f o r t h e c h e m i c a l s p e c i a t i o n o f C u , Z n , Cd and Pb i n s e a w a t e r . L i m n o l . O c e a n o g . 17: 6 6 1 - 6 7 1 . 78 A P P E N D I X 79 CRUISE: 72/29 DATE: July 17, 1972 (a) STATION: Indian 3 LOCATION: 49° 27.3' N SONIC DEPTH: 79 m 122° 52.5' W Depth (ml Sal.Voo T°C a t 0 2 (ml/11 Cu(ug/1) Pb(ug/1) 1 3.910 13.78 2. 38 7.90 0.41 0.13 10 21.362 10.52 16. 31 5.47 0. 62 0.20 30 23.473 9.51 18. 09 5.25 0.93 0.26 50 25.054 7.79 19. 55 5.22 0.79 0.10 70 26.799 6.76 21. 04 3.67 0.59 0.10 (b) STATION: Indian 2 Depth (ml Sal.°/oo 1 5.180 10 21.533 25 23.470 50 25.273 100 27.303 150 27.538 200 27.573 210 27.569 LOCATION: 49° 23.5' 122° 52.5' T' °C c t 02 (ml/11 16 .79 2. 86 8.10 10 .86 16. 39 5.46 10 .10 18. 00 5.17 7 .80 19. 72 5.18 6 .89 21. 42 3.69 6 .88 21. 60 3.73 6 .86 21. 63 3.65 6 .87 21. 63 3.66 N SONIC DEPTH: 216 m W Cu lug/1) Pb lug/l) 0.48 0.10 0.50 0.10 1.14 0.52 0.63 0.22 0.60 0.12 0.34 0.19 0.81 0.17 1.00 0.10 (c) STATION: Indian 1 LOCATION: 49° 20' N SONIC DEPTH: 61 m 122° 55.5 W Depth (m) Sal.Voo T°C 0 t 02 (ml/11 Cu lug/1) Pb lug/1) 1 8.079 16.60 5. 11 8.00 0.43 0.08 10 22.737 11.16 17. 28 5.39 0.57 0.10 30 24.208 10.32 18. 54 5.00 0.77 0.18 55 26.635 7.42 20. 83 4.34 . 0.84 0.15 80 (d) STATION: I n d i a n 0 LOCATION: 49° 18.2' N SONIC DEPTH: 32 m 122° 5 6 . 3 ' W D e p t h Cm) S a l . % o T°C a 0 2 (ml/1) C u ( u g / 1 ) P b ( u g / 1 ) 1 14.258 15.15 10.09 8.91 0.77 0.10 10 22.065 11.19 16.75 5.34 1.07 0.25 25 24.291 10.39 18.60 5.16 0.67 0.16 (e) STATION: B u r r a r d 2 LOCATION: 49° 1 7 . 9 ' N SONIC DEPTH: 59 m 123° 5 . 5 1 W D e p t h ( m ) S a l . 0 / 0 0 T°C a f c 0 2 (ml/1) C u ( u g / 1 ) P b ( u g / 1 ) 1 16.661 14.75 12.00 7.72 0.63 0.10 10 24.858 10.29 19.05 5.29 0.47 0.15 30 28.305 8.90 21.93 4.83 0.87 0.20 55 28.728 - - 4.76 0.55 0.07 ( f ) STATION: B u r r a r d 3 LOCATION 49° 1 9 . 0 5 ' N SONIC DEPTH: 39 m 123° 1 2 . 1 1 W D e p t h (m) Sal.Voo T ° C a f c O j C m l / l ) C u ( u g / 1 ) P b ( u g / 1 ) 1 18.479 15.67 13.22 7.39 1.00 0.28 10 26.887 9.72 2 0 . 7 1 5.15 0.42 0.15 25 28.654 8.84 22.21 4 .95 0..43 0.18 35 29.260 8.52 22.73 4.75 0.56 0.24 (g) STATION: B u r r a r d 4 LOCATION: 49° 18.0' N SONIC DEPTH: 240 m 123° 2 4 . 0 ' W D e p t h (m) Sal.Voo T ° C a f c 0 2 (ml/1) C u ( u g / 1 ) P b ( u g / 1 ) 1 15.939 - - 7.65 0.68 0.31 10 26.929 - - 5.80 0.23 0.15 25 28.684 - - 5.10 0.19 0.09 50 29.372 - - 4.92 0.19 <0.05 100 29.950 - - 4.58 0.20 <0.05 150 30.342 8.27 23.61 4.27 0.35 0.07 220 30.450 7.90 23.75 4.27 0.47 0.09 81 C R U I S E : 72/35 DATE: S e p t e m b e r 5, 1972 (a) STATION: I n d i a n 3 LOCATION: 4 9° 2 7 . 3 ' N SONIC DEPTH: 77 m 122. D e p t h Cm) S a l . ° / 0 0 T°C a f c 0 2 (ml/1) C u t y g / 1 ) P b ( u g / 1 ) 1 18.047 16.8 12.66 - 0.84 0.19 10 24.300 9.84 18.68 4.23 1.39 0.13 30 24.999 9.07 19.34 4.29 0.72 0.29 60 25.514 7.94 19.89 4.16 0.77 0.23 ( b l STATION: I n d i a n 2 LOCATION: 49° 2 3 . 5 ' N SONIC DEPTH: 220 m 122° 5 2 . 5 1 W D e p t h (m) S a l . ° / o o T°C a 0 2 ( m l / l ) C u t u g / 1 ) P b ( u g / 1 ) 1 - - 0.50 0.13 10 24.625 10.63 18.82 4.43 1.52 0.43 25 25.295 - - 4.42 1.20 0.28 50 25.998 11.06 19.81 4.42 0.93 0.14 100 2 7 . 4 2 1 6.89 21.51 3.30 0.97 0.21 150 27.543 6.90 21.60 3.38 1.04 0.35 200 27.561 6.88 21.62 3.28 1.18 0.38 215 27.562 6.91 21.62 3.16 1.02 0.32 Cc) STATION: I n d i a n 1 LOCATION: 49° 20' N SONIC DEPTH: 67 m 122° 55.5'W Depth(m) S a l . ° / 0 0 T°C a 02 Cml/1) C u t u g / 1 ) PbCyg/1) 1 20.686 14.27 15.17 7.02 0.75 0.29 10 24.794 - - 4.46 0.89 0.25 30 25.745 - - 4.72 0.94 0.33 60 2 6 . 2 9 1 10.13 20.19 4.07 0.65 0.23 82 (d) STATION: I n d i a n 0 LOCATION: 4 9° 18.2' N SONIC DEPTH: 32 m 122° 5 6 . 3 1 W D e p t h Cm) Sal.Voo T°C a f c 0 2 (ml/1) Cu (ug/1) Pb(ug/1) 1 24.408 14.27 18.02 5.46 0.69 0.40 10 25.339 12.05 19.05 4.84 0.99 0.40 25 25.963 11.22 19.76 4.48 1.03 0.46 (e) STATION: B u r r a r d 2 LOCATION: 49° 1 7 . 9 ' N SONIC DEPTH: 58 m 123° 5.5' W D e p t h Cm) Sal.Voo T°C a f c 0 2 (ml/1) Cu(ug/1) Pb(ug/1) 3 2 4 . 9 8 1 12.71 18.75 5.68 0.55 0.11 10 26.094 11.98 19.73 5.12 1.08 0.46 30 27.546 11.14 21.00 4.84 2.20 0.83 50 28.004 10.83 21.40 4.60 0.67 0.24 ( f l STATION: B u r r a r d 3 LOCATION: 49° 1 9 . 7 ' N SONIC DEPTH: 40 m 123° 1 2 . 1 ' W Depth(m) S a l . ° / 0 0 T°C a f c 0 2 (ml/1) C u lug/1) PbCug/D 1 21.124 15.16 15.33 7.02 1.02 0.32 10 27.498 11.98 20.81 4.95 0.56 0.15 25 28.569 - - 4.37 0.47 0.17 35 29.287 9.77 22.57 3.95 0.43 0.23 Igl STATION: B u r r a r d 4 LOCATION: 49° 18' N SONIC DEPTH: 245 m 123° 2 4 1 W D e p t h (m) Sal.Voo T°C a 0 2 (ml/1) Cu(yg/1) PbCyg/1) 1 22.807 16.32 16.38 6.58 0.72 0.30 10 26.973 12.95 20.24 6.59 0.49 0.30 25 28.449 9.71 21.92 4.51 0.49 0.12 50 29.579 9.16 22.89 3.90 0,41 0.05 100 30.312 8.86 23.50 3.78 0.44 0.07 150 30.612 8.55 23.78 3.51 0.45 0.08 225 30.830 8.62 23.94 3.48 0.50 0.10 83 C R U I S E : 72/39 DATE: O c t o b e r 1 2 , 1972 ( a l STATION: I n d i a n 3 LOCATION: 49° 2 7 . 3 ' N SONIC DEPTH: 83 m 122° 52.3' W D e p t h (ml S a l . ° / 0 0 T°C a 0 2 ( m l / 1 ) C u ( u g / 1 ) P b ( u g / 1 ) 10 25.526 9.97 19.62 4.28 0.54 0.05 20 25.966 9.90 19.97 3.82 0.41 0.07 30 26.147 9.78 20.13 3.73 0.87 0.13 50 26.298 9.21 20.33 3.61 0.89 0.15 (b) STATION: I n d i a n 2 LOCATION: 49° 2 3 . 5 ' N SONIC DEPTH: 220 m 122° 52.3' W D e p t h C m l S a l . ° / o o T°C a f c 0 2 (ml/1) C u ( u g / 1 ) P b ( u g / 1 ) 10 25.676 10.47 19.66 4.20 0.69 0.26 20 26.246 10.84 19.97 4.00 0.67 0.23 50 26.504 10.12 20.35 4.08 0.82 0.29 75 26.909 8.30 20.93 3.39 0.66 0.19 100 27.265 6.92 21.38 3.12 0.63 0.10 150 27.495 6.93 21.56 3.16 0.57 0.17 200 27.532 6.94 21.59 3.12 0.50 0.16 Cc) STATION: I n d i a n 1.5 LOCATION: 2 0 ^ 9 ' ^ SONIC DEPTH: 130 m D e p t h (ml S a l . ° / 0 0 T°C afc 0 2 (ml/1) C u t u g / 1 ) P b ( u g / 1 ) 10 26.058 10.80 19.90 - 0.80 0.54 30 26.304 10.29 20.17 4.43 0.71 0.08 50 26.495 10.14 20.34 4.54 0.90 0.28 75 26.786 9.29 20.70 3.81 0.49 0.10 100 27.314 7.04 21.41 2.97 0.46 0.21 125 27.437 - - 2.88 0.74 0.17 84 C R U I S E : 7 2 /41 DATE: O c t o b e r 2 5 , 1972 (a) STATION: B u r r a r d 4 LOCATION: 49° 18' N SONIC DEPTH: 238 m 123° 24' W D e p t h (m) S a l . % 0 T°C a f c 0 2 (ml/1) C u ( u g / 1 ) P b ( u g / 1 ) 3 27.319 9.73 21.04 6.84 0.64 0.38 10 2 7 . 8 4 6 * 9.65 21.47 6.04 0.72 0.22 25 29.346 8.79 22.76 4.03 0,66 0.18 50 29.963 9.01 23 .21 3.59 0.77 0.15 100 30.459 9.27 23.55 3.63 0.48 0.12 200 30.895 8.95 23.94 3.46 0.41 0.08 

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            data-media="{[{embed.selectedMedia}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
https://iiif.library.ubc.ca/presentation/dsp.831.1-0060223/manifest

Comment

Related Items