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Copper concentrations in surface waters off the south-eastern atlantic coast, U.S.A.
Marine Chemistry, 7(1979) 157--163 O Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands
157
C O P P E R C O N C E N T R A T I O N S IN S U R F A C E W A T E R S O F F T H E S O U T H E A S T E R N A T L A N T I C C O A S T , U.S.A.
HERBERT L. WINDOM and RALPH G. SMITH, Jr. Skidaway Institute of Oceanography, Savannah, GA 31406 (U.S.A.) (Received March 7, 1978; revision accepted October 5, 1978)
ABSTRACT Windom, H. L. and Smith, R. G., Jr., 1979. Copper concentrations in surface waters off the southeastern Atlantic coast, U.S.A. Mar. Chem., 7: 157--163. Copper concentrations in surface waters off the southeastern United States coast range from 0.02 to 0.33 pg/kg (0.3--5.2 nmol/kg). Mean concentrations are lowest in Onslow Bay (0.07 pg/kg) and highest over the Blake Plateau (0.20 pg/kg). An explanation, compatible with the hydrography and hydrodynamics of the area, is proposed for the observed regional variations. INTRODUCTION Variations in t r a c e - e l e m e n t c o n c e n t r a t i o n s in marine waters a t t e s t t o t h e i r n o n - c o n s e r v a t i v e chemical b e h a v i o r in t h e oceans. As a result o f careful sampling and refined analytical t e c h n i q u e s , marine chemists are n o w able to discriminate b e t w e e n small c o n c e n t r a t i o n differences and d e t e r m i n e the processes w h i c h cause these differences. In t h e o p e n o c e a n the vertical d i s t r i b u t i o n s o f trace e l e m e n t s such as c a d m i u m ( B o y l e et al., 1 9 7 6 ; Martin e t al., 1976}, nickel (Sclater et al., 1 9 7 7 ) , and c o p p e r ( B o y l e et al., 1977) are a p p a r e n t l y biologically m e d i a t e d . Regionally high surface c o n c e n t r a t i o n s o f some trace e l e m e n t s have b e e n a t t r i b u t e d to upwelling o f d e e p waters ( B o y l e and E d m o n d , 1 9 7 5 ; Martin e t al., 1 9 7 6 ) and to a t m o s p h e r i c inputs ( B o y l e et al., 1977). Many o f the processes influencing t r a c e - e l e m e n t distributions in the o p e n o c e a n m a y be intensified in coastal areas. A t m o s p h e r i c inputs m a y be m o r e significant, w a t e r mass e x c h a n g e is generally m o r e rapid and biological p r o d u c t i v i t y m a y be greater. During t h e past several years we have investigated t h e d i s t r i b u t i o n o f trace e l e m e n t s in A t l a n t i c coastal w a t e r o f f the s o u t h e a s t e r n U n i t e d States. O u r objective has been t o u n d e r s t a n d c o n c e n t r a t i o n d i f f e r e n c e s in relation t o physical, chemical and biological processes active in t h e region. This p a p e r discusses variations in surface-water c o p p e r c o n c e n t r a t i o n s and t h e i r relation t o some o f these processes.
158 SAMPLING AND ANALYTICAL PROCEDURES Surface water samples were collected at sixty stations (Fig.l) during four cruises, employing three different research vessels "Columbus Iselin", "Eastward" and "Advance II". Samples were collected with a peristaltic pump to which teflon tubing was connected. The tubing was extended o u t from the ship on a 10-m-long fiberglass boom. The intake was immersed to a depth of a b o u t 2--4 m aided by a teflon-coated weight. Water was pumped into teflon bottles which had been thoroughly (acid) cleaned. The system, including the sample bottles, was flushed with seawater prior to collecting each sample as the ship steamed slowly ahead. The sample bottles were stored, after acidification (sub-boiling red•stilled HC1) to pH 2, in plastic bags. I 84
I 80
I % ,~i~\ ~:fi
--36 /"~' Cape Lookaut
Cape Ramaln' 31
:.~ -• \
~¢1,
..
57
27~/I ...'~ 0~/ 3 Irsa
;~9~'•'•6ii5,i
25
/
, 37
- -
•
( .. ~~ ' ~ ~ .~ - ",3 A:P,0teau s ~ , # ~ .9
+"
\ "~E.~Cape Canaveral
~v~<.
--28
"v~i ~
,~t "~ {
~ I ¢::~ '~ "~..
,,,4
~ •1
~,
,,
~"-
\Approximate Eastern Boundary of the Gulf Stream
.~-;'
~,?>
Fig.1. Sample station number (circles, "Eastward"; squares, "Columbus Iselin"; triangles, "Advance II"). All "Advance II" stations are in Onslow Bay.
Samples were not filtered, to minimize the possibility of contamination. Concentrations reported in this paper therefore include dissolved copper and an additional small amount which may be leached from particles at pH 2. Copper was extracted from the samples using a dithizone/chloroform technique (Smith and Windom,.1978). The sample extracts were analyzed
159 with a Perkin Elmer model 403 atomic absorption system equipped with a HGA-2200 graphite furnace. Ten replicate analyses of each of two samples from continental shelf waters yielded values of 0.16 + 0.02 and 0.12 + 0.01 ~g/kg. The standard deviation of each analysis reported in this study, therefore, is estimated at between +0.01 and +0.02 pg/kg resulting in a coefficient of variation of about 10%. RESULTS AND DISCUSSION Copper concentrations in the region sampled (Table I) varied from 0.02 to 0.33 pg/kg (0.3--5.2 nanomoles/kg). This range is similar to that found by Boyle and Edmond (1975) and Boyle et al. (1977) in open-ocean surface waters of the Pacific. Concentrations in Sargasso Sea surface water have been estimated at a b o u t 0.12/~g/1 (Bender and Gagner, 1976). Other values from North Atlantic surface waters are generally higher than those reported here (Spencer and Brewer, 1969; Chester and Stoner, 1974; Alberts et al., 1976; Bewers et al., 1976). No systematic onshore--offshore trends in copper concentrations were observed, although there are apparent regional variations (Table II). Samples collected on two separate cruises to Onslow Bay indicated lower surfacewater concentrations than those in the Gulf Stream, Georgia E m b a y m e n t and Blake Plateau. Average values for waters over the Blake Plateau were higher than those of the Georgia E m b a y m e n t and the Gulf Stream which had similar concentrations. Surface shelf water in both Onslow Bay and the Georgia E m b a y m e n t is characterized by salinities generally less than 36 J.°~iowhich value was used to identify it from surface Gulf Stream water with salinities greater than 36 .%o. The salinity of surface water over the Blake Plateau is also greater than 36%o and these samples were differentiated on the basis of location outside the main stream of the Gulf Stream. Lateral motions of the Gulf Stream control the residence time of continental shelf waters. Shelf waters are well mixed while the Gulf Stream is stratified. Exchanges are governed by periodic intrusions of deeper, cooler, dense water from the Gulf Stream onto the shelf where it mixes with and displaces shelf waters (Blanton, 1971; Atkinson, 1977). The residence time of water in the Georgia Bight is a b o u t 2.7 months (Atkinson et alo, 1978), and in Onslow Bay about 1.4 months (Atkinson and Blanton, personal communication). Therefore Onslow Bay waters should more closely resemble intrusion source water. Intrusion source water is characterized by salinities of 35.5 to 36%° and temperatures between 15 and 20°C. This is typical of North Atlantic central water (NACW) occurring at a depth of a few hundred meters in the upper thermocline. In the central North Pacific copper concentrations decrease from a surface maximum of about 0.16 pg/kg (3 nmol/kg) to about 0.09 pg/kg (1.5 nmol/kg) in the upper thermocline (Boyle et al., 1977). Given a similar
160 TABLE I Surface water concentrations of total copper Station No.
Location
Copper concentration (pg/kg) (nm/kg)
"VEastward" (July--August 1974) 1 2 3a 4a 5 6 7 8 9 10 11a 12 a 13a 14 15 16 17 18 a 19" 20 a 21 22
32°38'N 32°20'N 32°13'N 31°48'N 31°55'N 32°04'N 32°17'N 32°22'N 31°59'N 31°38'N 31°30'N 30°54'N 30°59'N 31°30'N 30°55'N 30°50'N 30°41'N 30°33'N 30°12'N 30°15'N 30°18'N 30°23'N
79°48'W 79°18'W 79°02'W 79°16'W 79°28'W 79°48'W 80°08'W 80°18'W 80°42'W 79°51'W 79°36'W 79°24'W 79°37'W 81°03'W 81°12'W 80°56'W 80°10'W 79°35'W 79°54'W 80°11'W 80°30'W 81°18'W
0.07 0.24 0.11 0.23 0.10 0.15 0.31 0.04 0.20 0.18 0.04 0.10 0.24 0.31 0.09 0.05 0.I0 0.08 0.16 0.07 0.14 0.20
1.1 3.8 1.7 3.6 1.6 2.4 4.9 0.6 3.1 2.8 0.6 1.6 3.8 4.9 1.4 0.8 1.6 1.2 2.5 1.1 2.2 3.1
28°24'N 28°58'N 29°10'N 29°18'N 29°39'N 30°12'N 30°28'N 30°37'N 30°26'N 30°32'N 29°55'N 30°08'N 31°48'N 31°35'N 31°24'N 30°50'N 31°36'N 31°44'N 31°48'N 32°32'N 31°16'N
79°35'W 79°38'W 78°48'W 77°29'W 78°25'W 80°14'W 80°55'W 80°59'W 80°28'W 79°20'W 76°48'W 79°40'W 80°13'W 79°37'W 79°03'W 77°30'W 78°59'W 78°34'W 78°28'W 78°52'W 77°11'W
0.18 0.22 0.16 0.15 0.13 0.16 0.05 0.27 0.22 0.12 0.26 0.21 0.17 0.16 0.21 0.26 0.II 0.08 0.12 0.17 0.33
2.8 3.5 2.5 2.4 2.0 2.5 0.8 4.2 3.5 1.9 4.1 3.3 2.7 2.5 3.3 4.1 1.7 1.3 1.9 2.7 5.2
"Columbus Iselin" (March--April 1976) ia 2a 3b 45 5b 7 8 9 10 12" 14 b 15a 16 18 20 a 21 b 23a 24 a 25a 27 28 b
161 Station No.
Copper concentration (ug/kg) (nm/kg)
Location
30 a 31 32 35 b 37 b 38 b
32°15'N 33°10rN 32°51'N 31°32'N 31°58'N 32°32'N
77~46'W 78°40'W 78°10'W 76°08'W 76°05'W 74°58'W
0.10 0.17 0.12 0.11 0.30 0.16
1.6 2.7 1.9 1.7 4.7 2.5
21
34°21'N
77°02'W
24 26 ~:0
34°09'N 76°49'W 34°01'N 76°41'W 34°10'N 77°26'W
51 54 57
33°59'N 77°31'W 33°47'N 77°18'W 33°35'N 77°05'W
0.05 0.05 0.05 0.02 0.13 0.10 O.04 0.03 0.06 0.04
0.8 0.8 0.8 0.3 2.0 1.6 0.6 0.5 0.9 0.6
0.07 0.08 0.07 0.09 0.10 0.13 0.09 0.09
1.1 1.3 1.1 1.4 1.6 2.0 1.4 1.4
"Advance II" (October 1975) Onslow Bay
"Advance II" (December 1975) Onslow Bay 26
34°0 I'N
76°41'W
27
33°57'N 76°36'W
28
34°26'N 77°24'W
29
34°22tN 77°21'W
a Stations in the Gulf Stream. b Stations over the Blake Plateau. Other stations on the continental shelf.
TABLE II Regional variation in surface water copper concentrations Region
Gulf Stream Georgia Embaymenta Onslow Bay b Blake Plateau
Mean Cu concentration (pg/kg)
(nm/kg)
0.14 0.15 0.07 0.20
2.2 2.4 1.1 3.1
+ 0.05 + 0.08 + 0.03 + 0.08
+ 0.8 + 1.2 + 0.5 -+ 1.2
a The continental shelf between Cape Kennedy and Cape Fear. b The continental shelf between Cape Fear and Cape Lookout.
162 decrease w i t h d e p t h in t h e c e n t r a l N o r t h A t l a n t i c , i n t r u s i o n source w a t e r s s h o u l d h a v e a l o w e r c o p p e r c o n c e n t r a t i o n t h a n surface w a t e r o f the G u l f S t r e a m a n d Blake Plateau. This w o u l d e x p l a i n t h e l o w e r c o n c e n t r a t i o n s in O n s l o w Bay. Higher c o n c e n t r a t i o n s in t h e G e o r g i a E m b a y m e n t are p r o b a b l y m a i n t a i n e d b y c o n t i n e n t a l r u n o f f , w h i c h is m u c h g r e a t e r t h a n in the O n s l o w Bay area a n d b y a t m o s p h e r i c i n p u t s w h i c h s h o u l d have a greater i n f l u e n c e o n c o n c e n t r a t i o n s in t h e G e o r g i a E m b a y m e n t b e c a u s e o f longer w a t e r residence times. A t m o s p h e r i c i n p u t s a p p a r e n t l y explain high c o p p e r c o n c e n t r a t i o n s in surface w a t e r s o f t h e central N o r t h Pacific (Boyle et al., 1977). If such i n p u t s are also significant in t h e N o r t h Atlantic, the relatively high values o v e r the Blake Plateau are r e a s o n a b l e since these w a t e r s are the m o s t stratified. Also, relatively low p r o d u c t i v i t y w o u l d result in slow surface r e m o v a l o f c o p p e r . O u r e x p l a n a t i o n f o r the d i s t r i b u t i o n o f c o p p e r in surface w a t e r s is b a s e d o n a n u m b e r o f a s s u m p t i o n s w h i c h n e e d to be tested. Such a s s u m p t i o n s , h o w ever, serve as a guide f o r d e v e l o p i n g a b e t t e r u n d e r s t a n d i n g o f p r o c e s s e s w h i c h govern t r a c e - e l e m e n t v a r i a t i o n s in t h e ocean. ACKNOWLEDGEMENTS T h e a u t h o r s wish to t h a n k F. T a y l o r a n d D. W a s l e n c h u k f o r t h e i r h e l p and c o o p e r a t i o n in t h e c o l l e c t i o n o f s a m p l e s f o r this p r o j e c t . We also greatly a c k n o w l e d g e the s u p p o r t o f i n s t i t u t i o n s w h i c h o p e r a t e the research vessels used in this study. T h e y are t h e D u k e University " E a s t w a r d " , t h e University o f M i a m i " C o l u m b u s Iselin", a n d t h e Cape F e a r I n s t i t u t e " A d v a n c e I I " . Partial s u p p o r t f o r this s t u d y was p r o v i d e d b y the U.S. D e p a r t m e n t o f Energy under contract EY--76--S--09---0890.
REFERENCES Alberts, J. J., Leyden, D. E. and Patterson, T. A., 1976. Distribution of total A1, Cd, Co, Cu, Ni and Zn in the Tongue of the Ocean and the northwestern Atlantic Ocean. Mar. Chem., 4: 51--56. Atkinson, L. P., 1977. Modes of Gulf Stream intrusions into the South Atlantic Bight shelf waters. Geophys. Res. Lett., 4: 583--586. Atkinson, Lo P., Blanton, J. O. and Haines, E. B., 1978. Shelf flushing rates based on the distribution of salinity and freshwater in the Georgia Bight. Estuar. Coastal Mar. Sci., in press. Bender, M. L. and Gagner, C., 1976. Dissolved copper, nickel and cadmium in the Sargasso Sea. J. Mar. Res., 34: 327--339. Bewers, J. M., Sunby, B. and Yeats, P. A., 1976. The distribution of trace metals in the western North Atlantic off Nova Scotia. Geochim. Cosmochim. Acta, 40: 687--696. Blanton, J., 1971. Exchange of Gulf Stream water with North Carolina shelf water in Onslow Bay during stratified conditions. Deep-Sea Res., 18: 167--178. Boyle, E. A. and Edmond, J. M., 1975. Copper in surface waters south of New Zealand. Nature, 253: 107--109.
163 Boyle, E. A., Sclater, F. and Edmond, J. M., 1976. On the marine geochemistry of cadmium. Nature, 263: 42--44. Boyle, E. A., Sclater, F. R. and Edmond, J. M., 1977. The distribution of dissolved copper in the Pacific. Earth Planet. Sci. Lett., 37: 38--54. Chester, R. and Stoner, J. H., 1974. The distribution of zinc, nickel manganese, cadmium, copper and iron in some surface waters from the world ocean. Mar. Chem., 2: 17--32. Martin, J. H., Bruland, K. W. and Broenkow, W. W., 1976. Cadmium transport in the California current. In: H. L. Windom and R. A. Duce (Editors), Marine Pollutant Transfer. D. C. Heath, Lexington, pp. 159--184. Sclater, F. R., Boyle, E. and Edmond, J. M., 1976. On the marine geochemistry of nickel. Earth Planet. Sci. Lett., 31: 119--128. Smith, It. G., Jr., and Windom, H. L., 1978. A solvent extraction technique for determining nanogram per liter concentrations of cadmium, copper, nickel and zinc in sea water. Anal. Chim. Acta, submitted. Spencer, D.W. and Brewer, P.G., 1969. The distribution of copper, z~nc and nickel in sea water of the Gulf of Maine and the Sargasso Sea. Geochim. Cosmochim. Acta, 33: 325--339.
157
C O P P E R C O N C E N T R A T I O N S IN S U R F A C E W A T E R S O F F T H E S O U T H E A S T E R N A T L A N T I C C O A S T , U.S.A.
HERBERT L. WINDOM and RALPH G. SMITH, Jr. Skidaway Institute of Oceanography, Savannah, GA 31406 (U.S.A.) (Received March 7, 1978; revision accepted October 5, 1978)
ABSTRACT Windom, H. L. and Smith, R. G., Jr., 1979. Copper concentrations in surface waters off the southeastern Atlantic coast, U.S.A. Mar. Chem., 7: 157--163. Copper concentrations in surface waters off the southeastern United States coast range from 0.02 to 0.33 pg/kg (0.3--5.2 nmol/kg). Mean concentrations are lowest in Onslow Bay (0.07 pg/kg) and highest over the Blake Plateau (0.20 pg/kg). An explanation, compatible with the hydrography and hydrodynamics of the area, is proposed for the observed regional variations. INTRODUCTION Variations in t r a c e - e l e m e n t c o n c e n t r a t i o n s in marine waters a t t e s t t o t h e i r n o n - c o n s e r v a t i v e chemical b e h a v i o r in t h e oceans. As a result o f careful sampling and refined analytical t e c h n i q u e s , marine chemists are n o w able to discriminate b e t w e e n small c o n c e n t r a t i o n differences and d e t e r m i n e the processes w h i c h cause these differences. In t h e o p e n o c e a n the vertical d i s t r i b u t i o n s o f trace e l e m e n t s such as c a d m i u m ( B o y l e et al., 1 9 7 6 ; Martin e t al., 1976}, nickel (Sclater et al., 1 9 7 7 ) , and c o p p e r ( B o y l e et al., 1977) are a p p a r e n t l y biologically m e d i a t e d . Regionally high surface c o n c e n t r a t i o n s o f some trace e l e m e n t s have b e e n a t t r i b u t e d to upwelling o f d e e p waters ( B o y l e and E d m o n d , 1 9 7 5 ; Martin e t al., 1 9 7 6 ) and to a t m o s p h e r i c inputs ( B o y l e et al., 1977). Many o f the processes influencing t r a c e - e l e m e n t distributions in the o p e n o c e a n m a y be intensified in coastal areas. A t m o s p h e r i c inputs m a y be m o r e significant, w a t e r mass e x c h a n g e is generally m o r e rapid and biological p r o d u c t i v i t y m a y be greater. During t h e past several years we have investigated t h e d i s t r i b u t i o n o f trace e l e m e n t s in A t l a n t i c coastal w a t e r o f f the s o u t h e a s t e r n U n i t e d States. O u r objective has been t o u n d e r s t a n d c o n c e n t r a t i o n d i f f e r e n c e s in relation t o physical, chemical and biological processes active in t h e region. This p a p e r discusses variations in surface-water c o p p e r c o n c e n t r a t i o n s and t h e i r relation t o some o f these processes.
158 SAMPLING AND ANALYTICAL PROCEDURES Surface water samples were collected at sixty stations (Fig.l) during four cruises, employing three different research vessels "Columbus Iselin", "Eastward" and "Advance II". Samples were collected with a peristaltic pump to which teflon tubing was connected. The tubing was extended o u t from the ship on a 10-m-long fiberglass boom. The intake was immersed to a depth of a b o u t 2--4 m aided by a teflon-coated weight. Water was pumped into teflon bottles which had been thoroughly (acid) cleaned. The system, including the sample bottles, was flushed with seawater prior to collecting each sample as the ship steamed slowly ahead. The sample bottles were stored, after acidification (sub-boiling red•stilled HC1) to pH 2, in plastic bags. I 84
I 80
I % ,~i~\ ~:fi
--36 /"~' Cape Lookaut
Cape Ramaln' 31
:.~ -• \
~¢1,
..
57
27~/I ...'~ 0~/ 3 Irsa
;~9~'•'•6ii5,i
25
/
, 37
- -
•
( .. ~~ ' ~ ~ .~ - ",3 A:P,0teau s ~ , # ~ .9
+"
\ "~E.~Cape Canaveral
~v~<.
--28
"v~i ~
,~t "~ {
~ I ¢::~ '~ "~..
,,,4
~ •1
~,
,,
~"-
\Approximate Eastern Boundary of the Gulf Stream
.~-;'
~,?>
Fig.1. Sample station number (circles, "Eastward"; squares, "Columbus Iselin"; triangles, "Advance II"). All "Advance II" stations are in Onslow Bay.
Samples were not filtered, to minimize the possibility of contamination. Concentrations reported in this paper therefore include dissolved copper and an additional small amount which may be leached from particles at pH 2. Copper was extracted from the samples using a dithizone/chloroform technique (Smith and Windom,.1978). The sample extracts were analyzed
159 with a Perkin Elmer model 403 atomic absorption system equipped with a HGA-2200 graphite furnace. Ten replicate analyses of each of two samples from continental shelf waters yielded values of 0.16 + 0.02 and 0.12 + 0.01 ~g/kg. The standard deviation of each analysis reported in this study, therefore, is estimated at between +0.01 and +0.02 pg/kg resulting in a coefficient of variation of about 10%. RESULTS AND DISCUSSION Copper concentrations in the region sampled (Table I) varied from 0.02 to 0.33 pg/kg (0.3--5.2 nanomoles/kg). This range is similar to that found by Boyle and Edmond (1975) and Boyle et al. (1977) in open-ocean surface waters of the Pacific. Concentrations in Sargasso Sea surface water have been estimated at a b o u t 0.12/~g/1 (Bender and Gagner, 1976). Other values from North Atlantic surface waters are generally higher than those reported here (Spencer and Brewer, 1969; Chester and Stoner, 1974; Alberts et al., 1976; Bewers et al., 1976). No systematic onshore--offshore trends in copper concentrations were observed, although there are apparent regional variations (Table II). Samples collected on two separate cruises to Onslow Bay indicated lower surfacewater concentrations than those in the Gulf Stream, Georgia E m b a y m e n t and Blake Plateau. Average values for waters over the Blake Plateau were higher than those of the Georgia E m b a y m e n t and the Gulf Stream which had similar concentrations. Surface shelf water in both Onslow Bay and the Georgia E m b a y m e n t is characterized by salinities generally less than 36 J.°~iowhich value was used to identify it from surface Gulf Stream water with salinities greater than 36 .%o. The salinity of surface water over the Blake Plateau is also greater than 36%o and these samples were differentiated on the basis of location outside the main stream of the Gulf Stream. Lateral motions of the Gulf Stream control the residence time of continental shelf waters. Shelf waters are well mixed while the Gulf Stream is stratified. Exchanges are governed by periodic intrusions of deeper, cooler, dense water from the Gulf Stream onto the shelf where it mixes with and displaces shelf waters (Blanton, 1971; Atkinson, 1977). The residence time of water in the Georgia Bight is a b o u t 2.7 months (Atkinson et alo, 1978), and in Onslow Bay about 1.4 months (Atkinson and Blanton, personal communication). Therefore Onslow Bay waters should more closely resemble intrusion source water. Intrusion source water is characterized by salinities of 35.5 to 36%° and temperatures between 15 and 20°C. This is typical of North Atlantic central water (NACW) occurring at a depth of a few hundred meters in the upper thermocline. In the central North Pacific copper concentrations decrease from a surface maximum of about 0.16 pg/kg (3 nmol/kg) to about 0.09 pg/kg (1.5 nmol/kg) in the upper thermocline (Boyle et al., 1977). Given a similar
160 TABLE I Surface water concentrations of total copper Station No.
Location
Copper concentration (pg/kg) (nm/kg)
"VEastward" (July--August 1974) 1 2 3a 4a 5 6 7 8 9 10 11a 12 a 13a 14 15 16 17 18 a 19" 20 a 21 22
32°38'N 32°20'N 32°13'N 31°48'N 31°55'N 32°04'N 32°17'N 32°22'N 31°59'N 31°38'N 31°30'N 30°54'N 30°59'N 31°30'N 30°55'N 30°50'N 30°41'N 30°33'N 30°12'N 30°15'N 30°18'N 30°23'N
79°48'W 79°18'W 79°02'W 79°16'W 79°28'W 79°48'W 80°08'W 80°18'W 80°42'W 79°51'W 79°36'W 79°24'W 79°37'W 81°03'W 81°12'W 80°56'W 80°10'W 79°35'W 79°54'W 80°11'W 80°30'W 81°18'W
0.07 0.24 0.11 0.23 0.10 0.15 0.31 0.04 0.20 0.18 0.04 0.10 0.24 0.31 0.09 0.05 0.I0 0.08 0.16 0.07 0.14 0.20
1.1 3.8 1.7 3.6 1.6 2.4 4.9 0.6 3.1 2.8 0.6 1.6 3.8 4.9 1.4 0.8 1.6 1.2 2.5 1.1 2.2 3.1
28°24'N 28°58'N 29°10'N 29°18'N 29°39'N 30°12'N 30°28'N 30°37'N 30°26'N 30°32'N 29°55'N 30°08'N 31°48'N 31°35'N 31°24'N 30°50'N 31°36'N 31°44'N 31°48'N 32°32'N 31°16'N
79°35'W 79°38'W 78°48'W 77°29'W 78°25'W 80°14'W 80°55'W 80°59'W 80°28'W 79°20'W 76°48'W 79°40'W 80°13'W 79°37'W 79°03'W 77°30'W 78°59'W 78°34'W 78°28'W 78°52'W 77°11'W
0.18 0.22 0.16 0.15 0.13 0.16 0.05 0.27 0.22 0.12 0.26 0.21 0.17 0.16 0.21 0.26 0.II 0.08 0.12 0.17 0.33
2.8 3.5 2.5 2.4 2.0 2.5 0.8 4.2 3.5 1.9 4.1 3.3 2.7 2.5 3.3 4.1 1.7 1.3 1.9 2.7 5.2
"Columbus Iselin" (March--April 1976) ia 2a 3b 45 5b 7 8 9 10 12" 14 b 15a 16 18 20 a 21 b 23a 24 a 25a 27 28 b
161 Station No.
Copper concentration (ug/kg) (nm/kg)
Location
30 a 31 32 35 b 37 b 38 b
32°15'N 33°10rN 32°51'N 31°32'N 31°58'N 32°32'N
77~46'W 78°40'W 78°10'W 76°08'W 76°05'W 74°58'W
0.10 0.17 0.12 0.11 0.30 0.16
1.6 2.7 1.9 1.7 4.7 2.5
21
34°21'N
77°02'W
24 26 ~:0
34°09'N 76°49'W 34°01'N 76°41'W 34°10'N 77°26'W
51 54 57
33°59'N 77°31'W 33°47'N 77°18'W 33°35'N 77°05'W
0.05 0.05 0.05 0.02 0.13 0.10 O.04 0.03 0.06 0.04
0.8 0.8 0.8 0.3 2.0 1.6 0.6 0.5 0.9 0.6
0.07 0.08 0.07 0.09 0.10 0.13 0.09 0.09
1.1 1.3 1.1 1.4 1.6 2.0 1.4 1.4
"Advance II" (October 1975) Onslow Bay
"Advance II" (December 1975) Onslow Bay 26
34°0 I'N
76°41'W
27
33°57'N 76°36'W
28
34°26'N 77°24'W
29
34°22tN 77°21'W
a Stations in the Gulf Stream. b Stations over the Blake Plateau. Other stations on the continental shelf.
TABLE II Regional variation in surface water copper concentrations Region
Gulf Stream Georgia Embaymenta Onslow Bay b Blake Plateau
Mean Cu concentration (pg/kg)
(nm/kg)
0.14 0.15 0.07 0.20
2.2 2.4 1.1 3.1
+ 0.05 + 0.08 + 0.03 + 0.08
+ 0.8 + 1.2 + 0.5 -+ 1.2
a The continental shelf between Cape Kennedy and Cape Fear. b The continental shelf between Cape Fear and Cape Lookout.
162 decrease w i t h d e p t h in t h e c e n t r a l N o r t h A t l a n t i c , i n t r u s i o n source w a t e r s s h o u l d h a v e a l o w e r c o p p e r c o n c e n t r a t i o n t h a n surface w a t e r o f the G u l f S t r e a m a n d Blake Plateau. This w o u l d e x p l a i n t h e l o w e r c o n c e n t r a t i o n s in O n s l o w Bay. Higher c o n c e n t r a t i o n s in t h e G e o r g i a E m b a y m e n t are p r o b a b l y m a i n t a i n e d b y c o n t i n e n t a l r u n o f f , w h i c h is m u c h g r e a t e r t h a n in the O n s l o w Bay area a n d b y a t m o s p h e r i c i n p u t s w h i c h s h o u l d have a greater i n f l u e n c e o n c o n c e n t r a t i o n s in t h e G e o r g i a E m b a y m e n t b e c a u s e o f longer w a t e r residence times. A t m o s p h e r i c i n p u t s a p p a r e n t l y explain high c o p p e r c o n c e n t r a t i o n s in surface w a t e r s o f t h e central N o r t h Pacific (Boyle et al., 1977). If such i n p u t s are also significant in t h e N o r t h Atlantic, the relatively high values o v e r the Blake Plateau are r e a s o n a b l e since these w a t e r s are the m o s t stratified. Also, relatively low p r o d u c t i v i t y w o u l d result in slow surface r e m o v a l o f c o p p e r . O u r e x p l a n a t i o n f o r the d i s t r i b u t i o n o f c o p p e r in surface w a t e r s is b a s e d o n a n u m b e r o f a s s u m p t i o n s w h i c h n e e d to be tested. Such a s s u m p t i o n s , h o w ever, serve as a guide f o r d e v e l o p i n g a b e t t e r u n d e r s t a n d i n g o f p r o c e s s e s w h i c h govern t r a c e - e l e m e n t v a r i a t i o n s in t h e ocean. ACKNOWLEDGEMENTS T h e a u t h o r s wish to t h a n k F. T a y l o r a n d D. W a s l e n c h u k f o r t h e i r h e l p and c o o p e r a t i o n in t h e c o l l e c t i o n o f s a m p l e s f o r this p r o j e c t . We also greatly a c k n o w l e d g e the s u p p o r t o f i n s t i t u t i o n s w h i c h o p e r a t e the research vessels used in this study. T h e y are t h e D u k e University " E a s t w a r d " , t h e University o f M i a m i " C o l u m b u s Iselin", a n d t h e Cape F e a r I n s t i t u t e " A d v a n c e I I " . Partial s u p p o r t f o r this s t u d y was p r o v i d e d b y the U.S. D e p a r t m e n t o f Energy under contract EY--76--S--09---0890.
REFERENCES Alberts, J. J., Leyden, D. E. and Patterson, T. A., 1976. Distribution of total A1, Cd, Co, Cu, Ni and Zn in the Tongue of the Ocean and the northwestern Atlantic Ocean. Mar. Chem., 4: 51--56. Atkinson, L. P., 1977. Modes of Gulf Stream intrusions into the South Atlantic Bight shelf waters. Geophys. Res. Lett., 4: 583--586. Atkinson, Lo P., Blanton, J. O. and Haines, E. B., 1978. Shelf flushing rates based on the distribution of salinity and freshwater in the Georgia Bight. Estuar. Coastal Mar. Sci., in press. Bender, M. L. and Gagner, C., 1976. Dissolved copper, nickel and cadmium in the Sargasso Sea. J. Mar. Res., 34: 327--339. Bewers, J. M., Sunby, B. and Yeats, P. A., 1976. The distribution of trace metals in the western North Atlantic off Nova Scotia. Geochim. Cosmochim. Acta, 40: 687--696. Blanton, J., 1971. Exchange of Gulf Stream water with North Carolina shelf water in Onslow Bay during stratified conditions. Deep-Sea Res., 18: 167--178. Boyle, E. A. and Edmond, J. M., 1975. Copper in surface waters south of New Zealand. Nature, 253: 107--109.
163 Boyle, E. A., Sclater, F. and Edmond, J. M., 1976. On the marine geochemistry of cadmium. Nature, 263: 42--44. Boyle, E. A., Sclater, F. R. and Edmond, J. M., 1977. The distribution of dissolved copper in the Pacific. Earth Planet. Sci. Lett., 37: 38--54. Chester, R. and Stoner, J. H., 1974. The distribution of zinc, nickel manganese, cadmium, copper and iron in some surface waters from the world ocean. Mar. Chem., 2: 17--32. Martin, J. H., Bruland, K. W. and Broenkow, W. W., 1976. Cadmium transport in the California current. In: H. L. Windom and R. A. Duce (Editors), Marine Pollutant Transfer. D. C. Heath, Lexington, pp. 159--184. Sclater, F. R., Boyle, E. and Edmond, J. M., 1976. On the marine geochemistry of nickel. Earth Planet. Sci. Lett., 31: 119--128. Smith, It. G., Jr., and Windom, H. L., 1978. A solvent extraction technique for determining nanogram per liter concentrations of cadmium, copper, nickel and zinc in sea water. Anal. Chim. Acta, submitted. Spencer, D.W. and Brewer, P.G., 1969. The distribution of copper, z~nc and nickel in sea water of the Gulf of Maine and the Sargasso Sea. Geochim. Cosmochim. Acta, 33: 325--339.