- Email: [email protected]
Trace metals in carbonate and organic rich sediments
stations. A study of trace metals in the surface sediments of the North Sea has shown the levels to be related to the particle size. Those samples containing a high percentage of fine grain material also contained the highest concentration of metal (Nicholson, pers. comm.). It is therefore possible that a similar phenomenon may be an important factor in governing the distribution of trace metals associated with material suspended in the water. Also, the present survey was conducted at a time when the abundance of plankton was near its summer maximum. It is therefore most probable that a portion of the particulate heavy metals was present in organic combination. Hence the patchy nature of plankton would be an additional factor leading to a spatial complexity in the distribution of the metals. Table 2 lists the range of both particulate and dissolved metal values in the surface and near-bottom samples measured on the main survey. TABLE 3 The concentrations (.ag/g dry material) of selected trace metals in biological materials from the N o r t h Sea shoreline, September 1971 Element
Mn Zn Cd Cu Ni Fe Pb Ag
Geometric Range Geometric Range Geometric Range Geometrxc Range Geometric Range Geometric Range Geometric Range Geometric Range
mean mean mean mean mean mean mean mean
N u m b e r of observations: Limpets 4.
Fucus
Porphyra
spp.
spp.
110 46-200 85 27-400 1.1 0.5-2.7 7.8 2.5-24 8.6 3.2-17 290 170-760 4.5 3.1-10 0.4 0.1-1.4
33 15-96 56 32-170 0.42 0.27-0.76 13 5.9-67 2.9 1.4-5.9 370 150-980 2.8 0.8-7.3 0.4 0.2-0.5
Limpets (soft parts) 23 15-62 120 94-140 4.4 2.9-7.1 11 6.9-13 7.9 4.5-14 2000 1600-2700 3.7 1.5-9.3 2.0 1.5-2.6
metals in the three materials are given in Table 3. The mean concentrations for most metals are similar to those obtained from an earlier survey in the eastern Irish Sea in 1970 (Preston et al., 1972).
Conclusions This preliminary report on the first of a series of surveys in the North Sea has indicated that, with the exception of cadmium, the highest concentration of dissolved metals occurred in coastal waters. Compared with the Irish Sea, the range of metal concentrations measured generally did not have such high upper limits. However, the metal content of the biological material examined from both sea areas was similar. Further investigations in the North Sea are under way to establish a more detailed geographical picture of metal distribution, to determine the relationship between the particulate and dissolved phases, to detect any seasonal cycles involving metals, and to locate possible terrestrial sources of input whether they be man-made or natural. These investigations form part of an international programme of the working group for the study of pollution of the North Sea under the auspices of the International Council for the Exploration of the Sea. J. W. R. DUTTON D . F . JEFFERIES
Ministry of Agriculture, Fisheries and Food, Fisheries Radiobiological Laboratory, Lowestoft, Suffolk. A. R. FOLKARD P. G. W. JONES
Ministry of Agriculture, Fisheries and Food, Fisheries Laboratory, Lowestoft, Suffolk.
Fucus spp. 9, Porphyra spp. 7,
Samples of two seaweeds, Fucus vesiculosus and Porphyra umbilicalis, and the limpet, Patella vuIgata, were collected, where available, for use as biological indicator systems. The concentrations of individual
Abdullah, M. I., Royle, L. G. & Morris, A. W. (1972). Heavy metal concentration in coastal waters. Nature, Lond., 235: 158-60. Preston, A., Jefferies, D. F., Dutton, J. W. R., Harvey, B. R. & Steele, A. K. (1972). British Isles coastal waters: the concentrations of selected heavy metals in sea water, suspended matter and biological indicators--a pilot survey. Environ. Pollut., 3: 69-82.
Trace Metals in Carbonate and Organic Rich Sediments A great variety of man's activities on the coast result in metal contamination of the sea. Investigations at three sites, two in Florida and one in Bermuda reveal trace metals in sediments. I~ all tiu-ee cases these accumulations can be ascribed to local human~ activities, though their nature varies widely from one site to another. During an investigation of the trace transition metal distributions within carbonate and organic rich nearshore and estuarine sediments, three separate geogra-
tions of some metals have been found which may be ascribed to some of the various different influences of man's activities. The sediments in each of the three study areas are characterized by their high carbonate and organic contents and their generally low concentrations of transition metals (Table 1). The sediments contain variable amounts of quartz sand, and the Mangrove Lake sediments also contain halloysite.
phical locations, Card Sound and Turkey Point, Florida and Mangrove Lake, Bermuda have been studied. In each of these areas localized high concentra-
Sampling and Analysis
138
Sediment samples were obtained by hand coring tubes of 7.5 cm diameter forced into the sediments to
about 15 cm depth. The resulting samples were homogenized by vigorous stirring after addition of a little silica distilled water in a silica beaker• A subsample of about 10 g was freeze-dried to constant weight in a polyethylene bottle and broken into a fine powder with a teflon coated rod. Analysis of the dried sediment sample was carried out by flameless atom reservoir atomic absorption spectrophotometry after acid dissolution and solvent extraction of the metal pyrrolidine dithiocarbamates (Segar, 1973).
very rapidly flushed and whose sediments contain naturally high concentrations of trace metals which are strongly associated with clay minerals. Thus, only very small fractional changes in total sediment metal concentrations might be expected at most sites and any such changes may well be within the natural small scale geographical variations in the discharge area. The Turkey Point site is perhaps unique in that it is located on a very shallow estuary with carbonate/ organic sediments of low natural trace metal concentra-
Turkey Point Turkey Point is situated towards the south end of Biscayne Bay, Florida and at the time of sampling for this study, February 1972, two 450 megawatt oil-fired generators were operating at the Turkey Point power plant. These generators were drawing an average of 850 m3/min of cooling water from Biscayne Bay on the north side of Turkey Point and discharging this water to the bay through a network of canals about 1 mile to the south of the plant. Prior to this study the generating units had been operational for 3½ and 4½ years respectively. Extensive studies of the effects of the heated effluent upon the ecology of the discharge area (Roessler, 1971; Thorhaug et aI., 1973) and some preliminary studies of the chemistry of the discharge water (Gerchakov et al., 1971) have been reported. These preliminary investigations revealed that the power plant operation was probably causing the addition of small but perhaps significant amounts of transition metal contaminants to the discharge water. Similar observations have been made at other sites either directly or indirectly by observing increases in metal content of indicator organisms (Roosenberg, 1969). Apparently, significant changes in the sedimentary concentrations of trace elements in power plant discharge areas have not previously been reported. This is perhaps surprising in view of the studies of radionuclide releases from power plants which indicate that a considerable proportion of many of these radionuclides are in general quickly removed from the water to the underlying sediments (Rice & Wolfe, 1971; Joseph et al., 1971; Duursma & Gross, 1971). However, many power plants discharge into areas that are
(
i
"':L
....~ FPL POWER PLANT.
Q
I0
50 ~
!h Fig. 1 D i s t r i b u t i o n o f nickel ( p p m ) in s e d i m e n t s at T u r k e y Point.
TABLE I E l e m e n t a l c o n c e n t r a t i o n s o f v a r i o u s m a r i n e s e d i m e n t s (ppm). Element
D e e p sea carbonates*
D e e p sea clays*
Nearshore sediments*
V Fe Cd Pb Ag Zn Cu Ni Ca(ppt) Organic Carbon
20 9,000 -9 -35 30 30 --
120 65,000 0.42 80 0.11 165 250 225 --
130 --20 --48 55 --
--
--
(% dry wt)
--
Card Sound Florida**
24 1,900 0.07 1 0.5 4 2 ,(2 1-390
0.3-26
Turkey Point Florida***
Mangrove Lake Bermuda surface samplest
52 2,600 0.2 3 0.4 12 11 25 --
26 3,100 0.6
39 26 6 7 370
0.4-11
1-19
20 3
Mangrove Lake Bermuda core s a m p l e s f I" 22 (57) 1,800 (5,200) 0.8 (3)
(2) (0.8) (39) (27) (26)
18-38
* F r o m R i l e y a n d C h e s t e r (1971); ** a v e r a g e o f 82 s a m p l e s ; *** a v e r a g e o f 33 s a m p l e s ; t" a v e r a g e o f 18 s a m p l e s ; #J" a v e r a g e o f 14 samples. M a x i m u m v a l u e in p a r e n t h e s e s . 139
tions (Table 1). In addition, the hydrodynamical regime is such that rapid dispersion of the effluent is not encouraged. In fact the discharge water appears to be significantly recycled. The potential thus exists for a concentration build-up of trace metals in the sediments of the discharge area. The average concentrations of trace elements in 33 sediment samples from the area near Turkey Point are considerably lower than those observed in deep sea clay and average nearshore sediments (Table 1). The concentrations are also somewhat lower than those observed in deep sea carbonates and in Mangrove Lake, Bermuda. However, particularly for vanadium, iron, zinc, nickel and copper the concentrations observed are significantly higher than those observed in the sediments of an extremely similar but almost natural and uncontaminated ecosystem, Card Sound, Florida situated a few km to the south of Turkey Point. These data alone are not sufficient to indicate that the power plant is causing contamination of the sediments in its discharge area. However, when distribution of the metals within the Turkey Point area is considered the influence of the power plant becomes clear. Thus the concentrations of nickel (Fig. 1), vanadium (Fig. 2), copper (Fig. 3), iron, zinc, lead and possibly silver are particularly high in the sediments immediately adjacent to the power plant ouffaU canal and in the area just to the south of Turkey Point itself. The latter area is probably a low energy sedimentary sink. Physical parameters and water chemistry have indicated that the water in this area is occluded by the looping current of water released at the outfall canal and sweeping around Turkey Point to return to the intake canal on the north (Roessler, 1971). It appears that the construction and/or operation of the power plant at Turkey Point has led to significantly increased concentrations of a number of trace metals in the sediments within the discharge environment. The exact causes of this contamination are not known. However, several possibilities are presently under study. It is possible that the excess metal load was contributed to the bay sediments in the dredge spoil introduced to the bay during the initial construction of the power plant and canal system, although this spoil is predominately limestone oolite and low in metals. The effluent water from the power plant has been shown to contain higher dissolved concentrations of some metals, notably copper and iron, than the normal bay water and it is possible that this excess metal is partially removed to the sediments by biological and abiological scavenging mechanisms. Metallic particles may be introduced into the power plant effluent and may sediment out on reaching the bay where water velocities are lower. Sources of particulate and dissolved metal during construction of power plants are many and subsequently during operation of the power plant corrosion may contribute significant quantities of metals particularly from the cooling system itself. The cooling coils of the Turkey Point plant are constructed of copper/nickel, the two elements which are in greatest excess over their Card Sound concentrations in the Turkey Point area (Table 1). The distribution of nickel in the sediments at Turkey Point clearly indicates a 140
25.
FPL POWER PLANT
rn
•
150~
I001!
Fig. 2 Distribution of vanadium (ppm) in sediments at Turkey Point.
!
il0
I IO
.Q Fig. 3 Distribution of copper (ppm) in sediments at Turkey Point.
power plant source. The copper distribution, although indicating a similar source, is more complicated perhaps due to the intimate involvement of copper in biological processes and the occasional use of copper salts in lower Biscayne Bay as a shark repellent by the US Air Force. Some elements, particularly vanadium and lead, may be supplied to the discharge environment from the fuel oil used by the Turkey Point generators and gasoline used by automobiles, boats and construction vehicles. One factor contributing to the build up of metal concentrations in the sediments immediately adjacent to the canal ouffall may be the loss of rooted aquatic plants (Thalassia testudinum) from this area due either to heat stress or other effects of the power plant (Roessler, 1972; Thorhaug et al., 1973). It has recently been hypothesized that these plants are instrumental in recycling metals from deep within the sediments back into the water column and detritus food chain (Segar et al., 1972, 1973). Their destruction would mean that this possibly significant mechanism of removal of trace metals from the sediments was no longer operative and higher concentrations would probably result.
Card Sound Card Sound, Florida, a shallow, mangrove fringed estuarine embayment about 5-10 km to the south of Turkey Point, is an area little affected by the activities of man. This is reflected by the extremely low concentrations of metals in the sediments of the Sound (Table 1). Anomalously, high concentrations of metals have been observed in the sediments close to what is currently man's only major influence on the Sound, the Ocean Reef Yacht Club basin located on Key Largo at the middle of the eastern shore of the Sound. The I' /d - I:.V: :.l
sediments in the area of this yacht basin are loose and fine grained with high organic content and have high concentrations of nickel, zinc, lead, copper, vanadium and cadmium, compared to the sediments immediately to the north, south and west (e.g. Fig. 4). However, concentrations of these metals in the area of the boat basin are not appreciably greater than the highest values found in the rest of the Sound. Too few samples have been analysed from the area close to the boat basin to delineate the extent or magnitude of the contamination, but it is clear that trace metals are being or have been introduced to the sediments due to the operation and/or construction of this facility. Potential sources of metal include the untreated sewage, and corrosion and exhaust products from boats moored in the basin. Dredge and fill material probably does not contribute excess metals, particularly as significant anomalies were not observed in the sediments around the Model Land canal, a man-made structure on the western shore of Card Sound.
Mangrove Lake Mangrove Lake, Bermuda, is a small brackish water lake containing sediments of very high organic content and considerable depth. These sediments have been described by Hatcher et al. (1973). Analysis of the surface sediments has shown that the concentrations of iron, zinc and copper (e.g. Fig. 5) are considerably higher at one station at the centre of the western shoreline than in the rest of the lake. The lead concentration
5o. :.: ...""f/ .2...if"""
,ke
50.Ipo ~qo ... • ". " . -
~ :.l. . . . . . .
I00
1
zo
,
"
50100.
"i
1 20
1
li~
."
"" 2 0
zoo -... 2oo~
• "
30.5"
:i
l
~: i:
l
""
." : ' ; ' " !:
50
3o!
Fig. $ Distribution of zinc (ppm) in Mangrove Lake sediments.
1
Fig. 4 Distribution of vanadium (ppm) in sediments in Card
Sound.
at this station was also high compared to the rest of the western half of the lake (Fig. 6). However, the silver, cadmium, nickel and vanadium concentrations at this station were within the range of concentrations found in the rest of the lake. It has been reported that trash dumping has been practised by local residents in the area where the anomalous concentrations were observed. For example an old and rusting motorcycle has been observed lying on the lake bottom at this point. It seems reasonable to assume that such dumping has caused the observed increase in sedimentary metal concentrations.
141
The lead distribution in Mangrove Lake surface sediments indicates a strong source of the metal in the south-east corner of the lake (Fig. 6). No explanation for this can yet be advanced but it has been calculated that the lead involved in this anomaly could have been contributed from less than several hundred gallons of leaded gasoline. 2O0...:..'.. 100 ..../ "
.,:.'200
•
5.0, ." . ",.
.... : ,
.....
'
.~'200 .' 30,0
>
'oo
,,-
i..O0 0
/ "" ""
":"
5 0 .'"
"'1400 .'7 ." I40.0
• •
"
•
"'"
" I000 :: 4 0 0 "" 3 0 0
I00. 200
•
.:. ZOO
i:
3ob ,
200
,o.o
..
"
'"
...
.?200
Significance of Metal Contamination Although we have shown that metal contamination of marine sediments occurs in widely differing areas due to different types of human activity it is not known for certain whether or not such contamination can produce effects which are harmful to man. The contaminant element is normally introduced into the sediments in a physicochemical state such that it enters the natural active biogeochemical cycling of elements in the discharge ecosystem. Even pure metals and many oxides and minerals may be rapidly solubilized in organic rich environments such as are most nearshore sediments (e.g. Baker, 1973; Silverman & Ehrlich, 1971). Therefore, contamination by metals will normally increase biologically available trace metals in an ecosystem and this will inevitably lead to the increase of metal concentrations in many organisms. As most trace metals have toxic properties at some concentration and as maximum permissible concentrations are enforced for many trace metals in food, such increases in the concentration of trace metals in the biosphere are potentially harmful both to the aquatic biology and to man. This work was supported by National Science Foundation grant GA-33003 with additional support from the US Atomic Energy Commission. One of us (REP) was partially supported by the National Oceanic and Atmospheric Administration Sea Grant programme.
D. A. SEGAR R. E. PELLENBARG*
Fig. 6 Distribution of lead (ppm) in Mangrove Lake sediments.
Some idea of the possible influence of man's activities upon sedimentary environments may be obtained from a comparison of the average metal concentrations in Mangrove Lake surface sediments and in the sediments below 2 m depth in a 16 m vertical core taken in the centre of the lake (Table 1). The sediments analysed from this core are representative of the material deposited in Mangrove Lake over about 5,000 years and thus reflect possible depositional changes during that time. It is therefore highly significant that the silver and lead average concentration in the surface samples lie above the maximum concentrations observed in the core (Table 1). In addition, it is possibly significant that the average concentrations of iron, copper and zinc are higher in the surface sediments than in the core. Presumably the higher concentrations of metals in the surface sediments represent the effects of recent man-made changes on the relatively undeveloped Bermuda island. The increase in lead concentration is particularly striking with the average surface concentration being some twenty times the highest value observed in the core. Vanadium, nickel and cadmium do not appear to be significantly influenced by the changes that have produced the higher concentrations of other metals. Thus, it is unlikely that the changes in metal concentration are due to a change in the scavenging ability of the presently accumulating sedimentary material as compared to previously accreting material. For iron there exists the possibility of the upwards transport of metal during sediment diagenisis so that its concentration in the core may be low due to this mechanism. The solubilities of the sulphides of the other elements are low enough to prevent their migration from the reducing sediments during diagenisis. 142
Rosenstiel School of Marine and Atmospheric Science, Division of Chemical Oceanography, University of Miami, 10 Rickenbacker Causeway, Miami, Florida 33149, U.S.A. *Present address :
University of Delaware, College of Marine Studies, Newark, Delaware, U.S.A. Baker, W. E. (1973). Geochim. et. Cosmochim. Acta, 37, 269. Duursma, E. K. & Gross, M. G. (1971). In: Radioactivity in the marine environment, National Academy of Sciences, Washington DC, pp. 147-160. Gerchakov, S. M., Segar, D. A. & Stearns, R. D. (1973). Proc. 3rd National Symposium on Radioecology, Oak Ridge, Tennessee, May 1971. In Press. Hatcher, P. G., Neumann, A. C., Mackenzie, F.. Simoneit, B. R., Thorstenson, D., Segar, D. A. & Gerchakov, S. M. (1973). Mangrove Lake, Bermuda. An environment for possible oil formation. Nature (in press). Joseph, A. B., Gustafson, P. F., Russell, I. R., Schuert, E. A., Volchok, H. L. & Tamplin, A. (1971). in: Radioactivity in the marine environment, National Academy of Sciences, Washington, DC, pp. 6-41. Rice, T. R. & Wolfe, D. (1971). In: Impingement of man on the oceans, ed. D. W. Hood, Wiley Interscience, NY, pp. 325-380. Riley, J. P. & Chester, R. (1971). Introduction to marine chemistry, London: Academic Press. Roessler, M. A. (1971). Mar. Poll. Bull., 2 (4), 87. Roosenberg, W. H. (1969). Chesapeake Sci., 10, 241. Segar, D. A. (1973). Int. J. Environment Anal. Chem. (in press). Segar, D. A., Gilio, J. L. & Pellenbarg, R. E. (1972). Abstracts American Geophys. Union. Annual Meeting, San Francisco, Dec. 1972. Segar, D. A., Gilio J. L. & Pellenbarg, R. E. (1973). Abstracts Symposium on Environmental Biogeochemistry, Logan, Utah, March 1972, p. 19. Silverman, M. P. & Ehrlich, H. L. (1971). Adv. in Appl. Michobiol., 6, 153. Thorhaug, A., Segar, D. A. & Roessler, M. R. (1973). Mar. Poll. Bull. (in press).
Mn Zn Cd Cu Ni Fe Pb Ag
Geometric Range Geometric Range Geometric Range Geometrxc Range Geometric Range Geometric Range Geometric Range Geometric Range
mean mean mean mean mean mean mean mean
N u m b e r of observations: Limpets 4.
Fucus
Porphyra
spp.
spp.
110 46-200 85 27-400 1.1 0.5-2.7 7.8 2.5-24 8.6 3.2-17 290 170-760 4.5 3.1-10 0.4 0.1-1.4
33 15-96 56 32-170 0.42 0.27-0.76 13 5.9-67 2.9 1.4-5.9 370 150-980 2.8 0.8-7.3 0.4 0.2-0.5
Limpets (soft parts) 23 15-62 120 94-140 4.4 2.9-7.1 11 6.9-13 7.9 4.5-14 2000 1600-2700 3.7 1.5-9.3 2.0 1.5-2.6
metals in the three materials are given in Table 3. The mean concentrations for most metals are similar to those obtained from an earlier survey in the eastern Irish Sea in 1970 (Preston et al., 1972).
Conclusions This preliminary report on the first of a series of surveys in the North Sea has indicated that, with the exception of cadmium, the highest concentration of dissolved metals occurred in coastal waters. Compared with the Irish Sea, the range of metal concentrations measured generally did not have such high upper limits. However, the metal content of the biological material examined from both sea areas was similar. Further investigations in the North Sea are under way to establish a more detailed geographical picture of metal distribution, to determine the relationship between the particulate and dissolved phases, to detect any seasonal cycles involving metals, and to locate possible terrestrial sources of input whether they be man-made or natural. These investigations form part of an international programme of the working group for the study of pollution of the North Sea under the auspices of the International Council for the Exploration of the Sea. J. W. R. DUTTON D . F . JEFFERIES
Ministry of Agriculture, Fisheries and Food, Fisheries Radiobiological Laboratory, Lowestoft, Suffolk. A. R. FOLKARD P. G. W. JONES
Ministry of Agriculture, Fisheries and Food, Fisheries Laboratory, Lowestoft, Suffolk.
Fucus spp. 9, Porphyra spp. 7,
Samples of two seaweeds, Fucus vesiculosus and Porphyra umbilicalis, and the limpet, Patella vuIgata, were collected, where available, for use as biological indicator systems. The concentrations of individual
Abdullah, M. I., Royle, L. G. & Morris, A. W. (1972). Heavy metal concentration in coastal waters. Nature, Lond., 235: 158-60. Preston, A., Jefferies, D. F., Dutton, J. W. R., Harvey, B. R. & Steele, A. K. (1972). British Isles coastal waters: the concentrations of selected heavy metals in sea water, suspended matter and biological indicators--a pilot survey. Environ. Pollut., 3: 69-82.
Trace Metals in Carbonate and Organic Rich Sediments A great variety of man's activities on the coast result in metal contamination of the sea. Investigations at three sites, two in Florida and one in Bermuda reveal trace metals in sediments. I~ all tiu-ee cases these accumulations can be ascribed to local human~ activities, though their nature varies widely from one site to another. During an investigation of the trace transition metal distributions within carbonate and organic rich nearshore and estuarine sediments, three separate geogra-
tions of some metals have been found which may be ascribed to some of the various different influences of man's activities. The sediments in each of the three study areas are characterized by their high carbonate and organic contents and their generally low concentrations of transition metals (Table 1). The sediments contain variable amounts of quartz sand, and the Mangrove Lake sediments also contain halloysite.
phical locations, Card Sound and Turkey Point, Florida and Mangrove Lake, Bermuda have been studied. In each of these areas localized high concentra-
Sampling and Analysis
138
Sediment samples were obtained by hand coring tubes of 7.5 cm diameter forced into the sediments to
about 15 cm depth. The resulting samples were homogenized by vigorous stirring after addition of a little silica distilled water in a silica beaker• A subsample of about 10 g was freeze-dried to constant weight in a polyethylene bottle and broken into a fine powder with a teflon coated rod. Analysis of the dried sediment sample was carried out by flameless atom reservoir atomic absorption spectrophotometry after acid dissolution and solvent extraction of the metal pyrrolidine dithiocarbamates (Segar, 1973).
very rapidly flushed and whose sediments contain naturally high concentrations of trace metals which are strongly associated with clay minerals. Thus, only very small fractional changes in total sediment metal concentrations might be expected at most sites and any such changes may well be within the natural small scale geographical variations in the discharge area. The Turkey Point site is perhaps unique in that it is located on a very shallow estuary with carbonate/ organic sediments of low natural trace metal concentra-
Turkey Point Turkey Point is situated towards the south end of Biscayne Bay, Florida and at the time of sampling for this study, February 1972, two 450 megawatt oil-fired generators were operating at the Turkey Point power plant. These generators were drawing an average of 850 m3/min of cooling water from Biscayne Bay on the north side of Turkey Point and discharging this water to the bay through a network of canals about 1 mile to the south of the plant. Prior to this study the generating units had been operational for 3½ and 4½ years respectively. Extensive studies of the effects of the heated effluent upon the ecology of the discharge area (Roessler, 1971; Thorhaug et aI., 1973) and some preliminary studies of the chemistry of the discharge water (Gerchakov et al., 1971) have been reported. These preliminary investigations revealed that the power plant operation was probably causing the addition of small but perhaps significant amounts of transition metal contaminants to the discharge water. Similar observations have been made at other sites either directly or indirectly by observing increases in metal content of indicator organisms (Roosenberg, 1969). Apparently, significant changes in the sedimentary concentrations of trace elements in power plant discharge areas have not previously been reported. This is perhaps surprising in view of the studies of radionuclide releases from power plants which indicate that a considerable proportion of many of these radionuclides are in general quickly removed from the water to the underlying sediments (Rice & Wolfe, 1971; Joseph et al., 1971; Duursma & Gross, 1971). However, many power plants discharge into areas that are
(
i
"':L
....~ FPL POWER PLANT.
Q
I0
50 ~
!h Fig. 1 D i s t r i b u t i o n o f nickel ( p p m ) in s e d i m e n t s at T u r k e y Point.
TABLE I E l e m e n t a l c o n c e n t r a t i o n s o f v a r i o u s m a r i n e s e d i m e n t s (ppm). Element
D e e p sea carbonates*
D e e p sea clays*
Nearshore sediments*
V Fe Cd Pb Ag Zn Cu Ni Ca(ppt) Organic Carbon
20 9,000 -9 -35 30 30 --
120 65,000 0.42 80 0.11 165 250 225 --
130 --20 --48 55 --
--
--
(% dry wt)
--
Card Sound Florida**
24 1,900 0.07 1 0.5 4 2 ,(2 1-390
0.3-26
Turkey Point Florida***
Mangrove Lake Bermuda surface samplest
52 2,600 0.2 3 0.4 12 11 25 --
26 3,100 0.6
39 26 6 7 370
0.4-11
1-19
20 3
Mangrove Lake Bermuda core s a m p l e s f I" 22 (57) 1,800 (5,200) 0.8 (3)
(2) (0.8) (39) (27) (26)
18-38
* F r o m R i l e y a n d C h e s t e r (1971); ** a v e r a g e o f 82 s a m p l e s ; *** a v e r a g e o f 33 s a m p l e s ; t" a v e r a g e o f 18 s a m p l e s ; #J" a v e r a g e o f 14 samples. M a x i m u m v a l u e in p a r e n t h e s e s . 139
tions (Table 1). In addition, the hydrodynamical regime is such that rapid dispersion of the effluent is not encouraged. In fact the discharge water appears to be significantly recycled. The potential thus exists for a concentration build-up of trace metals in the sediments of the discharge area. The average concentrations of trace elements in 33 sediment samples from the area near Turkey Point are considerably lower than those observed in deep sea clay and average nearshore sediments (Table 1). The concentrations are also somewhat lower than those observed in deep sea carbonates and in Mangrove Lake, Bermuda. However, particularly for vanadium, iron, zinc, nickel and copper the concentrations observed are significantly higher than those observed in the sediments of an extremely similar but almost natural and uncontaminated ecosystem, Card Sound, Florida situated a few km to the south of Turkey Point. These data alone are not sufficient to indicate that the power plant is causing contamination of the sediments in its discharge area. However, when distribution of the metals within the Turkey Point area is considered the influence of the power plant becomes clear. Thus the concentrations of nickel (Fig. 1), vanadium (Fig. 2), copper (Fig. 3), iron, zinc, lead and possibly silver are particularly high in the sediments immediately adjacent to the power plant ouffaU canal and in the area just to the south of Turkey Point itself. The latter area is probably a low energy sedimentary sink. Physical parameters and water chemistry have indicated that the water in this area is occluded by the looping current of water released at the outfall canal and sweeping around Turkey Point to return to the intake canal on the north (Roessler, 1971). It appears that the construction and/or operation of the power plant at Turkey Point has led to significantly increased concentrations of a number of trace metals in the sediments within the discharge environment. The exact causes of this contamination are not known. However, several possibilities are presently under study. It is possible that the excess metal load was contributed to the bay sediments in the dredge spoil introduced to the bay during the initial construction of the power plant and canal system, although this spoil is predominately limestone oolite and low in metals. The effluent water from the power plant has been shown to contain higher dissolved concentrations of some metals, notably copper and iron, than the normal bay water and it is possible that this excess metal is partially removed to the sediments by biological and abiological scavenging mechanisms. Metallic particles may be introduced into the power plant effluent and may sediment out on reaching the bay where water velocities are lower. Sources of particulate and dissolved metal during construction of power plants are many and subsequently during operation of the power plant corrosion may contribute significant quantities of metals particularly from the cooling system itself. The cooling coils of the Turkey Point plant are constructed of copper/nickel, the two elements which are in greatest excess over their Card Sound concentrations in the Turkey Point area (Table 1). The distribution of nickel in the sediments at Turkey Point clearly indicates a 140
25.
FPL POWER PLANT
rn
•
150~
I001!
Fig. 2 Distribution of vanadium (ppm) in sediments at Turkey Point.
!
il0
I IO
.Q Fig. 3 Distribution of copper (ppm) in sediments at Turkey Point.
power plant source. The copper distribution, although indicating a similar source, is more complicated perhaps due to the intimate involvement of copper in biological processes and the occasional use of copper salts in lower Biscayne Bay as a shark repellent by the US Air Force. Some elements, particularly vanadium and lead, may be supplied to the discharge environment from the fuel oil used by the Turkey Point generators and gasoline used by automobiles, boats and construction vehicles. One factor contributing to the build up of metal concentrations in the sediments immediately adjacent to the canal ouffall may be the loss of rooted aquatic plants (Thalassia testudinum) from this area due either to heat stress or other effects of the power plant (Roessler, 1972; Thorhaug et al., 1973). It has recently been hypothesized that these plants are instrumental in recycling metals from deep within the sediments back into the water column and detritus food chain (Segar et al., 1972, 1973). Their destruction would mean that this possibly significant mechanism of removal of trace metals from the sediments was no longer operative and higher concentrations would probably result.
Card Sound Card Sound, Florida, a shallow, mangrove fringed estuarine embayment about 5-10 km to the south of Turkey Point, is an area little affected by the activities of man. This is reflected by the extremely low concentrations of metals in the sediments of the Sound (Table 1). Anomalously, high concentrations of metals have been observed in the sediments close to what is currently man's only major influence on the Sound, the Ocean Reef Yacht Club basin located on Key Largo at the middle of the eastern shore of the Sound. The I' /d - I:.V: :.l
sediments in the area of this yacht basin are loose and fine grained with high organic content and have high concentrations of nickel, zinc, lead, copper, vanadium and cadmium, compared to the sediments immediately to the north, south and west (e.g. Fig. 4). However, concentrations of these metals in the area of the boat basin are not appreciably greater than the highest values found in the rest of the Sound. Too few samples have been analysed from the area close to the boat basin to delineate the extent or magnitude of the contamination, but it is clear that trace metals are being or have been introduced to the sediments due to the operation and/or construction of this facility. Potential sources of metal include the untreated sewage, and corrosion and exhaust products from boats moored in the basin. Dredge and fill material probably does not contribute excess metals, particularly as significant anomalies were not observed in the sediments around the Model Land canal, a man-made structure on the western shore of Card Sound.
Mangrove Lake Mangrove Lake, Bermuda, is a small brackish water lake containing sediments of very high organic content and considerable depth. These sediments have been described by Hatcher et al. (1973). Analysis of the surface sediments has shown that the concentrations of iron, zinc and copper (e.g. Fig. 5) are considerably higher at one station at the centre of the western shoreline than in the rest of the lake. The lead concentration
5o. :.: ...""f/ .2...if"""
,ke
50.Ipo ~qo ... • ". " . -
~ :.l. . . . . . .
I00
1
zo
,
"
50100.
"i
1 20
1
li~
."
"" 2 0
zoo -... 2oo~
• "
30.5"
:i
l
~: i:
l
""
." : ' ; ' " !:
50
3o!
Fig. $ Distribution of zinc (ppm) in Mangrove Lake sediments.
1
Fig. 4 Distribution of vanadium (ppm) in sediments in Card
Sound.
at this station was also high compared to the rest of the western half of the lake (Fig. 6). However, the silver, cadmium, nickel and vanadium concentrations at this station were within the range of concentrations found in the rest of the lake. It has been reported that trash dumping has been practised by local residents in the area where the anomalous concentrations were observed. For example an old and rusting motorcycle has been observed lying on the lake bottom at this point. It seems reasonable to assume that such dumping has caused the observed increase in sedimentary metal concentrations.
141
The lead distribution in Mangrove Lake surface sediments indicates a strong source of the metal in the south-east corner of the lake (Fig. 6). No explanation for this can yet be advanced but it has been calculated that the lead involved in this anomaly could have been contributed from less than several hundred gallons of leaded gasoline. 2O0...:..'.. 100 ..../ "
.,:.'200
•
5.0, ." . ",.
.... : ,
.....
'
.~'200 .' 30,0
>
'oo
,,-
i..O0 0
/ "" ""
":"
5 0 .'"
"'1400 .'7 ." I40.0
• •
"
•
"'"
" I000 :: 4 0 0 "" 3 0 0
I00. 200
•
.:. ZOO
i:
3ob ,
200
,o.o
..
"
'"
...
.?200
Significance of Metal Contamination Although we have shown that metal contamination of marine sediments occurs in widely differing areas due to different types of human activity it is not known for certain whether or not such contamination can produce effects which are harmful to man. The contaminant element is normally introduced into the sediments in a physicochemical state such that it enters the natural active biogeochemical cycling of elements in the discharge ecosystem. Even pure metals and many oxides and minerals may be rapidly solubilized in organic rich environments such as are most nearshore sediments (e.g. Baker, 1973; Silverman & Ehrlich, 1971). Therefore, contamination by metals will normally increase biologically available trace metals in an ecosystem and this will inevitably lead to the increase of metal concentrations in many organisms. As most trace metals have toxic properties at some concentration and as maximum permissible concentrations are enforced for many trace metals in food, such increases in the concentration of trace metals in the biosphere are potentially harmful both to the aquatic biology and to man. This work was supported by National Science Foundation grant GA-33003 with additional support from the US Atomic Energy Commission. One of us (REP) was partially supported by the National Oceanic and Atmospheric Administration Sea Grant programme.
D. A. SEGAR R. E. PELLENBARG*
Fig. 6 Distribution of lead (ppm) in Mangrove Lake sediments.
Some idea of the possible influence of man's activities upon sedimentary environments may be obtained from a comparison of the average metal concentrations in Mangrove Lake surface sediments and in the sediments below 2 m depth in a 16 m vertical core taken in the centre of the lake (Table 1). The sediments analysed from this core are representative of the material deposited in Mangrove Lake over about 5,000 years and thus reflect possible depositional changes during that time. It is therefore highly significant that the silver and lead average concentration in the surface samples lie above the maximum concentrations observed in the core (Table 1). In addition, it is possibly significant that the average concentrations of iron, copper and zinc are higher in the surface sediments than in the core. Presumably the higher concentrations of metals in the surface sediments represent the effects of recent man-made changes on the relatively undeveloped Bermuda island. The increase in lead concentration is particularly striking with the average surface concentration being some twenty times the highest value observed in the core. Vanadium, nickel and cadmium do not appear to be significantly influenced by the changes that have produced the higher concentrations of other metals. Thus, it is unlikely that the changes in metal concentration are due to a change in the scavenging ability of the presently accumulating sedimentary material as compared to previously accreting material. For iron there exists the possibility of the upwards transport of metal during sediment diagenisis so that its concentration in the core may be low due to this mechanism. The solubilities of the sulphides of the other elements are low enough to prevent their migration from the reducing sediments during diagenisis. 142
Rosenstiel School of Marine and Atmospheric Science, Division of Chemical Oceanography, University of Miami, 10 Rickenbacker Causeway, Miami, Florida 33149, U.S.A. *Present address :
University of Delaware, College of Marine Studies, Newark, Delaware, U.S.A. Baker, W. E. (1973). Geochim. et. Cosmochim. Acta, 37, 269. Duursma, E. K. & Gross, M. G. (1971). In: Radioactivity in the marine environment, National Academy of Sciences, Washington DC, pp. 147-160. Gerchakov, S. M., Segar, D. A. & Stearns, R. D. (1973). Proc. 3rd National Symposium on Radioecology, Oak Ridge, Tennessee, May 1971. In Press. Hatcher, P. G., Neumann, A. C., Mackenzie, F.. Simoneit, B. R., Thorstenson, D., Segar, D. A. & Gerchakov, S. M. (1973). Mangrove Lake, Bermuda. An environment for possible oil formation. Nature (in press). Joseph, A. B., Gustafson, P. F., Russell, I. R., Schuert, E. A., Volchok, H. L. & Tamplin, A. (1971). in: Radioactivity in the marine environment, National Academy of Sciences, Washington, DC, pp. 6-41. Rice, T. R. & Wolfe, D. (1971). In: Impingement of man on the oceans, ed. D. W. Hood, Wiley Interscience, NY, pp. 325-380. Riley, J. P. & Chester, R. (1971). Introduction to marine chemistry, London: Academic Press. Roessler, M. A. (1971). Mar. Poll. Bull., 2 (4), 87. Roosenberg, W. H. (1969). Chesapeake Sci., 10, 241. Segar, D. A. (1973). Int. J. Environment Anal. Chem. (in press). Segar, D. A., Gilio, J. L. & Pellenbarg, R. E. (1972). Abstracts American Geophys. Union. Annual Meeting, San Francisco, Dec. 1972. Segar, D. A., Gilio J. L. & Pellenbarg, R. E. (1973). Abstracts Symposium on Environmental Biogeochemistry, Logan, Utah, March 1972, p. 19. Silverman, M. P. & Ehrlich, H. L. (1971). Adv. in Appl. Michobiol., 6, 153. Thorhaug, A., Segar, D. A. & Roessler, M. R. (1973). Mar. Poll. Bull. (in press).