Environ. Sci. Techno/. 1995,29,2261-2266
Patterns of Total Mercury Concentrations in Onondaga Lake, New York WE1 W A N G * A N D CHARLES T. DRISCOLL Department of Ciuil and Environmental Engineering, 220 Hinds Hall, Syracuse Uniuersity, Syracuse, N e w York 13244-1190
Onondaga Lake, located in central N e w York, received elevated inputs of mercury from a chloralkali facility over the period 1946-1970. Despite marked reductions in mercury loading since that time, concentrations of total mercury in Onondaga Lake remain among the highest values reported in the literature, comparable to other lakes with point sources of mercury. Concentrations of mercury varied markedly in the upper waters of Onondaga Lake during the ice-free period. A large accumulation of mercury was observed in the hypolimnion during the summer stratification. This accumulation coincided with increases in dissolved sulfide concentrations produced during the period of hypolimnetic anoxia. Chemical equilibrium calculations indicate that hypolimnetic waters of Onondaga Lake were oversaturated with respectto the solubility of mercuric sulfide, and mercury sulfide complexes dominate the speciation of aqueous mercury. The formation of strong aqueous complexes with dissolved sulfide may be an important mechanism facilitating the mobilization of mercury from pelagic sediments to the water column.
Hg are influenced by changes in pH and particularly concentrations of dissolved sulfide (H&) (11). Mason et al. (9)demonstrated the importance of particulate matter, especially iron (Fe) and manganese (Mn), in scavenging and transporting Hg from the water column. Onondaga Lake is a hypereutrophic, hardwater lake adjacent to Syracuse, NY. The lake is heavily polluted, having received municipal effluent and industrial waste for more than a century (12). It is estimated that approximately 76 000 kg of Hg was discharged to the lake by an adjoining soda ash/chloralkali facilitybetween 1946 and 1970 (13,14). Despite substantial decreases in Hg discharge since 1970, high concentrations of Hg have persisted in the water column, sediments, and fish tissue (15-18). The soda ash facility has also released elevated inputs of chloride (Cl-1, calcium (Ca2+),and sodium (Na+)to the lake (19). Onondaga Lake directly receives effluent from a wastewater treatment plant, resulting in high concentrations of total phosphorus (P) and high productivity (12,20,21). Finally, naturally occurring deposits of gypsum (CaS04.2H20) in the surrounding watershed release elevated concentrations of sulfate (SO4*-) to waters draining into the lake (12).Due to industrial waste, domestic effluent, and the bedrock geology of the watershed, Onondaga Lake has unique chemical characteristics that may directly and indirectly affect the chemistry and cycling of Hg. As the result of domestic effluent and industrial waste, the lake experiences several water quality problems in addition to Hg contamination. These include the following: (a) extended periods of hypolimnetic anoxia (12,221: (b) accumulation of H~ST under anoxic conditions in the hypolimnion (23-26'); and (c) high rates of particle deposition resulting from the high productivity and in-lake precipitation of calcite (CaC03) (19, 27, 28). The objective of this research was to investigate patterns of total Hg (HgT) concentrations and to evaluate the role of chemical parameters in regulating the behavior of Hg in Onondaga Lake.
Site Description and Methods Introduction Direct discharge of mercury (Hg) containing waste to the environment has substantially declined since contamination by this element was found to threaten human health. Nevertheless, high concentrations of Hg are still evident in the water column, sediments, and fish tissue of many lakes (1, 2). Contaminated sites provide a good opportunity to investigate the environmental chemistry of Hg, particularly because remediation of this toxic substance is difficult and requires a detailed understanding of the problem. The behavior of Hg in natural waters is strongly regulated by attendant chemical conditions. Concentrations of dissolved organic carbon (DOC) and chloride (Cl-), pH, and oxidation-reduction potential (redox potential) of a water body directly affect the biogeochemistry of Hg (310). In anoxic waters, the concentration and speciation of * Address correspondence to this author at his present address: Institute of Marine and Coastal Sciences, Rutgers University, P.O. Box231, New Brunswick, NJ 08903-0231;fax: (908) 932-8578;e-mail address:
[email protected].
0013-936)(195/0929-2261$09.00/0 @ 1995 American Chemical Society
Onondaga Lake has a surface area of 11.7 km2, a mean depth of 12 m, a maximum depth of 20 m, and a drainage basin of 600 km2. The lake flushes rapidly, an average of four times per year. The lake water is characterized by a high concentration of C1- (mean concentration 460 mg of CUL), SO4*-(51 mg S/L), soluble reactive P (460pg of P/L), Na' (220 mg of NalL), and Ca2+(176 mg of Ca/L) (23,24, 29). Lake water samples were collected biweekly from April to November 1992 at three depths (0, 10, and 19 m) at a station in the southern basin of Onondaga Lake. This location was found to be representative of overall lake conditions (30). Water was directly pumped from different depths into Teflon sample bottles. Sample bottles were appropriately cleaned for Hg analyses (31, 32) and rinsed with a lake water sample just prior to the final collection. The surface sample was collected about 0.5 m below the water surface to avoid contamination by the microlayer. The bottles were completely filled, tightened by gloved hands, and double bagged. Triplicate samples were collected at one site during each sampling period. Generally,
VOL. 29, NO. 9, 1995 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
2261
TABLE 1
Components, Initial Concentrations, and Conditions Used in pE and HS- Titration with MINEQL component
concn (molR)
condition
10-10 10-16 0.013 0.0016 10-16
1
20,
7.5 (fixed) (fixed) (fixed) 8 “C 14 to --6 (titration)
the samples were delivered to the analytical laboratory within 5 h of collection. Mercury samples were oxidized with bromine chloride (BrC1) solution (33) immediately after arriving at the laboratory. The excess oxidizing reagent in the samples was prereduced by hydroxylamine hydrochloride (NH2OHSHC1, 30%) (33). After the reduction of mercuric ion [Hg(II)I to metallic mercury (HgO) by stannous chloride (SnC12) solution, concentrations of total Hg (HgT) were measured by a two-stage gold amalgamation gas train (32) and cold vapor atomic fluorescence (34). Triplicate analytical measurements were periodically made. The coefficient of variation for sampling triplicates of HgT was 26%. The coefficient of variation for analytical triplicates of HgT was 13%. Water samples were also analyzed for other water chemistry parameters, including pH, dissolved oxygen (DO), DOC, and C1- using the procedures described by Driscoll and van Dreason (35). The lower water samples (10 and 19 m), which contained low concentrations of DO, were monitored for concentrations of H& (36). In order to gain insight on Hg chemistry in Onondaga Lake, three theoretical chemical equilibrium calculations were conducted. A Hg pE-pH [pE = -log (electron activity)]predominance area diagram was developed using concentrations of water chemistry parameters observed in the hypolimnion of Onondaga Lake (HgT = 1O-Io mol/L, Cl, = mol/L, Sr = 2 x mol/L). The thermodynamic data were obtained from Stumm and Morgan (37)and from Morel and Hering (38). The approach used in the construction of the pE-pH diagram is described in detail by Morel and Hering (38). Using measured values of DO, the pEof the epilimnion was estimated to be 12.4-12.9 during the study period. With field measurements of SO4’- and H~ST, the pE of the hypolimnion at 19 m was estimated to be -4.09 to -4.18. Two theoretical “titrations” were conducted with the chemical equilibrium model MINEQL (39): (a) futed pE conditions were varied from 14 to -6 and (b) the total S concentration (as HS-) was varied from 10-14 to mol/ L. In these “titrations”,Hg2+[asHg(OH121,Ha2+,C1-, S042-, and HS- were chosen as components (Table 1). During the calculations, the pH of the system was fixed at 7.5, and the temperature was assumed to be 8 “C, near mean conditions for Onondaga Lake (29). Two redox couples, Hg2”/Hg(OH)z and HS-/SOh2-, were included in the pE titration. In addition, solid and gaseous species formed in the titration were placed in the “species not considered” category (type VI), which assumes that the formation of solid and gaseous species does not affect the equilibrium concentration of dissolved Hg species. 2262
1
ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 29. NO. 9,1995
.
7L
8.6 1
I
I
I
N
D
8.0 I
a
7.6
7.0 A
M
J
J
A
S
O
Tlme
FIGURE 1. Water chemistry parameters (DO, H A DOC, and pH) in the water column (at 0, 10, and 19 m depths) of Onondaga Lake, 1992.
In the chemical equilibrium titration involving the addition of variable concentrations of total S (as HS-), the electron was not chosen as a component. Metacinnabar (HgS)was selected as a futed solid (type 1111,which implies that it serves as an infinite reservoir of solid Hg supplying dissolved Hg to the aqueous phase at equilibrium. As with the pE titration, other nondissolved Hg species were not considered in the chemical equilibrium calculations (type
VI).
Results and Discussion Onondaga Lake was stratified from May to the middle of October 1992 (Figure 1). During the stratification period, concentrations of DO were depleted below the 10 m depth. The concentrations of DO in upper waters (above 10 m) ranged from 6.4 to 14.1mg/L. The lower waters were largely anoxic from June to October. Dissolved sulfide was likely produced in the sediments and transported to the hypolimnion of the lake following depletion of DO (26). Concentrations of HZSTincreased through the summer, reaching a peak value of 14.5 mg of SIL at the 19 m depth in August (Figure 1). Dissolved organic carbon concentrations were low in April, increased at all depths by midsummer, declined in late summer, and increased again in November following fall turnover. Concentrations of DOC were generally highest in the surface waters during the early portion of the ice-free season. Concentrations of DOC were lowest at the 10 m depth and increased slightly at the 19 m depth. The surface waters had pH values near 8 from April to August, decreasing to around 7.5 in late summer
40
TABLE 2
a) Om
I
Comparison of H ~ Concentrations T in Onondaga Lake with Other Pristine and Polluted Systems lake system
20
L
W
b[r
I
total Hg
Remote Lakes Adirondacks Adirondacks Wisconsin Washington California Manitoba
Lake Union
Urban lakes Washington (state) 1.7
45
Erie Ontario
Great Lakes U.S./Canada U.S./Canada
1 1
Clear Lake Davis Creek
Mining Contaminated Lakes California 3.6-104 California 5.2-6.4
0.8-5.3 0.8 0.9-1.9
0.2 0.6 0.2-1.1
3.9 0.9
Chloralkali Contaminated Lakes Clay Lake Ontario 5-80 Onondaga Lake New York 2-35 New York 2.6-35.2 Onondaga Lak
c) 19m
1992 FIGURE 2. Total Hg concentrations in upper (0 m), middle (10 m), and lower (19 m) waters of Onondaga Lake, 1992.
and early fall (Figure 1). In the lower waters, the pH was similar to that at the surface during spring turnover and decreased during the stratification period (Figure 1). Concentrations of HgT were generally uniform over the entire water column during spring and fall turnover (April and November; Figure 2). The concentrations of HgT in surface water of Onondaga Lake ranged from 2.6 to 19.2 ng/L, with a mean concentration of 9.5 nglL. Concentrations of HgTin the upper waters were highly variable during the study period. High concentrations of HgT were observed in the middle of July and in the fall, with the highest value occurring in mid-November (19.2 nglL1. Patterns of HgT concentrations at the 10 m depth were similar to values at the lake surface. During summer stratification, concentrations of HgT gradually accumulated in the lower waters, with a peak value of 35 ng/L in September. Particulate matter undoubtedly plays an important role in the variability of HgT concentrations in epilimnion. High particle concentrations showing strong temporal variation have been reported in Onondaga Lake (28). Much of the particulate matter in Onondaga Lake is of biological origin andlor is characterized by elevated Ca content due to the high productivity and conditions of oversaturation with respect to the CaC03 solubility (21). Many investigators have documented the association between Hg and particulate matter (I,5,9,40,41). Organic particles produced by biological activity are effective sorbents facilitating the partitioning of Hg. Hurley et al. (11 ) reported high partition coefficients for HgT in the water column of Little Rock Lake (& = 4.5-5.7). Plankton could be an important determinant of patterns of HgT concentration (42). Because of the
ref
drainage seepage seepage drainage alpine drainage
l0Ii&mn 0
location
26 26 44 45 1 15
1 1 46 15 this study
high productivity of Onondaga Lake, factors affecting the biological activity, such as temperature, intensity of light, and input of nutrients, may influence the temporal and spatial variations in HgT concentrations. Therefore, the marked fluctuations in HgT concentrations observed in the upper waters of Onondaga Lake are not unexpected. Large particles with high density entering the lake via streamwater andlor formed in the lake by the precipitation of CaC03 may scavenge Hg from the surface water. In contrast, smaller biologically produced organic colloids and living organisms may tend to keep Hg in suspension. The most distinct pattern of HgT concentrations in Onondaga Lake was the large accumulation in the lower waters during the summer of 1992 (Figure 2). In April, during spring turnover, HgT concentrations were among the lowest values observed at 19 m during the ice-freeperiod (12.6 ng/L). As summer stratification proceeded, concentrations of HgT increased, reaching a maximum value of 35 nglL in September. The concentration of HgT decreased markedly in October and increased slightly in November. The sudden decrease in concentration of HgT in October was the likely result of saline water from a major tributary to the lake, Ninemile Creek. Ninemile Creek receives high ionic strength leachate from wastebeds associated with the soda ash facility. During the fall as stream temperature decreases, this saline water may not completely mix with the upper lake water but rather plunges to the hypolimnion (22). The mean concentration of HgT in the lower waters during the study period was 22 nglL. The pattern of high hypolimnetic concentration of HgTis similar to other deep lakes exhibiting anoxic hypolimnia (9-11, 41). The results of our study were generally consistent with the results obtained for apreliminarystudy at the same site in 1989 by Bloom and Effler (15) (Table 2 ) . Since samples were only collected on four dates in 1989, the temporal resolution of their study was not as detailed as reported here. However, they obtained information on fractions of Hg in the water column which facilitates the interpretation of our results. The range of HgT concentrations observed for 1992 were generally similar to values reported by Bloom and Effler (1.5) for 1989. They found that a large fraction VOL. 29. NO. 9 , 1 9 9 5 i ENVIRONMENTAL SCIENCE
TECHNOLOGY m 2263
20
A
I
1
H g T = 2.57(H*S)
-
1 .o
+ 6.0
30
0.5
m 3-
0)
Q
0
2
v
I
/
-0.5
-1
O ’W O ! 0
-20 0
2
4
8
6
I 0 1 2 1 4
PH
2
4
6
8
IO
L-1)
FIGURE 3. Mercury pE-pH
FIGURE 4. Relationship between concentrations of HgT and concentrations of HZSTin the lower waters of Onondaga Lake.
(60%)of the HgTat 0 and 10 m depths was associated with particulate matter. Bloom and Effler (15) also observed high concentrations of monomethyl mercury for Onondaga Lake. The mean concentrations of monomethyl mercury at the lake surface were 11% of HgT, and this fraction increased to 21% of HgT at the 19 m depth. Bloom and Effler (15) reported a pattern of increasing concentrations of HgT with increasing depth in the lake. However, the accumulation of high concentrations of Hg in the lower waters during summer stratification was not evident in 1989. This discrepancy is likely due to the limited temporal resolution of their study. Mercury stronglybinds with sulfide,forming an insoluble precipitate (HgSl,,)and strong aqueous complexes (37,47, 48). Chemical equilibrium calculations with MINEQL suggest that during summer stratification the lower waters of Onondaga Lake were oversaturated with respect to the solubility of HgSl,,. There is some uncertainty in these calculations due to the association of Hg with particulate matter and organic ligands and the presence of monomethyl mercury. Chemical equilibrium calculations would only apply to concentrations of aqueous inorganic mercuric ion in Onondaga Lake. Nevertheless, it seems likely that there is the strong potential for the precipitation of HgSl,] in the hypolimnion of Onondaga Lake in the presence of elevated concentrations of H&. The pE-pH predominance area diagram of Hg for Onondaga Lake (Figure 3) indicates that the formation of HgS(,,is pH-dependent. Under mildly reducing conditions and pH values below 7.0, production of H& may scavenge Hg by precipitation of HgS[,,. When pH values increase to above neutral conditions and concentrations of H~ST are elevated, Hg can be mobilized through the formation of soluble mercuric hydrosulfide [Hg(HS)z]and/or polysulfide [HgS22-]complexes (3,49). This mechanism is consistent with our observations for Onondaga Lake. The increase of HgT concentrations in hypolimnion was found to closely coincide with increases in H~ST concentrations (? = 0.79; Figure 4). According to chemical equilibrium calculations, under the conditions that prevail in the hypolimnion of Onondaga Lake, the major forms of Hg are the soluble complexes HgSz2-and Hg(HS)’ when the concentrations
of H Z Sare ~ in excess of HgT. Hurley et al. (11) reported similar findings for Little Rock Lake. Onondaga Lake is naturally enriched with SO4’- (mean value 51 mg of S/L) (29). High S042-concentrations and complete depletion of DO in the hypolimnion during the summer of 1992 facilitated the reduction of S O 8 to H&. The mean H& concentration at 19 m was 3.2 mg of SIL. Due to the high concentrations of H&, it seems likely that Hg in the lower waters of stratified Onondaga Lake largely existed as HgSls1with HgS& and/or Hg(HS)2as the major aqueous species. The production of HzST and the formation of strong mercuric sulfide complexes could shift the partitioning of Hg from the particulate phase to the aqueous phase. This process could facilitate the mobilization of Hg from the pelagic sediments or particles deposited from the epilimnion and subsequently contribute to the accumulation of HgT observed in the hypolimnion of Onondaga Lake. Hurley et al. (11)conducted a mass balance on Hg at the sediment-water interface of Little Rock Lake. They found that the accumulation of Hg in the hypolimnion was largely derived from recently deposited particulate matter. Particulate Hg transported from the upper waters could also be an important source of Hg to the hypolimnion of Onondaga Lake. Mercury inputs of the upper waters of Onondaga Lake are largely supplied from stream inflow (43). As mentioned above, the upper waters of Onondaga Lake are oversaturated with Ca” with respect to CaC03 (19). This condition has resulted in a high rate of CaC03 precipitation and deposition to the sediments. Particulate matter is also associated with the high rate of productivity. Elevated concentrations of particulates are likely to be effective in scavenging Hg from the upper waters and facilitating vertical transport. The Hg associated with particles could be mobilized in the hypolimnion under lower pH values and redox potential. Theoretical chemical equilibrium titration with pE indicates that mercuric chloride complexes (HgC1,) and mercuric hydroxide complexes [Hg(OH),] predominate under high pE conditions, which are anticipated in the epilimnion and throughout the water column during spring and fall (Figure 5a). Aqueous Hg predominantly occurs as soluble complexes in Onondaga Lake water; concentrations of aquo Hg (Hg2’) are calculated to be about 9 orders of magnitude lower than the concentration of the dominant
predominance area diagram for conditions that prevail in the hypolimnion of Onondaga Lake (HgT(,,l = M, CI-T = M, and ST = 2 x M), 1992.
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high sedimentation rate (50) coupled with elevated concentrations of H2S may decrease concentrations and availability of HgT in Onondaga Lake compared to other highly polluted sites.
Conclusions
-60
1
14
I
6
12
10
8
6
4
PHS FIGURE 5. Theoretical calculations of Hg species as a function of pE (a) and sulfide concentration (b) for conditions on Onondaga Lake (see Table 1).
species. As the pE decreases, the speciation of Hg remains relatively constant until values approach 2.5. Below this redox potential, concentrations of HgCl, and Hg(OH), complexes decrease moderately until the pE declines to -2.5 (Figure 5a). When the pE declines below -2.5, the concentration of S042- decreases markedly due to S042reduction, and concentrations of H2S and HS- increase. Under these conditions, the speciation of Hg shifts so that soluble mercury sulfide complexes [HgSZ2-and Hg(HS)21 are the predominant form of Hg, resulting in decreases in the concentration of chloro, hydroxo, and aquo complexes of Hg. Results of the HS- titration show again at low concentrations of H& that HgCl, and Hg(OH), complexes predominate the speciation of HgT. When added HSapproaches the concentration of total Hg in the system (HgT = M), there is a marked decrease in the concentrations of HgT due to the precipitation of HgS(,, (Figure 5b). Continued addition of HS- results in the mobilization of Hg as HgSZ2-and Hg(HS)2. Note the sum of these two species never reaches the total concentration of Hg added to the system in the calculation M) due to precipitation of HgS[,, in the presence of elevated concentrations of H&. Therefore, Hg is probably readily immobilized or suspended in the water column as colloidal particles in this highly reduced, high sulfide environment. Comparingobservationsof Hg from Onondaga Lake with other systems (Table 2), the concentrations of HgT in Onondaga Lake were about 1 order of magnitude higher than those found in pristine lakes and similar to values observed in polluted systems. Note that the highest concentrations of HgT in Onondaga Lake were not as high as those reported for Clear Lake and Clay Lake, both highly contaminated systems. High particle concentrations and
Concentrations of HgT in Onondaga Lake are among the highest reported in the literature. These concentrations are similar to the values reported for lakes with Hg discharge from chloralkali facilities or mining activities. Concentrations of HgT increased with increasing lake depth during the summer stratification due to the accumulation of HgT in the lower waters of Onondaga Lake. The increases in HgT concentrations in the hypolimnion coincided with increases in H& concentrations. Thermodynamic calculations indicate that under the conditions that prevail in the hypolimnion of Onondaga Lake, the soluble complexes HgS$ and Hg(HS12 are the stable form of Hg when concentrations of HZSTare in excess of HgT. Severely contaminated lake sediments and particulate substances may significantly contribute to the hypolimnetic accumulation of Hgthrough the release of Hg from particulate matter and the formation of mercuric sulfide complexes. Marked variability in HgT concentrations observed in the upper waters were likely related to the elevated particle content resulting from high productivity and in-lake formation of CaC03.
Acknowledgments Funding for this study was provided by the Onondaga Lake Management Conference. We would like to give special thanks to Dr. Tsai-Ming Lee for her selfless help to this study. We would like to thank Dr. Steven W. Effler and Dr. David L. Johnson for their technical advice and Mr. T. Mulvey for his support of this work. We appreciate the assistance of Sean Tenney and all the members of Upstate Freshwater Institute, New York. This is contribution No. 140 of the Upstate Freshwater Institute.
Literature Cited (1) Gill, G. A.; Bruland, K. W. Enuiron. Sci. Technol. 1990,24, 1392. (2) Southworth, G. R.; Peterson, M. J.; Adams, S. M. Bull. Environ. Contam. Toxicol. 1994, 53 (2), 211. (3) Benes, P.; Havlfk, B. in The Biogeochemistry of Mercury in the Environment; Nriagu, J. O., Ed.; ElsevierlNorth Holland Biomedical Press: Amsterdam, the Netherlands, 1979; p 175. (4) Verta, M. Publ. Water Enuiron. Res. Inst. 1990, No. 6. (5) Lindqvist, 0. Water Air Soil Pollut. 1991, 55. (6) Wang, J. S.; Huang, P. M.; Liaw, W. K.; Hammer, U. T. WaterAir Soil Pollut. 1991, 56, 533. (7) Andersson, T.; HAkanson, L. Hydrobiologia 1992, 2351236, 685. (8) Nilsson, A.; Hdkanson, L. Hydrobiologia 1992, 235/236, 675. (9) Mason, R. P.; Fitzgerald, W. F.; Hurley, J.; Hanson, A. K., Jr.; Donaghay, P. L.; Sieburth, J. M. Limnol. Oceanogr. 1993, 38 (6), 1227. (10) Mason, R. P.; Spliethoff, H. M.; Aurilio, A. C.; Hemond, H. F.
Preprints of Papers Presented at the 207th American Chemical Society (ACS) National Meeting American Chemical Society: Washington, DC, 1994; p 366. (11) Hurley, J. P.; Krabbenhoft, D. P.; Babiarz, C. L.; Andren, A. W. In Environmental Chemistry of Lakes and Reservoirs;Advances in Chemistry Series 237; Baker, L. A,, Ed.; American Chemical Society: Washington, DC, 1994; Chapter 13. (12) Effler, S. W., Ed. Onondaga Lake: Lessons in Limnology and EngineeringAnalysis; Springer-Verlag: New York, 1995 (in press). (13) Report of Mercury Source Investigation: Onondaga Lake, New York and Allied Chemical Corporation, Solvay, New York; U.S. Environmental Protection Agency, U.S. Government Printing Office: Washington, DC, 1973. (14) Effler, S. W.; Harnett, G. In Onondagahke: Lessons inLimnology andEngineeringAnalysis;Effler, S. W., Ed.; Springer-Verlag: New York, 1995 (in press).
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Onondaga Lake: Lessons in Limnology and EngineeringAnalysis; Effler, S . W., Ed.; Springer-Verlag: New York, 1995 (in press). (19) Driscoll, C. T.; Effler, S. W.; Doerr, S. M. Environ. Sci. Technol. 1994, 28, 1211. (20) Meyer, M.; Effler, S. W. Environ. Pollut. (Ser.A) 1980, 23, 131. (21) Auer, M. T.; Effler, S. W.; Story, M. L.; Sze, P. In OnondagaLake: Lessons in Limnologyand EngineeringAnalysis; Effler, S. W., Ed.; Springer-Verlag: New York, 1995 (in press). (22) Effler, S. W. Symposium on monitoring and mediating water quality; American Water Resources Association: Syracuse, NY, 1987; p 87. (23) Murphy, C. B.; Jr. Lakes ofivew York State; Bloomfield, J. A,, Ed.; Academic Press: New York, 1978; Vol. 11, p 223. (24) Effler, S. W. Water Air Soil Pollut. 1987, 33, 85. (25) Effler, S. W.; Hassett, H. P.; Auer, M. T.; Johnson, N. Water Air Soil Pollut. 1988, 39, 59. 126) Driscoll, C. T.; Effler, S. W.; Doerr, S. M.; Addess, J.; Brooks, C. M. In Onondaga Lake: Lessons in Limnology and Engineering Analysis; Effler, S . W., Ed.; Springer-Verlag: New York, 1995 (in press). (27) Effler, S. W.; Driscoll, C. T. Environ. Sci. Technol. 1985, 19 (E), 716. (28) Johnson, D. L.; Jiao, J ~ DosSantos, ; S. G.; Effler, S. W. Environ. Sci. Technol. 1991, 25, 736. (29) Driscoll, C. T.; Effler, S. W.; Auer, M. T.; Doerr, S. M.; Penn, M. R. Hydrobiologia 1993, 253, 61-72. (30) Field, S. D. Ph.D. Dissertation, Syracuse University, 1980. 131) Gill, G. A.; Fitzgerald, W. F. Deep Sea Res. 1985, 32, 287. (32) Gill, G. A.; Fitzgerald, W. F. Mar. Chem. 1987, 20, 227. (33) Bloom, N. S.; Crecelius, E. A. Mar. Chem. 1983, 14, 49.
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(34) Bloom, N. S.; Fitzgerald, W. F. Anal. Ckim. Acta 1988,208, 151. (35) Driscoll, C. T.; van Dreason, R. Water Air Soil Pollut. 1993, 67, 345. (36) American Public Health Association (APHA).Standard Methods for theExamination of Waterand Wastewater, 17th ed.; American Public Health Association: Washington, DC, 1989. (37) Stumm, W., Morgan, J. J., Eds. Aquatic Chemistry, 2nd ed.; John Wiley & Sons: New York, 1981. (38) Morel, F. M. M., Hering, J. G., Eds. Principles and Applications of Aquatic Chemistry; John Wiley & Sons: New York, 1993. (39) Schecher, W. D.; McAvoy, D. C. Comput. Environ. Urban Syst. 1992, 16, 65. (40) Fitzgerald, W. F. In The Biogeochemistry of Mercury in the Environment; Nriagu, J. O., Ed.; ElsevierlNorth Holland Biomedical Press: Amsterdam, The Netherlands, 1979; p 161. (41) Hurley, J. R.; Watras, C. J.; Bloom, N. S. Water Air Soil Pollut. 1991, 56, 54. (42) Hudson, R. J. M.; Gherini, S. A.; Watras, C. J.; Porcella, D. B. In Mercury as a Global Pollutant; Watras, C. J., Huckabee, J. W., Eds; Lewis Publishers: Chelsea, MI, 1994. (43) Driscoll, C. T.; Wang, W. Concentrationsand Transport ofMercury in Onondaga Lake; Onondaga Lake Management Conference: Syracuse, NY, 1994. (44) Fitzgerald, W. F.; Watras, C. J. Sci. Total Environ. 1989, 87/88, 223. (45) Bloom, N. S. Can. 1. Fish. Aquat. Sci. 1989, 46, 1131. (46) Parks, J. W.; Lutz, A.; Sutton, I. A. Can. 1. Fish. Aquat. Sci. 1989, 46, 2184. (47) Dyrssen, D. Mar. Chem. 1988, 24, 143. (48) Dyrssen, D.; Wedborg, M. Water Air Soil Pollut. 1991, 56, 507. (49) Winfrey, M.; Rudd, J. W. Environ. Toxicol. Chem. 1990, 9, 853. (50) Wodka, M. C.; Effler, S. W.; Driscoll, C. T. Limnol. Oceanogr. 1985, 30 (4), 833.
Received f o r review November 11, 1994. Revised manuscript received April 24, 1995. Accepted M a y 10, 1995.@
ES9406997 @Abstractpublished in Advance ACS Abstracts, June 15, 1995.
