RONMENTAL DISTRIBUTION OF MERCURY RELATED TO LA USE AND PHYSICOCHEMICAL SETTING IN WATERSHEDS OF THE APALACHICOLA-CHATTAHOOCHEE- BASIN Carol A. Couch

AUTHOR: Hydrologist , U.S. Geological Survey, Peachtree Business Center, 3039 Amwiler Road, Suite 130, Atlanta, GA 30360-2824. REFERENCE: Proceedings of the 1997 Water Resources Conference, held March 20-22, 1997, at the University of Georgia, Kathryn J. Hatcher, Editor, Institute of Ecology, The University of Georgia, Athens, Georgia.

Abstract. During 1992 and 1993, a survey was conducted to of Georgia's rivers and lakes to concentration levels for which determine the distribution of mercury (Hg) in bed sediments the State has recommended consumption restrictions (Georgia and aquatic biota in surface-water bodies of the Department of Natural Resources, 1996). For example, in the Apalachicola-Chattahoochee-Flint River basin. The objective Georgia part of the Apalachicola-Chattahoochee-Flint (ACF) of the survey was to relate broad-scale patterns in mercury River basin, restrictions on consumption are recommended for distribution to watershed land use and physicochemical largemouth bass, shoal bass, and bullheads caught in Lake setting. Concentrations of Hg in fine sediments (less than 63 Oliver, , and in certain locations in the Flint micrometers particle size) were determined at 41 River and Spring Creek. In the Apalachicola River basin in surface-water sites, and in whole tissue of aquatic biota Florida, consumption restriction advisories due to mercury (Asiatic clams or mosquitofish) at 34 of these sites. Typical contamination have been issued for largemouth bass, gar, and background Hg levels in fine sediments ranged from 0.04 to bowfm caught in the Chipola River and Dead Lake, and 0.08 micrograms per gam (gg/g). Among all sites sampled in Equaloxic and Sweetwater Creeks (Florida Department of this study, mean Hg concentration in fine sediment was 0.13, Environmental Protection, 1994). No consumption advisories and concentrations ranged from 0.04 to 0.56 µg/g. Mercury due to mercury contamination have been issued by the State of was detected in tissue at all but two sites. Mercury Alabama for the Chattahoochee and Apalachicola River concentration in tissue ranged from less than detection to 2.6 basins. tg/g of dry weight. Mean Hg concentration in clam tissue was This report presents the results of a survey of the 0.44 'ug/g, dry weight, and mean concentration in occurrence and distribution of Hg in bed sediments and aquatic mosquitofish tissue was 0.15 µg/g, dry weight. fauna of streams, reservoirs, and floodplain ponds in the ACF Although the highest concentrations of Hg in sediment River basin. The objective of this survey, conducted as,part of were measured in urban watersheds , in the Piedmont Province, the U.S. Geological Survey's (USGS) National Water-Quality the highest concentrations of Hg in clam tissue were measured Assessment (NAWQA) Program, was to relate broad-scale at sites in Coastal Plain watersheds draining mostly forest or patterns in the occurrence and distribution of Hg to watershed agricultural land, and where sediment Hg concentrations were land use and physicochemical setting. relatively low. Coastal Plain sites are characterized by During 1992 and 1993, Hg concentrations were determined physicochemical settings that enhance the formation of in the less than 63 micrometer (nn) aliquot of bed sediments methylmercury—the form of Hg that most rapidly from 34 stream and 7 reservoir sites in the ACF River basin, bioaccumulates. Comparison of Hg concentrations in and for 3 floodplain ponds adjacent to the Apalachicola River sediment and tissue suggests that Hg as methylmercury may (Figure 1, Table 1). Because Hg often is concentrated in the be more available to aquatic biota in the Coastal Plain than in smallest-size fractions of aquatic sediment (Horowitz, 1991), the Piedmont. Greater bioavailability of Hg in the Coastal fine sediment rather than whole sediment was analyzed in Plain is supported by consumption advisories for fish caught order to enhance the probability of detection. in widely distributed water bodies in the Coastal Plain. Mercury bioacciunulates in aquatic organisms as much as 100,000 times its concentration in water, and consequently, the INTRODUCTION analysis of biological tissue is useful for detecting its Environmental contamination by mercury (Hg), a metal occurrence (Chapman and others, 1968). Because of their that in its most toxic form as methylmercury (CH 3Hg+) ubiquitous distribution in the ACF River basin, Asiatic clams readily bioaccumulates and biomagnifies, is a water-quality (Corbicula fluminea) were collected and analyzed as concern of National importance. Mercury is one of only three bioindicators of Hg occurrence. Asiatic clams feed by filtering contaminants—in addition to polychlorinated biphenyls large volumes of water on a daily basis and can accumulate (PCBs) and chlordane—that have accumulated in fish in some contaminants that may be present in low concentrations in

45 Lake Sidney Lanier

33°•

Flint River basin

Lake/ Blackshear

Lake Walter F. George • Albany

3 EXPLANATION

Lake Seminole PHYSIOGRAPHIC PROVINCE GEORGIA Blue Ridge =1 / FLORIDA Piedmont Apalachicola River basin Coastal Plain

• 38 BED-SEDIMENT AND TISSUE- 30° SAMPLING SITES AND NUMBERS—Sites are 0 20 40 60 MILES identified in table 1 0 20 40 60 KILOMETERS

Figure 1. Location of the Apalachicola—Chattahoochee—Flint (ACF) River basin and sites sampled for Hg in bed sediments and tissue. dissolved and particulate material; and thereby, facilitate WATERSHED AND SITE SELECTION detection (Doherty, 1990). In addition, mosquitofish Watersheds and sites investigated in this study were (Gambusia), which are abundant in floodplain ponds, were selected to represent 4 major types of hydrologic settings m the collected at three sites where Asiatic clams do not naturally ACF River basin—(1) small tributaries (40 to 220 km 2 occur. Because Asiatic clams and mosquitofish are not drainage areas) in which water quality is influenced by a commonly consumed by humans, the tissue data presented in dominant land use or land, cover such as urban, agriculture, or this report are not intended for assessment of risks to human forest; (2) sites on tributary streams and mainsteras, where, health. However, in combination with sediment data, these because of larger drainage areas, watershed land use or cover tissue data may be useful for characterizing the land uses, and is mixed; (3) ponds in the Apalachicola River floodplain; and hydrologic and physicochemical factors associated with (4) mainstem reservoirs. In addition, sites were selected to watersheds where organisms, including game fish, may be at represent typical physicochemical settings in both the greater risk of Hg bioaccumulation (Crawford and Luoma, Piedmont and Coastal Plain physiographic provinces. 1993). Surface-water chemistry differs between the Piedmont and

46 Table 1. Drainage areas, physiographic province, and land use and'cover for sampled sites [Site locations, designated by site number shown in Figure 1, are by category and may not be successive; do., ditto]

Drainage USGS Site type Site area Physiographic Site name station (dominant watershed number above site province number (km2) land use/cover)

Chattahoochee River basin —stream sites at Cornelia 02331600 819 Piedmont mainstem (forest) 2 West Fork Little River 02332830 47 do. small tributary (agriculture) 4 Chattahoochee River at Norcross 02335000 3,026 do. mainstem (mixed) 5 Willeo Creek 02335790 41 do. small tributary (urban) 6 (Old Canton Road) 02335864 33 do. small tributary (urban) 7 Sewell Mill Creek 02335868 29 do. small tributary (urban) 8 Sope Creek (Lower Roswell Road) 02335870 80 do. small tributary (urban) 9 Rottenwood Creek 02335910 47 do. small tributary (urban) 10 North Fork 02336130 101 do. small tributary (urban) 11 South Fork Peachtree Creek 02336250 75 do. small tributary (urban) 12 Peachtree Creek 02336300 221 do. small tributary (urban) 13 Nancy Creek 02336380 90 do. small tributary (urban) 14 Proctor Creek 02336529 41 do. small tributary (urban) 15 Nickajack Creek 02336610 54 do. small tributary (urban) 16 Utoy Creek 02336728 88 do. small tributary (urban) 17 Snake Creek 02337500 92 do. small tributary (forest) 18 Chattahoochee River at Whitesburg 02338000 6,245 do. mainstem (mixed) 20 Flat Shoals Creek 02339935 115 do. small tributary (forest) 21 Chattahoochee River at Columbus 02341500 12,073 do. mainstem (mixed) 22 Bull Creek 023415605 177 do. small tributary (urban) 24 Chattahoochee River near Columbia 02343801 21,261 Coastal Plain mainstem (triixed)

Flint River basin —stream sites 26 Flint River near Lovejoy 02344350 344 Piedmont mainstem (mixed) 27 Flint River near Culloden 02347500 4,778 do. mainstem (mixed) 28 Lime Creek 02350080 161 Coastal Plain small tributary (agriculture) 30 02350900 1,351 do. large tributary (mixed) 31 Muckalee Creek 02351890 949 do. large tributary (mixed) 32 Cooleewahee Creek 02352980 437 do. large tributary (mixed) 33 Flint River at Newton 02353000 14,940 do. mainstem (mixed) 34 02355350 2,693 do. large tributary (mixed) 36 Aycocks Creek 02356980 123 do. small tributary (agriculture) 37 Spring Creek 02357000 1,227 do. large tributary (mixed)

Apalachicola River basin —stream and adjacentloodplain sites 38 Apalachicola River at Chattahoochee 02358000 44,491 do. mainstem/floodplain (mixed) 39 Apalachicola River near Blountstown 02358700 45,465 do. mainstern/floodplain (mixed) 41 Apalachicola River near Sumatra 02359170 49,834 do. mainstem/floodplain (mixed) Reservoir sites 3 Lake Sidney Lanier—Chattahoochee River 02334080 2,343 Piedmont reservoir (mixed) 19 — Chattahoochee River 02339190 8,410 do. reservoir (mixed) 23 Lake Walter F. George—Chattahoochee River 02343240 19,350 Coastal Plain reservoir (mixed) 25 Lake Seminole—Chattahoochee River arm 02344070 22,332 do. reservoir (mixed) 29 —Flint River 02350330 9,582 do. reservoir (mixed) 35 Lake Seminole—Flint River arm 02356025 19,842 do. reservoir (mixed) 40 Dead Lake—Chipola River 02359101 3,245 do. reservoir (mixed)

47 Coastal Plain Provinces as a consequence of differences in nitric acid-rinsed glass or plastic containers. Clams were geology, climate, and topography (Cherry, 1961; Couch and shipped frozen to the USGS, National Water-Quality others, 1996). Laboratory, in Denver, Co., where soft tissue was composited In order to integrate influences of watershed land uses, by site, digested in nitric acid, and the homogenate analyzed tributaries were sampled at the farthest downstream sites that for total Hg following the methods of Hoffman (1996). were accessible from bridges or boat landings. Mainstem sites Although empty Asiatic clam shells were seen at all on the Chattahoochee and Flint Rivers were located upstream riverine and reservoir sites, live individuals were not present at and downstream of the metropolitan areas of Atlanta, Ga.; 10 sites. The search for live individuals was limited to the Columbus, Ga.—Phenix City, Ala.; and Albany, Ga.; and major reach from which sediment samples were collected. Eight of reservoirs. Sites in the Apalachicola River were sampled in the sites where live clams were not collected were in urban upper, middle, and lower reaches of the river and adjacent watersheds draining parts of Metropolitan Atlanta. floodplain pools. Reservoirs were sampled in downstream Mosquitofish were collected in dip nets from floodplain segments of the impoundments in proximity to the dams. All ponds adjacent to reaches of the Apalachicola River where sites were sampled during August to November 1992; and four clams were collected. At each site, the number of individuals sites Sope Creek, Peachtree Creek, Chattahoochee River at required to provide 10 grams wet weight were composited and Whitesburg, and Chattahoochee River at Columbus—were frozen. Analysis of Hg in whole mosquitofish tissue was sampled a second time in August or September 1993. conducted by the USGS Sediment Partitioning Laboratory, in Atlanta, Ga., following the methods of Elrick and Horowitz METHODS (1986). Mercury concentration is reported as .tg/g dry weight Sediment methods of tissue. Fluvial and floodplain sediments were collected and Statistical methods processed following procedures modified from Shelton and Spearman's rank correlation was used to test the Capel (1994). At wadable sites, fine-grained surficial sediments significance of interrelations between sediment Hg (to about 1 centimeter depth) were collected from five locations concentration and organic carbon content, and between tissue using Teflon l/ scoops. At nonwadable sites, sediments were Hg concentration and mean shell length, sediment Hg collected from five locations with Ponar or Eckman grabs. concentration or organic carbon content. The Surficial sediments not in contact with grab or dredge walls Manning-Whitney U test for unpaired comparisons was used to were collected using a Teflon scoop. Composited sediments test for differences between Piedmont and Coastal Plain sites were homogenized by, stirring, and material passing through a for sediment and tissue Hg concentrations, sediment organic nitric acid-washed 63-pin nylon sieve was retained for analysis carbon content, and mean shell length. of total Hg and organic carbon. Sediment Hg concentration and organic carbon content were determined by the USGS, Geologic RESULTS AND DISCUSSION Division, Branch of Geochemistry, following the methods of Mercury concentration data for sediments and tissue from Arbogast (1990). Mercury concentration in sediment is reported all sites investigated during the ACF NAWQA study are in units of micrograms/gram (p.g/g) dry weight of sediment. reported in files accessible from the ACF NAWQA home page Tissue methods on the World Wide Web (http://www.usgs.govinawqa/) Procedures for collecting and processing clams followed (Garrett and others, 1997). methods described in Crawford and Luoma (1993). Clams were Sediment collected at wadable sites by sieving sediments using stainless Pre-industrial age concentrations of Hg in sediments of the steel baskets, and at unwadable sites using grabs or towed ACF River basin are not known. Because of atmospheric dredges. Clams were rinsed and held in native water at deposition from anthropogenic sources, contemporary Hg approximately 10 ° C for 24 hours to allow for clearance of background concentrations may be elevated beyond levels that digestive tract contents that could influence Hg concentrations would result from natural sources such as weathering of rocks in whole-body soft tissue. For each site, a variable number of or atmospheric deposition from biogenic sources. On a global clams necessary to provide a minimum of 10 grams wet weight scale, about 80 percent of anthropogenic sources of Hg are of soft tissue were retained and composited. Anterior to emissions to the atmosphere from fossil-fuel combustion, posterior shell length of each clam was measured to the nearest mining, smelting, and waste incineration. Another 15 percent millimeter using calipers, and the mean shell length of of anthropogenic emissions are applications directly to the land individuals composited by , site was calculated. All handling and in fungicides, fertilizers, and solid waste. Five percent of Hg processing was conducted using powder-free latex gloves and emissions occur as the direct discharge of effluent to water bodies (Stein and others, 1996). Because of atmospheric 1/The use of firm, trade, and brand names in this report is for transport, Hg background concentrations in the ACF River identification purposes only and does not constitute basin are influenced by deposition originating from widely endorsement by the U.S. Geological Survey. distributed sources. For example, in 1993 approximately 2 tons

48 •

of Hg were released into the atmosphere from facilities located 14 within a 300-m.ile radius of Albany, Ga. (U.S. Environmental Piedmont Protection Agency, 1995). u j 12 0 Mercury background concentrations in fine aquatic cc Coastal Plain CLLU 10 sediments in the Piedmont may be represented by the range from z 0.04 to 0.06 ug/g, as measured in small watersheds that have 8 50 Percentile greater than 80 percent forest cover and have no known local 0 I I 25 point-source inputs of Hg. Background concentrations in the cr 6 10- Coastal Plain, based on the lowest Hg concentrations measured 0 in this study, may be in the range from 0.06 to 0.08 ug/g. These • 4 background Hg concentrations are below the level of 0.10 ug/g lx 2 typical in sediments not contaminated by local point sources 0 (Horowitz, 1991). The mean Hg concentration in fine sediment of all sites investigated in this study was 0.13 p.g/g, and SEDIMENT ORGANIC CARBON concentration ranged from 0.04 to 0.56 ug/g (Figure 2). Figure 3. Organic carbon content of bed sediment In aquatic sediments, between 50 to 75 percent of Hg may be (<63 um particle size) for sites in the Apalachicola- adsorbed to organic matter (Stein and other, 1996). Sediment Hg Chattahoochee-Flint River basin. concentration was significantly correlated (p=0.0001) to organic carbon content among Coastal Plain sites, but not among The highest sediment Hg concentrations, those above the Piedmont sites. The relation between sediment Hg concentration 75th percentile (0.15 p.g/g), were measured at sites draining and organic matter content is influenced by sediment grain size. predominantly urban watersheds-Peachtree Creek, South Organic matter content tends to increase as sediment grain size Fork Peachtree Creek, Proctor Creek-and at sites decreases (Horowitz, 1991). However, the grain size downstream of urban areas-Flint River at Newton below distributions of the less than 63-um aliquots of sediment Albany, Ga., Muckalee Creek below Americus, Ga., analyzed in this study were not determined. Chattahoochee River below Columbus, Ga. Phenix City, Ala., Sediment organic carbon content was significantly greater Chattahoochee River at Whitesburg, Ga., and West Point (p=0.0001) among Coastal Plain sites than among Piedmont Lake, both below Metropolitan Atlanta. Other sites where sites. The mean organic carbon content of Coastal Plain sites sediment Hg concentrations were greater than 0.15 ug/g were was 4.5 percent, and content ranged from 1.8 to 11.9 percent. the Chipola River at Dead Lake, which is downstream of an Organic carbon content in the Piedmont ranged from lA to 4.7 abandoned battery plant a site in the Apalachicola River percent and the mean carbon content was 2.5 percent (Figure 3). floodplain that had high organic carbon content and four In both provinces, sediments with the lowest organic carbon Coastal Plain sites in the Flint River basin (Lake Blackshear, content were at sites in proximity to the tailwaters of reservoirs. Lake Seminole-Flint River arm, Spring Creek, and Sites where sediment organic carbon content was highest were Coolewahee Creek). in Coastal Plain watersheds draining large areas of wetlands. Tissue Mercury has no known biological functioa and its accumulation in tissue is the result of contamination from natural or antlu-opogenic sources (Eisler, 1987). Mercury was z detected in mosquitofish tissue at all three floodplain ponds, 0 and in clam tissue at 29 of 31 sites where clams were < collected. Concentrations of Hg in mosquitofish tissue from - 0.4 Z w floodplain ponds was 0.10 ug/g at Apalachicola River at LU >. Chattahoochee; and 0.20 ug/g at both the Apalachicola'River Z cc 0 0 at Blountstown and at Sumatra Mercury concentration in 0 - 3- Asiatic clams ranged from 0.10 to 2.60 ug/g, and the mean CC CD 0.04 was 0.44 pg/g• 0 Z CC The two sites where Hg was not detected in tissue-the - iedmont 2 Chattahoochee River at Norcross, and the Apalachicola River Coastal Plain at Chattahoochee-are both below the tailwaters of major reservoirs. Sites with the highest Hg concentration in clam 0.004 SEDIMENT ASIATIC CLAM tissue, those sites ranked above the 75 th percentile (0.60 Figure 2. Mercury concentration in bed sediment (<63 um ug/g), were all in the Coastal Plain. The mean concentration particle size) and Asiatic clam soft tissue for sites in the of Hg in tissue from Coastal Plain sites (0.74 ug/g) was Apalachicola-C hattahoochee-Flint River basin. significantly greater (p=0.02) than the mean concentration in

49 tissue in the Piedmont sites (0.20 nig). Mercury concentration in clam tissue was significantly correlated with mean shell length (p=0.01), and mean shell length was significantly larger (p=0.0005) among sites in the Coastal Plain (26 mm) than in the Piedmont (18 mm) The life span of Asiatic clams is o< pcc approximately 2 to 3 years (McMahon, 1982). Clams with larger <0 izw ...FE 0.1 shell lengths are presumably older; and therefore, have accumulated Hg over a longer time period. However, after Q CI) z adjusting for possible age differences by dividing tissue Hg 0< concentration by mean shell length, the same Coastal Plain sites rc 0 0.0 remained ranked above the 75th percentile, although their o cc rankings differed. Sites above the 75 th percentile for tissue Hg wcc concentration adjusted for shell length are, in rank order of g- largest to smallest concentration—lCinchafoonee Creek, Muckalee Creek, Aycocks Creek, Spring Creek, 0.00 Ichawaynochaway Creek, Apalachicola River at Sumatra, and 5 10 Lime Creek. SEDIMENT ORGANIC CARBON, IN PERCENT With the exception of clam tissue from the Apalachicola PIEDMONT COASTAL PLAIN River at Sumatra, Hg concentrations in tissues from all riverine SITE TYPE SITE TYPE and floodplain sites in the Apalachicola River basin ranged from • Agriculture 0 Agriculture less than detection to 020 j.ig/g. Previous studies (Elder and • Mixed Q Mixed Mattraw, 1984; Winger and others, 1984) also reported similarly A Urban V Reservoir low concentrations of Hg in Asiatic clam tissue from sites in the • Forest Apalachicola River basin. The concentration at the Apalachicola IF Reservoir at Sumatra (1.1 Kg/g) may be elevated as a result of its location Figure 4. Relation between sediment organic carbon and downstream from an abandoned battery plant on the Chipola mercury in clam tissue normalized to mean shell length. River. Relation between tissue and sediment Hg concentration Influence of land use and physicochemical setting On the average, the concentration of Hg in clam tissue was Sites where the highest sediment concentrations of Hg were five times greater than the concentration of Hg in fine sediments. measured either drained or were downstream of urban areas. However, Hg concentration in clam tissue was not correlated However, not all urban watersheds had sediment Hg with the concentration of Hg in sediments. Other studies have concentrations that were elevated substantially above estimated suggested that Hg bioavailability to Asiatic clams is not related background concentrations. Differences in Hg concentration to sediment Hg concentration (Elder and Mattraw, 1984; among urban watersheds may be attributed to differences in the Doherty, 1990). Asiatic clams filter and ingest seston particles presence of historic or active point-sources. Although the highest that typically are not representative of the sediment in which the concentrations of Hg in sediment were measured in urban clams are lodged. watersheds in the Piedmont, the highest concentrations of Hg in Mercury concentration in clams was significantly (p=0.02) clam tissue were measured at sites in Coastal Plain watersheds positively correlated with the organic carbon content of the with mixed land uses and where sediment Hg concentrations sediment (Figure 4). In contrast to the findings reported herein, were relatively low. Leland and Scudder (1990) indicated that concentrations of Hg Methylation of Hg is predominantly a microbial process that in Asiatic clams did not vary significantly with organic carbon is enhanced in physicochemical settings that are more prevalent content of fine sediments (less than 62 gm particle size) at sites in the Coastal Plain than in the Piedmont Province. Coastal Plain in the San Joaquin River basin, Calif However, the range in sites drain watersheds with wetland areas where anaerobic organic carbon content reported by Leland and Scudder conditions and the high organic matter content of sediments (1990)-0.56 to 1.9 percent—was much narrower than the range facilitate the transformation of mercury to methylmercury (Stein from 1 A to 11.9 percent determined in this investigation. and others, 1996). In addition, surface water in many Coastal Mercury concentration in clams, and sediment organic carbon Plain watersheds is characterized by low pH and high dissolved content, may covary if the organic-rich seston particles filtered organic carbon concentrations that are often associated with by clams also are the source of or are, resuspended organic enhanced rates of Hg methylation (Cherry, 1961; Stein and matter deposited in the sediment Methylmercury is almost others, 1996). Although, on the average, lower concentrations of entirely associated with organic matter (Stein and others, 1996).

50 Hg were present in Coastal Plain sediments than in Piedmont Doherty, F.G., 1990, The Asiatic Clam, Corbicula spp., as a sediments, a greater proportion of sediment Hg in the Coastal biological monitor in freshwater environments: Plain may have been methylmercury. Environmental Monitoring and Assessment, v. 15, p. Comparison of Hg concentrations in sediment and tissue 143-181. indicates that Hg may be more bioavailable as methylmercury to Eisler, R.E., 1987, Mercury hazards to fish, wildlife, and Asiatic clams and mosquitofish, and potentially other aquatic invertebrates-a synoptic review: U.S. Fish and Wildlife biota, in the Coastal Plain than in the Piedmont. The Asiatic Service, Contaminant Hazard Reviews, report no. 10, 90 p. clam is an introduced species that can reach abundances greater Elder, J.F., and Mattraw, H.C., Jr., 1984, Accumulation of trace than 1,000 per square meter in streams in Georgia (Stites and elements, pesticides, and polychlorinated biphenyl s in others, 1995). Although these clams are not native, they have sediments, and the clam Corbicula manilensis of the been demonstrated to be an important, novel food resource for Apalachicola River, Florida: Archives of Environmental benthic-feeding fish (McMahon, 1982), and also are consumed Contamination and Toxiciology, v. 13, p. 453-469. by raccoons (personal observation by author). Greater Elrick, K.A., and Horowitz, A.J., 1986, Analysis of rocks and bioavailability of Hg in the Coastal Plain is supported by sediments for mercury, by wet digestion and flameless cold consumption advisories for fish caught in widely distributed vapor atomic absorption: U.S. Geological Survey Open-File water bodies in the Coastal Plain. Because of the potential for Report 86-529, 12 p. greater risk of Hg bioaccumulation, the discharge of Hg into Florida Department of Environmental Protection, 1994, Florida Coastal Plain water bodies, or into the atmosphere in proximity water quality assessment 1994: Tallahassee, Fla., Florida to the Coastal Plain should be minimized. Department of Environmental Protection, 305(b) Main Acknowledgments Report, 261 p. This report is a contribution from the USGS National Garrett, J.W., Perlman, H.A., and Scholz, J.D., 1997, World Water-Quality Assessment Program. The extensive sampling Wide Web access to U.S. Geological Survey publications and required by this study involved the efforts of the ACF River data-Apalachicola-Chattahoochee-Flint River basin, basin study team including Gary R. Buell, Elizabeth A. Frick, Georgia, Florida, and Alabama, 1992-95, in Proceedings of Jerry W. Garrett, Evelyn H. Hopkins, John McCranie, and David the 1997 Georgia Water Resources Conference, Athens, Ga., J. Wangsness. The author also thanks Helen Light, USGS, March 20-22, 1997: Athens, Ga., The University of Georgia, Tallahassee, Fla., for her assistance in locating floodplain sites; Vinson Institute of Government. Alan M. Cressler and Howard H. Persinger, USGS, Atlanta, Ga., Georgia Department of Natural Resources, 1996, Guidelines for their assistance in the field; and Kent A. Elrick, USGS, for eating fish from Georgia waters: Atlanta, Ga., Georgia Atlanta, Ga., for analyzing mosquitofish tissue. Department of Natural Resources, Environmental Protection Division and Wildlife Resources Division, 32 p. LITERATURE CITED Hoffinan, G.L., 1996, Methods of analysis by the U.S. Atlanta Regional Commission, 1990, Land use/cover digital Geological Survey National Water-Quality Laboratory- data: Atlanta, Ga., Atlanta Regional Commission. Preparation procedure for aquatic biological material Arbogast, B., 1990, Quality assurance manual for the branch of determined for trace metals: U.S. Geological Survey Geochemistry: U.S. Geological Survey Open-File Report Open-File Report 96-362, 42 p. 90-668. Horowitz, A.J., 1991, Sediment-Trace Element Chemistry: Chapman, W.H., Fisher, H.L., and Pratt, M.W., 1968, Chelsea, Mich., Lewis Publishers, 136 p. Concentration factors of chemical elements in edible Leland, H.V., and Scudder, B.C., 1990, Trace elements in organisms: Livermore, Calif., Lawrence Radiation Laboratory, Corbicula fluminea from the San Joaquin River, California: UCRL-50564, 46 p. The Science of the Total Environment, v. 97/98, p. 641-672. Cherry, R.N., 1961, Chemical quality of water of Georgia McMahon, R.F., 1982, The occurrence and spread of the streams, 1957-58: Georgia Geologic Survey Bulletin 69, 100 introduced Asiatic freshwater clam, Corbkula fluminea P. (Muller), in North America: 1924-1982: The Nautilus v. 96, Couch, C.A., Hopkins, E.H., and Hardy, P.S., 1996, Influences p. 134-141. of environmental settings, on aquatic ecosystems in the Shelton, L.R., and Capel, P.D., 1994, Guidelines for collecting Apalachicola-Chattahoochee-Flint River basin: U.S. and processing samples of stream bed sediment for analysis Geological Survey Water-Resources Investigations Report of trace elements and organic contaminants for the National 95-4278, 58 p. Water-Quality Assessment Program: U.S. Geological Survey Crawford, J.K., and Luoma, S.N., 1993, Guidelines for studies Open-File Report 94-458, 22 p. of contaminants in biological tissues for the National Stein, E.D., Cohen, Y., and Winer, A.M., 1996, Environmental Water-Quality Assessment Program: U.S. Geological Survey distribution and transformation of mercury compounds: Open-File Report 92-494, 69 p. Critical Reviews in Environmental Science and Technology, v. 26, p. 1-43.

51 Stites, D.L., Benke, A.C., and Gillespie, D.M., 1995, Population dynamics, growth, and production of the Asiatic clam, Corbicula fluminea, in a blackwater river: Canadian Journal of Fisheries and Aquatic Science, v. 52, p. 425-437. U.S. Environmental Protection Agency, 1995, Toxics Release Inventory-geographic information system coverage files: Office of Pollution Prevention and Toxics, Environmental Assistance Division. U.S. Geological Survey, 1972-78, Land use and land cover digital data, 1972-78, Apalachicola, Atlanta, Dothan, Greenville, Macon, Phenix City, Rome, Tallahassee, and Waycross quadrangles: U.S. Geological Survey, Land-use map, 1:250,000 scale. Winger, P.V., Sieckman, C., May, T.W., and Johnson, W.W., 1984, Residues of organochlorine insecticides, polychlorinated biphenyls, and heavy metals in biota from Apalachicola River, Florida, 1978: Journal of the Association of Off cal Analytical Chemists, v. 67, p. 325-333.

52