West Branch of Canal Creek SITE BACKGROUND and HISTORY
MATERIALS and METHODSRESULTS and DISCUSSION
CONCLUSIONSLITERATURE CITEDBackgroundThe West Branch of Canal Creek site is located in the Canal Creek area of the U.S. Army Aberdeen Proving Ground-Edgewood Area (APG-EA), Aberdeen Proving Ground, Maryland. Five major production-scale activities occurred at Canal Creek which may have contributed to the contamination of the soils, groundwater, and marshes of the creeks. They included the manufacturing of chlorine, mustard, chloroacetophenone, impregnite material, and the impregnating of protective clothing. The plants were most active during World Wars I and II. Pilot, or experimental, manufacturing was performed to gather data on manufacturing processes in support of the larger production-size activities. Munitions filling operations have been conducted from 1918 to the present. Other activities that also may have affected the environment include the operation of machine and maintenance shops, motorpool garages, and an airfield. IntroductionThe West Branch of Canal Creek is located in the Canal Creek Area of the Edgewood Arsenal. The groundwater in the West Branch of Canal Creek site is contaminated with multiple heavy metals and chlorinated aliphatic hydrocarbons (chlorinated volatile organics). The contaminated groundwater discharges to the West Branch of Canal Creek and its surrounding marshes. In 1990, the Canal Creek area was placed on the National Priorities List established under the Federal Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA/Superfund). The toxicological evaluation of the West Branch of Canal Creek site groundwater contamination was designed to be conducted in two sequential phases. The primary objective of Phase 1 was a determination of the potential toxicity of the groundwater in situ. The Phase 1 study was conducted in situ for two reasons. First, if the evaluation showed that the groundwater was not toxic, further hazard assessment studies of the groundwater discharge into the West Branch of Canal Creek ecosystem may not have been necessary. Secondly, if the evaluation showed that the groundwater was not toxic, treatment of the groundwater may not be necessary as a remedial action alternative to comply with CERCLA. Phase 2, an evaluation of the potential toxicity of the groundwater as it moves through the marsh and bottom sediments into West Branch of Canal Creek, was to be implemented if 1) the groundwater proved to be toxic and 2) a concurrent chlorinated aliphatic hydrocarbon natural attenuation study by the United States Geological Survey (USGS) showed that the parent and secondary solvent concentrations were not reduced below levels that were shown to cause toxicity in the in situ groundwater studies. In addition to the groundwater toxicity evaluations, a secondary objective of Phase 1 was to evaluate, where test systems were appropriate for use in low salinity waters, the potential toxicity of West Branch of Canal Creek water. The West Branch of Canal Creek studies were conducted concurrently with the groundwater studies to obtain background data on the potential toxicity of the creek water. Preliminary 28-d sediment toxicity tests were also conducted with West Branch of Canal Creek sediments. In addition to the aquatic studies performed at West Branch of Canal Creek, real-time continuous biomonitoring by honey bees was conducted to identify possible chemical releases during removal activities. Preliminary immunotoxicity with Japanese medaka were also performed on the groundwater. The reader should consult the real-time air bee biomonitoring and fish immunotoxicity methods pages for further details. (Figure 2. Schematic showing the location of the study area) Site Background and HistoryGeographic Setting and Land UseThe Canal Creek area is bordered by the Bush River and Gunpowder River which both drain to the Chesapeake Bay. Lauderick Creek and Kings Creek discharge to the Bush River on the eastern boundary of the area. The East and West Branches of Canal Creek, which provide surface drainage for a major part of the Canal Creek area, flow into the Gunpowder River on the western boundary. The studies described below were conducted with contaminated groundwater obtained from a USGS natural attenuation study site located in the West Branch of Canal Creek study area. The West Branch of Canal Creek natural attenuation site is bounded approximately on the northeast by Hanlon Street, southwest by West Branch of Canal Creek marshes, southeast by 35th Street, to approximately 200 m southwest of Hanlon Street. Site description data for the Canal Creek area will be discussed where appropriate for the West Branch of Canal Creek study site. Canal Creek, which provides surface drainage for a major part of the Canal Creek area, drains a land surface of more than 1,215 ha ( 3,000 acres). The creek is tidally influenced; tidal ranges vary from about 0.15 to 0.46 m (÷0.5 to 1.5 ft) depending on the location. Wading birds, ducks, shorebirds, frogs, and muskrat can be seen in the wetland areas of Canal Creek. The creek supports a variety of freshwater and estuarine aquatic life. Marshes, which are classified as estuarine, emergent, irregularly flooded wetlands, surround West Branch of Canal Creek. The land immediately surrounding the West Branch consists of tall marsh vegetation, including grasses, sedges, cattails, Phragmites, arrowhead, and pickerelweed Historical UseThe Canal Creek area has been used for a number of activities since 1917 which may have contributed to the contamination of the soils, groundwater, and marshes of the creeks (Nemath, 1989). Five major production-scale activities occurred at Canal Creek. They included the manufacturing of chlorine, mustard (primarily sulfur mustard), chloroacetophenone, impregnite material [N,N -dichloro-bis-(2,4,6-trichlorophenyl)urea], and the impregnating of protective clothing. The plants were most active during World Wars I and II. Pilot, or experimental, manufacturing was performed to gather data on manufacturing processes in support of the larger production-size activities. Munitions filling operations have been conducted from 1917 to the present. Other activities that also may have affected the environment include the operation of machine and maintenance shops, motorpool garages, and the airfield. The primary method of waste disposal from WWI until recently was by discharge to sewer systems (Lorah and Vroblesky, 1989). The sewer lines from the majority of the manufacturing and munitions filling plants discharged to the East or West Branches of Canal Creek. Exceptions include a pilot plant east of the airport, which discharged to Kings Creek, and the mobile clothing-impregnating units that operated at Beach Point, which discharged to the Bush River and Kings Creek. Solid wastes, such as, sludges and tars, were discharged through the sewers if the wastes could be thinned with water or held at elevated temperatures to keep them fluid. Wastes generally received little or no treatment prior to discharge before and during WWII. Wastes that could not be discharged through the sewer systems were often dumped into the marshy areas along Canal Creek. A number of disposal pits, a sand pit, salvage yard, and a fire-training pit were used throughout Canal Creek for various operations. Waste treatment increased after WWII with the increased awareness of environmental concerns and regulations. Organic solvents, such as carbon tetrachloride, 1,1,2,2-tetrachloroethane, and trichloroethylene, were some of the most common wastes produced in large quantities from the manufacturing, munitions filling, and other miscellaneous activities in the Canal Creek area. All the major manufacturing plants, except for the chlorine plants, used solvents as raw materials, decontaminating agents, and cleaning agents. A number of heavy metals were used in various processes but in much smaller quantities than the organic solvents. HydrogeologyThe geology of the Canal Creek area has been described by in detail by USGS (Oliveros and Vroblesky, 1989; Lorah and Clark, 1996). Briefly, the Aberdeen Proving Ground- Edgewood Area is underlain by Coastal Plain sediments consisting of unconsolidated clay, silt, and sand layers with occasional gravel lenses. The Coastal Plain sediments dip southeastward, increasing to a thickness of ÷400 ft in the eastern part of the Canal Creek area. Three aquifers and two confining units are present in most of the Canal Creek area as follows: 1) the surficial aquifer; 2) the upper confining unit; 3) the Canal Creek aquifer; 4) the lower confining unit; and 5) the lower confined aquifer. The Canal Creek aquifer, which is the contaminated aquifer of interest, ranges from 9.1 to 21.3 m (30 to 70 ft) thick in the Canal Creed area. The Canal Creek aquifer is confined in the East Branch of Canal Creek and semi-confined or unconfined near the West Branch of Canal Creek. The lower confined aquifer, which underlies the lower confining unit is not known to be contaminated (Lorah and Clark, 1996). Within the West Branch of Canal Creek study area, the aquifer sediments consist of medium- to coarse-grained sand and gravel, intefingered with thin layers or lenses of clay and silt. Upgradient from the wetland, the aquifer is overlain by fill material and the sediments of the upper confining unit. Within the wetland, the Canal Creek aquifer is overlain by wetland sediments, which are about 1.8 to 3.6 m (6 to 12 ft) thick in the study area. The wetland sediments consist of peat, clay, silt, sandy clay, and clayey sand. Shallow groundwater on both sides of the West Branch of Canal Creek generally flows laterally and upward toward the creek channel (Lorah and Clark, 1996). Recharge, in the form of rainfall infiltration, occurs upgradient from the creek. Discharge occurs from the Canal Creek aquifer through the wetland sediments into the creek and marsh areas. Deep flow in the aquifer may enter the regional flow stem, which flows toward the southeast. Groundwater ContaminationFew studies of groundwater contamination were conducted prior to 1985 in the Canal Creek area. The USGS initiated a 5-year study in 1985 to determine the extent of groundwater contamination in the Canal Creek area (Lorah and Clark, 1996). Chemical monitoring (inorganic and organic constituents) by USGS confirmed that hazardous chemicals from prior activities were widespread in the surficial and Canal Creek aquifers. No contamination was detected in the lower confined aquifer, which is protected by a clay unit that underlies the Canal Creek aquifer. Fifteen inorganic constituents were present in the surficial aquifer in concentrations that exceed current or proposed drinking water regulations established by the U.S. Environmental Protection Agency (EPA). They included dissolved solids, chloride, iron, fluoride, manganese, aluminum, antimony, arsenic, beryllium, cadmium, chromium, lead, mercury, nickel, and thallium. In addition, copper and zinc were present in groundwater in elevated concentrations compared to background concentrations in the study area. Chlorinated volatile organic compounds were the dominant groundwater contaminants and included 1,1,2,2-tetrachloroethane, trichlorethylene, chloroform, 1,2-trans- dichloroethylene, and carbon tetrachloride. Additional volatile organic compounds included benzene, chlorinated benzenes, pentachloroethane, and several unknown compounds. Semi-volatile organic contaminants were not as widely distributed in the groundwater as the volatile compounds. Nitrobenzene, 1,2,3-trichlorobenzene, 1,2,4- trichlorobenzene, and two mustard degradation products (dithiane and 1,4-oxathine) were present at three or fewer sites. Other semi-volatile contaminants that were reported (tentatively identified) in some samples include hexachloroethane, 1,2-dibromoethene, tribromethane, naphthalene, and various compound related to petroleum fuels. Sediment ContaminationThe contaminants present in the sediments of Canal Creek have been investigated by ICF Kaiser (1995). A total of 14 sediment samples were taken from Canal Creek and analyzed for inorganic and organic contaminants and toxicity to an aquatic organism. Five samples were taken from West Branch of Canal Creek; five from East Branch of Canal Creek; and four below the confluence of the West and East Branches of Canal Creek. Most of EPA's priority pollutant heavy metals (selenium and thallium were not measured) were found in the sediments of all 14 stations with the exceptions of cadmium which was present at 9 of 14 stations, nickel at 11 of 14 stations, and silver at 7 of 14 stations. Cadmium, mercury, and zinc were judged by ICF Kaiser (1995) to be inorganic chemicals of potential concern which may impact benthic organisms. Cadmium was found at concentrations to be judged a chemical of concern in West Branch of Canal Creek sediment taken from the current study site. A number of organic contaminants were also found in the sediments at one or more of the 14 stations sampled during the ICF Kaiser (1995) study. The following organic chemicals of concern were found at the highest concentrations of the 14 stations in the sediments taken from the West Branch of Canal Creek study site: pesticides/aroclors (Aroclor-1260, -BHC, dieldrin, and endosulfan I); polycyclicaromatic hydrocarbons (phenanthrene); explosives [N,N-bis(2,4,6-trichlorophenyl)urea and nitroglycerin]; and other volatiles/semi- volatiles (1,2,4-trichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, 2,4,6- trichlorophenol, 4-chloroaniline, and pentachlorophenol). Surface Water ContaminationThe contamination of Canal Creek surface waters was also studied during the 5-year USGS study initiated in 1985 (Lorah and Clark, 1992). Five inorganic constituents were found in surface water samples that were collected from West Branch of Canal Creek in concentrations that exceed EPA's acute or chronic aquatic life criteria for freshwater organisms. The five inorganic contaminants included cadmium, iron, lead, mercury, and zinc. According to Lorah and Clark (1992), a major source of the inorganic contaminants may be the remobilization of metals that accumulated in bottom sediments from the discharge of untreated industrial wastewaters. The same volatile organic compounds that were the major groundwater contaminants were detected in surface water samples, although at much lower concentrations (Lorah and Clark, 1992). Phthalate esters, which are common laboratory contaminants, were the only organic compounds detected in the surface water samples in concentrations that exceeded either acute or chronic ambient water quality criteria for freshwater aquatic life. Materials and MethodsA number of biomonitoring assays covering several levels of biological complexity was used to maximize predictability of potential adverse pollutant effects of the groundwater to aquatic organisms during a 9-month evaluation. Where test systems were appropriate for use in low salinity waters, the potential toxicity of West Branch of Canal Creek water was also evaluated. The West Branch of Canal Creek studies were conducted concurrently with the groundwater studies to obtain background data on the potential toxicity of the creek water. Preliminary 28-d sediment toxicity tests were also conducted with West Branch of Canal Creek sediments. The sediment studies were conducted after the aqueous phase studies were completed. Toxicity TestsAqueous phase bioassays were conducted on groundwater withdrawn from well CC-27B (Harford County Permit No. HA-81-3062) which is one of two of the most highly contaminated wells at the West Branch of Canal Creek site. Groundwater was pumped continuously from the well at a rate of ~7.5 L/min (2 gal/min) to an on-site aquatic toxicity testing facility. Two sources of dilution water were used in the studies. The first was APG- EA potable drinking which was charcoal filtered, aerated before use, and adjusted to ~25ºC. The second source was surface water pumped at a rate of ~7.5 L/min from the West Branch of Canal Creek. The creek water was filtered at ~80 before use and adjusted to ~25ºC. Further details on the toxicity testing facility are given in Burton et al. (1995). An array of 8 toxicity tests was used to evaluate groundwater toxicity during a 9-month study. The toxicity tests included a number of endpoints that are summarized in Table 1. The pH of the groundwater from well CC-27B was ~4; thus, many of the assays were conducted at both pH 4 and pH 7. The toxicity at pH 7 was studied so that the data could ultimately be used in a risk assessment, if necessary, of the groundwater as it enters the West Branch of Canal Creek marsh and surface water which generally has a pH in the low neutral range. Comprehensive chemical analyses of the raw groundwater were performed five times at bimonthly intervals. The chemical analyses were conducted during the same periods that the bimonthly tests described below were conducted. The following is a brief description of the tier of toxicity tests employed in the evaluation; additional information may be found in Burton et al. (1995). Acute toxicity of the groundwater was evaluated three times each week using the 5- and 15-min Microtox assay which uses microbial (Photobacterium phosphoreum) bioluminescent activity (Microbics Corp., Carlsbad, CA, USA). In addition to providing rapid toxicity data, the test was also conducted to monitor the toxicity of the groundwater over time. Acute toxicity data were also obtained bimonthly at pH of 4 and 7 for the cladoceran (Ceriodaphnia dubia), fathead minnow (Pimephales promelas) and Japanese medaka (Oryzias latipes). Acute 96-h bimonthly toxicity tests were also conducted on Japanese medaka exposed to West Branch of Canal Creek surface water. The following 4- to 7-d short-term EPA toxicity tests, which were used to estimate chronic toxicity, were performed on a bimonthly basis: 96-h algal (Selenastrum capricornutum) growth test; 7-d cladoceran (C. dubia) survival and growth test; and 7-d fathead minnow (P. promelas) survival and growth test. Five bimonthly tests were conducted with each species at pH 4 and pH 7. In addition to the short-term methods used to estimate chronic toxicity, growth data at 6 and 9 months from a chronic Japanese medaka carcinogenicity test described below were also used as chronic toxicity endpoints. Gene mutation potential was determined using the Ames test with and without metabolic activation. Both unconcentrated and concentrated (100X) analyses were conducted on groundwater, APG-EA tap water, and West Branch of Canal Creek water. Developmental toxicity was determined for groundwater and dechlorinated APG-EA tap water by the 96-h frog embryo teratogenesis assay-Xenopus (FETAX) using embryos of the African clawed frog, Xenopus laevis. Genotoxicity and developmental toxicity assays were conducted at bimonthly intervals during the same periods as the above acute and short-term chronic tests were conducted. Chronic histopathological changes were evaluated using the Japanese medaka as the experimental model. The study design was based on the multistage model of carcinogenesis using diethylnitrosamine (DEN) as the initiator and the groundwater and West Branch of Canal Creek water as the promoting/progressing agents. DEN is a liver carcinogen in Japanese medaka. Half of the test fish were exposed to an initiating dose of DEN (10 mg/L) for 48 h at 13 d of age. Both initiated and uninitiated fry were then exposed continuously to 1, 5 and 25% groundwater by volume, or 100% diluent water (dechlorinated potable water) under flow-through test conditions for 9 months. Identical exposures were performed using both APG-EA tap water and West Branch of Canal Creek water as diluent water sources. Higher concentrations of groundwater could not be tested due to the low pH of the raw groundwater which would have caused excessive mortality over the 9-month exposure period. Comprehensive chemical analyses of the raw groundwater, test dilutions in the chronic histopathology exposure aquaria (1, 5, and 25% groundwater by volume), and diluent water were performed five times at bimonthly intervals. Routine water quality analyses in the Japanese medaka test aquaria were also conducted at various frequencies on a weekly basis. The routine water quality data are given in Burton et al. (1995). Table 1. Summary of Toxicity Tests Conducted on West Branch of Canal Creek Groundwater and Sediment
Chemical AnalysesComprehensive chemical analyses and explosive analyses were performed bimonthly on the groundwater and surface water taken from well CC-27B and West Branch of Canal Creek, respectively. The comprehensive chemical analyses included general water chemistry, metals, volatile organics, base neutrals, acid compounds, pesticides/PCBs, and herbicides. The elements and/or compounds analyzed in each group, detection limits, analytical methods, etc., are given in Burton et al. (1995). The explosive analyses included the following: 1) octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX); 2) hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX); 3) 1,3,5-trinitrobenzene (TNB); 4) N,2,4,6- tetranitro-N-methylaniline (tetryl); 5) trinitrotoluene (TNT); 6) 2,4-dinitrotoluene (2,4-DNT)); and 7) 2,6-dinitro-toluene (2,6-DNT). Comprehensive chemical, explosive, and SEM:AVS analysis were performed on an aliquot of each composite sediment sample. Results and DiscussionToxicity of the GroundwaterToxicity was detected at various groundwater concentrations by 6 of the 8 biomonitoring systems. The groundwater was acutely toxic at pH 4 to a green alga, cladoceran, fathead minnow and Japanese medaka. From an acute toxicity standpoint, the groundwater appeared to be less toxic to the green alga at pH 7. The groundwater was not acutely toxic at pH 7 to the cladoceran, fathead minnow, or Japanese medaka. The Microtox analyses (3 times/week) showed that the toxicity of the groundwater did not change appreciably over the course of the 9-month study. The lowest concentration of groundwater that caused no observable adverse effect (NOAEL; no-observed-adverse-effect level) at pH 4, in the test systems in which the NOAEL value could be determined, was 10% groundwater by volume. A NOAEL of 10% groundwater by volume occurred in 3 out of 5 tests for the green alga ; 4 out of 5 tests in both a 7-d cladoceran and a 96-h frog embryo teratogenesis assay - Xenopus (FETAX). A NOAEL of 18% groundwater by volume occurred in 2 of 5 tests in a 7-d fathead minnow test. The groundwater was not toxic at pH 7 in the 7-d fathead minnow test and in 2 of 5 FETAX assays. The NOAEL (18% groundwater by volume) was higher at pH 7 in 3 of the 5 FETAX assays. The 10% groundwater by volume NOAEL for the green alga and cladoceran at pH 4, however, was essentially the same when the organisms were exposed to buffered groundwater at pH 7. The Ames assay for mutagenicity was negative in all cases for groundwater, West Branch of Canal Creek water, and filtered APG-EA tap water. Differences in Japanese medaka growth were found in a chronic 9-month histopathology assay when the fish were exposed to 1, 5 and 25% groundwater by volume diluted with either APG-EA dechlorinated tap water or West Branch of Canal Creek surface water. In general, the fish were smaller when grown in groundwater diluted with West Branch of Canal Creek water compared to those reared in groundwater diluted with APG-EA dechlorinated tap water. Most females were larger than males when reared in groundwater diluted with either West Branch of Canal Creek water or APG-EA dechlorinated tap water. Experimental Pathology Laboratories, Inc. (EPL, 1996), analyzed the Japanese medaka in the chronic nine-month study for incidences of hepatocellular neoplasia, neoplasms other than hepatocellular neoplasms, and non-neoplastic lesions and concluded the following. "...at nine months among male and female medaka there was no effect of groundwater on the incidence of hepatocellular neoplasia [at concentrations up to 25% groundwater by volume (highest concentrations studied) when APG-EA dechlorinated tap water was used as diluent water]." "At nine months among the males there was a slight effect of 25% groundwater concentration on the incidence of hepatocellular neoplasia...[and]...among the females there was no effect of groundwater exposure on hepatocellular neoplasia [when West Branch of Canal Creek water was used as diluent water for six months and dechlorinated tap water for three additional months]." EPL found the following at the end of the nine-month study when Japanese medaka were initiated for 48 h at 13 days of age with 10 mg/L diethylnitrosamine (DEN). "At nine months there appeared to be a promotional effect of the groundwater at 25% concentration on hepatocellular neoplasia in male medaka (12 of 29 fish affected), although eight of 40 control medaka also had hepatocellular neoplasia at nine months [in fish exposed to 25% groundwater by volume diluted with APG-EA dechlorinated tap water]." "At nine months there appeared to be a trend of increasing percentage of hepatocellular neoplasms from controls in 25% groundwater, but the differences between groups in number of neoplasms was not great." In DEN-initiated fish exposed to West Branch of Canal Creek water for six months followed by three months of exposure to groundwater in APG-EA dechlorinated tap water, EPL concluded "At nine months among male medaka there appeared to be a promotional effect of the groundwater on hepatocellular neoplasia based on the apparently low incidence of hepatocellular neoplasms in controls...This low incidence may be spurious..." "At six months among female medaka there appeared to be a promotional effect of the Canal Creek water on hepatocellular neoplasia. At six and nine months among female medaka there was no effect of the groundwater on hepatocellular neoplasia. The number of medaka with hepatocellular neoplasia increased at nine months over six months in all groups and at nine months the incidence was greatest among control Groups..." Comprehensive Chemical Analyses of the GroundwaterA summary of the raw groundwater general water quality, heavy metals, and volatile organics measured during the four bimonthly comprehensive chemical analyses is given in Table 2. The range of the lowest and highest concentrations of the five analyses is presented. With one exception, no compounds in the following groups were detected in the groundwater, West Branch of Canal Creek, or APG-EA tap water at EPA's quantitation limits for groundwater: 1) acid or base/neutral compounds; 2) pesticides; 3) herbicides; or 4) organo-phosphorus pesticides. Bis-(2-ethylhexyl) phthalate was reported as an analyte in Test No. 5 only for the 5% groundwater by volume aquaria diluted with West Branch of Canal Creek water. The value appears t be spurious because the compound was not listed for the 1% groundwater by volume aquaria or the 100% West Branch of Canal Creek water which was used as the diluent water. None of the seven explosive listed above were found in the groundwater, West Branch of Canal Creek water, or APG-EA tap water at a quantitation limit of 50 µg/L. The general water chemistry parameters of the groundwater summarized in Table 2 show that the groundwater has a hardness that ranges from 58 to 66 mg/L as CaCO3. The pH of 3.6-4.3 is low relative to that which occurs in most surfaces waters. Some surface waters high in tannic acid or those waters impacted by acid rain may also have pH values in the same range. Ammonia nitrogen was <0.1 mg/L in all samples; thus, nonionized ammonia would not be expected to play a role in toxicity (Thurston et al., 1979). Several EPA priority pollutant heavy metals were found in the groundwater (Table 2). Copper, mercury, and silver concentrations in the groundwater exceeded in one or more tests the EPA freshwater chronic numerical water quality criteria of 9 µg/L for copper, 0.77 µg/L for mercury, and of 0.12 µg/L for silver (Buckman, 1999). The copper and silver criteria are hardness dependent criteria; 100 mg/L as CaCO3 was used. Aluminum was also present at high concentrations in the groundwater and exceeded the EPA freshwater chronic numerical water quality criteria of 87 µg/L for pH 6.5 to 9.0 (Buchman, 1999). Thirteen chlorinated aliphatic compounds were found in the groundwater (Table 2). Several of the organics were EPA priority pollutants. None of the priority pollutant organics found in the groundwater currently have numerical water quality criteria values because insufficient data exist to develop criteria. EPA does give the lowest observable effect level (LOEC) for several of the compounds where criteria are not available (carbon tetrachloride, chloroform, 1,2-dichloroethane, 1,1,2,2-tetrachloroethane, 1,1,1- trichloroethane, and 1,1,2-trichloroethane). However, all of the LOECs are one or more orders of magnitude higher than the concentrations found in the groundwater. Eleven of the 13 volatile organics found in the groundwater had octanol water partition coefficients (log kow or log P) less than 3. Bioaccumulation of a material up to 100-fold above background (bioconcentration factor or BCF = 100) can occur when the log Kow = 3 (U.S. EPA, 1991). Thus, bioaccumulation was not a potential toxicological problem for 11 of the 13 volatile organics present in the groundwater. 1,2-Dichlorobenzene and 1,2,4- trichlorobenzene have Kows of 3.4 and 4.2, respectively. Both compounds were found in only one groundwater sample. Because the two compounds were reported to be present in only one sample at the beginning of the study, it is difficult to determine how important bioaccumulation may be for the compounds. Table 2. Summary of the Five Bimonthly Chemical Analyses (Range of Concentrations) Conducted on Raw West Branch of Canal Creek Groundwater
a All units are mg/L parameter with the exception of alkalinity
Preliminary Toxicity and Chemical Analysis of West Branch of Canal Creek Surface WaterPreliminary studies of the potential toxicity of West Branch of Canal Creek surface water were conducted using the acute Japanese medaka bioassay (96-h LC50) and Ames mutagenicity assay. Five bimonthly assays using 100% surface water were conducted as described in detail in Burton et al. (1995). West Branch of Canal Creek surface water was not toxic to the Japanese medaka in any test. Two EPA priority pollutant heavy metals were found in the West Branch of Canal Creek surface water (Table 3) which exceed acute water quality criteria. The concentration of silver exceeded in one or more tests the EPA freshwater acute numerical water quality criteria of 1.7 µg/L for silver (Buckman, 1999). The acute silver criteria is hardness dependent criteria; 100 mg/L as CaCO3 was used. Aluminum exceeded the EPA freshwater acute numerical water quality criteria of 750 µg/L for pH 6.5 to 9.0 in at least one test (Buchman, 1999). None of the volatile organics found in the water column exceeded EPA's LOEC (Table 3). All unconcentrated and concentrated (100X) Ames assays of West Branch of Canal Creek surface water were found to be non-mutagenic (negative) with tester strains TA98 and TA100 in both the presence and absence of an exogenous metabolic activation system of mammalian microsomal enzymes derived from Aroclor-induced rat liver (S9 mix). Of the groundwater contaminants listed in Table 3, carbon tetrachloride, 1,2-dichloroethane, and trichloroethene have been reported to be chemical mutagens (Forum for Scientific Excellence, Inc., 1990). The lack of mutagenic activity in the surface water concentrated 100X suggests that the concentrations of the mutagens are too low to induce significant mutations in the Ames assay. A summary of the raw groundwater general water quality, heavy metals, and volatile organics measured during the five bimonthly comprehensive chemical analyses is given in Table 3. The range of the lowest and highest concentrations of the five analyses is presented. No compounds in the following groups were detected in the West Branch of Canal Creek surface water at EPA's quantitation limits for surface water 1) acid or base/neutral compounds; 2) pesticides; 3) herbicides; or 4) organo-phosphorus pesticides. None of the seven explosive listed above were found in West Branch of Canal Creek surface water at a quantitation limit of 50 µg/L. Several EPA priority pollutant heavy metals were found in the West Branch of Canal Creek surface water (Table 3). Copper, iron, lead, and silver concentrations in the surface water exceeded in one or more tests the EPA freshwater chronic numerical water quality criteria of 9 µg/L for copper, 1,000 µg/L for iron, 2.5 µg/L for lead and 0.12 µg/L for silver (Buckman, 1999). The copper, lead, and silver criteria are hardness dependent criteria; 100 mg/L as CaCO3 was used. Aluminum was also present at high concentrations in the surface water and exceeded the EPA freshwater chronic numerical water quality criteria of 87 µg/L for pH 6.5 to 9.0 (Buchman, 1999). Ten chlorinated aliphatic compounds were found in the groundwater in at least one sample (Table 3). Several of the organics were EPA priority pollutants. None of the priority pollutant organics found in the West Branch of Canal Creek surface water currently have numerical water quality criteria values because insufficient data exist to develop criteria. The EPA LOECs, where available, were one or more orders of magnitude higher than the concentrations found in the surface water. Table 3. Summary of the Five Bimonthly Chemical Analyses (Range of Concentrations) Conducted on Raw West Branch of Canal Creek Surface Water
a All units are mg/L parameter with the exception of alkalinity
Preliminary Toxicity and Chemical Analysis of West Branch of Canal Creek SedimentsPreliminary studies of the potential toxicity of West Branch of Canal Creek sediments were conducted concurrently by the University of Maryland (UMD) and the USGS Environmental and Contaminants Research Center (ECRC) Columbia, Missouri. The University of Maryland conducted chronic 28-d sediment bioassays on composite samples taken from three stations in West Branch of Canal Creek which were located as follows: 1) Magnolia Road Bridge (CC-01); 2) northern USGS walkway (CC-02); and 3) southern USGS walkway (CC-03) (Fig 2). Reference and control sediments were taken from Saltpeter Creek and Magothy River, respectively. Sediments were collected from the surface to <10 cm with a 0.02 m2 petite Ponar grab sampler. The entire contents of ~10 grabs were mixed to form a composite sample. Twenty-eight day partial life cycle sediment toxicity tests with the epifaunal amphipod Hyalella azteca and infaunal amphipod Leptocheirus plumulosus were initiated on day 10 after sediment collection. The bioassays followed the experimental and statistical analysis procedures given in Burton and Turley (1997). ECRC exposed H. azteca only to sediment taken from the same three stations in West Branch of Canal Creek (CC-01, CC-02 and CC-03) and reference sediment from Saltpeter Creek. ECRC used control sediment taken from West Bear Skin Lake, Minnesota. The amphipod was exposed to the sediments for 28 days followed by a 14-d grow out period in ECRC laboratory water. Endpoints measured included survival (day 28, 35, and 42), growth (as length and weight on day 28 and 42), and reproduction (number of young per female produced from day 28 to day 42). The chemical characterization of the sediments used in both the University of Maryland and ECRC studies were conducted by ECRC. Station CC-02 was found to be toxic to H. azteca in both the UMD and ECRC studies. Both UMD and ECRC found a significant reduction in growth (length) at 28 d relative to the controls. At day 42 ECRC found a difference between CC-01 relative to the controls; CC- 02 was not different from the controls at day 42 (Ingersoll, 1998). It is not clear why differences occurred between stations at day 28 and day 42. Ingersoll et al. (1998) suggested that the smaller lengths observed on day 42 may have been the result of measuring length on different replicates on day 28 compared to day 42. UMD did not find any difference at day 28 for number of young produced at any of the stations for H. azteca. In contrast, ECRC found a reduction in young production from day 28 to day 42 at station CC-02. UMD and ECRC both found no effect on survival at any station at day 28. Likewise, ECRC found no effect on survival at day 42. In contrast to H. azteca where significant mortality did not occur at any station, UMD found significant mortality in L. plumulosus at station CC-02 after 28 d of exposure. Stations CC-01, CC-03, and Saltpeter Creek did not affect growth or young production in L. plumulosus. Growth and young production could not be analyzed for station CC-02 because of significant mortality at that station. The chemical and physical analyses of the bulk sediment at West Branch of Canal Creek stations CC-01, CC-02, CC-03, and Saltpeter Creek, which were conducted by ECRC, are given in Table 4. Of the five heavy metals determined by ECRC, cadmium and lead exceeded NOAA's probable effects level (PEL) for freshwater sediment at CC-01; lead and zinc exceeded the PEL at CC-02; and zinc exceeded the PEL at CC-03 (Buchman, 1999). None of the five heavy metals in the Saltpeter Creek reference sediment exceeded their PELs. Freshwater sediments which have metals and/or organic compounds that exceed their PELs are considered to be potentially toxic to benthic organisms. The bioavailability and toxicity of metals in sediments are influenced by a number of physico-chemical properties of the sediment. In anaerobic sediments acid volatile sulfide (AVS) is the predominant determinant of the bioavailability and toxicity of metals. AVS is formed by the reduction of sulfate by direct bacterial reduction and indirectly as an electron acceptor in the bacterial oxidation of organic matter. A majority of sulfide in sediments is in the form of iron monosulfides (FeS) and manganese monosulfides (MnS). Iron and manganese sulfides have higher sulfide solubility products than the sulfides of cadmium, coper, nickel, lead, and zinc. As a result, these metals will displace manganese and iron whenever they are present together with iron and manganese monosulfides, thereby forming insoluble and biologically unavailable metal sulfides. A simultaneously extractable metal:acid volatile sulfide (SEM:AVS) model can be used to predict the relative bioavailability of sediment-associated divalent metals. SEM is defined as the summed molar concentration of the divalent metals: cadmium, copper, nickel, lead, and zinc. AVS preferentially binds divalent metals on a mole-to-mole basis. Thus, when the SEM:AVS ratio is <1, sediment associated metals should be bound and unavailable to cause toxicity to benthic organisms. The SEM:AVS ratios for CC-01, CC-02, and CC-03 are 0.37, 0.72, and 0.24, respectively (Table 4). Thus, the toxicity observed at CC-02 does not appear to be related divalent heavy metals. Several polycyclic aromatic hydrocarbons (PAHs) were detected in West Branch of Canal Creek sediments and Saltpeter Creek. Of the PAHs for which there are PELs available, pyrene and benz(a)anthracene at CC-02 exceeded NOAA's PELs. None of the PAHs, for which PELs are available, exceeded the PAH concentrations at CC-01, CC-3, or Saltpeter Creek. One may speculate that pyrene and benz(a)anthracene at CC-02 may have caused the toxicity observed for amphipods at that station. ECRC did not measure any chlorinated aliphatic hydrocarbons; thus, no conclusion can be made regarding the possible interaction of the chlorinated volatile organics known to be present in the groundwater with the PAHs found at station CC-02. As discussed below, it is unlikely that the volatile organics played a major role in the toxicity found at station CC-02. Table 4. Summary of the Physical and Chemical Analyses Conducted on West Branch of Canal Creek Sedimentsa
a Data taken from Ingersoll et al. (1998).
USGS Study of Chlorinated Volatile Organics in the Sediments of West Branch of Canal CreekThe USGS completed a natural attenuation study of the chlorinated volatile organic (VOCs) groundwater plume as it discharged into the tidal wetlands of West Branch of Canal Creek study area in 1997 (Lorah et al., 1997). The dominant parent contaminants in the groundwater (carbon tetrachloride, chloroform, 1,1,2,2-tetrachloroethane, and trichloroethene) were studied by USGS (Table 2). The aquifer was found to be aerobic, but the groundwater in the wetland sediments became increasingly more anaerobic along the upward flow direction. Iron-reducing conditions were predominant in the lower wetland sediment unit composed of clayey sand and silt, and methanogensis was predominant in the upper unit composed of peat. Total concentrations of VOCs and the relative proportions of parent compounds to anaerobic daughter products changed substantially as the contaminants were transported upward through these changing redox environments. High concentrations of the parent compounds were found in the aquifer beneath the wetland, whereas, concentrations of daughter products (1,2-dichloroethane, 1,1,2-trichloroethane, 1,2-dichloroethene, and vinyl chloride) were low or undetectable. In contrast, the parent compounds commonly were not detected in groundwater in the wetland sediments, but the daughter compounds were observed. USGS concluded that the presence of the daughter products in the wetland sediments indicates that trichloroethene and 1,1,2,2-tetrachloroethane are degraded by reductive dechlorination reactions in the naturally anaerobic wetland sediments. Although production of daughter products was observed, total VOC concentrations decreased upward through the 1.8 to 3.6 m (6 to 12 ft) thick peat wetland sediments and averaged less than 5 µg/L near the surface. The daughter products are apparently degraded by these anaerobic processes to non-chlorinated endproducts, or are removed by other attenuation processes, such as aerobic degradation or volatilization. The average total VOC concentration of <5 µg/L near the surface of the wetland sediments is below the concentrations found to be toxic to the bioassay systems tested in the groundwater bioassays. Although total VOCs were not measured during the toxicity studies, the total VOCs estimated from the data in Table 2 range from ~225 to 570 µg/L. The lowest NOAEL for the groundwater was 10%; thus, the total VOC concentrations at the lowest NOAEL would range from ~22.5 to 57 µg/L which are above the average VOC of < 5 µg/L found by USGS. Based on these data and the preliminary water column and sediment toxicity results, a decision was made not to proceed with a fully implemented Phase 2 evaluation of the potential toxicity of the groundwater as it moves through the marsh and bottom sediments into West Branch of Canal Creek. ConclusionsToxicity was detected at various groundwater concentrations by 6 of the 8 biomonitoring systems. The groundwater was acutely toxic at pH 4 to a green alga, cladoceran, fathead minnow and Japanese medaka. From an acute toxicity standpoint, the groundwater appeared to be less toxic to the green alga at pH 7. The groundwater was not acutely toxic at pH 7 to the cladoceran, fathead minnow, or Japanese medaka. The lowest concentration of groundwater that caused no observable adverse effect at pH 4 or 7, in the test systems in which the NOAEL value could be determined, was 10% groundwater by volume. The Ames assay for mutagenicity was negative in all cases for groundwater, West Branch of Canal Creek water, and filtered APG-EA tap water. Sporadic incidences of lesions were found in Japanese medaka at concentrations up to 25% ground by volume after 9 months of exposure. Fish growth was affected by 9 months of exposure; fish were smaller when grown in groundwater diluted with West Branch of Canal Creek water. Preliminary toxicity studies of West Branch of Canal Creek surface showed that the surface water was not acutely toxic to Japanese medaka. Both unconcentrated and concentrated (100X) Ames assays of West Branch of Canal Creek surface water were found to be non-mutagenic (negative). Preliminary chronic sediment toxicity studies showed that sediment from one of three West Branch of Canal Creek sites was toxic to both an epifaunal and infaunal amphipod. The toxicity did not appear to be related to divalent heavy metals. The toxicity may be related to polycyclic aromatic hydrocarbons. A natural attenuation study of the VOCs in the groundwater plume as it discharged into the tidal wetlands of West Branch of Canal Creek study area showed that an average total VOC concentration of <5 g/L occurs near the surface of the wetland sediments. The average total VOC concentration of <5 g/L is below the concentrations found to be toxic to the organisms tested in the groundwater bioassays. The lowest NOAEL for the groundwater was 10%; thus, the total VOC concentrations at the lowest NOAEL would range from ~22.5 to 57 g/L which are above the average total VOC of < 5 g/L found by USGS. Based on the above data, a decision was made not to proceed with a fully implemented Phase 2 evaluation of the potential toxicity of the groundwater as it moves through the West Branch of Canal Creek wetland sediments. A recommendation was made to the Army that they consider the wetland as a natural remediation process. The recommendation is currently being considered as a remediation option for the portion of the Canal Creek aquifer that flows into the West Branch of Canal Creek. Literature CitedBuchman, M.F. 1999. NOAA screening quick reference tables. NOAA HAZMAT Rep. No. 99-1. National Oceanic and Atmospheric Administration, Coastal Protection and Restoration Division, Seattle, WA. Burton, D.T. and S.D. Turley. 1997. Aquatic toxicity evaluation of selected sites during high surficial aquifer flow at J-Field, Aberdeen Proving Ground-Edgewood Area. AD A333363. Defense Technical Information Center, Alexandria, VA. Burton, D.T., R.S. Herriott, and S.D. Turley. 1995. Evaluation of biomonitoring systems for assessment of contaminated water and sediments at U.S. Army installations - Evaluation of contaminated groundwater at Aberdeen Proving Ground-Edgewood Area West Branch of Canal Creek - Phase I: Groundwater evaluation. AD A326455. Defense Technical Information Center, Alexandria, VA. EPL (Experimental Pathology Laboratories, Inc.). 1996. U.S. Army Biomedical Research and Development Laboratory test 410-002R West Branch Canal Creek carcinogenicity study with medaka, Vol. 1-3. EPL Project No. 406-035. Exp. Pathology Lab., Inc., Herndon, VA. Forum for Scientific Excellence, Inc. 1990. List of lists of worldwide hazardous chemicals and pollutants. J.B. Lippincott Co., New York, NY. ICF Kaiser. 1995. Terrestrial and ecological risk assessment at U.S. Army Aberdeen Proving Ground, Maryland. Interim technical report for the Canal Creek bioassessment investigation. Contract No. DAAA15-91-d-0014, Task Order No. 10. ICF Kaiser Engineers, Inc., Abingdon, MD. Ingersoll, C.G., E.L. Brunson, F.J. Dwyer, D.K. Hardesty, and N.E. Kemble. 1998. Use of sublethal endpoints in sediment toxicity tests with the amphipod Hyalella azteca. Environ. Toxicol. Chem. 17:1508-1523. Lorah, M.M. and D.A. Vroblesky. 1989. Inorganic and organic ground-water chemistry in the Canal Creek Area of Aberdeen Proving Ground, Maryland. 89-4002. U.S. Geological Survey, Towson, MD. Lorah, M.M. and J.S. Clark. 1992. Contamination of ground water, surface water, and soil and evaluation of selected pumpage scenarios in the Canal Creek Area of Aberdeen Proving Ground, Maryland. Draft Open File Report 92-. U.S. Geological Survey, Towson, MD. Lorah, M.M. and J.S. Clark. 1996. Contamination of ground water, surface water, and soil, and evaluation of selected ground-water pumping alternatives in the Canal Creek area of Aberdeen Proving Ground, Maryland. 95-282. U.S. Geological Survey, Baltimore, MD. Lorah, M.M., L.D. Olsen, B.L. Smith, M.A. Johnson, and W.B. Fleck. 1997. Natural attenuation of chlorinated volatile organic compounds in a freshwater tidal wetland, Aberdeen Proving Ground, Maryland. 97-4171. U.S. Geological Survey, Baltimore, MD. Nemath, G. 1989. RCRA facility assessment report Edgewood Area Aberdeen Proving Ground, Maryland. 39-26-0490-90. U.S. Army Environ. Hygiene Agency, Aberdeen Proving Ground, MD. Oliveros, J.P. and D.A. Vroblesky. 1989. Hydrogeology of the Canal Creek Area, Aberdeen Proving Ground, Maryland. 89-4021. U.S. Geological Survey, Towson, MD. Thurston, R.V., R.C. Russo, and K. Emerson. 1979. Aqueous ammonia equilibrium - Tabulation of percent ionized ammonia. EPA-600/3-79-091. U.S. Environmental Protection Agency, Environmental Research Laboratory, Duluth, MN. U.S. EPA. 1991. Assessment and control of bioconcentratable contaminants in surface waters. 1991 Draft Report. U.S Environmental Protection Agency, Washington, DC.
Last Modified Date: 02 Jul 2010
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Skip over navigation
