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(189) Biodegradation Of Chlorinated Hydrocarbons Discharged Through Ground Water Into A Wetlands.
Harman, Charles*,1, Gallo, Vanessa1, Posten, Stephen1, 1 AMEC Earth & Environmental, Somerset, New Jersey, USA
ABSTRACT- Biodegradation Of Chlorinated Hydrocarbons Discharged Through Ground Water Into A Wetlands. Harman, CR*; Gallo, VA; Posten, SE, AMEC Earth & Environmental, Inc., Somerset, NJ. Remedial investigations at an industrial facility in southern New York confirmed the release of solvents (primarily trichloroethene and 1,1,1-trichloroethane) into subsurface soils and ground water. Source area concentrations range from 10-200 mg/L, with plume concentrations at the property boundary on the order of 20 mg/L. The local ground water flow regime is shallow and oriented to discharge into an adjacent forested wetlands area. The presence of a high organic carbon substrate coupled with anoxic conditions in the wetlands sediments were identified as a favorable environment for dechlorination of residual dissolved solvent contamination by indigenous anaerobic microorganisms along the leading edge of the discharging ground water plume. This condition was subsequently documented through the performance of a comprehensive ground water geochemical investigation, and the sampling of surface water, shallow ground water, and sediments in the wetlands area for volatile organic compound analysis. The geochemical investigation indicated a depletion of electron acceptors and an increase in metabolic byproducts within the wetlands relative to upgradient areas on the project site (typified by sand-gravel terrace deposits). Increasing concentrations of dechlorination breakdown products were identified in surface waters and sediment within the wetlands area. Concentrations of detected contaminants in surface water were one or more orders of magnitude lower than aquatic life acute and chronic toxicity criteria, and the results of biological screening of the wetlands area indicated a healthy environment, with no evidence of ecotoxicological stress. Together with an aggressive source remediation program, natural attenuation of residual dissolved solvents within the leading edge of the discharging ground water contaminant plume is currently being implemented as a component of the site remedy.
Key words: Wetlands, Biodegradation, Volatile Organic Compounds
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