title: Biodegradation of PCE and TCE in landfill leachate predicted from concentrations of molecular hydrogen: a case study.
abstract: The Refuse Hideaway Landfill (23-acre) received municipal, commercial, and industrial waste between 1974 and 1988. It was designed as a "natural attenuation" landfill and no provision was made to collect and treat contaminated water. Natural biological degradation through sequential reductive dechlorination had been an important mechanism for natural attenuation at the site. We used the concentration of hydrogen to forecast whether reductive dechlorination would continue over time at particular locations in the plume. Based on published literature, reductive dechlorination and natural attenuation of PCE, TCE, and cis-DCE can be expected in the aquifer if the concentration of molecular hydrogen in monitoring wells are adequate (> 1 nanomolar). Reductive dechlorination can be expected to continue as the ground water moves down gradient. Natural attenuation through reductive dechlorination is not expected in flow paths that originate at down gradient monitoring wells with low concentrations of molecular hydrogen (< 1 nanomolar). In three monitoring wells at the margin of the landfill and in five monitoring wells down gradient of the landfill, ground water maintained a molecular hydrogen concentration, ranging from 1.30 to 9.17 nanomolar, that is adequate for reductive dechlorination. In three of the monitoring wells far down gradient of the landfill, the concentration of molecular hydrogen (0.33 to 0.83 nanomolar) was not adequate to support reductive dechlorination. In wells with adequate concentrations of hydrogen, the concentrations of chlorinated volatile organic compounds were attenuated over time, or concentrations of chlorinated volatile organics were below the detection limit. In wells with inadequate concentrations of hydrogen, the concentrations of chlorinated organic compounds attenuated at a slower rate over time. In wells with adequate hydrogen the first order rate of attenuation of PCE, TCE, cis-DCE and total chlorinated volatile organic compounds varies from 0.38 to 0.18 per year. In wells without adequate hydrogen the rate varies from 0.015 to 0.006 per year.
authors.affiliation: US Environmental Protection Agency, Robert Kerr Research Laboratory, OK 74820, USA.
authors.forename: Mary E
authors.initials: ME
authors.lastname: Gonsoulin
authors.forename: Barbara H
authors.initials: BH
authors.lastname: Wilson
authors.forename: John T
authors.initials: JT
authors.lastname: Wilson
mesh_terms: D001673:Biodegradation, Environmental; D006859:Hydrogen / Q000378:metabolism; D007700:Kinetics; D012997:Solvents / Q000378:metabolism; D013750:Tetrachloroethylene / Q000378:metabolism*; D014241:Trichloroethylene / Q000378:metabolism*; D018505:Waste Management; D014874:Water Pollutants, Chemical / Q000378:metabolism*; D014922:Wisconsin
chemical_list: D012997:Solvents; D014874:Water Pollutants, Chemical; D014241:Trichloroethylene; D006859:Hydrogen; D013750:Tetrachloroethylene