title: 3D-CSIA: carbon, chlorine, and hydrogen isotope fractionation in transformation of TCE to ethene by a Dehalococcoides culture.
abstract: Carbon (C), chlorine (Cl), and hydrogen (H) isotope effects were determined during dechlorination of TCE to ethene by a mixed Dehalococcoides (Dhc) culture. The C isotope effects for the dechlorination steps were consistent with data published in the past for reductive dechlorination (RD) by Dhc. The Cl effects (combined with an inverse H effect in TCE) suggested that dechlorination proceeded through nucleophilic reactions with cobalamin rather than by an electron transfer mechanism. Depletions of (37)Cl in daughter compounds, resulting from fractionation at positions away from the dechlorination center (secondary isotope effects), further support the nucleophilic dechlorination mechanism. Determination of C and Cl isotope ratios of the reactants and products in the reductive dechlorination chain offers a potential tool for differentiation of Dhc activity from alternative transformation mechanisms (e.g., aerobic degradation and reductive dechlorination proceeding via outer sphere mechanisms), in studies of in situ attenuation of chlorinated ethenes. Hydrogenation of the reaction products (DCE, VC, and ethene) showed a major preference for the (1)H isotope. Detection of depleted dechlorination products could provide a line of evidence in discrimination between alternative sources of TCE (e.g., evolution from DNAPL sources or from conversion of PCE).
authors.affiliation: School of Geology and Geophysics, University of Oklahoma , 100 E. Boyd Street, SEC 710, Norman, Oklahoma 73019, United States.
authors.forename: Tomasz
authors.initials: T
authors.lastname: Kuder
authors.forename: Boris M
authors.initials: BM
authors.lastname: van Breukelen
authors.forename: Mindy
authors.initials: M
authors.lastname: Vanderford
authors.forename: Paul
authors.initials: P
authors.lastname: Philp
mesh_terms: D002244:Carbon / Q000378:metabolism; D002247:Carbon Isotopes / Q000378:metabolism; D002713:Chlorine / Q000378:metabolism; D041862:Chloroflexi / Q000378:metabolism*; D005030:Ethylenes / Q000378:metabolism*; D008401:Gas Chromatography-Mass Spectrometry; D006859:Hydrogen / Q000378:metabolism; D010084:Oxidation-Reduction; D014241:Trichloroethylene / Q000378:metabolism*; D014874:Water Pollutants, Chemical / Q000378:metabolism*
chemical_list: D002247:Carbon Isotopes; D005030:Ethylenes; D014874:Water Pollutants, Chemical; D014241:Trichloroethylene; D002713:Chlorine; D002244:Carbon; D006859:Hydrogen; C036216:ethylene