title: Distinguishing abiotic and biotic transformation of tetrachloroethylene and trichloroethylene by stable carbon isotope fractionation.
abstract: Significant carbon isotope fractionation was observed during FeS-mediated reductive dechlorination of tetrachloroethylene (PCE) and trichloroethylene (TCE). Bulk enrichment factors (E(bulk)) for PCE were -30.2 +/- 4.3 per thousand (pH 7), -29.54 +/- 0.83 per thousand (pH 8), and -24.6 +/- 1.1 per thousand (pH 9). For TCE, E(bulk) values were -33.4 +/- 1.5 per thousand (pH 8) and -27.9 +/- 1.3 per thousand (pH 9). A smaller magnitude of carbon isotope fractionation resulted from microbial reductive dechlorination by two isolated pure cultures (Desulfuromonas michiganensis strain BB1 (BB1) and Sulfurospirillum multivorans (Sm)) and a bacterial consortium (BioDechlor INOCULUM (BDI)). The E(bulk) values for biological PCE microbial dechlorination were -1.39 +/- 0.21 per thousand (BB1), -1.33 +/- 0.13 per thousand (Sm), and -7.12 +/- 0.72 per thousand (BDI), while those for TCE were -4.07 +/- 0.48 per thousand (BB1), -12.8 +/- 1.6 per thousand (Sm), and -15.27 +/- 0.79 per thousand (BDI). Reactions were investigated by calculation of the apparent kinetic isotope effect for carbon (AKIEc), and the results suggest that differences in isotope fractionation for abiotic and microbial dechlorination resulted from the differences in rate-limiting steps during the dechlorination reaction. Measurement of more negative E(bulk) values at sites contaminated with PCE and TCE may suggest the occurrence of abiotic reductive dechlorination by FeS.
authors.affiliation: School of Civil Engineering and Environmental Science, University of Oklahoma, Norman, Oklahoma 73019, USA.
authors.forename: Xiaoming
authors.initials: X
authors.lastname: Liang
authors.forename: Yiran
authors.initials: Y
authors.lastname: Dong
authors.forename: Tomasz
authors.initials: T
authors.lastname: Kuder
authors.forename: Lee R
authors.initials: LR
authors.lastname: Krumholz
authors.forename: R Paul
authors.initials: RP
authors.lastname: Philp
authors.forename: Elizabeth C
authors.initials: EC
authors.lastname: Butler
mesh_terms: D002247:Carbon Isotopes / Q000378:metabolism*; D013750:Tetrachloroethylene / Q000493:pharmacokinetics*; D014241:Trichloroethylene / Q000493:pharmacokinetics*
chemical_list: D002247:Carbon Isotopes; D014241:Trichloroethylene; D013750:Tetrachloroethylene