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van Stone, N.* ; Elsner, M. ; Lacrampe-Couloume, G.* ; Mabury, S.* ; Sherwood Lollar, B.*

Potential for identifying abiotic chloroalkane degradation mechanisms using carbon isotopic fractionation.

Environ. Sci. Technol. 42, 126-132 (2008)
Open Access Green as soon as Postprint is submitted to ZB.
Degradation of 1,1- and 1,2-dichloroethane (1,1-DCA, 1,2-DCA) and carbon tetrachloride (CCl4) on Zn0 was investigated using compound specific isotope analysis (CSIA) to measure isotopic fractionation factors for chloroalkane degradation by hydrogenolysis, by ?-elimination, and by ?-elimination. Significant differences in enrichment factors (?) and associated apparent kinetic isotope effects (AKIE) were measured for these different reaction pathways, suggesting that carbon isotope fractionation by ?-elimination is substantially larger than fractionation by hydrogenolysis or by ?-elimination. Specifically, for 1,1-DCA, the isotopic composition of the reductive ?-elimination product (ethane) and the hydrogenolysis product (chloroethane) were the same, indicating that cleavage of a single C-Cl bond was the rate-limiting step in both cases. In contrast, for 1,2-DCA, ? = ?reactive position = -29.7 ± 1.5‰, and the calculated AKIE (1.03) indicated that ?-elimination was likely concerted, possibly involving two C-Cl bonds simultaneously. Compared to 1,1-DCA hydrogenolysis, the AKIE of 1.01 for hydrogenolysis of CCl4 was much lower, indicating that, for this highly reactive organohalide, mass transfer to the surface was likely partially rate-limiting. These findings are a first step toward delineating the relative contribution of these competing pathways in other abiotic systems such as the degradation of chlorinated ethenes on zerovalent iron (ZVI), iron sulfide, pyrite, or magnetite, and, potentially, toward distinguishing between degradation of chlorinated ethenes by abiotic versus biotic processes.
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Publication type Article: Journal article
Document type Scientific Article
Corresponding Author
ISSN (print) / ISBN 0013-936X
e-ISSN 1520-5851
Journal Environmental Science & Technology
Quellenangaben Volume: 42, Issue: , Pages: 126-132 Article Number: , Supplement: ,
Publisher ACS
Publishing Place Washington, DC
Non-patent literature Publications
Reviewing status Peer reviewed
Institute(s) Institute of Groundwater Ecology (IGOE)