title: Multiple dual C-Cl isotope patterns associated with reductive dechlorination of tetrachloroethene.
abstract: Dual isotope slopes are increasingly used to identify transformation pathways of contaminants. We investigated if reductive dechlorination of tetrachloroethene (PCE) by consortia containing bacteria with different reductive dehalogenases (rdhA) genes can lead to variable dual C-Cl isotope slopes and if different slopes also occur in the field. Two bacterial enrichments harboring Sulfurospirillum spp. but different rdhA genes yielded two distinct δ(13)C to δ(37)Cl slopes of 2.7 ± 0.3 and 0.7 ± 0.2 despite a high similarity in gene sequences. This suggests that PCE reductive dechlorination could be catalyzed according to at least two distinct reaction mechanisms or that rate-limiting steps might vary. At two field sites, two distinct dual isotope slopes of 0.7 ± 0.3 and 3.5 ± 1.6 were obtained, each of which fits one of the laboratory slopes within the range of uncertainty. This study hence provides additional insight into multiple reaction mechanisms underlying PCE reductive dechlorination. It also demonstrates that caution is necessary if a dual isotope approach is used to differentiate between transformation pathways of chlorinated ethenes.
authors.affiliation: Centre for Hydrogeology and Geothermics (CHYN), University of Neuchâtel , Rue Emile Argand 11, CH-2000 Neuchâtel, Switzerland.
authors.forename: Alice
authors.initials: A
authors.lastname: Badin
authors.forename: Géraldine
authors.initials: G
authors.lastname: Buttet
authors.forename: Julien
authors.initials: J
authors.lastname: Maillard
authors.forename: Christof
authors.initials: C
authors.lastname: Holliger
authors.forename: Daniel
authors.initials: D
authors.lastname: Hunkeler
mesh_terms: D002247:Carbon Isotopes / Q000032:analysis*; D002713:Chlorine / Q000032:analysis* / Q000378:metabolism; D020565:Epsilonproteobacteria / Q000378:metabolism*; D005798:Genes, Bacterial; D010084:Oxidation-Reduction; D013750:Tetrachloroethylene / Q000378:metabolism*
chemical_list: D002247:Carbon Isotopes; D002713:Chlorine; D013750:Tetrachloroethylene