title: Carbon isotope fractionation during dechlorination of 1,2,3,4-tetrachlorodibenzo-p-dioxin by a Dehalococcoides-containing culture.
abstract: Carbon isotope fractionation was observed during dechlorination of 1,2,3,4-tetrachlorodibenzo-p-dioxin (1,2,3,4-TeCDD) by a mixed culture containing Dehalococcoides ethenogenes strain 195. Fractionation was examined when 1,2,3,4-TeCDD was added as the only chlorinated compound and when 1,2,3,4-TeCDD was added with a known growth substrate, tetrachloroethene (PCE). The 1,2,3,4-TeCDD was dechlorinated to 1,2,4-trichlorodibenzo-p-dioxin (1,2,4-TrCDD) which was enriched in (13)C relative to 1,2,3,4-TeCDD with isotope separation factors, epsilon(C), of 1.3+/-0.2 per thousand and 1.7+/-0.4 per thousand (average+/-95% confidence interval (CI)) in cultures with and without PCE, respectively. The 1,2,4-TrCDD was further dechlorinated to 1,3-dichlorodibenzo-p-dioxin (1,3-DCDD) which was depleted in (13)C relative to 1,2,4-TrCDD with epsilon(C) of -2.4+/-0.4 per thousand and -2.9+/-0.8 per thousand (average+/-95% CI) in cultures with and without PCE, respectively. This demonstrates carbon isotope fractionation during sequential reductive dechlorination of PCDDs, where isotope fractionation during dechlorination of the intermediate was substantial and a (13)C depleted lightly chlorinated PCDD congener was ultimately formed during dechlorination of more highly chlorinated PCDD congeners. Despite reproducible, statistically significant differences between isotope compositions of the parent, 1,2,3,4-TeCDD and daughter, 1,2,4-TrCDD and 1,3-DCDD congeners in triplicate bottles of both treatments, fractionation factors for 1,2,3,4-TeCDD could not be determined for all replicates by regression analysis of the plot of the Rayleigh equation. It is possible that dissolution of 1,2,3,4-TeCDD imposed a kinetic limitation on dechlorination, thus masking isotope fractionation during its dechlorination.
authors.affiliation: Department of Environmental Sciences, Rutgers University, New Brunswick, NJ 08901, USA.
authors.forename: Fang
authors.initials: F
authors.lastname: Liu
authors.forename: Danuta
authors.initials: D
authors.lastname: Cichocka
authors.forename: Ivonne
authors.initials: I
authors.lastname: Nijenhuis
authors.forename: Hans-Hermann
authors.initials: HH
authors.lastname: Richnow
authors.forename: Donna E
authors.initials: DE
authors.lastname: Fennell
mesh_terms: D002247:Carbon Isotopes / Q000032:analysis / Q000378:metabolism*; D041862:Chloroflexi / Q000378:metabolism*; D054879:Halogenation; D000072317:Polychlorinated Dibenzodioxins / Q000031:analogs & derivatives* / Q000032:analysis / Q000378:metabolism
chemical_list: D002247:Carbon Isotopes; D000072317:Polychlorinated Dibenzodioxins; C092155:1,2,3,4-tetrachlorodibenzodioxin