title: Insights into reductive dechlorination of triclocarban in river sediments: Field measurements and in vitro mechanism investigations.
abstract: Triclocarban (TCC) reductive dechlorination was investigated using a combination of field and laboratory experiments. Field monitoring revealed that TCC reductive dechlorination in river sediments leads to formation of two isomers of its lesser chlorinated congener namely 3,4'-dichlorocarbanilide and 4,4'-dichlorocarbanilide. Monochlorocarbanilide was not detected in sediments supporting that transformation of dichlorocarbanilide into monochlorocarbanilide is the rate limiting step of TCC dechlorination. In vitro experiments were conducted to study TCC potential reductive dechlorination mechanisms. These experiments demonstrated that 4,4'-dichlorocarbanilide was specifically formed upon a nucleophilic addition reaction under anaerobic conditions. The 3,4'-diclorocarbanilide was formed upon a two steps radical mechanism under aerobic conditions which includes TCC activation by one electron oxidation followed by a nucleophilic substitution reaction with glutathione. In vitro results suggested that strict anaerobic conditions might not be required for TCC reductive dechlorination in the environment. Moreover, in vitro reactions were performed using biomimetic or enzymatic systems supposing that TCC dechlorination might occur through microbial action in situ. Measured dichlorocarbanilide isomers/triclocarban ratios were used to evaluate the relative significance of both dechlorination pathways and the pathway leading to 3,4'-dichlorocarbanilide was found significant in all investigated river sediment samples.
authors.affiliation: Veolia Recherche et Innovation, Chemin de la Digue, BP 76, 78603 Maisons-Laffitte Cedex, France.
authors.forename: Marine
authors.initials: M
authors.lastname: Souchier
authors.affiliation: UMR Hydrosciences 5569, Université Montpellier, 15 Avenue Ch. Flahault, 34093 Montpellier Cedex 5, France.
authors.forename: Claude
authors.initials: C
authors.lastname: Casellas
authors.affiliation: Veolia Recherche et Innovation, Chemin de la Digue, BP 76, 78603 Maisons-Laffitte Cedex, France.
authors.forename: Valérie
authors.initials: V
authors.lastname: Ingrand
authors.affiliation: UMR Hydrosciences 5569, Université Montpellier, 15 Avenue Ch. Flahault, 34093 Montpellier Cedex 5, France. Electronic address: Serge.Chiron@msem.univ-montp2.fr.
authors.forename: Serge
authors.initials: S
authors.lastname: Chiron
mesh_terms: D000332:Aerobiosis; D000693:Anaerobiosis; D001673:Biodegradation, Environmental; D002224:Carbanilides / Q000032:analysis* / Q000737:chemistry; D004784:Environmental Monitoring / Q000379:methods*; D005602:France; D019015:Geologic Sediments / Q000737:chemistry* / Q000382:microbiology; D054879:Halogenation; D010084:Oxidation-Reduction; D045483:Rivers / Q000737:chemistry* / Q000382:microbiology; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000737:chemistry
chemical_list: D002224:Carbanilides; D014874:Water Pollutants, Chemical; C009540:triclocarban
keywords: Nucleophilic addition; Nucleophilic substitution; Reductive dechlorination; Sediment; Triclocarban