title: Using compound-specific isotope analysis to assess the degradation of chloroacetanilide herbicides in lab-scale wetlands.
abstract: Compound-specific isotope analysis (CSIA) is a promising tool to study the environmental fate of a wide range of contaminants including pesticides. In this study, a novel CSIA method was developed to analyse the stable carbon isotope signatures of widely used chloroacetanilide herbicides. The developed method was applied in combination with herbicide concentration and hydrochemical analyses to investigate in situ biodegradation of metolachlor, acetochlor and alachlor during their transport in lab-scale wetlands. Two distinct redox zones were identified in the wetlands. Oxic conditions prevailed close to the inlet of the four wetlands (oxygen concentration of 212±24μM), and anoxic conditions (oxygen concentrations of 28±41μM) prevailed towards the outlet, where dissipation of herbicides mainly occurred. Removal of acetochlor and alachlor from inlet to outlet of wetlands was 56% and 51%, whereas metolachlor was more persistent (23% of load dissipation). CSIA of chloroacetanilides at the inlet and outlet of the wetlands revealed carbon isotope fractionation of alachlor (εbulk=-2.0±0.3‰) and acetochlor (εbulk=-3.4±0.5‰), indicating that biodegradation contributes to the dissipation of both herbicides. This study is a first step towards the application of CSIA to evaluate the transport and degradation of chloroacetanilide herbicides in the environment.
authors.affiliation: Laboratory of Hydrology and Geochemistry of Strasbourg (LHyGeS), UMR 7517, University of Strasbourg/ENGEES, CNRS, France; Génétique Moléculaire, Génomique, Microbiologie (GMGM), UMR 7156, University of Strasbourg, CNRS, France.
authors.forename: O F
authors.initials: OF
authors.lastname: Elsayed
authors.affiliation: Laboratory of Hydrology and Geochemistry of Strasbourg (LHyGeS), UMR 7517, University of Strasbourg/ENGEES, CNRS, France.
authors.forename: E
authors.initials: E
authors.lastname: Maillard
authors.affiliation: Génétique Moléculaire, Génomique, Microbiologie (GMGM), UMR 7156, University of Strasbourg, CNRS, France.
authors.forename: S
authors.initials: S
authors.lastname: Vuilleumier
authors.affiliation: Department of Isotope Biogeochemistry, Helmholtz Centre for Environmental Research (UFZ), Leipzig, Germany.
authors.forename: I
authors.initials: I
authors.lastname: Nijenhuis
authors.affiliation: Department of Isotope Biogeochemistry, Helmholtz Centre for Environmental Research (UFZ), Leipzig, Germany.
authors.forename: H H
authors.initials: HH
authors.lastname: Richnow
authors.affiliation: Laboratory of Hydrology and Geochemistry of Strasbourg (LHyGeS), UMR 7517, University of Strasbourg/ENGEES, CNRS, France. Electronic address: imfeld@unistra.fr.
authors.forename: G
authors.initials: G
authors.lastname: Imfeld
mesh_terms: D000081:Acetamides / Q000032:analysis / Q000737:chemistry*; D001673:Biodegradation, Environmental; D005591:Chemical Fractionation; D006540:Herbicides / Q000032:analysis / Q000737:chemistry*; D008956:Models, Chemical; D014052:Toluidines / Q000032:analysis / Q000737:chemistry; D053833:Wetlands
chemical_list: D000081:Acetamides; D006540:Herbicides; D014052:Toluidines; C000188:alachlor; C078188:2-chloro-N-(ethoxymethyl)-N-(2-methyl-6-(trifluoromethyl)phenyl)acetamide; C043377:acetochlor; C051786:metolachlor
keywords: Biodegradation; Carbon isotope fractionation; Herbicide; Wetland