title: Degradation of chloroacetanilide herbicides and bacterial community composition in lab-scale wetlands.
abstract: Degradation of chloroacetanilide herbicides rac-metolachlor, acetochlor, and alachlor, as well as associated bacterial populations, were evaluated in vertical upflow wetland columns using a combination of hydrochemical and herbicide analyses, and DNA-based approaches. Mass dissipation of chloroacetanilides, continuously supplied at 1.8-1.9 μM for 112 days, mainly occurred in the rhizosphere zone under nitrate and sulphate-reducing conditions, and averaged 61±14%, 52±12% and 29±19% for acetochlor, alachlor and rac-metolachlor, respectively. Metolachlor enantiomer fractions of 0.494±0.009 in the oxic zone and 0.480±0.005 in the rhizosphere zone indicated preferential biodegradation of the S-enantiomer. Chloroacetanilide ethane sulfonic acid and oxanilic acid degradates were detected at low concentrations only (0.5 nM), suggesting extensive degradation and the operation of yet unknown pathways for chloroacetanilide degradation. Hydrochemical parameters and oxygen concentration were major drivers of bacterial composition, whereas exposure to chloroacetanilides had no detectable impact. Taken together, the results underline the importance of anaerobic degradation of chloroacetanilides in wetlands, and highlight the potential of complementary chemical and biological approaches to characterise processes involved in the environmental dissipation of chloroacetanilides.
authors.affiliation: Laboratory of Hydrology and Geochemistry of Strasbourg (LHyGeS), University of Strasbourg/EOST, UMR 7517 CNRS, 1 rue Blessig, 67084 Strasbourg Cedex, France; Génétique Moléculaire, Génomique, Microbiologie (GMGM), University of Strasbourg, UMR 7156 CNRS, 28 rue Goethe, 67083 Strasbourg Cedex, France.
authors.forename: Omniea Fawzy
authors.initials: OF
authors.lastname: Elsayed
authors.affiliation: Laboratory of Hydrology and Geochemistry of Strasbourg (LHyGeS), University of Strasbourg/EOST, UMR 7517 CNRS, 1 rue Blessig, 67084 Strasbourg Cedex, France.
authors.forename: Elodie
authors.initials: E
authors.lastname: Maillard
authors.affiliation: Génétique Moléculaire, Génomique, Microbiologie (GMGM), University of Strasbourg, UMR 7156 CNRS, 28 rue Goethe, 67083 Strasbourg Cedex, France.
authors.forename: Stéphane
authors.initials: S
authors.lastname: Vuilleumier
authors.affiliation: Institute of Chemistry for Energy, Environment and Health (ICPEES), University of Strasbourg, UMR 7515 CNRS, 1 rue Blessig, 67084 Strasbourg Cedex, France.
authors.forename: Maurice
authors.initials: M
authors.lastname: Millet
authors.affiliation: Laboratory of Hydrology and Geochemistry of Strasbourg (LHyGeS), University of Strasbourg/EOST, UMR 7517 CNRS, 1 rue Blessig, 67084 Strasbourg Cedex, France. Electronic address: imfeld@unistra.fr.
authors.forename: Gwenaël
authors.initials: G
authors.lastname: Imfeld
mesh_terms: D000081:Acetamides / Q000032:analysis / Q000378:metabolism; D001419:Bacteria / Q000378:metabolism; D001673:Biodegradation, Environmental; D006540:Herbicides / Q000032:analysis / Q000378:metabolism*; D059013:Microbial Consortia; D014871:Water Microbiology; D053833:Wetlands
chemical_list: D000081:Acetamides; D006540:Herbicides; C078188:2-chloro-N-(ethoxymethyl)-N-(2-methyl-6-(trifluoromethyl)phenyl)acetamide
keywords: Bacterial diversity; Biodegradation; Chiral pesticides; Chloroacetanilides; Wetlands