title: Dissipation of hydrological tracers and the herbicide S-metolachlor in batch and continuous-flow wetlands.
abstract: Pesticide dissipation in wetland systems with regard to hydrological conditions and operational modes is poorly known. Here, we investigated in artificial wetlands the impact of batch versus continuous-flow modes on the dissipation of the chiral herbicide S-metolachlor (S-MET) and hydrological tracers (bromide, uranine and sulforhodamine B). The wetlands received water contaminated with the commercial formulation Mercantor Gold(®) (960 g L(-1) of S-MET, 87% of the S-enantiomer). The tracer mass budget revealed that plant uptake, sorption, photo- and presumably biodegradation were prominent under batch mode (i.e. characterized by alternating oxic-anoxic conditions), in agreement with large dissipation of S-MET (90%) under batch mode. Degradation was the main dissipation pathway of S-MET in the wetlands. The degradate metolachlor oxanilic acid (MOXA) mainly formed under batch mode, whereas metolachlor ethanesulfonic acid (MESA) prevailed under continuous-flow mode, suggesting distinct degradation pathways in each wetland. R-enantiomer was preferentially degraded under batch mode, which indicated enantioselective biodegradation. The release of MESA and MOXA by the wetlands as well as the potential persistence of S-MET compared to R-MET under both oxic and anoxic conditions may be relevant for groundwater and ecotoxicological risk assessment. This study shows the effect of batch versus continuous modes on pollutant dissipation in wetlands, and that alternate biogeochemical conditions under batch mode enhance S-MET biodegradation.
authors.affiliation: Laboratoire d'Hydrologie et de Géochimie de Strasbourg (LHyGeS), UMR 7517, Université de Strasbourg/EOST, CNRS, 1 rue Blessig, 67084 Strasbourg Cedex, France.
authors.forename: Elodie
authors.initials: E
authors.lastname: Maillard
authors.affiliation: Chair of Hydrology, University of Freiburg, Fahnenbergplatz, D-79098 Freiburg, Germany.
authors.forename: Jens
authors.initials: J
authors.lastname: Lange
authors.affiliation: Chair of Hydrology, University of Freiburg, Fahnenbergplatz, D-79098 Freiburg, Germany.
authors.forename: Steffi
authors.initials: S
authors.lastname: Schreiber
authors.affiliation: Laboratoire d'Hydrologie et de Géochimie de Strasbourg (LHyGeS), UMR 7517, Université de Strasbourg/EOST, CNRS, 1 rue Blessig, 67084 Strasbourg Cedex, France.
authors.forename: Jeanne
authors.initials: J
authors.lastname: Dollinger
authors.affiliation: Chair of Hydrology, University of Freiburg, Fahnenbergplatz, D-79098 Freiburg, Germany.
authors.forename: Barbara
authors.initials: B
authors.lastname: Herbstritt
authors.affiliation: Institut de Chimie et Procédés pour l'Energie, l'Environnement et la Santé ICPEES, UMR 7515, Groupe de Physico-Chimie de l'Atmosphère, Université de Strasbourg/CNRS, France.
authors.forename: Maurice
authors.initials: M
authors.lastname: Millet
authors.affiliation: Laboratoire d'Hydrologie et de Géochimie de Strasbourg (LHyGeS), UMR 7517, Université de Strasbourg/EOST, 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 / Q000378:metabolism*; D001673:Biodegradation, Environmental; D004785:Environmental Pollutants / Q000378:metabolism*; D006540:Herbicides / Q000378:metabolism*; D062070:Hydrology; D010944:Plants / Q000378:metabolism*; D053833:Wetlands
chemical_list: D000081:Acetamides; D004785:Environmental Pollutants; D006540:Herbicides; C051786:metolachlor
keywords: Chiral pesticides; Degradation; Enantioselectivity; Herbicides; Hydrological tracers; Wetlands