Degradation and Transport of the Chiral Herbicide S-Metolachlor at the Catchment Scale: Combining Observation Scales and Analytical Approaches - Ecole Nationale du Génie de l'Eau et de l'Environnement de Strasbourg Accéder directement au contenu
Article Dans Une Revue Environmental Science and Technology Année : 2017

Degradation and Transport of the Chiral Herbicide S-Metolachlor at the Catchment Scale: Combining Observation Scales and Analytical Approaches

Résumé

Evaluating pesticide degradation and transport in the soil-surface water continuum remains challenging at the catchment scale. Here we investigated the dissipation of the chiral herbicide S-metolachlor (SM) in soil in relation to its transport in runoff. Analyses of SM, transformation products (TPs, i.e., MESA and MOXA), and enantiomers were combined to determine SM degradation at plot and catchment scales. Assisted by modeling, we found that the main dissipation pathways of SM at the plot scale were degradation (71%), volatilization (5%), leaching (8%) and runoff (3%), while 13% of SM persisted in topsoil. This highlights the relevance of degradation processes. TPs could trace the different discharge contributions: MOXA prevailed in runoff water, whereas MESA was associated with slower flowpaths. At the catchment outlet, 11% of SM applied was exported in dissolved or particulate phases or as TPs (in SM mass equivalent). A single event 1 week after application exported 96% of SM, which underlined the potential importance of severe rainfall on seasonal SM export. Enantioselective degradation enriched SM in the R-enantiomer over longer periods and may be associated with slower flowpaths. Altogether, combining observation scales and analytical approaches enabled to quantify SM degradation and to identify how degradation controls SM export at the catchment scale.
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Dates et versions

hal-01831186 , version 1 (05-07-2018)

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Marie Lefrancq, Sylvain Payraudeau, Benoit Guyot, Maurice Millet, Gwenael Imfeld. Degradation and Transport of the Chiral Herbicide S-Metolachlor at the Catchment Scale: Combining Observation Scales and Analytical Approaches. Environmental Science and Technology, 2017, 51 (22), pp.13231-13240. ⟨10.1021/acs.est.7b02297⟩. ⟨hal-01831186⟩
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