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Efficiency of an artificial wetland and a forest buffer for pesticide pollution mitigation in a tile-drained agricultural watershed

Abstract : As part of the ArtWET LIFE environment project (06 ENV/F/000133), two buffer zones, an artificial wetland and a forest buffer, located at Bray (France) were assessed for their potential at reducing pesticide pollution coming from a 46-ha tile-drained watershed. Because of limited land availability, treating the entire volume was not possible but focusing on the most concentrated effluents appeared to be a good strategy to achieve pesticide abatement. The three-year results showed that both systems lowered down pesticide concentrations and loads by more than 40 %. However, a wide range of efficiencies was recorded. The most contrasted results were obtained for the fairly mobile herbicide isoproturon. On-site multi-tracer experiments concluded in a 66.5-h water residence time in the artificial wetland. Delay was observed in pesticide transfer probably due to adsorption, but desorption was also suspected. Wetland sediments, wetland plants, forest soil and litter were sampled on-site. On these substrates, 14C radio-labelled pesticides were used to study epoxiconazole (fungicide) degradation under flooded conditions as well as adsorption and desorption of isoproturon, metazachlor (herbicides) and epoxiconazole. Apart from plants, adsorption coefficients (Koc) for the three molecules were in the upper range of literature values indicating a high sorption potential of the buffer zone substrates. Epoxiconazole showed the lowest desorption properties whereas metazachlor was more easily released from most substrates. Epoxiconazole mineralization was low and occurred at a very slow rate. Degradation occurred as attested by metabolite production. Sorption-desorption seemed an important phenomenon to consider particularly for systems with low residence time in which degradation may not have time to occur. In addition, such temporarily anoxic environment does not prevent pesticide degradation from taking place but may slow it down by a factor depending on pesticide properties.
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  • HAL Id : tel-02594606, version 1
  • IRSTEA : PUB00031186

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Elodie Passeport. Efficiency of an artificial wetland and a forest buffer for pesticide pollution mitigation in a tile-drained agricultural watershed. Environmental Sciences. Doctorat Hydrologie Science de l'Eau, Institut des Sciences et Industries du Vivant et de l'Environnement AgroParisTech, 2010. English. ⟨tel-02594606⟩

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