Dynamique de transfert des produits phytosanitaires vers les eaux superficielles : de l'étude de terrain à l'approche modélisatrice

Abstract : Pesticides applied for agricultural purposes can generate a non-point source pollution of surface and ground water. The objectiv of this study was to understand the effects of soil structure, pesticide physicochemical properties and climate conditions on pesticide transfer. Experimentation was carried out after an herbicide application in spring on a field drained plot gathering two soil types (leached brown soil and pelosol). Measurements of pesticide contents in drain water and in the plough layer, together with studies of the sorption capacities of herbicides, suggested the occurrence of two ways for chemical transport : preferential flow and matrix flow. Both fluxes were dependent on the soil structural state, varying with time. Application of a water tracer (bromide) and of herbicides with different properties on soil cores filled wth calibrated aggregate sizes and watered with irrigation of variable intensities confirmed the effects of soil structure on chemical transfer and highlighted its dependency with rain intensity. The magnitude of exportations by matrix or preferential flow was not only dependant on the soil retention properties but also on the chemical localisation in the porous medium. These both approaches were completed with the use of AgriFlux, a mathematical model simulating pesticide fate. Water balance evaluated at the field and bromide losses in drain water were weil simulated. The simulation of metolachlor losses gave evidence for the inadequacy of the fast instantaneous sorption to describe the herbicide retention at the field scale. The integration of slow immobilisation processes yielded a better agreement between simulated and measured losses.
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Theses
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http://docnum.univ-lorraine.fr/prive/SCD_T_1999_0126_NOVAK.pdf
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Sandra Novak. Dynamique de transfert des produits phytosanitaires vers les eaux superficielles : de l'étude de terrain à l'approche modélisatrice. Sciences de la Terre. Université Henri Poincaré - Nancy 1, 1999. Français. ⟨NNT : 1999NAN10126⟩. ⟨tel-01747081⟩

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