Sequestration of veterinary medicines in soils

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The results of the first phase suggested that there is a residual fraction which controls the sequestration and thus the fate of SDZ and its OH metabolite in soil in the long-term run (>7 months). It has been hypothesized that this sequestration is controlled by diffusion and should thus be reversible, whereas N-Ac SDZ is not sequestered in significant amount due to its fast degradation and blocking of the amino group. Up to now, all experiments have been performed using homogenized soil in the absence of plants. The objectives of this second phase are therefore (i) to elucidate the sorption and sequestration of the individual SDZ metabolites as required by the central model, (ii) to evaluate the sorption/sequestration mechanisms responsible for the formation of a residual fraction in soil, (iii) to test the hypothesis that SDZ and its OH-metabolite may be re-mobilized from this residual fraction and thus induce effects in soil in the long-term, and (iv) to elucidate the role of the rhizosphere and field conditions for the sequestration dynamics of both SDZ and DIF in the central mesocosm and field experiments.