Many pesticides and associated metabolites are frequently detected in soils and groundwater. Most of these substances are fully biodegradable in soil under controlled conditions in the laboratory. Under field conditions, limiting factors of pesticide degradation leading to pesticide persistence in soils remain largely unclear. This project aims to elucidate microbial and physicochemical controls of pesticide degradation by process-based modeling.
We will use gene-based biogeochemical models informed by genetic data to find improved process descriptions of pesticide degradation in soils. We will develop and apply spatially distributed models (1D-3D) to quantify the effect of the encounter/ separation between pesticide degraders and substrates on pesticide degradation at the small-scale. Model development will be done for the herbicides 2-methyl-4-chlorophenoxyacetic acid and atrazine1,2 based on the PECCAD model3,4. Sensitivity studies and scenario simulations will elucidate the impact of small-scale processes on pedon-scale pesticide degradation. This will guide deriving conceptual approaches to find improved up-scaled expressions for pesticide turnover applicable in larger-scale soil-crop models (e.g., Expert-N).