ABSTRACT
ABSTRACT: Modelling is an effective tool for investigating leaching potential and groundwater contamination from non-point source pollutants. The aim of this study was to evaluate the most important factors that determine the leaching of 10 pesticides using the VLEACH model. A sensitivity analysis was carried out by varying inputs of hydrogeological properties (groundwater depth and recharge rate), management (application rate and depth of pesticide incorporation into the soil), pesticide properties (organic carbon partitioning coefficient) and properties for two typical soils (organic carbon content, bulk density, porosity and volumetric water content) of the Western Cape, South Africa. The leaching rate peaks and time required to reach these peaks were simulated after once-off pesticide application to the soil surface at the beginning of the simulation. Based on the simulations with VLEACH, the major factors affecting pesticide leaching are depth to groundwater, recharge, application rates, pesticide properties, particularly the organic carbonpartitioning coefficient, and soil organic matter content. Although the VLEACH model does not simulate pesticide degradation, it could be used for a comparative assessment and preliminary studies of the fate of contaminants.
