Modelling fate and transport of pesticides: the case study of the contamination in Valencia aquifers.

Predicting the fate of pesticides released into the natural environment is necessary to anticipate and minimize adverse effects far from the contamination source. These effects arise due to the movement of pesticides in surface water and can take place via drift, surface runoff and subsurface flow. A number of models have been developed to predict the behavior, mobility, and persistence of pesticides. These models should account for key hydrological processes, such as crop growth, pesticide application, transformation processes and field management practices.

In this work, Pesticide Water Calculator PWC model developed by the U.S. Environmental Protection Agency (USEPA) is applied to simulate the fate and transport of pesticides in the unsaturated zone of an aquifer. The model is used to estimate the daily concentrations of pesticides in the Valencia aquifers (Spain). In these aquifers, pesticide concentration values have been found to be greater than the Maximum Concentration Levels (MCLs) established by Spanish Legislation.

The simulations carried out in this work address different environmental scenarios and include a sensitivity analysis of the parameters used in the model. Results of the PWC model provide a crucial first step towards the development of pesticide risk assessment in Valencia region. Results also show that numerical simulation is a valid tool for the analysis and prediction of the fate and transport of pollutants in soil and groundwater.