Testing the PEARL model in the Netherlands and Sweden

The Plant Protection Product Directive (91/414/EEC) stresses the need of validated models to calculate predicted environmental concentrations. The use of models has become an unavoidable step before pesticide registration. In this context, the European Commission set up a FOrum for the Co-ordination of pesticide fate models and their USe (FOCUS). The main topic of research presented here is the validation of the PEARL model for two well-instrumented sites located in the Netherlands and Sweden. First the water transport module was calibrated, and then the solute transport module, using tracer measurements keeping unchanged the water transport parameters. The Vredepeel site is characterised by a sandy soil. PEARL predictions were very satisfactory for both soil moisture content, ground water level with efficiencies of 0.82 for soil moisture. Predictions for the tracer and pesticide concentration in the soil profile were quite successful with efficiencies ranging from 0.56 to 0.94. The Lanna site is characterised by a structured clay soil. PEARL was successful in predicting soil moisture profiles and the draining water, with efficiencies of 0.81 and 0.2. PEARL performed well in predicting the soil concentration of bentazone at different depths (efficiency of 0.52).