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. The main topic of the 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, keeping unchanged the water transport parameters. The Dutch site is characterised by a sandy soil. PEARL predictions were very satisfactory for both soil moisture content and groundwater level. Predictions for the tracer, bentazone and ethoprophos concentrations in the soil profile were also successful. The Swedish site is characterised by a structured clay soil. PEARL was successful in predicting soil moisture profiles and the draining water. PEARL performed well in predicting the soil concentration of bentazone at different depths, however, it did not predict accurately solute concentration in the drainage water. A sensitivity analysis of the PEARL model performed on the Swedish site showed the greater importance of the pesticide degradation properties over the soil hydraulic properties.