Monitoring And Modelling Pesticide Dynamics In Surface Water.

Pesticides occur frequently in surface water. We used a combination of monitoring and modelling to assess the fate of pesticides at the catchmentscale. We continuously (sampling interval of eight hours) monitored eight pesticides (atrazine, carbendazim, chloridazon, diuron, isoproturon, lenacil and simazine) in surface water of two Belgian catchments. The surface water showed hourly variations in pesticide concentrations, temporarily exceeding ecotoxicological thresholds. We used the SWAT model to predict hydrology and pesticide fluxes from agricultural land to the river at the catchment scale. In addition, we used an extended version of the RWQM1 model to calculate inriver transformation of pesticides. The models adequately reconstructed the highly dynamic behaviour of the pesticides in the river. The simulations further demonstrated the importance of point sources due to poor agricultural practices and the effectiveness of measures to reduce pesticide inputs into surface water. [ABSTRACT FROM AUTHOR]