Contribution of Land Runoff to the Release of Pesticides into Water Bodies in Arable Areas

The release of micropollutants into surface water bodies may be due to different pathways, including wastewater treatment plant effluent, combined sewer overflows and surface runoff. Many studies have dealt with the chemical characteristics of the first two types, whereas less attention has been paid to those of surface runoff in agricultural areas. Pesticides are the main micropollutants occurring in this stream and their impact on the receiving water body may be of great concern. In this context, the current chapter aims to provide a snapshot of the occurrence of common pesticides in the runoff of arable land and it discusses the main factors affecting their fate and behaviour once in the soil. Collected measured concentrations are compared with the corresponding predicted-no-effect concentrations in order to evaluate the potential risk due to surface runoff release into the receiving water body. It also presents some best practices that aim to mitigate their migration towards surface water. The chapter concludes with a focus on the main pesticides found in surface and groundwater in Italy, in particular in the Po Valley, and on the environmental risk posed by residues of a selection of pesticides in the surface water in two Spanish regions.