Measurement of selected pesticides and their impact on surface water in a research catchment

Results are reported of a field-scale project over several years to measure presence of pesticides in surface water as caused by regular agricultural practice. The catchment area covers the requirements for carrying out post- registration monitoring studies with regard to size, slope, relevant croppi ng, soil type, run-off triggering precipitation, and immediately neighbouri ng running waterbodies (streams and ditches). An example is given for the d etection of selected active ingredients (a.i) in surface water applied in t he main crops (sugar beet and cereals), which were collected via an automat ic sampling system. Under the conditions encountered during the project (e. g., strong precipitation immediately after pesticide application) all selec ted herbicides (isoproturon and diflufenican in cereals, metamitron, phenme dipham and ethofumesate in sugar beet) could be detected. Maximum concentra tions of up to 30 mu g/l were measured in 1998. Most detections of single p esticides were in the concentration range 0.1 to 1.0 mu g/l.