Balancing the fate of terbuthylazine in a water catchment area by immunochemical screening

The extensive use of a Geographical Information System fed with analytical data gathered by immunoassays is described. The aim of the study is to eluc idate the entry paths of pesticides into surface waters. The study area is characterized by sandy soils and extensive cattle breeding. Terbuthylazine, a maize herbicide of the triazine type, was selected as a model substance. The judgement of the contribution of different paths was partly based on e valuation of thematic maps set up by a Geographical Information System (GIS ). The GIS was also used to achieve representative sampling, storage and ha ndling of data, calculations and display of spatial residue information. A time-saving and cost-effective screening method for soil samples has been a pplied consisting of an aqueous extraction step and immunochemical measurem ent (ELISA). It is shown that this approach yields adequate information to judge the contribution of different migration paths of the herbicide into s urface water.