Occurrence of pesticides in Danish shallow ground water.

Shallow ground water from four different catchment areas, two sandy and two clayey locations, were investigated for content of pesticides and -degradation products. The samples were taken from screens in extraction wells placed from 1.5 to 5 meters below surface 46 different compounds were included in the study, and the analysis were performed with liquid chromatography mass spectrometry (LC-MS) with detection limits below 0.01 microgram/L. In total more than 300 samples were analysed and the most frequently found compounds being atrazine and its degradation products, bentazone, MCPA, metamitron, isoproturon and simazine. 23 out of the 46 compounds were detected in one or more samples. Four different sulfonylurea herbicides were included in the study as they to some extent have substituted phenoxyacid herbicides in agricultural practice and in much lower dosage. Sulfonylurea herbicides did not occur in any samples.