Field Study of Atrazine Contamination of Groundwater in Dane County, Wisconsin

Introduction: This report examines the occurrence of atrazine, an agricultural herbicide, and other herbicides and pesticides in groundwater in western Dane County, Wisconsin. Atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) is currently the most widely used herbicide in Wisconsin and the United States (Wehtje and others, 1983). In Wisconsin, atrazine is used to control annual broadleaf and grassy weeds in corn and sorghum, and, in 1985, was applied to 77% of all Wisconsin corn fields (Chesters and others, 1991). In soils and groundwater the parent atrazine compound degrades to two toxicologically significant metabolites, desisoproplyated atrazine and desethylated atrazine. Chesters and others (1991) summarize the chemistry of these two compounds. The current drinking water standards for atrazine in Wisconsin are an enforcement standard (ES) of 3.0 ng/l and a preventive action limit (PAL) of 0.3 ug/l (Chapter NR 140, Wisconsin Administrative Code). These two standards are based on the sum of the parent atrazine concentration plus the concentrations of the two atrazine metabolites.