Leaching of Metolachlor, Atrazine, and Atrazine Metabolites into Groundwater

A three-year field study was undertaken between 1988 and 1990 to investigate the leaching of metolachlor, atrazine and two of its N-dealkylated products, deethylatrazine and deisopropylatrazine, into the groundwater zone of two agricultural soils of Eastern Canada, a St-Amable sand and a St-Laurent clay. Atrazine and its N-dealkylated metabolites were found in the groundwater regime of both soils in all three years while metolachlor was detected in 1990 only. Herbicide and/or metabolite concentrations were usually higher in the groundwater of the loam than the sand field due to a restricting clay layer at shallow depths in the latter field.