Atrazine contamination of groundwaters in eastern France in relation to the hydrogeological properties of the agricultural land

In Alsace, groundwater contamination by atrazine has been studied on a seasonal basis at 6 sampling sites (5 groundwater wells and a river) covering an agricultural area of approximately 32 km2 where corn has been cultivated intensively for the previous 10 years. Three atrazine ‐ treated fields have also been analysed in order to follow the seasonal variations of the pesticide concentration in the soil following the annual treatment. During the three years of this study (May 1990 to August 1992), high atrazine concentrations (exceeding 0.2 μg 1‐1) were detected at all sites studied with higher concentrations present at the beginning of summer. Some of the sites were contaminated with atrazine at concentrations ranging from 250 μg 1‐1 to 1500 μg 1‐1. The contamination of a river, for which the main sources are groundwater and drainage water, by this herbicide reflects the events occurring in sub‐surface water. Atrazine concentrations reached 0.6 to 2.0 μg 1‐1 during the critical months (May to June) indicating that a river crossing an agricultural area has the capacity to transport large quantities of polluting atrazine which may consequently lead to the contamination of neighbouring lands. This 3 year study provides useful information concerning the persistence of atrazine in soil as well as studying the rate of groundwater contamination. The results demonstrate that a large amount of atrazine reaches groundwater a few days after spraying. Meteorological conditions, permeability of the treated soils and agricultural practices are the three major parameters which enhance water pollution by pesticides and prompt questions as to the danger of certain pesticides on vulnerable ecosystems.