PESTICIDE CONTAMINATION OF WATER-RESOURCES - A CASE-STUDY - THE RIVERS IN THE PARIS REGION

For a number of years, the Compagnie Generale des Eaux has been studyi ng pesticide contamination of surface water in order to better underst and the origins and the main transfer mechanisms of these pollutants i nto water resources. Sampling campaigns are being carried out on the t hree main rivers of the Paris area to monitor a number of products fro m the triazine and urea families. This monitoring has confirmed the ex tension of agricultural non-point source pollution. The products being sought are present in the three rivers and, in most cases, in signifi cant concentrations. Atrazine is the most important contaminant. Measu red concentrations exceed the value of 100 ng/l most of the time, thus proving that the aquifers drained by the three rivers are contaminate d. For a period of several months every year, concentrations approachi ng 1000 ng/l are observed in all the catchment areas being studied. Th ese are the result of rapid transfers of atrazine in run-off water. Th is surface run-off transfer mode also seems to be applicable to the ur eas found in surface water, especially during the periods when the pro ducts are used to treat crops. These works underline the complexity of agricultural non-point source pollution phenomena. They permit the id entification of the predominant mechanisms operating in the transfer o f the products. This is the first step towards setting up preventive m easures and developing pollution forecasting tools. Copyright (C) 1996 IAWQ.