CRA-W's Committee of Intervention : analyse of catchments polluted with pesticide

In the Walloon Region of Belgium, a commlttee of Intervention has been created to
Investigate problems of pesticide contamination of various catchments use for drinking water production. This commlttee Involves the Agricultural Research centre - Wallonla (CRA-W, project coordinator) and sorne University experts. It ls funded by the Société Publique de Gestion des Eaux (SPGE). The diagnosis method, base on the AQUAPLAlNE method (Arvalis - France), conslsts of 4 steps. The first step Is the preparation of diagnosls (at the office) that takes into account the paper r1sk of active ingredients. and thelr uses, the identification of the
agrtcultural parcels, the collection of cartographie and numeric data, the description of the hydrogeological and pedological contexts and the study of the meteorologlcal data ln relation with the period of pollution. The second step conslsts of maklng a plot diagnosls (on the field) ta Identify the way of transfer inside the plot and collecting data. At the thlrd step, the people who can apply ppp treatment close to the catchment are met (farmers and city services). Information are coJ!ected on treatments applied and on the state of parcels. Based on the hypathesls of pollution cause, the committee proposes solution to solve the problem. One of the catchment that has been investigated by the commlttee is located at Biesmerée, (Namur province, ln Belglum). A temporally contamination was caused by 4 pesticides: chlortoluron, isoproturon, trifluralln and diflufenlcan. After Investigations, it seems that the pollution was probably due ta the hydrogeologlcal context . As the river Is locally perched over the aqulfer, the presence of Poly-aromatic hydrocarbons (PAHs) could be due ta the Infiltration of surface water inside the catchment or/and to the presence of a sinkhole temparaHy activated durlng river flood period. Infiltration rate has ta be assessed and river bank Impermeabilization Is recommended