Etat de la contamination du Bassin d'Arcachon par les insecticides et les herbicides sur la période 2005-2006. Impact environnemental

Within the framework of the study on cup oyster breeding in the Arcachon Basin (IFREMER's SURGIBA Programme, co-financed by Europe, the Regional Council of Aquitaine, the Regional Council of Gironde and the Arcachon Basin's inter-communal Syndicate), some pesticides have been researched in the main waterways and in the waters of several of the Basin's zones (Figure 1), during the summer months (June to September) from 1999 to 2003 inclusive (Auby and Maurer, 2004). The presence of a certain number of molecules, mainly from herbicides, was found in the waters and it has generally been possible to identify their source. Certain substances come from agricultural uses or park maintenance; others are from nautical sources (anti-fouling paint for protecting the fairing of boats). The concentrations of herbicides for agricultural use (especially atrazine, alachlorine, and metolachlorine) are in general rather low, especially because treatments using these molecules are mainly done during the spring. However, these analyses made it possible to highlight a few summer peaks of contamination, particularly in products whose use had recently been prohibited (neburon) or was about to be (terbuthylazine), probably indicating an unauthorised discharge of these products in certain waterways. As regards biocides from nautical sources (diuron and irgarol used in anti-fouling paints), contamination can be seen in the background during the major part of the summer.