Risks assessment of water pollution by pesticides at local scale (PESTEAUX project): study of polluting pressure.

Pollution of water resources (surface waters and ground waters) by pesticide uses is one of the key point of the European policy with the implementation of the Water Frame Work Directive (2000/60/EC) and the thematic Strategy on the Sustainable use of pesticides. According to this legislation, the Member States must initiate measures to limit environmental and toxicological effects caused by pesticide uses. The Agricultural Research Centre of Wallonia (CRA-W) emphasized the need of a tool for spatial risk analysis and develOPs it within the framework of PESTEAUX project. The originality of the approach proposed by the CRA-W is to generate maps to identify the risk of pollution at locale scale (agricultural parcel). The risk will be assessed according to the study of different factors, grouped under 3 data's layers: polluting pressure, vulnerability of the physical environment (soil) and meteorological data. This approach is directly based on the risk's definition which takes into account the polluting pressure, linked to the human activities, and the vulnerability of the soil, defined by factors of physical environment which characterize the water flow in the parcel. Moreover, meteorological data influence the intensity and likelihood flow of water, and indirectly pesticide by leaching or runoff. The PESTEAUX's approach to study the pollution is based on the model "source-vector-target". The source is the polluting pressure, in other words, the pesticides which could reach the targets. The main vector is the water which vehicles the pesticide on and trough the soil until the target which are the surface waters or ground waters. In this paper we introduce the factors contributing to the polluting pressure. These factors are linking to the human activities and more precisely, to the pesticide uses. The factors considered have an influence on pesticide's transport by water (in its solid state or in dissolved state by leaching, run-off, or erosion) but also on a set of process controlling pesticide behavior in the environment such as degradation, sorption,....