Interpretation of data on pesticide residues in surface water in France, by grouping data within homogeneous spatial units

摘要

In France, the SOeS? manages a database which contains more than eight million analyses of pesticide concentrations in surface water. In order to interpret these analyses better, we tested methods based on a geographic grouping of data within homogeneous units, the hydro-ecoregions (HER). Our objectives were to find suitable descriptors and methods, and test them in order to describe the contamination and highlight explanatory factors. In the case of the examples studied, calculating the 90th percentile of analysis results for each 15-day period allowed us to identify the seasonal and inter-annual contamination patterns associated with the analytes. We observed differences between regions and years, which are consistent with the agricultural use of pesticides (application period and registration). Moreover, differences in contamination levels between areas and products can be partly explained by the type of crop on which the products are applied.