Quelques aspects hydrologiques des transferts de solutés par infiltration vers les nappes : nitrates et phytosanitaires

Some hydrologie aspects of solutes transport by infiltration towards the aquifers: nitrates and pesticides

¹ Service Géologique National, BRGM
² Direction de la Recherche, BRGM

Abstract

The contamination of groundwater by substances, mainly nitrates and pesticides, resulting from agricultural activities depends on three essential factors:

- the physical characteristics of the aquifer system: these characteristics play a major role in protecting the groundwater against pollutants (attenuation) and/or in postponing the outbreak of the contamination (delay);

- the intensity and mode of groundwater recharge: the infiltrating water is the transfer vector of contaminants towards the groundwater;

- the quantities of solutes available for infiltration towards the groundwater, i.e. the quantities not retained by the soil/plant/microorganism system. The paper presents some major characteristics of the main types of aquifer in France, notably with regard to pollution vulnerability, and data on the spatial variability and quantitative importance of infiltration, a mechanism that plays a key role in the pollutant concentrations likely to be reached in the groundwater.