Les nitrates : origine et impact sur le milieu

Origins, evolution and impact of nitrates

Agence de l'Eau, Loire-Bretagne

Abstract

Nitrates, an oxidized from of nitrogen, when found in water can have a natural origin. They could also be linked to human activity (industrial, domestic, agricultural). Nitrates carried out to the natural environment are mostly diffuse and in weak quantity as compared to the amounts at stake or stored in the soil. The transfer time towards water is quite varied according to the milieu: it may be of some days or some months. It might as well reach several decades at times. Nitrates, although they are essential to the working of aquatic ecosystems, whenever in excess may entail eutrophication on the sea shore (proliferation of algae). Furthermore, when they exceed 50 mg per liter, surface water can no longer be wed for water supply because water used for domestic water supply must not be over 50 mg per liter, whatever its origin. All this leads to important environmental costs for the community, particularly as far as water supply treatment is concerned.