Origine et devenir des produits phytosanitaires

Origin and Fate of pesticides

Laboratoire Sols et Environnement, ENSAIA/INRA

Abstract

Both agricultural practices and biophysicochemical properties of soils and chemicals play a significant part in the fate of pesticides in the environment.

A few farming types occupy the major area of cultivated lands. Due to their particular efficiency, some active ingredients are systematically used to protect these crop systems. As a consequence, soil ability to degrade or retain these pesticides should be insufficient. However, excess amounts of pesticides in soil are not the only cause of pollution.

The biocidal activity of these chemicals implies that they are available for living organisms, so that they are not strongly retained to soil and that they can enter the soil solution. As a consequence, pesticides in solution are potentially carried away by water movement. Yet retention of pesticides by soil components changes with time and should lead, at least temporally, to non-available residues. Pesticide residues strongly sorbed to soil could then move along with soil particles or be released when organic material is reorganized during humification processes. In that case, pesticide residues are liable to be responsible for non-point pollution.

Fate of pesticide in soil is also determined by biological decomposition. Degradation processes may lead to the disappearing of parent compound and to the formation of degradation products, which could temporally accumulate in soils. So, biodegradation may result in a more diversified environmental pollution.