The Mobility of Pesticides in Soil — Studies to Prevent Groundwater Contamination

Abstract

Extensive studies on the fate of pesticides in surface soils have been conducted for many years but, until recently, little has been done to understand the behaviour of these compounds beyond the root zone. However, concerns about the risks posed by residues of pesticides in ground and surface waters have stimulated research and there are recent studies which clearly indicate the potential for microbial degradation at considerable depth. Small, but significant, populations of microorganisms have been detected at all points of the soil profile down to, and beyond the water table and there is increasing evidence that these are able to degrade a range of compounds, including pesticides. Degradation rates are usually low compared to surface soils, but they can be sufficient, in view of the long residence times involved, to reduce significantly the concentrations of pesticide residues in ground waters. However, further work is needed if we are to develop a full understanding of the microbial ecology of the subsurface environment and the mechanisms of associated xenobiotic degradation. Only if we are successful in this, we will be able to predict the mobility of pesticide residues with confidence and retain the flexible use of pesticides without jeopardising our water reserves.