ORGANIC RESIDUES IN SOILS - MECHANISMS OF RETENTION AND EXTRACTABILITY

Retention of pesticides and related organic chemicals by the soil is an important process that affects the fate of these chemicals in the environment. Although a number of binding mechanisms have been postulated for the retention of these chemicals in the soil, few experimental methods are available to characterize the specific bonds involved in the retention process. Common indices used to depict soil sorption of pesticides are of limited value to elucidate the bonding mechanisms or bond strengths. This paper discusses the potential of using the solvent extraction procedure to gain an insight on the binding mechanisms. It can be demonstrated that the solvent action during an extraction is specific in removing a portion of the chemical which is presumably held by similar bonds in the soil. Examples of efficient extraction of chemicals held by ion exchange, hydrogen bonding, and metal complexation are given to illustrate this potential. © 1990 Gordon and Breach, Science Publishers, Inc.