Abstract

Pesticide sales have held steady at about 500,000 t annually in the United States since the 1970s. Groundwater monitoring studies show that a small percent of a few compounds are actually being detected in the parts per billion range. The degradation and retention processes in soils determine the amounts and types of pesticides that leach into groundwater. The principal reactions that degrade pesticides in the environment occur primarily on or in soils. Soil microorganisms catalyze the enzymatic oxidation, reduction, and hydrolysis of most pesticides. Chemical reactions in soils yield many of the same products as the biochemical reactions mediated by soil microorganisms. Sorption processes bind pesticides and prevent movement either within or outside the soil matrix. Soil organic matter is the principal sorbent for most organic pesticides. Pesticides are sorbed to soil particles by van der Waals forces, hydrogen bonding, dipole–dipole interactions, ion exchange, and covalent bonding mechanisms. Development of new active pesticides, biotechnology, sustainable agricultural practices, and evolving regulations will lower the future amounts of pesticides detected in soil and water.