An improved screening tool for predicting volatilization of pesticides applied to soils

Pesticide volatilization and vapor drift can have adverse effects on nontarget, sensitive ecosystems and human health. Four approaches for pesticide volatilization screening based on Fick's Law were investigated. In each approach, vapor pressures or environmentally relevant partition coefficients were used to describe pesticide behavior in an agricultural field system and to predict 24-h cumulative percentage volatilization (CPV(24h)) losses. The multiphase partitioning approach based on soil-air (K(soil-air)) and water-air (K(water-air)) partition coefficients was found to most accurately model literature-reported pesticide volatilization losses from soils. Results for this approach are displayed on chemical space diagrams for sets of hypothetical K(soil-air) and K(water-air) combinations under different temperature, relative humidity, and soil organic carbon conditions. The CPV(24h) increased with increasing temperature and relative humidity and with decreasing soil organic carbon content. Pesticides and the conditions under which the greatest volatilization losses exist were easily identified using this visual screening technique.