Review: Behavior of organic chemicals at soil, air, water interfaces as related to predicting the transport and volatilization of organic pollutants

Abstract

Abstract The transfer of organic pollutants into the atmosphere is discussed from the standpoint of mechanisms involved, factors influencing rates of volatilization, and progress in developing models for predicting transfer rates. The volatilization rate of soil-incorporated chemicals is controlled by vapor pressure of the chemical in soil and by its rate of movement to the soil surface by diffusion or by a combination of diffusion and convection in evaporating water. Vapor pressures of organic chemicals are greatly decreased by their interaction with soil mainly due to adsorption. The magnitude of the adsorption effect depends upon the nature of the chemical, its concentration, the soil water content and soil properties, such as organic matter and clay content. Vaporization of chemicals in soil or from disposal sites covered with soil can be estimated from considerations of the physical and chemical factors controlling concentrations at the soil surface and most models developed to estimate volatilization rates are based upon equations describing the rate of movement of the chemical to the soil surface by diffusion and/or convection. Considerable progress has been made in developing laboratory based models for predicting volatilization from soil. Since volatilization of soil-incorporated chemicals is controlled mainly by factors within the soil, predictions from laboratory based mathematical models should be sufficiently accurate for many purposes.