Chapter 11 - Estimation of the Volatilization of Organic Chemicals from Soil

Abstract

This chapter presents various models for estimating the volatilization of organic chemicals from the soil surface. Volatilization is a process by which a compound evaporates into the atmosphere from another environmental compartment. When the compartment from which a compound evaporates is soil, volatilization can be the most important mechanism for the loss of chemicals from it and their transfer to the air. The volatilization rate from a surface deposit depends on the rate of movement of the chemical away from the evaporating surface and its vapor pressure. Models developed for estimating volatilization rates are based on equations describing the rate of movement of the chemical to the surface by diffusion and/or by convection and away from the surface through the air boundary layer by diffusion. For estimating the rate of volatilization from a soil surface, two simple methods can be used: the so-called Dow method developed by the scientists of the Dow Chemical company and the one developed by Voutsas et al. The Dow method is a very simple and fast method for estimating the half-life of the depletion of an organic chemical from the soil surface. Voutsas et al. examined several simple correlations for estimating the half-life of the depletion of an organic chemical from a soil surface to air. For wet soils, Voutsas et al. proposed two models. The first model requires the knowledge of the soil/organic carbon partition coefficient and the Henry's law constant, and the second model requires the vapor pressure of the chemical involved. For dry soils, Voutsas et al. presented similar expressions such as those for wet soils.