Distribution and transport of abiotic & volatile pollutants in wetting and drying unsatuated soil

Abstract

A vertically one dimensional segment model (DATPUS) was developed for the prediction of equilibrium distribution and transport of pollutants in unsaturated soil zone during the water infiltration and drainage. The change of water content in soil profile was estimated using the method of characteristic on the kinematic unsaturated flow equation, and this was utilized for the estimation of mobile phase movement of soil water and soil air between segments and through boundaries of the atmosphere and the aquifer. Developed model of pollutant equilbrium distribution among soil grain (immobile phase), soil water, and soil air that can accommodate the effect of soil water content and temperature change was combined with above continuities at each segment through time steps. As the representative priority organic pollutant, nonbiodegradable, volatile, an toxic solvents of dichloromethane (DCM) and 1,1,1-trichloroethane (TCE) were studied experimentally and simulated in sandy soil and silt-clay mixture at 4, 20, and $40\,^\circ\!C$ s. The quantitative result showed that much severe soil pollution at lower temperatures, deeper DCM plume development in unsaturated soil than TCE, and thousand times higher DCM flux into groundwater as a pollution potential.