Diffusion of Sorbing Organic Chemicals in the Liquid and Gaseous Phases of Repacked Soil

Transport models for sorbing organic chemicals in soil require accurate predictions of the diffusion and sorption processes in both the liquid and gaseous phases. In this study, the ability of recently‐presented diffusivity models in combination with equilibrium sorption models to predict the effective (i.e., including sorption effects) diffusion coefficient, Deff, as a function of soil‐water content, θ, is tested for different sorbing organic chemicals in different soils. The water‐induced linear reduction (WLR) gas diffusivity model, combined with a two‐component (hydrophobic and vapor) equilibrium sorption model, well described short‐term ( 700 h. Consequently, an increasing KD value with time was required in the DATES model to obtain successful Deff(θ) predictions. Since chemical‐soil contact time and adsorption‐desorption history typically vary in each compartment of a soil profile, transport models, including sorption kinetics, will become very complex and DATES with a time‐dependent KD relation may represent a useful model alternative.