PREDICTING THE EFFECT OF MOISTURE ON VAPOR-PHASE SORPTION OF VOLATILEORGANIC-COMPOUNDS TO SOILS

Sorption from the vapor phase is an important factor controlling the t ransport of volatile organic compounds (VOCs) in the unsaturated zone. Accurate description of sorption from the vapor phase to soil in the unsaturated zone therefore is intrinsic to predicting the ultimate fat e of contaminants. Vapor-phase sorption of several VOCs onto seven soi ls at oven-dried, air-dried, typical field moisture and water-saturate d conditions was measured using a batch-equilibrium headspace method, An equilibrium partitioning model was developed to predict the effect of soil moisture content on vapor-phase sorption, The model was based on the soil pore-size distribution and BET isotherm sorption parameter s under oven-dried and water-saturated conditions. The model was shown to accurately predict observed experimental results.