Based on the theory of fluid flow in porous media and solute transport

a coupled dynamic mathematical model of migration of volatile organic compounds (VOC) in the unsaturated soil was established. The solution of the coupled equations was accomplished by using the finite difference method. The numerical model was used to predict the temporal and spatial distribution of VOC concentrations under the conditions of soil vapor extraction. The model solutions were compared to experiment values. Results showed that there was an obvious decrease both in the concentration and in the range of presence of volatile organic compounds during the period of soil vapor extraction. Soil vapor extraction had a large impact on VOC concentrations at the early stage

with reasonable agreement between model numerical solution and measured data

which provided a quantitative verification of the model. The theoretical and technical principles were provided for engineering design of soil vapor extraction system and for environmental prediction of vapor migration.