Effects of vapor extraction on contaminant flux to atmosphere and ground water

Numerical simulations were used to evaluate the effects of vapor extraction operations on contaminant loadings to the atmosphere, the ground water, and to the vapor extraction well under application of vapor extraction. A two-dimensional numerical model for simulating migration of a volatile contaminant partitioned between the nonaqueous phase liquid, air, water, and solid phases in the unsaturated zone was developed and used in this study. The model was based on an explicit finite difference scheme. The sensitivity of vapor extraction efficiency and contaminant migration to system parameters was investigated. Results from model simulations show that well vacuum, nonaqueous phase liquid-air mass transfer rate, and inhomogeneities in soil air conductivity have a significant influence on contaminant flux and the time required for contaminant removal. Contaminant loadings to the atmosphere and ground water were strongly dependent on well vacuum and soil air conductivity, but were almost independent on nonaqueous phase liquid-air mass transfer rate.