GROUNDWATER CLEANUP BY IN-SITU SPARGING .7. VOLATILE ORGANIC-COMPOUNDS CONCENTRATION REBOUND CAUSED BY DIFFUSION AFTER SHUTDOWN

The sparging of aquifers contaminated with volatile organic compounds (VOCs) is examined by means of a mathematical model which includes the kinetics of solution of nonaqueous phase liquid (NAPL) droplets and o f diffusion of VOCs from porous layers of low permeability. The well c onfiguration is that of a single vertical well screened only near the bottom. The dependence of cleanup rates on model parameters (well dept h, air flow rate, NAPL droplet diameter, thickness of low-permeability structures, etc.) is reported. The rebound of VOC concentration in th e mobile aqueous phase after the sparging well is shut down is examine d. Model runs require only a few minutes of computer time on currently available microcomputers.