Numerical Modeling Study to Evaluate the Significance of Vadose Zone Diffusion and Biodegradation of Hydrocarbon Compounds (Abstract)

摘要

The influence of vapor-phase diffusion and aerobic biodegradation, two important processes controlling the fate and transport of petroleum hydrocarbon compounds in the vadose zone, are evaluated within the context of the subsurface vapor transport to indoor air pathway. The objective of this study is to evaluate the relative importance of these processes for different contamination scenarios using a one-dimensional numerical model for diffusion and first- and zero-order aerobic biodegradation. The influence of variable moisture saturation within the capillary transition zone is evaluated through a fine model- grid discretization of the moisture content profile predicted from the Van Genuchten water retention model and curve-fitting parameters by Schaap and Leij. The flux and vertical concentration profile is simulated for several generalized scenarios consisting of gasoline and diesel contamination sources, two soil types (sand and loam), dissolved hydrocarbon in groundwater and non aqueous phase liquid (NAPL) contamination sce- narios, and biodegradation and no biodegradation cases.