CONVECTION, DISPERSION, AND INTERFACIAL TRANSPORT OF CONTAMINANTS - HOMOGENEOUS POROUS-MEDIA

The assumption of local mass equilibrium for describing the transport of a contaminant in an aquifer containing a trapped non-aqueous-phase liquid has been under investigation for the past decade. Laboratory and field studies have shown that this assumption fails under certain circumstances, and heuristic macroscopic models have been introduced to describe the dispersion process when the assumption of local mass equilibrium is removed from the analysis. In this paper, a macroscopic model is developed for homogeneous porous media using the method of local volume averaging. The resulting macroscopic equation involves a dispersion tenser that is influenced by the mass transfer process, additional convective transport terms, and a linear form for the interfacial mass flux. Two local closure problems are provided that allow one to compute the effective transport coefficients so that theory and experiment can be compared in the absence of adjustable parameters. Numerical methods are used to solve the two local closure problems, and preliminary results are presented for two-dimensional, spatially periodic models of porous media.