Interaction of soil air permeability and soil vapor extraction

A new theoretical model to analyze the measurements obtained from a typical soil column venting experiment is proposed. The principles of mass transfe r, Darcy's law, and air compressibility in the form of pressure-volume rela tionships were coupled to calculate the contaminant concentration in the ga s phase lair), and the rate of contaminant removal. The proposed model rela tes soil air permeability with the contaminant removal and is capable of ca lculating the variation of soil air permeability with time during the venti ng process. The contaminated sand sample was idealized as a system of strai ght capillary tubes in the direction of flow, lined by the liquid contamina nt. A closed-form solution for radial diffusion of the contaminants in a cy linder coupled with axial advection of air, was used to model contaminant r emoval. The results from the mass transfer model were then used to trace th e change of soil air permeability with time. The model also uses, as aa alt ernative approach, a modified form of Darcy's law for compressible flow.