Aggregate diffusion model applied to soil vapor extraction in unidirectional and radial flows

Abstract

An aggregate diffusion model for soil vapor extraction is applied in this paper. The model accounts for the diffusion within water- saturated aggregates and convective diffusion in air-filled macropores. Focusing only on the dominant and measurable mechanisms, we represent the kinetic term for the gas aggregate exchange by a convolution integral. The nondimensional transport equation involves only three basic parameters: (1) Peclet number, (2) ratio of advection time to aggregate diffusion time, and (3) ratio of mass within aggregate to mass in gas. Two examples of soil vapor extraction based on the model are studied. The first problem is concerned with vapor transport in a one-dimensional column, and the theory is compared with published experiments. The second example deals with vapor extraction by a well centered at a radially symmetric contaminated zone. Effects of the physical parameters on contaminant removal are discussed.