In most cases a period of high recovery has been followed by a sustained period of low recovery. This behavior has been attributed to multiple processes including slow interphase mass transfer, retarded vapor phase transport, and diffusion from unswept zones of low permeability. Imaging results will be used in conjunction with innovative modeling techniques to develop spatially and temporally dependent constitutive relations that describe the transient distribution of phases inside a column experiment. These constitutive relations will be incorporated into a site-scale transport model to evaluate how the different processes affect SVE performance in practical applications. Thomas Willingham Fine-grained soils are widely used to impede the migration of chemicals contained in leachate waste containment facilities.
Chemicals migrate through soil as a result of both advection and diffusion.
Advective transport is modeled with Darcy's law in which hydraulic conductivity controls the rate of transport. Diffusion is modeled with Fick's law, with an effective diffusion coefficient controlling the rate of transport. Although hydraulic conductivity and the effective diffusion coefficient are treated as deterministic parameters, they vary spatially. The variability of hydraulic conductivity has been documented in both natural geologic settings and in man-made earthen barriers. However, no study has been undertaken to define the spatial variability of effective diffusion in soil.