TRANSPORT OF ORGANIC-CHEMICALS BY GAS ADVECTION IN STRUCTURED OR HETEROGENEOUS POROUS-MEDIA - DEVELOPMENT OF A MODEL AND APPLICATION TO COLUMN EXPERIMENTS

The use of soil venting or vacuum extraction for remediation of contaminated soil has lead to an increased interest in modeling gas-phase processes. The majority of existing transport models have been developed assuming homogeneous porous media properties. It is well known, however, that the assumption of homogeneity will almost always be invalid for field systems. In addition, sorption has been described using the local equilibrium assumption. This assumption has also been shown to be invalid under certain conditions. A one-dimensional model is presented that accounts for a structured or heterogeneous porous medium and for rate-limited sorption. The model is designed for cases where transport occurs by advection and dispersion in the gas phase and where the liquid phase is immobile. A sensitivity analysis is presented, and parameter determination is discussed. The performance of the model was evaluated by comparing predicted simulations to data obtained from the literature. The model performed well, especially considering that the values for all input parameters were obtained independent of curve fitting.