CONVECTIVE-TRANSPORT OF GASES IN MOIST POROUS-MEDIA - EFFECT OF ABSORPTION, ADSORPTION, AND DIFFUSION IN SOIL AGGREGATES

The mass transport of volatile chemicals in porous media is of increasing interest due to efforts to remediate contaminated soil and groundwater. The convective movement of gaseous chemical species in porous media is influenced by absorption (partitioning) of the species in water that wets the surfaces of the soil particles. Four different mathematical models based on chromatographic systems are herein proposed and compared to describe the convection, dispersion, and mass transfer of the species in the voids of the porous medium and into the water. Adsorption-desorption at the liquid-solid interface is included. Mean retention time and concentration band variance (first and second moments) are compared for four models. The major influence on transport is retardation and band broadening due to the total capacity of the porous medium for the volatile chemical (in voids, in water films, and adsorbed at the water-solid interfaces). The relative influence of the different transport processes is assessed.