Pore Geometry Effect on Gaseous Diffusion and Convective Fluid Flow in Soils

In order to better manage and monitor fluid flow and migration of chemicals in gas and liquid phases, a fundamental understanding and knowledge of the saturation dependency of permeability, diffusion and electrical conductivity in a porous medium is required. The initial fundamental formulations and recent research for characterization of transport properties in porous media are discussed. To improve the predictive capability of transport models, physically based formulations that include understanding of the control of pore continuity and tortuosity (TC ) on transport are proposed. To understand the pore geometry effects of tortuosity and connectivity on the various considered transport processes, the fluid saturation dependency of hydraulic conductivity, air conductivity, gaseous diffusion and bulk soil electrical conductivity was measured for two different soils. While assuming that soils can be characterized by a lognormal pore size distribution function, simultaneous fitting of all 4 transport coefficients to measured data showed that the TC parameter of each transport coefficient is different. Specifically, the value of TC parameters for air conductivity and gaseous diffusion are much higher than for soil hydraulic conductivity. For the bulk soil electrical conductivity, the TC parameters are similar to parameters of gaseous diffusion when they are represented by term only. Furthermore, the contribution of both pore size distribution and tortuosityconnectivity is equally important for characterization of soil hydraulic. The moisture dependency of all 4-transport coefficients can be unique when normalized to their maximum measured values. TC Since natural soils are especially heterogeneous with soil properties varying in space and time, most uncertainty in the assessment of flow and transport processes in