EXTENSION OF THE PORE TREE MODEL TO DESCRIBE TRANSPORT IN SOIL

The ''pore tree'' model of pore structure was originally developed for catalyst and sorbent grains to allow coupled reactions and diffusion into and out of nonpermeable porous media in the absence of convection through the media. The pore tree model is extended herein to describe the permeable pore structure which characterizes the subsurface trans port of gas and water in soil, the dispersion of contaminants, and in situ remediation. The interconnectivity of the pore structure is obtai ned via a statistical determination of the ''branches'' that are commo n to several trees to allow convection and diffusion through the large scale (permeable) structure in addition to diffusion and reactions in the smaller scale (nonpermeable) structure. The extended pore tree mo del has successfully explained measurement errors in the permeability of soil due to the measurement scale size and has successfully predict ed the bulk gaseous diffusivity in partially saturated soil as a funct ion of a saturation scale size. The extended pore tree model provides an analytic: description of the pore structure of soil upon which bulk transport, small scale diffusion, and coupled chemical reactions may be added to accurately describe contaminant transport and in situ reme diation.