| Subsurface containment for environmental applications has received widespread attention as possible alternative to conventional remediation. Containment systems commonly consist of vertical barriers surrounding the area containing hazardous material. In this study, contaminant transport models are developed and tested for the analysis and design of vertical barriers. These models are developed for diffusion-dominated transport through low-permeability vertical barriers and advection-dominated transport through permeable reactive barriers. A generalized boundary framework is proposed and evaluated for both field and laboratory columns for diffusion dominated transport. Also, analytical and semi-analytical solutions are presented for transport of sequentially decaying contaminants influenced by nonequilibrium sorption. The developed solutions are used to simulate the migration of TCE and its reaction products in a zero-valent iron permeable treatment wall.; Model testing was conducted by performing a series of batch isotherm and column transport experiments. Column transport experiments were conducted using flexible wall permeameters to investigate diffusion-dominated transport through low-permeability media. Two types of barrier media were employed: (1) soil bentonite, and (2) soil bentonite modified with natural humus. It is shown that for vertical barriers constructed of soil bentonite matrix, the solute effective molecular diffusion coefficients reduce by a factor between 3–5 from their corresponding aqueous diffusion coefficients. Also, it is shown that the effective partitioning of organic contaminants in the flow-through soil bentonite matrices is significantly lower than that measured in batch isotherm experiments. Finally, it is shown that the addition of natural humus to increase the sorption capacity of the resulting soil bentonite matrix may significantly hinder the contaminant fluxes exiting the vertical barriers. |
