(602f) Development of an Analytical Modeling Framework for Matrix Diffusion in Multi-Layered Systems

Matrix diffusion is the process whereby a contaminated low-permeability geologic layer(s) acts as a long-term source to a higher permeability aquifer. A quantitative understanding of matrix diffusion processes is necessary to predict the long-term fate and transport of a wide variety of groundwater contaminants in subsurface environments that include clays or silts. In this work, a modeling framework for the analytical solution of the one-dimensional diffusion equation was developed to quantitatively describe matrix diffusion in multi-layered systems. The modeling framework was then applied to evaluate the potential long-term effects of matrix-diffusion at a field site contaminated with chlorinated hydrocarbons. Finally, an inverse model was constructed and applied to estimate historic contaminant loading with respect to time given measured vertical concentration profiles within a low-permeability formation. This framework has potential applications to groundwater contaminant fate and transport, remedial design, and environmental forensics.