Low-permeability zones such as silt and clay layers in the subsurface can serve as indirect, low-level sources of contamination to transmissive zones as a result of matrix diffusion. Matrix diffusion has the potential to sustain dissolved contaminant concentrations in groundwater after the source is removed or after remediation removes or isolates contamination from transmissive compartments. This persistent contaminant concentration can occur in the source zone or the downgradient plume.
The Matrix Diffusion Tool Kit equips the groundwater community with practical models and tools for evaluating matrix diffusion effects. Based on the Microsoft Excel® platform, the tool kit can be used to develop site conceptual models, support site characterization efforts, plan remedial designs, and determine if matrix diffusion will affect remediation goals for groundwater sites. The Matrix Diffusion Tool Kit uses a simplified conceptual model of a two-layer aquifer system to estimate mass discharge in the transmissive zone and contaminant mass in the low-permeability zone.
The User’s Manual details the tools provided to calculate and evaluate matrix diffusion effects. It includes a discussion of key parameters built into the tool kit and addresses frequently asked questions related to matrix diffusion. The Project Summary Presentation provides an overview of the tool kit.