Transfer Function Model for Pollutant Breakthrough in Geomedia

Pollutant transport in soil and geologic materials has been evaluated to prevent contamination of groundwater reservoirs. The objective of this project was to use two transfer function models for predicting X-ray computed tomography-measured chemical breakthrough in columns. Breakthrough experiments were conducted using undisturbed cores taken from a field site. Application of the convection-dispersion model is more limited to homogeneous columns while the lognormal and convection-dispersion probability density function (pdf) transfer function models worked well for both heterogeneous as well as homogeneous columns. The parameters for travel time pdf were accurately estimated by the solute breakthrough time distributions when the resolution of the scan was 0.5 x 0.5 mm. However, group-pixel averages of 2.0 x 2.0 mm or 5.0 x 5.0 mm worked best to reduce fluctuations of CT scan numbers. In this study, the application of the transfer function model was limited to conservative solute transport in undisturbed columns. Future studies can evaluate chemical adsorption and degradation processes.