Unsaturated-Zone Leaching and Saturated-Zone Mixing Model in Heterogeneous Layers

Summary

A screening level model was developed for simulation of pollutant migration through the unsaturated-zone and subsequent mixing within the saturated-zone. This one-dimensional finite difference model simulates the transport processes of liquid-phase advection, liquid- and vapor-phase dispersion, sorption, and decay of the contaminant. The model estimates contaminant concentration in the saturated-zone by using a simple mass balance technique for mixing of the unsaturated-zone leachate with the groundwater. The model can be a useful tool in making preliminary assessments of the potential impacts of contaminants in the subsurface. The model can handle vertical heterogeneity of the soil columns and non-uniform initial contaminant concentration. It was verified by comparing its simulation results to an analytical solution and laboratory soil column experiments. In addition the model was validated against laboratory experiments with three different soil sample sizes of Ottawa quartz sand and 480 ppm saline water as a groundwater contamination source.