An Investigation into the Effects of Heterogeneity on Subsurface Flow and Transport

The risk of groundwater contamination by land-applied organic chemicals is a growing concern. Prediction of the fate and persistence of contaminants in the subsurface is desirable. Soil hydraulic properties are rarely homogeneous and their transient nature has a profound effect on fluid flow and solute transport. Evidence suggests that sorption is a significant process impacting the movement of contaminants through the unsaturated zone. Sorption rate and equilibrium experiments were conducted in completely mixed batch reactors using metolachlor on two soil columns divided into 12 segments each. The equilibrium data were modeled with the linear model and the Freundlich expression. A surface-diffusion model was used to describe the rate data. The results of these laboratory studies were used in conjunction with field data acquired using soil columns in the vicinity of the site from whence the laboratory soils came to test the Pesticide Root Zone Model (PRZM). The results of these experiments showed that the equilibrium data were nonlinear and best fit with the Freundlich expression. However, the linear partition coefficients were highly correlated with the fraction of organic carbon in the soils. PRZM was able to predict field flow data quite well, but was unable to describe contaminant movement.Master of Science in Environmental Engineerin