Behavior of Dense, Immiscible Solvents in Fractured Clay-Rich Soils

This research program addresses the nature and distribution of chlorinated solvent DNAPL sources in fractured clays and weathered shales and the potential for natural attenuation of plumes derived from these sources. These investigations are needed to build the scientific framework for assessment of DNAPL fate in fractured clays and remediation or control options. Specific objectives include: 1. Determine whether chlorinated solvent DNAPLs are likely to enter fractures and/or fine matrix pores for a typical DNAPL spill scenario and determine how DNAPL will be distributed in the soil, using capillary pressure - saturation experiments in large undisturbed columns of fractured shale saprolite. 2. Determine whether values of fracture aperture and fracture porosity derived from the ''cubic law'' are useful indicators of DNAPL entry pressure and residual saturation. 3. Investigate the influence of ''matrix diffusion'' on the dissolution and apparent disappearance of residual DNAPL (t his mechanism can cause more rapid dissolution and spreading of the DNAPL, but does not actually cause disappearance of the contaminant). 4. Investigate potential for biodegradation of chlorinated solvents in fractured and weathered shales at an existing contaminated field site and through the use of laboratory studies in microcosms and undisturbed columns of fractured shale saprolite. 5. Comparison of DNAPL behavior in different types of fractured clay-rich materials, primarily clay-rich shale saprolite in east Tennessee, and clay-rich tills in southwestern Ontario