Pore-scale Characterization of Immiscible-Liquid Distribution in a Natural Carbonate-Karst Soil Using Synchrotron X-ray Microtomography

Successful remediation of sites contaminated by organic liquid compounds will highly depend upon immiscible liquid distribution and morphology present within the subsurface. This will require a fundamental understanding of the pore-scale processes controlling immiscible liquid distribution. A pore-scale study was conducted to characterize immiscible liquid distribution and morphology in a complex carbonate (karst-type) soil. Synchrotron X-ray microtomography was used to obtain high resolution 3-D images (9-micron image resolution) of the two-phase immiscible-liquid/water system. The image data were processed to generate quantitative measurements of immiscible liquid morphology such as blob size distribution, blob volume distribution, and specific surface area. The resulting immiscible liquid distribution within the carbonate soil was comprised of widely varying blob sizes, ranging from spherical blob singlets to relatively large immiscible- liquid filled cavities. These results demonstrate the utility of synchrotron X-ray microtomography for quantifying immiscible liquid distributions at the pore scale in complex karst-type sediments. These high resolution imaging techniques can provide invaluable insight for evaluating the effectiveness of remediation activities in karst regions contaminated with immiscible liquid.