The potential of X-ray tomography and image analysis for interpretation of spectral induced polarization measurements

The spectral induced polarization (SIP) method is a promising method for many near surface applications, including characterization of contaminated soil. In this study, SIP measurements, high-resolution X-ray tomography and image analysis are combined to investigate clean and tetrachloroethylene (PCE) contaminated sand. This is the first known combination of these methods and the aim of this paper is to demonstrate some powerful possibilities of using X-ray tomography in SIP research. X-ray tomography enables a direct visual control of the sample conditions and quantification of relevant sample properties via image analysis techniques. The image stacks from were processed with image analysis techniques, so that individual grains and PCE phases could be extracted from the sample volume. This enabled calculations of relevant sample properties such as PCE blob volumes, grain diameter,-surface area and-eccentricity as well as bulk porosity, specific surface area to pore volume and proportion of high-density grains. We conclude that the combination of SIP measurements and X-ray tomography have a great potential of increasing the understanding of SIP mechanisms in geological materials. The tomography results can be used both to calculate properties relevant for SIP interpretation as well as 3D modelling of the pore space.