Detailed Contaminant Plume Mapping Using Electrical Resistivity Tomography at an Ethylbenzene Contaminated Site

Abstract:

Detailed characterization of light non-aqueous phase liquid (LNAPL) contaminant plume is essential for effective mapping remediation scope. Traditional hydrogeological methods using drilled wells is expensive, and the accuracy of this method is affected by the position of boreholes. Electrical resistivity tomography (ERT) is increasingly popular for delineating the geometry of groundwater contamination because this method makes quickly investigation a large site without the need for wells drilling possible. In this study, the optimized arrays generated using the ‘Compare R’ method for ERT were conducted at an aged ethylbenzene contaminated site in Tianjin, China. Based on former results of geochemical sampling, eight electrical profile lines were arranged at this site. The inverted profiles show the electrical resistivity values of contaminated area is higher than those of non-contaminated zones because of the presence of ethylbenzene. High electrical resistivity values only appear in the ERT profiles inside the plant. Chemical data from boreholes agree well with the observations indicating the contaminant plume mainly distribute under the plant. 3-D ERT results acquired from interpolation of 2-D profiles was successfully used to confirm the position of the contaminant plume boundaries and sources, which help us to reconstruct the geometrical layout of the remediation scope. The refined scope is smaller and more precise than interpolation results from soil samples of drilled boreholes.