Delineation of LNAPL contaminant plumes at a former perfumery plant using electrical resistivity tomography

Abstract

Light non-aqueous phase liquids (LNAPLs) are commonly used in industrial processes, and they are well known for their potential to contaminate groundwater and their toxic effects on ecosystems. The adequate delineation of contaminant plume distribution is critical for the effective remediation of contaminated sites and aquifers. Electrical resistivity tomography (ERT) surveys on LNAPL contaminated soils have shown great potential in this regard. In this study in China, six ERT profiles were conducted at a former perfumery plant with a benzene and ethylbenzene spill history to evaluate whether ERT could be used to delineate the distribution of the LNAPL plume beneath the plant. Based on the survey results, the electrical resistivity was consistent with borehole sampling results, where high resistivity corresponded to increased LNAPL concentration. A linear relationship was built between resistivity and contaminant concentration, with a threshold value of 18 Ω·m used to identify contaminated areas. It was possible to construct a detailed three-dimensional characterization of the LNAPL distribution. In addition, four local sites were excavated to verify the results of the ERT profiles. The contamination sources were further categorized into four types that were considered useful for the selection of remediation strategies. In conclusion, ERT was an effective non-invasive technique for delineating LNAPL plume distribution at a high resolution.