Electrical resistivity tomography (ERT) monitoring of leachate seepage from an animal carcass waste (ACW) facility, South Korea

Abstract

The South Korean government culled and buried numerous pigs to contain the 2011 outbreak of foot-and-mouth disease. Pollutants were detected in groundwater samples collected from an observation well near animal carcass waste (ACW) facilities used to dispose of some of the culled animals. Pollutants appeared to be leachate seeping through damaged shields installed in the ACW facilities prior to burial of the carcasses. Because electric conductivity of leachate is relatively low compared to fresh groundwater, we assumed that electrical resistivity tomography (ERT) is effective to investigate the spatial distribution of the conductive materials. This research demonstrated the use of 3D ERT monitoring to characterize spatial and temporal changes of the leachate. Low-resistivity anomalies <23 Ωm were distributed adjacent to the ACW facilities in time-lapse ERT images. Although the size of the initial low-resistivity anomalies was the largest the time-lapse ERT images, the average resistivities were gradually reduced. We also identified that the resistivities of the low-resistivity anomalies gradually increased, whereas the resistivities decreased away from the ACW facilities using resistivity ratio maps. It was considered that these temporal and spatial changes were related to dilution of the leachate with rainwater and the leachate migration along the northwest slope. We therefore believed that the 3D ERT monitoring could be a useful tool for detecting both the distribution and migration of the leachate.