Geophysical mapping of residual pollution at the remediated Inčukalns acid tar lagoon, Latvia

Acid tar lagoons (ATLs) are a common environmental problem which is widespread in industrialized countries worldwide. Such lagoons have become significant and massive sources of environmental pollution affecting the soil, atmosphere and surface and ground waters. In this study, we characterize the distribution of the residual soil and groundwater pollution plume in the vicinity of the southern Inčukalns ATL (Latvia), using coupled ground-penetrating radar (GPR) and electrical resistivity tomography (ERT) data. The obtained geophysical data provide information about the geological structure and the distribution of the acid tar contamination plume. We determined the location of the low-resistivity zone and related it to the distribution of the contamination. Our study demonstrates that the applied combination of GPR and ERT is an effective tool for analysing the geospatial distribution of ground and groundwater pollution plumes caused by ATLs in areas with complex geological cross-sections.