Assessing chromite ore processing residue (COPR) waste dump site using electrical resistivity tomography (ERT): a case study from Umaran, Kanpur, India.

Leaching of chromium ions causes a serious threat to groundwater around chromite ore processing residue (COPR) dump sites in many countries. As a result, detailed subsurface characterization of the affected region is crucial for assessing the associated risks as well as initiating remedial measures. Though the conventional approaches (e.g., drilling and water sampling) provide important information but are expensive and unable to decipher detailed subsurface scenario. Thus, in the present study, electrical resistivity tomography (ERT) (a cost-effective and faster approach) method has been employed to assess the effect of unplanned COPR waste dump beside agricultural land at Umaran, Kanpur, India, in conjunction with the available geochemical information. Inverted 2-D ERT sections depicted resistivity variation in the subsurface, and its correlation with previous geochemical results reveals the resistivity boundary between contaminated and clean zones as ~ 15 Ω·m. The study also depicts that the contamination plume is slowly migrating towards NE direction below the agriculture land but rate of migration is faster along southern direction. Therefore, the agriculture land and corresponding groundwater at ~ 50 m away from the dump site in NE direction are not affected by COPR leachate. Vertically, the COPR leachate has affected mostly up to ~ 20 m depth in the region inside the dump boundary; however, at some places, it is migrating further downward. Thus, the study demonstrates the efficacy of ERT method in characterizing COPR dump site and provides crucial information in managing safe agriculture practices over the region as well as for initiating scientific remedial measures.