Study of Generation and Underground Flow of Acid Mine Drainage in Waste Rock Pile in an Uranium Mine Using Electrical Resistivity Tomography

Abstract

Mineral exploration is often associated with the generation of environmental liabilities, whose potential damages might imperil local water quality. An example of these environmental impacts is the acid mine drainage—AMD, caused by sulfides oxidation and production of acid and saline effluents. The analysis of critical areas with generation and spread of contamination plumes becomes more feasible due to the possibility to obtain geophysical models of water systems, especially to identify regions with accumulation of reactive minerals and preferential water flows. The rock-waste pile named BF-04 fits in this context of contamination, and it was studied based on the Electrical Resistivity Tomography technique, inversion models and isosurface models, providing conditions to recognize sulfide zones (> 10.1 mV/V), whereas chaotic high salt content underground flows, along several depths, were identified by low resistivity zones (< 75.8 Ω m). The complex behavior of groundwater flow in this kind of artificial granular aquifer is caused by its granulometric and lithologic heterogeneities, and compacted material. In addition, the results reveled a substantial water infiltration from Consulta creek, however the most critic zones for AMD generation are located at shallow levels where the waste rock material is more exposed to atmospheric O2 and meteoric water infiltration. The bedrock was not associated with significant low resistivity anomalies, which means that its contribution to AMD generation was considered relatively less important. The results will contribute to the environmental remediation management and also to demonstrate the potential applicability of geophysical methods in mining wastes.