Advancing acid and metalliferous drainage characterisation, prediction, and monitoring in mine waste systems using electrical methods: Challenges and future directions

Acid and metalliferous drainage (AMD) is one of the most persistent environmental liabilities faced by the mining industry, owing to its potential to cause long-term contamination. AMD encompasses acidic to neutral, metal-rich waters generated by the oxidation of sulfide minerals upon exposure to oxygen and water. With the energy transition, the volume of mine wastes stored in large-scale facilities is projected to increase, and the magnitude and complexity of AMD-related risks are likely to intensify. Consequently, early assessment and effective monitoring of the geochemical stability of mine wastes are critical for mitigating environmental impacts, avoiding unforeseen closure and remediation costs over the mine life cycle. At present, AMD assessment and monitoring largely rely on conventional geochemical testing methods, which are constrained by inherent uncertainties and provide point-scale data with limited spatial representativeness across heterogeneous mine waste structures. In this context, geophysical techniques, particularly electrical methods, offer a complementary, non-invasive, spatially continuous, and cost-effective alternative for the assessment of AMD potential. This review critically synthesises current knowledge on the application of electrical resistivity tomography (ERT) and induced polarisation (IP) methods for AMD investigations in mine waste systems. The review highlights the predominance of qualitative investigations and key barriers that limit the transition to quantitative and predictive AMD assessments, including the lack of validated petrophysical relationships and limited field-scale calibrations. By identifying critical knowledge gaps and future research priorities, the review provides a framework for advancing quantitative AMD prediction, monitoring, and risk-based mine waste management using electrical methods.