Using Blasting-Derived Perchlorate and Chloride for Hydrological Quantification in an Abandoned Mine Waste-Rock Pile

Mine wastes at active and abandoned mines comprise the largest volumes of anthropogenically generated solid wastes in the world. Release of contaminated water containing toxic metal(loid)s from mine wastes can cause long-term detrimental impacts to vulnerable watersheds. Quantifying hydrological processes is key to assessing the impacts of mining on receiving environments. Explosives (e.g., ammonium nitrate mixed with fuel oil) are used globally to break rock. Perchlorate is added to explosive mixtures as an accelerant, introducing this emerging contaminant to mining-impacted environments. Using an operational-scale mine waste-rock pile at one of Canada’s largest abandoned mine remediation sites as an example, we show that the blasting-derived residue perchlorate, and chloride, the reduction product of perchlorate, can be integrated to quantify hydrological processes in the waste-rock pile. This investigation demonstrates the potential of using the integration of perchlorate and chloride concentrations as a novel monitoring indicator to assess vertical water infiltration in waste-rock piles and similar mine-waste systems.