Passive Approaches for Long-term Management of Mine Wastes and Hazardous Substances

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Canada has abundant mineral resources that provide a source of metals (e.g., Cu, Zn and Ni) and specialized elements (e.g., Co, platinum group elements) required for buildings, transportation, energy, and communication systems. Extraction of these resources generates large volumes of waste materials, including waste rock, mill tailings, and refinery waste. Groundwater and nearby surface water bodies are frequently impacted by high concentrations of toxic metals, metalloids, and other inorganic and organic contaminants derived from these wastes. Acid generated through sulfide mineral oxidation causes dissolution of carbonate minerals and an increase in green-house gas (GHG) emissions. There is a pressing need to develop and evaluate the effectiveness of low-cost approaches to reduce both the release of toxic substances from mine sites and to lower GHG emissions. The research program has three principal themes: i) evaluating the effectiveness of existing management approaches (raised water table, low permeability cover systems, organic carbon-based cover systems) to stabilize tailings, ii) identifying the release of emerging contaminants of concern (EOCs) from organic carbon waste materials (OCWM) (e.g., municipal biosolids, landfill compost) used in mine site and other reclamation activities, and iii) modifying OCWM to promote stabilization or degradation of EOCs and mine-derived toxic elements. Research will be conducted at mine sites with previously installed or planned remediation systems, including sites where OCWM is utilized for tailings cover systems or as growth media for revegetation purposes. Solid-, gas- and aqueous-phase samples will be collected within the cover systems and underlying tailings to evaluate the effectiveness and longevity of the cover materials, and the impact of cover systems on GHG emissions, and on tailings mineralogy and pore-water chemistry. Detailed solid-phase analyses will be conducted using conventional mineralogical techniques and supplemented with advanced synchrotron-based spectroscopy. Water analyses will include major and trace elemental analyses. Leaching of EOCs (e.g., perfluorinated alkyl sulfonates) from OCWM will be evaluated through electrospray tandem mass spectrometry and next generation Orbitrap mass spectrometry. Ancillary studies will be conducted to evaluate the effects of OCWM through different treatments (e.g., pyrolysis to stabilize C, addition of mine-waste derived amendments to enhance reactivity) for use as reactive media for control of contaminants in cover materials, within engineered bank stabilization systems, and in passive reactors and permeable reactive barriers. Application of improved management approaches will benefit Canada, and the World, through cost savings and by providing effective remediation methods, which also reduce GHG emissions, and improve the health of local communities and ecosystems most impacted by mining and industrial activities.