Geoenvironmental characterisation of legacy mine wastes from Tasmania - Environmental risks and opportunities for remediation and value recovery.

A detailed characterisation of potential environmental risks is required to implement adequate mine waste management strategies at abandoned mine sites. This study assessed the long-term potential of six legacy mine wastes from Tasmania to generate acid and metalliferous drainage (AMD). Mineralogical analyses by X-ray diffraction (XRD) and mineral liberation analysis (MLA) revealed the mine wastes were oxidised onsite and contained up to 69% of pyrite, chalcopyrite, sphalerite, and galena. Oxidation of the sulfides under laboratory static and kinetic leach tests generated leachates with pH 1.9-6.5, suggesting long-term acid-forming potentials. The leachates contained some potentially toxic elements (PTE)s including Al, As, Cd, Cr, Cu, Pb, and Zn in concentrations exceeding the Australian freshwater guidelines by up to 10 times. The indices of contamination (IC) and toxicity factors (TF)s of the PTEs ranked between very low and very high relative to soils, sediments, and freshwater guidelines. The outcomes of this study highlighted the need for AMD remediation at the historical mine sites. Passive addition of alkalinity is the most practical remediation measure for these sites. They may also be opportunities for the recovery of quartz, pyrite, Cu, Pb, Mn, and Zn from some of the mine wastes.