“…These tailings are alkaline and oxic (mean pH 9.8; mean Eh +200 mV) with an ambient temperature of 1-2°C (Shaw et al, 2011). Mean Ca 2+ and SO 4 2− concentrations in the porewaters are~600 and~1500 mg/L, respectively, and Fe/As molar ratios of solid samples from the two tailings bodies in the DTMF are~52 and~10 (Shaw et al, 2011). Ferrihydrite is highly stable under the pH conditions and Fe/As ratios present at the DTMF (Das et al, 2011b).…”