Mobilization of Lead and Zinc in Acid Sulfate Mine Tailings

Abstract

In this thesis, column experiments were conducted in order to determine the effect of irrigation with local groundwater on mobilization of lead and zinc in 50 years old sulfate-acid mine tailings. In addition, the influence of soluble oxalic acid, a common rhizosphere organic acid, was assessed by varying its concentration across an environmentally relevant range. In general, metal contaminant dissolution was not affected by the presence of oxalic acid. In both tailings, Zn mobilization was higher than Pb suggesting the presence of more kinetically labile Zn phases, regardless of the treatment used. Lead mobilization was also low because effluent solutions were near to equilibrium conditions with respect to gypsum, preventing Pb dissolution from Pb-sulfate minerals. Geochemical modeling also indicated that lead release was controlled by anglesite and plumbojarosite dissolution. Zinc release appears to be controlled by Zn-talc and goslarite.