Formation and stability of Pb-, Zn- Cu-PO4 phases at low temperatures: Implications for heavy metal fixation in polar environments

Low temperatures and frequent soil freezeethaw in polar environments present challenges for the immobilisation of metals. To address these challenges we investigated the chemical forms of Pb, Zn and Cu in an Antarctic land�ll, examined in vitro reaction kinetics of these metals and orthophosphate at 2 and 22 C for up to 185 days, and subjected the products to freezeethaw. Reaction products at both temperatures were similar, but the rate of production varied, with Cu-PO4 phases forming faster, and the Zn- and Pb-PO4 phases slower at 2 C. All metal-orthophosphate phases produced were stable during a 2.5 h freezeethaw cycle to �30 C. Metal immobilisation using orthophosphate can be successful in polar regions, but treatments will need to consider differing mineral stabilities and reaction rates at low temperatures.