Remediation of metal-contaminated soil in polar environments: Phosphate fixation at Casey Station, East Antarctica

Remediation of metal-contaminated soils by phosphate fixation is successful in temperate environments, whereas its efficacy in cold and freezing environments is understudied. Phosphate fixation is a low-cost technique and is potentially very useful in these remote environments where the logistics of remediation are difficult and expensive. Here we describe a field study at Casey Station, East Antarctica, where phosphate (triple superphosphate and phosphate rock) and a buffer, Emag (magnesium carbonate and magnesium oxide), were introduced to contaminated soil from nearby Thala Valley landfill. A pilot scale experiment was set up, sampled and monitored from December 2008 to February 2010. Relative to levels in the untreated landfill material, concentrations of Cd, Cu, Co, Fe, Mn, Pb and Zn in leachates were decreased by phosphate addition (fixation most effective for Mn and Zn), whereas the technique increased concentrations of As, Cr and Ni. The most successful fixation was found for the 3:2 ratio of triple superphosphate and Emag, and the least effective fixation occurred with the 2:1:1 ratio of triple superphosphate, Emag and phosphate rock. Although there was an undesirable initial flush of metals from the contaminated soil in the 24-48. h after treatment addition, concentrations in leachate were reduced and stabilised in the second summer. During a full-scale field implementation, complementary techniques would be required to contain and treat contaminated runoff until leachates have reduced to acceptable concentrations.