Immobilization of Pb, Cu, and Zn in a multi-metal contaminated soil amended with triple superphosphate fertilizer and phosphate rock tailing

The objective of this study is to immobilize Pb, Cu, and Zn in a multi-metal contaminated soil using triple superphosphate fertilizer (TSP) and phosphate rock tailing (PR) materials, alone and in combination. The treatment effectiveness was evaluated with a column leaching experiment under simulated rainfall conditions. More than 90% of Pb and Cu were stabilized in the upper layer soil (0-10cm) in both untreated and P-treated soil columns. However, the significant downward migration of Zn was observed in either untreated or P-treated column soil profiles though the transport was inhibited by P treatments. In the untreated soil, 27.2% of Zn migrated down to the subsurface soil (10-20cm), while there were 7.45%, 13.0%, and 11.2% of Zn transported down in the TSP, PR, and PR+TSP treatments, respectively. Phosphate reduced the leaching of Pb and Cu from the contaminated soils, with reduction of Pb and Cu in the leachate by up to 71.2% and 34.8%, respectively. However, Zn leaching was enhanced by P treatments except for TSP. The results indicated that triple superphosphate fertilizer and phosphate rock tailing were effective in immobilizing Pb followed by Cu, but less for Zn in a multi-metal contaminated soil.