Influence of different phosphates on adsorption and leaching of Cu and Zn in red soil

Batch and soil column experiments were conducted to evaluate the influence of KH2PO4, (NH4)H2PO4 and Ca(H2PO4)2 on the adsorption and leaching characteristics of Cu and Zn in red soil. The results show that all the three phosphates can greatly improve the adsorption capacity of red soil for Cu and Zn, and the effect of different phosphates on Cu and Zn adsorption follows the order of Ca(H2PO4)2 >KH2PO4>(NH4)H2PO4. The addition of phosphate has little effect on the mobility of Cu. Ca(H2PO4)2 and (NH4)H2PO4 show a strong ability in immobilizing Zn while the immobilization ability of KH2PO4 is much weaker. All the three phosphates are helpful for modifying the partitioning of Cu and Zn from the non-residual phase to the residual phase; however, they could also enhance the contents of Cu and Zn associated with exchangeable and carbonates fractions.