Effect of amendments on contaminated soil of multiple heavy metals and accumulation of heavy metals in plants

The contamination of soil with heavy metals is a severe problem due to adverse impact of heavy metals on environmental safety and human health. It is essential to remediate soil contaminated with heavy metals. This study has evaluated the effects of pine biochar, kaolin, and triple super phosphate (TSP) on multiple heavy metals (Ni, Zn, Cu, and Cd) in contaminated soil and accumulation of heavy metals in plants. The amendments can reduce availability of heavy metals in soil by increasing pH, adsorption, complexation, or co-precipitation. Different amendments have variable effects on accumulation of heavy metals in plants and in soil due to its diverse mechanism of stability. The results showed that application of triple super phosphate (TSP) has significant reduced soil Cd exchangeable (EXC) fraction from 58.59 to 21.30%. Bound to carbonates (CAR) fraction decreased from 9.84 to 5.11%, and bound to Fe-Mn oxides (OX) fraction increased from 29.61 to 69.86%. The triple super phosphate (TSP) has the ability to stabilize Cu and especially Cd. However, triple super phosphate (TSP) has enhanced ecological risk of Zn and Ni. Application of pine biochar has significantly enhanced soil pH. The kaolin has significantly reduced EXC fraction of Cd and increased OX fraction of Cu. The amendments and heavy metals have not caused significant effect on SPAD value of Buxus microphylla Siebold & Zucc (B. microphylla). The triple super phosphate (TSP) has significant decreased biomass of B. microphylla and bamboo-williow (Salix sp.) by 24.91 and 57.43%, respectively. Pine biochar and kaolin have increased the accumulation of Zn and Cd in plants. It is concluded that triple super phosphate (TSP) was effective in remediation of Cd and kaolin was effective in remediation of Cd and Cu. Pine biochar was effective in remediation of Cd, Cu, and Zn.