CO-REMEDIATION OF THE LEAD, CADMIUM, AND ZINC CONTAMINATED SOIL USING EXOGENOUS HYDROXYAPATITE, ZEOLITE, LIMESTONE AND HUMIC ACIDS

Previous studies have suggested that natural minerals and humic acids each have positive effects on the remediation of metals contaminated soil. However, co-remediation of the two materials, where they are used together to address metals contamination, has not been investigated. In this study, a pot experiment was conducted to evaluate co-remediation effects, using hydroxyapatite, zeolite, and limestone with humic acid, to treat multiple heavy metals contaminated soil. This co-remediation effect was compared with remediation using hydroxyapatite, zeolite, and limestone with humic acid on their own. The metal contaminants used were Pb (lead),Cd (cadmium), and Zn (zinc). These metals were studied both in the soil, and their accumulation in the shoots and roots of pakchoi. Results showed that the co-application of the treatments decreased Pb, Cd, and Zn concentrations in pakchoi shoots and roots more than the single treatments. Furthermore, the co-remediation of natural minerals and humic acid reduced the nonresidual fraction of Pb, Cd and Zn, and enhanced the residual fraction compared to the single treatments. The co-remediation of 30g.kg(-1) hydroxyapatite with 20g.kg(-1) humic acid showed the best effect both in increasing pakchoi shoot and root biomass and reducing the amount of Pb, Cd and Zn taken up by the plant. In addition, co-remediation of 30g.kg(-1) hydroxyapatite with 20g.kg(-1) humic acid was most effective in decreasing the acid solution fraction and enhanced the residual fraction of Pb, Cd and Zn. Results suggest that co-remediation, using both natural minerals and humic acid, may be an efficient way to remediate Pb, Cd, and Zn contaminated soil.