Amendments for Simultaneous Stabilization of Lead, Zinc, and Cadmium in Smelter-Contaminated Topsoils

摘要

Stabilization treatment of soil is considered a cost-effective option for reducing the mobility and availability of heavy metal contaminants. To date, only a few studies have focused on simultaneous stabilization of Pb, Zn, and Cd with highly effective amendments for Pb/Zn smelter-contaminated soils. In the present study, six amendments, including red mud (RM), pulverized fuel ash (PFA), shell powder (SP), CaCO_(3) (CC), Na_(2)S (SS), and sulfur, were investigated for their ability to stabilize heavy metals in soils. After evaluating stabilization effectiveness of each single amendment with the toxicity characteristic leaching procedure (TCLP), three composite amendments, CA1 (2:1 SS:RM), CA2 (2:1:1 SS:RM:SP), and CA3 (2:1:1 SS:RM:PFA), were formed and applied to Pb/Zn smelter-contaminated soils. Treatment with 7% of any composite amendment resulted in a 90% reduction in Pb, Zn, and Cd concentrations in TCLP extracts of two contaminated soils. The same treatment also reduced the amount of bioaccessible Pb, Zn, and Cd by 21% in two soils according to simple bioaccessibility extraction testing. Compared to nonstabilized soil, the three composite amendments effectively transformed Pb, Zn, and Cd from acid-soluble to more stable soil fractions. These results indicate that these composites are highly effective amendments for stabilization of multiple heavy metals in Pb/Zn smelter-contaminated soils.