Leaching Behavior of Pb and Cd and Transformation of Their Speciation in Co-Contaminated Soil Receiving Different Passivators

摘要

Excessive release of heavy metals in ecosystem poses a serious threat to human beings and food security. Remediation of metals from contaminated soils is considered a complicated task for environmental safety. Among different techniques, immobilization of heavy metals using soil amendments has attained a greater attention as a promising solution for heavy metal remediation. A column leaching experiment was planned to estimate the influence of biochar (BC), slag (SL), and ferrous manganese ore (FMO) at 3% and 6% application rate on lead (Pb) and cadmium (Cd) leaching behavior and chemical fractionation in artificially contaminated soil. A sequential extraction procedure (Community Bureau of Reference), toxicity characteristic leaching procedure, and CaCl2 were performed after leaching was completed. Results showed that metal movements in the control soil were increased drastically, while with the addition of BC at 6% rate significantly reduced the Cd and Pb contents in the leachate. Greater reduction in acid soluble portion was observed in Cd by 35% and in Pb by 52% in the upper layer (L1) at 6% BC rate, while in L2 Cd was decreased by 32% and Pb by 51% when BC was added at 6% application rate. Similarly, CaCl2 extractable Pb (30.5%) and Cd (27.2%) in the upper soil layer were decreased with BC at a 6% rate. The application of SL also showed prominent reduction in heavy metal mobility. However, FMO incorporation showed the slight decrease in Pb and Cd mobility in contaminated soil. Overall, BC can be considered an efficient soil amendment to reduce Pb and Cd leaching, as well as increased stabilization within the soil profile.