Stabilization of toxic metals in three contaminated soils by residual impact of lime integrated with biochar and clays

Purpose Mine and smelter soil contaminations with Pb, Cu, Cd, and Zn have become serious problems in China, because of anthropogenic activities. Little is known about the efficacy of residual lime (RL) single and integrated with residual Ca-bentonite (RCB), residual tobacco biochar (RTB), and residual zeolite (RZ) on the stability of toxic metals and reduces their uptake by corn after harvesting of Chinese cabbage. Materials and methods A previous pot trial investigated L single and integrated with CB, TB, and Z on the stabilization and absorption of Pb, Cd, Cu, and Zn using Chinese cabbage, and corn was later selected as the test plant in the present work and grown in mine-contaminated (M-C), smelter heavily, and low contaminated (S-HC and S-LC) soils. Diethylenetriamine pentaacetic acid (DTPA)-extractable method was used to examine the bioavailability of Pb, Cd, Cu, and Zn in M-C, S-HC, and S-LC soils, through atomic adsorption spectrophotometer. Results and discussion The results indicated that the maximum immobilization of Pb reached 63.9% with RL + RZ, Cd 61.7% with RL + RTB, Cu 94.2% with RL + RZ, and Zn 62.4% with RL + RTB, but RL + RTB and RL + RZ treatments mobilized Pb up to 22.44 and 19.9% and RL + RCB mobilized the Cu nearly 53.1% than control. The residual impact of amendments did not support to corn dry biomass and height. The Pb absorption in the corn shoot was significantly reduced by 35.4% with RL + RZ, Cd 65.2% with RL + RTB, Cu 25.2% RL + RCB, and Zn 44.2% with RL + RZ. The accumulation of Pb in the corn root was significantly reduced by 52.1% with RL + RTB, Cd 38.6% with RL + RZ, Cu 51.01% with RL + RZ, and Zn 62.7% with RL + RZ rather than control. Conclusions Our results demonstrate that the RL alone and combined with RTB, RCB, and RZ could be a feasible approach for successful remediation of Cd and Zn in mine-contaminated soil and Pb, Cd, Cd, and Zn in smelter-contaminated soils. Overall, the long-term residual impact of amendments for the restoration of mine-/smelter-contaminated soils should be verified under field scale.