Effects Of Compound Passivators On Pb、Cd Contaminated Soils

In this paper,Pb and Cd composite contaminated soil was prepared by exogenous addition of two levels of heavy and light contamination using Jiaozuo city farmland soil as medium,and single and composite passivators were added to passivate the culture,and the morphological analysis of Pb and Cd in the soil during different incubation periods was used to evaluate the passivation effect of each combination of passivators on Pb and Cd.The results of the study can provide a scientific basis for the remediation of heavy metal contaminated soil.The main conclusions are as follows:(1)Each combination of passivators can effectively promote the conversion of F1 and F2 Pb and Cd to the F4,and the passivation effect of the combination of passivators is better than that of a single passivator.The passivation rate of each passivator for Pb and Cd in the two groups of contaminated soil gradually decreased with time,and for the heavy metal Pb,the passivation rate of the heavily contaminated group was significantly lower than that of the slightly contaminated group in the same period,and for the heavy metal Cd,the passivation rate of the heavily contaminated group was higher than that of the slightly contaminated group.(2)The passivation effect of each passivation agent on Pb is more stable than that of Cd,and the stability after passivation of the low pollution group is stronger than that of the high pollution group.(3)Through comprehensive screening,for the heavily polluted group,the combination of quicklime + sheep dung,quicklime + earthworm dung and apatite +earthworm dung passivation agents were more effective.The average passivation rates of heavy metal Pb passivation for 12 months were 81.39%,70.86% and 71.67%,and the percentage of residue state at the end of passivation increased by 18.59%,23.01%and 20.09%,respectively,compared with the control group;for The average passivation rate of Cd passivation for 12 months was 85.15%,83.83%,86.55%,and the percentage of residue state at the end of passivation increased by 17.35%,13.04%,24.82%,respectively,compared with the control group.For the slightly contaminated group,the passivation effects of quicklime + earthworm manure and bentonite +chicken manure were relatively good.The average passivation rates for 12 months for heavy metal Pb passivation were 104.1% and 103.7%,and the residue state at the end of passivation increased by 30.33% and 19.65%,respectively,compared with the control group;the average passivation rates for 12 months for Cd passivation were94.89% and 112.4%,respectively.The percentage of residual state at the end of passivation increased by 13.01% and 14.53%,respectively,compared with the control group.(4)After passivation,the activity ratio and activity coefficient of Pb are at a low level,the stability is enhanced,the bioavailability is low,and the passivation age can be more than 12 months;After passivation of Pb,January to June to stable gradually,the live stability coefficient and activity fell to the lowest,but it is still at a higher level,6 months to December,live stability than with the activity coefficient and increased to different extent,again released at higher risk,passivation aging sustainable about six months,should be regularly adding passivator,reduce the risk of has stable Cd release again.