| In this paper,in order to find some materials that can simultaneously passivate Cd,Pb and Zn and determine their appropriate application amount,soil culture experiments were conducted to study the passivation effects of several solidification/passivation materials(Cement,Sepiolite,Biochar,Rice husk ash,Manganese and phosphorus modified biochar,Manganese and phosphorus modified rice husk ash and Steel slag)on Cd,Pb and Zn-composite contaminated soil in a typical lead smelting site under different application levels.Furthermore,three kinds of selected solidification/passivation materials with the optimal application amount were used for long-term stability test to further explore the passivation effect on the Cd,Pb,and Zn content in the polluted soil under the different moisture conditions(wet and dry alternate)and the simulated acid rain.The results are as follows:1.The results showed that the passivated effect of Cd,Pb and Zn in polluted soil was better at the dosage of 4% solidification /passivation agent by the selected test of solidification/passivation materials,especially,soil p H value was increased and the content of Cd,Pb and Zn in polluted soil with the concentration of 4% Cement and steel slag,and the content of available Cd and Pb were reduced by 26.9% and 42.2% with the concentration of 4% modified biochar.2.The results of the experiments of solidification/passivation materials on the contents of Cd,Pb,and Zn in lead smelting site soil under different moisture showed that the content of available Cd,Pb,and Zn with steel slag and cement in polluted soil were reduced under wet moisture and drying-rewetting alternation moisture,especially,the content of available Cd and Pb with steel slag and cement in polluted soil were significantly reduced under wet moisture,and the content of available Zn with steel slag and cement in polluted soil was significantly reduced under drying-rewetting alternation.The passivation effect of Cd,Pb,and Zn with steel slag and cement in contaminated soil was decreased at the middle stage of treatments and was gradually stabled at the later stage of treatments.Under drying-rewetting alternation moisture,the exchangeable Cd and Pb with steel slag and cement in polluted soil was exchanged into the carbonate-bound Cd and the residual Pb,and under alternating drying-rewetting alternation moisture,the exchangeable Zn was exchanged into the residual Zn.The effective Cd,Pb,and Zn in contaminated soil were extracted using the sulfuric acid and nitric acid,water and DTPA extractants,the results showed that the trend of the content of Cd,Pb,and Zn with steel slag and cement in contaminated soil on was sulfuric acid and nitric acid extraction>water extraction>DTPA extraction,and the passivation efficiency was 82.2%,59.6%,83.2%,and 85.5%,56.6%,and 84.3%,respectively.3.Soil p H value and the electrical conductivity were increased and the contents of Cd,Pb and Zn were reduced in the liquid supernatant of the soil with steel slag and cement under different concentrations of acid rain. |
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