Experimental Study On Passive Remediation Of Typical Heavy Metal Contaminated Soils In Sichuan

According to the data of the survey of soil pollution in Sichuan Province,the total rate of soil over standard in Sichuan province is 28.7%,and the main pollution type is heavy metal pollution,among which the excess rate of cultivated soil is 34.3%,which is mainly mild and slightly exceeding the standard,and the main pollutant is Cd.The areas such as Panxi area,Chengdu plain area and southern Sichuan area are areas of heavy soil heavy metal pollution,and cadmium(Cd)is the main characteristic pollutant.Because of the low economic feasibility of heavy metal pollution in large area arable land,it is urgent to use passivating agents to alleviate heavy metal pollution in cultivated land.This research adopts the soil column leaching experiment,plant-based materials with inorganic passivation agent clay,sepiolite,bentonite and organic passivation agent biochar as passivation material,the passivation effect of different passivating agents is evaluated,examining three passivation materials under different proportion on level for the repair effect of contaminated soil.The complex effect provides a theoretical basis and technical support for the application of passivating agent technology to the treatment of heavy metals in vegetable bases in the plain of Anning River,southern Sichuan and Chengdu plain.The soil column leaching experiment was used in this study.The passivating material(sepiolite,bentonite)and organic passivating agent biological carbon were used as passivation materials to evaluate the passivation effect of different passivating agents.The effect of three kinds of passivating materials on the remediation of polluted soil such as heavy metal Cd under different proportions was investigated.It should be used to provide theoretical basis and technical support for the application of passivating agent in the control of heavy metal pollution in vegetable base of Anning River Plain,southern Sichuan and Chengdu plain.The results are as follows.(1)the reduction of effective content in soil heavy metals is not directly related to the strength of the passivation material itself,but is closely related to the pH change of the soil itself.The change of soil pH value is an important factor for sepiolite,bentonite and biochar to passivate and repair Cd pollution.In the leaching experiment,the effect of the passivating agent(sepiolite,bentonite and biological carbon)on the pH value of acid soil(Gulin and Shifang)in Sichuan is significant,but the effect on the pH value of alkaline soil(Miyi)is not obvious.However,the pH value of soil leachate in Southwest China increased with the increasing amount of sepiolite,bentonite and biochar.(2)Under the leaching condition,sepiolite,bentonite and biochar can reduce the available Cd content in the soil at different ratios,and there is a significant difference.In acid soil(Gulin and Shifang),the adsorption effect of clay mineral sepiolite and bentonite on Cd and Zn is better than that of biological carbon;in alkaline soil(Miyi region),the adsorption effect of biological carbon on Cd and Zn is better than that of clay mineral sepiolite and bentonite.(3)The adsorption of sepiolite,bentonite and biological carbon to Cd and Zn showed that the adsorption properties of the experimental group adding sepiolite,bentonite and biological carbon were higher than that of the control group that did not add passivating material,and sepiolite,bentonite and biological carbon were added to the sepiolite,bentonite and biological carbon.The adsorption properties of carbon to Cd and Zn were significantly enhanced.That is,the greater the proportion of sepiolite,bentonite and biochar in a certain range(5%),the smaller the content of Cd and Zn in leachate and the effective content of Cd and Zn in soil column,the better the passivation effect for Cd and Zn.(4)Adding bio carbon can significantly increase the organic matter content in the soil of Sichuan,and the addition amount in a certain range(5%)has a positive correlation with the increment of soil organic matter,and the addition of clay minerals(sepiolite and bentonite)has little influence on the organic matter content in the soil of Sichuan.