Remediation By Chemical Stabilization And Phytoextraction In A Heavy Metal Polluted Purple Soil

Heavy metal pollution in the farmland has posed a serious threat to agricultural production and human health.Therefore,the development of soil remediation program has risen people's attention.However,in the actual remediation process,the degree of soil pollution,the type of soil use and other factors will affect the selection of remediation program.In this paper,a polluted farmland around a lead-zinc mining area in West yunnan province was selected to study the influence of passivation agent application ratio on the safe production of oil peony,the influence of different precipitation on Cd and Zn in soil remediation with sedum plumbizincicola and the influence of different plants on the migration of Cd and Zn in soil under natural precipitation.The main research results are as follows:In the experiment of simulated precipitation,the soil environment with low water volume was not conducive to the growth of sedum plumbizincicola and affects the remediation efficiency of soil Cd and Zn.Sedum plumbizincicola had large biomass in the medium water treatment,and the remediation efficiency of Cd and Zn in soil was higher.There was no significant difference in the remediation capacity of soil Cd and Zn between high-water treatment and medium-water treatment with sedum plumbizincicola,but the soil leaching solution increased under high-water treatment,which made the soil Cd and Zn have potential migration risks.Sedum plumbizincicola can reduce the leaching of Cd and Zn in soil and reduce the migration risk of Cd and Zn in field restoration.The contribution rate of the absorption of the sedum plumbizincicola to the reduction of soil Cd was 70.5%,72.8% and 64.2%,and the contribution rate of the reduction of soil Zn was 78.5%,68.1% and 61.5% in the high,medium and low water treatment,respectively.In natural precipitation,the downward migration of Cd and Zn with sedum plumbizincicola was consistent with that of the control group,sedum plumbizincicola had no risk of increasing the leaching of heavy metal;The content of Cd and Zn in leaching solution and soil solution accounted for less than 1.0% of the soil decrease.The absorption of Cd and Zn by sedum plumbizincicola accounted for 88.1% and 77.4% of the decrease of Cd and Zn in soil column.The change of Cd and Zn in soil was less affected by maize due to its weak absorption capacity of Cd and Zn.The application of 10.1t /hm2 sepiolite and 1.12 t /hm2 quicklime on moderately polluted farmland had a good effect on soil restoration,while the application of 22.4t /hm2 sepiolite and 4.5t /hm2 quicklime on heavily polluted soil also had a good effect.The application of passivating agent had no significant effect on the survival rate and plant height of peonies in contaminated cultivated land,but significantly increased the root biomass and root length.The concentrations of Ca Cl2 extraction Cd and Pb in the soil were significantly reduced with different dosage of passivation agent,but the effect on Pb concentration of cortex moutan was not significant.After passivation,Cd concentration in cortex moutan still has a high risk of exceeding the standard.