| Soil contamination caused by heavy metals is the main problem which effect soil health and food safety.And soil contamination in southern is more serious than north China,and the contamination often appears in compound contamination,for example copper and zinc often exist simultaneously surrounding the copper smelter.It is essential to restore the productive function and ecosystem services of the soil by managing and using the polluted soil rationally.Chemical immobilization technology has been widely used because it has many advantages,such as low cost,easy operation and quick effect.And the effect of the combined immobile materials is better than the single material.In this paper,we selected Banlangen dregs which was raw material,two kinds of biochar?BC300,BC500?at 300?and 500?were prepared by pyrolysis under anoxic conditions,Fe was modified by BC500?Fe-BC500?,and then combined with maifanite?MFS?as a passivating agent,study on the passivation effect of Cu and Cd combined pollution rice fields around a copper smelter,analysis of the response characteristics of the plant ryegrass to the passivation effect,repair passivation effect and mechanism of plant niche-a combination of proven passivating agent on soil.The main findings are as follows:BC300,BC500,Fe-BC500 and MFS other four materials of Cu,Cd have better adsorption effect,Langmuir and Freundlich equation could well fit.Langmuir adsorption equation better fit BC300,BC500,and the Fe-BC500,And the maximum adsorption amount of Cu were 8.02mg·g-1?9.20mg·g-1?8.82mg·g-1;The Cd were 7.97mg·g-1?8.51mg·g-1?7.70mg·g-1.Freundlich equation can better fit the adsorption MFS.BET,and FT-IR analysis results show that the specific surface area of the material,the surface functional group hydroxyl group,carboxyl group,carbonyl group,ester group,iron hydroxyl group and silanol group can effectively increase the adsorption amount of the passivating agent on Cu and Cd.XRD results show that the four passivation materials do not form new crystalline materials with Cu and Cd.The results of a balanced adsorption desorption show that:The retention effect of Cu and Cd in soil increasedwiththe increaseofthe dosageofBC300,BC500,Fe-BC500 andMFS.However,theexternaladdition of the passivating agent may cause changes in the physical and chemical properties of the soil,so the amount added should not be too large.When the application rate was 2%?soil?,the soil Cu retention rates were 46.48%,59.48%,78.92%and 93.96%,respectively,and the soil Cd retention rates were 66.39%,74.17%,77.22%and81.06%,respectively.In this basis,control the amount of 2%was added?earth?,carbon materials,and combinationsofThreemaifanitefertilizeronthesoilCu,Cdretentioneffect,a carbonmaterial:maifaniteratio:1:8,1:6,1:4,1:2,1:1,2:1,4:1,6:1 and 8:1,27 treatments.The results show that the combined passivation agent increases the retention effect with the MFS ratio,and the combined passivation effect of the three carbon materialsisBC500+MFS>BC300+MFS>Fe-BC500+MFS.BC300,BC500,Fe-BC500,MFS,BC500:MFS?1:8?,BC500:MFS?1:1?and BC500:MFS?8:1?A total of 7 kinds of passivation materials?application amount 2%soil?The results of passivation and migration and transformation of soil Cu and Cd indicate that:The content of residual Cu and Cd in the soil increased significantly after the passivation agent was applied.Due to the different types of passivating agents,the sources are not completely consistent,but mainly in the acid extraction state.Among them,BC300,BC500,MFS and BC500:MFS?1:1?four passivation materials have better effect,and the residual Cu content is increased by 6.29%,16.08%,7.75%and 10.16%,respectively,and the weak acid extraction state is reduced by 0.13.%,9.19%,0.33%and 4.44%;the residual Cd increased by 29.63%,15.12%,58.69%and 85.25%,respectively,and the weak acid extracted Cd content decreased by 15.04%,6.43%,16.89%and26.36%,respectively.7 kinds of passivation material could significantly increase the soil pH value and CEC,BC300 soil organic matter,available phosphorus,nitrogen and other alkaline solutions were significantly improved,the processing of the other nutrients were not significant changes.Studies using BC300 as an indication of biological ryegrass,BC500,Fe-BC500,MFS,BC500:MFS?1:1?,Fe-BC500:MFS?1:1?a total of 6 passivating material?soil application rate of 2%?of passivation effect,results showed:Six-passivation treatment could significantly increase ryegrass underground and aboveground biomass,chlorophyll content,root activity,while significantly reducing ryegrass aboveground and underground portions Cu,Cd content.Administration of deactivating agent not only reduces the absorption of heavy metals in soil underground parts ryegrass Cu,Cd,further inhibiting heavy metals Cu,Cd transferred from the ground to the underground part portion.The comprehensive passivation effect is BC300>MFS>BC500+MFS>BC500>Fe-BC500+MFS>Fe-BC500. |
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