Study On The Effects Of Combined Biochar And Manure Functional Particles To Repair Heavy Metal Contaminated Soil

Soil is a crucial resource for human survival,a renewable natural resource in the ecosystem,and an important part of the agricultural ecosystem.However,heavy metals as pollutants entering the soils,especially agricultural soils,their harm is comparable to air pollution and water pollution due to its stability and non-microbial degradation and mineralization and long retention time because of various human production activities in recent years.The increasingly significant pollution of heavy metals in soil will not only seriously threaten human health and life safety,but also may cause other environmental pollution problems,such as water pollution and air pollution.So it is very urgent to repair heavy metal pollution in soil and restore ecosystem while soil heavy metal pollution has caused widespread concern.Biochar and manure have been widely used in remediation of soil heavy metal pollution,and the combination of biochar and manure has been proved to be a very effective method for remediation of soil heavy metal pollution.However,the existing researches mainly focus on the effects of certain proportion of combined biochar-manure on heavy metals in soil,while the researches on the effects of combined biochar and manure functional particles in different proportions on soil heavy metals are less more.Therefore,this study aimed to（1）evaluate the changes of different ratios of combined biochar and manure functional particles on the physic-chemical properties of soil after 60 days of incubation;（2）examine the effect of combined biochar and manure functional particles on the bioavailability of Cu,Pb,Zn in soil and the potential mechanism by Ca Cl₂-extraction procedure and discuss the underlying controlling processes mechanistically.（3）assess the effects of combined biochar and manure functional particles with various ratios on the total and speciation distribution of heavy metals in soil and its mechanism;（4）study the effects of combined biochar and manure functional particles on the physicochemical properties of contaminated soil in the process of phytoremediation.;（5）explore and analyze the effect and mechanism of plant remediation process on the changes of total and speciation distribution of heavy metals in root soil and non-root soil.The results showed that the p H,EC,TOC and WSOC of the soil were significantly higher than those of the soil without the compound restoration.The bioavailability,total and distribution of heavy metals in soil changed significantly after the application of composite remediation.The total of Cu,Pb,Zn and bioavailability in the soil were effectively reduced by the application of composite repair agent,and the effect of repair was the best when the application amount was 5%;the heavy metal Cu in soil mainly exists in the organic bound state and residue state.The increase of the organic bound state content of Cu indicates that the application of the soil composite repair agent promotes the transformation from the Fe Mn oxide bound state and residue state to the organic bound state of Cu.The content of Pb,Zn organic binding state and residue state was increased by using composite repairing agent.Pb is mainly organic binding state,followed by residue state.Zn is mainly in residue state,followed by organic binding state.The mobility and release ability of Zn can be effectively reduced by different proportion of composite restorations.In the process of plant restoration,the p H,EC,AP of root soil and no root soil increased obviously with the increase of the proportion of composite restoration agent,and reached the maximum value when the application amount was 5%.This may be the result of the interaction between biochar and manure functional particles,plant root activity and soil microorganism.All the ratios of composite restorations enhanced the affinity and adsorption of heavy metals.Among them,the adsorption affinity of plant roots to Cu is stronger than that of Pb and Zn,especially in 1%of composite restorations.The dissolved organic matter in soil has higher affinity and adsorption for Cu,and the increase of dissolved organic matter in soil is easy to enhance the migration ability of Cu.The organic matter in soil also has strong affinity and adsorption for Zn,which effectively promotes the stabilization of Zn and reduces the desorption and release of Zn in soil.Plant roots promote the transformation of Cu to exchangeable,organic combined and residual state,which indicates that Cu has high ecotoxicity.Plant roots promote the transformation of Pb to organic binding state,the solubility of organic matter in soil increases with the increase of p H,the complexation is strengthened,and the content of organic binding state of heavy metals increases with the increase of complexation.The properties of Pb and Cu are mainly influenced by the organic binding state.Soil p H,EC,CEC,organic matter,Fe-Mn oxides and so on are all the key factors affecting the speciation of heavy metals in soil.