The Remediation Of Heavy Metal Contaminated Farmland Soils By Typical Mineral Materials

With the development of agriculture and industry,a large amount of pollutants enter soil environment through various pathways,causing serious soil pollution.As an important factor that limits the sustainable development of agriculture in China,heavy metal contaminated farmland soil draws significant attention and urgently needs to be fixed.Passivation technology is one of the most potential technologies for remediation of heavy metal contaminated farmland soils.Natural mineral materials,especially clay minerals show great sorption capacity to heavy metals,are widely studied and applied as environmental friendly materials owing to the low price,wide distribution in nature,and large amounts.In this thesis,the research status of remediating heavy metal contaminated soil by clay minerals was reviewed.The effects of chicken manure derived dissolved organic matter（CM-DOM）on heavy metal sorption on clay minerals and the mechanisms were studied.Typical minerals were selected as the effective amendments applied in indoor simulation and in-situ remediation.Results were studied through comprehensive analysis to offer reference for further researches.The main original conclusions are drawn as follows:（1）The effects and mechanisms of CM-DOM on Cd²⁺ sorption on clay minerals were fully studied and discussed.CM-DOM obviously decreased heavy metal sorption on bentonite and zeolite,while the degree was deeper on zeolite than that on bentonite.The adsorbed CM-DOM was found mainly responsible for the overall decrease,and it was barrier effect that liminted Cd²⁺ sorption on bentonite while it was the combination of active sites occupation and barrier effect on zeolite.（2）Mineral materials were applied for the remediation of heavy metal contaminated farmland soils in simulation experiment and in-site test.1%or 2%zeolite,apatite,2%bentonite/apatite（1:1）and zeolite/apatite（1:1）effectively decreased the availability of Cd,Pb,Zn in contaminated farmland soils,and there was a positive correlation between the decrease in metal availability and the increase in soil pH.2%zeolite,apatite and zeolite/apatite obviously decreased Cd content of rice by 25.0%-58.9%.2%zeolite/apatite（1:1）was found to best decrease Cd content by 58.9%,and there was a synergistic effect.Cd content of rice kept in accordance with the availability of Cd in contaminated soils.