Effect Of Simulated Dry-wet Alternation On The Stability Of Cd/Pb/Zn In Remediated Soil And Its Mechanism

Chemical stabilization is one of the main techniques for in situ remediation of heavy metal contaminated soil,and realizing the long-term stability of soil heavy metal in remediated soil under the effect of environmental factors is a double test for immobilization remediation technology in terms of economic benefit and environmental risk.In this paper,iron oxide and its organic matter complex were used to remediated Cd/Pb/Zn contaminated soil,studying the effect of environmental dry-wet alternation condition on the long-term stability of Cd/Pb/Zn in soil.By analyzing the changes of Cd/Pb/Zn form distribution and the physicochemical properties of soil before and after simulated environmental dry-wet condition,combined with the adsorption properties and structure characterization of materials,the mechanism of environmental dry-wet alternation on the stability of Cd/Pb/Zn in remediated soil was preliminarily studied.Main conclusions are as follows:(1)After measuring the distribution of Cd/Pb/Zn in soil and the concentration of Cd/Pb/Zn in leachate under simulated dry-wet alternation condition,it was found that both GT and GTL effectively inhibited the release of Cd/Zn in the soil and reduced its mobility as well.The short-term and long-term inhibition/reduction effects of GTL were better than those of GT.(2)GT increased soil pH and CEC greatly,and both GT and GTL increased the proportion of crystalline iron oxides in the soil;both GT and GTL significantly reduced the contents of soil organic carbon,organically-complexed iron oxide,and inhibited the release of Fe in soil leachate.The degree of GTL on the reduction of above indexes was greater than that of GT.(3)During the process of simulated 50 years of environmental dry-wet alternation condition,the crystallinity,the specific area and pore volume of GT and GTL,as well as its adsorption capacity to Cd/Pb/Zn decreased.The decrease degree of above indexes of GTL was much lower than those of GT.The adsorption capacity for Cd/Pb/Zn was significantly better than that of GT all the time.(4)Pearson correlation analysis showed that the main soil physicochemical properties affecting the long-term stability of Cd and Zn in GT and GTL treated soil were pH,crystallized iron oxides,amorphous iron oxides and organically-complexed iron oxides.The activation and stabilization processes of Cd and Zn in the soil of GTL treatment coexisted and dominated by the stabilization process,while the activation of Cd and Zn in the soil of GT treatment mainly occurred during the dry-wet alternation condition.