| China is a large country in the production and consumption of coal resources.The mining and utilization of coal resources has caused large-scale surface subsidence.Coal gangue,which is an appendage generated during the production and utilization of coal resources,is used as a filling material for subsidence areas.Is of great significance.During the process of coal gangue filling and reclaiming the soil in the mining area,the heavy metal elements rich in it will enter the soil with leaching,surface runoff,etc.,which will cause the heavy metal pollution in the soil environment of the filling area.Vermiculite and montmorillonite are two environmentally friendly soil improvers,which have the characteristics of large yield and good adsorption performance.In this paper,the vermiculite filling soil in Xinzhuang coal mining subsidence reclamation area of Huainan is selected as the research object.The soil and growing crop samples in the research area are collected,and the pollution of heavy metal cadmium（Cd）in the vermiculite filling area soil and growing crops is analyzed.Modification of stone-montmorillonite,leafy vegetables with strong Cd enrichment capacity as test crops,and passivation and repair of Cd contaminated soil in coal gangue filling area under the conditions of indoor pot experiment Effects of Vermiculite-Montmorillonite on Cd-contaminated soil remediation and Cd uptake in vegetables.The main results are as follows:1、The study of soil physical and chemical properties shows that the pH value of the vermiculite-filled soil sample in Xinzhuang Coal Mining Subsidence Reclamation Area of Huainan is in the range of 6.57-7.21;the content of soil organic matter is in the range of 26.79-40.38 g·kg-1;the total nitrogen content is 3.89-6.21 g·kg-1range;total phosphorus is in the range of 0.37-0.51 g·kg-1.From the coefficient of variation of each index,it can be known that the coefficient of variation of organic matter,total nitrogen and total phosphorus is between 10-30%,which belongs to medium intensity variation,and the coefficient of variation of pH is small.After applying A vermiculite-montmorillonite,the average soil pH was 7.14,the average soil organic matter was 34.76 g·kg-1,the average total nitrogen was 5.46 g·kg-1,and the average total phosphorus 0.57 g·kg-1;the average value of soil pH after applying group B modified vermiculite-montmorillonite was 7.36,the average value of soil organic matter was 36.91 g·kg-1,and the average value of total nitrogen was 5.55g·kg-1,the average of total phosphorus is 0.63 g·kg-1;the average pH value of the soil after applying group C modified vermiculite-montmorillonite is 7.39,and the average soil organic matter is 38.01 g·kg-1,the average soil total nitrogen is 5.69 g·kg-1,and the average total phosphorus is 0.65g·kg-1.The application of vermiculite-montmorillonite can increase the pH of the soil,increase the content of organic matter,total nitrogen and total phosphorus in the soil,and the effect of the modified vermiculite-montmorillonite is more obvious.2、The heavy metal Cd content study showed that the total heavy metal Cd content and effective Cd content in the soil samples in the study area were significantly positively correlated.The average effective Cd content was 0.137 g·kg-1 and the average total Cd content was 0.385 g·kg-1,The effective Cd accounts for a large proportion of total Cd,and the coefficient of variation CV of the effective Cd and total Cd in the soil is between 10%and 30%,which is a medium-intensity variation,indicating that the Cd content in the soil in the study area has been affected The impact of activities.After applying vermiculite-montmorillonite,the total Cd and effective Cd content decreased,and the activation rate of Cd in the soil decreased.After comparison,when the concentration of MnO2 is 4.5mol·kg-1,the total Cd,effective Cd content and activation rate in the soil decrease the most.3、The study on the occurrence forms of heavy metals Cd showed that the residues of heavy metals Cd in soil samples in the study area had the highest proportion,followed by iron-manganese oxide-bound state,carbonate-bound state,and exchangeable state,and organic matter-bound state had the lowest proportion.After the application of modified vermiculite-montmorillonite with different variables,the residual Cd content in the soil increased the most,the carbonate-bound Cd and exchangeable Cd content decreased,the iron-manganese oxide-bound Cd content,and the organic-bound Cd The content change is not obvious.4、The results of bioaccumulation research showed that the distribution of Cd content in mature wheat parts in the study area was root>stem and leaf>seed,indicating that heavy metals Cd were mainly concentrated in the roots and Cd had a weak migration ability from the root system to the upper part and above ground.The distribution of Cd in each part of the cabbage after applying the improver was root>stem and leaf.Compared with the CK in the control group,the Cd content in stems and leaves of group A decreased by up to 64.15%,and the Cd content of roots decreased by up to 45.86%;the Cd content of stems and leaves of group B decreased by up to 69.81%,and the Cd content of roots decreased by up to 60.15%;The Cd content in stems and leaves decreased by up to 67.92%,and the Cd content in roots decreased by up to 66.17%.The effect of applying modifier on inhibiting Cd content in cabbage was obvious.5、The health ecological risk study showed that the average Cd content of wheat in the study area was 1.489 for THQ for adults and 2.839 for children.Therefore,the heavy metal Cd in wheat in the study area has potential health risks and needs attention.After applying the improver,the total Cd content in the greens of group A,B,and C was less than 1.0 for adults’THQ value and children’s THQ.Therefore,adults and children’s consumption of greens will not be threatened by the improvement. |
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