Study On Phytoremediation Of Soils With Different Pollution Levels Around Lead-zinc Tailings

The mining activities in the mining area not only bring economic benefits to human beings,but also bring a lot of environmental problems.In the process of mining,it will not only damage the structure of soil,but also damage the water environment and pose a serious threat to human health.In this paper,the land near the Yinshan lead-zinc mine in Shangyu District,Shaoxing City,Zhejiang Province was used as a remediation site,and the ecological utilization patterns of soils with different degrees of pollution were explored for the soils with different degrees of pollution previously studied.The results are as follows:(1)Adding activator has different effects on the leaching rule of soil heavy metals,soil physical and chemical properties,plant physiological and biochemical and enrichment and transport characteristics.The shock activation test shows that the higher the concentration of the activator,the better the leaching effect of heavy metals in the soil.Among them,the extraction of Zn by Oxalis corymbosa DC and Medicago sativa L biological source extracts was better than citric acid,and citric acid has the best extraction effect on Cd.The results of the pot experiment showed that the addition of citric acid significantly reduced the soil p H and organic matter content(p<0.05),and also caused a certain degree of stress on Sedum alfredii,while the addition of the two biological source extracts was basically no toxic on the Sedum alfredii and the soil.All three activators can increase the content of effective heavy metals in the soil,which is beneficial to the purification of Cd and Zn in Sedum alfredii.(2)The adsorption of the five amendments to heavy metals in the solution and soil all showed an increase with the increase of various factors,and finally reached equilibrium.The adsorption test showed that the adsorption efficiency of the five modifiers to Zn,Pb and Cd in the solution gradually increased with the increase of the initial concentration,and eventually stabilized.Lime has the highest adsorption efficiency for Zn and Cd,reaching 99.64% and 99.99%,followed by chitin.The adsorption efficiency of the modifier to Pb,Zn and Cd gradually increased with the increase of the adsorption time.Except for lime,the adsorption of the other modifiers to the three heavy metals all stabilized in about 15 min.When the p H value is 3,in addition to the adsorption of Pb by corn straw charcoal,the adsorption of the other four materials has reached equilibrium.The adsorption efficiency of lime to Zn reached the highest(99.98%)when the addition amount was 1%.Considering the cost and economic benefits of materials comprehensively,it is believed that lime and chitin have greater adsorption potential and higher adsorption efficiency for heavy metals,and can be considered as a good material for reducing heavy metal pollution.(3)The treatment with different modifiers not only improved the soil to a certain extent,but also reduced the accumulation of heavy metals in plants and the effects of enrichment and transport.The addition of amendments increases the p H of the soil.The addition of chitin significantly improves the soil organic matter in the intercropping system and the monocropping system of miscanthus floridulus,which can improve the soil texture and enhance the soil fertility.Adding amendments can significantly reduce the effective Cd content of the soil,with lime being the best.With the addition of lime and chitin,the accumulation and transport efficiency of three heavy metals in morus alba L decreased.In the combined intercropping mode of lime,the enrichment and transfer coefficient of miscanthus floridulus to the heavy metals Pb and Zn is minimized,and the combined action of intercropping and chitin is beneficial to reduce the accumulation and transport of heavy metals in the miscanthus floridulus.In summary,for moderately and lightly polluted soils,the combination of biological source extracts and hyperaccumulator can effectively remove heavy metals in the soil,and the repair mode of the amendments combined with economic crops is conducive to the economic use of heavily polluted soil and risk prevention and control,it has a positive significance for the prevention and control of heavy metal pollution in mining areas.