Study On The Improvement Ofsoil Inwaste Land Of Rare Earth Mine By Using The Passivator Modified Sludge

The reclamation of the abandoned land in the mining area,the restoration of vegetation and the rational disposal of the municipal sludge are all the hot issues for the construction of ecological civilization.The utilization of municipal sludge to improve the soil and promote vegetation recovery has attracted wide attention.In this Research,we first used the toxicity characteristic leaching procedure(TC LP)to analysis the passivation effect of different passivator dosage on the sludge of heavy metals.Then,we taking rare earth mine soil in Pingyuan Huang She County in Meizhou C ity of Guangdong province as the research object,study the influence on bulk density,porosity,water holding capacity,nutrient elements,organic matter and the effect of heavy metals of mine soil by adding passivation agent modified sludge.Finally,we select four kinds of plants(Eucalyptus urophylla S.T.Blake.,Acacia auriculiformis A.C unn.ex Benth.,Jat ropha curcas Linn.And Canavalia ensiformis(L.)DC.)as plant material,and using Pot experiment to study the effects of the plants growth,the plants nutrient and the accumulation of heavy metals after the modified sludge acting on the soil of the mine.and toselect the suitable plants for growth,and to provide reference for the application of municipal sludge and plants in restoring the soil environment of rare earth mining wasteland.The main results are as follows:1.When the applicationamount of passivating agent is 5%(massfraction),the comprehensive passivation effect of C u,Zn,Pb,Cd and N i is the best,and the exchangeable Zn content decreases 151.60mg/kg.2.Sludge and sludge mixed with bagasse fertilizer can improve the mine soil physicochemical properties,decrease soil bulk density,increase the soil total porosity and capillary moisture and p H physicochemical properties,increase the content of organic matter and nitrogen,phosphorus and potassium;The application of passivation agent modified sludge,but also improve the content of soil total nitrogen,total potassium,available phosphorus and available potassium and organic matter,but reduced soil available nitrogen and total phosphorus content;it is worth mentioning that after the application of passivation agent modified sludge,the mining soil p H increased from 4.36 to 7.22.3.After the singleapplication of sludge in soil,the exchangeable Pb decreased by 91.3%,the rest of the exchange heavy metals can be increased,the content of exchangeable Cd in mixed sludge and bagasse increased by 0.46mg/kg,Zn growth of 29.96mg/kg,and passivation agent could effectively inhibit the exchangeable content of heavy metals in soil.4.The effect of single sludge on the growth of different plants was different,which inhibited the growth of Eucalyptus urophyllaand Acacia auriculiformis,but promoted the growth of Canavalia ensiformisand Jatropha curcas,there has the most obvious effect to promote theCanavalia ensiformis;Sludge and bagasse can effectively promote the growth of Acacia auriculiformis,Canavalia ensiformis and Jatropha curcas,in which the dry weight of Canavalia ensiformis increased by 208.3%;while the mixture of the modified agent and the bagasse significantly increased the plant height and biomass of Eucalyptus urophylla,Jatropha curcas and Canavalia ensiformis,the dry weight of Jatropha curcas increased by 450.7%.5.Sludge,the mixed application of sludge and bagasse significantly increased the content of phosphorus and potassium in different parts of the plant.Among them,phosphorus content in all parts of plants increased by more than 200%;Compared with the control,the modified sludge had certain effect on the absorption of phosphorus and potassium in roots and leaves of each plant.6.Thesludge,the mixed application of sludge and bagasse significantly increased the contents of C u,Zn,Cd and N i in plant organs,Significantly reduce the content ofPb in plants,especially in roots.Compared with the control,the growth rate of Zn content in Eucalyptus urophylla root was higher than 498.2%,The Pb content in the stems of Eucalyptus urophylla decreased by 100%;The concentration of heavy metals in various organs of plants was significantly inhibited by the application of passivating agents,After the addition of the passivating age nt,the Cd elements in different plants decreased by more than 46.15%,among which the highest was 100%;After the addition of bagasse,the accumulation of Cu,Zn,Cd and N i was highest in the Canavalia ensiformis.7.Fuzzy membership function evaluation results show that,Acacia auriculiformis,Canavalia ensiformis and Jatropha curcas were the best in bagasse treatment,while Eucalyptus urophylla was the best in the treatment of passivation;The absorption of heavy metals in the four soils was the least,and the stress of heavy metals was the least;In the three treatment with sludge,the plants had the least function value when they were treated with passivating agents.It showed that the passivating agent could significantly reduce the activity of heavy metals in soil and weaken the absorption of heavy metals by plants.In conclusion,it is feasible to use the sludge modified by passivating agent as soil amendment for mine repair.Sludge can improve the physical and chemical properties of soil in mining wasteland,but it also carries the risk of heavy metal accumulation.The addition of the passivating agent can effectively inhibit the activity of heavy metals in soil,effectively alleviate the toxicity of heavy metals to plants,and promote the better growth of plants in the mine soil.