Combined Remediation And Improvement Techniques Of Plant-microorganism In Utilization Of Iron Tailings

With the development of mineral resources,the emission of iron tailings increases rapidly,but its comprehensive utilization rate is low and it is difficult to make large-scale use,which leads to the rapid increase of tailings storage and causes a series of environmental problems,such as soil heavy metal pollution,dust pollution,water pollution and so on,at the same time the tailings reservoir has the risk of dam collapse,there are serious safety problems.In view of the above series of environmental problems,traditional physical,chemical and biological treatment,use technology has high cost,difficult to operate,easy to produce two pollution,can not effectively control the use of tailings in the process of heavy metal pollution and so on,can not be effectively used for large-scale tailings.Thus,we proposed a new tailings utilization mechanism for the use of tailings in the soil,and plant-microbe technology is employed to improve the properties such as pH,water content,enzyme activity and porosity of the tailings to meet the requirements of planting soils.The heavy metal pollution can be controlled by reducing the heavy metal content of the tailings in the process of tailings soil utilization,so that the harm to the environment can be eliminated during the utilization process.This can not only realize the large-scale utilization of tailings,solve the problem of tailings dumping and occupying a large amount of land,but also benefit the construction of green mines and alleviate the increasingly serious shortage of cultivated land in China.In this study,a potted plant simulation experiment was employed to study the improvement of the physicochemical properties of the tailings and the repaired effect of heavy metal pollution by plant-microorganism technology.The results of the study were field-verified.The main findings are as follows:(1)Through the potted simulation method,Kochia scoparia,Cosmos and Festuca rubra were found having better adaptability to tailings and tolerance to heavy metals than other plants.(2)Using plant improvement technology and plant-microbe technology to improve the tailings,it was found that the combined technology can improve the physical and chemical properties of the tailings more efficiently than single phytoremediation technology.After testing,the three plant-microbe combined experimental groups of Kochia scoparia + bacteria,cosmos + bacteria,and Festuca + bacteria were compared with blank groups.Tailings pH was reduced from 8.03,8.06 and 8.11 respectively to 6.96,6.60,6.85,and the improvement effect was improved by 30%?50%compared with the single plant improvement technology;the tailing water holding capacity was increased from 7.1%to 14.9%;15.1%and 15.5%,which was about 20%higher than the plant improvement technology;tailing enzyme activity reached 23.2,21.2 and 21.7 ml/g,respectively,and microbial activity improved by 40%to 90%significantly compared to single plant improvement in the tailings;tailings porosity increased to 63.5%,57.2%and 65.2%,creating a good void structure for the growth of plants.(3)The combined plant-microbe remediation technology can repair heavy metal pollution in tailings more efficiently.The heavy metal content in the soil was measured and the removal rate of heavy metals was determined in the potted plant simulation experiment.The results showed that the plant-microbe restoration technology had a stronger effect on the remediation of heavy metals than the single plant restoration.After inoculation with microbial inocula,the removal rate of Pb of Kochia scoparia,Cosmos,and Festuca rubra reached 36.5%,51.2%,and 42.2%,repectively.The removal rate of Cd reached 47.5%,52.3%,and 64.4%,which increased by 36.5%and 45.7%respectively compared to single phytoremediation.(4)The plant-microbe combined improved remediation technology was applied to the project site.After sampling and analyzing,it was proved that this technology can improve the physical and chemical properties of the tailings and eliminate the heavy metal pollution effectively during tailings soil utilization.The results showed that the pH of the tailings on the project site was reduced by one unit after the combined restoration of plants and microorganisms,and the soil pH was reduced from the original strong alkaline to the weakly alkaline;the water content of the tailings was increased double and the total porosity was increased from 40%to 60%to ensure the conditions of soil biological respiration and nutrient requirements,and overall the iron tailings achieved the ability to retain water and fertilizers;the removal rate of Cu,Zn,Cd,Pb and Mn in tailings reached 53.5%,51.3%,52.4%,54.8%and 42.1%,respectively.