| Gold mine tailings contain heavy metals,lack of nutrients,which makes natural vegetation recovery difficult.It is of great significance to carry out ecological restoration research on it.Based on the national key research and development project,this paper takes the tailings of Sanshan Island Gold Mine in Shandong Province as the object.We explored the leaching and release characteristics of heavy metals and nutrient elements in the tailings,developed a new amendment based on improving the maintenance and fitness of tailings,and established a method for repairing the tailings of gold mine by combining the amendment with functional bacteria and tall fesgrass respectively.The effects of combined remediation on regulating nutrient and heavy metal morphology of tailings and improving plant habitability were revealed.The results of Igeo evaluation of the heavy metal accumulation index showed that As had extremely high pollution capacity,followed by Pb.The results of dynamic leaching test showed that the nutrient elements in tailings were more easily released than heavy metals,and the effects of different leaching rates and pH on the release of heavy metals were different.The release rates of Zn and Mn were higher than Cu,Pb and As.The double constant rate equation and first-order kinetic equation could be used to characterize the leaching kinetics of the five heavy metals.The developed compound modifier(1%peat+1%sludge+4%bentonite)improved the maintenance and viability of tailings,and the contents of available nitrogen,phosphorus,potassium and organic matter increased by 163%,225%,30%and 253%,respectively.The content of available potassium and organic matter in tailings was effectively increased by peat,and the content of available nitrogen and phosphorus in tailings was significantly improved by sludge.Bentonite can increase the fertilizer and water retention of tailings.The results of the combined repair of gold mine tailings with amendments and functional bacteria showed that combined repair could reduce the release of heavy metals in tailings and improve their nutrients content.It showed a certain passivation effect on heavy metals Pb,Zn and Cu.Ammonium nitrogen,nitrate nitrogen,available potassium and available phosphorus increased by 133.33%,114.55%,15.17%and 58.95%,respectively.The analysis of microbial community structure of tailings showed that the combined remediation resulted in a significant decrease in the abundance ofAcidobacteriota,which was negatively correlated with TN and TP contents in tailings,while the abundance of Actinomadura,which was beneficial to the improvement of physical and chemical properties of tailings,increased by 573.79 times.The results of repairing tailings of gold mine by the combination of amendments and Festuca elata Keng ex E.Alexeev showed that the available nitrogen,phosphorus and potassium in tailings increased by 42.21%-71.47%,the stem length(35.33%)and fresh weight(27.19%)of Festuca elata Keng ex E.Alexeev significantly increased,and the heavy metal activity decreased by 27.7153.44%,which resulted in the concentration of heavy metals in plant tissues decreased.It effectively alleviated the stress of heavy metal pollution of gold mine tailings on plant growth.Microbial community analysis showed that the amendments reduced the relative abundance of Thiobacillus in tailings,thus reducing the mobility and bioavailability of heavy metals in tailings,which was conducive to the vegetation recovery of tailings ponds.The research results of this paper can provide scientific reference for the risk assessment,prevention and control of the release of heavy metals and nutrients from gold tailings,and provide technical and theoretical support for the ecological restoration of tailings ponds in similar gold mines. |
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