Research On Copper Tailings Fertilization And Improvement Technology In High Altitude Ecologically Fragile Areas

Tailings are a waste or non-economic by-product of mining activities and mineral processing.Studies have shown that the resource utilisation rate of tailings is low,resulting in large amounts of residual tailings being deposited directly into the open environment,which can pollute the surrounding environment and create many health problems.The topsoil is stripped away after mining and the topography is severely damaged,resulting in a large number of exposed slopes with sparse vegetation and fragile ecosystems,which are not conducive to the survival and reproduction of plants and animals.Soil cover is the main method of mine ecological restoration,but the surface soil layer is thin in high altitude areas,so it is not feasible to use local top soil directly to cover the rocks;and due to the remote location of high altitude areas,the cost of transporting guest soil from overseas is high and the economic pressure on enterprises is great,so exploring a way to resource utilisation of high altitude tailings and an economic and effective way to restore the mine ecological environment has become an urgent problem.In this study,tailings are considered as a new type of soilforming material.The main purpose of this study is to restore the ecological environment of high-altitude ecologically fragile mines by using easily accessible and low-cost improvement materials to fertilise the tailings,improve their physical structure and increase their nutrient content,and then use them as greening soil in the vicinity.The tailings were tested with a single amendment material to obtain the ratio of several different composite amendment materials and to investigate the effects of different treatments on the physical structure,fertility enhancement and heavy metal content of the tailings.The feasibility of improving the tailings as green soil to restore the ecological environment was investigated.The main conclusions are as follows.(1)Five improvement materials,yak manure,grass ash,biochar,spent agrocybe aegerita compost,and spent tremella fuciformis compost,were used to investigate their effects on nutrient contents of tailings at 0%～10%(mass ratio)applied,respectively.The results showed that the selected five improvement materials could significantly increase at low addition rates.Still,the five materials had different abilities to improve the organic matter and nitrogen,phosphorus,and potassium contents of tailings.spent agrocybe aegerita compost,biochar,and spent tremella fuciformis compost can increase organic matter.Spent agrocybe aegerita compost also enhance fast-acting potassium;yak manure can significantly increase alkaline decomposition nitrogen,effective phosphorus,and total phosphorus content,and grass wood ash can significantly increase total potassium content.(2)In order to combine the advantages of these improvers,this study combined several low additive materials to form five different ratios of composite materials to improve tailings,namely 1% yak manure + 5% grass wood ash + 1% biochar + 2%spent tremella fuciformis compost(H1),2% yak manure + 2% grass wood ash + 2%biochar + 5% spent agrocybe aegerita compost(H2),5% yak manure + 1% grass wood ash + 1% biochar+2% spent tremella fuciformis compost(H3),2% yak dung+1% grass wood ash+1% biochar+5% spent agrocybe aegerita compost(H4),5% yak dung+2%grass wood ash+2% biochar+2% spent tremella fuciformis compost+5% spent agrocybe aegerita compost(H5).Amended tailings will significantly reduce the capacitance by applying these five different ratios of composite materials,increasing the permeability and water retention;organic matter,nitrogen,phosphorus,and potassium content compared with the unamended tailings differences.All of which exceeded the nutrient content required for green planting soil.In a comprehensive comparison,treatment with H4 and H3 was more economical and feasible.Since the added amendment material is low in its own copper and arsenic content,its application to the tailings will reduce the concentration of heavy metals in the tailings and reduce the effect of heavy metal poisoning on the plants.(3)The nutrient content of the tailings decreases as the number of rainfall drenches increases.After six drenches have been completed,the fertility of the tailings at 0-20 cm depth still meets the requirements of the greening soil,with H4 having the highest rate of nitrogen and potassium and phosphorus retention and H1 having the highest rate of potassium retention;some of the fertility indicators of the tailings at 20-40 cm depth are slightly increased,indicating that the fertility of the tailings without amendments is poor.During the leaching process,the heavy metals in the tailings will desorb and lead to an increase in content.The heavy metal content in the leachate is high,indicating that the heavy metal content in the tailings will gradually decrease as the rainfall increases,which can reduce the toxic effect on plants.(4)The pot experiment illustrated that the growth of plants correlates with the physical and chemical properties of tailings,and the modified tailings were more favorable to the growth of ryegrass.The plants did not show the toxic effects of copper and arsenic,which verified the effectiveness of the modified formula.The effectiveness of the improved formulation was verified by field trials showing that the improved tailings allowed the plants to grow better under natural conditions.In conclusion,the tailings treated with H4(2% yak dung+1% grass wood ash+1%biochar+5% spent agrocybe aegerita compost)had better physical and chemical properties,better ryegrass growth,better fertiliser retention capacity,and lower amendment dosage.