Improvement And Application Of Soil Water And Fertilizer Conservation Efficiency In Abandoned Rare Earth Mines In Dingnan, Ganzho

Ganzhou is an important rare earth producing area in Jiangxi Province.Due to the irrational mining of rare earth mines in the early stage,many rare earth mine sites have been exposed in large areas,vegetation has been seriously damaged,tailings bodies have ravages,and soil erosion has been serious.There are also some heavy metal ions in the tailings,causing heavy metal pollution and ecological harm.This paper takes the abandoned rare earth mine in Dingnan County,Ganzhou,Jiangxi as the research area,and finds that the soil environment and vegetation site conditions of the rare earth mine are poor through field investigation,sampling analysis and other preliminary investigation results.In order to respond to the national mine greening project construction,solve the soil problems and disaster problems of the abandoned rare earth mine in Dingnan County,Ganzhou,and make the abandoned mine produce economic value in the future,the indoor and outdoor experiments and research on the mine soil were carried out,and the water and fertilizer conservation efficiency of the soil was increased with the help of modified materials.After verification,the field application was extended to lay the foundation for the green mine construction.Soil substrate improvement and restoration is the key to ecological restoration and reconstruction.Adding appropriate amendments and modified materials to soil to increase soil moisture and fertility is an important strategy,and also the main means to shorten the time and improve the effect of phytoremediation.Due to the high content of sand in the soil of tailings land,exogenous nutrients are easy to be lost through surface soil and water loss and underground infiltration.Therefore,it is also extremely important to research and develop materials to promote soil fertilizer cultivation,water and fertilizer preservation and soil reinforcement and corrosion resistance.Based on literature review and field work experience,the adsorption efficiency of soil remediation in rare earth mines was analyzed and studied by using modified biomass carbon materials and attapulgite materials.(1)At room temperature of 25℃,by adding different proportions of experimental materials mixed with the soil of rare earth mining area,the laboratory experiment found that the water retention rate of the samples added with biochar was 0.25% and 0.47% higher than that of the blank group,respectively,while the water retention rate of the experimental group added with attapulgite was 1.94% lower than that of the blank group,among which the water retention performance of biochar No.2 was the most prominent.Under the condition of high temperature 35℃,the experimental results are basically consistent with those obtained at normal temperature.(2)During the indoor fertilizer retention performance test,the adsorption effect of nitrogen,phosphorus and potassium was improved after adding modified materials with different ratios and mixing with rare earth soil.Among them,biomass carbon No.2 has the best adsorption effect on nitrogen,phosphorus and potassium,and the material surface has a negatively charged part,which absorbs and maintains positively charged nutrient ions by electrostatic force.The adsorption effect of attapulgite on N,P and K is weak in the three materials.The content of nitrogen,phosphorus and potassium in the supernatant after desorption is not different,and the effect of the modified materials is similar.(3)In the process of ammonia nitrogen adsorption,the addition of three materials had better adsorption performance than the control group.However,with the increase of repair materials,some samples did not increase their adsorption effect on ammonia nitrogen,only attapulgite had the best adsorption effect on ammonia nitrogen,and it was in line with the quasi-second-order kinetic fitting formula.(4)In the outdoor test,the aggregate indexes of porosity,bulk density and water stability of the four blocks were significantly improved,and the second block had the best repair effect after adding biochar 2 material.p H values in the four plots were significantly improved to reduce acidification environment.The content of organic matter was increased obviously,which was 7 times higher than that of the control group.The content of N and P was also increased obviously,which increased the soil fertility.From the comprehensive fertility index,soil fertility of the first block to the fourth block rose to a medium level.Moreover,the fourth plot has the highest fertility index,which can be referred to in the later soil restoration allocation process.(5)In the process of heavy metal pollution analysis,the comprehensive pollution index of each block was not much different from that of the experimental group,and all were in the clean level.The addition of various repair materials had little effect,and the adsorption performance of attapulgite was the best.However,the cleaning grade of the control group was superior to that of the original indoor experiment.It was speculated that blueberry had phytoremediation effect and could adsorb heavy metals,so the cleaning grade of the control group was changed.During the experiment,the proportion of rare earth elements in each block was consistent with the results of laboratory experiment,and the content of Ce was the highest.In summary,the laboratory experiment results show that the use of biochar and attapulgite materials has a good effect on the water and fertilizer conservation of rare earth mines,and can improve the soil.The results of field and outdoor tests are good.The soil structure becomes loose and the soil environment is improved.The research on soil improvement in the mining area can provide technical support for soil remediation in rare earth mines and lay a foundation for the subsequent phytoremediation and the establishment of mine remediation system.