Vertical Distribution Of Residual Leaching Agent And Rare Earth In In-Situ Leaching Wasteland Of Ionic Rare Earth

As an important source of ionic rare earth minerals,the Minnan area is not only a large number of mineral deposits,but also has a large scale and complete distribution of rare earths.It is the first to be effectively developed and utilized.The in-situ leaching process is the third generation process of ionic rare earth mining.Thanks to its efficient leaching rate and low engineering operation cost,it has been widely promoted and applied in the past 40 years,At the same time,it has also produced a lot of environmental problems.Especially after leaching,the soil aggregate structure destruction and physical and chemical properties change in the mining area,which makes it difficult to grow surface vegetation,induce landslide and other problems,and the residual material of the ore body continues to enter the surrounding soil and water body,which seriously restricts the local social and economic development and mines.Ecological environmental protection work.Based on this,this paper selects an in-situ leaching and abandoned land in Jiangxi Province as the research object,investigates and analyzes the vertical distribution of residual leaching agent and rare earth in abandoned land,and discusses the research of residual nitrogen on slope prevention and environmental protection of mining area.The significance is summarized in the characteristics of rare earth partitions in abandoned land after leaching,in order to improve the remediation and treatment of rare earth waste land and the comprehensive utilization level of resources.The results are as follows:(1)Nitrogen residue in in-situ leaching wasteland of ionic rare earth is related to the nature of parent rock,weathering degree and permeability of ore body.The residual ammonium nitrogen and nitrate nitrogen in the foot of the mountain were higher than those in the top and the mountainside.The ammonium nitrogen content was 1.4-119.2 mg/kg and the nitrate nitrogen content was 0.3-55.1 mg/kg.The residual ammonium nitrogen in humus layer and residual slope layer is less than 5 mg/kg,which is lower than the normal growth requirement of plants.It is not suitable for vegetation growth.In the later stage of phytoremediation,it is necessary to supplement nitrogen fertilizer to improve soil fertility.Nitrogen content in total weathering layer increases with depth.The slice diagram shows that the permeability of the same part of the ore body is different in different directions.When the weathering degree is high and permeability is good in this area,most leaching agents can be taken out under the action of top water operation and atmospheric precipitation leaching,and the residual amount is small.On the contrary,there are more residues.By fitting the data of ammonium nitrogen content and nitrate nitrogen content,there is a quadraticfunction relationship between them.Nitrate nitrogen and ammonium nitrogen are negatively correlated with pH,and the correlation degree is low.This may be affected by ore body structure,rainfall,weathering degree and so on.(2)The sulfate content in waste land ranged from 19.3 mg/kg to 50 mg/kg,and its spatial distribution trend was not obvious.and the difference of sulfate content in different weathering layers is small.The residual sulfate is mainly absorbed by soil.The soil pH of humus layer and residual slope layer in the study area is not significantly different from that of red soil in the south.With the increase of depth,the overall pH value showed a downward trend.The pH value was 3.24 at the sampling depth of 5 meters.The grain size of abandoned soil is mainly sand,which indicates that the water holding capacity of the soil becomes worse.The organic matter and plasma nutrient elements adhering to the soil are easily lost,which leads to the problems of soil barrenness,soil erosion and slope instability.(3)According to the characteristics of in-situ leaching process,residual ammonium nitrogen concentration can be used to characterize the "preferential channel" of seepage flow.The isoconcentration map is drawn to visually express the seepage law of the fluid entering into the ionic rare earth ore body,to determine the location of the "priority channel",and to use it as a criterion element to qualitatively analyze and predict the possibility of slope instability.According to the judgment of the whole area of the study area,the probability of slope instability at 1,2 and 3 points in the west of the hilltop to the foot area is very high,and relevant landslide prevention measures need to be done well.(4)The residual rare earth and its distribution in abandoned land show medium and strong spatial variability in the interior of the ore body.The spatial distribution varies greatly,which is caused by the coupling of many factors,such as the parent rock of rare earth ore,the weathering degree of ore bed and the re-adsorption of leached rare earth.The humus layer and the residual slope layer have high rare earth element abundance,The highest residual rare earth concentration was 1821.54 mg/kg.which belong to the discarded rare earth mineral resources.Combining with the vertical distribution of the residual rare earth in the orebody,the content of the residual rare earth from the surface to the underground five meters has a high mining potential.(5)Remaining REEs were analyzed.It was found that there was a significant negative correlation between light REEs and heavy REEs in waste land,and there was a high correlation between REEs.Except Ce,all the light rare earth elements show good positive correlation.Through the study of Rare Earth Distribution in waste land,it is found that the ore belongs to the light rare earth selective high cerium and high lanthanum ore.The distributionvalue of Ce increases significantly compared with that of primary deposit,and the distribution of Rare Earth shows fractionation effect on the whole.The analysis of single point samples shows that the distribution of heavy rare earth elements decreases as the depth increases.