| Heap leaching technology, with the characteristics of little investment, simple technology,easy management and prominent efficiency, caught great attention in the early years of leaching rare earth exploitation in weathering crust. However, the rare earth elements released from the piled slag bricks and other pollutants like the leaching agents change the characteristics of the original soil, thus exerting serious impacts on the ecological environment.Choosing the leaching ores from weathered crust of the rare earth tailings in Gan Couty,Jiangxi Province as the study area, this thesis adopts the method of statistical analysis to study the contents of rare earth, rare earth binding forms, residual leaching agents and secondary products in the soils as well as their variations of spatial distribution, and uses the Kriging method to do the Seepage Dispersion.The experimental results indicate that:(1) The variation level of contents in rare earth that taken from the soil belongs to the moderate level or above, while the La element varies most drastically at the rate of 170%. The average amounts of rare earth elements in the studying soil fluctuate vastly, for instance, Tb is3.49 mg/kg, while Nd, Eu, and Dy are respectively 1479.22 mg/kg, 3642.81 mg/kg, and1919.56 mg/kg. The interpolation results show that the quantity of La element in the soil decreases from north to south step-wisely in a gradual manner while the distribution of Eu decreases on the other way around. The remaining rare earth elements show similar distribution status, with gradual increase from the northwest to the southeast. Minerals with high content of rare earth in the Southeast tailings could have secondary mining, soil with low content of rare earth could be used in building materials manufacturing or other industries such as the development of catalytic agents.(2) In the southern part of study area, the exchangeable rare earth elements in the soil are enormously enriched, because of that, they are strongly bioactive and liable to dissolve in the rainwater or follow the rainwater to flow into the low areas. The bonded form of rare earth carbonates is relatively equally distributed in their content without showing apparent enrichment in some areas. In the east part of study area, the bonded form of Fe-Mn oxide in rare earth is enriched in content, while in the northwest the content of which is relatively low.The bonded form of rare earth organics shows no obvious tendency of distribution in content,just in the southeast part of the study area, the content is relatively low with relatively obvious enrichment in some other parts. The content of residual rare earth in the study area gradually increases from the west to the east. Those rare earth elements are easily released and then absorbed by plants, thus affect their growth, as well as the neighboring environment enormously.(3) The p H value of the soil is from 3.75 to 5.57, showing strong or stronger acidity,while and the content of organic matter stands on the very inadequate level with 2.50 mg/kg as the minimum rate and 32.76 mg/kg as the maximum. Negative correlation exists between p H in the soil and ammonium nitrogen and the nitrate nitrogen. Through the space modeling of the residue leaching agents and secondary substance in the soil, it is proved that the concentration change of content in ammonium nitrogen in the soil is relatively stable,fluctuating between 3.0 and 7.0 mg/kg. Comparing the space distribution diagram of ammonium nitrogen and nitrate nitrogen, it is shown that where the ammonium nitrogen is featured by low concentration, the concentration of nitrate nitrogen is relatively high. In the northwest of the study area, the concentration of sulphuric acid is relatively low, while in the southeast and southwest direction, it is relatively high. As for the vegetation restoration, one proposal is to build bean plants, pines or ferns. |
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