| In recent years,in-situ leaching is dominant in the extraction of the rare earth ore,and has been favored.But in-situ leaching belongs to a chemical replacement process,leaching in the strong chemical displacement under the action of soil heavy metal ion migration into the life,liquor or external environment in soil,enriched gradually lead to heavy metal pollution,which poses a serious threat to the ecological environment of mining area.Therefore,it is of great significance to study the migration of heavy metals in the leaching process.In this paper,the ion-type rare earth ore of Longnan region is as the research object,through the simulation of mine soil sampling and laboratory test,soil heavy metal total and various forms of content,using SPSS statistical software for the effects of heavy metals in the soil in the vertical direction of migration of various factors into the analysis,to explore the influencing factors on the law the effect of heavy metals in soil.At the same time,by using the multiple stepwise regression method on the main influencing factors of heavy metals in soil were screened,the regression equation between the factor of heavy metal content and influence,and discussing the influence of leaching on the soil environment of mining area,and puts forward the corresponding control measures,the main achievements are as follows:1.Based on the study of the physical and chemical properties,mineral structure,heavy metal content and morphology of different soils in the mining area before and after the leaching,we find that: After leaching,the contents of pH,Eh and organic matter in different soil layers were reduced to a certain extent,and the mineral composition was also changed,which is mainly for feldspar reduction,clay mineral and quartz increased.The content of Cu and Cr was reduced to a certain extent than that of the other layers.Pb and Zn is decreased in the topsoil and weathered layer.and the content of semi weathered layer is increased by 2.1 times,and 1.21 times as compared with that of no leaching.Different heavy metals in each layer of the form is different,the performance of Cu,Cr before and after leaching are dominated by residual form and Pb,Zn leaching before mainly in acid soluble and reducible,leaching after a certain degree into residue2.Laboratory experiments showed that: Cu and Cr showed a trend of first increased and then decreased in different soils profile over time;Pb and Zn in the topsoil and weathered layer over time showed a trend of first increased and then decreased,and gradually accumulated gradually in semi weathered layer in soil;At the first,the concentrations of Cu2+,Pb2+,Zn2+ liquid pool with time is increasing and then decreasing,the maximum value is about 1.35mg/L,5.31mg/L,1.22mg/L,and the concentration of Pb2+ is far more than the "groundwater quality standards" in the class V standard,Cu2+,Zn2+ are up to the standard of class IV.3.Based on the analysis of the influencing factors of heavy metals in the soil,we find that: pH and organic matter on the influence mechanism of the mining area each layer of soil heavy metal was almost,as follows: pH was positively correlated with Pb and Zn,and was negatively correlated with Cu and Cr;organic matter was negatively correlated with organic matter,and was positively correlated with Cu and Cr,the effects of pH and organic matter on different heavy metals in different soil horizons were different;Eh which was for the influence mechanisms of heavy metals in different soil profile was more complex.4.Based on the correlation among heavy metals in soil in mining area were analyzed found that: Correlation of heavy metals area showed the same regularity,Cu was positively correlated with Cr and Pb was positively correlated with Zn in different soil,which is indicated that Cu and Cr,Pb and Zn have both the homologous relationship and geochemical characteristics are similar,and the heavy metals in various soil layers are from the same mother rock.5.By using the method of stepwise linear regression analysis for the impact factors of soil heavy metals in mining area,the study found that: in surface soil,the main influencing factor of Pb and Zn was pH;in the soil layer,the main influencing factors of Pb and Zn were pH,Eh and Cr,and the degree of influence consistent is pH>Eh>Cr;in the semi weathered layer,the main risk factors of Pb were pH and Cr,the influence degree is pH>Cr;the main risk factors of Zn were pH and Cu,the influence degree is Cu>p H.6.Combined with the field sampling and analysis of physicochemical properties and leaching of soil heavy metals migration simulation,it puts forward some corresponding preventive measures,in situ leaching leaching stage,which is adding some lime carbonate or other alkaline substances to improve soil pH value;and in the later,it adds some biological carbon,microbial improver to improve soil organic matter,thereby reducing the the release amount of soil heavy metal migration. |
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