| The continuous mining of coal mines has caused surface deformation,resulting in many cracks and subsidence on the surface,and finally forming a large area of coal mining subsidence.Meanwhile the by-products produced by mining will release heavy metals into the soil,which will cause the enrichment of heavy metals to exceed background value of local soil in mining area,causing heavy metal pollution.The environment is complex in the coal mining subsidence area of Linhuan.In the area,there are both open-air piles of large-scale coal gangue and other industrial solid wastes,as well as coal preparation plants,coking plants,coal-fired power plants and other production enterprises,which all make an impact.The research object is the Linhuan coal mining subsidence area in Huaibei,Anhui,mathematical statistics,Kriging interpolation and other methods used to study the content,time change and spatial distribution,and migration,and transformation characteristics of heavy metals（Cu,Zn,Cd,Cr,Ni,Pb,As and Hg）in the soil in the subsidence area.The research results showed that:（1）The pH content of the soil in the subsidence area ranged from 6.09 to 7.32,with an average value of 6.45.The weakly acidic samples accounted for 88.24%of the total samples.The soil was relatively acidic in this area,and the content of soil organic matter（OM）was relatively abundant at the level of the second standard.Available potassium（AK）The appropriate content concentration was at the third-level standard level,and the content of available phosphorus（AP）was lower at the fourth-level standard level.The Zn was greater than the soil pollution risk screening value of agricultural land in subsidence area soil;the average content of Cu,Cd,Cr,Ni,Pb,As and Hg was below the value;Cu was concentrated in the southern part of the industrial park,Zn and As were enriched in the intersection of the two rivers and in the south of the industrial park,Cd,Hg,and Pb were enriched in western part of the subsidence area,Cr and Ni were enriched in the east and west of the subsidence area.The maximum concentration of Cu in the profile distribution was enriched in 80 cm,Cd and Ni in40 cm,and Pb in 60 cm,and the maximum concentration of other heavy metals in 20 cm;Cd in the soil was the highest potentially mobile form,other heavy metals mainly exist in the residue state.The content of Pb and Hg in the soil decreased from 2013 to 2019,and the content of other heavy metals increased compared to 2013.（2）Power plant fly ash was the main source of Cu,Pb and Hg in soil,the content of three heavy metals in the soil was negatively correlated with the distance from the industrial park.The content of heavy metals in the soil with the upwind was higher than that in the soil with the downwind;Cd,Cr,Ni were related to the leaching of coal gangue accumulated in subsidence area soil,among them,the content of Cd and Cr in the soil was negatively correlated with the distance from the coal gangue,and other trace elements have no obvious regularity;Ni and As in soil were often related to soil parent materials and mineral types There was a certain connection;Zn was mainly affected by agricultural activities in the subsidence area soil.（3）The migration degree of heavy metals was Cu>Pb>Ni>Cd>Zn,Cr,Hg,As in the soil.The activation rates of Zn and As were lower,2.23%and 0.24×10-3%respectively in the subsidence area,lower than those in the non-sinking area,and the activation rates of heavy metals Cu,Cd,Cr,Ni,Pb and Hg in the subsidence area soil were higher than the non-subsidence area,the activation rates were 4.4%,27.13%,4.41%,0.9%,1.85%,and 0.14%,of which Cd had the highest activity,with the activation rate reaching 27.13%.（4）The multi-factor potential ecological risk index of heavy metals in the region indicated that the region was below ecological risk.According to the cumulative pollution index of the area,it could be seen that a few samples of Cu,Cd,Cr,and Ni had light pollution.The Nemeiro Comprehensive Pollution Index for heavy metals in the region indicates that there was light pollution in the region. |
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