Research On The Environmental Effects Of Underground Coal Mining In The Loess Hilly And Gully Region

Ground subsidence caused by underground coal mining is the root cause of geological ecological environment damage problems such as geological disasters,surface water level decline and soil properties deterioration.In this article,the change of the ecological and environmental effects of coal mining activities in ?,?,? Mine in Ordos is a research topic.A total of 135 soil samples were collected from the three mining areas on the spot,and geographic information data from 2008 to 2017 years were collected.This paper calculated the soil erosion modulus of the mining area before and after mining through the combination of RUSLE(The Revised Universal Soil Loss Equation)model and GIS,discussed the change trend of soil erosion modulus and erosion intensity before and after mining.It was clear that different environmental factors are affected by soil erosion,according to the superposition analysis of soil erosion intensity and influencing factors.The heavy metal content in the soil samples of the mining area was measured.The ecological risk assessment of heavy metals in the surface soil was carried out in combination with the evaluation methods such as Nemero index method,potential ecological comprehensive and geoaccumulation index method,and principal component analysis,cluster analysis,factor analysis methods were used for statistical analysis.The results are as follows:(1)The average erosion modulus of ? Mine is 20.06 t/(hm2·a),which is the highest among the three mines.The average soil erosion modulus of ? Mine and ? Mine increased by 1.22 t/(hm2·a)and 2.76 t/(hm2·a)respectively before mining.The main erosion intensity before mining is light and slight,the area of light erosion increases fastest after mining,and the area of slight erosion decreased the fastest.The slight erosion increase rate of the ? Mine is 14.69%,which is higher than the increase rate of 11.16%of the ? Mine and 2.61%of the I Mine.(2)When the slope range is<5°and 5°-8°,the mining area has the largest erosion area,mainly composed of moderate to light erosion in I Mine,slight erosion in ?Mine and light erosion in ? Mine.When the slope is 15°-25°,the erosion intensity of each mining area shows a downward trend.The highest proportion of soil erosion area in each mining area was forest grassland and bare land,while ?Mine was mainly eroded in forest grassland with a total area of 393.766 hm2,accounting for 70.364%.? Mine is dominated by slight erosion of bare land and grassland,covering an area of 552.431 hm2,accounting for 79.207%.The III Mine is dominated by slight erosion of bare land and grassland,with an area of 758.36 hm2,accounting for 73.539%.As the vegetation coverage increases,the erosion intensity gradually decreases,while the ? Mine is dominated by light erosion with a vegetation coverage greater than 65%,with a total area of 884.86 hm2,accounting for 85.82%.? Mine is dominated by mild and less than 60%coverage,with a total area of 606.12 hm2,accounting for 86.84%.The ? Mine is dominated by slight erosion and has little relationship with vegetation coverage.(3)The heavy metals in the mining area are within the scope of national risk control,but the mean mass concentration of Hg?Ni?Cd and Pb elements exceed the soil background value of Inner Mongolia,of which the spatial distribution of Mine ? is the most uneven,followed by ? Mine.The single factor pollution index shows that the pollution index of As,Cr,Ni and Pb elements of the three mines is under the warning line,and the pollution levels of Hg,Cu,Cd are all above the light pollution level.The Nemero index method shows that the pollution levels of As,Cr,Pb and Ni elements in the mining area are still clean,and the pollution levels of Hg,Cu and Cd elements are high.The potential ecological risk index shows that the Hg element has the highest level,followed by Cu,and the ecological risk level is in the order of ? Mine>? Mine>?Mine.According to the evaluation results of the geoaccumulation index method,the accumulation degree of heavy metals in each mine is similar.The order of the geoaccumulation index is ? Mine>? Mine>? Mine,while Cr pollution is the strongest,Hg and Cd pollution is the weakest.After multivariate statistical analysis,the heavy metals in the mining area are mainly divided into three categories,the first cumulative index of Cr in the mining area reaches above 10.07,the second category is Pb,Cu and Ni,and the third category is As,Hg,Cd.Figure[24]Table[25]Reference[70]...