With the increasing proportion of open-pit coal mining in the coal mining industry in China, a series of potential safety hazards, environmental pollution, ecological damage and other problems caused by open-pit coal mining have attracted a great deal of attention. Scientifically determining the appropriate mining right scope of an open-pit coal mine can prevent various problems caused by coal mining from the source. In this study, according to the characteristics of open-pit coal mining and the environmental characteristics in arid areas, 15 indicators were selected and their weights were determined from the three perspectives of geological environment, social environment and ecological environment by using the AHP. Based on the spatial analysis function of ArcGIS, a digital evaluation model was established for the corresponding influencing factors, and a comprehensive evaluation model for setting the mining right range was constructed by superimposing the weights. Finally, four mining areas were identified within the study area in Wuhai, Inner Mongolia, and their ecological values were calculated to determine the mining area with the lowest ecological impact.

The large amount of coal mining activity in the arid region of northwestern China leads to vegetation degradation and a greater probability of strong winds. The characteristics of windy fields directly affect the sand-dust transportation process. To capture the wind field characteristics in a mining area, numerical simulation of computational fluid dynamics (CFD) was conducted using the Reynolds-Averaged Naiver-Stokes (RANS) turbulence model based on open source software OpenFOAM，taking Xinxing Coal Mine in Wuhai, Inner Mongolia, China as an example. The field test results at several observation points in the mining area were adopted for validating the numerical results. The distributions of mean wind speed and turbulence kinetic energy in the mining area for the W, NW and E wind directions are discussed. The results show that the mean wind speed distributions of the mining area are greatly affected by the raised mountains or hills on the eastern and western sides. When the approaching wind comes from the W and E directions, the mean wind speed is relatively low behind the raised terrain due to the wake effect. However, the magnitude of turbulent kinetic energy shows a relatively large value. The wake effect of mountains or hills is less pronounced as the approaching wind comes from the NW direction. The reduced mean wind speed and increased turbulence kinetic energy are also observed near the low-lying pits in the mining area. The results of this study can provide a theoretical basis for the prevention and control of aeolian sand and its construction in mining areas.

Soil wind erosion is an important factor that inhibits social activities and economic development in the arid desert region of northwestern China. In order to reveal the distribution of soil wind erosion climate erosivity in the arid desert region of northwestern China, the spatial and temporal variation and transfer characteristics of wind erosion climate erosivity in the region were evaluated by referring to China’s regional ground long-time series meteorological element driving data, and applying the ArcGIS software analysis. The study results show that: (1) Against a backdrop that such meteorological factors as precipitation amount, wind speed, and average temperature over multiple years all increase progressively decade by decade, the wind erosion climate erosivity in the northwest arid desert region is decreasing as a whole. The C values of most areas are within the range of 0 to 100. However, the climate erosivity in the hinterland and a few areas is increasing, with C values higher than 150. (2) The monthly variation of the C value varies significantly. The greatest variation occurs in spring and summer, followed by the variation in winter, while the slightest variation occurs in autumn. Through the abrupt change test, it is found that the wind erosion climate erosivity in spring has the strongest variation, with four abrupt change points and a pattern of long-term fluctuating decline. (3) The soil wind erosion in the region gradually decreases from the hinterland to the peripheral areas, with the areas highly affected by erosion increasing yearly. (4) The spatial-temporal transfer and variation of wind erosion climate erosivity present an overall pattern of slight decrease. However, in some areas, they increase or show an apparent trend of increase. The study results have provided relevant theoretical evidence and scientific support for preventing and controlling wind?sand disasters in the arid desert region of northwestern China.

Exploring the status and sources of heavy metal pollution in the soil of the dump in Wuhai City, western Inner Mongolia, is of great significance. This study selected a sunny slope, a half-sunny slope and shady slope with plots of (A) Astragalus adsurgens + Agropyron desertorum + Elymus, (B) Caragana korshinskii+Astragalus adsurgens + Agropyron desertorum + Lolium, and (C) Medicago sativa + Artemisia ordosica+Astragalus adsurgens + Brassica juncea, and a naturally repaired slope for comparison, yielding a total of 10 types of sample plots. The soil heavy metal pollution levels and the potential ecological harm were assessed by the process of measuring the contents of seven heavy metal elements (As, Hg, Pb, Cr, Cd, Cu and Zn) in dump soil as a single factor pollution index, and then the comprehensive pollution index, potential ecological risk index and the mine soil heavy metal pollution sources were explored by correlation analysis and principal component analysis. The results showed three important aspects of the pollution levels, impacts and sources in this dump. (1) The heavy metal contents in Qifeng dump had little influence on the plant community composition type and no clear relationship with the slope direction, but the Cr content in the manually configured sample was significantly reduced compared with that in the naturally restored slope. The contents of Hg and Pb exceed their soil grade I standards, and Cd exceeds the National Grade II standard compared with the soil background values of Inner Mongolia. The As, Hg, Pb and Cd levels of the dump exceed their standards, so there is a certain degree of heavy metal accumulation in the soil of the dump. (2) The single factor pollution index in descending order is Cd > As > Pb > Cr > Hg > Cu > Zn, and all the dump samples are polluted by Cd. According to the Nemerow composite index, the heavy metals in the soil of the dump are at middlingor moderate pollution levels. The potential ecological risk index values of the individual heavy metals were in the order of Cd > As > Hg > Pb > Cr > Cu > Zn, so Cd was the most important potential ecological risk factor ranging from 108.650 to 180.600. The comprehensive potential ecological risk index ranged from 114.665 to 188.792, indicating that 50% of the plots were at slight or moderate potential ecological risks, respectively. According to the different evaluation methods, Qifeng dump is polluted by heavy metals, and the pollution degree and ecological risk associated with Cd are much higher than those of the other heavy metals. Therefore, timely control measures should be taken for Cd. (3) The correlation analysis and principal component analysis showed that Hg, Pb and Cd came from road coal dust diffusion and exhaust emissions, while Cu, Zn and Cr came from transportation and agricultural production activities, and As came from coal combustion pollution.