Abstract: Baorixile mine is a largesized openpit mine in eastern Inner Mongolia, with an annual coal output of 35 million tons. The long-term mining activities pose a risk to the accumulation of heavy metals in soils of the mining area. Landsat images were used to delimit the ecologically sensitive area of the mining area and to analyze the ecological quality of the mining area in different life stages. Soil samples were collected following the results from ecological quality assessment. The cumulative effects of soil heavy metals in the ecologically sensitive area of the mining area were quantitatively analyzed, and the ecological impact scope of Baorixile mine was delineated.  The 8 km extension of the mining area was the ecologically sensitive area of Baorixile mine. Ecological situation was better for startup period (from 2001 to 2007), worse for mass production period (from 2007 to 2011), tended to improve for highyield period (from 2011 to 2013), and showed a slight deterioration for stable production period (from 2013 to 2019).  The concentration of soil organic matter in mining area was lower than the mean value of the Second National Soil Survey of China. The concentrations of Cr, Cd, Pb, Zn, Cu, As, and Ni did not exceed the national environmental quality standards (GB 15618-2018). However, the concentrations of Cr, Cd, Zn, Cu, As, and Ni were higher than the corresponding background values. Cr and Zn showed a significant accumulation in soil. Overall, the concentrations of soil heavy metals were at low risk level, but there was a potential risk for Cd pollution.  Results of soil ecological quality evaluation indicated that 0-2 km extension range in the southeast of mining area was significantly affected by mining activities, and the 2-5 km extension range was not affected by mining activities. Our results are conducive to grasping the ecological conditions of the mining area and taking corresponding restoration measures timely. Our results provide practical reference and guidance for ecological restoration for coal mines with similar mining scale and conditions.

Key words: large-sized open-pit mine, ecologically sensitive area, heavy metal accumulation, GNDVI value, ecological risk.