宝日希勒大型露天矿敏感区划定及重金属累积效应

Delimitation of ecologically sensitive areas and accumulation effect of heavy metals in Baorixile large-sized open-pit mine

宝日希勒矿是内蒙古东部煤炭年产量3500万吨的大型露天矿,长期采矿活动造成矿区场地重金属累积风险增加。基于Landsat影像划定矿区生态敏感区范围,分析不同生命阶段生态敏感区的场地生态质量。根据生态质量评价结果,采集土壤样品,定量解析敏感区场地重金属累积效应,划定矿区地表生态影响范围。结果表明:矿区外扩8 km属生态敏感区;矿区投产阶段生态状况趋于良好,达产阶段生态状况有所恶化,丰产阶段生态状况有所好转,稳产阶段生态状况轻微恶化;矿区土壤有机质含量低于全国第二次土壤普查结果,Cr、Cd、Pb、Zn、Cu、As、Ni含量低于国家环境质量标准(GB 15618—2018),但Cr、Cd、Zn、Cu、As、Ni超过内蒙古土壤背景值,土壤中Cr、Zn累积明显;土壤重金属危害整体处于低生态风险水平,Cd是重要的潜在生态风险元素;矿区东南部外扩0~2 km范围受采矿活动影响较为明显,2~5 km范围受采矿活动不明显。研究结果有利于掌握矿区生态状况并及时采取相应的修复措施,为具有相似开采规模和条件的煤矿提供生态修复实践借鉴和指导。

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.