高原高寒露天煤矿区土壤重金属污染及潜在生态风险评价

Soil Heavy Metal Pollution and Potential Ecological Risk Assessment in Plateau Alpine Open-pit Coal Mining Area

关键词:  露天煤矿  高原高寒  矿区土壤  重金属  污染评价  潜在生态风险  木里矿区

Key words:  open-cast coal mine  plateau alpine  mine soil  heavy metal  pollution assessment  potential ecological risk  Muli mining area

摘要:

高原高寒露天煤矿区周边土壤重金属的含量及污染状况，与生态环境修复治理方案的制定密切相关。以青海省木里露天煤矿区周边土壤为研究对象，采集矿坑周边土壤和矿坑外围未受人为扰动和污染的草甸土壤样品共计54个，分析各土壤中重金属的含量及分布特征，运用单因子污染指数法、内梅罗综合污染指数法、地质累积指数法及潜在生态风险指数法对矿坑周边土壤重金属的污染程度和潜在生态风险进行综合评价。研究结果表明，各矿坑周边土壤重金属含量与背景值差异并不明显，仅Zn、Cd、Pb、Cr和Hg的平均含量高于背景值。矿区土壤重金属单因子污染指数总体表现为P_Pb>P_Hg=P_Cr>P_Cd>P_Zn>P_Cu>P_Ni>P_As，在清洁安全范围内。内梅罗综合污染指数在0.55-2.52，平均值为1.39，属于轻度污染，局部处于清洁、警戒线和中度状态。所有重金属地质累积指数平均值均为负值，污染级别为0级。重金属单项潜在生态风险程度从高到低依次表现为Hg>Cd>As>Pb>Cu>Ni>Cr>Zn，综合潜在风险生态指数平均值为110.38，以轻微风险为主。矿区周边土壤中Cu与Cr、Pb、Cd、Zn，Cr与Zn、Cd、Pb、Ni，Zn与Cd之间相关性显著，在空间分布上相互依存，具有相对专一的来源。总体来看，除了局部有轻度污染的迹象，矿区周边土壤并未受到重金属污染，但是Hg和As对露天开采、矸石堆积等人类活动表现敏感，在后期生态环境监测与修复治理过程中应予以重点关注。

Abstract:

The content and pollution status of heavy metals in the soil around the plateau alpine open-pit mining area are closely related to the formulation of the ecological environment governance and restoration plan. The soil around the Muli open-pit coal mining area in Qinghai Province was taken as the research object, a total of 54 samples were collected from the soil around the pit and the meadow soil that had not been disturbed by humans. The content and distribution characteristics of heavy metals in each soil were analyzed, and the single factor pollution index, Nemerow comprehensive pollution index, geological accumulation index and potential ecological risk index were used to comprehensively evaluate the pollution degree and potential ecological risks of heavy metals in the soil around the mine pit.The research results showed that there was no significant difference between the heavy metal content the background value in soil around each mine pit. Only the average contents of Zn, Cd, Pb, Cr and Hg was higher than the background value. The overall performance of the heavy metal single factor pollution index in the soil of mining area was P_Pb>P_Hg=P_Cr>P_Cd>P_Zn>P_Cu>P_Ni>P_As, which was within the range of clean and safety. The Nemerow comprehensive pollution index was between 0.55-2.52, the average value was 1.39, which belonged to light pollution and partly was in a clean, alert and moderate state. The average value of the accumulation index of all heavy metals was negative, and the pollution level was 0. The single potential ecological risk degree of heavy metals in descending order was Hg>Cd>As>Pb>Cu>Ni>Cr>Zn. The average value of the comprehensive potential risk ecological index was 110.38, mainly with slight risk. The correlation between Cu and Cr, Pb, Cd, Zn, Cr and Zn, Cd, Pb, Ni, Zn and Cd in the soil around the mining area was obvious, and the spatial distribution was interdependent and had a relatively specific source. Overall, the soil around the mining area was not polluted by heavy metals except for some mild pollution signs in some areas. However, Hg and As were sensitive to human activities such as open-pit mining and gangue accumulation, which should be paid attention in the later stage of ecological environment monitoring and remediation.