Risk Analysis and Evaluation of Heavy Metal Pollution of Coal Gangue Dumping Sites in Loess Areas
In order to explore spontaneous combustion and heavy metal pollution caused by long-term storage of coal gangue in loess areas,the coal gangue and soil in the Wangwa coal mine waste dump in Ningxia were taken as the research ob-jects.The physicochemical characteristics of the coal gangue and soil in the dump were analyzed,and the industrial value and spontaneous combustion risk of coal gangue were evaluated.The total and effective content characteristics of heavy metals in coal gangue and bottom soil were analyzed,and the potential ecological hazards of heavy metals were evaluated through meth-ods,Evaluate the ecological risks of heavy metals in soil caused by the accumulation process of coal gangue,and identify the potentially harmful heavy metal elements in the underlying soil.The results showed that:① both the coal gangue and the un-derlying soil are alkaline,and the total salt content of the soil with a thickness of 10 cm and 20 cm in the coal gangue pile is greater than 1.5 g/kg,showing a mild salinization level.The storage of coal gangue has a certain contribution to the accumula-tion of salt in the contact soil layer.(2)The average total amount of Cr,Cu,Pb,Ni,Zn,Cd,As and Hg in the bottom soil of coal gangue is lower than the background value of Ningxia soil.The total amount of 7 heavy metals in coal gangue,except for As ele-ment,is higher than the background values of the bottom soil,control point loess,and Ningxia soil.The effective content of Cr,Cu,Pb,Ni and Zn in the bottom soil is higher than that of the control point loess.③ Based on the evaluation of the total a-mount of 8 heavy metal elements in the underlying soil,the single element potential ecological risk index(Eir)is all below 40,the comprehensive potential ecological risk index(RI)is 85.83＜150,and the ecological risk level of heavy metal elements is all at level I with low ecological hazards.Therefore,the open-air storage of coal gangue in the Wangwa coal mine discharge site in Ningxia is not prone to spontaneous combustion.However,it can have a cumulative effect on the content of heavy metal ele-ments in the bottom soil,and the ecological risk level of heavy metals is at a mild level,with Hg and Cd elements being the main ecological risk contributing factors.The research results can provide theoretical guidance for the safe storage of coal mine solid waste and environmental ecological restoration in semi-arid loess hilly areas.
coal ganguesoilheavy metal pollutionecological riskloess areas
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