锰尾矿库溃坝后下游河流底泥重金属形态分布及风险评价

Morphological distribution and risk assessment of heavy metals in the downstream river sediment after a dam failure of manganese tailing pond

为研究尾矿溃坝后下游河流底泥重金属污染风险,以涪江上游某电解锰尾矿库溃坝事件为例,采集事后下游河流底泥,采用三酸(氢氟酸-硝酸-高氯酸)消解法、Tessier法并经ICP-MS检测,分析底泥中Mn、Pb和Cr的全量质量比及分形态质量分数,采用单一指数法和内梅罗综合指数法评价其污染程度,应用风险评价编码法(RAC)分析其风险等级。检测结果表明底泥中重金属全量质量比沿河下降明显;单一指数分析表明,底泥中Mn和Pb以轻-中等污染为主,Cr基本无污染;内梅罗综合污染指数分析表明,全河段达到中等污染;形态分析表明,铁锰氧化物结合态>残渣态>有机结合态>碳酸盐结合态>可交换态。RAC评价发现,溃坝后下游河流底泥Mn和Pb的潜在风险较低,而Cr则较高。

To exploit the pollution degrees and risk levels of the sediment heavy metals after a tailing dam failure,an incidence of a dam failure of manganese tailing pond,located at the upstream Fujiang River,was employed as one example,total and fractional heavy metals including Mn,Pb and Cr in downstream sediments were analyzed by ICP-MS after extractions with HF-HNO 3-HClO 4 method and Tessier sequential extraction procedure,respectively,the pollution degrees were assessed by using the method of single pollution index and Nemero comprehensive pollution index and risk levels were evaluated with the Risk Assessment Code(RAC).The results show that an obvious decrease occurs for heavy metal in sediments along with the study river,these sediments are slightly to moderately polluted by Mn and Pb but not polluted by Cr.A moderate pollution degree is found for the whole study river section by these metals in sediments.Morphological analysis shows that the heavy metals follows an order of ferromanganese bound>residue>organo-bound>carbanate bound>exchangeable form.Risk assessment show that a low potential ecological risk of heavy metals Mn and Pb,while a high potential ecological risk for Cr in sediments after the manganese tailing dam failure.