城市街尘重金属分布特征、风险评价及源解析以石家庄市为例

Temporal and spatial differences of heavy metal sources and ecological risks in street dust in the city: A case of Shijiazhuang City

  • 摘要: 为了从源头有效控制城市重金属污染, 本研究于夏冬两季测定了石家庄市不同功能区街尘中的重金属(Pb、Cr、Cu、Mn、Cd、Zn)含量, 结合单因子污染指数法、内梅罗综合污染指数法、潜在生态风险指数法和正定矩阵因子模型, 分析其时空分布特征、污染程度、生态风险及可能污染源。结果表明: 1)除冬季Mn外, 街尘其余重金属平均含量均高于石家庄市土壤背景值。其中, 冬季Cd平均含量为0.95 mg·kg−1, 是背景值的10.56倍, 超标率高达86%。总体上, 冬季各重金属的生态风险程度均高于夏季, 其中夏冬两季Cd的单因子生态风险指数分别为177.81和316.93, 属强生态风险, 冬季Pb为中等生态风险, 其余重金属为轻微生态风险。2)不同城市功能区街尘重金属污染程度均为重度污染, Cd和Pb是主要重金属污染物, 公园区污染最严重, 其次为商业区。各城市功能区街尘重金属的综合潜在生态风险程度冬季较夏季均有增加趋势。其中, 冬季公园区为极强生态风险区域。3)交通释放、工业排放、燃料燃烧是重金属Pb、Cu、Cd和Zn的主要来源, 自然源是Cr和Mn的主要贡献源。城市街尘污染控制应重点关注冬季公园区以及人流车流量大的区域, 在降低生态风险方面应侧重对街尘中的Cd和Pb进行精准控制。

     

    Abstract: To effectively manage urban heavy metal pollution at its source, this study analyzed the heavy metal contents (Pb, Cr, Cu, Mn, Cd, and Zn) in street dust from various functional districts in Shijiazhuang City during summer and winter. This was performed in conjunction with the single-factor pollution index method, Nemero comprehensive pollution index method, potential ecological risk index method, and the orthogonal matrix factor model. The spatial and temporal distribution characteristics, degree of pollution, ecological risk, and potential sources of pollution were thoroughly examined. The results showed that: 1) Except Mn in winter, the average contents of other heavy metals in street dust were higher than the background values of the soil in Shijiazhuang City. Among them, the average content of Cd in winter was 0.95 mg∙kg–1, which was 10.56 times of the background value, and the excess rate was as high as 86%. In general, the degree of ecological risk for all heavy metals was higher in winter than in summer. The single factor ecological risk index of Cd in summer and winter was 177.81 and 316.93, respectively, indicating a strong ecological risk; Pb in winter was a medium ecological risk, and other heavy metals had a slight ecological risk. 2) The degree of heavy metal pollution in street dust in different urban functional areas was heavy pollution; Cd and Pb were the main heavy metal pollutants, and pollution in the park area was the most serious, followed by the commercial area. The comprehensive potential ecological risk degree of heavy metals in the street dust of all urban functional areas increased in winter compared to summer. Winter park areas posed a very strong ecological risk. 3) Human activity was an important factor contributing to heavy metal pollution in street dust. Based on the results of the positive matrix factorization (PMF) model, traffic release, industrial emissions, and fuel combustion were the main sources of heavy metals (e.g. Pb, Cu, Cd and Zn) in street dust in Shijiazhuang, whereas natural sources were the main contributors of Cr and Mn. Urban street dust pollution control should focus on winter park areas and areas with large traffic flows and on the precise control of Cd and Pb in street dust in terms of reducing ecological risks.

     

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