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    滇西北典型流域土壤重金属生态风险及来源解析

    Ecological risk and source apportionment of soil heavy metals in a typical watershed of northwestern Yunnan

      摘要
    • 摘要:
      研究目的 研究区是金沙江中游典型小流域，查明流域内土壤重金属生态风险和污染来源，对金沙江流域生态环境保护具有重要现实意义。
      研究方法 系统采集了流域内土壤样品120件，岩石样品9件，分析了土壤和岩石中As、Cd、Cr、Cu、Hg、Ni、Pb和Zn元素和土壤pH，使用单因子污染指数与内梅罗综合指数法、地累积指数法评价重金属污染状况，采用主成分分析（PCA）和正定矩阵因子分析（PMF）模型解析土壤重金属来源。
      研究结果 土壤中pH中位值为6.48，Cd、Cu和Pb含量平均值分别达到背景值4.04、3和6.40倍，其余元素在1.06~2.50倍。Zn、Cu、Cr、Ni和Cd超过背景值的点位分别占总点位的86.67%、80.83%、78.33%、75.00%和73.33%，其余元素在32.5%~52.50%。Cu、Cd和Pb超过风险筛选值的点位比例分别为57.5%、50.83%和31.67%，Hg未有超过风险筛选值的点位，其余元素在10.83%~28.33%。单因子污染指数评价结果显示，研究区Cu、Cd、Pd和Cr污染相对较强，内梅罗综合指数法评价结果显示，研究区总体污染占比达到85.83%，污染情况较为严重。地累积指数法评价结果显示，Cd、Pb是主要污染元素，污染程度较高。PCA和PMF模型解析结果显示，研究区土壤重金属主要来源于矿体和广泛出露的玄武岩。
      结论 污染在流域内分布较为广泛，矿体是研究区土壤重金属主要来源，其次为玄武岩，农业活动影响较小。

       

      Abstract:
      This paper is the result of geological survey engineering.
      Objective The study area is a typical small watershed in the middle reaches of the Jinsha River. Identifying the ecological risks and pollution sources of soil heavy metals in the watershed is of great practical significance for the ecological and environmental protection of the Jinsha River Basin.
      Methods A total of 120 soil samples and 9 rock samples were systematically collected from the watershed. The contents of As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn in both soil and rock samples, as well as soil pH values, were analyzed. The single-factor pollution index, Nemerow comprehensive pollution index, and geo-accumulation index were employed to assess the status of heavy metal pollution. Principal Component Analysis (PCA) and the Positive Matrix Factorization (PMF) model were applied to quantitatively identify the sources of soil heavy metals.
      Results The median pH values of the soil was 6.48. The average concentrations of Cd, Cu and Pb were 4.04, 3 and 6.40 times the corresponding background values, while those of the other elements ranged from 1.06 to 2.50 times the background values.The proportions of sampling sites where Zn, Cu, Cr, Ni and Cd concentrations exceeded the background values were 86.67%, 80.83%, 78.33%, 75.00% and 73.33%, and the ratios for the remaining elements were between 32.5% and 52.50%. For Cu, Cd and Pb, the percentages of sites exceeding the risk screening values were 57.5%, 50.83% and 31.67%. No sampling sites were found with Hg concentrations above the risk screening value, and the proportions for other elements ranged from 10.83% to 28.33%.Single factor pollution index evaluation indicated that Cu, Cd, Pb and Cr presented relatively severe pollution in the study area. The Nemerow comprehensive pollution index evaluation revealed that 85.83% of the total sites were polluted, suggesting a serious pollution status. According to the geo-accumulation index assessment, Cd and Pb were the primary pollutants with high pollution levels. PCA and PMF model analysis demonstrated that heavy metals in the soils of the study area mainly originated from ore bodies and widely exposed basalt.
      Conclusions Pollution is widely distributed across the watershed. Ore bodies are the primary source of soil heavy metals in the study area, followed by basalt, while the impact of agricultural activities is relatively slight.

       

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