河湟谷地农田土壤重金属分布及人群健康风险评价以西宁市为例

Distribution of heavy metals in agricultural soils of the Hehuang Valley and assessment of human health risks: a case study of Xining City

    摘要
  • 摘要: 针对快速城市化背景下农田土壤重金属污染与健康风险问题，评估了河湟谷地区域内的西宁市农作物基地表层土壤中重金属（As、Cd、Co、Cr、Cu、Mn、Ni、Pb、Zn）的污染特征与健康风险，采用地累积指数（Igeo）和潜在生态风险指数（RI）评估污染程度与生态风险，运用美国国家环境保护局的健康风险模型计算成人与儿童经口摄入、皮肤接触和吸入途径下的非致癌风险（HI）与致癌风险（TCR），并结合正定矩阵因子分析（PMF）受体模型进行源解析。结果显示：研究区重金属浓度顺序为Mn>Zn>Cr>As>Ni>Pb>Cu>Co>Cd，其中As（35.38 mg/kg）、Cd（0.19 mg/kg）、Ni（30.63 mg/kg）、Pb（28.74 mg/kg）、Zn（72.15 mg/kg）超青海省土壤背景值，As达轻中度污染（Igeo=0.84）。PMF源解析识别4类源：自然和农业混合源（22.6%），工业、生活和交通混合源（24.2%），农业源（23.9%）及交通和自然混合源（29.3%）。RI为82.52表明整体为低生态风险，但Cd潜在风险需关注。健康风险评价揭示：儿童总非致癌风险（HI=1.21）高于成人（HI=0.47），总致癌风险（儿童TCR=1.73×10−4，成人TCR=1.25×10−4）虽未超标，但儿童暴露于Ni、As的风险显著。研究表明农业活动、工业与交通是该地区农用地的主要污染驱动因素，建议加强对As、Cd、Ni等元素的源头监控及农田管理措施。

     

    Abstract: This study addressed the ecological contamination and health risks associated with heavy metals in farmland soils under rapid urbanization. It evaluated the pollution characteristics and health risks of heavy metals (As, Cd, Co, Cr, Cu, Mn, Ni, Pb, Zn) in surface soils from vegetable farmlands in the Xining region of the Hehuang Valley. The geo-accumulation index (Igeo) and potential ecological risk index (RI) were employed to assess the pollution level and ecological risk, respectively. The U.S. EPA health risk assessment model was applied to estimate non-carcinogenic risk (HI) and total carcinogenic risk (TCR) for adults and children via oral ingestion, dermal contact, and inhalation pathways. The positive matrix factorization (PMF) receptor model was applied for source apportionment. Thirty surface soil samples were analyzed. The result showed the following concentration order: Mn>Zn>Cr>As>Ni>Pb>Cu>Co>Cd. Among these, As (35.38 mg/kg), Cd (0.19 mg/kg), Ni (30.63 mg/kg), Pb (28.74 mg/kg) and Zn (72.15 mg/kg) exceeded the background values of Qinghai. As exhibited light to moderate pollution (Igeo=0.84). PMF analysis identified four sources: natural and agricultural mixed source (22.6%), industrial, residential and traffic mixed source (24.2%), agricultural source (23.9%), and traffic and natural mixed source (29.3%). The ecological risk index (RI = 82.52) indicated an overall low risk, though the potential risk of Cd required attention. Health risk assessment showed that the total non-carcinogenic risk for children (HI=1.21) was higher than that for adults (HI=0.47). The total carcinogenic risk (TCR=1.73×10−4 for children, TCR=1.25×10−4 for adults) did not exceed thresholds, but children exhibited significant exposure risks to Ni, and As. The study demonstrated that agricultural activities alongside industrial and traffic emissions were the main drivers of pollution in this farmland area. It was recommended to strengthen source control and farmland management measures for elements such as As, Cd, and Ni.

     

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