城市轨道交通沿线地表灰尘重金属污染特征、来源及健康风险评价-以西安市为例
- Characteristics, Sources, and Health Risk Assessment of Heavy Metal Pollution in Surface Dust along Urban Rail Transit Lines: A Case Study of Xi'an City
- 基金项目：陕西省重点研发计划产业链项目(2024NC-ZDCYL-02-15)
- 摘要：为揭示城市轨道交通沿线地表灰尘重金属污染对生态环境质量的影响，采集西安市轨道交通7条线路59个地铁站点站外出入口灰尘样品，利用电感耦合等离子体质谱仪（ICP-MS）分别测定灰尘中6种重金属（Ni、Cu、Zn、As、Cd和Pb）含量，采用地累积指数法（Igeo）、内梅罗污染指数法（NPI）和克里金插值法分析灰尘重金属的污染程度和空间分布特征，通过相关性分析和正定矩阵因子分解（PMF）模型相结合的方法开展城市地表灰尘重金属来源探讨，利用美国环境保护署（US EPA）提出的健康风险评价模型来评价人体健康风险.结果表明，研究区地表灰尘中6种重金属含量除As外平均值均高于陕西省土壤背景值.6种重金属的地累积指数从大到小依次为：Cd（3.23）、Cu（1.43）、Zn（1.34）、Pb（0.75）、Ni（-0.53）、As（-0.98），依次为重度（Cd）、中度（Cu、Zn）、轻度（Pb、Ni）和无污染（As）.内梅罗污染指数平均值由高到低依次为：4号线（8.40）、3号线（7.48）、2号线（6.02）、1号线（5.64）、6号线（5.37）、14号线（5.19）、5号线（3.94）.两种污染评价方法均表明各条线路中Cd污染均最为显著，As基本处于无污染状态.克里金插值结果表明，不同站点重金属含量空间分布特征差异显著，表现为空间分布上的不均性.源解析结果表明，研究区重金属As主要来自以岩石风化、植物腐烂为主的自然源（24.3%），Zn和Ni主要来自以建筑防腐材料脱落、建筑运输设备部件磨损为主的建筑源（34.3%），Cd和Pb主要来自以机械制造、金属加工及热电厂废气排放为主的工业源（21.3%），Cu和Pb主要来自以交通密集区汽车频繁制动致零部件磨损、地铁隧道运行部件损耗及城市燃油轿车尾气排放为主的交通源（20%）.由健康风险评价可知，手口摄入为主要暴露途径，成人和儿童均不存在非致癌风险，手口摄入和皮肤接触途径存在一定致癌风险，且儿童的总非致癌风险指数和总致癌风险指数均高于成人.
- Abstract：To reveal the impact of heavy metal pollution in urban surface dust along metro lines on ecological and environmental quality, surface dust samples were collected from 59 metro station entrances across seven metro lines in Xi’an, China. The concentrations of six heavy metals (Ni, Cu, Zn, As, Cd, and Pb) in the dust were determined using inductively coupled plasma mass spectrometry (ICP-MS). The pollution levels and spatial distribution characteristics of these heavy metals were assessed using the geo-accumulation index method (Igeo), the Nemerow pollution index (NPI), and Kriging interpolation. A combination of correlation analysis and the positive matrix factorization (PMF) model was employed to investigate the sources of heavy metals in urban surface dust. Additionally, the health risks were evaluated using the health risk assessment model proposed by the U.S. Environmental Protection Agency (US EPA). The results showed that the mean concentrations of six heavy metals in surface dust exceeded the background values of soil in Shaanxi Province, except for As. The geo-accumulation index of the six heavy metals ranked in descending order was as follows: Cd (3.23) > Cu (1.43) > Zn (1.34) > Pb (0.75) > Ni (-0.53) > As (-0.98), indicating severe pollution (Cd), moderate pollution (Cu and Zn), minor pollution (Pb and Ni), and no pollution (As). The average values of the Nemero Pollution Index from high to low were as follows: Line 4 (8.40)>Line 3 (7.48)>Line 2 (6.02)>Line 1 (5.64)>Line 6 (5.37)>Line 14 (5.19)>Line 5 (3.94). Both pollution assessment methods consistently indicated that Cd pollution was the most significant among all the lines, while As was generally in a state of no pollution. Kriging interpolation revealed significant spatial heterogeneity in heavy metal concentrations among different stations. Source apportionment results indicated that heavy metal As in the study area primarily originated from natural sources, such as rock weathering and plant decay (24.3%). Zn and Ni mainly came from construction sources, including spalling of construction materials and wear of construction transportation equipment components (34.3%). Cd and Pb were predominantly derived from industrial sources, such as mechanical manufacturing, metal processing, and waste gas emissions from thermal power plants (21.3%). Cu and Pb were mainly associated with traffic sources, including frequent vehicle braking in high-traffic areas causing component wear, metro tunnel component abrasion, and exhaust emissions from urban fuel-powered vehicles (20%). Health risk assessment results indicated that hand-to-mouth ingestion was the primary exposure pathway. Both adults and children showed no non-carcinogenic risks, but there were certain carcinogenic risks associated with hand-to-mouth ingestion and dermal contact, with children exhibiting higher total non-carcinogenic and carcinogenic risk indices than adults.
