2019─2020年兰州市两城区大气多环芳烃污染特征、来源与健康风险评估
Pollution characteristics, sources, and risk assessment of polycyclic aromatic hydrocarbons in atmosphere of two districts of Lanzhou City from 2019 to 2020
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摘要:
背景 多环芳烃（PAHs）是大气中分布最广泛、对人群危害最大的有机污染物之一。
目的 探究2019─2020年兰州市两城区大气中PAHs的分布特征及组成来源，并评估PAHs经吸入途径对不同人群的健康风险。
方法 于2019年1月至2020年12月在兰州市两城区（城关区和西固区）定期对大气中16种PAHs质量浓度（后简称为浓度）进行检测，采用Mann-Whitney
U 秩和检验比较两组中位数的差异，采用特征比值法和主成分分析法对其来源进行解析，采用终生致癌风险（ILCR）模型对PAHs进行健康风险评估。结果 2019─2020年兰州市城关区、西固区PAHs年浓度
M （P 25，P 75）分别为24.04（14.59，41.81）ng·m−3和25.97（18.59，42.56）ng·m−3，差异无统计学意义（Z =−0.970，P >0.05）。季节分布特征显示，城关区多数PAHs单体浓度在夏季高于西固区，且苯并a 蒽和苯并g ,h ,i 芘在春秋季也高于西固区（P <0.05），但冬季两城区PAHs单体浓度无明显差异（P >0.05）。环数分布特征表明，在冬春季，城关区、西固区占比最高的均为4环PAHs，分别为37.32%~41.73%、35.20%~39.66%，在夏秋季，城关区、西固区占比最高的均为2~3环PAHs，分别为39.38%~49.54%47.17%~51.23%，具有季节波动性。特征比值法分析表明，两城区大气PAHs的主要来源是化石燃料、煤炭及生物质燃烧的混合来源。主成分分析法结果显示，四个主成分因子累计贡献率达到79.54%。主成分1包括菲、蒽、荧蒽、芘、屈、苯并a 蒽、苯并b 荧蒽、苯并k 荧蒽和苯并a 芘；主成分2包括二氢苊、二苯并a ,h 蒽；主成分3是茐；主成分4为萘。健康风险评估结果表明，城关区成年男性、成年女性及儿童的ILCR值分别为2.30×10−6、2.16×10−6和1.73×10−6；西固区男性、女性及儿童的ILCR值分别为1.58×10−6、1.48×10−6和1.19×10−6；均大于10−6。结论 兰州市两城区大气存在PAHs污染，其主要来源为化石燃料、煤炭及生物质燃烧的混合来源，且对人群存在潜在致癌风险。
Abstract:Background Polycyclic aromatic hydrocarbons (PAHs) are one of the most widely distributed and harmful organic pollutants in the atmosphere.
Objective To investigate the distribution characteristics and composition sources of PAHs in the atmosphere of two districts of Lanzhou from 2019 to 2020 and evaluate the health risks of PAHs via inhalation to different populations.
Methods The PAHs concentrations in two urban areas (Chengguan District and Xigu District) of Lanzhou City from January 2019 to December 2020 were regularly monitored. Mann-Whitney
U test was used to compare differences in target pollutant concentrations between the two areas. Diagnostic ratio method and principal component analysis were adopted for source identification. Incremental lifetime cancer risk (ILCR) model was applied to evaluate the health risks of PAHs.Results The
M (P 25,P 75) PAHs concentrations in Chengguan District and Xigu District were 24.04 (14.59, 41.81) ng·m−3 and 25.97 (18.59, 42.56) ng·m−3, respectively, with no significant difference (Z =−0.970,P >0.05). As to seasonal distribution, most PAHs monomer concentrations in Chengguan District were higher than those in Xigu District in summer, and the concentrations of benzoa anthracene and benzog ,h ,i perylene in Chengguan District were also higher than those in Xigu District in spring and autumn (P <0.05), but there were no significant differences in PAHs monomer concentrations between the two urban areas in winter (P >0.05). Ring number of PAHs exhibited seasonal fluctuations. In winter and spring, the highest proportions in Chengguan District and Xigu District were both 4-ring PAHs (37.32%-41.73%, 35.20%-39.66%), and in summer and autumn, the highest proportions were both 2- and 3-ring PAHs (39.38%-49.54%, 47.17%-51.23%). The results of diagnostic ratio method revealed mixed atmospheric PAHs sources in the two urban areas, including fossil fuel, coal, and biomass combustion. The results of principal component analysis showed that the cumulative contribution rate of the four principal component factors reached 79.54%. Principal component 1 included phenanthrene, anthracene, fluoranthene, pyrene, chrysene, benzoa anthracene, benzob fluoranthene, benzok fluoranthene, and benzoa pyrene; principal component 2 included acenaphthene and dibenzoa ,h anthracene; principal component 3 was fluorene; principal component 4 was naphthalene. The results of health risk assessment showed that the ILCR values of adult males, adult females, and children in Chengguan District were 2.30×10−6, 2.16×10−6, and 1.73×10−6, respectively; and those in Xigu District were 1.58×10−6, 1.48×10−6, and 1.19×10−6, respectively; all were greater than 10−6.Conclusion PAHs pollution exists in the atmosphere of the two urban areas of Lanzhou City, mainly comes from mixed sources of fossil fuels, coal, and biomass burning, and may pose potential carcinogenic risks to the population.
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