烟台地区供暖期PM2.5中多环芳烃浓度及源解析

Concentration and source analysis of polycyclic aromatic hydrocarbons in PM2.5 during heating period in Yantai City

  • 摘要:
    背景 多环芳烃(PAHs)是一类已知的广泛存在的大气污染物,可以对人体和生态环境造成严重危害。
    目的 分析烟台市芝罘区和龙口市供暖期大气PM2.5中PAHs的含量和来源。
    方法 选取烟台市芝罘区和龙口市两个监测点,于2023年4月至2024年3月进行PM2.5样品采集。应用气相色谱-质谱法分析供暖期(2023年11月至2024年3月)和非供暖期(2023年4月至10月)大气PM2.5中PAHs质量浓度(后称浓度),比较两个时期的PAHs浓度,采用特征比值法对供暖期PAHs来源进行分析。
    结果 供暖期间烟台芝罘区和龙口市两个监测点大气PM2.5中PAHs总浓度范围分别为(1.59~23.70)、(2.08~149.72)ng·m−3,浓度中位数(M)及第25、75百分位数(P25P75)分别为4.99(2.61,8.09)、15.46(8.15,29.05) ng·m−3,龙口市各月份均明显高于芝罘区(P<0.05)。两个监测点PAHs总浓度中位数最高的月份均为1月,分别为8.14、81.56 ng·m−3。非供暖期两个监测点PAHs总浓度MP25P75)分别为1.59(1.59,2.78)、4.11(2.94,7.97)ng·m−3,均明显低于供暖期(P<0.01)。两个监测点PM2.5中不同环数PAHs的构成均为4环>5环>6环,其中4环贡献率最高,所占百分比分别为65.33%和46.39%;PAHs中浓度最高的成分均为荧蒽,浓度MP25P75)为1.29(0.51,1.78)、2.32(1.30,3.82)ng·m−3。芝罘区特征比值荧蒽/(荧蒽+芘)、荧蒽/芘、苯并a蒽/(苯并a蒽+䓛)、芘/苯并a芘、苯并a芘/(苯并a芘+䓛)、苯并a芘/苯并g,h,i苝和茚并1,2,3-c,d芘/(茚并1,2,3-c,d芘+苯并g,h,i苝)分别为0.62、1.65、0.41、4.48、0.50、0.93和0.47,龙口特征比值分别为0.57、1.35、0.40、2.89、0.29、0.79和0.47,结果表明PAHs污染物是煤燃烧、机动车尾气排放和汽油燃烧共同作用产生。
    结论 烟台地区供暖期大气PM2.5中PAHs总浓度明显高于非供暖期,其中供暖期间龙口市污染程度明显高于芝罘区。PAHs呈混合污染特点,主要来源有汽油、煤炭燃烧和机动车尾气排放等。

     

    Abstract:
    Background Polycyclic aromatic hydrocarbons (PAHs) are widely known atmospheric pollutants, which can cause serious harm to human body and ecological environment.
    Objective To analyze the concentrations and sources of PAHs in atmospheric PM2.5 in Zhifu District and Longkou City during the heating period in Yantai.
    Methods Two monitoring sites in Zhifu District and Longkou City of Yantai were selected, and PM2.5 sample collection was carried out from April 2023 to March 2024. Gas chromatography-mass spectrometry was applied to analyze the concentrations of PAHs in atmospheric PM2.5 during the heating period (from November 2023 to March 2024) and the non-heating period (from April to October 2023). The concentrations of PAHs in the two periods were compared and the sources of PAHs during the heating period were analyzed by characteristic ratio method.
    Results During the heating period, the total concentration ranges of PAHs in atmospheric PM2.5 at the monitoring sites in Zhifu District and Longkou City of Yantai were (1.59-23.70) ng·m−3 and (2.08-149.72) ng·m−3 respectively, and the medians (M) and the 25th and 75th percentiles (P25, P75) were 4.99 (2.61, 8.09) ng·m−3 and 15.46 (8.15, 29.05) ng·m−3 respectively. The PAHs concentrations in Longkou City were significantly higher than those in Zhifu District in all months (P<0.05). The highest median total concentrations of PAHs in both sites were reported in January (8.14 ng·m−3 and 81.56 ng·m−3 respectively). In the non-heating period, the M (P25, P75) of the total PAHs concentrations at the two sites were 1.59 (1.59, 2.78) ng·m−3 and 4.11 (2.94, 7.97) ng·m−3 respectively, much lower than those in the heating period (P<0.01). The order of composition of PAHs by ring number in PM2.5 at both sites was 4-ring> 5-ring> 6-ring, with the 4-ring contributing the largest proportion (65.33% and 46.39% respectively). Fluoranthene had the highest concentration among PAHs at both sites, with concentrations M (P25, P75) of 1.29 (0.51, 1.78) ng·m−3 and 2.32 (1.30, 3.82) ng·m−3 respectively. The characteristic ratios of fluoranthene/(fluoranthene + pyrene), fluoranthene/pyrene, benzoaanthracene/(benzoaanthracene + chrysene), pyrene/benzoapyrene, benzoapyrene/(benzoapyrene + chrysene), benzoapyrene/benzog,h,ipyrene, and indeno1,2,3-c,dpyrene/(indeno1,2,3-c,dpyrene + benzog,h,ipyrene) in Zhifu District were 0.62, 1.65, 0.41, 4.48, 0.50, 0.93 and 0.47 respectively, and those in Longkou were 0.57, 1.35, 0.40, 2.89, 0.29, 0.79 and 0.47 respectively. The results showed that PAHs pollutants were generated by combination of coal combustion, vehicle exhaust emissions and gasoline combustion.
    Conclusion During the heating period in Yantai area, the total concentration of PAHs in atmospheric PM2.5 is significantly higher than that in the non-heating period. Among them, during the heating period, the pollution level in Longkou City is significantly higher than that in Zhifu District. The local PAHs may be sourced from mixed pollution, and the main sources include gasoline, and coal combustion and vehicle exhaust emissions.

     

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