Chemical composition, sources and optical properties of nitrated aromatic compounds in fine particulate matter during winter foggy days in Nanjing, China.
Chemical composition, sources and optical properties of nitrated aromatic compounds in fine particulate matter during winter foggy days in Nanjing, China.
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DOI：
10.1016/j.envres.2022.113255
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发表时间：
2022-04
影响因子：
8.3
通讯作者：
Chenjuan Gu;Shijie Cui;X. Ge;Zhiying Wang;Meijuan Chen;Zihe Qian;Zhiyi Liu;Xinfeng Wang
中科院分区：
文献类型：
--
作者：
Chenjuan Gu;Shijie Cui;X. Ge;Zhiying Wang;Meijuan Chen;Zihe Qian;Zhiyi Liu;Xinfeng Wang
功能化芳香化合物是细颗粒物(PM2.5)中最重要的光吸收有机发色团之一，也就是所谓的棕色碳(BRC)。在这项研究中，我们进行了冬季野外活动，在长江三角洲地区南京郊区的雾天和非雾天，利用液质联用仪(LC-MS)和空气动力高分辨率气溶胶质谱仪(AMS)等离线分析技术，对PM2.5中的8种硝基芳香化合物(NaC)进行了测定。平均而言，4-硝基苯酚可能是BRC中最重要的光吸收材料之一，占已鉴定发色团质量浓度的40%以上。雾天期间，2-甲基-4-硝基苯酚和2，6-二甲基-4-硝基苯酚的质量浓度明显增加，对总浓度的贡献率分别增加10%和5%。结合LC-MS和AMS数据集进行正矩阵分解分析，以确定NAC的主要来源和次要来源。主要污染源，如交通和固体燃料燃烧，占4-硝基苯酚、2，6-二甲基-4-硝基苯酚和3-硝基水杨酸总和的71%，表明初级排放对这些NAC有重要贡献。与两个含氧有机气溶胶有关的二次源对4-硝基苯酚的贡献可达66%，反映了这种硝化芳香族化合物与二次有机气溶胶源的联系。结合光学测量，4-硝基苯酚在250到550 nm的光范围内对已鉴定的BRC的吸光度有很高的贡献(>；50%)。这可能会突出这种NAC在环境BRC光吸收中的重要作用，尽管它对总有机碳的质量贡献可以忽略不计。我们的工作有助于了解BRC的光学性质与化学组成之间的联系，以及在典型污染大气条件下BRC发色团与非雾天和雾天的差异。
Functionalized aromatic compounds are one of the most important light-absorbing organic chromophores – so-called brown carbon (BrC) – in fine particulate matter (PM2.5). In this study, we conducted a wintertime field campaign to measure eight nitrated aromatic compounds (NACs) in PM2.5with offline analysis techniques, including liquid chromatograph mass spectrometer (LC-MS) and aerodyne high-resolution aerosol mass spectrometer (AMS) measurements, during foggy and nonfoggy days in suburban Nanjing in the Yangtze River Delta region, China. On average, 4-nitrophenol could be one of the most important light absorbing materials in the observed BrC, which accounted for over 40% of the mass concentration of identified chromophores. The mass concentration of 2-methyl-4-nitrophenol and 2,6-dimethyl-4-nitrophenol were evidently increased during foggy days, contribution of which to total NACs were increased by 10% and 5%, respectively. Positive matrix factorization analysis of combining LC-MS and AMS dataset was performed to identify the primary and secondary sources of NACs. Primary sources, e.g., traffic and solid-fuel combustion, accounted for 71% of the sum of 4-nitrophenol, 2,6-dimethyl-4-nitrophenol and 3-nitrosalicylic acid, suggesting important contribution of primary emissions to these NACs. The contribution of secondary sources, associated with two oxygenated organic aerosols, could contribute 66% to 4-nitrophenol, reflecting the link of such nitrated aromatic compounds to secondary organic aerosol source. Together with optical measurements, 4-nitrophenol presented a high contribution (>50%) to the identified BrC absorbance in the light range 250 and 550 nm was observed. This could highlight an important role of such NACs in ambient BrC light absorption, despite its mass contribution to total organic carbon was negligible. Our work could improve the understanding of the links between optical properties and chemical composition of BrC, and the difference between BrC chromophores from nonfoggy days and foggy days under the typical polluted atmospheric conditions.