Formation mechanism of secondary organic aerosol from ozonolysis of gasoline vehicle exhaust.
Formation mechanism of secondary organic aerosol from ozonolysis of gasoline vehicle exhaust.
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DOI：
10.1016/j.envpol.2017.12.048
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发表时间：
2018-03
影响因子：
8.9
通讯作者：
Bo Yang;Pengkun Ma;J. Shu;Peng Zhang;Jingyun Huang;Haixu Zhang
中科院分区：
文献类型：
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作者：
Bo Yang;Pengkun Ma;J. Shu;Peng Zhang;Jingyun Huang;Haixu Zhang
汽油车是人为二次有机气溶胶（SOA）的主要来源。然而，目前的模型的基础上已知的前体无法解释大量的SOA从汽车排放的形成机制的认识不足。为了提供更多关于这个问题的信息，从臭氧分解的四个轻型汽油车排气系统的SOA的形成进行了研究与真空紫外光电离质谱仪（VUV-PIMS）。观察到显著的SOA形成，并且SOA主要是脂肪族烯烃。来自所有车辆的SOA的PI质谱表现出相似的光谱模式（m/z为98、112、126的规则质量群）。有趣的是，观察到的主要气体产物的脂肪族烯烃的羰基产物具有特定的分子量，和SOA的主要形成途径可以很好地解释使用这些羰基的羟醛缩合反应。这是一个直接观察到的醇醛缩合作为一个占主导地位的途径SOAs的形成，并从汽油车尾气臭氧分解的SOAs的组成和形成机理的第一个报告。该研究表明，低分子量烯烃可能在车辆诱导的SOA形成中发挥比以前认为的更重要的作用。更重要的是，从车辆的SOA的PI质谱显示相似的领域气溶胶样品质谱，这表明在环境气溶胶形成的羟醛缩合反应的可能意义。由于羰基化合物是生物和人为VOCs通过大气氧化过程的主要降解产物，因此本研究中提出的机制可以更普遍地用于解释大气碳氢化合物氧化形成气溶胶。
Gasoline vehicles are a major source of anthropogenic secondary organic aerosols (SOAs). However, current models based on known precursors fail to explain the substantial SOAs from vehicle emissions due to the inadequate understanding of the formation mechanism. To provide more information on this issue, the formation of SOAs from ozonolysis of four light-duty gasoline vehicle exhaust systems was investigated with a vacuum ultraviolet photoionization mass spectrometer (VUV-PIMS). Remarkable SOAs formation was observed and the SOAs were primarily aliphatic alkenes. PI mass spectra of the SOAs from all vehicles exhibited similar spectral patterns (a regular mass group with m/z at 98, 112, 126 …). Interestingly, most carbonyl products of aliphatic alkenes observed as major gaseous products have specific molecular weights, and the main formation pathway of SOAs can be explained well using aldol condensation reactions of these carbonyls. This is a direct observation of the aldol condensation as a dominated pathway for SOAs formation, and the first report on the composition and formation mechanism of the SOAs from the ozonolysis of gasoline vehicle exhaust is given. The study reveals that low molecular weight alkenes may play a more significant role in vehicle-induced SOAs formation than previously believed. More importantly, the PI mass spectra of SOAs from vehicles show similarities to the field aerosol sample mass spectra, suggesting the possible significance of the aldol condensation reactions in ambient aerosol formation. Since carbonyls are a major degradation product of biogenic and anthropogenic VOCs through atmospheric oxidation processes, the mechanism proposed in this study can be applied more generally to explain aerosol formation from the oxidation of atmospheric hydrocarbons.