Enigma of Urban Gaseous Oxygenated Organic Molecules: Precursor Type, Role of NOx, and Degree of Oxygenation
Enigma of Urban Gaseous Oxygenated Organic Molecules: Precursor Type, Role of NOx, and Degree of Oxygenation
复制标题
城市气态氧化有机分子之谜：前体类型、氮氧化物的作用和氧化程度
DOI：
10.1021/acs.est.2c05047
复制
发表时间：
2022
期刊：
影响因子：
--
通讯作者：
Cheng Huang
中科院分区：
文献类型：
--
作者：
Linhui Tian;Dan Dan Huang;Yong Jie Li;Chao Yan;Wei Nie;Zhe Wang;Qian Wang;Liping Qiao;Min Zhou;Shuhui Zhu;Yuliang Liu;Yishuo Guo;Xiaohui Qiao;Penggang Zheng;Sheng’ao Jing;Shengrong Lou;Hongli Wang;Cheng Huang
挥发性有机化合物（VOCs）氧化形成含氧有机分子（OOMs），造成二次污染。本文报道了上海地区以硝酸盐为试剂离子的化学电离质谱法测定OOMs的结果。与森林和实验室研究相比，在这个城市地点检测到的OOMs的氧化程度相对较低。这是由于高浓度的nox (~ 44 ppb)，总体上显示出对繁殖反应的抑制。另一个结果是，在高NO/VOC比的条件下，观察到含氮OOMs的比例很大（75%），这一比例进一步增加到84%。通过应用一个新的OOM分类框架和VOC测量支持，50%和32%的OOM分别归属于芳香和脂肪族前体。此外，芳香族oom比脂肪族oom更富氧（有效氧值nOeff= 4-6），这可以部分解释为引发机制的差异，并指出终止反应可能存在区别。本研究强调了城市地区NOxin OOM形成的作用，以及可能显示芳香和脂肪族VOCs区别的含氮产物的形成。
Oxidation of volatile organic compounds (VOCs) forms oxygenated organic molecules (OOMs), which contribute to secondary pollution. Herein, we present measurement results of OOMs using chemical ionization mass spectrometry with nitrate as the reagent ion in Shanghai. Compared to those in forests and laboratory studies, OOMs detected at this urban site were of relatively lower degree of oxygenation. This was attributed to the high NOxconcentrations (∼44 ppb), which overall showed a suppression on the propagation reactions. As another result, a large fraction of nitrogenous OOMs (75%) was observed, and this fraction further increased to 84% under a high NO/VOC ratio. By applying a novel framework on OOM categorization and supported by VOC measurements, 50 and 32% OOMs were attributed to aromatic and aliphatic precursors, respectively. Furthermore, aromatic OOMs are more oxygenated (effective oxygen number,nOeff= 4–6) than aliphatic ones (nOeff= 3–4), which can be partly explained by the difference in initiation mechanisms and points to possible discrimination in termination reactions. This study highlights the roles of NOxin OOM formation in urban areas, as well as the formation of nitrogenous products that might show discrimination between aromatic and aliphatic VOCs.