Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China; University of the Chinese Academy of Sciences, Beijing 100049, China.
Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China; Institute for Atmospheric and Earth System Research, Physics, Faculty of Science, P.O. Box 64, 00014, University of Helsinki, Helsinki, Finland.
Sci Total Environ. 2021 Jun 15;773:145264. doi: 10.1016/j.scitotenv.2021.145264. Epub 2021 Jan 23.
The atmospheric oxidation capacity (AOC) and photochemical reactivity are of increasing concern owing to their roles in photochemical pollution. The AOC and OH reactivity were evaluated based on simultaneous measurements of volatile organic compounds (VOCs), trace gases and photolysis frequency during summer and winter campaigns at a suburban site in Xianghe. The AOC exhibited well-defined seasonal and diurnal patterns, with higher intensities during the summertime and daytime than during the wintertime and nighttime, respectively. The major reductants contributing to the AOC during the summertime were CO (41%) and alkenes (41%), whereas CO (40%) and oxygenated VOCs (OVOCs) (30%) dominated the AOC during the wintertime. The dominant oxidant contributor to the AOC during the daytime was OH (≥93%), while the contributions of O and NO (≥75%) to the AOC increased during the nighttime. High values during the wintertime and an increase at night were features of the speciated OH reactivity. Inorganic compounds (NO and CO) dominated the speciated OH reactivity (76% and 85% during the summer and winter campaigns, respectively). Among VOCs, the dominant contributors were alkenes (12%) and OVOCs (7%) during the summer and winter campaigns, respectively. The ratio of NO- and VOC-attributed OH reactivity indicated that O formation occurred under a VOC-limited regime during the summertime and that aromatics had the largest potential to form O Isoprene and m/p-xylene were the most important contributors to the AOC, OH reactivity and O-forming among VOCs during the summertime, biogenic sources and secondary formation and industrial production were the main sources of these species. During the wintertime, hexanal and ethylene were the key VOC species contributing to the AOC and OH reactivity, and solvent usage and traffic-related emissions were the main contributing sources. We recommend that priority measures for the control of VOC species and sources should be taken when suitable. CAPSULE: This study focused on the similarities and differences in the AOC and speciated OH reactivity during summer and winter campaigns.
大气氧化能力（AOC）和光化学反应活性由于它们在光化学污染中的作用而受到越来越多的关注。在香河郊区进行的夏季和冬季测量期间，基于挥发性有机化合物（VOC）、痕量气体和光解频率的同时测量，评估了 AOC 和 OH 反应性。AOC 表现出明显的季节性和日变化模式，夏季白天的强度高于冬季夜间。在夏季，对 AOC 贡献最大的还原剂是 CO（41%）和烯烃（41%），而在冬季，CO（40%）和含氧挥发性有机化合物（OVOCs）（30%）占主导地位。在白天，对 AOC 贡献最大的氧化剂是 OH（≥93%），而在夜间，O 和 NO（≥75%）对 AOC 的贡献增加。在冬季，特征 OH 反应性增加是高值的特征，夜间增加也是特征 OH 反应性的特征。在夏季和冬季测量中，无机化合物（NO 和 CO）分别占特征 OH 反应性的 76%和 85%。在 VOC 中，夏季和冬季的主要贡献者分别为烯烃（12%）和 OVOCs（7%）。NO 和 VOC 归因于 OH 反应性的比例表明，在夏季，O 的形成发生在 VOC 限制的条件下，并且芳烃具有形成 O 的最大潜力。异戊二烯和间/对二甲苯是夏季 VOC 中对 AOC、OH 反应性和 O 形成的最重要贡献者，生物源和二次形成以及工业生产是这些物种的主要来源。在冬季，己醛和乙烯是对 AOC 和 OH 反应性贡献最大的关键 VOC 物种，而溶剂使用和交通相关排放是主要的贡献源。我们建议在适当的时候采取控制 VOC 物种和来源的优先措施。
本研究重点研究了夏季和冬季测量期间 AOC 和特征 OH 反应性的异同。
