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- Title
Large Daytime Molecular Chlorine Missing Source at a Suburban Site in East China.
- Authors
Chen, Qianjie; Xia, Men; Peng, Xiang; Yu, Chuan; Sun, Peng; Li, Yuanyuan; Liu, Yuliang; Xu, Zhengning; Xu, Zheng; Wu, Rongrong; Nie, Wei; Ding, Aijun; Zhao, Yu; Wang, Tao
- Abstract
Molecular chlorine (Cl2) affects atmospheric oxidative capacity by generating chlorine radicals upon photolysis, but it is poorly simulated in atmospheric chemistry models. In this study, we observed up to 40 ppt Cl2 around noon at a suburban site in East China, and used a box model with up‐to‐date chlorine chemistry and comprehensive observational constraints to investigate Cl2 formation mechanisms. The standard model run with traditional Cl2 formation mechanisms underestimates the observed Cl2 by almost one order of magnitude around noon. The daytime Cl2 missing source was estimated, accounting for on average (69 ± 5)% of daytime Cl2 production for the 1‐week study period. It is likely caused by photochemistry within the aerosols, based on its correlation with observed environmental factors, such as sunlight intensity and aerosol abundances. With the daytime Cl2 missing source implemented into the model, the chlorine radical abundance increases by a factor of 4 in the afternoon, enhancing the oxidation of volatile organic compounds. A good understanding of daytime Cl2 formation mechanisms is critical while assessing the impacts of chlorine chemistry on air quality and climate. Plain Language Summary: The photolysis of molecular chlorine gases generates chlorine atoms, which are strong detergent in the lower atmosphere. Chlorine atoms react rapidly with hydrocarbon species in the atmosphere, affecting air quality and climate. High levels of molecular chlorine gases during daytime has been reported recently in China, but it remains unclear how they are formed. In this study, we used a box model to simulate molecular chlorine formation at a suburban site in East China. We propose aerosol photochemistry could be important for molecular chlorine formation during daytime. Key Points: Traditional mechanisms underestimate molecular chlorine observations by almost an order of magnitude around noonThe missing source accounts for about 70% of molecular chlorine production during daytimeThe daytime molecular chlorine missing source could be caused by aerosol photochemistry
- Subjects
CHINA; PHOTOLYSIS (Chemistry); AEROSOLS; OXIDATION; VOLATILE organic compounds
- Publication
Journal of Geophysical Research. Atmospheres, 2022, Vol 127, Issue 4, p1
- ISSN
2169-897X
- Publication type
Article
- DOI
10.1029/2021JD035796