Large Daytime Molecular Chlorine Missing Source at a Suburban Site in East China

Qianjie Chen, Men Xia, Xiang Peng, Chuan Yu, Peng Sun, Yuanyuan Li, Yuliang Liu, Zhengning Xu, Zheng Xu, Rongrong Wu, Wei Nie, Aijun Ding, Yu Zhao, Tao Wang

Research output: Journal article publicationJournal articleAcademic researchpeer-review

5 Citations (Scopus)


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.

Original languageEnglish
Article numbere2021JD035796
JournalJournal of Geophysical Research: Atmospheres
Issue number4
Publication statusPublished - 27 Feb 2022


  • aerosol
  • box model
  • daytime source
  • molecular chlorine
  • photolysis

ASJC Scopus subject areas

  • Atmospheric Science
  • Geophysics
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science


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