Pollution-Derived Br2 Boosts Oxidation Power of the Coastal Atmosphere

Men Xia, Tao Wang (Corresponding Author), Zhe Wang, Yi Chen, Xiang Peng, Yunxi Huo, Weihao Wang, Qi Yuan, Yifan Jiang, Hai Guo, Chiho Lau, Kenneth Leung, Alfred Yu, Shuncheng Lee

Research output: Journal article publicationJournal articleAcademic researchpeer-review

17 Citations (Scopus)


The bromine atom (Br) has been known to destroy ozone (O3) and accelerate the deposition of toxic mercury (Hg). However, its abundance and sources outside the polar regions are not well-known. Here, we report significant levels of molecular bromine (Br2)─a producer of Br─observed at a coastal site in Hong Kong, with an average noontime mixing ratio of 5 ppt. Given the short lifetime of Br2(∼1 min at noon), this finding reveals a large Br2daytime source. On the basis of laboratory and field evidence, we show that the observed daytime Br2is generated by the photodissociation of particulate nitrate (NO3-) and that the reactive uptake of dinitrogen pentoxide (N2O5) on aerosols is an important nighttime source. Model-calculated Brconcentrations are comparable with that of the OH radical─the primary oxidant in the troposphere, accounting for 24% of the oxidation of isoprene, a 13% increase in net O3production, and a nearly 10-fold increase in the production rate of toxic HgII. Our findings reveal that reactive bromines play a larger role in the atmospheric chemistry and air quality of polluted coastal and maritime areas than previously thought. Our results also suggest that tightening the control of emissions of two conventional pollutants (NOxand SO2)─thereby decreasing the levels of nitrate and aerosol acidity─would alleviate halogen radical production and its adverse impact on air quality.

Original languageEnglish
Pages (from-to)12055-12065
Number of pages11
JournalEnvironmental Science and Technology
Issue number17
Publication statusPublished - 6 Sept 2022


  • air quality
  • anthropogenic pollution
  • atmospheric oxidation
  • mercury
  • Molecular bromine
  • sea sprays

ASJC Scopus subject areas

  • General Chemistry
  • Environmental Chemistry


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