Enhanced ozone loss by active inorganic bromine chemistry in the tropical troposphere

Michael Le Breton, Thomas J. Bannan, Dudley E. Shallcross, M. Anwar Khan, Mathew J. Evans, James Lee, Richard Lidster, Stephen Andrews, Lucy J. Carpenter, Johan Schmidt, Daniel Jacob, Neil R.P. Harris, Stephane Bauguitte, Martin Gallagher, Asan Bacak, Kimberley E. Leather, Carl J. Percival

Research output: Contribution to journalArticle (Academic Journal)peer-review

13 Citations (Scopus)
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Abstract

Abstract Bromine chemistry, particularly in the tropics, has been suggested to play an important role in tropospheric ozone loss (Theys et al., 2011)) although a lack of measurements of active bromine species impedes a quantitative understanding of its impacts. Recent modelling and measurements of bromine monoxide (BrO) by Wang et al. (2015) have shown current models under predict BrO concentrations over the Pacific Ocean and allude to a missing source of BrO. Here, we present the first simultaneous aircraft measurements of atmospheric bromine monoxide, BrO (a radical that along with atomic Br catalytically destroys ozone) and the inorganic Br precursor compounds HOBr, BrCl and Br2 over the Western Pacific Ocean from 0.5 to 7 km. The presence of 0.17–1.64 pptv BrO and 3.6–8 pptv total inorganic Br from these four species throughout the troposphere causes 10–20% of total ozone loss, and confirms the importance of bromine chemistry in the tropical troposphere; contributing to a 6 ppb decrease in ozone levels due to halogen chemistry. Observations are compared with a global chemical transport model and find that the observed high levels of BrO, BrCl and HOBr can be reconciled by active multiphase oxidation of halide (Br− and Cl−) by HOBr and ozone in cloud droplets and aerosols. Measurements indicate that 99% of the instantaneous free Br in the troposphere up to 8 km originates from inorganic halogen photolysis rather than from photolysis of organobromine species.
Original languageEnglish
Pages (from-to)21-28
Number of pages8
JournalAtmospheric Environment
Volume155
Early online date3 Feb 2017
DOIs
Publication statusPublished - Apr 2017

Keywords

  • BrO
  • CIMS
  • Ozone
  • Troposphere

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