Preprints
https://doi.org/10.5194/egusphere-2023-860
https://doi.org/10.5194/egusphere-2023-860
30 May 2023
 | 30 May 2023

Observations of cyanogen bromide (BrCN) in the global troposphere and their relation to polar surface O3 destruction

James M. Roberts, Siyuan Wang, Patrick R. Veres, J. Andrew Neuman, Michael A. Robinson, Ilann Bourgeois, Jeff Peischl, Thomas B. Ryerson, Chelsea R. Thompson, Hannah M. Allen, John D. Crounse, Paul O. Wennberg, Samuel R. Hall, Kirk Ullmann, Simone Meinardi, Isobel J. Simpson, and Donald Blake

Abstract. Active bromine (e.g., Br2, BrCl, BrO, HOBr) promotes atmospheric ozone destruction and mercury removal. Here we report a previously unidentified participant in active-Br chemistry, cyanogen bromide (BrCN), measured during the NASA Atmospheric Tomography (ATom) mission. BrCN was confined to polar boundary layers, often appearing at concentrations higher than other Br compounds. The chemistry of BrCN determines whether it promotes or inhibits ozone and mercury removal. This dataset provides evidence that much of the BrCN was from atmospheric Br chemistry involving surface reactions with reduced nitrogen compounds. Since gas phase loss processes are known to be relatively slow, surface reactions must also be the major loss processes, with vertical profiles implying a BrCN atmospheric lifetime in the range 1–10 days. Liquid phase reactions of BrCN tend to convert Br to bromide (Br¯) or C-Br bonded organics, constituting a loss of active Br. Thus, accounting for BrCN chemistry is crucial to understanding polar Br cycling.

James M. Roberts, Siyuan Wang, Patrick R. Veres, J. Andrew Neuman, Michael A. Robinson, Ilann Bourgeois, Jeff Peischl, Thomas B. Ryerson, Chelsea R. Thompson, Hannah M. Allen, John D. Crounse, Paul O. Wennberg, Samuel R. Hall, Kirk Ullmann, Simone Meinardi, Isobel J. Simpson, and Donald Blake

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-860', Anonymous Referee #1, 19 Jun 2023
    • AC1: 'Reply on RC1', James Roberts, 21 Oct 2023
  • RC2: 'Comment on egusphere-2023-860', Anonymous Referee #2, 11 Jul 2023
    • AC2: 'Reply on RC2', James Roberts, 21 Oct 2023

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-860', Anonymous Referee #1, 19 Jun 2023
    • AC1: 'Reply on RC1', James Roberts, 21 Oct 2023
  • RC2: 'Comment on egusphere-2023-860', Anonymous Referee #2, 11 Jul 2023
    • AC2: 'Reply on RC2', James Roberts, 21 Oct 2023
James M. Roberts, Siyuan Wang, Patrick R. Veres, J. Andrew Neuman, Michael A. Robinson, Ilann Bourgeois, Jeff Peischl, Thomas B. Ryerson, Chelsea R. Thompson, Hannah M. Allen, John D. Crounse, Paul O. Wennberg, Samuel R. Hall, Kirk Ullmann, Simone Meinardi, Isobel J. Simpson, and Donald Blake
James M. Roberts, Siyuan Wang, Patrick R. Veres, J. Andrew Neuman, Michael A. Robinson, Ilann Bourgeois, Jeff Peischl, Thomas B. Ryerson, Chelsea R. Thompson, Hannah M. Allen, John D. Crounse, Paul O. Wennberg, Samuel R. Hall, Kirk Ullmann, Simone Meinardi, Isobel J. Simpson, and Donald Blake

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Latest update: 24 Feb 2024
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Bromine chemistry in polar regions is important for the composition of the atmosphere as well as climate. Reactive bromine strongly affects the oxidation capacity and the local ozone budget, and through the export to lower latitudes, it affects the ozone budget and the atmosphere's radiative properties outside polar regions. The newly identified bromine reservoir changes our understanding of the chemical budgets of polar halogens which will have implications for the ozone and mercury removal cycles.
Short summary
We measured cyanogen bromide (BrCN) in the troposphere for the first time as part of a series of survey flights around the globe. BrCN is found to be a product of the same active bromine chemistry that destroys ozone and removes mercury in polar surface environments, and so is a previously unrecognized participant in this chemistry. Accounting for BrCN chemistry is an important part of understanding polar Br cycling.