Modeling the observed tropospheric BrO background: Importance of multiphase chemistry and implications for ozone, OH, and mercury

Johan A. Schmidt; Daniel Jacob; Hannah M. Horowitz; Lu Hu; Tomás Sherwen; Mathew John Evans; Qing Liang; Raid M. Suleiman; D.E. Oram; Mike Le Breton; Carl J. Percival; Siyuan Wang; Barbara Dix; R  Volkamer

doi:10.1002/2015JD024229

Modeling the observed tropospheric BrO background: Importance of multiphase chemistry and implications for ozone, OH, and mercury

Johan A. Schmidt, Daniel Jacob, Hannah M. Horowitz, Lu Hu, Tomás Sherwen, Mathew John Evans, Qing Liang, Raid M. Suleiman, D.E. Oram, Mike Le Breton, Carl J. Percival, Siyuan Wang, Barbara Dix, R Volkamer

Chemistry

Research output: Contribution to journal › Article › peer-review

Abstract

Aircraft and satellite observations indicate the presence of ppt (ppt ≡ pmol/mol) levels of BrO in the free troposphere with important implications for the tropospheric budgets of ozone, OH, and mercury. We can reproduce these observations with the GEOS-Chem global tropospheric chemistry model by including a broader consideration of multiphase halogen (Br–Cl) chemistry than has been done in the past. Important reactions for regenerating BrO from its non-radical reservoirs include HOBr+Br−/Cl−
in both aerosols and clouds, and oxidation of Br− by ClNO3 and ozone. Most
tropospheric BrO in the model is in the free troposphere, consistent with observations, and originates mainly from the photolysis and oxidation of ocean-emitted CHBr3. Stratospheric input is also important in the upper troposphere. Including production of gas phase inorganic bromine from debromination of acidified sea salt aerosol increases free tropospheric Bry by about 30 %. We find HOBr to be the dominant gas-phase reservoir of inorganic bromine. Halogen (Br-Cl) radical chemistry as implemented here in GEOS-Chem drives 14 % and 11 % decreases in the global burdens of tropospheric ozone and OH, respectively, a 16 % increase in the atmospheric lifetime of methane, and an atmospheric lifetime of 6 months for elemental mercury. The dominant mechanism for the Br-Cl driven tropospheric ozone decrease is oxidation of NOx by formation and hydrolysis of BrNO3 and ClNO3.

Original language	English
Pages (from-to)	1-17
Number of pages	17
Journal	Journal of Geophysical Research: Atmospheres
Early online date	13 Sept 2016
DOIs	https://doi.org/10.1002/2015JD024229
Publication status	E-pub ahead of print - 13 Sept 2016

Bibliographical note

©2016, American Geophysical Union. This is an author-produced version of the published paper. Uploaded in accordance with the publisher’s self-archiving policy. Further copying may not be permitted; contact the publisher for details.

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10.1002/2015JD024229

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©2016, American Geophysical Union. This is an author-produced version of the published paper. Uploaded in accordance with the publisher’s self-archiving policy. Further copying may not be permitted; contact the publisher for details.
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Cite this

Schmidt, J. A., Jacob, D., Horowitz, H. M., Hu, L., Sherwen, T., Evans, M. J., Liang, Q., Suleiman, R. M., Oram, D. E., Le Breton, M., Percival, C. J., Wang, S., Dix, B., & Volkamer, R. (2016). Modeling the observed tropospheric BrO background: Importance of multiphase chemistry and implications for ozone, OH, and mercury. Journal of Geophysical Research: Atmospheres, 1-17. Advance online publication. https://doi.org/10.1002/2015JD024229

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title = "Modeling the observed tropospheric BrO background: Importance of multiphase chemistry and implications for ozone, OH, and mercury",

abstract = "Aircraft and satellite observations indicate the presence of ppt (ppt ≡ pmol/mol) levels of BrO in the free troposphere with important implications for the tropospheric budgets of ozone, OH, and mercury. We can reproduce these observations with the GEOS-Chem global tropospheric chemistry model by including a broader consideration of multiphase halogen (Br–Cl) chemistry than has been done in the past. Important reactions for regenerating BrO from its non-radical reservoirs include HOBr+Br−/Cl− in both aerosols and clouds, and oxidation of Br− by ClNO3 and ozone. Mosttropospheric BrO in the model is in the free troposphere, consistent with observations, and originates mainly from the photolysis and oxidation of ocean-emitted CHBr3. Stratospheric input is also important in the upper troposphere. Including production of gas phase inorganic bromine from debromination of acidified sea salt aerosol increases free tropospheric Bry by about 30 %. We find HOBr to be the dominant gas-phase reservoir of inorganic bromine. Halogen (Br-Cl) radical chemistry as implemented here in GEOS-Chem drives 14 % and 11 % decreases in the global burdens of tropospheric ozone and OH, respectively, a 16 % increase in the atmospheric lifetime of methane, and an atmospheric lifetime of 6 months for elemental mercury. The dominant mechanism for the Br-Cl driven tropospheric ozone decrease is oxidation of NOx by formation and hydrolysis of BrNO3 and ClNO3.",

author = "Schmidt, {Johan A.} and Daniel Jacob and Horowitz, {Hannah M.} and Lu Hu and Tom{\'a}s Sherwen and Evans, {Mathew John} and Qing Liang and Suleiman, {Raid M.} and D.E. Oram and {Le Breton}, Mike and Percival, {Carl J.} and Siyuan Wang and Barbara Dix and R Volkamer",

note = "{\textcopyright}2016, American Geophysical Union. This is an author-produced version of the published paper. Uploaded in accordance with the publisher{\textquoteright}s self-archiving policy. Further copying may not be permitted; contact the publisher for details.",

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Schmidt, JA, Jacob, D, Horowitz, HM, Hu, L, Sherwen, T , Evans, MJ, Liang, Q, Suleiman, RM, Oram, DE, Le Breton, M, Percival, CJ, Wang, S, Dix, B & Volkamer, R 2016, 'Modeling the observed tropospheric BrO background: Importance of multiphase chemistry and implications for ozone, OH, and mercury', Journal of Geophysical Research: Atmospheres, pp. 1-17. https://doi.org/10.1002/2015JD024229

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T1 - Modeling the observed tropospheric BrO background: Importance of multiphase chemistry and implications for ozone, OH, and mercury

AU - Schmidt, Johan A.

AU - Jacob, Daniel

AU - Horowitz, Hannah M.

AU - Hu, Lu

AU - Sherwen, Tomás

AU - Evans, Mathew John

AU - Liang, Qing

AU - Suleiman, Raid M.

AU - Oram, D.E.

AU - Le Breton, Mike

AU - Percival, Carl J.

AU - Wang, Siyuan

AU - Dix, Barbara

AU - Volkamer, R

N1 - ©2016, American Geophysical Union. This is an author-produced version of the published paper. Uploaded in accordance with the publisher’s self-archiving policy. Further copying may not be permitted; contact the publisher for details.

PY - 2016/9/13

Y1 - 2016/9/13

N2 - Aircraft and satellite observations indicate the presence of ppt (ppt ≡ pmol/mol) levels of BrO in the free troposphere with important implications for the tropospheric budgets of ozone, OH, and mercury. We can reproduce these observations with the GEOS-Chem global tropospheric chemistry model by including a broader consideration of multiphase halogen (Br–Cl) chemistry than has been done in the past. Important reactions for regenerating BrO from its non-radical reservoirs include HOBr+Br−/Cl− in both aerosols and clouds, and oxidation of Br− by ClNO3 and ozone. Mosttropospheric BrO in the model is in the free troposphere, consistent with observations, and originates mainly from the photolysis and oxidation of ocean-emitted CHBr3. Stratospheric input is also important in the upper troposphere. Including production of gas phase inorganic bromine from debromination of acidified sea salt aerosol increases free tropospheric Bry by about 30 %. We find HOBr to be the dominant gas-phase reservoir of inorganic bromine. Halogen (Br-Cl) radical chemistry as implemented here in GEOS-Chem drives 14 % and 11 % decreases in the global burdens of tropospheric ozone and OH, respectively, a 16 % increase in the atmospheric lifetime of methane, and an atmospheric lifetime of 6 months for elemental mercury. The dominant mechanism for the Br-Cl driven tropospheric ozone decrease is oxidation of NOx by formation and hydrolysis of BrNO3 and ClNO3.

AB - Aircraft and satellite observations indicate the presence of ppt (ppt ≡ pmol/mol) levels of BrO in the free troposphere with important implications for the tropospheric budgets of ozone, OH, and mercury. We can reproduce these observations with the GEOS-Chem global tropospheric chemistry model by including a broader consideration of multiphase halogen (Br–Cl) chemistry than has been done in the past. Important reactions for regenerating BrO from its non-radical reservoirs include HOBr+Br−/Cl− in both aerosols and clouds, and oxidation of Br− by ClNO3 and ozone. Mosttropospheric BrO in the model is in the free troposphere, consistent with observations, and originates mainly from the photolysis and oxidation of ocean-emitted CHBr3. Stratospheric input is also important in the upper troposphere. Including production of gas phase inorganic bromine from debromination of acidified sea salt aerosol increases free tropospheric Bry by about 30 %. We find HOBr to be the dominant gas-phase reservoir of inorganic bromine. Halogen (Br-Cl) radical chemistry as implemented here in GEOS-Chem drives 14 % and 11 % decreases in the global burdens of tropospheric ozone and OH, respectively, a 16 % increase in the atmospheric lifetime of methane, and an atmospheric lifetime of 6 months for elemental mercury. The dominant mechanism for the Br-Cl driven tropospheric ozone decrease is oxidation of NOx by formation and hydrolysis of BrNO3 and ClNO3.

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DO - 10.1002/2015JD024229

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JO - Journal of Geophysical Research: Atmospheres

JF - Journal of Geophysical Research: Atmospheres

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