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© 2019. This work is published under https://creativecommons.org/licenses/by/4.0/ (the “License”). Notwithstanding the ProQuest Terms and Conditions, you may use this content in accordance with the terms of the License.

Abstract

Bromine radicals influence global tropospheric chemistry by depleting ozone and by oxidizing elemental mercury and reduced sulfur species. Observations typically indicate a 50 % depletion of sea salt aerosol (SSA) bromide relative to seawater composition, implying that SSA debromination could be the dominant global source of tropospheric bromine. However, it has been difficult to reconcile this large source with the relatively low bromine monoxide (BrO) mixing ratios observed in the marine boundary layer (MBL). Here we present a new mechanistic description of SSA debromination in the GEOS-Chem global atmospheric chemistry model with a detailed representation of halogen (Cl, Br, and I) chemistry. We show that observed levels of SSA debromination can be reproduced in a manner consistent with observed BrO mixing ratios. Bromine radical sinks from the HOBr + S(IV) heterogeneous reactions and from ocean emission of acetaldehyde are critical in moderating tropospheric BrO levels. The resulting HBr is rapidly taken up by SSA and also deposited. Observations of SSA debromination at southern midlatitudes in summer suggest that model uptake of HBr by SSA may be too fast. The model provides a successful simulation of free-tropospheric BrO in the tropics and midlatitudes in summer, where the bromine radical sink from the HOBr + S(IV) reactions is compensated for by more efficient HOBr-driven recycling in clouds compared to previous GEOS-Chem versions. Simulated BrO in the MBL is generally much higher in winter than in summer due to a combination of greater SSA emission and slower conversion of bromine radicals to HBr. An outstanding issue in the model is the overestimate of free-tropospheric BrO in extratropical winter–spring, possibly reflecting an overestimate of the HOBr/HBr ratio under these conditions where the dominant HOBr source is hydrolysis ofBrNO3.

Details

Title
Effect of sea salt aerosol on tropospheric bromine chemistry
Author
Zhu, Lei 1   VIAFID ORCID Logo  ; Jacob, Daniel J 2 ; Eastham, Sebastian D 3   VIAFID ORCID Logo  ; Sulprizio, Melissa P 1 ; Wang, Xuan 1   VIAFID ORCID Logo  ; Sherwen, Tomás 4   VIAFID ORCID Logo  ; Evans, Mat J 4   VIAFID ORCID Logo  ; Chen, Qianjie 5   VIAFID ORCID Logo  ; Alexander, Becky 6   VIAFID ORCID Logo  ; Koenig, Theodore K 7   VIAFID ORCID Logo  ; Volkamer, Rainer 7   VIAFID ORCID Logo  ; Huey, L Gregory 8   VIAFID ORCID Logo  ; Michael Le Breton 9 ; Bannan, Thomas J 10   VIAFID ORCID Logo  ; Percival, Carl J 11 

 John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA 
 John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA; Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA, USA 
 Laboratory for Aviation and the Environment, Massachusetts Institute of Technology, Cambridge, MA, USA 
 Wolfson Atmospheric Chemistry Laboratories, Department of Chemistry, University of York, York, UK; National Centre for Atmospheric Science (NCAS), University of York, York, UK 
 Department of Atmospheric Sciences, University of Washington, Seattle, WA, USA; now at: Department of Chemistry, University of Michigan, Ann Arbor, MI, USA 
 Department of Atmospheric Sciences, University of Washington, Seattle, WA, USA 
 Department of Chemistry, University of Colorado, Boulder, CO, USA; Cooperative Institute for Research in Environmental Sciences (CIRES), Boulder, CO, USA 
 School of Earth and Atmospheric Sciences, Georgia Tech, Atlanta, Georgia, USA 
 The Centre for Atmospheric Science, School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Simon Building, Brunswick Street, Manchester M13 9PL, UK; Department of Chemistry and Molecular Biology, University of Gothenburg, Medicinaregatan 9 C, 40530 Gothenburg, Sweden 
10  The Centre for Atmospheric Science, School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Simon Building, Brunswick Street, Manchester M13 9PL, UK 
11  The Centre for Atmospheric Science, School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Simon Building, Brunswick Street, Manchester M13 9PL, UK; now at: Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA, USA 
Pages
6497-6507
Publication year
2019
Publication date
2019
Publisher
Copernicus GmbH
ISSN
16807316
e-ISSN
16807324
Source type
Scholarly Journal
Language of publication
English
ProQuest document ID
2225661787
Copyright
© 2019. This work is published under https://creativecommons.org/licenses/by/4.0/ (the “License”). Notwithstanding the ProQuest Terms and Conditions, you may use this content in accordance with the terms of the License.