Bromide and other ions in the snow, firn air, and atmospheric boundary layer at Summit during GSHOX

Authors

Jack E. Dibb, University of New HampshireFollow
Luke D. Ziemba, NASA
J Luxford, University of New Hampshire - Main Campus
P Beckman, University of New Hampshire - Main Campus

Abstract

Measurements of gas phase soluble bromide in the boundary layer and in firn air, and Br⁻ in aerosol and snow, were made at Summit, Greenland (72.5° N, 38.4° W, 3200 m a.s.l.) as part of a larger investigation into the influence of Br chemistry on HO_x cycling. The soluble bromide measurements confirm that photochemical activation of Br⁻ in the snow causes release of active Br to the overlying air despite trace concentrations of Br⁻ in the snow (means 15 and 8 nmol Br⁻ kg⁻¹ of snow in 2007 and 2008, respectively). Mixing ratios of soluble bromide above the snow were also found to be very small (mean <1 ppt both years, with maxima of 3 and 4 ppt in 2007 and 2008, respectively), but these levels clearly oxidize and deposit long-lived gaseous elemental mercury and may perturb HO_x partitioning. Concentrations of Br⁻ in surface snow tended to increase/decrease in parallel with the specific activities of the aerosol-associated radionuclides ⁷Be and ²¹⁰Pb. Earlier work has shown that ventilation of the boundary layer causes simultaneous increases in ⁷Be and ²¹⁰Pb at Summit, suggesting there is a pool of Br in the free troposphere above Summit in summer time. Speciation and the source of this free tropospheric Br⁻ are not well constrained, but we suggest it may be linked to extensive regions of active Br chemistry in the Arctic basin which are known to cause ozone and mercury depletion events shortly after polar sunrise. If this hypothesis is correct, it implies persistence of the free troposphere Br⁻ for several months after peak Br activation in March/April. Alternatively, there may be a ubiquitous pool of Br⁻ in the free troposphere, sustained by currently unknown sources and processes.

Department

Earth Sciences, Earth Systems Research Center

Publication Date

10-20-2010

Journal Title

Atmospheric Chemistry and Physics

Publisher

Copernicus Publications

Digital Object Identifier (DOI)

10.5194/acp-10-9931-2010

Document Type

Article

Recommended Citation

Dibb, J. E., Ziemba, L. D., Luxford, J., and Beckman, P.: Bromide and other ions in the snow, firn air, and atmospheric boundary layer at Summit during GSHOX, Atmos. Chem. Phys., 10, 9931-9942, doi:10.5194/acp-10-9931-2010, 2010.

Rights

© Author(s) 2010. This work is distributed under the Creative Commons Attribution 3.0 License.