globalchange  > 气候减缓与适应
DOI: 10.1038/ngeo1779
Photochemical production of molecular bromine in Arctic surface snowpacks
Author: Pratt K.A.; Custard K.D.; Shepson P.B.; Douglas T.A.; Pöhler D.; General S.; Zielcke J.; Simpson W.R.; Platt U.; Tanner D.J.; Gregory Huey L.; Carlsen M.; Stirm B.H.
Source Publication: Nature Geoscience
ISSN: 17520894
Publishing Year: 2013
Volume: 6, Issue:5
pages begin: 351
pages end: 356
Language: 英语
Scopus Keyword: airborne survey ; arctic environment ; atmospheric pollution ; bromine ; mercury (element) ; molecular analysis ; ozone depletion ; photochemistry ; sea ice ; snow cover ; snowpack ; surface area ; trace gas ; troposphere ; tundra ; Alaska ; Arctic ; United States
English Abstract: Following the springtime polar sunrise, ozone concentrations in the lower troposphere episodically decline to near-zero levels. These ozone depletion events are initiated by an increase in reactive bromine levels in the atmosphere. Under these conditions, the oxidative capacity of the Arctic troposphere is altered, leading to the removal of numerous transported trace gas pollutants, including mercury. However, the sources and mechanisms leading to increased atmospheric reactive bromine levels have remained uncertain, limiting simulations of Arctic atmospheric chemistry with the rapidly transforming sea-ice landscape. Here, we examine the potential for molecular bromine production in various samples of saline snow and sea ice, in the presence and absence of sunlight and ozone, in an outdoor snow chamber in Alaska. Molecular bromine was detected only on exposure of surface snow (collected above tundra and first-year sea ice) to sunlight. This suggests that the oxidation of bromide is facilitated by a photochemical mechanism, which was most efficient for more acidic samples characterized by enhanced bromide to chloride ratios. Molecular bromine concentrations increased significantly when the snow was exposed to ozone, consistent with an interstitial air amplification mechanism. Aircraft-based observations confirm that bromine oxide levels were enhanced near the snow surface. We suggest that the photochemical production of molecular bromine in surface snow serves as a major source of reactive bromine, which leads to the episodic depletion of tropospheric ozone in the Arctic springtime.
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Document Type: 期刊论文
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Affiliation: Department of Chemistry, Purdue University, West Lafayette, IN 47907, United States; Department of Earth, Atmospheric, and Planetary Sciences, Purdue Climate Change Research Center, Purdue University, West Lafayette, IN 47907, United States; US Army Cold Regions Research and Engineering Laboratory, Fort Wainwright, AK 99703, United States; Institute of Environmental Physics, University of Heidelberg, D-69117 Heidelberg, Germany; Geophysical Institute, Department of Chemistry, University of Alaska Fairbanks, Fairbanks, AK 99775, United States; School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA 30332, United States; Department of Aviation Technology, Purdue University, West Lafayette, IN 47907, United States

Recommended Citation:
Pratt K.A.,Custard K.D.,Shepson P.B.,et al. Photochemical production of molecular bromine in Arctic surface snowpacks[J]. Nature Geoscience,2013-01-01,6(5)
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