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| Titel |
Inorganic bromine in the marine boundary layer: a critical review |
| VerfasserIn |
R. Sander, W. C. Keene, A. A. P. Pszenny, R. Arimoto, G. P. Ayers, E. Baboukas, J. M. Cainey, P. J. Crutzen  , R. A. Duce, G. Hönninger, B. J. Huebert, W. Maenhaut, N. Mihalopoulos, V. C. Turekian, R. Dingenen |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 3, no. 5 ; Nr. 3, no. 5 (2003-09-10), S.1301-1336 |
| Datensatznummer |
250001247
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| Publikation (Nr.) |
 copernicus.org/acp-3-1301-2003.pdf |
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| Zusammenfassung |
| The cycling of inorganic bromine in the marine boundary layer
(mbl) has received increased attention in recent years. Bromide, a constituent of sea water, is injected into the atmosphere in
association with sea-salt aerosol by breaking waves on the ocean surface. Measurements reveal that supermicrometer sea-salt aerosol is
substantially depleted in bromine (often exceeding 50%) relative to conservative tracers, whereas marine submicrometer aerosol is often
enriched in bromine. Model calculations, laboratory studies, and field observations strongly suggest that the supermicrometer depletions
reflect the chemical transformation of particulate bromide to reactive inorganic gases that influence the processing of ozone and other
important constituents of marine air. Mechanisms for the submicrometer enrichments are not well understood. Currently available techniques
cannot reliably quantify many Br containing compounds at ambient concentrations and, consequently, our understanding of
inorganic Br cycling over the oceans and its global significance are uncertain. To provide a more coherent framework for future research,
we have reviewed measurements in marine aerosol, the gas phase, and in rain. We also summarize sources and sinks, as well as model and
laboratory studies of chemical transformations. The focus is on inorganic bromine over the open oceans outside the polar regions. The
generation of sea-salt aerosol at the ocean surface is the major tropospheric source producing about
6.2 Tg/a of bromide. The transport of Br from continents (as mineral aerosol, and as
products from biomass-burning and fossil-fuel combustion) can be of local importance. Transport of degradation products of long-lived
Br containing compounds from the stratosphere and other sources contribute lesser amounts. Available evidence suggests that,
following aerosol acidification, sea-salt bromide reacts to form Br2 and
BrCl that volatilize to the gas phase and photolyze in daylight to produce atomic
Br and Cl. Subsequent transformations can destroy tropospheric ozone, oxidize
dimethylsulfide (DMS) and hydrocarbons in the gas phase and S(IV) in aerosol solutions, and thereby potentially influence
climate. The diurnal cycle of gas-phase Br and the corresponding particulate
Br deficits are correlated. Higher values of Br in the gas phase during daytime are consistent
with expectations based on photochemistry. We expect that the importance of inorganic
Br cycling will vary in the future as a function of both increasing acidification of the atmosphere (through
anthropogenic emissions) and climate changes. The latter affects bromine cycling via meteorological factors including global wind
fields (and the associated production of sea-salt aerosol), temperature, and relative humidity. |
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