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| Titel |
Tropospheric bromine chemistry: implications for present and pre-industrial ozone and mercury |
| VerfasserIn |
J. P. Parrella, D. J. Jacob, Q. Liang, Y. Zhang, L. J. Mickley, B. Miller, M. J. Evans, X. Yang, J. A. Pyle, N. Theys, M. Roozendael |
| 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 ; 12, no. 15 ; Nr. 12, no. 15 (2012-08-01), S.6723-6740 |
| Datensatznummer |
250011353
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| Publikation (Nr.) |
 copernicus.org/acp-12-6723-2012.pdf |
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| Zusammenfassung |
| We present a new model for the global tropospheric chemistry of inorganic
bromine (Bry) coupled to oxidant-aerosol chemistry in the GEOS-Chem
chemical transport model (CTM). Sources of tropospheric Bry include
debromination of sea-salt aerosol, photolysis and oxidation of short-lived
bromocarbons, and transport from the stratosphere. Comparison to a GOME-2
satellite climatology of tropospheric BrO columns shows that the model can
reproduce the observed increase of BrO with latitude, the northern
mid-latitudes maximum in winter, and the Arctic maximum in spring. This
successful simulation is contingent on the HOBr + HBr reaction taking place in
aqueous aerosols and ice clouds. Bromine chemistry in the model decreases
tropospheric ozone mixing ratios by <1–8 nmol mol−1 (6.5%
globally), with the largest effects in the northern extratropics in spring.
The global mean tropospheric OH concentration decreases by 4%. Inclusion
of bromine chemistry improves the ability of global models (GEOS-Chem and
p-TOMCAT) to simulate observed 19th-century ozone and its seasonality.
Bromine effects on tropospheric ozone are comparable in the present-day and
pre-industrial atmospheres so that estimates of anthropogenic radiative
forcing are minimally affected. Br atom concentrations are 40% higher in
the pre-industrial atmosphere due to lower ozone, which would decrease by a
factor of 2 the atmospheric lifetime of elemental mercury against oxidation
by Br. This suggests that historical anthropogenic mercury emissions may
have mostly deposited to northern mid-latitudes, enriching the corresponding
surface reservoirs. The persistent rise in background surface ozone at
northern mid-latitudes during the past decades could possibly contribute to
the observations of elevated mercury in subsurface waters of the North
Atlantic. |
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