Tropospheric bromine chemistry: implications for present and pre-industrial ozone and mercury
We present a new model for the global tropospheric chemistry of inorganic bromine (Br<sub>y</sub>) coupled to oxidant-aerosol chemistry in the GEOS-Chem chemical transport model (CTM). Sources of tropospheric Br<sub>y</sub> include debrominatio...
| Main Authors: | , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2012-08-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | http://www.atmos-chem-phys.net/12/6723/2012/acp-12-6723-2012.pdf |
| _version_ | 1819128668200370176 |
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| author | 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. Van Roozendael |
| author_facet | 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. Van Roozendael |
| author_sort | J. P. Parrella |
| collection | DOAJ |
| description | We present a new model for the global tropospheric chemistry of inorganic bromine (Br<sub>y</sub>) coupled to oxidant-aerosol chemistry in the GEOS-Chem chemical transport model (CTM). Sources of tropospheric Br<sub>y</sub> 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<sup>−1</sup> (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. |
| first_indexed | 2024-12-22T08:31:29Z |
| format | Article |
| id | doaj.art-eedf6c7dfc684a418c88448d894741a3 |
| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-12-22T08:31:29Z |
| publishDate | 2012-08-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-eedf6c7dfc684a418c88448d894741a32022-12-21T18:32:30ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242012-08-0112156723674010.5194/acp-12-6723-2012Tropospheric bromine chemistry: implications for present and pre-industrial ozone and mercuryJ. P. ParrellaD. J. JacobQ. LiangY. ZhangL. J. MickleyB. MillerM. J. EvansX. YangJ. A. PyleN. TheysM. Van RoozendaelWe present a new model for the global tropospheric chemistry of inorganic bromine (Br<sub>y</sub>) coupled to oxidant-aerosol chemistry in the GEOS-Chem chemical transport model (CTM). Sources of tropospheric Br<sub>y</sub> 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<sup>−1</sup> (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.http://www.atmos-chem-phys.net/12/6723/2012/acp-12-6723-2012.pdf |
| spellingShingle | 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. Van Roozendael Tropospheric bromine chemistry: implications for present and pre-industrial ozone and mercury Atmospheric Chemistry and Physics |
| title | Tropospheric bromine chemistry: implications for present and pre-industrial ozone and mercury |
| title_full | Tropospheric bromine chemistry: implications for present and pre-industrial ozone and mercury |
| title_fullStr | Tropospheric bromine chemistry: implications for present and pre-industrial ozone and mercury |
| title_full_unstemmed | Tropospheric bromine chemistry: implications for present and pre-industrial ozone and mercury |
| title_short | Tropospheric bromine chemistry: implications for present and pre-industrial ozone and mercury |
| title_sort | tropospheric bromine chemistry implications for present and pre industrial ozone and mercury |
| url | http://www.atmos-chem-phys.net/12/6723/2012/acp-12-6723-2012.pdf |
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