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| Titel |
Model analyses of atmospheric mercury: present air quality and effects of transpacific transport on the United States |
| VerfasserIn |
H. Lei, X.-Z. Liang, D. J. Wuebbles, Z. Tao |
| 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 ; 13, no. 21 ; Nr. 13, no. 21 (2013-11-07), S.10807-10825 |
| Datensatznummer |
250085796
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| Publikation (Nr.) |
 copernicus.org/acp-13-10807-2013.pdf |
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| Zusammenfassung |
| Atmospheric mercury is a toxic air and water pollutant
that is of significant concern because of its effects on human health and
ecosystems. A mechanistic representation of the atmospheric mercury cycle is
developed for the state-of-the-art global climate-chemistry model, CAM-Chem
(Community Atmospheric Model with Chemistry). The model simulates the
emission, transport, transformation and deposition of atmospheric mercury
(Hg) in three forms: elemental mercury (Hg(0)), reactive mercury (Hg(II)),
and particulate mercury (PHg). Emissions of mercury include those from
human, land, ocean, biomass burning and volcano related sources. Land
emissions are calculated based on surface solar radiation flux and skin
temperature. A simplified air–sea mercury exchange scheme is used to
calculate emissions from the oceans. The chemistry mechanism includes the
oxidation of Hg(0) in gaseous phase by ozone with temperature dependence,
OH, H2O2 and chlorine. Aqueous chemistry includes both oxidation
and reduction of Hg(0). Transport and deposition of mercury species are
calculated through adapting the original formulations in CAM-Chem. The
CAM-Chem model with mercury is driven by present meteorology to simulate the
present mercury air quality during the 1999–2001 period. The resulting
surface concentrations of total gaseous mercury (TGM) are then compared with
the observations from worldwide sites. Simulated wet depositions of mercury
over the continental United States are compared to the observations from 26
Mercury Deposition Network stations to test the wet deposition simulations.
The evaluations of gaseous concentrations and wet deposition confirm a
strong capability for the CAM-Chem mercury mechanism to simulate the
atmospheric mercury cycle. The general reproduction of global TGM
concentrations and the overestimation on South Africa indicate that model
simulations of TGM are seriously affected by emissions. The comparison to
wet deposition indicates that wet deposition patterns of mercury are more
affected by the spatial variability of precipitation. The sensitivity
experiments show that 22% of total mercury deposition and 25% of TGM
concentrations in the United States result from domestic anthropogenic
sources, but only 9% of total mercury deposition and 7% of TGM
concentrations are contributed by transpacific transport. However, the
contributions of domestic and transpacific sources on the western United
States levels of mercury are of comparable magnitude. |
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