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| Titel |
Gas-particle partitioning of atmospheric Hg(II) and its effect on global mercury deposition |
| VerfasserIn |
H. M. Amos, D. J. Jacob, C. D. Holmes, J. A. Fisher, Q. Wang, R. M. Yantosca, E. S. Corbitt, E. Galarneau, A. P. Rutter, Mae Sexauer Gustin, A. Steffen, J. J. Schauer, J. A. Graydon, V. L. St. Louis, R. W. Talbot, E. S. Edgerton, Y. Zhang, E. M. Sunderland |
| 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. 1 ; Nr. 12, no. 1 (2012-01-11), S.591-603 |
| Datensatznummer |
250010453
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| Publikation (Nr.) |
 copernicus.org/acp-12-591-2012.pdf |
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| Zusammenfassung |
| Atmospheric deposition of Hg(II) represents a major input of mercury to
surface environments. The phase of Hg(II) (gas or particle) has important
implications for deposition. We use long-term observations of reactive
gaseous mercury (RGM, the gaseous component of Hg(II)), particle-bound
mercury (PBM, the particulate component of Hg(II)), fine particulate matter
(PM2.5), and temperature (T) at five sites in North America to derive an
empirical gas-particle partitioning relationship
log10(K−1) = (10±1)–(2500±300)/T
where K = (PBM/PM2.5)/RGM with PBM and RGM
in common mixing ratio units, PM2.5 in μg m−3, and T in K.
This relationship is within the range of previous work but is based on far
more extensive data from multiple sites. We implement this empirical
relationship in the GEOS-Chem global 3-D Hg model to partition Hg(II)
between the gas and particle phases. The resulting gas-phase fraction of
Hg(II) ranges from over 90 % in warm air with little aerosol to less than
10 % in cold air with high aerosol. Hg deposition to high latitudes
increases because of more efficient scavenging of particulate Hg(II) by
precipitating snow. Model comparison to Hg observations at the North
American surface sites suggests that subsidence from the free troposphere
(warm air, low aerosol) is a major factor driving the seasonality of RGM,
while elevated PBM is mostly associated with high aerosol loads. Simulation
of RGM and PBM at these sites is improved by including fast in-plume
reduction of Hg(II) emitted from coal combustion and by assuming that
anthropogenic particulate Hg(p) behaves as semi-volatile Hg(II) rather than
as a refractory particulate component. We improve the simulation of Hg wet
deposition fluxes in the US relative to a previous version of GEOS-Chem;
this largely reflects independent improvement of the washout algorithm. The
observed wintertime minimum in wet deposition fluxes is attributed to
inefficient snow scavenging of gas-phase Hg(II). |
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