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| Titel |
Quantitative assessment of upstream source influences on total gaseous mercury observations in Ontario, Canada |
| VerfasserIn |
D. Wen, J. C. Lin, F. Meng, P. K. Gbor, Z. He, J. J. Sloan |
| 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 ; 11, no. 4 ; Nr. 11, no. 4 (2011-02-16), S.1405-1415 |
| Datensatznummer |
250009356
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| Publikation (Nr.) |
 copernicus.org/acp-11-1405-2011.pdf |
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| Zusammenfassung |
| Hourly total gaseous mercury (TGM) concentrations at three monitoring sites
(receptors) in Ontario were predicted for four selected periods at different
seasons in 2002 using the Stochastic Time-Inverted Lagrangian Transport
(STILT) model, which transports Lagrangian air parcels backward in time from
the receptors to provide linkages to the source region in the upwind area.
The STILT model was modified to deal with Hg deposition and high stack Hg
emissions. The model-predicted Hg concentrations were compared with
observations at three monitoring sites. Estimates of transport errors
(uncertainties in simulated concentrations due to errors in wind fields) are
also provided that suggest such errors can reach approximately 10% of
simulated concentrations. Results from a CMAQ chemical transport model (CTM)
simulation in which the same emission and meteorology inputs were used are
also reported. The comparisons show that STILT-predicted Hg concentrations
usually agree better with observations than CMAQ except for a subset of
cases that are subject to biases in the coarsely resolved boundary
conditions. In these comparisons STILT captures high frequency concentration
variations better than the Eulerian CTM, likely due to its ability to
account for the sub-grid scale position of the receptor site and to minimize
numerical diffusion. Thus it is particularly valuable for the interpretation
of plumes (short-term concentration variations) that require the use of
finer mesh sizes or controls on numerical diffusion in Eulerian models. We
report quantitative assessments of the relative importance of different
upstream sources for the selected episodes, based on emission fluxes and
STILT footprints. The STILT simulations indicate that natural sources (which
include re-emission from historical anthropogenic activities) contribute
much more than current-day anthropogenic emissions to the Hg concentrations
observed at the three sites. |
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