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| Titel |
Modelling the impacts of ammonia emissions reductions on North American air quality |
| VerfasserIn |
P. A. Makar, M. D. Moran, Q. Zheng, S. Cousineau, M. Sassi, A. Duhamel, M. Besner, D. Davignon, L.-P. Crevier, V. S. Bouchet |
| 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 ; 9, no. 18 ; Nr. 9, no. 18 (2009-09-29), S.7183-7212 |
| Datensatznummer |
250007655
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| Publikation (Nr.) |
 copernicus.org/acp-9-7183-2009.pdf |
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| Zusammenfassung |
A unified regional air-quality modelling system (AURAMS) was used to
investigate the effects of reductions in ammonia emissions on regional air
quality, with a focus on particulate-matter formation. Three simulations of
one-year duration were performed for a North American domain: (1) a
base-case simulation using 2002 Canadian and US national emissions
inventories augmented by a more detailed Canadian emissions inventory for
agricultural ammonia; (2) a 30% North-American-wide reduction in
agricultural ammonia emissions; and (3) a 50% reduction in Canadian
beef-cattle ammonia emissions. The simulations show that a 30%
continent-wide reduction in agricultural ammonia emissions lead to
reductions in median hourly PM2.5 mass of <1 μg m−3 on an
annual basis. The atmospheric response to these emission reductions displays
marked seasonal variations, and on even shorter time scales, the impacts of
the emissions reductions are highly episodic: 95th-percentile hourly
PM2.5 mass decreases can be up to a factor of six larger than the
median values.
A key finding of the modelling work is the linkage between gas and aqueous
chemistry and transport; reductions in ammonia emissions affect gaseous
ammonia concentrations close to the emissions site, but substantial impacts
on particulate matter and atmospheric deposition often occur at considerable
distances downwind, with particle nitrate being the main vector of
ammonia/um transport. Ammonia emissions reductions therefore have
trans-boundary consequences downwind. Calculations of critical-load
exceedances for sensitive ecosystems in Canada suggest that ammonia emission
reductions will have a minimal impact on current ecosystem acidification
within Canada, but may have a substantial impact on future ecosystem
acidification. The 50% Canadian beef-cattle ammonia emissions reduction
scenario was used to examine model sensitivity to uncertainties in the new
Canadian agricultural ammonia emissions inventory, and the simulation
results suggest that further work is needed to improve the emissions
inventory for this particular sector. It should be noted that the model in
its current form neglects coarse mode base cation chemistry, so the
predicted effects of ammonia emissions reductions shown here should be
considered upper limits. |
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