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| Titel |
Analysis of passive-sampler monitored atmospheric ammonia at 74 sites across southern Ontario, Canada |
| VerfasserIn |
X. H. Yao, L. Zhang |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 10, no. 12 ; Nr. 10, no. 12 (2013-12-04), S.7913-7925 |
| Datensatznummer |
250085457
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| Publikation (Nr.) |
 copernicus.org/bg-10-7913-2013.pdf |
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| Zusammenfassung |
| Weekly/biweekly concentrations of atmospheric NH3
were collected using passive samplers at 74 sites across southern Ontario,
Canada, during the period from June 2006 to March 2007 with eighteen sites
running as early as March 2006. The annual average of NH3 (AAN) at all
the sites across southwestern Ontario was over 1 μg m−3, a value
that was recently proposed as the new critical level for protecting
vegetation. High AAN values (3.6–6.1 μg m−3) were observed at
eight sites located inside the intensive livestock production zones. AAN
values at the sites across southeastern Ontario were generally lower than 1 μg m−3
and the values were less than 0.4 μg m−3 at
non-agricultural sites. Agricultural sites generally showed the highest
concentrations in spring to summer and the lowest in winter, but the
occurrence time of the peak concentration varied among the sites, which
could be due to their different land use and thus different fertilizer
application intensities or periods. Seasonal trends of NH3
concentration at some non-agricultural sites were somewhat similar to those
at the agricultural sites, but the peak concentration appeared a few weeks
later than at the agricultural sites. Surprisingly, at several remote
non-agricultural sites, NH3 concentrations were not decreasing in
winter and were sometimes increasing to a level higher than those in summer,
which could be caused by different transport mechanisms in different
seasons. A sharp increase in NH3 concentration was also surprisingly
observed at 20 out of the 74 sites during the coldest two weeks when ambient
temperature was lower than −7 °C, and cannot be explained by
known sources or with existing knowledge. The NH3 emission inventory for the region of southern Ontario was evaluated using
the measurement data and emissions within two small zones in this region were identified
to be potentially underestimated. |
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