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| Titel |
Atmospheric ammonia measurements in Houston, TX using an external-cavity quantum cascade laser-based sensor |
| VerfasserIn |
L. Gong, R. Lewicki, R. J. Griffin, J. H. Flynn, B. L. Lefer, F. K. Tittel |
| 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. 18 ; Nr. 11, no. 18 (2011-09-20), S.9721-9733 |
| Datensatznummer |
250010091
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| Publikation (Nr.) |
 copernicus.org/acp-11-9721-2011.pdf |
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| Zusammenfassung |
| In order to improve the current understanding of the dynamics of ammonia
(NH3) in a major industrial and urban area, intensive measurements of
atmospheric NH3 were conducted in Houston during two sampling periods
(12 February 2010–1 March 2010 and 5 August 2010–25 September 2010). The
measurements were performed with a 10.4-μm external cavity quantum
cascade laser (EC-QCL)-based sensor employing conventional photo-acoustic
spectroscopy. The mixing ratio of NH3 ranged from 0.1 to 8.7 ppb with a
mean of 2.4 ± 1.2 ppb in winter and ranged from 0.2 to 27.1 ppb with a
mean of 3.1 ± 2.9 ppb in summer. The larger levels in summer probably are
due to higher ambient temperature. A notable morning increase and a mid-day
decrease were observed in the diurnal profile of NH3 mixing ratios.
Motor vehicles were found to be major contributors to the elevated levels
during morning rush hours in winter. However, changes in vehicular catalytic
converter performance and other local or regional emission sources from
different wind directions governed the behavior of NH3 during morning
rush hours in summer. There was a large amount of variability, particularly
in summer, with several episodes of elevated NH3 mixing ratios that
could be linked to industrial facilities. A considerable discrepancy in
NH3 mixing ratios existed between weekdays and weekends. This study
suggests that NH3 mixing ratios in Houston occasionally exceeded
previous modeling predictions when sporadic and substantial enhancements
occurred, potentially causing profound effects on particulate matter
formation and local air quality. |
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