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| Titel |
What determines the HONO daytime source? First results from field measurements in south west Spain. |
| VerfasserIn |
Matthias Sörgel, Zeinab Hosaynali Beygi, Eric Regelin, Heiko Bozem, Jose Antonio Adame, Hartwig Harder, Monica Martinez-Harder, Andreas Held, Cornelius Zetzsch |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250038323
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| Zusammenfassung |
| Tropospheric nitrous acid (HONO) undergoes rapid photolysis to OH and NO during daytime
and is thus known to be an efficient OH source in the early morning hours. A photostationary
state (PSS) is established, involving the well-known reaction of OH with NO as source and
photolysis (HONO + hν - OH + NO) and the reaction OH + HONO - H2O
+ NO2 as well-known loss processes. An unexplained daytime source sustains
HONO levels above this PSS and thus serves as an additional OH source even during
day. The unexplained daytime sources are an ongoing topic in field and laboratory
research.
All quantities necessary to calculate the PSS and quantify the daytime source were
measured during the Diel Oxidant Mechanism In relation to Nitrogen Oxides (DOMINO)
campaign. Measurements took place from mid November to mid Dezember 2008 at the
Atmospheric Sounding Station- El Arenosillo of the Spanish National Institute for
Aerospace Technology (INTA) 600m from the coast in a forested area about 20m
above sea level, close to Huelva in the south west of Spain (37Ë 5” N and 6Ë 44’
W).
HONO mixing ratios calculated from the PSS are compared to the values measured by a
wet chemical technique, the LOng Path Absorption Photometer, LOPAP (QUMA,
Wuppertal). Observed HONO mixing ratios were found to always exceed the calculated ones
considerably, thus HONO is an important primary OH source during the whole day at this
site. The required daytime source to sustain measured levels is analyzed regarding its
dependence on physicochemical factors like radiation, temperature and relative humidity. The
analysis comprises quite different pollution regimes, including clean marine air with HONO
mixing ratios around the detection limit of 2 ppt and local pollution up to 260ppt during
daytime.
Acknowledgements: The DOMINO campaign was supported by the Max-Planck-Society
and the Spanish National Institute for Aerospace Technology (INTA).Matthias Sörgel and
Cornelius Zetzsch wish to thank the German Science Foundation (DFG) for support
within the research bundle EGER (ExchanGe Processes in mountainous Regions). |
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