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| Titel |
A comparison of HONO budgets for two measurement heights at a field station within the boreal forest in Finland |
| VerfasserIn |
R. Oswald, M. Ermel, K. Hens, A. Novelli, H. G. Ouwersloot, P. Paasonen, T. Petäjä, M. Sipilä, P. Keronen, J. Bäck, R. Königstedt, Z. Hosaynali Beygi, H. Fischer, B. Bohn, D. Kubistin, H. Harder, M. Martinez, J. Williams, T. Hoffmann, I. Trebs, M. Sörgel |
| 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 ; 15, no. 2 ; Nr. 15, no. 2 (2015-01-23), S.799-813 |
| Datensatznummer |
250119340
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| Publikation (Nr.) |
 copernicus.org/acp-15-799-2015.pdf |
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| Zusammenfassung |
| Atmospheric concentrations of nitrous acid (HONO), one of the major
precursors of the hydroxyl radical (OH) in the troposphere, significantly
exceed the values predicted by the assumption of a photostationary state
(PSS) during daytime. Therefore, additional sources of HONO were intensively
investigated in the last decades. This study presents budget calculations of
HONO based on simultaneous measurements of all relevant species, including
HONO and OH at two different measurement heights, i.e. 1 m above the ground and
about 2 to 3 m above the canopy (24 m above the ground), conducted in a boreal
forest environment. We observed mean HONO concentrations of
about 6.5 × 108 molecules cm−3 (26 ppt) during daytime, more than 20 times
higher than expected from the PSS of 0.2 × 108 molecules cm−3 (1
ppt). To close the budgets at both heights, a strong additional source term
during daytime is required. This unidentified source is at its maximum at noon (up
to 1.1 × 106 molecules cm−3 s−1, 160 ppt h−1) and in
general up to 2.3 times stronger above the canopy than close to the ground.
The insignificance of known gas phase reactions and other processes
like dry deposition or advection compared to the photolytic decomposition
of HONO at this measurement site was an ideal prerequisite to study possible
correlations of this unknown term to proposed HONO sources. But neither the
proposed emissions from soils nor the proposed photolysis of adsorbed
HNO3 contributed substantially to the unknown source. However, the
unknown source was found to be perfectly correlated to the unbalanced
photolytic loss of HONO. |
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