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Quantification of the unknown HONO daytime source and its relation to NO2

Author(s): M. Sörgel | E. Regelin | H. Bozem | J.-M. Diesch | F. Drewnick | H. Fischer | H. Harder | A. Held | Z. Hosaynali-Beygi | M. Martinez | C. Zetzsch

Journal: Atmospheric Chemistry and Physics Discussions
ISSN 1680-7367

Volume: 11;
Issue: 5;
Start page: 15119;
Date: 2011;
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During the DOMINO (Diel Oxidant Mechanism In relation to Nitrogen Oxides) campaign in southwest Spain we measured simultaneously all quantities necessary to calculate a photostationary state for HONO in the gas phase. These quantities comprise the concentrations of OH, NO, and HONO and the photolysis frequency of NO2, j(NO2) as a proxy for j(HONO). This allowed us to calculate values of the unknown HONO daytime source. This unknown HONO source, normalized by NO2 mixing ratios and expressed as a conversion frequency (% h−1), showed a clear dependence on j(NO2) with values up to 43 % h−1 at noon. We compared our unknown HONO source with values calculated from the measured field data for two recently proposed processes, the light-induced NO2 conversion on soot surfaces and the reaction of electronically excited NO2* with water vapour, with the result that these two reactions normally contributed less than 10 % (

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Tangokurs Rapperswil-Jona

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