Regensburg 2007 – scientific programme

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UP: Fachverband Umweltphysik

UP 6: Heterogene Prozesse in der Atmosphäre - gemeinsam mit dem Arbeitskreis Athmosphärenchemie (AKAC) der GDCh

UP 6.8: Talk

Monday, March 26, 2007, 16:45–17:00, H48

The photolysis of methyl-substituted nitroaromatics: A new gas phase source of HONO — •Iustinian Bejan, Ian Barnes, Thorsten Benter, Peter Wiesen, and Jörg Kleffmann — Bergische Universität Wuppertal, Fachbereich C / Physikalische Chemie, Wuppertal, Germany

Nitrous acid is of considerable atmospheric importance since the photolysis leads to the formation of OH radicals, the key atmospheric oxidant in the degradation of most air pollutants and a crucial intermediate in the formation of photochemical smog in the troposphere. Recent field studies have demonstrated that the contribution of HONO to the oxidation capacity of the atmosphere has been underestimated and established the existence of yet unknown daytime sources of HONO. In the present laboratory study, the gas phase photolysis of different methyl substituted nitroaromatics has been studied in a flow tube photoreactor upon irradiation (λ=300-500 nm). HONO was detected using a selective and sensitive instrument (LOPAP), while the nitroaromatics were quantified by FTIR spectroscopy. Similar to a recent study on nitrophenols, instantaneous formation of HONO has been observed during the photolysis of methyl substituted nitroaromatics for the first time. A mechanism is presented to explain the experimental observation. In addition, the contribution of this new gas phase source to the oxidation capacity of the atmosphere is discussed.