Regensburg 2007 – wissenschaftliches Programm

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UP: Fachverband Umweltphysik

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

UP 6.1: Hauptvortrag

Montag, 26. März 2007, 14:00–14:30, H48

Photoenhanced conversion of NO₂ on dust — •Christian George¹, Marieme Ndour^1,2, Barbara D’Anna¹, Oumar Ka², Yves Balkanski³, Jörg Kleffmann⁴, Konrad Stemmler⁵, and Markus Ammann⁵ — ¹IRCELYON, Institut de recherches sur la catalyse et l*environnement de Lyon, 2 avenue Albert Einstein, Villeurbanne, F-69626 cedex, France ; CNRS, UMR5256, Villeurbanne F-69626, France ; Université de Lyon, Villeurbanne, F-69626, France ; Université Lyon 1, Villeurbanne, F-69626, France ; Université Claude Bernard Lyon 1, Villeurbanne, F-69626, France. — ²University Cheikh Anta Diop, Dakar-Fann Senegal. — ³Laboratoire des Sciences du Climat et l’Environnement (CEA-CNRS, F-91191 Gif-sur-Yvette Cedex — ⁴Physikalische Chemie - FB C, Bergische Universität Wuppertal, 42097 Wuppertal, Germany — ⁵Paul Scherrer Institute, Laboratory of Radio- and Environmental Chemistry, CH-5232 Villigen, Switzerland.

Up to 3000 Tg of mineral aerosol are uplifted annually into the mid troposphere and transported over very large distances. This huge amount of mineral aerosol has been questioned has being the support for the conversion or scavenging of nitrogen oxides. It was shown that mainly HNO₃ or N₂O₅ are taken up by dust particles while the interaction with NO2 was very limited due to surface saturation and a slow chemistry.. However, mineral dust contains small amounts of TiO₂ (of the order of 1 %wt) which has specific photocatalytic properties. This oxide when illuminated under ca. 440 nm will create oxidants on its surface that may react with all adsorbed compounds. The question is then can light promote the uptake and or conversion of NO₂ on mineral dust? Therefore, we investigated the effect of light (in the range 300-500 nm) on the uptake kinetics of NO₂ on various surfaces taken as proxies for dust particles encountered in the troposphere. In this study, the uptake kinetics and product formation rates were measured using different flow tube reactors in combination with different analytical methods for NO_x and HONO detection. We will show that there is a substantial effect of light on the NO₂ uptake kinetics on mineral surfaces containing TiO₂ and on the formation of nitrous acid.