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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: Invited Talk
Monday, March 26, 2007, 14:00–14:30, H48
Photoenhanced conversion of NO2 on dust — •Christian George1, Marieme Ndour1,2, 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 NOx 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.