Photoenhanced Conversion of NO2 on Solid Organic Compounds: an Important Source of HONO

HR: 0800h
AN: A51C-0085 [Abstracts]
TI: Photoenhanced Conversion of NO2 on Solid Organic Compounds: an Important Source of HONO
AU: * George, C
EM: christian.george@univ-lyon1.fr
AF: CNRS-LACE, Laboratoire d'Application de la Chimie … l 'Environnement 43 boulevard du 11 Novembre 1918 F-69622 Villeurbanne France, Villeurbanne, F-69622 France
AU: KLEFFMANN, J
EM: kleffman@uni-wuppertal.de
AF: Bergische Universit„t Wuppertal, Physikalische Chemie/FB C, Bergische Universit„t Wuppertal, 42097 Wuppertal, Germany., Wuppertal, D-42097 Germany
AU: STEMMLER, K
EM: konrad.stemmler@psi.ch
AF: Paul Scherrer Institut, Labor fr Radio- und Umweltchemie, Paul Scherrer Institut, 5232 Villigen, Switzerland., Villigen, CH-5232 Switzerland
AU: Ammann, M
EM: markus.ammann@psi.ch
AF: Paul Scherrer Institut, Labor fr Radio- und Umweltchemie, Paul Scherrer Institut, 5232 Villigen, Switzerland., Villigen, CH-5232 Switzerland
AB: The presence of nitrous acid (HONO) in the atmosphere was first detected more than two decades ago. Since then many studies have elucidated its important role as a major photochemical precursor of the hydroxyl radical- the key oxidant in the degradation of most air pollutants and a crucial intermediate in the formation of photochemical smog in the troposphere. However, the sources of HONO in the troposphere are still poorly understood, especially since recent atmospheric measurements revealed a strongly enhanced formation of HONO during daytime via an unknown mechanism. Here we show that reduction of NO2 on light-activated organics is a major source of gaseous HONO. Under atmospherically relevant conditions, this photosensitized formation of HONO is by magnitudes faster than the previously known disproportionation of NO2 on humid glass surfaces. This is the first example showing that solid surfaces containing traces of natural occurring organic matter have to be considered as photoreactive towards atmospheric oxidants and can explain the high daytime concentrations of HONO recently observed in the boundary layer, the photolysis of which accounts for up to 60% of the integrated OH radical source strengths. Thus this new photoinduced HONO source has a considerable impact on the oxidation capacity of the lower atmosphere.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0317 Chemical kinetic and photochemical properties
DE: 0345 Pollution: urban and regional (0305, 0478, 4251)
DE: 0365 Troposphere: composition and chemistry
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005