The impact of multiphase reactions of NO2 with aromatics: a modelling approach N. Lahoutifard1,*, M. Ammann2, L. Gutzwiller2, B. Ervens3,**, and Ch. George1 1Laboratoire d’Application de la Chimie à l’Environnement (LACE), CNRS-UCBL, 43, boulevard du 11 Novembre 1918, F-69622 Villeurbanne Cedex, France 2Paul Scherrer Institute, Laboratory for Radio- and Environmental Chemistry, CH-5232 Villigen, Switzerland 3Institut für Troposphärenforschung Permoserstr. 15, D-04303 Leipzig, Germany **now at: Department of Chemistry, University of Ottawa, Ontario, Canada **now at: Cooperative Institute for Research in the Atmosphere (CIRA), Colorado State University, Fort Collins, Colorado 80523, USA
Abstract. The impact of multiphase reactions involving nitrogen dioxide
(NO2) and aromatic compounds was simulated in this study. A mechanism (CAPRAM 2.4, MODAC Mechanism)
was applied for the aqueous phase reactions, whereas RACM was applied for the gas phase
chemistry. Liquid droplets were considered as monodispersed with a mean radius of
0.1 µm and a liquid content (LC) of 50 µg m-3. The multiphase mechanism has been further extended
to the chemistry of aromatics, i.e. reactions involving benzene, toluene, xylene, phenol and
cresol have been added. In addition, reaction of NO2 with dissociated hydroxyl substituted
aromatic compounds has also been implemented. These reactions proceed through charge
exchange leading to nitrite ions and therefore to nitrous acid formation. The strength of this
source was explored under urban polluted conditions. It was shown that it may increase gas
phase HONO levels under some conditions and that the extent of this effect is strongly pH
dependent. Especially under moderate acidic conditions (i.e. pH above 4) this source may
represent more than 75% of the total HONO/NO2- production rate, but this contribution drops down close to zero in acidic droplets (as those often encountered in urban environments).
Citation: Lahoutifard, N., Ammann, M., Gutzwiller, L., Ervens, B., and George, Ch.: The impact of multiphase reactions of NO2 with aromatics: a modelling approach, Atmos. Chem. Phys., 2, 215-226, doi:10.5194/acp-2-215-2002, 2002.