The reaction of N2O5 on aerosol particles plays a critical role in removing both NOx (NOx = NO+NO2) and ozone from the atmosphere at night, thus setting the initial conditions for ozone production at sunrise.  Until recently, measurements of the reactive uptake coefficient have been determined either through laboratory studies on model aerosol particles or via steady-state analyses.  We present results based on the first direct in situ observation of the reactive uptake of N2O5 to ambient particles using an entrained aerosol flow tube, coupled to a Chemical Ionization Mass Spectrometer (CIMS) and an Aerosol Time-of-Flight Mass Spectrometer (ATOFMS).  We combine these results with new laboratory measurements made on mixed organic/inorganic particles to formulate a parameterization for the reactive uptake coefficient (?) that can be incorporated into regional and/or global chemical transport models.  Ambient determinations of ?(N2O5), supported by laboratory results on aqueous particles, confirm a strong dependence of the reactive uptake coefficient (?) on particle liquid water, for particle water concentrations below 15 M, and the molar ratio of particle water to nitrate.  Measurements of ?(N2O5) on mixed chloride-nitrate particles indicate that the presence of trace chloride can negate the suppression of ?(N2O5) at high nitrate loadings with implications for polluted coastal regions.

Direct measurement of the heterogeneous reaction of N<sub>2</sub>O<sub>5</sub> on ambient aerosol particles

240th National Meeting (2010)

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Direct measurement of the heterogeneous reaction of N2O5 on ambient aerosol particles

Direct measurement of the heterogeneous reaction of N₂O₅ on ambient aerosol particles