Reaction probability of N₂O₅ on aqueous aerosols

Abstract

The reaction probability, γ, of N2O5 (to form HNO3) with monodisperse NH3/H2SO4/H2O aerosols has been measured in a flow tube reactor at atmospheric pressure. Experiments were performed at temperatures of 274 and 293 K and at relative humidities of 1–76%. It appears that the presence of a liquid phase is necessary for reaction. With NH4HSO4 aerosol, γ values are nonzero, even below the deliquescence point of the pure salt, and show a gradual increase with increasing relative humidity up to constant values of 0.05 and 0.09 for 293 and 274 K, respectively. Experiments with aerosols of varied NH3/H2SO4 ratios suggest that evaporation of NH3 from the NH4HSO4 aerosols creates excess H2SO4 on the surface. This can take up water vapor to provide the reactant for N2O5 below the deliquescence point of NH4HSO4. The present observations are consistent with the reaction of N2O5 with moist aerosols being a major removal mechanism for odd nitrogen and a major source of HNO3 in the nighttime troposphere. The same reaction on H2SO4 aerosols may be of significance in the stratosphere.

Chlorine activation indoors and outdoors via surface-mediated reactions of nitrogen oxides with hydrogen chloride

“…The weak signals typically observed for surface-adsorbed species using ATR-FTIR required the use of higher concentrations than found in the atmosphere. However, ionization of N 2 O 5 on surfaces is expected to be operational at lower concentrations as well (19,20 …”

“…In the case of N 2 O 5 , autoionization to NO 2 ϩ NO 3 Ϫ has also been proposed as a key intermediate step (19,20), and rapid reaction with water also occurs, forming nitric acid:…”

A parameterization of the heterogeneous hydrolysis of N<sub>2</sub>O<sub>5</sub> for mass-based aerosol models: improvement of particulate nitrate prediction

“…The applied particle-gas partitioning depends on temperature and humidity. As in ISORROPIA, under dry and warm conditions the equilibrium shifts toward the gas phase (Nenes et al, 1998). By using the equilibrium approach of Mozurkewich (1993), the partitioning scheme was comparable to Galperin and Sofiev (1998).…”

“…Several techniques could be employed to measure γ N 2 O 5 on the surface of different aqueous solutions (Hallquist et al, 2000;Robinson et al, 1997;Hu and Abbatt, 1997;Behnke et al, 1997;Fenter et al, 1996;Van Doren et al, 1990;Mozurkewich and Calvert, 1988). It was reported that the typical values for γ N 2 O 5 are on the order of 10 −2 .…”

“…Davis et al (2008) developed a parameterization scheme (Davis08) of γ N 2 O 5 for aerosols containing nitrate, sulfate, and ammonium. It was developed on the basis of numerous previous laboratory studies (Badger et al, 2006;Folkers et al, 2003;Hallquist et al, 2003;Folkers, 2002;Kane et al, 2001;Hu and Abbatt, 1997;Mozurkewich and Calvert, 1988) with respect to temperature, RH, and particle compositions.…”