Gas-phase reaction of N2O5 with water vapor:: Importance of heterogeneous hydrolysis of N2O5 and surface desorption of HNO3 in a large teflon chamber

Laboratory measurements of the gas-phase hydrolysis of N2O5 are always preturbed by wall reactions. Their contribution could be quantified in a large double-walled teflon bag chamber by introducing HNO3 into the chamber and analysing its temporal evolution in the gasphase at low and high relative humidities, and by varying the surface-to-volume ratio of the chamber. By fitting a model to the experimental results, a consistent set of rate coefficients for adsorption and desorption of HNO3 from the chamber walls could be obtained. The desorption is so slow that the gas-phase hydrolysis of N2O5 via the reactions N2O5 + H2O --> 2HNO(3) (k1 = 2.5.10(-22) cm(3)molec.(-1)s(-1)) and N2O5 + 2H(2)O --> 2HNO(3) + H2O (k2 = 1.8.10(-39) cm(6)molec.(-2)s(-1)) is influenced by wall effects to less than 5%. The importance of the gas-phase N2O5 hydrolysis in the troposphere is discussed.