Efficient bulk mass accommodation and dissociation of N 2 O 5 in neutral aqueous aerosol

An isotope exchange experiment with the short-lived radioactive tracer 13N is used to trace N2O5 uptake into nitrate-containing aqueous aerosol particles. While uptake of 13N-labelled N2O5 to deliquesced Na2SO4 aerosol is consistent with previous studies, efficient exchange of labelled nitrate with the non-labelled nitrate pool was observed in the presence of aerosol-phase nitrate. The experiments provide direct evidence for efficient bulk mass accommodation of N2O5 into aqueous solution with αb > 0.4 at room temperature, as well as for the fast dissociation into nitronium and nitrate. While for experimental reasons this study is limited to non-acidic nitrate-containing aerosol, it is likely that bulk mass accommodation and dissociation are not limiting N2O5 uptake under wider ranges of conditions.