Efficient bulk mass accommodation of N<sub>2</sub>O<sub>5</sub> into neutral aqueous aerosol

Abstract. 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, in presence of aerosol phase nitrate efficient exchange of labeled nitrate with the non-labeled nitrate pool was observed. The experiments provide direct evidence for efficient bulk mass accommodation of N2O5 into aqueous solution with an accommodation coefficient >0.4 at room temperature, as well as for the fast disproportionation into nitronium and nitrate. While for experimental reasons this study is limited to non-acidic aerosol, it is likely that mass accommodation is not limiting N2O5 uptake also under wider ranges of conditions.