N2O5 hydrolysis on the components of mineral dust and sea salt aerosol: Comparison study in an environmental aerosol reaction chamber

The kinetics of the heterogeneous hydrolysis of N2O5 on some of the major components of mineral dust and sea salt aerosol have been investigated in an environmental aerosol chamber. Gas-phase N2O5 undergoes heterogeneous reaction to form HNO3 on carbonate, clay and oxide minerals. The nitric acid hydrolysis product was promptly detected in the gas phase concomitant with the decay of N2O5 over time. The N2O5 decay kinetics were measured and analyzed assuming first-order reaction kinetics. When normalized for surface area, heterogeneous decay of N2O5 on the different minerals followed the reactivity trend; kaolinite > hematite > montmorillonite > calcite>quartz. N2O5 decay was faster on all of the mineral dust aerosol components relative to NaCl, a major component of sea salt, at a relative humidity (RH) below the NaCl deliquescence point. The measured heterogeneous uptake coefficients were over an order of magnitude larger on several of the mineral dust aerosol compared to NaCl. The uptake coefficient was found to increase with RH.