Relative importance of organic coatings for the heterogeneous hydrolysis of N 2 O 5 during summer in Europe

The heterogeneous reaction probability of N 2 O 5 depends largely on the aerosol chemical composition. Several recent laboratory studies have shown that the presence of organic coatings on aqueous aerosols can suppress heterogeneous N 2 O 5 hydrolysis. In this study we investigated the relative importance of organic coatings, formed via gas‐to‐particle conversion on aqueous aerosols, to N 2 O 5 hydrolysis on local and regional scales during summer in Europe. We present results of one‐dimensional process studies and of regional‐scale model simulations for Europe with the comprehensive model system COSMO‐ART. To treat N 2 O 5 hydrolysis, we used recent results from laboratory studies that quantified on the basis of the organic coating thickness. The simulations showed that during any episode the conditions for formation of N 2 O 5 and secondary organic compounds were very variable and depended strongly on the meteorological conditions. In regions of the model domain where both components were built‐up, the formation of organic coatings could decrease particulate nitrate concentrations by up to 90%. Where these conditions were not met, the impact of the organic coating was negligible.