ALBERT

Description: Modelling organic aerosol concentrations and properties during ChArMEx summer campaigns of 2012 and 2013 in the western Mediterranean region Mounir Chrit, Karine Sartelet, Jean Sciare, Jorge Pey, Nicolas Marchand, Florian Couvidat, Karine Sellegri, and Matthias Beekmann Atmos. Chem. Phys. Discuss., https//doi.org/10.5194/acp-2017-312,2017 Manuscript under review for ACP (discussion: open, 0 comments) In the framework of the Chemistry-Aerosol Mediterranean Experiment, a measurement site was set up at a remote site (Ersa) on Corsica Island in the northwestern Mediterranean Sea. Measurement campaigns performed during the summers of 2012 and 2013 showed high organic aerosol concentrations, mostly from biogenic origin. This work aims at representing the organic aerosol concentrations and properties (oxidation state and hydrophilic) using the air-quality model Polyphemus with a surrogate approach for secondary organic aerosol (SOA) formation. Biogenic precursors are isoprene, monoterpenes (with α-pinene and limonene as surrogate species) and sesquiterpenes. In this work, the following model oxidation products of monoterpenes are added: (i) a carboxylic acid (MBTCA) to represent multi-generation oxidation products in the low-NO x regime, (ii) organic nitrate chemistry, (iii) extremely low volatility organic compounds (ELVOCs) formed by ozonolysis. The model shows good agreement to measurements of organic concentrations for both 2012 and 2013 summer campaigns. The modeled oxidation state and hydrophilic properties of the organic aerosols also agree reasonably well with the measurements. The influence of the different chemical processes added to the model on the oxidation level of organics is studied. Measured and simulated water-soluble organic concentrations (WSOC) show that even at a remote site next to the sea, about 64 % of the organic carbon is soluble. The concentrations of WSOC vary with the origins of the air masses and the composition of organic aerosols. The marine organic emissions only contribute to a few percents of the organic mass in PM 1 , with maxima above the sea.