Modelling organic aerosol concentrations and properties during ChArMEx summer campaigns of 2012 and 2013 in the western Mediterranean region

Mounir Chrit (1) , Karine Sartelet (1) , Jean Sciare (2, 3) , Jorge Pey (4, 5) , Nicolas Marchand (4) , Florian Couvidat (6) , Karine Sellegri (7) , Matthias Beekmann (8)

1 CEREA - Centre d'Enseignement et de Recherche en Environnement Atmosphérique
2 LSCE - Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette]
3 CAE - Chimie Atmosphérique Expérimentale
4 LCE - Laboratoire Chimie de l'environnement
5 IGME - Instituto Geológico y Minero de España
6 INERIS - Institut National de l'Environnement Industriel et des Risques
7 LaMP - Laboratoire de Météorologie Physique
8 LISA (UMR_7583) - Laboratoire Interuniversitaire des Systèmes Atmosphériques

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 to represent the organic aerosol concentrations and properties (oxidation state and hydrophilicity) using the air-quality model Polyphemus with a surrogate approach for secondary organic aerosol (SOA) formation. Biogenic precursors are isoprene, monoterpenes 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-NOx regime, (ii) organic nitrate chemistry and (iii) extremely low-volatility organic compounds (ELVOCs) formed by ozonolysis. The model shows good agreement of measurements of organic concentrations for both 2012 and 2013 summer campaigns. The modelled oxidation property and hydrophilic organic carbon 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 carbon (WSOC) concentrations 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 percent of the organic mass in PM$_1$, with maxima above the sea.

Mots clés: ChArMEx

Domaines: Océan, Atmosphère; Autre

Mounir Chrit, Karine Sartelet, Jean Sciare, Jorge Pey, Nicolas Marchand, et al.. Modelling organic aerosol concentrations and properties during ChArMEx summer campaigns of 2012 and 2013 in the western Mediterranean region. Atmospheric Chemistry and Physics, 2017, 17 (20), pp.12509-12531. ⟨10.5194/acp-17-12509-2017⟩. ⟨hal-01724306⟩