Scientific publications - CHROMATOTEC

Large contribution of water-insoluble secondary organic aerosols in the region of Paris (France) during wintertime

Jean Sciare, Odile d’Argouges, Roland Sarda‐Estève, Cécile Gaimoz, Cristina Dolgorouky, Nicolas Bonnaire, Olivier Favez, Bernard Bonsang, and Valérie Gros

Near real-time measurements of carbonaceous aerosols were performed in fine aerosols for a 10-day period during winter at a suburban site of Paris (France). These measurements were performed using an OCEC Sunset Field instrument for elemental carbon (EC) and organic carbon (OC) ; a Particle-Into-Liquid- ampler coupled with a Total Organic Carbon (PILS-TOC) instrument for water-soluble OC (WSOC) ; and a 7-l aethalometer for absorption. A successful comparison was performed with filter sampling performed in parallel for EC, OC, and WSOC, providing further confidence on the results obtained by the online analyzers. A modified version of the aethalometer model was used to derive hourly concentrations of 3 organic aerosol (OA) sources : fossil fuel, wood burning, and secondary. This source apportionment was validated for primary OA (fossil fuel, wood burning) using time-resolved measurements of specific tracers (including levoglucosan, water-soluble potassium and methanol for wood burning) and showed that secondary organic aerosols (SOA) were the most abundant OA species during our study. Water-soluble properties of these different OA sources were investigated from the reconstruction of experimentally determined water- oluble/insoluble OC. About 23% of WSOC was found to be of a secondary (photochemical) origin. A large fraction of SOA was assigned as water-insoluble and could originate from semi-volatile primary OA from wood burning and/or anthropogenic emissions. These results have been obtained at a typical suburban site in France and may be then representative of a larger European area. They bring new light on the commonly accepted idea that SOA is mainly water-soluble.

Atmospheric Environment 80 (2013) 488e498

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