AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Evidence of Ambient Aqueous SOA Formation in the Po Valley, Italy
AMY P. SULLIVAN, Natasha Hodas, Barbara Turpin, Kate Skog, Frank Keutsch, Stefano Decesari, M. Cristina Facchini, Jeffrey Collett, Colorado State University
Abstract Number: 39 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract Laboratory experiments suggest that water-soluble products from the gas-phase oxidation of volatile organic compounds can partition into atmospheric waters (i.e., fogs, clouds, and aerosol water) where they are further oxidized forming low volatility products. These products can remain in the particle phase after water evaporation forming what is termed as aqueous secondary organic aerosol (SOA). There is evidence for ambient aqueous SOA in that smog chamber experiments form SOA that is less hygroscopic and oxygenated than atmospheric SOA and there appears to be a missing source of SOA based on the underestimation of model-predicted compared to measured SOA. However, few studies have attempted to observe ambient aqueous SOA. Therefore, a suite of measurements was made during the PEGASOS (Pan-European Gas-AeroSols-climate interaction Study) campaign conducted in June-July 2012 in the Po Valley, Italy to search for evidence of aqueous SOA. A key measurement for this analysis was water-soluble organic carbon (WSOC) as it is considered to be a good proxy for SOA. WSOC will be examined as a function of parameters known to play a role in aqueous SOA such as relative humidity (RH), liquid water content (LWC), and organic aerosol (OA) concentration. The conditions needed for aqueous SOA formation will be discussed. Our results suggest that, at this site, aqueous SOA appears to form in the dark. Elevated ammonia concentrations and the timing of its occurrence seem to play a large role in the formation of ambient aqueous SOA.