American Association for Aerosol Research - Abstract Submission

AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA

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Searching for Evidence of Aqueous SOA Formation in the Po Valley

AMY P. SULLIVAN, Natasha Hodas, Barbara Turpin, Kate Skog, Frank Keutsch, Stefano Decesari, M. Cristina Facchini, Jeffrey L. Collett, Jr., Colorado State University

     Abstract Number: 174
     Working Group: Carbonaceous Aerosols in the Atmosphere

Abstract
Laboratory experiments and predictions suggest that water-soluble products from the gas phase oxidation of volatile organic compounds can partition into atmospheric waters 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). A gap between model-predicted and observed SOA and a tendency for smog chamber experiments to form SOA that is less oxygenated and hygroscopic than atmospheric SOA both suggest that missing aqueous processing may be a key contributor to ambient SOA. To date, however, few studies have attempted to observe aqueous SOA formation in the ambient atmosphere. Here we report observations from the Po Valley, Italy during the PEGASOS (Pan-European Gas-AeroSols-climate interaction Study) campaign conducted in June-July 2012, a time of high pollution and humidity when aqueous SOA production is favorable. Measurements of light organic acids and inorganic anions/cations were made using a PILS-IC (Particle-into-Liquid Sampler – Ion Chromatography), water-soluble organic carbon (WSOC) using a PILS-TOC (Particle-into-Liquid Sampler – Total Organic Carbon), and gas phase glyoxal using a laser induced phosphorescence technique. Additional measurements at the study site included standard gases and meteorological parameters. The approach and results of the analysis on the combined data set to identify evidence of aqueous SOA will be presented. Parameters to be examined include observed concentrations of oxalate (a key product of postulated mechanisms for aqueous SOA production), sulfate (a secondary product with an important aqueous formation pathway), glyoxal (an important gas phase precursor for aqueous SOA production), and WSOC (a good proxy for SOA in the absence of biomass burning). Periods of WSOC increase will be examined to look for evidence of aqueous SOA production and how it depends on liquid water content, light, the availability of gas phase precursors, and photochemical oxidants.