AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Chemical Characterization of Secondary Organic Aerosol by Atmospheric Solid Analysis Probe Mass Spectrometry (ASAP-MS)
VERONIQUE PERRAUD, Carla Waring-Kidd, John Greaves, Barbara J. Finlayson-Pitts, University of California, Irvine
Abstract Number: 55 Working Group: Aerosol Chemistry
Abstract Secondary organic aerosol (SOA) is ubiquitous in the atmosphere and comprises a large fraction of the total aerosol budget. Although a lot of effort has been made over the years to develop specific analytical strategies, elucidation of SOA chemical composition and identification of key molecular species responsible for its formation and growth processes remains challenging. Understanding these processes is critical for assessing their impact on human health, visibility and climate. We report here the application of a relatively new technique, atmospheric solid analysis probe mass spectrometry (ASAP-MS), to laboratory-generated SOA. Οzonolysis of terpenes was studied using the unique UCI large volume slow flow aerosol flow tube under various relative humidity conditions (0 to >80%) in presence and absence of an OH-scavenger (i.e. cyclohexane). The particles were collected on 5 × 5 mm Si-wafers held on a commercial Sioutas impactor during sampling. Measurements were taken at different reaction times using two stages (stage C with a cut off diameter at 500 nm and, stage D with a cut off diameter at 250 nm) providing a size speciation of the particles. The Si-wafers were analyzed using a modified ASAP-MS probe that held the wafer in place without any need for transfer or modification of the sample prior to analysis, leading to a greater integrity of the sample and better reproducibility. Results include 1) the thermal desorption profile of the SOA by ramping the temperature from 20’C to 450’C; this provides insight into the volatility and thermal stability of the SOA and, 2) high resolution mass spectra, which provides accurate mass measurements and the identification of key species. Atmospheric implications of this study will be presented.