AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Real-Time Secondary Organic Aerosol Formation from Ambient Air using the Potential Aerosol Mass (PAM) – Aerosol Mass Spectrometer
JOSE-LUIS JIMENEZ, Amber Ortega, Brett Palm, Douglas Day, Pedro Campuzano-Jost, Patrick Hayes, William Brune, Rui Li, Daniel Bon, Joost de Gouw, Lisa Kaser, Thomas Karl, Juliane L. Fry, Kyle Zarzana, Steven Brown, et al., University of Colorado
Abstract Number: 657 Working Group: Aerosol Chemistry
Abstract To directly study SOA formation in ambient air in real-time, we have deployed a Potential Aerosol Mass (PAM; Kang et al. ACP 2007) photooxidation flow reactor with rapid cycling of the light intensity. The input and output of PAM are analyzed with an Aerodyne High Resolution Time-of-Flight Aerosol Mass Spectrometer, a Scanning Mobility Particle Sizer (SMPS), and a Proton Transfer Reaction-Mass Spectrometer (PTRMS). We have used this system to characterize SOA formation in (a) urban air during CalNex-LA-2010 in the Los Angeles area of California, (b) forest air at the USFS Manitou Forest in Colorado during BEACHON-RoMBAS-2011, and (c) biomass smoke at the USFS Fire Science Lab in Missoula, MT, during FLAME-3 in 2009. In some campaigns we used a gas-phase denuder to study heterogeneous OH processing of the pre-existing aerosol, or injected O3 or N2O5 in PAM without lights to investigate SOA formation from O3 or NO3 oxidation. In all cases PAM OH photoxidation enhances SOA at intermediate exposure but results in net loss of OA at very high exposures. SOA formation greatly exceeds that calculated from the measured precursors in urban air, but differences are much smaller in forest air. PAM oxidation also results in a similar slope in the Van Krevelen diagram to ambient oxidation, and in similar evolution in the AMS f44-f43 diagram as observed in PAM lab studies. New particle formation is often observed when using OH as an oxidant, but not when using O3 or NO3. Lab experiments are used to obtain SOA yields for the key precursors of the above campaigns under the same PAM conditions used in the field, and also to study SOA formation under conditions simulating the 2010 Gulf of Mexico oil spill.