AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Constraining the Contribution of Organic Acids to Organic Aerosol Using MOVI-HRToF-CIMS and AMS data
LAXMINARASIMHA YATAVELLI, Harald Stark, Douglas Day, Samantha Thompson, Brett Palm, Pedro Campuzano-Jost, Joel Kimmel, Manjula Canagaratna, Michael Cubison, Joel Thornton, John Jayne, Douglas Worsnop, Jose-Luis Jimenez, University of Colorado, Boulder
Abstract Number: 521 Working Group: Aerosol Chemistry
Abstract Using data collected during the Bio-hydro-atmosphere interactions of Energy, Aerosols, Carbon, H2O, Organics & Nitrogen - Rocky Mountain Biogenic Aerosol Study (BEACHON-RoMBAS; http://tinyurl.com/BEACHON-RoMBAS, July-August 2011) we estimate organic acid contribution (f$_(acid)) to organic aerosol (OA) in a ponderosa pine forest. Organic acids were measured using a micro-orifice volatilization impactor high-resolution time-of-flight chemical ionization mass spectrometer (MOVI-HRToF-CIMS; Yatavelli et al., AS&T, 2012) with acetate as the reagent ion. Organic aerosol mass concentration was measured using an Aerodyne aerosol mass spectrometer (AMS). During the BEACHON-RoMBAS, we observed strong correlations between MOVI-HRToF-CIMS measured organic acids and OA. Molecules containing one or more organic acid functional group contributed approximately 45% of the OA mass. Organic acid functional groups are also observed to correlate strongly with the AMS mass fragment (m/z 44, CO$_2$^+ ion) generally used as a marker for highly oxidized aerosol. We observe, on a molar basis, 2 acid molecules per CO$_2$^+ ion. We develop an empirical relationship between the f$_(acid) and f$_(44) (ratio of m/z 44 ion to total OA). Finally, using this new f$_(acid) - f$_(44) relationship and f$_(44) data from AMS measurements at various sites worldwide (Ng et al., ACP, 2010, and other studies), we estimate that molecules containing carboxyl group constitute 30-80% of OA.