AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Organic Aerosol Formation and Processing in the Los Angeles Basin: Role of Gasoline vs. Diesel Emissions
ROYA BAHREINI, Ann Middlebrook, Joost de Gouw, Carsten Warneke, Michael Trainer, Charles Brock, Harald Stark, Steven Brown, William P. Dube, Jessica Gilman, Katharine Hall, John Holloway, William C. Kuster, Anne Perring, Andre Prévôt, Joshua P. Schwarz, J. Ryan Spackman, Soenke Szidat, Nick Wagner, Rodney Weber, Peter Zotter, David D. Parrish, CU CIRES- NOAA ESRL
Abstract Number: 267 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract Laboratory experiments have shown that organic compounds in both gasoline fuel and diesel engine exhaust can form secondary organic aerosol (SOA); however, the fractional contribution from gasoline and diesel exhaust emissions to ambient SOA in urban environments is poorly known. Here we use airborne and ground-based measurements of organic aerosol (OA) in the Los Angeles (LA) Basin, California made during the CalNex field project (“Research at the Nexus of Air Quality and Climate Change, May and June 2010) to assess the amount of SOA formed from diesel emissions. Airborne black carbon (BC) measurements indicate that diesel emissions in the LA Basin are lower on weekends by 54%. Despite the lower contribution of diesel emissions on weekends, formation of OA in air masses with similar degrees of photochemical processing is the same on weekends and weekdays, within the measurement uncertainties. This result indicates that the contribution from diesel emissions to SOA formation is zero within our uncertainties. Using these uncertainties, we estimate that the maximum weekday contribution from diesel engine emissions to SOA is 20%. Therefore, a decrease in the emission of organic species from gasoline engines may significantly reduce SOA concentrations on local and global scales.