AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Secondary Organic Aerosol Formation Projection from Single-Ring Aromatic Tail Pipe and Evaporative Emissions from California Gasoline Vehicles
ANTONIO MIGUEL, University of California, Los Angeles
Abstract Number: 181 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract Biogenic and anthropogenic reactive organic gases (ROG) produce secondary organic aerosol (SOA) through photochemical reaction and partitioning processes. It is now recognized that SOA accounts for a significant fraction of the atmospheric burden of organic particulate mass. SOA formation follows a series of complex reactions and is dependent on a number of parameters including ROG type and concetration, existing PM, NOx and free-radical concentration, aerosol water content and relative humidity, actinic flux, and primary and intermediate organic compound concentrations. Over 80% of the ROGs in California are emitted from a wide range of sources including on-and off-road motor vehicles and equipment, aircrafts and ocean vessels, fuel storage and solvent evaporation. We estimate the SOA formation potential from tailpipe emission rates of the single-ring ROGs toluene, ethylbenzene, o-Xylene, 1,2,4-Trimethylbenzene and benzene for the 1995 to 2003 in-use California light-duty gasoline vehicle fleets. SOA formation yield (Y) data were obtained from reported well controlled smog chamber studies. The total mass concentration of organic aerosol, ΔMo, produced for a given amount of ROG reacted, ΔROG, was calculated from Y = ΔMo/ΔROG (Odum et al., 1997; Ng et al., 2007). Relative to the 1995 fleet, we estimate that the 2003 fleet decreased SOA production by 86%, at an average annual rate of about 10%, for the target single-ring aromatics. Evaporative single-ring ROGs fleet average emission rates decreased 63 to 90% from the 1999 to the 2003 fleet. Factors that contributed to the observed tail pipe precursor reduction for the periods considered include the retirement of non-catalyst vehicles, the increased use of emissions control technologies, and the switch to Phase III gasoline.