John Seinfeld
Mail Code 210-41
202A Spalding Lab
Department of Chemical Engineering
California Institute of Technology
Pasadena, CA 91125
626-395-4188
fax 626796-2591
Seinfeld@cco.caltech.edu

Carbonaceous material is a significant component of total aerosol mass in urban and regional areas of the U.S. Atmospheric carbonaceous material consists of both elemental (EC) and organic (OC) carbon. EC is only emitted directly by combustion sources; OC can either be emitted directly by sources (primary OC) or can result from condensation and absorption of low vapor pressure organics onto existing particles (secondary OC). Development of PM2.5 abatement strategies will require that one be able to relate aerosol EC and OC to primary particulate and gaseous emissions. This necessitates a fundamental understanding of the atmospheric transformations that lead to SOA. Ambient data on aerosol composition provides some information on the magnitude and structure of secondary organic aerosol but this information is incomplete and requires that significant assumptions be made in interpretation. A long-term goal of our research program is to understand fundamentally the processes that lead to the atmospheric formation of SOA, and to translate this understanding into three-dimensional urban and regional air quality models. We will perform a comprehensive series of chamber experiments on aerosol formation at low and elevated relative humidity and as a function of temperature for biogenic and aromatic hydrocarbons as well as other compounds. Aerosol yields will be studied for salt-organic-water systems, as well as systems without initial seed aerosol. The overall goal of the proposed research is two fold: (1) to identify through laboratory chamber experiments all the significant sources of ambient secondary organic aerosol (SOA), especially anthropogenic; and (2) to develop a molecular-level understanding of the SOA-forming process, including molecular speciation and gas-particle partitioning of gas-phase oxidation products to organic-inorganic-water aerosols.

Some further information can be found in the viewgraphs from a presentation at the Atmospheric Sciences Program Annual Meeting held in March 2002.