M. J. Molina
Bldg. 54-1814
Massachusetts Institute of Technology
77 Massachusetts Avenue
Cambridge, MA 02139
617-253-5081
fax 617-258-6525
mmolina@mit.edu

Aromatic hydrocarbons are important in the chemistry of the urban and regional atmosphere because of their abundance in motor vehicle emissions and because of their reactivity with respect to ozone and organic aerosol formation. The objective of this project is to investigate the various processes responsible for aerosol formation from aromatic hydrocarbons, toluene and the xylene isomers. The project consists of two parts: (1) investigation of the gas-phase mechanism that leads to the formation of precursor species of organic aerosols, and (2) investigation of organic aerosol formation and reactivity. In the first part of the project, a high-pressure turbulent-flow reactor, in conjunction with chemical ionization mass spectrometry (CIMS) detection, is used to study the oxidation reactions of aromatic compounds in order to elucidate the gas-phase mechanism leading to organic aerosol formation. The second part of the project employs a novel approach, based on a diffusive trapping technique, to generate organic aerosols in an aerosol chamber. Organic aerosols are produced from condensable organic acids at various partial pressures, temperatures, and relative humidity and in the presence of seeding inorganic aerosols. The methods for the characterization of organic aerosols will include the use of Scanning Mobility Particle Sizer (SMPS) and Fourier Transform Infrared (FTIR) spectroscopy for determination of the aerosol sizes, distributions, and chemical composition, in addition to CIMS detection of the gaseous species. The organic aerosols will be introduced into a flow reactor to study gas uptake of semi-volatile organic compounds in order to elucidate the heterogeneous processes controlling gas/particle partitioning.

This research should provide crucial information concerning the gas-phase mechanism that leads to the formation of precursor species of organic aerosols and heterogeneous processes that determine the gas/particle partitioning of organic species. Hence, the study will improve our ability to model and predict organic aerosol formation and their chemical composition.

More information on this research will become available later from the principal investigator.