In ambient field studies conducted with aerosol time-of-flight mass spectrometry (ATOFMS), individual particle mass spectra commonly contain ion peaks at mass/charge (m/z) 86, 101, 102, and 118. Particles with mass spectra containing these peaks show a strong correlation with high relative humidity and low temperatures. In an effort to identify these peaks, a series of smog chamber studies were conducted probing the chemistry of secondary and tertiary alkylamines. Specifically, in separate studies, trimethylamine, di- and triethylamine, and di- and tripropylamine were reacted in a 1 m3 Teflon outdoor smog chamber with naturally occurring levels of gas phase oxidants in ambient air. The aerodynamic sizes and individual mass spectra of the resulting aerosol particles were acquired continuously using aerosol time-of-flight mass spectrometry (ATOFMS). Both oxidation and acid-base reactions between amines and acids commonly present in the atmosphere (i.e., nitric and sulfuric acid) appear to play roles in the formation and chemistry of organic nitrogen-containing particle phase species. Ion peaks in the individual particle mass spectra indicate the presence of alkyl ammonium salts, as well as other tentatively identified organic N-containing compounds formed by oxidation processes. Also, for the first time, tertiary alkylamine-N-oxides have been identified as alkylamine oxidation products in the aerosol particle phase. Smog chamber reactions involving triethylamine produce ATOFMS mass spectra with similar ion peak combinations as those observed in the spectra of particles commonly detected in ambient and vehicular source characterization studies. The results of this study suggest that amine chemistry involving gas-to-particle conversion and photooxidation processes may play a significant role in particle formation in regions with high amine concentrations.

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Particle and meteorological instrumentation were used to characterize ambient atmospheric conditions, aerosol size distributions, aerosol mass concentrations, and single particle size and chemical composition in Bakersfield, CA for the period January 9, 1999 through January 28, 1999. The sampling period included four distinct meteorological periods of stagnation, clearing, haze, and rain. Particle number and mass concentrations were the highest during the stagnation episode when a heavy and extensive fog developed. Mass and number concentrations also approached these high levels during the haze period. Single particle size and composition data from an aerosol time-of-flight mass spectrometer (ATOFMS) are used to provide unique continuous information on the diversity in types of particles present, the effects of meteorology on particle size and composition, and the distribution of important chemical species within individual particles. Aerosol composition and mixing state are found to vary with meteorological conditions. Single particle data show that carbonaceous aerosol with secondary ammonium, nitrate, and sulfate dominate the aerosol concentration during a stagnation period with a dramatic composition shift occurring to sodium type particles during the haze period. The aerosol is internally mixed with respect to carbon, nitrate, sulfate, and ammonium during the stagnation period. The mixing state changes significantly over the haze period when much greater diversity in the associations of chemical species within individual particles occurs.