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Download fileReal-Time, Single-Particle Measurements of Oligomers in Aged Ambient Aerosol Particles
journal contribution
posted on 2007-08-01, 00:00 authored by Kerri A. Denkenberger, Ryan C. Moffet, John C. Holecek, Thomas P. Rebotier, Kimberly A. PratherUnique high mass negative ions in the −200 to −400
mass/charge range with repetitive spacings of 12, 14, and
16 units, representative of oligomeric species, have
been detected in single ambient submicrometer aerosol
particles using real-time single-particle mass spectrometry
during the Study of Organic Aerosols field campaign
conducted in Riverside, CA (SOAR) in August and November
2005. These oligomer-containing particles represented 33−40% of the total detected particles and contained other
indicators of aging including oxidized organic carbon, amine,
nitrate, and sulfate ion markers. Overall, the highest
mass oligomeric patterns were observed in small acidic 140−200 nm particles in the summer. Also during the summer,
increased oligomer intensities were observed when the
particles were heated with a thermodenuder. We hypothesize
that heat removed semivolatile species, thereby increasing
particle acidity, while concentrating the oligomeric
precursors and accelerating oligomer formation. Differences
in oligomer behavior with respect to particle size and
heating can be attributed to seasonal differences in
photochemical oxidation, the relative amount of ammonium,
and particle acidity.