Atmos. Chem. Phys. Discuss., 10, 27893-27924, 2010
© Author(s) 2010. This work is distributed
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Secondary aerosol formation from photochemical aging of aircraft exhaust in a smog chamber
M. A. Miracolo1, C. J. Hennigan1, M. Ranjan1, N. T. Nguyen1, T. D. Gordon1, E. M. Lipsky2, A. A. Presto1, N. M. Donahue1, and A. L. Robinson1
1Center for Atmospheric Particle Studies, Carnegie Mellon University, Pittsburgh, PA, 15213, USA
2Penn State Greater Allegheny, McKeesport, PA, 15123, USA

Abstract. Field experiments were performed to investigate the effects of photo-oxidation on fine particle emissions from an in-use CFM56-2B gas turbine engine mounted on a KC-135 Stratotanker airframe. Emissions were sampled into a portable smog chamber from a rake inlet installed one-meter downstream of the engine exit plane of a parked and chocked aircraft. The chamber was then exposed to sunlight and/or UV lights to initiate photo-oxidation. Separate tests were performed at different engine loads (4, 7, 30, 85%). Photo-oxidation created substantial secondary particulate matter (PM), greatly exceeding the direct PM emissions at each engine load after an hour or less of aging at typical summertime conditions. After several hours of photo-oxidation, the ratio of secondary-to-primary PM mass was on average 35 ± 4.1, 17 ± 2.5, 60 ± 2.2, and 2.7 ± 1.1 times the primary PM for the 4, 7, 30, and 85% load experiments, respectively. The composition of secondary PM formed strongly depended on load. At 4% load, secondary PM was dominated by secondary organic aerosol (SOA). At higher loads, the secondary PM was mainly secondary sulfate. Predictions of an SOA model are compared to the measured SOA formation. The SOA model predicts ~40% of the SOA produced during the 4% load experiment and ~60% for the 85% load experiment. Significant emissions of low-volatility compounds present in both the vapor- and particle-phase were measured in the exhaust and represent a significant pool of SOA precursors that appear to form SOA efficiently when oxidized. These results underscore the importance of accounting for atmospheric processing when assessing the influence of aircraft emissions on ambient PM levels.

Citation: Miracolo, M. A., Hennigan, C. J., Ranjan, M., Nguyen, N. T., Gordon, T. D., Lipsky, E. M., Presto, A. A., Donahue, N. M., and Robinson, A. L.: Secondary aerosol formation from photochemical aging of aircraft exhaust in a smog chamber, Atmos. Chem. Phys. Discuss., 10, 27893-27924, doi:10.5194/acpd-10-27893-2010, 2010.
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