ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-10-4111-2010 Elemental analysis of chamber organic aerosol using an aerodyne high-resolution aerosol mass spectrometer Chhabra P. S. 1 Flagan R. C. 1 2 Seinfeld J. H. 1 2 Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA, USA Division of Engineering and Applied Science, California Institute of Technology, Pasadena, CA, USA 03 05 2010 10 9 4111 4131 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/10/4111/2010/acp-10-4111-2010.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/10/4111/2010/acp-10-4111-2010.pdf

The elemental composition of laboratory chamber secondary organic aerosol (SOA) from glyoxal uptake, α-pinene ozonolysis, isoprene photooxidation, single-ring aromatic photooxidation, and naphthalene photooxidation is evaluated using Aerodyne high-resolution time-of-flight mass spectrometer data. SOA O/C ratios range from 1.13 for glyoxal uptake experiments to 0.30–0.43 for α-pinene ozonolysis. The elemental composition of α-pinene and naphthalene SOA is also confirmed by offline mass spectrometry. The fraction of organic signal at <i>m/z</i> 44 is generally a good measure of SOA oxygenation for α-pinene/O<sub>3</sub>, isoprene/high-NO<sub>x</sub>, and naphthalene SOA systems. The agreement between measured and estimated O/C ratios tends to get closer as the fraction of organic signal at <i>m/z</i> 44 increases. This is in contrast to the glyoxal uptake system, in which <i>m/z</i> 44 substantially underpredicts O/C. Although chamber SOA has generally been considered less oxygenated than ambient SOA, single-ring aromatic- and naphthalene-derived SOA can reach O/C ratios upward of 0.7, well within the range of ambient PMF component OOA, though still not as high as some ambient measurements. The spectra of aromatic and isoprene-high-NO<sub>x</sub> SOA resemble that of OOA, but the spectrum of glyoxal uptake does not resemble that of any ambient organic aerosol PMF component.

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