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Abstract
The collection efficiency (CE) of the aerosol mass spectrometer (AMS) for chamber-generated secondary organic aerosol (SOA) at elevated mass concentrations (range: 19–207 μg m−3; average: 64 μg m−3) and under dry conditions was investigated by comparing AMS measurements to scanning mobility particle sizer (SMPS), Sunset semi-continuous carbon monitor (Sunset), and gravimetric filter measurements. While SMPS and Sunset measurements are consistent with gravimetric filter measurements throughout a series of reactions with varying parent hydrocarbon/oxidant combinations, AMS CE values were highly variable ranging from unity to <15%. The majority of mass discrepancy reflected by low CE values does not appear to be due to particle losses either in the aerodynamic lens system or in the vacuum chamber as the contributions of these mechanisms to CE are low and negligible, respectively. As a result, the largest contribution to CE in the case of chamber-generated SOA appears to be due to particle bounce at the vaporizer surface before volatilization, which is consistent with earlier studies that have investigated the CE of ambient and select laboratory-generated particles. CE values obtained throughout the series of reactions conducted here are also well correlated with the f 44/f 57 ratio, thereby indicating both that the composition of the organic fraction has an important impact on the CE of chamber-generated SOA and that this effect may be linked to the extent to which the organic fraction is oxidized.
Copyright 2013 American Association for Aerosol Research
Acknowledgments
[Supplementary materials are available for this article. Go to the publisher's online edition of Aerosol Science and Technology to view the free supplementary files.]
The authors would like to acknowledge Doug Worsnop and Aerodyne Research, Inc., for the use of a beam width probe which was used to measure beam width dimensions. Jose L. Jimenez was supported by DOE (BER, ASR program) DE-SC0006035 and NASA NNX12AC03G. The U.S. Environmental Protection Agency, through its Office of Research and Development, funded and collaborated in the research described here under Contract EP-D-05-065 to Alion Science and Technology. The article is subjected to external peer review and has been cleared for publication. Mention of trade names or commercial products does not constitute endorsement or recommendation.
