Articles | Volume 10, issue 10
Atmos. Chem. Phys., 10, 4625–4641, 2010
Atmos. Chem. Phys., 10, 4625–4641, 2010

  20 May 2010

20 May 2010

Organic aerosol components observed in Northern Hemispheric datasets from Aerosol Mass Spectrometry

N. L. Ng1, M. R. Canagaratna1, Q. Zhang2,*, J. L. Jimenez3,4, J. Tian2, I. M. Ulbrich3,4, J. H. Kroll1,5, K. S. Docherty3,4, P. S. Chhabra6, R. Bahreini3,7, S. M. Murphy7, J. H. Seinfeld6, L. Hildebrandt8, N. M. Donahue8, P. F. DeCarlo3,9,10, V. A. Lanz10, A. S. H. Prévôt10, E. Dinar11, Y. Rudich11, and D. R. Worsnop1 N. L. Ng et al.
  • 1Aerodyne Research, Inc. Billerica, MA, USA
  • 2Atmospheric Sciences Research Center, State University of New York, Albany, NY, USA
  • 3CIRES, University of Colorado, Boulder, CO, USA
  • 4Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO, USA
  • 5Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
  • 6Department of Chemical Engineering, California Institute of Technology, Pasadena, CA, USA
  • 7NOAA, Earth System Research Laboratory, Boulder, CO, USA
  • 8Center for Atmospheric Particle Studies, Carnegie Mellon University, Pittsburgh, PA, USA
  • 9Department of Atmospheric and Oceanic Science, University of Colorado, Boulder, CO, USA
  • 10Laboratory of Atmospheric Chemistry, Paul Scherrer Institut, Villigen, Switzerland
  • 11Department of Environmental Sciences, Weizmann Institute of Science, Rehovot 76100, Israel
  • *now at: Department of Environmental Toxicology, University of California, Davis, CA, USA

Abstract. In this study we compile and present results from the factor analysis of 43 Aerosol Mass Spectrometer (AMS) datasets (27 of the datasets are reanalyzed in this work). The components from all sites, when taken together, provide a holistic overview of Northern Hemisphere organic aerosol (OA) and its evolution in the atmosphere. At most sites, the OA can be separated into oxygenated OA (OOA), hydrocarbon-like OA (HOA), and sometimes other components such as biomass burning OA (BBOA). We focus on the OOA components in this work. In many analyses, the OOA can be further deconvolved into low-volatility OOA (LV-OOA) and semi-volatile OOA (SV-OOA). Differences in the mass spectra of these components are characterized in terms of the two main ions m/z 44 (CO2+) and m/z 43 (mostly C2H3O+), which are used to develop a new mass spectral diagnostic for following the aging of OA components in the atmosphere. The LV-OOA component spectra have higher f44 (ratio of m/z 44 to total signal in the component mass spectrum) and lower f43 (ratio of m/z 43 to total signal in the component mass spectrum) than SV-OOA. A wide range of f44 and O:C ratios are observed for both LV-OOA (0.17±0.04, 0.73±0.14) and SV-OOA (0.07±0.04, 0.35±0.14) components, reflecting the fact that there is a continuum of OOA properties in ambient aerosol. The OOA components (OOA, LV-OOA, and SV-OOA) from all sites cluster within a well-defined triangular region in the f44 vs. f43 space, which can be used as a standardized means for comparing and characterizing any OOA components (laboratory or ambient) observed with the AMS. Examination of the OOA components in this triangular space indicates that OOA component spectra become increasingly similar to each other and to fulvic acid and HULIS sample spectra as f44 (a surrogate for O:C and an indicator of photochemical aging) increases. This indicates that ambient OA converges towards highly aged LV-OOA with atmospheric oxidation. The common features of the transformation between SV-OOA and LV-OOA at multiple sites potentially enable a simplified description of the oxidation of OA in the atmosphere. Comparison of laboratory SOA data with ambient OOA indicates that laboratory SOA are more similar to SV-OOA and rarely become as oxidized as ambient LV-OOA, likely due to the higher loadings employed in the experiments and/or limited oxidant exposure in most chamber experiments.

Final-revised paper