O/C and OM/OC ratios of primary, secondary, and ambient organic aerosols with high-resolution time-of-flight aerosol mass spectrometry

Allison C. Aiken, Peter F. Decarlo, Jesse H. Kroll, Douglas R. Worsnop, J. Alex Huffman, Kenneth S. Docherty, Ingrid M. Ulbrich, Claudia Mohr, Joel R. Kimmel, Donna Sueper, Yele Sun, Qi Zhang, Achim Trimborn, Megan Northway, Paul J. Ziemann, Manjula R. Canagaratna, Timothy B. Onasch, M. Rami Alfarra, Andre S H Prevot, Josef DommenJonathan Duplissy, Axel Metzger, Urs Baltensperger, Jose L. Jimenez

    Research output: Contribution to journalArticlepeer-review


    A recently developed method to rapidly quantify the elemental composition of bulk organic aerosols (OA) using a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) is improved and applied to ambient measurements. Atomic oxygen-to-carbon (O/C) ratios characterize the oxidation state of OA, and O/C from ambient urban OA ranges from 0.2 to 0.8 with a diurnal cycle that decreases with primary emissions and increases because of photochemical processing and secondary OA (SOA) production. Regional O/C approaches ∼0.9. The hydrogen-to-carbon (H/C, 1.4-1.9) urban diurnal profile increases with primary OA (POA) as does the nitrogen-to-carbon (N/C, ∼0.02). Ambient organic-mass-to-organic-carbon ratios (OM/OC) are directly quantified and correlate well with O/C (R2 = 0.997) for ambient OA because of low N/C. Ambient O/C and OM/OC have values consistent with those recently reported from other techniques. Positive matrix factorization applied to ambient OA identifies factors with distinct O/C and OM/OC trends. The highest O/C and OM/OC (1.0 and 2.5, respectively) are observed for aged ambient oxygenated OA, significantly exceeding values for traditional chamber SOA, while laboratory-produced primary biomass burning OA (BBOA) is similar to ambient BBOA, O/C of 0.3-0.4. Hydrocarbon-like OA (HOA), a surrogate for urban combustion POA, has the lowest O/C (0.06-0.10), similar to vehicle exhaust. An approximation for predicting O/C from unit mass resolution data is also presented. © 2008 American Chemical Society.
    Original languageEnglish
    Pages (from-to)4478-4485
    Number of pages7
    JournalEnvironmental Science and Technology
    Issue number12
    Publication statusPublished - 15 Jun 2008


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