Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
doi:10.5194/acp-2016-926
© Author(s) 2016. This work is distributed
under the Creative Commons Attribution 3.0 License.
Technical note
27 Oct 2016
Review status
A revision of this discussion paper was accepted for the journal Atmospheric Chemistry and Physics (ACP) and is expected to appear here in due course.
Technical Note: Relating functional group measurements to carbon types for improved model-measurement comparisons of organic aerosol composition
Satoshi Takahama and Giulia Ruggeri ENAC/IIE Swiss Federal Institute of Technology Lausanne (EPFL), Switzerland
Abstract. Functional group (FG) analysis provides a means by which functionalization in organic aerosol can be attributed to the abundances of its underlying molecular structures. However, performing this attribution requires additional, unobserved details about the molecular mixture to provide constraints in the estimation process. To address this issue, we present an approach for conceptualizing FG measurements of organic aerosol in terms of its functionalized carbon atoms. This reformulation facilitates estimation of mass recovery and biases in popular carbon-centric metrics that describe the extent of functionalization (such as oxygen to carbon ratio, organic mass to organic carbon mass ratio, and mean carbon oxidation state) for any given set of molecules and FGs analyzed. Furthermore, this approach allows development of parameterizations to more precisely estimate the organic carbon content from measured FG abundance. We use simulated photooxidation products of α-pinene secondary organic aerosol previously reported by Ruggeri et al. (Atmos. Chem. Phys., 16, 4401–4422, 2016) and FG measurements by Fourier Transform Infrared (FT-IR) spectroscopy in chamber experiments by Sax et al. (Aerosol Sci. Tech., 39, 822–830, 2005) to infer the relationships among molecular composition, FG composition, and metrics of organic aerosol functionalization. We find that for this simulated system, ~ 80 % of the carbon atoms should be detected by FGs for which calibration models are commonly developed, and ~ 7 % of the carbon atoms are undetectable by FT-IR analysis because they are not associated with vibrational modes in the infrared. Estimated biases due to undetected carbon fraction for these simulations are used to make adjustments in these carbon-centric metrics such that model-measurement differences are framed in terms of unmeasured heteroatoms (e.g., in hydroperoxide and nitrate groups for the case studied in this demonstration). The formality of this method provides framework for extending FG analysis to not only model-measurement but also instrument intercomparisons in other chemical systems.

Citation: Takahama, S. and Ruggeri, G.: Technical Note: Relating functional group measurements to carbon types for improved model-measurement comparisons of organic aerosol composition, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-926, in review, 2016.
Satoshi Takahama and Giulia Ruggeri
Interactive discussionStatus: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version      Supplement - Supplement
 
RC1: 'Functional group analysis', Anonymous Referee #1, 25 Nov 2016 Printer-friendly Version 
AC1: 'Response to Reviewer 1', Satoshi Takahama, 21 Feb 2017 Printer-friendly Version Supplement 
 
RC2: 'review', Anonymous Referee #2, 09 Jan 2017 Printer-friendly Version 
AC2: 'Response to Reviewer 2', Satoshi Takahama, 21 Feb 2017 Printer-friendly Version Supplement 
Satoshi Takahama and Giulia Ruggeri

Data sets

KPP G/P (model code)
S. Takahama, F. Bernhard, S. Shipley, and G. Ruggeri
doi:10.5281/zenodo.160810
SSP (preprocessing code)
S. Takahama
doi:10.5281/zenodo.34975
Satoshi Takahama and Giulia Ruggeri

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Short summary
We formalize a method for classifying carbon atoms in organic aerosols according to their functionalization. This conceptual approach allows estimation of carbon mass from functional group measurements, which previously required a series of assumptions that varied widely. We demonstrate how the proposed strategy can lead to better comparisons among functional group measurements, chemically explicit model simulations, and other measurements.
We formalize a method for classifying carbon atoms in organic aerosols according to their...
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