Gas/particle partitioning of total alkyl nitrates observed with TD-LIF in Bakersfield

Authors

  • A. W. Rollins,

    1. Department of Chemistry, University of California, Berkeley, California, USA
    2. Now at NOAA Earth System Research Laboratory, Chemical Sciences Division and CIRES, Boulder, Colorado, USA
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  • S. Pusede,

    1. Department of Chemistry, University of California, Berkeley, California, USA
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  • P. Wooldridge,

    1. Department of Chemistry, University of California, Berkeley, California, USA
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  • K.-E. Min,

    1. Now at NOAA Earth System Research Laboratory, Chemical Sciences Division and CIRES, Boulder, Colorado, USA
    2. Department of Earth and Planetary Sciences, University of California, Berkeley, California, USA
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  • D. R. Gentner,

    1. Department of Civil and Environmental Engineering, University of California, Berkeley, California, USA
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  • A. H. Goldstein,

    1. Department of Civil and Environmental Engineering, University of California, Berkeley, California, USA
    2. Department of Environmental Science Policy, and Management, University of California, Berkeley, California, USA
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  • S. Liu,

    1. Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California, USA
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  • D. A. Day,

    1. Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California, USA
    2. Now at CIRES, University of Colorado Boulder, Boulder, Colorado, USA
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  • L. M. Russell,

    1. Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California, USA
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  • C. L. Rubitschun,

    1. Department of Environmental Sciences and Engineering, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
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  • J. D. Surratt,

    1. Department of Environmental Sciences and Engineering, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
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  • R. C. Cohen

    Corresponding author
    1. Department of Chemistry, University of California, Berkeley, California, USA
    2. Department of Earth and Planetary Sciences, University of California, Berkeley, California, USA
    • Corresponding author: R. C. Cohen, Department of Chemistry, University of California, Berkeley, CA 94720 USA. (rccohen@berkeley.edu)

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Abstract

[1] Limitations in the chemical characterization of tropospheric organic aerosol (OA) continue to impede attempts to fully understand its chemical sources and sinks. To assess the role of organic nitrates in OA, we used a new thermal dissociation-laser induced fluorescence-based (TD-LIF) technique to obtain a high-time-resolution record of total aerosol organic nitrates (hereafter ΣANsaer) at the Bakersfield, CA supersite during the 2010 CalNex campaign. The TD-LIF measurements compare well with Fourier transform infrared measurements from collocated filter samples. These measurements show that ΣANs are a ubiquitous component of the OA with the –ONO2 subunit comprising on average 4.8% of the OA mass. Scaling this fraction by an estimate of the organic backbone mass yields an estimate that 17–23% of OA molecules contain nitrate functional groups. Measurements of both total ΣAN (gas + aerosol) and ΣANaer show that on average 21% of ΣANs are in the condensed phase, suggesting atmospheric organic nitrates have similar volatilities to analogous non-nitrate oxidized organic compounds. The fraction of ΣAN that is in the condensed phase increases with total OA concentration, providing direct evidence from the atmosphere that absorptive partitioning into OA has some control over the ΣAN phase partitioning. The specific molecular identity of the ΣAN is incompletely understood. Both biogenic hydrocarbons and long chain alkanes are calculated to be significant sources of low volatility nitrates in Bakersfield, and ultra performance liquid chromatography coupled to an electrospray ionization high-resolution quadrupole time-of-flight mass spectrometer measurements confirm the existence of particulate nitrooxy organosulfates derived from gas-phase oxidation of both isoprene and monoterpenes.

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