Diurnal cycle of fossil and nonfossil carbon using radiocarbon analyses during CalNex

Authors

  • Peter Zotter,

    1. Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, Villigen, Switzerland
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  • Imad El-Haddad,

    1. Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, Villigen, Switzerland
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  • Yanlin Zhang,

    1. Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, Villigen, Switzerland
    2. Department of Chemistry and Biochemistry, University of Bern, Bern, Switzerland
    3. Oeschger Centre for Climate Change Research, University of Bern, Bern, Switzerland
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  • Patrick L. Hayes,

    1. Department of Chemistry and CIRES, University of Colorado, Boulder, Colorado, USA
    2. Now at Département de Chimie, Université de Montréal, Montréal, Quebec, Canada
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  • Xiaolu Zhang,

    1. School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
    2. Now at Department of Civil and Environmental Engineering, University of California Davis, Davis, California, USA
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  • Ying-Hsuan Lin,

    1. Department of Environmental Sciences and Engineering, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
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  • Lukas Wacker,

    1. Laboratory of Ion Beam Physics, ETH Hönggerberg, Zürich, Switzerland
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  • Jürgen Schnelle-Kreis,

    1. Joint Mass Spectrometry Centre, Cooperation Group Comprehensive Molecular Analytics, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), Neuherberg, Germany
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  • Gülcin Abbaszade,

    1. Joint Mass Spectrometry Centre, Cooperation Group Comprehensive Molecular Analytics, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), Neuherberg, Germany
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  • Ralf Zimmermann,

    1. Joint Mass Spectrometry Centre, Cooperation Group Comprehensive Molecular Analytics, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), Neuherberg, Germany
    2. Joint Mass Spectrometry Centre, Institute of Chemistry, University of Rostock, Rostock, Germany
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  • Jason D. Surratt,

    1. Department of Environmental Sciences and Engineering, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
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  • Rodney Weber,

    1. School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
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  • José L. Jimenez,

    1. Department of Chemistry and CIRES, University of Colorado, Boulder, Colorado, USA
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  • Sönke Szidat,

    1. Department of Chemistry and Biochemistry, University of Bern, Bern, Switzerland
    2. Oeschger Centre for Climate Change Research, University of Bern, Bern, Switzerland
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  • Urs Baltensperger,

    1. Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, Villigen, Switzerland
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  • André S. H. Prévôt

    Corresponding author
    1. Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, Villigen, Switzerland
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Abstract

Radiocarbon (14C) analysis is a unique tool to distinguish fossil/nonfossil sources of carbonaceous aerosols. We present 14C measurements of organic carbon (OC) and total carbon (TC) on highly time resolved filters (3–4 h, typically 12 h or longer have been reported) from 7 days collected during California Research at the Nexus of Air Quality and Climate Change (CalNex) 2010 in Pasadena. Average nonfossil contributions of 58% ± 15% and 51% ± 15% were found for OC and TC, respectively. Results indicate that nonfossil carbon is a major constituent of the background aerosol, evidenced by its nearly constant concentration (2–3 μgC m−3). Cooking is estimated to contribute at least 25% to nonfossil OC, underlining the importance of urban nonfossil OC sources. In contrast, fossil OC concentrations have prominent and consistent diurnal profiles, with significant afternoon enhancements (~3 μgC m−3), following the arrival of the western Los Angeles (LA) basin plume with the sea breeze. A corresponding increase in semivolatile oxygenated OC and organic vehicular emission markers and their photochemical reaction products occurs. This suggests that the increasing OC is mostly from fresh anthropogenic secondary OC (SOC) from mainly fossil precursors formed in the western LA basin plume. We note that in several European cities where the diesel passenger car fraction is higher, SOC is 20% less fossil, despite 2–3 times higher elemental carbon concentrations, suggesting that SOC formation from gasoline emissions most likely dominates over diesel in the LA basin. This would have significant implications for our understanding of the on-road vehicle contribution to ambient aerosols and merits further study.

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