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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
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Volume 18, issue 21 | Copyright
Atmos. Chem. Phys., 18, 15535-15553, 2018
https://doi.org/10.5194/acp-18-15535-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 30 Oct 2018

Research article | 30 Oct 2018

Chlorine-initiated oxidation of n-alkanes under high-NOx conditions: insights into secondary organic aerosol composition and volatility using a FIGAERO–CIMS

Dongyu S. Wang and Lea Hildebrandt Ruiz Dongyu S. Wang and Lea Hildebrandt Ruiz
  • McKetta Department of Chemical Engineering, The University of Texas at Austin, Austin, TX 78712, USA

Abstract. Chlorine-initiated oxidation of n-alkanes (C8−12) under high-nitrogen oxide conditions was investigated. Observed secondary organic aerosol yields (0.16 to 1.65) are higher than those for OH-initiated oxidation of C8−12 alkanes (0.04 to 0.35). A high-resolution time-of-flight chemical ionization mass spectrometer coupled to a Filter Inlet for Gases and AEROsols (FIGAERO–CIMS) was used to characterize the gas- and particle-phase molecular composition. Chlorinated organics were observed, which likely originated from chlorine addition to the double bond present on the heterogeneously produced dihydrofurans. A two-dimensional thermogram representation was developed to visualize the composition and relative volatility of organic aerosol components using unit-mass resolution data. Evidence of oligomer formation and thermal decomposition was observed. Aerosol yield and oligomer formation were suppressed under humid conditions (35% to 67% RH) relative to dry conditions (under 5% RH). The temperature at peak desorption signal, Tmax, a proxy for aerosol volatility, was shown to change with aerosol filter loading, which should be constrained when evaluating aerosol volatilities using the FIGAERO–CIMS. Results suggest that long-chain anthropogenic alkanes could contribute significantly to ambient aerosol loading over their atmospheric lifetime.

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We investigated the formation of atmospheric pollutants from chlorine-initiated oxidation of alkanes, which may occur in polluted environments. We report for the first the formation of alkane-derived chlorinated organics. We also propose a new approach to representing the chemical composition, volatility, and thermal desorption behavior of organic aerosols. Overall, our study suggests that the oxidation of alkanes can be an important source of organic aerosols in polluted environments.
We investigated the formation of atmospheric pollutants from chlorine-initiated oxidation of...
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