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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
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Volume 17, issue 22 | Copyright
Atmos. Chem. Phys., 17, 13491-13508, 2017
https://doi.org/10.5194/acp-17-13491-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 14 Nov 2017

Research article | 14 Nov 2017

Secondary organic aerosol from chlorine-initiated oxidation of isoprene

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, Texas, USA

Abstract. Recent studies have found concentrations of reactive chlorine species to be higher than expected, suggesting that atmospheric chlorine chemistry is more extensive than previously thought. Chlorine radicals can interact with hydroperoxy (HOx) radicals and nitrogen oxides (NOx) to alter the oxidative capacity of the atmosphere. They are known to rapidly oxidize a wide range of volatile organic compounds (VOCs) found in the atmosphere, yet little is known about secondary organic aerosol (SOA) formation from chlorine-initiated photooxidation and its atmospheric implications. Environmental chamber experiments were carried out under low-NOx conditions with isoprene and chlorine as primary VOC and oxidant sources. Upon complete isoprene consumption, observed SOA yields ranged from 7 to 36%, decreasing with extended photooxidation and SOA aging. Formation of particulate organochloride was observed. A high-resolution time-of-flight chemical ionization mass spectrometer was used to determine the molecular composition of gas-phase species using iodide–water and hydronium–water cluster ionization. Multi-generational chemistry was observed, including ions consistent with hydroperoxides, chloroalkyl hydroperoxides, isoprene-derived epoxydiol (IEPOX), and hypochlorous acid (HOCl), evident of secondary OH production and resulting chemistry from Cl-initiated reactions. This is the first reported study of SOA formation from chlorine-initiated oxidation of isoprene. Results suggest that tropospheric chlorine chemistry could contribute significantly to organic aerosol loading.

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We investigated the formation of atmospheric pollutants from chlorine-initiated oxidation of isoprene. Our study is the first to report formation of airborne particles from these reactions. We analyzed the chemical composition of both gas- and particle-phase products and propose methods to better detect particle-phase pollutants. Overall, our study demonstrates that reactions between isoprene and chlorine can have important implications for atmospheric composition and therefore human health.
We investigated the formation of atmospheric pollutants from chlorine-initiated oxidation of...
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