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Volume 16, issue 3
Atmos. Chem. Phys., 16, 1761–1771, 2016
https://doi.org/10.5194/acp-16-1761-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Atmos. Chem. Phys., 16, 1761–1771, 2016
https://doi.org/10.5194/acp-16-1761-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 15 Feb 2016

Research article | 15 Feb 2016

Hydroxyl radicals from secondary organic aerosol decomposition in water

Haijie Tong1, Andrea M. Arangio1, Pascale S. J. Lakey1, Thomas Berkemeier1, Fobang Liu1, Christopher J. Kampf1,2, William H. Brune3, Ulrich Pöschl1, and Manabu Shiraiwa1 Haijie Tong et al.
  • 1Multiphase Chemistry Department, Max Planck Institute for Chemistry, Mainz, Germany
  • 2Institute for Inorganic and Analytical Chemistry, Johannes Gutenberg University Mainz, Mainz, Germany
  • 3Department of Meteorology, Pennsylvania State University, University Park, PA 16802, USA

Abstract. We found that ambient and laboratory-generated secondary organic aerosols (SOA) form substantial amounts of OH radicals upon interaction with liquid water, which can be explained by the decomposition of organic hydroperoxides. The molar OH yield from SOA formed by ozonolysis of terpenes (α-pinene, β-pinene, limonene) is  ∼  0.1 % upon extraction with pure water and increases to  ∼  1.5 % in the presence of Fe2+ ions due to Fenton-like reactions. Upon extraction of SOA samples from OH photooxidation of isoprene, we also detected OH yields of around  ∼  0.1 %, which increases upon addition of Fe2+. Our findings imply that the chemical reactivity and aging of SOA particles is strongly enhanced upon interaction with water and iron. In cloud droplets under dark conditions, SOA decomposition can compete with the classical H2O2 Fenton reaction as the source of OH radicals. Also in the human respiratory tract, the inhalation and deposition of SOA particles may lead to a substantial release of OH radicals, which may contribute to oxidative stress and play an important role in the adverse health effects of atmospheric aerosols.

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We provide experimental evidence that terpene and isoprene SOA form substantial amounts of OH radicals upon interaction with liquid water and iron. Our measurements and model results imply that the chemical reactivity of SOA in the atmosphere, particularly in clouds, can be faster than previously thought. Inhalation and deposition of SOA particles in the human respiratory tract may lead to a substantial release of OH radicals in vivo, causing oxidative stress and adverse aerosol health effects.
We provide experimental evidence that terpene and isoprene SOA form substantial amounts of OH...
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