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Volume 16, issue 20
Atmos. Chem. Phys., 16, 13105–13119, 2016
https://doi.org/10.5194/acp-16-13105-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Atmos. Chem. Phys., 16, 13105–13119, 2016
https://doi.org/10.5194/acp-16-13105-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 26 Oct 2016

Research article | 26 Oct 2016

Quantification of environmentally persistent free radicals and reactive oxygen species in atmospheric aerosol particles

Andrea M. Arangio1, Haijie Tong1, Joanna Socorro1, Ulrich Pöschl1, and Manabu Shiraiwa1,2 Andrea M. Arangio et al.
  • 1Multiphase Chemistry Department, Max Planck Institute for Chemistry, Mainz, Germany
  • 2Department of Chemistry, University of California, Irvine, CA, USA

Abstract. Fine particulate matter plays a central role in the adverse health effects of air pollution. Inhalation and deposition of aerosol particles in the respiratory tract can lead to the release of reactive oxygen species (ROS), which may cause oxidative stress. In this study, we have detected and quantified a wide range of particle-associated radicals using electron paramagnetic resonance (EPR) spectroscopy. Ambient particle samples were collected using a cascade impactor at a semi-urban site in central Europe, Mainz, Germany, in May–June 2015. Concentrations of environmentally persistent free radicals (EPFR), most likely semiquinone radicals, were found to be in the range of (1–7)  × 1011 spins µg−1 for particles in the accumulation mode, whereas coarse particles with a diameter larger than 1 µm did not contain substantial amounts of EPFR. Using a spin trapping technique followed by deconvolution of EPR spectra, we have also characterized and quantified ROS, including OH, superoxide (O2) and carbon- and oxygen-centered organic radicals, which were formed upon extraction of the particle samples in water. Total ROS amounts of (0.1–3)  × 1011 spins µg−1 were released by submicron particle samples and the relative contributions of OH, O2, C-centered and O-centered organic radicals were ∼  11–31, ∼  2–8, ∼  41–72 and ∼  0–25 %, respectively, depending on particle sizes. OH was the dominant species for coarse particles. Based on comparisons of the EPR spectra of ambient particulate matter with those of mixtures of organic hydroperoxides, quinones and iron ions followed by chemical analysis using liquid chromatography mass spectrometry (LC-MS), we suggest that the particle-associated ROS were formed by decomposition of organic hydroperoxides interacting with transition metal ions and quinones contained in atmospheric humic-like substances (HULIS).

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We have quantified environmentally persistent free radicals and reactive oxygen species (ROS) in size-segregated atmospheric aerosol particles. We suggest that ROS were formed by decomposition of secondary organic aerosols interacting with transition metal ions and quinones contained in humic-like substances. The results have significant implications for aqueous-phase and cloud processing of organic aerosols as well as adverse health effects upon respiratory deposition of aerosol particles.
We have quantified environmentally persistent free radicals and reactive oxygen species (ROS) in...
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