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Updated: Nov 12, 2025

Production and Measurement of Organic Particulate Matter in a Flow Tube Reactor
Published on: December 15, 2018
Photolytic radical persistence due to anoxia in viscous aerosol particles
Peter A Alpert1, Jing Dou2, Pablo Corral Arroyo3,4
1Laboratory of Environmental Chemistry, Paul Scherrer Institute, Villigen, Switzerland. peter.alpert@psi.ch.
Abstract:
In viscous, organic-rich aerosol particles containing iron, sunlight may induce anoxic conditions that stabilize reactive oxygen species (ROS) and carbon-centered radicals (CCRs). In laboratory experiments, we show mass loss, iron oxidation and radical formation and release from photoactive organic particles containing iron. Our results reveal a range of temperature and relative humidity, including ambient conditions, that control ROS build up and CCR persistence in photochemically active, viscous organic particles. We find that radicals can attain high concentrations, altering aerosol chemistry and exacerbating health hazards of aerosol exposure. Our physicochemical kinetic model confirmed these results, implying that oxygen does not penetrate such particles due to the combined effects of fast reaction and slow diffusion near the particle surface, allowing photochemically-produced radicals to be effectively trapped in an anoxic organic matrix.
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