30 Jan 2023
 | 30 Jan 2023

Measurement Report: Atmospheric aging of combustion-derived particles: impact on stable free radical concentration and its ability to produce reactive oxygen species in aqueous media

Heather L. Runberg and Brian J. Majestic

Abstract. Environmentally persistent free radicals (EPFR) are a pollutant found on fine atmospheric particulate matter (PM2.5), particularly on PM2.5 formed from combustion processes. EPFR are organic radicals that can endure in the environment for days to years. Interest in the toxicity of EPFR has increased significantly in recent years, as it has been shown to have substantial ability to form reactive oxygen species (ROS), but little is known about how its characteristics change as PM2.5 ages in the atmosphere. Here, we exposed newly produced hexane-generated soot to simulated sunlight for 24 hours. Changes to the EPFR characteristics of the particles were measured by electron paramagnetic resonance (EPR) spectroscopy. The soot was then added to water and a second exposure to light was used to measure hydroxyl radical (OH) formation from both photo-aged and dark-aged soot. There were no changes to EPFR characteristics (spin concentration, g-factor, peak width, or lineshape) due to the exposure to simulated sunlight, however the soot’s ability to form OH was greatly reduced by photo-aging. Photo-aged soot resulted in an almost 60 % reduction in OH formation over soot which had been aged in the dark for the same amount of time.

Heather L. Runberg and Brian J. Majestic

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-4', Guorui Liu, 18 Feb 2023
  • RC2: 'Comment on egusphere-2023-4', Xiao-San Luo, 24 Feb 2023

Heather L. Runberg and Brian J. Majestic

Data sets

Data Set for "Atmospheric Aging of Combustion-Derived Particles: Impact on Stable Free Radical Concentration and Its Ability to Produce Reactive Oxygen Species in Aqueous Media" Runberg, Heather and Majestic, Brian

Heather L. Runberg and Brian J. Majestic


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Short summary
Environmentally persistent free radicals (EPFR) are an emerging pollutant found in soot particles. Understanding how these change as they move through the atmosphere is important to human health. Here, soot was generated in the laboratory and exposed to simulated sunlight. The concentrations and characteristics of EPFR in the soot was measured and found to be unchanged. However, it was also found that the ability of soot to form hydroxyl radicals was stronger for fresh soot.