14 Feb 2023
 | 14 Feb 2023
Status: this preprint is currently under review for the journal AMT.

An Automated Online Field Instrument to Quantify the Oxidative Potential of Aerosol Particles via Ascorbic Acid Oxidation

Battist Utinger, Steven John Campbell, Nicolas Bukowiecki, Alexandre Barth, Benjamin Gfeller, Ray Freshwater, Hans-Rudolf Ruegg, and Markus Kalberer

Abstract. Large-scale epidemiological studies have consistently shown that exposure to ambient particulate matter (PM) is responsible for a variety of adverse health effects. However, the specific physical and chemical properties of particles that are responsible for observed health effects, as well as the underlying mechanisms of particle toxicity upon exposure, remain largely uncertain. Studies have widely suggested that the oxidative potential (OP) of aerosol particles is a key metric to quantify particle toxicity. OP is defined as the ability of aerosol particle components to produce reactive oxidative species (ROS) and deplete antioxidants in vivo. Traditional methods for measuring OP using acellular assays largely rely on analyzing PM collected in filters offline. This is labor intensive and involves a substantial time delay between particle collection and OP analysis. It therefore likely underestimates particle OP, because many reactive chemical components which are contributing to OP are short-lived and therefore degrade prior to offline analysis. Thus, new techniques are required to provide a robust and rapid quantification of particle OP, capturing the chemistry of oxidizing and short-lived highly reactive aerosol components and their concentration dynamics in the atmosphere. To address these measurement shortcomings, we developed a portable online instrument that directly samples particles into an ascorbic acid-based assay under physiologically relevant conditions of pH 6.8 and 37 °C, providing continuous accurate OP measurements with a high time resolution (5 mins). The instrument runs autonomously for up to three days and has a detection limit of about 5 µg/m3 in an urban environment, which allows the characterization of particle OP even in low-pollution areas.

Battist Utinger et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on amt-2023-14', Anonymous Referee #3, 26 Feb 2023
  • RC2: 'Comment on amt-2023-14', Anonymous Referee #1, 03 Mar 2023
  • RC3: 'Comment on amt-2023-14', Anonymous Referee #2, 06 Mar 2023

Battist Utinger et al.

Battist Utinger et al.


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Short summary
Exposure to atmospheric aerosols can lead to adverse health effect but particle components responsible for this are unknown. Redox-active compounds, some with very short lifetimes, are considered to be a toxic class of compounds in particles. We developed the first online field instrument to quantify short-lived and stable redox-active compounds with a physiological assay based on ascorbic acid and a high time resolution and detection limits to allow measurements also at unpolluted locations.