An interlaboratory comparison to quantify oxidative potential measurement in aerosol particles: challenges and recommendations for harmonisation

Atmospheric measurement techniques · 2025-01-13 · 14 citations

Abstract. This paper presents the findings from a collaborative interlaboratory comparison exercise designed to assess oxidative potential (OP) measurements conducted by 20 laboratories worldwide. This study represents an innovative effort as the first exercise specifically aimed at harmonising this type of OP assay, setting a new benchmark in the field. Over the last decade, there has been a noticeable increase in OP studies, with numerous research groups investigating the effects of exposure to air pollution particles through the evaluation of OP levels. However, the absence of standardised methods for OP measurements has resulted in variability in results across different groups, rendering meaningful comparisons challenging. To address this issue, this study engages in an international effort to compare OP measurements using a simplified method (with a dithiothreitol (DTT) assay). Here, we quantify the OP in liquid samples to focus on the protocol measurement itself, while future international OP interlaboratory comparisons (ILCs) should aim to assess the whole chain process, including the sample extraction. We analyse the similarities and discrepancies observed in the results, identifying the critical parameters (such as the instrument used, the use of a simplified protocol, the delivery and analysis time) that could influence OP measurements and provide recommendations for future studies and interlaboratory comparisons even if other crucial aspects, such as sampling PM methods, sample storage, extraction methods and conditions, and the evaluation of other OP assays, still need to be standardised. This collaborative approach enhances the robustness of the OP DTT assay and paves the way for future studies to build on a unified framework. This pioneering work concludes that interlaboratory comparisons provide essential insights into the OP metric and are crucial to move toward the harmonisation of OP measurements.

Inhalation of electrophilic and redox active electronic cigarette aerosol increases oxidative potential in the lung in an acute manner

Free Radical Biology and Medicine · 2025-08-28 · 1 citations

Towards Realizing Schawlow-Townes Limited Dual-comb Spectroscopy with an Analog Feed-Forward Approach

2025-01-01

Near Schawlow-Townes noise-limited dual-comb spectroscopy can be realized through analog feed-forward stabilization of carrier envelope phase. We present such a system, for applications in precision atmospheric sensing.

Cloud Water Chemistry and Aerosol Processing: Assessing the Hydroxyl Radical Burst in Newly Formed Cloud Droplets (Field Campaign Report)

2024-05-01

Aerosol particles are tiny liquid or solid particles in the atmosphere, ranging in size from a few nanometers to several micrometers in diameter. Aerosol-cloud interactions are the most uncertain aspect of the climate system, and models routinely underpredict aerosol particle formation. Clouds are well known to alter aerosol size, chemical composition, and radiative properties, but the processes are poorly characterized. Organics and sulfates are the most abundant materials in particles, and for each of these there are significant gaps in the understanding of the role of clouds in their formation and/or aging. Many of the cloud processes are driven by aqueous chemistry that depends on hydroxyl (OH) radicals, the subject of this project.

Coastal Cloud Chemistry during EPCAPE Field Campaign Report

2024-12-01

For this campaign, Principal Investigator Markus Petters deployed a suite of instruments inside Lynn Russell’s container that was sited at Mt. Soledad during the Eastern Pacific Cloud Aerosol Precipitation Experiment (EPCAPE) campaign. Funding for this activity was provided by National Science Foundation Award 2410536. The instrument rack (Figure 1) included a differential mobility analyzer, a condensation particle counter, a portable optical particle spectrometer, and a continuous flow diffusion cloud condensation nuclei counter (CCN). The instruments sampled from a counterflow virtual impactor (CVI) inlet and an isokinetic inlet. The measurements provided aerosol size distribution, size-resolved CCN activity, and denuded versus undenuded CCN activity of aerosols and cloud drop residuals.

Characterizing Hydroxyl Radical Formation from the Light-Driven Fe(II)–Peracetic Acid Reaction, a Key Process for Aerosol-Cloud Chemistry

Environmental Science & Technology · 2024-04-15 · 12 citations

The reaction of peracetic acid (PAA) and Fe(II) has recently gained attention due to its utility in wastewater treatment and its role in cloud chemistry. Aerosol-cloud interactions, partly mediated by aqueous hydroxyl radical (OH) chemistry, represent one of the largest uncertainties in the climate system. Ambiguities remain regarding the sources of OH in the cloud droplets. Our research group recently proposed that the dark and light-driven reaction of Fe(II) with peracids may be a key contributor to OH formation, producing a large burst of OH when aerosol particles take up water as they grow to become cloud droplets, in which reactants are consumed within 2 min. In this work, we quantify the OH production from the reaction of Fe(II) and PAA across a range of physical and chemical conditions. We show a strong dependence of OH formation on ultraviolet (UV) wavelength, with maximum OH formation at λ = 304 ± 5 nm, and demonstrate that the OH burst phenomenon is unique to Fe(II) and peracids. Using kinetics modeling and density functional theory calculations, we suggest the reaction proceeds through the formation of an [Fe(II)–(PAA)2(H2O)2] complex, followed by the formation of a Fe(IV) complex, which can also be photoactivated to produce additional OH. Determining the characteristics of OH production from this reaction advances our knowledge of the sources of OH in cloudwater and provides a framework to optimize this reaction for OH output for wastewater treatment purposes.

Association of ischemic placental disease in a Southern California Birth Cohort and PM_2.5 chemical species and oxidative potential markers

Environmental Research Health · 2024-05-24 · 1 citations

Abstract Road traffic is a significant source of particulate matter pollution, whose exposure is a significant risk factor in pregnancy-related health outcomes. The exact mechanisms behind the relationship between traffic-related air pollution (TRAP) exposure and adverse pregnancy outcomes remain unclear. We aim to assess the relationship between exposure to brake and tire wear-associated metals and oxidative potential and ischemic placental disease (IPD). Data were assembled from a final population of 178 women who sought specialized prenatal care at UCLA between 2016 and 2019 in Los Angeles, CA. Modeled first trimester exposures to chemical constituents and oxidative stress potential of PM 2.5 , black carbon, and PM 2.5 mass concentration. Speciated measurements included tracers of brake wear (barium), tire wear (zinc), and oxidative potential markers based on metal concentrations (KM-SUB-ELF ROS) or laboratory assays (DTT loss, OH radical formation). Exposures were modeled by integrating data from filter samples, a low-cost PM 2.5 sensor network, and land-use data. We used logistic regression to estimate the associations between air pollution exposures and IPD, adjusting for covariates assessed through medical records and interviews. Scaled to the interquartile range, odds ratios (95% CI) were as follows: barium OR: 1.7 (1.1, 2.7), zinc OR: 1.4 (.86, 2.4), and oxidative potential markers, both modeled as well as measured through DTT loss and OH formation assays (ORs ranging from 1.1-2.0). Point estimates of effect sizes for PM 2.5 and black carbon were lower than most measurements (ORs: 1.3-1.4). mass and black carbon. Our findings suggest two key points: (i) metals associated with brake and tire wear, currently unregulated, may play a role in the relationship between TRAP and adverse pregnancy outcomes, and (ii) reducing tailpipe emissions may not be sufficient to protect pregnant women from TRAP.

Supplementary material to "An interlaboratory comparison to quantify oxidative potential measurement in aerosol particles: challenges and recommendations for harmonisation"

2024-07-24