Development, characterization and first deployment of an improved online reactive oxygen species analyzer

Abstract

Abstract. Inhalation of atmospheric particles is linked to human diseases. Reactive oxygen species (ROS) present in these atmospheric aerosols may play an important role. However, the ROS content in aerosols and their formation pathways are still largely unknown. Here, we have developed an online and offline ROS analyzer using a 2 ,7 -dichlorofluorescin (DCFH) based assay. The ROS analyzer was calibrated with H 2 O 2 and its sensitivity was characterized using a suite of model organic compounds. The instrument detection limit determined as 3 times the noise is 1.3 nmol L −1 for offline analysis and 2 nmol m −3 of sampled air when the instrument is operated online at a fluorescence response time of approximately 8 min, while the offline method detection limit is 18 nmol L −1 . Potential interferences from gas-phase O 3 and NO 2 as well as matrix effects of particulate SO 2− 4 and NO − 3 were tested, but not observed. Fe 3+ had no influence on the ROS signal, while soluble Fe 2+ reduced it if present at high concentrations in the extracts. Both online and offline methods were applied to identify the ROS content of different aerosol types, i.e., ambient aerosols as well as fresh and aged aerosols from wood combustion emissions. The stability of the ROS was assessed by comparing the ROS concentration measured by the same instrumentation online in situ with offline measurements. We also analyzed the evolution of ROS in specific samples by conducting the analysis after storage times of up to 4 months. The ROS were observed to decay with increasing storage duration. From their decay behavior, ROS in secondary organic aerosol (SOA) can be separated into short-and long-lived fractions. The half-life of the shortlived fraction was 1.7 ± 0.4 h, while the half-life of the longlived fraction could not be determined with our uncertainties. All these measurements showed consistently that on average 60 ± 20 % of the ROS were very reactive and disappeared during the filter storage time. This demonstrates the importance of a fast online measurement of ROS.

Predominance of secondary organic aerosol to particle-bound reactive oxygen species activity in fine ambient aerosol

“…Thus, despite the widespread dominance of biogenic SOA, especially during summer, SOA formed from anthropogenic precursors might still dominate the PB-ROS burden in the atmosphere. Previously we have shown that the degree of oxygenation and the OA loading do influence the PB-ROS content of aerosols in a specific source (biomass burning) (Zhou et al, 2018b).…”

“…For the secondary wood burning emissions, only the experiments conducted with one of the conventional single-stage combustion logwood stoves and aged in the PSI-MSC are presented here, as it is more representative for the genuine atmospheric ag-ing (with an OH exposure of (2.6-4.8) ×10 7 molec cm −3 h), compared to the emissions from the other burning devices that were aged in the potential aerosol mass (PAM) chamber (with an OH exposure of (1.1-2.0) ×10 8 molec cm −3 h). More details of the experimental method as well as the evolution of PB-ROS formation during the aging can be found in our previous publication (Zhou et al, 2018b).…”

Seasonal Variations and Chemical Predictors of Oxidative Potential (OP) of Particulate Matter (PM), for Seven Urban French Sites

“…The association with NO 3 -, is much more surprising. Given that ammonium nitrate and ammonium sulphate do not exhibit any sensitivity towards both AA and DTT assays [28,74], this relation could be due to the redox organic pollutants (nitro-PAHs for instance) which can probably secondary be formed at the same time as NO 3 - [44].…”

Are reactive oxygen species (ROS) a suitable metric to predict toxicity of carbonaceous aerosol particles?

“…Most ROS analysis techniques mentioned above use offline filter-based methods, where aerosols are analyzed hours (h) or days after collection and therefore likely severely underestimate the true particle-bound, exogenous ROS concentrations because the reactive and short-lived components of ROS such as radicals or some peroxides decay before analysis Krapf et al, 2016;Zhou et al, 2018a;Bates et al, 2019). This makes it difficult to gauge their impact on human health, especially to identify which particle sources contribute to ROS and what atmospheric conditions affect ROS formation in a real-world urban environment.…”