Abstract
Abstract. Reactive oxygen species (ROS) are believed to contribute to the adverse health effects of aerosols. This may happen by inhaled particle-bound (exogenic) ROS (PB-ROS) or by ROS formed within the respiratory tract by certain aerosol components (endogenic ROS). We investigated the chemical composition of aerosols and their exogenic ROS content at the two contrasting locations Beijing (China) and Bern (Switzerland). We apportioned the ambient organic aerosol to different sources and attributed the observed water-soluble PB-ROS to them. The oxygenated organic aerosol (OOA, a proxy for secondary organic aerosol, SOA) explained the highest fraction of the exogenic ROS concentration variance at both locations. We also characterized primary and secondary aerosol emissions generated from different biogenic and anthropogenic sources in smog chamber experiments. The exogenic PB-ROS content in the OOA from these emission sources was comparable to that in the ambient measurements. Our results imply that SOA from gaseous precursors of different anthropogenic emission sources is a crucial source of water-soluble PB-ROS and should be additionally considered in toxicological and epidemiological studies in an adequate way besides primary emissions. The importance of PB-ROS may be connected to the seasonal trends in health effects of PM reported by epidemiological studies, with elevated incidences of adverse effects in warmer seasons, which are accompanied by more-intense atmospheric oxidation processes.
Highlights
Air pollution has been shown to adversely impact human health through cardiovascular and respiratory disorders, which may lead to a reduction in life expectancyPublished by Copernicus Publications on behalf of the European Geosciences Union.J
Source apportionment was performed on the organic Aerosol mass spectrometer (AMS) and Aerosol chemical speciation monitor (ACSM) data using positive matrix factorization (PMF) as implemented by the multilinear engine (ME-2; Paatero, 1997) and controlled via the interface SoFi coded in Igor WaveMetrics (Source Finder; Canonaco et al, 2013)
Within the a value approach, a priori information of one or more sources can be used as an additional input into the model, using the scalar a to regulate the strength of the constraints: fj,solution = fj ± a × fj, (4)
Summary
Air pollution has been shown to adversely impact human health through cardiovascular and respiratory disorders, which may lead to a reduction in life expectancy. The dithiothreitol (DTT) assay is strongly sensitive to redox-active components, i.e., transition metals and quinones, and is considered a good estimator of ROS generation in lung cells (Cho et al, 2005; Verma et al, 2012; Charrier and Anastasio, 2012; Fang et al, 2016; Weber et al, 2018), but it is sensitive to organic peroxides (Wang et al, 2018). Biomass burning and traffic contributed to the OP measured by DTT in most cases, while contributions by secondary PM components like ammonium sulfate or the more oxidized fraction of organic aerosol (OA) were only found in some studies (Verma et al, 2015; Fang et al, 2016; Bates et al, 2015; Weber et al, 2018).
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