Reactive species formed upon interaction of water with fine particulate matter from remote forest and polluted urban air
- 1Multiphase Chemistry Department, Max Planck Institute for Chemistry, 55128 Mainz, Germany
- 2School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
- 3École polytechnique fédérale de Lausanne, Lausanne 1015, Switzerland
- 4Institute of Inorganic and Analytical Chemistry, Johannes Gutenberg University, 55128 Mainz, Germany
- 5State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, 100029, China
- 6College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
- 7Institute of Surface-Earth System Science, Tianjin University, Tianjin, 300072, China
- 8School of Space and Environment, Beihang University, Beijing, 100191, China
- 9Institute for Atmospheric and Earth System Research/Physics, Faculty of Science, University of Helsinki, P.O. Box 64, FIN-00014, Helsinki, Finland
- 10Hyytiälä Forestry Field Station, Hyytiäläntie 124, FI-35500 Korkeakoski, Finland
- 11College of Environmental Sciences and Engineering, Peking University, Beijing, 100871, China
- 12Department of Meteorology, Pennsylvania State University, University Park, Pennsylvania 16802, United States
- 13Department of Chemistry, University of California, Irvine, California 92697-2025, USA
Abstract. Interaction of water with fine particulate matter leads to the formation of reactive species (RS) that may influence the aging, properties, and health effects of atmospheric aerosols. In this study, we explore the RS yields of fine PM from remote forest (Hyytiälä, Finland) and polluted urban air (Mainz, Germany and Beijing, China) and relate these yields to different chemical constituents and reaction mechanisms. Ultrahigh-resolution mass spectrometry was used to characterize organic aerosol composition, electron paramagnetic resonance (EPR) spectroscopy with a spin-trapping technique was used to determine the concentrations •OH, O2•−, and carbon- or oxygen-centered organic radicals, and a fluorometric assay was used to quantify H2O2 concentration. The mass-specific yields of radicals were lower for sampling sites with higher concentration of ambient PM2.5 (particles with a diameter < 2.5 µm), whereas the H2O2 yields exhibited no clear trend. The abundances of water-soluble transition metals and aromatics in ambient PM2.5 were positively correlated with the relative fraction of •OH to the totally detected radicals, but negatively correlated with the relative fraction of carbon-centered radicals. Moreover, we found that the relative fractions of different types of radicals formed by ambient PM2.5 were comparable to the surrogate mixtures comprising transition metals, organic hydroperoxide, H2O2, and humic or fulvic acids. Therein humic and fulvic acids exhibited strong radical scavenging effect to substantially decrease the radical yield of mixtures comprising cumene hydroperoxide and Fe2+. The interplay of transition metals (e.g., iron), highly oxidized compounds (e.g., organic hydroperoxides), and complexing agents (e.g., humic or fulvic acids), leads to non-linear concentration dependencies of production and yields of different types of RS. Our findings show that how the composition of PM2.5 influences the amount and nature of RS produced upon interaction with water, which may explain differences in the chemical reactivity and health effects of particulate matter in clean and polluted air.
Haijie Tong et al.
Haijie Tong et al.
Haijie Tong et al.
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