Role of Hydroperoxyl Radicals in Heterogeneous Oxidation of Oxygenated Organic Aerosols

Heterogeneous oxidative aging of organic aerosols (OA) occurs ubiquitously in the atmosphere, initiated by oxidants, such as the hydroxyl radicals (•OH). Hydroperoxyl radicals (HO2 •) are also an important oxidant in the troposphere, and its gas-phase chemistry has been well studied. However, the ro...

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Bibliographic Details
Published in:Environmental science & technology 2024-03, Vol.58 (10), p.4727-4736
Main Authors: Zhang, Wen, Issa, Kassem, Tang, Tiffany, Zhang, Haofei
Format: Article
Language:English
Subjects:
Aerosols
Aging
Deuterium
Free radicals
Hydrogen-deuterium exchange
Hydroxyl radicals
Instrumentation
Iodides
Ionization
Mass spectrometry
Mass spectroscopy
Occurrence, Fate, and Transport of Contaminants in Indoor Air and Atmosphere
Organic hydroperoxide
Oxidants
Oxidation
Oxidizing agents
Peroxy radicals
Peroxyl radicals
Scientific imaging
Troposphere
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Summary:Heterogeneous oxidative aging of organic aerosols (OA) occurs ubiquitously in the atmosphere, initiated by oxidants, such as the hydroxyl radicals (•OH). Hydroperoxyl radicals (HO2 •) are also an important oxidant in the troposphere, and its gas-phase chemistry has been well studied. However, the role of HO2 • in heterogeneous OA oxidation remains elusive. Here, we carry out •OH-initiated heterogeneous oxidation of several OA model systems under different HO2 • conditions in a flow tube reactor and characterize the molecular oxidation products using a suite of mass spectrometry instrumentation. By using hydrogen–deuterium exchange (HDX) with thermal desorption iodide-adduct chemical ionization mass spectrometry, we provide direct observation of organic hydroperoxide (ROOH) formation from heterogeneous HO2 • and peroxy radicals (RO2 •) reactions for the first time. The ROOH may contribute substantially to the oxidation products, varied with the parent OA chemical structure. Furthermore, by regulating RO2 • reaction pathways, HO2 • also greatly influence the overall composition of the oxidized OA. Last, we suggest that the RO2 • + HO2 • reactions readily occur at the OA particle interface rather than in the particle bulk. These findings provide new mechanistic insights into the heterogeneous OA oxidation chemistry and help fill the critical knowledge gap in understanding atmospheric OA oxidative aging.
ISSN:0013-936X
1520-5851
DOI:10.1021/acs.est.3c09024