Organic Peroxides in Aerosol: Key Reactive Intermediates for Multiphase Processes in the Atmosphere

Abstract

Organic peroxides (POs) are organic molecules with one or more peroxide (−O−O−) functional groups. POs are commonly regarded as chemically labile termination products from gas-phase radical chemistry and therefore serve as temporary reservoirs for oxidative radicals (HO x and RO x ) in the atmosphere. Owing to their ubiquity, active gasparticle partitioning behavior, and reactivity, POs are key reactive intermediates in atmospheric multiphase processes determining the life cycle (formation, growth, and aging), climate, and health impacts of aerosol. However, there remain substantial gaps in the origin, molecular diversity, and fate of POs due to their complex nature and dynamic behavior. Here, we summarize the current understanding on atmospheric POs, with a focus on their identification and quantification, state-of-the-art analytical developments, molecular-level formation mechanisms, multiphase chemical transformation pathways, as well as environmental and health impacts. We find that interactions with SO 2 and transition metal ions are generally the fast PO transformation pathways in atmospheric liquid water, with lifetimes estimated to be minutes to hours, while hydrolysis is particularly important for α-substituted hydroperoxides. Meanwhile, photolysis and thermolysis are likely minor sinks for POs. These multiphase PO transformation pathways are distinctly different from their gas-phase fates, such as photolysis and reaction with OH radicals, which highlights the need to understand the multiphase partitioning of POs. By summarizing the current advances and remaining challenges for the investigation of POs, we propose future research priorities regarding their origin, fate, and impacts in the atmosphere.

Mechanism of Fenton Oxidation of Levoglucosan in Water

“…The formed geminal diols and α-HHs would be in equilibrium with their corresponding carbonyls and H 2 O/H 2 O 2 in atmospheric condensed phases. By possessing a hydroperoxide (−OOH) moiety, α-HHs may be involved in reactions with other species of atmospheric condensed phases . In contrast with previous experiments examining the photochemical oxidation of Levo, we could not find evidence for the formation of Levo+≥4O products and smaller mass carboxylic acids, implying that Fenton oxidation under the present conditions was rather mild.…”

The fate of organic peroxides indoors: quantifying humidity-dependent uptake on naturally soiled indoor window glass

“…ROOHs have also been shown to hydrolyze in aqueous aerosols and form carbonyl compounds and H 2 O 2 ; 93 this is enabled by the presence of water 116 and catalyzed by acids. 96 For example, ROOHs generated from the ozonolysis of terpenes have been shown to readily decompose into aldehydes and H 2 O 2 on acidified aerosols, 96 including when acidified with small organic acids, which are ubiquitous species indoors.…”

“…In this work, 1,2-ISOPOOH was used as a model indoor ROOH to represent the dynamics of this class of indoor pollutants with real indoor surfaces. Like outdoors, 56,93,141–144 there is likely a plethora of ROOH compounds present indoors, due particularly to oxidation of indoor terpenes ( e.g. , from air fresheners, cleaning products, wood materials) 145,146 but also from polycyclic aromatic hydrocarbons ( e.g.…”

“…, from pest repellant, deodorant, cooking) 147,148 and a variety of other potential sources. 93 Indoor surfaces should be a key site for the generation and consumption of ROOHs derived from heterogeneous chemistry of O 3 (ref. 89) and OH 149 with sorbed organics and consumption of ROOHs derived from gas-phase oxidation.…”

An Automated Online Field Instrument to Quantify the Oxidative Potential of Aerosol Particles via Ascorbic Acid Oxidation

“…Overall, this will lead to a significant underestimation of the OP signal when using traditional offline analysis, especially if filter samples are not analyzed immediately. In a recent review Wang et al, 2023(Wang et al, 2023 reported lifetimes for peroxide from seconds to days. Therefore, the decomposition of these peroxides may contribute to reduced OP on filter samples, as they may well degrade prior to analysis.…”