[pam-users] Zhou et al., ES&T, 2024; Cooper et al., ACS ES&T Air, 2024

[pam-users]

Zhou, Liyuan, Liang, Zhancong, Qin, Yiming, Chan, Chak K.: Evaporation-Induced Transformations in Volatile Chemical Product-Derived Secondary Organic Aerosols: Browning Effects and Alterations in Oxidative Reactivity, Environ. Sci. Technol., 11105-11117, 58, 25,  https://doi.org/10.1021/acs.est.4c02316, 2024.

Abstract. Volatile chemical products (VCPs) are increasingly recognized as significant sources of volatile organic compounds (VOCs) in urban atmospheres, potentially serving as key precursors for secondary organic aerosol (SOA) formation. This study investigates the formation and physicochemical transformations of VCP-derived SOA, produced through ozonolysis of VOCs evaporated from a representative room deodorant air freshener, focusing on the effects of aerosol evaporation on its molecular composition, light absorption properties, and reactive oxygen species (ROS) generation. Following aerosol evaporation, solutes become concentrated, accelerating reactions within the aerosol matrix that lead to a 42% reduction in peroxide content and noticeable browning of the SOA. This process occurs most effectively at moderate relative humidity (∼40%), reaching a maximum solute concentration before aerosol solidification. Molecular characterization reveals that evaporating VCP-derived SOA produces highly conjugated nitrogen-containing products from interactions between existing or transformed carbonyl compounds and reduced nitrogen species, likely acting as chromophores responsible for the observed brownish coloration. Additionally, the reactivity of VCP-derived SOA was elucidated through heterogeneous oxidation of sulfur dioxide (SO2), which revealed enhanced photosensitized sulfate production upon drying. Direct measurements of ROS, including singlet oxygen (1O2), superoxide (O2•–), and hydroxyl radicals (•OH), showed higher abundances in dried versus undried SOA samples under light exposure. Our findings underscore that drying significantly alters the physicochemical properties of VCP-derived SOA, impacting their roles in atmospheric chemistry and radiative balance.

PAM Wiki - Publications Using Other Oxidation Flow Reactors (google.com)<https://sites.google.com/site/pamwiki/publications-using-other-oxidation-flow-reactors>

Cooper, Adam, Shenkiryk, Alexis, Chin, Henry, Morris, Maya, Mehndiratta, Lincoln, Roundtree, Kanuri, Tafuri, Tessa, and  Slade, Jonathan H.:  Photoinitiated Degradation Kinetics of the Organic UV Filter Oxybenzone in Solutions and Aerosols: Impacts of Salt, Photosensitizers, and the Medium: ACS ES&T Air, Articles ASAP, https://doi.org/10.1021/acsestair.4c00149, 2024.

Abstract. Organic UV filters like oxybenzone (BP3) in sunscreens are seawater pollutants suspected to transfer to the atmosphere via sea spray aerosol (SSA). This study examines the photoinitiated degradation of BP3 in artificial and real seawater compared to SSA mimics containing NaCl and 4-benzoylbenzoic acid (4-BBA). We investigated pure, binary, and ternary mixtures of BP3, NaCl, and 4-BBA using solar-simulated light to isolate the effects of salt and photosensitization on BP3 degradation. Results showed significantly faster degradation in the aerosol phase (Jeff,env ≈ 10–3–10–2 s–1 or t1/2 < 10 min) compared to bulk solutions (Jeff,env ≈ 10–6 s–1 or t1/2 > 1 day). The photosensitizer enhanced BP3 photodegradation in both phases more than when mixed with salt or all three components in solutions. BP3 photodegradation was most enhanced by salt in the aerosol phase. High-resolution molecular analysis via Orbitrap LC-MS/MS revealed more acutely toxic compounds (benzophenone, benzoic acid, and benzaldehyde) in irradiated aerosols than in solution, supported by electronic structure and toxicity modeling. These findings highlight that seawater may serve as a reservoir for BP3 and other organic UV filters and that upon transfer into SSA, BP3 rapidly transforms, increasing aerosol toxicity.

PAM Wiki - Publications Using the PAM Oxidation Flow Reactor (google.com)<https://sites.google.com/site/pamwiki/publications-using-the-pam-oxidation-flow-reactor?authuser=0>


Andrew Lambe
Principal Scientist
Aerodyne Research, Inc.

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