Seasonal variations in photooxidant formation and light absorption in aqueous extracts of ambient particles

Atmospheric chemistry and physics, Год журнала: 2024, Номер 24(1), С. 1 - 21

Опубликована: Янв. 2, 2024

Abstract. Fog/cloud drops and aerosol liquid water are important sites for the transformations of atmospheric species, largely through reactions with photoformed oxidants such as hydroxyl radical (⚫OH), singlet molecular oxygen (1O2∗), oxidizing triplet excited states organic matter (3C∗). Despite their importance, few studies have measured these or seasonal variations. To address this gap, we collected ambient PM2.5 from Davis, California, over course a year photooxidant concentrations light absorption in dilute aqueous extracts. Mass coefficients (MACs) normalized by dissolved carbon range 0.4–3.8 m2 per gram C at 300 nm. Concentrations ⚫OH, 1O2∗, 3C∗ extracts (0.2–4.7) × 10−15 M, (0.7–45) 10−13 (0.03–7.9) respectively, biomass burning brown playing major role formation 1O2∗ 3C∗. Extrapolating kinetics our particle to concentrated (ALW) conditions gives an estimated ⚫OH concentration 7 M ranges (0.6–7) 10−12 (0.2–1) respectively. Compared results Kaur et al. (2019), ALW predictions show roughly 10 times higher up 5 3C, that lower factors 20–100. These suggest dominate processing compounds react quickly (e.g., phenols furans, respectively), while is more less reactive organics.

Язык: Английский

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Predicting photooxidant concentrations in aerosol liquid water based on laboratory extracts of ambient particles

Atmospheric chemistry and physics, Год журнала: 2023, Номер 23(15), С. 8805 - 8821

Опубликована: Авг. 9, 2023

Abstract. Aerosol liquid water (ALW) is a unique reaction medium, but its chemistry poorly understood. For example, little known of photooxidant concentrations – including hydroxyl radicals (⚫OH), singlet molecular oxygen (1O2*), and oxidizing triplet excited states organic matter (3C*) even though they likely drive much ALW chemistry. Due to the very limited content particles, it difficult quantify oxidant in directly. To predict these values, we measured illuminated aqueous particle extracts as function dilution used resulting kinetics extrapolate conditions. We prepared series from two sets particles collected Davis, California: one winter (WIN) summer (SUM). Both periods are influenced by biomass burning, with dissolved carbon (DOC) ranging 10 495 mg C L−1. In sample, ⚫OH concentration independent mass concentration, an average value 5.0 (± 2.2) × 10−15 M, while increases DOC range (0.4–7.7) M. both samples, 3C* increase rapidly then plateau under more concentrated conditions, (0.2–7) 10−13 WIN SUM have same 1O2* concentrations, (0.2–8.5) 10−12 linearly DOC, approaches plateau. next extrapolated relationships formation rates sinks our dilute condition aerosol water. Predicted (including transport gas phase) (5–8) similar those fog/cloud waters. contrast, predicted approximately 100 times higher than cloud/fogs, values (4–9) M (1–5) respectively. Although often considered main sink for compounds atmospheric phase, suggest photooxidants will be important many organics

Язык: Английский

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Seasonal variations in the production of singlet oxygen and organic triplet excited states in aqueous PM_2.5 in Hong Kong SAR, South China

Atmospheric chemistry and physics, Год журнала: 2023, Номер 23(16), С. 9245 - 9263

Опубликована: Авг. 22, 2023

Abstract. Photooxidants drive many atmospheric chemical processes. The photoexcitation of light-absorbing organic compounds (i.e., brown carbon, BrC) in waters can lead to the generation reactive triplet excited states (3C∗), which undergo further reactions produce other photooxidants such as singlet oxygen (1O2∗). To determine importance these aqueous secondary aerosol (SOA) formation and transformation, we must know their steady-state concentrations quantum yields. However, there have been limited measurements 3C∗ 1O2∗ samples outside North America Europe. In this work, report first yields produced aerosols South China. We quantified production illuminated extracts PM2.5 collected different seasons at two urban sites one coastal semi-rural site during a year-round study conducted Hong Kong SAR, mass absorption coefficients 300 nm for BrC ranged from 0.49 2.01 m2 g-C−1 three sites. Both were year-round. ([1O2∗]ss) 1.56×10-14 1.35×10-12 M, with average (4.02±3.52)×10-13 M. At nearly 2 orders magnitude lower than [1O2∗]ss, ([3C∗]ss) 2.93×10-16 8.08×10-14 (1.09±1.39)×10-14 also spanned wide ranges across samples, range 1.19 % 13.74 an (5.19±2.63) 0.05 3.24 (0.56±0.66) 3C∗. [1O2∗]ss [3C∗]ss correlated concentration absorbance BrC, thus implying that amount drives photooxidants. locations (urban vs. semi-rural) did not significant effect on indicated local sources influence production. found be highest winter lowest summer all observed seasonal trends could attributed variations long-range air transport. Our analysis highlighted key role regional play influencing composition water-soluble contributed current results will useful modeling photochemistry China region.

Язык: Английский

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Ideas and perspectives: Microorganisms in the air through the lenses of atmospheric chemistry and microphysics

Biogeosciences, Год журнала: 2025, Номер 22(1), С. 243 - 256

Опубликована: Янв. 13, 2025

Abstract. Microorganisms in the atmosphere comprise a small fraction of Earth's microbiome. A significant portion this aeromicrobiome consists bacteria that typically remain airborne for few days before being deposited. Unlike other spheres (e.g., litho-, hydro-, phyllo-, cryospheres), atmospheric are aerosolized, residing individual particles and separated from each other. In atmosphere, encounter chemical physical conditions affect their stress levels survival. This article goes beyond previous overviews by placing these context fundamental microphysical concepts related to aerosols. We provide ranges water amounts surrounding bacterial cells both inside outside clouds suggest volumes cloud droplets lead nutrient oxidant limitations. may result greater limitation but lower oxidative than previously thought. Various factors enhance or reduce microbial oxidative, osmotic, UV-induced), affecting functioning survival bacteria. illustrate could impact under polluted conditions, indicating conclusions about role pollutants directly causing changes abundance can be erroneous. The perspectives presented here aim motivate future experimental modeling studies disentangle complex interplay with Such will help comprehensively characterize modifying Earth' microbiome, which regulates stability global ecosystems biodiversity.

Язык: Английский

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Kinetics of Different Substituted Phenolic Compounds’ Aqueous OH Oxidation in Atmosphere

Atmosphere, Год журнала: 2025, Номер 16(5), С. 567 - 567

Опубликована: Май 9, 2025

Atmospheric aqueous-phase reactions have been recognized as an important source of secondary organic aerosols (SOAs). However, the unclear reaction kinetics and mechanics hinder in-depth understanding SOA sources formation processes. This study selected ten different substituted phenolic compounds (termed PhCs) emitted from biomass burning precursors, to investigate using OH oxidation under simulated sunlight. The factors influencing rates were examined, contribution reactive oxygen species (ROS) was evaluated through quenching kinetic analysis experiments. results showed that pseudo-first-order rate constants (kobs) for ranged 1.03 × 10−4 7.85 s−1 sunlight irradiation with initial H2O2 concentration 3 mM. Precursors electron-donating groups (-OH, -OCH3, -CH3, etc.) exhibited higher electrophilic radical reactivity due enhanced electron density benzene ring, leading than those electron-withdrawing (-NO2, -CHO, -COOH). At pH 2, second-order (kPhCs, OH) lower at 5. kobs did not show dependence on pH. presence O2 facilitated phenols’ photodecay. Inorganic salts transition metal ions varying effects rates. Specifically, NO3− Cu2+ promoted kPhCs, OH, Cl− significantly while SO42− inhibited reaction. determined be in range 109~1010 L mol−1 via bimolecular method, a modest relationship their potential found. Additionally, multiple substituents can suppress toward •OH based Hammett plots. Quenching experiments revealed played dominant role compound degradation (exceeding 65%). Electron paramagnetic resonance confirmed generation singlet (1O2) system, probe-based quantification further explored concentrations 1O2 system. Based concentrations, atmospheric lifetimes estimated, providing valuable insights expanding databases chemical transformation persistence substances atmosphere.

Язык: Английский

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Evaluating the secondary contribution of photosensitized chemistry to OH production in aerosols

Environmental Science Atmospheres, Год журнала: 2024, Номер 4(10), С. 1170 - 1182

Опубликована: Янв. 1, 2024

This study explores the potential contribution of secondary production OH radicals in aerosols and cloud/fog conditions arising from brown carbon (BrC) triplet state chemistry.

Язык: Английский

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Biomass-burning organic aerosols as a pool of atmospheric reactive triplets to drive multiphase sulfate formation

Proceedings of the National Academy of Sciences, Год журнала: 2024, Номер 121(51)

Опубликована: Дек. 13, 2024

Biomass-burning organic aerosol(s) (BBOA) are rich in brown carbon, which significantly absorbs solar irradiation and potentially accelerates global warming. Despite its importance, the multiphase photochemistry of BBOA after light absorption remains poorly understood due to challenges determining oxidant concentrations reaction kinetics within aerosol particles. In this study, we explored photochemical reactivity particles S(IV) oxidation sulfate. We found that sulfate formation under is predominantly driven by photosensitization involving triplet excited states ( 3 * ) instead iron, nitrate, photochemistry. Rates three orders magnitude higher than those observed bulk solution, primarily fast interfacial reactions. Our results highlight chemistry can greatly contribute sulfate, as an example secondary pollutants. Photosensitization will likely become increasingly crucial intensified wildfires.

Язык: Английский

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Supplementary material to "Seasonal variations in photooxidant formation and light absorption in aqueous extracts of ambient particles"

Опубликована: Май 11, 2023

Язык: Английский

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Efficient production of singlet oxygen and organic triplet excited states in aqueous PM_2.5 in Hong Kong, South China

Опубликована: Апрель 20, 2023

Abstract. Photooxidants drive many atmospheric chemical processes. The photoexcitation of light-absorbing organic compounds (i.e., brown carbon (BrC)) in waters can lead to the generation reactive triplet excited states (3C∗), which undergo further reactions produce other photooxidants such as singlet oxygen (1O2). To determine importance these aqueous SOA formation and transformation, we must know their steady-state concentrations quantum yields. However, there has been limited measurements 3C∗ 1O2 samples outside North America Europe. In this work, report first yields produced aerosols South China. We quantified production illuminated extracts PM2.5 collected different seasons at two urban sites one coastal semi-rural site during a year-round study conducted Hong Kong, mass absorption coefficients 300 nm for BrC ranged from 0.49 × 104 2.01 cm2 g-C−1 three sites. Both were year-round. ([1O2]ss) spanned orders magnitude, ranging 1.56 10−14 1.35 10−12 M, with average (4.02 ± 3.52) 10−13 M. ([3C∗]ss) 2.93 10−16 8.08 (1.09 1.39) [1O2]ss [3C∗]ss correlated concentration absorbance BrC, thus implying that amount drives photooxidants. locations (urban vs. semi-rural) did not have significant effect on [1O2]ss, indicated local sources influence production. found be highest winter lowest summer all observed seasonal trends could attributed variations long-range air transport. Our analysis highlighted key role regional play influencing composition water-soluble contributed current results will useful modeling aerosol photochemistry China region.

Язык: Английский

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Revisiting triplet state dissolved organic matter (3DOM⁎): Advances in probes, photoreactivity, and environmental implications

The Science of The Total Environment, Год журнала: 2024, Номер 954, С. 176226 - 176226

Опубликована: Сен. 11, 2024

Язык: Английский

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