Formation of In‐Cloud Aqueous‐Phase Secondary Organic Matter and Related Characteristic Molecules

Journal of Geophysical Research Atmospheres, Год журнала: 2024, Номер 129(7)

Опубликована: Март 28, 2024

Abstract The formation process of in‐cloud aqueous‐phase secondary organic matter (aqSOM) and its characteristics are unclear. Herein, water‐soluble inorganic ions, oxalate, carbon (WSOC) were determined in cloud water aerosol (PM 2.5 ) samples simultaneously collected at a remote mountain site southern China during spring 2018 winter 2020. molecular compositions (WSOM) aerosols analyzed by Fourier transform ion cyclotron resonance mass spectrometer negative electrospray ionization (ESI‐) mode. results showed that the mean concentration WSOC was 6.27–8.54 mg C L −1 0.60–1.37 μg m −3 aerosols. strong correlation observed between WSOM aqueous (e.g., NO 3 − oxalate), positive matrix factorization results, elevated WSOM/K + ratios suggested enhanced aqSOM water. According to random forest analysis, factors related variation mainly included K , pH, atmospheric x . Additionally, 37 characteristic molecules, classified as ‐O ‐NO ‐N 2 O 1‐2 S, consisting dicarboxylic acids, nitrophenols, dinitrophenols, identified using linear discriminant analysis effect size (LefSe). N‐ S‐containing molecules with numbers >10 had low or extremely volatility; therefore, they might contribute after droplet evaporation. revealed modifying effects processes on composition level could improve our understanding aerosol–cloud interactions.

Язык: Английский

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Atmospheric Photochemical Oxidation of 4-Nitroimidazole

Atmosphere, Год журнала: 2025, Номер 16(5), С. 624 - 624

Опубликована: Май 20, 2025

Nitro-functionalized heterocycles, such as nitroimidazoles, are significant environmental contaminants and have been identified components of secondary organic aerosols (SOA) biomass-burning (BBOA). Their strong absorption in the near-UV (300–400 nm) makes photochemistry a critical aspect their atmospheric processing. This study investigates both direct hydroxyl radical (OH) oxidation 4-nitroimidazole (4-NI). The photolysis rate 4-NI was found to be J4-NI = 4.3 × 10−5 (±0.8) s−1, corresponding an lifetime 391 (±77) min under bulk aqueous conditions simulating cloud water. Electrospray ionization mass spectrometry (ESI-MS) analysis following irradiation indicated loss nitro group, while NO elimination observed more minor channel photolysis. In addition, constant for reaction with OH radicals, kNI+OH, determined 2.9 109 (±0.6) M−1s−1. Following oxidation, ESI-MS results show emergence dominant peak at m/z 130 amu, consistent hydroxylation 4-NI. Computational indicate that addition occurs lowest barrier C2 C5 positions combined from experiments suggest OH-mediated degradation is likely dominate aerosol-phase conditions, where concentrations elevated, expected primary mechanism high-humidity environments

Язык: Английский

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Different formation pathways of nitrogen-containing organic compounds in aerosols and fog water in northern China

Atmospheric chemistry and physics, Год журнала: 2024, Номер 24(12), С. 6987 - 6999

Опубликована: Июнь 18, 2024

Abstract. While aqueous-phase processing is known to contribute the formation of nitrogen-containing organic compounds (NOCs), specific pathways involved remain poorly understood. In this study, we aimed characterize NOCs present in both pre-fog aerosols and fog water collected at a suburban site northern China. Fourier-transform ion cyclotron resonance mass spectrometry was utilized analyze molecular composition negative positive modes electrospray ionization (ESI− ESI+). samples, constituted significant portion, accounting for over 60 % all assigned formulas ESI− more than 80 ESI+. By comparing originating from biomass burning, coal combustion, vehicle emissions, identified that 72.3 were attributed primary anthropogenic sources (pNOCs), while remaining categorized as secondary formed within (saNOCs). Unique found classified (sfNOCs). Through comprehensive “precursor–product pair” screening involving 39 reaction pathways, observed nitration reaction, amine pathway, intramolecular N-heterocycle pathway NH3 addition reactions contributed 43.6 %, 22.1 11.6 saNOCs, respectively. contrast, these 26.8 28.4 29.7 sfNOCs, This disparity likely influenced by diverse precursors, aqueous acidity, gas-phase species partitioning. Correspondingly, saNOCs contain higher abundance carbohydrate-like highly oxygenated with two nitrogen atoms compared pNOCs. Conversely, sfNOCs exhibited content lipid-like fewer oxygen atoms. These results underscore distinct processes contributing diversity water, which may lead their different climate effects.

Язык: Английский

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Seasonal Trends and Site Differences of Nitroaromatic Compounds in PM2.5 in Sichuan Basin and Their Effects on Light Absorption of Brown Carbon

Toxics, Год журнала: 2025, Номер 13(2), С. 124 - 124

Опубликована: Фев. 6, 2025

Nitroaromatic compounds (NACs) have adverse effects on human health and climate. Daily PM2.5 samples were collected in winter summer of 2022 two cities, Chengdu (CD) Mianyang (MY), located Sichuan Basin southwestern China. Four types NACs PM2.5, containing nitrophenols, nitrocatechols, nitrosalicylic acids, nitronaphthol, analyzed. The mean concentration a total 10 (ΣNACs) at the suburban MY site (71.7 ± 35.6 ng m−3) was higher than that urban CD (29.5 16.2 m−3), while summer, concentrations ΣNACs cities similar, around 2.2 m−3. much attributed to impact biomass burning. 4-Nitrocatechol (4NC) most abundant species during sampling period, accounting for 35–56% mass. In winter, light absorption coefficient methanol-soluble brown carbon (Abs365,M) 10.5 3.4 13.6 4.3 Mm−1 MY, respectively, which about 4–7 times summer. contributions 365 nm Abs365,M 1.6–3.6% 0.5–0.7% with 4NC contributing among all NACs. geographical origins potential sources both sites mainly distributed within basin.

Язык: Английский

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Non-negligible emissions of amines from vehicle and ship exhausts in China

Atmospheric Environment, Год журнала: 2025, Номер unknown, С. 121220 - 121220

Опубликована: Апрель 1, 2025

Язык: Английский

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Photoaging of phenolic secondary organic aerosol in the aqueous phase: evolution of chemical and optical properties and effects of oxidants

Atmospheric chemistry and physics, Год журнала: 2023, Номер 23(12), С. 7103 - 7120

Опубликована: Июнь 28, 2023

Abstract. While gas-phase reactions are well established to have significant impacts on the mass concentration, chemical composition, and optical properties of secondary organic aerosol (SOA), aqueous-phase aging SOA remains poorly understood. In this study, we performed a series long-duration photochemical experiments investigate evolution composition light absorption aqueous (aqSOA) from guaiacyl acetone (GA), semivolatile phenolic carbonyl that is common in biomass burning smoke. The aqSOA was produced GA with hydroxyl radical (•OH-aqSOA) or triplet excited state carbon (3C∗-aqSOA) then photoaged water under conditions simulate sunlight exposure northern California for up 48 h. effects increasing •OH 3C∗ concentration photoaging were also studied. High-resolution spectrometry (HR-AMS) UV–Vis spectroscopy utilized characterize absorptivity track their changes during aging. Compared •OH-aqSOA, 3C∗-aqSOA more rapidly shows less oxidation, greater abundance oligomers, higher absorption. Prolonged promotes fragmentation formation volatile light-absorbing products. More than half initial lost, substantial photobleaching occurs after 10.5 h prolonged simulated illumination •OH-aqSOA. By performing positive matrix factorization (PMF) analysis combined HR-AMS spectral data, resolved three generations distinctly different properties. first-generation oligomer enhanced at 340–400 nm. second-generation enriched functionalized species has highest coefficients 300–500 nm, while third-generation contains fragmented products least absorbing. These results suggest intermediately aged absorbing other generations, competition between brown (BrC) photobleaching, which dependent time. Although generally increases oxidation aqSOA, slightly decreased O/C •OH-aqSOA observed additional exposure. This likely due evaporation highly oxidized compounds. Increased oxidant accelerates transformation decay BrC chromophores, leading faster reduction photobleaching. addition, compared •OH, by produces low-volatility products, counterbalances part loss evaporation.

Язык: Английский

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Machine Learning Approach for the Estimation of Henry’s Law Constant Based on Molecular Descriptors

Atmosphere, Год журнала: 2024, Номер 15(6), С. 706 - 706

Опубликована: Июнь 13, 2024

In atmospheric chemistry, the Henry’s law constant (HLC) is crucial for understanding distribution of organic compounds across gas, particle, and aqueous phases. Quantitative structure–property relationship (QSPR) models described in scientific research are generally tailored to specific groups or categories substances often developed using a limited set experimental data. This study machine learning model an extensive dataset HLCs approximately 1100 compounds. Molecular descriptors calculated alvaDesc software (v 2.0) were used train models. A hybrid approach was adopted feature selection, ensuring alignment with domain knowledge. Based on root mean squared error (RMSE) training test data after cross-validation, Gradient Boosting (GB) selected as predicting HLC. The hyperparameters optimized automated hyperparameter optimization framework Optuna. impact features target variable assessed SHapley Additive exPlanations (SHAP). demonstrated strong performance training, evaluation, datasets, achieving coefficients determination (R2) 0.96, 0.78, 0.74, respectively. estimate HLC associated carbon capture storage (CCS) emissions secondary aerosols.

Язык: Английский

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Characterization of atmospheric nitroaromatic compounds in Southwest China by direct injection liquid chromatography-tandem mass spectrometry analysis of aerosol extracts

Chemosphere, Год журнала: 2024, Номер 363, С. 142845 - 142845

Опубликована: Июль 14, 2024

Язык: Английский

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Efficient Nitrate Formation in Fog Events Implicates Fog Interstitial Aerosols as Significant Drivers of Atmospheric Chemistry

Environmental Science & Technology, Год журнала: 2024, Номер unknown

Опубликована: Ноя. 21, 2024

Clouds and fogs, consisting of tiny water droplets formed by the condensation in supersaturated air, are vital atmospheric chemistry, as they facilitate multiphase reactions. While measuring high-altitude cloud is challenging, fog ground-level clouds offer a unique opportunity for direct observation. In this study, we explored radiation fogs North China Plain using an advanced aerosol-fog sampling system to measure chemical physical properties both inactivated interstitial aerosols activated droplet residues. Our findings revealed that efficient nitrate formation primarily occurred on rather than within droplets, with observed aerosol net production rates reaching up 3.6 μg m

Язык: Английский

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Mixing state and influence factors controlling diurnal variation of particulate nitrophenol compounds at a suburban area in northern China

Environmental Pollution, Год журнала: 2024, Номер 344, С. 123368 - 123368

Опубликована: Янв. 19, 2024

Язык: Английский

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