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Sulfuric acid (SA)‐dimethylamine (DMA)‐H2O cluster formation has been proven to be responsible for a significant part of new particle formation (NPF) in a Chinese megacity. However, the possible involvement of common atmospheric acids in the subsequent growth of SA‐DMA clusters remains elusive. We simulated formation and growth of clusters using atmospheric relevant concentrations of SA, DMA, and trifluoroacetic acid (TFA), a commonly observed atmospheric perfluorocarboxylic acid, using Density Functional Theory combined with Atmospheric Cluster Dynamics Code. The presence of TFA leads to complex cluster formation routes and an enhancement of NPF rates by up to 2.3 ([TFA] = 5.0 × 106 molecules cm−3, [SA] = 1.0 × 106 molecules cm−3, and [DMA] = 1.5 × 109 molecules cm−3). The agreement of (SA)1·(DMA)1‐2·(TFA)1 concentrations between simulations and ambient measurements during NPF events validates model predictions and implies that perfluorocarboxylic acids could potentially boost atmospheric SA‐DMA NPF rates. Plain Language Summary: Atmospheric nucleation is the earliest step to form new aerosol particles, which includes a complex transformation from gaseous molecules to small clusters, then to critical clusters, and finally to freshly nucleated nanoparticles. Sulfuric acid and dimethylamine have been proved to explain atmospheric nucleation events in urban China. However, whether other atmospheric acidic species could participate in this nucleation process remains elusive. Herein, we report a sulfuric acid‐dimethylamine based nucleation mechanism with the participation of trifluoroacetic acid, a commonly observed strong acid in the atmosphere, using theoretical calculation methods. The model predictions are then validated by ambient measurements in urban Shanghai. Our results suggest that perfluorocarboxylic acids could potentially boost the formation of nanoparticles. Key Points: Theoretical simulations indicate complex atmospheric new particle formation mechanisms involving sulfuric acid, dimethylamine, and trifluoroacetic acidGood agreement of key cluster concentrations between simulations and ambient measurements during new particle formation events is obtainedTrifluoroacetic acid can participate in the growth of sulfuric acid‐dimethylamine clusters and enhance the nucleation rates [ABSTRACT FROM AUTHOR]

Organosulfates (OSs) are an important component of secondary organic aerosols (SOA), accounting for ~30% of total organic aerosol. In this study, OSs in eastern China were investigated to understand their diurnal evolution, source, and volatility using high-resolution mass spectrometry. In polluted days, we identified a total of 5,147 organic molecules, including 1,206 OS molecules. The average molecular weight (m.w.) and carbon chain length of OSs in this study exceeded the commonly recognized range (500 Da). OSs were mostly composed of newly formed low oxidation state compounds as well as aged aliphatic and aromatic ones. The number and abundance of aromatic and aliphatic OSs with low saturation, volatility, O/C w as well as H/C w increased greatly with rising PM 2.5 concentrations. The daytime photo-oxidation resulted in a large number of high m.w. (HMW, > 500 Da) OSs. OSs with m.w. <500 Da, and many oxygen atoms were newly generated during the nighttime, mainly dominated by liquid-phase oxidation processes. The result of OSs with higher m.w. and lower volatility was due to increased dimerization and oligomerization. During pollution formatting, OSs with small DBE values (between 0 and 6) appeared; meanwhile, the number of highly unsaturated OSs with DBE > 7 (mainly aromatic OSs) increased by about 34%. This study is useful for clarifying the secondary formation and properties of HMW OSs in a polluted environment in China. • Diurnal variation of organosulfates were studied using FT-ICR MS in eastern China. • OSs were mainly composed of aliphatic and aromatic compounds. • Low-saturation and -volatility OSs increased greatly with arising PM 2.5. • Daytime photo-oxidation resulted in a large number of high m.w. (HMW, > 500 Da) OSs. • High m.w. and lower volatility OSs was enhanced by dimerization and oligomerization. [ABSTRACT FROM AUTHOR]

The newly developed Vocus proton-transfer-reaction time-of-flight mass spectrometer (Vocus PTR-TOF) is able to simultaneously detect hundreds of gaseous compounds including a big fraction of volatile organic compounds (VOCs) with outstanding mass resolution and sensitivity. Here, we present an application of Vocus PTR-TOF to monitor gaseous dimethylamine (DMA). The sensitivity towards DMA was improved by tuning the voltage settings of the segmented quadrupole following the molecular ion reactor to obtain a suitable ion transmission window. With the assistance of a permeation tube calibration method, the sensitivity of Vocus PTR-TOF for DMA detection was 2.68 cps pptv−1 at a TOF extraction frequency of 16 kHz and the detection limit was 1.44 pptv at 3σ of the background signal for a 1 min integration time. Laboratory experiments at a series of controlled relative humidity (RH) show that RH of the sample had little influences on the measurement of DMA. Vocus PTR-TOF with this hardware setup was deployed from December 2018 to January 2019 at Wangdu, Hebei Province, China. The temporal profile of C 2 -amines with a high time resolution was obtained, while the detection of VOCs remained successful. Such simultaneous measurements of these compounds are meaningful as these compounds are all relevant to aerosol nucleation and growth. Our results indicate that Vocus PTR-TOF can be a powerful tool in both field and laboratory studies for new particle formation research. [ABSTRACT FROM AUTHOR]

Ficus altissima, also known as lofty fig, is a monoecious plant from the Moraceae family commonly found in southern China. In this study, we isolated and identified one new isoflavone (1), three new hydroxycoumaronochromones (2a, 2b and 3a) and 12 known compounds from the fruits of F. altissima. Their chemical structures were determined using spectroscopic analysis methods. We also tested all the isolated compounds for their anti-proliferative activities against eight human tumour cell lines (A-549, AGS, K562, K562/ADR, HepG2, HeLa, SPC-A-1 and CNE2) using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. Our experiments showed that compound 6 exhibited obvious anti-proliferative activity against the K562 cell line with an IC 50 value of 1.55 μM. Additionally, compounds 8 and 9 showed significant anti-proliferative activities against the AGS and K562 cell lines, respectively. Moreover, compound 6 induced apoptosis in K562 cells through the caspase family signalling pathway., Competing Interests: Declaration of competing interest The authors declare no competing financial interest., (Copyright © 2023. Published by Elsevier B.V.)

Organic acids are important contributors to the acidity of atmospheric precipitation, but their existence in the Chinese atmosphere is largely unclear. In this study, twelve atmospheric gaseous organic acids, including C 1 -C 9 alkanoic acids, methacrylic acid, pyruvic acid, and benzoic acid, were observed in the suburb of Wangdu, Hebei Province, a typical rural site in the northern China plain from 16 th December, 2018 to 22 nd January, 2019, using a Vocus® Proton-Transfer-Reaction time-of-flight mass spectrometer (Vocus PTR-ToF). The quantification of C 2 -C 4 alkanoic acids by the Vocus PTR-ToF was calibrated according to the titration of a NaOH solution by C 2 -C 4 alkanoic acids from home-made permeation sources, and the other organic acids except for formic acid were quantified based on the k cap -sensitivity linearity in the Vocus PTR-ToF, whereas formic acid was not quantified because our instrument setting led to a significant underestimation in its concentration. The average total concentration of eleven gaseous organic acids was 6.96 ± 5.20 ppbv (parts per billion by volume). The average concentration of acetic acid was the highest (3.86 ± 3.00 ppbv), followed by propanoic acid, butyric acid, and methacrylic acid. Domestic straw burning was likely the dominant source of the observed gaseous organic acids according to the good correlations between acetonitrile and organic acids and between particulate K + and organic acids, and traffic emissions could also have contributed. During episodes with continuously high concentrations of organic acids, short-distance transport dominated in Wangdu according to the backward trajectory analysis. Baoding, Shijiazhuang, and Hengshui areas were the main source areas based on potential source contribution function and concentration weighing track analysis., (Copyright © 2021. Published by Elsevier B.V.)