Water Promotes the Oxidation of SO₂ by O₂ over Carbonaceous Aerosols

Environmental Science & Technology, Journal Year: 2020, Volume and Issue: 54(12), P. 7070 - 7077

Published: April 27, 2020

Severe haze episodes typically occur with concurrent high relative humidity. Here, the vital role of water in promoting oxidation SO2 by O2 on carbonaceous soot surfaces was identified at atomic level first-principles calculations. Water molecules can dissociate into surface hydroxyl groups through a self-catalyzed process under ambient conditions. The groups, acting as facilitators, significantly accelerate conversion to SO3 (precursor particulate sulfate) over aerosols reducing reaction barriers. Specifically, activate reactants and stabilize transition states products hydrogen-bonding interactions, making reactions both thermodynamically kinetically more favorable room temperature. findings indicate that atmospheric humidity plays an important enhancing capacity, thus exacerbating severe development. Also, this study unravels mechanism hydroxyl-assisted H2O dissociation metal-free carbocatalysts normal

Language: Английский

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Composition of Ultrafine Particles in Urban Beijing: Measurement Using a Thermal Desorption Chemical Ionization Mass Spectrometer

Environmental Science & Technology, Journal Year: 2021, Volume and Issue: 55(5), P. 2859 - 2868

Published: Feb. 12, 2021

Ultrafine particles (UFPs) dominate the particle number population in urban atmosphere and revealing their chemical composition is important. The thermal desorption ionization mass spectrometer (TDCIMS) can semicontinuously measure UFP at molecular level. We modified a TDCIMS deployed it Beijing. Radioactive materials for aerosol charging were replaced by soft X-ray ionizers so that be operated countries with tight regulations on radioactive materials. Protonated N-methyl-2-pyrrolidone ions used as positive reagent ion, which selectively detects ammonia low-molecular weight-aliphatic amines amides vaporized from phase. With superoxide negative wide range of inorganic organic compounds observed, including nitrate, sulfate, aliphatic acids carbon numbers up to 18, highly oxygenated CHO, CHON, CHOS compounds. latter two attributed parent or decomposition products organonitrates organosulfates/organosulfonates, respectively. Components both primary emissions secondary formation UFPs identified. Compared measured forest marine sites, those Beijing contain more nitrogen-containing sulfur-containing These observations illustrate unique features environment provide insights into origins.

Language: Английский

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Generation and Release of OH Radicals from the Reaction of H₂O with O₂ over Soot

Angewandte Chemie International Edition, Journal Year: 2022, Volume and Issue: 61(21)

Published: March 11, 2022

OH radicals in the air maintain oxidizing power of troposphere. A conventional view is that particulate matter (PM) atmosphere a major sink radicals, thereby lowering event high-level PM. By contrary, our joint experimental/theoretical study reveals new mechanism for generation gaseous by carbonaceous soot particles. We show water and O2 react on surfaces give rise to under irradiation. With ample delocalized π electrons, enable easy desorption hydroxyl groups produce evidenced direct observation steady surface. Our results reveal chemical production radicals.

Language: Английский

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Unexpected quenching effect on new particle formation from the atmospheric reaction of methanol with SO ₃

Proceedings of the National Academy of Sciences, Journal Year: 2019, Volume and Issue: 116(50), P. 24966 - 24971

Published: Nov. 25, 2019

Significance New particle formation (NPF) is an important global phenomenon, contributing nearly half of the cloud condensation nuclei in nature. Today, NPF believed to be mainly promoted by low-volatile species formed atmosphere. Herein, we show that certain cases, could undermine NPF. Specifically, identify previously unreported catalytic reactions between alcohols and SO 3 which yield organic sulfates. Rather than being a promoter NPF, sulfates can compete for consuming , thereby disfavoring H 2 4 formation. Such unexpected quenching effects on are most likely occur dry polluted regions with abundant alcohols, illustrating importance understanding interplay nucleation precursor subsequent

Language: Английский

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Influence of atmospheric conditions on sulfuric acid-dimethylamine-ammonia-based new particle formation

Chemosphere, Journal Year: 2019, Volume and Issue: 245, P. 125554 - 125554

Published: Dec. 10, 2019

Language: Английский

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Influence of Ammonia and Water on the Fate of Sulfur Trioxide in the Troposphere: Theoretical Investigation of Sulfamic Acid and Sulfuric Acid Formation Pathways

The Journal of Physical Chemistry A, Journal Year: 2019, Volume and Issue: 123(14), P. 3131 - 3141

Published: March 22, 2019

Reaction of ammonia with SO3 as a potential source sulfamic acid in the troposphere has been investigated by means electronic structure and chemical kinetic calculations. Besides, hydrolysis reaction, which is known to be major atmospheric decay channel SO3, also investigated. The catalytic effects water on both reactions have studied. Rate coefficients for all studied reaction channels were calculated using transition state theory employing pre-equilibrium approximation. Calculated rate number catalyzed ammonolysis processes found much higher (by ∼105 ∼109 times) than gas limit at ambient temperature. With decrease temperature because negative dependence coefficients, that difference became even larger (up ∼1016 times). Therefore, order remove discrepancies, master equation. results showed marked improvements, only one showing slightly coefficient above limit. obtained from equation dependence, albeit smaller extent. uncatalyzed similar corresponding hydrolysis, was too slow any practical implication. For reactions, ammonia-catalyzed pathways water-catalyzed ones. Between ammonolysis, latter coefficient. In spite that, expected negligible contribution tropospheric loss process large concentration values between troposphere.

Language: Английский

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Evolution of Condensable Fine Particle Size Distribution in Simulated Flue Gas by External Regulation for Growth Enhancement

Environmental Science & Technology, Journal Year: 2020, Volume and Issue: 54(7), P. 3840 - 3848

Published: March 2, 2020

Condensation fine particles (CFPs) from coal-fired flue gas harm humans and the environment after being emitted into atmosphere. Given their small size (<0.1 μm), difficulty arises in efficiently removing CFPs by wet electrostatic precipitators mist eliminators. In this work, a laboratory apparatus was used to study CFP growth under simulated power plant conditions. Four methods were independently investigated increase particle size: addition of ammonia, fly ash, decreasing temperature, applying an electrical discharge. Results demonstrated that distribution possessed unimodal structure with peak at 0.05 μm. At increased ammonia concentration 10 30 ppm, factor shifted rightward 1.21 1.35 range >1 significantly broadened due joint action multiple mechanisms. Fly ash acted as core, adhered surface when forming ash–salt droplets. Cooling could also enhance vapor condensation. decreased temperature 45 °C, median diameter 15%. Finally, agglomeration can be further enhanced external field utilized. The broadened, 8 kV applied voltage. research findings provide valuable guidance for effectively improving removal efficiency regulation enhancement.

Language: Английский

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The effect of water on the heterogeneous reactions of SO₂ and NH₃ on the surfaces of α-Fe₂O₃ and γ-Al₂O₃

Environmental Science Nano, Journal Year: 2019, Volume and Issue: 6(9), P. 2749 - 2758

Published: Jan. 1, 2019

In this study, wall-coated flow tube, in situ diffuse reflectance infrared Fourier transform spectroscopy and ion chromatography were used to investigate the effect of water on heterogeneous reactions SO₂ NH₃ α-Fe₂O₃ γ-Al₂O₃.

Language: Английский

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Influence of atmospheric conditions on the role of trifluoroacetic acid in atmospheric sulfuric acid–dimethylamine nucleation

Atmospheric chemistry and physics, Journal Year: 2021, Volume and Issue: 21(8), P. 6221 - 6230

Published: April 26, 2021

Abstract. Ambient measurements combined with theoretical simulations have shown evidence that the tropospheric degradation end-products of Freon alternatives, trifluoroacetic acid (TFA), one most important and abundant atmospheric organic substances, can enhance nucleation process based on sulfuric (SA) dimethylamine (DMA) in urban environments. However, TFA is widespread all over world under different conditions, such as temperature precursor concentration, which are factors potentially influencing thus inducing mechanisms. Herein, using density functional theory Atmospheric Cluster Dynamics Code, influence concentrations role SA–DMA has been investigated. The results indicate growth trends clusters involving increase decrease temperature. enhancement particle formation rate by contributions SA–DMA–TFA cluster to pathways be up 227-fold 95 %, respectively, at relatively low temperature, SA high DMA winter, boundary layer, or megacities far away from industrial sources sulfur-containing pollutants. These provide perspective realistic environments, revealing potential alternatives a wide range conditions.

Language: Английский

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Sulfur Dioxide Transported From the Residual Layer Drives Atmospheric Nucleation During Haze Periods in Beijing

Geophysical Research Letters, Journal Year: 2023, Volume and Issue: 50(6)

Published: March 14, 2023

Abstract New particle formation (NPF) is a global phenomenon that significantly influences climate. NPF also contributes to haze, with pronounced negative impacts on human health. Theory and observations both show nucleation favored during clean days inhibited haze episodes due high pre‐existing condensation sink (CS). Here we the surprising occurrence of in Beijing associated concentration sulfuric acid dimers. With field model simulations, demonstrate downward mixing sulfur dioxide (SO 2 ) from residual layer aloft enhances ground level SO , which turn elevates dimer after rapid oxidation polluted air. Our results address key gap between source its atmospheric products conditions megacity, Beijing, providing missing link complete chain describing atmosphere.

Language: Английский

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