Comment on egusphere-2024-693

Published: April 16, 2024

Abstract. The Atmospheric Oxidation Capacity (AOC), often referred to as the self-cleansing ability of atmosphere, considerably affects concentrations photochemical air pollutants. Despite substantial reductions in anthropogenic emissions key chemical compounds China, mechanisms that determine changes atmospheric oxidation capacity are still not sufficiently understood. Here, a regional transport model is employed quantify sensitivity pollutants and parameters specified emission China for conditions January July 2018 representative. simulations show that, winter, 50 % decrease nitrogen oxides (NO_x) leads an 8–10 ppbv (15–20 %) increase surface ozone across China. In summer, concentration decreases by 2–8 (3–12 NO_x-limited areas, while increases up 12 (15 volatile organic (VOCs)-limited areas. This associated with reduced NO_x-titration effect higher levels hydroperoxyl (HO₂) radical due decreased aerosol uptake. With additional reduction VOCs emission, predicted 5–12 (6–15 entire geographic area exception where role BVOCs crucial formation. Further, adopted NO_x AOC 18 VOC-limited specific combined enhanced cycles photolysis oxidized (OVOCs) alkenes hydroxyl (OH) O₃. A large daytime summer results from dominant contribution reaction OH alkenes, followed reactions depleted aromatics OVOCs. study highlights OVOCs urban areas when To mitigate rises joint species, including photodegradable OVOCs, should be implemented.

Language: Английский

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The atmospheric oxidizing capacity in China – Part 2: Sensitivity to emissions of primary pollutants

Atmospheric chemistry and physics, Journal Year: 2024, Volume and Issue: 24(22), P. 12943 - 12962

Published: Nov. 21, 2024

Abstract. Despite substantial reductions in anthropogenic emissions, ozone (O3) pollution remains a severe environmental problem urban China. These affect formation by altering levels of O3 precursors, intermediates, and the oxidation capacity atmosphere. However, underlying mechanisms driving changes are still not fully understood. Here, we employ regional chemical transport model to quantify due specified emission reduction (50 %) for winter summer conditions 2018. Our results indicate that nitrogen oxide (NOx) emissions increase surface concentrations 15 %–33 % on average across China up 17 volatile organic compound (VOC)-limited areas during summer. increases associated with reduced NOx titration effect higher OH radicals. Reducing significantly decreases concentration particulate nitrate, which enhances through increased HO2 radical aerosol uptake diminished extinction. Additionally, an enhanced atmospheric oxidative capacity, driven larger contributions from photolysis oxidized VOCs (OVOCs) OH-related reactions, also favors formation. With additional VOC summertime (VOC-limited areas) can be offset production radicals oxidations. To effectively mitigate pollution, simultaneous specific species should applied, especially regarding alkenes, aromatics, unsaturated OVOCs, including methanol ethanol.

Language: Английский

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Kinetic Modeling of the Photocatalytic Degradation of Chlorinated Aromatic Volatile Organic Compounds: Mass Transfer Enhancement

Applied Sciences, Journal Year: 2024, Volume and Issue: 14(4), P. 1507 - 1507

Published: Feb. 13, 2024

Chlorobenzene (CB) and Chloronaphthalene (CN) emissions from cement plant operations pose significant environmental risks. This study investigates the mass transfer effects of chlorinated aromatic Volatile Organic Compounds (VOCs), specifically CB CN, in gas phase a continuous-tangential-flow annular photocatalytic reactor. The experiments involved introducing CN into reactor, degradation kinetics were analyzed using Langmuir–Hinshelwood (L-H) model. L-H model was applied to assess impact flow rate, concentration, relative humidity (% RH) on rate (DR). results indicate that both experimental simulated rates improved with increased (1 9 m3·h−1) inlet concentrations (30 216 mg·m−3). enhancement DR correlates availability active OH* species TiO2 surface. emphasizes role H2O molecules VOC removal kinetics. rising water content (5 55%), but adverse conversion observed beyond 55% RH. reveals effect, internal diffusional limitations pores under operational conditions. predominantly controlled by chemical catalyst pore availability. Furthermore, this demonstrates higher than reactor For concentration 1.328 mM·m−3, ranged 0.70 2.84 µM·m2·s−1, as varied 1 m3·h−1. 0.60 2.20 µM·m2·s−1 within same range.

Language: Английский

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The Atmospheric Oxidizing Capacity in China: Part 2. Sensitivity to emissions of primary pollutants

Published: March 26, 2024

Abstract. The Atmospheric Oxidation Capacity (AOC), often referred to as the self-cleansing ability of atmosphere, considerably affects concentrations photochemical air pollutants. Despite substantial reductions in anthropogenic emissions key chemical compounds China, mechanisms that determine changes atmospheric oxidation capacity are still not sufficiently understood. Here, a regional transport model is employed quantify sensitivity pollutants and parameters specified emission China for conditions January July 2018 representative. simulations show that, winter, 50 % decrease nitrogen oxides (NOx) leads an 8–10 ppbv (15–20 %) increase surface ozone across China. In summer, concentration decreases by 2–8 (3–12 NOx-limited areas, while increases up 12 (15 volatile organic (VOCs)-limited areas. This associated with reduced NOx-titration effect higher levels hydroperoxyl (HO2) radical due decreased aerosol uptake. With additional reduction VOCs emission, predicted 5–12 (6–15 entire geographic area exception where role BVOCs crucial formation. Further, adopted NOx AOC 18 VOC-limited specific combined enhanced cycles photolysis oxidized (OVOCs) alkenes hydroxyl (OH) O3. A large daytime summer results from dominant contribution reaction OH alkenes, followed reactions depleted aromatics OVOCs. study highlights OVOCs urban areas when To mitigate rises joint species, including photodegradable OVOCs, should be implemented.

Language: Английский

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Simulation of Regional Secondary Organic Aerosol Formation From Monocyclic Aromatic Hydrocarbons Using a Near‐Explicit Chemical Mechanism Constrained by Chamber Experiments

Journal of Geophysical Research Atmospheres, Journal Year: 2024, Volume and Issue: 129(11)

Published: June 1, 2024

Abstract The formation of secondary organic aerosol (SOA) is inextricably linked to the photo‐oxidation aromatic hydrocarbons. However, models still exhibit biases in representing SOA mass and chemical composition. We implemented a box model coupled with near‐explicit photochemical mechanism, Master Chemical Mechanism (MCMv3.3.1), simulate series chamber studies assess simulating from representative monocyclic hydrocarbons, that is, toluene three xylene isomers (TX SOA). underpredicted yields xylenes by 4.7%–100%, which could be improved adjusting saturation vapor pressure (SVP) their oxidation products. After updating SVP values, concentration TX Yangtze River Delta region during summer doubled, there was also an approximate 3% enhancement total SOA. Compared lumped mechanism used for SOA, MCM predicted comparable concentrations but exhibited different volatility distributions states.

Language: Английский

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