Laboratory Investigation of Renoxification from the Photolysis of Inorganic Particulate Nitrate

Environmental Science & Technology, Journal Year: 2021, Volume and Issue: 55(2), P. 854 - 861

Published: Jan. 4, 2021

Nitrogen oxides (NOx) play a key role in regulating the oxidizing capacity of atmosphere through controlling abundance O3, OH, and other important gas particle species. Some recent studies have suggested that particulate nitrate, which is conventionally considered as ultimate oxidation product NOx, can undergo "renoxification" via photolysis, recycling NOx HONO back to phase. However, there are large discrepancies estimates importance this channel, with reported renoxification rate constants spanning three orders magnitude. In addition, previous laboratory derived constant using bulk samples collected on substrates instead suspended particles. work, we study submicron sodium ammonium nitrate controlled photolysis experiments an environmental chamber. We find that, under atmospherically relevant wavelengths relative humidities, inorganic releases less than 10 times rapidly gaseous nitric acid, putting our measurements low end recently constants. To extent conditions representative real atmosphere, from appears limited contributing OH budgets remote environments. These results based simplified model systems; future should investigate more complex aerosol mixtures represent broader spectrum properties better constrain ambient aerosols.

Language: Английский

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Aqueous secondary organic aerosol formation from the direct photosensitized oxidation of vanillin in the absence and presence of ammonium nitrate

Atmospheric chemistry and physics, Journal Year: 2022, Volume and Issue: 22(1), P. 273 - 293

Published: Jan. 10, 2022

Abstract. Vanillin (VL), a phenolic aromatic carbonyl abundant in biomass burning emissions, forms triplet excited states (3VL∗) under simulated sunlight leading to aqueous secondary organic aerosol (aqSOA) formation. Nitrate and ammonium are among the main components of aerosols cloud or fog water. Under atmospherically relevant conditions, solutions composed either VL only with nitrate were subjected irradiation compare aqSOA formation via direct photosensitized oxidation absence presence nitrate. The reactions characterized by examining decay kinetics, product compositions, light absorbance changes. Both conditions generated oligomers, functionalized monomers, oxygenated ring-opening products, promoted functionalization nitration, likely due its photolysis products (⚫OH, ⚫NO2, NO2- HONO). Moreover, potential imidazole derivative observed suggested that participated reactions. majority most from both brown carbon (BrC) chromophores. effects oxygen (O2), pH, reactants concentration molar ratios on also explored. Our findings show O2 plays an essential role reactions, oligomer was enhanced at pH <4. Also, dominant low concentrations, whereas oligomerization favored high concentrations. Furthermore, oligomers hydroxylated detected guaiacol (a non-carbonyl phenol) Last, pathways proposed. This study indicates may be important source areas influenced underscores importance aqueous-phase processing carbonyls.

Language: Английский

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Secondary Formation of Atmospheric Brown Carbon in China Haze: Implication for an Enhancing Role of Ammonia

Environmental Science & Technology, Journal Year: 2023, Volume and Issue: 57(30), P. 11163 - 11172

Published: July 5, 2023

Optical characteristics and molecular compositions of brown carbon (BrC) were investigated during winter 2019 at a rural site China with focus on nitro-aromatic compounds (NACs) imidazoles (IMs). The abundance gaseous nitrophenols relative to CO the campaign maximized noontime, being similar O3, while particulate NACs haze periods strongly correlated toluene NO2, suggesting that in region are largely formed from gas-phase photooxidation. Strong correlations IMs dry mass ratio EC/PM2.5 concentration levoglucosan observed, indicating events derived biomass burning emissions. However, an increase increasing aerosol liquid water content pH was observed humid events, along much lower abundances K+ PM2.5, mostly aqueous reactions periods. These exponentially increased NH3 owing reaction carbonyls free ammonia. Our findings for first time revealed enhancing effect ammonia BrC formation China, especially

Language: Английский

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Composition and light absorption of N-containing aromatic compounds in organic aerosols from laboratory biomass burning

Atmospheric chemistry and physics, Journal Year: 2019, Volume and Issue: 19(5), P. 2899 - 2915

Published: March 7, 2019

Abstract. This study seeks to understand the compositional details of N-containing aromatic compounds (NACs) emitted during biomass burning (BB) and their contribution light-absorbing organic carbon (OC), also termed brown (BrC). Three laboratory BB experiments were conducted with two United States pine forest understory fuels typical those consumed prescribed fires. During experiments, submicron aerosol particles collected on filter media subsequently extracted methanol examined for optical chemical properties. Significant correlations (p<0.05) observed between BrC absorption elemental (EC)∕OC ratios individual burns data. However, pooled experimental data indicated that EC∕OC alone cannot explain absorption. Fourteen NAC formulas identified in samples, most which simulated secondary (SOA) from photooxidation volatile (VOCs) NOx. molecular structures associated identical formula SOA are different. In this work, NACs featured by methoxy cyanate groups predominately generated flaming phase. The mass concentrations quantified using authentic surrogate standards, contributions bulk light solvent-extractable OC calculated. matter (OM) significantly higher flaming-phase samples than smoldering-phase they correlated ratio both data, indicating formation largely depends burn conditions. average overall at 365 nm ranged 0.087±0.024 % 1.22±0.54 %, is 3–10 times OM (0.023±0.0089 0.18±0.067 %), so work likely strong chromophores. Further studies warranted identify more unknown fraction (>98 %)

Language: Английский

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Nitrogen-Containing, Light-Absorbing Oligomers Produced in Aerosol Particles Exposed to Methylglyoxal, Photolysis, and Cloud Cycling

Environmental Science & Technology, Journal Year: 2018, Volume and Issue: 52(7), P. 4061 - 4071

Published: March 6, 2018

Aqueous methylglyoxal chemistry has often been implicated as an important source of oligomers in atmospheric aerosol. Here we report on chemical analysis brown carbon aerosol particles collected from cloud cycling/photolysis chamber experiments, where gaseous and methylamine interacted with glycine, ammonium, or methylammonium sulfate seed particles. Eighteen N-containing were identified the particulate phase by liquid chromatography/diode array detection/electrospray ionization high-resolution quadrupole time-of-flight mass spectrometry. Chemical formulas determined and, for 6 major oligomer products, MS2 fragmentation spectra used to propose tentative structures mechanisms. Electronic absorption calculated six product ab initio second order algebraic-diagrammatic-construction/density functional theory approach. For five structures, matching measured suggest that they are dominant light-absorbing species at their chromatographic retention times. Detected incorporated amines, expected, but also pyruvic acid, hydroxyacetone, significant quantities acetaldehyde. The finding ∼80% (by mass) detected contained acetaldehyde, a photolysis product, suggests daytime formation is dominated radical addition mechanisms involving CH3CO*. These evidently responsible enhanced browning observed during photolytic events.

Language: Английский

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Characterization of the light-absorbing properties, chromophore composition and sources of brown carbon aerosol in Xi'an, northwestern China

Atmospheric chemistry and physics, Journal Year: 2020, Volume and Issue: 20(8), P. 5129 - 5144

Published: April 30, 2020

Abstract. The impact of brown carbon aerosol (BrC) on the Earth's radiative forcing balance has been widely recognized but remains uncertain, mainly because relationships among BrC sources, chromophores and optical properties are poorly understood. In this work, light absorption chromophore composition were investigated for samples collected in Xi'an, northwestern China, from 2015 to 2016. Both Ångström exponent (AAE) mass efficiency (MAE) show distinct seasonal differences, which could be attributed differences sources BrC. Three groups light-absorbing organics found important chromophores, including compounds that have multiple peaks at wavelengths > 350 nm (12 polycyclic aromatic hydrocarbons their derivatives) a single peak < (10 nitrophenols nitrosalicylic acids 3 methoxyphenols). These measured contribute average about 1.1 % 3.3 methanol-soluble 365 summer winter, respectively, 7 5 times higher than corresponding fractions total organic carbon. resolved by positive matrix factorization (PMF) using these instead commonly used non-light-absorbing markers as model inputs. Our results vehicular emissions secondary formation major (∼ 70 %) spring, coal combustion fall, biomass burning become 80 dominates 60 summer.

Language: Английский

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Evidence for the Formation of Imidazole from Carbonyls and Reduced Nitrogen Species at the Individual Particle Level in the Ambient Atmosphere

Environmental Science & Technology Letters, Journal Year: 2020, Volume and Issue: 8(1), P. 9 - 15

Published: Oct. 27, 2020

While laboratory studies have demonstrated that aqueous reactions between carbonyls and reduced nitrogen species may contribute to the production of N-heterocycle brown carbon (BrC) such as imidazole, there is currently a lack evidence for this in atmosphere. We investigated mixing state carbonyls, ammonium, amines, imidazole (as surrogate BrC) cloud residual, interstitial, cloud-free particles by single-particle mass spectrometry. The results provide first ambient formation through ammonium/amines at individual particle level. key 60% are internally mixed with ammonium/amines. number fraction significantly enhanced ammonium (7.8%)/amines (26.7%), compared (1.4%) all particles. Furthermore, higher observed residual interstitial (2.9%) than (1.4%). This due enhancement amines and/or synergistic effect These findings extend current understanding evolution imidazole-based BrC.

Language: Английский

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Photolytic radical persistence due to anoxia in viscous aerosol particles

Nature Communications, Journal Year: 2021, Volume and Issue: 12(1)

Published: March 19, 2021

Abstract In viscous, organic-rich aerosol particles containing iron, sunlight may induce anoxic conditions that stabilize reactive oxygen species (ROS) and carbon-centered radicals (CCRs). laboratory experiments, we show mass loss, iron oxidation radical formation release from photoactive organic iron. Our results reveal a range of temperature relative humidity, including ambient conditions, control ROS build up CCR persistence in photochemically active, viscous particles. We find can attain high concentrations, altering chemistry exacerbating health hazards exposure. physicochemical kinetic model confirmed these results, implying does not penetrate such due to the combined effects fast reaction slow diffusion near particle surface, allowing photochemically-produced be effectively trapped an matrix.

Language: Английский

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Redox Potential and Cytotoxicity of N-heterocyclic Aromatic SOA from Indole oxidation in the Atmosphere

Atmospheric Environment, Journal Year: 2025, Volume and Issue: unknown, P. 121049 - 121049

Published: Jan. 1, 2025

Language: Английский

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Ammonium-Induced Stabilization of Imidazoles in Aerosol Particles

ACS Earth and Space Chemistry, Journal Year: 2025, Volume and Issue: unknown

Published: Feb. 13, 2025

Language: Английский

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