Chemical characterisation of benzene oxidation products under high- and low-NO<sub><i>x</i></sub> conditions using chemical ionisation mass spectrometry

Atmospheric chemistry and physics, Journal Year: 2021, Volume and Issue: 21(5), P. 3473 - 3490

Published: March 5, 2021

Abstract. Aromatic hydrocarbons are a class of volatile organic compounds associated with anthropogenic activity and make up significant fraction urban compound (VOC) emissions that contribute to the formation secondary aerosol (SOA). Benzene is one most abundant species emitted from vehicles, biomass burning industry. An iodide time-of-flight chemical ionisation mass spectrometer (ToF-CIMS) nitrate ToF-CIMS were deployed at Jülich Plant Atmosphere Chamber as part series experiments examining benzene oxidation by OH under high- low-NOx conditions, where range products detected. The scheme detects many high masses, ranging intermediate (IVOCs) extremely low (ELVOCs), including C12 dimers. In comparison, very few C≥6 O≥8 detected scheme, which more IVOCs semi-volatile (SVOCs) but ELVOCs (LVOCs). A total 132 195 CHO CHON in low- high-NOx respectively. Ring-breaking dominant signal 21 26 listed Master Chemical Mechanism (MCM) time highly oxidised (O≥6) ring-retaining (C6 double-bond equivalent = 4) equilibrate quickly, characterised square form profile, compared MCM ring-breaking increase throughout oxidation, exhibiting sawtooth profiles. Under all formulae attributed radical termination reactions first-generation products, auto-oxidation observed. Several N-containing either or also observed conditions. Hierarchical cluster analysis finds four clusters, two describe photo-oxidation. Cluster 2 shows negative dependency on NO2/NOx ratio, indicating it sensitive NO concentration thus likely contain addition alkoxy-derived products. This has highest average carbon state (OSC‾) lowest number. Where nitrogen present member 2, oxygen number even, expected for contrast, 1 no ratio so NO2 peroxy-derived contains fewer fragmented species, higher OSC‾ lower than an odd atoms. suggests clustering have features pertaining distinct regimes, example, perturbations, coupled priori knowledge, can provide insight into identification potential functionality.

Language: Английский

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Synergetic effects of NH<sub>3</sub> and NO<sub><i>x</i></sub> on the production and optical absorption of secondary organic aerosol formation from toluene photooxidation

Atmospheric chemistry and physics, Journal Year: 2021, Volume and Issue: 21(23), P. 17759 - 17773

Published: Dec. 6, 2021

Abstract. NH3 is the most important alkaline gas in atmosphere and one of key species affecting behaviors atmospheric aerosols. However, impact on secondary organic aerosol (SOA) formation remains poorly understood, especially dynamic evolution chemical compositions SOA process. In this study, a series chamber experiments were performed to probe individual common effects NOx toluene through OH photooxidation. The characterized using Aerodyne high-resolution time-of-flight mass spectrometer (AMS). yield increased from 28.1 % absence 34.7 presence but decreased 19.5 NOx. highest 42.7 lowest carbon oxidation state (OSC) occurred both NOx, indicating that higher-volatility products formed could partition into particle phase when was added. This resulted synergetic effect co-existed. heterogeneous reaction main pathway by which participated photooxidation also observed optical absorption. A peak at 280 nm, characteristic organonitrogen imidazole compounds, NH3, its intensity added chamber. work improves our understanding how synergistic interactions between influence offers new insights mitigating haze pollution.

Language: Английский

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Recent advances in mass spectrometry techniques for atmospheric chemistry research on molecular‐level

Mass Spectrometry Reviews, Journal Year: 2023, Volume and Issue: 43(5), P. 1091 - 1134

Published: July 13, 2023

Abstract The Earth's atmosphere is composed of an enormous variety chemical species associated with trace gases and aerosol particles whose composition chemistry have critical impacts on the climate, air quality, human health. Mass spectrometry analysis as a powerful popular analytical technique has been widely developed applied in atmospheric for decades. allows effective detection, identification, quantification broad range organic inorganic high sensitivity resolution. In this review, we summarize recently mass techniques, methods, applications research past several years molecular‐level. Specifically, new developments ion‐molecule reactors, various soft ionization unique coupling separation techniques are highlighted. laboratory studies field measurements focused improving detection limits traditional emerging volatile compounds, characterizing multiphase highly oxygenated molecules, monitoring particle bulk surface compositions.

Language: Английский

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Anthropogenic Volatile Organic Compound (AVOC) Autoxidation as a Source of Highly Oxygenated Organic Molecules (HOM)

The Journal of Physical Chemistry A, Journal Year: 2021, Volume and Issue: 125(41), P. 9027 - 9039

Published: Oct. 7, 2021

Gas-phase hydrocarbon autoxidation is a rapid pathway for the production of in situ aerosol precursor compounds. It highway to molecular growth and lowering vapor pressure, it produces hydrogen-bonding functional groups that allow molecule bind into substrate. crucial process formation atmospheric secondary organic (SOA). Recently, gas-phase several volatile compounds (VOC) has been shown yield highly oxygenated molecules (HOM). Most details on HOM have obtained from biogenic monoterpenes their surrogates, with cyclic structures double bonds both found strongly facilitate formation, especially ozonolysis reactions. Similar structural features common aromatic observed high yields, despite lack appreciable O

Language: Английский

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Highly oxygenated organic molecules produced by the oxidation of benzene and toluene in a wide range of OH exposure and NO<sub><i>x</i></sub> conditions

Atmospheric chemistry and physics, Journal Year: 2021, Volume and Issue: 21(15), P. 12005 - 12019

Published: Aug. 11, 2021

Abstract. Oxidation of aromatic volatile organic compounds (VOCs) leads to the formation tropospheric ozone and secondary aerosol, for which gaseous oxygenated products are important intermediates. We show, herein, experimental results highly molecules (HOMs) produced by oxidation benzene toluene in a wide range OH exposure NOx conditions. The suggest that multigeneration plays an role product distribution, likely proceeds more preferably via H subtraction than addition early generation from light aromatics. More present our study previous flow tube studies, highlighting impact conditions on distributions. dimeric products, however, was suppressed might be unfavorable under high low oxidation. Under high-NOx conditions, nitrogen-containing multifunctional formed, while other HOMs is suppressed. Products containing two nitrogen atoms become as level increases, concentrations these depend significantly NO2. peroxyacyl nitrates, implying prolonged effective lifetime RO2 facilitates regional pollution. Our call further investigation roles high-NO2 VOCs.

Language: Английский

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Enhancing effect of NO2 on the formation of light-absorbing secondary organic aerosols from toluene photooxidation

The Science of The Total Environment, Journal Year: 2021, Volume and Issue: 794, P. 148714 - 148714

Published: June 27, 2021

Language: Английский

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Chemical ionization mass spectrometry utilizing ammonium ions (NH₄⁺ CIMS) for measurements of organic compounds in the atmosphere

Atmospheric measurement techniques, Journal Year: 2022, Volume and Issue: 15(24), P. 7353 - 7373

Published: Dec. 22, 2022

Abstract. We describe the characterization and field deployment of chemical ionization mass spectrometry (CIMS) using a recently developed focusing ion-molecule reactor (FIMR) ammonium–water cluster (NH4+⋅H2O) as reagent ion (denoted NH4+ CIMS). show that NH4+⋅H2O is highly versatile for measurements wide range oxygenated organic compounds. The major product with produced via ligand-switching reactions. Other ions (e.g., protonated ion, NH4+⋅H2O, H3O+, H3O+⋅H2O) are also produced, but minor fractions most compounds studied here. instrument sensitivities (ion counts per second part billion by volume, cps ppbv−1) distributions strongly dependent on operating conditions, including ratio ammonia (NH3) H2O flows drift voltages, which should be carefully selected to ensure predominant optimize sensitivities. For monofunctional analytes, chemistry exhibits high sensitivity (i.e., >1000 ketones, moderate between 100 1000 aldehydes, alcohols, acids, monoterpenes, low 10 isoprene C1 C2 organics, negligible <10 reduced aromatics. instrumental analytes depend binding energy analyte–NH4+ cluster, can estimated voltage scanning. This offers possibility constrain no calibration standards exist. was deployed in RECAP campaign (Re-Evaluating Chemistry Air Pollutants California) Pasadena, California, during summer 2021. Measurement comparisons against co-located spectrometers CIMS capable detecting from classes. valuable quantification volatile (VOCs) complementary existing schemes.

Language: Английский

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Effects of Relative Humidity and Photoaging on the Formation, Composition, and Aging of Ethylbenzene SOA: Insights from Chamber Experiments on Chlorine Radical-Initiated Oxidation of Ethylbenzene

ACS Earth and Space Chemistry, Journal Year: 2024, Volume and Issue: 8(4), P. 675 - 688

Published: April 1, 2024

The oxidation of alkyl-substituted aromatic molecules produces oxygenated volatile organic compounds (OVOCs) and secondary aerosols (SOA) that are major components ambient urban air. Despite their ubiquity, the impacts variable conditions, such as relative humidity (RH) actinic exposure, on physicochemical processes contribute to SOA formation still subject ongoing research refinement. In this work, we perform laboratory environmental chamber experiments use an I– FIGAERO–CIMS examine molecular composition high-NOx ethylbenzene products in response varied (dry 40% RH, 60% RH) during either dark aging or photoaging (with ∼354 nm UV-A lights). Experiments performed a mixed Cl OH radical environment. Compared chemistry, chemistry forms greater amount nitroaromatic by enhancing benzaldehyde phenolic H abstraction while also forming several organochlorine may serve tracers for which C2H3ClO2 (presumably chloroacetic acid) appears be most consistent stable. Organonitrate (ON) undergo hydrolytic photolytic losses. Nitroaromatic condense more efficiently under humid presumably due relatively high solubility hydroxy dihydroxy molecules, but do not appear stable condensed phase photoaging. Small oxygenates make up substantial portion increases at RH (due increased uptake) photolysis fragmentation). Photoaging initially leads degree oligomerization before continued eventual loss these other compounds. Our results show substantially impact evolution many gas- particle-phase species produced suggest factors can exert strong control over evolution, particularly regions.

Language: Английский

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Oxidative destruction of chlorinated persistent organic pollutants by hydroxyl radicals via ozone and UV light irradiation

Green Chemistry, Journal Year: 2023, Volume and Issue: 25(23), P. 9695 - 9704

Published: Jan. 1, 2023

We demonstrate a simple, and economically feasible method for oxidative degradation of organochlorinated compounds persistent organic pollutants at room temperature using inexpensive eco-friendly ozone gas under ultraviolet irradiation.

Language: Английский

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Molecular Characterization of Oxygenated Organic Molecules and Their Dominating Roles in Particle Growth in Hong Kong

Environmental Science & Technology, Journal Year: 2023, Volume and Issue: 57(20), P. 7764 - 7776

Published: May 8, 2023

Oxygenated organic molecules (OOMs) are critical intermediates linking volatile compound oxidation and secondary aerosol (SOA) formation. Yet, the understanding of OOM components, formation mechanism, impacts still limited, especially for urbanized regions with a cocktail anthropogenic emissions. Herein, ambient measurements OOMs were conducted at regional background site in South China 2018. The molecular characteristics revealed dominant nitrogen-containing products, influences different factors on composition state elucidated. Positive matrix factorization analysis resolved complex species to featured fingerprint from pathways. A new method was developed identify key functional groups OOMs, which successfully classified majority into carbonyls (8%), hydroperoxides (7%), nitrates (17%), peroxyl (10%), dinitrates (13%), aromatic ring-retaining (6%), terpenes (7%). volatility estimation improved based their identified used simulate growth process contributed by condensation those low-volatile OOMs. results demonstrate predominant role contributing sub-100 nm particle SOA highlight importance products multistep oxidation.

Language: Английский

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