Secondary organic aerosol formation from mixed volatile organic compounds: Effect of RO2 chemistry and precursor concentration

npj Climate and Atmospheric Science, Journal Year: 2022, Volume and Issue: 5(1)

Published: Nov. 19, 2022

Abstract Secondary organic aerosol (SOA) plays a significant role in contributing to atmospheric fine particles, as well global air quality and climate. However, the current understanding of formation SOA its simulation is still highly uncertain due complexity precursor VOCs. In our study, different mixed VOC scenarios was investigated using 30 m 3 indoor smog chamber. By comparing individual scenarios, it found that yield from anthropogenic VOCs (AVOCs) can be positively (+83.9%) affected by coexisting AVOCs, while inhibited (−51.4%) presence isoprene, via OH scavenging effect. The cross-reactions peroxyl radical (RO 2 ) generated AVOCs were proved main contributor (up 39.0%) formation, highlighting importance RO + RʹO reactions scenarios. Meanwhile, gas-phase intermediates volatility categories also concentration, higher at lower concentrations larger contribution with volatility. Our study provides new insights into considering interactions between intermediate products

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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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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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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Radical chemistry and ozone production at a UK coastal receptor site

Atmospheric chemistry and physics, Journal Year: 2023, Volume and Issue: 23(22), P. 14393 - 14424

Published: Nov. 21, 2023

Abstract. OH, HO2, total and partially speciated RO2, OH reactivity (kOH′) were measured during the July 2015 ICOZA (Integrated Chemistry of OZone in Atmosphere) project that took place at a coastal site north Norfolk, UK. Maximum daily HO2 RO2 radical concentrations range 2.6–17 × 106, 0.75–4.2 108 2.3–8.0 molec. cm−3, respectively. kOH′ ranged from 1.7 to 17.6 s−1, with median value 4.7 s−1. data split by wind direction assess differences chemistry between air had passed over North Sea (NW–SE sectors) major urban conurbations such as London (SW sector). A box model using Master Chemical Mechanism (MCMv3.3.1) was reasonable agreement measurements, but it overpredicted observations NW–SE afternoon factor ∼ 2–3, although slightly better found for SW (factor 1.4–2.0 underprediction). The severely underpredicted both factors 8–9 on average. Measured levels measurement–model ratios displayed strong dependences NO mixing ratios, results suggesting peroxy is not well understood under high-NOx conditions. simultaneous measurement used derive experimental (i.e. observationally determined) budgets all species ROx + RO2). In air, budget could be closed daytime within uncertainty, rate destruction exceeded production, production greatly destruction, while opposite true RO2. analysis indicated missing sources, balanced, same imbalances air. For most severe high-NO best rates when coefficient reduced 5. photostationary-steady-state (PSS) calculation 35 %, whereas (∼ 15 %) instrumental uncertainty 26 % 2σ) situ ozone (P(Ox)) calculated ROx, NO2 compared MCM-modelled concentrations. MCM-calculated P(Ox) significantly measurement-calculated morning, degree underprediction scale NO.

Language: Английский

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Time-Resolved Molecular Characterization of Secondary Organic Aerosol Formed from OH and NO₃Radical Initiated Oxidation of a Mixture of Aromatic Precursors

Environmental Science & Technology, Journal Year: 2023, Volume and Issue: 57(31), P. 11572 - 11582

Published: July 27, 2023

Aromatic hydrocarbons (ArHCs) and oxygenated aromatic (ArHC–OHs) are emitted from a variety of anthropogenic activities important precursors secondary organic aerosol (SOA) in urban areas. Here, we analyzed compared the composition SOA formed oxidation mixture VOCs by OH NO3 radicals. The VOC was composed toluene (C7H8), p-xylene + ethylbenzene (C8H10), 1,3,5-trimethylbenzene (C9H12), phenol (C6H6O), cresol (C7H8O), 2,6-dimethylphenol (C8H10O), 2,4,6-trimethylphenol (C9H12O) proportion where were chosen to approximate day-time traffic-related emissions Delhi, alcohols make up 20% mixture. These prominent other cities as well, including those influenced biomass combustion. In experiments, large contributions CxHyOzN dimers (C15–C18) observed, corresponding fast formation within 15–20 min after start chemistry. Additionally, different combinations initial VOCs, highlighting importance exploring SOAs mixed systems. contrast, experiments with radicals yielded gradual mass formation, CxHyOz monomers (C6–C9) being dominant constituents. evolution time tracked degradation observed concurrent monomer species. rates dimer decomposition ∼2–3 times higher previously determined for α-pinene O3 SOA, dependence particle-phase reactions on oxidants. produced did not dramatically change over same frame. No measurable effects humidity SOA.

Language: Английский

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Oxygenated organic molecules produced by low-NO_x photooxidation of aromatic compounds: contributions to secondary organic aerosol and steric hindrance

Atmospheric chemistry and physics, Journal Year: 2024, Volume and Issue: 24(4), P. 2099 - 2112

Published: Feb. 19, 2024

Abstract. Oxygenated organic molecules (OOMs) produced by the oxidation of aromatic compounds are key components secondary aerosol (SOA) in urban environments. The steric effects substitutions and rings role reaction pathways altering OOM distributions remain unclear because lack systematic multi-precursor study over a wide range OH exposure. In this study, we conducted flow-tube experiments used nitrate adduct time-of-flight chemical ionization mass spectrometer (NO3--TOF-CIMS) to measure OOMs photooxidation six precursors under low-NOx conditions. For single precursors, detected peak clusters show an oxygen atom difference one or two, indicating involvement multi-step auto-oxidation alkoxy radical pathways. Multi-generation is needed explain diverse hydrogen numbers observed formulae. particular, for double-ring at higher exposure, multi-generation may have significantly enriched dimer results suggest that methyl precursor lead less fragmented products, while structure corresponds efficient formation closed-shell monomeric dimeric both highlighting significant molecular on formation. Naphthalene-derived however lower volatilities greater SOA contributions than other-type OOMs, which be more important initial particle growth. Overall, identified NO3--TOF-CIMS contributed up 30.0 % measured mass, suggesting oxygenated, undetected semi-volatile products. Our highlight roles progressive oxidation, substitution ring from need considered future model developments improve performance aerosol.

Language: Английский

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Chamber investigation of the formation and transformation of secondary organic aerosol in mixtures of biogenic and anthropogenic volatile organic compounds

Published: Jan. 6, 2022

Abstract. A comprehensive investigation of the photochemical secondary organic aerosol (SOA) formation and transformation in mixtures anthropogenic (o-cresol) biogenic (α-pinene isoprene) volatile compound (VOC) precursors presence NOx inorganic seed particles was conducted. Initial iso-reactivity used to enable direct comparison across systems, adjusting initial reactivity systems towards assumed dominant oxidant (OH). Comparing experiments conducted single precursor at various levels (referenced a nominal base case VOC reactivity) their binary ternary mixtures, we show that molecular interactions from mixing can be investigated discuss limitations interpretation. The observed average SOA yields descending order were found for α-pinene (32 ± 7 %), α-pinene/o-cresol (28 9 ½ (21 5 α-pinene/isoprene (16 1 ⅓ (15 4 o-cresol (13 3 α-pinene/o-cresol/isoprene (11 4%), o-cresol/isoprene (6 2 %) isoprene (0 0 %). We find clear suppression yield when it is mixed with isoprene, whilst addition may enhance mixture’s potential, however, difference too small unequivocal. system appeared increased compared calculated based on additivity, measured predicted comparable. However, where more than one contributes mass unclear whether changes potential are attributable physical or chemical interactions, since reference basis complex. Online offline composition particle volatility, water uptake “phase” behaviour measurements interpret introduced detailed elsewhere.

Language: Английский

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PM2.5-bound organosulfates in two Eastern Mediterranean cities: The dominance of isoprene organosulfates

Chemosphere, Journal Year: 2022, Volume and Issue: 297, P. 134103 - 134103

Published: Feb. 24, 2022

Language: Английский

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Low-NO-like Oxidation Pathway Makes a Significant Contribution to Secondary Organic Aerosol in Polluted Urban Air

Environmental Science & Technology, Journal Year: 2023, Volume and Issue: 57(37), P. 13912 - 13924

Published: Sept. 5, 2023

Anthropogenic pollutants can greatly mediate formation pathways and chemical compositions of secondary organic aerosol (SOA) in urban atmospheres. We investigated the molecular tracers for different types SOA PM2.5 under varying NO/NO2 conditions Guangzhou using source analysis particle-phase speciated organics obtained from an iodide ionization mass spectrometer with a Filter Inlet Gases AEROsols (FIGAERO-I-CIMS). Results show that low-NO-like (when < 0.2) explained ∼75% total measured FIGAERO-OA during regional transport periods, which was enriched more-oxidized C4-C6 non-nitrogenous compounds over ozone accumulation. Daytime high-NO chemistry played larger roles (38%) local pollution episodes, nitrates (ONs) nitrophenols increasing enhanced water content nitrate fraction. Nighttime NO3-initiated oxidation, characterized by monoterpene-derived ONs, accounted comparable percentages (10-12%) both two periods. Furthermore, presence organosulfates (OSs) improves understanding aqueous-phase processes production. Carbonyl-derived OSs exhibited preferential high acidity and/or abundant sulfate, correlated well SOA. Our results demonstrate importance ratios controlling compositions, as interactions between content, acidity, inorganic salts gas-to-particle partitioning condensable organics.

Language: Английский

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