Secondary organic aerosol formed by condensing anthropogenic vapours over China’s megacities

Nature Geoscience, Journal Year: 2022, Volume and Issue: 15(4), P. 255 - 261

Published: April 1, 2022

Language: Английский

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Organic Peroxides in Aerosol: Key Reactive Intermediates for Multiphase Processes in the Atmosphere

Chemical Reviews, Journal Year: 2023, Volume and Issue: 123(4), P. 1635 - 1679

Published: Jan. 11, 2023

Organic peroxides (POs) are organic molecules with one or more peroxide (−O–O−) functional groups. POs commonly regarded as chemically labile termination products from gas-phase radical chemistry and therefore serve temporary reservoirs for oxidative radicals (HOx ROx) in the atmosphere. Owing to their ubiquity, active gas-particle partitioning behavior, reactivity, key reactive intermediates atmospheric multiphase processes determining life cycle (formation, growth, aging), climate, health impacts of aerosol. However, there remain substantial gaps origin, molecular diversity, fate due complex nature dynamic behavior. Here, we summarize current understanding on POs, a focus identification quantification, state-of-the-art analytical developments, molecular-level formation mechanisms, chemical transformation pathways, well environmental impacts. We find that interactions SO2 transition metal ions generally fast PO pathways liquid water, lifetimes estimated be minutes hours, while hydrolysis is particularly important α-substituted hydroperoxides. Meanwhile, photolysis thermolysis likely minor sinks POs. These distinctly different fates, such reaction OH radicals, which highlights need understand By summarizing advances remaining challenges investigation propose future research priorities regarding fate,

Language: Английский

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Photo-oxidation of Aromatic Hydrocarbons Produces Low-Volatility Organic Compounds

Environmental Science & Technology, Journal Year: 2020, Volume and Issue: 54(13), P. 7911 - 7921

Published: June 9, 2020

To better understand the role of aromatic hydrocarbons in new-particle formation, we measured particle-phase abundance and volatility oxidation products following reaction with OH radicals. For this used thermal desorption an iodide-adduct Time-of-Flight Chemical-Ionization Mass Spectrometer equipped a Filter Inlet for Gases AEROsols (FIGAERO-ToF-CIMS). The measurements confirm that toluene naphthalene can contribute to initial growth newly formed particles. Toluene-derived (C7) have similar distribution α-pinene-derived (C10) products, while naphthalene-derived are much less volatile than those from or α-pinene; they thus stronger contributors growth. Rapid progression through multiple generations is more pronounced α-pinene, resulting but also favoring functional groups lower per added oxygen atom, such as hydroxyl carboxylic instead hydroperoxide groups. Under conditions typical polluted urban settings, may well nucleation smallest particles, whereas abundant alkyl benzenes overtake once particles grown beyond point where Kelvin effect strongly influences condensation driving force.

Language: Английский

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New Insights into the Radical Chemistry and Product Distribution in the OH-Initiated Oxidation of Benzene

Environmental Science & Technology, Journal Year: 2020, Volume and Issue: 54(21), P. 13467 - 13477

Published: Oct. 21, 2020

Emissions of aromatic compounds cause air pollution and detrimental health effects. Here, we explore the reaction kinetics products key radicals in benzene photo-oxidation. After initial OH addition with O2, effective production rates phenol bicyclic peroxy radical (BCP-peroxy) are experimentally constrained at 295 K to be 420 ± 80 370 70 s–1, respectively. These lead approximately 53% yield for 47% BCP-peroxy under atmospheric conditions. The NO produces hydroxy nitrate a branching ratio <0.2%, indicating efficient NOx recycling. Similarly, HO2 largely recycles HOx, producing corresponding alkoxy (BCP-oxy). Because presence C–C double bonds multiple functional groups, chemistry BCP-oxy other system is diverse. Experimental results suggest aldehydic H-shift ring-closure produce an epoxide functionality could competitive classic decomposition radicals. reactions potential sources highly oxygenated molecules. Finally, despite large number observed our study, unable account ∼20% carbon flow.

Language: Английский

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Experimental investigation into the volatilities of highly oxygenated organic molecules (HOMs)

Atmospheric chemistry and physics, Journal Year: 2020, Volume and Issue: 20(2), P. 649 - 669

Published: Jan. 20, 2020

Abstract. Secondary organic aerosol (SOA) forms a major part of the tropospheric submicron aerosol. Still, exact formation mechanisms SOA have remained elusive. Recently, newly discovered group oxidation products volatile compounds (VOCs), highly oxygenated molecules (HOMs), been proposed to be responsible for large fraction formation. To assess potential HOMs form and even take in new particle formation, knowledge their volatilities is essential. However, due exotic, partially unknown, structures, estimating volatility challenging. In this study, we performed set continuous flow chamber experiments, supported by box modelling, study HOMs, along with some less compounds, formed ozonolysis α-pinene, an abundant VOC emitted boreal forests. Along gaseous precursors, periodically injected inorganic seed into vary condensation sink (CS) low-volatility vapours. We monitored decrease gas phase response increasing CS, were able relate responses compounds. found that HOM monomers are mainly low volatility, small being semi-volatile. dimers all at least but probably extremely volatility; however, our method not directly distinguish between two. model terms carbon, hydrogen, oxygen nitrogen numbers. levels oxygenation correspond lower volatilities, as expected, steep than would expected based on many existing models such SIMPOL. The hydrogen number compound also predicted its independently carbon number, higher numbers corresponding volatilities. This can explained functional groups making up molecule: high associated with, e.g. hydroxy groups, which more than, carbonyls, number. presented should applicable systems other α-pinene ozonolysis, different loadings, order ranges.

Language: Английский

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Oxygenated products formed from OH-initiated reactions of trimethylbenzene: autoxidation and accretion

Atmospheric chemistry and physics, Journal Year: 2020, Volume and Issue: 20(15), P. 9563 - 9579

Published: Aug. 14, 2020

Abstract. Gas-phase oxidation pathways and products of anthropogenic volatile organic compounds (VOCs), mainly aromatics, are the subject intensive research, with attention paid to their contributions secondary aerosol (SOA) formation potentially new particle (NPF) in urban atmosphere. In this study, a series OH-initiated experiments trimethylbenzene (TMB, C9H12) including 1,2,4-TMB, 1,3,5-TMB, 1,2,3-TMB, 1,2,4-(methyl-D3)-TMBs (C9H9D3) were investigated an flow reactor (OFR) absence presence NOx. Products measured using suite state-of-the-art instruments, i.e. nitrate-based chemical ionization–atmospheric pressure interface time-of-flight mass spectrometer (nitrate CI-APi-TOF), iodide-adduct ionization (iodide CI-TOF) equipped Filter Inlet for Gases AEROsols (FIGAERO), Vocus proton-transfer-reaction (Vocus PTR). A large number C9 1–11 oxygen atoms C18 presumably formed from dimerization peroxy radicals observed, hinting at extensive existence autoxidation accretion reaction reactions TMBs. Oxidation deuterium different methyl substituents then used as molecular basis propose potential pathways. Accretion is most significant aromatics meta-substituents least ortho-substituents if size substituted groups identical. The NOx would suppress highly oxygenated molecules (HOMs) enhance organonitrates even dinitrate compounds. Our results show that TMB much more diverse could be than current mechanisms predict.

Language: Английский

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Contribution of Atmospheric Oxygenated Organic Compounds to Particle Growth in an Urban Environment

Environmental Science & Technology, Journal Year: 2021, Volume and Issue: 55(20), P. 13646 - 13656

Published: Sept. 29, 2021

Gas-phase oxygenated organic molecules (OOMs) can contribute substantially to the growth of newly formed particles. However, characteristics OOMs and their contributions particle rate are not well understood in urban areas, which have complex anthropogenic emissions atmospheric conditions. We performed long-term measurement gas-phase Beijing during 2018–2019 using nitrate-based chemical ionization mass spectrometry. OOM concentrations showed clear seasonal variations, with highest summer lowest winter. Correspondingly, calculated rates due condensation were summer, followed by spring, autumn, One prominent feature this environment was a high fraction (∼75%) nitrogen-containing OOMs. These contributed only 50–60% total led condensation, owing slightly higher volatility than non-nitrate By comparing observed rates, we that sulfuric acid its clusters main contributors sub-3 nm particles, significantly promoting 3–25 In wintertime Beijing, however, there missing particles above 3 nm, remain be further investigated.

Language: Английский

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Biomass-burning-derived particles from a wide variety of fuels – Part 2: Effects of photochemical aging on particle optical and chemical properties

Atmospheric chemistry and physics, Journal Year: 2020, Volume and Issue: 20(14), P. 8511 - 8532

Published: July 22, 2020

Abstract. Particles in smoke emitted from biomass combustion have a large impact on global climate and urban air quality. There is limited understanding of how particle optical properties – especially the contributions black carbon (BC) brown (BrC) evolve with photochemical aging smoke. We analyze evolution chemical composition particles produced wide variety fuels, largely western United States. The photochemically aged reaction chamber over atmospheric-equivalent timescales ranging 0.25 to 8 d. Various aerosol (e.g., single-scatter albedo, wavelength dependence absorption, BC mass absorption coefficient, MACBC) evolved aging, specific dependent initial conditions. coatings (the so-called lensing effect) was small, even after aging. BrC absorptivity (MACBrC) varied between individual burns but decreased consistently at longer times; generally increased observed changes result combination secondary organic (SOA) production heterogeneous oxidation primary OA mass, SOA being major driver changes. time, reflecting both formation precursors having range lifetimes respect OH evolving environment within chamber. Although decreases dilution-corrected may actually increase SOA. These experimental results provide context for interpretation ambient observations biomass-combustion-derived plumes.

Language: Английский

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Evaluation of the chemical composition of gas- and particle-phase products of aromatic oxidation

Atmospheric chemistry and physics, Journal Year: 2020, Volume and Issue: 20(16), P. 9783 - 9803

Published: Aug. 21, 2020

Abstract. Aromatic volatile organic compounds (VOCs) are key anthropogenic pollutants emitted to the atmosphere and important for both ozone secondary aerosol (SOA) formation in urban areas. Recent studies have indicated that aromatic hydrocarbons may follow previously unknown oxidation chemistry pathways, including autoxidation can lead of highly oxidised products. In this study we evaluate gas- particle-phase ions measured by online mass spectrometry during hydroxyl radical substituted C9-aromatic isomers (1,3,5-trimethylbenzene, 1,2,4-trimethylbenzene, propylbenzene isopropylbenzene) a polyaromatic hydrocarbon (1-methylnaphthalene) under low- medium-NOx conditions. A time-of-flight chemical ionisation spectrometer (ToF-CIMS) with iodide–anion was used filter inlet gases aerosols (FIGAERO) detection products particle phase, while Vocus proton-transfer-reaction (Vocus-PTR-MS) gas phase. The signal product observed spectra were compared different precursors experimental majority spectral phases comes from which common all precursors, though distributions distinct VOCs. Gas- composition one another. Ions corresponding contained near-explicit phase Master Chemical Mechanism (MCM version 3.3.1) utilised as benchmark current scientific understanding, comparison these observations shows MCM is missing range its mechanism. bulk ring scission ions, large proportion more than reported undergone further form oxygenated molecules (HOMs). Under perturbation OH increased NOx, contribution HOM-ion signals remains elevated precursors. Up 43 % ring-retaining HOMs; most aromatics. Unique minor component systems, many dominant ion formulae concurrent other highlighting challenges utilising marker SOA.

Language: Английский

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Multigeneration Production of Secondary Organic Aerosol from Toluene Photooxidation

Environmental Science & Technology, Journal Year: 2021, Volume and Issue: 55(13), P. 8592 - 8603

Published: June 17, 2021

Photooxidation of volatile organic compounds (VOCs) produces secondary aerosol (SOA) and light-absorbing brown carbon (BrC) via multiple reaction steps/pathways, reflecting significant chemical complexity relevant to gaseous oxidation subsequent gas-to-particle conversion. Toluene is an important VOC under urban conditions, but the fundamental mechanism leading SOA formation remains uncertain. Here, we elucidate multigeneration production from toluene by simultaneously tracking evolutions gas-phase in a chamber. Large size increase browning monodisperse sub-micrometer seed particles occur shortly after initiating hydroxyl radical (OH) at 10–90% relative humidity (RH). The evolution products properties (size/density/optical properties) speciation aerosol-phase indicate that growth result earlier generation consisting dominantly dicarbonyl carboxylic functional groups. While dicarbonyls engage aqueous reactions yield nonvolatile oligomers nitrogen heterocycles/heterochains (in presence NH3) high RH, acids contribute carboxylates ionic dissociation or acid–base wide RH range. We conclude contributes importantly SOA/BrC because their prompt yields photooxidation unique functionalities for participation reactions.

Language: Английский

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