Highly Oxygenated Organic Molecules (HOM) from Gas-Phase Autoxidation Involving Peroxy Radicals: A Key Contributor to Atmospheric Aerosol

Chemical Reviews, Journal Year: 2019, Volume and Issue: 119(6), P. 3472 - 3509

Published: Feb. 25, 2019

Highly oxygenated organic molecules (HOM) are formed in the atmosphere via autoxidation involving peroxy radicals arising from volatile compounds (VOC). HOM condense on pre-existing particles and can be involved new particle formation. thus contribute to formation of secondary aerosol (SOA), a significant ubiquitous component atmospheric known affect Earth's radiation balance. were discovered only very recently, but interest these has grown rapidly. In this Review, we define describe currently available techniques for their identification/quantification, followed by summary current knowledge mechanisms physicochemical properties. A main aim is provide common frame quite fragmented literature studies. Finally, highlight existing gaps our understanding suggest directions future research.

Language: Английский

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New Particle Formation in the Atmosphere: From Molecular Clusters to Global Climate

Journal of Geophysical Research Atmospheres, Journal Year: 2019, Volume and Issue: 124(13), P. 7098 - 7146

Published: June 25, 2019

Abstract New particle formation (NPF) represents the first step in complex processes leading to of cloud condensation nuclei. Newly formed nanoparticles affect human health, air quality, weather, and climate. This review provides a brief history, synthesizes recent significant progresses, outlines challenges future directions for research relevant NPF. developments include emergence state‐of‐the‐art instruments that measure prenucleation clusters newly nucleated down about 1 nm; systematic laboratory studies multicomponent nucleation systems, including collaborative experiments conducted Cosmics Leaving Outdoor Droplets chamber at CERN; observations NPF different types forests, extremely polluted urban locations, coastal sites, polar regions, high‐elevation sites; improved theories parameterizations account atmospheric models. The lack understanding fundamental chemical mechanisms responsible aerosol growth under diverse environments, effects SO 2 NO x on NPF, contribution anthropogenic organic compounds It is also critical develop can detect composition particles from 3 20 nm improve represent over wide range conditions precursor, temperature, humidity.

Language: Английский

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Accretion Product Formation from Self‐ and Cross‐Reactions of RO₂ Radicals in the Atmosphere

Angewandte Chemie International Edition, Journal Year: 2018, Volume and Issue: 57(14), P. 3820 - 3824

Published: Feb. 1, 2018

Abstract Hydrocarbons are emitted into the Earth's atmosphere in very large quantities by human and biogenic activities. Their atmospheric oxidation processes almost exclusively yield RO 2 radicals as reactive intermediates whose fate is not yet fully unraveled. Herein, we show that gas‐phase reactions of two produce accretion products composed carbon backbone both reactants. The rates for product formation high bearing functional groups, competing with those corresponding NO HO . This pathway, which has been considered modelling processes, can be important, or even dominant, all areas atmosphere. Moreover, vapor pressure formed remarkably low, characterizing them an effective source secondary organic aerosol.

Language: Английский

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Formation of highly oxygenated organic molecules from aromatic compounds

Atmospheric chemistry and physics, Journal Year: 2018, Volume and Issue: 18(3), P. 1909 - 1921

Published: Feb. 9, 2018

Abstract. Anthropogenic volatile organic compounds (AVOCs) often dominate the urban atmosphere and consist to a large degree of aromatic hydrocarbons (ArHCs), such as benzene, toluene, xylenes, trimethylbenzenes, e.g., from handling combustion fuels. These are important precursors for formation secondary aerosol. Here we show that oxidation aromatics with OH leads subsequent autoxidation chain reaction forming highly oxygenated molecules (HOMs) an O : C ratio up 1.09. This is exemplified five single-ring ArHCs (benzene, o-/m-/p-xylene, mesitylene (1,3,5-trimethylbenzene) ethylbenzene), well two conjugated polycyclic (naphthalene biphenyl). We report elemental composition HOMs differences in patterns these ArHCs. A potential pathway presented discussed. hypothesize AVOCs may contribute substantially new particle events have been detected areas.

Language: Английский

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Atmospheric autoxidation is increasingly important in urban and suburban North America

Proceedings of the National Academy of Sciences, Journal Year: 2017, Volume and Issue: 115(1), P. 64 - 69

Published: Dec. 18, 2017

Gas-phase autoxidation-regenerative peroxy radical formation following intramolecular hydrogen shifts-is known to be important in the combustion of organic materials. The relevance this chemistry oxidation organics atmosphere has received less attention due, part, lack kinetic data at relevant temperatures. Here, we combine computational and experimental approaches investigate rate autoxidation for radicals (RO

Language: Английский

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Anthropogenic enhancements to production of highly oxygenated molecules from autoxidation

Proceedings of the National Academy of Sciences, Journal Year: 2019, Volume and Issue: 116(14), P. 6641 - 6646

Published: March 18, 2019

Atmospheric oxidation of natural and anthropogenic volatile organic compounds (VOCs) leads to secondary aerosol (SOA), which constitutes a major often dominant component atmospheric fine particulate matter (PM2.5). Recent work demonstrates that rapid autoxidation peroxy radicals (RO2) formed during VOC results in highly oxygenated molecules (HOM) efficiently form SOA. As NOx emissions decrease, the chemical regime atmosphere changes one RO2 becomes increasingly important, potentially increasing PM2.5, while oxidant availability driving formation rates simultaneously declines, possibly slowing regional PM2.5 formation. Using suite situ aircraft observations laboratory studies HOM, together with detailed molecular mechanism, we show although an archetypal biogenic system more competitive as decreases, absolute HOM production decrease due reductions, leading overall positive coupling between localized SOA from autoxidation. This effect is observed Atlanta, Georgia, urban plume where enhanced presence elevated NO, predictions for Guangzhou, China, HOM-RO2 coincides increases NO 1990 2010. These suggest added benefits abatement strategies come emission reductions have implications aerosol-climate interactions global resulting since preindustrial era.

Language: Английский

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Multi-generation OH oxidation as a source for highly oxygenated organic molecules from aromatics

Atmospheric chemistry and physics, Journal Year: 2020, Volume and Issue: 20(1), P. 515 - 537

Published: Jan. 15, 2020

Abstract. Recent studies have recognised highly oxygenated organic molecules (HOMs) in the atmosphere as important formation of secondary aerosol (SOA). A large number focused on HOM from oxidation biogenically emitted monoterpenes. However, anthropogenic vapours has so far received much less attention. Previous identified importance aromatic volatile compounds (VOCs) for SOA formation. In this study, we investigated several compounds, benzene (C6H6), toluene (C7H8), and naphthalene (C10H8), their potential to form HOMs upon reaction with hydroxyl radicals (OH). We performed flow tube experiments all three VOCs detail Jülich Plant Atmosphere Chamber (JPAC). JPAC, also response NOx seed aerosol. Using a nitrate-based chemical ionisation mass spectrometer (CI-APi-TOF), observed reactor first OH attack. naphthalene, which were injected at lower concentrations, multi-generation seemed impact composition. tested more system allowed studying longer residence times. The results showed that apparent molar yield under our experimental conditions varied 4.1 % 14.0 %, strong dependence concentration, indicating majority formed through multiple OH-oxidation steps. composition spectrum supported hypothesis. By injecting only phenol into chamber, found cannot be solely responsible experiments. When was added changed many nitrogen-containing products CI-APi-TOF. Upon injection, loss rate higher than predicted by irreversible condensation, suggesting some undetected intermediates condensed onto aerosol, is line hypothesis oxidation. Based results, conclude systems strongly depend VOC concentration are needed fully understand effect and, consequently, SOA. suggest chamber may explain part variability yields reported literature advise monitoring future studies.

Language: Английский

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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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The Synergistic Role of Sulfuric Acid, Bases, and Oxidized Organics Governing New‐Particle Formation in Beijing

Geophysical Research Letters, Journal Year: 2021, Volume and Issue: 48(7)

Published: March 22, 2021

Abstract Intense and frequent new particle formation (NPF) events have been observed in polluted urban environments, yet the dominant mechanisms are still under debate. To understand key species governing processes of NPF we conducted comprehensive measurements downtown Beijing during January–March, 2018. We performed detailed analyses on sulfuric acid cluster composition budget, as well chemical physical properties oxidized organic molecules (OOMs). Our results demonstrate that fast clustering (H 2 SO 4 ) base triggered events, OOMs further helped grow newly formed particles toward climate‐ health‐relevant sizes. This synergistic role H , species, is likely representative environments where abundant usually co‐exist, with moderately low volatility when produced high NO x concentrations.

Language: Английский

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Evaluating the sensitivity of radical chemistry and ozone formation to ambient VOCs and NO<sub><i>x</i></sub> in Beijing

Atmospheric chemistry and physics, Journal Year: 2021, Volume and Issue: 21(3), P. 2125 - 2147

Published: Feb. 12, 2021

Abstract. Measurements of OH, HO2, complex RO2 (alkene- and aromatic-related RO2) total radicals taken during the integrated Study AIR Pollution PROcesses in Beijing (AIRPRO) campaign central summer 2017, alongside observations OH reactivity, are presented. The concentrations were elevated, with reaching up to 2.8×107moleculecm-3, HO2 peaking at 1×109moleculecm-3 concentration 5.5×109moleculecm-3. reactivity (k(OH)) peaked 89 s−1 night, a minimum afternoon ≈22s-1 on average. An experimental budget analysis, which rates production destruction compared, highlighted that although sources sinks balanced under high NO concentrations, exceeded known (by 15 ppbv h−1) very low conditions (<0.5 ppbv) experienced afternoons, demonstrating missing source consistent previous studies volatile organic compound (VOC) emissions loadings. Under highest mixing ratios (104 ppbv), rate by ≈50ppbvh-1, whilst same rate, indicating net propagation may be substantially slower than assumed. If just 10 % propagate upon reaction NO, budgets could closed but this lower revealed sink was similar magnitude source. A detailed box model incorporated latest Master Chemical Mechanism (MCM3.3.1) reproduced observed well over-predicted (<1 under-predicted (both fraction other types we classify as simple most significantly concentrations. also k(OH) consistently ≈10s-1 across all NOx levels, highlighting good agreement for fortuitous due cancellation terms its budget. Including heterogeneous loss aerosol surfaces did reduce modelled line only <0.3 ppbv. inclusion Cl atoms, formed from photolysis nitryl chloride, enhanced several mornings when atom calculated exceed 1×104atomscm-3 reconcile measured these times. However, mornings, lower, large under-predictions remained. Furthermore, chemistry not enhance beyond first few hours after sunrise so unable resolve under-prediction times day. Model scenarios, VOC included an additional converted RO2, sensitive choice product. level simple) improved if larger species able undergo followed isomerisation reactions reforming species, before eventually generating HO2. In work α-pinene-derived used example. simulation, underestimated uncertainty, regards present they form (HO2 directly or another species), leads over order less O3 predicted peroxy This demonstrates indeed needs understood accurately simulate ozone environments such Beijing, where multifunctional VOCs likely present.

Language: Английский

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