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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Gas-Phase Reactions of Isoprene and Its Major Oxidation Products

Chemical Reviews, Journal Year: 2018, Volume and Issue: 118(7), P. 3337 - 3390

Published: March 9, 2018

Isoprene carries approximately half of the flux non-methane volatile organic carbon emitted to atmosphere by biosphere. Accurate representation its oxidation rate and products is essential for quantifying influence on abundance hydroxyl radical (OH), nitrogen oxide free radicals (NO x), ozone (O3), and, via formation highly oxygenated compounds, aerosol. We present a review recent laboratory theoretical studies pathways isoprene initiated addition OH, O3, nitrate (NO3), chlorine atom. From this review, recommendation nearly complete gas-phase mechanism major developed. The compiled with aims providing an accurate flow while allowing quantification impact emissions HO x NO concentrations yields known be involved in condensed-phase processes. Finally, simplified (reduced) developed use chemical transport models that retains chemistry required accurately simulate under conditions where it occurs atmosphere-above forested regions remote from large emissions.

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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Rapid growth of organic aerosol nanoparticles over a wide tropospheric temperature range

Proceedings of the National Academy of Sciences, Journal Year: 2018, Volume and Issue: 115(37), P. 9122 - 9127

Published: Aug. 28, 2018

Significance Aerosol particles can form and grow by gas-to-particle conversion eventually act as seeds for cloud droplets, influencing global climate. Volatile organic compounds emitted from plants are oxidized in the atmosphere, resulting products drive particle growth. We measure growth biogenic vapors with a well-controlled laboratory setup over wide range of tropospheric temperatures. While higher temperatures lead to increased reaction rates concentrations highly molecules, lower allow additional, but less oxidized, species condense. rapid full temperature our study, indicating that organics play an important role aerosol throughout troposphere. Our finding will help sharpen predictions models.

Language: Английский

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Accretion Product Formation from Ozonolysis and OH Radical Reaction of α-Pinene: Mechanistic Insight and the Influence of Isoprene and Ethylene

Environmental Science & Technology, Journal Year: 2018, Volume and Issue: 52(19), P. 11069 - 11077

Published: Sept. 7, 2018

α-Pinene (C10H16) represents one of the most important biogenic emissions in atmosphere. Its oxidation products can significantly contribute to secondary organic aerosol (SOA) formation. Here, we report on formation mechanism C19 and C20 accretion from α-pinene oxidation, which are believed be efficient SOA precursors. Measurements have been performed a free-jet flow system. Detection RO2 radicals was carried out by recent mass spectrometric techniques using different ionization schemes. Observed C10-RO2 ozonolysis were O,O-C10H15(O2) xO2 with x = 0, 1, 2, 3 OH radical reaction HO-C10H16(O2)αO2 α 2. All detected explained via + R'O2 → ROOR' O2 starting measured radicals. We speculate that formed an analogous way assuming CH2O elimination. Addition isoprene (C5H8), producing C5-RO2 radicals, leads C15 cross-reactions This process is competing C19/C20 pure oxidation. A similar behavior has observed for ethylene additives form C12 products. In atmosphere, complex product spectrum self- available expected. Modeling atmospheric conditions revealed only reduced factor 1.2 or 3.6 isoprene-dominated environments 2- 15-fold concentration over α-pinene, respectively, as present forested areas.

Language: Английский

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Significant changes in the chemical compositions and sources of PM2.5 in Wuhan since the city lockdown as COVID-19

The Science of The Total Environment, Journal Year: 2020, Volume and Issue: 739, P. 140000 - 140000

Published: June 5, 2020

Language: Английский

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Tropospheric Ozone Assessment Report

Elementa Science of the Anthropocene, Journal Year: 2020, Volume and Issue: 8(1)

Published: Jan. 1, 2020

Our understanding of the processes that control burden and budget tropospheric ozone has changed dramatically over last 60 years. Models are key tools used to understand these changes, underscore there many important in controlling budget. In this critical review, we assess our evolving processes, both physical chemical. We review model simulations from International Global Atmospheric Chemistry Climate Model Intercomparison Project Modelling Initiative changes its 1850 2010. Analysis data indicates been significant growth 2000 (approximately 43 ± 9%) but smaller between 1960 16 10%) models simulate burdens well within recent satellite estimates. The budgets indicate net chemical production troposphere plateaued 1990s not since then inspite increases burden. There a shift being greatest northern mid high latitudes tropics, driven by regional evolution precursor emissions. An analysis through 21st century, as simulated Phase 5 models, reveals large source uncertainty associated with themselves (i.e., way they ozone). This structural is near term (two three decades), emissions scenarios dominate longer (2050–2100) ozone. intrinsic prevents robust predictions near-term burden, how progress can be made reduce limitation.

Language: Английский

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Quantitative constraints on autoxidation and dimer formation from direct probing of monoterpene-derived peroxy radical chemistry

Proceedings of the National Academy of Sciences, Journal Year: 2018, Volume and Issue: 115(48), P. 12142 - 12147

Published: Nov. 9, 2018

Organic peroxy radicals (RO 2 ) are key intermediates in the atmospheric degradation of organic matter and fuel combustion, but to date, few direct studies specific RO complex reaction systems exist, leading large gaps our understanding their fate. We show, using direct, speciated measurements a suite gas-phase dimers from O 3 -initiated oxidation α-pinene, that ∼150 gaseous (C 16–20 H 24–34 4–13 primarily formed through cross-reactions, with typical rate constant 0.75–2 × 10 −12 cm molecule −1 s lower-limit dimer formation branching ratio 4%. These findings imply yield varies strongly nitric oxide (NO) concentrations, at least 0.2–2.5% by mole (0.5–6.6% mass) for conditions forested regions low moderate anthropogenic influence (i.e., ≤50-parts per trillion NO). Given very volatility, C provide potentially important medium initial particle formation, alone can explain 5–60% α-pinene secondary aerosol mass yields measured atmospherically relevant loadings. The responses , dimers, highly oxygenated multifunctional compounds (HOM) reacted concentration NO an average ∼20% primary OH 10% ozonolysis autoxidize 3–10 ≥1 respectively, confirming both pathways produce HOM efficiently, even higher concentrations urban areas. Thus, autoxidation ubiquitous sources low-volatility capable driving growth.

Language: Английский

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Experimental budgets of OH, HO<sub>2</sub>, and RO<sub>2</sub> radicals and implications for ozone formation in the Pearl River Delta in China 2014

Atmospheric chemistry and physics, Journal Year: 2019, Volume and Issue: 19(10), P. 7129 - 7150

Published: May 29, 2019

Abstract. Hydroxyl (OH) and peroxy radicals (HO2 RO2) were measured in the Pearl River Delta, which is one of most polluted areas China, autumn 2014. The radical observations complemented by measurements OH reactivity (inverse lifetime) a comprehensive set trace gases including carbon monoxide (CO), nitrogen oxides (NOx=NO, NO2) volatile organic compounds (VOCs). was range from 15 to 80 s−1, about 50 % unexplained reactants. In 3 weeks campaign, maximum median concentrations 4.5×106 cm−3 for at noon 3×108 2.0×108 HO2 RO2, respectively, early afternoon. completeness daytime made it possible carry out experimental budget analyses all (OH, HO2, their sum (ROx). loss rates OH, RO2 reached values between 10 ppbv h−1 during daytime. largest fraction this can be attributed interconversion reactions while real rate ROx remained below h−1. Within uncertainties, destruction are balanced respective production rates. case could closed attributing missing unmeasured VOCs. Thus, presumption existence VOCs supported measurements. Although closure greatly improved additional VOCs, significant imbalance afternoon remains, indicating sink. morning compensated quantified sources photolysis (HONO O3), ozonolysis alkenes, recycling (HO2+NO). afternoon, however, indicates source 4 6 diurnal variation shows similar pattern that sink so both largely compensate each other budget. These suggest chemical mechanism converts without involvement NO, increasing 5.3 7.4 on average. photochemical net ozone calculated reaction with NO yields daily integrated amount 102 ozone, primary being 22 campaign. produced oxidation (18 %) (60 hydrocarbons, formaldehyde (14 %), CO (8 %). An even larger 140 would if react NO. However, unknown (evident budget) causes 30 less than expected VOC rate.

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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