H migration in peroxy radicals under atmospheric conditions

Atmospheric chemistry and physics, Journal Year: 2020, Volume and Issue: 20(12), P. 7429 - 7458

Published: June 26, 2020

Abstract. A large data set of rate coefficients for H migration in peroxy radicals is presented and supplemented with literature to derive a structure–activity relationship (SAR) the title reaction class. The SAR supports aliphatic RO2 radicals; unsaturated bonds β-oxo substitutions both endocyclic exocyclic transition state ring; α-oxo (aldehyde), –OH, –OOH, –ONO2 substitutions, including O-based hydrogen atoms. Also discussed are –C(=O)OH –OR substitutions. allows predictions k(T) temperature range 200 450 K, migrations spans ranging from 1,4 1,9-H shifts depending on functionalities. performance reflects uncertainty underlying data, reproducing scarce experimental average factor 2 wide theoretical 10 100, also quality data. evaluation discusses multi-functionalized species. For RO2, we present some product identification that validates expected mechanisms. proposed valuable tool mechanism development design guides future work, which should allow rapid improvements future. Relative multi-conformer theory (rel-MC-TST) kinetic introduced as an aid systematic studies.

Language: Английский

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Molecular understanding of new-particle formation from α-pinene between −50 and +25 °C

Atmospheric chemistry and physics, Journal Year: 2020, Volume and Issue: 20(15), P. 9183 - 9207

Published: Aug. 3, 2020

Abstract. Highly oxygenated organic molecules (HOMs) contribute substantially to the formation and growth of atmospheric aerosol particles, which affect air quality, human health Earth's climate. HOMs are formed by rapid, gas-phase autoxidation volatile compounds (VOCs) such as α-pinene, most abundant monoterpene in atmosphere. Due their abundance low volatility, can play an important role new-particle (NPF) early aerosols, even without any further assistance other low-volatility sulfuric acid. Both reaction forming NPF rates expected be strongly dependent on temperature. However, experimental data both effects limited. Dedicated experiments were performed at CLOUD (Cosmics Leaving OUtdoor Droplets) chamber CERN address this question. In study, we show that a decrease temperature (from +25 −50 ∘C) results reduced HOM yield oxidation state products, whereas (J1.7 nm) increase substantially. Measurements with two different chemical ionization mass spectrometers (using nitrate protonated water reagent ion, respectively) provide molecular composition gaseous two-dimensional volatility basis set (2D VBS) model provides distribution. The decreases from 6.2 % 25 ∘C 0.7 ∘C. there is strong reduction saturation vapor pressure each reduced. Overall, leads nucleation up 3 orders magnitude compared addition, enhancement ions decreasing temperature, since neutral clusters have increased stability against evaporation. resulting quantify how interplay between temperature-dependent pathways associated pressures biogenic level. Our measurements, therefore, improve our understanding pure for wide range tropospheric temperatures precursor concentrations.

Language: Английский

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Biogenic secondary organic aerosols: A review on formation mechanism, analytical challenges and environmental impacts

Chemosphere, Journal Year: 2020, Volume and Issue: 262, P. 127771 - 127771

Published: Aug. 7, 2020

Language: Английский

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High concentration of ultrafine particles in the Amazon free troposphere produced by organic new particle formation

Proceedings of the National Academy of Sciences, Journal Year: 2020, Volume and Issue: 117(41), P. 25344 - 25351

Published: Sept. 28, 2020

Significance The high-altitude tropics constitute one of the world’s largest aerosol reservoirs, which may significantly affect clouds, radiation, and hydrological cycle by delivering seeds on clouds form to lower altitudes maintaining stratospheric background. However, formation mechanisms these aerosols remain a scientific mystery. Through systematic experiment-based model representation organic chemistry new particle (NPF) combined with constraints from field measurements, we demonstrate that NPF driven extremely low volatility organics formed biogenic emissions plays key role in producing large number observed Amazon. This mechanism likely also prevailed during preindustrial times hence modulate anthropogenic forcing above baseline.

Language: Английский

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Size-dependent influence of NO _x on the growth rates of organic aerosol particles

Science Advances, Journal Year: 2020, Volume and Issue: 6(22)

Published: May 27, 2020

NO x is important for particle growth as it can participate in HOM formation and alter the volatility distribution.

Language: Английский

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