Rate constant of the reaction between CH3O2 and OH radicals

Bossolasco, Adriana; Faragó, Eszter Pongráczné; Schoemaecker, Coralie; Fittschen, Christa

doi:10.1016/j.cplett.2013.12.052

Cited by 74 publications

(129 citation statements)

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“…Reported experimental values for the rate constant of the reaction of the simplest peroxy radical, CH3O2, with OH disagree by more than a factor of 3. The highest value to date, reported by Bossolasco et al (2014) (2.8 × 10 −10 cm 3 molecule…”

Section: Overall Contribution Of Modelled Ro2 To Kohmentioning

confidence: 97%

“…A theoretical study identified R4c as a potentially significant source of methanol in the remote boundary layer and modelled its impacts (Müller et al, 2016). However this study predated the first (and, so far, only) experimental determination of the products of R4, and also used the very high value of k4 reported by Bossolasco et al (2014), which has since been revised to a value almost a factor of 2 lower than the original (as discussed in Section 5.1).…”

Section: The Ch3o2 + Oh Reaction and Product Branching Simulationsmentioning

confidence: 99%

“…has since been revised to a lower value (1.6 × 10 −10 cm 3 molecule −1 s −1 at T = 295 K) by the same group (Assaf et al, 2016): 10 the difference is thought to arise from complicating secondary chemistry due to the presence of electronically excited iodine atoms following the photolysis of the gaseous mixture used by Bossolasco et al (2014). However an even lower value has been reported by −11 cm 3 molecule −1 s −1 at T = 298 K), and the reason for the discrepancy between this study and that by Assaf et al is still unclear.…”

Section: Overall Contribution Of Modelled Ro2 To Kohmentioning

confidence: 99%

“…Assumptions had to be made on the individual values of OH+RO 2, , as only the rate constants of the reactions of OH with methyl (Assaf et 5 al., 2016(Assaf et 5 al., , 2017bBossolasco et al, 2014;Yan et al, 2016), ethyl (Assaf et al, 2017a;Faragó et al, 2015), propyl (Assaf et al, 2017a) and i-and n-butyl (Assaf et al, 2017a) peroxy radicals have been measured in the laboratory to date. Reported experimental values for the rate constant of the reaction of the simplest peroxy radical, CH3O2, with OH disagree by more than a factor of 3.…”

Section: Overall Contribution Of Modelled Ro2 To Kohmentioning

confidence: 99%

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Global modelling of the total OH reactivity: investigations on the missing OH sink and its atmospheric implications

Ferracci¹,

Heimann²,

Abraham³

et al. 2018

Preprint

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Abstract. The hydroxyl radical (OH) plays a crucial role in the chemistry of the atmosphere as it initiates the removal of most trace gases. A number of field campaigns have observed the presence of a "missing" OH sink in a variety of regions across the planet. Comparison of direct measurements of the OH loss frequency, also known as total OH reactivity (kOH), with the 10 sum of individual known OH sinks (obtained via the simultaneous detection of species such as volatile organic compounds and nitrogen oxides) indicates that, in some cases, up to 80 % of kOH is unaccounted for. In this work, the UM-UKCA chemistry-climate model was used to investigate the wider implications of the missing reactivity on the oxidising capacity of the atmosphere. Simulations of the present-day atmosphere were performed and the model was evaluated against an array of field measurements to verify that the known OH sinks were reproduced well, with a resulting good agreement found for most 15 species. Following this, an additional sink was introduced to simulate the missing OH reactivity as an emission of a hypothetical molecule, X, which undergoes rapid reaction with OH. The magnitude and spatial distribution of this sink were underpinned by observations of the missing reactivity. Model runs showed that the missing reactivity accounted for on average 6 % of the total OH loss flux at the surface, and up to 50 % in regions where emissions of the additional sink were high. The lifetime of the hydroxyl radical was reduced by 3 % in the boundary layer, while tropospheric methane lifetime increased by 20 2 % when the additional OH sink was included. The UM-UKCA simulations also allowed us to establish the atmospheric implications of the newly characterised reactions of peroxy radicals (RO2) with OH. While the effects of this chemistry on kOH were minor, the reaction of the simplest peroxy radical, CH3O2, with OH was found to be a major sink for CH3O2 and source of HO2 over remote regions at the surface and in the free troposphere. Inclusion of this reaction in the model increased tropospheric methane lifetime by up to 3 %, depending on its product branching. Simulations based on the latest kinetic and 25 product information showed that this reaction cannot reconcile models with observations of atmospheric methanol, in contrast to recent suggestions.Atmos. Chem. Phys. Discuss., https://doi

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Section: Overall Contribution Of Modelled Ro2 To Kohmentioning

confidence: 97%

Section: The Ch3o2 + Oh Reaction and Product Branching Simulationsmentioning

confidence: 99%

Section: Overall Contribution Of Modelled Ro2 To Kohmentioning

confidence: 99%

Section: Overall Contribution Of Modelled Ro2 To Kohmentioning

confidence: 99%

See 2 more Smart Citations

Global modelling of the total OH reactivity: investigations on the missing OH sink and its atmospheric implications

Ferracci¹,

Heimann²,

Abraham³

et al. 2018

Preprint

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“…However, low terpene and NO regimes, prevailing during CYPHEX, and the absence of limonene chemistry in the current model scheme, precluded a more rigorous analysis of the probable chemical pathways for RO2 degradation in the atmosphere. Further, there is evidence that the rate constant of CH3O2 with OH could be two times faster than used in the 30 current models (Bossolasco et al, 2014). Applying this in general to other peroxides, the rate constants need to be revisited as they will have a non-negligible impact on the chemical composition of the atmosphere, especially in remote low NOx environments where the peroxide lifetimes are relatively long.…”

Section: Discussionmentioning

confidence: 99%

Oxidation processes in the Eastern Mediterranean atmosphere: Evidence from the Modelling of HO<sub>x</sub> Measurements over Cyprus

Mallik¹,

Tomsche²,

Bourtsoukidis³

et al. 2018

Preprint

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Abstract. The Mediterranean is a climatically sensitive region located at the crossroads of air masses from three continents: 15Europe, Africa and Asia. The chemical processing of air masses over this region has implications not only for the air quality, but also for the long-range transport of air pollution. To obtain a comprehensive understanding of oxidation processes over the Mediterranean, atmospheric concentrations of the hydroxyl radical (OH) and the hydroperoxyl radical (HO2) were measured during an intensive field campaign (CYprus PHotochemistry EXperiment, CYPHEX-2014) in the north-west of Cyprus in the summer of 2014. Very low local anthropogenic and biogenic emissions around the measurement location 20 provided a vantage point to study the contrasts in atmospheric oxidation pathways under highly processed marine air masses and those influenced by relatively fresh emissions from mainland Europe.The CYPHEX measurements were used to evaluate OH and HO2 simulations using a photochemical box model (CAABA/MECCA) constrained with CYPHEX observations of O3, CO, NOx, hydrocarbons, peroxides and other major HOx (OH + HO2) sources and sinks in a low NOx environment (<100 pptv NO). The model simulations for OH showed very good 25 agreement with in-situ OH observations. Model simulations for HO2 also agreed fairly well with in-situ observations except when pinene levels exceeded 80 pptv. Different schemes to improve the agreement between observed and modelled HO2, including changing the rate coefficients for the reactions of terpene generated peroxy radicals (RO2) with NO and HO2 as well as the autoxidation of terpene generated RO2 species, are explored in this work. The main source of OH in Cyprus was its primary production from O3 photolysis during the day and HONO photolysis during early morning. Recycling contributed 30 about one-third of the total OH production, and the maximum recycling efficiency was about 70 %. CO, which was the largest OH sink was also the largest HO2 source. Lowest HOx production and losses occurred when the air masses had higher residence time over the oceans.Atmos. Chem. Phys. Discuss., https://doi.org/10. 5194/acp-2018-25 Manuscript under review for journal Atmos. Chem. Phys. Air pollution and HOx chemistryThe chemical and photochemical processing of air pollutants, in conjunction with local emissions, meteorology and atmospheric transport, strongly influences the air quality over a region. The regional air quality impacts human health, agriculture, the overall condition of the biosphere and subsequently the climate. Studies attribute 2-4 million premature 5 deaths globally to outdoor air pollution (Silva et al., 2013;Lelieveld et al., 2015). Oxidants in the Earth's atmosphere prevent the pollutants released into it from building up to toxic levels. These oxidants not only convert many toxic pollutants into less toxic forms (e.g. CO to CO2) but also help in their removal (e.g. NOx and SO2 are converted into soluble HNO3 and H2SO4 respectively), although some toxic chemicals may s...

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Comment on Paper: “Water Vapor Enhancement of Rates of Peroxy Radical Reactions” by Kumbhani et al., Int. J. Chem. Kinet. 47, 395–409, 2015

Jenkin¹

2016

Int J of Chemical Kinetics

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in Wiley Online Library (wileyonlinelibrary.com).Kumbhani et al. [1] have recently studied the selfreaction kinetics of the β-hydroxyethyl peroxy radical (HOCH 2 CH 2 O 2 ), generated from the 193-nm laser flash photolysis (LFP) of 2-chloroethanol in the presence of O 2 and N 2 . I contributed to the only previous HOCH 2 CH 2 O 2 kinetics study to use the same chemical system [2] and have a number of comments that are related to the discussion of the results of that study by Kumbhani et al. [1], and more generally to sources of HO 2 in the system and other possible complications.In our study [2], the self-reaction of HOCH 2 CH 2 O 2 was investigated using the 248-nm LFP of H 2 O 2 /C 2 H 4 /O 2 /N 2 mixtures. The 193-nm LFP of 2-chloroethanol in the presence of O 2 and N 2 was used to allow the prompt production of both HOCH 2 CH 2 O 2 and HO 2 , so that the kinetics of their reaction could also be investigated-and a recommended rate coefficient At the low end of our studied wavelength range, the cross sections of HOCH 2 CH 2 O 2 and HO 2 are comparable, whereas only HOCH 2 CH 2 O 2 absorbs significantly at the high end of the range, allowing straightforward discrimination of their contributions. Contrary to the suggestion of Kumbhani et al. [1], there was no evidence for significant formation of ozone in our study, which would have been very obvious from its strong absorption maximizing at about 255 nm, particularly as a residual absorption after the transient

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Rate constant of the reaction between CH3O2 and OH radicals

Cited by 74 publications

References 41 publications

Global modelling of the total OH reactivity: investigations on the missing OH sink and its atmospheric implications

Global modelling of the total OH reactivity: investigations on the missing OH sink and its atmospheric implications

Oxidation processes in the Eastern Mediterranean atmosphere: Evidence from the Modelling of HO<sub>x</sub> Measurements over Cyprus

Comment on Paper: “Water Vapor Enhancement of Rates of Peroxy Radical Reactions” by Kumbhani et al., Int. J. Chem. Kinet. 47, 395–409, 2015

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Rate constant of the reaction between CH3O2 and OH radicals

Cited by 74 publications

References 41 publications

Global modelling of the total OH reactivity: investigations on the missing OH sink and its atmospheric implications

Global modelling of the total OH reactivity: investigations on the missing OH sink and its atmospheric implications

Oxidation processes in the Eastern Mediterranean atmosphere: Evidence from the Modelling of HO&lt;sub&gt;x&lt;/sub&gt; Measurements over Cyprus

Comment on Paper: “Water Vapor Enhancement of Rates of Peroxy Radical Reactions” by Kumbhani et al., Int. J. Chem. Kinet. 47, 395–409, 2015

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Oxidation processes in the Eastern Mediterranean atmosphere: Evidence from the Modelling of HO<sub>x</sub> Measurements over Cyprus