Photo- And Radical induced Reactivity of Atmospheric Oxidants

Informations projet

PhARRAO

N° de convention de subvention: 746593

DOI

10.3030/746593

Projet clôturé le 23 Janvier 2019

Date de signature de la CE 17 Mars 2017

Date de début 1 Juillet 2017

Date de fin 31 Juillet 2020

Financé au titre de

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Coût total

€ 251 857,80

Contribution de l’UE

€ 251 857,80

Coordonné par

UNIVERSITY OF BRISTOL
United Kingdom

Periodic Reporting for period 1 - PhARRAO (Photo- And Radical induced Reactivity of Atmospheric Oxidants)

Période du rapport: 2017-07-01 au 2019-06-30

Résumé du contexte et des objectifs généraux du projet

Climate change and environmental sustainability are at the forefront of public interest as issues related to the emission of pollutants in the atmosphere. Although natural sources of pollutants (have always contributed to emission of chemical species in the atmosphere, air pollution has become a the second most complex manmade issue. The chemical processes which take place in the atmosphere are complex in nature and involve a wide range of chemical species in a composite environment, including reactions in the gas phase, aerosols, gas-liquid and gas-solid interfaces. Reactions between atmospheric molecular of anthropogenic and natural origin, can produce a rich variety of compounds. The outcomes of such reactions will heavily depend on the atmospheric conditions – e.g. pressure, temperature, humidity and presence of electromagnetic radiation (light). As such, direct investigation of atmospheric processes is challenging. On the contrary, laboratory studies are typically aimed at studying chemical reactions under more controlled and less complex conditions. Such studies aim at understanding the reaction mechanisms at a fundamental level and are therefore pivotal to help unravel the rich chemistry in the complex environments and aid in the predictions of the ways in which changes in conditions could affect the outcome of such processes. In this context, the project mainly focussed on the UV-Visible properties and photochemistry of carbonyl oxides, known as Criegee Intermediates (CIs) through laboratory studies. CIs are atmospheric species formed in the troposphere via reaction of unsaturated hydrocarbons (alkenes) with ozone, via a process known as ozonolysis. CIs are important as they are involved in the breakdown of many air pollutants and are a significant source of hydroxyl radicals (atmospheric detergents). The laboratory studies undertaken throughout the funding period were aimed at studying the interaction of CIs with electromagnetic radiation in the UV/Visible spectral region to determine efficient ways of detecting CIs and investigating their mechanisms of reaction with other atmospherically abundant species. The studies provided insights on the light-induced chemistry and physics which can also occur in the atmosphere due to absorption of sun light. The research included a pioneering synthesis which allowed for the first generation of ‘large’ CIs (MVK-oxide and MACR-oxide) in the laboratory and for the first time allowed recording their UV-Vis absorption spectrum across atmospherically relevant spectral range (300-500 nm). The outcomes of the laboratory studies are expected to guide field investigations of chemical reactions of CIs in the atmospheric environment.

Travail effectué depuis le début du projet jusqu’à la fin de la période considérée dans le rapport et principaux résultats atteints jusqu’à présent

Acetaldehyde oxide (CH3CHOO), the simplest alkyl substituted CI, was studied by velocity-map imaging (VMI). The primary aim of the study was to (i) detect photoproducts arising from UV-induced dissociation of the two conformers of CH3CHOO and (ii) unravel the distinct photodissociation dynamics of each conformer to separate their contribution to UV absorption spectrum.
The second part of the project were focussed on UV-Vis studies of larger CIs formed in the atmosphere via ozonolysis of isoprene. Ozonolysis of isoprene, one of the most abundant volatile organic compounds in the atmosphere, can produce methyl vinyl ketone oxide (MVK-oxide) and methacrolein oxide (MACR-oxide). The UV-visible spectrum of MVK-oxide was recorded and the UV-induced O-O bond fission was investigated using VMI. The results are expected to provide a sensitive method for detection of MVK-oxide that will enable further studies of its photochemistry and unimolecular and bimolecular reaction dynamics. Analogous studies were performed on MACR-oxide.
The project was carried out in the group of Prof. M.I. Lester (University of Pennsylvania). The project was multidisciplinary and included collaborations and exchange of scientific ideas and concept with synthetic chemists and collaborators within the theoretical and physical chemistry community.
A first high impact manuscript on the UV-Vis spectroscopy of MVK-oxide was published after peer-review in December 2018 (https://doi.org/10.1063/1.5064716).
Although the fellow has now moved to another institute, she is still collaborating with prof. Lester (University of Pennsylvania) to aid the interpretation of the experimental and theoretical results obtained during the project. She is also assisting in drafting the corresponding manuscripts for publication in peer-reviewed international journals.
The project was carried out in close interaction with younger group members. The fellow was the post-doctoral researcher mentoring two Ph.D. students, one Master student and one undergraduate student. For dissemination of the results, the fellow has presented the research project at events in the UK and US, reaching out to specialized audience and general public. In particular, the Marie-Curie open day took place in Bristol in September 2017. The event was aimed at informing young students and general public about various ongoing research projects at the University of Bristol. The fellow submitted a research statement describing the project in a language understandable to a broad audience. In addition, the Bristol ChemLabs project coordinates outreach activities aimed at engaging teachers and students at primary/secondary school in important themes of the current scientific research. The fellow contributed to the outreach project providing a research statement describing the project. This outreach article is available for download on the Bristol ChemLabs website.
At the University of Pennsylvania, the fellow had the change to discuss the research with perspective research students and research visitors.
Furthermore, the fellow participated to the ACS Younger Chemist Committee meeting (Temple University, Philadelphia, April 2018). The event attracted around 150 young researchers and students. The fellow was a poster judge for the event, therefore she had the opportunity to discuss cutting-edge research with several young researchers. The event included the participation of undergraduate and high school students to involve a wider audience. The fellow was also the co-author of a poster along with collaborators at Temple University for the event.

Progrès au-delà de l’état des connaissances et impact potentiel prévu (y compris l’impact socio-économique et les conséquences sociétales plus larges du projet jusqu’à présent)

The main target of the project was to provide insightful results on the chemistry of atmospherically relevant oxidants which play a fundamental role in the chemical processes occurring in the troposphere. To this end, novel theoretical and experimental methodologies and technologies were used. The project is closely related to themes of environmental chemistry which are important for society today, in times in which climate change and environmental sustainability are concrete issues. The outcomes of the project are thus expected to contribute greatly to this hot topic of global research, which is as important as full of challenges and unknown factors. The project has driven by close scientific interactions between experimental (organic and physical) and theoretical chemists which allowed great progresses to be achieved and expected to have high impact on both laboratory and field environmental studies.

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