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C332: ROAR: Reactions of Organic Atmospheric Radicals – a combined experimental and modelling study (Lead Supervisor: Markus Kalberer, Chemistry)

Supervisors: Markus Kalberer (Chemistry) and Alex Archibald (Chemistry)

Importance of the area of research:

Atmospheric chemistry is driven by oxidation of biogenic and anthropogenic volatile organic compounds triggered mainly by OH, O3 and NO3 radicals. One of the most important reactions in the troposphere is ozonolysis of alkenes contributing to photochemical smog and global climate change. Ozonolysis of alkenes occurs with a generally accepted mechanism via Criegee Intermediates (CI). Characterising the formation, reactivity and kinetics of CIs, is important in defining the oxidation of organic compounds in the atmosphere but is highly challenging due to the short lifetime of these biradicals. New techniques, developed over the last few years (Welz, 2012; Taatjes, 2013) allow now to characterise and quantify CIs and determine their fate under atmospherically relevant conditions.

Project summary:

This project aims to quantify CI formation yields and reaction kinetics with atmospheric trace gases. These pioneering new measurements will be incorporated into box and 3D models developed by members of the Department of Chemistry and will help to improve our understanding of the importance of atmospheric chemical processes to air quality and climate change.

We recently developed a new experimental mass spectrometry technique where CI are reacted in the gas phase with spin traps, which are compounds that react selectively with radicals to form stable products. This allows to identify and quantify any atmospherically relevant alkene directly in the gas phase and under realistic conditions.

What the student will do:

The student will perform laboratory experiment to characterise and quantify CI formation and reaction rates from several important atmospheric alkenes such as isoprene and terpenes with key atmospheric trace gas such as water, NO2 or SO2 and other volatile organic compounds. The student will then integrate these experimental results into atmospheric reaction schemes within the UKCA model, the UK community chemistry-climate model developed in Cambridge and a processes box-model to explore the full sensitivity of the complex chemical system.

Please contact the lead supervisor directly for further information relating to what the successful applicant will be expected to do, training to be provided, and any specific educational background requirements.

References:

O. Welz, J. D. Savee, D. L. Osborn, S. S. Vasu, C. J. Percival, D. E. Shallcross and C. A. Taatjes, Science, 2012, 335, 204–7.

C. A. Taatjes, O. Welz, A. J. Eskola, J. D. Savee, A. M. Scheer, D. E. Shallcross, B. Rotavera, E. P. F. Lee, J. M. Dyke, D. K. W. Mok, D. L. Osborn and C. J. Percival, Science, 2013, 340, 177–80.

Follow this link to find out about how to apply for this project

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