Poor air quality represents the greatest environmental risk to public health in the UK, and causes over 4.2 million premature deaths worldwide, costing the UK economy over 15 billion pounds. The properties and impacts of our air are governed by atmospheric composition, the understanding of which is vital to the development of policies aimed at improving air quality and requires knowledge of the emission rates, concentrations and chemistry of trace species in the atmosphere.
This project will investigate the chemistry and atmospheric impacts of Criegee intermediates (CIs), a family of reactive species generated in atmospheric oxidation processes initiated by the reactions of ozone (O3) with unsaturated hydrocarbons and other volatile organic compounds (VOCs). A particular challenge since the proposal of their existence in 1949 has been the direct measurement of CIs. The advent of photolytic sources for CIs, reported in 2012, has facilitated laboratory studies of CIs and has enabled greater understanding of the chemistry and properties of CIs, but there are still significant uncertainties regarding the kinetics and mechanisms of Criegee intermediate reactions under atmospherically relevant conditions.
Recent NERC-funded work in this group has used photolytic CI sources to develop novel techniques to monitor the kinetics and products of Criegee intermediate reactions under atmospherically relevant conditions, including time-resolved broadband UV absorption spectroscopy and time-resolved high-resolution IR absorption spectroscopy. This project will use these experiments to explore the kinetics of CI + water reactions, which are atmospherically important but have yet to be explored in detail. The combination of UV and IR techniques will enable the investigation of the kinetics, mechanisms, and product yields of these reactions, and provide insight to the potential role of CI-water complexes in the atmosphere.
In addition, the project will develop an experimental technique based on cavity enhanced UV absorption spectroscopy to explore Criegee intermediates directly, and quantitatively, in ozonolysis reactions. The development and subsequent application of this technique will significantly enhance our understanding of ozonolysis reactions and CI chemistry in the atmosphere, leading to improved understanding of atmospheric composition, air quality, and climate. This work links to the NERC objectives related to atmospheric pollution and human health, clean air, and climate.
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