Atmospheric chemistry of reactive trace species through direct real-time measurements

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"Poor air quality represents the greatest environmental risk to public health in the UK, and has been reported to affect every organ in the body, with links to illnesses including cardiovascular and respiratory diseases, vascular dementia, and Alzheimer's disease causing over 4.2 million premature deaths worldwide and costing the UK economy ~£15 billion each year. 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 reactive trace species in the atmosphere. This project will investigate the chemistry and atmospheric impacts of reactive species using time-resolved ultraviolet and infrared absorption spectroscopy to make direct measurements of reactive atmospheric species in real-time during the course of their reactions. Laboratory experiments will focus on the chemistry of Criegee intermediates (CIs), a family of reactive species generated in the atmosphere through the reactions of ozone (O3) with unsaturated 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. This project will investigate the kinetics of CI + water reactions, which are atmospherically important but have yet to be explored in detail. The combination of UV and IR absorption 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.There will also be opportunities to develop the UV absorption experiment to make field measurements of OH reactivity, a measure of the total loading of reactive pollutants in an air mass that oxidise to secondary pollutants, and to make measurements of CIs in an atmospheric simulation chamber to explore Criegee intermediates directly, and quantitatively, in ozonolysis reactions. This project links to the NERC objectives related to atmospheric pollution and human health, clean air, and climate. "