Abstract

The oxidative removal of volatile organic compounds from the Earth’s atmosphere is mostly by reactions initiated by hydroxyl (OH) radicals. However, there is growing recognition of the importance of reactions of ozone with unsaturated organic compounds, both as a source of OH and of other reactive intermediates. This talk will focus on the chemistry of carbonyl oxides (more commonly known as Criegee intermediates) produced by ozone reactions with alkenes. The zwitterionic / biradical character of the Criegee intermediates causes unusual reaction pathways with trace organic atmospheric constituents such as alcohols and carboxylic acids. The products of these reactions are polar, highly oxygenated organic species, the low vapour pressures of which encourage growth of secondary organic aerosol particles. The Bristol group’s studies combine laboratory measurements of reaction rates, synchrotron-based photoionization and mass spectrometry identification of reaction products, calculations of reaction pathways and kinetics, and modelling of the atmospheric chemistry to assess the importance of this Criegee intermediate chemistry in the troposphere.