Abstract

Biogenic volatile organic compounds (VOCs) account for about 90% of global VOC emissions and these are dominated by the unsaturated hydrocarbons isoprene and the monoterpenes. Ozone is ubiquitous throughout the troposphere, formed in the photolytic cycling of nitrogen oxides. The reaction of alkenes with ozone in the atmosphere has in recent years been increasingly recognised as playing a central role in tropospheric chemistry.

Alkene-ozone reactions are a significant source of the most important atmospheric oxidant, the hydroxyl radical (OH). Recent work has focussed on the production of Stabilized Criegee Intermediates (SCI) from these reactions. SCIs have been proposed to be important oxidants in the atmosphere, potentially representing a significant additional oxidation route for SO2 to sulfate aerosol. This has implications for our understanding of this part of the climate system.

Another role of alkene ozonolysis is the efficient formation of secondary organic aerosol. This can occur through the formation of low volatility products via standard oxidation mechanisms, via oligomerisation reactions, or via the recently elucidated ‘ELVOC’ auto-oxidation mechanism.