The objectives are to establish reliable kinetic and mechanistic data for key reactions controlling the aqueous chemistry of clouds and fog.
To a large measure, laboratory experiments have resolved the main features of the four principal processes which are thought to be responsible for the formation of acidity in cloud and fog water from sulphur oxidation. The present project and the former within the IVth CEC environmental R&D programme have contributed to this effort. It is timely to incorporate the reaction scheme which has been established into suitable computer models to clarify which processes are the most important in real atmospheric situations.
The laboratory work includes reactions responsible for the oxidation of sulphur species to sulphuric acid and the formation of organic acids.
Modern experimental techniques such as stopped-flow kinetics, laser flash photolysis, pulse radiolysis and advanced analytical techniques are employed to investigate:
the effects of transition metal ions on the oxidation of sulphur by strong oxidants such as hydrogen peroxide, ozone and hydrogen oxychloride.
catalysis of sulphur oxidation by transition metals, mainly by manganese and iron.
the occurrence of hydroxyl and oxy-sulphur radicals in atmospheric droplets during daylight hours.
the effects of transition metals upon free radicals.
The efforts of all participants will be combined to develop a list of key elementary reactions and the associated rate coefficients for application to atmospheric cloud and fog systems.
Funding SchemeCSC - Cost-sharing contracts
221 00 Lund
KT22 7SE Leatherhead
LS2 9JT Leeds