To investigate the tropospheric oxidation of selected aromatic compounds.
A fast cycle of odd hydrogen species is involved in the formation of tropospheric ozone. The chain length of the cycle and the number of NO molecules oxidised to NO2 per revolution, two central parameters of tropospheric chemistry, are critically dependent on the composition of VOC emissions.
The contribution of aromatic compounds to these parameters will be evaluated according to the following points :
1 Identification of the primary (i.e. stable, non-radical) products from the reactions of aromatic compounds initiated by the OH radical.
2 The number of HO2 radicals formed and the number of NO oxidised to NO2.
3 The atmospheric chemistry of the primary products initiated by photolysis or OH radicals and the secondary products formed.
The fundamental first point will be tackled from two sides :
a) Kinetic experiments with fast time resolution including cycling experiments and measurements of formation kinetics and yields of probable primary products.
b) Product studies with two approaches to overcome the problem of fast secondary reactions of the primary products :
(i) Measurements with total consumption of the aromatic precursor as low as possible at various low (including zero) concentrations of NOX.
(ii) Investigating the third point first, considering the results in the interpretation of product spectra formed from the parent aromatics.
The results of the project should improve models of the tropospheric free radical chemistry, which are used in planning photooxidant control strategies.
Funding SchemeCSC - Cost-sharing contracts