Computer modelling studies of the distribution of photochemical ozone production between different hydrocarbons

The formation of O₃ and other photochemically generated compounds has been modelled for the region downwind of London, during the slow easterly airflow and other conditions associated with a midsummer anticyclone. The model contains a comprehensive chemical mechanism, including the emissions of 37 hydrocarbons (HCs) and treats HC degradation explicitly in over 300 reactions. As a result it has been possible to disaggregate the production of O₃ amongst the various HCs present in the model, and the percentage of the O₃ production which can be attributed to each HC is therefore known. These results have been used, in conjunction with the emissions inventory, to attribute the O₃ production to the various sources of HCs. By further study the number of molecules of O₃ which are produced by each HC molecule have also been elucidated. The significance of the results both to control strategies for O₃ formation and to the representation of photochemical O₃ production in computational models is discussed.