HYDROCARBONS AND THE LONG-RANGE TRANSPORT OF OZONE AND PAN ACROSS EUROPE

The individual involvement of 69 hydrocarbons in photochemical ozone and PAN formation in Europe is examined using the Harwell photochemical trajectory model. A detailed chemical scheme has been built up involving 384 chemical species and 684 chemical reactions to describe formation of ozone and other photochemically-generated secondary pollutants. Trajectories across the southern British Isles, from the F.R.G. to the Republic of Ireland, and from France to Sweden have been studied. The concept of a photochemical ozone creating potential, POCP, has been developed to assist in the understanding of the role of each individual hydrocarbon. The POCP value for a given hydrocarbon assesses its ability to form ozone relative to ethylene for an identical atmospheric mass emission. The concept has been extended to PAN formation so that the assessment of the likely impact of control policies can be extended to a wider range of secondary pollutants other than ozone.