The contribution of gasoline fuelled vehicle exhaust to the UK speciated hydrocarbon inventory

Abstract Established techniques are briefly described for the generation of samples of exhaust from 25 gasoline fuelled cars, typical of the current (pre-1992 regulation) fleet, driven on a set of road tests which cover the normal range of UK conditions. Average emissions for 15 hydrocarbons which are of importance as precursors in the formation of photochemical oxidants (in particular, ozone) are given. These results demonstrate the speed dependent variation in composition, in particular, the respective contributions of unburnt fuel and combustion products. A technique is described to combine the results obtained above with the most recently published traffic statistics in order to produce an inventory which takes into account the observed variability of composition with speed. This inventory represents the UK base line situation before there is significant fleet penetration by three-way catalyst cars. The importance of this estimate of the contribution of gasoline fuelled cars to the overall UK speciated hydrocarbon emission is discussed in the light of the modelling of photochemical oxidant production and of the prediction of future vehicle contributions to the emissions of oxidant precursors.