Modelling the dispersion of vehicle-emitted pollutants

It is well known that certain vehicle-generated air pollutants may have adverse effects on human health, ecosystems and amenity. For many years, carbon monoxide and lead were the pollutants which received most attention. However, other problems have been identified, principally the role of nitrogen oxides in producing acid rain, the mutagenic and carcinogenic effects of polyaromatic hydrocarbons and the darkness of diesel-emitted smoke. The magnitude of some of the problems has been compounded by changes in engine design and fuel composition. An understanding of the impact of vehicle-emitted pollutants on the environment requires a knowledge of the processes which control their transport through the atmosphere. Short-range transport processes are best investigated using field data collected near to a rural motorway since in that situation the source is a well-defined line to which standard mathematical modelling techniques can be applied and non-vehicle sources of pollution are reduced to a minimum. This paper examines the use of desk-top and computer-based techniques to predict CO concentrations.