A SIMPLE-MODEL OF POLLUTANT CONCENTRATIONS IN A STREET CANYON

A single compartment model has been constructed for predicting hourly concentrations of pollutant concentrations arising from vehicular emis sions within a typical street canyon. The model takes account of traff ic densities and composition to estimate pollutant emissions within th e model compartment. Meteorological data on wind speed and direction a re used to define the exchanges of pollutants between the compartment and the surrounding air. A parameter is also included to describe the exchange in calm conditions. The pollutant concentrations are then est imated from a steady state mass balance equation for the compartment, assuming conservation of pollutants. The model was applied to the pred iction of carbon monoxide concentrations in Hope Street, Glasgow. Mode l parameters were fitted using field measurements, together with concu rrent meteorological data and traffic flows estimated from traffic cen sus data for Hope Street. The model accounted well for the observed va riations in carbon monoxide. It was found that the model parameters va ried seasonally, perhaps due to differences in atmospheric stability w hich have not so far been included in the model formulation.