TWO-DIMENSIONAL AIR POLLUTANT DISTRIBUTION IN STREET CANYONS

For many urban districts, the most severe air pollution caused by automobile emissions appears along a road surrounded by tall buildings: the so-called street canyon. This is due to the more and more crowded and ever increasing building height and increased traffic emissions and reduced natural ventilation in street canyons. The main traffic-related pollutants are CO, NOx, hydrocarbons, and particles. Main air pollutants and their effects on human health are briefly introduced at first. Secondly, three familiar two-dimensional flow patterns presented in street canyons and major factors governing the distribution of pollutants in them are analyzed. Then, pollutants dispersion and distribution results from field measurements, physical model tests, and numerical modellings are summed up from reference papers, thus their implications for urban district, street and building design are discussed. Finally, opinions for further research on air quality in urban canyons are discussed.