A two-dimensional air quality model in an urban street canyon: evaluation and sensitivity analysis

In order to predict the air quality impact by vehicle emissions within an urban street canyon, a two-dimensional air quality numerical model was developed based on atmospheric convection diffusion equations and a k-epsilon turbulent model. The numerical model has been evaluated using the database from a set of street canyon air tracer experiments carried out near the crossing of Aoyama ichome, Minato-ku, Tokyo in December 1980, by the Japan Environmental Management Association of Industry (JEMAI). Twenty-four cases have been studied for the sensitivity analysis, including more practical cases when the inflow wind has an inclination with the horizontal road and the two buildings have different heights. As a result, it has been shown that the concentration distributions of pollutants emitted from the street are governed by both the inflow wind and the street canyon geometry. A stable vortex was formed within the street canyon, which agrees with other researchers. Pollutant concentrations were predicted to have higher values on the leeward side compared to the windward side. It was concluded that the released pollutants from street canyon become more diluted in the following cases: a lower height of the street canyon, a faster wind speed, a higher height of the leeward building than the windward building and an inflow wind direction towards the street. It is also suggested that the numerical model is useful for predicting the air quality within a typical urban street canyon. (C) 2000 Elsevier Science Ltd. All rights reserved.