Measurements of air pollution due to the traffic in Bonaparte Street in Paris

The purpose of this article is to show how the dispersion of air pollutants in a street canyon could be evaluated (we take as an example Bonaparte Street in the 6th district of Paris) so as to estimate the pollutants concentrations in all points even if there are no stations of measurement. This study, which was made for Airparif, is based on a three dimensional air dispersion model called MISKAM. It is a case study. The model is a non-hydrostatic eulerian dispersion model, which means that it is able to evaluate turbulence created by urban morphology. The model includes emissions, urban morphology (buildings in three dimensions, roughness), climatology (wind direction and amplitude, turbulence). The eulerian model consists of an anisotropic grid, centred on the street being studied. The domain size is 450 m wide × 450 m long × 500 m high, which means 178200 cells. The model solves the equations of the mechanics of fluids (Navier-Stokes) for each cell of the domain. All the steps of the model are described and discussed. The paper will describe all the data and their uncertainty. The quality of the model will be discussed: the purpose of the model is to give information about air pollutants concentrations within short laps of time, in all places even if there is no data available. The influence of parameters, such as wind speed and direction, on air pollutants concentrations is shown. Finally the results of two models: a complex one and a simple one are compared, the main purpose is to make an operational tool to predict air concentrations in time.