Air pollution mapping over a city – virtual stations and morphological indicators

Air quality is a major concern in many large cities of the world, where people and sources of pollution are concentrated in the same place. Most cities have acquired a surveillance network of air pollution. But the cost of these networks is high and limits the knowledge of pollutant concentration to specific points of the town. Presently practitioners generate maps of concentration in pollutants by mean of interpolating and extrapolation methods, such as thin plate or kriging methods. Those methods are familiar and their quality depends on the number of input parameters. Other tools by modeling pollutant dispersion exist but turn to be insufficient and are not validated yet. Based on a multi-sources approach, this paper presents a methodology for the mapping of pollutant concentrations over the city of Strasbourg and its vicinity. Sources related to air pollution and urban shapes and morphology are exploited to densify the number of pollution data used for a mapping by interpolation. Several terms are introduced: “identity card of a measuring station”, “morphological indicators”, “pseudostation” and “virtual station”