Small-scale spatial variability of air pollution in a complex roadside environment : representativeness of monitoring data

Abstract : The strong spatial and temporal variability of air pollution detected at roadside locations in a number ofEuropean cities has raised the question of how representative the site and time period of air quality measurements actually can be. To address this question, a long-term sampling campaign was carried out on a major road axis leading to a very busy intersection in central Paris, covering the surroundings of a permanent air quality monitoring station. Diffusive BTX samplers as well as a mobile monitoring unit equipped with gas analysers and meteorological instruments were used to reveal the small-scale pollution gradients and temporal trends near the permanent monitoring station. The diffusive measurements were taken at different heights above the ground and distances from the kerb covering summer and winter periods. The analysis of this comprehensive data set may help to assess the representativeness of air quality monitoring information and generally revise the existing siting criteria for roadside receptors.