The impact of highway emissions on ozone and nitrogen oxide levels during specific meteorological conditions

The impact of highway emissions on O3 and NOx was assessed using a validated air-quality model (MCCM-Multiscale Climate Chemistry Model) applied to a region of Southern Germany. During a measuring campaign around the City of Augsburg (Southern Germany) in May 2001 modelling calculations were performed, including a scenario in which the highway emissions (ca. 80,000 vehicles/day) between Munich and Augsburg (distance ca. 40 km) were switched off. Based on the change in emissions, the variations in O3- and NOx-concentrations as well as the size of the influenced area within the region of interest are discussed. Additionally, an episode in August 2001 with elevated ozone values was modelled for comparison with the May episode. The model results show a very pronounced reduction of O3- and an increase of NO2-concentrations after passing the highway within a distance of more than 40 km. After turning off the highway emissions it could be demonstrated that the emission reduction causes a significant increase in the ozone levels downwind of the highway in the magnitude of 10– 20 ppbv depending on the time of the day.