Das Projekt "Entwicklung und Validierung von Instrumenten zur Umsetzung der europäischen Luftqualitätspolitik (VALIUM) - Teilprojekt 3: Erstellung eines auf Naturmessungen basierenden Validierungsdatensatzes zur Ausbreitung von Schadstoffen in Straßenschluchten" wird vom Umweltbundesamt gefördert und von Ingenieurbüro Lohmeyer GmbH & Co. KG durchgeführt. Objectives: The EU Air Quality Directives include air pollutant dispersion models as instruments of environmental politics. The quality of the models needs to be guaranteed. One part of the control process is the validation, a comparison of the modelled results with especially designed and acquired, trustworthy reference data sets from field and wind tunnel experiments. Activities: Air pollutants and meteorological parameters are measured continuously by in situ stations at different sites within Goettinger street in Hanover and its vicinity. Apart from these long-term measurements three intensive measurement campaigns are planned with additional tracer experiments. In August 2001 and August 2002 tracer experiments have been executed. A line source consisting of 8 pipe sections with a total length of about 96 m has been installed on the median of Goettinger Strasse. A mixture of the tracer gas SF6 and air, monitored by flow controllers, has been released from openings regularely spaced along the pipes. The source has been operated with a sufficient overpressure to avoid a feedback of external pressure fluctuations on the source strength and distribution. At 12 positions within the street canyon and on the roof of a nearby building, air samples have been collected simultaneously for at least 5 hours. Every 30 minutes a sampling bag has been started to be filled by the sampling equipment at each position. Afterwards, the 30 minutes averaged samples have been analysed on SF6 in the laboratory. Results: The experimental layout had been tested in August 2001. With minor reservations it also passed the second measurement campaign in August 2002 successful. The results of both campaigns exist now. As far as they have been scrutinized they show plausible distributions of the concentrations in the street area such as the typical windward-leeward-effect for street canyons. The influence of traffic induced turbulence and advection of the concentration field along the street by the traffic seems to be significant because the concentration field is shifted according to the direction of the motion of the traffic. Further measurements will be carried out in October 2002 and March 2003 to test and to corroborate that hypothesis and to complete the validation data set.