Measurements and modelling of air pollution in a street canyon in Helsinki

A measuring campaign was conducted in the street canyon 'Runeberg street' i n Helsinki in 1997. Hourly concentrations of carbon monoxide (CO), nitrogen oxides (NOx), nitrogen dioxide (NO2) and ozone (O-3) were measured at the street and roof levels, and the relevant hourly meteorological parameters w ere measured at the roof level. The hourly street level measurements and on -site electronic traffic counts were conducted during the whole year 1997, and roof level measurements were conducted during approximately two months, from 3 March to 30 April in 1997. The Operational Street Pollution Model ( OSPM) was used to calculate the street concentrations and the results were compared with the measurements. The overall agreement between measured and predicted concentrations was good for CO and NOx, but the model slightly ov erestimated the measured concentrations of NO2. The database, which contain s all measured and predicted data, is available for a further testing of ot her street canyon dispersion models.