STREET CANYON CONCENTRATIONS OF NITROGEN DIOXIDE IN OSLO, MEASUREMENTS AND MODEL CALCULATIONS

Nitrogen dioxide in the concentration ranges measured in a street canyon in Oslo in January 1981 (up to 300 ppb) is explained by a combination of mixing with aloft air, the reactions NO+O3→NO2+O2 and NO+NO+O2→NO2+NO2, and the direct release of NO2 in the car exhaust. The measurements showed that the ratio NO2/NOx fell between 0.10 and 0.30 (volume) when the NO2 concentration was high.