Evaluation of local trends of NOx emissions in urban areas by means of an emission model and an empirical model combining air dispersion calculations with air quality data.

Long term trends of NOx emissions in urban areas in Sweden are estimated with three different methods; calculated emissions by a Swedish emission model, the EMV-model, measured concentrations of NO2 in Swedish cities within the Swedish Urban Network and by an empirical model combining air dispersion calculations with measured concentrations. The three methods all show significant decrease of NOx emissions in Swedish cities. For some cities however the difference between calculated trends are large, indicating a lot of uncertainties in the methods including input data. (A)