NERI prepared a report (Palmgren et al., 2007) about assessment of SCR (Selective Catalytic Reduction) catalysts as an efficient tool to obtain compliance with the EU limit value for NO2. It is expected that <st1:place w:st="on"><st1:country-region w:st="on">Denmark</st1:country-region></st1:place> and the other EU member states are not able to comply with the limit value, 40 ?g/m3 as annual average, in 2010 without further measures, mainly due to higher direct emission of NO2 and increasing number of diesel passenger cars.
The available data from the literature about direct emission of NO2 from different vehicle categories were uncertain. In addition, the fraction of diesel passenger cars increased faster than expected. The first assessment was based on expected sales of new diesel passenger cars of 25 %, but a new forecast is 40-60 %. The present assessment is based on new NO2 emission data and fraction of diesel passenger cars in the future until 2020.
The new emission data lead to a lower number of exceedances of the limit value at 40 µg/m3 than the former assessment. This is partly due to the lower direct emission of NO2 based on new data from Germany (Dünnebeil & Lambrecht, 2007), and partly because the new calculations take into account the decreasing contribution from urban background due to decreasing emissions of NOx as a consequence of more strict EURO norms.
The larger fraction of diesel passenger cars (40 % and 60 % compared to earlier 23,4 %) acts towards increase of NO2 concentrations, due to a larger direct emission from diesel cars.
In our basis scenarios we expect about 90 exceedances at the 138 busiest street sections in <st1:place w:st="on"><st1:City w:st="on">Copenhagen</st1:City></st1:place> in 2010 and 1 in 2020. The number of exceedances will be a little lower, when the low emissions zone is introduced in <st1:place w:st="on"><st1:City w:st="on">Copenhagen</st1:City></st1:place> . Under the consequence of the low emission zone we assume that all EURO III heavy duty vehicles will be equipped with particle filters and all heavy vehicles older than EURO III will be replaced by EURO V vehicles.
A scenario that assumes SCR catalysts on all heavy duty vehicles with particle filters under the low emission zone scenario results in significant lower number of exceedances, approx. 40 %. A scenario with SCR catalysts on all diesel vehicles result in 75 % less exceedances. However, this is probably not technically realistic.
The results from <st1:place w:st="on"><st1:City w:st="on">Copenhagen</st1:City></st1:place> can easily be transferred to other large Danish cities based on information about traffic density, street configuration (street width) and data about urban background from the Danish Air Quality monitoring programme. The urban background levels of NO2 are 5-8 µg/m3 lower in the cities <st1:City w:st="on">Odense</st1:City> , Århus and <st1:place w:st="on">Aalborg</st1:place> . In combination with lower traffic density in these cities we do not expect any exceedances of the NO2 limit value in 2010 or 2020.
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