In Austria, the Federal Act on Ozone of 1992 contained the necessity to enact short-term action plans in the case of very high ozone levels. The relevant alarm threshold was 300 μg/m2 as three-hour mean value. The trigger for taking action was the concentration level exceeding 260 μg/m3 as three-hour mean value, taking into account that the implementation of plans takes some time. Most measures related to traffic (mainly ban of vehicles without catalytic converters). However, measures have never had to be taken, as the abovementioned level triggering action had never been reached. The regulation has been adapted to Directive 2002/3/EC in July 2003.

In general, ozone levels in Austria are mainly influenced by long range transport. In Alpine areas ozone shows a less pronounced diurnal cycle compared to other regions (UBA, 2002). As a consequence, relatively high long-term mean values are observed at those stations. However, levels in excess of the alarm threshold set in Directive 2002/3/EC (240 μg/m3) have not been recorded in the last couple of years in Alpine areas.

Highest ozone peak concentrations (with very few exceedances11 of 240 μg/m3 as one-hour mean value) can be observed in the plume of Vienna, usually in the north-eastern parts of Austria. The ozone levels can exceed the ozone levels outside the plume by up to 50 μg/m3 and more.

A photochemical transport model was developed to simulate ozone formation in this region (Baumann et al., 1998). Using this model, the effect of emission reductions within the study area on the ozone levels were investigated (Schneider, 1999).

The results are, in general, in line with results from other, more comprehensive studies and can be summarised as follows: The only significant effects of short-term emission reductions in Austria on ozone levels are predicted for the city of Vienna and in its plume. Within the city area of Vienna, where presumably exposure is most significant, slight reductions of NOx emissions (10 to 20 %) tend to increase ozone levels, while ozone production decreases as the air mass moves out of Vienna.

References:

UBA (2002). 6. Umweltkontrollbericht. Umweltbundesamt, Wien.

Baumann et al. (1997). Pannonisches Ozonprojekt. Zusammenfassender Endbericht. ÖFZS A-4136. Forschungszentrum Seibersdorf.

Schneider J. (1999). Untersuchungen über die Auswirkungen von Emissionsreduktionsmaßnahmen auf die Ozonbelastung in Nordostösterreich. UBA-BE-160.