2004/279/EC: Commission DecisionShow full title

2. U.K. GERMAN PROGRAMME OF CONTROL CONCEPTS AND MEASURES FOR OZONE - "SUMMER SMOG"

Objective

2.1. The aim of this research project was the determination and evaluation of the effectiveness of large scale (German-, respectively EU-wide) as well as of local emission control measures on elevated ground level ozone concentrations in midsummer episodes by applying photochemical dispersion models. Thus, the research project was designed to contribute to scientific conclusions as regards the effectiveness of ozone abatement strategies. Furthermore, taking into account the ongoing political discussions to advance legislation for ozone abatement at federal and at state levels, the findings of this project were to contribute to improving the basis for decision-making.

The simulations were among others conducted for an ozone episode in 1994 (from 23 July to 8 August). Ground-level peak ozone concentrations of 250 to 300 μg/m3 (1h-values) were observed in the afternoon. The results of the model calculations are summarised below.

Effect of various measures on ozone concentrations in Germany

2.2. Permanent reduction measures: By 2005, the emission control measures already implemented (EC Directives, national environmental legislation, etc.) will reduce the ozone precursor emissions nationwide by 37 % for NOx and by 42 % for VOC. For this scenario, decreases of the afternoon's ozone peak concentrations ranging from 15 to 25 % are calculated in large parts of the modelling domain. Peak values of 300 μg/m3, for instance, would thus be lowered by 60 μg/m3 on the average. The calculated number of grid hours(1) at ground level, during which in the base case run threshold values of 180, respectively 240 μg/m3, are exceeded, is reduced by 70 to 80 % in the scenario.

In the case of additional permanent reduction measures (-64 % NOx; -72 % VOC)(2), the calculated afternoon's peak concentrations are 30 to 40 % lower than in the base case run. The calculated frequency of number of grid hours exceeding threshold values of 180, respectively 240 μg/m3, is reduced by approximately 90 %.

Temporary reduction measures: In the case of a "severe" nationwide speed limit (-15 % NOx; -1 % VOC), the model simulations show a decrease in the calculated frequency of grid hours exceeding the threshold of ground-level ozone concentrations of 180 μg/m3 by approx. 14 %. The domain-related rates of reductions of peak ozone concentrations in the afternoon hours range from 2 to 6 %.

In the case of a nationwide driving ban for passenger cars without a three-way catalyst (-29 % NOx; -32 % VOC), the simulation shows a 29 % decrease of the calculated number of grid hours with ground-level ozone concentrations above 180 μg/m3. The domain-related rates of reduction of peak ozone concentrations in the afternoon hours range from 5 to 10 %. A hypothetical 48-hour earlier release of the measure results in an additional reduction of ozone peak concentrations of 2 %.

Effect of various measures on ozone concentrations in three selected German regions

2.3. The local scale analysis of the effectiveness of control measures was performed for three selected model regions: Rhine-Main-Neckar (Frankfurt), Dresden and Berlin-Brandenburg. In all three regions, ozone peak concentrations significantly exceeded 200 μg/m3 (1h-value) over several days in the episode studied.

Permanent reduction measures: On local scales, for the three model regions, the permanent large-scale control measures (up to -30 % NOx; up to -31 % VOC; both plus effects in Germany/Europe) result in a decrease of the calculated peak ozone concentrations in the range of 30 to 40 %. Afternoon peak values of 240 to 280 μg/m3 would thus drop below 200 μg/m3. The effectiveness of permanent large-scale control measures is significantly higher than that of temporary measures (see below), although the emission-related reduction effects are "only" in the magnitude of -30 to -40 %. The higher efficiency of permanent control measures is caused by the abovementioned decrease of the precursor emissions at the national (European) level. Thus, the background concentrations of ozone and ozone precursors are reduced.

Temporary reduction measures: Local speed limits (up to -14 % NOx; -1 % VOC) and local driving bans including non-low emission diesel cars (up to -25 % NOx; up to -28 % VOC) exert only minor effects on peak ozone concentrations, at maximum -4 % for speed limits and -7 % for traffic bans. As background concentrations of ozone and precursors remain unaffected by local measures, they solely have an impact on the local ozone production. This accounts for the low efficiency of this type of measures.

Local control strategies, temporarily implemented, are able to achieve moderate decreases in the afternoon peak ozone concentrations in the domain exposed to the measures when there are conditions of very little exchange of air masses. Even by exhausting all available local control potentials (and hence by applying the most stringent actions), the effects on peak ozone levels cannot be placed on a par with those of permanent emission control.

References:

Motz, G., Hartmann, A. (1997)

Determination and evaluation of effects of local, regional and larger-scale (national) emission control strategies on ground level peak ozone concentrations in summer episodes by means of emission analyses and photochemical modelling, summary of the study commissioned by the German Federal Environmental Agency - UFO-Plan Nr. 10402812/1).

www.umweltbundesamt.de/ozon-e

(1)

The number of grid hours corresponds to the number of hours throughout the entire episode during which a concentration threshold was exceeded in a given grid cell, summed up over all grid cells of the surface layer in the model domain.

(2)

The figures in brackets indicate the emission reductions.