English title: Influence of road conditions, vehicle speed and meteorological parameters on the PMx concentrations near roads. English abstract: On the basis field measurements of concentrations near 8 roads, the potential effect of PM10 reduction measures (improving road surface, upgrading of road, speed reduction, improving traffic flow) and the influence of meteorological parameters on the PM10 emissions and concentrations was analyzed. The influence of road surface improvements on the PMx concentrations could be investigated at Lützner Strasse in Leipzig, Berliner Strasse in Nauen and Bergstrasse in Erfurt. It was observed that by the renewal of bad road surfaces and adjacent pedestrian walkways, bad in the sense of PM10 emissions, at all three roads a PM10 reduction could be observed. The highest PM10 reduction was found at Berliner Strasse in Nauen. There, the reduction for the additional street concentration was 14 µpg/m3 i.e. approximately 60%, the non exhaust share of the PM10 emissions went down to about 1/3, that was much higher than at Lützner Strasse or at Bergstrasse in Erfurt. The amount of the reduction is probably dependent on the boundary conditions as for example baseline condition (state of the road before the improvement), vehicle speed and slope of the road. Further evaluations, especially for Bergstrasse in Erfurt, are therefore strongly recommended. Hint: The additional (road) concentration is the concentration caused by the road under consideration, i.e. the monitored "total concentration" at the road minus the regional and local background concentration, monitored at a station outside the direct influence of the road under consideration or of other roads. The influence of a speed limit on the PMx concentrations could be investigated by measurements at Schildhornstrasse in Berlin. There the speed limit was reduced from 50km/h to 30km/h with simultaneous radar supervision. By this measure, maintaining the smooth traffic flow conditions, a reduction during working days of about 2 µg/m3 i.e. approximately 15 to 27% of the PM10 additional road concentration can be derived. For soot and NOx no relevant reductions were noted. The influence of an upgrading of an urban road to Standard Federal Road Conditions with establishment of a "green wave" on the PMx concentrations could be investigated by at Bergstrasse in Dresden. The traffic flow after the upgrading has improved significantly in both directions. For the direction out of the city (into the city) before the upgrading, the flow of traffic was reported to be with medium (strong) jamming. After the upgrading, the Green Wave works well for the out of town direction (minor jamming), in the downtown direction there are delays at the traffic lights, but in general with only slight effects on the traffic flow. At the location of the monitoring station the average vehicle speed before the upgrading was in the range of 30km/h, after the expansion more than 40km/h. That does not mean, however, that before the upgrading the vehicle speed was permanently 30 km/h. As the percentiles (Q75, Q90) of the vehicle speeds show, the vehicles drove, if not hindered by the traffic lights, before the upgrading with mean speeds of 40 to 45km/h, after upgrading with 45 to 50km/h. By improving the traffic flow (Green Wave) despite higher vehicle speeds, a PM10 reduction of about 3 µg/m3, i.e. approximately 35% of the PM10 additional road concentration, can be derived. Concerning the influence of meteorological parameters, extensive data analysis were executed for the road B 10 near the city of Karlsruhe, for Merseburger Strasse in the city of Halle and for Jagtvej in Copenhagen, all incorporating the results of the representative background monitoring stations. As expected, clear dependencies of PM10 and PM2.5 concentrations on the meteorological parameters were observed. As there are a large number of correlations among the meteorological parameters themselves, the dependence of particle concentrations on the single meteorological parameters is not directly indicated. The strongest meteorological influences on the PM10 total concentrations come from the vertical atmospheric exchange conditions (indicator was here, for example, the vertical temperature gradient), the number of days without precipitation since the last rainfall event and the wind speed. The strongest meteorological influences on the PM10 additional concentrations come from the wind speed and direction as well as the ambient temperature. The PM10 emission factors exempli gratia for Merseburger Strasse during working days with precipitation show approximately a 30% lower mean value than for dry days. This reduction is significant. The PM10 emission factors during the first three dry days after a precipitation event are equal, showing no increase with the ongoing drought. As expected, the measurements did not show a PM2.5 emission factor reduction as an effect of rainfall. While the PM2.5 emission factors (largely engine (exhaust) emissions) are independent of the season, the emission of the PM2.5 to PM10 particles group (mostly consisting of non-exhaust emissions) increases significantly in the winter half of the year (over 100%). Causes could be the use of sand/salt as antiskid treatment and increased input of dirt on the road. In the winter half of the year the PM10 emission factors, as expected, are independent from the atmospheric exchange conditions and they are significantly (a factor of two) higher than in the summer half of the year. This increase in PM10 emissions under winter conditions could also explain why the PM10 emission factors, in contrast to PM2.5, are much higher at lower daily average temperatures than at high temperatures. The strong increase in PM10 concentrations during low (winter) atmospheric inversion layers could thus both be caused by the reduced exchange conditions as well as the significantly higher non exhaust PM10 emissions. Hint: Total emission = direct exhaust emission + non exhaust emission (road abrasion, tire wear, road dust re-suspension. On Jagtvej, also the height of the water level on the road could to be monitored by a sensor. This water level on the road was found to influence the PM10 concentrations. After a summer rain event the surface of Jagtvej dries completely after a mean time of about 7 hours. A reduction of emissions can be watched for an average of 3 to 5 hours after the end of the rainfall. At Jagtvej, for dry roadway conditions, the ratio of PM10 to NOx additional concentrations, as a measure of PM10 emission-specific conditions, was independent from the wind speed. Presently, in several research projects further work is done to improve the PM10 emission modeling and the assessment of mitigation measures. It is reserved to a separate evaluation to draw the conclusions from all these new results for advanced PM10 modeling. (Author/publisher)
Abstract