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OSPM: Comparison between modelled results obtained for the Erzeijstraat in the Netherlands and measurements

OSPM: een vergelijking tussen berekende resultaten en metingen in de Erzeijstraat in Nederland


RIVM has compared the results obtained with a Danish model for the calculation of air quality in streets, the OSPM (Operational Street Pollution Model), with measurements of the Dutch National Air Quality Monitoring Network (LML) and the calculations performed using the Dutch CAR-II (Calculation of Air pollution from Road traffic) model. The yearly average concentrations calculated using the OSPM are in reasonably good agreement with both the measurements and the calculations performed using CAR-II. However, there is a large scatter between the calculated and measured hourly concentrations. In the study reported here, the OSPM was used to calculate the NOx and NO2 concentrations in the Erzeijstraat in Utrecht, which is a good example of a typical Dutch street canyon. Calculations were performed for 2002, 2003 and 2006. Dutch municipalities use the CAR-II model to estimate local air quality in streets with traffic. Research by the RIVM in 2007 demonstrated that the annual concentrations calculated by CAR-II are in fairly good agreement with measurements. However, it is not possible to calculate hourly concentrations using the CAR-II model. Hourly concentrations can be calculated using the OSPM model, which is a more sophisticated and detailed model. This model has been tested successfully in Denmark. The yearly average concentrations of NO2, as calculated using the OSPM, were found to be one to two micrograms per cubic meter lower than the measured values. This result is comparable to that obtained using CAR-II. There is a good correlation between modelled total hourly concentrations and measured total hourly concentrations (background plus contribution from the traffic), but only a moderate correlation for modelled and measured street increment. The lack of accurate meteorological data is probably the main factor contributing to this latter result. There were also contributions from nearby roads and highways, but these can not be incorporated in the OSPM.

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