SIMAIR—Evaluation tool for meeting the EU directive on air pollution limits

Almost all Swedish cities need to determine air pollution levels—especially PM10—close to major streets. SIMAIR is an internet tool that can be used by all Swedish municipalities to assess PM10, NO2, CO and benzene levels and how they compare to the EU directive. SIMAIR is delivered to the municipalities with all required input data pre-loaded and is meant to be used prior to decisions if and where, monitoring campaigns are required. The system includes a road and vehicle database with emission factors and a model to calculate non-tailpipe PM10 emissions. Regional and urban background contributions are pre-calculated and stored as hourly values on a 1×1 km2 grid. The local contribution is calculated by the user, selecting either an open road or a street canyon environment.A comparison between measured and simulated concentrations in four street locations shows that SIMAIR is able to calculate statistics of yearly mean values, 90-percentile and 98-percentile daily mean values and the number of days exceeding the limit value that are well within ±50% that EU requires for model estimates of yearly mean values. In comparison, all values except one are within ±25% which is the quality objective for fixed measurements according to the EU directive.The SIMAIR model system is also able to separate the percentual contribution of the long-range transport from outside the city, the city contribution and the local contribution from the traffic of an individual street.