| Sumario: | The research focuses on the analysis of PM10 and PM2.5 concentrations variability at 11 stations in selected urbanized areas of Poland (Tricity, Poznań, Łódź, Kraków). Methods comprised: the analysis of basic statistical characteristics in yearly/monthly/daily/hourly scale and threshold exceedance frequencies. Also, correlations between PM10 and meteorological variables were investigated. GEV distribution analysis allowed the estimation of the return levels of monthly maxima of PM10 and PM2.5. Results show that in Tricity there are fewer than 5 % of days with PM10 and PM2.5 threshold exceedance. In Kraków, the standards are only met during summer and the frequency of daily PM limit exceedance in winter was around 65–90 %. GEV analysis indicates that 10y return level of PM10 monthly maximum daily average do not usually exceed 250 μg/m3 at most of the stations (Kraków agglomeration is an exception here). In winter, the meteorological conditions unfavourable to the pollutant's dispersion comprise: high-pressure systems, stable equilibrium in the atmosphere and limited turbulence occur quite often together with low wind speed and reduced height of the planetary boundary layer.
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