The Association between Intermodal (PM1-2.5) and PM1, PM2.5, Coarse Fraction and Meteorological Parameters in Various Environments in Central Europe

Fine and coarse fractions of atmospheric aerosol overlap in the particle size range of about 1-2.5 mu m (aerodynamic diameter). Sources of both fractions contribute to PM1-2.5 to different extents due to meteorological and spatial conditions. Therefore, there is ongoing discussion as to whether PM2.5 or PM1 should be included for monitoring as a fine particulate pollutant by the national ambient air quality standard (NAAQS). The aim of the presented study is to examine the association between the intermodal and PM1, PM2.5, coarse fraction, and meteorological parameters in various environments. Outdoor 24-h mass concentrations of size-resolved PM and meteorological conditions were measured at 12 sites within 42 campaigns between 11/2005 and 3/2015. The data set was divided into 10 environments reflecting season, locality, total measured PM, and placement of the impactor. We used two types of statistic methods: nonparametric correlation analysis and multiple linear regression (MLR). Median PM1-2.5 in PM10 or TSP percentages were 7% and 6% in summer and 7% and 9% in winter. On the other hand, PM1-2.5 accounted for a higher mass portion of PM2.5 during summer. Stronger positive correlation and relationship were identified between PM1-2.5 and the coarse fraction than between PM1-2.5 and PM1 in all environments. MLR confirmed the dependence of PM1-2.5 on PM1 in only 3 environments. This study found that PM1-2.5 in Central Europe represents mostly the "tail" of the coarse mode and probably has the same sources. Therefore, PM1 should be considered by the NAAQS as a fine particulate pollutant in Central Europe.