No abstract

No abstract

Due to the need to better characterise the ultrafine particles fraction and related personal exposure, several impactors have been developed to enable the collection of ultrafine particles (<100 nm). However, to the authors’ kno wledge there have been no field campaigns to-date intercomparing impactor collection of ultrafine particles. The purpose of this study was two-fold: 1) to assess the performance of a number of conventional and nano-range cascade impactors with regard to the particle mass size distribution under different environmental conditions and aerosol loads and types, and 2) to characterise aerosol size distributions including ultrafine particles using impactors in 2 European locations. The impactors used were: (i) Berner low-pressure impactor (BLPI; 26 nm - 13.5 μm), (ii) nano-Berner low-pressure impactor (nano-BLPI; 11 nm - 1.95 μm) and (iii) Nano-microorifice uniform deposit impactor (nano-Moudi; 10 nm-18 μm), and (iv) Personal cascade impactor Sioutas (PCIS; <250 nm - 10 μm). Taking the BLPI as an internal reference, the best agreement regarding mass size distributions was obtained with the nano-BLPI, independently of the aerosol load and aerosol chemical composition. The nano-Moudi showed a good agreement for part icle sizes >320 nm, whereas for particle diameters <320 nm this instrument recorded larger mass concentrations in outdoor air than the internal reference. This difference could be due to particle bounce, to the dissociation of semi volatiles in the coarser stages and/or to particle shrinkage during transport through the impactor due to higher temperature inside this impactor. Further research is needed to understand this behaviour. With regard to the PCIS, their size-resolved mass concentrations were compar able with other impactors for PM1, PM2 and PM10, but the cut-off at 250 nm did not seem to be consistent with that of the internal reference.

Fine and coarse fractions of atmospheric aerosol overlap in the particle size range of about 1-2.5 µm (aerodynamic diameter). Sources of both fractions contribute to PM 1-2.5 to different extents due to meteorological and spatial conditions. Therefore, there is ongoing discussion as to whether PM 2.5 or PM 1 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 PM 1 , PM 2.5 , 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 PM 1-2.5 in PM 10 or TSP percentages were 7% and 6% in summer and 7% and 9% in winter. On the other hand, PM 1-2.5 accounted for a higher mass portion of PM 2.5 during summer. Stronger positive correlation and relationship were identified between PM 1-2.5 and the coarse fraction than between PM 1-2.5 and PM 1 in all environments. MLR confirmed the dependence of PM 1-2.5 on PM 1 in only 3 environments. This study found that PM 1-2.5 in Central Europe represents mostly the "tail" of the coarse mode and probably has the same sources. Therefore, PM 1 should be considered by the NAAQS as a fine particulate pollutant in Central Europe.