Seasonal variability of size segregated particulate matter ratios: the use of a novel approach to its representation and study

The present study deals with a novel approach to represent the seasonal variability of the ratios between the mass concentrations of PM10, PM2.5 and PM1 (i.e., aerosol particles with aerodynamic diameters less than 10, 2.5 and 1 ?m, respectively). To this aim, studies presenting simultaneous measurements of PM10, PM2.5 and PM1 mass concentrations were considered and the corresponding ratios (i.e., PM1/PM10, PM2.5/PM10, PM1/PM2.5 and PM2.5- PM1/PM10-PM1) were calculated and displayed by a triangular diagram. Results point out that the data collected during winter season are mostly characterized by higher values of the PM2.5/PM10 and PM1/PM10 ratios and are displayed toward the upper left region of the triangular diagram, such that in some cases the intermodal size fraction can contribute substantially to fine fraction and in most cases that the intermodal size fraction can be of comparable magnitude with coarse size fraction. Moreover, the most of the data referring to winter season accumulate into a cluster. Instead, the data collected during summer season are mostly displayed toward lower values of PM2.5/PM10 and PM1/PM10 ratios with some exceptions for summer wildfire episodes. Finally, during the warm season no clusters are observed.