Ionic Composition of Fine Particulate Matter from Urban and Regional Background Sites in Poland

The work presents the results of the measurements of mass concentrations of fine particulate matter (PM2.5) and water-soluble ions (sulfates SO4 (2-), nitrates NO(3)(-)as well as ammonium NH4 (+), sodium Na+, chlorine Cl-, potassium K+, calcium Ca2+, and magnesium ions Mg2+) in PM2.5. The analysis regarded PM2.5 samples collected in three different measurement sites in Poland: Trzebinia (urban background), Szczecin (urban background), and Zloty Potok (regional background). The research was conducted during heating (Jan-Mar) and nonheating (May-Jul) seasons of 2013. PM was sampled by the medium-volume samplers, and the concentrations of the ions in PM2.5 were analyzed by ion chromatography. Clear spatiotemporal variability of PM2.5 concentrations was observed, with higher levels recorded during the heating period. Average PM2.5 concentrations over the entire measurement period equaled 17.11, 25.21, and 25.16 mu g/m(3) in Szczecin, Trzebinia, and Zloty Potok, respectively. Ionic composition of PM2.5 from all stations was dominated by SO4 (2-), NO3-, and NH4 (+) ions. The total share of these ions was similar to 78%, similar to 85%, and similar to 89% of the mass of all analyzed ions, and it was similar to 34%, similar to 30%, and similar to 18% of the PM2.5 mass in Szczecin, Trzebinia, and Zloty Potok, respectively. Contribution of secondary inorganic ions in the PM2.5 mass was relatively stable in the heating and nonheating seasons, although the shares of individual inorganic ions in PM2.5 displayed seasonal differences. It was found that seasonal variability of PM2.5 concentrations, as well as concentrations and contributions of PM2.5-related components was related with the impact of weather conditions and the changes in the intensity of the emission sources of PM2.5 and its precursors.