Mass Concentrations of Water-Soluble Ions in PM$_{2.5}$ Particle Fraction Measured at Urban Background Site in Croatia

Mass concentrations of PM$_{2.5}$ particle fraction, water-soluble anion species (Cl$^{-}$, NO$_{3}$$^{-}$, SO$_{4}$$^{2-}$) and cation species (Na$^{+}$, NH$_{4}$$^{+}$, K$^{+}$, Mg$^{2+}$, Ca$^{2+}$) were determined, to investigated the relationship between pollutant mass concentrations, contribution of measured species to PM$_{2.5}$ mass and prediction of the pollutant sources. Daily PM$_{2.5}$ samples were taken over three years 2014 – 2016 at urban background site (UBS) in northern part of Zagreb, Croatia.

Mass concentrations of PM$_{2.5}$ particle fraction were determined by gravimetry according to the standard HRN EN 14907:2006 (EN 14907:2005) and HRN EN 12341:2014 (EN 12341:2014). Water-soluble ionic species were analysed using Thermo Scientific – ICS 5000 Capillary ion chromatography.
Annual average PM$_{2.5}$ mass concentration ranged from 19.6 μg m$^{-3}$ to 22.7μg m$^{-3}$ respectively. The annual average ion mass concentrations at UBS followed the order SO$_{4}$$^{-2}$ > NO$_{3}$$^{-}$ > NH$_{4}$$^{+}$ > K$^{+}$ > Ca$^{2+}$ > Cl$^{-}$ > Na$^{+}$ > Mg$^{2+}$, respectively, contributed from 26.5% to 31.5% to the overall PM$_{2.5}$ mass, respectively. ... mehrAnnual average mass ratios of (NO$_{3}$$^{-}$)/(SO$_{4}$$^{2-}$) obtained in PM$_{2.5}$ ranged from 0.76 to 1.07, respectively, indicating that mobile source emission was an important contributor to particle mass at UBS.

The prediction of the pollutant sources, we ran the principal component analysis (PCA), which was performed using the STATISTICA 12.0 statistical packages. After varimax rotation, the obtained principal component factors were found to account for 95% of the variance. Factor loadings > 0.7 were considered significant.