Seasonal variations of chemical composition of PM2.5 fraction in the urban area of Krakow, Poland: PMF source attribution

The mass concentration of PM2.5 fraction in the atmosphere of Krakow, Poland, is 2.6 times higher in winter than in summer. Similar observations were made for countries with very low temperature during cold season as discussed by Rogula Kozlowska et al. (Air Qual Atmos Health 7:41-58, 2014, Int J Environ Res Public Health 13:715, 2016), Jeong et al. (Atmos Pollut Res 2:158-171, 2011), and Zwozdziak et al. (J Aerosol Sci 103:38-52, 2017). Fossil fuel combustion for heating of individual households is mainly responsible for high air pollution levels in urban areas during winter season as reported by Junninen et al. (Environ Sci Technol 43:7964-7970, 2009). Elemental concentrations were determined by energy dispersive X-ray fluorescence method, whereas ion concentrations were measured by ion chromatography. In addition, concentrations of elemental carbon (EC) and organic carbon (OC) were determined using OC/EC analyzer. Some elements like Br, Pb and Cl-, NO3-, NH4+ ions show significantly higher concentrations during winter, whereas in summer, higher Ca concentration was observed. The positive matrix factorization (PMF) receptor method was used for identification of air pollution sources and evaluation of their contribution to PM2.5 burden in the local atmosphere. Selected chemical species were used as indicators of particular sources of air pollution. Four source categories were identified through PMF analysis: (i) combustion, (ii) secondary aerosols, (iii) soil/industry/traffic, and (iv) biomass burning. For days with high PM2.5 concentrations (winter season), the contribution of combustion sometimes reaching 55% of PM2.5 mass was identified, whereas for days with low PM2.5 concentrations, it was reduced to approximately 28%.