The Role of PM2.5 Chemical Composition and Meteorology during High Pollution Periods at a Suburban Background Station in Southern Poland

This study conducted measurements of PM2.5 (particulate matter with a diameter <= 2.5 mu m) in Raciborz, Poland, during 2018. Samples were collected daily and analyzed for their chemical composition, specifically, the carbonaceous (elemental and organic carbon) and water-soluble ionic (Cl-, NO3-, SO42-, Na+, NH4+, K+, Ca2+ and Mg2+) components. Additionally, the secondary inorganic aerosol (SIA) as well as the secondary and primary organic carbon (SOC and POC, respectively) content was estimated. To identify the causes of elevated PM(2.)5 concentrations, the contributions of these chemical species were further investigated, and the role of meteorological factors was also examined. During the measurement period, PM2.5 concentrations exceeding 50 mu g m(-3) were recorded on 38 days, and 7 pollution episodes were detected. Such events, however, were observed only in the heating season, when stable meteorological conditions (low air temperatures, weak winds, high relative humidity and lack of precipitation) and increased emissions of PM and its precursors from anthropogenic sources favored the accumulation of pollutants. The PM2.5 was dominated by carbonaceous aerosol, especially POC, although the SOC rose significantly during high pollution periods. Furthermore, the fraction of SIA clearly decreased as the concentration of PM2.5 increased, and its variability was greatly affected by regional and/or long-range transport events. Our results can help guide the development of effective strategies for reducing air pollution from fine particulate matter. Such control measures are particularly important in Poland, where PM2.5 concentrations remain high compared to many European countries.