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

ABSTRACT In the present study the results from annual measurement campaign (2018) conducted in Raciborz are presented. Daily PM2.5 samples were analyzed for carbonaceous matter (elemental and organic carbon) and water-soluble ions (Cl-, NO3-, SO42-, Na+, NH4+, K+, Ca2+, Mg2+). The content of secondary inorganic aerosol (SIA) as well as secondary and primary organic carbon (SOC and POC, respectively) was estimated. The contributions of aerosol chemical species along with meteorological parameters were further investigated to reveal the causes of the elevated PM2.5 concentrations. Considering the entire measurement period, PM2.5 concentrations exceeding 50 µg·m-3 were recorded in 38 cases, of which 7 episodes were identified. Such events were only observed in the heating season, due to stable meteorological conditions (low air temperatures, weak winds, high relative humidity, no precipitation) and increased emission of PM and its precursors from anthropogenic sources. The carbonaceous aerosol was the dominant component of PM2.5, especially POC, although the SOC content increased significantly during high pollution periods. The share of SIA clearly decreased with increasing PM2.5 concentration, and its variability was affected to a large extent by regional and/or long-range transport events. The results of the study could provide insights on the development of effective control strategies related to air pollution with fine particulate matter. This is particularly important in Poland, where PM2.5 concentrations remain high compared to many European countries.