Source Apportionment of Atmospheric Aerosols in Krakow, Poland, before and during the COVID-19 Pandemic at a Traffic Monitoring Station

PM10 samples were collected at the Krak & oacute;w air quality traffic monitoring station during two periods: February-May 2018 and February-June 2020. The PM10 concentrations dropped by 50% from 74 +/- 29 mu g/m(3) to 37 +/- 13 mu g/m(3) in 2018 and 2020, respectively. The elemental concentrations were determined by the energy-dispersive X-ray fluorescence (EDXRF) method, and the ion concentrations were determined by ion chromatography (IC). The concentration ratios in 2018 to 2020 were greater than 1.7 for the following elements: S, Cl, K, Zn, Br, and the ions SO42-, Na+, and NH4+. Similar concentrations were observed in 2018 and 2020 for the following chemical species: Ca, Ti, Mn, Ni, Rb, Sr, K+, Mg2+, Ca2+, and PO43-. The Cr concentration was higher in 2020 compared to 2018. Four source profiles were obtained from the PMF (Positive Matrix Factorization) modelling. The following sources were attributed to this: solid fuel combustion, secondary inorganic aerosols, traffic/industry/construction work, and soil. The contributions of solid fuel combustion and secondary inorganic aerosols (SIA) were significantly lower in February and March 2020 than in February and March 2018. The relative differences were in the range 70-98%. Traffic/industry/construction work contributions were 6% and 36% lower in March and May 2020 compared to the same months in 2018, respectively. Two factors affected the characteristics of PM10: one was the ban of using coal and wood for heating purposes introduced in Krakow in September 2019, observed mainly in February and March, and the COVID-19 pandemic that was observed mainly in April and May.