Characterization of PM10 fraction before pandemic and during pandemic COVID-19 at the traffic station in Krakow, Poland

Samples of PM₁₀ were collected at the traffic station in Krakow, Poland during two periods: 2^nd February- 30^th May 2018 and 2^nd February 17^th June 2020. PM₁₀ concentrations were determined gravimetrically. PM₁₀ concentrations dropped by 50% from 74±29 µg/m³ to 37±13 µg/m³ in 2018 and 2020, respectively. Elemental concentrations were determined by energy dispersive X-ray fluorescence method (EDXRF) and ion concentrations by ion chromatography (IC). 18 elements and 8 ions were measured. Ratios of concentrations in 2018 to 2020 were above 1.7 for the following elements: S, Cl, K, Zn, Br and ions SO₄^2-, Na⁺, NH₄⁺. The above-mentioned ratio was equal to 1.4 for Cu, Fe and Co. Similar concentrations in 2018 and 2020 were observed for the following chemical species: Ca, Ti, Mn, Ni, Rb, Sr, K⁺, Mg²⁺, Ca²⁺, PO₄^3-. Cr concentration was higher in 2020 compared to 2018. Four factors were obtained from PMF (Positive Matrix Factorization) modelling. The following sources were attributed: solid fuel combustion, secondary inorganic aerosols, traffic/industry/construction work and soil. The contribution of traffic/industry/construction work to PM₁₀ mass was the highest. It was equal to 24.6 µg/m³ and 23.4 µg/m³ in 2018 and 2020, respectively. The contribution of solid fuel combustion and secondary inorganic aerosols was five times lower in 2020 than in 2018. Contribution of solid fuel combustion was 14.5 µg/m³ and 2.6 µg/m³ in 2018 compared to 2020. SIA was lowering from 15.7 µg/m³ in 2018 to 2.5 µg/m³ in 2020. Traffic/industry/construction work and soil contribution was on the similar level in both years. Two factors affected characteristic of PM₁₀: one was a ban of using coal and wood for heating purpose introduced in Krakow in September 2019 and second one was pandemic of COVID-19 started in March 2020. Our study will be helpful for the local authority in preparing future plans for reducing air pollution within the city.

Acknowledgments: This research project was supported/partly supported by the program “Excellence initiative—research university” for the University of Science and Technology. The bilateral cooperation  project nr BPN/BPT/2021/1/00001 between Poland and Republic of Portugal partially financed this work together with the subsidy of the Ministry of Science and Higher Education, grant number 16.16.220.842.