The objective of my work was to characterize urban particulate matter pollution in Debrecen during the years of the COVID crisis and to compare it with the data from the previous two years. For this purpose, PM2.5, PMcoarse, and PM10 aerosol samples were collected at an urban background site two times a week between March 2018 and Feb 2022. Concentration, elemental composition, and sources of APM pollution were determined, and the daily concentrations of NO2, CO, NOX, and PM10 were used from the Hungarian Air Quality Monitoring Network (OLM) stations as complementary data to our study. On this basis, changes in particulate matter pollution induced by lockdowns were studied. The elemental composition of the aerosol samples was determined by the particle-induced X-ray emission (PIXE) method at the new in-air millibeam PIXE setup of the ATOMKI Tandetron accelerator. The characterization of this newly developed PIXE measurement setup was also part of my work.