In this study, atmospheric particulate matter (APM) pollution was compared in urban background sites of two cities in Hungary—namely the capital Budapest and Debrecen—by analyzing daily aerosol samples collected between 8 December 2009 and 18 March 2010. Concentration, elemental composition, including BC, and sources of fine (PM_2.5) and coarse (PM_2.5–10) aerosol pollution, as well as their variation due to meteorological conditions and anthropogenic activities, were determined for both cities. The average PM_2.5 concentrations were 22 μg/m³ and 17 μg/m³ in Budapest and Debrecen, respectively. In the case of PM_10, the mean concentration was 32 μg/m³ in Budapest and 23 μg/m³ in Debrecen. The concentration of the coarse fraction decreased significantly over the weekends compared to working days. The number of exceedances of the WHO recommended limit value for PM_2.5 (15 μg/m³) were 67 in Budapest and 46 in Debrecen, which corresponds to 73% and 50% of the sampling days, respectively. At the time of the exceedances the daily average temperature was below freezing. The average PM_2.5/PM₁₀ ratio was 70% and 75% for the two sites, indicating the dominance of the fine fraction aerosol particles during the study period. Elements of natural origin (Al, Si, Ca, Ti, Mn, Fe, Ba) and chlorine were found to be dominant in the coarse fraction, while elements of anthropogenic origin (S, K, Cu, Zn, Pb) were characteristic to the fine fraction. Similar concentrations were measured in the two cities in the case of S which originates from regional transport and K which serves as a tracer for biomass combustion. Traffic-related elements were present in 2–3 times higher concentrations in Budapest. The episodic peaks in the Cl time series could be attributed to salting after snowfalls. The following sources of APM pollution were identified by using the EPA Positive Matrix Factorization (PMF) 5.0 receptor model: soil, traffic, road dust, secondary sulfate, biomass burning, and de-icing of streets. On polluted days when the PM_2.5 concentration exceeded the 25 μg/m³ value the contribution of secondary sulfate, domestic heating, and traffic increased significantly compared to the average. On weekends and holidays the contribution of soil and traffic decreased. The main pollution sources and their contributions were similar to the ones in other cities in the region. Comparing our findings to results from winter 2015 it can be concluded that while the PM_2.5 pollution level remained almost the same, a significant increase in the contribution of biomass burning was observed in both cities from 2010 to 2015, indicating a change of heating habits.

In this case study, aerosol pollution and passenger exposure were investigated while travelling on different public transport vehicles in Hungary. Two sampling campaigns were carried out: one in autumn 2012 and the other in spring 2014. Concentration, elemental composition and the size distribution of aerosol samples were determined in order to characterize the atmospheric particulate matter (APM) pollution inside the vehicles. The concentration of the PM_coarse fraction inside the different vehicles varied between 29 and 354 μg m⁻³, while the PM_2.5 concentrations were found to be between 12 and 192 μg m⁻³. This was significantly (2–19 times) higher than the outdoor concentration values. The main sources of the increased exposure were the resuspended mineral and road dust, including salt and fertilizers, and the direct exhaust of the vehicles. Rail abrasion and disinfectant and cleaning materials also contributed considerably to the aerosol pollution inside the vehicles. Moreover, organic fibrous particles were found in great number on the samples by single particle analysis using scanning electron microscopy (SEM).