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Abstract: This study summarizes measurements of atmospheric 14C and 137Cs in the Bratislava air since 1976. Higher 14C levels observed in spring and early summer months until the 1980’s confirm injection of the stratospheric air into the troposphere. Later, deep winter minima were observed in 14C concentrations, probably due to the depletion of the atmospheric 14C levels in winter months by the injection of large quantities of fossil CO2. Presently observed 14C maxima in summer and minima in winter were caused by the depletion of the atmospheric 14C in winter months, amplified by temperature inversions during winter, rather than by the injection of the stratospheric air into the troposphere. The observed 137Cs activity concentrations also showed an impact of the stratospheric air on the 137Cs levels until the early 1980’s, documented by typical spring/early summer maxima and winter minima. The global fallout 137Cs record was then disturbed by the Chernobyl accident (1986) when large quantities of 137Cs were released to the atmosphere. The recent 137Cs variations observed in the atmosphere, characterised by winter maxima and summer minima, are assumed to be mainly due to the resuspension of 137Cs from the soil. A correlation was found between the 137Cs activity concentration and the dust level in the air (the correlation coefficient r = 0.74), as well as an anticorrelation with the temperature (r = −0.56). [Copyright &y& Elsevier]

Radiocarbon measurements of total carbon (TC) fraction of aerosol samples collected at the campus of the Comenius University in Bratislava (Slovakia) during 2022-2023 were carried out. Based on radiocarbon activity of these samples and a source apportionment model we have determined the relative proportion of fossil and non-fossil carbon in collected atmospheric aerosols. The carbon from non-fossil sources (biomass burning and biogenic emissions) was dominant in this time period, on average it formed 72% of carbon present in the aerosols from the atmosphere of Bratislava. The whole range of determined non-fossil fraction was relatively small as it varied only from 0.67 (August-September) to 0.82 (December-January). These changes do not exhibit any significant seasonal variation as was previously observed in Bratislava during 2017-2018 in the elemental carbon (EC) aerosol fraction., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Aerosols dispersed in the atmosphere represent important factors influencing not only the environment, but also human health. Carbonaceous aerosols are one of the main components of total atmospheric aerosols, and their sources are of great interest. Radiocarbon analysis provides an excellent way to determine the fraction of fossil and non-fossil aerosols in the atmosphere. Over the period of one year (June 2017-June 2018), we sampled atmospheric aerosols with size greater than 0.3 μm in Bratislava, Slovakia and used the exposed quartz filters for radiocarbon analysis of the elemental carbon (EC) aerosol fraction. The results show that on average the fossil fuel combustion is the dominant source of EC aerosol particles in Bratislava. In summer months, they represent more than half (65-80%) of the total EC aerosols. The relative amount of EC particles derived from biomass burning was 20-35% in summer, which increased to 40-55% in winter months. The dominance of fossil fraction is caused by high degree of industrialization and urbanization of the city. The increase of biomass fraction in winter is probably caused by domestic wood burning in areas surrounding the Bratislava city., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Variations of aerosol radionuclides (2001-2015) in the ground-level air in Bratislava (Slovakia) showed 7 Be maxima in spring/early summer and minima in winter, however, an inverse trend was observed for 210 Pb, 137 Cs and 40 K. A decreasing amplitude and splitting of summer maxima for 7 Be in the last years has been found. A temporal behavior of the 7 Be/ 210 Pb activity ratio showed higher levels during warm seasons due to vertical convection of air masses from higher altitudes. The 137 Cs activity concentration in the surface air between 2003 and 2010 was decreasing with an effective half-life of 1.9 ± 0.3 years. The yearly average 137 Cs concentrations during 2009-2014 were almost constant, disturbed only by the Fukushima accident in 2011. The increased atmospheric 137 Cs and 40 K levels observed during the autumn-winter season may be due to surface soil resuspension, biomass burning and radionuclide transport by winds. Seasonal variations of 222 Rn activity concentrations were found with maxima at the end of autumn and in winter, and minima in spring. The variability of the average annual course of 222 Rn has been larger than that of 210 Pb. The 210 Pb/ 222 Rn activity ratio was highest at the end of winter and in the spring, while from June to December remained nearly constant. More intensive atmospheric mixing in spring months caused a decrease in the 222 Rn activity concentration, while the aerosol component of the atmosphere has been affected mainly during the autumn and winter seasons. The mean residence time of aerosols in the atmosphere was calculated using the 210 Pb/ 222 Rn method to be 4.5 ± 0.9 days., (Copyright © 2016 Elsevier Ltd. All rights reserved.)