Contributions of fossil and non-fossil fractions to total carbon in urban aerosols in Bratislava (Slovakia).

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.

Radiocarbon analysis of carbonaceous aerosols in Bratislava, Slovakia.

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.

Long-term variations of radionuclides in the Bratislava air.

Variations of aerosol radionuclides (2001-2015) in the ground-level air in Bratislava (Slovakia) showed 7Be maxima in spring/early summer and minima in winter, however, an inverse trend was observed for 210Pb, 137Cs and 40K. A decreasing amplitude and splitting of summer maxima for 7Be in the last years has been found. A temporal behavior of the 7Be/210Pb activity ratio showed higher levels during warm seasons due to vertical convection of air masses from higher altitudes. The 137Cs 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 137Cs concentrations during 2009-2014 were almost constant, disturbed only by the Fukushima accident in 2011. The increased atmospheric 137Cs and 40K levels observed during the autumn-winter season may be due to surface soil resuspension, biomass burning and radionuclide transport by winds. Seasonal variations of 222Rn 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 222Rn has been larger than that of 210Pb. The 210Pb/222Rn 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 222Rn 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 210Pb/222Rn method to be 4.5 ± 0.9 days.

Iodine-129 in seawater offshore Fukushima: distribution, inorganic speciation, sources, and budget.

The Fukushima nuclear accident in March 2011 has released a large amount of radioactive pollutants to the environment. Of the pollutants, iodine-129 is a long-lived radionuclide and will remain in the environment for millions of years. This work first report levels and inorganic speciation of (129)I in seawater depth profiles collected offshore Fukushima in June 2011. Significantly elevated (129)I concentrations in surface water were observed with the highest (129)I/(127)I atomic ratio of 2.2 × 10(-9) in the surface seawater 40 km offshore Fukushima. Iodide was found as the dominant species of (129)I, while stable (127)I was mainly in iodate form, reflecting the fact that the major source of (129)I is the direct liquid discharges from the Fukushima NPP. The amount of (129)I directly discharged from the Fukushima Dai-ichi nuclear power plant to the sea was estimated to be 2.35 GBq, and about 1.09 GBq of (129)I released to the atmosphere from the accident was deposited in the sea offshore Fukushima. A total release of 8.06 GBq (or 1.2 kg) of (129)I from the Fukushima accident was estimated. These Fukushima-derived (129)I data provide necessary information for the investigation of water circulation and geochemical cycle of iodine in the northwestern Pacific Ocean in the future.