M. Richtáriková

Forty years of atmospheric radiocarbon monitoring around Bohunice nuclear power plant, Slovakia.

Radiocarbon variations in the atmospheric CO(2) with attenuating amplitudes and decreasing mean values with typical maxima in summer and minima in winter have been observed since 1967 in two localities of Slovakia, in Bratislava and Zlkovce, situated about 60 km NE from Bratislava, only 5 km from the Bohunice Nuclear Power Plant (NPP). The (14)C record in Bratislava has been influenced mainly by fossil CO(2) emissions, in contrast to the Zlkovce record which has been more variable, as it has clearly been affected by operation of the Bohunice NPP. However, during specific meteorological conditions with NE transport of air masses to Bratislava, the effect of the Bohunice NPP has been visible in Bratislava as well. Maximum (14)C concentrations (up to 120% above a natural background) were observed around A1 NPP which used CO(2) with admixture of air as a cooling agent. The (14)C concentrations around four pressurized light water reactors were up to 30% above the background. The Delta(14)C values in the heavily polluted atmosphere of Bratislava were up to 10% and at Zlkovce up to 5% lower than the European clean air represented by the Jungfraujoch Delta(14)C data. Later the Delta(14)C values were similar at both sites, and from 2003 they were close to the European clean air levels. The observed Delta(14)C behaviour in the atmosphere provides a unique evidence of decreased fossil fuel CO(2) emissions in the region, as well as the long-term effect of the Bohunice NPP on the Bratislava and Zlkovce stations. The estimated annual radiation doses to the local public due to digestion of radiocarbon contaminated food have been estimated to be around 3 microSv.

Long-term variations of 14C and 137Cs in the Bratislava air – implications of different atmospheric transport processes

This study summarizes measurements of atmospheric (14)C and (137)Cs in the Bratislava air since 1976. Higher (14)C levels observed in spring and early summer months until the 1980s confirm injection of the stratospheric air into the troposphere. Later, deep winter minima were observed in (14)C concentrations, probably due to the depletion of the atmospheric (14)C levels in winter months by the injection of large quantities of fossil CO(2). Presently observed (14)C maxima in summer and minima in winter were caused by the depletion of the atmospheric (14)C in winter months, amplified by temperature inversions during winter, rather than by the injection of the stratospheric air into the troposphere. The observed (137)Cs activity concentrations also showed an impact of the stratospheric air on the (137)Cs levels until the early 1980s, documented by typical spring/early summer maxima and winter minima. The global fallout (137)Cs record was then disturbed by the Chernobyl accident (1986) when large quantities of (137)Cs were released to the atmosphere. The recent (137)Cs variations observed in the atmosphere, characterised by winter maxima and summer minima, are assumed to be mainly due to the resuspension of (137)Cs from the soil. A correlation was found between the (137)Cs 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).

Impact of the Bohunice Nuclear Power Plant on atmospheric radiocarbon.

Radiocarbon variations in the atmospheric CO(2) have been observed at two localities in Slovakia (Bratislava and Zlkovce). Zlkovce is situated about 60 km NE from Bratislava, and only 5 km from the Bohunice Nuclear Power Plant (NPP). The observed Delta(14)C levels provide a unique evidence of the long-term impact of the Bohunice NPP on the Bratislava region, as well as on the decreased fossil fuel CO(2) emissions. The radiation doses estimated to the local public have been around 3 microSv/year, 20% of the dose from global fallout (14)C present in the environment.

Spatial Radiocarbon and Stable Carbon Isotope Variability of Mineral and Thermal Waters in Slovakia

Isotope hydrology investigations were carried out with the aim to study isotope variability in mineral and thermal waters (MTW) of Slovakia. The aquifers of MTW were formed by Triassic limestones and dolomites, which are found in the mountains as well as in the pre-Tertiary substratum of depressions and lowlands. The MTW were of artesian and/or open structures. At present, there are only boreholes available, as natural outflows have already been captured by them. Large spatial isotope variability (14C between 2 and 33.6 pMC, δ18O between -11.8‰ and -9.8‰, and δ13C between -12.7‰ and -3.4‰ for bicarbonates and -21‰ and -4.9‰ for free CO2) and heterogeneity of MTW was observed, indicating different origins of MTW. Corrected radiocarbon apparent ages of MTW indicate that they mostly infiltrated during the W?rm and Holocene periods.

Radiocarbon in the Atmosphere of the Žlkovce Monitoring Station of the Bohunice NPP: 25 Years of Continuous Monthly Measurements

Radiocarbon variations in the atmosphere have been observed at the Žlkovce monitoring station of the Bohunice nuclear power plant (NPP), situated only 5 km ESE from the NPP. The observed 14 C levels provide unique evidence of a decreasing long-term impact of the Bohunice NPP on the region. Simultaneously, decreasing emissions of fossil fuel carbon dioxide in the atmosphere of the monitoring site have been found. The observed ∆ 14 C variations with time have attenuating amplitudes and decreasing mean values, showing maxima in summer and minima in winter, the latter primarily caused by increased emission of fossil CO 2 in winter months. Sporadic short-term releases of 14 C from the Bohunice NPP were observed at the Žlkovce station. The annual atmospheric ∆ 14 C variations compared with tree-ring data collected at the Žlkovce village show reasonable agreement. The observed ∆ 14 C levels after 2005 are close to the European clean-air levels as measured at the Jungfraujoch (3450 m asl) monitoring station. DOI: 10.2458/azu_rc.57.18364

Joint Bratislava–Prague studies of radiocarbon and uranium in the environment using accelerator mass spectrometry and radiometric methods

A research program has been established between Bratislava and Prague groups to study natural and anthropogenic radionuclides in the environment using both Accelerator Mass Spectrometry (AMS) and radiometric methods. The first studies have focused on 14C activity variations in the atmosphere and biosphere with the aim to evaluate an impact of Czech and Slovak Nuclear Power Plants (NPP) on the environment, and on the development of AMS technique for investigation of actinides (mainly uranium isotopes) in the environment.

Recent results from the AMS/IBA laboratory at the Comenius University in Bratislava: preparation of targets and optimization of ion sources

Developments of solid targets and optimizations of ion sources were carried out with the aim to produce high ion yields for applications of tandem accelerators as mass spectrometers. A comparison of Al− yields from different aluminum targets showed that the best results were obtained with AlN targets. Transmission studies of 9Be and 12C ions through the Pelletron accelerator showed highest efficiencies for 9Be2+ and 12C2+. First results obtained with a simplified version of the AMS line are presented as well.

Radiocarbon concentration in tree-ring samples collected in the south-west Slovakia (1974–2013)

Radiocarbon measurements of tree-ring samples collected in Vysoká pri Morave were compared with tree-ring data of the Žlkovce monitoring station situated 5km south-east from the Jaslovské Bohunice Nuclear Power Plant (NPP). Radiocarbon concentrations in Vysoká pri Morave and in Žlkovce tree rings were decreasing exponentially with decay constants of 14.48±1.23 y and 17.96±1.97 y, respectively, in agreement with similar results obtained at other radiocarbon stations. The Suess effect, represented by a dilution in 14C levels by fossil fuel CO2 emissions, was observed in both tree-ring data sets. The Vysoká pri Morave 14C data were during 1974-1995 systematically lower by about 50‰ than the Schauinsland (Germany) clean air reference values due to a regional fossil-fuel impact. However, after 1996 the Vysoká pri Morave 14C data were closer to the Schauinsland data due to lower CO2 emissions as a result of closing some of the heavy industry technologies in the region.