Search

Tritium, radiocarbon and radiocesium concentrations in water column samples in coastal waters offshore Fukushima and in the western North Pacific Ocean collected in 2011–2012 during the Ka'imikai-o-Kanaloa (KoK) cruise are compared with other published results. The highest levels in surface seawater were observed for 134 Cs and 137 Cs in seawater samples collected offshore Fukushima (up to 1.1 Bq L −1 ), which represent an increase by about three orders of magnitude when compared with the pre-Fukushima concentration. Tritium levels were much lower (up to 0.15 Bq L −1 ), representing an increase by about a factor of 6. The impact on the radiocarbon distribution was measurable, but the observed levels were only by about 9% above the global fallout background. The 137 Cs (and similarly 134 Cs) inventory in the water column of the investigated western North Pacific region was (2.7 ± 0.4) PBq, while for 3 H it was only (0.3 ± 0.2) PBq. Direct releases of highly contaminated water from the damaged Fukushima NPP, as well as dry and wet depositions of these radionuclides over the western North Pacific considerably changed their distribution patterns in seawater. Presently we can distinguish Fukushima labeled waters from global fallout background thanks to short-lived 134 Cs. However, in the long-term perspective when 134 Cs will decay, new distribution patterns of 3 H, 14 C and 137 Cs in the Pacific Ocean should be established for future oceanographic and climate change studies in the Pacific Ocean. [ABSTRACT FROM AUTHOR]

Abstract: Large quantities of radionuclides were released in March–April 2011 during the accident of the Fukushima Dai-ichi Nuclear Power Plant to the atmosphere and the ocean. Atmospheric and marine modeling has been carried out to predict the dispersion of radionuclides worldwide, to compare the predicted and measured radionuclide concentrations, and to assess the impact of the accident on the environment. Atmospheric Lagrangian dispersion modeling was used to simulate the dispersion of 137Cs over America and Europe. Global ocean circulation model was applied to predict the dispersion of 137Cs in the Pacific Ocean. The measured and simulated 137Cs concentrations in atmospheric aerosols and in seawater are compared with global fallout and the Chernobyl accident, which represent the main sources of the pre-Fukushima radionuclide background in the environment. The radionuclide concentrations in the atmosphere have been negligible when compared with the Chernobyl levels. The maximum 137Cs concentration in surface waters of the open Pacific Ocean will be around 20Bq/m3. The plume will reach the US coast 4–5y after the accident, however, the levels will be below 3Bq/m3. All the North Pacific Ocean will be labeled with Fukushima 137Cs 10y after the accident with concentration bellow 1Bq/m3. [Copyright &y& Elsevier]

Abstract: Results of radioactivity measurements in Bratislava aerosols following the Fukushima accident showed that at least three radioactive plumes arrived to Bratislava as indicated by 131I/137Cs activity ratios. When compared with the Chernobyl results available for the Bratislava station, the Fukushima radionuclide levels were almost five orders of magnitude lower, with the maximum values for 131I and 137Cs of 0.5 and 0.07 mBq/m3, respectively. The 131I and 137Cs vs. 7Be aerosol activity records showed that the increases in 131I and 137Cs activity concentrations were accompanied by 7Be increases, indicating that both the horizontal and vertical transports of radionuclides were responsible for observed radionuclide concentrations. The 134Cs/137Cs activity ratio was close to 1, as has also been reported by other investigators. [Copyright &y& Elsevier]

Abstract: Measurements of activity concentrations of 131I; 129mTe, 132Te, 134Cs and; 136Cs, 137Cs in aerosol were carried out in daily samples after the Fukushima accident during the period of March–April, 2011 in Vilnius. The maximum activity concentrations of 131I and 137Cs were found to be 3700μBqm−3 and 1040μBqm−3, respectively. Variations in activity ratios of 132Te/129mTe and 137Cs/136Cs observed after the accident were explained by the decay of the short-lived isotopes, while those in 134Cs/137Cs by the dilution effect of the Chernobyl-derived 137Cs. It was found that different behaviours of highly volatile 131I and 137Cs resulted in enrichment of ground level aerosol particles by 131I with respect to 137Cs. Simulated activity concentrations of 137Cs attached to aerosol particles for the Vilnius site reasonably agreed with measured activities in aerosol samples during the Fukushima accident. [Copyright &y& Elsevier]

Abstract: Analyses of 131I, 137Cs and 134Cs in airborne aerosols were carried out in daily samples in Vilnius, Lithuania after the Fukushima accident during the period of March–April, 2011. The activity concentrations of 131I and 137Cs ranged from 12 μBq/m3 and 1.4 μBq/m3 to 3700 μBq/m3 and 1040 μBq/m3, respectively. The activity concentration of 239,240Pu in one aerosol sample collected from 23 March to 15 April, 2011 was found to be 44.5 nBq/m3. The two maxima found in radionuclide concentrations were related to complicated long-range air mass transport from Japan across the Pacific, the North America and the Atlantic Ocean to Central Europe as indicated by modelling. HYSPLIT backward trajectories and meteorological data were applied for interpretation of activity variations of measured radionuclides observed at the site of investigation. 7Be and 212Pb activity concentrations and their ratios were used as tracers of vertical transport of air masses. Fukushima data were compared with the data obtained during the Chernobyl accident and in the post Chernobyl period. The activity concentrations of 131I and 137Cs were found to be by 4 orders of magnitude lower as compared to the Chernobyl accident. The activity ratio of 134Cs/137Cs was around 1 with small variations only. The activity ratio of 238Pu/239,240Pu in the aerosol sample was 1.2, indicating a presence of the spent fuel of different origin than that of the Chernobyl accident. [Copyright &y& Elsevier]

Abstract: 137Cs, 241Am and Pu isotopes collected in aerosol samples during 1994–2011 were analyzed with special emphasis on better understanding of Pu and Am behavior in the atmosphere. The results from long-term measurements of 240Pu/239Pu atom ratios showed a bimodal frequency distribution with median values of 0.195 and 0.253, indicating two main sources contributing to the Pu activities at the Vilnius sampling station. The low Pu atom ratio of 0.141 could be attributed to the weapon-grade plutonium derived from the nuclear weapon test sites. The frequency of air masses arriving from the North-West and North-East correlated with the Pu atom ratio indicating the input from the sources located in these regions (the Novaya Zemlya test site, Siberian nuclear plants), while no correlation with the Chernobyl region was observed. Measurements carried out during the Fukushima accident showed a negligible impact of this source with Pu activities by four orders of magnitude lower as compared to the Chernobyl accident. The activity concentration of actinides measured in the integrated sample collected in March–April, 2011 showed a small contribution of Pu with unusual activity and atom ratios indicating the presence of the spent fuel of different origin than that of the Chernobyl accident. [Copyright &y& Elsevier]