Bioaccumulation of gamma emitting radionuclides in Polysiphonia fucoides

The article presents the results of a study on the bioaccumulation abilities of Polysiphonia fucoides, a red algae specific to the southern Baltic Sea, towards (of) gamma emitting isotopes. A laboratory experiment was carried out to determine changes in the activities of some isotopes—⁵⁴Mn, ⁵⁷Co, ⁶⁵Zn, ^110mAg,¹¹³Sn, ¹³⁴Cs, ¹³⁷Cs and ²⁴¹Am—occurring in P. fucoides exposed to a seawater medium containing these isotopes over the course of 1 month. All analyzed isotopes showed the greatest increase of radioactive activity in plant tissue in the first 24 h of exposure. The temporary concentration factors of cesium isotopes were increasing linearly during the experiment from 114 to 274 in the case of ¹³⁷Cs, and from 144 to 351 in the case of ¹³⁴Cs. The level of the initial concentration factor of cesium isotopes in the plant proved to be independent of the initial concentration of the isotope in seawater and it took the lowest (125 dm³ kg^?1) level among the studied isotopes. In the case of a mixture of gamma emitting isotopes, a linear relation between the individual isotope activity in P. fucoides and its initial concentration in seawater was established after the first day of exposure; the isotopes initial concentration factors ranged from 767 to 874 dm³ kg^?1. Having reached the maximal concentration level, a statistically significant decline in radioactivity concentrations of the five isotopes in the plant tissue was observed. A half-life of biological removal of the isotopes from the plant tissue was established at: 3.8 days in the case of ⁵⁴Mn, 4 days—⁵⁷Co, 4 days—⁶⁰Co, 4.2 days—¹³⁷Cs and ²⁴¹Am—3.5 days.     

Radionuclides from Fukushima accident in Thessaloniki, Greece (40°N) and Milano, Italy (45°)

¹³¹I, ¹³⁷Cs and ¹³⁴Cs were observed in environmental samples in Milano (40°N), Italy and Thessaloniki (45°N), Greece, soon after the nuclear accident in Fukushima, Japan. The radionuclide concentrations were determined and studied as a function of time. In Thessaloniki the ¹³¹I in air was observed for the first time on March 24, 2011. In Milano, the first evidence of Fukushima fallout has been confirmed with ¹³¹I and ¹³⁷Cs measured in wet precipitation collected 2 days later. The maximum ¹³¹I activity concentration in air of 467 ± 25 μBq m^?3, observed in Milano on April 3–4, 2011, was almost similar to the highest value of 497 ± 53 μBq m^?3 observed in Thessaloniki. The ¹³⁴Cs/¹³⁷Cs activity ratio values in air were around 1 in both regions. Soil, grass and milk samples were contaminated with ¹³¹I and ¹³⁷Cs at a low level. Finally, a dose assessment for these two areas showed clearly that the detected activities in all environmental samples were far below levels of concern.     

Distribution of 131I, 134Cs, 137Cs and 239,240Pu concentrations in Korean rainwater after the Fukushima nuclear power plant accident

Radionuclides such as ¹³¹I, ¹³⁴Cs, ¹³⁷Cs, and ^239,240Pu in Korean rainwater have been analyzed by Korea Research Institute of Standards and Science (KRISS) since the Fukushima nuclear power plant accident in March 2011 to investigate the activity level, distribution pattern, and temporal variation and to assess the radiation dose the public is exposed to. The concentration of ¹³¹I in the Korean rainwater samples varied between 0.033 (minimum detectable activity; MDA) and 1.30 Bq kg^?1 and the concentrations tended to decrease exponentially with time. The concentrations of ¹³⁴Cs and ¹³⁷Cs in rainwater ranged from 0.01 to 334 ± 74 and 0.29 ± 0.01 to 276 ± 1 mBq kg^?1, respectively. The mean activity ratio of ¹³⁷Cs/¹³⁴Cs in the rainwater samples collected from April 18 to May 12 was estimated to be 0.44 ± 0.21, and this value is lower than that (ca. 1) observed in Fukushima, Japan, when there was an escape from the nuclear reactors. When an attempt was made to analyze Pu isotopes in rainwater samples, no Pu isotopes were detected above the MDA in any of the rainwater samples. Although the locations investigated were different from Asia to Europe, the concentrations of ¹³¹I, ¹³⁴Cs and ¹³⁷Cs in the rainwater are comparable, which suggests a global contamination of ¹³¹I, ¹³⁴Cs, and ¹³⁷Cs occurred because of the Fukushima nuclear power plant accident.     

Uptake and release kinetics of134Cs by Goldfish (Carassius auratus) and137Cs by Zebra Fish (Brachydanio rerio) in controlled aquatic environment

The uptake and release kinetics of¹³⁴Cs by Goldfish (Carassius auratus) and¹³⁷Cs by Zebra Fish (Brachydanio rerio) from aquatic media of different ionic compositions and temperature was studied in controlled laboratory conditions. The accumulation of radiocesium in the case ofBrachydanio rerio is observed to be strongly dependent on the potassium ion concentration of the aquatic medium, but in the case ofCarassius auratus this dependence is quite weak. The biological half-lives of the cesium isotopes incorporated into the fish investigated in the present work vary from 19 to 80 days and are influenced by the temperature and the ionic composition of the aquatic medium.     

Environmental radioactivity measurements in north–western Greece following the Fukushima nuclear accident

The impact of the Fukushima nuclear accident in north–western Greece was assessed through an environmental monitoring programme activated by the Nuclear Physics Laboratory of the University of Ioannina. Measurements of ¹³¹I were carried out in atmospheric particulate, ovine milk and grass samples. In daily aerosol samplings, radioiodine was first detected on March 25–26, 2011 and reached maximum levels, up to 294 μBq m^?3, between April 2 and April 4, 2011. In ovine milk samples, ¹³¹I concentrations ranged from 2.0 to 2.7 Bq L^?1 between April 2 and April 6, 2011, while an average activity of 2.7 Bq kg^?1 was measured in grass samples on April 4, 2011. The ^134,137Cs isotopes were below detection limits in all samples and could only be determined in the air, by analysis of multiple daily filters. A maximum average activity concentration of ¹³⁷Cs amounting to 24 μBq m^?3 was measured during the period from April 5 to April 9, 2011, with the ¹³⁴Cs/¹³⁷Cs activity ratio being close to unity. Activity concentrations were consistent with measurements conducted in other parts of the country and were well below those reported in May 1986 after the Chernobyl accident. The committed effective dose to the whole body and to the thyroid gland from inhalation of ¹³¹I was estimated for the adult and infant population and was found to be of no concern for the public health.     

Measurement of fallout with rain in Hiroshima and several sites in Japan from the Fukushima reactor accident

Fallout with rain from the Fukushima reactor accident was monitored for about two months in Higashi-Hiroshima City, Hiroshima, Japan, from March 20 to May 23, 2011. Gamma-ray (γ-ray) spectra measured using a low background HPGe spectrometer showed clear evidence of fission products—¹³¹I, ¹³⁷Cs, and ¹³⁴Cs. The ¹³¹I was observed on March 27 and April 8, while ¹³⁷Cs and ¹³⁴Cs were observed on March 27, April 18, and April 22. The ¹³¹I, ¹³⁷Cs, and ¹³⁴Cs activity concentrations in rainwater collected in Hiroshima reached 0.44 ± 0.09 on April 8, 0.17 ± 0.01 on April 18, and 0.15 ± 0.01 Bq/L on April 18, 2011, respectively. These activity levels were compared with global results collected from the Northern Hemisphere. Several samples of rainwater that were collected in Chiba (Kashiwa) on March 21, April 11, and May 12; Tokyo (Nerima) on March 21 and April 11; Osaka (Hirano) on April 8; Nara (Kitakatsuragi) on April 9; and Fukushima (Fukushima) on April 19, were also measured by our spectrometer and compared. Among these samples of rainwater collected at different locations in Japan, the one collected at Kashiwa City, Chiba Prefecture, on March 21 showed the highest activity concentrations of 6072 ± 1,   632 ± 4,   766 ± 3,   637 ± 1,   97.6 ± 0.8, and 752 ± 2 Bq/L for ¹³¹I,   ¹³²I,   ¹³²Te,   ¹³⁴Cs,   ¹³⁶Cs, and ¹³⁷Cs, respectively. The health risks due to these high activity levels were considered in terms of several regulations. The ratio of the activites for the isotopes ¹³¹I to ¹³⁷Cs and ¹³⁴Cs to ¹³⁷Cs were compared with the other measurements and discussed.     

Combination of atomic lines and molecular bands for uranium optical isotopic analysis in laser induced plasma spectrometry

Radionuclide concentrations in wharf roaches inhabiting coastal areas of Honshu, Japan, were investigated in October 2011 and June 2012. Relative high concentrations of ^110mAg (2.1–127 Bq kg-wet^?1), ¹³⁴Cs (2.6–61 Bq kg-wet^?1), and ¹³⁷Cs (3.5–92 Bq kg-wet^?1) were detected in specimens from the eastern Honshu areas. Significantly lower ¹³⁷Cs concentrations (0.7–1.6 Bq kg-wet^?1) were detected in specimens from western and northern Honshu. The decay-corrected ¹³⁷Cs concentration was significantly inversely correlated with the distance from the Fukushima Dai-ichi Nuclear Power Plant. Thus, wharf roach may serve as a good bioindicator for monitoring radioactive contamination of its habitats.     

Accumulation and discharge behavior of Cs-137 by zebra fish (Brachydanio rerio) in different aquatic environments

The uptake and release kinetics of¹³⁷Cs from water by the tropical fishBrachydanio rerio has been studied under controlled laboratory condition. The accumulation of this radionuclide from food was avoided by feeding the fishes separately in an inactive environment. A steep inverse dependence of bioconcentration factor (BCF) with potassium concentration has been observed. This can formally be described by the equation BCF=5.2 · [K⁺]^–0.44. The elimination rate constant K in fresh water conditions has been found to have a magnitude of 0.014±0.03 d^–1 which corresponds to a biological half-life of 51±10 days. The uptake and release kinetics ofBrachydanio rerio has been compared with earlier studies of fresh water fishes.     

Estimate of Fukushima-derived radiocaesium in the North Pacific Ocean in summer 2012

Distributions of radiocaesium (¹³⁴Cs and ¹³⁷Cs) derived from the Tokyo Electric Power Company (TEPCO) Fukushima Dai-ichi Nuclear Power Plant (FNPP1) accident in the North Pacific Ocean in the summer of 2012 were investigated. We have estimated the radiocaesium inventory in the surface layer using the optimal interpolation analysis and the subducted amount into the central mode water (CMW) by using vertical profiles of FNPP1-¹³⁴Cs and mass balance analysis as the first approach. The inventory of the ¹³⁴Cs in the surface layer in the North Pacific Ocean in August–December 2012 was estimated at 5.1?±?0.9 PBq on 1 October 2012, which corresponds to 8.6?±?1.5 PBq when it was decay corrected to the date of the FNPP1 accident, 11 March 2011. It was revealed that 56?±?10% of the released ¹³⁴Cs into the North Pacific Ocean, which was estimated at 15.3?±?2.6 PBq, transported eastward in the surface layer in 2012. The amount of ¹³⁴Cs subducted in the CMW was estimated to be 2.5?±?0.9 PBq based on the mass balance among the three domains of the surface layer, subtropical mode water, and CMW.     

Radionuclide concentration in sewage sludge at several location in Austria after the Chernobyl accident

The concentration of the radionuclides¹⁰³Ru,¹³⁴Cs and¹³⁷Cs in sewage sludge samples which were collected between July and September 1986, were measured by -ray spectrometry. High concentration of¹⁰³Ru,¹³⁴Cs and¹³⁷Cs were found in sewage sludge samples from Lower-Austria /Scheibbs, Zwettl/ and Styria /Eisenerz, Leoben/. the radioactivity concentration of¹³⁷Cs was two times higher than that of¹³⁴Cs. Following concentration values were found:¹⁰³Ru 0.1–63.0 nCi kg^–1,¹³⁴Cs 0.3–41.6 nCi kg^–1, and¹³⁷Cs 0.3–83.3 nCi kg^–1. The activity of these nuclides decreased from July 1986 to September 1986.     

Extraction of cesium in seawater off Japan using AMP-PAN resin and quantification via gamma spectroscopy and inductively coupled mass spectrometry

The March 2011 earthquake off the Japanese coast and subsequent tsunami that devastated the Fukushima Dai-Ichi nuclear power plant resulted in the largest accidental release of cesium 137 and 134 to the oceans. Seawater samples were collected in June 2011 from 30 to 600 km off the coast of Japan as part of initial mapping of the spread of contamination in the ocean. Cesium was extracted from unfiltered and filtered (<1.0 μm) seawater using an absorber based upon an organic polymer polyacrylonitrile (PAN) containing ammonium molybdophosphate (AMP) Sebesta and Stefula (J Radioanal Nucl Chem 140:15–21, 1990). The AMP-PAN resin can be counted directly using gamma spectroscopy for ¹³⁴Cs and ¹³⁷Cs. Stable ¹³³Cs was added to evaluate extraction efficiency and quantified by ICP-MS. Our 5 mL AMP-PAN resin column was on average 95 % efficient in the removal of cesium from 20 L samples at an average flow rate of 35 mL min^?1. Measured activities of ¹³⁴Cs and ¹³⁷Cs ranged from a few Bq m^?3 to >300 Bq m^?3. The extraction column can be adapted to different sample volumes and easily used in the field.     

Removal of some radionuclides from contaminated solution using natural clay: bentonite

Clays and specially bentonite are widely used as natural adsorbents for wastewater treatment and as a barrier in landfills to prevent the contamination of subsoil and groundwater by leachates containing radioactive materials. The adsorption of four radionuclides, ¹³⁴Cs(I), ⁹⁰Sr(II), ¹³³Ba(II) and ¹⁵²Eu(III) by an Egyptian bentonite (Bent) and its modified Na⁺ form (Na-Bent) collected from a deposit within Alexandria governorate was investigated as a function of different parameters. The batch equilibrium technique was used and the kinetic results showed that the equilibrium was mostly reached within 10 min and the kinetic data fit well to the pseudo-second order model. The Langmuir model fits well the experimental data of all metals adsorption on Bent and Na-Bent except for adsorption of ¹³³Ba on Bent, while ¹⁵²Eu adsorption on Na-Bent fits better to the Freundlich model rather than to the Langmuir. Both Bent and Na-Bent fit well to the D-R model with adsorption energy of E > 8 kJ mol^?1 that means that the adsorption reaction is expected to be controlled by both cation exchange and surface complexation reactions. At lower concentrations, the values of distribution coefficient (K _d), follow the order of ¹⁵²Eu > ⁹⁰Sr > ¹³⁴Cs > ¹³³Ba for Bent and Na-Bent. The K _d of ¹⁵²Eu is higher than that of ¹³⁴Cs in Bent up to 150 mg L^?1. This order changes at higher concentration where the K _d of ¹³⁴Cs becomes higher than ¹⁵²Eu after 150 mg L^?1 for Bent and after 200 mg L^?1 for Na-Bent. Na-Bent is preferred than Bent for the uptake of ⁹⁰Sr and ¹³⁴Cs especially at high concentration.     

Natural depuration rate and concentration of cesium-137 radionuclide in Black Sea macro algae

Cesium-137 concentrations in red, brown and green algae have been studied for the calculation of natural depuration rates. The algae species were collected from the same population of the Black Sea stations during the period of 1986–1995. The natural depuration rates are estimated as biological half-lives. The pattern of depuration results represented by a single component for each algae division. The biological half-lives of¹³⁷Cs in red (Phyllophora nervosa), green (Chaetomorpha linum) and brown (Cystoceira barbata) algae are estimated to be 18.5, 21.6 and 29.3 months, respectively.¹³⁷Cs and⁴⁰K activity levels and their ratios in algae species in two stations in Black Sea region of Turkey have been determined during the period of 1990–1995. The results showed that the Sinop region was more contaminated than the ile region on the Black Sea coast of Turkey from the Chernobyl accident.     

A complementary cesium coolant concentration ratio for localizing defective PWR fuel rods during reactor operation

Rough techniques for pinpointing defective fuel pins during actual reactor operation were developed for nuclear power plants. These techniques are based on various fission product concentration ratios. Here, a new cesium concentration ratio,¹³⁴Cs/¹³⁶Cs, was tested in combination with the more usual cesium ratio¹³⁴Cs/¹³⁷Cs. This new cesium ratio confirmed the conclusions drawn from the ratio¹³⁴Cs/¹³⁷Cs and provided some additional information on the location of the defective fuel rods. Application of this second cesium ratio improves the reliability of the rough localization method.     

Distribution of 137Cs and 134Cs in the North Pacific Ocean: impacts of the TEPCO Fukushima-Daiichi NPP accident

Impact of the TEPCO Fukushima-Daiichi NPP accident, FNPP1, to the North Pacific Ocean occurred through two pathways, namely direct release and atmospheric deposition to wide ocean surface. We collected more than 100 seawater samples in the North Pacific Ocean in April and May 2011 by seven commercial ships as VOS. Since the sample volume was 2 l each, we measured radiocaesium activity at Ogoya Underground Facility to obtain reliable activity. ¹³⁷Cs was detected at all stations and ¹³⁴Cs was detected at most of the stations in the North Pacific Ocean. The ¹³⁷Cs activity ranged from around 1 to 1,000 Bq m^?3 with activity ratios of ¹³⁴Cs/¹³⁷Cs close to 1 which is a signature of radiocaesium originated from the FNPP1 accident. At east of the International Date Line north of 40°N in the Pacific Ocean in April 2011, the ¹³⁴Cs activity ranged from 2 to 12 Bq m^?3.     

Semi-quantitative analysis of leaf surface contamination by radioactivity from the Fukushima Daiichi nuclear power plant accident using HPGe and imaging plate

After the nuclear power plant accident at Fukushima Daiichi on 11 March 2011, green-leaves from trees, dead-leaves and grass on ground were collected from March to June 2011 in Japan. Radioactive concentrations were measured by a high purity germanium detector. Five radionuclides including ^129mTe, ¹³²Te, ¹³¹I, ¹³⁴Cs and ¹³⁷Cs were detected. The fission product concentration of the dead-leaves was higher than those of the green-leaves in many cases. The highest concentration observed was found on the dead-leaves collected at Iwaki, 60 km far from Fukushima Daiichi. A total activity of 2,000 Bq g^?1 was measured for all 5 radionuclides. Clear images of radioactivity of the highly contaminated leaves were obtained with an imaging plate (IP) after <24 h exposure time without using a shielded box. The photostimulated luminescence values (PSL) of leaves arranged on half size of IP were roughly in proportion to their activities except for the low activity samples. Semi-quantitative analysis was possible by using PSL values with a large region of interest of half size of IP, because the radioactivity released in the case of the nuclear power plant accident was uniform in the early days.     

The ambient gamma dose-rate and the inventory of fission products estimations with the soil samples collected at Canadian embassy in Tokyo during Fukushima nuclear accident

In this study, soil samples were collected at Canadian embassy in Tokyo (about 300 km from Fukushima) on 23 March and 23 May of 2011 for purposes of estimating concentrations of radionuclides in fallout, the total fallout inventory, the depth distribution of radionuclide of interest and the elevated ambient gamma dose-rate at this limited location. Some fission products and actinides were analyzed using gamma-ray spectrometry, alpha spectrometry and liquid scintillation counting. The elevated activity concentration levels of ¹³¹I, ¹³²I, ¹³⁴Cs, ¹³⁷Cs, ¹³⁶Cs, ¹³²Te, ¹²⁹mTe, ¹²⁹Te, ¹⁴⁰Ba and ¹⁴⁰La were measured by the gamma-ray spectrometer in the first sample collected on 23 March. Two months after the accident, the ¹³⁴Cs and ¹³⁷Cs became only detectable nuclides. A mass relaxation depth of 3.0 g/cm² was determined by the activities on the depth distribution of ¹³⁷Cs in a soil core. The total fallout inventory was thus calculated as 225 kBq/m² on March sampling date and 25 kBq/m² on May sampling date. The ambient gamma dose-rates in the sampling area estimated by the fallout fission products inventory and ¹³⁷Cs depth distribution ranged from 184 to 38 nGy/h. There was no detectable americium or plutonium in the soil samples by alpha spectrometry. Although ⁹⁰Sr or ⁸⁹Sr were detected supposedly as a result of this accident, it was less than the detection limit, which was about 0.4 Bq/kg in the soil samples.     

Airborne gamma-ray emitters from Fukushima detected in New York State

An air-sampling network that operates continuously as part of New York State’s environmental surveillance program collected radionuclides emitted as a result of the Fukushima nuclear accident. Samples were collected, typically for 7 days each, by drawing ~600 m³ of air through a particulate-collecting filter followed in series by a canister containing activated charcoal. Additional air sampling was implemented at ~3-day intervals at two locations. Gamma-ray spectroscopy was used to confirm the detection of ¹³¹I, ¹³⁷Cs, ¹³⁴Cs, and ⁷Be in the particulate phase at all sites, with maximum concentrations near 1,260, 160, 160, and 5,200 μBq/m³, respectively. Gas-phase ¹³¹I, collected on activated charcoal, exhibited a maximum concentration of 3,400 μBq/m³ at the sites. Assessment of radionuclide levels in the air samples suggests that there were minimal health impacts from the airborne radionuclides as the activities contributed an insignificant amount to the annual human dose.     

Fast concentration of dissolved forms of cesium radioisotopes from large seawater samples

The method developed for cesium concentration from large freshwater samples was tested and adapted for analysis of cesium radionuclides in seawater. Concentration of dissolved forms of cesium in large seawater samples (about 100 L) was performed using composite absorbers AMP-PAN and KNiFC-PAN with ammonium molybdophosphate and potassium–nickel hexacyanoferrate(II) as active components, respectively, and polyacrylonitrile as a binding polymer. A specially designed chromatography column with bed volume (BV) 25 mL allowed fast flow rates of seawater (up to 1,200 BV h^?1). The recovery yields were determined by ICP-MS analysis of stable cesium added to seawater sample. Both absorbers proved usability for cesium concentration from large seawater samples. KNiFC-PAN material was slightly more effective in cesium concentration from acidified seawater (recovery yield around 93 % for 700 BV h^?1). This material showed similar efficiency in cesium concentration also from natural seawater. The activity concentrations of ¹³⁷Cs determined in seawater from the central Pacific Ocean were 1.5 ± 0.1 and 1.4 ± 0.1 Bq m^?3 for an offshore (January 2012) and a coastal (February 2012) locality, respectively, ¹³⁴Cs activities were below detection limit (<0.2 Bq m^?3).     

Activity concentration of radium-226 in agricultural soils

Both Indian mustard and sunflower were grown in a hydroponic solution treated with different concentration activities of ¹³⁴Cs or with different amounts of copper or with both in order to investigate the interaction between copper and radiocesium. It was found that ¹³⁴Cs activity concentration applied in the nutrient solution exerted more influence on the uptake and translocation of copper by Indian mustard than by sunflower. Indian mustard grown in hydroponic solution containing certain levels of copper and being treated with higher ¹³⁴Cs activity concentration showed higher uptake of copper than sunflower. However, in the case of root copper concentrations, sunflower showed significantly higher copper immobilization by roots than Indian mustard. It was also found that the presence of copper in the hydroponic solution did modify radiocesium uptake by both species. The application of 1 mg/l in the growth medium could greatly increase the uptake of ¹³⁴Cs by both species. With 3 mg/l concentration of copper amended to the solution, the accumulation of ¹³⁴Cs by both species was decreased compared to the 1 mg/l copper treatment. These lines of evidence show that there is stronger interaction between copper and radiocesium in Indian mustard than in sunflower during the root uptake through nutrient solution.