Studies on the radiolytic stability of newly developed solvent systems containing four calix-crown-6 ligands for radio-cesium recovery

Radiolytic stability of solvent systems containing four commercially available calix-crown-6 ligands termed as calix[4]arene-bis-crown-6 (CC), calix[4]arene-benzo-bis-crown-6 (CBC), calix[4]arene-naphtho-bis-crown-6 (CNC), and bis-(octyloxy)calix[4]arene-mono-crown-6 (CMC) dissolved in phenyl trifluoromethyl sulphone (PTMS) was studied which followed the order: CBC > CC > CNC ~ CMC. The radiolytic stability was evaluated by the absolute distribution ratio (D _Cs) vales at a given concentration of nitric acid as well as the nature of the extracted species. The radiolytic degradation products were identified by GC–MS analysis. The present study indicates that CBC in PTMS can be used as a solvent for radio-cesium recovery with good recycling possibilities.     

Evaluation of calix-crown ionophores for selective separation of radio-cesium from acidic nuclear waste solution

Extraction of Cs-137 from nitric acid was carried out using nitrobenzene solutions of calix-crowns such as calix[4]arene-bis(crown-6) (CC-A), calix[4]arene-bis(benzo crown-6) (CC-B) and calix[4]arene-bis(napthocrown-6) (CC-C). CC-C was found to be superior extractant for Cs(I) as compared to the other two calix-crown ligands used in the present study. The effect of diluent on the extraction of Cs(I) indicated the trend: nitrobenzene>dichloroethane>chloroform>decanol>carbon tetrachloride approximately n-hexane approximately toluene. Subsequently, the studies were carried out with nitrobenzene solutions of the calix-crown ligands (mainly CC-C) on the effects of (a) aqueous phase acidity, (b) ligand concentration, and (c) cesium concentration on Cs extraction from nitric acid media. Conditions for quantitative extraction and stripping were optimized and the extracted species conformed to {[CsL]+.[NO3]-.nH2O}. Selectivity studies were carried out using an irradiated natural U target involving tracer amount of fission products activities. Extraction of Cs(I) from a synthetic high level waste solution was also carried out. The promising results obtained in the present studies indicate possible use of the calix-crown ligand for Cs(I) recovery from the acidic high level waste.     

Measurement of 137Cs in the soil in Korea by low-level background gamma-ray spectrometer

¹³⁷Cs was measured in soil samples collected in Korea from 2006 to 2008 using a low-level background gamma-ray spectrometer that was designed and developed by KRISS (Korea Research Institute of Standards and Science). The objectives of this study are to evaluate the newly developed low-level background gamma-ray spectrometer and, consequently, to provide information on the horizontal and vertical distribution of ¹³⁷Cs in Korean soil. ¹³⁷Cs concentrations in surface soil varied from 12.8 ± 0.9 to 108 ± 4 Bq kg^?1, and the vertical profiles of ¹³⁷Cs from the Nari basin in Ulleung Island in the East Sea/Sea of Japan and Seongsan Ilchulbong Peak, Jeju Island, showed a higher concentration in the surface layer that gradually decreased with depth. On the other hand, the ¹³⁷Cs concentration in soil samples collected from Bukhan Mountain National Park in Seoul showed a subsurface maximum and decreased with depth. The ¹³⁷Cs inventories in the soil column were calculated to be 1,830–4,360 Bq m^?2 with a mean of 2,770 Bq m^?2, which was the same order of magnitude as the global fallout inventories in the mid-latitude region of the Northern Hemisphere.     

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.     

Radionuclides in redistributed sediments and ash from the Las Conchas fire in Northern New Mexico

The 2011 Las Conchas fire burned 632 km² of ponderosa pine forests and piñon–juniper woodlands in the Jemez Mountains in north central New Mexico. In the weeks following the fire, heavy rainfall caused extensive flooding and erosion of surface soil and ash from the affected areas. Samples from mud and ash flows were collected and analyzed for ¹³⁷Cs and Pu, which were originally deposited as global fallout during the era of atmospheric nuclear testing. The mean concentrations for ²³⁸Pu, ^239,240Pu and ¹³⁷Cs were 0.18 ± 0.05, 4.16 ± 1.95, and 111 ± 56 mBq/g, respectively. ^239,240Pu and ¹³⁷Cs are significantly elevated above non-fire affected regional background levels.     

Spatial and vertical distributions of natural and anthropogenic radionuclides and cesium fractionation in sediments of the Var river and its tributaries (southeast France)

This paper reports results on the natural and anthropogenic radionuclides activity concentrations in sediments of the Var river and its tributaries. Natural (²³⁸U, ²³²Th and ⁴⁰K) and artificial (¹³⁷Cs) radionuclides activities were measured using high purity germanium detector. Measured activity concentrations differ widely; they depend on the pertinent environmental situation such as the presence of dams, and sediments type. Other factors controlling the distribution of the studied radioisotopes have been discussed. A sequential extraction method consisting of six operationally-defined fractions has been used for determining the geochemical partitioning of anthropogenic radionuclide ¹³⁷Cs in a 405–410 cm deep sediments collected in the lower valley of the Var river. This method corresponds to a modification of the three-stage sequential extraction procedure proposed by the Commission of the European Communities Bureau of Reference (BCR, now Standards, Measurements and Testing Program). Two steps with weak reagents, (fraction A: water; fraction B: nitric acid 0.001 M), were added before the first step of BCR (carbonate fraction) in order to better detect anthropogenic components. A total acid digestion of solid residues by microwave assisted was also added. The 6-steps extraction method was tested and validated by certified reference materials. ¹³⁷Cs was found mostly in the hydrosoluble fraction (20–24 %), oxide and hydroxide fraction (22–25 %) and in the residue (51–58 %), while ¹³³Cs was mostly found in the residual fraction (>97 %).     

Concentrations of 137Cs and 40K in wild mushrooms collected in a forest on Noto Peninsula,Japan

A variety of wild mushrooms were collected in a forest on the Noto Peninsula, Japan, to determine the concentration of ¹³⁷Cs and ⁴⁰K. The wild mushroom species belong to the orders Agaricales and Aphyllophorales. The concentration of ¹³⁷Cs varied widely (1.4–4,100 Bq/kg dry weight) in mushrooms growing in soil. On the contrary, ¹³⁷Cs concentration levels were relatively low (1.9–20 Bq/kg-dry weight) in mushrooms growing on wood. The concentration of ⁴⁰K varied widely (12–2,400 Bq/kg-dry weight) in contrast with several previous reports that suggest relatively constant ⁴⁰K levels in mushrooms. Unusually low concentrations of ⁴⁰K were observed in a few mushroom species that had very hard fruiting bodies with peculiar shapes. The mean and median of ¹³⁷Cs concentration in the present study were similar to those previously reported for Japanese mushrooms. Among the Agaricales mushrooms, Entolomataceae and Tricholomataceae families growing in soil had the highest concentration of ¹³⁷Cs. Among the Aphyllophorales mushrooms, Gomphaceae and Ramariaceae families growing in soil also had the highest ¹³⁷Cs concentrations. The concentrations of ¹³⁷Cs and stable Cs in mushroom samples were positively correlated. The concentration ratio of ¹³⁷Cs/Cs differed between Agaricales and Aphyllophorales mushrooms. The average ¹³⁷Cs/Cs ratio in mushrooms growing in soil was similar to that calculated for the top soil (<5 cm deep) alone because the mycelia of the mushrooms were mainly distributed near the surface of the soil.     

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.     

GC–MS Studies of Thiophenes in the Supercritical Fluid CO2 and Solvent Extracts of Tagetes patula L.

The intact plant parts and genetically modified hairy root clone #TpA6 of Tagetes patula were extracted with supercritical fluid CO₂ extraction (SFE) and a conventional solvent extraction. SFE optimization included the variation of fluid CO₂ pressure, dynamic time, and the addition of methanol modifier co-solvent. The four characteristic thiophene metabolites, 5-(3-buten-1-ynyl)-2,2′-bithienyl (BBT), 2,2′:5′,2″-terthiophene (α-T), 5-(4-acetoxy-1-butynyl)-2,2′-bithienyl (BBTOAc), and 5-(3,4-diacetoxy-1-butynyl)-2,2′-bithienyl [BBT(OAc)₂], were analysed by GC–MS. The proposed SFE method allowed the selective extraction of thiophenes in 60 min dynamic time with supercritical CO₂ without modifier co-solvent, at 30 MPa and 40 °C. The SFE and the reference solvent extraction yielded similar results. The SFE of intact roots and flowers yielded 717 ± 31.3 and 480 ± 26.6 μg g^?1 α-T, respectively, while the leaves did not contain considerable amounts of thiophenes. Remarkable amounts of BBT, BBTOAc, and BBT(OAc)₂ were characteristic of the SFE of hairy root cultures.     

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.     

GC–MS Studies of Thiophenes in the Supercritical Fluid CO2 and Solvent Extracts of Tagetes patula L.

The intact plant parts and genetically modified hairy root clone #TpA6 of Tagetes patula were extracted with supercritical fluid CO₂ extraction (SFE) and a conventional solvent extraction. SFE optimization included the variation of fluid CO₂ pressure, dynamic time, and the addition of methanol modifier co-solvent. The four characteristic thiophene metabolites, 5-(3-buten-1-ynyl)-2,2′-bithienyl (BBT), 2,2′:5′,2″-terthiophene (α-T), 5-(4-acetoxy-1-butynyl)-2,2′-bithienyl (BBTOAc), and 5-(3,4-diacetoxy-1-butynyl)-2,2′-bithienyl [BBT(OAc)₂], were analysed by GC–MS. The proposed SFE method allowed the selective extraction of thiophenes in 60 min dynamic time with supercritical CO₂ without modifier co-solvent, at 30 MPa and 40 °C. The SFE and the reference solvent extraction yielded similar results. The SFE of intact roots and flowers yielded 717 ± 31.3 and 480 ± 26.6 μg g⁻¹ α-T, respectively, while the leaves did not contain considerable amounts of thiophenes. Remarkable amounts of BBT, BBTOAc, and BBT(OAc)₂ were characteristic of the SFE of hairy root cultures.

     

Novel Cesium‐Selective Electrodes Based on Lipophilic 1,3‐Bisbridged Cofacial‐calix[6]crowns

Five bisbridged calix[6]crowns have been investigated as Cs⁺ ionophore in PVC membrane electrodes. As ionophores, three 1,3‐bisbridged calix[6]crown‐4‐ethers( I–III ), 1,3‐bisbridged calix[6]crown‐5‐ether( IV ), and 1,3‐bisbridged calix[6]crown‐6‐ether( V ) have been evaluated. The membranes all give good Nernstian response in the concentration range from 1×10^?7 to 1×10^?1 M of cesium ion. The best detection limits (?log aequation/tex2gif-inf-1.gif=7.08–7.36) are obtained for electrode membranes containing 1,3‐bisbridged cofacial‐calix[6]crown‐4‐ethers( I‐III ), and the values are the lowest compared with those reported previously. The highest selectivity coefficients [ 3.74(Cs/K), 2.63(Cs/Rb)] are obtained for the membrane of 1,3‐bisbridged calix[6]crown‐4‐ether( II ), and these values are also the highest compared with previous reports for Cs⁺‐ISEs. The highest selectivity towards cesium ion is attributed to the geometrically cofacial positions of two crown‐ethers in calix[6]crowns in order to provide the complex of cesium ion and eight oxygens of cofacial crowns.     

Geographical and vertical distribution of radiocesium levels in coniferous forest soils in Izmir

Preliminary picture of ¹³⁷Cs radioactivity levels in forested areas in and around Izmir is illustrated. Both activity concentrations and activity depositions of ¹³⁷Cs in soil samples were determined. Their values varied from 8.29±0.27 to 445±3.16 Bq.kg⁻¹ (d.w.) and 0.63±0.01 to 11.6±0.08 kBq.m^–2 (d.w.), respectively. It was found that while activity deposition of ¹³⁷Cs is normally distributed, activity concentration of ¹³⁷Cs is log-normally distributed in forest soils and the activity deposition is less variable than the activity concentration. Cesium-137 activities in soils increase with increasing elevation, annual average rainfall and soil organic matter.     

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.     

137Cs, 40K, alkali–alkaline earth element and heavy metal concentrations in wild mushrooms from Turkey

In 2002, an extensive study was performed in forest sites of Izmir. This first study results led on the one hand, to quantify of ¹³⁷Cs and ⁴⁰K concentration in mushrooms collected in the Izmir region and to a first evaluation of dose in people due to the ingestion of radionuclide-contaminated mushrooms. The mushroom concentration values varied over a wide range from below detection limit to 401 ± 4 Bq kg^?1 (dry wt) for ¹³⁷Cs. The ⁴⁰K concentration values obtained for different species of mushrooms ranged from 588 ± 26 Bq kg^?1 to 2024 ± 63 Bq kg^?1 (dry wt). The annual effective dose values due to mushroom ingestion for ¹³⁷Cs are lower than the ICRP-2007’s reference level value of 1 mSv for “existing” exposure situation. Inductively coupled plasma-mass spectrometry was used to measure many alkali–alkaline earth elements and heavy metals in mushroom samples. The relationships among the concentrations of ¹³⁷Cs and the stable elements were presented and the occurrence of metals in mushrooms was evaluated.     

Radiometric analysis of rock and soil samples of Leepa Valley; Azad Kashmir, Pakistan

In this article, we present results obtained from a radiometric survey that was conducted in the Leepa Valley of Azad Jammu & Kashmir, Pakistan. The purpose of current study is to appraise the radioactivity levels and the associated health hazards due to the terrestrial radionuclide in soil and rock samples. In this regard, 16 soil and 17 rock samples were collected from different locations of the Leepa Valley. After processing the samples, activity concentrations of primordial (²³²Th, ²²⁶Ra and ⁴⁰K) and anthropogenic (¹³⁷Cs) radionuclides were determined using a P-type coaxial high purity germanium detector. From the results obtained the mean activity concentrations of radionuclides ²²⁶Ra, ²³²Th and ⁴⁰K in the soil samples were found to be 31.25 ± 0.46, 44.1 ± 1.07 and 575 ± 8.89 Bq kg^?1 respectively. Whilst, in rock samples ²²⁶Ra, ²³²Th and ⁴⁰K mean activities were found as 28.46 ± 0.45, 48.63 ± 1.12 and 666.7 ± 9.39 Bq kg^?1, respectively. The ¹³⁷Cs concentration level in soil and rock samples is found to be 15.04 ± 0.29 and 5.7 ± 0.16 Bq kg^?1, respectively. The average radium equivalent activity (R _aeq) was found as 143.16 and 142.93 Bq kg^?1 in soil and rock samples, respectively. These findings are less than the recommended safe value of 370 Bq kg^?1 as given in OECD report (1979). The values of external (H _ex) and internal hazard index (H _in) are also less than unity. Mean value of absorbed dose rate was found as 69.78 nGy h^?1 for the soil samples, which is in good agreement with the world wide average value (70 nGy h^?1). Mean value of absorbed dose rate from rock samples was found as 70.01 nGy h^?1. Mean values of the annual effective dose is also lower than the values reported for different other countries of the world.     

Extraction of cesium-137 from nitric acid medium in the presence of macrocyclic polyethers

Extraction behavior of¹³⁷Cs was studied from nitric acid medium using dibenzo 18 crown 6 (DB18C6), 4,4'(5')di-acetylbenzo 18 crown 6 (DAB18C6), 4, 4'(5')di-hexanoylbenzo 18 crown 6 (DHB18C6), 4,4'(5')di-nonanoylbenzo 18 crown 6 (DNB18C6) and 4,4'(5')di-t-butylbenzo 18 crown 6 (DTBB18C6) in nitrobenzene medium. The stoichiometry of the species extracted with dibenzo 18 crown 6 (L) conformed to ML⁺. NO₃ ⁻ TheD _Cs values were found not to be affected by the presence of aluminium nitrate in the aqueous phase. The separation behavior of fission products obtained from an irradiated natural uranium target was also studied. Presence of 0.004M phosphotungstic acid found to enhance theD _Cs values at lower acidities.     

Relationships among <Superscript>137</Superscript>Cs, <Superscript>133</Superscript>Cs,and K in plant uptake observed in Japanese agricultural fields

Plant uptake of radiocesium (¹³⁷Cs) was investigated in consideration of the relationships with naturally existing ¹³³Cs and potassium (K). We first determined plant-unavailable fraction of ¹³⁷Cs in soil by batch sorption and sequential extraction methods with a radiotracer. Then, using the data obtained from the batch sorption and extraction methods, we clarified the relationships of plant-available and plant-unavailable fractions between ¹³⁷Cs, ¹³³Cs, and K in soil. Additionally, ¹³⁷Cs concentrations in crop were estimated using ¹³⁷Cs in soil and several factors, i.e. fixation ratio of ¹³⁷Cs in soil, cation exchange capacity, and K concentration in crop. The results implied that the fixation ratio of ¹³⁷Cs in soil was a very important key to understanding ¹³⁷Cs plant uptake.     

The evaluation of 137Cs radioactivities in soils taken from the Babia Góra National Park

The aim of this work was to determine ¹³⁷Cs and ⁴⁰K radioactivities in soil samples taken from the Babia Góra National Park (BPN) in south Poland. The cluster analysis (CA) and principal component analysis (PCA) were used to discuss the obtained data. 10 cm thick soil cores were collected from the BPN area. Each sample was divided into three sub-samples. The samples were dried, homogenized and packed in polyethylene containers. The radioactivities of ¹³⁷Cs and ⁴⁰K were measured by means of gamma spectrometry. It was found that ¹³⁷Cs radioactivity in the whole 10 cm soil cores was in the range from 1,916 to 28,551 Bq m^?2. The radioactivity of ⁴⁰K varied from 1,642 to 25,654 Bq m^?2. Using CA it was possible to diverse the soils taking into account soil types. By use of the PCA method, it was chosen three factors which are appropriate to characterize researched parameters.     

Solvent extraction of Li+, H3O+ and NH4 + into nitrobenzene by using sodium dicarbollylcobaltate and calix[4]arene-bis(t-octylbenzo-18-crown-6)

From extraction experiments and $ \gamma $ -activity measurements, the exchange extraction constants corresponding to the general equilibrium M⁺ (aq) + NaL⁺ (nb) ? ML⁺ (nb) + Na⁺ (aq) taking place in the two–phase water–nitrobenzene system (M⁺= Li⁺, H₃O⁺, NH₄ ⁺; L = calix[4]arene-bis(t-octylbenzo-18-crown-6); aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Furthermore, the stability constants of the ML⁺ complexes in nitrobenzene saturated with water were calculated; they were found to increase in the following cation order: H₃O⁺ < Li⁺ < NH₄ ⁺.