Soil-to-plant transfer factors of fallout <Superscript>137</Superscript>Cs and native <Superscript>133</Superscript>Cs in various crops collected in Japan

In order to compare the soil-to-plant transfer factors (TFs) of fallout ¹³⁷Cs and those of native stable ¹³³Cs, concentrations of these isotopes were determined in various crops and the associated soils collected throughout Japan. The results showed that TF-¹³⁷Cs was 11 times higher than TF-native ¹³³Cs for brown rice, while those values were almost the same for leafy vegetables. Possibly, fallout ¹³⁷Cs would be more mobile and more easily adsorbed by plants than native ¹³³Cs in the soil because a part of the ¹³³Cs is in a soil structure where it is hard to replace with ¹³⁷Cs. However, ¹³⁷Cs and native ¹³³Cs have reached an approximately isotopic equilibrium in the bioavailable fraction in the soils, therefore, the TF-native ¹³³Cs can be used for long-term transfer of ¹³⁷Cs in the environment.     

Long-term transfer of <Superscript>137</Superscript>Cs from soil to mushrooms in a semi-natural environment

The radioactive contamination following the Chernobyl accident resulted in high concentrations of ¹³⁷Cs in several mushrooms species. Mushroom samples were collected in a forest environment between 1986 and 2007 and the transfer of ¹³⁷Cs to two edible species, Suillus variegatus and Cantharellus spp., was investigated. The ¹³⁷Cs uptake by the collected samples did not decrease over time and in Cantharellus spp. a significant increase was observed. Most of the ¹³⁷Cs in soil still appears to be available for uptake and radioactive decay of the radionuclide is likely the main factor for the reduction of ¹³⁷Cs in a forest ecosystem.     

Measuring <Superscript>137</Superscript>Cs, <Superscript>40</Superscript>K and decay products of <Superscript>226</Superscript>Ra and <Superscript>232</Superscript>Th in samples of different nature by a multidetector spectrometer

A coincidence method for measuring ¹³⁷Cs, ⁴⁰K, ²²⁶Ra and ²³²Th decay products activity in soil, vegetation and fish samples, was applied to the six-crystal gamma-coincidence spectrometer PRIPYAT-2M. In this way, some problems appeared in simultaneous measurement of ¹³⁷Cs, ²²⁶Ra and ²³²Th by NaI(Tl) detectors and the PRIPYAT-2M spectrometer were solved. The obtained results were agreeable with the HPGe spectrometer ones.     

Low level detection of <Superscript>135</Superscript>Cs and <Superscript>137</Superscript>Cs in environmental samples by ICP-MS

The measurement of fission product cesium isotopes ¹³⁵Cs and ¹³⁷Cs at low femtogram (fg) 10⁻¹⁵ levels in ground water by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) is reported. To eliminate the natural barium isobaric interference on the cesium isotopes, in-line chromatographic separation of the cesium from barium was performed followed by high sensitivity ICP-MS analysis. A high efficiency desolvating nebulizer system was employed to maximize ICP-MS sensitivity ~10 cps/fg. The three sigma detection limit for ¹³⁵Cs was 2 fg/mL (0.1 μBq/mL) and for ¹³⁷Cs 0.9 fg/mL (0.0027 Bq/mL) measured from the standard with analysis time of less than 30 min/sample. Cesium detection and 135/137 isotope ratio measurement at very low femtogram levels using this method in a spiked ground water matrix is also demonstrated.     

Distribution of <Superscript>137</Superscript>Cs, <Superscript>40</Superscript>K and <Superscript>7</Superscript>Be in silver fir-tree (<Emphasis Type="Italic">Abies alba</Emphasis> L.) from Gorski Kotar,Croatia

Distribution of ¹³⁷Cs, ⁴⁰K and ⁷Be in tissues of the silver fir-tree was studied. Samples of the shoots were taken at six locations in Croatia during five years. Shoots were cut according to the year of growth and analyzed. Distribution between needles and twigs was also studied. Samples of the tree rings and the bark were taken at three locations. ¹³⁷Cs and ⁴⁰K showed very similar distributions. ¹³⁷Cs and ⁴⁰K activities were age-dependent and increased in decreasing age of twigs and needles. The highest activities were measured in the youngest twigs. The highest ⁷Be activities were found in the twigs.     

Mixing of atmospheric <Superscript>210</Superscript>Pb and <Superscript>7</Superscript>Be and <Superscript>137</Superscript>Cs and <Superscript>90</Superscript>Sr fission products in four characteristic soil types

Depth distribution of atmospheric ²¹⁰Pb and ⁷Be and ⁹⁰Sr and ¹³⁷Cs fission products was measured in two types of aeolian soils (desert dust and volcanic ash), irrigated paddy soil and strongly acidic soil. The depth dependence of ²¹⁰Pb, ⁷Be and ¹³⁷Cs show that these radionuclides have been diffused as solid soil particles in surface soil layers. In aeolian soil layers, about 50% of ⁹⁰Sr were diffused in surface soil layer and the remaining 50% had penetrated to deeper layers. The half of the fission particles containing ⁹⁰Sr were shown to have decomposed over the past 35 years.     

Bioaccumulation of <Superscript>137</Superscript>Cs and <Superscript>60</Superscript>Co by bacteria isolated from spent nuclear fuel pools

This paper is focused on a characterization of bacterial contamination in pool water of the interim spent fuel storage (JAVYS Inc.) in Slovak Republic and on bioaccumulation of ¹³⁷Cs and ⁶⁰Co by isolated bacteria. Bacterial community in pool water is kept on very low level by extremely low concentration of solutes in deionized water and by the efficient water filtration system. Based on standard methods and sequencing of 16S rDNA four pure bacterial cultures were identified as Kocuria palustris, Micrococcus luteus, Ochrobactrum spp. and Pseudomonas aeruginosa. Isolated aerobic bacteria were able to bioaccumulate ¹³⁷Cs and ⁶⁰Co in laboratory experiments. The mechanism of Co and Cs binding involve rapid interactions with anionic groups of the components of cell surface and in the case of Cs⁺ ions is followed by transport processes across cytoplasm membranes and by intracellular distribution. The maximum specific uptake of Cs⁺ after 48 h cultivation in mineral medium (MM) reached 7.54 ± 0.48 μmol g^?1 dw (Ochrobactrum spp.), 19.6 ± 0.1 μmol g^?1 dw (M. luteus) and 20.1 ± 2.2 μmol g^?1 dw (K. palustris). The maximum specific uptake of Co²⁺ after 24 h cultivation in MM reached 31.1 ± 3.5 μmol g^?1 dw (Ochrobactrum spp.), 86.6 ± 12.2 μmol g^?1 dw (M. luteus) and 16.9 ± 1.2 μmol g^?1 dw (K. palustris). These results suggest that due to the long lasting uptake of ¹³⁷Cs, ⁶⁰Co and other radionuclides by biofilm in pool water high specific radioactivities (Bq m^?2) can be expected on stainless steel walls of pools.     

Distribution of <Superscript>137</Superscript>Cs, <Superscript>40</Superscript>K, <Superscript>232</Superscript>Th and <Superscript>238</Superscript>U in coastal marine sediments of Margarita Island,Venezuela

This work presents the results of ¹³⁷Cs, ⁴⁰K, ²³²Th and ²³⁸U concentration (Bq kg⁻¹) values in coastal marine sediments collected from 38 sites along the coastline of the island of Margarita, Venezuela. The purpose was to determine baseline values for these radionuclides in surface marine sediments and to detect if there were any anomalously high concentration values. Only three of the 38 sediments analyzed had measurable values above the detection limit of 0.9 Bq kg⁻¹ for ¹³⁷Cs and the highest only being 1.4 Bq kg⁻¹. While, the concentration (Bq kg⁻¹) ranges for the primordial radionuclides, ⁴⁰K, ²³²Th and ²³⁸U were as follows: 12.2–211.7, <1.5–9.8 and <4.4–20.7, respectively. These concentration ranges for the primordial radionuclides can be considered as baseline values for surface marine sediments for areas that are considered not polluted by man or contaminated by nature. Finally, the concentration range of ¹³⁷Cs can also be employed as baseline values, which only seem to have been the result of the atmospheric testing of nuclear weapons in the past.     

Improvement of <Superscript>137</Superscript>Cs analysis in small volume seawater samples using the Ogoya underground facility

¹³⁷Cs in seawater is one of the most powerful tracers of water motion. Large volumes of samples have been required for determination of ¹³⁷Cs in seawater. This paper describes improvement of separation and purification processes of ¹³⁷Cs in seawater, which includes purification of ¹³⁷Cs using hexachloroplatinic acid in addition to ammonium phosphomolybdate (AMP) precipitation. As a result, we succeeded the ¹³⁷Cs determination in seawater with a smaller sample volume of 10 liter by using ultra-low background gamma-spectrometry in the Ogoya underground facility. ¹³⁷Cs detection limit was about 0.1 mBq (counting time: 10⁶ s). This method is applied to determine ¹³⁷Cs in small samples of the South Pacific deep waters.     

Chemometrics of the distribution and origin of <Superscript>226</Superscript>Ra, <Superscript>228</Superscript>Ra, <Superscript>40</Superscript>K and <Superscript>137</Superscript>Cs in plants near the West Macedonia Lignite Center (Greece)

Summary The distribution and origin of ⁴⁰K, ²²⁶Ra, ²²⁸Ra and ¹³⁷Cs has been investigated in trees, mosses and lichens in the basin of the West Macedonia Lignite Centre. In tree leaves ¹³⁷Cs is negligible, while the ²²⁶Ra and ²²⁸Ra concentrations are affected by the fly ash particles. Concerning ²²⁶Ra and ²²⁸Ra values of mosses and lichens, which are systematically larger than those of unpolluted areas, the application of chemometrics proved that they originate mainly from the lignite fly ash.     

Migration and sorption of <Superscript>137</Superscript>Cs and <Superscript>152,154</Superscript>Eu in crushed crystalline rocks under dynamic conditions

In migration experiments, sorption of ¹³⁷Cs and ^152,154Eu in the columns of crushed crystalline rocks of 0.25–0.8 mm grain size under dynamic flow conditions from the synthetic groundwater (SGW) has been studied. Five samples of crystalline rocks from Cavernous Gas Reservoir near Příbram were taken. Plastic syringes of 8.8 cm length and 2.1 cm in diameter were used as columns. The water phase was pumped downward through the columns, using a multi-head peristaltic pump, with a seepage velocity of about 0.2 cm/min. The radioactive nuclides, containing chemical carriers, were added into the water stream individually in the form of a short pulse. Desorption experiments were carried out with 2:1 (v/v) mixture of H₂SO₄ and HNO₃. In the columns the longitudinal distribution of the residual ¹³⁷Cs and ^152,154Eu activities was also determined. By the evaluation of respective breakthrough and displacement curves, the experimental and theoretical retardation factors, distribution coefficients and hydrodynamic dispersion coefficients were determined using the integrated analytical form of a simple advection-dispersion equation (ADE). Dynamic sorption experiments were also compared with the results of static sorption experiments. The paper was presented in part as a poster No. PB1-1 at the 11th International Conference Migration’ 07, held in Munich, Germany, August 26–31, 2007, Abstracts, p. 212.     

Accumulation of <Superscript>137</Superscript>Cs and <Superscript>40</Superscript>K in aboveground organs of tropical woody fruit plants

Distribution of ⁴⁰K and ¹³⁷Cs in tissues of the Citrus aurantifolia was measured by gamma spectrometry. A simple theoretical model is also proposed to describe the temporal evolution of ⁴⁰K activity concentration in such tropical woody fruit species. This model exhibits close agreement with the ⁴⁰K experimental results, in the leaf growing and fruit ripening processes of lemon trees.     

Anomalously high activities of <Superscript>137</Superscript>Cs in soils and vegetation on and near a diabase outcrop in La Sierra de Lema,Venezuela

As a result of routine soil sampling to determine the ¹³⁷Cs background activities country-wide in Venezuela, it was decided to further investigate El Mirador (Lookout) area at the base of the Sierra de Lema mountain range. In April 2003 (A), soil samples were collected at eight sites on and around the edge of the diabase outcrop to confirm that this area had anomalously high ¹³⁷Cs activities. In July 2003 (B), not only soil samples were collected again, but also black mat, palm tree leaves and trunks, fruit bushes leaves and its fruit and fern leaves. The ¹³⁷Cs content was measured by high resolution gamma-ray spectroscopy by a comparative method with reference materials. The ¹³⁷Cs activity values range from 16.3 to 30.8 Bq·kg-1 in the soil samples collected in July 2003, 20.7–32.1 Bq·kg⁻¹ for the black mat, 26.3–38.4 Bq·kg⁻¹ for the palm leaves, 16.8–31.2 Bq·kg⁻¹ for the palm trunks and 17.6–27.3 Bq·kg⁻¹ for the fruit bush leaves, while, the ¹³⁷Cs activity values for the whole fruit were between 23.4 and 30.7 Bq·kg⁻¹; but, the value of the ¹³⁷Cs activity in the center of the fruit (the edible part) was 51.6 Bq·kg⁻¹, and the value of the ¹³⁷Cs activity for the fern leaves was 51.8 Bq·kg⁻¹. Thus, most of the ¹³⁷Cs activity values determined in the soil, black mat and vegetation samples from El Mirador (Lookout) were considered anomalously high with respect to those found near the equator and in other areas of Venezuela. Only the center of the fruit from the Clusia grandiflora bushes and the fern leaves had high activity ratios, about a factor of three and could be considered as biomonitors that concentrate and retain the ¹³⁷Cs. Finally, these anomalously high ¹³⁷Cs activities have been attributed not only to the rich organic soils, as sinks, but also due to the affect of the cloud forests.     

Monitoring of <Superscript>137</Superscript>Cs in electric arc furnace steel making process

This article presents the results of ¹³⁷Cs and other radionuclide monitoring in EAF steel-making process in the Croatian CMC Sisak Steel Mill. The presence of ¹³⁷Cs and natural isotopes ⁴⁰K, ²³²Th, ²²⁶Ra and ²³⁸U was established. Investigations on the occurrence of the isotope cesium, as well as natural isotopes and their distribution in waste from the process of carbon steel production by EAF have been conducted. Detection of artificial isotope cesium in EAF dust indicates that it might originate from steel scrap or from the residue of the material that was used in the technological process, thus deserving special attention.     

Concentration of <Superscript>137</Superscript>Cs in seawater surrounding East Malaysia

Studies of ¹³⁷Cs distribution in East Malaysia were carried out as part of a marine coastal environment project. The results of measurements will serve as baseline data and background reference level for Malaysia coastline. Twenty-one locations were identified along the coastline of East Malaysia, and from each location water samples were collected at the surface of the seawater. Ten near-shore locations were also selected and seawater was collected at three different depths. Large volumes of seawater were collected and the co-precipitation technique was employed to concentrate cesium. A known amount of ¹³⁴Cs tracer was added as yield determinant, followed by addition of copper(II) nitrate salt and a solution of potassium hexacyanoferrate(II) trihydrate, to precipitate the total cesium. The precipitate slurry was oven dried at 60 °C for 1–2 days, finely ground and counted using gamma-ray spectrometry. The activity of ¹³⁷Cs was determined by measuring the peak area under the photopeak of the gamma-spectrum at 661 keV, which is equivalent to gamma-intensity corrected for detection efficiency, percentage of gamma-ray abundance of the radionuclide and recovery of ¹³⁴Cs tracer. There were no significant differences of ¹³⁷Cs activities both in surface and bottom water samples at 95% confidence level. The activity of ¹³⁷Cs (for all samples) was found to be in the range of 1.47 to 3.36 Bq/m³ and 1.69 to 3.32 Bq/m³ for Sabah and Sarawak, respectively.     

Global fallout levels of <Superscript>99</Superscript>Tc and activity ratio of <Superscript>99</Superscript>Tc/<Superscript>137</Superscript>Cs in the Pacific Ocean

Summary Global fallout levels of ⁹⁹Tc and ¹³⁷Cs of surface seawater in the Pacific Ocean were measured. The ⁹⁹Tc concentrations ranged from 0.62 to 3.33 mBq^. m^-3and 5 of 6 samples showed less than 1 mBq^. m^-3except one sample taken in the Great Barrier Reef, Australia. The ¹³⁷Cs concentrations ranged from 2.13 to 3.14 Bq^. m^-3, showing a gradual decrease in the North Pacific toward the equator and a constant level in the South Pacific. The ⁹⁹Tc/¹³⁷Cs activity ratios ranged from 2.5^. 10^-4to 2.9^. 10^-4, which is very close to that calculated theoretically from the fission yield.     

European measurement comparison of <Superscript>137</Superscript>Cs, <Superscript>40</Superscript>K and <Superscript>90</Superscript>Sr in milk powder

Recently, the Institute for Reference Materials and Measurements (IRMM) has assumed responsibility for organizing regular measurement comparisons among those laboratories which provide radioactivity monitoring data from their country to authorities of the European Commission (EC) under various EC legislation articles. The most recent exercise under this International Comparison Scheme for Radioactivity Environmental Monitoring (ICS-REM) in measuring the ¹³⁷Cs, ⁴⁰K and the ⁹⁰Sr activity concentration in milk powder is presented here. The complete cycle of the comparison is described, including the establishment of reference values traceable to SI units, the demonstration of the homogeneity of the distributed samples, the treatment and measurement of samples in the participating laboratories, and the evaluation of the results.     

Modeling β-γ coincidence spectra of <Superscript>131m</Superscript>Xe, <Superscript>133</Superscript>Xe, <Superscript>133m</Superscript>Xe,and <Superscript>135</Superscript>Xe

In support of the Comprehensive Nuclear-Test-Ban Treaty (CTBT), improvements have been made to the model of the Automated Radioxenon Sampler/Analyzer (ARSA) β-γ coincidence detector for radioxenon monitoring. MCNPX is used to simulate the detector response for all the electrons and photons emitted from ^131mXe, ¹³³Xe, ^133mXe, ¹³⁵Xe, and ¹³⁷Cs signals. A MatLab code was written to incorporate the MCNPX results in the calculation of β-γ coincidence spectra. These will aid in the development of the Spectral Deconvolution Analysis Tool (SDAT)¹ and to calibrate β-γ coincidence systems. The models developed for this work include improvements over previous models in their ability to address Compton scattering in the β-cell, and the β-distribution offset in the 31 keV γ-ray region for ¹³³Xe.     

Migration processes of <Superscript>137</Superscript>Cs and <Superscript>90</Superscript>Sr in compartments of a lake ecosystem

Summary The dispersion of radioactive substances in the environment following nuclear weapon tests in atmosphere since 1954 and accidents to nuclear plants, like that in Chernobyl in 1986, have allowed us to study the migration processes of some radionuclides in complex ecosystems such as lakes are. In the present paper the behavior of ¹³⁷Cs and ⁹⁰Sr in different compartments of the Monterosi Lake (central Italy) was assessed. The ¹³⁷Cs concentration was measured in lake water as well as sediment, stream water, aquatic plant and fish samples. ⁹⁰Sr concentration in water and sediments was also determined. A total inventory of 4206±76 Bq ^. m^-2 and 958±79 Bq ^. m^-2 (on 27/6/01) has been found for ¹³⁷Cs and ⁹⁰Sr, respectively. The experimental data presented here allow to calibrate theoretical models predicting the temporal trend of radionuclide concentration in similar ecosystems. Moreover, information on cesium and strontium migration processes can be extended to other pollutants having similar environmental behavior.     

Determination and spatial distribution of <Superscript>137</Superscript>Cs in soils,mosses and lichens near Kavanayen,Venezuela

The activity of ¹³⁷Cs was determined in soils, mosses, lichens and other vegetation along the Caruay River and near the town of Kavanayen. The range of values for the soils was from <1.2 Bq·kg⁻¹ of ¹³⁷Cs (our detection limit) to 14.1 Bq·kg⁻¹. The range of ¹³⁷Cs activities in the mosses ranged from 9.9 to 17.9 Bq·kg⁻¹ with a mean value of 13.4±4 Bq·kg⁻¹; all the moss samples were found along the river. While the ¹³⁷Cs activities in the lichens ranged from 9.1 to 29.8 Bq·kg⁻¹; the two values along the river were about three factors higher than the one near Kavanayen. It was concluded that the ¹³⁷Cs activities in the soils, mosses and lichens are much higher along the river in respect to the nearby town of Kavanayen.