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.     

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.     

Depth distribution of137cesium,90strontium and210lead in sediments of lake Mondsee,Austria

¹³⁷Cs,⁹⁰Sr and²¹⁰Pb were determined in sediment cores from lake Mondsee /Austria/. The depth profiles show that¹³⁷Cs remains undisturbed, i.e. its distribution corresponds to the fallout deposition pattern.⁹⁰Sr, however, has been transported into the upper sediment layers. In this upper zone nearly constant levels of⁹⁰Sr and also of²¹⁰Pb/²¹⁰Po/were found. Comparison of the⁹⁰Sr and¹³⁷Cs profiles indicates that chemical processes must be responsible for the translocation of⁹⁰Sr as well as²¹⁰Pb, and not bioturbation, i.e. mixing of upper sediment layers by benthic organisms.Dedicated to Prof. Dr. Karl Schlögl, University of Vienna, for his 60th birthday.     

Atmospheric deposition fluxes of <Superscript>7</Superscript>Be, <Superscript>210</Superscript>Pb and <Superscript>210</Superscript>Po at Xiamen,China

The atmospheric deposition fluxes of ⁷Be, ²¹⁰Pb and ²¹⁰Po at Xiamen were measured. The samples were collected from March 2004 to April 2005 and the sampling period was one month. The ⁷Be and ²¹⁰Pb activity were measured using HPGe γ-spectrometer after concentration using Fe(OH)₃ co-precipitation method. The ²¹⁰Po was counted with an α-spectrometer after the sample was digested and spontaneous plated onto a silver planchet. At Xiamen, the atmospheric deposition fluxes of ⁷Be varied between 0.11 and 2.93 Bq·m⁻²·d⁻¹ and the average was 1.64 Bq·m⁻²·d⁻¹; ²¹⁰Pb fluxes varied between 0.04 and 0.85 Bq·m⁻²·d⁻¹, and the average was 0.51 Bq·m⁻²·d⁻¹; ²¹⁰Po fluxes varied between 0.002 and 0.133 Bq·m⁻²·d⁻¹, and the average was 0.061 Bq·m⁻²·d⁻¹. There were positive correlations between the deposition fluxes of ⁷Be, ²¹⁰Pb or ²¹⁰Po and the amount of precipitation. The residence time of aerosols varied between 6.0 and 54.0 days with a mean of 27.1 days, which were calculated by ²¹⁰Po/²¹⁰Pb fluxes ratios.     

Behavior of <Superscript>134</Superscript>Cs, <Superscript>90</Superscript>Sr,and <Superscript>238</Superscript>Pu in different Syrian soils

The experiment aimed to evaluate the vertical migration of ¹³⁴Cs, ⁹⁰Sr and ²³⁸Pu in the main types of Syrian soils; entisol, inceptisol, alluvial (rock outcrops) and gypsiferous soils, using soil columns through which the aqueous solution of the radionuclides percolated. The results show that the vertical migration of the studied radionuclides through the soil profile depend on the radionuclide and the soil type. More than 97% of ¹³⁴Cs and ²³⁸Pu concentrated in the upper 2 cm of the entisol, inceptisol, and alluvial soils, whereas only 46.2% to 68.6% of the ⁹⁰Sr was retained in the upper 2 cm of these soils. The vertical migration of the studied radionuclides in the gypsiferous soil was different from the other soils. The distribution of the radionuclides in the gypsiferous soil was irregular through the soil profile and reached the deeper layer of the soil. This may be due to its physical characteristics; poor structure stability, high permeability and low retention capacity.     

Behavior of <Superscript>7</Superscript>Be and <Superscript>210</Superscript>Pb deposited via rainwater on a coniferous forest,a broad-leaved forest,and grassland

Fall water, stem flow water and falling litter in a coniferous forest (C. japonica) and a broad-leaved forest (L. edulis), and rainwater on a grassland near the forests were collected, and their ⁷Be and ²¹⁰Pb contents were measured. The average residence times of ⁷Be and ²¹⁰Pb in the forest crowns were calculated from the balances of their radionuclides, those in the forest crown of C. japonica were 88 days for ⁷Be and 9.2 years for ²¹⁰Pb, and those in the forest crown of L. edulis were 52 days and <1 year, respectively.     

<Emphasis Type="Italic">Lycopodium cernuum</Emphasis> and <Emphasis Type="Italic">Funaria hygrometrica</Emphasis> as deposition indicators for radionuclides and trace metals

Summary Levels of ²¹⁰Pb, ²¹⁰Po, ¹³⁷Cs and some trace elements (Cu, Zn and Pb) in two most common mosses (Lycopodium cernuum and Funaria hygrometrica) distributed in the eastern Mediterranean sea region (Syrian coastal mountains series) have been determined. Radiochemical analysis has shown that these plants contain high levels of ²¹⁰Pb, ²¹⁰Po, ¹³⁷Cs. The highest concentration of ²¹⁰Pb, ²¹⁰Po and ¹³⁷Cs were found to be 1450, 1322 and 1140 Bq ^. kg^-1 dry wt. in L. cernuum, respectively. F. hygrometrica was found to have higher values of ²¹⁰Pb and ²¹⁰Po concentrations and reached 2392 and 2119 Bq ^. kg^-1 dry wt., respectively. Correlation coefficients for radionuclide levels in both plants versus their levels in soil have been determined: No correlation for ¹³⁷Cs for both plants has been observed. This indicates that ¹³⁷Cs in these plants is of atmospheric origin and the plants can be used as deposition indicators. In addition, a correlation with radionuclide levels was found only for ²¹⁰Pb and ²¹⁰Po in F. hygrometrica samples and was mainly related to ²²⁶Ra content in soil and the existing faults, which are the main source of these radionuclides. On the other hand, lead concentration in L. cernuum was found to be in the range of 5-86.6 ppm, while F. hygrometrica samples were found to contain around 58 ppm. Both plants seem to accumulate lead from the atmosphere where vehicle emissions are the main source of lead in the region. Comparable concentrations of Cu and Zn were found in all plant and soil samples.     

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.     

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.     

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.     

Determination of <Superscript>137</Superscript>Cs and <Superscript>90</Superscript>Sr in the bottom sediments from the Barents Sea

The aim of this paper was to determine the extent of contamination by anthropogeneous radionuclides ¹³⁷Cs and ⁹⁰Sr in the bottom sediments from the Barents Sea based on the radioactive activity of the samples taken up in August 1991, among others, from the area close to New Land Island and Francis Joseph Archipelago. The results are based on the phenomenon of vertical migration, in the bottom sediments which is of significant importance from the natural environment point of view.     

Distribution of <Superscript>210</Superscript>Po and <Superscript>210</Superscript>Pb in riverine environs of coastal Karnataka

The concentrations of ²¹⁰Po and ²¹⁰Pb have been measured in soil, sediment and rock samples collected from major rivers of coastal Karnataka, viz. Kali, Sharavathi and Netravathi. The activity of ²¹⁰Po and ²¹⁰Pb in the samples were separated by radiochemical methods and the activity was counted using ZnS(Ag) alpha-counter. The activity ratio of ²¹⁰Po and ²¹⁰Pb and the dependence of organic matter content on the activity of these radionuclides were studied.     

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.     

<Superscript>210</Superscript>Pb and <Superscript>137</Superscript>Cs dating of sediments from Zigetang Lake,Tibetan Plateau

Zigetang Lake located in the central Tibetan Plateau was selected for the purpose of understanding of recent sedimentation rates. Based on ¹³⁷Cs dating marker, the sediment rate was 0.077 cm·yr⁻¹. The sedimentation rate was calculated to be 0.071 cm·yr⁻¹ and 0.029 g·cm⁻²·yr⁻¹ on the basis of ²¹⁰Pb CIC model. ²¹⁰Pb CRS model was also used for understanding of recent sedimentation change. The sediment accumulation rates for the CRS model ranged from 0.022 to 0.038 g·cm⁻²·yr⁻¹ with an irregular high value of 0.12 g·cm⁻²·yr⁻¹ around 1932 at Zigetang Lake core in the past eighty years.     

Distributions of <Superscript>210</Superscript>Po and <Superscript>210</Superscript>Pb radioactivity in the intermediate layer of the northwestern North Pacific

The distributions of ²¹⁰Po and ²¹⁰Pb in the intermediate layer (400–2000 m) of the northwestern North Pacific were determined to elucidate the export flux of particulate matter. ²¹⁰Po generally showed depletion relative to ²¹⁰Pb in the intermediate layer, suggesting that ²¹⁰Po was scavenged by particles. Because the removal rate constants of ²¹⁰Po in the western region were higher than those in the eastern region and this trend coincided with that of the particle fluxes in the surface layer, the export production in the surface layer was assumed to influence the particle flux in the intermediate layer of the northwestern North Pacific.     

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.     

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.     

Methodology for determination of <Superscript>89</Superscript>Sr and <Superscript>90</Superscript>Sr in radiological emergency: II. Method development and evaluation

In this work a method for the determination of both ⁸⁹Sr and ⁹⁰Sr is presented. The method can potentially be used in radiological emergency and deliver results shortly after an incident. The method development was based on theoretical calculations of potential interferences from other fission products and how these could be discriminated when applying different chemical separation schemes. Validation was done on reactor coolant water containing short-lived fission products, and on a reference material. The results indicate that correct results of ⁸⁹Sr and ⁹⁰Sr can be obtained 4 and 9 days, respectively, after an incident.     

137Cs dating of lake cores from the Nahuel Huapi National Park, Patagonia, Argentina: Historical records and profile measurements

Historical records of short lived (¹⁴⁰Ba, ¹³¹I, ¹⁰³Ru and ⁹⁵Zr+⁹⁵Nb) and long-lived (¹³⁷Cs and ⁹⁰Sr) fission products by fallout measurements performed in Argentina since 1959 were analyzed in order to define the main characteristics of ¹³⁷Cs fallout time evolution in the Nahuel Huapi National Park, Patagonia, Argentina. Sedimentary cores were sampled from Lake Nahuel Huapi and Lake Morenito, which are located within Nahuel Huapi National Park. ¹³⁷Cs specific activity profiles were measured and ²¹⁰Pb dating was performed in each core. The time evolution of ¹³⁷Cs fallout shows different characteristics than records taken in the Northern Hemisphere.¹³⁷Cs specific activity profiles of the cores studied reproduce the fallout time sequence observed in the historical records, and the chronology obtained shows excellent agreement with ²¹⁰Pb dating.