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.     

Protein determination in single corns

The dynamics of¹³⁷Cs soil-to-plant transfer has been studied for 21 vegetal species in an agricultural area not far from Bucharest, during a two year experiment started one year after the Chemobyl nuclear accident. The results, generally fitting in the value ranges found in literature, are discussed in the strict sense of the definition for soil-to-plant transfer of radionuclides.     

Transfer of 137Cs and stable Cs in soil-grass-milk pathway in Aomori, Japan

The soil-to-grass transfer factors and grass-to-milk transfer coefficients were determined for ¹³⁷Cs and stable Cs in soil, grass and milk samples collected in Aomori Prefecture, Japan. The concentrations of ¹³⁷Cs in the soil and grass samples collected from 25 sampling sites were 13±12 Bq.kg^-1 and 2.0±2.1 Bq.kg^-1 dry wt., respectively. The geometric mean of soil-to-grass transfer factor of ¹³⁷Cs was 0.13 and its 95% confidence interval was 0.017-0.98. The transfer factor of ¹³⁷Cs was higher than that of stable Cs, and they had a positive correlation. The concentration of K in the soil affected both transfer factors. The concentration of ¹³⁷Cs in milk samples collected from 16 sites was 76±43 mBq.kg^-1 fresh wt. and had a good correlation with that of stable Cs. The geometric mean of grass-to-milk transfer coefficient of ¹³⁷Cs was 0.0027, assuming that a cow's total daily intake was 20 kg of dry grass. The transfer coefficient of ¹³⁷Cs was positively correlated with that of stable Cs.     

Prediction capacity of a sequential extraction scheme

The predictions of a sequential extraction scheme with respect to the mobility of some radionuclides (⁸⁵Sr,¹³⁴Cs and^110mAg) in two Mediterranean sandy and sandy-loam soils, are compared to short-term soil-to-plant transfer factors and soil migration. Total soil-to-plant transfer is higher in sandy soil than in sandy-loam soil, as expected and predicted by the scheme. The relative transfer to plants of¹³⁴Cs and⁸⁵Sr follows the scheme predictions about exchangeable radionuclide fraction, radiosilver being less mobile than expected. Migration in soil of radiocesium and radiostrontium is also higher in sandy soil, especially for the latter radionuclide, the relative behavior of these two radionuclides being nearer to the bioavailable radionuclide fraction defined by the scheme. However, the scheme fails in predicting radiosilver migration, which is lower than deduced by the scheme.     

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.     

Determination of transfer factors for 137Cs and 90Sr isotopes in soil–plant system

Studies on the determination of transfer factors (TF) for ¹³⁷Cs and ⁹⁰Sr isotopes from soil to plant are presented. Experiments were performed on grass from meadows of Bug river valleys and vegetables from Zwierzyniec region. The influence of potassium and calcium on the transfer factor of both isotopes is discussed.     

Soil-to-plant transfer of 137Cs and other essential and trace elements in cabbage plants

The concentrations of ¹³⁷Cs and other essential and trace elements were determined in soils and in cabbage heads collected from 8 agricultural fields in Aomori Prefecture, Japan and the soil-to-plant transfer factors were determined. The 95% confidence intervals of the elements, excluding ¹³⁷Cs, La and Ce, were within 2 orders of magnitude. The transfer factor of ¹³⁷Cs was approximately 4 times higher than that of Cs, and they were well correlated. In addition, the distributions of elemental concentrations in different leaf positions of a cabbage plant were also determined and were divided into three groups according to their different distribution patterns in the leaf positions. These patterns were as follows: (1) the concentrations of the elements in older (outer) leaves were higher than in younger (inner) ones (Ca, Sr, etc.), (2) the concentrations of the element had a relatively constant value independent of their leaf position (K, Rb, etc.), and (3) the concentrations of the elements were higher in both the older and younger leaves compared to the leaves in the middle portion (Zn). The percentage distribution of the dry weight contents in the edible leaves of cabbage plants was 41% at harvest time, however each element had different distribution patterns.     

Evaluation of <Superscript>137</Superscript>Cs soil-to-plant transfer: Natural and model experiments

Soil and meadow grass were sampled in the whole territory of Lithuania in 1992–2000. For the laboratory experiment, spring wheat Triticum aestivum L. “Nandu” was used because its root system type is similar to that of perennial meadow grass. The ¹³⁷Cs soil-to-plant transfer factor of spring wheat was determined and the results were compared with the predicted values using a compartment model of soil-to-plant transfer and with the results of the field experiment. The results of comparing the measured and calculated transfer factor using the model show rather good coincidence, however, the calculated values were overestimated. The reason for overestimation can be that the uptake rate is not influenced only by the soil-to-plant transfer. The results of the model experiment (from 0.005 m²·kg⁻¹ to 0.053 m²·kg⁻¹) are close to those of the field measurements for grass (from 0.013 m²·kg⁻¹ in 1992–1995 to 0.10 m²·kg⁻¹ in 1999–2000).     

Transfer of137Cs from soil to plants in a wet montane forest in subtropical Taiwan

The distribution of¹³⁷Cs in an undisturbed, multistoried, subtropical wet montane forest ecosystem surrounding Yuanyang Lake (lake surface level ca. 1670m, in northeastern Taiwan), was investigated. The mossy forest here represents a currently-rare perhumid temperate environment in subtropical region. The radioactivity concentration of¹³⁷Cs was determined by γ-spectroscopy with a Ge(Li) detector. Although the soil is extremely acidic (pH 3.3 to 3.6) and the rainfall is high,¹³⁷Cs is evidently retained in the organic layer. The radioactivity concentration of¹³⁷Cs in surface soil ranges from 28 to 71 Bq·kg⁻¹. The concentrations of¹³⁷Cs in the ground moss layer and litter were much lower than that in the soil organic layer, this suggests that¹³⁷Cs detected is not from the newly deposited radioactive fallout. The radioactivity concentration and transfer factor (TF) of¹³⁷Cs varied with plant species. Shrubs and ferns have higher values than a coniferous tree (Taiwan cedar). The TF in this ecosystem is as high as 0.21 to 1.88. The high values of TF is attributed to the abundance of the organic matter in the forest soils. The rapid recycling of¹³⁷Cs through the soil-plant system of this undisturbed multistoried ecosystem suggests the existence of an internal cycling that help the accumulation of¹³⁷Cs in this ecosystem.     

Sources of 137Cs fluvial export from a forest catchment evaluated by stable carbon and nitrogen isotopic characterization of organic matter

Fluvial export of particulate and dissolved ¹³⁷Cs was investigated to reveal its sources and transfer mechanisms in a broadleaved forest catchment using a continuous collection system. The finest size fraction (<75 µm), consisting of decomposed litter and surface mineral soil, was the dominant fraction in the particulate ¹³⁷Cs load, although the contribution of coarser size fractions increased during high water discharge in 2014. The dissolved ¹³⁷Cs originated from the decomposition of ¹³⁷Cs-contaminated litter. Temporal changes in ¹³⁷Cs distribution in the litter–mineral soil system indicated that the dissolved ¹³⁷Cs load will be moderated in several years, while particulate ¹³⁷Cs load has the potential to continue for a long time.

     

Soil-to-mushroom transfer of <Superscript>137</Superscript>Cs, <Superscript>40</Superscript>K,alkali–alkaline earth element and heavy metal in forest sites of Izmir,Turkey

The present work is devoted to an investigation on the soil to mushroom transfer parameters for ¹³⁷Cs and ⁴⁰K radionuclides, as well as for some stable elements and heavy metals. The results of transfer factors for ¹³⁷Cs and ⁴⁰K were within the range of 0.06–3.15 and 0.67–5.68, respectively and the most efficiently transferred radionuclide was ⁴⁰K. The TF values for ¹³⁷Cs typically conformed to a lognormal distribution, while for ⁴⁰K showed normal distribution. Statistically significant correlations between ¹³⁷Cs soil to mushroom transfer factors and agrochemical soil properties have been revealed. Although the concentration ratios varied within the species, the most efficiently transferred elements seems to have been K, followed by Rb, Zn, Cu, Cd, S, Cs and Hg.     

Adsorption of 137Cs on titanate nanostructures

Various types of sodium and potassium titanate nanostructures (nanotubes, nanofibers, nanoribbons, nanwires) were synthesized and characterized by X-ray diffraction, SEM and TEM, as well BET and BJH methods. Adsorption of radiotracer ¹³⁷Cs⁺ ions from aqueous solutions on synthesized titanate nanostructures was investigated in batch technique as a function of contact time, concentration of sodium ions and pH of the solutions. It was found that among the studied nanostructures nanotubes shows the highest selectivity for ¹³⁷Cs, which is related to a zeolitic character of Cs⁺ adsorption. The efficient adsorption of ¹³⁷Cs was obtained in Na⁺ solutions with concentration below 10^?2 M, at pH 7–9 and in contact time above 2 h. Moreover, nanotubes have the higher specific surface area than other nanostructures, which results in better availability of ion exchange groups and high ion exchange capacity. These properties of nanotubes indicate that they may be used for adsorption of ¹³⁷Cs from various types of nuclear wastes.     

Isolation of137Cs from excreta by dicarbolide of cobalt

Extraction by polyhedral complex compound of the formula H⁺ [(π-(3)-1,2-B₉C₂H₁₁)₂Co⁻] further on referred to as dicarbolide-H⁺ and its chloro-derivate H⁺[B₁₈C₄H₁₅Cl₇Co⁻] further on referred to as Cl-dicarbolide-H⁺ in nitrobenzene was used for the analysis of¹³⁷Cs in urine and faeces after internal contamination. The dependence of distribution ratio on the acidity of analysed solutions was determined. The effect of urine dilution was assessed as well as the effect of various concentrations of the extraction agents on the distribution ratio of¹³⁷Cs. The effect of phase ratio at the different concentrations of isotopic carrier was assessed, as well as the effect of potassium ions on the decrease of the distribution ratio at the extraction of¹³⁷Cs by dicarbolide-H⁺ or its chloro-derivate. The possibility of isolation of¹³⁷Cs by extraction and the isolation of¹³⁷Cs by ion-exchange absorbents and by ammonium molybdophosphate was compared. The values of distribution coefficient were determined at various concentrations of nitric acid and the isotopic carrier. The dependence of coextraction of some activated radionuclides and fission products by dicarbolide-H⁺ on the nitric acid concentration in the solute was determined. The effect of mass of contaminated faeces on the value of the distribution ratio of¹³⁷Cs by the extraction was evaluated. As a result, a suggestion was given for the rutine isolation procedure of¹³⁷Cs extraction with dicarbolide-H⁺ from the excreta contaminated by a mixture of radionuclides.     

An intercomparison of sampling techniques for measurements of radiocaesium in upland pasture and soil

An intercomparison of sampling procedures used by five laboratories for the determination of radiocaesium in vegetation and peaty soil was carried out at two locations in Cumbria. The multiple sampling has given information on the homogeneity of the parameters studied at each location. The parameters comprise soil bulk densities, total deposition of¹³⁷Cs, deposition of¹³⁷Cs in three soil layers, biomass densities, concentrations of¹³⁷Cs in pasture, and activity ratios (¹³⁴Cs/¹³⁷Cs) in soil and vegetation. The determination of total deposition of¹³⁷Cs gave no indication of differences between the laboratories. The results from the soil profiles do indicate significant differences between laboratories. One laboratory using a coring technique observed difficulties during sampling due to compression of the soil. The coring technique should thus be avoided or applied with extreme care for the sampling of depth profiles in peaty soil. The results from the sampling of pasture show no indication of differences between the laboratories. For the parameters studied the observed variabilities across soil depths and locations range from 10% to 81% in terms of relative standard deviations. A comparison across all results at the two locations indicate a 50% higher field variability at one of the sites relative to the other.     

Soil-to-plant transfer of 137Cs and 40K in an Atlantic blanket bog ecosystem

The transfer of ¹³⁷Cs and ⁴⁰K from soil to vegetation was studied in an Atlantic blanket bog ecosystem along the Atlantic coast of Ireland where the dominant vegetation is a mixture of Calluna vulgaris, Eriophorum vaginatum and Sphagnum mosses. The impact of soil chemistry and nutritional status of vegetation on the uptake of both radionuclides was also examined. Cesium-137 transfer factors values ranged from 1.9 to 9.6 and accumulation of ¹³⁷Cs was higher in the leaves of C. vulgaris than in the stems. Transfer factors values for ¹³⁷Cs in both C. vulgaris and E. vaginatum were similar indicating that for the vegetation studied, uptake is not dependent on plant species. The uptake of ¹³⁷Cs in bog vegetation was found to be positively correlated with the nutrient status of vegetation, in particular the secondary nutrients, calcium and magnesium. Potassium-40 transfer factors ranged from 0.9 to 13.8 and uptake was higher in E. vaginatum than in C. vulgaris, however, unlike ¹³⁷Cs, the concentrations of ⁴⁰K within the leaves and stems of C. vulgaris were similar. The concentration of both ¹³⁷Cs and ⁴⁰K found in moss samples were in general lower than those found in vascular plants.     

Separation of cesium-137 from uranium fission products via a Neoflon® column supporting tetraphenylboron

Cesium is a member of the Group I alkali metals, very reactive earth metals that react vigorously with both air and water. The chemistry of cesium is much like the chemistry of neighboring elements on the periodic table, potassium and rubidium. This close relation creates many problems in plant-life exposed to cesium because it is so easily confused for potassium, an essential nutrient to plants. Radioactive ¹³⁴Cs and ¹³⁷Cs are also chemically akin to potassium and stable cesium. Uptake of these radioactive isotopes from groundwater by plant-life destroys the plant-life and can potentially expose humans to the radioactive affects of ¹³⁴Cs and ¹³⁷Cs. Much experimental work has been focused on the separation of ¹³⁷Cs from uranium fission products. In previous experimental work performed a column consisting of Kel-F supporting tetraphenylboron (TPB) was utilized to separate ¹³⁷Cs from uranium fission products. It is of interest at this time to attempt the separation of ¹³⁴Cs from 0.01M EDTA using the same method and Neoflon in the place of Kel-F as the inert support. The results of this experiment give a separation efficiency of 88% and show a linear relationship between the column bed length and the separation efficiency obtained.     

Translocation and depuration of137Cs in tea plants

Translocation and percent distribution of¹³⁷Cs in different parts of the tea plant have been investigated from the foliar aborption and root uptake in Chemobyl contaiminated soil during 1987–1994. The results showed that the transfer of the radionuclide from soil to the plant occurred only in the roots during this long period. On the other hand, the present data confirmed that the new leaves of the plant directly accumulated¹³⁷Cs from the stem in growing seasons after translocation into the stem from leaves during the Chemobyl accident. The natural depuration rate of¹³⁷Cs in the stem part of tea plant is estimated as on effective half-life 1750 days.     

The Effect of Carbonate Soil on Transport and Dose Estimates for Long-Lived Radionuclides at a U.S. Pacific Test Site

The United States conducted a series of nuclear tests from 1946 to 1958 at Bikini, a coral atoll, in the Marshall Islands (MI). The aquatic and terrestrial environments of the atoll are still contaminated with several long-lived radionuclides that were generated during testing. The four major radionuclides found in terrestrial plants and soils are cesium-137, strontium-90, plutonium-239+240 and americium-241. Cesium-137 in the coral soils is more available for uptake by plants than ¹³⁷Cs associated with continental soils of North America or Europe. Soil-to-plant ¹³⁷Cs median concentration ratios (CR) (kBq·kg^-1 dry weight plant/kBq·kg^-1 dry weight soil) for tropical fruits and vegetables range between 0.8 and 36, much larger than the range of 0.005 to 0.5 reported for vegetation in temperate zones. Conversely, ⁹⁰Sr median CRs range from 0.006 to 1.0 at the atoll versus a range from 0.02 to 3.0 for continental silica-based soils. Thus, the relative uptake of ¹³⁷Cs and ⁹⁰Sr by plants in carbonate soils is reversed from that observed in silica-based soils. The CRs for ^239+240Pu and ²⁴¹Am are very similar to those observed in continental soils. Values range from 10^-6 to 10^-4 for both ^239+240Pu and ²⁴¹Am. No significant difference is observed between the two in coral soil. The uptake of ¹³⁷Cs by plants is enhanced because of the absence of mineral binding sites and the low concentration of potassium in the coral soil. Cesium-137 is bound to the organic fraction of the soil, whereas ⁹⁰Sr, ^239+240Pu and ²⁴¹Am are primarily bound to soil particles. Assessment of plant uptake for ¹³⁷Cs and ⁹⁰Sr into locally grown food crops was a major contributing factor in: (1) reliably predicting the radiological dose for returning residents and (2) developing a strategy to limit the availability and uptake of ¹³⁷Cs into locally grown food crops.     

A method for the replacement of 137Cs with 40K as a non-hazardous radioactive tracer for open-source decommissioning research applications

The potential of ⁴⁰K as a radioactive tracer analogue of ¹³⁷Cs in ion exchange experiments is reported. Solutions of varying concentrations of potassium chloride (KCl) have been monitored radiometrically in a sodium iodide well-counter to determine the activity-concentration relationship. Ion exchange reactions using an exemplar ion exchange resin, KCl and non-radioactive caesium chloride (CsCl) solutions have been studied radiometrically. The adsorbed amounts of potassium and caesium are observed, inferred from displaced K⁺ ions, to be consistent with the total exchange capacity of the resin. Adsorption isotherm models have been applied to the experimental data, with the Freundlich isotherm observed to fit the data with the highest degree of consistency. The reported results indicate that decontamination techniques involving hazardous isotopes of anthropogenic origin such as ¹³⁷Cs can be developed, evaluated and optimised by substituting a chemically and physically similar non-hazardous radioactive isotope, in this case ⁴⁰K. This represents a means by which innovative decontamination techniques and regimes might be identified without the need to use ¹³⁷Cs and thus avoids additional generation of radioactive wastes.     

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.