Dosimetric depth distribution of Fukushima-derived 137Cs in coniferous forest soil

Journal of Radioanalytical and Nuclear Chemistry - The ambient dose rate (ADR) in a coniferous forest floor contaminated by Fukushima-derived 137Cs was calculated for small temporal scale as a...     

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.     

Vertical distributions of global fallout 137Cs and 14C in a Japanese forest soil profile and their implications for the fate and migration processes of Fukushima-derived 137Cs

Vertical distributions of global fallout ¹³⁷Cs and ¹⁴C were investigated in a Japanese forest soil in 2001. Even 38 years after the fallout, ¹³⁷Cs was still observed mostly in the uppermost 5 cm. A preferential accumulation of ¹³⁷Cs was found in a 1-cm-thick transition layer between organic-rich A and underlying B horizons. This unique observation indicated that ¹³⁷Cs migrated through the A horizon at a rate of 0.20 % year⁻¹ and the transition layer acted as a barrier for ¹³⁷Cs migration to deeper layers. The vertical distributions of ¹³⁷Cs and ¹⁴C were significantly correlated, suggesting a coupled downward migration of ¹³⁷Cs and organic matter on a time scale of decades, along the same physical pathways.

     

Seasonal changes of 137Cs in benthic plants from the southern Baltic Sea

¹³⁷Cs activity concentrations were determined in samples of macrophytes Polysiphonia fucoides (red algae) and Zostera marina (vascular plant) collected during the entire vegetation season in the Gulf of Gdańsk in the southern Baltic Sea. The measurements showed considerable seasonality of ¹³⁷Cs activity in both species; an increase of cesium concentrations was observed from spring to autumn with maximal levels 49.1 ± 1.4 Bq kg_d.w.⁻¹ (P. fucoides) and 14.5 ± 1.0 Bq kg_d.w.⁻¹ (Z. marina) in late autumn. ¹³⁷Cs concentrations observed in a given season are the result of a number of processes, the intensity of which can differ depending on external environmental conditions. The effects of these processes can differ and their directions can frequently be opposite to one another. The examined macrophytobenthic plant species could serve as bioindicators of radionuclide pollution for monitoring purposes on condition that the samples of plants are taken within a strictly defined period of the year to give comparable results and to supply realistic information about pollution levels.     

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.     

Extraction-chromatographic separation of137mBa from137Cs

The possibilities of extraction-chromatographic separation of^137mBa from¹³⁷Cs in genetic succession were studied, using columns filled with support beads loaded with the extractant H⁺[)–(3)–1,2–B₉C₂H₁₁]₂Co^–, further referred to as dicarbolide-H⁺, in nitrobenzene. The dependence of the amount of separable activities on experimental conditions was established. Optimal conditions were selected for the separation process. The effects of isotopic and nonisotopic carriers of^137mBa on the separation and the degree on saturation of extraction-chromatographic column with Ba²⁺ ions were evaluated. The effects of acidity of the elution solutions, of flow-through velocity, the amount of elution solution and the quality of carrier beads on the separation process were assessed. The extraction-chromatographic yield was calculated and the number of possible repeated elution cycles for^137mBa with saline and some other eluents was determined.     

Variation of 14C, 137Cs and stable carbon composition in forest soil and its implications

In Japan, about 70% of land area is covered by forest. Therefore, forest ecosystem plays a vital role in ultimate fate of radionuclides and carbon cycle in terrestrial environment. In this study, three undisturbed forest soil profiles were collected from Ibaraki Prefecture, Japan. The ¹³⁷Cs data illustrate that maximum fallout deposition of ¹³⁷Cs took place around 1964. ¹⁴C determination shows that ¹⁴C also has peak values in the top 10 cm of the soil profiles ascribed to the highest bomb ¹⁴C level in 1960's. The ¹³C data show that the turnover dynamics of soil organic carbon could be described very well by progressive enrichment values of d¹³C.     

Transfer behaviors of 90Sr and 137Cs from soil to grass to cow milk under natural conditions in Central Italy and their exposure risk

Journal of Radioanalytical and Nuclear Chemistry - Based on the newly-developed techniques, the transfer behaviors of 90Sr and 137Cs under natural conditions were studied. The concentrations of...     

137Cs profiles in erosion plots with different soil cultivation

Summary Cesium-137 methodology has been successfully used to assess soil erosion. Seven erosion plots were sampled to determine the ¹³⁷Cs profile and to assess the erosion rates. Cesium-137 profile for native pasture plot showed an exponential decline below 5 cm depth, with little ¹³⁷Cs activity in the superficial layer (0-5 cm). Cesium-137 profile for wheat-soybean rotation plot in conventional tillage showed a uniform distribution with depth. For this plot, the soil loss occurs more in middle than upper and lower level. Cesium-137 profile for wheat-soybean rotation and wheat-maize rotation plots in no-tillage showed a similar result to the native pasture, with a minimum soil loss in the superficial layer. Cesium-137 profile for bare soil and cultivated pasture plots are similar, with a soil erosion rate of 229 t ha^-1 year ^-1 . In the plots with a conventional tillage a greater soil loss occur in middle than upper and lower level. In no-tillage cultivation plots occurs soil loss in lower level, but no sign of soil loss neither gain in the upper level is observed. Cesium-137 methodology is a good tool to assess soil erosion and the ¹³⁷Cs profile gives possibility to understand the soil erosion behavior in erosion plots.     

Separation of 137Cs from nuclear waste

Sodium zirconate is one member of a family of new inorganic ion exchange materials which have high affinity for all actinides and fission product cations except for Cs⁺. A combination of cold, tracer and high level liquid waste experiments with sodium zirconate has shown that 70–80 and 80–100% of the Cs⁺ in high level liquid waste remains in solution following batch or column equilibration, respectively. The fact that ¹³⁷Cs can be obtained in relatively pure form permits subsequent conversion directly to an insoluble radiation source. This is of prime importance in areas such as sewage sludge sterilization via γ-ray irradiation.     

Migration of85Sr and137Cs in vertical soil profiles

The vertical distribution of⁸⁵Sr and¹³⁷Cs in undisturbed single-contaminated agricultural soils have been studied during their irrigation with wet atmospheric precipitation in dependence on time under laboratory conditions for about one year. The soil samples were collected from several localities in the environment of nuclear power plants at Dukovany and Jaslovské Bohunice using a special auger. The samples were placed into polyethylene columns of 9 cm in diameter and 20 cm in height. The activity of radionuclides in soil profiles after their separation into single layers were counted by Ge(Li) semiconductor gamma-spectrometry. Based on the exponential depth distribution of radionuclides, the values of their migration parameters as relaxation depth, migration rate and retardation factor were calculated. The influence of the permanent grass cover and of the applied zeolite on the migration parameters of these radionuclides was also investigated. Presented at the Conference “Nukleonika '98”, Prague, Czech Republic, 9–10 September 1998, dedicated to late Professor František Běhounek in honour of his 100th birthday.     

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.     

In-situ spectrometry of137Cs in the soil by an unfolding method

The approach is based on in-situ measurements performed with a portable high-resolution germanium -spectrometer and on calculations of the depth distribution by an unfolding method. To unfold the depht distribution of¹³⁷Cs concentration in soil four detector responses and the iterative procedure SAND II were used. The detector responses consist of the responses to primary 662 keV photons and to photons scattered in soil with the rest energies of 620–655 keV. The detector is used with and without collimator. The method is sufficiently sensitive for measurements of¹³⁷Cs concentration in soil 10 years after the Chernobyl accident. The results are compared to laboratory analyses of collected soil samples and with a standard method of in-situ spectrometry.     

Uptake of134Cs by plants from three different types of soil

In¹³⁴Cs uptake by the roots of orchard grass and beans planted in three different lands of soil has been studied. For this purpose, a¹³⁴Cs radionuclide solution having 0.3086 Ci/pot radioactivity was added to Ando, Serpentine and Alluial and Clay soil which were fertilized by Standard, –K, +Ca, Water limited and Control for both orchard grass and bean groups. Thus, the above mentioned groups have been harvested and left to dry. The contamination levels these plants have been detected and measured by using an HPGe detector interactively working with MCA. Finally, it has been determined that the¹³⁴Cs uptakes depend primarily on soil characteristics. Besides the decrease in the¹³⁴Cs activity for the plants grown in soils to which the stable cesium or potassium was added 0.011–1.38 per cent activity for the root of plants grown in free K soils was observed. Moreover, highest¹³⁴Cs activity has been determined for the plants grown in –K fertilized soil with respect to the other soil samples.     

Determination of131I,134Cs,137Cs in plants and cheese after Chernobyl accident in Roumania

Various samples from the south-east region of Roumania/greens, fodder, cheese/were analyzed for¹³¹I,¹³⁴Cs and¹³⁷Cs concentrations in May and July 1986 by -ray spectrometry. The concentrations are reported in nCi. kg^–1 wet weight. For greens, a considerable decrease was observed for¹³¹I/to 3.0–7.0 nCi. kg^–1/,¹³⁴Cs/to 0.5–2.0 nCi.kg^–1/ and¹³⁷Cs /to 1.0–4.0 nCi. kg^–1/ from the first half /5–15 May/ till the end of May 1986. For cheese, maximum values were measured between 5 and 15 May /sheep cottage cheese: 500–800 nCi.kg^–1 for¹³¹I, 25–50 nCi. kg^–1 for¹³⁴Cs, 40–80 nCi. kg^–1 for¹³⁷Cs/; at the beginning of July a considerable decrease /to 5–10 nCi. kg^–1 for¹³¹I, 1.2–2.0 nCi.kg^–1 for¹³⁴Cs, 2.2–3.0 nCi. kg^–1 for¹³⁷Cs/ was observed. In autumn 1986 a small increase up to 2.0–3.0 nCi. kg^–1 for¹³⁴Cs and 3.4–5.0 nCi. kg^–1 for¹³⁷Cs /in November/ was reported. The population's internal possible contamination was strongly limited by the authorities' severe control of the food-stuff.     

Fallout 137Cs in soils from North Western Libya

Fallout levels of ¹³⁷Cs in surface soil from North WesternLibya have been measured using gamma-ray spectrometry. The activity concentrationsof ¹³⁷Cs in soil ranged from 975 to 1720 mBq . kg ^—1 . The areal activity concentrations ranged from 1300 to 2250 mBq .m ^—2 , and were higly correlated with annual precipitation.The effective dose from external exposure to ¹³⁷Cs is found tobe 3 nSv . y ^—1 .     

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.     

Determination and correlation of 137Cs and unsupported 210Pb activities in soil

To ascertain the feasibility of using ¹³⁷Cs and ²¹⁰Pb in soil erosion models a Compton suppression system with a Be window was used to simultaneous detect both of the naturally occurring isotopes. In particular, the system allowed the use of only 20 g of soil material instead of the usual needed 0.5-1.0 kg in similar soil studies.