Removal of226Ra(II) from uranium mining and processing effluents

The activity of¹³⁷Cs was determined in mosses and their surrounding soils in three Venezuelan cloud forests. The concentration of¹³⁷Cs in both the mosses and their respective soils were correlated with elevation (m.a.s.l.). This relationship was the result of the cloud forest effect, no direct deposition by condensation below the base of the clouds and increasing deposition of¹³⁷Cs with the density of the clouds. The ratio of the activity of¹³⁷Cs in the mosses to their surrounding soils was in general the same for sites near the top of the mountains, but the ratio at the Altos de pipe location was 3.5 times higher than that of the La Sierra mountain. This was explained by the difference in the water content of the surface and the top soil layer. It was concluded that the¹³⁷Cs measured in the mosses was from the soil effect rather than new deposition of¹³⁷Cs in the last three years.     

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.     

A laboratory approach for investigations into the potential effectiveness of potassium-based fertilisers in reducing radiocesium transfer from soil to plant

The paper presents a laboratory experimental model based on a simplesoil-plant system used to investigate the potential effectiveness of potassium-basedfertilisers in reducing soil-to-plant transfer of radiocesium. The soil-plantsystem, slightly modified comparing to that described originally in the NEUBAUER'splantlet method, consists in wheat plantlets grown from caryopsis phase onbrown acid soil contaminated with ¹³⁷Cs resulted from Chernobylnuclear accident and treated with potassium salt of 30%. The effectivenessof 30% potassium salt applied to the soil as treatment is discussed in termsof reduction factor for ¹³⁷Cs soil-to-plant transfer coefficientand ¹³⁷Cs ⁺ :K ⁺ ratio in soil and plantlets.     

Distribution of fallout radionuclides through soil surface layer

The distribution of¹³⁷Cs through soil layers has been investigated by field sampling. The investigation deals with¹³⁷Cs concentration found after the Chernobyl accident. The relationship between important soil characteristics, total precipitation and cesium distribution are analyzed. Cesium is strongly sorbed in the top soil layer and its migration downward is limited. Measurements performed over a 3-year period revealed that approximately 20–38 per cent of total¹³⁷Cs is located in the upper soil layer.     

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.     

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.     

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.     

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.

     

Influence of plant roots upon the mobility of radionuclides in soil, with respect to location of contamination below the surface

The movement of⁸⁵Sr,¹³⁷Cs,⁵⁴Mn and⁶⁰Co in the 50 cm soil profile was studied with and without the presence of plant roots (triticum aestivum) in order to investigate the influence of roots and depth contamination upon the migration of radionuclides. The water table was maintained manually at 3 cm from the bottom. The physiochemical characteristics (E_h Fe^–2, NH ₄ ⁺ , pH and moisture content) as well as the total and extractable radioactivity were investigated. In the discrete contamination, where the location of contamination varied within the soil profile (0–5, 25–30 or 45–50 cm from the top), the influence of location upon the movement of these radionuclides was also studied. It was found that the changes in the soil physicochemical characteristics influenced the mobility of the four radionuclides. The extractability of⁵⁴Mn and⁶⁰Co was significantly increased in the reducing region of the soil, whereas that of⁸⁵Sr,¹³⁷Cs was not. Plant roots excerted significant effects upon the soil characteristics, via, reducing the E_h pH and moisture content of the soil; increasing the extractability of both⁵⁴Mn and⁶⁰Co from the depth of 35 cm downwards. Radionuclide migration occurred via physicochemical and biological transport. The biological transport via plant roots was of particular importance for¹³⁷Cs. Location of contamination had a significant influence upon the mobility of radionuclides. The migration of radionuclides was in the sequence of contamination in middle>bottom>top. The degree of the influence varied with radionuclides concemed. In the top layer contamination, the rank of the migration from the contamination layers, on the other hand⁵⁴Mn,⁶⁰Co and¹³⁷Cs were more mobile and the movement was:⁸⁵Sr⁵⁴Mn⁶⁰Co>¹³⁷Cs. In the middle and bottom contamination layers, on the other hand,⁵⁴Mn and⁶⁰Co and¹³⁷Cs were more mobile and the movement was⁸⁵Sr⁵⁴Mn⁶⁰Co>¹³⁷Cs. The results provide evidence conceming the soil-root interaction influencing the transfer efficiency of radionuclides from below the soil surface into the human food chain.     

Radiological status of Rongelap Island in 1999

A radiological survey and whole body counting of ¹³⁷Cs were carried out in Rongelap Island (main island) of Rongelap Atoll in July 1999. The maximum values of ¹³⁷Cs contamination and of g-ray dose rate were 39 kBq/m² and 0.033 mSv/h, respectively. The maximum a and b gross counting rates on the surface of ground were 1 cpm and 182 cpm in active area of 72 cm², respectively. Activity of ^239,240Pu for soil was 80 Bq/kg in the top 5 cm and aerial deposition was 3.4 kBq/m² in Rongelap Island in 1999. The body burden of ¹³⁷Cs was observed to be 27±11 Bq/kg for 6 workers. Assessment of external and internal annual doses (0.1 and 0.07 mSv/y) indicates that as of 1999 there is no large risk to the inhabitants of Rongelap Island from a radiological point of view. The radiological status of Rongelap Island, which was severely contaminated by the radiological fallouts of nuclear testings carried out in 1954, has improved year by year as shown by the decrease of ¹³⁷Cs. The effective halftime of ¹³⁷Cs, which is estimated to be 6.6 y is much shorter than the physical half-life of ¹³⁷Cs. Radioactive contamination in Kaballe Island, (a part of the northern islands used for farming) which is located 25 km northeast of Rongelap Island, was still high in 1999. One site nearby a beach was highly contaminated with ¹³⁷Cs, where the maximum activity of ¹³⁷Cs was 3.4 MBq/m², a-ray of 2 cpm, b-ray of 1205 cpm and g-ray of 0.73 mSv/h. Activity of ^239,240Pu in soil (n = 1) was 294 Bq/kg (top 5 cm) and 16 kBq/m².     

Environmental radioactivity in Romania Danube river area during 1986–1990

This paper presents the results of radioactivity studies of environmental factors such as surface water, sediment, aquatic vegetation and soil. The concentrations of¹³⁷Cs,⁹⁰Sr,³H, U, Ca, and Mg in water samples were determined by radiochemical and chemical methods. Gamma-spectrometric analyses were performed for all the samples. The analysis showed a decrease in concentrations of¹³⁷Cs in water, aquatic vegetation and sediment, but a constant level of¹³⁷Cs activity in soil (0–5 cm depth). The average concentrations of⁹⁰Sr,³H, U, Ca and Mg were about 7 mBq/l, 11 Bq/l, 0.6 g/l 60 mg/l and 11 mg/l, respectively.     

Resuspension processes controll variations of 137Cs activity concentrations in the ground-level air

The ¹³⁷Cs activity concentration in the surface air between 1977 and 2007 was decreasing with an ecological half-life of 3.4?years, however, during 2007?C2010 the yearly averaged ¹³⁷Cs activity concentrations were almost constant. The increased atmospheric ¹³⁷Cs and ⁴⁰K levels observed during the winter may be due to surface soil resuspension and radionuclide transport by winds, particularly from open agricultural areas, as confirmed by high correlation coefficient between ¹³⁷Cs and ⁴⁰K atmospheric levels (R?=?0.84), and similar ¹³⁷Cs/⁴⁰K activity ratios in aerosols (0.07) and soils (0.05).     

Variability in 137Cs inventories and potential climatic and lithological controls in the central Ebro valley, Spain

The extent of soil erosion in some Spanish semiarid regions has caused great concern regarding the sustainability of soil resources. Accelerated soil erosion, particularly in some Mediterranean areas, is likely to be one of the main environmental problems associated with climate change. Fallout ¹³⁷Cs has been shown to provide a reliable basis for assessing soil erosion rates in different environments around the world. However, existing information concerning the spatial variation of ¹³⁷Cs inventories at reference sites has identified a need for further investigation of the factors affecting their spatial variability in semiarid environments, where stony and skeletal soils are predominant. Reference sites at three locations in the central Ebro valley were selected to investigate the ¹³⁷Cs content of several grain size fractions. Each site included both natural vegetated conditions and cultivated land and the three sites were characterized by different values of mean annual rainfall. The results obtained demonstrate the influence of lithology, land use and climate on the spatial variability of ¹³⁷Cs inventories that increase from 1190, to 1500 and 1710 Bq·m^?2 with increasing annual rainfall values from 300 to 500 mm at the study sites. The soils on marls at the Valareña site had the highest proportion of ¹³⁷Cs in the coarse fractions of cultivated soils (12%) in comparison with soils developed on limestones at Loma Negra (5%), whereas no ¹³⁷Cs content was found in the coarse fractions of soils on glacis-terrace materials at Peñaflor. The ¹³⁷Cs reference inventories are higher in soils on marls and sands at cultivated locations at Valareña and Peñaflor, but have similar values in soils at cultivated and uncultivated locations on limestones at Loma Negra. Therefore, in absence of level undisturbed soils with natural vegetation cover, cultivated flat soils on hard rocks could provide reliable reference inventories.     

The effect of sorption properties of soil minerals on the vertical migration rate of cesium in soil

The vertical distribution of¹³⁷Cs is shown for two types of soil: silly loamy “supposed” soil and silly lessive one, slightly eroded, occuring in the vicinity of Lublin (Eastern Poland). Based on the distribution data the vertical migration rates of¹³⁷Cs are calculated for both soils. These rates are found to be 0.045 and 0.3 cm/year respectively. The percent contribution of¹³⁷Cs originating from the damaged reactor in Chernobyl is also calculated. The kinetics of cesium adsorption and its adsorption isotherms on minerals separated from the tested soils are also studied. The sorption of Cs on soil minerals markedly affects the migration rate of¹³⁷Cs in soil. The experimental results indicate that, among the extracted mineral fractions, the largest adsorption takes place on marls from the silly loamy soil. This work is supplemented by results of a physicochemical analysis of the studied soils.     

Concentrations of 137Cs and 40K radionuclides and some heavy metals in soil samples from the eastern part of the Main Ridge of the Flysch Carpathians

The aim of the study is to present the results of determination of radioactivity of artificial ¹³⁷Cs and natural ⁴⁰K and certain heavy metals in soil samples collected from the eastern part of the Main Ridge of Carpathians, including the Beskid Niski Mts and the Bieszczady Mts. The evaluation of level of radionuclides was based on the bulk density analysis of the soil. A valuable finding of the study was a good linear correlation between the level of ¹³⁷Cs concentration and bulk density of the soil as well as an inverse correlation between radioactivity of natural ⁴⁰K and tested soil density. This might indicate though a high competitiveness of these elements between each other. Moreover, a good correlation between the concentrations of artificial element ¹³⁷Cs and Pb has been also observed in soil samples collected from the Beskid Niski Mts. In most cases, the level of artificial ¹³⁷Cs was lower comparing to an average ¹³⁷Cs concentration established for soils in Poland.     

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.     

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.     

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.     

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.