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.     

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.     

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.     

Determination of137Cs,90Sr and fallout Pu in the volcanic soil of Korea

The cumulative depositions of¹³⁷Cs,⁹⁰Sr and fallout Pu in the volcanic ash soil of Korea were determined. The average accumulated depositions of¹³⁷Cs,⁹⁰Sr and fallout Pu in the volcanic soil were much higher than those in other forest sites of Korea. From depth profiles, it was found that¹³⁷Cs,⁹⁰Sr and^239,240Pu in the volcanic soil are more mobile than those in other forest sites of Korea, and that the downward movement of⁹⁰Sr is faster than¹³⁷Cs and^239,240Pu. A significant correlation was found between the concentration of¹³⁷Cs and those of⁹⁰Sr and^239,240Pu. The activity ratios of²³⁸Pu/^239,240Pu and²⁴¹Pu/^239,240Pu in soils are close to those observed in the cumulative deposit from the global fallout of nuclear weapon testings.     

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.     

Geographical and vertical distribution of radiocesium levels in coniferous forest soils in Izmir

Preliminary picture of ¹³⁷Cs radioactivity levels in forested areas in and around Izmir is illustrated. Both activity concentrations and activity depositions of ¹³⁷Cs in soil samples were determined. Their values varied from 8.29±0.27 to 445±3.16 Bq.kg⁻¹ (d.w.) and 0.63±0.01 to 11.6±0.08 kBq.m^–2 (d.w.), respectively. It was found that while activity deposition of ¹³⁷Cs is normally distributed, activity concentration of ¹³⁷Cs is log-normally distributed in forest soils and the activity deposition is less variable than the activity concentration. Cesium-137 activities in soils increase with increasing elevation, annual average rainfall and soil organic matter.     

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.

     

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.     

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.

     

First measurements of anthropogenic and natural radionuclides in surface soils (10 cm) of Côte d'Ivoire

^239–240Pu and ¹³⁷Cs activities in soil samples were measured in two sites of the littoral part of Côte d'Ivoire: Abidjan and the classified forest of “la Comoé”. Two areas were chosen: a forest and a clearing. The aim of this work is to establish a starting point for nuclear contamination data of a non-nuclear country. Measured soil cores were of 10 cm depth. ¹³⁷Cs and ^239–240Pu activities, mainly due to weapon nuclear tests in the 1960s, were in the range 0.37–2.3 and 0.023–0.125 Bq kg⁻¹ respectively. ^239–240Pu/¹³⁷Cs values were found to be about 0.024–0.19 in agreement with the expected value for nuclear tests.     

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.     

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.     

Accumulation of137Cs by mushrooms from Rogozno area of Poland over the period 1984–1988

The concentration of naturally occurring⁴⁰K and¹³⁷Cs from fallout were determined in various mushrooms as well as in a few samples of forest soil from the same region over the period of 1984–1988. The¹³⁷Cs content in mushrooms before the reactor accident at Chernobyl was generally below 500 Bq kg⁻¹ dry matter, except Paxillus involutus /2700 Bq kg⁻¹/. A remarkable increase of the¹³⁷Cs activity /up to ten times/ was observed in 1986. For almost all examined species this activity remained basically at the same level for the next two years. No correlation between⁴⁰K and¹³⁷Cs in mushrooms has been found.     

Fallout 137Cs, 90Sr and 239+240Pu in soils polluted by heavy metals: Vertical distribution, residence half-times, and external gamma-dose rates

The industrial pollution of an ecosystem, e.g., by heavy metals, might also affect the behavior of fallout radionuclides in the soils of these areas. To study such effects, we determined at various distances from the huge copper-nickel smelters at Monchegorsk on the Kola Peninsula (Russia) and at a reference site: (1) the vertical distribution of fallout ¹³⁷Cs,⁹⁰Sr and^239+240Pu in the soil, (2) the corresponding residence half-times in different soil horizons, and (3) the resulting external gamma-dose rates at these sites in 1 m height due to ¹³⁷Cs in the soil. The data show that the residence half-times and the partitioning of the fallout radionuclides among the various soil horizons depend significantly on the extent of the heavy metal pollution at the sites. The resulting external gamma-dose rate in 1 m height due to ¹³⁷Cs in the soil is, however, rather similar at the various sites.     

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.     

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.     

An Efficient Approach to Model the Long-Term Radiocesium Contamination of Mushrooms and Berry Plants

Since 1987, a coniferous forest in Bavaria has continuously been monitored for radiocesium. About 350 soil samples and about 450 samples of different species of mushrooms and berry plants were analyzed for ¹³⁴Cs and ¹³⁷Cs. Based on this extensive data set a radioecological model for the long-term contamination of mushrooms and berry plants was developed. To keep the model as simple as possible without losing predictive power, it was especially designed to describe the vertical migration of radiocesium in forest soil, a key process which governs the temporal evolution of activity levels in mushrooms and berry plants.     

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.     

Deposition of long-lived radionuclides after the chernobyl accident in the forestal massif of boreon

After the reactor accident at Chernobyl, samples of soil, moss, lichen and fern were collected in the forest around the Vesubie valley in the South East of France and analyzed by low energy photon and gamma spectrometry. Activity concentrations as high as 42.8, 9.4 and 3.8 kBq.m^–2 were measured for¹³⁷Cs,¹³⁴Cs and¹⁰⁶Ru, respectively, in soil, in October 1988.¹²⁵Sb and^110mAg were also detected. The contamination was found to be the most important between 1400 and 1700 m altitude.