Movement Of 137Cs Research Articles

Mass balance and latest fluxes of radiocesium derived from the fukushima accident in the western North Pacific Ocean and coastal regions of Japan

This article summarizes and discusses mass balance calculations of the activities of Fukushima-derived 137Cs released to the atmosphere and ocean prior to 2018 as well as the 137Cs inventories on land and in the ocean, biota, and sediment. We propose that the consensus value of the total amount of 137Cs released to the atmosphere was 15–21 PBq; atmospheric deposition of 137Cs on land was 3–6 PBq; atmospheric deposition of 137Cs on the North Pacific was 12–15 PBq; and direct discharge of 137Cs to the ocean was 3–6 PBq. We also evaluated the movement of 137Cs from one domain to another for several years after the accident. We calculated that the amount of 137Cs transported by rivers might be 40 TBq. The annual deposition of 137Cs due to resuspension at Okuma during the period 2014–2018 was 4–10 TBq year−1. The 137Cs discharged to the ocean was 0.73–1.0 TBq year−1 in 2016–2018. The integrated amount of FNPP1-derived 137Cs that entered the Sea of Japan from the Pacific Ocean from 2011 until 2017 was 270 ± 20 TBq, 6.4% of the estimated amount of FNPP1-derived 137Cs in Subtropical Mode Water in the North Pacific. The integrated amount of FNPP1-derived 137Cs that returned to the North Pacific Ocean through the Tsugaru Strait from the Sea of Japan was 110 ± 10 TBq. Decontamination efforts removed 134 TBq of 137Cs from surface soil prior to February 2019, an amount that corresponded to 4% of the137Cs deposited on land in Japan.

Vertical/spatial movement and accumulation of 137Cs in a shallow lake in the initial phase after the Fukushima Daiichi nuclear power plant accident

Movement of 137Cs in the bottom sediment of a shallow lake was investigated by collecting columnar sediment cores from the entire area once a year, and also from three representative points every 3 months over 3 years from the 137Cs fallout in March 2011. The 137Cs inventory in the sediment increased remarkably near the mouths of urban rivers; however, the distribution of the 137Cs inventory did not change remarkably in most areas, and horizontally slow downstream movement of 137Cs was observed.

Some Indicators of the 137Cs Intake in Nutrient Solution with Root Exudates of Norway Spruce (Picea abies) in a Model Experiment

This study presents the results of a model experiment with Picea abies determining the role of root exudates in the intake of radiocaesium into soil solution. It has been established that the amount of consumed 137Cs depends on the weight of the root system, with the majority of the radionuclide presumably accumulating in the primary cortex of the root; i.e., it was not redistributed further between the structural components of the plant. The amount of 137Cs entering the aerial part is approximately 2.5% of its total storage in the plant. During the experiment (7 days), 37.4–53.8% of the radionuclide accumulated in the assimilating organs were transported into pure solution with root exudates and the radiocaesium storage transported into the solution exceeded that of the roots. The movement of 137Cs in the aqueous film on the surface of the root systems have not been recorded.

The Influence of Cultivation System on Distribution Profile Of 137cs and Erosion / Deposition Rate

137Cs radiogenic content in the soil can be used to estimate the rate of erosion and deposition in an area occurring since 1950’s, by comparing the content of the 137Cs in observed site with those in a stable reference site. This experiment aimed to investigate the influence of cultivation type on distribution profile of 137Cs and distribution of erosion and deposition rate in cultivated area. A study site was small cultivated area with slope steepness <10o and length 2 km located in Bojong – Ciawi. For this purpose, the top of a slope was chosen for reference site and three plot sites were selected namely Land Use I that using simple cultivation, Land Use II that using simple cultivation with ridge and furrow, and Land Use III using machine cultivation. The results showed that cultivation could make a movement of 137Cs to the deeper layer and ridges and furrows cultivation system could minimized an erosion process. The net erosion and deposition for land Use I, II and III were -25 t/ha/yr , 24 t/ha/yr and -58 t/ha/yr, respectively.

Different cesium-137 transfers to forest and stream ecosystems

Understanding the mechanisms of 137Cs movement across different ecosystems is crucial for projecting the environmental impact and management of nuclear contamination events. Here, we report differential movement of 137Cs in adjacent forest and stream ecosystems. The food webs of the forest and stream ecosystems in our study were similar, in that they were both dominated by detrital-based food webs and the basal energy source was terrestrial litter. However, the concentration of 137Cs in stream litter was significantly lower than in forest litter, the result of 137Cs leaching from litter in stream water. The difference in 137Cs concentrations between the two types of litter was reflected in the 137Cs concentrations in the animal community. While the importance of 137Cs fallout and the associated transfer to food webs has been well studied, research has been primarily limited to cases in a single ecosystem. Our results indicate that there are differences in the flow of 137Cs through terrestrial and aquatic ecosystems, and that 137Cs concentrations are reduced in both basal food resources and higher trophic animals in aquatic systems, where primary production is subsidized by a neighboring terrestrial ecosystem.

Comparison of vertical transport of 137Cs and organic carbon in agricultural cracking soils

The movement of soil organic carbon (SOC) down the soil profile has been compared to that of the environmental tracer 137Cs at two neighbouring field sites sharing the same land management history but comprising clay soils with different cracking characteristics (cracking black Vertisol and a red Luvisol). A finite element model (FEM) simulation of the vertical transport of SOC and 137Cs was developed for each site which accommodates the differing spatial and temporal trends of input and decay of the two species. From these models the diffusion and convection coefficients which best describe the movement of 137Cs at each site were determined. Both convection and diffusion coefficients were found to be substantially higher in cracking Vertisol soils (DCs=721mm2/yr, VCs=−0.84mm/yr) than in the neighbouring Luvisol soils (DCs=94mm2/yr, VCs=0mm/yr). Finally the 137Cs transport coefficients determined for each site were used in modelling the SOC profile. The excellent match between predicted and observed SOC profiles suggests that transport of the SOC and 137Cs down the soil column at the Luvisol site follows the same pathways. While the match between predicted and observed SOC profiles at the Vertisol site was weaker this was concluded to be more likely due to the impact of extensive soil cracking which is not explicitly accounted for in the SOC FEM rather than the result of the use of 137Cs transport coefficients.

Vertical distribution of 137Cs in cultivated and undisturbed areas

This paper introduces the distribution background and unique characteristics of 137Cs in cultivated and undisturbed areas. The samples were taken from three measuring points of the depth of 1 m. We examined all visible horizons and determined their classifications. There were four horizons in one profile. All four horizons had a different zone thickness. 137Cs is an artificial radionuclide that has been produced primarily as a result of atmospheric thermonuclear weapon tests since the 1950. Also, the great amount of 137Cs (~85 PBq) was released in the atmosphere during the Chernobyl accident. So, 137Cs has been globally distributed, with fallout rates generally related to latitude and precipitation depth. The movement of 137Cs in soil is primarily controlled by soil erosion processes, such as processes caused by water, wind, and tillage. Thus, 137Cs is a valuable tracer to study soil erosion. The specific activity of 137Cs in soil and sediment samples was determined by using the gamma-spectrometric method.

Distribution of cesium-137 in Japanese forest soils: Correlation with the contents of organic carbon

The spatial and vertical distributions of 137Cs in surface soils were surveyed and analyzed then correlated with the contents of organic carbon in the hinoki ( Chamaecyparis obtusa Sieb. et Zucc.) plantation forest and secondary forest dominated by red pine ( Pinus densiflora Sieb. et Zucc.) in Japan. The spatial variation of 137Cs activity was observed in the surface soil around the red pine. The average activity of 16 samples around the tree is 42.4 Bq/kg and the standard deviation is 25.9 Bq/kg. This finding indicates the importance in the selection of a sampling site and the number of samples from the surface soils especially around a tree. For the vertical distribution of 137Cs activity, it was found that the concentration in the surface soil is highest, 149 Bq/kg in the hinoki stand and 101 Bq/kg in the red pine stand, and decreases with depth. The relationship between 137Cs activity and carbon content in the forest soil was investigated in two undisturbed forest stands. The relations were more precisely expressed using an exponential equation than by a linear equation. From the same forest, similar regression equations were obtained. This indicates that the distribution of 137Cs could be characterized by the organic carbon content in an undisturbed forest. It is also suggested that the coefficient values in the regression equation help to define the movement of 137Cs accompanying the decomposition of organic matter.

Mobilization of cesium in organic rich soils: Correlation with production of dissolved organic carbon

A study of the downward movement of 137Cs in an undisturbed forest soil is presented. Seasonal variations and depth profiles of 137Cs activities were measured in seepage water, which is the transport medium for the downward movement of anthropogenic substances in soils. Furthermore the correlation of 137Cs mobilization and production of dissolved organic carbon (DOC) was investigated. Seasonal variations of both 137Cs and DOC fluxes in the seepage water in a depth of 5 cm depth were observed, where the maximum fluxes in the summer months were about one order of magnitude higher than the minimum fluxes in the winter months. 137Cs fluxes are found to be correlated with DOC fluxes with a correlation coefficient of r = 0.63, and both are highly correlated with soil temperature. This indicates that cesium is bound to soil organic material. The production of DOC is controlled by microbial decomposition of soil organic matter and we assume that this holds true for the 137Cs release as well. The actual transport velocity (0.2 ± 0.14 mm/a) of 137Cs (calculated by the weighed mean of 137Cs concentration in the seepage water and the total 137Cs content of the soil) is about one order of magnitude less than the mean transport velocity (1.2 ± 0.3 mm/a) over the past 25 years (calculated from the 137Cs depth profile). It is possible that the transport velocity of 137Cs in undisturbed soils decreases with time as it binds to aged organic material which is less easily decomposable than fresh organic material.

フォールアウトＣｓ‐１３７の水田環境内動態と米への蓄績 条件付きシミュレーション法を適用した評価

The Conditional Simulation, which has developed in the field of geostatistics, is one of the efficient methods to estimate the precision of parameter estimation. It is the method of creating the random fields that have the assumed stochastic characteristics and coincide with the observed data used for conditioning at sampling points. Conditional Simulation was applied to estimate the movement of fallout 137Cs in the environment, and following results were obtained. The uncertainty of the parameters that determined the movement of 137Cs in a paddy environment decreased more greatly by conditioning when the correlation of the parameters and the data used for conditioning was strong than by that when it was weak. There was the tendency for the estimated concentration of 137Cs in rice to come close to observed data as the number of data used for conditioning increased. Therefore, Conditional Simulation seemed to work effectively. The stochastic distribution of the concentration of 137Cs in rice estimated by Conditional Simulation was not normal at all. Therefore, the method that can estimate the stochastic distribution, such as Conditional Simulation, seems to be necessary for estimating the risk of 137Cs in rice.

Application of Radioactive Fallout Cesium‐137 for Measuring Soil Erosion and Sediment Accumulation Rates and Patterns: A Review

AbstractRadioactive fallout 137Cs (cesium‐137) deposited across the landscape from atmospheric nuclear tests is strongly absorbed on soil particles limiting its movement by chemical and biological processes. Most 137Cs movement in the environment is by physical processes; therefore, 137Cs is a unique tracer for studying erosion and sedimentation. Cesium‐137 loss from a watershed has been shown to correlate strongly with soil loss calculated by the Universal Soil Loss Equation (USLE) or measured from small runoff plates. By measuring spatial patterns of 137Cs in vertical and horizontal planes across the landscape, rates of soil loss or deposition can be measured for different parts of a watershed. Even within landscape units, redistribution of soil can be mapped and erosion or deposition rates for different parts of individual fields measured and mapped. Sediment accumulation rates can be measured by comparing the vertical distribution of 137Cs in sediments with the temporal deposition of fallout 137Cs from the atmosphere to locate sediment horizons. Using these dated sediment horizons, sediment accumulation rates can be measured. Interpretations about the location of these dated horizons must consider particle size of the sediments, reworking of deposited sediments, diffusional movement of 137Cs, and time rates of physical process in the sedimentation process. The 137Cs technique can be used to determine sediment accumulation rates in a wide variety of depositional environments including reservoirs, lakes, wetlands, coastal areas, and floodplains. The bibliography shows that 137Cs has been used widely for studying erosion and sedimentation in many different environments around the world.

A Laboratory Based Study On The Movement Of Radiocaesium In Some Soil Columns By Gamma Spectrometer

The fate and movement of 137Cs in different types of soil profiles of Chittagong City and Ishwardi Upazila of Bangladesh were investigated with laboratory based column method by γ-spectrometer. The diffusion coefficient, distribution coefficient and retardation factors of 137Cs were measured. The physio-chemical characteristics and radioactive concentration of natural radionuclides of the soil samples were also measured. The maximum diffusion coefficient was found 2.06 X 10-5 cm2/s in the investigated soils. The vertical movement of 137Cs in those soil samples found to be slow. Maximum of clay content corresponded with the maximum of retardation factor and with the minimum of diffusion coefficient. This experimental findings demonstrated that caesium is strongly absorbed in soil particles and therefore, do not pose any threat to ground water contamination by the approximated future accidental release of 137Cs in the study area. Moreover, the locally available clay can be used as an adsorbent for the decontamination of liquid radioactive waste generated at nuclear facilities without any pretreatment. Key words: Radioisotopes; Physio-chemical; Transport parameters; Soil column DOI: http://dx.doi.org/10.3329/jbas.v35i2.9417 JBAS 2011; 35(2): 141-151

Translocation of carrier-free 85Sr, 137Cs and 106Ru in woody plants

Carrier-free solutions of 137Cs and 106Ru were applied to the foliage of three genera of woody shrubs ( Ceanothus, Adenostoma and Quercus) and subsequent translocation into untreated portions of the plants was measured. In all cases the bulk of the retained dose remained with the directly treated material. The results indicate that in these genera foliarly applied 137Cs is no more mobile than Sr while 106Ru is considerably less mobile than either. In another series of experiments the distribution of 85Sr, 137Gs and 106Ru between the root, the old growth and the new growth was determined after incorporation of the isotopes into Ceanothus and Adenostoma via their root systems. 137Cs and especially 106Ru were largely retained in the root. A relatively large fraction of the retained dose of 85Sr was found in the shoot. In both series of experiments a preferential movement of 137Cs into new growth was observed.

Movement of 137Cs by Runoff, Erosion and Infiltration on the Alluvial Captina Silt Loam

Five millicuries of 137Cs were applied in the form of spray to the 5-m2 plots of Captina soil in Tennessee under bare, clipped meadow, and tall meadow cover conditions. During the initial 81-day period agreement was observed between predicted and experimental soil loss. A linear relationship on a full log scale was found between the soil and 137Cs loss. On the plots with vegetation, it was found that practically all of the 137Cs applied to the areas covered with vegetation was initially on the plant and litter material. The leaching of 137Cs from the vegetation began to level off towards the end of the study period (20.5 cm of rain). At the end of the 81-day period, the bare plot had lost 11.9 per cent of the cesium while the clipped meadow and tall meadow plots had lost 5.1 per cent and 2.6 per cent of their cesium, respectively.

STRONTIUM-90 AND CAESIUM-137 IN ANTARCTIC SNOWS.

THE strontium-90 content of snow samples indicates that the main influx of fission products in Antarctica occurred in 1955. The movement of 137Cs seems possible in Antarctic snow.

Absorption of caesium 137 from the gastro-intestinal tract of the rat.

SummaryThe absorption of 137Cs from the gastro-intestinal tract of the rat has been studied in vivo. The data suggest that the presence or absence of food in the digestive tract affects the movement of 137Cs through the digestive tract and the rate of absorption. 137Cs was absorbed rapidly from the gastro-intestinal tract of the rat. Absorption occurred from all anatomical areas investigated, the small intestine being the most important site of absorption. The stomach and caecum absorbed only minute quantities. Using Dowex 50, total endogenous secretion was estimated at approximately 24·5 per cent of the initial dose, as measured over the first hour after injection. Taking endogenous secretion into consideration, the total amount absorbed at the end of one hour was 98·2 per cent of the initial dose.