Migration Of Radiocesium Research Articles

Radioactive contamination in the Tokyo metropolitan area in the early stage of the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident and its fluctuation over five years.

Radioactive contamination in the Tokyo metropolitan area in the immediate aftermath of the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident was analyzed via surface soil sampled during a two-month period after the accident. 131I, 134Cs, and 137Cs were detected in these soil samples. The activity and inventory of radioactive material in the eastern part of Tokyo tended to be high. The 134Cs/137Cs activity ratio in soil was 0.978 ± 0.053. The 131I/137Cs ratio fluctuated widely, and was 19.7 ± 9.0 (weighted average 18.71 ± 0.13, n = 14) in the Tokyo metropolitan area. The radioactive plume with high 131I activity spread into the Tokyo metropolitan area and was higher than the weighted average of 6.07 ± 0.04 (n = 26) in other areas. The radiocesium activity and inventory surveyed in soil from a garden in Chiyoda Ward in the center of Tokyo, fell approximately 85% in the four months after the accident, and subsequently tended to rise slightly while fluctuating widely. It is possible that migration and redistribution of radiocesium occurred. The behavior of radiocesium in Tokyo was analyzed via monitoring of radiocesium in sludge incineration ash. The radiocesium activity in the incineration ash was high at wastewater treatment centers that had catchment areas in eastern Tokyo and low at those with catchment areas in western Tokyo. Similar to the case of the garden soil, even in incineration ash, the radiocesium activity dropped rapidly immediately after the accident. The radiocesium activity in the incineration ash fell steadily from the tenth month after the accident until December 2016, and its half-life was about 500 days. According to frequency analysis, in central Tokyo, the cycles of fluctuation of radiocesium activity in incineration ash and rainfall conformed, clearly showing that radiocesium deposited in urban areas was resuspended and transported by rainfall run-off.

Soil erosion and transport simulation and critical erosion area identification in a headwater catchment contaminated by the Fukushima nuclear accident

Radiocesium released by the accident at the Fukushima Dai-ichi Nuclear Power Plant in 2011 contaminated a large land surface area. Due to the strong and size-dependent adsorption capability of soil particles to radionuclides, a better understanding of erosion and transport of soil particles and identification of erosion prone areas within watersheds are significant for contaminant management. For this purpose, we simulated soil erosion and transport in a partially forested catchment for multiple particle size classes. Critical erosion areas were identified by the spatial distribution of net soil erosion. Comparisons between simulated and measured suspended solids concentration at multiple locations throughout the catchment demonstrated successful model performance. For the period Mar. 12, 2011 through Dec. 31, 2014, model results indicated that 5500 tonnes of clay, 52000 tonnes of silt, and 22000 tonnes of sand are transported from the catchment. The results showed that soil erosion in the middle part of the catchment is greater mainly because of steep slopes and large fraction of agricultural lands. These simulations suggest that soil decontamination of erosion-prone agricultural lands in the mid- catchment areas would be effective in reducing radiocesium migration with soil particles.

Vertical distribution and temporal dynamics of dissolved 137Cs concentrations in soil water after the Fukushima Dai-ichi Nuclear Power Plant accident

Radiocesium (137Cs) migration from headwater forested areas to downstream rivers has been investigated in many studies since the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident, which was triggered by a catastrophic earthquake and tsunami on 11 March 2011. The accident resulted in the release of a huge amount of radioactivity and its subsequent deposition in the environment. A large part of the radiocesium released has been shown to remain in the forest. The dissolved 137Cs concentration and its temporal dynamics in river water, stream water, and groundwater have been reported, but reports of dissolved 137Cs concentration in soil water remain sparse.In this study, soil water was sampled, and the dissolved 137Cs concentrations were measured at five locations with different land-use types (mature/young cedar forest, broadleaf forest, meadow land, and pasture land) in Yamakiya District, located 35 km northwest of FDNPP from July 2011 to October 2012. Soil water samples were collected by suction lysimeters installed at three different depths at each site. Dissolved 137Cs concentrations were analyzed using a germanium gamma ray detector. The dissolved 137Cs concentrations in soil water were high, with a maximum value of 2.5 Bq/L in July 2011, and declined to less than 0.32 Bq/L by 2012. The declining trend of dissolved 137Cs concentrations in soil water was fitted to a two-component exponential model. The rate of decline in dissolved 137Cs concentrations in soil water (k1) showed a good correlation with the radiocesium interception potential (RIP) of topsoil (0–5 cm) at the same site. Accounting for the difference of 137Cs deposition density, we found that normalized dissolved 137Cs concentrations of soil water in forest (mature/young cedar forest and broadleaf forest) were higher than those in grassland (meadow land and pasture land).

Study of the formation of the primary 137Cs vertical profile in the organic matter-rich sediments

A laboratory study of the formation of the primary vertical profile of the 137Cs activity concentration in the anaerobic organic matter-rich sediments was carried out. The incubation was performed using sediment baths method (initial thickness of the water layer over the sediments ∼40 cm, initial radiocesium activity concentration in water ∼14.53 Bq·L−1). An exponential profile (R2∼0.999) with the half-height width of ∼0.65 cm was formed after ∼32 days of the incubation. A further course of the experiment (sediments were sampled after 64, 130 and 293 days of the incubation) revealed deviations in the form of the radiocesium activity concentration profile related to the appearance of the additional Gauss factor with the increasing half-height width of ∼1.2, ∼1.3 and ∼3 cm, respectively. In spite of the evident growth of the half-height width, the radiocesium migration rate decreased from 0.02 cm·day−1 for the first 32 days of incubation down to 0.009 cm·day−1 at the end of the incubation experiment. Such a time-dependent decrease in the radiocesium migration is possibly related to the beginning of the second radiocesium migration phase depending on the retardation factor. Besides diffusion, the formation of vertical profiles of radiocesium activity concentrations in sediments was additionally induced by effects of buoyancy of the upper sediment layer due to the seepage of the above lying water into sediments.

Distribution and migration of radiocesium in sloping landscapes three years after the Fukushima-1 nuclear accident

The results of the study are presented on the distribution and migration of radiocesium in mountainous (580–620 m a.s.l.) landscapes in the northeast of Honshu Island (Tohoku Region, Miyagi Prefecture) subjected to radioactive contamination after the nuclear accident at Fukushima-1 NPP. In July 2014, the average contamination density with radiocesium (134Сs and 137Сs) over the territory (150 km to the northwest from NPP) was equal to 16 kBq/m2. This contamination is estimated at the acceptable level according to both Japanese and Russian standards and legislation. Three years after the accident, radiocesium is found to be unevenly distributed by the biogeocenosis components, i.e. 45% in litter, 40% in plants, 10% in soil, and 5% in roots. As for the distribution of total radiocesium (Cs tot = 134Сs + 137Сs) by the profile of volcanic podzolic-ocherous soil (Dystric Aluandic Andosols), its maximal content (about 80%) was found in the surface layer (0–2.5 cm), with the specific activity ranging from 250 to 10070 Bq/kg and sharply decreasing with the depth. Radiocesium amount in the soils of forest ecosystems was on average by 20% higher than in meadow ecosystems. Accumulation of radionuclides in soils of lower and middle parts of a slope with an insignificant vertical migration was found to be the most general regularity. The air dose rate did not exceed the maximal permissible level, and the snow cover acted as an absorbing and scattering screen.

Coupling the advection-dispersion equation with fully kinetic reversible/irreversible sorption terms to model radiocesium soil profiles in Fukushima Prefecture

Radiocesium is an important environmental contaminant in fallout from nuclear reactor accidents and atomic weapons testing. A modified Diffusion-Sorption-Fixation (mDSF) model, based on the advection-dispersion equation, is proposed to describe the vertical migration of radiocesium in soils following fallout. The model introduces kinetics for the reversible binding of radiocesium. We test the model by comparing its results to depth profiles measured in Fukushima Prefecture, Japan, since 2011. The results from the mDSF model are a better fit to the measurement data (as quantified by R2) than results from a simple diffusion model and the original DSF model. The introduction of reversible sorption kinetics means that the exponential-shape depth distribution can be reproduced immediately following fallout. The initial relaxation mass depth of the distribution is determined by the diffusion length, which depends on the distribution coefficient, sorption rate and dispersion coefficient. The mDSF model captures the long tails of the radiocesium distribution at large depths, which are caused by different rates for kinetic sorption and desorption. The mDSF model indicates that depth distributions displaying a peak in activity below the surface are possible for soils with high organic matter content at the surface. The mDSF equations thus offers a physical basis for various types of radiocesium depth profiles observed in contaminated environments.

Characteristics of radio-cesium transport and discharge between different basins near to the Fukushima Dai-ichi Nuclear Power Plant after heavy rainfall events

This paper describes watershed modeling of catchments surrounding the Fukushima Dai-ichi Nuclear Power Plant to understand radio-cesium redistribution by water flows and sediment transport. We extended our previously developed three-dimensional hydrogeological model of the catchments to calculate the migration of radio-cesium in both sediment-sorbed and dissolved forms. The simulations cover the entirety of 2013, including nine heavy rainfall events, as well as Typhoon Roke in September 2011. Typhoons Man-yi and Wipha were the strongest typhoons in 2013 and had the largest bearing on radio-cesium redistribution. The simulated 137Cs discharge quantities over the nine events in 2013 are in good agreement with field monitoring observations. Deposition mainly occurs on flood plains and points where the river beds broaden in the lower basins, and within dam reservoirs along the rivers. Differences in 137Cs discharge ratios between the five basins are explained by differences in the initial fallout distribution within the basins, the presence of dam reservoirs, and the input supply to watercourses. It is possible to use these simulation results to evaluate future radioactive material distributions in order to support remediation planning.

Mechanisms of Radiocesium Migration and Fixation in Forest Soils

Mechanisms of Radiocesium Migration and Fixation in Forest Soils

Post-deposition early-phase migration and retention behavior of radiocesium in a litter–mineral soil system in a Japanese deciduous forest affected by the Fukushima nuclear accident

The fate of radiocesium (137Cs) derived from the Fukushima nuclear accident and associated radiation risks are largely dependent on its migration and retention behavior in the litter–soil system of Japanese forest ecosystems. However, this behavior has not been well quantified. We established field lysimeters in a Japanese deciduous broad-leaved forest soon after the Fukushima nuclear accident to continuously monitor the downward transfer of 137Cs at three depths: the litter–mineral soil boundary and depths of 5 cm and 10 cm in the mineral soil. Observations were conducted at two sites within the forest from May 2011 to May 2015. Results revealed similar temporal and depth-wise variations in 137Cs downward fluxes for both sites. The 137Cs downward fluxes generally decreased year by year at all depths, indicating that 137Cs was rapidly leached from the forest-floor litter layer and was then immobilized in the upper (0–5 cm) mineral soil layer through its interaction with clay minerals. The 137Cs fluxes also showed seasonal variation, which was in accordance with variations in the throughfall and soil temperature at the sites. There was no detectable 137Cs flux at a depth of 10 cm in the mineral soil in the third and fourth years after the accident. The decreased inventory of mobile (or bioavailable) 137Cs observed during early stages after deposition indicates that the litter–soil system in the Japanese deciduous forest provides only a temporary source for 137Cs recycling in plants.

Do forests represent a long-term source of contaminated particulate matter in the Fukushima Prefecture?

The Fukushima Daiichi Nuclear Power Plant (FDNPP) accident resulted in radiocesium fallout contaminating coastal catchments of the Fukushima Prefecture. As the decontamination effort progresses, the potential downstream migration of radiocesium contaminated particulate matter from forests, which cover over 65% of the most contaminated region, requires investigation. Carbon and nitrogen elemental concentrations and stable isotope ratios are thus used to model the relative contributions of forest, cultivated and subsoil sources to deposited particulate matter in three contaminated coastal catchments. Samples were taken from the main identified sources: cultivated (n = 28), forest (n = 46), and subsoils (n = 25). Deposited particulate matter (n = 82) was sampled during four fieldwork campaigns from November 2012 to November 2014. A distribution modelling approach quantified relative source contributions with multiple combinations of element parameters (carbon only, nitrogen only, and four parameters) for two particle size fractions (<63 μm and <2 mm). Although there was significant particle size enrichment for the particulate matter parameters, these differences only resulted in a 6% (SD 3%) mean difference in relative source contributions. Further, the three different modelling approaches only resulted in a 4% (SD 3%) difference between relative source contributions. For each particulate matter sample, six models (i.e. <63 μm and <2 mm from the three modelling approaches) were used to incorporate a broader definition of potential uncertainty into model results. Forest sources were modelled to contribute 17% (SD 10%) of particulate matter indicating they present a long term potential source of radiocesium contaminated material in fallout impacted catchments. Subsoils contributed 45% (SD 26%) of particulate matter and cultivated sources contributed 38% (SD 19%). The reservoir of radiocesium in forested landscapes in the Fukushima region represents a potential long-term source of particulate contaminated matter that will require diligent management for the foreseeable future.

Contribution of radioactive 137Cs discharge by suspended sediment, coarse organic matter, and dissolved fraction from a headwater catchment in Fukushima after the Fukushima Dai-ichi Nuclear Power Plant accident

Radiocesium (137Cs) migration from headwaters in forested areas provides important information, as the output from forest streams subsequently enters various land-use areas and downstream rivers. Thus, it is important to determine the composition of 137Cs fluxes (dissolved fraction, suspended sediment, or coarse organic matter) that migrate through a headwater stream. In this study, the 137Cs discharge by suspended sediment and coarse organic matter from a forest headwater catchment was monitored. The 137Cs concentrations in suspended sediment and coarse organic matter, such as leaves and branches, and the amounts of suspended sediment and coarse organic matter were measured at stream sites in three headwater catchments in Yamakiya District, located ∼35 km northwest of Fukushima Dai-ichi Nuclear Power Plant (FDNPP) from August 2012 to September 2013, following the earthquake and tsunami disaster. Suspended sediment and coarse organic matter were sampled at intervals of approximately 1–2 months. The 137Cs concentrations of suspended sediment and coarse organic matter were 2.4–49 kBq/kg and 0.85–14 kBq/kg, respectively. The 137Cs concentrations of the suspended sediment were closely correlated with the average deposition density of the catchment. The annual proportions of contribution of 137Cs discharge by suspended sediment, coarse organic matter, and dissolved fraction were 96–99%, 0.0092–0.069%, and 0.73–3.7%, respectively. The total annual 137Cs discharge from the catchment was 0.02–0.3% of the deposition.

Numerical study of sediment and 137Cs discharge out of reservoirs during various scale rainfall events

Contamination of reservoirs with radiocesium is one of the main concerns in Fukushima Prefecture, Japan. We performed simulations using the three-dimensional finite volume code FLESCOT to understand sediment and radiocesium transport in generic models of reservoirs with parameters similar to those in Fukushima Prefecture. The simulations model turbulent water flows, transport of sediments with different grain sizes, and radiocesium migration both in dissolved and particulate forms. To demonstrate the validity of the modeling approach for the Fukushima environment, we performed a test simulation of the Ogaki Dam reservoir over Typhoon Man-yi in September 2013 and compared the results with field measurements. We simulated a set of generic model reservoirs systematically varying features such as flood intensity, reservoir volume and the radiocesium distribution coefficient. The results ascertain how these features affect the amount of sediment or 137Cs discharge downstream from the reservoirs, and the forms in which 137Cs is discharged. Silt carries the majority of the radiocesium in the larger flood events, while the clay-sorbed followed by dissolved forms are dominant in smaller events. The results can be used to derive indicative values of discharges from Fukushima reservoirs under arbitrary flood events. For example the generic model simulations indicate that about 30% of radiocesium that entered the Ogaki Dam reservoir over the flood in September 2015 caused by Typhoon Etau discharged downstream. Continued monitoring and numerical predictions are necessary to quantify future radiocesium migration in Fukushima Prefecture and evaluate possible countermeasures since reservoirs can be a sink of radiocesium.

Vertical distribution of radiocesium in soils of the area affected by the Fukushima Dai-ichi nuclear power plant accident

Presented are results of the study of radiocesium vertical distribution in the soils of the irrigation pond catchments in the near field 0.25 to 8 km from the Fukushima Dai-ichi NPP, on sections of the Niida River floodplain, and in a forest ecosystem typical of the territory contaminated after the accident. It is shown that the vertical migration of radiocesium in undisturbed forest and grassland soils in the zone affected by the Fukushima accident is faster than it was in the soils of the 30-km zone of the Chernobyl NPP for a similar time interval after the accident. The effective dispersion coefficients in the Fukushima soils are several times higher than those for the Chernobyl soils. This may be associated with higher annual precipitation (by about 2.5 times) in Fukushima as compared to the Chernobyl zone. In the forest soils the radiocesium dispersion is faster as compared to grassland soils, both in the Fukushima and Chernobyl zones. The study and analysis of the vertical distribution of the Fukushima origin radiocesium in the Niida gawa floodplain soils has made it possible to identify areas of contaminated sediment accumulation on the floodplain. The average accumulation rate for sediments at the study locations on the Niida gawa floodplain varied from 0.3 to 3.3 cm/year. Taking into account the sediments accumulation leading to an increase in the radiocesium inventory in alluvial soils is key for predicting redistribution of radioactive contamination after the Fukushima accident on the river catchments, as well as for decision-making on contaminated territories remediation and clean-up. Clean-up of alluvial soils does not seem to be worthwhile because of the following accumulation of contaminated sediments originating from more contaminated areas, including the exclusion zone.

Time Dependence of the (137)Cs Concentration in Particles Discharged from Rice Paddies to Freshwater Bodies after the Fukushima Daiichi NPP Accident.

The concentration of particulate (137)Cs in paddy fields, which can be a major source of (137)Cs entering the water system, was studied following the Fukushima Daiichi Nuclear Power Plant accident. To parametrize the concentration and to estimate the time dependence, paddy fields covering various levels of (137)Cs deposition were investigated over the period 2011-2013 (n = 121). The particulate (137)Cs concentration (kBq kg-SS(-1)) showed a significant correlation with the initial surface deposition density (kBq m(-2)). This suggests that the entrainment coefficient (m(2) kg-SS(-1)), defined as the ratio between the particulate (137)Cs concentration and the initial surface deposition density, is an important parameter when modeling (137)Cs wash-off from paddy fields. The entrainment coefficient decreased with time following a double exponential function. The decrease rate constant of the entrainment coefficient was clearly higher than that reported for other land uses and for river water. The difference in the decrease rates of the entrainment coefficient suggests that paddy fields play a major role in radiocesium migration through the water system. An understanding of the decrease rate of the entrainment coefficient of paddy fields is therefore crucial to understand the migration of radiocesium in the water system.

Investigating the source of radiocesium contaminated sediment in two Fukushima coastal catchments with sediment tracing techniques

The Fukushima Dai-ichi nuclear power plant accident resulted in the fallout of significant quantities of radiocesium. After deposition on the soil surface, rainfall and spring flood events transfer radiocesium downstream. Identifying the source of contaminated sediment is important for managing potential downstream radiocesium contamination. Soil (n = 37) and sediment (n = 211) were sampled from November 2011 to May 2014 in the Mano and the Niida coastal catchments. Two sediment fingerprinting approaches quantified the source of radiocesium contaminated sediment. First, cesium-137 activities in surface soil and sediment samples were modelled to determine the contribution of upstream, more contaminated areas, to sediment transiting the more densely populated coastal plain. Second, elemental geochemistry of three major soil types (zs, Cambisols and Fluvisols) was used to model the relative contribution of these soils to sediment sampled throughout the catchments. In the Niida catchment, 47% (σ 19%) of sediment sampled in the coastal plain was modelled to be derived from the upstream area whereas, it was only 19% (σ 19%) in the Mano catchment. The main factor driving this difference is the presence of a large dam on the main stem of the Mano River. Geochemical modelling results indicated that Fluvisols, an alluvial soil type on which paddy fields are typically cultivated, supply the majority of sediment (μ 76, σ 14%). The results confirm that the management of dams is fundamental to radiocesium migration. Moreover, this research indicates that Fluvisols and concomitantly, rice paddies on this soil type, supply a disproportionate amount of sediment. Managing sediment derived from Fluvisols, while incorporating potential impacts from major dams, should help mitigate the downstream migration of radiocesium contaminated sediment.

Radiocesium Migration in Soil and Outflow into River System

Radiocesium Migration in Soil and Outflow into River System

Behavior of accidentally released radiocesium in soil–water environment: Looking at Fukushima from a Chernobyl perspective

Quantitative characteristics of dissolved and particulate radiocesium wash-off from contaminated watersheds after the FDNPP accident are calculated based on published monitoring data. Comparative analysis is provided for radiocesium wash-off parameters and distribution coefficients, Kd, between suspended matter and water in rivers and surface runoff on Fukushima and Chernobyl contaminated areas for the first years after the accidents. It was found that radiocesium distribution coefficient in Fukushima rivers is essentially higher (1–2 orders of magnitude) than corresponding values for rivers and surface runoff within the Chernobyl zone. This can be associated with two factors: first, the high fraction of clays in the predominant soils and sediments of the Fukushima area and accordingly a higher value of the radiocesium Interception Potential, RIP, in general, and secondly the presence of water insoluble glassy particles containing radiocesium in the accidental fallout at Fukushima. It was found also that normalized dissolved wash-off coefficients for Fukushima catchments are 1–2 orders of magnitude lower than corresponding values for the Chernobyl zone. Normalized particulate wash-off coefficients are comparable for Fukushima and Chernobyl. Results of the investigation of radiocesium's (134Cs and 137Cs) vertical distribution in soils of the close-in area of the Fukushima Dai-ichi NPP – Okuma town and floodplain of the Niida river are presented. The radiocesium migration in undisturbed forest and grassland soils at Fukushima contaminated area has been shown to be faster as compared to the Chernobyl 30-km zone during the first three years after the accidents. This may be associated with higher annual precipitation (by about 2.5 times) in Fukushima as compared to the Chernobyl zone, as well as the differences in the soil characteristics and temperature regime throughout a year. Investigation and analysis of Fukushima's radiocesium distribution in soils of Niida river catchment revealed accumulation zones of contaminated sediments on its floodplain. Average sediment deposition rates varied from 0.3 to 3.3 cm/year.

Features of 137Cs distribution and dynamics in the main soils of the steppe zone in the southern European Russia

Data are presented on the concentration and vertical distribution of the artificial isotope 137Cs in soils (chestnut soils, chernozems, solonetzs, solonchaks, meadow soils and alluvial soils) of the steppe zone in the southern Russia. The work has been focused on the study of radiocesium distribution in undisturbed virgin lands. It has been shown that the mean concentration of the radionuclide in the upper (0 to 15cm) soil layer is 20.5Bq/kg. The proportions of adsorbed 137Cs in the soils increase with increasing humus content and decreasing pH level. Two types of the profile distribution of radiocesium were distinguished: (1) with the maximum concentration in the upper soil layer and a relatively abrupt decrease with depth (the majority of 137Cs is concentrated in the upper 0 to 15cm soil layer) and (2) with the maximum concentration of 137Cs shifted into the soil profile down to a depth of 45–55cm. This difference is related to the soil type, humus content, pH value, and regional climatic conditions. Long-term (2000–2013) studies of the vertical distribution of 137Cs in soil profiles have revealed a decrease in its total activity by 1.5 to 2.0 times. It has been shown that the migration of radiocesium in soil profiles depends on the soil type and the diffusion of the radionuclide itself, as well as on convective transfer, transpiration, infiltration, and colmatage.

Effect of the concentration of radiocesium dissolved in irrigation water on the concentration of radiocesium in brown rice

In 2011, the radiocesium concentration of brown rice grown (Oryza sativa L.) in mountainous areas with irrigation water that flowed from a nearby mountain forest, in Fukushima Prefecture, Japan, exceeded 500 Bq kg–1. Migration of radiocesium from contaminated irrigation water was suspected. Here, we investigated the migration of dissolved radiocesium (137Cs) from irrigation water into brown rice by determining the concentration of 137Cs in brown rice grown in pots irrigated with water containing dissolved 137Cs (0.1, 1.0 or 10 Bq L–1 137Cs). The treatment water was prepared by extracting 137Cs from conifer branches collected from the contaminated area and diluting the stock solution with tap water. We used two Gray Lowland soils (soils A and B) collected from two paddy fields in Fukushima Prefecture. Rice plants (Oryza sativa L. cv. Hitomebore) were grown in pots and treatment water was kept at a depth of 3–5 cm throughout the growing season. We calculated the amount of 137Cs absorbed by the plants by subtracting 137Cs concentrations in brown rice grown with tap water from that in brown rice grown with treatment water. The concentration of 137Cs in brown rice increased in proportion to that in the treatment water. The concentration of 137Cs in brown rice grown with water containing 10 Bq L–1 137Cs in soil A was 4.9 times that in brown rice grown in soil B, but the concentration of 137Cs in brown rice grown in either soil was not significantly different when grown with water containing 0.1 Bq L–1 137Cs. Before plants were grown, the exchangeable potassium in soil B was 3.8 times that in soil A. At least, even with irrigation water containing about 0.1 Bq L–1 of radiocesium, the migration of radiocesium into brown rice is negligible for the provisional regulation value for radiocesium in brown rice under the condition of our experiment.

福島第一原発事故で汚染された土壌の埋設場所からの放射性セシウムの移行に関する実証試験

福島第一原発事故で汚染された土壌の埋設場所からの放射性セシウムの移行に関する実証試験