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It has been 10 years since the accident at Fukushima Daiichi nuclear power plant in 2011. Large quantities of 131I, 134Cs, and 137Cs were released into the environment, and 80% of 137Cs still remains. In addition to the decrease by attenuation, the transfer of 137Cs to plants, animals, and humans is decreasing due to movement and changing fractions with elapsed time. The activity concentration of 137Cs in the atmosphere has decreased drastically, and the internal radiation dose due to inhalation is negligible. The activity concentration of 137Cs in agricultural plants is decreasing due to decontamination of soil, application of potassium, and lower levels in irrigation water. The activity concentration of 137Cs in wild animals is decreasing, and shows seasonal variation in wild boars. The activity concentration of 137Cs in offshore seawater has decreased to 0.01 Bq l−1. Therefore, the radiation dose is <1 mSv of the additional radiation dose. [ABSTRACT FROM AUTHOR]

The dispersion and deposition of radio‐cesium (137Cs) carried by two types (type A and type B) of water‐insoluble Cs‐bearing solid microparticles (CsMPs) released due to the Fukushima nuclear accident were simulated for the first time. The presence of type B CsMPs (70–400 μm found in soil and 1–5 μm found in air), associated with the hydrogen explosion of Unit 1 in the afternoon of March 12, could partly explain the simulated underestimation of total deposition over land by assuming that 100% of the Cs carriers were water‐soluble submicron particles (WSPs). Type A CsMPs (0.1–10 μm), released from Units 2 or 3 in the midnight between March 14 and 15, traveled over the Kanto Plain, the most populated plain in Japan. Differences in the size distribution of type A CsMPs altered the surface air concentration over Kanto substantially, by up to more than one order of magnitude. The major deposition mechanisms varied among dry, wet, and fog (and/or cloud) depositions depending on the size distribution and locations. The simulated activity fractions due to the CsMPs in the total deposition were compared to those observed in surface soil for the first time. The observations could be explained by the simulations for the locations under the influence of type B CsMPs. However, the simulations were substantially underestimated for the locations influenced by type A CsMPs. There could be more fractions of type A CsMPs emission in the source term and/or the simulated deposition rates of type A CsMPs were underestimated. Key Points: The regional impacts of two types (A and B) of Cs‐bearing solid microparticles (CsMPs) were numerically examined for the first timeType B CsMPs could partly explain the underestimation of simulated total deposition over landThe environmental behaviors of type A CsMPs could vary substantially depending on size [ABSTRACT FROM AUTHOR]

The Fukushima accident emitted radioactive substances into the environment, contaminating litter, algae, sand substrate, aquatic invertebrates, and fish in freshwater streams. Because these substances have substantial effects on stream ecology over many years, it is necessary to clarify the diffusion and decay mechanisms of radiocesium. The transfer coefficient differed among aquatic invertebrate groups, likely due to the differences in habitat. The ecological half-life of cesium was longer where the air dose rate was lower. The transfer coefficient was also higher in areas with lower air dose rate. The radiocesium concentration in algae was inversely related to stream current velocity in the radiocesium-contaminated area. However, this relationship was not observed in the lower air dose rate area: the radiocesium concentration in algae in the rapid-velocity areas tended to be higher than that in the slow-velocity areas. This reverse trend would lead to a longer period of freshwater contamination. The radiocesium concentration would continue to decrease in highly contaminated areas, but it would be difficult to reduce the radiocesium concentration in less-contaminated areas because different contamination mechanisms are at work. Controlling the water flow is key to regulating radiocesium concentration in freshwater ecosystems. [ABSTRACT FROM AUTHOR]

Radionuclides were deposited at forest areas in eastern parts of Japan following the Fukushima Daiichi Nuclear Power Plant incident in March 2011. Ectomycorrhizal (EM) fungi have important effects on radiocaesium dynamics in forest ecosystems. We examined the effect of colonization by the EM fungus Astraeus hygrometricus on the uptake of cesium (Cs) and potassium (K) by Pinus densiflora seedlings. Pine seedlings exhibited enhanced growth after the EM formation due to the colonization by A. hygrometricus. Additionally, the shoot Cs concentration increased after the EM formation when Cs was not added to the medium. This suggests that A. hygrometricus might be able to solubilize Cs fixed to soil particles. Moreover, the shoot K concentration increased significantly after the EM formation when Cs was added. However, there were no significant differences in the root K concentration between EM and non-EM seedlings. These results suggest that different mechanisms control the transfer of Cs and K from the root to the shoot of pine seedlings. [ABSTRACT FROM AUTHOR]

The management of vast forested zones contaminated by radiocesium (rCs) following the Chernobyl and Fukushima fallout is of great social and economic concern in affected areas and requires appropriate dynamic models as predictive or questioning tools. Generally, the existing radio-ecological models need less fragmented data and more ecological realism in their quantitative description of the rCs cycling processes. The model TRIPS (“Transfer of Radionuclide In Perennial vegetation Systems”) developed in this study privileged an integrated approach which makes the best use of mass balance studies and available explicit experimental data for Scots pine stands. A main challenge was the differentiation and calibration of foliar absorption as well as root uptake in order to well represent the rCs biocycling. The general dynamics of rCs partitioning was simulated with a relatively good precision against an independent series of observed values. In our scenario the rCs biological cycling enters a steady-state about 15 years after the atmospheric deposits. At that time, the simulations showed an equivalent contribution of foliage and root uptake to the tree contamination. But the root uptake seems not sufficient to compensate the activity decline in the tree. The initial foliar uptake and subsequent internal transfers were confirmed to have a great possible impact on the phasing of tree contamination. An extra finding concerns the roots system acting as a buffer in the early period. The TRIPS model is particularly useful in cases where site-specific integrated datasets are available, but it could also be used with adequate caution to generic sites. This development paves the way for simplification or integration of new modules, as well as for a larger number of other applications for the Chernobyl or Fukushima forests once the appropriate data become available. According to the sensitivity analysis that involves in particular reliable estimates of net foliar uptake as well as root uptake not disconnected from rCs exchange reactions in soil. [ABSTRACT FROM AUTHOR]

For the better understanding of radioactive contamination in Fukushima Prefecture at present and in future, Cs desorption experiments have been conducted mainly using weathered biotite (WB) collected from Fukushima Prefecture and considering the actual contamination level (∼10 −10  wt%) of radiocesium in Fukushima Prefecture. In the experiments, 137 Cs sorbed to WB by immersing in 137 Cs solution for one day was mostly desorbed by solutions of 1 M NaNO 3 , 1 M LiNO 3 , 10 −1  M HCl, and 10 −1  M HNO 3 , although it was barely desorbed by 1 M KNO 3 , 1 M CsNO 3 , 1 M NH 4 NO 3 , and natural seawater. X-ray diffraction analysis of WB after immersing in these solutions suggested that the collapse of the hydrated interlayers in WB suppressed the desorption of Cs. On the other hand, 137 Cs was barely desorbed from WB even by the treatments with solutions of NaNO 3 and LiNO 3 if the duration for the sorption was longer than approximately two weeks, as well as radioactive WB collected from actual contaminated soils in Fukushima Prefecture. This result implies that Cs sorbed in WB became more strongly fixed with time. Probably removal of radiocesium sorbed in weathered granitic soil at Fukushima Prefecture is difficult by any electrolyte solutions, as more than seven years have passed since the accident. [ABSTRACT FROM AUTHOR]

This study investigates the effective removal of cesium (Cs) from aqueous solution using sewage sludge molten (SSM) slag that has undergone the surface modification with alkali (NaOH) hydrothermal treatment. The raw and modified slags were characterised systematically using the BET method, the FESEM, the XRF, the XRD spectroscopy and the CEC analysis to understand the physicochemical changes of the materials, and its sensitivity to Cs ions adsorption. Batch adsorption experiments were carried out to investigate the effects of adsorbent dose, contact time, solution pH, different initial Cs concentrations, temperature and the effect of competitive ions on Cs adsorption. The adsorption isotherm, kinetic and thermodynamic studies were also evaluated based on the experimental results. A higher Cs removal efficiency of almost 100% (for 20–100 mg/L of initial concentration) was achieved by the modified SSM slag, and the maximum adsorption capacity was found to be 52.36 mg/g. Several types of synthetic zeolites such as zeolite X, zeolite Y, zeolite A, and sodalite were formed on surface of the modified slag through the modification process which might be enhanced the Cs adsorption capacity. Kinetic parameters were fitted by the pseudo-second order model. The adsorption isotherms data of modified slag were well-fitted to the Langmuir (R 2  = 0.989) and Freundlich isotherms (R 2  = 0.988). The thermodynamic studies indicated that the adsorption process by the modified slag was spontaneous and exothermic. In the competitive ions effect, the modified slag effectively captured the Cs ion in the presence of Na + and K + , especially at their lower concentrations. Moreover, the modified slag was reused for several cycles after the successful elution process with an appropriate eluting agent (0.5 M H 2 SO 4 ), without deterioration of its original performance. Therefore, the SSM modified slag could be effectively used as a low-cost potential adsorbent for high Cs adsorption from wastewater. [ABSTRACT FROM AUTHOR]

Radionuclides from the Chernobyl accident in 1986 still circulate in the Baltic marine ecosystem and activity levels in water, sediments and fish species such as herring and perch are monitored annually. However, the activity levels of radionuclides in marine mammals have only been sporadically reported. Tissue samples from a museum collection were analysed in two species of seals, and the trends over time in activity level of radioactive caesium (Cs-137) after the Chernobyl accident were reconstructed. We also performed a literature review summarizing activity levels in marine mammals world-wide. We found activity concentrations of Cs-137 in Baltic ringed seals and grey seals to be elevated also in the most recent samples, and during the entire study period measurements ranged between 19 and 248 Bq/kg wet weight. A declining trend in time over the last 30 years follow the general trend of decline in activity levels in other Baltic biota. Accumulation was found to be species specific in the two seal species studied, with 9 times higher activity concentration in grey seals compared to herring, and 3.5 times higher in ringed seals compared to herring. We discuss potential paths and rates of bioaccumulation of radioactive caesium in the Baltic Sea including species specific prey choice of the two seal species and estimate life time exposure. The study contributes one important piece of information to predictive models in risk assessments for nuclear accidents. [ABSTRACT FROM AUTHOR]

Radioactive cesium concentrations in the suspended matter of the coastal waters around the Fukushima Daiichi Nuclear Power Plant (FDNPP) were investigated between January 2014 and August 2015. The concentrations of radioactive cesium in the suspended matter were two orders higher in magnitude than those determined in the sediment. In addition, we discovered highly radioactive Cs particles in the suspended matter using autoradiography. The geometrical average radioactivity of particles was estimated to be 0.6 Bq at maximum and 0.2 Bq on average. The contribution ratio of highly radioactive Cs particles to each sample ranged from 13 to 54%, and was 36% on average. A major part of the radioactive Cs concentration in the suspended matter around the FDNPP was strongly influenced by the highly radioactive particles. The subsequent resuspension of highly radioactive Cs particles has been suggested as a possible reason for the delay in radioactive Cs depuration from benthic biota. [ABSTRACT FROM AUTHOR]

Radiocesium in water, soil, and air represents a severe threat to human health and the environment. It either acts directly on living organisms from external sources, or it becomes incorporated through the food chain, or both. Plants are at the base of the food chain; it is therefore essential to understand the mechanisms of plants for cesium retention and uptake. In this review we summarize investigations about sources of stable and radioactive cesium in the environment and harmful effects caused by internal and external exposure of plants to radiocesium. Uptake of cesium into cells occurs through molecular mechanisms such as potassium and calcium transporters in the plasma membrane. In soil, bioavailability of cesium depends on the chemical composition of the soil and physical factors such as pH, temperature and tilling as well as on environmental factors such as soil microorganisms. Uptake of cesium occurs also from air through interception and absorption on leaves and from water through the whole submerged surface. We reviewed information about reducing cesium in the vegetation by loss processes, and we extracted transfer factors from the available literature and give an overview over the uptake capacities of 72 plants for cesium from the substratum to the biomass. Plants with high uptake potential could be used to remediate soil and water from radiocesium by accumulation and rhizofiltration. Inside plants, cesium distributes fast between the different plant organs and cells, but cesium in soil is extremely stable and remains for decades in the rhizosphere. Monitoring of contaminated soil therefore has to continue for many decades, and edible plants grown on such soil must continuously be monitored. [ABSTRACT FROM AUTHOR]

To understand the formation process of radiologically contaminated areas in eastern Japan caused by the Fukushima Daiichi Nuclear Power Station (FDNPS) accident, the deposition mechanisms over complex topography are the key factors to be investigated. To characterize the atmospheric deposition processes of radionuclides over complex mountainous topography, we investigated the altitudinal distributions of the radiocesium deposited during the accident. In five selected areas, altitudinal characteristics of the air dose rates observed using airborne surveys were analyzed. To examine the deposition mechanisms, we supplementarily used vertical profiles of radiocesium deposition in each area calculated in the latest atmospheric dispersion model. In southern Iwate, the vertical profile of the observed air dose rate was uniform regardless of altitude. In western Tochigi, the areas with the highest levels of contamination were characteristically distributed in the middle of the mountains, while in southern Fukushima, the areas with the highest contamination levels were enhanced near the summits of mountains. In central Fukushima, high air dose rates were limited to the bottoms of basin-like valley. In the region northwest of FDNPS, the air dose rate was the highest at the bottom of valley topography and decreased gradually with altitude. The simulation results showed that calculated wet deposition and observed vertical profiles of total deposition were similar in areas of southern Iwate and northwest of FDNPS qualitatively, suggesting that the dominant deposition mechanism was wet deposition. In contrast, the atmospheric dispersion model failed to reproduce either the timing of precipitation events or vertical profiles of radiocesium deposition in three other areas. Although it was difficult to elucidate the deposition mechanisms in these areas due to uncertainties of the present model results, potential mechanisms such as cloud water deposition were still proposed based on circumstantial evidences of limited meteorological data during the early stage of the accident. [ABSTRACT FROM AUTHOR]

Trace U was released from the Fukushima Daiichi Nuclear Power Plant (FDNPP) during the meltdowns, but the speciation of the released components of the nuclear fuel remains unknown. We report, for the first time, the atomic-scale characteristics of nanofragments of the nuclear fuels that were released from the FDNPP into the environment. Nanofragments of an intrinsic U-phase were discovered to be closely associated with radioactive cesium-rich microparticles (CsMPs) in paddy soils collected ∼4 km from the FDNPP. The nanoscale fuel fragments were either encapsulated by or attached to CsMPs and occurred in two different forms: (i) UO2+X nanocrystals of ∼70 nm size, which are embedded into magnetite associated with Tc and Mo on the surface and (ii) Isometric (U,Zr)O2+X nanocrystals of ∼200 nm size, with the U/(U+Zr) molar ratio ranging from 0.14 to 0.91, with intrinsic pores (∼6 nm), indicating the entrapment of vapors or fission-product gases during crystallization. These results document the heterogeneous physical and chemical properties of debris at the nanoscale, which is a mixture of melted fuel and reactor materials, reflecting the complex thermal processes within the FDNPP reactor during meltdown. Still CsMPs are an important medium for the transport of debris fragments into the environment in a respirable form. [ABSTRACT FROM AUTHOR]

In light of the widespread Cs pollution that may follow nuclear disasters, the decontamination of post-accident soil has earned much attention due to the difficulty of Cs removal for its super-retention in micaceous minerals. Herein, we successfully used solvated Mg 2+ to desorb Cs from Cs-saturated vermiculitized biotite (VB) to clarify the microscale mechanism underlying a Cs removal process, and we applied this new method to actual radioactive soil to validate the practical remediation effect. The results revealed that sorbed Cs was uniformly fixed in the collapsed interlayers of VB crystals and thus was poorly and slowly desorbed by ambient treatment with Mg 2+ regardless of the treating concentration, duration time, and number of cycles. However, almost all Cs was effectively and efficiently removed by hydrothermal treatment at 250°C. Further characterizations of treated Cs-VB confirmed that Mg 2+ indeed diffused into Cs collapsed interlayers from the edge-side to the interior central region with the increase of the treating temperature, and the substituted anhydrous Cs + ensuing interlayer decollapsed. Similarly, a negligible amount of Cs was removed from the radioactive soil by treatment with Mg 2+ at 60 °C, whereas nearly complete Cs removal was achieved at 250 °C, which clearly validated the desorption process as achieved for Cs-VB and definitely reinforced the applicability of the current reported pathway for practical Cs decontamination with soil remediation. [ABSTRACT FROM AUTHOR]

The aim of this study was to select species with higher potential to accumulate 137 Cs among the available mushroom species, by determining the activity concentrations of 137 Cs in mushrooms collected along north and north-western part of Croatia. A total of 55 samples of 14 different species were analyzed and the potential of mycorrhizal and saprotrophic species to accumulate 137 Cs was compared. A wide range of the dry weight activity concentrations of 137 Cs was detected, ranging from 0.95 to 1210 Bq/kg (154 Bq/kg mean value; 52.3 Bq/kg geometric mean) in mycorrhizal and 1.05–36.8 Bq/kg (8.90 Bq/kg mean value; 5.49 Bq/kg geometric mean) in saprotrophic species. Statistical analyses showed that mycorrhizal species accumulate significantly higher concentrations of 137 Cs and thus could perform better as long-term bioindicators of environmental pollution by radiocaesium then saprotrophic species. The comparison of Boletus sp. and Hydnum repandum (both mycorrhizal species commonly found in Croatia) showed, in general order of magnitude, higher accumulation in Hydnum repandum. Clearly, mushrooms, especially mycorrhizal species, can be used as significant indicators even decades after the occurrence of any serious 137 Cs contamination event. However, as a wide range of values indicates that various parameters may influence the total uptake of the 137 Cs into the mushroom fruit bodies, it is necessary to emphasize that 137 Cs activity detected in a single mushroom sample is very site-specific. [ABSTRACT FROM AUTHOR]

Benchmarking the fallout 137Cs in the coastal marine environment assumes significance in view of expansion of nuclear power plants (NPPs) in India and the Asia-Pacific region. This paper presents a snapshot of 137Cs activity in marine coastal water samples collected around Kudankulam NPPsite across a 50 km stretch from Kanyakumari to Uvari and attempts to compare with the 137Cs concentration observed across Indian coastal region and Asia-Pacific regional seawater. 137Cs activity of the Kudankulam coast ranges from ≤0.40 to 1.92 mBq/L with a geometric mean (GM) value of 1.0 mBq/L. In general, 137Cs activity in seawater of the entire Indian coastal region varies from 0.30 to 1.25 mBq/L, which may be considered as global fallout. [ABSTRACT FROM AUTHOR]

The total radioactive Cs concentration in final-instar Stenopsyche marmorata larvae from the Mano River, Fukushima Prefecture, in 2013 was found to be >1000 Bq kg−1 in dry weight. The concentration of radioactive Cs in the river water itself was on the order of 0.01 Bq kg−1, while its concentration in drifting fine particulate organic matter (FPOM) was on the order of 10,000 Bq kg−1 in dry weight. When excretion experiments were performed in the summer and winter, significant decreases in the Cs concentrations in the whole body of S. marmorata were observed in both seasons. The biological half-life of Cs-137 was 5.3 and 8.8 h for the nonwintering generation and the wintering generation, respectively. Another elimination test using a stable Cs solution was performed, and the Cs concentration was observed to decrease rapidly to 7.5% of its original level in the digestive tract of S. marmorata after 72 h, but stable Cs remained in muscle and extra-alimentary tissue of S. marmorata. As the total radioactive Cs in the water was quite low, its concentration in S. marmorata from the Mano River reflects the fact that it feeds on FPOM. The radioactive Cs concentration in the FPOM significantly declined in 2015, but a corresponding decline was not observed for S. marmorata. We therefore infer that ultrafine particulate matter such as suspended vermiculite clay is strongly contaminated with radioactive Cs, and that this radioactive Cs passes continuously through the digestive tract of S. marmorata. [ABSTRACT FROM AUTHOR]

This study examined 137Cs detachment from needle litter of Japanese cedar (Cryptomeria japonica) through leaching and decomposition in a headwater stream located 45 km from Fukushima Daiichi Nuclear Power Plant. We placed litter bags in pools and riffles and removed them after 4, 15, 75, 150, and 240 days. The 137Cs activity concentration in litter collected after 4 and 15 days was 48–72 % of the initial 137Cs activity concentration in litter. The 137Cs activity concentration in litter after 240 days in the pools decreased by 26 %, while that in litter of riffles decreased by 9 % compared with the initial 137Cs activity concentration. The dry weight of litter became 71 and 86 % of initial weight after 75 days, and from 32 to 51 % after 150 days. The decay coefficient of litter (k = 0.0060) in the riffles was 1.6-fold higher than that in the pools (k = 0.0037). The greater decrease in litter weight with longer submergence time was possibly associated with a combination of leaching and decomposition, in particular in litter that was submerged for 100 days in the water column. The difference in the rate of decomposition and 137Cs detachment from litter between the riffles and pools was due to the substrate and flow conditions at the litter bag sites. Examining the different patterns of 137Cs detachment from litter among channel morphologies is necessary for comprehending the mechanisms of 137Cs accumulation in aquatic biota. The findings of this study suggest that elucidating leaching and decomposition processes in litter of stream channels is important for understanding 137Cs dynamics in forested headwater ecosystems. [ABSTRACT FROM AUTHOR]

The “Caddisfly Watch” program proposes the use of larvae of the caddisfly genus Stenopsyche (Trichoptera: Stenopsychidae) to monitor the radioactive cesium (137Cs) pollution, including that of suspended solids, in river environments, as a simple method was essential for this following the Fukushima nuclear disaster in March 2011. A variety of aquatic organisms were collected from rivers in Japan in 2012 and their levels of radioactive Cs measured. Amongst all the organisms collected, the highest concentrations of 137Cs were observed in caddisfly larvae. These larvae occur at a high density and can be collected at regular intervals in most rivers throughout Japan. It is proposed that caddisfly larvae can be used as bioindicators of radioactive Cs contamination in rivers, as their temporal and spatial changes are easily assessed. [ABSTRACT FROM AUTHOR]

The Great East Japan Earthquake that occurred on 11 March 2011 generated a series of massive tsunami waves that caused severe damage to the Fukushima Daiichi Nuclear Power Plant, following which large amounts of radioactive materials were discharged from the power plant into the environment. Given the recently developed technologies for unmanned helicopters and their potential application in airborne radiation monitoring, we developed a radiation monitoring system for aerial use. We then used unmanned helicopters to measure the radiation level in areas with soil contaminated by radiocesium emitted from the nuclear power plant to evaluate the ambient dose rate distribution around the site. We found that in dry riverbeds downstream of the highly contaminated watershed, especially in the upstream parts, that the ambient dose rate was higher than that in protected inland areas. In addition, we carried out soil sampling in dry riverbeds. The soil sample data agreed with the results obtained from the unmanned helicopter. A possible scenario is that river sediment and adjacent soil containing radioactive materials were carried downstream due to an event such as a rise in water level caused by, e.g., a typhoon, and that these remained in the riverbed after the water drained away. The vertical profile of radiocesium in the soil and the measurements of river sediment at river mouth areas corroborated this scenario. [ABSTRACT FROM AUTHOR]

We examined the cesium-137 (137Cs) contamination of river food webs in a gradient of initial fallout deposition (net density estimates 2.5–3.5 months after the Fukushima Daiichi Nuclear Power Plant accident in March 2011), in Fukushima Prefecture, Japan. Litter, aquatic insects, and salmonid fish were collected in five headwater stream reaches (watershed-average fallout density, 368.1–1398.4 kBq/m2) for the measurement of 137Cs concentration and stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) in June 2014. The stable isotope ratios suggested that the detrital food chain was a dominant energy pathway in rivers originating from a basal resource (litter) to primary (aquatic insects) and secondary (fish) consumers. The 137Cs concentration decreased with an increase in the trophic level, with the highest value for litter (10930 ± 5381 Bq/kg, mean ± SD), the lowest for fish (2825 ± 2451 Bq/kg), and the intermediate one for dominant (numerically and biomass-wise) detritivorous insect, Ephemera japonica McLachlan (4605 ± 1970 Bq/kg). 137Cs concentrations of three trophic levels were linearly predicted by the initial fallout amount of 137Cs. The evacuation of the gut contents of E. japonica during field experiments led to a reduction in their 137Cs concentration by approximately 50% within 1–2 day(s) without loss of body weight. This suggested that a substantial portion of 137Cs contamination of E. japonica was derived from highly contaminated fine solids deposited in depositional habitats at a disproportionately high density. Overall, the initial fallout amount of 137Cs was helpful in roughly predicting the contamination levels of headwater river-riparian ecosystems with the detrital food chain as a dominant energy pathway. Long-term monitoring of the dynamics and fates of 137Cs associated with fine organic and inorganic particulates appears important for better prediction of 137Cs contamination of food webs in forested headwater streams. [ABSTRACT FROM AUTHOR]

The 137 Cs deposited in soil and exposed tree roots have been widely applied to estimate medium-term soil erosion rates. However, comparative studies between these methods are scarce. For this purpose, three hillsides in two Mediterranean dehesas (rangeland with disperse tree cover) were selected. Regarding the 137 Cs technique, a reference site close to the study areas and with similar altitude and rainfall was selected. In order to reduce uncertainties related to the use of point soil profiles, all those collected in an area were combined to form a representative composite profile. The total inventory was 2790 ± 50 Bq/m 2 , and the relaxation coefficient indicated it was an undisturbed soil. The radiocaesium inventory in the study areas was 14–23% lower than in the reference area. The erosion rates for 137 Cs were in the range 20.9–38.1 t ha − 1 y − 1 . The exposed root technique was applied to holm oak trees (age about 90 years), and the erosion rates were in the range 22–34 t ha − 1 y − 1 . The ratio between exposed root and 137 Cs techniques was 1.02 ± 0.11 (S.D.) within the range 0.89–1.2. Both methods produced very similar results equally with respect to the mean erosion rate as well as the relative difference between the hillslope sections, i.e. displaying the same spatial variation in the study areas. As the accounting time for these two techniques is different, 50 and 90 y for 137 Cs and exposed roots respectively, results suggest that no change in mid-term erosion rates was implied for these areas for almost a century. The use of 137 Cs and exposed roots methodology for the determination of mean erosion rates can be reproduced in other ecosystems, but a careful selection of the reference site for 137 Cs is essential. [ABSTRACT FROM AUTHOR]

A wide area of paddy fields was contaminated by radiocesium derived from the Fukushima nuclear accident. Implement of agricultural countermeasures is one of the principle methods to reduce the contamination of rice plants. In this study, the effect of topsoil removal measure and fertilizer application on radiocesium uptake by rice plants was investigated over a four-year period. Some other available countermeasures carried out after the Fukushima nuclear accident were also summarized. The results indicate that the effect of topsoil removal measure on the accumulation of radiocesium in rice plants was effective, but the concentration ratio of radiocesium activity concentration between rice plant and soil increased. This may be correlated with the radiocesium imported from irrigation water and relatively high exchangeable radiocesium proportion of plowing soil in the topsoil removal paddy. We summarized four year's data to further confirm that potassium and nitrogen fertilizers had an opposite effect on the accumulation of radiocesium in rice plants. Increasing potassium and reducing nitrogen fertilizer conditions tended to inhibit the radiocesium uptake by rice plants. Moreover, of all the available countermeasures applied in the paddy fields, the most effective countermeasure was the application of phlogopite. However, further analyses are required to confirm the effectiveness of application of phlogopite considering the limited available information. [ABSTRACT FROM AUTHOR]

Large volumes of decontamination wastes (DW) generated by off-site decontamination activities in Fukushima Prefecture have been incinerated since 2015. The behavior of radioactive cesium during incineration of DW was investigated at a working incineration plant. The incineration discharged bottom ash (BA) and fly ash (FA) with similar levels of radiocesium, and the leachability of the radiocesium from both types of ash was very low (<1%). These results are significantly different from those obtained for the incineration of contaminated municipal solid waste (CMSW) reported in earlier studies. The source of radiocesium in DW-FA is chiefly small particles derived from DW and DW-BA blown into the flue gas, not the deposition of gaseous synthesized radiocesium compounds on the surfaces of ash particles in the flue gas as observed in CMSW incineration. This source difference causes the behavior of radiocesium during waste incineration to differ between DW and CMSW. [ABSTRACT FROM AUTHOR]

Following on from the successful development and validation of a prototype automated unit for the extraction of radiocaesium from seawater, the unit was redesigned to be smaller, easier to transport and better suited for field work. An extension of the validation process was undertaken to include robustness testing. Robustness testing evaluates the behaviour of a procedure when deliberate small changes are made. This requires the identification and testing of experimental factors which could have an impact on the results. The Plackett-Burman approach was adopted to minimise the number of experiments needed for testing. The study showed that the analytical method was not sensitive to any of the factors tested, indicating that the method is robust. [ABSTRACT FROM AUTHOR]

Contamination of waters of lake-river systems after many-year migration of Cs in water bodies was studied. In lakes with the Cs fallout density lower than 8 kBq m, the radionuclide concentrations in water after 24-29 years did not exceed 2-3 Bq m, and at a fallout level of 37 kBq m it was in the range 11-34 Bq m. The natural half-clearance time Т of lake waters from Cs was 6-7 years at the exposure of up to 20 years. The Cs migration in the lake-river systems that occurred during ~30 years did not lead to structural changes in the water contamination: The initially low Cs level in lake waters did not become high, and vice versa. Among rivers feeding Lake Ladoga, the Cs level in the Vuoksa River is ~3 times higher than in waters of the Volkhov and Svir rivers. During the period 1988-2015, 21.3 TBq of Cs was supplied to Lake Ladoga with Vuoksa waters. The Vuoksa source from the Saima lake system with increased contamination with Cs of Chernobyl origin leads to long-term supply of this radionuclide to Lake Ladoga. [ABSTRACT FROM AUTHOR]

This study investigated the use of napiergrass ( Pennisetum purpureum Schum.) to remediate soils highly contaminated with radiocesium-137 (Cs) in the town of Namie, Fukushima Prefecture, which is located around 9 km northwest of the Fukushima Daiichi Nuclear Power Plant, Japan. Field experiments were performed to investigate the remediation effects using two sites (paddy or upland grassland) as replicates, three planting densities (low, medium, and high density), and two different cutting frequencies (cut once or twice a year) over 2 consecutive years. Napiergrass can be more efficient than sorghum for Cs remediation. The maximum Cs removal ratio (CR, %) in napiergrass achieved with high-density planting (11 plants m) was between 0.32 and 0.57%. However, cutting frequency did not affect the CR. Higher biomass leads to a dilution of Cs in cutting frequency. Therefore, we suggest that the greatest CR could be achieved through a high above ground biomass (high-density planting). [ABSTRACT FROM AUTHOR]

The town of Marumori in southern Miyagi Prefecture borders on Fukushima Prefecture, and following the accident at the Fukushima Daiichi nuclear power plant, there were concerns about cesium deposition in forested areas. One of the authors of this paper has continually surveyed leaf litter from the forested areas. As leaf litter may be a source of cesium contamination from the forest to downstream areas, we considered a simplified version of wet oxidation, a method previously presented by one of the authors of this study, as a technology to reduce leaf litter weight and cesium concentration, separating radioactive nuclides from non-radioactive ones, in leaf litter. We tested our method in three experiments. Experiment 1 used new leaf litter (232 Bq/kg) from the surface of a small stream at the forest edge nearby an area with air dose level higher than the national standard threshold of 0.23 μSv/h for the implementation of governmental decontamination works. Experiment 2 applied wet oxidation to older leaf litter (705 Bq/kg) harvested from a pasture nearby the stream mentioned above. We also used the same leaf litter in experiment 3 for a cesium release tests using pure water. In experiment 1 and 2 we treated leaf litter with a sodium hypochlorite solution, optimizing sodium hypochlorite concentration and reaction temperature. We measured a 50–60% decrease in the leaf litter weight and a 60% decrease in the cesium concentration. Moreover, we also measured the amount of cesium washout. The cesium budget of experiment 1 showed no cesium gasification (wet oxidation avoids airborne cesium as this element is prone to be volatile at 600 °C), and that high sodium hypochlorite concentration and high temperature had a strong positive effect on leaf litter volume reduction and cesium decontamination. Experiment 2 confirmed the reproducibility of these results in leaves with different cesium concentration and harvested in different conditions. We could also explain the mechanism behind leaf litter weight and cesium concentration reduction. Experiment 3 helped us to investigate the effects of the matter present on the surface of the water and the contribution of water soluble cesium. Concurrent experiments on changes in leaf litter chemical composition confirmed that our modified wet oxidation method had an effect on the removal of acid-insoluble lignin. Removal of lignin, a refractory component, might allow for a better utilization of the residue left after implementation of the proposed simplified wet oxidation. Thus, real wastes could be smaller than the residues. Together with the observed smaller cesium concentration in the residue, the proposed method in this study is expected to contribute to mitigate the risk due to the fallen leaves containing cesium. [ABSTRACT FROM AUTHOR]

Due to the Chernobyl nuclear power plant accident in 1986, the environment of forest ecosystems is still contaminated by radiocaesium (137Cs). Currently the average surface soil activity of137Cs is 3.87 kBq m−2in the Czech Republic. Depending on the soil properties of the sample locality, the137Cs content in selected edible forest fruits and related radiocaesium soil-to-fruit transfer was analysed. In addition, radiation doses through ingestion were estimated with regards to the potential health risk caused by consumption of the fruits. Fruits (blueberry, rowanberry, blackberry and raspberry) and soil samples were collected in some locations of the Jeseníky Protected Landscape Area (PLA), the north-eastern mountains of the Czech Republic most severely contaminated with radiocaesium (137Cs). The average aggregated transfer coefficient (TFag) for radiocaesium (137Cs) reached values ranging from 2.73 × 10−5to 2.20 × 10−2 m2kg−1. The values of TFagcorrelated with the soil reaction, with the content of humus and with the content of clay particles in the soil of the sample areas, that is,r = –0.90 (p < 0.001),r = 0.81 (p < 0.001) andr = –0.68 (p < 0.01), respectively. Only the soil reaction pH (KCl) had an effect on TFag(p < 0.01). The highest radiation dose which the average Czech consumer would receive after consumption of the fruits was calculated as 1.78 × 10−2 mSv year−1, and such a dose of radiocaesium should not present a serious health problem. [ABSTRACT FROM PUBLISHER]

Distribution of the Cs activity concentrations, soil pH, content of organic matter and composition of mineral portion in humus were investigated in forest soils variably loaded by Chernobyl-derived fallout. Maximum in the Cs activity concentrations were found in the uppermost organic soil horizons. In forest humus the Cs activity concentrations was negatively related to pH and the content of organic matter. No significant content of clay minerals was detected in humus. Slow vertical migration (0.04-0.06 cm year) and effective half-life of Cs in humus about 20 years was found. The initial surface Cs activities in 1986 were estimated. [ABSTRACT FROM AUTHOR]

With the development of the nuclear power generation, it is expected that severe pollution of environmental water by radiocesium (r-Cs) may occur. We developed a r-Cs removal system with a continuous stirring tank reactor (CSTR) and r-Cs adsorbent of non-woven fiber immobilizing Prussian blue nanoparticles (PBN). Results confirmed that this system can remove r-Cs from environmental water with a removal rate higher than 80% at processing speed of 2 m 3 /h. In this study, the processing speed and processing capacity of this system were confirmed using kinetic and equilibrium analyses of Cs adsorption behavior on PBN. The equilibrium of Cs adsorption was analyzed using a Langmuir equation. Results show that the maximum adsorption capacity was 160 mg/g (PBN). The kinetic data were well fitted using a pseudo-first order kinetic model. This rate constant was correlated to the PBN/liquid ratio in the system. [ABSTRACT FROM AUTHOR]

Little attention has been paid to the uptake of 137 Cs in natural forests under low levels of the isotope fallout when no immediate ecological danger presents. Here we present the extended assessments of the soil-to-plant and canopy-to-litter flows of 137 Cs recently evaluated in a native Siberian forested area. The area undergoes a typical after-fire long term succession, with light-conifer upper story being followed by undergrowth of Siberian fir and other dark-conifer species. The one-year-old needles of Siberian fir were found to accumulate the largest concentration of the isotope, 4.10 Bq/kg oven-dry weight during the first growth season, as compared with older needles that accumulated 4.67 Bq/kg oven-dry weight in 2–3 years of growth. Based on these data an approach was developed that, hypothetically, can allow one to estimate the 137 Cs activity concentration in soil solutions. Direct activity measurements in the soil solutions were not possible. The isotope activity in soil solutions was estimated to be 0.0061–0.0105 Bq/L. Based on the original data from the litter fall the annual flow of the isotope from the upper canopy to on-ground litter was found to be 0.42–0.84 Bq/m 2 . The amount of 137 Cs that returns yearly back from canopy with falling litter was estimated to be 0.012–0.015% of the total soil isotope content. A combination of the estimations obtained in our study with the values of global 137 Cs fallout allowed us to assess the ages (the time of formation) of horizons of the soils in the area. [ABSTRACT FROM AUTHOR]

This study investigated the effects of different environmental factors on 137 Cs uptake in three subtropical estuarine fish, and the trophic transfer of 137 Cs in the fish from different preys. Our data showed that salinity, potassium, and temperature had appreciable effects on the dissolved uptake of 137 Cs in the fish, but no conclusive relationship was found between the effects of salinity and potassium concentration on the uptake. The dietary assimilation of 137 Cs was 51–55% in the omnivorous fish Siganus fuscescens when fed with macroalgae or bivalve tissues, and was much lower than those in carnivorous fish Sebastiscus marmoratus and Jarbua terapon (70–79%). Dietary pathway dominated the 137 Cs accumulation in the omnivorous and carnivorous fish, both of which exhibited strong potential to biomagnify 137 Cs from their preys. Using the biokinetic model, we demonstrated that salinity and temperature only had minor effects on the overall accumulation of 137 Cs in carnivorous species living in estuarine environment. Modeling calculation suggested that it would take 37–80 days for the fish to reach 95% of steady-state concentration, and lower somatic growth increased the time to reach steady-state in the fish. [ABSTRACT FROM AUTHOR]

Radiocesium ( 137 Cs) activity concentrations, mainly derived from the Fukushima accident of March 2011, were measured in green foliar parts without separation by age (bulk green foliar parts; GL) and litterfall (LF) of Japanese cedar ( Cryptomeria japonica ) from 2011 to 2015. In all samples, 137 Cs concentrations decreased exponentially over time, but were always higher in LF (7.36–0.58 Bq g-DW −1 ) than in GL (2.10–0.06 Bq g-DW −1 ). The difference in the decreasing rate between GL and LF would reflect a difference in the dominant factor of the decrease between living and dead tissues (i.e., internal translocation and weathering, respectively). Over this same timeframe, potassium (K) concentrations in both GL and LF experienced repetitive periodical changes within a certain range (0.38–3.0 mg g-DW −1 for LF and 2.08–4.77 mg g-DW −1 for GL, respectively). Thus, there was no specific correlation between 137 Cs and K concentrations in LF and GL. However, analyses of the age classified green foliar parts (GL-S) and dead foliar parts still retained on trees (DL) could indicate another view. The annual changes in residual rates of both 137 Cs and K concentrations in GL-S demonstrated very similar two-phase reductions (i.e., a faster reduction in each expansion year than in the following years) and an obvious linear correlation between each other. Radiocesium concentration in DL were always higher than in any part of GL-S sampled at the same timing, but K concentrations showed the reverse relation. It is probable that 137 Cs is basically translocated from older parts to the developing parts (as long as the former are alive) via a seasonal nutritional flow of K; however, a part of 137 Cs translocation would cease considerably earlier than the cessation of K translocation. [ABSTRACT FROM AUTHOR]

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 137 Cs discharge downstream from the reservoirs, and the forms in which 137 Cs 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. [ABSTRACT FROM AUTHOR]

The decreasing trend of the atmospheric 137 Cs concentration in two cities in Fukushima prefecture was analyzed by a regression model to clarify the relation between the parameter of the decrease in the model and the trend and to compare the trend with that after the Chernobyl accident. The 137 Cs particle concentration measurements were conducted in urban Fukushima and rural Date sites from September 2012 to June 2015. The 137 Cs particle concentrations were separated in two groups: particles of more than 1.1 μm aerodynamic diameters (coarse particles) and particles with aerodynamic diameter lower than 1.1 μm (fine particles). The averages of the measured concentrations were 0.1 mBq m −3 in Fukushima and Date sites. The measured concentrations were applied in the regression model which decomposed them into two components: trend and seasonal variation. The trend concentration included the parameters for the constant and the exponential decrease. The parameter for the constant was slightly different between the Fukushima and Date sites. The parameter for the exponential decrease was similar for all the cases, and much higher than the value of the physical radioactive decay except for the concentration in the fine particles at the Date site. The annual decreasing rates of the 137 Cs concentration evaluated by the trend concentration ranged from 44 to 53% y −1 with average and standard deviation of 49 ± 8% y −1 for all the cases in 2013. In the other years, the decreasing rates also varied slightly for all cases. These indicated that the decreasing trend of the 137 Cs concentration was nearly unchanged for the location and ground contamination level in the three years after the accident. The 137 Cs activity per aerosol particle mass also decreased with the same trend as the 137 Cs concentration in the atmosphere. The results indicated that the decreasing trend of the atmospheric 137 Cs concentration was related with the reduction of the 137 Cs concentration in resuspended particles. [ABSTRACT FROM AUTHOR]

Widespread use of products based on nanomaterials results in the release of nanoparticles into the environment. Nanoparticles can be taken up by organisms, but they can also coexist with other substances such as radionuclides, thus affecting their uptake or toxicity. In contrast, the sorption capacity of nanoparticles is exploited in water purification. The aim of the study was to investigate: (i) bioaccumulation of cesium and strontium by Pleurotus eryngii mycelia in the presence of alumina nanoparticles (Al 2 O 3 NPs); and (ii) sorption of radionuclides on the surface of nanoparticles. For the experiments, living and dried mycelia were used to permit distinguishing between active uptake and passive sorption of the NPs by P. eryngii . The results are discussed from the perspective of the use of P. eryngii in the mycoextraction of radionuclides. The sorption capacity of Al 2 O 3 NPs and the accumulation by P. eryngii mycelia differ for the applied radioisotopes. The efficiency of Cs and Sr sorption by alumina nanoparticles is 20% and 40%, respectively. Mycelia of P. eryngii have the ability to accumulate 30% of both radioisotopes from the medium. More than 60% of strontium can be removed accumulated from water by P. eryngii mycelia in coexistence with Al 2 O 3 NPs, while the efficiency of cesium removal accumulation is negligible. It was found that alumina nanoparticles do not enhance uptake of radionuclides by P. eryngii mycelia; mycoextraction of radionuclides by mycelia and sorption by Al 2 O 3 NPs are concurrent processes. There was no difference between live or dried mycelia uptake. [ABSTRACT FROM AUTHOR]

Anthropogenic radioactivity in the northern Adriatic Sea was assessed by analyzing Cs activity concentrations in seawater, sediment, and marine organisms in the period from 2006 to 2010. The investigated locations were the Po River delta, Lim Bay and the Rovinj coastal area. At all locations Cs activity concentrations in seawater were lower than pre-Chernobyl values (<4 Bq m). The highest Cs activity concentrations in sediment were found in the Po River delta (8.70 Bq kg). The data indicate that some species, such as sardine Sardina pilchardus, red mullet Mullus barbatus and the brown alga Fucus virsoides are better bioaccumulators of Cs than others. In addition, the ERICA Assessment Tool was used to calculate the total dose rates for reference organisms included in the software, as well as for specific sampled marine organisms. [ABSTRACT FROM AUTHOR]

30 years after the Chernobyl Nuclear Power Plant (CNPP) accident, its radioactive releases still remain of great interest mainly due to the long half-lives of many radionuclides emitted. Observations from the terrestrial environment, which hosts radionuclides for many years after initial deposition, are important for health and environmental assessments. Furthermore, such measurements are the basis for validation of atmospheric transport models and can be used for constraining the still not accurately known source terms. However, although the “Atlas of cesium deposition on Europe after the Chernobyl accident” (hereafter referred to as “Atlas”) has been published since 1998, less than 1% of the direct observations of 137 Cs deposition has been made publicly available. The remaining ones are neither accessible nor traceable to specific data providers and a large fraction of these data might have been lost entirely. The present paper is an effort to rescue some of the data collected over the years following the CNPP accident and make them publicly available. The database includes surface air activity concentrations and deposition observations for 131 I, 134 Cs and 137 Cs measured and provided by Former Soviet Union authorities the years that followed the accident. Using the same interpolation tool as the official authorities, we have reconstructed a deposition map of 137 Cs based on about 3% of the data used to create the Atlas map. The reconstructed deposition map is very similar to the official one, but it has the advantage that it is based exclusively on documented data sources, which are all made available within this publication. In contrast to the official map, our deposition map is therefore reproducible and all underlying data can be used also for other purposes. The efficacy of the database was proved using simulated activity concentrations and deposition of 137 Cs from a Langrangian and a Euleurian transport model. [ABSTRACT FROM AUTHOR]

The serious nuclear disaster in the Fukushima Daiichi nuclear energy plant was occurred by the Tsunami on March 11, 2011. The radioactive materials leaking from the power plant were widely diffused in and around Fukushima prefecture including the Pacific Ocean by wind, rain and river flow. It can't be always said that there is no risk of the condensation of radioactive materials in human body by ecological chain if fish take in radiation in the ocean contaminated by the radioactive materials. However the decontamination is less-advanced. The establishment of a new decontamination method is urgent need. Thus, in this study, it is aimed to establish a new decontamination technology of radioactive materials deposited on seabed or lake bed. In particular, the new adsorption material which can adsorb radioactive materials is developed and the new method which can move them from the bottom sediment to the adsorption material is proposed. It is expected that the proposed method and the developed adsorption material are efficient to remove radioactive materials from seabed or lake bed when they are expansively applied to the real decontamination. [ABSTRACT FROM AUTHOR]

The paper presents quantitative data on radiocesium wash-off (dissolved and particulate) from catchment areas after the accident at the Fukushima-1 nuclear power plant. The evaluations are conducted based on published data on radiocesium monitoring in streams in the accident zone and monitoring at standard USLE plots. The characteristics of radiocesium wash-off and its distribution coefficient in riverine waters and surface runoff are analyzed by comparing data obtained on the territories of the Fukushima and Chernobyl accidents within a few years after the accidents. The normalized radiocesium wash-off coefficients in solution for the Fukushima river catchment area are one to two orders of magnitude lower than the analogous values for the Chernobyl catchment area. The normalized wash-off coefficients of radiocesium on particulate matter in the Fukushima and Chernobyl catchment areas are comparable. However, at least twice higher mean annual precipitation and steeper slopes in the Fukushima catchment area result in a higher annual wash-off coefficient than that of the Chernobyl area. It is demonstrated that characteristics of radiocesium wash-off obtained at USLE plots can be utilized to evaluate the scales of natural catchment areas. [ABSTRACT FROM AUTHOR]

The density of global radioactive contamination was the most reliable estimated in marine regions and less accurate for intracontinental areas with semi-arid and arid climatic conditions. This work presents the results of using a new method developed for estimating the density of global radioactive contamination based on the calculation of Cs concentration in closed lake catchments. An average density of of Cs contamination in the model closed lake catchments of southwestern Siberian steppe landscapes is 0.80 ± 0.24 kBq m that is 2-3 times lower than the levels calculated on the basis of the published data. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The rate of natural removal of Cs from water bodies in Eastern Fennoscandia is evaluated. The half-time T of water purification from global Cs in lake-river systems was ~6.5 years and that for river systems was 6.5-10 years. For the 15- and 20-year exposure of Cs in watershed soils, its annual input in rivers was 0.021-0.120 and 0.017-0.070% of its reserve. The period of May-December 1986 showed maximal export of Cs, i.e., 1.1% of its reserve. Cs export into rivers decreased in the region from north to south because of changes in landscape and climate conditions that affect Cs migration on watersheds. [ABSTRACT FROM AUTHOR]

Fifty five soil samples collected in the Lithuania teritory in 2011 and 2012 were analyzed for 129 I, 137 Cs and Pu isotopes in order to investigate the level and distribution of artificial radioactivity in Lithuania. The activity and atomic ratio of 238 Pu/ 239,24 0 Pu, 129 I/ 127 I and 131 I/ 137 Cs were used to identify the origin of these radionuclides. The 238 Pu/ 239+240 Pu and 240 Pu/ 239 Pu ratios in the soil samples analyzed varied in the range of 0.02–0.18 and 0.18–0.24, respectively, suggesting the global fallout as the major source of Pu in Lithuania. The values of 10 −9 to 10 −6 for 129 I/ 127 I atomic ratio revealed that the source of 129 I in Lithuania is global fallout in most cases though several sampling sites shows a possible impact of reprocessing releases. Estimated 129 I/ 131 I ratio in soil samples from the southern part of Lithuania shows negligible input of the Chernobyl fallout. No correlation of the 137 Cs and Pu isotopes with 129 I was observed, indicating their different sources terms. Results demonstrate uneven distribution of these radionuclides in the Lithuanian territory and several sources of contamination i.e. Chernobyl accident, reprocessing releases and global fallout. [ABSTRACT FROM AUTHOR]

To investigate riverine transfers from contaminated soils of the Fukushima Prefecture in Japan to the marine environment, suspended sediments, filtered water, sediments and detrital organic macro debris deposited onto river beds were collected in November 2013 within small coastal rivers during conditions of low flow rates and low turbidity. River waters were directly filtered on the field and high efficiency well-type Ge detectors were used to analyse radiocaesium concentrations in very small quantities of suspended particles and filtered water (a few mg to a few g). For such base-flow conditions, our results show that the watersheds studied present similar hydro-sedimentary behaviours at their outlets and that the exports of dissolved and particulate radiocaesium are comparable. Moreover, the contribution of these rivers to the instantaneous export of radiocaesium to the ocean is similar to that of the Abukuma River. Our preliminary results indicate that, in the estuaries, radiocaesium concentrations in suspended sediments would be reduced by more than 80%, while radiocaesium concentration in filtered waters would be maintained. Significant correlations between radiocaesium concentrations and radiocaesium inventories in the soils of the catchments indicate that there was at that time little intra and inter-watershed variability in the transfer processes of radiocaesium from lands to rivers at this regional scale. The apparent liquid–solid partition coefficient (K D ) values acquired for the lowest loads/finest particles complement the values acquired by using sediment traps and highlight the strong capacity of the smallest particles to transfer radiocaesium. Finally, but not least, our observations suggest that there could be a significant transfer of highly contaminated detrital biomass from forest litter to the downstream rivers in a rather conservative way. [ABSTRACT FROM AUTHOR]

The environmental pollution by trace heavy metals is a severe problem for the environment and human health. In this paper, the liquid jet of CsNO 3 solution employed was introduced to the measurement chamber and detected using laser-induced breakdown spectroscopy (LIBS) directly at low pressure to determine the detection features of trace Cs element in liquid. The distinct and round plasma can be acquired when reducing the pressure. The interaction between the plasma core of the liquid jet and the surrounding gas can be controlled to enhance Cs detection ability. Cs emission was mainly in the surrounding area in the plasma. The influences of laser focal point and plasma measurement area on the measured signals were studied under low-pressure condition. When employing the defocus mode and varying the measurement area within a certain range, Cs signal and the signal-to-background ratio were improved. Cs detection limit can reach to 22.8 ppb (3σ/m s ) at pressure of 26 kPa in this paper. According to the discussion, the detection limit will be enhanced when improving the experimental conditions using this method, which shows the great application potential of liquid sample measurement. [ABSTRACT FROM AUTHOR]

Following the Chernobyl accident, the scientific community gained numerous data on the transfer of radiocesium in European forest ecosystems, including information regarding the short-term redistribution of atmospheric fallout onto forest canopies. In the course of international programs, the French Institute for Radiological Protection and Nuclear Safety (IRSN) developed a forest model, named TREE4 (Transfer of Radionuclides and External Exposure in FORest systems), 15 years ago. Recently published papers on a Japanese evergreen coniferous forest contaminated by Fukushima radiocesium fallout provide interesting and quantitative data on radioactive mass fluxes measured within the forest in the months following the accident. The present study determined whether the approach adopted in the TREE4 model provides satisfactory results for Japanese forests or whether it requires adjustments. This study focused on the interception of airborne radiocesium by forest canopy, and the subsequent transfer to the forest floor through processes such as litterfall, throughfall, and stemflow, in the months following the accident. We demonstrated that TREE4 quite satisfactorily predicted the interception fraction (20%) and the canopy-to-soil transfer (70% of the total deposit in 5 months) in the Tochigi forest. This dynamics was similar to that observed in the Höglwald spruce forest. However, the unexpectedly high contribution of litterfall (31% in 5 months) in the Tochigi forest could not be reproduced in our simulations (2.5%). Possible reasons for this discrepancy are discussed; and sensitivity of the results to uncertainty in deposition conditions was analyzed. [ABSTRACT FROM AUTHOR]

Quantitative understanding of the stability of sorbed radionuclides in smectite is necessary to assess the performance of engineering barriers used for nuclear waste disposal. Our previous study demonstrated that the spatial organization of the smectite platelets triggered by the divalent cations led to the apparent fixation of intrinsic Cs in smectite, because some Cs is retained inside the formed tactoids. Natural water is usually a mixture of Na+ and divalent cations (Ca2+ and Mg2+). This study therefore investigated the desorption behavior of intrinsic Cs in Na-smecite in mixed Na+-divalent cation solutions under widely various cation concentrations using batch experiments, grain size measurements, and cation exchange modeling (CEM). Results show that increased Na+ concentrations facilitate Cs desorption because Na+ serves as the dispersion agent. A linear relation was obtained between the logarithm of the Na+ fraction and the accessible Cs fraction in smectite. That relation enables the prediction of accessible Cs fraction as a function of solution cationic compositions. The corrected CEM considering the effects of the spatial organization suggests that the stability of intrinsic Cs in the smectite is governed by the Na+ concentration, and suggests that it is almost independent of the concentrations of divalent cations in natural water. [ABSTRACT FROM AUTHOR]

The high variability of the soil-to-plant transfer factor of radiocaesium (RCs) compels a detailed analysis of the radiocaesium interception potential (RIP) of soil, which is one of the specific factors ruling the RCs transfer. The range of the RIP values for agricultural soils in the Fukushima accident affected area has not yet been fully surveyed. Here, the RIP and other major soil chemical properties were characterised for 51 representative topsoils collected in the vicinity of the Fukushima contaminated area. The RIP ranged a factor of 50 among the soils and RIP values were lower for Andosols compared to other soils, suggesting a role of soil mineralogy. Correlation analysis revealed that the RIP was most strongly and negatively correlated to soil organic matter content and oxalate extractable aluminium. The RIP correlated weakly but positively to soil clay content. The slope of the correlation between RIP and clay content showed that the RIP per unit clay was only 4.8 mmol g − 1 clay, about threefold lower than that for clays of European soils, suggesting more amorphous minerals and less micaceous minerals in the clay fraction of Japanese soils. The negative correlation between RIP and soil organic matter may indicate that organic matter can mask highly selective sorption sites to RCs. Multiple regression analysis with soil organic matter and cation exchange capacity explained the soil RIP ( R 2 = 0.64), allowing us to map soil RIP based on existing soil map information. [ABSTRACT FROM AUTHOR]