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Releases of coal combustion and nuclear fission wastes create contaminated landscapes that pose long-term management challenges. Efforts to facilitate the natural attenuation of legacy wastes in the environment can provide attractive habitat for passerine birds. Passerines have diverse foraging and nesting behaviors that lead to heterogenous contaminant exposure, yet few studies investigate contaminant uptake in passerines on a community scale. This study evaluated whether variation in habitat use strategies among passerines predicted the ongoing uptake of waste-derived elements by birds inhabiting coal combustion and nuclear fission legacy waste areas on the Savannah River Site in South Carolina. Blood concentrations of selenium, arsenic, mercury, zinc, copper, and lead were measured in 362 birds from 35 species. Whole-body radioactivity concentrations due to cesium-137 were measured in vivo in 143 birds from 31 species using a novel, field-based gamma spectrometry system. Generalized linear mixed effects models were used to evaluate whether trophic category and degree of terrestriality predicted contaminant burdens among passerine communities. Selenium, mercury, arsenic, and cesium-137 were elevated in passerines inhabiting legacy waste sites compared to those at reference sites. Blood concentrations of selenium and mercury varied by trophic category, whereas arsenic and cesium-137 increased with degree of terrestriality. The behavioral correlates of contaminant uptake among passerines provide insight into the mobility of waste-derived elements in ecosystems and inform species-level risk assessments. Future studies should use in vivo gamma spectrometry to conduct long-term field studies that evaluate the effects of internal radiation in small-bodied wildlife., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The presence of the long-lived radionuclides 137 Cs and 90 Sr in ecosystems is a major environmental concern because bioavailable forms of the radionuclides are readily transferred to living organisms. The present study investigated how holometabolous insect development influences the fate of radiocaesium and radiostrontium by examining the behaviour of tracers ( 134 Cs and 84 Sr) and stable elements during the larval feeding stage (21-23 days old), the pupal stage, and the adult stage. We aimed to evaluate the degree to which an herbivore or a detritivore food chain could serve as transfer pathways to higher trophic levels in terms of accumulation potential, and during which stage of development the accumulation potential is highest. We used the Cabbage butterfly (Pieris brassicae) and the Black soldier fly (Hermetia illucens) as model insects in the herbivore food chain and the detritivore food chain, respectively. Both food chains showed similar patterns of radiocaesium transfer to the larvae, with concentration ratios of 0.26 to 1.15. Radiocaesium levels then gradually decreased during the transition from larva to adult. We also found strontium in the larvae of both model insects. However, while the transfer to P. brassicae was low and the majority of retained strontium was removed prior to the pupal stage, we found that strontium biomagnified in H. illucens larvae and pupae, showing high accumulation potentials. Overall, our results suggest that radiocaesium transfer to terrestrial holometabolous insects is predominantly determined by radiocaesium levels in their diet, whereas radiostrontium transfer is influenced by the insects' dietary need for calcium and the concentration of calcium in the diet., Competing Interests: Declaration of competing interest The authors declare that they have no competing interests., (Copyright © 2025 The Authors. Published by Elsevier B.V. All rights reserved.)

This study was conducted to elucidate the spatial and size variations, and food-web transfer of 137 Cs in freshwater fish in the upper reaches of the Ukedo River system, a highly contaminated river system flowing through the Fukushima evacuation zone. Fish collection and environmental surveys were conducted in the summer of 2020 at five forest rivers and at the Ogaki Dam reservoir (an artificial lake) with different air dose rates (mean 0.20-3.32 μSv/h). From the river sites, two salmonid species (masu salmon and white-spotted charr) were sampled, with masu salmon generally exhibiting higher 137 Cs concentrations, ranging widely (10.6 Bq/kg-wet to 13.0 kBq/kg-wet) depending on the fish size (size effect) and site. The 137 Cs concentrations in masu salmon were explained by the air dose rates, 137 Cs concentrations in water, sediments (excluding the lake site), and primary producers, with site-specific variations. In the rivers, masu salmon (fluvial type with parr marks) mainly fed on terrestrial insects with higher 137 Cs concentrations compared with those of aquatic insects, indicating that 137 Cs was transferred mainly to fish through the allochthonous forest food-web during summer. In the lake, masu salmon (lake-run type with larger size and silvery body coloration) mainly preyed on smaller fish with lower 137 Cs concentrations, demonstrating that 137 Cs is transferred to fish through the autochthonous lake food-web with biomagnification. Differences in  137 Cs concentrations among masu salmon (mean 441 Bq/kg-wet) and other fish species (mean 74.8 Bq/kg-wet to 2.35 kBq/kg-wet) were also found in the lake. The distinct 137 Cs transfers to river and lake fish were supported by stable isotope analysis: δ 15 N and δ 13 C values enriched stepwisely through the food-webs were, respectively, higher and lower in the lake. Our results obtained using multiple approaches clearly revealed the distinct food-web transfer of 137 Cs in river and lake ecosystems. These findings can contribute to prediction of radioactive contamination in freshwater fish in the Fukushima evacuation zone., Competing Interests: Declaration of competing interest The authors declare no conflicts of interest associated with this manuscript., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

A numerical model which simulates the adsorption of radionuclides by migrating bluefin tuna in the Mediterranean Sea is described, in order to determine the level of contamination of these fish after a hypothetical nuclear accident and thus be able to assess the possible impact on human consumption. A 4-species foodweb model is incorporated into a Lagrangian model describing physical transport (advection, mixing, radioactive decay and interactions of radionuclides with sediments). Tuna is the last trophic level in the foodweb model and the equation providing the temporal evolution of radionuclide concentration in its flesh is solved along the fish trajectories, which were obtained through electronic tagging of fishes. The model was applied to the western Mediterranean, where several worst-case hypothetical accidents were simulated, both from a coastal nuclear power plant and from a vessel. Resulting 137 Cs concentrations in migrating tuna were similar, or slightly higher, than reported background concentrations in these fishes and well below established safety levels. Maximum calculated concentrations in tuna flesh is in the order of 1 Bq/kg (wet weight). This is due to the rapid movement of the fishes, which spend only limited time over the most contaminated spots., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Following the Fukushima Daiichi Nuclear Power Plant accident in 2011, most of the released 137Cs remained in the litter and surface soil of the adjacent forest floor. However, 137Cs absorption by large soil invertebrates near this site has not been estimated. The aim of this study was to understand the role of soil macroinvertebrates in 137Cs uptake from forest litter into forest ecosystems. Breeding experiments were conducted using scarab beetle larvae (Protaetia orientalis). Dissection experiments revealed that 85% of the total 137Cs was concentrated in the digestive tract of larvae, while a low proportion was absorbed into the skin and muscle tissues. The 137Cs absorption rate, indicating the transfer of 137Cs from consumed litter to larval tissue, was low (0.39%). 137Cs concentrations decreased to one-fourth from larva to imago, possibly due to excretion from the digestive tract and during eclosion. In the elimination experiment, biological half-lives were 0.26-0.64 and 0.11-0.47 days and 3.35-48.30 and 4.01-17.70 days for the digestive tract and muscle/skin tissues in the fast and slow components, respectively, corresponding to 137Cs discharge from the gastrointestinal tract and physiological clearance. In the sequential extraction experiment, litter digestion by flower chafer larvae significantly reduced the bioavailable fraction of 137Cs including water-soluble, exchangeable, oxidized, and organic forms, from 23.2% in litter to 17.7% in feces. Residual 137Cs was not reduced by digestion, probably because it was fixed in soil clay. Our study on breeding experiments of the Scarabaeidae beetle confirmed the low bioavailability of 137Cs in the litter in Fukushima. However, litter feeders may play an important role in transferring 137Cs to higher trophic levels in the forest ecosystem by extracting the bioavailable fraction of the vast stock of 137Cs on the forest floor., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Jo et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

The present work documents potassium ferric hexacyanoferrate (KFCF) KFe[Fe(CN) 6 ] containing feed to be an effective and inexpensive countermeasure to reduce the 137 Cs contamination of fish. Laboratory aquarium experiments were performed to investigate the effect of feed containing potassium ferric hexacyanoferrate on 137 Cs uptake and excretion by silver Prussian carp (Carassius gibelio (Bloch, 1782)). After the 120-day period of 137 Cs uptake with feed, reaching equilibrium 137 Cs level in fish, fish in some aquariums received feeds containing either 0.1 % or 1 % KFCF for 180 days in combination with clean feed or with feed containing 137 Cs. These feeds resulted in 3.6 ± 0.7 and 4.4 ± 0.9 times, respectively, lower activity of 137 Cs in fish compared to control fish fed 137 Cs throughout the experiment and receiving feed without KFCF. Following the first 100 days with the KFCF containing feed, the 137 Cs level in fish fed contaminated feed was even lower than in fish receiving clean feed, with a half-life of 137 Cs activity in fish of only T 1/2  = 23-35 days. Using clean feed containing 0 %, 0.1 % and 1 % KFCF for 180 days after the 120-day 137 Cs uptake period, the excretion rates for 137 Cs activity in fish k b ' were (6.4 ± 0.2)⋅10 -3 day -1 , (1.08 ± 0.08)⋅10 -2 day -1 , and (1.3 ± 0.1)⋅10 -2 day -1 , respectively (T 1/2  = 108 ± 3 days, 64 ± 5 days, and 53 ± 4 days). The decrease rates for 137 Cs activity concentrations in fish k b were (8.4 ± 0.3)⋅10 -3 day -1 , (1.3 ± 0.1)⋅10 -2 day -1 , and (1.5 ± 0.1)⋅10 -2 day -1 , respectively (T 1/2  = 83 ± 3 days, 53 ± 4 days, and 46 ± 3 days). Our results demonstrate a statistically significant effect (p < 0.01) of KFCF on the excretion of 137 Cs from silver Prussian carp: T 1/2 decreased from 108 days with clean feeding to 53-64 days when KFCF is added., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Norway's Centre of Excellence for Environmental Radioactivity (CERAD) research programme included studies on transfer of radionuclides in various ecosystems within the context of environmental risk assessment. This article provides highlights from 10 years of research within this topic and summarises lessons learnt from the process. The scope has been extensive, involving laboratory-based experiments, field studies and the implementation of transfer models quantifying radionuclide uptake directly from the surrounding environment and via food chains. Field studies have had a global span and have, inter alia, covered sites contaminated with radionuclides associated with particles, ranging from nanoparticles to fragments, due to nuclear accidents (e.g., Chornobyl and Fukushima accidents) along with sites having enhanced levels of naturally occurring radioactive materials (e.g., Fen Complex in Norway and Taboshar in Tajikistan). Focus has been put on speciation and kinetics in determining radionuclide behavior and fate as well as on the influence of environmental factors that are potentially critical for the transfer of radionuclides. In particular, seasonal factors have been shown to greatly affect the dynamics of 137 Cs and 90 Sr bioaccumulation and loss in freshwater fish. The work has led to the collation of organism-specific (i) parameters important for kinetic models, i.e., uptake and depuration rates, and (ii) steady-state concentration ratios, CRs, where the use of stable analogue CRs as proxies for radionuclides has been brought into question. Dynamic models have been developed and applied for radiocaesium transfer to reindeer, radionuclide transfer in Arctic marine systems, transfer to fish via water and feed and commonly used agricultural food-chain transfer models applied in the context of nuclear emergency preparedness. The CERAD programme should contribute substantially to the scientific community's understanding of radionuclide transfer in environmental systems., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

In the long-term after atmospheric deposit onto a forest ecosystem, Cs-137 becomes incorporated into the biogeochemical cycle of stable elements and progressively reaches a quasi-equilibrium state. This study aimed at determining to what extent Cs-137 activity distribution in tree vegetation could be predicted from that of stable caesium (Cs-133) and potassium (K), which are known to be stable chemical analogues and competitors for Cs-137 intake in tree organs. Field campaigns that focused on beech trees (Fagus sylvatica L.) were conducted in 2021 in three French forest stands with contrasted characteristics regarding either the contribution of global vs. Chornobyl fallouts, soil or climatic conditions. Decades after Cs-137 fallouts, it was found that more than 80% of the total radioactive inventory in the system remained confined in the top 20 cm mineral layers, while organic layers and beech vegetation (including roots) contributed each to less than 1.5%. The enhanced downward migration of Cs-137 in cambisol than podzol forest sites was presumably due to migration of clay particles and bioturbation. The distribution of Cs-137 and Cs-133 inventories in beech trees was very similar among sites but differed from that of K due a higher accumulation of Cs isotopes in roots (40-50% vs. < 25% for K). The aggregated transfer factor (Tag) of Cs-137 calculated for aerial beech organs were all lower than those reported in literature more than 20 years ago, this suggesting a decrease of bioavailability in soil due to ageing processes. Regarding their variability, Tags were generally lower by a factor 5 at the cambisol site, which was fairly well explained by a much higher value of RIP (radiocesium immobilisation potential). Cs-137 concentrations in trees organs normalized by the soil exchangeable fractions were linearly correlated to those of Cs-133 and the best fit was found for the linear regression model without intercept indicating that no more contribution of the foliar uptake could be observed on long term. Provided that the vertical distribution of caesium concentrations and fine root density are properly measured or estimated, Cs-133 was shown to be a much better proxy than K to estimate the root transfer of Cs-137., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

This comprehensive review examines recent trends in phytoremediation strategies to address soil radionuclide contamination by cesium (Cs) and strontium (Sr). Radionuclide contamination, resulting from natural processes and nuclear-related activities such as accidents and the operation of nuclear facilities, poses significant risks to the environment and human health. Cs and Sr, prominent radionuclides involved in nuclear accidents, exhibit chemical properties that contribute to their toxicity, including easy uptake, high solubility, and long half-lives. Phytoremediation is emerging as a promising and environmentally friendly approach to mitigate radionuclide contamination by exploiting the ability of plants to extract toxic elements from soil and water. This review focuses specifically on the removal of 90 Sr and 137 Cs, addressing their health risks and environmental implications. Understanding the mechanisms governing plant uptake of radionuclides is critical and is influenced by factors such as plant species, soil texture, and physicochemical properties. Phytoremediation not only addresses immediate contamination challenges but also provides long-term benefits for ecosystem restoration and sustainable development. By improving soil health, biodiversity, and ecosystem resilience, phytoremediation is in line with global sustainability goals and environmental protection initiatives. This review aims to provide insights into effective strategies for mitigating environmental hazards associated with radionuclide contamination and to highlight the importance of phytoremediation in environmental remediation efforts., Competing Interests: Declaration of competing interest The authors declare that they have no conflicts of interest regarding the publication of this review article., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

In our previous study, the decontamination efficiency of cesium-137 ( 137 Cs) by Napier grass (Pennisetum purpureum Schum.) in the field was shown to be variable and often influenced by natural environmental factors. To elucidate the factors influencing this variable 137 Cs-decontamination efficiency, we investigated the influences of soil type and drought stress on Cs accumulation using cesium-133 ( 133 Cs) in Napier grass grown in plastic containers. The experiment was performed using two soil types (Soil A and B) and three different soil moisture conditions: well-watered control (CL), slight drought stress (SD), and moderate drought stress (MD). Overall, our results indicate that soil type and drought have a significant impact on plant growth and 133 Cs accumulation in Napier grass. Plant height (PH), tiller number (TN), leaf width (W leaf ), and dry matter weight of aboveground parts (DW above ) and root parts (DW root ) in Soil B were greater than those in Soil A. Drought stress negatively affected chlorophyll fluorescence parameters (maximal quantum efficiency of photosystem (PS) II photochemistry and potential activity of PS II), PH, TN, W leaf , DW above , DW root , and total 133 Cs content (TCs), but it had a positive effect on 133 Cs concentration. The 133 Cs concentration in the aboveground parts (Cs above ) was increased by MD approximately 1.62-fold in Soil A and 1.11-fold in Soil B compared to each CL counterpart. The TCs in the aboveground parts (TCs above ) decreased due to drought by approximately 19.9%-39.0% in Soil A and 49.9%-62.7% in Soil B; however, there was no significant effect on TCs above due to soil type. The results of this study indicate that soil moisture is a key factor in maintaining Napier grass 137 Cs-decontamination efficiency., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

To follow up field observations in the Chornobyl Exclusion Zone (ChEZ), a series of controlled model aquarium experiments were conducted to determine the uptake and depuration rates of 137 Cs and 90 Sr in silver Prussian carp (Carassius gibelio) in fresh water, varying in temperature from 5 to 27 °C, with daily feeding rates of 0-1.5 % fish weight day -1 . In the present study, the 137 Cs uptake rates in muscle tissues directly from water, 0.05-0.09 day -1  at temperatures of 5-27 °C, were significantly lower than previously reported for fish fed under natural conditions in contaminated lakes within the ChEZ. The rate of 90 Sr uptake in bone tissues of silver Prussian carp varied from 0.055 day -1  at a water temperature of 5 °C and feeding rates ≤0.15 % fish weight day -1 to 1.5 ± 0.2 day -1  at a temperature of 27 ± 1 °С and at the highest tested feeding rate of 1.5 % day -1 . The rate of decrease of 137 Cs concentration in muscle tissues was k b  = 0.0028 ± 0.0004 day -1 (T 1/2  = 248 ± 35 days) at the lowest water temperature tested (5 °С). At water temperatures between 13 and 26 °С and a feeding rate of 0.15 % day -1 , the rate increased to k b  = 0.0071-0.0092 day -1 (T 1/2  = 75-99 days). The rates of decrease of 90 Sr activity concentration in bone tissues at water temperatures between 22 and 25 °С and a feeding rate of 0.5 % day -1 were k b =0.004-0.0014 day -1 , and the associated biological half-life T 1/2 ranged 50-160 days, respectively. The present work supported conclusions related to the main pathways of 137 Cs and 90 Sr uptake by silver Prussian carp, and demonstrated the usefulness of combining field and laboratory uptake and depuration experiments., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Many patients treated for head and neck cancers experience salivary gland hypofunction due to radiation damage. Understanding the mechanisms of cellular damage induced by radiation treatment is important in order to design methods of radioprotection. In addition, it is crucial to recognize the indirect effects of irradiation and the systemic responses that may alter saliva secretion. In this study, radiation was delivered to murine submandibular glands (SMGs) bilaterally, using a 137Cs gamma ray irradiator, or unilaterally, using a small-animal radiation research platform (SARRP). Analysis at 3, 24 and 48 h showed dynamic changes in mRNA and protein expression in SMGs irradiated bilaterally. Unilateral irradiation using the SARRP caused similar changes in the irradiated SMGs, as well as significant off-target, bystander effects in the non-irradiated contralateral SMGs., Competing Interests: Competing interests The authors declare no competing or financial interests., (© 2022. Published by The Company of Biologists Ltd.)

Bioaccumulation studies of Zn and 137 Cs by the horse mussel (Modiolus micropterus) were conducted in a laboratory that used radiotracer. The study has been carried out on the effect of cesium and zinc concentrations and the effect of sea seawater salinity on the ability of M. micropterus to accumulate these two contaminants. The uptake of Zn and Cs according to the one-compartment model and the experiment was carried out until the steady-state conditions were reached. The concentration factor at steady-state Zn is 31.94-45.54 mL. g -1 and 23.22-33.26 mL. g -1 which are influenced by the concentration and salinity of seawater, respectively. The concentration factor of 137 Cs at steady-state conditions due to changes in concentration and salinity is 3.34-7.55 mL. g -1 and 4.23-9.66 mL. g -1 , respectively. The release rates of Zn were 30-47 % and 39-49 % at various concentrations and salinity. The depuration rate from concentration reaching 60 % and salinity at ranges 43-52 % was observed within 10 days after exposure. On the other hand, the release rates of 137 Cs were 60 % and 43-52 % at various changes in the concentration and salinity of seawater., (Copyright © 2021. Published by Elsevier B.V.)

Large quantities of radionuclides released by the Fukushima nuclear power plant accident entered terrestrial and marine ecosystems. The resulting radioactive contamination of large omnivorous wild mammals such as wild boar (Sus scrofa) and Asian black bear (Ursus thibetanus) varied greatly depending on location, season, and time after the accident. Quantitative modeling of how such factors influence radionuclide burdens in these species is important for enhancing current knowledge of chronic radionuclide exposure consequences in mammalian populations, and for assessing potential human risks from consumption of contaminated animal meat. Here we modeled the time course of radioactive cesium ( 134 Cs +  137 Cs) concentrations in boar and black bears from Fukushima Prefecture over ~ 7 years after the accident, using nonlinear robust and quantile regressions and mixed-effects modeling. To estimate predictive performance, models fitted to the full data set were compared with those fitted only to the first 3.5 years of data, and tested on the last 3.5 years of data. Ecological half-lives for radioactive cesium, and magnitudes and phase shifts for sinusoidal seasonal oscillations in cesium burdens, were estimated by each analysis method for each species. These results can improve the understanding and prediction of radionuclide concentrations in large mammals that inhabit radioactively contaminated areas.

137 Cs is a long-lived (30-year radioactive half-life) fission product dispersed globally by mid-20th century atmospheric nuclear weapons testing. Here we show that vegetation thousands of kilometers from testing sites continues to cycle 137 Cs because it mimics potassium, and consequently, bees magnify this radionuclide in honey. There were no atmospheric weapons tests in the eastern United States, but most honey here has detectable 137 Cs at >0.03 Bq kg -1 , and in the southeastern U.S., activities can be >500 times higher. By measuring honey, we show regional patterns in the biogeochemical cycling of 137 Cs and conclude that plants and animals receive disproportionally high exposure to ionizing radiation from 137 Cs in low potassium soils. In several cases, the presence of 137 Cs more than doubled the ionizing radiation from gamma and x-rays in the honey, indicating that despite its radioactive half-life, the environmental legacy of regional 137 Cs pollution can persist for more than six decades.

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.

A historic data set containing unpublished measurements of 137 Cs (radiocesium) in 238 pooled samples of pectoral muscle from 1892 birds representing 37 species was analyzed in order to determine if (i) birds were contaminated due to global weapons fallout and/or the Chernobyl accident, (ii) to understand baseline 137 Cs levels in birds across the country by examining potential effects of trophic position and geophysical region, and (iii) to determine if the harvested birds were safe to eat. Current work is taking advantage of this data set to improve capabilities to assess the impacts of releases of radionuclides on food chains of species harvested as country food. Samples obtained from 173 locations across Canada (including locations in the Arctic), mostly during the fall hunting seasons between 1989 and 1995, were analyzed by gamma spectrometry and decay-corrected for the date of collection. Various methods of correlating measurements with environmental 137 Cs levels and species' habits were explored in order to determine environmental radiological transfer factors. All 137 Cs measurements in the samples were much lower than the Health Canada (2018) guidance level for 137 Cs (1000 Bq kg -1 ); therefore, there was no evidence of a human health risk with respect to radiocesium. Environmental transfer factors for six different foraging groups were determined., (Crown Copyright © 2020. Published by Elsevier Ltd. All rights reserved.)

Since the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident, morphological abnormalities in lepidopteran insects, such as shrinkage and/or aberration of wings, have been reported. Butterflies experimentally exposed to radiocesium also show such abnormalities. However, because of a lack of data on absorbed dose and dose-effect relationship, it is unclear whether these abnormalities are caused directly by radiation. We conducted a low dose-rate exposure experiment in silkworms reared from egg to fully developed larvae on a 137 CsCl-supplemented artificial diet and estimated the absorbed dose to evaluate morphological abnormalities in pupal wings. We used 137 CsCl at 1.3 × 10 3  Bq/g fresh weight to simulate 137 Cs contamination around the FDNPP. Absorbed doses were estimated using a glass rod dosimeter and Monte Carlo particle transport simulation code PHITS. Average external absorbed doses were approximately 0.24 (on diet) and 0.016 mGy/day (near diet); the average internal absorbed dose was approximately 0.82 mGy/day. Pupal wing structure is sensitive to radiation exposure. However, no significant differences were observed in the wing-to-whole body ratio of pupae between the 137 CsCl-exposure and control groups. These results suggest that silkworms are insensitive to low dose-rate exposure due to chronic ingestion of high 137 Cs at a high concentration.

The objective of this study was to determine the radiocesium transfer rates of pigs fed haylage contaminated with low levels of cesium at different growth stages. We measured the body weight of juvenile and adult pigs during the treatment period to confirm their health status. We also performed pig blood hematologic and biochemical analyses at both growth stages. To our knowledge, this is the first study to report pig radiocesium transfer coefficient rates after 1 month of chronic oral treatment, which is the period assumed to be required for body equilibrium under a diet of radiocesium-contaminated food. The results showed higher radiocesium retention rates in the kidneys, liver, spleen, genitals, psoas major, bladder, thyroid, and urine than in the blood and bone (tibia and femur) of pigs at both growth stages. The radiocesium retention levels were generally higher in juvenile pigs than in adult pigs, with the highest transfer coefficient ratio in the kidneys (16.2%)., Competing Interests: The funding of "Japan Racing Association", the project leader is our colleague, same laboratory. I am a member of this project. The present research used pocH-100iV Diff hematology analyzer (Sysmex, Hyogo, Japan) for hematological parameters analyze, and using a DRI-CHEM 3500s (Fujifilm, Japan) did blood biochemistry analyze. Both of which was purchased by above grant. But present research mainly done by the grant of “Japan Society for the Promotion of Science KAKENHI Grant-in-Aid for Scientific Research (C) (no. JP25517004)”. I am the leader of this project. The corresponding author, on behalf of all authors declare no competing interests associated with this manuscript. This does not alter our adherence to PLOS ONE policies on sharing data and materials.

Data on the transfer of artificial radionuclides from the environment to the food supply is necessary for internal dose assessment. There is a necessity for expanding and improving the available information on these factors in order to make better dose models for specific scenarios. This paper describes the results of a field experiment with broiler chickens on the transfer factor (Ff) and concentration ratio (CR) for the long-term intake of 241Am and 137Cs with grass meal and soil. The broilers were divided into two groups, each group had nine subgroups and each subgroup had three broilers. The radionuclide concentrations in the feed and the thigh muscle, thigh bone, and liver of 54 broilers divided between the grass meal and soil groups were evaluated by gamma spectrometry for 241Am and 137Cs. The duration of feeding with "contaminated" sources ranged between 1-70 days. The equilibrium stage of 241Am in muscle and bone occurs on the 1st and 40th day, respectively; for 137Cs in muscle- 30th days of intake and for liver and bone- 7th days. For 241Am, the liver did not reach equilibrium stage during the 70 days of intake. Ff of 137Cs in the "forage-muscle" and "soil-muscle" systems were determined as 1.9±0.3 and 0.18±0.05; Ff of 241Am in the "soil-muscle" system was-7.5×10-5., Competing Interests: The authors have declared that no competing interests exist.

After the accident at the TEPCO Fukushima Daiichi Nuclear Power Plant in 2011, it became important to study radiation dynamics, assess internal radiation exposure and specify factors affecting radionuclide variation in wildlife. Therefore, it is necessary to investigate which physicochemical fractions of radiocaesium ( 137 Cs) are absorbed from ingested material in species with high activity concentrations of 137 Cs, such as wild boar. This study analysed the physicochemical fractions of 137 Cs in the stomach contents of wild boar to evaluate the transfer from ingested food to muscle. The 137 Cs activity concentration in muscle showed a significantly positive relationship with the 137 Cs activity concentration in the exchangeable fraction, and the sum of the 137 Cs activity concentrations in the exchangeable and bound to organic matter fractions. Seasonal variations were also found in the 137 Cs activity concentration in the exchangeable fraction, and the sum of the 137 Cs activity concentrations in the exchangeable and bound to organic matter fractions. These findings suggest that the proportions of the physicochemical fractions of 137 Cs in the exchangeable and bound to organic matter fractions in the stomach contents are important factors affecting the increases and seasonal dynamics of the activity concentrations of 137 Cs in wild boar muscle.

Objectives: Following the massive earthquake that struck eastern Japan on March 11, 2011, a large amount of radioactive material was released into the environment from the damaged reactor of the Fukushima Daiichi Nuclear Power Plant (FDNPP). After the FDNPP accident, radiocaesium was first detected in muscle samples from wild Japanese monkeys exposed to radioactive materials, and haematologic effects, changes in head size, and delayed body weight gain were also reported, but little is known about the distribution of 137 Cs in the organs and tissues of wild Japanese monkeys., Results: We detected the 137 Cs in various organ and tissue samples of 10 wild Japanese monkeys inhabiting the forested areas of Fukushima City that were captured between July and August 2012. Among muscle, brain, heart, kidney, liver, lung, and spleen, muscle exhibited the highest and the brain the lowest 137 Cs concentration. The concentration (mean ± SD) of 137 Cs in muscle, brain, heart, kidney, liver, lung, and spleen was 77 ± 66, 26 ± 22, 41 ± 35, 49 ± 41, 41 ± 38, 53 ± 41, and 53 ± 51 Bq/kg, respectively. These results can help us understand the biological effects of long-term internal radiation exposure in non-human primates.

Decreasing the transfer of radioactive cesium (RCs) from soil to crops has been important since the deposition of RCs in agricultural soil owing to the Fukushima nuclear power plant accident of 2011. We investigated the genotypic variation in RCs accumulation in 234 and 198 hexaploid wheat (Triticum spp.) varieties in an affected field in 2012 and 2013, respectively. The effects of soil exchangeable potassium (ExK) content to RCs accumulation in wheat varieties were also evaluated. A test field showed fourfold differences in soil ExK contents based on location, and the wheat varieties grown in areas with lower soil ExK contents tended to have higher grain RCs concentrations. RCs concentrations of shoots, when corrected by the soil ExK content, were positively significantly correlated between years, and RCs concentrations of shoots were significantly correlated with the grain RCs concentration corrected by the soil ExK content. These results indicated that there were genotypic variations in RCs accumulation. The grain to shoot ratio of RCs also showed significant genotypic variation. Wheat varieties with low RCs accumulations were identified. They could contribute to the research and breeding of low RCs accumulating wheat and to agricultural production in the area affected by RCs deposition.

Radiocesium contamination of forests has been a severe problem after the Fukushima Daiichi Nuclear Power Plant accident in 2011. Bed logs of Konara oak (Quercus serrata Murray), used for mushroom cultivation, were an economically important product from the forests prior to their contamination. One of the potential countermeasures to reduce radiocesium content in trees is potassium fertilization, but the evidence for the effect of K + in reducing Cs + uptake has not been obtained yet in the woody plant. Therefore, we investigated the ability of rhizospheric K + to suppress uptake and translocation of Cs + in Konara oak seedlings through hydroponic experiments in order to clarify the effect of K + . Elemental analysis showed that the seedlings cultivated for 4 weeks under low-K (K +  = 50 μM) contained higher amount of Cs comparing to the seedlings cultivated under high-K (K +  = 3 mM). Then, the uptake rate of Cs + and K + in the seedlings from the solution having 50 μM K + and 0.1 μM Cs + was calculated using radioactive 137 Cs + and 42 K + to evaluate the effect of growth condition on the ion uptake mechanism. The interference between Cs + and K + at the site of root uptake was also evaluated based on the Cs + and K + uptake rates at K + concentrations of 50 μM, 200 μM, and 3 mM in the seedlings grown under the medium-K (K +  = 200 μM) condition. As a result, the Cs + uptake rate at 50 μM K + was not influenced by the growth condition, whereas Cs + uptake decreased when the uptake solution itself was supplemented with 3 mM K + . In addition, the Cs/K ratio in the seedlings was found to rise to exceed the Cs/K ratio in the culture solution as the rhizospheric K + concentration increased, which was in contrast with previous findings in herbaceous plants. Our experiments demonstrated the first direct evidence for woody plants that a high K + concentration can suppress Cs accumulation in Konara oak and that it was derived from competition for uptake between K + and Cs + in the rhizosphere, not from the growth K + condition., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

The accident at the Fukushima Dai-ichi Nuclear Power Plant in 2011 released a large quantity of radiocesium into the surrounding environment. Radiocesium concentrations in some freshwater fish caught in rivers in Fukushima Prefecture in October 2018 were still higher than the Japanese limit of 100 Bq kg -1 for general foodstuffs. To assess the uptake of 137 Cs by freshwater fish living in mountain streams in Fukushima Prefecture, we developed a compartment model for the migration of 137 Cs on the catchment scale from forests to river water. We modelled a generic forest catchment with Fukushima-like parameters to ascertain the importance of three export pathways of 137 Cs from forests to river water for the uptake of 137 Cs by freshwater fish. The pathways were direct litter fall into rivers, lateral inflow from the forest litter layer, and lateral transfer from the underlying forest soil. Simulation cases modelling only a single export pathway did not reproduce the actual trend of 137 Cs concentrations in river water and freshwater fish in Fukushima Prefecture. Simulations allowing a combined effect of the three pathways reproduced the trends well. In the latter simulations, the decreasing trend of 137 Cs in river water and freshwater fish was due to a combination of the decreasing trend in the forest leaves/needles and litter compartments, and the increasing trend in soil. The modelled 137 Cs concentrations within the forest compartments were predicted to reach an equilibrium state at around ten years after the fallout due to the equilibration of 137 Cs cycling in forests. The model suggests that long term 137 Cs concentrations in freshwater fish in mountain streams will be controlled by the transfer of 137 Cs to river water from forest organic soils., (Copyright © 2019 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Models and approaches have been developed to predict radiation exposure of wildlife under field conditions. However, there have been few attempts to directly measure radiation exposure of wildlife in the field and confirm the doses predicted by models. This is a potential issue for stakeholder acceptance of modelling-based assessments. Here is presented a comprehensive study comparing the results of different dosimeters fitted to free-ranging reindeer inhabiting an area that received comparatively high radiocaesium deposition from the 1986 Chernobyl accident. The external dose of reindeer was measured using the four dosimeter types in aluminium box mounted on the GPS collar. The measurements were compared with two model predictions: (i) external dose to reindeer across the entire range area of the herd; and (ii) external doses of individual reindeer predicted using GPS tracking data to determine locations. It was found that although significant differences between the estimates of the various dosimeters were found these were small with no practical implication. Also, the mean predicted external doses using the GPS tracking data were not significantly different to estimates from two of the four passive dosimeter results. The average external dose predicted across the herd area was significantly lower than doses recorded by the dosimeters and also estimates using GPS data to determine reindeer location (and hence exposure). For 137 Cs the average external dose from the GPS tracking data was about twice that predicted across the herd area, because collared animals favoured the more contaminated area of the study site. This suggests that in some circumstances the assumption of averaging contamination over an assumed home range within assessments may be inadequate though this would need to be balanced against other uncertainties. Natural radiation was the greatest contribution to reindeer exposure and a function of the high altitude., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Norway is one of the main producers of farmed fish and the world's second-largest exporter of seafood. Farmed Atlantic salmon (Salmo salar) represents the most exported species. This is the first comprehensive survey of anthropogenic ( 137 Cs, 90 Sr, 238 Pu, 239,240 Pu and 241 Am) and natural ( 40 K, 226 Ra, 228 Ra, 210 Pb, 210 Po) radionuclides in farmed salmon and manufactured fish feed from Norway. The only anthropogenic radionuclide detected in salmon and fish feed was 137 Cs. The levels were low with arithmetic means in salmon and feed of 0.13 and 0.30 Bq/kg fresh weight (fw), respectively. The natural radionuclide 40 K exhibited the highest levels with arithmetic means in salmon and feed of 115 and 239 Bq/kg fw, respectively. The arithmetic means of 210 Po and 210 Pb in salmon were 0.013 and 0.044 Bq/kg fw, respectively, with a mean 210 Po: 210 Pb activity ratio of 0.32. For fish feed, the situation was reversed: the arithmetic means of 210 Po and 210 Pb were 3.8 and 0.67 Bq/kg fw, respectively, with a mean 210 Po: 210 Pb activity ratio of 5.7. The radionuclide levels found in farmed salmon in the present study are comparable to or lower than the levels found in other fish species in the North Atlantic Ocean. A highly conservative dose estimate for consumption showed that doses were no higher than 1.2 μSv/year for toddlers and 4.0 μSv/year for adults. This suggests that the risk associated with radioactivity in farmed salmon is very low even when considering individuals with high consumption and the highest radionuclide levels found in this study., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

A proper understanding of radioactive contamination levels of food resources near the Fukushima Dai-ichi Nuclear Power Plant is necessary to estimate the potential effects of radionuclide contamination on human health. This study was conducted to present a direct comparison of radiocesium ( 134 Cs and 137 Cs) concentrations in marine and freshwater fish inhabiting different water bodies in Fukushima Prefecture (coastal waters, 6.3-54.5 km from the plant; forest rivers and irrigation ponds, 1.4-71.6 km), and to reveal plausible contamination mechanisms for each habitat. In contrast to marine demersal fish (7 species, n = 50), which showed lower and less variable radiocesium concentrations (0.234-3.41 Bq kg -1 -wet), freshwater fish (6 species, n = 463) showed higher and more site-specific variations for each species and habitat (4.09 Bq kg -1 -wet - 25.6 kBq kg -1 -wet) in 2015-2016. The apparent concentration ratio (aCR, L/kg) of 137 Cs in fish to water is higher for fish of freshwater habitats (mean 1240-12900 for each site) than in those of coastal waters (mean 200). Radiocesium contamination is more severe and persistent in freshwater fish, especially those distributed within the designated evacuation zone (salmon in rivers and bass in ponds). Continuous radiocesium uptake through the food web in relation to fish feeding habits and size (size effect), and biotic/abiotic characteristics in water and surrounding environments are main factors affecting site/habitat-specific bioaccumulation of radiocesium in freshwater fish. By contrast, uniformly lower radiocesium concentrations in marine demersal fish are mainly attributable to decreased radiocesium transfer intensity from the benthic food web because of lowered radiocesium contamination in sediments, and low physiological ability to retain radiocesium. Our results revealed a strong contrast of radiocesium contamination levels and mechanisms between marine and freshwater fish in natural habitats. Particularly, a close relation between 137 Cs accumulation in river salmon and contamination of prey items in forest ecosystems (mainly terrestrial and aquatic insects) is peculiar to the upstream areas affected by the Fukushima accident., (Copyright © 2019 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Concentration ratios (CRs), expressed by dividing 137 Cs activity in seawater by that in marine biota (mainly fish), were obtained from the monitoring of 137 Cs in coastal areas around Japan between 1984 and 2016. Before the TEPCO Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident (1984-2010), mean CRs of 137 Cs, mainly from global fallout (i.e. CR GF ), were almost constant for each species throughout the monitoring period, but were different among species, while the values for several species were dependent on their length (i.e. CR GF-SIZE ). Thus, CR GF and CR GF-SIZE values for 29 of marketable species are given here as references for conditions where marine biota are in approximate equilibrium (or steady state) with their host water with respect to 137 Cs activities in the marine environment. After the FDNPP accident (2011-2016), the impact of the accident has been sustained in eastern Japan waters as indicated by apparent CRs (CR a s) which are being used here as indicators of disequilibrium between organisms and their host water. The recession rates of this disequilibrium (the effective CR a half-lives) ranged from 100 to 1100 days. The identified distinct variation was due to the sample locations, even for the same species, because of the change in 137 Cs activity concentrations in their host water and diet preference differences. Variation among species, even those captured from the same area, was mainly due to diet differences as well as metabolic-physiological differences in 137 Cs retention. Thus, our results from >30 years of systematically monitoring have helped quantify the recession rates of post-FDNPP disequilibrium of 137 Cs in biota for assessment of how long term is required from contaminated condition by underlying spatial, inter- and intra-species factors., (Copyright © 2019 The Authors. Published by Elsevier B.V. All rights reserved.)

As a result of activities such as nuclear weapons testing, nuclear power generation and waste disposal, and nuclear accidents, radiocesium ( 137 Cs) is a widely distributed radio-contaminant of concern that readily accumulates in exposed wildlife. Although bioaccumulation of 137 Cs is an important factor for understanding its fate within the environment, there are currently limited data available on bioaccumulation patterns of 137 Cs in amphibians, despite their widespread distribution and potential to transport contaminants between aquatic and terrestrial ecosystems. Therefore, the objective of this study was to determine the amount of time necessary for anuran larvae experimentally placed in a contaminated system to reach a steady-state whole-body 137 Cs concentration, and to determine the threshold at which that steady-state 137 Cs concentration occurred for tadpoles within our study system. By restricting uncontaminated bullfrog (Lithobates catesbeianus) larvae to three experimental enclosures located along a 137 Cs contaminated effluent canal on the U.S. Department of Energy's Savannah River Site, we modeled 137 Cs uptake through time using the von Bertalanffy modification of the Richards Model. The results of our modified Richards Model indicate that bullfrog tadpoles achieved steady-state 137 Cs concentrations of 3.68-4.34 Bq/g 137 Cs dry whole-body weight after 11.63-15.50 days of exposure among sampling sites, with an average of 3.94 Bq/g after 14.07 days exposure. Radiocesium accumulation in bullfrog tadpoles was more rapid than that reported for other biota studied from other contaminated systems, likely due to incidental ingestion of sediments and a diet consisting of periphyton and other items that accumulate high levels of 137 Cs. Given their rapid accumulation of 137 Cs and inability to leave aquatic environments prior to metamorphosis, our data suggest amphibian larvae may be useful indicators for monitoring 137 Cs distributions and bioavailability within aquatic systems., (Copyright © 2019. Published by Elsevier Ltd.)

The cesium depuration mechanisms were studied in Japanese rockfish Sebastes cheni off Fukushima, in which the radiocesium level remains higher than in other teleost. Samples were collected approximately 5 km south from the nuclear power plant during 2014-2016, and the 137 Cs concentrations in fish, stomach content and prey species were measured. The stable cesium content in fish was also analyzed and compared with fish age which was determined by annual ring analysis in otoliths. The 137 Cs concentrations in the dominant prey species, mysids and brown shrimp, were several Bq kg-w.w. -1 ; indicating that transfer via the food chain was substantial compared to that from seawater during the study period. The 137 Cs concentrations in S. cheni decreased from 2014 to 2016 due to the metabolic excretion and the rate of decrease in its diet. Biokinetic model analyses confirmed the slower turnover of stable cesium in S. cheni, represented as a biological half-life (Tb 1/2 ) of 140-215 d, and was associated with stable Cs levels in food of 5-7 ng g-w.w. -1 . The 137 Cs levels in S. cheni were also simulated, which showed that the 137 Cs depuration in fish exposed to the initial contaminated plume in 2011 resulted from slower metabolic excretion, while the 137 Cs levels in fish born after 2012 could be regarded as equilibrated with the environmental levels of 137 Cs. Furthermore, the simulation results suggest that 137 Cs depuration in S. cheni population was also caused by the alternation of generation, which can be substantial by the addition of new year class population hatched after 2012 that were not contaminated by the initial contaminated plume from the 2011 accident., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

137 Cs bioaccumulation and retention in seven different marine animal species, including crustaceans, mollusc larvae, and fish larvae were compared under different temperature conditions (10 °C, 18 °C and 25 °C). Replicate animals were experimentally exposed to 0.5 nM 137 Cs dissolved in filtered seawater for 3 days, and their 137 Cs contents were periodically measured using gamma spectrometry. Among the seven species, 137 Cs bioconcentration factors ranged from 14 to 239 at the end of the exposure periods. Following uptake, the 137 Cs loss rate constants from the animals ranged from 5 to 50% d -1 and were unaffected by temperature or animal size. The 137 Cs bioconcentration factors were directly related to animal size and hence their surface: volume ratios, consistent with the conclusion that Cs sorption from the aqueous phase is the principal uptake mechanism in these animals. With the exception of gastropods, temperature had no major influence on Cs uptake and efflux in the experimental species., (Copyright © 2019. Published by Elsevier Ltd.)

This study presents levels of 137 Cs and 40 K concentrations in the placentas of seals gathered in the period 2007-2015. The mean activity of 137 Cs and 40 K was 5.49 Bq kg -1 w.w. and 136.6 Bq kg -1 ww respectively. Statistically significant correlation was observed between the 137 Cs activities in placenta and in herring-the staple food for seals. The concentrations of 137 Cs and 40 K were also determined in other tissues (muscle, liver, lung, and brain) of wild seals. The concentrations of 137 Cs were from 2.59 Bq -1 ww (lungs) to 24.3 Bq kg -1 ww (muscles). The transfer factor values for 137 Cs (seal tissue/fish) ranged from 0.89 to 2.42 in the case of the placentas and from 1.35 to 8.17 in the case of the muscle. For adults seal, the effective dose from 137 Cs was 2.98 nGy h -1 . The mean external radiation dose to pup was 0.77 nGy h -1 from 137 Cs and 6.69 nGy h -1 from 40 K.

Numerous radioecological models have been developed to predict radionuclides transfer from contaminated soils to the food chain, which is an essential step in preparing and responding to nuclear emergencies. However, the lessons learned from applying these models to predict radiocaesium (RCs) soil-to-plant transfer following the Fukushima accident in 2011 renewed interest in RCs transfer modelling. To help guide and prioritise further research in relation to modelling RCs transfer in terrestrial environments, we reviewed existing models focussing on transfer to food crops and animal fodders. To facilitate the review process, we categorised existing RCs soil-to-plant transfer models into empirical, semi-mechanistic and mechanistic, though several models cross the boundaries between these categories. The empirical approach predicts RCs transfer to plants based on total RCs concentration in soil and an empirical transfer factor. The semi-mechanistic approach takes into account the influence of soil characteristics such as clay and exchangeable potassium content on RCs transfer. It also uses 'bioavailable' rather than total RCs in soil. The mechanistic approach considers the physical and chemical processes that control RCs distribution and uptake in soil-plant systems including transport in the root zone and root absorption kinetics. Each of these modelling approaches has its advantages and disadvantages. The empirical approach is simple and requires two inputs, but it is often associated with considerably uncertainty due to the large variability in the transfer factor. The semi-mechanistic approach factorises more soil and plant parameters than the empirical approach; therefore, it is applicable to a wider range of environmental conditions. The mechanistic approach is instrumental in understanding RCs mobility and transfer in soil-plant systems; it also helps to identify influential soil and plant parameters. However, the comlexity and the large amount of specific parameters make this approach impractical for nuclear emergency preparedness and response purposes. We propose that the semi-mechanistic approach is sufficiently robust and practical, hence more fit for the purpose of planning and responding to nuclear emergencies compared with the empirical and mechanistic approaches. We recommend further work to extend the applicability of the semi-mechanistic approach to a wide range of plants and soils., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Muscle, liver and kidney of 21 Barbary sheep (Ammotragus lervia) from Mosor Mountain, Croatia, were sampled to quantify the activity of caesium and potassium radionuclides and five toxic and ten essential stabile elements in order to establish reference values for this species and to evaluate the potential of Barbary sheep tissues to reflect environmental pollution. We also assessed seasonal diet (botanical composition and dry matter content) of Barbary sheep based on analyses of a rumen content of culled animals. None of the 19 plant species (mostly grasses) identified as part of the Barbary sheep diet is known as a stabile element or radionuclide hyperaccumulator. Measured levels reflected low environmental pollution with arsenic, cadmium, mercury and lead, with levels generally less than those reported for wild herbivorous ungulates. Methodological differences (detection limit of elements in muscle) were shown to hamper interpretation and comparison of the Toxic Contamination Index (TCI) values with those published for other species. There was no homeostasis disturbance of trace elements in Barbary sheep, either due to inadequate intake via food or as an adverse effect due to a high toxic metal(loid) burden. Consumption of the muscle and liver of wild Barbary sheep can be considered safe for the health of adult consumers regarding toxic metal(loid)s and radioactive caesium, though the liver should be avoided as a food item in vulnerable population groups due to the possible adverse effects of cadmium and lead. Otherwise, muscle and liver are a rich source of copper, iron, selenium and zinc for consumers and, as such, can benefit the overall dietary intake of essential elements.

The hepatic parameters (contents of glycogen, total lipids, nuclear and cytoplasmic proteins, DNA and RNA, fructose-6-phosphate, water, lipid peroxidation products, as well as activities of succinate dehydrogenase and glucose phosphate isomerase), radiometric data, and the relative population abundance of the pygmy wood mouse (Apodemus uralensis Pall., 1811) inhabiting natural (Middle Urals, Southern Urals, and Trans-Urals) areas and radioactivity territory (the EURT zone after of the Kyshtym accident in the South Urals in 1957) were analysed. Structural-functional modifications of the liver in A. uralensis from the EURT area are presented, taking into account irradiation power by dose-forming radionuclides (external and internal exposure to 137 Cs and 90 Sr), population size, and reproductive status (sexually immature and sexually mature yearlings, representing different ontogenetic patterns). The sexually immature mice from the EURT area can be considered to be the more sensitive (reactive) intrapopulation group to synergistic factors, such as radiation burden and population overabundance. The extent of structural-functional hepatic modification under current conditions of radionuclide exposure, in addition to the 60 year long effect of radioactive contamination in the EURT, can exceed the level of natural (geographic) variation observed in this species in the Urals region, which points to a long term evolutionary-ecological process., (Copyright © 2019. Published by Elsevier Ltd.)

As result of the great east Japan earthquake on March 2011 and the damages of the Fukushima Dai-ichi Nuclear Power Plant (FDNPP), huge amount of radionuclides, especially 137Cs, were released to the Japanese Pacific coast. By consequence, several marine species have been contaminated by direct uptake of radionuclides from seawater or through feeding on contaminated preys. In the present study we propose a novel radioecological modelling approach aiming to simulate the radionuclides transfer to pelagic marine species by giving to the organism body-size a key role in the model. We applied the model to estimate the 137Cs content in 14 commercially important species of the North-Western Pacific Ocean after the FDNPP accident. Firstly, we validated the model and evaluated its performance using various observed field data, and we demonstrated the importance of using such modelling approach in radioecological studies. Afterwards, we estimated some radioecological metrics, such as the maximum activity concentration, its corresponding time and the ecological half-life, which are important in assessment of the previous, current and future contamination levels of the studied species. Finally, we estimated the time duration required for each species to reach the pre-accident 137Cs activity concentrations. The results showed that the contamination levels in the planktivorous species have generally reached the pre-accident levels since about 5 years after the accident (since 2016). While in the case of the higher trophic level species, although the activity concentrations are much lower than the regulatory limit for radiocesium in seafood in Japan (100 Bq kg-1), these species still require another 6-14 years (2018-2026) to reach the pre-accident levels., Competing Interests: The authors have declared that no competing interests exist.

A better understanding of the fate of radiocesium in aquatic organisms is essential for making accurate assessments of potential impacts of radiocesium contamination on ecosystems and human health. Studies of the accumulation of 134 Cs, 136 Cs and 137 Cs in diverse biota have been the subject of many field investigations; however, it may often be difficult to understand all the mechanisms underlying the observations reported. To complement field investigations, laboratory experiments allow better understanding the observations and predicting dynamics of Cs within aquatic ecosystems by accurately assessing bioaccumulation of Cs in living organisms. The present review summarizes selected relevant laboratory studies carried out on Cs bioaccumulation in aquatic organisms over a period of more than 60 years. To date, 125 experimental studies have been carried out on 227 species of aquatic organisms since 1957. The present review provides a synthesis of the existing literature by highlighting major findings and identifying gaps of key information that need to be further addressed in future works on this topic. Thus, influences of some environmental parameters such as water chemistry both for marine and freshwater ecosystems, and biotic factors such as the life-stages and size of the organisms on radiocesium bioaccumulation should be examined and become priority topics for future research on Cs accumulation in aquatic organisms., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

This study was conducted to assess radiocesium accumulation in birds after the accident at Tokyo Electric Power Company's Fukushima Daiichi Nuclear Power Station in 2011, with a particular focus on 137 Cs, which has a long physical half-life. Results of 137 Cs monitoring in four game bird species including two pheasant species and two duck species (copper pheasant, green pheasant, spot-billed duck and mallard) were assessed in Fukushima Prefecture. We also obtained samples from rescued raptors that died during treatment or rehabilitation at the Wildlife Symbiosis Centre in Fukushima Prefecture because of severe injury. We measured the muscle concentrations of 137 Cs in four of these raptor species (black kite, northern goshawk, peregrine falcon and ural owl). Comparison of the two pheasant species showed that the copper pheasants inhabiting forested areas had higher 137 Cs concentrations in muscle (Bq/kg, fresh mass) than the green pheasants inhabiting mountainous areas near human habitation (i.e., Satoyama). No clear tendencies were observed in 137 Cs concentration in muscle of copper pheasants over time, but a tendency to decrease was observed in green pheasants over time. The difference in tendencies between species may be attributable to differences in their food habits and its 137 Cs concentration, and also differences in the situation of 137 Cs accumulation in their habitat. No significant differences were observed in 137 Cs concentration in muscle between the resident spot-billed duck and migratory mallard because of the comparatively short biological of effective half-life of radiocesium. Analysis of 137 Cs concentration in muscle of raptor revealed that the concentration was similar to, or lower than, those of pheasants and ducks., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

One potentially useful approach to fill data gaps for concentration ratios, CRs, is based upon the hypothesis that an underlying taxonomic and/or phylogenetic relationship exists for radionuclide transfer. The objective of this study was to explore whether these relationships could be used to explain variation in the transfer of radiocaesium to a wide range of marine organisms. CR data for 137 Cs were classified in relation to taxonomic family, order, class and phylum. A Residual Maximum Likelihood (REML) mixed-model regression modelling approach was adopted. The existence of any patterns were then explored using phylogenetic trees constructed with mitochondrial COI gene sequences from various biota groups and mapping the REML residual means onto these trees. A comparison of the predictions made using REML with blind datasets allowed the efficacy of the procedure to be tested. The only significant correlation between predicted and measured activity concentrations was revealed at the taxonomic level of order when comparing REML analysis output with data from the Barents Sea Region. For this single case a correlation 0.80 (Spearman rank) was derived which was significant at the 0.01 level (1-tailed test) although this was not the case once a (Bonferroni) correction was applied. The application of the REML approach to marine datasets has met with limited success, and the phylogenetic trees illustrate complications of using predictions based on values from different levels of taxonomic organization, where predicted values for the order level can mask the values at lower taxonomic levels. Any influence of taxonomy and phylogeny on transfer is not immediately conspicuous and categorizing marine organisms in this way is limited in providing a potentially robust prognostic extrapolation tool. Other factors may plausibly affect transfer to a much greater degree in marine systems, such as quite diverse life histories and different diets, which may confound any phylogenetic pattern., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Aggregated transfer factors (T ag ; m 2 kg -1 ) are often used to predict radionuclide activity concentrations in biota (Bq kg -1 ) from soil contamination levels (Bq m -2 ). Inherently large uncertainties in T ag values severely limit their predictive power. Many published T ag values have been derived from radionuclide deposition onto soil following weapons fallout, or the accidents at Chernobyl and Fukushima. In many cases the soil data used to derive a T ag value were collected for other purposes, and the spatial resolution of the soil data is much less than that of the biota data to which it is paired. We hypothesized that this disassociation and imprecision in paring deposition density and biota data may contribute to the large variations observed in T ag values. We tested the hypothesis by deriving T ag values for Japanese wild boar in two ways. One method used paired deposition density-biota contamination levels, with the soil data collected from each boar trap site. The second method used a soil radioactivity density map, of relatively low spatial resolution, generated by the Japanese government agency MEXT for fallout from the Fukushima accident. We hypothesized that T ag values derived from the method using paired deposition density-wild boar data would have less variation. Initial statistical test suggested significant differences in the predictive power of the two methods. However, removal of suspected outliers in the MEXT data set decreased the statistical differences and indicated that collecting 137 Cs soil deposition density measurements in the field did not reduce the large variation in our T ag values. More importantly, both methods revealed that soil contamination levels are a poor predictor of radiocesium concentrations in boar (r 2  < 0.23). The inadequacies of T ag to predict wild boar 137 Cs concentrations is an ominous indication of the lack of applicability of the T ag model as a rigorous research parameter. T ag values are best suited for their original intended purpose: upper tier, screening level computations. Further studies on how to reduce uncertainty when predicting 137 Cs concentrations in biota are needed to thoroughly understand the transfer of radiocesium within the environment., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Low dose radiation effects have been investigated in Chernobyl for many years but there is uncertainty about initial doses received by many animal species. However, the Fukushima Dai-ichi Nuclear Power Plant accident opens an opportunity to study the effects of the initial low historic dose on directly exposed species and their progeny during a time where the contaminating radionuclides are decaying. In this paper, it is proposed that historic acute exposure and its resulting non-targeted effects (NTEs) may be partially involved in the high mortality/abnormality rates seen across generations of pale grass blue butterflies (Zizeeria maha) around Fukushima. Data from Hiyama et al. (2012) on the morphological abnormality frequencies in Z. maha collected around Fukushima and their progeny were used in this paper. Two dose reconstruction methods based on the Gaussian plume model were used to determine the external absorbed dose to the first exposed generation from both ground shine and plume shine. One method involved the use of the dose rate recorded at the time of collection and only took Cs-137 into account. The other involved using release rates and atmospheric conditions to determine the doses and considered Cs-137 and Cs-134. The reconstructed doses were plotted against the mortality rates and abnormality frequencies across generations. The mortality rates of the progeny from irradiated progenitors increased linearly with the increasing historic radiation doses reconstructed using both Cs-137 and Cs-134 sources. Additionally, a higher level of morphological abnormalities was observed in progeny than in the progenitors. The mean abnormality frequencies also increased throughout generations. As these results are a sign of NTEs being involved, it can be suggested that increasing mutation levels across generations may result, in part, from NTEs induced by the initial low dose received by the first exposed generation. However, continual accumulation of mutations over generations in their natural contaminated habitats remains a likely contributor into the observed outcome., (Copyright © 2018. Published by Elsevier Inc.)

The effect of potassium (K) concentration gradient on stable caesium (Cs) uptake by Calla palustris was studied under hydroponic conditions after eight-day exposure in a greenhouse experiment. The plants were exposed to two different concentrations of Cs (provided as 0.5 and 1 mM CsCl) and five different concentrations of K (provided as K 2 SO 4 in 0.5, 1, 2, 5, and 10 mM). The results indicate negative dependence of Cs uptake on K concentrations for both Cs treatments. The application of K reduced the transfer of stable Cs from water to plant by about 44-72% for 0.5 mM CsCl and 56-74% for 1 mM CsCl. The highest efficiency of Cs removal from water was observed for plants in K + deficient solutions (plants starving), with an efficiency 8.0% for plants cultivated in 0.5 mM CsCl and 9.4% for plants in 1 mM CsCl. An increasing concentration of K also supported translocation of Cs from roots to leaves. Higher translocation was observed for the treatments with lower level of Cs, where the concentration of Cs in leaves became higher than that in roots. The Cs uptake and translocations were affected not only by the external concentration of K, but also the external concentration of stable Cs. A high concentration of K in the environment protects the food chain from Cs uptake by plants, but lowers the efficiency of phytoremediation techniques., (Copyright © 2018 Elsevier Inc. All rights reserved.)

The uptake and depuration kinetics of dissolved 109 Cd, 57 Co and 134 Cs were determined experimentally in the European flat oyster Ostrea edulis (Linnaeus, 1758) under different pH conditions (i.e., 8.1, 7.8 and 7.5) for 59 days. Uptake and depuration rates were variable within these elements; no effects were observed under different pH conditions for the uptake biokinetics of 109 Cd and 57 Co and depuration of 109 Cd and 134 Cs in oyster. The uptake and depuration rate constants of 134 Cs differed during the exposure phase between treatments, while the steady state concentration factors (CF ss ) were similar. The resulting Cs activity that was purged during short- and long-term depuration phases differed, while the remaining activities after thirty-nine days depuration phase (RA 39d ) were similar. Co-57 depuration was affected by pCO 2 conditions: RA 39d were found to be significantly higher in oysters reared in normocapnia (pCO 2  = 350 μatm) compared to high pCO 2 conditions. Co-57 tissue distribution did not differ among the variable pCO 2 conditions, while 109 Cd and 134 Cs accumulated in soft tissue of oysters were found to be higher under the highest pCO 2 . Additionally, Cd, Co and Cs were stored differently in various compartments of the oyster cells, i.e. cellular debris, metal-rich granules (MRG) and metallothionein-like proteins (MTLP), respectively. The subcellular sequestration of the elements at the end of the depuration phase did not differ among pH treatments. These results suggest that bioconcentration and tissue/subcellular distribution are element-specific in the oyster, and the effects of higher pCO 2 driven acidification and/or coastal acidification variably influence these processes., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

To understand the long-term behavior of radiocesium in the biological processes of a forest ecosystem, its concentration in Japanese epigeic earthworms (Megascolecidae), litter, and soil, and the ambient dose equivalent rates, were investigated after the Fukushima Dai-ichi Nuclear Power Plant accident. The metabolism of radiocesium in the earthworms was also investigated in the laboratory, and its biological half-life (T b ) was estimated. The concentration of 137 Cs in the habitat soil and litter changed from 2014 to 2016, with levels in the litter going from 44.9 Bq/g dw (in 2014) to 45.3 Bq/g dw (2015) and 10.7 Bq/g dw (2016); in soil, these values were 9.79 Bq/g dw, 7.14 Bq/g dw and 18.0 Bq/g dw, respectively. By contrast, no significant changes were observed in the concentrations in the earthworms, which were 4.87 Bq/g fw, 5.30 Bq/g fw and 4.67 Bq/g fw in 2014, 2015, and 2016, respectively. The ambient dose equivalent rates at the sampling site declined significantly over these three years, going from 2.15 μSv/h to 1.68 μSv/h and 1.35 μSv/h, mostly corresponding to physical decay of radiocesium. The majority (95%) of the 137 Cs in the earthworms, observed via autoradiography, was concentrated primarily in the intestine. The clearance of 137 Cs from the earthworms was described by dual exponential functions: the half-life in the rapid loss due to gut clearance was 0.10 days and a second slower loss due to physiological clearance was 27.4 days., (Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Cartilaginous dogfish Scyliorhinus canicula continued to transfer four anthropogenic radionuclides ( 65 Zn, 60 Co, 134 Cs and 241 Am) to their eggs for over six months, after two months of continued maternal exposure to radio-labelled food. Unexpectedly, rates of radionuclide transfers to eggs and their yolk & embryo during maternal depuration were equivalent for 60 Co and 241 Am, or even enhanced for 65 Zn and 134 Cs by factors of c.200-350%, over two-three months, compared to their maximal transfer rates at the end of the maternal uptake phase. These rates of maternal transfer of radionuclides to yolk & embryo were positively associated with their previously determined efficiencies of assimilation (AE) from ingested radio-labelled food. Thus progeny may be more exposed via maternal transfer to those radionuclides which have greater rates of maternal assimilation from food. As maternal depuration continued beyond 60-80 up to 180-200 days the transfers of all four radionuclides to eggs did diminish but were still substantial at mean values of 18% for 241 Am, 17% for 134 Cs and 9 and 8% for 60 Co and 65 Zn, respectively. In the yolk & embryo the mean rates of transfer over this period were further reduced for 241 Am (13.5%), 60 Co (2.5%) and 65 Zn (5.8%), but were still appreciable for 134 Cs at 56%. These results for S. canicula have demonstrated a potential enhanced radiological risk of extended duration due to the particular biokinetics of maternal transfer in this species. This study draws further attention to the current paucity of knowledge about the maternal: progeny transfer pathway, particularly in the context of the known heightened radio-sensitivity of early life stages in fish and other vertebrates, compared to later life stages., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Ocean acidification have been shown to not affect the capacity of bivalves to bioaccumulation 134 Cs in their tissue; but as this was studied on only one species to date. There is therefore a need to verify if this holds true for other bivalve species or other marine invertebrates. The present short communication confirms that in the scallop Mimachlamys varia and the prawn Penaeus japonicus, two species that supposedly have a record to preferentially concentrates this radionuclide, that bioconcentration of 134 Cs was shown not to be influenced by a decreasing pH (and thereby increasing seawater pCO 2 ). Although the dissolved 134 Cs was taken up in a similar manner under different pH values (8.1, 7.8, and 7.5) in both species, being described by a saturation state equilibrium model, the species displayed different bioconcentration capacities of 134 Cs: CF ss in the prawns was approximately 10-fold higher than in scallops. Such results suggest that the Cs bioconcentration capacity are mainly dependent of the taxa and that uptake processes are independent the physiological ones involved in the biological responses of prawns and scallops to ocean acidification., (Copyright © 2018. Published by Elsevier Ltd.)

To better understand bioaccumulation of radiocaesium in the commercially important Japanese flatfish, Paralichthys olivaceus, the uptake and depuration kinetics of caesium via both seawater and food were assessed simultaneously using controlled aquaria. The pre-conditioned fish were exposed to radionuclides via the two different pathways (aqueous versus dietary) concurrently using two isotopes of caesium, 137 Cs and 134 Cs, respectively. Dissolved caesium uptake was linear and did not reach a steady state over the course of the 8-day exposure period. Consumption of 134 Cs-labelled food led to higher bioaccumulation rates of radioactive Cs than via seawater exposure of 137 Cs during uptake and following depuration, though the model-derived long-lived biological half-lives of both pathways was approximately 66 d. Further development of this method for assessing multiple radiocaesium bioaccumulation pathways simultaneously could lead to a promising new approach for studying Cs contamination in marine organisms., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

The trophic transfer of radiocesium ( 134 Cs) was investigated in two tropical fish, the silver moony Monodactylus argenteus and the spotted scat Scatophagus argus. Juveniles of both species were exposed to dietary 134 Cs using the pulse-chase feeding methodology. The food was brine shrimp (Artemia salina) previously exposed to the dissolved radiotracer. Depuration kinetics of 134 Cs were followed for 45 d. Results showed that Cs was similarly efficiently assimilated by both species (AE > 50%). The estimated trophic transfer factors in the two species ranked from 1 to 2, suggesting that 134 Cs could be biomagnified in both omnivorous species. In complement, dissections of 7 body compartments were carried out at three different times in order to highlight 134 Cs organotropism. 134 Cs organotropism was similar in both species: more than 50% of 134 Cs was quickly distributed in the muscles and skeleton (after 3 days of depuration), which is likely related to the analogous behavior between Cs and K, an essential element for muscle contractions and bone formation., (Copyright © 2018 Elsevier Ltd. All rights reserved.)