Fukushima Daiichi Nuclear Power Plant Accident: Understanding Formation Mechanism of Radioactive Particles through Sr and Pu Quantities.

The Fukushima Daiichi Nuclear Power Plant accident released considerable radionuclides into the environment. Radioactive particles, composed mainly of SiO2, emerged as distinctive features, revealing insights into the accident's dynamics. While studies extensively focused on high-volatile radionuclides like Cs, investigations into low-volatile nuclides such as 90Sr and Pu remain limited. Understanding their abundance in radioactive particles is crucial for deciphering the accident's details, including reactor temperatures and injection processes. Here, we aimed to determine 90Sr and Pu amounts in radioactive particles and provide essential data for understanding the formation processes and conditions within the reactor during the accident. We employed radiochemical analysis on nine radioactive particles and determined the amounts of 90Sr and Pu in these particles. 90Sr and Pu quantification in radioactive particles showed that the 90Sr/137Cs radioactivity ratio (corrected to March 11, 2011) aligned with core temperature expectations. However, the 239+240Pu/137Cs activity ratio indicated nonvolatile Pu introduction, possibly through fuel fragments. Analyzing 90Sr and Pu enhances our understanding of the Fukushima Daiichi accident. Deviations in 239+240Pu/137Cs activity ratios underscore nonvolatile processes, emphasizing the accident's complexity. Future research should expand this data set for a more comprehensive understanding of the accident's nuances.

Social networks and posttraumatic stress symptoms five to ten years after the Fukushima nuclear power plant disaster.

Since the 2011 Fukushima nuclear power plant accident, multiple social network disruptions have been reported among the community in Fukushima, while posttraumatic stress symptoms among the residents have persisted. In this study, we aimed to explore the influence of time and social networks on the recovery of posttraumatic stress symptoms based on longitudinal data from community residents in Fukushima, following up five to ten years after the nuclear power plant accident. We conducted five questionnaire surveys quasi-annually, the targets of which were randomly sampled 4900 non-evacuee community residents. In this study, the data of 1809 respondents who participated in at least one survey were used (36.9% of the initial target). Setting posttraumatic stress symptoms as the outcome, we examined the interaction between time and social network size using a mixed model, adjusting for sociodemographic characteristics and disaster-related events. Their interaction was statistically significant, and the posttraumatic stress symptoms of those with small social networks persisted, while those with larger social networks recovered. Maintaining and promoting social networks may contribute to mental health recovery after a nuclear disaster.

Nuclear energy in Bangladesh: A SWOT analysis.

Zero-emission energy sources like nuclear energy are taken into account worldwide due to the negative environmental consequences of fossil fuels and their limited availability over the years. Bangladesh plans to add nuclear energy to its portfolio of energy sources by 2024. Under the scope of this study, the country's nuclear energy strategy was looked at in terms of its strengths, weaknesses, opportunities, and threats. This was done using a method known as SWOT analysis. It has come to light that Bangladesh has a significant number of aspects in terms of strengths as well as opportunities that make the possibility of doing an investment in the construction of a nuclear power plant a realistic choice. Difficulties such as a culture of poor maintenance, financial burden, lack of skilled manpower, a poor power grid, radioactive waste management, and corruption are the weaknesses and threats to the effective construction, operation, and maintenance activities of the nuclear power plant in Bangladesh. By mitigating these difficult aspects, Bangladesh's journey to adopt nuclear energy can be more smooth.

Downward migration of 137Cs promotes self-cleaning of forest ecosystem by reducing root uptake of Japanese cedar in Fukushima.

Approximately 70 % of the area highly 137Cs-contaminated by the Fukushima Daiichi Nuclear Power Plant accident is forested. Decontamination works in most of these forests have not progressed, and the forestry industry remains stagnant. Although the long-term dynamics of 137Cs in the forest ecosystem will be controlled by the amount of 137Cs absorbed by roots in the future, temporal changes in 137Cs of tree roots have rarely been reported. In the present study, we monitored the depth distribution of 137Cs in the soil and absorptive very fine (VF) roots of 0.5 mm or less in a Japanese cedar forest from 2011 to 2023. As a result, the 137Cs inventory in the mineral soil increased over time due to the migration from the forest canopy and litter layers, whereas that in the VF roots tended to decrease since 2020, although there was a large variation. Temporal decrease in the exchangeable 137Cs fraction with fixation and temporal increase in VF root biomass with their growth were not clearly observed, the 137Cs concentration in the VF roots at 0-2 cm decreased with the decrease in 137Cs concentration in the litter layers. Although the 137Cs concentration in the VF roots below 2 cm tended to increase with increasing 137Cs concentration in the soil at the same depth, the downward migration of 137Cs within the soil can reduce the amount of 137Cs absorbed by roots because the VF root biomass decreases exponentially with depth. In other words, 137Cs can be removed from the long-term active cycles of forest ecosystems as they migrate deeper into the soil. This natural migration process can be regarded as a "self-cleaning" of the forest ecosystem, the green and sustainable remediation using such self-cleaning should be actively adopted for the future forest management.

[Chemical Species Change of Radionuclides by Microorganisms: Effects of Exudated Siderophores].

Microbial exudates including siderophore, which changes chemical species of actinides and lanthanides. We have investigated effects of desferrioxamine B (DFOB; one of the siderophores) and siderophore-like organic molecules (SLOM) on the adsorption of lanthanides by microbial cells, aluminium oxide (Al2O3), and manganese (Mn) oxides. When DFOB was present, the distribution coefficients of cerium (Ce) were measured to be lower than those of neighboring elements of lanthanum (La) and praseodymium (Pr) (Negative anomaly of Ce adsorption). Even though initial oxidation state of Ce in the solution was III, that was changed to IV after the addition of DFOB, indicating that Ce(III) was oxidized by forming complex with DFOB. When lanthanides were adsorbed by biogenic Mn(IV) oxides, negative anomaly of Ce adsorption was observed in the sorption in alkaline solution. Ce(III) was oxidized to forme the complexes of Ce(IV) with SLOM in the solution. These results show that siderophore possesses high performance of oxidation of Ce(III) to Ce(IV) during association, affectiong the adsorption behavior of Ce. After Fukushima accident, radioactive Cs accumulation by Eleutherococcus sciadophylloides (Koshiabura) caused by the dissolution of Fe from soil around the roots, that was dominated by siderophore releasing microorganisms (SB). These SBs may enhance dissolution of iron (Fe) and uranium (U) phases in the nuclear fuel debris formed in the nuclear reactors in Fukushima Daiichi nuclear power plant. Thus, in the interaction between microorganisms and radionuclides, SLOMs discharged by microorganisms are deeply involved in the chemical state change of radionuclides.

Health Effects of Occupational and Environmental Exposures to Nuclear Power Plants: A Meta-Analysis and Meta-Regression.

PURPOSE OF REVIEW: Numerous epidemiological studies have shown increased health risks among workers and residents living near nuclear power plants exposed to radiation levels meeting regulatory dose limits. This study aimed to evaluate the association between radiation exposure and disease risks among these populations exposed to radiation levels meeting the current regulatory dose limits. RECENT FINDINGS: We searched four databases (Cochrane Library, PubMed, ScienceDirect, and Web of Science) for studies published before August 2023, screened eligible studies (inclusion and exclusion criteria based on population, exposure, comparator, and outcome framework), and collected data on exposure indicators and disease risks. We applied random-effects models of meta-analysis to estimate the pooled effects and meta-regression to assess the dose-response relationship (radiation dose rate for workers and distance for residents). We identified 47 studies, 13 with worker and 34 with resident samples, covering 175 nuclear power plants from 17 countries, encompassing samples of 480,623 workers and 7,530,886 residents. Workers had a significantly lower risk for all-cancer and a significantly higher risk for mesothelioma. Residents had significantly higher risks for all-cancer, thyroid cancer, and leukemia. Notably, children under 5 years old showed the highest risk for all-cancer. Our meta-regression showed a significantly positive dose-response relationship between cumulative dose of radiation exposure and risk for circulatory disease among workers. Our findings demonstrated higher risks for mesothelioma for workers and all-cancer, thyroid cancer, and leukemia for residents exposed to low-dose radiation from nuclear power plants. Some included studies did not adjust for cancer risk confounders, which could overestimate the association between radiation exposure and cancer risk and increase the risk of bias.

Risk perception in long-term evacuees of Futaba town, Fukushima: a cross-sectional study reveals greater concerns outside the prefecture, 12 years after the accident.

For over 12 years since the 2011 East Japan Earthquake, the decontamination of radioactive materials is still incomplete. Although evacuation orders had been lifted in ~15% of Futaba town, the site of the Fukushima Daiichi Nuclear Power Plant, by August 2022, anxiety regarding the effects of nuclear radiation persists among evacuees, and their intention to return (ITR) remains low. As of August 2023, only 90 residents lived there. As the only town with government functions relocated outside Fukushima Prefecture, Futaba has more residents who evacuated outside the prefecture. Although numerous factors affect risk perception and ITR to the place of previous residence, the impact of evacuation destination on risk perception remains unknown. Therefore, this study aimed to evaluate the impact of evacuation destination on radiation risk perception. In 2022, a survey was conducted on 404 evacuees aged >18 years. The responses were compared between groups outside and inside Fukushima using the chi-square test and multivariate logistic regression analysis. Significant relationships were found between the evacuation destination and risk perception of genetic effects in the next generation (odds ratio [OR] = 1.92, 95% confidence interval [CI]: 1.15-3.20) and of the health effects of radiation (OR = 1.76, 95%CI: 1.10-2.84), which were both higher in those who had evacuated outside Fukushima. These findings stress the importance of evacuation destination choice and information access for evacuees' risk perception. Enhanced education and support efforts are necessary to help evacuees not only in Fukushima but also throughout Japan.

Awareness of disaster preparedness between administrative staff and residents in the vicinity of the Genkai and Ikata nuclear power plants following the Fukushima Daiichi nuclear power plant disaster.

When considering disaster preparedness, one challenge is mitigating the health impacts of evacuations. Nuclear disaster preparedness has evolved based on past experiences from numerous disasters, including the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident. However, there is a lack of comprehensive reporting on the awareness of administrative staff, medical personnel, and residents in the areas surrounding nuclear power plants (NPPs). This study reports on a survey aimed at gaining insights into the understanding and current state of disaster preparedness and elucidating the differences in perceptions of nuclear disaster preparedness among the relevant stakeholders surrounding NPPs. Interview surveys were conducted from 14 to 16 September 2022 in the area surrounding Kyushu Electric Power's Genkai NPP in Saga Prefecture and from 11 to 13 January 2023 in the area around Shikoku Electric Power's Ikata NPP. The surveys targeted administrative, medical, and nursing care facilities and residents. Responses from 57 participants indicated a lack of awareness of natural and nuclear disasters, challenges in evacuation planning, and a gap between nuclear disaster training and residents' understanding of evacuation protocols. This study highlights inadequacies in nuclear disaster preparedness and the need for a better understanding among residents regarding evacuation procedures. This study identified three key issues: (1) a lack of awareness about disasters, including nuclear disasters; (2) concerns about complex disasters and the difficulties in creating evacuation plans; and (3) a discrepancy between nuclear disaster training and residents' understanding of evacuation procedures. To bridge this gap, it is important to deepen residents' understanding of nuclear disasters, continuously convey the lessons learned from the FDNPP accident, and regularly reassess and update nuclear disaster preparedness strategies.

"Invisible" radioactive cesium atoms revealed: Pollucite inclusion in cesium-rich microparticles (CsMPs) from the Fukushima Daiichi Nuclear Power Plant.

Understanding radioactive Cs contamination has been a central issue at Fukushima Daiichi and other nuclear legacy sites; however, atomic-scale characterization of radioactive Cs in environmental samples has never been achieved. Here we report, for the first time, the direct imaging of radioactive Cs atoms using high-resolution high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). In Cs-rich microparticles collected from Japan, we document inclusions that contain 27 - 36 wt% of Cs (reported as Cs2O) in a zeolite: pollucite. The compositions of three pollucite inclusions are (Cs1.86K0.11Rb0.19Ba0.22)2.4(Fe0.85Zn0.84X0.31)2.0Si4.1O12, (Cs1.19K0.05Rb0.19Ba0.22)1.7(Fe0.66Zn0.32X0.41)1.4Si4.6O12, and (Cs1.27K0.21Rb0.29Ba0.15)1.9(Fe0.60Zn0.32X0.69)1.6Si4.4O12 (X includes other cations). HAADF-STEM imaging of pollucite, viewed along the [111] zone axis, revealed an array of Cs atoms, which is consistent with a simulated image using the multi-slice method. The occurrence of pollucite indicates that locally enriched Cs reacted with siliceous substances during the Fukushima meltdowns, presumably through volatilization and condensation. Beta radiation doses from the incorporated Cs are estimated to reach 106 - 107 Gy, which is more than three orders of magnitude less than typical amorphization dose of zeolite. The atomic-resolution imaging of radioactive Cs is an important advance for better understanding the fate of radioactive Cs inside and outside of nuclear reactors damaged by meltdown events.

An Investigation of Efficiency Issues in a Low-Pressure Steam Turbine Using Neural Modelling.

This study utilizes neural networks to detect and locate thermal anomalies in low-pressure steam turbines, some of which experienced a drop in efficiency. Standard approaches relying on expert knowledge or statistical methods struggled to identify the anomalous steam line due to difficulty in capturing nonlinear and weak relations in the presence of linear and strong ones. In this research, some inputs that linearly relate to outputs have been intentionally neglected. The remaining inputs have been used to train shallow feedforward or long short-term memory neural networks using measured data. The resulting models have been analyzed by Shapley additive explanations, which can determine the impact of individual inputs or model features on outputs. This analysis identified unexpected relations between lines that should not be connected. Subsequently, during periodic plant shutdown, a leak was discovered in the indicated line.

Assessment of radiation in fishes derived from radiocesium in the port of Fukushima Daiichi nuclear power plant.

This study established specialized radiation dose models to evaluate the internal radiation doses derived from 137Cs and 134Cs in fishes in the port of the Fukushima Daiichi Nuclear Power Plant from 2012 to 2023. By August 2018, the activities of 134Cs and 137Cs in fishes decreased at the T1/2 of 176 d and 191 d, respectively. The corresponding mass concentrations were far lower than 1 mg/kg and the chemical toxicity can be negligible. Regarding radiotoxicity, 18,000 Bq/kgfresh weight of 134Cs and 137Cs in grouper Sebastes schlegelii produced 276 µGy/h of radiation dose, which was below the no-effect-dose-rate benchmarks (400 µGy/h). 740,000 Bq/kgfresh weight of 134Cs and 137Cs in greenling Hexagrammos otakii produced 12,600 µGy/h of radiation dose, which was much higher than 400 µGy/h, indicating the possibility of radiation effects. If a person eats these two reported fishes, the resulting committed effective doses for humans are 7.7 µSv and 6.31 mSv, respectively.

Assessment of the impact of Tianwan Nuclear Power Plant on the adjacent marine ecosystem.

Based on the monitoring data of 137Cs and 90Sr in Tian Bay in 2005-2023, the impacts of the operation of Tianwan Nuclear Power Plant on the marine ecosystem were assessed. The 137Cs and 90Sr activity concentrations in the seawater and sediment varied within the background ranges. The radiation dose rates derived from 137Cs and 90Sr for the marine organisms ranged from 2.4 × 10-5 to 2.2 × 10-4 nGy/h, it was far below the most conservative screening dose rate (10 µGy/h). The committed effective dose for humans was 0.070-0.094 µSv, 1/1500th of the world's mean annual effective dose (0.12 mSv) from ingesting food containing uranium and thorium series nuclides. Radiation risk assessment showed no radiation risk for the long-term discharge of nuclear wastes in the future. Overall, the long-term normal operation of TNPPs has almost no radiation impact on the adjacent marine ecosystem.

Determination and human health risk assessment of TFWT, OBT and carbon-14 in seafood around Qinshan Nuclear Power Plant.

This work aims to evaluate the effects of the operation of Qinshan nuclear Power Plant (QNPP) on tritium (3H) and carbon-14 (14C) levels in seafood and assess the health risks caused by seafood consumption. Five kinds of seafood, including marine fish, prawn, razor clam, crabs, and seaweed, were collected from QNPP and the sea around Hangzhou Bay. The activity concentrations of tissue free water tritium (TFWT), organically bound tritium (OBT) and 14C were determined, respectively, and the annual intake and annual effective dose (AED) were calculated. The results showed that the TFWT, OBT, and 14C activity concentrations of the seafood in the surrounding area of QNPP ranged from 2.00 to 74.75 Bq/L, <1.04 to 19.68 Bq/L and 0.09 to 0.17 Bq/g·C, respectively. The TFWT, OBT, and 14C activity concentrations of the seafood in Hangzhou Bay ranged from 1.36 to 10.55 Bq/L, 1.08 to 6.78 Bq/L and 0.07 to 0.13 Bq/g·C, respectively. The differences were not statistically significant. The total AED from 3H and 14C due to the seafood consumption for the residents in the surrounding of QNPP and Hangzhou Bay were 1.96 × 10-4 and 1.61 × 10-4 mSv/year, respectively. The results showed that the operation of QNPP had no obvious effect on 3H and 14C accumulation in seafood, and the dose burden of population was low.

Continuous southwestward spread of Fukushima-derived 137Cs in the subtropical western North Pacific and its intrusion flux into the South China Sea.

We provide transect profiles of 137Cs and 90Sr along 146.5°E, 136°E and 21°N in the subtropical western North Pacific (WNP) during May 2018. Exploiting the constant global fallout 137Cs/90Sr ratio, we separated Fukushima-derived 137Cs (137CsF) from background 137Cs. At most stations, 137CsF exhibited only one subsurface peak at 300 m depth, corresponding to subtropical mode water (STMW); however, at 25-28°N along 146.5°E and 25-26°N along 136°E, 137CsF exhibited two subsurface peaks, with another peak occurring at 500 m depth, corresponding to lighter central mode water (L-CMW). Temporal changes in 137CsF vertical profiles showed that 137CsF entrained by STMW has recirculated within the western subtropical gyre, while 137CsF entrained by L-CMW has turned southwestward and arrived the western basin in 2018. In the Luzon Strait, the entrance to the South China Sea (SCS), subsurface 137Cs increased since 2013 and peaked in approximately 2018. The estimated amount of 137CsF entering the SCS during 2013-2019 was 0.33 ± 0.10 PBq, equivalent to 1.7-2.2% of total leakage of 137CsF into the ocean. These results enhance our understanding of the protracted spread and fate of 137CsF in the subtropical WNP.

Soil Microbes and Plant-Associated Microbes in Response to Radioactive Pollution May Indirectly Affect Plants and Insect Herbivores: Evidence for Indirect Field Effects from Chernobyl and Fukushima.

The biological impacts of the nuclear accidents in Chernobyl (1986) and Fukushima (2011) on wildlife have been studied in many organisms over decades, mainly from dosimetric perspectives based on laboratory experiments using indicator species. However, ecological perspectives are required to understand indirect field-specific effects among species, which are difficult to evaluate under dosimetric laboratory conditions. From the viewpoint that microbes play a fundamental role in ecosystem function as decomposers and symbionts for plants, we reviewed studies on microbes inhabiting soil and plants in Chernobyl and Fukushima in an attempt to find supporting evidence for indirect field-specific effects on plants and insect herbivores. Compositional changes in soil microbes associated with decreases in abundance and species diversity were reported, especially in heavily contaminated areas of both Chernobyl and Fukushima, which may accompany explosions of radioresistant species. In Chernobyl, the population size of soil microbes remained low for at least 20 years after the accident, and the abundance of plant-associated microbes, which are related to the growth and defense systems of plants, possibly decreased. These reported changes in microbes likely affect soil conditions and alter plant physiology. These microbe-mediated effects may then indirectly affect insect herbivores through food-mass-mediated, pollen-mediated, and metabolite-mediated interactions. Metabolite-mediated interactions may be a major pathway for ecological impacts at low pollution levels and could explain the decreases in insect herbivores in Fukushima. The present review highlights the importance of the indirect field effects of long-term low-dose radiation exposure under complex field circumstances.

Biomass conversion and radiocaesium (Rad-Cs) leaching behaviors of radioactive grass in anaerobic wet fermentation systems: Effects of pre-treatments.

Persistent concerns regarding environmental hazards arise from the difficulty in disposing of radioactive plant-based wastes originating from the nuclear accident at the Fukushima Daiichi Nuclear Power Plant (FNPP) in Japan in 2011. In this study, three anaerobic digestion (AD) strategies were proposed: Sole anaerobic wet fermentation, and wet fermentations with either alkaline-heat or ultrasonic pre-treatment, which were employed for long-term anaerobic treatment of a genuine radioactive grass stemming from the FNPP accident. The objectives of this work are to investigate the effects of pre-treatments on biomass conversion efficiency and to gain insight into the leaching behavior of radiocaesium (Rad-Cs) within AD processes. Experimental results indicate that by introducing alkaline-heat and ultrasonic pre-treatments to AD systems, the removal efficiencies of total solids (TS) from the raw grass increased by 60.8 % and 42.5 %, respectively, compared to sole wet fermentation. Pre-treatments have been shown to enhance the stability of AD systems, both in terms of enhancing methane production and mitigating pH fluctuations triggered by the accumulation of organic acids. Remarkably, even though the Rad-Cs leaching rate was highest when the AD system was fed with the alkaline-heat pre-treated grass, it remained unsatisfactory at only 5.77 %. We inadvertently isolated a soil-like component from the raw grass, and analyzed both its proportion in the raw grass and the radioactivity intensity. The results indicate that although the soil constituted only 9.51 % TS of the raw grass, it accounted for a significant 81.35 % of the total radioactivity. The soil, which has a pronounced affinity for ionic Cs, being mixed into the raw grass, was identified as the primary factor limiting the leaching efficiency of Rad-Cs throughout both the pre-treatment and wet fermentation phases.

Longitudinal effects of disaster-related experiences on problem drinking among Fukushima nuclear plant workers.

BACKGROUND: In the Fukushima nuclear power plant disaster of March 11, 2011, plant workers were exposed to various traumatic events and reported a subsequent increase in alcohol use. To determine the relationship between disaster-related experiences and problem drinking, we conducted a three-year follow-up study. METHODS: Problem drinking among the nuclear plant workers was assessed annually from 2012-2014 using a modified version of the CAGE questionnaire that asked about current, rather than lifetime, drinking. A total of 1378 workers provided at least one CAGE response, and 2875 observations were used in the present analysis. Mixed-effects logistic regression models were used to analyze the relationship between disaster-related experiences and problem drinking over time. RESULTS: The prevalence of problem drinking (CAGE score ≥2) increased over time. At the baseline assessment in 2012, a year after the disaster, plant workers who had experienced life-threatening danger and discrimination had significantly more symptoms of problem drinking, which persisted over the following 2 years. Although at baseline, plant workers who had experienced major property loss or the death of a colleague showed no significant differences in problem drinking symptoms from those without such experiences, over the next 2 years their problem drinking increased significantly. CONCLUSIONS: Individuals who experienced life-threatening danger and discrimination during the Fukushima nuclear power plant disaster reported an increase in problem drinking. Although major property loss and the death of a colleague did not elevate problem drinking prevalence at baseline, it did so over the next 2 years. Different adverse effects of a natural disaster appear to differentially increase drinking behavior over time.

Wet scavenging of multi-mode 137Cs aerosols following the Fukushima accident: Size-resolved microphysics modeling with observed diameters.

Wet scavenging was critical in the atmospheric transport of 137Cs aerosols following the Fukushima accident. The aerosol size diversity and related microphysical processes produce complex behaviors during wet scavenging. Such behaviors are difficult to investigate using traditional simplified size distributions, resulting in inaccurate modeling. This study establishes an improved size-resolved wet scavenging model that considers the activation process. Using this model, five monodisperse simulations with five representative observed diameters with realistic solubility setting are performed to investigate the spatiotemporal wet scavenging behaviors of 137Cs aerosols. One polydisperse simulation with an empirical size distribution is also validated against the observation. The results reveal that 137Cs aerosols with diameters of 0.6 and 2.0 µm are mainly subject to below-cloud scavenging, which makes a significant contribution to low-deposition areas (<300 kBq/m2). For 137Cs aerosols with diameters of 6.4, 15, and 30 µm, in-cloud scavenging dominates, and the resulting depositions make significant contributions in high-deposition areas. The polydisperse results satisfy the criteria for good performance and better agree with the size, and deposition observations than the five monodisperse simulations, whereas for the concentration, the results show a similar RANK2 with the best mono1 and mono2 cases and reach the satisfactory criteria. These findings reveal the complex behavior and wet scavenging process of multi-mode 137Cs aerosols, improving our understanding and modeling.

Temporal variation of tritium concentration in monthly precipitation collected at a Difficult-to-Return Zone in Namie Town, Fukushima Prefecture, Japan.

This article discusses tritium concentrations in monthly precipitation in part of the Difficult-to-Return Zone in Namie Town during 2012-2021. The tritium concentrations, which were measured with a low background liquid scintillation counter after carrying out an enrichment procedure, fluctuated seasonally from 0.10 ± 0.02 to 0.85 ± 0.02 Bq L-1. This range of concentrations is concluded to not be unusual based on comparisons with the concentrations at other sites and estimates of the past range of the concentrations. Moreover, no significant variations in observed tritium concentrations were observed due to decommissioning work at the Fukushima Dai-ichi Nuclear Power Plant. These results contribute to understanding the background level of tritium concentration in precipitation before the oceanic discharge of treated water from the Fukushima plant. In addition, this article evaluates the amount of tritium supplied to the ocean by terrestrial rainwater pouring into the Pacific Ocean via Ukedo River, which flows through Namie Town; this information will contribute to the discussion on the impact of the oceanic discharge of treated water.

Root-associated microbial community and diversity in napiergrass across radiocesium-contaminated lands after the Fukushima-Daiichi nuclear disaster in Japan.

The microbiome derived from soil associated with plant roots help in plant growth and stress resistance. It exhibits potential benefits for soil remediation and restoration of radioactive-cesium (137Cs)-contaminated soils. However, there is still limited information about the community and diversity of root-associated microbiome in 137Cs-contaminated soil after the Fukushima-Daiichi Nuclear Power Plant (FDNPP) disaster. To address this, a comparative analysis of communities and diversity of root-associated microbiomes was conducted in two field types after the FDNPP disaster. In 2013, we investigated the community and diversity of indigenous root-associated microbiome of napiergrass (Pennisetum purpureum) grown in both grassland and paddy fields of 137Cs-contaminated land-use type within a 30-km radius around the FDNPP. Results showed that the root-associated bacterial communities in napiergrass belonged to 32 phyla, 75 classes, 174 orders, 284 families, and 521 genera, whereas the root-associated fungal communities belonged to 5 phyla, 11 classes, 31 orders, 59 families, and 64 genera. The most frequently observed phylum in both grassland and paddy field was Proteobacteria (47.4% and 55.9%, respectively), followed by Actinobacteriota (23.8% and 27.9%, respectively) and Bacteroidota (10.1% and 11.3%, respectively). The dominant fungal phylum observed in both grassland and paddy field was Basidiomycota (75.9% and 94.2%, respectively), followed by Ascomycota (24.0% and 5.8%, respectively). Land-use type significantly affected the bacterial and fungal communities that colonize the roots of napiergrass. Several 137Cs-tolerant bacterial and fungal taxa were also identified, which may be potentially applied for the phytoremediation of 137Cs-contaminated areas around FDNPP. These findings contribute to a better understanding of the distribution of microbial communities in 137Cs-contaminated lands and their long-term ecosystem benefits for phytoremediation efforts.