Planned release of contaminated water from the Fukushima storage tanks into the ocean: Simulation scenarios of radiological impact for aquatic biota and human from seafood consumption

Radionuclides in marine food web along China's coastal waters: Activity, distribution and trophic level bio-magnification

This study investigated the occurrence, activity, distribution, and trophic level bio-magnification of 4 radionuclides (polonium(210Po), strontium(90Sr), cesium(137Cs), and plutonium (239,240Pu)) in 16 kinds of marine organism along China's coastal waters: the Bohai Sea, Yellow Sea, East China Sea, and South China Sea. Results showed that none of radionuclides was detected at the level exceeding the established regulatory limits, with the highest measured activities of 210Po = 13.9 Bq/kg, 90Sr = 0.22 Bq/kg, 137Cs = 0.242 Bq/kg, 239,240Pu = 3.28 mBq/kg. In the sampled organisms, mollusks were found higher levels of activities of radionuclides, with 210Po activity reaching up to 11 Bq/kg. Stable isotope analysis revealed a significant positive correlation of radionuclide activities with the δ15N values (p < 0.001), It could be indicated that radionuclides are transferred through trophic levels rather than being influenced by food sources. Based on the δ15N values, a food web was constructed, and the consequently Trophic Magnification Factor (TMF) showed a bio-dilution effect of radionuclides. Significant difference of the values of δ13C and δ15N among marine organisms from China and from Japan was obtained, which means no migratory species from Japan was found. This study provides crucial data to support the safety of seafoods and informs risk assessment and management strategies in coastal regions.

Which radionuclides contribute most to seafood ingestion dose?

Radiological ingestion doses from eating seafood are regularly evaluated near coastal nuclear facilities, following accidents/events and frequently in national studies worldwide. However, a recent global review found that published seafood doses varied greatly depending on which radionuclides were selected for evaluation and that there has been a tendency to omit important radionuclides or focus on less significant ones. This indicates a need for clear guidance on which radionuclides to prioritise in such studies. Here, we use worldwide data for 16 key radionuclides contributing to typical background seafood ingestion dose. We account for the loss of radionuclides during cooking and the radioactive decay of the short-lived 210Po. Results indicate that for the typical world consumer, naturally-occurring radionuclides account for >99 % of the total seafood ingestion dose, of which about 84 % comes from 210Po and 8 % from 210Pb. About 5 % comes from 228Ra, a far greater proportion than the more frequently-assessed 226Ra (<1 %). Other Th- and U-series radionuclides provide far lower contributions (0.07 %-0.70 %), while 14C provides about 0.09 %. In comparison, the contribution to total seafood ingestion dose from background anthropogenic radionuclides is <1 %, with 137Cs contributing most (0.08 %) and 90Sr, 99Tc, 110mAg and 239Pu adding a further 0.05 % together. These percentage contributions to dose can vary somewhat depending on consumption patterns (e.g., differing proportions of fish, bivalves, etc.). However, 210Po is the dominant contributor irrespective of country-specific diets or restricted diet scenarios (fish-only, seaweed-only, etc.). Study results provide new guidance to improve the design, interpretation and communication of seafood ingestion dose assessments.

Fukushima Contaminated Water Risk Factor: Global Implications

The discharge of Fukushima radioactively contaminated water into the Pacific Ocean started in August 2023, posing comprehensive threats to marine ecosystems and human health globally. This study introduces the Fukushima Contaminated Water Risk Factor (FCWRF), which integrates three components─radionuclide diffusion, bioaccumulation, and global seafood trade─to evaluate the spatiotemporal distribution of risks based on actual discharge practices. Results suggest that comprehensive risks exceeding 2 orders of magnitude beyond the baseline will be transferred to six continents globally. Furthermore, the spread of such risks is projected to be six times faster than radionuclide diffusion. In the simulation, the results illustrated a small increase in radionuclide activity occurring in most regions of the Pacific Ocean. Nevertheless, the dimensionless FCWRF based on a novel integrated framework bridges the barriers among different fields in the risk assessment of radionuclides, thereby underpinning timely and effective responses from the global community.

Assessment of environmental impacts from authorized discharges of tritiated water from the Fukushima site to coastal and offshore regions

In August 2023, the long-planned discharging of radioactive wastewater from the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) started after the confirmation of its feasibility and safety. As this water contains elevated amounts of tritium even after being diluted, a lot of resources have been invested in the monitoring of the Fukushima coastal region where the discharge outlet is located. We compare the first 3H surface activity concentrations from these measurements (up to the end of November 2023) with the available background values to evaluate a possible impact of the long-term discharging on humans and environmental levels of the radionuclide of interest in the same or nearby area. From our results, we can conclude that the joint effect of horizontal and vertical mixing has been significant enough to reduce tritium concentrations at the monitored locations in the region close to the FDNPP port two days after the end of the respective phase of the discharging beyond the detection limit of the applied analytical methods (∼0.3 Bq L-1) which is by five orders of magnitude lower than safety limit for drinking water set by the World Health Organization (WHO). Moreover, the distant correlation analysis showed that tritium concentrations at stations located further than 1.4 km were very close to pre-discharge levels (∼0.4 Bq L-1). We also estimated that the 3H activity concentration in the offshore Fukushima region would be elevated by 0.01 Bq L-1 at maximum over a year of continuous discharging, which is in concordance with the already published modeling papers and much less than the impact of the FDNPP accident in 2011.

Internal dose rate due to intake of uranium and thorium by fish from a dam reservoir associated with a uranium mine in Brazil

Uranium mining can cause environmental impacts on non-human biota around mine sites. Because of this, the reduction in non-human biota exposure becomes an important issue. Environmental radioprotection results from the evolution of human radioprotection; it is based on dose rate to non-human biota and uses, as a biological target, and has harmful effects on populations. In the present study, a flooded impoundment created following dam construction in a uranium mine plant undergoing decommissioning was investigated. Internal dose rates due to activity concentration of natural uranium (Unat) and 232Th in omnivorous, phytophagous, and carnivorous fish species were estimated. Radionuclide activity concentrations were obtained by spectrophotometry with arsenazo III in the visible range. The dose rate contribution of 232Th was lower than that of Unat. There were no differences between the internal dose rates to studied fish species due to 232Th, but there were differences for Unat. A dose rate of 2.30·10-2 µGy∙d-1 was found due to the two studied radionuclides. Although this value falls below the benchmark for harmful effects, it is important to acknowledge that the assessment did not account for other critical radionuclides from uranium mining, which also contribute to the internal dose. Moreover, the study did not assess external doses. As a result, the possibility cannot be excluded that dose rates at the study area overcome the established benchmarks for harmful effects.

Efficient adsorption of radioactive iodine by covalent organic framework/chitosan aerogel

Radioactive iodine is considered one of the most dangerous radioactive elements in nuclear waste. Therefore, effective capture of radioactive iodine is essential for developing and using nuclear energy to solve the energy crisis. Some materials that have been developed for removing radioactive iodine still suffer from complex synthesis, low removal capacity, and non-reusability. Herein, covalent organic framework (COF)/chitosan (CS) aerogels were prepared using vacuum freeze-drying, and the COF nanoparticles were tightly attached on the green biomass material CS networks. Due to the synergistic effect of both COF and CS, the composite aerogel shows a three-dimensional porous and stable structure in the recycle usage. The COF/CS aerogel exhibits excellent iodine adsorption capacity of 2211.58 mg g-1 and 5.62 g g-1 for static iodine solution and iodine vapor, respectively, better than some common adsorbents. Furthermore, COF/CS aerogel demonstrated good recyclability performance with 87 % of the initial adsorption capacity after 5 cycles. In addition, the interaction between iodine and imine groups, amino groups, and benzene rings of aerogel are the possible adsorption mechanisms. COF/CS aerogel has excellent adsorption properties, good chemical stability, and reusable performance, which is a potential and efficient adsorbent for industrial radioactive iodine adsorption from nuclear waste.

A critical review and update of modelling of treated water discharging from Fukushima Daiichi NPP

Since the accident at the Fukushima Daiichi nuclear power plant (FDNPP) in March 2011 seawater is still needed to cool the reactor cores. This water, contaminated with radionuclides, has been collected in tanks and treated on the site of the FDNPP. In 2021, the Japanese government decided to gradually discharge treated water into the ocean, which started on the 24th of August 2023 and will continue for the next 30 years. This paper provides a critical analysis of the models that were used in the different radiological impact studies. Based on the analysis, a hydrodynamic and a compartment models with a harmonized setup were used to estimate the impact of the discharge on humans and biota. Doses obtained with these two models were within one order of magnitude for humans (<0.1 μSv/year) and for biota (<10-6 mGy/d) indicating that harmonization of the model parameters improved the reliability of the simulation results.

Thoughts, perceptions and concerns of coastal residents regarding the discharge of tritium-containing treated water from the Fukushima Daiichi Nuclear Power Plant into the Pacific Ocean

BACKGROUND

As a part of the decontamination process after the Fukushima Daiichi Nuclear Power Plant accident of 2011, 1.32 million tonnes of tritium-containing water will be discharged from the power plant into the Pacific Ocean. Although radiobiological impacts of the treated water discharge on the public and the environment were reported to be minimal, Tomioka and Okuma locals expressed unease regarding the long-term recovery of their towns, which are economically dependent on the agricultural, fishery, and tourism sectors. This study presents thoughts, perceptions and concerns of Tomioka and Okuma locals regarding the discharge of FDNPP-treated water containing tritium into the Pacific Ocean to facilitate a more inclusive decision-making process that respects local stakeholder interests.

METHODS

Conducted from November to December 2022, surveys were mailed to current residents and evacuees aged 20 years or older registered with the town councils.

RESULTS

Out of 1268 included responses, 71.5% were from those > 65 years. 65.6% were unemployed, 76.2% routinely visited hospitals, and 85.5% did not live with children. 61% did not want to return to Okuma/Tomioka. Anxiety about radiation-related health effects (38.7%), consuming food produced in Okuma/Tomioka (48.0%) and genetic effects (45.3%) were low. >50% reported poor physical and mental health. 40% were acceptive, 31.4% were unsure, and 29.7% objected to the discharge plans. Multinomial regression analysis revealed that, compared to acceptive responders, those who objected were more likely to be female, unemployed, and have anxiety about radiation-related genetic effects and poor mental health. Unsure responders were similarly more likely to be female, anxious about radiation-related genetic effects and have poor mental health.

CONCLUSION

The poor mental health of the locals, connected to high levels of risk perception and anxiety about the loss of economic opportunities related to the discharge plans, must be addressed. The 30-year discharge process could handicap local industries and hamper post-disaster socioeconomic recovery due to the circulation of false rumours among consumers. These results highlight the need to actively involve residents in the towns' recovery process to address local concerns. The focus should be on the judicious combination of transparent science with the human aspect of recovery and narratives highlighting dialogues between local stakeholders and experts to enable the locals and the general public to make informed decisions about their protection and future.

Tritium: Its relevance, sources and impacts on non-human biota

Tritium (³H) is a radioactive isotope of hydrogen that is abundantly released from nuclear industries. It is extremely mobile in the environment and in all biological systems, representing an increasing concern for the health of both humans and non-human biota (NHB). The present review examines the sources and characteristics of tritium in the environment, and evaluates available information pertaining to its biological effects at different levels of biological organisation in NHB. Despite an increasing number of publications in the tritium radiobiology field, there exists a significant disparity between data available for the different taxonomic groups and species, and observations are heavily biased towards marine bivalves, fish and mammals (rodents). Further limitations relate to the scarcity of information in the field relative to the laboratory, and lack of studies that employ forms of tritium other than tritiated water (HTO). Within these constraints, different responses to HTO exposure, from molecular to behavioural, have been reported during early life stages, but the potential transgenerational effects are unclear. The application of rapidly developing "omics" techniques could help to fill these knowledge gaps and further elucidate the relationships between molecular and organismal level responses through the development of radiation specific adverse outcome pathways (AOPs). The use of a greater diversity of keystone species and exposures to multiple stressors, elucidating other novel effects (e.g., by-stander, germ-line, transgenerational and epigenetic effects) offers opportunities to improve environmental risk assessments for the radionuclide. These could be combined with artificial intelligence (AI) including machine learning (ML) and ecosystem-based approaches.

Simulation study on 3H behavior in the Fukushima coastal region: Comparison of influences of discharges from the Fukushima Daiichi and rivers

The release of tritium (³H) to the ocean is planned on the coastal environment in the Fukushima coastal region from Spring or Summer of 2023. Before its release, we evaluate the effect of ³H discharges from the port of Fukushima Daiichi and rivers in the Fukushima coastal region using a three-dimensional hydrodynamic model (3D-Sea-SPEC). The simulation results showed that discharges from the port of Fukushima Daiichi dominantly affected the ³H concentrations in monitoring points within approximately 1 km. Moreover, the results indicate that the effect of riverine ³H discharge was limited around the river mouth under base flow conditions. However, its impact on the Fukushima coastal regions under storm flow conditions was found, and the ³H concentrations in seawater in the Fukushima coastal region were formed around 0.1 Bq/L (mean ³H concentrations in seawater in the Fukushima coastal region) in the near shore.

Radionuclide contents in sediment and seafood from Makoko Lagoon, Lagos State, Nigeria

Sediment and seafood samples were collected from Makoko Lagoon, Lagos state, Nigeria. Gamma-ray spectrometry was used to determine the activity concentrations of ⁴⁰K, ²²⁶Ra and ²³²Th in the samples. The average activity concentrations of ⁴⁰K, ²²⁶Ra and ²³²Th in the sediment were 41.04 ± 6.41, 10.15 ± 3.19 and 4.39 ± 2.10 Bq kg^-1, respectively, while the annual effective dose was 0.01 mSv/year. In seafood, the average activity concentrations of ⁴⁰K, ²²⁶Ra and ²³²Th were 15.66 ± 8.07, 1.72 ± 1.51 and 1.93 ± 0.30 Bq kg^-1, respectively. The cumulative effective ingestion dose obtained ranged from 0.016 μSv/year (giant prawn) to 1.08 μSv/year (Parrotgrunt). The mean activity concentrations and absorbed dose rate in sediment were below the worldwide average values. The cumulative dose from the ingestion of seafood was also significantly low. Sediment and seafood from the lagoon in Makoko pose no health risk from a radiological point of view to the population.

Impact of the Fukushima Accident on 3H and 14C Environmental Levels: A Review of Ten Years of Investigation

The investigation of the impact of the Fukushima accident is still going on although more than ten years have passed since the disaster. The main goal of this paper was to summarize the results of tritium and radiocarbon determinations in different environmental samples, possibly connected with the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident. A document containing compiled data may serve as a solid basis for further research in the selected fields. To accomplish such effort, we went through dozens of relevant published papers, reporting 3H and 14C activity concentrations in precipitations, groundwater, seawater, river systems, tree rings, and, in some more extraordinary samples, such as herbaceous plants or debris from the damaged reactor buildings. As the referenced results would not be obtainable without adequate analytical techniques, the most common methods for routine measurement of tritium and radiocarbon concentrations are discussed as well. We believe that the correct identification of the affected environmental compartments could help quantify the released 3H and 14C activities and track their following fate, which could be especially important for plans to discharge contaminated water from the FDNPP in the upcoming years.

Flux of tritium from the sea to the atmosphere around a nuclear reprocessing plant: Experimental measurements and modelling for the Western English channel

Tritium is released to the environment by nuclear industries in various forms, mainly HTO. In impact studies leading to estimated doses for the population, atmospheric discharges are mainly taken into consideration because they generally lead to values higher than those related to liquid discharges. However, the tritium released in liquid environments can be transferred to the atmosphere by evaporation and then be transported to terrestrial ecosystems by wind. This study was carried out in France near a fuel reprocessing plant (RP) which discharges tritium into the western English Channel. We highlighted the influence of a mass of water enriched with tritium on the HTO levels in atmospheric water vapour downwind through 18 field campaigns. A hydrodynamic model able to simulate tritium activity in the water was coupled with an evaporation an atmospheric transport model. It allows to reconstitute variations in atmospheric tritium on the coast, depending on liquid discharges of tritium from the reprocessing plant. On this basis, when seawater containing 20-100 Bq.L^-1 of tritium flows between 0 and 10 km off the coast, variations in atmospheric activity onshore can increase of 2-15 Bq.L^-1. Mean tritium quantities released by the sea into the atmosphere in the Western English Channel reached 130 TBq.y^-1 over the 2017-2020 period. Emissions were estimated at 0.9-11.3 GBq km^-2.y^-1 and depends principally on the distance from the liquid discharge point. If we compare the "marine" source term, in HTO form, with the direct source term for gaseous discharges, the marine source term is one order of magnitude greater for the marine region affected by liquid discharges. Finally, we estimate that approximately 1.1% of tritium stock discharged at sea (regulated and controlled) return to the atmosphere each year at the scale of the Western English Channel.

Development and calibration of a modifiable passive sampler for monitoring atmospheric tritiated water vapor in different environments

Anthropogenic release of tritium from nuclear facilities is expected to increase significantly in the coming decades, which may cause radiation exposure to humans through the contamination of water and food chains. It is necessary and urgent to acquire detailed information about tritium in various environments for studying its behavior and assessing the potential radiation risk. In the atmosphere, although the passive sampling technique provides a low-cost and convenient way to characterize the dynamics of tritiated water vapor (HTO), a single, simple sampler configuration makes it difficult to collect sufficient and representative samples within the expected period from different environments. In this study, we systematically studied the impacts of sampler configurations on sampling performance and proposed a modifiable sampler design by scaling sampler geometry and adjusting absorbent to achieve different monitoring demands. The samplers were subsequently deployed at five sites in China and Germany for the field calibration and the measured results exhibited a good agreement between the adsorption process obtained in sites corrected with diffusion coefficient and the one calibrated in Shanghai. This suggests the feasibility of predicting sampling performance in the field based on known data. Finally, we developed a strategy for sampler modification and selection in different environments and demonstrated that using easily obtainable environmental data, our sampler can be optimized for any area without any time-consuming preliminary experiments. This work provides a scientific basis for establishing high-resolution atmospheric HTO database and expands the conventional empirical sampler design paradigm by demonstrating the feasibility of using quantitative indices for sampler performance customization.

Overcoming the Fukushima Wastewater Crisis: What the Japanese Authorities Could Do to Address Opposing Views

ABSTRACT

In April 2021, the Japanese authorities' announcement of their decision to release processed wastewater from the damaged Fukushima Daiichi nuclear power plant into the Pacific Ocean over 30 y, beginning in 2023, triggered strong domestic and international opposition. Failure to handle this situation tactfully can lead to public disorder, civil disobedience, loss of trust in the authorities, and even diplomatic sanctions. In this article, we explain the underlying reasons behind this resistance, and we offer some strategic methods that the Japanese authorities can deploy to address opposing views and overcome the Fukushima wastewater crisis.

Viewpoint on the Integration of Geochemical Processes into Tracer Transport Models for the Marine Environment

Two types of models are used to describe the interactions of tracers dissolved in the ocean with marine sediments: equilibrium and dynamic models. A brief description of these models is given in this opinion paper, and some examples are presented to show that preference should be given to the dynamic descriptions in modern pollutant transport models to be used in emergencies as well as in the case of chronic tracer releases to the sea.