Radionuclides In Marine Environment Research Articles

Unfolding the interaction of radioactive Cs and Sr with polyethylene-derived microplastics in marine environment

To unveil the interaction of radioactive Cs and Sr with polyethylene-derived microplastics in the marine environment, a mesocosm study was conducted in a stepwise manner by investigating the uptake capability of microplastics at three different stages: pristine, radiation-exposed, and marine-exposed microplastics. The study demonstrates that the physio-chemical properties of microplastics undergo significant alterations upon exposure to the environment, leading to the emergence of biofilm formation upon marine exposure, while radiation exposure induces surface roughness and cracks. Biofilm growth enhances the uptake of radionuclides by microplastics. However, the growth of biofilms increases the density of microplastics through aggregation, leading to a buoyancy transition from positive to negative buoyancy. Various interaction mechanisms, such as electrostatic, ion–dipole, and physical diffusion interactions, were identified as important mechanisms playing key roles in radionuclide binding to polyethylene-derived microplastics. Despite the significantly lower apparent distribution coefficients observed for radio Cs (in the range of 7.3–23.6 L/kg) and Sr (in the range of 4.3–8.06 L/kg) in the marine system, typically 2–3 orders of magnitude lower than those on marine suspended sediment, this study offers compelling evidence that microplastics in marine environments are capable of sequestering radio Cs and Sr. Consequently, microplastics can potentially accumulate these radionuclides, highlighting their role as potential reservoirs as well as vectors of radionuclides in marine environments.

Artificial Mussels: A New Tool for Monitoring Radionuclides in Aquatic Environments

Existing methods for monitoring radionuclides in aquatic environments require frequent sampling of a large volume of water, followed by tedious concentration and analytical procedures, which often make it impractical. Mussels have also been commonly employed to monitor radionuclides but bioaccumulation is significantly affected by physical and biological factors. This study explored the feasibility of using the ‘Artificial Mussel’ (AM) as a new tool for monitoring radionuclides in marine environments. We showed that (a) the uptake and accumulation of 238U, 88Sr, and 133Cs by AMs are directly related to their concentration in water, and equilibrium could be reached within 7 to 8 weeks with high concentration factors. Our results suggest that AMs can serve as an effective and practical tool for monitoring radionuclides in the aquatic environment and overcoming the difficulties faced by existing methods in radionuclide monitoring.

Consequences of marine ecological environment and our preparedness for Fukushima radioactive wastewaterdischarge into the ocean

<p indent="0mm">Ten years after the Fukushima nuclear accident (FNA), Japan announced the planned discharge of over one million tons of Fukushima radioactive wastewater (FRW) into the Pacific Ocean in two years. This decision regarding FRW disposal has aroused worldwide concerns and public fears, which may be exacerbated by reputational damage and the lack of a clear public understanding of the possible adverse impacts of the FRW. As one of the countries surrounding the Pacific Ocean, China is a stakeholder in this decision regarding the FRW disposal. In this study, we compared the FRW source and its associated radionuclide components with the liquid effluent from routine operation of the nuclear power plant and its associated radionuclides. The activity concentrations of 13 radionuclides in the pre- and post-treated FRW by the Advanced Liquid Processing Systems (ALPS) were quantitatively compared with limits for radionuclide concentrations required by Japan law, guidance levels for radionuclides in drinking water provided by the World Health Organization (WHO), and baseline concentrations of radionuclides in surface seawater from the Pacific Ocean before the FNA. Sediment-seawater distribution coefficients and bioconcentration factors are also shown to provide insights into the mobility and biological availability of radionuclides derived from the FRW in the marine environment. Although 62 radionuclides can be recovered from the FRW by ALPS according to a report from the Tokyo Electric Power Company (TEPCO), a large amount of ³H remains in the ALPS-treated FRW. The total amount of ³H in the ALPS-treated FRW was approximately <sc>8.6×10¹⁴ Bq</sc> (by October 31, 2019), with an average concentration of <sc>7.3×10⁵ Bq/L,</sc> higher than the concentration limit <sc>(6×10⁴ Bq/L)</sc> required by Japan law and guidance level <sc>(10⁴ Bq/L)</sc> provided by the WHO. The amount of ³H in the ALPS-treated FRW <sc>(8.6×10¹⁴ Bq</sc> by October 31, 2019) is continually increasing, and is already higher than the amount of ³H (3×10¹⁴<sc>‒7×10¹⁴ Bq)</sc> released into the Pacific Ocean immediately after the FNA. Additionally, other radionuclides (e.g., ¹⁴C, ⁹⁰Sr, ¹²⁹I, etc.) in the ALPS-treated FRW with high bioconcentration factors and high activity-dose conversion factors relative to ³H should also be carefully monitored and evaluated. The measured results provided by the TEPCO indicated that ~70% of the current ALPS-treated FRW should be repurified to reduce concentrations of other radionuclides to meet Japan’s legal requirements. Despite several unresolved factors (e.g., the FRW source terms, discharging plan, hydrodynamic and biogeochemical processes, etc.) simultaneously influencing the fate of FRW in the marine environment, we qualitatively described the hydrodynamically driven passive transport pathway and the biologically driven active transport pathway of the FRW. The transport of the FRW should be comprehensively investigated from the perspective of physical-biogeochemical processes at multiple scales (e.g., large-scale wind-driven circulation, mesoscale eddies, small-scale turbulence) and three-dimensional (e.g., vertical and horizontal vectors) oceans. Key gateways and transport pathways relevant to the FRW entry into the China seas have been suggested to include the Luzon Strait, the outer continental shelf and cross-shelf penetrating fronts in the East China Sea, the Yellow Sea Warm Current, and the Korean Coastal Current. Under specific conditions, the neglected biologically driven active transport pathway may significantly accelerate transport speed for the FRW-derived radionuclides via migratory animals (e.g., Pacific bluefin tuna) and may impose relatively high radiological risk to humans via seafood consumption. Finally, the consequences of marine ecological environment and our preparedness for the FRW release were discussed from the perspectives of total radioactivity, radionuclide components in the FRW, transport pathways of the FRW, and enhancing capacity to meet radiological risk assessment needs. Nuclear power plants located near the coastal seas are gradually developing in China and play a significant role in China’s national strategy of “Carbon Neutrality”. Technical systems of measurement, tracer, and assessment of radionuclides in the marine environments should be given more attention and be continually enhanced in line with the development of nuclear power plants. Several directions including extremely low minimum detection activity for the analytical methods of radionuclides, buoy-based online and real-time measurement technology for marine radioactivity, construction and validation of numerical models for marine radioactivity, key marine biogeochemical processes for radionuclides, radiation dose-effect for marine biotas, radiological assessment models, and remediation technology for radionuclides in marine environments are emphasized as key technologies in nuclear emergency preparedness to protect marine environment security.

Biological transfer of radionuclides in marine environments - identifying and filling knowledge gaps for environmental impact assessments

Methodologies have been developed to allow impacts of ionising radiation on marine ecosystems to be evaluated within selected geographical settings. The stages in the assessment require initial information about unit concentrations of radionuclides in reference media to be collated. Activity concentrations for reference groups of flora and fauna and for representatives of these groups are then derived using an equilibrium concentration factor approach. Following this, dose-rates can be calculated using relevant dose conversion factors. Impacts on the environment are evaluated by comparison with dose-rates at which selected biological effects are known to occur and the natural radiation background. This paper focuses mainly on the transfer part of the assessment drawing attention to gaps in information that have been identified through review and providing an outline of methods that may be used to fill these gaps. Biokinetic models parameterised using allometric relationships have shown their utility in this respect. Initial work looking into the application of such models has met with some success with model predictions comparing favourably with the few empirical data available. Further work will be needed to validate the models for a large range of radionuclides and to consider uncertainty in model estimates through probabilistic analyses. 1. ENVIRONMENTAL IMPACT ASSESSMENT Methodologies to assess the impact of exposure to ionising radiation on flora and fauna have been developed in two recent European collaborative projects (1-3). The initial stage of the assessment requires the selection of appropriate reference biota and suitable representative organisms (normally defined at the species level) with concomitant collation of life history data sheets. Methods for deriving the transfer and fate of radionuclides are necessary during the assessment procedure as are methods for deriving (weighted or unweighted) dose-rates. Once exposures for reference biota have been derived, they need to be interpreted in terms of biological effects. The analyses cannot be termed a risk assessment at this stage because the probability of specified biological effects occurring has not been adequately considered.

Medical radionuclides in marine environment.

RADIOACTIVE discharges resulting from the practice of nuclear medicine are controlled by the Department of the Environment, who grant licences to individual hospitals for the discharge of liquid wastes under the Radioactive Substances Act, 1960. A few years ago most workers in nuclear medicine would have thought that the large degree of dilution occurring when hospital effluent enters a public sewage system would remove any possibility of it having any environmental effect. Because of the recent rapid increase in the medical use of radionuclides, however, there is now some concern regarding environmental contamination1,2.