Volume 96, Issue 7 - Special Issue: The global scenario and challenges of radioactive waste in the marine environment

This critical review explores the quantification, analysis, and detection of radionuclides in the environment using the diffusive gradients in thin films (DGT) technique. Radionuclides, unstable isotopes emitting ionising radiation, are present in the environment due to natural and anthropogenic sources for which concerns are raised about their impact on human health and ecosystems. DGT offers a unique passive sampling approach for understanding the behaviour of radionuclides and other trace elements. This review provides insights into method development, real case scenarios, advantages, limitations, and future perspectives of DGT in radionuclide analysis. In terms of method development, various isotopes have been analysed with varying significance based on origin, concentration, risks, and persistence. Notably, U, Th, Pu, Am, Cm, 99Tc, 226Ra, 137Cs, 134Cs, 232U, 237Np, and 152Eu have been measured, revealing their diverse roles in environmental radioactivity. Real case scenarios illustrate applications in uranium mining, water quality monitoring, and metal speciation studies, shedding light on mobility, bioavailability, and ecological impacts. DGT’s advantages include in-situ monitoring, time-averaged mean concentrations, and comprehensive speciation insights. Challenges include potential influences from biofouling, temperature changes and specifically the possible degradation of the binding and diffuse layer due to ionising radiation in long term exposures. In addition, the distinction between fully labile free metal ions and partially labile metal-ligand complexes introduces a potential limitation in the DGT technique, hence being an opportunity for future studies. Looking forward, DGT is expected to contribute to radiation dose modelling, environmental risk assessment, and water quality monitoring, with ongoing developments enhancing its utility and accuracy.

Radioactive materials may contain primordial radionuclides, and radionuclides of anthropogenic, nuclear accident, and waste disposal which are present in marine environments. This review explores various approaches for the effective sampling and detection of marine radionuclides. The different types of samples that can be collected, including water, sediment, biota, and suspended particulate matter are discussed. Additionally, this paper discusses the various analytical techniques employed for radionuclide detection, such as gamma spectrometry and radiochemical separation. The review emphasizes the importance of choosing appropriate sampling and detection methods based on the specific radionuclides, environmental conditions, and the desired level of sensitivity. It also highlights the challenges associated with their sampling and detection in complex marine environments. These include low radionuclide concentrations, interference from natural matrices, and contamination risks.

Most contaminants in the sea originate from land sources. Radionuclides in sea water are transported by sea currents. Marine sediment is a physical trap for pollutants that are introduced to the environment and play an important role in radiological studies. Radionuclides from seawater bound to particulates sink to the seabed. Their resuspension causes the reintroduction of pollutants to the water column. Remobilization and horizontal/vertical transport by various processes may occur. Long-lived radionuclides become buried in sub-surface sediment. Grain size sediment classification and sediment geochemical composition all play a significant role in the development of the radionuclide content of marine sediment. Atmospheric fallout from the Chernobyl and the Fukushima accidents, atmospheric nuclear weapon testing, releases from nuclear industry plants, river runoff, and to a lesser extent directed and submarine groundwater discharges are the major sources of radionuclides in the marine environment.

Fresh water outflows to sea are a source of marine contamination by radionuclides, most originating from nuclear industry operations. Usually, these lead to small amounts of radionuclides entering the sea, for example, because of the discharge of cooling water. However, under accident conditions large amounts of radionuclides may enter river systems. The extent of radionuclide transport along freshwater systems and their subsequent dispersal in the ocean depends upon their speciation. This manuscript examines the speciation of uranium, with particular reference to sulphate complexes, along the Shu River in Central Asia with a view to predict its transport along such rivers to receiving seas. The speciation of uranium isotopes in the Shu River (at the border of Kazakhstan and Kyrgyzstan) was determined. Calculations were based on the measured concentrations of Ca 2+ , Mg 2+ , Na + +K + , HCO 3 − , Cl − , SO 4 2− , and of uranium isotopes. These calculations were determined by either titrimetric methods, gravimetric methods or, for uranium isotopes, by alpha-particle spectrometry. Almost all uranium was present as one of three soluble complexes, either [UO 2 OH] + , [UO 2 (CO 3 ) 2 (H 2 O) 2 ] 2− or [UO 2 (CO 3 ) 3 ] 4− . However, despite the significant concentration of sulphate-ions in the water, especially for the Lower Shu in Kazakhstan, the probability of uranium being present as of sulphate complexes in the analyzed water was very low. The presence of soluble ions is consistent with their mobility along freshwater systems and their transfer to the marine environment. No evidence of an effect from influxes of sulphate was identified.

After the Fukushima Daiichi Nuclear Power Station (F1NPS) accident, 137 Cs activity concentrations have not yet decreased to pre-accident levels because of direct release from the site and fluvial discharges of 137 Cs deposited on land. It is necessary to consider dispersion processes in the coastal area to understand the impact of multiple river discharges and direct release. To achieve this goal, we carried out oceanic dispersion simulations that considered direct release and fluvial discharges and compared the results with the annual averages of observed data. We assumed that particulate 137 Cs discharged from rivers to the ocean quickly resuspended and re-leached after coagulation and precipitation, and that all of the 137 Cs was dispersed. The reproducibility of results was improved by considering fluvial discharges of particulate 137 Cs at all sites between 2013 and 2016, except near the F1NPS. In other words, particulate 137 Cs discharged from rivers was found to influence the results of ocean surface activity concentrations within a relatively short period of time. The impact of direct release was dominant for the observed 137 Cs activity concentrations adjacent to the F1NPS, which was used to estimate direct releases.

While 20 % of radionuclides released from the Fukushima Daiichi Nuclear Power Plant accident had been deposited in the terrestrial environment, rivers remain the long-term source for 137 Cs, primarily through particulate transfer, from terrestrial to marine ecosystems. In this study, we estimated the suspended 137 Cs flux to the ocean at 11 sites in the coastal area between October 2012 and December 2020 to be 17 TBq, based on our long-term monitoring data of concentrations of suspended 137 Cs and suspended solids. The cumulative loss of suspended 137 Cs from each site to the ocean ranged from 0.1 % to 1.7 % of initial deposition throughout the observation period, depending on the effect of dam lakes and normalized river discharge. The higher loss is also thought to be the large outflow of runoff during the typhoon. The current level of the suspended 137 Cs concentrations was lowered to 1/10–1/100 of those immediately after the accident. The average value of the decreasing trend for each site was approximated using the equation : y  =  a 1 e  − k 1 t  +  a 2 e  − k 2 t. The rate constant k 1 is higher in areas with intensive land use, such as pastures, bare land, and water surfaces, and k 2 is lower in urban areas.

Sea-to-land transfer of irradiated uranium in soil samples was measured along a transect from the Cumbrian coast south of the Windscale Sellafield nuclear site in a NE direction across the Cumbrian coastal plain. Soluble uranium components were extracted by ion exchange chromatography and ratios 236 U: 238 U and 235 U: 238 U were measured using multi-collector ICP-MS. The method employed demonstrated the utility of 236 U ratio measurements for the determination of irradiated uranium in environmental samples. The results produced for uranium were like those that have been reported for other fission product and nuclear fuel components that have been shown to be marine in origin. Measured 236 U levels were highest close to the seashore and decreased rapidly as an exponential function of distance. The results indicated the absence of depleted uranium, such as might result from the deposition of aerosols generated by the testing of DU munitions at the nearby Eskmeals firing range in all but one sample.

People’s perceptions concerning radiation inform decision making in relation to nuclear power production. There have been extensive studies of people’s perceptions of radiation including in relation to the Fukushima and Chernobyl nuclear events. This paper reports on a social science literature review study and is concerned with public responses to low dose radiation (LDR) and nuclear facilities, particularly in the marine environment. This review confirms that people with little knowledge about radiation have the highest risk perceptions in relation to nuclear power; conversely people with a broader knowledge have lower risk perceptions and are more favourable to nuclear power. Education can increase positive perceptions, but the influence of underlying experience of feeling, emotion, attachment, or mood may dampen this effect. This paper reports studies which document anxiety within the Japanese community in relation to the Fukushima nuclear accident. Literature concerning specific radionuclides released is described. While there are uncertainties about the presence of health impacts following LDR exposures, public attitudes are not in line. There is a need for better dialogue between nuclear professionals and scientists to achieve better nuclear education and public communication outcomes; more specific communication surrounding multi-isotopes, and multi-elements of nuclear power plant disaster releases is warranted. Trusted communicators should include nuclear and social scientists as well as regulators. Given the importance of decarbonization in the context of climate change, this is increasingly important.

The IUPAC Subcommittee on Polymer Education has been pursuing the development of a compact syllabus covering the essential topics required for a tertiary education in polymer science, with numerical and short answer exercises addressing each topic. The primary goal of the document is to provide a framework for a complete course made freely available worldwide so that any educator can implement a professionally-curated course in polymer science for their students without needing expensive textbooks or reliable internet access. An important secondary goal is to popularize the use of approved IUPAC terminology in polymer science by using it consistently throughout the document and providing references to IUPAC source documents. Professor Melissa Chin Han Chan was an active and enthusiastic participant in the project who played a significant role in its design and implementation. The late Professor Richard ‘Dick’ Jones also had a keen interest in the project and had a great influence on its direction and structure. This brief note is dedicated to these two illustrious polymer scientists.

Perovskites materials, due to their peculiar electronic and ionic properties, play a key role in the development of hydrogen-based technologies. Their flexible structure enables an easy tuning of various physical-chemical characteristics, such as ionic and electronic conductivity and redox active sites concentration, fundamental for these applications. Moreover, the same structure can exhibit different properties that can synergically act to improve the performance of the material for a specific application.