210Po in the marine environment with emphasis on its behaviour within the biosphere

Characteristics and radiological hazard assessment of 210Po in tilapia (Oreochromis niloticus) in Vietnam

210Po is one of the most toxic natural radionuclides. This isotope's characteristics and radiological hazard assessment have been concerned in different objects. In this study, the 210Po activities were determined in different tilapia organs/parts of 20 sample groups by alpha spectrometry. The 210Po activities in muscle, bone, intestine organs, and stomach contents unevenly distributed with a wide range from 0.5 ± 0.2 to 2.8 ± 0.4 and 1.4 ± 0.2 Bq·kg-1 wet.wt on average, from 0.6 ± 0.3 to 6.3 ± 0.7 and 3.5 ± 0.4 Bq·kg-1 wet.wt on average, from 46.3 ± 2.9 to 263 ± 9.7 and 115 ± 6 Bq·kg-1 wet.wt on average, and 20.9 ± 1.2 to 800 ± 29 and 197 ± 9 Bq·kg-1 wet.wt on average, respectively. The average 210Po activities in different parts of tilapia trend in order of CMuscle < CBone < CIntestine < CStomach contents. Insignificant correlations were observed between 210Po activities in tilapia organs with their total fish mass. The result could depend on feeding types, diet, different nutrient levels, metabolism, and excretion of 210Po in different ages. The concentration ratios (CRs) of tilapia muscle and bone organs were recorded with low values, while it was far greater than the CRs for the intestine organ. Annual committed effective doses contributing from 210Po concentration due to tilapia fish consumption were within the allowable limits for muscle and bone organs, while those values for intestine organs were far higher than the allowable limit value (assuming similar amount consumption of 30 kg·year-1 for each organ). The Erica tool was used to estimate the dose and risk to tilapia from 210Po exposure. Based on the calculated results, it can be seen that there was insignificant concern for tilapia due to ionizing radiation in the study area.

Combined Use of Short-Lived Radionuclides (234Th and 210Po) as Tracers of Sinking Particles in the Ocean

Radionuclides can provide key information on the temporal dimension of environmental processes, given their well-known rates of radioactive decay and production. Naturally occurring radionuclides, such as 234Th and 210Po, have been used as powerful particle tracers in the marine environment to study particle cycling and vertical export. Since their application to quantify the magnitude of particulate organic carbon (POC) export in the 1990s, 234Th and, to a lesser extent, 210Po have been widely used to characterize the magnitude of the biological carbon pump (BCP). Combining both radionuclides, with their different half-lives, biogeochemical behaviors, and input sources to the ocean, can help to better constrain POC export and capture BCP dynamics that would be missed by a single tracer. Here, we review the studies that have simultaneously used 234Th and 210Po as tracers of POC export, emphasizing what can be learned from their joint application, and provide recommendations and future directions.

The concentration of radioisotopes (Potassium-40, Polonium-210, Radium-226, and Thorium-230) in fillet tissue carp fishes: A systematic review and probabilistic exposure assessment

Chemical contamination of seafood has become a global health concern. Carp fish is one of the most widely consumed globally, and several studies have been conducted on the contamination of carp fish with radioisotopes. In the current study, a meta-analysis and probabilistic exposure assessment regarding the Potassium-40 (40K), Polonium-210 (210Po), Radium-226 (226Ra), and Thorium-230 (230Th) in the fillet tissue of carp fish were performed. In this regard, Scopus and PubMed were screened to retrieve the associated citations with on the concentration of radioisotopes in the fillet tissue of carp fish until October 2021. The rank order of radioisotopes in fillet tissue carp fish was 40K (103.49 Bq kg-1) > 210Po (9.39 Bq kg-1) > 226Ra (0.62 Bq kg-1) > 230Th (0.39 Bq kg-1). The highest effective dose due to 210Po ingestion was observed in Spain (male; 4.44E-05 Sv y-1, female; 2.67E-06 Sv y-1); 40K (female, 5.07E-07 Sv y-1); 226Ra (male, 9.93E-09 Sv y-1). The mean of effective dose (ED) in the male and females in India due to ingestion of 230Th as result of carp fish consumption was (1.70E-06 Sv y-1) and (7.01E-08 Sv y-1), respectively. The probabilistic exposure assessment by the Monte Carlo simulation method revealed that consumers of fillet tissue carp fish content of radioisotopes are at a safe range (0.001 Sv y-1).

Seafood dose parameters: Updating 210Po retention factors for cooking, decay loss and mariculture

210Po has been identified as one of the main contributors to ingestion doses to humans, particularly from the consumption of seafood. The amount of 210Po activity concentration data for various types of seafood has increased greatly in recent times. However, to provide realistic seafood dose assessments, most 210Po data requires correction to account for losses that can occur before the seafood is actually consumed. Here we develop generic correction factors for the main processes associated with reduction of 210Po in seafood - leaching during cooking, radioactive decay between harvest and consumption, and sourcing from mariculture versus wild-caught. When seafood is cooked, the overall mean fraction of 210Po retained is 0.74 for all cooking and seafood types, with the means for various seafood types and cooking categories ranging from 0.56 to 1.03. When considering radioactive decay during the period between harvest and consumption, the overall mean fraction remaining is 0.81 across all seafood preservation/packaging types, with estimates ranging from 0.50 (canned seafood) to 0.98 (fresh seafood). Regarding mariculture influence, the available limited data suggest marine fish and crustaceans raised with processed feed have about one order of magnitude lower (×0.10) 210Po muscle content than wild-caught seafood of the same or similar species, although this ratio varies. Overall, this study concludes that 210Po activity concentrations in seafood at the time of ingestion may be reduced to only about 55% compared to when it was harvested. Therefore, correction factors must be applied to any data derived from environmental monitoring in order to achieve realistic dose estimates. The data also suggest lower 210Po ingestion doses for consumers who routinely favour cooked, long shelf-life and farmed fish/crustaceans. However, more data is needed in some categories, especially for cooking of molluscs and seaweed, and for the 210Po content in all farmed seafood.

Variation of 210-polonium in the cephalopod community from the Bay of Biscay, North-East Atlantic

Among natural radionuclides, 210Po is the major contributor to the radiation dose received by marine organisms. In cephalopods, 210Po is concentrated in the digestive gland, which contains over 90% of the whole-body burden of the nuclide. Although previous studies showed that 210Po was taken up independently of 210Pb, its parent nuclide, very little is known about the factors influencing its levels in cephalopods. To the best of our knowledge, no studies investigated 210Po levels in different species at the same time. In the present study, 210Po was analysed in the digestive gland of 62 individuals from 11 species representing a large range of feeding ecologies and habitats, including squids, cuttlefish and octopus species from coastal to deep-oceanic habitats. Among species, the highest activity was measured in Loligo vulgaris (5720 ± 3606 Bq/kg) and the lowest in T. megalops (188 Bq/kg). However, considering the habitats (benthic vs pelagic and neritic vs oceanic), no significant differences appeared. At the species level, no differences between sexes were found so both sexes were plotted together to test the size effect for species with at least 8 individuals (i.e., Eledone cirrhosa, L. vulgaris, L. forbesi and Sepia officinalis). In the first three species, 210Po levels decreased significantly with increasing size or weight but not in S. officinalis. In squid, this could be related to ontogenetic changes in diet from a high proportion of crustaceans (high Po content) in small individuals to fish (low Po content) in larger individuals, while the high dietary plasticity of S. officinalis at all stages of its life cycle could explain the lack of decrease in 210Po with size. In comparison to the few data from the literature, the levels of 210Po concentrations in the cephalopod community of the Bay of Biscay were overall in the same range than those reported in other cephalopods, varying across 4 orders of magnitude. Further studies are needed to understand the mechanism of retention in the cephalopod digestive gland.

Detection of Polonium-210 in Environmental, Biological and Food Samples: A Review

Ingestion of polonium-210 from environmental media and food can cause serious health hazards (e.g., gastrointestinal symptoms, tumours, etc.) and has been a public health concern worldwide since the 2006 poisoning of Agent Litvinenko 210Po in Russia. With the development of uranium mining and applications of nuclear technology in recent decades, the radioactive hazards posed by 210Po to living organisms and the environment have become increasingly prominent. In order to strengthen the monitoring of environmental 210Po and protect both the environment and human health, a series of explorations on the methods of 210Po determination have been ongoing by researchers across the globe. However, previous reviews have focused on individual sample types and have not provided a comprehensive account of environmental, food, and biological samples that are closely related to human health. In this work, the sources, health hazards, chemical purification, and detection methods of trace 210Po in different sample types are systematically reviewed. In particular, the advantages and disadvantages of various pretreatment methods are compared, and relevant domestic and international standards are integrated, which puts forward a new direction for the subsequent establishment of rapid, simple, and efficient measurement methods.

Experimental optimization of physicochemical factors for spontaneous deposition of 210Po using newly designed deposition kit

A simple spontaneous deposition kit for ²¹⁰Po determination using alpha spectrometry was newly designed, and polonium deposition characteristics under various physicochemical conditions were evaluated using it. The high-purity silver disc (99.99%) showed high deposition efficiencies of over 85.1% in the HCl concentration range of 0.01-6 M. Optimal physicochemical factors were determined to be a temperature of 90 °C, deposition time of 90 min, and the use of ascorbic acid as a reducing agent in an amount similar to that of the interfering element (Fe).

Ocean Acidification-Mediated Food Chain Transfer of Polonium between Primary Producers and Consumers

Phytoplankton and zooplankton are key marine components that play an important role in metal distribution through a food web transfer. An increased phytoplankton concentration as a result of ocean acidification and warming are well-established, along with the fact that phytoplankton biomagnify 210Po by 3−4 orders of magnitude compared to the seawater concentration. This experimental study is carried out to better understand the transfer of polonium between primary producers and consumers. The experimental produced data highlight the complex interaction between the polonium concentration in zooplankton food, i.e. phytoplankton, its excretion via defecated fecal pellets, and its bioaccumulation at ambient seawater pH and a lower pH of 7.7, typical of ocean acidification scenarios in the open ocean. The mass of copepods recovered was 11% less: 7.7 pH compared to 8.2. The effects of copepod species (n = 3), microalgae species (n = 3), pH (n = 2), and time (n = 4) on the polonium activity in the fecal pellets (expressed as % of the total activity introduced through feeding) was tested using an ANOVA 4. With the exception of time (model: F20, 215 = 176.84, p < 0.001; time: F3 = 1.76, p = 0.16), all tested parameters had an impact on the polonium activity (copepod species: F2 = 169.15, p < 0.0001; algae species: F2 = 10.21, p < 0.0001; pH: F1 = 9.85, p = 0.002) with complex interactions (copepod x algae: F2 = 19.48, p < 0.0001; copepod x pH: F2 = 10.54, p < 0.0001; algae x pH: F2 = 4.87, p = 0.009). The experimental data underpin the hypothesis that metal bioavailability and bioaccumulation will be enhanced in secondary consumers such as crustacean zooplankton due to ocean acidification.

Determining baseline radiation levels in marine biota - A comparison of SE Queensland commercial species

Limited data exists on the contribution to radiological dose to members of the public from ingestion of radioactivity in seafood in the Australian diet. There is also a lack of data available to assess the radiological dose to marine fauna in Australian waters. Natural and anthropogenic radionuclides and trace metals were measured in the edible flesh of prawns to determine the radiological dose to humans. The remaining tissues were combined and analysed to enable uptake and environmental radiological doses to be assessed. Although in international studies, the edible flesh is generally measured to determine radiation dose or ingestion of trace metals, the effects of preparation and cooking techniques are rarely assessed. In this study, cooking and preparation techniques that may influence the radiological dose to humans were assessed. Eggs were also removed from a selected number of samples to assess the potential dose in sensitive developmental tissues and possible implications for environmental effects. Order of magnitude differences in 210Po activity concentrations and Cd concentrations were observed between whole animals and the edible flesh of Australian caught King (Melicertus spp.) and Tiger (Penaeus spp.) prawns, with the hepatopancreas primarily responsible for this difference. Most 210Po was unsupported by 210Pb and activity concentrations of all other radionuclides measured (137Cs, 210Pb, 226Ra, 232Th, and 238U) were very low. The major contribution to radiation dose via the ingestion pathway and to the organism itself was from 210Po. Cooking techniques that may lead to leaching of 210Po from the hepatopancreas could substantially increase the radiological dose from ingestion of this isotope. Organism dose estimates using different input assumptions in the radiological assessment tool "ERICA", including site-specific tissue activity concentrations with site- or region-specific media concentrations, were compared with ERICA default distribution coefficients (Kd) and concentration ratios.

Evaluation of the radiological dose due to 210Po in commercial clupeid fish collected in the near-shore environment of the high background natural radiation area (HBNRA) on the southwest coast of India

In this study, we quantified the tissue concentration of ²¹⁰Po in a variety of commercial sardine fish species of the family Clupeidae from an area of high background natural radiation area on the southwest coast of India. The smooth belly sardine Amblygaster leiogaster had the lowest ²¹⁰Po concentration in its muscle (45.6 ± 7.9 Bq kg^-1 fresh), while the goldstripe sardine Sardinella gibbosa had the highest (103.4 ± 10.1 Bq kg^-1 fresh). The Annual Committed Effective Dose (ACED) of fried sardine and sardine curry were 134.3-304.3 μSv y^-1 and 226.6-513.5 μSv y^-1, respectively. Of the ²¹⁰Po loss, 20 % was due to frying and 10 % to preparing sardine curry. The effective dose was found to be globally comparable and well below the world limit. Consumption of sardines containing ²¹⁰Po would not pose a health hazard to the residents of Manavalakurchi.

Scavenging of select radionuclides and trace elements by pelagic Sargassum in the Caribbean Sea

In recent years, the North Atlantic and the Caribbean Sea have experienced unusual and unprecedented pelagic Sargassum blooms, which may adversely affect coastal ecosystems and productive ocean. Sargassum has the potential to scavenge trace elements and radionuclides from seawater, and when bioaccumulated and thus concentrated, can pose a potential threat to higher trophic organisms, including humans that consume impacted seafood. In this study, trace elements and naturally-occurring U/Th-series radionuclides were measured in Sargassum that were collected in the coastal waters of the Caribbean Sea (Antigua/Barbuda, Belize, and Barbados) to better define baseline concentrations and activities, and to assess the scavenging potential for these trace elements and radionuclides. The mean concentration of trace elements observed in Sargassum collected across these three Caribbean Sea are ranked accordingly to the following descending order: Sr > As>Fe > Mn > Zn > Ni > V > C > Cd > Se > Co > Cr > Pb > Ag > Hg. 210-Po and 210Pb activities in Sargassum were observed to be more elevated than previously reported values.

Sources of Polonium 210Po and Radio-Lead 210Pb in Human Body in Poland

This article contains and discusses the results of research on the source of polonium 210Po and radio-lead 210Pb in the human body of adults living in Poland. An adult inhabitant of Poland receives an effective annual radiation dose of 309 µSv from inhalation and absorption of 210Po and 210Pb. The main sources of both radionuclides in the body is cigarette and marijuana smoking. In terms of food, the consumption of fish, cereals, vegetables and fruit as well as mushrooms have the largest contribution to annual dose. This study highlights the importance of cigarette smoking and the growing importance of marijuana hash smoking as the main source of 210Po and 210Pb for adults living in Poland. The calculated dose that results from the decay of both radionuclides in body is 1/10 of the annual radiation dose received by a Polish inhabitant from natural sources (2.8 mSv) and is almost five times lower than the dose resulting from the inhalation of 222Rn.

The concentration and health risk assessment of radionuclides in the muscle of tuna fish: A worldwide systematic review and meta-analysis

Exposure to radionuclides, especially in food, can endanger the health of consumers. In this study, a systematic review and meta-analysis were performed regarding the concentration of radionuclides in tuna fish muscle. International databases including PubMed, Scopus, and Embase were searched to find articles regarding the concentration of radionuclides in tuna fish muscle from 1 January 2000 to 20 February 2021. The lowest and highest concentration of radionuclides was related to Caesium-137 (¹³⁷Cs) and Potassium-40 (⁴ K), respectively. The rank order of radionuclides based on their pooled concentration was ⁴ K (370.157 Bq/kg) > ²¹⁰Po Polonium-210 (26.312 Bq/kg) > ²¹⁰Pb (5.339 Bq/kg) > ²²⁶Ra (4.005 Bq/kg) > ¹³⁷Cs (0.415 Bq/kg). The health risk assessment based on annual effective dose indicates that consumers are at the safe range of health risk (H < 1 mSv/y). The continuous monitoring concentration of radionuclides in seafood and health risk assessment should be recommended.

Background 210Po activity concentrations in Greenland marine biota and dose assessment

Polonium-210 (²¹⁰Po) is a radionuclide sentinel as it bioaccumulates in marine organisms, thereby being the main contributor to committed dietary doses in seafood consumers. Although seafood and marine mammals are an important part of the traditional Inuit diet, there is a general lack of information on the ²¹⁰Po concentrations in the Greenlandic marine food chain leading to the human consumer. Here, we determine background ²¹⁰Po concentrations in edible parts of different marine organisms from Greenland and provide a dose assessment. Blue mussels (Mytilus edulis), organs of ringed seal (Pusa hispida) and polar bear (Ursus maritimus) displayed significantly elevated ²¹⁰Po concentrations in respect to all other studied organisms (p < 0.001). ²¹⁰Po concentrations ranged from 0.02 Bq kg^-1, w.w. in Greenland halibut (Reinhardtius hippoglossoides) muscle to 78 Bq kg^-1, w.w. and 202 Bq kg^-1, w.w. in ringed seal muscle and kidneys, respectively. ²¹⁰Po concentration ratio for edible parts increases in the order bladderwrack (Fucus Vesiculosus), northern shrimp (Pandalus borealis), blue mussels, and from fish species to ringed seal and polar bear. ²¹⁰Po distribution in fish, ringed seal, and polar bear follows a general pattern, the lowest concentrations were in muscle, and the highest concentrations were in the organs involved in metabolism. The derived ²¹⁰Po annual absorbed dose in edible parts of studied marine organisms are several orders of magnitude lower than the recommended dose rate screening value of 10 μGy h^-1. Effective doses from intake of ²¹⁰Po to Greenland average children (1.4 mSv y^-1), and high seafood and marine mammal consumers (2 mSv y^-1 for adults and 3.6 mSv y^-1 for children) are higher than the world average annual effective dose due to ingestion of naturally occurring radionuclides.

Current understanding and research needs for ecological risk assessments of naturally occurring radioactive materials (NORM) in subsea oil and gas pipelines

Thousands of offshore oil and gas facilities are coming to the end of their life in jurisdictions worldwide and will require decommissioning. In-situ decommissioning, where the subsea components of that infrastructure are left in the marine environment following the end of its productive life, has been proposed as an option that delivers net benefits, including from: ecological benefits from the establishment of artificial reefs, economic benefits from associated fisheries, reduced costs and improved human safety outcomes for operators. However, potential negative impacts, such as the ecological risk of residual contaminants, are not well understood. Naturally occurring radioactive materials (NORM) are a class of contaminants found in some oil and gas infrastructure (e.g. pipelines) and includes radionuclides of uranium, thorium, radium, radon, lead, and polonium. NORM are ubiquitous in oil and gas reservoirs around the world and may form contamination products including scales and sludges in subsea infrastructure due to their chemistries and the physical processes of oil and gas extraction. The risk that NORM from these sources pose to marine ecosystems is not yet understood meaning that decisions made about decommissioning may not deliver the best outcomes for environments. In this review, we consider the life of NORM-contamination products in oil and gas systems, their expected exposure pathways in the marine environment, and possible ecological impacts following release. These are accompanied by the key research priorities that need to better describe risk associated with decommissioning options.

Assessment of residual radionuclide levels at the Bokak and Bikar Atolls in the northern Marshall Islands

The Bikar and Bokak Atolls, located in the northern Marshall Islands, are extremely isolated and consist of pristine marine and terrestrial ecosystems. Both atolls may have experienced significant radioactive deposition following the nuclear weapon testing conducted at Bikini and Enewetak proving grounds. Here we report activity concentrations of artificial radionuclides (²³⁹Pu, ²⁴⁰Pu, ²⁴¹Pu, ²⁴¹Am, ¹³⁷Cs and ⁹⁰Sr) in marine and terrestrial samples collected from Bikar and Bokak Atolls. Artificial radionuclides in soil from the Majuro Atoll are also reported and form a radiological baseline against which the levels at the other atolls can be compared. We observed low levels of artificial radionuclides in soil from Majuro and Bokak, but significantly higher levels in soil from Bikar. The residual radioactivity in the Bikar environment is comparable to the levels previously reported for other nearby atolls, including Taka and Utrik, but lower than for Rongerik, Rongelap, Bikini and Enewetak. An analysis of ²⁴⁰Pu/²³⁹Pu isotope ratios and estimations of the dates of contamination from ²⁴¹Am/²⁴¹Pu activity ratios both indicated that the Bikar Atoll was contaminated mainly by radioactive fallout from the Castle Bravo test in 1954. We compare the results of our measurements at Bikar and Bokak to data from other atolls in the Marshall Islands and to regions of the world affected by both global and regional fallout from atmospheric nuclear weapons testing and nuclear accidents.

Correlation of phytoplankton satellite observations and radiological doses in molluscs

In this work data of salinity, temperature, suspended particulate matter (SPM), chlorophyll-a, and phytoplankton concentration in the Gibraltar Strait coast, in the confluence of the Mediterranean Sean and the Atlantic Ocean, were analyzed together with ²¹⁰Po, ⁴⁰K, ²¹⁰Pb and ²³⁴Th activity concentration in different types of bivalve molluscs at the same time-period. The physicochemical parameters were evaluated using the Copernicus Marine Environment Monitoring Service (CMEMS) products based on satellite observations. A multivariate statistical analysis, including contrasted natural radioactivity contents, allowed the discrimination of bivalve molluscs from Atlantic and Mediterranean coasts. Additionally, a cluster analysis determined a highly significant negative correlation ²¹⁰Po concentration in molluscs and phytoplankton concentration suggesting that phytoplankton concentration in the water column is a determinant factor to regulate ²¹⁰Po concentration in those animals. These results introduce a useful tool to calculate the radiological doses in seafood from chlorophyll satellite image.

Effect of physiological conditions and biochemical factors of mussels Mytilus galloprovincialis in radioactivity monitoring programs along the Algerian coast

A study was carried out to determine the activities of radionuclides (¹³⁷Cs, ⁴⁰K, ²²⁶Ra, ²¹⁴Bi, ²¹⁴Pb, and ²¹⁰Pb) and the levels of biochemical components (lipids, carbohydrates, and proteins) in mussels (Mytilus galloprovincialis) along the Algerian coast. The goal was to evaluate the effect of mussels' biological parameters on radionuclide concentrations, through two coastal water biomonitoring programs. The mussels were taken from three study areas on the Algerian coast: Kristel (Oran), Surcouf (Alger), and Collo (Skikda), for the passive biomonitoring program and transplanted from each study area into the control site of Surcouf. Biochemical components were determined by means of UV-visible colorimetric assays, while the activity concentrations of radionuclides were measured by gamma-ray spectrometry. The results showed that carbohydrates were the most abundant biochemical components (40-60%) compared with proteins (20-40%) and lipids (15-20%). ¹³⁷Cs activity concentrations were below the lower limit of detection (LOD) for all samples, while the high activities of ⁴⁰K are the result of its behavior as stabile potassium K which is extensively used in the metabolism of mussels reflects the conditional state of mussels. ²¹⁰Pb concentration reflects the conditional state of mussels (morphometric parameters and proteins content). The mussels' bioaccumulation capacity for radionuclides was found to be dependent on the growing site and the biomonitoring time period.

Distribution and annual committed effective dose assessment of 210Po in popular marine species at the near-shore Binh Thuan province, Vietnam

²¹⁰Po concentration in thirty popular marine species (twenty five fishes, four bivalves and one crab) with different habitats, feeding types, and trophic levels at the near-shore Binh Thuan, Vietnam was analyzed using the alpha detectors. The ²¹⁰Po activities were widely ranged from 3.07 ± 0.18 in a fish species (Bumpnose trevally) to 78.6 ± 5.3 Bq/kg w.w in a bivalve species (Green mussel) with the average value of 16.6 Bq/kg w.w. The results showed that the species with lower trophic level value have higher ²¹⁰Po concentration. Regarding the feeding types, the ²¹⁰Po concentration in the omnivorous species is about 2.9 times higher than in the carnivorous species. The species living in demersal zone accumulated a high ²¹⁰Po in comparison with species living in reef-associated and pelagic-neritic zones. The calculated annual committed effective dose from ²¹⁰Po due to the ingestion of seafood from demersal zone and bivalve species of the area was significant high.

Levels and Distributions of 210Pb and 210Po in Selected Seafood Samples in China and Assessment of Related Dose to Population

In this study, the activity concentrations levels of 210Pb and 210Po in the edible portions of eight seafood samples collected from the Fujian coast of China were determined. The activity concentrations ranged from 0.74 ± 0.08 to 12.6 ± 1.0 Bq/kg for 210Po and from the minimum detectable limit (MDL, 0.80 Bq/kg) to 11. 7 ± 1.1 Bq/kg for 210Pb. The 210Po activity concentration in all the fish organs ranged from 0.68 to 204 Bq/kg (w.w.), and the 210Po activity was mainly concentrated in the stomach, spleen, heart, liver, gonad, and intestine samples. The 210Pb activity concentration in all the fish organs ranged from the MDL to 15.2 Bq/kg (w.w.), and the 210Pb activity was concentrated in the head, fish scale, and gill samples. The annual effective ingestion doses ranged from 82.8 to 255 μSv/a for all age groups, and the lifetime risk of cancers were estimated. Both the effective ingestion doses and cancer risk to humans were within the acceptable ranges.

210Po concentration in different size fractions of aerosol likely contribution from industrial sources

²¹⁰Po, being a highly radiotoxic isotope, could contribute to significant inhalation dose to humans. This study establishes the first set of atmospheric ²¹⁰Po data in aerosol samples collected across Kuwait. The primary focus of this study is to investigate spatio-temporal variability of atmospheric ²¹⁰Po and assess its sources, including anthropogenic contributions. Measurements of ²¹⁰Po in aerosols collected over a period of 23 months (January 2018-November 2019) from three different locations, i.e., a remote area (120 km) north of Kuwait City, Kuwait city and an industrial site (60 km from Kuwait City center). Specific activities of ²¹⁰Po were determined in 3 different size fractions (0.39-2.5 μm, 2.5-10 μm and ≥10 μm) and the highest activity was observed in the fine fraction (PM_{0.39- 2.5}) across all sampling stations during both the summer and winter seasons. The highest activities in all the size fractions were measured downwind of the Industrial site that houses oil refineries, cement factory and some other industries including a Power and Desalination Plant. In terms of temporal variations, higher summertime activities were observed across the spatial domain. Longer residence time of atmospheric ²²²Rn-produced ²¹⁰Pb resulting in lower scavenging of atmospheric ²¹⁰Pb, due to very little precipitation in summer, will result in higher atmospheric ²¹⁰Po.

210Po levels and distribution in different environmental compartments from a coastal lagoon. The case of Briozzo lagoon, Uruguay

This paper presents the levels and distribution of ²¹⁰Po in different compartments of a coastal lagoon on the east coast of Uruguay (South America). Activity concentrations of ²¹⁰Po have been obtained in different matrices, such as water, superficial sediments, clams (Diplodon sp.), freshwaters snails (Pomacea sp.), zooplankton, and fishes (Jenynsia sp.), collected at different points of the lagoon and during several sampling campaigns. In addition, the organic matter content of the sediment was determined to study the variation of ²¹⁰Po along the lagoon. The activity concentrations of ²¹⁰Po in the water samples are in the range between 1.1 ± 0.2-3.5 ± 0.4 mBq/L while in the sediment samples vary between 17.1 ± 1.4 and 540 ± 12 Bq/kg, DW. In the case of biota, the ranges obtained were 182 ± 5-265 ± 6 Bq/kg, DW in clams and 134 ± 4-1245 ± 16 Bq/kg, DW in snail samples. A good correlation of ²¹⁰Po with the organic fractions of the sediment was observed (r = 0.8798, p-value < 0.001), being obtained high values for the distribution coefficient Kd (10⁴ -10⁵). In the biota samples, a clear difference was observed in the ²¹⁰Po concentration values in both species, mainly due to the different feeding habits of both aquatic organisms, as it is reflected in the associated concentration ratios (CR). In this paper, a good set of results of ²¹⁰Po, Kd, and CR have been obtained in different matrices, enhancing the limited archives available for modelers concerning these parameters for ²¹⁰Po and freshwater systems.

210Po in Сrimean salt lakes

This paper presents the results of radioecological monitoring study of natural radionuclide ²¹⁰Po in 11 lakes located in different regions of the Crimean peninsula. These investigations of the Crimean salt lakes were conducted for the first time in the history. The main objectives of this work were: to determine the features of the ²¹⁰Ро behavior in the salt lakes ecosystems, as well as calculation of the doses received by the lakes hydrobionts from α-radiation of absorbed ²¹⁰Po. Concentrations of ²¹⁰Po in the water, suspended matter, the bottom sediments and biota were determined by radiochemical processing and α-spectroscopy measurements. The concentrations of dissolved ²¹⁰Po in the water of investigated lakes were in 0.9-327.1 times higher than in the Black Sea closest regions. The highest concentrations of ²¹⁰Po in water were determined in the lakes of the Kerchenskaya group. These lakes are located on the territory of Crimea where oil is produced. The ²¹⁰Ро activity concentrations in the bottom sediments from Crimean salt lakes were comparable with those of the Black Sea coastal zone. Concentration ratio (CR) of polonium in suspended matter ranged from 10 to 10⁴ for different lakes. A significant trend in a decrease of CR values of ²¹⁰Ро for suspended matter with increasing water salinity was revealed. High levels of ²¹⁰Po accumulation were noted for adult crustacean Artemia spp. (typical inhabitant of the Crimean saline lakes). The CR of ²¹⁰Po for adult Artemia spp. reached 10⁵ while the CR of this radionuclide by their cysts was significantly lower. The absorbed doses from ²¹⁰Po α-radiation calculated for adult Artemia spp. were more than 60 times lower than the permissible dose rate for biota (IAEA, 1992).The obtained results will be used to identify the biogeochemical peculiarities in behavior of the main dose-formative radionuclide ²¹⁰Po, in the water ecosystems with different salinity, including water reservoirs poorly studied in the radioecological aspect and having extreme condition for the existence of lots of species of hydrobionts, such as hypersaline Crimean lakes.

Assessment of the annual committed effective dose due to the 210Po ingestion from selected sea-food species in Vietnam

Activity concentration of ²¹⁰Po in the edible muscle tissues of twelve sea-food species (the most common marine food consumed of population in Vietnam) were analyzed using the PIPS detectors ORTEC Alpha-Ensemble spectrometer. The ²¹⁰Po activity concentration in studied samples was found to vary from 0.82 ± 0.47 to 70.3 ± 8.5 Bq/kg fresh weight. The highest activity concentration was recorded for the Blood cockle (Anadara granosa) and the lowest for Silver pomfret (Pampus argenteus). The annual committed effective dose (CED) of ²¹⁰Po to humans (the local residents) due to ingestion of each studied species was calculated from 18.5 to 1586 μSv/y. The average annual committed effective dose value was reported 394 μSv/y, which is marginally higher than the average CED contributed from ingestion of food and water total in global background (290 μSv/y).

Distribution of 239,240Pu in marine products from the seas around the Korean Peninsula after the Fukushima nuclear power plant accident

In March 2011, an earthquake caused the shutdown of the active reactors at the Fukushima Daiichi Nuclear Power Plant (NPP), with the succeeding tsunami resulting in the release of radioactively contaminated water into the adjacent Japanese coastal waters. Marine biota selected from various trophic levels were collected in Korean coastal waters throughout 2014 and 2015 and their plutonium levels were measured to evaluate the radioactive contamination levels in the marine organisms that constitute the primary seafood diet in the Republic of Korea (ROK). The results showed that the activity concentrations of ^239,240Pu in plankton, macroalgae, mollusks, crustaceans, and cephalopods ranged from 13 to 58, 0.64 to 0.80, 0.94 to 5.40, 0.06 to 0.50, and 0.26 mBq kg^-1 of wet weight (w.w.), respectively. The activity concentrations of ^239,240Pu measured in the muscles of fish varied from 0.09 to 0.30 mBq kg^-1 (w.w.), relatively low values compared to those in other groups regardless of fish species, size, and sampling area. The concentration characteristics of ^239,240Pu in the various organs in the respective marine products revealed that the internal organs showed higher concentrations than the muscle or skin (or exoskeleton). The highest concentration of ^239,240Pu was measured in the viscera of an abalone, which had an activity concentration of 6.31 mBq kg^-1 (w.w.). The concentration factors (CFs) in the >300-μm fraction of plankton and in anchovy, shrimp, and mackerel ranged 67-84% of the International Atomic Energy Agency (IAEA)-recommended values, although the CF in macroalgae was much lower at approximately 5% of IAEA values, suggesting a wide range of ^239,240Pu CF in macroalgae. The mean transfer factor (TF) between macroalgae (0.6-0.8 mBq kg^-1) and abalone (5.4 mBq kg^-1) was estimated to be 7.5, implying that effective Pu transfer occurred between the two species. These figures equate to annual effective doses of ^239,240Pu to Koreans through consumption of macroalgae, shellfish, and fish of 1.8 × 10^-6, 1.4 × 10^-6, and 7.1 × 10^-7 mSv yr^-1, respectively, and a total dose of 3.9 × 10^-6 mSv yr^-1, values that are negligible compared to the annual effective dose limit of 1 mSv yr^-1.

210Po and 210Pb activity concentrations in Greenlandic seabirds and dose assessment

Naturally occurring radionuclides, in particular, polonium-210 (²¹⁰Po), have a greater contribution than anthropogenic radionuclides to the annual effective dose received by the general public due to consumption of seafood. Knowledge of potential trophic sources and transfer of ²¹⁰Po to seabird species and subsequently to the Greenlandic people is, however, still poor. Here, we assess the transfer of ²¹⁰Po and ²¹⁰Pb to seabirds sampled during autumn and winter 2017 and 2018 in Greenland and provide a dose assessment. The activity concentrations of ²¹⁰Po in muscle and liver, respectively, ranged from 0.2 ± 0.1 Bq kg^-1 w.w. in glaucous gull (Larus hyperboreus) to 21.2 ± 22.6 Bq kg^-1 w.w. in thick-billed murre (Uria lomvia) and from 32.0 ± 9.4 Bq kg^-1 w.w. in common eider (Somateria mollissima) to 40.5 ± 49.0 Bq kg^-1 w.w. in thick-billed murre. ²¹⁰Po was non-uniformly distributed in the body of thick-billed murre. Kidneys and feathers showed higher ²¹⁰Po activity concentrations than heart and bone. The ²¹⁰Po/²¹⁰Pb activity concentration ratios are higher than unity, indicating that ²¹⁰Po is preferentially taken up by seabirds compared to its progenitor ²¹⁰Pb. The derived annual absorbed dose from ²¹⁰Po to the whole body of thick-billed murre was 6.4 × 10² ± 3.0 × 10² μGy. The annual effective dose to the average adult and representative person in Greenland due to ingestion of ²¹⁰Po in seabirds was estimated to 13.0 μSv and 57.0 μSv, respectively. This derived dose is low and poses a slight risk, and risk communication is therefore deemed unnecessary.

Po uptake in microalgae at different seawater pH: An experimental study simulating ocean acidification

Climate change effects such as ocean acidification (OA) are known to affect the trace metal distribution. This experimental study provides the first data on ²⁰⁹Po uptake rates and ²¹⁰Po concentration in five microalgae species under different pH scenarios. The experiment was conducted in replicates at three pH conditions 8.2, 8.0, and 7.5, representing the current and future climate change scenario as per IPCC RCP8.5. The ²⁰⁹Po uptake in the phytoplankton was highest in Thalassiosira weissflogi, i.e. 83% of the ²⁰⁹Po tracer was taken up at 8.2 pH whereas the lowest uptake was observed in Dunaliella salina equivalent to 20% at 7.5 pH. Similar behavior was observed in ²¹⁰Po concentrations in these microalgae, where ²¹⁰Po ranged between 3.16 ± 0.03 and 11.6 ± 0.04 Bq kg^-1 wet weight (ww), with the highest in the Thalassioria weissflogi at 8.2 pH, and the lowest in Dunaliella salina at 7.5 pH. The difference in ²⁰⁹Po uptake and ²¹⁰Po concentration was statistically significant (p < 0.001) both among species and the pH treatments in the order: Thalassiosira weissflogi > Tetraselmis suecica > Chaetoceros muelleri > Isochrysis galbana > Dunaliella salina and 8.2 > 8.0 > 7.5. A higher concentration of ²⁰⁹Po in seawater was measured at low pH condition in all the experimental tanks. Though the data clearly show the difference in concentration and uptake of polonium at different pH conditions, it is not known if lower pH is affecting the adsorbed or absorbed fraction. A detailed investigation will be required to understand the process as it can have a significant effect on biomagnification and marine food chain transfer under changing climatic scenarios.

Levels of radionuclide concentrations in benthic invertebrate species from the Balearic Islands, Western Mediterranean, during 2012-2018

Baseline levels of radionuclides in the marine environment of the Balearic Islands in Western Mediterranean have not been reported in literature. Because of their ecological role and acknowledged sensitivity to pollutants, herein, the activity concentrations of ²¹⁰Po, ⁴⁰K, ²¹⁰Pb, ⁹⁰Sr, and ²³⁴Th were measured in two types of benthic invertebrate species (mussels and sea urchins) sampled during 2012-2018. The activity concentrations of ²¹⁰Po, ⁴⁰K, ²¹⁰Pb, and ²³⁴Th ranged from 38 ± 1 to 325 ± 11 Bq kg^-1 dry weight (d.w.), 220 ± 10 to 996 ± 46 Bq kg^-1 d.w., ND (lower than the limit of detection) to 55 ± 8 Bq kg^-1 d.w., and ND to 70 ± 15 Bq kg^-1 d.w., respectively. In all cases, no artificial ⁹⁰Sr activity was detected in the collected samples. The committed effective dose to humans was calculated to be in the range of 48-640 μSv year^-1.

Mercury and Po-210 in mollusc species in the island of Gökçeada in the north-eastern Aegean Sea: Bioaccumulation and risk assessment for human consumers

Among the radioactive pollutants ²¹⁰Po is the most substantial one in terms of seafood safety due to its efficient accumulation in marine animals and high irradiation of its alpha emission. Mercury is a highly toxic metal for both marine organisms and human beings. Biomagnification of MeHg (methylmercury) through marine food chains has made Hg concern of ecotoxicology and seafood safety. In the current study, the bioaccumulation of ²¹⁰Po and THg (total mercury) were determined in 20 mollusc species, including 8 bivalves, 7 gastropods and 5 cephalopods collected from the island of Gökçeada in the north-eastern Aegean Sea. The highest accumulation of ²¹⁰Po and Hg was seen in bivalves and cephalopods, respectively. Elevated Hg concentrations in all body parts (arms, mantle and viscera) were observed in octopus' species. The results of this study suggests that filter feeder bivalves and gastropods have a capacity to concentrate ²¹⁰Po in their bodies, whereas predator gastropods and cephalopods have a capacity to concentrate Hg in their bodies. 7.0 kg (3.2-14.2) bivalve flesh intake is adequate due to ²¹⁰Po ingestion in the studied region to reach 1 mSv which is the annual committed effective dose. Octopus consumption of 705 g in a week alone is needed to reach Provisional Tolerable Weekly Intake (PTWI) of mercury, 5 μg kg^-1 body weight. Due to very low non-fish seafood consumption in Turkey there is no risk of Hg intake and alpha radiation of ²¹⁰Po above the limit values through mollusc consumption.

Assessment of loss of 210Po from fish and shrimp by cooking and its effect on dose estimates to humans ingesting seafood

An experimental study was conducted to assess loss of ²¹⁰Po due to cooking fresh seafood, and provide a more realistic and reliable dose estimate that humans may receive from consuming cooked seafood. Fresh fish and shrimp samples from Northern Gulf waters were grilled and boiled to simulate the effect of different cooking methods. Sixteen different species of fish were compared and significant differences in ²¹⁰Po concentration in uncooked samples were observed between species (ANOVA I, F_15,79 = 362.81, p < 0.0001). The effect of the treatment (uncooked, grilled, boiled and stock) was compared for each species and it was found that cooking led to a significant decrease in ²¹⁰Po concentration ranging from 14 to 58% compared to the uncooked samples, with no difference between grilled or boiled treatments. The effect of the cooking and shrimp treatment on ²¹⁰Po concentration was tested using ANOVA II after logarithmic transformation. Cooking led to a significant 38% reduction of ²¹⁰Po concentration as compared to uncooked treatments with no difference between grilled and boiled samples (ANOVA I: F_3,99 = 14.72, p < 0.0001). The two treatments with deveined shrimp led to a 75% decrease in ²¹⁰Po concentration as compared to all other treatments. As a consequence, cooked deveined shrimp contained an 84% lower ²¹⁰Po concentration than whole uncooked shrimp. As ²¹⁰Po is known to be the major contributor to radiation dose in humans consuming seafood, based on the results obtained, it is evident there is a need to re-examine how committed effective doses (CEDs) are best calculated for seafood consuming populations considering that most populations consume fish and shellfish cooked.

Concentration of 210Po and 210Pb in macroalgae from the northern Gulf

This baseline study highlights the 210Po and 210Pb concentration in seven macroalgae species from the northern Gulf that are frequently washed ashore during the bloom season from February to April. The highest concentrations of 210Po and 210Pb were 2.947 ± 0.032 and 1.057 ± 0.145 Bq kg-1 wwt, respectively, in brown algae Sargassum boveanum, and the lowest in green algae Ulva prolifera with 1.533 ± 0.058 and 0.170 ± 0.069 Bq kg-1 wwt, respectively. A 210Po enrichment was observed in both brown and green algae species, with the 210Po/210Pb ratio being >1 for all the samples. The mean concentration of 210Po in all species was an order of magnitude higher than 210Pb, and the difference in mean concentration is statistically significant (p < 0.001). At the same time, the mean concentration of dissolved 210Po and 210Pb in seawater was 0.28 ± 0.01 and 0.52 ± 0.01Bq m-3 with a 210Po/210Pb ratio of 0.54 ± 0.02 indicating that 210Po was absorbed from water and more concentrated by macroalgae. The measured concentration factor (CF) for 210Po in these macroalgae for the northern Gulf varied between 5 × 103-1 × 104, higher than the IAEA recommended value of 1 × 103 which suggests that a revision of that value may be needed. The field derived CFs for 210Pb vary between 3 × 102-1.8 × 103, comparable to the ICRP recommended value of 2 × 103.

Review of the status of radioactivity profile in the oil and gas producing areas of the Niger delta region of Nigeria

There is widespread degradation of the environment of the Niger Delta region of Nigeria such that the United Nations Environment Program described it as an ecological wasteland. The contamination is due mainly to unregulated oil and gas production activities leading to oil spills and illegal disposal of contaminated materials, indiscriminate industrial and domestic discharges into water bodies. This widespread contamination includes naturally occurring radioactive materials (NORM) and technologically enhanced radioactive materials (TENORM). NORMs are naturally associated with every mineral in the earth crust, thus the exploitation of such minerals may transport NORM to the surface as TENORM. If uncontrolled by operators and unregulated by government agencies, NORM can find its way into surface and ground water, seafood and even crops consumed by humans. The Niger Delta region is the hub of oil and gas activities providing huge employment and socioeconomic benefits to its indigenes and accounting for more than 90% of foreign exchange earnings for the country. However, uncontrolled spills and discharges from these activities have left the land desolate, degrading most of its aquifers and surface waters, leaving the indigenes with a Hobson choice, eating and drinking contaminated substances everyday of their lives. It is expedient that attention be drawn to this area as radionuclides such as Po-210, Pb-210 and Ra-226 have been confirmed as radiotoxic and may be responsible for several new cases of health challenges reported in the study area over the years.

Estimation of Radionuclide Concentrations and Average Annual Committed Effective Dose due to Ingestion for the Population in the Red River Delta, Vietnam

Radioactivity concentrations of nuclides of the 232Th and 238U radioactive chains and 40K, 90Sr, 137Cs, and 239+240Pu were surveyed for raw and cooked food of the population in the Red River delta region, Vietnam, using α-, γ-spectrometry, and liquid scintillation counting techniques. The concentration of 40K in the cooked food was the highest compared to those of other radionuclides ranging from (23 ± 5) (rice) to (347 ± 50) Bq kg-1 dw (tofu). The 210Po concentration in the cooked food ranged from its limit of detection (LOD) of 5 mBq kg-1 dw (rice) to (4.0 ± 1.6) Bq kg-1 dw (marine bivalves). The concentrations of other nuclides of the 232Th and 238U chains in the food were low, ranging from LOD of 0.02 Bq kg-1 dw to (1.1 ± 0.3) Bq kg-1 dw. The activity concentrations of 90Sr, 137Cs, and 239+240Pu in the food were minor compared to that of the natural radionuclides. The average annual committed effective dose to adults in the study region was estimated and it ranged from 0.24 to 0.42 mSv a-1 with an average of 0.32 mSv a-1, out of which rice, leafy vegetable, and tofu contributed up to 16.2%, 24.4%, and 21.3%, respectively. The committed effective doses to adults due to ingestion of regular diet in the Red River delta region, Vietnam are within the range determined in other countries worldwide. This finding suggests that Vietnamese food is safe for human consumption with respect to radiation exposure.

210Po concentration in selected calanoid copepods in the northern Arabian Gulf

Copepods are the most abundant metazoans, forming a vital food chain link between the primary producers the phytoplankton and fish. This study presents baseline information on the concentration of ²¹⁰Po among calanoid copepods isolated from the Kuwait marine area. The concentration of ²¹⁰Po in six species of copepod, including Subeucalanus flemingeri, Parvocalanus crassirostis, Acartia pacifica, Calanopia elliptica, Acrocalanus gibber, and Euterpina acutifrons were 151.3-158.8 Bq kg^-1 wwt, 121.1-129.5 Bq kg^-1 wwt, 51.23-54.91 Bq kg^-1 wwt, 38.88-40.09 Bq kg^-1 wwt, 38.07-38.29 Bq kg^-1 wwt, and 33.46-36.50 Bq kg^-1 wwt, respectively. The ²¹⁰Po concentration in seawater shows a seasonal variation, with a higher concentration range of 0.58-0.70 mBq L^-1 during summer and autumn, while a lower concentration is found (0.30-0.38 mBq L^-1) during winter and spring. The concentration factor among the copepods varies between 8 ∗ 10⁴ and 5 ∗ 10⁵ that is an order of magnitude higher than the diatoms and dinoflagellates.

210Po concentration in selected diatoms and dinoflagellates in the northern Arabian Gulf

Marine phytoplankton is a primary producer in the ocean that forms the base of the marine food web and supports the pelagic food chain. The two dominant groups of phytoplankton observed in northern Gulf waters are diatoms and dinoflagellates. The diatoms outnumber dinoflagellates in the Gulf waters. This study presents baseline information on the concentration of ²¹⁰Po among selected phytoplankton in the northern Gulf. The concentration among diatoms varies between 6.99 and 11.4 Bq kg^-1 wwt, whereas a higher concentration range of 8.51-15.41 Bq kg^-1 wwt was observed among dinoflagellates. The diatoms analyzed includes Thalassiosira spp. - 10.2-11.4 Bq kg^-1 wwt; Chaetoceros spp. - 6.99-7.14 Bq kg^-1 wwt; Rhizosolenia spp. - 9.12-9.95 Bq kg^-1 wwt. The analyzed dinoflagellate genera include Gymnodinium spp. - 8.51-8.78 Bq kg^-1 wwt; Noctiluca spp. - 15.2-15.4 Bq kg^-1 wwt; and Karenia spp. - 14.1-14.9 Bq kg^-1 wwt. The ²¹⁰Po concentration in seawater shows a seasonal variation, with a higher concentration range of 0.70 and 0.58 mBq L^-1 during summer and autumn, whereas a lower range in concentration of 0.38 and 0.30 mBq L^-1 occurring during winter and spring. The resultant computed concentration factors vary between 2 ∗ 10⁴-5 ∗ 10⁴ demonstrating a significant ²¹⁰Po enrichment in the base of the pelagic food chain.

Naturally Occurring Radioactive Material (NORM) in seawater of the northern Arabian Gulf - Baseline measurements

This study focuses on creating baseline for ²³⁸U, ²³⁵U, ²³⁴U, ²¹⁰Pb, ²¹⁰Po and ⁴⁰K concentrations in the northern Arabian Gulf. The respective concentration ranges were 0.047-0.050, 0.00186-0.00198, 0.054-0.057, 0.00085-0.00092, 0.00051-0.00062 and 18.6-19.1Bql^-1. These results suggest that the levels are generally comparable to other marine waters in the northern hemisphere. There were no hot spots observed from oil and gas industry. These data will serve as a baseline to gauge possible future inputs of TENORMs in the northern Gulf. A positive and linear correlation was observed between ^238,234U, ⁴⁰K isotopes and seawater salinity. The results also suggest significant fractionation between ²¹⁰Po and ²¹⁰Pb, attributed to rapid removal of ²¹⁰Po by biota compared to ²¹⁰Pb. The mean residence time for ²¹⁰Po in the study area was 371days. The ²³⁴U/²³⁸U and ²³⁸U/²³⁵U activity ratios in seawater samples vary between 1.14-1.15, and 0.038-0.040. The ²³⁴U/²³⁸U and ²³⁵U/²³⁸U ratio is similar to the expected composition of seawater (1.148±0.002) and 0.0462.

Radioactive impacts on nekton species in the Northwest Pacific and humans more than one year after the Fukushima nuclear accident

This study investigated the radioactive impacts on 10 nekton species in the Northwest Pacific more than one year after the Fukushima Nuclear Accident (FNA) from the two perspectives of contamination and harm. Squids were especially used for the spatial and temporal comparisons to demonstrate the impacts from the FNA. The radiation doses to nekton species and humans were assessed to link this radioactivity contamination to possible harm. The total dose rates to nektons were lower than the ERICA ecosystem screening benchmark of 10μGy/h. Further dose-contribution analysis showed that the internal doses from the naturally occurring nuclide ²¹⁰Po were the main dose contributor. The dose rates from ¹³⁴Cs, ¹³⁷Cs, ⁹⁰Sr and ^110mAg were approximately three or four orders of magnitude lower than those from naturally occurring radionuclides. The ²¹⁰Po-derived dose was also the main contributor of the total human dose from immersion in the seawater and the ingestion of nekton species. The human doses from anthropogenic radionuclides were ~ 100 to ~ 10,000 times lower than the doses from naturally occurring radionuclides. A morbidity assessment was performed based on the Linear No Threshold assumptions of exposure and showed 7 additional cancer cases per 100,000,000 similarly exposed people. Taken together, there is no need for concern regarding the radioactive harm in the open ocean area of the Northwest Pacific.

Accumulation of 210Po in coastal waters (Gulf of Trieste, northern Adriatic Sea)

The total activity of ²¹⁰Po was determined by alpha-spectrometry in various samples (matrices) collected in the Gulf of Trieste (northern Adriatic Sea) where fresh water inflows, especially from the Isonzo River in the northern part, affect water quality. Observed ²¹⁰Po levels were: 1) 0.56-3.75 mBq/L in the dissolved phase (<0.45 μm) in the seawater column and local rivers, 2) 0.35-3.11 mBq/L (400-2300 Bq/kg, dry weight, dw) in suspended particulate matter (SPM, 0.45-20 μm) in the seawater column and local rivers, 3) 40 (Isonzo River) -158 Bq/kg (in a surface sediment cores collected in a NS transect in the gulf and sectioned to the depth of 20 cm) and 4) 239 (autumn) - 415 to 1800 (spring) Bq/kg (dw) in meso(zoo)plankton (>200 μm). In seawater and tributaries, up to 80% (mean 49%) of total ²¹⁰Po was found in particulate form. In sediments, slightly higher levels were encountered in the Isonzo prodelta and in the central (depocenter) part of the gulf. K_D (L/kg) calculated between seawater and SPM, and seawater and sediment amounted to about 5 × 10⁶ and 6 × 10⁴, respectively. Lower autumn ²¹⁰Po levels can be a consequence of biological dilution by higher mesozooplankton biomass in the autumn compared to spring. Plankton fractionation revealed in general the highest levels in the >200 μm mesoplankton fraction (239-1800 Bq/kg) followed by 50-200 μm (388-996 Bq/kg) and 20-50 μm (318-810 Bq/kg) microplankton fractions. Obtained data show higher ²¹⁰Po levels in all matrices analyzed in the Gulf of Trieste compared to other Adriatic (central Adriatic) and western Mediterranean areas. The ²¹⁰Po/²¹⁰Pb ratios in water, plankton and sediments were mostly below or around 1, while this ratio was much higher at higher trophic levels (up to about 50), reflecting a preferential bioaccumulation of ²¹⁰Po over ²¹⁰Pb. ²¹⁰Po accumulation between seawater and SPM and seawater and mesozooplankton amounted to 3.7 × 10⁴ and 1.1 × 10⁴, respectively, similar to other Adriatic areas. Comparison of the relative importance of pelagic and benthic bioaccumulation pathways, excluding the filter feeder bivalves, suggests greater accumulation in pelagic-feeding species.

210Po bioaccumulation and trophic transfer in marine food chains in the northern Arabian Gulf

The tendency of ²¹⁰Po to concentrate in body tissue poses a serious concern of radiological safety. This study compiles available information and presents recent ²¹⁰Po data for the marine food web in the northern Gulf waters. Since ²¹⁰Po is concentrated in marine biota, a large number of samples of various marine organisms covering several trophic levels, from microalgae to sharks, were analyzed. ²¹⁰Po was found to be highly concentrated in several marine species with the highest ²¹⁰Po concentrations found in yellowfin tuna, i.e. 37.3-44.9, 451-548, and 1511-1693 Bq kg^-1 wwt in muscle, digestive system and liver, respectively. In most dissected fish samples, ²¹⁰Po showed increasing concentrations in the following order: edible tissue, gills, digestive system, liver and fecal matter. Fish feces had ²¹⁰Po concentrations several orders of magnitude higher than that in seawater, fish muscle, and the fishes' ingested food. The high ²¹⁰Po concentration in fish fecal matter suggests that the bulk of ²¹⁰Po content in fish is eventually excreted back into the environment as fecal pellets. In most fish high concentrations were noted in liver, with the highest ²¹⁰Po concentration recorded in yellowfin tuna liver. Moreover, ²¹⁰Po concentration in the soft tissue of tunicate and bryozoan samples were 872-1012 and 402-527 Bq kg^-1 wwt, respectively, far higher than that in fish muscle (0.04-44.9 Bq kg^-1 wwt). It was observed that the maximum ²¹⁰Po concentration in edible fish tissue among the fish in trophic level 2 was an order of magnitude lower than those in trophic level 3 and two orders of magnitude lower compared to fish in trophic level 4. The highest concentrations in the muscle tissue were observed in the following order: tunicate > bryozoan > mollusc > crustacean > algae > fish. Among all the biota analyzed, the highest overall concentration of ²¹⁰Po was noted in yellowfin tuna (Thunnus albacores) indicating a potential biomagnification of ²¹⁰Po in this particular top predator species. In general, ²¹⁰Po concentrations found in the commercially important fish from Kuwaiti waters were comparable to levels that have been reported for similar fish species from several other marine areas worldwide.

210Po in the marine biota of Korean coastal waters and the effective dose from seafood consumption

The activity concentrations of ²¹⁰Po were determined in plankton and selected species of macroalgae, crustaceans, molluscs, and fish from Korean coastal waters to understand ²¹⁰Po distribution in these trophic levels and to assess the effective dose of ²¹⁰Po from seafood ingested by the average Korean. The activity concentration of ²¹⁰Po in macroalgae, mixed plankton, anchovy (whole body), abalone muscle, and abalone viscera was 0.97-1.43, 32-137, 59-392, 2.93 ± 0.86, and 1495 ± 484 Bq kg^-1 (w.w.), respectively. Polonium-210 concentration in the whole flesh of mussel and oyster were 47.8 ± 5.9 and 45.3 ± 7.1 Bq kg^-1 (w.w.), respectively. Polonium-210 concentration in the muscle of the five tested species of fish other than anchovy ranged from 0.51 to 5.56 Bq kg^-1 (w.w.), with the lowest amount in a demersal species. In fish, ²¹⁰Po activity concentration was as much as three orders of magnitude higher in viscera than in muscle. The average annual effective ²¹⁰Po dose per average Korean adult, who consumes 42.8 kg of seafood a year (excluding anchovy), was estimated to be 94 μSv y^-1, with 42-71% of this attributed to shellfish. Further studies are required to assess the dose of ²¹⁰Po from anchovy owing to its high activity concentration and the manner in which anchovy is consumed.

Modelling the relationship between zooplankton biomass and environmental variations in the distribution of 210Po during a one year cycle in northwestern Mediterranean coastal waters

To clarify the relationship between zooplankton biomass and the environmental kinetics of the natural radionuclide ²¹⁰Po during a one-year period (October 1995 to November 1996) in northwestern Mediterranean coastal waters, a modelling analysis was applied. Using ²¹⁰Po concentrations in seawater and zooplankton, the ²¹⁰Po uptake rate constant from food for zooplankton was evaluated using a biokinetics calculation involving the uptake and the excretion rate constants between seawater and zooplankton. Using the transfer constants obtained, the ²¹⁰Po concentrations in zooplankton were reconstructed and validated by observed concentrations. The simulation results were in good agreement with the measured ²¹⁰Po concentrations in zooplankton. Assuming that ²¹⁰Po fecal excretion represents the majority of the excretion of ²¹⁰Po from zooplankton, the fecal matter associated ²¹⁰Po vertical flux was calculated, and compared with the observed vertical fluxes of ²¹⁰Po measured in sediment traps. The modelling evaluation showed that fecal pellet vertical transport could not fully explain the observed sinking fluxes of particulate organic matter at 150 m depth, suggesting that other sinking biodetrital aggregates are also important components of the plankton-derived vertical flux of ²¹⁰Po. The relationship between ²¹⁰Po concentration in seawater and that in rain and dry fallout and their potential effect on ²¹⁰Po concentrations in zooplankton at this location were also examined. A similar, but diphased trend between ²¹⁰Po in zooplankton and ²¹⁰Po in rain and dry fallout deposition rate was demonstrated. ²¹⁰Po concentrations in the dissolved phase of seawater tended to diminish as mean daily rainfall increased suggesting that rain inputs serve as a ²¹⁰Po dilution mechanism in seawater at this location.

Radionuclides (210Po and 210Pb) and Some Heavy Metals in Fish and Sediments in Lake Bafa, Turkey, and the Contribution of 210Po to the Radiation Dose

The pollution level of Lake Bafa was investigated by collecting fish samples {Dicentrarchus labrax (sea bass), Liza ramada (mullet) and Anguilla anguilla (eel)}, surface sediment, and core samples. In all these samples, ²¹⁰Po and ²¹⁰Pb concentrations were estimated, and total annual dose rates were obtained for each species. Some heavy metal (Cr, Ni, Pb, Cd, Mn, Fe, and Zn) concentration levels were obtained for the fish and a core sample. The sediment mass accumulation rate was found to be 3.27 g·m^-2·day^-1 (0.119 g·cm^-2·y^-1) from a core sample. The heavy metal concentrations in the vertical profile of samples from the core were also observed. The measured concentration of Zn, Pb, Cd, and Cr were between the ERL (effects range low) and ERM (effects range median) limits, while Ni concentrations were higher than the ERM limit. The observed concentrations of Cd, Pb, and Zn in fish samples did not exceed the limits in accordance with Turkish Food Regulations. Further, the maximum effective dose equivalent of ²¹⁰Po in the area was found to be 1.169 µSv·y^-1.

Baseline concentration of Polonium-210 ((210)Po) in tuna fish

Several species of tuna fish were analyzed for (210)Po content in their edible muscle tissues. This study was carried out as a part of baseline data generation around a large nuclear power plant situated at Kudankulam, southeast coast of India. The concentration of (210)Po in the muscle tissue ranged from 40.9±5.2 to 92.5±7.9Bq/kg of fresh fish, and the highest activity was recorded for the tuna Euthynnus affinis and the lowest for Auxis thazard. The committed effective dose to the local residents was calculated to be 62.7-141.8μSvyear(-1).

Influence of submarine groundwater discharge on (210)Po and (210)Pb bioaccumulation in fish tissues

This study presents the results of the accumulation of (210)Po and (210)Pb in fish tissues and organs in a brackish-water marshland that is characterized by high concentrations of (222)Rn and (226)Ra supplied by submarine groundwater discharge (SGD). Tissues and organs from Cyprinus carpio, Chelon labrosus and Carassius auratus in the wetland were significantly enriched by both (210)Pb and (210)Po (up to 55 and 66 times, respectively) compared to blanks. The major input route of (210)Pb and (210)Po into the fish body seems to be through ingestion, due to the high levels of (210)Pb and (210)Po found in the gut content as well as in organs involved in digestion and metabolism (i.e. gut, kidney and hepatopancreas). Results showed that (210)Po was more accumulated in all fish tissues and organs except for the spine, which showed a higher affinity for (210)Pb, due to its capacity to replace Ca from apatite in bones. Over all the variables analyzed, fish tissues/organs and, secondarily, fish species were the most important factors explaining the concentration of radionuclides, whereas fish length and the sampling location played a minor role. The relationship of the two radionuclides varied markedly among tissues and their concentration levels were only correlated in gills, gut and, marginally, in spines. In general, the highest values of (210)Pb and (210)Po concentrations in tissues were found on C. labrosus tissues rather C. auratus and C. carpio. This study demonstrates that inputs of natural radionuclides supplied by SGD to coastal semi-enclosed areas (such as marshlands, lagoons or ponds) may significantly increase the contents of (210)Pb and (210)Po in fish tissues/organs. Thus, this study represents one of the first evidences of direct ecological effects derived from SGD.