Biomagnification of 7Be, 234Th, and 228Ra in marine organisms near the northern Pacific coast of Japan

Interactions between Metals and Eudistomins of Ascidian Origin: A Computational Study

Ascidians are marine animals that adopt unusual techniques to deter predation. The three main methods are sequestration of unusual metals, high concentrations of sulfuric acid/sulfate ions in tunicate cells, and the presence of eudistomins. In this study, we hypothesize that ascidians sequester metals in their sulfate form, and the complexation of eudistomins with the metals could liberate the sulfate ion. Three representative metal aqua ions were chosen, viz., vanadyl, uranyl, and thorium ions, as well as four simple eudistomins which act as bidentate ligands, viz., eudistomin-W, debromoeudistomin-K, eudistomidin-C, and eudistomidin-B. By designing 7 model reactions, we tested our hypothesis using density functional theory (DFT) methods PBE-D3, BLYP, and B3LYP. The ΔG values of the model reactions provide strong support for our hypothesis. To verify the hypothesis further, we calculated the metal-eudistomin interactions with Be, Zn, and Pb. Based on our results, we suggest that ascidians may not prefer any particular metal. In addition, despite using different DFT functionals, we have observed similar ΔG values for each case. With our work, we have successfully used computational tools in our attempt to understand the unique behavior of ascidians.

Beryllium contamination and its risk management in terrestrial and aquatic environmental settings

Beryllium (Be) is a relatively rare element and occurs naturally in the Earth's crust, in coal, and in various minerals. Beryllium is used as an alloy with other metals in aerospace, electronics and mechanical industries. The major emission sources to the atmosphere are the combustion of coal and fossil fuels and the incineration of municipal solid waste. In soils and natural waters, the majority of Be is sorbed to soil particles and sediments. The majority of contamination occurs through atmospheric deposition of Be on aboveground plant parts. Beryllium and its compounds are toxic to humans and are grouped as carcinogens. The general public is exposed to Be through inhalation of air and the consumption of Be-contaminated food and drinking water. Immobilization of Be in soil and groundwater using organic and inorganic amendments reduces the bioavailability and mobility of Be, thereby limiting the transfer into the food chain. Mobilization of Be in soil using chelating agents facilitates their removal through soil washing and plant uptake. This review provides an overview of the current understanding of the sources, geochemistry, health hazards, remediation practices, and current regulatory mandates of Be contamination in complex environmental settings, including soil and aquatic ecosystems.

Tissue-Specific Toxicokinetics of Aqueous Radium-226 in an Estuarine Mussel, Geukensia demissa

Radiological contamination of coastal habitats poses potential risk for native fauna, but the bioavailability of aqueous radium (Ra) and other dissolved metals to marine bivalves remains unclear. This study was the first to examine the tissue-specific disposition of aqueous ²²⁶Ra in a coastal mussel, specifically the Atlantic ribbed mussel Geukensia demissa. Most organ groups reached steady-state concentrations within 7 days during experimental exposure, with an average uptake rate constant of 0.0013 mL g^-1 d^-1. When moved to Ra-free synthetic seawater, mussels rapidly eliminated aqueous ²²⁶Ra (average elimination rate constant 1.56 d^-1). The biological half-life for aqueous ²²⁶Ra ranged from 8.9 h for the gills and labial palps to 15.4 h for the muscle. Although previous field studies have demonstrated notable ²²⁶Ra accumulation in the soft tissues of marine mussels and that, for freshwater mussels, tissue-incorporated ²²⁶Ra derives primarily from the aqueous phase, our tissue-specific bioconcentration factors (BCFs) were on the order of (8.3 ± 1.5) × 10^-4 indicating low accumulation potential of aqueous ²²⁶Ra in estuarine mussels. This suggests marine and estuarine mussels obtain ²²⁶Ra from an alternate route, such as particulate-sorbed Ra ingested during filter-feeding or from a contaminated food source.

Effect of Radionuclides and Trace Elements on Antioxidant System of Brown Seaweeds

Ecological effects in marine living can be understood via the determination of antioxidant molecules in aquatic organisms against pollutants. This study aims to evaluate the radionuclides and trace element stress with response molecules. Cystoseira crinita and Halopteris scoparia have been chosen as study materials because of their susceptibility to pollution. The radionuclides ²¹⁰Po, ²³⁸U, ²³²Th and ⁴⁰K and trace elements Al, Fe, Mn, Cr, As, Zn and Pb levels were analysed as well as antioxidants and antioxidant enzymes in two brown algae, seasonally. Marine pollutants in terms of radionuclides and trace elements were correlated with antioxidant molecules in these species and may be used as biomarkers for assessing the radioactive stress. The ²¹⁰Po and Mn concentrations in C. crinita seem to activate catalase (CAT) and superoxide dismutase (SOD) enzyme activities while ²¹⁰Po concentrations inclined the proline amount in H. scoparia. This study demonstrated the radiation stress-induced the antioxidant defence system in macroalgae, the primary producers of the marine environment.

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.

Spatiotemporal change of cesium-137 in the Pacific coast of Tohoku, Japan: The mussel watch approach

We measured radiocesium in mussel tissue collected from the Pacific coast of Tohoku from 2011 to 2015 to investigate the temporal and spatial dynamics of radiocesium in the coastal area. Radioactive ¹³⁷Cs was detected in all the samples collected in 2011, but it was not found in samples from localities north of Sendai after 2012. In contrast, ¹³⁷Cs was detected in many sites in the Fukushima area even from 2012 to 2015. The fluctuation of ¹³⁷Cs concentration in mussel tissue seems to reflect the ¹³⁷Cs concentration in suspended particles in the seawater, suggesting that there was an influx of soil deposition and resuspension of seabed sediment. These results suggest that the ¹³⁷Cs concentration in mussel tissue sensitively indicates the ¹³⁷Cs concentration in the environment, and that the "mussel watch" approach is an effective way to understand the dynamics of radiocesium concentrations in coastal areas.

Forensic tracers of exposure to produced water in freshwater mussels: a preliminary assessment of Ba, Sr, and cyclic hydrocarbons

Hydraulic fracturing is often criticized due in part to the potential degradation of ground and surface water quality by high-salinity produced water generated during well stimulation and production. This preliminary study evaluated the response of the freshwater mussel, Elliptio complanata, after exposure to produced water. A limited number of adult mussels were grown over an 8-week period in tanks dosed with produced water collected from a hydraulically fractured well. The fatty tissue and carbonate shells were assessed for accumulation of both inorganic and organic pollutants. Ba, Sr, and cyclic hydrocarbons indicated the potential to accumulate in the soft tissue of freshwater mussels following exposure to diluted oil and gas produced water. Exposed mussels showed accumulation of Ba in the soft tissue several hundred times above background water concentrations and increased concentrations of Sr. Cyclic hydrocarbons were detected in dosed mussels and principle component analysis of gas chromatograph time-of-flight mass spectrometer results could be a novel tool to help identify areas where aquatic organisms are impacted by oil and gas produced water, but larger studies with greater replication are necessary to confirm these results.

The fate of the main naturally occurring radionuclides in mussels (Mytilus edulis) and their radiological impact on human beings

A comprehensive study was made on the activity concentrations, concentration factors, and radiation exposure impact of the main naturally occurring radionuclides in blue mussels collected in the Mediterranean Sea. The results showed that the concentrations of the measured radionuclides were site-specific and all detectable in gram-size samples of the soft tissues of the mussels, especially, some activity concentrations can reach as high as 16.8-102 Bq kg^-1 for ²¹⁰Po, 16.7-66.8 Bq kg^-1 for ⁴⁰K and 0.602-3.21 Bq kg^-1 for ²¹⁰Pb. The obtained mean concentration factors in the soft tissues of the mussel samples are 6.30 ± 2.40 for ²³⁸U and ²³⁴U, 4.68 ± 1.73 for ²³⁵U, (2.72 ± 1.73) × 10⁴ for ²³²Th and ²³⁰Th, 480 ± 265 for ²²⁸Th, 33.3 ± 13.3 for ²²⁶Ra, 100 ± 52 for ²²⁴Ra and 29.0 ± 14.7 for ²²⁸Ra, (1.22 ± 0.72) × 10⁴ for ²¹⁰Po, 517 ± 280 for ²¹⁰Pb and 2.57 ± 0.80 for ⁴⁰K. The estimated mean committed effective doses of ²³⁸U, ²³⁴U, ²³⁵U, ²³²Th, ²³⁰Th, ²²⁸Th, ²²⁶Ra, ²²⁴Ra, ²²⁸Ra, ²¹⁰Po, ²¹⁰Pb and ⁴⁰K to an adult due to mussel ingestion are 0.073 ± 0.027, 0.089 ± 0.035, 0.0030 ± 0.0011, 0.128 ± 0.098, 0.117 ± 0.081, 0.056 ± 0.031, 0.145 ± 0.058, 0.0487 ± 0.0250, 0.395 ± 0.200, 352 ± 209, 6.00 ± 3.25 and 1.74 ± 0.54 μSv a^-1, respectively. Among the elements or nuclides, ²¹⁰Po is the dominant dose contributor which contributes 96.9% of total dose fraction, and the relative dose contribution is in the order of ²¹⁰Po > ²¹⁰Pb > ⁴⁰K > radium ≥ thorium ≥ uranium.

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.

Geographical origin of bivalve molluscs in coastal areas using natural radioactivity fingerprinting and multivariate statistical analyses: Andalusian coast as case of study

The presence of natural and artificial radionuclides in the marine environment produces the accumulation of radionuclides in bivalve molluscs consumed by humans, and therefore it could result in a radiological hazard. In this study, the activity concentrations of ²¹⁰Po, ⁴⁰K, ²¹⁰Pb and ²³⁴Th were determined in different types of bivalve molluscs sampled during the period of May 2014-June 2015, along coastal areas from the Andalusian region (South of Spain), through alpha-particle spectrometry and low-level gamma-ray spectrometry. The activity concentrations of ²¹⁰Po; ⁴⁰K; ²¹⁰Pb and ²³⁴Th varied between 40 ± 2 and 515 ± 9 Bq kg^-1 dry weight (d.w.); 121 ± 7 and 674 ± 34 Bq kg^-1 d.w.; ND (lower than limit of detection) and 73 ± 10 Bq kg^-1 d.w.; and ND and 126 ± 27 Bq kg^-1 d.w., respectively. The committed effective dose to humans was calculated to range from 41 to 479 μSv year^-1. Both activity concentrations and dose levels were comparable to previous studies from other countries. Finally, a multivariate statistical analysis of natural radioactivity content allowed the discrimination between bivalve molluscs from Atlantic and Mediterranean coasts.

Natural radioactivity in algae arrivals on the Canary coast and dosimetry assessment

Nowadays, the use of wild and culture harvest seaweed in food industry is a booming productive sector. In this context, a radiological characterization of five globally common seaweed species that were collected in arrival on Gran Canaria coast was carried out. The studied algae species were Cymopolia barbata, Lobophora variegata, Sargassum vulgare, Dictyota dichotoma and Haliptilon virgatum. Radionuclides analysed by alpha and gamma spectrometry were ²³⁸U, ²³⁴U, ²³⁵U, ²¹⁰Po, ²³⁴Th, ²²⁶Ra, ²¹⁰Pb, ²²⁸Th, ²²⁴Ra, ⁴⁰K and ⁷Be. Activity concentrations, ratios, and concentration factors (CF) were determined for all samples collected. The CF in algae was higher for reactive-particle radionuclides (²¹⁰Po, ²³⁴Th, ²²⁸Th and ²¹⁰Pb) than for conservative ones (⁴⁰K and the uranium isotopes). ²¹⁰Po, ²²⁸Th and ²³⁴Th CF were one or two orders of magnitude higher than those recommended by the IAEA. L. variegata, C. barbata and S. vulgare showed a clear preference for ²¹⁰Pb and ²¹⁰Po, for uranium radioisotopes, and for ⁴⁰K and ²³⁴Th, respectively. A dosimetry assessment due to seaweed ingestion showed considerable values of annual committed effective dose for H. virgatum (605 ± 19 μSv/y), L. variegata (574 ± 17 μSv/y) and D. dichotoma (540 ± 30 μSv/y). Hence, this study suggests that an algae radiological characterization is recommended as part of the product valorising process.

Adaptation prevents the extinction of Chlamydomonas reinhardtii under toxic beryllium

The current biodiversity crisis represents a historic challenge for natural communities: the environmental rate of change exceeds the population’s adaptation capability. Integrating both ecological and evolutionary responses is necessary to make reliable predictions regarding the loss of biodiversity. The race against extinction from an eco-evolutionary perspective is gaining importance in ecological risk assessment. Here, we performed a classical study of population dynamics—a fluctuation analysis—and evaluated the results from an adaption perspective. Fluctuation analysis, widely used with microorganisms, is an effective empirical procedure to study adaptation under strong selective pressure because it incorporates the factors that influence demographic, genetic and environmental changes. The adaptation of phytoplankton to beryllium (Be) is of interest because human activities are increasing the concentration of Be in freshwater reserves; therefore, predicting the effects of human-induced pollutants is necessary for proper risk assessment. The fluctuation analysis was performed with phytoplankton, specifically, the freshwater microalgae Chlamydomonas reinhardtii, under acute Be exposure. High doses of Be led to massive microalgae death; however, by conducting a fluctuation analysis experiment, we found that C. reinhardtii was able to adapt to 33 mg/l of Be due to pre-existing genetic variability. The rescuing adapting genotype presented a mutation rate of 9.61 × 10⁻⁶ and a frequency of 10.42 resistant cells per million wild-type cells. The genetic adaptation pathway that was experimentally obtained agreed with the theoretical models of evolutionary rescue (ER). Furthermore, the rescuing genotype presented phenotypic and physiologic differences from the wild-type genotype, was 25% smaller than the Be-resistant genotype and presented a lower fitness and quantum yield performance. The abrupt distinctions between the wild-type and the Be-resistant genotype suggest a pleiotropic effect mediated by an advantageous mutation; however, no sequencing confirmation was performed.

Mussels (Mytilus galloprovincialis) as a bio-indicator species in radioactivity monitoring of Eastern Adriatic coastal waters

Croatian Adriatic coastal waters are systematically monitored within the Mediterranean Mussel Watch Project using mussels (Mytilus galloprovincialis) as a bio-indicator species. The study includes determination of naturally occurring ((7)Be, (40)K, (232)Th, (226)Ra and (238)U), as well as anthropogenic (137)Cs radionuclides. Activity concentrations in dry weight of mussels' soft tissue along the Croatian Adriatic coast are presented, with spatial and seasonal variations given and discussed. Samples were collected in spring and autumn for the period between 2009 and 2013. Radionuclides were determined by gamma-ray spectrometry. Activity concentrations of (7)Be were the highest in spring periods, especially in the areas with significant fresh water discharges. Activity concentrations of (40)K did not vary significantly with season or location. (137)Cs activities were low, while (232)Th, (226)Ra and (238)U activities were mostly below the detection limit of performed gamma-spectrometric measurement.

Radioactivity levels in mussels and sediments of the Golden Horn by the Bosphorus Strait, Marmara Sea

The Golden Horn is an estuary located in the center of İstanbul receiving freshwater discharges from two creeks and connecting to the Bosphorus Strait. Activity concentrations of natural and artificial radionuclides were determined in mussels (Mytilus galloprovincialis) and sediments from the Golden Horn sampled in February 2012. Mean activity concentrations of (137)Cs, (40)K, (226)Ra, (228)Ra, (210)Po and (210)Pb in the mussels were determined at 1.03±0.23, 389±41.6, 2.61±1.23, not detected (ND), 91.96±37.88 and 11.48±4.85 Bq kg(-1), respectively. In sediments, it was observed that (137)Cs, (40)K, (226)Ra, (228)Ra, (210)Po and (210)Pb activity concentrations in<63 μm particle fraction of sediment were generally higher than those determined in mussels. Po-210 and (210)Po/(210)Pb ratios in mussels from the Golden Horn were much lower than in mussels from other coastal regions and this was related to low plankton productivity and eutrophication of the Golden Horn.

A study of radium bioaccumulation in freshwater mussels, Velesunio angasi, in the Magela Creek catchment, Northern Territory, Australia

Freshwater mussels, Velesunio angasi, along Magela Creek in Australia's Northern Territory were examined to study radionuclide activities in mussel flesh and to investigate whether the Ranger Uranium mine is contributing to the radium loads in mussels downstream of the mine. Radium loads in mussels of the same age were highest in Bowerbird Billabong, located 20 km upstream of the mine site. Variations in the ratio of [Ra]:[Ca] in filtered water at the sampling sites accounted for the variations found in mussel radium loads with natural increases in calcium (Ca) in surface waters in a downstream gradient along the Magela Creek catchment gradually reducing radium uptake in mussels. At Mudginberri Billabong, 12 km downstream of the mine, concentration factors for radium have not significantly changed over the past 25 years since the mine commenced operations and this, coupled with a gradual decrease of the (228)Ra/(226)Ra activity ratios observed along the catchment, indicates that the (226)Ra accumulated in mussels is of natural rather than mine origin. The (228)Th/(228)Ra ratio has been used to model radium uptake and a radium biological half-life in mussels of approximately 13 years has been determined. The long biological half-life and the low Ca concentrations in the water account for the high radium concentration factor of 30,000-60,000 measured in mussels from the Magela Creek catchment.

Background dose-rates to reference animals and plants arising from exposure to naturally occurring radionuclides in aquatic environments

In order to put dose-rates derived in environmental impact assessments into context, the International Commission on Radiological Protection (ICRP) has recommended the structuring of effects data according to background exposure levels. The ICRP has also recommended a suite of reference animals and plants (RAPs), including seven aquatic organisms, for use within their developing framework. In light of these propositions, the objective of this work was to collate information on activity concentrations of naturally occurring primordial radionuclides for marine and freshwater ecosystems and apply appropriate dosimetry models to derive absorbed dose-rates. Although coverage of activity concentration data is comprehensive for sediment and water, few, or in some cases no, data were found for some RAPs, e.g. for frogs (Ranidae) and freshwater grasses (Poaceae) for most radionuclides. The activity concentrations for individual radionuclides in both organisms and their habitat often exhibit standard deviations that are substantially greater than arithmetic mean values, reflecting large variability in activity concentrations. To take account of variability a probabilistic approach was adopted. The dominating radionuclides contributing to exposure in the RAPs are (40)K, (210)Po and (226)Ra. The mean unweighted and weighted dose-rates for aquatic RAPs are in the ranges 0.07-0.39 microGy h(-1) and 0.37-1.9 microGy h(-1) respectively.

The uses and adverse effects of beryllium on health

CONTEXT

This review describes the health effects of beryllium exposure in the workplace and the environment.

AIM

To collate information on the consequences of occupational and environmental exposure to beryllium on physiological function and well being.

MATERIALS AND METHODS

The criteria used in the current review for selecting articles were adopted from proposed criteria in The International Classification of Functioning, Disability, and Health. Articles were classified based on acute and chronic exposure and toxicity of beryllium.

RESULTS

The proportions of utilized and nonutilized articles were tabulated. Years 2001-10 gave the greatest match (45.9%) for methodological parameters, followed by 27.71% for 1991-2000. Years 1971-80 and 1981-90 were not significantly different in the information published and available whereas years 1951-1960 showed a lack of suitable articles. Some articles were published in sources unobtainable through requests at the British Library, and some had no impact factor and were excluded.

CONCLUSION

Beryllium has some useful but undoubtedly harmful effects on health and well-being. Measures need to be taken to prevent hazardous exposure to this element, making its biological monitoring in the workplace essential.

High levels of natural radioactivity in biota from deep-sea hydrothermal vents: a preliminary communication

Hydrothermal deep-sea vent fauna is naturally exposed to a peculiar environment enriched in potentially toxic species such as sulphides, heavy metals and natural radionuclides. It is now well established that some of the organisms present in such an environment accumulate metals during their lifespan. Though only few radionuclide measurements are available, it seems likely that hydrothermal vent communities are exposed to high natural radiation doses. Various archived biological samples collected on the East Pacific Rise and the Mid-Atlantic Ridge in 1996, 2001 and 2002 were analysed by ICP-MS in order to determine their uranium contents ((238)U, (235)U and (234)U). In addition (210)Po-Pb were determined in 2 samples collected in 2002. Vent organisms are characterized by high U, and Po-Pb levels compared to what is generally encountered in organisms from outside hydrothermal vent ecosystems. Though the number of data is low, the results reveal various trends in relation to the site, the location within the mixing zone and/or the organisms' trophic regime.

(137)Cs baseline levels in the Mediterranean and Black Sea: a cross-basin survey of the CIESM Mediterranean Mussel Watch programme

The common mussel Mytilus galloprovincialis was selected as unique biomonitor species to implement a regional monitoring programme, the CIESM Mediterranean Mussel Watch (MMW), in the Mediterranean and Black Seas. As of today, and upon standardization of the methodological approach, the MMW Network has been able to quantify (137)Cs levels in mussels from 60 coastal stations and to produce the first distribution map of this artificial radionuclide at the scale of the entire Mediterranean and Black Seas. While measured (137)Cs levels were found to be very low (usually < 1 Bq kg(-1) wet wt) (137)Cs activity concentrations in the Black Sea and North Aegean Sea were up to two orders of magnitude higher than those in the western Mediterranean Basin. Such effects, far from representing a threat to human populations or the environment, reflect a persistent signature of the Chernobyl fallout in this area.

Radionuclides and metals in freshwater mussels of the upper South Alligator River, Australia

During an inspection of the old Rockhole Mine area in Kakadu National Park in 1999, it was found that a small amount of tailings from the former South Alligator uranium (U) mill had been uncovered by wet season rain and road works. Samples of sediment, water and freshwater mussels, Velesunio angasi, were collected from the South Alligator River, near and at the confluence of Rockhole Mine Creek, and adjacent to the exposed tailings. The 228Ra/226Ra activity ratios in sediments and mussel tissue indicate a small influence from the tailings and from Rockhole Mine adit water on 226Ra concentrations. The uptake of 226Ra in mussels does not correlate with other alkaline-earth metals. Mussel U concentrations are higher immediately downstream of Rockhole Mine Creek, but there is no noticeable increase in the immediate vicinity of the tailings area. A hypothetical ingestion of 2 kg of mussels from the sites was used to estimate the committed effective dose for a 10-year-old child resulting in a figure of 0.23 mSv per annum, of this total dose, 69% is attributed to 210Po. Only 0.03 mSv per annum can be directly linked to impacts of the tailings.

Radionuclide concentrations in benthic invertebrates from Amchitka and Kiska Islands in the Aleutian Chain, Alaska

Concentrations of 13 radionuclides (137Cs, 129I, 60Co, 152Eu, 90Sr, 99Tc, 241Am, 238Pu, 239,249Pu, 234U, 235U, 236U, 238U) were examined in seven species of invertebrates from Amchitka and Kiska Islands, in the Aleutian Chain of Alaska, using gamma spectroscopy, inductively coupled plasma mass spectroscopy, and alpha spectroscopy. Amchitka Island was the site of three underground nuclear test (1965-1971), and we tested the null hypotheses that there were no differences in radionuclide concentrations between Amchitka and the reference site (Kiska) and there were no differences among species. The only radionuclides where composite samples were above the Minimum Detectable Activity (MDA) were 137Cs, 241Am, 239,249Pu, 234U, 235U, 236U, and 238U. Green sea urchin (Strongylocentrotus polyacanthus), giant chiton (Cryptochiton stelleri), plate limpets (Tectura scutum) and giant Pacific octopus (Enteroctopus dofleini) were only tested for 137Cs; octopus was the only species with detectable levels of 137Cs (0.262 +/- 0.029 Bq/kg, wet weight). Only rock jingle (Pododesmus macroschisma), blue mussel (Mytilus trossulus) and horse mussel (Modiolus modiolus) were analyzed for the actinides. There were no interspecific differences in 241Am and 239,240Pu, and almost no samples above the MDA for 238Pu and 236U. Horse mussels had significantly higher concentrations of 234U (0.844 +/- 0.804 Bq/kg) and 238U (0.730 +/- 0.646) than the other species (both isotopes are naturally occurring). There were no differences in actinide concentrations between Amchitka and Kiska. In general, radionuclides in invertebrates from Amchitka were similar to those from uncontaminated sites in the Northern Hemisphere, and below those from the contaminated Irish Sea. There is a clear research need for authors to report the concentrations of radionuclides by species, rather than simply as 'shellfish', for comparative purposes in determining geographical patterns, understanding possible effects, and for estimating risk to humans from consuming different biota.

Seasonal variation of 228Ra/226Ra ratio in seaweed: implications for water circulation patterns in coastal areas of the Noto Peninsula, Japan

To examine water circulation patterns of coastal water, 72 seaweed (Sargasso) samples and 27 coastal water samples were collected from coastal areas of the Noto Peninsula, Japan, during the period from December 1998 to June 2002. The (228)Ra and (226)Ra activities of those samples were measured by low-background gamma-ray spectrometry. There was a wide range of activities of (228)Ra (0.5-2Bq/kg-fresh) and (226)Ra (0.5-1.2Bq/kg-fresh) in the Sargasso samples. The (228)Ra/(226)Ra activity ratio of Sargasso samples exhibited seasonal variation with minimum values in June ((228)Ra/(226)Ra= approximately 1) and maximum values in December (1.5-2.5), which was mainly governed by changes in (228)Ra activity. It is also notable that the seasonal variation of the (228)Ra/(226)Ra ratio of Sargasso is in approximate agreement with that of the ambient coastal water. Sargasso samples appear to have retained the (228)Ra/(226)Ra ratio of the ambient coastal waters, and the temporal variations in that ratio provide insight into seasonal changes in water circulation in the Noto Peninsula coastal area.