Anthropogenic Radionuclides Research Articles

Vertical distribution of plutonium isotopes from the floodplain and lacustrine sediments in Poyang Lake, China

Anthropogenic radionuclides deposited in sediments have been used for environmental radiation risk valuation as well as source identification. In this study, we investigated the vertical distribution of plutonium (Pu) isotopes and 240Pu/239Pu atom ratios in both floodplain and lacustrine sediments in Poyang Lake. The 239+240Pu activity concentrations in floodplain sediment cores were found to range from 0.002 to 0.085 Bq kg−1, with a maximum value at the subsurface layer. The activity in lacustrine sediment cores was from 0.062 to 0.351 Bq kg−1 with a mean of 0.138 ± 0.053 Bq kg−1. The inventory of 43.15 Bq m−2 in lacustrine sediment core is comparable to the average value of global fallout expected at the same latitude. The average 240Pu/239Pu atomic ratios (0.183 ± 0.032) for sediment cores indicated that the global fallout is the major source of Pu in the studied region. The results are of great significance to the further understanding of sources, records, and environmental impacts of regional nuclear activities in the environment.

Experimental determination of concentration factors of Mn, Zn and I in the phytoplankton species Phaeodactylum Tricornutum

Anthropogenic radionuclides released into the environment cause a radiation dose to wildlife and humans which must be quantified, both to assess the effect of normal releases, and to predict the consequences of a larger, unplanned release. To estimate the spread of the radioactive elements, the ecosystem around release points is modelled, and element uptake is usually quantified by concentration factors (CF), which relates the concentration of an element in an organism to the concentration of the same element in a medium under equilibrium conditions. In this work, we experimentally determine some phytoplankton CF that are needed for improved modelling of the marine ecosystems around nuclear facilities and release points. CFs that require better determination have been identified through literature search. Sensitivity studies, using the currently used ecosystem modelling software PREDO, show that for most studied groups, the dose committed by the respective radionuclides is almost proportional to the corresponding phytoplankton CFs. In the present work, CFs are determined through laboratory experiments with cultured phytoplankton and radionuclides of the concerned elements, assessing the element uptake by the phytoplankton through detection of the emitted radiation. The three CF assessed in this work were those for manganese, zinc and iodine in phytoplankton. Conservative estimates of these CF based on the present data are 40 000 L/kg for manganese, 50 000 L/kg for zinc and 180 L/kg for iodine with the phytoplankton masses referring to their dry weight.

Potential Airborne Releases and Deposition of Radionuclides from the Santa Susana Field Laboratory during the Woolsey Fire.

The Santa Susana Field Laboratory (SSFL), located in southern California, is a former research facility, and past activities have resulted in residual radioactive contamination in Area IV of the Site. The Woolsey Fire burned across the site, including some of the contaminated areas, on 8-11 November 2018. Atmospheric transport modeling was performed to determine where the smoke plume went while the fire burned across the SSFL and the deposition footprint of particulates in downwind communities. Any radionuclides on vegetation and in surface soil released by the fire were assumed to follow particulate matter transport path and deposition. The predicted deposition footprint was used to guide confirmatory soil sampling at 16 locations including background. Highest offsite deposition was determined to be northeast of the Oak Park community, which is located about 6 km southwest of SSFL. Depth-profile sampling was used to evaluate whether radionuclides of SSFL origin were potentially emitted and deposited during the Woolsey Fire. If radionuclides had been deposited from the Woolsey Fire at sufficient concentrations, then they would be detected in the surface layer and would be expected to be higher within the plume footprint than outside it. An upper bound estimate of the hypothetical effective dose to a person in Oak Park based on measured radionuclide concentrations in soil and vegetation on the SSFL was less than 0.0002 mSv. The occurrence of naturally occurring radionuclides at concentrations above the established background for the SSFL was attributed to natural variability in geologic formations and not SSFL. No anthropogenic radionuclides were measured at levels above those expected from global fallout. The soil sampling confirmed that no detectable levels of SSFL-derived radionuclides migrated from SSFL at the locations sampled because of the Woolsey Fire or from past operations of the SSFL.

Modelling simultaneous transport of natural and anthropogenic radionuclides in fractured media — Diffusion into the heterogeneous layered rock matrix for an arbitrary length decay chain

Transport models used for assessing the safety of radioactive waste repositories hosted in fractured bedrock typically do not consider fluxes of naturally occurring radionuclides in the rock and their further migration in flow-bearing fractures. A consistent model that simultaneously describes the transport of radionuclides from both natural and anthropogenic sources has been developed, where decay chains and rock heterogeneity are accounted for. The model accounts for advective flow in the fracture, a decay chain of arbitrary length, and diffusion into and out of the adjacent rock matrix composed of different geological layers. The proposed solution has been verified against a previously published steady state case which considers a homogeneous rock matrix of infinite extent where porewater ingrowth is not accounted for. The model is also applied to some different calculation examples for both transient and limiting steady state cases to represent typical applications of the model as well as to illustrate the effect of different parameters and processes on the transport of natural radionuclides in fractured rocks. This study presents a novel and powerful tool to simulate migration of both anthropogenic and natural radionuclides in and from crystalline rocks to the biosphere. The presented modelling is essential in safety and performance assessment of deep geological disposal of radioactive waste in fractured rocks. The obtained analytical solution can be used to compare relative fluxes of natural and anthropogenic radionuclides, which is useful for validation of the radionuclide transport parameters obtained from field and laboratory experiments.

Natural and anthropogenic radioactivity and radiological hazard indices in organic Sangyod rice samples collected from Don Pradu sub-district in Pak Phayun district in Phatthalung province, Thailand

It is well known that Thai people and many other Asian countries consume rice as the main dish. Minor contamination of natural and anthropogenic radionuclides in rice dishes may cause illness, fever or unwell for no apparent reason. For this reason, the research team was interested in the measurement and analysis of the concentrations of natural and anthropogenic radionuclides in 28 samples of organic Sangyod rice from courtesy of rice farmers in the Don Pradu sub-district, Pak Phayun District, Songkhla province. In addition, the research team was also received courtesy of the National Institute of Nuclear Technology (Public Organization) or TINT to use semiconductor detector measuring instruments and gamma spectrometry analysis systems for this research. It was found that the mean specific activity values of 40K, 226Ra, 232Th and 137Cs were 24.11 ± 2.01, 0.28 ± 0.07, 0.17 ± 0.06 and 0.10 ± 0.03 Bq/kg, respectively. The four relevant radiological indices which were gamma-absorbed dose rate (D), radium equivalent activity (Raeq), external hazard index (Hex) and annual external effective dose rate (AEDout), were also calculated and presented. Furthermore, the excess lifetime cancer risk (ELCR(outdoor)) was also evaluated by using the AEDout value from the investigated area. The results of this research were taken to compare with the values measured by the Office of Atoms for Peace (OAP) and research groups that have been measured and analyzed both at home and abroad. In conclusion, the results in this study were found to be lower than the values recommended by some international organizations and is safe for consumers and farmers who produce organic Sang Yod rice in the study area.

Systematic Radioecological Experiments in the United Arab Emirates (UAE) for Nuclear Safety and Emergency-Preparedness

Nuclear power and other radioactivity-producing industries like oil and gas, desalination, etc. are rapidly maturing in the arid countries, most importantly in the United Arab Emirates (UAE). Thus, it becomes vital to study and model the transfers and impacts of radionuclides’ release into the local environments. Baseline or predictive studies on this subject are extremely scarce for the UAE-like desert-marine ecosystems. In global literature, the retention and transfer mechanisms of natural and anthropogenic radionuclides in arid soils and plants are grossly underrepresented. We debrief the recent research activities in the UAE and nearby nations on background radioactivity measurements in soils and plants, as well as those estimating the radioecological transfer factors or concentration ratios. Soil to plant transfer is a key sought after data for arid region radioecology. We further outline some systematic field and laboratory experiments executed by Khalifa University of the UAE, which includes numerous field surveys, identifying radionuclides and crop categories of importance, sampling in representative localities in the Abu Dhabi emirate, developing protocols for sample management and processing, and radiometry using gamma-spectrometry and inductively coupled plasma mass-spectrometry.

Temporal evolution of Pu and Cs sediment contamination in a seasonally stratified pond.

There remains a lack of knowledge regarding ecosystem transfer, transport processes, and mechanisms, which influence the long-term mobility of Pu-239 and Cs-137 in natural environments. Monitoring the distribution and migration of trace radioisotopes as ecosystem tracers has the potential to provide insight into the underlying mechanisms of geochemical cycles. This study investigated the distribution of anthropogenic radionuclides Pu-239 and Cs-137 along with total organic carbon, iron, and trace element in contaminated sediments of Pond B at the Savannah River Site (SRS). Pond B received reactor cooling water from 1961 to 1964, and trace amounts of Pu-239 and Cs-137 during operations. Our study collected sediment cores to determine concentrations of Pu-239, Cs-137, and major and minor elements in solid phase, pore water and an electrochemical method was used on wet cores to determine dissolved elemental concentrations. More than 50 years after deposition, Pu-239 and Cs-137 in sediments are primarily located in the upper 5 cm in area where deposition of particulate-bound contaminants was prevalent and located between 5 and 10 cm in areas of high sedimentation, showing a limited migration of Pu-239 and Cs-137. A Factor analysis demonstrated different sediment facies across the pond resulting in a range of geochemical processes controlling accumulation of Pu and Cs. Highest concentrations appear to be controlled by particulate input from the influent canal, dominated by clay, silt, and sand minerals bearing Fe. Elevated Pu-239 in the sediments were observed in areas with high organic matter and higher deposition rate relative to the Pond B system near the outlet indicating strong association of Pu with OM and particulates. Therefore, organic matter cycling likely plays a role in Pu redistribution between sediment and overlying pond water, and deposition in organic rich sediments accumulating near the outlet. Though Pu appears to have been distributed throughout the pond, Cs-137 concentrations remained the highest near the influent canal.

Radioactivity Content and Dosimetric Assessment in Bovine Meat from the Calabria Region, Southern Italy

In this article, the assessment of the radioactivity content in bovine meat from the Calabria region, Southern Italy, was performed. For this purpose, High Purity Germanium (HPGe) gamma spectrometry measurements were carried out in order to investigate any possible radioactive contamination by natural (40K) and anthropogenic (137Cs) radionuclides. Experimental mean values were found to be in the range from (78.9 ± 10.5) Bq kg−1 to (88.2 ± 12.5) Bq kg−1 for 40K and lower than the minimum detectable activity (MDA) in all cases for 137Cs, respectively. Moreover, any possible radiological health risk was also estimated, by calculating the total annual effective dose due to the ingestion of bovine meat by adult members of the population and by comparing it with the total natural radioactivity value (external + internal) for humans. Obtained values are in the range from 10.3 µSv y−1 to 11.5 µSv y−1, several orders of magnitude lower than the value of the total exposure to natural radioactivity for human beings, i.e., 2.4 mSv y−1. It is worth noting that the used approach could be used, in principle, for the evaluation of the radiological risk due to the presence of radionuclides in a large variety of food samples of particular interest, and thus it can constitute a guideline for investigations focused on the monitoring of food quality.

90Sr and stable element levels in bones of brown bears: long-term trends in bear populations from Croatia and Poland.

The aim of this study was to investigate the temporal trends and geographical differences in 90Sr and stable element (Ba, Ca, Mn, Sr, Pb, Zn) levels in the bones of Croatian and Polish brown bear (Ursus arctos) populations. Experimental data suggest that in the decades after nuclear weapon tests and the Chernobyl accident, 90Sr bone activity concentrations decreased from 352 to 11Bqkg-1 in the Croatian bear population (period 1982-2015) and from 831 to 27Bqkg-1 in Polish bears (period 1962-2020). Calculated effective and ecological half-lives were 9 and 13years for Croatian bears, and 15 and 31years for Polish bears, respectively. Different temporal trends were noted in levels of Ba, Mn, Pb and Zn between the two countries with majority of bones having lower Pb, Sr and Zn in Croatian than in Polish bears. Estimated values for the soil-to-bear transfer of 90Sr were the same order of magnitude in the studied populations. Contrary to this, the estimated transfer of stable Sr was an order of magnitude lower for the Croatian bear population compared to Polish bears. The observed differences in soil-to-bear transfer between stable Sr and 90Sr found for Croatian bears might suggest the need for careful consideration on the use of stable Sr data as an analogue for 90Sr. To our knowledge, this is the first study that analysed 90Sr activity in tissue of brown bears. As such, it provides insight into the fate and behaviour of one of the most relevant anthropogenic radionuclides at the top of the food chain.

Natural Radioactivity and Background Values of Anthropogenic Radionuclides in Groundwater around the Leningrad NPP Area

Natural Radioactivity and Background Values of Anthropogenic Radionuclides in Groundwater around the Leningrad NPP Area

A study on natural and anthropogenic radionuclides in farmed fish and shellfish in Singapore

A study on natural and anthropogenic radionuclides in farmed fish and shellfish in Singapore

Natural and anthropogenic radionuclides in karstic coastal area (Kaštela Bay, Adriatic Sea, Croatia) exposed to anthropogenic activities: distribution, sources, and influencing factors

Abstract 40K, 226Ra, 232Th, 238U, and 137Cs massic activities were determined by gamma-spectrometry in limestones, marls, stream sediments, and soils of Kaštela Bay (Adriatic Sea, Croatia) coastal area. Their distribution, sources and potential influencing factors were studied. The lowest 40K, 226Ra, 232Th, and 238U massic activities were determined in limestones and the highest in soils, with the following median values, respectively: 7.2, 14, 0.8, and 5.3 Bq/kg in limestones and 518, 72, 71, and 31 Bq/kg in soils. All four radionuclides were of natural origin and reflected background values of the karstic area influenced by flysch/marl and terra rossa soil. Local TENORM disposal site did not influence the study area, but it will be needed to study its potential influence on marine sediments. Strong disequilibrium between 226Ra and 238U was found in limestones s.l. and soils, but not in marls and only moderately in stream sediments. This implies that limestones are more susceptible to selective 238U leaching than marls, and soils more than stream sediments. 137Cs was the only radionuclide of anthropogenic origin, with a global source only. It was detected in stream sediments and soils with median values of 5.4 and 31 Bq/kg, respectively. 137Cs distribution was more heterogeneous in stream sediments than in soils, but soils generally presented higher activities. Soil is considered the most important reservoir of 137Cs and its potential source.

Distribution of Natural and Anthropogenic Radionuclides in Soil Samples in Recreational Zones of Moscow

Distribution of Natural and Anthropogenic Radionuclides in Soil Samples in Recreational Zones of Moscow

Estimation of Physicochemical Parameters and Vertical Migration of Atmospheric Radionuclides in a Raised Peat Bog in the Arctic Zone of Russia

The article presents the results of a study of activity levels and features of the vertical distribution of 210Pb, 137Cs, 234U, 238U and their relationship with the physicochemical parameters of peat deposits. Analysis of the data showed that the vertical distribution of 137Cs and 210Pb was related to the content of water-soluble salts, the water saturation of the deposit, and the values of Eh (oxidation–reduction potential) and rH (relative humidity), which indicates a complex geochemical barrier at a depth of 20 cm in the peat core. The 210Pb dating of the peat core, carried out according to the CF model using the Monte Carlo method (to improve the dating accuracy), showed that the above horizon corresponded to 1963, which is consistent with the data of the 137Cs reference horizon and in terms of several physicochemical parameters (in particular, ash content) also corresponds to the age of 1963, which confirms the correctness and adequacy of the chosen peat core dating model. The peak of anthropogenic radionuclides in peat deposits correlates with a particular major event in the history of radioactive fallout, the Partial Nuclear Test Ban Treaty of 1963, providing a benchmark for geochronological research. The obtained results of the linear accumulation rate, the mass accumulation rate of the peat deposit, and the value of the atmospheric flux of 210Pb are congruent with the data on the peatlands of Northern Europe and the data obtained by earlier analysts of the Subarctic region of European Russia.

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.

DISTRIBUTION OF RADIOCESIUM CONCENTRATIONS OF SOILS IN THE EIGHT IZU ISLANDS AFTER THE FUKUSHIMA DAIICHI NUCLEAR POWER PLANT ACCIDENT

Large amounts of anthropogenic radionuclides, such as 134Cs and 137Cs(radiocesium), were released into the atmosphere due to the Fukushima Daiichi Nuclear Power Plant (F1-NPP) accident and were transported into various environments. The soil accumulations of diffused radionuclides are marked by large differences in their horizontal distributions, and the vertical air dose rates vary depending on the topography, altitude and other factors. In this study, soil activity concentrations of eight islands in the Izu Islands, ~334-563km south of the F1-NPP, were analyzed from both horizontal and vertical perspectives. Soil samples were collected over a 4-y period from 2012 to 2016, and their activity concentrations of radiocesium were measured. The activity concentrations in the soil were categorized for intervals of a 100-m altitude above sea level, and the relationship between the maximum activity concentration in each category and the distance from the F1-NPP was analyzed. The correlation was good at the lower altitudes.

Water mass composition in Fram Strait determined from the combination of 129I and 236U: Changes between 2016, 2018, and 2019

Changes in the provenance and composition of waters exported from the Arctic Ocean have the potential to impact large-scale ocean circulation processes in the sub-polar North Atlantic. The main conveyor of waters from the Arctic Ocean to lower latitudes is the East Greenland Current (EGC), flowing southward through Fram Strait. It is therefore crucial to determine and monitor the composition of the EGC, a mixture of polar waters of different origins. Here we present a pilot study on the potential of the long-lived anthropogenic radionuclides 129I and 236U as tracers of the EGC water mass composition, based on a time series of 236U and 129I concentrations measured across Fram Strait in the years 2016, 2018, and 2019. The overall spatial distribution of 236U and 129I was similar among the three sampling years, but a decrease in concentration was observed in the upper water column of the EGC. The observed changes could only partly be attributed to the transient nature of the radionuclide signals, but instead pointed to changes in the EGC water mass composition. To investigate these changes, 236U and 129I were first combined in a mixing model featuring the endmembers expected in the upper EGC. We distinguished between Pacific Water (PAC), Atlantic Water advected from the Arctic Ocean (ATL), and Atlantic Water recirculating in Fram Strait (RAC). In 236U-129I tracer space, PAC and RAC showed similar tracer signatures, but were well distinguished from ATL. From 2016 to 2018/19, a decrease in the ATL fraction was evident for the upper EGC. Secondly, the respective combination of 236U and 129I with salinity showed differences in absolute water mass fractions, but similar temporal trends. Both suggested an increase in PAC of about 20% for the uppermost layer of the EGC (samples with potential densities below 26.5) and an increase in RAC of about 10−20 % for denser samples. 129I and 236U, in combination with salinity, were shown to be suitable tracers to investigate water mass composition in Fram Strait, with the advantage that they can distinguish Atlantic Water advected from the Arctic Ocean from that recirculating in Fram Strait.

Nuclear Reprocessing Tracers Illuminate Flow Features and Connectivity Between the Arctic and Subpolar North Atlantic Oceans.

Releases of anthropogenic radionuclides from European nuclear fuel reprocessing plants enter the surface circulation of the high-latitude North Atlantic and are transported northward into the Arctic Ocean and southward from the Nordic Seas into the deep North Atlantic, thereby providing tracers of water circulation, mixing, ventilation, and deep-water formation. Early tracer studies focused on 137Cs, which revealed some of the first significant insights into the Arctic Ocean circulation, while more recent work has benefited from advances in accelerator mass spectrometry to enable the measurement of the conservative, long-lived radionuclide tracers 129I and 236U. The latest studies of these tracers, supported by simulations using the North Atlantic-Arctic Ocean-Sea Ice Model (NAOSIM) and enhanced by the use of transit time distributions to more precisely accommodate mixing, have provided a rich inventory of transport data for circulation in the Arctic and North Atlantic Oceans that are of great importance to global thermohaline circulation and climate.

Cherenkov radiation technique for the determination of fission product 90Sr in milk

ABSTRACT Monitoring of the anthropogenic radionuclides (90Sr, 135Cs and 137Cs) in different components such as spinach, milk, meat, soil and the grass is important for the environmental radiological survey. Nuclear weapons testing in the atmosphere, nuclear power plant accidents and leaks from the nuclear fuel cycle are the main sources of these radionuclides. The amounts of 90Sr/90Y detected in the environment are mostly due to fallout from nuclear weapons testing. Because of its long physical (28.5 years) and biological half-lives (approximately 12 years) and high fission yield, the measurement of 90Sr is also necessary for radiation protection purposes. It accumulates in bone tissue when ingested by humans through the food chain, and 90Y, a daughter nuclide of 90Sr, emits high-energy beta particles, raising the risk of bone cancer. Strontium has been widely measured in milk samples by using various classical methods. In this study, the procedure we used is based on the separation of 90Y by HDEHP extraction and counting the Cherenkov radiation using a liquid scintillation spectrometer, Quantulus 1220. Prior to analyses, spiked milk samples were dried and prepared as milk powder. The microwave ashing programme was optimised, and recovery of the radiochemical separation steps was tested for spiked milk powder samples before routine analysis. This method is found to be applicable for the routine analysis of 90Sr in milk samples after validation of the method by measuring IRMM milk powder samples, too. A lower limit of detection of about 0.02 Bq.kg−1 was obtained for samples in the case of 84–99% Y chemical yield, 1.45 cpm reagent blank, 4 × 60 minutes counting time and about 83.5 ± 2.1% counting efficiency.

Ten years of investigations of Fukushima radionuclides in the environment: A review on process studies in environmental compartments

In March 2011, severe nuclear accident happened at the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) after the gigantic earthquake and following huge tsunami wave. A lot of investigations to assess environmental and radiological impacts of released radionuclides have been conducted by domestic and international organizations. Environmental radioactivity research related to the FDNPP accident has spread widely over different scientific fields due to specific features of the accident, and specifically its impact on the marine environment. The present paper summarizes major lessons learned from the environmental investigations of the FDNPP accident. Environmental radioactivity studies have typical interdisciplinary character; especially physics and chemistry are fundamental as a base of process studies in the environment. In this sight, we review chemical aspects regarding FDNPP-derived radiocesium transfer within and between compartments (atmosphere, ocean and land). We also discuss future trends in investigations of behavior of anthropogenic radionuclides in the environment, important not only for a better understanding of impacts of the FDNPP accident on the environment, but also for improving our general knowledge of the total environment in the Anthropocene era and its protection for the future.