Transfer of naturally occurring radionuclides from soil to wild forest flora in an area with enhanced legacy and natural radioactivity in Norway

Transfer of radionuclides through ecological systems: Lessons learned from 10 years of research within CERAD CoE

Norway's Centre of Excellence for Environmental Radioactivity (CERAD) research programme included studies on transfer of radionuclides in various ecosystems within the context of environmental risk assessment. This article provides highlights from 10 years of research within this topic and summarises lessons learnt from the process. The scope has been extensive, involving laboratory-based experiments, field studies and the implementation of transfer models quantifying radionuclide uptake directly from the surrounding environment and via food chains. Field studies have had a global span and have, inter alia, covered sites contaminated with radionuclides associated with particles, ranging from nanoparticles to fragments, due to nuclear accidents (e.g., Chornobyl and Fukushima accidents) along with sites having enhanced levels of naturally occurring radioactive materials (e.g., Fen Complex in Norway and Taboshar in Tajikistan). Focus has been put on speciation and kinetics in determining radionuclide behavior and fate as well as on the influence of environmental factors that are potentially critical for the transfer of radionuclides. In particular, seasonal factors have been shown to greatly affect the dynamics of 137Cs and 90Sr bioaccumulation and loss in freshwater fish. The work has led to the collation of organism-specific (i) parameters important for kinetic models, i.e., uptake and depuration rates, and (ii) steady-state concentration ratios, CRs, where the use of stable analogue CRs as proxies for radionuclides has been brought into question. Dynamic models have been developed and applied for radiocaesium transfer to reindeer, radionuclide transfer in Arctic marine systems, transfer to fish via water and feed and commonly used agricultural food-chain transfer models applied in the context of nuclear emergency preparedness. The CERAD programme should contribute substantially to the scientific community's understanding of radionuclide transfer in environmental systems.

A pioneering study of the radiological mapping in the world's largest mangrove forest (the Sundarbans) and implications for the public and environment

Coastal Mangroves are facing growing threats due to the harmful consequences of human activities. This first-ever detailed study of natural radioactivity in soil samples collected from seven tourist destinations within the Sundarbans, the world's largest mangrove forest, was conducted using HPGe gamma-ray spectrometry. Although the activity levels of 226Ra (11 ± 1-44 ± 4 Bq/kg) and 232Th (13 ± 1-68 ± 6 Bq/kg) generally align with global averages, the concentration of 40K (250 ± 20-630 ± 55 Bq/kg) was observed to surpass the worldwide average primarily due to factors like salinity intrusion, fertilizer application, agricultural runoff, which suggests the potential existence of potassium-rich mineral resources near the study sites. The assessment of the hazard parameters indicates that the majority of these parameters are within the recommended limits. The soil samples do not pose a significant radiological risk to the nearby population. The results of this study can establish important radiological baseline data before the Rooppur Nuclear Power Plant begins operating in Bangladesh.

M. J, Alam MS, Rashid MB, Hossain Z, Khandaker MU, Bradley DA, Yeasmin S. Measurement of radioactivity in soils of Karamjal and Harbaria mangrove forest of Sundarbans for establishment of radiological database

This work presents the first in-depth study of soil radioactivity in the mangrove forest of Bangladesh part of the Sundarbans. It used HPGe gamma-ray spectrometry to measure the amount of natural radioactivity in soil samples from Karamjal and Harbaria sites of the world's largest mangrove forest. The activity concentrations of most of the 226Ra (14±2 Bqkg-1 to 35±4 Bqkg-1) and 232Th (30±5 Bqkg-1 to 50±9 Bqkg-1) lie within the world average values, but the 40K concentration (370± 44 Bqkg-1 to 660±72 Bqkg-1) was found to have exceeded the world average value. The evaluation of radiological hazard parameters revealed that the outdoor absorbed dose rate (maximum 73.25 nGyh-1) and outdoor annual effective dose (maximum 0.09 mSvy-1) for most samples exceeded the corresponding world average values. The elevated concentration of 40K is mainly due to the salinity intrusion, usage of fertilizers and agricultural runoff, and migration of waste effluents along the riverbanks. Being the pioneering comprehensive research on the Bangladesh side of the Sundarbans, this study forms a baseline radioactivity for the Sundarbans before the commissioning of the Rooppur Nuclear Power Plant in Bangladesh.

Accumulation of scandium, cerium, europium, hafnium, and tantalum in oats and barley grown in soils that differ in their characteristics and level of contamination

Up to now, information about biogeochemistry of many trace elements is scarce. Meanwhile, all the elements are always present in soil and plants. It may be suggested that the trace elements also play certain role in the biogeochemical processes. The aim of the research was to study bioaccumulation of poorly investigated trace elements (scandium, cerium, europium, hafnium, and tantalum) and well-known elements (chromium, iron, cobalt, zinc, and arsenic) in two crops, oats and barley, and examine how these elements interact with each other as they absorbed by plants. The plants were grown in the soils that differed in their parameters and in level of contamination. Although oats and barley are botanically similar and were grown under the same conditions, the plants differed in the ability to accumulate many elements. The uptake of the elements by the plants also depended on type of soil. For example, concentrations of Cr, Fe, Co, As, Sc, Ce, Eu, Hf, and Ta in roots of the oats grown in slightly contaminated soil were much higher as compared to the concentrations of the elements in roots of the barley grown in the same soil. In leaves of the oats grown in moderately contaminated soil, the concentrations of Cr, As, Ce, Eu, and Ta were statistically significantly higher than those in leaves of the barley grown in the soil. In soils and in plants, relationships between elements were both similar and different. A statistically significant correlation was found between the poorly investigated trace elements and well-studied elements.

Societal aspects of NORM: An overlooked research field

While technical aspects of exposures to the naturally occurring radioactive material (NORM) are well explored, social science research on NORM is scarce, poorly indexed and dispersed across peer-reviewed literature, as well as various academic disciplines. Through an exploratory review of grey literature and a systematic review of scientific peer-reviewed articles published until December 2020, this paper addresses the following questions: (a) What are the societal challenges related to NORM? (b) What type of scientific research is being conducted on the societal aspects of NORM and (c) To what extent do the findings answer the identified challenges? Unfortunately, results of this study demonstrate a research gap related to the social, economic and cultural aspects of NORM management. Although the few existing studies offer some insights, for instance in relation to risk perception and risk communication, most of the societal challenges identified have not been addressed yet. This demonstrates the strong need for evidence based social science studies in order to improve the management of NORM.

Assimilation of natural Radionuclides in the wheat plant from cultivated soil

The intake of naturally nuclides 238U, 232Th, and 40K by wheat crop from two different fertilization soils of Iraq was studied under natural farm conditions. The overall mean of soil to wheat cereal transfer factors (TF) was studied and observed to be in the range of 0.6 × 10-3 to 0.70 × 10-3 for 238U, 0.11 × 10-3 to 0.13 × 10-3 for 232Th and 0.054 to 0.055 for 40K. The calculated values of TF for wheat grain denote that 40K are the significant radionuclides that are transferred in grain. This evaluation is most important for the production of foodstuffs with low contents of radionuclides. The assimilation of radionuclides by consuming wheat cereals from the farms studied gives a small fraction to the total annual ingestion dose received by a person due to naturally existent radioactivity material in the environment. This study proves that the natural radioactivity and Ingestion effective dose was lower than the safe, which the total of the dose received from 238U and 232Th due to consumption of wheat grains alone from fertilized field 0.056 and 0.045 mSv y-1 from the unfertilized field total ingestion dose, the dose received from 40K due to the consumption from the unfertilized and fertilized field was 0.0102 and 0.0137 respectively. The dose values were less than the limit value of 0.30 mSv y-1. Therefore, the consumption of these foods has no health risks. This process may help to obtain basics on radiological health regulations The activity concentration of natural radionuclides 238U, 232Th, and 40K in fertilized and unfertilized soil and wheat plants growing into is statistically significant at 1% level of significance using an independent t-test.

Distribution and transfer of naturally occurring radionuclides and 137Cs in the freshwater system of the Plitvice Lakes, Croatia, and related dose assessment to wildlife by ERICA Tool

The aim of this study was to investigate the natural radioactivity of Plitvice Lakes, under the assumption that due to its status as a National Park, the area can be considered an example of a natural freshwater system. Also, considering the transfer parameter data as the largest source of uncertainty in radiological risk assessments, the impact of site-specific data on dose rate assessment, as opposed to currently available data, was investigated. The study included gamma and alpha spectrometric measurements of ²³⁸U, ²²⁶Ra, ²¹⁰Pb, ²²⁸Ra, and ⁴⁰K in water, sediment, and fish samples, as well as ¹³⁷Cs due to the coinciding of the study with the Fukushima accident. The content of naturally occurring radionuclides significantly varied in sediments of different Lakes, probably as a reflection of the different underlying geology of the area. Also, the ²¹⁰Pb distribution in sediments indicated an up to 312 Bq kg^-1 of the allochthonous contribution of this radionuclide at the beginning of the Lake's watercourse, which probably entered into the lake system by the major inlet river with its steady decrease along downstream lakes. Low ⁴⁰K activity concentrations (27.5 ± 20.1 mBq L^-1) in the Lake's waters might be one of the causes of increased ¹³⁷Cs activity concentrations in fish samples (1.5 ± 0.4 Bq kg^-1), which was found to be an order of magnitude higher than average values for different fish species from other Croatian freshwater systems (0.2 ± 0.1 Bq kg^-1). A temporary increase of ¹³⁷Cs activity concentrations was measured in water samples collected immediately after the Fukushima accident. Calculated site-specific sediment/water distribution coefficients and fish/water concentration ratios for radium and caesium were on average lower than generic ones found in the literature. Background dose rate assessments performed by the ERICA Tool indicated a profound impact of different input data on assessment results with water activity concentrations resulting in significantly higher dose rates (0.1-67 μGy h^-1) in comparison to sediment activity concentrations (0.03-9 μGy h^-1). An incremental dose rate due to ¹³⁷Cs was found to be in the range of < 0.001-0.023 μGy h^-1 which, in comparison to background dose rates, can be considered negligible.