Analysis of the different source terms of natural radionuclides in a river affected by NORM (Naturally Occurring Radioactive Materials) activities

Tools for harmonized data collection at exposure situations with naturally occurring radioactive materials (NORM)

Naturally occurring radioactive materials (NORM) contribute to the dose arising from radiation exposure for workers, public and non-human biota in different working and environmental conditions. Within the EURATOM Horizon 2020 RadoNorm project, work is ongoing to identify NORM exposure situations and scenarios in European countries and to collect qualitative and quantitative data of relevance for radiation protection. The data obtained will contribute to improved understanding of the extent of activities involving NORM, radionuclide behaviours and the associated radiation exposure, and will provide an insight into related scientific, practical and regulatory challenges. The development of a tiered methodology for identification of NORM exposure situations and complementary tools to support uniform data collection were the first activities in the mentioned project NORM work. While NORM identification methodology is given in Michalik et al., 2023, in this paper, the main details of tools for NORM data collection are presented and they are made publicly available. The tools are a series of NORM registers in Microsoft Excel form, that have been comprehensively designed to help (a) identify the main NORM issues of radiation protection concern at given exposure situations, (b) gain an overview of materials involved (i.e., raw materials, products, by-products, residues, effluents), c) collect qualitative and quantitative data on NORM, and (d) characterise multiple hazards exposure scenarios and make further steps towards development of an integrated risk and exposure dose assessment for workers, public and non-human biota. Furthermore, the NORM registers ensure standardised and unified characterisation of NORM situations in a manner that supports and complements the effective management and regulatory control of NORM processes, products and wastes, and related exposures to natural radiation worldwide.

Environmental evaluation of radioactivity levels and associated radiation hazards in groundwater around the WIPP site

Groundwater may contain radioactive substances which can be dangerous to human health. Concentrations of natural radionuclides polonium (Po), thorium (Th), uranium (U), and radium (Ra) isotopes were measured in groundwater samples collected from different locations in the vicinity of the Waste Isolation Pilot Plant (WIPP) site in Carlsbad, New Mexico. The average values of gross activity concentrations of ²¹⁰Po, ²²⁸Th, ²³⁸U, ²³⁴U, ²²⁶Ra and ²²⁸ Ra isotopes were determined to be 1.62 Bq L^-1 in shallow groundwater and 5.88 Bq L^-1 in deep groundwater, respectively. The total radioactivity in deep groundwater was higher than that in shallow groundwater, and most of the radioactivity in the water is from ²²⁶Ra. Furthermore, the effective doses for ingestion of natural radionuclides were about 0.333 mSv y^-1 for shallow groundwater and about 1.338 mSv y^-1 for deep groundwater samples, which are higher than the World Health Organization (WHO, 2017) guideline level (0.1 mSv y^-1) for drinking water. Ra dominated the total ingestion dose, contributing 93.06 % and 75.40 % of the total effective doses to the deep and shallow groundwater, respectively. The ingrowth and decay of natural radionuclides suggested that ²²⁸Ra/²²⁶Ra ratio can be a useful indicator of the source of radioactive contamination. The radioactivity data obtained from the investigated groundwater samples can be used to establish a baseline for radioactivity levels in groundwater around the WIPP site.

Investigating the sources and dynamics of naturally occurring radioactive material (NORM) in the Red Deer River, Alberta, Canada

Distinguishing between natural and anthropogenic controls on the proportions of naturally occurring radioactive materials (NORMs) in the environment is important for water resource management. In this study, the dynamics of uranium (U) and thorium (Th), two of the most prominent NORM elements, were investigated in the Red Deer River basin using monitoring data collected from 2015 to 2018. More than twofold increases in median proportions of total U (from 0.73 to 1.53 µg/L) and Th (from 0.008 to 0.104 µg/L) were observed for sites located downstream of the Steveville badlands, an area of highly erodible bedrock that a ~ 300 km section of the river flows through. Input is highly variable, coinciding mainly with increases in total suspended solids during intense rainstorms in the late summer. In-depth examination of monitoring data through factor analysis, multiple linear regression, mass balance calculations, and land use analysis highlights the importance of erosion and subsequent particle transport along river banks in the badlands area on the distribution of total U and Th, while also revealing that groundwater-surface water interaction affects proportions of dissolved U throughout the river. No significant influence from industry or land use on U and Th export was found, and proportions of U and Th in water and suspended sediment are within the natural ranges expected for surface waters and sediments/soils. Methodology employed in this study provides a basic framework for analysis of environmental monitoring datasets, which can be employed in the absence of radiochemical data to study the fate, transport, and sources of NORMs.

Characterization of Thorium-Pyrazinoic acid complexation and its decorporation efficacy in human cells and blood

Thorium (Th) exposure to the human beings is a radiochemical hazard and the chelation therapy by suitable drugs is the major prevention approach to deal with. The present studies aimed at usage of pyrazinoic acid (PCA), which is a prodrug to treat tuberculosis, for its usage as decorporating agent for thorium from human body. The present studies provide a comprehensive knowledge on the chemical interaction and biological efficacy of pyrazinoic acid (PCA) for decorporation of Thorium from the human body. The thermodynamic parameters for Th-PCA speciation are determined by both experiment and theory. The potentiometric data analysis and Electro-Spray Ionization Mass Spectrometry (ESI-MS) studies revealed the formation of ML_i (i = 1-4) species with the decrease in stepwise stability constants. All the species formations are endothermic reactions and are predominantly entropy-driven. Biological experiments using human erythrocytes, whole blood and normal human lung cells showed cytocompatibility and decorporation ability of PCA for Thorium. Density functional calculations have been carried out to get insights on interaction process at molecular level. The experimental results and theoretical predictions found to be in line with each other. Present findings on complexation of Th by PCA and its evaluation in human cells and blood would further motivate determination of its safety levels and decorporation efficacy in animal models.

MEASUREMENT OF NATURAL RADIONUCLIDES AND EXTERNAL RADIATION EXPOSURE DUE TO FLY ASH FROM A COAL-FIRED POWER PLANT (SPAIN) DEPOSITED ON SOILS. COMPARISON USING TWO DIFFERENT MEASUREMENT TECHNIQUES

The evaluation of the radiological impact in soils due to the fly-ash ponds using both in situ techniques and laboratory based measurements is presented. In order to check the in situ techniques capabilities for monitoring this type of industries, a comparison between both techniques was performed. A characterization of external radiation exposure in the fly-ash pond and in its surrounding soils was made. The associated external radiological hazard due to the fly-ash pond has been evaluated. In situ techniques could be used to determine the radiological impact on soils due to fly-ash deposition, but its use could be limited due to the associated uncertainties.

Uranium in agricultural soils and drinking water wells on the Swiss Plateau

Mineral phosphorus fertilizers are regularly applied to agricultural sites, but their uranium (U) content is potentially hazardous to humans and the environment. Fertilizer-derived U can accumulate in the soil, but might also leach to ground-, spring and surface waters. We sampled 19 mineral fertilizers from the canton of Bern and soils of three arable and one forest reference sites at each of four locations with elevated U concentrations (7-28 μg L^-1) in nearby drinking water wells. The total U concentrations of the fertilizers were measured. The soils were analysed at three depth intervals down to 1 m for general soil parameters, total Cd, P, U and NaHCO₃-extractable U concentrations, and ^234/238U activity ratios (AR). The U concentrations and AR values of the drinking water samples were also measured. A theoretical assessment showed that fertilizer-derived U may cause high U concentrations in leaching waters (up to approx. 25 μg L^-1), but normally contributes only a small amount (approx. 0-3 μg L^-1). The arable soils investigated showed no significant U accumulation compared to the forest sites. The close positive correlation of AR with NaHCO₃-extractable U (R = 0.7, p < 0.001) indicates that application of fertilizer can increase the extractable U pool. The lack of depth gradients in the soil U concentrations (1.5-2.7 mg kg^-1) and AR (0.90-1.06) ratios are inconsistent with the accumulation of U in the surface soil, and might indicate some leaching of fertilizer-derived U. The AR values in the water samples were close to 1, possibly suggesting an influence of fertilizer-derived U. However, based on findings from the literature and considering the heterogeneity of the catchment area, the agricultural practices, and the comparatively long distance to the groundwater, we conclude that fertilizer-derived U makes only a minor contribution to the elevated U concentrations in the water samples.

Radionuclides as natural tracers of the interaction between groundwater and surface water in the River Andarax, Spain

The identification of specific aquifers that supply water to river systems is fundamental to understanding the dynamics of the rivers' hydrochemistry, particularly in arid and semiarid environments where river flow may be discontinuous. There are multiple methods to identify the source of river water. In this study of the River Andarax, in the Southeast of Spain, an analysis of natural tracers (physico-chemical parameters, uranium, radium and radon) in surface water and groundwater indicates that chemical parameters and uranium clearly identify the areas where there is groundwater-surface water interaction. The concentration of uranium found in the river defines two areas: the headwaters with U concentrations of 2 μg L^-1 and the lower reaches, with U of 6 μg L^-1. Furthermore, variation in the ²³⁴U/²³⁸U isotopic ratio allowed us to detect the influence that groundwater from the carbonate aquifer has on surface water in the headwaters of the river, where the saline content is lower and the water has a calcium bicarbonate facies. The concentration of ²²⁶Ra and ²²²Rn are low in the surface waters: <1.6 × 10^-6 μg L^-1 and <5.1 × 10^-12 μg L^-1, respectively. There is a slight increase in the lower reaches where the water has a permanent flow, greater salinity and a calcium-magnesium-sulphate facies. All this is favoured by the influence of groundwater from the detritic aquifer on the surface waters. The results of this study indicate the utility in the use of physico-chemical and radiological data conjointly as tracers of groundwater-surface water interaction in semiarid areas where the lithology of aquifers is diverse (carbonate and detritic) and where evaporitic rocks are present.

Soil radioactivity levels, radiological maps and risk assessment for the state of Kuwait

An evaluation of the radioactivity levels associated with naturally occurring radioactive materials has been undertaken as part of a systematic study to provide a surface radiological map of the State of Kuwait. Soil samples from across Kuwait were collected, measured and analysed in the current work. These evaluations provided soil activity concentration levels for primordial radionuclides, specifically members of the (238)U and (232)Th decay chains and (40)K which. The (238)U and (232)Th chain radionuclides and (40)K activity concentration values ranged between 5.9 ↔ 32.3, 3.5 ↔ 27.3, and 74 ↔ 698 Bq/kg respectively. The evaluated average specific activity concentrations of (238)U, (232)Th and (40)K across all of the soil samples have mean values of 18, 15 and 385 Bq/kg respectively, all falling below the worldwide mean values of 35, 40 and 400 Bq/kg respectively. The radiological risk factors are associated with a mean of 33.16 ± 2.46 nG/h and 68.5 ± 5.09 Bq/kg for the external dose rate and Radium equivalent respectively. The measured annual dose rates for all samples gives rise to a mean value of 40.8 ± 3.0 μSv/y while the internal and internal hazard indices have been found to be 0.23 ± 0.02 and 0.19 ± 0.01 respectively.

Removal of 226Ra and 228Ra from TENORM sludge waste using surfactants solutions

The feasibility of using surfactants as extracting agent for the removal of radium species from TENORM sludge produced from petroleum industry is evaluated. In this investigation cationic and nonionic surfactants were used as extracting agents for the removal of radium radionuclides from the sludge waste. Two surfactants namely cetyltrimethylammonium bromide (CTAB) and Triton X-100 (TX100) were investigated as the extracting agents. Different parameters affecting the removal of both (226)Ra and (228)Ra by the two surfactants as well as their admixture were studied by the batch technique. These parameters include effect of shaking time, surfactants concentration and temperature as well as the effect of surfactants admixture. It was found that, higher solution temperature improves the removal efficiency of radium species. Combined extraction of nonionic and cationic surfactants produces synergistic effect in removal both (226)Ra and (228)Ra, where the removals reached 84% and 80% for (226)Ra and (228)Ra, respectively, were obtained using surfactants admixture.

Association of naturally occurring radionuclides in sludges from Drinking Water Treatment Plants previously optimized for their removal

The raw water used in Drinking Water Treatment Plants (DWTPs) can present high values of naturally occurring radionuclides. In order to reduce this content, the routine working conditions of DWTPs were successfully modified. This meant that those radionuclides were accumulated in the sludges generated, whose radioactive content was frequently above the exemption levels. It therefore becomes necessary to assess the association of naturally occurring radionuclides in the sludges for their potential use as agricultural fertilizers. Two approaches were studied: (a) the effect of different sequential extraction methods applied to a selected sludge; and (b) the effect of the different contents of inorganic complexes dissolved in the input water on the composition of the sludges generated by two DWTPs with different origins of their input water. Uranium and radium were mainly associated with the carbonated and reducible fractions, while (210)Po and (228)Th were associated with the residual fraction. There were differences between the two speciation methods, but the order of bioavailable radionuclides was roughly the same: (226)Ra≈(234,238)U>(228)Th>(210)Po. The major inorganic complexes content, mainly carbonate, in the raw water affected the radionuclide association. The greater the carbonate content in the raw water, the greater was the association of uranium and radium with the carbonated and easily reducible fractions.

Statistical analysis of the spatial distribution of radionuclides in soils around a coal-fired power plant in Spain

Coal-fired power-plants (CFPP) can be a source of contamination because the coal contains trace amounts of natural radionuclides, such as (40)K and (238)U, (232)Th and their decay products. These radionuclides can be released as fly ash from the CFPP and deposited from the atmosphere on the nearby top soils, therefore modifying the natural radioactivity background levels, and subsequently increasing the total radioactive dose received for the nearby population. In this paper, an area of 64 km(2) around the CFPP of Velilla del Río Carrión (Spain) has been studied by collecting 67 surface soil samples and measuring the activities of one artificial and six natural radionuclides by gamma spectrometry. The found results are similar to the background natural levels and ranged from 0 to 209 for (137)Cs, 11 to 50 for (238)U, 14 to 67 for (226)Ra, 29 to 380 for (210)Pb, 15 to 68 for (232)Th, 17 to 78 for (224)Ra, 97 to 790 for (40)K (all values in Bq kg(-1)). Besides the classical radiochemical tools, Analysis of Variance (ANOVA), Principal Component Analysis (PCA), Hierarchical Clustering Analysis (HCA), and kriging mapping have been used to the experimental dataset, allowing us to find the existence of two different models of spatial distribution around the CFPP. The first, followed by (238)U, (226)Ra, (232)Th, (224)Ra and (40)K can be assigned to 'natural background radioactivity', whereas the second model, followed by (210)Pb and (137)Cs, is based on 'atmospheric fallout radioactivity'. The main conclusion of this work is that CFPP has not influence on the radioactivity levels measured in the studied area, with has a mean annual outdoor effective dose E = 71 ± 22 μSv, very close to the average UNSCEAR value of 70 μSv, thus confirming the almost non-existent radioactive risk posed by the presence of the CFPP.

Chemometric interpretation of vertical profiles of radionuclides in soils near a Spanish coal-fired power plant

The study of the vertical distribution of seven radionuclides in soils around a coal fired power plant in a mountain region in the north of Spain has been performed, in order to know if some deposition and migration of these radionuclides has taken place. Thirteen profiles of 30 cm depth have been selected, and every fraction of 5 cm has been analyzed until of a total of 72 soil samples. The activity concentration of (238)U, (226)Ra, (210)Pb, (232)Th, (224)Ra, (40)K and (137)Cs has been measured by gamma-ray spectrometry. The data were analyzed using multivariate statistical techniques, founding the best result when using a simple two-factor model, which can explain the 81.1% of the total variance. Additionally, on the basis of the significant differences found in the concentration of lead in the soil top and deep layers, the evaluation of excess of (210)Pb and the K-parameter was done. A good correlation between the excess of (210)Pb and the concentration of anthropogenic radionuclide (137)Cs in surface soil was found. These results confirm the atmospheric deposition of lead as a decay product of exhaled Rn.

Environmental impact of natural radionuclides from a coal-fired power plant in Spain

This paper is a study of the radiological impact of a coal-fired power plant in Spain. Activity concentrations of six natural radionuclides were determined in coal, ash, mine wastes and sediments by gamma-ray spectrometry. The average activity concentrations of (238)U, (226)Ra, (224)Ra, (210)Pb, (232)Th and (40)K in coal were 24, 30, 28, 41, 23 and 242 Bq kg(-1)  and in ash were 103, 128, 101, 124, 88 and 860 Bq kg(-1), respectively. The enrichment factor, radium equivalent activity and alpha index in the ash sample have been estimated. For the five waste pile samples, the absorbed dose rate was higher than the world average dose rate (60 nGy h(-1)). The dependence of radionuclide concentration on the grain size of nine sediments was also studied. The analysis of the radionuclides in waste and sediment samples will demonstrate the distribution and mobility of these elements through the environment, where a potential risk of contamination can be detected.

Enhancement of natural radionuclides in the surroundings of the four largest coal-fired power plants in Spain

The production of electricity in coal-fired power plants (CFPP) is considered a NORM (Naturally Occurring Radioactive Materials) activity because the coals they burn can present relatively high contents of the naturally occurring radionuclides. In this study, the main radiological impact pathways into the surrounding environments of the four largest coal-fired power plants in Spain were analyzed. These pathways are, first, atmospheric evacuations and wind resuspension and, second, effluent evacuations to nearby rivers or directly to the sea. The atmospheric releases of radionuclides were evaluated by the analyses of soil profiles in the vicinities of the CFPPs. No significant enhancement of radionuclides in the surface soil was observed at the points of maximum deposition of combustion gases, located from 4.3 to 13 km away depending on the considered CFPP. However, an increase of (40)K, (226)Ra, and (232)Th in the surface soils was observed in the first kilometre from the chimney for two CFPPs. This suggested that these radionuclides were released in particulate form. There was also a net influence of the climate in which the CFPPs were located. This was observed in the two CFPPs that were in dry environments, while no increase was observed in the other two, located in more humid environments. The liquid effluents released usually presented an enhancement of dissolved chemical species regarding the initial intake water. Enrichments of the (234,238)U and (226)Ra contents in the water used in the plants' routine procedures were observed, and of (210)Po in the wastewater of just one of the plants. In any case, this enhancement was below the parametric value for the Total Indicative Dose for the hypothetical human consumption of the released waters. As a consequence of these releases of radionuclides, local products destined for human consumption produced in the vicinity of the facilities might incorporate natural radionuclides by these pathways, finding no significant enhancement of the natural radionuclide contents due to the CFPPs.