Comparative study of different analytical methods for the determination of 238U, 234U, 235U, 230Th and 232Th in NORM samples (Southern Catalonia)

Uranium isotopes in groundwater in Ho Chi Minh City and related issues: Health risks, environmental effects, and mitigation methods

Groundwater is regularly used for many purposes, such as drinking and agricultural irrigation systems. Still, it contains high levels of radionuclides (e.g., ²³⁸U, ²³²Th, and ²²⁶Ra) that are potentially hazardous to humans and the environment. In this study, activity concentrations of uranium isotopes were analyzed in 15 groundwater samples taken from 15 bored wells in Thu Duc district, Ho Chi Minh City, Vietnam. Environmental effects of the irrigation system with groundwater on agricultural soil in the study area were assessed by models. It was found that the activity concentrations of ²³⁸U and ²³⁴U in groundwater samples were in the ranges of (13.5-268.7) mBq l^-1 and (20.2-438.3) mBq l^-1, respectively. The ratio ²³⁴U/²³⁸U values were ranged from 1.12 to 2, with an average value of 1.44. Based on the model prediction, 25 years irrigation with the groundwater can inject 94.8 Bq both uranium isotopes in 1 kg topsoil. For investigated groundwater samples, the proposed removal method using K₂FeO₄ removed 74.28% and 81.04% for ²³⁴U and ²³⁸U, respectively.

Role of lithology in the presence of natural radioactivity in drinking water samples from Tarragona province

One hundred and ninety-six drinking water samples from the different regions of Tarragona province (Catalonia, Spain) were analysed to determine the gross alpha and beta activity. Individual alpha emitting isotope activities were also determined to evaluate a possible relationship between their radiological content and the lithological and hydrogeological formations present in the studied area. The results obtained showed that approximately 23% of the analysed samples, mainly from five of the evaluated regions, had a gross alpha index exceeding the parametric value of 0.1 Bq/L for waters intended for human consumption according to the current legislation. This could be related to the presence of natural radionuclides in these water samples. The differences between the radiological content in these samples could be related to the different lithological conditions of the areas included in this study. High activity levels of ²³⁴U, ²³⁸U, ²²⁴Ra, ²²⁶Ra and ²²⁸Ra were detected in specific samples, mainly from granitic and carbonate areas. This research also focuses on evaluating the radiological risk associated with water ingestion. In this regard, consuming 95.5% of the drinking water samples analysed would not imply a health risk to the population as the annual effective doses calculated were below 0.1 mSv/year. There was only one sample that exceeded this level with a value of 0.33 mSv/year. ²²⁶Ra activity concentration was the radionuclide that mainly contributed to this dose.

Flow-through magnetic-stirring assisted system for uranium(VI) extraction: First 3D printed device application

A 3D printed solid-phase extraction (SPE) device for uranium(VI) extraction has been fabricated using stereolithographic 3D printing. The 3D printed device is shaped as a stirred reactor chamber containing a network of small cubes, which were impregnated with TEVA resin for the extraction of U(VI) from water matrices without doing any previous pretreatment. A flow-through system was combined with off-line ICP-MS detection for the accurate and rapid determination of U(VI) at trace levels. The automatic system was satisfactorily optimized using experimental design, obtaining 0.03 and 0.09 ng U(VI) of detection and quantification limits, respectively, and a durability of 11 consecutive extractions. The reliability of the proposed system was confirmed through the analysis of a reference water material (CSN/CIEMAT 2011), and to water samples (tap, mineral and groundwater) by addition/recovery assays obtaining recoveries between 95 and 106%. This study present for the first time the design of a 3D printing SPE device impregnated with TEVA resin for the on-line extraction of U(VI), showing that 3D printing is a powerful tool for simplifying the construction of complex experimental devices and its operation in analytical procedures for pretreatment applications in water matrices.

Bioaccumulation of natural radionuclides in molluscs from the Ebro Delta area

²¹⁰Po, ²¹⁰Pb, ²³⁴U, ²³⁸U, ²³²Th and ²³⁰Th were analysed in the edible part of four different species of bivalves typically produced and consumed in the Ebro Delta area. The results show that the main contributor to the radioactive content in these species was ²¹⁰Po, with values ranging between 263.1 ± 26.6 and 813.0 ± 72.9 Bq/kg (d.w.), which are higher than the usual reported activity levels in other geographical areas. This can probably be attributed to the activities of a phosphate industrial plant located upstream on the Ebro River, which may lead to enhanced levels of naturally occurring radioactive isotopes in the aquatic ecosystem. To determine the possible impact on health, the committed effective doses through the consumption of the different species were evaluated and the cumulative total annual effective dose for their consumption was estimated to 187.6 μSv/year, which is in the range of 200-1000 μSv/year given by UNSCEAR.

Recovery of NORM from scales generated by oil extraction

Scales, containing naturally occurring radioactive materials (NORM), are a major problem in oil production that lead to costly remediation and disposal programmes. In view of environmental protection, radio and chemical characterisation is an essential step prior to waste treatment. This study focuses on developing of a protocol to recover (226)Ra and (210)Pb from scales produced by petroleum industry. X-ray diffractograms of the scales indicated the presence of barite-strontium (Ba0.75Sr0.25SO4) and hokutolite (Ba0.69Pb0.31SO4) as main minerals. Quartz, galena and Ca2Al2SiO6(OH)2 or sphalerite and iron oxide were found in minor quantities. Incineration to 600 °C followed by enclosed-digestion and acid-treatment gave complete digestion. Using (133)Ba and (210)Pb tracers as internal standards gave recovery ranged 87-91% for (226)Ra and ca. 100% for (210)Pb. Radium was finally dissolved in concentrated sulphuric acid, while (210)Pb dissolved in the former solution as well as in 8 M nitric acid. Dissolving the scales would provide better estimation of their radionuclides contents, facilitate the determination of their chemical composition, and make it possible to recycle NORM wastes in terms of radionuclides production.

Radon in spring waters in the south of Catalonia

Spring waters in the south of Catalonia were analysed to determine the (222)Rn activity in order to be able to establish a correlation between the obtained values with the geology of the area of origin of these samples, and also estimate the potential health risks associated with (222)Rn. Most of the analysed samples (90%) show (222)Rn activities lower than 100Bq/L (exposure limit in water recommended by the World Health Organisation and EU directive 2013/51/EURATOM). However, in some cases, the activity values found for this isotope exceeded those levels and this can be attributed to the geology of the area where the spring waters are located, which is predominantly of granitic characteristics. To verify the origin of the radon present in the analysed samples, the obtained activity values were compared with the activities of its parents ((226)Ra, (238)U and (234)U). Finally, we have calculated the annual effective dose from all the radionuclides measured in spring water samples. The results showed that the higher contribution due to spring water ingestion come from (222)Rn and (226)Ra. The resulting contribution to the annual effective dose due to radon ingestion varies between 10.2 and 765.8 μSv/y, and the total annual effective dose due to his parents, (226)Ra, (234)U and (238)U varies between 0.8 and 21.2 μSv/y so the consumption of these waters does not involve any risks to population due to its natural radioactivity content.

Assessment of elemental and NROM/TENORM hazard potential from non-nuclear industries in North Sinai, Egypt

Non-nuclear industries use raw materials containing significant levels of naturally occurring radioactive material (NORM). The processing of these materials may expose workers engaged in or even people living near such sites to technologically enhanced naturally occurring radioactive material (TENORM) above the natural background. Inductively coupled plasma and gamma ray spectrometry have been used to determine major and trace elements and radionuclide concentrations in various samples, respectively, in order to investigate the environmental impact of coal mining and cement plant in North Sinai, Egypt. Generally, very little attention was directed to the large volumes of waste generated by either type of industrial activities. Different samples were analyzed including various raw materials, coal, charcoal, Portland and white cement, sludge, and wastes. Coal mine and cement plant workers dealing with waste and kaolin, respectively, are subjected to a relatively high annual effective dose. One of the important finding is the enhancement of all measured elements and radionuclides in the sludge found in coal mine. It may pose an environmental threat because of its large volume and its use as combustion material. The mine environment may have constituted Al, Fe, Cr, and V pollution source for the local area. Higher concentration of Al, Fe, Mn, B, Co, Cr, Mn, Ni, Sr, V, and TENORM were found in Portland cement and Zn in white cement. Coal has higher concentrations of Al, Fe, B, Co, Cr, and V as well as (226)Ra and (232)Th. The compiled results from the present study and different worldwide investigations demonstrate the obvious unrealistic ranges normally used for (226)Ra and (232)Th activity concentrations in coal and provided ranges for coal, Portland and white cement, gypsum, and limestone.

Uranium and thorium sequential separation from norm samples by using a SIA system

This study presents a sequential radiochemical separation method for uranium and thorium isotopes using a novel Sequential Injection Analysis (SIA) system with an extraction chromatographic resin (UTEVA). After the separation, uranium and thorium isotopes have been quantified by using alpha-particle spectrometry. The developed method has been tested by analyzing an intercomparison sample (phosphogypsum sample) from International Atomic Energy Agency (IAEA) with better recoveries for uranium and thorium than the obtained by using a classical method (93% for uranium using the new methodology and 82% with the classical method, and in the case of thorium the recoveries were 70% for the semi-automated method and 60% for the classical strategy). Afterwards, the method was successfully applied to different Naturally Occurring Radioactive Material (NORM) samples, in particular sludge samples taken from a drinking water treatment plant (DWTP) and also sediment samples taken from an area of influence of the dicalcium phosphate (DCP) factory located close to the Ebro river reservoir in Flix (Catalonia). The obtained results have also been compared with the obtained by the classical method and from that comparison it has been demonstrated that the presented strategy is a good alternative to existing methods offering some advantages as minimization of sample handling, reduction of solvents volume and also an important reduction of the time per analysis.