Groundwater radon, radium and uranium concentrations in Região dos Lagos, Rio de Janeiro State, Brazil

Estimation of radiological impact of the activities of Olusosun Dump Site on workers and dwellers of Olusosun, in Lagos Southwest Nigeria

This study assessed the potential radiological risks associated with the activities on Olusosun dump site on workers and dwellers of Olusosun community. The activity concentrations of 238U, 232Th and 40K from of soil and water samples were determined using High-Purity Germanium (HPGe) detector. The background radiation level of Olusosun dump site was measured using a portable Geiger-Müller counter-Radeye B20 survey meter. The mean value of background radiation was 1.46 mSv/yr. This value is about 46% higher than the recommended reference level of 1.0 mSv/yr for the public. The mean activity concentrations of 238U, 232Th and 40K in the soil samples were 19.1 ± 3.2, 29.1 ± 4.4 and 171.5 ± 6.1 Bq/kg respectively which are about 45.4%, 35.3% and 59.2% lower than the world's average levels. For the water samples, the mean activity concentrations obtained for 238U, 232Th and 40K are 0.4 ± 0.4, 0.8 ± 0.2 and 0.8 ± 0.3 Bq/l respectively. These are about 99.9% and 20% lower than WHO reference levels for 238U and 232Th. The mean absorbed dose rate in air (D), Annual effective dose (AED) outdoor, Radium Equivalent (Req), External hazard index (Hex) internal hazard index (Hin) and Excess lifetime cancer risk (ELCR) from soil samples were 33.6 nGy/h, 41.0 μSv/yr, 73.1 Bq/kg and 0.2, 0.3 and $1.4\times{10}^{-4}$, respectively. Absorbed dose in air D, AED outdoor, Req, Hex, Hin and ELCR are 41.1%, 41.4%, 80.3%, 80%, 75% and 50% lower than their corresponding world's average and references. The estimated AEDw from ingestion of water is 148.9 ± 50.4 μSv/yr, this is about 49% higher than the WHO reference level of 100.0 μSv/y from ingestion of water. The radiological hazard indices estimated from soil samples do not indicate any potential risks to the users. The elevated background radiation level of the dump site, and AEDw from ingestion of water, however, suggest that the activities on Olusosun dump site pose potential radiological risks on workers on the site and the public from consumption of water from Olusosun community.

Radiological risk associated with 222Rn occurrence in groundwater sources of rural communities in the semiarid region of Paraíba, Brazil

Rural and isolated communities traditionally lack adequate water treatment and distribution systems, and water quality assessment often does not include radioactivity measurement. Here we present, for the first time, the results of Rn measurements and the evaluation of the associated dose in groundwaters of rural communities in a semiarid area in Paraiba State, Brazil. Water samples were analysed using a low-level liquid scintillation spectrometer (LSS). Radon concentrations were higher than EPA and WHO recommended levels in water for most of the wells (range of 5.5-1107.0 Bq/L, average 252.8 Bq/L). Higher Rn concentration was measured in deeper wells and located in area rich in granite and diorite rocks. The annual effective doses varied between 0.021 and 4.317 mSv/y for infants, 0.016-3.182 mSv/y for children, and 0.015-3.022 mSv/y for adults, exceeding, in some cases, the 1 mSv/y reference level recommended by the WHO and UNSCEAR for the public. Thus, water consumption from half of the wells should be avoided unless adequate treatment is provided. Results highlight the need to perform actions to supply water with appropriate quality to the local population.

A critical review of uranium contamination in groundwater: Treatment and sludge disposal

Dissolved uranium in groundwater at high concentrations is an emerging global threat to human and ecological health due to its radioactivity and chemical toxicity. Uranium can enter groundwater by geochemical reactions, natural deposition from minerals, mining, uranium ore processing, and spent fuel disposal. Although much progress has been made in uranium remediation in recent years, most published reviews on uranium treatment have focused on specific methods, particularly adsorption. This article systematically reviews the major treatment technologies, explains their mechanism and progress of uranium removal, and compares their performance under various environmental conditions. Of all treatment methods, adsorption has received much attention due to its ease of use and adaptability under various conditions. However, salinity and competition from other ions limit its application in actual field conditions. Biosorption and bioremediation are also promising methods due to their low-cost and chemical-free operation. Strong base anion exchange resins are more effective at typical groundwater pH conditions. Advanced oxidation processes like photocatalysis produce less sludge and are effective even at low uranium concentrations. Electrocoagulation shows significantly improved performance when organic ligands are added prior to treatment. The significant advantages of membrane filtration are high removal efficiency and the ability to recover uranium. While each technology has its merits and demerits, no single technology is entirely suitable under all conditions. One major area of concern with all technologies is the need to dispose of liquid and solid waste generated after treatment safely. Future research must focus on developing hybrid and state-of-the-art technologies for effective and sustainable uranium removal from groundwater. Developing holistic management strategies for uranium removal will hinge on understanding its speciation, mechanisms of fate and transport, and socio-economic conditions of the affected areas.

Occurrence of 222Rn and 226,228Ra in underground water and 222Rn in soil and their mutual correlations for underground water supplies in southern Greater Poland

European Union Council Directive 2013/51/EURATOM recently sets out so-called indicator parameters for: radon, tritium and indicative dose of water intended for human consumption. The aim of this research was to elaborate an effective procedure for determination of radon and radium ^226,228Ra isotopes (which are potentially the main contributors to the internal dose from drinking and cooking water) and to find the possible relationships between these radionuclides in underground water reservoirs and ²²²Rn concentration in the soil gas in their vicinity. The research was performed by applying a non-volatile and water-immiscible scintillation cocktail based on a pure diisopropylnaphthalene (Ultima Gold F: UGF), which allow for efficient radon extraction from 0.5 dm³ of water samples to 20 cm³ of scintillation phase and its direct determination with a detection limit of 5 × 10^-3 Bq dm^-3. The further preliminary concentration of 3 dm³ of crude water samples by evaporation to 0.5 dm³ samples led to the removal of all unsupported ²²²Rn activity and allowed the ²²⁶Ra determination via equivalent ²²²Rn detection after one-month samples storage using a low-background Triathler liquid scintillation counter in the α/β separation counting mode. Together with determination of ²²⁶Ra isotope in water samples, the simultaneous measurements of ²²⁸Ra and ²²²Rn radionuclides concentrations in water as well as ²²²Rn activity in the soil gas around the water supply sites were performed. The achieved limit of ²²⁶Ra detection was at a very low level of 10^-3 Bq dm^-3. The measured values of ²²⁶Ra concentration in 50 public underground water supply units for the Kalisz district of Poland were relatively low and ranged from below detection limit to 28.5 × 10^-3 Bq dm^-3 with arithmetic mean and median values of 12.9 and 12.2 × 10^-3 Bq dm^-3, respectively. Weak correlations were observed between activity concentrations of ²²⁶Ra and ²²²Rn in the crude water samples (R² = 0.31) and ²²²Rn in water and its concentration in the nearby soil gas (R² = 0.48).

Estimation of uranium in groundwater and assessment of age-dependent radiation dose in Nalbari district of Assam, India

Uranium concentration has been estimated in 31 groundwater samples collected from the Nalbari district of Assam in pre-monsoon and post-monsoon season. Fourteen other water quality parameters have also been monitored to study their correlation with uranium. The uranium concentration varies from 0.3 to 7.1 µg/L with the mean value of 2.15 µg/L in pre-monsoon and 0.6–10.3 µg/L with the mean value of 2.75 µg/L in the post-monsoon season. The higher concentration of uranium in post-monsoon may be ascribed to the dissolution of uranium from soil sediments in the rainy season. It has been observed that the uranium content in both seasons is far lower than the WHO (2011) permissible limit of 30 µg/L. In both seasons, nitrate, sulphate, and especially phosphate show a positive correlation with uranium, which may be due to different agricultural activities. Agricultural nitrate and phosphate fertilization might be the carrier of uranium in groundwater through dissolution. For all life stage groups, the annual effective dose was appeared to be far below the WHO (2011) prescribed limit of 100 µSv/y. In consideration to adults, the ingestion dose for infants was turned out to be higher. The carcinogenic and non-carcinogenic risk was less than the permissible limits for both children and adults. Both dose value and risk indices were found higher in the post-monsoon season.

Natural radioactivity in Brazil: a systematic review

Natural radioactivity is a public health concern worldwide. Its deleterious effects are largely associated with emitting ionizing particles which generate innumerable toxicological consequences to human being. The present study aimed to describe the research state of the art on natural radioactivity in Brazil through a systematic review limited to articles published in the twenty-first century in the PubMed, SciELO, Lilacs, and Google Scholar databases. A total of 55 research articles were considered for this purpose. Based on the collected sample types, the radiation analysis in most of the scientific reports was performed on solid samples (soil/sediment/rocks), followed by water and air. In fact, most of the available information came from geological studies. A wide range of concentrations and a variety of radionuclides have been assessed, with radium being the most cited. Most of the studies described radiation levels above the international guidelines, and consider the Brazilian territory as a high natural background radiation region (HNBR). In comparison with other HNBR areas, the scientific information about the related risks to human health is still scarce. There is uncertainty about the real impact of natural radioactivity on human health, as there is a lack of scientific information for most of the country about this issue. The analysis and comparison of the available information highlights the potential risks linked to natural radioactivity and the need to incorporate suitable environmental management policies about this issue.

A DISCUSSION ON ISSUES WITH RADON IN DRINKING WATER

The majority of the world's population relies on surface water or large public supply systems of groundwater, where radon is low and a guidance value for radon in drinking water is not necessary. However, the International Commission on Radiological Protection (ICRP) recently issued a dose coefficient for radon ingestion, raising questions among some radiation protection authorities about whether radon guidance values should be calculated for drinking water and how this might be done. Unlike many other radionuclides considered in drinking water management, radon has special characteristics and therefore requires special considerations. This note discusses some of these considerations, and also provides a brief review of radon concentrations measured in well-water supplies, especially private well-water systems, and cold tap water consumption rates reported in different countries.

Fate and transport of radioactive gypsum stack water entering the Floridan aquifer due to a sinkhole collapse

Groundwater aquifers are an essential source of drinking water, and must be protected against contamination. Phosphogypsum stacks originating from the processing of phosphate rock contain small amounts of radionuclides, such as ²²⁶Ra. In September 2016, a sinkhole located beneath a phosphogypsum stack collapsed under central Florida’s carbonate karst terrain, where the aquifer is mostly confined, raising concern over water quality in the regions nearby. Monitoring and modeling the transport of the contaminated plume is vital to ensure drinking water criteria are met and to improve decision making regarding treatment. To achieve this, a geochemical modeling using PHREEQC software was employed to investigate the trajectory of the plume based on hydraulic and hydrologic conditions. Adsorption was simulated as a removal mechanism that could further reduce the intensity of the plume. The aquifer’s response to the release of contaminated water from the collapsed stack was quantified by simulating a number of scenarios, including variable radionuclide leakage quantities. Results suggest that it may take between 11–17 years and between 5.2 to 8.3 km from the sinkhole leak to reduce radionuclide concentrations to previous levels. Coupling the adsorption effect by minerals in Floridan aquifer (e.g. ferrihydrite, carbonate) can reduce radionuclide migration time to 9–16 years and distances between 4.3 to 7.8 km from the sinkhole leak. It can also reduce the distance needed to lower radionuclide concentrations, though not significantly. Additionally, due to the complexities of soil chemistry, the importance of groundwater remediation is emphasized.

A review of the analytical methodology to determine Radium-226 and Radium-228 in drinking waters

Radium-228 (228Ra) and Radium-226 (226Ra) isotopes in drinking water are significant from the aspect of radiation protection and human health. In this paper, the three most common preconcentration methods, i.e.coprecipitation, absorption and evaporation, were reviewed with emphasis on routinely measurement techniques. The reviewed measurement techniques include low background γ-spectrometry, α-spectrometry and liquid scintillation counting. The γ-spectrometry technique is the good selection, when the maximum sensitivity is considered. The Environmental Protection Agency guideline has provided the maximum concentration level 0.74 Bq/L for 226Ra and 228Ra. Also, the World Health Organization guideline limit is 1 Bq/L and 0.1 Bq/L for 226Ra and 228Ra, respectively.

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.

Natural radioactivity in the groundwater of Wadi Nu'man, Mecca Province, Saudi Arabia

Twenty-nine groundwater samples, collected from Wadi Nu'man wells, were analyzed for natural radioactivity to check for compliance with the national guideline values. Gross α and gross β screening, in addition to radon ( 222Rn) measurements, were performed for all samples. Samples of gross activity levels exceeding the national guideline values set out for drinking water were subjected to further investigation for radium and uranium isotopes using liquid scintillation counting and α-spectrometry, respectively. The results showed that the anomalous source was natural uranium. The water contains high concentrations of 222Rn and considerable levels of natural uranium. The 222Rn concentration ranged from 10–100 Bq/L with an average value of about 40 Bq/L. The uranium concentration, in samples of gross activity levels exceeding the national guideline value, ranged from 9 to 55 μg/L. The levels of 226Ra and 228Ra were below the detection limit of the counting system in all samples. The variation in the 222Rn and uranium concentrations was found to be linked with the local lithology. The higher values were recorded in the wells of Nu'man complex aquifer, where the predominating mineral is foliated monzonite. Recommendations and advices for water management to reduce radiation exposure to users are presented.

Uranium in the surrounding of San Marcos-Sacramento River environment (Chihuahua, Mexico)

The main interest of this study is to assess whether uranium deposits located in the San Marcos outcrops (NW of Chihuahua City, Mexico) could be considered as a source of U-isotopes in its surrounding environment. Uranium activity concentrations were determined in biota, ground, and surface water by either alpha or liquid scintillation spectrometries. Major ions were analyzed by ICP-OES in surface water and its suspended matter. For determining uranium activity in biota, samples were divided in parts. The results have shown a possible lixiviation and infiltration of uranium from geological substrate into the ground and surface water, and consequently, a transfer to biota. Calculated annual effective doses by ingestion suggest that U-isotopes in biota could not negligibly contribute to the neighboring population dose. By all these considerations, it is concluded that in this zone there is natural enhancement of uranium in all environmental samples analyzed in the present work.

Uranium sorption on bentonite modified by octadecyltrimethylammonium bromide

The sorption of U(VI) on octadecyltrimethyl-bentonite was investigated at the pH values of the aqueous phase ranging from 3 to 10 and the concentrations of U(VI): 0.1-1 mmol/dm(3). The concentrations of alkylammonium cation in bentonite were increased from 21% to 150% of CEC (cation exchange capacity). It was determined that the sorption of U(VI) on modified bentonite, i.e. the distribution constant -K(d) decreases with the percent of mineral modification until it attains a minimum at 76% of CEC and then increases again. The effective sorption of U(VI) was found to be in the pH range: 6-10 for the modified bentonite and was explained as the consequence of U(VI) anionic hydroxy complexes sorption. Both FT-IR and XRD spectra of the modified bentonite were analyzed and provided arguments for the existence of surfactant cations in the form of monolayer and bilayer in the interlamellar space of bentonite. In turn the luminescence spectra of bentonite suspensions, i.e. their character at different values of pH, proved the existence of hydroxide-like planar polymeric U(VI) species in the bentonite phase at pH 9.

Radium and uranium levels in vegetables grown using different farming management systems

Vegetables grown with phosphate fertilizer (conventional management), with bovine manure fertilization (organic management) and in a mineral nutrient solution (hydroponic) were analyzed and the concentrations of (238)U, (226)Ra and (228)Ra in lettuce, carrots, and beans were compared. Lettuce from hydroponic farming system showed the lowest concentration of radionuclides 0.51 for (226)Ra, 0.55 for (228)Ra and 0.24 for (238)U (Bq kg(-1) dry). Vegetables from organically and conventionally grown farming systems showed no differences in the concentration of radium and uranium. Relationships between uranium content in plants and exchangeable Ca and Mg in soil were found, whereas Ra in vegetables was inversely correlated to the cation exchange capacity of soil, leading to the assumption that by supplying carbonate and cations to soil, liming may cause an increase of U and a decrease of radium uptake by plants. The soil to plant transfer varied from 10(-4) to 10(-2) for (238)U and from 10(-2) to 10(-1) for (228)Ra.

Radium and (40)K in Algerian bottled mineral waters and consequent doses

Concentrations of (226)Ra, (228)Ra and (40)K in the five most popular Algerian bottled mineral waters have been found to be 13.9 to 148.9 mBq l(-1), 7.2 to 52.9 mBq l(-1) and <0.07 to 2.19 Bq l(-1), respectively. Ratios of (226)Ra to (228)Ra activities ranged from 1.0 to 13.66 with a mean of 5.62. The annual effective doses due to ingestion of these waters have been estimated for three age categories (infants, children and adults) using the measured activities of these radionuclides and assuming the World Health Organisation's default water intake rate. Annual doses for children and adults have been found to be well below the 0.1 mSv y(-1) reference dose level, whereas for the most vulnerable group the annual effective dose from all the waters exceeds the reference value and contributes 12% to the mean annual dose from natural exposure.

Ultratrace-level radium-226 determination in seawater samples by isotope dilution inductively coupled plasma mass spectrometry

An improved and novel sample preparation method for 226Ra determination in liquid samples by isotope dilution inductively coupled plasma sector field mass spectrometry using laboratory-prepared 228Ra tracer has been developed. The procedure involves a selective preconcentration achieved by applying laboratory-prepared MnO2 resin followed by cation exchange chromatographic separation. In order to completely eliminate possible molecular interferences, medium mass resolution (R = 4,000) combined with chemical separation was found to be a good compromise that enhanced the reliability of the method. The detection limit of 0.084 fg g(-1) (3.1 mBq kg(-1)) achieved is comparable to that of the emanation method or alpha spectrometry and is suitable for low-level environmental measurements. The chemical recovery of the sample preparation method ranged from 72 to 94%. The proposed method enables a rapid, accurate and less labor-intensive approach to routine environmental 226Ra determination than the radioanalytical techniques conventionally applied.

Simultaneous measurement of (226)Ra and (228)Ra in natural water by liquid scintillation counting

Several types of bottled drinking water originating from three different areas in Egypt are studied through measurement of radium activity, assessment of related annual dose for adults and finally to define the role of water quality on radium levels. The mean levels of (226)Ra activity range from 0.44 to 0.92 Bq/L and the mean levels of (228)Ra from 0.30 to 0.78 Bq/L, with related (226)Ra/(228)Ra ratios ranging from 2.61 to 0.56. Water types originating from the Eastern Nile Delta area are characterized by low (226)Ra levels and relatively high (228)Ra activity, presumably due to the muddy agricultural nature of this area, which is subject to water from several surface resources for irrigation. In general, the mean activity levels for both (226)Ra and (228)Ra are within those in drinking water in several other countries and the annual ingested dose is comparable with the typical range reported by UNSCEAR. Also, the effect of TDS, pH, calcium, bicarbonate, sulphate and chloride ion concentrations on radium levels is studied and discussed.

A prediction method for radon in groundwater using GIS and multivariate statistics

Radon (222Rn) in groundwater constitutes a source of natural radioactivity to indoor air. It is difficult to make predictions of radon levels in groundwater due to the heterogeneous distribution of uranium and radium, flow patterns and varying geochemical conditions. High radon concentrations in groundwater are not always associated with high uranium content in the bedrock, since groundwater with a high radon content has been found in regions with low to moderate uranium concentrations in the bedrock. This paper describes a methodology for predicting areas with high concentrations of 222Rn in groundwater on a general scale, within an area of approximately 185x145km2. The methodology is based on multivariate statistical analyses, including principal component analysis and regression analysis, and investigates the factors of geology, land use, topography and uranium (U) content in the bedrock. A statistical variable based method (the RV method) was used to estimate risk values related to different radon concentrations. The method was calibrated and tested on more than 4400 drilled wells in Stockholm County. The results showed that radon concentration was clearly correlated to bedrock type, well altitude and distance from fracture zones. The weighted index (risk value) estimated by the RV method provided a fair prediction of radon potential in groundwater on a general scale. Risk values obtained using the RV method were compared to radon measurements in 12 test areas (on a local scale, each of area 25x25km2) in Stockholm County and a high correlation (r=-0.87) was observed. The study showed that the occurrence and spread of radon in groundwater are guided by multiple factors, which can be used in a radon prediction method on a general scale. However, it does not provide any direct information on the geochemical and flow processes involved.

Activity concentrations of 226Ra and 228Ra in drilled well water in Finland

The activity concentrations of (226)Ra and (228)Ra in drinking water were determined in water samples from 176 drilled wells. (226)Ra activity concentrations were in the range of <0.01-1.0 Bq l(-1) and (228)Ra activity concentrations in the range of <0.03-0.3 Bq l(-1). The mean activity concentration of (226)Ra and (228)Ra were 0.041 and 0.034 Bq l(-1), respectively. High radium activity concentrations in drinking water were rare. Only 2-4% of the drilled wells exceeded a (226)Ra concentration of 0.5 Bq l(-1) and 1-2% of the wells exceeded a (228)Ra concentration of 0.2 Bq l(-1). These are the activity concentrations that cause a 0.1 mSv annual effective dose for users of drinking water. The maximum annual effective doses from (226)Ra and (228)Ra for users of drilled wells were 0.21 mSv, and 0.16 mSv respectively. The elevated activity concentrations of (226)Ra and (228)Ra did not occur simultaneously in the same groundwaters and the correlation between (226)Ra and (228)Ra was small.

Natural radioactivity in Brazilian groundwater

More than 220 groundwater samples were analyzed for 228Ra, 226Ra, 222Rn, 210Pb, U(nat), Th(nat), pH, conductivity, fluoride and some additional elements determined by ICP-MS. Since samples from several Brazilian states were taken, involving areas with quite different geologies, no general trend was observed relating the chemical composition and the natural radionuclide content. On the other hand, 210Pb strongly depends on the water content of its progenitor, 222Rn. The values obtained during the present work were compared with those reported by Hainberger et al. [Hainberger, P.L., de Oliveira Paiva, I.R., Salles Andrade, H.A., Zundel, G., Cullen, T.L., 1974. Radioactivity in Brazilian mineral waters. Radiation Data and Reports, 483-488.], when more than 270 groundwater samples were analyzed, mainly, for 226Ra. Based on the results of both works, it was possible to build a database including the results of both works, generating a set with the radium content of circa 350 groundwater sources. It was demonstrated that 228Ra, 226Ra, 222Rn, 210Pb and U(nat) content in Brazilian groundwater follows a lognormal distribution and the obtained geometric mean were 0.045, 0.014, 57.7, 0.040 BqL(-1) and 1.2 microgL(-1), respectively.