High naturally occurring radioactivity in fossil groundwater from the Middle East

Radiation dose and lifetime risk for radiation-induced cancer due to natural radioactivity in tap water from Jordan

The purpose of this study was to investigate the radiological quality of drinking water in Ma'an governorate, which includes the archeological city of Petra and is one of Jordan's most important tourist destinations. To the best of the authors' knowledge, this is the first study in southern Jordan that investigates radioactivity in drinking water and its potential to cause cancer. A liquid scintillation detector was used to measure gross alpha and gross beta activities in tap water samples from Ma'an governorate. A high-purity Germanium detector was used to measure the activity concentrations of ²²⁶Ra and ²²⁸Ra. Gross alpha, gross beta, ²²⁶Ra, and ²²⁸Ra activities were < 110-724 mBq/l, < 220-362 mBq/l, < 11-241 mBq/l, and < 32-49 mBq/l, respectively. The results were compared to internationally recommended levels and literature values. Annual effective doses ([Formula: see text]) from ²²⁶ and ²²⁸Ra intake were calculated for infants, children, and adults. The highest doses were found for children while the lowest were found for infants. For each water sample, the lifetime risk of radiation-induced cancer (LTR) was calculated for the whole population. All of the LTR values were lower than the value recommended by the World Heath Organisation. It is concluded that there are no significant radiation-related health risks associated with consumption of tap water from the studied region.

Hydrochemical and geological controls on dissolved radium and radon in northwestern Algeria hydrothermal groundwaters

This study presents the results of the first investigation on natural occurrence of radium and radon in Algerian thermal water systems. Activity concentrations of Rn and Ra isotopes were measured in sixteen hydrothermal springs of northwestern Algeria. Samples displayed high activities, especially for ²²²Rn, ²²⁴Ra and ²²⁶Ra (up to 377 × 10³ Bq/m³, 730 Bq/m³ and 4470 Bq/m³, respectively). Approximately, 50% of the investigated springs displayed activities of combined long-lived Ra (²²⁶Ra + ²²⁸Ra) in excess of the maximum contaminant level (MCL) of the WHO and EPA for drinking water. Factors controlling the distribution of radionuclides in the aquifer system are investigated. The observed correlation between Ra isotope and TDS suggests that adsorption/desorption is not the dominant process controlling the distribution of Ra in waters. Our results indicate that the excess SO₄^2- limits the concentration of dissolved Ba²⁺ and thereby, the elevated Ra activities in these hydrothermal systems are not simply limited by co-precipitation with BaSO₄ (barite). The data shows that Ra activities are likely dominated by the recoil process of parent isotopes in the aquifer solids. The minimal abundance of clay minerals and oxides in the aquifer, in addition to thermal activities in northwestern Algeria, significantly enhances the mobilization of Ra into waters.

A rapid method for determining low concentrations of 210Pb in drinking water using MnO2 fibers

A rapid method for determining low activity concentrations of ²¹⁰Pb in drinking water was developed and tested. The method consists of a few stages for sample preparation that involve passing 12 L of water through a column with acrylic fibers implanted with MnO₂ (used to adsorb ²¹⁰Pb). The MnO₂ fibers are oven-dried, compressed and measured by a broad-energy germanium detector used to quantify ²¹⁰Pb via its characteristic 46.5 keV γ-ray. The time taken for sample preparation is approximately 4 h and recovery factors for lead in tap water of 87 ± 3% were achieved. After a measurement duration of 4 h, the minimum detectable activity concentration reaches 0.02 Bq/L for ²¹⁰Pb, being well below the respective limit for drinking water in Israel (0.2 Bq/L) as well as the value recommended by the World Health Organization (0.1 Bq/L). Furthermore, a measurement duration of 48 h provides a minimum detectable activity concentration of ∼0.006 Bq/L, which is similar in magnitude to other, well-established methods that rely on lengthy and rather complex procedures. Thus, the combination of MnO₂ fibers and gamma-ray spectrometry may be attractive for routine use by analytical laboratories that monitor radioactivity in drinking water.

Radium radioactivity in soil profiles following long term irrigation with high radioactivity fossil groundwater

High radioactivity in a relatively saline confined aquifer water in different locations of the Disi area (South East of Jordan) was reported by some authors who recommended further investigation on the impact of that water on irrigated soils. Five well water samples (jointly used for irrigation and drinking) and 28 surface and subsurface soil samples from five profiles were collected from that area for the purpose of this study. Selected mineralogical, chemical, and physical properties of the soil samples were determined. Mineralogical compositions of the 28 soil samples were identified using x-ray diffraction, x-ray fluorescence, and ICP-MS techniques. Determination of activity concentrations of ²³⁸U, ²²⁶Ra and ²²⁸Ra in the five well waters and 22 soil samples from 4 sites (including a native soil) were determined using γ-ray spectroscopy. The results showed low salinity levels of both soil and water samples and low clay and organic matter contents in all soil samples. Kaolinite and mica were the dominant clay minerals with Fe substituting Al in the octahedral layer of these minerals. The average activity concentration of ²²⁶Ra and ²²⁸Ra in the well-water samples were 0.31 ± 0.09 and 1.74 ± 0.12 BqL^-1, respectively. Such a high specific activity could be ascribed to the water enrichment with ²²⁸Ra diffusing from ²³²Th-rich sandstone geologic strata. Average concentrations of ²³⁸U and ²³²Th in the soil samples (0-120 cm depth) were 1.48 ± 0.38 mg kg^-1 and 4.78 ± 1.55 mg kg^-1, respectively. High correlation between these two radionuclides (R² = 0.90) indicated no specific enhancement of these two metals from external sources, especially through chemical precipitation from irrigation water. Average activity concentration of ²³⁸U, ²²⁶Ra, and ²²⁸Ra in the soil samples were substantially low (20.8 ± 5.6, 16.94 ± 4.48, and 20.7 ± 6.2 Bq kg^-1, respectively). No particular changes were observed when comparing concentration or radioactivity of these radionuclides with depth of a given soil or between irrigated and native soil samples at comparable depths. This could lead to the conclusion that there was no appreciable precipitation or adsorption of these radioactive metals from the percolating irrigation water onto the sandy soil complex.

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.

Shale gas wastewater characterization: Comprehensive detection, evaluation of valuable metals, and environmental risks of heavy metals and radionuclides

Shale gas wastewater (SGW) has great potential for the recovery of valuable elements, but it also poses risks in terms of environmental pollution, with heavy metals and naturally occurring radioactive materials (NORM) being of major concerns. However, many of these species have not been fully determined. For the first time, we identify the elements present in SGW from the Sichuan Basin and consequently draw a comprehensive periodic table, including 71 elements in 15 IUPAC groups. Based on it, we analyze the elements possessing recycling opportunities or with risk potentials. Most of the metal elements in SGW exist at very low concentrations (< 0.2 mg/L), including rare earth elements, revealing poor economic feasibility for recovery. However, salts, strontium (Sr), lithium (Li), and gallium (Ga) are in higher concentrations and have impressive market demands, hence great potential to be recovered. As for environmental burdens related to raw SGW management, salinity, F, Cl, Br, NO₃^-, Ba, B, and Fe, Cu, As, Mn, V, and Mo pose relatively higher threats in view of the concentrations and toxicity. The radioactivity is also much higher than the safety range, with the gross α activity and gross β activity in SGW ranging from 3.71-83.4 Bq/L, and 1.62-18.7 Bq/L, respectively and radium-226 as the main component. The advanced combined process "pretreatment-disk tube reverse osmosis (DTRO)" with pilot-scale is evaluated for the safe reuse of SGW. This process has high efficiency in the removal of metals and total radioactivity. However, the gross α activity of the effluent (1.3 Bq/L) is slightly higher than the standard for discharge (1 Bq/L), which is thus associated with potential long-term environmental hazards.

Occurrence and behavior of uranium and thorium series radionuclides in the Permian shale hydraulic fracturing wastes

Over the last decade, there has been a rapid growth in the use of hydraulic fracturing (fracking) to recover unconventional oil and gas in the Permian Basin of southeastern New Mexico (NM) and western Texas. Fracking generates enormous quantities of wastes that contain technologically enhanced naturally occurring radioactive materials (TENORM), which poses risks to human health and the environment because of the relatively high doses of radioactivity. However, very little is known about the chemical composition and radioactivity levels of Permian Basin fracking wastes. Here, we report chemical as well as radiochemical compositions of hydraulic fracking wastes from the Permian Basin. Radium, the major TENORM of interest in unconventional drilling wastes, varied from 19.1 ± 1.2 to 35.9 ± 3.2 Bq/L for ²²⁶Ra, 10.3 ± 0.5 to 21.5 ± 1.2 Bq/L for ²²⁸Ra, and 2.0 ± 0.05 to 3.7 ± 0.07 Bq/L for ²²⁴Ra. In addition to elevated concentrations of radium, these wastewaters also contain elevated concentrations of dissolved salts and divalent cations such as Na⁺ (31,856-43,000 mg/L), Ca²⁺ (668-4123 mg/L), Mg²⁺ (202-2430 mg/L), K⁺ (148-780 mg/L), Sr²⁺ (101-260 mg/L), Cl^- (5160-66,700 mg/L), SO₄^2- (291-1980 mg/L), Br^- (315-596 mg/L), SiO₂ (20-32 mg/L), and high total dissolved solid (TDS) of 5000-173,000 mg/L compared to background waters. These elevated levels are of radiological significance and represent a major source of Ra in the environment. The recent discovery of large deposits of recoverable oil and gas in the Permian Basin will lead to more fracking, TENORM generation, and radium releases to the environment. This paper evaluates the potential radiation risks associated with TENORM wastes generated by the oil and gas recovery industry in the Permian Basin.

Widespread and increased drilling of wells into fossil aquifers in the USA

Most stored groundwater is ‘fossil’ in its age, having been under the ground for more than ~12 thousand years. Mapping where wells tap fossil aquifers is relevant for water quality and quantity management. Nevertheless, the prevalence of wells that tap fossil aquifers is not known. Here we show that wells that are sufficiently deep to tap fossil aquifers are widespread, though they remain outnumbered by shallower wells in most areas. Moreover, the proportion of newly drilled wells that are deep enough to tap fossil aquifers has increased over recent decades. However, this widespread and increased drilling of wells into fossil aquifers is not necessarily associated with groundwater depletion, emphasizing that the presence of fossil groundwater does not necessarily indicate a non-renewable water supply. Our results highlight the importance of safeguarding fossil groundwater quality and quantity to meet present and future water demands.

Fossil groundwater has been under the ground for more than ~12 thousand years. Here the authors show that many wells in the United States tap fossil groundwater resources, and that the frequency that wells are drilled into fossil aquifers is increasing, highlighting the importance of safeguarding fossil groundwater quality and quantity to meet present and future water demands.

A critical review on the occurrence and distribution of the uranium- and thorium-decay nuclides and their effect on the quality of groundwater

This critical review presents the key factors that control the occurrence of natural elements from the uranium- and thorium-decay series, also known as naturally occurring radioactive materials (NORM), including uranium, radium, radon, lead, polonium, and their isotopes in groundwater resources. Given their toxicity and radiation, elevated levels of these nuclides in drinking water pose human health risks, and therefore understanding the occurrence, sources, and factors that control the mobilization of these nuclides from aquifer rocks is critical for better groundwater management and human health protection. The concentrations of these nuclides in groundwater are a function of the groundwater residence time relative to the decay rates of the nuclides, as well as the net balance between nuclides mobilization (dissolution, desorption, recoil) and retention (adsorption, precipitation). This paper explores the factors that control this balance, including the relationships between the elemental chemistry (e.g., solubility and speciation), lithological and hydrogeological factors, groundwater geochemistry (e.g., redox state, pH, ionic strength, ion-pairs availability), and their combined effects and interactions. The various chemical properties of each of the nuclides results in different likelihoods for co-occurrence. For example, the primordial ²³⁸U, ²²²Rn, and, in cases of high colloid concentrations also ²¹⁰Po, are all more likely to be found in oxic groundwater. In contrast, in reducing aquifers, Ra nuclides, ²¹⁰Pb, and in absence of high colloid concentrations, ²¹⁰Po, are more mobile and frequently occur in groundwater. In highly permeable sandstone aquifers that lack sufficient adsorption sites, Ra is often enriched, even in low salinity and oxic groundwater. This paper also highlights the isotope distributions, including those of relatively long-lived nuclides (²³⁸U/²³⁵U) with abundances that depend on geochemical conditions (e.g., fractionation induced from redox processes), as well as shorter-lived nuclides (²³⁴U/²³⁸U, ²²⁸Ra/²²⁶Ra, ²²⁴Ra/²²⁸Ra, ²¹⁰Pb/²²²Rn, ²¹⁰Po/²¹⁰Pb) that are strongly influenced by physical (recoil), lithological, and geochemical factors. Special attention is paid in evaluating the ability to use these isotope variations to elucidate the sources of these nuclides in groundwater, mechanisms of their mobilization from the rock matrix (e.g., recoil, ion-exchange), and retention into secondary mineral phases and ion-exchange sites.

AGE-DEPENDENT DOSE DUE TO INTAKE OF 40K, 228RA, 226RA IN SPRING WATER IN PETRA DISTRICT, JORDAN

A HpGe detector was used to measure radioactivity concentrations of 40K, 228Ra and 226Ra in spring water from villages in Petra district in southern Jordan. The concentrations of 40K, 228Ra, 226Ra were 0.64-2.72 Bq/l, 0.05-0.08 Bq/l and 0.15-0.22 Bq/l, respectively. These values were compared to the concentrations of the corresponding radionuclides in studies from Jordan and near countries. The annual effective doses (${D}_{\mathrm{eff}}$) due to the intake of 40K, 228Ra and 226Ra, for the different age groups were calculated. The highest ${D}_{\mathrm{eff}}$ values due to the intake of 226Ra and 228Ra were found in the infants age group, whereas the lowest were found in the adults age group in every site. The annual effective doses in this study were compared to the committed annual effective doses from ingestion in UNSCEAR. The annual effective doses in this study were much higher than the committed values in UNSCEAR. The life time risk for radiation-induced cancer for the whole population was calculated for every sample and it revealed no extra risk over the one recommended by WHO.

Elevated radium levels in Nubian Aquifer groundwater of Northeastern Africa

The Nubian Sandstone Aquifer System in Northeast Africa and the Middle East is a huge water resource of inestimable value to the population. However, natural radioactivity impairs groundwater quality throughout the aquifer posing a radiological health risk to millions of people. Here we present measurements of radium isotopes in Nubian Aquifer groundwater from population centers in the Western Desert of Egypt. Groundwater has ²²⁶Ra and ²²⁸Ra activities ranging from 0.01 to 2.11 and 0.03 to 2.31 Bq/L, respectively. Most activities (combined ²²⁶Ra + ²²⁸Ra) exceed U.S. EPA drinking water standards. The estimated annual radiation doses associated with ingestion of water having the highest measured Ra activities are up to 138 and 14 times the WHO-recommended maxima for infants and adults, respectively. Dissolved Ra activities are positively correlated with barium and negatively correlated with sulfate, while barite is approximately saturated. In contrast, Ra is uncorrelated with salinity. These observations indicate the dominant geochemical mechanisms controlling dissolved Ra activity may be barite precipitation and sulfate reduction, along with input from alpha-recoil and dissolution of aquifer minerals and loss by radioactive decay. Radium mitigation measures should be adopted for water quality management where Nubian Aquifer groundwater is produced for agricultural and domestic consumption.

Utica Shale Play Oil and Gas Brines: Geochemistry and Factors Influencing Wastewater Management

The Utica and Marcellus Shale Plays in the Appalachian Basin are the fourth and first largest natural gas producing plays in the United States, respectively. Hydrocarbon production generates large volumes of brine ("produced water") that must be disposed of, treated, or reused. Though Marcellus brines have been studied extensively, there are few studies from the Utica Shale Play. This study presents new brine chemical analyses from 16 Utica Shale Play wells in Ohio and Pennsylvania. Results from Na-Cl-Br systematics and stable and radiogenic isotopes suggest that the Utica Shale Play brines are likely residual pore water concentrated beyond halite saturation during the formation of the Ordovician Beekmantown evaporative sequence. The narrow range of chemistry for the Utica Shale Play produced waters (e.g., total dissolved solids = 214-283 g/L) over both time and space implies a consistent composition for disposal and reuse planning. The amount of salt produced annually from the Utica Shale Play is equivalent to 3.4% of the annual U.S. halite production. Utica Shale Play brines have radium activities 580 times the EPA maximum contaminant level and are supersaturated with respect to barite, indicating the potential for surface and aqueous radium hazards if not properly disposed of.

Geochemical and hydrogeological factors influencing high levels of radium contamination in groundwater in arid regions

One of the most challenging environmental issues in arid regions is radionuclide groundwater contamination; typically, radionuclide sources, mobility, and spatial distributions are not well understood. The main objectives of this study are to investigate the groundwater hydrochemistry and identify the factors governing the radium occurrences and mobility. Groundwater samples were collected from shallow unconfined zone and deep confined Saq sandstone aquifer in the Hail area, Saudi Arabia. They were analyzed for major, minor, and trace elements as well as radium isotopes (²²⁶Ra and ²²⁸Ra). The hydrochemical relationships, water facies, spatial distribution, and the factor analysis were integrated to elucidate the governing processes in the system. The hydrochemical facies exhibited four water types characterized by earth alkaline and alkaline elements. Most samples contained sulfates and chlorides. The hydrochemical processes affecting groundwater included the dissolution of certain minerals, mixing between modern and fossil water types, and reverse ion exchange. There are high concentrations of nitrate in the unconfined zone, with low concentrations in areas under confining conditions. High radium concentrations were recorded in the groundwater, and the ²²⁶Ra and ²²⁸Ra activity concentrations of the examined samples were 11% and 98% above the World Health Organization (WHO) guidelines, respectively. The spatial distribution of ²²⁶Ra showed high activity concentration in the shallow zone under prevailing oxidizing conditions. High ²²⁸Ra contamination was identified in the confined zone where the redox potential appears to decrease and the temperature increases result in higher mobility or desorption of the radium ions. In the unconfined zone, the oxidation of Fe⁺² in the groundwater and precipitation of Fe⁺³ in the aquifer pore spaces and co-precipitation with barite can accelerate radium adsorption. The ²²⁸Ra/²²⁶Ra ratio classified the radium groundwater enrichment into three main clusters, namely, those depending on the redox potential values, the primary source distribution, and enrichment in ²²⁶Ra relative to ²²⁸Ra. Five major factors influencing groundwater hydrochemistry were identified using factor analysis. The first factor explained the processes resulting in the dissolution of the silicate minerals and thereby increased the uranium mobility. The second factor encompassed processes leading to a rise in the groundwater salinity. The third factor identified thorium minerals as the source of the ²²⁸Ra. The fourth factor was ascribed to the decrease in radium through sorption processes or co-precipitation with barite. The fifth factor referred to by the uneven distribution of Th and U containing minerals in the aquifer.

Application of Doehlert experimental design for the removal of radium from aqueous solution by cross-linked phenoxycalix[4]pyrrole-polymer using Ba(II) as a model

Ra-226 is a naturally occurring radionuclide that is derived from uranium-238 series, and it is present at low concentrations in rocks, soil, and groundwater. Many efforts have been exerted for the decontamination of radium from aqueous media in order to meet the increasing water demand of the population. To this aim, a new polymer based on cross-linked phenoxycalix[4]pyrrole was designed and employed in solid/liquid extractions in order to remove radium from aqueous solutions. Preliminary experiments have highlighted the capability of this polymer to extract 22% of Ra-226 from aqueous acidic solution. The optimization of the extraction experimental factors in the direction to attend the maximum removal of Ra-226 from water was carried out employing Ba²⁺ due to its similar chemical behavior as radium, in order to minimize the consumption of Ra-226 solutions and the risk of radioactive contamination. Doehlert experimental plan was then applied to determine the optimal conditions (pH, time, temperature) for the removal of Ba²⁺ from aqueous solutions.

Measurement of gross alpha and beta activity concentration in groundwater of Jordan: groundwater quality, annual effective dose and lifetime risk assessment

The current study was conducted to measure the activity concentration of the gross alpha and beta in 87 groundwater samples collected from the productive aquifers that constitute a major source of groundwater to evaluate the annual effective dose and the corresponding health impact on the population and to investigate the quality of groundwater in Jordan. The mean activity concentration of gross alpha and beta in groundwater ranges from 0.26 ± 0.03 to 3.58 ± 0.55 Bq L^-1 and from 0.51 ± 0.07 to 3.43 ± 0.46 Bq L^-1, respectively. A very strong relationship was found between gross alpha and beta activity concentrations. The annual effective dose for alpha and beta was found in the range of 0.32-2.40 mSv with a mean value of 0.89 mSv, which is nine times higher than the World Health Organization (WHO) recommended limit and one and half times higher than the national regulation limit. The mean lifetime risk was found to be 45.47 × 10^-4 higher than the Jordanian estimated upper-bound lifetime risk of 25 × 10^-4. The data obtained in the study would be the baseline for further epidemiological studies on health effects related to the exposure to natural radioactivity in Jordan.

Occurrence and Sources of Radium in Groundwater Associated with Oil Fields in the Southern San Joaquin Valley, California

Geochemical data from 40 water wells were used to examine the occurrence and sources of radium (Ra) in groundwater associated with three oil fields in California (Fruitvale, Lost Hills, South Belridge). ²²⁶Ra+²²⁸Ra activities (range = 0.010-0.51 Bq/L) exceeded the 0.185 Bq/L drinking-water standard in 18% of the wells (not drinking-water wells). Radium activities were correlated with TDS concentrations (p < 0.001, ρ = 0.90, range = 145-15,900 mg/L), Mn + Fe concentrations (p < 0.001, ρ = 0.82, range = <0.005-18.5 mg/L), and pH (p < 0.001, ρ = -0.67, range = 6.2-9.2), indicating Ra in groundwater was influenced by salinity, redox, and pH. Ra-rich groundwater was mixed with up to 45% oil-field water at some locations, primarily infiltrating through unlined disposal ponds, based on Cl, Li, noble-gas, and other data. Yet ²²⁸Ra/²²⁶Ra ratios in pond-impacted groundwater (median = 3.1) differed from those in oil-field water (median = 0.51). PHREEQC mixing calculations and spatial geochemical variations suggest that the Ra in the oil-field water was removed by coprecipitation with secondary barite and adsorption on Mn-Fe precipitates in the near-pond environment. The saline, organic-rich oil-field water subsequently mobilized Ra from downgradient aquifer sediments via Ra-desorption and Mn/Fe-reduction processes. This study demonstrates that infiltration of oil-field water may leach Ra into groundwater by changing salinity and redox conditions in the subsurface rather than by mixing with a high-Ra source.

Gross alpha/beta radioactivity and radiation dose in thermal and non-thermal spas groundwaters

Gross alpha and gross beta activities have been determined in thermal and non-thermal spas groundwaters (75) occurring at São Paulo and Minas Gerais states in Brazil as they are ingested in public places, bottled and used for bathing purposes, among other. The samples provided from springs and pumped tubular wells drilled at different aquifer systems inserted in Paraná and Southeastern Shield hydrogeological provinces. The WHO guideline reference value proposed in 2011 for the drinking water quality was never reached for the gross alpha activity (0.5 Bq/L) but it was exceeded in 13 groundwater samples for the gross beta activity (1 Bq/L). Available activity concentration data of the natural radionuclides ⁴⁰K, ²²⁸Ra (²³²Th-daughter), ²³⁸U and descendants (²³⁴U, ²²⁶Ra, ²²²Rn, ²¹⁰Pb, ²¹⁰Po) allowed calculate the total Committed Effective Dose (CED) based on a drinking water ingestion rate of 2 L/day. The WHO reference level of 0.1 mSv per year for the CED was surpassed in a high number of water sources (62 (83%) or 41 (55%), disregarding radon), denoting the relevance of the radiological surveys detailing as much as possible the dissolved radionuclides present in potable waters, despite the analytical difficulties and costs involved.

An Assessment of Groundwater Contamination Risk with Radon Based on Clustering and Structural Models

There is currently some controversy in the scientific community regarding the efficiency of the water–rock interaction process in the contamination of radon in groundwater. In this study, some difficulties were found in the sampling phase. Many of the water collection points are used for human consumption. As such, some municipalities did not want to collaborate. When this natural contaminant is undetectable to the human sense and may cause pulmonary neoplasms in the long term, it is difficult to obtain collaboration from the municipalities concerned. To overcome this controversy, it is important to understand that geogenic, climatic, hydrological, and topographic features may contribute to the effective transfer of radon from rocks to groundwater. In brief, this new approach combines the radon transfer from the geological substrate to the groundwater circulation through hierarchic agglomerative clustering (HAC) and partial least squares-path modeling (PLS-PM) methods. The results show that some lithologies with higher radon production may not always contribute to noticeable groundwater contamination. In this group, the high-fracturing density confirms the recharge efficiency, and the physical-chemical properties of the hydraulic environment (electric conductivity) plays the main role of radon unavailability in the water intended for human consumption. Besides, the hydraulic turnover time of the springs can be considered an excellent radiological indicator in groundwater. In the absence of an anomalous radioactive source near the surface, it means that the high-turnover time of the springs leads to a low-radon concentration in the water. Besides linking high-risk areas with a short period required to free local flow discharges, this study exposes the virtues of a new perspective of a groundwater contamination risk modeling.

Origin of Flowback and Produced Waters from Sichuan Basin, China

Shale gas extraction through hydraulic fracturing and horizontal drilling is increasing in China, particularly in Sichuan Basin. Production of unconventional shale gas with minimal environmental effects requires adequate management of wastewater from flowback and produced water (FP water) that is coextracted with natural gas. Here we present, for the first time, inorganic chemistry and multiple isotope (oxygen, hydrogen, boron, strontium, radium) data for FP water from 13 shale gas wells from the Lower Silurian Longmaxi Formation in the Weiyuan gas field, as well as produced waters from 35 conventional gas wells from underlying (Sinian, Cambrian) and overlying (Permian, Triassic) formations in Sichuan Basin. The chemical and isotope data indicate that the formation waters in Sichuan Basin originated from relics of different stages of evaporated seawater modified by water-rock interactions. The FP water from shale gas wells derives from blending of injected hydraulic fracturing water and entrapped saline (Cl ∼ 50,000 mg/L) formation water. Variations in the chemistry, δ¹⁸O, δ¹¹B, and ⁸⁷Sr/⁸⁶Sr of FP water over time indicate that the mixing between the two sources varies with time, with a contribution of 75% (first 6 months) to 20% (>year) of the injected hydraulic fracturing water in the blend that compose the FP water. Mass-balance calculation suggests that the returned hydraulic fracturing water consisted of 28-49% of the volume of the injected hydraulic fracturing water, about a year after the initial hydraulic fracturing. We show differential mobilization of Na, B, Sr, and Li from the shale rocks during early stages of operation, which resulted in higher Na/Cl, B/Cl, Li/Cl, and ⁸⁷Sr/⁸⁶Sr and lower δ¹¹B of the FP water during early stages of FP water formation relative to the original saline formation water recorded in late stages FP water. This study provides a geochemical framework for characterization of formation waters from different geological strata, and thus the ability to distinguish between different sources of oil and gas wastewater in Sichuan Basin.

Preparation of MnO2 coated fibers for gamma spectrometric measurements - A comparison of four practical approaches

The analysis of natural radium-in-water activity concentrations is for two reasons of general interest: (1) radium in natural waters may pose a problem with regard to radiation protection and (2) radium isotopes in natural waters can be used as environmental tracers in hydrological studies. A state-of-the-art method for radium extraction from (generally large) water sample volumes is radium adsorption onto MnO₂ coated acrylic fibers. In our study we comparatively evaluated four methodical approaches for post-extraction preparation of the fiber to allow gamma spectrometric measurements. The methods included (1) straightforward measurement of the loose fiber, (2) compressing the fiber after mixing it with an adhesive, (3) combustion of the fiber and embedding the ash in candlewax, and (4) leaching of the fiber and embedding the resulting precipitate in candlewax. The aim of the study was to compare the advantages and disadvantages of the four preparation approaches with respect to their individual practicability. Even though the methodical fiber preparation approaches have been suggested in the literature before (as cited in this paper), results of their direct practical comparison have not been presented yet. Our study revealed that balancing practical sample preparation effort against data reproducibility suggests a measurement of the compressed fiber applying an adhesive to be the preferable approach.

A STUDY OF THE RADIOACTIVITY IN THE DUST STORM EVENT OF APRIL 2015 IN ARABIAN PENINSULA

Gulf countries are often affected by dust storms which have a significant influence on the environment and public health. The present work examines the radioactivity content in the intense dust storm occurred over Gulf countries on 1 April 2015. The results showed that the average value of 137Cs in dust samples (±SD) is 14.4 ± 1.6 Bq/kg, which is almost two orders of magnitude larger than those in soil samples. 7Be was detected with a considerable amount only in dust samples. The activity concentrations of the natural radionuclides (234,238U, 228,230,232Th, 226,228Ra and 40K) in dust samples were found to be approximately two to three times higher than the corresponding values in soil samples, which is attributed to the abundance of the finest particle size in the dust samples. Also, the activity ratios and the correlations between the detected radionuclides were investigated to assess the origin and activities associated with any variation of the radionuclides in the environment. Moreover, the total annual effective dose due to ingestion of dust was estimated to be 89.7 and 34.9 nSv for infants and adults, respectively, which is well below the world average internal dose of 290 μSv. The main contributor to the annual effective dose was 228Ra, which contributes ~69.6 and 43.3% for infants and adults, respectively, followed by: 226Ra » 232,230,228Th > 234,238U > 40k, 137Cs » 7Be.

Geological and hydrogeochemical controls on radium isotopes in groundwater of the Sinai Peninsula, Egypt

Radium isotopes (²²⁶Ra and ²²⁸Ra) were analyzed in 18 groundwater samples from the Nubian Sandstone Aquifer System (NSAS) and the shallow alluvial aquifers overlying the basement complex of the Sinai Peninsula, Egypt. Groundwater samples from deep Nubian aquifer wells (total depths 747 to 1250m) have ²²⁶Ra and ²²⁸Ra activities ranging from 0.168 to 0.802 and 0.056 to 1.032Bq/L, respectively. The shallower Nubian aquifer wells (63 to 366m) have ²²⁶Ra and ²²⁸Ra activities ranging from 0.033 to 0.191 and 0.029 to 0.312Bq/L, respectively. The basement shallow alluvial aquifers have ²²⁶Ra and ²²⁸Ra activities ranging from 0.014 to 0.038 and 0.007 to 0.051Bq/L, respectively. Combined Ra activities in most wells were generally in excess of the US Environmental Protection Agency (EPA), the European Union (EU), and the World Health Organization (WHO) maximum contaminant levels (MCL) for drinking water. Radium in groundwater is produced mainly by decay of parent nuclides in the aquifer solids, and observed activities of dissolved Ra isotopes result from a combination of alpha-recoil, adsorption/desorption, co-precipitation/dissolution processes. The observed correlation between Ra activities and salinity indicates that adsorption/desorption processes may be the dominant factor controlling Ra mobility in Sinai groundwater. Radium activities in central and northern Sinai are generally higher than those in southern Sinai, consistent with a gradual increase in salinity and water-rock interaction with increasing groundwater age. Barite is approximately saturated in the groundwater and may limit maximum dissolved Ra concentration. The results of this study indicate that Sinai groundwater should be used with caution, possibly requiring Ra removal from water produced for domestic and agricultural consumption.

Temporal changes in radiological and chemical composition of Cambrian-Vendian groundwater in conditions of intensive water consumption

Intensive groundwater uptake is a process at the intersection of the anthroposphere, hydrosphere, and lithosphere. In this study, groundwater uptake on a peninsula where only one aquifer system - the Cambrian-Vendian (CmV) - is available for drinking water uptake is observed for a period of four years for relevant radionuclides and chemical parameters (Cl, Mn, Fe, δ¹⁸O). Intensive groundwater uptake from the CmV aquifer system may lead to water inflow either from the sea, through ancient buried valleys or from the under-laying crystalline basement rock which is rich in natural radionuclides. Changes in the geochemical conditions in the aquifer may in turn bring about desorption of Ra from sediment surface. Knowing the hydrogeological background of the wells helps to predict possible changes in water quality which in turn are important for sustainable groundwater management and optimization of water treatment processes. Changes in Cl and Ra concentrations are critical parameters to monitor for sustainable management of the CmV groundwater. Radionuclide activity concentrations in groundwater are often considered rather stable, minimum monitoring frequency of the total indicative dose from drinking water is set at once every ten years. The present study demonstrates that this is not sufficient for ensuring stable drinking water quality in case of aquifer systems as sensitive as the CmV aquifer system. Changes in Cl concentrations can be used as a tool to predict Ra activity concentrations and distribute the production between different wells opening to the same aquifer system.

Radon-222 and radium-226 occurrence in water: a review

A total of 2143 dissolved radon-222 and radium-226 activity concentrations measured together in water samples was compiled from the literature. To date, the use of such a large database is the first attempt to establish a relationship for the 226Ra–222Rn couple. Over the whole dataset, radon and radium concentrations range over more than nine and six orders of magnitude, respectively. Geometric means yield 9.82±0.73 Bq l−1 for radon and 54.6±2.7 mBq l−1 for radium. Only a few waters are in 226Ra–222Rn radioactive equilibrium, with most of them being far from equilibrium; the geometric mean of the radium concentration in water/radon concentration in water (CRa/CRn) ratio is estimated to be 0.0056±0.0004. Significant differences in radon and radium concentrations are observed between groundwaters and surface waters, on the one hand, and between hot springs and cold springs, on the other. Within water types, typical ranges of radon and radium concentrations can be associated with subgroups of waters. While the radium concentration characterizes the geochemistry of the groundwater–rock interaction, the radon concentration, in most cases, is a signal of non-mobile radium embedded in the encasing rocks. Thus, the 226Ra–222Rn couple can be a useful tool for the characterization of water and for the identification of water source rocks, shedding light on the various water–rock interaction processes taking place in the environment.

Blending as the best compliance option for the management of radioactivity in drinking water supplied from the deep sandstone aquifer in Southern Jordan

This paper describes management options and interventions taken by the Government of Jordan to ensure that the quality of drinking water supplied to consumers via the Disi Water Conveyance Project (DWCP) meets Jordanian drinking water standards and WHO guidelines for drinking water quality in respect of their radiological composition. Results from an initial survey of radioactivity present in water abstracted from each of the 55 wells (which comprise the operational well field) indicated an average radiological dose of 0.8 milliSieverts per year (mSv/y) would be accrued by members of the population if consuming water directly from the well head. During full scale operation, the estimated accrued dose from the well field as a whole decreased to an average of 0.7 mSv/y which was still approximately 1.4 times the Jordanian reference radiological limit for drinking water (0.5 mSv/y). Following assessment of treatment options by relevant health and water authorities, blending prior to distribution into the consumer network was identified as the most practicable remedial option. Results from monthly sampling undertaken after inline blending support the adoption of this approach, and indicate a reduction in the committed effective dose to 0.4 mSv/y, which is compliant with Jordanian standards.

Activity ratios of (234)U/(238)U and (226)Ra/(228)Ra for transport mechanisms of elevated uranium in alluvial aquifers of groundwater in south-western (SW) Punjab, India

The concentrations of total dissolved uranium (U), its isotopic composition ((234)U, (235)U, (238)U) and two long lived Ra isotopes ((226)Ra and (228)Ra) in alluvial aquifers of groundwater were determined to investigate the groundwater flow pattern in the south-western (SW) Punjab, India. Particular attention was given to the spatial variability of activity ratios (ARs) of (234)U/(238)U and (226)Ra/(228)Ra to predict the possible sources and supply process of U into the water from the solid phase. The measured groundwater (234)U/(238)U ARs were ∼1 or >1 in the shallow zone (depth < 30 m) with high U concentration and <1 in the deeper zone (depth > 30 m) with relatively low U concentration. The simultaneous elevated U concentration and (234)U/(238)U ARs in waters were possibly due to differences in imprints of rock-water interactions under hydrologic conditions. However, (234)U/(238)U ARs < 1 clearly indicate the lack of recharge from surface water to groundwater leading to (234)U deficit in groundwater. This deficit might be also attributed to alpha recoil processes under strong dissolution. Overall, the decreasing pattern of (234)U/(238)U ARs observed from SE to SW or NW ward clearly indicates a groundwater flow paths from SE to SW/NW. Similarly, (226)Ra/(238)U ARs < 1 for all water samples reflect that the precursor (238)U is fairly mobile relative to (226)Ra. This might be due to unusually high amount of (238)U in groundwaters and subsequently the different geochemistry of the two isotopes. On the other hand, (226)Ra/(228)Ra ARs in groundwaters varied widely and observed about 50-300 times higher than (238)U/(232)Th ARs in granitic rocks or soils. Such elevation in ARs might be attributed to different dissolution properties of their parents during water-rock interactions or lattice damage during decay or local enrichments of uranium in the aquifers.

Dissolved uranium, radium and radon evolution in the Continental Intercalaire aquifer, Algeria and Tunisia

Natural, dissolved (238)U-series radionuclides (U, (226)Ra, (222)Rn) and activity ratios (A.R.s: (234)U/(238)U; (228)Ra/(226)Ra) in Continental Intercalaire (CI) groundwaters and limited samples from the overlying Complexe Terminal (CT) aquifers of Algeria and Tunisia are discussed alongside core measurements for U/Th (and K) in the contexts of radiological water quality, geochemical controls in the aquifer, and water residence times. A redox barrier is characterised downgradient in the Algerian CI for which a trend of increasing (234)U/(238)U A.R.s with decreasing U-contents due to recoil-dominated (234)U solution under reducing conditions allows residence time modelling ∼500 ka for the highest enhanced A.R. = 3.17. Geochemical modelling therefore identifies waters towards the centre of the Grand Erg Oriental basin as palaeowaters in line with reported (14)C and (36)Cl ages. A similar (234)U/(238)U trend is evidenced in a few of the Tunisian CI waters. The paleoage status of these waters is affirmed by both noble gas recharge temperatures and simple modelling of dissolved, radiogenic (4)He-contents both for sampled Algerian and Tunisian CI and CT waters. For the regions studied these waters therefore should be regarded as "fossil" waters and treated effectively as a non-renewable resource.

Radium isotopes ((226)Ra and (228)Ra) in Na-Cl type groundwaters from Tohoku District (Aomori, Akita and Yamagata Prefectures) in Japan

A total of 28 Na-Cl type groundwater samples were collected from Aomori, Akita and Yamagata Prefectures, in the Tohoku District of Japan, and their radium isotope ((226)Ra and (228)Ra) concentrations were measured along with their chemical components and stable isotope ratios (δ(2)H and δ(18)Os). The (226)Ra concentrations in groundwater samples varied widely, ranging from 8.8 to 1587 mBq kg(-1). These concentrations showed an increasing tendency with the increase of the total dissolved solid (TDS) contents. The (228)Ra/(226)Ra activity ratios were in the range from 0.3 to 4.2, with most data being around 0.5-2. These ratios were within those of (232)Th/(238)U found in granitic and related rocks and so on in Japan, indicating that Ra isotopes mainly ejected into the groundwater by the alpha-recoil process. The relationship between (226)Ra and other parameters suggested that Ra isotopes in groundwater samples in this study were mainly constrained by adsorption-desorption reactions depending on salinity with wide variation. Clear correlation between (226)Ra-Ca, (226)Ra-Sr, (226)Ra-Ba and (226)Ra-TDS observed in sulfate-free groundwater samples indicated that Ra isotopes of them were constrained by adsorption-desorption reactions depending on salinity under reducing condition. In contrast, relationship of (226)Ra-Ca, (226)Ra-Sr, (226)Ra-Ba and (226)Ra-TDS in sulfate-containing groundwater samples varied widely, and then, removal or enhanced mobility of Ra isotopes of them were observed.

Natural radioactivity in tap water and associated age-dependent dose and lifetime risk assessment in Amman, Jordan

With the aim of assessing potential public impact, preliminary investigations on tap waters collected from highly populated areas in Amman and Aqaba, Jordan were conducted by measuring gross alpha and beta activities as well as uranium and radium radionuclides. Gross activities deduced by liquid scintillation counting (LSC) were ranged in <50-250 ± 23 mBq l(-1) for alpha and <188-327 ± 29 mBq l(-1) for beta in Amman whereas higher concentrations were found in Aqaba. The results show that gross β activities are generally higher than the corresponding gross α activities and direct correlations between gross activities and total dissolved solids (TDS) exist. Moreover, the effect of TDS on gross analyses was studied and devoted to the optimization of LSC parameters. (234)U, (235)U and (238)U concentrations were determined by alpha spectrometry after separation from the matrix by extraction chromatography and electroplating. (226)Ra and (228)Ra concentrations were measured, respectively, using de-gassing and gas proportional counter techniques. Uranium and radium concentrations do not reach the WHO recommended levels and the radioisotopic activity ratios were discussed. The associated age-dependent dose from water ingestion in Amman was estimated. The total dose for adults had an average value of 0.15 mSv y(-1), which exceeds the WHO recommended limit of 0.1 mSv y(-1) but still below the Jordanian limit of 0.5 mSv y(-1). Although the Jordanian limit was exceeded for babies and infants, the lifetime risk assessment showed values as low as 10(-4). Thereby it is concluded that tap waters of Amman is radiologically safe and pose no significant hazard to the public. Finally, a comparison of the investigated waters with worldwide data was made.

Natural radionuclides in major aquifer systems of the Paraná sedimentary basin, Brazil

This paper describes the natural radioactivity of groundwater occurring in sedimentary (Bauru and Guarani) and fractured rock (Serra Geral) aquifer systems in the Paraná sedimentary basin, South America that is extensively used for drinking purposes, among others. The measurements of gross alpha and gross beta radioactivity as well the activity concentration of the natural dissolved radionuclides ⁴⁰K, ²³⁸U, ²³⁴U, ²²⁶Ra, ²²²Rn, ²¹⁰Po and ²¹⁰Pb were held in 80 tubular wells drilled in 21 municipalities located at São Paulo State and its border with Mato Grosso do Sul State in Brazil. Most of the gross alpha radioactivity data were below 1 mBq/L, whereas values exceeding the gross beta radioactivity detection limit of 30 mBq/L were found. The radioelement solubility in the studied systems varied according to the sequence radon>radium>other radionuclides and the higher porosity of sandstones relatively to basalts and diabases could justify the enhanced presence of dissolved radon in the porous aquifer. The implications of the data obtained in terms of standards established for defining the drinking water quality have also been discussed. The population-weighted average activity concentration for these radionuclides was compared to the guideline value of 0.1 mSv/yr for the total effective dose and discussed in terms of the choice of the dose conversion factors.

Chromosomal aberration analysis among underground water well workers in Saudi Arabia

In the absence of permanent rivers or bodies of water, half of the Saudi Arabia domestic water consumption is provided through desalination. The other half is derived from groundwater. Groundwater from the Disi aquifer is already used for drinking water in parts of Jordan and, more extensively, in Saudi Arabia, where it is known as the Saq aquifer. Some of the geological analyses of the host sandstone aquifer rocks show (228)Ra and (226)Ra. The usefulness of chromosomal aberrations analysis as a bioindicator for ionising radiation effect was tested in underground water well workers of Saudi Arabia in this industry producing technologically enhanced naturally occurring radioactive material. The incidence of chromosomal aberrations was evaluated using the metaphase analysis method in the lymphocytes of peripheral blood of 10 persons working in underground water well. The age range of the workers was 25-40 y and their duration of service ranged from 3-7 y. For comparison, blood samples were also collected from 10 subjects (controls) who belonged to same age and socioeconomic status. Subjects in the both groups were non-smokers and non-alcoholics. Results showed that the mean frequencies of dicentrics and acentrics in underground water well workers are significantly higher than those in controls. The higher frequency of chromosomal aberration in lymphocytes of underground water well workers compared with controls could be due to the accumulative effect of radiation. The results of this study demonstrated that occupational exposure to radiation leads to a significant induction of cytogenetic damage in peripheral lymphocytes of workers engaged in underground water well.

The politics of assessment: water and sanitation MDGs in the Middle East

The Middle East and North Africa (MENA) is generally considered to be making adequate progress towards meeting Target 10 of the Millennium Development Goals (MDGs), which calls for halving the proportion of the population with inadequate access to drinking water and sanitation. Progress towards achieving Target 10 is evaluated by the Joint Monitoring Programme (JMP), run by UNICEF and WHO. This article shows that the assessment methodologies employed by the JMP significantly overstate coverage rates in the drinking water and sanitation sectors, by overlooking and ‘not counting’ problems of access, affordability, quality of service and pollution. The authors show that states in MENA often fail to provide safe drinking water and adequate sanitation services, particularly in densely populated informal settlements, and that many centralized water and sanitation infrastructures contribute to water pollution and contamination. Despite the glaring gap between the MDG statistics and the evidence available from national and local reports, exclusionary political regimes in the region have had few incentives to adopt more accurate assessments and improve the quality of service. While international organizations have proposed some reforms, they too lack incentives to employ adequate measures that gauge access, quality and affordability of drinking water and sanitation services.

Radium isotopes in Estonian groundwater: measurements, analytical correlations, population dose and a proposal for a monitoring strategy

In some areas of Estonia, groundwater contains a significant number of natural radionuclides, especially radium isotopes, which may cause radiation protection concern depending on the geological structure of the aquifer. Indeed, the parametric value of 0.1 mSv y⁻¹ for the total indicative dose established by European Directive 98/83/EC, adopted as a limit value in Estonian national legislation, is often exceeded. A Twinning Project between Estonia and Italy was carried out within the framework of the Estonian Transition Facility Programme, sponsored by the European Union. Its aims were to assess the radiological situation of Estonian groundwater and related health consequences. The first step was a study of Estonian aqueducts and the population served by them, and a thorough analysis of the radiological database for drinking water, from which the relevant effective doses for the population were obtained. Particular attention was devoted to doses to children and infants. Correlations between the chemical parameters were investigated, in order to suggest the best possible analytical approach. Lastly, a monitoring strategy, i.e. sampling points and sampling frequencies, was proposed.