238U and 232Th isotopes in groundwater of Jordan: Geological influence, water chemistry, and health impact
Introduction
Natural environmental radioactivity mainly arises from the occurrence of the natural radionuclides of 232Th, 238U, and their decay products, in addition to 40K (UNSCEAR, 2000). As groundwater moves through fractures in the bedrock, natural radionuclides can get into groundwater as a water-rock interaction (Abdurabu et al., 2016b; Kitto et al., 2005; Shabana et al., 2013). Groundwater has acted as a medium of transporting and enhancing uranium in an environment away from its origin (Aliyu et al., 2015). Nearly all the radionuclides occurring in drinking water supplies are naturally occurring (Lopes et al., 2017). The specific elements of concern are 238U and 232Th, which decay mainly by alpha-particle emission to nuclides that themselves are radioactive (Cothern and Reberts, 1990). Natural 232Th has one single isotope that is 100% 232Th and 238U comprises 99.25% of natural uranium (Gilmore, 2008). 238U is widely dispersed in groundwater (Dinh Chau et al., 2011). Human exposure to uranium has long been considered to pose a radiological and chemical hazard (Milvy and Cothern, 1990).
Uranium has many oxidation states (+4, +5 and +6) in nature. In groundwater, uranium is generally found in the +6-oxidation state where the oxidizing environments are prevailed (Kraemer and Genereux, 1998). Uranium (+6) is most soluble in oxidizing water. Naturally occurring uranium components exist in groundwater through the dissolution of the uranium-bearing minerals such as uraninite (UO2) (Langmuir, 1978). Insoluble uraninite is readily oxidized through water-rock interactions to soluble uranyl ions (UO2+2) (Banks et al., 1995). The uranyl ions are the most soluble form of uranium. In the presence of phosphates or carbonates highly soluble complexes are formed mainly in the pH range between 6 and 8. These are typical pH values for a large majority of groundwater systems (Wanty and Schoen, 1992). Under reducing conditions, uranium (+4) is a dominant form. In aquatic environments, under reducing conditions uranium (+4) forms insoluble precipitates strongly adsorbed on suspended particles or mineral surfaces (Hem, 1985). One of the most insoluble radioactive elements in water is 232Th, it has only one oxidation state in nature (+4). 232Th forms insoluble hydroxides under most natural conditions (Dinh Chau et al., 2011).
In the last decades, studies of the natural radioactivity in groundwater and the hosting rock type had received attention worldwide (Abdurabu et al., 2016b; Ammar et al., 2010; Charalambous et al., 2013; Chkir et al., 2009; Cowart, 1987; Da Silva and Bonotto, 2015; Dinh Chau et al., 2011; El-Sharkawy, 2018; Gilkeson et al., 1983; Kanellopoulos et al., 2018; M. Isam Salih et al., 2002; Malov, 2016; Michel, 1990; Porcelli and Swarzenski, 2003; Post et al., 2017; Smith et al., 1996; Szabo and Zapecza, 1991; Wu et al., 2018). Most of these studies were focused on investigating the activity concentration levels of natural radionuclides 238U and 232Th and correlated to rocks type to evaluate the factors that control their presence in groundwater. The concentration of 238U series radionuclides in groundwater may vary over several orders of magnitude depending on hosting rocks and physicochemical parameters that control the release (Dinh Chau et al., 2011; M. Isam Salih et al., 2002). 238U concentration in water wells is directly controlled by the lithology of the aquifer solids adjacent to the wells (Cothern and Reberts, 1990). Consequently, the 238U activity concentration in groundwater should reflect some extent the type of rocks that host the given aquifer system, and this will lead in using aquifer type to predict the occurrence of 238U in groundwater.
Chemistry of groundwater plays an important role in determining the quality and suitability of water for drinking and other domestic purposes (Sadashivaiah et al., 2008; Subramani et al., 2010). Interaction of groundwater with aquifer minerals through which it flows greatly controls the groundwater chemistry (Subramani et al., 2010). Chemical characters of water may also affect the source and mobility of natural radionuclides in groundwater (Abdurabu et al., 2016b; Sharma et al., 2019; Srilatha et al., 2014). Several studies in recent years have focused on the chemical characters of water to evaluate the chemical factors that may affect the source and mobility of natural radionuclides in groundwater (Abdurabu et al., 2016b; Bajwa et al., 2017; Jobbágy et al., 2009; Mittal et al., 2017; Ramadan et al., 2014; Singh et al., 2003; Srilatha et al., 2014). The studies revealed that there is a strong to the weak link between activity concentrations of natural radionuclides 238U and 232Th and the chemical characters. Understanding 238U and 232Th mobility are vital to minimizing its concentrations in potential drinking water sources (Wu et al., 2018).
Groundwater globally provides 25–40% of the world's drinking water (Selvi et al., 2016). In Jordan, people rely almost 100% on groundwater for drinking, irrigation and other domestic purposes. In recent years, there has developed an increasing national concern for an assessment of the natural radioactivity in drinking water. A few studies have been conducted to evaluate radioactivity levels of drinking water. However, based on existing literature, extensive field measurement of natural radionuclides related to geological formations and to evaluate the effective dose to the public and related health impact of natural radionuclides in groundwater has yet to be conducted.
Therefore, the current study, the first of its kind in Jordan forms part of the pioneer study, represents a comprehensive investigation on 238U and 232Th levels and aims to measure the 238U and 232Th activity concentrations in the groundwater sources to investigate the influence of geological formations as well as the chemical characters of groundwater on 238U and 232Th activity concentrations. Also, this study aims to estimate the annual effective dose and assessment of the lifetime risk related to Jordan groundwater. It can contribute to establishing national recommendations to limit 238U and 232Th activity concentrations as well as chemical characters in drinking groundwater. The results may also be used as baseline data for monitoring possible radioactivity pollution in anticipation of the possibility that Jordan will have a nuclear power plant in the future (Xoubi, 2015).
Section snippets
Study area
Jordan is classified as a Mediterranean country with a total area of about 90,000 km2, and a population of around 10 million people (Jordan Department of statistics, 2017). It lies between latitudes (29° 11' - 33° 22') N and between longitudes (34° 59' - 39° 18') E. Jordan is located at the western edge of the Arabian Plate, and stands out from the remaining part of the Arabian Peninsula by its abundance in radioactive elements, mainly uranium, in a way so far not found elsewhere on the Arabian
Descriptive statistics of 238 U and 232 Th activity concentrations in groundwater
The basic descriptive statistics such as minimum, maximum, mean, standard deviation, Kurtosis, and skewness are presented in Table 1. The activity concentration of 238U ranged from MDA to 312 ± 47 mBq L−1 with a mean value of 33 ± 5 mBq L−1. The obtained values are lower than the recommended level of 360 mBq L−1 (USEPA, 2018; WHO, 2011). The WHO and USEPA guidelines for drinking-water quality recognized 238U as a potential chemical risk.
The frequency distribution of 238U activity concentration
Conclusion
Natural radioactivity of 238U and 232Th in groundwater from the Cambrian-Ordovician, upper Cretaceous, Tertiary, Quaternary and lower Cretaceous geological formations in Jordan was investigated. 238U activity concentrations were found to be in the range of MDA to 312 ± 47 mBq L−1. The activity concentration of 232Th was found to be in the range of MDA to 0.177 ± 0.027 mBq L−1. The highest value of 238U and 232Th activity concentrations were found for upper Cretaceous geological formation
CRediT authorship contribution statement
Ahmad Hussein Alomari: Conceptualization, Methodology, Software, Writing - original draft, Formal analysis, Investigation, Validation, Writing - review & editing. Muneer Aziz Saleh: Conceptualization, Methodology, Software, Formal analysis, Supervision, Writing - review & editing. Suhairul Hashim: Conceptualization, Supervision, Writing - review & editing. Amal Alsayaheen: Methodology, Formal analysis, Investigation, Validation. Ismail Abdeldin: Methodology, Investigation, Validation. Ahmad
Declaration of competing interest
The authors declare that they have no conflict of interest.
Acknowledgement
The authors would like to thank the Water Authority of Jordan. All the measurements were conducted at isotopes and chemical analysis laboratories. The authors would like to thank Mr. Refaat bani Khalaf from the Water Authority of Jordan for his help in preparing the hydrogeological and rainfall level maps of Jordan. The authors would like to thank the ministry of higher education Malaysia (MOHE) and Universiti Teknologi Malaysia (UTM) for support and funding under UTM Research university Grant;
References (85)
- et al.
Disequilibrium of uranium isotopes in some Syrian groundwater
Appl. Radiat. Isot.
(2001) - et al.
The activity concentrations of 222Rn and corresponding health risk in groundwater samples from basement and sandstone aquifer; the correlation to physicochemical parameters
Radiat. Phys. Chem.
(2016) - et al.
Radon in the groundwater in the Amman-Zarqa Basin and related environments in Jordan
Groundw. Sustain. Dev.
(2018) - et al.
Uranium and other heavy toxic elements distribution in the drinking water samples of SW-Punjab, India
J. Radiat. Res. Appl. Sci.
(2017) Estimating the concentration of uranium in some environmental samples in Kuwait after the 1991 Gulf War
Appl. Radiat. Isot.
(1995)- et al.
Uranium levels in Cypriot groundwater samples determined by ICP-MS and α-spectroscopy
J. Environ. Radioact.
(2013) - et al.
Uranium isotopes in groundwater from the continental intercalaire aquifer in Algerian Tunisian Sahara (Northern Africa)
J. Environ. Radioact.
(2009) - et al.
Uranium isotopes in groundwater occurring at Amazonas State, Brazil
Appl. Radiat. Isot.
(2015) - et al.
Natural radioactivity of ground and hot spring water in some areas in Yemen
Desalination
(2013) 234U/238U activity ratios in groundwaters from two aquifers in Saudi Arabia, and correlation with water chemistry
J. Radiat. Res. Appl. Sci.
(2018)
Uranium determination in water samples with elevated salinity from Southern Poland by micro coprecipitation using alpha spectrometry
Microchem. J.
Health risk assessment for uranium in Korean groundwater
J. Environ. Radioact.
Radionuclide and chemical concentrations in mineral waters at Saratoga Springs, New York
J. Environ. Radioact.
Applications of Uranium-And Thorium-Series Radionuclides in Catchment Hydrology Studies Isotope tracers in Catchment Hydrology
Uranium solution-mineral equilibria at low temperatures with applications to sedimentary ore deposits
Geochem. Cosmochim. Acta
Estimation of uranium migration parameters in sandstone aquifers
J. Environ. Radioact.
High levels of uranium in groundwater of Ulaanbaatar, Mongolia
Sci. Total Environ.
Natural radioactivity of drinking water in the southern and middle parts of Syria
Environ. Int.
Investigating groundwater processes using U-and Th-series nuclides
Radioact. Environ.
High uranium concentrations in groundwater in Burundi
Procedia Earth Planet. Sci.
Assessments of radioactivity concentration of natural radionuclides and radiological hazard indices in sediment samples from the East coast of Tamilnadu, India with statistical approach
Mar. Pollut. Bull.
Gross alpha radioactivity of drinking water in Venezuela
J. Environ. Radioact.
Prediction of terrestrial gamma dose rate based on geological formations and soil types in the Johor State, Malaysia
J. Environ. Radioact.
Uranium distribution in groundwater and assessment of age dependent radiation dose in Amritsar, Gurdaspur and Pathankot districts of Punjab, India
Chemosphere
Distribution and potential health risk of groundwater uranium in Korea
Chemosphere
The transport of U-and Th-series nuclides in a sandy unconfined aquifer
Geochem. Cosmochim. Acta
Occurrence, behavior and distribution of high levels of uranium in shallow groundwater at Datong basin, northern China
Sci. Total Environ.
Variations of uranium concentrations in a multi-aquifer system under the impact of surface water-groundwater interaction
J. Contam. Hydrol.
Occurrence of 222Rn, 226Ra, 228Ra and U in groundwater in Fujian province, China
J. Environ. Radioact.
Occurrence of natural radioactivity and corresponding health risk in groundwater with an elevated radiation background in Juban District, Yemen
Environ. Earth Sci.
Natural radioactivity of ground and drinking water in some areas of upper Egypt
Turk. J. Eng. Environ. Sci.
Determination of radium, uranium and 222Rn in groundwater samples from different regions in Saudi Arabia
Indian J. Appl. Res.
Over exploitation of groundwater in the Centre of Amman Zarqa Basin—Jordan: evaluation of well data and GRACE satellite observations
Resources
Health and ecological hazards due to natural radioactivity in soil from mining areas of Nasarawa State, Nigeria
Isot. Environ. Health Stud.
Activity concentrations of 226 Ra, 228 Ra, 222 Rn and their health impact in the groundwater of Jordan
J. Radioanal. Nucl. Chem.
Uranium isotopes in groundwater from the “Jeffara coastal aquifer”(southeastern Tunisia)
J. Environ. Radioact.
Standard Methods for the Examination of Water and Wastewater
Hydrochemical evaluation of groundwater in Azraq Basin, Jordan using environmental isotopes and GIS techniques
Radioelement (U, Th, Rn) concentrations in Norwegian bedrock groundwaters
Environ. Geol.
Geology of Jordan. (Authority, N. R., Trans. Vol. 7) Berlin, Germany: Natural Resources Authority and German Geological Mission in Jordan
Occurrence of natural radioactivity in public water supplies in Germany: 238U, 234U, 235U, 228Ra, 226Ra, 222Rn, 210Pb, 210Po and gross α activity concentrations
Radiat. Prot. Dosim.
Radon, Radium, and Uranium in Drinking Water
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2022, Journal of Contaminant HydrologyCitation Excerpt :Many studies were measuring the 234U and 238U concentrations in groundwater in the world. Most of the results showed that the activity concentrations of U isotopes in groundwater were higher than those in other water types such as rainwater, surface water, seawater, tap water, etc. (Byong and Chang, 2019; Ahmad et al., 2020; Ahmed, 2018; Sharma et al., 2019). In groundwater in Saudi Arabia, the average activity concentrations of 234U and 238U were 180.9 and 119.9 mBq l−1, respectively (El-Sharkawy, 2018).
INITIAL RESULTS OF THE INTEGRATED ISOTOPE-HYDROGEOCHEMICAL STUDIES OF THE NOVOBIBEEVO OCCURRENCE OF RADON-RICH WATERS
2022, Bulletin of the Tomsk Polytechnic University, Geo Assets Engineering