Research Article, J Nucl Ene Sci Power Generat Technol Vol: 9 Issue: 2

Determination of Natural Radionuclides and Radiation Exposure Levels in Underground Water in Riyadh city, Saudi Arabia

Afraa Alotaibi¹, Abdelrazig M Abdelbagi^2* and Ahmed H Azzam²

¹Department of Physics, College of Science, Princess Nourah Bint Abdulrahman University, Riyadh, Saudi Arabia

²Department of Physics, Science College, Shaqra University, Dawadmi, KSA

*Corresponding Author : Abdelrazig M Abdelbagi, Department of Physics
Science College, Shaqra University, Dawadmi, KSA,
E-mail: abdelbagi@su.edu.sa/razig2000@hotmail.com

Received: April 20, 2020; Accepted: May 05, 2020; Published: May 10, 2020

Citation: Alotaibi A, Abdelbagi AM, Azzam AH (2020) Determination of Natural Radionuclides and Radiation Exposure Levels in Underground Water in Riyadh City, Saudi Arabia. J Nucl Ene Sci Power Generat Technol 9:2. doi: 10.4172/2325-9809.1000193

Abstract

Keywords:

Radionuclide elements; Gamma spectrometer; Ground water; Uranium ²³⁸U; Radiation indices

Introduction

Recent progress in radiation detection in the environment for natural radionuclides has led to an increased interest search of radiation impact on plants, water, and soil for human health. The uranium, thorium, radium and potassium and radiation level assessment in the groundwater and other sources of water used is important knowledge for the environmental effect. The anthropogenic activities contributed to the environment and other source contamination such as the sediment and building materials that can affect plant and human living. The aquifer rocks in the mineral and storing underground water normally contain natural radioactive can released in the water via the process of erosion [1]. Mainly, the radionuclide in underground water has different types on the soil and rocks in variable concentration and other sources of water contaminated by isotope’s influences from the atmosphere. Natural radionuclide materials that are more abundant in the water are ²³⁸U, ²³²Th, and ²²⁶Ra released from inner soil layer and rocks, while ⁴⁰K potassium, is widespread natural radionuclide element [2]. The radiation emits from the isotope’s influence in the environment. Water contamination is strongly dependent on the types of rocks and soils which is caused by the process of leaching underground and geological matrix and earth's crust [3]. The radioactive contamination in the soil is backed by other sources of radioactivity such as the widespread use of fertilizers in phosphates for agricultural purposes that annihilate in food through water from the soil [4].

The environment is affected by the natural radioactive materials and humans, animals, and plants are exposed to radiation generated from different sources such as activity, medicine, and atmosphere [5]. The alpha, beta and gamma radiation have affected the human by radioisotopes elements in rocks, soil, and water that is exiting in various concentrations and can pose a potential health risk for human natural life [6].

The radioactive elements such as ²³⁸U, ²³²Th,²²⁶Ra and ⁴⁰K are affected by soil, rock, and water on the geology of the region and the topographical site of the land are important factors enhancing the background of natural radiation [7]. The radioactive isotopes presents in water results from different sources, such as either released from the soil, or rocks that originates in the earth’s crust in the province and the atmosphere, and windblown dust due to the geographical location [8]. The series of the ²³⁸U decays to ²³⁴Th and reaches ²⁰⁶Pb (lead) in several process and emits alpha, beta, and gamma radiation from ²³⁴Th, ²³⁴Pa (protactinium), ²³⁴U, ²³⁰Th, ²²⁶Ra (radium), ²²²Rn (radon), ²¹⁸Po (polonium), ²¹⁴Pb (lead), ²¹⁴Bi (bismuth), ²¹⁴Po (polonium), ²¹⁰Pb (lead), ²¹⁰Bi (bismuth), ²¹⁰Pb, and ²⁰⁶Pb that contributed to the soil, rocks, water resources and the atmosphere [9]. The daily human intake is about two litres as recommended by the World Health Organization (WHO, 1993). The uranium and thorium decay series are the common radioactive materials penetrated in the natural water cycle that contributed to the drinking water from all sources of radionuclide from the earth's crust and rocks (WHO, 2006). Consequently, water radioactive contamination requests frequently detection for radiation hazard indices that can give reference data for the decision-makers to control the possible future anthropomorphic impact in environmental radioactive contamination on human health risk [10-12]. Therefore, the radioisotopes measurement of groundwater for the daily use by the human is an important subject of interests to govern the radiation hazards relative to the dose rate concentration, radiation equivalent level, the internal hazard index (H_in) and the external hazard index (H_ex) [13-15]. The Radium activity equivalent detection is measured in relation to the following equation [16]:

Ra_eq = C_Ra+1.43C_Th+0.07C_K (1)

where C_Ra, C_Th, and C_K represents the concentration of Radium, Thorium, and Potassium in mBq/L respectively.

The relation of the internal hazard index is measured due to the following equation [17].

H_in =C_Ra/185+1.43C_Th/259+0.07C_K/4810 ≤ 1 (2)

The external hazard index is determined relative to the following equation.

H_ex=C_Ra/370+1.43C_Th/259+0.07C_K/4810 ≤ 1 (3)

The level of the absorbed dose rate is assessed from the relation:

D=0.446CU+0.662C_Th+0.048C_K

where C_U, C_Th, and C_K represents the Uranium, Thorium Potassium concentration in mBq/L and equivalent to factor in mSv/ year respectively.

Experimental Methods

The radioisotope measurement and radiation dose in underground water and drinking water investigate from the different areas around Riyadh and in the middle of the major producers of drinking water across the area. The gamma detector-HPGe (GMX40P-Ortec) uses to analysis the radioactivity of the isotope to investigate the level of ²³⁸U by the gamma detection of ²¹⁴Bi, ²³²Th via ²⁰⁸Tl and ²²⁸Ac gamma radiation, ²²⁶Ra analyses by the gamma radiation of ²¹⁴Pb, while the ⁴⁰K emits gamma radiation in underground water samples from different locations [17]. The gamma spectrometer efficiency calibrated using Europium ¹⁵⁵Eu, Antimony ¹²⁵Sb, Cesium ¹³⁷Cs and Cobalt ⁶⁰Co for the pure germanium detector [18]. Figure 1 provides the energy relation and detector efficiency due to the evaluation of the radiation. It also presents the results obtained from the measurement, analysis of radionuclides ²³⁸U, ²³²Th, ²²⁶Ra and ⁴⁰K concentration in ground water.

Figure 1: The efficiency calibration of the gamma spectrometer.

Several samples collected from the area due to the different supply of the cities from groundwater for drinking and other uses. However, the groundwater sample measurement of the radiation collected from various areas in Riyadh and the analysis was carried out using a germanium gamma detector. The sample element's concentration of ²³⁸U, ²³²Th, ²²⁶Ra, and ⁴⁰K have been analysed from deep wells and company's bottles, drinking water to investigate the levels of radioactive isotopes [19]. Mainly, the water is more used in this area due to the desert region and an increase in the temperature in the summer session.

Results and Discussion

Gamma spectrometer technique is the accurate detection equipment used for analysis, gamma radiations emitted from isotopes. Samples of groundwater analysed for radioactive elements that show various concentrations of elements in five locations in Riyadh city besides drinking water bottles from three companies (Figure 2). The results of this study shows that Uranium ²³⁸U activity calculated from the gamma line of ²¹⁴Bi and energy 1120 KeV and thorium ²³²Th by measuring the gamma energy of ²²⁸Ac of 911.204 KeV and 338.32 KeV and the activity of ²⁰⁸Tl gamma energy of 583 KeV. The two gammaray lines of ²¹⁴Pb of the energy 295.224 KeV and 351.932 KeV are used to measure ²²⁶Ra the activity, while the gamma line of ⁴⁰K is measured directly by the energy of 1460 KeV.

Figure 2: Average of elements radioactive activity levels (mBq/L) in water in different locations in Riyadh.

Statistical analysis determined the analysis of the Principal component that provides the difference in elemental variation of ²³⁸U, ²³²Th, ²²⁶Ra and ⁴⁰K in factor loadings and factor score coefficients, based on correlations (²³⁸U.sta) in the Riyadh area. Statistical factor score coefficients have analyzed the data based on the correlation on ²³⁸U indicates a positive value in the factors associated with ⁴⁰K in Table 1. The principal components analysis, factor loading in Tables 2 and 3 provides the ²³⁸U correlation and ⁴⁰K and with a minimum value of ²³²Th. However, the ²³⁸U and ⁴⁰K relation is exiting in all locations under investigation that possibly related to the same sources of contamination. Figures 3 and 4 shows the plane projection of ²³⁸U value ⁴⁰K that indicates the variable values of the two radionuclides are associated in all locations to one source of rocks and soil [20]. Figure 3 displays the factors values of ²³⁸U and the value of ⁴⁰K exists in a quarter of the diagram, which indicates concentration variation of the same origin of contamination of ground water. Accordingly, the factor values of ²²⁶Ra and ²³²Th have concentrations show the random values. Figure 4 shows the projection of the factor 1 and factor 3 confirmed that the ²³⁸U value and ⁴⁰K concentrations are related to the same source and ²²⁶Ra and ²³²Th indicates different factor values and concentrations. Table 1 illustrates the range of the radioactive element concentrations of the present work compared to the international lectures. Uranium levels in the water were found in the east of Riyadh and the lowest level in the centre of the city, while the bottles, drinking water products by the companies in minimum radiation average values compared to the international standard level [21].

Table 1: Presents the international data compare to the present work.

Table 2: Factor score coefficients, based on correlations (U238.sta).

Table 3: Factor loadings (Varimax normalized) (U238.sta).

Figure 3: The projection of the variable on the factor plane.

Figure 4: The projection of the variable on the factor plane.

Conclusion

The present study was designed to detect the radionuclide elements in ground water in Riyadh city in Saudi Arabia. The gamma spectrometer investigation has shown that analysis of groundwater sample concentration of ²³⁸U, ²³²Th, ²²⁶Ra and ⁴⁰K in various locations in Riyadh and bottle drinking water from three companies. The results of this study show the groundwater sample concentration of ²³⁸U in the range 2.86 ± 1.9 mBq/L to 14.25 ± 3.31 mBq/L, ²³²Th vary from 3.358 ± 0.96 mBq/L to 6.344 ± 0.96 mBq/L, ²²⁶Ra in the range from 1.33 ± 0.199 mBq/L to 3.65 ± 0.6 mBq/L and ⁴⁰K 32.5 ± 4.06 mBq/L to 73.639 ± 8.126 mBq/L that show optimal values. The contribution of this data analysis has supported the results of drinking bottles filter water from the companies revealed the average concentration of ²³⁸U 7.125 ± 1.9 mBq/L, ²³²Th: 3.202 ± 0.96 mBq/L, ²²⁶Ra: 3.539 ± 0.66 mBq/L and ⁴⁰K: 39.274 ± 4.74 mBq/L that indicates best values. The findings from this work compare the two results that reveal the least value of radioactive elements of filter bottle water.

The investigation of radium equivalent (R_eq) calculated from the concentration that the activity in the range of 10.021 mBq/L to 20.123 mBq/L. This study set out to find the internal hazard index (H_in) of 0.0495 and the external hazard index (H_ex) indicted 0.0435. In addition to the level of absorbed dose rates is varied from 0.29 mSv/ year to 1.16 mSv/year as compared to the corresponding international literature values show lower values (ICRP). The results of this research confirmed the average values of radiation exposure in ground water and bottle water in a lower limit than recommended international data.

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