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ORIGINAL ARTICLE
Year : 2013  |  Volume : 36  |  Issue : 3  |  Page : 115-121  

Natural radioactivity of ground water in some areas in Aden governorate South of Yemen Region


1 Departments of Physics, Faculty of Science, Qena 83523, South Valley University, Egypt
2 Faculty of Science Assiut University, Egypt
3 Faculty of Science for Girls, King, Abdel Aziz University, KSA
4 Faculty of Science and Education Sabir, Aden University, Yemen

Date of Web Publication28-Jul-2014

Correspondence Address:
F A Ahmed
Department of Physics, Faculty of Science Assiut University, Egypt

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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0972-0464.137476

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  Abstract 

This paper presents the concentrations of naturally occurring radionuclides 226 Ra, 232 Th and 40 K measured in groundwater samples collected from Aden governorate South of Yemen Region using gamma spectroscopy. A total of 37 groundwater samples were collected from four areas in Aden governorate. The average activity concentrations for groundwater from Beer Ahmed area were 1.60 Bq/L, 1.25 Bq/L and 16.90 Bq/L for 226 Ra, 232 Th and 40 K respectively and from Beer Fadle area were 1.45 Bq/L, 0.87 Bq/L and 19.8 Bq/L for 226 Ra, 232 Th and 40 K, respectively, while that for groundwater samples from Daar-saad area were 1.27 Bq/L, 1.18 Bq/L and 18.28 Bq/L for 226 Ra, 232 Th and 40 K, respectively and Al-Masabian area were 1.55 Bq/L, 1.421 Bq/L and 19.03 Bq/L for 226 Ra, 232 Th and 40 K respectively. Furthermore, annual effective dose equivalent of ingestion of these waters was calculated. The results showed that the annual dose obtained in the present study was much higher than the recommended value (0.1 mSv/year) as reported by WHO. The results were compared with those for drinking water.

Keywords: Aden governorate, annual effective dose, groundwater, radioactivity, South Yemen


How to cite this article:
Harb S, El-Kamel A H, Zahran A M, Abbady A A, Ahmed F A. Natural radioactivity of ground water in some areas in Aden governorate South of Yemen Region. Radiat Prot Environ 2013;36:115-21

How to cite this URL:
Harb S, El-Kamel A H, Zahran A M, Abbady A A, Ahmed F A. Natural radioactivity of ground water in some areas in Aden governorate South of Yemen Region. Radiat Prot Environ [serial online] 2013 [cited 2019 Jul 17];36:115-21. Available from: http://www.rpe.org.in/text.asp?2013/36/3/115/137476


  Introduction Top


Determination of naturally occurring radionuclides in groundwater is useful as a direct input to environmental and public health studies. [1] Considering the high radiotoxicity of 226 Ra and 228 Ra, their presence in water and the associated health risks require particular attention. The presence of 226 Ra in water depends on the water's origin. For well or mineral water, it depends on the content of 238 U in the solids of the aquifer where the water is stored. The geochemical characteristics of the aquifer determine the dissolution of radium from the solids into the water. 226 Ra is known to be removed by the treatment of water in purification plants. [2] Radium has two natural isotopes, which are of concern in public water supplies: 226 Ra, an alpha emitter with a half-life of 1622 years generated in 238 U decay series, and 228 Ra a shorter-lived beta-emitter (half-life 5.7 years), which is generated in 232 Th decay series. The distributions of 226 Ra and 228 Ra in water are a function of the Th and U contents in the aquifer, the geochemical properties of the aquifer solids, and the half-lives of each isotope (ICRP, 1993). The groundwater in Aden governorate is used for drinking. The main water sources in the Aden governorate south Yemen are wells. Since the base line concentration of natural radioactivity in groundwater in Aden governorate south Yemen is not known, the levels of 226 Ra, 232 Th and 40 K were investigated in representative drinking water samples to assess the radiological risk resulting from the consumption of this water.


  Materials and methods Top


Description of study areas

The Republic of Yemen is located in the southern sector of the Arabian Peninsula [Figure 1]. The study Aden governorate area (~750 km 2 ) is located some (400 km) south of Sana'a and located in Lat. 12°54'.211N and long 12°53'.294E Aden governorate area consists of tertiary volcano that is comprised of basalt flows, ignimbrites and tuffaceous rocks. [3],[4],[5]
Figure 1: Illustrates the areas under study

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Sample collection and preparation techniques

Because there is no running water in this study area, 37 groundwater samples were collected from the study area that used as drinking water. Measuring pH values as well as conductivity of for the water samples were measured in the laboratory. Standard polyethylene Marinelli beakers (1 L) were used as a sampling and measuring container. Before use, the containers were washed with dilute hydrochloric acid and rinsed with distilled water. Each beaker was filled up to brim and an air-tight cap was put on the beaker inserted pressed on so that the air was completely removed from it. The collected water samples were left for an overnight period in polyethylene containers to allow settling of any suspended solid materials and for each samples a clear supernatant liquid was separated by decantation from each sample. The clear solution was acidified by adding 0.5 ml of conc. HNO 3 /L, to prevent any loss of radium isotopes on around the container walls, and to avoid growth of microorganisms. [6] The water samples were then homogenized well by shaking. The final acidity of water samples reaches pH of the samples was maintained at 2. The samples were stored for over 30 days to reach secular equilibrium before radiometric analysis.

Gamma-ray detection system

Each sample was measured with a gamma-ray spectrometer consisting of a NaI (Tl) setup and multi-channel analyzer 8192 channel, with the following specifications: Resolution (FWHM) at 1.33MeV 60 Co is 60keV-relative efficiency at 1.33MeV 60 Co is 7.5%. The detector is shielded in a chamber of two layers starting with stainless steel (10 mm thick) and leads (30 mm thick). This shield serves to reduce different background radioactivity. The system was calibrated for energy and efficiency. The spectrometer was calibrated for efficiency and energy using multi-nuclide standard solution (QCYB41) DKD (Germany). The standard source peaked in the same geometry as that used for measured samples. For calibration, the standard source is placed above the detector, and the measurement started. The dependence of the efficiency on the radiation energy was determined at 0.0 mm sample detector distance. The absolute efficiency of the NaI (Tl) detector was determined using the standard solution QCYB41DKD (Germany). The detector efficiency decreases continuously with energy. The dependence of the efficiency on the volume of the sample was determined by a Marinelli beaker (1 L). It can be noticed that the detector efficiency decreases with the volume of the sample in the energy range of interest. Finally, each sample was placed in a Marinelli beaker of the same size as that of the multi-element standard. Then each sample spectrum was acquired for 24 h. The spectra were either evaluated with the computer software program Genie 2000 V2.0 (S501C) or manually with the use of a spread sheet (Microsoft Excel) to calculate the natural radioactivity. Furthermore, the measurement uncertainty is reported. 226 Ra activity of the samples was determined via its daughters ( 214 Pb and 214 Bi) through the intensity of the 295.22, 351.93keV, for 214 Pb gamma-lines and 609.31, 1120, 1764.49keV, for 214 Bi gamma-lines. 232 Th activity of the sample was determined from the daughters ( 228 Ac), ( 212 Pb) and ( 208 Tl) through the intensity of 209.25, 338.32, 911.2keV gamma-lines for ( 228 Ac), ( 212 Pb) emissions at 238.63keV and ( 208 Tl) emissions at 583.19, 2614keV gamma-lines. 40 K activity determined from the 1460.7keV gamma-lines.

Dose calculation

In order to evaluate potential health hazards, doses due to ingestion of these waters were estimated to assess the contribution of these radionuclides to public exposure from natural radioactivity. The following equation was used to calculate the doses. [7],[8],[17]

DR W = A W × IR W × ID F (1)

Where DR w the effective dose (mSv/year), A w activity (Bq/L), IR w intake of water for person in 1 year and ID F the effective dose conversion factor (mSv/Bq). Doses were estimated by considering a consumption rate (150, 350 and 500 L/year) for infants, children and adults, respectively, and the conversion factors (2.8 × 10−7 , 2.3 × 10−7 and 5 × 10−9 SvB/q) for 226 Ra, 232 Th and 40 K, respectively, for adults (8×10−7 , 2.9×10−7 and 5×10−9 SvBq−1 ) for children and (9.6×10−7 , 4.5×10−7 and 5×10−9 SvBq−1 ) for infants reported by ICRP, International Atomic Energy Agency (IAEA) and WHO. [9],[10],[11]


  Results and discussion Top


The activity concentrations of 226 Ra, 232 Th and 40 K in the groundwater that is used as drinking water in Beer Ahmed, Beer Fadle, Daar-Saad and Al-Masabian areas in Aden governorate South of Yemen Region together with location, pH and conductivity are presented in [Table 1]. As seen, water samples from Beer Ahmed area have pH ranging from 7.79 to 8.31, while that from Beer Fadle area have pH ranging from 8.25 to 8.53. For Daar-Saad and Al-Masabian area have pH ranging from 8.13 to 8.55 and 8.24-8.45. The concentrations of 226 Ra, 232 Th and 40 K varied from 0.33 to 2.67Bq/L, 0.15-2.72 Bq/L and 7.87-19.48Bq/L and from 0.46 to 2.44 Bq/L, 0.53-1.22 Bq/L and 18.29-21.32 Bq/L respectively, at Beer Ahmed and Beer Fadle area, For Daar-Saad and Al-Masabian area the concentrations of 226 Ra, 232 Th and 40 K ranged from 0.22 to 2.45 Bq/L, 0.18-2.31Bq/L and 13.07-26.02Bq/L and from 1.07 to 2.29Bq/L, 0.57-3.06 Bq/L and 15.55 23.97 Bq/L respectively. The values of 226 Ra in groundwater samples from Beer Ahmed, Beer Fadle, Daar-Saad and Al-Masabian areas in Aden governorate are much higher than the maximum contaminant levels of 1.85 mBq/L proposed in the USA (US [7] ) for drinking water in the other hand the concentrations of radionuclide's 226 Ra, 232 Th and 40 K in water samples from Beer Ahmed, Beer Fadle, Daar-Saad and Al-Masabian areas in Aden governorate were found in the narrow range, this probably is due to the fact that the sites studied cover an area with similar aquifer lithologies and consequently no large differences in radionuclide solubilities and mobilities. [12] The abundance of 40 K activity observed in the water samples from Beer Ahmed, Beer Fadle, Daar-Saad and Al-Masabian areas in Aden governorate area may be due to agricultural activities going on in the area that involve the use of potassium fertilizers which may have been transported to the groundwater, given that 40 K is a highly soluble element it should be noted that in all the sites studied, concentrations of 226 Ra is higher than that of 232 Th and this reflects the fact that radium is more soluble in groundwater than its thorium and uranium precursors, and its solubility is enhanced by: (1) The common-ion effect (when dissolved solids are high), (2) an oxygen-poor environment, and (3) the fragmentation of uranium-bearing minerals. [13]
Table 1: Associated characteristics and activity concentration (Bq/L) of natural radionuclides in groundwater at various sampling sites in Aden governorate South of Yemen Region


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Comparison of results with similar in other countries

[Table 2] summarizes the values of 226 Ra, 232 Th and 40 K concentrations in other countries and those from the present work. As can be seen from [Table 2], 226 Ra values from the present work are higher than that reported by [14] for ground water at Egypt (Qena) and Egypt (Safaga), [15] Sudan for ground water, [16] Syria for spring water, [19] China for ground water and [18] Italy for drinking water and lower than the values reported by. [19],[20],[1],[13],[22],[21],[23],[24] Also 232 Th activity concentrations obtained in this study are matches than that reported by [22] for hot spring water at Afra, Barbeita and Al-Amir sites in Jordan and is higher than that reported by [19] for groundwater in Egypt and [13] for groundwater in Sudan and lower than that reported by [25] for lake water in Nigeria. On the other hand, 40 K values in the present study match with those values reported by [1] for spring water Yemen (Dempt) and lower than value reported by [19] for lake water in Nigeria.
Table 2: The activity concentration in Bq/L of water samples in the present investigation in comparison with other countries


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Radiation dose estimation

[Table 3] shows the calculated effective dose for different age groups infants, children and adults, considering only the ingestion from 226 Ra and 232 Th. The reason for not considering 40 K in these calculations is due to the absorption of the essential element potassium is under homeostatic control and takes place mainly from ingested food. Thus, the contribution to dose from the ingestion of 40 K in water, with its relatively low dose conversion factor (5 × 10−9 Sv/Bq), will be much less than that of many other radionuclides. It should be noted that doses were ranged from 0.064-0.66 mSv year−1 with average value of 0.37 mSv year−1 for water from Beer Ahmed area, from 0.20-0.40 mSv year−1 with average value of 0.30 mSv year−1 for water from Beer Fadle area, from 0.058-0.61 mSv year−1 with average value of 0.31 mSv year−1 for water from Daar-Saad and from 0.23-0.60 mSv year−1 area with average value of 0.38 for adults. From [Table 3], it can be observed that, doses received by children are higher than that received by infants and adults and the main dose contribution of these waters is caused by 226 Ra in the bones. According to the recommended reference level of 0.26, 0.2 and 0.1 mSv/year for effective dose for infants, children and adults, respectively, published by WHO, IAEA and United Nations Scientific Committee on the Effects of Atomic Radiation, [26],[27],[28] from 1 year consumption of drinking water, the doses obtained in our study are much higher than the recommended reference level and consequently, it can be recommended that, the investigated waters are not acceptable for life-long human consumption and a reduction in consumption or radionuclide concentration is necessary.
Table 3: Estimates of annual effective doses mSv year−1 due to ingestion of 226Ra and 232Th for different age groups


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  Conclusion Top


The natural radioactivity levels of 226 Ra, 232 Thand 40 K have been measured in water samples in Beer Ahmed, Beer Fadle, Daar-Saad and Al-Masabian areas in Aden governorate using gamma ray spectroscopy. The activity profiles of the radionuclides have clearly showed high activity concentrations across the study areas. The high activity concentrations for 226 Ra and 232 Th measured in water samples explain the relationship between the groundwater and bedrocks in these areas, for this reason we suggest that the investigated groundwater may not be acceptable as drinking water.


  Acknowledgments Top


The authors are thankful to the residents of the study area for their cooperation during the sample collection and the group of work in Ashaab region in Aden city for their help and logistical support during the collection of the samples.

 
  References Top

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    Figures

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    Tables

  [Table 1], [Table 2], [Table 3]



 

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