226Ra, 232Th and 40K contents in water samples in part of central deserts in Iran and their potential radiological risk to human population
© Ehsanpour et al.; licensee BioMed Central Ltd. 2014
Received: 15 October 2013
Accepted: 14 April 2014
Published: 1 May 2014
The radiological quality of 226Ra, 232Th and 40K in some samples of water resources collected in Anarak-Khour a desertic area, Iran has been measured by direct gamma ray spectroscopy using high purity germanium detector in this paper.
The concentration ranged from ≤0.5 to 9701 mBq/L for 226Ra; ≤0.2 to 28215 mBq/L for 232Th and < MDA to 10332 mBq/L for 40K. The radium equivalent activity was well below the defined limit of 370Bq/L. The calculated external hazard indices were found to be less than 1 which shows a low dose.
These results can be contributed to the database of this area because it may be used as disposal sites of nuclear waste in future.
The presence of naturally occurring radionuclides as well as some elements provides important information about the quality of water resources especially drinking water .
Naturally occurring radioactive materials (NORM) consist of uranium, thorium, potassium and any of their decay products such as radium and radon. Concentrations of these natural radioactive elements are very low in the earth’s crust and atmosphere. These elements can be brought to the surface by human activities. Although the radioactive elements in the earth’s crust are the reasons of presence of radioactivity in water resources, high concentration of radioactive materials in water resources might be accidentally or intentionally [2, 3]. The public can be affected by the environment where is adjacent to the released point of the radioactive materials . If radioactive materials are released into the environment, radionuclides may be moved into the body by inhalation and ingestion, which causes internal exposure. Fakeha et al. analyzed samples from well water and bottled drinking water from the Western Province of Arabia for concentrations of natural radioactivity and their contribution to the absorbed dose from water samples using gamma spectroscopy method . Fasunwon et al. studied the activity concentrations of natural radionuclide levels in well waters of Ago Iwoye, Nigeria by HPGe (high purity germanium) spectrometer . They estimated that radiological health burden on the human populace is very minimal and has neither health implications nor affect the background ionization radiation. In a research article studied that natural radioactivity of different brands of commonly sold bottled drinking water in the federal capital Islamabad and Rawalpindi city of Pakistan and found mean concentrations of 226Ra, 232Th and 40K were 11.3 ± 2.3, 5.2 ± 0.4 and 140.9 ± 30.6 mBq/L, respectively using gamma spectroscopy technique .
The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) estimated that exposure to natural radionuclides contributes around 70% of the population radiation dose. The global average human exposure to natural sources is 2.4mSv/y and the weight of water and food is about 0.3mSv/y.
The objective of this study is to obtain a representative estimate of the concentration levels of natural radionuclides in water resources which might be used as drinking water in some our studied sites from the central deserts of Iran, also estimate the corresponding radiation doses for people consuming this water. With water analysis, soil analyses have been performed in this area. The obtained results can be contributed to the baseline data of radionuclide concentrations in this area.
Description of the study area
In the Anarak-Khour area there are a few compositionally complex hydrothermal Cu-Ni-Co deposits which always interested for researchers. Apart from Cu, Ni and Co the ores contain As and U and occasionally Pb, Zn, Au and Ag. All these deposits are localized in the same area under similar geological environment along the north-western and western surroundings of Anarak-Khour massif (Figure 1). These deposits contain a distinctive set of elements and minerals. In the Anarak area, Co, Ni and As are abundant but there is little Ag or Bi . The deposits also show some U. Cu is different because its concentration is high and in particular the abundance of copper arsenides. As with other deposits, Fe is present in only small amounts and S is rare in the arsenide stage of mineralization. Talmessi and Meskani mines are ancient mines for Cu, Ni and Co products that mining activities have ceased since 1960. Recently, exploration activities were conducted by the atomic energy organization of Iran in the course of uranium exploration but there is not any U mine in this area until now. The most important active mine in the area is Nakhlak lead deposit, 40 Km east of Anarak. In geology and geochemistry, the radioactive deposits are associated with high concentrations of heavy metals such as As, Cd, Co, Cr, Cu, Fe, Hg, Ni, Pb, S, Sb and Zn. It seems the presence of deposits and location of this area along the fault is caused these materials coming from the deeper layers to the surface layers and this can be a reason for founding the radionuclides and assessing the radiological risk in this area.
Sampling spots information
Site no.1 (Talmessi mine)
Site no.2 (Nakhlak mine)
Site no.3 (Calkafi mine)
54° 5’34.70” E
Site no.4 (Mesr village)
34° 2’34.59” N
55° 1’27.22” E
Site no.5 (Ordib zone)
Site no.6 (Irakan zone)
55° 7’15.04” E
34° 1’44.81” N
55° 6’13.56” E
34° 7’51.60” N
55° 6’35.85” E
Gamma-ray detection system
Where the constant values a, b, c, d, e, f and g are -0.0004 ± 0.0001, -0.02 ± 0.004, -0.01 ± 0.0006, 0.0001 ± 0.00004, 0.0003 ± 0.00005, 0.000000008 ± 0.000000001 and -0.00000006 ± 0.000000001, respectively.
A wide range of different gamma-ray energy transition lines ranging from about 100 keV up to 1765 keV, associated with the decay products of the 226Ra, 232Th and 40K. The known photopeak lines with background subtraction were used to determine 226Ra, 232Th and 40K. The counting time of sample spectra was also 24 hours.
where N, t, m, p and ϵ (E) are net area counts, time, intensity, weight of sample and absolute photopeak efficiency at specific energy, respectively . The specific activity of 226Ra was evaluated from gamma-ray lines of 214Bi at 609.3, 1120.3 and 1764.5keV and 214Pb at 295 and 351keV, while the specific activity of 232Th was evaluated from gamma-ray lines of 228Ac at 338.4, 911.1 and 968.9keV. The specific activity of 40K and 137Cs was determined from its 1460.8 and 661.6keV gamma-ray lines . The minimum detectable activity for each radionuclide was 0.54 mBq/L for 226Ra, 0.21 mBq/L for 232Th and 0.01 mBq/L for 40K.
Results and discussion
Comparison of radionuclide concentrations of 241 Am, 137 Cs and 152 Eu in POLATOM standard reference material
Reference activity (kBq)
Determined activity (kBq)
Determined activity (Bq/L)
18.13 ± 0.004
18.03 ± 0.004
7.77 ± 0.002
7.18 ± 0.002
4.07 ± 0.001
3.42 ± 0.001
Radioactivity characterization of the subground waters
Average activity concentration of 226 Ra, 232 Th and 40 K in water sampling sites
120 ± 30
257 ± 39
7168 ± 1067
350 ± 54
562 ± 61
3727 ± 577
128 ± 30
287 ± 44
2930 ± 490
270 ± 49
390 ± 80
2951 ± 496
341 ± 63
914 ± 138
5325 ± 837
2836 ± 274
7465 ± 607
6196 ± 670
Radiological risk assessment
where ARa, ATh and AK are the activity concentrations of 226Ra, 232Th and 40K, respectively.
Calculated average values of absorbed dose rate and annual effective dose, radium equivalent activity, external and internal radiation hazard
Absorbed dose rate (nGy/h)
Radium equivalent activity (Bq/L)
External radiation hazard index (Hex)
Internal radiation hazard index (Hin)
Our estimate of water radioactivity concentration on Anarak-khour area in central of Iran is done using gamma-ray spectrometry. The maximum activity concentration of 226Ra and 232Th is found in Irakan Zone. The maximum activity concentration of 40K is found in Talmessi mine. The measured activities of 226Ra in the samples did not exceed the guidance level recommended by WHO but the measured activities of 232Th in Irakan Zone exceeded. The calculated total gamma dose rate varied from 0.29 to 6.102 nGy/h. The annual effective dose obtained from 0.36 to 7.502μSv for the background area. The internal radiation hazard index (Hin) in water varied from 0.002 to 0.0448. The parameters of absorbed dose rate, annual effective dose, radium equivalent activity, external radiation hazard index and internal radiation hazard index is calculated and their results showed there is no potential internal radiation hazard. This study can be followed by analyzing the deep soil and plants of the studied area. Moreover, because there are a lot of people who physically are impaired, the birth rate of children with defects should be compared with the radiounuclide concentrations in soils, waters and plants in every few years. Our results will contribute to the data base of this area in future. Then it is necessary that after operating the disposal site of nuclear waste all environment samples of the studied area should be performed every year and compared with our results.
The authors wish to thank the office of graduate studies of the University of Isfahan for its support. They would also like to thank the staff of central laboratory of University of Isfahan for their assistance. Also, the authors wish to thank Dr. Rezaee for her help and her valuable guidance.
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