Ten soil samples from Jabal Al Qur, Wadi Baba, and Wadi Sieh in Sinai, Egypt, were analyzed by XRD spectroscopy. The XRD spectroscopy results indicate that the major, minor and trace constituents varied from one sample to another. Samples were also analyzed by HPGe gamma spectrometer to determine the activity concentration of U-238, Th-232 series and K-40. The concentrations for 238U ranged from 57.03 to 4220.41 Bq/kg with an average 1110.75 Bq/kg, for 232Th, ranged from 13.55 to130.46 Bq/kg with an average 71.85 Bq/Kg . The concentrations for 40K were in the range from 12.18 to 948.93 Bq/kg with an average value 457.09 Bq/kg. The average activity concentration values of 226Ra, 232Th, and 40K, in all the collected samples were higher than the world average. The radium equivalent (Req), absorbed dose rate (DR), the effective dose rate (Deff), and hazard indices resulted due to the natural radionuclides in soil are also calculated. The Results show that the study area is not safe for human and environments.
Measurement of the concentrations of natural radionuclides in soil give information’s on the natural radionuclide sources. Beck suggested that 50% - 80% of the total gamma flux at the earth’s surface arises from 40K and 232Th, 238U series [
X-Ray Diffraction (XRD) is a non-destructive analytical technique. When X-ray strikes on a crystal surface at an angle θ, a portion of the X-ray is scattered by a layer of atoms at the surface. Un-scattered X-ray penetrates to the second layer of atoms where again a fraction is scattered. The remaining X-ray passes to the third layer until the energy of the X-ray is dissipated completely. An X-ray detector measures the cumulative effect of the scattering beams. The X-ray appear to be reflected from the crystal only if the angle of incidence satisfies the condition of Bragg Equation, nλ = 2dhklsinθ. The X-ray pattern shows the peaks at various angles of incidence [
The objectives of the present study are to determine some metal concentrations and measure the natural radioactivity levels of 226Ra, 232Th, and 40K in the soil samples taken from selected places in Sinai region, Egypt, also to assess the radiological Hazard indices in air and to compare the results with international levels. Radionuclides 226Ra, 232Th and 40K were measured with a well-type gamma-ray detector, and metal concentrations were determined by X-Ray diffraction, patterns were recorded using X’Pert PRO Powder X-Ray Diffraction with Cu Kα radiation (λ = 0.1542 nm), Ni-filter and general area detector. The data generated in this study provide baseline values of natural radioactivity in Sinai soils and may be useful for authorities in the implementation of radiation protection standards for the general population in the country as well as to plan and conduct further studies on this issue.
Sinai can be divided into three areas: The northern region consists of sand dunes and fossil beaches formed by the changing levels of the Mediterranean Sea during the glacial periods two million years ago. The landscape is flat and uniform, interrupted by sand and limestone hills. The central area with limestone dating from the Tertiary Period is the highlands extend towards the south. The third area consists of granite and volcanic rocks. Limestone and sandstone sediments are replaced by granite and basalt. Both rocks are produced by volcanic activity on the bottom of the ocean. Ten soil samples were collected from different areas of Sinai; Jabal Al Qur (28˚49'46.06''N - 33˚17'45.41''E) is located inland south-east of Sinai and consists of granite and volcanic rocks, Limestone and sandstone sediments. Wadi Baba (28˚58'30.80''N - 33˚17'31.47''E) is a low altitude system located inland south-east of Wadi Gharandel. The system consists of several smaller interconnecting wadis with gravel beds and high rise sandstone cliffs either side. Wadi Sieh (29˚03'27.28''N - 33˚26'14.84''E) is located further inland north-east of Wadi Baba; the wadi has a sandy bed with sandstone canyons rising either side, as shown in
Ten soil samples were collected from different areas of Sinai; Jabal Al Qur, Wadi Baba and Wadi Sieh. These collected samples have different Descriptions as shown in
Description | Sample Code |
---|---|
Sandy dolostone, medium hard to hard, grey. | Soil 1 |
Siltstone with ferruginous Shale, mainly red and grey. | Soil 2 |
Sandstone, red, medium hard with pebbles. | Soil 3 |
Gibbsite, soft, brownish yellow. | Soil4 |
Gibbsite-bearing shale, soft to medium hard, yellowish brown. | Soil 5 |
Siltstone, soft to medium hard, brown. | Soil 6 |
Gibbsite, soft, brown. | Soil 7 |
Ferruginous siltstone soft to medium hard. | Soil 8 |
Conglomeratic sandstone, pale brown, medium hard. | Soil 9 |
Clay stone, creamy, soft to medium hard. | Soil 10 |
The concentration of 226Ra was determined from the average concentration of gamma-ray lines of energies 351.87 keV of 214Pb and 609.31 keV of 214Bi (since there is secular radioactivity equilibrium in226Ra series). Also, the concentration of 232Th, which it is in secular radioactivity equilibrium with its short half-life daughters, was determined from the average concentrations of 228Ac (with gamma-ray line 911.16 kev) and of 208Tl (with gamma-ray line 583.10 keV). The analysis of 40K concentrations was based on its single peak in the spectrum at energy 1460.80 kev. The activity concentrations “As” of the natural radionuclides in the measured samples were computed using the following relation [
where: Ca is the net gamma counting rate (counts per second), ε the detector efficiency of the specific γ-ray, Pr the absolute transition probability of Gamma-decay and Ms the mass of the sample (kg).
To assess the real activity level of 226Ra, 232Th and 40K in soil, a common radiological index has been defined in terms of radium equivalent activity (Raeq) in Bq/kg can be used, provides a very useful guideline in regulating the safety standards in radiation protection for a human population. The index was calculated through the following formula is based on the assumption that 370 Bq/kg of 226Ra, 259 Bq/kg of 232Th and 4810 Bq/kg of 40K produce the same gamma-ray dose rate [
where: CRa, CTh and CK are the specific activities (Bq/kg dry weight) of 226Ra, 232Th and 40K, respectively.
The measured activity of 226Ra, 232Th and 40K were converted into doses by applying the factors 0.4551, 0.5835 and 0.0429(nGyh−1/Bqkg−1) for radium, thorium and potassium, respectively. These factors were used to calculate the total absorbed gamma dose rate in air at 1 m above the ground level using the following equation [
where: CRa, CTh and CK are the activity concentrations (Bq/kg) of 226Ra, 232Th and 40K, respectively.
Annual estimated average effective dose equivalent received by a member is calculated using a conversion factor of 0.7 Sv/Gy, which is used to convert the absorbed dose rate to annual effective dose with an outdoor occupancy of 20% [
In the literature a number of criterion formulae have been derived over the years to assess the radiation dose rate due to exposure to gamma radiation from the natural radionuclides contained in soil. To limit the annual external gamma-ray dose to 1.5 Gy for the samples under investigation [
where: CRa, CTh and CK are the activity concentrations in Bq/kg of 226Ra,232Th and 40K Respectively. The value of this index must be less than unity for the radiation hazard to be negligible.
The internal exposure to 222Rn and its radioactive progeny is controlled by the internal hazard index (Hin) [
where: C denotes the respective specific activity in Bq/kg, for the safety, Hin should be less than unity.
Representative level index (Iγr) is used to estimate the level of γ-radiation hazard associated with the natural radionuclides in specific building materials, is defined as [
where: CRa, CTh and Ck are the activity concentrations of 226Ra, 232Th and 40K in Bq/k, respectively.
X-ray diffraction is a non-destructive analytical technique, which provides detailed information about the atomic structure of crystalline substances, chemical composition, and physical properties of materials. In the present study, the XRD results indicate that the main major, minor and trace constituents varied from one sample to another, as shown in
Sample code | MAJOR | MINOR | TRACE |
---|---|---|---|
Soil 1 | Calcium Thorium Phosphate (Whitlockite-type)* | thorium(V) sulfide | Thorium |
Soil 2 | Thorium Oxide Phosphate Thorium germanide | Sodium Beryllium Thorium Fluoride Na Cesium Thorium Fluoride | Thorium |
Soil 3 | Uranium Oxide Sulfide Uranium Fluoride | Uranium Arsenic | Uranium |
Soil 4 | Uranium Imide | Copper Uranium Oxide | Uranium |
Soil 5 | Thorium Rhodium Boride | Uranium Ytterbium Sulfide Oxide Nickel Vanadium Uranium Oxide Hydrate | Thorium |
Soil 6 | Thorium Selenium Uranium Boron Chloride Urea Hydrate | Thorium Carbide Uranium Phosphoryl Chloride | Thorium |
Soil 7 | Uranium Imide Chloride | Thorium Arsenic | Uranium Uranyl Sulfate Hydroxide Hydrate (Uranopilite) |
Soil 8 | ----- | ------- | Uranium Thulium Thorium Iodide |
Soil 9 | Nickel Vanadium Uranium Oxide Hydrate (Meta-autunite) | Uranium Arsenide Sulfide Uranium Fluoride Hydrate | Uranium |
Soil 10 | Uranium Chromium Selenium (Hidalgoite) | Aluminum Uranium | Uranium Barium Uranium Gadolinium Oxide |
*[
Compound name/Chemical composition | Description |
---|---|
Calcium Thorium Phosphate (Whitlockite-type) Ca10.26 Th0.12(PO4)7 | Synthesis and new crystal structure refinement. |
Thorium(V) sulfide-Th2S5 | An inorganic chemical compound composed of two thorium atom ionically bonded to five atoms of sulfur. |
Thorium-Th | Chemical element and radioactive actinide metal. |
Thorium Oxide Phosphate-Th2(PO4)2O | The compound was synthesized under wet hydrothermal conditions. |
Thorium germanide-Th3Ge2 | Compound composed of Th(rare earth), Ge(Metalloid). |
Sodium Beryllium Thorium Fluoride-NaBeTh3F15 | An inorganic chemical compound with one Na, and Be , three Th atom ionically bonded to fifteen F. |
Cesium Thorium Fluoride-CsTh6F25 | Compound composed of Cs(Alkali Earth), Th(rare earth), and F (Metalloids). |
Uranium Oxide Sulfide-UOS | Compound composed of U (rare earth), O (Non-Metals), and S (Non-Metals). |
Uranium Fluorid-UF4 | UF4 is a solid composed of particles with a texture and soluble in water. |
Uranium Arsenic-U3As4 | Compound composed of U (rare earth), and As ((Metalloid). |
Uranium-U | Uranium is heavy metal. In nature, uranium is found as an xide. |
Copper Uranium Oxide-CuU3O10 | Compound composed of Cu (Transition Metals), U(rare earth), and O (Non-metal) |
Thorium Rhodium Boride Th Rh4B4 | This compound composed of Th, Rh, B. |
Uranium Ytterbium Sulfide Oxide-U2YbS3O2 | Compound composed of U, Yb, S, O |
Nickel Vanadium Uranium Oxide Hydrate Ni(VUO6)24H2O | This compound contains U (RARE EARTH), Ni and V (transition Metals), H, O ((Non-metal). |
Thorium Selenium-Th7Se12 | Seven atoms of Th and twelve atoms of Se bonded. |
Uranium Boron Chloride Urea Hydrate U(B12Cl12)2・8Co(NH2)2・2H2O | Compound composed of U, B, Cl, Co, N, H, AND O. |
Thorium Carbide-ThC2 | Thorium carbide structure. |
---|---|
Uranium Phosphoryl Chloride-U3(PO)6Cl32 | Compound composed of U, P, O, Cl. |
Thorium Arsenic-ThAs | Compound composed of Th (rare earth) and As (Metalloid). |
Uranium Imide Chloride-U(NH)Cl | Compound composed of U and (NH)Cl (Volcanic fumaroles, burning coal seams and quano deposits). |
Uranyl Sulfate Hydroxide Hydrate (Uranopilite) (UO2)6(SO4)(OH)10・12H2O | Secondary mineral found on altering uraninite. |
Thorium Thulium Iodide-Th TmI6 | Compound composed of Th (rare earth), Tm (rare earth), and I (Metalloids). |
(Meta autunite)-Ca(UO2)2(PO4)2∙4(H2O) | Associated with autunite in fractures in uraniferous igneous rocks. |
Uranium Arsenide Sulfide-U2AsS | Compound composed of U (rare earth), As (Metalloid), and S (Non-Metal). |
Uranium Fluoride Hydrate-UF4(H2O)0.7 | Uranium tetrafluoride (UF4) and water vapor. |
Uranium Chromium Selenium-UCrSe3 | Compound composed of U (rare earth), Cr (Transition Metal), and Se (Non-Metal). |
(Hidalgoite)-PbAl3AsO4SO4(OH)6 | Secondary mineral of the oxide zone of polymetallic sulfide deposits. |
Aluminum Uranium-UAl3 | Inorganic compound composed of U and Al. |
Barium Uranium Gadolinium Oxide-Ba2UGdO5.944 | Chemical compound composed of Be, U, Gd, and O. |
As shown in
The results of the present work indicate that:
・ XRD measurements show that the major, minor, and some of trace elements concentrations for the samples are uranium compounds and thorium compounds.
・ The study area shows very high values of 238U and 232Th concentrations except sample 3. Also, 40K has high concentrations except sample 3 and 5.
・ These average values for the soil samples from these regions (Jabal Al Qur, Wadi Baba, and Wadi Sieh) are considered to be very high levels of radioactivity compared to the world standard.
・ The average of absorbed dose rate, annual effective dose, radium equivalent, and the radioactivity hazard in-
Sample code | Radioactivity concentration (Bq/kg) | ||
---|---|---|---|
226Ra | 232Th | 40K | |
Soil 1 | 591.34 ± 0.0005 | 100.22 ± 0.001 | 948.93 ± 0.0004 |
Soil 2 | 4220.41 ± 0.0004 | 77.22 ± 0.001 | 248.65 ± 0.0006 |
Soil 3 | 57.03 ± 0.0004 | 15.30 ± 0.001 | 12.18 ± 0.0004 |
Soil4 | 704.21 ± 0.0005 | 82.53 ± 0.002 | 569.67 ± 0.0005 |
Soil 5 | 1571.29 ± 0.0004 | 13.55 ± 0.002 | 54.79 ± 0.0006 |
Soil 6 | 560.76 ± 0.0005 | 23.66 ± 0.002 | 172.72 ± 0.0005 |
Soil 7 | 779.30 ± 0.0006 | 87.21 ± 0.002 | 569.14 ± 0.0005 |
Soil 8 | 1250.81 ± 0.0005 | 125.57 ± 0.002 | 654.47 ± 0.0005 |
Soil 9 | 381.36 ± 0.0005 | 86.44 ± 0.002 | 641.97 ± 0.0004 |
Soil 10 | 924.90 ± 0.0005 | 130.46 ± 0.002 | 685.53 ± 0.0005 |
Range | 57.03 - 4220.41 | 13.55 - 130.46 | 12.18 - 948.93 |
Average | 1104.14 | 74.21 | 455.80 |
Sample code | Radium equivalent Raeq (Bq/kg) | External index Hex | Internal index Hin | Gamma index Iγr | Dose rate DR outdoor (nGy/h) | Annual effective Dose Deff (mSv/y) |
---|---|---|---|---|---|---|
Soil 1 | 807.74 | 2.18 | 3.78 | 5.58 | 355.75 | 0.4363 |
Soil 2 | 4349.98 | 11.76 | 23.16 | 29.07 | 1860.91 | 2.282 |
Soil 3 | 79.85 | 0.22 | 0.37 | 0.541 | 34.41 | 0.0422 |
Soil 4 | 866.08 | 2.34 | 4.24 | 5.9 | 376.60 | 0.4619 |
Soil 5 | 1594.88 | 4.31 | 8.56 | 10.65 | 681.73 | 0.8361 |
Soil 6 | 607.88 | 1.64 | 3.16 | 4.09 | 261.61 | 0.3208 |
Soil 7 | 947.83 | 2.56 | 4.67 | 6.45 | 411.57 | 0.5047 |
Soil 8 | 1480.77 | 4.00 | 7.38 | 10.03 | 640.47 | 0.7855 |
Soil 9 | 554.39 | 1.5 | 2.53 | 3.83 | 244.29 | 0.2996 |
Soil 10 | 1164.24 | 3.15 | 5.65 | 7.93 | 505.69 | 0.6202 |
Average | 1245.37 | 3.37 | 6.35 | 8.41 | 537.30 | 0.6589 |
World standard | 370 | ≤1 | ≤1 | ≤1 | 57 | 0.07 |
dices values are much higher than the corresponding world average.
・ Precautions and recommendations should be taken into consideration for high levels of radioactivity concentrations in these samples especially when people may inhabit in these areas. I recommend that this study to be taken as a base line for any future studies in this area.