Passive radium measurements in soil samples from North Western desert of Egypt using LR-115 nuclear track detector

Ahmed Saad Hussein

doi:10.4103/jrcr.jrcr_47_20

ORIGINAL ARTICLE

Year : 2020 | Volume : 11 | Issue : 4 | Page : 183-187

Passive radium measurements in soil samples from North Western desert of Egypt using LR-115 nuclear track detector

Ahmed Saad Hussein
Department of Security Sciences, Nuclear Security Program, Naif Arab University for Security Sciences, Riyadh, KSA; Department of Radiation and Environmental Protection, Nuclear Power Plants Authority, Cairo, Egypt

Date of Submission	11-Sep-2020
Date of Acceptance	31-Oct-2020
Date of Web Publication	30-Dec-2020

Correspondence Address:
Dr. Ahmed Saad Hussein
Department of Security Sciences, Nuclear Security Program, Naif Arab University for Security Sciences, Riyadh; Department of Radiation and Environmental Protection, Nuclear Power Plants Authority, Cairo

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/jrcr.jrcr_47_20

Abstract

Background: The knowledge of the distribution of radionuclides and radiation levels in the environment is important for assessing the effects of radiation exposure to human beings. Radium (²²⁶Ra) and its ultimate precursor uranium (²³⁸U) are the parent sources of radon (²²²Rn).²²²Rn is the main natural radiation source of exposure of human beings and has been recognized as a carcinogenic gas. Measurement of radon and radium in soil samples is useful in studying the health risks. Objectives: The purpose of this study was to investigate the radium content in soil samples from northwestern desert of Egypt. Materials and Methods: A total of 40 soil samples were collected from four regions named El-Alamin, El-Dabaa, Marsa Matrouh, and El-Negala cities in northwestern desert of Egypt. The radium contents in soil samples were estimated by sealed cup technique using LR-115 nuclear track detectors. Results: Radium concentration has been found to vary from 11.58 to 29.11 Bq/kg with an average value of 20.63 ± 1.46 Bq/kg. Conclusion: The observed values of radium concentration in all soil samples are less than the permissible value of 370 Bq/kg recommended by the UNSCEAR 2000 and OCED 1979. Hence, the result shows that these areas under study are safe as far as the health hazard effects of radium are concerned.

Keywords: Cup technique, Egypt, LR-115, radium content, soil, western desert

How to cite this article:
Hussein AS. Passive radium measurements in soil samples from North Western desert of Egypt using LR-115 nuclear track detector. J Radiat Cancer Res 2020;11:183-7

How to cite this URL:
Hussein AS. Passive radium measurements in soil samples from North Western desert of Egypt using LR-115 nuclear track detector. J Radiat Cancer Res [serial online] 2020 [cited 2021 Jan 19];11:183-7. Available from: https://www.journalrcr.org/text.asp?2020/11/4/183/305725

Introduction

Radium (²²⁶Ra) and radon (²²²Rn) mainly come from naturally occurring uranium (²³⁸U) which is present in all types of rocks, soil, building materials, and ground water.²²⁶Ra is one million times more radioactive than the same mass of²³⁸U.^[1]²²²Rn has been classified as a human carcinogen.^{[2],[3],[4],[5],[6]} Environmental radon and its progeny, on average, account for about half of all human exposure to ionizing radiation from natural sources.^[7] Increasing attention has been paid to exposure to radon and its associated health risk in both industrialized and developing countries.^[4],[8]

Some radiation hazard indices of the soil samples at various areas in Egypt were investigated, using cup technique with LR-115 and CR-39 nuclear track detectors because of the high potential of being used as building materials.^{[9],[10],[11],[12],[13]}

The aim of the present work is to determine the radium activity concentrations in soil samples from four cities in the western north desert of Egypt using cup technique with LR-115 nuclear track detectors.

Materials and Methods

In the present investigation, “sealed cup technique”^{[1],14],[15],[16]} was used to study the radium content. A total of 40 soil samples were collected from four cities, 10 samples from each region, in western north desert in Egypt as shown in [Figure 1]. The samples were dried and saved at room temperature to 1 mm grain size, each sample divided into three equal volumes, weighed, and then placed in cylindrical containers made of aluminum. Each sample container was capped tightly to an inverted cylindrical cup of 3.5 cm radius and 11 cm high. A piece of LR-115 type II (Kodak Pathé, France) detector with area 1.5 cm² is fixed at the top center of the inverted cup. The experimental arrangement is shown in [Figure 2]. This device is called radon only device due to the configuration of the measuring cup and the chemical etching conditions of the irradiated detectors. LR-115 detector is free from self-plate out effect. Thus, it does not record tracks due to self-plating daughters, α-particles of energy 6 MeV (²¹⁸Po) and 7.69 MeV (²¹⁴Po).^{[14],[15],[17]} The cups were left undisturbed at room temperature for a 3-month exposure time. During this time, α-particles from the decay of radon bombarded the LR-115 detector inside the inverted cup through the α-decay of radium contents of the samples. After the irradiation period, the bombarded detectors were collected and chemically etched in 2.5 M NaOH solution at 60°C during 2 h. Subsequently, α-tracks were counted using an optical microscope. The diffusion cups were calibrated at the National Institute for Measurements and Standards, Cairo, Egypt. During the calibration process, the cups were placed inside a radon chamber with a concentration of 17.4 ± 0.5 kBq/m³ for different exposure times.

Figure 1: Schematic diagram of the passive radon devices

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Figure 2: The map of Egypt shown the studied regions

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The radon activity concentration (C_Rn) is calculated using the equation:^{[14],[16],[18],[19]}

Where η the track density (tracks/cm²), η the sensitivity factor of LR115 detector (tracks/cm²/d¹/Bq/m³), and t the exposure time (d). The value of η depends on the height and radius of the measuring cylinder cup.^[9],[17] An effective equilibrium (about 98%) for radon members of the decay series is reached in about 30 days.^[20] Once the radioactive equilibrium is established, one may use the radon alpha analyses for the determination of the steady-state activity of radium. The effective radium content (C_Ra) is calculated using equations:^[17]

Where η_Rn is the radon decay constant (d^-1), h is the distance between the detector and the top of the soil samples (m), A is the area of cross section of the cylindrical cup (m²), M is the mass of the soil samples (kg), and T_e is effective exposure time given by:

Results and Discussion

The calibration coefficient η for radon measurement using the LR-115 detector obtained from the calibration experiment is 0.036 ± 0.006 α–tracks/cm²/d^-1 per Bq/m³. This value is in good agreement with that reported by other investigators.^{[1],[14],[19]}

[Table 1] represents the values of radium content (C_Ra) for soil samples collected from four regions in Egypt using the sealed cup technique with LR-115 nuclear track detectors. Radium content values were found to vary from 11.58 to 29.11 Bq/kg with an average value of 20.63 Bq/kg. Maximum value or radium content of 20.11±1.37 Bq/kg has observed in El-Alamin region and minimum value of 111.58±1.66 Bq/kg is found in El-Negala region. The obtained results are within the range (from 5 to 64 Bq/kg) of the UNSCEAR 2000 survey of natural radionuclide content in Egyptian soil.^[7]

Table 1: Passive measurement of radium content in different surface soil samples in Egypt

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The average value of radium content obtained from this study of soil samples is less than the world value of 35 Bq/kg as reported in UNSCEAR 2000^[7] and much lower than the maximum permissible value of 370 Bq/kg for building materials recommended by the UNSCEAR 2000^[7] and OECD 1979.^[21] Thus, results reveal that the surface soil samples analyzed radiologically safe and can be used as building materials without posing significant radiological threat to the population.

[Table 2] shows the comparison between the obtained results of radium content (C_Ra) in surface soil samples collected from different regions in Egypt using passive technique using sealed cup with LR-115 and CR-39 nuclear track detectors. The obtained values of radium content from this study were found to consistent with data obtained by other Egyptian investigators except the maximum values of the study of Youssef et al. 2015^[12] and the study of Ashry et al., 2019^[13] where the soil samples are rich in phosphate, which is used as agricultural fertilizer in the studied region.

Table 2: The comparison between the obtained results of radium content in soil samples collected from different regions in Egypt using different detectors

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[Table 3] shows radium content (C_Ra) in soil samples from this study in comparison to these values in some countries using α-spectrometry with LR-115 or CR-39 nuclear track detectors. The table shows the compatibility of the values from this study with the measured values in many regions of the world except Ethiopia,^[22],[23] Ghana,^[24] and India.^[25] This is because these regions are characterized by a high level of natural background radiation.

Table 3: The comparison with the other published data in different countries

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Conclusion

Radium content has been measured successfully using LR-115 detectors by the sealed cup technique. The sealed cup technique is a passive and convenient useful tool for determining the radon exhalation rates as well as the radium contents in some surface soil samples from four cities in western desert of Egypt. The observed values of radium concentration in all soil samples are less than the permissible value of 370 Bq/kg recommended by UNSCEAR 2000 and OCED 1979. Thus, the studied regions are safe as for the health hazard effects of radium are concerned. It is possible to establish a national database of surface soil samples using low-cost passive technique with large-scale screening measurements. The measured values were compared with national and some other countries.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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