Analysis of radionuclides and radiation hazards in soil, sediment, water, and rock in Sylhet, Bangladesh

Abstract

The natural radioactivity level in soil, sediment, and water samples collected from the Bisnakandi region in Sylhet was measured using a high-purity germanium detector. The mean activity concentrations of radionuclides in samples from the Bisnakandi were: ²³²Th (surface soil: 28.60 ± 6.44 Bq/kg, depth soil: 34.97 ± 7.37 Bq/kg, sediment: 41.70 ± 8.22 Bq/kg, water: 16.37 ± 2.13 Bq/L), ²²⁶Ra (surface soil: 33.70 ± 6.85 Bq/kg, depth soil: 40.09 ± 8.06 Bq/kg, sediment: 47.60 ± 9.38 Bq/kg, water: 19.76 ± 3.16 Bq/L), and ⁴⁰K (surface soil: 304.60 ± 20 Bq/kg, depth soil: 375 ± 23.10 Bq/kg, sediment: 455.80 ± 19.2 Bq/kg, water: 241 ± 19.70 Bq/L). The average activity concentrations in rock samples for ²³²Th, ²²⁶Ra, and ⁴⁰K in (Jaflong, Bholagonj) were (45.69 ± 14.32 Bq/kg, 40.06 ± 12.71 Bq/kg), (36.27 ± 16.89 Bq/kg, 36.84 ± 13.02 Bq/kg), and (430.34 ± 36.82 Bq/kg, 426.7 ± 78.98 Bq/kg), respectively. All the hazard parameters, such as radium equivalent activity, absorbed dose, annual effective dose, and external hazard index, were found within the acceptable level recommended by international organizations.

Introduction

The naturally occurring radionuclides of the ²³²Th (Thorium-232), ²³⁸U (Uranium-238), and ²³⁵U (Uranium-235) radioactive series, as well as ⁴⁰K (Potassium-40), are the source of natural radioactivity and contribute significantly to the natural irradiation of humans and other organisms. The concentration of natural radionuclides is dependent upon the soil composition. Besides the natural radionuclides, different manmade radionuclides entered the environment. The most significant among them is ¹³⁷Cs (Cesium-137) (T_1/2 = 30 y). ¹³⁷Cs is bound in the surface layers of soil and is washed out and redistributed in the ecosystem for a longer period due to their long half-life [1]. Cosmic, terrestrial, and anthropogenic radiation are the primary sources of radioactive material available in the environment [2]. Prolonged exposure to elevated levels of natural radionuclides such as ²³²Th and ²³⁸U may increase the risk of cancer, especially in areas with high concentrations [3]. These alpha-emitting radionuclides and their decay products can accumulate and pose significant health risks when inhaled or ingested. Thus, it is crucial to understand the radiation dose individuals may receive from naturally occurring sources. It is vital to conduct research on artificial radioactivity, particularly on radionuclides such as ¹³⁷Cs (Cesium-137), which enter the environment through nuclear testing and accidents. Due to its long half-life and ability to bind to surface soil, it can persist for extended periods, posing long-term radiological risks to the environment and human health. Understanding both natural and artificial sources of radioactivity is essential for a comprehensive assessment of radiological impacts in affected areas.

To prevent unwanted radiation exposure, we require a well-mapped area with experimental data that can provide a clear warning of the risk. This type of information can assist individuals and organizations in making educated decisions regarding activities that may expose them to radiation, such as home construction of buildings and scientific research related to nuclear radiation. By studying the natural background radiation levels in a region, it is feasible to identify areas where additional measures or monitoring may be required to protect public health and safety [3]. In addition, given the concentration of radionuclides may fluctuate over time, possibly owing to radionuclide leakage accidents, periodic measurements should be undertaken to generate real-time exposure risk alerts [4]. ²³²Th and ²³⁸U both alpha-emitting radionuclides have the slowest decay. Their decay series including long-lived radioisotopes persist in the environment for an extended period. These radionuclides and their decay products can accumulate in soil, rocks, and other natural materials, contributing to natural background radiation levels. ¹⁴C (Carbon-14), ³⁶Cl (Chlorine-36), and ¹⁰Be (Beryllium-10) are cosmogenic radionuclides primarily produced in the stratosphere. These radionuclides are redistributed in the environment—such as soil, rocks, and water—by wind, rain, or other geological processes. They can pose a health risk if exposure is high or prolonged, especially if inhaled or ingested [5]. Understanding the potential health impacts of both natural and anthropogenic radionuclides is vital, as exposure to radiation has been linked not only to cancer but also to genetic mutations and other long-term health effects. This makes continuous monitoring and assessment of radiation levels a necessary step for safeguarding public health, particularly in high-risk areas.

The aim of this research is to measure the radioactivity in soil, sediment, water, and rock samples, and to assess how these levels might affect human exposure, especially since the sample locations are popular tourist destinations. To investigate the effect of sample area on radiation exposure, it is necessary to compare measurements made at multiple spots and assess the data to find potential dangers. Our primary objectives are: to observe the spectrum of gamma radiation from radionuclides of soil, sediment, and water samples such as ²³²Th, ²³⁸U, and ⁴⁰K; to measure the activity concentration of these nuclides in different types of environmental samples; to quantitatively determine the radium equivalent dose, absorbed dose rate, external hazard index, and these radionuclides’ annual effective dose equivalent; and to compare the mean value of each measurement with the worldwide average value and reported value of other countries.

Materials and methods

Study areas

To conduct a comprehensive radioactive measurement, samples of rock, soil, sediment, and water were collected from three locations in Sylhet District, northeastern Bangladesh. The first area is Bisnakandi, located in the Rustompur Union (latitude: 25°10′10.36″ N, longitude: 91°53′12.21″ E). This area is characterized by limestone formations that have been eroded over time by water flow from the nearby river. Soil, sediment, and water samples were collected here due to the area’s geological significance and its potential for human exposure, given its proximity to local communities and tourist activities.

The second area is Jaflong, situated in East Jaflong Union (latitude: 25°10′51.114″ N, longitude: 92°01′ E), selected for rock sample collection. Jaflong is a popular tourist destination known for its scenic beauty and geological features. The increased human interaction in this area may lead to higher exposure to radionuclides, making it a critical location for our study.

The third location, selected for rock samples, is Bholagonj (latitude: 25°9′39″ N, longitude: 91°45′13″ E), under Companiganj Upazila. This area is notable for its stone quarrying activities, which can introduce anthropogenic radionuclides into the environment through mining processes. The geological significance of these areas, combined with the potential for human exposure to both natural and anthropogenic radionuclides, makes them ideal for this study.

The three regions Bisnakandi, Jaflong, and Bholagonj have almost the same latitude. Bisnakandi is suitable for collecting soil, sediment and water samples, and Jaflong and Bholagonj are suitable for rock samples. These three places are situated near the border of India and adjacent to the hilly region of the Meghalaya province of India.

The geological locations of all the areas are depicted in Fig. 1.

Sampling and sample preparation

From Bisnakandi, soil samples were collected from both the surface (0–5 cm) and depth (5–10 cm) of the soil. Overall, 20 soil samples were collected from 10 different locations, two sets of samples, one from the surface and the other from the depth of each location. 10 sediment samples and 6 water samples from different locations were taken for investigation. 10 rock samples from 10 locations of Jaflong, as well as Bholagonj, were collected. Figure 2 shows the map of the geographical locations of these collected soil, sediment, water, and rock samples.

Sample weights for soil were 287 to 302 gm in pot geometry (plastic container), weights for sediment sample were 278 to 283 gm in pot geometry (plastic container) and weights for water samples were 500 ml in Marinelli beaker. All the locations selected for rock sample collection were on the lakeside. All samples were carefully collected from the surface and each of the rock samples weighed ~500 gm.

Soil, sediment, and rock samples were first sun-dried by spreading them out in a clean area to ensure the removal of moisture [6]. After sun-drying, the samples were crushed into a fine powder using a mortar and pestle to ensure uniformity and homogeneity. The crushed samples were then passed through a standard sieve with a mesh size of 2 mm to further ensure consistency in particle size. The sieved samples were then placed in an oven at about 105°C for complete drying. The dried samples were labeled with appropriate sample codes and sealed in plastic containers for storage. After sun-drying, the samples were crushed into a fine powder using a mortar and pestle to ensure uniformity and homogeneity. The crushed samples were then placed in an oven at about 105°C for complete drying. The dried samples were then labeled with appropriate sample codes and sealed in plastic containers for storage. Prior to collecting water samples, 1-l capacity bottles were sterilized to avoid contamination. The 1-l Pyrex beakers used for evaporation were cleaned with distilled water and dried thoroughly. Each water sample was treated with 1 ml of concentrated nitric acid (HNO₃) to prevent organic buildup and maintain ion stability. Samples were then evaporated in a water bath at 105°C, reducing the volume to 500 ml. Finally, all samples were stored for at least 4 weeks to attain secular equilibrium between ²²⁶Ra and its decay products before being transferred to the Health Physics Division laboratories at the Atomic Energy Centre, Dhaka, Bangladesh, for measurement.

Instrumentation

A high-resolution High-Purity Germanium detector (GCD-30185, NATS, USA) was used to measure the gamma-ray-emitting radionuclides in the samples. The detector was shielded from external radiation by a cylindrical lead (Pb) enclosure with a thickness of 15 cm, designed with a sliding cover on the top and a fixed base.

To identify the isotopes from the sample, we need a spectrum corresponding to gamma energy, or the relation between channel number and energy must be known; this process is known as energy calibration. In practice, for a known source peaks are identified first then their corresponding true energy and channel number for peak position are listed manually. Recent instruments only require energy corresponding to the peak and can auto-calibrate the system. The linear calibration can be written as, |$E\ \left(\mathrm{keV}\right)=I\ \left(\mathrm{keV}\right)+G\times C\ \left(\mathrm{channel}\right)$|⁠; where I and G are the intercept and gradient of the calibration line and C is the channel position [7].

²³⁸U, ²³²Th, and ²²⁶Ra cannot be determined directly by gamma spectrometry, but the presence of their daughter radionuclides can be determined, and these in secular equilibrium represent the presence of the parent nuclides. ²³²Th is the parent radionuclide of the thorium decay series with a half-life of 1.41 × 10¹⁰ y. The presence of the ²³²Th series is determined from the spectra of ²¹²Pb (Lead-212) (photon energy 238 keV), ²⁰⁸Tl (Thallium-208) (583 keV, 2614.5 keV), and ²²⁸Ac (Actinium-228) (911 keV). From the ²¹⁴Pb (Lead-214) (352 keV) and ²¹⁴Bi (Bismuth-214) (609 keV, 1764 keV) spectral line the ²²⁶Ra (²³⁸U series) radionuclide is estimated. The 186 keV photon peak of ²²⁶Ra was not used because of the interfering peak of ²³⁵U with the energy of 185.7 keV. The presence of ¹³⁷Cs was determined from its characteristic 661.6 keV gamma-ray peak. ⁴⁰K radionuclide was estimated using 1461 keV photo-peak from ⁴⁰K itself [8]. The gamma-ray spectrum of the surface soil sample with ID BSS-5 collected from Bisnakandi is shown in Fig. 3. For the estimation, the activity is calculated as the average for different activities deduced by different photopeaks of radionuclides belonging to each series [9]. Measurement is performed on the assumption that radionuclides in each series are in secular equilibrium which might not be accurate in each case.

Analysis of radionuclide activity and radiological hazard parameters

The radioactive concentration of radionuclide can be calculated by the formula

where A is the activity in unit Bq/kg, N is the subtraction of counts per second of the sample to the background, I is the intensity, ϵ is the efficiency, and M is the mass of the sample [10].

A weighted sum of activities of ²²⁶Ra, ²³²Th, and ⁴⁰K is known as radium equivalent activity which is a measure of the total effective dose equivalent of gamma dose that could be received from the decay of all radionuclides present in a sample and is used to represent the activity concentrations of ²²⁶Ra, ²³²Th, and ⁴⁰K by a single quantity, |${\mathrm{Ra}}_{\mathrm{eq}}$|[11]. For the assessment of radiological hazard, radium equivalent is an important parameter and can be used to determine compliance with regulatory limits. The radium equivalent activity is given by

where |${C}_{\mathrm{Ra}}$|⁠, |${C}_{\mathrm{Th}}$|⁠, and |${C}_{\mathrm{K}}$| are the activity concentrations of ²²⁶Ra, ²³²Th, and ⁴⁰K in Bq/kg. The permissible limit of the parameter is 370 Bq/kg recommended by the Organization for Economic Cooperation and Development (OECD) [12].

The amount of radiation energy absorbed per unit mass of tissue is measured by calculating the absorbed dose rate, |$D$|⁠, expressed in units of gray (Gy), which is equivalent to one joule of energy deposited per kilogram. Absorbed dose is an important parameter [13].

To assess the health effects of the absorbed dose, the annual effective dose equivalent,  |${D}_{\mathrm{eff}}$|⁠, considering exposure through dermal contact, in the air should be calculated for assessing any radiological hazard parameter to interpret tissue damage and other biological effects that may result from exposure to ionizing radiation. The annual effective dose equivalent, D_eff is given by [14],

Values of the absorbed dose rate are calculated by applying the dose conversion factor of 0.7 Sv/Gy and the outdoor occupancy factor of 0.2 (people spend about 20% of their lives outdoors) [15].

The formula used to calculate the external hazard index is

This parameter is to limit the radiation dose to the permissible dose equivalent limit of 1 [14].

The equation for Excess Lifetime Cancer Risk (ELCR) for direct exposure of samples is expressed as (considering exposure through dermal contact)

By using an average duration of life of 70 y and with |$0.05/\mathrm{Sv}$| as a risk factor suggested by ICRP 103 for public exposure [16].

Results and discussion

The activity concentration of ²³²Th measured from the surface soil sample ranges from 23.90 ± 5.48 to 34 ± 6.98 Bq/kg with an average of 28.60 ± 6.44 Bq/kg. In the case of ²²⁶Ra, the measured activity concentration ranges from 28 ± 5.21 to 37 ± 9.24 Bq/kg with an average of 33.70 ± 6.85 Bq/kg. The values of activity concentration of ⁴⁰K extend from 247 ± 19.66 to 360 ± 21 Bq/kg with an average of 304.60 ± 20.09 Bq/kg. For the depth soil samples, the activity concentration of ²³²Th ranges from 32 ± 8.38 to 39.7 ± 6.08 Bq/kg with an average of 34.97 ± 7.37 Bq/kg then the activity concentration of ²²⁶Ra spans from 33.90 ± 7.48 to 47 ± 6.06 Bq/kg with an average of 40.09 ± 8.06 Bq/kg and the activity concentration of ⁴⁰K varies from 342 ± 22.97 to 430 ± 20.56 Bq/kg averaging at 375 ± 23.10 Bq/kg. For the sediment samples, the activity concentration of ²³²Th fluctuates between 37 ± 6.76 and 46 ± 8.70 Bq/kg with an average of 41.70 ± 8.22 Bq/kg. The activity concentration of ²²⁶Ra ranges from 43 ± 7.89 to 53 ± 10.48 Bq/kg with an average of 47.60 ± 9.38 Bq/kg, and the activity concentration of ⁴⁰K varies from 410 ± 22 to 493 ± 19.97 Bq/kg with an average of 455.80 ± 19.2 Bq/kg. For water samples, the activity concentration of ²³²Th ranges from 14.40 ± 2.73 to 19.02 ± 1.77 Bq/L with an average of 16.37 ± 2.13 Bq/L. The activity concentration of ²²⁶Ra ranges from 15.70 ± 3.21 to 23.50 ± 4.08 Bq/L with an average of 19.76 ± 3.16 Bq/L. The activity concentration of ⁴⁰K ranges from 211 ± 14 to 273 ± 21 Bq/L with an average of 241 ± 19.70 Bq/L. For the rock samples collected from the Bholagonj region, it is found that the activity concentration of ²²⁶Ra ranges from 27 ± 4.21 to 71 ± 4.14 Bq/kg with a mean of 36.84 ± 13.02 Bq/kg, the activity concentration of ²³²Th ranges from 24 ± 2.88 to 62 ± 3.37 Bq/kg with a mean of 40.06 ± 12.71 Bq/kg, and the activity concentration of ⁴⁰K ranges from 310 ± 49.62 to 550 ± 56.06 Bq/kg with a mean of 426.70 ± 78.98 Bq/kg. For the rock samples collected from the Jaflong region, the activity concentration of ²²⁶Ra ranges from 23.30 ± 1.96 to 93 ± 3.82 Bq/kg with a mean of 36.27 ± 16.89 Bq/kg, the activity concentration of ²³²Th ranges from 45 ± 1.57 to 69 ± 3.06 Bq/kg with a mean of 45.70 ± 14.32 Bq/kg, and the activity concentration of ⁴⁰K ranges from 318 ± 24.90 to 600 ± 57.84 Bq/kg with a mean of 430.34 ± 36.82 Bq/kg.

Figure 4 compares the activity concentrations of ²²⁶Ra, ²³²Th, and ⁴⁰K for surface soil, depth soil, sediment, water, and rock samples collected from different geographical locations.

The activity concentrations of ²²⁶Ra, ²³²Th, and ⁴⁰K for each sample, along with their respective location points, have been presented in Table 1. Among all solid samples, the activity concentrations of ²³²Th ranged from 24 to 69 Bq/kg, whereas the activity concentration of ²²⁶Ra ranged from 23.30 to 93 Bq/kg, and that of ⁴⁰K ranged from 247 to 620 Bq/kg. Among soil, sediment, and rock samples the Jaflong rock samples, showed the maximum presence of all radioactive elements.

However, the values of radium activity concentration in Jaflong rock samples fluctuated in a wide range, as we could also find the minimum concentration in this same group. On average, Bisnakandi surface soil samples had the lowest concentrations of all. Throughout the calculation, ⁴⁰K had a much higher concentration in all groups of the samples. On the other hand, water samples, measured in a different unit, cannot be directly compared to the concentrations of other samples. However, they exhibit a mirrored pattern in concentration relative to the other samples. Additionally, water samples show a more uniform activity concentration compared to the other examined samples.

A comparison of each radiological hazard parameter (radium equivalent activity Ra_eq, absorbed dose rate D, annual effective dose equivalent D_eff, external hazard index 𝐻_ex, ELCR) measured in the present study with that of others is presented in Table 2.

The Radium Equivalent Activities Ra_eq ranges from 91.53 to 107.33 Bq/kg with a mean of 98.05 ± 4.88 Bq/kg for the Bisnakandi surface soil samples, for the depth soil samples they range from 110.68 to 126.57 Bq/kg with a mean of 118.98 ± 6.19 Bq/kg, for the sediment samples, they range from 130.99 to 154.74 Bq/kg with a mean of 142.33 ± 7.26 Bq/kg. It ranges from 91.78 to 184.74 Bq/kg with a mean of 127.75 ± 37.28 Bq/kg for the Bholagonj region rock samples and ranges from 114.59 to 200.69 Bq/kg with a mean of 134.75 ± 40.22 Bq/kg for the Jaflong region rock samples. According to the OECD, the recommended safety limit of Ra_eq is 370 Bq/kg [12]. In measurements, all the values are lower than the limit.

The absorbed dose rate, D ranges from 42.94 to 48.37 nGy/h with a mean of 45.54 ± 2.37 nGy/h for surface soil samples; for the depth soil samples, they range from 51.53 to 58.79 nGy/h with a mean of 55.28 ± 2.82 nGy/h; for the sediment samples, they range from 61.04 to 71.82 nGy/h with a mean of 66.18 ± 3.32 nGy/h; and for the water samples, they range from 26.22 to 30.88 nGy/h with a mean of 29.09 ± 1.48 nGy/h. In the rock samples of the Bholagonj region, the estimated absorbed dose rate, D varies from 42.77 to 74.28 nGy/h, with a mean value of 59.34 ± 16.98 nGy/h, while for the Jaflong rock samples, it ranges from 60.56 to 93.96 nGy/h, with a mean value of 62.29 ± 17.99 nGy/h. Except for the sediment and rock samples, all other samples give values that are lower than the world average value of 60 nGy/h still within the worldwide average values range from 18 to 93 nGy/h [32].

The Annual Effective Dose Equivalent D_eff ranges from 52.66 to 61.64 μSv/y with a mean of 55.85 ± 2.91 μSv/y for surface soil samples, for the depth soil samples they range from 63.19 to 72.01 μSv/y with a mean of 67.79 ± 3.44 μSv/y, for the sediment samples they range from 74.86 to 88.08 μSv/y with a mean of 81.16 ± 4.07 μSv/y and for the water samples they range from 32.16 to 37.88 μSv/y with a mean of 35.67 ± 1.82 μSv/y. For the Bholagonj region in this study, it varies from 52.46 to 105.1 μSv/y, with a mean value of 72.77 ± 20.83 μSv/y, and for the Jaflong region, it varies from 64.39 to 115.2 μSv/y with a mean value of 76.40 ± 22.07 μSv/y. Each of these is comparable with the world average value of 70 μSv/y [32].

The values of the External Hazard Index H_ex range from 0.27 to 0.29 with a mean of 0.26 ± 0.01 for surface soil samples; for the depth soil samples, they range from 0.29 to 0.34 with a mean of 0.32 ± 0.02; for the sediment samples, they range from 0.35 to 0.42 with a mean of 0.38 ± 0.02; and for the water samples, they range from 0.15 to 0.18 mSvh⁻¹ with a mean of 0.166 ± 0.008. The computed values of the External Hazard Index H_ex in rock samples from the Bholagonj area range from 0.26 to 0.49, with an average value of 0.35 ± 0.10, and for the Jaflong region, the calculated values range from 0.31 to 0.54, with an average value of 0.36 ± 0.11. Each calculated value is less than 1 and within the permitted limit given by the ICRP 60 [30].

The ELCR parameter for surface soil samples ranged from 0.18 × 10⁻³ to 0.22 × 10⁻³ with an average (0.19 ± 0.01) × 10⁻³. Similarly for depth soil samples, the values ranged from 0.22 × 10⁻³ to 0.25 × 10⁻³ with an average (0.23 ± 0.01) × 10⁻³. For sediment samples, the parameter ranged from 0.26 × 10⁻³ to 0.30 × 10⁻³ with the average value (0.28 ± 0.01) × 10⁻³. For water samples, it ranged from 0.11 × 10⁻³ to 0.13 × 10⁻³ with an average value (0.12 ± 0.06) × 10⁻³. For rock samples from the Bholagonj area, this parameter ranged from 0.18 × 10⁻³ to 0.36 × 10⁻³ with an average (0.25 ± 0.05) × 10⁻³. For rock samples from the Jaflong area, this parameter ranged from 0.22 × 10⁻³ to 0.40 × 10⁻³ with an average (0.29 ± 0.04) × 10⁻³. Values for sediment and rock samples are higher than the world average of 0.29 × 10^–3 [31].

A comparison of each radiological hazard parameter is also shown in Fig. 5 by bar diagrams.

In terms of intercomparison, the radiological hazard parameters for Bisnakandi, both surface and depth soil samples, are generally lower than those reported for other locations within Bangladesh, such as Savar, Ashulia, and Barapukuria. For instance, the radium equivalent activity (Ra_eq) values of 98.05 Bq/kg (surface) and 118.90 Bq/kg (depth) at Bisnakandi are notably below those of Savar & Ashulia (263.80 Bq/kg) and Barapukuria (249.50 Bq/kg). Similarly, the outdoor absorbed dose rates (D) and effective dose rates (D_eff) are also lower in Bisnakandi compared to these regions. However, when comparing Bisnakandi’s sediment samples, the values (142.30 Bq/kg) are slightly higher than those found at Inani Beach (135.20 Bq/kg) within Bangladesh, but remain lower than those at the Rooppur nuclear power plant site (201 Bq/kg). These results reflect regional variations in natural radioactivity levels and highlight Bisnakandi’s relatively moderate hazard potential compared to industrial or nuclear-adjacent areas. The radium equivalent activity is much lower than the values reported for sediment and soil, as expected. In terms of rock samples, Bisnakandi’s radiological hazard parameters are slightly lower than those observed in Jaintiapur and slightly above those from Patuartek Sea Beach, reflecting moderate radioactivity levels in rocks from this region. These comparisons emphasize that while the radiological hazard in Bisnakandi remains within safer limits, it is notably lower when compared to more industrialized or heavily mineralized areas.

Conclusions

Gamma spectrometry was used to measure the radioactivity concentration of soil, sediment, and water samples collected from the Bisnakandi region, and rock samples from the Bholagonj and Jaflong regions. No alarming data is noticed in any sample; activity concentrations of ²³²Th, ²²⁶Ra, and ⁴⁰K in the studied samples are found to be normal and comparable to similar studies in other regions and countries. The result indicates an insignificant level of radiological hazard parameters and implies low-level radiation exposure to inhabitants. Also, the absence of artificial radionuclide fallout can be expected as no noticeable amount of ¹³⁷Cs concentration is found. The study area can be marked as safe, and the experimental data can provide a guideline for future measurements to observe the environmental changes as Bangladesh is now a step ahead of its nuclear science development journey with its first nuclear power plant expected to become operational soon.

Acknowledgments

The authors Khairum Haque Orthi, Thuheda Sultana, and Abdul Hannan are very much grateful to the SUST Research Centre, Shahjalal University of Science and Technology (SUST), Sylhet, Bangladesh for its financial support under the research grant with Project ID: PS/2021/2/20.

Conflict of interest

The authors have no relevant financial or non-financial interests to disclose.

Funding

This work was supported by the SUST Research Centre, Shahjalal University of Science and Technology (SUST), Sylhet, Bangladesh (Project ID: PS/2021/2/20).

References