ABSTRACT In recent years, climate change-induced drought has increasingly led to water shortages for domestic and industrial use in Dong Nai Province, Vietnam. Within this province, the Tri An hydropower reservoir plays a crucial role in the sustainability of regional water resources. This study aims to assess groundwater recharge mechanisms in the lower Tri An hydropower reservoir (LTAHR) region using isotopic technique based on the water stable isotope ratios (δD and δ¹⁸O) in groundwater, surface water and local precipitation. The results obtained indicate that the stable isotope values of precipitation in the region exhibit significant seasonal variations, whereas that values of surface water in the reservoir maintains more stability. On the other hand, stable isotopic compositions in groundwater are significantly influenced by monsoonal activity and temperature fluctuations. Applying the end-member mixing analysis (EMMA) method, the study revealed that surface water is the primary contributor to groundwater recharge, accounting for 60–85 %, while precipitation contributes 15–40 %, depending upon the season. Thus, the change of water storage level in the Tri An hydropower reservoir, along with the impacts of El Niño and climate variability, may disrupt seasonal water balance and significantly reduce annual groundwater recharge.

ABSTRACT Stable isotopes are crucial for understanding water cycles and climate dynamics, particularly in tropical regions. However, establishing and maintaining precipitation sampling stations in Southeast Asia is challenging due to high costs and logistical issues. Consequently, many areas in this region have limited or no sampling stations with adequate stable isotope data. To address this problem, developing models that simulate stable isotope contents using machine learning (ML) techniques, especially deep learning, is a promising solution. In this study, the influence of large-scale climate modes (teleconnection indices) and local meteorological parameters on the stable isotope contents of precipitation was examined across six key stations in Southeast Asia, including Bangkok, Kuala Lumpur, Jakarta, Kota Bharu, Jayapura, and Singapore. A deep neural network (DNN) model was applied for simulation, and its performance was compared with a partial least squares regression (PLSR) model using various evaluation metrics. The DNN consistently demonstrated superior accuracy across all studied stations, highlighting the efficacy of DNNs, in accurately simulating stable isotope contents in tropical precipitation. The importance ranking derived from the SHapley Additive exPlanations (SHAP) technique aligns perfectly with the results obtained from the DNN importance function. In addition, the SHAP summary plot highlights the contributions of key features, such as precipitation and potential evaporation, to the model's predictions. The dependence plots further illustrate the relationship between these features and the predicted response, revealing nonlinear interactions that influence model behaviour. This research provides new insights into the complex interactions between large-scale climate drivers and local weather patterns, advancing the use of ML for isotope-based climate studies. The techniques used in this study offer a framework for applying ML to isotope analysis in tropical climates and can be extended to similar regions worldwide.

ABSTRACT Environmental radioactivity is significantly elevated by coal combustion, posing risks to communities living near coal-fired thermal power plants (CFTPPs). This study presents the first comprehensive assessment of radiological impacts around the Rampal Thermal Power Plant, a 1320 MW facility located in Rampal Upazila, near the UNESCO World Heritage site of Sundarbans, Bangladesh. Thirty soil samples were systematically collected from distances of 100, 500, 1000, 2000, and 3000 m from the power plant. The activity concentrations of 226Ra, 232Th, and 40K in soil ranged from 17–31, 29–51, and 350–670 Bq kg–1, respectively, with a few samples exceeding the population-weighted global averages for 226Ra (32 Bq kg–1) and 232Th (45 Bq kg–1), and almost all the samples exceeding the average for 40K (420 Bq kg–1). The elevated levels of 226Ra, 232Th, and 40K in the soil samples can be attributed to several interconnected factors, including the presence of thorium-rich minerals such as monazite and zircon, granitic geological formations, and anthropogenic inputs like bottom ash discharge from the plant and coal combustion byproducts. While the radium equivalent activity and hazard indices generally fell within safety limits, the higher outdoor and indoor absorbed dose rates, effective doses, and increased lifetime cancer risk raised alarms about potential health threats for nearby residents over time. Moreover, the long-term radiological effects on the Sundarbans ecosystem could disturb its fragile balance, impacting both biodiversity and the local communities that rely on its resources. These results highlight the necessity for further evaluations and remediation efforts to ensure the safe use of these soils in agricultural and construction activities. This research also seeks to develop a radiological distribution map, which will provide crucial baseline data for the forthcoming Rooppur Nuclear Power Plant.

ABSTRACT In Harnai, Balochistan, Pakistan, the levels of 226Ra and 222Rn were measured with a high purity germenium (HPGe) detector and a RAD7 detector, respectively, in drinking water. The concentration of 222Rn in the spring water under investigation ranged from 2.8 ± 0.59–8.5 ± 0.80 Bq L−1 with an average of 4.96 ± 0.7 Bq L−1, while the concentration of 226Ra varied from 1.36 ± 0.55–6.8 ± 0.99 mBq L−1 with an average of 3.54 ± 0.74 mBq L−1. All concentrations of 222Rn and 226Ra were found to be below the global averages of 11.1 Bq L–1 and 555 mBq L−1, respectively. There was a positive connection (R2 = 0.9398) between the concentrations of 222Rn and 226Ra. There are very weak associations between phyco-chemical characteristics and 222Rn and 226Ra. For various age groups, the estimated annual effective dosages from ingesting of 226Ra and 222Rn were determined to be below the advised threshold of 0.1 mSv y−1. Based on the results, it has been concluded that the population in the research region is not significantly affected by 226Ra and 222Rn in spring water.

ABSTRACT In this paper, the results of indoor radon level measurements in thirteen single-family houses, on different floors, are presented. The measurement was performed using the AlphaE radon metre device, and in each house, the measurements lasted six days, on average. The mean values of the radon activity concentration were in the range of 32.32–525.65 and 18.41–185.25 Bq m−3 for the ground floor and first floor rooms, respectively. The results of the statistical analyses on the variation of the radon level have shown that in nine houses (69 %), there is a significant difference in radon levels, with higher levels on the ground floor compared to the first floor. The variations of the radon levels during the night and daytime hours were also statistically analysed.

ABSTRACT Farmers and residents of homes built with soil bricks may be impacted by naturally occurring radionuclides in farmed soil. Using high purity germanium (HPGe) and sodium iodide (NaI) detectors, soil samples from apple orchards in Pishin have been examined to look into radioactive materials and related health impacts. The average values of 226Ra were 22.71 and 15.19 Bq kg−1, respectively, while those of 232Th were 29.84 and 14.62 Bq kg−1, respectively. The values of 40K were 329.48 and 113.08 Bq kg−1 using HPGe and NaI detectors, respectively. It was discovered that each of these values was below the 35, 45, and 420 Bq kg−1 permissible limits. Positive correlations (R 2 = 0.912 for 226Ra), (R 2 = 0.9148 for 232Th) and (R 2 = 0.9026 for 40K) were found among the results obtained from HPGe and NaI detectors. The average radium equivalent activity (Raeq) values obtained from both methods were 90.77 and 44.81 Bq kg−1, respectively, which were lower than the world average. The average results for outdoor and indoor absorbed doses and outdoor and indoor annual effective doses from the HPGe and NaI detectors were also found to be within the respective permissible limits. It was discovered that the alpha (Iα) and gamma (Iγ) indices were below the limit. Thus, it is determined that farmers and residents of homes constructed with soil bricks are not at risk for any health problems from the soil in the studied region.

ABSTRACT Assessing soil radioactivity and associated risks in areas surrounding gas fields is essential due to potential natural radionuclide accumulation during extraction activities. This study investigates the radioactivity levels in surface soil from the Haripur gas field. 21 soil samples were analyzed using a high purity germanium (HPGe) detector. The activity concentrations of 226Ra, 232Th, and 40K in the soil samples were found to range between 11–19, 20–38, and 280–500 Bq kg–1, respectively. All 226Ra values and the majority of 232Th and 40K values fell within the global average levels for soil, which are 35, 30, and 400 Bq kg–1, respectively. Radiation hazard indices were found to be below the internationally accepted safety limits set by organizations such as the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) and the International Commission on Radiological Protection (ICRP), indicating that the soil poses no significant radiological risks for construction and agricultural applications. This research offers essential baseline data on soil radioactivity at the Haripur gas field, supporting public health, environmental protection, and regulatory compliance efforts.

ABSTRACT Humans are daily exposed to natural background radiations. These are from terrestrial, extra-terrestrial, and anthropogenic radiation sources. Soil is one of the largest contributors to terrestrial radioactivity. The aim of this research was to assess the concentrations of the primordial radionuclides uranium (238U), thorium (232Th) and potassium (40K) as well as radiological hazard parameters in soil samples selected from Al-Salam playground in Al-Najaf governorate of Iraq. Gamma ray spectroscopy and a CR-39 detector were used to evaluate both external exposure and internal exposures arising from radon concentrations, respectively. The average activity concentration (Bq kg–1) for 238U, 232Th, and 40K were 17.48 ± 1.89, 8.59 ± 0.77, and 298.31 ± 18.40, respectively. Quantified radiological risk factors were 116.23 ± 5.76 µR h–1 (exposure), 0.142 ± 0.007 (external hazard (Hex), 25.71 ± 1.28 nGy h–1 (absorbed dose rate (Dr), 0.031 ± 0.001 (annual effective dose outdoor (AEDoutdoor), and 0.110 ± 0.005 (cancer risk (ELCR × 10–3), respectively. It was concluded that all values of the activity concentration for natural radionuclides and radiological hazard parameters in study area were within safe limits based on standards set by UNSCEAR, ICRP, and OECD.

ABSTRACT Natural radioactivity is receiving a lot of attention worldwide due to its essential role in human health. Sugar is a generic term for sweet, soluble carbohydrates, many of which find their way into food. Therefore, measuring natural radioactivity is critical as it has a direct impact on human safety. This research analyzed natural radionuclide activity levels in 22 samples of commonly consumed sugar from the Kurdistan Region of Iraq. High-purity germanium (HPGe) detectors are used in gamma-ray spectrometers. Measurements in this study showed that 226Ra activity concentrations ranged from below minimum detectable activity (BMDA) to 5.16 ± 2.55 Bq kg−1 with an average value of 0.80 ± 0.15 Bq kg−1. In contrast, 232Th radionuclide activity concentrations ranged from BMDA to 3.11 ± 1.67 Bq kg−1 with an average value of 0.51 ± 0.10 Bq kg−1. Also, the activity concentration of 40K ranged from BMDA to 30.71 ± 10.77 Bq kg−1 with a mean of 6.44 ± 2.54 Bq kg−1. Based on these results, a radiation risk index associated with sugar intake was calculated. It was verified that the radiation exposure due to sugar consumption in the Kurdistan Region of Iraq was below the permissible level of 290 μSv y−1, and did not pose a radiation risk to public health.