Assessment of radiological impacts of natural radionuclides and radon exhalation rate measured in the soil samples of Himalayan foothills of Uttarakhand, India

A study of 222Rn/220Rn exhalation rate and indoor 222Rn/220Rn levels in higher Himalayan terrain

The noble radioactive gas radon and its isotope thoron dominate terrestrial radiation in the indoor environment. These gases eventually disintegrate generating radioactive ions that readily adhere to aerosol particles. This study was conducted in a tectonically active location with significant radon concentrations. The obtained average values of radon mass exhalation and thoron surface exhalation rate from this study are higher than the global average values of 56 mBq kg-1 h-1 and 1000 mBq m-2 s-1, respectively. As the exhalation rates are higher, naturally the average radon and thoron concentrations are also greater than the worldwide average values of 40 and 10 Bq m-3, respectively. No significant correlation was observed between 222Rn and 220Rn exhalation rate and indoor 222Rn/220Rn concentration. The exposure dose due to 222Rn, 220Rn and their progenies shows no significant health risk.

Monitoring of terrestrial gamma dose rate from the Kumaun Himalayan region of the Bageshwar district in Uttarakhand, India

The present study is carried out in 42 sampling sites for the measurement of background gamma dose rate in six tehsils of the Bageshwar district that comes under the Kumaun Himalaya, Uttarakhand. The annual effective dose in the pre-monsoon and post-monsoon seasons was estimated from the measured values of the Gamma dose rate. It is found that the minimum and maximum values ranged between 0.01-0.39 mSv per y (Arithmetic Mean = 0.19 mSv per y) in the pre-monsoon and 0.11-0.42 mSv per y (Arithmetic Mean = 0.20 mSv per y) in the post-monsoon season of the year. The finding of the present study shows that the annual effective dose equivalent is higher than the worldwide average value recommended by the United Nations Scientific Committee on the Effects of Atomic Radiation.

Game-theoretic optimization of landslide susceptibility mapping: a comparative study between Bayesian-optimized basic neural network and new generation neural network models

Landslide susceptibility mapping is essential for reducing the risk of landslides and ensuring the safety of people and infrastructure in landslide-prone areas. However, little research has been done on the development of well-optimized Elman neural networks (ENN), deep neural networks (DNN), and artificial neural networks (ANN) for robust landslide susceptibility mapping (LSM). Additionally, there is a research gap regarding the use of Bayesian optimization and the derivation of SHapley Additive exPlanations (SHAP) values from optimized models. Therefore, this study aims to optimize DNN, ENN, and ANN models using Bayesian optimization for landslide susceptibility mapping and derive SHAP values from these optimized models. The LSM models have been validated using the receiver operating characteristics curve, confusion matrix, and other twelve error matrices. The study used six machine learning-based feature selection techniques to identify the most important variables for predicting landslide susceptibility. The decision tree, random forest, and bagging feature selection models showed that slope, elevation, DFR, annual rainfall, LD, DD, RD, and LULC are influential variables, while geology and soil texture have less influence. The DNN model outperformed the other two models, covering 7839.54 km2 under the very low landslide susceptibility zone and 3613.44 km2 under the very high landslide susceptibility zone. The DNN model is better suited for generating landslide susceptibility maps, as it can classify areas with higher accuracy. The model identified several key factors that contribute to the initiation of landslides, including high elevation, built-up and agricultural land use, less vegetation, aspect (north and northwest), soil depth less than 140 cm, high rainfall, high lineament density, and a low distance from roads. The study's findings can help stakeholders make informed decisions to reduce the risk of landslides and ensure the safety of people and infrastructure in landslide-prone areas.

A review on radionuclide pollution in global soils with environmental and health hazards evaluation

Human populations are being exposed to a wide spectrum of radiation from soils as a result of the availability of radiation sources. Assessing the ecological and health effects of radionuclides in soils is crucial to support the optimal soil management practices but large-scale studies are limited. This study compiled data on radionuclides (226Ra, 232Th, 40K, 238U, and 137Cs) in soils located across the world (44 countries and 159 places) between 2008 and 2022 and applied radiological hazards indices and several multivariate statistical approaches. The average activity concentration (Bq/kg) of 226Ra, 232Th, 40K, 238U, and 137Cs were 408.56, 144.80, 508.78, 532.78, and 83.12, respectively, whereas 226Ra, 232Th, 40K, and 238U exceeded the standard limits. The principal component analysis explained more than 91% of variation in soils. Based on the geoaccumulation index, 40K posed moderately to heavy contamination whereas 238U and 226Ra posed moderate contamination in soils. Moreover, the mean values of radiological hazards evaluation such as radium equivalent activity (487.17 Bq/kg), external radiation hazard indices (1.32), internal hazard indices (2.15), absorbed dose rate (247.86 nGyh-1), annual effective dose rate (1.82 mSvy-1), activity utilization index (4.54) and excess lifetime cancer risk (63.84 × 10-4) were higher than recommended limit suggesting significant radiological risks in study region soils. The findings indicated that the study area soils were contaminated by radionuclides and unsafe for hazards in terms of the health risks linked with studied radioactive contents. The study is valuable for mapping radioactivity across the globe to determine the level of radioactivity hazards.

Measurement of radon concentration in soil gas and radon exhalation rate from soil samples along and across the Main Central Thrust of Garhwal Himalaya, India

The present study focuses on measuring radon concentrations in soil gas at various depths, radon exhalation rate (surface and mass) from soil samples, and gamma dose rate along and across the Main Central Thrust of Garhwal Himalaya, India. Radon concentration in soil gas, surface, and mass exhalation rates was measured using a portable SMART radon monitor (RnDuo). Furthermore, the gamma dose rate was measured using a pocket radiation monitor. The soil gas radon concentration varied from 15 ± 4 to 579 ± 82 Bq m-3 at a depth of 25 cm, 10 ± 2 to 533 ± 75 Bq m-3 at a depth of 30 cm, and 9 ± 1 to 680 ± 95 Bq m-3 at a depth of 35 cm. The surface and mass exhalation rates were found 3 ± 0.7 to 98 ± 3 Bq m-2 h-1 (with AM ± SD = 36 ± 28 Bq m-2 h-1) and 1 ± 0.2 to 95 ± 2 mBq kg-1 h-1 (with AM ± SD = 30 ± 22 mBq kg-1 h-1), respectively. The gamma dose rate for the present study area varies from 0.11 ± 0.05 to 0.28 ± 0.05 µSv h-1 with a mean value of 0.17 ± 0.05 µSv h-1. The correlation analysis between the exhalation rates (mass and surface) and radon concentration of soil gas at various depths was carried out in the current study.

Advances in the management of radioactive wastes and radionuclide contamination in environmental compartments: a review

Several anthropogenic activities produce radioactive materials into the environment. According to reports, exposure to high concentrations of radioactive elements such as potassium (⁴⁰K), uranium (²³⁸U and ²³⁵U), and thorium (²³²Th) poses serious health concerns. The scarcity of reviews addressing the occurrence/sources, distribution, and remedial solutions of radioactive contamination in the ecosystems has fueled data collection for this bibliometric survey. In rivers and potable water, reports show that several parts of Europe and Asia have recorded radionuclide concentrations much higher than the permissible level of 1 Bq/L. According to various investigations, activity concentrations of gamma-emitting radioactive elements discovered in soils are higher than the global average crustal values, especially around mining activities. Adsorption technique is the most prevalent remedial method for decontaminating radiochemically polluted sites. However, there is a need to investigate integrated approaches/combination techniques. Although complete radionuclide decontamination utilizing the various technologies is feasible, future research should focus on cost-effectiveness, waste minimization, sustainability, and rapid radionuclide decontamination. Radioactive materials can be harnessed as fuel for nuclear power generation to meet worldwide energy demand. However, proper infrastructure must be put in place to prevent catastrophic disasters.

Radon and thoron exhalation rate in the soil of Western Haryana, India

This study reports the exhalation rates of radon and thoron from surface soil collected from 60 rural sites of district Hisar, Haryana, India. The exhalation rates of Rn²²² (radon) and Rn²²⁰ (thoron) were measured by portable SMART RnDuo (AQTEK SYSTEMS) using a mass accumulation chamber which was equipped with a scintillation material-coated cell. Dose rates due to natural gamma radiations ranged from 0.526 to 1.139 mSv y^-1. The Rn²²² mass exhalation rate in soil samples varied from 0.14 to 94.65 mBq kg^-1 h^-1. Thoron surface exhalation rates ranged from 46.42 to 619.88 Bq m^-2 h^-1. This study gives an idea about the differences in Rn²²² and Rn²²⁰ exhalation at different locations which may be due to variations in geological features of the locations and characteristics of the topsoil. The findings show that usage of study area soil as building material is safe.

Application of RESRAD and ERICA tools to estimate dose and cancer risk for artisanal gold mining in Nigeria

Despite the fact that disruption of the environment through mining of minerals poses severe radiological hazards, there is a dearth of radiological information from gold mining sites in Nigeria. In this study, state-of- the-art computational tools - RESRAD ONSITE, RESRAD OFFSITE and ERICA were applied to a typical representative artisanal goldmining area for a more comprehensive evaluation of radiological risks associated with artisanal gold mining in Nigeria. The estimated doses received by an offsite receptor is within the radiation basic safety limit, while for onsite receptor it is greater than the basic radiation safety limit. It was observed that onsite dwellers of the artisanal goldmining areas may suffer high cancer burden when compared with the US EPA acceptable levels. For non-human biota, the hazard quotient was greater than unity and the total dose rate per organism was greater than the screening dose rate of 10μGy h^-1. It was observed that ²³²Th and ²²⁶Ra were the main contributors to the total dose and the pathways that contributed most to the dose were; external exposure (via direct and airborne radiation from soil and Radon) as well as water independent plant, meat and milk consumption. Therefore, monitoring food production will lead to an informed decision making and risk communication towards sustainable mining will contribute in minimizing the level of the anticipated risks as low as reasonably achievable.

Human exposure levels to ionizing radiation in Agbara Industrial Estate: an impact of Industrial activities in Nigeria

A total of fifty-five soil samples were collected from four locations, namely, residential, industrial, dumpsite, and sewage in Agbara industrial estate, Ogun state, Nigeria. The samples were analyzed using a high purity germanium detector (HPGe) to measure the activity concentration of radionuclides. Background radiation measurements were also taken at each point where soil samples were collected using Geiger Muller (GM) counter. The mean activity concentrations measured in the soil samples were 171.33 for ⁴⁰K, 9.11 for ²³²Th, and 5.05 for ²²⁶Ra in Bq/kg. The mean absorbed dose rate in the air due to radionuclides (⁴⁰K, ²³²Th, and ²²⁶Ra) in the soil is calculated to be 14.77 nGy/h, and the mean annual effective dose equivalent (AEDE) is 0.02 mSv/year. The mean equivalent dose rate (EDR) from GM counter for background radiation is 0.22 μSv/h, and the mean annual effective dose rate (AEDR) is 0.39 mSv/year. These values are below the world average values, except EDR and AEDR with mean values higher than the world standard. The comparison of radiation dose rates revealed that radionuclides contributed 6.7% to background radiation. The equivalent dose (ED_organs) for various organs of the body was calculated, and results showed that values do not pose any immediate health hazard. The excess lifetime cancer risk (ELCR) due to exposure to background radiation indicated that the dwellers and industrial workers in the study area may develop cancer over a lifetime due to accumulated dose.