Determination of naturally occurring radionuclides in selected rocks from Hetaunda area, central Nepal

Assessment of natural radioactivity levels and hazard indicators in Tarakeshwor Municipality, Nepal through in-situ technique and multivariate analysis

The evaluation of primordial radionuclide concentrations in rapidly urbanized and concrete-laden areas through the importation of construction materials from various regions of Nepal is both important and essential. This study utilized a portable gamma-ray spectrometer (PGIS 2) to analyze the distribution of three natural radionuclides: uranium (238U), thorium (232Th), and potassium (40K) in Tarakeshwor Municipality, Kathmandu, Nepal. The measured dose rates ranged from 70.22 nSv hr-1 to 163.66 nSv hr-1, with an average of 124.65±20.29 nSv hr-1, surpassing the global average of 59 nSv hr-1. The activity concentrations of 40K, 238U, and 232Th exceeded global averages, indicating relatively higher natural radioactivity concentrations in the region. Specifically, the average values for 40K, 238U, and 232Th were 935.26±172.30 Bq kg-1, 80.47±15.53 Bq kg-1, and 80.44±18.58 Bq kg-1, respectively. The calculated radium equivalent (Ra eq ) ranged from 132.26 to 351.22 Bq kg-1, and the annual gonadal equivalent dose (A G E D ) varied from 372.61 to 1028.81 μSv yr-1. The annual effective dose rates for indoor and outdoor environments were 0.54±0.09 mSv yr-1 and 0.15±0.03 mSv yr-1, respectively, both exceeding the global average. The representative level index (RLI) within the study area averaged 1.96±0.32, indicating an elevated radiation risk. The excess lifetime cancer risk (E L C R ) values for outdoor and indoor environments were 0.52× 10 - 3 ±0.09 × 10 - 3 and 1.87 × 10 - 3 ±0.31× 10 - 3 , respectively, surpassing the world average. Additionally, external hazard indices (H ex ) ranged from 0.36 to 0.59, while internal hazard indices (H in ) ranged from 0.38 to 1.20, both indicating values higher than UNSCEAR recommendations. These findings underscore the necessity for further experimental analysis employing ex-situ equipment. The data generated in this study can provide a valuable baseline for future assessments and interventions in radiation risk management guidelines within the country.

Assessing radioactive contaminants in Kathmandu soils: measurement and risk analysis

Soil samples from vegetable farmland in densely populated wards of Nepal were analyzed for natural radionuclide levels, employing a NaI(Tl) 3" [Formula: see text] 3" gamma detector. The study aimed to evaluate the causes of radiation risk, attributing it to soil contamination resulting from the rapid urbanization and concretization that followed the earthquake in 2015. The activity concentration of radium-226, thorium-232, and potassium-40 and the ranges observed are 2.080±0.084-33.675±1.356 Bq kg[Formula: see text], 17.222±0.198-119.949±1.379 Bq kg[Formula: see text], and 11.203 ± 0.325-748.828±21.716 Bq kg[Formula: see text], respectively. The average values obtained for hazard indices are as follows: radium equivalent activity (82.779 Bq kg[Formula: see text]), absorbed dose rate (36.394 nGy h[Formula: see text]), annual effective dose equivalent (0.045 mSv yearr[Formula: see text]), gamma index (0.291), external hazard index (0.224), internal hazard index (0.253), excess lifetime cancer risk (0.159), annual gonadal dose equivalent (243.278 mSv year[Formula: see text]), alpha index (0.054), and activity utilization index (0.716). However, in most places, thorium-232 concentration is greater than those of the world average and recommended values. In specific locations such as Ward 4 in Baluwatar, the soil was found to have concentrations of Ra[Formula: see text] and K[Formula: see text] exceeding recommended limits. Despite this localized concern, the overall analysis of hazard indices across the studied areas revealed that most values were within permissible limits. This suggests that, on a broader scale, radiation exposure may not be a significant concern in the investigated regions. Nonetheless, the study recommends regular monitoring in additional locations to ensure a comprehensive and ongoing assessment of radiation levels.

Monitoring of radionuclides in soil and bone samples from Austria

The activity concentrations of anthropogenic (⁹⁰Sr, ¹³⁷Cs) and natural (²³⁸U, ²³²Th, ⁴⁰K, ²¹⁰Pb) radionuclides were determined in eight soil profiles from three different regions in Austria (Styria, Carinthia and Salzburg). A direct correlation between the activity concentration of ⁹⁰Sr and ¹³⁷Cs in soil samples and site altitude was found. ⁹⁰Sr and ²¹⁰Pb activity concentrations were also determined in bone ash of deer hunted in these regions. Additional bone samples were collected all over Austria. Totally 39 deer bones were investigated for this work, and some values were adopted from our earlier publications to give an overview of samples collected from sites covering a broad range of altitudes. The bone and soil samples were collected in the time period of 2001-2009. The ⁹⁰Sr values in deer bones are directly proportional to the values in the respective soil samples and also to the age of the animals. For the ⁹⁰Sr and ²¹⁰Pb determinations in bone samples first Pb was separated on a Dowex column, then Sr was purified using Sr·Spec® resin. In soil samples an additional hydroxide precipitation was employed to eliminate interfering iron. For the first time also the 3M Empore® Sr Rad disk method was successfully applied to bone samples. With this method the chemical procedure can be shortened by more than a factor of 2. The ⁹⁰Sr and ²¹⁰Pb fractions were measured by liquid scintillation counting, while the chemical yields were determined by ICP-MS. The activity concentrations of ⁴⁰K, ²³⁸U, ²³²Th and ¹³⁷Cs in soil samples were evaluated using gamma-ray spectrometry. The investigation was part of the PhD work of the first author.