Natural radioactivity measurements and evaluation of radiological hazards in sediment ofOguta Lake, South East Nigeria

Estimation of natural radioactivity and radiological hazards in river sediments (sand) used as building materials in South Africa

This study presents an investigation into the natural radioactivity levels of 238U, 232Th, and 40K using a thallium-doped sodium iodide (NaI(TI)) detector and associated radiological hazards in river sediments, specifically sand, which serves as a crucial building material in the KwaZulu-Natal Province of South Africa. The assessment aims to provide insights into potential radiological risks posed by the utilization of these sediments in construction activities. The mean activity concentrations of 238U, 232Th, and 40K are 145.33, 38.67, and 362.67 Bq kg-1, 124.64, 60.60, and 353.00 Bq kg-1, 144.00, 48.80, and 371.00 Bq kg-1, 92.95, 52.00, and 368.75 Bq kg-1, 133.55, 45.60, and 324.40 Bq kg-1, and 109.50, 52.50, 381.50 Bq kg-1 for Umngeni River, Umsunduzi River, Ashburton Sarupen, Hammersdale, Kwanjobekazi, and Cator Ridge, respectively. The obtained values of the radiological hazard indices (radium equivalent activity, external hazard index, internal hazard index, and activity utilization index) were below the world average values reported for building materials. Therefore, the studied samples are radiologically safe for use as building materials in the study area because they may not constitute any severe radiological hazards to residents.

Natural radioactivity in crude oil-spilled soils of Baralue and Korokoro communities, Ogoniland, Nigeria, and the assessment of radiological risks using Monte Carlo simulations

Radiation measurements and their health hazard assessments were carried out in the crude oil spill-affected communities of Baralue and Korokoro in Ogoniland, Rivers State, Nigeria. The study utilized both in situ and laboratory methods. In situ measurements were taken with a GQ GMC-500/GMC-500 + digital Geiger Muller counter, while a cesium iodide (thallium-doped) gamma-ray spectrometer was used for laboratory measurements. Data were collected from forty (40) locations within the creeks with a history of crude oil spillage and ten (10) locations with no such history serving as control. For the in situ method, both the annual effective dose equivalent (AEDE) and excess lifetime cancer risk (ELCR) in the crude oil-impacted communities were higher than those in the non-crude oil-impacted areas, and all values are lower than the global average background radiation dose of 0.48 mSv year-1. Laboratory methods measured activity concentrations of naturally occurring radionuclides (40 K, 232Th, and 226Ra) to compute radiological parameters such as Dout, AEDE, Raeq, AGED, AUI, Iγ, Hout, Hin, and ELCR. These results indicated a slight increase in radiation levels and health hazards in the crude oil spillage areas compared to non-spillage areas, although they remained below the world permissible levels. This suggests that crude oil spillages may have altered natural radiation concentrations and increased radiological health hazards in the impacted areas. Additionally, in situ measurement values are higher than laboratory measurement values due to environmental radiation interference, unlike the controlled laboratory environment where gamma radiation was shielded from environmental and cosmic interference. Monte Carlo simulation results show that the study area has a minimal probability of cancer risks to the public as a result of exposure to external radiation.

Application of gamma spectrum analysis techniques for natural radioactivity measurements using NaI(Tl) detector

Sodium iodide (NaI(Tl)) scintillation detector is commonly used for gamma-ray spectrometric evaluations in airborne surveys and geophysical well logging. However, the applications related to environment monitoring are often encountered with challenges of low-level counting (LLC), demanding a high-resolution spectrometry system, such as a high purity germanium (HPGe) system. HPGe systems are expensive and cannot be used continuously due to the necessary supply of liquid nitrogen. In this paper, the possibility to use relatively poor resolution NaI(Tl) detector for measuring low-level radioactivity due to principal nuclides by spectrum unfolding has been explored. We quantified the activities of principal radionuclides, 232Th, 238U, and 40 K, in soil samples from NaI(Tl) spectral measurements by spectrum decomposition (SD) and matrix deconvolution (MD) techniques. The specific activities of radionuclides were statistically characterized with respect to the measurements made with HPGe detector. The comparison suggests that activities determined with NaI(Tl) detector were underestimated in the majority of cases. However, the activity of 238U measured with the MD method was overestimated. The results of SD were closer to the HPGe detector measurements as compared to the MD method. Considering the normal distribution of measurements from both detectors, correlation coefficients were computed that led to the development of linear regression models to numerically transform NaI(Tl) measurements to HPGe equivalent activities within statistically acceptable bounds. Thus, a low-resolution but high-efficiency NaI(Tl) detector provides a cost-effective and time-saving alternative to HPGe measurements for the routine environmental radioactivity surveys, since it offers continuous operation and provision for carrying in fields as well, which facilitates sample characterization and thereby quick assessment of radiological hazards.

Comparison of environmental radioactivity in road dust between a city and a megacity: geo-environmental evaluation, health risks, and potential remediation

This pioneering study represents a comprehensive comparative analysis of naturally occurring radioactive materials (NORMs: 226Ra (≈238U),232Th, 40K) on the roadside dust samples collected from a coastal city (Khulna) and a highly urban megacity (Dhaka), Bangladesh. The corresponding radioactivity was calculated based on Instrumental Neutron Activation Analysis of elemental abundances (uranium [U], thorium [Th], and potassium [K]). Averagen=30 radioactivity levels of 226Ra (≈238U), 232Th, and 40K in the road dust of Khulna city were 46.82 ± 24, 74.79 ± 25, and 541.14 ± 160.8, whereas in Dhaka city, they were 84.4 ± 13, 126 ± 11, and 549 ± 48 (Bq.kg-1), respectively. Khulna city had 1.3, 2.5, and 1.4 times greater 226Ra (≈238U), 232Th, and 40K radioactivity than the global average values, respectively. For Dhaka city, the following values were 2.42, 4.2, and 1.4 times elevated. The levels of radioactivity in Dhaka city are significantly higher than those in Khulna city; however, both cities have exceeded the world average values. The mechanisms for the enrichment and dispersion of NORMs from their fundamental source (surface soil) were studied, considering waterlogging, relative solubility-controlled leaching and translocation, climate conditions, and aerodynamic fractionations (dry and wet air deposition). The computation of standard radiological indices indicates risks to human health. Respiratory harm can be inflicted by α-particles originating from the radioactive decay products of 232Th and 238U. In addition to public awareness, policymakers should prioritize limiting the evolution of dust particles to mitigate the associated health risks.

Evaluation of natural radioactivity levels and radiation hazards of Nkalagu limestone deposit, southeastern Nigeria

Levels of natural radioactivity due to 40 K, 232Th, and 226Ra in limestone deposits and corresponding surface soil samples from the Nkalagu community of Ebonyi State were investigated. Gamma spectroscopic analysis using a NaI (TI) detector was employed to measure the activity concentrations (ACs) of the natural radionuclides in the collected samples. The average AC of 226Ra, 232Th, and 40 K was found to be 64.62 ± 11.63, 54.27 ± 8.52, and 313.06 ± 25.33 Bq/kg, respectively, in limestone, whereas in the soil, the value was 60.80 ± 11.71, 44.97 ± 10.74, and 185.90 ± 18.20 Bq/kg, respectively. Except for 40 K, the obtained mean ACs of the radionuclides were in excess of the worldwide averages reported by the United Nations Scientific Committee on the Effect of Atomic Radiation (UNSCEAR). The mean value of Raeq, Hex, Hin, Iγ, and AUI was obtained as 166.33 Bq/kg, 0.45, 0.62, 1.18, and 1.28, respectively, in the limestone, and 139.42 Bq/kg, 0.38, 0.54, 0.98, and 1.12, respectively, in the surface soil. The radiation doses in limestone ranged from 120.78-168.89 nGyh-1 and 63.86-88.88 nGyh-1 for indoor and outdoor, respectively, whereas in the soil, the range was 104.47-129.77 nGyh-1 and 54.60-68.02 nGyh-1 for indoor and outdoor, respectively. The total annual effective dose ranged from 0.671 to 0.937 mSvy-1 with an average of 0.800 mSvy-1 in limestone and 0.579 to 0.720 mSvy-1 with an average of 0.667 mSvy-1 in the soil. Values of representative gamma index and activity utilization index, and indoor and outdoor radiation doses in limestone were above the recommended world average of ≤ 1, and 84 nGyh-1 and 59 nGyh-1, respectively, suggesting a restriction in the use of the limestone in construction of houses. The study therefore recommends that the use of limestone in building construction, especially in house interiors, should be discontinued.

Radionuclides' Dispersion from Coal-Fired Brick Kilns: Geo-Environmental Processes, Potential Risks and Management

In order to investigate the distributions and possible dispersion mechanism(s) of naturally occurring radioactive materials (NORMs: 226Ra, 232Th, and 40K) from coal-based brick kilns, a systematic set (n = 60) of coal, ash, surface-soil, and subsurface soil samples were analyzed. High-quality analytical data of U, Th and K obtained from HPGe detector and TRIGA Mark-II research reactor-based neutron activation analysis were converted to the corresponding radioactivities. Average (n = 10) radioactivities of 226Ra, 232Th, and 40 K in coal samples were 15.6, 16.7, and 145.5 Bq.kg-1, respectively, where only 40 K surpassed the corresponding global mean value. Average (n = 10) radioactivities of 226Ra, 232Th, and 40 K in ash samples were 62.7, 88.5, and 521 Bq.kg-1, respectively, where only 226Ra was within the established limit. In soil samples, average (n = 40) activities of 226Ra, 232Th, and 40 K were 62.7, 95.1, and 641 Bq.kg-1, respectively, which have surpassed the corresponding worldwide mean values. The observed differences in activity levels between soil samples collected near and far from the kilns, as well as between topsoil and subsoil samples, suggest the presence of distinct transport mechanisms for NORMs within the pedosphere. Dispersions of NORMs from the brick kilns to the ambient pedosphere are largely governed by aerodynamic convection and hydrodynamic leaching. These mechanisms are also influenced by geochemical mobility and relative solubility of NORMs, as well as factors such as rainfall patterns and wind-flow direction. Radiological indices invoke long-term carcinogenic-risks, whereas aerodynamic convection of finer particles (coal fly ash) from chimneys can cause significant health hazards to the nearby dwellers. Scientific processes as well as public awareness are essential to mitigate the risks.

Exploring the alteration of environmental radioactivity in terms of compositional elements of heavy minerals in an anthropogenically affected urban river: Radiological and ecological risks assessment

This study explored the alteration of naturally occurring radioactive materials (NORMs: 226Ra (≈238U), 232Th, 40K) in an anthropogenically disrupted urban river-basin (Turag, Bangladesh) in terms of constitutional substances (Sc, Ti, V, Fe, La, Ce, Sm, Eu, Tb, Dy, Ho, Yb, Lu, Hf, Ta, W, Th, U) of heavy-minerals. Average activity concentrations of 226Ra (≈238U), 232Th, and 40K were 41.5 ± 12.9, 72.1 ± 27.1, and 639 ± 100 Bqkg-1, respectively which were relatively higher compared to crustal origin. ∑REEs, Ta, W, Th, and U were ~2 times higher compared to crustal values with Ce and Eu-anomalies. APCS-MLR and PMF receptor models were used to determine the various anthropogenic and/or geogenic sources of NORMs and elements. Layer-wise variations of NORMs and elements were observed to trace the response of sedimentary processes towards the incoming pollution load. Presence of REEs indicates moderate degree of ecological risk to aquatic biota. However, carcinogenic risk (3.84 × 10-4 Sv-1) were significantly higher than threshold limit.

Natural radionuclide profiles and radiological risks in soils and rocks of the Koytash-Ugam Range, Uzbekistan

This investigation quantifies the activity concentrations of natural radionuclides (226Ra, 232Th, and 40K) in the soils and certain rocks of the Koytash-Ugam Range, Uzbekistan, and assesses their radiological risks. Gamma-spectrometric analysis of soil and rock samples revealed activity concentrations ranging from 456.2 ± 56.0 to 813.9 ± 76.0 Bq kg-1 for 40K, 18.2 ± 6.3 to 70.0 ± 12.0 Bq kg-1 for 226Ra, and 30.1 ± 2.9 to 57.9 ± 10 Bq kg-1 for 232Th. This data indicates a heterogeneous distribution of radionuclides, informing radiation safety and health risk assessments on a global scale. The calculation of radiological hazard indices, including the alpha-index (ranging from 0.09 to 0.35), gamma-index (ranging from 0.40 to 0.73), and both internal (ranging from 0.40 to 0.54) and external (ranging from 0.36 to 0.54) hazard indices, was undertaken to ascertain potential health risks. The radium equivalent activity ranged from 108.4 to 199.3 Bq kg-1, and the absorbed dose rates were 51.0-93.3 nGy h-1 indoors and 96.6-178.2 nGy h-1 outdoors. These metrics underlie the estimated annual effective dose of 536.5-988.5 × 10-3 mSv y-1, highlighting the variability in radiation exposure. Additionally, the potential lifetime cancer risk was projected at 1770.4 to 3262.0 per million, with an annual gonadal dose equivalent of 361.9 to 655.5 μSv y-1, reflecting natural background radiation influence. The results underscore the importance of safe material use in construction and the necessity for routine natural radioactivity monitoring. Radon flux density (RFD) values within acceptable construction limits (26-176 mBq m-2 s-1) suggest the area's suitability for development, considering recommended safety guidelines. This study not only aids local environmental and public health frameworks but also enriches the international knowledge base, facilitating comparative studies for the advancement of global radiation protection standards. Through a detailed examination of radionuclide distribution in an under-researched area, our research highlights the critical need for integrated international approaches to natural radiological hazard assessment.

Elevated levels of environmental radioactivity in fluvial sediment: origin and health risk assessment

To study the geogenic processes of naturally occurring radioactive materials' (NORMs') distribution, a transboundary Himalayan river (Punarbhaba) is chosen due to its trivial anthropogenic impacts. In explaining the genesis of radionuclides, transition elements (Sc, Ti, V, and Fe), rare-earth-elements (REEs: La, Eu, Ce, Yb, Sm, and Lu), Ta, Hf, Th, and U were analysed in 30 riverbed sediments collected from the Bangladeshi portion of the river. Elemental abundances and NORMs' activity were measured by neutron activation analysis and HPGe-gamma-spectrometry, respectively. Averagen=30 radioactivity concentrations of 226Ra (68.4 Bq kg-1), 232Th (85.7 Bq kg-1), and 40K (918 Bq kg-1) were 2.0-2.3-fold higher, which show elevated results compared to the corresponding world mean values. Additionally, mean-REE abundances were 1.02-1.38-times higher than those of crustal origin. Elevated (relative to earth-crust) ratios of Th/U (=3.95 ± 1.84) and 232Th/40K and statistical demonstrations invoke Th-dominant heavy minerals, indicating the role of kaolinite clay mineral abundance/granitic presence. However, Th/Yb, La/V, Hf/Sc, and Th/Sc ratios reveal the presence of felsic abundances, hydrodynamic sorting, and recycling of sedimentary minerals. Geo-environmental indices demonstrated the enrichment of chemical elements in heavy minerals, whereas radiological indices presented ionizing radiation concerns, e.g., the average absorbed-gamma-dose rate (123.1 nGy h-1) was 2.24-fold higher compared to the threshold value which might cause chronic health impacts depending on the degree of exposure. The mean excess lifetime cancer risk value for carcinogen exposure was 5.29 × 10-4 S v-1, which is ∼2-times greater than the suggested threshold. Therefore, plausible extraction of heavy minerals and using residues as building materials can alleviate the two-reconciling problems: (1) radiological risk management and (2) fluvial navigability.

Fractionation of environmental radioactivity in road dust from a megacity: external and internal health risks

Naturally occurring radioactive materials (NORMs: 232Th, 226Ra, 40K) can reach our respiratory system by breathing of road dust which can cause severe health risks. Targeting the pioneering consideration of health risks from the NORMs in road dust, this work reveals the radioactivity abundances of NORMs in road dust from a megacity (Dhaka) of a developing country (Bangladesh). Bulk chemical compositions of U, Th, and K obtained from neutron activation analysis were converted to the equivalent radioactivities. Radioactivity concentrations of 226Ra, 232Th, and 40K in road dust ranged from 60-106, 110-159, and 488-709 Bq kg-1 with an average of 84.4 ± 13.1, 126 ± 11, and 549 ± 48 Bq kg-1, respectively. Estimated 226Ra, 232Th, and 40K radioactivities were, respectively, 1.7-3.0-, 3.7-5.3-, and 1.2-1.8-folds greater than the affiliated world average values. Mechanistic pathway of NORMs' enrichment and fractionation relative to the major origin (pedosphere) were evaluated concerning the water logging, relative solubility-controlled leaching and translocation, climatic conditions, and aerodynamic fractionations (dry and wet atmospheric depositions). Computation of customary radiological risk indices invokes health risks. Noticing the ingress of NOMR-holding dust into the human respiratory system along with the associated ionizing radiations, the computed radiological indices represent only the least probable health hazards. Nevertheless, in real situations, α-particles from the radioactive decay products of 232Th and 238U can create acute radiation damages of respiratory system. Policymakers should emphasize on limiting the dust particle evolution, and public awareness is required to alleviate the health risks.

Evaluation of soil radioactivity in the areas of underground nuclear explosions at the Pomuk gas field site in Uzbekistan

This study investigates soil radioactivity at the Pomuk gas field in Uzbekistan, a region with history of underground nuclear activity. Using a NaI (Tl) scintillation gamma spectrometer, soil samples were analyzed for concentrations of 232Th, 226Ra, 40K, and 137Cs. Concentrations were found to be in the range of 19.0-31.0 Bq/kg for 232Th, 12.0-32.0 Bq/kg for 226Ra, 450.0-634.0 Bq/kg for 40K, and 2.4-11.0 Bq/kg for 137Cs. Surface radon flux density was measured using a coal sorbent-based passive method, with values ranging from 26.1 to 79.0 mBq/m2s. Mean activity values for radium equivalent (Raeq) and gamma representative level index (Iγ) were calculated to be 75.2-96.5 Bq/kg and 0.3-0.4 Bq/kg, respectively. The absorbed airborne gamma dose rates (GDR) varied between 41.0 and 52.0 nGy/h, while annual effective dose rates (AEDR) were 0.3-0.4 μSv/year. The radiological risk assessment indicates the area is within safe limits for the population and environment, providing a foundation for future radiological monitoring programs.

Assessment of radiological indices and physiochemical characterization of sediments in Chashma Lake, Pakistan

Twenty surface sediment samples were gathered from Chasma Lake, deciding the radionuclides 137Cs, 226Ra, 228Ra, 232Th, and 40K and their associated hazard indices. The deliberate radionuclide activities of present research have been contrasted with earlier research, and acquired outcomes in the present study are found below the results in the world. The radiation hazard indices following the presence of natural radionuclides in sediment samples were estimated, and the results assigned the values of all the determined radiological indices found inside the worldwide suggested limits. It was concluded from the current review that the sediment of Chashma Lake is safe for construction and agriculture and does not make radiation dangerous to the nearby local area of the lake.

Evaluation of radon hazards at the rural settlements of Uzbekistan

The "passive" sorption detectors based on the activated charcoal together with scintillation spectrometry were utilized to measure radon flux density from the soil surface as well as volumetric activity of indoor radon at the dwellings of rural areas of Uzbekistan. Additionally, gamma dose rates as well as concentrations of natural radionuclides in soil and building materials samples were determined. Based on the values of natural radionuclides, common radiological indices have been calculated. It was found that varying greatly, 94% radon flux density values did not exceed 80 mBq/(m²·s), while volumetric activities of radon were in the range of 35-564 Bq/m³. The radium equivalent activity for studied soil and building materials samples were below the allowed limit of 370 Bq/kg. Computed gamma dose rates were in the range of 55.50-73.89 ƞGyh^-1 below the limit of 80 ƞGyh^-1 and annual effective dose rate 0.068-0.091 mSvy^-1, the average value of which was higher than the standard limit > 0.47 mSvy^-1. The gamma representative index range was 0.89-1.19 with an average of 1.002 which was higher than the standard limit of 1.0. The range of activity utilization index was equal to 0.70-0.86 with an average value 0.77 which was lower than the recommended level ≤ 2.0. And lastly, excess lifetime cancer risk index values were from 1.9 × 10^-4 to 2.5 × 10^-4 and were lower than the recommended value 2.9 × 10^-4 indicating low radiological risk. The results are consistent with the research conducted by other authors earlier, implying suitability of employing the method for the assessment of residential areas.

Assessment of natural radiation in contaminated automobile workshop soils

The presented study aims to identify and quantify the natural radionuclides activity concentrations on the top and sub-soils around mechanic workshops in Ojo and Ijegun, Lagos, Nigeria. Based on these measured radionuclides activity concentrations, radiological hazard indices are assessed. Twenty oil-contaminated soil samples were collected, and the levels of natural radionuclides activity are measured by applying gamma spectrometry The measured radionuclides with authoritative regularity are linked with the natural decay series of ²³⁸U (²²⁶Ra) and ²³²Th as well as the series of non-decay ⁴⁰K. The obtained results show that the mean radionuclides activity concentrations in the collected oil-contaminated soils samples are 14 ± 4 Bq kg^-1, 105 ± 55 Bq kg^-1, and 90 ± 33 Bq kg^-1, for ²²⁶Ra, ²³²Th, and ⁴⁰K respectively. It was founded that the ²²⁶Ra radionuclide is the lower present in the oil-contaminated soils samples. The radiological assessments were evaluated in terms internal hazard index (0.54), and external hazard index (0.55) both of which are below the UNSCEAR-2000 standard limit. Consequently, the radiological assessment indicated that long-time exposure to those radionuclide's strength confuses integral hazards.

Primordial radionuclides in the dust samples from the educational institutions of central Bangladesh: radiological risk assessment

For the first time, this study presents the radio-activity concentrations of primordial radionuclides in a suite of classroom-dusts collected from 23 schools in central part of Bangladesh. Bulk elemental compositions from instrumental neutron activation analysis (INAA) were transformed into accompanied radio-activity contents (Bq.kg-1). Mean activity contents of 226Ra, 232Th, & 40K in dust samples were 86.0, 43.4, and 448 Bq.kg-1, respectively, which were comparatively elevated relative to the relevant world average value. Higher NORMs abundances were due to the surface soil weathering and aerodynamic fractionations. Estimation of typical radiological-risk indices demonstrates human health risks. Bearing in mind that the greater susceptibility of school-going juveniles & children to the ionizing-radiations & the entering of NORMs-comprising dust-particle into human lungs, calculated radiological indices merely represent the least potential risk. However, in actual cases, α-particles from the 238U and 232Th-decay series can create significant radiation-damage to the respiratory-system.

Environmental geochemistry of higher radioactivity in a transboundary Himalayan river sediment (Brahmaputra, Bangladesh): potential radiation exposure and health risks

This study of a downstream segment (Brahmaputra, Bangladesh) of one of the longest transboundary (China-India-Bangladesh) Himalayan rivers reveals elevated radioactivity compared to other freshwater basins across the world. Naturally occurring radioactive nuclides (²²⁶Ra, ²³²Th, and ⁴⁰K) and metal contents (transition metals, Fe, Ti, Sc, and V; rare earth elements, La, Ce, Eu, Sm, Dy, Yb, and Lu; high field strength elements, Ta and Hf; and actinides, Th and U) in thirty sediment samples were measured by HPGe γ-spectrophotometry and research reactor-based neutron activation analysis, respectively. We systematically investigated the mechanism of the deposition of higher radioactivity concentrations and rare earth elements (REEs) associated with heavy minerals (HMs) and photomicrograph-based mineralogical analysis. The results show that total REEs (∑REE) and Ta, Hf, U, and Th are generally 1.5- to 3.0-fold elevated compared to crustal values associated with -δEu and -δCe anomalies, suggesting a felsic source provenance. The enrichment of light REEs (×1.5 upper continental crust (UCC)) and Th (×1.9 UCC), besides Th/U (=7.74 ± 2.35) and ²³²Th/⁴⁰K ratios, along with the micrographic and statistical approaches, revealed the elevated presence of HMs. Fluvial suspended sedimentary transportation (from upstream) followed by mineralogical recycling and sorting enriched the HM depositions in this basin. Bivariate plots, including La/Th-Hf, La/Th-Th/Yb, and La/V-Th/Yb, revealed significant contributions of felsic source rock compared to mafic sources. The assessment of radiological hazards demonstrates ionizing-radiation-associated health risks to the local residents and people inhabiting houses made from Brahmaputra River sediments (as construction material).

Assessment of Natural Radionuclide Distribution Pattern and Radiological Risk from Rocks in Precambrian Oban Massif, Southeastern Nigeria

A gamma spectrometric analysis of rock samples collected from the Precambrian Oban Massif, southeastern Nigeria, was performed to determine some primordial radioelements’ activity concentrations: U-238, Th-232, and K-40, and their associated radiological hazards. The mean activity of the primordial radionuclides was determined to be 1073.06 ± 0.65, 160.74 ± 1.32, and 250.76 ± 0.91 Bq·kg−1 for 40K, 238U, and 232Th, respectively, showing that they are inhomogeneously distributed, with activity changing with the rock type and location. The activity concentrations are highest in biotite garnet schist, quartz diorite, and biotite gneiss rock domains. The mean values of the radiological hazards are 0.08 Bq·kg−1 (alpha index), 2.15 Bq·kg−1(gamma index), 2.06 Bq·kg−1(internal) and 1.63 Bq·kg−1 (external4.30 Bq·kg−1(representative level index6), 602.23 Bq·kg−1, (radium equivalent), 780 nGy·h−1 (total absorbed dose rate), 270.91 nGy·h−1 (indoor), 509.78 nGy·h−1 (outdoor), 624.99, 1329.07 and 1954.06 mSv·yr−1 (outdoor, indoor and total annual effective dose equivalent, respectively), 6448.40 (cumulative excess lifetime cancer risk) and 248.94–3761.47 Bq·kg−1 (annual gonadal dose equivalent). These results are higher than their various permissible limits (except at Ako Community) and suggest that rocks in the area may be unsuitable for constructing dwelling places. It is strongly advised that basic safety standards and precautionary measures recommended by the European Commission should be strictly adhered to while dealing with these rocks.

Radiological risk assessment in sediment of Namal Lake, Mianwali, Pakistan

This study is concentrated on the radiological risk assessment of sixteen surface sediment samples recovered from Namal Lake, District Mianwali, Punjab, Pakistan. The activity of ¹³⁷Cs, ⁴⁰ K, ²²⁶Ra, ²²⁸Ra, and ²³²Th was carried out with the help of a high purity germanium detector (HPGe) in the sediment, varied in the ranges of > 0.02-3.73 ± 1.31, 98.32 ± 21.45-341.02 ± 58.67, 18.34 ± 2.16-34.23 ± 4.34, 1.62 ± .30-2.34 ± .52, and 0.14 ± 0.10-2.34 ± 0.59 Bq kg^-1 with average values 0.74 ± 0.29, 237.26 ± 37.97, 25.06 ± 4.74, 1.97 ± 0.39, and 1.73 ± 0.33 Bq kg^-1, respectively. The measured concentrations in the current study have been compared with other earlier studies in the world. The data was also used for determining the other useful parameters like radium equivalent activity, absorbed dose rate, annual effective dose rate, and external and internal hazards index to assess the radiological risk assessment for the environment around the study area. The ERICA Tool software was also applied for radiological risk assessment for lake fish due to the radioactivity present in the lake sediments. It was concluded from the results of ERICA tool that the risk quotient in this study is less than one indicating that no toxic effects of radioactivity for Namal Lake fish.

DETERMINATION OF NATURAL RADIOACTIVITY AND RADIOLOGICAL HAZARD ASSOCIATED WITH SEDIMENTS SOURCED FROM OGUNPA RIVER CHANNELS, IBADAN, NIGERIA

The natural radionuclides content and radiological assessment of sediments of the Ogunpa waste-water channel were evaluated to ascertain the radiological safety of the sediments as a building material. The mean activity concentrations of 40K, 226Ra and 232Th in Bq kg-1 were found to be 171 ± 69, 11 ± 5 and 10 ± 4, respectively. The overall mean radium equivalent 29 ± 13 Bq kg-1 was <370 Bq kg-1 that can give the maximum recommended dose of 1 mSv to the general public. The activity concentrations of the radionuclides were all less than world average for soils and sediments. Thus, the use of the sediments from the Ogunpa water channel as building material is safe and would not pose any significant radiological health hazards.

Mechanism of elevated radioactivity in Teesta river basin from Bangladesh: Radiochemical characterization, provenance and associated hazards

This work presents a river basin (Teesta River, Bangladesh) which possesses significantly higher radioactivity compared to other freshwater basins around the globe. A total of thirty sediment samples were collected to determine the naturally occurring radionuclides (²²⁶Ra, ²³²Th, and ⁴ K)and elemental abundances using the HPGe gamma spectrometry and instrumental neutron activation analysis (INAA), respectively. To understand the provenance of higher radioactivity, the compositional elements (Sc, Ti, V, Fe, La, Ce, Sm, Eu, Dy, Yb, Lu, Hf, Ta, Th, and U) of heavy minerals are thoroughly studied, where ∑REEs (rare earth elements), Hf, Ta, Th, and U are ∼2 times higher than the crustal values with negative Ce and Eu anomalies. Mechanism to co-occurrence among radioactivity concentrations and REEs has been explored in this work. Enrichment of light rare earth elements ( × 2.01 UCC) and thorium ( × 2.8 UCC), and Th/U (=5.54 ± 1.05), ²³²Th/⁴ K ratio and statistical analyses demonstrate the presence of heavy minerals with monazite predominance. Accumulations of these minerals are most likely due to the fluvial suspended sediments transported by the hydrodynamic forces from up-stream. Elemental ratios including La/V, Th/Yb, Th/Sc, and Hf/Sc confirm the dominance of felsic-source over the mafic-components and the source of sediment has experienced major recycling and sorting during transportation. Evaluation of radiological risks invokes ionizing radiation related hazards to the local inhabitants and the householders residing in the buildings comprised with sandy river sediments. However, minute probability of REEs, Th, and U entrance to the human body through food chain can cause trivial health risks.

MEASUREMENTS OF SEASONAL VARIATIONS OF RADIOACTIVITY DISTRIBUTIONS IN RIVERINE SOIL SEDIMENT OF ADO-ODO OTA, SOUTH-WEST NIGERIA: PROBABILISTIC APPROACH USING MONTE CARLO

The radioactivity levels were measured using a hand-held gamma-ray survey meter and NaI (Tl) based gamma spectroscopy to evaluate the seasonal variation of radioactivity levels in the riverine area of Ado-Odo Ota. The measured iso-dose map reported higher gamma dose rate of 79 nGy/h, approximately 34% higher than the world average of 59 nGy/h. The values for U-238, Th-232 and K-40 activity levels ranged between 29.9 and 21.6; 103.2 and 31.2; 802.2 and 233.5 with mean values of 26.1, 55.6 and 499.3 Bq/kg, respectively. According to the mean, 5th and 95th percentiles of the probabilities using the Monte Carlo simulation, the Radium equivalent activities and the absorbed dose rates are within their respective recommended limits of 370 Bq/kg and 84 nGy/h. This study could be used to monitor dose rates and radiological risks for the areas covering the small area (Ado-Odo Ota) to the larger area (West African Region) as baseline data.

Baseline levels of natural radionuclides concentration in sediments East coastline of North Cyprus

In this study, surface sediment samples from the North Cyprus East coast of the Mediterranean Sea were collected to determine the concentrations of three main natural radionuclides (²²⁶Ra, ²³²Th, and ⁴⁰K) using a high-resolution HPGe gamma-spectroscopy system. The activity concentrations of ²²⁶Ra, ²³²Th, and ⁴⁰K in the selected sediment samples ranged from 11.5 to 31.6, 11.8 to 24.9, and 391.7 to 1014 Bq kg^-1 dw (dry weight), respectively. The concentration distribution analysis showed that the kurtosis statistics parameter was negative, and the concentration distribution was less peaked than the normal curve. The mean activity concentrations of ⁴⁰K (628.1 Bq kg^-1) in the sediment samples was higher than the worldwide average (420 Bq kg^-1) concentration. The radium equivalent activity, external hazard, internal hazard and gamma activity concentration indexes were calculated to assess the pollution and risk level of radionuclides. The radiological risk assessment indicated that observed values were below the threshold values.

Spatial distribution of gamma radiation dose rates from natural radionuclides and its radiological hazards in sediments along river Iju, Ogun state Nigeria

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Radioactivity in soil sediments of Iju River was found to be within the limit level.

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Excess lifetime cancer risks on human and ecosystem found to be higher slightly in some sites.

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Activity utilization index from gamma radiation of natural radionuclides found to be within the permissible level.

This study assessed the radioactivity level of Iju River sediments and its associated radiological risks exposure to human. Gamma absorbed dose rates were measured using a portable gamma spectrometer at an interval of 50 m between each point (Model No:RS-125 manufactured by Canadian Geophysical Institute). The measured absorbed gamma dose rates range from 22 to 59 nGy/h with the highest value noted in site 13. The mean activity concentrations of U-238, Th-232 and K-40 from Iju river sediments were 24.1 ± 0.4 Bq/kg, 35.2 ± 1.1 Bq/kg and 501.0 ± 11.1 Bq/kg, which were lower than the world average values of 32 and 45 for U-238 and Th-232 by 25% and 21% and higher than 412 Bq/kg for K-40 by a factor of 0.22 (22%).•

This highest value of K-40 found in site 6 may be due to the presence of feldspartic minerals buried in the sediments.

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Consequently, the radiological hazard indices were below the permissible limits except the mean value of 28 × 10⁻² for excess lifetime cancer risk (ELCR) for the samples collected in site 6, which is higher than the average world value of 0.29 × 10⁻³ by a factor of 0.03.

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The regression model indicates that Th-232 attributes more radioactivity impacts on the soil sediments than the contributions of U-232 and K-40, as such, presumed to be the radionuclide parameter controlling the depositional process in the region.

RADIOMETRIC SURVEY OF THE TYAA RIVER SAND MINE IN KITUI, KENYA

Gamma spectroscopic analyses of sand and rock samples from Tyaa River report an average activity concentration of 33 ± 1, 55 ± 2.8 and 812 ± 40.46 Bqkg-1 for 226Ra, 232Th and 40K, respectively in the sand. A similar analysis of rock samples reveals a mean of 21 ± 2.47, 49 ± 2.47 and 782 ± 39.13 Bqkg-1 for 226Ra, 232Th and 40K, respectively. The absorbed dose rate in rocks averaged 75 ± 3.78 nGyh-1, while in the sand was 86.2 ± 4.31 nGyh-1. The ranges and mean radiological hazard indices (radium equivalent, internal and external) were within the permissible limits and the use of sand and rocks from this mine as construction material pose no health risks. Correlation analysis between the radioactivity in the sand and rocks reveals weak non-linear positive relationships suggesting that they might be from different bedrocks.

Dataset on ground radiometric survey in part of the Eastern Dahomey Basin, SW Nigeria

The dataset for this article contains the measured activity concentration of radionuclides and gamma-radiation dose rate obtained from the radiometric survey in Ota, Ado-Odo Local Government Area, Ogun State, Nigeria. The data were manually collected in fifty (50) locations using the Super SPEC RS-125 spectrometer for about three (3) weeks in January, 2017. The descriptive statistical analysis of the data were equally explored for possible statistical relationships. The field dataset is made available publicly for further extended analyses that can provide insights into the safety status of the study area from radiological health concerns. The dataset could also serve as a significant baseline radiometric data for future epidemiology researches and monitoring initiative in Ota and its environs.

Radionulide analyses of ingested water from some estuaries within the coastal area of Akwa Ibom State, Nigeria

Radionuclide analyses of ingested water from three selected estuaries within the coastal areas of Akwa Ibom State, Nigeria have been carried out. Fifteen water samples collected at strategic points from the estuaries were pre-treated and each placed on the sodium iodide NaI (Tl) -model 802 detector for 3600 s to obtain the gamma radiation count rate. The activity concentrations and other radiological risk parameters were computed. The effective dose rate of radiation due to ingested water (E.D.I.W.) ranged between 0.25 and 1.86 mSv yr^-1, the effective equivalent dose rate due to absorbed radiation in air (Deq) ranged between 0.0065 and 0.0369 mSv yr^-1 and the total equivalent dose rate of radiation ranged between 0.257 and 1.87 mSv yr^-1. The E.D.I.W exceeded the International Commission on Radiological Protection (ICRP) permissible limit of 0.1 mSv yr^-1 set for ingested radionuclides from food. Most surveyed points had their total equivalent dose rate of radiation greater than the ICRP permissible dose limit of 1 mSv yr^-1 for radiation exposure from all internal and external sources. The annual gonadal dose equivalent ranged between 0.008 and 0.041 mSv yr^-1 and are below the world average value of 0.3 mSv yr^-1. The excess lifetime cancer risk ranged between 0.7 × 10^-3 and 5.07 × 10^-3 and are above the world average value of 0.29 × 10^-3. The elevation of most of the radiation risk parameters over the standard limits shows that oil production activities may have raised the background radiation levels of the area. This research also revealed that computing only the Deq and neglecting the E.D.I.W would mean under estimating the radiation doses received by an impacted person by 97.4%-98.3%. Water consumed from these sources could enhance the radionuclide content and the percentage probabilities of developing cancer by impacted persons.

Natural radioactivity assessment of surface sediments in the Yangtze Estuary

The activities of the natural radionuclides (²³⁸U, ²³²Th, ²²⁶Ra and ⁴⁰K) of the surface sediments in the Yangtze Estuary were determined and used to evaluate radiation hazards in the study area. The of activities of ²³⁸U, ²³²Th, ²²⁶Ra and ⁴⁰K ranges from 14.1 to 62.3, 26.1 to 71.9, 13.7 to 52.3, and 392 to 898Bqkg^-1, respectively, which were comparable to values of other regions in China. The activities of ²³²Th, ⁴⁰K and ²²⁶Ra were clearly different from the global recommended values. The radium equivalent activity was less than the recommended limit of 370Bqkg^-1; therefore, the sediment in this area can be safely used for reclamation. The external hazard index values were less than one. The average absorbed gamma dose rate and annual effective dose equivalent values were slightly greater than the world average value. ²²⁶Ra/²³⁸U and ²³²Th/²³⁸U ratios could potentially be applied for tracing sediment source.