Vertical distribution and radiological risk assessment of 137Cs and natural radionuclides in soil samples

Radioecological perspective: The concentration of natural radionuclides around the coast of PLTU Labuan

The utilization of coal in Power Plants (PLTUs) can lead to the generation of fly ash waste, which may contain natural radionuclides that can potentially contaminate the surrounding environment. Despite Labuan PLTU's land-coastal location, marine environment monitoring remains minimal. A recent study conducted sediment and seawater sampling, revealing varying levels of natural radionuclides 226Ra, 232Th, and 40K ranging from 3.4 to 27.5 Bq kg-1, 3.9 to 34.9 Bq kg-1, and 64.0 to 275.0 Bq kg-1 in sediments, respectively. Meanwhile, the activity concentration of natural radionuclides 226Ra and 232Th in seawater ranges from 0.5 to 1.1 Bq L-1 to 0.7-1.5 Bq L-1, respectively. These findings provide baseline data for marine radiation levels around PLTU Labuan. Additionally, risk assessments were conducted, indicating Raeq, Hin, and Hex ranges of 13.80-91.00 Bq kg-1, 0.04-0.25, and 0.05-0.31, respectively. The study concludes that Labuan's radiation levels are within safe limits for exposure.

Investigation of radioactivity and heavy metal levels in soil samples from neutral and vegetation land of Punjab, India

In this work, radioactivity investigations of soil samples from neutral and agricultural sites in Punjab (India) have been carried out to study the impact of land use patterns. Analyzing soil samples radiological, mineralogical, and physicochemical attributes has employed state-of-the-art techniques. The mean activity concentration of 238U/226Ra, 232Th, 40K, 235U, and 137Cs, measured using a carbon fiber endcap p-type HPGe detector, in neutral land was observed as 58.03, 83.95, 445.18, 2.83, and 1.16 Bq kg-1, respectively. However, in vegetation land, it was found to be 40.07, 64.68, 596.74, 2.26, and 1.90 Bq kg-1, respectively. In the detailed activity analysis, radium equivalent (Raeq) radioactivity is in the safe prescribed limit of 370 Bq kg-1 for all investigated soil samples. However, the dosimetric investigations revealed that the outdoor absorbed gamma dose rate (96.08 nGy h-1) and consequent annual effective dose rate (0.12 mSv y-1) for neutral land and the gamma dose rate (82.46 nGy h-1) and subsequent annual effective dose rate (0.10 mSv y-1) for vegetation land marginally exceeded the global average. The soil's physicochemical parameters (pH, EC, and porosity) from both sites were measured, and their correlations with radionuclides were analyzed. Various heavy metals of health concern, namely, chromium (Cr), arsenic (As), copper (Cu), cobalt (Co), cadmium (Cd), lead (Pb), mercury (Hg), selenium (Se), and zinc (Zn), were also evaluated in soil samples using Inductively Coupled Plasma-Mass Spectroscopy (ICP-MS). Pollution Load Index (PLI) and Ecological Risk Index (RI) revealed that vegetation land was more anthropogenically contaminated than neutral land, with maximum contamination from Hg and As.

Evaluation of the potentially toxic elements and radionuclides in the soil sample of Novaya Zemlya in the Arctic Circle

The study presented here elucidate the concentrations of radionuclides and potentially toxic elements in the soil samples around the Novaya Zemlya in the Russian Arctic zone, determined using HPGe gamma spectrometry, inductively coupled plasma optical emission spectrometry and direct mercury analyzer. The average detected concentrations for 226Ra, 232Th, 40K, 235U and 137Cs were 36.40, 46.06, 768, 2.06 and 4.71 Bq/kg, respectively. At many sampling sites, the concentrations of potentially toxic elements (Zn, Cu, Pb, Cd, Ni, and Cr) were higher than the natural levels. Positive Matrix Factorization analysis revealed the contribution of oil dumps (32%), natural sources (16%), bird colonies (32%) and atmospheric deposition (20%) for elevated elements content. In the case of radionuclides, the natural occurring contamination (38%) was primary source followed by dumped material (32%) and bird colonies (30%). The radiological risk from radionuclides was relatively high, yet still under permissible levels. For potentially toxic elements, Fe was predominant non-carcinogenic pollutant and Ni emerged as major carcinogenic contaminant. Keeping in view the high content of some elements, future studies are required to keep the human and ecological risk low, and to establish scientific grounds for the contribution of settled bird species. The findings of the study advance the present knowledge about the contamination of the study area and lays the path for further effort.

Response of bacterial ecological and functional properties to anthropogenic interventions during maturation of mine sand soil

Soil formation is a complex process that starts from the biological development. The ecological principles and biological function in soil are of great importance, whereas their response to anthropogenic intervention has been poorly understood. In this study, a 150-day microcosmic experiment was conducted with the addition of sludge and/or fermented wood chips (FWC) to promote the soil maturation. The results showed that, compared to the control (natural development without anthropogenic intervention), sludge, FWC, and their combination increased the availability of carbon, nitrogen, and potassium, and promoted the soil aggregation. They also enhanced the cellulase activity, microbial biomass carbon (MBC) and bacterial diversity, indicating that anthropogenic interventions promoted the maturation of sand soil. Molecular ecology network and functional analyses indicated that soil maturation was accomplished with the enhancement of ecosystem functionality and stability. Specifically, sludge promoted a transition in bacterial community function from denitrification to nitrification, facilitated the degradation of easily degradable organic matter, and enhanced the autotrophic nutritional mode. FWC facilitated the transition of bacterial function from denitrification to ammonification, promoted the degradation of recalcitrant organic matter, and simultaneously enhanced both autotrophic and heterotrophic nutritional modes. Although both sludge and FWC promoted the soil functionality, they showed distinct mechanistic actions, with sludge enhancing the physical structure, and FWC altering chemical composition. It is also worth emphasizing that sludge and FWC exhibited a synergistic effect in promoting biological development and ecosystem stability, thereby providing an effective avenue for soil maturation.

A review of the occurrence of naturally occurring radioactive materials and radiological risk assessment in South African soils

According to reports, exposure to high concentrations of naturally occurring radioactive substances like Uranium-238, Thorium-232, and Potassium-40 poses serious health concerns. This review study aims to report the concentrations of radionuclides in various South African soil and their equivalent risk assessments, which have been sparingly reported. For South Africa, most radionuclide concentrations above the permissible limits of 33, 45, and 420 Bq.kg-1 for 238U, 232Th, and 40K, respectively, have been found in some soil samples taken near industrialization activities, including mining and oil exploration and production. Thus, the amount of radionuclides is a good indicator of the kind of soil, the local geology, and the mineral make-up of the parent rocks. The increases in radiation exposure to people and the environment have been reported to cause various radiological health hazards. Thus, this review study can be used as a data source to track probable radioactive contamination from soils found in South Africa.

Distribution and impacts of contamination by natural and artificial radionuclides in attic dust and urban soil samples from a former industrial Hungarian city: A case study from Salgótarján

Primordial radionuclides can be found in all environmental compartments. Since coal-fired power plants (CFPP) can be a source of additional radionuclide contamination because coal contains natural radioactive isotopes such as 238U (226Ra) and 232Th. This study investigated the impact of such possible radionuclide contamination from former heavy industrial activities, namely a former local coal-fired power plant, in urban soils and attic dust in Salgótarján, Hungary. Even today, industrial by-products, e.g., coal ash, in this city represent significant threat to its residents. A total of 36 attic dust samples (family houses, kindergartens, churches and blockhouses) were collected and 19 urban soil samples (playgrounds, kindergartens, parks and others) were selected no further than 500 m from the corresponding attic dust sampling sites. Additionally, a coal ash and a brown forest soil sample were also collected to differentiate between the anthropogenic and geogenic sources in the residential area. The sampled houses, built between 1890 and 1990, are considered to be representative sampling sites for long-term accumulations of attic dust. The mean values of the total U, Th and Cs (mg kg-1) concentrations as well as those of K (m/m %) in attic dust and urban soil samples are 2.4, 3.6, 1.7 and 0.6 and 1.1, 4.4, 1.2 and 0.3, respectively, measured using ICP-MS. The mean activity concentrations of 226Ra, 232Th, 40K and 137Cs in attic dust and urban soil samples are 43.3, 34.0, 534.4 and 88.5 and 25.1, 32.8, 386.4 and 5.6 Bq kg-1, respectively, by using a low-background iron chamber with a well-type HPGe and a n-type coaxial HPGe detector. The elemental compositions (U, Th) and activity concentrations (226Ra, 232Th) along with their abundances in coal ash from the CFPP increase in both studied media as the distance of the sampling sites from the CFPP decreases. Two outlier attic dust samples in particular show significantly high activity concentrations of 226Ra: 145 and 143, of 232Th: 83 and 94 Bq kg-1, which can be considered as a proxy of unweathered coal ash. The calculated total absorbed gamma dose rate (D) and annual effective dose (E) received from urban soils indicate that the presence of the CFPP, coal ash cone and slag dumps does not cause an increase in the level of background radiation in Salgótarján. However, the concentrations of the studied radionuclides are much higher (except for 232Th) and exhibit higher degree of variability in the samples of attic dustthan in those of urban soils. The study suggests that attic dust preserves the undisturbed 'fingerprints' of long-term atmospheric deposition thanks to its chemical and physical properties unlike urban soil.

The spatiotemporal variation, background, and baseline activities of radionuclides in the soil of Aragats Massif (Armenia)

The present study was performed to reveal the distribution patterns and spatiotemporal changes of radionuclides in the soil of the highest mountain of Armenia: Aragats Massif. In this regard, two surveys were implemented in 2016-2018 and 2021 with an altitudinal sampling strategy. The activities of radionuclides were determined by gamma spectrometry system with HPGe detector (CANBERRA). Correlation and linear regression analysis were applied to determine the dependence of radionuclides' distribution from altitude. Classical and robust statistical methods were used to assess the local background and baseline values. In two sampling profiles, the spatiotemporal variation of radionuclides was studied. A significant correlation was revealed between ¹³⁷Cs and altitude pointing to global atmospheric migration as a primary source of ¹³⁷Cs in Armenian environment. The predicted values of regression model revealed a 0.08-Bq/kg and 0.03-Bq/kg increase of ¹³⁷Cs in each m on average, for the old and new survey, respectively. The assessment of background activities of NOR (naturally occurring radionuclides) enables setting the local background for ²²⁶Ra, ²³²Th, and ⁴⁰ K in soils of Aragats Massif: 831.3 ± 20.2 Bq/kg and 540.6 ± 18.3 Bq/kg for ⁴⁰ K, 85.5 ± 3.1 Bq/kg and 27.7 ± 2.6 Bq/kg for ²²⁶Ra, and 66.8 ± 3.2 and 46.4 ± 3.0 Bq/kg for ²³²Th, respectively, for the years of 2016-2018 and 2021. ¹³⁷Cs baseline activity was estimated by altitude: 350 ± 3.7 Bq/kg and 108 ± 2.5 Bq/kg, respectively, for the years of 2016-2018 and 2021.

Composition of deposited sediment and its temporal variation in a disturbed tropical catchment in the Kelantan river basin, Peninsular Malaysia

Pristine tropical river systems are coming under increasing pressure from the development of economic resources such as forestry and mining for valuable elements. The Lebir catchment, north eastern Malaysia, is now under development as a result of unregulated tree felling and mining for essential and rare metals. Two sediment cores, one in the upstream reaches and the other from the downstream reaches, were taken from flood prone area of the Lebir River, Malaysia, and analysed for their elemental composition by XRF, specifically Al, Si, Fe, Ca, K, Mg, Mn, V, Cu, Ni, Pb, Cr, Zn, As, Th and U. Activities of fallout radionuclides, ¹³⁷Cs and ²¹⁰Pb were also determined to from a geochronological context. The elemental concentrations in the soils were assessed in terms of their enrichment factor and Si, Ca, K, Mg, Mn, V, Cu, Ni and Zn were found not to be enriched, whereas As, Th and U had elevated enrichment factors. The Th and U were particularly enriched in the downstream core indicating inputs from a tributary that drains a catchment with known deposits of Th and possibly U. The results suggest that the growth in economic development is fostering the transport of contaminants by the major rivers which, in turn, is contaminating the riverine floodplains. This points to the need for a more integrated and holistic approach to river basin management to maintain the environmental quality of these fragile aquatic systems.

Influence of soil chemical composition on U, 226Ra and 210Pb uptake in leaves and fruits of Quercus ilex L

To determine their transfer factors, activity concentrations of natural radionuclides were measured in the leaves and acorns of holm oak (Quercus ilex L.) trees collected from seven locations with different soil properties and radionuclide activity concentrations. The chemical and mineralogical compositions of the soils were also analysed to investigate the effect these had on radionuclide absorption by the trees. Soil chemistry showed significant effects on radionuclide incorporation into Quercus ilex L. tissues. A significant relationship was established between activity concentrations and soil content of Ca and P with ²³⁸U and ²²⁶Ra in the leaves and acorns of Quercus ilex L. Differentiated transfer was found for ⁴⁰K, which showed greater transfer to the leaves than the other radionuclides. The activity concentration of U and ²²⁶Ra was higher in the fruits than in the leaves, with the opposite effect being observed for ⁴⁰K. The risk of U and ²²⁶Ra transfer into the food chain through acorn consumption by livestock is predicted to increase in soils poor in Ca and rich in P.

Synthesis of heated aluminum oxide particles impregnated with Prussian blue for cesium and natural organic matter adsorption: Experimental and machine learning modeling

Heated aluminum oxide particles impregnated with Prussian blue (HAOPs-PB) are synthesized for the first time using different molar ratios of aluminum sulfate and PB to improve the adsorption of cesium (¹³³Cs⁺) and natural organic matter (NOM) from an aqueous solution. The Cs⁺ adsorption from various aqueous solutions, including surface, tap and deionized water by synthesized HAOPs-PB, is investigated. The influencing factors such as HAOPs-PB mixing ratio, pH and dosage are studied. In addition, pseudo 1st and 2nd order is tested for adsorption kinetics study. A machine learning model is developed using gene expression programming (GEP) to evaluate and optimize the adsorption process for Cs⁺ and NOM removal. Synthesized adsorbent showed maximum adsorption at a 1:1 M ratio of aluminum sulfate and PB in DI, tap, and surface water. The pseudo 2nd order kinetics model described the Cs ⁺ adsorption by HAOPs-PB more accurately that indicating physiochemical adsorption. Adsorption of Cs⁺ showed an increasing trend with higher HAOPs-PB concentration, while high pH also favored the adsorption. Maximum NOM adsorption is found at a higher HAOPs-PB dosage and a neutral pH value. Furthermore, the proposed GEP model shows outstanding performance for Cs⁺ adsorption modeling, whereas a modified-GEP model presents promising results for NOM adsorption prediction for testing dataset by learning the relationship between inputs and output with R² values of 0.9348 and 0.889, respectively.

Activity concentrations and radiological hazard assessments of 226Ra, 232Th, and 40K in soil samples of oil-producing areas of South Africa

The specific activity of natural radionuclide in soil samples of the oil-producing areas of South Africa was measured using a High Purity Germanium detector. The activity of226Ra, 232Th, and 40K in the soil range from 16.5 ± 1.3 to 64.9 ± 3.1, 16.8 ± 1.5 to 88.6 ± 1.2, 135.2 ± 17.5 to 604.8 ± 13.4 Bqkg-1 for Mossel Bay; 14.3 ± 1.2 to 48.9 ± 8.2, 22.3 ± 1.4 to 45.1 ± 3.2, 237.7 ± 10.9 to 486.5 ± 40.1 Bqkg-1 for Cape Town; 10.5 ± 1.1 to 25.8 ± 3.2, 13.1 ± 1.9 to 44.3 ± 5.2, 140.2 ± 10.9 to 229.8 ± 12.8 Bqkg-1 for Nelson Mandela Bay and 5.6 ± 2.2 to 13.1 ± 2.9, 4.5 ± 2.5 to 14.1 ± 2.7, 62.7 ± 22.6 to 126.5 ± 21.2 Bqkg-1 for Msunduzi. Most soil samples' radiological hazards were within the world average.

Health risk assessment of radioactive footprints of the urban soils in the residents of Dera Ghazi Khan, Pakistan

The aim of the study was to evaluate the radiation levels, radiological doses and excess lifetime cancer risk possessed by the urban soils that were collected from the vicinity of the exclusive mining and excavation centers of Dera Ghazi Khan. The high purity germanium detector was utilized for assessment of naturally occurring radionuclides (NORMs) in soil and results showed that the average activity concentrations of ²²⁶Ra, ²³²Th, and ⁴⁰K (37 Bq/kg, 43.07 Bq/kg, 737 Bq/kg respectively) surpassed the world's average documented values (35 Bq/kg, 30 Bq/kg, and 400 Bq/kg respectively). Moreover, the average values of radiological hazards assessment like radium equivalent, internal and external hazard indices, absorbed dose rate, annual gonadal dose equivalent and excess lifetime cancer risk were 155.70 (Bq/kg), 0.4, 0.5, 73.96 (nGy/h) 90.73 (μSv/y), 476.24 (μSv/y) and 0.31(10^-3) respectively. The data acquired was analyzed using descriptive statistics, cluster analysis and principal component analysis. ArcGIS (10.5) software was utilized for developing maps of radionuclide's concentration for the study area. Results of the study may serve as an important baseline radiometric data for future epidemiological studies and monitoring initiatives in the study area.

On the 30th anniversary of the Chernobyl Nuclear Power Plant Accident, assessment of the activity concentrations and the radiological hazard parameters of soil samples collected from Rize province and districts

Uranium, thorium and potassium are the main terrestrial sources of radiation that are located at different levels in the soil depending on the geographical and geological conditions and contribute to increase of the natural radiation levels of the regions. In addition to the natural radiation sources, Cesium-137 which can spread from nuclear tests and accidents such as Chernobyl Nuclear Power Plant Accident is also an important artificial radiation source of that contributes to the increase of radioactivity in the soil. Determination of both natural and artificial radioactivity levels of soil is important in terms of assessing people's possible exposure to the internal radiation and ensuring that people can be protected from the harmful effects of the external radiation. In this study, on the 30th anniversary of the Chernobyl Nuclear Power Plant Accident, soil samples were collected from Rize province which was affected by the Chernobyl Nuclear Power Plant Accident in 1986 and the activity concentrations of natural and artificial radionuclides were measured and radiological hazard parameters were calculated. Radioactivity measurements were caried out with gamma spectrometry system with a high purity germanium detector. The activity concentrations were measured in range of 4.45 ± 0.39 to 32.19 ± 0.78 Bq kg^-1 with an average of 17.68 ± 0.68 Bq kg^-1 for ²²⁶Ra, 5.58 ± 0.65 to 43.61 ± 1.67 Bq kg^-1 with an average of 22.53 ± 1.26 Bq kg^-1 for ²³²Th, 28.82 ± 1.37 to 773.19 ± 12.14 Bq kg^-1 with an average of 277.14 ± 6.24 Bq kg^-1 for ⁴⁰K and 1.99 ± 0.17 to 376.85 ± 2.52 Bq kg^-1 with an average of 110.11 ± 0.98 Bq kg^-1. The average activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K were found below the world median activity concentrations of 35, 30 and 400 Bq kg^-1, respectively. Despite the high ¹³⁷Cs activity concentrations were determined in present study compared to similar works being done in Turkey and other countries, the average activity concentration of ¹³⁷Cs in investigated samples was significantly found lower than the ¹³⁷Cs values in soil samples from Rize in 1990 carried out by TAEA. In present study, the average radium equivalent activity (Ra_eq), external hazard index (H_ex) and internal hazard index (H_in) values were below the recommended limits by UNSCEAR. The average absorbed dose rate in air (D) and annual effective dose equivalent (AEDE) values were found lower than the world median values. The calculated excess lifetime cancer risk (ELCR) values for soil samples were obtained less than the precautionary limit of 0.29 × 10^-3.

Assessment of naturally occurring radiation in lithofacies of oil field in Niger Delta region and its possible health implications

The accumulation and increase in radionuclide activities of NORMs beyond permissible levels, will lead to health hazards and environmental damages if proper measures are not taken to control their occurrence as well as protect the lives of drillers and the environment. Therefore, evaluations and risk assessments of subsurface lithofacies is inevitable in order to protect people and the environment. Lack of existing Federal environmental regulations to address the presence of NORMs in oil and gas exploration activities in Nigeria, gives credence to this study. However, before these regulations can be developed, adequate research knowledge is needed to better understand the occurrence and distribution of Norms in subsurface lithofacies, as well as quantify the hazards posed by these NORMs to the people in the environment. This study then investigates the occurrence of natural radiation in lithofacies of an oil field region in Niger-Delta area using Hyper Germanium (HPGe) detector. Six (6) samples of different subsurface layers of lithofacies were collected during drilling, and analyzed. The results showed that the measured activity concentration of ²³⁸U decreased as the depth increased; the activity concentration of ²³²Th ranged between 11.8 ± 9.29 Bq/kg and 23.1 ± 8.43 Bq/kg, while the activity concentration of ⁴ K ranged from 161.8 Bq/kg to 245.4 Bq/kg. The estimated radiological risks such as absorbed dose rates, annual effective dose rates, radium equivalent index, external hazard index and internal hazard index were determined. The mean values for the estimated radiological parameters were 12.32 nGyh^-1, 15.1049 Svy^-1, 44.7720 Bqkg^-1, 0.1209 and 0.1318 respectively. The gamma index estimated for the samples used were within the standard values recommended by Unscear, 2000. Significantly, this study reveals a distinctive decrease in 232Th activity with depth within the area under consideration. Based on the compared results, the measured radioactive concentrations and estimated radiological risks were below international reference values.