Study on the radioactivity and soil-to-plant transfer factor of (226)Ra, (234)U and (238)U radionuclides in irrigated farms from the northwestern Saudi Arabia

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.

Application and Experimental Substantiation of the Radioecological Model for Prediction in Behavior 90Sr in Cultivated Soil-Crop System: A Case Study of Two Experimental Agricultural Fields

The radioactive fission product 90Sr has a sufficient half-life (28.8 years) to be detected long after its appearance in the environment. After its uptake into the soil-edible plant system, it enters the food chain and represents a potential source of contamination that threatens human health. Due to these facts, tracking the distribution of the artificial radionuclide 90Sr in the soil-edible plant system is a subject of intense research. The tracking of the 90Sr radionuclide distribution in the soil profile, as well as in the crops on the long-term experimental fields was carried out using beta radiation spectrometry. The radiochemical analytical method was used to analyze the 90Sr content in cultivated soil and crops. The conducted study focused on the experimental substantiation of the developed model for predicting the behavior of 90Sr in the cultivated soil-crop system. The results of using the applied radioecological model for the transfer of 90Sr from the soil to the above-ground part of crops showed a relatively good agreement with the experimentally determined values of the soil-crop transfer factor, which indicates that the used model can be successfully applied for the prediction of the behavior of 90Sr in the soil-soil solution-crop system.

Health Impacts of Natural Background Radiation in High Air Pollution Area of Thailand

Chiang Mai province of Thailand is known for having the highest natural background radiation in the country, as well as being recognized as one of the world's most polluted cities for air quality. This represents the major contributor to the development of lung cancer. This research aims to estimate the comprehensive dose of both internal and external exposure due to natural background radiation and related health perspectives in the highly polluted area of Chiang Mai. The average values of indoor radon and thoron concentrations in 99 houses over 6 months were 40.8 ± 22.6 and 17.8 ± 16.3 Bq/m3, respectively. These results exceed the worldwide value for indoor radon and thoron (40 and 10 Bq/m3), respectively. During burning season, the average values of indoor radon (56.7 ± 20 Bq/m3) and thoron (20.8 ± 20.4 Bq/m3) concentrations were higher than the world-wide averages. The radon concentration in drinking water (56 samples) varied from 0.1 to 91.9 Bq/L, with an average value of 9.1 ± 22.8 Bq/L. Most of the drinking water samples (87%) fell below the recommended maximum contamination limit of 11.1 Bq/L. The average values of natural radionuclide (226Ra, 232Th and 40K) in 48 soil samples were 47 ± 20.9, 77.9 ± 29.7 and 700.1 ± 233 Bq/kg, respectively. All values were higher than the worldwide average of 35, 30 and 400 Bq/kg, respectively. The average value of outdoor absorbed gamma dose rate (98 ± 32.5 nGy/h) exceeded the worldwide average of 59 nGy/h. Meanwhile, the average activity concentrations of 226Ra, 232Th and 40K in 25 plant food samples were 2.7 ± 0.1, 3.2 ± 1.6 and 1000.7 ± 1.9 Bq/kg, respectively. The 40K concentration was the most predominant in plant foods. The highest concentrations of 226Ra, 232Th and 40K were found in Chinese cabbage, celery and cilantro, respectively. The total annual effective dose for residents in the study area varied from 0.6 to 4.3 mSv, with an average value of 1.4 mSv. This indicates a significant long-term public health hazard due to natural background radiation and suggests a heightened radiation risk for the residents. The excess lifetime cancer risk value (5.4) associated with natural background radiation was found to be higher than the recommended value. Moreover, the number of lung cancer cases per year per million average of 25.2 per million persons per year was in the limit range 170-230 per million people. Overall, our results will be used for future decision making in the prevention of lung cancer risk associated with natural background radiation.

Study of activity concentrations of 40K, 238U and 232Th for assessment of radiation dose in agricultural soils of southwestern Nigeria

Gamma spectrometric measurement of natural radionuclides activity concentrations by HPGe detectors was conducted in 150 agricultural soil samples collected from six states of southwestern Nigeria. The overall activity concentrations of radionuclides ranged from 15.27 to 972.00 Bqkg-1 for 40K, 0.66 to 336.19 Bqkg-1 for 232Th and 1.32 to 123.01 Bqkg-1 for 238U, with mean values of 143.95, 17.02 and 22.92 Bqkg-1, respectively. The overall averages results from this study were generally lower than worldwide average value of 420, 33 and 45 Bqkg-1 for 40K, 238U and 232Th, respectively, thus minimal transfer to plant may be expected. The estimated radiation dose levels of the soil indicated acceptable limits for general public exposure. The radioactivity levels of 40K, 232Th and 238U in the investigated agricultural soil of southwestern Nigeria are within acceptable limits. Therefore, stochastic radiological health effects of radiation exposure by farmers may not be feasible at the current moment.

Excess lifetime cancer risk due to ingestion of fish from a dam reservoir associated with a nuclear facility in Brazil

Fish from a Funil dam reservoir associated with a Nuclear Fuel Factory were sampled aiming to assess the radiological risk due to ingestion. Funil dam reservoir is a strategic site, once it receives effluent from the industrial complex that performs isotopic enrichment of uranium and conversion of UF6. The mean activity concentrations obtained for 40K, 226Ra, 228Ra and 228Th were 57.81, 0.41, 0.92 and 0.49 Bq·kg-1, respectively. Lifetime cancer risk was estimated in ∼10-5 and no action needs to be taken.

Soil to plant transfer of 226Ra, 232Th and 137Cs to some medicinal and aromatic plants growing in Bitlis (Turkey)

Medicinal plants consumed in Bitlis were analysed for ²²⁶Ra, ²³²Th and ¹³⁷Cs using HPGe gamma spectroscopy system. Both plant samples and the corresponding soils were analysed. Using these values, the transfer factors for ²²⁶Ra, ²³²Th and ¹³⁷Cs were calculated in the ranges of (0.09-2.18), (0.01-0.19) and (0.01-2.8), respectively. Based on the plant concentrations observed, unless consumed in excessive amounts, these medicinal plants do not have any radiological harm to health.

Dynamics of Major and Trace Elements in Water-Soil-Tree Interaction: Translocation in Pyrus malus in Chihuahua, Mexico Using ICP-OES and Its Health Risk Implications

The transference of metals from water irrigation and soil to plants is a possible pathway of contamination for the trophic chain. This research is focused on the distribution of 16 analytes in the water-soil-tree (Pyrus malus) interaction in an agricultural region in the state of Chihuahua in Mexico from August 2019 (first sampling) to August 2020 (second sampling). The apple variety under investigation was Golden Delicious; it was found that the trace elements of As (0.18-0.34 mg·kg^-1) and Cd (0.11-0.14 mg·kg^-1) in the apple were above the corresponding permissible limit, according to FAO/WHO, and Cr (0.08-0.86 mg·kg^-1) was below the limit. Furthermore, the health risk implications were estimated by the Hazard Quotients (HQ) and carcinogenic risk (CR). For carcinogenic risk, As, Cd, and Cr exceeded the risk limit (CR > 10^-4). This investigation as well provides a link for similar research around the globe. Major and trace elements detection was performed with the Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) technique, along with a prior homogenization of samples and microwave acid digestion. To obtain the statistical behavior, an analysis of variance and correlation was performed.

Conceptualization of arid region radioecology strategies for agricultural ecosystems of the United Arab Emirates (UAE)

Since the last decade, ambitious nuclear power programmes have begun maturing in the Arab countries, most importantly in the United Arab Emirates (UAE). The region's environment and population, therefore, are prone to adverse, long-term impacts of radionuclide discharges. To calculate the associated exposure scenarios, to estimate doses and their consequences, and finally, to lay out a radiological emergency management plan, arid region radioecology is taking shape in the UAE as a major field of research. Geography, demography, food habits, weather, soil, water, flora, and fauna of the desert-marine regions are quite distinct from their temperate counterparts. This results in the need to increase the knowhows of environmental migration and bioaccumulation of radionuclides in the region's agricultural ecosystems. In this paper, we present a detailed review of the measured data from the UAE and nearby nations, generating insights for the soil radioactivity and soil-to-plant transfer phenomena under local arid conditions. In the literature, the radionuclide activity concentrations (in Bq kg^-1) vary over five orders of magnitude depending on nuclide type, sample type, and locality. Variabilities over six orders of magnitude are observed for transfer parameters too, and in-depth studies on the transfer mechanisms are usually scarce. We discuss the recent progresses made in root and foliar uptake studies with methods relatively new to sandy soils, like controlled potting, and soil K_d measurements. Showing the serious gaps in the data and interpretations, we provide a justification for the immediate experimentation in the understudied aspects of radioecology in the UAE and in arid lands in general.

Soil to tobacco component transfer factors for natural radionuclides 40K, 226Ra, and 232Th and the risk assessment of tobacco leaf in smoking

This study determined the activity concentrations and corresponding transfer factors (TF) of ⁴⁰K, ²²⁶Ra, and ²³²Th in three tobacco components (root, stem, and leaf). The radiation hazard index parameters were assessed for the tobacco leaf. The activity concentrations in the soil were 589-762, 32-43, and 49-59 Bq kg-dw^-1 (dry weight) for ⁴⁰K, ²²⁶Ra, and ²³²Th, respectively. The average activity concentrations of ⁴⁰K, ²²⁶Ra, and ²³²Th were 447, 5.41 and 5.69 Bq/kg-dw for the root, 670, 9.64 and 7.61 Bq kg-dw^-1 for the stem, and 793, 6.79 and 6.15 Bq kg-dw^-1 for the leaf, respectively. The TF values were 0.42-1.42, 0.10-0.49 and 0.06-0.23 for ⁴⁰K, ²²⁶Ra, and ²³²Th, respectively. The stem and leaf ⁴⁰K TF values were significantly higher than the root values. The stem ²²⁶Ra TF values were significantly higher than the root values. The ²²⁶Ra and ²³²Th activity concentrations and TFs of tobacco components had a significant positive correlation. Based on the activity concentrations of the tobacco leaves, the annual inhalation effective dose to the lungs for an adult smoker was 0.32-0.81 mSv y^-1 (average 0.60 mSv y^-1). The Excess Lifetime Cancer Risk (ELCR) caused by smoking was an average of 2.39 × 10^-3.

Effect of mineral fertilisers application on the transfer of natural radionuclides from soil to radish (Raphanus sativus L.)

Non-controlled usage of mineral fertilisers in agriculture land of Kazakhstan is a concerning issue, due to possible contamination of the soil by radionuclides. Pot experiment of growing of R. sativus with application of mineral fertilisers was carried out under natural conditions. Two commonly used mineral fertilisers, mono-potassium phosphate and ammonium nitrate, were chosen in the frame of current research to determine the impact of mineral fertiliser on transfer of natural radionuclides from soil to R. sativus edible part. For this goal, the activity concentrations of natural radionuclides U-234, U-238, Th-230, Th-232 and Ra-226, were determined in both R. sativus edible part and the investigated soil by using alpha-particle spectrometry. The highest activity concentrations were found for R. sativus edible part growing on soil that was fertilised by mono-potassium phosphate and were equal to 174 ± 17, 134 ± 15, 62 ± 4, 15 ± 2 and 2.8 ± 0.6 Bq/kg for U-234, U-238, Th-230, Th-232 and Ra-226, respectively. The results of soil-to- R. sativus edible part transfer factor for different radionuclides varied depending on the mineral fertiliser used. For evaluation of impact during consumption of R. sativus edible part by a population of Kazakhstan, annual effective ingestion dose and excess lifetime cancer risk were determined. The highest annual effective ingestion dose was found for R. sativus edible part cultivated in mono-potassium phosphate-fertilised soil and was equal to 4.4 μSv year^-1.

Effectiveness of soil conditioners to enhance salt extraction ability of Salicornia ramosissima in saline-sodic soil for different soil moisture contents

Soil salinity is considered one of the main types of soil degradation in semiarid environments around the globe. This work aims to evaluate the effectiveness of soil conditioners to enhance the growth and salt extraction ability of Salicornia ramosíssima for different soil moisture contents. Salicornia plants were cultivated in pots in which the soils were treated with the following conditioners: control; gypsum + organic matter; elemental sulfur + organic matter; and gypsum + elemental sulfur + organic matter. Salicornia plants were subjected to two soil moisture rates - at 35 and 85% field capacity. Soil conditioners associated with higher contents of soil moisture promoted significant increases, compared to control, in fresh (6.20 - 11.13 g) and dry matter (1.20 - 2.07 g), relative biomass (100 - 179%) as well as significantly increased the concentrations of Na⁺ (56.09 - 65.64 mg kg^-1) and Cl^- (110.83 - 150.0 mg kg^-1) in plant tissues. Soil conditioners significantly increased salt extraction ability under the two moisture levels, mainly by promoting higher values for both transfer factor and phytoremediation potential. The best performance of Salicornia in terms of plant yield and salt extraction, regardless of the moisture level, was the gypsum + organic matter.Novelty statementThere are no studies in the literature relating the use of conditioners as a strategy to enhance Salicornia's ability to extract salts.This work contributes to the management of salinized areas around the globe in two main aspects. The first is that many of these salt-degraded areas are desertified and through this study, it is possible to revegetate and recover them. The second one is that, since Salicornia is a plant with economic value, this can serve as an incentive for farmers to grow Salicornia in saline areas.

Soil-to-plant transfer factors of 238U and 232Th in rice from Ezillo paddy fields, Ebonyi State, Nigeria

The uptake of radionuclides by plants and their subsequent relocation to the human body through ingestion is one major pathway of human internal exposure. Thus, the present study was conducted to examine the levels of natural radionuclides, ²³⁸U and ²³²Th, in soil of Ezillo paddy fields (field 1 and field 2) at depths 0-4 cm and 4-8 cm, their transfer and accumulation in rice grains. The mean concentrations of both radionuclides in the soil were clearly greater than the UNSCEAR estimated worldwide average while that of the rice with values of 11.7 ± 4.3 and 3.0 ± 1.3 Bq/kg in field 1 and 8.5 ± 4.2 and 4.3 ± 1.6 Bq/kg in field 2 for ²³⁸U and ²³²Th respectively, were well below the worldwide average. The radionuclide transfer factors (TFs) across both depths ranged from 0.03 to 0.67 and 0.01 to 1.20 for ²³⁸U and ²³²Th respectively. The overall geometric means and geometric standard deviations of the TF estimated in field 1 were respectively 0.22 and 1.52 for ²³⁸U and 0.18 and 4.21 for ²³²Th (soil_,0-4cm); 0.43 and 1.80 for ²³⁸U and 0.18 and 3.79 for ²³²Th (soil_,4-8cm) whereas in field 2 the values were respectively 0.12 and 2.62 for ²³⁸U and 0.06 and 4.15 for ²³²Th (soil_,0-4cm); 0.11 and 1.85 for ²³⁸U and 0.12 and 4.15 for ²³²Th (soil_,4-8cm). The nuclide concentrations in the rice and the present TFs are within the ranges of values in the literature.

Substratum influences uptake of radium-226 by plants

Radium-226, an alpha emitter with half-life 1600 years, is ubiquitous in natural environments. Present in rocks and soils, it is also absorbed by vegetation. The efficiency of ²²⁶Ra uptake by plants from the soil is important to assess for the study of heavy metals uptake by plants, monitoring of radioactive pollution, and the biogeochemical cycle of radium in the Critical Zone. Using a thoroughly validated measurement method of effective ²²⁶Ra concentration (EC_Ra) in the laboratory, we compare EC_Ra values of the plant to that of the closest soil, and we infer the ²²⁶Ra soil-to-plant transfer ratio, R_SP, for a total of 108 plant samples collected in various locations in France. EC_Ra values of plants range over five orders of magnitude with mean (min-max) of 1.66 ± 0.03 (0.020-113) Bq kg^-1. Inferred R_SP values range over four orders of magnitude with mean (min-max) of 0.0188 ± 0.0004 (0.00069-0.37). The mean R_SP value of plants in granitic and metamorphic context (0.073 ± 0.002; n = 50) is significantly higher (12 ± 1 times) than that of plants in calcareous and sedimentary context (0.0058 ± 0.0002; n = 58). This difference, which cannot be attributed to a systematic difference in emanation coefficient, is likely due to the competition between calcium and radium. In a given substratum context, the compartments of a given plant species show coherent and decreasing R_SP values in the following order (acropetal gradient): roots > bark > branches and stems ≈ leaves. Oak trees (Quercus genus) concentrate ²²⁶Ra more than other trees and plants in this set. While this study clearly demonstrates the influence of substratum on the ²²⁶Ra uptake by plants in non-contaminated areas, our measurement method appears as a promising practical tool to use for (phyto)remediation and its monitoring in uranium- and radium-contaminated areas.

Assessment of 232Th, 226Ra, 137Cs, and 40 K concentrations and annual effective dose due to the consumption of Vietnamese fresh milk

Vietnam has little data on radionuclide concentrations in milk, despite steadily increasing domestic consumption. Eight milk brands were investigated by gamma-spectrometry, and the resulting ingestion dose was calculated. The 232Th, 226Ra, 137Cs, and 40K concentrations varied from 0.60 ± 0.19 to 1.21 ± 0.24, 1.45 ± 0.18 to 2.45 ± 0.24, below detection limit to 0.13 ± 0.06, and 341 ± 6 to 387 ± 7 Bq/kg (dry w.t). The total average Annual Effective Dose for all age groups were similar for all brands, and concentrations are far less than the WHO guidance level. All brands are safe for consumption.

The Potential Use of Zeolite, Montmorillonite, and Biochar for the Removal of Radium-226 from Aqueous Solutions and Contaminated Groundwater

The present work investigated the potential of using zeolite (clinoptilolite), montmorillonite (Swy2), and Conocarpus biochar as adsorbents to remove 226Ra from aqueous solution. The effect of the initial 226Ra concentrations on sorbents’ equilibrium activity concentrations and sorbents’ radium removal efficiency were investigated. The results showed that zeolite has a higher removal efficiency for 226Ra in comparison with the efficiencies of montmorillonite and biochar. In addition to the linear isotherm model, the Freundlich model, followed by Temkin’s model, provided a better description of the adsorption process than the Langmuir model. Kinetic studies indicated that a pseudo-second-order kinetic model could be the best fit for the adsorption of 226Ra onto the three investigated sorbents, which suggests that the mechanism of adsorption of 226Ra by sorbents was chemisorption. The intraparticle diffusion model indicated that adsorption of 226Ra onto the sorbents involves a multistep process: (i) boundary layer diffusion and (ii) intraparticle diffusion. Moreover, the remediation of groundwater samples polluted with 226Ra was assessed using the investigated sorbents; the results showed that zeolite also has the highest removal efficiency among other sorbents. Thus, the low cost, availability, and the high adsorption efficiency of zeolite can be a promising sorbent on 226Ra removal from aqueous solutions and groundwater remediation.

Estimation of the soil to plant transfer factor and the annual organ equivalent dose due to ingestion of food crops in Ho Chi Minh city, Vietnam

In this study, soil-to-plant transfer factor and annual organ equivalent dose due to ingestion of natural radionuclides in 13 popular food crop samples in Ho Chi Minh city, Vietnam were estimated. The obtained data show that the radioactive elements transported from soil to plants play an essential role as indicators for the nutritional needs of plant and the ability to accumulate radioisotopes and heavy metal elements for environmental decontamination. It is found that B. alba and C. gigantean is useful for decontamination of high content potassium in soil, otherwise, P. fruticosa and C. gigantean may be used for soil with high concentration of ²¹⁰Pb and ²²⁶Ra. In addition, biological effects of the plant ingestion in human body were assessed. The doses due to ingestion of food crop samples varied from organ to organ, depending on the organotrophic properties of the radionuclides. For examples, equivalent dose for ⁴⁰K in large intestine is higher than other organs. In contrast, equivalent dose for ²³⁸U, ²²⁶Ra, ²¹⁰Pb and ²³²Th were mostly at bone surface. In general, the obtained dose values of lower than the average value recommended by UNSCEAR for food crop ingestion pose no threat to the public's health. However, close investigations are needed in the near future.

Accumulation rates of natural radionuclides (40K, 210Pb, 226Ra, 238U, and 232Th) in topsoils due to long-term cultivations of water spinach (Ipomoea Aquatica Forssk.) and rice (Oryza Sativa L.) based on model assessments: A case study in Dong Nai province, Vietnam

In topsoils, the activity concentrations of natural radionuclides (hereafter NRs) increase due to the addition of NRs from fertilizers, irrigation water, and air dust pollution. On the other hand, various physical-chemical and environmental processes such as radioactive decay, volatilization, leaching, erosion, and plant uptake were responsible for the decrease of the activity concentrations of NRs in the topsoils. In this study, behaviours of ⁴⁰K, ²¹⁰Pb, ²²⁶Ra, ²³⁸U, and ²³²Th in topsoils were modelled by the CEMC soil model and the HYDRUS-1D model. An exponential equation was proposed for estimating the accumulation rates of these radionuclides in the topsoils. Long-term accumulation of radionuclides was assessed for water spinach (Ipomoea Aquatica Forssk.) soil (hereafter VES) and rice (Oryza sativa L.) soil (hereafter RIS). We found that the current agricultural practices caused the increase of ⁴⁰K activity concentration in the water spinach soil, and ⁴⁰K, ²¹⁰Pb, ²²⁶Ra, and ²³²Th activity concentrations in the rice soil. The accumulation rates of radionuclides were in the order ²³⁸U < ²³²Th < ²²⁶Ra < ²¹⁰Pb < ⁴⁰K. 25 years of cultivation with water spinach can increase/decrease + (165 ± 6) Bq of ⁴⁰K, - (8.2 ± 0.7) Bq of ²¹⁰Pb, - (4.3 ± 0.2) Bq of ²²⁶Ra, - (7 0.3 ± 0.3) Bq of ²³⁸U, and - (1.8 ± 0.1) Bq of ²³²Th in 1 kg soil. For rice cultivation, these values are + (1004 ± 39), + (3.3 ± 0.2), + (3.0 ± 0.2), - (5.1 ± 0.3), (2.2 ± 0.1) Bq kg^-1 for ⁴⁰K, ²¹⁰Pb, ²²⁶Ra, ²³⁸U, and ²³²Th, respectively.

Concentrations of TENORMs in the petroleum industry and their environmental and health effects

Crude oil and its products and wastes are among the significant sources of naturally occurring radioactive materials (NORMs). These materials may be enhanced to high levels due to technological and human activities, which are called technologically enhanced naturally occurring radioactive materials (TENORMs). Thus, the average radioactivity of these radionuclides sometimes exceeds the exemption level of 10 000 Bq kg-1, which is recommended by the IAEA's safety standards. TENORMs in the oil and gas industry may generate greater radioactivity levels, which eventually represents potential environmental and health risks. This will require continuous attention by monitoring and surveillance during routine processes in the petroleum industry. In this paper, a comprehensive review of the published literature is conducted to evaluate the TENORM concentrations in the oil and gas industry. Moreover, their environmental and health hazards in different regions of the world are discussed.

Soil-to-cassava plant transfer factor of natural radionuclides on a mining impacted soil in a tropical ecosystem of Nigeria

The transfer factors (TFs) of naturally occurring radionuclides, ²³⁸U and ²³²Th from soil to different cassava plant compartments were calculated. Cassava is widely cultivated in Nigeria and contributes significantly to the food supply of the nation. There is sparsity of data on the TFs in Nigeria, and no TF data from any African country were included in the International Atomic Energy Agency's compilation of TFs for the tropical ecosystem. Samples of tin tailings and soil samples from virgin land were used to formulate three soil groups; group-A (soil from virgin land only), group-B (tailings only) and group-C (equal dry mass combination of tailings and soil from virgin land). Pot experiments were set up to determine the TFs of ²³⁸U and ²³²Th. The activity concentrations of ²³⁸U and ²³²Th in the dried samples of the soil and plant compartments were determined using a sodium iodide detector. The TF of ²³⁸U ranged from below detection limit (BDL) to 0.01 in the tuber samples, BDL to 0.23 in the stem samples and BDL to 0.90 in the leaf samples, while the TF of ²³²Th ranged between 0.006 and 0.49 for tuber samples, 0.03 and 0.65 in stem samples and 0.03 and 1.54 in the leaf samples. There were significant difference in the TF of ²³⁸U and ²³²Th between the soil groups. The leaf compartment generally had most of the highest TF values while the tuber samples had most of the lowest TF values for both radionuclides.

Distribution of naturally occurring radionuclides in soil around a coal-based power plant and their potential radiological risk assessment

Coal-fly-ash is one of the major byproducts of coal-based power plant in which naturally occurring radioactive materials (NORMs) are drastically enriched compared to those of feed coals. Thus, improper management of fly-ash may introduce additional radioactivity to the surrounding environment and cause radiological risk. So, in order to study the distribution of radionuclides in soil around a coal-based power plant and to evaluate their radiological risk, soil, coal and fly-ash samples were analyzed by using a HPGe detector for U-238, Ra-226, Th-232 and K-40 radioactivity concentrations. Furthermore, soil minerals were also studied by X-ray diffractometer to assess the mineralogical provenance of the radionuclides. Mean radioactivity concentrations (in Bq·kg−1) of U-238, Ra-226, Th-232 and K-40 in soil samples are 102.9±41.4, 63.6±7.4, 103.4±13.9 and 494.2±107.5, respectively which are comparatively higher than the typical world mean value. Elevated levels of radioactivity are likely due to the presence of illite, kaolinite, monazite, rutile and zircon minerals in the soil samples rather than technogenic contributions from the power plant. Furthermore, mean soil contamination factor (CF) are close to unity and mean pollution load index (PLI) is below unity while the average radium equivalent activity (Raeq in Bq·kg−1), external hazard index (Hex), absorbed γ dose rate (D in nGyh−1), annual effective dose rate (E in mSv·y−1) and excess lifetime cancer risk (ELCR in Sv−1) are 249.5±21.7, 0.67±0.06, 114.2±9.4, 0.20±0.02, 4.9×10−4±0.4×10−4, respectively, which are within the permissible limit. Thus, in terms of radioactivity concentrations and associated environmental and radiological indices, the effect of the power plant is insignificant.

Multiple environmental factors influence 238U, 232Th and 226Ra bioaccumulation in arbuscular mycorrhizal-associated plants

Ecological consequences of low-dose radioactivity from natural sources or radioactive waste are important to understand but knowledge gaps still remain. In particular, the soil transfer and bioaccumulation of radionuclides into plant roots is poorly studied. Furthermore, better knowledge of arbuscular mycorrhizal (AM) fungi association may help understand the complexities of radionuclide bioaccumulation within the rhizosphere. Plant bioaccumulation of uranium, thorium and radium was demonstrated at two field sites, where plant tissue concentrations reached up to 46.93 μg g^{-1 238}U, 0.67 μg g^{-1 232}Th and 18.27 kBq kg^{-1 226}Ra. High root retention of uranium was consistent in all plant species studied. In contrast, most plants showed greater bioaccumulation of thorium and radium into above-ground tissues. The influence of specific soil parameters on root radionuclide bioaccumulation was examined. Total organic carbon significantly explained the variation in root uranium concentration, while other soil factors including copper concentration, magnesium concentration and pH significantly correlated with root concentrations of uranium, radium and thorium, respectively. All four orders of Glomeromycota were associated with root samples from both sites and all plant species studied showed varying association with AM fungi, ranging from zero to >60% root colonisation by fungal arbuscules. Previous laboratory studies using single plant-fungal species association had found a positive role of AM fungi in root uranium transfer, but no significant correlation between the amount of fungal infection and root uranium content in the field samples was found here. However, there was a significant negative correlation between AM fungal infection and radium accumulation. This study is the first to examine the role of AM fungi in radionuclide soil-plant transfer at a community level within the natural environment. We conclude that biotic factors alongside various abiotic factors influence the soil-plant transfer of radionuclides and future mechanistic studies are needed to explain these interactions in more detail.

Distribution of Chemical Species in the Water-Soil-Plant (Carya illinoiensis) System near a Mineralization Area in Chihuahua, Mexico-Health Risk Implications

The aim of this study was to quantify major and trace elements in the water, soil, and plants (Carya illionensis) in an agricultural area; and to determine the health risks associated with the walnuts ingestion by calculating the risk quotient. Samples of water, soil, tree leaves, and walnuts were collected; in total, 135 samples were analyzed. Physicochemical parameters were obtained in irrigation water and soil samples. Elemental measurements were performed in an ICP, -OES and -MS. In addition, the distribution coefficient (soil–water), transfer factor (soil–plant), and hazard quotient were evaluated. In the irrigation water, As, Cr, and Pb, showed concentrations above the maximum allowable limits. Likewise, high concentrations of As, Cr, Pb, and Sb were found in tree leave samples, indicating a possible tendency of hyperaccumulation of those elements. Furthermore, Cr concentrations in walnuts were high by far than the reference value (FAO/WHO). A possible competition between chemical congeners were detected from transfer factors. Although, Sb concentrations in walnuts were also high, and no legislation for it in fruits exists. The hazard risk quotient for Sb did indicate a potential health risk. Finally, it is important to consider that the health risk increases when exposure through consumption takes place over a prolonged period of time, even in low concentrations.

Geological and hydrogeochemical controls on radium isotopes in groundwater of the Sinai Peninsula, Egypt

Radium isotopes (²²⁶Ra and ²²⁸Ra) were analyzed in 18 groundwater samples from the Nubian Sandstone Aquifer System (NSAS) and the shallow alluvial aquifers overlying the basement complex of the Sinai Peninsula, Egypt. Groundwater samples from deep Nubian aquifer wells (total depths 747 to 1250m) have ²²⁶Ra and ²²⁸Ra activities ranging from 0.168 to 0.802 and 0.056 to 1.032Bq/L, respectively. The shallower Nubian aquifer wells (63 to 366m) have ²²⁶Ra and ²²⁸Ra activities ranging from 0.033 to 0.191 and 0.029 to 0.312Bq/L, respectively. The basement shallow alluvial aquifers have ²²⁶Ra and ²²⁸Ra activities ranging from 0.014 to 0.038 and 0.007 to 0.051Bq/L, respectively. Combined Ra activities in most wells were generally in excess of the US Environmental Protection Agency (EPA), the European Union (EU), and the World Health Organization (WHO) maximum contaminant levels (MCL) for drinking water. Radium in groundwater is produced mainly by decay of parent nuclides in the aquifer solids, and observed activities of dissolved Ra isotopes result from a combination of alpha-recoil, adsorption/desorption, co-precipitation/dissolution processes. The observed correlation between Ra activities and salinity indicates that adsorption/desorption processes may be the dominant factor controlling Ra mobility in Sinai groundwater. Radium activities in central and northern Sinai are generally higher than those in southern Sinai, consistent with a gradual increase in salinity and water-rock interaction with increasing groundwater age. Barite is approximately saturated in the groundwater and may limit maximum dissolved Ra concentration. The results of this study indicate that Sinai groundwater should be used with caution, possibly requiring Ra removal from water produced for domestic and agricultural consumption.

Natural radionuclides in plants, soils and sediments affected by U-rich coal mining activities in Brazil

Mining activities can increase the mobility of metals by accelerating the dissolution and leaching of minerals from the rocks and tailing piles to the environment and, consequently, their availability for plants and subsequent transfer to the food chain. The weathering of minerals and the disposal of coal waste in tailing piles can accelerate the generation of acid mine drainage (AMD), which is responsible for the higher dissolution of metals in mining areas. In this context, the behavior of U, Th and K in soils and sediment, and the transfer factor (TF) of ²³⁸U, ²³⁴U and ²¹⁰Po for soybean, wheat, pine and eucalyptus cultivated around a coal mine in southern Brazil was evaluated. Alpha and gamma spectrometry were used for the measurements of the activity concentration of the radioelements. ²¹⁰Po was the radionuclide that is most accumulated in the plants, especially in the leaves. When comparing the plant species, pine showed the highest TF values for ²³⁴U (0.311 ± 0.420) for leaves, while eucalyptus showed the highest TF for ²³⁸U (0.344 ± 0.414) for leaves. In general, TF were higher for the leaves of soybean and wheat when compared to the grains, and grains of wheat showed higher TF for ²¹⁰Po and ²³⁸U than grains of soybean. Deviations from the natural U isotopic ratio were recorded at all investigated areas, indicating possible industrial and mining sources of U for the vegetables. A safety assessment of transport routes and accumulation of radionuclides in soils with a potential for cultivation is important, mainly in tropical areas contaminated with solid waste and effluents from mines and industry.

Gross alpha and beta activity and annual committed effective dose due to natural radionuclides in some water spinach (ipomoea aquatica Forssk) samples in Ho Chi Minh City, Vietnam

The results of gross alpha and beta radioactivity measurement in water spinach samples from some districts in Ho Chi Minh City, Vietnam are presented in this paper. The measurements were performed using a low-background proportional counters LB4200 manufactured by Canberra Company, Inc. Mean concentrations of gross alpha and beta activity were found to be 1.50 ± 0.38 Bq kg^-1 to 84.25 ± 8.67 Bq kg^-1. In order to keep the recommended dose level, a recommended maximum intake of water spinach was proposed to be 6 kg fresh per year. The total annual committed effective dose due to natural radionuclides in water spinach samples was then found in range from 0.07 mSv y^-1 to 0.82 mSv y^-1. The dose from 26.32% of samples exceeds the exemption mean dose criterion of 0.3 mSv y^-1 but complies with the upper dose principle of 1 mSv y^-1 provided in UNSCEAR 2008 report. The estimated soil-to-plant transfer factors for gross alpha and beta for water spinach samples were also presented.

Assessment of natural radioactivity and gamma-ray dose in monazite rich black Sand Beach of Penang Island, Malaysia

Activity concentrations of primordial radionuclides in sand samples collected from the coastal beaches surrounding Penang Island have been measured using conventional γ-ray spectrometry, while in-situ γ-ray doses have been measured through use of a portable radiation survey meter. The mean activity concentrations for ²²⁶Ra, ²³²Th and ⁴⁰K at different locations were found to be less than the world average values, while the Miami Bay values for ²²⁶Ra and ²³²Th were found to be greater, at 1023±47 and 2086±96Bqkg^{̶ 1} respectively. The main contributor to radionuclide enrichment in Miami Bay is the presence of monazite-rich black sands. The measured data were compared against literature values and also recommended limits set by the relevant international bodies. With the exception of Miami Bay, considered an elevated background radiation area that would benefit from regular monitoring, Penang island beach sands typically pose no significant radiological risk to the local populace and tourists visiting the leisure beaches.