Soil to rice transfer factors for (226)Ra, (228)Ra, (210)Pb, (40)K and (137)Cs: a study on rice grown in India

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.

Dose and transfer factor ofn 40K in medicinal plants

The presence of naturally occurring radionuclides is common in all living and non-living frameworks, which are part of our environment. The activity concentration of 40K radionuclide was estimated using gamma spectrometry in some medicinal plants and transfer factors (TF), and Average Annual Committed Effective Dose (AACED) was evaluated. The standard methods were followed in the process of sample collection and processing. The mean activity concentrations of 40K were 223 and 1330 Bq kg-1 in soil and medicinal plants, respectively. The mean TF and AACED were found to be 6.5 and 8.2 μ Sv y-1, respectively. Higher activity concentration was observed in some medicinal plants due to the selective and preferential uptake of this radionuclide depending on their medicinal utility. The study may help to form the database and safety regulations connected with 40K activity in medicinal plants.

Ingestion exposure of public to natural radionuclides and committed effective dose and cancer risk through tuber crops cultivated in Ebonyi State, Nigeria

Internal exposure of public to radiation arising from ingestion of natural radionuclides in tuber crops of Ebonyi State origin was investigated in this study. Committed effective doses and lifetime cancer risk of 40K, 226Ra, and 232Th in cassava, cocoyam, water yam, and white yam were calculated. The average activity concentrations of 40K, 226Ra, and 232Th determined by gamma spectrometric Na (TI) detector were, respectively, 199.15 ± 23.51, 77.57 ± 7.98, and 118.20 ± 10.72 Bq/kg in cassava; 146.62 ± 40.69, 43.42 ± 7.63, and 75.61 ± 2.89 Bq/kg in cocoyam; 162.81 ± 20.43, 63.17 ± 11.36, and 81.50 ± 10.27 Bq/kg in water yam; and 184.50 ± 20.22, 80.23 ± 10.93, and 116.29 ± 5.93 Bq/kg in white yam. The total committed effective dose via ingestion aligned in this order of cassava (7.05 mSv/year) > white yam (4.38 mSv/year) > water yam (0.42 mSv/year) > cocoyam (0.21 mSv/year) with overall average dose of 3.12 mSv/year. The values of dose were higher than world average of 0.29 mSv/year given by United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). The lifetime cancer risk values were above tolerance level of >10-4 prescribed by United States Environmental Protection Agency (USEPA), suggesting probable evolvement of radiogenic cancer morbidity. The data presented in this study contributes to baseline information on radiological characteristics of tuber crops in Ebonyi, which would be valuable to WHO/FAO food safety policy in Nigeria and rest of the world.

Gamma spectroscopy study of soil-plant transfer factor characteristics of 40K, 232Th and 226Ra in some crops cultivated in southwestern region of Nigeria

Soil-plant transfer factor (TF) is one of the vital variables employed in assessing plants uptake of radionuclides and their transfer to food chain for predictive ingestion dose and risk evaluation. To further this goal, the TF characteristics of natural 40K, 232Th and 226Ra were thus investigated in some crops (yam, cassava, rice, maize, groundnut, cowpea, okra, pumpkin leaf, banana and pawpaw) cultivated in southwestern part of Nigeria using HPGe gamma spectroscopy. The obtained results of activity concentration (AC) of the radionuclides across all the cultivated soil samples indicated average values that are less than the global average, whereas in the crops, average values of 226Ra and 232Th, were higher than reference values for different crops group. The overall range of the calculated TF of 40K, 232Th and 226Ra across all the crops was 0.05 (in maize and cowpea) to 15.01 (in banana), 0.01 (in pumpkin leaf and groundnut) to 19.80 (in pawpaw), and 0.04 (in cassava) to 21.30 (in cowpea), respectively. Overall arithmetic mean and geometric mean were estimated as 2.66 and 1.60, 1.11 and 0.43, and 1.10 and 0.54 for 40K, 232Th and 226Ra, respectively. TFs mostly correlated negatively with soil radionuclides, while positive correlation was mostly noticeable in the case of crop. Log normal transform of the TFs data indicated a near normal distribution as against the calculated data. The derived results of this study is here presented as a baseline data suggested for possible radiological risk assessment of food chain of the local population.

Evaluation of transfer factors of 226Ra, 232Th, and 40K radionuclides from soil to grass and mango in the northern region of Bangladesh

Bangladesh is a rapidly developing country, which is vulnerable to various types of pollution due to the large-scale industrial and associated human activities that might potentially affect the locally harvested foodstuffs. Therefore, the transfer factor is an essential tool to assess the safety of foodstuffs due to the presence of natural radioactivity in environmental matrix and/or strata. This is a first study of its kind conducted in a well-known region for mango farming in Bangladesh, measuring the uptake of naturally occurring radioactive materials (NORMs) by grass and mango from soil to assess the ingestion doses to humans. The HPGe gamma-ray detector was used to determine the concentrations of NORMs in samples of soil (20), grass (10), and mango (10), which were then used to calculate the transfer factors of soil to grass and soil to mango. Average activity concentrations of ²²⁶Ra, ²³²Th, and ⁴⁰K in associated soil samples (47.27 ± 4.10, 64.49 ± 4.32, 421.60 ± 28.85) of mango and ²²⁶Ra and ²³²Th in associated soil samples (45.07 ± 3.93, 52.17 ± 3.95) of grass were found to exceed the world average values. The average transfer factors (TFs) for mango were obtained in the order of ⁴⁰K(0.80) > ²²⁶Ra (0.61) > ²³²Th (0.31), and for grass, it shows the order of ⁴⁰K (0.78) > ²³²Th (0.64) > ²²⁶Ra (0.56). However, a few values (3 mango samples and 3 grass samples) of the estimated TFs exceeded the recommended limits. Moreover, Bangladesh lacks the transfer factors for most of the food crops; therefore, calculation of TFs in the major agricultural products is required all over Bangladesh, especially the foodstuffs produced near the Rooppur Nuclear Power Plant, which is scheduled to be commissioned in 2023.

Quantification of excess Carbon-14 specific activity in terrestrial biota in the off-site locations of the PHWR nuclear power plant at Kaiga, India

This is the first detailed study on ¹⁴C activity in the environment surrounding a nuclear facility in India. Samples of food matrices and wild plants from the off-site locations of the PHWR nuclear power plant (NPP) at Kaiga were analysed by liquid scintillation spectrometry, results were validated by accelerator mass spectrometry, and an extensive database (N = 142) was established. The stable isotope ratio of carbon (δ¹³C) in terrestrial plants varied from -33.5 to -23.3 ‰. The maximum excess ¹⁴C activity recorded in terrestrial biota was 44 Bq kg^-1C (19 pMC). About 75 % of the samples exhibited specific activity in the range 228-249 Bq kg^-1C (101-110 pMC). Statistical tests on the ¹⁴C specific activity dataset for 2.3-5, 5-10, and 10-20 km radial zones confirmed that the impact of the operation of the NPP on the environment beyond 5 km is minimal. The study suggests that the ¹⁴C activity released through gaseous effluents from Kaiga NPP is transported to greater distances along the axis of the valley than that predicted by the Gaussian plume model and those reported for other NPP sites worldwide. This is due to the unique topography of the Kaiga valley in which wind flow channelling, strong winds in the valley mouth, and calm wind within the valley due to the blocking effect by hills for the south-westerly wind regime play dominant roles in the transport of gaseous effluents. The ¹⁴C specific activity values at upwind monitoring stations located at >5 km distance from the NPP during the south-westerly wind regime were higher than those observed during the north-easterly wind regime when the same monitoring stations were located on the downwind side. The ingestion dose to the population in the 2.3-5 km radius zone, attributable to the release of ¹⁴C from the NPP, was 0.75 μSv y^-1. This is a negligibly small fraction of the ICRP recommended dose limit of 1000 μSv y^-1 for the public from other than natural sources. The dose due to the natural ¹⁴C activity in the Kaiga region was 12 µSv y^-1, corresponding to the ambient natural activity of 230 Bq kg^-1 C.

Carbon-14 emission from the pressurized heavy water reactor nuclear power plant at Kaiga, India

This is a detailed study on oxide (CO2) and reduced (hydrocarbons, CnHm) forms of 14C releases through gaseous effluents from the Kaiga nuclear power plant (NPP), on the West Coast of India, where 4 × 220 MW(e) pressurized heavy water reactors (PHWRs) are operating. The gaseous effluent from the common stack of reactor units 3 and 4 (each of 220 MW(e)) was sampled from 2017 to 2020 for 14C activity monitoring and analysed for 14C activity by liquid scintillation counting. The normalized release rate corresponding to the four-year monitoring period had a geometric mean value of 0.12 TBq GW(e)-1 a-1 (geometric standard deviation = 7.4), and the arithmetic mean with associated standard deviation was 0.75 ± 1.47 TBq GW(e)-1 a-1. The relative percentage contribution of reduced form (CH4) of 14C species was less than 1.27% of the total release. The normalized release rate from Kaiga NPP was similar to those reported for the other PHWR NPPs of the world. The 14C specific activity in the ambient air in the vicinity of the NPP was monitored at four locations. The maximum excess 14C activity values in the ambient air in the vicinity of the NPP, evaluated by comparing the specific activity recorded for the clean air region at ∼300 km from the NPP, were 65.1 Bq kg-1C (28.76 pMC) and 222.4 Bq kg-1C (98.23 pMC) for the years 2019 and 2020 respectively. In addition, the release rates were calculated from the Gaussian plume model using site-specific atmospheric dilution factors and the excess 14C specific activity measured at four off-site monitoring stations. The calculated values of release rates were in agreement (within a factor of ∼3) with the measured values.

A REVIEW OF 137CS TRANSFER FACTOR STUDIES FOR INDIAN ENVIRONS

In recent years there have been conscious efforts put by researchers in India to generate the soil-to-plant 137Cs transfer factor values. This review study is aimed at providing a comprehensive background of 137Cs transfer rates around the environs of a few nuclear power plant sites of India. As a part of this, the study looked into 137Cs transfer rates from soil to various plant species. The effort was made to quantify the transfer rates of 137Cs and various parameters affecting the movement of 137Cs in the terrestrial environment. The past and current knowledge on 137Cs transfer factors available in the literature were reviewed thoroughly and highlighted the need for incorporating lesser known and overlooked aspects of radionuclide behaviour for future studies. The paper also tried to identify and highlight the gaps and inconsistencies in the reported values of 137Cs transfer factors.

Environmental transfer parameters of strontium for soil to cow milk pathway for tropical monsoonal climatic region of the Indian subcontinent

The radionuclide transfer between compartments is commonly described by transfer parameters representing the ratio of concentrations of an element in two compartments for equilibrium conditions. This is a comprehensive study on the soil-to-grass transfer factor (Fv) and grass-to-cow milk transfer coefficient (Fm) for stable strontium (Sr) for soil-grass (pasture)-cow (Bos taurus) milk environmental pathway under field conditions for a high rainfall tropical monsoonal climatic region of the Indian subcontinent. The study was conducted in the vicinity of the Kaiga nuclear power plant (NPP), situated ~ 58 km inland of the West Coast of the Indian subcontinent. A grass field was developed exclusively for this study, and two cows of the native breed were raised to graze on it. The soil, grass, and milk were analyzed to evaluate the Fv and the Fm values for the stable Sr. For comparison, several pasture lands and the cows raised by the villagers and a dairy farm were also studied. The Fv values were in the range 0.18-8.6, the geometric mean (GM) being 1.8. The correlations of Fv values with a range of physicochemical parameters are presented. The GM values for Fm were 2.2 × 10-3 d L-1 and 7.2 × 10-3 d L-1 for the two cows raised for this study, 2.6 × 10-3 d L-1 for those raised by the villagers, and 4.2 × 10-3 d L-1 for the dairy farm. The site-specific Fm value for the region was determined as 3.2 × 10-3 d L-1. The concentration ratio (CR), defined as the ratio of Sr concentration in milk to that in feed under equilibrium conditions, exhibited less variability (1.8 × 10-2-5.4 × 10-2) among the three categories of cows.

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.

The plant transfer factor of natural radionuclides and the soil radiation hazard of some crops

In the present study, the transfer factors of the natural radionuclides ²³⁸U, ²³²Th, and ⁴⁰K were estimated for several crops cultivated in farms in the suburbs of Baghdad and one farm in Al-Najaf. The transfer factor (T_F) is the ratio of activity transfers from soil to plant. The specific activities of the natural radionuclides were measured with a gamma-ray spectrometer with a HPGe detector. The crops include cereals (rice and wheat), fruits (lemons and oranges), podded vegetables (vigna and okra), fruity vegetables (chili peppers and Solanum melongena), and leafy vegetables (Apium graveolens, Raphanus sativus, and Ocimum basilicum). The results showed that the highest transfer factors for ²³⁸U, ²³²Th, and ⁴⁰K are 0.32, 0.70, and 3.44, respectively, in wheat. The average transfer factors for ²³⁸U and ²³²Th were founded 0.23 and 0.2 which are lower than the default unitiy value but the 1.85 were reported for ⁴⁰K higher than unity.

Natural radionuclides and assessment of radiological hazards in MuongHum, Lao Cai, Vietnam

²²⁶Ra, ²³⁸U, ⁴ K, and ²³²Th (²²⁸Ra) activity concentrations of 61 soil samples distributed surrounding the rare earth element mine (NORM), MH, Lao Cai, Vietnam have been measured by HPGe detector. The activity concentrations of ²²⁶Ra, ²³⁸U, ⁴ K, and ²³²Th (²²⁸Ra) range from 1179 to 6291 Bq/kg, from 1024 to 8351 Bq/kg, from 260 to 3519 Bq/kg, and from 1476 to 35546 Bq/kg in the ore body and from 21.3 to 964 Bq/kg, from 23.4 to 1635 Bq/kg, from 124 to 3788 Bq/kg, and from 40.9 to 6107 Bq/kg outside the ore body in respective. The study area is considered as the high local natural background radiation with the concentration of ²²⁶Ra, ²³⁸U, ⁴ K, and ²³²Th (²²⁸Ra) of 156, 254, 647, and 908 Bq/kg in respective. Regarding the spatial distribution, the measured radionuclide concentrations are independent of the distance from measured points to the ore body. With regard to the hazard indices, the average calculated radiological hazard indices, including absorbed gamma dose rate, effective dose equivalent, and excess lifetime cancer risk significantly exceed the global average values. There is a disequilibrium between ²³⁸U/²²⁶Ra concentrations in studied soil samples. The results also found that the ²³²Th (²²⁸Ra) concentration and total absorbed gamma dose rate show a strong positive correlation (coefficient of determination, R² = 1).

Optimisation of CO2 absorption and liquid scintillation counting method for carbon-14 specific activity measurement in atmospheric air

A method for the determination of ¹⁴C activity in the ambient air was optimised with the development of a simple setup for the regeneration of CO₂ from carbonate sample and saturating the absorber in <45 min for direct determination of activity by liquid scintillation counting (LSC). Atmospheric CO₂ was trapped in NaOH solution and precipitated as BaCO₃ by adding BaCl₂. The carbonate sample was taken in a newly designed regeneration system, subjected to acid hydrolysis, and the absorber (CarboSorb-E) was saturated with the CO₂ regenerated from carbonate sample. This allowed optimisation of CO₂ absorption by the absorber (up to ~ 2.3941 g of CO₂/10 mL with an average of 2.1688 g) and a minimum detectable activity value of 14 Bq kg^-1C for a counting time of 300 min (8 Bq kg^-1C for 1000 min) was achieved with Quantulus - 1220 LSC system. The necessity of (i) the measurement of the total volume of air sampled, (ii) the determination of trapping efficiency for CO₂ in the NaOH, recovery of ¹⁴C in chemical processing of BaCO₃, and subsequent regeneration and absorption processes, and (iii) independent determination of carbon content in the air for expressing the results in terms of ¹⁴C specific activity (Bq kg^-1C), are avoided in this method. The method is capable of yielding accurate results, in a considerably shorter time when compared to previously reported methods, with a deviation of <2.2% from the target value (with a relative standard deviation of 1.1%, and a relative error of 0.53%) when ambient air samples from clean air region (region not affected by local anthropogenic sources of ¹⁴C) are analysed. Validation of the method was performed by (i) analysing BaCO₃ sample derived from ambient air by accelerator mass spectrometry, and (ii) analysing the CO₂ produced from the combustion of IAEA C3 reference material. Upon validation, the suitability of the method for determining small excess ¹⁴C specific activity in the vicinity of a nuclear power plant was demonstrated.

Optimisation of a batch thermal combustion method using a tube furnace oxidation system (pyrolyser) and LSC for carbon-14 determination in environmental matrices

Accelerator mass spectrometry and benzene synthesis coupled with liquid scintillation spectrometry are often used for accurate measurements of ¹⁴C activity in the environmental matrices. Thermal oxidation is one of the methods employed for ¹⁴C determination in environmental matrices. In this method, the sample is oxidised at high temperature (600-900 °C) to convert carbon species to CO₂ and trapped in an amine-based absorber for determining the activity in a liquid scintillation counting (LSC) system. In this study, the performance of a commercially available tube furnace system (pyrolyser), for batch combustion of samples, was evaluated for the determination of ¹⁴C specific activity in terrestrial biota samples. Significant improvements over the manufacturer specified method, which is primarily designed for analysis of samples with activity well above the environmental background level, was implemented to achieve accurate determination of ¹⁴C specific activity at ambient background level. In the improved method, the CO₂ produced from the combustion of the sample was isolated from the combustion products through cryogenic trapping and then absorbed in the absorber (Carbo-Sorb E) through a simple off-line transfer process. This allowed (i) optimisation of CO₂ absorption by the absorber (2.2477 g of CO₂/10 mL), (ii) achieving good accuracy and precision in the measurements, and a minimum detectable activity value of 13 Bq kg^-1C for a counting time of 300 min (7 Bq kg^-1C for 1000 min), (iii) avoiding uncertainty associated with the determination of recovery of ¹⁴C in the combustion and trapping process, and (iv) elimination of the need for an independent determination of carbon content (%) for expressing the results in terms of ¹⁴C specific activity. The method is capable of yielding accurate results with a deviation of <2.4% from the target value for IAEA C3 quality assurance reference material (with a relative standard deviation of 1.40%, and relative error of 0.34%). The combined uncertainty (1σ) associated with the measurements was computed to be 3.4%. Upon optimisation, the suitability of the method for the determination of ¹⁴C specific activity in typical terrestrial biota samples of clean air region (region not affected by local anthropogenic sources) and for the quantification of a small increase in the ¹⁴C activity above ambient levels in the vicinity of a nuclear power plant is demonstrated.

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.

Study on Trace Elements Concentration in Medicinal Plants Using EDXRF Technique

Ten medicinal plants used as ingredients of folklore and Ayurvedic medicine belonging to the Malnad Kerala region of South India, were analysed for concentrations of trace elements Fe, Cr, Mn, Co, Ni, Cu, Zn, As, and Pb using the Energy Dispersive X-ray Fluorescence (EDXRF) technique. The soil from the root area of these medicinal plants was also analysed, and the soil to plant transfer factor (TF) of the elements was estimated. Iron (Fe) recorded higher concentration than the other trace elements estimated in the medicinal plants, followed by manganese (Mn) and zinc (Zn). The mean TF was found to be highest for Zn. Plectranthus amboinicus (Lour.) Spreng recorded the maximum value of TF for Zn. Most of the essential elements were found to be present in Centella asiatica (L.) Urban and indicated its medicinal importance. The data obtained in the present investigation may add up to the trace elemental database of medicinal plants in the world.

An innovative technique of harvesting soil gas as a highly efficient source of 222Rn for calibration applications in a walk-in type chamber: part-1

The paper describes a novel technique to harvest 222Rn laden air from soil gas of natural origin as a highly efficient source of 222Rn for calibration applications in a walk-in type 222Rn calibration chamber. The technique makes use of a soil probe of about 1 m to draw soil gas, through a dehumidifier and a delay volume, using an air pump to fill the calibration chamber. 222Rn concentration in the range of a few hundred Bq m-3 to a few tens of kBq m-3 was easily attained in the chamber of volume 22.7 m3 within a short pumping duration of 1 h. A new technique referred to as "semi-dynamic mode of operation" in which soil gas is injected into the calibration chamber at regular intervals to compensate for the loss of 222Rn due to decay and leak is discussed. Harvesting soil gas has many important advantages over the traditional methods of 222Rn generation for calibration experiments using finite sources such as solid flow-through, powdered emanation, and liquid sources. They are: (1) soil gas serves as an instantaneous natural source of 222Rn, very convenient to use unlike the high strength 226Ra sources used in the calibration laboratories, and has no radiation safety issues, (2) does not require licensing from the regulatory authority, and (3) it can be used continuously as a non-depleting reservoir of 222Rn, unlike other finite sources. The newly developed technique would eliminate the need for expensive radioactive sources and thereby offers immense application in a variety of day to day experiments-both in students and research laboratories.

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.

A WALK-IN TYPE CALIBRATION CHAMBER FACILITY FOR 222Rn MEASURING DEVICES AND INTER-COMPARISON EXERCISES

A walk-in type 222Rn calibration chamber of volume 22.7 m3, which has traceability to international standards, is established at the Centre for Advanced Research in Environmental Radioactivity, Mangalore University, India. It has a human-machine interface communication system, a programmable logic controller and sensor feedback circuit for controlling and data acquisition of relative humidity (RH) and temperature (T). An innovative method for the generation of desired 222Rn concentration (a few hundred Bq m-3 up to about 36 kBq m-3) using soil gas as a source was adopted. Leak rates of 222Rn from the chamber for the mixing fan ON and OFF conditions were determined to be 0.0011 and 0.00018 h-1 respectively. With the exhaust system fully turned on, the maximum clearance rate of the chamber was 0.58 ± 0.07 h-1. Excellent spatial uniformity in 222Rn concentration in the chamber was confirmed (with a mean value of relative standard deviation < 12%) through measurements at 23 locations using CR-39 film-based passive devices. Demonstration of calibration applications was performed using charcoal canister and PicoRad vials as the 222Rn adsorption devices. The study shows that gamma spectrometry is a convenient alternative approach to liquid scintillation analysis of PicoRad vials for 222Rn measurement.

Depthprofile distribution of Cs and its toxicity for canola plants grown on arid rainfed soils as affected by increasing K-inputs

Radioactive cesium (Cs) is more likely to be trans-located via rainfall into surrounding environments. Upon Cs-contaminated water reaching soil, Cs is retained on soil components, mainly organic matter and clay fraction. This study aims are i) comparing the relative ability of five arid soils, differing in their textural and chemical properties, to accumulate Cs when subjected to Cs-artificially contaminated rain droplets and ii) testing whether K fertilizer can decrease the uptake of Cs and its translocation within plants or not. A lab experiment was then conducted to simulate artificial rain droplets contaminated with 1000 becquerel (Bq) of ¹³⁴Cs L^-1 precipitated on soil columns each of 10.5 cm inner diameter at a rate of 1.15 mL cm^-2 over a period of 2-months. At least 89% of ¹³⁴Cs accumulated within the uppermost 5-cm layer of these soils. Another greenhouse experiment was set to test the hypothesis which indicates that Cs uptake increases unexpectedly by supplying plants with K-fertilizers. In this experiment, canola (Brassica napus L.) seeds were cultivated into three K-deficient soils (Typic Haplotorrent, Typic Haplocalcid, and Typic Torripsamment) which were contaminated with 100 mg Cs kg^-1 soil (stable-Cs was used instead of radioactive-Cs to designate its behavior on the long run). Canola plants were fertilized with 0, 80 and 120 mg K₂SO₄ kg^-1 soil. Results carried on Typic Haplotorrent soil confirmed the aforementioned assumption as K-addition increased Cd-uptake up to 40.1%. Contradictory results were achieved in the other two soils where Cs-uptake decreased by 21.5 and 15.3% in Typic Haplocalcid and Typic Torripsamment soils, respectively due to the application of the aforementioned dose of K. In the K non-amended soils, Cs shoot-root translocation factor was >1; yet, it was <1 in response to K addition, regardless of its application rate.

137Cs and 40K concentration ratios (CRs) in annual and perennial plants in the Caspian coast

This research attempted to investigate the plant/soil concentration ratios (CRs) of ¹³⁷Cs and ⁴⁰K in plants that grow on the Anzali Lagoon of the Caspian coast, Iran. The activity concentrations of ¹³⁷Cs and ⁴⁰K were measured in soil samples, annual plants (Echinochloa crus-galli, Digitaria sanguinalis, and Trifolium repens), and perennial plants (Phragmites australis, and Cynodon dactylon). The relationship of activity concentration with soil particle density, and pH of soil samples, CR, and ¹³⁷Cs/⁴⁰K discrimination factor (DF) were determined. The activity concentration of ¹³⁷Cs in the soil, annual plants, and perennial plants ranged between 12- and 124 (Bq/kg dry weight), 2- and 17 (Bq/kg dw), and 2 - and 14 (Bq/kg dw), respectively. The geometric mean (GM) values of DF in annual and perennial plants were 0.57 and 0.55, respectively. The CR for ¹³⁷Cs and ⁴⁰K varied as a non-linear relation in annual plants and perennial plants. This study showed that the CRs for ¹³⁷Cs in annual plants were higher than the CRs for perennial plants.

Assessment of radionuclide transfer factors and transfer coefficients near phosphate industrial areas of South Tunisia

The activity concentrations of naturally occurring and anthropogenic radionuclides in agriculture soils as well as in several food products at four locations within the phosphate area of South Tunisia were investigated. Soil-to-plant transfer factors as well as feed-to-animal products transfer coefficients were determined for the first time for the region. Activity concentrations of ⁴⁰K, ²¹⁰Pb, ²²⁶Ra, ²²⁸Ra and ¹³⁷Cs in soils of agriculture fields were lower than worldwide average values. The soil-to-plant transfer factors (TFs) for ⁴⁰K in leafy vegetables were higher than those in fruit vegetables. Soil-to-grass transfer factor (F_v) values were in the following order: ⁴⁰K > ²¹⁰Pb > ²²⁶Ra. The grass-to-milk transfer coefficient (F_m) values for ⁴⁰K and ²¹⁰Pb ranged between 2 × 10^-3 and 4 × 10^-3(day L^-1). The concentration ratios for the animal products (CR_milk-feed, CR_meat-feed and CR_egg-feed) varied in the ranges of 2 × 10^-2-4 × 10^-2 L kg^-1, 1 × 10^-2-2 × 10^-1 (L kg^-1) and 5 × 10^-2-1 (L kg^-1)for ⁴⁰K, ²¹⁰Pb and ²²⁶Ra, respectively. Transfer parameters determined in the present study were compared with those reported in International Atomic Energy Agency reports and other published values. The absorbed gamma dose rate in air and the external hazard index associated with these natural radionuclides were computed to assess the radiation hazard of radioactivity in this region, and the results indicated that these areas are within set safety limits.

BASELINE STUDIES ON RADIONUCLIDE CONCENTRATION IN FOOD MATERIALS AND ESTIMATION OF THE COMMITTED RADIATION DOSE AROUND THE PHOSPHATE INDUSTRIAL AREA OF SOUTH TUNISIA

The activity concentration of natural and anthropogenic radionuclides was determined in different vegetable samples, and foods derived from animal origin, from different locations in the four cities of Southern Tunisia, where large-scale phosphate industries are operating. The aim of the studies was to establish a baseline database on radionuclide concentration in food materials and to evaluate the radiation dose to the general population due to its ingestion through the food chain. The activity concentrations of 40K, 210Pb, 226Ra, 228Ra and 137Cs was determined by gamma spectrometry using a HPGe detector, and from the measured activity concentrations, the doses were estimated using the dose coefficients given by the ICRP. The dose due to intake of radionuclides through mineral water was also determined. The total annual effective doses were found to be 2.2, 1.4, and 0.7 mSv y-1 for 1 y, 5-15 y and adult (>17 y) age groups, respectively. Among the radionuclides studied, 210Po was the highest contributor to the total dose, followed by 210Pb.

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.

Estimation of air-to-grass mass interception factors for iodine

Air-to-grass mass interception factors for radionuclide are important basic input parameter for the estimation of radiation dose to the public around a nuclear power plant. In this paper, we present the determination of air-to- grass mass interception factors for iodine using a 2 m × 2 m × 2 m (l × b × h) size environmental chamber. The temperature, humidity, and rainfall inside the environmental chamber was controlled to required values to simulate different environmental conditions. Grass (Pennisetum purpureum, Schum), grown in pots, was kept inside the environmental chamber and stable iodine in elemental form was sublimed quickly inside the chamber to simulate an accidental release of iodine to the environment. The concentration of iodine in the air was measured periodically by drawing air through a bubbling setup, containing 1% sodium carbonate solution. The mass interception factor for dry deposition varied in the range of 0.25-7.7 m² kg^-1 with mean value of 2.2 m² kg^-1 with respect to fresh weight of grass, and that due to wet deposition varied in the range of 0.6-4.8 m² kg^-1 with mean value of 2.3 m² kg^-1. The mass interception factor was inversely correlated with the total iodine deposited through dry deposition as well as with the rainfall.

Outdoor dose rate mapping in Kuwait

As part of ongoing efforts to develop the data base required for the gamma dose rate baseline in Kuwait, a survey of ambient outdoor gamma-ray dose rates was carried out in 112 locations within the country. Measurements were performed, during the period from August 2013 to March 2016, in various undisturbed open areas in the desert using a NaI dosimeter/spectrometer. The dose rates were recorded along with the corresponding gamma-ray spectra for in-situ relative contribution of the primordial radionuclides and ¹³⁷Cs in the outdoor environment. Soil samples were also collected from the surface layers in a few locations for laboratory gamma spectrometric analysis and dose rate calculations. The dose rates obtained range from 31 to 59 nSv/h with a mean value of 46.5 nSv/h. There was no anomaly in the relative contributions of the primordial radionuclides to the dose rate values, while ¹³⁷Cs was not detected within the investigated locations. The significance of using the NaI-based dosimeter in the present survey is discussed in the paper.

Annual Effective Dose of Gamma Emitters in Adults and Children for Some Types of Rice Consumed in Iraq

This work studies the activity concentration of natural radioactivity in 20 different types of rice, including imported rice and that produced locally. The rice samples were collected from markets and farms in Iraq, and then a natural radioactivity investigation was done in the environmental laboratory of the Kufa University, using gamma-ray spectrometer systems. The research focused on measuring the activity concentration of natural radioactivity (²³⁸U, ²³²Th, and ⁴⁰K) to determine the level of the radium equivalent activity, internal hazard indices, and annual effective dose. The results show that all these parameters are within the permissible limits and that radioactivity is present in almost all foodstuffs at levels ranging from 40 to 600 Bq/kg of food. Radioactivity in foodstuffs is attributed to a natural source, potassium-40, and to artificial sources, which include industrial radioactivity, weapons testing, and accidents involving radioactivity. In this article, radionuclides have been identified for most of the common species of rice available in Iraqi markets; in addition, radium equivalent activity, internal hazard indices, and annual effective dose were calculated and compared with the permissible dose to estimate the risk of radioactive isotopes in the rice crop.

Transfer factors of natural radionuclides and (137)Cs from soil to plants used in traditional medicine in central Serbia

Transfer factors of natural radionuclides and (137)Cs from soil to plants used in traditional medicine were determined. The transfer factors (TF) were calculated as Bq kg(-1) of dry plant per Bq kg(-1) of dry soil. Mass activity concentrations of (226)Ra, (232)Th, (40)K and (137)Cs in soil and plant samples were measured with high purity germanium detector (HPGe). The concentrations of As, Co, Cr, Cu, Mn, Ni, Pb and Zn were determined, as well as the cation exchange capacity (CEC) and the content of exchangeable cations (Ca, Mg, K, Na). Wide ranges of values were obtained for all the metals, especially for Cr and Ni. The Absalom model was used for determination of the amount of (137)Cs transferred from soil to plant based on soil characteristics such as pH, exchangeable potassium, humus and clay contents. The estimated transfer factors were in the range from 0.011 to 0.307 with an arithmetic mean of 0.071, median of 0.050, geometric mean of 0.053 and geometric standard deviation (GSD) of 2.08. This value agreed well with that calculated from the measurements of 0.069, geometric mean 0.040 and GSD 3.19. Correlations between radionuclides, metals, physicochemical properties and transfer factors were determined by Spearman correlation coefficient. There was a strong positive correlation between (137)Cs transfer factor and the ratio of transfer factor for K and (137)Cs. Principal Component Analysis (PCA) was performed in order to identify some pattern of data.

Radioactivity levels and heavy metals in the urban soil of Central Serbia

Radioactivity concentrations and heavy metal content were measured in soil samples collected from the area of Kragujevac, one of the largest cities in Serbia. The specific activities of (226)Ra, (232)Th, (40)K and (137)Cs in 30 samples were measured by gamma spectrometry using an HPGe semiconductor detector. The average values ± standard deviations were 33.5 ± 8.2, 50.3 ± 10.6, 425.8 ± 75.7 and 40.2 ± 26.3 Bq kg(-1), respectively. The activity concentrations of (226)Ra, (232)Th and (137)Cs have shown normal distribution. The annual effective doses, radium equivalent activities, external hazard indexes and excess lifetime cancer risk were also estimated. A RAD7 device was used for measuring radon exhalation rates from several samples with highest content of (226)Ra. The concentrations of As, Co, Cr, Cu, Mn, Ni, Pb and Zn were measured, as well as their EDTA extractable concentrations. Wide ranges of values were obtained, especially for Cr, Mn, Ni, Pb and Zn. The absence of normal distribution indicates anthropogenic origin of Cr, Ni, Pb and Zn. Correlations between radionuclide activities, heavy metal contents and physicochemical properties of analysed soil were determined by Spearman correlation coefficient. Strong positive correlation between (226)Ra and (232)Th was found.

Evaluation of the radioactive Cs concentration in brown rice based on the K nutritional status of shoots

The radioactive cesium ((134,137)Cs) concentration in brown rice is correlated with that in the straw/husk. The distribution of (134,137)Cs, resembles that of potassium (K), a homologous element of Cs, in the rice plant body. The relative isotopic abundance of (40)K is 0.0117 %; thus, 1 g K contains 30.4 Bq ⁴⁰K, and the mass of 4,000 Bq (40)K is 0.0154 g, indicating that the K concentration can be calculated from (40)K concentration. We examined if the radioactive Cs concentration in brown rice can be estimated from (40)K concentrations in straw, and especially might be predicted from the (40)K:(134,137)Cs ratio in straw. We determined the concentrations of (40)K and radioactive Cs in straw and brown rice, and found a strong correlated-equation (y = 72.922 x(-0.759); r = 0.907) between the radioactive Cs concentration in brown rice and the ⁴⁰K:(134,137)Cs ratio in straw. The estimated-radioactive Cs concentration in brown rice can be as much as double, depending on the K nutritional status changing the ⁴⁰K:(134,137)Cs ratio in straw. We herein propose a nutritional diagnosis that radioactive Cs concentrations in brown rice can be predicted from the ⁴⁰K:(134,137)Cs ratio in shoots.