Uptake and distribution of natural radioactivity in wheat plants from soil

Transfer factors for natural radioactivity into olive mill pomace

The transfer factor (TF) of naturally occurring radioactivity between soil and olive mill pomace (OMP) was calculated in this study. Nine samples were collected from three locations in north Jordan. The study focused on calculating the 226Ra, 232Th, 40K, and 137Cs activity concentrations in both soil and OMP samples using high-purity germanium (HPGe) gamma-ray spectrometry. The average activity levels in the soil samples were determined to be 24.0±10.1, 31.3±9.1, 323.7±68.4, and 1.0±0.4 (Bqkg-1), respectively. In the OMP samples, the average activity levels of 226Ra, 232Th, and 40K were 6.7±1.8, 3.2±1.2, and 185.5±56.6 (Bqkg-1), respectively, while no trace of 137Cs was detected. The activity concentrations of 226Ra, 232Th, and 40K in the soils and OMP samples are within the average worldwide ranges. The calculated values of the TF geometric mean (geometric standard deviation) for 226Ra, 232Th, and 40K were determined to be 0.35 (0.2), 0.11 (0.05), and 0.59 (0.19), respectively. This research offers valuable information about the behavior and movement of radionuclides in the environment.

Evaluation of radioactivity levels and radiological hazards of some endemic plants used as medicine in Ankara, Turkey

In this study, natural radioactivity levels (226Ra, 232Th, and 4 K) of some medicinal plant samples with known anti-oxidative properties, which are frequently consumed by animals and humans, were obtained from Ankara province and its surroundings (Mamak, Kızılcahamam, Beypazarı, Kahramankazan, and Polatlı districts) were determined using a thallium-doped sodium iodide NaI(Tl) gamma spectrometry. By using the determined natural radioactivity concentrations in the collected plant samples, the number of radiological doses that people could be exposed by consuming these plants was calculated. As a result of the study, 226Ra, 232Th, and 4 K radioactivity concentration ranges of the plant samples were found be 14.69 ± 1.27-59.08 ± 3.12 Bq kg-1, 1.78 ± 0.04-50.05 ± 2.76 Bq kg-1 and 207.24 ± 34.09-826.13 ± 25.40 Bq kg-1, respectively. The highest 226Ra, 232Th, and 4 K activity concentrations were measured in Astragalus densifolius subsp. ayashensis (Kahramankazan), Astragalus kochakii (Kahramankazan) and Rumex patientia (Patience Dock) (Kahramankazan) plants, respectively. The lowest 226Ra, 232Th and,4 K activity concentration plants were determined respectively as Rumex patientia (Mamak), Lavandula angustifolia (Kızılcahamam), and Astragalus acikirensis (Polatlı). The establishment and routine repetition of environmental radioactivity monitoring programs in each region are important for human and animal health, and the results of this study gain importance for Ankara and its surroundings in terms of environmental health.

Activity concentrations and bioconcentration factors (BCFs) of natural radionuclides (40 K, 226Ra, and 232Th) from cultivated substrates to mushrooms

This study examined 42 mushroom samples and corresponding cultivated substrates. The radionuclide activity concentrations and bioconcentration factor (BCF) from substrate-to-mushroom were determined. The substrate activity concentrations were 59.1-727.5, 4.5-37.6, and 4.0-53.0 Bq/kg dw (dry weight) for 40 K, 226Ra, and 232Th, respectively. The average 40 K concentrations were 1546.5, 1115.7, and 749.3 Bq/kg dw; the BCFs were 2.49, 3.56, and 5.58 for A. bisporus, F. velutipes, and L. edodes, respectively. The 40 K concentrations were insignificantly correlated with each species' corresponding substrate concentration. The 40 K BCFs had a significantly negative correlation with the substrate concentration for each species. Each mushroom species' 40 K concentration was almost stable, suggesting that 40 K has a regulated homeostasis for a given species. The average 226Ra concentrations were 5.5, 5.4, and 3.4 Bq/kg dw; the BCFs were 0.58, 0.17, and 0.50 for L. edodes, A. bisporus, and F. velutipes, respectively. The average 232Th concentrations were 4.7, 4.7, and 3.0 Bq/kg dw; the BCFs were 0.50, 0.11, and 0.53 for L. edodes, A. bisporus, and F. velutipes, respectively. The 226Ra and 232Th concentrations in mushrooms had a weak to moderate correlation with the cultivated substrate concentrations. The absorption of the 226Ra and 232Th from substrate-to-mushroom was similar to the hypothesis of the linear model that mushroom concentration yields a positive correlation with substrate concentration.

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.

Radium in New Zealand agricultural soils: Crop uptake and estimation of current and future ionising radiation dose

Crop uptake of ²²⁶Ra over a range of key New Zealand agricultural and horticultural growing areas was analysed to establish the dietary implications of an increase in soil ²²⁶Ra activity concentrations. Thirty crop samples, covering both feed and food commodities, were quantified for ²²⁶Ra activity concentrations, and concentration ratio (CRs) from the soil activity were calculated. The calculated CRs correlated with international default values for estimating crop uptake. Variation in CRs established that there was no increase in the crop activity concentration, relative to soil ²²⁶Ra from pasture foliage at a fertiliser impacted site, with a gradient of soil ²²⁶Ra activity concentrations. Based on the calculated CRs, the upper bound of the theoretical range of dietary exposures to ²²⁶Ra was 78.1 μSv/yr for teenage boys. Future forecasting of the increased dietary dose of ²²⁶Ra that might occur at the current soil loading rate, based on current fertiliser activity concentrations, confirmed that long-term loading of soil with ²²⁶Ra is unlikely to present a dietary risk. The forecast model calculated that the increase in dietary ionising radiation burden is unlikely to reach thresholds requiring regulatory intervention for two millennia.

Long Term Application of Fertilizers in Eastern Amazon and Effect on Uranium and Thorium Levels in Soils

In recent years, the use of fertilizers has increased in the Amazon. Phosphate fertilizers, which are commonly used, can present high concentrations of radioelements. In the present study, the activity concentrations of uranium (U) and thorium (Th) in Oxisols and Ultisols cultivated with citrus (Citrus sinensis (L.) Osbeck), oil palm (Elaeis guineensis Jacq.) and black pepper (Piper nigrum L.), with 26, 10 and 5 years of implantation, respectively, were evaluated. The potential risk of contamination was estimated by the enrichment (EF) and bioaccumulation (BAF) factors. Pearson’s correlation coefficients indicated a significant relationship between the concentrations of U and Th in soil and plant and the soil properties pH, Ca2+, Mg2+, K+ and P. The enrichment (EF < 2) and bioaccumulation (0.01 < BAF < 0.05) factors were low. In plant tissues, the concentrations of 238U followed the order: citrus > black pepper > oil palm, and the concentrations of 232Th followed the sequence: black pepper >> citrus > oil palm. The activity concentrations of 238U and 232Th in the soil cultivated with black pepper, as well as in the soil of the reference area close to the citrus plantation, were higher than the world average values of 35 and 30 Bq kg−1, respectively, established by the United Nations Scientific Committee on Effects of Atomic Radiation. Perennial crops that are fertilized annually must be monitored by environmental agencies due the accumulation of elements that can promote potential risks to human health.

Radionuclides and stable elements in vegetation in Australian arid environments: Concentration ratios and seasonal variation

Data on the uptake of elements and radionuclides by flora from soils in arid environments are underrepresented in international databases, especially when comparing across seasons. This study improved the understanding on the uptake of natural uranium-series radionuclides, as well as more than 30 elements, in a range of Australian native flora species that are internationally representative of an arid/semi-arid zone (e.g. Acacia, Astrebla, Atriplex, and Dodonea). Results indicate that the soil-to-plant uptake ratios were generally higher when compared with international data for grasses and shrubs from more temperate environments. The majority of the elemental concentrations in grasses were higher in winter than in summer and the opposite trend was found in shrubs, which suggests that the season of collection potentially introduces variability in the reported concentration ratios. The data also suggest that grasses, being dominant and widespread species in arid zones, may be effective as a reference organism to ensure comparative assessment across sites of interest. The results of this study will improve the confidence of environmental assessments in arid zones.

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.

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 natural radionuclide transfer factors and partition coefficients in some Syrian soils

Transfer factors of radium 226(²²⁶Ra), lead 210(²¹⁰Pb), polonium 210 (²¹⁰Po), uranium 238 (²³⁸U) and thorium 234(²³⁴Th) from five different agricultural soils in Syria to coriander, parsley and mint were investigated in a pot culture experiment. Geometric means of transfer factors (TF)were²²⁶Ra (0.13),²¹⁰Pb(0.03), ²¹⁰Po (0.02) and ²³⁸U (1.76) were within worldwide values, while TF values for ²³⁴Th (1.35) were higher than those recorded globally. The available transfer factor (ATF) values ranged between 0.03 and 1.45, 0.33 and 3.2, 0.10 and 3.36, 1.30 and 16.2 and 1.0 and 6.95 for²²⁶Ra,²¹⁰Pb,²¹⁰Po, ²³⁸U and ²³⁴Th, respectively. However, it is worth mentioning that the data from pot experiments may not represent field conditions. Liquid/solid partition coefficients (K_d)of ²²⁶Ra, U, ²¹⁰Pb and ²¹⁰Po for55 soils representing the dominant types of soils in Syria were also determined. Geometric means of K_d values ranged from 280 to1200, 750 to1600, 350to 4800 and 100-120 L kg^-1 for ²²⁶Ra, ²³⁸U, ²¹⁰Pb and ²¹⁰Po, respectively at pH = 4.0, and from 200 to 6700, 670 to 2400, 150 to 2100 and 100 to 160Lkg^-1at pH = 5.5, and from 370 to 790, 130 to 550, 60 to 330 and370 to 920Lkg^-1at pH = 7.0. The effects of soil mineral content, CEC, ECE, pH and soluble ions on the K_d values were investigated. In general, there were logarithmic relationships between the activity concentrations in soil and the K_d values (R² ranged from 0.59 to 1.00 at pH 4.0). There were no relationships between the K_d values and soil pH.

Assessment of Natural Radioactivity and Radiological Risks in River Sediments from Calabria (Southern Italy)

This study was developed to carry out a comprehensive radiological assessment of natural radioactivity for river sediment samples from Calabria, southern Italy, and to define a baseline background for the area on a radiation map. In the studied area, elevated levels of natural radionuclides are expected, due to the outcropping acidic intrusive and metamorphic rocks from which the radioactive elements derive. To identify and quantify the natural radioisotopes, ninety river sediment samples from nine selected coastal sampling points (ten samples for each point) were collected as representative of the Ionian and the Tyrrhenian coastline of Calabria. The samples were analyzed using a gamma ray spectrometer equipped with a high-purity germanium (HPGe) detector. The values of mean activity concentrations of 226Ra, 232Th and 40K measured for the studied samples are (21.3 ± 6.3) Bq kg−1, (30.3 ± 4.5) Bq kg−1 and (849 ± 79) Bq kg−1, respectively. The calculated radiological hazard indices showed average values of 63 nGy h−1 (absorbed dose rate), 0.078 mSv y−1 (effective dose outdoors), 0.111 mSv y−1 (effective dose indoors), 63 Bq kg−1 (radium equivalent), 0.35 (Hex), 0.41 (Hin), 0.50 (activity concentration index) and 458 µSv y−1 (Annual Gonadal Equivalent Dose, AGED). In order to delineate the spatial distribution of natural radionuclides on the radiological map and to identify the areas with low, medium and high radioactivity values, the Surfer 10 software was employed. Finally, the multivariate statistical analysis was performed to deduce the interdependency and any existing relationships between the radiological indices and the concentrations of the radionuclides. The results of this study, also compared with values of other locations of the Italian Peninsula characterized by similar local geological conditions, can be used as a baseline for future investigations about radioactivity background in the investigated area.

Assessment of the Levels of Pollution and of Their Risks by Radioactivity and Trace Metals on Marine Edible Fish and Crustaceans at the Bay of Bengal (Chattogram, Bangladesh)

Marine environmental pollution is a longstanding global problem and has a particular impact on the Bay of Bengal. Effluent from different sources directly enters rivers of the region and eventually flows into the Bay of Bengal. This effluent may contain radioactive materials and trace metals and pose a serious threat to the coastal environment, in addition to aquatic ecosystems. Using gamma spectrometry and atomic absorption spectrometry, a comprehensive study was carried out on the radioactivity (226Ra, 232Th, 40K, and 137Cs) and trace metal (Cd, Pb, Zn, Cu, Ni, Fe, Mn, and Cr) concentrations, respectively, in fish and crustacean species collected from the coastal belt of the Bay of Bengal (Chattogram, Bangladesh). The analysis showed a noticeable increment in the levels of different radioactive pollutants in the marine samples, although the consumption of the studied fish and crustacean species should be considered safe for human health. Anthropogenic radionuclide (137Cs) was not detected in any sample. Furthermore, the metal concentrations of a small number of trace elements (Pb, Cd, Cr) were found to be higher in most of the samples, which indicates aquatic fauna are subject to pollution. The estimated daily intake (EDI), target hazard quotient (THQ), hazard index (HI), and target cancer risk (TR) were calculated and compared with the permissible safety limits. It was found that consuming the seafood from the Bay of Bengal may cause adverse health impacts if consumption and/or means of pollution are not controlled.

Elemental and radionuclide exposures and uptakes by small rodents, invertebrates, and vegetation at active and post-production uranium mines in the Grand Canyon watershed

The effects of breccia pipe uranium mining in the Grand Canyon watershed (Arizona) on ecological and cultural resources are largely unknown. We characterized the exposure of biota to uranium and co-occurring ore body elements during active ore production and at a site where ore production had recently concluded. Our results indicate that biota have taken up uranium and other elements (e.g., arsenic, cadmium, copper, molybdenum, uranium) from exposure to ore and surficial contamination, like blowing dust. Results indicate the potential for prolonged exposure to elements and radionuclides upon conclusion of active ore production. Mean radium-226 in deer mice was up to 4 times greater than uranium-234 and uranium-238 in those same samples; this may indicate a potential for, but does not necessarily imply, radium-226 toxicity. Soil screening benchmarks for uranium and molybdenum and other toxicity thresholds for arsenic, copper, selenium, uranium (e.g., growth effects) were exceeded in vegetation, invertebrates, and rodents (Peromyscus spp., Thomomys bottae, Tamias dorsalis, Dipodomys deserti). However, the prevalence and severity of microscopic lesions in rodent tissues (as direct evidence of biological effects of uptake and exposure) could not be definitively linked to mining. Our data indicate that land managers might consider factors like species, seasonal changes in environmental concentrations, and bioavailability, when determining mine permitting and remediation in the Grand Canyon watershed. Ultimately, our results will be useful for site-specific ecological risk analysis and can support future decisions regarding the mineral extraction withdrawal in the Grand Canyon watershed and elsewhere.

SOIL-SOYBEAN TRANSFER FACTOR OF NATURAL RADIONUCLIDES IN DIFFERENT SOIL TEXTURES AND THE ASSESSMENT OF COMMITTED EFFECTIVE DOSE

From three different soil textures (clay, silt and sand), 36 soil and soybeans samples were accumulated from the agricultural area of EL-Mynia governorate in Upper Egypt, between (27°36'19.44″N; 30°30'14.14″ E) and (28°48'28.45″ N; 31°00'32.27″ E). Soil textures were prepared by particle size distribution through a pipette method. Its radioactivity measurements were performed with a NaI (Tl) and 3 × 3 inch crystal. The transfer factor (TF) of natural radionuclides from soil to soybeans was calculated. The value of the TF for 226Ra in clay soil ranges from 0.27 ± 0.03 to 0.42 ± 0.05, in sandy soil it ranges from 0.21 ± 0.02 to 0.57 ± 0.07 and in silt soil it ranges from 0.25 ± 0.03 to 0.53 ± 0.06. The TF for 232Th in clay soil ranges from 0.22 ± 0.03 to 0.90 ± 0.12, in sandy soil it ranges from 0.21 ± 0.03 to 1.00 ± 0.13, while in silt soil it ranges from 0.25 ± 0.03 to 0.88 ± 0.12. The TF for 40K in clay soil ranges from 0.95 ± 0.13 to 2.05 ± 0.29, in sandy soil it ranges from 1.21 ± 0.17 to 2.52 ± 0.35 and in silt soil it ranges and from 1.01 ± 0.14 to 1.46 ± 0.26.The results show that the committed effective dose from soybean consumption is between 54.5 and 103.4 μSv y-1 assuming consumption of 20 kg y-1.

An overview on the concentration of radioactive elements and physiochemical analysis of soil and water in Iraq

In the last decade, radiation physics brought about a revolution in health science by improving scientific equipment and useful methodologies for measurement. Human beings are affected by ionizing radiations that radiate from radioactive elements. The quantity of radioactive elements is different inside and outside the earth's surface. Soil and water are exigencies of human lives which are contaminated by radioactive elements. These radioactive elements enter into the human body through drinking, eating and breathing. On reaching hazardous limits in the human body, these radioactive elements cause stomach cancer, lung cancer and leukemia. Measurement of radioactive elements in soil and water is helpful in monitoring the health issues caused by exposure to these elements. In Iraq, numerous studies about natural radioactivity, radon concentration and physiochemical parameters have been conducted by different researchers, of which most of the studies were conducted in Barsa, Nasirya, Najaf, Karbala, Baghdad, Balad, Kirkuk, Erbil, Mosul and Dohuk cities. This article aims to review and compile the studies conducted in these cities of Iraq from 2011 to 2019. In most articles, high-purity germanium (HPGe), RAD7 and CR-39 detectors are used for radioactivity and radon measurement. These cities are located in the low-high folded and Mesopotamian zones. From this study, it can be concluded that radon concentration in soil and water was greater in the Mesopotamian and lower in the low-high folded zones. Higher concentrations of natural radioactivity in water and soil were found in the low-high folded zone in Iraq. However, most of the conducted studies show that concentrations of radon and natural radioactivity are above the permissible limits recommended by the International Commission on Radiological Protection (ICRP) and World Health Organization (WHO). The values of physiochemical parameters were found to be greater in the Mesopotamian zone, but overall they are not above the permissible limits.

Environmental radiological risk assessment of a coal ash and slag disposal site with the use of the ERICA Tool

The aim of this study was to assess the environmental radiological risk of coal ash and slag to terrestrial wildlife. The research site used in this study was a disposal site of coal ash and slag with enhaced content of uranium decay chain radionuclides. With the use of the ERICA Tool, total dose rates to wildlife and risk of resultant radiobiological effects were estimated. As input data for the assessment, experimental activity concentrations of ²³⁸U, ²²⁶Ra and ²¹⁰Pb in coal ash and slag and best estimates of activity concentrations for related daughter radionuclides and ²³⁵U decay chain were used. Where possible, the experimental data for activity concentrations of ²³⁸U, ²²⁶Ra and ²¹⁰Pb in plants and related concentration ratios were used. Results were compared to background dose rates, also estimated by the Tool. The Tool's assessment data indicated internal exposure as the prevalent exposure pathway with ²²⁶Ra and ²¹⁰Po as the main dose contributors. Also, the contribution of ²³⁵U decay chain to the total dose rate was not negligible since for some organisms it represented up to 11% of the total dose rate. The risk of an occurrence of radiobiological effects in plants on the coal ash and slag disposal site can be considered negligible since the estimated total dose rates were below the screening dose of 10 μGyh^-1 and near the dose rates estimated for plants in the control area. However, the estimated dose rates for reference animals and Lichen & Bryophytes were above the screening dose rate for most organisms and on average 13 times higher than the estimated background dose rates. At the given dose rates, an occurrence of different radiobiological effects could not be excluded for animals in close contact with coal ash and slag such as earthworms and small burrowing mammals. A separate assessment performed on an example of reference plants showed that the use of activity concentrations in organisms as input data can result in an order of magnitude smaller estimates of dose rates in comparison to activity concentration in coal and ash as input data. Our study highlighted the need for experimental data in radiological risk assessments to mitigate the conservatism of the ERICA Tool and its tendency to overestimate dose rates.

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.

Phosphorus Stress-Induced Changes in Plant Root Exudation Could Potentially Facilitate Uranium Mobilization from Stable Mineral Forms

Apparent deficiency of soil mineral nutrients often triggers specific physio-morphological changes in plants, and some of these changes could also inadvertently increase the ability of plants to mobilize radionuclides from stable mineral forms. This work, through a series of sand-culture, hydroponics, and batch-equilibration experiments, investigated the differential ability of root exudates of Andropogon virginicus grown under conditions with variable phosphorus (P) availability (KH₂PO₄, FePO₄, Ca₃(PO₄)₂, and no P) to solubilize uranium (U) from the uranyl phosphate mineral Chernikovite. The mineral form of P, and hence the bioavailability of P, affected the overall composition of the root exudates. The lower bioavailable forms of P (FePO₄ and Ca₃(PO₄)₂), but not the complete absence of P, resulted in a higher abundance of root metabolites with chelating capacity at 72 hrs after treatment application. In treatments with lower P-bioavailability, the physiological amino acid concentration inside of the roots increased, whereas the concentration of organic acids in the roots decreased due to the active exudation. In batch dissolution experiments, the organic acids, but not amino acids, increase the dissolution U from Chernikovite. The root exudate matrix of plants exposed to low available forms of P induced a >60% increase in U dissolution from Chernikovite due to 5-16 times greater abundance of organic acids in these treatments. However, this was ca. 70% of the theoretical dissolution achievable by this exudate matrix. These results highlight the potential of using active management of soil P as an effective tool to alter the plant-mediated mobilization of U in contaminated soil.

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.

Assessment of gamma radiation levels and natural radioactivity in soils along a subtropical river basin, China

The activities of natural radionuclides in the environment can be used to assess radiological effects. Monitoring the radiation level in soils is important for public health. It also has important geochemical implications as most of the sediment eroded from river basins is from soil. Therefore, we carried out a soil sampling campaign along a subtropical river basin in southeastern China (Jiulong River). Surface and depth profile soils were collected, and the natural radionuclide activities were measured. The activities of the natural radionuclides 238U, 232Th, and 40K in the surface soils varied from 31.6 to 132.1 Bq kg-dry−1, 37.8 to 174.0 Bq kg-dry−1, and 52.3 to 596.2 Bq kg-dry−1, with average values of 56.7±30.3 Bq kg-dry−1, 86.7±41.3 Bq kg-dry−1, and 352.8±190.6 Bq kg-dry−1, respectively. The absorbed gamma dose in air and the annual effective dose equivalent (AEDE) in surface soils along the river basin were both higher than the world average. In the depth profiles, excess 210Pb (210Pbex) decreased with depth and significant correlation between 210Pbex and TOC was observed, suggesting that they are affected by similar processes (leaching and sorption).

Transfer factors for natural radioactivity into date palm pits

Palm pits are used in various human and animal feed products. In this study, the natural radioactivity levels from soil and date palm pits of 9 samples collected from major date palm farms in three different regions (Buraidah, Al-Zulfi and Al-Majmaah) of Saudi Arabia were determined by using the high purity germanium (HPGe) gamma-ray spectrometer. The mean activity concentrations of ²²⁶Ra, ²³²Th, ¹³⁷Cs and ⁴⁰K in soil samples were 12.8 ± 2.2, 10.2 ± 2.1, 0.28 ± 0.10 and 329 ± 87 Bg kg^-1, respectively. Similarly the mean activity concentrations of ²²⁶Ra, ²³²Th, and ⁴⁰K in date palm pits were 5.6 ± 1.2, 2.8 ± 0.4 and 181 ± 17 Bq kg^-1, respectively, whereas ¹³⁷Cs could not be detected. The geometric mean of TF values (geometric standard deviation in parentheses) of ²²⁶Ra, ²³²Th, and ⁴⁰K were 0.33 (2.1), 0.22 (1.8) and 0.51 (2.0), respectively.

Effect of low molecular weight organic acids on the uptake of 226Ra by corn (Zea mays L.) in a region of high natural radioactivity in Ramsar-Iran

To study the benefit of including citric and oxalic acid treatments for phytoremediation of ²²⁶Ra contaminated soils a greenhouse experiment with corn was conducted. A soil was sampled from a region of high natural ²²⁶Ra radioactivity in Ramsar, Iran. After cultivation of corn seed and using organic acid treatments at 1, 10 and 100 mM concentrations, plants (shoots and roots) were harvested, digested and prepared to measure ²²⁶Ra activity. Simultaneously, sequential selective extraction were performed to estimate the partitioning of ²²⁶Ra among geochemical extraction. Results showed that the maximum uptake of ²²⁶Ra in plants was observed in citric acid (6.3%) and then oxalic acid (6%) at 100 mM concentration. These treatments increased radium uptake by a factor of 1.5 than the control. Enhancement of radium uptake by plants was related to soil pH reduction of organic acids in comparison to control. Also, the maximum uptake of this radionuclide in all treatments was obtained in roots compared to shoots. ²²⁶Ra fractionations results revealed that 91.8% of radium was in the residual phase of the soil and the available fractions were less than 2%. As the main percent of ²²⁶Ra was in the residual phase of the soil in this region, it seems that organic acids had not significant effect on the uptake of ²²⁶Ra for phytoremediation by corn in this condition.

Effective radium concentration in agricultural versus forest topsoils

Effective radium-226 activity concentration (ECRa), the radon-222 source term, was measured in the laboratory with 724 topsoil samples collected over a ∼110 km(2) area located ∼20 km south of Paris, France. More than 2100 radon accumulation experiments were performed, with radon concentration measured using scintillation flasks, leading to relative uncertainties on ECRa varying from 10% for ECRa = 2 Bq⋅kg(-1) to less than 6% for ECRa > 5 Bq⋅kg(-1). Small-scale dispersion, studied at one location with 12 samples, and systematically at 100 locations with three topsoils separated by 1 m, was of the order of 7%, demonstrating that a single soil sample is reasonably representative. Agricultural topsoils (n = 540) had an average (arithmetic) ECRa of 8.09 ± 0.11 Bq⋅kg(-1), and a range from 2.80 ± 0.22 to 19.5 ± 1.1 Bq⋅kg(-1), while forest topsoils (n = 184), with an average of 3.21 ± 0.14 Bq⋅kg(-1) and a range from 0.45 ± 0.12 to 9.09 ± 0.55 Bq⋅kg(-1), showed a clear systematic reduction of ECRa when compared with the closest agricultural soil sample. Large-scale organization of ECRa was impressive for agricultural topsoils, with homogeneous domains of several kilometers size, characterized by smooth variations smaller than 10%. These patches emerged despite heavy human remodeling; they are controlled by the main geographical units, but do not necessarily coincide with them. Valleys were characterized by larger dispersion and less organization. This study illustrates how biosphere and anthroposphere modify the soil distribution inherited from geological processes, an important baseline needed for the study of contaminated sites. Furthermore, the observed depletion of forest topsoils suggests an atmospheric radon signature of deforestation.

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

The present study addresses the soil-to-plant transfer factors (TFs) of (226)Ra, (234)U and (238)U for 13 types of vegetables and agricultural crops planted under semi-arid environment in the northwestern part of Saudi Arabia. Crop plants along with plant-growing soils were collected from selected farms, which are irrigated from the non-renewable Saq aquifer, and investigated for their radioactivity content by means of alpha spectrometry after applying a radiochemical separation procedure. Hence, TF data for plant roots, green parts (stem and leaves) and fruits were calculated and contrasted to those reported in the literature. Substantial differences were observed in the TFs of Ra and U radioisotopes among plant species. In crop fruits, eggplant exhibited the highest uptake of (226)Ra (TF value of 0.11), while beans (0.16) have the highest TF for (234)U and (238)U. The geometric mean TF values indicated that the crop roots tend to accumulate Ra and U about four to six-folds higher than fruits. The relation between TF values and soil concentrations showed a weak correlation. Activity ratios between radionuclides in crop plants indicated the preferential translocation of U in fruits than Ra even though Ra is more available for root uptake. The fruit/root (F/R) ratios obtained for the investigated plants shown that pepper had the smallest F/R ratios (0.07 ± 0.01, 0.12 ± 0.02 and 0.11 ± 0.02 for (226)Ra, (234)U and (238)U, respectively), while the highest F/R ratios were observed in potatoes (0.71 ± 0.15, 0.44 ± 0.10 and 0.40 ± 0.08 for (226)Ra, (234)U and (238)U, respectively). The TF and F/R ratios data of natural radionuclides in the study region can hopefully improve the scientific knowledge for future studies.

Radioactivity and the environment: technical approaches to understand the role of arbuscular mycorrhizal plants in radionuclide bioaccumulation

Phytoaccumulation of radionuclides is of significant interest with regards to monitoring radionuclide build-up in food chains, developing methods for environmental bioremediation and for ecological management. There are many gaps in our understanding of the characteristics and mechanisms of plant radionuclide accumulation, including the importance of symbiotically-associated arbuscular mycorrhizal (AM) fungi. We first briefly review the evidence that demonstrates the ability of AM fungi to enhance the translocation of (238)U into plant root tissues, and how fungal association may prevent further mobilization into shoot tissues. We then focus on approaches that should further advance our knowledge of AM fungi-plant radionuclide accumulation. Current research has mostly used artificial cultivation methods and we consider how more ecologically-relevant analysis might be performed. The use of synchrotron-based X-ray fluorescence imaging and absorption spectroscopy techniques to understand the mechanisms of radionuclide transfer from soil to plant via AM fungi is evaluated. Without such further knowledge, the behavior and mobilization of radionuclides cannot be accurately modeled and the potential risks cannot be accurately predicted.

Vegetation composition and ²²⁶Ra uptake by native plant species at a uranium mill tailings impoundment in South China

A field investigation was conducted for the vegetation composition and (226)Ra uptake by native plant species at a uranium mill tailings impoundment in South China. 80 species belonging to 67 genera in 32 families were recorded in the sampling sites. The Poaceae and Asteraceae were the dominant families colonizing the impoundment. The number of the plant species and vegetation community composition in the sampling sites seemed most closely related to the activities of (226)Ra and the pH value of the uranium tailings. The plant species in the sampling sites with relatively low activities of (226)Ra and relatively high pH value formed a relatively stable vegetation community. The plant species in the sampling sites with medium activities of (226)Ra and medium pH value formed the transitional vegetation community. The plant species in the sampling sites with relatively high activities of (226)Ra and relatively low pH value formed a simple unstable vegetation community that was similar to that on the unused grassland. The activities of (226)Ra and transfer factors (TFs) varied greatly with the plant species. The high activities of (226)Ra and TFs were found in the leaves of Pteris multifida (150.6 Bq/g of AW; 9.131), Pteridium aquilinum (122.2 Bq/g of AW; 7.409), and Dryopteris scottii (105.7 Bq/g of AW; 6.408). They satisfied the criteria for a hyperaccumulator for (226)Ra. They may be the candidates for phytoremediation of (226)Ra in the uranium mill tailings impoundment areas and the contaminated soils around.

Radium concentration factors in passionfruit (Passiflora foetida) from the Alligator Rivers Region, Northern Territory, Australia

In this study, uptake of Ra from soil into the edible fruit of the wild passionfruit species Passiflora foetida was investigated, using selective extraction from the soil samples. A wide range of environmental exposure conditions were represented by the locations that were sampled, including both natural soils, and soils influenced by past and present uranium mining activities. The bioavailable (226)Ra fraction in soils was found to be a better predictor of (226)Ra fruit activity concentrations than the total soil activity concentration, or any of the other fractions studied. Concentration Factors (CFs) derived using the bioavailable fraction varied by only a factor of 7 between different locations, whereas CFs derived using other fractions and total soil varied by up to two orders of magnitude. CFs were highest for those soils containing the lowest concentrations of Mg, Ca and Ba, and approached a saturation value at higher soil concentrations. This finding suggests that group II elements influence radium uptake, most likely the result of increased pressure on the plant to take up essential nutrient group II elements from soil with the lower concentrations, with Ra being taken up as an analogue element. It is also possible that at higher concentrations of bioavailable Ca and Mg in the soil, these ions will outcompete Ra for adsorption sites in the soil and/or on the root surfaces. The study also shows that (228)Ra can potentially be a significant contributor to ingestion doses and should also be considered when assessing committed effective doses from the ingestion of fruits.

Composition of hydroponic medium affects thorium uptake by tobacco plants

The ability of thorium uptake as well as responses to heavy metal stress were tested in tobacco cultivar La Burley 21. Thorium was accumulated preferentially in the root system. The presence of citric, tartaric and oxalic acids in hydroponic medium increased thorium accumulation in all plant organs. On the other hand, the addition of diamines and polyamines, the important antioxidants in plants, resulted in decrease of thorium accumulation, especially in the root system. Negative correlation was found between putrescine concentration and thorium accumulation. Nevertheless, the most important factor influencing the accumulation of thorium was the absence of phosphate ions in a hydroponic medium that caused more than 10-fold increase of thorium uptake in all plant parts. Accumulation and distribution of thorium was followed in six cultivars and 14 selected transformants. Cultivar La Barley 21 represented an average between the tested genotypes, having a very good distribution ratio between roots, stems and leaves.

A review of the behaviour of U-238 series radionuclides in soils and plants

The U-238 series of radionuclides is of relevance in a variety of environmental contexts ranging from the remediation of former uranium mining and milling facilities to the deep geological disposal of solid radioactive wastes. Herein, we review what is known concerning the behaviour of radionuclides from the U-238 decay chain in soils and plants. This review is intended to provide a single comprehensive source of information to anyone involved in undertaking environmental impact assessment studies relating to this decay chain. Conclusions are drawn relating to values and ranges of distribution coefficients appropriate to uranium, thorium, radium, lead and polonium in different soil types and under various environmental conditions. Similarly, conclusions are drawn relating to plant:soil concentration ratios for these elements for different plant and soil types, and consideration is given to the distribution of these elements within plants following both root uptake and foliar application.

Correlations of natural radionuclides in soil with those in sediment from the Danube and nearby irrigation channels

The correlation between activity concentrations of some natural radionuclides ((238)U, (226)Ra, (232)Th, (40)K) measured in soil and in sediment taken from the Danube River and nearby irrigation channels was studied. The soil samples were collected from the northern part of Serbia and the sediment from the Serbian part of the Danube River and from the surrounding irrigation channels. The correlation between (238)U and other natural radionuclides in irrigation channel sediments was not as good as in the Danube. One of the possible explanations for this weak correlation can be the different chemical dynamics of (238)U in the irrigation channel sediment or changes of the (238)U activity concentration in irrigation channel sediment due to some human activities. The evaluation of ratios of activity concentrations of some natural radionuclides could be a more sensitive method for the determination of contaminant, rather than the straightforward analysis of activity concentrations.

Ingestion dose from 238U, 232Th, 226Ra, 40K and 137Cs in cereals, pulses and drinking water to adult population in a high background radiation area, Odisha, India

A natural high background radiation area is located in Chhatrapur, Odisha in the eastern part of India. The inhabitants of this area are exposed to external radiation levels higher than the global average background values, due to the presence of uranium, thorium and its decay products in the monazite sands bearing placer deposits in its beaches. The concentrations of (232)Th, (238)U, (226)Ra, (40)K and (137)Cs were determined in cereals (rice and wheat), pulses and drinking water consumed by the population residing around this region and the corresponding annual ingestion dose was calculated. The annual ingestion doses from cereals, pulses and drinking water varied in the range of 109.4-936.8, 10.2-307.5 and 0.5-2.8 µSv y(-1), respectively. The estimated total annual average effective dose due to the ingestion of these radionuclides in cereals, pulses and drinking water was 530 µSv y(-1). The ingestion dose from cereals was the highest mainly due to a high consumption rate. The highest contribution of dose was found to be from (226)Ra for cereals and drinking water and (40)K was the major dose contributor from the intake of pulses. The contribution of man-made radionuclide (137)Cs to the total dose was found to be minimum. (226)Ra was found to be the largest contributor to ingestion dose from all sources.

Evaluation of internal dose to members of the public at the Kaiga site, India, due to the ingestion of primordial radionuclide 40K

Four 220 MWe pressurised heavy water reactors are under operation at Kaiga in the state of Karnataka in India. Environmental radiological survey of the surrounding areas of the Kaiga site is carried out by Bhabha Atomic Research Centre, Mumbai. The estimated dose to the members of the public due to ingestion of radioactive isotope of potassium, a natural radionuclide, in the surroundings of the Kaiga site is 136 μSv (13.6 mrem) per year. The value indicates that the dose to the public due to operation of the nuclear reactors in Kaiga is insignificant in comparison with the dose due to unavoidable natural radioactivity.

Potential sources affecting the activity concentrations of 238U, 235U, 232Th and some decay products in lettuce and wheat samples

The activity concentrations of radionuclides within the uranium and thorium series were determined in wheat and lettuce at five sites in France, and in their respective potential sources: crop soils of wheat and crop soils and irrigation waters of lettuce. These data were used to calculate concentration ratios and to enrich the database supported by the technical report series N°472 of the IAEA (2010). For wheat and lettuce, the activity concentrations were in the same range for all radionuclides studied, except for (210)Pb, which had higher activity concentrations in wheat, ranging between 1.3 and 11 Bq kg(−1) (fresh weight) as compared to 0.4 and 0.7 Bq kg(−1) (fresh weight) for lettuce. For wheat, the range of activity concentrations (mBq kg(−1); fresh weight) decreased as (210)Pb > (226)Ra (56–1511) ≈ (228)Ra (86–769) > (228)Th (19–176) ≈ (238)U (11–169) ≈ (234)U (12–150) ≈ (230)Th (9.08–197.18) ≈ (232)Th (8.61–121.45) > (235)U (0.53–7.9). For lettuce, it decreased as (228)Ra (<320–1221) > (210)Pb (409–746) > (226)Ra (30–599) ≈ (228)Th (<29–347) > (238)U (8–120) ≈ (234)U (8–121) ≈ (230)Th (5.21–134.63) ≈ (232)Th (5.25–156.99) > (235)U (0.35–5.63). The species differences may reflect different plant physiologies. Through the study of activity ratios of wheat and lettuce in relation with those of the various radionuclide sources it has been possible to highlight the contribution of the main sources of natural radionuclides. Indeed, irrigation water when the uranium concentration is enhanced (>30 mBq L(−1)) contributed significantly to the activity concentration of uranium in lettuces. Concerning the high activity concentrations of (210)Pb, it could be explained by atmospheric particle deposition. The effect of soil particles resuspension and their adhesion to the plant surface seemed to be important in some cases. The soil-to-plant transfer factors were calculated for lettuce and wheat. The values were lower in wheat than in lettuce except for (210)Pb which had similar values in the two species (0.11–0.13 respectively). For both species, (210)Pb followed by (228)Ra (0.015–0.10) and (226)Ra (0.010–0.051) displayed the highest transfer factor, whereas (238)U had intermediate values (0.0015–0.030) and (232)Th exhibited the lowest (0.0014–0.013).

Polonium-210 and lead-210 in the terrestrial environment: a historical review

The radionuclides (210)Po and (210)Pb widely present in the terrestrial environment are the final long-lived radionuclides in the decay of (238)U in the earth's crust. Their presence in the atmosphere is due to the decay of (222)Rn diffusing from the ground. The range of activity concentrations in ground level air for (210)Po is 0.03-0.3 Bq m(-3) and for (210)Pb 0.2-1.5 Bq m(-3). In drinking water from private wells the activity concentration of (210)Po is in the order of 7-48 mBq l(-1) and for (210)Pb around 11-40 mBq l(-1). From water works, however, the activity concentration for both (210)Po and (210)Pb is only in the order of 3 mBq l(-1). Mosses, lichens and peat have a high efficiency in capturing (210)Po and (210)Pb from atmospheric fallout and exhibit an inventory of both (210)Po and (210)Pb in the order of 0.5-5 kBq m(-2) in mosses and in lichens around 0.6 kBq m(-2). The activity concentrations in lichens lies around 250 Bq kg(-1), dry mass. Reindeer and caribou graze lichen which results in an activity concentration of (210)Po and (210)Pb of about 1-15 Bq kg(-1) in meat from these animals. The food chain lichen-reindeer or caribou, and Man constitutes a unique model for studying the uptake and retention of (210)Po and (210)Pb in humans. The effective annual dose due to (210)Po and (210)Pb in people with high consumption of reindeer/caribou meat is estimated to be around 260 and 132 μSv a(-1) respectively. In soils, (210)Po is adsorbed to clay and organic colloids and the activity concentration varies with soil type and also correlates with the amount of atmospheric precipitation. The average activity concentration levels of (210)Po in various soils are in the range of 20-240 Bq kg(-1). Plants become contaminated with radioactive nuclides both by absorption from the soil (supported Po) and by deposition of radioactive fallout on the plants directly (unsupported Po). In fresh leafy plants the level of (210)Po is particularly high as the result of the direct deposition of (222)Rn daughters from atmospheric deposition. Tobacco is a terrestrial product with high activity concentrations of (210)Po and (210)Pb. The overall average activity concentration of (210)Po is 13 ± 2 Bq kg(-1). It is rather constant over time and by geographical origin. The average median daily dietary intakes of (210)Po and (210)Pb for the adult world population was estimated to 160 mBq day(-1) and 110 mBq day(-1), corresponding to annual effective doses of 70 μSv a(-1) and 28 μSv a(-1), respectively. The dietary intakes of (210)Po and (210)Pb from vegetarian food was estimated to only 70 mBq day(-1) and 40 mBq day(-1) corresponding to annual effective doses of 30.6 μSv a(-1) and 10 μSv a(-1), respectively. Since the activity concentration of (210)Po and (210)Pb in seafood is significantly higher than in vegetarian food the effective dose to populations consuming a lot of seafood might be 5-15 fold higher.

Actinides and decay products in selected produce and bioindicators in the vicinity of a uranium plant

Cypress needles collected at the edge of the Malvési uranium facility (SW France) exhibit enhanced activities of actinides and some decay products (uranium, americium, plutonium, (230)Th, (226)Ra) compared to a remote site. These enhanced activities resulted from the release of U via smokestacks and passive release from former artificial ponds located inside the nuclear site. Enhanced activities are also observed in selected produce (wheat, lettuce, fruits) sampled from the edge of the site. However, excess actinides measured in wheat grains in 2007 are inconsistent with the activities and the uranium ratio measured in the soils. This result suggests that the studied annual crops were contaminated mainly through the short-term release of airborne actinides, and that other transfer pathways, such as, uptake through the roots or adhesion of soil particles, were negligible.