Natural radionuclides and metals intake into soya,corn and lettuce grown on soil amended with phosphogypsum

Phosphogypsum is a by-product of the phosphate fertilizer industry. It is produced by precipitation during wet process of phosphate rocks, thus posing serious problems with its utilization and safe disposal. In Brazil, three main industries are responsible for the production and storage of about 5.5?×?10⁶ tons per year. Phosphogypsum may contain trace metals and radionuclides of U and Th series. Since, in Brazil, phosphogypsum has been used for many years as soil amendment, it is important to know its availability in the environment. The main objective of this study is to evaluate the radionuclides and metals transfer in the soil-to-plant system. To accomplish this task an experiment was carried out in a green house, where two major crop groups (soya bean and corn) and leafy vegetables (lettuce) were grown in two types of soil (clay and sandy) amended with phosphogypsum. The transfer-factors were evaluated for the metals (As, Cd, Cu, Ni and Pb, Ba, Co, Cr, Fe, Zn and REE) and for the radionuclides U, Th, ²²⁶Ra, ²²⁸Ra, ²¹⁰Pb and ²¹⁰Po. The addition of PG to the two soils studied, did not significantly alter the TFs values for all the elements studied.     

Comparison of transfers for natural radionuclides (238U, 234Th, 226Ra, 210Pb & 210Po) from five different soils to four different barley genotypes

Transfer Factors (Fv) of ²³⁸U, ²²⁶Ra, ²³⁴Th, ²¹⁰Po and ²¹⁰Pb from five different agricultural soils in semi-arid region (Syria) to four different barley genotypes were studied in an agricultural potted experiment. The geometric mean of the Fv values were (0.08) for ²¹⁰Pb, and (0.02) for ²¹⁰Po, while it ranged from 0.18 to 0.42 ,from 0.08 to 0.15 and from 0.22 to 0.4 for ²³⁸U, ²³⁴Th and ²²⁶Ra, respectevily. The Fv values of ²³⁸U and ²²⁶Ra were within the recommended global medians, while the Fv values of ²³⁴Th, ²¹⁰Pb and ²¹⁰Po were higher. There is no clear relationship between the soil properties and Fv of all studied radionuclides to barley genotypes. Moreover, the expression of glutathione (GSH) gene, which is belived to be involoved in heavy metal removal was generally low in all studied varieties grown in all soil types.

     

Disequilibrium of uranium series radionuclides in soil and plants of South India

Soil and plants of South India were analysed using standard methods for equilibrium state between radionuclides ²²⁶Ra, ²¹⁰Pb, and ²¹⁰Po of uranium series. A disequilibrium state was observed, with mean ²¹⁰Pb/²²⁶Ra, ²¹⁰Po/²²⁶Ra, and ²¹⁰Po/²¹⁰Pb as 21.71, 5.52, and 0.40; 10.01, 4.21, and 0.43; and 30.86, 9.34, and 0.35 in Coastal Karnataka, Malnad Karnataka, and Malnad Kerala, respectively. ²¹⁰Po/²¹⁰Pb in soil was 0.29, 0.30, and 0.49 respectively, for the three regions. Unsupported ²¹⁰Pb and ²¹⁰Po might have caused the observed disequilibrium state. The investigation helps to monitor radionuclide distribution and dynamics in soil and plants of the study area.

     

Distribution of 210Po and 210Pb radionuclides and their dependence on physico-chemical parameters of soil in Madikeri taluk,Coorg district,Karnataka, India

The paper deals with distribution of ²¹⁰Po and ²¹⁰Pb radionuclides in a vertical profile of illuviated soil, in Madikeri taluk of Coorg district, Karnataka, India. The activity concentration of ²¹⁰Po and ²¹⁰Pb radionuclides was determined using radioanalytical method and the dependence of these radionuclides on physico-chemical parameters of soil was also investigated through a statistical study. In all the layers of the soil in a vertical profile, the ²¹⁰Po nuclides were found to be in disequilibrium with ²¹⁰Pb. The frequency distribution of ²¹⁰Po and ²¹⁰Pb radionuclides was analysed using Kolgomorov–Smirnov test.

     

The natural radioactivity of Brazilian phosphogypsum

Phosphogypsum is a high volume by-product from the phosphoric acidindustries containing naturally occurring radionuclides. Envisaging the usesof phosphogypsum, a characterization of this material in terms of spatialdistribution of radionuclides was carried out by core samples taken from stacksof two important Brazilian phosphoric acid facilities. Samples were analyzedfor ²³⁸U, ²³⁴U, ²³²Th, ²²⁶Ra, ²²⁸Ra, ²¹⁰Pb and ²¹⁰Po using alpha- and gamma-spectrometryand UV-VIS spectrophotometry. Specific activities of ²³⁸U, ²³⁴U, ²²⁶ Ra and ²¹⁰Po obtained were comparablewith data reported in the phosphogypsum literature, while higher values werefound for ²³² Th and ²²⁸Ra.     

Radiochemical characterization of spring waters in Balaton Upland, Hungary, estimation of radiation dose to members of public

Hungary is rich in spring waters. A survey studying the naturally occurring alpha emitter radionuclides in 30 frequently visited and regularly consumed spring waters was conducted out in the Balaton Upland region of Hungary.²²⁶Ra, ²²⁴Ra, ²³⁴U, ²³⁸U and ²¹⁰Po activity concentrations were determined by using alpha spectrometry after separation from matrix elements. Average concentration (mBq L^{− 1}) of ²²⁶Ra, ²²⁴Ra, ²³⁴U, ²³⁸U and ²¹⁰Po in the spring waters is varied from 2.1 to 601, from < 1.1 to 65.4, from 3.9 to 741.9, from < 0.44 to 274.3 and from 2 to 15.2 respectively. In most cases radioactive disequilibrium was observed between uranium and radium isotopes. The doses for the analyzed samples of spring water are in the range 3.59–166.73 μSv y^{− 1} with an average 18.2 μSv y^{− 1} .This is well below the 100 μSv y^{− 1} reference level of the committed effective dose recommended by WHO. Only one water sample had a dose higher than 100 μSv y^{− 1}, mainly due to the contribution from radium (²²⁶Ra, ²²⁴Ra) and ²¹⁰Po isotopes. This study provides important information for consumers and authorities about their internal radiological exposure risk from spring water intake.     

Comparative plant uptake and environmental behavior of U-series radionuclides at a uranium mine-mill

Concentrations of U, Th, Ra, Pb, and Po were determined in native vegetation and underlying substrate (soil and tailings) at various sites around a conventional open pit, acid leach uranium production operation in the Western United States. Radionuclide concentrations in substrate and vegetation were generally elevated above background at all sites disturbed by mining and milling activities. Observed plant/soil CR values for vegetation growing on exposed, weathered tailings were ordered as follows:²³⁸U>²³⁰Th>²¹⁰Po,²²⁶Ra>²¹⁰Pb. We suspect that in the case of sulfuric acid leached tailings, Ra and Pb are sequestered as sulfates, which are highly insoluble relative to U and Th sulfates, resulting in reduced availability for plant uptake. Soil acidity and the saturation condition at the tailings impoundment edge tend to enhance radionuclide availability for plant uptake. The transport of radionuclides to foliage and subsequent retention and absorption may play a role in plant contamination.     

Natural radionuclides in Austrian bottled mineral waters

All commercially available mineral waters of Austrian origin were investigated with regard to the natural radionuclides ²²⁸Ra, ²²⁶Ra, ²¹⁰Pb, ²¹⁰Po, ²³⁸U and ²³⁴U. From 1 to 1.5 L of sample the nuclides were extracted and measured sequentially: the radium isotopes as well as ²¹⁰Pb were measured by liquid scintillation counting after separation on a membrane loaded with element-selective particles (Empore Radium Disks), ²¹⁰Po was determined by α-particle spectroscopy after spontaneous deposition onto a copper planchette and uranium was determined also by α-particle spectroscopy after anion separation and microprecipitation with NdF₃. The calculated committed effective doses for adults, teens and babies were compared to the total indicative dose of 0.1 mSv/year given in the EC Drinking Water Directive. The dominant portion of the committed effective dose was due to ²²⁸Ra. Highly mineralised waters showed also higher ²²⁶Ra and ²²⁸Ra levels.     

Partitioning of natural radionuclides in sediments around a former uranium mine and mill

Partitioning of natural radionuclides in sediments from streams affected by the waste piles of the former uranium mine and mill located at ?irovski vrh, Slovenia, was performed by applying a sequential extraction procedure. The sediments were collected at three sites located upstream and three sites located downstream of the waste piles. Then the four-step Community Bureau of Reference (BCR) sequential extraction protocol was applied to the samples and the natural radionuclides ²³⁸U, ²³⁰Th, ²²⁶Ra, ²¹⁰Pb and ²¹⁰Po were analysed in each extraction fraction. It was expected that the fractionation of natural radionuclides originating from the waste piles would differ from that upstream of the influence of waste piles because their chemical environment had been altered during the processes of uranium extraction. This difference could allow tracing of the radionuclides coming from the waste piles downstream of the affected watercourses. The results definitely showed that the total activity concentrations at sites downstream of the influence of the waste piles were higher than at sites upstream of the piles. However, this difference was geographically very limited and could no longer be detected already at a distance of about 5 km downstream. Unexpectedly, the fractionation of radionuclides upstream and downstream of the area of influence of the waste piles did not appear to be significantly altered. The sole differences found were for ²³⁸U and ²²⁶Ra in the second fraction (the “Fe/Mn oxides” fraction) and for ²¹⁰Po in the fourth fraction (the “residue” fraction) of the BCR sequential extraction protocol.     

A sequential radiochemical procedure for isotopic analysis of uranium and thorium in soil

A sequential radiochemical procedure for isotopic analysis of uranium and thorium in soil has been developed. Analysis involves total dissolution of the samples to allow equilibration of the natural isotopes with added tracers, followed by radiochemical separation using anion exchange chromatography (BioRad AG 1–X8). Further separation and purification is performed employing solvent extraction techniques. Finally, the U and Th fractions are co-precipitated with lanthanum and cerium fluoride, respectively, and quantified by alpha-particle spectrometry. Overall chemical yields range from 60 to 90%. Under normal operating conditions and present counting set up, the minimum detectable concentration (MDC) is approximately 2 Bq/kg for soil samples. This is based on one gram aliquot of sample, 80% chemical yield, and 1000 minute counting with a detector having about 15% counting efficiency. The procedure has been successfully tested with Standard Reference Materials. Various soil samples were analyzed with high chemical yields and fine quality of alpha-spectra. Decontamination factor studies were performed to determine the extent of the carry over of²¹⁰Po,²²⁵Ac,²²⁶Ra, and²²⁹Th into U fraction and²¹⁰Po,²²⁵Ac,²²⁶Ra, and²³²U into Th fraction.     

Assessment of radioactivity contribution and transfer characteristics of natural radionuclides in agroecosystem

Taking into account the importance of distribution and transfer of radionuclides in the soil–plant system, especially in agricultural fields, the aim of this research was assessment of radioactivity contribution and transfer characteristics of natural radionuclides in agroecosystem. The measurement of the natural radioactivity distribution was conducted in organic and sustainable farming management systems. Statistical evaluation of the physical and chemical properties of soils subjected to different farming systems, revealed the existence of differences in some parameters. Balanced distribution of natural radionuclides in soil-crop system was observed. Radionuclide ⁴⁰K was the most accessible to the investigated crops via uptake from the soil, then ²³²Th and ²²⁶Ra. The obtained results are useful for understanding the behavior of the radionuclides and provide an insight into the cumulative deposition of radioactivity in the agroecosystem.

     

Correlated concentration distributions of natural alpha-radionuclides in sediment samples along the Romanian sector of the Danube river and the Black Sea coast

The concentrations of²³⁸U and²³²Th were determined by neutron activation analysis using epithermal irradiation in 12 sediment samples, collected along the Romanian sector of the Danube river and the Black Sea coast during 1994. The concentrations of²²⁶Ra were determined by the emanation method in the same sediment samples. The concentration ranges obtained were compared also with the²¹⁰Po concentration range for the same sector, reported in a previous paper. The accumulation potential of -emitting radionuclides in the analysed sediments is discussed.     

The dietary intake of238U,234U,230Th,232Th,228Th and226Ra from food and drinking water by inhabitants of the Walbrzych region

Intake with food and water of the natural radionuclides of the uranium and thorium series was determined for adult population of the south-western region in Poland, where in the 1950-ies an exploration of uranium ore was conducted. Concentration of the radionuclides was determined in food products and drinking water and their annual intake was estimated on the basis of the average annual consumption. The intake of²³⁸U,²³⁴U and²³⁰Th occurred mainly with water (33% to 68%), whereas the intake of²³²Th,²²⁸Th and²²⁶Ra was mainly with vegetables, potatoes, milk and flour. From the intake and dose coefficients the annual effective doses from the ingested radionuclides were calculated. The total dose was 5.6 Sv, of which 74% originated from²²⁶Ra.     

A new reference material for radionuclides in the mussel sample from the Mediterranean Sea (IAEA-437)

A new Reference Material (RM) for radionuclides in mussel (Mytilus galloprovincialis) from the Mediterranean Sea (IAEA-437) is described and the results of the certification process are presented. Four radionuclides (⁴⁰K, ²³⁴U, ²³⁸U, and ^239+240Pu) have been certified, and information values on massic activities with 95% confidence intervals are given for nine radionuclides (¹³⁷Cs, ²¹⁰Pb(²¹⁰Po), ²²⁶Ra, ²²⁸Ra, ²²⁸Th, ²³⁰Th, ²³²Th, ²³⁵U, and ²⁴¹Am). Results for less frequently reported radionuclides (⁹⁰Sr, ¹²⁹I, ²³⁸Pu, ²³⁹Pu, and ²⁴⁰Pu) are also reported. The RM can be used for quality assurance/quality control of the analysis of radionuclides in mussel samples, for the development and validation of analytical methods and for training purposes. The material is available in 200 g units.     

Determination of natural radioactivity in Euphrates river

Levels of naturally occuring radionuclides (radium isotopes, U isotopes, ²¹⁰Po and ²¹⁰Pb) in water, sediments and biota samples collected from Euphrates river during the 1999–2000 period have been determined. Results have shown that the water contained relatively high levels of ²²⁶Ra; the largest value of 1150 mBq·l^–1 was observed. These relatively high levels of ²²⁶Ra, which is one of the main radioactive contaminants in the oil industry, may be due to past discharges of production water from the oil fields situated near the river banks. ²²⁶Ra/²³⁸U activity ratio was found to be more than unity in all water samples varying between 13 and 242. In addition, the results of sediment analyses have also shown lower values for ²²⁸Ra/²²⁶Ra activity ratio than unity in those samples collected nearby the oil fields. Moreover, concentrations of other naturally occurring radionuclides such as uranium isotopes, ²¹⁰Po and ²¹⁰Pb for most samples (water, sediments and biota) were found to be within the natural levels and in agreement with those values reported for other local and international studies. Only mussel species were found to contain high levels of ²¹⁰Po, about 1335 Bq·kg^–1 dry mass was observed in Anodonta sp species. However, the results of this study can be considered a baseline for monitoring of future changes. A regional research project (including Turkey, Syria and Iraq) to study this river (from the Anatolia Mountains to the Arabian Gulf) is necessary to determine the impact of all potential sources of contaminants.This revised version was published online in November 2005 with corrections to the Cover Date.     

Transfer factors of 40K, 226Ra, 232Th from soil to different types of local vegetables,radiation hazard indices and their annual doses

This work aims to determine the transfer factors (TFs) of ⁴⁰K, ²²⁶Ra and ²³²Th from soil to vegetables, because there are few surveys of them in Iraq. The samples were taken from three important agricultural areas supplying the vegetable products needed by the Iraqi population. Using NaI(Tl) technique, the average values of TFs of the above radioactive isotopes were found to be 0.60, 0.41, 0.59 and 0.05, 0.03, 0.05 from soil to dry and fresh samples, respectively. The radiation hazard indices and the total annual dose were found to be within the range of the world values.     

Leaching of uranium,radium and thorium from vertisol soil by ground water

Shallow land burial is routinely used for the disposal of low-level radioactive waste. Natural processes causing leaching of radionuclides can lead to contamination of surrounding ground water and soil by the radionuclides. The comparative leachability of radionuclides U_(nat), ²²⁶Ra, ²²⁸Ra and Th_(nat) from the soil of a radioactive waste disposal site, by ground water was evaluated. The probability of leaching was obtained in the following order Ra (≈77%) > U (≈40%) > Th (≈20%). Observed ratios (OR) were calculated to correlate leachability of radionuclides to that of major cations Ca²⁺ and Mg²⁺. The leaching of the radionuclides was seen to be dependent on Ca²⁺ and SO₄²⁻ leached from the soil. This study provides sitespecific leachability of radionuclides, that can be used as indicator of the tendency for migration or retention in soil. It can play an important role during an unforeseen accident like breach of containment at the waste disposal site leading to contamination of soil and ground water and causing hazard to public via drinking water route.     

Influence of freezing on physicochemical forms of natural and technogenic radionuclides in Chernozem soil

Sharp variations of different climatic parameters influence the transport, transfer, and deposition of contaminants in nature. Investigations of the impact of environmental temperature on the fractionation of radionuclides in soil are necessary for adequate assessment of their distribution and bioavailability in case of a nuclear accident. The impact of a sharp decrease of environmental temperature shortly after radioactive contamination on the physicochemical fractionation of natural and technogenic radionuclides in Chernozem soil and its influence on their potential migration ability and bioavailability in case of subsequent warming were evaluated. The soil was contaminated in a laboratory with ²⁴¹Am, ⁶⁰Co, ¹³⁷Cs, ²²⁸Ra, ²³⁴Th, and U and two temperature regimes were used for storage. Changes of the radionuclides association with various soil phases in the first weeks after contamination were studied. Physicochemical forms of ²⁴¹Am, ⁶⁰Co, ²²⁸Ra, ²³⁴Th, and U were determined using two sequential extraction procedures. The ion-exchangeable forms of ¹³⁷Cs were evaluated by single extraction with 1 M NH₄NO₃. The data showed that the freezing, following the radioisotope contamination of the soil, causes an increase of the amount of potentially mobile forms of radiocobalt, radiocesium, radium, and thorium and has an insignificant impact on the fractionation of americium and uranium.     

Natural radionuclides in Syrian diet and their daily intake

More than one hundred different food stuffs (meat, vegetables cereals, seafood,..) have been collected during 1998, 1999 and 2000 and analyzed for radioactivity as part of the National Food Monitoring Program in Syria. Results have shown that most of the observed concentrations were within the range of the worldwide values with the exception of relatively high levels of ²¹⁰Po being observed in fish, vegetables, mushrooms, herbs and flowers. The daily intakes of the radionuclides studied have been evaluated. Relatively high values, in comparison with some countries, were found for ²¹⁰Po (1.9 Bq/day). This is due to high content of ²¹⁰Po in wheat (2.3 Bq/kg) consumed by Syrians, the daily consumption of wheat by Syrians is about 526 g. In addition, natural and artificial radionuclides in some manufactured food of Syrian infant and their intake rates have been determined. Seventeen manufactured food and eleven types of canned milk were collected from the local market and their radioactivity analyzed. ²¹⁰Po activity concentration varied between 0.38 and 2.89 Bq/kg dry wt. in canned milk while the highest concentration in infant food was found to be 1.69 Bq/kg dry wt. Other radionuclide concentrations were below the limit of detection of 3 Bq/kg dry wt. and 4 Bq/kg dry wt. for ²²⁶Ra and ²²⁸Ra, respectively, while uranium concentration varied between 2.2 and 10.5 μg/kg dry wt. in milk samples and 0.78-6.0 μg/kg dry wt. in other food samples. This revised version was published online in July 2006 with corrections to the Cover Date.     

The radiation dose and distribution coefficient of 210Po and 210Pb concentrations in aquatic environs of major rivers of coastal Karnataka

The activity of ²¹⁰Po and ²¹⁰Pb was measured in different matrices of aquatic ecosystem of the major rivers of Coastal Karnataka viz, Kali, Sharavathi and Netravathi. The environmental samples such as surface water, suspended particulate matter and sediment have been subjected to analyses. The activity of these two radionuclides were determined by radiochemical separation of ²¹⁰Po and counting the activity using a ZnS(Ag) alpha counter. The activity ratio of ²¹⁰Po and ²¹⁰Pb and correlation between the activity of these radionuclides were studied. From the measured concentration of ²¹⁰Po and ²¹⁰Pb, the internal Committed Effective Dose to the population for the study area was calculated. The distribution coefficient K_d between water, suspended particulate matter and sediments have been calculated to understand the distribution and accumulation of these radionuclides in different matrices of the aquatic environment.