Distribution of uranium in sediment of creek ecosystem

The present study was carried on distribution of uranium isotopes and Thorium in marine sediment from creek of Mumbai Harbour Bay (MHB) using radiochemical separation followed by alpha spectrometry. The activity concentration of uranium and thorium in sediment of MHB has ranged between 1–4 and 1.8–4.5 ppm respectively. The activity ratio of ²³⁴U/²³⁸U in sediment was found close to unity at most of the locations of creek suggesting a conservative behaviour. The observed Th/U ratio (0.9) in comparison to global Th/U ratio (?3.5) in the creek sediment indicates that it receives low radiogenic nature of terronenous input.     

Studies on natural and anthropogenic radionuclides in sediment and biota of Mumbai Harbour Bay

Mumbai Harbour Bay (MHB) is a recipient of low level treated effluents from BARC, Trombay and its also a recipient of domestic and industrial wastes from the city of Mumbai and adjoining areas. Sediment samples were collected from various locations of MHB to determine the concentrations of naturally occurring radionuclides like ²²⁶Ra, ²²⁸Ra and ⁴⁰K which varied between 4.0 and 26.0, 5.5 and 19.9, 249.6 and 557.6 Bq kg _(dry) ^?1 respectively and are comparable to the worldwide average concentration. The mean value ratio of ²²⁸Ra/²²⁶Ra in sediment was found to be 1.4, indicating a relatively higher mobility of ²³⁸U compared to ²³²Th. The concentration of anthropogenic radionuclide ¹³⁷Cs in sediment and biota ranged between 3.6 and 54.5 Bq kg _(dry) ^?1 , <0.08 and 0.5 Bq kg _(wet) ^?1 respectively. The ingestion dose to ‘General Public’ due to ¹³⁷Cs intake is 0.02 μSv years^?1 which is negligible compared to the internationally accepted limit of 1,000 μSv years^?1 to ‘members of public’.     

Determination of chronological heavy metal deposition and pollution intensity in the bottom sediments of Mumbai Harbour Bay, India using 137Cs as tracer

Downcore variation of trace metals in sediment cores along the coastal line is one of the markers to assess the intrusion of industrial pollutants into the aquatic environment. Fifty sediment core samples from the Mumbai Harbour Bay (MHB), were studied for the trace element content. MHB is a recipient of effluents from different industries situated all along its coast around Thane–Belapur region. The average concentrations of Titanium (Ti), Manganese (Mn), Iron (Fe), Nickel (Ni), Copper (Cu), Zinc (Zn) were determined by inductively coupled plasma-optical emission spectroscopy and complemented by analysing with energy dispersive X-ray fluorescence spectrometry. In addition to this, depth profiles of K and Ca were also studied to assess the homogeneity of the geological strata of the region. Trace metals such as Cu, Ni and Zn show enrichment between 16 to 28 cm, whereas, uniform distribution through out the core was observed for K, Ca, Ti, Mn and Fe. Chronology of the heavy metal deposition was predicated based on the average sedimentation rate (0.92 ± 0.08 cm year⁻¹) derived using depth-wise ¹³⁷Cs concentration profile in core of bottom sediment. The results of the analysis showed that MHB had received excess inputs of Cu, Ni and Zn in the year 1981, 1988 and 1982, respectively. Surface concentration of Cu, Ni, Zn and Fe compared to the reference site indicates moderate pollution in the recent years whereas for elements K, Ca, Ti and Mn, the values are normal indicating MHB unpolluted for the latter elements.     

Uranium concentration measurements in human blood for some governorates in Iraq using CR-39 track detector

The sensitive and simple technique of fission track etch has been applied to determine trace concentration of uranium in blood samples for occupational and non-occupational workers, male and female, using CR-39 track detector that is employed for registration of induced fission tracks. The results show that the highest recorded uranium concentration in human blood of workers in the ministry of Science and Technology were 1.90 ppb (male, 36 years old, 12 years' work experience, and living in Basrah governorate) and minimum concentration 0.26 ppb (female, 40 years old, 10 years' work experience, and living in Baghdad), while for non-occupational worker, the maximum uranium concentration was 1.76 ppb (female, 63 years old, and living in Al-Muthana) and minimum concentration was 0.28 ppb (female, 20 years old, and living in Baghdad). It has also been found that the uranium concentration in human blood samples of workers in the ministry of Science and Technology are higher than those of non-occupational workers, and the uranium concentrations for female workers and for non-occupational workers were higher than those for male workers and non-occupational workers.     

Study of uranium isotopic composition in groundwater and deviation from secular equilibrium condition

Uranium concentration in groundwater reflect both redox conditions and uranium content in host rock. In the present study an attempt has been made to study the uranium concentration and activity ratios of uranium isotopes to present the geochemical conditions of the groundwater in Malwa region of Punjab state, India and the reason for high uranium levels and variation of activity ratios from secular equilibrium conditions. Uranium concentration in groundwater samples was found to be in the range of 13.9 ± 1.2 to 172.8 ± 12.3 μg/l with an average value of 72.9 μg/l which is higher than the national and international guideline values. On the basis of uranium concentration, the groundwater of the study region may be classified as oxidized aquifer on normal uranium content strata (20 %) or oxidized aquifer on enhanced uranium content strata (80 %). The ²³⁸U, ²³⁵U and ²³⁴U isotopic concentration in groundwater samples was found to be in the range of 89.2–1534.5, 4.4–68.5, and 76.4–1386.2 mBq/l, respectively. Activity ratios of ²³⁴U/²³⁸U varies from 0.94 to 1.85 with a mean value of 1.11 which is close to unity that shows secular equilibrium condition. High value of ²³⁴U isotope than ²³⁸U may be due to alpha recoil phenomenon. The plot of AR of ²³⁴U/²³⁸U against the total uranium content in log scale reveals that the groundwaters of the study region either belongs to stable accumulation or normal oxidized aquifer.     

Uranium concentration in blood samples of Southern Iraqi leukemia patients using CR-39 track detector

The simple and effective technique of fission track etch has been applied to determine trace concentration of uranium in human blood samples taken from two groups of male and female participants: leukemia patients and healthy subjects group. The blood samples of leukemia patients and healthy subjects were collected from three key southern governorates namely, Basrah, Muthanna and Dhi-Qar. These governorates were the centers of intensive military activities during the 1991 and 2003 Gulf wars, and the discarded weapons are still lying around in these regions. CR-39 track detector was used for registration of induced fission tracks. The results show that the highest recorded uranium concentration in the blood samples of leukemia patients was 4.71 ppb (female, 45 years old, from Basrah) and the minimum concentration was 1.91 ppb (male, 3 years old, from Muthanna). For healthy group, the maximum uranium concentration was 2.15 ppb (female, 55 years old, from Basrah) and the minimum concentration was 0.86 ppb (male, 5 years old, from Dhi-Qar). It has been found that the uranium concentrations in human blood samples of leukemia patients are higher than those of the healthy group. These uranium concentrations in the leukemia patients group were significantly different (P < 0.001) from those in the healthy group.     

Occurrence of uranium in groundwater of a shallow granitic aquifer and its suitability for domestic use in southern India

Groundwater used for domestic purpose without proper treatment should be free from chemical and biological contaminants. This study was carried out to assess the groundwater quality with respect to uranium in a part of Nalgonda district, Andhra Pradesh, India. Groundwater was regularly monitored for uranium concentration by collection of samples once every two months from March 2008 to November 2009 from 44 wells. The concentration of uranium in groundwater ranged from 0.2 to 118.4 ppb. Groundwater is unsuitable for domestic use in 2 % of this area based on the limit of 60 ppb prescribed by the Atomic Energy Regulatory Board of India. However, due the wide variation in limit suggested by different organizations and countries, the no-observed-adverse-effect level and lowest-observed-adverse-effect level (in mg/kg day) was used to understand the dosage of uranium that reaches the people through drinking water pathway. This level varied from 0 to 0.02 mg/kg day and 0 to 0.08 mg/kg day based on an uncertainty factor of 10 and 50 respectively for the mean uranium concentration in groundwater in each well. With an uncertainty factor of 50, 5 groundwater samples had uranium above 0.06 mg/kg day which is the lowest-observed-adverse-effect level. This study showed that with the presence of present level of uranium concentration in groundwater of this area there is no major threat to humans through the drinking water pathway.     

Uranium electrodeposition for alpha spectrometric source preparation

In this paper a simple method was used to design and set up an electrodeposition device for uranium source preparation for alpha spectrometry measurements. The aim of this work is to find the optimal parameters to be used to achieve uranium alpha sources with good spectral properties and maximum yield of the electrodeposition process. Samples with specific uranium activity were prepared from aqueous solution of uranyl nitrate hexahydrate (UO₂ (NO₃)₂·6H₂O). A series of preliminary experiments was conducted to establish the main parameters that have a significant influence on the deposition efficiency. Among these, the electrodeposition time was studied and the optimum time was found to be 1 h, in the case of our home-made deposition cell. It was also shown that a current of 1,500 mA, plating time of 60 min and pH range of 2–2.2 are the best conditions for deposition of uranium. The alpha spectrometry results show a good spectral resolution for the uranium sources obtained by the electrodeposition using the optimal parameters.     

Adsorption and kinetic behavior of uranium and thorium in seawater-sediment system

The adsorption and kinetic mechanism of uranium (U) and thorium (Th) in seawater-sediments system of Mumbai Harbour Bay (MHB) has been studied by K _d values of two sets of experimental determinations using a batch experiment. After equilibrium time (7 days), under static conditions, K _d for U and Th ranged from 25,030 to 55,662 mL/g (mean: 42,140 mL/g) and 24,926 to 38,561 mL/g (mean: 34,256 L/kg), respectively. Extraction studies showed that both U and Th were strongly bound to sediment components due to insignificant difference in their mean concentration in equilibrium solution. Rate constants (k) for transfer between seawater and the exchangeable fraction were found to be similar for the sediments as 1.02 ± 0.03 day^?1 for uptake of U and Th. The resulting adsorption data were fitted to Freundlich, linear and Langmuir isotherm models. All the three models showed a significant correlation (R ² >0.9), indicating that there is more complex relationships with adsorption behavior of U and Th on sediment surface. Since, the Freundlich constant (n) for U and Th was found to be closer to unity. Therefore linear model was observed to be highly suitable. Based on the linear model, the distribution coefficient (k _d) of Th was about 1.5 times higher than U. According to Freundlich model, sorption of U in sediments observed to be higher than Th. However, Langmuir model considered in opposite to Freundlich and showed a higher value of K _L constant for Th than U. The pH (water) of the sediments ranged from 7.8 to 8.2 and the estimated total carbon (determined by C H N S–O elemental analyser) ranged from 1.7 to 3.4 %.     

Application of fission track technique for estimation of uranium concentration in drinking waters of Punjab

Drinking water samples were collected from four different districts, namely Bhatinda, Mansa, Faridkot and Firozpur, of Punjab for ascertaining the U(nat.) concentrations. All samples were preserved, processed and analyzed by laser fluorimetry (LF). To ensure accuracy of the data obtained by LF, few samples (10 nos) from each district were analyzed by alpha spectrometry as well as by fission track analysis (FTA) technique. For FTA technique few μl of water sample was transferred to polythene tube, lexan detector was immersed in it and the other end of the tube was also heat-sealed. Two samples and one uranium standard were irradiated in DHRUVA reactor. Irradiated detectors were chemically etched and tracks counted using an optical microscope. Uranium concentrations in samples ranged from 3.2 to 60.5 ppb and were comparable with those observed by LF.     

Precipitation and purification of uranium from rock phosphate

This study was carried-out to leach uranium from rock phosphate using sulphuric acid in the presence of potassium chlorate as an oxidant and to investigate the relative purity of different forms of yellow cakes produced with ammonia, magnesia and sodium hydroxide as precipitants, as well as purification of the products with TBP and matching its impurity levels with specifications of the commercial products. Alpha-particle spectrometry was used for determination of activity concentration of uranium isotopes in rock phosphate, resulting phosphoric acid, and in different forms of the yellow cake. Likewise, atomic absorption spectroscopy was used for determination of impurities. On the average, the equivalent mass concentration of uranium was 119.38 ± 79.66 ppm (rock phosphate) and 57.85 ± 20.46 ppm (phosphoric acid) with corresponding low percent of dissolution (48 %) which is considered low. The isotopic ratio (²³⁴U:²³⁸U) in all stages of hydrometallurgical process was not much different from unity indicating lack of fractionation. Upon comparing the levels of impurities in different form of crude yellow cakes, it was found that the lowest levels were measured in hydrated trioxide (UO₃·xH₂O). This implies that saturated magnesia is least aggressive relative to other precipitants and gives relatively pure crude cake. Therefore, it was used as an index to judge the relative purity of other forms of yellow cakes by taking the respective elemental ratios. The levels of impurities (Fe, Zn, Mn, Cu, Ni, Cd and Pb) in the purified yellow cake were found comparable with those specified for commercial products.     

Performance of alpha spectrometry in the analysis of uranium isotopes in environmental and nuclear materials

The accuracy of alpha spectrometry in the determination of uranium isotopes at various concentrations levels and with various isotope ratios was tested in a round robin international intercomparison exercise. Results of isotope activity/mass and isotope mass ratios obtained by alpha spectrometry were accurate in a wide range of uranium masses and in isotopic ratios typical of depleted, natural, and low enriched uranium samples. Determinations by alpha spectrometry compared very satisfactorily in accuracy with those by mass spectrometry. For example, determination of U isotopes in natural uranium by alpha spectrometry agreed with mass spectrometry determinations at within ±1%. However, the ²³⁶U isotope, particularly if present in activities much lower than ²³⁵U, might not be determined accurately due to overlap in the alpha particle energies of these two uranium isotopes.     

Uranium isotopes in carbonate aquifers of arid region setting

Groundwater in arid and semiarid regions is vital resource for many uses and therefore information about concentrations of uranium isotopes among other chemical parameters are necessary. In the study presented here, distribution of ²³⁸U and ²³⁵U in groundwater of four selected locations in the southern Arabian peninsula, namely at two locations within the United Arab Emirates (UAE) and two locations in Oman are discussed. The analyses of the uranium isotopes were performed using ICP-MS and the results indicated a range of concentrations for ²³⁵U and ²³⁸ U at 3–39 ng L^?1 (average: 18 ng L^?1) and 429–5,293 ng L^?1 (average: 2,508 ng L^?1) respectively. These uranium concentrations are below the higher permissible WHO limit for drinking water and also comparable to averages found in groundwater from similar aquifers in Florida and Tunisia. Negative correlation between rainfall and uranium concentrations suggests that in lithologically comparable aquifers, climate may influence the concentration of uranium in subtropical to arid regions.     

Accumulation of uranium by filamentous green algae under natural environmental conditions

The capacity of algae to concentrate uranium under natural environmental conditions is measured by a-spectrometry. Spirogyra, a filamentous green fresh-water alga, has concentrated uranium from a surface concrete ponds with elevated uranium levels (140-1140 ppb). The concentration factors (CFs) ranged from 8.9-67 with an average value of 22.Cladophora spp, a filamentous green marine alga has concentrated uranium from the marine water with a concentration factor ranged from 220–280. The average concentration factor was 250. The factors affecting the sorption process are discussed in detail. This revised version was published online in July 2006 with corrections to the Cover Date.     

Comparison of uranium extraction from model fresh water on TiO–PAN and NaTiO–PAN composite absorbers

Possibility of uranium extraction on titanium oxide (TiO)–polyacrylonitrile (PAN) and sodium titanate (NaTiO)–PAN composite absorbers prepared from hydrated TiO and NaTiO embedded into a matrix of PAN binder was studied. Both TiO–PAN and NaTiO–PAN absorbers might be advantageous for repeated extraction of uranium from fresh water. Appropriate flow rates were found up to 60 BV h^?1 for both the absorbers. Elution of uranium and regeneration of both the absorbers may be accomplished by hydrochloric acid solutions of concentration 0.1 mol L^?1 and more. Practical sorption capacity (up to 10 % break-through) from tap water containing 2.3 μg U mL^?1 was ~4.6 and ~1.5 mg of uranium per 1 mL of swollen TiO–PAN and NaTiO–PAN absorber, respectively.     

Plutonium in Gorce Mountains area (Southern Poland)

Paper presents results of the plutonium deposition measurements in Gorce Mountains—a small part of western Polish Carpathians, Southern Poland where a national park was established in 1981. Samples were collected in both forest and alp areas. They were analyzed by means of alpha spectrometry preceded by radiochemical treatment. The results for activity concentration are then used to calculate cumulated deposition which range from 45.7 ± 4.3 to 164 ± 19 Bq/m², what means that it reach in maximum almost three times higher value than UNSCEAR average for global fallout, expected for our latitude. The isotopic activity ratio ²³⁸Pu to ^239+240Pu indicates global fallout as the main if not the only source of Pu. Nevertheless, presented results for plutonium reveal more uniform Pu deposition pattern in Gorce Mountains than it was observed for ¹³⁷Cs in earlier study using the same samples.     

238U and 222Rn activity concentrations and total radioactivity levels in lake waters

The concentrations and distributions of natural radioactivity, uranium and radon in lake waters from around Van, Turkey were investigated with an aim of evaluating the environmental radioactivity. Fourteen lake waters were collected from different six lakes around Van (Turkey) to determine ²³⁸U, ²²²Rn and total alpha and total beta distributions in 2009. The total α and total β activities were counted by using α/β counter of the multi-detector low background system (PIC-MPC-9604) and the ²³⁸U concentrations were determined by inductively coupled plasma-mass spectrometry (Thermo Scientific Element 2) and radon concentrations were measured with the solid state nuclear track detector technique. The activity concentrations ranging from ND to 0.039 Bq L^?1 and from 0.026 to 3.728 Bq L^?1 for total alpha and beta, respectively, and uranium concentrations ranging from 0.083 to 3.078 μg L^?1, and radon concentrations varying between 47.80 and 354.86 Bq m^?3 were observed in the lake waters.     

Determination of uranium isotopes in environmental samples

The determination of isotopes of uranium by alpha spectrometry in different environmental components (sediments, soil, water, plants and phosphogypsum) is presented and discussed in this paper. The alpha spectrometry is a very convenient and good technique for activity concentration of natural uranium isotopes (²³⁴U, ²³⁵U, ²³⁸U) in environmental samples and provides the most accurate determination of isotopic activity ratios between ²³⁴U and ²³⁸U. The analysis were provided information about possible sources of high concentrations of uranium in the examined sites determined by anthropogenic sources. The calculation of values ²³⁴U/²³⁸U in all analyzed samples was applied to identifying natural or anthropogenic uranium origin. Activity concentration of uranium isotopes in analyzed environmental samples shows that measurement of uranium levels is of great importance for environmental and safety assessment especially in contaminated areas (phosphogypsum waste heap).     

Estimation of uranium in bioassay samples of occupational workers by laser fluorimetry

A newly established uranium processing facility has been commissioned at BARC, Trombay. Monitoring of occupational workers is essential to assess intake of uranium in this facility. A group of 21 workers was selected for bioassay monitoring to assess the existing urinary excretion levels of uranium before the commencement of actual work. Bioassay samples collected from these workers were analyzed by ion-exchange technique followed by laser fluorimetry. Standard addition method was followed for estimation of uranium concentration in the samples. The minimum detectable activity by this technique is about 0.2 ng. The range of uranium observed in these samples varies from 19 to 132 ng/L. Few of these samples were also analyzed by fission track analysis technique and the results were found to be comparable to those obtained by laser fluorimetry. The urinary excretion rate observed for the individual can be regarded as a ‘personal baseline’ and will be treated as the existing level of uranium in urine for these workers at the facility.     

Optimization of operating parameters and rate of uranium bioleaching from a low-grade ore

In this study the bioleaching of a low-grade uranium ore containing 480 ppm uranium has been reported. The studies involved extraction of uranium using Acidithiobacillus ferrooxidans derived from the uranium mine samples. The maximum specific growth rate (µ ^max) and doubling time (t _d) were obtained 0.08 h^?1 and 8.66 h, respectively. Parameters such as Fe²⁺ concentration, particle size, temperature and pH were optimized. The effect of pulp density (PD) was also studied. Maximum uranium bio-dissolution of 100 ± 5 % was achieved under the conditions of pH 2.0, 5 % PD and 35 °C in 48 h with the particles of d ₈₀ = 100 μm. The optimum concentration of supplementary Fe²⁺ was dependent to the PD. This value was 0 and 10 g of FeSO₄·7H₂O/l at the PD of 5 and 15 %, respectively. The effects of time, pH and PD on the bioleaching process were studied using central composite design. New rate equation was improved for the uranium leaching rate. The rate of leaching is controlled with the concentrations of ferric and ferrous ions in solution. This study shows that uranium bioleaching may be an important process for the Saghand U mine at Yazd (Iran).