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PubMedDate not supplied

Uptake of uranium, molybdenum, copper, and selenium by the radish from uranium-rich soils.

Radishes were grown in the naturally occurring uranium-containing soils found in the Okanagan Valley of British Columbia. The movement of uranium, molybdenum, copper, and selenium from the soil to the roots and the above-ground plant was investigated. Bioaccumulation was not observed for uranium, copper, and with some exceptions, selenium. Molybdenum bioaccumulates readily in the radish. Uranium and molybdenum uptake appears to be pH-dependent in this plant. Radish roots can be a significant source of uranium and molybdenum. Ingestion of radishes from these soils could easily surpass the maximum daily intake levels of uranium set by the Canadian government. Other crops and possible sources of uranium exposure around these deposits should be investigated.

Animals↗

PubMed1997

Solubility characterization of airborne uranium from an in situ uranium processing plant.

Solubility profiles of uranium dusts in the Irigaray uranium processing plant were determined by performing in vitro solubility tests on breathing zone air samples conducted in all process areas of the processing plant. The dissolution rate of the uranium on the air samples was then determined over the next 28 d in a simulant solution of the extracellular airway lining fluid (Gamble's solution). Airborne uranium in the wet process areas of the processing plant was highly soluble, with 97% dissolving in a 0.3 d half-time and 3% with a half-time of 15.6 d. The airborne uranium dusts in the drum load out area were also soluble, with 97% dissolving with a T1/2 of 0.25 d and the remainder with a T1/2 of 20 d. Exhaust from the drier stack and areas of the processing plant that had only this airborne uranium was slightly more insoluble, with 46% dissolving with a T1/2 of 0.4 d and 53% with an 18 d half-time. These results compare well with x-ray diffraction analysis of the uranium samples and the bioassay program for the processing plant workers.

Air Pollutants, Radioactive↗

PubMed2003

Stimulating the in situ activity of Geobacter species to remove uranium from the groundwater of a uranium-contaminated aquifer.

The potential for removing uranium from contaminated groundwater by stimulating the in situ activity of dissimilatory metal-reducing microorganisms was evaluated in a uranium-contaminated aquifer located in Rifle, Colo. Acetate (1 to 3 mM) was injected into the subsurface over a 3-month period via an injection gallery composed of 20 injection wells, which was installed upgradient from a series of 15 monitoring wells. U(VI) concentrations decreased in as little as 9 days after acetate injection was initiated, and within 50 days uranium had declined below the prescribed treatment level of 0.18 micro M in some of the monitoring wells. Analysis of 16S ribosomal DNA (rDNA) sequences and phospholipid fatty acid profiles demonstrated that the initial loss of uranium from the groundwater was associated with an enrichment of Geobacter species in the treatment zone. Fe(II) in the groundwater also increased during this period, suggesting that U(VI) reduction was coincident with Fe(III) reduction. As the acetate injection continued over 50 days there was a loss of sulfate from the groundwater and an accumulation of sulfide and the composition of the microbial community changed. Organisms with 16S rDNA sequences most closely related to those of sulfate reducers became predominant, and Geobacter species became a minor component of the community. This apparent switch from Fe(III) reduction to sulfate reduction as the terminal electron accepting process for the oxidation of the injected acetate was associated with an increase in uranium concentration in the groundwater. These results demonstrate that in situ bioremediation of uranium-contaminated groundwater is feasible but suggest that the strategy should be optimized to better maintain long-term activity of Geobacter species.

Acetates↗

PubMed2005

Modeling of geochemical processes related to uranium mobilization in the groundwater of a uranium mine.

This paper describes the processes leading to uranium distribution in the groundwater of five boreholes near a restored uranium mine (dug in granite), and the environmental impact of restoration work in the discharge area. The groundwater uranium content varied from <1 microg/L in reduced water far from the area of influence of the uranium ore-containing dyke, to 104 microg/L in a borehole hydraulically connected to the mine. These values, however, fail to reflect a chemical equilibrium between the water and the pure mineral phases. A model for the mobilization of uranium in this groundwater is therefore proposed. This involves the percolation of oxidized waters through the fractured granite, leading to the oxidation of pyrite and arsenopyrite and the precipitation of iron oxyhydroxides. This in turn leads to the dissolution of the primary pitchblende and, subsequently, the release of U(VI) species to the groundwater. These U(VI) species are retained by iron hydroxides. Secondary uranium species are eventually formed as reducing conditions are re-established due to water-rock interactions.

Journal Article↗

PubMed2004

Adsorption of uranium from acidic solution by microbes and effect of thorium on uranium adsorption by Streptomyces levoris.

The adsorption of uranium from an acidic solution by microbes was examined. High uranium adsorption ability was exhibited by actinomycetes. Streptomyces levoris cells could adsorb about 380 micromol of uranium per gram dry cells from the solution. The cells could adsorb uranium over a wide acidic pH range and very rapidly. The amount of uranium adsorbed from a solution containing uranium and thorium was affected by the thorium concentration. The amount adsorbed was reduced and an uranyl-thorium ion exchange reaction occurred in the case of adsorption from a solution containing both metals.

Journal Article↗

PubMed2005

Oxidation states of uranium in depleted uranium particles from Kuwait.

The oxidation states of uranium in depleted uranium (DU) particles were determined by synchrotron radiation based mu-XANES, applied to individual particles isolated from selected samples collected at different sites in Kuwait. Based on scanning electron microscopy with X-ray microanalysis prior to mu-XANES, DU particles ranging from submicrons to several hundred micrometers were observed. The median particle size depended on sources and sampling sites; small-sized particles (median 13 microm) were identified in swipes taken from the inside of DU penetrators holes in tanks and in sandy soil collected below DU penetrators, while larger particles (median 44 microm) were associated with fire in a DU ammunition storage facility. Furthermore, the (236)U/(235)U ratios obtained from accelerator mass spectrometry demonstrated that uranium in the DU particles originated from reprocessed fuel (about 10(-2) in DU from the ammunition facility, about 10(-3) for DU in swipes). Compared to well-defined standards, all investigated DU particles were oxidized. Uranium particles collected from swipes were characterized as UO(2), U(3)O(8) or a mixture of these oxidized forms, similar to that observed in DU affected areas in Kosovo. Uranium particles formed during fire in the DU ammunition facility were, however, present as oxidation state +5 and +6, with XANES spectra similar to solid uranyl standards. Environmental or health impact assessments for areas affected by DU munitions should therefore take into account the presence of respiratory UO(2), U(3)O(8) and even UO(3) particles, their corresponding weathering rates and the subsequent mobilisation of U from oxidized DU particles.

Kuwait↗

PubMed1992

Uranium in vitro bioassay action level used to screen workers for chronic inhalation intakes of uranium mill tailings.

A uranium in vitro bioassay (urinalysis) action level was derived for use at the Department of Energy's Uranium Mill Tailings Remedial Action Project sites to identify chronic inhalation intakes of uranium mill tailings causing 0.5 mSv (50 mrem) annual effective dose equivalent. All radionuclides in the 238U decay chain that contribute 1% or more to the annual effective dose equivalent from an inhalation intake of uranium mill tailings were included in the derivation of the urinalysis action level. Using a chronic inhalation intake model, the uranium urinalysis action level for a 24-h urine sample, collected on a quarterly schedule, was calculated to be 1.5 micrograms.

Humans↗

PubMed2001

A review of the effects of uranium and depleted uranium exposure on reproduction and fetal development.

Depleted uranium (DU) is used in armor-penetrating munitions, military vehicle armor, and aircraft, ship and missile counterweighting/ballasting, as well as in a number of other military and commercial applications. Recent combat applications of DU alloy [i.e., Persian Gulf War (PGW) and Kosovo peacekeeping objective] resulted in human acute exposure to DU dust, vapor or aerosol, as well as chronic exposure from tissue embedding of DU shrapnel fragments. DU alloy is 99.8% 238Uranium, and emits approximately 60% of the alpha, beta, and gamma radiation found in natural uranium (4.05 x 10(-7) Ci/g DU alloy). DU is a heavy metal that is 160% more dense than lead and can remain within the body for many years and slowly solubilize. High levels of urinary uranium have been measured in PGW veterans 10 years after exposure to DU fragments and vapors. In rats, there is strong evidence of DU accumulation in tissues including testes, bone, kidneys, and brain. In vitro tests indicate that DU alloy may be both genotoxic and mutagenic, whereas a recent in vivo study suggests that tissue-embedded DU alloy may be carcinogenic in rats. There is limited available data for reproductive and teratological deficits from exposure to uranium per se, typically from oral, respiratory, or dermal exposure routes. Alternatively, there is no data available on the reproductive effects of DU embedded. This paper reviews published studies of reproductive toxicity in humans and animals from uranium or DU exposure, and discusses ongoing animal research to evaluate reproductive effects in male and female rats embedded with DU fragments, and possible consequences in F1 and F2 generations.

Aerosols↗

PubMed2006

Can we predict uranium bioavailability based on soil parameters? Part 1: effect of soil parameters on soil solution uranium concentration.

Present study aims to quantify the influence of soil parameters on soil solution uranium concentration for (238)U spiked soils. Eighteen soils collected under pasture were selected such that they covered a wide range for those parameters hypothesised as being potentially important in determining U sorption. Maximum soil solution uranium concentrations were observed at alkaline pH, high inorganic carbon content and low cation exchange capacity, organic matter content, clay content, amorphous Fe and phosphate levels. Except for the significant correlation between the solid-liquid distribution coefficients (K(d), L kg(-1)) and the organic matter content (R(2)=0.70) and amorphous Fe content (R(2)=0.63), there was no single soil parameter significantly explaining the soil solution uranium concentration (which varied 100-fold). Above pH=6, log(K(d)) was linearly related with pH [log(K(d))=-1.18 pH+10.8, R(2)=0.65]. Multiple linear regression analysis did result in improved predictions of the soil solution uranium concentration but the model was complex.

Adsorption↗

PubMed2002

Multiple influences of nitrate on uranium solubility during bioremediation of uranium-contaminated subsurface sediments.

Microbiological reduction of soluble U(VI) to insoluble U(IV) has been proposed as a remediation strategy for uranium-contaminated groundwater. Nitrate is a common co-contaminant with uranium. Nitrate inhibited U(VI) reduction in acetate-amended aquifer sediments collected from a uranium-contaminated site in New Mexico. Once nitrate was depleted, both U(VI) and Fe(III) were reduced concurrently. When nitrate was added to sediments in which U(VI) had been reduced, U(VI) reappeared in solution. Parallel studies with the dissimilatory Fe(III)-, U(VI)- and nitrate-reducing microorganism, Geobacter metallireducens, demonstrated that nitrate inhibited reduction of Fe(III) and U(VI) in cell suspensions of cells that had been grown with nitrate as the electron acceptor, but not in Fe(III)-grown cells. Suspensions of nitrate-grown G. metallireducens oxidized Fe(II) and U(IV) with nitrate as the electron acceptor. U(IV) oxidation was accelerated when Fe(II) was also added, presumably due to the Fe(III) being formed abiotically oxidizing U(IV). These studies demonstrate that although the presence of nitrate is not likely to be an impediment to the bioremediation of uranium contamination with microbial U(VI) reduction, it is necessary to reduce nitrate before U(VI) can be reduced. These results also suggest that anaerobic oxidation of U(IV) to U(VI) with nitrate serving as the electron acceptor may provide a novel strategy for solubilizing and extracting microbial U(IV) precipitates from the subsurface.

Ferric Compounds↗

PubMed2001

Variations of the isotopic ratios of uranium in environmental samples containing traces of depleted uranium: theoretical and experimental aspects.

The possibility of using conventional analysis, such as gamma spectrometry and alpha spectrometry, for the detection of traces of depleted uranium (DU) in environmental samples has been investigated. The expected values have been compared with the experimental results obtained by using mollusc samples gathered in the Adriatic Sea. The analysis has shown that it is possible to detect DU. if the percentage composition is about 20% depleted uranium and 80% natural uranium, for a sample containing 10 Bq x kg(-1) of 238U. The possibility of extending this approach to samples with any given uranium concentration is investigated.

Environmental Monitoring↗

PubMed1984

Predicted deposition rates of uranium yellowcake aerosols sampled in uranium mills.

Uranium aerosols generated during normal yellowcake packaging operations were sampled at four uranium mills. Samplers located in the packaging area were operated before, during and after drums of yellowcake were filled and sealed. Median aerosol concentrations in the packaging areas ranged from 0.04 micrograms U/1 to 0.34 micrograms U/1. The aerosols were heterogeneous and included a broad range of particle sizes such that 14% to 76% (by weight) of the airborne uranium was in particles with aerodynamic diameters greater than 12 micron. Air concentrations and particle-size distributions varied with time as larger particles settled or more aerosols were suspended. Aerosol characteristics could often be related to individual packaging steps. The results show that appreciable amounts of airborne uranium would be expected to deposit in the nasopharyngeal compartment of the respiratory tract if inhaled by a worker not wearing respiratory protection.

Aerosols↗

PubMed1995

A study of uranium lung clearance at a uranium processing plant.

A study has been made of the retention of uranium in the lungs of persons exposed chronically to low levels of uranium aerosols at the Y-12 Plant. A new characterization of the workplace aerosols shows an activity median aerodynamic diameter of 8 microns to be representative of the uranium oxides handled at the Y-12 Plant. The usual ICRP respiratory-system model is employed in conjunction with bioassay data from worker exposures to deduce a new set of parameters to describe lung clearance of these aerosols. This new assessment leads to good agreement between in vivo estimates of uranium lung burdens.

Aerosols↗

PubMed1996

A histological kidney study of uranium and non-uranium workers.

Kidney tissue sections were obtained at autopsy from seven persons with a history of low level occupational exposure to uranium and histologically compared in a blind study with similar sections obtained from six reference cases. The pathologist was unable to identify the uranium workers or any uranium-specific nephropathy. This suggests that the chronic low level of kidney uranium concentration experienced by these workers, which was an order of magnitude lower than the accepted permissible level of 3 microgram per gram, did not induce any identifiable permanent tissue damage.

Aged↗

PubMed1985

[Uranium, thorium and potassium contents and radioactive equilibrium states of the uranium and thorium series nuclides in phosphate rocks and phosphate fertilizers].

Uranium, thorium and potassium contents and radioactive equilibrium states of the uranium and thorium series nuclides have been studied for 2 phosphate rocks and 7 phosphate fertilizers. Uranium contents were found to be rather high (39-117 ppm) except for phosphate rock from Kola. The uranium series nuclides were found to be in various equilibration states, which can be grouped into following three categories. Almost in the equilibrium state, 238U approximately 230Th greater than 210Pb greater than 226Ra and 238U greater than 230Th greater than 210Pb greater than 226Ra. Thorium contents were found to be, in general, low and appreciable disequilibrium of the thorium series nuclides was not observed except one sample. Potassium contents were also very low (less than 0.3% K2O) except for complex fertilizers. Based on the present data, discussions were made for the radiation exposure due to phosphate fertilizers.

Alpha Particles↗

PubMed2005

Reactions of laser-ablated uranium atoms with H2O in excess argon: a matrix infrared and relativistic DFT investigation of uranium oxyhydrides.

Laser-ablated U atoms react with H2O during condensation in excess argon. Infrared absorptions at 1416.3, 1377.1, and 859.4 cm(-1) are assigned to symmetric H-U-H, antisymmetric H-U-H, and U=O stretching vibrations of the primary reaction product H(2)UO. Uranium monoxide, UO, also formed in the reaction, inserts into H2O to produce HUO(OH), which absorbs at 1370.5, 834.3, and 575.7 cm(-1). The HUO(OH) uranium(IV) product undergoes ultraviolet photoisomerization to a more stable H2UO2 uranium(VI) molecule, which absorbs at 1406.4 and 885.9 cm(-1). Several of these species, particularly H2UO2, appear to form weak Ar-coordinated complexes. The predicted vibrational frequencies, relative absorption intensities, and isotopic shifts from relativistic DFT calculations are in good agreement with observed spectra, which further supports the identification of novel uranium oxyhydrides from matrix infrared spectra.

Journal Article↗

PubMed1992

Uranium-loaded apoferritin with antibodies attached: molecular design for uranium neutron-capture therapy.

A method is described to deliver 235U to tumors; the isotope would then be fissioned by incident neutrons, producing localized lethal radiation sufficient for therapy. Apoferritin was loaded with an average of approximately 800 238U atoms per molecule. Stability of the loaded apoferritin in solution was improved, so that only 8% loss of uranium occurred after 8 days at pH 7. Fab' antibody fragments were covalently attached to the uranium-loaded apoferritin, and the immunoreactivity of the conjugate was 92% of that for antibody alone. Such bio-uranium constructions should provide significant advantages over boronated antibodies to meet the requirements for clinical neutron-capture therapy.

Apoferritins↗

PubMed1995

Uranium dust exposure and lung cancer risk in four uranium processing operations.

We examined the relation between uranium dust exposure and lung cancer mortality among workers employed in four uranium processing or fabrication operations located in Missouri, Ohio, and Tennessee. Among workers who had at least 30 years of potential follow-up, we identified 787 lung cancer cases from death certificates and matched one control to each case. Health physicists estimated individual annual lung doses from occupational exposure primarily to insoluble uranium compounds, using contemporary monitoring data. With a 10-year lag, cumulative lung doses ranged from 0 to 137 centigrays (cGy) for cases and from 0 to 80 cGy for controls. Health physicists assigned annual external radiation doses to workers having personal monitoring records. Archivists collected smoking information from occupational medical records. Odds ratios for lung cancer mortality for seven cumulative internal dose groups did not demonstrate increasing risk with increasing dose. We found an odds ratio of 2.0 for those exposed to 25 cGy and higher, but the 95% confidence interval of 0.20 to 20 showed great uncertainty in this estimate. There was a suggestion of an exposure effect for workers hired at age 45 years or older. Further analyses for cumulative external doses and exposures to thorium, radium, and radon did not reveal any clear association between exposure and increased risk, nor did dichotomizing workers by facility.

Adult↗