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PubMed1994

Environmental and medical effects of nuclear weapon production in the southern Urals.

As a result of the activities of the 'Mayak' facility producing weapon's grade plutonium, large territories of the Urals Region (Russia) were exposed to radioactive contamination and the population residing in these territories was exposed to elevated radiation levels. Due to three radiation incidents and normal operation of the plant, significant radiation doses were received in a number of cases by the residents of the communities located in the close vicinity of the facility, along with its workers. Cases of chronic radiation sickness were registered within the early period of exposure and in the later years increased morbidity and mortality from leukosis and malignant neoplasms were noted. Problems of irradiation dose reconstruction, and the health status in the offspring of the exposed population are discussed.

Accidents↗

PubMed2005

Metal binding by bacteria from uranium mining waste piles and its technological applications.

Uranium mining waste piles, heavily polluted with radionuclides and other toxic metals, are a reservoir for bacteria that have evolved special strategies to survive in these extreme environments. Understanding the mechanisms of bacterial adaptation may enable the development of novel bioremediation strategies and other technological applications. Cell isolates of Bacillus sphaericus JG-A12 from a uranium mining waste pile in Germany are able to accumulate high amounts of toxic metals such as U, Cu, Pb, Al, and Cd as well as precious metals. Some of these metals, i.e. U, Cu, Pd(II), Pt(II) and Au(III), are also bound by the highly orderd paracrystalline proteinaceous surface layer (S-layer) that envelopes the cells of this strain. These special capabilities of the cells and the S-layer proteins of B. sphaericus JG-A12 are highly interesting for the clean-up of uranium contaminated waste waters, for the recovery of precious metals from electronic wastes, and for the production of metal nanoclusters. The fabricated nanoparticles are promising for the development of novel catalysts. This work reviews the molecular biology of the S-layer of the strain JG-A12 and the S-layer dependent interactions of the bacterial cells with metals. It presents future perspectives for their application in bioremediation and nanotechnology.

Bacillus↗

PubMed2004

Anomalous transport of colloids and solutes in a shear zone.

Transport experiments with colloids and radionuclides in a shear zone were conducted during the Colloid and Radionuclide Retardation experiment (CRR) at Nagra's Grimsel Test Site. Breakthrough curves of bentonite colloids and uranine, a non-sorbing solute, were measured in an asymmetric dipole flow field. The colloid breakthrough is earlier than that of uranine. Both breakthrough curves show anomalously long late time tails and the slope of the late time tails for the colloids is slightly higher. Anomalous late time tails are commonly associated with matrix diffusion processes; the diffusive interaction of solutes transported in open channels with the adjacent porous rock matrix or zones of stagnant water. The breakthrough curves for different colloid size classes are very similar and show no signs of fractionation due to their (size-dependent) diffusivity. It is proposed that tailing of the colloids is mainly caused by the structure of the flow field and that for the colloid transport, matrix diffusion is of minor importance. This has consequences for the interpretation of the uranine breakthrough. Comparisons of experimental results with numerical studies and with the evaluation of the colloid breakthrough with continuous time random theory imply that the tailing in the conservative solute breakthrough in this shear zone is not only caused by matrix diffusion. Part of the tailing can be attributed to advective transport in fracture networks and advection in low velocity regions. Models based on the advection-dispersion equation and matrix diffusion do not properly describe the temporal and spatial evolution of colloid and solute transport in such systems with a consistent set of parameters.

Bentonite↗

PubMed2004

Radiocarbon behaviour in seawater and the brown algae Fucus serratus in the vicinity of the COGEMA La Hague spent fuel reprocessing plant (Goury)--France.

Extensive studies of the radiocarbon (14C) distribution and transfer in the marine environment of the North-Cotentin peninsula and along the English Channel have been carried out. The main aims of these studies have been to estimate the spatial and temporal variation of the 14C concentration in seawater and to calculate 14C concentration factors for some biological species. Such information will be helpful in order to calculate precisely radiation doses to humans. First results obtained in the vicinity of the COGEMA La Hague nuclear plant (Goury) indicate a 14C labelling of the dissolved inorganic carbon (DIC) in seawater (8.0-26.2 Bq.m(-3)) and a tight relationship between the 14C in the liquid releases from the plant and the 14C concentrations in DIC. The particulate organic carbon (POC) is also labelled. The concentration factor calculations for the brown algae (Fucus serratus) sampled from Goury, and also along the English Channel, give 14C values around 3000 Bq.kg(-1) fresh weight / Bq.L(-1).

Atlantic Ocean↗

PubMed2006

Transfer of radiocarbon liquid releases from the AREVA La Hague spent fuel reprocessing plant in the English Channel.

The recent risk assessment by the North-Cotentin Radioecology Group (, 1999) outlined that (14)C has become one of the major sources of the low dose to man through seafood consumption. It was recommended that more data should be collected about (14)C in the local marine environment. The present study aims to respond to this recommendation. The estimation of (14)C activity in marine species is based on concentration factor values. The values reported here ranged from 1x10(3) to 5x10(3)Bqkg(-1)ww/BqL(-1). A comparison was made between the observed and predicted values. The accuracy of (14)C activity calculations was estimated between underestimation by a factor of 2 and over-estimation by 50% (95% confidence interval). However, the use of the concentration factor parameter is based on the biological and seawater compartments being in steady state. This assumption may not be met at short distances from the point of release of discharges, where rapid changes in seawater concentration may be smoothed out in living organisms due to transfer kinetics. The data processing technique, previously published by Fiévet and Plet (2003. Estimating biological half-lives of radionuclides in marine compartments from environmental time-series measurements. Journal of Environmental Radioactivity 65, 91-107), was used to deal with (14)C transfer kinetics, and carbon half-lives between seawater and a few biological compartments were thus estimated.

Animals↗

PubMed2003

Cesium migration in Hanford sediment: a multisite cation exchange model based on laboratory transport experiments.

Cs+ transport experiments carried out in columns packed with uncontaminated Hanford formation sediment from the SX tank farm provide strong support for the use of a multisite, multicomponent cation exchange model to describe Cs+ migration in the Hanford vadose zone. The experimental results indicate a strong dependence of the effective Cs+ Kd on the concentrations of other cations, including Na+ that is present at high to extremely high concentrations in fluids leaking from the Hanford SX tanks. A strong dependence of the Cs+ Kd on the aqueous Cs+ concentration is also apparent, with retardation of Cs+ increasing from a value of 41 at a Cs+ concentration of 10(-4) M in the feed solution to as much as 282 at a Cs+ concentration of 5x10(-7) M, all in a background of 1 M NaNO3. The total cation exchange capacity (CEC) of the Hanford sediment was determined using 22Na isotopic equilibrium exchange in a flow-through column experiment. The value for the CEC of 120 microeq/g determined with this method is compatible with a value of 121.9 microeq/g determined by multi-cation elution. While two distinct exchange sites were proposed by Zachara et al. [Geochim. Cosmochim. Acta 66 (2002) 193] based on binary batch exchange experiments, a third site is proposed in this study to improve the fit of the Cs+-Na+ and Cs+-Ca+ exchange data and to capture self-sharpened Cs+ breakthrough curves at low concentrations of Cs+. Two of the proposed exchange sites represent frayed edge sites (FES) on weathered micas and constitute 0.02% and 0.22% of the total CEC. Both of the FES show a very strong selectivity for Cs+ over Na+ (K(Na-Cs)=10(7.22) and 10(4.93), respectively). The third site, accounting for over 99% of the total CEC, is associated with planar sites on expansible clays and shows a smaller Na+-Cs+ selectivity coefficient of 10(1.99). Parameters derived from a fit of binary batch experiments alone tend to under predict Cs+ retardation in the column experiments. The transport experiments indicate 72-90% of the Cs+ sorbed in experiments targeting exchange on FES was desorbed over a 10- and 24-day period, respectively. At high Cs+ concentrations, where sorption is controlled primarily by exchange on planar sites, 95% of the Cs+ desorption was desorbed. Most of the difficulty in desorbing Cs+ from FES is a result of the extremely high selectivity of these sites for Cs+, although truly irreversible sorption as high as 23% was suggested in one experiment. The conclusion that Cs+ exchange is largely reversible in a thermodynamic sense is supported by the ability to match Cs+ desorption curves almost quantitatively with an equilibrium reactive transport simulation. The model for Cs+ retardation developed here qualitatively explains the behavior of Cs+ in the Hanford vadose zone underneath a variety of leaking tanks with differing salt concentrations. The high selectivity of FES for Cs+ implies that future desorption and migration is very unlikely to occur under natural recharge conditions.

Adsorption↗

PubMed2001

Radon emanation from NORM-contaminated pipe scale and soil at petroleum industry sites.

Radon-222 emanation fractions were determined for barite scale deposits associated with petroleum production tubing and soil contaminated with naturally occurring radioactive material (NORM). Samples were analyzed for 226Ra concentration, the results of which were used to calculate the 222Rn emanation fraction for the sample. An important parameter determining the overall Rn activity flux from a solid medium, 222Rn emanation fraction represents the fraction of 222Rn produced that enters the interconnected pore space within a medium contaminated with 226Ra before the 222Rn undergoes radioactive decay. The primary objective of the study was to determine whether 222Rn emanation fractions from pipe scale and soil from petroleum production sites are similar to those of uranium mill tailings. Pipe scale samples were collected at four sites representing a wide geographical area, and consisted primarily of barite scale where Ra atoms have replaced a fraction of the Ba within the crystal lattice of the scale. Soil samples were collected at five sites, from areas exhibiting elevated surface gamma exposure rates indicating the presence of NORM. For comparison, 226Ra concentrations and 222Rn emanation fraction were also determined for uranium mill tailings samples provided from a site in Utah. Although 2226Ra concentrations from pipe scale samples were similar to those found in uranium mill tailings, 222Rn emanation fractions from scale were generally lower. Emanation fractions from each data set were statistically different from those of mill tailings (p < or = 0.01). The differences are probably due to physical differences between the two media and to the method by which the Ra is deposited in the material. Radon emanation from soils was extremely variable owing not only to differences in physical and chemical soil properties, but also to the means by which NORM has entered the soil. Although additional emanation measurements from other sites are needed, the data collected at these sites indicate that regulations intended to protect human health from 222Rn inhalation should consider the type and properties of the medium in which the NORM is contained, rather than relying strictly on concentrations of the parent 226Ra.

Industry↗

PubMed2002

Radioactivity near the sunken submarine "Kursk" in the Southern Barents Sea.

Radioactivity measurements were conducted on seawater, sediment, and biota samples collected in the vicinity of the Russian submarine "Kursk" in September, 2000, within 1 month of the vessel's sinking in the Barents Sea to determine whether leakage of radioactivity from the vessel's two nuclear reactors had occurred and to assess the impact on one of the most productive fishing areas in the world. Levels of radioactivity in surface sediments and biota are within the range of values previously measured in the Barents Sea and can be ascribed to inputs from global fallout, European nuclear fuel reprocessing facilities, and the Chernobyl accident. However, levels of 1291 in seawater in the Southern Barents Sea increased by 500% between 1992 and 2000, and the 129I/137Cs ratio increased by more than an order of magnitude during this time, owing to long-range transport of releases from reprocessing facilities at Sellafield (U.K.) and La Hague (France). Although these results indicate that, at the time of sampling, leakage from the Kursk had a negligible impact on the environment, they also show that regional background levels of artificial radioactivity are varying rapidly on annual timescales and that Europe's nuclear reprocessing facilities are the leading contributor of anthropogenic radioactivity to the region.

Environmental Monitoring↗

PubMed2006

Pilot-scale in situ bioremedation of uranium in a highly contaminated aquifer. 2. Reduction of u(VI) and geochemical control of u(VI) bioavailability.

In situ microbial reduction of soluble U(VI) to sparingly soluble U(IV) was evaluated at the site of the former S-3 Ponds in Area 3 of the U.S. Department of Energy Natural and Accelerated Bioremediation Research Field Research Center, Oak Ridge, TN. After establishing conditions favorable for bioremediation (Wu, et al. Environ. Sci. Technol. 2006, 40, 3988-3995), intermittent additions of ethanol were initiated within the conditioned inner loop of a nested well recirculation system. These additions initially stimulated denitrification of matrix-entrapped nitrate, but after 2 months, aqueous U levels fell from 5 to approximately 1 microM and sulfate reduction ensued. Continued additions sustained U(VI) reduction over 13 months. X-ray near-edge absorption spectroscopy (XANES) confirmed U(VI) reduction to U(IV) within the inner loop wells, with up to 51%, 35%, and 28% solid-phase U(IV) in sediment samples from the injection well, a monitoring well, and the extraction well, respectively. Microbial analyses confirmed the presence of denitrifying, sulfate-reducing, and iron-reducing bacteria in groundwater and sediments. System pH was generally maintained at less than 6.2 with low bicarbonate level (0.75-1.5 mM) and residual sulfate to suppress methanogenesis and minimize uranium mobilization. The bioavailability of sorbed U(VI) was manipulated by addition of low-level carbonate (< 5 mM) followed by ethanol (1-1.5 mM). Addition of low levels of carbonate increased the concentration of aqueous U, indicating an increased rate of U desorption due to formation of uranyl carbonate complexes. Upon ethanol addition, aqueous U(VI) levels fell, indicating that the rate of microbial reduction exceeded the rate of desorption. Sulfate levels simultaneously decreased, with a corresponding increase in sulfide. When ethanol addition ended but carbonate addition continued, soluble U levels increased, indicating faster desorption than reduction. When bicarbonate addition stopped, aqueous U levels decreased, indicating adsorption to sediments. Changes in the sequence of carbonate and ethanol addition confirmed that carbonate-controlled desorption increased bioavailability of U(VI) for reduction.

Bacteria↗

PubMed1967