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Chemnitz, Germany

Marten A.,Friedrich - Schiller University of Jena | Berger D.,Friedrich - Schiller University of Jena | Kohler M.,Wismut GmbH | Merten D.,Friedrich - Schiller University of Jena
Environmental Science and Pollution Research | Year: 2015

We reconstructed the contamination history of an area influenced by 40 years of uranium mining and subsequent remediation actions using dendroanalysis (i.e., the determination of the elemental content of tree rings). The uranium content in the tree rings of four individual oak trees (Quercus sp.) was determined by laser ablation with inductively coupled plasma mass spectrometry (LA-ICP-MS). This technique allows the investigation of trace metals in solid samples with a spatial resolution of 250 μm and a detection limit below 0.01 μg/g for uranium. The investigations show that in three of the four oaks sampled, there were temporally similar uranium concentrations. These were approximately 2 orders of magnitude higher (0.15 to 0.4 μg/g) than those from before the period of active mining (concentrations below 0.01 μg/g). After the mining was terminated and the area was restored, the uranium contents in the wood decreased by approximately 1 order of magnitude. The similar radial uranium distribution patterns of the three trees were confirmed by correlation analysis. In combination with the results of soil analyses, it was determined that there was a heterogeneous contamination in the forest investigated. This could be confirmed by pre-remediation soil uranium contents from literature. The uranium contents in the tree rings of the oaks investigated reflect the contamination history of the study area. This study demonstrates that the dendrochemical analysis of oak tree rings is a suitable technique for investigating past and recent uranium contamination in mining areas. © 2015, Springer-Verlag Berlin Heidelberg. Source

Krawczyk-Barsch E.,Helmholtz Center Dresden | Lunsdorf H.,Helmholtz Center for Infection Research | Arnold T.,Helmholtz Center Dresden | Brendler V.,Helmholtz Center Dresden | And 3 more authors.
Science of the Total Environment | Year: 2011

The uranium mine in Königstein (Germany) is currently in the process of being flooded. Huge mass of Ferrovum myxofaciens dominated biofilms are growing in the acid mine drainage (AMD) water as macroscopic streamers and as stalactite-like snottites hanging from the ceiling of the galleries. Microsensor measurements were performed in the AMD water as well as in the biofilms from the drainage channel on-site and in the laboratory. The analytical data of the AMD water was used for the thermodynamic calculation of the predominance fields of the aquatic uranium sulfate (UO2SO4) and UO2 ++ speciation as well as of the solid uranium species Uranophane [Ca(UO2)2(SiO3OH)2.5H2O] and Coffinite [U(SiO4)1-x(OH)4x], which are defined in the stability field of pH>4.8 and Eh<960mV and pH>0 and Eh<300mV, respectively. The plotting of the measured redox potential and pH of the AMD water and the biofilm into the calculated pH-Eh diagram showed that an aqueous uranium(VI) sulfate complex exists under the ambient conditions. According to thermodynamic calculations a retention of uranium from the AMD water by forming solid uranium(VI) or uranium(IV) species will be inhibited until the pH will increase to >4.8. Even analysis by Energy-filtered Transmission Electron Microscopy (EF-TEM) and electron energy loss spectroscopy (EELS) within the biofilms did not provide any microscopic or spectroscopic evidence for the presence of uranium immobilization. In laboratory experiments the first phase of the flooding process was simulated by increasing the pH of the AMD water. The results of the experiments indicated that the F. myxofaciens dominated biofilms may have a substantial impact on the migration of uranium. The AMD water remained acid although it was permanently neutralized with the consequence that the retention of uranium from the aqueous solution by the formation of solid uranium species will be inhibited. © 2011 Elsevier B.V. Source

Loser R.,C and e Consulting und Engineering GmbH | Schneider P.,C and e Consulting und Engineering GmbH | Meyer J.,Wismut GmbH | Schramm A.,Wismut GmbH | Gottschalk N.,C and e Consulting und Engineering GmbH
The New Uranium Mining Boom: Challenge and Lessons Learned | Year: 2011

Within the frame of the environmental monitoring of the former uranium mining sites in Schlema-Alberoda have been established in 1999 soil hydrological test fields on covered and revegetated waste heap dumps. The objectives of the long term investigations on the test fields are the quantification of infiltration rates as well as the evaluation of the dynamics of the soil water balance. The data, obtained from more than one decade of observation, provide the time development of the water balance in the system soil - vegetation - atmosphere. The data were used to optimize the covering and revegetation concept for the mine dumps. At the Schlema-Alberoda mine dumps the rehabilitation has been successfully carried out using of a 2-cover-layer which contains a humus surface layer. © Springer 2011. Source

Arnold T.,Helmholtz Center Dresden | Baumann N.,Helmholtz Center Dresden | Krawczyk-Barsch E.,Helmholtz Center Dresden | Brockmann S.,Helmholtz Center Dresden | And 4 more authors.
Geochimica et Cosmochimica Acta | Year: 2011

The subsurface acid mine drainage (AMD) environment of an abandoned underground uranium mine in Königstein/Saxony/Germany, currently in the process of remediation, is characterized by low pH, high sulfate concentrations and elevated concentrations of heavy metals, in particular uranium. Acid streamers thrive in the mine drainage channels and are heavily coated with iron precipitates. These precipitates are biologically mediated iron precipitates and related to the presence of Fe-oxidizing microorganisms forming copious biofilms in and on the Fe-precipitates. Similar biomineralisations were also observed in stalactite-like dripstones, called snottites, growing on the gallery ceilings. The uranium speciation in these solutions of underground AMD waters flowing in mine galleries as well as dripping from the ceiling and forming stalactite-like dripstones were studied by time resolved laser-induced fluorescence spectroscopy (TRLFS). The fluorescence lifetime of uranium species in both AMD water environments were best described with a mono-exponential decay, indicating the presence of one major species. The detected positions of the emission bands and by comparing it in a fingerprinting procedure with spectra obtained for acid sulfate reference solutions, in particular Fe(III) - SO4 2- - UO2 2+ reference solutions, indicated that the uranium speciation in the AMD environment of Königstein is dominated in the pH range of 2.5-3.0 by the highly mobile aquatic uranium sulfate species UO2SO4(aq) and formation of uranium precipitates is rather unlikely as is retardation by sorption processes. The presence of iron in the AMD reduces the fluorescence lifetime of the UO2SO4(aq) species from 4.3μs, found in iron-free uranium sulfate reference solutions, to 0.7μs observed in both AMD waters of Königstein and also in the iron containing uranium sulfate reference solutions. Colloids were not observed in both drainage water and dripping snottite water as photon correlation spectroscopy analyses and centrifugation experiments at different centrifugal accelerations between 500. g and 46000. g revealed. Thus transport and uranium speciation at the investigated AMD sites is neither influenced by U(IV) or U(VI) eigencolloids nor by uranium adsorbed on colloidal particles. This study shows that TRLFS is a suitable spectroscopic technique to identify the uranium speciation in bulk solutions of AMD environments. © 2011 Elsevier Ltd. Source

Lobner W.,Wismut GmbH | Schramm C.,Wismut GmbH | Regner J.,Wismut GmbH | Geringswald K.,Wismut GmbH | And 2 more authors.
Kerntechnik | Year: 2012

In areas featuring air-filled mine workings the convective radon transport through the disturbed bedrock is a frequent cause of high radon concentrations in dwellings. The vertical transport distance of the radon propagation can be more than one hundred meters. The application of tracer gases that can be detected by gas chromatography at extreme low concentrations allows the clear detection of mine-originated radon in dwellings and provides knowledge on the complex processes of radon transport. The successful application of the method is demonstrated on the basis of investigations of the impact of former uranium mine sites on the radon situation in dwellings. © Carl Hanser Verlag, München. Source

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