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- Johnsson, Anna, 1975, et al.
(författare)
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Solid-aqueous phase partitioning of radionuclides by complexing compounds excreted by subsurface bacteria
- 2006
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Ingår i: Geomicrobiology Journal. - : Informa UK Limited. - 0149-0451 .- 1521-0529. ; 23(8), s. 621-630
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Tidskriftsartikel (refereegranskat)abstract
- Radionuclides are present in numerous aerobic and anaerobic subsurface environments due to nuclear weapons testing, leakage from process and storage facilities, and discharge of radioactive waste. The partitioning of radionuclides between liquid and solid phases by complexing compounds excreted by subsurface bacteria was studied. The solid-aqueous phase partitioning of pico- to submicromolar amounts of 59 Fe, 147 Pm, 234 Th, and 241 Am was analyzed in the presence of quartz sand and exudates from three species of subsurface bacteria: Pseudomonas fluorescens, Pseudomonas stutzeri, and Shewanella putrefaciens. All were grown under aerobic conditions, and P. stutzeri and S. putrefaciens were grown under anaerobic conditions as well. The supernatants of the aerobic and anaerobic cultures were collected and radionuclide was added. Quartz sand, with a Brunauer, Emmett, and Teller (BET) surface area of 0.1 m 2 g -1 , was added to the supernatant radionuclide mix, and the pH was adjusted to approximately 8. After centrifuging, the amount of radionuclide in the liquid phase of the samples and controls was analyzed using scintillation. Relative to the control, aerobic supernatants maintained more than 50% of the added 59 Fe, 234 Th, and 241 Am. The highest amount of metal present in the liquid phase of the anaerobic supernatants was found in the case of 241 Am, with 40% more 241 Am in samples than in controls. Both aerobic and anaerobic supernatants tested positive for complexing compounds when analyzed using the Chrome Azurol S assay. The great amounts of radionuclides in the liquid phases of samples were likely due to complexation with such compounds. Bacterially excreted complexing compounds hence seem able to influence the solid-aqueous phase partitioning of radionuclides. This could influence the mobility of radionuclides in contaminated subsurface environments.
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- Kalinowski, Birgitta E., 1900, et al.
(författare)
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Microbial leaching of uranium and other trace elements from shale mine tailings at Ranstad
- 2004
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Ingår i: Geoderma. - : Elsevier BV. - 0016-7061. ; 122:2-4, s. 177-194
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Tidskriftsartikel (refereegranskat)abstract
- High levels of heavy metals have been found in the surroundings of the closed uranium (U) mine in Ranstad in southern Sweden. These findings cannot be explained entirely by abiotic processes. It was not until recently that biology was taken into account in the discussion about mobilization of metals at this site. It is well known that bacteria produce short-chain organic acids and element-specific ligands (siderophores) that are able to change pH and enhance chelation, which results in increased mobilization of many trace elements. Other (nonessential) elements, such as thallium (Tl), lanthanides, and actinides, may also be mobilized as a result of such bacterial action. This paper describes the mobilization of U and other elements from U ores by bacteria. Three common siderophore-producing bacterial species, Pseudomonas fluorescens, Shewanella putrefaciens and Pseudomonas stutzeri, were incubated in a chemically defined medium supplemented with tailings material with a content of 0.0013% U by weight, which had been exposed to natural weathering for 30 years. Nonleached U ore (0.61% U by weight) from the same area was incubated with P. fluorescens and S. putrefaciens for comparison. P. fluorescens grown with ore caused a change in pH in the growth medium from 4.7 to 9.3, which was significantly higher than for the other two species, for which pH was about 5.2. P. fluorescens was the only species that thrived and mobilized measurable amounts of U from the two ores, leaching out 0.0010.005% of the total amount of U from both. The release of U is attributed to the production of pyoverdine chelators, since U could not be detected either in sterile controls or in the experiments with the other two bacteria. P. fluorescens also doubled the chromium (Cr) concentration in solution as compared with the sterile controls, whereas P. stutzeri and S. putrefaciens caused a five to sixfold increase in Cr concentration. Thallium, cobalt (Co), zinc (Zn), manganese (Mn), and vanadium (V) concentrations initially resembled those in the sterile controls, but from day 2 of the experiment, a decrease was observed. The difference in leaching behavior between the bacteria used in this study is likely to have been due to the production of different chelators rather than being an effect of pH, since many metals have low solubility at neutral to alkaline pH. This study using laboratory incubations shows that mobilization of U from ore can occur aerobically at neutral to alkaline conditions, which may be an important process behind the high content of heavy metals in the surroundings of the closed U mine at Ranstad.
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- Kalinowski, Birgitta E., et al.
(författare)
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Microbial mobilization of uranium from shale mine waste
- 2006
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Ingår i: Geomicrobiology Journal. - : Informa UK Limited. - 0149-0451 .- 1521-0529. ; 23:3-4, s. 157-164
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Tidskriftsartikel (refereegranskat)abstract
- The alum shale in the Billingen area in southern Sweden was mined in Ranstad for 5 years during the 1960s. The crushed tailings (processed and unprocessed) were left behind when the Ranstad mine was closed that has caused leaching of metals to the surroundings. The siderophore producing bacterium Pseudomonas fluorescens (sp, SE Sweden) was grown in batch cultures for 5 to 8 days with naturally weathered (unprocessed) uranium ore (0.0029% U by weight), kolm (0.52% U by weight) and acid-leached ore (0.0099% U by weight) in chemically defined media (unbuffered and buffered). Pseudomonas fluorescens grown with ore and unbuffered medium changed the pH from 4.7 to 9.3 and leached out 0.016 to 0.9% (normalized to surface area) of the total amount of U from the different ores. Incubation of the acid-leached ore with bacteria in buffered medium leached out 0.04% of the total U. Uranium was leached out selectively at all conditions, but this could be a pH effect, as pH increased at the same time as the U concentrations did. The observed release of Fe was most likely attributed to the production of microbial siderophores (Fe3+ specific chelators) since Fe3+ has a low solubility at pH > 4. As siderophores contain a number of chelating groups they may still function as complexators even in partly degraded form also for other metals than Fe. Thus, the production of microbial chelators could contribute to the elevated metal concentrations in the drainage water from the closed Ranstad mine, as abiotic processes cannot fully explain these high metal concentrations. In the extension: ligand promoted leaching of toxic elements could also be the key to bioremediation as there is a need for nontoxic cleanup methods for metal contaminated sites.
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- Pedersen, Karsten, 1952, et al.
(författare)
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Distribution, diversity and activity of microorganisms in the hyper-alkaline spring waters of Maqarin in Jordan
- 2004
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Ingår i: Extremophiles. - : Springer Science and Business Media LLC. - 1431-0651 .- 1433-4909. ; 8:2, s. 151-164
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Tidskriftsartikel (refereegranskat)abstract
- The hyper-alkaline, high-Ca2+ springs of Maqarin, Jordan, were investigated as an analogue for various microbial processes at the extremely high pH generated by cement and concrete in some underground radioactive waste repositories. Leaching of metamorphic, cementitious phases in Maqarin has produced current, hyper-alkaline groundwater with a maximum pH of 12.9. Six consecutive expeditions were undertaken to the area during 19942000. The total number of microorganisms in the alkaline waters was 103105 cells/ml. Analysis of the 16S-ribosomal ribonucleic acid (rRNA) diversity revealed microorganisms mainly belonging to the Proteobacteria. Obvious similarities between the obtained sequences and sequences from other alkaline sites could not be found. Numerous combinations of culture media compositions were inoculated with spring, seepage and groundwaters and incubated under aerobic and anaerobic conditions with various carbon sources. Assimilation studies were performed using identical radio-labeled carbon sources. Glucose seemed to be the preferred carbon source for assimilation, followed by acetate, lactate, and leucine. The results demonstrate that microorganisms from the hyper-alkaline springs of Maqarin could grow and be metabolically active under aerobic and anaerobic hyper-alkaline conditions. However, the growth and activity found were not vigorous; instead, slow growth, low numbers, and a generally low metabolic activity were found. This suggests that microbial activity will be low during the hyper-alkaline phase of cementitious repositories
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