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Accurate estimation of contaminant transport in cementitious material using numerical tools plays a key role in the risk assessments of nuclear waste disposal. At the pore scale, the increase of microbial activity, such as microbially induced calcite precipitation on cementitious material, causes changes in solid surface topography, pore network geometry, and pore water chemistry, which affect contaminant transport at the core scale and beyond. Consequently, a meaningful estimation of contaminant migration in the subsurface requires a pore-scale investigation of the influence of microbial activity on transport processes. In this study, a pore-scale reactive transport model is presented to simulate the physicochemical processes resulting from microbially induced calcite precipitation on a cement surface. Numerical investigations focus on modeling the reactive transport in a two-dimensional flow-through cell. The model results are validated by experimental data showing an increase in pH and a decrease in calcium concentration due to microbially induced calcite precipitation. Our results show heterogeneous calcite precipitation under transport-limited conditions and homogeneous calcite precipitation under reaction-limited conditions, resulting in non-uniform and uniform changes in the material surface topography. Moreover, power spectral density analysis of the surface data demonstrates that microbially induced calcite precipitation affects the surface topography via both general changes over the entire frequency and local modifications in the high-frequency region. The sensitivity studies provide a comprehensive understanding of the evolution of surface topography due to the microbially induced calcite precipitation at the pore scale, thus contributing to an improved predictability of contaminant transport at the core scale and beyond.

High-level radioactive waste needs to be stored for long-term and safe in a deep geological repository (DGR) by using a multi-barrier system. Different materials with desirable properties are combined in this system to prevent an early release of radionuclides into the biosphere. For this reason, it is necessary to select suitable barrier materials, which ideally combine long-term stability and integrity. In this study, we combined different container materials (copper and cast iron) and pore waters (Opalinus Clay pore water and cap rock solution) with a Bavarian bentonite in static batch experiments to investigate the microbial influenced corrosion. The increasing concentration of iron and copper in solution as well as detected corrosion products on the metal surface are indicative for an occurring anaerobic corrosion of the respective metals during an incubation of 400 days at 37°C. However, although the intrinsic microbial bentonite community was stimulated with either lactate or H2, an acceleration of cast iron- and copper corrosion did not occur. Furthermore, neither corrosive bacteria nor conventional bacterial corrosion products, such as metal-sulfides, were detected in any of the analyzed samples. The analyses of geochemical parameters (e.g. ferrous iron-, iron-, copper- and potassium concentration as well as redox potential) showed significant changes in some cast iron- and copper-containing setups, but these changes do not correlate with the microbial community structure in respective microcosms, as confirmed by statistical analyses. Thus, we assume that the analyzed Bavarian bentonite (type B25) shows no significant contribution to cast iron and copper corrosion under the applied conditions after long incubation of 400 days. From this perspective, bentonite B25 could be a suitable candidate as geotechnical barrier in future DGRs.

The stored data sets represent both the raw data and the evaluated data that were used for the publication about speciation-dependent uranium(VI) reduction by an iron-reducing bacteria in both pure culture and artificial multispecies bio-aggregates.

High-energy-resolution fluorescence-detected X-ray absorption near-edge structure (HERFD-XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopy was used to investigate the reduction of U(VI) by the sulfate-reducing bacterium Desulfosporosinus hippei DSM 8344T, confirming the partial reduction of U(VI) and the presence of U(V).

The talk gives a short overview about the combination of flash lamp annealing and roll-to-roll applications including the application fields of inkjet printing with nanoparticle inks, transparent conduction oxides, and energy materials.

Ongoing miniaturization down to a few nanometers will lead to further significant reductions in the power consumption of microchips and sensors. The number of innovative applications immediately arise from the potential of integrating a microbattery as a power source for flexible electronics, wearables, the Internet of Things, medical implants and sensor chips. In this work, a thin film lithium-Ion battery (TF-LIB) is demonstrated. The TF-LIB consists of a high potential copper silicide anode (CuSi-anode) that can be integrated on a Siwafer with standard semiconductor technology and a hybrid polymer electrolyte with a high lithium-ion transference number. Two cathode materials were tested: LiFePO4 and NCA. The CuSi-anode is fabricated by Si sputtering followed by flash lamp annealing (FLA). This anode material replaces metallic lithium for reaching high energy densities and provides the thermal stability required in microelectronics (> 230 °C for soldering). The hybrid polymer electrolyte is mechanically stable against the volume change of the silicon during the lithiation/ delithiathion processes. The electrolyte is unreactive and thermally stable at high temperatures during operation.

I. EINLEITUNG Für eine umfassende Sicherheitsbewertung der geologi-schen Tiefenlagerung hochradioaktiver Abfälle müssen verschiedene Aspekte berücksichtigt werden. Neben den geologischen, geochemischen und geophysikalischen Eigen-schaften spielt der Einfluss von natürlich vorkommenden Mikroorganismen im umgebenden Wirtsgestein und im Verfüllmaterial eine entscheidende Rolle in der Umgebung eines solchen Endlagers. Tongesteine sind potenzielle Wirts-gesteine für die Endlagerung dieser Abfälle, während Ben-tonite als Verfüllmaterial nicht nur für ein Endlager in Ton-gesteinen, sondern auch in kristallinen Gesteinen vorgesehen sind. Wenn im ungünstigsten Fall Wasser in das Endlager eindringt, können Radionuklide aus den Abfallbehältern austreten und mit den Mikroorganismen interagieren. Dies kann z. B. zu Veränderungen der chemischen Speziation oder des Oxidationszustandes der Metallionen führen. II. ERGEBNISSE UND DISKUSSION Unter endlagerrelevanten Bedingungen stellen Desul-fosporosinus spp. wichtige Vertreter der sulfatreduzierenden anaeroben Bakterien dar, welche sowohl in Tonformatio-nen als auch im Verfüllmaterial Bentonit vorkommen (Bagnoud et al. 2016, Matschiavelli et al. 2019). Verschie-dene Studien zeigen, dass sie eine wichtige Rolle in den mik-robiellen Gemeinschaften dieser Umgebung spielen. Ein mit den isolierten Arten eng verwandter Mikroorganismus ist Desulfosporosinus hippei DSM 8344T (Vatsurina et al. 2008). Daher wurde dieses Bakterium ausgewählt, um des-sen Wechselwirkungen mit Uran(VI) zu untersuchen, insbe-sondere im Hinblick auf die Reduktion zum weniger mobi-len Uran(IV), welches günstige Eigenschaften wie eine gerin-gere Mobilität aufweist und damit eine verbesserte Rückhal-tung des Radionuklids im Wirtgestein ermöglicht wird. Zeitabhängige Reduktionsexperimente in künstlichem Opalinuston-Porenwasser (Wersin et al. 2011) mit einer Uran(VI)-Konzentration von 100 µM bei einem pH von 5.5 zeigten eine Abnahme der Uran(VI)-Konzentrationen von ca. 8

Redox transformations have a strong influence on the mobility of different metal ions in the environment. A key process in influencing the migration of uranium is the reduction of highly mobile and water-soluble uranium(VI) to less mobile uranium(IV). Especially in the surroundings of former uranium mines, this radionuclide represents an important contaminant whose entry into the environment must be prevented. Different microorganisms, e.g. sulfate- and iron-reducing bacteria, are capable of reducing uranium under various conditions. Thus, microbes can offer an environmentally friendly remediation strategy for radionuclide-contaminated environments. Moreover, in this study, we introduce the use of artificial bio-aggregates of different bacterial genera as a potential bioremediation approach combining advantageous properties of the microorganisms in a complementary way. Desulfitobacterium sp. G1-2, which was isolated from bentonite samples, was chosen as an important representative of iron-reducing bacteria in anaerobic environments. Furthermore, different Desulfitobacterium species were found in other natural environments, like clay formations as well. These bacteria were used to form artificial bio-aggregates with different other bacterial strains (e.g. aerobic marine inhabitant Cobetia marina DSM 50416) based on electrostatic modifications of the surface charge of the bacterial cells. Time-dependent experiments of a pure Desulfitobacterium sp. G1-2 culture in 30 mM bicarbonate buffer as background electrolyte showed a decrease in uranium concentration in the supernatants (100 µM uranium(VI), 10 mM lactate, pH 6.8/5.5). Approximately 80% of the uranium were removed from the supernatants within one week. UV/Vis studies of the dissolved cell pellets verified the reduction of uranium(VI) in the samples. STEM imaging of ultra-thin sectioned samples of uranium-incubated cells coupled with EDX spectroscopy showed the presence of two different uranium-containing aggregate

In the near future, silicon will play a key role as anode material for rechargeable lithium ion batteries (LIBs). It shows a low discharge potential and an extremely high specific theoretical capacity of about 4200 mAhg-1 in comparison to that of graphite with a theoretical capacity of 370 mAhg-1. However, the intrinsic volume change of Si particles of more than 400 % during the lithiation and delithiation processes hinders the Si to fully replace the conventional graphite in commercial LIBs. Using planar flash-lamp annealing (FLA) with annealing times in the sub-second range directly after the deposition of a Si thin film on a copper foil, we fabricated a copper silicide anode (CuSi-anode) with outstanding electrical and electrochemical properties. Herein, structural investigations using scanning electron microscopy and X-ray diffraction show a Cu-mediated silicidation at generating mixed phases of copper silicides, SiOx, Cu, and Si nanoparticles. The performance of battery cells with CuSi-anode having a Si thickness of 5 µm versus LiFePO4 shows a surface capacity of 2mAh/cm2 over 100 cycles with capacity loss in the course of cycling but with good electrical conductivity between the anode and current collector. Finally, we compare the electrochemical performance of the CuSi-anode with a conventional graphite anode at the same cell configuration and chemical conditions.

In der Umwelt beeinflussen physikalische, chemische und biologische Prozesse das Wanderungsverhalten von langlebigen Radionukliden (RN). Ziel der Forschung der Abteilung Biogeochemie ist es, dominierende Prozesse der Wechselwirkung von Radionukliden in der Biosphäre einschließlich der Nahrungskette zu identifizieren, die Biochemie dieser Prozesse auf molekularer Ebene zu verstehen und ihre Relevanz für Radionuklidmigration und -transfer nicht nur in der Natur, sondern auch im Umfeld eines Endlagers für hochradioaktive Abfälle zuverlässiger abschätzen zu können. Für den sensitiven Nachweis, die Identifikation des Chemismus sowie der Lokalisation von Radionukliden in verschiedenen biologischen Matrices und aquatischen Systemen nutzen wir eine Vielzahl von spektroskopischen und mikroskopischen Verfahren. Eine zentrale Rolle spielt dabei die Laser-induzierte Anregung der Lumineszenz von Actiniden und Lanthaniden, welche in Verbindung mit hochauflösender Mikroskopie die Beschreibung radioökologischer Prozesse in einer neuen Detailtiefe erlaubt. Mit dieser einzigartigen Kombination konnte zum Beispiel eine Actinid-induzierte Stressantwort bei Pflanzenzellen nachgewiesen, und die chemische Bindungsform von Uran in komplexen Umweltproben analysiert werden. Ein wichtiger Teilaspekt ist dabei außerdem die qualitative und quantitative Erfassung der chemo- und radiotoxischen Wirkung endlagerrelevanter als auch natürlich vorkommender Radionuklide (naturally occuring radioactive materials - NORM) in Organismen und ihre Zellen. Weitere Arbeiten befassen sich aktuell mit der Fragestellung, wie sich eine Uranbelastung in der Umgebung von Goldminen auf die im Umland lebende Bevölkerung auswirkt. Dazu wird gegenwärtig in einem gemeinsamen Projekt mit dem VKTA und der Wismut GmbH der Schwermetallgehalt in Haarproben von Personen mittels massenspektrometrischer Methoden bestimmt und bewertet, die im Umland von Johannisburg und nahe des weltweit größten Goldvorkommens, der Witwatersrand

Dissimilatory iron reduction is an anaerobic respiratory pathway, wherein ferric (Fe³) reducers couple the oxidation of organic acids, sugars and aromatic hydrocarbons to the reduction of Fe³-species [1]. This may lead to the formation of minerals such as magnetite (Fe²Fe³₂O₄) and siderite (Fe²CO₃) [2], which, in turn, can mediate the reduction of soluble pollutants as pertechnetate (Tc⁷O₄⁻) to insoluble oxides (Tc⁴O₂) [3]. The genus Desulfitobacterium contains obligate anaerobic bacteria that are capable of utilizing a wide range of electron acceptors, including nitrite, sulfite, metals, humic acids and halogenated organic compounds [4]. In this work, the Fe³ reduction of a Desulfitobacterium species was examined. The microorganism has been isolated from bentonite, which is potentially used as geotechnical barrier in deep geological repositories for radioactive waste [5]. The cultivation conditions included DSMZ 579 medium with Na-acetate as electron donor to reduce Fe³ citrate [6]. During cultivation, the formation of white precipitates was observed. The phases were collected both under aerobic and anaerobic conditions and repeatedly investigated by using Raman microscopy and powder X-ray diffraction (pXRD). It was noticed that the phases turned immediately to blue-greenish overnight under oxic conditions. Both Raman spectra and pXRD diffractograms can be attributed to vivianite (Fe²₃(PO₄)₂). Moreover, Raman spectra revealed the possible presence of pyrite (Fe²S₂), siderite, magnetite and hematite (Fe³₂O₃). These results suggest the ability of the bacterium of forming different Fe²-minerals. Notwithstanding, both methods indicate the change of the chemistry of the precipitates according to environmental factors. The Fe²-minerals formation by this microorganism depending on Fe³-compounds and background electrolytes is currently ongoing. The biogenic ferrous minerals will be studied regarding the reduction of Tc⁷O₄⁻. The authors acknowledge the German Federal Minist

The reduction of highly mobile and water soluble U(VI) to less mobile U(IV) represents a key process influencing the migration of this radionuclide in the environment. Microorganisms such as for example iron and sulfate-reducers are capable of reducing U(VI) under various conditions. This interaction mechanism between microbes and U could play an important role in a final disposal site for high-level radioactive waste deposited in deep geological layers. Different host rocks are suitable for the long-term storage of nuclear waste, e.g. clay formations, crystalline rock and rock salt. Besides the geochemical, geophysical and geological properties of such a repository, little is known about the influence of naturally occurring microorganism on the safety of such a site. In a worst-case scenario, if water enters the repository, radionuclides can get distributed in the surrounding host rock and thus interact with the native microorganisms, potentially leading to an immobilization of radionuclides via bioreduction. Furthermore, a reduction of U(VI) could also play an important role in the development of different bioremediation approaches for radionuclide-contaminated environments. As a potential component of new remediation strategies, we introduce the use of artificial bio-aggregates of different bacterial genera. By the use of these artificial biofilms insights into the complex interactions in a multi-species environment can be obtained. In this study, we used derivatized polyelectrolytes to form aggregates of two different microorganisms to connect advantageous properties of the microorganisms in a complementary way and to investigate the reduction of U(VI) under different conditions. Desulfitobacterium sp. G1-2 was chosen as an important representative of iron-reducing bacteria in anaerobic environments. This bacterial strain was isolated from bentonite samples of the Full-scale Engineered Barrier Experiment – Dismantling Project (FEBEX-DP) at the Helmholtz Center D

The safe disposal of high-level radioactive waste represents a major scientific and societal challenge. In addition to geological, geochemical and geophysical properties of such a repository, the influence of naturally occurring microorganisms from deep geological layers has to be taken into account for a comprehensive safeguard concept. Various sulfate- and iron-reducing bacteria are present in different clay formations, which can serve as a potential host rock for the long-term storage of the waste, as well as in the backfill material bentonite. In the event of a worst-case scenario, if water enters the repository, those microorganisms can interact with the waste and change for example the oxidation state or the chemical speciation, which can influence the mobility of the radionuclides. In this study, the reduction of highly-mobile, water-soluble U(VI) to less mobile U(IV) by the iron-reducing microorganism Desulfitobacterium sp. G1-2 and the sulfate-reducer Desulfosporosinus hippei DSM 8344T were investigated. Desulfitobacterium sp. G1-2 has been isolated from a bentonite sample and Desulfosporosinus hippei DSM 8344T represents a genus of sulfate-reducing bacteria present in clay rock and bentonite. During time-dependent experiments in bicarbonate buffer (30 mM, 100/550 µM U(VI)), Desulfitobacterium sp. G1-2 showed a removal of up to 80% of U within 5 days, whereas samples of Desulfosporosinus hippei DSM 8344T showed no decrease in U concentrations over time. Therefore, experiments were carried out in artificial Opalinus Clay pore water with this bacterium (100 µM U(VI), pH 5.5). In this case, the U concentration showed a decrease of up to 80% of the radionuclide from the supernatants within 48 h. UV/Vis studies of dissolved cell pellets of both bacteria after U incubation showed an almost complete reduction to U(IV) for Desulfitobacterium sp. G1-2. On the other hand, samples of Desulfosporosinus hippei DSM 8344T exhibited only a partial reduction. TEM imaging co

The energy transition in Germany is one of the greatest challenges for the coming decades. An important part of this is the phase-out of nuclear power generation and the safe long-term storage of highly radioactive waste in a future deep geological repository. When considering safety aspects of a potential repository, the influence of biological processes on the integrity of a potential repository is increasingly taken into account in addition to the necessary (physical-) chemical data basis. The effects of the bio-factor are manifold. Our research shows that the interaction of radionuclides with whole (micro)organisms or organic substances produced by them form complexes that alter the migration behavior of radionuclides. In addition, the mineral phases of the host rock are altered by bio-degradation and biomineralization processes. Another important aspect is that microbial induced electron transfer processes cause corrosion that reduces the integrity of potential containers. Last but not least, metabolic processes, especially under anaerobic conditions, lead to gas production that directly alters physical parameters such as pressure. However, the knowledge gained will not only be incorporated into state-of-the-art algorithms for modeling hydrogeological and ecological systems, but will also be important far beyond repository research. Studying the interaction of radionuclides with bacteria, for example, has provided new insights that have led to the development of an innovative process for plastic electroplating. The novel process allows the coating of highly complex polymer parts with functional metal surfaces while at the same time substituting highly toxic chemicals and saving resources. The investigation and comparison of different mine waters from former uranium ore mining has also led to the development of a new concept for the cost-effective, biotechnological purification of contaminated mine waters. The process and the potential of the procedure are curre

Multi-barrier concept is a favorable option to store high-level nuclear waste (HLW) in a deep geological repository. Bentonites are processed clay materials that are considered as a geotechnical barrier for metal containers storing HLW. To understand the impact of indigenous microorganisms from bentonites on these metal materials, anaerobic microcosms incubating Calcigel bentonite, synthetic Opalinus clay (OPA) porewater, lactate (one of the organic acids in natural OPA porewater) or H2 gas (product from anaerobic metal corrosion) with or without cast iron metal plates were conducted for up to 9 months in triplicates for each condition and time point (sampling every 3 months). The amplicon sequencing targeting V4 region of 16S rRNA genes showed that microbial communities of raw Calcigel bentonites mainly comprised phyla Acidobacteria, Actinobacteria, Chloroflexi, Firmicutes, Proteobacteria and Methylomirabilota. In the microcosms with lactate, enrichment of Bacillaceae (Firmicutes) and uncultured MB-A2-108 (Actinobacteriota) were observed; whereas in the presence of both lactate and cast iron, genera of Firmicutes, namely Desulfotomaculum, Desulfitobacterium and Desulfallas-Sporotomaculum, were highly enriched (relative abundance ranged from 60% to 95%) associating with large decrease in sulfate and lactate concentration. These bacteria appeared to be driven by H2 gas generated from metal corrosion. Moreover, SEM-EDX analyses showed that the metal surface was corroded and covered by a carbonate passivation layer. In this layer, FeS appeared to be formed, further suggesting the influence on cast iron corrosion and formation of secondary minerals induced by sulfate-reducing bacteria. On the other hand, we supplied N2 gas mixed with H2 and CO2 (80:10:10) to stimulate growth of H2-oxidizing sulfate reducers. GC analyses showed that in the microcosms without cast iron, the content of H2 gas in the headspace decreased accompanying with decrease in sulfate concentration (m

Deep geological repositories (DGR) will be used for the final disposal of highly radioactive waste. For the safety assessment of the DGR, it is important to consider accident scenarios such as the ingress of water, which might lead to a release of radionuclides (RNs) from the repository into the groundwater. RNs in groundwater can migrate to the surface soil where they can interact with indigenous microorganisms and plants, entering the food chain and posing a health risk to humans. The reliable modelling of the RN uptake into plants requires more than just transfer factors. A more detailed process understanding of the RN uptake into plants, including the effects of soil microorganisms, is necessary. RNs may affect the soil microbial community altering the natural community composition and interactions. Root exudates from plants and microorganisms can alter the speciation of RNs, affecting their bioavailability and mobility. We study the impact of soil microorganisms on the RN transport and uptake into plants at the molecular level. The experiments discussed focus on studying the modulation of soil microbial diversity in the presence of RNs and selected root exudates. In addition, radiation-resistant soil microorganisms will be isolated to study their interaction with RNs and their effect on the degradation of root exudates. This will include characterization of the degradation products and their interactions with RNs. These findings will be used to elaborate radioecological models for the assessment of the RN transport and uptake into the food chain.

The microbial reduction of U(VI) to U(IV) can decrease the mobility of U contaminants in the environment and may have a significant impact on the safety of a nuclear waste repository, as well as, the potential to serve as a component in bioremediation strategies for U-contaminated environments. In this study, we show significant differences in the reduction mechanisms for iron- and sulfate-reducing bacteria, highlighting the importance of investigating microbe-uranium interaction of different bacterial genera. Moreover, we introduce the use of artificial bio-constructs to study U reduction by microbial communities to gain insights into the complex interactions in a multi-species environment. To gain molecular process understanding regarding microbial U reduction Desulfosporosinus and Desulfitobacterium spp. were chosen as important representatives of sulfate- and iron-reducing bacteria in anaerobic environments. Furthermore, their U reduction capabilities were investigated using artificial bio-constructs with different other microbial species. Time-dependent experiments of pure cultures in bicarbonate buffer (30 mM, 100 µM U(VI), 10 mM lactate) showed a decrease of U concentrations in the supernatant of Desulfitobacterium sp. G1-2, whereas no changes occurred for Desulfosporosinus hippei DSM 8344T. In contrast, in artificial Opalinus Clay pore water (100 µM U(VI), pH 5.5, 10 mM lactate) up to 80% of the radionuclide got removed by both microorganisms. UV/Vis studies verified the reduction of U(VI) to U(IV) in the cell pellets. STEM-EDXX revealed the presence of two different U-containing aggregates inside the cells of Desulfitobacterium sp. G1-2, while cells of Desulfosporosinus hippei DSM 8344T showed almost no U uptake but U-aggregates on the cell surface. First experiments with artificial bio-constructs that were formed from different bacterial genera using polyelectrolyte-controlled aggregation showed a promising U reduction capacity. Such artificial biostructur

Dissimilatory iron reduction is an anaerobic respiratory pathway, wherein ferric (Fe(III)) reducers couple the oxidation of organic acids, sugars and aromatic hydrocarbons to the reduction of Fe(III)-species [1]. This may lead to the formation of minerals such as magnetite (Fe(II)Fe(III)₂O₄) and siderite (Fe(II)CO₃) [2], which, in turn, can mediate the reduction of soluble pollutants as pertechnetate (Tc(VII)O₄⁻) to insoluble oxides (Tc(IV)O₂) [3]. The genus Desulfitobacterium contains obligate anaerobic bacteria that are capable of utilizing a wide range of electron acceptors, including nitrite, sulfite, metals, humic acids and halogenated organic compounds [4]. In this work, the Fe(III) reduction of a Desulfitobacterium species was examined. The microorganism has been isolated from bentonite, which is potentially used as geotechnical barrier in deep geological repositories for radioactive waste [5]. The cultivation conditions included DSMZ 579 medium with Na-acetate as electron donor to reduce Fe(III) citrate [6]. During cultivation, the formation of white precipitates was observed. The phases were collected both under aerobic and anaerobic conditions and repeatedly investigated by using Raman microscopy and powder X-ray diffraction (pXRD). It was noticed that the phases turned immediately to blue-greenish overnight under oxic conditions. Both Raman spectra and pXRD diffractograms can be attributed to vivianite (Fe(II)₃(PO₄)₂). Moreover, Raman spectra revealed the possible presence of pyrite (Fe(II)S₂), siderite, magnetite and hematite (FeIII₂O₃). These results suggest the ability of the bacterium of forming different Fe(II)-minerals. Notwithstanding, both methods indicate the change of the chemistry of the precipitates according to environmental factors. The Fe(II)-minerals formation by this microorganism depending on Fe(III)-compounds and background electrolytes is currently ongoing. The biogenic ferrous minerals will be studied regarding the reduction of Tc(VII

Microbial U(VI) reduction influences the uranium mobility in contaminated subsurface environments and can affect the disposal of high-level radioactive waste by transform-ing the water-soluble U(VI) to less mobile U(IV). The reduction of U(VI) by the sulfate-reducing bacterium Desulfosporosinus hippei DSM 8344T, a close phylogenetic relative to naturally occurring microorganism present in clay rock and bentonite, was investigat-ed. D. hippei DSM 8344T showed a relatively fast removal of uranium from the superna-tants in artificial Opalinus Clay pore water. Combined speciation calculations and lumi-nescence spectroscopic investigations showed the dependence of U(VI) reduction on the initial U(VI) species. Scanning transmission electron microscopy coupled with ener-gy-dispersive X-ray spectroscopy showed uranium-containing aggregates on the cell surface and the formation of membrane vesicles. By combining different spectroscopic techniques, including UV/Vis spectroscopy, as well as uranium M4-edge X-ray absorp-tion near-edge structure (XANES) recorded in high-energy-resolution fluorescence-detection (HERFD) mode and extended X-ray absorption fine structure (EXAFS) analy-sis, the partial reduction of U(VI) could be verified, whereby the formed U(IV) product has an unknown structure. Furthermore, the U M4 HERFD-XANES showed the presence of U(V) during the process, suggesting a single-electron transfer mechanism for the microbial U(VI) reduction by sulfate reducers. These findings offer new insights into the U(VI) reduction by sulfate-reducing bacteria and contribute to a comprehensive safety concept for a repository for high-level radioactive waste.

Microorganisms show a high affinity for trivalent actinides and lanthanides, which play an important role in the safe disposal of high-level radioactive waste as well as in the mining of various rare earth elements. The interaction of the lanthanide Eu(III) with the sulfate-reducing microorganism Desulfosporosinus hippei DSM 8344T, a representative of the genus Desulfosporosinus that naturally occurs in clay rock and bentonite, was in-vestigated. Eu(III) is often used as a non-radioactive analogue for the trivalent actinides Pu(III), Am(III), and Cm(III), which contribute to a major part of the radiotoxicity of the nuclear waste. D. hippei DSM 8344T showed a weak interaction with Eu(III), most likely due to a complexation with lactate in artificial Opalinus Clay pore water. Hence, a low removal of the lanthanide from the supernatant was observed. Scanning transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy revealed a bioprecipitation of Eu(III) with phosphates potentially excreted from the cells. This demonstrates that the ongoing interaction mechanisms are more complex than a sim-ple biosorption process. The bioprecipitation was also verified by luminescence spec-troscopy, which showed that the formation of the Eu(III) phosphate compounds starts almost immediately after the addition of the cells. Moreover, chemical microscopy pro-vided information on the local distribution of the different Eu(III) species in the formed cell aggregates. These results provide first insights into the interaction mechanisms of Eu(III) with sulfate-reducing bacteria and contribute to a comprehensive safety concept for a high-level radioactive waste repository, as well as to a better understanding of the fate of heavy metals (especially rare earth elements) in the environment.

The stored data sets represent both the raw data and the evaluated data that were used for the publication about interactions of a sulfate-reducing bacterium with europium(III).