Thorsten Schäfer

Thorsten Schäfer
Friedrich Schiller University Jena | FSU · Institute of Geosciences, Applied Geology

Professor

About

230
Publications
26,996
Reads
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4,682
Citations
Citations since 2016
65 Research Items
2214 Citations
20162017201820192020202120220100200300
20162017201820192020202120220100200300
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20162017201820192020202120220100200300
Introduction
We study the dynamics at the solid-water interface to understand mechanistically the fate of metals/metalloids. Our research can be grouped in the interdisciplinary field of earth and material science with special focus on biogeochemical processes. Applications include i.e. cement hydration (CO2 footprint reduction), nanoparticle formation, nuclear waste repository research, mineral reaction retroaction on hydrodynamics, biogeochemical cycling and phytoremediation/ biomass production strategies.
Additional affiliations
October 2014 - May 2017
Karlsruhe Institute of Technology
Position
  • Professor (Full)
August 2008 - September 2014
Freie Universität Berlin
Position
  • Lecturer
January 2001 - January 2020
Karlsruhe Institute of Technology
Position
  • Senior Researcher

Publications

Publications (230)
Conference Paper
Full-text available
Single particle (sp)ICP-MS is a powerful tool to characterise nanoparticles and colloids in aqueous suspensions with respect to their size, concentration and elemental composition. However, analysing suspensions containing water reactive particles is still challenging. For instance, Calcium-Silicate-Hydrates (C-S-H) develop during the early stages...
Article
Full-text available
Concentrations and spatial distribution of trace elements in secondary minerals provide valuable information about mobility controlling processes in natural fractures. Important examples include rare-earth element contents that act as analogues for the retention of trivalent actinides such as Am/Cm or Pu(III). The secondary phases (carbonates) inve...
Article
To assess a reliable safety case for future deep underground repositories for highly active nuclear waste the retention of radionuclides by the surrounding host rock must be understood comprehensively. Retention is influenced by several parameters such as mineral heterogeneity and surface roughness, as well as pore water chemistry (e.g., pH). Howev...
Article
Full-text available
The modeling of fresh concrete flow is still very challenging. Nevertheless, it is of highest relevance to simulate these industrially important materials with sufficient accuracy. Often, fresh concrete is assumed to show a Bingham-behavior. In numerical simulations, regularization must be used to prevent singularities. Two different regularization...
Article
Full-text available
It is our great pleasure to briefly introduce our motivation to collect scientific contributions for this Special Issue, entitled "Nano Geochemistry" [...].
Article
Fungi living in heavy metals and radionuclides contaminated environments, namely the Chernobyl Exclusion Zone need to be able to cope with these pollutants. In this study, the wood-rot fungus Schizophyllum commune was investigated for its metal tolerance mechanisms, and for its ability to transport such metals through its hyphae. Effects of tempera...
Article
The Long-term In-situ Test (LIT) of the Colloid Formation and Migration project (CFM) at the Grimsel Test Site, investigates the generation of bentonite colloids and, hence, radionuclide mobilization within a well-defined and controlled shear zone in a crystalline rock. In this context, the determination of radionuclide aqueous speciation is essent...
Presentation
Full-text available
The focus of the present work was to study HTO, 36Cl , and 85Sr2+ diffusion behavior through four Na-saturated smectites and to compare the results with the diffusion through their four Na-saturated reduced charge materials (RCM). RCM contained Li+ and had collapsed interlayers (Fig. 1), which were no longer accessible for water. The aim was to cla...
Article
Full-text available
Chromite ore processing residues (COPR) are real environmental threats, leading to CrO4²⁻, i.e., Cr (VI) leaching into groundwater. It is of serious concern as Cr (VI) is proven to be carcinogenic. Here we emphasize the application of novel and eco-friendly chitin functionalized iron-enriched hydroxyapatite nanocomposite (HAP-Fe⁰-Ct) in the remedia...
Conference Paper
Full-text available
Anthropogenic phosphorus (P) input from different fertilised agricultural topsoils into surface water and re-dissolution from sediments play a vital role in eutrophication. This study aimed to (i) analyse the P input and re-dissolution processes into streams/rivers and (ii) to study the effectiveness of the riparian strip in reducing P emissions fr...
Article
The effect of fracture geometry on bentonite erosion for a generic repository site in crystalline host rock environment was investigated by means of 2-d numerical simulations. Fracture geometry was varied systematically using random aperture normal distributions with a mean aperture of 1 mm and standard deviations between 0 and 0.7 mm, respectively...
Article
Surface chemistry of mineral phases in aqueous environments generates the electrostatic forces involved in particle-particle interactions. However, few models directly take into account the influence of surface speciation and changes in solution speciation when the diffuse layer potential profiles of approaching particles overlap and affect each ot...
Article
Elevated levels of particulate matter (PM) in urban atmospheres are one of the major environmental challenges of the Anthropocene. To effectively lower those levels, identification and quantification of sources of PM is required. Biomonitoring methods are helpful tools to tackle this problem but have not been fully established yet. An example is th...
Conference Paper
Trace elements (TE) and rare earth elements (REE) commonly coprecipitate in secondary carbonates and provide valuable information about the fluid chemistry and system parameters at the times of their formation. REE share similar chemical properties with trivalent actinides and are therefore used as analogues to estimate the retention potential of c...
Article
Full-text available
Atmospheric particulate matter has become a major issue in urban areas from both a health and an environmental perspective. In this context, biomonitoring methods are a potential complement to classical monitoring methods like impactor samplers, being spatially limited due to higher costs. Monitoring using spider webs is compared with the more comm...
Article
Bentonite is planned to be used as a backfill material in deep geological repositories (DGR) notably for those to be established in crystalline rock. Potential erosion processes have to be clearly understood in order to properly assess its long-term barrier function. A likely scenario over the lifetime of a DGR in certain geographical locations is...
Article
Full-text available
Uranium and thorium decay series disequilibria in deep geothermal brines are a result of water-rock interaction processes. The migratory behavior of radionuclides provides valuable site-specific information and can therefore be an important tool for reservoir characterization and sustainable management of geothermal sites. In this study, we present...
Article
For the prevention of freshwater reservoirs from contamination through industrial effluents, eco-friendly adsorbents with minimal aging impact are required. Here, redox-sensitive nanoscale zero-valent iron(nZVI) particles were supported on four different surfaces with varying bentonite(B)/charcoal(C) ratio to mimic layered and porous surfaces. Diff...
Technical Report
Full-text available
In order to assess the relevance of colloidal influences on radionuclide transport for the longterm safety of a radioactive waste repository, the KOLLORADO-e2 project integrates the results of in-vitro (geochemical), in-situ and in-silico (hydrogeological) studies. From the commonly considered set of necessary conditions (colloid presence/generatio...
Article
Full-text available
The rheological properties of fresh cement paste are highly influenced by a large number of parameters, among which the most important factors are the applied shear stress, and the shear history, the age of the sample and the temperature. The effects of these parameters on the yield stress (designated as structural limit stress in this work), the v...
Article
Full-text available
In this study, the critical coagulation concentration (CCC) for FEBEX bentonite colloids is determined by colloid coagulation studies under variation of pH, electrolyte concentration, and fulvic acid (GoHy-573FA) content. For CaCl2 electrolyte solution, a pH-independent Ca-CCC of 1 mmol L−1 is found. In the case of NaCl background electrolyte, a pH...
Article
An open question in predicting the rheological properties of cement suspensions has been whether changes of rheology during hydration are merely a result of shifts in the electrostatic interaction patterns of the particles over time, or whether and to which extent steric bridging by hydration products occurs. The latter could explain phenomena such...
Article
A methodology for fracture zone identification in geothermal reservoirs was tested at the Bruchsal geothermal site, located close to the eastern main boundary fault of the Upper Rhine Graben. The site is explored and developed by a well doublet (GB1 and GB2). Fracture zones provide substantial contribution to the effective hydraulic conductivity an...
Poster
Low pH cement is investigated as potential barrier material in deep geological repositories for nuclear waste. During the relatively long period of disposal, this material will undergo alterations, changing its chemical and physical properties affecting the migration of radionuclides. In order to determine its effectiveness as barrier, solute trans...
Poster
Because of its long half-life and high mobility, 36Cl- present in spent nuclear fuel and in low- and intermediate-level radioactive waste is of potential concern in the context of nuclear waste disposal. Understanding the mechanism of 36Cl- migration in hardened cement paste at trace concentrations through a cementitious material is of great import...
Article
In the frame of studies on the safe disposal of nuclear waste, there is a great interest for understanding the migration behavior of ⁹⁹Tc. ⁹⁹Tc originating from nuclear energy production and global fallout shows environmental levels down to 10⁷ atoms/g of soil (~2 fg/g). Extremely low concentrations are also expected in groundwater after diffusion...
Article
The impact of fracture geometry and aperture distribution on fluid movement and on non-reactive solute transport was investigated experimentally and numerically in single fractures. For this purpose a hydrothermally altered and an unaltered granite drill core with axial fractures were investigated. Using three injection and three extraction locatio...
Presentation
Full-text available
In the last 15 years, a substantial effort has been made in predictive simulations of the long term interactions between different clays and cementitious materials. Cement-clay interactions have been mainly modelled as a Thermo-Hydro-Chemical coupled processes in continuum scale with various degrees of complexity. The main challenge of these models...
Presentation
In this study, three hydrated low pH cements have been prepared by mixing different solids and characterized after 90 days of hydration using various complementary analytical techniques. The samples were prepared at a water/binder ratio of 0.6. Scanning electron Microscopy – energy dispersive X-ray (SEM-EDX) analyses show that the main hydrated pha...
Article
Experimental and theoretical studies were conducted to identify the molecular-scale reaction mechanism for Cr(VI) removal by a ferrous phosphate mineral, vivianite. The surface-normalized rate constant for Cr(VI) removal in a vivianite suspension at pH 7 was higher than those obtained for other Fe(II)-containing minerals (i.e. magnetite and pyrite)...
Technical Report
Full-text available
The BELBaR project was a collaborative project based on the desire to improve the long-term safety assessments for geological disposal facility concepts for spent fuel/high level waste that combine a clay engineered barrier system (EBS) with a fractured rock. Colloids may be mobile in groundwater and are thus potentially significant for safety beca...
Article
Scale formation processes in the surface installations of geothermal power plants may have a negative effect on power plant performance. In addition, scales formed within the geothermal water circuit frequently accumulate natural radionuclides. Consequently, scale formation may lead to radiation dose rates, which are of radiological concern, and de...
Article
An extensive microanalytical study of calcite precipitated from groundwater flowing into boreholes at >400 m depth in the Äspö Hard Rock Laboratory, Sweden, has been carried out. Hydrochemical variations in packed-off sections, isolating water-conducting fractures intersected by two boreholes, were documented over a period of 17 years. The extracti...
Article
Understanding metal scavenging by calcite in deep aquifers in granite is of importance for deciphering and modelling hydrochemical fluctuations and water-rock interaction in the upper crust, and for retention mechanisms associated with underground repositories for toxic wastes. Metal scavenging into calcite has generally been established in laborat...
Article
Full-text available
In this study, we report results of the analysis of a particularly interesting scaling sample from the geothermal plant in Neustadt-Glewe in northern Germany, which contained 19% Galena (PbS) and 81% of a heterogeneous assemblage of (Ba,Sr)SO4 crystals with varying compositions, 0.15 < XBa < 0.53. A main fraction of the sample (~56%) has a barite c...
Article
Full-text available
Earth’s crust offers a vast resource of heat that can be used and converted into energy both for electricity and heating/cooling purposes. The utilization of this geothermal energy can make an important contribution to meet the targets of the envisaged energy turnaround. So-called “conventional” geothermal plants exploiting hot hydrothermal reservo...
Article
Experimental investigations on the uptake of divalent cations (Sr, Co and Zn) onto illite (Illite du Puy, Le-Puy-en-Velay, France) were carried out by three different international research groups (Institute for Nuclear Waste Disposal, KIT (Germany), Group Waste & Disposal, SCK-CEN, (Belgium) and Laboratory for Waste Management, PSI (Switzerland))...
Poster
Diffusion processes of contaminants through potential geotechnical barriers of nuclear waste repositories have been thoroughly studied using representatives of smectite, illite, or clay rock. Surface properties of clays minerals are known to influence the diffusion behaviour. The negative permanent charge of clays leads to the exclusion of diffusin...
Article
The multi-actinide analysis with AMS was applied to samples collected from the run 13-05 of the Colloid Formation and Migration (CFM) experiment at the Grimsel test site (GTS). In this in situ radionuclide tracer test the environmental behavior of U-233, Np-237, Pu-242 and Am-243 was investigated in a water conductive shear zone under conditions re...
Article
This study investigates the appropriateness of monodisperse carboxylated polystyrene spheres as clay colloid analogues. Colloid transport experiments using Na-illite are conducted within a parallel-plate fracture flow cell with an aperture of 0.75 mm at pH 5 under low ionic strength (1 mM NaCl) and laminar flow (7 mL/h) conditions. The effects of c...
Article
The interaction of Tc(VII) with crushed crystalline rock (Äspö diorite; 1–2 mm size fraction) from the Äspö Hard Rock Laboratory (HRL) (Sweden) was studied by laboratory batch sorption and desorption experiments under Ar atmosphere using both natural and synthetic groundwater. The Äspö diorite used in the experiments was drilled, transported and ha...
Article
Uranium redox states and speciation in magnetite nanoparticles co-precipitated with U(VI) for uranium loadings varying from 1000 to 10000 ppm are investigated by X-ray absorption spectroscopy (XAS). It is demonstrated that the U M4 high energy resolution X-ray absorption near edge structure (HR-XANES) method is capable to clearly characterize U(IV)...
Article
Full-text available
The potential to provide base-load electricity as well as industrial and domestic heat places geothermal energy in a unique position in the future energy mix. As estimated by the International Energy Agency, geothermal power can contribute to 3.5% to the worldwide power and 3.9% to heat production by 2050. This includes the development of Enhanced...
Article
Full-text available
The safe containment of radioactive waste in a disposal system has to be proven in the Safety Case. It is a prerequisite to know how the disposal system will develop over time. Safety relevant scenarios will be derived in the so called scenario development. The question arises of what would be the requirements and assets of a universal method that...
Article
Full-text available
The redox variations and changes in local atomic environment of uranium (U) interacted with the magnetite nanoparticles were studied in a proof of principle experiment by the U L3 and M4 edges high energy resolution X-ray absorption near edge structure (HR-XANES) technique. We designed and applied a mixed flow reactor (MFR) set-up to maintain dynam...
Article
The interaction of monodisperse fluorescent carboxylated polystyrene colloids (25nm and 1000nm diameter) with a cut granodiorite surface (Grimsel granodiorite; Switzerland) and with acrylic glass is investigated both experimentally and numerically. Colloid transport experiments are conducted in a parallel plate type fracture flow cell with an apert...
Article
Full-text available
The presence of colloids in groundwater can enhance contaminant migration by reducing retardation effects. The field experiments performed in a water-conducting feature of a shear zone at the Grimsel Test Site in Switzerland indicate that the sorption processes for contaminants on mobile and immobile colloids are kinetically controlled and that col...
Article
Full-text available
In the framework of the feasibility studies on the radioactive waste disposal in deep argillaceous formations, it isnow well established that the transport properties of solutes in clay rocks, i.e. parameter values for Fick’s law, are mainlygoverned by the negatively charged clay mineral surface. While a good understanding of the diffusive behaviou...