Research

Erosion of bentonite under in-situ conditions by the action of natural waters in deep geological repositories

BMWi grant 02 E 12153A

Duration: 01.06.2023 - 30.05.2026

Project leader: Prof. Thorsten Schäfer

Person in charge: Léon Frederic Van Overloop

Key words: bentonite, multi-barrier system, Na-montmorillonite, accessory minerals, erosion, colloids, CFM-iBET, CFM-LIT, effect of thermal stress                           

Description: 

The overall objective of the project is to increase the mechanistic understanding of the processes critical for the integrity of the geotechnical barrier under near-natural, repository-relevant conditions in fractured granite systems and to provide a robust predictive modeling of the bentonite buffer and colloid-borne radionuclide transport.

The work is embedded in the CFM project at the Grimsel Rock Laboratory and builds in part on the findings obtained in Kollorado-e³ (FKZ: 02 E 11759A), but also considers completely new aspects.

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X-ray microscopy for understanding the mechanism of the deposition of environmentally relevant microplastics in saturated porous media - Towards understanding plastic accumulation in soils

DAAD-India PPP Project 57683132

Duration: 01.01.2024 – 31.12.2025

Personnel in charge: Prof. Thorsten Schäfer de, Prof. Gopala Krishna Darbha, Dr. Marcus Böhm de, Msc. Aniket Choudhary

Key words: Mikroplastic, pore space characterisation, 3D X-ray microscopy

Description:

This study deals with preparing environmentally relevant microplastics (E-MPs) and their transport in saturated porous media. Further, our study aims to investigate the impact of Fe and Al hydroxide mineral-coated sand grains on the transport of E-MPs in porous media. Understanding the adsorption of E-MPs onto mineral-coated sands is an important step toward developing scalable reaction models that can ultimately describe and predict the fate and transport of E-MPs in the subsurface environment.

Spatially resolved spectroscopies for the identification of interfacial processes and species of 3 - valent lanthanides and actinides

BMBF grant 02NUK089C

Duration: 01.04.2024 – 31.08.2027

Project leader: Prof. Thorsten Schäfer

Person in charge: Valentin Gabert

Key words: Transport properties of radionuclides, correlative spectroscopy, LA-ICP-MS

Description: In the BMBF-funded project SPIEG3L - Spatially resolved spectroscopies for the identification of interfacial processes and species of trivalent lanthanides and actinides, the transport properties of radionuclides, which are relevant for the realistic modeling of potential release scenarios, are investigated. The methodological focus of this project is on the use of LA-ICP-MS for the geochemical characterization of interfaces.

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Component additive approach to predict Cement paste Rheology considering Secondary Cementitious Materials and their special effect on thixotropy and concrete de-airing behaviour (CONCERT-CCair)

SPP2005 DFG grant SCHA 1854/7-1

Duration: 01.03.2021 - 31.07.2024

Project leader: Prof. Thorsten Schäfer

Personnel in charge: Steffen Hellmann, Dr. Dirk Merten, Frank Heberlein, Johannes Lützenkirchen, Teba Gil-Diaz (all KIT-INE)

Key words: CSH-phases, calcined clays, spICP-MS, AFM, surface complexation models

Description: The cement industry is stirring its research towards Secondary Cementitious Materials (SCMs) that will allow reducing the CO₂ footprint of concrete. The goal of this project is to identify promising SCM alternatives such as calcined clays (CCs) and limestone powders (LSP). The first approach is to characterize the rheological behaviour of fresh cement admixtures with these SCM during the early stages of hydration in casting process. The second one focuses on their potential role in avoiding unwanted air-bubble entrapment before hardening. Experimental approaches involve characterization of particle interactions and paste rheology in model and realistic systems via a national collaboration between FSU, KIT, BUW and LUH.

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Control of biological investigations during the decontamination of heterogeneous, low-level radioactively contaminated geosubstrates for precautionary radiation protection (KOBIOGEO)

Project leadership:
Prof. Dr. Georg Büchel, Dr. Dirk Merten

Description:

Low-level radioactive heterogeneous geosubstrates can be biologically decontaminated by phytoremediation, thus contributing to radiation prevention. By identifying the processes relevant for phytoremediation on a laboratory scale using the innovative rare earth element (SEE) fractionation method and transferring them to natural conditions, an increase in efficiency is achieved compared to previous, empirical approaches and experiences of decontamination of low-level radioactive geosubstrates. Naturally occurring rare earth elements and their distribution are used for process control and optimization in the uptake of heavy metals/radionuclides from geogenic materials into plant material. This provides the opportunity to identify biological and/or physical/chemical processes that occur during selective uptake of radionuclides and heavy metals through different fractionation patterns of SEE. Thus, effective transport processes during transfer can be inferred. Beyond the identification as well as control, an optimization of the biological decontamination processes can be achieved.

Funding period:
01.10.2004 bis 31.10.2008

Funding code:
02S8294

KOLLORADO-e2 (Integrity of the bentonite barrier for the retention of radionuclides in crystalline host rock - experiments and modeling)

Persons in charge: Thorsten Schäfer (FSU) & Francesca Quinto, Madeleine Stoll, Franz Rinderknecht (all KIT-INE)

Description:
The knowledge on the colloid/nanoparticle problem, in particular on the prediction of the colloid/nanoparticle source term, colloid/nanoparticle stability and nanoparticle/colloid-mineral-surface interaction, including the surface roughness, has made great progress in recent years. In addition to the description of colloid/nanoparticle stability by means of electrostatic approaches, quantitative data on the erosion of the bentonite barrier have been generated in laboratory tests. All data on the colloid/nanoparticle -supported radionuclide transport indicate a strong dependence of the colloid/nanoparticle mobility on the fracture geometry / surface roughness, the complete dissociation of tetravalent actinides from the clay colloid surface being still an open question. The main objective of the project is to improve the mechanistic understanding of the erosion of the compacted bentonite and the radionuclide-colloid interactions under near-natural conditions by means of in-situ experiments and the relevance of the nanoparticle/colloid-borne radionuclide transport with regard to the long-term safety of a repository in crystalline rock formations. In addition, generic statements on colloid relevance and the mobility of radionuclides are developed.

Funding: 3/2016 – 2/2019

The BEACON project is funded under the Euratom research and training programme 2014-2018 Grant Agreement No 745 942.

Project Transaqua - Hydrochemical and/or microbial impact on the transfer of radionuclides in groundwater

Radionuclides are released through water/rock interactions getting finally to drinking and surface water. Up to now, there is little known on the role of microbes in this process of release and transport.

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Transport and transfer behavior of long-lived radionuclides along the causal chain Groundwater - soil surface - plant, taking into account long-term climatic changes

Funding body + grant number:  Federal Ministry of Education and Research 02NUK051A-E

Duration: 01.09.2017 bis 30.06.2022

Project leader: Prof. Dr. T. Schäfer

Personnel in charge: Marcus Böhm, Dr. Daniel Jara Heredia

Key words: radionuclides, lysimeter, natural nanoparticulate phases, reactive transport

Description:

For long-term safety detection of potential repositories, the current radioecological models in accident scenarios proceed from a radionuclide entry into the biosphere via the water path. In addition to the path over rainfall and irrigation, the entry is particular interesting in the soil via fluctuating groundwater level changes. The aim is to provide a deeper understanding of the complex mechanisms of radionuclide transport from the groundwater zone to the plants, including climatic changes, which should lead to improved risk assessments for the exposure of the population over long periods. A significant step forward is the elucidation of the host mechanisms of radionuclides in crop plants at the molecular level, a concept which allows for far-reaching explanatory power beyond previous transfer factors.

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Implementation of heavy metal landfarming for sustainable landscaping and for exploitation of renewable energies on radionuclide contaminated Areas (USER)

Project leadership: Prof. E. KotheExternal link, Prof. G. Büchel

Funding period:  01.12.2014 to 30.11.2018  

Soil and water pollution by heavy metals and radionuclides (HM/R) is a major concern in many areas of the world, influencing the health of local populations, the use of the natural resources and the environmental equilibrium. In particular, soil, surface water and groundwater are likely to get an important input in different of these persistent pollutants, compromising the biosphere including humans on large areas. Bare soil or heaps are furthermore more likely to erode through the action of wind and precipitation, causing an eluviation of soil parallel to a spreading of contaminants in the air and water phase. 

In this context, field scale investigations are applied to areas of moderate HM/R contaminated substrates at the testsites Gessenwiese and Kanigsberg, near Ronneburg, to investigate phytoremediation strategies (USER-project, PTKA, FKZ 02S9194). Here, the main focuses lie on designing sustainable landscapes by reducing the bioavailability of contaminants with carbonatic soil material (rendzina) and microbial amendments (VA-mycorrhiza Rhizophagus irregularis, actinobacteria Strepromyces mirabilis P16-B1), as well as the production of renewable energy with metal tolerant plants (Festuca rubra, Secale multicaule) within a short-rotation-coppice (SRC, landfarming). In this connection, production of woody biomass with fast growing plants (Betula pendula, Sorbus aucuparia, Alnus, Pinus, Salix) in SRC provides a positive effect on biodiversity and erosion protection. 

Furthermore, quantification of biomass productivity and HM/R-transfer within the soil-plant-water system by using soil and microbial amendments are scopes of this project, and should lead to reduction in leaching of HM/R and soil erosion as well. Therefore, soil hydrological measurement stations and a lysimeter station are installed to get information about distribution, changes, transfer and output of HM/R in the water phase. 

Additionally, biomass productivity, plant vitality and erosion processes should be monitored with a multispectral camera and a high resolution camera system (accuracy 5 mm) installed on a microdrone (project TerraSensE, FKZ 13007-715).

Funding code 

15S9194