Specific research programs PDF Print
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Is there microbial activity that substantially modifies the processes of weathering, reactive transport in the water phase, and remineralization? Evidence for microbial activity has accumulated in several different areas of research, e.g. biocorrosion (see Santo Domingo et al., 1998), microbial metal reduction (Hamilton, 2003), and deep drilling projects (Schippers et al., 2005). Microbes have also the potential for altering pH, Eh, and chemical properties so as to allow transformation of minerals (see also: Lovley, 2000). Exogenic processes in near-surface subsystems which were thought to be driven merely by physical or chemical parameters are now reconsidered because of increasing evidence for microbial influence (Schmidt et al., 2005*). Temperature, pressure, and time, for instance, have been thought to control the smectite-to-illite reaction, which is an important diagenetic process used in basin analysis and hydrocarbon exploration. Kim et al. (2004) demonstrated that microorganisms can promote this clay mineral reaction at room temperature and within 14 days. These findings are a challenge to conventional concepts of the smectite-illite reaction and of reaction kinetic models. It is likely that microbial interferences with many other exogenic mineral transformations exist with considerable bearing on our understanding of Earth surface processes.
Since the first question is undoubtedly to be answered with yes, the next question must be: How big is the influence through biotransformation and bioaccumulation of microbes? So far, in most research fields, this question has not been answered and has not even been addressed as the microbial influence on geological and mineralogical processes is far from being understood at a molecular level.

The central idea of the proposed project is to enhance our understanding of molecular processes driven by biological parameters at the mineral-microbe interface. Even if quantification cannot be achieved ad hoc, the direction of our research aims into this field. Since for a first estimation a singular geological setting has to be chosen, the scope of the proposed basic research is directed at understanding an acid mine drainage influenced site which poses the opportunity to concentrate on the three main areas of weathering, reactive transport and remineralization in a setting that allows predictions of the microbial taxa present and their potential activities. In the long run, the experimental data will allow to refine strategies for remediation including microbiological processes in geochemical barrier and plant extraction schemes for future land-use of large catchment areas that are heterogeneously contaminated with heavy metals (see Barkay and Schaefer, 2001). Similarly, this project will be internationally competitive with respect to remediation and land-use projects in other mine waste associated areas.
Thus, the graduate program will be associated with the Earth Sciences, specifically with exogenic, surface related and applied geosciences. Microbiological influence on natural attenuation will be determined which will lead to first quantitative estimates which have been  often underestimated in the past. The urgent need for this research program can be seen by the current interest in sedimentology processes involving microbiologists (including the recently established Research Group at Göttingen which investigates evolution of geobiosphere in surface water and underground settings).
Microbes can influence the substrate on which they grow through their metabolic activity (Hurst et al., 2001). There are at least three types of microbial processes that can influence the toxicity and transport of metals: biotransformation, biosorption/bioaccumulation, and degradation or synthesis of organic ligands that affect the solubility of the contaminants. The capacity of microbes to influence redox conditions, pH, oxygen supply as well as processes of direct uptake and chelation lead to orders of magnitude of enhancement in geochemical processes (Hurst et al., 2001). There has been an increasing awareness of  the function of microbes in geobiological processes in deep biosphere processes (which in contrast to the proposed topic allows only very low generation times, like once in thousand years) and in soil related processes (which are dominated by plant litter degradation allowing short generation times). However, the definition of the impact (depending on the molecular mechanisms) of microbes on bioattenuation in acid mine drainage related substrates is still missing.
In the first funding period the proposed research will focus on the determination of the influence of the microbial world on known processes in acid mine contaminated areas. All three subprojects are related to this topic of alteration of rock material in its broadest sense. Alteration here is used for any change including mobilization, demobilization and any other influence leading to altered phases like, e.g., incrustation, secondary mineral formation, co-precipitation, or changes in element mobilities. The identification and potential quantitative addition to physico-chemicial processes of microbes under natural and laboratory conditions unites the three subprojects.
 
  • 1.    Influence of microbes on rock alteration is crucial for a better understanding of  weathering of geogenic heavy metal sources and black shales, and microbial biotransformation reactions at the surface are one aspect of biotransformation studied.
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  •  2.    Reactive transport in the water phase is a central aspect of transfer of any element into biological systems and involves the action of microbiologically derived acids, reductants or chelates on the environment with respect to mobilization and demobilization of metals.
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  •  3.    Remineralization and influence of altered redox conditions by bacterial activity.
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At a later stage, a more mechanistic understanding of the processes shown to have the highest impact in the phenomenon of natural attenuation and the development of risk assessment and bioremediation strategies will prevail.
The work is at all stages divided into field and laboratory scale experiments where the more mechanistic approach is investigated in laboratory experiments with single strains and consortia of microbes while the field studies are aimed at determining the hydrogeochemical processes in the field and defining microbial communities at the most active compartments.

2005-10-04The research site is a field site of 2,500 square meter rented for a ten-year period by the Friedrich-Schiller-Universität from the community of Kauern in the former Ronneburg Uranium mining district. It is located on the area of the former, 28.7 ha leaching heap “Gessenhalde” north of Kauern. The dump material consisted of Upper Ordovician shales and sandstones and Lower Silurian siliceous shales containing sulphides such as pyrite, marcasite and various amounts of Pb-, Zn-, Cu-sulphides, Ni-arsenides as well as dolomite and organic carbon. During the leaching process, heavy metal enriched fluids infiltrated and contaminated the underlying glacial sediments consisting of sand, gravel sand, silt, and varved clay of the Elster-Ice-Age. Starting in 1990, the WISMUT GmbH remediated the area removing the waste rock material and part of the underlying glacial sediments. However, areas with minor contamination by heavy metals are still present making inexpensive remediation strategies desirable. The Friedrich-Schiller-Universität has installed three planted fields (20m x 20m), divided into a grid with 3 x 3 subplots, a lysimeter to measure percolation water, three additional percolate water observation points, a meteorological station, several groundwater wells and an automatic discharge and withdrawal station at the field-site “Gessenwiese”, where precipitates of sulphate containing Fe and Al hydroxides, and as well as high concentrations of  sulphate (up to 13.5 g/L), Ni (up to 65 mg/L), Al and Mn (both up to 270 mg/L),  F (up to 70 mg/L) and U (up to 0.4 mg/L) in the seepage water (pH 3.3) are found. At the same time, an area where natural attenuation has established itself and which presents itself as a reference system to see which processes have led to stable systems during 40 years of adaptation is found nearby in the downstream parts of the catchment area, the Gessen creek. The location therefore presents ideal test situations for acid mine drainage related research projects.
All groups are integrated in field projects that will compare the adapted (40 years) versus the newly established site (remediation of the Gessen heap closed 4 years ago). Specific process oriented studies will be performed in laboratory to study in more detail processes involved in rock alteration, retention from the water phase , and kinetics of geochemical processes . All Ph.D. projects will have an interdisciplinary subject in one specific question with geological and microbiological parts.
14 Ph.D. projects are specified, and three more projects will start after the first seven are finished. Their topics will result from the research of the first phase.


 
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