Project Details
Projekt
FOR 580: Electron Transfer Processes in Anoxic Aquifers
Subject Area
Geosciences
Term
from 2006 to 2015
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 5471696
Limited supply of oxygen implies that anaerobic processes play a major role for the decomposition of organic matter in aquifers compared to aerobic processes. Knowledge about the mechanisms and pathways of electron flow under these conditions is therefore crucial, in particular with respect to fundamental questions such as drinking water supply or contaminant degradation. Our present understanding of the underlying microbial and chemical processes and their interaction, however, is only rudimentary. This Research Unit, therefore, aims to establish principal concepts about the pathways and control of electron transfer processes in anoxic aquifers. Of particular relevance is the element iron, which is the predominant redox sensitive species in most aquifers and which is closely linked to the redox cycles of the elements carbon, nitrogen and sulphur.
In this Research Unit we intend to resolve the metabolic network related to the electron transfer on ferric oxides to which we attribute a key role for the understanding of ground-water biogeochemistry. Therefore, Scientists from different disciplines are collaborating in order to study the following general hypotheses:
(1) Immobile electron acceptors, particularly iron oxides, play a prominent role in organic carbon oxidation. They may serve as electron acceptors both for carbon mineralisation and the recycling of reduced species.
(2) Mobile reduced species formed in high-reactivity zones in aquifers either through sulphate and iron reduction or from metabolisation of organic compounds are important electron carriers and will serve as electron donors downgradient at zones of higher oxidation state.
These hypotheses are studied in six subprojects through a series of controlled experiments that take place mainly in the laboratory and to some extent also in the field. We wish to identify and characterise the most important pathways for the electron flow, which we hypothesise to be linked to the redox properties of iron mineral surfaces, humic substances, sulphur compounds and iron colloids. Overall, this Research Unit aims to establish a broader scientific basis for a comprehensive biogeochemical model for the regulation of anaerobic carbon turnover in aquifers coupled to the iron and sulphur cycle.
In this Research Unit we intend to resolve the metabolic network related to the electron transfer on ferric oxides to which we attribute a key role for the understanding of ground-water biogeochemistry. Therefore, Scientists from different disciplines are collaborating in order to study the following general hypotheses:
(1) Immobile electron acceptors, particularly iron oxides, play a prominent role in organic carbon oxidation. They may serve as electron acceptors both for carbon mineralisation and the recycling of reduced species.
(2) Mobile reduced species formed in high-reactivity zones in aquifers either through sulphate and iron reduction or from metabolisation of organic compounds are important electron carriers and will serve as electron donors downgradient at zones of higher oxidation state.
These hypotheses are studied in six subprojects through a series of controlled experiments that take place mainly in the laboratory and to some extent also in the field. We wish to identify and characterise the most important pathways for the electron flow, which we hypothesise to be linked to the redox properties of iron mineral surfaces, humic substances, sulphur compounds and iron colloids. Overall, this Research Unit aims to establish a broader scientific basis for a comprehensive biogeochemical model for the regulation of anaerobic carbon turnover in aquifers coupled to the iron and sulphur cycle.
DFG Programme
Research Units
Projects
- A novel mechanism of electron transfer from microorganisms to insoluble iron phases (Applicant Meckenstock, Rainer Udo )
- Characterization of redox reactions and phase transformation processes at iron mineral surfaces (Applicant Haderlein, Stefan )
- Coupling and competitiveness of iron-, sulfate-, and CO2-reduction along gradients (Applicant Knorr, Klaus-Holger )
- Electron transfer reactions at iron mineral surfaces in the presence of organic sorbates (Applicant Haderlein, Stefan )
- Fluxes of redox equivalents in metabolic networks at active zones in aquifers (Applicant Richnow, Hans Hermann )
- Identification of polysulfides and their importance as intermediate sulfur species for electron transfers processes in anoxic aquifers (Applicant Planer-Friedrich, Britta )
- Interaction of iron species and colloids with dissolved organic matter (DOM), dissolved organic sulfur compounds (DOSC) and low-molecular weight acids (LMWA) (Applicant Zwiener, Christian )
- Redox activity of humic substances and their role as electron shuttles between microorganisms and Fe(III)-minerals (Applicant Kappler, Andreas )
- Support in Mössbauer spectroscopy and chemical speciation modelling for elucidation of reactive iron species in geochemically heterogeneous anoxic aquifer systems, scientific coordination and management of the DFG-Research Group: Electron transfer processes in anoxic aquifers (Applicants Haderlein, Stefan ; Peiffer, Stefan )
- The effect of iron(III)-sulfide interactions on electron transfer processes in anoxic aquifers (Applicant Peiffer, Stefan )
Spokesperson
Professor Dr. Stefan Peiffer
