The Effect of Iron(III)-Sulfide Interactions on Electron Transfer Processes in Anoxic Aquifers
FOR 580 PEIFrom 02/2006 to 01/2009
Principal Investigator: Stefan Peiffer
Staff: Katrin Hellige
Grant: FOR 580 Electron Transfer Processes in Anoxic Aquifers
The interaction between sulphide and ferric oxides is of paramount importance for the redox state of ground waters. It affects the transfer of electrons in anoxic aquifers in many regards. In particular it interferes with the microbial respiration of iron oxides and influences the redox properties of dissolved organic matter (DOM). It affects the stability and reactivity of iron oxides and is a key reaction to drive the sulfur cycle in aquifers. Due to their mobility, sulfide and its dissolved oxidation products are also prominent constituents of the metabolic network in aquifers. This subproject aims to resolve the individual pathways of these interactions and to understand their effect on competition between microorganisms and sulphide for ferric iron. To this end, we will study the reaction kinetics between sulphide and ferric oxides both in the laboratory in the presence and absence of DOM with different chemical properties. We will investigate the mechanisms and kinetics of solid-phase transformations associated with this reaction, such as formation of pyrite and transformation of ferric oxides induced by Fe(II) generated from oxidation of sulphide at the mineral surface, using modern analytical instrumentation (in particular Mössbauer spectroscopy). In this context we are interested in understanding the effect of advective flow on reaction pathways, yield and product formation of the interaction between sulphide and ferric oxides, which will be studied in laboratory experiments both in the absence and presence of iron reducing bacteria.