Iron sulfide formation and element mobility in sulfidogenic environments
Sulfate-reducing bacteria are ubiquitous in many anoxic subsurface environments, including wetland soils, benthic sediments and groundwater systems. These bacteria couple the anaerobic oxidation of organic carbon with the reduction of sulfate in order to gain energy. This results in the generation of sulfide, which may subsequently interact with a range of environmentally-important elements, including iron and arsenic.
Our research on sulfidogenic environments integrates field observations, experiments and modelling.
Microbial sulfidogenesis can strongly affect iron geochemistry through a variety of processes. Aqueous sulfide is a powerful and facile reductant of ferric iron that can drive the rapid reductive dissolution of poorly ordered ferric (hydr)oxides. However, in the presence of ferrous iron, sulfidogenesis can also sequester iron by facilitating the precipitation of iron sulfide minerals.
Since trace element behaviour is often coupled to iron geochemistry, any sulfidogenesis-induced changes in iron geochemistry can also cause associated changes in trace element behaviour. For example, our recent work shows that sulfidogenesis may promote arsenic mobilization by triggering ferric (hydr)oxide dissolution and the formation of iron sulfide minerals, with a weak sorptive affinity for arsenic.