Dynamics of trace metal speciation in periodically reduced soils - Subproject: Speciation of Cu, Cd, and Zn over soil reduction-oxidation cycles

PhD student: Beate Fulda
Supervisors: Ruben Kretzschmar, Andreas Voegelin (EAWAG)

Freshwater wetlands form the interface between dryland soils and aquatic environments. They thus play a key role in the transfer of nutrients and contaminants between these systems and may strongly affect surface and groundwater quality. Anthropogenic emissions from mining, industry and agriculture have led to the accumulation of trace metals in riparian floodplain soils in industrialized regions worldwide. The potential remobilization of accumulated trace metals is threfore a major concern.

Periodic flooding and variations in groundwater level result in regular changes of soil redox state. Compared to the present state of knowledge of trace metal dynamics in fully oxidized soils and fully reduced sediments, our understanding of the biogeochemical processes controlling trace metal chemistry under periodically changing redox conditions is still limited

The chemical speciation is one of the key factors controlling trace metal bioavailability and mobility in soils. Major factors affecting trace metal speciation over reduction-oxidation cycles in soils include

• Temperature due to its effect on microbial activity and reaction kinetics

• The presence of calcite due to its control on soil pH

• Reducible sulfate due to the high stability of trace metal sulfides

• Interactions of trace metals in adsorption and precipitation reactions

We propose to study the influence of these factors on the dynamics of the speciation of Cu, Cd and Zn over reduction-oxidation cycles in well-controlled laboratory studies with natural soil material. The results support the transfer of knowledge from pure model systems to natural environments.

Link to ETH research database

Funding and Duration

Research grant from the Swiss National Science Foundation (SNSF): January 2008 - 2011