Beginning with my graduate work, I have worked on several projects that are best characterized as explorations of how metals interact with sediments at the sediment-water interface. Brief descriptions of these projects are gathered here along with links to journal articles and posters presented at conferences.
My graduate work involved exploring the utility of using x-ray photoelectron spectroscopy (XPS) to study the adsorption of Cd2+, Cu2+, Co2+, and Zn2+ on hydrous ferric oxide (HFO). In our work we showed that it was possible to introduce amorphous HFO into the ultrahigh vacuum necessary for XPS measurements without significantly altering those water molecules chemically bound to the HFO's surface. In addition, our XPS studies explained anomalous results reported by others for the adsorption of Zn2+ on HFO by identifying the surface precipitation of Zn(OH)2, a result later confirmed by other researchers using theoretical modeling and other surface analysis techniques.
Freshwater sediments play an important role in the biogeochemical cycling of trace metals, serving as a sink for trace metals by removing them from the overlying water. In this work, completed in cooperation with Dr. Fred Soster of DePauw University's Department of Geosciences, we showed that tubificid worms, a benthic organism that lives in and extensively modifies the upper 10 cm of sediment, significantly increases the movement of Zn2+ into sediments.
A natural sediment is a complex mixture of inorganic and organic phases, include metal carbonates, hydrous metal oxides, metal sulfides, and organic matter. Because the ease with which a trace metal is absorbed by or released from a sediment depends on the sediment's composition, there is a long-standing interest in identifying chemical reagents that will selectively release metals from a single sediment phase. By applying such chemical reagents in sequence, the hope is that it is possible to determine the distribution of metal ions between different sediment phases. One such scheme is the Bureau of Community Reference's (BCR) sequential extraction procedure. Although some researchers question the validity of sequential extraction schemes, there are no definitive studies that establish the general viability of such schemes. In our work we find evidence that the standard BCR sequential extraction scheme likely is not valid when used to analyze carbonate-rich sediments.