Kaye Savage
Ph.D. Stanford University, 2001
Environmental Geochemistry

office: 6702 Stevenson Center
phone: 615-322-2986
email: kaye.s.savage@vanderbilt.edu

Kaye Savage is interested in processes which control the distribution, speciation and transport of trace elements at and near the earth’s surface, particularly in mineralized and contaminated environments. Chemical reactions control the form and toxicity of many environmental contaminants, while physical and biological processes control their distribution through soils, surface waters, and ground waters. Together, these processes impact water quality, the health of watershed ecosystems, and global biogeochemical cycles. Characterization of soils, sediments, and weathering rock, and waters in contact with these materials, are Kaye’s primary focus. Understanding the behavior of toxic trace elements in natural systems is critical for assessing their potential health effects and mitigating hazards in watersheds. This type of research aids efforts to remediate contaminated sites, as well as providing fundamental information about interactions between mineral surfaces and aqueous environments. Savage currently has funding from the National Science Foundation, the U.S. Environmental Protection Agency, and the Office of Naval Research-ESTCP program.

Kaye’s current research encompasses three principal areas related to trace element geochemistry, united by the recognition that trace element toxicity is often related to its chemical form. The first is aimed at assessing the effects of minor element impurities on mineral stability. Kaye and her students have lately focused on crystal properties and reactivity of pyrite, a common source of acid mine drainage when it decomposes via oxidation. They are studying how the oxidation rate of pyrite is affected by the presence of various minor elements which impart semiconducting properties to the mineral. They synthesize pyrite crystals with minor element impurities, then test how each impurity affects the electrical properties of the crystals, and carry out oxidation rate experiments. The observed relationships among chemical composition, electrical properties, and oxidation behavior provide insight into the properties of natural pyrite crystals. Natural pyrite is typically heterogeneous and thus more difficult to investigate, but as the most common sulfide mineral in Earth’s crust, it is an important source of trace elements to Earth surface environments when it breaks down. 

Kaye’s second focus area is the mobility of potentially toxic trace elements. The pathway that an element takes through its environment depends partly on how it associates with the surrounding materials: it may be incorporated into a mineral structure, bonded weakly or strongly to a mineral surface, or associated with organic matter (including living organisms). The mechanism of association has consequences for the release of the trace elements to solution, which makes them more available to biota. The host mineral may degrade, or the element may become detached from a mineral or organic surface. In many soils and aquifers, contaminants are associated with the smallest particles, namely colloids, whose mobility is controlled by both chemical and physical characteristics of their environment. To characterize the chemical environment of trace elements at the molecular scale, Kaye and her research group use analytical techniques that take advantage of high-flux X-rays generated at synchrotron sources, such as X-ray absorption spectroscopy. They use the results, together with other analytical data and thermodynamic models, to predict what conditions may perturb the stability of an element in its local environment, causing it to become mobile. Kaye has also used synchrotron X-ray diffraction in a new way to monitor the mobility of colloids in real time, to directly link the chemical composition of solutions and particles with their physical effects on colloid transport and colloidally mediated contaminant transport. 

The third theme of Kaye’s research is really the motivation for the first two: studying field sites where potentially toxic trace elements demonstrate their impacts on organisms, soil, and water quality. Differences in trace element uptake mechanisms, mineral stability, and biological processes in these environments have significant consequences for dispersal of potentially toxic elements. Kaye and her students are currently studying trace element distribution related to organisms, soils and streams from contaminants that are introduced to Earth’s surface by mining activities, smelters, poultry litter fertilizer applications, and urban runoff. Study sites are in California’s Mother Lode Gold District, the Puget Sound and Tennessee. Field investigations are often accompanied by development of physical and computational models that focus on specific aspects of a problem.

There are opportunities for students with a wide assortment of interests and backgrounds to participate in environmental geochemistry/water resources research.  The use of information at different spatial scales, from field maps to molecular interactions, provides a means of introducing students to a variety of environmental geochemistry approaches.  Students use a variety of techniques to address environmental problems: field mapping and sampling, spectroscopic analysis, wet chemical experimentation with model analogs to field conditions, and predictive modeling using equilibrium concepts and irreversible reaction paths.  Students interested in public policy or economics will also find opportunities to explore, since many sites with significant contamination are also targets of public interest and government action.