Nearly 40 years of nuclear power and weapons production has left behind a legacy of contaminated facilities, soils, and surface water. The migration of radionuclides in the environment occurs mainly through transport in aqueous media. The properties that determine the rate of migration include solubility, sorption, and interactions with environmental surfaces. Our research is devoted to the determination of actinide solubility, sorption and interactions with mineral and microbial surfaces.

We are advancing the molecular understanding of actinide sorption by studying the behavior of the actinides uranium, neptunium, plutonium, americium, and curium on environmentally relevant solid substrates using modern spectroscopic techniques. Knowledge of the actinide speciation in solution is a prerequisite for the sorption studies. In addition to conventional speciation techniques, such as spectrophotometry, potentiometric titration, and solvent extraction, we use sensitive laser spectroscopic techniques including TRLFS and SFG, as well as synchrotron-based X-ray absorption spectroscopy (XAS) to provide molecular-level structural information for solids, solutions, and solution/solid interfaces.

Microbes in soil, sediment, and water can have a significant influence on the mobility of actinides in the evironment. We are studying the interaction of actinides with common aerobic and anaerobic soil bacteria to elucidate the binding mechanisms and electron transfer processes. Actinides may be stabilized or precipitated by enzymatic, direct, or indirect microbial action. The chemical form of the actinide and the environmental conditions play an important role in the type, rate, and magnitude of microbial activity. Redox conditions also influence the solubility of actinides. Enzymatic secretion of phosphate can lead to the precipitation, and thus immobilization, of actinide phosphates. A better understanding of these processes will provide the basis for applying microorganisms to biostabilization and bioremediation of actinide-contaminated environments.