WATERSHED CONTROLS ON URANIUM CONCENTRATIONS TIED INTO NATURAL ORGANIC MATTER AND IRON INTERACTIONS IN STREAMBEDS AND WETLANDS
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Collaborative Research: Watershed Controls On Uranium Concentrations Tied To Natural Organic Matter In Streambeds And Wetlands PI: Santschi, P.H., Texas A&M University, TX; Co-PI: Kaplan, D.I., Savannah River National Laboratory, Aiken, SC; Co-PI: Yeager, C.M., Los Alamos National Laboratory, Los Alamos, NM Wetlands and their hyporheic zones, e.g., regions where groundwater and surface water exchange, display complex and seasonally-varied dynamics in hydraulic, chemical, physical and microbial properties, which result in their functioning as a sink or source of organic matter (OM) and associated contaminants, such as uranium (U). Molecular-scale understanding of the interactions between OM, U and microbes under seasonally-varied hydrological conditions (temperature, pH, Eh, water table height, rainfall, nutrient loading, etc.) in these critical zones is still not well understood, yet a full understanding of these regulating processes is crucial for the development of fundamentally sound watershed reactive transport models. Through field-oriented studies at the Argonne Wetland Hydrobiogeochemistry SFA field site (a wetland contaminated by U for over 50 years) and accompanying laboratory experiments this project seeks to 1) establish linkage of watershed hydrological conditions to U concentrations and to OM sources, abundance and composition by monitoring temporal hydrological parameters and events; 2) establish a seasonal U mass balance and flux model between solid and water bodies; 3) reveal the molecular characteristics of the organic moieties that are responsible for U binding from four types of solids that represent the major solid bodies in the wetlands and their hyporheic zones; and lastly 4) to determine relationships between the microbial community structure and gene content of wetland interfacial zones with OM properties that influence U transport. By addressing these key knowledge gaps in wetland hydro-biogeochemical processes, we will contribute to Earth System Models and help DOE advance a robust predictive understanding of how watersheds function as integrated systems and how these systems influence water quality and contaminant release.
