Uranium interactions with colloids within redox dynamic wetland environments
EMSL Project ID
51807
Abstract
The presence of high levels of organic matter is a distinguishing feature of most wetland soils and sediments, and contaminant metals such as uranium (U) are known to bind to sedimentary minerals and organic matter; in this context wetland sediments can be viewed as sinks for these contaminants. Wetland sediments can also have high levels of mineral and porewater DOC colloids, which can form complexes with U and other metals. These stable metal-nanominerals and metal-DOC complexes can potentially mobilize contaminants; however, the degree to which U-DOC and U-mineral colloid complexes contribute to the pool of stable U in redox-dynamic sedimentary porewater is highly variable, making it difficult to determine the extent to which they are a vector for U transport. It is likely that variability in the extent to which U-DOC complexes enhance the solubility and potential mobility of U is strongly dependent on DOC abundance, nominal size, and its structure and composition, which are highly variable and difficult to characterize due to its complexity. Similarly, changes in redox conditions can result in changes in U-mineral colloid stability. To address these difficulties, we propose the following objective as part of a larger effort to understand the fate and transport of U in redox dynamic riparian wetlands within the Tims Branch watershed (Savannah River Site, Aiken, SC): Objective-Characterization of size fractionated groundwater colloids in Tims Branch wetland sediments. We will achieve these objectives through application of unique experimental expertise and state-of-the-art facilities at EMSL, in particular EMSL's world-class Fourier transform ion cyclotron resonance mass spectrometer (FTICR-MS), and electron microscopy and Mossbauer capabilities, in combination with resources and expertise at Argonne National Laboratory (Argonne) [radiochemistry, synchrotron-based x-ray absorption spectroscopy] and Savannah River National Laboratory (SRNL). Completion of our objective will provide insight into co-associations between U and size fractionated colloidal minerals and DOC within riparian wetland groundwater as influenced by hydrologic conditions (gaining verses losing stream) that create redox dynamic environments in Tims Branch. This information is critical for studies of U-DOC and U-mineral colloid complexation and the potential for transport of these complexes with groundwater flow. In addition, it will provide a foundation for complimentary x-ray absorption spectroscopy studies of U molecular complexation investigations of size fractionated samples within the Argonne SBR Wetland Hydrobiogeochemistry SFA.
Project Details
Start Date
2021-01-20
End Date
2022-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Co-Investigator(s)