Skip to main content

Influence of DOM amendment and molecular form on uranium reduction rates in U-contaminated sediments


EMSL Project ID
48248

Abstract

Long-term stewardship of remediated sites relies on the sequestration capability of sediments to retain contaminants, such as uranium (U) over many decades. Natural organic matter (NOM) in the form of detritus, microbial biomass, or metabolites can interact with aqueous and soil-bound U, potentially re-solubilizing it into the water column under certain redox conditions or conversely, enhancing its precipitation through increased electron shuttling activities by microbes. While the influence of NOM on U dissolution process has been investigated from a bulk chemical standpoint (e.g. humic versus fulvic acids; hydrophobic versus hydrophilic compounds), we still lack a clear understanding of how NOM form and structure influences U sequestration and microbial activity. The use of Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) with electrospray ionization (ESI) allows a molecular scale characterization of NOM from complex systems, such as freshwater aquifers. Ongoing studies described here are investigating NOM signatures from a U-contaminated aquifer in Rifle, CO and its influence on system biogeochemistry. Samples taken from 10 hydrologic locations at Rifle show differing number of peaks and heteroatom composition that relate to their redox condition. Dissolved organic matter (DOM) extracted from the Colorado River was amended to Rifle sediments and groundwater to assess changes in its molecular form resulting from microbial modification. Preliminary DOM signatures were analyzed at EMSL using ESI-FT-ICR MS; however, analysis of additional time-series samples is necessary to complete this research. These results are expected to provide new insight into the relationship between DOM composition and U reduction rates in contaminated subsurface sediments.

Project Details

Project type
Limited Scope
Start Date
2014-02-17
End Date
2014-03-20
Status
Closed

Team

Principal Investigator

Paula Mouser
Institution
University of New Hampshire

Co-Investigator(s)

John Lenhart
Institution
The Ohio State University

Team Members

Michael Wilkins
Institution
Colorado State University

Kenneth Williams
Institution
Lawrence Berkeley National Laboratory