Electron donor dependence of the extent and forms of microbially reducible uranium from contaminated sediments
EMSL Project ID
22191
Abstract
Uranium immobilization has been achieved in microcosms containing contaminated sediments from the DOE-Oak Ridge Reservation. Removal of uranium from the solution phase is accomplished through the addition of electron donors, including either glucose, ethanol, and methanol, which stimulate the natural microbial community to reduce the U(VI) to relatively insoluble U(IV). One major goal of this project is to determine the principal microbial and geochemical factors which lead to effective and efficient uranium immobilization. In this complex system, are microbial community diversity and heterogeneity important, or is the community diverse enough such that any reasonable electron donor will bring about similar uranium immobilization?Uranium concentrations in microcosm experiments result from short-term equilibration between freshly obtained contaminated sediments and added water. Results from many microcosm experiments have shown that the rate of uranium removal depends on the form of electron donor. Methanol addition led to U reduction only in a subset of microcosm experiments that were characterized by the largest lag times and lowest rates. This electron donor dependence suggests that heterogeneity and diversity in the indigenous microbial community are important to the U reduction rate. Preliminary XANES spectroscopic characterization of biostimulated sediments suggests that the extent of reduction is also donor-dependent. If the extent and rate of uranium reduction are donor-dependent, it is likely that the microbial community is reducing different pools of uranium species (i.e., soluble, sorbed, precipitated). The forms of U(VI) will be compared between microcosm sediments with different donors and control without donor addition using cryogenic Time-Resolved Laser-Induced Fluorescence Spectroscopy.
Project Details
Project type
Exploratory Research
Start Date
2007-01-01
End Date
2008-01-06
Status
Closed
Released Data Link
Team
Principal Investigator