Environmental Management Science Program Project Number 87016 Co-Precipitation of Trace Metals in Groundwater and Vadose Zone Calcite: In Situ Containment and Stabilization of Strontium-90 and Other Divalent Metals and Radionuclides at Arid Western Doe Sites

Ferris, F. Grant ; Fujita, Yoshiko ; Smith, Robert W.

University of Toronto

关键词: Acceleration;    Urea;    Radioisotopes;    Acid Neutralizing Capacity;    12 Management Of Radioactive Wastes, And Non-Radioactive Wastes From Nuclear Facilities;   

DOI  :  10.2172/839299
RP-ID  :  EMSP-87016--2004
RP-ID  :  FG07-02ER63494
RP-ID  :  839299

美国|英语

来源: UNT Digital Library

【 摘 要 】

Radionuclide and metal contaminants are present in the vadose zone and groundwater throughout the U.S. Department of Energy (DOE) weapons complex. In situ containment and stabilization of these contaminants in vadose zones or groundwater is a cost-effective treatment strategy. Our facilitated approach relies upon the hydrolysis of introduced urea to cause the acceleration of calcium carbonate precipitation (and trace metal coprecipitation) by increasing groundwater pH and alkalinity (Fujita et al., 2000; Warren et al., 2001). Subsurface urea hydrolysis is catalyzed by the urease enzyme, which may be either introduced with the urea or produced in situ by ubiquitous subsurface urea hydrolyzing microorganisms. Because the precipitation processes are irreversible and many western aquifers are saturated with respect to calcite, the co-precipitated metals and radionuclides will be effectively removed from groundwater. The rate at which trace metals are incorporated into calcite is a function of calcite precipitation kinetics, adsorption interactions between the calcite surface and the trace metal in solution (Zachara et al., 1991), solid solution properties of the trace metal in calcite (Tesoriero and Pankow, 1996), and also the surfaces upon which the calcite is precipitating. A fundamental understanding of the coupling of calcite precipitation and trace metal partitioning, and how this occurs in aquifers and vadose environments is lacking. This report summarizes work undertaken during the second year of this project.