Trace Metals in Groundwater & Vadose Zone Calcite: In Situ Containment & Stabilization of 90Strontium & Other Divalent Metals & Radionuclides at Arid West DOE Sites

Technical Report · Tue Jun 01 00:00:00 EDT 2004

DOI:https://doi.org/10.2172/839261· OSTI ID:839261

Smith, Robert W; Fujita, Yoshiko; Ferris, F Grant; Cosgrove, Donna M; Colwell, Rick S

Radionuclide and metal contaminants such as 90Sr are present beneath U.S. Department of Energy (DOE) lands in both the groundwater (e.g., 100-N area at Hanford, WA) and vadose zone (e.g., Idaho Nuclear Technology and Engineering Center (INTEC) at the Idaho National Engineering and Environmental Laboratory). In situ containment and stabilization of these contaminants is a cost-effective treatment strategy. However, implementing in situ containment and stabilization approaches requires definition of the mechanisms that control contaminant sequestration. We are investigating the in situ immobilization of radionuclides or contaminant metals (e.g., 90Sr) by their facilitated co-precipitation with calcium carbonate in groundwater and vadose zone systems. Our facilitated approach, shown schematically in Figure 1, relies upon the hydrolysis of introduced urea to cause the acceleration of calcium carbonate precipitation (and trace metal co-precipitation) by increasing pH and alkalinity. 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 process tends to be irreversible and many western aquifers are saturated with respect to calcite, the co-precipitated metals and radionuclides will be effectively removed from the aqueous phase over the long-term. Another advantage of the ureolysis approach is that the ammonium ions produced by the reaction can exchange with radionuclides sorbed to subsurface minerals, thereby enhancing the availability of the radionuclides for re-capture in a more stable solid phase (co-precipitation rather than adsorption).

• Research Organization: University of Idaho-Idaho Falls; FG07-02ER63486 (US)
• Sponsoring Organization: USDOE Office of Science (SC) (US)
• DOE Contract Number: FG07-02ER63494
• OSTI ID: 839261
• Report Number(s): EMSP-87016-2004; TRN: US200509%%584
• Resource Relation: Other Information: PBD: 1 Jun 2004
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
54 ENVIRONMENTAL SCIENCES
59 BASIC BIOLOGICAL SCIENCES
ACCELERATION
ACID NEUTRALIZING CAPACITY
ADSORPTION
AQUIFERS
AVAILABILITY
CALCITE
CALCIUM CARBONATES
CONTAINMENT
HYDROLYSIS
MICROORGANISMS
PRECIPITATION
RADIOISOTOPES
STABILIZATION
UREA
UREASE