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

Technical Report · Wed Jun 01 00:00:00 EDT 2005

DOI:https://doi.org/10.2172/885256· OSTI ID:885256

Smith, Robert W

Radionuclide and metal contaminants such as strontium-90 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 Laboratory [INL]). 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., strontium-90) by their facilitated co-precipitation with calcium carbonate (primarily calcite) in groundwater and vadose zone systems. Our facilitated approach relies upon the hydrolysis of introduced urea to cause the acceleration of calcium carbonate precipitation (and trace metal co-precipitation) by (a) increasing pH and alkalinity and (b) liberating cations from the aquifer matrix by cation exchange reactions. Subsurface urea hydrolysis is catalyzed by the urease enzyme, which is produced in situ by native 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. We are currently conducting field based activities at both the INL Vadose Zone Research Park (VZRP), an uncontaminated surrogate site for the strontium-90 contaminated vadose zone at INTEC and at the strontium-90 contaminated aquifer of 100-N area of the Hanford site.

• Research Organization: University of Idaho, Idaho Fall, ID
• Sponsoring Organization: USDOE Office of Science (SC)
• DOE Contract Number: FG07-02ER63486
• OSTI ID: 885256
• Report Number(s): EMSP-87016-2005; R&D Project: EMSP 87016; TRN: US0603831
• Country of Publication: United States
• Language: English

Related Subjects

12 MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
54 ENVIRONMENTAL SCIENCES
58 GEOSCIENCES
ACCELERATION
ACID NEUTRALIZING CAPACITY
AQUIFERS
CALCITE
CALCIUM CARBONATES
CATIONS
CONTAINMENT
HYDROLYSIS
MICROORGANISMS
PRECIPITATION
RADIOISOTOPES
STABILIZATION
STRONTIUM 90
UREA
UREASE