HR: 1330h
AN: B12C-0796    [PDF]
TI: Strontium Partitioning in Calcite Precipitated by Ureolysis
AU: * Zachary, C
EM: zachceci@if.uidaho.edu
AF: University of Idaho-Idaho Falls, 1776 Science Center Drive, Idaho Falls, ID 83402 United States
AU: Fujita, Y
EM: fujiy@inel.gov
AF: Idaho National Engineering and Environmental Laboratory, PO Box 1625, Idaho Falls, ID 83415
AU: Smith, R W
EM: smithbob@uidaho.edu
AF: University of Idaho-Idaho Falls, 1776 Science Center Drive, Idaho Falls, ID 83402 United States
AB: Strontium incorporation into calcite generated by ureolysis is being investigated as part of an assessment of a proposed in situ containment and stabilization approach for $^{90}$Sr contamination in groundwater. The remediation approach relies on the ability of indigenous urea hydrolyzing bacteria to, upon the addition of urea create conditions that accelerate calcite precipitation, and associated co-precipitation of metal and radionuclide contaminants. Urea hydrolysis produces ammonium carbonate and result in elevated pH, causing an increase in the saturation index for calcite. In our experiments both urea hydrolyzing bacteria and extracellular urease are used to promote urea hydrolysis and subsequent calcite precipitation in a medium designed to mimic the chemistry of the Snake River Plain Aquifer in Idaho. Measured distribution coefficients for Sr in calcite produced by ureolysis are significantly higher (D $>$ 0.5) than values reported in the literature for natural and synthetic calcites (D $\sim$ 0.1). They were also higher than values for calcite produced non-ureolytically in this study (D $\sim$ 0.3). The extent of Sr incorporation appeared to be driven primarily by the overall rate of calcite precipitation, where faster precipitation was associated with greater Sr uptake into the solid. Because bacterial ureolysis can generate high rates of calcite precipitation, this approach is promising for remediation of $^{90}$Sr contamination in environments where calcite is stable over the long term.
DE: 1045 Low-temperature geochemistry
DE: 1065 Trace elements (3670)
DE: 3630 Experimental mineralogy and petrology
SC: Biogeosciences [B]
MN: 2003 Fall Meeting