Strontium Incorporation into Calcite Generated by Bacterial Ureolysis
Strontium incorporation into calcite generated by bacterial ureolysis was investigated as part of an assessment of a proposed remediation approach for 90Sr contamination in groundwater. Urea hydrolysis produces ammonium and carbonate and elevates pH, resulting in the promotion of calcium carbonate precipitation. Urea hydrolysis by the bacterium Bacillus pasteurii in a medium designed to mimic the chemistry of the Snake River Plain Aquifer in Idaho resulted in a pH rise from 7.5 to 9.1. Measured average distribution coefficients (DEX) for Sr in the calcite produced by ureolysis (0.5) were up to an order of magnitude higher than values reported in the literature for natural and synthetic calcites (0.02–0.4). They were also higher than values for calcite produced abiotically by ammonium carbonate addition (0.3). The precipitation of calcite in these experiments was verified by X-ray diffraction. Time-of-flight secondary ion mass spectrometry (ToF SIMS) depth profiling (up to 350 nm) suggested that the Sr was not merely sorbed on the surface, but was present at depth within the particles. X-ray absorption near edge spectra showed that Sr was present in the calcite samples as a solid solution. 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. The presence of bacterial surfaces as potential nucleation sites in the ammonium carbonate precipitation treatment did not enhance overall precipitation or the Sr distribution coefficient. Because bacterial ureolysis can generate high rates of calcite precipitation, the application of this approach is promising for remediation of 90Sr contamination in environments where calcite is stable over the long term.
- Research Organization:
- Idaho National Lab. (INL), Idaho Falls, ID (United States)
- Sponsoring Organization:
- DOE - SC
- DOE Contract Number:
- DE-AC07-99ID-13727
- OSTI ID:
- 912209
- Report Number(s):
- INEEL/JOU-03-00889; TRN: US0800316
- Journal Information:
- Geochimica Cosmochimica Acta, Vol. 68, Issue 15
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ABSORPTION
AMMONIUM CARBONATES
AQUIFERS
BACILLUS
CALCITE
CALCIUM CARBONATES
CARBONATES
CHEMISTRY
CONTAMINATION
HYDROLYSIS
MASS SPECTROSCOPY
NUCLEATION
PRECIPITATION
SNAKE RIVER PLAIN
SOLID SOLUTIONS
SPECTRA
STRONTIUM
UREA
X-RAY DIFFRACTION
90Sr
bacterial ureolysis
calcite
groundwater
remediation
strontium