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Geochimica et Cosmochimica Acta | 2004

Kinetics of calcite precipitation induced by ureolytic bacteria at 10 to 20°C in artificial groundwater

F.G. Ferris; Vernon R. Phoenix; Y. Fujita; Robert W. Smith

The kinetics of calcite precipitation induced in response to the hydrolysis of urea by Bacillus pasteurii at different temperatures in artificial groundwater (AGW) was investigated. The hydrolysis of urea by B. pasteurii exhibited a temperature dependence with first order rate constants of 0.91 d−1 at 20°C, 0.18 d−1 at 15°C, and 0.09 d−1 at 10°C. At all temperatures, the pH of the AGW increased from 6.5 to 9.3 in less than 1 d. Dissolved Ca2+ concentrations decreased in an asymptotic fashion after 1 d at 20°C and 15°C, and 2 d at 10°C. The loss of Ca2+ from solution was accompanied by the development of solid phase precipitates that were identified as calcite by X-ray diffraction. The onset of calcite precipitation at each temperature occurred after similar amounts of urea were hydrolyzed, corresponding to 8.0 mM NH4+. Specific rate constants for calcite precipitation and critical saturation state were derived from time course data following a second-order chemical affinity-based rate law. The calcite precipitation rate constants and critical saturation states varied by less than 10% between the temperatures with mean values of 0.16 ± 0.01 μmoles L−1 d−1 and 73 ±3, respectively. The highest calcite precipitation rates (ca. 0.8 mmol L−1 d−1) occurred near the point of critical saturation. While unique time course trajectories of dissolved Ca2+ concentrations and saturation state values were observed at different temperatures, calcite precipitation rates all followed the same asymptotic profile decreasing with saturation state regardless of temperature. This emphasizes the fundamental kinetic dependence of calcite precipitation on saturation state, which connects the otherwise dissimilar temporal patterns of calcite precipitation that evolved under the different temperature and biogeochemical regimes of the experiments.


Geochemical Transactions | 2012

The Effect of the CO32- to Ca2+ Ion activity ratio on calcite precipitation kinetics and Sr2+partitioning

Tsigabu A. Gebrehiwet; George D. Redden; Yoshiko Fujita; Mikala Beig; Robert W. Smith

BackgroundA proposed strategy for immobilizing trace metals in the subsurface is to stimulate calcium carbonate precipitation and incorporate contaminants by co-precipitation. Such an approach will require injecting chemical amendments into the subsurface to generate supersaturated conditions that promote mineral precipitation. However, the formation of reactant mixing zones will create gradients in both the saturation state and ion activity ratios (i.e., aCO32-/aCa2+). To better understand the effect of ion activity ratios on CaCO3 precipitation kinetics and Sr2+ co-precipitation, experiments were conducted under constant composition conditions where the supersaturation state (Ω) for calcite was held constant at 9.4, but the ion activity ratio (r=aCO32-/aCa2+) was varied between 0.0032 and 4.15.ResultsCalcite was the only phase observed, by XRD, at the end of the experiments. Precipitation rates increased from 41.3 ± 3.4 μmol m-2 min-1 at r = 0.0315 to a maximum rate of 74.5 ± 4.8 μmol m-2 min-1 at r = 0.306 followed by a decrease to 46.3 ± 9.6 μmol m-2 min-1 at r = 1.822. The trend was simulated using a simple mass transfer model for solute uptake at the calcite surface. However, precipitation rates at fixed saturation states also evolved with time. Precipitation rates accelerated for low r values but slowed for high r values. These trends may be related to changes in effective reactive surface area. The aCO32-/aCa2+ ratios did not affect the distribution coefficient for Sr in calcite (DPSr2+), apart from the indirect effect associated with the established positive correlation between DPSr2+ and calcite precipitation rate.ConclusionAt a constant supersaturation state (Ω = 9.4), varying the ion activity ratio affects the calcite precipitation rate. This behavior is not predicted by affinity-based rate models. Furthermore, at the highest ion ratio tested, no precipitation was observed, while at the lowest ion ratio precipitation occurred immediately and valid rate measurements could not be made. The maximum measured precipitation rate was 2-fold greater than the minima, and occurred at a carbonate to calcium ion activity ratio of 0.306. These findings have implications for predicting the progress and cost of remediation operations involving enhanced calcite precipitation where mineral precipitation rates, and the spatial/temporal distribution of those rates, can have significant impacts on the mobility of contaminants.


Geochemical Transactions | 2011

Geophysical monitoring and reactive transport modeling of ureolytically-driven calcium carbonate precipitation

Yuxin Wu; Jonathan B. Ajo-Franklin; Nicolas Spycher; Susan S. Hubbard; Guoxiang Zhang; Kenneth H. Williams; Joanna Taylor; Yoshiko Fujita; Robert W. Smith

Ureolytically-driven calcium carbonate precipitation is the basis for a promising in-situ remediation method for sequestration of divalent radionuclide and trace metal ions. It has also been proposed for use in geotechnical engineering for soil strengthening applications. Monitoring the occurrence, spatial distribution, and temporal evolution of calcium carbonate precipitation in the subsurface is critical for evaluating the performance of this technology and for developing the predictive models needed for engineering application. In this study, we conducted laboratory column experiments using natural sediment and groundwater to evaluate the utility of geophysical (complex resistivity and seismic) sensing methods, dynamic synchrotron x-ray computed tomography (micro-CT), and reactive transport modeling for tracking ureolytically-driven calcium carbonate precipitation processes under site relevant conditions. Reactive transport modeling with TOUGHREACT successfully simulated the changes of the major chemical components during urea hydrolysis. Even at the relatively low level of urea hydrolysis observed in the experiments, the simulations predicted an enhanced calcium carbonate precipitation rate that was 3-4 times greater than the baseline level. Reactive transport modeling results, geophysical monitoring data and micro-CT imaging correlated well with reaction processes validated by geochemical data. In particular, increases in ionic strength of the pore fluid during urea hydrolysis predicted by geochemical modeling were successfully captured by electrical conductivity measurements and confirmed by geochemical data. The low level of urea hydrolysis and calcium carbonate precipitation suggested by the model and geochemical data was corroborated by minor changes in seismic P-wave velocity measurements and micro-CT imaging; the latter provided direct evidence of sparsely distributed calcium carbonate precipitation. Ion exchange processes promoted through NH4+ production during urea hydrolysis were incorporated in the model and captured critical changes in the major metal species. The electrical phase increases were potentially due to ion exchange processes that modified charge structure at mineral/water interfaces. Our study revealed the potential of geophysical monitoring for geochemical changes during urea hydrolysis and the advantages of combining multiple approaches to understand complex biogeochemical processes in the subsurface.


Geochimica et Cosmochimica Acta | 2004

Strontium Incorporation into Calcite Generated by Bacterial Ureolysis

Yoshiko Fujita; George D. Redden; Jani C. Ingram; Marnie M Cortez; F. Grant Ferris; Robert W. Smith


Applied Geochemistry | 2004

U(VI) adsorption on natural iron-coated sands: comparison of approaches for modeling adsorption on heterogeneous environmental materials

Brian A. Logue; Robert W. Smith; John C. Westall


Applied Geochemistry | 2014

Precipitation of calcium carbonate and calcium phosphate under diffusion controlled mixing

Tsigabu A. Gebrehiwet; Luanjing Guo; Don Fox; Hai Huang; Yoshiko Fujita; Robert W. Smith; James Henriksen; George D. Redden


Journal of Volcanology and Geothermal Research | 2016

Wellbore and groundwater temperature distribution eastern Snake River Plain, Idaho: Implications for groundwater flow and geothermal potential

Travis L. McLing; Richard P. Smith; Robert W. Smith; David Blackwell; Robert C. Roback; Andrus J. Sondrup


Archive | 2003

Microbially-Mediated Subsurface Calcite Precipitation for Removal of Hazardous Divalent Cations

Frederick S. Colwell; Robert W. Smith; F. Gratn Ferris; Jani C. Ingram; Anna-Louise Reysenbach; Yoshiko Fujita; T.L. Tyler; Judy Taylor; Amy Banta; Mark E. Delwiche; Travis L. McLing; Cortez, Marnie, M.; Mary E. Watwood


Vadose Zone Journal | 2010

Cation Exchange on Vadose Zone Research Park Subsurface Sediment, Idaho National Laboratory

Leslie L. Baker; Daniel G. Strawn; Robert W. Smith


Energy Procedia | 2014

Utilizing rare earth elements as tracers in high TDS reservoir brines in CCS applications

Travis L. McLing; William L Smith; Robert W. Smith

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Amy Banta

Portland State University

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Bernie Zavata

United States Environmental Protection Agency

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Brian A. Logue

South Dakota State University

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