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

Abstract

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 modelingmore » 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 NH{sub 4}{sup +} 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.« less

Authors:
; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
Earth Sciences Division
OSTI Identifier:
1051644
Report Number(s):
LBNL-5149E
Journal ID: ISSN 1467-4866
DOE Contract Number:  
DE-AC02-05CH11231
Resource Type:
Journal Article
Journal Name:
Geochemical Transactions
Additional Journal Information:
Journal Volume: 12; Journal Issue: 7; Related Information: Journal Publication Date: 2011; Journal ID: ISSN 1467-4866
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; 58 GEOSCIENCES

Citation Formats

Wu, Y., Ajo-Franklin, J.B., Spycher, N., Hubbard, S.S., Zhang, G., Williams, K.H., Taylor, J., Fujita, Y., and Smith, R. Geophysical monitoring and reactive transport modeling of ureolytically-driven calcium carbonate precipitation. United States: N. p., 2011. Web. doi:10.1186/1467-4866-12-7.
Wu, Y., Ajo-Franklin, J.B., Spycher, N., Hubbard, S.S., Zhang, G., Williams, K.H., Taylor, J., Fujita, Y., & Smith, R. Geophysical monitoring and reactive transport modeling of ureolytically-driven calcium carbonate precipitation. United States. doi:10.1186/1467-4866-12-7.
Wu, Y., Ajo-Franklin, J.B., Spycher, N., Hubbard, S.S., Zhang, G., Williams, K.H., Taylor, J., Fujita, Y., and Smith, R. Fri . "Geophysical monitoring and reactive transport modeling of ureolytically-driven calcium carbonate precipitation". United States. doi:10.1186/1467-4866-12-7. https://www.osti.gov/servlets/purl/1051644.
@article{osti_1051644,
title = {Geophysical monitoring and reactive transport modeling of ureolytically-driven calcium carbonate precipitation},
author = {Wu, Y. and Ajo-Franklin, J.B. and Spycher, N. and Hubbard, S.S. and Zhang, G. and Williams, K.H. and Taylor, J. and Fujita, Y. and Smith, R.},
abstractNote = {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 NH{sub 4}{sup +} 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.},
doi = {10.1186/1467-4866-12-7},
journal = {Geochemical Transactions},
issn = {1467-4866},
number = 7,
volume = 12,
place = {United States},
year = {2011},
month = {7}
}