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  • Articles  (4)
  • Latest Papers from Table of Contents or Articles in Press  (4)
  • Wiley  (4)
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  • Nature Publishing Group (NPG)
  • Oxford University Press
  • 2010-2014  (4)
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  • Water Resources Research  (2)
  • Journal of Geophysical Research JGR - Solid Earth  (2)
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  • 1
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    Heterogeneity-Enhanced Gas Phase Formation in Shallow Aquifers During Leakage of CO2-Saturated Water from Geologic Sequestration Sites (2014)
    Wiley
    Details
    Publication Date: 2014-11-05
    Description: ABSTRACT A primary concern for geologic carbon storage is the potential for leakage of stored carbon dioxide (CO 2 ) into the shallow subsurface where it could degrade the quality of groundwater and surface water. In order to predict and mitigate the potentially negative impacts of CO 2 leakage, it is important to understand the physical processes that CO 2 will undergo as it moves through naturally heterogeneous porous media formations. Previous studies have shown that heterogeneity can enhance the evolution of gas phase CO 2 in some cases, but the conditions under which this occurs have not yet been quantitatively defined, nor tested through laboratory experiments. This study quantitatively investigates the effects of geologic heterogeneity on the process of gas phase CO 2 evolution in shallow aquifers through an extensive set of experiments conducted in a column that was packed with layers of various test sands. Soil moisture sensors were utilized to observe the formation of gas phase near the porous media interfaces. Results indicate that the conditions under which heterogeneity controls gas phase evolution can be successfully predicted through analysis of simple parameters, including the dissolved CO 2 concentration in the flowing water, the distance between the heterogeneity and the leakage location, and some fundamental properties of the porous media. Results also show that interfaces where a less permeable material overlies a more permeable material affect gas phase evolution more significantly than interfaces with the opposite layering.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 2
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    Multiscale modeling of chemotaxis in homogeneous porous media (2011)
    Wiley
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    Publication Date: 2011-06-19
    Description: We present a predictive, multiscale modeling framework for chemotaxis in porous media. This model results from volume averaging the governing equations for bacterial transport at the microscale and is expressed in terms of effective medium coefficients that are predicted from the solution of the associated closure problems. As a result, the averaged chemotactic velocity is an explicit function of the attractant concentration field and diffusivity, rather than an empirical effective chemotactic sensitivity coefficient. The model was validated by comparing the transverse bacterial concentration profiles with experimental measurements for Escherichia coli HCB1 in a T-sensor. The averaged chemotactic velocity predicted by the model was found to be within the range of values reported in the literature. Reasonable agreement (approximately 10% mean absolute error) between theory and experiments was found for several flow rates. In order to assess the potential for decreasing the computational demands of the model, the macroscale domain was divided into subdomains for the coupling of bacterial transport to that of the attractant. Sensitivity analysis was performed regarding the number of subdomains chosen, and the results indicate that bacterial transport (as measured by concentration profiles) was not highly affected by this choice. Overall, these results suggest that the predictive, multiscale modeling framework is reliable for modeling chemotaxis in porous media when chemotactic transport is significant compared to convective transport.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 3
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    Shear wave velocities in the Pampean flat-slab region from Rayleigh wave tomography: Implications for slab and upper mantle hydration (2012)
    Wiley
    Details
    Publication Date: 2012-11-03
    Description: The Pampean flat-slab region, located in central Argentina and Chile between 29° and 34°S, is considered a modern analog for Laramide flat-slab subduction within western North America. Regionally, flat-slab subduction is characterized by the Nazca slab descending to ∼100 km depth, flattening out for ∼300 km laterally before resuming a more “normal” angle of subduction. Flat-slab subduction correlates spatially with the track of the Juan Fernandez Ridge, and is associated with the inboard migration of deformation and the cessation of volcanism within the region. To better understand flat-slab subduction we combine ambient-noise tomography and earthquake-generated surface wave measurements to calculate a regional 3D shear velocity model for the region. Shear wave velocity variations largely relate to changes in lithology within the crust, with basins and bedrock exposures clearly defined as low- and high-velocity regions, respectively. We argue that subduction-related hydration plays a significant role in controlling shear wave velocities within the upper mantle. In the southern part of the study area, where normal-angle subduction is occurring, the slab is visible as a high-velocity body with a low-velocity mantle wedge above it, extending eastward from the active arc. Where flat-slab subduction is occurring, slab velocities increase to the east while velocities in the overlying lithosphere decrease, consistent with the slab dewatering and gradually hydrating the overlying mantle. The hydration of the slab may be contributing to the excess buoyancy of the subducting oceanic lithosphere, helping to drive flat-slab subduction.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 4
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    Shear wave velocities in the Pampean flat-slab region from Rayleigh wave tomography: Implications for slab and upper mantle hydration (2013)
    Wiley
    Details
    Publication Date: 2013-01-03
    Description: [1]  The Pampean flat-slab region, located in central Argentina and Chile between 29° and 34°S, is considered a modern analog for Laramide flat-slab subduction within western North America. Regionally, flat-slab subduction is characterized by the Nazca slab descending to ∼100 km depth, flattening out for ∼300 km laterally before resuming a more “normal” angle of subduction. Flat-slab subduction correlates spatially with the track of the Juan Fernandez Ridge, and is associated with the inboard migration of deformation and the cessation of volcanism within the region. To better understand flat-slab subduction we combine ambient-noise tomography and earthquake-generated surface wave measurements to calculate a regional 3D shear velocity model for the region. Shear wave velocity variations largely relate to changes in lithology within the crust, with basins and bedrock exposures clearly defined as low- and high-velocity regions, respectively. We argue that subduction-related hydration plays a significant role in controlling shear wave velocities within the upper mantle. In the southern part of the study area, where normal-angle subduction is occurring, the slab is visible as a high-velocity body with a low-velocity mantle wedge above it, extending eastward from the active arc. Where flat-slab subduction is occurring, slab velocities increase to the east while velocities in the overlying lithosphere decrease, consistent with the slab dewatering and gradually hydrating the overlying mantle. The hydration of the slab may be contributing to the excess buoyancy of the subducting oceanic lithosphere, helping to drive flat-slab subduction.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
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