Effect of Grain Size on Uranium(VI) Surface Complexation Kinetics and Adsorption Additivity

Shang, Jianying; Liu, Chongxuan; Wang, Zheming; Zachara, John M.

doi:10.1021/es200920k

Cited by 62 publications

(78 citation statements)

References 31 publications

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“…The weight was used to incorporate the effect of observation uncertainty on parameter estimation. It is traditionally assumed to be equal or proportional to the inverse of the variance of observation errors (5 % for this case, Shang et al 2011). The standard deviation of observation errors often equals the product of a coefficient of variation and a concentration observation (Hill and Tiedeman 2007).…”

Section: Inverse Modelmentioning

confidence: 99%

“…The additivity model, which uses grain-size distribution to scale reaction properties, has been proposed to address the scaling challenge (Shang et al 2011;Stoliker et al 2013;Sparks 1995). The approach assumes that the sediment reaction properties for numerical grid cells in a specific geological unit or faces can be described by linearly adding corresponding reaction properties for individual grain-size fractions that comprise the sediment.…”

Section: Introductionmentioning

confidence: 99%

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Grain-Size Based Additivity Models for Scaling Multi-rate Uranyl Surface Complexation in Subsurface Sediments

Zhang

Liu

et al. 2015

Math Geosci

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The additivity model assumed that field-scale reaction properties in a sediment including surface area, reactive site concentration, and reaction rate can be predicted from field-scale grain-size distribution by linearly adding reaction properties estimated in laboratory for individual grain-size fractions. This study evaluated the additivity model in scaling mass transfer-limited, multi-rate uranyl (U(VI)) surface complexation reactions in a contaminated sediment. Experimental data of rate-limited U(VI) desorption in a stirred flow-cell reactor were used to estimate the statistical properties of the rate constants for individual grain-size fractions, which were then used to predict rate-limited U(VI) desorption in the composite sediment. The result indicated that the additivity model with respect to the rate of U(VI) desorption provided a good prediction of U(VI) desorption in the composite sediment. However, the rate constants were not directly scalable using the additivity model. An approximate additivity model for directly scaling rate constants was subsequently proposed and evaluated. The result found that the approximate model provided a good prediction of the experimental results within statistical uncertainty. This study also found that a gravel-size fraction (2 to 8 mm), which is often ignored in modeling U(VI) sorption and desorption, is statistically significant to the U(VI) desorption in the sediment.

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Section: Inverse Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Grain-Size Based Additivity Models for Scaling Multi-rate Uranyl Surface Complexation in Subsurface Sediments

Zhang

Liu

et al. 2015

Math Geosci

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“…These measurements have most commonly been performed on the <2-mm size fraction of the sediment isolated by dry-sieving because sorbed U(VI) in contaminated sediments is primarily associated with this fraction (Shang et al 2011). (Note that dry-sieving is not free of artifacts because fine-grained particles bind tenaciously to larger ones and are not effectively separated by this method.)…”

Section: Laboratory Measurements Of Adsorption and Desorptionmentioning

confidence: 99%

“…A noteworthy, consistent database of laboratory adsorption/desorption measurements has been developed by IFRC researchers who have investigated sediments from the South Process Pond, the North Process Pond, the Process Trenches, and select intervening areas Bond et al 2008;Liu et al 2009;Um et al 2010;Shang et al 2011;Stoliker et al 2011;Murray et al 2012;Stoliker et al In Press 1 ). Chemical conditions were used for the measurements that simulate ambient 300 Area groundwater conditions (no river water component) in terms of pH, and major cations (Ca 2+ , Mg 2+ , Na + , and K + ) and anions (HCO 3 -, SO 4 2+ , and NO 3 -).…”

Section: Laboratory Measurements Of Adsorption and Desorptionmentioning

confidence: 99%

Updated Conceptual Model for the 300 Area Uranium Groundwater Plume

Zachara¹,

Freshley²,

Last³

et al. 2012

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SummaryThe 300 Area uranium groundwater plume in the 300-FF-5 Operable Unit is residual from past discharge of nuclear fuel fabrication wastes to a number of liquid (and solid) disposal sites. The source zones in the disposal sites were remediated by excavation and backfilled to grade, but sorbed uranium remains in deeper, unexcavated vadose zone sediments. Despite source term removal, the groundwater plume has shown remarkable persistence, with concentrations exceeding the drinking water standard over an area of approximately 1 km 2 . The plume resides within a coupled vadose zone, groundwater, river zone system of immense complexity and scale. Interactions between geologic structure, the hydrologic system driven by the Columbia River, groundwater-river exchange points, and the geochemistry of uranium contribute to persistence of the plume.The U.S. Department of Energy (DOE) recently completed a Remedial Investigation/Feasibility Study (RI/FS) to document characterization of the 300 Area uranium plume and plan for beginning to implement proposed remedial actions. As part of the RI/FS document, a conceptual model was developed that integrates knowledge of the hydrogeologic and geochemical properties of the 300 Area and controlling processes to yield an understanding of how the system behaves and the variables that control it. Recent results from the Hanford Integrated Field Research Challenge (IFRC) site and the Subsurface Biogeochemistry Scientific Focus Area Project funded by the DOE Office of Science were used to update the conceptual model and provide an assessment of key factors controlling plume persistence.Hanford IFRC research identified several refinements to the conceptual model that can be extended to the 300 Area. Studies at the IFRC site with geophysics, hydraulic testing, and tracers confirm the presence of a lower permeability intermediate zone within the Hanford formation that has a large impact on the hydrologic system. Resulting vertical borehole flows have implications for monitoring, persistence of the uranium plume, and remediation approach. Research at the IFRC site has shown that uranium is mobilized in a heterogeneous way from the lower vadose zone in concentrations exceeding the drinking water standard during the spring high water table event, showing large fluctuations in concentrations over the approximate 3-month period of spring snowmelt. The observed behaviors of uranium strongly impact monitoring results, and should be considered in their interpretation. Improved persistence calculations should address more accurate adsorption-desorption parameters (e.g., surface complexation) for the saturated zone derived from fitting of new IFRC field experiment data.

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“…This complex topic requires understanding of the interactions of radioactive, multivalent actinide species with a host of geomaterials, along with the simultaneous effects of biologically driven processes. Over the past few years, there has been continual and marked progress in understanding the biogeochemistry of U, Tc, and Pu, which have been found to be remarkably rich from a scientific perspective (Cologgi et al 2011;Malvankar et al 2011;Shang et al 2011). Tremendous opportunities for scientific advancements exist for this topic and have been relatively 3.15 unexplored because of its complexity.…”

Section: Fundamental Actinide Biogeochemistry/environmental Sciencementioning

confidence: 99%

Compact X-ray Light Source Workshop Report

Thevuthasan¹,

Evans²,

Terminello³

et al. 2012

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Executive SummaryThis report is the result of a workshop held in September 2011 that examined the utility of a compact x-ray light source (CXLS) in addressing many scientific challenges critical to advancing energy science and technology. The U.S. Department of Energy (DOE) and National Academy of Sciences (NAS) have repeatedly described the need for advanced instruments that "predict, control, and design the components of energetic processes and environmental balance," most notably in biological, chemical, environmental, and materials science. In numerous DOE and NAS reports, direct molecular-scale imaging and timedependent studies are seen as a powerful means to develop an atomistic-level understanding of scientific issues associated with current and future energy and environmental needs, including energy production and storage from both fossil-based and fossil-free sources and cleanup of government and industrial sites worldwide.One of the major enabling capabilities for meeting these needs is a high-brightness x-ray light source. The DOE report, Next-Generation Photon Sources for Grand Challenges in Science and Energy, identifies "spectroscopic and structural imaging of nano-objects (or nanoscale regions of inhomogeneous materials) with nanometer spatial resolution and ultimate spectral resolution" as one of the two aspects of energy science in which current and next-generation x-ray light sources will have the deepest and broadest impact. The report further stresses the power of direct observation in understanding transformational chemical processes. The report also discusses the importance of molecular "movies" of complex reactions that show bond breaking and reforming in natural time scales, along with the intermediate states to understand the mechanisms that govern chemical transformations. Existing accelerator-based x-ray sources have greatly extended capabilities in the time and space domain for scientific investigations in many disciplines. Despite these successes, a number of scientific challenges would benefit greatly from having an x-ray resource that has much of the attractive capability of these large machines but lends itself to operating in conjunction with other characterization tools in a correlative fashion. Such an integrated multiscale and multimodal approach could fully address the fundamental needs expressed by DOE's Office of Biological and Environmental Research (BER) in regards to understanding how genomic information is translated with confidence to redesign microbes, plants, or ecosystems (http://science.energy.gov/).Fortunately, recent advances in laser and super-cooled linear particle accelerator, or linac, technology have enabled development of a long-promised CXLS that uses inverse Compton scattering for generating x-rays. The new CXLS holds the promise of simultaneous energy tuning-from the soft to hard x-ray regime-as well as a pulsed structure closely coupled to the laser pulse duration of pico-to femtoseconds. With a projected brilliance equal to third-generation light sourc...

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Effect of Grain Size on Uranium(VI) Surface Complexation Kinetics and Adsorption Additivity

Cited by 62 publications

References 31 publications

Grain-Size Based Additivity Models for Scaling Multi-rate Uranyl Surface Complexation in Subsurface Sediments

Grain-Size Based Additivity Models for Scaling Multi-rate Uranyl Surface Complexation in Subsurface Sediments

Updated Conceptual Model for the 300 Area Uranium Groundwater Plume

Compact X-ray Light Source Workshop Report

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