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Influences of Flow Transients and Porous Medium Heterogeneity on Colloid-Associated Contaminant Transport in the Vadose Zone

Description: Our research is guided by an EMSP objective to improve conceptual and predictive models of contaminant movement in vadose-zone environments. As described in the report National Roadmap for Vadose-Zone Science and Technology [DOE, 2001], soil-water colloids are capable of adsorbing contaminants, such as radionuclides and metals, and facilitating their migration through the vadose zone and towards groundwater reservoirs. Our research centers on advancing understanding of this phenomenon. In particular, we are combining mathematical modeling with laboratory experimentation at pore and column scales to (1) elucidate the effects of porewater-flow transients on colloid mobilization in unsaturated porous media; (2) explore the sensitivity of colloid deposition rates to changes in porewater chemistry and colloid mineralogy; (3) develop mathematical models appropriate for simulating colloid mobilization, transport, and deposition under both steady-flow and transient-flow conditions; (4) identify mechanisms that govern mineral-colloid mobilization and deposition in unsaturated porous media; (5) quantify the effects of mineral-grain geometry and surface roughness on colloid-filtration rates; and (6) evaluate the influences of colloids on the transport of strontium and cesium (i.e., DOE-contaminants-of-concern) through soils and sediments.
Date: June 1, 2005
Creator: Saiers, James & Ryan, Joseph
Partner: UNT Libraries Government Documents Department

The Role of Natural Organic Matter and Mineral Colloids in the Transport of Contaminants through Heterogeneous Vadose-Zone Environments

Description: Our research was guided by a key objective of the Environmental Management Science Program (EMSP), which is to improve conceptual and predictive models for contaminant movement in complex vadose zone environments. In this report, increases in the understanding of colloidcontaminant interactions, colloid mobilization, and colloid deposition within unsaturated soils are cited as requisite needs for predicting contaminant fate and distribution in the vadose zone. We addressed these needs by pursuing three key goals: 1. Identify the mechanisms that govern OM and mineral-colloid reaction and transport in heterogeneous, unsaturated porous media; 2. Quantify the role of OM and mineral colloids in scavenging and facilitating the transport of contaminants of concern to DOE; and 3. Develop and test a mathematical model suitable for simulating the movement of OM- and colloid-associated contaminants through heterogeneous, unsaturated porous media.
Date: January 31, 2009
Creator: Saiers, James & Ryan, Joseph
Partner: UNT Libraries Government Documents Department

Influences of Flow Transients and Porous Medium Heterogeneity on Colloid Associated Contaminant Transport in the Vadose Zone

Description: We are investigating the role of colloids in the movement of radionuclides through water unsaturated porous media. This research is guided by a key objective of the Environmental Management Science Program (EMSP), which is to improve conceptual and predictive models for contaminant movement in complex vadose zone environments. In the report entitled National Roadmap for Vadose Zone Science and Technology [DOE, 2001], increases in the understanding of colloid-contaminant interactions, colloid mobilization, and colloid deposition within unsaturated soils are cited as requisite needs for predicting contaminant fate and distribution in the vadose zone. We seek to address these needs by pursuing three overarching goals: (1) identify the mechanisms that govern colloid mobilization, transport, and deposition within unsaturated porous media; (2) quantify the role of colloids in scavenging and facilitating the transport of radionuclides; and (3) develop and test a mathematical model suitable for simulating the movement of colloid associated radionuclides through variably saturated porous media.
Date: June 1, 2003
Creator: Ryan, Joseph
Partner: UNT Libraries Government Documents Department

Influences of Flow Transients and Porous Medium Heterogeneity on Colloid-Associated Contaminant Transport in the Vadose Zone

Description: We are investigating the role of colloids in the movement of radionuclides through water unsaturated porous media. This research is guided by a key objective of the Environmental Management Science Program (EMSP), which is to improve conceptual and predictive models for contaminant movement in complex vadose zone environments. In the report entitled National Roadmap for Vadose Zone Science and Technology [DOE, 2001], increases in the understanding of colloid-contaminant interactions, colloid mobilization, and colloid deposition within unsaturated soils are cited as requisite needs for predicting contaminant fate and distribution in the vadose zone. We seek to address these needs by pursuing three overarching goals: (1) identify the mechanisms that govern colloid mobilization, transport, and deposition within unsaturated porous media; (2) quantify the role of colloids in scavenging and facilitating the transport of radionuclides; and (3) develop and test a mathematical model suitable for simulating the movement of colloid-associated radionuclides through variably saturated porous media.
Date: June 1, 2003
Creator: Saiers, James & Ryan, Joseph
Partner: UNT Libraries Government Documents Department

Gleenglass Swarf Research

Description: Objective: John Sauer, Gleenglass principal, asked for research into innovative uses for a reclaimed glass slurry, also referred to as swarf. Through our research we were to determine a product and a market that could be manufactured using this fully recycled glass swarf. Background: Mr. Sauer receives the swarf from major glass manufacturers as a fine powder glass suspended in an organic dispersant and water. The swarf is produced through an industrial glass cutting process that results in the glass powder dispersed in water and recyclable glass disks; both are used in the project. Mr. Sauer's swarf studio testing has yet to produce any product with a value great enough to justify processing the swarf. Many of these limitations were believed to be due to the unknown composition and characteristics of the swarf as well as the limited lab testing ability of Mr. Sauer in his studio space. Deliverables: 1. The valuable characteristics of the swarf. 2. Products that can be produced with the swarf. 3. Market for developed products. 4. Capital investment needed to create developed product. 5. Any other applications of the swarf that were outside the scope of residential and commercial building material for use in future DOE grant proposals to the glass manufacturing facilities. 6. Additives that could change the color of the final piece to white, gray, or green.
Date: April 1, 2010
Creator: Turo, Laura A.; Skorski, Daniel C.; Schweiger, Michael J. & Ryan, Joseph V.
Partner: UNT Libraries Government Documents Department

Engineering Glass Passivation Layers -Model Results

Description: The immobilization of radioactive waste into glass waste forms is a baseline process of nuclear waste management not only in the United States, but worldwide. The rate of radionuclide release from these glasses is a critical measure of the quality of the waste form. Over long-term tests and using extrapolations of ancient analogues, it has been shown that well designed glasses exhibit a dissolution rate that quickly decreases to a slow residual rate for the lifetime of the glass. The mechanistic cause of this decreased corrosion rate is a subject of debate, with one of the major theories suggesting that the decrease is caused by the formation of corrosion products in such a manner as to present a diffusion barrier on the surface of the glass. Although there is much evidence of this type of mechanism, there has been no attempt to engineer the effect to maximize the passivating qualities of the corrosion products. This study represents the first attempt to engineer the creation of passivating phases on the surface of glasses. Our approach utilizes interactions between the dissolving glass and elements from the disposal environment to create impermeable capping layers. By drawing from other corrosion studies in areas where passivation layers have been successfully engineered to protect the bulk material, we present here a report on mineral phases that are likely have a morphological tendency to encrust the surface of the glass. Our modeling has focused on using the AFCI glass system in a carbonate, sulfate, and phosphate rich environment. We evaluate the minerals predicted to form to determine the likelihood of the formation of a protective layer on the surface of the glass. We have also modeled individual ions in solutions vs. pH and the addition of aluminum and silicon. These results allow us to understand the pH ...
Date: August 8, 2011
Creator: Skorski, Daniel C.; Ryan, Joseph V.; Strachan, Denis M. & Lepry, William C.
Partner: UNT Libraries Government Documents Department

Influences of Flow Transients and Porous Medium Heterogeneity on Colloid-Associated Contaminant Transport in the Vadose Zone

Description: Radionuclides, metals, and dense non-aqueous phase liquids have contaminated about six billion cubic meters of soil at Department of Energy (DOE) sites. The subsurface transport of many of these contaminants is facilitated by colloids (i.e., microscopic, waterborne particles). The first step in the transport of contaminants from their sources to off-site surface water and groundwater is migration through the vadose zone. Developing our understanding of the migration of colloids and colloid-associated contaminants through the vadose zone is critical to assessing and controlling the release of contaminants from DOE sites. In this study, we examined the mobilization, transport, and filtration (retention) of mineral colloids and colloidassociated radionuclides within unsaturated porous media. This investigation involved laboratory column experiments designed to identify properties that affect colloid mobilization and retention and pore-scale visualization experiments designed to elucidate mechanisms that govern these colloid-mass transfer processes. The experiments on colloid mobilization and retention were supplemented with experiments on radionuclide transport through porous media and on radionuclide adsorption to mineral colloids. Observations from all of these experiments – the column and visualization experiments with colloids and the experiments with radionuclides – were used to guide the development of mathematical models appropriate for describing colloids and colloid-facilitated radionuclide transport through the vadose zone.
Date: July 2, 2006
Creator: Saiers, James & Ryan, Joseph
Partner: UNT Libraries Government Documents Department

Influences of Flow Transients and Porous Medium Heterogeneity on Colloid-Associated Contaminants Transport in the Vadose Zone

Description: During the past year (June 2003 to June 2004), work at Yale has centered on investigating the influences of porewater pH, flow transients, and the presence of natural organic matter (NOM) on the deposition and mobilization of clay colloids (kaolinite and illite) within columns packed with unsaturated porous media. The experiments on pH and flow-transient effects were described in our First-Term Progress Report (which covered the initial 18 months of the study) and will not be repeated here. More recent experiments on the role of NOM in colloid transport proved equally as interesting. Even at porewater concentrations as low as 0.2 mg/L, soil-humic acid substantially lowered clay-colloid deposition rates compared to the case in which soil-humic acid was absent from the porewater. We attribute this to adsorption of the humic acid to the positively charged edge sites of the clay colloids, which effectively reduced the colloid affinity for negatively charged air- and solid-water interfaces. Comparison of the results of the column experiments to calculations of a new mathematical model has sharpened our inferences regarding mechanisms that govern the rate-limited deposition and mobilization of colloids. We are testing these inferences by carrying out flow-and-transport visualization experiments. We have constructed a semi-transparent representation of a porous medium, consisting of a rectangular parallel-plate chamber that encloses 3-5 layers of uniformly sized sand grains. Ceramic plates fused to the ends of the chamber maintain the capillary tension and syringe pumps (located at the inlet and outlet ends) regulate the flow of water and colloids through the partially saturated sand. By placing the chamber beneath a microscope, we can examine the distribution of colloids between air-water and solid-water interfaces, directly measure the kinetics of deposition onto these interfaces, and observe the mechanisms that contribute to the release of immobile colloids. To date, we have used ...
Date: June 15, 2003
Creator: Saiers, James E. & Ryan, Joseph
Partner: UNT Libraries Government Documents Department

FY08 Annual Report: Amorphous Semiconductors for Gamma Radiation Detection (ASGRAD)

Description: This is the annual report for an old project funded by NA22. The purpose of the project was to develop amorphous semiconductors for use as radiation detectors. The annual report contains information about the progress made in synthesizing, characterizing, and radiation response testing of these new materials.
Date: February 1, 2009
Creator: Johnson, Bradley R.; Riley, Brian J.; Crum, Jarrod V.; Ryan, Joseph V.; Sundaram, S. K.; McCloy, John S. et al.
Partner: UNT Libraries Government Documents Department

Baseline Glass Development for Combined Fission Products Waste Streams

Description: Borosilicate glass was selected as the baseline technology for immobilization of the Cs/Sr/Ba/Rb (Cs), lanthanide (Ln) and transition metal fission product (TM) waste steams as part of a cost benefit analysis study.[1] Vitrification of the combined waste streams have several advantages, minimization of the number of waste forms, a proven technology, and similarity to waste forms currently accepted for repository disposal. A joint study was undertaken by Pacific Northwest National Laboratory (PNNL) and Savannah River National Laboratory (SRNL) to develop acceptable glasses for the combined Cs + Ln + TM waste streams (Option 1) and Cs + Ln combined waste streams (Option 2) generated by the AFCI UREX+ set of processes. This study is aimed to develop baseline glasses for both combined waste stream options and identify key waste components and their impact on waste loading. The elemental compositions of the four-corners study were used along with the available separations data to determine the effect of burnup, decay, and separations variability on estimated waste stream compositions.[2-5] Two different components/scenarios were identified that could limit waste loading of the combined Cs + LN + TM waste streams, where as the combined Cs + LN waste stream has no single component that is perceived to limit waste loading. Combined Cs + LN waste stream in a glass waste form will most likely be limited by heat due to the high activity of Cs and Sr isotopes.
Date: June 29, 2009
Creator: Crum, Jarrod V.; Billings, Amanda Y.; Lang, Jesse B.; Marra, James C.; Rodriguez, Carmen P.; Ryan, Joseph V. et al.
Partner: UNT Libraries Government Documents Department

Summary Report for the Development of Materials for Volatile Radionuclides

Description: The materials development summarized here is in support of the Waste Forms campaign, Volatile Radionuclide task. Specifically, materials are being developed for the removal and immobilization of iodine and krypton, specifically 129I and 85Kr. During FY 2010, aerogel materials were investigated for removal and immobilization of 129I. Two aerogel formulations were investigated, one based on silica aerogels and the second on chalcogenides. For 85Kr, metal organic framework (MOF) structures were investigated.
Date: November 22, 2010
Creator: Strachan, Denis M.; Chun, Jaehun; Henager, Charles H.; Matyas, Josef; Riley, Brian J.; Ryan, Joseph V. et al.
Partner: UNT Libraries Government Documents Department

Summary Report on the Volatile Radionuclide and Immobilization Research for FY2011 at PNNL

Description: The materials development summarized here is in support of the Waste Forms campaign, Volatile Radionuclide task. Specifically, materials are being developed for the removal and immobilization of iodine and krypton, specifically 129I and 85Kr. During FY 2011, aerogel materials were investigated for removal and immobilization of 129I. Two aerogel formulations were investigated, one based on silica aerogels and the second on chalcogen-based aerogels (i.e., chalcogels). A silica aerogel was tested at ORNL for total I2 sorption capacity. It was determined to have 48 mass% capacity while having little physisorbed I2 (I2 not taken up in the aerogel pores). For 85Kr, metal organic framework (MOF) structures were investigated and a new MOF with about 8 mass% capacity for Xe and Kr. The selectivity can be changed from Xe > Kr to Xe < Kr simply by lowering the temperature below 0 C. A patent disclosure has been filed. Lastly, silicon carbide (SiC) was loaded with Kr. The diffusion of Kr in SiC was found to be less than detectable at 500 C.
Date: September 1, 2011
Creator: Strachan, Denis M.; Chun, Jaehun; Matyas, Josef; Lepry, William C.; Riley, Brian J.; Ryan, Joseph V. et al.
Partner: UNT Libraries Government Documents Department