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Complexation of Actinides in Solution: Thermodynamic Measurementsand Structural Characterization

Description: This paper presents a brief introduction of the studies of actinide complexation in solution at Lawrence Berkeley National Laboratory. An integrated approach of thermodynamic measurements and structural characterization is taken to obtain fundamental understanding of actinide complexation in solution that is of importance in predicting the behavior of actinides in separation processes and environmental transport.
Date: February 1, 2007
Creator: Rao, L.
Partner: UNT Libraries Government Documents Department

Suspended sediment transport in the benthic nepheloid layer in southeastern Lake Michigan

Description: Time series observations of water temperature, water transparency, and current velocity were made at four stations located on the lake slope of southeastern Lake Michigan. The observations show that during stratified conditions the benthic nepheloid layer is probably not maintained by the local resuspension of bottom sediment. A more likely source is sediment resuspended further inshore and then transported across the shelf and slope during downwelling events. Internal wave action may be an important source of energy for this transport. Although sediment trap studies suggest that resuspension does occur, it is more likely that increased fluxes observed near the bottom are due to the vertical redistribution of material already in suspension. A benthic nepheloid layer also exists at times during the unstratified period, when occassionally enough energy reaches the bottom to directly resuspend bottom material at the sites.
Date: February 1, 1995
Creator: Hawley, N. & Lesht, B.M.
Partner: UNT Libraries Government Documents Department

STREAM2 Revision 1: An aqueous release emergency response model

Description: This report documents the revision for STREAM2 code and its input files. STREAM2 is an aqueous transport module of the WIND system. As requested by the Emergency Response Department, two surface aqueous release locations (McQueen Branch and Tims Branch) were added in the STREAM2 code. In addition, the revised STREAM2 has the capability to vary the channel-segment volume based on channel flow to better represent the open channel hydraulics. Thus, the updated version of STREAM2 improves the contaminant transport calculation
Date: April 14, 2000
Creator: Chen, K.F.
Partner: UNT Libraries Government Documents Department

A modified invasion percolation model for low-capillary number immiscible displacements in horizontal rough-walled fractures: Influence of local in-plane

Description: The authors develop and evaluate a modified invasion percolation (MIP) model for quasi-static immiscible displacement in horizontal fractures. The effects of contact angle, local aperture field geometry, and local in-plane interracial curvature between phases are included in the calculation of invasion pressure for individual sites in a discretized aperture field. This pressure controls the choice of which site is invaded during the displacement process and hence the growth of phase saturation structure within the fracture. To focus on the influence of local in-plane curvature on phase invasion structure, they formulate a simplified nondimensional pressure equation containing a dimensionless curvature number (C) that weighs the relative importance of in-plane curvature and aperture-induced curvature. Through systematic variation of C, they find in-plane interracial curvature to greatly affect the phase invasion structure. As C is increased from zero, phase invasion fronts transition from highly complicated (IP results) to microscopically smooth. In addition, measurements of fracture phase saturations and entrapped cluster statistics (number, maximum size, structural complication) show differential response between wetting and nonwetting invasion with respect to C that is independent of contact angle hysteresis. Comparison to experimental data available at this time substantiates predicted behavior.
Date: January 28, 2000
Partner: UNT Libraries Government Documents Department

Visualization of micro-scale phase displacement processes in retention and outflow experiments: Non-uniqueness of unsaturated flow properties

Description: Methods to determine unsaturated hydraulic properties can exhibit random and non-unique behavior. The authors assess the causes for these behaviors by visualizing micro-scale phase displacement processes during equilibrium retention and transient outflow experiments. They observe that the drainage process is composed of a fast fingering followed by a slower backfilling. The influence of each these processes is controlled by the size and the speed of the applied boundary step, the initial saturation and its structure and by small-scale heterogeneities. Because the mixture of these micro-scale processes yields macro-scale effective behavior, measured unsaturated flow properties are also a function of these controls. These results suggest limitations on the current definitions and uniqueness of unsaturated hydraulic properties.
Date: March 9, 2000
Partner: UNT Libraries Government Documents Department

Factors controlling satiated relative permeability in a partially-saturated horizontal fracture

Description: Recent work demonstrates that phase displacements within horizontal fractures large with respect to the spatial correlation length of the aperture field lead to a satiated condition that constrains the relative permeability to be less than one. The authors use effective media theory to develop a conceptual model for satiated relative permeability, then compare predictions to existing experimental measurements, and numerical solutions of the Reynolds equation on the measured aperture field within the flowing phase. The close agreement among all results and data show that for the experiments considered here, in-plane tortuosity induced by the entrapped phase is the dominant factor controlling satiated relative permeability. They also find that for this data set, each factor in the conceptual model displays an approximate power law dependence on the satiated saturation of the fracture.
Date: February 16, 2000
Partner: UNT Libraries Government Documents Department

Atmospheric Data Package for the Composite Analysis

Description: The purpose of this data package is to summarize our conceptual understanding of atmospheric transport and deposition, describe how this understanding will be simplified for numerical simulation as part of the Composite Analysis (i.e., implementation model), and finally to provide the input parameters needed for the simulations.
Date: September 1, 2005
Creator: Napier, Bruce A. & Ramsdell, James V.
Partner: UNT Libraries Government Documents Department

Modeling the wind-fields of accidental releases with an operational regional forecast model

Description: The Atmospheric Release Advisory Capability (ARAC) is an operational emergency preparedness and response organization supported primarily by the Departments of Energy and Defense. ARAC can provide real-time assessments of atmospheric releases of radioactive materials at any location in the world. ARAC uses robust three-dimensional atmospheric transport and dispersion models, extensive geophysical and dose-factor databases, meteorological data-acquisition systems, and an experienced staff. Although it was originally conceived and developed as an emergency response and assessment service for nuclear accidents, the ARAC system has been adapted to also simulate non-radiological hazardous releases. For example, in 1991 ARAC responded to three major events: the oil fires in Kuwait, the eruption of Mt. Pinatubo in the Philippines, and the herbicide spill into the upper Sacramento River in California. ARAC`s operational simulation system, includes two three-dimensional finite-difference models: a diagnostic wind-field scheme, and a Lagrangian particle-in-cell transport and dispersion scheme. The meteorological component of ARAC`s real-time response system employs models using real-time data from all available stations near the accident site to generate a wind-field for input to the transport and dispersion model. Here we report on simulation studies of past and potential release sites to show that even in the absence of local meteorological observational data, readily available gridded analysis and forecast data and a prognostic model, the Navy Operational Regional Atmospheric Prediction System, applied at an appropriate grid resolution can successfully simulate complex local flows.
Date: September 11, 1995
Creator: Albritton, J.R.; Lee, R.L. & Sugiyama, G.
Partner: UNT Libraries Government Documents Department

A brief review of bacterial transport in natural porous media

Description: This report reviews advances in the descriptions of microbial transport processes. The advances can often be translated into technological advances for solute transport, with potential applicability to a number of subsurface concerns related to solutes. The processes involved in microbial transport include physically controlled processes, chemically controlled processes, and biologically controlled processes. The physical processes involved in the transport of microbes include advection, diffusion, dispersion, straining, filtration, and exclusion. Biomass removal by chemical reactions has received less attention, and included electrostatic attraction and hydrophobic sorption. In addition, microbiologic processes affecting the fate and transport of microbes in the subsurface include growth and decay; motility and chemotaxis; biological adhesion; and predation. Interdependencies among these processes arise through coupling, e.g., as multiscale mixing in heterogeneous environments affects nutrient availability (growth) and filtration velocities (attachment).
Date: December 1, 1995
Creator: Ginn, T.R.
Partner: UNT Libraries Government Documents Department

The effect of microscale urban canyon flow on mesoscale puff dispersion

Description: When modeling mesoscale plume or puff transport over distances of one to ten kilometers, the initial small-scale near-source effects are often ignored or parameterized in a crude way. If the release is in an urban environment, buildings and other urban structures can significantly impact the local plume dispersion (e.g., Davidson et al., 1995). In this paper, the authors investigate whether the building-scale effects are important on the longer time-scale mesoscale dispersion process.
Date: June 1, 1997
Creator: Brown, M.J. & Muller, C.
Partner: UNT Libraries Government Documents Department

Direct calculation of leak path factors for highly compartmentalized buildings

Description: The large, highly compartmentalized configurations of buildings at many Department of Energy (DOE) facilities call the validity of traditional, simplistic methods for estimating contaminant leak path factors (LPFs) into question. Conversely, rigorous calculation of LPFs using detailed flow-field analysis computer codes is impractical for routine analysis. This paper describes a recent application of a rigorous, yet practical, method of calculating LPFs for the Chemical and Metallurgical Research (CMR) Facility at Los Alamos National Laboratory (LANL). The approach involves computer simulation of airborne contaminant transport using the MELCOR computer code. MELCOR is a general-purpose, fluid flow and aerosol transport analysis code originally developed by the US Nuclear Regulatory Commission to evaluate the release, transport, and deposition of radionuclides in nuclear reactor systems. However, the fundamental mathematical models in the code and the modular code architecture make it suitable to the CMR analysis.
Date: December 1, 1998
Creator: Leonard, M.T. & McClure, P.R.
Partner: UNT Libraries Government Documents Department

Update to modeling soil selenium concentrations in the shallow soil profile at Kesterson Reservoir Merced County, California

Description: A mass balance model was developed to predict concentrations of water-extractable selenium in surface and subsurface soil by extrapolating the trend observed from 6 years of soil monitoring data collected at Kesterson Reservoir. Correlations between observed and calculated concentrations indicate that the major trends and year-to-year variations are well represented with the model. Results from this exercise were then used, under three climatic scenarios, to simulate the evolution of the soluble selenium inventory 25 years into the future. Based on these simulations, we expect that the availability of the soluble selenium inventory has most likely reached peak levels, and is now declining. However, year-to-year climatic variations may influence the rate of decline, and occasionally reverse this prevailing trend.
Date: January 1, 1996
Creator: Wahl, C. & Benson, S. M.
Partner: UNT Libraries Government Documents Department

Concentrations of a water soluble, gas-phase mercury species in ambient air: Results from measurements and modeling

Description: There are few reliable data on the speciation of Hg in ambient air, although this information is critical to understanding the fate of Hg once released from point sources. The water soluble species of Hg that are thought to exist in flue gases would be subject to far greater local removal rates than is elemental Hg vapor, but methods are lacing to quantify this species. The authors developed a method using refluxing mist chambers to measure the airborne concentrations of reactive gaseous mercury (RGM) in short-term samples under ambient conditions. The method exhibits an effective detection limit of 0.02 ng/m{sup 3} and a precision for ambient concentration levels of {+-}20--30%. Using a model that simulates atmospheric transport and fate of anthropogenic mercury emissions over the contiguous United States, the authors generated 24-hr RGM concentrations to compare to the measurement data. The average RGM concentrations measured with their mist chambers at sites in Tennessee (TN) and Indiana (IN) were 0.065 ng/m{sup 3} and 0.100 ng/m{sup 3}, respectively. These averages represent about 3% of total gaseous mercury (TGM), and RGM generally exceeds regional particulate Hg. The 24-hr model-simulated RGM concentration averages in the modeling grid cells representing TN and IN are 0.051 ng/m{sup 3} and 0.098 ng/m{sup 3} respectively, in good agreement with the data. The measured concentrations at the two sites exhibit weak positive correlations with temperature, solar radiation, O{sub 3}, SO{sub 2}, and TGM. These concentrations are high enough to suggest that RGM can play an important role in both wet and dry deposition on a regional scale.
Date: December 31, 1997
Creator: Lindberg, S. E.; Stratton, W. J.; Pai, P. & Allan, M. A.
Partner: UNT Libraries Government Documents Department

Atmospheric Transport of Radionuclides

Description: The purpose of atmospheric transport and diffusion calculations is to provide estimates of concentration and surface deposition from routine and accidental releases of pollutants to the atmosphere. This paper discusses this topic.
Date: March 3, 2003
Creator: Crawford, T.V.
Partner: UNT Libraries Government Documents Department

Wind Climate Analyses for SRTC's Central Climatology Site

Description: This report was written to present climatological summaries of the wind data at the Central Climatology (CC) tower in a convenient format and to point out some features of the wind speed and direction that have not been widely appreciated in the past. Short-term (two-week) wind roses provide a means to demonstrate the temporal and spatial relationships that wind speed and direction undergo using a ten-year database from the CC tower. These relationships are best demonstrated by examining the figures provided in this report or looking at loops of computer-generated images provided by the authors.
Date: June 23, 2003
Creator: Weber, A.H.
Partner: UNT Libraries Government Documents Department

Diagnostic modeling for real-time emergency response

Description: The Atmospheric Release Advisory Capability (ARAC) provides real-time dose assessments for airborne pollutant releases. ARAC is currently in the process of developing an entirely new suite of models and system infrastructure. Diagnostic and dispersion algorithms are being created in-house and a prognostic model NO-RAPS, imported from the Naval Research Laboratory, Monterey, is currently being adapted to ARAC`s needs. Diagnostic models are essential for an emergency response capability since they provide the ability to rapidly assimilate available meteorological data and generate the mass-consistent three-dimensional wind fields required by dispersion models. The resulting wind fields may also serve to initialize and validate prognostic models. In general, the performance of diagnostic models strongly correlates with the density and distribution of measurements in the area of interest and the resolution of the terrain. problem, data can be extracted from user-specified databases within a region defined by a metdata grid. Typically the data collection region will cover a geographic domain significantly larger than the area involved in the dispersion simulation in order to provide the most complete set of meteorological information relevant to the problem. This also permits the user to redefine the problem grid size and location, within limits, without reaccessing the meteorological data extraction system. After the data has been collected, an associated meteorological preprocessor places it in a standard form for further processing. The pre-processor does not alter or interpolate wind values; it only performs reversible transformations to convert the data to a standard unambiguous form, e.g. latitude, longitude, height, wind speed and direction. This allows the diagnostic models to use a generalized data ingest routine, not dependent on the form or format of the meteorological data source or database.
Date: September 7, 1995
Creator: Sugiyama, G.; Rodriguez, D. & Lee, R.
Partner: UNT Libraries Government Documents Department

Pollutant transfer through air and water pathways in an urban environment

Description: The authors are attempting to simulate the transport and fate of pollutants through air and water pathways in an urban environment. This cross-disciplinary study involves linking together models of mesoscale meteorology, air pollution chemistry and deposition, urban runoff and stormwater transport, water quality, and wetland chemistry and biology. The authors are focusing on the transport and fate of nitrogen species because (1) they track through both air and water pathways, (2) the physics, chemistry, and biology of the complete cycle is not well understood, and (3) they have important health, local ecosystem, and global climate implications. The authors will apply their linked modeling system to the Los Angeles basin, following the fate of nitrates from their beginning as nitrate-precursors produced by auto emissions and industrial processes, tracking their dispersion and chemistry as they are transported by regional winds and eventually wet or dry deposit on the ground, tracing their path as they are entrained into surface water runoff during rain events and carried into the stormwater system, and then evaluating their impact on receiving water bodies such as wetlands where biologically-mediated chemical reactions take place. In this paper, the authors wish to give an overview of the project and at the conference show preliminary results.
Date: December 31, 1998
Creator: Brown, M.; Burian, S.; McPherson, T.; Streit, G.; Costigan, K. & Greene, B.
Partner: UNT Libraries Government Documents Department

Photon burst mass spectrometry for the measurement of {sup 85}Kr at ambient levels

Description: Photon Burst Mass Spectrometry has been used to measure {sup 85}Kr in a sample with an abundance of 6 x 10{sup {minus}9}. Improvements in detection efficiency by the use of avalanche photodiodes cooled to liquid nitrogen temperature are reported, which should make possible measurement of {sup 85}Kr at the ambient atmospheric abundance of 10{sup {minus}11}. Potential applications include nuclear monitoring, atmospheric transport, and dating young ground water up to 40 years.
Date: December 1, 1998
Creator: Fairbank, W.M. Jr.; LaBelle, R.D. & Hansen, C.S.
Partner: UNT Libraries Government Documents Department

Retardation of volatile organic compounds in ground water in low organic carbon sediments

Description: It is postulated that adsorption onto aquifer matrix surfaces is only one of the processes that retard contaminants in ground water in unconsolidated sediments; others include hydrodynamic dispersion, abiotic/biotic degradation, matrix diffusion, partitioning to organic carbon, diffusion into and retention in dead-end pores, etc. This work aims at these processes in defining the K{sub d} of VOCs in sediments with low organic carbon content. Experiments performed include an initial column experiment for VOC (TCE and perchloroethylene(PCE)) retardation tests on geological materials, PCE and TCE data from LLNL sediments, and a preliminary multilayer sampler experiment. The VOC K{sub d}s in low organic carbon permeable aquifer materials are dependent on the VOC composition and independent of aquifer grain size, indicating that sorption was not operative and that the primary retarding factors are diffusion controlled. The program of future experiments is described.
Date: April 1, 1995
Creator: Hoffman, F.
Partner: UNT Libraries Government Documents Department

Characterization of anaerobic chloroethene-dehalogenating activity in several subsurface sediments

Description: Anaerobic microcosms of subsurface soils from four locations were used to investigate the separate effects of several electron donors on tetrachloroethylene (PCE) dechlorination activity. The substrates tested were methanol, formate, lactate, acetate, and sucrose. Various levels of sulfate-reducing, acetogenic, fermentative, and methanogenic activity were observed in all sediments. PCE dechlorination was detected in all microcosms, but the amount of dehalogenation varied by several orders of magnitude. Trichloroethylene was the primary dehalogenation product; however, small amounts of cis-1,2-dichloroethylene, 1,1-dichloroethylene, and vinyl chloride were also detected in several microcosms. Lactate-amended microcosms showed large amounts of dehalogenation. in three of the four sediments. One of the two sediments which showed positive activity with lactate also had large amounts of delialogenation with methanol. Sucrose, formate, and acetate also stimulated large amounts of delialogenation in one sediment that showed activity with lactate. These results suggest that lactate may be an appropriate substrate for screening sediments for PCE or TCE delialogenation activity, but that the microbial response is not sufficient for complete in situ bioremediation. A detailed study of the Victoria activity revealed that delialogenation rates were more similar to the Cornell culture than to rates measured for methanogens, or a methanol-enriched sediment culture. This may suggest that these sediments contain a highly efficient delialogenation activity similar to the Cornell culture. This assertion is supported further by the fact that an average of 3% of added reducing equivalents could be diverted to dehalogenation in tests which were conducted using PCE-saturated hexadecane as a constant source of PCE during incubation. Further evidence is needed to confirm this premise. The application of these results to in situ bioremediation of highly contaminated areas are discussed.
Date: November 1, 1996
Creator: Skeen, R.S.; Gao, J.; Hooker, B.S. & Quesenberry, R.D.
Partner: UNT Libraries Government Documents Department