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Molecular Mechanism of Microbial Technetium Reduction Final Report

Description: Microbial Tc(VII) reduction is an attractive alternative strategy for bioremediation of technetium-contaminated subsurface environments. Traditional ex situ remediation processes (e.g., adsorption or ion exchange) are often limited by poor extraction efficiency, inhibition by competing ions and production of large volumes of produced waste. Microbial Tc(VII) reduction provides an attractive alternative in situ remediation strategy since the reduced end-product Tc(IV) precipitates as TcO2, a highly insoluble hydrous oxide. Despite its potential benefits, the molecular mechanism of microbial Tc(VII) reduction remains poorly understood. The main goal of the proposed DOENABIR research project is to determine the molecular mechanism of microbial Tc(VII) reduction. Random mutagenesis studies in our lab have resulted in generation of a set of six Tc(VII) reduction-deficient mutants of Shewanella oneidensis. The anaerobic respiratory deficiencies of each Tc(VII) reduction-deficient mutant was determined by anaerobic growth on various combinations of three electron donors and 14 terminal electron acceptors. Results indicated that the electron transport pathways to Tc(VII), NO3 -, Mn(III) and U(VI) share common structural or regulatory components. In addition, we have recently found that wild-type Shewanella are also able to reduce Tc(IV) as electron acceptor, producing Tc(III) as an end-product. The recent genome sequencing of a variety of technetium-reducing bacteria and the anticipated release of several additional genome sequences in the coming year, provides us with an unprecedented opportunity to determine the mechanism of microbial technetium reduction across species and genus lines.
Date: April 30, 2013
Creator: DiChristina, Thomas J.
Partner: UNT Libraries Government Documents Department

Exploratory data analysis on data generated in the DOE subsurface microbiology program

Description: The preliminary results from the innovative subsurface microbiology research program indicate that new data on the nature of the link between the geosphere and biosphere have been generated. The diversity of scientific disciplines represented in the subsurface microbiology program reflects the complexity of the system under study. The research carried out by national laboratory and university research scientists is addressing fundamental questions about the abundance of microorganisms and factors controlling microbial activity in the complex subsurface hydrologic and geochemical environment. Long-term implications of this research for mitigating contamination are clear and researchers share the broader objective of linking the basic science with applied work.
Date: June 1, 1990
Creator: Meglen, R.R.
Partner: UNT Libraries Government Documents Department

On preferential flow and its measurement

Description: Preferential flow is a useful generic term for describing the process whereby water movement through a porous medium follows favored routes bypassing other parts of the medium. This term does not give any indication of the pore scales involved. Sometimes macropore flow is used to describe preferential flow and this term implies that large pores of some sort are conductive. There is no consensus definition of what constitutes a macropore so one needs to carefully determine what is meant when that term is used. The main focus of this report is on the measurement and characterization of preferential flow through structured soils, however, preferred path flow also occurs in sandy soils. Fingering flow in soils, a result of wetting front instability, is a third type of preferential flow that occurs in porous media with more or less random pore arrangement. There may not be any physically defined channels in the soil to account for this type of flow. A larger scale flow described as funnel flow by Kung et al. (1990) results from profile heterogeneity. Low permeability layers or coarse lenses in a profile may restrict vertical drainage redirecting flow laterally through specific regions of the profile (like a funnel). Water repellency can also be a factor in the development of preferential flow. 34 refs.
Date: January 1, 1991
Creator: Luxmoore, R.J.
Partner: UNT Libraries Government Documents Department

The role of laboratory analog experiments in assessing the performance of waste package materials

Description: There is an immediate need to begin to validate models that can be used for assessing the performance of waste package materials in an unsaturated repository environment. This paper examines available testing information and testing approaches that could support validation of models for engineering barrier system (EBS) radionuclide release. The content is presented in the context of the general methodology that has been proposed for validating performance assessment models. Available experimental observations are used to test some of the EBS release rate modeling premises. These observations include evidence of fluid film formation on waste glass surfaces in isothermal humid environments, accelerated waste glass reaction rates under repository service conditions of large glass surface area to water volume ratio, and mobilization of radionuclides as solutes and colloids. It is concluded that some important modeling premises may not be consistent with available experimental information. However, it is also concluded that future laboratory testing, which simulates the integrated waste package systems, is needed to evaluate the significance of these inconsistencies and to test the system level models. A small-scale apparatus which was developed and tested to examine the feasibility of laboratory analog testing for the unsaturated Yucca Mountain repository environment is described. 16 refs., 4 figs., 1 tab.
Date: December 31, 1990
Creator: Cunnane, J.C. & Bates, J.K.
Partner: UNT Libraries Government Documents Department

Preliminary assessment of the impact of conceptual model uncertainty on site performance

Description: The US Department of Energy is responsible for the design, construction, operation, and decommission of a site for the deep geologic disposal of high-level radioactive waste (HLW). This involves site characterization and the use of performance assessment to demonstrate compliance with regulations for HLW disposal from the US Environmental Protection Agency (EPA) and the US Nuclear Regulatory Commission. The EPA standard states that a performance assessment should consider the associated uncertainties involved in estimating cumulative release of radionuclides to the accessible environment. To date, the majority of the efforts in uncertainty analysis have been directed toward data and parameter uncertainty, whereas little effort has been made to treat model uncertainty. Model uncertainty includes conceptual model uncertainty, mathematical model uncertainty, and any uncertainties derived from implementing the mathematical model in a computer code. Currently there is no systematic approach that is designed to address the uncertainty in conceptual models. The purpose of this investigation is to take a first step at addressing conceptual model uncertainty. This will be accomplished by assessing the relative impact of alternative conceptual models on the integrated release of radionuclides to the accessible environment for an HLW repository site located in unsaturated, fractured tuff. 4 refs., 2 figs.
Date: October 1, 1990
Creator: Gallegos, D.P.; Pohl, P.I.; Olague, N.E.; Knowlton, R.G. & Updegraff, C.D.
Partner: UNT Libraries Government Documents Department

V-TOUGH: An enhanced version of the TOUGH code for the thermal and hydrologic simulation of large-scale problems in nuclear waste isolation

Description: The TOUGH code developed at Lawrence Berkeley Laboratory (LBL) is being extensively used to numerically simulate the thermal and hydrologic environment around nuclear waste packages in the unsaturated zone for the Yucca Mountain Project. At the Lawrence Livermore National Laboratory (LLNL) we have rewritten approximately 80 percent of the TOUGH code to increase its speed and incorporate new options. The geometry of many problems requires large numbers of computational elements elements in order to realistically model detailed physical phenomena, and, as a result, large amounts of computer time are needed. In order to increase the speed of the code we have incorporated fast linear equation solvers, vectorization of substantial portions of code, improved automatic time stepping, and implementation of table look-up for the steam table properties. These enhancements have increased the speed of the code for typical problems by a factor of 20 on the Cray 2 computer. In addition to the increase in computational efficiency we have added several options: vapor pressure lowering; equivalent continuum treatments of fractures; energy and material volumetric, mass and flux accounting; and Stefan-Boltzmann radiative heat transfer. 5 refs.
Date: November 6, 1989
Creator: Nitao, J.J.
Partner: UNT Libraries Government Documents Department

NNWSI [Nevada Nuclear Waste Storage Investigations] waste form testing at Argonne National Laboratory; Semiannual report, January--June 1988

Description: The Chemical Technology Division of Argonne National Laboratory is performing experiments in support of the waste package development of the Yucca Mountain Project (formerly the Nevada Nuclear Waste Storage Investigations Project). Experiments in progress include (1) the development and performance of a durability test in unsaturated conditions, (2) studies of waste form behavior in an irradiated atmosphere, (3) studies of behavior in water vapor, and (4) studies of naturally occurring glasses to be used as analogues for waste glass behavior. This report documents progress made during the period of January--June 1988. 21 refs., 37 figs., 12 tabs.
Date: April 1990
Creator: Bates, J. K.; Gerding, T. J.; Ebert, W. L.; Mazer, J. J. & Biwer, B. M.
Partner: UNT Libraries Government Documents Department

The underground retrievable storage (URS) high-level waste management concept

Description: This papers presents the concept of long-term underground retrievable storage (URS) of spent reactor fuel in unsaturated rock. Emplacement would be incremental and the system is planned to be experimental and flexible. The rationale for retrievability is examined, and a technical basis for 300-year retrievability is presented. Maximum isolation is the rationale for underground as opposed to surface storage. Although the potential repository site at Yucca Mountain Nevada would be suitable for a URS, alternate sites are discussed. The technical issues involved in licensing a URS for 300 years are simpler than licensing a 10,000 year repository. 16 refs.
Date: February 15, 1991
Creator: Ramspott, L.D.
Partner: UNT Libraries Government Documents Department

Groundwater phenomena and the theory of mixtures

Description: The phenomena of groundwater motion and the recent developments in the Theory of Mixtures are reviewed. Comparisons of these results with those from classical theory are presented. Phenomena of interest that are not well explained are discussed and the potential of the Theory of Mixtures in addressing these phenomena is presented. 16 refs.
Date: January 1, 1991
Creator: Lee, D.W. (Oak Ridge National Lab., TN (USA)) & Wineman, A.S. (Michigan Univ., Ann Arbor, MI (USA). Dept. of Mechanical Engineering and Applied Mechanics)
Partner: UNT Libraries Government Documents Department

Phylogenetic relationships among subsurface microorganisms. Progress report

Description: This project involves the development of group specific 16S ribosomal RNA-targeted oligonucleotide hybridization probes for the rapid detection of specific types of subsurface organisms (e.g., groups of microbes that share certain physiological traits). Major accomplishments for the period of 6/91 to 12/1/91 are described. Nine new probes have been synthesized on the basis of published 16S rRNA sequence data from the Ribosomal Database Project. We have initiated rapid screening of many of the subsurface microbial isolates obtained from the P24 borehole at the Savannah River Site. To date, we have screened approximately 50% of the isolates from P24. We have optimized our {und in situ} hybridization technique, and have developed a cell blot hybridization technique to screen 96 samples on a single blot. This is much faster than reading 96 individual slides. Preliminary experiments have been carried out which indicate specific nutrients can be used to amplify rRNA only in those organisms capable of metabolizing those nutrients. 1 tab., 2 figs.
Date: December 31, 1991
Creator: Nierzwicki-Bauer, S. A.
Partner: UNT Libraries Government Documents Department

Three-dimensional inversion of travel time data for structurally complex geology

Description: Modeling and inversion techniques for the seismic prospecting problem are described. A concisely-parametrized geological model of the site under study is constructed, and the forward problem'' of simulating the effects of shots on this model is solved by ray-tracing. We then use constrained optimization techniques to choose values for the model parameters so that the predicted response to the shots matches the observed response in either the least-squares or least {ell}{sub 1} sense. Numerical experience is reported. 14 refs., 2 figs., 8 tabs.
Date: August 1, 1990
Creator: Pereyra, V. (Weidlinger Associates, Los Altos, CA (USA)) & Wright, S.J. (Argonne National Lab., IL (USA))
Partner: UNT Libraries Government Documents Department

Surfactant screening of diesel-contaminated soil

Description: At one installation, approximately 60,000 gal of No. 2 diesel fuel leaked into the subsurface environment, with contamination at depths of 6 to 34 m below the surface. Argonne National Laboratory was contracted to perform treatability studies for site remediation. The treatability studies focused on four separate phases: (1) leachability studies on the various contaminated soil borings, (2) air stripping studies, (3) bioremediation studies, and (4) surfactant screening/surfactant flooding studies. This paper summarizes the fourth phase of the research program in which twenty-one surfactants were screened for possible use to mobilize the organics from the contaminated soil prior to bioremediation. Anionic surfactants resulted in the greatest degree of diesel mobilization. The most promising surfactants will be employed on actual contaminated soil samples obtained from the site. 18 refs., 16 figs., 1 tab.
Date: January 1, 1990
Creator: Peters, R.W.; Montemagno, C.D.; Shem, L. (Argonne National Lab., IL (USA)) & Lewis, B.A. (Northwestern Univ., Evanston, IL (USA). Dept. of Civil Engineering)
Partner: UNT Libraries Government Documents Department

Earth Sciences Division annual report 1990

Description: This Annual Report presents summaries of selected representative research activities grouped according to the principal disciplines of the Earth Sciences Division: Reservoir Engineering and Hydrogeology, Geology and Geochemistry, and Geophysics and Geomechanics. Much of the Division`s research deals with the physical and chemical properties and processes in the earth`s crust, from the partially saturated, low-temperature near-surface environment to the high-temperature environments characteristic of regions where magmatic-hydrothermal processes are active. Strengths in laboratory and field instrumentation, numerical modeling, and in situ measurement allow study of the transport of mass and heat through geologic media -- studies that now include the appropriate chemical reactions and the hydraulic-mechanical complexities of fractured rock systems. Of particular note are three major Division efforts addressing problems in the discovery and recovery of petroleum, the application of isotope geochemistry to the study of geodynamic processes and earth history, and the development of borehole methods for high-resolution imaging of the subsurface using seismic and electromagnetic waves. In 1989 a major DOE-wide effort was launched in the areas of Environmental Restoration and Waste Management. Many of the methods previously developed for and applied to deeper regions of the earth will in the coming years be turned toward process definition and characterization of the very shallow subsurface, where man-induced contaminants now intrude and where remedial action is required.
Date: June 1, 1991
Partner: UNT Libraries Government Documents Department

In situ changes in the moisture content of heated, welded tuff based on thermal neutron measurements

Description: Thermal neutron logs were collected to monitor changes in moisture content within a welded tuff rock mass heated from a borehole containing an electrical heater which remained energized for 195 days. Thermal neutron measurements were made in sampling boreholes before, during and after heating. The results generally corroborated our conceptual understanding of hydrothermal flow as well as most of the numerical modeling conducting for this study. Conceptual models have been developed in conjunction with the numerical model calculations to explain differences in the drying and re-wetting behavior above and below the heater. Numerical modeling indicated that the re-wetting of the dried-out zone was dominated by the binary diffusion of water vapor through fractures. Saturation gradients in the rock matrix resulted in relative humidity gradients which drove water vapor (primarily along fractures) back to the dried-out zone where it condensed along the fracture walls and was imbibed by the matrix. 4 refs., 28 figs.
Date: July 1, 1991
Creator: Ramirez, A.L.; Carlson, R.C. & Buscheck, T.A.
Partner: UNT Libraries Government Documents Department

Overview of chemical modeling of nuclear waste glass dissolution

Description: Glass dissolution takes place through metal leaching and hydration of the glass surface accompanied by development of alternation layers of varying crystallinity. The reaction which controls the long-term glass dissolution rate appears to be surface layer dissolution. This reaction is reversible because the buildup of dissolved species in solution slows the dissolution rate due to a decreased dissolution affinity. Glass dissolution rates are therefore highly dependent on silica concentrations in solution because silica is the major component of the alteration layer. Chemical modeling of glass dissolution using reaction path computer codes has successfully been applied to short term experimental tests and used to predict long-term repository performance. Current problems and limitations of the models include a poorly defined long-term glass dissolution mechanism, the use of model parameters determined from the same experiments that the model is used to predict, and the lack of sufficient validation of key assumptions in the modeling approach. Work is in progress that addresses these issues. 41 refs., 7 figs., 2 tabs.
Date: February 1, 1991
Creator: Bourcier, W.L.
Partner: UNT Libraries Government Documents Department

Equations for predicting release rates for waste packages in unsaturated tuff

Description: Nuclear waste will be placed in the potential repository at Yucca Mountain in waste packages. Spent fuel assemblies or consolidated fuel rods and borosilicate glass in steel pour canisters will be enclosed in sealed containers. The waste package consists of the waste form, the cladding on spent fuel or the defense-waste pour canister, and the outside container. Current design calls for the waste packages to be surrounded by an air gap. Although the waste package is generally not seen as the primary barrier for nuclear waste isolation it must in fact meet specific regulatory requirements: substantially complete requirement and release-rate from the engineered barrier system [USNRC 1983]. This report gives derivations of equations for predicting releases rates. We consider the release of three types of species: solubility-limited species, species released congruent with solid-solid alteration of spent-fuel matrix or borosilicate glass, and readily soluble species from the fuel-cladding gap, gas plenum, and readily accessible grain boundaries. We develop analytic expressions for the release rates of individual constituents from each of these mechanisms. For a given species and for given parameters, the mechanism that results in the lowest predicted release rate is to be adopted as the rate-controlling mechanism for that species. Some of the equations are newly derived for this report, others are restated from earlier work. Release rates have been calculated for key radionuclides in a companion report. 11 refs., 7 figs.
Date: August 1, 1990
Creator: Sadeghi, M.M.; Pigford, T.H.; Chambre, P.L. & Lee, W.W.L.
Partner: UNT Libraries Government Documents Department

C-14 release and transport from a nuclear waste repository in an unsaturated medium

Description: The release of {sup 14}C as {sup 14}CO{sub 2} from partly failed spent fuel containers has been analyzed by the flow of gases into and out of the containers. This flow of gases is driven by pressure differences, which are in turn caused by heating by the spent fuel. In this analysis, the timing and size of holes in the containers are assumed to be given. A better means of predicting the time distribution and sizes of penetrations in nuclear waste containers is needed. For the purposes of far-field transport calculations, we have adopted release rates that are shown to be bonding for the large range of hole sizes studied. The transport of released {sup 14}CO{sub 2} has been analyzed by transport in equivalent porous medium. The peak {sup 14}CO{sub 2} concentration in pore gas at 350 m above the repository does not depend on the time of hole occurrence, although the time of penetration obviously affects the arrival and duration of exposure to {sup 14}C. Nor does water saturation have much effect on peak concentration. In this analysis we have used a constant gas Darcy velocity. We performed limited sensitivity analysis on gas Darcy velocity by using values one order of magnitude above and below the published value. This probably gives us bounds on the likely gas Darcy velocity. Our calculations show that essentially all the released {sup 14}C will reach the ground surface in less than one half-life of {sup 14}C. However, the quantities of {sup 14}C reaching the ground surface are so small that even if all containers fail at emplacement and conservative dose factors are used, the resultant inhalation dose to the maximally exposed individual is about 0.1% of natural background radiation. 14 refs., 18 figs., 3 tabs.
Date: June 1, 1990
Creator: Light, W.B.; Zwahlen, E.D.; Pigford, T.H.; Chambre, P.L. & Lee, W.W.L.
Partner: UNT Libraries Government Documents Department

A Lagrangian reactive transport simulator with successive paths and stationary-states: Concepts, implementation and verification; Revision 1

Description: A geochemical software package which models static, single-path kinetic water-rock interactions, EQ3/6 has been modified to incorporate successive-paths and stationary states under high Peclet number transport conditions in a Lagrangian reference frame. These modifications permit calculation of reactive transport with reasonable computational requirements. Results from the new option in EQ3/6 have been compared with analytical results for the simple HCl{endash}SiO{sub 2} system; excellent agreements were achieved. Results have also been compared with published results for a portion of the Al{sub 2}O{sub 3}{endash}HCl{endash}K{sub 2}O{endash}SiO{sub 2} system. The results are in good qualitative and, in some cases, good quantitative agreement. However, the values of some variables differ substantially; these differences can be attributed to use of a different set of Al and Si aqueous species. 16 refs., 12 figs., 3 tabs.
Date: September 1, 1989
Creator: Knapp, R.B.
Partner: UNT Libraries Government Documents Department

Quantifying Silica Reactivity in Subsurface Environments: Reaction Affinity and Solute Matrix Controls on Quartz and SiO2 Glass Dissolution Kinetics

Description: During the three years of this project, Professor Dove's laboratory made tremendous progress in understanding controls on amorphous silica dissolution kinetics in aqueous solutions. Our findings have already received considerable attention. In hydrothermal and low temperature studies, the work focused on determining quantitative and mechanistic controls on the most abundant silica polymorphs in Earth environments--quartz and amorphous silica. Our studies achieved goals set forth in the original proposal to establish a new quantitative understanding of amorphous silica dissolution. This support has resulted in 10 journal, 12 abstracts and 2 thesis publications. The PI and students were also recognized with 6 awards during this period. The 1998 EMSP conference in Chicago was an important meeting for our project. The symposium, enabled P.I. Dove to establish valuable contacts with ''users'' having specific needs for the findings of our EMSP project related to the urgency of problems in the Tanks Focus Area (TFA). Since that time, our working relations developed as Dove interacted with TFA scientists and engineers on the problems of waste glass properties. These interactions refined our experimental objectives to better meet their needs. Dove presented the results of EMSP research findings to a TFA subgroup at a Product Acceptance Workshop held in Salt Lake City during December 1998. The travel costs to attend this unanticipated opportunity were paid from EMSP project funds. In January 2000, Dove also attended a similar meeting in Atlanta with PNNL, SRL and BNF scientists/engineers to discuss new issues and make another level of decisions on the Product Acceptance goals. Our EMSP-funded research interfaced very well with the ongoing studies of Dr. Pete McGrail and colleagues in the Applied Geochemistry Group at PNNL. The value of our work to ''users'' was further demonstrated when Dove's EMSP-funded Postdoc, Dr. Jonathan Icenhower was hired by the same PNNL ...
Date: December 13, 2000
Creator: Dove, Patricia M.
Partner: UNT Libraries Government Documents Department

Advances in downhole sampling of high temperature solutions

Description: A fluid sampler capable of sampling hot and/or deep wells has been developed at Los Alamos National Laboratory. In collaboration with Leutert Instruments, an off-the-shelf sampler design was modified to meet gas-tight and minimal chemical reactivity/contamination specifications for use in geothermal wells and deep ocean drillholes. This downhole sampler has been routinely used at temperatures up to 300{degrees}C and hole depths of greater than 5 km. We have tested this sampler in various continental wells, including Valles Caldera VC-2a and VC-2b, German KTB, Cajon Pass, and Yellowstone Y-10. Both the standard commercial and enhanced samplers have also been used to obtain samples from a range of depths in the Ocean Drilling Project's hole 504B and during recent mid-ocean ridge drilling efforts. The sampler has made it possible to collect samples at temperatures and conditions beyond the limits of other tools with the added advantage of chemical corrosion resistance.
Date: January 1, 1991
Creator: Bayhurst, G.K. & Janecky, D.R.
Partner: UNT Libraries Government Documents Department

Imaging of reservoirs and fracture systems using microearthquakes induced by hydraulic injections

Description: Predicting the future performance of a geothermal reservoir and planning a strategy for increasing productivity from the reservoir require an intimate knowledge of the fracture system through which geothermal fluids permeate. Microearthquakes often accompany hydraulic fracturing as well as normal production activities in geothermal fields. The waveforms from the se microearthquakes provide valuable information that can be used to infer the three-dimensional structure of the fracture system in the reservoir. The locations of the microearthquakes can be used to infer the presence of large fractures along which shear slip has occurred. Tomographic imaging using arrival times of the seismic waves, provides a three-dimensional image of the P and S wave velocity structure of the reservoir. These velocities yield information about the presence of microfractures in the rock. Waveform stacking methods can be used to both corroborate seismic velocities and image seismic scatters in the reservoir. The most prominent seismic scatters are likely to be fluid-filled fractures. Thus, seismic data provide information about a fractures over a large scale range which can be of use in reservoir engineering. 32 refs., 4 figs.
Date: January 1, 1991
Creator: Fehler, M.; House, L.; Phillips, W.S. (Los Alamos National Lab., NM (USA)); Block, L. & Cheng, C.H. (Massachusetts Inst. of Tech., Cambridge, MA (USA). Earth Resources Lab.)
Partner: UNT Libraries Government Documents Department

HYDROGEOCHEM: A coupled model of HYDROlogic transport and GEOCHEMical equilibria in reactive multicomponent systems

Description: This report presents the development of a hydrogeochemical transport model for multicomponent systems. The model is designed for applications to proper hydrological setting, accommodation of complete suite of geochemical equilibrium processes, easy extension to deal with chemical kinetics, and least constraints of computer resources. The hydrological environment to which the model can be applied is the heterogeneous, anisotropic, saturated-unsaturated subsurface media under either transient or steady state flow conditions. The geochemical equilibrium processes included in the model are aqueous complexation, adsorption-desorption, ion exchange, precipitation-dissolution, redox, and acid-base reactions. To achieve the inclusion of the full complement of these geochemical processes, total analytical concentrations of all chemical components are chosen as the primary dependent variables in the hydrological transport equations. Attendant benefits of this choice are to make the extension of the model to deal with kinetics of adsorption-desorption, ion exchange, precipitation-dissolution, and redox relatively easy. To make the negative concentrations during the iteration between the hydrological transport and geochemical equilibrium least likely, an implicit form of transport equations are proposed. To alleviate severe constraints of computer resources in terms of central processing unit (CPU) time and CPU memory, various optional numerical schemes are incorporated in the model. The model consists of a hydrological transport module and geochemical equilibrium module. Both modules were thoroughly tested in code consistency and were found to yield plausible results. The model is verified with ten examples. 79 refs., 21 figs., 17 tabs.
Date: November 1, 1990
Creator: Yeh, G.T. & Tripathi, V.S.
Partner: UNT Libraries Government Documents Department

Sampling plans for site characterization

Description: The problem of characterizing a subsurface site, whether it be a candidate for mineral extraction, a potential waste repository or a site designated for cleanup, is in mathematical terms seriously undetermined. That is, the number of observations that can be made prior to major decisions about the site's future is a very small fraction of what would be needed to determine the complete spatial distribution of such distributed properties as mineral or contaminant concentrations, transmissivity, or density. The geostatistical procedures that have been developed to handle these problems are methods of regularization which identify a unique solution by including additional information, such as an estimated spatial covariance model. Kriging, in particular, is best linear unbiased prediction (BLUP) within a superpopulation model for the spatial distribution. Explicit recognition of the inverse structure of the problem and the associated BLUP formulations are particularly useful in developing and presenting field sampling plans based both on prior information and on the proposed use of resulting information. This framework also facilitates consideration of model-robustness of the optimality of proposed sampling plans, which is important in the context of site characterization problems where poorly determined priors are a prominent feature. 10 refs.
Date: January 1, 1990
Creator: Campbell, K.
Partner: UNT Libraries Government Documents Department

Pacific Northwest Laboratory annual report for 1987 to the DOE office of energy research: Part 2, Environmental sciences

Description: This report summarizes progress in environmental sciences research conducted by Pacific Northwest Laboratory (PNL) for the Office of Health and Environmental Research in FY 1987. Research is directed toward developing a fundamental understanding of processes controlling the long-term fate and biological effects of fugitive chemicals and other stressors resulting from energy development. The research, focused on terrestrial, subsurface, and coastal marine systems, forms the basis for defining and quantifying processes that affect humans and the environment at the regional and global levels. Research is multidisciplinary and multitiered, providing integrated system-level insights into critical environmental processes. Research initiatives in subsurface microbiology and transport, global change, radon, and molecular sciences are building on PNL technical strengths in biogeochemistry, hydrodynamics, molecular biology, and theoretical ecology. Unique PNL facilities are used to probe multiple phenomena complex relationships at increasing levels of complexity. Intermediate-scale experimental systems are used to examine arid land watershed dynamics, aerosol behavior and effects, and multidimensional subsurface transport. In addition, field laboratories (the National Environmental Research Park and Marine Research Laboratory) are used in conjunction with advanced measurement techniques to validate concepts and models, and to extrapolate the results to the system and global levels. Strong university liaisons now in existence are being markedly expanded so that PNL resources and the specialized technical capabilities in the university community can be more efficiently integrated.
Date: July 1, 1988
Partner: UNT Libraries Government Documents Department