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Abiotic degradation rates for carbon tetrachloride and chloroform: Final report.

Description: This report documents the objectives, technical approach, and progress made through FY 2012 on a project initiated in FY 2006 to help address uncertainties related to the rates of hydrolysis in groundwater for carbon tetrachloride (CT) and chloroform (CF). The project also sought to explore the possible effects of contact with minerals and sediment (i.e., heterogeneous hydrolysis) on these rates. We conducted 114 hydrolysis rate experiments in sealed vessels across a temperature range of 20-93 °C for periods as long as 6 years, and used the Arrhenius equation to estimate activation energies and calculate half-lives for typical Hanford groundwater conditions (temperature of 16 °C and pH of 7.75). We calculated a half-life of 630 years for hydrolysis for CT under these conditions and found that CT hydrolysis was unaffected by contact with sterilized, oxidized minerals or Hanford sediment within the sensitivity of our experiments. In contrast to CT, hydrolysis of CF was generally slower and very sensitive to pH due to the presence of both neutral and base-catalyzed hydrolysis pathways. We calculated a half-life of 3400 years for hydrolysis of CF in homogeneous solution at 16 °C and pH 7.75. Experiments in suspensions of Hanford sediment or smectite, the dominant clay mineral in Hanford sediment, equilibrated to an initial pH of 7.2, yielded calculated half-lives of 1700 years and 190 years, respectively, at 16 °C. Experiments with three other mineral phases at the same pH (muscovite mica, albite feldspar, and kaolinite) showed no change from the homogeneous solution results (i.e., a half-life of 3400 years). The strong influence of Hanford sediment on CF hydrolysis was attributed to the presence of smectite and its ability to adsorb protons, thereby buffering the solution pH at a higher level than would otherwise occur. The project also determined liquid-vapor partition coefficients for CT under ...
Date: December 1, 2012
Creator: Amonette, James E.; Jeffers, Peter M.; Qafoku, Odeta; Russell, Colleen K.; Humphrys, Daniel R.; Wietsma, Thomas W. et al.
Partner: UNT Libraries Government Documents Department

Fixed-fugacity option for the EQ6 geochemical reaction path code

Description: EQ3/6 is a software package used to model aqueous geochemical systems. The EQ6 code allows reaction paths of dynamic systems to be calculated. This report describes a new option for the EQ6 computer program that permits the fugacity of any gas in the EQ6 data base to be set to a fixed value. This capability permits simulation of the effect of rapid chemical exchange with a large external gas reservoir by allowing the user to fix the fugacities of selected gas species. Geochemical environments such as groundwater systems open to the atmosphere (e.g., the unsaturated zone), natural aqueous systems that form closed systems at depth, and experimental systems that use controlled atmospheres can be modeled. Two of the principal geochemical weathering agents, CO{sub 2} and O{sub 2}, are the most likely gas species for which this type of exchange may be important. An example of the effect of constant CO{sub 2} fugacity on both open and closed systems is shown for the case of albite dissolution (NaAlSi{sub 3}O{sub 8}) in distilled water. This example demonstrates that the effects of imposed fugacities on geochemical systems can be considerable. This computer code is used in the Nevada Nuclear Waste Storage Investigations Project. 15 refs., 8 figs.
Date: December 20, 1984
Creator: Delany, J.M. & Wolery, T.J.
Partner: UNT Libraries Government Documents Department

Characterization of surface processes on mineral surfaces in aqueous solutions. Annual report for fiscal year 1993

Description: Performance assessments by Los Alamos National Laboratory for the DOE`s Yucca Mountain Site Characterization Project (YMP) are being done investigating the environmental risk related to long-term disposal of hazardous wastes resulting from the use of radioactive materials that must subsequently be isolated from the environment. The YMP site, located in southwestern Nevada, is intended for the storage of high-level wastes generated by nuclear energy-related activities, including spent fuel and waste from reprocessed fuel rods. The work covered by this contract is necessary for producing a defensible model and dataset, and may be critical for evaluation of repository compliance. This work, performed by the Environmental Engineering and Science research group at Stanford University, will quantify the adsorption of uranyl on various minerals. The project`s principle objective is to provide sorption coefficients for uranyl and other ions of interest to predict radionuclide movements form the repository to accessible environments. This adsorption data is essential for the unambiguous interpretation of field experiments and observations. In this report, details of the activity and progress made with respect to the study of uranyl adsorption on mineral surfaces is presented and discussed.
Date: November 1, 1993
Creator: Leckie, J.O.
Partner: UNT Libraries Government Documents Department

Neptunium(V) sorption on quartz and albite in aqueous suspension; Annual progress report

Description: The behavior of neptunium in the subsurface environment is of interest since neptunium isotopes are included in nuclear waste. Previous work investigated the sorption behavior of Np onto {alpha}-Fe{sub 2}O{sub 3} (hematite), an accessory mineral of the Yucca Mountain repository. The work reported herein involves the much more abundant silicate minerals quartz and albite, and is a logical continuation of the ongoing task. In previous work increased sorption was observed in systems containing hematite and EDTA, a ligand which acts as a surrogate for organic complexing agents. In addition, increased partial pressures of CO{sub 2} are common in many ground waters and the effects of carbonate on sorption of radionuclides have to be studied as well. At concentration levels of 10{sup {minus}7} M, Np(V) does not adsorb strongly on quartz and albite up to pH values of approximately 9 at solid/solution ratios of 30 to 40 g/l. Significant adsorption (> 20%) occurs on both minerals only at pH > 9. Pretreatment of albite affects the sorption behavior of this mineral at pH > 9, possibly due to the formation of secondary mineral phases at the albite surface. EDTA does not adsorb on quartz at concentrations of 10{sup {minus}6} M. In the presence of 50 {mu}M EDTA, Np(V) sorption seems to be restricted. EDTA at the 10{sup {minus}6} M level adsorbs onto albite to an appreciable degree at pH values < 7.5. One {mu}M EDTA has no effect on Np(V) adsorption onto albite. Carbonate species adsorb on quartz and albite, both cases showing a maximum in sorption at pH 6.5 to 7 where HCO{sub 3}{sup {minus}} is the predominant solution species.
Date: October 1, 1991
Creator: Kohler, M. & Leckie, J.O.
Partner: UNT Libraries Government Documents Department

Reactive fluid flow models and applications to diagenesis, mineral deposits and crustal rocks

Description: This project is obtaining new results and developing new techniques along three directions: (a) experimental studies of water-rock reactions (b) theoretical modeling of coupled fluid flow-chemical reactions and (c) isotopic measurements of both regional isotopic compositions as well as isotopic zoning within individual mineral grains. An important part of the project is the integration of all three approaches into a concerted effort aimed at new understanding of the behavior of fluids and their chemical reactions with minerals in the crust. The experimental work pioneered in our laboratories has produced several startling results on the kinetic rate laws of silicate-water reactions. The approach to equilibrium has been shown to follow a non-linear path in rate constant-free energy space. This behavior is quite distinct from most work done by geochemists on modeling silicate behavior in diagenesis, weathering, hydrothermal systems or environmental models. The work to date has involved albite, kaolinite and gibbsite, which together with silica would comprise a kinetic granite system prototype''. The theoretical modeling has produced a state-of-the-art computer code that can efficiently handle dozens of chemical species, many mineral reactions and variations of fluid flow properties and temperature in both one and two dimensions. In addition the code can now treat oxidation-reduction reactions and isotopic exchange between fluids and minerals. The main thrust of the theoretical modeling has been to develop further the differences between equilibrium, steady state, and non-steady-state behavior of the chemical evolution of open fluid-rock systems. These differences have not been fully appreciated in previous models.
Date: January 1, 1992
Creator: Lasaga, A.C. & Rye, D.M.
Partner: UNT Libraries Government Documents Department

Experimental alteration of a granodiorite in a circulation system

Description: Reaction of granodiorite from the Fenton Hill Hot Dry Rock Geothermal Site with distilled water at 300/sup 0/C and 345 bars total pressure for 8 months has produced many morphological and chemical effects. Eight polished rock disks were mounted on a tantalum pedestal inside a 500 ml autoclave. The autoclave is part of a circulation system designed for operation to 400/sup 0/C and 345 bars. Solution samples were taken at 32, 56, 176, 368, 752, 1544, 3104, and 5816 hr. Rock disks were removed also at the latter four times. The reactivity of phases was found to be quartz/microcline/plagioclase/mafics, opaques and trace phases. Quartz was removed congruently. The albite component of the plagioclase was dissolved essentially congruently changing plagioclase from oligoclase (fresh) to bytownite (8 mo.). Microcline showed congruent dissolution. Other phases were inert. Secondary mineralization included phillipsite, thomosonite, and vermiculite.
Date: January 1, 1978
Creator: Charles, R.W.
Partner: UNT Libraries Government Documents Department

Hydrothermal alteration at the Roosevelt Hot Springs Thermal Area, Utah. Final report

Description: Hot spring deposits in the Roosevelt thermal area consist of opaline sinter, and siliceous-sinter-cemented alluvium. Alluvium, granite to granodiorite plutonic rocks, and amphibolite facies gneiss have been altered by acid-sulfate water to alunite and opal at the surface, and to kaolinite, alunite, montmorillonite, and muscovite to a depth of 60 m. Marcasite and pyrite occur below the water table at about 30m. Deeper alteration sampled to a depth of 2.26 km consists of muscovite, chlorite, calcite, K-feldspar, albite, and epidote with pyrite and sparse chalcopyrite. Thermal water is dilute (ionic strength 0.1 to 0.2) sodium chloride brine. Surface water contains 10 times as much calcium and 100 times as much magnesium as the deep water. Sulfate varies from 48 to 200 mg/l. Present-day spring temperature is 25/sup 0/C but in 1950 the spring temperature was 85/sup 0/C. Computed Na-K-Ca temperature is 241/sup 0/C for the present-day spring, 274/sup 0/C for a well and 283/sup 0/C for the 1957 spring. Quartz saturation temperatures are 170/sup 0/C for the present-day spring, 283/sup 0/C for the well, and 213/sup 0/C for the 1957 spring. A plausible model for development of the near-surface alteration consists of hydrothermal fluid which convectively rises along major fractures. Water cools by conduction and steam separation, and hydrogen ion is produced by oxidation of hydrogen sulfide. The low pH water percolates from the surface downward and reacts with rocks to produce alunite, kaolinite, montmorillonite, and muscovite as hydrogen is consumed.
Date: November 1, 1978
Creator: Parry, W.T.; Bryant, N.L.; Dedolph, R.E.; Ballantyne, J.M.; Ballantyne, G.H.; Rohrs, D.T. et al.
Partner: UNT Libraries Government Documents Department

Use of precalciners to remove alkali from raw material in the cement industry. Quarterly technical progress report, May-June 1979

Description: Tests were made to determine the best method for volatilizing the alkalis in high-alkali clays, feldspars, and similar argillaceous materials. MgCl/sub 2/ was more effective in removing alkalis from feldspars than from the other minerals. Reducing conditions (graphite + CaCO/sub 3//CaCl/sub 2/) increased alkali volatility slightly exept in the case of illite. Water vapor had a negative effect. FeCl/sub 3/.6H/sub 2/O is not a very effective additive. Alkalis can be removed rapidly by heating to 1450/sup 0/C. (DLC)
Date: August 1, 1979
Creator: Gartner, E.M.
Partner: UNT Libraries Government Documents Department

Experimental geothermal loop: I, 295/sup 0/C study

Description: Reaction of granodiorite from the Fenton Hill Hot Dry Rock Geothermal Site with distilled water at 300/sup 0/C and 345 bars total pressure for 8 months has produced many morphological and chemical effects. Eight polished rock disks were mounted on a tantalum pedestal inside a 500-ml autoclave. The autoclave is part of a circulation system designed for operation to 400/sup 0/C and 345 bars. Solution samples were taken at 32, 56, 176, 368, 752, 1544, 3104, and 5816 h. Rock disks were removed also at the latter four times. The reactivity of phases was shown to be quartz>>microcline>plagioclase>mafics, opaques, and trace phases. Quartz was removed congruently. The albite component of the plagioclase was dissolved essentially congruently changing plagioclase from oligoclase (fresh) to bytownite (8 mo.). Microcline showed congruent dissolution. Other phases were inert. Secondary mineralization included phillipsite, thomsonite, and vermiculite.
Date: July 1, 1978
Creator: Charles, R.W.
Partner: UNT Libraries Government Documents Department

Chemical reactions in the bedrock-groundwater system of importance for the sorption of actinides

Description: Most suggested alternatives for deep underground disposal of high-level radioactive wastes rely upon several independent barriers like resistant canister materials, waste forms of low solubility in groundwaters and the use of back-fill material of low permeability and with nuclide retaining capacity. These barriers would retard the eventual release of radionuclides from the repository into the groundwater/bedrock system. The final and the only non-engineered barrier would be the host-rock itself. It would be desirable if the rock alone would be able to retain the long-lived radionuclides coming from the waste for long enough times to allow decay to harmless activity levels before they might reach the biosphere. The biological hazards from high-level reprocessng waste as well as from unreprocessed spent uranium fuel are dominated by the actinides and their daughter products (americium, plutonium, neptunium, thorium, radium) from about three hundred years after discharge from the reactor up to millions of years. In order to allow predictions of the migration of the actinides in the ground, the chemical behavior of these elements in groundwater under environmental conditions and their interactions with geologic media must be studied in detail. In this paper, studies of the sorption of americium (trivalent) and neptunium (pentavalent under oxic conditions) on some major rock-forming minerals of igneous rocks and accessory minerals are reported.
Date: January 1, 1979
Creator: Beall, G.W.; Allard, B.; Krajewski, T. & O'Kelley, G.D.
Partner: UNT Libraries Government Documents Department

Development of models for use in the assessment of waste repository performance

Description: Any repository suitable for the disposal of radioactive waste comprises a combination of various man-made and natural barriers which aim to prevent transfer of the radionuclides from the canister to the external environment. Our group has developed the techniques needed to model the equilibrium chemistry of complex multicomponent rock/water systems over a range of ionic strengths and temperatures. These models, show remarkable agreement with field measurements when applied to natural systems. They have been applied successfully to interpret a variety of geochemical processes: studies of ancient and modern marine evaporite systems, studies of the solar evaporation of seawater studies of mineral formation in lakes and in fluid inclusions. At present our models are limited to the components of the seawater system (Na{sup +}, Mg{sup 2+}, Ca{sup 2+}, H{sup +}, SO{sub 4}{sup 2{minus}}, HCO{sub 3}{sup {minus}}, CO{sub 3}{sup 2{minus}}, CO{sub 2}), together with the borate species and SiO{sub 2}. 2 tabs.
Date: September 30, 1989
Creator: Dickson, A.G. (Scripps Institution of Oceanography, San Diego, CA (USA). Marine Physical Lab.) & Weare, J.H. (California Univ., San Diego, La Jolla, CA (USA). Dept. of Chemistry)
Partner: UNT Libraries Government Documents Department

Fundamental geosciences program. Annual report, 1977

Description: The geoscience program relating to geothermal energy consists of four projects. In the project on reservoir dynamics, sophisticated codes have been written to simulate the dynamics of heat flow in geothermal reservoir systems. These codes have also been applied to the investigations of natural aquifers as a storage system for thermal energy. In the second project, core samples are studied to determine the high temperature and high pressure behavior of aquifers in the presence of saturating fluids. The third project covers the systematic evaluation of the thermodynamic properties of electrolytes in order to interpret the behavior of geothermal fluids. The fourth project involves hydrothermal solubility measurements of various minerals to elucidate the chemistry and mass transfer in geothermal systems. The second major program includes four projects which involve precise measurements and analysis of physical and chemical properties of geologic materials. These include measurements of the thermodynamic properties (viscosity, density and heat capacity) of silicate materials to help understand magma genesis and evolution, high-precision neutron activation analysis of rare and trace elements in magmatic materials, and the precise measurement of seismic wave velocities near geological faults, in order to determine the buildup of stress in the earth's crust. Third, the development program in fundamental geosciences includes six innovative projects. These projects include research in the in situ leaching of uranium ore, properties of magmas, removal of pyrite from coal, properties of soils and soft rocks, stress flow behavior of fractured rock systems, and high-precision mass spectrometry.
Date: January 1, 1977
Creator: Witherspoon, P.A. & Apps, J.A.
Partner: UNT Libraries Government Documents Department