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General Report of Stable Isotope Separation

Description: Abstract: "The Calutron has been successfully employed to separate the stable isotopes of twenty-one elements. The standard Beta M-2 unit modified to handle charge materials of various temperature ranges has proven adequate for a majority of separations. The problem of K life has received considerable attention but is still to be solved. Other operational problems are similar in most respects to those of uranium. The E design has, of necessity, varied greatly from the "Beta Gloria" type. A desire to keep construction simple, yet adequate for efficient collection and readily adaptable for use with many elements, has dictated the trend in E design. Water cooling on the receiver pockets was necessary with many of the elements separated. The chemical purification of the separated samples, although following a general pattern, varies with the type of pockets used and the element collected."
Date: January 20, 1947
Creator: Ketler, W. R.; Chelius, L. G. & Keim, C. P.
Partner: UNT Libraries Government Documents Department

Infrared Spectroscopy and Stable Isotope Geochemistry of Hydrous Silicate Glasses

Description: The focus of this DOE-funded project has been the study of volatile components in magmas and the atmosphere. Over the twenty-one year period of this project, we have used experimental petrology and stable isotope geochemistry to study the behavior and properties of volatile components dissolved in silicate minerals and melts and glasses. More recently, we have also studied the concentration and isotopic composition of CO2 in the atmosphere, especially in relation to air quality issues in the Los Angeles basin.
Date: March 5, 2007
Creator: Stolper, Edward
Partner: UNT Libraries Government Documents Department

Chromium isotopes as indicators of hexavalent chromium reduction

Description: This is the final report for a university research project which advanced development of a new technology for identifying chemical reduction of hexavalent chromium contamination in groundwater systems. Reduction renders mobile and toxic hexavalent chromium immobile and less toxic. The new method uses stable isotope ratio measurements, which are made using multicollector ICP-mass spectrometry. The main objectives of this project were completed during the project period and two peer-reviewed articles were published to disseminate the information gained.
Date: March 20, 2012
Creator: Johnson, Thomas M.
Partner: UNT Libraries Government Documents Department

Final Project Report: "€œExploratory Research: Mercury Stable Isotopes as Indicators of the Biogeochemical Cycling of Mercury"€

Description: This is the final project report for award DE-SC0005351, which supported the research project "€œExploratory Research: Mercury Stable Isotopes as Indicators of the Biogeochemical Cycling of Mercury."€ This exploratory project investigated the use of mercury (Hg) stable isotope measurements as a new approach to study how Hg moves and changes its chemical form in environmental systems, with particular focus on the East Fork of Poplar Creek (EFPC) near the DOE Y-12 plant (a Hg contamination source). This study developed analytical methods and collected pilot data that have set the stage for more detailed studies and have begun to provide insights into Hg movement and chemical changes. The overall Hg stable isotope approach was effective. The Hg isotope analysis methods yielded high-precision measurements of the sediment, water, and fish samples analyzed; quality control measures demonstrated the precision. The pilot data show that the 202Hg/198Hg, 199Hg/198Hg, and 201Hg/198Hg isotope ratios vary in this system. 202Hg/198Hg ratios of the Hg released from the Y-12 plant are relatively high, and those of the regional Hg background in soils and river sediments are significantly lower. Unfortunately, 202Hg/198Hg differences that might have been useful to distinguish early Hg releases from later releases were not observed. However, 202Hg/198Hg ratios in sediments do provide insights into chemical transformations that may occur as Hg moves through the system. Furthermore, 199Hg/198Hg and 201Hg/198Hg ratio analyses of fish tissues indicate that the effects of sunlight-driven chemical reactions on the Hg that eventually ends up in EFPC fish are measureable, but small. These results provide a starting point for a more detailed study (already begun at Univ. of Michigan) that will continue Hg isotope ratio work aimed at improving understanding of how Hg moves, changes chemically, and does or does not take on more highly toxic forms in the Oak Ridge area. ...
Date: August 1, 2012
Creator: Johnson, Thomas M
Partner: UNT Libraries Government Documents Department

Investigations of (Delta)14C, (delta)13C, and (delta)15N in vertebrae of white shark (Carcharodon carcharias) from the eastern North Pacific Ocean

Description: The white shark (Carcharodon carcharias) has a complex life history that is characterized by large scale movements and a highly variable diet. Estimates of age and growth for the white shark from the eastern North Pacific Ocean indicate they have a slow growth rate and a relatively high longevity. Age, growth, and longevity estimates useful for stock assessment and fishery models, however, require some form of validation. By counting vertebral growth band pairs, ages can be estimated, but because not all sharks deposit annual growth bands and many are not easily discernable, it is necessary to validate growth band periodicity with an independent method. Radiocarbon ({sup 14}C) age validation uses the discrete {sup 14}C signal produced from thermonuclear testing in the 1950s and 1960s that is retained in skeletal structures as a time-specific marker. Growth band pairs in vertebrae, estimated as annual and spanning the 1930s to 1990s, were analyzed for {Delta}{sup 14}C and stable carbon and nitrogen isotopes ({delta}{sup 13}C and {delta}{sup 15}N). The aim of this study was to evaluate the utility of {sup 14}C age validation for a wide-ranging species with a complex life history and to use stable isotope measurements in vertebrae as a means of resolving complexity introduced into the {sup 14}C chronology by ontogenetic shifts in diet and habitat. Stable isotopes provided useful trophic position information; however, validation of age estimates was confounded by what may have been some combination of the dietary source of carbon to the vertebrae, large-scale movement patterns, and steep {sup 14}C gradients with depth in the eastern North Pacific Ocean.
Date: June 8, 2006
Creator: Kerr, L A; Andrews, A H; Cailliet, G M; Brown, T A & Coale, K H
Partner: UNT Libraries Government Documents Department

Annual Growth Bands in Hymenaea courbaril

Description: One significant source of annual temperature and precipitation data arises from the regular annual secondary growth rings of trees. Several tropical tree species are observed to form regular growth bands that may or may not form annually. Such growth was observed in one stem disk of the tropical legume Hymenaea courbaril near the area of David, Panama. In comparison to annual reference {Delta}{sup 14}C values from wood and air, the {Delta}{sup 14}C values from the secondary growth rings formed by H. courbaril were determined to be annual in nature in this one stem disk specimen. During this study, H. courbaril was also observed to translocate recently produced photosynthate into older growth rings as sapwood is converted to heartwood. This process alters the overall {Delta}{sup 14}C values of these transitional growth rings as cellulose with a higher {Delta}{sup 14}C content is translocated into growth rings with a relatively lower {Delta}{sup 14}C content. Once the annual nature of these growth rings is established, further stable isotope analyses on H. courbaril material in other studies may help to complete gaps in the understanding of short and of long term global climate patterns.
Date: February 9, 2004
Creator: Westbrook, J A; Guilderson, T P & Colinvaux, P A
Partner: UNT Libraries Government Documents Department

Temperature and vital effect controls on Bamboo coral (Isididae) isotopegeochemistry: A test of the "lines method"

Description: Deep-sea bamboo corals hold promise as long-term climatic archives, yet little information exists linking bamboo coral geochemistry to measured environmental parameters. This study focuses on a suite of 10 bamboo corals collected from the Pacific and Atlantic basins (250-2136 m water depth) to investigate coral longevity, growth rates, and isotopic signatures. Calcite samples for stable isotopes and radiocarbon were collected from the base the corals, where the entire history of growth is recorded. In three of the coral specimens, samples were also taken from an upper branch for comparison. Radiocarbon and growth band width analyses indicate that the skeletal calcite precipitates from ambient dissolved inorganic carbon and that the corals live for 150-300 years, with extension rates of 9-128 {micro}m/yr. A linear relationship between coral calcite {delta}{sup 18}O and {delta}{sup 13}C indicates that the isotopic composition is influenced by vital effects ({delta}{sup 18}O:{delta}{sup 13}C slope of 0.17-0.47). As with scleractinian deep-sea corals, the intercept from a linear regression of {delta}{sup 18}O versus {delta}{sup 13}C is a function of temperature, such that a reliable paleotemperature proxy can be obtained, using the 'lines method.' Although the coral calcite {delta}{sup 18}O:{delta}{sup 13}C slope is maintained throughout the coral base ontogeny, the branches and central cores of the bases exhibit {delta}{sup 18}O:{delta}{sup 13}C values that are shifted far from equilibrium. We find that a reliable intercept value can be derived from the {delta}{sup 18}O:{delta}{sup 13}C regression of multiple samples distributed throughout one specimen or from multiple samples within individual growth bands.
Date: March 1, 2011
Creator: Hill, T M; Spero, H J; Guilderson, T P; LaVigne, M; Clague, D; Macalello, S et al.
Partner: UNT Libraries Government Documents Department

High-resolution metagenomics targets major functional types in complex microbial communities

Description: Most microbes in the biosphere remain uncultured and unknown. Whole genome shotgun (WGS) sequencing of environmental DNA (metagenomics) allows glimpses into genetic and metabolic potentials of natural microbial communities. However, in communities of high complexity metagenomics fail to link specific microbes to specific ecological functions. To overcome this limitation, we selectively targeted populations involved in oxidizing single-carbon (C{sub 1}) compounds in Lake Washington (Seattle, USA) by labeling their DNA via stable isotope probing (SIP), followed by WGS sequencing. Metagenome analysis demonstrated specific sequence enrichments in response to different C{sub 1} substrates, highlighting ecological roles of individual phylotypes. We further demonstrated the utility of our approach by extracting a nearly complete genome of a novel methylotroph Methylotenera mobilis, reconstructing its metabolism and conducting genome-wide analyses. This approach allowing high-resolution genomic analysis of ecologically relevant species has the potential to be applied to a wide variety of ecosystems.
Date: August 1, 2009
Creator: Kalyuzhnaya, Marina G.; Lapidus, Alla; Ivanova, Natalia; Copeland, Alex C.; McHardy, Alice C.; Szeto, Ernest et al.
Partner: UNT Libraries Government Documents Department

Phase Preference by Active, Acetate-Utilizing Bacteria at the Rifle, CO Integrated Field Research Challenge Site

Description: Previous experiments at the Rifle, Colorado Integrated Field Research Challenge (IFRC) site demonstrated that field-scale addition of acetate to groundwater reduced the ambient soluble uranium concentration. In this report, sediment samples collected before and after acetate field addition were used to assess the active microbes via {sup 13}C acetate stable isotope probing on 3 phases [coarse sand, fines (8-approximately 150 {micro}m), groundwater (0.2-8 {micro}m)] over a 24-day time frame. TRFLP results generally indicated a stronger signal in {sup 13}C-DNA in the 'fines' fraction compared to the sand and groundwater. Before the field-scale acetate addition, a Geobacter-like group primarily synthesized {sup 13}C-DNA in the groundwater phase, an alpha Proteobacterium primarily grew on the fines/sands, and an Acinetobacter sp. and Decholoromonas-like OTU utilized much of the {sup 13}C acetate in both groundwater and particle-associated phases. At the termination of the field-scale acetate addition, the Geobacter-like species was active on the solid phases rather than the groundwater, while the other bacterial groups had very reduced newly synthesized DNA signal. These findings will help to delineate the acetate utilization patterns of bacteria in the field and can lead to improved methods for stimulating distinct microbial populations in situ.
Date: February 21, 2011
Creator: Kerkhof, L.; Williams, K.H.; Long, P.E. & McGuinness, L.
Partner: UNT Libraries Government Documents Department

Thermal-neutron capture in light nuclei

Description: We have made considerable progress toward the goal of carrying out thermal-neutron capture {gamma}-ray measurements on all stable isotopes below A=60. Information processed till now has significantly augmented the existing knowledge on the detailed nuclear level structure of many light nuclides. Most of this knowledge comes from our {gamma}-ray energies, level placements, and branching ratios of secondary transitions between low-lying states. Spectroscopic information is also contained in the cross sections of the primary transitions originating from the capturing state. This is deduced from the success of ``direct`` theories of neutron capture for many nuclides, especially those of light and near closed-shell character. 23 refs, 1 tab, 3 figs.
Date: October 1, 1996
Creator: Raman, S.; Jurney, E.T. & Lynn, J.E.
Partner: UNT Libraries Government Documents Department

New approach for the determination of the nuclear level density parameters

Description: The nuclear level density parameters of the stable nuclides have been determined from the neutron resonance data on the basis of new values for the spin dispersion parameter. The latter parameter is deduced from the spin dependent average level spacings of s-wave neutron resonances of odd target nuclides. In addition, the temperature dependence of the level density parameter is studied and an analytical relation for it is presented.
Date: August 1, 1998
Creator: Mughabghab, S.F. & Dunford, C.L.
Partner: UNT Libraries Government Documents Department

Advanced diffusion studies with isotopically controlled materials

Description: The use of enriched stable isotopes combined with modern epitaxial deposition and depth profiling techniques enables the preparation of material heterostructures, highly appropriate for self- and foreign-atom diffusion experiments. Over the past decade we have performed diffusion studies with isotopically enriched elemental and compound semiconductors. In the present paper we highlight our recent results and demonstrate that the use of isotopically enriched materials ushered in a new era in the study of diffusion in solids which yields greater insight into the properties of native defects and their roles in diffusion. Our approach of studying atomic diffusion is not limited to semiconductors and can be applied also to other material systems. Current areas of our research concern the diffusion in the silicon-germanium alloys and glassy materials such as silicon dioxide and ion conducting silicate glasses.
Date: November 14, 2004
Creator: Bracht, Hartmut A.; Silvestri, Hughes H. & Haller, Eugene E.
Partner: UNT Libraries Government Documents Department

High-purity, isotopically enriched bulk silicon

Description: The synthesis and characterization of dislocation-free, undoped, single crystals of Si enriched in all 3 stable isotopes is reported: {sup 28}Si (99.92%), {sup 29}Si (91.37%), and {sup 30}Si (89.8%). A silane-based process compatible with the relatively small amounts of isotopically enriched precursors that are practically available was used. The silane is decomposed to silicon on a graphite starter rod heated to 700-750 C in a recirculating flow reactor. A typical run produces 35 gm of polycrystalline Si at a growth rates of 5 {micro}m/min and conversion efficiency >95%. Single crystals are grown by the floating zone method and characterized by electrical and optical measurements. Concentrations of shallow dopants (P and B) are as low as mid-10{sup 13} cm{sup -3}. Concentrations of C and O lie below 10{sup 16} and 10{sup 15} cm{sup -3}, respectively.
Date: November 17, 2004
Creator: Ager III, J.W.; Beeman, J.W.; Hansen, W.L.; Haller, E.E.; Sharp, I.D.; Liao, C. et al.
Partner: UNT Libraries Government Documents Department

Stable isotope customer list and summary of shipments, FY 1977

Description: The compilation of stable isotope customers and shipments is divided into four parts. There are alphabetical lists of domestic and foreign customers, alphabetical list of isotopes with cross-references to customers, alphabetical list of states and customers with cross-reference to customers, and tabulation of shipments, quantities, and dollars. (JSR)
Date: April 1, 1978
Creator: Davis, W.C.
Partner: UNT Libraries Government Documents Department

Release of Methane from Bering Sea Sediments During the Last Glacial Period

Description: Several lines of evidence suggest that during times of elevated methane flux the sulfate-methane transition zone (SMTZ) was positioned near the sediment-water interface. We studied two cores (from 700 m and 1457 m water depth) from the Umnak Plateau region. Anomalously low d13C and high d18O in benthic and planktonic foraminifera in these cores are the consequence of diagenetic overgrowths of authigenic carbonates. There are multiple layers of authigenic-carbonate-rich sediment in these cores, and the stable isotope compositions of the carbonates are consistent with those formed during anaerobic oxidation of methane (AOM). The carbonate-rich layers are associated with biomarkers produced by methane-oxidizing archaea, archaeol and glyceryl dibiphytanyl glyceryl tetraether (GDGT). The d13C of the archaeol and certain GDGTs are isotopically depleted. These carbonate- and AOM-biomarker-rich layers were emplaced in the SMTZ during episodes when there was a high flux of methane or methane-rich fluids upward in the sediment column. The sediment methane in the Umnak Plateau region appears to have been very dynamic during the glacial period, and interacted with the ocean-atmosphere system at millennial time scales. The upper-most carbonate-rich layers are in radiocarbon-dated sediment deposited during interstitials 2 and 3, 28-20 ka, and may be associated with the climate warming during this time.
Date: November 30, 2007
Creator: Cook, Mea & Keigwin, Lloyd
Partner: UNT Libraries Government Documents Department

A dynamic soil chamber system coupled with a tunable diode laser for online measurements of delta-13C, delta-18O, and efflux rate of soil respired CO2

Description: High frequency observations of the stable isotopic composition of CO(2) effluxes from soil have been sparse due in part to measurement challenges. We have developed an open-system method that utilizes a flow-through chamber coupled to a tunable diode laser (TDL) to quantify the rate of soil CO(2) efflux and its delta(13)C and delta(18)O values (delta(13)C(R) and delta(18)O(R), respectively). We tested the method first in the laboratory using an artificial soil test column and then in a semi-arid woodland. We found that the CO(2) efflux rates of 1.2 to 7.3 micromol m(-2) s(-1) measured by the chamber-TDL system were similar to measurements made using the chamber and an infrared gas analyzer (IRGA) (R(2) = 0.99) and compared well with efflux rates generated from the soil test column (R(2) = 0.94). Measured delta(13)C and delta(18)O values of CO(2) efflux using the chamber-TDL system at 2 min intervals were not significantly different from source air values across all efflux rates after accounting for diffusive enrichment. Field measurements during drought demonstrated a strong dependency of CO(2) efflux and isotopic composition on soil water content. Addition of water to the soil beneath the chamber resulted in average changes of +6.9 micromol m(-2) s(-1), -5.0 per thousand, and -55.0 per thousand for soil CO(2) efflux, delta(13)C(R) and delta(18)O(R), respectively. All three variables initiated responses within 2 min of water addition, with peak responses observed within 10 min for isotopes and 20 min for efflux. The observed delta(18)O(R) was more enriched than predicted from temperature-dependent H(2)O-CO(2) equilibration theory, similar to other recent observations of delta(18)O(R) from dry soils (Wingate L, Seibt U, Maseyk K, Ogee J, Almeida P, Yakir D, Pereira JS, Mencuccini M. Global Change Biol. 2008; 14: 2178). The soil chamber coupled with the TDL was found to be an effective method for capturing soil ...
Date: January 1, 2009
Creator: Powers, Heath H; Mcdowell, Nate; Hanson, David & Hunt, John
Partner: UNT Libraries Government Documents Department

Nitrogen isotopes in the recent solar wind from the analysis of genesis targets: evidence for large scale isotope heterogeneity in the nascent solar system

Description: Nitrogen, the fifth most abundant element in the universe, displays the largest stable isotope variations in the solar system reservoirs after hydrogen. Yet the value of isotopic composition of solar nitrogen, presumably the best proxy of the protosolar nebula composition, is not known. Nitrogen isotopes trapped in Genesis spacecraft target material indicate a 40 % depletion of {sup 15}N in solar wind N relative to inner planets and meteorites, and define a composition for the present-day Sun undistinguishable from that of Jupiter's atmosphere. These results indicate that the isotopic composition of of nitrogen in the outer convective zone of the Sun (OCZ) has not changed through time, and is representative of the protosolar nebula. Large {sup 15}N enrichments during e.g., irradiation, or contributions from {sup 15}N-rich presolar components, are required to account for planetary values.
Date: January 1, 2009
Creator: Wiens, Roger C; Marty, Bernard; Zimmermann, Laurent; Burnard, Peter G; Burnett, Donald L; Heber, Veronika S et al.
Partner: UNT Libraries Government Documents Department

Quantification of absorption, retention and elimination of two different oral doses of vitamin A in Zambian boys using accelerator mass spectrometry

Description: A recent survey indicated that high-dose vitamin A supplements (HD-VAS) had no apparent effect on vitamin A (VA) status of Zambian children <5 y of age. To explore possible reasons for the lack of response to HD-VAS among Zambian children, we quantified the absorption, retention, and urinary elimination of either a single HDVAS (60 mg) or a smaller dose of stable isotope (SI)-labeled VA (5 mg), which was used to estimate VA pool size, in 3-4 y old Zambian boys (n = 4 for each VA dose). A 25 nCi tracer dose of [{sup 14}C{sub 2}]-labeled VA was co-administered with the HD-VAS or SI-labeled VA, and 24-hr stool and urine samples were collected for 3 and 7 consecutive days, respectively, and 24-hr urine samples at 4 later time points. Accelerator Mass Spectrometry (AMS) was used to measure the cumulative excretion of {sup 14}C in stool and urine 3d after dosing to estimate, respectively, absorption and retention of the VAS and SI-labeled VA. The urinary elimination rate (UER) was estimated by plotting {sup 14}C in urine vs. time, and fitting an exponential equation to the data. Estimates of mean absorption, retention and the UER were 83.8 {+-} 7.1%, 76.3 {+-} 6.7%, and 1.9 {+-} 0.6%/d, respectively, for the HD-VAS and 76.5 {+-} 9.5%, 71.1 {+-} 9.4%, and 1.8 {+-} 1.2%/d, respectively for the smaller dose of SI-labeled VA. Estimates of absorption, retention and the UER did not differ by size of the VA dose administered (P=0.26, 0.40, 0.88, respectively). Estimated absorption and retention were negatively associated with reported fever (P=0.011) and malaria (P =0.010). HD-VAS and SI-labeled VA were adequately absorbed, retained and utilized in apparently healthy Zambian preschool-age boys, although absorption and retention may be affected by recent infections.
Date: October 12, 2009
Creator: Aklamati, E K; Mulenga, M; Dueker, S R; Buchholz, B A; Peerson, J M; Kafwembe, E et al.
Partner: UNT Libraries Government Documents Department

Isotopic evidence for the infiltration of mantle and metamorphic CO2-H2O fluids from below in faulted rocks from the San Andreas Fault System

Description: To characterize the origin of the fluids involved in the San Andreas Fault (SAF) system, we carried out an isotope study of exhumed faulted rocks from deformation zones, vein fillings and their hosts and the fluid inclusions associated with these materials. Samples were collected from segments along the SAF system selected to provide a depth profile from upper to lower crust. In all, 75 samples from various structures and lithologies from 13 localities were analyzed for noble gas, carbon, and oxygen isotope compositions. Fluid inclusions exhibit helium isotope ratios ({sup 3}He/{sup 4}He) of 0.1-2.5 times the ratio in air, indicating that past fluids percolating through the SAF system contained mantle helium contributions of at least 35%, similar to what has been measured in present-day ground waters associated with the fault (Kennedy et al., 1997). Calcite is the predominant vein mineral and is a common accessory mineral in deformation zones. A systematic variation of C- and O-isotope compositions of carbonates from veins, deformation zones and their hosts suggests percolation by external fluids of similar compositions and origin with the amount of fluid infiltration increasing from host rocks to vein to deformation zones. The isotopic trend observed for carbonates in veins and deformation zones follows that shown by carbonates in host limestones, marbles, and other host rocks, increasing with increasing contribution of deep metamorphic crustal volatiles. At each crustal level, the composition of the infiltrating fluids is thus buffered by deeper metamorphic sources. A negative correlation between calcite {delta}{sup 13}C and fluid inclusion {sup 3}He/{sup 4}He is consistent with a mantle origin for a fraction of the infiltrating CO{sub 2}. Noble gas and stable isotope systematics show consistent evidence for the involvement of mantle-derived fluids combined with infiltration of deep metamorphic H{sub 2}O and CO{sub 2} in faulting, supporting the involvement of ...
Date: December 15, 2010
Creator: Pili, E.; Kennedy, B.M.; Conrad, M.E. & Gratier, J.-P.
Partner: UNT Libraries Government Documents Department

Use of Stable Noble Gases as a Predictor of Reactor Fuel Type and Exposure

Description: Ensuring spent reactor fuel is not produced to provide weapons-grade plutonium is becoming a major concern as many countries resort to nuclear power as a solution to their energy problems. Proposed solutions range from the development of proliferation resistant fuel to continuous monitoring of the fuel. This paper discusses the use of the stable isotopes of the fissiogenic noble gases, xenon and krypton, for determining the burnup characteristics, fuel type, and the reactor type of the fuel from which the sample was obtained. The gases would be collected on-stack as the fuel is reprocessed, and thus confirm that the fuel is as declared.
Date: August 30, 1999
Creator: Fearey, B.L.; Charlton, W.S.; Perry, R.T.; Poths, J.; Wilson, W.B.; Hemberger, P.H. et al.
Partner: UNT Libraries Government Documents Department

Experimental Geochemical Studies Relevant to Carbon Sequestration

Description: The authors are conducting laboratory studies to determine: (i) the thermophysical properties and phase relations of CO{sub 2}CH{sub 4}-H{sub 2}O fluids; (ii) the magnitude of stable isotope partitioning during calcite precipitation; and (iii) the utility of natural isotopic tracers in quantifying CO{sub 2} residence times, storage capacity and reaction mechanisms in the subsurface. The ultimate aim of the research on CO{sub 2}-CH{sub 4}H{sub 2}O fluids is to develop a comprehensive equation of state for binary and ternary mixtures of CO{sub 2}, CH{sub 4} and H{sub 2}O at pressure-temperature (P-T) conditions representative of those in deep gas fields and saline aquifers. To acquire the data needed to create the model, two unique, custom-designed devices at the Oak Ridge National Laboratory--a high pressure vibrating-tube densimeter, and a hydrogen-service internally heated pressure vessel--are being used to measure the densities, excess molar volumes, miscibility limits and activity-composition relations of CO{sub 2}H{sub 2}O, CH{sub 4}-H{sub 2}O and ternary CO{sub 2}-CH{sub 4}-H{sub 2}O mixtures at P-T conditions near the vapor-saturation phase boundary in the H{sub 2}O system. In another project, experiments are being conducted to determine the kinetics of carbonate precipitation from CO{sub 2}-rich saline waters, and associated isotope partitioning. Both inorganic and microbially mediated processes are being investigated under environmental conditions encountered during CO{sub 2} injection into the subsurface. Our results indicate that the behavior of isotopes, especially oxygen isotopes, is affected by the composition of water and the precipitation rate of carbonate minerals. We have also observed significant carbon isotope partitioning (4 to 8{per_thousand}) between CO{sub 2} and hydrocarbon-saturated rock (an EOR injection scenario) reacted statically at 25 C. These preliminary results suggest that a light isotopic component of CO{sub 2} may be retained in the reservoir, leading to isotopically heavier CO, further down the flow path.
Date: January 10, 2001
Creator: Blencoe, J. G.
Partner: UNT Libraries Government Documents Department

Stable isotope investigations of chlorinated aliphatic hydrocarbons.

Description: Stable isotope ratio measurements for carbon (C) and chlorine (Cl) can be used to elucidate the processes affecting transformation and transportation of chlorinated aliphatic hydrocarbons (CAHs) in the environment. Methods recently developed in our laboratory for isotopic analysis of CAHs have been applied to laboratory measurements of the kinetic isotope effects associated with aerobic degradation of dichloromethane (DCM) and with both anaerobic and aerobic cometabolic degradation of trichlomethene (TCE) in batch and column microbial cultures. These experimental determinations of fractionation factors are crucial for understanding the behavior of CAHs in complex natural systems, where the extent of biotransformation can be masked by dispersion and volatilization. We have also performed laboratory investigations of kinetic isotope effects accompanying evaporation of CAHs, as well as field investigations of natural attenuation and in situ remediation of CAHs in a number of contaminated shallow aquifers at sites operated by the federal government and the private sector.
Date: June 1, 1999
Creator: Abrajano, T.; Heraty, L. J.; Holt, B. D.; Huang, L. & Sturchio, N. C.
Partner: UNT Libraries Government Documents Department