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Sample records for abundance carbon isotope

  1. Carbonate abundances and isotopic compositions in chondrites

    NASA Astrophysics Data System (ADS)

    Alexander, C. M. O'd.; Bowden, R.; Fogel, M. L.; Howard, K. T.

    2015-04-01

    We report the bulk C abundances, and C and O isotopic compositions of carbonates in 64 CM chondrites, 14 CR chondrites, 2 CI chondrites, LEW 85332 (C2), Kaba (CV3), and Semarkona (LL3.0). For the unheated CMs, the total ranges of carbonate isotopic compositions are ?13C ? 25-75‰ and ?18O ? 15-35‰, and bulk carbonate C contents range from 0.03 to 0.60 wt%. There is no simple correlation between carbonate abundance and isotopic composition, or between either of these parameters and the extent of alteration. Unless accretion was very heterogeneous, the uncorrelated variations in extent of alteration and carbonate abundance suggests that there was a period of open system behavior in the CM parent body, probably prior to or at the start of aqueous alteration. Most of the ranges in CM carbonate isotopic compositions can be explained by their formation at different temperatures (0-130 °C) from a single fluid in which the carbonate O isotopes were controlled by equilibrium with water (?18O ? 5‰) and the C isotopes were controlled by equilibrium with CO and/or CH4 (?13C ? -33‰ or -20‰ for CO- or CH4-dominated systems, respectively). However, carbonate formation would have to have been inefficient, otherwise carbonate compositions would have resembled those of the starting fluid. A quite similar fluid composition (?18O ? -5.5‰, and ?13C ? -31‰ or -17‰ for CO- or CH4-dominated systems, respectively) can explain the carbonate compositions of the CIs, although the formation temperatures would have been lower (~10-40 °C) and the relative abundances of calcite and dolomite may play a more important role in determining bulk carbonate compositions than in the CMs. The CR carbonates exhibit a similar range of O isotopes, but an almost bimodal distribution of C isotopes between more (?13C ? 65-80‰) and less altered samples (?13C ? 30-40‰). This bimodality can still be explained by precipitation from fluids with the same isotopic composition (?18O ? -9.25‰, and ?13C ? -21‰ or -8‰ for CO- or CH4-dominated systems, respectively) if the less altered CRs had higher mole fractions of CO2 in their fluids. Semarkona and Kaba carbonates have some of the lightest C isotopic compositions of the meteorites studied here, probably because they formed at higher temperatures and/or from more CO2-rich fluids. The fluids responsible for the alteration of chondrites and from which the carbonates formed were almost certainly accreted as ices. By analogy with cometary ices, CO2 and/or CO would have dominated the trapped volatile species in the ices. The chondrites studied are too oxidized for CO-dominated fluids to have formed in their parent bodies. If CH4 was the dominant C species in the fluids during carbonate formation, it would have to have been generated in the parent bodies from CO and/or CO2 when oxidation of metal by water created high partial pressures of H2. The fact that the chondrite carbonate C/H2O mole ratios are of the order predicted for CO/CO2-H2O ices that experienced temperatures of >50-100 K suggests that the chondrites formed at radial distances of <4-15 AU.

  2. Natural abundances of carbon isotopes in acetate from a coastal marine sediment

    NASA Technical Reports Server (NTRS)

    Blair, N. E.; Martens, C. S.; Des Marais, D. J.

    1987-01-01

    Measurements of the natural abundances of carbon isotopes were made in acetate samples isolated from the anoxic marine sediment of Cape Lookout Bight, North Carolina. The typical value of the total acetate carbon isotope ratio (delta 13C) was -16.1 +/- 0.2 per mil. The methyl and carboxyl groups were determined to be -26.4 +/- 0.3 and -6.0 +/- 0.3 per mil, respectively, for one sample. The isotopic composition of the acetate is thought to have resulted from isotopic discriminations that occurred during the cycling of that molecule. Measurements of this type, which have not been made previously in the natural environment, may provide information about the dominant microbial pathways in anoxic sediments as well as the processes that influence the carbon isotopic composition of biogenic methane from many sources.

  3. Carbon and nitrogen biogeochemistry in the ocean: A study using stable isotope natural abundance

    NASA Technical Reports Server (NTRS)

    Rau, G. H.; Desmarais, David J.

    1985-01-01

    Determining the biogeochemical pathways traveled by carbon and nitrogen in the ocean is fundamental to the understanding of how the ocean participates in the cycling of these elements within the biosphere. Because biological production, metabolism, and respiration can significantly alter the natural abundance of C-13 and N-15, these abundances can provide important information about the nature of these biological processes and their variability in the marine environment. The research initially seeks to characterize the spatial and temporal patterns of stable isotope abundances in organic matter, and to relate these abundances to C and N biogeochemical processes within selected areas of the northeastern Pacific Ocean.

  4. Abundances in red giant stars - Nitrogen isotopes in carbon-rich molecular envelopes

    NASA Technical Reports Server (NTRS)

    Wannier, P. G.; Andersson, B.-G.; Olofsson, H.; Ukita, N.; Young, K.

    1991-01-01

    Results are presented of millimeter- and submillimeter-wave observations of HCN and HCCCN that were made of the circmustellar envelopes of eight carbon stars, including the two protoplanetary nebulae CRL 618 and CRL 2688. The observations yield a measure of the double ratio (N-14)(C-13)/(N-15)(C-12). Measured C-12/C-13 ratios are used to estimate the N-14/N-15 abundance ratio, with the resulting lower limits in all eight envelopes and possible direct determinations in two envelopes. The two determinations and four of the remaining six lower limits are found to be in excess of the terrestrial value of N-14/N-15 = 272, indicating an evolution of the nitrogen isotope ratio, which is consistent with stellar CNO processing. Observations of thermal SiO (v = 0, J = 2-1) emission show that the Si-29/Si-28 ratio can be determined in carbon stars, and further observations are indicated.

  5. Carbon, nitrogen and sulfur in lunar fines 15012 and 15013 - Abundances, distributions and isotopic compositions

    NASA Technical Reports Server (NTRS)

    Chang, S.; Lawless, J.; Romiez, M.; Kaplan, I. R.; Petrowski, C.; Sakai, H.; Smith, J. W.

    1974-01-01

    Lunar fines 15012,16 and 15013,3 were analyzed by stepwise pyrolysis and acid hydrolysis as well as complete combustion in oxygen to determine carbon, nitrogen and sulfur. In addition, hydrogen was analysed during pyrolysis as well as during hydrolysis. By comparison of the distribution frequencies of C, N, S, H2 and Fe with He-4, considered to have arisen from solar wind contribution, it is concluded that nitrogen and hydrogen have largely a solar origin. Carbon has a significant solar contribution, and metallic iron may have resulted from solar wind interaction with ferrous minerals on the lunar surface. Sulfur probably has a predominantly lunar origin. There is no direct evidence for meteorotic contribution to these samples. Solar wind interaction also has a marked effect on the stable isotope distribution of C-13/C-12, N-15/N-14, and S-34/S-32. In all cases, the heavy isotope was most enriched in the smallest grain-size fraction.

  6. Temporal variation in mycorrhizal diversity and carbon and nitrogen stable isotope abundance in the wintergreen meadow orchid Anacamptis morio.

    PubMed

    Ercole, Enrico; Adamo, Martino; Rodda, Michele; Gebauer, Gerhard; Girlanda, Mariangela; Perotto, Silvia

    2015-02-01

    Many adult orchids, especially photoautotrophic species, associate with a diverse range of mycorrhizal fungi, but little is known about the temporal changes that might occur in the diversity and functioning of orchid mycorrhiza during vegetative and reproductive plant growth. Temporal variations in the spectrum of mycorrhizal fungi and in stable isotope natural abundance were investigated in adult plants of Anacamptis morio, a wintergreen meadow orchid. Anacamptis morio associated with mycorrhizal fungi belonging to Tulasnella, Ceratobasidium and a clade of Pezizaceae (Ascomycetes). When a complete growing season was investigated, multivariate analyses indicated significant differences in the mycorrhizal fungal community. Among fungi identified from manually isolated pelotons, Tulasnella was more common in autumn and winter, the pezizacean clade was very frequent in spring, and Ceratobasidium was more frequent in summer. By contrast, relatively small variations were found in carbon (C) and nitrogen (N) stable isotope natural abundance, A. morio samples showing similar (15)N enrichment and (13)C depletion at the different sampling times. These observations suggest that, irrespective of differences in the seasonal environmental conditions, the plant phenological stages and the associated fungi, the isotopic content in mycorrhizal A. morio remains fairly constant over time. PMID:25382295

  7. The Solar Oxygen Abundance, and the Rare Isotopes of C and O, Derived from Infrared Spectra of Carbon Monoxide

    NASA Astrophysics Data System (ADS)

    Ayres, T. R.; Plymate, C.; Keller, C.; Kurucz, R. L.

    2005-05-01

    A detailed abundance analysis is presented for solar oxygen based on the ?V=1 fundamental (4.6~?m) and ?V=2 (2.3~?m) first-overtone rovibrational bands of carbon monoxide observed above the Earth's atmosphere at very high spectral resolution and high signal-to-noise by the Shuttle-borne ATMOS Fourier transform spectrometer (FTS). Additional observations to define the reference photospheric thermal structure were taken of the CO fundamental bands in an atmospheric window at 2145~cm-1 (4.6~?m) using the 1~m FTS of the McMath-Pierce telescope at Kitt Peak and a fast tip/tilt image stabilization system. The latter allowed measurements at the extreme limb where the highly slanted rays probe into the outer layers of the photosphere. High spatial resolution "movies" of weak CO lines at disk center taken under excellent seeing conditions with the Infrared Imaging Spectrometer (IRIS), also on the McMath-Pierce telescope, further constrained thermal and velocity fluctuations in the layers in which the abundance-sensitive CO lines form. This work is meant to complement a series of recent studies which have revised the previously recommended solar oxygen abundance downward by nearly a factor of two; although in fact our conclusions do not support such a revision. The oxygen abundance recovered in the present work is 700±70~ppm (parts per million relative to hydrogen) compared with the proposed downward revision to 460±60~ppm, and the recommended value of 650±100~ppm of a decade ago. In our analysis, a fixed C/O ratio of 0.5, derived in independent work, was assumed; so the associated carbon abundance is 350~ppm. New accurate values for the solar abundance ratios of the rare isotopes of C and O also are reported: 12C/13C= 70, 16O/17O= 400, and 16O/18O= 2000. All three ratios are lower than terrestrial or meteoritic values (indicating higher isotopic abundances). We find no evidence in the ATMOS3 spectra for measurable 14C16O lines.

  8. Millimeter-scale variations of stable isotope abundances in carbonates from banded iron-formations in the Hamersley Group of Western Australia

    NASA Technical Reports Server (NTRS)

    Baur, M. E.; Hayes, J. M.; Studley, S. A.; Walter, M. R.

    1985-01-01

    Several diamond drill cores from formations within the Hamersley Group of Western Australia have been studied for evidence of short-range variations in the isotopic compositions of the carbonates. For a set of 32 adjacent microbands analyzed in a specimen from the Marra Mamba Iron Formation, carbon isotope compositions of individual microbands ranged from -2.8 to -19.8 per mil compared to PDB and oxygen isotope compositions ranged from 10.2 to 20.8 per mil compared to SMOW. A pattern of alternating abundances was present, with the average isotopic contrasts between adjacent microbands being 3.0 per mil for carbon and 3.1 per mil for oxygen. Similar results were obtained for a suite of 34 microbands (in four groups) from the Bruno's Band unit of the Mount Sylvia Formation. Difficulties were experienced in preparing samples of single microbands from the Dales Gorge Member of the Brockman Iron Formation, but overall isotopic compositions were in good agreement with values reported by previous authors. Chemical analyses showed that isotopically light carbon and oxygen were correlated with increased concentrations of iron. The preservation of these millimeter-scale variations in isotopic abundances is interpreted as inconsistent with a metamorphic origin for the isotopically light carbon in the BIF carbonates. A biological origin is favored for the correlated variations in 13C and Fe, and it is suggested that the 13C-depleted carbonates may derive either from fermentative metabolism or from anaerobic respiration. A model is presented in which these processes occur near the sediment-water interface and are coupled with an initial oxidative precipitation of the iron.

  9. Natural Abundance Carbon Isotope Composition of Isoprene Reflects Incomplete Coupling between Isoprene

    E-print Network

    leaves is dynamically coupled to photosynthesis through the use of primary and recent photosyn- thate, carbon source(s). This contribution increased when photosynthesis was inhibited by CO2-free air between isoprene and photosynthesis (Sharkey et al., 1991a), although uncertainty remains concerning

  10. Stellar Isotopic Abundances in the Milky Way: Insights into the Origin of Carbon and Neutron-Capture Elements

    NASA Astrophysics Data System (ADS)

    Guo, Michelle; Zhang, A.; Kirby, E. N.; Guhathakurta, P.

    2014-01-01

    Elements heavier than iron are formed by the capture of neutrons onto lighter nuclei. Neutron capture happens via two separate processes: the rapid neutron capture process (r-process) that occurs in supernovae, and slow neutron capture process (s-process) that occurs in less-massive stars. This work used high-resolution spectroscopy, synthetic model spectra, and a least-squares fit to show that the ratio of 12C to 13C increases proportionally with [Fe/H]. The new results agree with the conclusions of Lucatello et al. (2006) and Frebel (2008), and show significant improvement that contains less scattering of data points. Analysis of the obtained isotope ratios suggests that the carbon in most stars of the sample originated in supernovae. This paper also presents a method to calculate the europium isotope ratio by modeling the shapes of absorption lines. The range of europium isotopic ratios agrees with previous theoretical predictions about the classical model of heavy element nucleosynthesis, and the work presents new insight into the origins of life in the universe. We thank the US National Science Foundation, the UCSC Science Internship Program, and the Lick Observatory where the spectra were obtained.

  11. Carbon isotope techniques

    SciTech Connect

    Coleman, D.C. ); Fry, B. )

    1991-01-01

    This book is a hands-on introduction to using carbon isotope tracers in experimental biology and ecology. It is a bench-top reference with protocols for the study of plants, animals, and soils. The {sup 11}C, {sup 12}C, {sup 13}C, and {sup 14}C carbon isotopes are considered and standard techniques are described by established authors. The compilation includes the following features: specific, well-established, user-oriented techniques; carbon cycles in plants, animals, soils, air, and water; isotopes in ecological research; examples and sample calculations.

  12. ISOTOPIC TITANIUM ABUNDANCES IN LOCAL M DWARFS

    SciTech Connect

    Chavez, Joy; Lambert, David L. E-mail: dll@astro.as.utexas.edu

    2009-07-10

    Relative abundances of the five stable isotopes of titanium ({sup 46}Ti to {sup 50}Ti) are measured for 11 M dwarfs belonging to the thin disk (four stars), thick disk (three stars), the halo (one star), and either the thick or the thin disk (three stars). Over the metallicity range of the sample (-1< [Fe/H] <0), the isotopic ratios are approximately constant at the solar system ratios. There is no discernible difference between the isotopic ratios for thin and thick disk stars. Isotopic ratios are in fair accord with recent calculations of Galactic chemical evolution despite the fact that such calculations underpredict [Ti/Fe] by about 0.4 dex at all metallicities.

  13. NITROGEN AND CARBON STABLE ISOTOPE ABUNDANCES SUPPORT THE MYCO-HETEROTROPHIC NATURE AND HOST-SPECIFICITY OF CERTAIN ACHLOROPHYLLOUS PLANTS

    EPA Science Inventory


    ? Over 400 species of achlorophyllous vascular plants are thought to obtain all carbon from symbiotic fungi. Consequently, they are termed ?myco-heterotrophic.' However, direct evidence of myco-heterotrophy in these plants is limited.
    ? During an investigation of the pat...

  14. Distribution, abundance and carbon isotopic composition of gaseous hydrocarbons in Big Soda Lake, Nevada - An alkaline, meromictic lake

    NASA Technical Reports Server (NTRS)

    Oremland, R. S.; Des Marais, D. J.

    1983-01-01

    The study of the distribution and isotopic composition of low molecular weight hydrocarbon gases at the Big Soda Lake, Nevada, has shown that while neither ethylene nor propylene were found in the lake, ethane, propane, isobutane and n-butane concentrations all increased with water column depth. It is concluded that methane has a biogenic origin in both the sediments and the anoxic water column, and that C2-C4 alkanes have biogenic origins in the monimolimnion water and shallow sediments. The changes observed in delta C-13/CH4/ and CH4/(C2H6 + C3H8) with depth in the water column and sedimeents are probably due to bacterial processes, which may include anaerobic methane oxidation and different rates of methanogenesis, and C2-to-C4 alkane production by microorganisms.

  15. Isotope-abundance variations of selected elements (IUPAC technical report)

    USGS Publications Warehouse

    Coplen, T.B.; Böhlke, J.K.; De Bievre, P.; Ding, T.; Holden, N.E.; Hopple, J.A.; Krouse, H.R.; Lamberty, A.; Peiser, H.S.; Revesz, K.; Rieder, S.E.; Rosman, K.J.R.; Roth, E.; Taylor, P.D.P.; Vocke, R.D., Jr.; Xiao, Y.K.

    2002-01-01

    Documented variations in the isotopic compositions of some chemical elements are responsible for expanded uncertainties in the standard atomic weights published by the Commission on Atomic Weights and Isotopic Abundances of the International Union of Pure and Applied Chemistry. This report summarizes reported variations in the isotopic compositions of 20 elements that are due to physical and chemical fractionation processes (not due to radioactive decay) and their effects on the standard atomic-weight uncertainties. For 11 of those elements (hydrogen, lithium, boron, carbon, nitrogen, oxygen, silicon, sulfur, chlorine, copper, and selenium), standard atomic-weight uncertainties have been assigned values that are substantially larger than analytical uncertainties because of common isotope-abundance variations in materials of natural terrestrial origin. For 2 elements (chromium and thallium), recently reported isotope-abundance variations potentially are large enough to result in future expansion of their atomic-weight uncertainties. For 7 elements (magnesium, calcium, iron, zinc, molybdenum, palladium, and tellurium), documented isotope variations in materials of natural terrestrial origin are too small to have a significant effect on their standard atomic-weight uncertainties. This compilation indicates the extent to which the atomic weight of an element in a given material may differ from the standard atomic weight of the element. For most elements given above, data are graphically illustrated by a diagram in which the materials are specified in the ordinate and the compositional ranges are plotted along the abscissa in scales of (1) atomic weight, (2) mole fraction of a selected isotope, and (3) delta value of a selected isotope ratio.

  16. Study of the Role of Terrestrial Processes in the Carbon Cycle Based on Measurements of the Abundance and Isotopic Composition of Atmospheric CO2

    SciTech Connect

    Piper, Stephen C; Keeling, Ralph F

    2012-01-03

    The main objective of this project was to continue research to develop carbon cycle relationships related to the land biosphere based on remote measurements of atmospheric CO2 concentration and its isotopic ratios 13C/12C, 18O/16O, and 14C/12C. The project continued time-series observations of atmospheric carbon dioxide and isotopic composition begun by Charles D. Keeling at remote sites, including Mauna Loa, the South Pole, and eight other sites. Using models of varying complexity, the concentration and isotopic measurements were used to study long-term change in the interhemispheric gradients in CO2 and 13C/12C to assess the magnitude and evolution of the northern terrestrial carbon sink, to study the increase in amplitude of the seasonal cycle of CO2, to use isotopic data to refine constraints on large scale changes in isotopic fractionation which may be related to changes in stomatal conductance, and to motivate improvements in terrestrial carbon cycle models. The original proposal called for a continuation of the new time series of 14C measurements but subsequent descoping to meet budgetary constraints required termination of measurements in 2007.

  17. Carbon isotopic fractionation in heterotrophic microbial metabolism

    NASA Technical Reports Server (NTRS)

    Blair, N.; Leu, A.; Munoz, E.; Olsen, J.; Kwong, E.; Des Marais, D.

    1985-01-01

    Differences in the natural-abundance carbon stable isotopic compositions between products from aerobic cultures of Escherichia coli K-12 were measured. Respired CO2 was 3.4 percent depleted in C-13 relative to the glucose used as the carbon source, whereas the acetate was 12.3 percent enriched in C-13. The acetate C-13 enrichment was solely in the carboxyl group. Even though the total cellular carbon was only 0.6 percent depleted in C-13, intracellular components exhibited a significant isotopic heterogeneity. The protein and lipid fractions were -1.1 and -2.7 percent, respectively. Aspartic and glutamic acids were -1.6 and +2.7 percent, respectively, yet citrate was isotopically identical to the glucose. Probable sites of carbon isotopic fractionation include the enzyme, phosphotransacetylase, and the Krebs cycle.

  18. Carbon isotopic fractionation in heterotrophic microbial metabolism

    SciTech Connect

    Blair, N.; Leu, A.; Munoz, E.; Olsen, J.; Kwong, E.; Des Marais, D.

    1985-10-01

    Differences in the natural-abundance carbon stable isotopic compositions between products from aerobic cultures of Escherichia coli K-12 were measured. Respired CO2 was 3.4 percent depleted in C-13 relative to the glucose used as the carbon source, whereas the acetate was 12.3 percent enriched in C-13. The acetate C-13 enrichment was solely in the carboxyl group. Even though the total cellular carbon was only 0.6 percent depleted in C-13, intracellular components exhibited a significant isotopic heterogeneity. The protein and lipid fractions were -1.1 and -2.7 percent, respectively. Aspartic and glutamic acids were -1.6 and +2.7 percent, respectively, yet citrate was isotopically identical to the glucose. Probable sites of carbon isotopic fractionation include the enzyme, phosphotransacetylase, and the Krebs cycle. 38 references.

  19. Distribution, abundance and carbon isotopic composition of gaseous hydrocarbons in Big Soda Lake, Nevada: An alkaline, meromictic lake

    USGS Publications Warehouse

    Oremland, R.S.; Des Marais, D.J.

    1983-01-01

    Distribution and isotopic composition (??13C) of low molecular weight hydrocarbon gases were studied in Big Soda Lake (depth = 64 m), an alkaline, meromictic lake with permanently anoxic bottom waters. Methane increased with depth in the anoxic mixolimnion (depth = 20-35 m), reached uniform concentrations (55 ??M/l) in the monimolimnion (35-64 m) and again increased with depth in monimolimnion bottom sediments (>400 ??M/kg below 1 m sub-bottom depth). The ??13C[CH4] values in bottom sediment below 1 m sub-bottom depth (<-70 per mil) increased with vertical distance up the core (??13C[CH4] = -55 per mil at sediment surface). Monimolimnion ??13C[CH4] values (-55 to -61 per mil) were greater than most ??13C[CH4] values found in the anoxic mixolimnion (92% of samples had ??13C[CH4] values between -20 and -48 per mil). No significant concentrations of ethylene or propylene were found in the lake. However ethane, propane, isobutane and n-butane concentrations all increased with water column depth, with respective maximum concentrations of 260, 80, 23 and 22 nM/l encountered between 50-60 m depth. Concentrations of ethane, propane and butanes decreased with depth in the bottom sediments. Ratios of CH4 [C2H6 + C3H8] were high (250-620) in the anoxic mixolimnion, decreased to ~161 in the monimolimnion and increased with depth in the sediment to values as high as 1736. We concluded that methane has a biogenic origin in both the sediments and the anoxic water column and that C2-C4 alkanes have biogenic origins in the monimolimnion water and shallow sediments. The changes observed in ??13C[CH4] and CH4 (C2H6 + C3H8) with depth in the water column and sediments are probably caused by bacteria] processes. These might include anaerobic methane oxidation and different rates of methanogenesis and C2 to C4 alkane production by microorganisms. ?? 1983.

  20. Organic chemistry of Murchison meteorite: Carbon isotopic fractionation

    NASA Technical Reports Server (NTRS)

    Yuen, G. U.; Blair, N. E.; Desmarais, D. J.; Cronin, J. R.; Chang, S.

    1986-01-01

    The carbon isotopic composition of individual organic compounds of meteoritic origin remains unknown, as most reported carbon isotopic ratios are for bulk carbon or solvent extractable fractions. The researchers managed to determine the carbon isotopic ratios for individual hydrocarbons and monocarboxylic acids isolated from a Murchison sample by a freeze-thaw-ultrasonication technique. The abundances of monocarboxylic acids and saturated hydrocarbons decreased with increasing carbon number and the acids are more abundant than the hydrocarbon with the same carbon number. For both classes of compounds, the C-13 to C-12 ratios decreased with increasing carbon number in a roughly parallel manner, and each carboxylic acid exhibits a higher isotopic number than the hydrocarbon containing the same number of carbon atoms. These trends are consistent with a kinetically controlled synthesis of higher homologues for lower ones.

  1. Carbon Isotope Chemistry in Molecular Clouds

    NASA Technical Reports Server (NTRS)

    Robertson, Amy N.; Willacy, Karen

    2012-01-01

    Few details of carbon isotope chemistry are known, especially the chemical processes that occur in astronomical environments like molecular clouds. Observational evidence shows that the C-12/C-13 abundance ratios vary due to the location of the C-13 atom within the molecular structure. The different abundances are a result of the diverse formation pathways that can occur. Modeling can be used to explore the production pathways of carbon molecules in an effort to understand and explain the chemical evolution of molecular clouds.

  2. THE ATOMIC WEIGHTS COMMISSION AND ISOTOPIC ABUNDANCE RATIO DETERMINATIONS.

    SciTech Connect

    HOLDEN, N.E.

    2005-08-07

    Following Thomson's discovery of stable isotopes in non-radioactive chemical elements, the derivation of atomic weight values from mass spectrometric measurements of isotopic abundance ratios moved very slowly. Forty years later, only 3 1/2 % of the recommended values were based on mass spectrometric measurements and only 38% in the first half century. It might be noted that two chemical elements (tellurium and mercury) are still based on chemical measurements, where the atomic weight value calculated from the relative isotopic abundance measurement either agrees with the value from the chemical measurement or the atomic weight value calculated from the relative isotopic abundance measurement falls within the uncertainty of the chemical measurement of the atomic weight. Of the 19 chemical elements, whose atomic weight is based on non-corrected relative isotopic abundance measurements, five of these are two isotope systems (indium, iridium, lanthanum, lutetium and tantalum) and one is a three-isotope system (oxygen).

  3. Climatic/Hydrologic Oscillations since 155,000 yr B.P. at Owens Lake, California, Reflected in Abundance and Stable Isotope Composition of Sediment Carbonate

    USGS Publications Warehouse

    Menking, K.M.; Bischoff, J.L.; Fitzpatrick, J.A.; Burdette, J.W.; Rye, R.O.

    1997-01-01

    Sediment grain size, carbonate content, and stable isotopes in 70-cm-long (???1500-yr) channel samples from Owens Lake core OL-92 record many oscillations representing climate change in the eastern Sierra Nevada region since 155,000 yr B.P. To first order, the records match well the marine ??18O record. At Owens Lake, however, the last interglaciation appears to span the entire period from 120,000 to 50,000 yr B.P., according to our chronology, and was punctuated by numerous short periods of wetter conditions during an otherwise dry climate. Sediment proxies reveal that the apparent timing of glacial-interglacial transitions, notably the penultimate one, is proxy-dependent. In the grain-size and carbonate-content records this transition is abrupt and occurs at ??? 120,000 yr B.P. In contrast, in the isotopic records the transition is gradual and occurs between 145,000 and 120,000 yr B. P. Differences in timing of the transition are attributed to variable responses by proxies to climate change. ?? 1997 University of Washington.

  4. (Carbon isotope fractionation inplants)

    SciTech Connect

    O'Leary, M.H.

    1990-01-01

    The objectives of this research are: To develop a theoretical and experimental framework for understanding isotope fractionations in plants; and to develop methods for using this isotope fractionation for understanding the dynamics of CO{sub 2} fixation in plants. Progress is described.

  5. Coupling a high-temperature catalytic oxidation total organic carbon analyzer to an isotope ratio mass spectrometer to measure natural-abundance delta13C-dissolved organic carbon in marine and freshwater samples.

    PubMed

    Panetta, Robert J; Ibrahim, Mina; Gélinas, Yves

    2008-07-01

    The stable isotope composition of dissolved organic carbon (delta(13)C-DOC) provides powerful information toward understanding carbon sources and cycling, but analytical limitations have precluded its routine measurement in natural samples. Recent interfacing of wet oxidation-based dissolved organic carbon analyzers and isotope ratio mass spectrometers has simplified the measurement of delta(13)C-DOC in freshwaters, but the analysis of salty estuarine/marine samples still proves difficult. Here we describe the coupling of the more widespread high-temperature catalytic oxidation-based total organic carbon analyzer to an isotope ratio mass spectrometer (HTC-IRMS) through cryogenic trapping of analyte gases exiting the HTC analyzer for routine analysis of delta(13)C-DOC in aquatic and marine samples. Targeted elimination of major sources of background CO2 originating from the HTC analyzer allows for the routine measurement of samples over the natural range of DOC concentrations (from 40 microM to over 2000 microM), and salinities (<0.1-36 g/kg). Because consensus reference natural samples for delta(13)C-DOC do not exist, method validation was carried out with water-soluble stable isotope standards as well as previously measured natural samples (IAEA sucrose, Suwannee River Fulvic Acids, Deep Sargasso Sea consensus reference material, and St. Lawrence River water) and result in excellent delta(13)C-DOC accuracy (+/-0.2 per thousand) and precision (+/-0.3 per thousand). PMID:18529015

  6. LITERATURE SURVEY ON ISOTOPIC ABUNDANCE RATIO MEASUREMENTS - 2001-2005

    SciTech Connect

    HOLDEN, N.E.

    2005-08-13

    Along with my usual weekly review of the published literature for new nuclear data, I also search for new candidates for best measurements of isotopic abundances from a single source. Most of the published articles, that I previously had found in the Research Library at the Brookhaven Lab, have already been sent to the members of the Atomic Weights Commission, by either Michael Berglund or Thomas Walczyk. In the last few days, I checked the published literature for any other articles in the areas of natural variations in isotopic abundance ratios, measurements of isotopic abundance ratios on samples of extra-terrestrial material and isotopic abundance ratio measurements performed using ICPMS instruments. Hopefully this information will be of interest to members of the Commission, the sub-committee on isotopic abundance measurements (SIAM), members of the former sub-committee on natural isotopic fractionation (SNIF), the sub-committee on extra-terrestrial isotope ratios (SETIR), the RTCE Task Group and the Guidelines Task Group, who are dealing with ICPMS and TIMS comparisons. In the following report, I categorize the publications in one of four areas. Measurements performed using either positive or negative ions with Thermal Ionization Mass Spectrometer, TIMS, instruments; measurements performed on Inductively Coupled Plasma Mass Spectrometer, ICPMS, instruments; measurements of natural variations of the isotopic abundance ratios; and finally measurements on extra-terrestrial samples with instrumentation of either type. There is overlap in these areas. I selected out variations and ET results first and then categorized the rest of the papers by TIMS and ICPMS.

  7. Isotopic abundance in atom trap trace analysis

    DOEpatents

    Lu, Zheng-Tian; Hu, Shiu-Ming; Jiang, Wei; Mueller, Peter

    2014-03-18

    A method and system for detecting ratios and amounts of isotopes of noble gases. The method and system is constructed to be able to measure noble gas isotopes in water and ice, which helps reveal the geological age of the samples and understand their movements. The method and system uses a combination of a cooled discharge source, a beam collimator, a beam slower and magneto-optic trap with a laser to apply resonance frequency energy to the noble gas to be quenched and detected.

  8. Literature survey of isotopic abundance data for 1987-1989

    SciTech Connect

    Holden, N.E. )

    1989-08-09

    I have compiled all of the data on isotopic abundance measurements and their variation in nature for the time period since the last General Assembly. Most of the data deals with the variations in the abundances as given by per mil deviations from some standard. As such, they are not of major interest to the Atomic Weights Commission. However, there were some measurements which are of general interest in this list.

  9. Carbon-13 isotopic abundance and concentration of atmospheric methane for background air in the Southern and Northern Hemispheres from 1978 to 1989

    SciTech Connect

    Stevens, C.M.; Sepanski; Morris, L.J.

    1995-03-01

    Atmospheric methane (CH{sub 4}) may become an increasingly important contributor to global warming in future years. Its atmospheric concentration has risen, doubling over the past several hundred years, and additional methane is thought to have a much greater effect on climate, on a per molecule basis, than additional C0{sub 2} at present day concentrations (Shine et al. 1990). The causes of the increase of atmospheric CH{sub 4} have been difficult to ascertain because of a lack of quantitative knowledge of the fluxes (i.e., net emissions) from the numerous anthropogenic and natural sources. The goal of CH{sub 4} isotopic studies is to provide a constraint (and so reduce the uncertainties) in estimating the relative fluxes from the various isotopically distinct sources, whose combined fluxes must result in the measured atmospheric isotopic composition, after the fractionating effect of the atmospheric removal process is considered. In addition, knowledge of the spatial and temporal changes in the isotopic composition of atmospheric CH{sub 4}, along with estimates of the fluxes from some of the major sources, makes it possible to calculate growth rates for sources whose temporal emissions trends would be difficult to measure directly.

  10. Isotope tracers of organic carbon during artificial recharge

    SciTech Connect

    Davisson, M.L.

    1998-02-09

    This project developed an analytical technique for measuring the isotope abundance for 14C and 13C in total organic carbon (TOC) in order to test whether these measurements can trace TOC interaction with sedimentary material at the bottom of rivers and lakes, soils, and subsurface aquifer rocks.

  11. Developing Model Constraints on Northern Extra-Tropical Carbon Cycling Based on measurements of the Abundance and Isotopic Composition of Atmospheric CO2

    SciTech Connect

    Keeling, Ralph

    2014-12-12

    The objective of this project was to perform CO2 data syntheses and modeling activities to address two central questions: 1) how much has the seasonal cycle in atmospheric CO2 at northern high latitudes changed since the 1960s, and 2) how well do prognostic biospheric models represent these changes. This project also supported the continuation of the Scripps time series of CO2 isotopes and concentration at ten baseline stations distributed globally.

  12. Carbon isotopic composition of Amazon shelf sediments

    SciTech Connect

    Showers, W.J.; Angle, D.G.; Nittrouer, C.A.; Demaster, D.J.

    1985-02-01

    The distribution of carbon isotopes in Amazon shelf sediment is controlled by the same processes that are forming the modern subaqueous delta. The terrestrial (-27 to -25 per thousand) isotopic carbon signal observed in surficial sediments near the river mouth extends over 400 km northwest along the shelf. Terrestrial carbon is associated with areas of rapid sediment accumulation (topset and foreset regions). A sharp boundary between terrestrial (-27 to -25 per thousand) and marine (-23 to -22 per thousand) isotopic carbon values in surficial sediments is associated with a change in depositional conditions (foreset to bottomset regions) and a decrease in sediment accumulation rate. POC water-column isotopic values (-27 per thousand) near the river mouth are similar to the underlying surficial-sediment TOC isotopic values, but POC water-column samples collected 20 km off the river mouth have marine carbon isotopic values (-22 to -19 per thousand) and differ from the underlying surficial-sediment TOC isotopic values. These water column observations are related to variations in turbidity and productivity. Down-core isotopic variation is only observed in cores taken in areas of lower sediment accumulation rates. These observations indicate that the organic carbon in Amazon shelf sediment is dominantly terrestrial in composition, and the location of deposition of this carbon is controlled by modern processes of sediment accumulation. The modern Amazon shelf is similar to large clinoform shale deposits of the Cretaceous in North America. Thus, the stratigraphic setting may help predict the isotopic variations of carbon in ancient deposits.

  13. Rheniumosmium isotope and highly-siderophile-element abundance systematics of angrite meteorites

    E-print Network

    Rhenium­osmium isotope and highly-siderophile-element abundance systematics of angrite meteorites Keywords: angrites osmium isotopes highly-siderophile-elements planetary differentiation impact processes) abundances at 10­15 Â CI-chondrite, and their Os- isotope and HSE abundance variations represent mixtures

  14. A Clumped Isotope Calibration for Lacustrine Carbonates

    NASA Astrophysics Data System (ADS)

    Mitsunaga, B. A.; Mering, J. A.; Petryshyn, V. A.; Dunbar, R. B.; Cohen, A. S.; Liu, X.; Kaufman, D. S.; Eagle, R.; Tripati, A.

    2014-12-01

    Our capacity to understand Earth's environmental history is highly dependent on the accuracy of past climate reconstructions. Unfortunately, many terrestrial proxies—tree rings, speleothems, leaf margin analyses, etc.—are influenced by the effects of both temperature and precipitation. Methods that can isolate the effects of temperature alone are needed, and clumped isotope thermometry has the potential to be a useful tool for determining terrestrial climates. Multiple studies have shown that the fraction of 13C—18O bonds in carbonates is inversely related to the temperature at which the rocks formed and may be a useful proxy for reconstructing temperatures on land. An in-depth survey of lacustrine carbonates, however, has not yet been published. Therefore we have been measuring the abundance of 13C18O16O in the CO2 produced by the dissolution of modern lake samples' carbonate minerals in phosphoric acid and comparing results to independently known estimates of lake water temperature and air temperature. Some of the sample types we have investigated include endogenic carbonates, freshwater gastropods, bivalves, microbialites, and ooids.

  15. The Abundance and Isotopic Composition of Hg in Extraterrestrial Materials

    NASA Technical Reports Server (NTRS)

    Lauretta, D. S.

    2004-01-01

    During the past three year grant period we made excellent progress in our study of the abundances and isotopic compositions of Hg and other volatile trace elements in extraterrestrial materials. As part of my startup package I received funds to construct a state-of-the-art experimental facility to study gas-solid reaction kinetics. Much of our effort was spent developing the methodology to measure the abundance and isotopic composition of Hg at ultratrace levels in solid materials. In our first study, the abundance and isotopic composition of Hg was determined in bulk samples of the Murchison (CM) and Allende (CV) carbonaceous chondrites. We have continued our study of mercury in primitive meteorites and expanded the suite of meteorites to include other members of the CM and CV chondrite group as well as CI and CO chondrites. Samples of the CI chondrite Orgueil, the CM chondrites Murray, Nogoya, and Cold Bokkeveld, the CO chondrites Kainsaz, Omans, and Isna, and the CV chondrites Vigarano, Mokoia, and Grosnaja were tested. We have developed a thermal analysis ICP-MS technique and applied it to the study of a suite of thermally labile elements (Zn, As, Se, Cd, In, Sn, Sb, Te, Hg, Au, Tl, Pb, and Bi) in geologic materials as well.

  16. Mass Spectrometric Measurement of Martian Krypton and Xenon Isotopic Abundance

    NASA Technical Reports Server (NTRS)

    Mahaffy, P.; Mauersberger, K.

    1993-01-01

    The Viking gas chromatograph mass spectrometer experiment provided significant data on the atmospheric composition at the surface of Mars, including measurements of several isotope ratios. However, the limited dynamic range of this mass spectrometer resulted in marginal measurements for the important Kr and Xe isotopic abundance. The Xe-129 to Xe-132 ratio was measured with an uncertainty of 70%, but none of the other isotope ratios for these species were obtained. Accurate measurement of the Xe and Kr isotopic abundance in this atmosphere provides an important data point in testing theories of planetary formation and atmospheric evolution. The measurement is also essential for a stringent test for the Martian origin of the SNC meteorites, since the Kr and Xe fractionation pattern seen in gas trapped in glassy nodules of an SNC (EETA 79001) is unlike any other known solar system resevoir. Current flight mass spectrometer designs combined with the new technology of a high-performance vacuum pumping system show promise for a substantial increase in gas throughput and the dynamic range required to accurately measure these trace species. Various aspects of this new technology are discussed.

  17. The carbon and oxygen isotopic composition of meteoritic carbonates

    SciTech Connect

    Grady, M.M.; Wright, I.P.; Swart, P.K.; Pillinger, C.T. )

    1988-12-01

    The {sup 13}C/{sup 12}C and {sup 18}O/{sup 16}O isotopic ratios of carbonates from carbonaceous and ordinary chondrites have been measured on CO{sub 2} released by the action of H{sub 3}PO{sub 4} on whole-rock samples. Carbonates from CI, CM and CR carbonaceous chondrites exhibit a range in {delta}{sup 18}O of ca. 15{per thousand} (+20.5{per thousand} to +35.1{per thousand} relative to SMOW). Limited data from CO{sub 2}-water equilibration experiments suggest that meteoritic carbonates do not possess grossly anomalous {sup 17}O isotopic compositions; therefore, they are truly enriched in {sup 13}C, with {delta}{sup 13}C between +23.7{per thousand} and +80.7{per thousand} relative to PDB. Large internal variations in {delta}{sup 13}C and {delta}{sup 18}O were found in individual meteorites and suggest that two or more isotopically distinct carbonates of different origin may be present. The abundance, {delta}{sup 13}C and {delta}{sup 18}O of carbonate in CM2 chondrites may be related to the extent of aqueous alteration of the meteorites. Carbonates in CI and CR chondrites have a median {delta}{sup 13}C ca. +50 to +60{per thousand}, whereas {delta}{sup 13}C of CM meteorites lie in the range +40 to +50 {per thousand}, although exceptions exist in both sets of samples. CV3 and CO3 carbonaceous chondrites and unequilibrated ordinary chondrites release small amounts of CO{sub 2} on acid treatment, which might be from carbonate dissolution, but which is not enriched in {sup 13}C, exhibiting {delta}{sup 13}C values ca. 0 {plus minus} 10{per thousand}. The exception to this is Bishunpur, with {delta}{sup 13}C ca. {minus}23.5{per thousand}. The difference in {delta}{sup 13}C of the CI, CM and CR vs. CV, CO and ordinary chondrite carbonates may be a result of the progressive enrichment in {sup 13}C of percolating fluids, brought about by increasing solubilization of exotic {sup 13}C-enriched grains.

  18. Carbon isotope effects associated with aceticlastic methanogenesis

    NASA Technical Reports Server (NTRS)

    Gelwicks, J. T.; Risatti, J. B.; Hayes, J. M.

    1994-01-01

    The carbon isotope effects associated with synthesis of methane from acetate have been determined for Methanosarcina barkeri 227 and for methanogenic archaea in sediments of Wintergreen Lake, Michigan. At 37 degrees C, the 13C isotope effect for the reaction acetate (methyl carbon) --> methane, as measured in replicate experiments with M. barkeri, was - 21.3% +/- 0.3%. The isotope effect at the carboxyl portion of acetate was essentially equal, indicating participation of both positions in the rate-determining step, as expected for reactions catalyzed by carbon monoxide dehydrogenase. A similar isotope effect, - 19.2% +/- 0.3% was found for this reaction in the natural community (temperature = 20 degrees C). Given these observations, it has been possible to model the flow of carbon to methane within lake sediment communities and to account for carbon isotope compositions of evolving methane. Extension of the model allows interpretation of seasonal fluctuations in 13C contents of methane in other systems.

  19. Carbon isotope effects associated with aceticlastic methanogenesis.

    PubMed

    Gelwicks, J T; Risatti, J B; Hayes, J M

    1994-02-01

    The carbon isotope effects associated with synthesis of methane from acetate have been determined for Methanosarcina barkeri 227 and for methanogenic archaea in sediments of Wintergreen Lake, Michigan. At 37 degrees C, the 13C isotope effect for the reaction acetate (methyl carbon) --> methane, as measured in replicate experiments with M. barkeri, was - 21.3% +/- 0.3%. The isotope effect at the carboxyl portion of acetate was essentially equal, indicating participation of both positions in the rate-determining step, as expected for reactions catalyzed by carbon monoxide dehydrogenase. A similar isotope effect, - 19.2% +/- 0.3% was found for this reaction in the natural community (temperature = 20 degrees C). Given these observations, it has been possible to model the flow of carbon to methane within lake sediment communities and to account for carbon isotope compositions of evolving methane. Extension of the model allows interpretation of seasonal fluctuations in 13C contents of methane in other systems. PMID:11536629

  20. The carbon monoxide abundance in interstellar clouds

    NASA Technical Reports Server (NTRS)

    Langer, W.

    1976-01-01

    The steady-state abundance of carbon monoxide in interstellar clouds is calculated as a function of optical depth, density, and temperature. The molecular reactions which lead to CO can be initiated by the following ion-molecule reactions: H(+) + O yields O(+) + H, C(+) + H2 yields CH2(+) + a photon, and H3(+) + C and O. As the ultraviolet radiation field is attenuated, C(+) is transformed primarily into CO and C I. There are characteristic column densities for the transition to CO corresponding to the optical depths for attenuating this field at different wavelengths. For thick, low-temperature clouds the attenuation of the fields which ionize carbon, sulfur, and heavy metals is important for CO production initiated by H3(+). Complete conversion to CO does not necessarily occur, and considerable neutral carbon may be expected even in optically thick clouds. Comparison of integrated column densities of CO with extinction are in reasonable agreement with observations.

  1. Carbon and nitrogen isotope studies in an arctic ecosystem

    SciTech Connect

    Schell, D.M.

    1989-12-31

    This proposal requests funding for the completion of our current ecological studies at the MS-117 research site at Toolik Lake, Alaska. We have been using a mix of stable and radioisotope techniques to assess the fluxes of carbon and nitrogen within the ecosystem and the implications for long-term carbon storage or loss from the tundra. Several tentative conclusions have emerged from our study including: Tundra in the foothills is no longer accumulating carbon. Surficial radiocarbon abundances show little or no accumulation since 1000--2500 yrs BP. Coastal plain tundra is still accumulating carbon, but the rate of accumulation has dropped in the last few thousand years. Carbon export from watersheds in the Kuparuk and Imnavait Creek drainages are in excess of that expected from estimated primary productivity; and Nitrogen isotope abundances vary between species of plants and along hydrologic gradients.

  2. Carbon and nitrogen isotope studies in an arctic ecosystem

    SciTech Connect

    Schell, D.M.

    1989-01-01

    This proposal requests funding for the completion of our current ecological studies at the MS-117 research site at Toolik Lake, Alaska. We have been using a mix of stable and radioisotope techniques to assess the fluxes of carbon and nitrogen within the ecosystem and the implications for long-term carbon storage or loss from the tundra. Several tentative conclusions have emerged from our study including: Tundra in the foothills is no longer accumulating carbon. Surficial radiocarbon abundances show little or no accumulation since 1000--2500 yrs BP. Coastal plain tundra is still accumulating carbon, but the rate of accumulation has dropped in the last few thousand years. Carbon export from watersheds in the Kuparuk and Imnavait Creek drainages are in excess of that expected from estimated primary productivity; and Nitrogen isotope abundances vary between species of plants and along hydrologic gradients.

  3. Carbon isotope effects associated with autotrophic acetogenesis

    USGS Publications Warehouse

    Gelwicks, J.T.; Risatti, J.B.; Hayes, J.M.

    1989-01-01

    The carbon kinetic isotope effects associated with synthesis of acetate from CO2 and H2 during autotrophic growth of Acetobacterium woodii at 30??C have been measured by isotopic analyses of CO2, methyl-carbon, and total acetate. Closed systems allowing construction of complete mass balances at varying stages of growth were utilized, and the effects of the partitioning of carbon between CO2 and HCO3- were taken into account. For the overall reaction, total carbonate ??? total acetate, isotope effects measured in replicate experiments ranged from -59.0 ?? 0.9% to - 57.2 ?? 2.3z%. Taking into account all measurements, the weighted mean and standard deviation are -58.6 ?? 0.7%. There is no evidence for intramolecular ordering in the acetate. The carbon isotopic composition of sedimentary acetate, otherwise expected to be near that of sedimentary organic carbon, is likely to be depleted in environments in which autotrophic acetogenesis is occurring. ?? 1989.

  4. Low Carbon Abundance in Type Ia Supernovae

    E-print Network

    G. H. Marion; P. Hoeflich; J. C. Wheeler; E. L. Robinson; C. L. Gerardy; W. D. Vacca

    2006-01-26

    We investigate the quantity and composition of unburned material in the outer layers of three normal Type Ia supernovae (SNe Ia): 2000dn, 2002cr and 20 04bw. Pristine matter from a white dwarf progenitor is expected to be a mixture of oxygen and carbon in approximately equal abundance. Using near-infrared (NIR, 0.7-2.5 microns) spectra, we find that oxygen is abundant while carbon is severely depleted with low upper limits in the outer third of the ejected mass. Strong features from the OI line at rest wavelength = 0.7773 microns are observed through a wide range of expansion velocities approx. 9,000 - 18,000 km/s. This large velocity domain corresponds to a physical region of the supernova with a large radial depth. We show that the ionization of C and O will be substantially the same in this region. CI lines in the NIR are expected to be 7-50 times stronger than those from OI but there is only marginal evidence of CI in the spectra and none of CII. We deduce that for these three normal SNe Ia, oxygen is more abundant than carbon by factors of 100 - 1,000. MgII is also detected in a velocity range similar to that of OI. The presence of O and Mg combined with the absence of C indicates that for these SNe Ia, nuclear burning has reached all but the extreme outer layers; any unburned material must have expansion velocities greater than 18,000 km/s. This result favors deflagration to detonation transition (DD) models over pure deflagration models for SNe Ia.

  5. Carbon and its isotopes in mid-oceanic basaltic glasses

    USGS Publications Warehouse

    Des Marais, D.J.; Moore, J.G.

    1984-01-01

    Three carbon components are evident in eleven analyzed mid-oceanic basalts: carbon on sample surfaces (resembling adsorbed gases, organic matter, or other non-magmatic carbon species acquired by the glasses subsequent to their eruption), mantle carbon dioxide in vesicles, and mantle carbon dissolved in the glasses. The combustion technique employed recovered only reduced sulfur, all of which appears to be indigenous to the glasses. The dissolved carbon concentration (measured in vesicle-free glass) increases with the eruption depth of the spreading ridge, and is consistent with earlier data which show that magma carbon solubility increases with pressure. The total glass carbon content (dissolved plus vesicular carbon) may be controlled by the depth of the shallowest ridge magma chamber. Carbon isotopic fractionation accompanies magma degassing; vesicle CO2 is about 3.8??? enriched in 13C, relative to dissolved carbon. Despite this fractionation, ??13CPDB values for all spreading ridge glasses lie within the range -5.6 and -7.5, and the ??13CPDB of mantle carbon likely lies between -5 and -7. The carbon abundances and ??13CPDB values of Kilauea East Rift glasses apparently are influenced by the differentiation and movement of magma within that Hawaiian volcano. Using 3He and carbon data for submarine hydrothermal fluids, the present-day mid-oceanic ridge mantle carbon flux is estimated very roughly to be about 1.0 ?? 1013 g C/yr. Such a flux requires 8 Gyr to accumulate the earth's present crustal carbon inventory. ?? 1984.

  6. Clumped isotope thermometry of cryogenic cave carbonates

    NASA Astrophysics Data System (ADS)

    Kluge, Tobias; Affek, Hagit P.; Zhang, Yi Ge; Dublyansky, Yuri; Spötl, Christoph; Immenhauser, Adrian; Richter, Detlev K.

    2014-02-01

    Freezing of cave pool water that is increasingly oversaturated with dissolved carbonate leads to precipitation of a very specific type of speleothems known as cryogenic cave carbonates (CCC). At present, two different environments for their formation have been proposed, based on their characteristic carbon and oxygen isotope ratios. Rapidly freezing thin water films result in the fast precipitation of fine-grained carbonate powder (CCCfine). This leads to rapid physicochemical changes including CO2 degassing and CaCO3 precipitation, resulting in significantly 13C-enriched carbonates. Alternatively, slow carbonate precipitation in ice-covered cave pools results in coarse crystalline CCC (CCCcoarse) yielding strongly 18O-depleted carbonate. This is due to the formation of relatively 18O-enriched ice causing the gradual depletion of 18O in the water from which the CCC precipitates. Cryogenic carbonates from Central European caves were found to have been formed primarily during the last glacial period, specifically during times of permafrost thawing, based on the oxygen isotope ratios and U-Th dating. Information about the precise conditions of CCCcoarse formation, i.e. whether these crystals formed under equilibrium or disequilibrium conditions with the parent fluid, however, is lacking. An improved understanding of CCCcoarse formation will increase the predictive value of this paleo-permafrost archive. Here we apply clumped isotopes to investigate the formation conditions of cryogenic carbonates using well-studied CCCcoarse from five different cave systems in western Germany. Carbonate clumped isotope measurements yielded apparent temperatures between 3 and 18 °C and thus exhibit clear evidence of isotopic disequilibrium. Although the very negative carbonate ?18O values can only be explained by gradual freezing of pool water accompanied by preferential incorporation of 18O into the ice, clumped isotope-derived temperatures significantly above expected freezing temperatures indicate incomplete isotopic equilibration during precipitation of CCC. Fine-crystalline carbonate powder (<50 ?m, CCCfine) is thought to have formed in thin water films. Fast freezing causes strong isotopic disequilibrium effects related to rapid reaction rates, fast CO2 degassing, and limited isotopic equilibration (Clark and Lauriol, 1992) resulting in very positive ?13C (up to +18‰) and ?18O values (up to -2‰; Lacelle, 2007; Spötl, 2008; Žák et al., 2008). Larger crystals (mm to cm size, CCCcoarse) are thought to have formed in slow gradually freezing pool water (Žák et al., 2008), where super-saturation is created through ion rejection from the forming ice. This leads to slow mineral growth and strongly 18O-depleted CaCO3 (?18O: -24‰ to -10‰; Žák et al., 2012), but it is unknown whether CCCcoarse grows at isotopic equilibrium. Carbonate clumped isotope analyses (reported as ?47) are typically used to determine the formation temperature of carbonate minerals (Eiler, 2007, 2011; Affek, 2012). However, the sensitivity of ?47 to degassing makes it valuable also for the investigation of isotopic disequilibrium (Guo, 2008; Kluge and Affek, 2012). The carbonate clumped isotope thermometry is based on the temperature-dependent overabundance of 13C-18O bonds in the crystal lattice compared to a stochastic distribution.Depending on the conditions during carbonate formation, a varying degree of disequilibrium has been observed in clumped and oxygen isotopes of 'normal' speleothems (e.g., Mickler et al., 2006; Tremaine et al., 2011) complicating their interpretation. For stalagmites, an offset in ?18O of about 1‰ with respect to the isotopic equilibrium value is typically observed (McDermott et al., 2011) with a corresponding large offset in clumped isotopes (Affek et al., 2008; Daëron et al., 2011; Kluge and Affek, 2012). Initial degassing of CO2 from water that enters the low pCO2 cave environment (compared to the high CO2 levels found in soils) leads to an enrichment in 13C and 18O in DIC and depletion in ?47. Oxygen isotope e

  7. Carbon Isotope and Isotopomer Fractionation in Dense Molecular Cloud Cores

    NASA Astrophysics Data System (ADS)

    Furuya, K.; Aikawa, Y.; Sakai, N.; Yamamoto, S.

    2011-05-01

    Observations of 13C species would be useful to investigate chemistry of carbon-bearing species. Recent observations in TMC-1 indicate that the abundances are different among carbon isotopomers of the same species. For instance, Takano et al. (1998) found that HCC13CN is more abundant than HC13CCN and H13CCCN, which indicates the three carbon atoms are not equivalent in HC_3N. Sakai et al. (2007; 2010) reported the abundance ratios of C13CS/13CCS and CCH/13CCH to be 4.2 and 1.6, respectively. Again, two carbon atoms are not equivalent in CCS and CCH. Sakai et al. (2007; 2010) discussed an origin of these anomalies and pointed out two possibilities: (i) fractionation during the formation of the species and (ii) rearrangements of the 13C position after the formation of molecules by isotopomer-exchange reactions. We construct a gas-grain chemical network model which includes carbon isotopes (12C and 13C) and isotopomers in order to investigate the evolution of molecular abundances, the carbon isotope ratios (12CX/13CX) and the isotopomer ratios (12C13CX/13C12CX) of CCH and CCS in dense molecular cores. We confirm that the isotope ratios of molecules, both in the gas phase and on grain surfaces, mostly depend on whether the species is formed from the carbon atom (ion) or the CO molecule; the isotope ratio is larger than the elemental abundance ratio of 12C/13C if the species is formed from the carbon atom, while the ratio is smaller if the species is formed from the CO molecule (cf. Langer et al. 1984). We successfully reproduce the observed C13CH/13CCH ratio in TMC-1 by considering the isotopomer-exchange reaction, 13CCH + H rightleftharpoons C13CH + H + 8.1 K. However, the C13CS/13CCS ratio remains lower than observed in TMC-1. We then assume the isotopomer-exchange reaction catalyzed by the H atom, 13CCS + H rightleftharpoons C13CS + H + 17.4 K. In the model with this reaction, the observed C13CS/13CCS, CCS/C13CS and CCS/13CCS ratios can be reproduced simultaneously.

  8. The Abundance and Isotopic Composition of Hg in Extraterrestrial Materials

    NASA Technical Reports Server (NTRS)

    Blum, J. D.; Klaue, Bjorn

    2005-01-01

    During the three year grant period we made excellent progress in our study of the abundances and isotopic compositions of Hg and other volatile trace elements in extraterrestrial materials. At the time the grant started, our collaborating PI, Dante Lauretts, was a postdoctoral research associate working with Peter Buseck at Arizona State University. The work on chondritic Hg was done in collaboration with Dante Lauretta and Peter Buseck and this study was published in Lauretta et a1 (2001a). In July, 2001 Dante Lauretta accepted a position as an Assistant Professor in the Lunar and Planetary Laboratory at the University of Arizona. His funding was transferred and this grant has supported much of his research activities during his first two years at the U of A. Several other papers are in preparation and will be published soon. We presented papers on this topic at Goldschmidt Conferences, the Lunar and Planetary Science Conferences, and the Annual Meetings of the Meteoritical Society. The work done under this grant has spurred several new directions of inquiry, which we are still pursuing. Included in this paper are the studies of bulk abundances and isotopic compositions of metreoritic Mercury, and the development of a thermal analysis ICP-MS technique applied to thermally liable elements.

  9. Nitrogen isotope abundances in the recent solar wind.

    PubMed

    Kim, J S; Kim, Y; Marti, K; Kerridge, J F

    1995-06-01

    Although lunar crystalline rocks are essentially devoid of nitrogen, the same is not true of the lunar regolith. The nitrogen contents of individual regolith samples (which can be as high as 0.012% by mass) correlate strongly with abundances of noble gases known to be implanted in the lunar surface by solar radiation, indicating that lunar regolith nitrogen is also predominantly of solar origin. The large variability in 15N/14N ratios measured in different regolith samples may thus reflect long-term changes in the isotopic composition of the solar radiation. But attempts to explain these variations have been hampered by the lack of any firm constraint on 15N/14N in the present solar wind. Here we report measurements of nitrogen isotopes from two lunar samples that have had simple (and relatively recent) exposure histories. We find that nitrogen implanted in the lunar surface during the past 10(5) to 5 x 10(7) years has a 15N/14N ratio approximately 40% higher than that in the terrestrial atmosphere, which is substantially lower than most previous estimates. This isotopic signature probably represents the best measure of 15N/14N in the present-day solar wind. PMID:7760930

  10. Evidence from carbon isotope measurements for diverse origins of sedimentary hydrocarbons

    NASA Technical Reports Server (NTRS)

    Freeman, K. H.; Hayes, J. M.; Trendel, J. M.; Albrecht, P.

    1990-01-01

    The organic matter found in sedimentary rocks must derive from many sources; not only from ancient primary producers but also from consumers and secondary producers. In all of these organisms, isotope effects can affect the abundance and distribution of 13C in metabolites. Here, by using an improved form of a previously described technique in which the effluent of a gas chromatograph is continuously analysed isotopically, we report evidence of the diverse origins of sedimentary organic matter. The record of 13C abundances in sedimentary carbonate and total organic carbon can be interpreted in terms of variations in the global carbon cycle. Our results demonstrate, however, that isotope variations within sedimentary organic mixtures substantially exceed those observed between samples of total organic carbon. Resolution of isotope variations at the molecular level offers a new and convenient means of refining views both of localized palaeoenvironments and of control mechanisms within the global carbon cycle.

  11. Clumped Isotopes Applied to Carbonate Diagenesis and High Temperature Systems

    NASA Astrophysics Data System (ADS)

    John, C. M.; Jourdan, A.; Kluge, T.; Dale, A.; Davis, S.; Vandeginste, V.

    2012-12-01

    The field of clumped isotopes is concerned with the state of ordering of natural substances and aims at constraining the abundance of 18O-13C bonds (i.e. a 'clump') within the lattice of carbonate minerals. Measuring the difference between the abundance of 18O-13C bonds in a sample relative to a stochastic distribution of isotopologues offers a single-phase paleothermometer applicable to all carbonate phases. Most of the applications of clumped isotopes to date have been in the field of paleoclimate, but applications to diagenetic systems are becoming more common. The independence of clumped isotopes from the isotopic composition of the diagenetic fluid reduces ambiguities when interpreting paragenesis, fluid flow history, and thermal history of basins. This presentation will synthesize the results of several projects within our group that collectively aim at understanding and applying clumped isotopes to diagenetic systems. One example of project including diagenesis and clumped isotope is a study of low-temperature diagenetic calcite in a salt dome in Oman (Jebel Madar). Jebel Madar is an ideal case study as large fracture-related crystals can be sampled for both clumped isotopes and fluid inclusions. Results show a good match between single-phase fluid inclusions suggesting temperature of precipitations below 90-50°C, and clumped isotope data measured on the same crystals. The low-temperature study reveals the history of gradual cooling and progressive mixing between two sources of diagenetic fluids in the fracture of Jebel Madar, and highlights the potential of clumped isotope for diagenetic studies. However, applications at high-temperatures are currently more challenging because of the lack of empirical calibrations above 50°C. A second project is thus focused on a series of high-temperature lab precipitation experiments for calibrations at high temperature, while a third project explores applicability of clumped isotopes to cemented siliciclastic units. The long-term aim of our research efforts is thus calibration at subsurface conditions, and application of clumped isotope to unravel the diagenetic history of both carbonate and siliciclastic sequences. We would like to acknowledge the financial support of QCCSRC (funded jointly by Qatar Petroleum, Shell and the Qatar Science & Technology Park) and a BP Case studentship from the EPSRC.

  12. Preliminary report on isotope abundance measurements in groundwater samples from the Talbert Injection Barrier Area, Orange County Water District

    SciTech Connect

    Hudson, G.B.; Davisson, M.L.; Velsko, C.; Niemeyer, S.; Esser, B.; Beiriger, J.

    1995-02-01

    This report discusses isotope abundance measurements made on a collection of groundwater samples from the Orange County Water District. The water samples were collected in May, 1994 as part of a preliminary study conducted by LLNL to assess the feasibility of tracing and dating reclaimed water used in the Talbert Injection Barrier. A set of samples were collected both near to and far from the barrier and also at different depths in available monitoring wells. A variety of elements were selected for isotopic analysis; hydrogen (tritium), helium, neon, carbon, chlorine and strontium. The tritium abundance combined with the {sup 3}He and {sup 20}Ne abundance provides a method for age dating young (< 40 yr.) groundwater. The abundance of {sup 14}C provides an age dating technique for older (1,000--50,000 yr.) groundwater. The concentrations of {sup 36}Cl and {sup 87}Sr/{sup 86}Sr give information on sea water mixing and water-rock chemical interactions.

  13. Carbonate clumped isotope thermometry in continental tectonics

    NASA Astrophysics Data System (ADS)

    Huntington, Katharine W.; Lechler, Alex R.

    2015-04-01

    Reconstructing the thermal history of minerals and fluids in continental environments is a cornerstone of tectonics research. Paleotemperature constraints from carbonate clumped isotope thermometry have provided important tests of geodynamic, structural, topographic and basin evolution models. The thermometer is based on the 13C-18O bond ordering in carbonates (mass-47 anomaly, ?47) and provides estimates of the carbonate formation temperature independent of the ?18O value of the water from which the carbonate grew; ?47 is measured simultaneously with conventional measurements of carbonate ?13C and ?18O values, which together constrain the isotopic composition of the parent water. Depending on the geologic setting of carbonate growth, this information can help constrain paleoenvironmental conditions or basin temperatures and fluid sources. This review examines how clumped isotope thermometry can shed new light on problems in continental tectonics, focusing on paleoaltimetry, basin evolution and structural diagenesis applications. Paleoaltimetry is inherently difficult, and the precision in carbonate growth temperature estimates is at the limit of what is useful for quantitative paleoelevation reconstruction. Nevertheless, clumped isotope analyses have enabled workers to address previously intractable problems and in many settings offer the best chance of understanding topographic change from the geologic record. The portion of the shallow crust residing at temperatures up to ca. 200 °C is important as host to economic resources and records of tectonics and climate, and clumped isotope thermometry is one of the few proxies that can access this critical range with sensitivity to temperature alone. Only a handful of studies to date have used clumped isotopes to investigate diagenesis and other sub-surface processes using carbonate crystallization temperatures or the sensitivity of ?47 values to a sample's thermal history. However, the thermometer is sufficiently precise to answer many important questions in this area, making the investigation of sub-surface processes an excellent target for future investigations.

  14. STABLE CARBON ISOTOPE ANALYSIS OF NUCLEIC ACIDS TO TRACE SOURCES OF DISSOLVED SUBSTRATES USED BY ESTUARINE BACTERIA

    EPA Science Inventory

    The natural abundance of stable carbon isotopes measured in bacterial nucleic acids that were extracted from estuarine bacterial concentrates were used to trace sources of organic matter for bacteria in.aquatic environments. he stable carbon isotope ratios of P. aeruginosa and nu...

  15. Site-Specific Carbon Isotopes in Organics

    NASA Astrophysics Data System (ADS)

    Piasecki, A.; Eiler, J. M.

    2012-12-01

    Natural organic molecules exhibit a wide range of internal site-specific isotope variation (i.e., molecules with same isotopic substitution type but different site). Such variations are generally unconstrained by bulk isotopic measurements. If known, site-specific variations might constrain temperatures of equilibrium, mechanisms of formation or consumption reactions, and possibly other details. For example, lipids can exhibit carbon isotope differences of up to 30‰ between adjacent carbon sites as a result of fractionations arising during decarboxylation of pyruvate and other steps in lipid biosynthesis(1). We present a method for site-specific carbon isotope analysis of propane, based on high-resolution, multi-collector gas source mass spectrometry, using a novel prototype instrument - the Thermo MAT 253 Ultra. This machine has an inlet system and electron bombardment ion source resembling those in conventional stable isotope gas source mass spectrometers, and the energy filter, magnet, and detector array resembling those in multi-collector ICPMS and TIMS. The detector array has 7 detector positions, 6 of which are movable, and each of which can collect ions with either a faraday cup (read through amplifiers ranging from 107-1012 ohms) or an SEM. High mass resolving power (up to 27,000, MRP = M/dM definition) is achieved through a narrow entrance slit, adjustable from 250 to 5 ?m. Such resolution can cleanly separate isobaric interferences between isotopologues of organic molecules having the same cardinal mass (e.g., 13CH3 and 12CH2D). We use this technology to analyze the isotopologues and fragments of propane, and use such data to solve for the site-specific carbon isotope fractionation. By measuring isotopologues of both the one-carbon (13CH3) and the two-carbon (13C12CH4) fragment ion, we can solve for both bulk ?13C and the difference in ?13C between the terminal and central carbon position. We tested this method by analyzing mixtures between natural propane and labeled propane (13CH3-12CH2-12CH3). Results are consistent with the expected relative fractionations between the two fragments, indicating limited 'scrambling' of carbon positions of less than 2% in the source. The limits of precision of this method are currently ~0.5 ‰, sufficient to resolve known or suspected position-specific isotope effects in propane. We have explored the expected temperature-dependent equilibrium isotopic distributions of propane using density functional theory and quantum mechanical models of vibrational isotope effects. These models predict the homogeneous isotope exchange equilibria among the various isotopologues of propane, which include several of a wide range of effects that should be measurable by our methods. At 300 K we predict that the central carbon site is 15‰ higher in ?13C and 95 ‰ higher in ?D than the terminal carbon site; similarly the molecule containing both a 13C and D in the central site is enriched by ~120 ‰ relative to a random isotopic distribution at 300 K. These predictions present targets for future experimental and empirical studies of the temperature dependence of isotopic ordering in propane. More generally, the methods we are developing for the study of intramolecular isotopic distributions in propane will serve as a model for future study of similar effects in other organic compounds. [1]DeNiro, Epstein (1977) Science Volume 197, 261-263.

  16. The stable carbon isotopes in enstatite chondrites and Cumberland Falls

    NASA Astrophysics Data System (ADS)

    Deines, P.; Wickman, F. E.

    1985-01-01

    The carbon-isotopic composition (CIC) of the total carbon in the enstatite chondrites Indarch, Abee, St. Marks, Pillistfer, Hvittis and Daniel's Kuil and the enstatite achondrite Cumberland Falls has been measured. The empirical relationship between CIC and total carbon content is distinct from that of carbonaceous and ordinary chondrites. Within the enstatite chondrite group the average C-13 content increases with petrographic type: E4 less than E5 less than E6. Daniel's Kuil shows the largest C-13 enrichment in the bulk carbon of any meteorite. The CIC is most clearly correlated with the abundance of the elements Zn, Cd, and In. Insofar as these elements may hold the key to the understanding of enstatite chondrites, more detailed combined CIC and trace-element studies of these meteorites will play an important role in the deciphering of their history.

  17. Isotopic inferences of ancient biochemistries - Carbon, sulfur, hydrogen, and nitrogen

    NASA Technical Reports Server (NTRS)

    Schidlowski, M.; Hayes, J. M.; Kaplan, I. R.

    1983-01-01

    In processes of biological incorporation and subsequent biochemical processing sizable isotope effects occur as a result of both thermodynamic and kinetic fractionations which take place during metabolic and biosynthetic reactions. In this chapter a review is provided of earlier work and recent studies on isotope fractionations in the biogeochemical cycles of carbon, sulfur, hydrogen, and nitrogen. Attention is given to the biochemistry of carbon isotope fractionation, carbon isotope fractionation in extant plants and microorganisms, isotope fractionation in the terrestrial carbon cycle, the effects of diagenesis and metamorphism on the isotopic composition of sedimentary carbon, the isotopic composition of sedimentary carbon through time, implications of the sedimentary carbon isotope record, the biochemistry of sulfur isotope fractionation, pathways of the biogeochemical cycle of nitrogen, and the D/H ratio in naturally occurring materials.

  18. Coprecipitation and isotopic fractionation of boron in modern biogenic carbonates

    SciTech Connect

    Vengosh, A. Hebrew Univ., Jerusalem ); Chivas, A.R.; McCulloch, M.T. ); Kolodny, Y.; Starinsky, A. )

    1991-10-01

    The abundances and isotopic composition of boron in modern, biogenic calcareous skeletons from the Gulf of Elat, Israel, the Great Barrier Reef, Australia, and in deep-sea sediments have been examined by negative thermal-ionization mass spectrometry. The selected species (Foraminifera, Pteropoda, corals, Gastropoda, and Pelecypoda) yield large variations in boron concentration that range from 1 ppm in gastropod shells to 80 ppm in corals. The variations of {delta}{sup 11}B may be controlled by isotopic exchange of boron species in which {sup 10}B is preferentially partitioned into the tetrahedral species, and coprecipitation of different proportions of trigonal and tetrahedral species in the calcium carbonates. The B content and {delta}{sup 11}B values of deep-sea sediments, Foraminifera tests, and corals are used to estimate the global oceanic sink of elemental boron by calcium carbonate deposition. As a result of enrichment of B in corals, a substantially higher biogenic sink of 6.4 {plus minus} 0.9 {times} 10{sup 10} g/yr is calculated for carbonates. This is only slightly lower than the sink for desorbable B in marine sediments (10 {times} 10{sup 10} g/yr) and approximately half that of altered oceanic crust (14 {times} 10{sup 10} g/yr). Thus, carbonates are an important sink for B in the oceans being {approximately}20% of the total sinks. The preferential incorporation of {sup 10}B into calcium carbonate results in oceanic {sup 11}B-enrichment, estimated as 1.2 {plus minus} 0.3 {times} 10{sup 12} per mil {center dot} g/yr. The boron-isotope composition of authigenic, well-preserved carbonate skeletons may provide a useful tool to record secular boron-isotope variations in seawater at various times in the geological record.

  19. On the pros and cons of the IRMS technique of data processing: uncertainty in results, a case study for determining carbon and oxygen isotopic abundance ratios as CO_2^+

    E-print Network

    Datta, B P

    2011-01-01

    The properties of different relationships, representing the basic evaluation as well as its inputs and outputs shaping processes in the CO_2^+ isotope ratio mass spectrometry (IRMS), are studied. It is thus shown that the input generation by using only one auxiliary reference CO2 gas (ARCG) is an accuracy enhancing process, and clarified how the input-by-measurement uncertainty-ratio(s) could be ensured to be tens of folds less than unity. However, the known relationship for using two ARCGs appears to be neither of a logistical base nor better by application. A mathematically correct means for involving two or more than two ARCGs is worked out. However, the same is observed to be worse by behavior, i.e. causes the scale converted data to be more inaccurate than the measured data. The basic evaluation requires solving a set of equations. Using a typical set, it is exemplified that, and explained why, the solutions (determined elemental isotopic abundance ratios (EIARs)) are generally as representative as the i...

  20. Isotope abundance of {sup 180}Ta{sup m} and p-process nucleosynthesis

    SciTech Connect

    Laeter, J.R. de; Bukilic, N.

    2005-08-01

    The p-process of stellar nucleosynthesis produces the stable neutron-deficient nuclides heavier than the iron peak elements. An accurate determination of the isotopic composition of tantalum is required to enable p-process nucleosynthetic calculations to be evaluated in terms of an accurate isotope abundance for {sup 180}Ta. This odd-odd nuclide has the remarkable property of having a long-lived isomeric state and a short-lived ground state, so that in reality one is measuring the isotope abundance of {sup 180}Ta{sup m}, which is a unique situation in nature. {sup 180}Ta{sup m} is the rarest isotope of nature's rarest element and is therefore an important isotope in deciphering the origin of the p-process. Because the isotopic composition of tantalum has only been measured on two occasions with relatively large uncertainties, an accurate determination is required to provide a better basis for p-process production calculations. A thermal ionization mass spectrometer was used to measure the isotope abundance of {sup 180}Ta{sup m} with high precision. The linearity of this instrument was verified by measuring the isotopically certified reference material for potassium (NIST 985), whose isotopes span a wide range of isotope ratios. The abundance sensitivity of the mass spectrometer for the measured ion beams has been examined to ensure the absence of tailing effects and interfering isotopes. These procedures are essential because of the extremely low isotope abundance of {sup 180}Ta{sup m}. The isotope fractionation of the tantalum isotopes was estimated by reference to the isotope fractionation of the isotopically certified reference material for rhenium (NIST 989). The isotopic composition of tantalum has been determined to be {sup 181}Ta/{sup 180}Ta{sup m}=8325 {+-} 43, which gives isotope abundances for {sup 180}Ta{sup m}=0.0001201 {+-} 0.0000008 and {sup 181}Ta=0.9998799 {+-} 0.0000008. This gives a Solar System abundance of {sup 180}Ta{sup m} of 2.49 x 10{sup -6} with reference to silicon=10{sup 6}. These isotope abundances, together with the relative atomic masses, give an atomic weight for tantalum of 180.947878 {+-} 0.000002.

  1. Carbon isotope fractionation during microbial methane oxidation

    NASA Astrophysics Data System (ADS)

    Barker, James F.; Fritz, Peter

    1981-09-01

    Methane, a common trace constituent of groundwaters, occasionally makes up more than 20% of the total carbon in groundwaters1,2. In aerobic environments CH4-rich waters can enable microbial food chain supporting a mixed culture of bacteria with methane oxidation as the primary energy source to develop3. Such processes may influence the isotopic composition of the residual methane and because 13C/12C analyses have been used to characterize the genesis of methanes found in different environments, an understanding of the magnitude of such effects is necessary. In addition, carbon dioxide produced by the methane-utilizing bacteria can be added to the inorganic carbon pool of affected groundwaters. We found carbon dioxide experimentally produced by methane-utilizing bacteria to be enriched in 12C by 5.0-29.6‰, relative to the residual methane. Where methane-bearing groundwaters discharged into aerobic environments microbial methane oxidation occurred, with the residual methane becoming progressively enriched in 13C. Various models have been proposed to explain the 13C/12C and 14C content of the dissolved inorganic carbon (DIC) of groundwaters in terms of additions or losses during flow in the subsurface4,5. The knowledge of both stable carbon isotope ratios in various pools and the magnitude of carbon isotope fractionation during various processes allows geochemists to use the 13C/12C ratio of the DIC along with water chemistry to estimate corrected 14C groundwater ages4,5. We show here that a knowledge of the carbon isotope fractionation between CH4 and CO2 during microbial methane-utilization could modify such models for application to groundwaters affected by microbial methane oxidation.

  2. The Late Miocene Carbon Isotope Shift and Marine Biological Productivity.

    NASA Astrophysics Data System (ADS)

    Diester-Haass, L.; Billups, K.; Emeis, K. C.

    2004-12-01

    The late Miocene global carbon isotope shift of approximately 1 per mil is not well understood. Is it linked to ocean-related processes such as the AƒAøAøâ_sA¬A.â_oBiologic BloomAƒAøAøâ_sA¬ \\(Farrell et al., 1995\\), or to changes in type \\(C3/C4 plants\\) or cover of terrestrial vegetation? Here we examine the evolution of marine biological productivity during the isotope shift at ODP Site 846 \\(Pacific equatorial upwelling, where the AƒAøAøâ_sA¬A.â_oBiologic BloomAƒAøAøâ_sA¬ has been first described, Farrell al, 1995\\) and at Indian Ocean Site 721 \\(monsoon-driven upwelling\\), and compare their productivity history with non upwelling locations in the Atlantic Ocean. The onset of the carbon isotope shift is accompanied at all locations by an increase in paleoproductivity derived from benthic foraminiferal accumulation rates \\(expressed as gC/cm2 * ky; Huerguera, 2000\\) and increased abundance of Uvigerina spp.. At the equatorial upwelling sites the increase is comparable to half present-day values to present-day values; in the Atlantic Ocean paleoproductivity increases from present-day up to 3 times present-day values. But the productivity maxima are not concurrent. The carbon isotope shift is accompanied by severe carbonate dissolution and reduced ventilation of bottom waters, as reflected in the occurrence of pyrite and good preservation of cartilageous fish debris. Carbonate preservation is good since about 6 Ma despite high productivity. We discuss changing deep water circulation patterns, increased weathering and continental nutrient delivery, as well as erosion of terrestrial vegetation as possible factors to explain our findings.

  3. Carbon isotopes in biological carbonates: Respiration and photosynthesis

    USGS Publications Warehouse

    McConnaughey, T.A.; Burdett, J.; Whelan, J.F.; Paull, C.K.

    1997-01-01

    Respired carbon dioxide is an important constituent in the carbonates of most air breathing animals but is much less important in the carbonates of most aquatic animals. This difference is illustrated using carbon isotope data from freshwater and terrestrial snails, ahermatypic corals, and chemoautotrophic and methanotrophic pelecypods. Literature data from fish otoliths and bird and mammal shell and bone carbonates are also considered. Environmental CO2/O2 ratios appear to be the major controlling variable. Atmospheric CO2/O2 ratios are about thirty times lower than in most natural waters, hence air breathing animals absorb less environmental CO2 in the course of obtaining O2. Tissue CO2 therefore, does not isotopically equilibrate with environmental CO2 as thoroughly in air breathers as in aquatic animals, and this is reflected in skeletal carbonates. Animals having efficient oxygen transport systems, such as vertebrates, also accumulate more respired CO2 in their tissues. Photosynthetic corals calcify mainly during the daytime when photosynthetic CO2 uptake is several times faster than respiratory CO2 release. Photosynthesis, therefore, affects skeletal ??13C more strongly than does respiration. Corals also illustrate how "metabolic" effects on skeletal isotopic composition can be estimated, despite the presence of much larger "kinetic" isotope effects. Copyright ?? 1997 Elsevier Science Ltd.

  4. Daily Variation of Isotope Ratios in Mars Atmospheric Carbon Dioxide

    NASA Astrophysics Data System (ADS)

    Livengood, Timothy A.; Kostiuk, Theodor; Kolasinski, John R.; Hewagama, Tilak; Henning, Wade G.; Sornig, Manuela; Stangier, Tobias; Krause, Pia; Sonnabend, Guido; Mahaffy, Paul R.

    2014-11-01

    The atmosphere of Mars has been shown by ground based high-resolution infrared spectroscopy and in situ measurements with the Phoenix lander and Mars Science Laboratory Curiosity rover to be enriched in C and O heavy isotopes, consistent with preferential loss of light isotopes in eroding Mars’ primordial atmosphere. The relative abundance of heavy isotopes, combined with contemporary measurements of loss rates to be obtained with MAVEN, will enable estimating the primordial atmospheric inventory on Mars. IR spectroscopy of Mars collected in May 2012 as well as in March and May of 2014 from the NASA IRTF has resolved transitions of all three singly-substituted minor isotopologues of carbon dioxide in addition to the normal isotope, enabling remote measurements of all the carbon and oxygen isotope ratios as a function of latitude, longitude, and time of day. Earlier measurements obtained in October 2007 demonstrated that the relative abundance of O-18 increased linearly with increasing surface temperature over a relatively warm early-afternoon temperature range, but did not extend far enough to inspect the effect of late-afternoon cooling. These results imply that isotopically enriched gas is sequestered overnight when surface temperature is minimum and desorbs through the course of the day as temperature increases. Current spectroscopic constants indicate that the peak isotopic enrichment could be significantly greater than what has been measured in situ, apparently due to sampling the atmosphere at different time of day and surface temperature. The observing runs in 2012 and 2014 measured O-18 enrichment at several local times in both morning and afternoon sectors as well as at the subsolar, equatorial, and anti-subsolar latitudes. The two runs in 2014 have additionally observed O-17 and C-13 transitions in the morning sector, from local dawn to noon. These observations include a limited sampling of measurements over Gale Crater, which can be compared with contemporary in situ measurements by the Curiosity rover to investigate the degree of agreement between in situ and remote methods and potentially to calibrate the spectroscopic constants required to accurately evaluate isotope ratios all over Mars.

  5. Laser ablation molecular isotopic spectrometry of carbon isotopes

    NASA Astrophysics Data System (ADS)

    Bol?shakov, Alexander A.; Mao, Xianglei; Jain, Jinesh; McIntyre, Dustin L.; Russo, Richard E.

    2015-11-01

    Quantitative determination of carbon isotopes using Laser Ablation Molecular Isotopic Spectrometry (LAMIS) is described. Optical emission of diatomic molecules CN and C2 is used in these measurements. Two quantification approaches are presented: empirical calibration of spectra using a set of reference standards and numerical fitting of a simulated spectrum to the experimental one. Formation mechanisms of C2 and CN in laser ablation plasma are briefly reviewed to provide insights for implementation of LAMIS measurements. A simulated spectrum of the 12C2 Swan system was synthesized using four constituents within 473.5-476.5 nm. Simulation included three branches of 12C2 (1-0), branches R(0-0) and R(1-1), and branch P(9-8) of 12C2. Spectral positions of the tail lines in R(0-0) and R(1-1) were experimentally measured, since they were not accurately known before. The Swan band (1-0) of the isotopologue 13C12C was also simulated. Fitting to the experimental spectrum yielded the ratio 13C/12C = 1.08% in a good agreement with measurements by isotope ratio mass spectrometry. LAMIS promises to be useful in coal, oil and shale exploration, carbon sequestration monitoring, and agronomy studies.

  6. Natural gas constituent and carbon isotopic composition in petroliferous basins, China

    NASA Astrophysics Data System (ADS)

    Zhu, Guangyou; Wang, Zhengjun; Dai, Jinxing; Su, Jing

    2014-02-01

    There are abundant gas resources in petroliferous basins of China. Large to midsize gas fields are found in Eastern, central and Western of China. However, origin, constituents and isotopic composition of natural gas in different gas fields are varied distinctly, and some present strong chemical secondary alteration and show variation both in age and space. Based on the systematic analysis of constituents and carbon isotope of a large number of gas samples, combined with the geological characteristics, this paper classifies the origins of the gases, explores the gas isotope characteristics and evolutionary regulation with the variation time and space, and further discusses the distinctive geochemistry of the gases in China. These gases are dominated by dry gas, its methane carbon isotope values range from -10‰ to -70‰, ethane from -16‰ to -52‰, propane from -13‰ to -43‰, and butane from -18‰ to -34‰. The carbon isotopes of most gases show the characteristics of humic-derived gas and crude oil cracked gas. In addition, large primary biogenic gas fields have been discovered in the Qaidam basin; inorganic-derived alkane gases have been discovered in deep of the Songliao Basin. Half of these gas fields are characterized by the alkane carbon isotope reversal in different degrees. Research indicates there are several reasons can result in carbon isotope reversal. Firstly, gas charge of different genetic types or different source in one gas reservoir may cause carbon isotope reversal. Besides, high-over mature evolution of gas can also lead to the carbon isotopic reversal of alkanes. Thirdly, secondary alteration of hydrocarbons may also result in abnormal distribution of carbon isotope, isotope transforms to unusual light and heavy.

  7. Isotope Variations in Terrestrial Carbonates and Thermal Springs as Biomarkers: Analogs for Martian Processes

    NASA Technical Reports Server (NTRS)

    Socki, Richard A.; Gibson, Everett K., Jr.; Bissada, K. K.

    2006-01-01

    Stable isotope measurements of carbonate minerals contained within ALH84001 [1] suggest that fluids were present at 3.9 Gy on Mars [2, 3, 4, 5]. Both oxygen and carbon isotopes provide independent means of deciphering paleoenvironmental conditions at the time of carbonate mineral precipitation. In terrestrial carbonate rocks oxygen isotopes not only indicate the paleotemperature of the precipitating fluid, but also provide clues to environmental conditions that affected the fluid chemistry. Carbon isotopes, on the other hand, can indicate the presence or absence of organic compounds during precipitation (i.e. biogenically vs. thermogenically-generated methane), thus serving as a potential biomarker. We have undertaken a study of micro scale stable isotope variations measured in some terrestrial carbonates and the influence of organic compounds associated with the formation of these carbonates. Preliminary results indicate that isotope variations occur within narrow and discrete intervals, providing clues to paleoenvironmental conditions that include both biological and non-biological activity. These results carry implications for deciphering Martian isotope data and therefore potential biological prospecting on the planet Mars. Recently, Fourier Transform Spectrometer observations have detected methane occurring in the Martian atmosphere [6] that could be attributed to a possible biogenic source. Indeed, Mars Express has detected the presence of methane in the Martian atmosphere [7], with evidence indicating that methane abundances are greatest above those basins with high water concentrations.

  8. Is my C isotope excursion global, local, or both? Insights from the Mg and Ca isotopic composition of primary, diagenetic, and authigenic carbonates

    NASA Astrophysics Data System (ADS)

    Higgins, J. A.; Blättler, C. L.; Husson, J. M.

    2014-12-01

    The C isotopic composition of ancient limestones and dolomites is a widely used proxy for the global geochemical cycles of carbon and oxygen in the ocean-atmosphere system and a critical tool for chemostratigraphy in Precambrian rocks. Although relatively robust to diagenesis, the C isotopic composition of bulk carbonates can be reset when conditions favor high water-to-rock ratios or fluids with high C concentrations and distinct isotopic compositions. Authigenic carbonates and different pools of primary carbonate (e.g. calcite vs. aragonite) may also bias the C isotopic composition of bulk carbonates if they are both abundant and isotopically distinct. New approaches to quantifying contributions from diagenesis, authigenesis, and mixing of primary carbonates to the C isotopic composition of bulk sedimentary carbonates are needed. Here we present preliminary Mg and Ca isotope data sets of primary, diagenetic, and authigenic carbonates, both modern and ancient. We show that recrystallization, dolomitization, and authigenesis produce Mg and Ca isotope fingerprints that may be used to identify and characterize these processes in ancient carbonate sediments.

  9. Carbon abundances of sdO stars from SPY

    NASA Astrophysics Data System (ADS)

    Hirsch, Heiko; Heber, Uli

    2009-06-01

    Ströer et al. (2007) recently suggested a classification of sdOs according to supersolar and subsolar helium abundances, with only the helium-enriched stars showing signes of carbon and/or nitrogen in their optical spectra. We aim to derive reliable carbon and nitrogen abundances by fitting synthetic spectra to data obtained with the UVES spectrograph at ESO. Here we present our first results of the analysis of carbon abundances in hot subdwarf O stars. By constructing a grid of model atmospheres consisting of hydrogen, helium and carbon we were able to derive atmospheric parameters of nine carbon rich sdOs. We find log(NC/Ntotal) up to ten times higher than the solar value, while the mean value for the effective temperature and the surface gravity is slightly lower than derived by helium-hydrogen models only. Surprisingly, we also find three fast rotators among our program stars.

  10. Precision performance of a Cavity Ring-down isotope spectrometer for carbon and oxygen isotopes of carbonate materials

    NASA Astrophysics Data System (ADS)

    Cunningham, K. L.; Hoffnagle, J.; He, Y.; Fleck, D.; Saad, N.; Dennis, K.

    2013-12-01

    We have developed a novel laser spectrometer intended specifically for the measurement of ?18O and ?13C in solid carbonate material. Carbonate carbon and oxygen isotopes provide key contributions into our understanding of climate, biogeochemical processes and the carbon cycle. For this reason, the isotopic measurements of carbonates are one of the most abundant measures made by Earth scientists today. Conventional measurement techniques using isotope ratio mass spectrometry (IRMS), although optimized and prevalent, require dedicated personnel and can be expensive to operate. Here we present a new laser-based technique that will simplify measurements of ?18Ocarb and ?13Ccarb without compromising precision. To date, there have been no laser-based instruments with a demonstrated ability to meet the requirements of the carbonates community -- typically better than 0.1 ‰ for ?13C and ?18O for CO2 evolved from 1 mg of pure CaCO3. We will present data showing that the new Picarro G2171-i spectrometer meets these requirements. The spectrometer uses the laser-based spectroscopy technique of Cavity Ring-Down Spectroscopy (CRDS), a technology that has been successfully applied to many other isotopic ratio measurements including ?13C of CO2, ?13C of CH4, and ?18O and ?D of H2O. The spectrometer has been optimized to analyze the absorption spectra of concentrated CO2, specifically the isotopologues 12C16O16O, 13C16O16O, 12C16O18O, and 12C18O16O. We employ a new sample delivery technique that enables a longer integration time period, and hence more precise data. Long-term results for a run of 540 pulses of tank CO2 (90 hours) records a 1? standard deviation precision for ?18O and ?13C of < 0.08 ‰ and < 0.055 ‰, respectively. We coupled the CRDS spectrometer to an optimized sample acidification system and analyzed standards to assess the accuracy of the CRDS. We will present an inter-comparison between CRDS and IRMS for carbonates using standards commonly used as isotopic reference material for the calibration of IRMS instruments. The new CRDS spectrometer will provide researchers with a simplified option to accelerate the pace and breadth of carbonates-based research.

  11. Carbon isotopic composition of individual Precambrian microfossils

    NASA Technical Reports Server (NTRS)

    House, C. H.; Schopf, J. W.; McKeegan, K. D.; Coath, C. D.; Harrison, T. M.; Stetter, K. O.

    2000-01-01

    Ion microprobe measurements of carbon isotope ratios were made in 30 specimens representing six fossil genera of microorganisms petrified in stromatolitic chert from the approximately 850 Ma Bitter Springs Formation, Australia, and the approximately 2100 Ma Gunflint Formation, Canada. The delta 13C(PDB) values from individual microfossils of the Bitter Springs Formation ranged from -21.3 +/- 1.7% to -31.9 +/- 1.2% and the delta 13C(PDB) values from microfossils of the Gunflint Formation ranged from -32.4 +/- 0.7% to -45.4 +/- 1.2%. With the exception of two highly 13C-depleted Gunflint microfossils, the results generally yield values consistent with carbon fixation via either the Calvin cycle or the acetyl-CoA pathway. However, the isotopic results are not consistent with the degree of fractionation expected from either the 3-hydroxypropionate cycle or the reductive tricarboxylic acid cycle, suggesting that the microfossils studied did not use either of these pathways for carbon fixation. The morphologies of the microfossils suggest an affinity to the cyanobacteria, and our carbon isotopic data are consistent with this assignment.

  12. Carbon isotopic composition of individual Precambrian microfossils

    NASA Astrophysics Data System (ADS)

    House, Christopher H.; Schopf, J. William; McKeegan, Kevin D.; Coath, Christopher D.; Harrison, T. Mark; Stetter, Karl O.

    2000-08-01

    Ion microprobe measurements of carbon isotope ratios were made in 30 specimens representing six fossil genera of microorganisms petrified in stromatolitic chert from the ˜850 Ma Bitter Springs Formation, Australia, and the ˜2100 Ma Gunflint Formation, Canada. The ?13CPDB values from individual microfossils of the Bitter Springs Formation ranged from -21.3 ± 1.7‰ to -31.9 ± 1.2‰, and the ?13CPDB values from microfossils of the Gunflint Formation ranged from -32.4 ± 0.7‰ to -45.4 ± 1.2‰. With the exception of two highly 13C-depleted Gunflint microfossils, the results generally yield values consistent with carbon fixation via either the Calvin cycle or the acetyl-CoA pathway. However, the isotopic results are not consistent with the degree of fractionation expected from either the 3-hydroxypropionate cycle or the reductive tricarboxylic acid cycle, suggesting that the microfossils studied did not use either of these pathways for carbon fixation. The morphologies of the microfossils suggest an affinity to the cyanobacteria, and our carbon isotopic data are consistent with this assignment.

  13. Diurnal and Interannual Variation in Absorption Lines of Isotopic Carbon Dioxide in Mars Atmosphere

    NASA Astrophysics Data System (ADS)

    Livengood, Timothy A.; Kostiuk, Theodor; Hewagama, Tilak; Kolasinski, John R.; Henning, Wade G.

    2015-11-01

    Groundbased observations of Mars in 2003, 2007, 2012, and 2014 have detected transitions of carbon dioxide containing the stable minor isotopes of oxygen and carbon as well as the primary isotopes, using the ultrahigh resolution spectrometer HIPWAC at the NASA Infrared Telescope Facility. The most well characterized minor isotope is O-18, due to strong lines and observational opportunities. The average estimated O-18/O-16 isotope ratio is roughly consistent with other in situ and remote spectroscopic measurements but demonstrates an additional feature in that the retrieved ratio appears to increase with greater ground surface temperature. These conclusions primarily come from analyzing a subset of the 2007 data. Additional observations have been acquired over a broad range of local time and meridional position to evaluate variability with respect to ground surface temperature. These additional observations include one run of measurements with C-13. These observations can be compared to local in situ measurements by the Curiosity rover to narrow the uncertainty in absolute isotope ratio and extend isotopic measurements to other regions and seasons on Mars. The relative abundance of carbon dioxide heavy isotopes on Mars is central to estimating the primordial atmospheric inventory on Mars. Preferential freeze-distillation of heavy isotopes means that any measurement of the isotope ratio can be only a lower limit on heavy isotope enrichment due to past and current loss to space.

  14. Carbon and Strontium Abundances of Metal-Poor Stars

    E-print Network

    David K. Lai; Jennifer A. Johnson; Michael Bolte; Sara Lucatello

    2007-06-20

    We present carbon and strontium abundances for 100 metal-poor stars measured from R$\\sim $7000 spectra obtained with the Echellette Spectrograph and Imager at the Keck Observatory. Using spectral synthesis of the G-band region, we have derived carbon abundances for stars ranging from [Fe/H]$=-1.3$ to [Fe/H]$=-3.8$. The formal errors are $\\sim 0.2$ dex in [C/Fe]. The strontium abundance in these stars was measured using spectral synthesis of the resonance line at 4215 {\\AA}. Using these two abundance measurments along with the barium abundances from our previous study of these stars, we show it is possible to identify neutron-capture-rich stars with our spectra. We find, as in other studies, a large scatter in [C/Fe] below [Fe/H]$ = -2$. Of the stars with [Fe/H]$<-2$, 9$\\pm$4% can be classified as carbon-rich metal-poor stars. The Sr and Ba abundances show that three of the carbon-rich stars are neutron-capture-rich, while two have normal Ba and Sr. This fraction of carbon enhanced stars is consistent with other studies that include this metallicity range.

  15. Anatomy of a cluster IDP. Part 2: Noble gas abundances, trace element geochemistry, isotopic abundances, and trace organic chemistry of several fragments from L2008#5

    NASA Technical Reports Server (NTRS)

    Thomas, K. L.; Clemett, S. J.; Flynn, G. J.; Keller, L. P.; Mckay, David S.; Messenger, S.; Nier, A. O.; Schlutter, D. J.; Sutton, S. R.; Walker, R. M.

    1994-01-01

    The topics discussed include the following: noble gas content and release temperatures; trace element abundances; heating summary of cluster fragments; isotopic measurements; and trace organic chemistry.

  16. BOREAS TE-5 Leaf Carbon Isotope Data

    NASA Technical Reports Server (NTRS)

    Hall, Forrest G. (Editor); Curd, Shelaine (Editor); Ehleriinger, Jim; Brooks, J. Renee; Flanagan, Larry

    2000-01-01

    The BOREAS TE-5 team collected measurements in the NSA and SSA on gas exchange, gas composition, and tree growth. This documentation describes leaf carbon isotope data that were collected in 1993 and 1994 at the NSA and SSA OJP sites, the SSA OBS site, and the NSA UBS site. In addition, leaf carbon isotope data were collected in 1994 only at the NSA and SSA OA sites. These data was collected to provide seasonal integrated physiological information for 10 to 15 common species at these 6 BOREAS sites. The data are stored in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

  17. Oxygen isotopic composition of carbon dioxide in the middle atmosphere

    PubMed Central

    Liang, Mao-Chang; Blake, Geoffrey A.; Lewis, Brenton R.; Yung, Yuk L.

    2007-01-01

    The isotopic composition of long-lived trace molecules provides a window into atmospheric transport and chemistry. Carbon dioxide is a particularly powerful tracer, because its abundance remains >100 parts per million by volume (ppmv) in the mesosphere. Here, we successfully reproduce the isotopic composition of CO2 in the middle atmosphere, which has not been previously reported. The mass-independent fractionation of oxygen in CO2 can be satisfactorily explained by the exchange reaction with O(1D). In the stratosphere, the major source of O(1D) is O3 photolysis. Higher in the mesosphere, we discover that the photolysis of 16O17O and 16O18O by solar Lyman-? radiation yields O(1D) 10–100 times more enriched in 17O and 18O than that from ozone photodissociation at lower altitudes. This latter source of heavy O(1D) has not been considered in atmospheric simulations, yet it may potentially affect the “anomalous” oxygen signature in tropospheric CO2 that should reflect the gross carbon fluxes between the atmosphere and terrestrial biosphere. Additional laboratory and atmospheric measurements are therefore proposed to test our model and validate the use of CO2 isotopic fractionation as a tracer of atmospheric chemical and dynamical processes. PMID:17190796

  18. Oxygen isotopic composition of carbon dioxide in the middle atmosphere.

    PubMed

    Liang, Mao-Chang; Blake, Geoffrey A; Lewis, Brenton R; Yung, Yuk L

    2007-01-01

    The isotopic composition of long-lived trace molecules provides a window into atmospheric transport and chemistry. Carbon dioxide is a particularly powerful tracer, because its abundance remains >100 parts per million by volume (ppmv) in the mesosphere. Here, we successfully reproduce the isotopic composition of CO(2) in the middle atmosphere, which has not been previously reported. The mass-independent fractionation of oxygen in CO(2) can be satisfactorily explained by the exchange reaction with O((1)D). In the stratosphere, the major source of O((1)D) is O(3) photolysis. Higher in the mesosphere, we discover that the photolysis of (16)O(17)O and (16)O(18)O by solar Lyman-alpha radiation yields O((1)D) 10-100 times more enriched in (17)O and (18)O than that from ozone photodissociation at lower altitudes. This latter source of heavy O((1)D) has not been considered in atmospheric simulations, yet it may potentially affect the "anomalous" oxygen signature in tropospheric CO(2) that should reflect the gross carbon fluxes between the atmosphere and terrestrial biosphere. Additional laboratory and atmospheric measurements are therefore proposed to test our model and validate the use of CO(2) isotopic fractionation as a tracer of atmospheric chemical and dynamical processes. PMID:17190796

  19. Determination of lithium isotopes at natural abundance levels by atomic absorption spectrometry

    USGS Publications Warehouse

    Meier, A.L.

    1982-01-01

    The relationships of the absorption of 6Li and 7Li hollow cathode lamp emissions are used to determine lithium isotopic composition in the natural abundance range of geologic materials. Absorption was found to have a nonlinear dependence upon total lithium concentration and isotopic composition. A method using nonlinear equations to describe the relationship of the absorption of 6Li and 7Li lamp radiation is proposed as a means of calculating isotopic composition that is independent of total lithium concentration.

  20. Breath carbon stable isotope ratios identify changes in energy balance and substrate utilization in humans

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Rapid detection of shifts in substrate utilization and energy balance would provide a compelling biofeedback tool to enable individuals to lose weight. In a pilot study, we tested whether the natural abundance of exhaled carbon stable isotope ratios (breath d13C values) reflects shifts between negat...

  1. Equations for Lipid Normalization of Carbon Stable Isotope Ratios in Aquatic Bird Eggs

    PubMed Central

    Elliott, Kyle H.; Davis, Mikaela; Elliott, John E.

    2014-01-01

    Stable isotope ratios are biogeochemical tracers that can be used to determine the source of nutrients and contaminants in avian eggs. However, the interpretation of stable carbon ratios in lipid-rich eggs is complicated because 13C is depleted in lipids. Variation in 13C abundance can therefore be obscured by variation in percent lipids. Past attempts to establish an algebraic equation to correct carbon isotope ratios for lipid content in eggs have been unsuccessful, possibly because they relied partly on data from coastal or migratory species that may obtain egg lipids from different habitats than egg protein. We measured carbon, nitrogen and sulphur stable isotope ratios in 175 eggs from eight species of aquatic birds. Carbon, nitrogen and sulphur isotopes were enriched in lipid-extracted egg samples compared with non extracted egg samples. A logarithmic equation using the C?N ratio and carbon isotope ratio from the non extracted egg tissue calculated 90% of the lipid-extracted carbon isotope ratios within ±0.5‰. Calculating separate equations for eggs laid by species in different habitats (pelagic, offshore and terrestrial-influenced) improved the fit. A logarithmic equation, rather than a linear equation as often used for muscle, was necessary to accurately correct for lipid content because the relatively high lipid content of eggs compared with muscle meant that a linear relationship did not accurately approximate the relationship between percent lipids and the C?N ratio. Because lipid extraction alters sulphur and nitrogen isotope ratios (and cannot be corrected algebraically), we suggest that isotopic measurement on bulk tissue followed by algebraic lipid normalization of carbon stable isotope ratio is often a good solution for homogenated eggs, at least when it is not possible to complete separate chemical analyses for each isotope. PMID:24465384

  2. Calcium isotope evidence for suppression of carbonate dissolution in carbonate-bearing organic-rich sediments

    NASA Astrophysics Data System (ADS)

    Turchyn, Alexandra V.; DePaolo, Donald J.

    2011-11-01

    Pore fluid calcium isotope, calcium concentration and strontium concentration data are used to measure the rates of diagenetic dissolution and precipitation of calcite in deep-sea sediments containing abundant clay and organic material. This type of study of deep-sea sediment diagenesis provides unique information about the ultra-slow chemical reactions that occur in natural marine sediments that affect global geochemical cycles and the preservation of paleo-environmental information in carbonate fossils. For this study, calcium isotope ratios (? 44/40Ca) of pore fluid calcium from Ocean Drilling Program (ODP) Sites 984 (North Atlantic) and 1082 (off the coast of West Africa) were measured to augment available pore fluid measurements of calcium and strontium concentration. Both study sites have high sedimentation rates and support quantitative sulfate reduction, methanogenesis and anaerobic methane oxidation. The pattern of change of ? 44/40Ca of pore fluid calcium versus depth at Sites 984 and 1082 differs markedly from that of previously studied deep-sea Sites like 590B and 807, which are composed of nearly pure carbonate sediment. In the 984 and 1082 pore fluids, ? 44/40Ca remains elevated near seawater values deep in the sediments, rather than shifting rapidly toward the ? 44/40Ca of carbonate solids. This observation indicates that the rate of calcite dissolution is far lower than at previously studied carbonate-rich sites. The data are fit using a numerical model, as well as more approximate analytical models, to estimate the rates of carbonate dissolution and precipitation and the relationship of these rates to the abundance of clay and organic material. Our models give mutually consistent results and indicate that calcite dissolution rates at Sites 984 and 1082 are roughly two orders of magnitude lower than at previously studied carbonate-rich sites, and the rate correlates with the abundance of clay. Our calculated rates are conservative for these sites (the actual rates could be significantly slower) because other processes that impact the calcium isotope composition of sedimentary pore fluid have not been included. The results provide direct geochemical evidence for the anecdotal observation that the best-preserved carbonate fossils are often found in clay or organic-rich sedimentary horizons. The results also suggest that the presence of clay minerals has a strong passivating effect on the surfaces of biogenic carbonate minerals, slowing dissolution dramatically even in relation to the already-slow rates typical of carbonate-rich sediments.

  3. Low temperature Rosseland opacities with varied abundances of carbon and nitrogen

    E-print Network

    Michael T. Lederer; Bernhard Aringer

    2008-12-09

    We attempt to produce low temperature opacity data incorporating the effects of varied abundances of the elements carbon and nitrogen. For our temperature range of interest, molecules represent the dominant opacity source. Our dataset covers a wide metallicity range and is meant to provide important input data for stellar evolution models and other applications. We conduct chemical equilibrium calculations to evaluate the partial pressures of neutral atoms, ions, and molecules. Based on a large dataset containing atomic line and continuum data and, most importantly, a plethora of molecular lines, we calculate Rosseland mean opacity coefficients not only for a number of different metallicities, but also for varied abundances of the isotopes ^{12}C and ^{14}N at each metallicity. The molecular data comprise the main opacity sources for either an oxygen-rich or carbon-rich chemistry. We tabulate the opacity coefficients as a function of temperature and, basically, density. Due to the special role of the CO molecule, within a certain chemistry regime an alteration to the carbon abundance causes considerable changes in the Rosseland opacity. The transition from a scaled solar (i. e. oxygen-rich) mixture to a carbon-rich regime results in opacities that can, at low temperatures, differ by orders of magnitude from to the initial situation. The reason is that the mean opacity in either case is due to different molecular absorbers. Variations in the abundance of nitrogen have less pronounced effects but, nevertheless, cannot be neglected. [abridged

  4. Abundance of atomic carbon /C I/ in dense interstellar clouds

    NASA Technical Reports Server (NTRS)

    Phillips, T. G.; Huggins, P. J.

    1981-01-01

    The abundance of interstellar neutral atomic carbon is investigated by means of its ground state fine-structure line emission at 492 GHz using the 91.5 cm telescope of NASAs Kuiper Airborne Observatory. Atomic carbon is found to be very abundant in dense interstellar molecular clouds with column densities of about 10 to the 19th per sq cm. Because the observations have considerably greater column densities than current theories of carbon chemistry, it is suggested that the physical conditions of these clouds are not as simple as assumed in the models. Various situations are discussed which would lead to large C I abundances, including the possibility that the chemical lifetimes of the clouds are relatively short.

  5. Further carbon isotope measurements of LEW 88516

    NASA Astrophysics Data System (ADS)

    Wright, I. P.; Douglas, C.; Pillinger, C. T.

    1993-03-01

    Douglas et al. have previously analyzed the carbon content and isotopic composition of a crushed sample (sub-sample 13) of the shergottite, LEW 88516. The powder, which was from a relatively large portion of the meteorite in order to obtain a representative sample, was distributed amongst the scientific community. However, it is probable that the preparation procedure was not optimized for the purposes of carbon measurements. Indeed, it was found that LEW 88516,13 contained over 1200 ppm carbon, a concentration which is greater than that present in any other SNC meteorite. That a close relative, ALH A77005, contains only 141 ppm carbon seems to implicate the preparation procedure as being responsible for the apparently high carbon content of LEW 88516. However, it may also be the nature of the fine powder which has resulted in contamination. The observation of high carbon content in LEW 88516,13 highlights the extreme difficulty of trying to obtain representative samples of whole meteorites for this kind of investigation. Presented herein are some further measurements of LEW 88516 which should serve to clarify some of the issues raised by the previous investigation.

  6. Isotope labeling pattern study of central carbon metabolites using GC/MS.

    PubMed

    Jung, Joon-Young; Oh, Min-Kyu

    2015-01-01

    Determination of fluxes by (13)C tracer experiments depends on monitoring the (13)C labeling pattern of metabolites during isotope experiments. In metabolome-based (13)C metabolic flux analysis, liquid chromatography combined with mass spectrometry or tandem mass spectrometry (LC/MS or LC/MS/MS, respectively) has been mainly used as an analytical platform for isotope pattern studies of central carbon metabolites. However, gas chromatography with mass spectrometry (GC/MS) has several advantages over LC/MS, such as high sensitivity, low cost, ease of operation, and availability of mass spectra databases for comparison. In this study, analysis of isotope pattern for central carbon metabolites using GC/MS was demonstrated. First, a proper set of mass ions for central carbon metabolites was selected based on carbon backbone information and structural isomers of mass fragment ions. A total of 34 mass fragment ions was selected and used for the quantification of 25 central carbon metabolites. Then, to quantify isotope fractions, a natural mass isotopomer library for selected mass fragment ions was constructed and subtracted from isotopomer mass spectra data. The results revealed a surprisingly high abundance of partially labeled (13)C intermediates, such as 56.4% of fructose 6-phosphate and 47.6% of dihydroxyacetone phosphate at isotopic steady state, which were generated in the pentose phosphate pathway. Finally, dynamic changes of isotope fragments of central metabolites were monitored with a U-(13)C glucose stimulus response experiment in Kluyveromyces marxianus. With a comprehensive study of isotope patterns of central carbon metabolites using GC/MS, 25 central carbon metabolites and their isotopic fractions were successfully quantified. Dynamic and precise acquisition of isotope pattern can then be used in combination with proper kinetic models to calculate metabolic fluxes. PMID:25463204

  7. Ion Mobility Mass Spectrometry Direct Isotope Abundance Analysis

    SciTech Connect

    Manuel J. Manard, Stephan Weeks, Kevin Kyle

    2010-05-27

    The nuclear forensics community is currently engaged in the analysis of illicit nuclear or radioactive material for the purposes of non-proliferations and attribution. One technique commonly employed for gathering nuclear forensics information is isotope analysis. At present, the state-of-the-art methodology for obtaining isotopic distributions is thermal ionization mass spectrometry (TIMS). Although TIMS is highly accurate at determining isotope distributions, the technique requires an elementally pure sample to perform the measurement. The required radiochemical separations give rise to sample preparation times that can be in excess of one to two weeks. Clearly, the nuclear forensics community is in need of instrumentation and methods that can expedite their decision making process in the event of a radiological release or nuclear detonation. Accordingly, we are developing instrumentation that couples a high resolution IM drift cell to the front end of a MS. The IM cell provides a means of separating ions based upon their collision cross-section and mass-to-charge ratio (m/z). Two analytes with the same m/z, but with different collision cross-sections (shapes) would exit the cell at different times, essentially enabling the cell to function in a similar manner to a gas chromatography (GC) column. Thus, molecular and atomic isobaric interferences can be effectively removed from the ion beam. The mobility selected chemical species could then be introduced to a MS for high-resolution mass analysis to generate isotopic distributions of the target analytes. The outcome would be an IM/MS system capable of accurately measuring isotopic distributions while concurrently eliminating isobaric interferences and laboratory radiochemical sample preparation. The overall objective of this project is developing instrumentation and methods to produce near real-time isotope distributions with a modular mass spectrometric system that performs the required gas-phase chemistry and separations. The system couples a high-resolution ion mobility (IM) drift cell to the front end of a mass spectrometer (MS) allowing for chemical separation prior to isotope distribution analyses. This will yield isotope ratio measurement capabilities with minimal sample preparation.

  8. Radiogenic Carbon Isotopes in Authigenic Carbonate from Lake Neusiedl, Austria

    NASA Astrophysics Data System (ADS)

    Neuhuber, Stephanie; Steier, Peter; Gier, Susanne; Draganits, Erich; Kogelbauer, Ilse

    2015-04-01

    Formation of authigenic carbonate in Lake Neusiedl, Austia, has been reported since the 1960ies. The reaction pathways resulting in carbonate precipitation (protodolomite and high magnesium calcite) have yet to be identified. Lake Neusiedl is a shallow lake without significant sediment accumulation but constant reworking of sediment due to its shallow depth (1.8m) and influence by wind. The sediments are water-saturated silts and clays that overly Neogene sediments. The age of Lake Neusiedl is unknown due to its low sedimentation rate and constant remixing of sediment. Dating of authigenic minerals is an alternative method to determine the minimum age of water present - even episodically - at the location. We characterize the sediments mineralogy in different size fractions by X-Ray Diffractometry (XRD), Simultaneous Themo Analysis (STA) and Fourier Transform Infra Red Spectroscopy, stable carbon and oxygen isotopes as well as radiogenic carbon. To describe the authigenic carbonates and find the fractions with highest authigenic carbonate minerals we investigate the size fractions <4 µm, <3 µm, <2 µm, <1 µm, 0.5 µm and <0.2 µm. The "coarser" fractions (4 µm to 2 µm) contain detrital minerals such as chlorite, muscovite, quartz, feldspar, stoichiometric calcite and stoichiometric dolomite as well as authigenic high Mg calcite. Radiogenic carbon ages increase with increasing grain size from 850 years before present to 2300 years before present and indicate a very slow growth rate or episodic growth of authigenic carbonate phases.

  9. Barium even-to-odd isotope abundance ratios in thick disk and thin disk stars

    E-print Network

    L. Mashonkina; G. Zhao

    2006-07-06

    We present the Ba even-to-odd isotope abundance ratios in 25 cool dwarf stars with the metallicity [Fe/H] ranged between 0.25 and --1.35. Our method takes advantage of the hyperfine structure (HFS) affecting the \\ion{Ba}{ii} resonance line of the odd isotopes. The fractional abundance of the odd isotopes of Ba is derived from a requirement that Ba abundances from the resonance line $\\lambda 4554$ and subordinate lines $\\lambda 5853$ and $\\lambda 6496$ must be equal. The results are based on NLTE line formation and analysis of high resolution (R $\\sim60000$) high signal-to-noise (S/N $\\ge 200$) observed spectra. We find that the fraction of the odd isotopes of Ba grows toward the lower Ba abundance (or metallicity) and the mean value in the thick disk stars equals 33 $\\pm$ 4%. This indicates the higher contribution of the $r-$process to barium in the thick disk stars compared to the solar system matter. The obtained fraction increases with the [Eu/Ba] abundance ratio growth in agreement with expectations. A significant fraction of the \\emph{even} isotopes of Ba found in old Galactic stars (the thick disk stars), $\\sim67$%, is in contrast to the prediction of the "classical" model of the $s-$process and favors the value predicted by the "stellar" models of Arlandini et al. (1999) and Travaglio et al. (1999).

  10. Biomarker and molecular isotope approaches to deconvolve the terrestrial carbon isotope record: modern and Eocene calibrations

    NASA Astrophysics Data System (ADS)

    Diefendorf, A. F.; Freeman, K. H.; Wing, S.; Currano, E. D.

    2010-12-01

    Climate, biome, and plant community are important predictors of carbon isotope patterns recorded in leaves and leaf waxes. However, signatures recorded by terrestrial organic carbon and lipids that have mixed floral sources (e.g., n-alkanes) potentially reflect both plant community changes and climate. More taxonomically specific proxies for plants (i.e., di- and tri-terpenoids for conifers and angiosperms, respectively), can help to resolve the relative influences of changing community and climate, provided differences in biomarker production and lipid biosynthetic fractionation among plants can be better constrained. We present biomarker abundance and carbon isotope values for lipids from leaves, branches and bark of 44 tree species, representing 21 families including deciduous and evergreen conifers and angiosperms. n-alkane production differs greatly between conifer and angiosperm leaves. Both deciduous and evergreen angiosperms make significantly more n-alkanes than conifers, with n-alkanes not detected in over half of the conifers in our study. Terpenoid abundances scale strongly with leaf habit: evergreen species have significantly higher abundances. We combine these relative differences in lipid production with published estimates of fluxes for leaf litter from conifer and angiosperm trees to develop a new proxy approach for estimating paleo plant community inputs to ancient soils and sediments. To test our modern calibration results, we have evaluated n-alkanes and terpenoids from laterally extensive (~18 km) carbonaceous shales and mudstones in Eocene sediments (52.6 Ma) at Fifteenmile Creek in the Bighorn Basin (WY, USA). Our terpenoid-based proxy predicts on average a 40% conifer community, which is remarkably close in agreement with a fossil-based estimate of 36%. n-alkane carbon isotope fractionation (leaf-lipid) differs among plant types, with conifer n-alkanes about 2-3‰ 13C enriched relative to those in angiosperms. Since conifer leaves are generally 2-3‰ enriched relative to angiosperm leaves, we project that the far more abundant angiosperm lipids will be about 4-6 ‰ depleted relative to small amounts of conifer n-alkanes in natural samples. In addition, we report carbon isotope values of the terpenoids from the MVA (triterpenoids) and MEP (diterpenoids) synthesis pathways for our plant sample set. Bulk leaf tissue-to-lipid fractionation factors for terpenoids are similar and generally small, -0.4 and -0.6‰, for MVA and MEP products, respectively. Estimates of precipitation from fossil leaves at the Fifteenmile site allow us to predict leaf fractionation values for different plant types (bulk) and for triterpenoid and diterpenoid compound classes. Our fractionation factors, when applied to an estimate for the ?13C value of late Eocene CO2, agree well with bulk and molecular data. An understanding of molecular production biases greatly improves our ability to reconstruct both paleovegetation and ?13C of atmospheric CO2.

  11. Stable Carbon Isotope Fractionation during Aerobic Biodegradation of

    E-print Network

    Chu, Kung-Hui "Bella"

    Stable Carbon Isotope Fractionation during Aerobic Biodegradation of Chlorinated Ethenes K U N G and Caldwell, 201 North Civic Drive, Walnut Creek, California 94596, and Center for Isotope Geochemistry, MS 70A-4418, Lawrence Berkeley National Laboratory, Berkeley, California 94720 Stable isotope analysis

  12. Oxygen and carbon isotope disequilibria in Galapagos corals: isotopic thermometry and calcification physiology

    SciTech Connect

    McConnaughey, T.A.

    1986-01-01

    Biological carbonate skeletons are built largely from carbon dioxide, which reacts to form carbonate ion within thin extracellular solutions. The light isotopes of carbon and oxygen react faster than the heavy isotopes, depleting the resulting carbonate ions in /sup 13/C and /sup 18/O. Calcium carbonate precipitation occurs sufficiently fast that the skeleton remains out of isotopic equilibrium with surrounding fluids. This explanation for isotopic disequilibrium in biological carbonates was partially simulated in vitro, producing results similar to those seen in non-photosynthetic corals. Photosynthetic corals have higher /sup 13/C//sup 12/C ratios due to the preferential removal of /sup 12/C (as organic carbon) from the reservoir of dissolved inorganic carbon. The oxygen isotopic variations in corals can be used to reconstruct past sea surface temperatures to an accuracy of about 0.5/sup 0/C. The carbon isotopic content of photosynthetic corals provides an indication of cloudiness. Using isotopic data from Galapagos corals, it was possible to construct proxy histories of the El Nino phenomenon. The physiology of skeletogenesis appears to be surprisingly similar in calcium carbonate, calcium phosphate, and silica precipitating systems.

  13. Carbon chain abundance in the diffuse interstellar medium

    NASA Technical Reports Server (NTRS)

    Allamandola, L. J.; Hudgins, D. M.; Bauschlicher, C. W. Jr; Langhoff, S. R.

    1999-01-01

    Thanks to the mid-IR sensitivities of the ISO and IRTS orbiting spectrometers it is now possible to search the diffuse interstellar medium for heretofore inaccessible molecular emission. In view of the recent strong case for the presence of C(7-) (Kirkwood et al. 1998, Tulej et al. 1998),and the fact that carbon chains possess prominent infrared active modes in a very clean portion of the interstellar spectrum, we have analyzed the IRTS spectrum of the diffuse interstellar medium for the infrared signatures of these species. Theoretical and experimental infrared band frequencies and absolute intensities of many different carbon chain species are presented. These include cyanopolyynes, neutral and anionic linear carbon molecules, and neutral and ionized, even-numbered, hydrogenated carbon chains. We show that--as a family--these species have abundances in the diffuse ISM on the order of 10(-10) with respect to hydrogen, values consistent with their abundances in dense molecular clouds. Assuming an average length of 10 C atoms per C-chain implies that roughly a millionth of the cosmically available carbon is in the form of carbon chains and that carbon chains can account for a few percent of the visible to near-IR diffuse interstellar band (DIB) total equivalent width (not DIB number).

  14. Carbon allocation in plants and ecosystems - insights from stable isotope studies

    NASA Astrophysics Data System (ADS)

    Gessler, Arthur

    2014-05-01

    Trees are large global stores of carbon (C) that will be impacted by increased carbon dioxide levels and climate change. However, at present we cannot properly predict the carbon balance of forests in future as we lack knowledge on how plant physiological processes, the transfer of carbon within the plant, carbon storage, and remobilization in the plant tissues as well as the release of carbon from the roots to the soil interact with environmental drivers and ecosystem-scale processes. This paper will summarise how stable isotope techniques can give new insights in the fate of newly assimilated C in plants and ecosystems on time scales from hours to seasons and it will include studies either characterizing temporal and spatial variation in the natural abundance of carbon and oxygen isotopes or applying isotopically enriched tracers. It comprises the assessment of the mechanisms of C partitioning among specific metabolic pathways, between plant organs and into various ecosystem C pools with different residence times. Moreover stable isotopes are highly suitable tools to characterise the role of the phloem, which is the central long-distance conveyer distributing C from source to sinks and thus plays a central role in linking sites and structures of storage, growth and other metabolic activities. A deeper understanding of these processes and their interaction with environmental drivers is critical for predicting how trees and ecosystems will respond to coming global environmental changes, including increased temperature, altered precipitation, and elevated carbon dioxide concentrations.

  15. A carbon isotope mass balance for an anoxic marine sediment: Isotopic signatures of diagenesis

    NASA Technical Reports Server (NTRS)

    Boehme, Susan E.

    1993-01-01

    A carbon isotope mass balance was determined for the sediments of Cape Lookout Bight, NC to constrain the carbon budgets published previously. The diffusive, ebullitive and burial fluxes of sigma CO2 and CH4, as well as the carbon isotope signatures of these fluxes, were measured. The flux-weighted isotopic signature of the remineralized carbon (-18.9 plus or minus 2.7 per mil) agreed with the isotopic composition of the remineralized organic carbon determined from the particulate organic carbon (POC) delta(C-13) profiles (-19.2 plus or minus 0.2), verifying the flux and isotopic signature estimates. The measured delta(C-13) values of the sigma CO2 and CH4 diffusive fluxes were significantly different from those calculated from porewater gradients. The differences appear to be influenced by methane oxidation at the sediment-water interface, although other potential processes cannot be excluded. The isotope mass balance provides important information concerning the locations of potential diagenetic isotope effects. Specifically, the absence of downcore change in the delta(C-13) value of the POC fraction and the identical isotopic composition of the POC and the products of remineralization indicate that no isotopic fractionation is expressed during the initial breakdown of the POC, despite its isotopically heterogeneous composition.

  16. s-process studies - Xenon and krypton isotopic abundances

    NASA Technical Reports Server (NTRS)

    Clayton, D. D.; Ward, R. A.

    1978-01-01

    We propose an analysis of the s-process contributions to the isotopes of xenon and krypton. The object is to aid studies of the possibility that meteorites may contain gas that was carried in presolar grains that were grown in stellar ejecta and that were not degassed prior to incorporation into parent bodies. That model suggests routine interstellar fractionation of s-isotopes from r-isotopes owing to differential incorporation into dust. We show that a deficiency of s-process nuclei cannot yield details of Xe-X, but the gross similarities are strong enough to lead one to think that such a deficiency may play a role in a more complicated explanation. We predict the existence of an s-rich complement somewhere if fractional separation of this type has played a role in Xe-X. We show that the analogous decomposition of krypton is more uncertain, and we call for measurements of neutron-capture cross sections to alleviate these uncertainties.

  17. NATURAL STABLE CARBON ISOTOPE TAG TRACES TEXAS SHRIMP MIGRATIONSl

    E-print Network

    NATURAL STABLE CARBON ISOTOPE TAG TRACES TEXAS SHRIMP MIGRATIONSl BRIAN FRy2 ABSTRACf A 1978 spring and early summer survey of Texas brown shrimp, Penaeus aztecus, showed that stable carbon isotope t13 C/12 C or 1l'3C) analysis is useful for tracing shrimp movements. At least four isotopi- cally distinct shrimp

  18. On krypton isotopic abundances in the sun and in the solar wind

    NASA Technical Reports Server (NTRS)

    Marti, K.

    1980-01-01

    The Kr isotopic systematics in the meteorite Pesyanoe which is known to contain solar-type gases, are reported. Discrepancies in the isotopic data of fractions released at stepwise increasing temperatures cannot be reconciled with spallation Kr components, although spallation effects are significant. Fractionation mechanisms on the parent body and in the solar wind source region are considered and the implications for solar abundances discussed.

  19. Total carbon and nitrogen abundances in lunar samples.

    PubMed

    Moore, C B; Lewis, C F; Gibson, E K; Nichiporuk, W

    1970-01-30

    Total carbon and nitrogen abundances were determined by using combustion-gas chromatographic techlniques. Weighited mean analyses for butlk fines were 225 and 140 ppm total carbon and 150 anid 100 ppm total nitrogen. Total carbon in fine breccia was 230 ppm; in coarse breccia, 100 ppmn; in fine-grained rock, 70 ppm; and in mediumn-grained rock, 64 ppm. The finest sieved fraction had the highest carbon content. Total nitrogen in fine breccia was 125 ppm; in coarse breccia, 100 ppm; in fine-grained rock, 115 ppm; and in medium-grained rock, 30 ppm. The total carbon and nitrogen finies appeat to be mixtuires of indigenous lunar material togetheer with meteoritic and solar wind components. PMID:17781467

  20. Paleoenvironmental controls on the abundance of {sup 13}C in sedimentary organic carbon

    SciTech Connect

    Hayes, J.M.; Hollander, D.J.; Wakeham, S.G.; Pease, T.

    1996-12-31

    Variations in the {sup 13}C content of sedimentary organic molecules are often interpreted in terms of processes likely to have occurred in ancient water columns. The interpretations are based mainly on principles rather than on isotopic analyses of related compounds in modem water columns. Seeking to bridge the gap between interpretation and experience, we have analyzed lipids extracted from particulate organic carbon ({open_quotes}POC{close_quotes}, two size fractions, >20 {mu}m and 20 - 0.2 {mu}m) recovered from depths of 40, 100, 650 and 800 in the water column of the Santa Monica Basin, offshore southern California and from underlying sediments. The sampling has been replicated six times in order to complete an annual cycle covering a range of upwelling conditions and levels of productivity. Isotopic compositions of individual organic compounds and their relationships to hydrographic conditions indicate that the abundance of {sup 13}C in organic materials is related to availability of macronutrients as well as to concentrations of dissolved carbon dioxide. Coupled with observations by others, these observations indicate strong control of carbon isotopic compositions by rate of growth and by paleoceanographic conditions (e.g., upwelling) that regulate availability of nutrients. In general, values of {sup 13}{delta} for sedimentary materials match those for the most productive portions of the annual cycle and thus selectively record oceanographic conditions from that portion of each year.

  1. Paleoenvironmental controls on the abundance of [sup 13]C in sedimentary organic carbon

    SciTech Connect

    Hayes, J.M. ); Hollander, D.J. ); Wakeham, S.G.; Pease, T. )

    1996-01-01

    Variations in the [sup 13]C content of sedimentary organic molecules are often interpreted in terms of processes likely to have occurred in ancient water columns. The interpretations are based mainly on principles rather than on isotopic analyses of related compounds in modem water columns. Seeking to bridge the gap between interpretation and experience, we have analyzed lipids extracted from particulate organic carbon ([open quotes]POC[close quotes], two size fractions, >20 [mu]m and 20 - 0.2 [mu]m) recovered from depths of 40, 100, 650 and 800 in the water column of the Santa Monica Basin, offshore southern California and from underlying sediments. The sampling has been replicated six times in order to complete an annual cycle covering a range of upwelling conditions and levels of productivity. Isotopic compositions of individual organic compounds and their relationships to hydrographic conditions indicate that the abundance of [sup 13]C in organic materials is related to availability of macronutrients as well as to concentrations of dissolved carbon dioxide. Coupled with observations by others, these observations indicate strong control of carbon isotopic compositions by rate of growth and by paleoceanographic conditions (e.g., upwelling) that regulate availability of nutrients. In general, values of [sup 13][delta] for sedimentary materials match those for the most productive portions of the annual cycle and thus selectively record oceanographic conditions from that portion of each year.

  2. The isotopic and elemental abundances of neon nuclei accelerated in solar flares

    NASA Technical Reports Server (NTRS)

    Dietrich, W. F.; Simpson, J. A.

    1979-01-01

    The relative isotopic abundances of Ne-20 and Ne-22 in seven solar flares were determined from measurements of the satellite IMP 8, yielding the ratio Ne-20/Ne-22 = 7.7 (+2.3, -1.5) for solar chromospheric matter. This value is in agreement with the ratio for the component neon-A (the 'primordial' component) found in carbonaceous chondrites. An elemental abundance ratio Ne/O = 0.14 + or - 0.01 also has been obtained which agrees closely with earlier reported measurements. It is shown that the effects of preferential acceleration relative to solar-system abundances with increasing charge number observed for some solar flares - though biasing the elemental ratio - does not appear to influence the neon isotopic abundances.

  3. Global simulation of the carbon isotope exchange of terrestrial ecosystems

    NASA Astrophysics Data System (ADS)

    Ito, A.; Terao, Y.; Mukai, H.

    2009-12-01

    There remain large uncertainties in our quantification of global carbon cycle, which has close interactions with the climate system and is subject to human-induced global environmental change. Information on carbon isotopes is expected to reduce the uncertainty by providing additional constraints on net atmosphere-ecosystem exchange. This study attempted to simulate the dynamics of carbon isotopes at the global scale, using a process-based terrestrial ecosystem model: Vegetation Integrative SImulator for Trace gases (VISIT). The base-model of carbon cycle (Sim-CYCLE, Ito 2003) has already considered stable carbon isotope composition (13C/12C), and here radioactive carbon isotope (14C) was included. The isotope ratios characterize various aspects of terrestrial carbon cycle, which is difficult to be constrained by sole mass balance. For example, isotopic discrimination by photosynthetic assimilation is closely related with leaf stomatal conductance and composition of C3 and C4 plant in grasslands. Isotopic disequilibrium represents mean residence time of terrestrial carbon pools. In this study, global simulations (spatial resolution 0.5-deg, time-step 1-month) were conducted during the period 1901 to 2100 on the basis of observed and projected atmospheric CO2, climate, and land-use conditions. As anthropogenic CO2 accumulates in the atmosphere, heavier stable carbon isotope (13C) was diluted, while radioactive carbon isotope (14C) is strongly affected by atomic bomb experiments mainly in the 1950s and 1960s. The model simulated the decadal change in carbon isotope compositions. Leaf carbon with shorter mean residence time responded rapidly to the atmospheric change, while plant stems and soil humus showed substantial time-lag, leading to large isotopic disequilibrium. In the future, the isotopic disequilibrium was estimated to augment, due to accelerated rate of anthropogenic CO2 accumulation. Spatial distribution of stable isotope composition (12C/13C, or d13C) was primarily dominated by C3/C4 plant composition and then ancillary environmental conditions. Along latitude, plant and litter carbon pools in northern ecosystems have slower turnover rates (i.e., higher 14C/12C) than those in tropical ecosystems. However, humus carbon in northern ecosystems with very long mean residence times has lower 14C/12C ratio, most of bomb-derived radioactive carbon lingered still in plant biomass. Now, we are attempting to examine the model estimations by comparing with atmospheric measurements.

  4. Current and relic carbon using natural abundance carbon-13

    SciTech Connect

    layse,MF; Clapp,CE; Allmaras,RR; Linden,D.R; Molina, JAE.; Copeland,SM; Dowdy,RH

    2002-05-01

    The role of agricultural practices on soil carbon (C) dynamics is critical to improved soil management. The main objective was to examine the C interactions resulting from crop changes under different tillage and residue treatments.

  5. Carbon Isotope Stratigraphy of the Triassic-Jurassic Boundary, Northern Calcareous Alps, Southern Bavaria.

    NASA Astrophysics Data System (ADS)

    Blom, Vincent P. C.; Prave, Anthony R.; Raub, Timothy D.

    2014-05-01

    The end Triassic is recognized as a period of increased marine biotic turnover, culminating in one of the five major mass extinction events of the Phanerozoic at the Triassic-Jurassic boundary. Carbon isotope excursions have been reported globally that may be in response to a perturbation to the earth system. Here we present findings from a succession of early Mesozoic Tethyan carbonate strata from the Northern Calcareous Alps (NCA) of southern Bavaria, Germany. The succession ranges from Carnian to Middle Jurassic in age and is part of the Bavarian Syncline, which trends East-West along the northern extent of the NCA. The two field areas studied, Wallberg and Buchstein, contain the Tr-J boundary, which is marked by an abrupt change from underlying reefal carbonate rocks to a deeper basinal setting dominated by marls, as well as the disappearance of abundant brachiopod, bivalve and colonial coral populations. The boundary is also characterized by a carbonate carbon isotope excursion. Carbonate C isotope values in the underlying reefal carbonate rocks are marked by values of 2.0 to 2.5‰. Above the contact, the carbonate C isotopes show a 1.5 - 2.0‰ decline, which coincides with the change from shallow to deeper marine carbonate sedimentation. Following the excursion, and whilst the succession maintains a basinal palaeoenvironmental setting, the C isotopes return to values similar to those present beneath the Tr-J boundary ranging from 2.0 - 2.5‰. The negative excursion may be recording a global perturbation to the carbon cycle, however the change from a shallow to deep marine depositional environment must also be considered as a possible influence on isotopic composition. Cross-plots of C and O isotopes show no correlation hence we prefer to interpret the carbonate C isotopic data to record original seawater values. Post-depositional diagenetic and lithification processes, however, likely modified the O isotope values. Our results urge caution in identifying C isotopic excursions as global until potential palaeoenvironmental-related changes can be excluded.

  6. Empirical Solar Abundance Scaling Laws of Supernova {gamma} Process Isotopes

    SciTech Connect

    Hayakawa, Takehito; Iwamoto, Nobuyuki; Kajino, Toshitaka; Shizum, Toshiyuki; Umeda, Hideyuki; Nomoto, Ken'Ichi

    2008-11-11

    Analyzing the solar system abundances, we have found two empirical abundance scaling laws concerning the p- and s-nuclei with the same atomic number. They are evidence that the 27 p-nuclei are synthesized by the supernova {gamma}-process. The scalings lead to a novel concept of 'universality of {gamma}-process' that the s/p and p/p ratios of nuclei produced by individual {gamma}-processes are almost constant, respectively. We have calculated the ratios of materials produced by the {gamma}-process based on core-collapse supernova explosion models under various astrophysical conditions and found that the scalings hold for individual {gamma}-processes independent of the conditions assumed. The results further suggest an extended universality that the s/p ratios in the {gamma}-process layers are not only constant but also centered on a specific value of 3. With this specific value and the scaling of the s/p ratios, we estimate that the ratios of the s-process abundance contributions from the AGB stars to the massive stars are almost 6.7 for the s-nuclei of A>90 in the solar system.

  7. Carbon isotopic characterization of formaldehyde emitted by vehicles in Guangzhou, China

    NASA Astrophysics Data System (ADS)

    Hu, Ping; Wen, Sheng; Liu, Yonglin; Bi, Xinhui; Chan, Lo Yin; Feng, Jialiang; Wang, Xinming; Sheng, Guoying; Fu, Jiamo

    2014-04-01

    Formaldehyde (HCHO) is the most abundant carbonyl compound in the atmosphere, and vehicle exhaust emission is one of its important anthropogenic sources. However, there is still uncertainty regarding HCHO flux from vehicle emission as well as from other sources. Herein, automobile source was characterized using HCHO carbon isotopic ratio to assess its contributions to atmospheric flux and demonstrate the complex production/consumption processes during combustion in engine cylinder and subsequent catalytic treatment of exhaust. Vehicle exhausts were sampled under different idling states and HCHO carbon isotopic ratios were measured by gas chromatograph-combustion-isotopic ratio mass spectrometry (GC-C-IRMS). The HCHO directly emitted from stand-alone engines (gasoline and diesel) running at different load was also sampled and measured. The HCHO carbon isotopic ratios were from -30.8 to -25.7‰ for gasoline engine, and from -26.2 to -20.7‰ for diesel engine, respectively. For diesel vehicle without catalytic converter, the HCHO carbon isotopic ratios were -22.1 ± 2.1‰, and for gasoline vehicle with catalytic converter, the ratios were -21.4 ± 0.7‰. Most of the HCHO carbon isotopic ratios were heavier than the fuel isotopic ratios (from -29 to -27‰). For gasoline vehicle, the isotopic fractionation (?13C) between HCHO and fuel isotopic ratios was 7.4 ± 0.7‰, which was higher than that of HCHO from stand-alone gasoline engine (?13Cmax = 2.7‰), suggesting additional consumption by the catalytic converter. For diesel vehicle without catalytic converter, ?13C was 5.7 ± 2.0‰, similar to that of stand-alone diesel engine. In general, the carbon isotopic signatures of HCHO emitted from automobiles were not sensitive to idling states or to other vehicle parameters in our study condition. On comparing these HCHO carbon isotopic data with those of past studies, the atmospheric HCHO in a bus station in Guangzhou might mainly come from vehicle emission for the accordance of carbon isotopic data.

  8. Carbon isotopic fractionation in the biosynthesis of bacterial fatty acids. Ozonolysis of unsaturated fatty acids as a means of determining the intramolecular distribution of carbon isotopes

    NASA Astrophysics Data System (ADS)

    Monson, K. David; Hayes, J. M.

    1982-02-01

    Methods for the determination of 13C abundances at individual olefinic carbon positions have been developed, tested, and shown to perform accurately. (1) The double bond is oxidized with ozone; (2) silver oxide is used to cleave the resulting ozonide quantitatively to carboxylic-acid fragments; (3) a modified Schmidt decarboxylation is used to produce CO 2 quantitatively from the carboxyl groups of the separated cleavage products; (4) the CO 2 is utilized for mass spectrometric analysis. The results of intramolecular isotopic analyses are combined with molecular-average isotopic compositions determined by total combustion in order to show that fatty acids biosynthesized by Escherichia coli grown aerobically with glucose as the sole carbon source and harvested at late log phase are depleted by approximately 3%. in 13C relative to the glucose. This fractionation arises in the formation of acetylcoenzyme A by pyruvate dehydrogenase and is localized at the carboxyl position in the acetyl-CoA product. The isotopic order in that two-carbon subunit is carried through the biosynthesis of fatty acids so that alternate positions in the fatty-acid chains are depleted in 13C by an amount equal to twice the molecular-average depletion. The kinetic isotope effect at C-2 for pyruvate dehydrogenase in vivo is shown to be approximately 2.3%. While it appears that no other fractionation mechanism has controlled the overall depletion of 13C in these fatty acids, a separate process responsible for control of isotopic abundances in the carboxyl groups has been identified and described elsewhere [Monson K.D. and Hayes J.M. (1980) J. Biol. Chem. 255, 11435-11441]. It is concluded that kinetic, rather than thermodynamic, factors have controlled isotopic distributions in these cells and that kinetic factors will be dominant in most biological reactions.

  9. Cryogenian glaciation and the onset of carbon-isotope decoupling.

    PubMed

    Swanson-Hysell, Nicholas L; Rose, Catherine V; Calmet, Claire C; Halverson, Galen P; Hurtgen, Matthew T; Maloof, Adam C

    2010-04-30

    Global carbon cycle perturbations throughout Earth history are frequently linked to changing paleogeography, glaciation, ocean oxygenation, and biological innovation. A pronounced carbonate carbon-isotope excursion during the Ediacaran Period (635 to 542 million years ago), accompanied by invariant or decoupled organic carbon-isotope values, has been explained with a model that relies on a large oceanic reservoir of organic carbon. We present carbonate and organic matter carbon-isotope data that demonstrate no decoupling from approximately 820 to 760 million years ago and complete decoupling between the Sturtian and Marinoan glacial events of the Cryogenian Period (approximately 720 to 635 million years ago). Growth of the organic carbon pool may be related to iron-rich and sulfate-poor deep-ocean conditions facilitated by an increase in the Fe:S ratio of the riverine flux after Sturtian glacial removal of a long-lived continental regolith. PMID:20431011

  10. Carbon and its isotopes in mid-oceanic basaltic glasses

    NASA Technical Reports Server (NTRS)

    Des Marais, D. J.; Moore, J. G.

    1984-01-01

    Sample surface carbon, mantle carbon dioxide in vesicles, and mantle carbon dissolved in glasses, are the three carbon components evident in the 11 mid-oceanic basalts presently analyzed. The total carbon content may be controlled by the depth of the shallowest ridge magma chamber, and carbon isotopic fractionation accompanies magma degassing. Using He-3 and carbon data for submarine hydrothermal fluids, the present day midoceanic ridge carbon flux is approximately estimated to be 1.0 x 10 to the 13th g C/yr, requiring 8 Gyr to accumulate the earth's present crustal carbon inventory.

  11. SIMS ANALYSIS OF WATER ABUNDANCE AND HYDROGEN ISOTOPE IN LUNAR HIGHLAND PLAGIOCLASE. Hejiu Hui1

    E-print Network

    Rossman. George R.

    of lunar materials. Recent FTIR analyses have shown that plagioclases in lunar ferroan anorthosite contain ~6 ppm H2O [12]. So far, ferroan anorthosite is the only available lithol- ogy that is believed measurements of water abundances and H isotopes in plagioclase of two ferroan anorthosites and one troctolite

  12. Distribution and carbon isotope patterns of diterpenoids and triterpenoids in modern temperate C3 trees and their geochemical significance

    NASA Astrophysics Data System (ADS)

    Diefendorf, Aaron F.; Freeman, Katherine H.; Wing, Scott L.

    2012-05-01

    Tricyclic diterpenoids and pentacyclic triterpenoids are nearly exclusively produced by gymnosperms and angiosperms, respectively. Even though both classes of terpenoids have long been recognized as plant biomarkers, their potential use as phylogenetically specific ?13C proxies remains largely unexplored. Little is known of how terpenoid abundance and carbon isotope composition vary either with plant phylogenetic position, functional group, or during synthesis. Here, we report terpenoid abundances and isotopic data for 44 tree species in 21 families, representing both angiosperms and gymnosperms, and both deciduous and evergreen leaf habits. Di- and triterpenoid abundances are significantly higher in evergreens compared to deciduous species, reflecting differences in growth strategies and increased chemical investment in longer-lived leaves. Carbon isotope abundances of terpenoid lipids are similar to leaf tissues, indicating biosynthetic isotope effects are small for both the MVA (-0.4‰) and MEP (-0.6‰) pathways. Leaf and molecular isotopic patterns for modern plants are consistent with observations of amber, resins and plant biomarkers in ancient sediments. The ?13C values of ancient diterpenoids are higher than triterpenoids by 2-5‰, consistent with observed isotopic differences between gymnosperms and angiosperms leaves, and support the relatively small lipid biosynthetic effects reported here. All other factors being equal, evergreen plants will dominate the abundance of terpenoids contributed to soils, sediments and ancient archives, with similar inputs estimated for angiosperm and gymnosperm trees when scaled by litter flux.

  13. Fractionation between inorganic and organic carbon during the Lomagundi (2.222.1 Ga) carbon isotope excursion

    E-print Network

    Bekker, Andrey

    April 2008 Editor: H. Elderfield Keywords: Precambrian carbon cycle Lomagundi Event carbon isotope. carbonate carbon isotopic values on the shallow-marine carbonate platform suggests that the carbon cyclingFractionation between inorganic and organic carbon during the Lomagundi (2.22­2.1 Ga) carbon

  14. Chemical and Isotopic Study of Lab-formed Carbonates Under Cryogenic and Hydrothermal Conditions

    NASA Technical Reports Server (NTRS)

    Niles, P. B.; Leshin, L. A.; Socki, R. A.; Guan, Y.; Golden, D. C.; Ming, D. W.; Gibson, E. K.

    2004-01-01

    Aqueous environments on early Mars were probably relatively short-lived and localized, as evidenced by the lack of abundant secondary minerals detected by the TES instrument. In order to better understand the aqueous history of early Mars we need to be able to interpret the evidence preserved in secondary minerals formed during these aqueous events. Carbonate minerals, in particular, are important secondary minerals for interpreting past aqueous environments as illustrated by the carbonates preserved in ALH84001. Carbonates formed in short-lived, dynamic aqueous events often preserve kinetic rather than equilibrium chemical and isotopic processes, and predicting the behavior of such systems is facilitated by empirical data.

  15. Isotopic studies of Yucca Mountain soil fluids and carbonate pedogenesis

    SciTech Connect

    McConnaughey, T.A.; Whelan, J.F.; Wickland, K.P.; Moscati, R.J.

    1994-12-31

    Secondary carbonates occurring within the soils, faults, and subsurface fractures of Yucca Mountain contain some of the best available records of paleoclimate and palehydrology for the potential radioactive waste repository site. This article discusses conceptual and analytical advances being made with regard to the interpretation of stable isotope data from pedogenic carbonates, specifically related to the {sup 13}C content of soil CO{sub 2}, CaCO{sub 3}, precipitation mechanisms, and isotopic fractionations between parent fluids and precipitating carbonates. The {sup 13}C content of soil carbon dioxide from Yucca Mountain and vicinity shows most of the usual patterns expected in such contexts: Decreasing {sup 13}C content with depth decreasing {sup 13}C with altitude and reduced {sup 13}C during spring. These patterns exist within the domain of a noisy data set; soil and vegetational heterogeneities, weather, and other factors apparently contribute to isotopic variability in the system. Several soil calcification mechanisms appear to be important, involving characteristic physical and chemical environments and isotopic fractionations. When CO{sub 2} loss from thin soil solutions is an important driving factor, carbonates may contain excess heavy isotopes, compared to equilibrium precipitation with soil fluids. When root calcification serves as a proton generator for plant absorption of soil nutrients, heavy isotope deficiencies are likely. Successive cycles of dissolution and reprecipitation mix and redistribute pedogenic carbonates, and tend to isotopically homogenize and equilibrate pedogenic carbonates with soil fluids.

  16. An isotopic study of biogeochemical relationships between carbonates and organic carbon in the Greenhorn Formation

    NASA Technical Reports Server (NTRS)

    Hayes, J. M.; Popp, Brian N.; Takigiku, Ray; Johnson, Marcus W.

    1989-01-01

    Carbon-isotopic compositions of total carbonate, inoceramid carbonate, micritic carbonate, secondary cements, total organic carbon, and geoporphyrins have been measured in 76 different beds within a 17-m interval of a core through the Greenhorn Formation, an interbedded limestone and calcareous shale unit of Cretaceous age from the Western Interior Seaway of North America. Results are considered in terms of variations in the processes of primary production and in secondary processes. It is shown that the porphyrin isotopic record reflects primary isotopic variations more closely than the TOC isotopic record and that, in these sediments, TOC is enriched in C-13 relative to its primary precursor by 0.6 to 2.8 percent. This enrichment is attributed to isotope effects within the consumer foodweb and is associated with respiratory heterotrophy. Variation in this secondary enrichment are correlated with variations in the isotopic composition of marine carbonate.

  17. A new solar carbon abundance based on non-LTE CN molecular spectra

    NASA Technical Reports Server (NTRS)

    Mount, G. H.; Linsky, J. L.

    1975-01-01

    A detailed non-LTE analysis of solar CN spectra strongly suggest a revised carbon abundance for the sun. We recommend a value of log carbon abundance = 8.35 plus or minus 0.15 which is significantly lower than the presently accepted value of log carbon abundance = 8.55. This revision may have important consequences in astrophysics.

  18. Predicted Abundances of Carbon Compounds in Volcanic Gases on Io

    E-print Network

    Laura Schaefer; Bruce Fegley Jr

    2004-09-17

    We use chemical equilibrium calculations to model the speciation of carbon in volcanic gases on Io. The calculations cover wide temperature (500-2000 K), pressure (10^-8 to 10^+2 bars), and composition ranges (bulk O/S atomic ratios \\~0 to 3), which overlap the nominal conditions at Pele (1760 K, 0.01 bar, O/S ~ 1.5). Bulk C/S atomic ratios ranging from 10^-6 to 10^-1 in volcanic gases are used with a nominal value of 10^-3 based upon upper limits from Voyager for carbon in the Loki plume on Io. Carbon monoxide and CO2 are the two major carbon gases under all conditions studied. Carbonyl sulfide and CS2 are orders of magnitude less abundant. Consideration of different loss processes (photolysis, condensation, kinetic reactions in the plume) indicates that photolysis is probably the major loss process for all gases. Both CO and CO2 should be observable in volcanic plumes and in Io's atmosphere at abundances of several hundred parts per million by volume for a bulk C/S ratio of 10^-3.

  19. Regional variations in volatile composition: Isotopic evidence for carbonate recycling in the

    E-print Network

    Fehn, Udo

    Regional variations in volatile composition: Isotopic evidence for carbonate recycling; subduction recycling; volatiles. Index terms: Isotopic composition/chemistry; geochemical cycles; physics: Isotopic evidence for carbonate recycling in the Central American volcanic arc, Geochem. Geophys. Geosyst

  20. Mechanisms for “Vital Effects” in Biogenic Carbonates: New Perspectives Based on Abundances of 13C-18O Bonds

    NASA Astrophysics Data System (ADS)

    Guo, W.; Kim, S.; Thiagarajan, N.; Adkins, J. F.; Eiler, J. M.

    2009-12-01

    Many biogenic carbonates exhibit correlated depletions in ?18O and ?13C relative to the compositions expected for isotopic equilibrium with ambient waters and dissolved inorganic carbon (DIC). Such ‘vital effects’ complicate the use of biogenic carbonates in paleoclimate studies, particularly efforts to quantify carbonate growth temperature using carbonate-water oxygen isotope thermometry. Two general classes of models have been proposed to account for such vital effects: equilibrium models in which carbonate grows in isotope equilibrium with local body water, but at a pH and/or body water isotopic composition that differs from ambient environmental water; and kinetic models in which dissolved inorganic carbon and co-existing water do not achieve local isotope exchange equilibrium. Here we examine the constraints on this problem implied by measurements of proportions of 13C-18O bonds in biogenic carbonates, expressed as ?47, the abundance anomaly of mass 47 isotopologues of CO2 (mainly 13C18O16O) derived from phosphoric acid digestion of carbonate minerals [1]. Despite the significant differences in equilibrium carbon and oxygen isotope compositons between dissolved HCO3- and CO32- (i.e. ~2‰ in ?13C and ~7‰ in ?18O at 300 K), physical-chemistry models (based on ab initio and statistical thermodynamic theory) predict only subtle (~0.02‰) difference in their proportions of 13C-18O bonds, corresponding to a relatively low, positive slope of ~0.003 for ?(?47)/?(?18O) in carbonates in which vital effects reflect equilibrium processes with locally exotic pH. In contrast, we infer that kinetic vital effects should lead to relatively strong increases in proportions of 13C-18O bonds in precipitated carbonate relative to those expected for equilibrium growth. This is because random incorporation of an oxygen atom from H2O or OH- during the hydration or hydroxylation of CO2 will yield a relatively steep negative slope for ?(?47)/?(?18O) in the product HCO3- and thus in carbonates, on the order of -0.01 to -0.05 at 300K. We are currently elaborating on this relatively simple kinetic model to include kinetic isotope effects accompanying hydration or hydroxylation of aqueous CO2. Isotopic analyses of deep-sea corals having marked vital effects for ?13C and ?18O yield equilibrium ?47 over a significant range of ?18O disequilibrium (~4.5‰) [2]. This observation is so far most consistent with equilibrium models of vital effects, as are the isotopic analyses of a variety of other biogenic carbonates grown at known temperatures [3]. The absence of significant “vital effects” in the clumped isotope compositions of biogenic carbonates constitutes another advantage of carbonate clumped isotope thermometer in paleo-temperature reconstruction, compared to the conventional carbonate-water oxygen isotope thermometer. Reference: [1] Ghosh et. al.(2006) GCA, 70: 1439-1456; [2] Thiagarajan et. al. (2009), GCA, 73: A1324; [3] Eiler J. M. (2007) EPSL, 262: 309-327.

  1. The carbon isotope biogeochemistry of methane production in anoxic sediments. 1: Field observations

    NASA Technical Reports Server (NTRS)

    Blair, Neal E.; Boehme, Susan E.; Carter, W. Dale, Jr.

    1993-01-01

    The natural abundance C-13/C-12 ratio of methane from anoxic marine and freshwater sediments in temperate climates varies seasonally. Carbon isotopic measurements of the methanogenic precursors, acetate and dissolved inorganic carbon, from the marine sediments of Cape Lookout Bight, North Carolina were used to determine the sources of the seasonal variations at that site. Movement of the methanogenic zone over an isotopic gradient within the dissolved CO2 pool appears to be the dominant control of the methane C-13/C-12 ratio from February to June. The onset of acetoclastic methane-production is a second important controlling process during mid-summer. An apparent temperature dependence on the fractionation factor for CO2-reduction may have a significant influence on the isotopic composition of methane throughout the year.

  2. Carbon Isotopic Measurements of Amino Acids in Stardust-Returned Samples

    NASA Technical Reports Server (NTRS)

    Elsila, Jamie

    2009-01-01

    NASA's Stardust spacecraft returned to Earth samples from comet 81P/Wild 2 in January 2006. Preliminary examinations revealed the presence of a suite of organic compounds including several amines and amino acids, but the origin of these compounds could not be identified. Here, we present the carbon isotopic ratios of glycine and e-aminocaproic acid (EACA), the two most abundant amino acids, in Stardust-returned foil samples measured by gas chromatography-combustion-isotope ratio mass spectrometry coupled with quadrupole mass spectrometry (GC-CAMS/IRMS).

  3. Carbon Isotopic Ratios of Amino Acids in Stardust-Returned Samples

    NASA Technical Reports Server (NTRS)

    Elsila, Jamie E.; Glavin, Daniel P.; Dworkin, Jason P.

    2009-01-01

    NASA's Stardust spacecraft returned to Earth samples from comet 81P/Wild 2 in January 2006. Preliminary examinations revealed the presence of a suite of organic compounds including several amines and amino acids, but the origin of these compounds could not be identified. Here. we present the carbon isotopic ratios of glycine and E-aminocaproic acid (EACH), the two most abundant amino acids observed, in Stardust-returned foil samples measured by gas chromatography-combustion-isotope ratio crass spectrometry coupled with quadrupole mass spectrometry (GC-QMS/IRMS).

  4. The Barium Isotopic Abundance in the Metal-Poor Star HD140283

    E-print Network

    R. Collet; M. Asplund; P. E. Nissen

    2008-11-27

    We derive the mixture of odd to even barium isotopes in the atmosphere of the metal-poor subgiant HD140283 from the analysis of the Ba II transition at 455.4 nm in a high-resolution high signal-to-noise spectrum of the star. The detailed shape of this spectral line depends on the relative contributions of odd and even isotopes via isotopic and hyperfine splitting. We measure the fractional abundance of odd Ba isotopes by modelling the formation of the Ba II 455.4 nm line profile with the use of both a classical 1D hydrostatic and a 3D hydrodynamical model atmosphere of HD140283. We interpret the results in terms of contributions by the slow (s-) and rapid (r-) neutron-capture processes to the isotopic mix. While the result of the 1D analysis of the Ba II feature indicates a (64 +/- 36)% contribution of the r-process to the isotopic mix, the 3D analysis points toward a mere (15 +/- 34)% contribution from this process, that is consistent with a solar-like mixture of barium isotopes.

  5. The Origin of Fluorine: Abundances in AGB Carbon Stars Revisited

    E-print Network

    Abia, C; Cristallo, S; de Laverny, P

    2015-01-01

    Revised spectroscopic parameters for the HF molecule and a new CN line list in the 2.3 mu region have been recently available, allowing a revision of the F content in AGB stars. AGB carbon stars are the only observationally confirmed sources of fluorine. Nowadays there is not a consensus on the relevance of AGB stars in its Galactic chemical evolution. The aim of this article is to better constrain the contribution of these stars with a more accurate estimate of their fluorine abundances. Using new spectroscopic tools and LTE spectral synthesis, we redetermine fluorine abundances from several HF lines in the K-band in a sample of Galactic and extragalactic AGB carbon stars of spectral types N, J and SC spanning a wide range of metallicities. On average, the new derived fluorine abundances are systematically lower by 0.33 dex with respect to previous determinations. This may derive from a combination of the lower excitation energies of the HF lines and the larger macroturbulence parameters used here as well as...

  6. Model-based estimation of the global carbon budget and its uncertainty from carbon dioxide and carbon isotope records

    E-print Network

    Jain, Atul K.

    Model-based estimation of the global carbon budget and its uncertainty from carbon dioxide and the terrestrial biosphere based on carbon dioxide and carbon isotope records, and prior information on model of carbon dioxide and the resulting atmospheric concentration of carbon dioxide determined from the behavior

  7. Origin of petroporphyrins. 2. Evidence from stable carbon isotopes

    NASA Technical Reports Server (NTRS)

    Boreham, C. J.; Fookes, C. J.; Popp, B. N.; Hayes, J. M.

    1990-01-01

    Compared with the carbon-13 isotopic composition of the ubiquitous C32DPEP (DPEP, deoxophylloerythroetioporphyrin) the heavy but equivalent carbon-13 isotopic composition for the porphyrin structures 15(2)-methyl-15,17-ethano-17-nor-H-C30DPEP and 15,17-butano-, 13,15-ethano-13(2),17-propano-, and 13(1)-methyl-13,15-ethano-13(2),17-propanoporphyrin suggests a common precursor, presumably chlorophyll c, for these petroporphyrins isolated from the marine Julia Creek oil shale and the lacustrine Condor oil shale. Similarly, the heavy but variable carbon-13 isotopic composition of 7-nor-H-C31DPEP compared with C32DPEP is consistent with an origin from both chlorophyll b and chlorophyll c3. The equivalent carbon-13 isotopic composition for 13(2)-methyl-C33DPEP compared with C32DPEP suggests a common origin resulting from a weighted average of chlorophyll inputs.

  8. Carbon stable isotopes suggest that hippopotamus-vectored nutrients subsidize

    E-print Network

    Lewison, Rebecca

    Carbon stable isotopes suggest that hippopotamus-vectored nutrients subsidize aquatic consumers that hippopotamus-vectored nutrients subsidize aquatic consumers in an East African river. Ecosphere 6(4):52. http

  9. BIODEGRADATION OF FLUORANTHENE AS MONITORED USING STABLE CARBON ISOTOPES

    EPA Science Inventory

    The measurement of stable isotope ratios of carbon (d13C values) was investigated as a viable technique to monitor the intrinsic bioremediation of polycyclic aromatic hydrocarbons (PAHs). Biometer-flask experiments were conducted in which the bacterium, Sphingomonas paucimobilis,...

  10. Bromine and carbon isotope effects during photolysis of brominated phenols.

    PubMed

    Zakon, Yevgeni; Halicz, Ludwik; Gelman, Faina

    2013-12-17

    In the present study, carbon and bromine isotope effects during UV-photodegradation of bromophenols in aqueous and ethanolic solutions were determined. An anomalous relatively high inverse bromine isotope fractionation (?reactive position up to +5.1‰) along with normal carbon isotope effect (?reactive position of -12.6‰ to -23.4‰) observed in our study may be attributed to coexistence of both mass-dependent and mass-independent isotope fractionation of C-Br bond cleavage. Isotope effects of a similar scale were observed for all the studied reactions in ethanol, and for 4-bromophenol in aqueous solution. This may point out related radical mechanism for these processes. The lack of any carbon and bromine isotope effects during photodegradation of 2-bromophenol in aqueous solution possibly indicates that C-Br bond cleavage is not a rate-limiting step in the reaction. The bromine isotope fractionation, without any detectable carbon isotope effect, that was observed for 3-bromophenol photolysis in aqueous solution probably originates from mass-independent fractionation. PMID:24245662

  11. Temperature and Oxygen Isotope Composition of The Ediacaran Ocean: Constraints From Clumped Isotope Carbonate Thermometry

    NASA Astrophysics Data System (ADS)

    Bonifacie, M.; Eiler, J. M.; Fike, D. A.

    2008-12-01

    The temperature and chemical variations of the early oceans on Earth are highly debated, particularly for periods associated with significant evolutionary change and/or extinction. The temperature of past oceans has been estimated based on conventional carbonate-water and/or silicate-water stable oxygen isotope thermometry. Precambrian carbonates and silicates both exhibit a long-term secular trend of increasing ?18O values with decreasing age. This trend has been used to support two opposite - though related - interpretations: the Earth's oceans gradually cooled over the course of the Proterozoic eon, from a maximum of ~ 60-90°C at ~ 2.5Ga (and were, on average, relatively warm during much of the Paleozoic era) [1]. This interpretation has been supported by Si-isotope proxies and the thermal tolerances of proteins in various classes of microbial organisms [2-3]. Alternatively, the ?18O value of the oceans has gradually increased through time [4-5], and mean Earth surface temperatures varied over a narrow range similar to modern conditions. In other terms, one either assumes an ocean of constant ?18O and infers that climate varied dramatically, or vise versa. Finally, it is possible that post- depositional processes (e.g., diagenesis, burial metamorphism, weathering) has modified the ?18O values of all or most Precambrian sedimentary carbonates and silicates, overprinting any paleoclimatic variations. Carbonate 'clumped isotope' thermometry provides a new way to independently test these hypotheses because it allows one to determine the apparent growth temperatures of carbonate minerals based on their abundances of 13C-18O bonds, as reflected by the '?47' value of CO2 extracted by phosphoric acid digestion [6]. This method is thermodynamically based and independent of the ?18O of water from which the carbonate grew. We will report the initial results of measurements of '?47 for a suite of carbonates from the Sultanate of Oman. This Ediacaran age (~ 635 to ~ 548 Myr) suite was buried to a range of depths that generally decrease with distance from the basin center. These Omanese dolomites vary in ?18OPDB from ~ -7 to +1 ‰, inversely correlated with their apparent crystallization temperatures from 28 to 76°C (using the unpublished calibration for temperature dependence of ?47 of dolomite). The lowest ?18O values and highest temperatures are measured for samples with petrographic evidence for post-depositional re-crystallization (e.g. coarse crystals and low porosity) and likely to have experienced the most intense burial metamorphism. The correlation we observe between ?18Ocarb. and temperature suggests that the maximum temperature of the Ediacaran oceans was 28°C and that burial metamorphism has systematically modified the ?18O values of most of the analyzed carbonates. The ?18OSMOW for seawater for this period was between -1‰ (if depositional temperatures were 28°C - the maximum permitted by our data) and -4‰ (in the unlikely case that the ocean was at its minimum possible temperature permitting the existence of liquid water). [1] Knauth and Lowe, EPSL. (1978), 41, 209-222. [2] Robert and Chaussidon (2006), Nature, 443, 969-972. [3] Gaucher et al. (2008), Nature, 451, 704-707. [4] Shields and Veizer (2002), G3, 3. [5] Jaffres et al., (2006), ESR, 83-122. [6] Ghosh et al., (2006), GCA, 70, 1439-1456.

  12. Carbon and Nitrogen Abundances in Early-type Galaxies

    E-print Network

    Elisa Toloba; Patricia Sanchez-Blazquez; Javier Gorgas; Brad K. Gibson

    2008-11-21

    For the first time, we undertake a systematic examination of the nitrogen abundances for a sample of 35 early-type galaxies spanning a range of masses and local environment. The nitrogen-sensitive molecular feature at 3360\\AA has been employed in conjunction with a suite of atomic- and molecular-sensitive indices to provide unique and definitive constraints on the chemical content of these systems. By employing NH3360, we are now able to break the carbon, nitrogen, and oxygen degeneracies inherent to the use of the CN-index. We demonstrate that the NH3360 feature shows little dependency upon the velocity dispersion (our proxy for mass) of the galaxies, contrary to what is seen for carbon- and magnesium-sensitive indices. At face value, these results are at odds with conclusions drawn previously using indices sensitive to both carbon and nitrogen, such as cyanogen (CN). With the aid of stellar population models, we find that the N/Fe ratios in these galaxies are consistent with being mildly-enhanced with respect to the solar ratio. We also explore the dependence of these findings upon environment, by analyzing the co-added spectra of galaxies in the field and the Coma cluster. We confirm the previously found differences in carbon abundances between galaxies in low- and high-density environments, while showing that these differences do not seem to exist for nitrogen. We discuss the implications of these findings for the derivation of the star formation histories in early-type galaxies, and for the origin of carbon and nitrogen, themselves.

  13. Ar-39 Detection at the 10^-16 Isotopic Abundance Level with Atom Trap Trace Analysis

    E-print Network

    W. Jiang; W. D. Williams; K. Bailey; A. M. Davis; S. -M. Hu; Z. -T. Lu; T. P. O'Connor; R. Purtschert; N. C. Sturchio; Y. R. Sun; P. Mueller

    2011-01-15

    Atom Trap Trace Analysis (ATTA), a laser-based atom counting method, has been applied to analyze atmospheric Ar-39 (half-life = 269 yr), a cosmogenic isotope with an isotopic abundance of 8x10^-16. In addition to the superior selectivity demonstrated in this work, counting rate and efficiency of ATTA have been improved by two orders of magnitude over prior results. Significant applications of this new analytical capability lie in radioisotope dating of ice and water samples and in the development of dark matter detectors.

  14. Configuration mixing effects in neutron-rich carbon isotopes

    E-print Network

    C. X. Yuan; F. R. Xu; C. Qi

    2015-07-24

    Shell model calculations are done to study the structure of neutron-rich carbon isotopes. For both even-A and odd-A neutron-rich carbon isotopes, the energy levels are strongly affected by the configuration mixing of valence neutrons. The calculated energy levels in the nucleus $^{17}$C are significantly improved compared with experimental values when the model space of the three valence neutrons is enlarged from pure $\

  15. Intramolecular carbon isotope distribution in chlorophyll and its geochemical derivatives

    NASA Astrophysics Data System (ADS)

    Bogacheva, M. P.; Kodina, L. A.; Galimov, E. M.

    Data are presented on the carbon isotope distribution (? 13C values) in fragments of chlorophyll and hemin molecules, and certain main groups of oil hydrocarbons with special reference to isoprenoids. The same relationship is observed between the carbon isotope compositions of the tetrapyrrole nucleus, phytol and possible precursors of the n-alkanes (fatty acids), on one hand, and petroporphyrins, isoprenoids and n-alkanes respectively in oil, on the other hand.

  16. The origin of fluorine: abundances in AGB carbon stars revisited

    NASA Astrophysics Data System (ADS)

    Abia, C.; Cunha, K.; Cristallo, S.; de Laverny, P.

    2015-09-01

    Context. Revised spectroscopic parameters for the HF molecule and a new CN line list in the 2.3 ?m region have recently become available, facilitating a revision of the F content in asymptotic giant branch (AGB) stars. Aims: AGB carbon stars are the only observationally confirmed sources of fluorine. Currently, there is no consensus on the relevance of AGB stars in its Galactic chemical evolution. The aim of this article is to better constrain the contribution of these stars with a more accurate estimate of their fluorine abundances. Methods: Using new spectroscopic tools and local thermodynamical equilibrium spectral synthesis, we redetermine fluorine abundances from several HF lines in the K-band in a sample of Galactic and extragalactic AGB carbon stars of spectral types N, J, and SC, spanning a wide range of metallicities. Results: On average, the new derived fluorine abundances are systematically lower by 0.33 dex with respect to previous determinations. This may derive from a combination of the lower excitation energies of the HF lines and the larger macroturbulence parameters used here as well as from the new adopted CN line list. Yet, theoretical nucleosynthesis models in AGB stars agree with the new fluorine determinations at solar metallicities. At low metallicities, an agreement between theory and observations can be found by handling the radiative/convective interface at the base of the convective envelope in a different way. Conclusions: New fluorine spectroscopic measurements agree with theoretical models at low and at solar metallicity. Despite this, complementary sources are needed to explain its observed abundance in the solar neighbourhood.

  17. Stable isotopes of carbon from basaltic rocks and their possible relation to atmospheric isotope excursions

    NASA Astrophysics Data System (ADS)

    Hansen, Hans Jørgen

    2006-11-01

    Repeated short-time negative excursions from the general trend of organic carbon isotopes occur at, and shortly after, the Permo-Triassic and Cretaceous-Tertiary mass extinctions. The cause of these excursions is unexplained since an extinction event can only explain one excursion at each boundary. At the P/T boundary one negative excursion occurs shortly before the boundary proper followed by one at the boundary, followed by several excursions that can be correlated in both marine and terrestrial environments over larger geographical distances. Also at the K/T boundary negative excursions in organic carbon, which can be correlated, occur after the boundary in both marine and terrestrial settings. As both mass extinctions occurred contemporaneously with major continental flood basalts, the present study focuses on the possible effect of eruption of flood basalts on the atmospheric carbon isotopic budget. The carbon isotopic compositions of forty different basalts, from the time span of Albian to the Recent, and predominantly continental flood, were measured. The isotopic composition of the CO 2 gas released by basalts is generally accepted as being rather heavy (- 5‰ PDB) based on observations from Hawaii. This is in strong contrast to the observed values in this study, which showed that the gas released had an average isotopic value of around - 23‰ PDB. Acid digestion by HF left a residue of elemental carbon with isotopic values in the range of - 24 to almost - 28‰ PDB. This corresponds to the carbon released during stepped heating experiments in the temperature range from 200 to 600 °C. Since basalt in a molten state has a temperature of > 600 °C and since the most negative carbon (i.e. the elemental carbon) is released below that temperature, it suggests that the most isotopically negative component is not present as elemental carbon above temperatures of 600 °C. In view of the recorded isotopic composition of - 24‰ for gas collected at a temperature between 700 and 800 °C from Mauna Loa, it seems that the generally assumed - 5‰ is unrepresentative for flood basalts. It is therefore possible that high intensity volcanic episodes have caused the repeated negative excursions. It is further suggested that the short-time non-secular isotopic variation pattern of organic carbon through time may be a record of volcanic activity. The episodic nature of volcanism precludes it from being causally related to the secular variations. Elemental carbon from four different kimberlites yielded carbon isotopic values similar to those from basalts. It is suggested that the Boudouard reaction (2CO = C + CO 2) may be responsible for the formation of the elemental carbon.

  18. Observations of Carbon Isotopic Fractionation in Interstellar Formaldehyde

    NASA Technical Reports Server (NTRS)

    Wirstrom, E. S.; Charnley, S. B.; Geppert, W. D.; Persson, C. M.

    2012-01-01

    Primitive Solar System materials (e.g. chondrites. IDPs, the Stardust sample) show large variations in isotopic composition of the major volatiles (H, C, N, and O ) even within samples, witnessing to various degrees of processing in the protosolar nebula. For ex ample. the very pronounced D enhancements observed in IDPs [I] . are only generated in the cold. dense component of the interstellar medium (ISM), or protoplanetary disks, through ion-molecule reactions in the presence of interstellar dust. If this isotopic anomaly has an interstellar origin, this leaves open the possibility for preservation of other isotopic signatures throughout the form ation of the Solar System. The most common form of carbon in the ISM is CO molecules, and there are two potential sources of C-13 fractionation in this reservoir: low temperature chemistry and selective photodissociation. While gas-phase chemistry in cold interstellar clouds preferentially incorporates C-13 into CO [2], the effect of self-shielding in the presence of UV radiation instead leads to a relative enhancement of the more abundant isotopologue, 12CO. Solar System organic material exhibit rather small fluctuations in delta C-13 as compared to delta N-15 and delta D [3][1], the reason for which is still unclear. However, the fact that both C-13 depleted and enhanced material exists could indicate an interstellar origin where the two fractionation processes have both played a part. Formaldehyde (H2CO) is observed in the gas-phase in a wide range of interstellar environments, as well as in cometary comae. It is proposed as an important reactant in the formation of more complex organic molecules in the heated environments around young stars, and formaldehyde polymers have been suggested as the common origin of chondritic insoluable organic matter (IOM) and cometary refractory organic solids [4]. The relatively high gas-phase abundance of H2CO observed in molecular clouds (10(exp- 9) - 10(exp- 8) relative to H2) makes it feasible to observe its less common isotopologues. As a step in our investigation of C-13 fractionation patterns in the ISM, we here present comparisons between observations of the C-13 fraction in formaldehyde, and chemical fractionation models.

  19. Vegetation succession and carbon sequestration in a coastal wetland in northwest Florida: Evidence from carbon isotopes

    E-print Network

    . Measurements of stable carbon isotopic ratios as well as carbon (C), nitrogen (N), and phosphorus (P) contents are sandy, hypersaline environments that support sparse vegetation. The marshes are dominated by black

  20. Biological control of calcium isotopic abundances in the global calcium cycle

    SciTech Connect

    Skulan, J.; DePaolo, D.J.; Owens, T.L.

    1997-06-01

    Measurements of {sup 44}Ca/{sup 40}Ca, expressed as {delta}{sup 44}Ca, were made on igneous rocks and on shell and bone material from modern organisms to investigate the magnitude and origins of calcium isotopic fractionation in nature. The results document a span of 4{per_thousand} in {delta}{sup 44}Ca, measured with the double spike technique to a precision of {+-}0.15{per_thousand}. Volcanic rocks, including basalt and rhyolite, show little variability and cluster near {delta}{sup 44}Ca = 0 {+-}0.2. Systematic analysis of biological samples indicates that biological processing of calcium discriminates against heavy isotopes, and that biological fractionation is the primary generator of calcium isotopic fractionation in nature. Preliminary data suggest that calcium becomes isotopically lighter as it moves through food chains. Calcium carbonate shells of marine microorganisms and deep-sea carbonate ooze have {delta}{sup 44}Ca about 1.0{per_thousand}, lower than seawater; this fractionation causes seawater to be enriched in heavy calcium ({delta}{sup 44}Ca = +0.9) relative to igneous rocks. Marine organisms consequently are isotopically heavier than their terrestrial counterparts at similar trophic level. The calcium isotopic composition of living and fossil organisms may record information on diet and environment. 22 refs., 3 figs., 2 tabs.

  1. Isotopic fractionation of alkali earth metals during carbonate precipitation

    NASA Astrophysics Data System (ADS)

    Yotsuya, T.; Ohno, T.; Muramatsu, Y.; Shimoda, G.; Goto, K. T.

    2014-12-01

    The alkaline earth metals such as magnesium, calcium and strontium play an important role in a variety of geochemical and biological processes. The element ratios (Mg/Ca and Sr/Ca) in marine carbonates have been used as proxies for reconstruction of the past environment. Recently several studies suggested that the study for the isotopic fractionation of the alkaline earth metals in marine carbonates has a potentially significant influence in geochemical research fields (e.g. Eisenhauer et al., 2009). The aim of this study is to explore the influence of carbonate polymorphs (Calcite and Aragonite) and environmental factors (e.g., temperature, precipitation rate) on the level of isotopic fractionation of the alkaline earth metals. We also examined possible correlations between the level of isotopic fractionation of Ca and that of other alkaline earth metals during carbonate precipitation. In order to determine the isotope fractionation factor of Mg, Ca and Sr during carbonate precipitation, calcite and aragonite were synthesized from calcium bicarbonate solution in which the amount of magnesium was controlled based on Kitano method. Calcium carbonates were also prepared from the mixture of calcium chlorite and sodium hydrogen carbonate solutions. The isotope fractionation factors were measured by MC-ICPMS. Results suggested that the level of isotopic fractionation of Mg during carbonate precipitation was correlated with that of Sr and that the change of the carbonate crystal structure could make differences of isotopic fractionations of Mg and Ca, however no difference was found in the case of Sr. In this presentation, the possible mechanism will be discussed.

  2. Carbon isotope systematics of a mantle ``hotspot'': a comparison of Loihi Seamount and MORB glasses

    NASA Astrophysics Data System (ADS)

    Exley, R. A.; Mattey, D. P.; Clague, D. A.; Pillinger, C. T.

    1986-06-01

    The carbon isotope geochemistry of glasses from Loihi Seamount has been compared with that of MORB glasses. Stepped heating shows two carbon components in both sample suites: (1) isotopically light carbon ( avg. ? 13C = -26.3‰ ) released < 600°C, ascribed to surficial contamination, and (2) isotopically heavy carbon released > 600°C, regarded as indigenous. The high-temperature component in MORB samples varied from 52 to 169 ppm C, average ? 13C = -6.6‰ , consistent with previous studies (overall MORD average ? 13C = -6.4 ± 0.9‰ ), and new results for Indian Ocean glasses are similar to Atlantic and Pacific Ocean samples. Carbon release profiles produced by stepped heating may be typical of locality, but there are no significant differences in ? 13C values between MORB samples from different areas. Lower yields (17-110 ppm C) correlated with depth in the Loihi samples suggest that they are partially degassed. This degassing has not affected ? 13C values significantly (avg. -5.8‰). Loihi tholeiites have higher ? 13C (avg. -5.6‰) than the alkali basalts (avg. -7.1‰). Carbon abundances correlate well with He concentration data. Comparison of the ? 13C values with trace element and He, Sr, Nd, and Pb isotope data from the literature suggests that the Loihi samples with highest ? 13C have high 3He/ 4He and possibly the least depleted 143Nd/ 144Nd and 87Sr/ 86Sr. The carbon isotope data are consistent with previous models for Loihi involving several mantle sources, lithospheric contamination, and mixing. The slightly higher ? 13C of Loihi tholeiites suggests that the undegassed "plume" component manifested by high 3He/ 4He values might have ? 13C about 1‰ higher than the MORB average.

  3. Locations of marine animals revealed by carbon isotopes

    PubMed Central

    MacKenzie, Kirsteen M.; Palmer, Martin R.; Moore, Andy; Ibbotson, Anton T.; Beaumont, William R. C.; Poulter, David J. S.; Trueman, Clive N.

    2011-01-01

    Knowing the distribution of marine animals is central to understanding climatic and other environmental influences on population ecology. This information has proven difficult to gain through capture-based methods biased by capture location. Here we show that marine location can be inferred from animal tissues. As the carbon isotope composition of animal tissues varies with sea surface temperature, marine location can be identified by matching time series of carbon isotopes measured in tissues to sea surface temperature records. Applying this technique to populations of Atlantic salmon (Salmo salar L.) produces isotopically-derived maps of oceanic feeding grounds, consistent with the current understanding of salmon migrations, that additionally reveal geographic segregation in feeding grounds between individual philopatric populations and age-classes. Carbon isotope ratios can be used to identify the location of open ocean feeding grounds for any pelagic animals for which tissue archives and matching records of sea surface temperature are available. PMID:22355540

  4. Experimental determination of carbon isotope fractionation between graphite and carbonated silicate melt under upper mantle conditions

    NASA Astrophysics Data System (ADS)

    Mizutani, Shogo; Satish-Kumar, M.; Yoshino, Takashi

    2014-04-01

    Carbon isotope fractionation between graphite and carbonated silicate melt was determined at 5 GPa and in the temperature range between 1400 and 1900 °C. High pressure experiments were carried out in the carbon-saturated model harzbergite system (Enstatite-Magnesite-Olivine-Graphite), where carbonated silicate melt and graphite were the two stable carbon-bearing phases in the run products. Carbonated silicate melting resulted in an isotopic fractionation between graphite and carbon in the silicate melt, where the carbon in the melt is 13C enriched than co-existing graphite. 13C enrichment in carbonate melt when compared to graphite was further confirmed in experiments where redox melting between olivine and graphite produced carbonate melt as well as carbonate reduction experiments to form graphite. Although a quantitative estimate of fractionation between carbonate melt and graphite could not be obtained, our results indicate that mantle melting in the presence of graphite can result in progressive 13C carbon isotope enrichment in carbonate melt and depletion in graphite, which can be an alternate explanation for the carbon isotopic heterogeneity observed in the mantle derived carbon.

  5. Carbon isotopic studies of organic matter in Precambrian rocks.

    NASA Technical Reports Server (NTRS)

    Oehler, D. Z.; Schopf, J. W.; Kvenvolden, K. A.

    1972-01-01

    A survey has been undertaken of the carbon composition of the total organic fraction of a suite of Precambrian sediments to detect isotopic trends possibly correlative with early evolutionary events. Early Precambrian cherts of the Fig Tree and upper and middle Onverwacht groups of South Africa were examined for this purpose. Reduced carbon in these cherts was found to be isotopically similar to photosynthetically produced organic matter of younger geological age. Reduced carbon in lower Onverwacht cherts was found to be anomalously heavy; it is suggested that this discontinuity may reflect a major event in biological evolution.

  6. Submicron Measurements of Mg Isotopes in Biogenic Carbonates Using Laser Ablation-MC-ICPMS: New Window into Biomineralisation

    NASA Astrophysics Data System (ADS)

    Sadekov, A.; Lloyd, N. S.; Misra, S.; Funcke, A.; Shuttleworth, S.; Langer, G.; Bijma, J.; Elderfield, H.

    2014-12-01

    Magnesium is one of the most abundant elements in the earth's crust and in seawater. Fractionation of its stable isotopes has been shown to be useful indicators of many geological, chemical and biological processes. For example, biogenic carbonates display ~5‰ range of d26Mg values, which is attributed to variable degree of biological control on Mg ions during biomineralisation. Understanding this biological control is essential for developing proxies based on biogenic carbonates. Current methods of magnesium isotope measurements in carbonates are often time consuming and require relatively large volumes of samples. In this work, we present a new approach of measuring Mg isotopes in biogenic carbonates using Laser Ablation MC-ICP-MS. We will show that this microanalytical approach provides accurate and relatively fast measurements of Mg isotopes in biological carbonate with precision down to 0.2‰ (1sd). We will also present examples on how this new method can provide additional information about foraminiferal biomineralisation. For example, we will demonstrate submicron variation in Mg isotopes across shells of Orbulina universa, which are linked to high and low Mg/Ca layers in this species. We will also report changes in Mg isotope composition of benthic foraminifera Amphistegina sp. cultured in seawater with different Mg/Ca values. Both examples will be used to draw attention to the complexity and possibilities of multiple mechanisms of Mg incorporation into biogenic carbonates during biomineralisation.

  7. Terrestrial carbon and nitrogen isotopic ratios from cretaceous-tertiary boundary nanodiamonds.

    PubMed

    Gilmour, I; Russell, S S; Arden, J W; Lee, M R; Franchi, I A; Pillinger, C T

    1992-12-01

    One hypothesis for the origin of the nanometer-size diamonds found at the Cretaceous-Tertiary (K-T) boundary is that they are relict interstellar diamond grains carried by a postulated asteroid. The (13)C/(12)C and (15)N/(14)N ratios of the diamonds from two sites in North America, however, show that the diamonds are two component mixtures differing in carbon and nitrogen isotopic composition and nitrogen abundance. Samples from a site from Italy show no evidence for either diamond component. All the isotopic signatures obtained from the K-T boundary are material well distinguished from known meteoritic diamonds, particularly the fine-grain interstellar diamonds that are abundant in primitive chondrites. The K-T diamonds were most likely produced during the impact of the asteroid with Earth or in a plasma resulting from the associated fireball. PMID:17742530

  8. [Carbon isotope fractionation inplants]. Final report

    SciTech Connect

    O`Leary, M.H.

    1990-12-31

    The objectives of this research are: To develop a theoretical and experimental framework for understanding isotope fractionations in plants; and to develop methods for using this isotope fractionation for understanding the dynamics of CO{sub 2} fixation in plants. Progress is described.

  9. An investigation of techniques for the measurement and interpretation of cosmic ray isotopic abundances. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Wiedenbeck, M. E.

    1977-01-01

    An instrument, the Caltech High Energy Isotope Spectrometer Telescope was developed to measure isotopic abundances of cosmic ray nuclei by employing an energy loss - residual energy technique. A detailed analysis was made of the mass resolution capabilities of this instrument. A formalism, based on the leaky box model of cosmic ray propagation, was developed for obtaining isotopic abundance ratios at the cosmic ray sources from abundances measured in local interstellar space for elements having three or more stable isotopes, one of which is believed to be absent at the cosmic ray sources. It was shown that the dominant sources of uncertainty in the derived source ratios are uncorrelated errors in the fragmentation cross sections and statistical uncertainties in measuring local interstellar abundances. These results were applied to estimate the extent to which uncertainties must be reduced in order to distinguish between cosmic ray production in a solar-like environment and in various environments with greater neutron enrichments.

  10. Carbon and nitrogen isotopic compositions of alkyl porphyrins from the Triassic Serpiano oil shale

    NASA Technical Reports Server (NTRS)

    Chicarelli, M. I.; Hayes, J. M.; Popp, B. N.; Eckardt, C. B.; Maxwell, J. R.

    1993-01-01

    The carbon and nitrogen isotopic compositions of seven of the most abundant alkylporphyrins from the Serpiano oil shale (marine, Triassic) were determined. For the C31 and C32 butanoporphyrins, values of delta 13CPDB and delta 15NAIR averaged -24.0% and -3.1%. In contrast, the C31 and C32 methylpropanoporphyrins, DPEP, and a C30 13-nor etioporphyrin had delta 13C and delta 15N values averaging -27.5 and -3.3%, respectively. Carbon and nitrogen isotopic values for kerogen averaged -30.8 and -0.9, whereas those for total extract averaged -31.6, and -4.0%. The butanoporphyrins apparently derive from a biological source different from that giving rise to the other porphyrins, their 13C enrichment not being related to carbon isotopic fractionation accompanying diagenetic reactions. The delta 15N values for all the porphyrins indicate that the depletion of 15N observed in the kerogen is of primary origin. Consistent with the very high abundance of hopanoids and methyl hopanoids in the aliphatic hydrocarbon fraction, it is suggested that cyanobacterial fixation of N2 may have been the main cause of 15N depletion.

  11. Paleogene plants fractionated carbon isotopes similar to modern plants

    NASA Astrophysics Data System (ADS)

    Diefendorf, Aaron F.; Freeman, Katherine H.; Wing, Scott L.; Currano, Ellen D.; Mueller, Kevin E.

    2015-11-01

    The carbon isotope composition (?13 C) of terrestrial plant biomarkers, such as leaf waxes and terpenoids, provides insights into past carbon cycling. The ?13 C values of modern plant biomarkers are known to be sensitive to climate and vegetation type, both of which influence fractionation during lipid biosynthesis by altering plant carbon supply and its biochemical allocation. It is not known if fractionation observed in living plants can be used to interpret fossil lipids because plant biochemical characteristics may have evolved during the Cenozoic in response to changes in global climate and atmospheric CO2. The goal of this study was to determine if fractionation during photosynthesis (?leaf) in the Paleogene was consistent with expectations based on living plants. To study plant fractionation during the Paleogene, we collected samples from eight stratigraphic beds in the Bighorn Basin (Wyoming, USA) that ranged in age from 63 to 53 Ma. For each sample, we measured the ?13 C of angiosperm biomarkers (triterpenoids and n-alkanes) and, abundance permitting, conifer biomarkers (diterpenoids). Leaf ?13 C values estimated from different angiosperms biomarkers were consistently 2‰ lower than leaf ?13 C values for conifers calculated from diterpenoids. This difference is consistent with observations of living conifers and angiosperms and the consistency among different biomarkers suggests ancient ?lipid values were similar to those in living plants. From these biomarker-based ?13Cleaf values and independent records of atmospheric ?13 C values, we calculated ?leaf. These calculated ?leaf values were then compared to ?leaf values modeled by applying the effects that precipitation and major taxonomic group in living plants have on ?leaf values. Calculated and modeled ?leaf values were offset by less than a permil. This similarity suggests that carbon fractionation in Paleogene plants changed with water availability and major taxonomic group to about the same degree it does today. Further, paleoproxy data suggest at least two of the stratigraphic beds were deposited at times when pCO2 levels were higher than today. Biomarker data from these beds are not consistent with elevated ?leaf values, possibly because plants adapted carbon uptake and assimilation characteristics to pCO2 changes over long timescales.

  12. A Novel Airborne Carbon Isotope Analyzer for Methane and Carbon Dioxide Source Fingerprinting

    NASA Astrophysics Data System (ADS)

    Berman, E. S.; Huang, Y. W.; Owano, T. G.; Leifer, I.

    2014-12-01

    Recent field studies on major sources of the important greenhouse gas methane (CH4) indicate significant underestimation of methane release from fossil fuel industrial (FFI) and animal husbandry sources, among others. In addition, uncertainties still exist with respect to carbon dioxide (CO2) measurements, especially source fingerprinting. CO2 isotopic analysis provides a valuable in situ measurement approach to fingerprint CH4 and CO2as associated with combustion sources, leakage from geologic reservoirs, or biogenic sources. As a result, these measurements can characterize strong combustion source plumes, such as power plant emissions, and discriminate these emissions from other sources. As part of the COMEX (CO2 and MEthane eXperiment) campaign, a novel CO2 isotopic analyzer was installed and collected data aboard the CIRPAS Twin Otter aircraft. Developing methods to derive CH4 and CO2 budgets from remote sensing data is the goal of the summer 2014 COMEX campaign, which combines hyperspectral imaging (HSI) and non-imaging spectroscopy (NIS) with in situ airborne and surface data. COMEX leverages the synergy between high spatial resolution HSI and moderate spatial resolution NIS. The carbon dioxide isotope analyzer developed by Los Gatos Research (LGR) uses LGR's patented Off-Axis ICOS (Integrated Cavity Output Spectroscopy) technology and incorporates proprietary internal thermal control for high sensitivity and optimal instrument stability. This analyzer measures CO2 concentration as well as ?13C, ?18O, and ?17O from CO2 at natural abundance (100-3000 ppm). The laboratory accuracy is ±1.2 ppm (1?) in CO2 from 370-1000 ppm, with a long-term (1000 s) precision of ±0.012 ppm. The long-term precision for both ?13C and ?18O is 0.04 ‰, and for ?17O is 0.06 ‰. The analyzer was field-tested as part of the COWGAS campaign, a pre-cursor campaign to COMEX in March 2014, where it successfully discriminated plumes related to combustion processes associated with dairy activities (tractor exhaust) from plumes and sources in air enriched in methane and ammonia from bovine activities including waste maintenance. Methodology, laboratory data, field data from COWGAS, and field data from the COMEX campaign acquired by LGR's carbon isotope analyzer as well as other COMEX analyzers are presented.

  13. Isotopic compositions of carbonates and organic carbon from upper Proterozoic successions in Namibia: stratigraphic variation and the effects of diagenesis and metamorphism

    NASA Technical Reports Server (NTRS)

    Kaufman, A. J.; Hayes, J. M.; Knoll, A. H.; Germs, G. J.

    1991-01-01

    The carbon isotope geochemistry of carbonates and organic carbon in the late Proterozoic Damara Supergroup of Namibia, including the Nama, Witvlei, and Gariep groups on the Kalahari Craton and the Mulden and Otavi groups on the Congo Craton, has been investigated as an extension of previous studies of secular variations in the isotopic composition of late Proterozoic seawater. Subsamples of microspar and dolomicrospar were determined, through petrographic and cathodoluminescence examination, to represent the "least-altered" portions of the rock. Carbon-isotopic abundances in these phases are nearly equal to those in total carbonate, suggesting that 13C abundances of late Proterozoic fine-grained carbonates have not been significantly altered by meteoric diagenesis, although 18O abundances often differ significantly. Reduced and variable carbon-isotopic differences between carbonates and organic carbon in these sediments indicate that isotopic compositions of organic carbon have been altered significantly by thermal and deformational processes, likely associated with the Pan-African Orogeny. Distinctive stratigraphic patterns of secular variation, similar to those noted in other, widely separated late Proterozoic basins, are found in carbon-isotopic compositions of carbonates from the Nama and Otavi groups. For example, in Nama Group carbonates delta 13C values rise dramatically from -4 to +5% within a short stratigraphic interval. This excursion suggests correlation with similar excursions noted in Ediacaran-aged successions of Siberia, India, and China. Enrichment of 13C (delta 13C> +5%) in Otavi Group carbonates reflects those in Upper Riphean successions of the Akademikerbreen Group, Svalbard, its correlatives in East Greenland, and the Shaler Group, northwest Canada. The widespread distribution of successions with comparable isotopic signatures supports hypotheses that variations in delta 13C reflect global changes in the isotopic composition of late Proterozoic seawater. Within the Damara basin, carbon-isotopic compositions of carbonates provide a potentially useful tool for the correlation of units between the Kalahari and Congo cratons. Carbonates depleted in 13C were deposited during and immediately following three separate glacial episodes in Namibia. The correspondence between ice ages and negative delta 13C excursions may reflect the effects of lowered sea levels; enhanced circulation of deep, cold, O2-rich seawater; and/or the upwelling of 13C-depleted deep water. Iron-formation is additionally associated with one of the glacial horizons, the Chuos tillite. Carbon-13 enriched isotopic abundances in immediately pre-glacial carbonates suggest that oceanographic conditions favored high rates of organic burial. It is likely that marine waters were stratified, with deep waters anoxic. A prolonged period of ocean stratification would permit the build-up of ferrous iron, probably from hydrothermal sources. At the onset of glaciation, upwelling would have brought 13C-depleted and iron-rich deep water onto shallow shelves where contact with cold, oxygenated surface waters led to the precipitation of ferric iron.

  14. Investigation of tubular handling of bicarbonate in man. A new approach utilizing stable carbon isotope fractionation.

    PubMed Central

    Burbea, Z H; Luz, B; Lazar, B; Winaver, J; Better, O S

    1983-01-01

    Two alternative mechanisms have been proposed for tubular reabsorption of bicarbonate: (a) H+ secretion and CO2 reabsorption and (b) direct reabsorption of HCO-3. In an attempt to differentiate between the two mechanisms, the present study utilized the natural abundance of stable carbon isotopes (13C, 12C) in the urinary total CO2. This novel methodology used mass spectrometric analysis of 13C/12C ratios in urinary total CO2 under normal conditions and during acetazolamide treatment. Blood and respiratory CO2 were analyzed to yield reference values. The results demonstrate that alkaline urine is preferentially enriched with 13C relative to the blood. It is suggested that this fractionation results from reaction out of isotopic equilibrium in which HCO-3 converts to CO2 during the reabsorption process in the distal nephron. The presence of carbonic anhydrase in the proximal nephron results in rapid isotopic exchange between CO2 and HCO-3 and keeps them in isotopic equilibrium. The ratio of urinary 13C/12C increases strikingly after acetazolamide administration and consequent inhibition of carbonic anhydrase in the proximal tubule. Although it is possible that in the latter case high HCO-3 generates the CO2 (ampholyte effect), the isotope fractionation indicates that CO2 rather than HCO-3 is reabsorbed. In contrast, at low urinary pH and total CO2 values, the carbon isotope composition approaches that of blood CO2. This indicates rapid CO2 exchange between urine and blood, through luminal membrane highly permeable to CO2. These results could be anticipated by a mathematical model constructed to plot 13C concentration of urinary total CO2. It is concluded that the mechanism of HCO-3 reclamation in man (and, by inference, in other mammals as well) works by conversion of HCO-3 to CO2 and reabsorption of CO2. PMID:6417168

  15. The Evolution Of Carbon, Sulphur, and Titanium Isotopes from High-Redshift to the Local Universe

    E-print Network

    G. L. Hughes; B. K. Gibson; L. Carigi; P. Sanchez-Blazquez; J. M. Chavez; D. L. Lambert

    2008-08-26

    Recent observations of carbon, sulphur, and titanium isotopes at redshifts z~1 and in the local stellar disc and halo have opened a new window into the study of isotopic abundance patterns and the origin of the chemical elements. Using our Galactic chemical evolution code GEtool, we have examined the evolution of these isotopes within the framework of a Milky Way-like system. We have three aims in this work: first, to test the claim that novae are required, in order to explain the carbon isotope patterns in the Milky Way; second, to test the claim that sulphur isotope patterns at high-redshift require an initial mass function biased towards massive stars; and third, to test extant chemical evolution models against new observations of titanium isotopes that suggest an anti-correlation between trace-to-dominant isotopes with metallicity. Based upon our dual-infall galactic chemical evolution modelling of a Milky Way-like system, and the subsequent comparison with these new and unique datasets, we conclude the following: novae are not required to understand the evolution of 12C/13C in the solar neighbourhood; a massive star-biased initial mass function is consistent with the low ratios of 12C/13C and 32S/34S seen in one high-redshift late-type spiral, but the consequent super-solar metallicity prediction for the interstellar medium in this system seems highly unlikely; and deficient isotopes of titanium are predicted to correlate positively with metallicity, in apparent disagreement with the new datasets; if confirmed, classical chemical evolution models of the Milky Way (and the associated supernovae nucleosynthetic yields) may need a substantial overhaul to be made consistent.

  16. Cr isotopic composition of modern carbonates and seawater

    NASA Astrophysics Data System (ADS)

    Bonnand, P.; Parkinson, I. J.; James, R. H.; Fehr, M.; Connelly, D. P.

    2010-12-01

    Recent development in MC-ICP-MS instrumentation, coupled with double-spike techniques has led to the improvement of stable Cr isotopes measurements and allows the determination of Cr isotopes in low concentration samples such as carbonates and seawater. Cr is a redox sensitive element and its isotopes are fractionated during the reduction of Cr(VI) to Cr(III) [1]. Chromium isotopic variations in BIFs have been linked to the redox conditions of ancient oceans[2]. However, in order to understand Cr isotopic fractionation in the past it is important to constrain the Cr isotopic composition of modern seawater. Chromium concentrations in seawater are between 2 and 5nM, and therefore the measurement of stable Cr isotopes in seawater is an analytical challenge. We have developed a new technique to measure Cr isotopes in seawater based on the Cr co-precipitation with Fe[3], the chemical purification of Cr using an anion exchange chromatography and analyses using the double-spike technique with a ThermoFisher Neptune MC-ICP-MS. Using this method, seawater samples from the Argentinean Basin and from Southampton Water (UK) have been analysed, which have Cr concentrations of ~6nM of Cr. Chromium isotopic composition of our seawater samples is consistently heavier than continental crust and mantle values (?53Cr -0.18‰)[4] with ?53Cr values of ~+0.5‰. We have also measured Cr isotopic compositions in ooids from the Bahamas Banks, which represent chemical precipitates from modern seawater. These also record consistently heavy ?53Cr values (0.6-0.8‰), which overlap the range of modern seawater. We conclude that heavy ?53Cr in seawater reflect either redox cycling of Cr in the oceans[3] or fractionation during the weathering of the continental crust. Moreover, Cr isotopes in modern carbonates are not significantly offset from seawater and therefore, these carbonates reflect the Cr composition of seawater. Thus, Cr isotopes in carbonates can be used to reconstruct the Cr isotopic composition variations in past oceans. [1]Ellis et al., Science, 2002, 295, 2060-2062. [2] Frei et al., Nature, 2009, 461, 250-253.[3] Conelly et al., Deep Sea Res. Part I, 2006, 53, 1975-1988. [4] Schoenberg et al., Chem. Geol. 2008, 249, 294-306.

  17. Yucca Mountain Area Saturated Zone Dissolved Organic Carbon Isotopic Data

    SciTech Connect

    Thomas, James; Decker, David; Patterson, Gary; Peterman, Zell; Mihevc, Todd; Larsen, Jessica; Hershey, Ronald

    2007-06-25

    Groundwater samples in the Yucca Mountain area were collected for chemical and isotopic analyses and measurements of water temperature, pH, specific conductivity, and alkalinity were obtained at the well or spring at the time of sampling. For this project, groundwater samples were analyzed for major-ion chemistry, deuterium, oxygen-18, and carbon isotopes of dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC). The U.S. Geological Survey (USGS) performed all the fieldwork on this project including measurement of water chemistry field parameters and sample collection. The major ions dissolved in the groundwater, deuterium, oxygen-18, and carbon isotopes of dissolved inorganic carbon (DIC) were analyzed by the USGS. All preparation and processing of samples for DOC carbon isotopic analyses and geochemical modeling were performed by the Desert Research Institute (DRI). Analysis of the DOC carbon dioxide gas produced at DRI to obtain carbon-13 and carbon-14 values was conducted at the University of Arizona Accelerator Facility (a NSHE Yucca Mountain project QA qualified contract facility). The major-ion chemistry, deuterium, oxygen-18, and carbon isotopes of DIC were used in geochemical modeling (NETPATH) to determine groundwater sources, flow paths, mixing, and ages. The carbon isotopes of DOC were used to calculate groundwater ages that are independent of DIC model corrected carbon-14 ages. The DIC model corrected carbon-14 calculated ages were used to evaluate groundwater travel times for mixtures of water including water beneath Yucca Mountain. When possible, groundwater travel times were calculated for groundwater flow from beneath Yucca Mountain to down gradient sample sites. DOC carbon-14 groundwater ages were also calculated for groundwaters in the Yucca Mountain area. When possible, groundwater travel times were estimated for groundwater flow from beneath Yucca Mountain to down gradient groundwater sample sites using the DOC calculated groundwater ages. The DIC calculated groundwater ages were compared with DOC calculated groundwater ages and both of these ages were compared to travel times developed in ground-water flow and transport models. If nuclear waste is stored in Yucca Mountain, the saturated zone is the final barrier against the release of radionuclides to the environment. The most recent rendition of the TSPA takes little credit for the presence of the saturated zone and is a testament to the inadequate understanding of this important barrier. If radionuclides reach the saturated zone beneath Yucca Mountain, then there is a travel time before they would leave the Yucca Mountain area and flow down gradient to the Amargosa Valley area. Knowing how long it takes groundwater in the saturated zone to flow from beneath Yucca Mountain to down gradient areas is critical information for potential radionuclide transport. Radionuclide transport in groundwater may be the quickest pathway for radionuclides in the proposed Yucca Mountain repository to reach land surface by way of groundwater pumped in Amargosa Valley. An alternative approach to ground-water flow and transport models to determine the travel time of radionuclides from beneath Yucca Mountain to down gradient areas in the saturated zone is by carbon-14 dating of both inorganic and organic carbon dissolved in the groundwater. A standard method of determining ground-water ages is to measure the carbon-13 and carbon-14 of DIC in the groundwater and then correct the measured carbon-14 along a flow path for geochemical reactions that involve carbon containing phases. These geochemical reactions are constrained by carbon-13 and isotopic fractionations. Without correcting for geochemical reactions, the ground-water ages calculated from only the differences in carbon-14 measured along a flow path (assuming the decrease in carbon-14 is due strictly to radioactive decay) could be tens of thousands of years too old. The computer program NETPATH, developed by the USGS, is the best geochemical program for correcting carbon-14 activities for geochemical r

  18. Late Glacial Tropical Savannas in Sundaland Inferred From Stable Carbon Isotope Records of Cave Guano

    NASA Astrophysics Data System (ADS)

    Wurster, C. M.; Bird, M. I.; Bull, I.; Dungait, J.; Bryant, C. L.; Ertunç, T.; Hunt, C.; Lewis, H. A.; Paz, V.

    2008-12-01

    During the Last Glacial Period (LGP), reduced global sea level exposed the continental shelf south of Thailand to Sumatra, Java, and Borneo to form the contiguous continent of Sundaland. However, the type and extent of vegetation that existed on much of this exposed landmass during the LGP remains speculative. Extensive bird and bat guano deposits in caves throughout this region span beyond 40,000 yr BP, and contain a wealth of untapped stratigraphic palaeoenvironmental information. Stable carbon isotope ratios of insectivorous bird and bat guano contain a reliable record of the animal's diet and, through non-specific insect predation, reflect the relative abundance of major physiological pathways in plants. Various physiological pathways of carbon fixation in plants yield differing stable carbon isotope ratios. Stable carbon isotope values of C3 plants are lower than C4 vegetation due to different enzymatic discriminations of the heavy isotope through the carbon fixing pathways. In tropical locales, grasses nearly always follow the C4 photosynthetic pathway, whereas tropical rainforest uses C3 photosynthesis, providing a proxy for vegetation and therefore climate change in the past. Here we discuss four guano stable-isotope records, based on insect cuticle and n-alkane analysis, supplemented by pollen analysis. All sites suggest a C3 dominated ecosystem for the Holocene, consistent with the wet tropical forest vegetation present at all locations. Two sites from Palawan Island, Philippines, record stable carbon isotope values of guano that document a drastic change from C3 (forest) to C4 (savanna) dominated ecosystems during the Last Glacial Maximum (LGM). A third location, at Niah Great Cave, Malaysia, indicates C3-dominant vegetation throughout the record, but does display variation in stable carbon isotope values likely linked to humidity changes. A fourth location, Batu Caves in Peninsular Malaysia, also indicates open vegetation during the LGM. Vegetation models disagree as to the nature of vegetation during the LGM in Sundaland, but our results suggest major contraction of forest area with significant implications for carbon storage during the LGM and also for understanding the development of modern biogeographic and genetic patterns in the region. Additional cave guano sites will provide further constraints on the nature of environmental change in the region over the last glacial cycle.

  19. Stable Carbon Isotope Fractionation by Methylotrophic Methanogenic Archaea

    PubMed Central

    Penger, Jörn; Conrad, Ralf

    2012-01-01

    In natural environments methane is usually produced by aceticlastic and hydrogenotrophic methanogenic archaea. However, some methanogens can use C1 compounds such as methanol as the substrate. To determine the contributions of individual substrates to methane production, the stable-isotope values of the substrates and the released methane are often used. Additional information can be obtained by using selective inhibitors (e.g., methyl fluoride, a selective inhibitor of acetoclastic methanogenesis). We studied stable carbon isotope fractionation during the conversion of methanol to methane in Methanosarcina acetivorans, Methanosarcina barkeri, and Methanolobus zinderi and generally found large fractionation factors (?83‰ to ?72‰). We further tested whether methyl fluoride impairs methylotrophic methanogenesis. Our experiments showed that even though a slight inhibition occurred, the carbon isotope fractionation was not affected. Therefore, the production of isotopically light methane observed in the presence of methyl fluoride may be due to the strong fractionation by methylotrophic methanogens and not only by hydrogenotrophic methanogens as previously assumed. PMID:22904062

  20. LITHIUM ABUNDANCES IN CARBON-ENHANCED METAL-POOR STARS

    SciTech Connect

    Masseron, Thomas; Johnson, Jennifer A.; Lucatello, Sara; Karakas, Amanda; Plez, Bertrand; Beers, Timothy C.; Christlieb, Norbert E-mail: jaj@astronomy.ohio-state.edu

    2012-05-20

    Carbon-enhanced metal-poor (CEMP) stars are believed to show the chemical imprints of more massive stars (M {approx}> 0.8 M{sub Sun }) that are now extinct. In particular, it is expected that the observed abundance of Li should deviate in these stars from the standard Spite lithium plateau. We study here a sample of 11 metal-poor stars and a double-lined spectroscopic binary with -1.8 < [Fe/H] < -3.3 observed with the Very Large Telescope/UVES spectrograph. Among these 12 metal-poor stars, there are 8 CEMP stars for which we measure or constrain the Li abundance. In contrast to previous arguments, we demonstrate that an appropriate regime of dilution permits the existence of 'Li-Spite plateau and C-rich' stars, whereas some of the 'Li-depleted and C-rich' stars call for an unidentified additional depletion mechanism that cannot be explained by dilution alone. We find evidence that rotation is related to the Li depletion in some CEMP stars. Additionally, we report on a newly recognized double-lined spectroscopic binary star in our sample. For this star, we develop a new technique from which estimates of stellar parameters and luminosity ratios can be derived based on a high-resolution spectrum alone, without the need for input from evolutionary models.

  1. The Carboniferous carbon isotope record from sedimentary organic matter: can we disentangle the carbon cycle?

    NASA Astrophysics Data System (ADS)

    Davies, S. J.; Bennett, C. E.; Leng, M. J.; Kearsey, T.; Marshall, J. E.; Millward, D.; Reeves, E. J.; Snelling, A.; Sherwin, J. E.

    2014-12-01

    A comprehensive analysis of the ?13C composition of sedimentary organic matter from Euramerican Carboniferous successions indicates there are significant shifts in ?13C through this key time interval. Our studies have revealed that, at an individual location, the source and delivery mechanism of the sediment contribute to the type of organic matter preserved and, in turn this influences the measured ?13C values from bulk sedimentary organic matter of organic matter. In general, where marine-derived organic matter is dominant in these Carboniferous successions then ?13C values are characteristically lower compared to the higher values encountered where terrestrial plant-derived material is most abundant. The implication of these observations is that an apparent carbon isotope excursion identified from the bulk organic matter may reflect a change in transport processes, or depositional environment, rather than a perturbation in the global carbon cycle. In our most recent studies, however, we compare ?13C values from specific wood fragments and bulk sedimentary organic matter from non-marine, marine basinal, and marine shelfal successions from the earliest Mississippian through to the early Pennsylvanian. These data indicate that early Mississippian ?13C of organic matter is far less negative (around -22%0) than material of Late Mississippian age (around -26%0), however by the early Pennsylvanian, ?13C values return to -22%0. There are some ?13C data from brachiopod carbonate from this time interval and similar shifts are indicated. Our data are beginning to address whether we can identify a primary carbon cycle signal from the Carboniferous record using ?13C from a range of sedimentary environments. If we can, there are still questions around what the record is telling us about the global carbon cycle during a period when plant groups, including lycopods and seed ferns, rapidly diversified.

  2. Isotopic anomalies from neutron reactions during explosive carbon burning

    NASA Technical Reports Server (NTRS)

    Lee, T.; Schramm, D. N.; Wefel, J. P.; Blake, J. B.

    1978-01-01

    The possibility that the newly discovered correlated isotopic anomalies for heavy elements in the Allende meteorite were synthesized in the secondary neutron capture episode during the explosive carbon burning, the possible source of the O-16 and Al-26 anomalies, is examined. Explosive carbon burning calculations under typical conditions were first performed to generate time profiles of temperature, density, and free particle concentrations. These quantities were inputted into a general neutron capture code which calculates the resulting isotopic pattern from exposing the preexisting heavy seed nuclei to these free particles during the explosive carbon burning conditions. The interpretation avoids the problem of the Sr isotopic data and may resolve the conflict between the time scales inferred from 1-129, Pu-244, and Al-26.

  3. Abundance and isotopic composition of gases in the martian atmosphere from the Curiosity rover.

    PubMed

    Mahaffy, Paul R; Webster, Christopher R; Atreya, Sushil K; Franz, Heather; Wong, Michael; Conrad, Pamela G; Harpold, Dan; Jones, John J; Leshin, Laurie A; Manning, Heidi; Owen, Tobias; Pepin, Robert O; Squyres, Steven; Trainer, Melissa

    2013-07-19

    Volume mixing and isotope ratios secured with repeated atmospheric measurements taken with the Sample Analysis at Mars instrument suite on the Curiosity rover are: carbon dioxide (CO2), 0.960(±0.007); argon-40 ((40)Ar), 0.0193(±0.0001); nitrogen (N2), 0.0189(±0.0003); oxygen, 1.45(±0.09) × 10(-3); carbon monoxide, < 1.0 × 10(-3); and (40)Ar/(36)Ar, 1.9(±0.3) × 10(3). The (40)Ar/N2 ratio is 1.7 times greater and the (40)Ar/(36)Ar ratio 1.6 times lower than values reported by the Viking Lander mass spectrometer in 1976, whereas other values are generally consistent with Viking and remote sensing observations. The (40)Ar/(36)Ar ratio is consistent with martian meteoritic values, which provides additional strong support for a martian origin of these rocks. The isotopic signature ?(13)C from CO2 of ~45 per mil is independently measured with two instruments. This heavy isotope enrichment in carbon supports the hypothesis of substantial atmospheric loss. PMID:23869014

  4. Beyond temperature: Clumped isotope signatures in dissolved inorganic carbon species and the influence of solution chemistry on carbonate mineral composition

    NASA Astrophysics Data System (ADS)

    Tripati, Aradhna K.; Hill, Pamela S.; Eagle, Robert A.; Mosenfelder, Jed L.; Tang, Jianwu; Schauble, Edwin A.; Eiler, John M.; Zeebe, Richard E.; Uchikawa, Joji; Coplen, Tyler B.; Ries, Justin B.; Henry, Drew

    2015-10-01

    "Clumped-isotope" thermometry is an emerging tool to probe the temperature history of surface and subsurface environments based on measurements of the proportion of 13C and 18O isotopes bound to each other within carbonate minerals in 13C18O16O22- groups (heavy isotope "clumps"). Although most clumped isotope geothermometry implicitly presumes carbonate crystals have attained lattice equilibrium (i.e., thermodynamic equilibrium for a mineral, which is independent of solution chemistry), several factors other than temperature, including dissolved inorganic carbon (DIC) speciation may influence mineral isotopic signatures. Therefore we used a combination of approaches to understand the potential influence of different variables on the clumped isotope (and oxygen isotope) composition of minerals. We conducted witherite precipitation experiments at a single temperature and at varied pH to empirically determine 13C-18O bond ordering (?47) and ?18O of CO32- and HCO3- molecules at a 25 °C equilibrium. Ab initio cluster models based on density functional theory were used to predict equilibrium 13C-18O bond abundances and ?18O of different DIC species and minerals as a function of temperature. Experiments and theory indicate ?47 and ?18O compositions of CO32- and HCO3- ions are significantly different from each other. Experiments constrain the ?47-?18O slope for a pH effect (0.011 ± 0.001; 12 ? pH ? 7). Rapidly-growing temperate corals exhibit disequilibrium mineral isotopic signatures with a ?47-?18O slope of 0.011 ± 0.003, consistent with a pH effect. Our theoretical calculations for carbonate minerals indicate equilibrium lattice calcite values for ?47 and ?18O are intermediate between HCO3- and CO32-. We analyzed synthetic calcites grown at temperatures ranging from 0.5 to 50 °C with and without the enzyme carbonic anhydrase present. This enzyme catalyzes oxygen isotopic exchange between DIC species and is present in many natural systems. The two types of experiments yielded statistically indistinguishable results, and these measurements yield a calibration that overlaps with our theoretical predictions for calcite at equilibrium. The slow-growing Devils Hole calcite exhibits ?47 and ?18O values consistent with lattice equilibrium. Factors influencing DIC speciation (pH, salinity) and the timescale for DIC equilibration, as well as reactions at the mineral-solution interface, have the potential to influence clumped-isotope signatures and the ?18O of carbonate minerals. In fast-growing carbonate minerals, solution chemistry may be an important factor, particularly over extremes of pH and salinity. If a crystal grows too rapidly to reach an internal equilibrium (i.e., achieve the value for the temperature-dependent mineral lattice equilibrium), it may record the clumped-isotope signature of a DIC species (e.g., the temperature-dependent equilibrium of HCO3-) or a mixture of DIC species, and hence record a disequilibrium mineral composition. For extremely slow-growing crystals, and for rapidly-grown samples grown at a pH where HCO3- dominates the DIC pool at equilibrium, effects of solution chemistry are likely to be relatively small or negligible. In summary, growth environment, solution chemistry, surface equilibria, and precipitation rate may all play a role in dictating whether a crystal achieves equilibrium or disequilibrium clumped-isotope signatures.

  5. ISO/GUM UNCERTAINTIES AND CIAAW (UNCERTAINTY TREATMENT FOR RECOMMENDED ATOMIC WEIGHTS AND ISOTOPIC ABUNDANCES)

    SciTech Connect

    HOLDEN,N.E.

    2007-07-23

    The International Organization for Standardization (ISO) has published a Guide to the expression of Uncertainty in Measurement (GUM). The IUPAC Commission on Isotopic Abundance and Atomic Weight (CIAAW) began attaching uncertainty limits to their recommended values about forty years ago. CIAAW's method for determining and assigning uncertainties has evolved over time. We trace this evolution to their present method and their effort to incorporate the basic ISO/GUM procedures into evaluations of these uncertainties. We discuss some dilemma the CIAAW faces in their present method and whether it is consistent with the application of the ISO/GUM rules. We discuss the attempt to incorporate variations in measured isotope ratios, due to natural fractionation, into the ISO/GUM system. We make some observations about the inconsistent treatment in the incorporation of natural variations into recommended data and uncertainties. A recommendation for expressing atomic weight values using a tabulated range of values for various chemical elements is discussed.

  6. Variability in the carbon isotopic composition of foliage carbon pools (soluble carbohydrates, waxes) and respiration fluxes

    E-print Network

    Martin, Timothy

    Variability in the carbon isotopic composition of foliage carbon pools (soluble carbohydrates measured the d13 C of assimilated carbon (foliage organic matter (dCOM), soluble carbohydrates (d pools (soluble carbohydrates, waxes) and respiration fluxes in southeastern U.S. pine forests, J

  7. BOREAS TE-5 Tree Ring and Carbon Isotope Ratio Data

    NASA Technical Reports Server (NTRS)

    Hall, Forrest G. (Editor); Curd, Shelaine (Editor); Ehleriinger, Jim; Brooks, J. Renee; Flanagan, Larry

    2000-01-01

    The BOREAS TE-5 team collected several data sets to investigate the vegetation-atmosphere CO2 and H2O exchange processes. These data include tree ring widths and cellulose carbon isotope data from coniferous trees collected at the BOREAS NSA and SSA in 1993 and 1994 by the BOREAS TE-5 team. Ring width data are provided for both Picea mariana and Pinus banksiana. The carbon isotope data are provided only for Pinus banksiana. The data are provided in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

  8. Carbon isotope systematics of a mantle "hotspot": a comparison of Loihi Seamount and MORB glasses

    USGS Publications Warehouse

    Exley, R.A.; Mattey, D.P.; Clague, D.A.; Pillinger, C.T.

    1986-01-01

    The carbon isotope geochemistry of glasses from Loihi Seamount has been compared with that of MORB glasses. Stepped heating shows two carbon components in both sample suites: (1) isotopically light carbon (avg. ??13C = -26.3???) released 600??C, regarded as indigenous. The high-temperature component in MORB samples varied from 52 to 169 ppm C, average ??13C = -6.6???, consistent with previous studies (overall MORD average ??13C = -6.4 ?? 0.9???), and new results for Indian Ocean glasses are similar to Atlantic and Pacific Ocean samples. Carbon release profiles produced by stepped heating may be typical of locality, but there are no significant differences in ??13C values between MORB samples from different areas. Lower yields (17-110 ppm C) correlated with depth in the Loihi samples suggest that they are partially degassed. This degassing has not affected ??13C values significantly (avg. -5.8???). Loihi tholeiites have higher ??13C (avg. -5.6???) than the alkali basalts (avg. -7.1???). Carbon abundances correlate well with He concentration data. Comparison of the ??13C values with trace element and He, Sr, Nd, and Pb isotope data from the literature suggests that the Loihi samples with highest ??13C have high 3He/4He and possibly the least depleted 143Nd/144Nd and 87Sr/86Sr. The carbon isotope data are consistent with previous models for Loihi involving several mantle sources, lithospheric contamination, and mixing. The slightly higher ??13C of Loihi tholeiites suggests that the undegassed "plume" component manifested by high 3He/4He values might have ??13C about 1??? higher than the MORB average. ?? 1986.

  9. Light Nuclei and Isotope Abundances in Cosmic Rays. Results from AMS-01

    E-print Network

    N. Tomassetti

    2012-10-26

    Observations of the chemical and isotopic composition of light cosmic-ray nuclei can be used to constrain the astrophysical models of cosmic-ray transport and interactions in the Galaxy. Nearly 200,000 light nuclei (Z>2) have been observed by AMS-01 during the 10-day flight STS-91 in June 1998. Using these data, we have measured the relative abundance of light nuclei Li, Be, B and C in the kinetic energy range 0.35 - 45 GeV/nucleon.

  10. Combining stable isotope isotope geochemistry and carbonic anhydrase activity to trace vital effect in carbonate precipitation experiments

    NASA Astrophysics Data System (ADS)

    Thaler, C.; Ader, M.; Menez, B.; Guyot, F. J.

    2013-12-01

    Carbonates precipitated by skeleton-forming eukaryotic organisms are often characterized by non-equilibrium isotopic signatures. This specificity is referred to as the "vital effect" and can be used as an isotopic evidence to trace life. Combining stable isotope geochemistry and enzymology (using the enzyme carbonic anhydrase) we aim to demonstrate that prokaryotes are also able to precipitate carbonate with a non-equilibrium d18OCaCO3. Indeed, if in an biomineralization experiment carbonates are precipitated with a vital effect, the addition of carbonic anhydrase should drive the system to isotope equilibrium, And provide a comparison point to estimate the vital effect range. This protocol allowed us to identify a -20‰ vital effect for the d18O of carbonates precipitated by Sporosarcina pasteurii, a bacterial model of carbonatogen metabolisms. This approach is thus a powerfull tool for the understanding of microbe carbonatogen activity and will probably bring new insights into the understanding of bacterial activity in subsurface and during diagenesis.

  11. Paleodietary reconstruction using stable isotopes and abundance analysis of bovids from the Shungura Formation of South Omo, Ethiopia.

    PubMed

    Negash, Enquye W; Alemseged, Zeresenay; Wynn, Jonathan G; Bedaso, Zelalem K

    2015-11-01

    Preservation of the stable carbon isotopic composition of fossil tooth enamel enables us to estimate the relative proportion of C3 versus C4 vegetation in an animal's diet, which, combined with analysis of faunal abundance, may provide complementary methods of paleoenvironmental reconstruction. To this end, we analyzed stable carbon isotopic composition (?(13)C values) of tooth enamel from four bovid tribes (Tragelaphini, Aepycerotini, Reduncini, and Alcelaphini) derived from six members of the Shungura Formation (Members B, C, D, F, G, and L; ages from ca. 2.90-1.05 Ma (millions of years ago) in the Lower Omo Valley of southwestern Ethiopia. The bovids show a wide range of ?(13)C values within taxa and stratigraphic members, as well as temporal changes in the feeding strategies of taxa analyzed throughout the middle to late Pliocene and early Pleistocene. Such variation suggests that the use of actualistic approaches for paleoenvironmental reconstruction may not always be warranted. Alcelaphini was the only taxon analyzed that retained a consistent dietary preference throughout the sequence, with entirely C4-dominated diets. Reduncini had a mixed C3/C4 to C4-dominated diet prior to 2.4 Ma, after which this taxon shifted to a largely C4-dominated diet. Aepycerotini generally showed a mixed C3/C4 diet, with a period of increased C4 diet from 2.5 to 2.3 Ma. Tragelaphini showed a range of mixed C3/C4 diets, with a median value that was briefly nearer the C4 end member from 2.9 to 2.4 Ma but was otherwise towards the C3 end member. These isotopic results, combined with relative abundance data for these bovids, imply that the environment of the Lower Omo Valley consisted of a mosaic of closed woodlands, with riverine forests and open grasslands. However, our data also signify that the overall environment gradually became more open, and that C4 grasses became more dominant. Finally, these results help document the range and extent of environments and potential diets that were available to the four hominin species encountered in the Shungura sequence. PMID:26341031

  12. Constraining paleotemperature and water isotope signals at Lake Bonneville using carbonate clumped isotopes

    NASA Astrophysics Data System (ADS)

    Mering, J. A.; Oviatt, C. G.; Petryshyn, V. A.; Canet, J.; Tripati, A.

    2013-12-01

    Lake Bonneville was the largest pluvial system in the Great Basin during the Last Glacial Maximum (23-19 ka BP), reaching nearly 50,000 square kilometers at its high stand. Carbonate clumped isotope paleothermometry provides a new avenue to evaluate lake and atmospheric conditions by constraining the temperature and oxygen isotope ratios of lake water. Here, we present estimates of lake temperature, the oxygen isotope composition of paleowater, and Mean Annual Air Temperature (MAAT) from LGM paleoshoreline sites in Utah and Eastern Nevada. Multiple phases of ancient carbonate were evaluated, including endogenic carbonate from the ubiquitous Bonneville marl stratigraphic unit, and aragonitic shells of two species of aquatic gastropods (genera Pyrgulopsis and Stagnicola) collected from littoral deposits adjacent to the marl. These phases should record surface water conditions. Preliminary results indicate that paleotemperature estimates from gastropods and marl are similar at any given site. However, the latitudinal water isotope gradient reconstructed using marls is steeper than that reconstructed from gastropods, indicating that perhaps carbonate precipitation in marl is more evaporation-driven than shell growth of aquatic snails. Comparison with recent climate data, and clumped isotope measurements of modern samples from the Great Salt Lake, supports moderate temperature change in the Great Basin from the Last Glacial Maximum to present.

  13. CARBON ISOTOPE DISCRIMINATION AND GROWTH RESPONSE TO STAND DENSITY REDUCTIONS IN OLD PINUS PONDEROSA TREES

    EPA Science Inventory

    Carbon isotope ratios ( 13C) of tree rings are commonly used for paleoclimatic reconstruction and for inferring canopy water-use efficiency (WUE). However, the responsiveness of carbon isotope discrimination ( ) to site disturbance and resource availability has only rarely been ...

  14. The isotopic abundances of neon, magnesium and silicon nuclei accelerated in solar flares

    NASA Technical Reports Server (NTRS)

    Dietrich, W. F.; Simpson, J. A.

    1980-01-01

    Direct measurements of the relative abundance of the isotopes Ne-20 and Ne-22 are reported along with a preliminary value for the Mg-26/Mg-24 ratio and an upper limit to the abundance of Si-30 in solar flare accelerated nuclei. A Ne-20/Ne-22 ratio of 7.7 plus 2.3 or minus 1.7 is in agreement with the ratio for the component Neon-A found in carbonaceous chondrites, while a preliminary value of 0.22 plus or minus 0.07 for Mg-26/Mg-24 is larger by approximately one standard deviation than the expected ratio of 0.14 given by Cameron (1973).

  15. Interpreting the Ca isotope record of marine biogenic carbonates

    NASA Astrophysics Data System (ADS)

    Sime, Neil G.; De La Rocha, Christina L.; Tipper, Edward T.; Tripati, Aradhna; Galy, Albert; Bickle, Michael J.

    2007-08-01

    An 18 million year record of the Ca isotopic composition (? 44/42Ca) of planktonic foraminiferans from ODP site 925, in the Atlantic, on the Ceara Rise, provides the opportunity for critical analysis of Ca isotope-based reconstructions of the Ca cycle. ? 44/42Ca in this record averages +0.37 ± 0.05 (1 ? SD) and ranges from +0.21‰ to +0.52‰. The record is a good match to previously published Neogene Ca isotope records based on foraminiferans, but is not similar to the record based on bulk carbonates, which has values that are as much as 0.25‰ lower. Bulk carbonate and planktonic foraminiferans from core tops differ slightly in their ? 44/42Ca (i.e., by 0.06 ± 0.06‰ ( n = 5)), while the difference between bulk carbonate and foraminiferan values further back in time is markedly larger, leaving open the question of the cause of the difference. Modeling the global Ca cycle from downcore variations in ? 44/42Ca by assuming fixed values for the isotopic composition of weathering inputs (? 44/42Ca w) and for isotope fractionation associated with the production of carbonate sediments (? sed) results in unrealistically large variations in the total mass of Ca 2+ in the oceans over the Neogene. Alternatively, variations of ±0.05‰ in the Ca isotope composition of weathering inputs or in the extent of fractionation of Ca isotopes during calcareous sediment formation could entirely account for variations in the Ca isotopic composition of marine carbonates. Ca isotope fractionation during continental weathering, such as has been recently observed, could easily result in variations in ? 44/42Ca w of a few tenths of permil. Likewise a difference in the fractionation factors associated with aragonite versus calcite formation could drive shifts in ? sed of tenths of permil with shifts in the relative output of calcite and aragonite from the ocean. Until better constraints on variations in ? 44/42Ca w and ? sed have been established, modeling the Ca 2+ content of seawater from Ca isotope curves should be approached cautiously.

  16. ­­A Clumped Isotope Calibration for Terrestrial Microbial Carbonates

    NASA Astrophysics Data System (ADS)

    Petryshyn, V. A.; Mering, J. A.; Mitsunaga, B. A.; Eagle, R.; Dunbar, R. B.; Bhattacharya, A.; Tripati, A.

    2014-12-01

    Accurate terrestrial paleotemperature records are key pieces of information in the paleoenvironmental reconstruction of Earth history. These records aid in building reliable climate models and help scientists understand the links between continental and oceanic climate data. Many different types of analyses are used to estimate terrestrial climate shifts, including leaf margin analysis, palynology, glacial deposits, elemental ratios, organic geochemistry, and stable isotopes of lacustrine deposits. Here we report a carbonate clumped isotope calibration for microbial carbonates. Application of the clumped isotope paleothermometer can potentially provide a direct temperature measurement of the water at the time of carbonate formation. Although different calibrations of the paleothermometer have been published for both inorganic and biotic carbonate minerals, the effects of clumping in microbialites (structures built under the influence of microbial activity) have not yet been quantified. Lacustrine microbialites present a potentially large, untapped archive of terrestrial climate data, however they are not strictly biotic or abiotic, but bio-induced carbonate, meaning that organisms (such as photosynthetic bacteria) influence but do not directly control precipitation. We have measured modern microbialites from multiple lacustrine sites and will report a comparison of these results to known water temperatures. Additionally we will compare lacustrine samples to marine microbialites (e.g., samples from Shark Bay) to assess potential differences between lacustrine and marine intertidal environments on clumped isotope compositions.

  17. Behaviour of Structural Carbonate Stable Carbon and Oxygen Isotope Compositions in Bioapatite During Burning of Bone

    NASA Astrophysics Data System (ADS)

    Munro, L. E.; Longstaffe, F. J.; White, C. D.

    2003-12-01

    Bioapatite, the principal inorganic phase comprising bone, commonly contains a small fraction of carbonate, which has been substituted into the phosphate structure during bone formation. The isotopic compositions of both the phosphate oxygen and the structural carbonate oxygen are now commonly used in palaeoclimatological and bioarchaeological investigations. The potential for post-mortem alteration of these isotopic compositions, therefore, is of interest, with the behaviour of structural carbonate being of most concern. In bioarchaeological studies, alteration of bone isotopic compositions has the potential to occur not only during low-temperature processes associated with burial but also during food preparation involving heating (burning, boiling). Here, we examine the stable isotopic behaviour of structural carbonate oxygen and carbon, and coexisting phosphate oxygen during the burning of bone. Freshly deceased (6<8 months) white-tailed deer leg bones (Odocoileus virginianus) were collected from Pinery Provincial Park, Ontario, Canada. Each long bone was sectioned and incrementally heated from 25 to 900° C, in 25° intervals. The samples were then ground to a standardized grain-size (45<63? m), and changes in bioapatite crystallinity (CI) were determined using powder X-ray diffraction (pXRD), and Fourier transform infra-red spectroscopy (FTIR). Combined differential thermal and thermogravimetric analyses (DTA/TG) were used to evaluate weight loss and associated reactions during heating. Stable carbon isotope compositions of the bioapatite remain relatively constant (+/-1‰ ) during heating to 650° C. A 4‰ increase in stable carbon isotopic composition then occurs between 650-750° C, accompanied by an increase in CI, followed by a 10‰ decline at temperatures above 800° C, as carbonate carbon is lost. Carbonate and phosphate oxygen isotopic compositions are correlated over the entire heating range, with carbonate being enriched relative to phosphate by about 8-10‰ below 500° C, 5-6‰ between 500-700° C, and 8-10‰ above 700° C. CI and oxygen isotopic compositions of carbonate and phosphate are not well correlated. Only modest CI changes are recorded from 25-675° C, compared with much larger changes in oxygen isotopic composition, especially above 300° C. On average, original isotopic compositions are largely preserved for both phosphate (+/-1‰ ) and carbonate (+/-2‰ ) oxygen at <300° C. At higher temperatures, however, both phosphate and carbonate oxygen in the bioapatite are systematically depleted of oxygen-18 relative to original values.

  18. Magnesium isotopic compositions of the Mesoproterozoic dolostones: Implications for Mg isotopic systematics of marine carbonates

    NASA Astrophysics Data System (ADS)

    Huang, Kang-Jun; Shen, Bing; Lang, Xian-Guo; Tang, Wen-Bo; Peng, Yang; Ke, Shan; Kaufman, Alan J.; Ma, Hao-Ran; Li, Fang-Bing

    2015-09-01

    Available Mg isotope data indicate that dolostones of different ages have overlapping range of Mg isotopic composition (?26Mg) and there is no systematic difference among different types of dolomites. To further explore the Mg isotopic systematics of dolomite formation, we measured Mg isotopic compositions of Mesoproterozoic dolostones from the Wumishan Formation in North China Block, because dolomite formation in Mesoproterozoic might have been fundamentally different from the younger counterparts. Based on petrographic observations, three texturally-different dolomite phases (dolomicrite, subhedral dolomite and anhedral dolomite) are recognized in the Wumishan dolostones. Nevertheless, these three types of dolomites have similar ?26Mg values, ranging from -1.35‰ to -1.72‰, which are indistinguishable from Neoproterozoic and Phanerozoic dolostones. To explain ?26Mg values of dolostones, we simulate the Mg isotopic system during dolomite formation by applying the one-dimensional Diffusion-Advection-Reaction (1D-DAR) model, assuming that the contemporaneous seawater is the Mg source of dolostone. The 1D-DAR modeling results indicate that the degree of dolomitization is controlled by sedimentation rate, seawater Mg concentration, temperature, and reaction rate of dolomite formation, whereas Mg isotopic composition of dolostone is not only dependent on these factors, but also affected by ?26Mg of seawater and isotope fractionation during dolomite formation. Moreover, the 1D-DAR model predicts that dolomite formation within sediments has limited range of variation in ?26Mg with respect to limestones. Furthermore, the modeling results demonstrate that dolostone is always isotopically heavier than Ca-carbonate precipitated from seawater, explaining the systematic isotopic difference between dolostones and limestones. Finally, we can infer from the 1D-DAR model that early-formed dolostone at shallower depth of sediments is always isotopically lighter than that formed in deeper sediments, suggesting the potential application of Mg isotope as a proxy for constraining dolostone formation.

  19. Optimizing sample pretreatment for compound-specific stable carbon isotopic analysis of amino sugars in marine sediment

    NASA Astrophysics Data System (ADS)

    Zhu, R.; Lin, Y.-S.; Lipp, J. S.; Meador, T. B.; Hinrichs, K.-U.

    2014-09-01

    Amino sugars are quantitatively significant constituents of soil and marine sediment, but their sources and turnover in environmental samples remain poorly understood. The stable carbon isotopic composition of amino sugars can provide information on the lifestyles of their source organisms and can be monitored during incubations with labeled substrates to estimate the turnover rates of microbial populations. However, until now, such investigation has been carried out only with soil samples, partly because of the much lower abundance of amino sugars in marine environments. We therefore optimized a procedure for compound-specific isotopic analysis of amino sugars in marine sediment, employing gas chromatography-isotope ratio mass spectrometry. The whole procedure consisted of hydrolysis, neutralization, enrichment, and derivatization of amino sugars. Except for the derivatization step, the protocol introduced negligible isotopic fractionation, and the minimum requirement of amino sugar for isotopic analysis was 20 ng, i.e., equivalent to ~8 ng of amino sugar carbon. Compound-specific stable carbon isotopic analysis of amino sugars obtained from marine sediment extracts indicated that glucosamine and galactosamine were mainly derived from organic detritus, whereas muramic acid showed isotopic imprints from indigenous bacterial activities. The ?13C analysis of amino sugars provides a valuable addition to the biomarker-based characterization of microbial metabolism in the deep marine biosphere, which so far has been lipid oriented and biased towards the detection of archaeal signals.

  20. Optimizing sample pretreatment for compound-specific stable carbon isotopic analysis of amino sugars in marine sediment

    NASA Astrophysics Data System (ADS)

    Zhu, R.; Lin, Y.-S.; Lipp, J. S.; Meador, T. B.; Hinrichs, K.-U.

    2014-01-01

    Amino sugars are quantitatively significant constituents of soil and marine sediment, but their sources and turnover in environmental samples remain poorly understood. The stable carbon isotopic composition of amino sugars can provide information on the lifestyles of their source organisms and can be monitored during incubations with labeled substrates to estimate the turnover rates of microbial populations. However, until now, such investigation has been carried out only with soil samples, partly because of the much lower abundance of amino sugars in marine environments. We therefore optimized a procedure for compound-specific isotopic analysis of amino sugars in marine sediment employing gas chromatography-isotope ratio mass spectrometry. The whole procedure consisted of hydrolysis, neutralization, enrichment, and derivatization of amino sugars. Except for the derivatization step, the protocol introduced negligible isotopic fractionation, and the minimum requirement of amino sugar for isotopic analysis was 20 ng, i.e. equivalent to ~ 8 ng of amino sugar carbon. Our results obtained from ?13C analysis of amino sugars in selected marine sediment samples showed that muramic acid had isotopic imprints from indigenous bacterial activities, whereas glucosamine and galactosamine were mainly derived from organic detritus. The analysis of stable carbon isotopic compositions of amino sugars opens a promising window for the investigation of microbial metabolisms in marine sediments and the deep marine biosphere.

  1. Sims Analysis of Water Abundance and Hydrogen Isotope in Lunar Highland Plagioclase

    NASA Technical Reports Server (NTRS)

    Hui, Hejiu; Guan, Yunbin; Chen, Yang; Peslier, Anne H.; Zhang, Youxue; Liu, Yang; Rossman, George R.; Eiler, John M.; Neal, Clive R.

    2015-01-01

    The detection of indigenous water in mare basaltic glass beads has challenged the view established since the Apollo era of a "dry" Moon. Since this discovery, measurements of water in lunar apatite, olivine-hosted melt inclusions, agglutinates, and nominally anhydrous minerals have confirmed that lunar igneous materials contain water, implying that some parts of lunar mantle may have as much water as Earth's upper mantle. The interpretation of hydrogen (H) isotopes in lunar samples, however, is controversial. The large variation of H isotope ratios in lunar apatite (delta Deuterium = -202 to +1010 per mille) has been taken as evidence that water in the lunar interior comes from the lunar mantle, solar wind protons, and/or comets. The very low deuterium/H ratios in lunar agglutinates indicate that solar wind protons have contributed to their hydrogen content. Conversely, H isotopes in lunar volcanic glass beads and olivine-hosted melt inclusions being similar to those of common terrestrial igneous rocks, suggest a common origin for water in both Earth and Moon. Lunar water could be inherited from carbonaceous chondrites, consistent with the model of late accretion of chondrite-type materials to the Moon as proposed by. One complication about the sources of lunar water, is that geologic processes (e.g., late accretion and magmatic degassing) may have modified the H isotope signatures of lunar materials. Recent FTIR analyses have shown that plagioclases in lunar ferroan anorthosite contain approximately 6 ppm H2O. So far, ferroan anorthosite is the only available lithology that is believed to be a primary product of the lunar magma ocean (LMO). A possible consequence is that the LMO could have contained up to approximately 320 ppm H2O. Here we examine the possible sources of water in the LMO through measurements of water abundances and H isotopes in plagioclase of two ferroan anorthosites and one troctolite from lunar highlands.

  2. Rhenium-osmium isotope and highly-siderophile-element abundance systematics of angrite meteorites

    NASA Astrophysics Data System (ADS)

    Riches, Amy J. V.; Day, James M. D.; Walker, Richard J.; Simonetti, Antonio; Liu, Yang; Neal, Clive R.; Taylor, Lawrence A.

    2012-11-01

    Coupled 187Os/188Os compositions and highly-siderophile-element (HSE: Os, Ir, Ru, Pt, Pd, and Re) abundance data are reported for eight angrite achondrite meteorites that include quenched- and slowly-cooled textural types. These data are combined with new major- and trace-element concentrations determined for bulk-rock powder fractions and constituent mineral phases, to assess angrite petrogenesis. Angrite meteorites span a wide-range of HSE abundances from <0.005 ppb Os (e.g., Northwest Africa [NWA] 1296; Angra dos Reis) to >100 ppb Os (NWA 4931). Chondritic to supra-chondritic 187Os/188Os (0.1201-0.2127) measured for Angra dos Reis and quenched-angrites correspond to inter- and intra-sample heterogeneities in Re/Os and HSE abundances. Quenched-angrites have chondritic-relative rare-earth-element (REE) abundances at 10-15×CI-chondrite, and their Os-isotope and HSE abundance variations represent mixtures of pristine uncontaminated crustal materials that experienced addition (<0.8%) of exogenous chondritic materials during or after crystallization. Slowly-cooled angrites (NWA 4590 and NWA 4801) have fractionated REE-patterns, chondritic to sub-chondritic 187Os/188Os (0.1056-0.1195), as well as low-Re/Os (0.03-0.13), Pd/Os (0.071-0.946), and relatively low-Pt/Os (0.792-2.640). Sub-chondritic 187Os/188Os compositions in NWA 4590 and NWA 4801 are unusual amongst planetary basalts, and their HSE and REE characteristics may be linked to melting of mantle sources that witnessed prior basaltic melt depletion. Angrite HSE-Yb systematics suggest that the HSE behaved moderately-incompatibly during angrite magma crystallization, implying the presence of metal in the crystallizing assemblage. The new HSE abundance and 187Os/188Os compositions indicate that the silicate mantle of the angrite parent body(ies) (APB) had HSE abundances in chondritic-relative proportions but at variable abundances at the time of angrite crystallization. The HSE systematics of angrites are consistent with protracted post-core formation accretion of materials with chondritic-relative abundances of HSE to the APB, and these accreted materials were rapidly, yet inefficiently, mixed into angrite magma source regions early in Solar System history.

  3. Carbon Reservoir History of Mars Constrained by Atmospheric Isotope Signatures

    NASA Astrophysics Data System (ADS)

    Hu, Renyu; Kass, David M.; Ehlmann, Bethany L.; Yung, Yuk

    2014-11-01

    The evolution of the atmosphere on Mars is one of the most intriguing problems in the exploration of the Solar System, and the climate of Mars may have evolved from a warmer, wetter early state to the cold, dry current state. Because CO2 is the major constituent of Mars’s atmosphere, its isotopic signatures offer a unique window to trace the evolution of climate on Mars. Here we use a box model to trace the evolution of the carbon reservoir and its iso-topic signature on Mars, with carbonate deposition and atmospheric escape as the two sinks and magmatic activity as the sole source. We derive new quantitative constraints on the amount of carbonate deposition and the atmospher-ic pressure of Mars through time, extending into the Noachian, ~3.8 Gyr before present. This determination is based on recent Mars Science Laboratory (MSL) isotopic measurements of Mars’s atmosphere, recent orbiter, lander, and rover measurements of Mars’s surface, and a newly identified mechanism (photodissociation of CO) that efficiently enriches the heavy carbon isotope. In particular, we find that escape via CO photodissociation on Mars has a frac-tionation factor of 0.6 and hence, photochemical escape processes can effectively enrich 13C in the Mars’s atmos-phere during the Amazonian. As a result, modest carbonate deposition must have occurred early in Mars’s history to compensate the enrichment effects of photochemical processes and also sputtering, even when volcanic outgassing up to 200 mbar occurred during the Hesperian. For a photochemical escape flux that scales as the square of the solar EUV flux or more, at least 0.1 bar of CO2 must have been deposited as carbonates in the Noachian and Hesperian. More carbonate deposition would be required if carbonate deposition only occurred in the Noachian or with low fractionation factors.

  4. Alkane distribution and carbon isotope composition in fossil leaves: An interpretation of plant physiology in the geologic past

    NASA Astrophysics Data System (ADS)

    Graham, H. V.; Freeman, K. H.

    2014-12-01

    The relative chain-length distribution and carbon-isotope composition of n-alkanes extracted from sedimentary rocks are important geochemical tools for investigating past terrestrial ecosystems. Alkanes preserved in ancient sediments are assumed to be contemporaneous, derived from the same ecosystem, and integrated from the biomass present on the landscape at the time of deposition. Further, there is an underlying assumption that ancient plants exhibited the same metabolic and physiological responses to climate conditions that are observed for modern plants. Interpretations of alkane abundances and isotopic signatures are complicated by the strong influence of phylogenetic affiliation and ecological factors, such as canopy structure. A better understanding of how ecosystem and taxa influence alkane properties, including homologue abundance patterns and leaf-lipid carbon isotope fractionation would help strengthen paleoecological interpretations based on these widely employed plant biomarkers. In this study, we analyze the alkane chain-length distribution and carbon-isotope composition of phytoleim and alkanes (d13Cleaf and d13Clipid) extracted from a selection of Cretaceous and Paleocene fossil leaves from the Guaduas and Cerrejon Formations of Colombia. These data were compared with data for the same families in a modern analogue biome. Photosynthetic and biosynthetic fractionation (?leaf and elipid) values determined from the fossil material indicate carbon metabolism patterns were similar to modern plants. Fossil data were incorporated in a biomass-weighted mixing model to represent the expected lipid complement of sediment arising from this ecosystem and compared with alkane measurements from the rock matrix. Modeled and observed isotopic and abundance patterns match well for alkane homologs most abundant in plants (i.e., n-C27 to n-C33). The model illustrates the importance of understanding biases in litter flux and taphonomic pressures inherent in the fossil lipid record, and it highlights the influence of community composition and forest structure on sedimentary lipids.

  5. Carbon and sulfur isotopes as tracers of fluid-fluid and fluid-rock interaction in geothermal systems

    NASA Astrophysics Data System (ADS)

    Stefansson, A.; Keller, N. S.; Gunnarsson Robin, J.; Kjartansdottir, R.; Ono, S.; Sveinbjörnsdottir, A. E.

    2014-12-01

    Carbon and sulfur are among major components in geothermal systems. They are found in various oxidation state and present in solid phases and fluids (water and vapor). In order to study the reactions and mass movement within multiphase geothermal systems, we have combined geochemical fluid-fluid and fluid-rock modelling with sulfur and carbon isotope fractionation modelling and compared the results with measured carbon and sulfur isotopes in geothermal fluids (water and vapor) for selected low- and high-enthalpy geothermal systems in Iceland. In this study we have focused on ?34S for H2S in vapor and water and SO4 in water as well as ?13C for CO2 in vapor and water phases. Isotope fractionations for CO2 and H2S between vapor and liquid water, upon aqueous speciation and upon carbonate and sulfide mineral formation were revised. These were combined with reaction modelling involving closed system boiling and progressive water-rock interaction to constrain the mass movement and isotope abundance between various phases. The results indicate that for a closed system, carbon and sulfur isotope abundance is largely dependent on progressive fluid-fluid and fluid-rock interaction and the initial total ?34S and ?13C value of the system. Initially, upon progressive fluid rock interaction the ?34S and ?13C values for the bulk aqueous phase approach that of the host rocks. Secondary mineral formation may alter these values, the exact isotope value of the mineral and resulting aqueous phase depending on aqueous speciation and isotope fractionation factor. In turn, aqueous speciation and mineral saturation depends on progressive fluid-rock interaction, fluid-fluid interaction, temperature and acid supply to the system. Depressurization boiling also results in isotope fractionation, the exact isotope value of the vapor and aqueous phase depending on aqueous speciation and isotope fractionation fractor. In this way, carbon and sulfur isotopes may be used combined with measured values for natural fluids to constrain mass movement upon fluid-fluid and fluid-rock interaction in geothermal systems.

  6. Low stable carbon isotope fractionation by coccolithophore RubisCO

    NASA Astrophysics Data System (ADS)

    Boller, Amanda J.; Thomas, Phaedra J.; Cavanaugh, Colleen M.; Scott, Kathleen M.

    2011-11-01

    The 13C/ 12C ratio of carbon compounds is used to identify sources and sinks in the global carbon cycle. However, the relatively enriched 13C content observed for marine organic carbon remains enigmatic. The majority of oceanic carbon is fixed by algae and cyanobacteria via the Calvin-Benson-Bassham cycle, yet isotopic discrimination by the CO 2 fixation enzyme, RubisCO (ribulose 1,5-bisphosphate carboxylase/oxygenase), has only been measured for a single marine cyanobacterium. Different forms of RubisCO occur in different phytoplankton species (overall amino acid identity varying by as much as ˜75%) and thus may vary in the degree to which they fractionate carbon. Here we measured isotope discrimination by RubisCO from the coccolithophore Emiliania huxleyi, a cosmopolitan species used as a marine algal model .E. huxleyi RubisCO discriminated substantially less ( ? = 11.1‰) against 13CO 2 than other RubisCO enzymes (18-29‰), despite having Michaelis-Menten kinetic parameters ( K = 72 ?M; Vmax = 0.66 ?mol min -1 mg -1 protein) similar to those measured for RubisCO enzymes from different organisms. If widespread, decreased isotope discrimination of 13C by phytoplankton RubisCO may be a major factor influencing the enriched 13C content of marine organic carbon. This finding emphasizes the necessity of (a) determining ? values for RubisCOs of other marine phytoplankton and (b) re-evaluation of ?13C values from physiological, environmental, and geological studies.

  7. Strontium, oxygen and carbon isotope records of Permian seawater

    NASA Astrophysics Data System (ADS)

    Korte, C.; Kozur, H. W.; Joachimski, M. M.; Veizer, J.

    2003-04-01

    Strontium, oxygen and carbon isotope values of stratigraphically well defined Permian conodonts and brachiopods were analyzed. The samples were screened by optical microscopy, SEM and ICP-AES to determine their degree of preservation. Brachiopod shells with less than 250 ppm Mn and more than 400 ppm Sr, as well as conodonts with alteration indices between 1 and 2.5 were classified as diagenetically unaltered. The strontium isotope ratios show a gradual decrease from 0.7082 in the lowermost Permian to 0.7069 in the Middle Permian, coincident with the advancing deglaciation of Gondwana. In the late Capitanian and Late Permian the Sr isotope ratios increase, reaching 0.7072 at the Permian/Triassic boundary. The oxygen isotope values of brachiopod shells from the Tethys realm and the Delaware Basin vary between --2 and --4 ppm (V-PDB). Late Permian conodonts from the Tethyan realm have comparable oxygen isotope values between --10.5 and --12.5 ppm (V-PDB), if the theoretically predicted difference in the oxygen isotope composition of carbonate and phosphate of approximately 8.5 ppm is taken into account (Longinelli and Nuti 1973). Assuming --1 ppm (V-SMOW) for the oxygen isotope value of seawater, brachiopods and conodonts yield paleotemperatures of 20 to 30^oC for low latitude Permian seawater. The moderate latitude Asselian and Sakmarian (Lower Permian) Cis-Uralian samples reveal somewhat higher oxygen isotope values (--1 to --3.4 ppm V-PDB) coincident with the glaciation of Gondwana and storage of isotopically light oxygen in the ice caps and may indicate somewhat lower seawater temperatures. The carbon isotope values show a decreasing trend from approximately 5 ppm (V-PDB) in the lowermost Permian to the 3 ppm (V-PDB) in the Middle Permian. In the Dzhulfian (Late Permian) the data are about 4 ppm and in the Dorshamian (Late Permian) the values decrease. References Longinelli A, Nuti S (1973) Revised phosphate-water isotopic temperature scale. Earth Planet Sci Lett 19:373-376.

  8. Absolute isotopic composition of molybdenum and the solar abundances of the p-process nuclides {sup 92,94}Mo

    SciTech Connect

    Wieser, M. E.; Laeter, J. R. De

    2007-05-15

    The isotopic composition of molybdenum has been measured with high precision using a thermal ionization mass spectrometer, the linearity of which has been verified by measuring the isotopically-certified reference material for strontium (NIST 987). The abundance sensitivity of the mass spectrometer in the vicinity of the molybdenum ion beams has been carefully examined to ensure the absence of tailing effects. Particular care was given to ensuring that potential isobaric interferences from zirconium and ruthenium did not affect the measurement of the isotopic composition of molybdenum. Gravimetric mixtures of two isotopically enriched isotopes, {sup 92}Mo and {sup 98}Mo, were analyzed mass spectrometrically to calibrate the mass spectrometer, in order to establish the isotope fractionation of the spectrometer for the molybdenum isotopes. This enabled the ''absolute'' isotopic composition of molybdenum to be determined. An accurate determination of the isotopic composition is required in order to calculate the atomic weight of molybdenum, which is one of the least accurately known values of all the elements. The absolute isotope abundances (in atom %) of molybdenum measured in this experiment are as follows: {sup 92}Mo=14.5246{+-}0.0015; {sup 94}Mo=9.1514{+-}0.0074; {sup 95}Mo=15.8375{+-}0.0098; {sup 96}Mo=16.672{+-}0.019; {sup 97}Mo=9.5991{+-}0.0073; {sup 98}Mo=24.391{+-}0.018; and {sup 100}Mo=9.824{+-}0.050, with uncertainties at the 1s level. These values enable an atomic weight A{sub r}(Mo) of 95.9602{+-}0.0023 (1s) to be calculated, which is slightly higher than the current Standard Atomic Weight A{sub r}(Mo) =95.94{+-}0.02 and with a much improved uncertainty interval. These 'absolute' isotope abundances also enable the Solar System abundances of molybdenum to be calculated for astrophysical purposes. Of particular interest are the Solar System abundances of the two p-process nuclides--{sup 92}Mo and {sup 94}Mo, which are present in far greater abundance than p-process theory suggests. The Solar System abundances for {sup 92}Mo and {sup 94}Mo of 0.364{+-}0.012 and 0.230{+-}0.008 respectively, (with respect to silicon =10{sup 6} atoms), are the most accurate values measured to date, and should therefore be adopted in future p-process calculations, rather than the existing values of 0.378{+-}0.021 and 0.236{+-}0.013, respectively.

  9. Carbon stars in local group dwarf galaxies: C and O abundances

    E-print Network

    R. Wahlin; K. Eriksson; B. Gustafsson; K. H. Hinkle; D. L. Lambert; N. Ryde; B. Westerlund

    2006-05-10

    We present abundances of carbon and oxygen as well as abundance ratios 12C/13C for a sample of carbon stars in the LMC, SMC, Carina, Sculptor and Fornax dwarf galaxies. The overall metallicities in these dwarf galaxies are lower than in the galactic disc. The observations cover most of the AGB and we discuss the abundance patterns in different regions along the AGB. The abundances are determined from infrared spectra obtained with the ISAAC spectrometer on VLT (R=1500) and the Phoenix Spectrometer on Gemini South (R=50000). The synthetic spectra used in the analysis were computed with MARCS model atmospheres. We find that the oxygen abundance is decreasing with decreasing overall metallicity of the system while the C/O ratio at a given evolutionary phase is increasing with decreasing oxygen abundance. keywords Stars: abundances -- Stars: carbon -- Stars: AGB and post-AGB -- Galaxies: dwarf -- Local Group -- Infrared: stars

  10. The evolution of the global selenium cycle: Secular trends in Se isotopes and abundances

    NASA Astrophysics Data System (ADS)

    Stüeken, E. E.; Buick, R.; Bekker, A.; Catling, D.; Foriel, J.; Guy, B. M.; Kah, L. C.; Machel, H. G.; Montañez, I. P.; Poulton, S. W.

    2015-08-01

    The Earth's surface has undergone major transitions in its redox state over the past three billion years, which have affected the mobility and distribution of many elements. Here we use Se isotopic and abundance measurements of marine and non-marine mudrocks to reconstruct the evolution of the biogeochemical Se cycle from ?3.2 Gyr onwards. The six stable isotopes of Se are predominantly fractionated during redox reactions under suboxic conditions, which makes Se a potentially valuable new tool for identifying intermediate stages from an anoxic to a fully oxygenated world. ?82/78Se shows small fractionations of mostly less than 2‰ throughout Earth's history and all are mass-dependent within error. In the Archean, especially after 2.7 Gyr, we find an isotopic enrichment in marine (+0.37 ± 0.27‰) relative to non-marine samples (-0.28 ± 0.67‰), paired with increasing Se abundances. Student t-tests show that these trends are statistically significant. Although we cannot completely rule out the possibility of volcanic Se addition, these trends may indicate the onset of oxidative weathering on land, followed by non-quantitative reduction of Se oxyanions during fluvial transport. The Paleoproterozoic Great Oxidation Event (GOE) is not reflected in the marine ?82/78Se record. However, we find a major inflection in the secular ?82/78Se trend during the Neoproterozoic, from a Precambrian mean of +0.42 ± 0.45‰ to a Phanerozoic mean of -0.19 ± 0.59‰. This drop probably reflects the oxygenation of the deep ocean at this time, stabilizing Se oxyanions throughout the water column. Since then, reduction of Se oxyanions has likely been restricted to anoxic basins and diagenetic environments in sediments. In light of recent Cr isotope data, it is likely that oxidative weathering before the Neoproterozoic produced Se oxyanions in the intermediate redox state SeIV, whereas the fully oxidized species SeVI became more abundant after the Neoproterozoic rise of atmospheric oxygen.

  11. Carbon-Isotopic Dynamics of Streams, Taylor Valley, Antarctica: Biological Effects

    NASA Technical Reports Server (NTRS)

    Neumann, K.; DesMarais, D. J.

    1998-01-01

    We have investigated the role of biological processes in the C-isotopic dynamics of the aquatic ecosystems in Taylor Valley, Antarctica. This cold desert ecosystem is characterized by the complete lack of vascular plants, and the presence of algal mats in ephemeral streams and perennially ice covered lakes. Streams having abundant algal mats and mosses have very low sigma CO2 concentrations, as well as the most depleted delta C-13 values (-4%). Previous work has shown that algal mats in these streams have delta C-13 values averaging -7.01%. These values are similar to those observed in the algal mats in shallow areas of the lakes in Taylor Valley, where CO2 is thought to be colimiting to growth. These low Sigma CO2 concentrations, and delta C(13) signatures heavier than the algal mats, suggest that CO2 may be colimiting in the streams, as well. Streams with little algal growth, especially the longer ones in Fryxell Basin, have higher Sigma CO2 concentrations and much more enriched isotopic signatures (as high as +8%). In these streams, the dissolution of isotopically enriched, cryogenic CaCO3 is probably the major source of dissolved carbonate. The delta C(13) geochemistry of Antarctic streams is radically different from the geochemistry of more temperate streams, as it is not affected by terrestrially produced, isotopically depleted Sigma CO2. These results have important implications for the understanding of "biogenic" carbonate that might have been produced from aquatic ecosystems in the past on Mars.

  12. How the oxygen isotope ratio of rain water influences the isotope ratio of chicken eggshell carbonate

    NASA Astrophysics Data System (ADS)

    Price, Gregory; Grimes, Stephen

    2015-04-01

    The stable oxygen isotope ratio of chicken eggshell carbonate was analysed from chicken eggs laid under free range, and organic farming regimes from across the UK. The eggshell carbonate oxygen isotope data shows a clear depletion in delta18O distribution from the southwest to the northeast. Although consistently offset by around 1 permil, the same isotopic distribution as that seen in eggshell carbonate is observed in the delta18O ratio of rainfall and groundwater from across the UK. This distribution is related to the Rayleigh distillation of rainfall driven by westerly winds across the UK landmass. The clear relationship observed between eggshell delta18O values and that of rainwater presumably reflects the nature of free range chickens which must be drinking locally derived rainwater and supplementing their diet and water intake with locally derived food. These results suggest that the oxygen isotope value of chicken eggshells can be used as a forensic tool to identify the locality that free range and organic eggs were laid within the UK. Furthermore, if suitable material is preserved in the archaeological and geological record then such a relationship can potentially be used to establish the oxygen isotope value of rainwater from which ancient and / or ancestral birds lived.

  13. Stable carbon isotope fractionation by sulfate-reducing bacteria

    NASA Technical Reports Server (NTRS)

    Londry, Kathleen L.; Des Marais, David J.

    2003-01-01

    Biogeochemical transformations occurring in the anoxic zones of stratified sedimentary microbial communities can profoundly influence the isotopic and organic signatures preserved in the fossil record. Accordingly, we have determined carbon isotope discrimination that is associated with both heterotrophic and lithotrophic growth of pure cultures of sulfate-reducing bacteria (SRB). For heterotrophic-growth experiments, substrate consumption was monitored to completion. Sealed vessels containing SRB cultures were harvested at different time intervals, and delta(13)C values were determined for gaseous CO(2), organic substrates, and products such as biomass. For three of the four SRB, carbon isotope effects between the substrates, acetate or lactate and CO(2), and the cell biomass were small, ranging from 0 to 2 per thousand. However, for Desulfotomaculum acetoxidans, the carbon incorporated into biomass was isotopically heavier than the available substrates by 8 to 9 per thousand. SRB grown lithoautotrophically consumed less than 3% of the available CO(2) and exhibited substantial discrimination (calculated as isotope fractionation factors [alpha]), as follows: for Desulfobacterium autotrophicum, alpha values ranged from 1.0100 to 1.0123; for Desulfobacter hydrogenophilus, the alpha value was 0.0138, and for Desulfotomaculum acetoxidans, the alpha value was 1.0310. Mixotrophic growth of Desulfovibrio desulfuricans on acetate and CO(2) resulted in biomass with a delta(13)C composition intermediate to that of the substrates. The extent of fractionation depended on which enzymatic pathways were used, the direction in which the pathways operated, and the growth rate, but fractionation was not dependent on the growth phase. To the extent that environmental conditions affect the availability of organic substrates (e.g., acetate) and reducing power (e.g., H(2)), ecological forces can also influence carbon isotope discrimination by SRB.

  14. Carbonate "clumped" isotope signatures in aragonitic scleractinian and calcitic gorgonian deep-sea corals

    DOE PAGESBeta

    Kimball, J.; Tripati, R. E.; Dunbar, R.

    2015-12-04

    Deep-sea corals are a potentially valuable archive of the temperature and ocean chemistry of intermediate and deep waters. Living in near constant temperature, salinity and pH, and having amongst the slowest calcification rates observed in carbonate-precipitating biological organisms, deep-sea corals can provide valuable constraints on processes driving mineral equilibrium and disequilibrium isotope signatures. Here we report new data to further develop "clumped" isotopes as a paleothermometer in deep-sea corals as well as to investigate mineral-specific, taxon-specific, and growth-rate related effects. Carbonate clumped isotope thermometry is based on measurements of the abundance of the doubly-substituted isotopologue 13C18O16O2 in carbonate minerals, analyzedmore »in CO2 gas liberated on phosphoric acid digestion of carbonates and reported as ?47 values. We analyzed ?47 in live-collected aragonitic scleractinian (Enallopsammia sp.) and calcitic gorgonian (Isididae and Coralliidae) deep-sea corals, and compared results to published data for other aragonitic scleractinian taxa. Measured ?47 values were compared to in situ temperatures and the relationship between ?47 and temperature was determined for each group to investigate taxon-specific effects. We find that aragonitic scleractinian deep-sea corals exhibit higher values than calcitic gorgonian corals and the two groups of coral produce statistically different relationship between ?47-temperature calibrations. These data are significant in the interpretation of all carbonate "clumped" isotope calibration data as they show that distinct ?47-temperature calibrations can be observed in different materials recovered from the same environment and analyzed using the same instrumentation, phosphoric acid composition, digestion temperature and technique, CO2 gas purification apparatus, and data handling. There are three possible explanations for the origin of these different calibrations. The offset between the corals of different mineralogy is in the same direction as published theoretical predictions for the offset between calcite and aragonite, although the magnitude of the offset is different. One possibility is that the deep-sea coral results reflect that crystals may attain nominal mineral equilibrium clumped isotope signatures only under conditions of extremely slow growth. In that case, a possible explanation for the attainment of disequilibrium bulk isotope signatures and equilibrium clumped isotope signatures by deep-sea corals is that extraordinarily slow growth rates can promote the occurrence of isotopic reordering in the interfacial region of growing crystals. We also cannot rule out a component of a biological "vital-effect" influencing clumped isotope signatures in one or both orders of coral. Based on published experimental data and theoretical calculations, these biological "vital" effects could arise from kinetic isotope effects due to the source of carbon used for calcification, temperature- and pH-dependent rates of CO2 hydration and/or hydroxylation, calcifying fluid pH, the activity of carbonic anhydrase, the residence time of dissolved inorganic carbon in the calcifying fluid, and calcification rate. A third possible explanation is the occurrence of variable acid digestion fractionation factors. Although a recent study has suggested that dolomite, calcite, and aragonite may have similar clumped isotope acid digestion fractionation factors, the influence of acid digestion kinetics on ?47 is a subject that warrants further investigation.« less

  15. Carbon and Oxygen Isotopic Ratios for Miras

    NASA Astrophysics Data System (ADS)

    Hinkle, Kenneth H.; Lebzelter, Thomas; Straniero, Oscar

    2016-01-01

    We have measured vibration-rotation first and second overtone 12C16O, 13C16O, 12C17O, 12C18O lines in 1.5 to 2.5 micron spectra of 41 Mira and SRa stars. These measurements have been used to derive 12C/13C, 16O/17O, and 16O/18O isotopic ratios. The ratios are compared to available literature values for the individual stars and the ratios are compared to isotopic ratios for various samples of evolved stars. Models for solar composition AGB stars of different initial masses are compared to the results. We find that the majority of the M stars had main sequence masses <1.5 solar mass and have not experienced the third dredge up. The progenitors of the S and C Miras in the sample were more massive but no stars in the sample show evidence of hot bottom burning.

  16. Analysis of isotope and organic carbon signatures in hillslope hydrographs

    NASA Astrophysics Data System (ADS)

    Dusek, Jaromir; Vogel, Tomas; Dohnal, Michal; Jankovec, Jakub; Sanda, Martin; Votrubova, Jana

    2015-04-01

    Headwater catchments are among the most important areas for investigation of isotope and carbon fluxes because their small sizes best enable separation of above- and below ground compartments for improved understanding of the respective transport mechanisms. So far, only few studies utilized stable isotope information in modeling and even fewer linked dissolved carbon fluxes to mixing or transport models. Stable isotopes of water and dissolved organic carbon provide basis for studying transport processes ranging from soil profile scale to hillslope and catchment scale. In this study, stormflow dynamics of oxygen-18 and dissolved organic carbon was analyzed using a physically based modeling approach. One-dimensional dual-continuum vertical flow and transport model, based on Richards and advection-dispersion equations, was used to simulate the subsurface processes during significant rainfall-runoff episodes of a summer season. Water flow and transport of solutes were assumed to take place in two mutually communicating continua, the soil matrix and the network of preferential pathways. Oxygen-18 and dissolved organic carbon were observed in soil water, stormflow discharge in the experimental hillslope trench, and stream discharge at the catchment outlet. In the present study, we analyzed the transformation of input solute signals into signatures observed in the stormflow discharge. The research was supported by the Czech Science Foundation Project No. 14-15201J.

  17. How much do carbon isotope measurements constrain glacial ocean circulation?

    NASA Astrophysics Data System (ADS)

    Schmittner, A.; Mix, A. C.

    2010-12-01

    Reconstructions of the isotopic composition of dissolved inorganic carbon in seawater (d13DIC) are often interpreted as a ventilation or circulation proxy in paleoceanography. The modern deep-sea distribution of d13C in dissolved inorganic carbon (d13DIC) is highly anti-correlated to macronutrient (PO4, NO3) and apparent oxygen utilization (AOU) patterns due to fractionation during photosynthetic carbon uptake by phytoplankton. Nutrient and AOU concentrations in freshly ventilated North Atlantic Deep Water, for example, are low (d13DIC is high), whereas older water masses contain more respired nutrients and (isotopically light) carbon and have high AOU. However, d13DIC is also influenced by fractionation during air sea gas exchange - a process that decouples d13DIC from changes in nutrients and AOU. Moreover, biological fractionation is not constant but spatially and temporally variable. Here we are using a new global three-dimensional model of stable carbon isotope cycling that includes variable biological and air-sea gas exchange fractionation effects in conjunction with modern and glacial d13C observations to reconstruct ocean circulation patterns. Model versions with different rates and patterns of ocean circulation are produced and the resulting d13C patterns are compared to a compilation of measurements from ocean sediment cores in a probabilistic approach. The method allows us to quantify the uncertainty of deep ocean mass fluxes given available d13C observations/reconstructions and provide a quantitative test of the assumption of d13C as a ventilation proxy.

  18. The isotope geochemistry of carbon in groundwater at Stripa

    SciTech Connect

    Fritz, P.; Frape, S.K. ); Fontes, J.Ch.; Louvat, D.; Michelot, J.L. ); Balderer, W. )

    1989-08-01

    The carbon isotopic composition of the total dissolved inorganic carbon in groundwater associated with a granitic pluton at Stripa (Sweden) reflects both inorganic and organic carbon sources. Following the uptake of soil carbon-dioxide, calcite dissolution dominates the geochemical evolution of shallow groundwater. Calcite saturation is reached at a depth of about 100 m. In deeper waters geochemical release of Ca and increasing pH cause calcite precipitation. Radiocarbon contents suggest carbon (and water ) ages in excess of 20,000 years for waters 300-400 m depth. In deep ground waters with enhanced salinities organic carbon is added to the dissolved inorganic carbon either through bacterial activity (e.g. sulfate reducing bacteria) or the oxidation of organic compounds such as methane. The lowest radiocarbon contents were measured at the 300-400 meter levels and not in the deepest fluids. The distribution of {sup 13}C in the deep ground waters suggests the existence of well-defined flow systems with limited active hydraulic interaction. Isotope analyses on fracture calcites substantiate the complex geochemical history of the pluton.

  19. Sources of carbon isotope variation in kangaroo bone collagen and tooth enamel

    NASA Astrophysics Data System (ADS)

    Murphy, Brett P.; Bowman, David M. J. S.; Gagan, Michael K.

    2007-08-01

    The stable carbon isotopic composition (expressed as ? 13C) of herbivore remains is commonly used to reconstruct past changes in the relative abundance of C 4 versus C 3 grass biomass (C 4 relative abundance). However, the strength of the relationship between herbivore ? 13C and C 4 relative abundance in extant ecosystems has not been thoroughly examined. We determined sources of variation in ? 13C of bone collagen and tooth enamel of kangaroos ( Macropus spp.) collected throughout Australia by measuring ? 13C of bone collagen (779 individuals) and tooth enamel (694 individuals). An index of seasonal water availability, i.e. the distribution of rainfall in the C 4 versus C 3 growing seasons, was used as a proxy for C 4 relative abundance, and this variable explained a large proportion of the variation in both collagen ? 13C (68%) and enamel ? 13C (68%). These figures increased to 78% and 77%, respectively, when differences between kangaroo species were accounted for. Vegetation characteristics, such as woodiness and the presence of an open forest canopy, had no effect on collagen or enamel ? 13C. While there was no relationship between collagen ? 13C and kangaroo age at death, tooth enamel produced later in life, following weaning, was enriched in 13C by 3.5‰ relative to enamel produced prior to weaning. From the observed relationships between seasonal water availability and collagen and enamel ? 13C, enrichment factors ( ??) for collagen-diet and enamel-diet (post-weaning) were estimated to be 5.2‰ ± 0.5 (95% CI) and 11.7‰ ± 0.6 (95% CI), respectively. The findings of this study confirm that at a continental scale, collagen and enamel ? 13C of a group of large herbivores closely reflect C 4 relative abundance. This validates a fundamental assumption underpinning the use of isotopic analysis of herbivore remains to reconstruct changes in C 4 relative abundance.

  20. Major and trace element abundances, and Sr and Nd isotopic composition of Carbonatites from Amba Dongar, Gujarat, India

    NASA Astrophysics Data System (ADS)

    Chandra, Jyoti; Paul, Debajyoti; Viladkar, Shrinivas G.; Sensarma, Sarajit

    2015-04-01

    Despite significant progress during the last decade, the petrogenesis of carbonatites is still highly debated regarding the exact mechanism of carbonatite magma generation (fractional crystallization of carbonated-silicate magmas, liquid immiscibility of carbonated-silicate magmas, partial melting of carbonated mantle peridotite or carbonated lherzolitic mantle) and its evolution. The Amba Dongar carbonatite complex in Chhota Udaipur district, Gujarat is the youngest Indian carbonatite complex, which intruded into the ~ 90 Ma Bagh sandstones and limestone and 68-65 Ma Deccan flood basalts. The emplacement age (40Ar/39Ar age of 65±0.3 Ma; Ray and Pande, 1999) coincides with the age of main pulse of Deccan flood basalts at ca. 65 Ma. We report new geochemical data (major oxide and trace element abundances, and Sr and Nd isotopic ratios) on 23 carbonatite samples from Amba Dongar. The Amba Dongar carbonatite complex consists of carbonatite (sövite, and ankerite), and associated nephelinite, phonolite, and both pre- and post-carbonatite basalts. Detailed minerology of carbonatite include dominant calcite along with pyrochlore, apatite, magnetite, aegirine-augite and accessory phases. Apatite crystals are observed in carbonatite as well as in nephelinite. In sövites, apatite occur in various forms including cumulus, clusters and scattered within and along the boundary of calcite crystals. Two generation of apatite crystals are commonly observed in sövite and nephelinite; textural changes suggest presence of different five pulses of sövitic magma during the emplacement of the sövite ring dike. Bulk major oxides and trace element (including REEs) compositions of carbonatites and associated silicate rocks are determined by WD-XRF and ICP-MS, respectively. Major oxides abundances are consistent with the already available data on the Amba Dongar carbonatite complex. Trace element concentrations for the sövite reveals high concentrations of Sr (929-7476 ppm), Ba (344-52072 ppm) and Nb (35-2115 ppm). The ankeritic carbonatites are extremely enriched in the incompatible trace elements (e.g., ~7-32 times higher Ba, highest REE ~40,000 ppm and ~600 ppm of Th). Chondrite-normalized REE patterns show high degree of LREE enrichment suggesting low-degree partial melting of the source. The chondrite normalized La/Yb ratio of sövite and ankeritic carbonatite vary in the range 70-411. The radiogenic Sr-Nd isotopic composition of sövites (87Sr/86Sr: 0.7055-0.7066; É?Nd: -6.0 to -2.2) and ankerites (0.7058-0.7081; -3.8 to -1.9) reveal more isotopic variability compared to the available data (sövites 0.7054-0.706; -2.5 to -1.5; ankerites 0.7056-0.7065; -2.5 to -1.5). It is likely that EM I and II type sources are involved in the generation of Amba Dongar carbonatite complex. More data on carbonatites and associated silicate rocks will be helpful to establish the composition of parental carbonatite melts, depth of generation (lithosphere vs asthenosphere), their spatial relation with associated silicate rocks, and the evolution of the primary carbonatite melt over time.

  1. Isotopic Hg in an Allende carbon-rich residue

    NASA Technical Reports Server (NTRS)

    Reed, G. W., Jr.; Jovanovic, S.

    1990-01-01

    A carbon-rich residue from Allende subjected to stepwise heating yielded two isotopically resolvable types of Hg: one with an (Hg-196)/(Hg-202) concentration ratio the same as terrestrial (monitor) Hg; the other enriched in Hg-196 relative to Hg-202 by about 60 percent. Hg with the 202 isotope enriched relative to 196, as is found in bulk Allende, was not observed. Whether the result of mass fractionation or nucleosynthesis, the distinct types of Hg entered different carrier phases and were not thermally mobilized since the accretion of the Allende parent body.

  2. USE OF FATTY ACID STABLE CARBON ISOTOPE RATIO TO INDICATE MICROBIAL CARBON SOURCE IN TROPICAL SOILS

    EPA Science Inventory


    We use measurements of the concentration and stable carbon isotope ratio of individual microbial phospholipid fatty acids (PLFAs) in soils as indicators of live microbial biomass levels, broad microbial community structure, and microbial carbon source. For studies of soil o...

  3. Carbon and hydrogen isotope fractionation by microbial methane oxidation: Improved determination

    SciTech Connect

    Mahieu, Koenraad . E-mail: Koenraad.Mahieu@Ugent.be; Visscher, Alex De; Vanrolleghem, Peter A.; Cleemput, Oswald Van

    2006-07-01

    Isotope fractionation is a promising tool for quantifying methane oxidation in landfill cover soils. For good quantification an accurate determination of the isotope fractionation factor ({alpha}) of methane oxidation based on independent batch experiments with soil samples from the landfill cover is required. Most studies so far used data analysis methods based on approximations of the Rayleigh model to determine {alpha}. In this study, the two most common approximations were tested, the simplified Rayleigh approach and the Coleman method. To do this, the original model of Rayleigh was described in measurable variables, methane concentration and isotopic abundances, and fitted to batch oxidation data by means of a weighted non-linear errors-in-variables regression technique. The results of this technique were used as a benchmark to which the results of the two conventional approximations were compared. Three types of batch data were used: simulated data, data obtained from the literature, and data obtained from new batch experiments conducted in our laboratory. The Coleman approximation was shown to be acceptable but not recommended for carbon fractionation (error on {alpha} - 1 up to 5%) and unacceptable for hydrogen fractionation (error up to 20%). The difference between the simplified Rayleigh approach and the exact Rayleigh model is much smaller for both carbon and hydrogen fractionation (error on {alpha} - 1 < 0.05%). There is also a small difference when errors in both variables (methane concentration and isotope abundance) are accounted for instead of assuming an error-free independent variable. By means of theoretical calculations general criteria, not limited to methane, {sup 13}C, or D, were developed for the validity of the simplified Rayleigh approach when using labelled compounds.

  4. Abundance and isotopic composition of noble gases in metal and graphite of the Bohumilitz IAB iron meteorite

    NASA Astrophysics Data System (ADS)

    Maruoka, Teruyuki; Matsuda, Jun-Ichi; Kurat, Gero

    2001-05-01

    Abundances and isotopic compositions of noble gases in metal and graphite of the Bohumilitz IAB iron meteorite were measured. The abundance ratios of spallogenic components in metal reveal a 3He deficiency which is due to the diffusive loss of parent isotopes, i.e., tritium (Tilles, 1963; Schultz, 1967). The diffusive loss likely has been induced by thermal heating by the Sun during cosmic ray exposure (( 160 My; Lavielle et al., 1999). Thermal process such as impact-induced partial loss may have affected the isotopic composition of spallogenic Ne. The 129Xe/131Xe ratio of cosmogenic components in the metal indicates an enhanced production of epi-thermal neutrons. The abundance ratios of spallogenic components in the graphite reveal that it contained small amounts of metal and silicates. The isotopic composition of heavy noble gases in graphite itself was obtained from graphite treated with HF/HCl. The isotopic composition of the etched graphite shows that it contains two types of primordial Xe, i.e., Q-Xe and El Taco Xe. The isotopic heterogeneity preserved in the Bohumilitz graphite indicates that the Bohumilitz graphite did not experience any high(temperature event and, consequently, must have been emplaced into the metal at subsolidus temperatures. This situation is incompatible with an igneous model as well as the impact melting models for the IAB-IIICD iron meteorites as proposed by Choi et al. (1995) and Wasson et al. (1980).

  5. Triple oxygen isotopes in biogenic and sedimentary carbonates

    NASA Astrophysics Data System (ADS)

    Passey, Benjamin H.; Hu, Huanting; Ji, Haoyuan; Montanari, Shaena; Li, Shuning; Henkes, Gregory A.; Levin, Naomi E.

    2014-09-01

    The 17O anomaly (?17O) of natural waters has been shown to be sensitive to evaporation in a way analogous to deuterium excess, with evaporated bodies of water (e.g., leaf waters, lake waters, animal body waters) tending to have lower ?17O than primary meteoric waters. In animal body water, ?17O relates to the intake of evaporated waters, evaporative effluxes of water, and the ?17O value of atmospheric O2, which itself carries signatures of global carbon cycling and photochemical reactions in the stratosphere. Carbonates have the potential to record the triple oxygen isotope compositions of parent waters, allowing reconstruction of past water compositions, but such investigations have awaited development of methods for high-precision measurement of ?17O of carbonate. We describe optimized methods based on a sequential acid digestion/reduction/fluorination approach that yield ?17O data with the high precision (?0.010‰, 1?) needed to resolve subtle environmental signals. We report the first high-precision ?17O dataset for terrestrial carbonates, focusing on vertebrate biogenic carbonates and soil carbonates, but also including marine invertebrates and high-temperature carbonates. We determine apparent three-isotope fractionation factors between the O2 analyte derived from carbonate and the parent waters of the carbonate. These in combination with appropriate temperature estimates (from clumped isotope thermometry, or known or estimated body temperatures) are used to calculate the ?18O and ?17O of parent waters. The clearest pattern to emerge is the strong 17O-depletion in avian, dinosaurian, and mammalian body water (from analyses of eggshell and tooth enamel) relative to meteoric waters, following expected influences of evaporated water (e.g., leaf water) and atmospheric O2 on vertebrate body water. Parent waters of the soil carbonates studied here have ?17O values that are similar to or slightly lower than global precipitation. Our results suggest that ?17O will have useful application to paleoenvironmental studies of continental environments where the effects of evaporation are important, and where vertebrate body water may record an isotopic signal of evaporated water sources and atmospheric oxygen.

  6. Carbon isotope fractionation during experimental crystallisation of diamond from carbonate fluid at mantle conditions

    NASA Astrophysics Data System (ADS)

    Reutsky, Vadim; Borzdov, Yuri; Palyanov, Yuri; Sokol, Alexander; Izokh, Olga

    2015-12-01

    We report first results of a systematic study of carbon isotope fractionation in a carbonate fluid system under mantle PT conditions. The system models a diamond-forming alkaline carbonate fluid using pure sodium oxalate (Na2C2O4) as the starting material, which decomposes to carbonate, CO2 and elementary carbon (graphite and diamond) involving a single source of carbon following the reaction 2Na2C2O4 ? 2Na2CO3 + CO2 + C. Near-liquidus behaviour of carbonate was observed at 1300 °C and 6.3 GPa. The experimentally determined isotope fractionation between the components of the system in the temperature range from 1300 to 1700 °C at 6.3 and 7.5 GPa fit the theoretical expectations well. Carbon isotope fractionation associated with diamond crystallisation from the carbonate fluid at 7.5 GPa decreases with an increase in temperature from 2.7 to 1.6 ‰. This trend corresponds to the function ?Carbonate fluid-Diamond = 7.38 × 106 T-2.

  7. Clumped isotope thermometry of modern and early Cretaceous molluscan carbonate from high-latitude seas (Invited)

    NASA Astrophysics Data System (ADS)

    Henkes, G. A.; Price, G. D.; Ambrose, W. G.; Carroll, M. L.; Passey, B. H.

    2010-12-01

    The carbonate clumped isotope thermometer is based on the temperature sensitivity of the relative abundance of carbonate ion groups containing 13C-18O bonds. One application of clumped isotope thermometry is to determine the temperature of ancient seawater from the skeletal material of calcium carbonate-secreting marine organisms. The relationship between ?47, a parameter describing isotopic clumping, and the temperature of carbonate biomineralization has been well-defined for fish otoliths, corals, foraminifera, and coccolithophore tests, but few data have been published for brachiopods and bivalve mollusks. A comprehensive evaluation of the ?47-temperature relationship for mollusks is required for paleotemperature interpretations from the marine fossil record. Here we present a more comprehensive calibration for modern mollusks, including bivalves, cephalopods, and gastropods. Further, we focus on a subset of cold water, high-latitude species collected in the northern Barents Sea. The observed ?47-temperature relationship is similar to the theoretical relationship presented by Guo et al. (2009) but deviates at low temperatures from the original Ghosh et al. (2007) calibration curve. This divergence could be related to methodological differences or unaccounted differences in the biomineralization of mollusks versus that of other carbonate-secreting organisms at low temperature. One advantage of clumped isotope thermometry over traditional oxygen isotope thermometry is that it does not require assumptions about the isotopic composition of the water in which the carbonate formed. This may be particularly useful in Mesozoic paleoceanography where the oxygen isotope value of seawater is uncertain. Using clumped isotope thermometry applied to early Cretaceous (Valangian) belemnite carbonate from the Yatria River, sub-polar Urals, Siberia, we find shell growth temperatures of 20-26°C at a paleolatitude of ~60-65°N. Our data imply average seawater ?18O values of 0.5-1.5‰ when used in conjunction with published temperature-?18Ocarb-?18Osw calibrations. This ?18O range is higher than is traditionally assumed for high-latitude Cretaceous seawater. We argue, however, that such values are plausible and may be related to different basin- or global-scale hydrologies or belemnite body fluid that was in isotopic disequilibrium with the seawater. The paired ?47 and ?18O from the fossils rule out isotopic exchange with high temperature fluids or later diagenesis in 18O-depleted meteoric waters. We observe no textual or chemical evidence of recrystallization, and we hypothesize that these shells faithfully record early Cretaceous high-latitude seawater temperatures. The inferred temperature range of 20-26°C is substantially higher than 60-70°N modern mean annual sea surface temperature (˜-1.0 to 10.0°C) and mean summer surface temperatures (˜-0.5 to 14.5°C), implying a substantially shallower latitudinal temperature gradient during the early Cretaceous.

  8. Titan Aerosol Formation as a Sink for Stable Carbon and Nitrogen Isotopes

    NASA Astrophysics Data System (ADS)

    Trainer, Melissa G.; Stern, Jennifer C.; Sebree, Joshua A.; Gautier, Thomas J.; Fuentes, Javier A.; Domagal-Goldman, Shawn D.; Mandt, Kathleen E.

    2015-11-01

    Stable isotope ratios of major elements can be used to infer much about local- and global-scale processes on a planet. On Titan, aerosol production is a significant sink of carbon and nitrogen in the atmosphere, and isotopic fractionation of these elements may be introduced during the advanced organic chemistry that leads to the condensed phase products. Several stable isotope pairs, including 12C/13C and 14N/15N, have been measured in situ or probed spectroscopically by Cassini-borne instruments, space telescopes, or through ground-based observations. However, the effect of a potentially critical pathway for isotopic fractionation – organic aerosol formation and subsequent deposition onto the surface of Titan – has not been considered due to insufficient data regarding fractionation during aerosol formation. To better understand the nature of this process, we have measured the isotopic fractionation associated with the formation of Titan aerosol analogs via far-UV irradiation of several methane (CH4) and nitrogen (N2) mixtures.Our initial results probed the fractionation of the aerosol product, relative to the reactant gases, as a function of CH4 abundance [1]. Our results show that the direction of carbon isotope fractionation during aerosol formation is in contrast to the expected result if the source of the fractionation is a kinetic isotope effect. The resultant fractionation in nitrogen favored the light (14N) isotope in the aerosol, with N/C ratios varying from 0.13 – 0.31. Ongoing work includes probing the effects of pressure and temperature on the direction and magnitude of the stable isotope fractionation. We will present results alongside interpretation of the driving processes, as well as implications for Titan if similar fractionation occurred during aerosol formation in the atmosphere.[1] Sebree, J.A., Stern, J.C., Mandt, K.E., Domagal-Goldman, S.D., and Trainer, M.G.: 13C and 15N Fractionation of CH4/N2 Mixtures during Photochemical Aerosol Formation: Relevance to Titan, Icarus, in press, 2015, doi:10.1016/j.icarus.2015.04.016.

  9. STABLE CARBON ISOTOPE ANALYSIS OF SUBFOSSIL WOOD FROM AUSTRIAN ALPS

    PubMed Central

    K?USEK, MARZENA; PAWE?CZYK, S?AWOMIRA

    2015-01-01

    The presented studies were carried out in order to check the usefulness of subfossil wood for stable isotope analysis. The aim of research was also to define the optimal method of subfossil samples preparation. Subfossil samples used during the presented studies are a part of the multi-century dendrochronological scale. This chronology originates in an area situated around a small mountain lake — Schwarzersee, in Austria. The obtained results of stable carbon isotope measurements confirmed that the method of ?-cellulose extraction by the application of acidic sodium chlorite and sodium hydroxide solutions removes resins and other mobile compounds from wood. Therefore, in the case of the analysed samples, the additional chemical process of extractives removing was found to be unnecessary. Studied wood samples contained an adequate proportion of ?-cellulose similar to the values characteristic for the contemporary trees. This proved an adequate wood preservation which is essential for the conduction of isotopic research. PMID:26346297

  10. Contrasting the CO2-He Isotope and Relative Abundance Systematics of the Central American and IBM Arcs

    NASA Astrophysics Data System (ADS)

    Hilton, D. R.; Fischer, T. P.; Shaw, A. M.; Hauri, E.; Walker, J.

    2006-12-01

    We report CO2 and He isotope and relative abundance data obtained utilizing high-T fumaroles, geothermal wells, boiling mud pots, hot springs and phenocryst-bearing lavas from both MARGINS-targeted regions. In Central America, we collected ~140 fluid and ~30 lava samples covering a total of 41 volcanic centers in Costa Rica (7), Nicaragua (8), El Salvador (10), Honduras (9) and Guatemala (7). Along the IBM arc, we sampled the islands of Uracas, Agrigan, Pagan and Alamagan in the CNMI and Oshima, Niijima, Shikinajima, Hachijojima and Aogashima in the Izu islands. Helium isotope ratios (3He/4He) reach a maximum of 8RA (where RA = air 3He/4He) with most values > 5 RA. The majority of samples have CO2/3He ratios between 1010 and 1011, as at other arcs. The ?13C of the CO2 for the majority of samples fall between -5 and 0 ‰ (PDB) consistent with a major slab input to the carbon inventory. The entire database has been assessed to identify samples unmodified by localised crustal processes (~75% of total), thereby defining the He and C systematics of the underlying mantle source. At both arcs, we utilize along-strike He-C variations to consider the relative influence of various subduction zone forcing functions on the output C-flux. We show that subducted sediment lithology, particularly down-hole C distribution and the nature (oxidized/reduced) of the C, is a major control on the output as opposed to other factors such as angle of slab dip, convergence rate, and thickness of overlying arc crust.

  11. Carbon isotope fractionation of methyl bromide during agricultural soil fumigations

    USGS Publications Warehouse

    Bill, M.; Miller, L.G.; Goldstein, Allen H.

    2002-01-01

    The isotopic composition of methyl bromide (CH3Br) has been suggested to be a potentially useful tracer for constraining the global CH3Br budget. In order to determine the carbon isotopic composition of CH3Br emitted from the most significant anthropogenic application (pre-plant fumigation) we directly measured the ??13C of CH3Br released during commercial fumigation. We also measured the isotopic fractionation associated with degradation in agricultural soil under typical field fumigation conditions. The isotopic composition of CH3Br collected in soil several hours after injection of the fumigant was -44.5??? and this value increased to -20.7??? over the following three days. The mean kinetic isotope effect (KIE) associated with degradation of CH3Br in agricultural soil (12???) was smaller than the reported value for methylotrophic bacterial strain IMB-1, isolated from previously fumigated agricultural soil, but was similar to methylotrophic bacterial strain CC495, isolated from a pristine forest litter zone. Using this fractionation associated with the degradation of CH3Br in agricultural soil and the mean ??13C of the industrially manufactured CH3Br (-54.4???), we calculate that the agricultural soil fumigation source has a carbon isotope signature that ranges from -52.8??? to -42.0???. Roughly 65% of industrially manufactured CH3Br is used for field fumigations. The remaining 35% is used for structural and post-harvest fumigations with a minor amount used during industrial chemical manufacturing. Assuming that the structural and post-harvest fumigation sources of CH3Br are emitted without substantial fractionation, we calculate that the ??13C of anthropogenically emitted CH3Br ranges from -53.2??? to -47.5???.

  12. Towards a better understanding of magnesium-isotope ratios from marine skeletal carbonates

    E-print Network

    Paytan, Adina

    Towards a better understanding of magnesium-isotope ratios from marine skeletal carbonates Dorothee 3 August 2009 Abstract This study presents magnesium stable-isotope compositions of various biogenic) on magnesium-isotopic (d26 Mg) ratios of skeletal carbonates. Using high-precision multi- collector inductively

  13. Carbonate clumped isotope compositions of modern marine mollusk and brachiopod shells

    E-print Network

    Grossman, Ethan L.

    Carbonate clumped isotope compositions of modern marine mollusk and brachiopod shells Gregory A online 3 January 2013 Abstract We present an empirical calibration of the carbonate clumped isotope temperatures of À1.0 to 29.5 °C. The clumped isotope data (D47) are normalized to CO2 gases with equilibrium

  14. Associations between carbon isotope ratios of ecosystem respiration, water availability and canopy conductance

    E-print Network

    Ehleringer, Jim

    regulation of carbon isotope discrimination (D). Soil water content (SWC) and vapor pressure deficit (vpdAssociations between carbon isotope ratios of ecosystem respiration, water availability and canopy Division, Los Alamos National Laboratory, MS-D462 Los Alamos, NM 87545, USA, wStable Isotope Ratio Facility

  15. From isotope labeled CH3CN to N2 inside single-walled carbon nanotubes

    E-print Network

    Maruyama, Shigeo

    From isotope labeled CH3CN to N2 inside single-walled carbon nanotubes Christian Kramberger to this peculiar place? We have used N15 and C13 isotope labeled acetonitrile during the synthesis of single-walled carbon nanotubes to investigate this process. The isotope shifts of phonons and vibrons are observed

  16. Large carbon isotope fractionation associated with oxidation of methyl halides by

    E-print Network

    Goldstein, Allen

    Large carbon isotope fractionation associated with oxidation of methyl halides by methylotrophic isotopes observed in nature occur during production of methane by metha- nogenic archaea report that a stable carbon isotopic fractionation of compa- rable magnitude (up to 70) occurs during

  17. Isotope-induced elastic scattering of optical phonons in individual suspended single-walled carbon nanotubes

    E-print Network

    Maruyama, Shigeo

    Isotope-induced elastic scattering of optical phonons in individual suspended single-walled carbon 10, 2011) Isotope-induced scattering of optical phonons in individual single-walled carbon nanotubes (SWNTs) was investigated by resonance Raman scattering measurements of more than 600 sus- pended, isotope

  18. Variable carbon isotope fractionation expressed by aerobic CH4-oxidizing bacteria

    E-print Network

    Chu, Kung-Hui "Bella"

    Variable carbon isotope fractionation expressed by aerobic CH4-oxidizing bacteria Alexis S Engineering, Texas A&M University, College Station, TX 77843-3136, USA d Center for Isotope Geochemistry 2005; accepted in revised form 5 December 2005 Abstract Carbon isotope fractionation factors reported

  19. Kinetic isotope effects during carbonate mineral formation Z. Sade*, R. Yam, A. Shemesh and I. Halevy

    E-print Network

    Einat, Aharonov

    Kinetic isotope effects during carbonate mineral formation Z. Sade*, R. Yam, A. Shemesh and I. Halevy Weizmann Institute of Science, Rehovot 76100, Israel *ziv.sade@weizmann.ac.il The oxygen isotopic ambient water to determine the temperature at which the carbonates formed and the oxygen isotope

  20. Carbon and Nitrogen Isotope Variation in Peat Bogs in the Midwestern US: Implications for Holocene Climate Reconstruction

    NASA Astrophysics Data System (ADS)

    Wong, D.; Paytan, A.; Jackson, S.

    2008-12-01

    A peat core, from near the center of Minden Bog in Michigan, representing about 3500 years of accumulation was previously analyzed for plant macrofossils, colorimetric humification, and testate amoebae to yield three independent climate proxies (Booth and Jackson, 2003). The plant macrofossil data show the site to be sensitive to bog water table fluctuations. The data suggest that this may be related to regional climatic changes. We analyzed the carbon and nitrogen isotopes, as well as the carbon-nitrogen ratios in the bulk peat samples to determine if fluctuations of these records correspond to climate events as seen in the plant microfossil and amoebae records. The degree to which peat-based carbon and nitrogen isotope records reflect changes in the relative distribution of vegetation and, in turn, reflect temperature changes in effective precipitation (precipitation minus evapotranspiration) will be assessed. Peat carbon and nitrogen isotope records will be compared with existing proxy climate records and with a temperature reconstruction based on testate amoebae in bogs. We expect that climate-related changes, in the relative abundance of vegetation remains accumulating in the peat bogs, will be recorded in the organic matter in forms of carbon and nitrogen isotopes.

  1. Carbon and nitrogen isotope studies in an arctic ecosystem. Final report

    SciTech Connect

    Schell, D.M.

    1994-06-01

    The dynamics of carbon fixation and storage in tundra soils has received considerable attention with respect to global carbon cycling. Recent findings by investigators using chamber measurements of fixation/respiration rates in arctic tundra have led to the conclusion that tundra is no longer storing carbon but is instead a source of carbon dioxide to the atmosphere. The author has sought to test these conclusions and to determine methods by which the long-term accumulation or loss of carbon in tundra can be determined. Little is known, however, of the processes that control storage and the current rates of carbon fixation and peat formation in arctic Alaska. This project focused on several aspects of carbon dynamics and the roles of decomposition and herbivory at the DOE research site at Imnavait Creek, Alaska. Through the use of natural abundance stable and radioisotope techniques, several conclusions emerged. Peat carbon continues to accumulate in wetter areas of foothill valleys and on the coastal plain of arctic Alaska. Radiocarbon profiles of bomb {sup 14}C were used to date layers of vegetation and litter to obtain decomposition rates and to extrapolate these values to intersection with the permafrost horizon where further decomposition is assumed to cease. Carbon storage in riparian moss at Imnavait Creek was estimated at 3 g C/m{sup 2}-yr. Profiles of {sup 137}Cs closely matched those of {sup 14}C and may provide a more expeditious means of assessing recent carbon accumulation rates in tundra. Carbon and nitrogen stable isotope ratios in tundra vegetation vary markedly over hydrologic gradients in apparent response to changing growth rates and sources of nitrogenous nutrients. Within a taxon, {delta}{sup 15}N values varied by several {per_thousand} over a tens of meters distance.

  2. Molecular carbon isotopic evidence for the origin of geothermal hydrocarbons

    USGS Publications Warehouse

    Des Marais, D.J.; Donchin, J.H.; Nehring, N.L.; Truesdell, A.H.

    1981-01-01

    Previous interest in light hydrocarbons from geothermal systems has focused principally on the origin of the methane1 and the estimation of subsurface temperatures from the carbon isotopic content of coexisting methane and carbon dioxide1-3. Higher molecular weight hydrocarbons were first reported in gases from Yellowstone National Park4, and have since been found to occur commonly in geothermal emanations in the western United States5. Isotopic measurements of individual geothermal hydrocarbons are now reported which help to explain the origin of these hydrocarbons. The thermal decomposition of sedimentary or groundwater organic matter is a principal source of hydrocarbons in four geothermal areas in western North America. ?? 1981 Nature Publishing Group.

  3. Descriptions of carbon isotopes within the energy density functional theory

    SciTech Connect

    Ismail, Atef; Cheong, Lee Yen; Yahya, Noorhana; Tammam, M.

    2014-10-24

    Within the energy density functional (EDF) theory, the structure properties of Carbon isotopes are systematically studied. The shell model calculations are done for both even-A and odd-A nuclei, to study the structure of rich-neutron Carbon isotopes. The EDF theory indicates the single-neutron halo structures in {sup 15}C, {sup 17}C and {sup 19}C, and the two-neutron halo structures in {sup 16}C and {sup 22}C nuclei. It is also found that close to the neutron drip-line, there exist amazing increase in the neutron radii and decrease on the binding energies BE, which are tightly related with the blocking effect and correspondingly the blocking effect plays a significant role in the shell model configurations.

  4. Isotope Effects on Heat Conduction of Carbon Nanotubes Shigeo Maruyama, Yuki Taniguchi and Yasushi Shibuta

    E-print Network

    Maruyama, Shigeo

    Isotope Effects on Heat Conduction of Carbon Nanotubes Shigeo Maruyama, Yuki Taniguchi and Yasushi that the inclusion of only 1 % of 13 C natural isotope dramatically reduces the thermal conductivity of diamond. However, isotope effects on heat conduction of SWNTs have not been elucidated. We estimated isotope

  5. Abstract.-Stable nitrogen (/ll5Nl and carbon (/ll3CI isotope measure-

    E-print Network

    540 Abstract.-Stable nitrogen (/ll5Nl and carbon (/ll3CI isotope measure- ments were used stable nitrogen isotope ratios. These were attributed to isotopic variations at the base of the food and the Gulfof Mexico Loop Current. Use of stable isotopes to assess groups of king mackerel, Scomberomorus caval

  6. A stable carbon isotope and biological marker study of Polish bituminous coals and carbonaceous shales

    USGS Publications Warehouse

    Kotarba, M.J.; Clayton, J.L.

    2003-01-01

    Biological marker and carbon isotopic compositions of coals and carbonaceous shales from the Upper Carboniferous strata of the Upper Silesian (USCB), Lower Silesian (LSCB), and Lublin (LCB) coal basins were determined to assess depositional conditions and sources of the organic matter. n-Alkane, sterane, and isoprenoid distribution, and carbon isotope ratios are consistent with an origin from higher plants. In some cases, pristane/phytane (Pr/Ph) ratios of carbonaceous shales (roof and floor shales) are < 1.0, while the associated coals have high ratios (??? 1.0). This suggests that reducing conditions prevailed during deposition of the shales, but a period of oxidizing conditions accompanied deposition of the coals. Steranes present in coal extracts are dominated by the 14??(H)17??(H)20R C29 stereoisomers, typical, but not conclusive, of higher plant origin. Carbonaceous shales exhibit a wider range of sterane composition, suggesting local, significant input of algal organic matter. Significant amounts of benzohopanes and gammacerane are present in some coals. Although benzohopanes are present at least in small amounts in samples from many different environments, they have been reported to occur most commonly in marine environments. The present study seems to provide the first example where benzohopanes have been reported in significant amounts in terrestrial organic matter. Gammacerane is abundant in rocks or sediments deposited in carbonate or highly saline marine environments. The finding of high gammacerane concentrations in the coals expands the depositional settings in which it has been observed and questions its utility as an independent indicator of hypersaline carbonate environments. Stable carbon isotope composition of coals, and type III kerogen in carbonaceous shales as well as correlation of stable carbon isotope composition of saturated and aromatic hydrocarbons in carbonaceous shales from both the USCB and the LSCB indicate terrigenous origin. Bitumens are always co-genetic with associated coals and kerogens. Isotopic data reveal that Sofer's genetic classification of oils is not applicable to organic matter in coals. ?? 2003 Elsevier B.V. All rights reserved.

  7. Carbon isotopes in xenoliths from the Hualalai Volcano, Hawaii, and the generation of isotopic variability

    SciTech Connect

    Pineau, F. ); Mathez, E.A. )

    1990-01-01

    The isotopic composition of carbon has been determined in a suite of xenoliths from lava of the 1800-1801 Kaupulehu eruption of Hualalai Volcano, Hawaii. Several lithologies are represented in the suite, including websterite, dunite, wehrlite, pyroxenite, and gabbro. In addition, there are composite xenoliths in which contacts between lithologies are preserved. Most of the xenoliths represent deformed cumulates. The contact relations in the composite samples indicate that the lithologies originated from the same source region, which, based on pressures determined from fluid inclusions, is estimated to be at a depth of {approx}20 km, or near the crust-mantle boundary. The observations and isotopic results demonstrate that isotopic variability can be generated by multistage fractionation processes such as degassing of CO{sub 2} from magma and precipitation of CO{sub 2}-rich fluids to form graphitic compounds. Such processes operated over regions the scales of which were determined by style and intensity of deformation and by lithology.

  8. ANALYSIS OF RICIN TOXIN PREPARATIONS FOR CARBOHYDRATE AND FATTY ACID ABUNDANCE AND ISOTOPE RATIO INFORMATION

    SciTech Connect

    Wunschel, David S.; Kreuzer-Martin, Helen W.; Antolick, Kathryn C.; Colburn, Heather A.; Moran, James J.; Melville, Angela M.

    2009-12-01

    This report describes method development and preliminary evaluation for analyzing castor samples for signatures of purifying ricin. Ricin purification from the source castor seeds is essentially a problem of protein purification using common biochemical methods. Indications of protein purification will likely manifest themselves as removal of the non-protein fractions of the seed. Two major, non-protein, types of biochemical constituents in the seed are the castor oil and various carbohydrates. The oil comprises roughly half the seed weight while the carbohydrate component comprises roughly half of the remaining “mash” left after oil and hull removal. Different castor oil and carbohydrate components can serve as indicators of specific toxin processing steps. Ricinoleic acid is a relatively unique fatty acid in nature and is the most abundant component of castor oil. The loss of ricinoleic acid indicates a step to remove oil from the seeds. The relative amounts of carbohydrates and carbohydrate-like compounds, including arabinose, xylose, myo-inositol fucose, rhamnose, glucosamine and mannose detected in the sample can also indicate specific processing steps. For instance, the differential loss of arabinose relative to mannose and N-acetyl glucosamine indicates enrichment for the protein fraction of the seed using protein precipitation. The methods developed in this project center on fatty acid and carbohydrate extraction from castor samples followed by derivatization to permit analysis by gas chromatography-mass spectrometry (GC-MS). Method descriptions herein include: the source and preparation of castor materials used for method evaluation, the equipment and description of procedure required for chemical derivatization, and the instrument parameters used in the analysis. Two types of derivatization methods describe analysis of carbohydrates and one procedure for analysis of fatty acids. Two types of GC-MS analysis is included in the method development, one employing a quadrupole MS system for compound identification and an isotope ratio MS for measuring the stable isotope ratios of deuterium and hydrogen (D/H) in fatty acids. Finally, the method for analyzing the compound abundance data is included. This study indicates that removal of ricinoleic acid is a conserved consequence of each processing step we tested. Furthermore, the stable isotope D/H ratio of ricinoleic acid distinguished between two of the three castor seed sources. Concentrations of arabinose, xylose, mannose, glucosamine and myo-inositol differentiated between crude or acetone extracted samples and samples produced by protein precipitation. Taken together these data illustrate the ability to distinguish between processes used to purify a ricin sample as well as potentially the source seeds.

  9. Maturation of Green River Shale Kerogen with Hydrous Pyrolysis: Characterization of Geochemical Biomarkers and Carbon Isotopes

    NASA Astrophysics Data System (ADS)

    Fu, Q.; Darnell, M.; Bissada, K. K.

    2014-12-01

    To fully understand controlling factors of organic compound generation during oil shale maturation, and systematically assess associated carbon isotope values, a series of hydrous pyrolysis experiments are performed. Kerogen was isolated from Green River shale by a set of acid treatment. Experiments are conducted at 350 °C and 300 bars of total pressure with running time of 24, 48 and 72 hours, respectively. In each experiment, the reactor contains 1.5 grams of kerogen and 30 grams of deionized water. After experiments, gaseous products are removed under cryogenic conditions for chemical and carbon isotope analyses (GC-IRMS). The bitumen product is retrieved and separated into saturated hydrocarbons, aromatics, resins, and asphaltenes (SARA) by HPLC before subsequent analyses (GC, GC-MS, and IRMS). The gaseous compounds from experiments consisted of CO2 and C1 to C4 hydrocarbons. Semiquantitative analysis indicates the yield of n-alkanes decreases with carbon number, with CO2 being more abundant than all alkanes. The ?13C value of alkanes increases with molecular weight, with CO2 having the highest value. Methane and ethane become enriched in 13C with time. In bitumen products, gravimetric analysis has shown that the abundance of aromatics increases with time, while that of asphaltenes decreases. After 72 hours, the weight percentages of saturated hydrocarbons, aromatics, resins and asphaltenes are 2.6, 42.3, 40.1, and 15.0, respectively. High resolution GC-MS results indicate low kerogen maturation after 72 hours using saturated biomarker compounds as thermal maturity indicator, such as 22S/(22S + 22R) of C31 to C35 homohopanes, tricyclics/17(H)-hopanes, and Ts/(Ts + Tm). Bulk carbon isotope value of bitumen decreases with time, with 2.5‰ lighter than original kerogen after 72 hours. In terms of different groups, saturated hydrocarbons and resins become depleted in 13C with longer reaction time, while aromatics and asphaltenes become enriched in 13C. Experiments with longer reaction time and under different physicochemical conditions are underway. That would facilitate a better understanding of oil and gas generation and carbon isotope systematics during kerogen maturation processes for effective conventional and unconventional exploration.

  10. The use of carbon stable isotope ratios in drugs characterization

    SciTech Connect

    Magdas, D. A. Cristea, G. Bot, A. Mirel, V.

    2013-11-13

    Isotopic Ratio Mass Spectrometry (IRMS) is an effective toll to be used for drug product authentication. The isotopic composition could be used to assist in the differentiation between batches of drugs and assist in the identification of counterfeit materials on the market. Only two factors affect the isotopic ratios in pharmaceutical components: the isotopic composition of the raw materials and the synthetic processes performed upon them. Counterfeiting of pharmaceutical drugs threatens consumer confidence in drug products companies' economical well-being. In this preliminary study, the analyzed samples consist in two types of commercially available analgesics, which were purchases from Romanian pharmacies. Differences in ?{sup 13}C between batches from ?29.7 to ?31.6% were observed, demonstrating that this method can be used to differentiate among individual drug batches and subsequently identify counterfeits on the market. On the other hand, carbon isotopic ratios differences among producers were recorded, the variations being between ?31.3 to ?34.9% for the same type of analgesic, but from different manufactures.

  11. The use of carbon stable isotope ratios in drugs characterization

    NASA Astrophysics Data System (ADS)

    Magdas, D. A.; Cristea, G.; Bot, A.; Mirel, V.

    2013-11-01

    Isotopic Ratio Mass Spectrometry (IRMS) is an effective toll to be used for drug product authentication. The isotopic composition could be used to assist in the differentiation between batches of drugs and assist in the identification of counterfeit materials on the market. Only two factors affect the isotopic ratios in pharmaceutical components: the isotopic composition of the raw materials and the synthetic processes performed upon them. Counterfeiting of pharmaceutical drugs threatens consumer confidence in drug products companies' economical well-being. In this preliminary study, the analyzed samples consist in two types of commercially available analgesics, which were purchases from Romanian pharmacies. Differences in ?13C between batches from -29.7 to -31.6% were observed, demonstrating that this method can be used to differentiate among individual drug batches and subsequently identify counterfeits on the market. On the other hand, carbon isotopic ratios differences among producers were recorded, the variations being between -31.3 to -34.9% for the same type of analgesic, but from different manufactures.

  12. Ratios of Carbon Isotopes in Microbial Lipids as an Indicator of Substrate Usage

    PubMed Central

    Abraham, Wolf-Rainer; Hesse, Christian; Pelz, Oliver

    1998-01-01

    The occurrence and abundance of microbial fatty acids have been used for the identification of microorganisms in microbial communities. However, these fatty acids can also be used as indicators of substrate usage. For this, a systematic investigation of the discrimination of the stable carbon isotopes by different microorganisms is necessary. We grew 11 strains representing major bacterial and fungal species with four different isotopically defined carbon sources and determined the isotope ratios of fatty acids of different lipid fractions. A comparison of the differences of ?13C values of palmitic acid (C16:0) with the ?13C values of the substrates revealed that the isotope ratio is independent of the growth stage and that most microorganisms showed enrichment of C16:0 with 13C when growing on glycerol. With the exception of Burkholderia gladioli, all microorganism showed depletion of 13C in C16:0 while incorporating the carbons of glucose, and most of them were enriched with 13C from mannose, with the exception of Pseudomonas fluorescens and the Zygomycotina. Usually, the glycolipid fractions are depleted in 13C compared to the phospholipid fractions. The ?13C pattern was not uniform within the different fatty acids of a given microbial species. Generally, tetradecanoic acid (C14:0) was depleted of 13C compared to palmitic acid (C16:0) while octadecanoic acid (C18:0) was enriched. These results are important for the calibration of a new method in which ?13C values of fatty acids from the environment delineate the use of bacterial substrates in an ecosystem. PMID:9797266

  13. Carbon Abundance Plateaus among Carbon-Enhanced Metal-Poor Stars

    NASA Astrophysics Data System (ADS)

    Yoon, Jinmi; He, Siyu; Placco, Vinicius; Carollo, Daniela; Beers, Timothy C.

    2016-01-01

    A substantial fraction of low-metallicity stars in the Milky Way, the Carbon-Enhanced Metal-Poor (CEMP) stars, exhibit enhancements of their carbon-to-iron relative to the solar value ([C/Fe] > +0.7). They can be divided into several sub-classes, depending on the nature and degree of the observed enhancements of their neutron-capture elements, providing information on their likely progenitors. CEMP-s stars (which exhibit enhanced s-process elements) are thought to be enhanced by mass transfer from an evolved AGB companion, while CEMP-no stars (which exhibit no over-abundances of neutron-capture elements) appear to be associated with explosions of the very first generations of stars. High-resolution spectroscopic analyses are generally required in order to make these sub-classifications.Several recent studies have suggested the existence of bimodality in the distribution of absolute carbon abundances among CEMP stars -- most CEMP-no stars belong to a low-C band ((A(C) ? 6.5), while most CEMP-s stars reside on a high-C band (A(C) ? 8.25). The number of CEMP stars considered by individual studies is, however, quite small, so we have compiled all available high-resolution spectroscopic data for CEMP stars, in order to further investigate the existence of the claimed carbon bi-modality, and to consider what can be learned about the progenitors of CEMP-s and CEMP-no stars based on the observed distribution of A(C) on the individual plateaus.We acknowledge partial support from the grant PHY 14-30152; Physics Frontier Center/JINA Center for the Evolution of the Elements (JINA-CEE), awarded by the US National Science Foundation.

  14. Stable carbon and nitrogen isotope enrichment in primate tissues

    PubMed Central

    Carter, Melinda L.; Karpanty, Sarah M.; Zihlman, Adrienne L.; Koch, Paul L.; Dominy, Nathaniel J.

    2010-01-01

    Isotopic studies of wild primates have used a wide range of tissues to infer diet and model the foraging ecologies of extinct species. The use of mismatched tissues for such comparisons can be problematic because differences in amino acid compositions can lead to small isotopic differences between tissues. Additionally, physiological and dietary differences among primate species could lead to variable offsets between apatite carbonate and collagen. To improve our understanding of the isotopic chemistry of primates, we explored the apparent enrichment (?*) between bone collagen and muscle, collagen and fur or hair keratin, muscle and keratin, and collagen and bone carbonate across the primate order. We found that the mean ?* values of proteinaceous tissues were small (?1‰), and uncorrelated with body size or phylogenetic relatedness. Additionally, ?* values did not vary by habitat, sex, age, or manner of death. The mean ?* value between bone carbonate and collagen (5.6 ± 1.2‰) was consistent with values reported for omnivorous mammals consuming monoisotopic diets. These primate-specific apparent enrichment values will be a valuable tool for cross-species comparisons. Additionally, they will facilitate dietary comparisons between living and fossil primates. Electronic supplementary material The online version of this article (doi:10.1007/s00442-010-1701-6) contains supplementary material, which is available to authorized users. PMID:20628886

  15. The Determination of the Natural Abundance of the Isotopes of Chlorine: An Introductory Experiment in Mass Spectrometry.

    ERIC Educational Resources Information Center

    O'Malley, Rebecca M.

    1982-01-01

    Describes a laboratory experiment which introduces basic principles and experimental techniques of mass spectrometry for fourth year undergraduate (B.Sc.) students. Laboratory procedures, background information, and discussion of results are provided for the experiment in which the natural isotopic abundance of chlorine is determined. (Author/JN)

  16. Oxygen isotope ratio measurements on carbon dioxide generated by reaction of microliter quantities of biological fluids with guanidine hydrochloride

    SciTech Connect

    Wong, W.W.; Lee, L.S.; Klein, P.D.

    1987-03-01

    Guanidine hydrochloride was used to convert water in biological fluids to carbon dioxide for oxygen isotope ratio measurements. Five 10-..mu..L aliquots each of five different saliva, urine, plasma, and human milk samples were allowed to react with 100 mg of guanidine hydrochloride at 260/sup 0/C to produce ammonia and carbon dioxide. Ammonia was removed with 100% phosphoric acid and carbon dioxide was cryogenically purified before isotope ratio measurement. At natural abundances, the delta/sup 18/O values of the biological fluids were reproducible to within 0.16% (standard deviation) and accurate to within 0.11 +/- 0.73% (x vector +/- SD) of the H/sub 2/O-CO/sub 2/ equilibration values. At a 250% enrichment level of /sup 18/O, the delta/sup 18/O values of the biological fluids were reproducible to within 0.95% and accurate to -1.27 +/- 2.25%.

  17. Carbonate concretions as a significant component of ancient marine carbon cycles: Insights from paired organic and inorganic carbon isotope analyses of a Cretaceous shale

    NASA Astrophysics Data System (ADS)

    Loyd, S. J.

    2014-12-01

    Carbonate concretions often occur within fine-grained, organic-rich sedimentary rocks. This association reflects the common production of diagenetic minerals through biologic cycling of organic matter. Chemical analysis of carbonate concretions provides the rare opportunity to explore ancient shallow diagenetic environments, which are inherently transient due to progressive burial but are an integral component of the marine carbon cycle. The late Cretaceous Holz Shale (~80 Ma) contains abundant calcite concretions that exhibit textural and geochemical characteristics indicative of relatively shallow formation (i.e., near the sediment-water interface). Sampled concretions contain between 5.4 and 9.8 wt.% total inorganic carbon (TIC), or ~45 and 82 wt.% CaCO3, compared to host shale values which average ~1.5 wt.% TIC. Organic carbon isotope compositions (?13Corg) are relatively constant in host and concretion samples ranging from ­-26.3 to -24.0‰ (VPDB). Carbonate carbon isotope compositions (?13Ccarb) range from -22.5 to -3.4‰, indicating a significant but not entirely organic source of carbon. Concretions of the lower Holz Shale exhibit considerably elevated ?13Ccarb values averaging -4.8‰, whereas upper Holz Shale concretions express an average ?13Ccarb value of -17.0‰. If the remaining carbonate for lower Holz Shale concretions is sourced from marine fluids and/or dissolved marine carbonate minerals (e.g., shells), a simple mass balance indicates that ~28% of concretion carbon was sourced from organic matter and ~72% from late Cretaceous marine inorganic carbon (with ?13C ~ +2.5‰). Upper Holz Shale calculations indicate a ~73% contribution from organic matter and a ~27% contribution from inorganic carbon. When normalized for carbonate, organic contents within the concretions are ~2-13 wt.% enriched compared to host contents. This potentially reflects the protective nature of cementation that acts to limit permeability and chemical destruction of organic material. These data imply that concretion growth in shallow sediments can act as a significant and long-term sink for both marine inorganic and organic carbon.

  18. Anomalous Oxygen Isotopic Fractionation in Vacuum Ultraviolet Photodissociation of Carbon Monoxide and Test of Self-Shielding: Relevance for Meteorite Oxygen Isotopes

    NASA Astrophysics Data System (ADS)

    Chakraborty, S.; Ahmed, M.; Jackson, T. L.; Thiemens, M. H.

    2008-12-01

    Oxygen is the predominant elemental constituent of rocky planets and asteroids. It is the third most abundant element in the solar system after hydrogen and helium. The isotopic compo-sition of oxygen in three-isotope space (?18O vs. ?17O plot) exhibits large heterogeneity among different bodies formed from the same primordial gas and dust mixture, termed the solar nebula. It is not possible to fully understand the formation and evolution of our own planetary system, unless we resolve the source of the oxygen isotopes. At present, there are two models: self shielding photochemistry in the solar nebula, and symmetry driven gas-phase and/or surface chemistry in the solar nebula, which can also involve photochemistry, but isn't required. Photochemistry is a dominant process at the outer layers of the nebular disk and isotopically selective photodissociation (a process known as isotopic self-shielding) of carbon monoxide, the most abundant nebular oxygen bearing molecule, has been suggested as a source of isotopically anomalous oxygen in the solar reservoir [1-3]. However, these models have had no experimental verification of the relevant isotopic fractionation associated with VUV-CO photodissociation at the relevant wavelengths. Recently, we have performed a series of CO photodissociation experiment with a windowless flow chamber at the Advanced Light Source (LBNL) synchrotron at Berkeley. These experiments demonstrate an anomalously enriched atomic oxygen reservoir is generated through CO photo-dissociation, but, without requiring isotopic self shielding [4]. These results emphasize the importance of chemistry in the solar nebula as we have previously demonstrated through recent laboratory experiments [5]. It is clear that the mass- independent oxygen isotopic composition, as observed in some of the first condensed solids in the solar system (Calcium-Aluminum rich Inclusions- CAIs, Chondrules etc.), can be generated through symmetry driven gas-phase chemical reactions. We will present new oxygen isotope data of VUV photodissociation of CO and discuss the relevance of this data to address the anomalous oxygen isotopic compositions of meteorites. References: [1] Clayton R. N. (2002) Nature, 415, 860-861. [2] Yurimoto H. and Kuramoto K. (2004) Science, 305, 1763-1766. [3] Lyons J. R. and Young E. D. and (2005) Nature, 435, 317-320. [4] Chakraborty S., Ahmed M., Jackson, T. L. and Thiemens M.H. (2008) Science, 321, 1328-1331. [5] Kimura Y., Nuth J. A., Chakraborty S., and Thiemens M. H. (2007) Meteoritics and Planetary Science, 42, 1429-1439.

  19. Coupling Organic Carbon and Nitrogen Isotope with Carbonate Carbon Isotope Excursion Across the Early Mississippian Kinderhookian-Osagean Boundary in Great Basin, Western USA

    NASA Astrophysics Data System (ADS)

    Maharjan, D. K.; Jiang, G.; Peng, Y.; Sahoo, S. K.; Henry, R. A.

    2014-12-01

    The Early Mississippian Kinderhookian-Osagean (K-O) boundary transition represents one of the largest global perturbations of carbon cycle during Phanerozoic. This interval is characterized by large positive carbonate carbon isotope anomaly (?13Ccarb) enriched to more than + 5‰ that has been globally recognized. Controversies exit regarding the origin and nature of this carbon isotope excursion. Here we report that a primary preservation of the K-O ?13Ccarb excursion was coupled by organic carbon isotope (?13Corg) and organic nitrogen isotope (?15Norg) from carbonate successions of Great Basin in Western USA. Our samples were obtained from Mountain Home (MH) and Alamo (AL) sections, represent shallow and deeper depositional environment, respectively. The values of ?13Ccarb covaried with ?13Corg in both sections, indicating photosynthetic origin of organic carbon isotope excursion during K-O. ?13Ccarb values from AL records 1-1.5‰ higher than MH, possibly related to locally higher production. Carbonate-organic carbon isotope differences (?13C = ?13Ccarb - ?13Corg) increase across the peak of ?13Ccarb excursion in AL section but remain invariant ??13C in MH, suggesting that ?13Corg values in AL may have been imprinted with signature from secondary (chemo- and methanotrophic) biomass contribution as anoxia was developed in the distal carbonate platform. The contrasting ??13C profiles in time-equivalent sections questioned the general concept that increase in ??13C records elevated O2/CO2 ratios, as have been suggested for Late Cambrian and Permo-Carboniferous. Only when the temporal depositional environments did not change, the ??13C may have implications for changes in O2/CO2 ratios. Nitrogen isotopes values increased to 4‰ across the K-O ?13C excursion indicating increased pelagic denitrification in response to the development of oxygen minimum zone as a result of enhanced organic carbon production, global cooling and sea-level fall. The integrated ?13Ccarb, ?13Corg, and ?15Norg data across the K-O transition support an organic carbon burial event associated with global cooling/oxygenation occurred during the Early Mississippian.

  20. Boron Isotope Intercomparison Project (BIIP): Development of a new carbonate standard for stable isotopic analyses

    NASA Astrophysics Data System (ADS)

    Gutjahr, Marcus; Bordier, Louise; Douville, Eric; Farmer, Jesse; Foster, Gavin L.; Hathorne, Ed; Hönisch, Bärbel; Lemarchand, Damien; Louvat, Pascale; McCulloch, Malcolm; Noireaux, Johanna; Pallavicini, Nicola; Rodushkin, Ilia; Roux, Philippe; Stewart, Joseph; Thil, François; You, Chen-Feng

    2014-05-01

    Boron consists of only of two isotopes with a relatively large mass difference (~10 %). It is also volatile in acidic media and prone to contamination during analytical treatment. Nevertheless, an increasing number of isotope laboratories are successfully using boron isotope compositions (expressed in ?11B) in marine biogenic carbonates to reconstruct seawater pH. Recent interlaboratory comparison efforts [1] highlighted the existence of a relatively high level of disagreement between laboratories when measuring such material, so in order to further strengthen the validity of this carbonate system proxy, appropriate reference materials need to be urgently characterised. We describe here the latest results of the Boron Isotope Intercomparison Project (BIIP) where we aim to characterise the boron isotopic composition of two marine carbonates: Japanese Geological Survey carbonate standard materials JCp-1 (coral porites) [2] and JCt-1 (Giant Clam) [3]. This boron isotope interlaboratory comparison study has two aims: (i) to assess to what extent chemical pre-treatment, aimed at removing organic material, can influence the resulting carbonate ?11B; (ii) to determine the isotopic composition of the two reference materials with a number of analytical techniques to provide the community with reference ?11B values for JCp-1 and JCt-1 and to further explore any differences related to analytical technique. In total eight isotope laboratories participated, of which one determined ?11B via negative thermal ionisation mass spectrometry (NTIMS) and seven used multi collector inductively coupled plasma mass spectrometry (MC-ICPMS). For the latter several different introduction systems and chemical purification methods were used. Overall the results are strikingly consistent between the participating labs. The oxidation of organic material slightly lowered the median ?11B by ~0.1 ‰ for both JCp-1 and JCt-1, while the mean ?11B of all labs for both standards was lowered by 0.20 ‰ for JCp-1 and 0.15 ‰ for JCt-1, hence within uncertainty of the reported values. With the exception of one MC-ICPMS lab that provided significantly lower JCp-1 ?11B data for unoxidised material (1.7 ‰ below median), the remaining JCp-1 results reproduced within ± 0.54 ‰ for unoxidised (n=21) and ± 0.37 ‰ for oxidised standards (n=21). The JCt-1 standards did not reproduce as well, resulting in a 2 s.d. of 1.0 ‰ for both unoxidised and oxidised powders (n=21) and in places the effect of oxidation appeared to be laboratory dependent. Exclusion of one MC-ICPMS lab resulted in an improved reproducibility of 0.52 ‰ (n=18) for oxidised JCt-1 material. The mean difference for the two standard materials in the respective labs (i.e., ??11B = mean ?11B(JCp-1) - mean ?11B(JCt-1)) was 7.9 ± 0.9 ‰ for unoxidised (n=7) and 8.1 ± 0.7 ‰ for oxidised standards (n=7). In this presentation emphasis will also be placed on distinguishing factors leading to increased/decreased interlaboratory consistency during the preparation and analysis of biogenic carbonates for other isotopic systems. References [1] Foster, G.L. et al. (2013) Chemical Geology 358: p. 1-14. [2] Okai, T. et al. (2002) Geostandards Newsletter 26: p. 95-99. [3] Inoue, M. et al. (2004) Geostandards and Geoanalytical Research 28: p. 411-416.

  1. STABLE ISOTOPIC EVIDENCE OF CARBON AND NITROGEN USE IN CULTURED ECTOMYCORRHIZAL AND SAPROTROPHIC FUNGI

    EPA Science Inventory

    Stable isotopes in sporocarps have proven useful for inferring ectomycorrhizal or saprotrophic status and understanding carbon (C) and nitrogen (N) utilization. However, greater understanding of processes producing isotopic concentrations is needed. We measured natural abundanc...

  2. Were carbon isotopic gradients in post-snowball oceans inverted?

    NASA Astrophysics Data System (ADS)

    Halverson, G. P.; Hoffman, P. F.; MacDonald, F. A.; Higgins, J. A.; Schrag, D. P.

    2008-12-01

    In the Otavi Group of Namibia, 900 m of platform carbonate strata above the 635-Ma post-glacial cap dolostone are consistently lighter in ?13C by up to 2.5 per mil than the adjacent 180-320 m of correlative, >0.6-km-deep, foreslope strat. Assuming the foreslope carbonate was equilibrated with deeper water, the normal isotopic gradient dynamically sustained by the biological 'pump' was inverted. Geochronology of isotopically correlative Doushantuo strata in South China suggests that the inverted gradient lasted for ~2 Myr after the glacial termination. Thereafter, the inverted gradient disappears. A similar transient inverse gradient follows the older Cryogenian glaciation in Arctic Alaska. We hypothesize that the inverse gradients reflect high pCO2 in the glacial aftermaths. This had two consequences. First, the size of the DIC pool was enlarged, reducing the isotopic effect of the biological pump. Second, isotopic fractionation was strongly temperature-dependent due to the large fractionation between CO2 and CO32- coupled with the dominance of CO2(gas) among carbon species at pH<7.2. A difference in SST of ~25° between the areas of air-sea equilibration is required to account for a 2.5 per mil gradient in ?13C. This is realized in non-upwelling zones of the southern hemisphere today, where warm subtropical surface waters are underlain by Antarctic Intermediate Water. For our hypothesis to be valid, a large meridional temperature gradient must have coexisted with strong CO2 radiative forcing.

  3. A continuous 250,000 yr record of oxygen and carbon isotopes in ostracode and bulk-sediment carbonate from Bear Lake, Utah-Idaho

    USGS Publications Warehouse

    Bright, Jordon; Kaufman, D.S.; Forester, R.M.; Dean, W.E.

    2006-01-01

    Oxygen and carbon isotopes from a continuous, 120-m-long, carbonate-rich core from Bear Lake, Utah-Idaho, document dramatic fluctuations in the hydrologic budget of the lake over the last 250,000 yr. Isotopic analyses of bulk sediment samples capture millennial-scale variability. Ostracode calcite was analyzed from 78 levels, mainly from the upper half of the core where valves are better preserved, to compare the isotopic value of purely endogenic carbonate with the bulk sediment, which comprises both endogenic and detrital components. The long core exhibits three relatively brief intervals with abundant endogenic aragonite (50??10%) and enriched ??18O and ??13C. These intervals are interpreted as warm/dry periods when the lake retracted into a topographically closed basin. We correlate these intervals with the interglacial periods of marine oxygen-isotope stages 1, 5e, and 7a, consistent with the presently available geochronological control. During most of the time represented by the core, the lake was fresher than the modern lake, as evidenced by depleted ??18O and ??13C in bulk-sediment carbonate. ?? 2006 Elsevier Ltd. All rights reserved.

  4. Carbon and oxygen abundances across the Hertzsprung gap

    SciTech Connect

    Adamczak, Jens; Lambert, David L. E-mail: dll@astro.as.utexas.edu

    2014-08-10

    We derived atmospheric parameters and spectroscopic abundances for C and O for a large sample of stars located in the Hertzsprung gap in the Hertzsprung-Russell diagram in order to detect chemical peculiarities and get a comprehensive overview of the population of stars in this evolutionary state. We have observed and analyzed high-resolution spectra (R = 60,000) of 188 stars in the mass range 2-5 M{sub ?} with the 2.7 m Harlan J. Smith Telescope at the McDonald Observatory including 28 stars previously identified as Am/Ap stars. We find that the C and O abundances of the majority of stars in the Hertzsprung gap are in accordance with abundances derived for local lower-mass dwarfs but detect expected peculiarities for the Am/Ap stars. The C and O abundances of stars with T{sub eff} < 6500 K are slightly lower than for the hotter objects but the C/O ratio is constant in the analyzed temperature domain. No indication of an alteration of the C and O abundances of the stars by mixing during the evolution across the Hertzsprung gap could be found before the homogenization of their atmospheres by the first dredge-up.

  5. Constraint of the CO2 rise by new atmospheric carbon isotopic measurements during the last deglaciation

    E-print Network

    Chappellaz, Jérôme

    debated. We analyzed the parallel evolution of CO2 and its stable carbon isotopic ratio (d13 CO2Click Here for Full Article Constraint of the CO2 rise by new atmospheric carbon isotopic increase of atmospheric carbon dioxide (CO2) during the last glacialinterglacial climatic transition remain

  6. c0011 Carbon Isotope Stratigraphy M.R. Saltzman and E. Thomas

    E-print Network

    Chapter 11 c0011 Carbon Isotope Stratigraphy M.R. Saltzman and E. Thomas Chapter Outline 11.1. Principles of Carbon Isotope Stratigraphy 221 11.2. Spatial Heterogeneity of d13C of Dissolved Inorganic Carbon 223 11.3. Materials and Methods 224 11.3.1. Depositional Setting: Deep (Pelagic) Versus Shallow

  7. SIO269 Special Topics in Marine Chemistry Seminar Carbon Cycle from an Isotope Perspective

    E-print Network

    Aluwihare, Lihini

    SIO269 Special Topics in Marine Chemistry Seminar ­ Carbon Cycle from an Isotope Perspective 1 Changes in the ocean carbon cycle readings: Broecker et al. (2007) Quay et al. (2003) November 27th Stable Carbon Isotopes: A quick introduction (Reading: Gruber et al., 1999; Kroopnick, 1985) October 9th

  8. Sensitivity analysis and quantification of uncertainty for isotopic mixing relationships in carbon cycle research

    E-print Network

    Keener, James P.

    relationships is critical to isotopic applications in carbon cycle studies at all spatial and temporal scales ecosystems represents one of the current challenges in carbon cycle research (Schimel et al., 1994, 2001Sensitivity analysis and quantification of uncertainty for isotopic mixing relationships in carbon

  9. Carbon and oxygen isotopes in apatite CO/sub 2/ and co-existing calcite

    SciTech Connect

    Kolodny, Y.; Kaplan, I. R.

    1981-04-01

    Carbon and oxygen isotopes were analyzed in carbonate apatite CO/sub 2/ and in co-existing calcite. Both C and O in apatite CO/sub 2/ are enriched in the respective light isotopes relative to calcite. These results confirm the proposition that carbonate is part of the apatite structure.

  10. Carbon isotopic composition of deep carbon gases in an ombrogenous peatland, northwestern Ontario, Canada

    SciTech Connect

    Aravena, R. . Center for Groundwater Research and Wetlands Research Center); Warner, B.G. . Wetlands Research Center and Dept. of Geography); Charman, D.J. . Dept. of Geographical Sciences); Belyea, L.R. . School of Biological Sciences); Mathur, S.P. ); Dinel, H. )

    1993-01-01

    Radiocarbon dating and carbon isotope analyses of deep peat and gases in a small ombrogenous peatland in northwestern Ontario reveals the presence of old gases at depth that are 1000-2000 yr younger than the enclosing peat. The authors suggest that the most likely explanation to account for this age discrepancy is the downward movement by advection of younger dissolved organic carbon for use by fermentation and methanogens bacteria. This study identifies a potentially large supply of old carbon gases in peatlands that should be considered in global carbon models of the terrestrial biosphere.

  11. Photosynthetic fractionation of the stable isotopes of oxygen and carbon

    SciTech Connect

    Guy, R.D. ); Fogel, M.L.; Berry, J.A. )

    1993-01-01

    Isotope discrimination during photosynthetic exchange of O[sub 2] and CO[sub 2] was measured using enzyme, thylakoid, and whole cell preparations. Evolved oxygen from isolated spinach thylakoids was isotopically identical (within analytical error) to its source water. Similar results were obtained with Anacystis nidulans Richter and Phaeodactylum tricornutum Bohlin cultures purged with helium. For consumptive reactions, discrimination ([triangle], where 1 + [triangle]/1000 equals the isotope effect, k[sup 16]/k[sup 18] or k[sup 12]/k[sup 13]) was determined by analysis of residual substrate (O[sub 2] or CO[sub 2]). The [triangle] for the Mehler reaction, mediated by ferredoxin or methylviologen, was 15.3[per thousand]. Oxygen isotope discrimination during oxygenation of ribulose-1,5-bisphosphate (RuBP) catalyzed by RuBP carboxylase/oxygenase (Rubisco) was 21.3[per thousand] and independent of enzyme source, unlike carbon isotope dicrimination: 30.3[per thousand] for spinach enzyme and 19.6 to 23[per thousand] for Rhodospirillum rubrum and A. nidulans enzymes, depending on reaction conditions. The [triangle] for O[sub 2] consumption catalyzed by glycolate oxidase was 22.7[per thousand]. Consistent with this, when Asparagus sprengeri Regel mesopyll cells approached the compensation point within a sealed vessel, the [delta][sup 18]O of dissolved O[sub 2] came to a steady-state value of about 21.5[per thousand] relative to the source water. The results provide improved estimates of discrimination factors in several reactions prominent in the global oxygen cycle and indicate that photorespiration plays a significant part in determining the isotopic composition of atmospheric oxygen. 47 refs., 8 figs., 2 tabs.

  12. Photosynthetic Fractionation of the Stable Isotopes of Oxygen and Carbon.

    PubMed

    Guy, R. D.; Fogel, M. L.; Berry, J. A.

    1993-01-01

    Isotope discrimination during photosynthetic exchange of O2 and CO2 was measured using enzyme, thylakoid, and whole cell preparations. Evolved oxygen from isolated spinach thylakoids was isotopically identical (within analytical error) to its source water. Similar results were obtained with Anacystis nidulans Richter and Phaeodactylum tricornutum Bohlin cultures purged with helium. For consumptive reactions, discrimination ([delta], where 1 + [delta]/1000 equals the isotope effect, k16/k18 or k12/k13) was determined by analysis of residual substrate (O2 or CO2). The [delta] for the Mehler reaction, mediated by ferredoxin or methylviologen, was 15.3[per mille (thousand) sign]. Oxygen isotope discrimination during oxygenation of ribulose-1,5-bisphosphate (RuBP) catalyzed by RuBP carboxylase/oxygenase (Rubisco) was 21.3[per mille (thousand) sign] and independent of enzyme source, unlike carbon isotope discrimination: 30.3[per mille (thousand) sign] for spinach enzyme and 19.6 to 23[per mille (thousand) sign] for Rhodospirillum rubrum and A. nidulans enzymes, depending on reaction conditions. The [delta] for O2 consumption catalyzed by glycolate oxidase was 22.7[per mille (thousand) sign]. The expected overall [delta] for photorespiration is about 21.7[per mille (thousand) sign]. Consistent with this, when Asparagus sprengeri Regel mesophyll cells approached the compensation point within a sealed vessel, the [delta]18O of dissolved O2 came to a steady-state value of about 21.5[per mille (thousand) sign] relative to the source water. The results provide improved estimates of discrimination factors in several reactions prominent in the global O cycle and indicate that photorespiration plays a significant part in determining the isotopic composition of atmospheric oxygen. PMID:12231663

  13. Carbon and Nitrogen Isotope Variation in Sphagnum from Peat Bogs in the Midwestern Us: Implications for Holocene Climate Reconstruction

    NASA Astrophysics Data System (ADS)

    Wong, D.; Paytan, A.; Jackson, S. T.

    2009-12-01

    A peat core taken from near the center of Minden Bog in Michigan, representing about 3500 years of accumulation was previously analyzed for plant macrofossils, colorimetric humification, and testate amoebae to yield three independent climate proxies. The data show the site to be sensitive to bog water table fluctuations and suggest that this may be related to regional climatic changes. We analyzed the carbon and nitrogen isotopes and the carbon-nitrogen ratios in the bulk peat samples and determined that the changes in these isotopes and ratios can be attributed to one or more of the following: (1) changes in the relative abundance of vegetation taxa in the site, (2) changes in the metabolism that impact isotope ratios in the vegetation contributing to the bulk organic, and (3) selective preservation and regeneration of specific organic compounds within the bulk organic matter. We analyzed the carbon and nitrogen isotopes and the carbon-nitrogen ratios in a specific taxum, Sphagnum, to differentiate between these mechanisms and relate the record to water level and climate in the region.

  14. Carbon, sulfur, and oxygen isotope evidence for a strong depth gradient and oceanic oxidation after the Ediacaran

    E-print Network

    Kaufman, Alan Jay

    Carbon, sulfur, and oxygen isotope evidence for a strong depth gradient and oceanic oxidation after Ccarb), carbonate oxygen isotopes (d18 Ocarb), carbonate associated sulfate sulfur (d34 SCAS) and oxygen isotopes (d18 OCAS), and pyrite sulfur isotopes (d34 Spy) of a cap dolostone atop the Ediacaran

  15. Chemical method for nitrogen isotopic analysis of ammonium at natural abundance.

    PubMed

    Liu, Dongwei; Fang, Yunting; Tu, Ying; Pan, Yuepeng

    2014-04-15

    We report a new chemical method to determine the (15)N natural abundance (?(15)N) for ammonium (NH4(+)) in freshwater (e.g., precipitation) and soil KCl extract. This method is based on the isotopic analysis of nitrous oxide (N2O). Ammonium is initially oxidized to nitrite (NO2(-)) by hypobromite (BrO(-)) using previously established procedures. NO2(-) is then quantitatively converted into N2O by hydroxylamine (NH2OH) under strongly acid conditions. The produced N2O is analyzed by a commercially available purge and cryogenic trap system coupled to an isotope ratio mass spectrometer (PT-IRMS). On the basis of a typical analysis size of 4 mL, the standard deviation of ?(15)N measurements is less than 0.3‰ and often better than 0.1‰ (3 to 5 replicates). Compared to previous methods, the technique here has several advantages and the potential to be used as a routine method for (15)N/(14)N analysis of NH4(+): (1) substantially simplified preparation procedures and reduced preparation time particularly compared to the methods in which diffusion or distillation is involved since all reactions occur in the same vial and separation of NH4(+) from solution is not required; (2) more suitability for low volume samples including those with low N concentration, having a blank size of 0.6 to 2 nmol; (3) elimination of the use of extremely toxic reagents (e.g., HN3) and/or the use of specialized denitrifying bacterial cultures which may be impractical for many laboratories. PMID:24654992

  16. PHOTOCHEMICALLY-INDUCED ALTERATION OF STABLE CARBON ISOTOPE RATIOS (DELTA C-13) IN TERRIGENOUS DISSOLVED ORGANIC CARBON

    EPA Science Inventory

    Exposure of riverine waters to natural sunlight initiated alterations in stable carbon isotope ratios (delta C-13) of the associated dissolved organic carbon (DOC). Water samples were collected from two compositionally distinct coastal river systems in the southeastern United Sta...

  17. Strontium isotopes in carbonate deposits at Crater Flat, Nevada

    SciTech Connect

    Marshall, B.D.; Futa, K.; Peterman, Z.E.; Stuckless, J.S.

    1991-01-01

    Strontium isotope studies of carbonates from soils, veins, eolian dust and Paleozoic basement samples near Crater Flat, southwest of Yucca Mountain, provide evidence for the origins of these materials. Vein and soil carbonates have nearly identical ranges of {sup 87}Sr/{sup 86}Sr ratios at the lower end of the pedogenic range. The average {sup 87}Sr/{sup 86}Sr of Paleozoic basement from Black Marble Hill is similar to the {sup 87}Sr/{sup 86}Sr in the eolian dust, perhaps indicating a local source for this material. Possible spring deposits have generally higher {sup 87}Sr/{sup 86}Sr than the other carbonates. These data are compared with similar data from areas east of Yucca Mountain. 7 refs., 5 figs.

  18. Stable carbon isotopic analysis of pyrolysis products of kerogens

    SciTech Connect

    Hoeld, I.M.; Schouten, S.; Sinninghe Damste, J.S.

    1996-12-31

    The origin of insoluble organic matter in sediments is still a matter of debate. The application of isotope-ratio-monitoring gas chromatography-mass spectrometry (irm-CYC-MS) in combination with pyrolytic and chemolytic methods allows the determination of the 13C-content of products released from the kerogen and provides a tool to determine the structure and origin of kerogen. Analysis of the pyrolysis products of several marine kerogens revealed that the stable carbon isotopic compositions of the n-alkanes (C10-C25) are quite similar to those of the n-alkenes. This suggests that they have a common origin such as algal biopolymers. The isoprenoid alkanes (C13-C20) also have similar isotopic compositions but differ from the values of the n-alkanes and n-alkenes. These isoprenoids could be derived from an isoprenoid algaenan similar to that biosynthesised by the freshwater algae Botryococcus braunii race L. The analysis of products in the aromatic fraction of the pyrolysates, showed a wide range of isotopic values, which suggest multiple origins.

  19. Environmental drivers of carbon and nitrogen isotopic signatures in peatland vascular plants along an altitude gradient.

    PubMed

    Gavazov, Konstantin; Hagedorn, Frank; Buttler, Alexandre; Siegwolf, Rolf; Bragazza, Luca

    2016-01-01

    Peatlands are important sinks of atmospheric carbon (C) that, in response to climate warming, are undergoing dynamic vegetation succession. Here we examined the hypothesis that the uptake of nutrients by different plant growth forms (PGFs) is one key mechanism driving changes in species abundance in peatlands. Along an altitude gradient representing a natural climate experiment, we compared the variability of the stable C isotope composition (?(13)C) and stable nitrogen (N) isotope composition (?(15)N) in current-year leaves of two major PGFs, i.e. ericoids and graminoids. The climate gradient was associated with a gradient of vascular plant cover, which was parallelled by different concentrations of organic and inorganic N as well as the fungal/bacterial ratio in peat. In both PGFs the (13)C natural abundance showed a marginal spatial decrease with altitude and a temporal decrease with progression of the growing season. Our data highlight a primary physical control of foliar ?(13)C signature, which is independent from the PGFs. Natural abundance of foliar (15)N did not show any seasonal pattern and only in the ericoids showed depletion at lower elevation. This decreasing ?(15)N pattern was primarily controlled by the higher relative availability of organic versus inorganic N and, only for the ericoids, by an increased proportion of fungi to bacteria in soil. Our space-for-time approach demonstrates that a change in abundance of PGFs is associated with a different strategy of nutrient acquisition (i.e. transfer via mycorrhizal symbiosis versus direct fine-root uptake), which could likely promote observed and predicted dwarf shrub expansion under climate change. PMID:26433961

  20. Isotope-based Fluvial Organic Carbon (ISOFLOC) Model: Model formulation, sensitivity, and evaluation

    NASA Astrophysics Data System (ADS)

    Ford, William I.; Fox, James F.

    2015-06-01

    Watershed-scale carbon budgets remain poorly understood, in part due to inadequate simulation tools to assess in-stream carbon fate and transport. A new numerical model termed ISOtope-based FLuvial Organic Carbon (ISOFLOC) is formulated to simulate the fluvial organic carbon budget in watersheds where hydrologic, sediment transport, and biogeochemical processes are coupled to control benthic and transported carbon composition and flux. One ISOFLOC innovation is the formulation of new stable carbon isotope model subroutines that include isotope fractionation processes in order to estimate carbon isotope source, fate, and transport. A second innovation is the coupling of transfers between carbon pools, including algal particulate organic carbon, fine particulate and dissolved organic carbon, and particulate and dissolved inorganic carbon, to simulate the carbon cycle in a comprehensive manner beyond that of existing watershed water quality models. ISOFLOC was tested and verified in a low-gradient, agriculturally impacted stream. Results of a global sensitivity analysis suggested the isotope response variable had unique sensitivity to the coupled interaction between fluvial shear resistance of algal biomass and the concentration of dissolved inorganic carbon. Model calibration and validation suggested good agreement at event, seasonal, and annual timescales. Multiobjective uncertainty analysis suggested inclusion of the carbon stable isotope routine reduced uncertainty by 80% for algal particulate organic carbon flux estimates.

  1. Physiological and environmental factors related to carbon isotopic variations in mollusc shell carbonate

    SciTech Connect

    Krantz, D.E.; Williams, D.F.; Jones, D.S.

    1985-01-01

    The carbon isotopic composition of mollusc shell carbonate has been used as a general environmental indicator in numerous studies, but relatively little is known of the factors which affect within-shell variation. Primary control of delta/sup 13/C values in shell carbonate comes from the dissolved bicarbonate source, particularly as related to marine versus fresh water. Present models explain cyclic variations in the delta/sup 13/C profiles of mollusc shells due to upwelling, phytoplankton productivity and stratification, disequilibrium with rapid shell growth, and infaunal versus epifaunal habitat. Carbon and oxygen isotopic profiles in this study were obtained from specimens of Spisula solidissima (surf clam) and Placopecten magellanicus (sea scallop) collected alive from 14 to 57 m water depths off the Virginia coast. Three main factors appear to affect the delta/sup 13/C profiles in these specimens. Isotopically light values commonly associated with the spring and occasionally the fall correspond with seasonal phytoplankton productivity. A significant negative delta/sup 13/C offset of the infaunal Spisula relative to the epifaunal Placopecten probably relates to the inclusion of isotopically more negative pore-water bicarbonate by Spisula. Additionally, occasional transient spikes in both the delta/sup 18/O and delta/sup 13/C profiles correspond to intrusion of reduced-salinity water.

  2. Beech carbon productivity as driver of ectomycorrhizal abundance and diversity.

    PubMed

    Druebert, Christine; Lang, Christa; Valtanen, Kerttu; Polle, Andrea

    2009-08-01

    We tested the hypothesis that carbon productivity of beech (Fagus sylvatica) controls ectomycorrhizal colonization, diversity and community structures. Carbon productivity was limited by long-term shading or by girdling. The trees were grown in compost soil to avoid nutrient deficiencies. Despite severe limitation in photosynthesis and biomass production by shading, the concentrations of carbohydrates in roots were unaffected by the light level. Shade-acclimated plants were only 10% and sun-acclimated plants were 74% colonized by ectomycorrhiza. EM diversity was higher on roots with high than at roots with low mycorrhizal colonization. Evenness was unaffected by any treatment. Low mycorrhizal colonization had no negative effects on plant mineral nutrition. In girdled plants mycorrhizal colonization and diversity were retained although (14)C-leaf feeding showed almost complete disruption of carbon transport from leaves to roots. Carbohydrate storage pools in roots decreased upon girdling. Our results show that plant carbon productivity was the reason for and not the result of high ectomycorrhizal diversity. We suggest that ectomycorrhiza can be supplied by two carbon routes: recent photosynthate and stored carbohydrates. Storage pools may be important for ectomycorrhizal survival when photoassimilates were unavailable, probably feeding preferentially less carbon demanding EM species as shifts in community composition were found. PMID:19344334

  3. Methodologies for extraction of dissolved inorganic carbon for stable carbon isotope studies : evaluation and alternatives

    USGS Publications Warehouse

    Hassan, Afifa Afifi

    1982-01-01

    The gas evolution and the strontium carbonate precipitation techniques to extract dissolved inorganic carbon (DIC) for stable carbon isotope analysis were investigated. Theoretical considerations, involving thermodynamic calculations and computer simulation pointed out several possible sources of error in delta carbon-13 measurements of the DIC and demonstrated the need for experimental evaluation of the magnitude of the error. An alternative analytical technique, equilibration with out-gassed vapor phase, is proposed. The experimental studies revealed that delta carbon-13 of the DIC extracted from a 0.01 molar NaHC03 solution by both techniques agreed within 0.1 per mil with the delta carbon-13 of the DIC extracted by the precipitation technique, and an increase of only 0.27 per mil in that extracted by the gas evolution technique. The efficiency of extraction of DIC decreased with sulfate concentration in the precipitation technique but was independent of sulfate concentration in the gas evolution technique. Both the precipitation and gas evolution technique were found to be satisfactory for extraction of DIC from different kinds of natural water for stable carbon isotope analysis, provided appropriate precautions are observed in handling the samples. For example, it was found that diffusion of atmospheric carbon dioxide does alter the delta carbon-13 of the samples contained in polyethylene bottles; filtration and drying in the air change the delta carbon-13 of the samples contained in polyethylene bottles; filtration and drying in the air change the delta carbon-13 of the precipitation technique; hot manganese dioxide purification changes the delta carbon-13 of carbon dioxide. (USGS)

  4. Isotope composition of carbon in the carbonates of the Gumbeykan scheelite deposits in the southern Urals

    SciTech Connect

    Korzhinskii, A.F.; Mamchur, G.P.; Yarynych, O.A.

    1980-10-01

    Through investigations of the isotope composition of carbon of various generations and carbonates from marbles, skarns, and nested and vein scheelite orebodies, the probable source of carbon of these carbonates has been established as a mixture of sedimentary carbonates, carbon dioxide with carbonic acid that was formed by oxidation of the organic matter from sedimentary terrane (..delta..C/sup 13/ - 0.05 to -0.62%). In the calcite and dolomite phenocrysts of marble and the coarse-grained dolostone, containing scheelite, the carbon was lighter (..delta..C/sup 13/ from -0.60 to -0.87%). For the dolomite and ankerite from scheelite pockets of the Balkan deposit and quartz veins of the Buranovo, ..delta..C/sup 13/ varied from -0.44 to -0.87%. The lightest carbon found in strontianite (..delta..C/sup 13/ = -1.32%), located near the coating of the organic matter (..delta..C/sup 13/ = -1.26%) in fractures of the quartz vein of the Buranovo deposit. In the section through the orebodies and near-ore diffusion-metasomatic zones of the Balkan deposit, the lessening of carbon in the carbonates was observed, with increasing distance away from the fracture. ..delta..C/sup 13/ in the altered granitoids ranged from -0.44 to -1.03%; while in the diopside-wollastonite hornfels, from -0.89 to 1.13%. The lessening in weight of the carbon is explained by diffusional fractionation of the isotopes caused apparently by the differential movement of volatile mixtures of carbon during ore-forming processes and the formation of their diffusion-metasomatic zones.

  5. A process-based model for non-equilibrium clumped isotope effects in carbonates

    NASA Astrophysics Data System (ADS)

    Watkins, J. M.; Hunt, J. D.

    2015-12-01

    The equilibrium clumped isotope composition of carbonate minerals is independent of the composition of the aqueous solution. However, many carbonate minerals grow at rates that place them in a non-equilibrium regime with respect to carbon and oxygen isotopes with unknown consequences for clumped isotopes. We develop a process-based model that allows one to calculate the oxygen, carbon, and clumped isotope composition of calcite as a function of temperature, crystal growth rate, and solution pH. In the model, carbon and oxygen isotope fractionation occurs through the mass-dependent attachment/detachment kinetics of the isotopologues of HCO-3 and CO2-3 to and from the calcite surface, which in turn, influence the clumped isotope composition of calcite. At experimental and biogenic growth rates, the mineral is expected to inherit a clumped isotopic composition that is similar to that of the DIC pool, which helps to explain (1) why different organisms share the same clumped isotope versus temperature calibration curves, (2) why many inorganic calibration curves are slightly different from one another, and (3) why foraminifera, coccoliths, and deep sea corals can have near-equilibrium clumped isotope compositions but far-from-equilibrium carbon and oxygen isotope compositions. Some aspects of the model can be generalized to other mineral systems and should serve as a useful reference in future efforts to quantify kinetic clumped isotope effects.

  6. {sup 39}Ar Detection at the 10{sup -16} Isotopic Abundance Level with Atom Trap Trace Analysis

    SciTech Connect

    Jiang, W.; Williams, W.; Bailey, K.; O'Connor, T. P.; Mueller, P.; Davis, A. M.; Hu, S.-M.; Sun, Y. R.; Lu, Z.-T.; Purtschert, R.; Sturchio, N. C.

    2011-03-11

    Atom trap trace analysis, a laser-based atom counting method, has been applied to analyze atmospheric {sup 39}Ar (half-life=269 yr), a cosmogenic isotope with an isotopic abundance of 8x10{sup -16}. In addition to the superior selectivity demonstrated in this work, the counting rate and efficiency of atom trap trace analysis have been improved by 2 orders of magnitude over prior results. The significant applications of this new analytical capability lie in radioisotope dating of ice and water samples and in the development of dark matter detectors.

  7. Carbon isotope ratios and impurities in diamonds from Southern Africa

    NASA Astrophysics Data System (ADS)

    Kidane, Abiel; Koch-Müller, Monika; Morales, Luiz; Wiedenbeck, Michael; De Wit, Maarten

    2015-04-01

    We are investigating the sources of diamonds from southern Africa by studying both their carbon isotopic composition and chemical impurities. Our samples include macro-sized diamonds from River Ranch kimberlite in Zimbabwe and the Helam and Klipspringer kimberlitic deposits from South Africa, as well as micro-sized diamonds from Klipspringer and Premier kimberlites in South Africa. We have characterized the samples for their structurally bounded nitrogen, hydrogen and platelets defect using a Fourier Transmission Infrared Spectroscopy (FTIR). Using the DiaMap routine, open source software (Howell et al., 2012), IR spectra were deconvulated and quantified for their nitrogen (A, B and D components) and hydrogen contents. High to moderate nitrogen concentrations (1810 to 400 µg/g; 400 to 50 µg/g respectively) were found in diamonds from Klipspringer and Helam. Moderate to low (<50 µg/g) nitrogen concentrations were observed in diamonds from Premier and River Ranch. Type II diamonds, i.e. diamonds with no N impurities, which are presumed to have been derived from ultramafic sources, are found in the River Ranch deposit. The macro- and micro-size diamonds from the Klipspringer deposit display similar nitrogen defects, with higher nitrogen concentration and more frequent D components found in the macro-size diamonds. One of the first steps towards reliable carbon isotope studies is the development of calibration materials for SIMS carbon isotopic analyses. We have investigated candidate materials both from a polycrystalline synthetic diamond sheet and two natural gem quality diamonds from Juina (Brazil). Electron-based images of the synthetic diamond sheet, obtained using GFZ Potsdam's dual beam FIB instrument, show many diamond grains with diameters greater than 35 µm. SIMS testing of the isotopic homogeneity of the back and front sides of the synthetic sheets reveal similar 13C/12C ratio within a RSD of <1 ‰ . SIMS isotopic analyses of the two natural diamond RMs yield a constant 13C/12C ratio with RSD of better than 0.5 ‰ . Using the natural diamond as calibratrant, a preliminary result on a selected diamond from the four kimberlitic sample suites yields a ?13C in range between -3 to -7 ‰ . Reference: Howell, D., O'Neill, C. J., Grant, K. J., Griffin, W. L., Pearson, N. J., & O'Reilly, S. Y. (2012). ?-FTIR mapping: Distribution of impurities in different types of diamond growth. Diamond and Related Materials, 29, 29-36. doi:10.1016/j.diamond.2012.06.003.

  8. Small mammal tooth enamel carbon isotope record of C4 grasses in late Neogene China

    NASA Astrophysics Data System (ADS)

    Arppe, Laura; Kaakinen, Anu; Passey, Benjamin H.; Zhang, Zhaoqun; Fortelius, Mikael

    2015-10-01

    The spatiotemporal pattern of the late Cenozoic spread of C4 vegetation is an important indicator of environmental change that is intertwined with the uplift of the Himalaya and Tibetan Plateau, and the development of the East Asian monsoons. To explore the spread of C4 vegetation in China and shed new light on regional climatic evolution, we measured ?13C values of more than 200 small mammal teeth (primarily rodents and lagomorphs) using a laser ablation isotope ratio mass spectrometry approach. Small mammals are highly sensitive indicators of their environment because they have limited spatial ranges and because they have minimal time-averaging of carbon isotope signatures of dietary components. The specimens originate from four classic Late Miocene fossil localities, Lufeng, Yuanmou, Lingtai, and Ertemte, along a southwest-northeast transect from Yunnan Province to Inner Mongolia. In Yunnan (Lufeng, Yuanmou) and on the Loess Plateau (Lingtai), the small mammal ?13C values record nearly pure C3 ecosystems, and mixed but C3-based ecosystems, respectively, in agreement with previous studies based on carbon isotopes of large herbivores and soil carbonates. In Inner Mongolia, the micromammalian tooth enamel ?13C record picks up the presence of C4 vegetation where large mammal samples do not, indicating a mixed yet C3-dominated ecosystem at ~ 6 Ma. As a whole, the results support a scenario of northward increasing C4 grass abundance in a pattern that mirrors northward decreasing precipitation of the summer monsoon system. The results highlight differences between large and small mammals as indicators of C4 vegetation in ancient ecosystems, particularly the ability of small mammal ?13C values to detect the presence of minor components of the vegetation structure.

  9. Comparisons between Antarctic and non-Antarctic meteorites based on carbon isotope geochemistry

    SciTech Connect

    Grady, M.M.; Wright, I.P.; Pillinger, C.T. )

    1991-01-01

    The whole-rock C isotopic composition of a suite of ordinary chondrites indicates that there is a difference between Antarctic and non-Antarctic meteorites. However, this apparent distinction is not due to an inherent difference in the meteorite source populations, but is rather a result of the presence of Antarctic weathering products, mainly bicarbonates, which affect the overall {delta}{sup 13}C of these meteorites. When these weathering products are removed, either by acid-washing or combustion to 500{degree}C, the perceived division also disappears, leading to the conclusion that ordinary chondrites (both Antarctic and non-Antarctic) have similar {delta}{sup 13}C values. The C chemistry of CI, CM, and CR chondrites is also subject to problematic interpretation. Whilst the indigenous C abundance is too high to be compromised by the addition of terrestrial weathering products, the inhomogeneous distribution of an array of components with widely varying isotopic signatures leads to a random distribution of {delta}{sup 13}C values. Analyses of individual components (insoluble macromolecular material, carbonates, and silicon carbide) reveal that there are no gross differences in C chemistry between Antarctic and non-Antarctic chondrites. The few distinctions that do exist might readily be explained by weathering or isotopic exchange in Antarctic. Whilst not forming a separate population, Antarctic carbonaceous chondrites may extend the range of properties of non-Antarctic chondrites beyond the currently known limits.

  10. Modeling Chemical and Isotopic Variations in Lab Formed Hydrothermal Carbonates

    NASA Technical Reports Server (NTRS)

    Niles, P. B.; Leshin, L. A.; Golden, D. C.; Socki, R. A.; Guan, Y.; Ming, D. W.

    2005-01-01

    Chemical and mineralogical data (e.g. [1]) from Mars suggest that the history of liquid water on the planet was more sporadic in nature than long-lived. The non-equilibrium chemical and isotopic compositions of the carbonates preserved in the martian meteorite ALH84001 are direct evidence of ancient secondary minerals that have not undergone significant diagenesis or stabilization processes typical of long-lived aqueous systems on Earth. Thus secondary minerals and sediments on Mars may primarily record the characteristics of the aqueous environment in which they formed without being significantly overprinted by subsequent diagenetic processes during burial.

  11. Abundance Anomaly of the 13C Isotopic Species of c-C3H2 in the Low-mass Star Formation Region L1527

    NASA Astrophysics Data System (ADS)

    Yoshida, Kento; Sakai, Nami; Tokudome, Tomoya; López-Sepulcre, Ana; Watanabe, Yoshimasa; Takano, Shuro; Lefloch, Bertrand; Ceccarelli, Cecilia; Bachiller, Rafael; Caux, Emmanuel; Vastel, Charlotte; Yamamoto, Satoshi

    2015-07-01

    The rotational spectral lines of c-C3H2 and two kinds of the 13C isotopic species, c-{}13{{CCCH}}2 ({C}2v symmetry) and c-{{CC}}13{{CH}}2 (Cs symmetry), have been observed in the 1-3 mm band toward the low-mass star-forming region L1527. We have detected 7, 3, and 6 lines of c-C3H2, c-{}13{{CCCH}}2, and c-{{CC}}13{{CH}}2, respectively, with the Nobeyama 45 m telescope and 34, 6, and 13 lines, respectively, with the IRAM 30 m telescope, where seven, two, and two transitions, respectively, are observed with both telescopes. With these data, we have evaluated the column densities of the normal and 13C isotopic species. The [c-C3H2]/[c-{}13{{CCCH}}2] ratio is determined to be 310 ± 80, while the [c-C3H2]/[c-{{CC}}13{{CH}}2] ratio is determined to be 61 ± 11. The [c-C3H2]/[c-{}13{{CCCH}}2] and [c-C3H2]/[c-{{CC}}13{{CH}}2] ratios expected from the elemental 12C/13C ratio are 60-70 and 30-35, respectively, where the latter takes into account the statistical factor of 2 for the two equivalent carbon atoms in c-C3H2. Hence, this observation further confirms the dilution of the 13C species in carbon-chain molecules and their related molecules, which are thought to originate from the dilution of 13C+ in the gas-phase C+ due to the isotope exchange reaction: {}13{{{C}}}++{CO}\\to {}13{CO}+{{{C}}}+. Moreover, the abundances of the two 13C isotopic species are different from each other. The ratio of c-{}13{{CCCH}}2 species relative to c-{{CC}}13{{CH}}2 is determined to be 0.20 ± 0.05. If 13C were randomly substituted for the three carbon atoms, the [c-{}13{{CCCH}}2]/[c-{{CC}}13{{CH}}2] ratio would be 0.5. Hence, the observed ratio indicates that c-{{CC}}13{{CH}}2 exists more favorably. Possible origins of the different abundances are discussed. Based on observations carried out with the IRAM 30 m Telescope and the NRO 45 m Telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain). NRO is a branch of the National Astronomical Observatory of Japan, National Institutes of Natural Sciences, Japan.

  12. Chemical and carbon isotopic composition of dissolved organic carbon in a regional confined methanogenic aquifer

    USGS Publications Warehouse

    Aravena, R.; Wassenaar, L.I.; Spiker, E. C.

    2004-01-01

    This study demonstrates the advantage of a combined use of chemical and isotopic tools to understand the dissolved organic carbon (DOC) cycle in a regional confined methanogenic aquifer. DOC concentration and carbon isotopic data demonstrate that the soil zone is a primary carbon source of groundwater DOC in areas close to recharge zones. An in-situ DOC source linked to organic rich sediments present in the aquifer matrix is controlling the DOC pool in the central part of the groundwater flow system. DOC fractions, 13C-NMR on fulvic acids and 14C data on DOC and CH4 support the hypothesis that the in-situ DOC source is a terrestrial organic matter and discard the Ordovician bedrock as a source of DOC. ?? 2004 Taylor and Francis Ltd.

  13. CNO ABUNDANCES OF HYDROGEN-DEFICIENT CARBON AND R CORONAE BOREALIS STARS: A VIEW OF THE NUCLEOSYNTHESIS IN A WHITE DWARF MERGER

    SciTech Connect

    Garcia-Hernandez, D. A.; Lambert, David L.; Eriksson, K. E-mail: hinkle@noao.edu E-mail: Kjell.Eriksson@astro.uu.se

    2009-05-10

    We present high-resolution (R {approx} 50, 000) observations of near-IR transitions of CO and CN of the five known hydrogen-deficient carbon (HdC) stars and four R Coronae Borealis (RCB) stars. We perform an abundance analysis of these stars by using spectrum synthesis and state-of-the-art MARCS model atmospheres for cool hydrogen-deficient stars. Our analysis confirms reports by Clayton and colleagues that those HdC stars exhibiting CO lines in their spectrum and the cool RCB star S Aps are strongly enriched in {sup 18}O (with {sup 16}O/{sup 18}O ratios ranging from 0.3 to 16). Nitrogen and carbon are in the form of {sup 14}N and {sup 12}C, respectively. Elemental abundances for CNO are obtained from C I, C{sub 2}, CN, and CO lines. Difficulties in deriving the carbon abundance are discussed. Abundances of Na from Na I lines and S from S I lines are obtained. Elemental and isotopic CNO abundances suggest that HdC and RCB stars may be related objects, and that they probably formed from a merger of an He white dwarf with a C-O white dwarf.

  14. Carbon isotope fractionation of sapropelic organic matter during early diagenesis

    USGS Publications Warehouse

    Spiker, E. C.; Hatcher, P.G.

    1984-01-01

    Study of an algal, sapropelic sediment from Mangrove Lake, Bermuda shows that the mass balance of carbon and stable carbon isotopes in the major organic constituents is accounted for by a relatively straightforward model of selective preservation during diagenesis. The loss of 13C-enriched carbohydrates is the principal factor controlling the intermolecular mass balance of 13C in the sapropel. Results indicate that labile components are decomposed leaving as a residual concentrate in the sediment an insoluble humic substance that may be an original biochemical component of algae and associated bacteria. An overall decrease of up to about 4??? in the ?? 13C values of the organic matter is observed as a result of early diagenesis. ?? 1984.

  15. Carbon isotope variation in mid-continent Ordovician-type oils: relationship to a major middle Ordovician carbon isotope shift

    SciTech Connect

    Hatch, J.R.; Jacobson, S.R.; Witzke, B.J.; Anders, D.E.; Watney, W.L.; Newell, K.D.

    1985-05-01

    Detailed organic geochemical comparisons of Mid-Continent Ordovician oils with extracts of potential source rocks show that in the Forest City basin of northeastern Kansas and southeastern Nebraska, oil source rocks are Middle Ordovician shales of the Simpson Group. For the Keota Dome field, Washington County, Iowa, the oil source rock is the Middle Ordovician Glenwood Shale Member of the Platteville Formation. Analyses of saturated and aromatic hydrocarbon fractions of Ordovician-type oils from the Forest City basin, Keota Dome field, and the Michigan basin show that sigma TC of the two fractions are similar and that sigma T varies over a considerable range, from -32.5 per mil to -25.5 per mil (PDB). This large range in sigma TC reflects a major shift in the carbon isotope composition of organic matter during the Middle Ordovician. This shift is shown in a 62.5-ft (19 m) interval of core from the Decorah and Platteville Formations in the E.M. Greene 1 well in Washington County, Iowa, where organic carbon sigma TC changes regularly upward from -32.2 per mil to -22.7 per mil (PDB). The change in organic carbon sigma TC in this core is not related to variations in amount (0.13-41.4% TOC) or type (hydrogen index = 69 to 1000 mg HC/g TOC) of the marginally mature (T/sub max/ = 440 +/- 5C) organic matter. Ordovician-type oils in both the Forest City and Michigan basins show variable sigma TC, suggesting that the sigma TC shift displayed in the Middle Ordovician rocks of southeastern Iowa is a regional and possibly a global effect, related to changes in the sigma TC of the ocean-atmosphere carbon reservoir. Isotopic analyses of coexisting carbonate minerals support this interpretation.

  16. Genesis of carbonates within Abalak and Bazhenov formations (West Siberia), revealed from stable carbon and oxygen isotopes distribution

    NASA Astrophysics Data System (ADS)

    Yurchenko, A.; Blinova, V.; Kalmikov, G. A.; Balushkina, N. S.

    2013-12-01

    Upper Jurassic deposits of Bazhenov formation are the main source rocks of the West Siberia Basin. Now the Bazhenov suite is intensively investigated not only as a source rock, but as unconventional reservoir of oil due to its vertical and lateral heterogeneity. The rocks of Bazhenov formation are composed of four main units: silica minerals, clay (predominantly hydromica), kerogen and carbonates. To predict the distribution of different lithological units it is important to reveal their genesis and facial conditions during their formation. One of the reservoir types is presented by cavernous-porous carbonates. Stable carbon and oxygen isotopes investigations has been carried out to reveal origin of carbonate material in Late Abalak - Bazhenov time. Four genetic types of carbonates have been subdivided according to mineralogical composition and stable carbon and oxygen isotopes distribution: 1) belemnites and other faunal remains; 2) secondary dolomites of Bazhenov formation; 3) secondary calcite filling cracks and composing inclusions of Abalak deposits; 4) methane-derived authigenic carbonates of Abalak formation. The first three types are presented by normal marine carbonates according to their carbon isotopes composition. Light oxygen isotopes composition indicates high temperatures during their precipitation (diagenesis). The fourth type is characterized by light carbon isotopes composition, which indicates presence of isotopically light biogenic CO2 in the environment. According to oxygen isotopic composition the carbonate material is primary and precipitated in subsurface conditions. Such carbon and oxygen isotopes composition is characteristic for methane-derived carbonates formed in the areas of active fluids discharge to the seafloor (cold seeps) as a result of Anaerobic Oxidation of Methane (AOM). Thus in Late Jurassic time active fluid escape to the sea floor took place in the West Siberia Basin.

  17. Carbon stable isotopes as indicators of coastal eutrophication.

    PubMed

    Oczkowski, Autumn; Markham, Erin; Hanson, Alana; Wigand, Cathleen

    2014-04-01

    Coastal ecologists and managers have frequently used nitrogen stable isotopes (delta15N) to trace and monitor sources of anthropogenic nitrogen (N) in coastal ecosystems. However, the interpretation of delta15N data can often be challenging, as the isotope values fractionate substantially due to preferential retention and uptake by biota. There is a growing body of evidence that carbon isotopes may be a useful alternative indicator for eutrophication, as they may be sensitive to changes in primary production that result from anthropogenic nutrient inputs. We provide three examples of systems where delta13C values sensitively track phytoplankton production. First, earlier (1980s) mesocosm work established positive relationships between delta13C and dissolved inorganic nitrogen and dissolved silica concentrations. Consistent with these findings, a contemporary mesocosm experiment designed to replicate a temperate intertidal salt marsh environment also demonstrated that the system receiving supplementary nutrient additions had higher nutrient concentrations, higher chlorophyll concentrations, and higher delta13C values. This trend was particularly pronounced during the growing season, with differences less evident during senescence. And finally, these results were replicated in the open waters of Narragansett Bay, Rhode Island, USA, during a spring phytoplankton bloom. These three examples, taken together with the pre-existing body of literature, suggest that, at least in autotrophic, phytoplankton-dominated systems, delta13C values can be a useful and sensitive indicator of eutrophication. PMID:24834733

  18. Method for the identification and elimination of contamination during carbon isotopic analyses of extraterrestrial samples

    SciTech Connect

    Swart, P.K.; Grady, M.M.; Pillinger, C.T.

    1983-06-30

    A stepped combustion method for the elimination of carbon-containing contamination and weathering products from meteorite and lunar samples is presented. Samples of the Allende CV3 chondrite, the Sharps and Weston ordinary chondrite falls, one ordinary and five Antarctic finds, and lunar soils from Apollo 11 were oxidized in pure O2 at increasing temperatures, from 200 to 1200 C in 100-C, 30-min steps and C yield and delta-(C-13) were measured after each step. It is found that some C contamination is present in all samples and can adversely affect C-isotopic-abundance measurements. Except for C1 and C2 carbonaceous chondrites, C combustion below 425 + or - 25 C is limited to the terrestrial contaminants, demonstrating the usefulness of stepped combustion in removing them. Graphs and tables of the results are presented and discussed. 34 references.

  19. Carbon isotope analysis of carbonaceous compounds in Puget Sound and Lake Washington

    SciTech Connect

    Swanson, J.R.

    1980-01-01

    A new method has been developed and tested for determining chronological profiles of organic pollutants. This method, Carbon Isotope Analysis (CIA), involves measurements of /sup 12/C, /sup 13/C and /sup 14/C in carbonaceous compounds found in layers of sediment. Lipids, total aliphatic hydrocarbons (TAHs) and polycyclic aromatic hydrocarbons (PAHs) are separated from kg quantities of sediment. Large Soxhlet extractors are used to remove the extractable organics, using ultra-pure benzene-methanol solution and having an extraction efficiency of about 86% for compounds with boiling points higher than n-tetradecane (n-C/sub 14/). The basic steps in compound separation include freeze-drying, extraction, fractionation, column chromatography and evaporation. Isolating the TAH and PAH fractions is accomplished by eluting samples from Sephadex and alumina/silica-gel columns. The amount of each fraction recovered is determined by converting the hydrocarbons to carbon dioxide and measuring this gas manometrically. Variations in /sup 12/C and /sup 13/C abundances for carbonaceous compounds are primarily due to thermodynamic, photosynthetic and metabolic fractionation processes. Thus, the source of a particular organic compound can often be determined by measuring its /sup 13/C//sup 12/C ratio. Combining the information from both the /sup 13/C analysis and /sup 14/C analysis makes source identification more certain. In addition, this investigation reviews carbon isotopic data and carbon cycling and analyzes organic pollution in two limited ecosystems (Puget Sound and Lake Washington). Specifically, distinct carbonaceous species are analyzed for pollution in sediments of Lake Washington, Elliott Bay, Commencement Bay, central Puget Sound and northern Puget Sound near the Cherry Point oil refineries.

  20. Noble gas content and isotope abundances in phases of the Saint-Aubin (UNGR) iron meteorite

    NASA Astrophysics Data System (ADS)

    Nishimura, Chikako; Matsuda, Jun-Ichi; Kurat, Gero

    2008-08-01

    We analyzed the noble gas isotopes in the Fe-Ni metal and inclusions of the Saint-Aubin iron meteorite, utilizing the stepwise heating technique to separate the various components of noble gases. The light noble gases in all samples are mostly cosmogenic, with some admixture from the terrestrial atmosphere. Total abundances of noble gases in metal are one of the lowest found so far in iron meteorites and the 4He/21Ne ratio is as high as 503, suggesting that the Saint-Aubin iron meteorite was derived from a very large meteoroid in space. The exposure ages obtained from cosmogenic 3He were 9-16 Ma. Saint-Aubin is very peculiar because it contains very large chromite crystals, which—like the metal—contain only cosmogenic and atmospheric noble gases. The noble gases in all the samples do not reveal any primordial components. The only exception is the 1000 °C fraction of schreibersite which contained about 5% of the Xe-HL component. The Xe-Q and the El Taco Xe components were not found and only the Xe-HL is present in this fraction. Some presolar diamond, the only carrier for the HL component known today, must have been available during growth of the schreibersite. However, it is also possible that this excess is due to the addition of cosmogenic and fission components. In this case, all the primordial components are masked (or lost) by the later events such as cosmic-ray irradiation, heating, and radioactive decay.

  1. Unusually high stable carbon isotopic values of methane from low organic carbon Mars analog hypersaline environments

    NASA Astrophysics Data System (ADS)

    Kelley, C. A.; Poole, J. A.; Tazaz, A.; Chanton, J.; Bebout, B.

    2010-12-01

    Motivated by the Mars rovers’ findings of past hypersaline environments and the discovery of methane in the atmosphere of Mars, we examined methanogenesis in hypersaline ponds in Baja California Sur and in the Don Edwards National Wildlife Refuge in northern California. Methane-rich bubbles were observed to be released from below gypsum/halite crusts in these environments. The stable carbon isotopic composition of these bubbles ranged from about -30 to -40 ‰. Methane with these relatively high isotopic values would typically be considered non-biogenic, however incubations of crust and sediments samples over time resulted in the production of methane. We therefore undertook a series of measurements aimed at understanding the isotopic composition of methane in these environments. The concentrations and isotopic composition of the particulate organic carbon (POC) in these environments were measured. POC content was low (relative to most methane-producing sedimentary environments), generally less than 1%, and always less than 2% of the total mass. The isotopic composition of the POC ranged from -13 to -22 ‰. To determine the substrates used by the methanogens, 13C-labeled trimethylamine (TMA), monomethylamine, methanol, acetate and bicarbonate were added to incubation vials and the methane produced was monitored for 13C content. The main substrates used by the methanogens in these hypersaline environments were the non-competitive substrates, the methylamines and methanol. When unlabeled, but isotopically known, TMA was added to incubation vials in varying concentrations, the isotopic composition of the methane produced also varied. Little, if any, difference in the isotopic composition between the TMA and methane occurred at the lowest TMA concentration (10 µM final concentration). The lowest methane ?13C values (and so greatest fractionation between methane and TMA) occurred when the most TMA was added (1000 µM final concentration). This change in the isotopic composition of the methane produced with varying TMA concentrations, along with the high in situ methane ?13C values, suggest that the methanogens in these environments are operating at low substrate concentrations. Apparently, substrate limitation decreases isotopic fractionation during methanogenesis, which results in the abnormally high biogenic methane ?13C values.

  2. Heat conduction of single-walled carbon nanotube isotope-superlattice structures: A molecular dynamics study

    E-print Network

    Maruyama, Shigeo

    1 Heat conduction of single-walled carbon nanotube isotope-superlattice structures: A molecular-mail address: maruyama@photon.t.u-tokyo.ac.jp Heat conduction of single-walled carbon nanotubes (SWNTs) isotope and junctions, which alter the heat conduction. In general, these nanoscale impurities, having scales comparable

  3. Accepted Manuscript Uranium isotopes and dissolved organic carbon in loess permafrost: modeling

    E-print Network

    Accepted Manuscript Uranium isotopes and dissolved organic carbon in loess permafrost: modeling isotopes and dissolved organic carbon in loess permafrost: modeling the age of ancient ice, Geochimica et errors may be discovered which could affect the content, and all legal disclaimers that apply

  4. Aust. J. Plant Physiol., 1992, 19, 171-84 Carbon Isotope Discrimination and Gas Exchange

    E-print Network

    Crisosto, Carlos H.

    exchange, and growth were monitored in container-grown coffee (Coffuurubicu L.) plants for 120 days underAust. J. Plant Physiol., 1992, 19, 171-84 Carbon Isotope Discrimination and Gas Exchange in Coffea, Abstract Although carbon isotope discrimination (A) has been reported to decline in plants growing under

  5. Distinguishing feral and managed honeybees (Apis mellifera) using stable carbon isotopes

    E-print Network

    Delaplane, Keith S.

    Distinguishing feral and managed honeybees (Apis mellifera) using stable carbon isotopes Lucy M to distinguish feral and managed honeybees (Apis mellifera) has applications in studies of population genetics. We evaluated (1) if carbon isotope ratios can distinguish feral and managed honeybees and (2

  6. Stable carbon isotope values document how a Late Holocene expansion in grasslands impacted vertebrates in northwestern Madagascar

    NASA Astrophysics Data System (ADS)

    Crowley, B. E.; Samonds, K.

    2012-12-01

    Madagascar is home to some of the world's most distinctive plants and animals. Unfortunately, forest loss and habitat degradation has had a dramatic impact on both floral and faunal communities. Here we use carbon isotope values in radiocarbon-dated bones to examine how the vertebrate community at Anjohibe Cave, northwestern Madagascar, responded to a Late Holocene increase in C4 grass abundance. Our data demonstrate that major changes in the vegetation and animal community are recent phenomena at Anjohibe. Extinct lemurs and hippopotamuses were present until ca. 1500 years ago. These taxa relied exclusively on C3 resources. Locally extirpated fauna were present until 300 years ago. The majority of these species also relied on C3 resources. Their presence strongly suggests that the region surrounding the cave was more wooded than it is now, possibly as recently as 300 years ago. All introduced individuals are modern. Rats (Rattus sp.), shrews (Suncus murinus), and the giant frog Hoplobatrachus cf. tigrinus, have remarkably high carbon isotope values, implicating substantial ingestion of C4 foods. It is possible that grass abundance has increased dramatically in the past 100 years. Alternatively, opportunistically granivorous rats and shrews may selectively consume seeds from C4 grasses. In agreement with previous studies, stable isotope data reveal details of vegetation and faunal turnover in Northwestern Madagascar. Grasses have increased, forest dwelling species have vanished, and introduced taxa are exploiting a novel niche.

  7. First results on stable isotopes in fluid inclusions in cryogenic carbonates from Ural Mountains (Russia)

    NASA Astrophysics Data System (ADS)

    Dublyansky, Yuri; Luetscher, Mark; Spötl, Christoph; Töchterle, Paul; Kadebskaya, Olga

    2015-04-01

    Cryogenic cave carbonates (CCC) were found in a number of caves in the Ural. In contrast to the CCC previously reported from Central Europe, the Uralian CCC have larger sizes (up to 4-5 cm), which allows for more detailed petrographic and geochemical studies. CCCs from Uralian caves commonly show spherulitic shapes due to crystal splitting, supporting the model of calcite precipitating in a freezing water pond. ?18O values of studied CCCs are lower by 1 to 14 o compared to noncryogenic speleothems of Pleistocene and Holocene age from the same caves. ?18O and ?13C values are inversely correlated and typically show a fractionation between the core and the rim of individual samples. These trends are similar to those reported for CCCs from European caves (Žák et al., 2004). Petrographic observations performed on doubly polished, 100-150 micron-thick sections revealed abundant fluid inclusions, trapped between fibres of the spherulites. Petrographic relationships suggest that these inclusions are primary. The isotopic composition of water trapped in fluid inclusions in CCCs from two caves was analyzed following mechanical crushing at 120 °C, cryo-trapping of released water, pyrolysis on glassy carbon at 1400 °C (TC/EA device; Thermo), and analysis of the evolved gases on an isotope ratio mass spectrometer (Delta V Advantage; Thermo Fisher). The lack of peaks on the m/z 2 trace during the heating of the loaded crushing cell attests for a good sealing of the fluid inclusions. The measured ?D values range between -136 o and -145 o VSMOW. The values measured in CCCs are more negative than the typical values of fluid inclusion water measured in the Holocene stalagmites from central Ural (-99 to -108 ). This shift toward more negative values is attributed to the isotopic fractionation between ice and water during the freezing. Reference: Žák et al., 2004, Chemical Geology, 2006, 119-136.

  8. Reactive transport modeling of stable carbon isotope fractionation in a multi-phase multi-component system during carbon sequestration

    SciTech Connect

    Zhang, Shuo; DePaolo, Donald J.; Zheng, Liange; Mayer, Bernhard

    2014-12-31

    Carbon stable isotopes can be used in characterization and monitoring of CO2 sequestration sites to track the migration of the CO2 plume and identify leakage sources, and to evaluate the chemical reactions that take place in the CO2-water-rock system. However, there are few tools available to incorporate stable isotope information into flow and transport codes used for CO2 sequestration problems. We present a numerical tool for modeling the transport of stable carbon isotopes in multiphase reactive systems relevant to geologic carbon sequestration. The code is an extension of the reactive transport code TOUGHREACT. The transport module of TOUGHREACT was modified to include separate isotopic species of CO2 gas and dissolved inorganic carbon (CO2, CO32-, HCO3-,…). Any process of transport or reaction influencing a given carbon species also influences its isotopic ratio. Isotopic fractionation is thus fully integrated within the dynamic system. The chemical module and database have been expanded to include isotopic exchange and fractionation between the carbon species in both gas and aqueous phases. The performance of the code is verified by modeling ideal systems and comparing with theoretical results. Efforts are also made to fit field data from the Pembina CO2 injection project in Canada. We show that the exchange of carbon isotopes between dissolved and gaseous carbon species combined with fluid flow and transport, produce isotopic effects that are significantly different from simple two-component mixing. These effects are important for understanding the isotopic variations observed in field demonstrations.

  9. Reactive transport modeling of stable carbon isotope fractionation in a multi-phase multi-component system during carbon sequestration

    DOE PAGESBeta

    Zhang, Shuo; DePaolo, Donald J.; Zheng, Liange; Mayer, Bernhard

    2014-12-31

    Carbon stable isotopes can be used in characterization and monitoring of CO2 sequestration sites to track the migration of the CO2 plume and identify leakage sources, and to evaluate the chemical reactions that take place in the CO2-water-rock system. However, there are few tools available to incorporate stable isotope information into flow and transport codes used for CO2 sequestration problems. We present a numerical tool for modeling the transport of stable carbon isotopes in multiphase reactive systems relevant to geologic carbon sequestration. The code is an extension of the reactive transport code TOUGHREACT. The transport module of TOUGHREACT was modifiedmore »to include separate isotopic species of CO2 gas and dissolved inorganic carbon (CO2, CO32-, HCO3-,…). Any process of transport or reaction influencing a given carbon species also influences its isotopic ratio. Isotopic fractionation is thus fully integrated within the dynamic system. The chemical module and database have been expanded to include isotopic exchange and fractionation between the carbon species in both gas and aqueous phases. The performance of the code is verified by modeling ideal systems and comparing with theoretical results. Efforts are also made to fit field data from the Pembina CO2 injection project in Canada. We show that the exchange of carbon isotopes between dissolved and gaseous carbon species combined with fluid flow and transport, produce isotopic effects that are significantly different from simple two-component mixing. These effects are important for understanding the isotopic variations observed in field demonstrations.« less

  10. The Stable and Radio- Carbon Isotopic Content of Labile and Refractory Carbon in Atmospheric Particulate Matter

    NASA Astrophysics Data System (ADS)

    McNichol, A. P.; Rosenheim, B. E.; Gerlach, D. S.; Hayes, J. M.

    2006-12-01

    Studies of the isotopic content of atmospheric particulate matter are hampered by difficulties in chemically defining the pools of carbon and analytically isolating the different pools. We are conducting studies on reference materials and atmospheric aerosol samples to develop a method to measure stable and radio- carbon isotopes on the labile and refractory carbon. We are using a flow-through combustion system that allows us to combust, collect and measure the isotopic content of the gases produced at all stages of heating/oxidizing. We compare our results to those measured using a chemothermal oxidation method (CTO) (Gustafsson et al., 2001). In this method, refractory carbon is defined as the material remaining after pre- combusting a sample at 375°C in the presence of oxygen for 24 hours. The reference materials are diesel soot, apple leaves and a hybrid of the two (DiesApple), all from NIST. These provide carbon with two well-defined fractions -- the soot provides refractory carbon that is radiocarbon dead and the apple leaves provide organic carbon that is radiocarbon modern. Radiocarbon results from DiesApple indicate that the "refractory" carbon defined by the CTO method is actually a mixture of old and modern carbon that contains over 25% modern carbon. This suggests that charred material formed from the apples leaves during the pre-combustion step is contributing to the fraction we identify as refractory carbon. We are studying this by analyzing the individual materials and the mixture using our flow-through system. First results with this system indicate that the refractory fraction trapped from the DiesApple contains much less modern carbon than the CTO method, less than 7%. We will present detailed concentration and isotopic results of the generation of carbon dioxide during programmed combustion of each of the reference materials. We studied the radiocarbon content of both the total carbon (TC) and refractory carbon in the fine particulate matter (PM2.5) collected on quartz fiber filters as part of the Southeastern Aerosol Research and Characterization (SEARCH) program. The five samples were collected at two sites (Birmingham, AL and Atlanta, GA) with very different sources of atmospheric particulate matter. In all instances, the refractory carbon contained significantly less radiocarbon than the TC suggesting, not unexpectedly, a source of particulate carbon from the combustion of fossil material. We will present results from the analysis of the same filters in the flow-through system. The implication of our results for the use of radiocarbon in the quantitative apportionment of atmospheric particulate matter sources will be discussed. Gustafsson O., T. Bucheli, Z. Kukulska, M. Andersson, C. Largeau, J-N. Rouzaud, C. Reddy and T. Eglinton (2001) Evaluation of a protocol for the quantification of black carbon in sediments. GBD 15, 881-890.

  11. Cryogenic Calcite: A Morphologic and Isotopic Analog to the ALH84001 Carbonates

    NASA Technical Reports Server (NTRS)

    Niles, P. B.; Leshin, L. A.; Socki, R. A.; Guan, Y.; Ming, D. W.; Gibson, E. K.

    2004-01-01

    Martian meteorite ALH84001 carbonates preserve large and variable microscale isotopic compositions, which in some way reflect their formation environment. These measurements show large variations (>20%) in the carbon and oxygen isotopic compositions of the carbonates on a 10-20 micron scale that are correlated with chemical composition. However, the utilization of these data sets for interpreting the formation conditions of the carbonates is complex due to lack of suitable terrestrial analogs and the difficulty of modeling under non-equilibrium conditions. Thus, the mechanisms and processes are largely unknown that create and preserve large microscale isotopic variations in carbonate minerals. Experimental tests of the possible environments and mechanisms that lead to large microscale isotopic variations can help address these concerns. One possible mechanism for creating large carbon isotopic variations in carbonates involves the freezing of water. Carbonates precipitate during extensive CO2 degassing that occurs during the freezing process as the fluid s decreasing volume drives CO2 out. This rapid CO2 degassing results in a kinetic isotopic fractionation where the CO2 gas has a much lighter isotopic composition causing an enrichment of 13C in the remaining dissolved bicarbonate. This study seeks to determine the suitability of cryogenically formed carbonates as analogs to ALH84001 carbonates. Specifically, our objective is to determine how accurately models using equilibrium fractionation factors approximate the isotopic compositions of cryogenically precipitated carbonates. This includes determining the accuracy of applying equilibrium fractionation factors during a kinetic process, and determining how isotopic variations in the fluid are preserved in microscale variations in the precipitated carbonates.

  12. Carbon-isotope stratigraphy of Early Cretaceous (Urgonian) shoal-water deposits: Diachronous changes in carbonate-platform production in the north-western Tethys

    E-print Network

    Gilli, Adrian

    Carbon-isotope stratigraphy of Early Cretaceous (Urgonian) shoal-water deposits: Diachronous changes in carbonate-platform production in the north-western Tethys S. Huck a,c, , U. Heimhofer a , A Northern Tethys Urgonian carbonate platform Carbon isotopes Orbitolinids Carbonate platforms are highly

  13. Atmospheric Parameters and Carbon Abundance for Hot DB White Dwarfs

    NASA Astrophysics Data System (ADS)

    Koester, Detlev; Provencal, Judi; Gänsicke, Boris T.

    2015-06-01

    Accurate atmospheric parameters for DB (helium atmosphere) white dwarfs near 25000 K are difficult to determine, but are needed to help or confirm the asteroseismic analysis of these objects. Another important aspect is the new class of white dwarfs - the hot DQ - whose spectra are dominated by carbon lines. The origin of these stars is not yet understood, but they may have an evolutionary link with the hotter DBs as studied here. We use absolutely calibrated high-resolution UV spectra of five DBs in addition to available optical spectroscopy. We find photospheric C and no other heavy elements - with extremely high limits on the C/Si ratio - in two of the five objects. We compare various explanations for this unusual composition that have been proposed in the literature: accretion of interstellar or circumstellar matter, radiative levitation, carbon dredge-up from the deeper interior below the helium layer, and a residual stellar wind. None of these explanations is completely satisfactory, and the problem of the origin of the hot DQ remains an open question.

  14. Carbon isotope composition of latex does not reflect temporal variations of photosynthetic carbon isotope discrimination in rubber trees (Hevea brasiliensis).

    PubMed

    Kanpanon, Nicha; Kasemsap, Poonpipope; Thaler, Philippe; Kositsup, Boonthida; Gay, Frédéric; Lacote, Régis; Epron, Daniel

    2015-11-01

    Latex, the cytoplasm of laticiferous cells localized in the inner bark of rubber trees (Hevea brasiliensis Müll. Arg.), is collected by tapping the bark. Following tapping, latex flows out of the trunk and is regenerated, whereas in untapped trees, there is no natural exudation. It is still unknown whether the carbohydrates used for latex regeneration in tapped trees is coming from recent photosynthates or from stored carbohydrates, and in the former case, it is expected that latex carbon isotope composition of tapped trees will vary seasonally, whereas latex isotope composition of untapped trees will be more stable. Temporal variations of carbon isotope composition of trunk latex (?(13)C-L), leaf soluble compounds (?(13)C-S) and bulk leaf material (?(13)C-B) collected from tapped and untapped 20-year-old trees were compared. A marked difference in ?(13)C-L was observed between tapped and untapped trees whatever the season. Trunk latex from tapped trees was more depleted (1.6‰ on average) with more variable ?(13)C values than those of untapped trees. ?(13)C-L was higher and more stable across seasons than ?(13)C-S and ?(13)C-B, with a maximum seasonal difference of 0.7‰ for tapped trees and 0.3‰ for untapped trees. ?(13)C-B was lower in tapped than in untapped trees, increasing from August (middle of the rainy season) to April (end of the dry season). Differences in ?(13)C-L and ?(13)C-B between tapped and untapped trees indicated that tapping affects the metabolism of both laticiferous cells and leaves. The lack of correlation between ?(13)C-L and ?(13)C-S suggests that recent photosynthates are mixed in the large pool of stored carbohydrates that are involved in latex regeneration after tapping. PMID:26358051

  15. Modelling carbon isotope composition of dissolved inorganic carbon and methane in marine porewaters

    NASA Astrophysics Data System (ADS)

    Meister, Patrick; Liu, Bo; Khalili, Arzhang; Barker Jørgensen, Bo

    2014-05-01

    Carbon isotope compositions of dissolved inorganic carbon (DIC) and methane (CH4) in marine sedimentary porewaters at near surface temperatures show extremely large variation in apparent fractionation covering a range from -100 ‰ to +30 ‰. This fractionation is essentially the result of microbial activity, but the mechanisms and factors controlling this fractionation are still incompletely understood. This study provides a reaction transport model approach to evaluate the effects of the most important processes and factors on carbon isotope distribution with the goal to better understand carbon isotope distribution in modern sediment porewaters and in the geological record. Our model results show that kinetic fractionation during methanogenesis, both through the acetoclastic and autotrophic pathways, results in a nearly symmetrical distribution of ?13C values in DIC and CH4 with respect to the isotope value of buried organic matter. An increased fractionation factor during methanogenesis leads to a larger difference between ?13CDIC and ?13CCH4. Near the sulphate methane transition zone, DIC is more depleted in 13C due to diffusive mixing with DIC produced by anaerobic oxidation of methane (AOM) and organoclastic sulphate reduction. The model also shows that an upward decrease in ?13CCH4 near the SMT can only be caused by equilibrium fractionation during AOM including a backward "leakage" of carbon from DIC to CH4 through the enzymatic pathway. However, this effect of reversibility has no influence on the DIC pool as long as methane is completely consumed at the SMT. Only a release of methane at the sediment-water interface, due to a fraction of the methane escaping re-oxidation, results in a small shift towards more positive ?13CDIC values. Methane escape at the SMT is possible if either the methane flux is too high to be entirely oxidized by AOM, or if bubbles of methane gas by-pass the sulphate reduction zone and escape episodically into the water column. A small but significant isotope effect is also caused by differential diffusion of the 12C and 13C isotopes of CH4 leading to somewhat more positive ?13CCH4 values, while DIC remains unaffected by this process. The consideration of all these effects allows a relatively good reproduction of ?13CDIC and ?13CCH4 profiles in marine sediments in diffusive systems. However, the model cannot reproduce profiles measured in seep environments, where CH4 and DIC profiles are perturbed by upward advecting, possibly thermogenic methane from greater depth. The model is now available to be applied for non-steady state systems, which ultimately will help to understand past dynamics of ?13C compositions and their diagenetic records as a result of changing microbial activity.

  16. Lithium isotopes and light lithophile element abundances in shergottites: Evidence for both magmatic degassing and subsolidus diffusion

    NASA Astrophysics Data System (ADS)

    Udry, Arya; McSween, Harry Y.; Hervig, Richard L.; Taylor, Lawrence A.

    2015-12-01

    Degassed magmatic water was potentially the major source of surficial water on Mars. We measured Li, B, and Be abundances and Li isotope profiles in pyroxenes, olivines, and maskelynite from four compositionally different shergottites—Shergotty, QUE 94201, LAR 06319, and Tissint—using secondary ion mass spectrometry (SIMS). All three light lithophile elements (LLE) are incompatible: Li and B are soluble in H2O-rich fluids, whereas Be is insoluble. In the analyzed shergottites, Li concentration decreases and Be concentration increases from cores to rims in pyroxenes. However, B concentrations do not vary consistently with Li and Be abundances, except in QUE 94201 pyroxenes. Additionally, abundances of these three elements in olivines show a normal igneous-fractionation trend consistent with the crystallization of olivine before magma ascent and degassing. We expect that kinetic effects would lead to fractionation of 6Li in the vapor phase compared to 7Li during degassing. The Li isotope profiles, with increasing ?7Li from cores to rims, as well as Li and B profiles indicate possible degassing of hydrous fluids only for the depleted shergottite QUE 94201, as also supported by degassing models. Conversely, Shergotty, LAR 06319, and Tissint appear to have been affected by postcrystallization diffusion, based on their LLE and Li isotope profiles, accompanied by diffusion models. This process may represent an overlay on a degassing pattern. The LLE profiles and isotope profiles in QUE 94201 support the hypothesis that degassing of some basaltic shergottite magmas provided water to the Martian surface, although evidence may be obscured by subsolidus diffusion processes.

  17. Carbon Isotope Ratio in 12 CO/ 13 CO toward Local Molecular Clouds with Near-Infrared High Resolution Spectroscopy of

    E-print Network

    Usuda, Tomonori

    Carbon Isotope Ratio in 12 CO/ 13 CO toward Local Molecular Clouds with Near-Infrared High@duke.ifa.hawaii.edu ABSTRACT We report the carbon monoxide isotope ratio in local molecular clouds toward LkH#11; 101, AFGL 490 The main isotope of carbon ( 12 C) is a primary product of the 3 #11; process in the stellar

  18. Carbonic anhydrase is abundant in fenestrated capillaries of cherry hemangioma.

    PubMed

    Eichhorn, M; Jungkunz, W; Wörl, J; Marsch, W C

    1994-01-01

    A strong correlation has been found between carbonic anhydrase (CA) activity and fenestrations in juxtaepithelial capillaries of several tissues, including psoriatic lesions of human skin. In the present study we demonstrate that the majority of the capillaries in cherry hemangiomas are fenestrated and histochemically react CA positively. Obviously the occurrence of CA in these capillaries corresponds to the fenestrations of venous capillaries, which are numerously revealed by electron microscopy. In normal undiseased skin no capillary staining for CA was observed. Therefore in a large proportion of the capillaries of cherry hemangiomas the correlation between fenestrations and CA activity also exists. We suggest that the histochemical demonstration of CA activity might serve as a sensitive and simple marker for fenestrated capillaries in skin tissue. PMID:7908484

  19. Stable isotope analysis of dissolved carbon species of Hot Lake, WA

    NASA Astrophysics Data System (ADS)

    Courtney, S.; Moran, J.; Cory, A. B.; Lindemann, S. R.; Fredrickson, J.

    2013-12-01

    Hot Lake is a hypersaline, meromictic lake in north-central Washington. The lake is epsomitic, with seasonably-variable salinity (.2 to 2 M magnesium sulfate) and produces carbonates and salt precipitates. The maximum depth of the lake is around 2.5 m, and below a thermocline there is intense solar heat retention in the monolimnion, often exceeding 50°C. Despite these extreme and variable conditions, a microbial mat of up to 1.5 cm thick thrives annually in Hot Lake. The mat is widespread throughout the lake at water depths (during our experiments) ranging from 60cm-140cm. It is comprised of a variety of cyanobacteria along with other autotrophic and heterotrophic bacteria. These populations are visibly stratified with four consistent laminae displaying differences in bacterial pigmentation. Many of the layers contain carbonate species, but the full relationship between the mat and the carbonate crystallization is not known. We are studying the microbial interactions and carbon cycling of the mat communities, using stable isotope analysis of the mat and the lake water, both in situ and ex situ. We are exploring the incorporation and movement of carbon in the mat, spatially and temporally, to understand the fixation mechanisms and metabolic processes at play in this environment. This was done primarily using stable isotope ratio mass spectrometry. The focus of this work is on the study and measurement of dissolved organic and inorganic carbon using a GasBench and IRMS setup, following methods adapted from Lang et al. (2012). To account for the unique chemistry of Hot Lake, trials on the effects of oxidation conditions and salinity were done on lab-synthesized samples to compare to Hot Lake results. The majority of lake water analyses were done in conjunction with a stable isotope probing (SIP) experiment, completed during two 24-hour periods at Hot Lake in June and July of 2013. The SIP experiments included ex situ incubations (in separate glass containers on the shore of the lake immediately after removal from the lake) under various conditions (with labeled and unlabeled substrate, in the presence and absence of daylight, with and without undermat sediment) performed as both constant labeling and pulse-chase experiments. We incubated mat sections in lake water (from equivalent depth to the collected mat) spiked either with 13C-labeled or natural abundance organic (acetate or glucose) or inorganic (bicarbonate) substrates. For those conditions in which inorganic carbon was added, we measured the DOC of the water in each condition to measure conversion from DIC to DOC and vice versa for consumption/conversion of DOC to DIC. By comparing the GasBench DIC/DOC results of these various conditions over the course of the experiments, we assessed carbon flow into and out of the mat around a daily cycle. The assessments were made using the ?13C values and data of the lake water samples from the IRMS in conjunction with bulk mat isotope values. Our data show significant interactions between DIC and DOC pools and allow us to estimate the daily balance between carbon fixation and remineralization mediated by the microbial mat.

  20. Seasonal variation in stable carbon and nitrogen isotope values of bats reflect environmental baselines.

    PubMed

    Popa-Lisseanu, Ana G; Kramer-Schadt, Stephanie; Quetglas, Juan; Delgado-Huertas, Antonio; Kelm, Detlev H; Ibáñez, Carlos

    2015-01-01

    The stable carbon and nitrogen isotope composition of animal tissues is commonly used to trace wildlife diets and analyze food chains. Changes in an animal's isotopic values over time are generally assumed to indicate diet shifts or, less frequently, physiological changes. Although plant isotopic values are known to correlate with climatic seasonality, only a few studies restricted to aquatic environments have investigated whether temporal isotopic variation in consumers may also reflect environmental baselines through trophic propagation. We modeled the monthly variation in carbon and nitrogen isotope values in whole blood of four insectivorous bat species occupying different foraging niches in southern Spain. We found a common pattern of isotopic variation independent of feeding habits, with an overall change as large as or larger than one trophic step. Physiological changes related to reproduction or to fat deposition prior to hibernation had no effect on isotopic variation, but juvenile bats had higher ?13C and ?15N values than adults. Aridity was the factor that best explained isotopic variation: bat blood became enriched in both 13C and 15N after hotter and/or drier periods. Our study is the first to show that consumers in terrestrial ecosystems reflect seasonal environmental dynamics in their isotope values. We highlight the danger of misinterpreting stable isotope data when not accounting for seasonal isotopic baselines in food web studies. Understanding how environmental seasonality is integrated in animals' isotope values will be crucial for developing reliable methods to use stable isotopes as dietary tracers. PMID:25700080

  1. The biodegradation of fluoranthene as monitored using stable carbon isotopes

    SciTech Connect

    Trust, B.A.; Mueller, J.G.; Coffin, R.B.; Cifuentes, L.A.

    1995-12-31

    The measurement of stable isotope ratios of carbon ({delta}{sup 13}C values) was investigated as a viable technique to monitor the intrinsic bioremediation of polycyclic aromatic hydrocarbons (PAHs). Biometer flask experiments were conducted in which the bacterium, Sphingomonas paucimobilis, designated EPA505, was grown on fluoranthene. During growth of EPA505 on fluoranthene, bacterial biomass, respired CO{sub 2}, and dissolved organic carbon (DOC), as well as fluoranthene, were sampled over 8 days. The concentrations and {delta}{sup 13}C values of each of these carbon pools were determined. The concentration of fluoranthene decreased from 12.1 {+-} 2.0 (n = 2) to 3.0 {+-} 0.9 (n = 2) mg C per flask over 188 h, and CO{sub 2} increased from undetectable levels to 7.1 {+-} 0.3 (n = 4) mg C per flask. A total of 55.5% mineralization resulted. DOC concentrations remained fairly constant with time, averaging 2.2 to 3.6 mg C per flask. The {delta}{sup 13}C value of fluoranthene remained constant over the course of the experiment, averaging {minus}24.5 {+-} 0.2{per_thousand} (n = 8). Bacterial nucleic acids and respired CO{sub 2} took on {delta}{sup 13}C values similar to those of fluoranthene within 47 h, measuring {minus}22.6 and {minus}24.3{per_thousand}, respectively.

  2. The carbon isotopic composition of dissolved inorganic carbon in perennially ice-covered Antarctic lakes: searching for a biogenic

    E-print Network

    Priscu, John C.

    ; Hoffman and Schrag, 2002). The perennially ice-covered closed-basin lakes of the McMurdo Dry Valleys (MCMThe carbon isotopic composition of dissolved inorganic carbon in perennially ice-covered Antarctic to investigate the biogeochemical dynamics of carbon. We studied seven perennially ice-covered lakes in the Mc

  3. Accurate experimental determination of the isotope effects on the triple point temperature of water. I. Dependence on the 2H abundance

    NASA Astrophysics Data System (ADS)

    Faghihi, V.; Peruzzi, A.; Aerts-Bijma, A. T.; Jansen, H. G.; Spriensma, J. J.; van Geel, J.; Meijer, H. A. J.

    2015-12-01

    Variation in the isotopic composition of water is one of the major contributors to uncertainty in the realization of the triple point of water (TPW). Although the dependence of the TPW on the isotopic composition of the water has been known for years, there is still a lack of a detailed and accurate experimental determination of the values for the correction constants. This paper is the first of two articles (Part I and Part II) that address quantification of isotope abundance effects on the triple point temperature of water. In this paper, we describe our experimental assessment of the 2H isotope effect. We manufactured five triple point cells with prepared water mixtures with a range of 2H isotopic abundances encompassing widely the natural abundance range, while the 18O and 17O isotopic abundance were kept approximately constant and the 18O?????17O ratio was close to the Meijer–Li relationship for natural waters. The selected range of 2H isotopic abundances led to cells that realised TPW temperatures between approximately???140 ?K to??+2500 ?K with respect to the TPW temperature as realized by VSMOW (Vienna Standard Mean Ocean Water). Our experiment led to determination of the value for the ?2H correction parameter of A2H??=??673 ?K / (‰ deviation of ?2H from VSMOW) with a combined uncertainty of 4 ?K (k??=??1, or 1?).

  4. Laboratory calibration of the calcium carbonate clumped isotope thermometer in the 25-250 °C temperature range

    NASA Astrophysics Data System (ADS)

    Kluge, Tobias; John, Cédric M.; Jourdan, Anne-Lise; Davis, Simon; Crawshaw, John

    2015-05-01

    Many fields of Earth sciences benefit from the knowledge of mineral formation temperatures. For example, carbonates are extensively used for reconstruction of the Earth's past climatic variations by determining ocean, lake, and soil paleotemperatures. Furthermore, diagenetic minerals and their formation or alteration temperature may provide information about the burial history of important geological units and can have practical applications, for instance, for reconstructing the geochemical and thermal histories of hydrocarbon reservoirs. Carbonate clumped isotope thermometry is a relatively new technique that can provide the formation temperature of carbonate minerals without requiring a priori knowledge of the isotopic composition of the initial solution. It is based on the temperature-dependent abundance of the rare 13C-18O bonds in carbonate minerals, specified as a ?47 value. The clumped isotope thermometer has been calibrated experimentally from 1 °C to 70 °C. However, higher temperatures that are relevant to geological processes have so far not been directly calibrated in the laboratory. In order to close this calibration gap and to provide a robust basis for the application of clumped isotopes to high-temperature geological processes we precipitated CaCO3 (mainly calcite) in the laboratory between 23 and 250 °C. We used two different precipitation techniques: first, minerals were precipitated from a CaCO3 supersaturated solution at atmospheric pressure (23-91 °C), and, second, from a solution resulting from the mixing of CaCl2 and NaHCO3 in a pressurized reaction vessel at a pressure of up to 80 bar (25-250 °C). The calibration lines of both experimental approaches overlap and agree in the slopes with theoretical estimates and with other calibration experiments in which carbonates were reacted with phosphoric acid at temperatures above 70 °C. Our study suggests a universal ?47-T calibration (T in K, ?47 in ‰):

  5. The magnesium isotope record of cave carbonate archives

    NASA Astrophysics Data System (ADS)

    Riechelmann, S.; Buhl, D.; Schröder-Ritzrau, A.; Riechelmann, D. F. C.; Richter, D. K.; Vonhof, H. B.; Wassenburg, J. A.; Geske, A.; Spötl, C.; Immenhauser, A.

    2012-05-01

    Here we explore the potential of time-series magnesium (?26Mg) isotope data as continental climate proxies in speleothem calcite archives. For this purpose, a total of six Pleistocene and Holocene stalagmites from caves in Germany, Morocco and Peru and two flowstones from a cave in Austria were investigated. These caves represent the semi-arid to arid (Morocco), the warm-temperate (Germany), the equatorial-humid (Peru) and the cold-humid (Austria) climate zones. Changes in the calcite magnesium isotope signature with time are placed against carbon and oxygen isotope records from these speleothems. Similar to other proxies, the non-trivial interaction of a number of environmental, equilibrium and non-equilibrium processes governs the ?26Mg fractionation in continental settings. These include the different sources of magnesium isotopes such as rain water or snow as well as soil and hostrock, soil zone biogenic activity, shifts in silicate versus carbonate weathering ratios and residence time of water in the soil and karst zone. Pleistocene stalagmites from Morocco show the lowest mean ?26Mg values (GDA: -4.26 ± 0.07 ‰ and HK3: -4.17 ± 0.15 ‰) and the data are well explained in terms of changes in aridity over time. The Pleistocene to Holocene stalagmites from Peru show the highest mean value (NC-A and NC-B ?26Mg: -3.96 ± 0.04 ‰) but only minor variations in Mg-isotope composition, which is in concert with the rather stable equatorial climate at this site. Holocene stalagmites from Germany (AH-1 mean ?26Mg: -4.01 ± 0.07 ‰; BU 4 mean ?26Mg: -4.20 ± 0.10 ‰) record changes in outside air temperature as driving factor rather than rainfall amount. The alpine Pleistocene flowstones from Austria (SPA 52: -3.00 ± 0.73 ‰; SPA 59: -3.70 ± 0.43 ‰) are affected by glacial versus interglacial climate change with outside air temperature affecting soil zone activity and weathering balance. Several data points in the Austrian and two data points in the German speleothems are shifted to higher values due to sampling in detrital layers (Mg-bearing clay minerals) of the speleothems. The data and their interpretation shown here highlight the potential but also the limitations of the magnesium isotope proxy applied in continental climate research. An obvious potential lies in its sensitivity for even subtle changes in soil-zone parameters, a hitherto rather poorly understood but extremely important component in cave archive research. Limitations are most obvious in the low resolution and high sample amount needed for analysis. Future research should focus on experimental and conceptual aspects including quantitative and well calibrated leaching and precipitation experiments.

  6. The magnesium isotope record of cave carbonate archives

    NASA Astrophysics Data System (ADS)

    Riechelmann, S.; Buhl, D.; Schröder-Ritzrau, A.; Riechelmann, D. F. C.; Richter, D. K.; Vonhof, H. B.; Wassenburg, J. A.; Geske, A.; Spötl, C.; Immenhauser, A.

    2012-11-01

    Here we explore the potential of magnesium (?26Mg) isotope time-series data as continental climate proxies in speleothem calcite archives. For this purpose, a total of six Pleistocene and Holocene stalagmites from caves in Germany, Morocco and Peru and two flowstones from a cave in Austria were investigated. These caves represent the semi-arid to arid (Morocco), the warm-temperate (Germany), the equatorial-humid (Peru) and the cold-humid (Austria) climate zones. Changes in the calcite magnesium isotope signature with time are compared against carbon and oxygen isotope records from these speleothems. Similar to other proxies, the non-trivial interaction of a number of environmental, equilibrium and disequilibrium processes governs the ?26Mg fractionation in continental settings. These include the different sources of magnesium isotopes such as rainwater or snow as well as soil and host rock, soil zone biogenic activity, shifts in silicate versus carbonate weathering ratios and residence time of water in the soil and karst zone. Pleistocene stalagmites from Morocco show the lowest mean ?26Mg values (GDA: -4.26 ± 0.07‰ and HK3: -4.17 ± 0.15‰), and the data are well explained in terms of changes in aridity over time. The Pleistocene to Holocene stalagmites from Peru show the highest mean value of all stalagmites (NC-A and NC-B ?26Mg: -3.96 ± 0.04‰) but only minor variations in Mg-isotope composition, which is consistent with the rather stable equatorial climate at this site. Holocene stalagmites from Germany (AH-1 mean ?26Mg: -4.01 ± 0.07‰; BU 4 mean ?26Mg: -4.20 ± 0.10‰) suggest changes in outside air temperature was the principal driver rather than rainfall amount. The alpine Pleistocene flowstones from Austria (SPA 52: -3.00 ± 0.73‰; SPA 59: -3.70 ± 0.43‰) are affected by glacial versus interglacial climate change with outside air temperature affecting soil zone activity and weathering balance. Several ?26Mg values of the Austrian and two ?26Mg values of the German speleothems are shifted to higher values due to sampling in detrital layers (Mg-bearing clay minerals) of the speleothems. The data and their interpretation shown here highlight the potential but also the limitations of the magnesium isotope proxy applied in continental climate research. An obvious potential lies in its sensitivity for even subtle changes in soil-zone parameters, a hitherto rather poorly understood but extremely important component in cave archive research. Limitations are most obvious in the low resolution and high sample amount needed for analysis. Future research should focus on experimental and conceptual aspects including quantitative and well-calibrated leaching and precipitation experiments.

  7. Lower Mississippian Positive Carbon Isotope Excursion in Shallow Water Carbonates, Wyoming and Montana

    NASA Astrophysics Data System (ADS)

    Katz, D. A.; Swart, P. K.; Buoniconti, M. R.; Eberli, G. P.; Smith, L. B.

    2004-12-01

    Lower Mississippian carbonates from Wyoming and Montana show a positive carbon isotope excursion (maximum \\delta13C values range from +5 to +7.5 \\permil PDB) within North American-Lower Mississippian/Kinderhookian to Osagean (Tournasian to Lower Visean) intervals, indicating a fluctuation in the global carbon cycle at that time. This carbon isotope excursion is found along the entire Madison ramp in cores (Elk and Bighorn Basins) and in measured sections in Wyoming and Montana. The excursion is independent of facies and occurrs in pervasively dolomitized up dip locations as well as basinward locations composed entirely of limestone. Positive carbon values are intimately associated with sequence stratigraphy previously determined in the measured sections. The onset of the transgression in Sequence II coincides with the most depleted carbon values (ca. 1 \\permil PDB) and a progressive increase of enrichment during the transgression. It reaches a maximum enrichment (ca. 7 \\permil PDB) at the turnaround to the regression, followed by a gradual trend from maximum values at the turnaround to minimum values (ca. 2 \\permil PDB) at the top of the sequence. On the Madison ramp, the positive carbon excursion can be used to correlate third order sequence boundaries across the 1100 km ramp system, providing a time line within otherwise undatable sections. On a larger scheme, these enriched values also correlate to time-equivalent strata discovered in previous studies from Utah, Nevada, Idaho, Wyoming, Iowa, and Western Europe, indicating its potential use as a global chronostratigraphic tool. The timing of this event probably coincides with low atmospheric CO2 levels and the initiation of conditions that lead to the Icehouse Earth in the Upper Mississippian. In order to confirm this interpretation we are measuring the \\delta13C of coexisting organic material to compare the difference between \\delta13C of the inorganic and organic components and assess pCO2 levels and associated changes within the marine organic and inorganic carbon pools.

  8. Abundances of carbon-enhanced metal-poor stars as constraints on their formation

    E-print Network

    Hansen, C J; Hansen, T T; Kennedy, C R; Placco, V M; Beers, T C; Andersen, J; Cescutti, G; Chiappini, C

    2015-01-01

    An increasing fraction of carbon-enhanced metal-poor (CEMP) stars is found as their iron abundance, [Fe/H], decreases below [Fe/H] = -2.0. The CEMP-s stars have the highest absolute carbon abundances, [C/H], and are thought to owe their enrichment in carbon and the slow neutron-capture (s-process) elements to mass transfer from a former asymptotic giant-branch (AGB) binary companion. The most Fe-poor CEMP stars are normally single, exhibit somewhat lower [C/H] than CEMP-s stars, but show no s-process element enhancement (CEMP-no stars). CNO abundance determinations offer clues to their formation sites. C, N, Sr, and Ba abundances (or limits) and 12C/13C ratios where possible are derived for a sample of 27 faint metal-poor stars for which the X-shooter spectra have sufficient S/N ratios. These moderate resolution, low S/N (~10-40) spectra prove sufficient to perform limited chemical tagging and enable assignment of these stars into the CEMP sub-classes (CEMP-s and CEMP-no). According to the derived abundances,...

  9. Genetic Effect on Carbon-Isotope Composition of a Plant

    NASA Astrophysics Data System (ADS)

    Yeh, H.

    2005-05-01

    Stable carbon isotopes of organic sediments are potential tools in investigating a wide spectrum of geological problems. These include paleoclimate, paleoecology, and the origin of life. The quality of the information the tools provides depends largely on our knowledge on the factors determining the isotopic composition of a plant. This is because most biogenic organic sediments are derived from plants. The factors can be grouped into internal and external. The internal factors are ultimately attributable to the genetic make-up of a plant. The most well known internal factor is the photosynthetic pathway. Others include structure of the leave tissue and metabolic characteristics of a plant. External factors are concentration and the isotopic composition of the source CO2 and the physical and chemical conditions of the plant's growth environments. This study addresses primarily the genetic effect, the internal factors. Based on the results of two suites of natural plant samples, it is concluded that the difference in photosynthetic pathway entails about 20.0 % of spread in terms of ä13CPDB values. Genetic effect is also accountable for up to 7.0 to 8.0 % spread in ä13CPDB values within a single category of photosynthetic pathway (i.e. the Calvin cycle). With constrains from the relevant known knowledge, it is concluded that the ä13CPDB values of terrestrial plants are probably ranging from - 8.0 to equal or less than -44.9 %. This range of ä13CPDB values may also be considered the bio-signature of organic sediments of great antiquity.

  10. Observation of Large Enhancement of Charge Exchange Cross Sections with Neutron-Rich Carbon Isotopes

    E-print Network

    I. Tanihata; S. Terashima; R. Kanungo; F. Ameil; J. Atkinson; Y. Ayyad; D. Cortina-Gil; I. Dillmann; A. Estradé; A. Evdokimov; F. Farinon; H. Geissel; G. Guastalla; R. Janik; R. Knoebel; J. Kurcewicz; Yu. A. Litvinov; M. Marta; M. Mostazo; I. Mukha; C. Nociforo; H. J. Ong; S. Pietri; A. Prochazka; C. Scheidenberger; B. Sitar; P. Strmen; M. Takechi; J. Tanaka; H. Toki; J. Vargas; J. S. Winfield; H. Weick

    2015-12-02

    Production cross sections of nitrogen isotopes from high-energy carbon isotopes on hydrogen and carbon targets have been measured for the first time for a wide range of isotopes. The fragment separator FRS at GSI was used to deliver C isotope beams. The cross sections of the production of N isotopes were determined by charge measurements of forward going fragments. The cross sections show a rapid increase with the number of neutrons in the projectile. Since the production of nitrogen is mostly due to charge exchange reactions below the proton separation energies, the present data suggests a concentration of Gamow-Teller and Fermi transition strength at low excitation energies for neutron-rich isotopes. It was also observed that the cross sections were enhanced much more strongly for neutron rich isotopes in the C-target data.

  11. On strontium isotopic anomalies and odd-A p-process abundances. [in solar system

    NASA Technical Reports Server (NTRS)

    Clayton, D. D.

    1978-01-01

    Several aspects of the nucleosynthesis of Sr isotopes are considered in an attempt to shed light on the problem of the Sr isotopic anomalies discovered in an inclusion of the Allende meteorite. Decomposition of the Sr isotopes into average r-, s-, and p-process nucleosynthetic classes is performed. It is suggested that the Allende inclusion most likely has an excess of s-process Sr and that the initial Sr-87/Sr-86 isotopic ratio is probably slightly more primitive than basaltic achondrites. The results also show that Sn-115 is mostly due to the r-process and that odd-A yields are very small. It is concluded that if the Sr anomaly in the inclusion is an average s enhancement, it argues somewhat in favor of a model of gas/dust fractionation of s and r isotopes during accumulation of the inclusion parent in the protosolar cloud.

  12. On the Stability and Abundance of Single Walled Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Hedman, Daniel; Reza Barzegar, Hamid; Rosén, Arne; Wågberg, Thomas; Andreas Larsson, J.

    2015-11-01

    Many nanotechnological applications, using single-walled carbon nanotubes (SWNTs), are only possible with a uniform product. Thus, direct control over the product during chemical vapor deposition (CVD) growth of SWNT is desirable, and much effort has been made towards the ultimate goal of chirality-controlled growth of SWNTs. We have used density functional theory (DFT) to compute the stability of SWNT fragments of all chiralities in the series representing the targeted products for such applications, which we compare to the chiralities of the actual CVD products from all properly analyzed experiments. From this comparison we find that in 84% of the cases the experimental product represents chiralities among the most stable SWNT fragments (within 0.2?eV) from the computations. Our analysis shows that the diameter of the SWNT product is governed by the well-known relation to size of the catalytic nanoparticles, and the specific chirality is normally determined by the product’s relative stability, suggesting thermodynamic control at the early stage of product formation. Based on our findings, we discuss the effect of other experimental parameters on the chirality of the product. Furthermore, we highlight the possibility to produce any tube chirality in the context of recent published work on seeded-controlled growth.

  13. On the Stability and Abundance of Single Walled Carbon Nanotubes

    PubMed Central

    Hedman, Daniel; Reza Barzegar, Hamid; Rosén, Arne; Wågberg, Thomas; Andreas Larsson, J.

    2015-01-01

    Many nanotechnological applications, using single-walled carbon nanotubes (SWNTs), are only possible with a uniform product. Thus, direct control over the product during chemical vapor deposition (CVD) growth of SWNT is desirable, and much effort has been made towards the ultimate goal of chirality-controlled growth of SWNTs. We have used density functional theory (DFT) to compute the stability of SWNT fragments of all chiralities in the series representing the targeted products for such applications, which we compare to the chiralities of the actual CVD products from all properly analyzed experiments. From this comparison we find that in 84% of the cases the experimental product represents chiralities among the most stable SWNT fragments (within 0.2?eV) from the computations. Our analysis shows that the diameter of the SWNT product is governed by the well-known relation to size of the catalytic nanoparticles, and the specific chirality is normally determined by the product’s relative stability, suggesting thermodynamic control at the early stage of product formation. Based on our findings, we discuss the effect of other experimental parameters on the chirality of the product. Furthermore, we highlight the possibility to produce any tube chirality in the context of recent published work on seeded-controlled growth. PMID:26581125

  14. PoS(NIC-IX)150 Present-Day Carbon Abundances

    E-print Network

    Przybilla, Norbert

    both topics even in galaxies beyond our own. Unfortunately the history of carbon abundance.g. observations of main sequence stars in the Magellanic Clouds, which have become feasible recently-formation computations. These are based on line-blanketed plane-parallel, homogeneous and hydrostatic LTE model

  15. Abundant and Stable Char Residues in Soils: Implications for Soil Fertility and Carbon Sequestration

    E-print Network

    Lehmann, Johannes

    Abundant and Stable Char Residues in Soils: Implications for Soil Fertility and Carbon earths in Amazonia that were enriched with char >800 years ago) consist predominantly of char residues% of organic C). Our findings indicate that these oxidized char residues represent a particularly stable

  16. The abundance and excitation of the carbon chains in interstellar molecular clouds

    NASA Technical Reports Server (NTRS)

    Bujarrabal, V.; Guelin, M.; Morris, M.; Thaddeus, P.

    1981-01-01

    Emission lines from the carbon chains HC3N, HC5N, HC7N and HC9N were observed at 3 mm, 7 mm, and 1.4 cm in a number of dark clouds, Orion A and IRC(plus)10216. Non-LTE models were constructed to describe excitation and column densities. Component models for the Taurus dark cloud TMC-1 suggested that relative molecular abundances do not vary substantially along the cloud ridge, whereas the H2 density does by a factor of three. Data available for other dark clouds showed that the decrease in abundance with length from one carbon chain to the next is nearly constant, being close to 2.3. The decline in carbon chain abundance with length is steeper in Orion KL than in dark clouds by a factor of approximately four. Abundance ratios derived for the carbon star IRC(plus)10216 are uncertain, due to difficulties in modeling excitation rates in this environment.

  17. Carbon isotopic evidence for methane hydrate instability during quaternary interstadials

    PubMed

    Kennett; Cannariato; Hendy; Behl

    2000-04-01

    Large (about 5 per mil) millennial-scale benthic foraminiferal carbon isotopic oscillations in the Santa Barbara Basin during the last 60,000 years reflect widespread shoaling of sedimentary methane gradients and increased outgassing from gas hydrate dissociation during interstadials. Furthermore, several large, brief, negative excursions (up to -6 per mil) coinciding with smaller shifts (up to -3 per mil) in depth-stratified planktonic foraminiferal species indicate massive releases of methane from basin sediments. Gas hydrate stability was modulated by intermediate-water temperature changes induced by switches in thermohaline circulation. These oscillations were likely widespread along the California margin and elsewhere, affecting gas hydrate instability and contributing to millennial-scale atmospheric methane oscillations. PMID:10753115

  18. Abundance anomalies of carbon and nitrogen in the IUE spectra of Algol-type interacting binaries

    NASA Technical Reports Server (NTRS)

    Mccluskey, Carolina P. S.

    1990-01-01

    There are two primary ways in which the products of nucleosynthesis in stellar interiors may appear at the surface of a star. These are mixing and/or loss of the original unburned stellar envelope. In interacting binaries, overflow can contribute dramatically to envelope loss. The simplest abundance anomalies to be expected from nuclear burning of hydrogen, helium, or carbon would be under or over abundances H, He, C, O, Ne, and Mg. In addition, it is expected that carbon is initially severely depleted, while nitrogen is enhanced during hydrogen burning via the CNO cycle in stars above two solar masses. Other, more subtle anomalies are also expected, and elements heavier than magnesium can be created during very late evolution by nuclear burning in massive stars. Consequently, it is expected that abundance anomalies of various kinds should occur in interacting binaries where one or both stars have lost significant amounts of mass.

  19. Elucidating carbon uptake from vinyl chloride using stable isotope probing and Illumina sequencing.

    PubMed

    Paes, Fernanda; Liu, Xikun; Mattes, Timothy E; Cupples, Alison M

    2015-09-01

    Vinyl chloride (VC), a known human carcinogen, is a common and persistent groundwater pollutant at many chlorinated solvent contaminated sites. The remediation of such sites is challenging because of the lack of knowledge on the microorganisms responsible for in situ VC degradation. To address this, the microorganisms involved in carbon assimilation from VC were investigated in a culture enriched from contaminated site groundwater using stable isotope probing (SIP) and high-throughput sequencing. The mixed culture was added to aerobic media, and these were amended with labeled ((13)C-VC) or unlabeled VC ((12)C-VC). The cultures were sacrificed on days 15, 32, and 45 for DNA extraction. DNA extracts and SIP ultracentrifugation fractions were subject to sequencing as well as quantitative PCR (qPCR) for a functional gene linked to VC-assimilation (etnE). The gene etnE encodes for epoxyalkane coenzyme M transferase, a critical enzyme in the pathway for VC degradation. The relative abundance of phylotypes was compared across ultracentrifugation fractions obtained from the (13)C-VC- and (12)C-VC-amended cultures. Four phylotypes were more abundant in the heavy fractions (those of greater buoyant density) from the (13)C-VC-amended cultures compared to those from the (12)C-VC-amended cultures, including Nocardioides, Brevundimonas, Tissierella, and Rhodoferax. Therefore, both a previously identified VC-assimilating genus (Nocardioides) and novel microorganisms were responsible for carbon uptake. Enrichment of etnE with time was observed in the heavy fractions, and etnE sequences illustrated that VC-assimilators harbor similar Nocardioides-like etnE. This research provides novel data on the microorganisms able to assimilate carbon from VC. PMID:25981993

  20. Stable carbon isotopic apportionment of individual PAH in sediments from marine and estuarine environments

    SciTech Connect

    O`Malley, V.P.; Abrajano, T.A. Jr.; Hellou, J.

    1995-12-31

    Much interest has recently focused on the quantitative apportionment of multiple sources of organic contaminants in natural aquatic systems. Polycyclic aromatic hydrocarbons (PAH) are of great interest in this regard because in addition to their suspected toxic and carcinogenic properties, they also have a wide range of potential natural and anthropogenic sources. Here we present the results of a study where the primary source inputs of PAH to sediments of a Harbor and Estuary are quantitatively assessed using a combination of molecular abundance and carbon isotope measurements of individual (4- and 5-ring) PAH. Mass balance calculations using a simple two-component mixing model show that approximately 50 to 80% of the PAH input to the Harbour sediments is of combustion origin, and likely dominated by vehicular emissions. Direct petrogenic contribution, possibly crankcase oil, accounts for the remaining 20 to 50% of the total PAH input. PAH inputs to the Estuary seemed to be predominately of wood combustion origin but the presence of an unidentified isotopically depleted PAH source was also apparent.

  1. Carbon isotope systematics of individual hydrocarbons in hydrothermal petroleum from Escanaba Trough, Northeastern Pacific Ocean

    USGS Publications Warehouse

    Simoneit, B.R.T.; Schoell, M.; Kvenvolden, K.A.

    1997-01-01

    We submitted individual aliphatic and polycyclic aromatic hydrocarbons in samples of hydrothermal petroleum from Escanaba trough to compound specific isotope analysis to trace their origins. The carbon isotope compositions of the alkanes and polycyclic aromatic hydrocarbons (means -27.5 and -24.7%, respectively) reflect a primarily terrestrial organic matter source.We submitted individual aliphatic and polycyclic aromatic hydrocarbons in samples of hydrothermal petroleum from Escanaba Trough to compound specific isotope analysis to trace their origins. The carbon isotope compositions of the alkanes and polycyclic aromatic hydrocarbons (means -27.5 and -24.7 per mill, respectively) reflect a primarily terrestrial organic matter source.

  2. Effects of environmental and biotic factors on carbon isotopic fractionation during decomposition of soil organic matter

    PubMed Central

    Wang, Guoan; Jia, Yufu; Li, Wei

    2015-01-01

    Decomposition of soil organic matter (SOM) plays an important role in the global carbon cycle because the CO2 emitted from soil respiration is an important source of atmospheric CO2. Carbon isotopic fractionation occurs during SOM decomposition, which leads to 12C to enrich in the released CO2 while 13C to enrich in the residual SOM. Understanding the isotope fractionation has been demonstrated to be helpful for studying the global carbon cycle. Soil and litter samples were collected from soil profiles at 27 different sites located along a vertical transect from 1200 to 4500?m above sea level (a.s.l.) in the south-eastern side of the Tibetan Plateau. Their carbon isotope ratios, C and N concentrations were measured. In addition, fiber and lignin in litter samples were also analyzed. Carbon isotope fractionation factor (?) during SOM decomposition was estimated indirectly as the slope of the relationship between carbon isotope ratios of SOM and soil C concentrations. This study shows that litter quality and soil water play a significant role in isotope fractionation during SOM decomposition, and the carbon isotope fractionation factor, ?, increases with litter quality and soil water content. However, we found that temperature had no significant impact on the ? variance. PMID:26056012

  3. Effects of environmental and biotic factors on carbon isotopic fractionation during decomposition of soil organic matter

    NASA Astrophysics Data System (ADS)

    Wang, Guoan; Jia, Yufu; Li, Wei

    2015-06-01

    Decomposition of soil organic matter (SOM) plays an important role in the global carbon cycle because the CO2 emitted from soil respiration is an important source of atmospheric CO2. Carbon isotopic fractionation occurs during SOM decomposition, which leads to 12C to enrich in the released CO2 while 13C to enrich in the residual SOM. Understanding the isotope fractionation has been demonstrated to be helpful for studying the global carbon cycle. Soil and litter samples were collected from soil profiles at 27 different sites located along a vertical transect from 1200 to 4500?m above sea level (a.s.l.) in the south-eastern side of the Tibetan Plateau. Their carbon isotope ratios, C and N concentrations were measured. In addition, fiber and lignin in litter samples were also analyzed. Carbon isotope fractionation factor (?) during SOM decomposition was estimated indirectly as the slope of the relationship between carbon isotope ratios of SOM and soil C concentrations. This study shows that litter quality and soil water play a significant role in isotope fractionation during SOM decomposition, and the carbon isotope fractionation factor, ?, increases with litter quality and soil water content. However, we found that temperature had no significant impact on the ? variance.

  4. Oxygen isotopic abundances in calcium- aluminum-rich inclusions from ordinary chondrites: implications for nebular heterogeneity.

    PubMed

    McKeegan, K D; Leshin, L A; Russell, S S; MacPherson, G J

    1998-04-17

    The oxygen isotopic compositions of two calcium-aluminum-rich inclusions (CAIs) from the unequilibrated ordinary chondrite meteorites Quinyambie and Semarkona are enriched in 16O by an amount similar to that in CAIs from carbonaceous chondrites. This may indicate that most CAIs formed in a restricted region of the solar nebula and were then unevenly distributed throughout the various chondrite accretion regions. The Semarkona CAI is isotopically homogeneous and contains highly 16O-enriched melilite, supporting the hypothesis that all CAI minerals were originally 16O-rich, but that in most carbonaceous chondrite inclusions some minerals exchanged oxygen isotopes with an external reservoir following crystallization. PMID:9545215

  5. Sniffing for Clues to the Dinosaurs Demise: Measurement of Osmium Isotope Compositions and Platinum Group Element Abundances in Volcanic Emissions

    NASA Astrophysics Data System (ADS)

    Sims, K. W.; Peucker-Ehrenbrink, B.; Mather, T.; Pyle, D.; Martin, R.; Gauthier, P.; Aiuppa, A.

    2005-12-01

    Platinum Group Elements (PGE: Os, Ir, Rh, Ru, Pt, Pd) and osmium isotopes measured in marine and terrestrial sediment, snow and ice records are important paleo-tracers of riverine, hydrothermal, extraterrestrial, volcanic and anthropogenic inputs into the global surficial environment. For instance, the marine Os isotope record across the Cretaceous-Tertiary Boundary (KTB) indicates that the onset of the main phase of Deccan volcanism and the transient late Maastrichtian warming preceded the large extraterrestrial impact and the related KTB mass extinction by several hundred thousand years [Ravizza and Peucker-Ehrenbrink, 2003]. Distinguishing extraterrestrial from volcanic PGE sources has been difficult due to the similarity in Os isotopic compositions, complex PGE fractionations, and our lack of knowledge of the Os isotopic composition and PGE abundances in volcanic aerosols. These difficulties have fueled vigorous debate about extraterrestrial vs. volcanic triggers of mass extinctions in the geologic record. To assess the volcanic contribution to the global Re-Os-PGE cycle we have initiated a study of Os isotopic compositions and PGE abundances in volcanic emissions from volcanoes around the globe. Here we report preliminary data on PGE abundances and Os isotopes measured in gas and aerosol filter samples from Vulcan Masaya, Nicaragua and Mt Etna, Italy. Samples were analyzed by ID-ICPMS (ThermoFinnigan ELEMENT 2 and NEPTUNE) at the Woods Hole Oceanographic Institution. Osmium isotope compositions of the filters are unradiogenic (0.1272 to 0.187). Osmium concentrations range from 28 to 97 pg/cubic meter and are 3-4 orders of magnitude lower than those measured by Krahenbuhl et al. [1992] during the spring 1984 eruption of Mauna Loa just after the lava fountaining phase. Normalized PGE abundance patterns are fractionated relative to carbonaceous chondrites and two important features distinguish the pattern from other important PGE sources: 1) Os/Ir is much higher than that of the continental crust, the mantle and extraterrestrial matter; and 2) Pt/Pd is much lower than that of the continental crust, mantle, extraterrestrial matter and catalytic converters. If these PGE patterns from Masaya and Etna are typical of volcanic emissions worldwide they indicate that volcanic emission PGE patterns are distinct from the globally integrated KTB patterns [Tredoux et al. 1989; Evans et al., 1993] and that a volcanic source is not the cause of the elevated PGE abundances across the KTB. The PGE pattern of volcanic emissions is also different from catalytic converters enabling us to distinguish between volcanic sources and contamination from catalytic converters in places such as the Greenland Ice sheet [Barbante et al., 2001]. While these data have important implications for understanding the contribution of volcanic emissions to the global Re-Os-PGE cycles they need to be augmented with further analyses from other volcanoes.

  6. Diffusional Contribution to Carbon Isotope Fractionation during Dark CO2 Fixation in CAM Plants 1

    PubMed Central

    O'Leary, Marion H.; Osmond, C. Barry

    1980-01-01

    A mathematical model is developed which can be used to predict in vivo carbon isotope fractionations associated with carbon fixation in plants in terms of diffusion, CO2 hydration, and carboxylation components. This model also permits calculation of internal CO2 concentration for comparison with results of gas-exchange experiments. The isotope fractionations associated with carbon fixation in Kalanchoë daigremontiana and Bryophyllum tubiflorum have been measured by isolation of malic acid following dark fixation and enzymic determination of the isotopic composition of carbon-4 of this material. Corrections are made for residual malic acid, fumarase activity, and respiration. Comparison of these data with calculations from the model indicates that the rate of carbon fixation is limited principally by diffusion, rather than by carboxylation. Processes subsequent to the initial carboxylation also contribute to the over-all isotopic composition of the plant. PMID:16661555

  7. Stable carbon isotope discrimination and microbiology of methane formation in tropical anoxic lake sediments

    NASA Astrophysics Data System (ADS)

    Conrad, R.; Noll, M.; Claus, P.; Klose, M.; Bastos, W. R.; Enrich-Prast, A.

    2011-03-01

    Methane is an important end product of degradation of organic matter in anoxic lake sediments. Methane is mainly produced by either reduction of CO2 or cleavage of acetate involving different methanogenic archaea. The contribution of the different methanogenic paths and of the diverse bacteria and archaea involved in CH4 production exhibits a large variability that is not well understood. Lakes in tropical areas, e.g. in Brazil, are wetlands with high potential impact on the global CH4 budget. However, they have hardly been studied with respect to methanogenesis. Therefore, we used samples from 16 different lake sediments in the Pantanal and Amazon region of Brazil to measure production of CH4, CO2, analyze the content of 13C in the products and in intermediately formed acetate, determine the abundance of bacterial and archaeal microorgansisms and their community composition and diversity by targeting the genes of bacterial and archaeal ribosomal RNA and of methyl coenzyme M reductase, the key enzyme of methanogenic archaea. These experiments were done in the presence and absence of methyl fluoride, an inhibitor of acetoclastic methanogenesis. While production rates of CH4 and CO2 were correlated to the content of organic matter and the abundance of archaea in the sediment, values of 13C in acetate, CO2, and CH4 were related to the 13C content of organic matter and to the path of CH4 production with its intrinsic carbon isotope fractionation. Isotope fractionation was small (average 10‰) for conversion of Corg to acetate-methyl, which was hardly further fractionated during CH4 production. However, fractionation was strong for CO2 conversion to CH4 (average 75‰), which generally accounted for >50% of total CH4 production. Canonical correspondence analysis did not reveal an effect of microbial community composition, despite the fact that it exhibited a pronounced variability among the different sediments.

  8. Stable carbon isotope discrimination and microbiology of methane formation in tropical anoxic lake sediments

    NASA Astrophysics Data System (ADS)

    Conrad, R.; Noll, M.; Claus, P.; Klose, M.; Bastos, W. R.; Enrich-Prast, A.

    2010-11-01

    Methane is an important end product of degradation of organic matter in anoxic lake sediments. Methane is mainly produced by either reduction of CO2 or cleavage of acetate involving different methanogenic archaea. The contribution of the different methanogenic paths and of the diverse bacteria and archaea involved in CH4 production exhibits a large variability that is not well understood. Lakes in tropical areas, e.g. in Brazil, are wetlands with high potential impact on the global CH4 budget. However, they have hardly been studied with respect to methanogenesis. Therefore, we used samples from 16 different lake sediments in the Pantanal and Amazon region of Brazil to measure production of CH4, CO2, analyze the content of 13C in the products and in intermediately formed acetate, determine the abundance of bacterial and archaeal microorgansisms and their community composition and diversity by targeting the genes of bacterial and archaeal ribosomal RNA and of methyl coenzyme M reductase, the key enzyme of methanogenic archaea. These experiments were done in the presence and absence of methyl fluoride, an inhibitor of acetoclastic methanogenesis. While production rates of CH4 and CO2 were correlated to the content of organic matter and the abundance of archaea in the sediment, values of 13C in acetate and CH4 were related to the 13C content of organic matter and to the path of CH4 production with its intrinsic carbon isotope fractionation. Isotope fractionation was small (average 10‰) for conversion of Corg to acetate-methyl, which was hardly further fractionated during CH4 production. However, fractionation was strong for CO2 conversion to CH4 (average 75‰), which generally accounted for >50% of total CH4 production. Canonical correspondence analysis did not reveal an effect of microbial community composition, despite the fact that it exhibited a pronounced variability among the different sediments.

  9. Stable carbon isotope discrimination and microbiology of methane formation in tropical anoxic lake sediments

    NASA Astrophysics Data System (ADS)

    Conrad, R.; Noll, M.; Claus, P.; Klose, M.; Enrich-Prast, A.

    2010-12-01

    Methane is an important end product of degradation of organic matter in anoxic lake sediments. Methane is produced by either reduction of CO2 or cleavage of acetate involving different methanogenic archaea. The contribution of the different methanogenic paths and of the diverse bacteria and archaea involved in CH4 production exhibits a large variability that is not well understood. Lakes in tropical areas, e.g. in Brazil, are wetlands with high potential impact on the global CH4 budget. However, they have hardly been studied with respect to methanogenesis. Therefore, we used samples from 16 different lake sites in the Pantanal and Amazon region of Brazil to measure production of CH4, CO2, analyze the content of 13C in the products and in intermediately formed acetate, determine the abundance of bacterial and archaeal microorganisms and their community composition and diversity by targeting the genes of bacterial and archaeal ribosomal RNA and of methyl coenzyme M reductase, the key enzyme of methanogenic archaea. These experiments were done in the presence and absence of methyl fluoride, an inhibitor of acetoclastic methanogenesis. While production rates of CH4 and CO2 were correlated to the content of organic matter and the abundance of archaea in the sediment, values of 13C in acetate and CH4 were related to the 13C content of organic matter and to the path of CH4 production with its intrinsic carbon isotope fractionation. Isotope fractionation was small (average 10‰) for conversion of C-org to acetate-methyl, which was hardly further fractionated during CH4 production. However, fractionation was strong for CO2 conversion to CH4 (average 75‰), which generally accounted for >50% of total CH4 production. Canonical correspondence analysis did not reveal an effect of microbial community composition, despite the fact that it exhibited a pronounced variability among the different sediments.

  10. Carbonate "Clumped" Isotope Determination of Seawater Temperature During the End-Triassic Extinction Event

    NASA Astrophysics Data System (ADS)

    Gammariello, R. T., Jr.; Petryshyn, V. A.; Ibarra, Y.; Greene, S. E.; Corsetti, F. A.; Bottjer, D. J.; Tripati, A.

    2014-12-01

    Stromatolites are laminated sedimentary structures that are commonly thought to be created by cyanobacteria, either through the trapping and binding of sediment, or through metabolically-induced precipitation. However, stromatolite formation is poorly understood. In general, stromatolite abundance was higher in the Proterozoic than the Phanerozoic, but notable increases in stromatolite abundance occur in association with Phanerozoic mass extinction events. Here, we focus on stromatolites from the latest Triassic Cotham Marble (United Kingdom) that are associated with the extinction interval. The end-Triassic mass extinction is coincident with large-scale volcanism in the Central Atlantic Magmatic Province (CAMP) and the associated breakup of Pangea. Some hypothesize that CAMP-associated increases in atmospheric CO2 led to a rise in global temperatures and ocean acidification that caused or enhanced the extinction. In order to quantify the role of climate change with respect to the end-Triassic mass extinction, we applied the carbonate "clumped" isotope paleothermometer to the well-preserved Cotham Marble stromatolites. The stromatolites were deposited in the shallow Tethys Sea, and today occur in several localities across the southwestern UK. The stromatolites alternate on the cm scale between laminated and dendrolitic microstructures and each was microdrilled for clumped isotope analysis. The two microstructures display different temperatures of formation, where the dendrolitic portions apparently grew under cooler conditions than laminated layers, and younger layers grew in cooler conditions than older layers. Our results suggest that temperature fluctuated and potentially trended towards amelioration of the warm temperatures during the deposition of the Cotham Marble.

  11. Stable carbon isotope evidence for nitrogenous fertilizer impact on carbonate weathering in a small agricultural watershed.

    PubMed

    Brunet, F; Potot, C; Probst, A; Probst, J-L

    2011-10-15

    The isotopic signature of Dissolved Inorganic Carbon (DIC), ?(13)C(DIC), has been investigated in the surface waters of a small agricultural catchment on calcareous substratum, Montoussé, located at Auradé (south-west France). The Montoussé catchment is subjected to intense farming (wheat/sunflower rotation) and a moderated application of nitrogenous fertilizers. During the nitrification of the NH(4)(+), supplied by fertilization, nitrate and H(+) ions are produced in the soil. This anthropogenic acidity is combined with the natural acidity due to carbonic acid in weathering processes. From an isotopic point of view, with 'natural weathering', using carbonic acid, ?(13)C(DIC) is intermediate between the ?(13)C of soil CO(2) produced by organic matter oxidation and that of the carbonate rocks, while it has the same value as the carbonates when carbonic acid is substituted by another acid like nitric acid derived from nitrogen fertilizer. The ?(13)C(DIC) values range from -17.1‰ to -10.7‰ in Montoussé stream waters. We also measured the ?(13)C of calcareous molassic deposits (average -7.9‰) and of soil organic carbon (between -24.1‰ and -26‰) to identify the different sources of DIC and to estimate their contribution. The ?(13) C(DIC) value indicates that weathering largely follows the carbonic acid pathway at the springs (sources of the stream). At the outlet of the basin, H(+) ions, produced during the nitrification of N-fertilizer, also contribute to weathering, especially during flood events. This result is illustrated by the relationship between ?(13)C(DIC) and the molar ratio NO(3)(-)/(Ca(2+) + Mg(2+)). Consequently, when the contribution of nitrate increases, the ?(13)C(DIC) increases towards the calcareous end-member. This new isotopic result provides evidence for the direct influence of nitrogen fertilizer inputs on weathering, CO(2) consumption and base cation leaching and confirms previous results obtained using the chemistry of the major ions present in the field, and in soil column experiments. PMID:21913244

  12. Calculation of isotope shifts and relativistic shifts in C I, C II, C III, and C IV J. C. Berengut*

    E-print Network

    Titov, Anatoly

    Calculation of isotope shifts and relativistic shifts in C I, C II, C III, and C IV J. C. Berengut of calculating isotope shifts and relativistic shifts in atomic spectra. We test the method on neutral carbon the lifetime of the Universe. Carbon isotope shifts can be used to measure isotope abundances in gas clouds

  13. A molecular organic carbon isotope record of miocene climate changes

    SciTech Connect

    Schoell, M. ); Schouten, S.; Sinninghe Damste', J.S.; Leeuw, J.W. de ); Summons, R.E. )

    1994-02-25

    The difference in carbon-13 ([sup 13]C) contents of hopane and sterane biomarkers in the Monterey formation (Naples Beach, California) parallels the Miocene inorganic record of the change in [sup 18]O ([delta][sup 18]O), reflecting the Miocene evolution from a well-mixed to a highly stratified photic zone (upper 100 meters) in the Pacific. Steranes ([delta][sup 13]C = 25.4 [+-] 0.7 per mil versus the Pee Dee belemnite standard) from shallow photic-zone organisms do not change isotopically throughout the Miocene. In contrast, sulfur-bound C[sub 35] hopanes (likely derived from bacterial plankton living at the base of the photic zone) have systematically decreasing [sup 13]C concentrations in Middle and Late Miocene samples ([delta][sup 13]C = 29.5 to [minus]31.5 per mil), consistent with the Middle Miocene formation of a carbon dioxide-rich cold water mass at the base of the photic zone.

  14. Short-term carbon isotopic fractionation in plants

    SciTech Connect

    Rooney, M.A.

    1988-01-01

    A system was developed for measuring carbon isotopic fractionation in plants over a time interval of 1-3 hours, in contrast to leaf combustion studies which give long-term, integrated discrimination measurements. The system was used to study environmental effects on soybean (Glycine max) and corn (Zea mays) discrimination. Changes in leaf temperature, photon flux density (PFD), O{sub 2} concentration, and CO{sub 2} concentration produced little or no change in measured discrimination ({Delta}). For soybean, {Delta} increased with decreasing PFD. For corn, {Delta} decreased with decreasing O{sub 2} concentration. For both soybean and corn, {Delta} increased with increasing CO{sub 2} concentration. These changes in {Delta} were interpreted as environmental effects on stomatal conductance and photosynthetic capacity, which indirectly affect {Delta} by altering C{sub i}/C{sub a}. Respiratory discrimination in the dark and light was also investigated. Respired CO{sub 2} was 5{per thousand} and 0-1{per thousand} more positive than leaf carbon for soybean and corn, respectively. Photorespiratory discrimination was 6-7{per thousand} for soybean, supporting the contention that glycine decarboxylase may be the source of discrimination in the photorespiratory pathway.

  15. Spatial Variability in Instantaneous Photosynthetic Carbon and Oxygen Isotope Discrimination

    NASA Astrophysics Data System (ADS)

    Barbour, M. M.

    2007-12-01

    Stable carbon and oxygen isotope ratios of CO2 are useful tracers in studies of carbon and water cycling between the terrestrial biosphere and the atmosphere. Interpretation of variation in 13CO2 and C16O18O relies on models describing physical and biochemical processes and their associated fractionations. A layer of complexity not currently quantified or accounted for in canopy models is spatial variation in photosynthetic discrimination within a single leaf. A new measurement technique, employing tunable diode laser absorption spectrometry coupled to an open gas exchange system, enables online measurement of photosynthetic discrimination at high temporal resolution. Using this system, photosynthetic 13C and 18O discrimination was measured along leaves of a C3 monocot. For the forage cereal Triticale, 13C discrimination increased by 2‰ and 18O by 20‰ from the base to the tip of mature leaves when measured at saturating irradiance. The increase in 13C discrimination was associated with an increase in the leaf internal conductance of CO2, and 18O discrimination with carry-forward of evaporative enrichment along the leaf. When numerical averages are compared to flux- and area-weighted averages, the portion of the leaf approximately one third of the way from the base can be shown to provide the most representative area for scaling up.

  16. Isotopic composition of Murchison organic compounds: Intramolecular carbon isotope fractionation of acetic acid. Simulation studies of cosmochemical organic syntheses

    NASA Technical Reports Server (NTRS)

    Yuen, G. U.; Cronin, J. R.; Blair, N. E.; Desmarais, D. J.; Chang, S.

    1991-01-01

    Recently, in our laboratories, samples of Murchison acetic acid were decarboxylated successfully and the carbon isotopic composition was measured for the methane released by this procedure. These analyses showed significant differences in C-13/C-12 ratios for the methyl and carboxyl carbons of the acetic acid molecule, strongly suggesting that more than one carbon source may be involved in the synthesis of the Murchison organic compounds. On the basis of this finding, laboratory model systems simulating cosmochemical synthesis are being studied, especially those processes capable of involving two or more starting carbon sources.

  17. Near-infrared spectroscopy of M dwarfs. I. CO molecule as an abundance indicator of carbon

    NASA Astrophysics Data System (ADS)

    Tsuji, Takashi; Nakajima, Tadashi

    2014-10-01

    Based on the near-infrared spectra of 42 M dwarfs, carbon abundances are determined from the ro-vibrational lines of the CO (2-0) band. We apply Teff values based on the angular diameters if available or use the Teff values in a log Teff-M3.4 relation (M3.4 is the absolute magnitude at 3.4 ?m based on the WISE W1 flux and the Hipparcos parallax) to estimate Teff values of objects for which angular diameters are unknown. Also, we discuss briefly the HR diagram of low-mass stars. On the observed spectrum of the M dwarf, the continuum is depressed by the numerous weak lines of H2O and only the depressed continuum or the pseudo-continuum can be seen. On the theoretical spectrum of the M dwarf, the true continuum can be evaluated easily but the pseudo-continuum can also be evaluated accurately thanks to the recent H2O line database. Then spectroscopic analysis of the M dwarf can be done by referring to the pseudo-continuum both on the observed and theoretical spectra. Since the basic principle of the spectroscopic analysis should be the same whether the true- or pseudo-continuum is referred to, the difficulty related to the continuum in cool stars can in principle be overcome. Then, the numerous CO lines can be excellent abundance indicators of carbon, since almost all the carbon atoms are in stable CO molecules which suffer little effect of the uncertainties in photospheric structure, and carbon abundances in late-type stars can best be determined in M dwarfs rather than in solar type stars. The resulting C/Fe ratios for most M dwarfs are nearly constant at about the solar value based on the classical high carbon abundance rather than on the recently revised lower value. This result implies that the solar carbon abundance is atypical for its metallicity among the stellar objects in the solar neighborhood if the downward revised carbon abundance is correct.

  18. On the volatile inventory of Titan from isotopic abundances in nitrogen and methane

    E-print Network

    Lorenz, Ralph D.

    the initial volatile abundances on Saturn's giant moon Titan. The nitrogen data are interpreted in terms that these data do not, in fact, strongly constrain the abundance of nitrogen present in Titan's early atmosphere of Saturn's largest moon by Voyager 1. As is the case for the issue of the origin of nitrogen, water

  19. Carbon and hydrogen isotope fractionation of benzene and toluene during hydrophobic sorption in multistep batch experiments.

    PubMed

    Imfeld, G; Kopinke, F-D; Fischer, A; Richnow, H-H

    2014-07-01

    The application of compound-specific stable isotope analysis (CSIA) for evaluating degradation of organic pollutants in the field implies that other processes affecting pollutant concentration are minor with respect to isotope fractionation. Sorption is associated with minor isotope fractionation and pollutants may undergo successive sorption-desorption steps during their migration in aquifers. However, little is known about isotope fractionation of BTEX compounds after consecutive sorption steps. Here, we show that partitioning of benzene and toluene between water and organic sorbents (i.e. 1-octanol, dichloromethane, cyclohexane, hexanoic acid and Amberlite XAD-2) generally exhibits very small carbon and hydrogen isotope effects in multistep batch experiments. However, carbon and hydrogen isotope fractionation was observed for the benzene-octanol pair after several sorption steps (??(13)C=1.6 ± 0.3‰ and ??(2)H=88 ± 3‰), yielding isotope fractionation factors of ?C=1.0030 ± 0.0005 and ?H=1.195 ± 0.026. Our results indicate that the cumulative effect of successive hydrophobic partitioning steps in an aquifer generally results in insignificant isotope fractionation for benzene and toluene. However, significant carbon and hydrogen isotope fractionation cannot be excluded for specific sorbate-sorbent pairs, such as sorbates with ?-electrons and sorbents with OH-groups. Consequently, functional groups of sedimentary organic matter (SOM) may specifically interact with BTEX compounds migrating in an aquifer, thereby resulting in potentially relevant isotope fractionation. PMID:24726480

  20. Abundances and isotopic compositions of rhenium and osmium in pyrite samples from the Huaibei coalfield, Anhui, China

    USGS Publications Warehouse

    Liu, Gaisheng; Chou, C.-L.; Peng, Z.; Yang, G.

    2008-01-01

    Two pyrite samples from the Shihezi Formation (Lower Permian), Huaibei coalfield, Anhui, China, have been analyzed for abundances and isotopic compositions of rhenium and osmium using negative thermal ion mass spectrometry. The Re-Os ages of the pyrites are 64.4 and 226 Ma, which are younger than the formation age of the coal seam. The pyrite samples may consist of pyrite formed at various stages during the history of coal formation. The ??Osvalues of the two pyrite samples are +17 and +18, respectively. Such high ??Osvalues are reported for the first time for recycles crustal materials from a sedimentary basin. ?? Springer-Verlag 2007.

  1. Measuring Carbon and Oxygen Isotope Uptake into Inorganic Calcite using Crystal Growth Experiments

    NASA Astrophysics Data System (ADS)

    Baker, E. B.; Watkins, J. M.

    2014-12-01

    Carbon and oxygen isotopes measured on natural calcite crystals provide a record of paleo-environment conditions. Despite the importance of measuring stable isotopes in calcite for paleo-environment reconstructions, there is neither a general theory nor an experimental data set that fully separates the effects of pH, temperature, and precipitation rate on isotope discrimination during calcite growth. Many stable isotope studies of calcite have focused on either carbon or oxygen isotope compositions individually, but few have measured both carbon and oxygen isotope uptake in the same set of crystals. We are precipitating inorganic calcite across a range in temperature, pH, and precipitation rate to guide the development of a general theory for combined carbon and oxygen isotope uptake into calcite crystals grown on laboratory timescales. In our experiments, dissolved inorganic carbon (DIC) is added to an aqueous solution (15 mM CaCl2 + 5 mM NH4Cl) by CO2 bubbling. Once a critical supersaturation is reached, calcite crystals nucleate spontaneously and grow on the beaker walls. A key aspect of this experimental approach is that the ?13C of DIC is relatively constant throughout the crystal growth period, because there is a continuous supply of DIC from the CO2-bearing bubbles. Carbonic anhydrase, an enzyme promoting rapid equilibration of isotopes between DIC and water, was added to ensure that the solution remained isotopically equilibrated during calcite growth. We have conducted experiments at T = 25°C and pH = 8.3 - 9.0. We observe that the fractionation of oxygen isotopes between calcite and water decreases with increasing pH, consistent with available data from experiments in which the enzyme carbonic anhydrase was used. Our results for carbon isotopes extend the available data set, which previously ranged from pH 6.62 to 7.75, to higher pH. At pH 8.3, we observe that calcite is isotopically heavier than DIC with respect to carbon isotopes by about 0.25‰. At pH 9.0, calcite is isotopically indistinguishable from, or perhaps slightly lighter than, DIC. We will present data from additional high-pH experiments and discuss the results in the context of recently developed ion-by-ion growth models for calcite.

  2. DOE's Enriched Background Isotope Study Data Improved a Classic Ecosystem Carbon Cycling Model

    E-print Network

    Post, Wilfred M.

    DOE's Enriched Background Isotope Study Data Improved a Classic Ecosystem Carbon Cycling Model functional mechanisms within the classic carbon cycling model ­ DayCent. · EBIS field studies quantified not currently included in forest carbon cycle models. · Major revisions to the DayCent model included (1) adding

  3. Iron and carbon isotope evidence for microbial iron respiration throughout the Archean

    E-print Network

    Iron and carbon isotope evidence for microbial iron respiration throughout the Archean Paul R: iron-formation Hamersley Isua iron carbonates iron respiration Banded Iron-Formations (BIFs that reaction between carbon and iron through microbial iron respiration [2Fe2O3nH2O+CH2O+7H+ 4Fe2+ + HCO3

  4. Carbon isotopes in the ocean model of the Community Earth System Model (CESM1)

    NASA Astrophysics Data System (ADS)

    Jahn, A.; Lindsay, K.; Giraud, X.; Gruber, N.; Otto-Bliesner, B. L.; Liu, Z.; Brady, E. C.

    2014-11-01

    Carbon isotopes in the ocean are frequently used as paleo climate proxies and as present-day geochemical ocean tracers. In order to allow a more direct comparison of climate model results with this large and currently underutilized dataset, we added a carbon isotope module to the ocean model of the Community Earth System Model (CESM), containing the cycling of the stable isotope 13C and the radioactive isotope 14C. We implemented the 14C tracer in two ways: in the "abiotic" case, the 14C tracer is only subject to air-sea gas exchange, physical transport, and radioactive decay, while in the "biotic" version, the 14C additionally follows the 13C tracer through all biogeochemical and ecological processes. Thus, the abiotic 14C tracer can be run without the ecosystem module, requiring significantly less computational resources. The carbon isotope module calculates the carbon isotopic fractionation during gas exchange, photosynthesis, and calcium carbonate formation, while any subsequent biological process such as remineralization as well as any external inputs are assumed to occur without fractionation. Given the uncertainty associated with the biological fractionation during photosynthesis, we implemented and tested three parameterizations of different complexity. Compared to present-day observations, the model is able to simulate the oceanic 14C bomb uptake and the 13C Suess effect reasonably well compared to observations and other model studies. At the same time, the carbon isotopes reveal biases in the physical model, for example a too sluggish ventilation of the deep Pacific Ocean.

  5. sup 13 C and sup 18 O isotopic disequilibrium in biological carbonates: II. In vitro simulation of kinetic isotope effects

    SciTech Connect

    McConnaughey, T. )

    1989-01-01

    Biological carbonates are built largely from CO{sub 2}, which diffuses across the skeletogenic membrane and reacts to form HCO{sub 3}{sup {minus}}. Kinetic discrimination against the heavy isotopes {sup 18}O and {sup 13}C during CO{sub 2} hydration and hydroxylation apparently causes most of the isotopic disequilibrium observed in biological carbonates. These kinetic isotope effects are expressed when the extracytosolic calcifying solution is thin and alkaline, and HCO{sub 3}{sup {minus}} precipitates fairly rapidly as CaCO{sub 3}. In vitro simulation of the calcifying environment produced heavy isotope depletions qualitatively similar to, but somewhat more extreme than, those seen in biological carbonates. Isotopic equilibration during biological calcification occurs through CO{sub 2} exchange across the calcifying membrane and by admixture ambient waters (containing HCO{sub 3}{sup {minus}}) into the calcifying fluids. Both mechanisms tend to produce linear correlations between skeletal {delta}{sup 13}C and {delta}{sup 18}O.

  6. Triple oxygen isotope composition of tropospheric carbon dioxide and terrestrial carbonates

    NASA Astrophysics Data System (ADS)

    Hofmann, M. E.; Horváth, B.; Pack, A.

    2011-12-01

    The triple oxygen isotope composition of tropospheric CO2 is a potential new tracer in urban air studies and for biosphere-atmosphere interactions [1]. In this study, we are analyzing CO2 from different provenances in order to trace the influx of anthropogenic CO2 to urban air and to test predictions on the stratosphere-troposphere exchange flux. Since July 2010, we are monitoring the triple oxygen isotope composition of CO2 in urban air in a two-week interval. For this purpose, carbon dioxide was extracted from ~450L of ambient air on the campus of the University of Göttingen using a Russian Doll type cryogenic trap [2]. The CO2 was analyzed by CO2-CeO2 equilibration at 685°C and subsequent IR laser fluorination of CeO2 and CF-irmMS [3]. All triple oxygen isotope data are reported as ?17OTFL values relative to the terrestrial fractionation line (TFL) with a slope ?TFL=0.5251 and an intercept ?TFL=-0.014%. On average, the ?17OTFL value of ambient CO2 was -0.11±0.05% (SD) with a seasonal cycle of 0.04±0.01%. Lower ?17O values were observed during wintertime. In order to test the potential of ?17O as a tracer for anthropogenic CO2, we analyzed CO2 from different combustion processes. Our results showed that the ?17O anomaly of tropospheric O2 [4] is passed on fully, or partially to the combustion CO2 [5]. We estimate that elevated anthropogenic emission during wintertime could be responsible for a decrease in ?17O of urban air CO2 of -0.02±0.01%. In order to predict the triple oxygen isotope composition of tropospheric CO2 on a global scale, we revised the box model calculation from Hoag et al. [1]. For the exponent ? for CO2-water equilibrium, we assume that ?CO2-water=0.522±0.001 [6]. Furthermore, we took into account that the ?17OTFL value of CO2 released from soils is affected by kinetic fractionation. Thus, we obtained a ?17OTFL value for global tropospheric CO2 of -0.13%. The model calculation agrees well with the ?17OTFL value determined for ambient air CO2. The triple oxygen isotope composition of terrestrial carbonates should provide additional information on the formation process of biogenic and abiotic carbonates. In order to determine the triple oxygen isotope composition on carbonates, phosphoric acid decomposition of carbonates was carried out. Subsequently, the liberated CO2 was also analyzed by the CO2-CeO2 equilibration method [3]. The ?17OTFL of CO2 released from Solnhofen limestone was -0.11±0.09% (SE, t0.95, n=6). We are currently determining the exponent ? for phosphoric acid decomposition. [1] Hoag, K.J., et al., Geophys. Res. Lett., 2005. 32: p. 1-5. [2] Brenninkmeijer, C.A.M. and T. Röckmann, Anal. Chem., 1996. 68(17): p. 3050-3053. [3] Hofmann, M. and A. Pack, Anal. Chem., 2010. 82: p. 4357-4361. [4] Barkan, E. and B. Luz, Rapid Commun. Mass Spec., 2005. 19(24): p. 3737-3742. [5] Horváth, B., M.E.G. Hofmann, and A. Pack, 2011. XI Isotope Workshop. Budapest. [6] Hofmann, M., et al., 2011. EGU. Vienna.

  7. Radioactive Carbon Isotope Monitoring System Based on Cavity Ring-down Laser Spectroscopy for Decommissioning Process of Nuclear Facilities

    NASA Astrophysics Data System (ADS)

    Tomita, Hideki; Watanabe, Kenichi; Takiguchi, Yu; Kawarabayashi, Jun; Iguchi, Tetsuo

    In decommissioning process of nuclear facilities, large amount of radioactive isotopes are discharged as waste. Radioactive carbon isotope (14C) is one of the key nuclides to determine the upper limit of concentration in the waste disposal. In particular, 14C on the graphite reactor decommissioning should be separated from stable carbon isotopes (12C and 13C) and monitored for the public health and safety. We propose an isotope analysis system based on cavity ring-down laser spectroscopy (CRDS) to monitor the carbon isotopes (12C, 13C and 14C) in the isotope separation process for the graphite reactor decommissioning. This system is compact and suitable for a continuous monitoring, because the concentration of molecules including the carbon isotope is derived from its photo absorbance with ultra high sensitive laser absorption spectroscopy. Here are presented the necessary conditions of CRDS system for 14C isotope analysis through the preliminary experimental results of 13C isotope analysis with a prototype system.

  8. The reduction and oxidation of ceria: A natural abundance triple oxygen isotope perspective

    NASA Astrophysics Data System (ADS)

    Hayles, Justin; Bao, Huiming

    2015-06-01

    Ceria (CeO2) is a heavily studied material in catalytic chemistry for use as an oxygen storage medium, oxygen partial pressure regulator, fuel additive, and for the production of syngas, among other applications. Ceria powders are readily reduced and lose structural oxygen when subjected to low pO2 and/or high temperature conditions. Such dis-stoichiometric ceria can then re-oxidize under higher pO2 and/or lower temperature by incorporating new oxygen into the previously formed oxygen site vacancies. Despite extensive studies on ceria, the mechanisms for oxygen adsorption-desorption, dissociation-association, and diffusion of oxygen species on ceria surface and within the crystal structure are not well known. We predict that a large kinetic oxygen isotope effect should accompany the release and incorporation of ceria oxygen. As the first attempt to determine the existence and the degree of the isotope effect, this study focuses on a set of simple room-temperature re-oxidation experiments that are also relevant to a laboratory procedure using ceria to measure the triple oxygen isotope composition of CO2. Triple-oxygen-isotope labeled ceria powders are heated at 700 °C and cooled under vacuum prior to exposure to air. By combining results from independent experimental sets with different initial oxygen isotope labels and using a combined mass-balance and triangulation approach, we have determined the isotope fractionation factors for both high temperature reduction in vacuum (?10-4 mbar) and room temperature re-oxidation in air. Results indicate that there is a 1.5‰ ± 0.8‰ increase in the ?18O value of ceria after being heated in vacuum at 700 °C for 1 h. When the vacuum is broken at room temperature, the previously heated ceria incorporates 3-19% of its final structural oxygen from air, with a ?18O value of 2.1-4.1+7.7 ‰ for the incorporated oxygen. The substantial incorporation of oxygen from air supports that oxygen mobility is high in vacancy-rich ceria during re-oxidation at room temperature. The quantified oxygen isotope fractionation factors are consistent with the direct involvement of O2 in the rate limiting step for ceria reoxidation in air at room temperature. While additional parameters may reduce some of the uncertainties in our approach, this study demonstrates that isotope effects can be an encouraging tool for studying oxygen transport kinetics in ceria and other oxides. In addition, our finding warns of the special cares and limits in using ceria as an exchange medium for laboratory triple oxygen isotope analysis of CO2 or other oxygen-bearing gases.

  9. Photosynthetic Carbon Isotope Discrimination Increases with Elevated CO2 in a Grassland Ecosystem

    NASA Astrophysics Data System (ADS)

    Zelikova, T. J.; Pendall, E.; Williams, D. G.; LeCain, D. R.

    2014-12-01

    Paleoecological reconstructions and land-surface ecosystem models assume that as atmospheric CO2 changes, photosynthetic carbon isotope discrimination and the ratio of leaf internal to ambient CO2 concentration (ci/ca) remains unchanged, but this assumption has rarely been tested. Atmospheric CO2 concentrations are expected to rise to at least 600ppm by the end of the 21st century, with global temperatures and precipitation regimes concurrently changing and interacting to influence plant photosynthetic gas exchange. In the PHACE (Prairie Heating and CO2 Enrichment) experiment, we examined the influence of elevated CO2, warming, and summer irrigation on carbon isotope discrimination among C3 and C4 graminoid and dicot species to understand species and ecosystem responses to over 7 years of experimental climate change. Carbon isotope discrimination increased for all species when exposed to elevated CO2, but this effect did not emerge until the third year of the experiment. In addition, though species inherently differed in their carbon isotope discrimination, their ranking remained stable under elevated CO2. Quantifying the relative importance of factors that influence plant carbon isotope discrimination can guide our understanding of how individual plant species, plant communities, and ecosystems may react to global change. Evidence that plant carbon isotope discrimination shifts with changes in atmospheric CO2 and temperature has important implications for interpretation of the paleo record from archival organic materials and for modeling carbon cycling processes in future environments.

  10. Dissolution of barite for the analysis of strontium isotopes and other chemical and isotopic variations using aqueous sodium carbonate

    USGS Publications Warehouse

    Breit, G.N.; Simmons, E.C.; Goldhaber, M.B.

    1985-01-01

    A simple procedure for preparing barite samples for chemical and isotopic analysis is described. Sulfate ion, in barite, in the presence of high concentrations of aqueous sodium carbonate, is replaced by carbonate. This replacement forms insoluble carbonates with the cations commonly in barite: Ba, Sr, Ca and Pb. Sulfate is released into the solution by the carbonate replacement and is separated by filtration. The aqueous sulfate can then be reprecipitated for analysis of the sulfur and oxygen isotopes. The cations in the carbonate phase can be dissolved by acidifying the solid residue. Sr can be separated from the solution for Sr isotope analysis by ion-exchange chromatography. The sodium carbonate used contains amounts of Sr which will affect almost all barite 87Sr 86Sr ratios by less than 0.00001 at 1.95?? of the mean. The procedure is preferred over other techniques used for preparing barite samples for the determination of 87Sr 86Sr ratios because it is simple, rapid and enables simultaneous determination of many compositional parameters on the same material. ?? 1985.

  11. Nonequilibrium clumped isotope signals in microbial methane

    E-print Network

    Wang, David T.

    Methane is a key component in the global carbon cycle with a wide range of anthropogenic and natural sources. Although isotopic compositions of methane have traditionally aided source identification, the abundance of its ...

  12. Towards an understanding of the carbon isotopic changes across the Toarcian oceanic anoxic event

    E-print Network

    Cohen, Alison Margaret

    2005-01-01

    A combination of bulk carbon, biomarker and compound specific isotopic analyses were used in order to investigate the changes which accompanied the deposition of black shales during the upper tenuicostatum and lower ...

  13. Analysis of the ecology of Anchialine Caves using carbon and nitrogen stable isotopes 

    E-print Network

    Pohlman, John William

    1995-01-01

    Carbon and nitrogen stable isotopes were used to investigate the biogeochemical and ecological processes that govern anchialine cave ecosystems in the Yucatan Peninsula, Quintana Roo, Mexico. Anchialine caves are subterranean passages...

  14. Stable Isotopes in Foraminiferal Carbonate Steve Cooke and Eelco J. Rohling

    E-print Network

    Rohling, Eelco

    the fundamental controls on 18 O and 13 C in foraminiferal carbonate. Several have only recently been discovered 2.1. Oxygen isotope ratios in sea water 2.1.1. Evaporation 2.1.2. Precipitation and atmospheric

  15. Carbon Isotope Compositions of Fatty Acids in Mussels from Newfoundland Estuaries

    NASA Astrophysics Data System (ADS)

    Murphy, Dena E.; Abrajano, Teofilo A.

    1994-09-01

    This paper examines the carbon isotopic compositions of free fatty acids of two species of mussels (i.e. Mytilus edulis and Modiolus modiolus) from two estuarine environments around Newfoundland. Gas chromatography and conventional isotope ratio mass spectrometry were employed to characterize bulk fatty acids and gas chromatography/combustion/isotope ratio mass spectrometry was utilized to characterize the carbon isotope compositions of individual fatty acids. The bulk fatty acid distribution (dominance of 16:0, 20:5n3, 22:6n3 and 16:1) and carbon isotopic compositions (-27·3 to -25·8 per mil) indicate a dominant marine phytoplankton dietary source for the mussels. In contrast to the narrow range of bulk fatty acid ? 13C values, up to 7 per mil variation in ? 13C of individual fatty acids was observed. In general, saturated fatty acids are isotopically heavier than corresponding mono- and polyunsaturates, consistent with previously suggested kinetic isotope effect associated with de novo desaturation reactions. The depletion of 13 C in 18:4n3 compared with 22:6n3 and 20:5n3 indicates a distinct dietary source for 18:4n3. The present study shows the potential for detailed assessment of carbon flow in benthic ecosystems using fatty acids and other compound classes by gas chromatography/combustion/isotope ratio mass spectrometry.

  16. Soil drying effects on the carbon isotope composition of soil respiration

    EPA Science Inventory

    Stable isotopes are used widely as a tool for determining sources of carbon (C) fluxes in ecosystem C studies. Environmental factors that change over time, such as moisture, can create dynamic changes in the isotopic composition of C assimilated by plants, and offers a unique opp...

  17. Isotopic analysis of tooth enamel carbonate from modern North American feral horses

    E-print Network

    Amundson, Ronald

    Isotopic analysis of tooth enamel carbonate from modern North American feral horses: implications from modern feral horses. We compared those values with the N13 C values of local vegetation and the N isotope analyses of fecal material and tooth enamel suggest that horses consumed primarily grass, but some

  18. Lipid Correction for Carbon Stable Isotope Analysis of Deep-sea Fishes

    EPA Science Inventory

    Lipid extraction is used prior to stable isotope analysis of fish tissues to remove variability in the carbon stable isotope ratio (d13C) caused by varying lipid content among samples. Our objective was to evaluate an application of a mass balance correction for the effect of lip...

  19. Spatial and Temporal Trends in Stable Carbon and Oxygen Isotope Ratios of Juvenile Winter Flounder

    EPA Science Inventory

    Isotopic ratios of fish otoliths have been used in numerous studies as natural tags or markers to aid the study of connectivity among fish populations. We investigated the use of spatial and temporal changes in the stable carbon and oxygen isotope ratios of otoliths to different...

  20. Evaporation and carbonic anhydrase activity recorded in oxygen isotope signatures of net CO2 fluxes from

    E-print Network

    Mencuccini, Maurizio

    Evaporation and carbonic anhydrase activity recorded in oxygen isotope signatures of net CO2 fluxes, it records the isotopic signal of water pools subjected to precipitation and evaporation events. The d18 O) progressive enrichment of water in the upper soil by evaporation, and (2) catalytic acceleration

  1. A New Method for Evaluating the Carbon Isotope Characteristics of Carbonate Formed Under Cryogenic Conditions Analogous to Mars

    NASA Technical Reports Server (NTRS)

    Niles, P. B.; Socki, R. A.; Hredzak, P. L.

    2007-01-01

    The two upcoming robotic missions to Mars, Phoenix and MSL, will both have the capability of measuring the carbon isotopic composition of CO2 in the martian atmosphere, as well as possible CO2 trapped in carbonate minerals in the Martian soil. Results from orbital and landed missions now clearly indicate that no large scale deposits of carbonate materials exist at the surface. However, some results from orbital remote sensing have been interpreted to indicate that carbonate minerals are present as fine particles interspersed at low concentrations (approx. 2%) in the martian dust. One likely mechanism for the production of these carbonates is during the freezing of transient water near the surface. Large deposits of near surface ice and photographic evidence for flowing water on the surface suggest that transient melting and refreezing of H2O is an active process on Mars. Any exposure of these fluids to the CO2 rich atmosphere should al-low the production of HCO3- solutions. Carbonates are likely precipitates from these solutions during freezing as extensive CO2 degassing, driven by the fluid s decreasing volume, drives CO2 out. This rapid CO2 degassing increases the pH of the solution and drives carbonate precipitation. It has been shown in previous studies that this rapid CO2 degassing also results in a kinetic isotopic fractionation where the CO2 gas has a much lighter isotopic composition causing a large isotope enrichment of C-13 in the precipitated carbonate. This kinetic isotope enrichment may be very common in the current martian environment, and may be a very important factor in understanding the very high deltaC-13 values of carbonates found in the martian meteorites. However, while previous studies have succeeded in generally quantifying the magnitude of this effect, detailed studies of the consistency of this effect, and the freezing rates needed to produce it are needed to understand any carbon isotope analyses from carbonate minerals in the martian soil or dust. This study demonstrates an innovative new method for measuring the isotopic composition of gas evolved from the freezing of carbonate solutions in real time, which allows for a much clearer view of the chemical processes involved. This method now sets the stage for detailed analysis of the chemical and isotopic mechanisms that produce cryogenic carbonates.

  2. Strontium and carbon isotope stratigraphy of the Late Jurassic shallow marine limestone in western Palaeo-Pacific, northwest Borneo

    E-print Network

    Gilli, Adrian

    Strontium and carbon isotope stratigraphy of the Late Jurassic shallow marine limestone in western-Pacific a b s t r a c t Strontium and carbon isotope stratigraphy was applied to a 202 m-thick shallow marine, which was deposited in the western Palaeo-Pacific. Strontium isotopic ratios of rudist specimens suggest

  3. PII S0016-7037(99)00097-6 Nitrogen and carbon isotopic ratios of chlorophyll from marine phytoplankton

    E-print Network

    Sachs, Julian P.

    PII S0016-7037(99)00097-6 Nitrogen and carbon isotopic ratios of chlorophyll from marine) Abstract--The relationship between the nitrogen and carbon isotopic ratios of chlorophyll a and total biomass was explored in cultured marine phytoplankton to assess the utility of chlorophyll as an isotopic

  4. Using compound-specific stable carbon isotope analysis to trace metabolism and trophic transfer of PCBs and PBDEs in fish from an e-waste site, South China.

    PubMed

    Zeng, Yan-Hong; Luo, Xiao-Jun; Yu, Le-Huan; Chen, Hua-Shan; Wu, Jiang-Ping; Chen, She-Jun; Mai, Bi-Xian

    2013-05-01

    Two fish species (mud carp and northern snakehead) forming a predator/prey relationship and sediment samples were collected from a pond contaminated by e-waste. The concentrations and stable carbon isotope ratios (?(13)C) of individual polychlorinated biphenyl (PCB) and polybrominated diphenyl ether (PBDE) congeners were measured to determine if compound-specific carbon isotope analysis (CSIA) could be used to provide insight into the metabolism and trophic dynamics of PCBs and PBDEs. Significant correlations were found in the isotopic data of PCB congeners between the sediment and the fish species and between the two fish indicating identical origin of PCBs in sediment and fish. Most PCB congeners in the fish species were enriched in (13)C compared with the PCB congeners in the sediments as a result of isotopic fractionation during the metabolism of PCBs in fish. The isotopic data of several PCB congeners showing isotopic agreement or isotopic depletion could be used for source apportionment or to trace the reductive dechlorination process of PCBs in the environment. The PCB isotopic data covaried more in the northern snakehead than in the mud carp when compared to the sediment, implying that a similar isotopic fractionation occurs from the prey to the predator fish for a PCB congener possibly due to similar metabolic pathways. The PBDE congener patterns differed in the three sample types with a high abundance of BDE209, 183, 99, and 47 in the sediment, BDE47, 153, and 49 in the mud carp and BDE47, 100, and 154 in the northern snakehead. The isotopic change of BDE congeners, such as BDE47 and BDE49, in two fish species, provides evidence for biotransformation of PBDEs in biota. The results of this study suggest that CSIA is a promising tool for deciphering the fate of PCBs and PBDEs in the environment. PMID:23560888

  5. Factors Affecting the Clumped Isotope Signature of Dissolved Inorganic Carbon and Carbonate Minerals

    NASA Astrophysics Data System (ADS)

    Hill, P. S.; Tripati, A. K.; Schauble, E. A.

    2011-12-01

    18O/16O ratios[a] and 13C-18O bond ordering[b] in many natural and synthetic carbonate minerals may reflect the extent of isotopic equilibration of dissolved inorganic carbon (DIC) species, rather than the crystalline equilibrium. In the simplest case where transport and surface-reaction steps do not impart their own fractionations, the clumped isotope signature (?47: the enrichment in per mil of 13C18O16O above the amount expected for a random distribution of isotopes among all CO2 isotopologues) of a carbonate mineral precipitating from solution would preserve the temperature of DIC equilibration at the time of precipitation. We examine the consequences of (1) the time scale of DIC equilibration and (2) precipitation rate on ?47 values of carbonate minerals, using electronic structure models of molecular clusters that approximate aqueous and crystalline chemical environments. Our use of cluster models for both the aqueous and the mineral phases of the clumped isotope system has the advantage of enabling us to compare aqueous and mineral systems with the same electronic structure methods, partially canceling systematic model errors. Fluid cluster models containing 21-32 water molecules are generated from periodic-boundary-condition molecular dynamics simulations. Mineral clusters are derived from measured crystal structures, with boundaries terminated by link atoms so as to retain Pauling bond strengths with severed distal lattice bonds[c]. Different combinations of density functional theory (DFT) methods and basis sets are compared. These studies, combined with concurrent controlled precipitation experiments, will add to our understanding of the extent of disequilibrium effects on clumping while providing a framework to include previous studies (such as the work of Guo et al. on the kinetic effects of CO2 dehydration and dehydroxyation and acid digestion[e]). [a] Zeebe, R.E. (2007) G3, 8, Q09002,; Zeebe, R.E. (1999) GCA 63, 2001-2007 [b] Tripati, A.K. et al., (2010) GCA 74 5697-5717 [c] Rustad et al., J. Phys. Chem. A (2008), 112, 542-555; [d] Guo, W., PhD thesis, California Institute of Technology (2009); Guo, W. et al., GCA 73 (2009) 7203-7225; Guo, W. et al., GCA Supp 72 (2008) A336; Schauble et al. (2006) GCA 70,1439-1456

  6. Carbon-14 and deuterium isotope effects in the borderline solvolysis of isopropyl. beta. -naphthalenesulfonate

    SciTech Connect

    Ando, T.; Yamataka, H.; Tamura, S.; Hanafusa, T.

    1982-10-06

    The present investigation verifies that ..cap alpha..- and ..beta..-carbon-14 kinetic isotope effects are sensitive to mechanistic changes in the borderline solvolysis. Model calculations of kinetic isotope effects using the observed data for all the carbons and deuteriums enables one to describe the variable transition-state structures of the solvolysis of simple secondary substrates, which is still a subject of much debate in recent years. A study along this line is now in progress.

  7. USE OF THE COMPOSITION AND STABLE CARBON ISOTOPE RATIO OF MICROBIAL FATTY ACIDS TO STUDY CARBON CYCLING

    EPA Science Inventory

    We use measurements of the concentration and stable carbon isotopic ratio (Gamma 13C) of individual microbial phospholipid fatty acids (PLFAS) in soils and sediments as indicators of live microbial biomass levels and microbial carbon source. For studies of soil organic matter (SO...

  8. USE OF STABLE CARBON ISOTOPE RATIOS OF FATTY ACIDS TO EVALUATE MICROBIAL CARBON SOURCES IN TERRESTRIAL ENVIRONMENTS

    EPA Science Inventory

    We use measurements of the concentration and stable carbon isotopic ratio (D 13C) of individual microbial phospholipid fatty acids (PLFAs) in soils as indicators of live microbial biomass levels and microbial carbon source. We found that intensive sugar cane cultivation leads to ...

  9. PRODUCTION AND TRANSPORT OF CARBON DIOXIDE IN A CONTAMINATED VADOSE ZONE: A STABLE AND RADIOACTIVE CARBON ISOTOPE STUDY

    EPA Science Inventory

    Analyses of soil gas compositions and stable and radioactive carbon isotopes in the vadose zone above an alluvial aquifer were conducted at an organic solvent disposal site in southeast Phoenix, AZ. The study investigated the source and movement of carbon dioxide above a plume of...

  10. PRODUCTION AND TRANSPORT OF CARBON DIOXIDE IN A CONTAMINATED VADOSE ZONE: A STABLE AND RADIOACTIVE CARBON ISOTOPE STUDY

    EPA Science Inventory

    Analyses of soil gas compositions and stable and radioactive carbon isotopes in the vadose zone above an alluvial aquifer were conducted at an organic solvent disposal site in southeast Phoenix, AZ. he study investigated the source and movement of carbon dioxide above a plume of ...

  11. Dual-Carbon sources fuel the OCS deep-reef Community, a stable isotope investigation

    USGS Publications Warehouse

    Sulak, Kenneth J.; Berg, J.; Randall, Michael; Dennis, George D., III; Brooks, R.A.

    2008-01-01

    The hypothesis that phytoplankton is the sole carbon source for the OCS deep-reef community (>60 m) was tested. Trophic structure for NE Gulf of Mexico deep reefs was analyzed via carbon and nitrogen stable isotopes. Carbon signatures for 114 entities (carbon sources, sediment, fishes, and invertebrates) supported surface phytoplankton as the primary fuel for the deep reef. However, a second carbon source, the macroalga Sargassum, with its epiphytic macroalgal associate, Cladophora liniformis, was also identified. Macroalgal carbon signatures were detected among 23 consumer entities. Most notably, macroalgae contributed 45 % of total carbon to the 13C isotopic spectrum of the particulate-feeding reef-crest gorgonian Nicella. The discontinuous spatial distribution of some sessile deep-reef invertebrates utilizing pelagic macroalgal carbon may be trophically tied to the contagious distribution of Sargassum biomass along major ocean surface features.

  12. Carbon allocation belowground in Pinus pinaster using stable carbon isotope pulse labeling technique

    NASA Astrophysics Data System (ADS)

    Dannoura, M.; Bosc, A.; Chipeaux, C.; Sartore, M.; Lambrot, C.; Trichet, P.; Bakker, M.; Loustau, D.; Epron, D.

    2010-12-01

    Carbon allocation belowground competes with aboveground growth and biomass production. In the other hand, it contributes to resource acquisition such as nutrient, water and carbon sequestration in soil. Thus, a better characterization of carbon flow from plant to soil and its residence time within each compartment is an important issue for understanding and modeling forest ecosystem carbon budget. 13C pulse labeling of whole crown was conducted at 4 seasons to study the fate of assimilated carbon by photosynthesis into the root on 12 year old Pinus pinaster planted in the INRA domain of Pierroton. Maritime pine is the most widely planted species in South-West Europe. Stem, root and soil CO2 effluxes and their isotope composition were measured continuously by tunable diode laser absorption spectroscopy with a trace gas analyzer (TGA 100A; Campbell Scientific) coupled to flow-through chambers. 13CO2 recovery and peak were observed in respiration of each compartment after labeling. It appeared sequentially from top of stem to bottom, and to coarse root. The maximum velocity of carbon transfer was calculated as the difference in time lag of recovery between two positions on the trunk or on the root. It ranged between 0.08-0.2 m h-1 in stem and between 0.04-0.12 m h-1 in coarse root. This velocity was higher in warmer season, and the difference between time lag of recovery and peak increased after first frost. Photosynthates arrived underground 1.5 to 5 days after labeling, at similar time in soil CO2 effluxes and coarse root respiration. 0.08-1.4 g of carbon was respired per tree during first 20 days following labeling. It presented 0.6 -10% of 13C used for labeling and it is strongly related to seasons. The isotope signal was detected in fine root organs and microbial biomass by periodical core sampling. The peak was observed 6 days after labeling in early summer while it was delayed more than 10 days in autumn and winter with less amount of carbon allocated belowground.

  13. Ca Cycle Constraints from the Ca Isotope Composition of Precambrian Sedimentary Carbonates

    NASA Astrophysics Data System (ADS)

    Blättler, C. L.; Higgins, J. A.

    2014-12-01

    The geochemical cycle of Ca in seawater is relatively straightforward - Ca is ultimately sourced from the weathering of silicates and largely removed as carbonates. Most of these carbonates are then recycled through subsequent uplift and weathering, but some are metamorphosed or returned to the mantle via subduction. Ca isotopes in sedimentary marine carbonates can provide new insights into the global Ca (and by corollary, C) cycle by constraining the flux and isotopic composition of the recycled and subducted Ca sinks on billion-year timescales. Precambrian applications of Ca isotopes have so far been limited to relatively small datasets which cover unusual, dynamic intervals of the Proterozoic. In order to address questions about long-timescale Ca cycling, Ca isotopes were measured on an extensive suite of Precambrian carbonates (n > 300) which represent environments, textures, and morphologies that are typical for their age, and whose carbon isotope values have been interpreted as reflecting precipitation from seawater. Because marine carbonates constitute the dominant geological sink for Ca, this representative sample set places specific limits on the evolution of the sedimentary and crustal Ca reservoirs and suggests further applications for Ca isotopes in Precambrian time.

  14. Sulfur and carbon isotope biogeochemistry of a rewetted brackish fen

    NASA Astrophysics Data System (ADS)

    Koebsch, Franziska; Gehre, Matthias; Winkel, Matthias; Koehler, Stefan; Koch, Marian; Jurasinski, Gerald; Spitzy, Alejandro; Liebner, Susanne; Sachs, Torsten; Schmiedinger, Iris; Kretzschmann, Lisett; Saborowski, Anke; Böttcher, Michael E.

    2015-04-01

    Coastal wetlands are at the interface between terrestrial freshwater and marine and exhibit very specific biogeochemical conditions. Intermittent sea water intrusion affects metabolic pathways, i. e. anaerobic carbon metabolism is progressively dominated by sulfate reduction with lower contribution of methanogenesis whilst methane production is increasingly shifted from acetoclastic to hydrogenotrophic. Due to expanding anthropogenic impact a large proportion of coastal ecosystems is degraded with severe implications for the biogeochemical processes. We use concentration patterns and stable isotope signatures of water, sulfate, dissolved carbonate, and methane (?2H, ?13C, ?18O, ?34S) to investigate the S and C metabolic cycle in a rewetted fen close to the southern Baltic Sea border. Such studies are crucial to better predict dynamic ecosystem feedback to global change like organic matter (OM) decomposition or greenhouse gas emissions. Yet, little is known about the metabolic pathways in such environments. The study site is part of the TERENO Observatory "Northeastern German Lowlands' and measurements of methane emissions have run since 2009. High methane fluxes up to 800 mg m-2 hr-1 indicate that methanogenesis is the dominant C metabolism pathway despite of high sulfate concentrations (up to 37 mM). The presented data are part of a comprehensive biogeochemical investigation that we conducted in autumn 2014 and that comprises 4 pore water profiles and sediment samples within a transect of 300-1500 m distance to the Baltic Sea. Depth of organic layers ranged from 25 to 140 cm with high OM contents (up to 90 dwt.%). Sulfate/chloride ratios in the pore waters were lower than in the Baltic Sea for most sites and sediment depths indicated a substantial net sulfate loss. Sulfide concentrations were negligible at the top and increased parallel to the sulfate concentrations with depth to values of up to 0.3 mM. One pore water profiles situated 1150 m from the Baltic Sea coast line exhibited a significant excess of sulfate. Preliminary sulfur isotope analysis of pore water sulfate from a location nearest to this profile revealed an enrichment in 34S (24.9 to 41.8o ) in comparison to Baltic Sea sulfate (21o ). This confirms high degrees of net sulfate reduction. Considering the yet high sulfate concentrations we hypothesize that local processes might supply additional sulfate and that the sulfide produced from sulfate reduction might either be lost by upwards diffusion towards the atmosphere or converted into other S compounds such as pyrite or organic compounds. The isotopic signatures of methane (?13C: -68 to -57o and ?2H: -133 to -157o respectively) indicated acetoclastic methanogenesis to be the most dominant methane production pathway. However, estimated fractionation factors are comparatively high (1.050-1.065). Enrichment of heavy 13C in methane at the top of the sediment was either caused by methane oxidation or variation in substrate availability (e. g. due to peat degradation). The interpretation of our data in the light of further results will provide deeper insights into metabolic pathways and possible interactions between both coupled element cycles for coastal ecosystems.

  15. Effects of carbonate leaching on foraminifer stable isotopes ratios

    NASA Astrophysics Data System (ADS)

    Obrochta, S.; Yokoyama, Y.; Sakai, S.; Ishimura, T.

    2011-12-01

    Stable carbon and oxygen isotope ratios were measured on 125 individual epifaunal and infaunal benthic foraminifers from two discrete Holocene intervals in a shallow-water sediment core (~ 450 m) from the Timor Sea. Methane seeps are common in the area, resulting in significant precipitation of secondary calcite that is confirmed by SEM photomicrographs and has likely resulted in inconsistent downcore results. To assess the degree of removal of contaminants, individual Uvigerina peregrina were subjected to varying degrees of pretreatment prior to analysis. All foraminifers received standard cleaning with ethanol and brief sonication. A subset were further cleaned and sonicated in a dilute HCl solution (~ 0.003 M). Foraminifer tests were photographed using both reflected light and scanning electron microscopes during the course of treatment to monitor the changing degree of contaminant removal as increasingly aggressive cleaning methods were employed. Visible contamination remained on individuals not subjected to HCl treatment. The leached individuals exhibit a lower overall relative standard deviation and consistent results within morphotype groups. Based on these results, a 2% value is expected to be typical of the Holocene, though further downcore analyses are pending restoration of equipment adversely effected by the Eastern Japan 3/11 earthquake.

  16. Stable carbon isotopic compositions of intact polar lipids reveal complex carbon flow patterns among hydrocarbon degrading microbial communities at the Chapopote asphalt volcano

    NASA Astrophysics Data System (ADS)

    Schubotz, Florence; Lipp, Julius S.; Elvert, Marcus; Hinrichs, Kai-Uwe

    2011-08-01

    Seepage of asphalt forms the basis of a cold seep system at 3000 m water depth at the Chapopote Knoll in the southern Gulf of Mexico. Anaerobic microbial communities are stimulated in the oil-impregnated sediments as evidenced by the presence of intact polar membrane lipids (IPLs) derived from archaea and Bacteria at depths up to 7 m below the seafloor. Detailed investigation of stable carbon isotope composition (? 13C) of alkyl and acyl moieties derived from a range of IPL precursors with distinct polar head groups resolved the complexity of carbon metabolisms and utilization of diverse carbon sources by uncultured microbial communities. In surface sediments most of the polar lipid-derived fatty acids with phosphatidylethanolamine (PE), phosphatidylglycerol (PG) and diphosphatidylglycerol (DPG) head groups could be tentatively assigned to autotrophic sulfate-reducing bacteria, with a relatively small proportion involved in the anaerobic oxidation of methane. Derivatives of phosphatidyl-( N)-methylethanolamine (PME) were abundant and could be predominantly assigned to heterotrophic oil-degrading bacteria. Archaeal IPLs with phosphate-based hydroxyarchaeols and diglycosidic glyceroldibiphytanylglyceroltetraethers (GDGTs) were assigned to methanotrophic archaea of the ANME-2 and ANME-1 cluster, respectively, whereas ? 13C values of phosphate-based archaeols and mixed phosphate-based and diglycosidic GDGTs point to methanogenic archaea. At a 7 m deep sulfate-methane transition zone that is linked to the upward movement of gas-laden petroleum, a distinct increase in abundance of archaeal IPLs such as phosphate-based hydroxyarchaeols and diglycosidic archaeol and GDGTs is observed; their ? 13C values are consistent with their origin from both methanotrophic and methanogenic archaea. This study reveals previously hidden, highly complex patterns in the carbon-flow of versatile microbial communities involved in the degradation of heavy oil including hydrocarbon gases that would not have been evident from classical compound-specific isotope analyses of either bulk IPL or apolar lipid derivatives.

  17. Determining the Local Abundance of Martian Methane and its 13-C/l2-C and D/H Isotopic Ratios for Comparison with Related Gas and Soil Analysis on the 2011 Mars Science Laboratory (MSL) Mission

    NASA Technical Reports Server (NTRS)

    Webster, Christopher R.; Mahaffy, Paul R.

    2011-01-01

    Understanding the origin of Martian methane will require numerous complementary measurements from both in situ and remote sensing investigations and laboratory work to correlate planetary surface geophysics with atmospheric dynamics and chemistry. Three instruments (Quadrupole Mass Spectrometer (QMS), Gas Chromatograph (GC) and Tunable Laser Spectrometer (TLS)) with sophisticated sample handling and processing capability make up the Sample Analysis at Mars (SAM) analytical chemistry suite on NASA s 2011 Mars Science Laboratory (MSL) Mission. Leveraging off the SAM sample and gas processing capability that includes methane enrichment, TLS has unprecedented sensitivity for measuring absolute methane (parts-per-trillion), water, and carbon dioxide abundances in both the Martian atmosphere and evolved from heated soil samples. In concert with a wide variety of associated trace gases (e.g. SO2, H2S, NH3, higher hydrocarbons, organics, etc.) and other isotope ratios measured by SAM, TLS will focus on determining the absolute abundances of methane, water and carbon dioxide, and their isotope ratios: 13C/12C and D/H in methane; 13C/12C and 18O/17O/16O in carbon dioxide; and 18O/17O/16O and D/H in water. Measurements near the MSL landing site will be correlated with satellite (Mars Express, Mars 2016) and ground-based observations.

  18. Carbon-bearing iron phases and the carbon isotope composition of the deep Earth

    PubMed Central

    Horita, Juske; Polyakov, Veniamin B.

    2015-01-01

    The carbon budget and dynamics of the Earth’s interior, including the core, are currently very poorly understood. Diamond-bearing, mantle-derived rocks show a very well defined peak at ?13C ? ?5 ± 3‰ with a very broad distribution to lower values (??40‰). The processes that have produced the wide ?13C distributions to the observed low ?13C values in the deep Earth have been extensively debated, but few viable models have been proposed. Here, we present a model for understanding carbon isotope distributions within the deep Earth, involving Fe?C phases (Fe carbides and C dissolved in Fe?Ni metal). Our theoretical calculations show that Fe and Si carbides can be significantly depleted in 13C relative to other C-bearing materials even at mantle temperatures. Thus, the redox freezing and melting cycles of lithosphere via subduction upwelling in the deep Earth that involve the Fe?C phases can readily produce diamond with the observed low ?13C values. The sharp contrast in the ?13C distributions of peridotitic and eclogitic diamonds may reflect differences in their carbon cycles, controlled by the evolution of geodynamical processes around 2.5–3 Ga. Our model also predicts that the core contains C with low ?13C values and that an average ?13C value of the bulk Earth could be much lower than ??5‰, consistent with those of chondrites and other planetary body. The heterogeneous and depleted ?13C values of the deep Earth have implications, not only for its accretion?differentiation history but also for carbon isotope biosignatures for early life on the Earth. PMID:25512520

  19. Carbon-bearing iron phases and the carbon isotope composition of the deep Earth.

    PubMed

    Horita, Juske; Polyakov, Veniamin B

    2015-01-01

    The carbon budget and dynamics of the Earth's interior, including the core, are currently very poorly understood. Diamond-bearing, mantle-derived rocks show a very well defined peak at ?(13)C ? -5 ± 3‰ with a very broad distribution to lower values (?-40‰). The processes that have produced the wide ?(13)C distributions to the observed low ?(13)C values in the deep Earth have been extensively debated, but few viable models have been proposed. Here, we present a model for understanding carbon isotope distributions within the deep Earth, involving Fe-C phases (Fe carbides and C dissolved in Fe-Ni metal). Our theoretical calculations show that Fe and Si carbides can be significantly depleted in (13)C relative to other C-bearing materials even at mantle temperatures. Thus, the redox freezing and melting cycles of lithosphere via subduction upwelling in the deep Earth that involve the Fe-C phases can readily produce diamond with the observed low ?(13)C values. The sharp contrast in the ?(13)C distributions of peridotitic and eclogitic diamonds may reflect differences in their carbon cycles, controlled by the evolution of geodynamical processes around 2.5-3 Ga. Our model also predicts that the core contains C with low ?(13)C values and that an average ?(13)C value of the bulk Earth could be much lower than ?-5‰, consistent with those of chondrites and other planetary body. The heterogeneous and depleted ?(13)C values of the deep Earth have implications, not only for its accretion-differentiation history but also for carbon isotope biosignatures for early life on the Earth. PMID:25512520

  20. Metabolome analysis and pathway abundance profiling of Yarrowia lipolytica cultivated on different carbon sources.

    PubMed

    Zhao, Chen; Gu, Deqing; Nambou, Komi; Wei, Liujing; Chen, Jun; Imanaka, Tadayuki; Hua, Qiang

    2015-07-20

    Yarrowia lipolytica, a model microorganism of oleaginous yeasts with developed sophisticated genetic tools, is able to metabolize a wide range of substrates and accumulate large amounts of lipids. However, there is a lack of literature reporting the metabolic characteristics of Y. lipolytica metabolizing these substrates in a systematic view. In this study, Y. lipolytica was cultivated on a variety of carbon sources, among which cell growth and production characteristics on two representative substrates (glucose and oleic acid) were investigated in detail at metabolomic level. Metabolic pathway abundance was computed to interpret the metabolome data in a straightforward way. The results showed that most pathway abundances decreased in the shift from growth to production phase. Specifically, when cultivated on glucose, abundances of twelve pathways decreased markedly between the growth and lipid production phases, while thirteen pathways reduced and only three pathways increased significantly in abundances on oleic acid. In comparison, for the same cultivation phase only a few pathways exhibited significant changes between glucose-grown and oleic acid-grown cells. This study revealed that the pathway abundance could be used to effectively show the activity changes of pathways, providing a new perspective to employ metabolomics data for understanding cell metabolism and enhancing the production of target metabolites. PMID:25912211

  1. Carbonate petrography, kerogen distribution, and carbon and oxygen isotope variations in an early Proterozoic transition from limestone to iron-formation deposition, Transvaal Supergroup, South Africa

    NASA Technical Reports Server (NTRS)

    Beukes, N. J.; Klein, C.; Kaufman, A. J.; Hayes, J. M.

    1990-01-01

    The transition zone comprises Campbellrand microbialaminated (replacing "cryptalgalaminate") limestone and shale, with minor dolomite, conformably overlain by the Kuruman Iron Formation of which the basal part is characterized by siderite-rich microbanded iron-formation with minor magnetite and some hematite-containing units. The iron-formation contains subordinate intraclastic and microbialaminated siderite mesobands and was deposited in deeper water than the limestones. The sequence is virtually unaltered with diagenetic mineral assemblages reflecting a temperature interval of about 110 degrees to 170 degrees C and pressures of 2 kbars. Carbonate minerals in the different rock types are represented by primary micritic precipitates (now recrystallized to microsparite), early precompactional sparry cements and concretions, deep burial limpid euhedral sparites, and spar cements precipitated from metamorphic fluids in close contact with diabase sills. Paragenetic pathways of the carbonate minerals are broadly similar in all lithofacies with kerogen intimately associated with them. Kerogen occurs as pigmentation in carbonate crystals, as reworked organic detritus in clastic-textured carbonate units, and as segregations of kerogen pigment around late diagenetic carbonate crystals. Locally kerogen may also be replaced by carbonate spar. Carbon isotope compositions of the carbonate minerals and kerogen are dependent on their mode of occurrence and on the composition of the dominant carbonate species in a specific lithofacies. Integration of sedimentary, petrographic, geochemical, and isotopic results makes it possible to distinguish between depositional, early diagenetic, deep burial, and metamorphic effects on the isotopic compositions of the carbonate minerals and the kerogen in the sequence. Major conclusions are that deep burial thermal decarboxylation led to 13C depletion in euhedral ferroan sparites and 13C enrichment in kerogen (organic carbon). Metamorphic sparites are most depleted in 13C. Carbonates in oxide-rich iron-formations are more depleted in 13C than those in siderite-rich iron-formation whereas the kerogens in oxide banded iron-formations (BIF) are more enriched. This implies that the siderite-rich iron-formations were not derived from oxide-rich iron-formation through reduction of ferric iron by organic matter. Organic matter oxidation by ferric iron did, however, decrease the abundance of kerogen in oxide-rich iron-formation and led to the formation of isotopically very light sparry carbonates. Siderite and calcmicrosparite both represent recrystallized primary micritic precipitates but differ in their 13C composition, with the siderites depleted in 13C by 4.6 per mil on average relative to calcmicrosparite. This means that the siderites were precipitated from water with dissolved inorganic carbon depleted in 13C by about 9 per mil relative to that from which the limestones precipitated. This implies an ocean system stratified with regard to total carbonate, with the deeper water, from which siderite-rich iron-formation formed, depleted in 13C. Iron-formations were deposited in areas of very low organic matter supply. Depletion of 13C may, therefore, derive not from degradation of organic matter but from hydrothermal activity, a conclusion which is supported by 18O composition of the carbonate minerals and trace element and rare earth element (REE) compositions of the iron-formations.

  2. Carbonate petrography, kerogen distribution, and carbon and oxygen isotope variations in an early Proterozoic transition from limestone to iron-formation deposition, Transvaal Supergroup, South Africa.

    PubMed

    Beukes, N J; Klein, C; Kaufman, A J; Hayes, J M

    1990-01-01

    The transition zone comprises Campbellrand microbialaminated (replacing "cryptalgalaminate") limestone and shale, with minor dolomite, conformably overlain by the Kuruman Iron Formation of which the basal part is characterized by siderite-rich microbanded iron-formation with minor magnetite and some hematite-containing units. The iron-formation contains subordinate intraclastic and microbialaminated siderite mesobands and was deposited in deeper water than the limestones. The sequence is virtually unaltered with diagenetic mineral assemblages reflecting a temperature interval of about 110 degrees to 170 degrees C and pressures of 2 kbars. Carbonate minerals in the different rock types are represented by primary micritic precipitates (now recrystallized to microsparite), early precompactional sparry cements and concretions, deep burial limpid euhedral sparites, and spar cements precipitated from metamorphic fluids in close contact with diabase sills. Paragenetic pathways of the carbonate minerals are broadly similar in all lithofacies with kerogen intimately associated with them. Kerogen occurs as pigmentation in carbonate crystals, as reworked organic detritus in clastic-textured carbonate units, and as segregations of kerogen pigment around late diagenetic carbonate crystals. Locally kerogen may also be replaced by carbonate spar. Carbon isotope compositions of the carbonate minerals and kerogen are dependent on their mode of occurrence and on the composition of the dominant carbonate species in a specific lithofacies. Integration of sedimentary, petrographic, geochemical, and isotopic results makes it possible to distinguish between depositional, early diagenetic, deep burial, and metamorphic effects on the isotopic compositions of the carbonate minerals and the kerogen in the sequence. Major conclusions are that deep burial thermal decarboxylation led to 13C depletion in euhedral ferroan sparites and 13C enrichment in kerogen (organic carbon). Metamorphic sparites are most depleted in 13C. Carbonates in oxide-rich iron-formations are more depleted in 13C than those in siderite-rich iron-formation whereas the kerogens in oxide banded iron-formations (BIF) are more enriched. This implies that the siderite-rich iron-formations were not derived from oxide-rich iron-formation through reduction of ferric iron by organic matter. Organic matter oxidation by ferric iron did, however, decrease the abundance of kerogen in oxide-rich iron-formation and led to the formation of isotopically very light sparry carbonates. Siderite and calcmicrosparite both represent recrystallized primary micritic precipitates but differ in their 13C composition, with the siderites depleted in 13C by 4.6 per mil on average relative to calcmicrosparite. This means that the siderites were precipitated from water with dissolved inorganic carbon depleted in 13C by about 9 per mil relative to that from which the limestones precipitated. This implies an ocean system stratified with regard to total carbonate, with the deeper water, from which siderite-rich iron-formation formed, depleted in 13C. Iron-formations were deposited in areas of very low organic matter supply. Depletion of 13C may, therefore, derive not from degradation of organic matter but from hydrothermal activity, a conclusion which is supported by 18O composition of the carbonate minerals and trace element and rare earth element (REE) compositions of the iron-formations. PMID:11538478

  3. Stable-carbon isotope variability in tree foliage and wood. [Iunipeus; Pinus edulis

    SciTech Connect

    Leavitt, S.W.; Long, A.

    1986-08-01

    This study documents variation of stable-carbon isotope ratios (/sup 13/C//sup 12/C) in trees of genera Juniperus and Pinus under field conditions. Results are from cellulose analysis on leaves, twigs, and wood from a number of localities in the southwestern US. Substantial variability, typically 1-3%, exists among leaves, within wood (radially, vertically, circumferentially), and between individuals at a site. These results may help guide sampling in tracer-type studies with stable-carbon isotope ratios and aid in the interpretation of isotopic results from such studies.

  4. Simultaneous determination of stable carbon, oxygen, and hydrogen isotopes in cellulose.

    PubMed

    Loader, N J; Street-Perrott, F A; Daley, T J; Hughes, P D M; Kimak, A; Levani?, T; Mallon, G; Mauquoy, D; Robertson, I; Roland, T P; van Bellen, S; Ziehmer, M M; Leuenberger, M

    2015-01-01

    A technological development is described through which the stable carbon-, oxygen-, and nonexchangeable hydrogen-isotopic ratios (?(13)C, ?(18)O, ?(2)H) are determined on a single carbohydrate (cellulose) sample with precision equivalent to conventional techniques (?(13)C 0.15‰, ?(18)O 0.30‰, ?(2)H 3.0‰). This triple-isotope approach offers significant new research opportunities, most notably in physiology and medicine, isotope biogeochemistry, forensic science, and palaeoclimatology, when isotopic analysis of a common sample is desirable or when sample material is limited. PMID:25495958

  5. Stable isotope natural abundance of nitrous oxide emitted from Antarctic tundra soils: effects of sea animal excrement depositions.

    PubMed

    Zhu, Renbin; Liu, Yashu; Li, Xianglan; Sun, Jianjun; Xu, Hua; Sun, Liguang

    2008-11-01

    Nitrous oxide (N2O), a greenhouse gas, is mainly emitted from soils during the nitrification and denitrification processes. N2O stable isotope investigations can help to characterize the N2O sources and N2O production mechanisms. N2O isotope measurements have been conducted for different types of global terrestrial ecosystems. However, no isotopic data of N2O emitted from Antarctic tundra ecosystems have been reported although the coastal ice-free tundra around Antarctic continent is the largest sea animal colony on the global scale. Here, we report for the first time stable isotope composition of N2O emitted from Antarctic sea animal colonies (including penguin, seal and skua colonies) and normal tundra soils using in situ field observations and laboratory incubations, and we have analyzed the effects of sea animal excrement depositions on stable isotope natural abundance of N2O. For all the field sites, the soil-emitted N2O was 15N- and 18O-depleted compared with N2O in local ambient air. The mean delta values of the soil-emitted N2O were delta15N = -13.5 +/- 3.2 per thousand and delta18O = 26.2 +/- 1.4 per thousand for the penguin colony, delta15N = -11.5 +/- 5.1 per thousand and delta18O = 26.4 +/- 3.5 per thousand for the skua colony and delta15N = -18.9 +/- 0.7 per thousand and delta18O = 28.8 +/- 1.3 per thousand for the seal colony. In the soil incubations, the isotopic composition of N2O was measured under N2 and under ambient air conditions. The soils incubated under the ambient air emitted very little N2O (2.93 microg N2O--N kg(-1)). Under N2 conditions, much more N2O was formed (9.74 microg N2O--N kg(-1)), and the mean delta15N and delta18O values of N2O were -19.1 +/- 8.0 per thousand and 21.3 +/- 4.3 per thousand, respectively, from penguin colony soils, and -17.0 +/- 4.2 per thousand and 20.6 +/- 3.5 per thousand, respectively, from seal colony soils. The data from in situ field observations and laboratory experiments point to denitrification as the predominant N2O source from Antarctic sea animal colonies. PMID:18932270

  6. Carbon Stable Isotope Analysis of Methylmercury Toxin in Biological Materials by Gas Chromatography Isotope Ratio Mass Spectrometry.

    PubMed

    Masbou, Jeremy; Point, David; Guillou, Gaël; Sonke, Jeroen E; Lebreton, Benoit; Richard, Pierre

    2015-12-01

    A critical component of the biogeochemical cycle of mercury (Hg) is the transformation of inorganic Hg to neurotoxic monomethylmercury (CH3Hg). Humans are exposed to CH3Hg by consuming marine fish, yet the origin of CH3Hg in fish is a topic of debate. The carbon stable isotopic composition (?(13)C) embedded in the methyl group of CH3Hg remains unexplored. This new isotopic information at the molecular level is thought to represent a new proxy to trace the carbon source at the origin of CH3Hg. Here, we present a compound-specific stable isotope analysis (CSIA) technique for the determination of the ?(13)C value of CH3Hg in biological samples by gas chromatography combustion isotope ratio mass spectrometry analysis (GC-C-IRMS). The method consists first of calibrating a CH3Hg standard solution for ?(13)C CSIA. This was achieved by comparing three independent approaches consisting of the derivatization and halogenation of the CH3Hg standard solution. The determination of ?(13)CCH3Hg values on natural biological samples was performed by combining a CH3Hg selective extraction, purification, and halogenation followed by GC-C-IRMS analysis. Reference ?(13)C values were established for a tuna fish certified material (ERM-CE464) originating from the Adriatic Sea (?(13)CCH3Hg = -22.1 ± 1.5‰, ± 2 SD). This value is similar to the ?(13)C value of marine algal-derived particulate organic carbon (?(13)CPOC = -21‰). PMID:26511394

  7. Moving-wire device for carbon isotopic analyses of nanogram quantities of nonvolatile organic carbon.

    PubMed

    Sessions, Alex L; Sylva, Sean P; Hayes, John M

    2005-10-15

    We describe a moving-wire analyzer for measuring 13C in dissolved, involatile organic materials. Liquid samples are first deposited and dried on a continuously spooling nickel wire. The residual sample is then combusted as the wire moves through a furnace, and the evolved CO2 is analyzed by continuous-flow isotope ratio mass spectrometry. A typical analysis requires 1 microL of sample solution and produces a CO2 peak approximately 5 s wide. The system can measure "bulk" delta13C values of approximately 10 nmol of organic carbon with precision better than 0.2 per thousand. For samples containing approximately 1 nmol of C, precision is approximately 1 per thousand. Precision and sensitivity are limited mainly by background noise derived from carbon within the wire. Instrument conditions minimizing that background are discussed in detail. Accuracy is better than 0.5 per thousand for nearly all dissolved analytes tested, including lipids, proteins, nucleic acids, sugars, halocarbons, and hydrocarbons. The sensitivity demonstrated here for 13C measurements represents a approximately 1000-fold improvement relative to existing elemental analyzers and should allow the use of many new preparative techniques for collecting and purifying nonvolatile biochemicals for isotopic analysis. PMID:16223235

  8. Isotopic tracer evidence for the amorphous calcium carbonate to calcite transformation by dissolution-reprecipitation

    NASA Astrophysics Data System (ADS)

    Giuffre, Anthony J.; Gagnon, Alexander C.; De Yoreo, James J.; Dove, Patricia M.

    2015-09-01

    Observations that some biogenic and sedimentary calcites grow from amorphous calcium carbonate (ACC) raise the question of how this mineralization process influences composition. However, the detailed pathway and geochemical consequences of the ACC to calcite transformation are not well constrained. This experimental study investigated the formation of calcite from ACC by using magnesium and calcium stable isotope labeling to directly probe the transformation pathway and controls on composition. Four processes were considered: dissolution-reprecipitation, solid state transformation, and combinations of these end-members. To distinguish between these scenarios, ACC was synthesized from natural isotope abundance solutions and subsequently transferred to spiked solutions that were enriched in 43Ca and 25Mg for the transformation to calcite. Isotope measurements by NanoSIMS determined the 43Ca/40Ca, and 25Mg/24Mg ratios of the resulting calcite crystals. Analysis of the data shows the transformation is best explained by a dissolution-reprecipitation process. We find that when a small amount of ACC is transferred, the isotopic signals in the resulting calcite are largely replaced by the composition of the surrounding spiked solution. When larger amounts of ACC are transferred, calcite compositions reflect a mixture between the ACC and initial solution end-member. Comparisons of the measurements to the predictions of a simple mixing model indicate that calcite compositions (1) are sensitive to relative amounts of ACC and the surrounding solution reservoir and (2) are primarily governed by the conditions at the time of ACC transformation rather than the initial ACC formation. Shifts in calcite composition over the duration of the transformation period reflect the progressive evolution of the local solution conditions. This dependence indicates the extent to which there is water available would change the end point composition on the mixing line. While these findings have significant geochemical implications, the question remains whether this transformation pathway is generally followed when biomineralization involves ACC or is particular to these inorganic experiments. Insights from this study nonetheless suggest that some types of compositional variability, such as 'vital effects', may be explained in-part by a co-evolution of reservoir and products over the duration of the transformation.

  9. Seasonal Variation in Stable Carbon and Nitrogen Isotope Values of Bats Reflect Environmental Baselines

    PubMed Central

    Popa-Lisseanu, Ana G.; Kramer-Schadt, Stephanie; Quetglas, Juan; Delgado-Huertas, Antonio; Kelm, Detlev H.; Ibáñez, Carlos

    2015-01-01

    The stable carbon and nitrogen isotope composition of animal tissues is commonly used to trace wildlife diets and analyze food chains. Changes in an animal’s isotopic values over time are generally assumed to indicate diet shifts or, less frequently, physiological changes. Although plant isotopic values are known to correlate with climatic seasonality, only a few studies restricted to aquatic environments have investigated whether temporal isotopic varia-tion in consumers may also reflect environmental baselines through trophic propagation. We modeled the monthly variation in carbon and nitrogen isotope values in whole blood of four insectivorous bat species occupying different foraging niches in southern Spain. We found a common pattern of isotopic variation independent of feeding habits, with an overall change as large as or larger than one trophic step. Physiological changes related to reproduction or to fat deposition prior to hibernation had no effect on isotopic variation, but juvenile bats had higher ?13C and ?15N values than adults. Aridity was the factor that best explained isotopic variation: bat blood became enriched in both 13C and 15N after hotter and/or drier periods. Our study is the first to show that consumers in terrestrial ecosystems reflect seasonal environmental dynamics in their isotope values. We highlight the danger of misinterpreting stable isotope data when not accounting for seasonal isotopic baselines in food web studies. Understanding how environmental seasonality is inte-grated in animals’ isotope values will be crucial for developing reliable methods to use stable isotopes as dietary tracers. PMID:25700080

  10. Carbon cycling and carbon metabolism by soil fungi in a boreal forest: impacts of wildfire and permafrost on functional genes, isotope signatures, and ectomycorrhizae

    NASA Astrophysics Data System (ADS)

    Waldrop, M. P.; Harden, J. W.

    2006-12-01

    Understanding the mechanisms that control the stabilization and destabilization of soil carbon within boreal forest ecosystems is of great importance to the global carbon budget. Much is currently known about boreal soil carbon dynamics in relation to biophysical and landscape variables such as temperature, moisture, wildfire intensity, and stand age. We have less information regarding the controls on decomposition at the molecular scale, where interactions between microbial communities, their genetic `potential' for decomposition, functional genes, enzyme synthesis, and organic matter transformations occur. We have entered an age in which these connections can be made at the molecular scale, but what form do they take, and can they scale up to affect carbon dynamics at the level of the ecosystem? We examined these molecular scale processes in mature boreal forest soils and soils that had been impacted by wildfire near Delta Junction, Alaska. We also examined the interactive effect of permafrost presence, which reduces soil drainage, with wildfire. We focused on three themes: linking microbial communities and laccase functional genes to soil laccase enzyme activity and lignin decomposition, assessing substrate availability using the natural abundance ?13C isotope ratios of microbial biomass, and the influence of ectomycorrhizal mats on decomposition. Wildfire reduced fungal biomass, laccase functional gene abundance, laccase activity, and ?13C-lignin decomposition. Relationships between gene abundance and microbial activity were significant and logarithmic in form. Soil drainage, which is mediated by the presence of permafrost, had little effect on the abundance of fungi, functional genes, or potential process rates. Microbial biomass ?13C was always enriched relative to soil organic matter, and this difference was greater in control soils compared to wildfire-affected soils, indicating that Ä??13C MB-SOIL may indicate the level of bioavailability of soil carbon for microbial metabolism. Ectomycorrhizal mats occurred only in control soils and increased fungal biomass, functional gene abundance, enzyme activities and process rates compared to non-mat soils. Taken together these results indicate that linkages can be made between the distribution of soil microbial communities, molecular scale information, and soil carbon dynamics.

  11. Stable Isotope Measurements of Carbon Dioxide, Methane, and Hydrogen Sulfide Gas Using Frequency Modulation Spectroscopy

    NASA Astrophysics Data System (ADS)

    Nowak-Lovato, K.

    2014-12-01

    Seepage from enhanced oil recovery, carbon storage, and natural gas sites can emit trace gases such as carbon dioxide, methane, and hydrogen sulfide. Trace gas emission at these locations demonstrate unique light stable isotope signatures that provide information to enable source identification of the material. Light stable isotope detection through surface monitoring, offers the ability to distinguish between trace gases emitted from sources such as, biological (fertilizers and wastes), mineral (coal or seams), or liquid organic systems (oil and gas reservoirs). To make light stable isotope measurements, we employ the ultra-sensitive technique, frequency modulation spectroscopy (FMS). FMS is an absorption technique with sensitivity enhancements approximately 100-1000x more than standard absorption spectroscopy with the advantage of providing stable isotope signature information. We have developed an integrated in situ (point source) system that measures carbon dioxide, methane and hydrogen sulfide with isotopic resolution and enhanced sensitivity. The in situ instrument involves the continuous collection of air and records the stable isotope ratio for the gas being detected. We have included in-line flask collection points to obtain gas samples for validation of isotopic concentrations using our in-house isotope ratio mass spectroscopy (IRMS). We present calibration curves for each species addressed above to demonstrate the sensitivity and accuracy of the system. We also show field deployment data demonstrating the capabilities of the system in making live dynamic measurements from an active source.

  12. Carbon Isotopes in the Ocean Model of the Community Earth System Model (CESM)

    NASA Astrophysics Data System (ADS)

    Jahn, A.; Lindsay, K. T.; Otto-Bliesner, B. L.; Brady, E. C.; Liu, Z.

    2014-12-01

    Carbon isotopes are frequently used to infer changes in past ocean circulation based on proxy records. Climate models on the other hand simulate the full climate system, but not the isotopic proxy record that corresponds to the climate state, making it difficult to compare model results with isotopic proxy data. In order to bridge this gap, we have implemented carbon isotopes (13C and 14C) in the ocean model of a state-of-the-art earth system model, the Community Earth System Model (CESM1). These improvements will allow us to more directly compare the model results to paleo proxies in future paleo simulations with the widely used CESM. Furthermore, simulating carbon isotopes in the model will allow us to investigate the details of the relationship between physical changes in the ocean circulation and isotopic changes in the self-consistent model system. We will discuss the implementation of abiotic and biotic radiocarbon and biotic 13C in the ocean model of the CESM1, to introduce these new features to the community. Then we will show how the model performs compared to present-day data, characterize the sensitivity of the simulated ?13C distributions to different biological fractionation parameterizations, and show results from idealized freshwater hosing experiments. In the near future, we plan to use the carbon-isotope enabled CESM to study changes in the ocean circulation during the LGM and the deglaciation.

  13. Evaluation of TASTEX task H: measurement of plutonium isotopic abundances by gamma-ray spectrometry

    SciTech Connect

    Gunnink, R.; Prindle, A.L.; Asakura, Y.; Masui, J.; Ishiguro, N.; Kawasaki, A.; Kataoka, S.

    1981-10-01

    This report describes a computer-based gamma spectrometer system that was developed for measuring isotopic and total plutonium concentrations in nitric acid solutions. The system was installed at the Tokai reprocessing plant where it is undergoing testing and evaluation as part of the Tokai Advanced Safeguards Exercise (TASTEX). Objectives of TASTEX Task H, High-Resolution Gamma Spectrometer for Plutonium Isotopic Analysis, the methods and equipment used, the installation and calibration of the system, and the measurements obtained from several reprocessing campaigns are discussed and described. In general, we find that measurements for gamma spectroscopy agree well with those of mass spectrometry and of other chemical analysis. The system measures both freshly processed plutonium from the product accountability tank and aged plutonium solutions from storage tanks. 14 figures, 15 tables.

  14. Theoretical effect of diffusion on isotopic abundance ratios in rocks and associated fluids

    USGS Publications Warehouse

    Senftle, F.E.; Bracken, J.T.

    1955-01-01

    Diffusion is considered as a possible process of isotope fractionation taking place throughout geologic time. Both diffusion in solids and diffusion in liquids are taken as possible mechanisms, the latter being more important. Arguments are presented to show that if significant fractionation takes place within a crystal by outward diffusion under solid-state conditions, enrichment will be evident only in elements of minor concentration. Similar conclusions are inferred for solid-state diffusion across a boundary or for diffusion in liquids. No isotopic enrichment can be expected in relatively large bodies of diffusion transported material. Although the necessary data to confirm these conclusions are scanty, it seems worth while to undertake further work in this direction. ?? 1955.

  15. Models of earth structure inferred from neodymium and strontium isotopic abundances

    PubMed Central

    Wasserburg, G. J.; DePaolo, D. J.

    1979-01-01

    A simplified model of earth structure based on the Nd and Sr isotopic characteristics of oceanic and continental tholeiitic flood basalts is presented, taking into account the motion of crustal plates and a chemical balance for trace elements. The resulting structure that is inferred consists of a lower mantle that is still essentially undifferentiated, overlain by an upper mantle that is the residue of the original source from which the continents were derived. PMID:16592688

  16. Distribution of stable carbon isotopes in an agrochernozem during the transition from C3 vegetation to a corn monoculture

    NASA Astrophysics Data System (ADS)

    Larionova, A. A.; Stulin, A. F.; Zanina, O. G.; Yevdokimov, I. V.; Khokhlova, O. S.; Buegger, F.; Schloter, M.; Kudeyarov, V. N.

    2012-08-01

    The distribution of carbon in an agrochernozem's profile was studied by the natural 13C abundance method during the C3-C4 vegetation transition and the analysis of the soil phytolith complex under a continuous corn monoculture. A young pool of soil organic matter (SOM) formed during 43 years of monoculture growing was detected by the isotope analysis in the 0-to 60-cm layer, while the analysis of the phytolith complex identified this pool deeper: corn phytoliths were detected in the 0- to 80-cm layer. The maximum size of the young pool was found in the upper soil horizon; it reached 6.4% of the SOM in the 0- to 20-cm layer. The apparent time of the SOM turnover was 635 and 2225 years in the 0- to 20- and 40- to 60-cm layers, respectively. The high values of the mean residence time were related to the low input of plant residues to the soil at the growing of corn for silage and the high initial content of organic carbon in the chernozem. The changes in the isotope composition after the decalcification of the soil to remove carbonates and the variation of the ?13C in the corn biomass during the vegetation period significantly affected the calculated value of the mean residence time.

  17. Growth versus metabolic tissue replacement in mouse tissues determined by stable carbon and nitrogen isotope analysis

    NASA Astrophysics Data System (ADS)

    Macavoy, S. E.; Jamil, T.; Macko, S. A.; Arneson, L. S.

    2003-12-01

    Stable isotope analysis is becoming an extensively used tool in animal ecology. The isotopes most commonly used for analysis in terrestrial systems are those of carbon and nitrogen, due to differential carbon fractionation in C3 and C4 plants, and the approximately 3‰ enrichment in 15N per trophic level. Although isotope signatures in animal tissues presumably reflect the local food web, analysis is often complicated by differential nutrient routing and fractionation by tissues, and by the possibility that large organisms are not in isotopic equilibrium with the foods available in their immediate environment. Additionally, the rate at which organisms incorporate the isotope signature of a food through both growth and metabolic tissue replacement is largely unknown. In this study we have assessed the rate of carbon and nitrogen isotopic turnover in liver, muscle and blood in mice following a diet change. By determining growth rates, we were able to determine the proportion of tissue turnover caused by growth versus that caused by metabolic tissue replacement. Growth was found to account for approximately 10% of observed tissue turnover in sexually mature mice (Mus musculus). Blood carbon was found to have the shortest half-life (16.9 days), followed by muscle (24.7 days). Liver carbon turnover was not as well described by the exponential decay equations as other tissues. However, substantial liver carbon turnover was observed by the 28th day after diet switch. Surprisingly, these tissues primarily reflect the carbon signature of the protein, rather than carbohydrate, source in their diet. The nitrogen signature in all tissues was enriched by 3 - 5‰ over their dietary protein source, depending on tissue type, and the isotopic turnover rates were comparable to those observed in carbon.

  18. A chart of cosmic ray isotopes. [showing radioactive decay, abundance and nucleosynthesis

    NASA Technical Reports Server (NTRS)

    Waddington, C. J.

    1975-01-01

    A chart has been prepared that lists some of the properties relevant to cosmic ray studies of all the significant nuclides between lithium and nickel. On this chart there are shown all the possible decays that might be of interest in the unique conditions experienced by cosmic ray nuclei, various abundance figures and the probable nucleosynthesis processes of origin.

  19. The Abundance and Isotopic Composition of Water in Howardite-Eucrite-Diogenite Meteorites

    NASA Astrophysics Data System (ADS)

    Barrett, T. J.; Tartèse, R.; Anand, M.; Franchi, I. A.; Grady, M. M.; Greenwood, R. C.; Charlier, B. L. A.

    2014-09-01

    Using SIMs techniques we measure OH abundances and D/H ratios in apatite grains from two Eucrites (DaG 945, DaG 844).The average ?D values of these two samples are also similar to carbonaceous chondrites, the Earth and the Moon.

  20. Carbon isotope fractionation of chlorinated ethenes during oxidation by Fe2+ activated persulfate.

    PubMed

    Marchesi, Massimo; Aravena, Ramon; Sra, Kanwartej S; Thomson, Neil R; Otero, Neus; Soler, Albert; Mancini, Silvia

    2012-09-01

    The increased use of persulfate (S(2)O(8)(2-)) for in situ chemical oxidation to treat groundwater and soils contaminated by chlorinated hydrocarbon compounds (CHCs) requires unbiased methods to assess treatment performance. Stable carbon isotope analysis offers a potential tool for assessing the in situ treatment performance of persulfate at sites contaminated with CHCs. This study investigated the extent of C isotope fractionation during oxidation of tetrachloroethene (PCE), trichloroethene (TCE) and cis-dichloroethene (cis-DCE) by persulfate activated by ferrous ion (Fe(2+)). An average carbon isotope enrichment factor ?(bulk) of -4.9‰ for PCE, -3.6‰ for TCE and -7.6‰ for cis-DCE were obtained in batch experiments. Variations in the initial S(2)O(8)(2-)/Fe(2+)/CHC molar ratios did not result in any significant differences in carbon isotope fractionation. The occurrence of carbon isotope fractionation during oxidation and the lack of dependence of enrichment factors upon the S(2)O(8)(2-)/Fe(2+)/CHC molar ratio demonstrate that carbon isotope analysis can potentially be used at contaminated sites as an additional technique to estimate treatment efficacy during oxidation of CHCs by Fe(2+) activated persulfate. PMID:22814410

  1. Local variations in carbon isotopes and nitrogen contents in diamonds from placers of the northeastern portion of the Siberian Platform

    NASA Astrophysics Data System (ADS)

    Shatskii, V. S.; Zedgenizov, D. A.; Ragozin, A. L.; Kalinina, V. V.; Reutskii, V. N.

    2011-09-01

    Variations in the isotopic composition of carbon and the nitrogen contents in diamonds from placers of the northeastern portion of the Siberian Platform have been examined. The results obtained indicate that there is no correlation between local variations in the isotopic composition of carbon and the nitrogen content and the degree of nitrogen aggregation. It has been demonstrated that changes in oxygen fugacity in the course of the growth of diamonds of the V variety do not affect the isotopic composition of carbon. The nature of the variations in the isotopic composition of carbon and the nitrogen contents indicate that there were at least two sources of carbon. The sources of lightweight and weighted compositions of carbon in the diamonds could be organic carbon and carbon in marine carbonates of the subducted crust of the Earth, respectively. Mantle carbon was involved in the diamond formation process at the final stages of the growth.

  2. Variability in carbon and nitrogen isotope fractionation associated with bacterial hydrolysis of atrazine

    NASA Astrophysics Data System (ADS)

    Meyer, A.; Penning, H.; Elsner, M.

    2009-04-01

    Even after legislative prohibition in 1991 by the European Union, the pesticide atrazine and its metabolites are still detected in surface and ground water frequently exceeding the permitted drinking water concentration limit of 0,1 g/L. Despite much recent research on atrazine, its risk assessment in the environment is still a major challenge because of the difficulty of establishing mass balances in the subsurface. To obtain a better insight into the fate of atrazine, we developed compound-specific stable isotope analysis (CSIA) for atrazine. CSIA has proven valuable for assessing organic contaminants in subsurface environments, on the one hand for source identification and on the other hand to trace (bio)chemical degradation reactions through isotope fractionation in the compounds. Such assessment is based on the Rayleigh equation and therein on the isotope enrichment factor É?, which must be determined experimentally beforehand. In ongoing work, we therefore measured carbon and nitrogen isotope fractionation associated with biotic hydrolsis of atrazine. C and N isotope enrichment factors were determined in resting cell experiments for Pseudomonas sp. ADP, Chelatobacter heintzii and Arthrobacter aurescens TC1, strains that hydrolyse atrazine in the initial transformation reaction. Carbon and nitrogen isotope enrichment factors were distinctly different between the bacterial strains. However, when plotting shifts in carbon isotope ratios versus shifts in nitrogen isotope ratios the slopes of the different degradation experiments coincided well. These results give evidence that all bacterial strains were carrying out the same initial biochemical degradation reaction, but that the associated isotope fractionation, as represented by the enrichment factors, was masked to a different extent owing to different rate determining steps prior to the isotopically sensitive bond cleavage (commitment to catalysis). Our study therefore illustrates the benefit of multi-element isotope approaches to assess the environmental fate of atrazine by CSIA.

  3. Accurate experimental determination of the isotope effects on the triple point temperature of water. II. Combined dependence on the 18O and 17O abundances

    NASA Astrophysics Data System (ADS)

    Faghihi, V.; Kozicki, M.; Aerts-Bijma, A. T.; Jansen, H. G.; Spriensma, J. J.; Peruzzi, A.; Meijer, H. A. J.

    2015-12-01

    This paper is the second of two articles on the quantification of isotope effects on the triple point temperature of water. In this second article, we address the combined effects of 18O and 17O isotopes. We manufactured five triple point cells with waters with 18O and 17O abundances exceeding widely the natural abundance range while maintaining their natural 18O/17O relationship. The 2H isotopic abundance was kept close to that of VSMOW (Vienna Standard Mean Ocean Water). These cells realized triple point temperatures ranging between???220 ?K to 1420 ?K with respect to the temperature realized by a triple point cell filled with VSMOW. Our experiment allowed us to determine an accurate and reliable value for the newly defined combined 18, 17O correction parameter of AO??=??630 ?K with a combined uncertainty of 10 ?K. To apply this correction, only the 18O abundance of the TPW needs to be known (and the water needs to be of natural origin). Using the results of our two articles, we recommend a correction equation along with the coefficient values for isotopic compositions differing from that of VSMOW and compare the effect of this new equation on a number of triple point cells from the literature and from our own institute. Using our correction equation, the uncertainty in the isotope correction for triple point cell waters used around the world will be??<1 ?K.

  4. MGA: A gamma-ray spectrum analysis code for determining plutonium isotopic abundances. Volume 3, FORTRAN listing of the GA code

    SciTech Connect

    Gunnink, R

    1991-09-01

    Nondestructive measurements of x-ray and gamma-ray emissions can be used to determine the abundances of various actinides in a sample. Volume 1 of this report describes the methods and algorithms we have developed to determine the relative isotopic abundances of actinides in a sample, by analyzing gamma-ray spectra obtained using germanium detector systems. Volume 2 is a guide to using the MGA (Multiple Group Analysis) computer program we have written to perform plutonium isotopic analyses. This report contains a listing of the FORTRAN instructions of the code.

  5. Comparison of the isotopic abundance of U235 and U238 and the radium activity ratios in Colorado Plateau uranium ores

    USGS Publications Warehouse

    Senftle, F.E.; Stieff, L.; Cuttitta, F.; Kuroda, P.K.

    1957-01-01

    The isotopic abundances of uranium and the radium activity ratios of eleven samples of uranium ore from the Colorado Plateau have been measured. No significant variation in the isotopic abundance of the uranium was noted; with'in the experimental error, the average U235/U238 ratio is 137.7. There is a significant variation in the Ra226/Ra223 activity ratios (0.048-0.143), which indicates a relatively recent alteration of the ore samples. The variations do not, however, explain the lead-uranium and lead-lead age discrepancies. ?? 1957.

  6. Carbonate minerals, oxygen and carbon isotopes in modern temperate bryozoa, eastern Tasmania, Australia

    NASA Astrophysics Data System (ADS)

    Prasada Rao, C.

    1993-12-01

    X-ray analysis of cool temperate bryozoa from eastern shelf carbonates indicates the occurrence of a spectrum of low-Mg calcite to high-Mg calcite with variable amounts of aragonite. Bryozoa contain variable amounts of CaCO 3 cements. In bryozoa ?18O values increase and ?13C values decrease with increasing aragonite content probably due to the occurrence of vaterite. Aragonite contents decrease with decreasing water temperatures as established by oxygen isotope thermometry. Tasmanian bryozoa may be enriched in ?18O up to 0.7‰ due to aragonite and high Mg-calcite contents. ?13C values of bryozoa composed of pure calcite are similar to those of associated brachiopods. ?18O and ?13C values of bryozoa are unaffected by kinetic and metabolic effects. The isotopic field of temperate bryozoa differs from tropical carbonates by having heavier ?18O ( 1.3‰ ± 0.5) and lighter ?13C ( 1.8‰ ± 0.8) values than bulk tropical carbonates. The bryozoa are in equilibrium with upwelling deep seawater and surface subantarctic water and therefore intersect seafloor diagenesis and upwelling water trend lines. Mol% MgCO 3 content ranges from 2 to 11 in calcite and corresponds to 5-14°C water temperatures. The ?18O values of bryozoa give a range of temperatures from 7° to 13°C, slightly less than the 4-15°C obtained from ?18O of Tasmanian brachiopods. This discrepancy is probably due to either minor biochemical fractionation or to bryozoa being in equilibrium with warmer waters.

  7. Canopy-scale kinetic fractionation of atmospheric carbon dioxide and water vapour isotopes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The isotopic fluxes of carbon dioxide (CO2) and water vapour (H2O) between the atmosphere and terrestrial plants provide powerful constraints on carbon sequestration on land 1-2, changes in vegetation cover 3 and the Earth’s Dole effect 4. Past studies, relying mainly on leaf-scale observations, hav...

  8. Oxygen and Carbon Isotope Variations in a Modern Rodent Community Implications for

    E-print Network

    Schöne, Bernd R.

    Oxygen and Carbon Isotope Variations in a Modern Rodent Community ­ Implications of seven sympatric modern rodent species collected from owl pellets at a single locality were measured coexisting carbonate (d18 OCO3) and phosphate (d18 OPO4) in rodent bioapatite was determined, and d18 O

  9. Isotopic fractionations associated with phosphoric acid digestion of carbonate minerals: Insights from first-principles theoretical

    E-print Network

    Goddard III, William A.

    Isotopic fractionations associated with phosphoric acid digestion of carbonate minerals: Insights 27 May 2009; available online 23 June 2009 Abstract Phosphoric acid digestion has been used with phosphoric acid digestion of carbonates at 25 °C are 10.72&, 0.220&, 0.137&, 0.593& for, respectively, 18 O

  10. Soil moisture effects on the carbon isotopic composition of soil respiration

    EPA Science Inventory

    The carbon isotopic composition ( 13C) of recently assimilated plant carbon is known to depend on water-stress, caused either by low soil moisture or by low atmospheric humidity. Air humidity has also been shown to correlate with the 13C of soil respiration, which suggests indir...

  11. Pre-Existing Carbon Structure and Its Effect on Site-Specific Carbon Isotopes in Small Organic Molecules

    NASA Astrophysics Data System (ADS)

    Piasecki, A.; Eiler, J. M.

    2014-12-01

    The ability to measure site-specific isotopes in organic molecules allows for better understanding of the mechanisms of their biosynthetic and/or catagenic formation and destruction. Here we examine for site-specific isotopic composition of propane from natural and synthetic sources using novel instruments and techniques gas source mass spectrometry 1, and discuss the possible relationship of our findings to recent independent evidence from NMR measurements for the isotopic structures of long-chain alkanes2. A recent NMR study2 demonstrates that n-alkanes can be divided into three groups according to their site-specific carbon isotope structure: long (C16+) even carbon number, long (C17+) odd carbon number , and short (C11-C15). We modeled the isotopic site-specific composition of propane derived from these three distinct groups. If propane is cleaved from such long-chain hydrocarbons without fractionation, the long odd-numbered and the shorter alkanes would produce propane with an average terminal position 6-7‰ lighter than the center position, while the long even-numbered chain compounds would produce propane with a terminal position averaging around 7‰ heavier than the center. If, instead the fractionation associated with cleaving propane from such parent molecules is ~10‰ (as seems likely), then these average terminal — center differences should be decreased by ~5 ‰ (i.e., to -11-12 and +1-2 ‰, respectively). We will compare these predictions with our previous demonstrations of the changes in bulk and site specific compositions in propane due to isotope exchange equilibria, diffusion and conventional models of kerogen 'cracking', and will use these models as a framework for interpreting the observed site-specific isotopic compositions of propane from diverse natural gas deposits. 1. Piasecki, A. et al. Site-Specific Carbon Isotope Measurement of Organics by Gas Source Mass Spectrometry. Mineralogical Magazine 77, (2013). 2. Gilbert, A., Yamada, K. & Yoshida, N. Organic Geochemistry. Organic Geochemistry 62, 56-61 (2013).

  12. Stable Isotopic Composition of Interstitial Waters and Authigenic Carbonates, New Jersey Shelf: Origin of Carbonates and Implication for Methane Flux

    NASA Astrophysics Data System (ADS)

    Malone, M. J.; Claypool, G.; Martin, J. B.; Dickens, G. R.

    2001-12-01

    We report the oxygen and carbon isotopic composition of interstitial waters and authigenic carbonate nodules and cemented layers from the New Jersey shelf, which are used to interpret the origin of the carbonates and make inferences about evolution of methane within the shelf sediments. Mineralogically, most of the nodules are siderites, the exception being two calcite nodules. Dolomite is found primarily as a cement in well-lithified layers. One calcite cemented layer was also recovered. Despite the presence of a modern fresh-brackish water lens within the pore waters off New Jersey that can be detected at least as far as the drill sites, about 130 km from the coast, the oxygen isotopic composition of the authigenic carbonates (1.3 to 6.5 per mil PDB) clearly indicates that they formed in marine pore fluids. The carbon isotopic composition of dolomite cements range from -16.4 to -8.8 per mil PDB, consistent with formation within the zone of sulfate reduction. Siderite carbon isotopic values show a greater range (-17.67 to 16.4 per mil), but are largely positive (mean = 2.8 per mil). We interpret the carbon isotopic composition of the shelf siderites to indicate formation throughout the zone of methanogenesis. In contrast, calcite carbon isotopic values are highly negative (as low as -41.7 per mil) and must have formed from waters with a large component of dissolved inorganic carbon derived from methane oxidation. Despite complete sulfate reduction, methanogenesis is not an important process presently occurring in the upper 400 m of the outer New Jersey shelf. In contrast, the carbon isotopic composition of the siderites and calcites document an active methanogenic zone during their formation. We infer that the methane was either oxidized or vented out of the shelf sediments, probably related to effects associated with sea-level fluctuations. If this previously unrecognized flux is an areally important process during Neogene sea-level fluctuations, then it may have important consequences to long-term carbon cycling.

  13. The Precambrian Biogeochemical Carbon Isotopic Record: Contributions of Thermal Versus Biological Processes

    NASA Technical Reports Server (NTRS)

    DesMarais, David J.; DeVincenzi, Donald L. (Technical Monitor)

    2000-01-01

    Superplumes offer a new approach for understanding global C cycles. Isotopes help to discern the impacts of geological, environmental and biological processes ujpun the evolution of these cycles. For example, C-13/C-12 values of coeval sedimentary organics and carbonates give global estimates of the fraction of C buried as organics (Forg), which today lies near 0.2. Before Oxygenic photosynthesis arose, our biosphere obtained reducing power for biosynthesis solely from thermal volatiles and rock alteration. Thus Forg was dominated by the mantle redox state, which has remained remarkably constant for greater than Gy. Recent data confirm that the long-term change in Forg had been small, indicating that the mantle redox buffer remains important even today. Oxygenic photosynthesis enabled life to obtain additional reducing power by splitting the water molecule. Accordingly, biological organic production rose above the level constrained by the mantle-derived flux of reduced species. For example, today, chemoautotrophs harvesting energy from hydrothermal emanations can synthesize at most between 0.2 x 10(exp 12) and 2x 10(exp 12) mol C yr-1 of organic C globally. In contrast, global photosynthetic productivity is estimated at 9000 x 10(exp 12) mol C yr-1. Occasionally photosynthetic productivity did contribute to dramatically -elevated Forg values (to 0.4 or more) as evidenced by very high carbonate C-13/C-12. The interplay between biological, tectonic and other environmental factors is illustrated by the mid-Archean to mid-Proterozoic isotopic record. The relatively constant C-13/C-12 values of Archean carbonates support the view that photosynthetically-driven Forg increases were not yet possible. In contrast, major excursions in C-13/C-12, and thus also in Forg, during the early Proterozoic confirmed the global importance of oxygenic photosynthesis by that time. Remarkably, the superplume event at 1.9 Ga did not trigger another major Forg increase, despite the favorable conditions for organic burial that were evidenced by elevated sea levels and higher black shale abundances. Perhaps those superplume-rated processes that favored enhanced organic burial were offset by the ability of mantle-derived redox buffering, which was enhanced during the superplume event, to limit excursions in Forg.

  14. Compound-specific carbon isotopic fractionation during transport of phthalate esters in sandy aquifer.

    PubMed

    Liu, Hui; Li, YanXi; He, Xi; Sissou, Zakari; Tong, Lei; Yarnes, Chris; Huang, Xianyu

    2016-02-01

    The present paper aims to evaluate the carbon isotopic fractionation of phthalate esters (PAEs) during transport in an sandy aquifer. Breakthrough curves of di-methyl phthalate (DMP), di-ethyl phthalate (DEP), and di-n-butyl phthalate (DBP) in mixed solution were determined by miscible displacement experiment, and simulated using HYDRUS-1D software. The stable carbon isotopes (?(13)C) of 3 PAEs in effluent were analyzed at different times. Results showed that, in the transport process in sandy sediment, PAEs are mainly trapped into the pore space instead of being adsorbed on the surface of particles. At the initial stage of transport, PAEs with lighter carbon tend to run faster in the sandy sediment, and PAEs with heavier carbon run after. However, there is no priority for the transport of PAEs with different carbon isotopes at Stage ? with mainly time-limited sorption. So the transport-based isotope fractionation occurs in the front area of contaminant plume. This effect may be relevant for interpreting carbon isotope signatures in the real contaminant site. PMID:26539707

  15. [Provenance difference in stable carbon isotope discrimination of Schima superba].

    PubMed

    Lin, Lei; Zhou, Zhi-Chun; Fan, Hui-Hua; Jin, Guo-Qing; Chen, Yi-Liang; Hong, Gui-Mu

    2009-04-01

    The difference in leaf stable carbon isotope discrimination (delta) of 18 representative Schima superba provenances was investigated based on three provenance trails located at Jian' ou of Fujian Province and Chun' an and Qingyuan of Zhejiang Province, and the geographic variation pattern and the effects of trial site and provenances growth rate were studied. Significant differences in leaf delta were observed among the provenaces, and the differences in leaf delta value between the highest and lowest provenances reached 6.9%, 3.0%, and 3.7% in 3 experimental sites, respectively. A classic latitudinal clinical variation pattern was found, because there were significant correlations between the leaf delta value and the latitude of seed sources in all the 3 sites while no significant correlations were observed between the leaf delta value and the longitude of the seed sources. The southern provenances showed higher leaf delta value than the northern provenances, indicating that the water use efficiency (WUE) was lower in southern provenances. The leaf delta value of different provenances was demonstrated to be greatly affected by the environment of trial sites. The leaf delta value increased significantly with the improvement of site environment and with the increase of annual rainfall. Significant positive correlations were observed between the leaf delta value and the growth traits including tree height, DBH, total number of lateral branches, and length of the strongest lateral branch, which indicated that the provenances with higher growth rate and denser crown had larger leaf delta value. Two and four superior provenances with high growth rate and low leaf delta value (or high WUE) were selected for Jian' ou of Fujian and Chun' an of Zhejiang, respectively. PMID:19565749

  16. Cretaceous shales from the western interior of North America: sulfur/carbon ratios and sulfur-isotope composition.

    USGS Publications Warehouse

    Gautier, D.L.

    1986-01-01

    Sulphur/carbon ratios in cores of selected Cretaceous marine shales average 0.67, a value greater than that observed in recent marine sediments and much higher than global values calculated for the Cretaceous. This may be ascribed to generally low levels of bioturbation and enhanced efficiency of sulphate reduction due to low oxygen levels in Cretaceous seaways. Isotopic compositions of pyrite sulphur vary systematically with level of oxygenation of the depositional environment and therefore with organic carbon abundance and type of organic matter. Samples with >4% organic carbon are extremely depleted in 34S (mean delta 34S -31per mille) and contain hydrogen-rich organic matter. Samples containing <1.5% organic carbon display relatively 'heavy' but wide-ranging delta 34S values (-34.6 to +16.8per mille) and contain hydrogen-poor organic matter. Samples with intermediate amounts of organic carbon have average delta 34S of -25.9per mille and contain both types of organic matter. Relations between the nature of these shales, and their sedimentation rate and depositional environment are discussed.-L.C.H.

  17. Fluids in the damage zone: Insights from clumped isotope thermometry of fault-hosted carbonate cements

    NASA Astrophysics Data System (ADS)

    Crider, Juliet G.; Hodson, Keith R.; Huntington, Katharine W.

    2015-04-01

    Carbonate cements in fault zone rocks contain both chemical and physical information about the interaction and coevolution of their source fluids with surrounding fault rock. In this work, we present an analysis of textural relationships and isotopic compositions of carbonate cements in sandstone, within a well-characterized upper-crustal fault intersection zone, 'Courthouse Junction' along the Moab Fault in southeast Utah, USA. Structures exposed at the outcrop record several phases of overprinting brittle deformation, including cataclastic deformation bands, fracturing and faulting. Carbonate diagenesis is thought to be a later stage, possibly facilitated by an increase in fault parallel permeability. Calcite is hosted within joints and concretions associated with both deformation-band faults and fracture-based faults. We have used cathodoluminescence, oxygen and carbon isotopes, and clumped isotope paleothermometry to differentiate two populations of calcite cement in the fault intersection zone: cool (

  18. Carbon and hydrogen isotopic composition of bacterial methane in a shallow freshwater lake

    SciTech Connect

    Woltemate, I.; Whiticar, M.J.; Schoell, M.

    1984-09-01

    Anoxic sediments from freshwater environments such as bogs, swamps, and lakes undergoing early diagenesis are frequently characterized by the formation of biogenic methane. Freshwater biogenic methanes exhibit carbon and hydrogen isotopic values strongly depleted in C-13 and deuterium relative to the respective values for carbon dioxide and formation water. The percentages of methane generated by fermentation and carbon dioxide reduction can be estimated by comparison of hydrogen isotopes in the formation water and methane. On the basis of these hydrogen isotope data, about 75% of the methane formation in Wurmsee comes from acetate reduction. Fermentation is thus the dominant although not exclusive process. Carbon dioxide reduction contributed the balance of the bacterial methane generated. 35 references, 5 figures, 1 table.

  19. Carbon isotope records reveal synchronicity between carbon cycle perturbation and the "Carnian Pluvial Event" in the Tethys realm (Late Triassic)

    NASA Astrophysics Data System (ADS)

    Dal Corso, Jacopo; Gianolla, Piero; Newton, Robert J.; Franceschi, Marco; Roghi, Guido; Caggiati, Marcello; Raucsik, Béla; Budai, Tamás; Haas, János; Preto, Nereo

    2015-04-01

    In the early Late Triassic a period of increased rainfall, named the Carnian Pluvial Event (CPE), is evidenced by major lithological changes in continental and marine successions worldwide. The environmental change seems to be closely associated with a negative carbon isotope excursion that was identified in a stratigraphic succession of the Dolomites (Italy) but the temporal relationship between these phenomena is still not well defined. Here we present organic-carbon isotope data from Carnian deep-water stratigraphic sections in Austria and Hungary, and carbonate petrography of samples from a marginal marine section in Italy. A negative 2-4‰ ?13C shift is recorded by bulk organic matter in the studied sections and is coincident with a similar feature highlighted in higher plant and marine algal biomarker carbon-isotope records from the Dolomites (Italy), thus testifying to a global change in the isotopic composition of the reservoirs of the exchangeable carbon. Our new observations verify that sedimentological changes related to the CPE coincide with the carbon cycle perturbation and therefore occurred synchronously within the western Tethys. Consistent with modern observations, our results show that the injection of 13C-depleted CO2 into the Carnian atmosphere-ocean system may have been directly responsible for the increase in rainfall by intensifying the Pangaean mega-monsoon activity. The consequent increased continental weathering and erosion led to the transfer of large amounts of siliciclastics into the basins that were rapidly filled up, while the increased nutrient flux triggered the local development of anoxia. The new carbonate petrography data show that these changes also coincided with the demise of platform microbial carbonate factories and their replacement with metazoan driven carbonate deposition. This had the effect of considerably decreasing carbonate deposition in shallow water environments.

  20. Carbon and nitrogen abundances of individual stars in the Sculptor dwarf spheroidal galaxy

    E-print Network

    Lardo, C; Pancino, E; Romano, D; de Boer, T J L; Starkenburg, E; Tolstoy, E; Irwin, M J; Jablonka, P; Tosi, M

    2015-01-01

    We present [C/Fe] and [N/Fe] abundance ratios and CH({\\lambda}4300) and S({\\lambda}3883) index measurements for 94 red giant branch (RGB) stars in the Sculptor dwarf spheroidal galaxy from VLT/VIMOS MOS observations at a resolving power R= 1150 at 4020 {\\AA}. This is the first time that [N/Fe] abundances are derived for a large number of stars in a dwarf spheroidal. We found a trend for the [C/Fe] abundance to decrease with increasing luminosity on the RGB across the whole metallicity range, a phenomenon observed in both field and globular cluster giants, which can be interpreted in the framework of evolutionary mixing of partially processed CNO material. Both our measurements of [C/Fe] and [N/Fe] are in good agreement with the theoretical predictions for stars at similar luminosity and metallicity. We detected a dispersion in the carbon abundance at a given [Fe/H], which cannot be ascribed to measurement uncertainties alone. We interpret this observational evidence as the result of the contribution of differ...

  1. Carbon Stable Isotopes as Indicators of Coastal Eutrophication

    EPA Science Inventory

    Coastal ecologists and managers have frequently used nitrogen stable isotopes (?15N) to trace and monitor anthropogenic nitrogen (N) in coastal ecosystems. However, the interpretation of ?15N data can often be challenging, if not confounding, as the isotope values fractionate su...

  2. Carbon isotopic fractionation in lipids from methanotrophic bacteria: Relevance for interpretation of the geochemical record of biomarkers

    NASA Astrophysics Data System (ADS)

    Summons, Roger E.; Jahnke, Linda L.; Roksandic, Zarko

    1994-07-01

    Experiments with cultured aerobic methane oxidising bacteria confirm that their biomarker lipids will be significantly depleted in 13C compared to the substrate. The methanotrophic bacteria Methylococcus capsulatus and Methylomonas methanica, grown on methane and using the RuMP cycle for carbon assimilation, show maximum 13C fractionation of approximately 30%. in the resultant biomass. In M. capsulatus, the maximum fractionation is observed in the earliest part of the exponential growth stage and decreases to approximately 16%. as cells approach stationary phase. This change may be associated with a shift from the particulate form to the soluble form of the methane monooxygenase enzyme. Less than maximum fractionation is observed when cells are grown with reduced methane availability. Biomass of M. capsulatus grown on methanol was depleted by 9%. compared to the substrate. Additional strong 13C fractionation takes place during polyisoprenoid biosynthesis in methanotrophs. The ?13C values of individual hopanoid and steroid biomarkers produced by these organisms were as much as 10%. more negative than total biomass. In individual cultures, squalene was 13C-enriched by as much as 14%. compared to the triterpane skeleton of bacteriohopaneaminopentol. Much of the isotopic dispersion in lipid metabolites could be attributed to shifts in their relative abundances, combined with an overall reduction in fractionation during the growth cycle. In cells grown on methanol, where there was no apparent effect of growth stage on overall fractionation there were still significant isotopic differences between closely related lipids including a 5.3%. difference between the hopane and 3 ?-methylhopane skeletons. Hopane and sterane polyisoprenoids were also 13C-depleted compared to fatty acids. These observations have significant implications for the interpretation of specific compound isotopic signatures now being measured for hydrocarbons and other lipids present in sediments and petroleum. In particular, biomarker lipids produced by a single organism do not necessarily have the same carbon isotopic composition.

  3. Carbon isotopic fractionation in lipids from methanotrophic bacteria: relevance for interpretation of the geochemical record of biomarkers

    NASA Technical Reports Server (NTRS)

    Summons, R. E.; Jahnke, L. L.; Roksandic, Z.

    1994-01-01

    Experiments with cultured aerobic methane oxidising bacteria confirm that their biomarker lipids will be significantly depleted in 13C compared to the substrate. The methanotrophic bacteria Methylococcus capsulatus and Methylomonas methanica, grown on methane and using the RuMP cycle for carbon assimilation, show maximum 13C fractionation of approximately 30% in the resultant biomass. In M. capsulatus, the maximum fractionation is observed in the earliest part of the exponential growth stage and decreases to approximately 16% as cells approach stationary phase. This change may be associated with a shift from the particulate form to the soluble form of the methane monooxygenase enzyme. Less than maximum fractionation is observed when cells are grown with reduced methane availability. Biomass of M. capsulatus grown on methanol was depleted by 9% compared to the substrate. Additional strong 13C fractionation takes place during polyisoprenoid biosynthesis in methanotrophs. The delta 13C values of individual hopanoid and steroid biomarkers produced by these organisms were as much as l0% more negative than total biomass. In individual cultures, squalene was 13C-enriched by as much as 14% compared to the triterpane skeleton of bacteriohopaneaminopentol. Much of the isotopic dispersion in lipid metabolites could be attributed to shifts in their relative abundances, combined with an overall reduction in fractionation during the growth cycle. In cells grown on methanol, where there was no apparent effect of growth stage on overall fractionation there were still significant isotopic differences between closely related lipids including a 5.3% difference between the hopane and 3 beta-methylhopane skeletons. Hopane and sterane polyisoprenoids were also 13C-depleted compared to fatty acids. These observations have significant implications for the interpretation of specific compound isotopic signatures now being measured for hydrocarbons and other lipids present in sediments and petroleum. In particular, biomarker lipids produced by a single organism do not necessarily have the same carbon isotopic composition.

  4. Insights into early Earth from the Pt-Re-Os isotope and highly siderophile element abundance systematics of Barberton komatiites

    NASA Astrophysics Data System (ADS)

    Puchtel, Igor S.; Walker, Richard J.; Touboul, Mathieu; Nisbet, Euan G.; Byerly, Gary R.

    2014-01-01

    Highly siderophile element (HSE: Os, Ir, Ru, Pt, Pd, and Re) abundance and Pt-Re-Os isotopic data are reported for well-preserved komatiites from the Komati and Weltevreden Formations of the Barberton Greenstone Belt in South Africa. The Re-Os data for whole-rock samples and olivine and chromite separates define isochrons with ages of 3484 ± 38 and 3263 ± 12 Ma for the Komati and Weltevreden systems, respectively. The respective initial 187Os/188Os = 0.10335 ± 15 (?187Os = +0.34 ± 0.15) and 0.10442 ± 4 (?187Os = -0.14 ± 0.04) are well within the range defined by chondritic meteorites. When considered together with the Re-Os data for late Archean komatiite systems, these data indicate that the mantle sources of most Archean komatiites evolved with essentially uniform long-term Re/Os that is well within the chondritic range. By contrast, the initial 186Os/188Os = 0.1198283 ± 9 (?186Os = -0.12 ± 0.08) and 0.1198330 ± 8 (?186Os = +0.22 ± 0.07) for the Komati and Weltevreden systems, respectively, are outside of known chondritic evolution paths, indicating that the mantle sources of these two komatiite systems evolved with fractionated time-integrated Pt/Os. The new 186,187Os isotopic data for these early Archean komatiite systems, combined with published 142,143Nd and 176Hf isotopic data for these systems, are consistent with formation and long-term isolation of deep-seated mantle domains with fractionated time-integrated Sm/Nd, Lu/Hf, and Pt/Os ratios, at ca. 4400 Ma. These domains may have been generated as a result of late-stage crystallization of a primordial magma ocean involving Mg-perovskite, Ca-perovskite and Pt-alloys acting as the fractionating phases. The inferred fractionated mantle domains were sampled by the early Archean komatiites, but were largely mixed away by 2.7 Ga, as evidenced by uniform time-integrated Sm/Nd, Lu/Hf, and Pt/Os ratios inferred for the sources of most late Archean komatiite systems. The calculated total Pt + Pd abundances present in the sources of the early Archean komatiite systems fall only 7-14% short of those present in estimates for the modern primitive mantle. These are also within the range of the total Pt + Pd abundances present in the sources of late Archean komatiite systems, indicating little change in the HSE abundances in the Archean mantle between 3.5 and 2.7 Ga. The new HSE data for the early Archean komatiite systems may implicate late accretion of HSE to the mantle prior to completion of crystallization of a final terrestrial magma ocean, followed by sluggish mixing of diverse, post-magma ocean domains characterized by variably fractionated lithophile element and HSE abundances.

  5. The relationship between carbon monoxide abundance and visual extinction in interstellar clouds

    NASA Technical Reports Server (NTRS)

    Frerking, M. A.; Langer, W. D.; Wilson, R. W.

    1982-01-01

    Carbon monoxide column densities are compared to visual extinctions toward field stars in the rho Oph and Taurus molecular cloud complexes. The relationship of C(0-18) column density to extinction is established, and new determinations for (C-13)O column densities are given for a range of visual extinctions extended to beyond 20 mag. A prescription for determining hydrogen column densities and masses of molecular clouds from observations of CO isotopes is presented and discussed critically. These measurements agree well with the predictions of gas phase chemistry models which include chemical fractionation and selective isotopic photodestruction. The functional dependence of the C(O-18) column density on extinction is characterized by two different regimes separated by a distinct transition observed to occur at 4 mag in both molecular cloud complexes, whereas the functional dependence of (C-13)O is quite different in the two regions. Some saturation is found to occur for C(O-18) emission at high visual extinction and use the rarer isotopic species C(O-17) and (C-13)(O-18) to correct for it.

  6. Seasonal variation in kangaroo tooth enamel oxygen and carbon isotopes in southern Australia

    NASA Astrophysics Data System (ADS)

    Brookman, Tom H.; Ambrose, Stanley H.

    2012-09-01

    Serial sampling of tooth enamel growth increments for carbon and oxygen isotopic analyses of Macropus (kangaroo) teeth was performed to assess the potential for reconstructing paleoseasonality. The carbon isotope composition of tooth enamel apatite carbonate reflects the proportional intake of C3 and C4 vegetation. The oxygen isotopic composition of enamel reflects that of ingested and metabolic water. Tooth enamel forms sequentially from the tip of the crown to the base, so dietary and environmental changes during the tooth's formation can be detected. ?13C and ?18O values were determined for a series of enamel samples drilled from the 3rd and 4th molars of kangaroos that were collected along a 900 km north-south transect in southern Australia. The serial sampling method did not yield pronounced seasonal isotopic variation patterns in Macropus enamel. The full extent of dietary isotopic variation may be obscured by attenuation of the isotopic signal during enamel mineralisation. Brachydont (low-crowned) Macropus teeth may be less sensitive to seasonal variation in isotopic composition due to time-averaging during mineralisation. However, geographic variations observed suggest that there may be potential for tracking latitudinal shifts in vegetation zones and seasonal environmental patterns in response to climate change.

  7. Effectiveness of leaded petrol phase-out in Tianjin, China based on the aerosol lead concentration and isotope abundance ratio.

    PubMed

    Wang, Wan; Liu, Xiande; Zhao, Liwei; Guo, Dongfa; Tian, Xiaodan; Adams, Freddy

    2006-07-01

    The phase-out of leaded petrol has been a measure widely used to reduce atmospheric lead pollution. Since the 1980s, China began to promote unleaded petrol. In order to assess the effectiveness of the measure an isotope fingerprint technique was applied for aerosol samples in the city of Tianjin. After dilute acid leaching, the lead concentration and isotope abundance ratios were determined for 123 samples collected in Tianjin during eight years (1994-2001). The 206Pb/207Pb ratio was lower in summer, when coal combustion emission was low and vehicle exhaust became more important, indicating that the 206Pb/207Pb ratio of leaded petrol in Tianjin is lower than that of aerosol samples. The 206Pb/207Pb ratio gradually increased from 1994 to 2001, a trend that suggests that the contribution from vehicle exhaust was diminishing. Overall, the measurements matched well with national statistical data of leaded and unleaded petrol production. After the nationwide switch to unleaded gasoline, comprehensive control measures are urgently needed to reduce air lead pollution in China, as aerosol lead reduced slightly but remains at a relatively high level. PMID:16165188

  8. Iron and Carbon Isotope Evidence for Microbial Iron Respiration Throughout the Archean

    NASA Astrophysics Data System (ADS)

    Craddock, P. R.; Dauphas, N.

    2010-12-01

    Banded Iron-Formations (BIFs) are voluminous chemical sediments that are rich in iron-oxide, carbonate and silica and whose occurrence is unique to the Precambrian. Their preservation in the geological records offers insights to the surface chemical and biological cycling of iron and carbon on early Earth. However, many details regarding the role of microbial activity in BIF deposition and diagenesis are unresolved. Laboratory studies have shown that reaction between carbon and iron through microbial iron respiration (4Fe(OH)3 + [CH2O] + 7H+ ? 4Fe2+ + HCO3- + 10H2O + chemical energy) can impart fractionation to the isotopic compositions of these elements. Here, we report iron (?56Fe, vs. IRMM-014) and carbon isotopic (?13C, vs. V-PDB) compositions of magnetite and of iron-rich (siderite, ankerite) and iron-poor carbonates (calcite, dolomite) in BIFs from the late Archean (~2.5 Ga) Hamersley Basin, Australia and the early Archean (~3.8 Ga) Isua Supracrustal Belt (ISB), Greenland. The range of ?56Fe values measured in the Hamersley Basin, including light values in magnetite (as low as -1.0 ‰) and heavy values in iron-rich carbonates (up to +1.2 ‰), are incompatible with their precipitation in equilibrium with seawater. Rather, the isotopic compositions of Fe-rich carbonates together with previously reported light ?13C values in these same carbonates record evidence for diagenetic reduction of ferric oxide precursors to magnetite and carbonate through microbial iron respiration (i.e., dissimilatory iron reduction, DIR). Iron and carbon isotope data of iron-rich metacarbonates from the ISB are similar to those of late Archean BIFs. The isotopic signatures of these metacarbonates are supportive of an early diagenetic origin despite metasomatic overprint, and preserve evidence for microbial iron catabolism at ~3.8 Ga, within the oldest recognized sedimentary rocks on Earth.

  9. Secondary ion mass spectrometry combined with alpha track detection for isotope abundance ratio analysis of individual uranium-bearing particles.

    PubMed

    Esaka, Fumitaka; Magara, Masaaki

    2014-03-01

    Secondary ion mass spectrometry (SIMS) was used in combination with alpha track detection for the efficient analysis of uranium-bearing particles with higher (235)U abundances in environmental samples. A polycarbonate film containing particles was prepared and placed in contact with a CR-39 plastic detector. After exposure for 28 days, the detector was etched in a NaOH solution and each uranium-bearing particle was identified through observation of the alpha tracks recorded in the detector. A portion of the film containing each uranium-bearing particle was cut out and put onto a glassy carbon planchet. The films on the planchet were decomposed through plasma ashing for subsequent uranium abundance ratio analysis with SIMS. The alpha track-SIMS analysis of 10 uranium-bearing particles in a sample taken from a nuclear facility enabled n((235)U)/n((238)U) abundance ratios in the range 0.0072-0.25 to be detected, which were significantly higher than those obtained by SIMS without alpha track detection. The duration of the whole analytical process for analysis of 10 particles was about 32 days. The detection efficiency was calculated to be 27.1±6.5%, based on the analysis of the particles in uranium reference materials. The detection limits, defined as the diameter of the particle which produces alpha tracks more than one for a 28-days exposure, were estimated to be 0.8, 0.9, 1.1, 2.1 and 3.0 ?m for the particles having the same uranium abundance ratios with NBL CRM U850, U500, U350, U050 and U010 reference materials, respectively. The use of alpha track detection for subsequent SIMS analysis is an inexpensive and an efficient way to measure uranium-bearing particles with higher (235)U abundances. PMID:24468381

  10. Ozone Abundance in a Nitrogen-Carbon Dioxide Dominated Terrestrial Paleoatmosphere

    E-print Network

    B. C. Thomas; A. L. Melott; L. D. Martin; C. H. Jackman

    2004-10-22

    We compute the ozone distribution for a model terrestrial paleoatmosphere in which the present oxygen abundance is largely replaced by carbon dioxide, which we argue is a reasonable working assumption. In principle, the presence of carbon dioxide might supplement the ozone shield as compared with models based on nitrogen without high carbon dioxide abundance so that early life need not have been as UV-resistant as often assumed. An extrasolar planet with a high-CO2 atmosphere might contain enough O3 to be a source of false positive biomarkers. We find that the globally averaged O3 column density can be the same, or nearly four times higher (depending upon the O2 partial pressure) when CO2 is used in place of N2 as the replacement component for lowered O2 in a 1-atm terrestrial planet with solar radiation. The effect is important for making quantitative deductions from future data, but does not invalidate the use of O3 as a biomarker for free oxygen. These results make prospects for detection of extrasolar planetary O3 absorption somewhat better than before.

  11. THE FIRST FLUORINE ABUNDANCE DETERMINATIONS IN EXTRAGALACTIC ASYMPTOTIC GIANT BRANCH CARBON STARS

    SciTech Connect

    Abia, C.; Cristallo, S.; Dominguez, I.; Cunha, K.; Smith, V. V.; De Laverny, P.; Recio-Blanco, A.; Straniero, O.

    2011-08-10

    Fluorine ({sup 19}F) abundances (or upper limits) are derived in six extragalactic asymptotic giant branch (AGB) carbon stars from the HF(1-0) R9 line at 2.3358 {mu}m in high-resolution spectra. The stars belong to the Local Group galaxies, Large Magellanic Cloud, Small Magellanic Cloud, and Carina dwarf spheroidal, spanning more than a factor of 50 in metallicity. This is the first study to probe the behavior of F with metallicity in intrinsic extragalactic C-rich AGB stars. Fluorine could be measured only in four of the target stars, showing a wide range in F enhancements. Our F abundance measurements together with those recently derived in Galactic AGB carbon stars show a correlation with the observed carbon and s-element enhancements. The observed correlations, however, display a different dependence on the stellar metallicity with respect to theoretical predictions in low-mass, low-metallicity AGB models. We briefly discuss the possible reasons for this discrepancy. If our findings are confirmed in a larger number of metal-poor AGBs, the issue of F production in AGB stars will need to be revisited.

  12. A balloon measurement of the isotopic composition of galactic cosmic ray boron, carbon and nitrogen. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Zumberge, J. F.

    1981-01-01

    The isotopic compositions of galactic cosmic ray boron, carbon, and nitrogen were measured at energies near 300 MeV amu, using a balloon-borne instrument at an atmospheric depth of approximately 5 g/sq cm. The calibrations of the detectors comprising the instrument are described. The saturation properties of the cesium iodide scintillators used for measurement of particle energy are studied in the context of analyzing the data for mass. The achieved rms mass resolution varies from approximately 0.3 amu at boron to approximately 0.5 amu at nitrogen, consistent with a theoretical analysis of the contributing factors. Corrected for detector interactions and the effects of the residual atmosphere the results are B-10/B=0.33 (+0.17, -0.11), C-13/C=0.06 (+0.13, -0.11), and N-15/N=0.42 (+0.19, -0.17). A model of galactic propagation and solar modulation is described. Assuming a cosmic ray source composition of solar-like isotopic abundances, the model predicts abundances near Earth consistent with the measurements.

  13. Variable magnitude of carbon isotope excursions in organic and inorganic terrestrial carbon pools during the Paleocene/Eocene Thermal Maximum

    NASA Astrophysics Data System (ADS)

    Cotton, J. M.; Sheldon, N. D.; Hren, M. T.; Gallagher, T. M.

    2012-12-01

    The Paleocene/Eocene Thermal Maximum (PETM) is the highest magnitude rapid warming event in recent geologic history and is analogous to current climate change, yet the amount and rate of release of carbon is poorly constrained. The size of the carbon isotope excursion (CIE) during the PETM has been used to determine source and amount of carbon released during the event, as well as the subsequent rise in atmospheric pCO2. However, the magnitude of this CIE is highly variable in different environments (marine vs. terrestrial) as well as in different terrestrial carbon records (organic vs. inorganic C). Pedogenic carbonates were first used to identify the carbon isotope excursion on land. Pedogenic carbonates are precipitated from CO2 in the soil atmosphere, the majority of which is derived from the degradation of plant material and so the isotopic composition of these carbonates should be representative of the ?13Corg of plants. However, we find that the CIE is larger in carbonates than in organic material preserved in the same paleosols for two difference sites in the western United States. Previously published data from the Bighorn Basin in Wyoming show a CIE that is up to 3‰ larger in the pedogenic carbonates than the preserved organic material. In Axhandle Canyon in Utah, our new data indicates that the CIE is 2‰ greater in the carbonates than in the preserved organic material. This discrepancy in CIE causes a regional ?13C (?13Ccarb - ?13Corg) excursion during the global warming event. Mechanisms for this ?13C excursion will be discussed with regard to the rapid warming during the PETM as well as implications for pedogenic carbonate paleobarometry.

  14. Carbon and nitrogen abundances of individual stars in the Sculptor dwarf spheroidal galaxy

    NASA Astrophysics Data System (ADS)

    Lardo, C.; Battaglia, G.; Pancino, E.; Romano, D.; de Boer, T. J. L.; Starkenburg, E.; Tolstoy, E.; Irwin, M. J.; Jablonka, P.; Tosi, M.

    2016-01-01

    We present [C/Fe] and [N/Fe] abundance ratios and CH(?4300) and S(?3883) index measurements for 94 red giant branch (RGB) stars in the Sculptor dwarf spheroidal galaxy from VLT/VIMOS MOS observations at a resolving power R = 1150 at 4020 Å. This is the first time that [N/Fe] abundances are derived for a large number of stars in a dwarf spheroidal. We found a trend for the [C/Fe] abundance to decrease with increasing luminosity on the RGB across the whole metallicity range, a phenomenon observed in both field and globular cluster giants, which can be interpreted in the framework of evolutionary mixing of partially processed CNO material. Both our measurements of [C/Fe] and [N/Fe] are in good agreement with the theoretical predictions for stars at similar luminosity and metallicity. We detected a dispersion in the carbon abundance at a given [Fe/H], which cannot be ascribed to measurement uncertainties alone. We interpret this observational evidence as the result of the contribution of different nucleosynthesis sources over time to a not well-mixed interstellar medium. We report the discovery of two new carbon-enhanced, metal-poor stars. These are likely the result of pollution from material enriched by asymptotic giant branch stars, as indicated by our estimates of [Ba/Fe] >+1. We also attempted a search for dissolved globular clusters in the field of the galaxy by looking for the distinctive C-N pattern of second population globular clusters stars in a previously detected, very metal-poor, chemodynamical substructure. We do not detect chemical anomalies among this group of stars. However, small number statistics and limited spatial coverage do not allow us to exclude the hypotheses that this substructure forms part of a tidally shredded globular cluster. Based on observations made with ESO Telescopes at the La Silla Paranal Observatory under programme ID 091.D-0089

  15. Rise in seawater sulphate concentration associated with the Paleoproterozoic positive carbon isotope excursion: evidence

    E-print Network

    Bekker, Andrey

    isotope excursion: evidence from sulphate evaporites in the 2.2­2.1 Gyr shallow-marine Lucknow Formation beds are abundant in Phanerozoic and Neo- proterozoic shallow-marine evaporite deposits, signalling.2 Gyr (Pope and Grotzinger, 2003). Inferred Archean sulphate evaporites (e.g. Buick and Dunlop, 1990

  16. Detection of oxygen isotopic anomaly in terrestrial atmospheric carbonates and its implications to Mars.

    PubMed

    Shaheen, R; Abramian, A; Horn, J; Dominguez, G; Sullivan, R; Thiemens, Mark H

    2010-11-23

    The debate of life on Mars centers around the source of the globular, micrometer-sized mineral carbonates in the ALH84001 meteorite; consequently, the identification of Martian processes that form carbonates is critical. This paper reports a previously undescribed carbonate formation process that occurs on Earth and, likely, on Mars. We identified micrometer-sized carbonates in terrestrial aerosols that possess excess (17)O (0.4-3.9‰). The unique O-isotopic composition mechanistically describes the atmospheric heterogeneous chemical reaction on aerosol surfaces. Concomitant laboratory experiments define the transfer of ozone isotopic anomaly to carbonates via hydrogen peroxide formation when O(3) reacts with surface adsorbed water. This previously unidentified chemical reaction scenario provides an explanation for production of the isotopically anomalous carbonates found in the SNC (shergottites, nakhlaites, chassignites) Martian meteorites and terrestrial atmospheric carbonates. The anomalous hydrogen peroxide formed on the aerosol surfaces may transfer its O-isotopic signature to the water reservoir, thus producing mass independently fractionated secondary mineral evaporites. The formation of peroxide via heterogeneous chemistry on aerosol surfaces also reveals a previously undescribed oxidative process of utility in understanding ozone and oxygen chemistry, both on Mars and Earth. PMID:21059939

  17. Detection of oxygen isotopic anomaly in terrestrial atmospheric carbonates and its implications to Mars

    PubMed Central

    Shaheen, R.; Abramian, A.; Horn, J.; Dominguez, G.; Sullivan, R.; Thiemens, Mark H.

    2010-01-01

    The debate of life on Mars centers around the source of the globular, micrometer-sized mineral carbonates in the ALH84001 meteorite; consequently, the identification of Martian processes that form carbonates is critical. This paper reports a previously undescribed carbonate formation process that occurs on Earth and, likely, on Mars. We identified micrometer-sized carbonates in terrestrial aerosols that possess excess 17O (0.4–3.9‰). The unique O-isotopic composition mechanistically describes the atmospheric heterogeneous chemical reaction on aerosol surfaces. Concomitant laboratory experiments define the transfer of ozone isotopic anomaly to carbonates via hydrogen peroxide formation when O3 reacts with surface adsorbed water. This previously unidentified chemical reaction scenario provides an explanation for production of the isotopically anomalous carbonates found in the SNC (shergottites, nakhlaites, chassignites) Martian meteorites and terrestrial atmospheric carbonates. The anomalous hydrogen peroxide formed on the aerosol surfaces may transfer its O-isotopic signature to the water reservoir, thus producing mass independently fractionated secondary mineral evaporites. The formation of peroxide via heterogeneous chemistry on aerosol surfaces also reveals a previously undescribed oxidative process of utility in understanding ozone and oxygen chemistry, both on Mars and Earth. PMID:21059939

  18. Natural 15N- and 13C-abundance as indicators of forest nitrogen status and soil carbon dynamics

    SciTech Connect

    Garten Jr, Charles T; Hanson, Paul J; Todd Jr, Donald E; Lu, Benwhea Bonnie; Brice, Deanne Jane

    2007-09-01

    This book highlights new and emerging uses of stable isotope analysis in a variety of ecological disciplines. While the use of natural abundance isotopes in ecological research is now relatively standard, new techniques and ways of interpreting patterns are developing rapidly. The second edition of this book provides a thorough, up-to-date examination of these methods of research. As part of the Ecological Methods and Concepts series which provides the latest information on experimental techniques in ecology, this book looks at a wide range of techniques that use natural abundance isotopes to: {sm_bullet} follow whole ecosystem element cycling {sm_bullet} understand processes of soil organic matter formation {sm_bullet} follow the movement of water in whole watersheds {sm_bullet} understand the effects of pollution in both terrestrial and aquatic environments {sm_bullet} study extreme systems such as hydrothermal vents {sm_bullet}follow migrating organisms In each case, the book explains the background to the methodology, looks at the underlying principles and assumptions, and outlines the potential limitations and pitfalls. Stable Isotopes in Ecology and Environmental Science is an ideal resource for both ecologists who are new to isotopic analysis, and more experienced isotope ecologists interested in innovative techniques and pioneering new uses.

  19. Stable isotope composition of dissolved inorganic carbon and particulate organic carbon in sea ice from the Ross Sea, Antarctica

    NASA Astrophysics Data System (ADS)

    Munro, David R.; Dunbar, Robert B.; Mucciarone, David A.; Arrigo, Kevin R.; Long, Matthew C.

    2010-09-01

    We examined controls on the carbon isotopic composition of sea ice brines and organic matter during cruises to the Ross Sea, Antarctica in November/December 1998 and November/December 2006. Brine samples were analyzed for salinity, nutrients, total dissolved inorganic carbon (?CO2), and the 13C/12C ratio of ?CO2 ? Particulate organic matter from sea ice cores was analyzed for percent particulate organic carbon (POC), percent total particulate nitrogen (TPN), and stable carbon isotopic composition (?13CPOC). ?CO2 in sea ice brines ranged from 1368 to 7149 ?mol kg-1, equivalent to 1483 to 2519 ?mol kg-1 when normalized to 34.5 psu salinity (s?CO2), the average salinity of Ross Sea surface waters. Sea ice primary producers removed up to 34% of the available ?CO2, an amount much higher than the maximum removal observed in sea ice free water. Carbonate precipitation and CO2 degassing may reduce s?CO2 by a similar amount (e.g., 30%) in the most hypersaline sea ice environments, although brine volumes are low in very cold ice that supports these brines. Brine ? ranged from -2.6 to +8.0‰ while ?13CPOC ranged from -30.5 to -9.2‰. Isotopic enrichment of the ?CO2 pool via net community production accounts for some but not all carbon isotopic enrichment of sea ice POC. Comparisons of s?CO2, ? and ?13CPOC within sea ice suggest that ?p (the net photosynthetic fractionation factor) for sea ice algae is ˜8‰ smaller than the ?p observed for phytoplankton in open water regions of the Ross Sea. These results have implications for modeling of carbon uptake and transformation in the ice-covered ocean and for reconstruction of past sea ice extent based on stable isotopic composition of organic matter in sediment cores.

  20. Large carbon isotope fractionation associated with oxidation of methyl halides by methylotrophic bacteria

    USGS Publications Warehouse

    Miller, L.G.; Kalin, Robert M.; McCauley, S.E.; Hamilton, John T.G.; Harper, D.B.; Millet, D.B.; Oremland, R.S.; Goldstein, Allen H.

    2001-01-01

    The largest biological fractionations of stable carbon isotopes observed in nature occur during production of methane by methanogenic archaea. These fractionations result in substantial (as much as ???70???) shifts in ??13C relative to the initial substrate. We now report that a stable carbon isotopic fractionation of comparable magnitude (up to 70???) occurs during oxidation of methyl halides by methylotrophic bacteria. We have demonstrated biological fractionation with whole Cells of three methylotrophs (strain IMB-1, strain CC495, and strain MB2) and, to a lesser extent, with the purified cobalamin-dependent methyltransferase enzyme obtained from strain CC495. Thus, the genetic similarities recently reported between methylotrophs, and methanogens with respect to their pathways for C1-unit metabolism are also reflected in the carbon isotopic fractionations achieved by these organisms. We found that only part of the observed fractionation of carbon isotopes could be accounted for by the activity of the corrinoid methyltransferase enzyme, suggesting fractionation by enzymes further along the degradation pathway. These observations are of potential biogeochemical significance in the application of stable carbon isotope ratios to constrain the tropospheric budgets for the ozone-depleting halocarbons, methyl bromide and methyl chloride.

  1. Fractionation of carbon and hydrogen isotopes by methane-oxidizing bacteria

    USGS Publications Warehouse

    Coleman, D.D.; Risatti, J.B.; Schoell, M.

    1981-01-01

    Carbon isotopic analysis of methane has become a popular technique in the exploration for oil and gas because it can be used to differentiate between thermogenic and microbial gas and can sometimes be used for gas-source rock correlations. Methane-oxidizing bacteria, however, can significantly change the carbon isotopic composition of methane; the origin of gas that has been partially oxidized by these bacteria could therefore be misinterpreted. We cultured methane-oxidizing bacteria at two different temperatures and monitored the carbon and hydrogen isotopic compositions of the residual methane. The residual methane was enriched in both 13C and D. For both isotopic species, the enrichment at equivalent levels of conversion was greater at 26??C than at 11.5??C. The change in ??D relative to the change in ??13C was independent of temperature within the range studied. One culture exhibited a change in the fractionation pattern for carbon (but not for hydrogen) midway through the experiment, suggesting that bacterial oxidation of methane may occur via more than one pathway. The change in the ??D value for the residual methane was from 8 to 14 times greater than the change in the ??13C value, indicating that combined carbon and hydrogen isotopic analysis may be an effective way of identifying methane which has been subjected to partial oxidation by bacteria. ?? 1981.

  2. Stable carbon and nitrogen isotopes in vertical peat profiles of natural and drained boreal peatlands

    NASA Astrophysics Data System (ADS)

    Nykänen, Hannu; Mpamah, Promise; Rissanen, Antti; Pitkänen, Aki; Turunen, Jukka; Simola, Heikki

    2015-04-01

    Peatlands form a significant carbon pool in the global carbon cycle. Change in peat hydrology, due to global warming is projected to change microbiological processes and peat carbon pool. We tested if bulk stable carbon and nitrogen isotopes serve as indicators of severe long term drying in peatlands drained for forestry. Depth profile analysis of peat, for their carbon and nitrogen content as well as their carbon and nitrogen stable isotopic signatures, were conducted for peatlands in southern and eastern Finland, having ombrotrophic and minerotrophic natural and corresponding drained pairs or separate drained sites. The selection of sites allowed us to compare changes due to different fertility and changes due to long term artificial drying. Drainage lasting over 40 years has led to changes in hydrology, vegetation, nutrient mineralization and respiration. Furthermore, increased nutrient uptake and possible recycling of peat nitrogen and carbon trough vegetation back to the peat surface, also possibly has an effect on the stable isotopic composition of peat carbon and nitrogen. We think that drainage induced changes somehow correspond to those caused by changed hydrology due to climate change. We will present data from these measurements and discuss their implications for carbon and nitrogen flows in peatlands.

  3. Stable carbon isotope ratios of ambient secondary organic aerosols in Toronto

    NASA Astrophysics Data System (ADS)

    Saccon, M.; Kornilova, A.; Huang, L.; Moukhtar, S.; Rudolph, J.

    2015-09-01

    A method to quantify concentrations and stable carbon isotope ratios of secondary organic aerosols has been applied to study atmospheric nitrophenols in Toronto, Canada. The sampling of five nitrophenols, all with substantial secondary formation from the photooxidation of aromatic volatile organic compounds (VOCs), was conducted in the gas phase and particulate matter (PM) together and in PM alone. Their concentrations in the atmosphere are in the low ng m-3 range and, consequently, a large volume of air (> 1000 m3) is needed to analyze samples for stable carbon isotope ratios, resulting in sampling periods of typically 24 h. While this extended sampling period increases the representativeness of average values, it at the same time reduces possibilities to identify meteorological conditions or atmospheric pollution levels determining nitrophenol concentrations and isotope ratios. Average measured carbon isotope ratios of the different nitrophenols are between -34 and -33 ‰, which is well within the range predicted by mass balance. However, the observed carbon isotope ratios cover a range of nearly 9 ‰ and approximately 20 % of the isotope ratios of the products have isotope ratios lower than predicted from the kinetic isotope effect of the first step of the reaction mechanism and the isotope ratio of the precursor. This can be explained by isotope fractionation during reaction steps following the initial reaction of the precursor VOCs with the OH radical. Limited evidence for local production of nitrophenols is observed since sampling was done in the Toronto area, an urban center with significant anthropogenic emission sources. Strong evidence for significant local formation of nitrophenols is only found for samples collected in summer. On average, the difference in carbon isotope ratios between nitrophenols in the particle phase and in the gas phase is insignificant, but for a limited number of observations in summer, a substantial difference is observed. This indicates that at high OH radical concentrations, photochemical formation or removal of nitrophenols can be faster than exchange between the two phases. The dependence between the concentrations and isotope ratios of the nitrophenols and meteorological conditions as well as pollution levels (NO2, O3, SO2 and CO) demonstrate that the influence of precursor concentrations on nitrophenol concentrations is far more important than the extent of photochemical processing. While it cannot be excluded that primary emissions contribute to the observed levels of nitrophenols, overall the available evidence demonstrates that secondary formation is the dominant source for atmospheric nitrophenols in Toronto.

  4. Stable carbon isotope ratios of ambient secondary organic aerosols in Toronto

    NASA Astrophysics Data System (ADS)

    Saccon, M.; Kornilova, A.; Huang, L.; Moukhtar, S.; Rudolph, J.

    2015-06-01

    A method to quantify concentrations and stable carbon isotope ratios of secondary organic aerosols (SOA) has been applied to study atmospheric nitrophenols in Toronto, Canada. The sampling of five nitrophenols, all primarily formed from the photo-oxidation of aromatic volatile organic compounds (VOC), in the gas phase and particulate matter (PM) together and PM alone was conducted. Since all of the target compounds are secondary products, their concentrations in the atmosphere are in the low ng m-3 range and consequently a large volume of air (> 1000 m3) is needed to analyze samples for stable carbon isotope ratios, resulting in sampling periods of typically 24 h. While this extended sampling period increases the representativeness of average values, it at the same time reduces possibilities to identify meteorological conditions or atmospheric pollution levels determining nitrophenol concentrations and isotope ratios. Average measured carbon isotope ratios of the different nitrophenols are between -34 and -33‰, which is well within the range predicted by mass balance calculations. However, the observed carbon isotope ratios cover a range of nearly 9‰, and approximately 20% of the isotope ratios of the products have isotope ratios lower than predicted from the kinetic isotope effect of the first step of the reaction mechanism and the isotope ratio of the precursor. This can be explained by isotope fractionation during reaction steps following the initial reaction of the precursor VOCs with the OH radical. Limited evidence for local production of nitrophenols is observed since sampling was done in the Toronto area, an urban centre with significant anthropogenic emission sources. Strong evidence for significant local formation of nitrophenols is only found for samples collected in summer. On average, the difference in carbon isotope ratios between nitrophenols in the particle phase and in the gas phase is insignificant, but for a limited number of observations in summer, a substantial difference is observed. This indicates that at high OH radical concentrations, photochemical formation or removal of nitrophenols can be faster than exchange between the two phases. The dependence between the concentrations and isotope ratios of the nitrophenols and meteorological conditions as well as pollution levels (NO2, O3, SO2 and CO) demonstrate that the influence of precursor concentrations on nitrophenol concentrations is far more important than the extent of photochemical processing.

  5. Stable carbon kinetic isotope effects for the production of methacrolein and methyl vinyl ketone from the gas-phase reactions of isoprene with ozone and hydroxyl radicals

    NASA Astrophysics Data System (ADS)

    Iannone, Richard; Koppmann, Ralf; Rudolph, Jochen

    2010-11-01

    The stable-carbon kinetic isotope effects (KIEs) associated with the production of methacrolein (MACR) and methyl vinyl ketone (MVK) from the reactions of isoprene with ozone and OH radicals were studied in a 25 L reaction chamber at (298±2) K and ambient pressure. The time dependence of both the stable-carbon isotope ratios and the concentrations was determined using a gas chromatography combustion isotope ratio mass spectrometry (GCC-IRMS) system. The average yields of 13C-containing MACR and MVK generated from the ozone reaction of 13C-containing isoprene differed by -3.6‰ and -4.5‰, respectively, from the yields for MACR and MVK containing only 12C. For MACR and MVK generated from the OH-radical oxidation of isoprene the corresponding values were -3.8‰ and -2.2‰, respectively. These values indicate a significant depletion in the 13C abundance of MACR and MVK upon their formation relative to isoprene's pre-reaction 13C/ 12C ratio, which is supported by theoretical interpretations of the oxidation mechanism of isoprene and its 13C-substituted isotopomers. Numerical model calculations of the isoprene + O 3 reaction predicted a similar depletion in 13C for both reaction products upon production. Furthermore, the model predicts mixing ratios and stable carbon delta values for isoprene, MACR, and MVK that were in agreement with the experimental results. The combined knowledge of isotope enrichment values with KIEs will reduce uncertainties in determinations of the photochemical histories of isoprene, MACR, and MVK in the troposphere. The studies presented here were conducted with using isoprene without any artificial isotope enrichment or depletion and it is therefore very likely that these results are directly applicable to the interpretation of studies of isoprene oxidation using stable carbon isotope ratio measurements.

  6. Empirical High-Temperature Calibration for the Carbonate Clumped Isotopes Paleothermometer

    NASA Astrophysics Data System (ADS)

    Kluge, T.; John, C. M.; Jourdan, A.; Davis, S.; Crawshaw, J.

    2013-12-01

    The clumped isotope paleothermometer is being used in a wide range of applications related to carbonate mineral formation, focusing on temperature and fluid ?18O reconstruction. Whereas the range of typical Earth surface temperatures has been the focus of several studies based on laboratory experiments and biogenic carbonates of known growth temperatures, the clumped isotope-temperature relationship above 70 °C has not been assessed by direct precipitation of carbonates. We investigated the clumped isotope-temperature relationship by precipitating carbonates between 20 and 200°C in the laboratory. The setup consists of a pressurized vessel in which carbonate minerals are precipitated from the mixture of two solutions (CaCl2, NaHCO3). Both solutions are thermally and isotopically equilibrated before injection in the pressure vessel. Minerals precipitated in this setup generally consist of calcite. Samples were reacted with 105% orthophosphoric acid for 10 min at 90°C. The evolved CO2 was continuously collected and subsequently purified with a Porapak trap held at -35°C. Measurements were performed on a MAT 253 using the protocol of Huntington et al. (2009) and Dennis et al. (2011). Clumped isotope values from 20-90°C are consistent with carbonates that were precipitated from a CaCO3 super-saturated solution using the method of McCrea (1950). This demonstrates that the experimental setup does not induce any kinetic fractionation, and can be used for high-temperature carbonate precipitation. The new clumped isotope calibration at high temperature follows the theoretical calculations of Schauble et al. (2006) adjusted for phosphoric acid digestion at 90°C. We gratefully acknowledge funding from Qatar Petroleum, Shell and the Qatar Science and Technology Park.

  7. Geometry of 2,5-dihydrofuran from the free jet rotational spectra of the 13C and 18O isotopic species in natural abundance

    NASA Astrophysics Data System (ADS)

    Melandri, S.; Velino, B.; Caminati, W.

    2001-05-01

    The rotational spectra of all singly substituted 13C and 18O isotopic species of the ground vibrational state of 2,5-dihydrofuran have been measured in natural abundance with millimeter-wave free jet technique and the rs and r0 heavy atom geometries have been determined.

  8. Quantifying the Carbon Abundances in the Secondary Stars of SS Cygni, RU Pegasi, and GK Persei

    E-print Network

    Harrison, Thomas E

    2015-01-01

    We use a modified version of MOOG to generate large grids of synthetic spectra in an attempt to derive quantitative abundances for three CVs (GK Per, RU Peg, and SS Cyg) by comparing the models to moderate resolution (R $\\sim$ 25,000) $K$-band spectra obtained with NIRSPEC on Keck. For each of the three systems we find solar, or slightly sub-solar values for [Fe/H], but significant deficits of carbon: for SS Cyg we find [C/Fe] = $-$0.50, for RU Peg [C/Fe] = $-$0.75, and for GK Per [C/Fe] = $-$1.00. We show that it is possible to use lower resolution (R $\\sim$ 2,000) spectra to quantify carbon deficits. We examine realistic veiling scenarios and find that emission from H I or CO cannot reproduce the observations.

  9. Quantifying the Carbon Abundances in the Secondary Stars of SS Cygni, RU Pegasi, and GK Persei

    NASA Astrophysics Data System (ADS)

    Harrison, Thomas E.; Hamilton, Ryan T.

    2015-11-01

    We use a modified version of MOOG to generate large grids of synthetic spectra in an attempt to derive quantitative abundances for three CVs (GK Per, RU Peg, and SS Cyg) by comparing the models to moderate resolution (R ? 25,000) K-band spectra obtained with NIRSPEC on Keck. For each of the three systems we find solar, or slightly sub-solar values for [Fe/H], but significant deficits of carbon: for SS Cyg we find [C/Fe] = ?0.50, for RU Peg [C/Fe] = ?0.75, and for GK Per [C/Fe] = ?1.00. We show that it is possible to use lower resolution (R ? 2000) spectra to quantify carbon deficits. We examine realistic veiling scenarios and find that emission from H i or CO cannot reproduce the observations.

  10. Evolution of stable carbon-isotope compositions for methane and carbon dioxide in freshwater wetlands and other anaerobic environments

    NASA Astrophysics Data System (ADS)

    Hornibrook, Edward R. C.; Longstaffe, Frederick J.; Fyfe, William S.

    2000-03-01

    Two types of distribution for ? C values are observed in anaerobic environments when ? 13C-?CO 2 and ? 13C-CH 4 values are measured across gradients of depth or age of organic debris. The type-I distribution involves a systematic increase in ? C values with depth as a result of decreasing ? 13C-CH 4 and increasing ? 13C-?CO 2 values. This behavior corresponds to a progressive increase in the prevalence of methanogenesis by the CO 2 reduction pathway relative to acetate fermentation. Utilization of autotrophically formed acetate by methanogens would also cause an increase in ? C values. The type-II distribution occurs when both ? 13C-CH 4 and ? 13C-?CO 2 values decrease with depth, resulting in approximately constant ? C values. This condition corresponds with a strong dependence of methanogens on porewater ?CO 2 as a carbon source by way of either the CO 2 reduction pathway or utilization of autotrophically formed acetate. Freshwater wetlands possess both types of ? C value distribution. Wetlands with type-I distributions exhibit curves with slopes that vary probably as a function of deposition and preservation of labile organic carbon. An abundance of labile substrates in anaerobic soils yields steeper curves because aceticlastic methanogenesis predominates and ? 13C-CH 4 and ? 13C-CO 2 values are high. Diminished transfer of labile carbon to the methanogenic zone results in an increased prevalence of the CO 2 reduction pathway, yielding low ? 13C-CH 4 values and shallowly sloping curves. Aerobic oxidation of organic matter or decay involving sulfate reduction produces CO 2 with low ? 13C values, which also will contribute to shallowly sloping curves. The size of the dissolved CO 2 pool can influence the sensitivity of ? 13C-CO 2 values to change during methanogenesis. Regression curves of ? 13C-CH 4 and ? 13C-?CO 2 values from four wetlands with type-I distributions intersect at ? 13C-CH 4 = -40.7 ± 6.1‰ (1?) and ? 13C-?CO 2 = -23.9 ± 4.8‰ (1?). These values are similar to ? 13C values for methyl and carboxyl moieties within acetate produced by anaerobic degradation of fresh C 3 plant matter. A low abundance of acetate during aceticlastic methanogenesis will result in minimal expression of metabolic kinetic isotope effects (KIEs) and production of CH 4 and CO 2 with ? 13C values similar to the intramolecular distribution of sedimentary acetate. The type-II distribution is prevalent in marine environments, probably because of substrate depletion in the sulfate reduction zone. The type-I distribution does occur in marine settings where deposition rates of organic matter are high. Landfills possess only the type-I distribution of ? C values and exhibit unusually steep curves, possibly because methanogenesis occurs predominantly from acetate produced by fermentation at mesophilic temperatures. The high abundance of acetate in landfill leachate may permit varying degrees of expression of the KIE associated with aceticlastic methanogenesis. Outgassing of 12CO 2 may contribute further to the steepening of ? C curves in landfills and other anaerobic environments possessing a type-I distribution. Defining the type of ? C distributions in different wetlands could reduce uncertainty in estimating the ? 13C value of CH 4 emissions. Hence, the prevalence of type-I vs. type-II ? C distributions in wetlands may have practical importance for the refinement of global CH 4 budgets that rely on 13C/ 12C ratios for mass balance.

  11. High-Resolution Carbon Isotope Stratigraphy, Pennsylvanian Snaky Canyon Formation, East-Central Idaho: Implications for Regional and Global Correlations 

    E-print Network

    Jolley, Casey

    2012-07-16

    Nearly 550 samples of fine grained carbonates, collected every 0.5 to 1.0 m from the Bloom Member of the Snaky Canyon Formation at Gallagher Peak, Idaho, were analyzed to determine the high-resolution carbon isotope ...

  12. Seasonal variation of Fatty acids and stable carbon isotopes in sponges as indicators for nutrition: biomarkers in sponges identified.

    PubMed

    Koopmans, Marieke; van Rijswijk, Pieter; Boschker, Henricus T S; Marco, Houtekamer; Martens, Dirk; Wijffels, Rene H

    2015-02-01

    To get a better understanding of sponge feeding biology and efficiencies, the fatty acid (FA) composition and (13)C natural abundance of sponges and of suspended particulate matter (SPM) from surrounding seawater was studied in different seasons at three locations. Haliclona oculata and Haliclona xena from the Oosterschelde, the Netherlands, Halichondria panicea and H. xena from Lake Veere, the Netherlands, and Aplysina aerophoba and Dysidea avara from the Mediterranean, Spain, were studied. Several FA biomarkers for different algal groups, bacteria and sponge biomass were identified in all sponges. The FA concentration variation in sponges was related to changes in fatty acid concentration in SPM. Stable carbon isotopic ratios (?(13)C) in sponge specific FAs showed very limited seasonal variation at all sites. Algal FAs in sponges were mainly acquired from the SPM through active filtration in all seasons. At the two sites in the Netherlands only in May (spring), the sponge specific FAs had similar ?(13)C ratios as algal FAs, suggesting that sponges were mainly growing during spring and probably summer. During autumn and winter, they were still actively filtering, but the food collected during this period had little effect on sponge ?(13)C values suggesting limited incorporation of filtered material into the sponge body. The sponge A. aerophoba relied mostly on the symbiotic bacteria. In conclusion, fatty acid composition in combination with stable carbon isotope analysis can be used to analyze the food source of sponges. PMID:25107690

  13. Determination of nitrogen to carbon abundance ratios from transition layer emission lines

    NASA Technical Reports Server (NTRS)

    Boehm-Vitense, Erika

    1992-01-01

    We have finished studying the nitrogen to carbon abundance ratios for stars with different effective temperatures T(sub eff) and luminosities using transition layer emission lines and using spectra available in the IUE archives. The N/C abundance ratio determinations using transition layer emission lines are as accurate as the photospheric abundance determinations as found by comparison of results obtained by both methods for the same stars. Our measurements confirm photospheric abundance determinations in regions of the HR diagram where they can be obtained. Our studies have extended the temperature range to higher temperatures. They have shown the exact positions in the HR diagram where the mixing due to the outer convection zones reaches deep enough to bring nuclear processed material to the surface. This occurs at effective temperatures which are higher by delta log T(sub eff) approximately 0.04 or roughly 400 K than expected theoretically. Since the depth of the convection zone increases rapidly with decreasing T(sub eff) this may indicate considerable overshoot beyond the lower boundary of the convection zone. Our N/C abundance ratio determinations from transition layer emission lines have confirmed that the actual enrichment observed for some cool giants is larger than expected theoretically, again indicating a larger degree of mixing in several stars either from below or from above. For the supergiants it probably indicates overshoot above the convective core in the progenitor main sequence stars. For the more massive giants this may also be the case, though we did not find a correlation between delta log N/C and the absolute magnitudes, but these are rather uncertain. As byproducts of these studies we also found anomalies in Si/C and N/C abundance ratios for F giants which can be understood as the relict of surface abundance changes for their main sequence progenitors due to diffusion. This anomaly disappears for G giants, for which the depths of the convection zones are apparently deep enough to wipe out these element separations (Bohm-Vitense 1992).