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Sample records for carbon acquisition isotope

  1. Carbon isotope geochemistry and geobiology

    Science.gov (United States)

    Desmarais, D.

    1985-01-01

    Carbon isotope fractionation values were used to understand the history of the biosphere. For example, plankton analyses confirmed that marine extinctions at the end of the Cretaceous period were indeed severe (see Hsu's article in Sundquist and Broeker, 1984). Variations in the isotopic compositions of carbonates and evaporitic sulfates during the Paleozoic reflect the relative abundances of euxinic (anoxic) marine environments and organic deposits from terrestrial flora. The carbon isotopic composition of Precambrian sediments suggest that the enzyme ribulose bisphosphate carboxylase has existed for perhaps 3.5 billion years.

  2. Carbon isotopes in mollusk shell carbonates

    Science.gov (United States)

    McConnaughey, Ted A.; Gillikin, David Paul

    2008-10-01

    Mollusk shells contain many isotopic clues about calcification physiology and environmental conditions at the time of shell formation. In this review, we use both published and unpublished data to discuss carbon isotopes in both bivalve and gastropod shell carbonates. Land snails construct their shells mainly from respired CO2, and shell δ13C reflects the local mix of C3 and C4 plants consumed. Shell δ13C is typically >10‰ heavier than diet, probably because respiratory gas exchange discards CO2, and retains the isotopically heavier HCO3 -. Respired CO2 contributes less to the shells of aquatic mollusks, because CO2/O2 ratios are usually higher in water than in air, leading to more replacement of respired CO2 by environmental CO2. Fluid exchange with the environment also brings additional dissolved inorganic carbon (DIC) into the calcification site. Shell δ13C is typically a few ‰ lower than ambient DIC, and often decreases with age. Shell δ13C retains clues about processes such as ecosystem metabolism and estuarine mixing. Ca2+ ATPase-based models of calcification physiology developed for corals and algae likely apply to mollusks, too, but lower pH and carbonic anhydrase at the calcification site probably suppress kinetic isotope effects. Carbon isotopes in biogenic carbonates are clearly complex, but cautious interpretation can provide a wealth of information, especially after vital effects are better understood.

  3. Carbon and oxygen isotope microanalysis of carbonate.

    Science.gov (United States)

    Velivetskaya, Tatiana A; Ignatiev, Alexander V; Gorbarenko, Sergey A

    2009-08-30

    Technical modification of the conventional method for the delta(13)C and delta(18)O analysis of 10-30 microg carbonate samples is described. The CO(2) extraction is carried out in vacuum using 105% phosphoric acid at 95 degrees C, and the isotopic composition of CO(2) is measured in a helium flow by gas chromatography/isotope ratio mass spectrometry (GC/IRMS). The feed-motion of samples to the reaction vessel provides sequential dropping of only the samples (without the sample holder) into the acid, preventing the contamination of acid and allowing us to use the same acid to carry out very large numbers of analyses. The high accuracy and high reproducibility of the delta(13)C and delta(18)O analyses were demonstrated by measurements of international standards and comparison of results obtained by our method and by the conventional method. Our method allows us to analyze 10 microg of the carbonate with a standard deviation of +/-0.05 per thousand for delta(13)C and delta(18)O. The method has been used successfully for the analyses of the oxygen and carbon isotopic composition of the planktonic and benthic foraminifera in detailed palaeotemperature reconstructions of the Okhotsk Sea. PMID:19603476

  4. Chromium isotope uptake in carbonates

    DEFF Research Database (Denmark)

    Rodler, Alexandra

    composition of contemporaneous seawater. Marine carbonates are ubiquitous throughout Earth’s rock record rendering them a particularly interesting archive for constraining past changes in ocean chemistry. This thesis includes an investigation of the fractionation behavior of Cr isotopesduring coprecipitation.......The redox changes of past surface environments can be explored using the Cr isotope composition of ancient marine carbonates, where a marginal offset compared to contemporaneous seawater δ53Cr is expected and the degree of contamination and later diagenetic alteration can be evaluated. Improved...

  5. Robust optical carbon dioxide isotope analyzer Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Isotopic analysis of carbon dioxide is an important tool for characterization of the exchange and transformation of carbon between the biosphere and the atmosphere....

  6. Carbon isotope effects in carbonate systems

    Science.gov (United States)

    Deines, Peter

    2004-06-01

    Global carbon cycle models require a complete understanding of the δ 13C variability of the Earth's C reservoirs as well as the C isotope effects in the transfer of the element among them. An assessment of δ 13C changes during CO 2 loss from degassing magmas requires knowledge of the melt-CO 2 carbon isotope fractionation. In order to examine the potential size of this effect for silicate melts of varying composition, 13C reduced partition functions were computed in the temperature range 275 to 4000 K for carbonates of varying bond strengths (Mg, Fe, Mn, Sr, Ba, Pb, Zn, Cd, Li, and Na) and the polymorphs of calcite. For a given cation and a given pressure the 13C content increases with the density of the carbonate structure. For a given structure the tendency to concentrate 13C increases with pressure. The effect of pressure (‰/10 kbar) on the size of the reduced partition function of aragonite varies with temperature; in the pressure range 1 to 10 5 bars the change is given by: Δ 13C p average=-0.01796+0.06635∗ 10 3/T+0.006875∗ 10 6/T2 For calcite III the pressure effect is on average 1.4× larger than that for aragonite at all temperatures. The nature of the cation in a given structure type has a significant effect on the carbon isotope fractionation properties. The tendency to concentrate 13C declines in the series magnesite, aragonite, dolomite, strontianite, siderite, calcite, smithonite, witherite, rhodochrosite, otavite, cerrusite. For divalent cations a general expression for an estimation of the reduced partition function (β) from the reduced mass (μ = [M Cation × M Carbonate]/[M Cation + M Carbonate]) is: 1000 lnβ=(0.032367-0.072563∗ 10 3/T-0.01073∗ 10 6/T2)∗μ-14.003+29.953∗ 10 3/T+9.4610∗ 10 6/T2 For Mg-calcite the 13C content varies with the Mg concentration. The fractionation between Mg-calcite (X = mole fraction of MgCO 3) and calcite is given by: 1000 ln(α MgCalite- Calcite)=[0.013702-0.10957× 10 3/T+1.35940× 10 6/T2

  7. Structure and isotopic composition of bacterial lipids : Insight into distribution and carbon acquisition mechanisms of bacteria in hot spring microbial mats

    NARCIS (Netherlands)

    van der Meer, M.T.J.

    2002-01-01

    The results described in this thesis thus support the possibility that Precambrian organic matter enriched in ¹³C relative to what would be expected for organic matter produced by the Calvin cycle could be due to organisms using carbon fixation pathways other than the Calvin cycle.

  8. Structure and isotopic composition of bacterial lipids: insights into distribution and carbon acquisition mechanisms of bacteria in hot spring microbial mats

    NARCIS (Netherlands)

    Meer, M.T.J. van der

    2002-01-01

    The results described in this thesis thus support the possibility that Precambrian organic matter enriched in l3C relative to what would be expected for organic matter produced by the Calvin cycle could be due to organisms using carbon fixation pathways other than the Calvin cycle.

  9. Carbon isotopic fractionation in heterotrophic microbial metabolism

    Science.gov (United States)

    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.

  10. Exotic structure of carbon isotopes

    International Nuclear Information System (INIS)

    Ground state properties of C isotopes, deformation and electromagnetic moments, as well as electric dipole transition strength are investigated. We first study the ground state properties of C isotopes using a deformed Hartree-Fock (HF) + BCS model with Skyrme interactions. Isotope dependence of the deformation properties is investigated. Shallow deformation minima are found in several neutron-rich C isotopes. It is also shown that the deformation minima appear in both the oblate and the prolate sides in 17C and 19C having almost the same binding energies. Next, we carry out shell model calculations to study electromagnetic moments and electric dipole transitions of C isotopes. We point out the clear configuration dependence of the quadrupole and magnetic moments in the odd C isotopes, which will be useful to find out the deformation and spin-parties of the ground states of these nuclei. Electric dipole states of C isotopes are studied focusing on the interplay between low energy Pigmy strength and giant dipole resonances. Low peak energies, two-peak structure and large widths of the giant resonances show deformation effects. Calculated transition strength below dipole giant resonance in heavier C isotopes than 15C is found to exhaust 12∼15% of the Thomas-Reiche-Kuhn sum rule value and 50∼ 80% of the cluster sum rule value. (author)

  11. Carbon isotope geochemistry in the Yalujiang estuary

    Institute of Scientific and Technical Information of China (English)

    吴莹; 张经

    2001-01-01

    The distribution of particulate organic carbon (POC) along the lower reaches is similar between the dry season and the flood season in the Yalujiang Estuary, North China. However, the values of particulate organic carbon of the upperstream in the dry season are one magnitude lower than the concentrations in the flood season. Stable carbon isotope ratios have been used to study the sources of particulate organic carbon in the Yalujiang Estuary. The isotopic composition of POC shows a range from -23.1‰ to -29.4‰ with a little seasonal variation. The isotopic evidence indicates that the POC in the Yalujiang Estuary is predominantly of terrestrial origin rather than a result of in situ plankton. The study of the ratio of POC: Chla shows that the turbidity maximum plays an important role in POC cycle in the Yalujiang Estuary. Organic detritus and soil erosion are the main contributions to POC in the turbidity maximum, especially in the flood season.

  12. Inorganic carbon acquisition in red tide dinoflagellates.

    Science.gov (United States)

    Rost, Björn; Richter, Klaus-Uwe; Riebesell, Ulf; Hansen, Per Juel

    2006-05-01

    Carbon acquisition was investigated in three marine bloom-forming dinollagellates-Prorocentrum minimum, Heterocapsa triquetra and Ceratium lineatum. In vivo activities of extracellular and intracellular carbonic anhydrase (CA), photosynthetic O2 evolution, CO2 and HCO3- uptake rates were measured by membrane inlet mass spectrometry (MIMS) in cells acclimated to low pH (8.0) and high pH (8.5 or 9.1). A second approach used short-term 14C-disequilibrium incubations to estimate the carbon source utilized by the cells. All three species showed negligible extracellular CA (eCA) activity in cells acclimated to low pH and only slightly higher activity when acclimated to high pH. Intracellular CA (iCA) activity was present in all three species, but it increased only in P. minimum with increasing pH. Half-saturation concentrations (K1/2) for photosynthetic O2 evolution were low compared to ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) kinetics. Moreover, apparent affinities for inorganic carbon (Ci) increased with increasing pH in the acclimation, indicating the operation of an efficient CO2 concentration mechanism (CCM) in these dinoflagellates. Rates of CO2 uptake were comparably low and could not support the observed rates of photosynthesis. Consequently, rates of HCO3- uptake were high in the investigated species, contributing more than 80% of the photosynthetic carbon fixation. The affinity for HCO3- and maximum uptake rates increased under higher pH. The strong preference for HCO3- was also confirmed by the 14C-disequilibrium technique. Modes of carbon acquisition were consistent with the 13C-fractionation pattern observed and indicated a strong species-specific difference in leakage. These results suggest that photosynthesis in marine dinoflagellates is not limited by Ci even at high pH, which may occur during red tides in coastal waters. PMID:17087465

  13. Carbon isotope anomalies in carbonates of the Karelian series

    Science.gov (United States)

    Iudovich, Ia. E.; Makarikhin, V. V.; Medvedev, P. V.; Sukhanov, N. V.

    1990-07-01

    Results are presented on carbon isotope distributions in carbonates of the Karelian complex. A highly anomalous isotopic composition was found in carbonate rocks aged from 2.6 to 1.9 b.y. In the stromatolitic carbonates of the Onega water table, delta-(C-13) reaches a value of +18 percent, while the shungite layer of the Zaonega horizon is characterized by a wide dispersion (from +7.9 to -11.8 percent). These data are in good agreement with the known geochemical boundary (about 2.2 b.y. ago) in the history of the earth.

  14. Stable carbon isotope analysis of heavy oils

    Energy Technology Data Exchange (ETDEWEB)

    Fixari, B.; Le Perchec, P.; Bigois, M.; Casabianca, H.; Jame, P. [CNRS, Vernaison (France). Lab. des Materiaux Organiques

    1994-03-01

    Stable carbon isotope analysis of various heavy oils and some thermo-catalytically converted products was performed with a thermal analyser coupled with an isotopic ratio mass spectrometer. The temperature-programmed oxidative pyroanalysis technique subdivides the classical {sup 13}C/{sup 12}C ratio, affording new insights into the structural composition of heavy oils such as the contribution of naphthenoaromatics, and appears to be of interest for following their thermal refining. 24 refs., 11 figs., 2 tabs.

  15. Carbon isotope separation by absorptive distillation

    International Nuclear Information System (INIS)

    The feasibility of separating carbon isotopes by absorptive distillation has been studied for CO absorption by cryogenic solvents. Phase equilibrium, isotopic separation, and mass transfer data were taken between 77.4 and 114.3 K for the following solvents: propane, propylene, 1:1 propane-propylene, 1-butene, isobutane and nitrogen. Carbon monoxide solubility followed Henry's Law, with a maximum experimental solubility of 6.5 mole percent. Isotopic separation between CO in the gas and liquid phases using hydrocarbon solvents was several times that for pure CO vapor-liquid equilibrium. The maximum observed isotopic separation factor was 1.029 at 77.4 K with the propane-propylene solvent mixture. Mass transfer measurements yielded calculated HETP's of 2 to 5 cm for a possible separation system. An attempt has been made to correlate isotopic separation data using Hildebrand's theory of solutions. The differential absorption of isotopic CO species is expressed as a difference in solubility of the isotopic CO molecules. Data for propane, propylene, and 1-butene show approximately the same behavior at varying temperatures

  16. Carbon isotope separation by absorptive distillation

    International Nuclear Information System (INIS)

    The feasibility of separating carbon isotopes by absorptive distillation has been studied for CO absorption by cryogenic solvents. Phase equilibrium, isotopic separation, and mass transfer data were taken between 77.4 and 114.3 K for the following solvents: propane, propylene, 1:1 propane-propylene, 1-butene, isobutane and nitrogen. Carbon monoxide solubility followed Henry's Law, with a maximum experimental solubility of 6.5 mole per cent. Isotopic separation between CO in the gas and liquid phases using hydrocarbon solvents was several times that for pure CO vapor-liquid equilibrium. The maximum observed isotopic separation factor was 1.029 at 77.4 K with the propane-propylene solvent mixture. Mass transfer measurements yielded calculated HTU's of 2 to 5 cm for a possible separation system. An attempt has been made to correlate isotopic separation data using Hildebrand's theory of solutions. The differential absorption of isotopic CO species is expressed as a difference in solubility of the isotopic CO molecules. Data for propane, propylene, and 1-butene show approximately the same behavior at varying temperatures

  17. Exotic Structure of Carbon Isotopes

    CERN Document Server

    Suzuki, T; Hagino, K; Suzuki, Toshio; Sagawa, Hiroyuki; Hagino, Kouichi

    2002-01-01

    We studied firstly the ground state properties of C-isotopes using a deformed Hartree-Fock (HF)+ BCS model with Skyrme interactions. Shallow deformation minima are found in several neutron$-$rich C-isotopes. It is shown also that the deformation minima appear in both the oblate and the prolate sides in $^{17}$C and $^{19}$C having almost the same binding energies. Secondly, we carried out shell model calculations to study electromagnetic moments and electric dipole transitions of the C-isotopes. We point out the clear configuration dependence of the quadrupole and magnetic moments in the odd C-isotopes, which will be useful to find out the deformations and the spin-parities of the ground states of these nuclei. We studied electric dipole states of C-isotopes focusing on the interplay between low energy Pigmy strength and giant dipole resonances. Reasonable agreement is obtained with available experimental data for the photoreaction cross sections both in the low energy region below $\\hbar \\omega $=14 MeV and ...

  18. Carbon and Carbon Isotope Cycling in the Western Canadian Arctic

    Science.gov (United States)

    Mol, Jacoba; Thomas, Helmuth

    2016-04-01

    Increasing carbon dioxide levels in the atmosphere are having drastic effects on the global oceans. The Arctic Ocean is particularly susceptible to change as warming, sea-ice loss and a weak buffering capacity all influence this complicated semi-enclosed sea. In order to investigate the inorganic carbon system in the Canadian Arctic, water samples were collected in the Beaufort Sea, on the Alaskan shelf, at the Mackenzie river delta, and in Amundsen Gulf during the summer of 2014 and were analyzed for dissolved inorganic carbon (DIC), total alkalinity (TA), DI13C and 18O isotopes. Carbon isotopes are used to investigate the role of biological production on the uptake and transfer of inorganic carbon to depth. A preferential uptake of the lighter 12C relative to the heavier 13C isotope during biological production leads to a fractionation of the 13C/12C isotopes in both the organic matter and the water column. This results in an enrichment of DI13C in the high productivity surface waters and a depletion of DI13C at depth. Physical processes including freshwater input, brine rejection, and water mass mixing are investigated through the measurement of oxygen isotopes. Differences in the carbon system across the study area due to both biological and physical processes are assessed using depth profiles of DI13C and related carbon system parameters.

  19. Carbon isotopes as indicators of peatland growth?

    Science.gov (United States)

    Alewell, Christine; Krüger, Jan Paul; von Sengbusch, Pascal; Szidat, Sönke; Leifeld, Jens

    2016-04-01

    As undisturbed and/or growing peatlands store considerable amounts of carbon and are unique in their biodiversity and species assemblage, the knowledge of the current status of peatlands (growing with carbon sequestration, stagnating or degrading with carbon emissions) is crucial for landscape management and nature conservation. However, monitoring of peatland status requires long term measurements and is only feasible with expert knowledge. The latter determination is increasingly impeded in a scientific world, where taxonomic expert knowledge and funding of long term monitoring is rare. Stable carbon and nitrogen isotopes depth profiles in peatland soils have been shown to be a useful tool to monitor the degradation of peatlands due to permafrost thawing in Northern Sweden (Alewell et al., 2011; Krüger et al., 2014), drainage in Southern Finland (Krüger et al., 2016) as well as land use intensification in Northern Germany (Krüger et al., 2015). Here, we tackle the questions if we are able to differentiate between growing and degrading peats with the use of a combination of carbon stable (δ13C) and radiogenic isotope data (14C) with peat stratification information (degree of humification and macroscopic plant remains). Results indicate that isotope data are a useful tool to approximate peatland status, but that expert taxonomic knowledge will be needed for the final conclusion on peatland growth. Thus, isotope tools might be used for landscape screening to pin point sites for detailed taxonomic monitoring. As the method remains qualitative future research at these sites will need to integrate quantitative approaches to determine carbon loss or gain (soil C balances by ash content or C accumulation methods by radiocarbon data; Krüger et al., 2016). Alewell, C., R. Giesler, J. Klaminder, J. Leifeld, and M. Rollog. 2011. Stable carbon isotopes as indicators for micro-geomorphic changes in palsa peats. Biogeosciences, 8, 1769-1778. Krüger, J. P., Leifeld, J

  20. Deciphering Carbon Isotope Excursions in Separated Biogenic and Diagenetic Carbonates

    Science.gov (United States)

    Hermoso, M.; Minoletti, F.; Hesselbo, S.; Jenkyns, H.; Rickaby, R.; Diester-Haass, L.; Delsate, D.

    2008-12-01

    The long-term evolution of the carbon-isotope ratio in the sedimentary archive is classically linked with changes in primary productivity and organic matter burial. There have been sudden and pronounced shifts, so-called Carbon Isotope Excursions (CIEs) in the long-term trends as evidenced by synchronous shifts from various basins. These geochemical perturbations may have various explanations such as changes of the efficiency of the carbon sink; sudden infusion of isotopically-light carbon into the Ocean-Atmosphere system; or advection of 12C-rich source from bottom water in a stratified water column. Beside the record of primary changes in seawater chemistry, a possible diagenetic overprint may also mime such CIEs in the sedimentary record. The aim of this contribution is to illustrate through three critical intervals (the Early Toarcian, the K-P boundary and the Mid-Miocene Montery Event) how the various micron-sized sedimentary particles specifically record these CIEs, which are respectively associated with major paleoceanographical events. New techniques for getting monotaxic calcareous nannofossil assemblages from the sediment (Minoletti et al., accepted) enable the isotopic measurement at various depths within the surface water and from bottom water by analyzing early diagenetic precipitations (rhombs and micarbs). The integration of these high-resolution isotopic signals in terms of amplitudes affords to recognize diagenetic artifacts in some sections displaying coeval decrease in the carbonate content. For both Early Toarcian and K-P events, corroborative records of CIE records in both primary calcite and bottom water carbonate indicate a global C-isotope perturbation of the water column. For the Monterey event, the evolution of calcareous nannoplankton and the foraminifera isotopic records are in overall agreement, but in detail, the coccolith-discoaster and foraminifer ratio in the sediment, related to environmental changes, is likely to produce isotopic

  1. Laser ablation molecular isotopic spectrometry of carbon isotopes

    Energy Technology Data Exchange (ETDEWEB)

    Bol' shakov, Alexander A. [Applied Spectra, Inc., Fremont, CA (United States); Jain, Jinesh [National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States); Russo, Richard E. [Applied Spectra, Inc., Fremont, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); McIntyre, Dustin [National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States); Mao, Xianglei [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2015-08-28

    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 spectrumyielded 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

  2. Laser ablation molecular isotopic spectrometry of carbon isotopes

    Science.gov (United States)

    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.

  3. Carbon isotopes in biological carbonates: Respiration and photosynthesis

    Science.gov (United States)

    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. Carbonate Ion Effects on Coccolith Carbon and Oxygen Isotopes

    Science.gov (United States)

    Ziveri, P.; Probert, I.; Stoll, H. M.

    2006-12-01

    The stable oxygen and carbon isotopic composition of biogenic calcite constitutes one of the primary tools used in paleoceanographic reconstructions. The δ18O of shells of ocean floor microfossils and corals reflects the composition of the paleo-seawater as they use the oxygen to build up their calcite and aragonite shells. The δ13C is used to reconstruct variations in the carbon isotopic composition of dissolved inorganic carbon in the ocean, which is controlled by biological productivity through the removal of isotopically light carbon in organic matter. To be effective and sensitive tools for understanding photic zone processes it is first necessary to understand the various biological fractionations associated with carbonate precipitation. To date, isotopic fractionation models are mainly based on foraminifera and corals but not on coccoliths, tiny plates produced by coccolithophore algae, which are often the most dominant carbonate contributors to pelagic sediments. As photosynthetic organisms, their chemistry can provide a sensitive tool for understanding photic zone processes. Coccoliths may be the most important carbonate phase for geochemical analysis in sediments where foraminifera are less common and/or core material is limited, such as in subpolar regions and for Early Cenozoic and Mesozoic sediments. Here we report experimental results on a common living coccolithophore species showing that the 13C/12C and 18O/16O ratios decrease with the increase of HCO^{3-} (CO32-). The selected species are among the heaviest calcifying extant coccolithophores and are major contributors to present coccolith carbonate export production. Because coccolithophores are photosynthetic organisms that calcify intracellularly in specialized vesicles, the challenge lies in ascertaining how kinetic and thermodynamic processes of isotopic fractionation are linked to cellular carbon "transport" and carbonate precipitation. This is a daunting challenge since studies have not

  5. Carbon isotopic composition of individual Precambrian microfossils

    Science.gov (United States)

    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.

  6. Carbon isotopic composition of individual Precambrian microfossils.

    Science.gov (United States)

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

  7. Fractionation behavior of chromium isotopes during coprecipitation with calcium carbonate

    DEFF Research Database (Denmark)

    Rodler, Alexandra; Sánchez-Pastor, Nuria; Fernández-Díaz, Lurdes;

    2015-01-01

    Interest in chromium (Cr) isotope incorporation into carbonates arises from the observation that Cr isotopic composition of carbonates could be used as a paleoclimate proxy to elucidate past fluctuations of oxygen contents in atmosphere and hydrosphere. The use of Cr isotopes to track...

  8. Carbon Isotope Chemistry in Molecular Clouds

    Science.gov (United States)

    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.

  9. Carbonate clumped isotope bond reordering and geospeedometry

    Science.gov (United States)

    Passey, Benjamin H.; Henkes, Gregory A.

    2012-10-01

    Carbonate clumped isotope thermometry is based on the preference of 13C and 18O to form bonds with each other. At elevated temperatures such bond ordering is susceptible to resetting by diffusion of C and O through the solid mineral lattice. This type of bond reordering has the potential to obscure primary paleoclimate information, but could also provide a basis for reconstructing shallow crustal temperatures and cooling rates. We determined Arrhenius parameters for solid-state reordering of C-O bonds in two different calcites through a series of laboratory heating experiments. We find that the calcites have different susceptibilities to solid-state reordering. Reaction progress follows a first order rate law in both calcites, but only after an initial period of non-first order reaction that we suggest relates to annealing of nonequilibrium defects when the calcites are first heated to experimental temperature. We show that the apparent equilibrium temperature equations (or "closure temperature" equations) for carbonate clumped isotope reordering are analogous Dodson's equations for first order loss of daughter isotopes. For each calcite, the sensitivity of apparent equilibrium temperature to cooling rate is sufficiently high for inference of cooling rates within a factor of ˜5 or better for cooling rates ranging from tens of degrees per day to a few degrees per million years. However, because the calcites have different susceptibilities to reordering, each calcite defines its own cooling rate-apparent equilibrium temperature relationship. The cooling rates of Carrara marble inferred from carbonate clumped isotope geospeedometry are 10-6-10-3 degrees per annum and are in broad agreement with rates inferred from thermochronometric methods. Cooling rates for 13C-depleted calcites from the late Neoproterozoic Doushantou cap carbonates in south China are on the order of 102-104 degrees per annum, consistent with rapid cooling following formation of these calcites by a

  10. Oxygen isotope fractionation in divalent metal carbonates

    Science.gov (United States)

    O'Neil, J.R.; Clayton, R.N.; Mayeda, T.K.

    1969-01-01

    Equilibrium fractionation factors for the distribution of 18O between alkaline-earth carbonates and water have been measured over the temperature range 0-500??C. The fractionation factors ?? can be represented by the equations CaCO3-H2O, 1000 ln??=2.78(106 T-2)-3.39, SrCO3-H 2O, 1000 ln??=2.69(106 T-2)-3.74, BaCO3-H2O, 1000 ln??=2.57(106 T -2)-4.73. Measurements on MnCO3, CdCO3, and PbCO3 were made at isolated temperatures. A statistical-mechanical calculation of the isotopic partition function ratios gives reasonably good agreement with experiment. Both cationic size and mass are important in isotopic fractionation, the former predominantly in its effect on the internal vibrations of the anion, the latter in its effect on the lattice vibrations.

  11. The Precambrian marine carbonate isotope database: version 1.1.

    OpenAIRE

    G. A. Shields; Veizer, J.

    2002-01-01

    We present a compilation of strontium, carbon, and oxygen isotope compositions of roughly 10,000 marine carbonate rocks of Archean - Ordovician age (3800 Ma – 450 Ma). The Precambrian Marine Carbonate Isotope Database (PMCID) has been compiled from 152 published and 3 unpublished articles and books of the past 40 years. Also included are 30 categories of relevant “metadata” that allow detailed comparisons and quality assessments of the isotope data to be made. The PMCID will be updated period...

  12. Carbon and Oxygen isotopic composition in paleoenvironmental determination

    International Nuclear Information System (INIS)

    This work reports that the carbon and oxygen isotopic composition separate the mollusks from marine environment of the mollusks from continental environment in two groups isotopically different, making the biological control outdone by environment control, in the isotopic fragmentation mechanisms. The patterns from the continental environment are more rich in O16 than the patterns from marine environments. The C12 is also more frequent in the mollusks from continental environments. The carbon isotopic composition in paterns from continental environments is situated betwen - 10.31 and - 4,05% and the oxygen isotopic composition is situated between - 6,95 and - 2,41%. To the marine environment patterns the carbon isotopic composition is between - 2,08 and + 2,65% and the oxigen isotopic composition is between - 2,08 and + 0,45%. Was also analysed fossil marine mollusks shells and their isotopic composition permit the formulation of hypothesis about the environment which they lived. (C.D.G.)

  13. Organic chemistry of Murchison meteorite: Carbon isotopic fractionation

    Science.gov (United States)

    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.

  14. Carbon isotope fractionation in synthetic magnesian calcite

    Science.gov (United States)

    Jimenez-Lopez, Concepción; Romanek, Christopher S.; Caballero, Emilia

    2006-03-01

    Mg-calcite was precipitated at 25 °C in closed system, free-drift experiments, from solutions containing NaHCO 3, CaCl 2 and MgCl 2. The carbon stable isotope composition of bulk solid and solution were analyzed from subsamples collected during time course experiments of 24 h duration. Considering only the Mg-content and δ 13C values for the bulk solid, the carbon isotope fractionation factor for the Mg-calcite-HCO 3(aq)- system (as 103lnα) increased with average mol percentage of Mg (X Mg) in the solid at a rate of (0.024 ± 0.011) per mol% MgCO 3. Extrapolation of this relationship to the pure calcite end member yields a value of 0.82 ± 0.09, which is similar to published values for the calcite-HCO 3(aq)- system. Although 103lnα did not vary for precipitation rates that ranged from 10 3.21 to 10 4.60 μmol m -2 h -1, it was not possible to hold Mg-content of the solid constant, so kinetic effect on 10 3 ln α could not be evaluated from these experiments.

  15. Carbon isotope fractionation for cotton genotype selection

    Directory of Open Access Journals (Sweden)

    Giovani Greigh de Brito

    2014-09-01

    Full Text Available The objective of this work was to evaluate the carbon isotope fractionation as a phenomic facility for cotton selection in contrasting environments and to assess its relationship with yield components. The experiments were carried out in a randomized block design, with four replicates, in the municipalities of Santa Helena de Goiás (SHGO and Montividiu (MONT, in the state of Goiás, Brazil. The analysis of carbon isotope discrimination (Δ was performed in 15 breeding lines and three cultivars. Subsequently, the root growth kinetic and root system architecture from the selected genotypes were determined. In both locations, Δ analyses were suitable to discriminate cotton genotypes. There was a positive correlation between Δ and seed-cotton yield in SHGO, where water deficit was more severe. In this site, the negative correlations found between Δ and fiber percentage indicate an integrative effect of gas exchange on Δ and its association with yield components. As for root robustness and growth kinetic, the GO 05 809 genotype performance contributes to sustain the highest values of Δ found in MONT, where edaphoclimatic conditions were more suitable for cotton. The use of Δ analysis as a phenomic facility can help to select cotton genotypes, in order to obtain plants with higher efficiency for gas exchange and water use.

  16. The Oxidant Budget of Dissolved Organic Carbon Driven Isotope Excursions

    Science.gov (United States)

    Bristow, T. F.; Kennedy, M. J.

    2008-12-01

    Negative carbon isotope values, falling below the mantle average of about -5 per mil, in carbonate phases of Ediacaran age sedimentary rocks are widely regarded as reflecting negative excursions in the carbon isotopic composition of seawater lasting millions of years. These isotopic signals form the basis of chemostratigraphic correlations between Ediacaran aged sections in different parts of the world, and have been used to track the oxidation of the biosphere. However, these isotopic values are difficult to accommodate within limits prescribed by the current understanding of the carbon cycle, and a hypothetical Precambrian ocean dissolved organic carbon (DOC) pool 100 to 1000 times the size of the modern provides a potential source of depleted carbon not considered in Phanerozoic carbon cycle budgets. We present box model results that show the remineralization of such a DOC pool to drive an isotope excursion of the magnitude observed in the geological record exhausts global budgets of free oxygen and sulfate in 800 k.y. These results are incompatible with the estimated duration of late Ediacaran isotope excursions of more than 10 m.y., as well as geochemical and biological indicators that oceanic sulfate and oxygen levels were maintained or even increased at the same time. Therefore the carbon isotope record is probably not a useful tool for monitoring oxygen levels in the atmosphere and ocean. Covariation between the carbon and oxygen isotope records is often observed during negative excursions and is indicative of local processes or diagenetic overprinting.

  17. Degradation changes stable carbon isotope depth profiles in palsa peatlands

    Directory of Open Access Journals (Sweden)

    J. P. Krüger

    2014-01-01

    Full Text Available Palsa peatlands are a significant carbon pool in the global carbon cycle and are projected to change by global warming due to accelerated permafrost thaw. Our aim was to use stable carbon isotopes as indicators of palsa degradation. Depth profiles of stable carbon isotopes generally reflect organic matter dynamics in soils with an increase of δ13C values during aerobic decomposition and stable or decreasing δ13C values with depth during anaerobic decomposition. Stable carbon isotope depth profiles of undisturbed and degraded sites of hummocks as well as hollows at three palsa peatlands in northern Sweden were used to investigate the degradation processes. The depth patterns of stable isotopes clearly differ between intact and degraded hummocks at all sites. Erosion and cryoturbation at the degraded sites significantly changes the stable carbon isotope depth profiles. At the intact hummocks the uplifting of peat material by permafrost is indicated by a turning in the δ13C depth trend and this assessment is supported by a change in the C / N ratios. For hollows isotope patterns were less clear, but some hollows and degraded hollows in the palsa peatlands show differences in their stable carbon isotope depth profiles indicating enhanced degradation rates. We conclude that the degradation of palsa peatlands by accelerated permafrost thawing could be identified with stable carbon isotope depth profiles. At intact hummocks δ13C depth patterns display the uplifting of peat material by a change in peat decomposition processes.

  18. Phanerozoic and Neoproterozoic Negative Carbon Isotope Excursions, Diagenesis and Terrestrialization

    Science.gov (United States)

    Paul, K.; Kennedy, M. J.

    2008-12-01

    Comprehensive data sets of Phanerozoic and late Precambrian carbon isotope data derived from carbonate rocks show a similar positive relation when cross-plotted with oxygen isotope values. The range and slope between the time periods is identical and the processes responsible for the relation have been well documented in Quaternary sediments. These processes include the stabilization of isotope values to ambient meteoric water values during shallow burial and flushing of carbonate sediments. Both data sets show strongly depleted carbon (-9 per mil PDB) and oxygen isotope values that retain seemingly systematic stratigraphic patterns with the Quaternary and Phanerozoic examples that demonstrably record meteroric water values. Similar values and patterns in the Precambrian are interpreted as primary marine in origin with significant implications for an ocean carbon mass balance not possible in the Phanerozoic carbon cycle. A similar compilation of carbonates older than one billion years do not show a relation between carbon and oxygen isotopes, lacking the negative carbon values evident in the younger record. We hypothesize that this difference records the onset of significant organic carbon on the land surface and the alteration of meteoric waters toward Phanerozoic values. We demonstrate the meteoric affinities of Neoproterozoic carbonates containing prominent negative isotope excursions recorded in the Shuram and Wonoka Formations of Oman and South Australia commonly attributed to whole ocean isotope variation. The conspicuous absence of negative carbon isotope values with normal marine oxygenisotope values in the Phanerozoic and Neoproterozic identifies a consistent relation between these time intervals and suggests that, as well accepted in the Phanerozoic, negative carbon isotope excursions less than -3 per mil are not a record of marine processes, but rather the later terrestrial biotic influence on meteoric water values.

  19. Carbonate isotopic records of paleoclimate changes in Chinese loess

    Institute of Scientific and Technical Information of China (English)

    韩家懋; 姜文英; 刘东生; 吕厚远; 郭正堂; 吴乃琴

    1996-01-01

    Oxygen and carbon isotopes of carbonate in concretion and bulk samples collected from Xifeng. Luochuan and Weinan loess sections, China, have been analyzed. It has been found that carbon and oxygen isotopic ratios of concretion in paleosol, as useful paleodimatic indicators, recorded temperature and humidity variation during their formation. Comparison of isotopic data from different locations may offer a spatial picture of past environmental changes. Isotopic data from carbonate of bulk sample also include useful environmental information. Carbon and oxygen isotopic curves of past 150ka in Weinan completely reflect the fluctuations of the paleodimate with different stratigraphical units. The curves can correlate well with those of other dimatic proxies and of the deep sea sediments.

  20. Carbon isotope fractionation in protoplanetary disks

    CERN Document Server

    Woods, Paul M

    2008-01-01

    We investigate the gas-phase and grain-surface chemistry in the inner 30 AU of a typical protoplanetary disk using a new model which calculates the gas temperature by solving the gas heating and cooling balance and which has an improved treatment of the UV radiation field. We discuss inner-disk chemistry in general, obtaining excellent agreement with recent observations which have probed the material in the inner regions of protoplanetary disks. We also apply our model to study the isotopic fractionation of carbon. Results show that the fractionation ratio, 12C/13C, of the system varies with radius and height in the disk. Different behaviour is seen in the fractionation of different species. We compare our results with 12C/13C ratios in the Solar System comets, and find a stark contrast, indicative of reprocessing.

  1. Progressive extraction method applied to isotopic exchange of carbon-14

    International Nuclear Information System (INIS)

    Isotopic exchange in natural settings is essentially an irreversible process, so that it progresses continuously until there is complete isotopic equilibrium. In soils, this process involves interaction between isotopes in the liquid and solid phases, and complete isotopic equilibrium may take a very long time. Measurements after partial isotopic exchange have been used to characterize the labile fraction of elements in soils. We describe a method to characterize the extent of isotopic exchange, with application here to incorporation of inorganic carbon-14 (14C) into mineral carbonates and organic matter in soils. The procedure uses a continuous addition of extractant, acid, or H2O2in the examples presented here, coupled with sequential sampling. The method has been applied to demonstrate the degree of isotopic exchange in soil. The same strategy could be applied to many other elements, including plant nutrients. (author)

  2. Clumped-isotope thermometry of magnesium carbonates in ultramafic rocks

    Science.gov (United States)

    García del Real, Pablo; Maher, Kate; Kluge, Tobias; Bird, Dennis K.; Brown, Gordon E.; John, Cédric M.

    2016-11-01

    Magnesium carbonate minerals produced by reaction of H2O-CO2 with ultramafic rocks occur in a wide range of paragenetic and tectonic settings and can thus provide insights into a variety of geologic processes, including (1) deposition of ore-grade, massive-vein cryptocrystalline magnesite; (2) formation of hydrous magnesium carbonates in weathering environments; and (3) metamorphic carbonate alteration of ultramafic rocks. However, the application of traditional geochemical and isotopic methods to infer temperatures of mineralization, the nature of mineralizing fluids, and the mechanisms controlling the transformation of dissolved CO2 into magnesium carbonates in these settings is difficult because the fluids are usually not preserved. Clumped-isotope compositions of magnesium carbonates provide a means to determine primary mineralization or (re)equilibration temperature, which permits the reconstruction of geologic processes that govern magnesium carbonate formation. We first provide an evaluation of the acid fractionation correction for magnesium carbonates using synthetic magnesite and hydromagnesite, along with natural metamorphic magnesite and low-temperature hydromagnesite precipitated within a mine adit. We show that the acid fractionation correction for magnesium carbonates is virtually indistinguishable from other carbonate acid fractionation corrections given current mass spectrometer resolution and error. In addition, we employ carbonate clumped-isotope thermometry on natural magnesium carbonates from various geologic environments and tectonic settings. Cryptocrystalline magnesite vein deposits from California (Red Mountain magnesite mine), Austria (Kraubath locality), Turkey (Tutluca mine, Eskişehir district) and Iran (Derakht-Senjed deposit) exhibit broadly uniform Δ47 compositions that yield apparent clumped-isotope temperatures that average 23.7 ± 5.0 °C. Based on oxygen isotope thermometry, these clumped-isotope temperatures suggest

  3. Contrasting modes of inorganic carbon acquisition amongst Symbiodinium (Dinophyceae) phylotypes.

    Science.gov (United States)

    Brading, Patrick; Warner, Mark E; Smith, David J; Suggett, David J

    2013-10-01

    Growing concerns over ocean acidification have highlighted the need to critically understand inorganic carbon acquisition and utilization in marine microalgae. Here, we contrast these characteristics for the first time between two genetically distinct dinoflagellate species of the genus Symbiodinium (phylotypes A13 and A20) that live in symbiosis with reef-forming corals. Both phylotypes were grown in continuous cultures under identical environmental conditions. Rubisco was measured using quantitative Western blots, and radioisotopic (14) C uptake was used to characterize light- and total carbon dioxide (TCO2 )-dependent carbon fixation, as well as inorganic carbon species preference and external carbonic anhydrase activity. A13 and A20 exhibited similar rates of carbon fixation despite cellular concentrations of Rubisco being approximately four-fold greater in A13. The uptake of CO2 over HCO3 - was found to support the majority of carbon fixation in both phylotypes. However, A20 was also able to indirectly utilize HCO3 - by first converting it to CO2 via external carbonic anhydrase. These results show that adaptive differences in inorganic carbon acquisition have evolved within the Symbiodinium genus, which thus carries fundamental implications as to how this functionally key genus will respond to ocean acidification, but could also represent a key trait factor that influences their productivity when in hospite of their coral hosts.

  4. 48 CFR 252.225-7030 - Restriction on Acquisition of Carbon, Alloy, and Armor Steel Plate.

    Science.gov (United States)

    2010-10-01

    ... of Carbon, Alloy, and Armor Steel Plate. 252.225-7030 Section 252.225-7030 Federal Acquisition... Acquisition of Carbon, Alloy, and Armor Steel Plate. As prescribed in 225.7011-3, use the following clause: Restriction on Acquisition of Carbon, Alloy, and Armor Steel Plate (DEC 2006) (a) Carbon, alloy, and...

  5. Chromium isotope fractionation during coprecipitation with calcium carbonate

    DEFF Research Database (Denmark)

    Rodler, Alexandra; Sánchez-Pastor, Nuria; Fernández-Díaz, Lurdes;

    The chromium (Cr) isotopic composition of carbonates can potentially be used as a paleoclimate proxy to elucidate past fluctuations of oxygen contents in atmosphere and hydrosphere. The use of Cr isotopes to track paleoenvironmental changes, for example related to the rise of oxygen during...

  6. Probing the Isotopic Composition of Surface Waters Across Isotopic Extremes of Cryogenian Carbonates

    Science.gov (United States)

    Bosak, T.; Matys, E. D.; Bird, L. R.; Macdonald, F. A.; Freeman, K. H.

    2012-12-01

    Neoproterozoic carbonate strata record unusually large and positive carbon isotope values (δ13Ccarb from 4 to 10 per mil), and stratigraphically extensive large negative carbon isotope excursions (δ13Ccarb isotopically extreme carbonates in Neoproterozoic successions remain poorly understood. Little is also known about organisms and metabolisms that cycled carbon in these carbonate strata, because they rarely contain well-preserved organic-rich fossils. To better understand the cycling of carbon during the deposition of the 715-635 Ma Tayshir member of the Tsagaan Oloom Formation, Mongolia, we analyzed δ13Cfossil of two types of organic fossils that occur in 13C- enriched carbonates (+ 5 to 9.9 per mil) and within 13C-depleted carbonates of the Tayshir anomaly (-3 to -6 per mil). Because these organic microfossils are remarkably similar to the tests of modern planktonic, herbivorous tintinnid ciliates and benthic macroscopic red algae, respectively, they can be used as tracers of organic matter production in surface waters. Fossil tests were extracted by acid maceration, cleaned and analyzed morphologically and microscopically. Their carbon isotopic composition was measured using a nano-scaled elemental analyzer inlet (nano-EA-IRMS), with ±1 per mil analytical precision. To date, we analyzed 12 samples of 100-150 organic tests, representing 3 different fossiliferous parts of the Tayshir anomaly (δ13Ccarb +5 per mil), respectively. More samples, including those of fossil algae and tests from the carbonate strata overlying the Tayshir anomaly, are currently being analyzed. Initial data reveal a rather constant isotopic composition of organic carbon in fossil tests (δ13Cfossil), with values of -23 ±1 per mil both within 13C-enriched and 13C-depleted carbonates. The isotopic difference between δ13Cfossil and 13C-enriched carbonates is 28 to 30 per mil, suggesting maximal isotopic fractionation by primary producers, and little environmental (or diagenetic

  7. Isotope aided studies of atmospheric carbon dioxide and other greenhouse gases. Phase II

    International Nuclear Information System (INIS)

    The substantial increase in atmospheric greenhouse gas concentrations and their role in global warming have become major concerns of world governments. Application of isotope techniques to label sources and sinks of CO2 and other greenhouse gases has emerged as a potentially powerful method for reducing uncertainties in the global CO2 budgets and for tracing pathways and interaction of terrestrial, oceanic, and atmospheric pools of carbon. As with CO2 concentration measurements, meaningful integration of isotopes in global models requires careful attention to quality assurance, quality control and inter-comparability of measurements made by a number of networks and laboratories. To support improvements in isotope measurement capabilities, the IAEA began implementing Co-ordinated Research Projects (CRPs) in 1992. The first project, entitled Isotope Variations of Carbon Dioxide and other Trace Gases in the Atmosphere, was implemented from 1992 to 1994. A significant contribution was made towards a better understanding of the global carbon cycle and especially of the sources and sinks of carbon with data on the 14C and 13C content of atmospheric CO2, pointing to a better understanding of the problem of the 'missing sink' in the global carbon cycle. Important methodological developments in the field of high precision stable isotope mass spectrometry and improved data acquisition procedures emerged from work carried out within the framework of this programme. The development of pressurized gas standards and planning for an associated interlaboratory calibration were initiated. Due to the good progress and long standing nature of the required work a second CRP was initiated and implemented from 1996 to 1999. It was entitled Isotope aided Studies of Atmospheric Carbon Dioxide and Other Trace Gases - Phase II, to document the close relationship of both programmes. This publication provides an overview of the scientific outcomes of the studies conducted within Phase II of

  8. Study of neutron rich carbon isotopes

    Science.gov (United States)

    Fallon, Paul

    2012-03-01

    Electric quadrupole (E2) matrix elements are important quantities in nuclear structure. In particular they are sensitive to nuclear deformation, the decoupling of proton and neutron degrees of freedom, and are often affected by small components of the nuclear wave function. Neutron-rich carbon isotopes have attracted a great deal of attention recently, both experimentally and theoretically, with regards to the question of spatially extended (halo-like) and decoupled valence neutrons. For example, 19C and the drip-line nucleus 22C are proposed to have ground-state neutron halo structures. Electric quadrupole transition rates in 16C 18C and 20C are among the lowest found throughout the nuclear chart and this fact has been cited by some as evidence for a reduced coupling between the valence neutrons and the core nucleons. In this talk I will present the results from our experiments to measure the transition rates in 16,18,20C and discuss the evidence for a ``decoupling'' of valence neutrons from the core that goes beyond the usual shell model approach. Data will be compared to shell model and no-core (ab-initio) shell model calculations with NN and NN+NNN interactions.

  9. Stable-carbon isotope variability in tree foliage and wood

    International Nuclear Information System (INIS)

    This study documents variation of stable-carbon isotope ratios (13C/12C) 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

  10. Modeling the carbon isotope composition of bivalve shells (Invited)

    Science.gov (United States)

    Romanek, C.

    2010-12-01

    The stable carbon isotope composition of bivalve shells is a valuable archive of paleobiological and paleoenvironmental information. Previous work has shown that the carbon isotope composition of the shell is related to the carbon isotope composition of dissolved inorganic carbon (DIC) in the ambient water in which a bivalve lives, as well as metabolic carbon derived from bivalve respiration. The contribution of metabolic carbon varies among organisms, but it is generally thought to be relatively low (e.g., organism and high (>90%) in the shells from terrestrial organisms. Because metabolic carbon contains significantly more C-12 than DIC, negative excursions from the expected environmental (DIC) signal are interpreted to reflect an increased contribution of metabolic carbon in the shell. This observation contrasts sharply with modeled carbon isotope compositions for shell layers deposited from the inner extrapallial fluid (EPF). Previous studies have shown that growth lines within the inner shell layer of bivalves are produced during periods of anaerobiosis when acidic metabolic byproducts (e.g., succinic acid) are neutralized (or buffered) by shell dissolution. This requires the pH of EPF to decrease below ambient levels (~7.5) until a state of undersaturation is achieved that promotes shell dissolution. This condition may occur when aquatic bivalves are subjected to external stressors originating from ecological (predation) or environmental (exposure to atm; low dissolved oxygen; contaminant release) pressures; normal physiological processes will restore the pH of EPF when the pressure is removed. As a consequence of this process, a temporal window should also exist in EPF at relatively low pH where shell carbonate is deposited at a reduced saturation state and precipitation rate. For example, EPF chemistry should remain slightly supersaturated with respect to aragonite given a drop of one pH unit (6.5), but under closed conditions, equilibrium carbon isotope

  11. Carbon isotope excursions in paleosol carbonate marking five early Eocene hyperthermals in the Bighorn Basin, Wyoming

    OpenAIRE

    H. A. Abels; Lauretano, V.; A. van Yperen; T. Hopman; Zachos, J.C.; L. J. Lourens; Gingerich, P. D.; G. J. Bowen

    2015-01-01

    Transient greenhouse warming events in the Paleocene and Eocene were associated with the addition of isotopically-light carbon to the exogenic atmosphere–ocean carbon pool, leading to substantial environmental and biotic change. The magnitude of an accompanying carbon isotope excursion (CIE) can be used to constrain both the sources and amounts of carbon released during an event, as well as to correlate marine and terrestrial records with high precision. The ...

  12. Carbon isotopes in oil and gas exploration. Examples of applications

    International Nuclear Information System (INIS)

    The use of carbon isotopes in hydrocarbon exploration is reviewed. Examples of the application of stable carbon isotopes are discussed in the fields of: (1) gas exploration, where source rocks of gas deposits or gas shows can be identified by 13C/12C analyses of methane and the exploration efforts redirected; (2) wildcat drilling, in which the carbon isotope composition of methane from the head space of canned cuttings characterizes autochthonous methane and gives information on the maturity of organic matter in relation to depth; (3) oil/oil and source-rock/oil correlation, where the 'isotopic type curve technique', a recently developed sensitive oil/oil and source-rock/oil correlation method, is discussed and applied to correlation problems in the British North Sea region. (author)

  13. Carbon allocation belowground in Pinus pinaster using stable carbon isotope pulse labeling technique

    Science.gov (United States)

    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

  14. Variations in carbon and nitrogen stable isotopes of cryoconite

    Science.gov (United States)

    Takeuchi, N.

    2012-12-01

    Cryoconite is biogenic surface dust on snow and ice, and is commoly observed on glaciers worldwide. Because of their dark coloration, cryoconite substantially reduce surface albedo and accelerate melting of glaciers. Therefore, it is important to understand formation process of cryoconite to evaluate its effect on glacier melting. Although cryoconite consists of mineral particles and organic matter, organic fraction is more important in terms of albedo effect because it is usually darker color and accounts for major part of cryoconite in volume. The organic matter is derived from photosynthetic microbes such as cyanobacteria, and/or from windblown organic matter from ground soil around glaciers. Carbon (C) and nitrogen (N) stable isotopes of the organic matter could be useful to know their sources and to understand their cycles on glaciers. In this study, I analyzed carbon and nitrogen stable isotopes of cryoconite collected from 6 sites of different elevation from May to September on an Alaska glacier (Gulkana Glacier) to know their spatial and seasonal variations. I also analyze those collected from glaciers in Asia and Arctic to compare them among different geographical locations. Results on the Alaska glacier show that C and N stable isotopes of cryoconite organic mater significantly varied among elevations and seasons. C isotope was generally higher in lower elevation, probably due to higher photosynthetic activity in the lower elevation. In contrast, N isotope was constant on the ice area, but was lower in the snow area where the red snow algae were blooming. N isotope may be reflective of nitrogen availavility on the glacier surface. Geograpical comparison shows large variations in C and N isotopes among regions: higher C and N isotopes on Asian glaciers, lower C and N isotopes in Alaska, and lower C and higher N isotopes on Arctic glaciers. The isotope values suggest that algal production is a major carbon source on most of glaciers, but their productivity

  15. Biogeochemistry of the stable carbon isotopes in carboxylic acids

    International Nuclear Information System (INIS)

    The carbon isotopic compositions of the carboxyl carbons of fatty acids were determined by measuring the isotopic composition of the carbon dioxide quantitatively released from the acid. A modified version of the Schmidt decarboxylation developed and tested in this work was employed. A study of the evolution of CO2 at 5 +- 20C from the Schmidt decarboxylation of octanoic acid during the developmental program revealed two kinetic phases, each characterized by different rate constants and carbon isotope effects. The first, slower reaction phase displayed overall first-order kinetics, its rate being independent of HN3 concentration. Both pre-equilibration of the HN3-CHCl3 decarboxylation reagent with H2SO4 and saturation of the catalytic H2SO4 phase with KHSO4 drastically altered the rate of evolution and isotopic composition of the product CO2. The mechanistic implications of these results were discussed. A review of the metabolism of saturated fatty acids was made in which the impact of potential isotope fractionations in the various chemical reactions comprising the biosynthetic pathways on the intramolecular carbon isotope distribution within fatty acids was discussed

  16. Carbon and oxygen isotope fractionation in dense interstellar clouds

    Science.gov (United States)

    Langer, W. D.; Graedel, T. E.; Frerking, M. A.; Armentrout, P. B.

    1984-01-01

    It is pointed out that isotope fractionation as a result of chemical reactions is due to the small zero-point energy differences between reactants and products of isotopically distinct species. Only at temperatures near absolute zero does this energy difference become significant. Favorable conditions for isotope fractionation on the considered basis exist in space within dense interstellar clouds. Temperatures of approximately 10 K may occur in these clouds. Under such conditions, ion-molecule reactions have the potential to distribute isotopes of hydrogen, carbon, oxygen unequally among the interstellar molecules. The present investigation makes use of a detailed model of the time-dependent chemistry of dense interstellar clouds to study cosmological isotope fractionation. Attention is given to fractionation chemistry and the calculation of rate parameters, the isotope fractionation results, and a comparison of theoretical results with observational data.

  17. Stable carbon isotope biogeochemistry of lakes along a trophic gradient

    NARCIS (Netherlands)

    de Kluijver, A.; Schoon, P.L.; Downing, J.A.; Schouten, S.; Middelburg, J.J.

    2014-01-01

    The stable carbon (C) isotope variability of dissolved inorganic and organic C (DIC and DOC), particulate organic carbon (POC), glucose and polar-lipid derived fatty acids (PLFAs) was studied in a survey of 22 North American oligotrophic to eutrophic lakes. The d13C of different PLFAs were used as p

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

    Science.gov (United States)

    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.

  19. Carbon isotopic study of individual alcohol compounds in modern sediments from Nansha Islands sea area, China

    Institute of Scientific and Technical Information of China (English)

    段毅; 文启彬; 郑国东; 罗斌杰

    1997-01-01

    Carbon isotopic compositions of individual n-alkanols and sterols in modern sediments from the Nan-sha Islands sea area are measured after derivatization to trimethylsilyl ethers by the new isotopic analytical technique of GC/C/IRMS. The effects of the three added silyl carbon atoms in every alcohol molecule on these compound isotopic compositions and the characteristics of their carbon isotopic compositions are studied. Then their biological sources are discussed using their carbon isotopic compositions.

  20. Carbon and oxygen isotope compositions of the carbonate facies in the Vindhyan Supergroup, central India

    Indian Academy of Sciences (India)

    S Banerjee; S K Bhattacharya; S Sarkar

    2006-02-01

    The Vindhyan sedimentary succession in central India spans a wide time bracket from the Paleopro- terozoic to the Neoproterozoic period.Chronostratigraphic significance of stable carbon and oxygen isotope ratios of the carbonate phase in Vindhyan sediments has been discussed in some recent studies.However,the subtle controls of facies variation,depositional setting and post-depositional diagenesis on stable isotope compositions are not yet clearly understood.The Vindhyan Super- group hosts four carbonate units,exhibiting a wide variability in depositional processes and paleogeography.A detailed facies-specific carbon and oxygen isotope study of the carbonate units was undertaken by us to investigate the effect of these processes and to identify the least altered isotope values.It is seen that both carbon and oxygen isotope compositions have been affected by early meteoric water diagenesis.The effect of diagenetic alteration is,however,more pronounced in case of oxygen isotopes than carbon isotopes.Stable isotope compositions remained insensitive to facies only when sediments accumulated in a shallow shelf setting without being exposed.Major alteration of original isotope ratios was observed in case of shallow marine carbonates,which became exposed to meteoric fluids during early diagenetic stage.Duration of exposure possibly determined the magnitude of alteration and shift from the original values.Moreover,dolomitization is found to be accompanied by appreciable alteration of isotope compositions in some of the carbonates.The present study suggests that variations in sediment depositional settings,in particular the possibility of subaerial exposure,need to be considered while extracting chronostratigraphic signi ficance from 13C data.

  1. Stable carbon isotope ratios of ambient aromatic volatile organic compounds

    Science.gov (United States)

    Kornilova, Anna; Huang, Lin; Saccon, Marina; Rudolph, Jochen

    2016-09-01

    Measurements of mixing ratios and stable carbon isotope ratios of aromatic volatile organic compounds (VOC) in the atmosphere were made in Toronto (Canada) in 2009 and 2010. Consistent with the kinetic isotope effect for reactions of aromatic VOC with the OH radical the observed stable carbon isotope ratios are on average significantly heavier than the isotope ratios of their emissions. The change of carbon isotope ratio between emission and observation is used to determine the extent of photochemical processing (photochemical age, ∫ [OH]dt) of the different VOC. It is found that ∫ [OH]dt of different VOC depends strongly on the VOC reactivity. This demonstrates that for this set of observations the assumption of a uniform ∫ [OH]dt for VOC with different reactivity is not justified and that the observed values for ∫ [OH]dt are the result of mixing of VOC from air masses with different values for ∫ [OH]dt. Based on comparison between carbon isotope ratios and VOC concentration ratios it is also found that the varying influence of sources with different VOC emission ratios has a larger impact on VOC concentration ratios than photochemical processing. It is concluded that for this data set the use of VOC concentration ratios to determine ∫ [OH]dt would result in values for ∫ [OH]dt inconsistent with carbon isotope ratios and that the concept of a uniform ∫ [OH]dt for an air mass has to be replaced by the concept of individual values of an average ∫ [OH]dt for VOC with different reactivity.

  2. Chromium Isotopes in Marine Carbonates - an Indicator for Climatic Change?

    Science.gov (United States)

    Frei, R.; Gaucher, C.

    2010-12-01

    Chromium (Cr) stable isotopes experience an increased interest as a tracer of Cr (VI) reduction in groundwater and thus showed their potential as a monitor of remediation of anthropogenic and natural contamination in water (Berna et al., 2009; Izbicki et al., 2008). Chromium stable isotopes in Fe-rich chemical sediments (BIFs and Fe-cherts) have recently also been used as a tracer for Earth's atmospheric oxygenation through time (Frei et al., 2009). We have applied the Cr isotope system to organic-rich carbonates from a late Ediacaran succession in Uruguay (Polanco Formation), from which we have previously analyzed BIFs with extremely fractionated (δ53Cr up to 5.0 ‰) Cr isotope signatures that are part of an underlying deep water clastic sediment (shale-dominated) sequence (Yerbal Formation) deposited in a glacio-marine environment (Gaucher et al.,2004). δ53Cr values of organic rich carbonates correlate with positive and negative carbon isotope excursions (δ13C PDB between -3 and +3 ‰) and with systematic changes in strontium isotope compositions, commonly interpreted as to reflect fluctuations in organic (photosynthetic algae) production related to fluctuations in atmospheric oxygen and weathering intensities, respectively. Slightly positively fractioned δ53Cr values (up to +0.25‰), paralleling positive (δ13C PDB and 87Sr/86Sr ratio excursions would thereby trace elevated atmospheric oxygen levels/pulses possibly related to glacier retreat/melting stages that caused bioproductivity to increase. While the causal link between these multiple isotopic tracers and the mechanisms of Cr stripping into carbonates has to be further investigated in detail, the first indications from this study point to a potentially promising use of stable Cr isotopes in organic-rich carbonates to monitor fluctuations of atmospheric oxygen, particularly over the Neoproterozoic and Phanerozoic ice age periods. E.C. Berna et al. (2010) Cr stable isotopes as indicators of Cr

  3. Temperature dependence of carbon isotope fractionation in CAM plants

    Energy Technology Data Exchange (ETDEWEB)

    Deleens, E.; Treichel, I.; O' Leary, M.H.

    1985-09-01

    The carbon isotope fractionation associated with nocturnal malic acid synthesis in Kalanchoe daigremontiana and Bryophyllum tubiflorum was calculated from the isotopic composition of carbon-4 of malic acid, after appropriate corrections. In the lowest temperature treatment (17/sup 0/C nights, 23/sup 0/C days), the isotope fractionation for both plants is -4% per thousand (that is, malate is enriched in /sup 13/C relative to the atmosphere). For K. daigremontiana, the isotope fractionation decreases with increasing temperature, becoming approximately 0% per thousand at 27/sup 0/C/33/sup 0/C. Detailed analysis of temperature effects on the isotope fractionation indicates that stomatal aperture decreases with increasing temperature and carboxylation capacity increases. For B. tubiflorum, the temperature dependence of the isotope fractionation is smaller and is principally attributed to the normal temperature dependences of the rates of diffusion and carboxylation steps. The small change in the isotopic composition of remaining malic acid in both species which is observed during deacidification indicates that malate release, rather than decarboxylation, is rate limiting in the deacidification process. 28 references, 1 figure, 4 tables.

  4. Can stable isotope fractionation in diatom and coccolith biominerals elucidate the significance of carbon concentrating mechanisms (CCMs) in the past?

    Science.gov (United States)

    Stoll, H.; Bolton, C.; Isensee, K.; Mendez-Vicente, A.; Rubio-Ramos, M.; Mejia-Ramirez, L. M.

    2012-04-01

    Carbon isotopic fractionation in fossil algal biomarkers is typically interpreted to reflect atmospheric CO2 changes assuming simple diffusive uptake of CO2 by cells, however modern algae employ a diverse array of additional strategies to concentrate DIC inside the cell (CCMs). We previously hypothesized that the size-correlated range of vital effects in carbonate liths produced by different coccolithophore species was due to variable significance of CCMs in their C acquisition, and that an absence of interspecific vital effects may reflect a reduced importance of CCMs (or more similar CCMs employed). Here, we present stable isotope data from size-separated deep-sea sediments dominated by small, intermediate and large coccoliths from time slices throughout the Cenozoic. We show that the range of coccolith vital effects is distinct during several major Cenozoic proxy-inferred climate-CO2 transitions, and where vital effects are significant their magnitude scales with cell size in the same sense as modern culture genera (increasing C and O isotope enrichment with decreasing coccolith size). Our new culture experiments with coccolithophorids reveal strong plasticity in the magnitude of stable carbon isotope vital effects in coccoliths of Calcidiscus leptoporus and Emiliania huxleyi with variable CO2. At high CO2 coccoliths of both species are more isotopically enriched, but the magnitude is greater in C. leptoporus leading to reduced interspecific offsets at high CO2. In the case of E. huxleyi, higher CO2 conditions resulted in significant reduction in the magnitude of DIC accumulation in the intracellular carbon pool, and more positive carbon isotopic values inside the particulate organic matter. A model of carbon acquisition incorporating both photosynthetic and carbonate production is used to explore mechanisms for these relationships. We also investigate fractionation in diatom organic matter and diatom biomineral-bound organic matter. While the carbon isotopic

  5. Aptian Carbon Isotope Stratigraphy in Sierra del Rosario, Northeastern Mexico

    Science.gov (United States)

    Barragan-Manzo, R.; Moreno-Bedmar, J.; Nuñez, F.; Company, M.

    2013-05-01

    In most recent years Aptian carbon isotope stratigraphy has been widely studied in Europe where isotopic stages have been developed to correlate global events. Two negative excursions have been recorded in the Lower Aptian, the older is OAE 1a in the middle part, and a younger negative excursion labeled "Aparein level", which occurs in the uppermost part of the Lower Aptian. In Mexico previous works reported a carbon isotope negative excursion in the lowermost part of the La Peña Formation that was assigned to the onset of Oceanic Anoxic Event 1a (=OAE 1a). In this work we study the isotopic record of the δ13Ccarb of 32 bulk rock samples of limestone from the uppermost part of the Cupido Formation and the lower part of the La Peña Formation at the Francisco Zarco Dam Section (=FZD), Durango State, northeastern Mexico. The isotopic data are calibrated using the latest ammonite biostratigraphic biozonation of the Aptian. This age calibration allows us to make a precise correlation between the carbon isotopic record of Mexico and several European sections (e.g. Spain and France). In the studied Francisco Zarco Dam section we recognize a negative carbon isotopic excursion in the Dufrenoyia justinae ammonite Zone that corresponds to the "Aparein level", which we correlate using the ammonite zonation of others European sections (Figure 1). This correlation allows us to see how the negative excursion that characterizes the "Aparein level" is consistent with the C7 segment. Thus, our recent stratigraphic study allows us to conclude that the ammonite record in the lowermost part of the La Peña Formation is regionally isochronous, and correlates with the Dufrenoyia justinae Zone and Lower Aptian isotope interval C7. In agreement to these biostratigraphic data, the supposed record of the OAE 1a in the lowermost part of the La Peña Formation is not correct, and the carbon isotope negative excursion must be assigned to the younger event "Aparein level". Taking this into

  6. The clumped isotopic record of Neoproterozoic carbonates, Sultanate of Oman

    Science.gov (United States)

    Bergmann, K. D.; Eiler, J. M.; Fischer, W. W.; Osburn, M. R.; Grotzinger, J. P.

    2011-12-01

    The Huqf Supergroup of the Sultanate of Oman records several important events in latest Precambrian time, including two glaciations in the Abu Mahara Group (ca. 725 - isotope excursion in the Nafun Group (ca. Precambrian-Cambrian boundary in the Ara Group (ca. 547-540 Ma). This interval contains several extreme isotopic excursions, hypothesized to record perturbations of the surficial Earth carbon cycle or post-depositional diagenetic processes. Rigorous interpretation of these records requires a more thorough assessment of diagenetic processes. To better understand the significance and cause of these large amplitude isotopic excursions, we employed carbonate clumped isotope thermometry. This method allows us to estimate the absolute temperature of carbonate precipitation, including recrystallization, based on the temperature dependent abundance of carbonate ions containing both 13C and 18O. These estimates are accompanied by a measurement of carbonate δ18O, which in conjunction with temperature, can be used to calculate the oxygen isotopic composition of the fluid from which the carbonate precipitated. We analyzed stratigraphically constrained samples from a range of paleoenvironments with differing burial histories (1 - >10km maximum burial depth) to constrain the temperature and fluid composition of recrystallization. Clumped isotope temperatures from Huqf Supergroup samples range from 35-175°C. The isotopic composition of the fluid these rocks equilibrated with ranges from -3.7 to 15.7% VSMOW. This large range in temperature and fluid composition separates into distinct populations that differ systematically with independent constraints on petrography, stratigraphy and burial history. The data indicate the Abu Mahara, Nafun and Ara groups have unique diagenetic histories. In central Oman, the post-glacial Abu Mahara cap dolostone shows high temperature, rock buffered diagenesis (Tavg = 176°C; δ18Ofluid = 15% VSMOW), the Nafun Group generally experienced

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

    Science.gov (United States)

    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 (6determined 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

  8. Vital effects in coccolith calcite: Cenozoic climate-pCO2 drove the diversity of carbon acquisition strategies in coccolithophores?

    Science.gov (United States)

    Bolton, Clara T.; Stoll, Heather M.; Mendez-Vicente, Ana

    2012-12-01

    Coccoliths, calcite plates produced by the marine phytoplankton coccolithophores, have previously shown a large array of carbon and oxygen stable isotope fractionations (termed "vital effects"), correlated to cell size and hypothesized to reflect the varying importance of active carbon acquisition strategies. Culture studies show a reduced range of vital effects between large and small coccolithophores under high CO2, consistent with previous observations of a smaller range of interspecific vital effects in Paleocene coccoliths. We present new fossil data examining coccolithophore vital effects over three key Cenozoic intervals reflecting changing climate and atmospheric partial pressure of CO2 (pCO2). Oxygen and carbon stable isotopes of size-separated coccolith fractions dominated by different species from well preserved Paleocene-Eocene thermal maximum (PETM, ˜56 Ma) samples show reduced interspecific differences within the greenhouse boundary conditions of the PETM. Conversely, isotope data from the Plio-Pleistocene transition (PPT; 3.5-2 Ma) and the last glacial maximum (LGM; ˜22 ka) show persistent vital effects of ˜2‰. PPT and LGM data show a clear positive trend between coccolith (cell) size and isotopic enrichment in coccolith carbonate, as seen in laboratory cultures. On geological timescales, the degree of expression of vital effects in coccoliths appears to be insensitive topCO2 changes over the range ˜350 ppm (Pliocene) to ˜180 ppm (LGM). The modern array of coccolith vital effects arose after the PETM but before the late Pliocene and may reflect the operation of more diverse carbon acquisition strategies in coccolithophores in response to decreasing Cenozoic pCO2.

  9. High Resolution Carbon and Oxygen Isotope Measurements of Laminations in Pedogenic Carbonate

    Science.gov (United States)

    Breecker, D.; Sharp, Z.

    2005-12-01

    Stable carbon and oxygen isotope ratios in pedogenic carbonate from buried soils provide a proxy for low-resolution Quaternary climate and environmental conditions. Samples of carbonate are taken from clast rinds, nodules or filaments in calcic soils. Most clast rinds exhibit micro-laminations that may preserve isotopic ratios of formation. The techniques typically utilized to sample pedogenic carbonate, however, are too coarse to sample individual laminations and likely result in time averages and therefore limit temporal resolution. We investigated the heterogeneity of both carbon and oxygen isotopes ratios in clast rinds at a 100 μm scale using a rapid CO2 laser extraction technique (Sharp and Cerling, 1996). A single 20 msec burst at low power releases CO2 from polished carbonate slabs and the CO2 is then analyzed using continuous flow GC-IRMS. Analyses take less than 5 minutes with a reproducibility of better than ±0.3‰ (δ13C) and ±0.4‰ (δ18O). We have made a two dimensional map of a thick carbonate rind on a limestone clast from a stage V soil to explore the potential for preservation of isotopic ratios in well developed soils and plan to analyze additional rinds from less well developed calcic horizons for comparison. The isotopic map reveals heterogeneities in δ13C of up to 4‰ at a sub-millimeter scale, possibly corresponding to 30% changes in the fraction of C4 plants. Also imaged are abrupt changes in δ13C of approximately 2‰ across sub-100 μm scale boundaries. One well-defined carbon isotope boundary is sub parallel to, but crosses, the lamination boundaries. Oxygen isotope compositions do not change systematically across the same boundary and generally appear more random. These observations are most easily explained by alteration of initial isotopic compositions. Alteration may preferentially affect oxygen isotope ratios leaving carbon isotope distributions relatively intact. It is also possible that both carbon and oxygen isotopes

  10. Terrestrial carbon isotope excursions and biotic change during Palaeogene hyperthermals

    NARCIS (Netherlands)

    Abels, H.A.; Clyde, W.C.; Gingerich, P.D.; Hilgen, F.J.; Fricke, H.C.; Bowen, G.J.; Lourens, L.J.

    2012-01-01

    Pronounced transient global warming events between 60 and 50 million years ago have been linked to rapid injection of isotopically-light carbon to the ocean–atmosphere system1,2. It is, however, unclear whether the largest of the hyperthermals, the Palaeocene–Eocene Thermal Maximum (PETM; ref. 3), h

  11. Carbon dioxide gasification of carbon black: isotope study of carbonate catalysis

    International Nuclear Information System (INIS)

    Temperature-programmed reaction was used with labeled isotopes (13C and 18O) to study interactions between carbon black and potassium carbonate in pure He and 10% CO2/90% He atmospheres. Catalytic gasification precursor complexes were observed. Carbon and oxygen-bearing carbon surface groups interacted with the carbonate above 500 K to form surface complexes. Between 500 and 950 K, and in the presence of gaseous CO2, the complexes participated in C and O exchange with the gas phase while oxygen atoms within the complexes also exchanged with those on the carbon surface. As the temperature rose, the complexes decomposed, with CO2 the initial product. Decomposition started around 500 K in pure He, and around 950 K in CO2/He. Catalytic gasification began only after decomposition of significant portions of the complexes. Elemental potassium formed, and the active catalyst appears to alternate between being potassium metal and a potassium-oxygen-carbon complex. Potassium carbonate is not part of the catalytic cycle. 20 references, 10 figures

  12. Isotopic composition of carbon-13 and oxygen-18 from authigenic carbonates, Black Sea region

    Science.gov (United States)

    Logvina, E.; Mazurenko, L.; Prasolov, E.

    2004-05-01

    Several types of authigenic carbonates related to the fluid discharge zones were sampled during the international expeditions onboard R/V "Professor Vodyanitskiy" (56th cruise) and R/V "Professor Logachev" (11th cruise of UNESCO-TTR) in the northwest part of the Black sea. These carbonates are represented as mounds, build-ups and chimney-like structures, cemented sediments, crusts and concretions. The isotope analyses of carbonates were conducted using mass-spectrometer MS-20 in the Laboratory of Isotope Geology (St.Petersburg State University). The obtained values of oxygen-18 varied from +0,6 to -1,9 per mille (up to C0.8 per mille on average). This value is corresponding to normal seawater oxygen-18 value (about 0 per mille); we suspect, that the source of oxygen for carbonate formation is the seawater. The carbonates are characterized by low carbon-13 (from -35,4 to -42,6 per mille) in comparison with normal marine carbonates (about 0 per mille). We have reason to suppose that carbonates associated with fluid venting were formed by light isotopic composition of carbon dioxide (carbon-13 -45 to -52 per mille), which forming under methane microbiologic oxidation with such isotopic composition. This is because of crossing fluid process of carbon dioxide to carbonate with 8~10 degrees temperature carbon became heaver to 10- 11 per mille. The isotopic composition study of carbonate build-ups is of interest because its association with the gas hydrate accumulations is quite often in the gas seeps. This work is financially supported by Russian Foundation for Basic Research, grant 02-05-64346.

  13. Optimization and comparison of simultaneous and separate acquisition protocols for dual isotope myocardial perfusion SPECT

    Science.gov (United States)

    Ghaly, Michael; Links, Jonathan M.; Frey, Eric C.

    2015-07-01

    Dual-isotope simultaneous-acquisition (DISA) rest-stress myocardial perfusion SPECT (MPS) protocols offer a number of advantages over separate acquisition. However, crosstalk contamination due to scatter in the patient and interactions in the collimator degrade image quality. Compensation can reduce the effects of crosstalk, but does not entirely eliminate image degradations. Optimizing acquisition parameters could further reduce the impact of crosstalk. In this paper we investigate the optimization of the rest Tl-201 energy window width and relative injected activities using the ideal observer (IO), a realistic digital phantom population and Monte Carlo (MC) simulated Tc-99m and Tl-201 projections as a means to improve image quality. We compared performance on a perfusion defect detection task for Tl-201 acquisition energy window widths varying from 4 to 40 keV centered at 72 keV for a camera with a 9% energy resolution. We also investigated 7 different relative injected activities, defined as the ratio of Tc-99m and Tl-201 activities, while keeping the total effective dose constant at 13.5 mSv. For each energy window and relative injected activity, we computed the IO test statistics using a Markov chain Monte Carlo (MCMC) method for an ensemble of 1,620 triplets of fixed and reversible defect-present, and defect-absent noisy images modeling realistic background variations. The volume under the 3-class receiver operating characteristic (ROC) surface (VUS) was estimated and served as the figure of merit. For simultaneous acquisition, the IO suggested that relative Tc-to-Tl injected activity ratios of 2.6-5 and acquisition energy window widths of 16-22% were optimal. For separate acquisition, we observed a broad range of optimal relative injected activities from 2.6 to 12.1 and acquisition energy window of widths 16-22%. A negative correlation between Tl-201 injected activity and the width of the Tl-201 energy window was observed in these ranges. The results

  14. Modeling stable isotope and organic carbon in hillslope stormflow

    Science.gov (United States)

    Dusek, Jaromir; Vogel, Tomas; Dohnal, Michal; Marx, Anne; Jankovec, Jakub; Sanda, Martin; Votrubova, Jana; Barth, Johannes A. C.; Cislerova, Milena

    2016-04-01

    Reliable prediction of water movement and fluxes of dissolved substances (such as stable isotopes and organic carbon) at both the hillslope and the catchment scales remains a challenge due to complex boundary conditions and soil spatial heterogeneity. In addition, microbially mediated transformations of dissolved organic carbon (DOC) are known to affect balance of DOC in soils, hence the transformations need to be included in a conceptual model of a DOC transport. So far, only few studies utilized stable isotope information in modeling and even fewer linked dissolved carbon fluxes to mixing and/or transport models. In this study, stormflow dynamics of oxygen-18 isotope 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 transport processes in a forest soil during several observed rainfall-runoff episodes. The transport of heat in the soil profile was described by conduction-advection equation. Water flow and transport of solutes and heat were assumed to take place in two mutually communicating porous domains, the soil matrix and the network of preferential pathways. The rate of microbial transformations of DOC was assumed to depend on soil water content and soil temperature. Oxygen-18 and dissolved organic carbon concentrations were observed in soil pore water, hillslope stormflow (collected in the experimental hillslope trench), and stream discharge (at the catchment outlet). The modeling was used to analyze the transformation of input solute signals into output hillslope signals observed in the trench stormflow. Signatures of oxygen-18 isotope in hillslope stormflow as well as isotope concentration in soil pore water were predicted reasonably well. Due to complex nature of microbial transformations, prediction of DOC rate and transport was associated with a high uncertainty.

  15. Carbon isotope fluctuations in Precambrian carbonate sequences of several localities in Brazil

    Directory of Open Access Journals (Sweden)

    SIAL ALCIDES N.

    2000-01-01

    Full Text Available Carbon isotope fluctuations in Precambrian sedimentary carbonates between 2.8 Ga and 0.60 Ga in Brazil are examined in this study. The carbonate facies of the BIF of the 2.8 Ga-old Carajás Formation, state of Pará in northern Brazil, has rather homogeneous delta13C (-5 o/ooPDB, compatible with carbonatization of a silicate protolith by a CO2-rich fluid from mantle degassing. The Paleoproterozoic Gandarela Formation, state of Minas Gerais, displays a narrow delta13C variation (-1.5 to +0.5 o/oo compatible with carbon isotope signatures of carbonates deposited around 2.4 Ga worldwide. The Fecho do Funil Formation has probably recorded the Lomagundi delta13C positive anomaly (+6.4 to +7.1 o/ooPDB. The magnesite-bearing carbonates of the Orós mobile belt, state of Ceará, exhibit carbon isotope fluctuation within the range for carbonates deposited at 1.8 Ga. The C-isotope record of the Frecheirinha Formation, northwestern state of Ceará, shows negative delta13C values in its lower portion (-2 o/oo and positive values up section (+1 to +3 o/oo, which suggests this sequence is a cap carbonate deposited after a glacial event around 0.95 Ga. The Jacoca and Acauã sedimentary carbonate Formations, state of Sergipe, NE Brazil, show carbon isotope fluctuations very similar to each other (average around -5 o/oo, compatible with a deposition around 0.76 Ga. The younger Olho D'Água carbonate Formation, however, also in the state of Sergipe, displays negative delta13C values at the lower portion of the Formation, changing dramatically up section to positive values as high as +10 o/oo, a characteristic compatible with a Sturtian cap carbonate deposited around 0.69 Ga. On the light of the C isotope data discussed in this study, it seems that delta13C fluctuations in Paleoproterozoic carbonates in Brazil are within the range found globally for metasedimentary carbonates of this age. Carbon isotope data proved to be very useful in establishing relative

  16. Carbon abundances and isotope ratios in 70 bright M giants

    International Nuclear Information System (INIS)

    Approximate carbon abundances and 12C/13C isotope ratios are obtained for 70 M giant stars from intermediate-resolution spectrophotometry of the CO bands near 2.3 μm. A low mean carbon abundance ([C/H]=-0.64±0.29) is obtained, suggesting that standard mixing is insufficient to explain atmospheric abundances in M giants. HR 8795 appears to be exceptionally carbon deficient, and is worthy of further study as a possible weak G-band star descendant. (author)

  17. Carbon abundances and isotope ratios in 70 bright M giants

    Energy Technology Data Exchange (ETDEWEB)

    Lazaro, C. (Inst. de Astrofisica de Canarias, Tenerife (Spain)); Lynas-Gray, A.E. (University Coll., London (UK). Dept. of Physics and Astronomy); Clegg, R.E.S. (Royal Greenwich Observatory, Cambridge (UK)); Mountain, C.M.; Zadrozny, A. (Imperial Coll. of Science and Technology, London (UK))

    1991-03-01

    Approximate carbon abundances and {sup 12}C/{sup 13}C isotope ratios are obtained for 70 M giant stars from intermediate-resolution spectrophotometry of the CO bands near 2.3 {mu}m. A low mean carbon abundance ((C/H)=-0.64+-0.29) is obtained, suggesting that standard mixing is insufficient to explain atmospheric abundances in M giants. HR 8795 appears to be exceptionally carbon deficient, and is worthy of further study as a possible weak G-band star descendant. (author).

  18. Carbon and oxygen isotope separation by plasma chemical reactions in carbon monoxide glow discharge

    International Nuclear Information System (INIS)

    The separation of carbon and oxygen isotopes in CO glow discharge has been studied. The isotope enrichment in the products was measured by quadru-pole mass spectrometer. The reaction yield and empirical formula of solid phase products were determined by the gas-volumetric analysis. The stable products obtained in our experiment are CO2 and solid polymers formed on the discharge wall. The polymer consists of both carbon and oxygen and the oxygen/carbon mole ratio in the polymer is 0.35±0.05. Thi isotope enrichment coefficients show a strong negative dependence on discharge current though the relative reaction yields have an opposite tendency. Consequently, the maximum isotope enrichment coefficients for 13C in wall deposit of 2.31 and for 18O in CO2 of 1.37 are obtained when the discharge current and the reaction yields are minimum in our experimental range. The experimental results of isotope enrichment have been compared with theoretical values estimated by an analytical model of literature. The dilution mechanism of the isotope enrichment of stable products is inferred from the isotopic distributions of 13C and 18O in products and theoretical predictions for isotope enrichment. (author)

  19. Characteristics of carbon and hydrogen isotopic compositions of light hydrocarbons

    Institute of Scientific and Technical Information of China (English)

    沈平

    1995-01-01

    Light hydrocarbons named in the present paper refer to the natural gas-associated light oil and condensate 46 light oil and condensate samples from 11 oil-bearing basins of China were collected and their carbon and hydrogen isotopic compositions were analysed in terms of their total hydrocarbons, saturated hydrocarbons and a part of aromatic fractions, and gas-source materials and their sedimentary environments were discussed based on the above-mentioned data and the geological background of each area. From the view of carbon and hydrogen isotopic composition of total hydrocarbons and saturated hydrocarbons, it is revealed that the condensate related to coal-bearing strata is enriched in 13C and D while that related to the source material of type I-II is enriched in 12C. In general, the isotopic composition of carbon is mainly attributed to the inheriting effect of their source materials, whereas that of hydrogen principally reflects the correlationship between hydrogen isotopes and the sedimentary envi

  20. Magnesium isotope fractionation in bacterial mediated carbonate precipitation experiments

    Science.gov (United States)

    Parkinson, I. J.; Pearce, C. R.; Polacskek, T.; Cockell, C.; Hammond, S. J.

    2012-12-01

    Magnesium is an essential component of life, with pivotal roles in the generation of cellular energy as well as in plant chlorophyll [1]. The bio-geochemical cycling of Mg is associated with mass dependant fractionation (MDF) of the three stable Mg isotopes [1]. The largest MDF of Mg isotopes has been recorded in carbonates, with foraminiferal tests having δ26Mg compositions up to 5 ‰ lighter than modern seawater [2]. Magnesium isotopes may also be fractionated during bacterially mediated carbonate precipitation and such carbonates are known to have formed in both modern and ancient Earth surface environments [3, 4], with cyanobacteria having a dominant role in carbonate formation during the Archean. In this study, we aim to better constrain the extent to which Mg isotope fractionation occurs during cellular processes, and to identify when, and how, this signal is transferred to carbonates. To this end we have undertaken biologically-mediated carbonate precipitation experiments that were performed in artificial seawater, but with the molar Mg/Ca ratio set to 0.6 and with the solution spiked with 0.4% yeast extract. The bacterial strain used was marine isolate Halomonas sp. (gram-negative). Experiments were run in the dark at 21 degree C for two to three months and produced carbonate spheres of various sizes up to 300 μm in diameter, but with the majority have diameters of ~100 μm. Control experiments run in sterile controls (`empty` medium without bacteria) yielded no precipitates, indicating a bacterial control on the precipitation. The carbonate spheres are produced are amenable to SEM, EMP and Mg isotopic analysis by MC-ICP-MS. Our new data will shed light on tracing bacterial signals in carbonates from the geological record. [1] Young & Galy (2004). Rev. Min. Geochem. 55, p197-230. [2] Pogge von Strandmann (2008). Geochem. Geophys. Geosys. 9 DOI:10.1029/2008GC002209. [3] Castanier, et al. (1999). Sed. Geol. 126, 9-23. [4] Cacchio, et al. (2003

  1. Application of stable carbon isotopes in long term mesocosm studies for carbon cycle investigation

    Science.gov (United States)

    Esposito, Mario

    2016-04-01

    Carbon dioxide (CO2) is an effective greenhouse gas. The Oceans absorb ca. 30% of the anthropogenic CO2 emissions and thereby partly attenuate deleterious climate effects. A consequence of the oceanic CO2 uptake is a decreased seawater pH and planktonic community shifts. The quantification of the anthropogenic perturbation was investigated through stable carbon isotope analysis in three "long term" mesocosm experiments (Sweden 2013, Gran Canaria 2014, Norway 2015) which reproduced near natural ecosystem conditions under both controlled and modified future CO2 level (up to 2000 ppm) scenarios. Parallel measurements of the stable isotope composition of dissolved inorganic carbon (δ13CDIC) dissolved organic carbon (δ13CDOC) and particulate carbon (δ13CTPC) both from the mesocosms water column and sediment traps showed similar trends in all the three experiments. A CO2 response was noticeable in the isotopic dataset, but increased CO2 levels had only a subtle effect on the concentrations of the dissolved and particulate organic carbon pool. Distinctive δ13C signatures of the particulate carbon pool both in the water column and the sediments were detectable for the different CO2 treatments and they were strongly correlated with the δ13CDIC signatures but not with the δ13CDOC pool. The validity of the isotopic data was verified by cross-analyses of multiple substances of known isotopic signatures on a GasBench, Elemental Analyser (EA) and on an in-house TOC-IRMS setup for the analysis of δ13CDIC, δ13CTPC and δ13CDOC, respectively. Results from these mesocosm experiments proved the stable carbon isotope approach to be an effective tool for quantifying the uptake and carbon transfer among the various compartments of the marine carbon system.

  2. Isotopic Hg in an Allende carbon-rich residue

    Science.gov (United States)

    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.

  3. Clumped-isotope geochemistry of carbonates: A new tool for the reconstruction of temperature and oxygen isotope composition of seawater

    Energy Technology Data Exchange (ETDEWEB)

    Bernasconi, Stefano M., E-mail: Stefano.bernasconi@erdw.ethz.ch [Geological Institute, ETH Zuerich, Sonneggstrasse 5, 8092 Zuerich (Switzerland); Schmid, Thomas W.; Grauel, Anna-Lena [Geological Institute, ETH Zuerich, Sonneggstrasse 5, 8092 Zuerich (Switzerland); Mutterlose, Joerg [Institut fuer Geologie, Mineralogie und Geophysik, Ruhr Universitaet Bochum, Universitaetsstr. 150, 44801 Bochum (Germany)

    2011-06-15

    Highlights: > Clumped-isotope thermometry of carbonates is discussed. > Clumped isotopes of Belemnites show higher sea surface temperatures than commonly assumed for the lower Cretaceous. > The potential of clumped-isotope measurement on foraminifera is discussed. - Abstract: Clumped-isotope geochemistry deals with State of ordering of rare isotopes in molecules, in particular with their tendency to form bonds with other rare isotopes rather than with the most abundant ones. Among its possible applications, carbonate clumped-isotope thermometry is the one that has gained most attention because of the wide potential of applications in many disciplines of the earth sciences. In particular, it allows reconstructing the temperature of formation of carbonate minerals without knowledge of the isotopic composition of the water from which they were formed. In addition, the O isotope composition of the waters from which they were formed can be calculated using the {delta}{sup 18}O of the same carbonate sample. This feature offers new approaches in paleoclimatology for reconstructing past global geochemical cycles. In this contribution two applications of this method are presented. First the potential of a new analytical method of measurement of clumped isotopes on small samples of foraminifera, for high-resolution SST and seawater {delta}{sup 18}O reconstructions from marine sediments is shown. Furthermore the potential of clumped isotope analysis of belemnites, for reconstructing seawater {delta}{sup 18}O and temperatures in the Cretaceous is shown.

  4. Impact of flood events on lacustrine carbonate isotope records

    Science.gov (United States)

    Kämpf, Lucas; Plessen, Birgit; Lauterbach, Stefan; Nantke, Carla; Meyer, Hanno; Chapligin, Bernhard; Höllerer, Hannes; Brauer, Achim

    2016-04-01

    Stable oxygen (δ 18O) and carbon (δ 13C) isotope compositions of lacustrine carbonates are among the most frequently used proxies in palaeolimnological / -environmental studies. Stable isotope analyses are often carried out on bulk carbonate samples, which are prone to contamination with detrital carbonates, transported into the lake by runoff processes and carrying the isotopic signal of catchment rocks, thus hampering the interpretation of the data in terms of past climatic and/or environmental changes. Despite the awareness of a likely detrital bias, the degree of contamination in most cases remains unknown and discrete contaminated samples undetected due to a lack of methods to disentangle endogenic and detrital carbonates in sediment records. To address this issue and provide more comprehensive insights into effects of flood-related detrital input on the bulk carbonate isotopic composition, we conducted stable isotope measurements on sediments trapped on a 3-12 day basis over a three-year period (January 2011 to November 2013) at two locations in pre-Alpine Lake Mondsee, close to the inflow of the main tributary and in the deepest part of the lake basin. Lake Mondsee was chosen for the monitoring since the pelagic sediments are annually laminated consisting of couplets of light calcite layers and dark layers made up by a mixture of detrital clastic and organic matter. Maximum calcite flux rates >1.5 g m2 d-1 were trapped between May and September, indicating the seasonal endogenic precipitation of calcite crystals. The comparison of the δ 18O composition of trapped carbonates, rain and epilimnion lake water revealed equilibrium calcite precipitation, allowing us to infer purely endogenic δ 18O (-9 to -11.3‰ VPDB) and δ 13C values (-6 to -9‰ VPDB) throughout the summer season. The endogenic calcite precipitation was interrupted by 14 peaks in carbonate flux (4 to 175 g m2 d-1) triggered by runoff events of different magnitudes (10-110 m3 s-1 peak

  5. Investigating the Formation of Pedogenic Carbonate Using Stable Isotopes

    Science.gov (United States)

    Breecker, D. O.; Sharp, Z. D.; McFadden, L.

    2006-12-01

    The stable isotope composition of pedogenic carbonate has been used as a paleoenvironmental proxy because it is thought to form in isotopic equilibrium with soil CO2 and soil water, which are influenced by vegetation type and atmospheric circulation patterns, respectively. However, the isotopic composition of soil CO2 and soil water change seasonally and it is not known what portion of this variability is recorded by the isotopic composition of pedogenic carbonate. It is generally believed that carbonate precipitation in soils is driven by evaporative concentration of Ca ions and/or decreasing soil pCO2. We seek to improve the proxy by determining the seasonality of pedogenic carbonate formation, in particular whether pedogenic carbonate forms during the wet season after individual rainstorms or during seasonal drying following the wet season. This was done by comparing the variations in carbon and oxygen isotope composition of soil CO2 with the isotopic composition of proximally located, newly-formed carbonates. Soil CO2 and incipient pedogenic carbonate coatings were collected in a very young (soil developing in an inset terrace on the piedmont of the Sandia Mountains, central New Mexico. We also measure soil temperatures at the same site. In May 2006, at the end of the driest 6-month period on record in central New Mexico, soil CO2 profiles displayed a 2‰ decrease in δ13C values with depth from 9 to 100 cm. In August 2006, the shapes of the profiles were similar, but the δ13C values were 3-4‰ lower at each depth than in May. These results can be explained by an increase in respiration rate during the latter half of the summer (the wettest on record) when monsoon rainfall maintained high moisture contents in soils across New Mexico. Calculated δ13C values of calcite in equilibrium with May (but not August) soil CO2 agree with measured carbonate δ13C values below 20 cm depth. Very shallow carbonate has anomalously high δ13C values. Measurements of the

  6. Economically important applications of carbon isotope data of natural gases and crude oil: a brief review

    International Nuclear Information System (INIS)

    Carbon isotope fractionations in hydrocarbons are briefly reviewed and examples of practical applications in the exploration of crude oil are given. Carbon isotope fractionations of natural gases are discussed. It is shown that the carbon isotope ratio of methane is predominantly determined by the environment (humic or sapropelic) and the maturity of its organic source material. In this way, isotope analyses of natural gases can be quantitatively used to characterize the maturity of their source rocks. (author)

  7. Simultaneous tracing of carbon and nitrogen isotopes in human cells.

    Science.gov (United States)

    Nilsson, Roland; Jain, Mohit

    2016-05-24

    Stable isotope tracing is a powerful method for interrogating metabolic enzyme activities across the metabolic network of living cells. However, most studies of mammalian cells have used (13)C-labeled tracers only and focused on reactions in central carbon metabolism. Cellular metabolism, however, involves other biologically important elements, including nitrogen, hydrogen, oxygen, phosphate and sulfur. Tracing stable isotopes of such elements may help shed light on poorly understood metabolic pathways. Here, we demonstrate the use of high-resolution mass spectrometry to simultaneously trace carbon and nitrogen metabolism in human cells cultured with (13)C- and (15)N-labeled glucose and glutamine. To facilitate interpretation of the complex isotopomer data generated, we extend current methods for metabolic flux analysis to handle multivariate mass isotopomer distributions (MMIDs). We find that observed MMIDs are broadly consistent with known biochemical pathways. Whereas measured (13)C MIDs were informative for central carbon metabolism, (15)N isotopes provided evidence for nitrogen-carrying reactions in amino acid and nucleotide metabolism. This computational and experimental methodology expands the scope of metabolic flux analysis beyond carbon metabolism, and may prove important to understanding metabolic phenotypes in health and disease.

  8. Carbon Isotope and Isotopomer Fractionation in Cold Dense Cloud Cores

    CERN Document Server

    Furuya, Kenji; Sakai, Nami; Yamamoto, Satoshi

    2011-01-01

    We construct the gas-grain chemical network model which includes carbon isotopes (12C and 13C) with an emphasis on isotopomer-exchange reactions. Temporal variations of molecular abundances, the carbon isotope ratios (12CX/13CX) and the isotopomer ratios (12C13CX/13C12CX) of CCH and CCS in cold dense cloud cores are investigated by numerical calculations. We confirm that the isotope ratios of molecules, both in the gas phase and grain surfaces, are significantly different depending on whether the molecule is formed from the carbon atom (ion) or the CO molecule. Molecules formed from carbon atoms have the CX/13CX ratios greater than the elemental abundance ratio of [12C/13C]. On the other hand, molecules formed from CO molecules have the CX/13CX ratios smaller than the [12C/13C] ratio. We reproduce the observed C13CH/13CCH ratio in TMC-1, if the isotopomer exchange reaction, 13CCH + H C13CH + H + 8.1 K, proceeds with the forward rate coefficient kf > 10^-11 cm3 s-1. However, the C13CS/13CCS ratio is lower tha...

  9. Triple oxygen isotopes in biogenic and sedimentary carbonates

    Science.gov (United States)

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

    2014-09-01

    The 17O anomaly (Δ17O) 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 Δ17O than primary meteoric waters. In animal body water, Δ17O relates to the intake of evaporated waters, evaporative effluxes of water, and the Δ17O 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 Δ17O of carbonate. We describe optimized methods based on a sequential acid digestion/reduction/fluorination approach that yield Δ17O data with the high precision (∼0.010‰, 1σ) needed to resolve subtle environmental signals. We report the first high-precision Δ17O 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 δ18O and Δ17O 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 Δ17O values that are similar to or slightly lower than global precipitation. Our results suggest

  10. Carbon and Oxygen Isotope Stratigraphy of the Oxfordian Carbonate Rocks in Amu Darya Basin

    Institute of Scientific and Technical Information of China (English)

    Rongcai Zheng; Yanghui Pan; Can Zhao; Lei Wu; Renjin Chen; Rui Yang

    2013-01-01

    Based on the detailed research on petrologic and geochemical characteristics of deposition and diagenesis of Oxfordian carbonate rocks in Amu Darya Basin,Turkmenistan,carbon and oxygen isotopes were analyzed.The results show that the paleoenvironmental evolution reflected by the samples with well-preserved original carbon isotopes coincides with the carbon-isotope stratigraphic carve and is almost consistent with the global sea-level curve,the Mid-Oxfordian wide transgression,and the positive carbon-isotope excursion event.The Mid-Oxfordian continuing transgression not only laid the foundation for the development of the Oxfordian reef and shoal reservoirs in Amu Darya Basin but also provided an example for the Oxfordian global transgression and the resulting development of reefs and banks and high-speed organic carbon burial events.The response of oxygen isotopes in diagenetic environment showed that micrite limestones and granular limestones underwent weak diagenetic alteration,and the samples largely retained the original seawater features.Dolomitization and the precipitation of hydrothermal calcites tilling solution vugs and fractures before hydrocarbon accumulation occurred in a closed diagenetic environment where the main controlling factor is the temperature,and the diagenetic fluids were from the deep hot brine.The chalkification of the limestones after hydrocarbon accumulation occurred in the oiltield water systems.

  11. Shear heating and clumped isotope reordering in carbonate faults

    Science.gov (United States)

    Siman-Tov, Shalev; Affek, Hagit P.; Matthews, Alan; Aharonov, Einat; Reches, Ze'ev

    2016-07-01

    Natural faults are expected to heat rapidly during seismic slip and to cool quite quickly after the slip event. Here we examine clumped isotope thermometry for its ability to identify such short duration elevated temperature events along frictionally heated carbonate faults. Our approach is based on measured Δ47 values that reflect the distribution of oxygen and carbon isotopes in the calcite lattice, measuring the abundance of 13Csbnd 18O bonds, which is affected by temperature. We examine three types of calcite rock samples: (1) crushed limestone grains that were rapidly heated and then cooled in static laboratory experiments, simulating the temperature cycle experienced by fault rock during an earthquake slip; (2) limestone samples that were experimentally sheared to simulate earthquake slip events; and (3) samples from Fault Mirrors (FMs) collected from principle slip surfaces of three natural carbonate faults. Extensive FM surfaces are believed to form during earthquake slip. Our experimental results show that Δ47 values decrease rapidly (in the course of seconds) with increasing temperature and shear velocity. On the other hand, carbonate shear zones from natural faults do not show such Δ47 decrease. We suggest that the Δ47 response may be controlled by nano-size grains, the high abundance of defects, and highly stressed/strained grain boundaries within the carbonate fault zone that can reduce the activation energy for diffusion, and thus lead to an increased rate of isotopic disordering during shear experiments. In our laboratory experiments the high stress and strain on grain contacts and the presence of nanograins thus allows for rapid disordering so that a change in Δ47 occurs in a very short and relatively low intensity heating events. In natural faults it may also lead to isotopic ordering after the cessation of frictional heating thus erasing the high temperature signature of Δ47.

  12. Respiration and assimilation processes reflected in the carbon isotopic composition of atmospheric carbon dioxide

    International Nuclear Information System (INIS)

    The paper presents diurnal variations of concentration and carbon isotopic composition of atmospheric carbon dioxide caused by respiration and assimilation processes. Air samples were collected during early and late summer in 1998 in unpolluted area (village Guciow located near Roztocze National Park, SE Poland) in three different environments: uncultivated field on a hill, a meadow in the Wieprz river valley and a forest. The effect is very strong during intensive vegetation growth on a sunny day and clear night. The largest diurnal variations in atmospheric CO2 concentration and its carbon isotopic composition in June above the meadow were about 480 ppm and 10 pro mille, respectively. (author)

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

    Science.gov (United States)

    KŁUSEK, MARZENA; PAWEŁCZYK, SŁAWOMIRA

    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 α-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 α-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

  14. Boron isotope fractionation in magma via crustal carbonate dissolution.

    Science.gov (United States)

    Deegan, Frances M; Troll, Valentin R; Whitehouse, Martin J; Jolis, Ester M; Freda, Carmela

    2016-01-01

    Carbon dioxide released by arc volcanoes is widely considered to originate from the mantle and from subducted sediments. Fluids released from upper arc carbonates, however, have recently been proposed to help modulate arc CO2 fluxes. Here we use boron as a tracer, which substitutes for carbon in limestone, to further investigate crustal carbonate degassing in volcanic arcs. We performed laboratory experiments replicating limestone assimilation into magma at crustal pressure-temperature conditions and analysed boron isotope ratios in the resulting experimental glasses. Limestone dissolution and assimilation generates CaO-enriched glass near the reaction site and a CO2-dominated vapour phase. The CaO-rich glasses have extremely low δ(11)B values down to -41.5‰, reflecting preferential partitioning of (10)B into the assimilating melt. Loss of (11)B from the reaction site occurs via the CO2 vapour phase generated during carbonate dissolution, which transports (11)B away from the reaction site as a boron-rich fluid phase. Our results demonstrate the efficacy of boron isotope fractionation during crustal carbonate assimilation and suggest that low δ(11)B melt values in arc magmas could flag shallow-level additions to the subduction cycle. PMID:27488228

  15. Boron isotope fractionation in magma via crustal carbonate dissolution

    Science.gov (United States)

    Deegan, Frances M.; Troll, Valentin R.; Whitehouse, Martin J.; Jolis, Ester M.; Freda, Carmela

    2016-08-01

    Carbon dioxide released by arc volcanoes is widely considered to originate from the mantle and from subducted sediments. Fluids released from upper arc carbonates, however, have recently been proposed to help modulate arc CO2 fluxes. Here we use boron as a tracer, which substitutes for carbon in limestone, to further investigate crustal carbonate degassing in volcanic arcs. We performed laboratory experiments replicating limestone assimilation into magma at crustal pressure-temperature conditions and analysed boron isotope ratios in the resulting experimental glasses. Limestone dissolution and assimilation generates CaO-enriched glass near the reaction site and a CO2-dominated vapour phase. The CaO-rich glasses have extremely low δ11B values down to ‑41.5‰, reflecting preferential partitioning of 10B into the assimilating melt. Loss of 11B from the reaction site occurs via the CO2 vapour phase generated during carbonate dissolution, which transports 11B away from the reaction site as a boron-rich fluid phase. Our results demonstrate the efficacy of boron isotope fractionation during crustal carbonate assimilation and suggest that low δ11B melt values in arc magmas could flag shallow-level additions to the subduction cycle.

  16. Hirnantian Isotope Carbon Excursion in Gorny Altai, southwestern Siberia

    Directory of Open Access Journals (Sweden)

    Nikolay V. Sennikov

    2015-08-01

    Full Text Available The Hirnantian Isotope Carbon Excursion (HICE, a glaciation-induced positive δ13C shift in the end-Ordovician successions, has been widely used in chemostratigraphic correlation of the Ordovician–Silurian boundary beds in many areas of the world. However, large regions with Ordovician sediments in Siberia are almost unstudied for stable isotope chemostratigraphy. The Burovlyanka section in the Altai area is one of the rare Hirnantian–Rhuddanian sections with both carbonates and graptolitiferous shales occurring in the succession. Here we report the discovery of the HICE in the uppermost beds of the Tekhten¢ Formation, the Dalmanitina Beds in the Burovlyanka section. The Dalmanitina limestone Member between the graptolitiferous shales may correspond to the mid-Hirnantian glacial episode, which led to a global sea level drop and major extinction of marine fauna.

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

    Energy Technology Data Exchange (ETDEWEB)

    Ismail, Atef [Fundamental and Applied Sciences Department, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 31750 Tronoh, Perak, Malaysia and Department of Physics, Al-Azhar University, 71524 Assiut (Egypt); Cheong, Lee Yen; Yahya, Noorhana [Fundamental and Applied Sciences Department, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 31750 Tronoh, Perak (Malaysia); Tammam, M. [Department of Physics, Al-Azhar University, 71524 Assiut (Egypt)

    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.

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

    International Nuclear Information System (INIS)

    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 δ13C 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

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

    Energy Technology Data Exchange (ETDEWEB)

    Magdas, D. A., E-mail: gabriela.cristea@itim-cj.ro; Cristea, G., E-mail: gabriela.cristea@itim-cj.ro; Bot, A., E-mail: gabriela.cristea@itim-cj.ro; Mirel, V., E-mail: gabriela.cristea@itim-cj.ro [National Institute for Research and Development of Isotopic and Molecular Technologies, 65-103 Donath Str., 400293 Cluj-Napoca (Romania)

    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 δ{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.

  20. Low stable carbon isotope fractionation by coccolithophore RubisCO

    Science.gov (United States)

    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 ( ɛ = 11.1‰) against 13CO 2 than other RubisCO enzymes (18-29‰), despite having Michaelis-Menten kinetic parameters ( K = 72 μM; Vmax = 0.66 μmol 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 ɛ values for RubisCOs of other marine phytoplankton and (b) re-evaluation of δ13C values from physiological, environmental, and geological studies.

  1. Constraining the global bromomethane budget from carbon stable isotopes

    Science.gov (United States)

    Bahlmann, Enno; Wittmer, Julian; Greule, Markus; Zetzsch, Cornelius; Seifert, Richard; Keppler, Frank

    2016-04-01

    Despite intense research in the last two decades, the global bromomethane (CH3Br) budget remains unbalanced with the known sinks exceeding the known sources by about 25%. The reaction with OH is the largest sink for CH3Br. We have determined the kinetic isotope effects for the reactions of CH3Br with the OH and Cl radical in order to better constrain the global CH3Br budget from an isotopic perspective. The isotope fractionation experiments were performed at 20±1°C in a 3500 L Teflon smog-chamber with initial CH3Br mixing ratios of about 2 and 10 ppm and perflourohexane (25 ppb) as internal standard. Atomic chlorine (Cl) was generated via photolysis of molecular chlorine (Cl2) using a solar simulator with an actinic flux comparable to that of the sun in mid-summer in Germany. OH radicals were generated via the photolysis of ozone (O3) at 253.7 nm in the presence of water vapor (RH = 70%).The mixing ratios of CH3Br, and perflourohexane were monitored by GC-MS with a time resolution of 15 minutes throughout the experiments. From each experiment 10 to 15 sub samples were taken in regular time intervals for subsequent carbon isotope ratio determinations by GC-IRMS performed at two independent laboratories in parallel. We found a kinetic isotope effect (KIE) of 17.6±3.3‰ for the reaction of CH3Br with OH and a KIE of 9.8±1.4 ‰ for the reaction with Cl*. We used these fractionation factors along with new data on the isotopic composition of CH3Br in the troposphere (-34±7‰) and the surface ocean (-26±7‰) along with reported source signatures, to constrain the unknown source from an isotopic perspective. The largest uncertainty in estimating the isotopic composition of the unknown source arises from the soil sink. Microbial degradation in soils is the second largest sink and assigned with a large fractionation factors of about 50‰. However, field experiments revealed substantially smaller apparent fractionation factors ranging from 11 to 22‰. In addition

  2. Late Carboniferous to Late Permian carbon isotope stratigraphy

    DEFF Research Database (Denmark)

    Buggisch, Werner; Krainer, Karl; Schaffhauser, Maria;

    2015-01-01

    . Negative δ13C excursions are related to low-stand deposits and caused by diagenetic processes during subaerial exposure. The comparison with δ13C records from other parts of the world demonstrate that δ13C values are high in most unaltered samples, an overall negative trend during the Permian, as recently...... published, is not obvious and negative excursions related to changes in the carbon isotope composition of the global oceanic carbon pool cannot be confirmed, except for the Permian–Triassic boundary interval....

  3. Environmental impact and magnitude of paleosol carbonate carbon isotope excursions marking five early Eocene hyperthermals in the Bighorn Basin, Wyoming

    NARCIS (Netherlands)

    Abels, H.A.; Lauretano, V.; van Yperen, Anna E.; Hopman, Tarek; Zachos, J.C.; Lourens, L.J.; Gingerich, P.D.; Bowen, G.J.

    2016-01-01

    Transient greenhouse warming events in the Paleocene and Eocene were associated with the addition of isotopically light carbon to the exogenic atmosphere–ocean carbon system, leading to substantial environmental and biotic change. The magnitude of an accompanying carbon isotope excursion (CIE) can b

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

    Science.gov (United States)

    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 δ11B) 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 δ11B; (ii) to determine the isotopic composition of the two reference materials with a number of analytical techniques to provide the community with reference δ11B 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 δ11B 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 δ11B by ~0.1 ‰ for both JCp-1 and JCt-1, while the mean δ11B of all labs for both standards was lowered by 0

  5. The Li isotope composition of modern biogenic carbonates

    Science.gov (United States)

    Dellinger, M.; West, A. J.; Adkins, J. F.; Paris, G.; Eagle, R.; Freitas, P. S.; Bagard, M. L.; Ries, J. B.; Corsetti, F. A.; Pogge von Strandmann, P.; Ullmann, C. V.

    2015-12-01

    The lithium stable isotope composition (δ7Li) of sedimentary carbonates has great potential to unravel weathering rates and intensity in the past, with implications for understanding the carbon cycle over geologic time. However, so far very little is known about the potential influence of fractionation of the stable Li isotope composition of biogenic carbonates. Here, we investigate the δ7Li of various organisms (particularly mollusks, echinoderms and brachiopods) abundant in the Phanerozoic record, in order to understand which geologic archives might provide the best targets for reconstructing past seawater composition. The range of measured samples includes (i) modern calcite and aragonite shells from variable natural environments, (ii) shells from organisms grown under controlled conditions (temperature, salinity, pCO2), and (iii) fossil shells from a range of species collected from Miocene deposits. When possible, both the inner and outer layers of bivalves were micro-sampled to assess the intra-shell heterogeneity. For calcitic shells, the measured δ7Li of bivalve species range from +32 to +41‰ and is systematically enriched in the heavy isotope relative to seawater (31 ‰) and to inorganic calcite, which is characterized by Δ7Licalcite-seawater = -2 to -5‰ [1]. The Li isotope composition of aragonitic bivalves, ranging from +16 to +22‰, is slightly fractionated to both high and low δ7Li relative to inorganic aragonite. The largest intra-shell Li isotope variability is observed for mixed calcite-aragonite shells (more than 20‰) whereas in single mineralogy shells, intra-shell δ7Li variability is generally less than 3‰. Overall, these results suggest a strong influence of vital effects on Li isotopes during bio-calcification of bivalve shells. On the contrary, measured brachiopods systematically exhibit fractionation that is very similar to inorganic calcite, with a mean δ7Li of 27.0±1.5‰, suggesting that brachiopods may provide good

  6. Isotopic investigations of carbonate growth on concrete structures

    Energy Technology Data Exchange (ETDEWEB)

    Krishnamurthy, R.V.; Schmitt, D.; Atekwana, E.A.; Baskaran, M

    2003-03-01

    Stable C and O isotope ratios were measured in carbonate minerals, growing under concrete structures from two locations in the United States. These locations were under a bridge in Michigan and under an overpass in New York. The {delta}{sup 13}C of the carbonate samples ranged from -21.6 to -31.4 per mille (with respect to V-PDB) and clearly indicated precipitation under non-equilibrium conditions. Indeed, the values in some cases were more negative than could be accounted for by existing models that invoke 4 stages of kinetic fractionation. There have been suggestions that microbial activity involving C from gasoline and other fossil fuel sources might be responsible for the relatively low C isotope ratios measured in these carbonates. To explore this possibility, {sup 14}C measurements were made in some of the samples. All samples measured for {sup 14}C contained bomb C. The range of {sup 14}C concentrations suggested a non-uniform growth rate, although possible fossil fuel-derived carbon in the system needs future investigation. The {delta}{sup 18}O values of the carbonates analyzed from Michigan range from 12.5 to 15.7 per mille (with respect to V-SMOW), with a mean value of 13.7 per mille. The {delta}{sup 18}O values of the NY samples range from 11.8 to 15.2 per mille, with a mean value of 13.1 per mille. The nearly identical mean values at both locations favors incorporation of O from atmospheric CO{sub 2} in carbonate precipitation. Additionally, the {sup 210}Pb radiometric technique was also attempted to explore the applicability of this technique in dating concrete derived carbonates as well as recent carbonates forming in a wide variety of environments. The results gave ages between 64 and 3.8 a and are consistent when compared with the date the bridge was constructed.

  7. The clumped isotope geothermometer in soil and paleosol carbonate

    Science.gov (United States)

    Quade, J.; Eiler, J.; Daëron, M.; Achyuthan, H.

    2013-03-01

    We studied both modern soils and buried paleosols in order to understand the relationship of temperature (T°C(47)) estimated from clumped isotope compositions (Δ47) of soil carbonates to actual surface and burial temperatures. Carbonates from modern soils with differing rainfall seasonality were sampled from Arizona, Nevada, Tibet, Pakistan, and India. T°C(47) obtained from these soils shows that soil carbonate forms in the warmest months of the year, in the late morning to afternoon, and probably in response to intense soil dewatering. T°C(47) obtained from modern soil carbonate ranges from 10.8 to 39.5 °C. On average, T°C(47) exceeds mean annual temperature by 10-15 °C due to summertime bias in soil carbonate formation, and to summertime ground heating by incident solar radiation. Secondary controls on T°C(47) are soil depth and shading. Site mean annual air temperature (MAAT) across a broad range (0-30 °C) of site temperatures is highly correlated with T°C(47) from soils, following the equation: MAAT(°C)=1.20(T°C(47)0)-21.72(r2=0.92) where T°C(47)0 is the effective air temperature at the site estimated from T°C(47). The effective air temperature represents the air temperature required to account for the T°C(47) at each site, after consideration of variations in T°C(47) with soil depth and ground heating. The highly correlated relationship in this equation should now permit mean annual temperature in the past to be reconstructed from T°C(47) in paleosol carbonate, assuming one is studying paleosols that formed in environments generally similar in seasonality and ground cover to our calibration sites. T°C(47)0 decreases systematically with elevation gain in the Himalaya, following the equation: elevation(m)=-229(T°C(47)0)+9300(r2=0.95) Assuming that temperature varied similarly with elevation in the past, this equation can be used to reconstruct paleoelevation from clumped isotope analysis of ancient soil carbonates. We also measured T°C(47

  8. Diet control on carbon isotopic composition of land snail shell carbonate

    Institute of Scientific and Technical Information of China (English)

    LIU ZongXiu; GU ZhaoYan; WU NaiQin; XU Bing

    2007-01-01

    Carbon isotope compositions for both the carbonate shells and soft bodies (organic tissue) of living land snails collected mostly from the Loess Plateau, China have been measured. The result shows that δ13C values range from -13.1‰ to -4.3‰ for the aragonite shell samples and from -26.8‰ to -18.0‰ for the soft body samples. Although the shells are enriched in 13C relative to the bodies averagely by 14.2(±0.8)‰, the shell δ13Ca values are closely correlated to the body δ13Corg values, expressed as δ13Ca = 1.021 δ13Corg + 14.38 (R = 0.965; N = 31). This relationship indicates that δ13Ca is primarily a function of the isotopic composition of the snail diets since previous studies have proved that the snail body is the same as their food in carbon isotope composition. In other words, carbon isotope compo-sition of the carbonate shell can be used as a proxy to estimate the dietary 13C abundance of the land snails. The data also support that the 13C enrichment of the carbonate shells results mainly from the equilibrium fractionations between the metabolic CO2, HCO3- in the hemolymph and shell aragonite, and partially from kinetic fractionations when snail shells form during their activity.

  9. Allochthonous carbon hypothesis for bulk OM and n-alkane PETM carbon isotope discrepancies

    Science.gov (United States)

    Baczynski, A. A.; McInerney, F. A.; Wing, S. L.; Kraus, M. J.; Fricke, H. C.

    2011-12-01

    The Paleocene-Eocene Thermal Maximum (PETM), a period of abrupt, transient, and large-scale global warming fueled by a large release of isotopically light carbon, is a relevant analogue for episodes of rapid global warming and recovery. The PETM is recorded in pedogenic carbonate, bulk organic matter, and n-alkanes as a prominent negative carbon isotope excursion (CIE) in paleosols exposed in the Bighorn Basin, WY. Here we present a composite stable carbon isotope record from n-alkanes and dispersed soil organic δ13C records from five individual sections that span the PETM in the southeastern Bighorn Basin. Four sections are from a 10km transect in the Cabin Fork area and one section was collected at Sand Creek Divide. These five new dispersed organic carbon (DOC) isotope records are compared to the previously published Polecat Bench (Magioncalda et al. 2004) and Honeycombs (Yans et al. 2006) isotope records. The high-resolution n-alkane curve shows an abrupt, negative shift in δ13C values, an extended CIE body, and a rapid recovery to more positive δ13C values. Although the five DOC records show similarly abrupt negative shifts in δ13C values, the DOC CIEs are compressed, smaller in magnitude, and return to more positive δ13C values more gradually relative to the n-alkane record. Moreover, the stratigraphic thickness of the body of the excursion and the pattern of the recovery phase are not consistent among the five DOC records. We modeled predicted DOC δ13C values from the n-alkane record by applying enrichment factors based on modern plants to the n-alkane δ13C values. The anomaly, difference between the expected and observed DOC δ13C values, was calculated for the PETM records and compared to weight percent carbon and grain size. There is no correlation between pre- and post-PETM anomaly values and grain size or weight percent carbon. PETM anomaly values, however, do trend with both grain size and weight percent carbon. The largest PETM anomaly values

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

    Energy Technology Data Exchange (ETDEWEB)

    Guy, R.D. (Carnegie Institution of Washington, Stanford, CA (United States)); Fogel, M.L.; Berry, J.A. (Carnegie Inst. of Washington, Washington, DC (United States))

    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.

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

    Science.gov (United States)

    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

  12. Organic carbon isotopes of the Sinian and Early Cambrian black shales on Yangtze Platform, China

    Institute of Scientific and Technical Information of China (English)

    李任伟; 卢家烂; 张淑坤; 雷加锦

    1999-01-01

    Organic matter of the Sinian and early Cambrian black shales on the Yangtze Platform belongs to the light carbon group of isotopes with the δ13C values from - 27 % to -35 % , which are lower than those of the contemporaneously deposited carbonates and phosphorites. A carbon isotope-stratified paleooceanographic model caused by upwelling is proposed, which can be used not only to interpret the characteristics of organic carbon isotopic compositions of the black shales, but also to interpret the paleogeographic difference in the organic carbon isotope compositions of various types of sedimentary rocks.

  13. Carbon isotopes in the ocean model of the Community Earth System Model (CESM1)

    OpenAIRE

    A. Jahn; Lindsay, K; Giraud, X.; Gruber, N.; Otto-Bliesner, B. L.; Liu, Z.; E. C. Brady

    2014-01-01

    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 "ab...

  14. Carbon isotopes in the ocean model of the Community Earth System Model (CESM1)

    OpenAIRE

    A. Jahn; Lindsay, K; Giraud, X.; Gruber, N.; Otto-Bliesner, B. L.; Liu, Z.; E. C. Brady

    2015-01-01

    Carbon isotopes in the ocean are frequently used as paleoclimate 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 data set, 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 "ab...

  15. Control strategies for laser separation of carbon isotopes

    Indian Academy of Sciences (India)

    V Parthasarathy; A K Nayak; S K Sarkar

    2002-12-01

    Laser isotope separation (LIS) by infrared laser chemistry of polyatomic molecules has come a long way since its discovery. The last decade has seen considerable efforts in scaling up of the process for light elements like carbon, oxygen and silicon. These efforts aim at ways to improve both the enrichment factor and the throughput. The achievement is quite significant especially for carbon isotope separation wherein macroscopic operating scales have been realized. We report our studies on the IR laser chemistry of two promising systems, viz. neat CF2HCl and CF3Br/Cl2. We have investigated conditions for optimizing the dissociation yield and selectivity using natural samples containing 1.1 % C-13. We also highlight our current efforts for scaling up the process. These include the design aspects of a photochemical reactor with multipass refocusing Herriott optics for efficient photon utilization, development of a cryogenic distillation set up and a preparative gas chromatograph for large scale separation/collection of the isotopically enriched photoproduct in the post-irradiation stage.

  16. Carbon and oxygen isotopes in apatite CO2 and co-existing calcite

    International Nuclear Information System (INIS)

    Carbon and oxygen isotopes were analyzed in carbonate apatite CO2 and in co-existing calcite. Both C and O in apatite CO2 are enriched in the respective light isotopes relative to calcite. These results confirm the proposition that carbonate is part of the apatite structure

  17. Stable isotope composition of atmospheric carbon monoxide. A modelling study

    International Nuclear Information System (INIS)

    This study aims at an improved understanding of the stable carbon and oxygen isotope composition of the carbon monoxide (CO) in the global atmosphere by means of numerical simulations. At first, a new kinetic chemistry tagging technique for the most complete parameterisation of isotope effects has been introduced into the Modular Earth Submodel System (MESSy) framework. Incorporated into the ECHAM/MESSy Atmospheric Chemistry (EMAC) general circulation model, an explicit treatment of the isotope effects on the global scale is now possible. The expanded model system has been applied to simulate the chemical system containing up to five isotopologues of all carbon- and oxygen-bearing species, which ultimately determine the δ13C, δ18O and Δ17O isotopic signatures of atmospheric CO. As model input, a new stable isotope-inclusive emission inventory for the relevant trace gases has been compiled. The uncertainties of the emission estimates and of the resulting simulated mixing and isotope ratios have been analysed. The simulated CO mixing and stable isotope ratios have been compared to in-situ measurements from ground-based observatories and from the civil-aircraft-mounted CARIBIC-1 measurement platform. The systematically underestimated 13CO/12CO ratios of earlier, simplified modelling studies can now be partly explained. The EMAC simulations do not support the inferences of those studies, which suggest for CO a reduced input of the highly depleted in 13C methane oxidation source. In particular, a high average yield of 0.94 CO per reacted methane (CH4) molecule is simulated in the troposphere, to a large extent due to the competition between the deposition and convective transport processes affecting the CH4 to CO reaction chain intermediates. None of the other factors, assumed or disregarded in previous studies, however hypothesised to have the potential in enriching tropospheric CO in 13C, were found significant when explicitly simulated. The inaccurate surface

  18. An analytical system for stable isotope analysis on carbon monoxide using continuous-flow isotope-ratio mass spectrometry

    NARCIS (Netherlands)

    Pathirana, S. L.; Van Der Veen, C.; Popa, M. E.; Röckmann, T.

    2015-01-01

    A fully automated system for the determination of δ13C and δ18O in atmospheric CO has been developed. CO is extracted from an air sample and converted into carbon dioxide (CO2) using the Schütze reagent. The isotopic composition is determined with an isotope-ratio mass spectrometer (IRMS) technique.

  19. Environmental impact and magnitude of paleosol carbonate carbon isotope excursions marking five early Eocene hyperthermals in the Bighorn Basin, Wyoming

    OpenAIRE

    Abels, Hemmo A.; Lauretano, Vittoria; van Yperen, Anna E.; Hopman, Tarek; Zachos, James C.; Lourens, Lucas J.; Gingerich, Philip D.; Gabriel J Bowen

    2016-01-01

    Transient greenhouse warming events in the Paleocene and Eocene were associated with the addition of isotopically light carbon to the exogenic atmosphere–ocean carbon system, leading to substantial environmental and biotic change. The magnitude of an accompanying carbon isotope excursion (CIE) can be used to constrain both the sources and amounts of carbon released during an event and also to correlate marine and terrestrial records with high precision. The Paleocene–Eocene ...

  20. A global deglacial negative carbon isotope excursion in speleothem calcite

    Science.gov (United States)

    Breecker, D.

    2015-12-01

    δ13C values of speleothem calcite decreased globally during the last deglaciation defining a carbon isotope excursion (CIE) despite relatively constant δ13C values of carbon in the ocean-atmosphere system. The magnitude of the CIE varied with latitude, increasing poleward from ~2‰ in the tropics to as much as 7‰ at high latitudes. This recent CIE provides an interesting comparison with CIEs observed in deep time. A substantial portion of this CIE can be explained by the increase in atmospheric pCO2 that accompanied deglaciation. The dependence of C3 plant δ13C values on atmospheric pCO2 predicts a 2‰ δ13C decrease driven by the deglacial pCO2 increase. I propose that this signal was transferred to caves and thus explains nearly 100% of the CIE magnitude observed in the tropics and no less than 30% at the highest latitudes in the compilation. An atmospheric pCO2 control on speleothem δ13C values, if real, will need to be corrected for using ice core data before δ13C records can be interpreted in a paleoclimate context. The decrease in the magnitude of the equilibrium calcite-CO2 carbon isotope fractionation factor explains a maximum of 1‰ of the CIE at the highest northern latitude in the compilation, which experienced the largest deglacial warming. Much of the residual extratropical CIE was likely driven by increasing belowground respiration rates, which were presumably pronounced at high latitudes as glacial retreat exposed fresh surfaces and/or vegetation density increased. The largest increases in belowground respiration would have therefore occurred at the highest latitudes, explaining the meridional trend. This work supports the notion that increases in atmospheric pCO2 and belowground respiration rates can result in large CIEs recorded in terrestrial carbonates, which, as previously suggested, may explain the magnitude of the PETM CIE as recorded by paleosol carbonates.

  1. Carbon isotope excursions in paleosol carbonate marking five early Eocene hyperthermals in the Bighorn Basin, Wyoming

    Directory of Open Access Journals (Sweden)

    H. A. Abels

    2015-05-01

    Full Text Available Transient greenhouse warming events in the Paleocene and Eocene were associated with the addition of isotopically-light carbon to the exogenic atmosphere–ocean carbon pool, leading to substantial environmental and biotic change. The magnitude of an accompanying carbon isotope excursion (CIE can be used to constrain both the sources and amounts of carbon released during an event, as well as to correlate marine and terrestrial records with high precision. The Paleocene Eocene Thermal Maximum (PETM is well documented, but CIE records for the subsequent warming events are still rare especially from the terrestrial realm. Here, we provide new CIE records for two of the smaller hyperthermal events, I1 and I2, in paleosol carbonate, as well as two additional records of ETM2 and H2 in the Bighorn Basin. Stratigraphic comparison of this expanded, high-resolution terrestrial carbon isotope record to the deep-sea benthic foraminifera records from ODP Sites 1262 and 1263, Walvis Ridge, in the southern Atlantic Ocean corroborates that the Bighorn Basin fluvial sediments record global atmospheric change. The stratigraphic thicknesses of the eccentricity-driven hyperthermals in these archives are in line with precession-forcing of the 7 m thick fluvial overbank-avulsion sedimentary cycles. Using the CALMAG bulk oxide mean annual precipitation proxy, we reconstruct similar or slightly wetter than background soil moisture contents during the four younger hyperthermals, in contrast to drying observed during the PETM. Soil carbonate CIEs vary in magnitude proportionally with the marine CIEs for the four smaller early Eocene hyperthermals. This relationship breaks down for the PETM, with the soil carbonate CIE ~ 2–4‰ less than expected if all five linearly relate to marine CIEs. If the PETM CO2 forcing was similar but scaled to the younger hyperthermals, photosynthetic isotope fractionation or soil environmental factors are needed to explain this anomaly. We

  2. A molecular organic carbon isotope record of Miocene climate changes

    OpenAIRE

    Schoell, M.; Schouten, S.; Sinninghe Damsté, J.S.; J. W. de Leeuw; Summons, R. E.

    1994-01-01

    The difference in carbon-13 (13C) contents of hopane and sterane biomarkers in the Monterey formation (Naples Beach, California) parallels the Miocene inorganic record of the change in 18O (δ18O), reflecting the Miocene evolution from a well-mixed to a highly stratified photic zone (upper 100 meters) in the Pacific. Steranes (δ13C = 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, sulfu...

  3. Carbon isotope excursions across the Permian-Triassic boundary in the Meishan section, Zhejiang Province, China

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Both gradual and sharp decrease in organic and carbonate carbon isotope values were detected across the Permian-Triassic boundary in the Meishan section, Changxing, Zhejiang Province, China. The gradual decrease in organic carbon isotope values started at the bottom of Bed 23, coinciding with the strong oscillations of total organic carbon (TOC) contents, indicates increasing fluxes from carbonate to organic carbon reservoir during this interval. A 2.3‰ sharp drop of inorganic carbon isotope values occurred at the uppermost part of Bed 24e. A 3.7‰ sharp drop of organic carbon isotope values occurred in Bed 26. The dramatic drop of inorganic carbon isotope value of 8‰ reported previously is not confirmed from the unweathered carbonate samples in Bed 27. The large-scale fluctuation of organic carbon isotope values in the Yinkeng Formation reflects different extent of mixing of marine and terrestrial organic matters. The gradual depletion and subsequent sharp drop of carbon isotopes near the Permian-Triassic boundary might indicate complex causes of the end-Permian mass extinction.

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

    OpenAIRE

    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

    2015-01-01

    “Clumped-isotope” thermometry is an emerging tool to probe the temperature history of surface and subsurface environments based on measurements of the proportion of ^(13)C and ^(18)O isotopes bound to each other within carbonate minerals in ^(13)C^(18)O^(16)O_2^(2−) 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 solutio...

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

    Science.gov (United States)

    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.

  6. Carbon isotopes and water use efficiency in C4 plants.

    Science.gov (United States)

    Ellsworth, Patrick Z; Cousins, Asaph B

    2016-06-01

    Drought is a major agricultural problem worldwide. Therefore, selection for increased water use efficiency (WUE) in food and biofuel crop species will be an important trait in plant breeding programs. The leaf carbon isotopic composition (δ(13)Cleaf) has been suggested to serve as a rapid and effective high throughput phenotyping method for WUE in both C3 and C4 species. This is because WUE, leaf carbon discrimination (Δ(13)Cleaf), and δ(13)Cleaf are correlated through their relationships with intercellular to ambient CO2 partial pressures (Ci/Ca). However, in C4 plants, changing environmental conditions may influence photosynthetic efficiency (bundle-sheath leakiness) and post-photosynthetic fractionation that will potentially alter the relationship between δ(13)Cleaf and Ci/Ca. Here we discuss how these factors influence the relationship between δ(13)Cleaf and WUE, and the potential of using δ(13)Cleaf as a meaningful proxy for WUE.

  7. Mantle Degassing and Diamond Genesis:A Carbon Isotope Perspective

    Institute of Scientific and Technical Information of China (English)

    郑永飞

    1994-01-01

    The effect of Co2 and CH4 degassing from the mantle on the carbon isotopic composition of diamond has been quantitatively modeled in terms of the principles of Rayleigh distillation.Assuming the δ13 C value of -5‰ for the mantle,the outgassing of CO2 can result in the large negative δ13 C values of diamond,whereas the outgassing of CH4 can drive the δ13C values of diamond in the positive direction.The theoretical expectations can be used to explain the full range of δ13 C values from-34.4‰5 to+5‰ observed for natural diamonds.It is possible that diamond formation was triggered by the degassing of Co2 and/or CH4 from the mantle and the associated fractional crystallization of carbonate-bearing melt.

  8. A molecular organic carbon isotope record of miocene climate changes.

    Science.gov (United States)

    Schoell, M; Schouten, S; Damsté, J S; de Leeuw, J W; Summons, R E

    1994-02-25

    The difference in carbon-13 ((13)C) contents of hopane and sterane biomarkers in the Monterey formation (Naples Beach, California) parallels the Miocene inorganic record of the change in (18)O (delta(18)O), reflecting the Miocene evolution from a well-mixed to a highly stratified photic zone (upper 100 meters) in the Pacific. Steranes (delta(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(35) hopanes (likely derived from bacterial plankton living at the base of the photic zone) have systematically decreasing (13)C concentrations in Middle and Late Miocene samples (delta(13)C = -29.5 to -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. PMID:17831625

  9. Application of carbon isotope analyses in food technology

    International Nuclear Information System (INIS)

    The vast economic size of the food market offers great temptations for the production and sale of fraudulent products, adulterated products and synthetic products that are labeled as natural ones. Conventional techniques of chemical analyses have served the food industry well for many years but are limited in their ability to detect certain types of fraudulent or mislabelled products. The aversion to added sugar and the demand for 'all natural' food products among consumers has led to a great deal of mislabelling on the part of food processors in order to achieve greater economic gain. The nature of deceptions detectable by carbon Stable Isotope Ratio Analysis (SIRA) in food technology falls into three broad categories. The most common is the adulteration of an expensive natural product, such as apple juice, with a much cheaper natural product such as cane sugar or high fructose corn syrup (HFCS). The second is outright falsification of a food. An example is maple syrup produced by simple addition of maple flavoring to a sugar syrup or HFCS. The third general category is the sale of synthetic materials as natural ones or the addition of synthetic materials to natural ones in order to increase the volume of the product. The procedure for using carbon SIRA in monitoring food products involves two stages. It must first be established that the product to be analyzed, or some specific component of it, has a particular isotopic composition that can be distinguished from that of the materials that might be used to adulterate it. Potential adulterating components are then analyzed to establish their isotopic identity. The carbon SIRA method cannot, in general, be used to establish purity unequivocally but it can be used to establish impurity or adulteration with a high degree of success. The overall process of carbon SIRA consists of three stages: selection of the sample or the isolation of the particular compound to be analyzed, conversion of this compound into CO2 gas

  10. Carbon isotope fluctuations in Precambrian carbonate sequences of several localities in Brazil

    OpenAIRE

    SIAL ALCIDES N.; FERREIRA VALDEREZ P.; DEALMEIDA AFONSO R.; ROMANO ANTONIO W.; PARENTE CLOVIS V.; DACOSTA MARCONDES L.; SANTOS VICTOR H.

    2000-01-01

    Carbon isotope fluctuations in Precambrian sedimentary carbonates between 2.8 Ga and 0.60 Ga in Brazil are examined in this study. The carbonate facies of the BIF of the 2.8 Ga-old Carajás Formation, state of Pará in northern Brazil, has rather homogeneous delta13C (-5 o/ooPDB), compatible with carbonatization of a silicate protolith by a CO2-rich fluid from mantle degassing. The Paleoproterozoic Gandarela Formation, state of Minas Gerais, displays a narrow delta13C variation (-1.5 to +0.5 o/...

  11. Abundances in red giant stars - Carbon and oxygen isotopes in carbon-rich molecular envelopes

    Science.gov (United States)

    Wannier, P. G.; Sahai, R.

    1987-01-01

    Millimeter-wave observations have been made of isotopically substituted CO toward the envelopes of 11 carbon-rich stars. In every case, C-13O was detected and model calculations were used to estimate the C-12/C-13 abundance ratio. C-17O was detected toward three, and possibly four, envelopes, with sensitive upper limits for two others. The CO-18 variant was detected in two envelopes. New results include determinations of oxygen isotopic ratios in the two carbon-rich protoplanetary nebulae CRL 26688 and CRL 618. As with other classes of red giant stars, the carbon-rich giants seem to be significantly, though variably, enriched in O-17. These results, in combination with observations in interstellar molecular clouds, indicate that current knowledge of stellar production of the CNO nuclides is far from satisfactory.

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

    Science.gov (United States)

    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. The thermal history of char as disclosed by carbon isotope ratios

    DEFF Research Database (Denmark)

    Egsgaard, Helge; Ambus, Per; Ahrenfeldt, Jesper;

    pyrolysis and isotope ratio mass spectrometry. The results demonstrate that the temperature history of the char is reflected in the fine variation of carbon isotopes. The compound classes responsible for the variation were identified. Key words: Isotope ratio, flash pyrolysis, hot gas cleaning...

  14. Carbon allocation and carbon isotope fluxes in the plant-soil-atmosphere continuum: a review

    Science.gov (United States)

    Brüggemann, N.; Gessler, A.; Kayler, Z.; Keel, S. G.; Badeck, F.; Barthel, M.; Boeckx, P.; Buchmann, N.; Brugnoli, E.; Esperschütz, J.; Gavrichkova, O.; Ghashghaie, J.; Gomez-Casanovas, N.; Keitel, C.; Knohl, A.; Kuptz, D.; Palacio, S.; Salmon, Y.; Uchida, Y.; Bahn, M.

    2011-11-01

    The terrestrial carbon (C) cycle has received increasing interest over the past few decades, however, there is still a lack of understanding of the fate of newly assimilated C allocated within plants and to the soil, stored within ecosystems and lost to the atmosphere. Stable carbon isotope studies can give novel insights into these issues. In this review we provide an overview of an emerging picture of plant-soil-atmosphere C fluxes, as based on C isotope studies, and identify processes determining related C isotope signatures. The first part of the review focuses on isotopic fractionation processes within plants during and after photosynthesis. The second major part elaborates on plant-internal and plant-rhizosphere C allocation patterns at different time scales (diel, seasonal, interannual), including the speed of C transfer and time lags in the coupling of assimilation and respiration, as well as the magnitude and controls of plant-soil C allocation and respiratory fluxes. Plant responses to changing environmental conditions, the functional relationship between the physiological and phenological status of plants and C transfer, and interactions between C, water and nutrient dynamics are discussed. The role of the C counterflow from the rhizosphere to the aboveground parts of the plants, e.g. via CO2 dissolved in the xylem water or as xylem-transported sugars, is highlighted. The third part is centered around belowground C turnover, focusing especially on above- and belowground litter inputs, soil organic matter formation and turnover, production and loss of dissolved organic C, soil respiration and CO2 fixation by soil microbes. Furthermore, plant controls on microbial communities and activity via exudates and litter production as well as microbial community effects on C mineralization are reviewed. A further part of the paper is dedicated to physical interactions between soil CO2 and the soil matrix, such as CO2 diffusion and dissolution processes within the

  15. Carbon and oxygen isotopic ratios of carbon dioxide of a stratospheric profile over Japan

    OpenAIRE

    GAMO, Toshitaka; Tsutsumi, Makoto; SAKAI, Hitoshi; NAKAZAWA, Takakiyo; Tanaka, Masayuki; Honda, Hideyuki; Kubo, Haruya; ITOH, Tomizo

    2011-01-01

    Four stratospheric air samples from 19 to 25 km altitudes over Japan were collected by using a balloon-borne cryogenic sampling system to measure the vertical profiles of carbon and oxygen stable isotopic ratios of the lower stratospheric CO2. The δ13C value of the stratospheric CO2 increased with increasing altitude, while the CO2 mixing ratios decreased, in accordance with anthropogenic input of the isotopically light, fuel CO2 into the atmosphere. However, the relationship between δ13C an...

  16. Tracing organic matter sources of estuarine tidal flat nematodes with stable carbon isotopes

    NARCIS (Netherlands)

    Moens, T.; Luyten, C.; Middelburg, J.J.; Herman, P.M.J.; Vincx, M.

    2002-01-01

    The present study explores the use of stable carbon isotopes to trace organic matter sources of intertidal nematodes in the Schelde estuary (SW Netherlands). Stable carbon isotope signatures of nematodes from a saltmarsh and 4 tidal flat stations were determined in spring and winter situations, and

  17. Long-range transport of continentally-derived particulate carbon in the marine atmosphere: evidence from stable carbon isotope studies

    OpenAIRE

    Cachier, Héléne; BUAT-MÉNARD, PATRICK; Fontugne, Michel; Chesselet, Roger

    2011-01-01

    Since 1979, we have investigated marine and non-marine sources of particulate carbon in the marine atmosphere from measurements of carbon concentration and isotopic composition 13C/12C). Aerosol samples were collected, mostly during the Sea/Air Exchange (SEAREX) Program experiments, in the northern and southern hemispheres (Sargasso Sea, Enewetak Atoll, Peru upwelling, American Samoa, New Zealand, Amsterdam Island). The concentration and the isotopic composition of particulate carbon of marin...

  18. Using Carbon Isotopes in Cenozoic Soil Carbonates to Quantify Primary Productivity from Mid-Latitude Regions

    Science.gov (United States)

    Caves, J. K.; Kramer, S. H.; Ibarra, D. E.; Chamberlain, C. P.

    2015-12-01

    The carbon isotope composition of pedogenic carbonates (δ13Ccarb) from paleosols has been extensively used as a proxy to estimate atmospheric pCO2 over the Phanerozoic. However, a number of other factors - including the concentration of plant-respired CO2 and the isotopic composition of both atmospheric and plant-respired carbon - influence the δ13C of pedogenic carbonates. For example, δ13Ccarb records from the mid-latitudes in central Asia and western North America show increasing trends in δ13Ccarb despite decreasing pCO2 during the late Cenozoic, which suggests that other factors play an important role in determining the isotopic composition of pedogenic carbonates. Instead, we suggest that these records are primarily recording changes in primary productivity rather than changes in atmospheric pCO2 and therefore propose a novel use of paleosol carbonate records to understand paleo-ecosystem dynamics. Here, we compile existing paleosol carbonate records, and present three new records from Wyoming, to estimate soil respiration and primary productivity in western North America during the Paleogene and early Neogene. We observe both an overall increase in δ13Ccarb after the early Eocene, and spatially heterogeneous δ13Ccarb values across western US basins. We combine this δ13Ccarb data with compilations of atmospheric pCO2 to estimate soil respiration and plant productivity. The long-term increase in δ13Ccarb indicates a decrease in plant productivity as conditions became more arid across much of the western US, congruent with both records of regional uplift and of global cooling. Furthermore, significant spatial heterogeneity in δ13Ccarb indicates that regional factors, such as the presence of paleolakes and/or local paleotopography may have provided a second-order control on local and regional productivity. Thus, our results provide a first-order estimate linking changes in primary productivity with regional tectonics and global climatic change.

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

    Science.gov (United States)

    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 (δ(13)C-L), leaf soluble compounds (δ(13)C-S) and bulk leaf material (δ(13)C-B) collected from tapped and untapped 20-year-old trees were compared. A marked difference in δ(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 δ(13)C values than those of untapped trees. δ(13)C-L was higher and more stable across seasons than δ(13)C-S and δ(13)C-B, with a maximum seasonal difference of 0.7‰ for tapped trees and 0.3‰ for untapped trees. δ(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 δ(13)C-L and δ(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 δ(13)C-L and δ(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

  20. Regional prediction of carbon isotopes in soil carbonates for Asian dust source tracer

    Science.gov (United States)

    Chen, Bing; Cui, Xinjuan; Wang, Yaqiang

    2016-10-01

    Dust particles emitted from deserts and semi-arid lands in northern China cause particulate pollution that increases the burden of disease particularly for urban population in East Asia. The stable carbon isotopes (δ13C) of carbonates in soils and dust aerosols in northern China were investigated. We found that the δ13C of carbonates in surface soils in northern China showed clearly the negative correlation (R2 = 0.73) with Normalized Difference Vegetation Index (NDVI). Using Moderate Resolution Imaging Spectroradiometer (MODIS) satellite-derived NDVI, we predicted the regional distribution of δ13C of soil carbonates in deserts, sandy lands, and steppe areas. The predictions show the mean δ13C of -0.4 ± 0.7‰ in soil carbonates in Taklimakan Desert and Gobi Deserts, and the isotope values decrease to -3.3 ± 1.1‰ in sandy lands. The increase in vegetation coverage depletes 13C in soil carbonates, thus the steppe areas are predicted by the lowest δ13C levels (-8.1 ± 1.7‰). The measurements of atmospheric dust samples at eight sites showed that the Asian dust sources were well assigned by the 13C mapping in surface soils. Predicting 13C in large geographical areas with fine resolution offers a cost-effective tracer to monitor dust emissions from sandy lands and steppe areas which show an increasing role in Asian dust loading driven by climate change and human activities.

  1. Stable Carbon and Oxygen Isotopes of Pedogenic Carbonates in Ustic Vertisols: Implications for Paleoenvironmental Change

    Institute of Scientific and Technical Information of China (English)

    HUANG Cheng-Min; WANG Cheng-Shan; TANG Ya

    2005-01-01

    Pedogenic carbonates, found extensively in arid and semiarid regions, are important in revealing regional climatic and environmental changes as well as the carbon cycle. In addition, stable carbon and oxygen isotopic compositions of pedogenic carbonates have been used to rebuild paleoecology (biomass and vegetation) and to estimate paleotemperature and paleoprecipitation during past geological time. By utilizing the stable carbon and oxygen isotopic compositions (δ13C and δ18O) of secondary nodules in Ustic Vertisols, this study looked into the climatic and environmental changes in the dry valleys of the Yuanmou Basin, Yunnan Province, in southwestern China. The results showed that during the early Holocene, a warm-humid or hot-humid climate existed in the Yuanmou Basin, but since then fluctuations in climate have occurred, with a dry climate prevailing. A highly significant correlation (r = 0.92, n= 9) between δ13C and δ18O values of carbonates illustrated that there had been a continual shifting between cold-humid and warm-dry climates in southwestern China including the Yuanmou Basin since the early Holocene.

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

    Science.gov (United States)

    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 δ18O 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 δ18O 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 δ18O 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 δ18O 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 'Δ47' value of CO2 extracted by phosphoric acid digestion [6]. This method is thermodynamically based and independent of the δ18O of water from which the carbonate grew. We will report the initial results of measurements of 'Δ47 for a suite of carbonates from the Sultanate of Oman. This Ediacaran age (~ 635 to

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

    Science.gov (United States)

    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 (PM

  4. Carbon and Oxygen Isotopic Composition of Surface-Sediment Carbonate in Bosten Lake (Xinjiang, China) and its Controlling Factors

    Institute of Scientific and Technical Information of China (English)

    ZHANG Chengjun; Steffen MISCHKE; ZHENG Mianping; Alexander PROKOPENKO; GUO Fangqin; FENG Zhaodong

    2009-01-01

    Bosten Lake is a mid-latitude lake with water mainly supplied by melting ice and snow in the Tianshan Mountains. The depositional environment of the lake is spatially not uniform due to the proximity of the major inlet and the single outlet in the western part of the lake. The analytical results show that the carbon and oxygen isotopic composition of recent lake sediments is related to this specific lacustrine depositional environment and to the resulting carbonate mineralogy. In the southwestern lake region between the Kaidu River inlet and the Kongqi River outlet, carbon isotope composition (δ13C) values of the carbonate sediment (-1‰ to -2‰) have no relation to the oxygen isotope composition of the carbonate (δ18O) values (-7‰ to -8‰), with both isotopes showing a low variability. The carbonate content is low (<20%). Carbonate minerals analyzed by X-ray diffraction are mainly composed of calcite, while aragonite was not recorded. The salinity of the lake water is low in the estuary region as a result of the Kaidu River inflow. In comparison, the carbon and oxygen isotope values are higher in the middle and eastern parts of the lake, with δ13C values between approximately +0.5‰ and +3‰, and δ18O values between -1‰ and -5‰. There is a moderate correlation between the stable oxygen and carbon isotopes, with a coefficient of correlation r of approximately 0.63. This implies that the lake water has a relatively short residence time. Carbonate minerals constitute calcite and aragonite in the middle and eastern region of the lake. Aragonite and Mg-calcite are formed at higher lake water salinity and temperatures, and larger evaporation effects. More saline lake water in the middle and eastern region of the lake and the enhanced isotopic equilibrium between water and atmospheric CO2 cause the correlating carbon and oxygen isotope values determined for aragonite and Mg-calcite. Evaporation and biological processes are the main reasons for the salinity

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

    Science.gov (United States)

    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

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

    Directory of Open Access Journals (Sweden)

    Ana G Popa-Lisseanu

    Full Text Available 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 δ13C and δ15N 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.

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

    Science.gov (United States)

    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 δ13C and δ15N 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

  8. The magnesium isotope record of cave carbonate archives

    Directory of Open Access Journals (Sweden)

    S. Riechelmann

    2012-11-01

    Full Text Available Here we explore the potential of magnesium (δ26Mg 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 δ26Mg 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 δ26Mg 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 δ26Mg: −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 δ26Mg: −4.01 ± 0.07‰; BU 4 mean δ26Mg: −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

  9. The magnesium isotope record of cave carbonate archives

    Directory of Open Access Journals (Sweden)

    S. Riechelmann

    2012-05-01

    Full Text Available Here we explore the potential of time-series magnesium (δ26Mg 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 δ26Mg 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 δ26Mg 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 δ26Mg: −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 δ26Mg: −4.01 ± 0.07 ‰; BU 4 mean δ26Mg: −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

  10. Stable Isotope Studies of Crop Carbon and Water Relations: A Review

    Institute of Scientific and Technical Information of China (English)

    ZHANG Cong-zhi; ZHANG Jia-bao; ZHAO Bing-zi; ZHANG Hui; HUANG Ping

    2009-01-01

    Crop carbon and water relations research is important in the studies of water saving agriculture,breeding program,and energy and material cycles in soil plant atmosphere continuum (SPAC).The purpose of this paper is to review the current state of knowledge on stable isotopes of carbon,oxygen,and hydrogen in the research of crop carbon and water relations,such as carbon isotope discrimination (△13C) during carbon fixation process by photosynthesis,application of △13C in crop water use efficiency (WUE) and breeding programs,oxygen isotope enrichment during leaf water transpiration,CO2 fixation by photosynthesis and release by respiration,application of hydrogen isotope composition (δD) and oxygen isotope composition (δ18O) for determination of water source used by a crop,stable isotope coupling Keeling plot for investigating the carbon and water flux in ecosystem,energy and material cycle in SPAC and correlative integrative models on stable isotope.These aspects contain most of the stable isotope researches on crop carbon and water relations which have been widely explored internationally while less referred in China.Based on the reviewed literatures,some needs for future research are suggested.

  11. The Strontium Isotope Record of Zavkhan Terrane Carbonates: Strontium Isotope Stability Through the Ediacaran-Cambrian Transition

    OpenAIRE

    Petach, Tanya N.

    2015-01-01

    First order trends in the strontium isotopic (87Sr/86Sr) composition of seawater are controlled by radiogenic inputs from the continent and non-radiogenic inputs from exchange at mid-ocean ridges. Carbonates precipitated in seawater preserve trace amounts of strontium that record this isotope ratio and therefore record the relative importance of mid-ocean ridge and weathering chemical inputs to sea water composition. It has been proposed that environmental changes during the Ediacaran-Cambria...

  12. On-site isotopic analysis of dissolved inorganic carbon using an isotope ratio infrared spectrometer

    Science.gov (United States)

    Stoltmann, Tim; Mandic, Magda; Stöbener, Nils; Wapelhorst, Eric; Aepfler, Rebecca; Hinrichs, Kai-Uwe; Taubner, Heidi; Jost, Hj; Elvert, Marcus

    2016-04-01

    An Isotope Ratio Infrared Spectrometer (IRIS) has been adapted to perform measurements of δ13C of dissolved inorganic carbon (DIC) in marine pore waters. The resulting prototype allowed highly automated analysis of δ13C isotopic ratios and CO2 concentration. We achieved a throughput of up to 70 samples per day with DIC contents as low as 1.7 μmol C. We achieved an internal precision of 0.066 ‰ and an external precision of 0.16 ‰, which is comparable to values given for Isotope Ratio Mass Spectrometers (IRMS). The prototype instrument is field deployable, suitable for shipboard analysis of deep sea core pore waters. However, the validation of the prototype was centered around a field campaign in Eckernförde Bay, NW- Baltic Sea. As a proof of concept, a shallow site within an area of submarine groundwater discharge (SGD) and a site outside this area was investigated. We present profiles of δ13C of DIC over 50 cm exhibiting well understood methane turnover processes (anaerobic oxidation of methane). At the lowest point below the seafloor, microbial reduction of CO2 to CH4 dominates. 12CO2 is reduced preferentially over 13CO2, leading to more positive δ13C values in the remaining DIC pool; in layers closer to the surface, the oxidation of CH4 to CO2 becomes more prominent. Since the CH4 pool is enriched in 12C a shift to more negative δ13C can be observed in the DIC pool. In the upper 15 cm, the pore water DIC mixes with the sea water DIC, increasing δ13C again. Finally, we will present recent developments to further improve performance and future plans for deployments on research cruises.

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

    CERN Document Server

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

    2015-01-01

    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.

  14. Isotopic disequilibrium in Globigerina bulloides and carbon isotope response to productivity increase in Southern Ocean

    Science.gov (United States)

    Prasanna, K.; Ghosh, Prosenjit; Bhattacharya, S. K.; Mohan, K.; Anilkumar, N.

    2016-02-01

    Oxygen and carbon isotope ratios in planktonic foraminifera Globigerina bulloides collected from tow samples along a transect from the equatorial Indian ocean to the Southern Ocean (45°E and 80°E and 10°N to 53°S) were analysed and compared with the equilibrium δ18O and δ13C values of calcite calculated using the temperature and isotopic composition of the water column. The results agree within ~0.25‰ for the region between 10°N and 40°S and 75-200 m water depth which is considered to be the habitat of Globigerina bulloides. Further south (from 40°S to 55°S), however, the measured δ18O and δ13C values are higher than the expected values by ~2‰ and ~1‰ respectively. These enrichments can be attributed to either a ‘vital effect’ or a higher calcification rate. An interesting pattern of increase in the δ13C(DIC) value of the surface water with latitude is observed between 35°S and~ 60°S, with a peak at~ 42°S. This can be caused by increased organic matter production and associated removal. A simple model accounting for the increase in the δ13C(DIC) values is proposed which fits well with the observed chlorophyll abundance as a function of latitude.

  15. Stable Carbon Isotope Record in a Palau Sclerosponge

    Science.gov (United States)

    Grottoli, A. G.

    2002-12-01

    The ratio of stable carbon isotopes (δ13C) deposited in the calcium carbonate skeleton of marine sclerosponges appears to record the carbon isotopic composition of seawater mixed-layer dissolved inorganic carbon (δ13CDIC). Thus the δ13C signature chronicled in sclerosponge skeletons offers a promising multi-century proxy record of seawater mixed-layer δ13CDIC throughout the tropics. Here, a high-resolution (0.1 mm) δ13C record for a 7.7 cm Acanthocheatetes wellsi sclerosponge from Palau (7N, 134W) is presented. At a published growth rate of 0.45 mm per year, this record spans ~s170 years beginning in July 2001 and going back to 1831. The δ13C values for a definitive 10-year A. wellsi record spanning 1989-1998 were similar to δ13C values here for the first 4.7 mm of the record providing supporting evidence for the growth rate. The sclerosponge δ13C shows a distinct Seuss Effect. At the time this abstract was submitted, the analysis of the first 16 mm of the sclerosponge revealed a significant decrease in δ13C with time [δ13C = 0.02 (distance) + 2.64, r2 = 0.73, p < 0.0001, where time is marked by distance in millimeters from the growing edge] corresponding to a decrease in δ13C of 0.076‰ per decade. For comparison, published low-frequency measurements in Australian, New Caledonian and Jamaican sclerosponges have yielded decreases in δ13C of ~s0.05 to 0.08 ‰ per decade over the past 40 years. Preliminary interpretation of the data indicates that the amount of atmospheric CO2 contributing to the seawater δ13CDIC at Palau is intermediate to Australia and Jamaica. In addition, visual examination of the δ13C record reveals regular fluctuation in δ13C that may correspond to annual variability in δ13CDIC. This research presents the first century or longer sclerosponge δ13C record from the northwester equatorial Pacific.

  16. Application of carbon and oxygen stable isotopes to the study of Brazilian precambrian

    International Nuclear Information System (INIS)

    Samples of carbonated rocks of precambrian age are studied. The stable carbon and oxygen isotopes are applied to the study of terrestrial materials considering the variations of some element isotopic composition in function of the environment of sedimentation. The isotopic analysis was done using mass spectrometers. The analytical results and the description of region geology of the site of each sample are presented. The isotopic data are interpreted aiming to the environment of sedimentation. New techniques for better improvement of carbon and oxygen ratios, are proposed, such as: to use the analysis of surface trend and the isotopic logging in mapping of surface and subsurface. A new method for approximated determination of the ages of precambrian carbonated rocks, considering the limitations of their new technique, is also presented. (M.C.K.)

  17. Molecular and carbon isotopic compositions of gas inclusions of deep carbonate rocks in the Tarim Basin

    Institute of Scientific and Technical Information of China (English)

    ZHOU Shixin; WANG Xianbin; MENG Zifang; LI Yuan; Paul Farrimond; LI Liwu; DUAN Yi

    2004-01-01

    Gaseous components of gas inclusions in deep carbonate rocks (>5700 m) from the Tacan 1 well were analyzed by online mass spectrometry by means of either the stepwise heating technique or vacuum electromagnetism crushing. The carbon isotopic compositions of gases released by vacuum electromagnetism crushing were also measured. Although the molecular compositions of gas inclusions show differences between the two methods, the overall characteristics are that gas inclusions mainly contain CO2, whilst hydrocarbon gases, such as CH4, C2H6 and C3H8, are less abundant. The content of CO is higher in the stepwise heating experiment than that in the method of vacuum electromagnetism crushing, and there are only minor amounts of N2, H2 and O2 in gas inclusions. Methane δ13C values of gas inclusions in Lower Ordovician and Upper Cambrian rocks (from 5713.7 to 6422 m; -52‰-63‰) are similar to those of bacterial methane, but their chemical compositions do not exhibit the dry character in comparison with biogenic gases. These characteristics of deep gas inclusions may be related to the migration fractionation. Some deep natural gases with light carbon isotopic characteristics in the Tazhong Uplift may have a similar origin. The δ13C1 values of gas inclusions in Lower Cambrian rocks (7117-7124 m) are heavier (-39‰), consistent with highly mature natural gases. Carbon isotopic compositions of CO2 in the gas inclusions of deep carbonate rocks are similar (from -4‰ to -13‰) to those of deep natural gases, indicating predominantly an inorganic origin.

  18. Carbon isotope systematics of individual hydrocarbons in hydrothermal petroleum from Escanaba Trough, Northeastern Pacific Ocean

    Science.gov (United States)

    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.

  19. Carbon isotopic studies of individual lipids in organisms from the Nansha sea area, China

    Institute of Scientific and Technical Information of China (English)

    DUAN Yi; SONG Jinming; ZHANG Hui

    2004-01-01

    Carbon isotopes of individual lipids in typical organisms from the Nansha sea area were measured by the GC-IRMS analytical technique. δ13C values of saturated fatty acids in different organisms examined are from -25.6‰ to -29.7‰ with the average values ranging from -26.4‰ to -28.2‰ and the variance range of 1.8‰ between different organisms is also observed.Unsaturated fatty acids have heavy carbon isotopic compositions and the mean differences of 2.9‰-6.8‰ compared to the same carbon number saturated fatty acids. δ13C values of n-alkanes range from -27.5‰ to -29.7‰ and their mean values, ranging from -28.6‰ to -28.9‰, are very close in different organisms. The mean difference in δ13C between the saturated fatty acids and n-alkanes is only 1.5‰, indicating that they have similar biosynthetic pathways. The carbon isotopic variations between the different carbon-number lipids are mostly within ±2.0‰, reflecting that they experienced a biosynthetic process of the carbon chain elongation. At the same time, the carbon isotopic genetic relationships between the biological and sedimentary lipids are established by comparative studies of carbon isotopic compositions of individual lipids in organisms and sediments from the Nansha sea area, which provides scientific basis for carbon isotopic applied research of individual lipids.

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

    Science.gov (United States)

    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.

  1. Mesozoic black shales, source mixing and carbon isotopes

    Science.gov (United States)

    Suan, Guillaume

    2016-04-01

    Over the last decades, considerable attention has been devoted to the paleoenvironmental and biogeochemical significance of Mesozoic black shales. Black shale-bearing successions indeed often display marked changes in the organic carbon isotope composition (δ13Corg), which have been commonly interpreted as evidence for dramatic perturbations of global carbon budgets and CO2 levels. Arguably the majority of these studies have discarded some more "local" explanations when interpreting δ13Corg profiles, most often because comparable profiles occur on geographically large and distant areas. Based on newly acquired data and selected examples from the literature, I will show that the changing contribution of organic components with distinct δ13C signatures exerts a major but overlooked influence of Mesozoic δ13Corg profiles. Such a bias occurs across a wide spectrum of sedimentological settings and ages, as shown by the good correlation between δ13Corg values and proxies of kerogen proportions (such as rock-eval, biomarker, palynofacies and palynological data) recorded in Mesozoic marginal to deep marine successions of Triassic, Jurassic and Cretaceous age. In most of these successions, labile, 12C-enriched amorphous organic matter of marine origin dominates strata deposited under anoxic conditions, while oxidation-resistant, 13C-rich terrestrial particles dominate strata deposited under well-oxygenated conditions. This influence is further illustrated by weathering profiles of Toarcian (Lower Jurassic) black shales from France, where weathered areas dominated by refractory organic matter show dramatic 13C-enrichment (and decreased total organic carbon and pyrite contents) compared to non-weathered portions of the same horizon. The implications of these results for chemostratigraphic correlations and pCO2 reconstructions of Mesozoic will be discussed, as well as strategies to overcome this major bias.

  2. Distribution and fractionation mechanism of stable carbon isotope of coalbed methane

    Institute of Scientific and Technical Information of China (English)

    QIN; Shengfei; TANG; Xiuyi; SONG; Yan; WANG; Hongyan

    2006-01-01

    The stable carbon isotope values of coalbed methane range widely,and also are generally lighter than that of gases in normal coal-formed gas fields with similar coal rank.There exists strong carbon isotope fractionation in coalbed methane and it makes the carbon isotope value lighter.The correlation between the carbon isotope value and Ro in coalbed methane is less obvious.The coaly source rock maturity cannot be judged by coalbed methane carbon isotope value.The carbon isotopes of coalbed methane become lighter in much different degree due to the hydrodynamics.The stronger the hydrodynamics is,the lighter the CBM carbon isotopic value becomes.Many previous investigations indicated that the desorption-diffusion effects make the carbon isotope value of coalbed methane lighter.However,the explanation has encountered many problems.The authors of this article suggest that the flowing groundwater dissolution to free methane in coal seams and the free methane exchange with absorbed one is the carbon isotope fractionation mechanism in coalbed methane.The flowing groundwater in coal can easily take more 13CH4 away from free gas and comparatively leave more 12CH4.This will make 12CH4 density in free gas comparatively higher than that in absorbed gas.The remaining 12CH4 in free gas then exchanges with the adsorbed methane in coal matrix.Some absorbed 13CH4 can be replaced and become free gas.Some free 12CH4 can be absorbed again into coal matrix and become absorbed gas.Part of the newly replaced 13CH4 in free gas will also be taken away by water,leaving preferentially more 12CH4.The remaining 12CH4 in free gas will exchange again with adsorbed methane in the coal matrix.These processes occur all the time.Through accumulative effect,the 12CH4 will be greatly concentrated in coal.Thus,the stable carbon isotope of coalbed methane becomes dramatically lighter.Through simulation experiment on water-dissolved methane,it had been proved that the flowing water could fractionate the

  3. Environmental forcing of terrestrial carbon isotope excursion amplification across five Eocene hyperthermals

    Science.gov (United States)

    Bowen, G. J.; Abels, H.

    2015-12-01

    Abrupt changes in the isotope composition of exogenic carbon pools accompany many major episodes of global change in the geologic record. The global expression of this change in substrates that reflect multiple carbon pools provides important evidence that many events reflect persistent, global redistribution of carbon between reduced and oxidized stocks. As the diversity of records documenting any event grows, however, discrepancies in the expression of carbon isotope change among substrates are almost always revealed. These differences in magnitude, pace, and pattern of change can complicate interpretations of global carbon redistribution, but under ideal circumstances can also provide additional information on changes in specific environmental and biogeochemical systems that accompanied the global events. Here we evaluate possible environmental influences on new terrestrial records of the negative carbon isotope excursions (CIEs) associated with multiple hyperthermals of the Early Eocene, which show a common pattern of amplified carbon isotope change in terrestrial paleosol carbonate records relative to that recorded in marine substrates. Scaling relationships between climate and carbon-cycle proxies suggest that that the climatic (temperature) impact of each event scaled proportionally with the magnitude of its marine CIE, likely implying that all events involved release of reduced carbon with a similar isotopic composition. Amplification of the terrestrial CIEs, however, does not scale with event magnitude, being proportionally less for the first, largest event (the PETM). We conduct a sensitivity test of a coupled plant-soil carbon isotope model to identify conditions that could account for the observed CIE scaling. At least two possibilities consistent with independent lines of evidence emerge: first, varying effects of pCO2 change on photosynthetic carbon isotope discrimination under changing background pCO2, and second, contrasting changes in regional

  4. Paleogene plants fractionated carbon isotopes similar to modern plants

    Science.gov (United States)

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

    2015-11-01

    The carbon isotope composition (δ13 C) of terrestrial plant biomarkers, such as leaf waxes and terpenoids, provides insights into past carbon cycling. The δ13 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 (Δleaf) 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 δ13 C of angiosperm biomarkers (triterpenoids and n-alkanes) and, abundance permitting, conifer biomarkers (diterpenoids). Leaf δ13 C values estimated from different angiosperms biomarkers were consistently 2‰ lower than leaf δ13 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 εlipid values were similar to those in living plants. From these biomarker-based δ13Cleaf values and independent records of atmospheric δ13 C values, we calculated Δleaf. These calculated Δleaf values were then compared to Δleaf values modeled by applying the effects that precipitation and major taxonomic group in living plants have on Δleaf values. Calculated and modeled Δleaf 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

  5. Transfer of carbon isotope in human and animal bodies

    International Nuclear Information System (INIS)

    For realistic estimation of internal dose due to 14C released from nuclear facilities, the one compartment model for 14C metabolism in the human body which ICRP recommends may be too simple to be applied, and precise information on metabolism of radioactive nuclides in the human body is essential. In this study, the exhalation rate of carbon from human and livestock animal bodies was investigated using stable carbon isotope 13C. A 13C amount of 200 mg was administered as 13C-labeled rice to 5 human subjects, and 13C ratios in expiration of the subjects were measured during 2 weeks after the administration. From 2 days prior to the administration to the end of the experiment, meals with a slightly controlled 13C ratio of carbon were offered to the subjects to reduce the fluctuation of background 13C ratio in their breath air. The averaged background 13C ratio in expiration among the subjects was -24.7±0.7 per mille before the ingestion of 13C enriched rice. The highest 13C ratio of 73.0±6.6 per mille was observed 350 min after the ingestion. In the temporal changes in 13C ratio in breath air, three components were observed to have decreasing half times of 3.8, 14.4 and 52.8 h, which may indicate the existence of three compartments in carbon metabolism in the human body. In addition, in order to investigate the transfer of 14C from plants to animal milk, which is one of the important pathways for the assessment of radiation dose due to radionuclides, an experiment to measure the excretion rate of carbon from goats which were given 13C labeled feed (1.174 13C atom%), as representative livestock ruminant, was carried out. The 13C ratio of milk was 1.191% when it reached a plateau, whereas the 13C ratio of serum continued to increase during the feeding period. (author)

  6. Nitrogen and carbon isotope variability in the green-algal lichen Xanthoria parietina and their implications on mycobiont-photobiont interactions.

    Science.gov (United States)

    Beck, Andreas; Mayr, Christoph

    2012-12-01

    Stable isotope patterns in lichens are known to vary largely, but effects of substrate on carbon and nitrogen stable isotope signatures of lichens were previously not investigated systematically. N and C contents and stable isotope (δ(15)N, δ(13)C) patterns have been measured in 92 lichen specimens of Xanthoria parietina from southern Bavaria growing on different substrates (bark and stone). Photobiont and mycobiont were isolated from selected populations and isotopically analyzed. Molecular investigations of the internal transcribed spacer of the nuclear ribosomal DNA (ITS nrDNA) region have been conducted on a subset of the specimens of X. parietina. Phylogenetic analysis showed no correlation between the symbionts X. parietina and Trebouxia decolorans and the substrate, isotope composition, or geographic origin. Instead specimens grown on organic substrate significantly differ in isotope values from those on minerogenic substrate. This study documents that the lichens growing on bark use additional or different N sources than the lichens growing on stone. δ(15)N variation of X. parietina apparently is controlled predominantly by the mass fraction of the mycobiont and its nitrogen isotope composition. In contrast with mycobionts, photobionts of X. parietina are much more (15)N-depleted and show less isotopic variability than mycobionts, probably indicating a mycobiont-independent nitrogen acquisition by uptake of atmospheric ammonia. PMID:23301178

  7. Carbon isotopes in the ocean model of the Community Earth System Model (CESM1

    Directory of Open Access Journals (Sweden)

    A. Jahn

    2015-08-01

    Full Text Available Carbon isotopes in the ocean are frequently used as paleoclimate 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 data set, 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 fewer 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, too sluggish ventilation of the deep Pacific Ocean.

  8. Carbon isotopes in the ocean model of the Community Earth System Model (CESM1)

    Science.gov (United States)

    Jahn, A.; Lindsay, K.; Giraud, X.; Gruber, N.; Otto-Bliesner, B. L.; Liu, Z.; Brady, E. C.

    2015-08-01

    Carbon isotopes in the ocean are frequently used as paleoclimate 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 data set, 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 fewer 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, too sluggish ventilation of the deep Pacific Ocean.

  9. Carbon isotopes in the ocean model of the Community Earth System Model (CESM1

    Directory of Open Access Journals (Sweden)

    A. Jahn

    2014-11-01

    Full Text Available 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.

  10. Observations of Carbon Isotopic Fractionation in Interstellar Formaldehyde

    Science.gov (United States)

    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

  11. Carbon allocation and carbon isotope fluxes in the plant-soil-atmosphere continuum: a review

    Directory of Open Access Journals (Sweden)

    N. Brüggemann

    2011-11-01

    Full Text Available The terrestrial carbon (C cycle has received increasing interest over the past few decades, however, there is still a lack of understanding of the fate of newly assimilated C allocated within plants and to the soil, stored within ecosystems and lost to the atmosphere. Stable carbon isotope studies can give novel insights into these issues. In this review we provide an overview of an emerging picture of plant-soil-atmosphere C fluxes, as based on C isotope studies, and identify processes determining related C isotope signatures. The first part of the review focuses on isotopic fractionation processes within plants during and after photosynthesis. The second major part elaborates on plant-internal and plant-rhizosphere C allocation patterns at different time scales (diel, seasonal, interannual, including the speed of C transfer and time lags in the coupling of assimilation and respiration, as well as the magnitude and controls of plant-soil C allocation and respiratory fluxes. Plant responses to changing environmental conditions, the functional relationship between the physiological and phenological status of plants and C transfer, and interactions between C, water and nutrient dynamics are discussed. The role of the C counterflow from the rhizosphere to the aboveground parts of the plants, e.g. via CO2 dissolved in the xylem water or as xylem-transported sugars, is highlighted. The third part is centered around belowground C turnover, focusing especially on above- and belowground litter inputs, soil organic matter formation and turnover, production and loss of dissolved organic C, soil respiration and CO2 fixation by soil microbes. Furthermore, plant controls on microbial communities and activity via exudates and litter production as well as microbial community effects on C mineralization are reviewed. A further part of the paper is dedicated to physical interactions between soil CO2 and the soil matrix, such as

  12. Combination of carbon isotope ratio with hydrogen isotope ratio determinations in sports drug testing.

    Science.gov (United States)

    Piper, Thomas; Emery, Caroline; Thomas, Andreas; Saugy, Martial; Thevis, Mario

    2013-06-01

    Carbon isotope ratio (CIR) analysis has been routinely and successfully applied to doping control analysis for many years to uncover the misuse of endogenous steroids such as testosterone. Over the years, several challenges and limitations of this approach became apparent, e.g., the influence of inadequate chromatographic separation on CIR values or the emergence of steroid preparations comprising identical CIRs as endogenous steroids. While the latter has been addressed recently by the implementation of hydrogen isotope ratios (HIR), an improved sample preparation for CIR avoiding co-eluting compounds is presented herein together with newly established reference values of those endogenous steroids being relevant for doping controls. From the fraction of glucuronidated steroids 5β-pregnane-3α,20α-diol, 5α-androst-16-en-3α-ol, 3α-Hydroxy-5β-androstane-11,17-dione, 3α-hydroxy-5α-androstan-17-one (ANDRO), 3α-hydroxy-5β-androstan-17-one (ETIO), 3β-hydroxy-androst-5-en-17-one (DHEA), 5α- and 5β-androstane-3α,17β-diol (5aDIOL and 5bDIOL), 17β-hydroxy-androst-4-en-3-one and 17α-hydroxy-androst-4-en-3-one were included. In addition, sulfate conjugates of ANDRO, ETIO, DHEA, 3β-hydroxy-5α-androstan-17-one plus 17α- and androst-5-ene-3β,17β-diol were considered and analyzed after acidic solvolysis. The results obtained for the reference population encompassing n = 67 males and females confirmed earlier findings regarding factors influencing endogenous CIR. Variations in sample preparation influenced CIR measurements especially for 5aDIOL and 5bDIOL, the most valuable steroidal analytes for the detection of testosterone misuse. Earlier investigations on the HIR of the same reference population enabled the evaluation of combined measurements of CIR and HIR and its usefulness regarding both steroid metabolism studies and doping control analysis. The combination of both stable isotopes would allow for lower reference limits providing the same statistical

  13. On the isotope ratio of hydrogen, oxygen, carbon, nitrogen, and sulfur in man

    International Nuclear Information System (INIS)

    Experimental investigations of the isotope ratio of hydrogen, oxygen, carbon, nitrogen and sulfur in urine of persons living at different locations show considerable variations. A distinct relation to the isotope ratio of the local drinking water has only been observed in the case of hydrogen. The variations are far from being within the experimental limits of error. Therefore, they are decisive in selecting the relative abundance of the labelling isotope in tracer experiments on human metabolism. (author)

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

    Science.gov (United States)

    Zobitz, J. M.; Keener, J. P.; Bowling, D. R.

    2004-12-01

    Quantifying and understanding the uncertainty in isotopic mixing relationships is critical to isotopic applications in carbon cycle studies at all spatial and temporal scales. Studies associated with the North American Carbon Program will depend on stable isotope approaches and quantification of isotopic uncertainty. An important application of isotopic mixing relationships is determination of the isotopic content of large-scale respiration (δ 13CR) via an inverse relationship (a Keeling plot) between atmospheric CO2 concentrations ([CO2]) and carbon isotope ratios of CO2 (δ 13C). Alternatively, a linear relationship between [CO2] and the product of [CO2] and δ 13C (a Miller/Tans plot) can also be applied. We used an extensive dataset from the Niwot Ridge Ameriflux Site of [CO2] and δ 13C in forest air to examine contrasting approaches to determine δ 13CR and its uncertainty. These included Keeling plots, Miller/Tans plots, Model I, and Model II regressions Our analysis confirms previous observations that increasing the range of measurements ([CO2] range) reduces the uncertainty associated with δ 13CR. For carbon isotope studies, uncertainty in the isotopic measurements has a greater effect on the uncertainty of δ 13CR than the uncertainty in [CO2]. Reducing the uncertainty of isotopic measurements reduces the uncertainty of δ 13CR even when the [CO2] range of samples is small (13CR. We also find for carbon isotope studies no inherent advantage to using either a Keeling or a Miller/Tans approach to determine δ 13CR.

  15. Radioactive Carbon Isotope Monitoring System Based on Cavity Ring-down Laser Spectroscopy for Decommissioning Process of Nuclear Facilities

    Science.gov (United States)

    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.

  16. [Effects of lipid extraction on stable carbon and nitrogen isotope analyses of Ommastrephes bartramii muscle].

    Science.gov (United States)

    Gong, Yi; Chen, Xin-Jun; Gao, Chun-Xia; Li, Yun-Kai

    2014-11-01

    Stable isotope analysis (SIA) has become an important tool to investigate diet shift, habitat use and trophic structure of animal population. Muscle is considered to be the most common tissue for SIA, however, lipid content in muscle causes a considerable bias to the interpretation of isotopic ratios of animals. Neon flying squid (Ommastrephes bartramii) is an important economic cephalopod of Chinese distant water fishery, and plays a major role in marine ecosystems. In this study, the effects of lipid extraction on stable isotope ratios of the muscles of 53 neon flying squids were investigated and the interference mechanism of lipid in SIA was clarified with the aim of contrasting the suitability of different lipid correction models of stable carbon isotope. Results showed that the stable carbon and nitrogen isotopic values of non-lipid extracted samples significantly increased after lipid extractions by 0.71 per thousand and 0.47 per thousand, respectively, which suggested that lipid extraction in cephalopod isotope study is needed prior to stable carbon isotope analysis but not recommended for stable nitrogen isotope analysis. The results could help remove the effects of lipid contents and standardize SIA muscle samples, thereby getting better understanding of the isotopic change of neon flying squids in the future. PMID:25898636

  17. Non-destructive measurement of carbonic anhydrase activity and the oxygen isotope composition of soil water

    Science.gov (United States)

    Jones, Sam; Sauze, Joana; Ogée, Jérôme; Wohl, Steven; Bosc, Alexandre; Wingate, Lisa

    2016-04-01

    Carbonic anhydrases are a group of metalloenzymes that catalyse the hydration of aqueous carbon dioxide (CO2). The expression of carbonic anhydrase by bacteria, archaea and eukarya has been linked to a variety of important biological processes including pH regulation, substrate supply and biomineralisation. As oxygen isotopes are exchanged between CO2 and water during hydration, the presence of carbonic anhydrase in plants and soil organisms also influences the oxygen isotope budget of atmospheric CO2. Leaf and soil water pools have distinct oxygen isotope compositions, owing to differences in pool sizes and evaporation rates, which are imparted on CO2during hydration. These differences in the isotopic signature of CO2 interacting with leaves and soil can be used to partition the contribution of photosynthesis and soil respiration to net terrestrial CO2 exchange. However, this relies on our knowledge of soil carbonic anhydrase activity and currently, the prevalence and function of these enzymes in soils is poorly understood. Isotopic approaches used to estimate soil carbonic anhydrase activity typically involve the inversion of models describing the oxygen isotope composition of CO2 fluxes to solve for the apparent, potentially catalysed, rate of oxygen exchange during hydration. This requires information about the composition of CO2 in isotopic equilibrium with soil water obtained from destructive, depth-resolved soil water sampling. This can represent a significant challenge in data collection given the considerable potential for spatial and temporal variability in the isotopic composition of soil water and limited a priori information with respect to the appropriate sampling resolution and depth. We investigated whether we could circumvent this requirement by constraining carbonic anhydrase activity and the composition of soil water in isotopic equilibrium with CO2 by solving simultaneously the mass balance for two soil CO2 steady states differing only in the

  18. Do stable carbon isotopes of brown coal woods record changes in Lower Miocene palaeoecology?

    NARCIS (Netherlands)

    Poole, I.J.; Dolezych, M.; Kool, J.; Burgh, J. van der; Bergen, P.F. van

    2006-01-01

    Stable carbon isotope ratios of fossil wood from the Miocene brown coal deposits in former East Germany are compared with palaeobotanical and sedimentological data to test the use of stable isotopes in determining palaeoenvironment. Significant differences in the chemical composition of samples from

  19. Spatial and Temporal Trends in Stable Carbon and Oxygen Isotope Ratios of Juvenile Winter Flounder

    Science.gov (United States)

    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. Carbon isotope systematics of individual hydrocarbons in hydrothermal petroleum from Escanaba Trough, northeastern Pacific Ocean.

    Science.gov (United States)

    Simoneit, B R; 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. PMID:11541391

  1. Soil drying effects on the carbon isotope composition of soil respiration

    Science.gov (United States)

    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...

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

    Science.gov (United States)

    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.

  3. Application of isotope techniques to carbonate rock aquifers: Some Indian examples

    International Nuclear Information System (INIS)

    Isotope hydrological investigations were carried out to study the origin of ground water and surface water-ground water interactions in two carbonate rock terrains - Jhamarkotra rock phosphate mine, Rajasthan and Amner river basin, Madhya Pradesh - situated in different settings

  4. Stable isotopes of carbon and nitrogen in suspended matter and sediments from the Godavari estuary

    Digital Repository Service at National Institute of Oceanography (India)

    Sarma, V.V.S.S.; Arya, J.; Subbaiah, Ch.V.; Naidu, S.A.; Gawade, L.; PraveenKumar, P.; Reddy, N.P.C.

    Spatial distribution of the carbon and nitrogen content and their isotopic enrichment in suspended matter and sediments were measured in the Godavari estuary to identify the sources and transformation mechanism of organic matter. Significant...

  5. The evolution of Carbon isotopes in calcite in the presence of cyanobacteria

    Science.gov (United States)

    Grimm, Christian; Mavromatis, Vasileios; Pokrovsky, Oleg S.; Oelkers, Eric H.

    2016-04-01

    Stable isotopic compositions in carbonates are widely used as indicators of environmental conditions prevailing during mineral formation. This reconstruction is substantially based on the assumption that there is no change in the mineral composition over geological time. However, recent experimental studies have shown that carbon and magnesium isotopes in hydrous Mg-carbonates undergo continuous re-equilibration with the ambient solution even after mineral precipitation stopped ([1] and [2], respectively). To verify whether this holds true for anhydrous Ca-bearing carbonates which readily form at earth's surface environments, a series of batch system calcite precipitation experiments were performed in the presence of actively growing cyanobacteria Synechococcus sp. The bacteria were grown at ambient temperature in a BG11 culture medium (SIGMA C3061) and continuous stirring, air-bubbling and illumination. Calcite precipitation was initiated by the addition of 8.5mM CaCl2 and 0-50 mM NaHCO3 or NaHCO3-Na2CO3 mixtures. The presence of cyanobacteria is on one hand promoting CaCO3 formation due to increasing pH resulting from photosynthesis. On the other hand, actively growing cyanobacteria drastically change carbon isotope signature of the aqueous fluid phase by preferably incorporating the lighter 12C isotope into biomass [1]. This study explores the effect of continuously changing carbon isotope compositions in dissolved inorganic carbon (DIC) on precipitated calcite which is in chemical equilibrium with the ambient fluid phase. [1] Mavromatis et al. (2015). The continuous re-equilibration of carbon isotope compositions of hydrous Mg-carbonates in the presence of cyanobacteria. Chem. Geol. 404, 41-51 [2] Mavromatis et al. (2012). Magnesium isotope fractionation during hydrous magnesium carbonate precipitation with and without cyanobacteria. Geochim. Cosmochim. Acta 76, 161-174

  6. Carbon isotopic record from Upper Devonian carbonates at Dongcun in Guilin, southern China, supporting the world-wide pattern of carbon isotope excursions during Frasnian-Famennian transition

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Two positive δ13C excursions are presented in records from the Frasnian-Famennian (F-F) marine carbonate sediments in Europe, America, Africa, and Australia, having been considered as a worldwide pattern, and attributed to enhanced organic carbon burial during the F-F biological mass extinction. However, this worldwide pattern has not been revealed from the well-deposited Late Devonian sequences in southern China. In this paper, a detailed investigation has been made on the Late Devonian section at Dongcun, Guilin, southern China to constrain perturbations in δ13C of carbonates in the F-F deposited sequence. The result from this section also indicates two positive δ13C excursions during the F-F transition. The first excursion with an amplitude of 1.5‰ occurred at the bottom of linguiformis Zone, later than the early excursion existing in the Late rhenana Zone of the Late Devonian profiles in other continents, especially, in central Europe. This difference has been expected to be a result as conodont Palmatolepis linguiformis occurred earlier in southern China than other sites. The second excursion with an amplitude of 2.1‰ is located at the F-F boundary, same as the records from other continents. This result strongly supports the view that two carbon isotope positive excursions during the F-F transition are common in carbonate sediments, resulting from worldwide increases of organic carbon burial intensity.

  7. Sulfur and carbon isotope biogeochemistry of a rewetted brackish fen

    Science.gov (United States)

    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 (δ2H, δ13C, δ18O, δ34S) 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

  8. Stable carbon isotope discrimination in the smut fungus Ustilago violacea

    International Nuclear Information System (INIS)

    Haploid strains 15.10, I.C429, and I.C2y and diploid strain JK2 of Ustilago Piolacea were grown on one or more of the following carbon sources: glucose, sucrose, maltose, inulin, starch, inositol, glycerol, casein, and yeast extract. The media, both before and after fungal growth, and the fungal cells were analyzed for 13C/12C content (δ13 values) using an isotope ratio mass spectrometer after combustion to CO2. In all cases, the used and unused media had identical δ13C values. Strain 15.10 had significantly less 13C than the media when grown on glucose, sucrose, maltose, and inositol; significantly more 13C when grown on inulin, starch, and glycerol; and no significant difference in δ13C values when grown on casein and yeast extract media. Other haploid strains responded similarly to 15.10. Diploid strain JK2 was also depleted in 13C when grown on glucose and enriched in 13C when grown on glycerol; however, JK2 was slightly depleted in 13C when grown on casein, whereas all the tested haploid strains were enriched in 13C

  9. Decoupling of carbon isotope records between organic matter and carbonate prior to the Toarcian Oceanic Anoxic Event (Early Jurassic)

    Science.gov (United States)

    Bodin, Stephane; Kothe, Tim; Krencker, Francois-Nicolas; Suan, Guillaume; Heimhofer, Ulrich; Immenhauser, Adrian

    2014-05-01

    Across the Pliensbachian-Toarcian boundary (P-To, Early Jurassic), ca. 1 Myr before the Toarcian Oceanic Anoxic Event (T-OAE), an initial negative carbon isotope excursion has been documented in western Tethys sedimentary rocks. In carbonate, its amplitude (2-3 permil) is similar to the subsequent excursion recorded at the onset of the T-OAE. Being also associated with a rapid warming event, the significance of this first carbon isotope shift, in terms of paleoenvironmental interpretation and triggering mechanism, remains however elusive. Taking advantage of expanded and rather continuous sections in the High Atlas of Morocco, several high-resolution, paired organic-inorganic carbon isotope records have been obtained across the Upper Pliensbachian - Lower Toarcian interval. At the onset of the T-OAE, an abrupt 1-2 permil negative shift is recorded in both organic and inorganic phases, succeeded by a relatively longer term 1-2 permil negative trend and a final slow return to pre-excursion conditions. In accordance with previous interpretations, this pattern indicates a perturbation of the entire exogenic carbon isotope reservoir at the onset of the T-OAE by the sudden release of isotopically light carbon into the atmosphere. By contrast, there is no negative shift in carbon isotopes for the P-To event recorded in bulk organic matter of Morocco. Given the strong dominance of terrestrial particles in the bulk organic matter fraction, this absence indicates that massive input of 12C-rich carbon into the atmosphere is not likely to have happened during the P-To event. A pronounced (2 permil) and abrupt negative shift in carbon isotope is however recorded in the bulk carbonate phase. We suggest that this decoupling between organic and inorganic phase is due to changes in the nature of the bulk carbonate phase. Indeed, the negative shift occurs at the lithological transition between Pliensbachian-lowermost Toarcian limestone-marl alternations and the Lower Toarcian marl

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

    Science.gov (United States)

    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 δ13C 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 δ13CDIC and δ13CCH4. 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 δ13CCH4 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 δ13CDIC 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

  11. Data acquisition and quantitative analysis of stable hydrogen isotope in liquid and gas in the liquid phase catalytic exchange process

    International Nuclear Information System (INIS)

    A pilot plant for the Liquid Phase Catalytic Exchange process was built and has been operating to test the hydrophobic catalyst developed to remove the tritium generated at the CANDU nuclear power plants. The methods of quantitative analysis of hydrogen stable isotope were compared. Infrared spectroscopy was used for the liquid samples, and gas chromatography with hydrogen carrier gas showed the best result for gas samples. Also, a data acquisition system was developed to record the operation parameters. This record was very useful to investigate the causes of the system trip

  12. The modeling of carbon isotope kinetics and its application to the evaluation of natural gas

    Institute of Scientific and Technical Information of China (English)

    Xianqing LI; Xianming XIAO; Yongchun TANG; Hui TIAN; Qiang ZHOU; Yunfeng YANG; Peng DONG; Yan WANG; Zhihong SONG

    2008-01-01

    The modeling of carbon isotope kinetics of natural gas is an issue driving pioneering research in the oil and gas geochemistry in China and internationally.Combined with the sedimentary burial history and basin geothermal history,the modeling of carbon isotope kinetics provides a new and effective means for the determination of the origin and accumulation history of natural gas pools.In this paper,we introduce the modeling of carbon isotope kinetics of natural gas formation and its applications to the assessment of natural gas maturity,the determination of the gas source,the history of gas accumulation,and the oil-gas ratio.It is shown that this approach is of great value for these applications.The carbon isotopic characteristics of natural gas are not only affected by the gas source and maturity of the source rock,but also are related to the accumulation condition and geothermal gradient in a basin.There are obvious differences in the characteristics of carbon isotope ratios between instantaneous gas and cumulative gas.Different basins have different kinetic models of carbon isotope fractionation,which depends on the gas source condition,the accumulation history and the sedimentary-tectonic history.Since the origin of natural gas in the superimposed basin in China is very complicated,and the natural gas pool is characterized by multiphase and variable gas-sources,this paper may provide a new perspective on the study and evaluation of natural gas.

  13. USE OF STABLE CARBON ISOTOPE RATIOS OF FATTY ACIDS TO EVALUATE MICROBIAL CARBON SOURCES IN TERRESTRIAL ENVIRONMENTS

    Science.gov (United States)

    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 ...

  14. Carbon isotopic evidence for microbial control of carbon supply to Orca Basin at the brine-seawater interface

    Directory of Open Access Journals (Sweden)

    S. R. Shah

    2012-12-01

    Full Text Available Orca Basin, an intraslope basin on the Texas–Louisiana continental slope, hosts a hypersaline, anoxic brine in its lowermost 200 m. This brine contains a large reservoir of reduced and aged carbon, and appears to be stable at decadal time scales: concentrations and the isotopic composition of dissolved inorganic (DIC and organic carbon (DOC are similar to previous reports. Both DIC and DOC are more "aged" within the brine pool than in overlying water, and the isotopic contrast between brine carbon and seawater carbon is much greater for DIC than DOC. While the stable carbon isotopic composition of brine DIC points towards a combination of methane and organic carbon re-mineralization as its source, radiocarbon and box model results point to the brine interface as the major source region for DIC with oxidation of methane diffusing upwards from sediments supplying only limited DIC to the brine. This conclusion is consistent with previous studies reporting microbial activity focused at the seawater-brine interface. Isotopic similarities between DIC and DOC suggest a different relationship between these two carbon reservoirs than is typically observed in deep ocean basins. Radiocarbon values implicate the seawater-brine interface region as the likely source region for DOC as well as DIC. Further investigations of the seawater-brine interface are needed to advance our understanding of the specific microbial processes contributing to dissolved carbon storage in the Orca Basin brine.

  15. Carbon mass-balance modeling and carbon isotope exchange processes in the Curonian Lagoon

    Science.gov (United States)

    Barisevičiūtė, Rūta; Žilius, Mindaugas; Ertürk, Ali; Petkuvienė, Jolita

    2016-04-01

    The Curonian lagoon one of the largest coastal lagoons in Europe is located in the southeastern part of the Baltic Sea and lies along the Baltic coast of Lithuania and the Kaliningrad region of Russia. It is influenced by a discharge of the Nemunas and other smaller rivers and saline water of the Baltic Sea. The narrow (width 0.4 km, deep 8-14 m) Klaipėda Strait is the only way for fresh water run-off and brackish water intrusions. This research is focused on carbon isotope fractionations related with air - water exchange, primary production and organic carbon sedimentation, mineralization and uptake from both marine and terrestrial sources.

  16. Analysis of the site-specific carbon isotope composition of propane by gas source isotope ratio mass spectrometer

    Science.gov (United States)

    Piasecki, Alison; Sessions, Alex; Lawson, Michael; Ferreira, A. A.; Neto, E. V. Santos; Eiler, John M.

    2016-09-01

    Site-specific isotope ratio measurements potentially provide valuable information about the formation and degradation of complex molecules-information that is lost in conventional bulk isotopic measurements. Here we discuss the background and possible applications of such measurements, and present a technique for studying the site-specific carbon isotope composition of propane at natural abundance based on mass spectrometric analysis of the intact propane molecule and its fragment ions. We demonstrate the feasibility of this approach through measurements of mixtures of natural propane and propane synthesized with site-specific 13C enrichment, and we document the limits of precision of our technique. We show that mass balance calculations of the bulk δ13C of propane based on our site-specific measurements is generally consistent with independent constraints on bulk δ13C. We further demonstrate the accuracy of the technique, and illustrate one of its simpler applications by documenting the site-specific carbon isotope signature associated with gas phase diffusion of propane, confirming that our measurements conform to the predictions of the kinetic theory of gases. This method can be applied to propane samples of moderate size (tens of micromoles) isolated from natural gases. Thus, it provides a means of studying the site-specific stable isotope systematics of propane at natural isotope abundances on sample sizes that are readily recovered from many natural environments. This method may also serve as a model for future techniques that apply high-resolution mass spectrometry to study the site-specific isotopic distributions of larger organic molecules, with potential applications to biosynthesis, forensics and other geochemical subjects.

  17. Carbon acquisition by Cyanobacteria: Mechanisms, Comparative Genomics and Evolution

    Energy Technology Data Exchange (ETDEWEB)

    Kaplan, Aaron; Hagemann, Martin; Bauwe, Hermann; Kahlon, Shira; Ogawa, Teruo

    2008-01-01

    In this chapter we mainly focus on the mechanisms of inorganic carbon uptake, photorespiration, and the regulation between the metabolic fluxes involved in photoautotrophic, photomixotrophic and heterotrophic growth. We identify the genes involved, their regulation and phylogeny. Living in an environment where the CO₂ concentration is considerably lower than required to saturate their carboxylating enzyme, ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco), cyanobacteria acquired the CO₂ concentrating mechanism (CCM) that enables them to accumulate CO₂ at the carboxylation site. All the cyanobacteria examined to date are able to fix CO₂ into carbohydrates. However, in addition to variance in the range of physical growth conditions, cyanobacteria also vary substantially in their ability to consume organic carbon from their surroundings. Many strains are obligate photoautotrophs where the sole carbon source is CO₂, while others are able to perform photomixotrophic or even heterotrophic growth using a wide variety of organic substances (c.f. Rippka et al., 1979; Stal and Moezelaar, 1997b). Cyanobacteria constitute a unique case where the anabolic and catabolic carbohydrate metabolisms function in the same cellular compartment. In addition, the photosynthetic and respiratory electron transport pathways share components in the thylakoid membranes. Despite its importance to our understanding of cyanobacterial metabolism, little is known about the mechanisms involved in the shifts between photoautotrophic, heterotrophic and photomixotrophic modes of growth, and their regulation; between the different pathways of carbohydrate breakdown- glycolysis, fermentation, the oxidative pentose phosphate, the Krebs cycle and the photorespiratory pathways. In this chapter we shall briefly focus on recent advances in our understanding of the CCM and carbon metabolism in cyanobacteria.

  18. Carbon Acquisition by Cyanobacteria: Mechanisms, Comparative Genomics, and Evolution

    Energy Technology Data Exchange (ETDEWEB)

    Kaplan, Aaron; Hagemann, Martin; Bauwe, Hermann; Kahlon, Shira; Ogawa, Teruo

    2008-01-01

    In this chapter we mainly focus on the mechanisms of inorganic carbon uptake, photorespiration, and the regulation between the metabolic fluxes involved in photoautotrophic, photomixotrophic and heterotrophic growth. We identify the genes involved, their regulation and phylogeny. Living in an environment where the CO₂ concentration is considerably lower than required to saturate their carboxylating enzyme, ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco), cyanobacteria acquired the CO₂ concentrating mechanism (CCM) that enables them to accumulate CO₂ at the carboxylation site. All the cyanobacteria examined to date are able to fix CO₂ into carbohydrates. However, in addition to variance in the range of physical growth conditions, cyanobacteria also vary substantially in their ability to consume organic carbon from their surroundings. Many strains are obligate photoautotrophs where the sole carbon source is CO₂, while others are able to perform photomixotrophic or even heterotrophic growth using a wide variety of organic substances (c.f. Rippka et al., 1979; Stal and Moezelaar, 1997b). Cyanobacteria constitute a unique case where the anabolic and catabolic carbohydrate metabolisms function in the same cellular compartment. In addition, the photosynthetic and respiratory electron transport pathways share components in the thylakoid membranes. Despite its importance to our understanding of cyanobacterial metabolism, little is known about the mechanisms involved in the shifts between photoautotrophic, heterotrophic and photomixotrophic modes of growth, and their regulation; between the different pathways of carbohydrate breakdown- glycolysis, fermentation, the oxidative pentose phosphate, the Krebs cycle and the photorespiratory pathways. In this chapter we shall briefly focus on recent advances in our understanding of the CCM and carbon metabolism in cyanobacteria.

  19. Isotopic composition of carbon and nitrogen in ureilitic fragments of the Almahata Sitta meteorite

    OpenAIRE

    Downes, Hilary; Abernethy, F.A.J.; Smith, C.L.; Ross, A. J.; Verchovsky, A. B.; Grady, M. M.; Jenniskens, P.; Shaddad, M.H.

    2015-01-01

    This study characterizes carbon and nitrogen abundances and isotopic compositions in ureilitic fragments of Almahata Sitta. Ureilites are carbon-rich (containing up to 7 wt% C) and were formed early in solar system history, thus the origin of carbon in ureilites has significance for the origin of solar system carbon. These samples were collected soon after they fell, so they are among the freshest ureilite samples available and were analyzed using stepped combustion mass spectrometry. They co...

  20. Carbon and Oxygen Isotopic Ratios for Nearby Miras

    Science.gov (United States)

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

    2016-07-01

    Carbon and oxygen isotopic ratios are reported for a sample of 46 Mira and SRa-type variable asymptotic giant branch (AGB) stars. Vibration-rotation first and second-overtone CO lines in 1.5-2.5 μm spectra were measured to derive isotopic ratios for 12C/13C, 16O/17O, and 16O/18O. Comparisons with previous measurements for individual stars and with various samples of evolved stars, as available in the extant literature, are discussed. Models for solar composition AGB stars of different initial masses are used to interpret our results. We find that the majority of M-stars have main sequence masses ≤2 M ⊙ and have not experienced sizable third dredge-up (TDU) episodes. The progenitors of the four S-type stars in our sample are slightly more massive. Of the six C-stars in the sample three have clear evidence relating their origin to the occurrence of TDU. Comparisons with O-rich presolar grains from AGB stars that lived before the formation of the solar system reveal variations in the interstellar medium chemical composition. The present generation of low-mass AGB stars, as represented by our sample of long period variables (LPVs), shows a large spread of 16O/17O ratios, similar to that of group 1 presolar grains and in agreement with theoretical expectations for the composition of mass 1.2-2 M ⊙ stars after the first dredge-up. In contrast, the 16O/18O ratios of present-day LPVs are definitely smaller than those of group 1 grains. This is most probably a consequence of the the decrease with time of the 16O/18O ratio in the interstellar medium due to the chemical evolution of the Milky Way. One star in our sample has an O composition similar to that of group 2 presolar grains originating in an AGB star undergoing extra-mixing. This may indicate that the extra-mixing process is hampered at high metallicity, or, equivalently, favored at low metallicity. Similarly to O-rich grains, no star in our sample shows evidence of hot bottom burning, which is expected for

  1. Carbon and Oxygen Isotopic Ratios for Nearby Miras

    Science.gov (United States)

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

    2016-07-01

    Carbon and oxygen isotopic ratios are reported for a sample of 46 Mira and SRa-type variable asymptotic giant branch (AGB) stars. Vibration–rotation first and second-overtone CO lines in 1.5–2.5 μm spectra were measured to derive isotopic ratios for 12C/13C, 16O/17O, and 16O/18O. Comparisons with previous measurements for individual stars and with various samples of evolved stars, as available in the extant literature, are discussed. Models for solar composition AGB stars of different initial masses are used to interpret our results. We find that the majority of M-stars have main sequence masses ≤2 M ⊙ and have not experienced sizable third dredge-up (TDU) episodes. The progenitors of the four S-type stars in our sample are slightly more massive. Of the six C-stars in the sample three have clear evidence relating their origin to the occurrence of TDU. Comparisons with O-rich presolar grains from AGB stars that lived before the formation of the solar system reveal variations in the interstellar medium chemical composition. The present generation of low-mass AGB stars, as represented by our sample of long period variables (LPVs), shows a large spread of 16O/17O ratios, similar to that of group 1 presolar grains and in agreement with theoretical expectations for the composition of mass 1.2–2 M ⊙ stars after the first dredge-up. In contrast, the 16O/18O ratios of present-day LPVs are definitely smaller than those of group 1 grains. This is most probably a consequence of the the decrease with time of the 16O/18O ratio in the interstellar medium due to the chemical evolution of the Milky Way. One star in our sample has an O composition similar to that of group 2 presolar grains originating in an AGB star undergoing extra-mixing. This may indicate that the extra-mixing process is hampered at high metallicity, or, equivalently, favored at low metallicity. Similarly to O-rich grains, no star in our sample shows evidence of hot bottom burning, which is expected

  2. An analytical system for stable isotope analysis on carbon monoxide using continuous-flow isotope-ratio mass spectrometry

    OpenAIRE

    S. L. Pathirana; C. van der Veen; Popa, M. E.; T. Röckmann

    2015-01-01

    A fully automated system for the determination of δ13C and δ18O in atmospheric CO has been developed. CO is extracted from an air sample and converted into carbon dioxide (CO2) using the Schütze reagent. The isotopic composition is determined with an isotope-ratio mass spectrometer (IRMS) technique. The entire system is continuously flushed with high-purity helium (He), the carrier gas. The blank signal of the Schütze reagent is ~ 4 nmol mol−1, or 1–3 % of the typical sam...

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

    Science.gov (United States)

    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 δ13C, δ18O, and δ17O from CO2 at natural abundance (100-3000 ppm). The laboratory accuracy is ±1.2 ppm (1σ) in CO2 from 370-1000 ppm, with a long-term (1000 s) precision of ±0.012 ppm. The long-term precision for both δ13C and δ18O is 0.04 ‰, and for δ17O 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

  4. Stable Isotope Measurements of Carbon Dioxide, Methane, and Hydrogen Sulfide Gas Using Frequency Modulation Spectroscopy

    Science.gov (United States)

    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.

  5. Carbon Isotope Composition of Carbohydrates and Polyols in Leaf and Phloem Sap of Phaseolus vulgaris L. Influences Predictions of Plant Water Use Efficiency.

    Science.gov (United States)

    Smith, Millicent; Wild, Birgit; Richter, Andreas; Simonin, Kevin; Merchant, Andrew

    2016-08-01

    The use of carbon isotope abundance (δ(13)C) to assess plant carbon acquisition and water use has significant potential for use in crop management and plant improvement programs. Utilizing Phaseolus vulgaris L. as a model system, this study demonstrates the occurrence and sensitivity of carbon isotope fractionation during the onset of abiotic stresses between leaf and phloem carbon pools. In addition to gas exchange data, compound-specific measures of carbon isotope abundance and concentrations of soluble components of phloem sap were compared with major carbohydrate and sugar alcohol pools in leaf tissue. Differences in both δ(13)C and concentration of metabolites were found in leaf and phloem tissues, the magnitude of which responded to changing environmental conditions. These changes have inplications for the modeling of leaf-level gas exchange based upon δ(13)C natural abundance. Estimates of δ(13)C of low molecular weight carbohydrates and polyols increased the precision of predictions of water use efficiency compared with those based on bulk soluble carbon. The use of this technique requires consideration of the dynamics of the δ(13)C pool under investigation. Understanding the dynamics of changes in δ(13)C during movement and incorporation into heterotrophic tissues is vital for the continued development of tools that provide information on plant physiological performance relating to water use. PMID:27335348

  6. The impact of recycling of organic carbon on the stable carbon isotopic composition of dissolved inorganic carbon in a stratified marine system (Kyllaren fjord, Norway)

    NARCIS (Netherlands)

    Breugel, Y. van; Schouten, S.; Paetzel, M.; Nordeide, R.; Sinninghe Damsté, J.S.

    2005-01-01

    A negative carbon isotope shift in sedimentary organic carbon deposited in stratified marine and lacustrine systems has often been inferred to be a consequence of the process of recycling of respired and, therefore, 13C-depleted, dissolved inorganic carbon (DIC) formed from mineralization of descend

  7. Effects of inorganic anions on carbon isotope fractionation during Fenton-like degradation of trichloroethene.

    Science.gov (United States)

    Liu, Yunde; Zhou, Aiguo; Gan, Yiqun; Li, Xiaoqian

    2016-05-01

    Understanding the magnitude and variability in isotope fractionation with respect to specific processes is crucial to the application of stable isotopic analysis as a tool to infer and quantify transformation processes. The variability of carbon isotope fractionation during Fenton-like degradation of trichloroethene (TCE) in the presence of different inorganic ions (nitrate, sulfate, and chloride), was investigated to evaluate the potential effects of inorganic anions on carbon isotope enrichment factor (ε value). A comparison of ε values obtained in deionized water, nitrate solution, and sulfate solution demonstrated that the ε values were identical and not affected by the presence of nitrate and sulfate. In the presence of chloride, however, the ε values (ranging from -6.3±0.8 to 10±1.3‰) were variable and depended on the chloride concentration, indicating that chloride could significantly affect carbon isotope fractionation during Fenton-like degradation of TCE. Thus, caution should be exercised in selecting appropriate ε values for the field application of stable isotope analysis, as various chloride concentrations may be present due to naturally present or introduced with pH adjustment and iron salts during Fenton-like remediation. Furthermore, the effects of chloride on carbon isotope fractionation may be able to provide new insights about reaction mechanisms of Fenton-like processes. PMID:26835895

  8. Carbon and hydrogen isotopic effects of stomatal density in Arabidopsis thaliana

    Science.gov (United States)

    Lee, Hyejung; Feakins, Sarah J.; Sternberg, Leonel da S. L.

    2016-04-01

    Stomata are key gateways mediating carbon uptake and water loss from plants. Varied stomatal densities in fossil leaves raise the possibility that isotope effects associated with the openness of exchange may have mediated plant wax biomarker isotopic proxies for paleovegetation and paleoclimate in the geological record. Here we use Arabidopsis thaliana, a widely used model organism, to provide the first controlled tests of stomatal density on carbon and hydrogen isotopic compositions of cuticular waxes. Laboratory grown wildtype and mutants with suppressed and overexpressed stomatal densities allow us to directly test the isotope effects of stomatal densities independent of most other environmental or biological variables. Hydrogen isotope (D/H) measurements of both plant waters and plant wax n-alkanes allow us to directly constrain the isotopic effects of leaf water isotopic enrichment via transpiration and biosynthetic fractionations, which together determine the net fractionation between irrigation water and n-alkane hydrogen isotopic composition. We also measure carbon isotopic fractionations of n-alkanes and bulk leaf tissue associated with different stomatal densities. We find offsets of +15‰ for δD and -3‰ for δ13C for the overexpressed mutant compared to the suppressed mutant. Since the range of stomatal densities expressed is comparable to that found in extant plants and the Cenozoic fossil record, the results allow us to consider the magnitude of isotope effects that may be incurred by these plant adaptive responses. This study highlights the potential of genetic mutants to isolate individual isotope effects and add to our fundamental understanding of how genetics and physiology influence plant biochemicals including plant wax biomarkers.

  9. Zinc isotope evidence for a large-scale carbonated mantle beneath eastern China

    Science.gov (United States)

    Liu, Sheng-Ao; Wang, Ze-Zhou; Li, Shu-Guang; Huang, Jian; Yang, Wei

    2016-06-01

    A large set of zinc (Zn) stable isotope data for continental basalts from eastern China were reported to investigate the application of Zn isotopes as a new tracer of deep carbonate cycling. All of the basalts with ages of 120 Ma basalts from eastern China (0.27 ± 0.06‰; 2sd). Given that Zn isotope fractionation during magmatic differentiation is limited (≤0.1‰), the elevated δ66Zn values reflect the involvement of isotopically heavy crustal materials (e.g., carbonates with an average δ66Zn of ∼0.91‰) in the mantle sources. SiO2 contents of the recycled Mg (Zn)-rich carbonates in the mantle beneath eastern China since the Late Mesozoic. Since Zn is a trace element in the mantle and Zn isotopic compositions of marine carbonates and the mantle differ markedly, we highlight Zn isotopes as a new and useful tool of tracing deep carbonate cycling in the Earth's mantle.

  10. Stable Isotopic Evidence for a Pedogenic Origin of Carbonates in Trench 14 near Yucca Mountain, Nevada.

    Science.gov (United States)

    Quade, J; Cerling, T E

    1990-12-14

    Layered carbonate and silica encrust fault fractures exposed in Trench 14 near Yucca Mountain, site of the proposed high-level nuclear waste repository in southern Nevada. Comparison of the stable carbon and oxygen isotopic compositions of the fracture carbonates with those of modern soil carbonates in the area shows that the fracture carbonates are pedogenic in origin and that they likely formed in the presence of vegetation and rainfall typical of a glacial climate. Their isotopic composition differs markedly from that of carbonate associated with nearby springs. The regional water table therefore remained below the level of Trench 14 during the time that the carbonates and silica precipitated, a period probably covering parts of at least the last 300,000 years. PMID:17818282

  11. Oxygen isotopic constraints on the genesis of carbonates from Martian meteorite ALH84001

    Science.gov (United States)

    Leshin, Laurie A.; McKeegan, Kevin D.; Harvey, Ralph P.

    1997-03-01

    With a crystallization age of 4.5 Ga, ALH84001 is unique among the Martian meteorites. It is also the only Martian meteorite that contains an appreciable amount of carbonate, and significantly, this carbonate occurs without associated secondary hydrated minerals. Moreover, McKay et al. (1996) have suggested that ALH84001 contains evidence of past Martian life in the form of nanofossils, biogenic minerals, and polycyclic aromatic hydrocarbons. The presence of carbonate in ALH84001 is especially significant. The early Martian environment is thought to have been more hospitable to life than todays cold, dry climate. In order to better assess the true delta-O-18 values, as well as the isotopic diversity and complexity of the ALH84001 carbonates, direct measurements of the oxygen and carbon isotopic compositions of individual carbonate phases are needed. Here we report in situ analyses of delta-O-18 values in carbonates from two polished thin sections of ALH84001.

  12. Carbon Stable Isotopes as Indicators of Coastal Eutrophication

    Science.gov (United States)

    Coastal ecologists and managers have frequently used nitrogen stable isotopes (δ15N) to trace and monitor anthropogenic nitrogen (N) in coastal ecosystems. However, the interpretation of δ15N data can often be challenging, if not confounding, as the isotope values fractionate su...

  13. Carbon isotope fractionation of amino acids in fish muscle reflects biosynthesis and isotopic routing from dietary protein.

    Science.gov (United States)

    McMahon, Kelton W; Fogel, Marilyn L; Elsdon, Travis S; Thorrold, Simon R

    2010-09-01

    1. Analysis of stable carbon isotopes is a valuable tool for studies of diet, habitat use and migration. However, significant variability in the degree of trophic fractionation (Delta(13)C(C-D)) between consumer (C) and diet (D) has highlighted our lack of understanding of the biochemical and physiological underpinnings of stable isotope ratios in tissues. 2. An opportunity now exists to increase the specificity of dietary studies by analyzing the delta(13)C values of amino acids (AAs). Common mummichogs (Fundulus heteroclitus, Linnaeus 1766) were reared on four isotopically distinct diets to examine individual AA Delta(13)C(C-D) variability in fish muscle. 3. Modest bulk tissue Delta(13)C(C-D) values reflected relatively large trophic fractionation for many non-essential AAs and little to no fractionation for all essential AAs. 4. Essential AA delta(13)C values were not significantly different between diet and consumer (Delta(13)C(C-D) = 0.0 +/- 0.4 per thousand), making them ideal tracers of carbon sources at the base of the food web. Stable isotope analysis of muscle essential AAs provides a promising tool for dietary reconstruction and identifying baseline delta(13)C values to track animal movement through isotopically distinct food webs. 5. Non-essential AA Delta(13)C(C-D) values showed evidence of both de novo biosynthesis and direct isotopic routing from dietary protein. We attributed patterns in Delta(13)C(C-D) to variability in protein content and AA composition of the diet as well as differential utilization of dietary constituents contributing to the bulk carbon pool. This variability illustrates the complicated nature of metabolism and suggests caution must be taken with the assumptions used to interpret bulk stable isotope data in dietary studies. 6. Our study is the first to investigate the expression of AA Delta(13)C(C-D) values for a marine vertebrate and should provide for significant refinements in studies of diet, habitat use and migration using

  14. Carbon Isotopic tests on the Origins of the Shuram Anomaly from the San Juan Fm., Peru

    Science.gov (United States)

    Hodgin, E. B.

    2015-12-01

    Carbon isotope anomalies are associated with perturbations to the carbon cycle that offer insight into the geochemical evolution of the Earth. The largest Carbon isotope anomaly in earth history is the Shuram, which remains poorly understood in spite of being linked to the oxygenation of earth, the rise of metazoans, and a complete reorganization of the carbon cycle. From a basin transect of the carbonate-dominated San Juan Formation in southern Peru, we present evidence for the first clear example of the Shuram isotope anomaly in South America. Unique to this succession are ~140 meters of organic-rich black shale within the anomaly, containing as much as 4% TOC. Preliminary data from the organic-rich black shales of the San Juan Fm. confirm that δ13Corg is relatively invariant and does not covary with δ13Ccarb. These observations are consistent with other Shuram sections and support various models: an exogenous carbon source, an enlarged dissolved organic carbon pool, as well as authigenic carbonate production in organic-rich anoxic sediments. Critical tests of these models have been complicated by a paucity of organics in Shuram facies worldwide. Further analyses of the robust organics from the Shuram facies of the San Juan Fm. therefore hold promise in shedding light on the origin of the Shuram isotope anomaly and critical earth history events to which it has been linked.

  15. Canopy-scale kinetic fractionation of atmospheric carbon dioxide and water vapour isotopes

    Science.gov (United States)

    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...

  16. Analysis of carbon isotope in phytoliths from C3 and C4 plants and modern soils

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The analysis of carbon isotope in phytoliths from modern plants and surface soils in China shows that the values of carbon isotope are consistent with those from C3 and C4 plants,and the processes of photosynthesis of the original plants can be clearly identified by carbon isotope in phytoliths.The value of carbon isotope varied from -23.8‰ to -28‰,with the maximum distributed in the latitude zone from 34° N to 40° N in North China and East China areas,and the minimum in the Northeast China and South China regions.The values of carbon of phytoliths tend to increase from low to high and then reduce to low value again as the latitude increases.In the same latitude zone,the carbon isotope in phytoliths from grassland soil under the trees is obviously lower than that from grassland soil without any trees with the difference of 1‰-2‰.

  17. Significance of Carbon Isotopes in Carbonate Sequence Stratigraphy—As Exemplified by the Permian System in Southwest China

    Institute of Scientific and Technical Information of China (English)

    覃建雄; 杨作升; 等

    1999-01-01

    Based on the research on sequence stratigraphy of the Permian in Southwest China,in conjunction with the carbon isotope data from the typical sections at Ganluo,Sichuan and Tianlin and Masan,Guangxi,the authors suggest that the genetic framework and internal architicture of different sequences possess quite different carbon isotopic characteristics.Therefore ,the following problems can be solved in terms of carbon isotopic values,evolutionary curve patterns and structures of carbonate sequences:(1) to determe the nature of sequence boundary surface and related geological events;(2) to recognize various kinds of sedimentary system tracts;(3) to discuss the internal architicture and genetic framework of the sequences and their evolution;(4) to subdivide and correlate sedimentary sequences on a regional or global scale; and (5)to enhance the resolution of sequence stratigraphic analysis.Stable carbon isotopes have proved themselves to be valid in sequence stratigraphic studies of carbonate rocks,as demonstrated by our results presented in this paper.

  18. Seasonal variation in kangaroo tooth enamel oxygen and carbon isotopes in southern Australia

    Science.gov (United States)

    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. δ13C and δ18O 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.

  19. Trophic ecology of small yellow croaker (Larimichthys polyactis Bleeker): stable carbon and nitrogen isotope evidence

    Institute of Scientific and Technical Information of China (English)

    JI Weiwei; CHEN Xuezhong; JIANG Yazhou; LI Shengfa

    2011-01-01

    The trophic ecology of the small yellow croaker (Larimichthys polyactis) was studied using stable isotope analyses.Samples were collected from July to September 2009 and 34 individuals from eight sites were examined for stable carbon and nitrogen isotopes.Stable carbon isotope ratios (δ13C)ranged from -20.67 to -15.43,while stable nitrogen isotope ratios (δ15N) ranged 9.18-12.23.The relationship between δ13C and δ15N suggested high resource partitioning in the sampling area.Significant differences in stable isotope values among the eight sampling sites may be linked to environmental diversities involving various physical processes (such as ocean current,wind and tide) and different carbon sources.Furthermore,the stable isotope ratios may also explain the ontogenetic variability in diet and feeding,because δ13C and δ15N varied significantly with increasing body size.The findings are consistent with other studies on diet analyses in small yellow croaker.It was also demonstrated that stable isotope analysis could be used to estimate the trophic characters of small yellow croaker in feeding patterns and migrating habits.

  20. Carbon isotope anomaly in the major plant C1 pool and its global biogeochemical implications

    Directory of Open Access Journals (Sweden)

    J. T. G. Hamilton

    2004-08-01

    Full Text Available We report that the most abundant C1 units of terrestrial plants, the methoxyl groups of pectin and lignin, have a unique carbon isotope signature exceptionally depleted in 13C. Plant-derived C1 volatile organic compounds (VOCs are also anomalously depleted in 13C compared with Cn+1 VOCs. The results confirm that the plant methoxyl pool is the predominant source of biospheric C1 compounds of plant origin such as methanol, chloromethane and bromomethane. Furthermore this pool, comprising ca. 2.5% of carbon in plant biomass, represents an important substrate for methanogenesis and could be a significant source of isotopically light methane entering the atmosphere. Our findings have significant implications for the use of carbon isotope ratios in elucidation of global carbon cycling. Moreover methoxyl groups could act as markers for biological activity in organic matter of terrestrial and extraterrestrial origin.

  1. Carbon isotope anomaly in the major plant C1 pool and its global biogeochemical implications

    Directory of Open Access Journals (Sweden)

    F. Keppler

    2004-01-01

    Full Text Available We report that the most abundant C1 units of terrestrial plants, the methoxyl groups of pectin and lignin, have a unique carbon isotope signature exceptionally depleted in 13C. Plant-derived C1 volatile organic compounds (VOCs are also anomalously depleted in 13C compared with Cn+1 VOCs. The results confirm that the plant methoxyl pool is the predominant source of biospheric C1 compounds of plant origin such as methanol, chloromethane and bromomethane. Furthermore this pool, comprising ca 2.5% of carbon in plant biomass, could be an important substrate for methanogenesis and thus be envisaged as a possible source of isotopically light methane entering the atmosphere. Our findings have significant implications for the use of carbon isotope ratios in elucidation of global carbon cycling. Moreover methoxyl groups could act as markers for biological activity in organic matter of terrestrial and extraterrestrial origin.

  2. Organic Carbon Isotope Geochemistry of the Neoproterozoic Doushantuo Formation, South China

    Institute of Scientific and Technical Information of China (English)

    GUO Qingjun; LIU Congqiang; Harald STRAUSS; Tatiana GOLDBERG; ZHU Maoyan; PI Daohui; WANG Jian

    2006-01-01

    The Neoproterozoic Doushantuo Formation on the Yangtze Platform, South China,documents a sedimentary succession with different sedimentary facies from carbonate platform to slope and to deep sea basin, and hosts one of the world-class phosphorite deposits. In these strata,exquisitely preserved fossils have been discovered: the Weng'an biota. This study presents carbon isotope geochemistry which is associated paired carbonate and organic matter from the Weng'an section of a carbonate platform (shelf of the Yangtze Platform, Guizhou Province) from the Songtao section and Nanming section of a transition belt (slope of the Yangtze Platform, Guizhou Province) and from the Yanwutan section (basin area of the Yangtze Platform, Hunan Province). Environmental variations and bio-events on the Yangtze Platform during the Late Neoproterozoic and their causal relationship are discussed. Negative carbon isotope values for carbonate and organic carbon (mean δ13Corg = -35.0%) from the uppermost Nantuo Formation are followed by an overall increase in δ13C up-section. Carbon isotope values vary between -9.9% and 3.6% for carbonate and between -35.6% and -21.5% for organic carbon, respectively. Heavier δ13Ccarb values suggest an increase in organic carbon burial, possibly related to increasing productivity (such as the Weng'an biota). The δ13C values of the sediments from the Doushantuo Formation decreased from the platform via the slope to basin,reflecting a reduced environment with minor dissolved inorganic carbon possibly due to a lower primary productivity. It is deduced that the classical upwelling process, the stratification structure and the hydrothermal eruption are principally important mechanisms to interpret the carbon isotopic compositions of the sediments from the Doushantuo Formation.

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

    Science.gov (United States)

    Hippler, Dorothee; Buhl, Dieter; Witbaard, Rob; Richter, Detlev K.; Immenhauser, Adrian

    2009-10-01

    This study presents magnesium stable-isotope compositions of various biogenic carbonates of several marine calcifying organisms and an algae species, seawater samples collected from the western Dutch Wadden Sea, and reference materials. The aim of this study is to explore the influence of mineralogy, taxonomy and environmental factors (e.g., seawater isotopic composition, temperature, salinity) on magnesium-isotopic (δ 26Mg) ratios of skeletal carbonates. Using high-precision multi-collector inductively coupled plasma mass spectrometry, we observed that the magnesium-isotopic composition of seawater from the semi-enclosed Dutch Wadden Sea is identical to that of open marine seawater. We further found that a considerable component of the observed variability in δ 26Mg values of marine skeletal carbonates can be attributed to differences in mineralogy. Furthermore, magnesium-isotope fractionation is species-dependent, with all skeletal carbonates being isotopically lighter than seawater. While δ 26Mg values of skeletal aragonite and high-magnesium calcite of coralline red algae indicate the absence or negligibility of metabolic influences, the δ 26Mg values of echinoids, brachiopods and bivalves likely result from a taxon-specific level of control on Mg-isotope incorporation during biocalcification. Moreover, no resolvable salinity and temperature effect were observed for coralline red algae and echinoids. In contrast, Mg-isotope data of bivalves yield ambiguous results, which require further validation. The data presented here, point to a limited use of Mg isotopes as temperature proxy, but highlight the method's potential as tracer of seawater chemistry through Earth's history.

  4. Highly Efficient Quantum Sieving in Porous Graphene-like Carbon Nitride for Light Isotopes Separation

    Science.gov (United States)

    Qu, Yuanyuan; Li, Feng; Zhou, Hongcai; Zhao, Mingwen

    2016-01-01

    Light isotopes separation, such as 3He/4He, H2/D2, H2/T2, etc., is crucial for various advanced technologies including isotope labeling, nuclear weapons, cryogenics and power generation. However, their nearly identical chemical properties made the separation challenging. The low productivity of the present isotopes separation approaches hinders the relevant applications. An efficient membrane with high performance for isotopes separation is quite appealing. Based on first-principles calculations, we theoretically demonstrated that highly efficient light isotopes separation, such as 3He/4He, can be reached in a porous graphene-like carbon nitride material via quantum sieving effect. Under moderate tensile strain, the quantum sieving of the carbon nitride membrane can be effectively tuned in a continuous way, leading to a temperature window with high 3He/4He selectivity and permeance acceptable for efficient isotopes harvest in industrial application. This mechanism also holds for separation of other light isotopes, such as H2/D2, H2/T2. Such tunable quantum sieving opens a promising avenue for light isotopes separation for industrial application. PMID:26813491

  5. Highly Efficient Quantum Sieving in Porous Graphene-like Carbon Nitride for Light Isotopes Separation

    Science.gov (United States)

    Qu, Yuanyuan; Li, Feng; Zhou, Hongcai; Zhao, Mingwen

    2016-01-01

    Light isotopes separation, such as 3He/4He, H2/D2, H2/T2, etc., is crucial for various advanced technologies including isotope labeling, nuclear weapons, cryogenics and power generation. However, their nearly identical chemical properties made the separation challenging. The low productivity of the present isotopes separation approaches hinders the relevant applications. An efficient membrane with high performance for isotopes separation is quite appealing. Based on first-principles calculations, we theoretically demonstrated that highly efficient light isotopes separation, such as 3He/4He, can be reached in a porous graphene-like carbon nitride material via quantum sieving effect. Under moderate tensile strain, the quantum sieving of the carbon nitride membrane can be effectively tuned in a continuous way, leading to a temperature window with high 3He/4He selectivity and permeance acceptable for efficient isotopes harvest in industrial application. This mechanism also holds for separation of other light isotopes, such as H2/D2, H2/T2. Such tunable quantum sieving opens a promising avenue for light isotopes separation for industrial application.

  6. Stable Carbon Isotope Ratios of Phenolic Compounds in Secondary Particulate Organic Matter Formed by Photooxidation of Toluene

    CERN Document Server

    Irei, Satoshi; Huang, Lin; Auld, Janeen; Collin, Fabrice; Hastie, Donald

    2014-01-01

    Compound-specific stable carbon isotope ratios for phenolic compounds in secondary particulate organic matter (POM) formed by photooxidation of toluene were studied. Secondary POM generated by photooxidation of toluene using a continuous-flow reactor and an 8 cubic meter indoor smog chamber was collected, and then extracted with acetonitrile. Eight phenolic compounds were identified in the extracts by a gas chromatograph coupled with a mass spectrometer, and their compound-specific stable carbon isotope ratios were determined by a gas chromatograph coupled with a combustion furnace followed by an isotope ratio mass spectrometer. The majority of the products, including methylnitrophenols and methylnitrocatechols, were isotopically depleted by 5 to 6 permil compared to the initial isotope ratio for toluene, whereas the isotope ratio for 4_nitrophenol remained the same as the initial isotope ratio for toluene. Based on the reaction mechanisms postulated in literature, stable carbon isotope ratios of these produc...

  7. 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

    Energy Technology Data Exchange (ETDEWEB)

    Monson, K.D.; Hayes, J.M. (Indiana Univ., Bloomington (USA). Dept. of Chemistry; Indiana Univ., Bloomington (USA). Dept. of Geology)

    1982-02-01

    Methods for the determination of /sup 13/C 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/sub 2/ quantitatively from the carboxyl groups of the separated cleavage products; and (4) the CO/sub 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 parts per thousand in /sup 13/C relative to the glucose. This fractionation arises in the formation of acetyl-coenzyme 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 /sup 13/C 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%.

  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

    International Nuclear Information System (INIS)

    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 CO2 quantitatively from the carboxyl groups of the separated cleavage products; and (4) the CO2 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 parts per thousand in 13C relative to the glucose. This fractionation arises in the formation of acetyl-coenzyme 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%. (author)

  9. Analyzing carbon losses from dry soils after precipitation pulses by stable carbon isotopes

    Science.gov (United States)

    Unger, Stephan; Máguas, Cristina; Santos-Pereira, João.; Werner, Christiane

    2010-05-01

    Rain events after drought periods strongly increase soil respiration (Birch effect) and affect plant activity, and thus, may influence the isotopic signal of ecosystem respiration. These CO2-pulses may largely affect the C-balance of arid and semi-arid systems. Here, we evaluate the origins of the Birch effect in a Mediterranean forest and its influence on the isotopic signal of ecosystem (δ13CR) and soil respiration (δ13CSoil). We conducted artificial rain pulses in May and August 2005 and estimated δ13CSoil on intact vegetation, bare and root-free soil in response to watering. After watering in May δ13CSoil showed strong enrichment (-18) and a rapid return to initial values (-27). This transient enrichment was smaller in August than in May (ca. -22). Further, we compared δ13CR and δ13CSoil after first natural rains in October 2005, where both revealed a good relationship over the diurnal and the fortnight cycle. We hypothesize that the 'Birch effect' immediately after irrigation is the result of a hypo-osmotic stress response of the soil microbial community: during sudden moisture changes enriched osmoregulants are rapidly released and mineralized by the soil microbes to avoid cell lysis. After the pulse soil respiration followed a common moisture response. The overall impact of the Birch effect on C-sequestration will depend on both timing and frequency of the rains and thus, on whether the respired CO2 source is microbial or soil organic matter carbon.

  10. The atmospheric signal of terrestrial carbon isotopic discrimination and its implication for partitioning carbon fluxes

    International Nuclear Information System (INIS)

    The 13C/12C ratio in atmospheric carbon dioxide has been measured in samples taken in the NOAA/CMDL network since 1991. By examining the relationship between weekly anomalies in 13C and CO2 at continental sites in the network, we infer temporal and spatial values for the isotopic signature of terrestrial CO2 fluxes. We can convert these isotopic signatures to values of discrimination if we assume the atmospheric starting point for photosynthesis. The average discrimination in the Northern Hemisphere between 30 and 50 deg N is calculated to be 16.6 ± 0.2 per mil. In contrast to some earlier modeling studies, we find no strong latitudinal gradient in discrimination. However, we do observe that discrimination in Eurasia is larger than in North America, which is consistent with two modeling studies. We also observe a possible trend in the North American average of discrimination toward less discrimination. There is no apparent trend in the Eurasian average or at any individual sites. However, there is interannual variability on the order of 2 per mil at several sites and regions. Finally, we calculate the northern temperate terrestrial CO2 flux replacing our previous discrimination values of about 18 per mil with the average value of 16.6 calculated in this study. We find this enhances the terrestrial sink by about 0.4 GtC/yr

  11. Coordinated In Situ Nanosims Analyses of H-C-O Isotopes in ALH 84001 Carbonates

    Science.gov (United States)

    Usui, T.; Alexander, C. M. O'D.; Wang, J.; Simon, J. I.; Jones, J. H.

    2016-01-01

    The surface geology and geomorphology of Mars indicate that it was once warm enough to maintain a large body of liquid water on its surface, though such a warm environment might have been transient. This study reports the hydrogen, carbon, and oxygen isotope compositions of the ancient atmosphere/hydrosphere of Mars based on in situ ion microprobe analyses of approximately 4 Ga-old carbonates in Allan Hills (ALH) 84001. The ALH 84001 carbonates are the most promising targets because they are thought to have formed from fluid that was closely associated with the Noachian atmosphere. While there are a number of carbon and oxygen isotope studies of the ALH 84001 carbonates, in situ hydrogen isotope analyses of these carbonates are limited and were reported more than a decade ago. Well-documented coordinated in situ analyses of carbon, oxygen and hydrogen isotopes provide an internally consistent dataset that can be used to constrain the nature of the Noachian atmosphere/hydrosphere and may eventually shed light on the hypothesis of ancient watery Mars.

  12. Stable carbon isotope ratios of ambient secondary organic aerosols in Toronto

    Science.gov (United States)

    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

  13. Fractionation of carbon and hydrogen isotopes by methane-oxidizing bacteria

    Science.gov (United States)

    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.

  14. Large carbon isotope fractionation associated with oxidation of methyl halides by methylotrophic bacteria

    Science.gov (United States)

    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.

  15. Carbon and oxygen isotope variations of the Middle-Late Triassic Al Aziziyah Formation, northwest Libya

    Science.gov (United States)

    Moustafa, Mohamed S. H.; Pope, Michael C.; Grossman, Ethan L.; Mriheel, Ibrahim Y.

    2016-06-01

    This study presents the δ13C and δ18O records from whole rock samples of the Middle-Late Triassic (Ladinian-Carnian) Al Aziziyah Formation that were deposited on a gently sloping carbonate ramp within the Jifarah Basin of Northwest Libya. The Al Aziziyah Formation consists of gray limestone, dolomite, and dolomitic limestone interbedded with shale. The Ghryan Dome and Kaf Bates sections were sampled and analyzed for carbon and oxygen isotope chemostratigraphy to integrate high-resolution carbon isotope data with an outcrop-based stratigraphy, to provide better age control of the Al Aziziyah Formation. This study also discusses the relation between the facies architecture of the Al Aziziyah Formation and the carbon isotope values. Seven stages of relative sea level rise and fall within the Ghryan Dome were identified based on facies stacking patterns, field observations and carbon stable isotopes. The Al Aziziyah Formation δ13C chemostratigraphic curve can be partially correlated with the Triassic global δ13C curve. This correlation indicates that the Al Aziziyah Formation was deposited during the Ladinian and early Carnian. No straight-forward relationship is seen between δ13C and relative sea level probably because local influences complicated systematic environmental and diagenetic isotopic effects associated with sea level change.

  16. Carbon and oxygen isotopic composition of the carbonates from the Jacupiranga and Catalao I carbonatite complexes, Brazil

    Energy Technology Data Exchange (ETDEWEB)

    Morikiyo, Toshiro (Shinshu Univ., Matsumoto, Nagano (Japan). Faculty of Science); Hirano, Hideo; Matsuhisa, Yukihiro

    1990-11-01

    Carbon and oxygen isotope compositions were measured for carbonates from the Jacupiranga and Catalao I carbonatite complexes in Brazil. The {delta}{sup 13}C values of the Jacupiranga carbonates are uniform, ranging from -6.4 to -5.6 per mille with the average of -6.07 per mille. Except for one sample, the {delta}{sup 18}O values of the carbonates are between 7.1 and 8.1 per mille, and the average value is 7.6 per mille. The isotopic compositions of the Jacupiranga carbonates represent the value of primary igneous carbonatite. The {delta}{sup 13}C values of dolomites are about 0.5 per mille higher than those of calcites. The {delta}{sup 13}C values of carbonates from the Catalao I complex range from -6.8 to -5.2 per mille with the average of -5.83 per mille. Those values are similar to the values of the Jacupiranga carbonates. However, oxygen isotopic compositions of the Catalao I carbonates show a wide range of 8.4 to 22.3 per mille. Carbonates with the lowest {delta}{sup 18}O values in the complex are considered to represent the igneous stage. Carbonates with extremely high {delta}{sup 18}O values of about 22 per mille are considered to have precipitated from low-temperature hydrothermal fluids. The group of intermediate {delta}{sup 18}O values indicates a variable degree of contamination by the {delta}{sup 18}O-rich hydrothermal carbonates. The contribution of secondary stage hydrothermal carbonates seems to be significant in the Catalao I complex as compared with the Jacupiranga complex. The development of a network structure in the Catalao I complex may have enhanced the circulation of the later stage hydrothermal fluids. (author).

  17. Marine Carbon-Sulfur Biogeochemical Cycles during the Steptoean Positive Carbon Isotope Excursion (SPICE) in the Jiangnan Basin, South China

    Institute of Scientific and Technical Information of China (English)

    Yang Peng; Yongbo Peng; Xianguo Lang; Haoran Ma; Kangjun Huang; Fangbing Li; Bing Shen

    2016-01-01

    ABSTRACT:Global occurrences of Steptoean Positive Carbon Isotope Excursion (SPICE) during Late Cambrian recorded a significant perturbation in marine carbon cycle, and might have had profound impacts on the biological evolution. In previous studies, SPICE has been reported from the Jiangnan slope belt in South China. To evaluate the bathymetric extent of SPICE, we investigate the limestone samples from the upper Qingxi Formation in the Shaijiang Section in the Jiangnan Basin. Our results show the positive excursions for both carbonate carbon (δ13C) and organic carbon (δ13Corg) isotopes, as well as the concurrent positive shifts in sulfur isotopes of carbonate associated sulfate (CAS, δ34SCAS) and pyrite (δ34Spyrite), unequivocally indicating the presence of SPICE in the Jiangnan Basin. A 4‰increase inδ13Ccarb of the Qingxi limestone implies the increase of the relative flux of organic carbon burial by a factor of two. Concurrent positive excursions inδ34SCAS andδ34Spyrite have been attributed to the enhanced pyrite burial in oceans with extremely low concentration and spatially heterogeneous isotopic composition of seawater sulfate. Here, we propose that the seawater sulfur isotopic heterogeneity can be generated by volatile organic sulfur compound (VOSC, such as methanethiol and dimethyl sulfide) formation in sulfidic continental margins that were widespread during SPICE. Emission of 32S-enriched VOSC in atmosphere, followed by lateral transportation and aerobic oxidation in atmosphere, and precipitation in open oceans result in a net flux of 32S from continental margins to open oceans, elevatingδ34S of seawater sulfate in continental margins. A simple box model indicates that about 35%to 75%of seawater sulfate in continental margins needs to be transported to open oceans via VOSC formation.

  18. Carbon isotope ratios and isotopic correlations between components in fruit juices

    Science.gov (United States)

    Wierzchnicki, Ryszard

    2013-04-01

    Nowadays food products are defined by geographical origin, method of production and by some regulations concerning terms of their authenticity. Important data for confirm the authenticity of product are providing by isotopic methods of food control. The method checks crucial criteria which characterize the authenticity of inspected product. The European Union Regulations clearly show the tendency for application of the isotopic methods for food authenticity control (wine, honey, juice). The aim of the legislation steps is the protection of European market from possibility of the commercial frauds. Method of isotope ratio mass spectrometry is very effective tool for the use distinguishably the food products of various geographical origin. The basic problem for identification of the sample origin is the lack of databases of isotopic composition of components and information about the correlations of the data. The subject of the work was study the isotopic correlations existing between components of fruits. The chemical and instrumental methods of separation: water, sugars, organic acids and pulp from fruit were implemented. IRMS technique was used to measure isotopic composition of samples. The final results for original samples of fruits (apple, strawberry etc.) will be presented and discussed. Acknowledgement: This work was supported by the Polish Ministry of Science and Higher Education under grant NR12-0043-10/2010.

  19. Carbon-14 production compared to oxygen isotope records from Camp Century, Greenland and Devon Island, Canada

    International Nuclear Information System (INIS)

    Carbon-14 production rate variations that are not explainable by geomagnetic changes are thought to be in antiphase with solar activity and as such should be in antiphase with paleotemperature records or proxy temperature histories such as those obtainable from oxygen isotope analyses of ice cores. Oxygen isotope records from Camp Century, Greeland and Devon Island Ice Cap are in phase with each other over thousands of years and in antiphase to the 14C production rate residuals. (Auth.)

  20. Carbon Stable Isotope Analysis of Methylmercury Toxin in Biological Materials by Gas Chromatography Isotope Ratio Mass Spectrometry.

    Science.gov (United States)

    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 (δ(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 δ(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 δ(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 δ(13)C(CH3Hg) values on natural biological samples was performed by combining a CH3Hg selective extraction, purification, and halogenation followed by GC-C-IRMS analysis. Reference δ(13)C values were established for a tuna fish certified material (ERM-CE464) originating from the Adriatic Sea (δ(13)C(CH3Hg) = -22.1 ± 1.5‰, ± 2 SD). This value is similar to the δ(13)C value of marine algal-derived particulate organic carbon (δ(13)CPOC = -21‰).

  1. Variability of carbonate diagenesis in equatorial Pacific sediments deduced from radiogenic and stable Sr isotopes

    Science.gov (United States)

    Voigt, Janett; Hathorne, Ed C.; Frank, Martin; Vollstaedt, Hauke; Eisenhauer, Anton

    2015-01-01

    The recrystallisation (dissolution-precipitation) of carbonate sediments has been successfully modelled to explain profiles of pore water Sr concentration and radiogenic Sr isotope composition at different locations of the global ocean. However, there have been few systematic studies trying to better understand the relative importance of factors influencing the variability of carbonate recrystallisation. Here we present results from a multi-component study of recrystallisation in sediments from the Integrated Ocean Drilling Program (IODP) Expedition 320/321 Pacific Equatorial Age Transect (PEAT), where sediments of similar initial composition have been subjected to different diagenetic histories. The PEAT sites investigated exhibit variable pore water Sr concentrations gradients with the largest gradients in the youngest sites. Radiogenic Sr isotopes suggest recrystallisation was relative rapid, consistent with modelling of other sediment columns, as the 87Sr/86Sr ratios are indistinguishable (within 2σ uncertainties) from contemporaneous seawater 87Sr/86Sr ratios. Bulk carbonate leachates and associated pore waters of Site U1336 have lower 87Sr/86Sr ratios than contemporaneous seawater in sediments older than 20.2 Ma most likely resulting from the upward diffusion of Sr from older recrystallised carbonates. It seems that recrystallisation at Site U1336 may still be on-going at depths below 102.5 rmcd (revised metres composite depth) suggesting a late phase of recrystallisation. Furthermore, the lower Sr/Ca ratios of bulk carbonates of Site U1336 compared to the other PEAT sites suggest more extensive diagenetic alteration as less Sr is incorporated into secondary calcite. Compared to the other PEAT sites, U1336 has an inferred greater thermal gradient and a higher carbonate content. The enhanced thermal gradient seems to have made these sediments more reactive and enhanced recrystallisation. In this study we investigate stable Sr isotopes from carbonate-rich deep

  2. Carbon and hydrogen isotopic composition and generation pathway of biogenic gas in China

    Institute of Scientific and Technical Information of China (English)

    SHEN Ping; WANG Xiaofeng; XU Yin; SHI Baoguang; XU Yongchang

    2009-01-01

    The carbon and hydrogen isotopic composition of biogenic gas is of great importance for the study of its generation pathway and reservoiring characteristics. In this paper, the formation pathways and reservoiring characteristics of biogenic gas reservoirs in China are described in terms of the carbon and hydrogen isotopic compositions of 31 gas samples from 10 biogenic gas reservoirs. The study shows that the hydrogen isotopic compositions of these biogenic gas reservoirs can be divided into three intervals:δDCH4>-200‰,-250‰<δDCH4<-200‰ and δDCH4<-250‰. The forerunners believed that the main generation pathway of biogenic gas under the condition of continental fresh water is acetic fermentation. Our research results showed that the generation pathway of biogenic gas under the condition of marine facies is typical CO2- reduction, the biogenic gas has heavy hydrogen isotopic composition: its δDCH4 values are higher than -200‰; that the biogenic gas under the condition of continental facies also was generated by the same way, but its hydrogen isotopic composition is lighter than that of biogenetic gas generated under typical marine facies condition: -250‰<δDCH4<-200‰, the δDCH4 values may be related to the salinity of the water medium in ancient lakes. From the relevant data of the Qaidam Basin, it can be seen that the hydrogen isotopic composition of biogenic methane has the same variation trend with increasing salinity of water medium. There are biogenic gas reservoirs formed in transitional regions under the condition of continental facies. These gas reservoirs resulted from both CO2- reduction and acetic fermentation, the formation of which may be related to the non-variant salinity of ancient water medium and the relatively high geothermal gradient, as is the case encountered in the Baoshan Basin. The biogenic gas generating in these regions has light hydrogen isotopic composition: δDCH4<-250‰, and relatively heavy carbon isotopic

  3. The specific carbon isotopic compositions of branched and cyclic hydrocarbons from Fushun oil shale

    Institute of Scientific and Technical Information of China (English)

    DUAN Yi; WU Baoxiang; ZHENG Guodong; ZHANG Hui; ZHENG Chaoyang

    2004-01-01

    Various branched and cyclic hydrocarbons are isolated from the Fushun oil shale and their carbon isotopes are determined. The analytical results show that the branched and cyclic hydrocarbons are fully separated from n-alkanes by 5 A Molecular-sieve adduction using long time and cold solvent. The branched and cyclic hydrocarbon fraction obtained by this method is able to satisfy the analytic requests of GC-IRMS. The carbon isotopic compositions of these branched and cyclic hydrocarbons obtained from the sample indicate that they are derived from photoautotrophic algae, chemoautotrophic bacteria (-3.4‰ --39.0‰) and methanotrophic bacteria (-38.4‰--46.3‰). However the long-chain 2-methyl-branched alkanes indicate that their carbon isotopic compositions reflect biological origin from higher plants. The carbon isotopic composition of C30 4-methyl sterane (-22.1‰) is the heaviest in all studied ste- ranes, showing that the carbon source or growth condition for its precursor, dinoflagellate, may be different from that of regular steranes. The variation trend of δ13C values between isomers of hopanes shows that 13C-enriched precursors take precedence in process of their epimerization. Methanotrophic hopanes presented reveal the processes of strong transformation of organic matter and cycling of organic carbon in the water column and early diagenesis of oil shale.

  4. Determination of the origin of dissolved inorganic carbon in groundwater around a reclaimed landfill in Otwock using stable carbon isotopes

    Energy Technology Data Exchange (ETDEWEB)

    Porowska, Dorota, E-mail: dorotap@uw.edu.pl

    2015-05-15

    Highlights: • Research showed the origin of DIC in the groundwater around a reclaimed landfill. • Carbon isotope was used to evaluate the contributions of carbon from different sources. • The leachate-contaminated water was isotopically distinct from the natural groundwater. • DIC in the natural groundwater comes from organic matter and dissolution of carbonates. • In the contaminated water, DIC comes from organic matter in the aquifer and landfill. - Abstract: Chemical and isotopic analyses of groundwater from piezometers located around a reclaimed landfill in Otwock (Poland) were performed in order to trace the origin of dissolved inorganic carbon (DIC) in the groundwater. Due to differences in the isotopic composition of carbon from different sources, an analysis of stable carbon isotopes in the groundwater, together with the Keeling plot approach and a two-component mixing model allow us to evaluate the relative contributions of carbon from these sources in the groundwater. In the natural (background) groundwater, DIC concentrations and the isotopic composition of DIC (δ{sup 13}C{sub DIC}) comes from two sources: decomposition of organic matter and carbonate dissolution within the aquifer sediments, whereas in the leachate-contaminated groundwater, DIC concentrations and δ{sup 13}C{sub DIC} values depend on the degradation of organic matter within the aquifer sediments and biodegradation of organic matter stored in the landfill. From the mixing model, about 4–54% of the DIC pool is derived from organic matter degradation and 96–46% from carbonate dissolution in natural conditions. In the leachate-contaminated groundwater, about 20–53% of the DIC is derived from organic matter degradation of natural origin and 80–47% from biodegradation of organic matter stored in the landfill. Partial pressure of CO{sub 2} (P CO{sub 2}) was generally above the atmospheric, hence atmospheric CO{sub 2} as a source of carbon in DIC pool was negligible in the

  5. Determination of organic milk authenticity using carbon and nitrogen natural isotopes.

    Science.gov (United States)

    Chung, Ill-Min; Park, Inmyoung; Yoon, Jae-Yeon; Yang, Ye-Seul; Kim, Seung-Hyun

    2014-10-01

    Natural stable isotopes of carbon and nitrogen ((12)C, (13)C, (14)N, (15)N) have abundances unique to each living creature. Therefore, measurement of the stable isotope ratio of carbon and nitrogen (δ(13)C=(13)C/(12)C, δ(15)N=(15)N/(14)N) in milk provides a reliable method to determine organic milk (OM) authenticity. In the present study, the mean δ(13)C value of OM was higher than that of conventional milk (CM), whereas the mean δ(15)N value of OM was lower than that of CM; nonetheless both δ(13)C and δ(15)N values were statistically different for the OM and CM (Pauthenticity using stable isotopes of carbon and nitrogen.

  6. Forensic utility of the carbon isotope ratio of PVC tape backings

    Science.gov (United States)

    Stern, L. A.; Thompson, A. H.; Mehltretter, A. H.; McLaskey, V.; Parish, A.; Aranda, R.

    2008-12-01

    Forensic interest in adhesive tapes with PVC-backings (polyvinyl chloride, electrical tapes) derives from their use in construction of improvised explosive devices, drug packaging and in a variety of other illicit activities. Due to the range of physical characteristics and chemical compositions of such tapes, traditional microscopic and chemical analysis of the tape backings and adhesives offer a high degree of discrimination between tapes from different manufacturers and products. To evaluate whether carbon isotope ratios may be able to increase discrimination of electrical tapes, particularly with regards to different tapes of the same product, we assessed the PVC-backings of 87 rolls of black electrical tape for their δ13C values. The adhesive on these tapes was physically removed with hexane, and plasticizers within the PVC tape backings were removed by three-20 minute extractions with chloroform. The δ13C values of the PVC tape backings ranged between -23.8 and -41.5 (‰ V-PDB). The carbon isotopic variation within a product (identical brand and product identification) is significant, based on five products with at least 3 rolls (ranges of 7.4‰ (n=3), 10.0‰ (n=6), 4.2‰ (n=16), 3.8‰ (n=6), and 11.5‰ (n=8), respectively). There was no measurable carbon isotope variation in regards to the following: a) along the length of a roll (4 samples from 1 roll); b) between the center and edge of a strip of tape (1 pair); c) between rolls assumed to be from the same lot of tape (2 pairs); d) between different rolls from the same batch of tape (same product purchased at the same time and place; 5 pairs); and e) between samples of a tape at room temperature, heated to 50° C and 80° C for 1 week. For each sample within the population of 87 tapes, carbon isotopes alone exclude 80 to 100% of the tapes as a potential match, with an average exclusion power of 92.5%, using a window of ± 0.4‰. Carbon isotope variations originate from variations in starting

  7. Carbon Isotopic Fractionation in Fischer-Tropsch Type Reactions and Relevance to Meteorite Organics

    Science.gov (United States)

    Johnson, Natasha M; Elsila, Jamie E.; Kopstein, Mickey; Nuth, Joseph A., III

    2012-01-01

    Fischer-Tropsch-Type (FTT) reactions have been hypothesized to contribute to the formation of organic compounds in the early solar system, but it has been difficult to identify a signature of such reactions in meteoritic organics. The work reported here examined whether temperature-dependent carbon isotopic fractionation of FTT reactions might provide such a signature. Analyses of bulk organic deposits resulting from FTT experiments show a slight trend towards lighter carbon isotopic ratios with increasing temperature. It is unlikely, however, that these carbon isotopic signatures could provide definitive provenance for organic compounds in solar system materials produced through FTT reactions, because of the small scale of the observed fractionations and the possibility that signatures from many different temperatures may be present in any specific grain.

  8. Chromium isotopes in carbonates — A tracer for climate change and for reconstructing the redox state of ancient seawater

    DEFF Research Database (Denmark)

    Frei, Robert; Gaucher, Claudio; Døssing, Lasse Nørbye;

    2011-01-01

    climatic changes. We here present results of a new isotopic tracer system – stable chromium isotopes – applied to a late Ediacaran marine carbonate sequence exposed in the Calera de Recalde syncline, Arroyo del Soldado Group, Uruguay. The aim was to compare Cr isotope signatures directly to d13C, 87Sr/86Sr...

  9. POSSIBILITY OF USING CARBON ISOTOPES IN THE ASSESSMENT OF THE POLLUTION OF GAS PHASE IN ENVIRONMENTAL RESEARCH

    Directory of Open Access Journals (Sweden)

    Dorota Porowska

    2015-10-01

    Full Text Available Carbon isotope analyses can be used for knowledge and practical purpose. They can be used to assess the genesis of carbon in geochemical environment, and may also be used to indicate environmental contamination by carbon-containing compounds. The aim of the paper is to indicate the possibilities of using carbon isotope composition for interpretation concerning the following elements of the natural environment: atmospheric air, subsurface zone (gases in soils and aeration zone in terms of natural and anthropogenic factors influencing on their quality. This method can be applied universally, when carbon sources are different in isotopic composition.

  10. Carbon isotope fractionation of chlorinated ethenes during oxidation by Fe{sup 2+} activated persulfate

    Energy Technology Data Exchange (ETDEWEB)

    Marchesi, Massimo, E-mail: m2marche@uwaterloo.ca [Departament de Cristallografia, Mineralogia i Diposits Minerals, Universitat de Barcelona, Barcelona, Catalunya 08028 (Spain); Earth and Environmental Department, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1 (Canada); Aravena, Ramon [Earth and Environmental Department, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1 (Canada); Sra, Kanwartej S. [Department of Civil and Environmental Engineering, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1 (Canada); Golder Associates Inc, Toronto, Ontario, Canada L5N 5Z7 (Canada); Thomson, Neil R. [Department of Civil and Environmental Engineering, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1 (Canada); Otero, Neus; Soler, Albert [Departament de Cristallografia, Mineralogia i Diposits Minerals, Universitat de Barcelona, Barcelona, Catalunya 08028 (Spain); Mancini, Silvia [Golder Associates Inc, Toronto, Ontario, Canada L5N 5Z7 (Canada)

    2012-09-01

    The increased use of persulfate (S{sub 2}O{sub 8}{sup 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{sup 2+}). An average carbon isotope enrichment factor {epsilon}{sub bulk} of - 4.9 Per-Mille-Sign for PCE, - 3.6 Per-Mille-Sign for TCE and - 7.6 Per-Mille-Sign for cis-DCE were obtained in batch experiments. Variations in the initial S{sub 2}O{sub 8}{sup 2-}/Fe{sup 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{sub 2}O{sub 8}{sup 2-}/Fe{sup 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{sup 2+} activated persulfate. Highlights: Black-Right-Pointing-Pointer The performance of in situ chemical oxidation (ISCO) is still difficult to assess. Black-Right-Pointing-Pointer We investigated the potential of carbon isotope analysis as a new assessing tool. Black-Right-Pointing-Pointer C isotope of PCE, TCE and DCE oxidized by persulfate activated by Fe{sup 2+} was measured. Black-Right-Pointing-Pointer Enrichment factors of - 4.9 Per-Mille-Sign for PCE, - 3.6 Per-Mille-Sign for TCE and - 7.6 Per-Mille-Sign for cisDCE were obtained. Black-Right-Pointing-Pointer Carbon isotope can potentially be used to estimate the ISCO treatment efficacy.

  11. Uranium isotopes in carbonate aquifers of arid region setting

    DEFF Research Database (Denmark)

    Alshamsi, Dalal M.; Murad, Ahmed A.; Aldahan, Ala;

    2013-01-01

    Groundwater in arid and semiarid regions is vital resource for many uses and therefore information about concentrations of uranium isotopes among other chemical parameters are necessary. In the study presented here, distribution of 238U and 235U in groundwater of four selected locations in the so......Groundwater in arid and semiarid regions is vital resource for many uses and therefore information about concentrations of uranium isotopes among other chemical parameters are necessary. In the study presented here, distribution of 238U and 235U in groundwater of four selected locations...... in the southern Arabian peninsula, namely at two locations within the United Arab Emirates (UAE) and two locations in Oman are discussed. The analyses of the uranium isotopes were performed using ICP-MS and the results indicated a range of concentrations for 235U and 238 U at 3–39 ng L-1 (average: 18 ng L-1...

  12. Linking mercury, carbon, and nitrogen stable isotopes in Tibetan biota: Implications for using mercury stable isotopes as source tracers.

    Science.gov (United States)

    Xu, Xiaoyu; Zhang, Qianggong; Wang, Wen-Xiong

    2016-05-06

    Tibetan Plateau is located at a mountain region isolated from direct anthropogenic sources. Mercury concentrations and stable isotopes of carbon, nitrogen, and mercury were analyzed in sediment and biota for Nam Co and Yamdrok Lake. Biotic mercury concentrations and high food web magnification factors suggested that Tibetan Plateau is no longer a pristine site. The primary source of methylmercury was microbial production in local sediment despite the lack of direct methylmercury input. Strong ultraviolet intensity led to extensive photochemical reactions and up to 65% of methylmercury in water was photo-demethylated before entering the food webs. Biota displayed very high Δ(199)Hg signatures, with some highest value (8.6%) ever in living organisms. The δ(202)Hg and Δ(199)Hg in sediment and biotic samples increased with trophic positions (δ(15)N) and %methylmercury. Fish total length closely correlated to δ(13)C and Δ(199)Hg values due to dissimilar carbon sources and methylmercury pools in different living waters. This is the first mercury isotope study on high altitude lake ecosystems that demonstrated specific isotope fractionations of mercury under extreme environmental conditions.

  13. Linking mercury, carbon, and nitrogen stable isotopes in Tibetan biota: Implications for using mercury stable isotopes as source tracers

    Science.gov (United States)

    Xu, Xiaoyu; Zhang, Qianggong; Wang, Wen-Xiong

    2016-05-01

    Tibetan Plateau is located at a mountain region isolated from direct anthropogenic sources. Mercury concentrations and stable isotopes of carbon, nitrogen, and mercury were analyzed in sediment and biota for Nam Co and Yamdrok Lake. Biotic mercury concentrations and high food web magnification factors suggested that Tibetan Plateau is no longer a pristine site. The primary source of methylmercury was microbial production in local sediment despite the lack of direct methylmercury input. Strong ultraviolet intensity led to extensive photochemical reactions and up to 65% of methylmercury in water was photo-demethylated before entering the food webs. Biota displayed very high Δ199Hg signatures, with some highest value (8.6%) ever in living organisms. The δ202Hg and Δ199Hg in sediment and biotic samples increased with trophic positions (δ15N) and %methylmercury. Fish total length closely correlated to δ13C and Δ199Hg values due to dissimilar carbon sources and methylmercury pools in different living waters. This is the first mercury isotope study on high altitude lake ecosystems that demonstrated specific isotope fractionations of mercury under extreme environmental conditions.

  14. A versatile method for simultaneous stable carbon isotope analysis of DNA and RNA nucleotides by liquid chromatography/isotope ratio mass spectrometry

    NARCIS (Netherlands)

    Moerdijk-Poortvliet, T.C.W.; Brasser, J.; de Ruiter, G.; Houtekamer, M.; Bolhuis, H.; Stal, L.J.; Boschker, H.T.S.

    2014-01-01

    RATIONALELiquid chromatography/isotope ratio mass spectrometry (LC/IRMS) is currently the most accurate and precise technique for the measurement of compound-specific stable carbon isotope ratios (C-13/C-12) in biological metabolites, at their natural abundance. However, until now this technique cou

  15. On the interference of Kr during carbon isotope analysis of methane using continuous-flow combustion–isotope ratio mass spectrometry

    NARCIS (Netherlands)

    Schmitt, J.; Seth, B.; Bock, M; van der Veen, C.; Möller, L.; Sapart, C.J.; Prokopiou, M.; Sowers, T.; Röckmann, T.; Fischer, H

    2013-01-01

    Stable carbon isotope analysis of methane ( 13C of CH4) on atmospheric samples is one key method to constrain the current and past atmospheric CH4 budget. A frequently applied measurement technique is gas chromatography (GC) isotope ratio mass spectrometry (IRMS) coupled to a combustion-preconcentra

  16. Stable carbon isotope depth profiles and soil organic carbon dynamics in the lower Mississippi Basin

    Science.gov (United States)

    Wynn, J.G.; Harden, J.W.; Fries, T.L.

    2006-01-01

    Analysis of depth trends of 13C abundance in soil organic matter and of 13C abundance from soil-respired CO2 provides useful indications of the dynamics of the terrestrial carbon cycle and of paleoecological change. We measured depth trends of 13C abundance from cropland and control pairs of soils in the lower Mississippi Basin, as well as the 13C abundance of soil-respired CO2 produced during approximately 1-year soil incubation, to determine the role of several candidate processes on the 13C depth profile of soil organic matter. Depth profiles of 13C from uncultivated control soils show a strong relationship between the natural logarithm of soil organic carbon concentration and its isotopic composition, consistent with a model Rayleigh distillation of 13C in decomposing soil due to kinetic fractionation during decomposition. Laboratory incubations showed that initially respired CO 2 had a relatively constant 13C content, despite large differences in the 13C content of bulk soil organic matter. Initially respired CO2 was consistently 13C-depleted with respect to bulk soil and became increasingly 13C-depleted during 1-year, consistent with the hypothesis of accumulation of 13C in the products of microbial decomposition, but showing increasing decomposition of 13C-depleted stable organic components during decomposition without input of fresh biomass. We use the difference between 13C / 12C ratios (calculated as ??-values) between respired CO 2 and bulk soil organic carbon as an index of the degree of decomposition of soil, showing trends which are consistent with trends of 14C activity, and with results of a two-pooled kinetic decomposition rate model describing CO2 production data recorded during 1 year of incubation. We also observed inconsistencies with the Rayleigh distillation model in paired cropland soils and reasons for these inconsistencies are discussed. ?? 2005 Elsevier B.V. All rights reserved.

  17. Evaluating reaction pathways of hydrothermal abiotic organic synthesis at elevated temperatures and pressures using carbon isotopes

    Science.gov (United States)

    Fu, Qi; Socki, Richard A.; Niles, Paul B.

    2015-04-01

    Experiments were performed to better understand the role of environmental factors on reaction pathways and corresponding carbon isotope fractionations during abiotic hydrothermal synthesis of organic compounds using piston cylinder apparatus at 750 °C and 5.5 kbars. Chemical compositions of experimental products and corresponding carbon isotopic values were obtained by a Pyrolysis-GC-MS-IRMS system. Alkanes (methane and ethane), straight-chain saturated alcohols (ethanol and n-butanol) and monocarboxylic acids (formic and acetic acids) were generated with ethanol being the only organic compound with higher δ13C than CO2. CO was not detected in experimental products owing to the favorable water-gas shift reaction under high water pressure conditions. The pattern of δ13C values of CO2, carboxylic acids and alkanes are consistent with their equilibrium isotope relationships: CO2 > carboxylic acids > alkanes, but the magnitude of the fractionation among them is higher than predicted isotope equilibrium values. In particular, the isotopic fractionation between CO2 and CH4 remained constant at ∼31‰, indicating a kinetic effect during CO2 reduction processes. No "isotope reversal" of δ13C values for alkanes or carboxylic acids was observed, which indicates a different reaction pathway than what is typically observed during Fischer-Tropsch synthesis under gas phase conditions. Under constraints imposed in experiments, the anomalous 13C isotope enrichment in ethanol suggests that hydroxymethylene is the organic intermediate, and that the generation of other organic compounds enriched in 12C were facilitated by subsequent Rayleigh fractionation of hydroxymethylene reacting with H2 and/or H2O. Carbon isotope fractionation data obtained in this study are instrumental in assessing the controlling factors on abiotic formation of organic compounds in hydrothermal systems. Knowledge on how environmental conditions affect reaction pathways of abiotic synthesis of organic

  18. Carbon Isotope Discrimination and Salinity Tolerance in Rice

    International Nuclear Information System (INIS)

    The relationship between carbon isotope discrimination (CID, Δ13C, Δ) and salinity tolerance in rice was investigated in six experiments during 2004-09. In Experiment 1, quantitative trait loci (QTLs) for Δ were analyzed in an IR29 / Pokkali mapping population of 79 recombinant inbred lines (RILs) grown under salt stress imposed at the seedling stage. Three QTLs for flag leaf-Δ were detected on chromosomes 1, 3, and 11 with R2 values ranging from 18 to 33%, and all three co-located with mapped QTLs for salinity tolerance and Na+: K+ ratio. In Experiment 2, a set of 80 breeding lines and varieties were evaluated at the seedling stage for Δ and salinity tolerance using visual standard evaluation system (SES) scores, growth, salt uptake, and δ13C composition of leaves. While the first experiment using a mixture of sensitive and tolerant RILs showed strong correlations between Δ and salt-stress traits, the data from the breeding lines showed relatively weaker correlation, possibly due to the low genetic variability within this set and the high tolerance level of most of the lines. The correlation between Δ and salinity tolerance at the reproductive stage was tested in Experiment 3 using flag leaf and grain samples across a set of 80 tolerant and sensitive lines, including 46 breeding lines and 34 varieties and landraces. The flag leaf-Δ values correlated well with grain-Δ, and both correlated positively with grain yield of single plants, suggesting that flag leaf-Δ can potentially be used to select for salinity tolerance during the reproductive stage, which agreed with results obtained at the early vegetative stage. While the varieties and landraces showed larger variation across the different traits, the breeding lines were much more uniform. This data was found useful to select contrasting parental lines used for the development of new populations for subsequent studies. In Experiment 4, the same set of 80 tolerant and sensitive lines were evaluated at the

  19. Evaluation of clumped isotope paleotemperatures across carbon isotope excursions from lacustrine strata of the Aptian Xiagou Formation, China

    Science.gov (United States)

    Suarez, M. B.; Gonzalez, L. A.; Ludvigson, G. A.; You, H.

    2014-12-01

    Carbon cycle perturbations associated with Ocean Anoxic Event 1a have been implicated in global climate and environmental changes in the Early Aptian, in particular evidence for high sea surface temperatures (SST) and carbonate platform drowning. Records of environmental changes in the terrestrial realm remain sparse. This study provides additional data on clumped isotope derived temperatures (T(Δ47)) from lacustrine carbonates of the Xiagou Formation, Gansu Province, China. In addition, Vitrinite reflectance and the Rock-Eval parameter Tmax were used to evaluate the potential for 13C-18O bonds in the carbonates to have experienced reordering. Clumped isotope derived temperatures range from 28.8 °C to 45.9°C. Vitrinite reflectance values range from 0.67 to 0.72 and Tmax ranges from 429 °C to 443 °C. The warmest temperature, derived from a very fine-grained calcareous sandstone, is at the upper limit of known modern Earth surface temperatures, and prompts concern that the T(Δ47) may be shifted to warmer temperatures as a result of burial diagenesis. Vitrinite reflectance and Tmax values indicate the samples have reached early maturity for oil generation (oil window from 60 °C to 150°C), so may have reached the lower end of temperatures for bond reordering to have occurred (~100 °C for ~100 million years). Despite this, the T(Δ47) are consistent with summer temperatures in a warm Cretaceous. In addition, temperature variations are similar to TEX86 records, especially from SST of the tropical Pacific. Two temperature increases and decreases occur, with the first peak in temperature occurring at the negative carbon isotope excursion (C3) associated with the initiation of the Selli Event (OAE1a). This study provides evidence that climate variations occurring during the Selli Event were experienced in terrestrial environments, and provides maximum summer temperatures for this part of the Asian continent during the Cretaceous. While it was intended that thermal

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

    Science.gov (United States)

    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 (Δ47) and δ18O 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 δ18O of different DIC species and minerals as a function of temperature. Experiments and theory indicate Δ47 and δ18O compositions of CO32- and HCO3- ions are significantly different from each other. Experiments constrain the Δ47-δ18O slope for a pH effect (0.011 ± 0.001; 12 ⩾ pH ⩾ 7). Rapidly-growing temperate corals exhibit disequilibrium mineral isotopic signatures with a Δ47-δ18O slope of 0.011 ± 0.003, consistent with a pH effect. Our theoretical calculations for carbonate minerals indicate equilibrium lattice calcite values for Δ47 and δ18O 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

  1. Molecular and stable carbon isotopic compositions of hopanoids in seep carbonates from the South China Sea continental slope

    Science.gov (United States)

    Guan, Hongxiang; Sun, Yongge; Mao, Shengyi; Zhu, Xiaowei; Wu, Nengyou

    2014-10-01

    The lipid biomarkers of hopanoids in cold seep carbonates from the South China Sea continental slope were investigated by gas chromatography-mass spectrometer (GC-MS) and gas chromatography-isotope ratio-mass spectrometer (GC-ir-MS). The distribution of hopanes/hopenes shows a preference for the ‘biological’ 17β(H), 21β(H)-over the ‘geological’ 17α(H), 21β(H)-configuration. This interpretation is in agreement with the strong odd-even preference of long-chain n-alkanes in those samples, suggesting that the ββ hopanes may be the early diagenetic products of biohopanoids and the αβ, βα configurations of hopanes were mainly derived from allochthonous sources contributing to the organic matter of the carbonates. In terms of hopanoid acids, the C30 to C33 17β(H), 21β(H)-hopanoid acids were detected with C32 17β(H), 21β(H)-hopanoid acid being the most abundant. However, there is a significant difference in stable carbon isotopic compostions of the C32 17β(H), 21β(H)-hopanoic acid among samples (-30.7‰ to -69.8‰). The δ13C values match well with the carbon isotopic compositions of SRB-derived iso-/anteiso-C15:0 fatty acids in the samples, which strongly depend on the carbon utilization types by microbe. The most abundant compound of hopanols detected in the samples, C30-17β(H), 21β(H)-hopanol, may be a good indicator of diagenetic product of type I methanotrophs. The molecular and carbon isotopic compositions of hopanoids demonstrate clearly that there is a combination contribution of both SRB and type I or type X methanotrophs to the source organism in the seep carbonates from the South China Sea continental slope.

  2. Intercontinental correlation of organic carbon and carbonate stable isotope records: evidence of climate and sea-level change during the Turonian (Cretaceous)

    NARCIS (Netherlands)

    Jarvis, I.; Trabucho-Alexandre, João; Gröcke, D.R.; Uličný, D.; Laurin, J.

    2015-01-01

    Carbon (d13Corg, d13Ccarb) and oxygen (d18Ocarb) isotope records are presented for an expanded Upper Cretaceous (Turonian–Coniacian) hemipelagic succession cored in the central Bohemian Cretaceous Basin, Czech Republic. Geophysical logs, biostratigraphy and stable carbon isotope chemostratigraphy pr

  3. ­­A Clumped Isotope Calibration for Terrestrial Microbial Carbonates

    Science.gov (United States)

    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.

  4. Climatic forcing of carbon-oxygen isotopic covariance in temperate-region marl lakes

    Science.gov (United States)

    Drummond, C. N.; Patterson, W. P.; Walker, J. C.

    1995-01-01

    Carbon and oxygen stable isotopic compositions of lacustrine carbonate from a southeastern Michigan marl lake display linear covariance over a range of 4.0% Peedee belemnite (PDB) in oxygen and 3.9% (PDB) in carbon. Mechanisms of delta 13 C-delta 18 O coupling conventionally attributed to lake closure in arid-region basins are inapplicable to hydrologically open lake systems. Thus, an alternative explanation of isotopic covariance in temperate region dimictic marl lakes is required. We propose that isotopic covariance is a direct record of change in regional climate. In short-residence-time temperate-region lake basins, summer meteoric precipitation is enriched in 18O relative to winter values, and summer organic productivity enriches epilimnic dissolved inorganic carbon in 13C. Thus, climate change toward longer summers and/or shorter winters could result in greater proportions of warm-month meteoric precipitation, longer durations of warm-month productivity, and net long-term enrichment in carbonate 18O and 13C. Isotopic covariance observed in the Michigan marl lake cores is interpreted to reflect postglacial warming from 10 to 3 ka followed by cooler mean annual temperature, a shift toward greater proportions of seasonal summer precipitation, a shortening of the winter season, or some combination of these three factors.

  5. Transient carbon isotope changes in complex systems: Finding the global signal, embracing the local signal

    Science.gov (United States)

    Bowen, G. J.; Schneider-Mor, A.; Filley, T. R.

    2008-12-01

    Global, transient carbon isotope excursions (CIEs) in the geological record are increasingly invoked as evidence of short-lived changes in carbon fluxes to/from the ocean-atmosphere-biosphere (exogenic) system. Reconstructing the dynamics of carbon cycle perturbation and response during such events requires that the global extent, magnitude, and temporal pattern of carbon isotope change are well understood. Unfortunately, no simple, globally integrated measure of exogenic δ13C change exists in the geological record: during major global perturbations even the best-case candidates such as deep-ocean carbonate δ13C values likely respond to a complex of factors including ocean carbonate chemistry and circulation. Here we consider the utility of organic carbon isotope records from two complex depositional systems common in the geological record, fossil soils and continental margin sediments, which are of interest in terms of their relationship to organic carbon cycling and records of past ecological change. Within both systems changes in ecology, climate, carbon source, residence time, and molecular composition have clear potential to modulate the preserved record of global exogenic δ13C change, compromising 1st-order interpretations of bulk or compound-specific isotopic records. Process-explicit eco- geochemical models, ideally combined with multi-substrate data, provide one approach to the isolation of global δ13C change and identification of local or regional processes reflected in such records. Examples from both systems drawn from ongoing work on the Paleocene-Eocene thermal maximum illustrate the potential pitfalls, as well as opportunities, afforded by coupled data/model assessment of transient δ13C changes in complex systems.

  6. Calcium and calcium isotope changes during carbon cycle perturbations at the end-Permian

    Science.gov (United States)

    Komar, Nemanja; Zeebe, Richard

    2016-04-01

    Negative carbon and calcium isotope excursions, as well as climate shifts, took place during the most severe mass extinction event in Earth's history, the end-Permian (˜252 Ma). Investigating the connection between carbon and calcium cycles during transient carbon cycle perturbation events, such as the end-Permian, may help resolve the intricacies between the coupled calcium-carbon cycles, as well as provide a tool for constraining the causes of mass extinction. Here, we identify the deficiencies of a simplified calcium model employed in several previous studies and we demonstrate the importance of a fully coupled carbon-cycle model when investigating the dynamics of carbon and calcium cycling. Simulations with a modified version of the LOSCAR model, which includes a fully coupled carbon-calcium cycle, indicate that increased weathering rates and ocean acidification (potentially caused by Siberian Trap volcanism) are not capable of producing trends observed in the record, as previously claimed. Our model results suggest that combined effects of carbon input via Siberian Trap volcanism (12,000 Pg C), the cessation of biological carbon export, and variable calcium isotope fractionation (due to a change in the seawater carbonate ion concentration) represents a more plausible scenario. This scenario successfully reconciles δ13C and δ44Ca trends observed in the sediment record, as well as the proposed warming of >6oC.

  7. Carbon and oxygen isotope geochemistry of Ediacaran outer platform carbonates, Paraguay Belt, central Brazil

    Directory of Open Access Journals (Sweden)

    Claudio Riccomini

    2007-09-01

    Full Text Available After the late Cryogenian glaciation the central region of Brazil was the site of extensive deposition of platformal carbonates of the Araras Group. This group includes a basal cap carbonate sequence succeeded by transgressive, deep platform deposits of bituminous lime mudstone and shale. Facies and stratigraphic data combined with carbon and oxygen isotopic analyses of the most complete section of the transgressive deposits, exposed in the Guia syncline, were used to evaluate the depositional paleoenvironment and to test the correlation of these deposits along the belt and with other units worldwide. The studied succession consists of 150 m thick tabular beds of black to grey lime mudstone and shale with predominantly negative delta13C PDB values around -2.5 to -1‰ . The delta13C PDB profile of Guia syncline shows a clear correlation with the upper portion of Guia Formation in the Cáceres region, about 200 km to the southwest. The delta13C PDB profile of the Araras Group is comparable with delta13C PDB profiles of Ediacaran units of the southern Paraguay Belt, western Canada, and the Congo and Kalahari cratons. Moreover, facies distribution, stratigraphy and the carbon isotopic profile of the Araras Group match the middle Tsumeb Subgroup in Namibia, which reinforces the Ediacaran age assigned to the Araras Group.Após a glaciação do final do Criogeniano, a região central do Brasil foi palco de extensa deposição de carbonatos plataformais do Grupo Araras. Este grupo inclui na sua base uma seqüência de capa carbonática sucedida por depósitos transgressivos de calcilutitos betuminosos e folhelhos de plataforma profunda. Dados de fácies e estratigráficos combinados com análises isotópicas de carbono e oxigênio da seção mais completa desses depósitos transgressivos, expostos no sinclinal da Guia, foram empregados para avaliar o paleambiente deposicional e para testar a correlação desses depósitos ao longo da faixa e tamb

  8. Vertical Stratification Changes During the Last Deglaciation Based on Foraminiferal Neodymium and Carbon Isotopes

    Science.gov (United States)

    Piotrowski, A. M.; Noble, T. L.; Roberts, N. L.; Yu, J.

    2011-12-01

    Reorganizations of the vertical structure of the ocean are believed to have occurred during major climate transitions. Some studies utilizing nutrient tracers have suggested that North Atlantic intermediate and deep ocean circulation changed together during the last deglaciation, in a manner consistent with reorganizations of the global thermohaline circulation (Rickaby and Elderfield, 2005). A strong vertical gradient in carbon isotopes, or chemocline, existed at ~2.5 km-bsl the glacial South Atlantic sector of the Southern Ocean, which may have been due to different intermediate and deep water sourcing (Hodell et al., 2003). We present new Nd isotope records from globally-distributed intermediate sites in the North Atlantic, South Atlantic, and Pacific Ocean, comparing them to Nd isotope records from proximal deep sites to examine whether there is a global coherency to changes in intermediate and deep water mass sourcing. Comparison of Nd isotopes from vertical transects in the ocean also allows us to address an important geochemical debate about REE cycling in the ocean; whether long-distance horizontal advection or local boundary exchange from sediments plays a more important role in labelling the Nd isotopic composition of seawater. Down-slope vertical transport of sediments from the continental shelf to the deep ocean should mean that under conditions where boundary exchange is dominant, intermediate and deep waters will be labelled with similar Nd isotopic compositions and it will also cause them to covary together through time. We show that the Nd isotopic composition of intermediate depth cores in the South Atlantic and Pacific sectors of the Southern Ocean record small changes of ~1 epsilon unit or less during the deglaciation. As is the case with C isotopes, a stronger vertical Nd isotope gradient existed in the South Atlantic during the last glacial. Nd and C isotopes changed together at intermediate-depth ODP Site 1088 in the South Atlantic in a manner

  9. Extreme hydrogen, oxygen and carbon isotope anomalies in the pore waters and carbonates of the sediments and basalts from the Norwegian Sea: Methane and hydrogen from the mantle?

    Science.gov (United States)

    Lawrence, J. R.; Taviani, M.

    1988-08-01

    D/H ratios in the pore waters of the sediments from the Norwegian Sea decrease as a function of depth to values as low as -14%. Oxygen isotope ratios in the pore waters and carbon and oxygen isotope ratios in carbonates both in the sediments and basalts are low. Extensive alteration of basalt has been given as the explanation for the low oxygen isotope ratios. Material balance calculations suggest that alteration of volcanic material and oxidation of organic matter cannot explain the hydrogen and carbon isotope anomalies. Arguments are presented suggesting that methane and hydrogen from the mantle are oxidized to carbon dioxide and water by sulfate and ferric iron in the basaltic crust to yield the low hydrogen and carbon isotope ratios.

  10. Extreme hydrogen, oxygen and carbon isotope anomalies in the pore waters and carbonates of the sediments and basalts from the Norwegian Sea: Methane and hydrogen from the mantle

    Energy Technology Data Exchange (ETDEWEB)

    Lawrence, J.R. (Univ. of Houston, University Park, TX (USA)); Taviani, M. (Instituto di Geologia Marina, del C.N.R., Bologna (Italy))

    1988-08-01

    D/H ratios in the pore waters of the sediments from the Norwegian Sea decrease as a function of depth to values as low as {minus}14{per thousand}. Oxygen isotope ratios in the pore waters and carbon and oxygen isotope ratios in carbonates both in the sediments and basalts are low. Extensive alteration of basalt has been given as the explanation for the low oxygen isotope ratios. Material balance calculations suggest that alteration of volcanic material and oxidation of organic matter cannot explain the hydrogen and carbon isotope anomalies. Arguments are presented suggesting that methane and hydrogen from the mantle are oxidized to carbon dioxide and water by sulfate and ferric iron in the basaltic crust to yield the low hydrogen and carbon isotope ratios.

  11. Triassic-Jurassic organic carbon isotope stratigraphy of key sections in the western Tethys realm (Austria)

    Science.gov (United States)

    Ruhl, Micha; Kürschner, Wolfram M.; Krystyn, Leopold

    2009-05-01

    The late Triassic period is recognized as one of the five major mass extinctions in the fossil record. All these important intervals in earth history are associated with excursions in C-isotope records thought to have been caused by perturbations in the global carbon cycle. The nature and causes of C-isotopic events across the Triassic-Jurassic (T-J) transition however, are poorly understood. We present several new high resolution organic C-isotope records from the Eiberg Basin, Austria, including the proposed Global boundary Stratotype Section and Point (GSSP) for the base of the Jurassic. The Triassic-Jurassic boundary interval in these records is characterized by the initial and main negative organic carbon isotope excursions (CIE) of up to 8‰. The initial and main CIEs are biostratigraphically constrained by first and last occurrences of boundary defining macro- and microfossils (e.g. ammonites). High resolution C-isotope records appear to be an excellent correlation proxy for this period in the Eiberg Basin. Pyrolysis analysis demonstrates increased Hydrogen Index (HI) values for organic matter coinciding with the initial CIE. Terrestrial organic matter influx and mass occurrences of green algae remains may have influenced the C-isotope composition of the sedimentary organic matter. This may have contributed to the extreme amplitude of the initial CIE in the Eiberg Basin.

  12. Stable carbon isotope ratios of toluene in the boundary layer and the lower free troposphere

    Directory of Open Access Journals (Sweden)

    J. Wintel

    2013-04-01

    Full Text Available Measurements of stable carbon isotope ratios in VOC are a powerful tool to identify sources or to track both dynamical and chemical processes. During the field campaign ZEPTER-2 in autumn 2008 whole air samples were collected on board a Zeppelin NT airship in the planetary boundary layer and the lower free troposphere over south-west Germany. These samples were analysed with respect to VOC mixing ratios and stable carbon isotope ratios using a gas chromatograph combustion isotope ratio mass spectrometer. In this study we present the results for toluene, one of the major anthropogenic pollutants. In the boundary layer we observed rather fresh emissions mixing into the background and derived a toluene source isotope ratio of δ13C = −28.2 ± 0.5 ‰. Using the concept of the effective kinetic isotope effect, we were able to separate the effects of dilution processes and photochemical degradation in the free troposphere. We estimated the photochemical age of toluene in the atmosphere in two different ways (using isotope ratios and mixing ratios, respectively. The results differ strongly in the planetary boundary layer, probably due to mixing processes, but are compatible with each other in the free troposphere.

  13. Carbon isotopic records inpaleosols over the Pliocene in Northern China: Implication on vegetation developmentand Tibetan uplift

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Carbon isotopic composition of pedogenic carbonate can be used to estimate the proportion of C4 and C3 plants. Here we present carbon isotopic data of carbonate in a red earth section at Xifeng, central Loess Plateau. Results show that C4 vegetation increased in ~4.4 Ma B.P., stabilized between 4.0 and 3.0 Ma B.P. The character and timing of C4 expansion on the Loess Plateau are similar, but different with other localities, e.g. Pakistan and Africa, implying that regional climate changes were main factors driving the expansion of C4 plants. This event is comparable in timing with increased aridity evidenced by Xifeng grain size and North Pacific eolian dust records. Therefore we argue that the Pliocene expansion of C4 plants in northern China might have been caused by the increased aridity, which in turn might be related to rapid uplift of the Tibetan Plateau.

  14. Development of a computer systems for operational data acquisition of uranium isotopic enrichment pilot plant

    International Nuclear Information System (INIS)

    A pilot plant for uranium enrichment using the jet nozzle process was transfered from Federal Republic of Germany to Brazil, to train Brazilian technicist in its operation and to improve the process. This pilot plant is monitored by a data acquisition system and the possibility of faulty events would cause serious dificulties, as far as maintenance is concerned (for instance, unvailable special components). It is described the development of a new system, which is proposed in order to minimize difficulties with maintenance that utilizes in the assembling integrated circuits of large scale of integration. It is controlled by a microcomputer. (Author)

  15. Oxygen and carbon isotope composition from the UHP Shuanghe marbles, Dabie Mountains, China

    Institute of Scientific and Technical Information of China (English)

    王清晨; Douglas; Rumble

    1999-01-01

    Investigations on the oxygen and carbon isotope compositions from the ultrahigh-pressure (UHP)-metamorphosed Shuanghe marbles, that occur as a member of a UHP slab, show that the δ18O values range from +11.1‰ to+20.5‰ SMOW, and δ13C from+1.0‰ to+5.7‰ PDB, respectively. The variations in isotope compositions show a centimeter scale of homogeneity and a heterogeneity of regional scale larger than 1 meter. In contrast to the eclogite marbles from Norway, the Shuanghe marbles have inherited the carbon isotope compositions from their sedimentary precursor. The δ13C shows positive correlation to the content of dolomite. The depletion in 18O, compared with the protolithic carbonate strata, might result from three possible geological processes: 1) exchanging oxygen isotope with meteoric water before the UHP metamorphism, 2) decarbonation during the UHP metamorphism, and 3) exchanging oxygen isotope with country gneiss at local scale during retrograde metamorphism. It seems that the adveetion

  16. Carbon isotope fractionation reveals distinct process of CH4 emission from different compartments of paddy ecosystem

    Science.gov (United States)

    Zhang, Guangbin; Yu, Haiyang; Fan, Xianfang; Ma, Jing; Xu, Hua

    2016-06-01

    Carbon isotopic fractionations in the processes of CH4 emission from paddy field remain poorly understood. The δ13C-values of CH4 in association with production, oxidation and transport of CH4 in different pools of a paddy field were determined, and the stable carbon isotope fractionations were calibrated to assess relative contribution of acetate to CH4 production (fac) and fraction of CH4 oxidized (fox) by different pathways. The apparent isotope fractionation for CO2 conversion to CH4 (αapp) was 1.041-1.056 in the soil and 1.046-1.080 on the roots, indicating that fac was 10-60% and 0-50%, respectively. Isotope fractionation associated with CH4 oxidation (αox) was 1.021 ± 0.007 in the soil and 1.013 ± 0.005 on the roots, and the transport fractionation (ɛtransport) by rice plants was estimated to be -16.7‰ ~ -11.1‰. Rhizospheric fox was about 30-100%, and it was more important at the beginning but decreased fast towards the end of season. Large value of fox was also observed at the soil-water interface and soil and roots surfaces, respectively. The results demonstrate that carbon isotopic fractionations which might be different in different conditions were sensitive to the estimations of fac and fox in paddy field.

  17. Metal isotopes and carbonate proxy archives: Model-based perspectives on diagenesis

    Science.gov (United States)

    Fantle, M. S.; Higgins, J. A.; Griffith, E. M.

    2014-12-01

    Metal isotopes are novel tools, and have expanded the geochemical toolbox for elucidating the functioning of the Earth over various time scales. Carbonate-based stable isotope proxies now extend well beyond the traditional major elements (C and O) to include Ca, as well as trace elements such as Sr, S, Mg, B, Li, Cd, and U. Such trace isotopic proxies may contain invaluable information about the Earth system in the past, but can be susceptible to diagenetic alteration over long time scales. It is therefore critical that diagenetic effects are understood and can be recognized in ancient rocks. The extent of alteration depends on reaction rate and advection velocity in the sedimentary section, and elemental partitioning and isotopic effects associated with diagenesis. Numerical approaches, such as reactive transport models, are extremely useful tools for constraining such variables, and for testing hypotheses related to alteration of proxy records. Reactive transport models allow for constraints on calcite recrystallization rates in natural systems; data from ODP Sites 807A, 1170A, 1171A, and 806B suggest rapid recrystallization in relatively young sediments, as well as a Ca isotopic fractionation factor (α) associated with calcite recrystallization close to 1 (Δ=0). While the former is critical for addressing the fidelity and accuracy of a variety of geochemical proxies, the latter is distinctly different from that associated with the formation of carbonates in the surface ocean (Δ~ -1.35‰), suggesting considerable isotopic leverage to alter Ca isotopes during diagenesis. While Ca isotopes are generally well buffered in carbonate-rich sediments, this leverage to alter may be expressed as a reduction in the amplitude of geochemical variability in the solid or as a result of reactions near the sediment-seawater interface (as seen at ODP Site 1221 associated with chemical burndown during the PETM). Further, the Ca and Mg isotopic compositions of shallow water

  18. Carbon isotope fractionation of dissolved inorganic carbon (DIC) due to outgassing of carbon dioxide from a headwater stream

    Science.gov (United States)

    Doctor, D.H.; Kendall, C.; Sebestyen, S.D.; Shanley, J.B.; Ohte, N.; Boyer, E.W.

    2008-01-01

    The stable isotopic composition of dissolved inorganic carbon (??13C-DIC) was investigated as a potential tracer of streamflow generation processes at the Sleepers River Research Watershed, Vermont, USA. Downstream sampling showed ?? 13C-DIC increased between 3-5??? from the stream source to the outlet weir approximately 0??5 km downstream, concomitant with increasing pH and decreasing PCO2. An increase in ??13C-DIC of 2.4 ?? 0??1??? per log unit decrease of excess PCO2 (stream PCO2 normalized to atmospheric PCO2) was observed from downstream transect data collected during snowmelt. Isotopic fractionation of DIC due to CO2 outgassing rather than exchange with atmospheric CO2 may be the primary cause of increased ?? 13C-DIC values downstream when PCO2 of surface freshwater exceeds twice the atmospheric CO2 concentration. Although CO2 outgassing caused a general increase in stream ??13C-DIC values, points of localized groundwater seepage into the stream were identified by decreases in ??13C-DIC and increases in DIC concentration of the stream water superimposed upon the general downstream trend. In addition, comparison between snowmelt, early spring and summer seasons showed that DIC is flushed from shallow groundwater flowpaths during snowmelt and is replaced by a greater proportion of DIC derived from soil CO2 during the early spring growing season. Thus, in spite of effects from CO2 outgassing, ??13C of DIC can be a useful indicator of groundwater additions to headwater streams and a tracer of carbon dynamics in catchments. Copyright ?? 2007 John Wiley & Sons, Ltd.

  19. Preliminary Study: Application of Off-Axis ICOS to Determine Stable Carbon Isotope in Dissolved Inorganic Carbon

    Science.gov (United States)

    Kim, Y. T.; Lee, J. M.; Hwang, J. H.; Piao, J.; Woo, N. C.

    2015-12-01

    CO2 is one of the major causes for global climate change. Because stable carbon isotope ratio is used to trace carbon source, several analytical techniques likes IRMS (Isotope Ratio Mass Spectrometry) and LAS (Laser Absorption Spectrometry) were extensively used. Off-axis ICOS, a kind of LAS, has merits on long-term stability and field application, therefore it is widely being used in CCS (Carbon Capture and Storage) field. The aim of this study is to extend the application scope of OA-ICOS to determine dissolved inorganic carbon (DIC). Because OA-ICOS showed dependence of δ13C on CO2 concentration, data processing is required. We tested CO2 Carbon Isotope Analyzer (CCIA-36-EP, Los Gatos Research) with both reference gas (δ13C= -28.28‰) and aqueous solutions prepared by dissolving sodium bicarbonate standards (δ13C= -12.26‰ and +3.96‰). The differences of δ13C between reference and measurement values are plotted by CO2 concentrations, then compared. At first, we checked the similarity between our curve pattern for reference gas and Guillon's research (δ13C= -43.99‰) by other Analyzer. To analyze aqueous samples, more errors can be caused than gas analysis. The carbon isotope fractionation occurs during dissolving standard reagents and extracting DIC as CO2 gas form. This effect is mixed with CO2 concentration dependence effect, therefore the curve patterns are different with that for reference gas. Our experiments are done for various δ13C values. It could be an important point to use OA-ICOS to analyze DIC, too.

  20. Li isotopes in foraminifera: a new proxy for past ocean dissolved inorganic carbon

    Science.gov (United States)

    Vigier, N.; Rollion-Bard, C.; Erez, J.

    2009-12-01

    Past ocean pH and pCO2 are critical parameters for establishing relationships between Earth climate and carbon cycle. For the Miocene-Pleistocene period, two main proxies have been used: carbon isotopes of di-unsaturated alkenones extracted from sea cores, and boron isotope signatures of marine carbonates [1, 2]. Both techniques lead to selfconsistent palaeooceanic pH or pCO2 estimates, but are associated with large uncertainties. Moreover, the paleovariations calculated from boron isotope measurements are a matter of debate. Additional proxies are therefore needed. Based on an in-situ analytical technique recently developed [3], we analysed a series of foraminifera - Amphistegina - cultured under various conditions (in pH, T and Dissolved Inorganic Carbon). We show that the lithium isotope signature of the foraminifera correlates with the DIC (r2 = 0.93). Conversely, there is no dependency of Li isotope signature on pH or T. A simple model of biomineralization in which growth rate is a key parameter can fit the whole dataset, including published values for other foraminifera species [4, 5]. This strongly suggests that the DIC-δ7Li correlation highlighted by the cultured Amphistegina can also be applied to other species. These results, combined with the published oceanic Li and B isotope paleovariations [2, 4, 5], allow us to estimate the ocean DIC and pCO2 evolution for the past 18Ma. The similarity with the pCO2 curve given by carbon isotopes measured in di-unsaturated alkenones is striking. This supports the use of Li isotopes as a new proxy and adds support to the existing data. It also suggests, in contrast with the common view, a less significant role of river input on the variation of the ocean Li isotope composition, at least for the period considered. [1] Pagani et al. (2005) Science 309, 600-603. [2] Pearson & Palmer (2000) Nature 406, 695-699. [3] Vigier et al. (2007) G-cubed 8, Q01003 [4] Hall et al. (2005) Mar. Geology 217, 255-265 [5] Hathorne

  1. Molecular, radioactive and stable carbon isotope characterization of estuarine particulate organic matter

    OpenAIRE

    Megens, L.; van der Plicht, J.; De Leeuw, JW; Leeuw, Jan W. de; Mook, W.G.

    1998-01-01

    Organic matter in sediments and suspended matter is a complex mixture of constituents with different histories, sources and stabilities. To study these components in a suspended matter sample from the Ems-Dollard Estuary, we used combined molecular analysis with pyrolysis/gas chromatography/mass spectrometry and stable and radioactive carbon isotope analyses of the bulk and separated chemical fractions. Carbohydrates and proteins, ca. 50% of the total organic carbon (TOC), are much younger th...

  2. Food sources for the mangrove tree crab aratus pisonii: a carbon isotopic study

    International Nuclear Information System (INIS)

    Muscle tissues from the mangrove tree crab Aratus pisonii was analysed for carbon isotopic composition, in order to trace its major food sources. Potential food sources: mangrove leaves epi phytic green algae, mangrove sediments and open water and mangrove suspended matter; were also analysed. The results show that A. pisonii is basically omnivorous, with major food sources from marine origin. However, mangrove carbon can contribute with 16% to 42% in the crab's diet. (author)

  3. Mass spectrometric analysis of stable carbon isotopes in abiogenic and biogenic natural compounds

    International Nuclear Information System (INIS)

    This report describes the general methodology of sup/13/ carbon analysis on mass spectrometer and various preparation systems developed for conversion of samples into isotopically non-fractionated and purified carbon dioxide. Laboratory standards required for sup/13/ C analysis have been calibrated against international standards. The reproducibility/accuracy of sample preparation and analysis on mass spectrometer for sup/13/ C or sup/12/ C measurement is well within the internationally acceptable limits. (author)

  4. Effect of Different Carbon Substrates on Nitrate Stable Isotope Fractionation During Microbial Denitrification

    DEFF Research Database (Denmark)

    Wunderlich, Anja; Meckenstock, Rainer; Einsiedl, Florian

    2012-01-01

    .1 ± 0.8‰; ε18O, −23.7 ± 1.8‰ to −19.9 ± 0.8‰). The observed isotope effects did not depend on the growth kinetics which were similar for the three types of electron donors. We suggest that different carbon sources change the observed isotope enrichment factors by changing the relative kinetics of......-labeled water and 18O-labeled nitrite were added to the microcosm experiments to study the effect of putative backward reactions of nitrite to nitrate on the stable isotope fractionation. We found no evidence for a reverse reaction. Significant variations of the stable isotope enrichment factor ε were observed...

  5. Assessing diet in savanna herbivores using stable carbon isotope ratios of faeces

    Directory of Open Access Journals (Sweden)

    D. Codron

    2005-06-01

    Full Text Available In African savannas, browse-based resources (@3 plants are isotopically distinct from grasses (@4 plants. The carbon isotopic composition of the basic plant diet is recorded in animal tissues. Mammal faeces are a readily accessible, non-invasive, sample material for temporally resolved dietary reconstructions. Faeces, however, include both undigested plant matter and waste, hence accuracy of dietary calculations could potentially be compromised by shifts in plant isotopic values related to seasonal or spatial differences, or by variability in the isotopic differences between faeces and diet. A controlled feeding study of four ungulate species showed a small, consistent difference between diet and faeces of-0.9 o, irrespective of whether the diet was @3 or C4-based. Results from faeces oftaxa known to be pure grazers, pure browsers, and mixed-feeders from the Kruger National Park were entirely consistent with their diets, but the accuracy of dietary reconstructions is enhanced with data from local plant communities.

  6. Stable Carbon Isotope Fractionation by Methylotrophic Methanogenic Archaea

    OpenAIRE

    Penger, Jörn; Conrad, Ralf; Blaser, Martin

    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 methanoge...

  7. Constraints on the formation and diagenesis of phosphorites using carbonate clumped isotopes

    Science.gov (United States)

    Stolper, Daniel A.; Eiler, John M.

    2016-05-01

    The isotopic composition of apatites from sedimentary phosphorite deposits has been used previously to reconstruct ancient conditions on the surface of the Earth. However, questions remain as to whether these minerals retain their original isotopic composition or are modified during burial and lithification. To better understand how apatites in phosphorites form and are diagenetically modified, we present new isotopic measurements of δ18O values and clumped-isotope-based (Δ47) temperatures of carbonate groups in apatites from phosphorites from the past 265 million years. We compare these measurements to previously measured δ18O values of phosphate groups from the same apatites. These results indicate that the isotopic composition of many of the apatites do not record environmental conditions during formation but instead diagenetic conditions. To understand these results, we construct a model that describes the consequences of diagenetic modification of phosphorites as functions of the environmental conditions (i.e., temperature and δ18O values of the fluids) during initial precipitation and subsequent diagenesis. This model captures the basic features of the dataset and indicates that clumped-isotope-based temperatures provide additional quantitative constraints on both the formational environment of the apatites and subsequent diagenetic modification. Importantly, the combination of the model with the data indicates that the δ18O values and clumped-isotope temperatures recorded by phosphorites do not record either formation or diagenetic temperatures, but rather represent an integrated history that includes both the formation and diagenetic modification of the apatites.

  8. Stable carbon isotope analyses in sediments and its implications for reconstructing climatic and environmental changes

    International Nuclear Information System (INIS)

    The relative significance of the 20th-century climatic and environmental changes must be assessed form the long-term global-scale perspective available from a spectrum of proxy histories. In many cases geochemical proxies in sediments are needed to supplement the established use of the stable isotope analyses for paleotemperature and paleo-hydrological modeling so as to understand the past environment conditions and evaluate predictive models of climate. The stable carbon isotope fractionation during photosynthesis and the system CO2 (gas)-CO2-(aqueous)-HCO3- (aqueous) are reviewed; and application of the stable carbon isotope to reconstruction of palaeo-climatic and palaeo-environmental changes, especially CO2 levels during the late Quaternary are discussed

  9. Determination of the geographical origin of Chinese teas based on stable carbon and nitrogen isotope ratios

    Institute of Scientific and Technical Information of China (English)

    Long ZHANG; Jia-rong PAN; Cheng ZHU

    2012-01-01

    The objective of this study was to investigate the geographical origin of Chinese teas using carbon and nitrogen stable isotope ratio technology.The results showed that inter-provincial dispersion of teas in Guangdong (GD),Guangxi (GX),Hainan (HA),Fujian (F J),Shandong (SD),Sichuan (SC),Chongqing (CQ),and Henan (HN) provinces was high,while in Zhejiang (ZJ),Hubei (HB),Yunnan (YN),and Anhui (AH) provinces,it was low.Tea samples from GD,GX,HA,and FJ provinces were clustered in one group and separated from those from AH and HB provinces.Thus,carbon and nitrogen stable isotope ratio technology could discriminate teas from among some provinces of China,but not from among others.Better separation might be obtained with a combination of isotopic ratios and other indexes,such as elemental data and organic components.

  10. Isotopes of carbon monoxide in the free troposphere and their implications to atmospheric chemistry. Doctoral thesis

    Energy Technology Data Exchange (ETDEWEB)

    Mak, J.E.

    1992-01-01

    The thesis project was designed to provide information for the following questions: what is the oxidative capacity of the troposphere, and how are the source strengths of carbon monoxide partitioned. Because of its active role in tropospheric chemistry, carbon monoxide is important in determining the fate of a number of species, including hydroxyl radicals. (14)CO serves as a natural tracer for its destruction, as the source function can be well contrained. By determining the tropospheric inventory of (14)CO and calculating its source strength, one may realize the rate of destruction. Similarly, because certain sources have unique stable isotope signatures, an analysis of the stable isotopes provides information on the relative source strengths. A sampling system was built which allowed for the collection of large, whole air samples from an aircraft platform. CO was extracted and the isotopes were determined, and from these data an OH abundance was calculated using a 2-D transport model.

  11. Carbon isotopes characterize rapid changes in atmospheric carbon dioxide during the last deglaciation

    Science.gov (United States)

    Bauska, Thomas K.; Baggenstos, Daniel; Brook, Edward J.; Mix, Alan C.; Marcott, Shaun A.; Petrenko, Vasilii V.; Schaefer, Hinrich; Severinghaus, Jeffrey P.; Lee, James E.

    2016-03-01

    An understanding of the mechanisms that control CO2 change during glacial-interglacial cycles remains elusive. Here we help to constrain changing sources with a high-precision, high-resolution deglacial record of the stable isotopic composition of carbon in CO2 (δ13C-CO2) in air extracted from ice samples from Taylor Glacier, Antarctica. During the initial rise in atmospheric CO2 from 17.6 to 15.5 ka, these data demarcate a decrease in δ13C-CO2, likely due to a weakened oceanic biological pump. From 15.5 to 11.5 ka, the continued atmospheric CO2 rise of 40 ppm is associated with small changes in δ13C-CO2, consistent with a nearly equal contribution from a further weakening of the biological pump and rising ocean temperature. These two trends, related to marine sources, are punctuated at 16.3 and 12.9 ka with abrupt, century-scale perturbations in δ13C-CO2 that suggest rapid oxidation of organic land carbon or enhanced air-sea gas exchange in the Southern Ocean. Additional century-scale increases in atmospheric CO2 coincident with increases in atmospheric CH4 and Northern Hemisphere temperature at the onset of the Bølling (14.6-14.3 ka) and Holocene (11.6-11.4 ka) intervals are associated with small changes in δ13C-CO2, suggesting a combination of sources that included rising surface ocean temperature.

  12. Carbon isotopes characterize rapid changes in atmospheric carbon dioxide during the last deglaciation

    Science.gov (United States)

    Bauska, Thomas K.; Baggenstos, Daniel; Brook, Edward J.; Mix, Alan C.; Marcott, Shaun A.; Petrenko, Vasilii V.; Schaefer, Hinrich; Lee, James E.

    2016-01-01

    An understanding of the mechanisms that control CO2 change during glacial–interglacial cycles remains elusive. Here we help to constrain changing sources with a high-precision, high-resolution deglacial record of the stable isotopic composition of carbon in CO2 (δ13C-CO2) in air extracted from ice samples from Taylor Glacier, Antarctica. During the initial rise in atmospheric CO2 from 17.6 to 15.5 ka, these data demarcate a decrease in δ13C-CO2, likely due to a weakened oceanic biological pump. From 15.5 to 11.5 ka, the continued atmospheric CO2 rise of 40 ppm is associated with small changes in δ13C-CO2, consistent with a nearly equal contribution from a further weakening of the biological pump and rising ocean temperature. These two trends, related to marine sources, are punctuated at 16.3 and 12.9 ka with abrupt, century-scale perturbations in δ13C-CO2 that suggest rapid oxidation of organic land carbon or enhanced air–sea gas exchange in the Southern Ocean. Additional century-scale increases in atmospheric CO2 coincident with increases in atmospheric CH4 and Northern Hemisphere temperature at the onset of the Bølling (14.6–14.3 ka) and Holocene (11.6–11.4 ka) intervals are associated with small changes in δ13C-CO2, suggesting a combination of sources that included rising surface ocean temperature. PMID:26976561

  13. Noble gas isotopic composi-tions of deep carbonate rocks from the Tarim Basin

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Abundances and isotopic compositions of noble gases (He, Ne, Ar, Kr) with various existence states in carbonate rocks from the Tacanl Well have been investigated by means of the stepwise heating technique. The elemental abundance patterns of noble gases in the samples show the enrichment of heavy noble gases and depletion of 20Ne relative to the atmosphere, which are designated as type- I and are similar to that observed in water, natural gases and sedimentary rocks. The 3He/4He ratios of deep carbonate samples at lower and medium temperature (300-700℃) and a majority of samples at higher temperature (1100-1500℃) steps are very similar to those of natural gases in the same strata in this area, this feature of radiogenic crustal helium shows that the Tazhong Uplift is relatively stable.However, significant helium and argon isotopic anomalies are found at the 1100℃ step in the Middle-Upper Ordoviclan carbonate rock, suggesting the incorporation of manfie-derived volatiles, this may be due to minor igneous minerals contained in sedimentary carbonate rocks. The 40Ar/36Ar ratios in the Cambrian carbonate rock are slightly higher than those in Ordovician carbonate rocks, which may reflect the influence of the chronologic accumulation effect of crust radiogenic 40Ar. Argon isotopes of various existence states in source rocks are much more different, both 38Ar/36Ar and 40Ar/36Ar ratios at the higher temperature steps are higher than those at the lower temperature steps.``

  14. Combined carbon and hydrogen isotope fractionation investigations for elucidating benzene biodegradation pathways

    NARCIS (Netherlands)

    Fischer, A.; Herklotz, I.; Herrmann, S.; Thullner, M.; Weelink, S.A.B.; Stams, A.J.M.; Richnow, H.H.; Vogt, C.

    2008-01-01

    Recently, combined carbon and hydrogen isotope fractionation investigations have emerged as a powerful tool for the characterization of reaction mechanisms relevant for the removal of organic pollutants. Here, we applied this approach in order to differentiate benzene biodegradation pathways under o

  15. Natural carbon isotopes used to study methane consumption and production in soil

    DEFF Research Database (Denmark)

    Ambus, Per; Andersen, Bertel Lohmann; Kemner, Marianne;

    2002-01-01

    Changes in the isotopic composition of carbon can be used to reveal simultaneous occurrence of methane production and oxidation in soil. The method is conducted in laboratory jar experiments as well as in the field by using flux chambers. Simultaneous occurrence of production and oxidation...

  16. Feeding ecology of harbour porpoises: stable isotope anlaysis of carbon and nitrogen in muscle and bone

    NARCIS (Netherlands)

    Jansen, O.E.; Aarts, G.M.; Das, K.; Lepoint, G.; Michel, L.; Reijnders, P.J.H.

    2012-01-01

    Harbour porpoises are the most common small cetaceans in the North Sea and Dutch coastal waters. To study their trophic level and feeding location, stable carbon and nitrogen isotope ratios (d13C and d15N) were analysed in muscle and bone samples collected from 157 porpoises stranded along the Dutch

  17. Production of exotic, short lived carbon isotopes in ISOL-type facilities

    CERN Document Server

    Franberg, Hanna; Köster, Ulli; Ammann, Markus

    2008-01-01

    The beam intensities of short-lived carbon isotopes at Isotope Separation On-Line (ISOL) facilities have been limited in the past for technical reasons. The production of radioactive ion beams of carbon isotopes is currently of high interest for fundamental nuclear physics research. To produce radioactive ions a target station consisting of a target in a container connected to an ion source via a transfer line is commonly used. The target is heated to vaporize the product for transport. Carbon in elementary form is a very reactive element and react strongly with hot metal surfaces. Due to the strong chemisorption interaction, in the target and ion source unit, the atoms undergo significant retention on their way from the target to the ion source. Due to this the short lived isotopes decays and are lost leading to low ion yields. A first approach to tackle these limitations consists of incorporating the carbon atoms into less reactive molecules and to use materials for the target housing and the transfer line ...

  18. ANALYTICAL EMPLOYMENT OF STABLE ISOTOPES OF CARBON, NITROGEN, OXYGEN AND HYDROGEN FOR FOOD AUTHENTICATION

    Directory of Open Access Journals (Sweden)

    E. Novelli

    2011-04-01

    Full Text Available Stable isotopes of carbon, nitrogen, oxygen and hydrogen were used for analytical purposes for the discrimination of the type of production (farming vs. fishing in the case of sea bass and for geographical origin in the case of milk. These results corroborate similar experimental evidences and confirm the potential of this analytical tool to support of food traceability.

  19. Factors that control the stable carbon isotopic composition of methane produced in an anoxic marine sediment

    Science.gov (United States)

    Alperin, M. J.; Blair, Neal E.; Albert, D. B.; Hoehler, T. M.; Martens, C. S.

    1993-01-01

    The carbon isotopic composition of methane produced in anoxic marine sediment is controlled by four factors: (1) the pathway of methane formation, (2) the isotopic composition of the methanogenic precursors, (3) the isotope fractionation factors for methane production, and (4) the isotope fractionation associated with methane oxidation. The importance of each factor was evaluated by monitoring stable carbon isotope ratios in methane produced by a sediment microcosm. Methane did not accumulate during the initial 42-day period when sediment contained sulfate, indicating little methane production from 'noncompetitive' substrates. Following sulfate depletion, methane accumulation proceeded in three distinct phases. First, CO2 reduction was the dominant methanogenic pathway and the isotopic composition of the methane produced ranged from -80 to -94 per thousand. The acetate concentration increased during this phase, suggesting that acetoclastic methanogenic bacteria were unable to keep pace with acetate production. Second, acetate fermentation became the dominant methanogenic pathway as bacteria responded to elevated acetate concentrations. The methane produced during this phase was progressively enriched in C-13, reaching a maximum delta(C-13) value of -42 per thousand. Third, the acetate pool experienced a precipitous decline from greater than 5 mM to less than 20 micro-M and methane production was again dominated by CO2 reduction. The delta(C-13) of methane produced during this final phase ranged from -46 to -58 per thousand. Methane oxidation concurrent with methane production was detected throughout the period of methane accumulation, at rates equivalent to 1 to 8 percent of the gross methane production rate. Thus methane oxidation was too slow to have significantly modified the isotopic signature of methane. A comparison of microcosm and field data suggests that similar microbial interactions may control seasonal variability in the isotopic composition of methane

  20. Oxygen-18 Carbon Dioxide Isotope Ratio in Mars Atmosphere

    Science.gov (United States)

    Kostiuk, T.; Livengood, T. A.; Hewagama, T.; Smith, R.; Fast, K. E.; Annen, J.; Sonnabend, G.; Sornig, M.

    2012-09-01

    The determination of isotopic ratios on Mars is important to the study of atmospheric evolution [1]. The relative abundance of isotopes of CO2 provides insight into the loss of Mars' primordial atmosphere. Isotopic ratios also provide markers in the study of geochemistry of Mars meteorites and future returned samples formed in equilibrium with ambient atmosphere, and are probes of biogenic and abiotic chemistry, which differ in isotope fractionation. Due to its lesser gravity and relatively thin residual atmosphere, Mars' atmosphere should be enriched in heavy isotopes [1]. However Viking [2] results indicated an Earth-like singly substituted oxygen-18 CO2 isotopic ratio, 18OCO/OCO, with δ18O = 0±50‰ relative to Vienna Standard Mean Ocean Water (VSMOW). By comparison, isotopic ratios in Earth atmospheric CO2 are not uniquely defined due to seasonal and biotic variability, but have a range 0-41‰ relative to VSMOW [3, 4]. Phoenix lander TEGA [3] measurements found a modest enrichment of δ18O = 31.0±5.7‰. Only the Viking and Phoenix landers have carried a mass spectrometer to Mars, so far, until the arrival of Mars Science Laboratory in August 2012. Using ground-based spectroscopic techniques Krasnopolsky et al. [5] also found modest enrichment δ18O = 18±18‰. We present results from fully resolved spectroscopic measurements near 10.6 μm of both the normal and singly substituted oxygen- 18 CO2 lines, taken with the Goddard Space Flight Center Heterodyne Instrument for Planetary Winds And Composition (HIPWAC) at the NASA Infrared Telescope Facility on Mauna Kea, Hawaii. Measurements with spectral resolving power λ/Δλ=107 were obtained in October 2007 with an instantaneous field-of-view on the planet of ~1 arcsec, at the locations shown in Fig. 1 as open squares. The solid and broken line tracks show Mars SPICAM measurements of ozone corresponding to ozone measurements also obtained with HIPWAC and shown as hatched and solid regions [6]. Figure 1

  1. The time has changed: Middle Triassic climate changes revealed by carbon isotopes

    Science.gov (United States)

    Schmid, S.; Worden, R.; Fisher, Q.

    2003-04-01

    The Middle Triassic stratigraphy in Europe can be subdivided into a marine section of the Germanic and Paris Basin and a continental red-bed succession of Western Europe (Irish Basin, Wessex Basin). The link between the marine and continental is uncertain due to a lack of biostratigraphic information but recent palaeomagnetic studies have given a better understanding of the two environments (Hounslow et. al, 2001). In this study we have produced geochemical evidence which emphasize the implications of the palaeomagnetic data. We show that the marine and continental strata can be correlated using carbon isotopes. Throughout Europe the Middle Triassic is characterized by limestone deposits of the Muschelkalk Formation that contain evidence of a hiatus in sedimentation due to sea-level fall in the Middle Muschelkalk with the consequent deposition of evaporites. The Sherwood Sandstone Group (SSG) characterizes the Middle Triassic of Western Europe. The SSG is dominated by fluvial deposits with intercalated floodplain deposits, sand-flats and playas, which are penetrated by dolocretes and calcretes. The abundance of fluvial channels and sandflats are dependent on the fluvial activity and the water table height. In both depositional environments water plays a major role in the type of sediment. The volume of water is controlled by the prevalent climate. Climate signals are stored in carbon isotopes in both the marine Muschelkalk and the continental SSG. Carbon isotopes from the SSG from the Corrib Field, Slyne Basin, west of Ireland and from the Muschelkalk of the Germanic Basin have thus been interpreted in terms of climate change linked to stratigraphy. The continental sediments show a distinct positive carbon isotope excursion (taken from dolocretes), which is interpreted to present a more arid climate. In contrast the marine limestones exhibit a negative carbon isotopes excursion from a sea level low stand for the same time interval. The plot of both carbon isotopes

  2. Intra-lake stable isotope ratio variation in selected fish species and their possible carbon sources in Lake Kyoga (Uganda): implications for aquatic food web studies

    NARCIS (Netherlands)

    Mbabazi, D.; Makanga, B.; Orach-Meza, F.; Hecky, R.E.; Balirwa, J.S.; Ogutu-Ohwayo, R.; Verburg, P.H.; Chapman, L.; Muhumuza, E.

    2010-01-01

    The stable isotopes of nitrogen (delta 15N) and carbon (delta 13C) provide powerful tools for quantifying trophic relationships and carbon flow to consumers in food webs; however, the isotopic signatures of organisms vary within a lake. Assessment of carbon and nitrogen isotopic signatures in a suit

  3. Combined oxygen- and carbon-isotope records through the Early Jurassic: multiple global events and two modes of carbon-cycle/temperature coupling

    DEFF Research Database (Denmark)

    Hesselbo, Stephen P.; Korte, Christoph

    2010-01-01

    , to the extent that meaningful comparisons between these events can begin to be made. Here we present new carbon and oxygen isotope data from mollusks (bivalves and belemnites) and brachiopods collected through the marine Early Jurassic succession of NE England, including the Sinemurian-Plienbachian boundary...... GSSP. All materials have been screened by chemical analysis and scanning electron microscopy to check for diagenetic alteration. Analysis of carbon isotopes from marine calcite is supplemented by analysis of carbon-isotope values from fossil wood collected through the same section. It is demonstrated...... that both long-term and short-term carbon-isotope shifts from the UK Early Jurassic represent global changes in carbon cycle balances. The Sinemurian-Pliensbachian boundary event is an event of global significance and shows several similarities to the Toarcian OAE (relative sea-level change, carbon...

  4. Oxygen-18 Carbon Dioxide Isotope Ratio in Mars Atmosphere

    Science.gov (United States)

    Kostiuk, T.; Livengood, T. A.; Hewagama, T.; Smith, R.; Fast, K. E.; Annen, J.; Sonnabend, G.; Sornig, M.

    2012-09-01

    The determination of isotopic ratios on Mars is important to the study of atmospheric evolution [1]. The relative abundance of isotopes of CO2 provides insight into the loss of Mars' primordial atmosphere. Isotopic ratios also provide markers in the study of geochemistry of Mars meteorites and future returned samples formed in equilibrium with ambient atmosphere, and are probes of biogenic and abiotic chemistry, which differ in isotope fractionation. Due to its lesser gravity and relatively thin residual atmosphere, Mars' atmosphere should be enriched in heavy isotopes [1]. However Viking [2] results indicated an Earth-like singly substituted oxygen-18 CO2 isotopic ratio, 18OCO/OCO, with δ18O = 0±50‰ relative to Vienna Standard Mean Ocean Water (VSMOW). By comparison, isotopic ratios in Earth atmospheric CO2 are not uniquely defined due to seasonal and biotic variability, but have a range 0-41‰ relative to VSMOW [3, 4]. Phoenix lander TEGA [3] measurements found a modest enrichment of δ18O = 31.0±5.7‰. Only the Viking and Phoenix landers have carried a mass spectrometer to Mars, so far, until the arrival of Mars Science Laboratory in August 2012. Using ground-based spectroscopic techniques Krasnopolsky et al. [5] also found modest enrichment δ18O = 18±18‰. We present results from fully resolved spectroscopic measurements near 10.6 μm of both the normal and singly substituted oxygen- 18 CO2 lines, taken with the Goddard Space Flight Center Heterodyne Instrument for Planetary Winds And Composition (HIPWAC) at the NASA Infrared Telescope Facility on Mauna Kea, Hawaii. Measurements with spectral resolving power λ/Δλ=107 were obtained in October 2007 with an instantaneous field-of-view on the planet of ~1 arcsec, at the locations shown in Fig. 1 as open squares. The solid and broken line tracks show Mars SPICAM measurements of ozone corresponding to ozone measurements also obtained with HIPWAC and shown as hatched and solid regions [6]. Figure 1

  5. Carbon isotopic composition of fossil leaves from the Early Cretaceous sediments of western India

    Indian Academy of Sciences (India)

    S Chakraborty; B N Jana; S K Bhattacharya; I Robertson

    2011-08-01

    Stable carbon isotope analysis of fossil leaves from the Bhuj Formation, western India was carried out to infer the prevailing environmental conditions. Compression fossil leaves such as Pachypteris indica, Otozamite kachchhensis, Brachyphyllum royii and Dictyozamites sp. were recovered from three sedimentary successions of the Bhuj Formation, Early Cretaceous in age. A chronology was established based on faunal assemblage and palyno-stratigraphy and further constrained by carbon isotope stratigraphy. The three sampling sites were the Karawadi river bank near Dharesi; the Chawad river bank near Mathal; and the Pur river section near Trambau village in Gujarat. The Dharesi sample was also analyzed to investigate intra-leaf 13C variability. The mean 13C of the leaf was −24.6 ± 0.4‰ which implied negligible systematic change along the leaf axis. The Mathal sample was fragmented in nature and showed considerable variation in carbon isotopic composition. The Trambau sample considered to be the oldest, dating to the middle of Aptian (ca. 116 Ma), shows the most depleted value in 13C among all of them. The overall 13C trend ranging from mid Aptian (ca. 116 Ma) to early Albian (ca. 110 Ma) shows a progressive increase in 13C from −26.8 to −20.5‰. Based on these measurements the carbon isotopic composition of atmospheric carbon dioxide of the Aptian–Albian period is estimated to be between −7.4 and −1.7‰. The ratio of the partial pressure of carbon dioxide in leaf to that of the ambient atmosphere calculated based on a model is estimated to be similar to that of the modern plants. This indicates that the Early-Cretaceous plants adapted to the prevailing high carbon dioxide regime by increasing their photosynthetic uptake.

  6. Carbon isotope ratios of Phanerozoic marine cements: Re-evaluating the global carbon and sulfur systems

    Science.gov (United States)

    Carpenter, Scott J.; Lohmann, Kyger C.

    1997-11-01

    Original δ 13C values of abiotically precipitated marine cements from a variety of stratigraphic intervals have been used to document secular variations in the δ 13C values of Phanerozoic oceans. These, together with the ° 34S values of coeval marine sulfates, are used to examine the global cycling of carbon and sulfur. It is generally accepted that secular variation in δ 13C and δ 34S values of marine carbonates and sulfates is controlled by balanced oxidation-reduction reactions and that their long-term, steady-state variation can be predicted from the present-day isotopic fractionation ratio (Δ c/Δ s) the ratio of the riverine flux of sulfur and carbon ( Fs/ Fc). The predicted slope of the linear relation between δ 13C carb and δ 34S sulfate values is approximately -0.10 to -0.14. However, temporal variation observed in marine cement δ 13C values and the 6345 values of coeval marine sulfates produces a highly significant linear relation ( r2 = 0.80; α > 95%) with a slope of -0.24; approximately twice the predicted value. This discordance suggests that either the Phanerozoic average riverine Fs/ Fc was 1.6-3.3 times greater than today's estimates or that an additional source of 34S-depleted sulfur or 13C-enriched carbon, other than continental reservoirs, was active during the Phanerozoic. This new relation between marine δ 13C and δ 34S values suggests that the flux of reduced sulfur, iron, and manganese from seafloor hydrothermal systems affects oceanic O2 levels which, in turn, control the oxidation or burial of organic matter, and thus the δ 13C value of marine DIC. Therefore, the sulfur system (driven by seafloor hydrothermal systems) controls the carbon system rather than organic carbon burial controlling the response of δ 34S values (via formation of sedimentary pyrite). Secular variation of marine 87Sr/86Sr ratios and δ 13C values argues for a coupling of δ 34S and δ 34S values to variation in the relative contribution of seafloor

  7. Carbon and oxygen isotope composition of carbonates from an L6 chondrite: Evidence for terrestrial weathering from the Holbrook meteorite

    Science.gov (United States)

    Socki, R. A.; Gibson, E. K.; Jull, A. J. T.; Karlsson, H. R.

    1991-01-01

    Terrestrial weathering in meteorites is an important process which alters pristine elemental and isotopic abundances. The Holbrook L6 chondrite fell in 1912. Material was recovered at the time of the fall, in 1931, and 1968. The weathering processes operating on the freshly fallen meteorite in a semi-arid region of northeastern Arizona have been studied after a ground residence of 19 and 56 years. It has been shown that a large portion of the carbonate material in 7 Antarctic ordinary chondrites either underwent extensive isotopic exchange with atmospheric CO2, or formed recently in the Antarctic environment. In fact it has been demonstrated that hydrated Mg-carbonates, nesquehonite and hydromagnesite, formed in less than 40 years on LEW 85320. In order to help further constrain the effects of terrestrial weathering in meteorites, the carbon and oxygen isotopes extracted from carbonates of three different samples of Holbrook L6: a fresh sample at the time of the fall in 1912, a specimen collected in 1931, and a third specimen collected at the same site in 1968.

  8. Isotopic Approach to Soil Carbonate Dynamics and Implications for Paleoclimatic Interpretations

    Science.gov (United States)

    Pendall, E.G.; Harden, J.W.; Trumbore, S.E.; Chadwick, O.A.

    1994-01-01

    The radiocarbon content and stable isotope composition of soil carbonate are best described by a dynamic system in which isotopic reequilibration occurs as a result of recurrent dissolution and reprecipitation. Depth of water penetration into the soil profile, as well as soil age, determines the degree of carbonate isotope reequilibration. We measured ??13C, ??18O and radiocarbon content of gravel rinds and fine (soils of 3 .different ages (1000, 3800, and 6300 14 C yr B.P.) to assess the degree to which they record and preserve a climatic signal. In soils developing in deposits independently dated at 3800 and 6300 radiocarbon yr B.P., carbonate radiocarbon content above 40 cm depth suggests continual dissolution and reprecipitation, presumably due to frequent wetting events. Between 40 and 90 cm depth, fine carbonate is dissolved and precipitated as rinds that are not redissolved subsequently. Below 90 cm depth in these soils, radiocarbon content indicates that inherited, fine carbonate undergoes little dissolution and reprecipitation. In the 3800- and 6300-yr-old soils, ??13C in rind and fine carbonate follows a decreasing trend with depth, apparently in equilibrium with modern soil gas, as predicted by a diffusive model for soil CO2. ??18O also decreases with depth due to greater evaporative enrichment above 50 cm depth. In contrast, carbonate isotopes in a 1000-yr-old deposit do not reflect modern conditions even in surficial horizons; this soil has not undergone significant pedogenesis. There appears to be a lag of at least 1000 but less than 3800 yr before carbonate inherited with parent material is modified by ambient climatic conditions. Although small amounts of carbonate are inherited with the parent material, the rate of pedogenic carbonate accumulation indicates that Ca is derived primarily from eolian and rainfall sources. A model describing carbonate input and radiocarbon decay suggests that fine carbonate below 90 cm is mostly detrital (inherited

  9. Differential effects of ocean acidification on carbon acquisition in two bloom-forming dinoflagellate species.

    Science.gov (United States)

    Eberlein, Tim; Van de Waal, Dedmer B; Rost, Björn

    2014-08-01

    Dinoflagellates represent a cosmopolitan group of phytoplankton with the ability to form harmful algal blooms. Featuring a Ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO) with very low CO2 affinities, photosynthesis of this group may be particularly prone to carbon limitation and thus benefit from rising atmospheric CO2 partial pressure (pCO2) under ocean acidification (OA). Here, we investigated the consequences of OA on two bloom-forming dinoflagellate species, the calcareous Scrippsiella trochoidea and the toxic Alexandrium tamarense. Using dilute batch incubations, we assessed growth characteristics over a range of pCO2 (i.e. 180-1200 µatm). To understand the underlying physiology, several aspects of inorganic carbon acquisition were investigated by membrane-inlet mass spectrometry. Our results show that both species kept growth rates constant over the tested pCO2 range, but we observed a number of species-specific responses. For instance, biomass production and cell size decreased in S. trochoidea, while A. tamarense was not responsive to OA in these measures. In terms of oxygen fluxes, rates of photosynthesis and respiration remained unaltered in S. trochoidea whereas respiration increased in A. tamarense under OA. Both species featured efficient carbon concentrating mechanisms (CCMs) with a CO2-dependent contribution of HCO3(-) uptake. In S. trochoidea, the CCM was further facilitated by exceptionally high and CO2-independent carbonic anhydrase activity. Comparing both species, a general trade-off between maximum rates of photosynthesis and respective affinities is indicated. In conclusion, our results demonstrate effective CCMs in both species, yet very different strategies to adjust their carbon acquisition. This regulation in CCMs enables both species to maintain growth over a wide range of ecologically relevant pCO2 .

  10. Anomalous carbon-isotope ratios in nonvolatile organic material.

    Science.gov (United States)

    Kaplan, I R; Nissenbaum, A

    1966-08-12

    Organic mats are associated with sulfur deposits in Upper Pleistocene sand ridges of the coastal plain of southern Israel; black, brittle, and non-volatile, they show parallel layering but no other apparent cellular structure. Two independent carbon-14 determinations yielded ages of 27,750+/-500 and 31,370+/-1400 years. Four carbon-13:carbon-12 determinations fell within the range deltaC(13) =-82.5 to -89.3 per mille relative to the PDB standard; these appear to be the lowest values yet reported for naturally occurring high-molecular-weight organic material. The origin of the carbon is probably complex; it must have passed through at least one biologic cycle before final deposition.

  11. Carbon Isotopic Fractionation During Formation of Macromolecular Organic Grain Coatings via FTT Reactions

    Science.gov (United States)

    Nuth, J. A.; Johnson, N. M.; Elsila-Cook, J.; Kopstein, M.

    2011-01-01

    Observations of carbon isotopic fractionation of various organic compounds found in meteorites may provide useful diagnostic information concerning the environments and mechanisms that were responsible for their formation. Unfortunately, carbon has only two stable isotopes, making interpretation of such observations quite problematic. Chemical reactions can increase or decrease the C-13/C-12 ratio by various amounts, but the final ratio will depend on the total reaction pathway followed from the source carbon to the final product, a path not readily discernable after 4.5 billion years. In 1970 Libby showed that the C-13/C-12 ratios of terrestrial and meteoritic carbon were similar by comparing carbon from the Murchison meteorite to that of terrestrial sediments. More recent studies have shown that the C-13/C-12 ratio of the Earth and meteorites may be considerably enriched in C-13 compared to the ratio observed in the solar wind [2], possibly suggesting that carbon produced via ion-molecule reactions in cold dark clouds could be an important source of terrestrial and meteoritic carbon. However, meteoritic carbon has been subjected to parent body processing that could have resulted in significant changes to the C-13/C-12 ratio originally present while significant variation has been observed in the C-13/C-12 ratio of the same molecule extracted from different terrestrial sources. Again we must conclude that understanding the ratio found in meteorites may be difficult.

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

    Science.gov (United States)

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

    2015-12-01

    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, analyzed in CO2 gas liberated on phosphoric acid digestion of carbonates and reported as Δ47 values. We analyzed Δ47 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 Δ47 values were compared to in situ temperatures and the relationship between Δ47 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 Δ47-temperature calibrations. These data are significant in the interpretation of all carbonate "clumped" isotope calibration data as they show that distinct Δ47-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

  13. Calibration of the carbonate `clumped isotope' paleotemperature proxy using mollusc shells and benthic foraminiferal tests

    Science.gov (United States)

    Came, R. E.; Curry, W. B.; Weidman, C. R.; Eiler, J. M.

    2007-12-01

    It has recently been shown that the carbonate `clumped isotope' thermometer can provide temperature constraints that depend only on the isotopic composition of carbonate (in particular, on the proportion of 13C and 18O that form bonds with each other), and that do not require assumptions about the isotopic composition of the water in which the carbonate formed (Ghosh et al., 2006). Furthermore, this novel method permits the calculation of seawater δ18O based on the clumped isotope temperature estimates and the simultaneously obtained δ18O of carbonate, thereby enabling the extraction of global ice volume estimates for both the recent and distant geologic past. Here we present clumped isotope analyses of several naturally occurring marine carbonates that calcified at known temperatures in the modern ocean. First, we analyzed benthic foraminiferal tests from six high-quality multicore tops collected in the Florida Strait, spanning a temperature range of 9.3-20.2 degrees C. Second, we analyzed shallow-water mollusc shells from a variety of different climate regimes, spanning a temperature range of 2.5-26.0 degrees C. We find that the calcitic foraminiferal species Cibicidoides spp. agrees well with the inorganic calcite precipitation experiments of Ghosh et al. (2006), while the aragonitic species Hoeglundina elegans is significantly offset. Similarly, clumped isotope results obtained from aragonitic mollusc shells also reveal an offset from the Ghosh et al. (2006) trend, although the offset observed in mollusc aragonite is quite different in nature from that observed in foraminiferal aragonite. Assuming our estimates of the growth temperatures of these naturally occurring organisms are correct, these results suggest that there are vital effects associated with the stable isotope compositions of the aragonite-precipitating organisms examined in this study; further work will be required to determine their cause. Nevertheless, the internal coherence of trends for

  14. Carbon-isotope stratigraphy from terrestrial organic matter through the Monterey event, Miocene, New Jersey margin (IODP Expedition 313)

    DEFF Research Database (Denmark)

    Fang, Linhao; Bjerrum, Christian J.; Hesselbo, Stephen P.;

    2013-01-01

    The stratigraphic utility of carbon-isotope values from terrestrial organic matter is explored for Miocene siliciclastic sediments of the shallow shelf, New Jersey margin, USA (Integrated Ocean Drilling Program [IODP] Expedition 313). These shallow marine strata, rich in terrestrial organic matter......, provide a record of deposition equivalent to the Monterey event, a prolonged interval of time characterized by relatively positive carbon-isotope values recorded from foraminiferal carbonate in numerous oceanic settings. Coherent stratigraphic trends and short-term isotopic excursions are observed...... on the basis of measured C/N ratios, a high degree of conformity with the woody phytoclast record is observed. However, assuming that the correlations based on strontium-isotope values and biostratigraphy are correct, the carbon-isotope record from the New Jersey margin contrasts with that previously...

  15. Stable carbon isotope ratios of intact GDGTs indicate heterogeneous sources to marine sediments

    Science.gov (United States)

    Pearson, Ann; Hurley, Sarah J.; Walter, Sunita R. Shah; Kusch, Stephanie; Lichtin, Samantha; Zhang, Yi Ge

    2016-05-01

    Thaumarchaeota, the major sources of marine glycerol dibiphytanyl glycerol tetraether lipids (GDGTs), are believed to fix the majority of their carbon directly from dissolved inorganic carbon (DIC). The δ13C values of GDGTs (δ13CGDGT) may be powerful tools for reconstructing variations in the ocean carbon cycle, including paleoproductivity and water mass circulation, if they can be related to values of δ13CDIC. To date, isotope measurements primarily are made on the C40 biphytane skeletons of GDGTs, rather than on complete tetraether structures. This approach erases information revealed by the isotopic heterogeneity of GDGTs within a sample and may impart an isotopic fractionation associated with the ether cleavage. To circumvent these issues, we present δ13C values for GDGTs from twelve recent sediments representing ten continental margin locations. Samples are purified by orthogonal dimensions of HPLC, followed by measurement of δ13C values by Spooling Wire Microcombustion (SWiM)-isotope ratio mass spectrometry (IRMS) with 1σ precision and accuracy of ±0.25‰. Using this approach, we confirm that GDGTs, generally around -19‰, are isotopically "heavy" compared to other marine lipids. However, measured δ13CGDGT values are inconsistent with predicted values based on the 13C content of DIC in the overlying water column and the previously-published biosynthetic isotope fractionation for a pure culture of an autotrophic marine thaumarchaeon. In some sediments, the isotopic composition of individual GDGTs differs, indicating multiple source inputs. The data appear to confirm that crenarchaeol primarily is a biomarker for Thaumarchaeota, but its δ13C values still cannot be explained solely by autotrophic carbon fixation. Overall the complexity of the results suggests that both organic carbon assimilation (ca. 25% of total carbon) and multiple source(s) of exogenous GDGTs (contributing generally <30% of input to sediments) are necessary to explain the observed

  16. Stable isotopic investigations of early development in extant and fossil chambered cephalopods I. Oxygen isotopic composition of eggwater and carbon isotopic composition of siphuncle organic matter in Nautilus

    Science.gov (United States)

    Crocker, Kimberley C.; DeNiro, Michael J.; Ward, Peter D.

    1985-12-01

    Eggwaters from the chambered cephalopod Nautilus are depleted in both 18O and deuterium relative to ambient seawater. Eggwaters from six other species, including the related chambered cephalopod Sepia, do not show such depletion. These observations indicate that the previously observed step towards more positive δ 18O values in calcium carbonate laid down after Nautilus hatches, relative to carbonate precipitated prior to hatching, can be explained by equilibration of the carbonate with water in the egg before hatching and with seawater after hatching. The presence of an oxygen isotope difference between eggwater and seawater for Nautilus and its absence for Sepia suggest that hatching will be recorded in the δ 18O values of shell carbonates for some but not all extinct and extant chambered cephalopods. The δ 13C values of the organic fraction of the siphuncle in Nautilus do not show any consistent pattern with regard to the time of formation before or after hatching. This observation suggests that the minimum in δ 13C values previously observed for calcium carbonate precipitated after Nautilus hatches is not caused by a change in food sources once the animal becomes free-swimming, as has been suggested.

  17. Stable isotope composition of dissolved inorganic carbon and particulate organic carbon in sea ice from the Ross Sea, Antarctica

    Science.gov (United States)

    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 (ΣCO2), and the 13C/12C ratio of ΣCO2 ? 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 (δ13CPOC). ΣCO2 in sea ice brines ranged from 1368 to 7149 μmol kg-1, equivalent to 1483 to 2519 μmol kg-1 when normalized to 34.5 psu salinity (sΣCO2), the average salinity of Ross Sea surface waters. Sea ice primary producers removed up to 34% of the available ΣCO2, an amount much higher than the maximum removal observed in sea ice free water. Carbonate precipitation and CO2 degassing may reduce sΣCO2 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 δ13CPOC ranged from -30.5 to -9.2‰. Isotopic enrichment of the ΣCO2 pool via net community production accounts for some but not all carbon isotopic enrichment of sea ice POC. Comparisons of sΣCO2, ? and δ13CPOC within sea ice suggest that ɛp (the net photosynthetic fractionation factor) for sea ice algae is ˜8‰ smaller than the ɛp 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.

  18. On-line coupling of the MAT 251 with a Carlo Erba elemental analyzer for carbon isotope ratio measurements

    International Nuclear Information System (INIS)

    For carbon isotope investigations with a moderate precision demand of about 0.2 per mil in the isotope ratio fast and reliable results are attained by on line combination of the ANA 1500 Elemental Analyzer and the MAT 251 Isotope Mass Spectrometer. The crucial point hereof is the gas splitting device. By proper design and adjustment of the analytical parameters, good sample efficiency and a sharp CO2 bulk within the He stream is reached. The main characteristics of this combined equipment are described and some isotopic results of organic and anorganic carbon in lake sediment-samples are given as well as deltasup13C-analyses of spiritous liquors. (Author)

  19. The chromium isotopic composition of an Early to Middle Ordovician marine carbonate platform, eastern Precordillera, San Juan, Argentina

    DEFF Research Database (Denmark)

    D'Arcy, Joan Mary; Frei, Robert; Gilleaudeau, Geoffrey Jon;

    A broad suite of redox proxy data suggest that despite ocean and atmosphere oxygenation in the late Neoproterozoic, euxinic conditions persisted in the global deep oceans until the at least Ordovician [1,2,3]. Major changes in the sulphur isotopic composition of carbonate associated sulphate and co......-existing pyrite in the later Middle Ordovician are consistent with oxygen mixing at depth and ventilation of euxinic bottom waters [4]. We measured the Cr isotopic composition of an Early to Middle Ordovician carbonate platform to test whether Cr isotopes record ocean oxygenation. The Cr isotopic composition...

  20. Determination of the coefficient of iodine absorption carbon materials adsorber ventilation NPP using stable isotopes

    International Nuclear Information System (INIS)

    Submitted by nuclear-physical methods of determining the coefficient of absorption of iodine carbon materials using stable isotopes of iodine. Designed and created by pumping and measuring iodine content units. The processes of dynamic sorption of iodine on industrial carbon adsorbents studied the possibility of determining the iodine content of nuclear-physical methods and presents the metrological characteristics x-ray method. Application methods allow for the certification of carbon adsorbents gas cleaning systems and improve the safety of nuclear power plant operation

  1. Organic Carbon Isotopic Evolution during the Ediacaran-Cambrian Transition Interval in Eastern Guizhou, South China: Paleoenvironmental and Stratigraphic Implications

    Institute of Scientific and Technical Information of China (English)

    YANG Xinglian; ZHU Maoyan; GUO Qingjun; ZHAO Yuanlong

    2007-01-01

    Secular variations of carbon isotopic composition of organic carbon can be used in the study of global environmental variation, the carbon cycle, stratigraphic delimitation, and biological evolution, etc. Organic carbon isotopic analysis of the Nangao and Zhalagou sections in eastern Guizhou reveals a negative excursion near the Precambrian-Cambrian boundary that correlates with a distinct carbonate carbon isotopic negative excursion at this boundary globally. Our results also demonstrate that several alternating positive and negative shifts occur in the Meishucunian, and an obvious negative anomaly appears at the boundary between the Meishucunian and Qiongzhusian. The isotope values are stable in the middle and lower parts but became more positive in the upper part of the Qiongzhusian. Evolution of organic carbon isotopes from the two sections in the deepwater facies can be well correlated with that of the carbonate carbon isotopes from the section in the shallow water facies. Integrated with other stratigraphic tools, we can precisely establish a lower Cambrian stratigraphic framework from shallow shelf to deep basin of the Yangtze Platform.

  2. Global Cr-isotope distributions in surface seawater and incorporation of Cr isotopes into carbonate shells

    OpenAIRE

    Paulukat, Cora Stefanie; Frei, Robert; Vögelin, Andrea Regula; Samankassou, Elias

    2015-01-01

    In this study we present the Cr-isotope composition of surface seawater from several locations worldwide. In addition to the samples from the oceans (Atlantic Ocean, Pacific Ocean, Southern Ocean and Artic Ocean) we analysed water samples from areas with a more limited water exchange (Mediterranean Sea, Baltic Sea, Øresund and Kattegat). The long residence time of Cr (7,000 to 40,000 years) [1,2,3] relative to the ocean mixing time (1,000 to 2,000 years) [4] could lead to the expectation that...

  3. Mixing of water in a carbonate aquifer, southern Italy, analysed through stable isotope investigations

    Directory of Open Access Journals (Sweden)

    Petrella Emma

    2013-01-01

    Full Text Available Mixing of water was analysed in a carbonate aquifer, southern Italy, through stable isotope investigations (18O,δ2H. The input signal (rainwater was compared with the isotopic content of a 35-meter groundwater vertical prof ile, over a 1-year period. Within the studied aquifer, recharge and f low are diffuse in a well-connected f issure network.At the test site, the comparison between input and groundwater isotopic signals illustrates that no eff icient mixing takes place in the whole unsaturated zone, between the fresh inf iltration water and the stored water.When analysing the stable isotope composition of groundwater, signif icant variations were observed above the threshold elevation of 1062 m asl, while a nearly constant composition was observed below the same threshold. Thus, temporal variations in stable isotope composition of rainwater are completely attenuated just in the deeper phreatic zone.On the whole, taking into consideration also the results of previous studies in the same area, the investigations showed that physical characteristics of the carbonate bedrock, as well as aquifer heterogeneity, are factors of utmost importance in inf luencing the complete mixing of water. These f indings suggest a more complex scenario at catchment scale.

  4. Carbon and oxygen isotopic ratios for nearby miras

    CERN Document Server

    Hinkle, K H; Straniero, O

    2016-01-01

    C and O isotopic ratios are reported for a sample of 46 Mira and SRa-type variable AGB stars. Vibration-rotation 1st and 2nd overtone CO lines in 1.5 to 2.5 $\\mu$m spectra were measured to derive isotopic ratios for 12C/13C, 16O/17O, and 16O/18O. Comparisons with previous measurements for individual stars and with various samples of evolved stars are discussed. Models for solar composition AGB stars of different initial masses are used to interpret our results. We find that the majority of the M stars had main sequence masses < 2 Msun and have not experienced sizable third dredge-up episodes. The progenitors of the four S-type stars in our sample are slightly more massive. Of the 6 C stars in the sample three have clear evidence relating their origin to the occurrence of the third dredge-up. Comparisons with O-rich presolar grains from AGB stars that lived before the formation of the solar system reveal variations in the interstellar medium chemical composition. The present generation of low-mass AGB stars...

  5. Chromium Isotopes in Carbonate Rocks: New Insights into Proterozoic Atmospheric Oxygenation

    Science.gov (United States)

    Kah, L. C.; Gilleaudeau, G. J.; Frei, R.; Kaufman, A. J.; Azmy, K.; Bartley, J. K.; Chernyavskiy, P.; Knoll, A. H.

    2015-12-01

    There has been a long-standing debate in geobiology about the role that Earth's oxygenation played in the evolution of complex life. Temporal linkages exist between the Great Oxidation Event (GOE) and the evolution of eukaryotes, as well as Neoproterozoic rise in oxygen and the diversification of metazoans. Further advances have been hampered, however, by the lack of direct proxies that mark specific levels of atmospheric pO2 in the geologic past. Chromium (Cr) isotopes show promise in this regard because the oxidation of Cr during terrestrial weathering—which results in isotopic fractionation—is dependent on a specific threshold of atmospheric pO2 (0.1-1% of the present atmospheric level [PAL]). This threshold value broadly coincides with recent estimates of the oxygen requirements of early animals. Here we report new Cr-isotope data from four late Mesoproterozoic carbonate-dominated successions. Samples were collected from the Turukhansk Uplift (Siberia), the El Mreiti Group (Mauritania), the Vazante Group (Brazil), and the Angmaat Formation (Canada). We emphasize the application of Cr-isotopes to carbonate rocks because the broad temporal range of this lithology in the geologic record provides an opportunity to significantly expand our understanding of Proterozoic oxygenation on shorter time scales. Our data indicate that pO2 levels required to support early animals were attained long before Neoproterozoic metazoan diversification, although the large degree of isotopic heterogeneity in our dataset may indicate that pO2 > 0.1-1% PAL was only a transient phenomenon in the Mesoproterozoic. This study demonstrates the utility of Cr-isotopes as an atmospheric redox proxy in carbonate rocks and helps inform future avenues of research on Proterozoic pO2 thresholds.

  6. Assessing the duration and possible causes of the earliest Toarcian carbon isotopic excursion

    Science.gov (United States)

    Krencker, Francois-Nicolas; Bodin, Stéphane; Suan, Guillaume; Kabiri, Lahcen; Immenhauser, Adrian

    2013-04-01

    The early Toarcian stage (Early Jurassic) records two short-lived events of major faunal turnover and environmental perturbation. The first event (eT-E) occurs during the earliest Toarcian (early Polymorphum chronozone) and has been documented only in a few sites worldwide. The second event, better known as the Toarcian Oceanic Anoxic Event (T-OAE) has been documented in numerous sites from Northern Siberia to Argentina. Both events are marked by negative carbon isotope excursions (CIE) recorded in carbonate and organic substrate. Therefore they are thought to be associated with major changes in carbon cycling. Similarities between the eT-E and the T-OAE thus lead to the conclusion that these events might have been triggered by similar mechanisms. If this is the case, the CIEs associated with both events should have a comparable duration. In order to valid or falsify this hypothesis, it is therefore crucial to constrain the duration of both events. The duration of the T-OAE CIE was assessed in several papers by cyclostratigraphic analyses thanks to favourable outcropping condition. It is however not the case for the eT-E CIE, this latter being often associated with sedimentary condensation or hiatal surfaces. We make use of the high palaeo-subsidence rates of the Lower Toarcian Moroccan shelf leading to extended sections in the High Atlas Basin. The Foum Tillicht section was sampled in increments of 20 cm across a stratigraphic interval of 50 m, covering the Polymorphum chronozone. Carbon and oxygen isotopes analyses were performed on micritic and organic matter. Ammonites and nannofossils biostratigraphy aided in calibrating geochemical analyses. Carbon isotopes data display a rhythmic pattern. Preliminary results indicate that the eT-E negative carbon isotope excursion lasted around 400 kyr.

  7. Magnesium isotope fractionation during hydrous magnesium carbonate precipitation with and without cyanobacteria

    Science.gov (United States)

    Mavromatis, Vasileios; Pearce, Christopher R.; Shirokova, Liudmila S.; Bundeleva, Irina A.; Pokrovsky, Oleg S.; Benezeth, Pascale; Oelkers, Eric H.

    2012-01-01

    The hydrous magnesium carbonates, nesquehonite (MgCO 3·3H 2O) and dypingite (Mg 5(CO 3) 4(OH) 2·5(H 2O)), were precipitated at 25 °C in batch reactors from aqueous solutions containing 0.05 M NaHCO 3 and 0.025 M MgCl 2 and in the presence and absence of live photosynthesizing Gloeocapsa sp. cyanobacteria. Experiments were performed under a variety of conditions; the reactive fluid/bacteria/mineral suspensions were continuously stirred, and/or air bubbled in most experiments, and exposed to various durations of light exposure. Bulk precipitation rates are not affected by the presence of bacteria although the solution pH and the degree of fluid supersaturation with respect to magnesium carbonates increase due to photosynthesis. Lighter Mg isotopes are preferentially incorporated into the precipitated solids in all experiments. Mg isotope fractionation between the mineral and fluid in the abiotic experiments is identical, within uncertainty, to that measured in cyanobacteria-bearing experiments; measured δ 26Mg ranges from -1.54‰ to -1.16‰ in all experiments. Mg isotope fractionation is also found to be independent of reactive solution pH and Mg, CO 32-, and biomass concentrations. Taken together, these observations suggest that Gloeocapsa sp. cyanobacterium does not appreciably affect magnesium isotope fractionation between aqueous fluid and hydrous magnesium carbonates.

  8. Carbon isotopic analysis of atmospheric methane by isotope-ratio-monitoring gas chromatography-mass spectrometry

    Science.gov (United States)

    Merritt, Dawn A.; Hayes, J. M.; Des Marais, David J.

    1995-01-01

    Less than 15 min are required for the determination of delta C(sub PDB)-13 with a precision of 0.2 ppt(1 sigma, single measurement) in 5-mL samples of air containing CH4 at natural levels (1.7 ppm). An analytical system including a sample-introduction unit incorporating a preparative gas chromatograph (GC) column for separation of CH4 from N2, O2, and Ar is described. The 15-min procedure includes time for operation of that system, high-resolution chromatographic separation of the CH4, on-line combustion and purification of the products, and isotopic calibration. Analyses of standards demonstrate that systematic errors are absent and that there is no dependence of observed values of delta on sample size. For samples containing 100 ppm or more CH4, preconcentration is not required and the analysis time is less than 5 min. The system utilizes a commercially available, high-sensitivity isotope-ratio mass spectrometer. For optimal conditions of smaple handling and combustion, performance of the system is within a factor of 2 of the shot-noise limit. The potential exists therefore for analysis of samples as small as 15 pmol CH4 with a standard deviation of less than 1 ppt.

  9. Oxygen isotope fractionation in the vacuum ultraviolet photodissociation of carbon monoxide: Wavelength, pressure and temperature dependency.

    Energy Technology Data Exchange (ETDEWEB)

    Chakraborty, Subrata; Davis, Ryan; Ahmed, Musahid; Jackson, Teresa L.; Thiemens, Mark H.

    2012-01-03

    Several absorption bands exist in the VUV region of Carbon monoxide (CO). Emission spectra indicate that these bands are all predissociative. An experimental investigation of CO photodissociation by vacuum ultraviolet photons (90 to 108 nm; ~13 to 11 eV) from the Advanced Light Source Synchrotron and direct measurement of the associated oxygen isotopic composition of the products are presented here. A wavelength dependency of the oxygen isotopic composition in the photodissociation product was observed. Slope values (δ'{sup 18}O/ δ'{sup 17}O) ranging from 0.76 to 1.32 were observed in oxygen three-isotope space (δ'{sup 18}O vs. δ'{sup 17}O) which correlated with increasing synchrotron photon energy, and indicate a dependency of the upper electronic state specific dissociation dynamics (e.g., perturbation and coupling associated with a particular state). An unprecedented magnitude in isotope separation was observed for photodissociation at the 105 and 107 nm synchrotron bands and are found to be associated with accidental predissociation of the vibrational states ({nu} = 0 and 1) of the upper electronic state E{sup 1}Π. For each synchrotron band, a large (few hundred per mil) extent of isotopic fractionation was observed and the range of fractionation is a combination of column density and exposure time. A significant temperature dependency in oxygen isotopic fractionation was observed, indicating a rotational level dependency in the predissociation process.

  10. Technical Note: Constraining stable carbon isotope values of microphytobenthos (C3 photosynthesis) in the Arctic for application to food web studies

    OpenAIRE

    Oxtoby, L. E.; Mathis, J. T.; Juranek, L. W.; M. J. Wooller

    2013-01-01

    Microphytobenthos (MPB) tends to be omitted as a possible carbon source to higher trophic level consumers in high latitude marine food web models that use stable isotopes. Here, we used previously published relationships relating the concentration of aqueous carbon dioxide ([CO2]aq), the stable carbon isotopic composition of dissolved inorganic carbon (DIC) (δ13CDIC), and algal growth rates (μ) to estimate the stable carbon isotop...

  11. Regeneration of the iodine isotope-exchange efficiency for nuclear-grade activated carbons

    International Nuclear Information System (INIS)

    The removal of radioactive iodine from air flows passing through impregnated activated carbons depends on a minimum of three distinguishable reactions: (1) adsorption on the carbon networks of the activated carbons, (2) iodine isotope exchange with impregnated iodine-127, and (3) chemical combination with impregnated tertiary amines when present. When a carbon is new, all three mechanisms are at peak performance and it is not possible to distinguish among the three reactions by a single measurement; the retention of methyl iodide-127 is usually equal to the retention of methyl iodide-131. After the carbon is placed in service, the three mechanisms of iodine removal are degraded by the contaminants of the air at different rates; the adsorption process degrades faster than the other two. This behavior will be shown by comparisons of methyl iodide-127 and methyl iodide-131 penetration tests. It was found possible to regenerate the iodine isotope-exchange efficiency by reaction with airborne chemical reducing agents with little or no improvement in methyl iodine-127 retention. Examples will be given of the chemical regeneration of carbons after exhaustion with known contaminants as well as for many carbons removed from nuclear power operations. The depth profile of methyl iodide-131 penetration was determined in 2-inch deep layers before and after chemical treatments

  12. Acquisition of isotopic composition for surface snow in East Antarctica and the links to climatic parameters

    Science.gov (United States)

    Touzeau, Alexandra; Landais, Amaëlle; Stenni, Barbara; Uemura, Ryu; Fukui, Kotaro; Fujita, Shuji; Guilbaud, Sarah; Ekaykin, Alexey; Casado, Mathieu; Barkan, Eugeni; Luz, Boaz; Magand, Olivier; Teste, Grégory; Le Meur, Emmanuel; Baroni, Mélanie; Savarino, Joël; Bourgeois, Ilann; Risi, Camille

    2016-04-01

    The isotopic compositions of oxygen and hydrogen in ice cores are invaluable tools for the reconstruction of past climate variations. Used alone, they give insights into the variations of the local temperature, whereas taken together they can provide information on the climatic conditions at the point of origin of the moisture. However, recent analyses of snow from shallow pits indicate that the climatic signal can become erased in very low accumulation regions, due to local processes of snow reworking. The signal-to-noise ratio decreases and the climatic signal can then only be retrieved using stacks of several snow pits. Obviously, the signal is not completely lost at this stage, otherwise it would be impossible to extract valuable climate information from ice cores as has been done, for instance, for the last glaciation. To better understand how the climatic signal is passed from the precipitation to the snow, we present here results from varied snow samples from East Antarctica. First, we look at the relationship between isotopes and temperature from a geographical point of view, using results from three traverses across Antarctica, to see how the relationship is built up through the distillation process. We also take advantage of these measures to see how second-order parameters (d-excess and 17O-excess) are related to δ18O and how they are controlled. d-excess increases in the interior of the continent (i.e., when δ18O decreases), due to the distillation process, whereas 17O-excess decreases in remote areas, due to kinetic fractionation at low temperature. In both cases, these changes are associated with the loss of original information regarding the source. Then, we look at the same relationships in precipitation samples collected over 1 year at Dome C and Vostok, as well as in surface snow at Dome C. We note that the slope of the δ18O vs. temperature (T) relationship decreases in these samples compared to those from the traverses, and thus caution is

  13. Acquisition of isotopic composition for surface snow in East Antarctica and the links to climatic parameters

    Directory of Open Access Journals (Sweden)

    A. Touzeau

    2015-11-01

    Full Text Available The isotopic composition of oxygen and hydrogen in ice cores are invaluable tools for the reconstruction of past climate variations. Used alone, they give insights into the variations of the local temperature, whereas taken together they can provide information on the climatic conditions at the point of origin of the moisture. However, recent analyses of snow from shallow pits indicate that the climatic signal can become erased in very low accumulation regions, due to local processes of snow reworking. The signal to noise ratio decreases and the climatic signal can then only be retrieved using stacks of several snow pits. Obviously, the signal is not completely lost at this stage, otherwise it would be impossible to extract valuable climate information from ice cores as has been done, for instance, for the last glaciation. To better understand how the climatic signal is passed from the precipitation to the snow, we present here results from varied snow samples from East Antarctica. First, we look at the relationship between isotopes and temperature from a geographical point of view, using results from three traverses across Antarctica, to see how the relationship is built up through the distillation process. We also take advantage of these measures to see how second order parameters (d-excess and 17O-excess are related to δ18O and how they are controlled. d-excess increases in the interior of the continent (i.e. when δ18O decreases, due to the distillation process, whereas 17O-excess decreases in remote areas, due to kinetic fractionation at low temperature. In both cases, these changes are associated with the loss of original information regarding the source. Then, we look at the same relationships in precipitation samples collected over one year at Dome C and Vostok, as well as in surface snow at Dome C. We note that the slope of the δ18O / T relationship decreases in these samples compared to those from the traverses, and thus advocate

  14. Carbon, cesium and iodine isotopes in Japanese cedar leaves from Iwaki, Fukushima

    DEFF Research Database (Denmark)

    Xu, Sheng; Cook, Gordon T.; Cresswell, Alan J.;

    2016-01-01

    Japanese cedar leaves from Iwaki, Fukushima were analyzed for carbon, cesium and iodine isotopic compositions before and after the 2011 nuclear accident. The Δ14C values reflect ambient atmospheric 14C concentrations during the year the leaves were sampled/defoliated, and also previous year......(s). The elevated 129I and 134,137Cs concentrations are attributed to direct exposure to the radioactive fallout for the pre-fallout-expended leaves and to internal translocation from older parts of the tree for post-fallout-expended leaves. 134Cs/137Cs and 129I/137Cs activity ratios suggest insignificant isotopic...

  15. Authenticity and Traceability of Vanilla Flavors by Analysis of Stable Isotopes of Carbon and Hydrogen

    DEFF Research Database (Denmark)

    Hansen, Anne-Mette Sølvbjerg; Fromberg, Arvid; Frandsen, Henrik Lauritz

    2014-01-01

    . The authenticity of the flavor compound vanillin was evaluated on the basis of measurements of ratios of carbon stable isotopes (delta C-13). It was found that results of delta C-13 for vanillin extracted from Vanilla planifolia and Vanilla tahitensis were significantly different (t test) and that it was possible...... to differentiate these two groups of natural vanillin from vanillin produced otherwise. Vanilla flavors were also analyzed for ratios of hydrogen stable isotopes (delta H-2). A graphic representation of delta C-13 versus delta H-2 revealed that vanillin extracted from pods grown in adjacent geographic origins...

  16. Coniacian-maastrichtian calcareous nannofossil biostratigraphy and carbon-isotope stratigraphy in the Zagros Basin (Iran)

    DEFF Research Database (Denmark)

    Razmjooei, Mohammad Javad; Thibault, Nicolas; Kani, Anoshiravan;

    2014-01-01

    Calcareous nannofossil biostratigraphy and stable isotope stratigraphy have been investigated in the Shahneshin section of the Gurpi Formation from the Zagros Basin (Iran). The results show that the Gurpi Formation spans the late early Coniacian to late Thanetian. The age-model shows that the...... magnetostratigraphy in the Santonian-early Campanian interval. The δ13C correlation, supported by calcareous nannofossil biostratigraphy, brings insights into: (1) the position of the Coniacian/Santonian, Santonian/Campanian and Campanian/Maastrichtian boundaries with respect to carbon-isotope stratigraphy and...

  17. Centennial evolution of the atmospheric methane budget: what do the carbon isotopes tell us?

    OpenAIRE

    K. R. Lassey; Etheridge, D. M.; Lowe, D. C.; Smith, A M; D. F. Ferretti

    2007-01-01

    Little is known about how the methane source inventory and sinks have evolved over recent centuries. New and detailed records of methane mixing ratio and isotopic composition (12CH4, 13CH4 and 14CH4) from analyses of air trapped in polar ice and firn can enhance this knowledge. We use existing bottom-up constructions of the source history, including "EDGAR"-based constructions, as inputs to a model of the evolving global budget for methane and for its carbon isotope composition thro...

  18. Inorganic carbon acquisition in potentially toxic and non-toxic diatoms: the effect of pH-induced changes in the seawater carbonate chemistry

    DEFF Research Database (Denmark)

    Trimborn, S; Lundholm, Nina; Thoms, S;

    2008-01-01

    The effects of pH-induced changes in seawater carbonate chemistry on inorganic carbon (C-i) acquisition and domoic acid (DA) production were studied in two potentially toxic diatom species, Pseudo-nitzschia multiseries and Nitzschia navis-varingica, and the non-toxic Stellarima stellaris. In vivo...

  19. Carbon rhizodeposition by plants of contrasting strategies for resource acquisition: responses to various nitrogen fertility regimes

    Science.gov (United States)

    Baptist, Florence; Aranjuelo, I.; Lopez-Sangil, L.; Rovia, P.; Nogués, S.

    2010-05-01

    Rhizodeposition by plants is one of the most important physiological mechanisms related to carbon and nitrogen cycling which is also believed to vary along the acquisition-conservation continuum. However, owing to methodological difficulties (i.e. narrow zone of soil around roots and rapid assimilation by soil microbes), root exudation and variations between species are one of the most poorly understood belowground process. Although previous approaches such as hydroponic culture based system, permit the chemical analysis of exudates, the fact that this protocol is qualitative, conditions its utility (see review in Phillips et al. 2008). Others techniques based on pulse-labelling approach have been developed to quantify rhizodeposition but are rarely sufficient to uniformly label all plant inputs to soil. Consequently with this typical pulse chase methods, recent assimilates are labeled but the recalcitrant carbon will not be labeled and therefore the contribution of this carbon will not be considered. Hence, traditional pulse labelling is not a quantitative means of tracing carbon due to inhomogeneous labelling and so limits greatly comparative studies of rhizodeposition fluxes at the interspecific level. In this study we developped a new protocole based on a long-term (3 months) steady state 13C labelling in order (1) to quantify rhizodeposition fluxes for six graminoid species caracterized by contrasted nutrient acquisition strategies and (2) to investigate to what extent various level of nitrogen fertility regimes modulate rhizodeposition fluxes. This method will enable to quantify under natural soil conditions both the accumulation of 13C in the soil but also the quantity that has been respired by the microorganisms during a given time and so will give an integrated picture of rhizodeposition fluxes for each species under each nitrogen fertility level. Results are currently being processed and will be presented at the conference. References: Phillips RP, Erlitz

  20. Stable carbon isotope fractionation during the biodegradation of lambda-cyhalothrin

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Xiaoli [MOE Key Laboratory of Environmental Remediation and Ecosystem Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058 (China); Department of Environmental Engineering, Quzhou University, Quzhou 324000 (China); Xu, Zemin [MOE Key Laboratory of Environmental Remediation and Ecosystem Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058 (China); Zhang, Xichang [Laboratory for Teaching in Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058 (China); Yang, Fangxing, E-mail: fxyang@zju.edu.cn [MOE Key Laboratory of Environmental Remediation and Ecosystem Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058 (China); Department of Effect-Directed Analysis, Helmholtz Centre for Environmental Research — UFZ, Leipzig 04318 (Germany)

    2015-11-01

    In this study, the microbial degradation of lambda-cyhalothrin in soil was investigated using compound-specific stable isotope analysis. The results revealed that lambda-cyhalothrin was biodegraded in soil under laboratory conditions. The half-lives of lambda-cyhalothrin were determined to be 49 and 161 days in non-sterile and sterile soils spiked with 2 mg/kg lambda-cyhalothrin and 84 and 154 days in non-sterile and sterile soils spiked with 10 mg/kg lambda-cyhalothrin, respectively. The biodegradation of lambda-cyhalothrin resulted in carbon isotope fractionation, which shifted from − 29.0‰ to − 26.5‰ in soil spiked with 2 mg/kg lambda-cyhalothrin, and to − 27.5‰ with 10 mg/kg lambda-cyhalothrin. A relationship was established between the stable carbon isotope fraction and the residual concentrations of lambda-cyhalothrin by the Rayleigh equation in which the carbon isotope enrichment factor ε of the microbial degradation of lambda-cyhalothrin in the soil was calculated as − 2.53‰. This study provides an approach to quantitatively evaluate the biodegradation of lambda-cyhalothrin in soil in field studies. - Highlights: • Abiotic and biotic degradation of lambda-cyhalothrin were observed in soil. • Biodegradation of lambda-cyhalothrin was evaluated by CSIA. • Biodegradation of lambda-cyhalothrin leads to carbon isotope fractionation. • An enrichment factor ε of lambda-cyhalothrin was determined as − 2.53‰.

  1. Large amplitude carbon isotope excursion during the Late Silurian Lau Event

    Science.gov (United States)

    Schoenmaker, N. R.; Reichart, G. J.; Nierop, K. G. J.; Mann, U.; White, T.; Sancay, R. H.

    2010-05-01

    High magnitude excursions in the stable carbon isotope record reveal that the Silurian greenhouse world (443.7-416.0 Ma) represents a period of globally unstable environmental conditions. Fundamental changes in the global carbon cycle were more frequent and had a larger impact during the Silurian compared to any other period of the Phanerozoic [1]. The late Silurian "Lau event" is the largest of four major positive d13Ccarb excursions. The carbon isotope excursion associated with the "Lau event" is recognized globally and reaches values ranging from +6‰ from the Eastern Baltic, +8.5‰ on Gotland, 11‰ from southern Sweden and even up to 12‰ in Australia, Queensland. This makes the "Lau event" the strongest d13C excursion of the entire Phanerozoic, comparable in amplitude to Precambrian events. However, the mechanism underlying the Silurian stable isotope excursions is ill understood. Scenarios proposed include enhanced carbon burial due to anoxic conditions [2] and/or enhanced productivity [3]. Alternative hypotheses range from alternating wet and humid periods influencing global ocean circulation [4], weathering of carbonates [5] to changes in the primary producer community [6]. Evaluating these different scenarios critically relies on establishing the true magnitude of the isotopic excursions and rates of change. Existing stable carbon isotope studies of the Lau event were based on analyses of bulk carbonates or bulk organic matter. Both signal carriers are subject to admixing of organic matter or carbonates from various sources. Moreover, preferential preservation of some organic moieties, e.g. lipids, over other potentially offsets isotopic records, since the carbon isotopic signatures between these moieties substantially differ. A stable organic geochemical composition over the isotope events is thus crucial to ensure capturing the true amplitude of the excursion. Here we therefore investigate, using Curie point pyrolysis GC-MS, the composition of the

  2. Vegetational ecotype of the Gyirong Basin in Tibet, China and its response in stable carbon isotopes of mammaltooth enamel

    Institute of Scientific and Technical Information of China (English)

    DENG Tao; LI Yumei

    2005-01-01

    Carbon isotope analysis of modern herbaceous plants in the Gyirong Basin (Tibet, China) indicates that although C3 plants are dominant, C4 plants rarely comprise of the vegetation in the area at 4000 m above sea level. The C4 plants discovered in the Gyirong Basin are Salsola nepalensis of Chenopodiaceae and Pennisetum flaccidum of Gramineae, affirming that C4 plants affected by high solar gain can be distributed at high altitude, which supports the opinion that some C4 plants can exist in areas of high elevation. Carbon isotope analysis of herbivore tooth enamel from the Gyirong Basin indicates that carbon isotopes of structural carbonate in biogenic apatite at high altitude still keep a stable enrichment relationship with those of plants in their diet. Carbon isotopes in tooth enamel are therefore an accurate proxy for vegetation ecotypes and should reflect climatic and environmental features.

  3. Dual carbon isotope characterization of total organic carbon in wintertime carbonaceous aerosols from northern India

    Science.gov (United States)

    Bikkina, Srinivas; Andersson, August; Sarin, M. M.; Sheesley, R. J.; Kirillova, E.; Rengarajan, R.; Sudheer, A. K.; Ram, K.; Gustafsson, Örjan

    2016-05-01

    Large-scale emissions of carbonaceous aerosols (CA) from South Asia impact both regional climate and air quality, yet their sources are not well constrained. Here we use source-diagnostic stable and radiocarbon isotopes (δ13C and Δ14C) to characterize CA sources at a semiurban site (Hisar: 29.2°N, 75.2°E) in the NW Indo-Gangetic Plain (IGP) and a remote high-altitude location in the Himalayan foothills (Manora Peak: 29.4°N, 79.5°E, 1950 m above sea level) in northern India during winter. The Δ14C of total aerosol organic carbon (TOC) varied from -178‰ to -63‰ at Hisar and from -198‰ to -1‰ at Manora Peak. The absence of significant differences in the 14C-based fraction biomass of TOC between Hisar (0.81 ± 0.03) and Manora Peak (0.82 ± 0.07) reveals that biomass burning/biogenic emissions (BBEs) are the dominant sources of CA at both sites. Combining this information with δ13C, other chemical tracers (K+/OC and SO42-/EC) and air mass back trajectory analyses indicate similar source regions in the IGP (e.g., Punjab and Haryana). These results highlight that CA from BBEs in the IGP are not only confined to the atmospheric boundary layer but also extend to higher elevations of the troposphere, where the synoptic-scale circulations could substantially influence their abundances both to the Himalayas and over the downwind oceanic regions such as the Indian Ocean. Given the vast emissions of CA from postharvest crop residue combustion practices in the IGP during early Northeast Monsoon, this information is important for both improved process and model understanding of climate and health effects, as well as in guiding policy decision aiming at reducing emissions.

  4. Geochemistry of carbon stable isotopes in the sea

    International Nuclear Information System (INIS)

    This paper describes geochemical process which affect the distribution in the sea of the 13C/12C ratio of total inorganic dissolved CO2; synthesis of the biomass and respiratory phenomena; oxidation of organic matter; dissolution of carbonates; run off waters; exchange of CO2 between sea and atmosphere. Some applications to the paleoclimatology are presented. (author)

  5. A molecular organic carbon isotope record of Miocene climate changes

    NARCIS (Netherlands)

    Schoell, M.; Schouten, S.; Sinninghe Damsté, J.S.; Leeuw, J.W. de; Summons, R.E.

    1994-01-01

    The difference in carbon-13 (13C) contents of hopane and sterane biomarkers in the Monterey formation (Naples Beach, California) parallels the Miocene inorganic record of the change in 18O (δ18O), reflecting the Miocene evolution from a well-mixed to a highly stratified photic zone (upper 100 meters

  6. Temporal Variability in Carbon Isotope Composition of Leaf-Respired Carbon Dioxide

    Science.gov (United States)

    Barbour, M. M.; Hanson, D. T.; Bickford, C. P.; McDowell, N. G.

    2005-12-01

    The stable carbon isotope composition of leaf-respired CO2 (δ13CRl) has enormous potential to allow partitioning of ecosystem respiration into various components, to provide information on key physiological processes, and to trace carbon fluxes through plants and ecosystems. However, difficulties in measuring and understanding variation in δ13CRl have limited its application. We coupled an open gas exchange system (LI-6400, LiCor) to a tunable diode laser (TGA100A, Campbell Scientific) enabling measurement of leaf respiratory CO2 fluxes and δ13CRl every three minutes, with a precision of at least ±0.3 per mil. We also measured oxygen consumption rates, allowing calculation of the respiratory quotient ( RQ) and indicating likely respiratory substrates. Castor bean ( Ricinus communis) plants grown at high and low light were placed in the dark after different lengths of time exposed to sunlight and variation in δ13CRl measured to test the patterns in variation in δ13CRl predicted by existing biochemical models. CO2 respired by leaves previously exposed to high cumulative incident irradiance was up to 11 per mil more enriched than phloem sap sugars for the first 10 to 15 minutes after plants had been moved into the dark . This enrichment rapidly decreased, so that by 30 minutes in the dark δ13CRl was 5 per mil more enriched than phloem sap sugars. CO2 production rates were also initially very high and rapidly decreased. RQ for plants grown in high light varied between 0.8 and 1.2, indicating that carbohydrates and/or organic acids were the respiratory substrates. δ13CRl measured 30 to 80 minutes after plants had been moved into the dark increased with increasing δ13C of phloem sap sugars. The RQ values of plants grown at low light suggested that the respiratory substrates were fatty acids or amino acids ( RQ of around 0.6), or lipids ( RQ less than 0.4). δ13CRl values were enriched by either 4 per mil ( RQ = 0.3) or 12 per mil ( RQ = 0.5) compared to phloem

  7. Soil organic carbon assessments in cropping systems using isotopic techniques

    Science.gov (United States)

    Martín De Dios Herrero, Juan; Cruz Colazo, Juan; Guzman, María Laura; Saenz, Claudio; Sager, Ricardo; Sakadevan, Karuppan

    2016-04-01

    Introduction of improved farming practices are important to address the challenges of agricultural production, food security, climate change and resource use efficiency. The integration of livestock with crops provides many benefits including: (1) resource conservation, (2) ecosystem services, (3) soil quality improvements, and (4) risk reduction through diversification of enterprises. Integrated crop livestock systems (ICLS) with the combination of no-tillage and pastures are useful practices to enhance soil organic carbon (SOC) compared with continuous cropping systems (CCS). In this study, the SOC and its fractions in two cropping systems namely (1) ICLS, and (2) CCS were evaluated in Southern Santa Fe Province in Argentina, and the use of delta carbon-13 technique and soil physical fractionation were evaluated to identify sources of SOC in these systems. Two farms inside the same soil cartographic unit and landscape position in the region were compared. The ICLS farm produces lucerne (Medicago sativa Merrill) and oat (Avena sativa L.) grazed by cattle alternatively with grain summer crops sequence of soybean (Glicine max L.) and corn (Zea mays L.), and the farm under continuous cropping system (CCS) produces soybean and corn in a continuous sequence. The soil in the area is predominantly a Typic Hapludoll. Soil samples from 0-5 and 0-20 cm depths (n=4) after the harvest of grain crops were collected in each system and analyzed for total organic carbon (SOC, 0-2000 μm), particulate organic carbon (POC, 50-100 μm) and mineral organic carbon (MOC, ANOVA and Tukey statistical analysis were carried out for all data. The SOC was higher in ICLS than in CCS at both depths (20.8 vs 17.7 g kg-1 for 0-5 cm and 16.1 vs 12.7 g kg-1 at 0-20 cm, respectively, P<0.05). MOC was similar at both depths, and POC was higher in CCS than in ICLS at 0-5 cm, while at 0-20 cm this trend was opposite. This is probably due to the presence of deep roots under pastures in ICLS. Delta

  8. Exogenous carbon acquisition of photosynthesis in Porphyra haitanensis (Bangiales,Rhodophyta) under emersed state

    Institute of Scientific and Technical Information of China (English)

    ZOU Dinghui; GAO Kunshan

    2004-01-01

    The photosynthetic performances of Porphyra haitanensis thalli were investigated in order to understand its mechanisms for exogenous carbon acquisition during emersion at low tide. The emersed photosynthesis was studied by altering the pH value in the water film on the thalli surface, treating them with carbonic anhydarase inhibitors (acetazolamide and 6-ethoxyzolamide), adjusting the CO2 concentrations in the air, and comparing the theoretical maximum CO2 supply rates within the adherent water film with the observed photosynthetic CO2 uptake rates. It was found that the principal exogenous inorganic carbon source for the photosynthesis of P. haitanensis during emersion was atmospheric CO2. The driving force of CO2 flux across the water film was the CO2 concentration gradient within it. Carbonic anhydrase accelerated both extracellular and intracellular CO2 transport. The emersed photosynthesis of P. haitanensis was limited by the present atmospheric CO2 level, and would be enhanced by atmospheric CO2 rise that would trigger global warming.

  9. Carbon and Oxygen Isotope Measurements of Ordinary Chondrite (OC) Meteorites from Antarctica Indicate Distinct Terrestrial Carbonate Species using a Stepped Acid Extraction Procedure Impacting Mars Carbonate Research

    Science.gov (United States)

    Evans, M. E.; Niles, P. B.; Locke, D.

    2015-12-01

    The purpose of this study is to characterize the stable isotope values of terrestrial, secondary carbonate minerals from five OC meteorites collected in Antarctica. These samples were selected for analysis based upon their size and collection proximity to known Martian meteorites. They were also selected based on petrologic type (3+) such that they were likely to be carbonate-free before falling to Earth. This study has two main tasks: 1) characterize the isotopic composition of terrestrial, secondary carbonate minerals formed on meteorites in Antarctica, and 2) study the mechanisms of carbonate formation in cold and arid environments with Antarctica as an analog for Mars. Two samples from each meteorite, each ~0.5g, was crushed and dissolved in pure phosphoric acid for 3 sequential reactions: a) Rx0 for 1 hour at 30°C, b) Rx1 for 18 hours at 30°C, and c) Rx2 for 3 hours at 150°C. CO2 was distilled by freezing with liquid nitrogen from each sample tube, then separated from organics and sulfides with a TRACE GC using a Restek HayeSep Q 80/100 6' 2mm stainless column, and then analyzed on a Thermo MAT 253 IRMS in Dual Inlet mode. This system was built at NASA/JSC over the past 3 years and proof tested with known carbonate standards to develop procedures, assess yield, and quantify expected uncertainties. Two distinct species of carbonates are found based on the stepped extraction technique: 1) Ca-rich carbonate released at low temperatures, and 2) Mg, or Fe-rich carbonate released at high temperatures. Preliminary results indicate that most of the carbonates present in the ordinary chondrites analyzed have δ13C=+5‰, which is consistent with formation from atmospheric CO2 δ13C=-7‰ at -20°C. The oxygen isotopic compositions of the carbonates vary between +4‰ and +34‰ with the Mg-rich and/or Fe-rich carbonates possessing the lowest δ18O values. This suggests that the carbonates formed under a wide range of temperatures. However, the carbonate oxygen

  10. Carbon isotope geochemistry of the Cretaceous-Tertiary section of the Wasserfallgraben, Lattengebirge, southeast Germany

    Science.gov (United States)

    Arneth, J.-D.; Matzigkeit, U.; Boos, A.

    1985-09-01

    Carbonates and organic matter in sediments of the Cretaceous-Tertiary (C/T) section of the Wasserfallgraben, Lattengebirge (Bavaria) have been investigated. All parameters—the carbonate content (C carb), its isotopic composition ( δ 13C carb, δ 18O carb) as well as the organic carbon content (C org), its isotopic composition ( δ 13C org) and the H/C ratio of the sedimentary organic matter—display systematic variations across the C/T boundary which cannot be attributed to a single cause. The boundary zone as a whole is tectonically disturbed and shows significant features of detrital contaminations. Unidirectional shift in δ 13C carb and δ 13C org are observed when directly comparing Maastrichtian (latest Cretaceous) and Danian (earliest Tertiary) sediments. These synchronous isotope displacements towards more negative readings are interpreted to reflect the reduced photosynthetic activity as consequence of the mass extinction at the C/T boundary. The results may have some bearings on other C/T profiles investigated where measurements on the reduced carbon species are still lacking.

  11. Late Ordovician (Turinian-Chatfieldian) carbon isotope excursions and their stratigraphic and paleoceanographic significance

    Science.gov (United States)

    Ludvigson, Greg A.; Witzke, B.J.; Gonzalez, Luis A.; Carpenter, S.J.; Schneider, C.L.; Hasiuk, F.

    2004-01-01

    Five positive carbon isotope excursions are reported from Platteville-Decorah strata in the Upper Mississippi Valley. All occur in subtidal carbonate strata, and are recognized in the Mifflin, Grand Detour, Quimbys Mill, Spechts Ferry, and Guttenberg intervals. The positive carbon isotope excursions are developed in a Platteville-Decorah succession in which background ??13C values increase upward from about -2??? at the base to about 0??? Vienna Pee Dee belemnite (VPDB) at the top. A regional north-south ??13C gradient, with lighter values to the north and heavier values to the south is also noted. Peak excursion ??13C values of up to +2.75 are reported from the Quimbys Mill excursion, and up to +2.6 from the Guttenberg excursion, although there are considerable local changes in the magnitudes of these events. The Quimbys Mill, Spechts Ferry, and Guttenberg carbon isotope excursions occur in units that are bounded by submarine disconformities, and completely starve out in deeper, more offshore areas. Closely spaced chemostratigraphic profiles of these sculpted, pyrite-impregnated hardground surfaces show that they are associated with very abrupt centimeter-scale negative ??13C shifts of up to several per mil, possibly resulting from the local diagenetic effects of incursions of euxinic bottom waters during marine flooding events. ?? 2004 Elsevier B.V. All rights reserved.

  12. Can Mg isotopes be used to trace cyanobacteria-mediated magnesium carbonate precipitation in alkaline lakes?

    Science.gov (United States)

    Shirokova, L. S.; Mavromatis, V.; Bundeleva, I.; Pokrovsky, O. S.; Bénézeth, P.; Pearce, C.; Gérard, E.; Balor, S.; Oelkers, E. H.

    2011-07-01

    The fractionation of Mg isotopes was determined during the cyanobacterial mediated precipitation of hydrous magnesium carbonate precipitation in both natural environments and in the laboratory. Natural samples were obtained from Lake Salda (SE Turkey), one of the few modern environments on the Earth's surface where hydrous Mg-carbonates are the dominant precipitating minerals. This precipitation was associated with cyanobacterial stromatolites which were abundant in this aquatic ecosystem. Mg isotope analyses were performed on samples of incoming streams, groundwaters, lake waters, stromatolites, and hydromagnesite-rich sediments. Laboratory Mg carbonate precipitation experiments were conducted in the presence of purified Synechococcus sp cyanobacteria that were isolated from the lake water and stromatolites. The hydrous magnesium carbonates nesquehonite (MgCO3·3H2O) and dypingite (Mg5(CO3)4(OH)25(H2O)) were precipitated in these batch reactor experiments from aqueous solutions containing either synthetic NaHCO3/MgCl2 mixtures or natural Lake Salda water, in the presence and absence of live photosynthesizing Synechococcus sp. Bulk precipitation rates were not to affected by the presence of bacteria when air was bubbled through the system. In the stirred non-bubbled reactors, conditions similar to natural settings, bacterial photosynthesis provoked nesquehonite precipitation, whilst no precipitation occurred in bacteria-free systems in the absence of air bubbling, despite the fluids achieving a similar or higher degree of supersaturation. The extent of Mg isotope fractionation (Δ26Mgsolid-solution) between the mineral and solution in the abiotic experiments was found to be identical, within uncertainty, to that measured in cyanobacteria-bearing experiments, and ranges from -1.4 to -0.7 ‰. This similarity refutes the use of Mg isotopes to validate microbial mediated precipitation of hydrous Mg carbonates.

  13. Climate warming, euxinia and carbon isotope perturbations during the Carnian (Triassic) Crisis in South China

    Science.gov (United States)

    Sun, Y. D.; Wignall, P. B.; Joachimski, M. M.; Bond, D. P. G.; Grasby, S. E.; Lai, X. L.; Wang, L. N.; Zhang, Z. T.; Sun, S.

    2016-06-01

    The Carnian Humid Episode (CHE), also known as the Carnian Pluvial Event, and associated biotic changes are major enigmas of the Mesozoic record in western Tethys. We show that the CHE also occurred in eastern Tethys (South China), suggestive of a much more widespread and probably global climate perturbation. Oxygen isotope records from conodont apatite indicate a double-pulse warming event. The CHE coincided with an initial warming of 4 °C. This was followed by a transient cooling period and then a prolonged ∼7 °C warming in the later Carnian (Tuvalian 2). Carbon isotope perturbations associated with the CHE of western Tethys occurred contemporaneously in South China, and mark the start of a prolonged period of carbon cycle instability that persisted until the late Carnian. The dry-wet transition during the CHE coincides with the negative carbon isotope excursion and the temperature rise, pointing to an intensification of hydrologic cycle activities due to climatic warming. While carbonate platform shutdown in western Tethys is associated with an influx of siliciclastic sediment, the eastern Tethyan carbonate platforms are overlain by deep-water anoxic facies. The transition from oxygenated to euxinic facies was via a condensed, manganiferous carbonate (MnO content up to 15.1 wt%), that records an intense Mn shuttle operating in the basin. Significant siliciclastic influx in South China only occurred after the CHE climatic changes and was probably due to foreland basin development at the onset of the Indosinian Orogeny. The mid-Carnian biotic crisis thus coincided with several phenomena associated with major extinction events: a carbonate production crisis, climate warming, δ13 C oscillations, marine anoxia, biotic turnover and flood basalt eruptions (of the Wrangellia Large Igneous Province).

  14. Comparison of bulk and n-alkane PETM carbon isotope trends from the Bighorn Basin, Wyoming

    Science.gov (United States)

    Baczynski, A. A.; McInerney, F. A.; Kraus, M. J.; Wing, S.

    2010-12-01

    The Paleocene-Eocene Thermal Maximum (PETM), a period of abrupt, short-term, and large-scale global warming fueled by a large release of isotopically light carbon, is recorded in terrestrial and marine carbonates and organic carbon as a prominent negative carbon isotope excursion (CIE). Here we present a composite stable carbon isotope record from n-alkanes and four bulk organic carbon records from individual sections spanning the PETM interval in the Cabin Fork area of the southeastern Bighorn Basin, Wyoming. The n-alkane curve shows an abrupt, negative shift in δ13C values, an extended CIE body, and a rapid recovery to pre-PETM δ13C values. While the bulk organic carbon records show similarly abrupt negative shifts in δ13C values, the CIE appears to be compressed as well as smaller in magnitude, and the return to more positive δ13C values is often more gradual. Furthermore, the stratigraphic thickness of the most negative CIE values and the pattern of the recovery phase are not consistent among the four bulk organic carbon records. The discrepancy between the bulk organic matter and n-alkane CIE may arise because of changes in soil organic matter cycling during the PETM. Bulk soil organic matter δ13C values are influenced by degradation and selective preservation whereas n-alkanes are resistant to diagenesis. Variations in sediment accumulation rates across the basin may be responsible for the differences between the four bulk organic carbon δ13C records. Sites with extended CIE bodies likely present more complete isotope records with greater time resolution and less time averaging than those with reduced CIEs. The shape of the high-resolution n-alkane curve presented here is similar to the newest 3He-based timescale for the PETM using data from Walvis Ridge, IODP site 1266 (Murphy et al., 2010). The most significant difference between this revised PETM timescale and previously published age models is the allocation of time within the PETM event. Murphy et

  15. Arctic herbivore diet can be inferred from stable carbon and nitrogen isotopes in C3 plants, faeces and wool

    DEFF Research Database (Denmark)

    Kristensen, Ditte; Kristensen, Erik; Forchhammer, Mads C.;

    2011-01-01

    for studying arctic herbivore diets. In this study, we examined the potential of both stable carbon and nitrogen isotopes to reconstruct the diet of an arctic herbivore, here the muskox (Ovibos moschatus (Zimmermann, 1780)), in northeast Greenland. The isotope composition of plant communities and functional......% graminoids and up to 20% willows. In conclusion, the diet composition of an arctic herbivore can indeed be inferred from stable isotopes in arctic areas, despite the lack of C4 plants...

  16. Sulfur, carbon, hydrogen, and oxygen isotope geochemistry of the Idaho cobalt belt

    Science.gov (United States)

    Johnson, Craig A.; Bookstrom, Arthur A.; Slack, John F.

    2012-01-01

    Cobalt-copper ± gold deposits of the Idaho cobalt belt, including the deposits of the Blackbird district, have been analyzed for their sulfur, carbon, hydrogen, and oxygen isotope compositions to improve the understanding of ore formation. Previous genetic hypotheses have ranged widely, linking the ores to the sedimentary or diagenetic history of the host Mesoproterozoic sedimentary rocks, to Mesoproterozoic or Cretaceous magmatism, or to metamorphic shearing. The δ34S values are nearly uniform throughout the Blackbird dis- trict, with a mean value for cobaltite (CoAsS, the main cobalt mineral) of 8.0 ± 0.4‰ (n = 19). The data suggest that (1) sulfur was derived at least partly from sedimentary sources, (2) redox reactions involving sulfur were probably unimportant for ore deposition, and (3) the sulfur was probably transported to sites of ore for- mation as H2S. Hydrogen and oxygen isotope compositions of the ore-forming fluid, which are calculated from analyses of biotite-rich wall rocks and tourmaline, do not uniquely identify the source of the fluid; plausible sources include formation waters, metamorphic waters, and mixtures of magmatic and isotopically heavy meteoric waters. The calculated compositions are a poor match for the modified seawaters that form vol- canogenic massive sulfide (VMS) deposits. Carbon and oxygen isotope compositions of siderite, a mineral that is widespread, although sparse, at Blackbird, suggest formation from mixtures of sedimentary organic carbon and magmatic-metamorphic carbon. The isotopic compositions of calcite in alkaline dike rocks of uncertain age are consistent with a magmatic origin. Several lines of evidence suggest that siderite postdated the emplacement of cobalt and copper, so its significance for the ore-forming event is uncertain. From the stable isotope perspective, the mineral deposits of the Idaho cobalt belt contrast with typical VMS and sedimentary exhalative deposits. They show characteristics of deposit

  17. Method for determination of stable carbon isotope ratio of methylnitrophenols in atmospheric PM

    Directory of Open Access Journals (Sweden)

    S. Moukhtar

    2011-05-01

    Full Text Available A technique for the measurement of the stable isotope ratio of methylnitrophenols in atmospheric particulate matter (PM is presented. It has been found in numerous laboratory studies that these compounds are photooxidation products of toluene in PM. Atmospheric samples from rural and suburban areas were collected for evaluation of the procedure. PM was collected on quartz fibre filters using dichotomous high volume air samplers for PM 2.5. Methylnitrophenols were extracted from the filters using acetonitrile. The sample was then purified using a combination of high-performance liquid chromatography (HPLC and solid phase extraction (SPE. The final solution was then divided into two aliquots. To one aliquot, a derivatising agent, Bis(trimethylsilyltrifluoroacetamide (BSTFA, was added to the solution for Gas Chromatography/Mass Spectroscopy (GC/MS analysis. The second half of the sample was stored at low temperature. When GC/MS analysis showed high enough concentrations the remaining sample was derivatized with BSTFA and analysed for stable isotope ratio using a Gas Chromatography/Isotope Ratio Mass Spectrometry (GC-IRMS.

    In all atmospheric PM samples analysed, 2-methyl-4-nitrophenol was found to be the most abundant methylnitrophenol. Nevertheless, due to low pollution levels occurring in the rural area, no samples had concentrations high enough to perform stable carbon isotope composition measurements of the methylnitrophenols. Samples collected in the suburban area could be analysed for carbon stable isotope ratio using GC-IRMS.

    The procedure described in this paper provides a very sensitive and selective method for the analysis of methylnitrophenols in atmospheric PM at concentrations as low as 1 pg m−3. For accurate (within ±0.5‰ stable isotope ratio analysis significantly higher concentrations in the range of 100 pg m−3 or more are required.

  18. Carbon isotopic characteristics and their genetic relationships for individual lipids in plants and sediments from a marsh sedimentary environment

    Institute of Scientific and Technical Information of China (English)

    DUAN Yi; ZHANG Hui; ZHENG Chaoyang; WU Baoxiang; ZHENG Guodong

    2005-01-01

    The carbon isotopes of individual lipids in herbaceous plants and tree leaves in Ruoergai marsh were measured by the GC-IRMS analytical technique in order to understand the inherent relationships of carbon isotopes between sedimentary and plant lipids from typical marsh environment. The analytical results show that the carbon isotopic compositions of n-alkanes in different kinds of plants differ significantly. Mean δ13C values of n-alkanes in herbaceous plants (-32.2‰―-36.9‰) are 3.3‰ lower than those in woody plant (-27.2‰― -35.0‰). The carbon isotopic compositions of fatty acids in organisms (-30.3‰― -36.2‰) are very similar to those of n-alkanes and the δ13C values for unsaturated fatty acids are within the range of those for saturated fatty acids. The differences in δ13C values between plant lipids are obvious and range from 2.4‰ to 7.8‰. It is observed that the carbon isotopic compositions of sedimentary lipids are closely related to those of plant lipids. The carbon isotopic compositions (-27.0‰―-36.9‰) of n-alkanes, ≥C16 fatty acids, n-alkanols, sterols and n-alkanones in the sediments are similar to those of plant lipids and the carbon isotopic compositions of short-chain sedimentary lipids are similar to those of long-chain sedimentary homologues. These indicate that the sedimentary lipids are derived from high plants. However, the δ13C values of C14:0 and C15:0 fatty acids in the sediments are lighter than those of the same carbon number saturated homologues in plants, reflecting the genetic features partially derived from bacteria. These data provide scientific evidence for carbon isotope-applied research of individual lipids.

  19. An analytical system for stable isotope analysis on carbon monoxide using continuous-flow isotope-ratio mass spectrometry

    Science.gov (United States)

    Pathirana, S. L.; van der Veen, C.; Popa, M. E.; Röckmann, T.

    2015-12-01

    A fully automated system for the determination of δ13C and δ18O in atmospheric CO has been developed. CO is extracted from an air sample and converted into carbon dioxide (CO2) using the Schütze reagent. The isotopic composition is determined with an isotope-ratio mass spectrometer (IRMS) technique. The entire system is continuously flushed with high-purity helium (He), the carrier gas. The blank signal of the Schütze reagent is ~ 4 nmol mol-1, or 1-3 % of the typical sample size. The repeatability is 0.1 ‰ for δ13C and 0.2 ‰ for δ18O. The peak area allows for simultaneous determination of the mole fraction with an analytical repeatability of ~ 0.7 nmol mol-1 for 100 mL of ambient air (185.4 nmol mol-1 of CO). An automated single measurement is performed in only 18 min, and the achieved time efficiency (and small volume of sample air) allows for repetitive measurements practically.

  20. Carbon Isotopic Studies of Assimilated and Ecosystem Respired CO2 in a Southeastern Pine Forest. Final Report and Conference Proceedings

    Energy Technology Data Exchange (ETDEWEB)

    Conte, Maureen H

    2008-04-10

    Carbon dioxide is the major “greenhouse” gas responsible for global warming. Southeastern pine forests appear to be among the largest terrestrial sinks of carbon dioxide in the US. This collaborative study specifically addressed the isotopic signatures of the large fluxes of carbon taken up by photosynthesis and given off by respiration in this ecosystem. By measuring these isotopic signatures at the ecosystem level, we have provided data that will help to more accurately quantify the magnitude of carbon fluxes on the regional scale and how these fluxes vary in response to climatic parameters such as rainfall and air temperature. The focus of the MBL subcontract was to evaluate how processes operating at the physiological and ecosystem scales affects the resultant isotopic signature of plant waxes that are emitted as aerosols into the convective boundary layer. These wax aerosols provide a large-spatial scale integrative signal of isotopic discrimination of atmospheric carbon dioxide by terrestrial photosynthesis (Conte and Weber 2002). The ecosystem studies have greatly expanded of knowledge of wax biosynthetic controls on their isootpic signature The wax aerosol data products produced under this grant are directly applicable as input for global carbon modeling studies that use variations in the concentration and carbon isotopic composition of atmospheric carbon dioxide to quantify the magnitude and spatial and temporal patterns of carbon uptake on the global scale.

  1. The significance of an Early Jurassic (Toarcian) carbon-isotope excursion in Haida Gwaii (Queen Charlotte Islands), British Columbia, Canada

    Science.gov (United States)

    Caruthers, Andrew H.; Gröcke, Darren R.; Smith, Paul L.

    2011-07-01

    During the Early Toarcian there was a significant disruption in the short-term active carbon reservoir as revealed by carbon-isotope records, which show a broad positive shift that is interrupted by a large 5-7‰ negative excursion (δ 13C org). Carbon-isotope excursion co-occurs with the deposition of organic-rich shales in many areas. This perturbation in carbon isotopes is thought to be indicative of severe climate change and marine anoxia. The two leading hypotheses as to the cause of this event invoke either global or regional controls. Here we present carbon-isotope data from Haida Gwaii, British Columbia, Canada showing a significant perturbation within a temporally constrained Early Toarcian succession that was deposited in the northeastern paleo-Pacific Ocean. These data reinforce the concept that the short-term active carbon reservoir was affected globally, and assist with the correlation of ammonite zonal schemes between western North America and Europe. The δ 13C org data show a broad positive shift that is interrupted by a sharp and pronounced negative excursion of 7‰ (8.5‰ in δ 13C wood) in the Early Toarcian Kanense Zone. This negative excursion also coincides with increasing total organic carbon (TOC) from ~ 0.4% to ~ 1.2%. These data suggest that the Early Toarcian carbon-isotope perturbation was indeed global and imprinted itself on all active global reservoirs of the exchangeable carbon cycle (deep marine, shallow marine, atmospheric).

  2. Using a laser-based CO2 carbon isotope analyser to investigate gas transfer in geological media

    International Nuclear Information System (INIS)

    CO2 stable carbon isotopes are very attractive in environmental research to investigate both natural and anthropogenic carbon sources. Laser-based CO2 carbon isotope analysis provides continuous measurement at high temporal resolution and is a promising alternative to isotope ratio mass spectrometry (IRMS). We performed a thorough assessment of a commercially available CO2 Carbon Isotope Analyser (CCIA DLT-100, Los Gatos Research) that allows in situ measurement of C-13 in CO2. Using a set of reference gases of known CO2 concentration and carbon isotopic composition, we evaluated the precision, long-term stability, temperature sensitivity and concentration dependence of the analyser. Despite good precision calculated from Allan variance (5.0 ppm for CO2 concentration, and 0.05 per thousand for δC-13 at 60 s averaging), real performances are altered by two main sources of error: temperature sensitivity and dependence of C-13 on CO2 concentration. Data processing is required to correct for these errors. Following application of these corrections, we achieve an accuracy of 8.7 ppm for CO2 concentration and 1.3 per thousand for δC-13, which is worse compared to mass spectrometry performance, but still allowing field applications. With this portable analyser we measured CO2 flux degassed from rock in an underground tunnel. The obtained carbon isotopic composition agrees with IRMS measurement, and can be used to identify the carbon source. (authors)

  3. Using a laser-based CO2 carbon isotope analyser to investigate gas transfer in geological media

    Science.gov (United States)

    Guillon, S.; Pili, E.; Agrinier, P.

    2012-05-01

    CO2 stable carbon isotopes are very attractive in environmental research to investigate both natural and anthropogenic carbon sources. Laser-based CO2 carbon isotope analysis provides continuous measurement at high temporal resolution and is a promising alternative to isotope ratio mass spectrometry (IRMS). We performed a thorough assessment of a commercially available CO2 Carbon Isotope Analyser (CCIA DLT-100, Los Gatos Research) that allows in situ measurement of δ 13C in CO2. Using a set of reference gases of known CO2 concentration and carbon isotopic composition, we evaluated the precision, long-term stability, temperature sensitivity and concentration dependence of the analyser. Despite good precision calculated from Allan variance (5.0 ppm for CO2 concentration, and 0.05 ‰ for δ 13C at 60 s averaging), real performances are altered by two main sources of error: temperature sensitivity and dependence of δ 13C on CO2 concentration. Data processing is required to correct for these errors. Following application of these corrections, we achieve an accuracy of 8.7 ppm for CO2 concentration and 1.3 ‰ for δ 13C, which is worse compared to mass spectrometry performance, but still allowing field applications. With this portable analyser we measured CO2 flux degassed from rock in an underground tunnel. The obtained carbon isotopic composition agrees with IRMS measurement, and can be used to identify the carbon source.

  4. Organic carbon and nitrogen stable isotopes in the intertidal sediments from the Yangtze Estuary, China

    International Nuclear Information System (INIS)

    The natural isotopic compositions and C/N elemental ratios of sedimentary organic matter were determined in the intertidal flat of the Yangtze Estuary. The results showed that the ratios of carbon and nitrogen stable isotopes were respectively -29.8 per mille to - 26.0 per mille and 1.6 per mille -5.5 per mille in the flood season (July), while they were -27.3 per mille to - 25.6 per mille and 1.7 per mille -7.8 per mille in the dry season (February), respectively. The δ 13C signatures were remarkably higher in July than in February, and gradually increased from the freshwater areas to the brackish areas. In contrast, there were relatively complex seasonal and spatial changes in stable nitrogen isotopes. It was also reflected that δ 15N and C/N compositions had been obviously modified by organic matter diagenesis and biological processing, and could not be used to trace the sources of organic matter at the study area. In addition, it was considered that the mixing inputs of terrigenous and marine materials generally dominated sedimentary organic matter in the intertidal flat. The contribution of terrigenous inputs to sedimentary organic matter was roughly estimated according to the mixing balance model of stable carbon isotopes

  5. Isotope effects for carbon and hydrogen with bacterial oxidation of oils and certain petroleum hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Mekhtiyeva, V.L.; Guriyeva, S.M.; Kondrat' yeva, G.F.

    1983-01-01

    Results are presented of experiments on bacterial oxidation of oils, decane and hexadecane. Oxidation of oils was done by natural biocenosis isolated from bed waters, hydrocarbons by pure culture of bacteria from the river Pseudomonas. As a result of bacterial transformation, the methane oils were enriched with the isotope C/sup 12/, the methane-naphthene by isotope C/sup 13/. The carbon dioxide formed during oxidation of oils was fairly close in deltaC/sup 13/ values to the original oils. The oils exposed to biodegradation in aerobic conditions were enriched with deuterium, in anaerobic--they were slightly depleted. With oxidation of individual hydrocarbons, the isotope effects for carbon were extremely small, and for hydrogen were missing altogether. As a result of analysis of the presented data, as well as the previously published materials, conclusions were drawn about the nature of the isotope effects with bacterial oxidation of the oils and scales were defined with different degree of oxidation of the oils.

  6. Bivalve tissue as a carbon and nitrogen isotope baseline indicator in coastal ecosystems

    Science.gov (United States)

    Fukumori, Kayoko; Oi, Misa; Doi, Hideyuki; Takahashi, Daisuke; Okuda, Noboru; Miller, Todd W.; Kuwae, Michinobu; Miyasaka, Hitoshi; Genkai-Kato, Motomi; Koizumi, Yoshitsugu; Omori, Koji; Takeoka, Hidetaka

    2008-08-01

    Pinctada fucata martensii mantle tissue and gut contents were examined as baseline indicators of carbon and nitrogen isotope composition at six stations in the Uwa Sea, Japan. Substantial variations in δ13C and δ15N values of oysters among stations were observed, with δ13C being consistently lower at Hiburi Island (-18.1‰) than at other stations (-17.2‰). Oysters from fish farm sites were enriched in δ15N (8.1‰) relative to those from unaffected sites (6.8‰), suggesting that fish farming tends to increase baseline δ15N values. The mean Δ δ13C (0.8‰) was consistent over space and time, whereas the average Δ δ15N slightly increased in summer. The relatively low δ15N enrichment compared to the theoretical isotope fractionation factor (3.4‰) may be due to oyster-specific physiological attributes. Carbon and nitrogen isotope turnover rates were roughly similar within a tissue, and mantle tissue turnover rate was estimated to be 120-180 days. These results indicated that oysters are long-term integrators of δ13C and δ15N from their diet and that δ13C of oysters is a more accurate bioindicator of isotopic baselines than δ15N for marine ecological studies.

  7. Tracking Seasonal Habitats Using Carbon and Nitrogen Stable Isotopes of Osprey Primary Flight Feathers

    Science.gov (United States)

    Velinsky, D.; Zelanko, P.; Rice, N.

    2011-12-01

    The majority of bird migration studies use the latitudinal precipitation effect of hydrogen and oxygen stable isotopes of feathers to determine wintering and breeding grounds. Few studies have considered carbon and nitrogen stable isotopes to accomplish the same goal; exploiting the variation in dietary constitutes throughout yearly migration cycles. Also, there is no standard procedure of feather sampling; some use body, while others use wing feathers. This sampling discrepancy is not an issue for most migratory species since the majority of birds molt completely in one location, i.e. wintering verse breeding ground. Large birds of prey however, have a continuous molt that may last years, growing feathers on their breeding and wintering grounds. Therefore, a stable isotopic study of Osprey could not randomly sample feathers because it is impossible to know where individual feathers were grown. Here we present an in depth study of carbon and nitrogen stable isotopes from Mid-Atlantic Osprey primary flight feathers. Not only did we observe three signatures indicating the breeding ground and two distinct wintering grounds, we recorded dietary seasonality shifts within 2 to 3 year olds that remain on the wintering grounds for multiple years.

  8. Carbon isotope fractionation by thermophilic phototrophic sulfur bacteria: evidence for autotrophic growth in natural populations

    Science.gov (United States)

    Madigan, M. T.; Takigiku, R.; Lee, R. G.; Gest, H.; Hayes, J. M.

    1989-01-01

    Purple phototrophic bacteria of the genus Chromatium can grow as either photoautotrophs or photoheterotrophs. To determine the growth mode of the thermophilic Chromatium species, Chromatium tepidum, under in situ conditions, we have examined the carbon isotope fractionation patterns in laboratory cultures of this organism and in mats of C. tepidum which develop in sulfide thermal springs in Yellowstone National Park. Isotopic analysis (13C/12C) of total carbon, carotenoid pigments, and bacteriochlorophyll from photoautotrophically grown cultures of C. tepidum yielded 13C fractionation factors near -20%. Cells of C. tepidum grown on excess acetate, wherein synthesis of the Calvin cycle enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase ribulose bisphosphate carboxylase) was greatly repressed, were isotopically heavier, fractionation factors of ca. -7% being observed. Fractionation factors determined by isotopic analyses of cells and pigment fractions of natural populations of C. tepidum growing in three different sulfide thermal springs in Yellowstone National Park were approximately -20%, indicating that this purple sulfur bacterium grows as a photoautotroph in nature.

  9. Carbon Isotope Composition of Mysids at a Terrestrial-Marine Ecotone, Clayoquot Sound, British Columbia, Canada

    Science.gov (United States)

    Mulkins, L. M.; Jelinski, D. E.; Karagatzides, J. D.; Carr, A.

    2002-04-01

    The relative contribution of summertime terrestrial versus marine carbon to an estuary on coastal British Columbia, Canada was explored using stable carbon isotopic (δ 13C values) analysis of mysid crustaceans (Malacostraca: Peracarida: Mysidacea). We hypothesized that landscape linkages between the forested upland and adjacent inshore marine waters, via river, groundwater and overland flows, may influence carbon content and metabolism in the coastal zone. We sampled 14 stations spatially distributed in a grid and found δ 13C compositions of mysids ranged from -15·2 to -18·4‰. There was, however, no obvious spatial distribution of δ 13C values relative to the estuarine gradient in Cow Bay. Heavy tidal mixing is suggested to disperse marine and terrestrial carbon throughout the entire bay. From a temporal perspective however, mysid δ 13C signatures became enriched over the sampling period (mid-July to mid-August), which is representative of a stronger marine influence. This may arise because mysids are exposed to greater marine-derived carbon sources later in the summer, a decrease in freshwater input (and hence terrestrial carbon), changes in phytoplankton or macrophyte community structure, or that mysids preferentially feed on marine food sources. Overall, the recorded isotopic values are characteristic of marine organic carbon signatures suggesting that in summer, despite the proximity to shore, little or no terrestrial carbon penetrates the food web at the trophic level of mysids. This notwithstanding we believe there is a strong need for additional study of carbon flows at the marine-terrestrial interface, especially for disturbed watersheds.

  10. Isotopic distribution of carbon from sewage sludge and eutrophication in the sediments and food web of estuarine ecosystems

    International Nuclear Information System (INIS)

    Stable isotope ratios (δ13C) from samples of water, sediments, and biota traced the behavior of organic carbon for 3 summer months in estuarine mesocosms (three controls, three with added sewage sludge, three with added inorganic nutrients). Isotope ratios proved to be a useful quantitative tracer for sewage carbon as well as for the fresh phytoplanktonic carbon produced during nutrient fertilization. Sewage sludge sedimented within hours of its addition, and approximately 50% remained in sediments after 99 days. The sludge was not inert, but was biologically oxidized at rates similar to those of phytoplankton carbon. Its residence time in the water column was too short for uptake by zooplankton, but it was readily assimilated by some benthic organisms. Fresh phytoplanktonic carbon from nutrient-induced blooms was isotopically heavy and thus distinguishable from old primary production (fixed before the experiment). It flowed through the pelagic and benthic food webs more extensively and more uniformly than did sludge carbon

  11. Sr isotopic chemostratigraphy of Precambrian carbonate rocks in the Amderma Rise, Pai-Khoi Ridge

    Science.gov (United States)

    Kuznetsov, A. B.; Starikova, E. V.; Maslov, A. V.; Konstantinova, G. V.

    2016-08-01

    The Sr and C isotopic compositions of Precambrian carbonate rocks are determined for Amderma Rise, in the northeastern margin of Pai-Khoi Ridge. Based on the Sr isotopic chemostratigraphy, it is established for the first time that the Amderma Formation is referred to the Early Vendian, while the Morozovsk Formation is Late Riphean in age. This conclusion along with detailed mapping proves that the Precambrian "section" of the Amderma Rise is a series of tectonic plates combined in a nonchronostratigraphic order. Volcanic and sedimentary rocks of the Morozovsk and Sokolninsk formations make up the allochthon proper, while carbonate rocks of the Amderma Formation make up the para-autochthon. The high values of δ13C (up to +9.5‰) identified in limestones of both formations suggest a considerable distance of the Pai-Khoi paleobasin from the passive margin of the Baltic Region upon facies similarity to the Laurentia active margins.

  12. Isotopic evidence of magmatism and a sedimentary carbon source at the Endeavour hydrothermal system

    Energy Technology Data Exchange (ETDEWEB)

    Brown, T A; Proskurowski, G; Lilley, M D

    2004-01-07

    Stable and radiocarbon isotope measurements made on CO{sub 2} from high temperature hydrothermal vents on the Endeavour Segment of the Juan de Fuca Ridge indicate both magmatic and sedimentary sources of carbon to the hydrothermal system. The Endeavour segment is devoid of overlying sediments and has shown no observable signs of surficial magmatic activity during the {approx}20 years of ongoing studies. The appearance of isotopically heavy, radiocarbon dead CO{sub 2} after a 1999 earthquake swarm requires that this earthquake event was magmatic in origin. Evidence for a sedimentary organic carbon source suggests the presence of buried sediments at the ridge axis. These findings, which represent the first temporally coherent set of radiocarbon measurements from hydrothermal vent fluids, demonstrate the utility of radiocarbon analysis in hydrothermal studies. The existence of a sediment source at Endeavour and the occurrence of magmatic episodes illustrate the extremely complex and evolving nature of the Endeavour hydrothermal system.

  13. Variation in dietary histories among the immigrants of Machu Picchu: Carbon and nitrogen isotope evidence

    International Nuclear Information System (INIS)

    This study estimates dietary composition during infancy and childhood among 71 adults interred at the site of Machu Picchu, a royal Inca estate in the southern highlands of Peru. Recent research suggests that the majority of individuals were members of the cosmopolitan yana and aclla servant classes, and immigrated to the site from different regions; individual dietary histories may have been similarly varied. Diet was estimated at multiple points in early life through characterization of carbon and nitrogen isotope ratios in tooth enamel and dentin, which preserve isotopic values from the first years of life. These data were compared to isotopic data from modern food samples, and analyzed using recently-published statistical models. A subset of individuals also has existing bone collagen isotopic data, which reflects diet from the last decade of life and thus permits comparison over the life course. Results indicate significant variation in enamel δ13C (approximately 12%o), dentin δ13C (approximately 9%o) and δ15N (approximately 8%o) between individuals across the study population. These findings suggest substantial variability in diet during infancy and childhood, and support interpretations that this population was primarily yanacona or mixed yanaconalacllacona. This study also highlights the utility of multi-tissue isotopic analysis in more nuanced reconstruction of diet in the ancient Andes

  14. Carbon isotope ratios in assessing the origin of water in dam leakage problems

    International Nuclear Information System (INIS)

    The investigation of the origin and dynamics of groundwater in the vicinity of dams and reservoirs is a major concern of the responsible authorities in case of important leakage problems. In most cases, local groundwater and water related tot he leakage emerge downstream of the dam with a complex mixing pattern. The proper characterization of the flow rate and flow patterns of water derived from the reservoir requires the use of several hydrological techniques, including environmental isotopes and artificial tracers. Among the common isotope tools, oxygen-18 deuterium and tritium are routinely used. The different origin of surface waters stored in the reservoir, and local groundwaters, usually derived from local recharge, result in distinct isotope signatures, allowing a proper characterization of each water type. However, practical work in investigating this type of problems under different geographic and climatic conditions has shown that in many cases, hydrochemistry and these isotopes do not provide a convincing and complete evidence about the origin and mixing patterns of the two types of waters. The proximity of the recharge areas and the short transit time of local groundwater do not result in significant differences in the chemical and/or isotope contents. 13C/12C ratios in the Total Dissolved Inorganic Carbon (TDIC) has been successfully used to investigate some aspects of leakage problems in several dams located in temperate and tropical climates

  15. Stable carbon and radiocarbon isotope compositions of particle size fractions to determine origins of sedimentary organic matter in an estuary

    NARCIS (Netherlands)

    Megens, L; van der Plicht, J; de Leeuw, JW; Smedes, F; Altabet, M.

    2002-01-01

    Stable and radioactive carbon isotopic compositions of particle size fractions of a surface sediment from the Ems-Dollard estuary vary considerably with particle size. The organic material in the fine fractions (

  16. Carbon and strontium isotope variations and responses tosea-level fluctuations in the Ordovician of the Tarim Basin

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Abstract In the Ordovician, a carbonate platform system grading from the platformal interioreastwards to basin was developed in the Tazhong area of the Tarim Basin, and the study column islocated in the place where the paleoslope occurred. The isotope compositions of the carbonatesthere are thus considered as having reflected those of simultaneous sea waters in view of its goodconnection with the open seas. The carbon and strontium isotope compositions of the Ordoviciancarbonates in the Tazhong area are analyzed, and their relationships to the sea-level fluctuationsare discussed as well. Studies have revealed that the carbon isotope composition is related posi-tively with the sea-level fluctuations, whereas an opposing situation occurs to the strontium isotopevariation. Similar responses of carbon and strontium isotope compositions to the sea-level fluctua-tions are reported elsewhere in the world, suggesting that the Ordovician sea-level fluctuations ofthe Tarim Basin were of eustatic implication.

  17. Stable carbon isotopes of invertebrate remains: do they reveal past methane release from lakes?

    OpenAIRE

    van Hardenbroek-van Ammerstol, M. R.

    2010-01-01

    Lakes are a source of methane, an important greenhouse gas in the atmosphere. In order to understand increasing methane emissions in the present, it is important to study the variations of methane release during past periods of climate change. However, records of methane release from lakes over time scales longer than a few years are extremely rare. In this thesis a method is explored to reconstruct past methane availability in lakes based on the stable carbon isotope composition (delta 13C) ...

  18. Stable carbon isotopes as indicators for micro-geomorphic changes in palsa peats

    Directory of Open Access Journals (Sweden)

    C. Alewell

    2011-01-01

    Full Text Available Palsa peats are unique northern ecosystems formed under an arctic climate and characterized by an unique biodiversity and ecology. The stability of the palsas are seriously threatened by climate warming which will change the permafrost dynamic and results in degradation of the mires. We used stable carbon isotope depth profiles in two palsa mires of Northern Sweden to track environmental change during the formation of the mires. Carbon isotope13C depth profile of the yet undisturbed mire Storflaket indicated very low to no degradation of the peat in the water saturated depressions (hollows but increased rates of anaerobic degradation at the Stordalen site. The latter might be induced by degradation of the permafrost cores in the uplifted areas (hummocks and subsequent braking and submerging of the hummock peat into the hollows due to climate warming. Carbon isotope depth profiles of hummocks indicated a turn from aerobic mineralisation to anaerobic degradation at a peat depth between 4 to 25 cm. The age of these turning point was 14C dated between 150 and 670 years and could thus not be caused by anthropogenically induced climate change. We found the uplifting of the hummocks due to permafrost heave the most likely explanation for our findings. We thus concluded that differences in carbon isotope profiles of the hollows might point to the disturbance of the mires due to climate warming or due to differences in hydrology. The characteristic profiles of the hummocks are indicators for micro-geomorphic change during permafrost up heaving.

  19. Carbon isotope composition of carbonaceous matter from the precambrian of the witwatersrand system.

    Science.gov (United States)

    Hoefs, J; Schidlowski, M

    1967-03-01

    Polymerized hydrocarbons occurring in the gold-uranium conglomerates of the Witwatersrand System (South Africa) show deltaC(13) values between -22.4 and -32.8 per mille, their isotopic composition thus falling into the range of sedimentary organic carbon. Accordingly, organic derivation of the material seems very probable. This conclusion is consistent with a model of the existence of organic evolution and biologic activity in times certainly older than 2.15 x 10(9) years.

  20. Stable carbon isotope reconstruction of ungulate diet changes through the seasonal cycle

    OpenAIRE

    Codron, D.; Lee-Thorp, J A; M. Sponheimer; J. Codron

    2007-01-01

    We analysed stable carbon isotope ratios (13C) in faeces of 11 African ungulate species from three South African savanna environments to determine whether this approach is sufficiently sensitive to record short-term seasonal diet changes in browsers (BR), mixed-feeders (IM), and grazers (GR). At monthly intervals, faecal 13C revealed variations in proportions of C3 (browse) to C4 (grass) biomass consumed that were not detected by broader dry versus wet season comparisons, including subtle die...

  1. Mechanisms controlling the carbon stable isotope composition of phytoplankton in karst reservoirs

    OpenAIRE

    Baoli Wang; Cong-Qiang Liu; Xi Peng; Fushun Wang

    2013-01-01

    In order to systematically understand the mechanisms controlling the carbon stable isotope composition of phytoplankton (δ13CPHY)in freshwater ecosystems, seasonal changes in δ13CPHY and related environmental factors were determined in karst reservoirs from the Wujiang river basin, China. Substantial and systematic differences within seasons and reservoirs were observed for δ13CPHY, which ranged from -39.2‰ to -15.1‰. An increase in water temperature triggered fast growth of phytoplankton whi...

  2. Tracing paleo-ocean redox using Cr isotopes in carbonates spanning the Great Oxidation Event

    Science.gov (United States)

    Holmden, C. E.; Bekker, A.

    2013-12-01

    Cr is an element whose isotopes are fractionated by redox reactions in the Earth's exogenic system, such as those occuring during oxidative weathering on the continents and scavenging into reduced marine sediments. Frei et al. (2009) proposed that the range of Cr isotope fractionation in exogenic materials in the absence of molecular oxygen would likely not extend beyond the range in igneous rocks, which is quite small (δ53Cr = -0.1 ×0.1‰). They tested their hypothesis on iron formations spanning the Great Oxidation Event (GOE) and found small fractionations that predated the GOE, but no permil level fractionation until the Neoproterozoic. We tested whether δ53Cr values in shallow-water carbonates spanning the GOE might record steps in the rise of atmospheric oxygen between 2.45 and 2.06 Ga. Carbonates representing 15 formations were chosen with depositonal ages ranging between 2.5 Ga and 1.9 Ga. We find very little Cr isotope fractionation recorded in carbonates deposited during this time with the exception of those corresponding to the peak of the Lomagundi Event at ca. 2.15 Ga. A defining characterisitic of the Lomagundi Event is the widespread prevalance of shallow-water carbonate platforms with abundant stromatolites, making their deposits an ideal lithology to record the state of the seawater Cr cycle. Five formations deposited during this time yield δ53Cr values with permil level fractionation recorded in some examples, in both positive and negative directions with respect to the igenous rock baseline. The data suggests that although the oxidative part of the Cr cycle started at least during the peak of the Lomagundi Event, the Cr(VI) reservoir and its residence time remained small, making it susceptible to local processes. 1. Frei et al. (2009) Fluctuations in Precambrian atmospheric oxygen recorded by Cr isotopes, Nature, v. 461, 250-253.

  3. Stable carbon isotope fractionation in the search for life on early Mars

    Science.gov (United States)

    Rothschild, L. J.; Desmarais, D.

    1989-01-01

    The utility of measurements of C-13/C-12 ratios in organic vs inorganic deposits for searching for signs of life on early Mars is considered. It is suggested that three assumptions are necessary. First, if there was life on Mars, it caused the fractionation of carbon isotopes in analogy with past biological activity on earth. Second, the fractionation would be detectable. Third, if a fractionation would be observed, there exist no abiotic explanations for the observed fractionation pattern.

  4. Compositional and stable carbon isotopic fractionation during non-autocatalytic thermochemical sulfate reduction by gaseous hydrocarbons

    Science.gov (United States)

    Xia, Xinyu; Ellis, Geoffrey S.; Ma, Qisheng; Tang, Yongchun

    2014-01-01

    The possibility of autocatalysis during thermochemical sulfate reduction (TSR) by gaseous hydrocarbons was investigated by examination of previously reported laboratory and field data. This reaction was found to be a kinetically controlled non-autocatalytic process, and the apparent lack of autocatalysis is thought to be due to the absence of the required intermediate species. Kinetic parameters for chemical and carbon isotopic fractionations of gaseous hydrocarbons affected by TSR were calculated and found to be consistent with experimentally derived values for TSR involving long-chain hydrocarbons. Model predictions based on these kinetic values indicate that TSR by gaseous hydrocarbon requires high-temperature conditions. The oxidation of C2–5 hydrocarbons by sulfate reduction is accompanied by carbon isotopic fractionation with the residual C2–5 hydrocarbons becoming more enriched in 13C. Kinetic parameters were calculated for the stable carbon isotopic fractionation of gaseous hydrocarbons that have experienced TSR. Model predictions based on these kinetics indicate that it may be difficult to distinguish the effects of TSR from those of thermal maturation at lower levels of hydrocarbon oxidation; however, unusually heavy δ13C2+ values (>−10‰) can be diagnostic of high levels of conversion (>50%). Stoichiometric and stable carbon isotopic data show that methane is stable under the investigated reaction conditions and is likely a product of TSR by other gaseous hydrocarbons rather than a significant reactant. These results indicate that the overall TSR reaction mechanism for oxidation of organic substrates containing long-chain hydrocarbons involves three distinct phases as follows: (1) an initial slow and non-autocatalytic stage characterized by the reduction of reactive sulfate by long-chain saturated hydrocarbons; (2) a second autocatalytic reaction phase dominated by reactions involving reduced sulfur species and partially oxidized hydrocarbons; (3

  5. A synthetic standard for the analysis of carbon isotopes of carbon in silicates, and the observation of a significant water-associated matrix effect

    OpenAIRE

    House, Christopher H.

    2015-01-01

    Background Due to the biogeochemical fractionation of isotopes, organic material can be heterogeneous at the microscale. Because this heterogentiy preserves in the rock record, the microscale measurement of carbon isotopes is an important frontier of geobiology. Such analyses via secondary ion mass spectrometry (SIMS) have been, however, held back by the lack of an appropriate homogeneous synthetic standard that can be shared between laboratories. Such a standard would need to yield a carbon ...

  6. Mantle CO2 degassing through the Icelandic crust: Evidence from carbon isotopes in groundwater

    Science.gov (United States)

    Stefánsson, Andri; Sveinbjörnsdóttir, Árný E.; Heinemeier, Jan; Arnórsson, Stefán; Kjartansdóttir, Ríkey; Kristmannsdóttir, Hrefna

    2016-10-01

    Carbon isotopes of groundwater in Iceland were studied in order to determine the source and reactions of carbon at divergent plate boundaries not associated with active volcanic systems. All the waters were of meteoric origin, with temperatures of 1-130 °C, pH of ∼4.5-10.5 and dissolved inorganic carbon (∑CO2) between 1.8 and 4100 ppm. The measured range of δ13CO2 and 14CO2 in these waters was large, -27.4 to +2.0‰ and 0.6-118 pMC, respectively. The sources and reactions of dissolved inorganic carbon were studied by comparing the measured chemical and isotope composition with those simulated using isotope geochemical models. Three major sources of CO2 were identified: (1) dissolution of partially degassed basaltic rocks formed at the surface or shallow depths, (2) atmospheric CO2 through air-water exchange at surface, and (3) input of gas at depth into the groundwater systems that has similar carbon and isotope composition as the pre-erupted melt of the upper mantle and lower crust beneath Iceland. In the groundwater systems the CO2 chemistry and isotope content are modified due to carbonate mineral precipitation and changes in aqueous species distribution upon progressive water-rock interaction; these changes needed to be quantified in order to reveal the various CO2 sources. The CO2 flux of the Icelandic crust was estimated to be ∼5-10 · 1010 mol/yr with as high as 50% of the flux not associated with active volcanic centers but placed off-axis where a significant proportion of the CO2 may originate from the mantle. The mantle input of the groundwater off-axis corresponds to CO2 partial pressures of ∼10-6-1 bar and to a mantle CO2 flux of <5 · 105 mol/km2/yr for most areas and up to 125 · 105 and 1600 · 105 for the Southern Lowlands and Snæfellsnes Peninsula, respectively. The CO2 flux from active volcanic geothermal systems in Iceland was estimated to be ∼500-3000 · 105 mol CO2/km2/yr, considerably greater than the highest values observed off-axis.

  7. Tracing carbon sources through aquatic and terrestrial food webs using amino acid stable isotope fingerprinting.

    Directory of Open Access Journals (Sweden)

    Thomas Larsen

    Full Text Available Tracing the origin of nutrients is a fundamental goal of food web research but methodological issues associated with current research techniques such as using stable isotope ratios of bulk tissue can lead to confounding results. We investigated whether naturally occurring δ(13C patterns among amino acids (δ(13CAA could distinguish between multiple aquatic and terrestrial primary production sources. We found that δ(13CAA patterns in contrast to bulk δ(13C values distinguished between carbon derived from algae, seagrass, terrestrial plants, bacteria and fungi. Furthermore, we showed for two aquatic producers that their δ(13CAA patterns were largely unaffected by different environmental conditions despite substantial shifts in bulk δ(13C values. The potential of assessing the major carbon sources at the base of the food web was demonstrated for freshwater, pelagic, and estuarine consumers; consumer δ(13C patterns of essential amino acids largely matched those of the dominant primary producers in each system. Since amino acids make up about half of organismal carbon, source diagnostic isotope fingerprints can be used as a new complementary approach to overcome some of the limitations of variable source bulk isotope values commonly encountered in estuarine areas and other complex environments with mixed aquatic and terrestrial inputs.

  8. Carbonate Chemistry and Isotope Characteristics of Groundwater of Ljubljansko Polje and Ljubljansko Barje Aquifers in Slovenia

    Science.gov (United States)

    2013-01-01

    Ljubljansko polje and Ljubljansko Barje aquifers are the main groundwater resources for the needs of Ljubljana, the capital of Slovenia. Carbonate chemistry and isotope analysis of the groundwater were performed to acquire new hydrogeological data, which should serve as a base for improvement of hydrogeological conceptual models of both aquifers. A total of 138 groundwater samples were collected at 69 sampling locations from both aquifers. Major carbonate ions and the stable isotope of oxygen were used to identify differences in the recharging areas of aquifers. Four groups of groundwater were identified: (1) Ljubljansko polje aquifer, with higher Ca2+values, as limestone predominates in its recharge area, (2) northern part of Ljubljansko Barje aquifer, with prevailing dolomite in its recharge area, (3) central part of Ljubljansko Barje aquifer, which lies below surface cover of impermeable clay and is poor in carbonate, and (4) Brest and Iški vršaj aquifer in the southern part of Ljubljansko Barje with higher Mg2+ in groundwater and dolomite prevailing in its recharge area. The radioactive isotope tritium was also used to estimate the age of groundwater. Sampled groundwater is recent with tritium activity between 4 and 8 TU and residence time of up to 10 years. PMID:24453928

  9. Carbon Biogeochemistry: A Stable Isotope Approach to Trophic Dynamics in an Indian Coastal Ecosystem

    Science.gov (United States)

    Mathukumalli, B.; Alagappan, R.

    2005-12-01

    Stable isotope(δ13C & δ15N) approach was applied to understand carbon biogeochemistry and trophic dynamics in an Indian coastal mangrove wetland. The δ13C and δ15N values of potential nutrient sources (mangrove plant leaves, lichen, sediment and suspended material) and in seven species of consumers (invertebrates) were measured. The value of δ13C and δ15N isotopes of different potential nutrient sources and the consumers determine the sources of nutrients for the invertebrate consumer community of the mangrove. There is a significant variation in the stable carbon in the nutrient sources; however, δ15N signatures were not significantly different among the different potential nutrient sources. Organic matter in the sediments under the mangrove vegetation was characterized by relatively negatively fractionated and moderately high C:N ratios, indicating that mangrove derived organic matter was the principal diet source for the invertebrate consumer communities in the mangrove ecosystem. Invertebrates in the mangrove showed a wide range of δ13C signatures and are enriched relative to the mangrove leaf stable isotope values. Micro-environmental differences certainly drive the variability in the nutrient sources and consumable nature among the different regions of the ecosystem. Therefore, further research is needed to determine whether carbon assimilation is different from one zone to another.

  10. Carbon isotope excursions and the oxidant budget of the Ediacaran atmosphere and ocean

    Science.gov (United States)

    Bristow, Thomas F.; Kennedy, Martin J.

    2008-11-01

    A possible global drop in marine carbon isotope values to aslow as -12 Peedee belemnite (PDB), recorded in the EdiacaranShuram Formation of Oman, has been attributed to the non-steady-stateoxidation of oceanic dissolved organic carbon (DOC) resultingfrom the rise in atmospheric oxygen to near modern values atthe end of the Precambrian. Geologic constraints indicate thatthe excursion lasted between 25 and 50 m.y., requiring a DOCpool thousands of times to 10,000 times the modern inventoryto conform with carbon isotope mass balance calculations fora -12 excursion. At the consequent rates of DOC oxidation,oceanic sulfate and oxygen in the atmosphere and oceans areexhausted on a time scale of 800 k.y. Oxidant depletion isincompatible with independent geochemical and biological indicatorsthat show oceanic sulfate and oxygen levels were maintainedor increased during the Shuram excursion. Furthermore, a DOC-drivenexcursion does not explain strong covariation between the carbonand oxygen isotope record. These indicators show that negativeisotope excursions recorded in the Shuram and other Ediacaransections are unlikely to represent a global ocean signal.

  11. Carbonate Chemistry and Isotope Characteristics of Groundwater of Ljubljansko Polje and Ljubljansko Barje Aquifers in Slovenia

    Directory of Open Access Journals (Sweden)

    Sonja Cerar

    2013-01-01

    Full Text Available Ljubljansko polje and Ljubljansko Barje aquifers are the main groundwater resources for the needs of Ljubljana, the capital of Slovenia. Carbonate chemistry and isotope analysis of the groundwater were performed to acquire new hydrogeological data, which should serve as a base for improvement of hydrogeological conceptual models of both aquifers. A total of 138 groundwater samples were collected at 69 sampling locations from both aquifers. Major carbonate ions and the stable isotope of oxygen were used to identify differences in the recharging areas of aquifers. Four groups of groundwater were identified: (1 Ljubljansko polje aquifer, with higher Ca2+ values, as limestone predominates in its recharge area, (2 northern part of Ljubljansko Barje aquifer, with prevailing dolomite in its recharge area, (3 central part of Ljubljansko Barje aquifer, which lies below surface cover of impermeable clay and is poor in carbonate, and (4 Brest and Iški vršaj aquifer in the southern part of Ljubljansko Barje with higher Mg2+ in groundwater and dolomite prevailing in its recharge area. The radioactive isotope tritium was also used to estimate the age of groundwater. Sampled groundwater is recent with tritium activity between 4 and 8 TU and residence time of up to 10 years.

  12. Tracing carbon sources through aquatic and terrestrial food webs using amino acid stable isotope fingerprinting.

    Science.gov (United States)

    Larsen, Thomas; Ventura, Marc; Andersen, Nils; O'Brien, Diane M; Piatkowski, Uwe; McCarthy, Matthew D

    2013-01-01

    Tracing the origin of nutrients is a fundamental goal of food web research but methodological issues associated with current research techniques such as using stable isotope ratios of bulk tissue can lead to confounding results. We investigated whether naturally occurring δ(13)C patterns among amino acids (δ(13)CAA) could distinguish between multiple aquatic and terrestrial primary production sources. We found that δ(13)CAA patterns in contrast to bulk δ(13)C values distinguished between carbon derived from algae, seagrass, terrestrial plants, bacteria and fungi. Furthermore, we showed for two aquatic producers that their δ(13)CAA patterns were largely unaffected by different environmental conditions despite substantial shifts in bulk δ(13)C values. The potential of assessing the major carbon sources at the base of the food web was demonstrated for freshwater, pelagic, and estuarine consumers; consumer δ(13)C patterns of essential amino acids largely matched those of the dominant primary producers in each system. Since amino acids make up about half of organismal carbon, source diagnostic isotope fingerprints can be used as a new complementary approach to overcome some of the limitations of variable source bulk isotope values commonly encountered in estuarine areas and other complex environments with mixed aquatic and terrestrial inputs. PMID:24069196

  13. CO2 production by impact in carbonates? An ATEM and stable isotope (C,O) study

    Science.gov (United States)

    Martinez, I.; Agrinier, P.; Guyot, F.; Ildefonse, PH.; Javoy, M.; Schaerer, U.; Hornemann, U.; Deutsch, A.

    1993-01-01

    Carbonates may have been a common target for large impacts on the Earth and possible related CO2 outgassing would have important consequences for the composition of the atmosphere. To estimate volatile release during such impacts, isotopic ratios (C-13/C-12 and O-18/O-16) were determined on highly shocked carbonate samples in combination with SEM and analytical transmission electron microscopy (ATEM) investigations. The study was performed on both naturally and experimentally shocked rocks, i.e. 50-60 GPa shocked limestone-dolomite fragments from the Haughton impact crater (Canada), and carbonates shocked in shock recovery experiments. For the experiments, unshocked carbonates consisting of mixture of dolomite and calcite from the Haughton area were used. Naturally shocked samples were collected in the polymict breccia near the center of the Haughton crater.

  14. [Humus composition and stable carbon isotope natural abundance in paddy soil under long-term fertilization].

    Science.gov (United States)

    Ma, Li; Yang, Lin-Zhang; Ci, En; Wang, Yan; Yin, Shi-Xue; Shen, Ming-Xing

    2008-09-01

    Soil samples were collected from an experimental paddy field with long-term (26 years) fertilization in Taihu Lake region of Jiangsu Province to study the effects of different fertilization on the organic carbon distribution and stable carbon isotope natural abundance (delta 13C) in the soil profile, and on the humus composition. The results showed that long-term fertilization increased the organic carbon content in top soil significantly, and there was a significantly negative exponential correlation between soil organic carbon content and soil depth (P humus (humin) was the main humus composition in the soil, occupying 50% or more, and the rest were loosely and stably combined humus. Long-term fertilization increased the content of loosely combined humus and the ratio of humic acid (HA) to fulvic acid (FA).

  15. Mechanisms controlling the carbon stable isotope composition of phytoplankton in karst reservoirs

    Directory of Open Access Journals (Sweden)

    Baoli Wang

    2013-02-01

    Full Text Available In order to systematically understand the mechanisms controlling the carbon stable isotope composition of phytoplankton (δ13CPHYin freshwater ecosystems, seasonal changes in δ13CPHY and related environmental factors were determined in karst reservoirs from the Wujiang river basin, China. Substantial and systematic differences within seasons and reservoirs were observed for δ13CPHY, which ranged from -39.2‰ to -15.1‰. An increase in water temperature triggered fast growth of phytoplankton which assimilated more dissolved inorganic carbon (DIC, resulting in the increase of δ13CPHY, δ13CDIC and pH. When the concentration of dissolved carbon dioxide (CO2 was less than 10 mmol L–1, phytoplankton shifted to using HCO3– as a carbon source. This resulted in the sharp increase of δ13CPHY. The carbon stable isotope composition of phytoplankton tended to decrease with the increase of Bacillariophyta, which dominated in January and April, but tended to increase with the increase of Chlorophyta and Dinophyta, which dominated in July. Multiple regression equations suggested that the influence of biological factors such as taxonomic difference on δ13CPHY could be equal or more important than that of physical and chemical factors. Thus, the effect of taxonomic differences on δ13CPHY must be considered when explaining the δ13C of organic matter in lacustrine ecosystem.

  16. Drivers of carbon isotopic fractionation in a coral reef lagoon: Predominance of demand over supply

    Science.gov (United States)

    Carvalho, Matheus C.; Santos, Isaac R.; Maher, Damien T.; Cyronak, Tyler; McMahon, Ashly; Schulz, Kai G.; Eyre, Bradley D.

    2015-03-01

    The carbon isotopic signature (δ13C) of coral skeletons is influenced by isotopic fractionation (εorg) during photosynthetic dissolved inorganic carbon (DIC) fixation, but only a few direct εorg measurements are available in coral communities. In particular, observations of εorg at the ecosystem scale are lacking. Here we present high frequency (hourly) measurements of DIC and its δ13C in the water column and benthic chambers in a highly productive coral reef lagoon (Heron Island, Great Barrier Reef, Australia) and apply simple molar balance calculations to infer community εorg. Variation in εorg was between 3.7‰ and 25.2‰ in the open lagoon, with lower values during the mid-afternoon and higher values in early morning and evening. The εorg range was broader (0.3-30.1‰) in enclosed benthic chambers with a similar diel pattern. There was a strong correlation between carbon uptake rates and εorg in closed incubations, suggesting that C demand largely controlled εorg. Benthic chamber incubations revealed increased εorg as water circulation increased, implying that C supply to photosynthesizing algae on the sediment also influenced εorg. Hysteresis in carbon uptake through the day complicated the expected straightforward influence of irradiance on C demand, and consequently on εorg. These results highlight the need for more in depth understanding on carbon uptake rates to fully understand δ13C variation in coral paleo-records.

  17. River under anthropogenic stress: An isotope study of carbon cycling in the Vistula, Poland

    International Nuclear Information System (INIS)

    Rivers play an important role in global carbon cycling as they transform and transport substantial amounts of carbon derived from the terrestrial systems to the oceans. Riverine carbon cycling is affected by anthropogenic influences on hydrology, chemistry and biology of the river and its catchment. The Vistula, one of the most mineralized rivers of the world, drains industrialized and agriculturally-used areas populated by almost 23 million inhabitants. Moreover, much of the industrial and domestic wastewaters discharged into the Vistula river are untreated or insufficiently treated. High levels of pollution have serious environmental and economical consequences. For example, they limit use of Vistula waters as a source of drinking water and for industrial purposes. Pollutants transported by the Vistula river significantly influence water quality far into the open Baltic Sea. The aim of the paper is to show how stable isotope techniques can be used to assess human impact on sources, fluxes and fate of dissolved inorganic carbon (DIC) and other pollutants in rivers, taking the Vistula river as an example. Vistula waters were sampled over a one-year period at Krakow (upper reaches), where the anthropogenic influences are at the extreme, and at the river mouth. Two campaigns were undertaken to sample the Vistula river along its course in summer and in autumn. Analyses of river water included temperature, pH, alkalinity, conductivity, dissolved oxygen, δ13C of dissolved inorganic carbon and stable isotope composition of water (δ18O and δ2H)

  18. Boron isotopic fractionation in laboratory inorganic carbonate precipitation: Evidence for the incorpora-tion of B(OH)3 into carbonate

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    A laboratory inorganic carbonate precipitation experiment at high pH of 8.96 to 9.34 was conducted, and the boron isotopic fractionations of the precipitated carbonate were measured. The data show that boron isotopic fractionation factors (αcarb-3) between carbonate and B(OH)3 in seawater range 0.937 and 0.965, with an average value of 0.953. Our results together with those reported by Sanyal and collabo-rators show that the αcarb-3 values between carbonate and B(OH)3 in solution are not constant but are negatively correlated with the pH of seawater. The measured boron isotopic compositions of carbonate precipitation (δ11Bcarb) do not exactly lie on the best-fit theoretical δ 11B4-pH curves and neither do they exactly parallel any theoretical δ 11B4-pH curves. Therefore, it is reasonable to argue that a changeable proportion of B(OH)3 with pH of seawater should also be incorporated into carbonate except for the dominant incorporation of B(OH)4- in carbonate . Hence, in the reconstruction of the paleo-pH of sea-water from boron isotopes in marine biogenic carbonates, the use of theoretical boron isotopic frac-tionation factor (α4-3) between B(OH)4- and B(OH)3 is not suitable. Instead, an empirical equation should be established.

  19. Springtime carbon emission episodes at the Gosan background site revealed by total carbon, stable carbon isotopic composition, and thermal characteristics of carbonaceous particles

    Science.gov (United States)

    Jung, J.; Kawamura, K.

    2011-11-01

    In order to investigate the emission of carbonaceous aerosols at the Gosan background super-site (33.17° N, 126.10° E) in East Asia, total suspended particles (TSP) were collected during spring of 2007 and 2008 and analyzed for particulate organic carbon, elemental carbon, total carbon (TC), total nitrogen (TN), and stable carbon isotopic composition (δ13C) of TC. The stable carbon isotopic composition of TC (δ13CTC) was found to be lowest during pollen emission episodes (range: -26.2‰ to -23.5‰, avg. -25.2 ± 0.9‰), approaching those of the airborne pollen (-28.0‰) collected at the Gosan site. Based on a carbon isotope mass balance equation, we found that ~42% of TC in the TSP samples during the pollen episodes was attributed to airborne pollen from Japanese cedar trees planted around tangerine farms in Jeju Island. A negative correlation between the citric acid-carbon/TC ratios and δ13CTC was obtained during the pollen episodes. These results suggest that citric acid emitted from tangerine fruit may be adsorbed on the airborne pollen and then transported to the Gosan site. Thermal evolution patterns of organic carbon during the pollen episodes were characterized by high OC evolution in the OC2 temperature step (450 °C). Since thermal evolution patterns of organic aerosols are highly influenced by their molecular weight, they can be used as additional information on the formation of secondary organic aerosols and the effect of aging of organic aerosols during the long-range atmospheric transport and sources of organic aerosols.

  20. Springtime carbon emission episodes at the Gosan background site revealed by total carbon, stable carbon isotopic composition, and thermal characteristics of carbonaceous particles

    Directory of Open Access Journals (Sweden)

    J. Jung

    2011-11-01

    Full Text Available In order to investigate the emission of carbonaceous aerosols at the Gosan background super-site (33.17° N, 126.10° E in East Asia, total suspended particles (TSP were collected during spring of 2007 and 2008 and analyzed for particulate organic carbon, elemental carbon, total carbon (TC, total nitrogen (TN, and stable carbon isotopic composition (δ13C of TC. The stable carbon isotopic composition of TC (δ13CTC was found to be lowest during pollen emission episodes (range: −26.2‰ to −23.5‰, avg. −25.2 ± 0.9‰, approaching those of the airborne pollen (−28.0‰ collected at the Gosan site. Based on a carbon isotope mass balance equation, we found that ~42% of TC in the TSP samples during the pollen episodes was attributed to airborne pollen from Japanese cedar trees planted around tangerine farms in Jeju Island. A negative correlation between the citric acid-carbon/TC ratios and δ13CTC was obtained during the pollen episodes. These results suggest that citric acid emitted from tangerine fruit may be adsorbed on the airborne pollen and then transported to the Gosan site. Thermal evolution patterns of organic carbon during the pollen episodes were characterized by high OC evolution in the OC2 temperature step (450 °C. Since thermal evolution patterns of organic aerosols are highly influenced by their molecular weight, they can be used as additional information on the formation of secondary organic aerosols and the effect of aging of organic aerosols during the long-range atmospheric transport and sources of organic aerosols.

  1. Constraints on Phanerozoic paleotemperature and seawater oxygen isotope evolution from the carbonate clumped isotope compositions of Late Paleozoic marine fossils (Invited)

    Science.gov (United States)

    Henkes, G. A.; Passey, B. H.; Grossman, E. L.; Pérez-Huerta, A.; Shenton, B.; Yancey, T. E.

    2013-12-01

    A long-standing geoscience controversy has been the interpretation of the observed several per mil increase in the oxygen isotope compositions of marine calcites over the Phanerozoic Eon. Explanations for this trend have included decreasing seawater paleotemperatures, increasing seawater oxygen isotope values, and post-depositional calcite alteration. Carbonate clumped isotope paleothermometry is a useful geochemical tool to test these hypotheses because of its lack of dependence on the bulk isotopic composition of the water from which carbonate precipitated. This technique is increasingly applied to ancient marine invertebrate shells, which can be screened for diagenesis using chemical and microstructural approaches. After several years of clumped isotope analysis of these marine carbonates in a handful of laboratories, a long-term temperature and isotopic trend is emerging, with the results pointing to relatively invariant seawater δ18O and generally decreasing seawater temperatures through the Phanerozoic. Uncertainties remain, however, including the effects of reordering of primary clumped isotope compositions via solid-state diffusion of C and O through the mineral lattice at elevated burial temperatures over hundred million year timescales. To develop a quantitative understanding of such reordering, we present data from laboratory heating experiments of late Paleozoic brachiopod calcite. When combined with kinetic models of the reordering reaction, the results of these experiments suggest that burial temperatures less than ~120 °C allow for preservation of primary brachiopod clumped isotope compositions over geological timescales. Analyses of well-preserved Carboniferous and Permian brachiopods reinforce these results by showing that shells with apparent clumped isotope temperatures of ~150 °C are associated with deep sedimentary burial (>5 km), whereas those with putatively primary paleotemperatures in the 10-30 °C range experienced no more than ~1.5 km

  2. Stable isotopic composition of pedogenic carbonate in soils of Minusinsk Hollow

    Science.gov (United States)

    Vasil'chuk, Jessica; Krechetov, Pavel; Budantseva, Nadine; Chizhova, Julia; Vasil'chuk, Yurij

    2016-04-01

    The purpose of the research is to characterize the isotopic composition of carbonate neoformations in soils and estimate its correlation with isotopic composition of water and parent material. The study site is located in the Minusinsk Hollow that is situated among Kuznetsk Alatau and Sayan Mountains. Three key-sites with in different parts of hollow, under mainly steppe vegetation with calciphilic grasses and diverse parent material were studied including: 1) Kazanovka Khakass state national reserve in foothills of Kuznetsk Alatau 2) Hankul salt lake that is considered as natural monument 3) region of Sayanogorsk aluminum smelter on a left bank of the Yenisei river. The samples of pedogenic and lithogenic carbonates as well as water samples were analyzed using the Delta-V mass spectrometer with a standard option of a gas bench according to standard methods. Carbonate coatings (also called pendants or cutans) is one of the most common types of carbonate neoformations occurring in the region. Fine coatings' layers one over another usually can be found on the bottom sides of rubble and gravel inside the soil profile colour varies from white to brownish and yellowish (probably depending on the impurities of organic matter). In Petric Calcisols, Chernozems and Kastanozems δ18O values of coatings vary in a rather small range from - 8.9 to - 10.1 ‰ PDB. This probably shows that their forming took place approximately in the same climatic conditions. While δ18O values of carbonate parent rocks are close to them and are vary from - 11.1 to - 11.9 ‰ PDB. Also, δ13C values of coatings strongly decrease from inner (older) to outer (younger) layers, that can indicate differences connected with the diffusion of organic material. River waters' δ18O values also show a small range from - 16.62 to - 17.66‰ SMOW, while salt lakes' waters due to the fractionation evaporation effects demonstrate much heavier values from - 4.73 to - 9.22‰ SMOW. The groundwater shows δ18O

  3. Stable isotopic composition of pedogenic carbonate in soils of Minusinsk Hollow

    Science.gov (United States)

    Vasil'chuk, Jessica; Krechetov, Pavel; Budantseva, Nadine; Chizhova, Julia; Vasil'chuk, Yurij

    2016-04-01

    The purpose of the research is to characterize the isotopic composition of carbonate neoformations in soils and estimate its correlation with isotopic composition of water and parent material. The study site is located in the Minusinsk Hollow that is situated among Kuznetsk Alatau and Sayan Mountains. Three key-sites with in different parts of hollow, under mainly steppe vegetation with calciphilic grasses and diverse parent material were studied including: 1) Kazanovka Khakass state national reserve in foothills of Kuznetsk Alatau 2) Hankul salt lake that is considered as natural monument 3) region of Sayanogorsk aluminum smelter on a left bank of the Yenisei river. The samples of pedogenic and lithogenic carbonates as well as water samples were analyzed using the Delta-V mass spectrometer with a standard option of a gas bench according to standard methods. Carbonate coatings (also called pendants or cutans) is one of the most common types of carbonate neoformations occurring in the region. Fine coatings' layers one over another usually can be found on the bottom sides of rubble and gravel inside the soil profile colour varies from white to brownish and yellowish (probably depending on the impurities of organic matter). In Petric Calcisols, Chernozems and Kastanozems δ18O values of coatings vary in a rather small range from ‑ 8.9 to ‑ 10.1 ‰ PDB. This probably shows that their forming took place approximately in the same climatic conditions. While δ18O values of carbonate parent rocks are close to them and are vary from ‑ 11.1 to ‑ 11.9 ‰ PDB. Also, δ13C values of coatings strongly decrease from inner (older) to outer (younger) layers, that can indicate differences connected with the diffusion of organic material. River waters' δ18O values also show a small range from ‑ 16.62 to ‑ 17.66‰ SMOW, while salt lakes' waters due to the fractionation evaporation effects demonstrate much heavier values from ‑ 4.73 to ‑ 9.22‰ SMOW. The

  4. Environmental impact and magnitude of paleosol carbonate carbon isotope excursions marking five early Eocene hyperthermals in the Bighorn Basin, Wyoming

    Science.gov (United States)

    Abels, Hemmo A.; Lauretano, Vittoria; van Yperen, Anna E.; Hopman, Tarek; Zachos, James C.; Lourens, Lucas J.; Gingerich, Philip D.; Bowen, Gabriel J.

    2016-05-01

    Transient greenhouse warming events in the Paleocene and Eocene were associated with the addition of isotopically light carbon to the exogenic atmosphere-ocean carbon system, leading to substantial environmental and biotic change. The magnitude of an accompanying carbon isotope excursion (CIE) can be used to constrain both the sources and amounts of carbon released during an event and also to correlate marine and terrestrial records with high precision. The Paleocene-Eocene Thermal Maximum (PETM) is well documented, but CIE records for the subsequent warming events are still rare, especially from the terrestrial realm.Here, we provide new paleosol carbonate CIE records for two of the smaller hyperthermal events, I1 and I2, as well as two additional records of Eocene Thermal Maximum 2 (ETM2) and H2 in the Bighorn Basin, Wyoming, USA. Stratigraphic comparison of this expanded, high-resolution terrestrial carbon isotope history to the deep-sea benthic foraminiferal isotope records from Ocean Drilling Program (ODP) sites 1262 and 1263, Walvis Ridge, in the southern Atlantic Ocean corroborates the idea that the Bighorn Basin fluvial sediments record global atmospheric change. The ˜ 34 m thicknesses of the eccentricity-driven hyperthermals in these archives corroborate precession forcing of the ˜ 7 m thick fluvial overbank-avulsion sedimentary cycles. Using bulk-oxide mean-annual-precipitation reconstructions, we find soil moisture contents during the four younger hyperthermals that are similar to or only slightly wetter than the background, in contrast with soil drying observed during the PETM using the same proxy, sediments, and plant fossils.The magnitude of the CIEs in soil carbonate for the four smaller, post-PETM events scale nearly linearly with the equivalent event magnitudes documented in marine records. In contrast, the magnitude of the PETM terrestrial CIE is at least 5 ‰ smaller than expected based on extrapolation of the scaling relationship established

  5. Spatio-temporal carbon isotope variation during the Ediacaran period in South China and its impact on bio-evolution

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The Ediacaran period is characterized by the extremely negative carbon isotope anomalies and great biotic evolution in Earth history. At least four negative carbon isotope anomalies have been reported from this interval in South China so far. It is traditionally argued that the isotope variations can be used as a useful tool for global correlation of Ediacaran succession; however, more and more researches argued against this idea. We reviewed the previously published carbon isotope data in South China, and distributed the mean values of a certain time to the paleogeographic maps. The results show that the carbon isotope values (δ 13C) vary greatly in different environments, but a clear tendency of becoming lighter from shallow platform to deep basin, with a maximum variation up to 11‰. Moreover, the important changes in Ediacaran biota, marked by the introducing of new taxa or ecologic groups, seemed to always postdate the negative anomalies but coincide with the positive shift. If the negative excursions represented the oxidation of a large dissolved organic carbon (DOC) reservoir in the ocean, the diverse Ediacaran organisms and the carbon isotope anomalies may suggest totally different environments: oxic and anoxic/euxinic. We also suggest that the elimination of euxinic state through precipitation of pyrites is one of the important environment factors in prompting the Ediacaran bio-evolution.

  6. Realization of an apparatus for the synthesis and detection of carbon 11 labelled fatty acids and of a data acquisition system for the study of the myocardial methabolism of radiopharmaceuticals

    International Nuclear Information System (INIS)

    This thesis describes the study and the realization of an apparatus to synthesize fatty acids labelled with carbon 11, a radioactive isotope with an half-life of 20.38 minutes. A system of gamma-ray detection with data processing designed for the study of the myocardiac metabolism of radiopharmaceuticals using isolated rat hearts as experimental models. The synthesis of carbon 11 labelled fatty acids required a preliminary study of the manufacture of this isotope at the synchrocyclotron of the I.P.N. (Lyon). The method chosen is the nuclear reaction (d,xn) with naturally occurring boron trioxide as the target. The apparatus was designed so as extract carbon 11 from the target in the form of 11CO2 which can then be used in the synthesis of carbon 11 labelled hexadecanoique, heptadecanoic and beta-methyl hexadecanoic acids. The time scale of this synthesis must be compatible with the short half-like of the isotope. In order to study these compounds 'in vivo' on the experimental model of isolated rat hearts, a system of detection, which functions either in a simple gamma mode or in a gamma-gamma coincidence mode, was developed. This apparatus can attain a rate of approximately 50 000 counts/sec. per channel, thus it is possible to obtain information about rapid phases of metabolism with a satisfactory statistical precision. Moreover the spectral analysis of the gamma-ray permits the simultaneous detection of different radioisotopes. Hence it was possible to compare the behaviour of carbon 11 labelled fatty acids with homologous molecules marked with iodine 123. The analysis of the experimental results was achieved witha computer based on an I.B.M. compatible PC-XT. The essential parts of this system are a data-acquisition card for the PC, code for the acquisition and the data processing

  7. Carbon isotopes in otolith amino acids identify residency of juvenile snapper (Family: Lutjanidae) in coastal nurseries

    Science.gov (United States)

    McMahon, K. W.; Berumen, M. L.; Mateo, I.; Elsdon, T. S.; Thorrold, S. R.

    2011-12-01

    This study explored the potential for otolith geochemistry in snapper (Family: Lutjanidae) to identify residency in juvenile nursery habitats with distinctive carbon isotope values. Conventional bulk otolith and muscle stable isotope analyses (SIA) and essential amino acid (AA) SIA were conducted on snapper collected from seagrass beds, mangroves, and coral reefs in the Red Sea, Caribbean Sea, and Pacific coast of Panama. While bulk stable isotope values in otoliths showed regional differences, they failed to distinguish nursery residence on local scales. Essential AA δ13C values in otoliths, on the other hand, varied as a function of habitat type and provided a better tracer of residence in different juvenile nursery habitats than conventional bulk otolith SIA alone. A strong linear relationship was found between paired otolith and muscle essential AA δ13C values regardless of species, geographic region, or habitat type, indicating that otolith AAs recorded the same dietary information as muscle AAs. Juvenile snapper in the Red Sea sheltered in mangroves but fed in seagrass beds, while snapper from the Caribbean Sea and Pacific coast of Panama showed greater reliance on mangrove-derived carbon. Furthermore, compound-specific SIA revealed that microbially recycled detrital carbon, not water-column-based new phytoplankton carbon, was the primary carbon source supporting snapper production on coastal reefs of the Red Sea. This study presented robust tracers of juvenile nursery residence that will be crucial for reconstructing ontogenetic migration patterns of fishes among coastal wetlands and coral reefs. This information is key to determining the importance of nursery habitats to coral reef fish populations and will provide valuable scientific support for the design of networked marine-protected areas.

  8. Isotope Biogeochemistry of Sulfur in a Cold-Water Carbonate Mound (IODP Site 1317)

    Science.gov (United States)

    Ferdelman, T. G.; Boettcher, M. E.

    2007-12-01

    To establish a depositional model for cold-water carbonate mounds, Challenger Mound and adjacent continental slope sites were drilled during IODP Expedition 307 in May 2005. Although a role for methane seepage and subsequent anaerobic oxidation was discounted both as a hard-round substrate for mound initiation and as a principal source of carbonate within the mound succession, interstitial water profiles of sulfate, alkalinity, Mg, and Sr indicated a tight coupling between carbonate diagenesis and mircrobial sulfate reduction. The reaction of sulfide with siliciclastic iron-bearing minerals to form pyrite was proposed to account for enhanced diagenetic carbonate precipitation (Ferdelman et al., 2006; Proc. IODP, vol. 307; doi:10.2204/iodp.proc.307.2006). To characterize these geomicrobial sulfur transformations in the carbonate mound sediments, the inorganic and stable isotope geochemical compositions of pore water sulfate and solid phase reduced sulfur compounds were performed. Acid-volatile sulfur (AVS) and pyrite del 34S compositions were usually similar and exhibited an increasing trend of from -40 per mil near surface to -20 per mil at the mound base at 132 mbsf. However, several excursions to more 34S sulfur enriched pyrite to values >0 per mil were observed in the deeper sections of the mound sequence. These excursions may be linked transitory changes in the depth of the methane-sulfate transition zone during mound build-up. The oxygen isotopic composition of residual dissolved sulfate indicates intracellular isotope exchange processes within the cells of SRBs, leading to increasing equilibration between extracellular pore water and sulfate.

  9. Carbon isotopes in otolith amino acids identify residency of juvenile snapper (Family: Lutjanidae) in coastal nurseries

    KAUST Repository

    McMahon, Kelton

    2011-08-26

    This study explored the potential for otolith geochemistry in snapper (Family: Lutjanidae) to identify residency in juvenile nursery habitats with distinctive carbon isotope values. Conventional bulk otolith and muscle stable isotope analyses (SIA) and essential amino acid (AA) SIA were conducted on snapper collected from seagrass beds, mangroves, and coral reefs in the Red Sea, Caribbean Sea, and Pacific coast of Panama. While bulk stable isotope values in otoliths showed regional differences, they failed to distinguish nursery residence on local scales. Essential AA δ13C values in otoliths, on the other hand, varied as a function of habitat type and provided a better tracer of residence in different juvenile nursery habitats than conventional bulk otolith SIA alone. A strong linear relationship was found between paired otolith and muscle essential AA δ13C values regardless of species, geographic region, or habitat type, indicating that otolith AAs recorded the same dietary information as muscle AAs. Juvenile snapper in the Red Sea sheltered in mangroves but fed in seagrass beds, while snapper from the Caribbean Sea and Pacific coast of Panama showed greater reliance on mangrove-derived carbon. Furthermore, compound-specific SIA revealed that microbially recycled detrital carbon, not water-column-based new phytoplankton carbon, was the primary carbon source supporting snapper production on coastal reefs of the Red Sea. This study presented robust tracers of juvenile nursery residence that will be crucial for reconstructing ontogenetic migration patterns of fishes among coastal wetlands and coral reefs. This information is key to determining the importance of nursery habitats to coral reef fish populations and will provide valuable scientific support for the design of networked marine-protected areas. © 2011 Springer-Verlag.

  10. Authenticity of carbon dioxide bubbles in French ciders through multiflow-isotope ratio mass spectrometry measurements.

    Science.gov (United States)

    Gaillard, Laetitia; Guyon, Francois; Salagoïty, Marie-Hélène; Médina, Bernard

    2013-12-01

    A procedure to detect whether carbon dioxide was added to French ciders has been developed. For this purpose, an optimised and simplified method is proposed to determine (13)C/(12)C isotope ratio of carbon dioxide (δ(13)C) in ciders. Three critical steps were checked: (1) influence of atmospheric CO2 remaining in the loaded vial, (2) impact of helium flush, (3) sampling speed. This study showed that atmospheric CO2 does not impact the measurement, that helium flush can lead to isotopic fractionation and finally, that a fractionation occurs only 5h after bottle opening. The method, without any other preparation, consists in sampling 0.2 mL of cold (4 °C) cider in a vial that is passed in an ultrasonic bath for 10 min at room temperature to enhance cider de-carbonation. The headspace CO2 is then analysed using the link Multiflow®-isotope ratio mass spectrometer. Each year, a data bank is developed by fermenting authentic apples juices in order to control cider authenticity. Over a four year span (2008-2011), the CO2 produced during the fermentation step was studied. This set of 61 authentic ciders, from various French production areas, was used to determine a δ(13)C value range of -22.59±0.92‰ for authentic ciders CO2 bubbles. 75 commercial ciders were analysed with this method. Most of the samples analysed present a gas δ(13)C value in the expected range. Nevertheless, some ciders have δ(13)C values outside the 3σ limit, revealing carbonation by technical CO2. This practice is not allowed for organic, "Controlled Appellation of Origin" ciders and ciders specifying natural carbonation on the label.

  11. Recent planktic foraminifers in the Fram Strait (Arctic Ocean): carbon and oxygen stable isotope composition

    Science.gov (United States)

    Pados, T.; Spielhagen, R. F.; Bauch, D.; Meyer, H.; Segl, M.

    2012-12-01

    In paleoceanographic reconstructions the carbon isotopic compositions (δ13C) of fossil foraminifers refer to, e.g., paleoproductivity and stratification, while oxygen isotopic (δ18O) records provide information about variations in sea surface temperatures and salinities in the past. However, for a correct interpretation of the fossil data it is important to improve our understanding of the correlation between recent oceanic variability and the composition of shells of living calcareous microorganisms. For this, the upper water column and sediment surface in the Fram Strait (Arctic Ocean, 78°50'N, 5°W-8°E) were sampled for planktic foraminifer species Neogloboquadrina pachyderma (sin.) and Turborotalita quinqueloba with a large-diameter multinet and a multicorer, respectively. The δ13C and δ18O values of the shells are compared to the stable isotope composition of the ambient water and to equilibrium calcite values to define the preferred calcification depths of the foraminifers and to determine the factors controlling the isotopic signature of these calcareous microorganisms. The study area was chosen because of its high oceanographic variability: in the eastern Fram Strait the northward flowing West Spitsbergen Current (WSC) carries Atlantic Water, with a thin mixed layer on top, while in the west the upper 200 m consists of cold, low-saline Arctic outflow waters of the East Greenland Current (EGC) and warmer, saline waters of Atlantic origin underneath. Despite this variable oceanographic regime along the studied transect, the stable carbon isotope ratios of the shells do not show major differences according to their horizontal but to their vertical distribution: the δ13C values of N. pachyderma (sin.) from plankton tow samples vary roughly between -1 and -0.1‰ depending on the water depth, while the δ18O values of the tests differ more between the stations.

  12. The carbon isotope study of biomarkers in the Maoming and the Jianghan tertiary oil shale

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    In terms of the individual carbon isotope data of biomarkers present in the typical freshwater lake sediment (Maoming oil shale) and saline lake sediment lake (Jianghan oil shale) of China, this paper discusses their precursors and depositional environments of biomarkers in both sediment samples. Our studies showed that phytane and pristane of the Maoming oil shale were derived from the phytol side chain of chlorophyll a. By comparing the isotopic composition of 4-methyl sterane with that of sterane and hopane, it is suggested that 4-methyl sterane which has a higher abundance in the Maoming oil shale come from bacteria. The isotopic composition of biomarkers from the Jianghan rock sample (saline lake sediment ) is significantly different from that of the Maoming oil shale (freshwater lake sediment). Gammacerane was derived from haloprotozoan, with δ13C being about -25.8‰, just in consistency with the value reported in previous studies. The isotopic composition of phytane and pristane in the Jianghan rock is similar to that of sterane and 4-methyl sterane derived from phytoplanktons, illustrating their commonprecursors were algae. This paper reported for the first time the carbon isotope data of porphyrin obtained by GC-IRMS techniques. The approximate δ13C of C32DPEP and C31DPEP porphyrin from the Jianghan Basin indicated that the porphyrin was derived from chlorophyll. In the Maomingoil shale C32DPEP was enriched in 13C relative to C32etio and C31DPEP, implying that C32DPEP came from chlorophyll, and C32etio and C31DPEP are of other origins.

  13. Carbon isotope fractionation of 1,1,1-trichloroethane during base-catalyzed persulfate treatment

    Energy Technology Data Exchange (ETDEWEB)

    Marchesi, Massimo, E-mail: m2marche@uwaterloo.ca [Department of Civil and Environmental Engineering, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1 (Canada); Department of Earth and Environmental Sciences, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1 (Canada); Thomson, Neil R. [Department of Civil and Environmental Engineering, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1 (Canada); Aravena, Ramon [Department of Earth and Environmental Sciences, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1 (Canada); Sra, Kanwartej S. [Department of Civil and Environmental Engineering, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1 (Canada); Golder Associates Inc, Toronto, Ontario, Canada L5N 5Z7 (Canada); Otero, Neus; Soler, Albert [Departament de Cristal.lographia, Mineralogia i Diposits Minerals, Facultat de Geologia, Universitat de Barcelona, Barcelona, Spain 08028 (Spain)

    2013-09-15

    Highlights: • Treatability and C fractionation of 1,1,1-TCA by base-catalyzed S{sub 2}O{sub 8}{sup 2−} was studied. • The rate of degradation of 1,1,1-TCA increased with a higher OH{sup −}:S{sub 2}O{sub 8}{sup 2−} ratio. •Base-catalyzed S{sub 2}O{sub 8}{sup 2−} can potentially treat recalcitrant compound like 1,1,1-TCA. • An enrichment factor of −7.0‰ independent of the OH{sup −}:S{sub 2}O{sub 8}{sup 2−} ratio was obtained. • Carbon isotope can potentially be used to estimate the ISCO treatment efficacy. -- Abstract: The extent of carbon isotope fractionation during degradation of 1,1,1-trichloroethane (1,1,1-TCA) by a base-catalyzed persulfate (S{sub 2}O{sub 8}{sup 2−}) treatment system was investigated. Significant destruction of 1,1,1-TCA was observed at a pH of ∼12. An increase in the NaOH:S{sub 2}O{sub 8}{sup 2−} molar ratio from 0.2:1 to 8:1 enhanced the reaction rate of 1,1,1-TCA by a factor of ∼5 to yield complete (>99.9%) destruction. An average carbon isotope enrichment fractionation factor which was independent of the NaOH:S{sub 2}O{sub 8}{sup 2−} molar ratio of −7.0 ± 0.2‰ was obtained. This significant carbon isotope fractionation and the lack of dependence on changes in the NaOH:S{sub 2}O{sub 8}{sup 2−} molar ratio demonstrates that carbon isotope analysis can potentially be used in situ as a performance assessment tool to estimate the degradation effectiveness of 1,1,1-TCA by a base-catalyzed persulfate system.

  14. A reconstruction of atmospheric carbon dioxide and its stable carbon isotopic composition from the penultimate glacial maximum to the last glacial inception

    Directory of Open Access Journals (Sweden)

    R. Schneider

    2013-11-01

    δ13Catm level in the Penultimate (~ 140 000 yr BP and Last Glacial Maximum (~ 22 000 yr BP, which can be explained by either (i changes in the isotopic composition or (ii intensity of the carbon input fluxes to the combined ocean/atmosphere carbon reservoir or (iii by long-term peat buildup. Our isotopic data suggest that the carbon cycle evolution along Termination II and the subsequent interglacial was controlled by essentially the same processes as during the last 24 000 yr, but with different phasing and magnitudes. Furthermore, a 5000 yr lag in the CO2 decline relative to EDC temperatures is confirmed during the glacial inception at the end of MIS5.5 (120 000 yr BP. Based on our isotopic data this lag can be explained by terrestrial carbon release and carbonate compensation.

  15. Stable isotope composition of bulk and secondary carbonates from the Quaternary loess-paleosol sequence in Sutto, Hungary

    DEFF Research Database (Denmark)

    Koeniger, Paul; Barta, Gabriella; Thiel, Christine;

    2014-01-01

    , and microscale secondary (authigenic) carbonates (calcified root cells, carbonate coatings, hypocoatings, and earthworm biospheroids) and concretions at 10 cm resolution were analysed to interpret stable isotope variations. Isotope values of bulk samples were in the range of 2.6 parts per thousand to -13.9 parts......, secondary carbonates showed more depleted values than bulk samples. Calcified root cells have the most depleted isotope composition with mean values of -16.0 parts per thousand and -11.8 parts per thousand for delta C-13 and 8180, respectively. Results indicate that loess and paleosol secondary carbonates...... or vegetation. Secondary carbonates are more reliable than bulk samples because of their direct connection to the host strata. (C) 2012 Elsevier Ltd and INQUA. All rights reserved....

  16. Stable and radioactive carbon in forest soils of Chhattisgarh, Central India: Implications for tropical soil carbon dynamics and stable carbon isotope evolution

    Science.gov (United States)

    Laskar, A. H.; Yadava, M. G.; Ramesh, R.

    2016-06-01

    Soils from two sites viz. Kotumsar and Tirathgarh, located ∼5 km apart in a tropical reserve forest (18°52‧N, 81°56‧E) in central India, have been explored for soil organic carbon (SOC) content, its mean residence time (MRT) and the evolution of stable carbon isotopic composition (δ13C). SOC stocks in the upper 30 cm of soil layers are ∼5.3 kg/m2 and ∼3.0 kg/m2; in the upper 110 m are ∼10.7 kg/m2 and ∼7.8 kg/m2 at Kotumsar and Tirathgarh, respectively. SOC decreases with increasing depth. Bomb carbon signature is observed in the upper ∼10 cm. Organic matters in the top soil layers (0-10 cm) have MRTs of the order of a century which increases gradually with depths, reaching 3500-5000 yrs at ∼100 cm. δ13C values of SOC increase with depth, the carbon isotopic fractionation is obtained to be -1.2‰ and -3‰ for soils at Kotumsar and Tirathgarh, respectively, confirmed using Rayleigh isotopic fractionation model. The evolution of δ13C in soils was also studied using a modified Rayleigh fractionation model incorporating a continuous input into the reservoir: the depth profiles of δ13C for SOC show that the input organic matter from surface into the deeper soil layers is either insignificant or highly labile and decomposes quite fast in the top layers, thus making little contribution to the residual biomasses of the deeper layers. This is an attempt to understand the distillation processes that take place in SOC, assess the extent of decomposition by microbes and effect of percolation of fresh organic matter into dipper soil layers which are important for stable isotope based paleoclimate and paleovegetation reconstruction and understanding the dynamics of organic carbon in soils.

  17. The succession of Hirnantian events based on data from Baltica: brachiopods, chitinozoans, conodonts, and carbon isotopes

    Directory of Open Access Journals (Sweden)

    Kaljo, Dimitri

    2008-12-01

    Full Text Available The Hirnantian (late Ordovician environment was complex and dynamic. Understanding the correct order of events and their precise correlation with a time scale are extremely important for the development of different kinds of environmental interpretations. The lower boundary of the Hirnantian Stage is officially defined by “the lowest occurrence of Normalograptus extraordinarius, the base of major positive carbon-13 isotope excursion, and the beginning of a pronounced sea-level fall associated with onset of a major glaciation” (ICS website. Our aim is to check if these events are synchronous, particularly how the situation is with respect to the Baltic. Thus several sections were analysed using mainly East Baltic data (drill cores, but also data from elsewhere, including brachiopod, chitinozoan, and conodont biostratigraphy combined with graptolite and carbon isotope data. Brachiopod faunas of the Pirgu and Porkuni stages are rather similar to those of the Ellis Bay Formation of Anticosti Island, Quebec, but the Pirgu assemblage, as well as that of the lower Ellis Bay Fm. lack key elements of the Hirnantian faunas. The primary criterion quoted above is stable, but auxiliary data like the isotope curve are less convincing. When the latter is used, it should be specified, e.g. that the carbon isotope excursion begins usually slightly earlier (in the Diceratograptus mirus Biozone, but it might be conventionally placed into the N. extraordinarius Biozone when a biostratigraphical proxy is available. The peak of the excursion is in the lower N. persculptus Biozone, but the main increase in values takes place in the N. extraordinarius Biozone. The Spinachitina taugourdeaui Biozone marks at many localities the bottom of the Hirnantian, and only the recent chitinozoan–graptolite data from the topmost Lousy Cove Member (on Anticosti Island suggest a mid-Hirnantian age, which is at variance with common correlation schemes.

  18. Hominins, sedges, and termites: new carbon isotope data from the Sterkfontein valley and Kruger National Park.

    Science.gov (United States)

    Sponheimer, Matt; Lee-Thorp, Julia; de Ruiter, Darryl; Codron, Daryl; Codron, Jacqui; Baugh, Alexander T; Thackeray, Francis

    2005-03-01

    Stable carbon isotope analyses have shown that South African australopiths did not have exclusively frugivorous diets, but also consumed significant quantities of C4 foods such as grasses, sedges, or animals that ate these foods. Yet, these studies have had significant limitations. For example, hominin sample sizes were relatively small, leading some to question the veracity of the claim for australopith C4 consumption. In addition, it has been difficult to determine which C4 resources were actually utilized, which is at least partially due to a lack of stable isotope data on some purported australopith foods. Here we begin to address these lacunae by presenting carbon isotope data for 14 new hominin specimens, as well as for two potential C4 foods (termites and sedges). The new data confirm that non-C3 foods were heavily utilized by australopiths, making up about 40% and 35% of Australopithecus and Paranthropus diets respectively. Most termites in the savanna-woodland biome of the Kruger National Park, South Africa, have intermediate carbon isotope compositions indicating mixed C3/C4 diets. Only 28% of the sedges in Kruger were C4, and few if any had well-developed rhizomes and tubers that make some sedges attractive foods. We conclude that although termites and sedges might have contributed to the C4 signal in South African australopiths, other C4 foods were also important. Lastly, we suggest that the consumption of C4 foods is a fundamental hominin trait that, along with bipedalism, allowed australopiths to pioneer increasingly open and seasonal environments.

  19. A high resolution record of atmospheric carbon dioxide and its stable carbon isotopic composition from the penultimate glacial maximum to the glacial inception

    Directory of Open Access Journals (Sweden)

    R. Schneider

    2013-04-01

    Full Text Available The reconstruction of the stable carbon isotope evolution in atmospheric CO2 (δ13Catm, as archived in Antarctic ice cores, bears the potential to disentangle the contributions of the different carbon cycle fluxes causing past CO2 variations. Here we present a highly resolved record of δ13Catm before, during and after the Marine Isotope Stage 5.5 (155 000 to 105 000 yr BP. The record was derived with a well established sublimation method using ice from the EPICA Dome C (EDC and the Talos Dome ice cores in East Antarctica. We find an 0.4‰ offset between the mean δ13Catm level in the Penultimate (~140 000 yr BP and Last Glacial Maximum (~22 000 yr BP, which can be explained by either (i changes in the isotopic composition or (ii intensity of the carbon input fluxes to the combined ocean/atmosphere carbon reservoir or (iii by long-term peat buildup. Our isotopic data suggest that the carbon cycle evolution along Termination II and the subsequent interglacial was controlled by essentially the same processes as during the last 24 000 yr, but with different phasing and magnitudes. Furthermore, a 5000 yr lag in the CO2 decline relative to EDC temperatures is confirmed during the glacial inception at the end of MIS 5.5 (120 000 yr BP. Based on our isotopic data this lag can be explained by terrestrial carbon release and carbonate compensation.

  20. Utilization of Tritium and Carbon-14 in Studies of Isotope Effects

    International Nuclear Information System (INIS)

    The utility of tritium in organic research has been augmented by the development of a simple method for determining C14 and tritium in the same sample. The non-volatile, radioactive material, in a film that is 'infinitely thick' to tritium radiation, is counted in a windowless, gas-fiow proportional counter; the film is then re-counted when covered with a screen that stops all radiation from tritium but allows a fraction of that from C14 to pass. By introduction of one isotope at a point removed from the reaction centre, an isotope effect for the other can be determined from changes in the tritium-C14 ratio in the reactant and/or products as the reaction proceeds. Carriers of reactant, products or derivatives can be added at any point to facilitate isolation, because the analytical method depends primarily on the tritium-C14 ratio. Methods for utilizing the double-label technique will be illustrated by a study of isotope effects in the oxidation of the penultimate carbon of certain labelled polyols with Acetobacter suboxydans. Six D-mannitols position-labelled either with C14 or with tritium at C1, C2 or C3 were prepared. For these, isotope effects (k*/k) of 0.93, 0.23, and 0.71, respectively, were found with C14 at C2, tritium at C2, and tritium at C3; no detectable isotope effects were found for the remaining Dmannitols. In the oxidation of position-labelled D-glucitols, an isotope effect of 0.24 was found for tritium at C5; no detectable effect was found for either C14 or tritium at C1. The techniques are suitable for studying a variety of chemical and biological reactions. (author)

  1. Carbon isotope characterization of vegetation and soil organic matter in subtropical forests in Luquillo, Puerto Rico

    International Nuclear Information System (INIS)

    We examined natural abundances of 13C in vegetation and soil organic maner (SOM) of subtropical wet and rain forests to characterize the isotopic enrichment through decomposition that has been reported for temperate forests. Soil cores and vegetative samples from the decomposition continuum (leaves, new litter, old liner, wood, and roots) were taken from each of four forest types in the Luquillo Experimental Forest, Puerto Rico. SOM δ13C was enriched 1.60/00 relative to aboveground litter. We found no further enrichment within the soil profile. The carbon isotope ratios of vegetation varied among forests, ranging from -28.20/00 in the Colorado forest to -26.90/00 in the Palm forest. Isotope ratios of SOM differed between forests primarily in the top 20 em where the Colorado forest was again most negative at -28.00/00, and the Palm forest was most positive at -26.50/00. The isotopic differences between forests are likely attributable to differences in light regimes due to canopy density variation, soil moisture regimes, and/or recycling of CO2. Our data suggest that recalcitrant SOM is not derived directly from plant lignin since plant lignin is even more 13C depleted than the bulk vegetation. We hypothesize that the anthropogenic isotopic depletion of atmospheric CO2, (ca 1.50/00 in the last 150 years) accounts for some of the enrichment observed in the SOM relative to the more modern vegetation in this study and others. This study also supports other observations that under wet or anaerobic soil environments there is no isotopic enrichment during decomposition or with depth in the active profile. (author)

  2. Isotopic evolution of the terminal Neoproterozoic and early Cambrian carbon cycle on the northern Yangtze Platform, South China

    Institute of Scientific and Technical Information of China (English)

    GUO Qingjun; LIU Congqiang; Harald STRAUSS; Tatiana GOLDBERG

    2003-01-01

    Profound geotectonic, climatic and biological changes occur during the terminal Neoproterozoic and its transition into the early Cambrian. These are reflected in temporal variations of the chemical and isotopic composition of seawater. We are studying a sequence of sedimentary rocks at the Shatan section, northern Yangtze Platform, Sichuan Province of China. This succession comprises, in ascending stratigraphic order, predominantly calcareous sediments of the Sinian upper Dengying Formation and black shales of the lower Cambrian Guojiaba Formation (time equivalent of Niutitang Fm.). Paleoenvironmental setting represents shallow-water shelf deposits. The objective of our study is to provide temporal records for the isotopic compositions of organic and carbonate carbon throughout this time interval. Organic carbon isotope values display a range between -35.8‰ and -30.1‰ with clear stratigraphic variations. Carbonate carbon isotope data vary between -3.5‰ and +0.5‰. These secular variations are interpreted to reflect perturbations of the global carbon cycle, specifically changes in the fractional burial of organic carbon. However, local conditions have further affected the isotopic signals.

  3. The Carnian (Late Triassic) carbon isotope excursion: new insights from the terrestrial realm

    Science.gov (United States)

    Miller, Charlotte; Kürschner, Wolfram; Peterse, Francien; Baranyi, Viktoria; Reichart, Gert-Jan

    2016-04-01

    The geological record contains evidence for numerous pronounced perturbations in the global carbon cycle, some of which are associated with eruptions from large igneous provinces (LIP), and consequently, ocean acidification and mass extinction. In the Carnian (Late Triassic), evidence from sedimentology and fossil pollen points to a significant change in climate, resulting in biotic turnover: during a period termed the 'Carnian Pluvial Event' (CPE). Additionally, during the Carnian, large volumes of flood basalts were erupted from the Wrangellia LIP (western North America). Evidence from the marine realm suggests a fundamental relationship between the CPE, a global 'wet' period, and the injection of light carbon into the atmosphere from the LIP. Here we provide the first evidence from the terrestrial realm of a significant negative δ13C excursion through the CPE recorded in the sedimentary archive of the Wiscombe Park Borehole, Devon (UK). Both total organic matter and plant leaf waxes reflect a gradual carbon isotope excursion of ~‑5‰ during this time interval. Our data provides evidence for the global nature of this isotope excursion, supporting the hypothesis that the excursion was likely the result of an injection of light carbon into the atmosphere from the Wrangellia LIP.

  4. Pyrogenic carbon from tropical savanna burning: production and stable isotope composition

    Science.gov (United States)

    Saiz, G.; Wynn, J. G.; Wurster, C. M.; Goodrick, I.; Nelson, P. N.; Bird, M. I.

    2015-03-01

    Widespread burning of mixed tree-grass ecosystems represents the major natural locus of pyrogenic carbon (PyC) production. PyC is a significant, pervasive and yet poorly understood "slow-cycling" form of carbon present in the atmosphere, hydrosphere, soils and sediments. We conducted 16 experimental burns on a rainfall transect through northern Australian savannas with C4 grasses ranging from 35 to 99% of total biomass. Residues from each fire were partitioned into PyC and further into recalcitrant (HyPyC) components, with each of these fluxes also partitioned into proximal components (>125 μm), likely to remain close to the site of burning, and distal components (residence time, with shorter duration fires resulting in higher HyPyC yields. The carbon isotope (δ13C) compositions of PyC and HyPyC were generally lower by 1-3‰ relative to the original biomass, with marked depletion up to 7‰ for grasslands dominated by C4 biomass. δ13C values of CO2 produced by combustion were computed by mass balance and ranged from ~0.4 to 1.3‰. The depletion of 13C in PyC and HyPyC relative to the original biomass has significant implications for the interpretation of δ13C values of savanna soil organic carbon and of ancient PyC preserved in the geologic record, as well as for global 13C isotopic disequilibria calculations.

  5. Investigating Carbonate System Perturbations across the Cretaceous-Palaeogene Transition using Boron Isotopes in Planktonic Foraminifera.

    Science.gov (United States)

    Henehan, M. J.; Hull, P. M.; Planavsky, N. J.; Huber, B. T.; Thomas, E.

    2014-12-01

    The interval spanning the latest Maastrichtian to the early Palaeocene has great potential in helping to elucidate the stabilising mechanisms on the Earth's carbonate system on both long and very short geological timescales, from the geologically-instantaneous production of sulphate-rich aerosols and nitrogen oxides from the K-Pg bolide impact to the relatively more gradual degassing from Deccan volcanism in the latest Maastrichtian. The extent to which ocean pH (and atmospheric CO2 concentrations) changed in response to these contrasting acidification pressures, and the timescales of their recovery, may provide unique insight into the efficiency of the Earth's oceans in buffering greenhouse gas increases (through carbonate dissolution, weathering-derived alkalinity flux, and biological carbon cycling). The boron isotope palaeo-pH proxy in planktic foraminifera is well suited to such investigations, but its application over this interval has been problematic, not least due to a scarcity of sample material and a near-complete turnover of planktonic foraminiferal species across the K-Pg boundary. To attempt to circumvent these issues, we investigate the biological influences on boron isotope signals in Maastrichtian and Danian planktonic foraminifera, with the goal of producing more accurate palaeo-pH reconstructions. With these findings in mind, we present preliminary constraints on ocean pH and carbonate system dynamics across this critical interval of geological time.

  6. The Carnian (Late Triassic) carbon isotope excursion: new insights from the terrestrial realm

    Science.gov (United States)

    Miller, Charlotte; Kürschner, Wolfram; Peterse, Francien; Baranyi, Viktoria; Reichart, Gert-Jan

    2016-04-01

    The geological record contains evidence for numerous pronounced perturbations in the global carbon cycle, some of which are associated with eruptions from large igneous provinces (LIP), and consequently, ocean acidification and mass extinction. In the Carnian (Late Triassic), evidence from sedimentology and fossil pollen points to a significant change in climate, resulting in biotic turnover: during a period termed the 'Carnian Pluvial Event' (CPE). Additionally, during the Carnian, large volumes of flood basalts were erupted from the Wrangellia LIP (western North America). Evidence from the marine realm suggests a fundamental relationship between the CPE, a global 'wet' period, and the injection of light carbon into the atmosphere from the LIP. Here we provide the first evidence from the terrestrial realm of a significant negative δ13C excursion through the CPE recorded in the sedimentary archive of the Wiscombe Park Borehole, Devon (UK). Both total organic matter and plant leaf waxes reflect a gradual carbon isotope excursion of ~-5‰ during this time interval. Our data provides evidence for the global nature of this isotope excursion, supporting the hypothesis that the excursion was likely the result of an injection of light carbon into the atmosphere from the Wrangellia LIP.

  7. Dynamics of carbon in deep soils inferred from carbon stable isotopes signatures : a worldwide meta-analysis

    Science.gov (United States)

    Balesdent, Jérôme; Basile-Doelsch, Isabelle; Chadoeuf, Joël; Cornu, Sophie; Derrien, Delphine; Fekiacova, Zuzana; Hatté, Christine

    2014-05-01

    The contribution of soil carbon deeper than 30 cm to the atmospheric carbon balance is still poorly understood. A very straightforward quantification of the gross exchange of carbon between the atmosphere and soil organic matter can be obtained at places where the 13C/12C signature of vegetation has been changed for known durations, due to switch of the photosynthetic metabolism (C3 or C4) or to Free Air Carbon Enrichment experiments. We compiled C and 13C profile data of 113 sites of this type, either gahered from the literature or from our own measurements. Each site comprised two profiles : one where the 13C/12C of the vegetation had been changed, and a reference profile with unchanged vegetation 13C/12C. An isotope mixing equation was used, which takes into account the natural isotope enrichments with depth and decay. Three main variables were calculated at any depth from 0 to 100 cm and in a few sites down to 200 cm : the carbon content, the proportion of new carbon (aged less than the duration of change t) and the amount of new carbon. The database concerned 23 countries, various climates (58% intertropical and 42% between 23° to 56° latitude) and various soil types and textures. Landuses and vegetation consisted in 26% of forests and woodlands, 35% of grasslands and 38% of cropped systems. The duration of the natural labelling t ranged from 2 years to ca. 4000 years. Peatlands, boreal, and desert environments were absent from the database. Non-linear regressions with time across the dataset yielded kinetic parameters of the age distribution on one hand and of the flux of new carbon incorporation (kg C m-2 yr-1) on the other, each calculated by 10 cm depth increments. On the average, the median ages of carbon increase from ca. 15 years at 0 cm to more than 1000 years at 100 cm. Turnover is on the average 2 to 3 times slower for the subsoil (30-100 cm) than for the topsoil (0-30 cm). Based on the incorporation of new C in the first decades, the carbon input

  8. Skeletal and isotopic composition and paleoclimatic significance of late Pleistocene carbonates, Ross Sea, Antarctica

    Energy Technology Data Exchange (ETDEWEB)

    Taviani, M. (Ist. per la Geologia Marina, Bologna (Italy)); Reid, D.E.; Anderson, J.B. (Rice Univ., Houston, TX (United States))

    1993-01-01

    Carbonates cover an extensive area of the northwestern Ross Sea continental shelf. Radiocarbon dates yield late Pleistocene (stage 3) ages for these deposits, hence the carbonates appear to be correlative with widespread tills and glacial marine deposits in the region. Four carbonate facies are recognized on the basis of skeletal composition: a barnacle/foraminifer facies, a muddy bryozoan facies, a bryozoan/barnacle/pelecypod/foraminifer facies, and a planktonic foraminiferal facies. These deposits occur on the shelf and upper slope, while carbonate turbidities derived from them occur on the adjacent continental slope and rise. Compositional analyses of Ross Sea carbonates lend support to previously recognized criteria for identifying cold water carbonates. These include: (1) the presence of an associated ice-rafted component (including dropstones); (2) a dominance of calcite relative to other carbonate minerals (the remaining fraction consists solely of aragonite); (3) allochems that are entirely skeletal; and (4) heavy oxygen isotopic compositions (in the range of +3.0 to +5.1% PDB).

  9. Carbon isotope discrimination in leaf juice of Acacia mangium and its relationship to water-use efficiency

    Institute of Scientific and Technical Information of China (English)

    lvliu ZOU; Guchou SUN; Ping ZHAO; Xian CAI; Xiaoping ZENG; Xiaojing LIU

    2009-01-01

    Using the PMS pressure chamber and isotope mass spectrometer (MAT-252), the leaf juice of Acacia mangium was obtained, and the carbon isotope discrimination (△) representing the most recently fixed carbon in the juice was determined. At the same time, the water-use efficiency of A. mangium was estimated. The results indicated that the carbon isotope ratio in the air of forest canopy (δa), 10m high above ground averaged -7.57 1.41‰ in cloudy days, and - 8.54±0.67 ‰ in sunny days, respectively. The diurnal change of the carbon isotope ratio in the photosynthetic products of the leaf juice (δp) was of saddle type in cloudy days, but dropped down from morning to later afternoon in sunny days. A strong negative correlation betweenδp and leaf-to-air vapor pressure deficit (D) was observed in sunny days, but a slight change inδp, was found in cloudy days. Theδp also decreased with decreasing leaf water potential (ψ), reflecting that water stress could cause the decrease ofδp. The carbon isotope discrimination of the leaf juice was positively correlated with the ratio between intercellular (Pi) and atmospheric (Pa) partial pressure of CO2. For A. mangium, the isotope effect on diffusion of atmospheric CO2 via stomata was denoted by a = 4.6 %>, and that in net C3 diffusion with respect to Pi was indicated by b = 28.2 ‰. The results were in reasonable accord with the theoretically diffusive and biochemical fractionation of carbon isotope. It was defined that carbon isotope discrimination of photosynthetic products in A. mangium leaf juice was in proportion to that from photosynthetic products in dry material. The water-use efficiency estimated by the carbon isotope discrimination in leaf juice, fit well with that measured by gas exchange system (R2 = 0.86, p< 0.0001). The application of leaf juice in measuring the stable carbon isotope discrimination would reduce the effects of fluctuating environmental factors during the synthesis of dry matter, and improve

  10. Estimation of food composition of Hodotermes mossambicus (Isoptera: Hodotermitidae) based on observations and stable carbon isotope ratios

    Institute of Scientific and Technical Information of China (English)

    Craig T. Symes; Stephan Woodborne

    2011-01-01

    The diet of the harvester termite Hodotermes mossambicus was investigated at two sites with distinct dietary components: C4 grasses (δ13 C isotope values, -13.8‰to -14.0‰) and C3 plants (δ13C isotope values, -25.6‰ to -27.1‰). By comparing observations of food items carried into the colony by the termites and carbon isotope ratios of whole termites (that determined assimilated carbon), the relative proportion of the C3 and C4 plant food components of the termite diet was estimated. There was agreement between the observational data and stable carbon isotopic data, with grass representing approximately 93% of the diet of H, mossambicus at two study sites (urban and rural) on the South African highveld. However, when correcting for mass of food items, that is, C3 and C4, carried by termites, the proportion of grass (C4) in the diet may be underestimated.

  11. Mechanistic insights into the formation of chloroform from natural organic matter using stable carbon isotope analysis

    Science.gov (United States)

    Breider, Florian; Hunkeler, Daniel

    2014-01-01

    Chloroform can be naturally formed in terrestrial environments (e.g. forest soils, peatland) by chlorination of natural organic matter (NOM). Recently, it was demonstrated that natural and anthropogenic chloroform have a distinctly different carbon isotope signature that makes it possible to identify its origin in soil and groundwater. In order to evaluate the contribution of different functional groups to chloroform production and factors controlling the isotopic composition of chloroform, carbon isotope trends during chlorination of model compounds, soil organic matter (SOM) and humic acids were evaluated, and apparent kinetic isotope effects (AKIEs) quantified. Phenol and propanone were selected as model compounds representing common functional groups in NOM. Chlorination was induced by hypochlorous acid to mimic natural chlorination. The pH ranged between 4 and 8 to cover typical soil conditions. For each model compound and pH, different AKIEs were observed. For phenol, the AKIE was normal at pH 4 (1.0156 ± 0.0012) and inverse at pH 8 (0.9900 ± 0.0007). For 2-propoanol, an opposite pH dependence was observed with an inverse AKIE at pH 4 (0.9935 ± 0.0007) and a normal AKIE at pH 8 (1.0189 ± 0.0016). The variations of the AKIE values suggest that the rate-limiting step of the reaction is either the re-hybridization of the carbon atom involved in chloroform formation or the hydrolysis of trichloroacetyl intermediates depending on the nature of functional group and pH. The chloroform formation from humic acid and SOM gives rise to small isotope variations. A comparison of the isotopic trends of chloroform formed from humic acid and SOM with those found for the model compounds suggest that opposed AKIE associated with the chlorination of phenolic and ketone moieties of NOM partly compensate each other during chlorination of NOM indicating that different types of functional groups contribute to chloroform formation.

  12. Insights into deep-time terrestrial carbon cycle processes from modern plant isotope ecology

    Science.gov (United States)

    Sheldon, N. D.; Smith, S. Y.

    2012-12-01

    While the terrestrial biosphere and soils contain much of the readily exchangeable carbon on Earth, how those reservoirs function on long time scales and at times of higher atmospheric CO2 and higher temperatures is poorly understood, which limits our ability to make accurate future predictions of their response to anthropogenic change. Recent data compilation efforts have outlined the response of plant carbon isotope compositions to a variety of environmental factors including precipitation amount and timing, elevation, and latitude. The compilations involve numerous types of plants, typically only found at a limited number of climatic conditions. Here, we expand on those efforts by examining the isotopic response of specific plant groups found both globally and across environmental gradients including: 1) ginkgo, 2) conifers, and 3) C4 grasses. Ginkgo is presently widely distributed as a cultivated plant and the ginkgoalean fossil record spans from the Permian to the present, making it an ideal model organism to understand climatic influence on carbon cycling both in modern and ancient settings. Ginkgo leaves have been obtained from a range of precipitation conditions (400-2200 mm yr-1), including dense sampling from individuals and populations in both Mediterranean and temperate climate areas and samples of different organs and developmental stages. Ginkgo carbon isotope results plot on the global C3 plant array, are consistent among trees at single sites, among plant organs, and among development stages, making ginkgo a robust recorder of both climatic conditions and atmospheric δ13C. In contrast, a climate-carbon isotope transect in Arizona highlights that conifers (specifically, pine and juniper) record large variability between organs and have a very different δ13C slope as a function of climate than the global C3 plant array, while C4 plants have a slope with the opposite sign as a function of climate. This has a number of implications for paleo

  13. Origin of graphite, and temperature of metamorphism in Precambrian Eastern Ghats Mobile Belt, Orissa, India: A carbon isotope approach

    Science.gov (United States)

    Sanyal, Prasanta; Acharya, B. C.; Bhattacharya, S. K.; Sarkar, A.; Agrawal, S.; Bera, M. K.

    2009-09-01

    The carbon isotope composition of graphite and carbon and oxygen isotope composition of associated calcite from different locations of the Eastern Ghats Mobile Belt (EGMB) of Orissa have been measured in order to understand the origin of graphite. The δ 13C values of graphite range from -2.4‰ to -26.6‰. Forty-four of sixty-one samples have δ 13C values less than -20‰. Most of these low δ 13C values graphite corresponds to schists and disseminations in khondalite and calc-silicate granulites, thus indicating graphitization of organic matter. The remaining light-carbon-graphite occurs as veins which is the result of graphitization of transported organic matter. The graphite with intermediate δ 13C value (-13‰ to -19‰) indicates carbon contributions from both organic and carbonates sources and/or mantle sources. The higher δ 13C values graphite (-2.4‰ to -8.8‰) represent mantle carbon and/or carbonate sources without significant contribution from organic carbon. The temperatures of metamorphism have been estimated using carbon isotope ratios of graphite and associated calcite of calc-silicate granulites, where typical cation exchange thermometer assemblages are lacking and significant mineral reaction textures used to calculate pressure-temperature of metamorphic events are absent. Metamorphic temperatures obtained 945 °C are close to the ultrahigh-temperature reported from the EGMB. The minimum temperature estimated using the graphite-carbonate carbon isotope ratio is 90 °C. The lower estimates of temperatures probably indicate changes in the carbon isotope ratio of calcite by decarbonation reaction or armoring of carbonaceous matter in silicates during metamorphism preventing continuous exchange with calcite.

  14. Molecular isotopic engineering (MIE): industrial manufacture of naproxen of predetermined stable carbon-isotopic compositions for authenticity and security protection and intellectual property considerations

    Science.gov (United States)

    Jasper, J. P.; Farina, P.; Pearson, A.; Mezes, P. S.; Sabatelli, A. D.

    2016-05-01

    Molecular Isotopic Engineering (MIE) is the directed stable-isotopic synthesis of chemical products for reasons of product identification and of product security, and also for intellectual property considerations. We report here a generally excellent correspondence between the observed and predicted stable carbon-isotopic (δ13C) results for a successful directed synthesis of racemic mixture from its immediate precursors. The observed results are readily explained by the laws of mass balance and isotope mass balance. Oxygen- and hydrogen isotopic results which require an additional assessment of the effects of O and H exchange, presumably due to interaction with water in the reaction solution, are addressed elsewhere. A previous, cooperative study with the US FDA-DPA showed that individual manufacturers of naproxen could readily be differentiated by their stable-isotopic provenance (δ13C, δ18O, and δD ref. 1). We suggest that MIE can be readily employed in the bio/pharmaceutical industry without alteration of present manufacturing processes other than isotopically selecting and/or monitoring reactants and products.

  15. In situ carbon isotope analysis of Archean organic matter with SIMS

    Science.gov (United States)

    Williford, K. H.; Ushikubo, T.; Lepot, K.; Hallmann, C.; Spicuzza, M. J.; Eigenbrode, J. L.; Summons, R. E.; Valley, J. W.

    2011-12-01

    Spatiotemporal variability in the carbon isotope composition of sedimentary organic matter (OM) preserves information about the evolution of the biosphere and of the exogenic carbon cycle as a whole. Primary compositions, and imprints of the post-depositional processes that obscure them, exist at the scale of individual sedimentary grains (mm to μm). Secondary ion mass spectrometry (SIMS) (1) enables analysis at these scales and in petrographic context, (2) permits morphological and compositional characterization of the analyte and associated minerals prior to isotopic analysis, and (3) reveals patterns of variability homogenized by bulk techniques. Here we present new methods for in situ organic carbon isotope analysis with sub-permil precision and spatial resolution to 1 μm using SIMS, as well as new data acquired from a suite of Archean rocks. Three analytical protocols were developed for the CAMECA ims1280 at WiscSIMS to analyze domains of varying size and carbon concentration. Average reproducibility (at 2SD) using a 6 μm spot size with two Faraday cup detectors was 0.4%, and 0.8% for analyses using 1 μm and 3 μm spot sizes with a Faraday cup (for 12C) and an electron multiplier (for 13C). Eight coals, two ambers, a shungite, and a graphite were evaluated for μm-scale isotopic heterogeneity, and LCNN anthracite (δ13C = -23.56 ± 0.1%, 2SD) was chosen as the working standard. Correlation between instrumental bias and H/C was observed and calibrated for each analytical session using organic materials with H/C between 0.1 and 1.5 (atomic), allowing a correction based upon a 13CH/13C measurement included in every analysis and a 12CH measurement made immediately after every analysis. The total range of the H/C effect observed for the Archean samples analyzed was < 3%. Analyses of Archean OM domains for which 12C count rate varies with the proportions of organic carbon, carbonate carbon, and quartz suggest that instrumental bias is consistent for 12C count

  16. Environmental inputs that can influence carbon isotopic compositions of hot spring biofilms

    Science.gov (United States)

    Donatelli, J. L.; Havig, J. R.; Shock, E.

    2011-12-01

    The carbon isotopic compositions of hydrothermal biofilms are influenced by microbial carbon cycling, and can be correlated with the presence or absence of specific genes in environmental genomic analyses (Havig et al., 2011, JGR). Additional isotopic data on potential environmental sources of carbon will enable further tests of the specific pathways of carbon assimilation and cycling throughout hydrothermal ecosystems. Hot springs at Yellowstone National Park (YNP) are often located in open meadows or forested areas with varying amounts of vegetation and exposed soil surrounding the pools. These pools are open systems which have the potential to accumulate allochthonous materials via physical and biogenic processes. These inputs may affect the δ13C signatures of the hot spring waters and the biofilms associated with them. In the YNP hot springs we have studied since 2003, biofilms range in δ13C from -1.2 to -30.7%. Dissolved inorganic carbon (DIC) in coexisting fluids ranges from 4.3 to -3.9%. The heaviest biofilms typically show minimal isotopic fractionation from the DIC in coexisting fluids. DIC values are strongly influenced by inputs from magma degassing, water-rock reactions in the hydrothermal system, and the atmosphere. Dissolved organic carbon (DOC) values for the coexisting fluids range from -16.5 to -26.8%, which are within the range of biofilm δ13C values. DOC values will also be affected by diverse processes as precipitation infiltrates, reacts, and eventually returns to the surface as hydrothermal fluids, but may also be influenced by biologically derived inputs from the local environments where hot springs occur. In an effort to characterize the environmental context of hot springs, we have collected isotopic data on lodgepole pine needles, grasses, soils, insects and bison feces. Of these, the δ13C data for bison feces (-27.7 to -29.6%) are lighter than any of the DOC data. Pine needles (-26.3 to -29.1%) and soils (-24.8 to -27.1%) overlap with

  17. Applications of compound-specific carbon isotope ratios in organic contaminant studies

    International Nuclear Information System (INIS)

    In this paper results are presented on the application of compound-specific isotope ratios measurements to assess biodegradation of chlorinated solvents, in particularly on microbial dechlorination of tetrachloroethene (PCE) and trichloroethene (TCE). Analytical aspects and isotope data from laboratory and field studies are discussed. The analytical tests showed that both headspace and SPME techniques provide accurate δ13C values with a similar precision for a wide range of chlorinated solvents. However, the SPME method is generally more sensitive. The microcosm experiments show that a significant isotopic fractionation occurs during dechlorination of PCE and TCE to ethene. The largest fractionation factors are observed in the steps DCE-VC and VC-Ethene. In general, the δ13C of each dechlorination product was always more negative than the δ13C of the corresponding precursor. In addition, the δ13C values of each compound increased with time. A similar pattern was observed for dechlorination of PCE at a field site. These results show that compound-specific carbon isotope ratios technology is a very sensitive tool for evaluation of natural attenuation of chlorinated solvents in groundwater. (author)

  18. Stable carbon isotope composition of monoterpanes in essential oils and crude oils

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Twenty-five monoterpanes from six types of essential oils and hydrogenated turpentine oil have been identified and their stable carbon isotope composition determined.Monoterpanes in essential oils sourced from terrestrial higher plants display a δ13C value in the range of-34‰-26‰,and mostly between-29‰ and-27‰.The δ13C value of any single monoterpane is very consistent in different essential oils.Acyclic monoterpanes show closer isotope composition between-28.6‰ and-26.2‰,with an average value of-27.7‰.In contrast,the isotope composition of cyclic monoterpanes is more scattered with an average value of-28.6‰.Isotopic fractionation with 13C enrichment has been observed during both artificial and geological hydrogenation of monoterpenoids to monoterpanes,and this is more obvious for the acyclic monoterpenoids.In addition to higher plants,acyclic monoterpane 2,6-dimethylheptane in crude oil can also be originated from other organic inputs.

  19. Carbon-13 and oxygen-18 kinetic isotope effects on methanolysis of p-nitrostyrene oxide

    Energy Technology Data Exchange (ETDEWEB)

    Jacober, S.P.; Hanzlik, R.P.

    1986-04-02

    Kinetic isotope effects for the acid- and base-catalyzed methanolysis of (epoxide-/sup 18/O)- and (8-/sup 13/C)-p-nitrostyrene oxide have been measured at 30.0/sup 0/. In acid 94.7% of the reaction occurs at the benzylic carbon, while in base 83.5% occurs at the primary carbon (C(8)). In base the isotope effects kappa/sub 16//kappa/sub 1/( and kappa/sub 1/''/kappa /sub 1/number were 1.035 +/- 0.013 and 1.082 +/- 0.012, while in acid they were 1.012 +/- 0.011 and 0.995 +/- 0.012, respectively. These data complement previously determined deuterium isotope effects for the reaction in base. They suggest a late transition state in base with considerable ring opening via an S/sub N/2 mechanism. However, in acid, the data suggest a somewhat earlier transition state with less ring opening and weaker bonding to the nucleophile than in base.

  20. The carbon isotopic compositions of Non-methane Hydrocarbons in atmosphere

    Institute of Scientific and Technical Information of China (English)

    PENG Lin; ZHANG HuiMin; REN ZhaoFang; MU Ling; SHI RuiLiang; CHANG LiPing; LI Fan

    2009-01-01

    Carbon isotopic compositions of atmospheric Non-methane Hydrocarbons (NMHCs) in the urban areas of Taiyuan and Lanzhou in summer were reported and the sources of NMHCs are discussed.Carbon isotopic ratios (δ13C) of vehicle exhaust,coal-combustion exhaust,fuel volatiles and cooking exhaust were also measured with thermal desorption-gas chromatography-isotope ratio-mass spectrometry (TD-GC-IR-MS).δ13C values of NMHCs in the urban areas of Lanzhou and Taiyuan range from -32.3‰ to -22.3‰ and from -32.8‰ to -18.1‰.δ13C values of vehicle exhaust,coal-combustion exhaust,fuel volatiles and cooking exhaust are -32.5‰--21.7‰,-24.5‰--22.3‰,-32.5%--27.4‰ and -31.6‰--24.5‰,respectively.The data indicate that vehicle exhaust and cooking exhaust make a significant contribution to the atmospheric NMHCs.Therefore,to reduce emissions of vehicle exhaust and cook-ing exhaust is critical for controlling atmospheric NMHCs pollution in summer.

  1. Carbon and Oxygen Stable Isotope Measurements of Martian Atmospheric CO2 by the Phoenix Lander

    Science.gov (United States)

    Niles, Paul B.; Boynton, W. V.; Hoffman, J. H.; Ming, D. W.; Hamara, D.

    2010-01-01

    Precise stable isotope measurements of the CO2 in the martian atmosphere have the potential to provide important constraints for our understanding of the history of volatiles, the carbon cycle, current atmospheric processes, and the degree of water/rock interaction on Mars [1]. The isotopic composition of the martian atmosphere has been measured using a number of different methods (Table 1), however a precise value (carbonates in martian meteorites [2-4] it has been proposed that the martian atmosphere was enriched in 13C [8]. This was supported by measurements of trapped CO2 gas in EETA 79001[2] which showed elevated Delta(sup 13)C values (Table 1). More recently, Earth-based spectroscopic measurements of the martian atmosphere have measured the martian CO2 to be depleted in C-13 relative to CO2 in the terrestrial atmosphere[ 7, 9-11]. The Thermal and Evolved Gas Analyzer (TEGA) instrument on the Mars Phoenix Lander [12] included a magnetic-sector mass spectrometer (EGA) [13] which had the goal of measuring the isotopic composition of martian atmospheric CO2 to within 0.5%. The mass spectrometer is a miniature instrument intended to measure both the martian atmosphere as well as gases evolved from heating martian soils.

  2. Carbon isotope turnover as a measure of arrival time in migratory birds

    Science.gov (United States)

    Oppel, Steffen; Powell, Abby N.

    2009-01-01

    Arrival time on breeding or non-breeding areas is of interest in many ecological studies exploring fitness consequences of migratory schedules. However, in most field studies, it is difficult to precisely assess arrival time of individuals. Here, we use carbon isotope turnover in avian blood as a technique to estimate arrival time for birds switching from one habitat or environment to another. Stable carbon isotope ratios (δ13C) in blood assimilate to a new equilibrium following a diet switch according to an exponential decay function. This relationship can be used to determine the time a diet switch occurred if δ13C of both the old and new diet are known. We used published data of captive birds to validate that this approach provides reliable estimates of the time since a diet switch within 1–3 weeks after the diet switch. We then explored the utility of this technique for King Eiders (Somateria spectabilis) arriving on terrestrial breeding grounds after wintering and migration at sea. We estimated arrival time on breeding grounds in northern Alaska (95% CI) from red blood cell δ13C turnover to be 4–9 June. This estimate overlapped with arrival time of birds from the same study site tracked with satellite transmitters (5–12 June). Therefore, we conclude that this method provides a simple yet reliable way to assess arrival time of birds moving between isotopically distinct environments.

  3. Carbon and helium isotopic composition of fumarolic gases and hot spring gases from Kirishima volcanic area

    International Nuclear Information System (INIS)

    When a structure survey on the Kirishima volcano was conducted in 1994, authors conducted a chemical investigation on volcanic volatile components. In this paper, on volcanic and fumarolic gases samples adopted at that time, their analytic results such as carbon isotopic compositions of CH4 and CO2, and 3-He/4-He ratio were reported, according to which here was described on a forecasting result on origin of volcanic gas of the Kirishima volcanic area under a relation of volcano structure. As a result, it was thought that CO2/3-He and delta 13-C(CO2) distributed at a nearly duplicated region with another island volcano area, and most of CO2 seemed to form at an origin of mantle. As at the Iwoyama CH4 formed by thermolytic origin was emitted, at the Sinmoe-dake CH4 showing delta 13-C reaching isotope equilibrium with CO2 of magma origin at 400 centigrade was emitted. And, the carbon isotope ratio of CH4 showed high possibility to be increased by living actions or organic oxidation. (G.K.)

  4. Exotic Structures of Odd-A Carbon Isotopes in the Deformed Relativistic Mean-Field Theory

    Institute of Scientific and Technical Information of China (English)

    JIANG Wei-Zhou; REN Zhong-Zhou; ZHU Zhi-Yuan; WANG Ting-Tai; HE Ze-Jun

    2004-01-01

    We study contributions of the pion meson and spatial component of the omega meson in the odd-A carbon isotopes. The pion and spatial omega provide small attractions in odd-A nuclei, giving rise to considerable influences on the single-particle energies rather than the bulk properties such as total binding energies, and root-mean-square (rms) radii. The ±Ω (spin) splittings, arising from the spatial omega, are large in 11C and 13 C and drop as the isospin rises in odd-A carbon isotopes. As an isovector, the pion can shift slightly the relative potential depth of neutron and proton, contrary to the role of the rho meson. There is a general trend that both the pion and spatial omega fields reduce with the rise of isospin in the isotopic chain. From the normal nucleus to halo nucleus, an abnormal drop of the pion or spatial omega field may occur, as can be seen in 19C, 15C, and 21C.

  5. Comparative assessment of air quality in two health resorts using carbon isotopes and palynological analyses

    Energy Technology Data Exchange (ETDEWEB)

    Gorka, M.; Jedrysek, M.O.; Maj, J.; Worobiec, A.; Buczynska, A.; Stefaniak, E.; Krata, A.; Van Grieken, R.; Zwozdziak, A.; Sowka, I.; Zwozdziak, J.; Lewicka-Szczebak, D. [University of Wroclaw, Wroclaw (Poland). Inst. of Geological Science

    2009-01-15

    This paper describes results of applying the palynological and carbon isotopic analysis of the organic fraction of Total Suspended Particles (TSP) to discriminate distinct pollution sources and assess the anthropogenic impact for the investigated areas. The samples of atmospheric particles were collected in Czerniawa and Cieplice (two health resorts in Lower Silesia, SW Poland) twice a year in summer and winter season (from July 2006 to February 2008). The palynological spectra represent in the vast majority local plant communities without a noticeable contribution of long-transported plant particles. Palynological analysis revealed also differences in the specificity of the two sampling areas, i.e. the higher contribution of identified organic material in Czerniawa stands for more natural character of this site, but is also responsible for the higher allergic pressure when compared to Cieplice. The carbon isotopic composition of TSP varied seasonally ({delta}{sup 13}C value from -27.09 parts per thousand in summer to -25.47 parts per thousand in winter). The increased {delta} {sup 13}C value in winter (heating period) is most probably caused by uncontrolled contribution of coal soot. On the basis of isotopic mass balance the calculated contribution of anthropogenic organic particles in the atmosphere reached in winter season 72% in Czerniawa and 79% in Cieplice.

  6. Test/QA Plan for Verification of Isotopic Carbon Dioxide Analyzers for Carbon Sequestration Monitoring

    Science.gov (United States)

    The purpose of this verification test is to generate performance data on isotopic CO2 analyzers with a particular focus on applications relevant to GCS monitoring applications, specifically for the sequestration of CO2 from a coal-fired power plant. The data generated from this ...

  7. Pyrolysis of oil at high temperatures: Gas potentials, chemical and carbon isotopic signatures

    Institute of Scientific and Technical Information of China (English)

    TIAN Hui; XIAO XianMing; YANG LiGuo; XIAO ZhongYao; GUO LiGuo; SHEN JiaGui; LU YuHong

    2009-01-01

    Although the gas cracked from oil has been believed to be one of the important sources in highly ma-tured marine basins, there are still some debates on its resource potentials and chemical and isotopic compositions. In this study a Cambrian-sourced marine oil sample from the Silurian reservoir of well TZ62 in the central Tarim basin was pyrolyzed using sealed gold tubes with two different pyrolysis schemes: continuous pyrolysis in a closed system and stepwise semi-open pyrolysis. The results show that the maximum weight yield of C1-5 gases occurs at EasyRo=2.3% and the residual gas poten-tial after this maturity is only 43.4 mL/g, about 12% of the yield of 361 mL/g at EasyRo=2.3%. Combined with the results of kinetic modeling, the main stage of gas generation from oil cracking is believed within the EasyRo=1.6%-2.3%. The increase in the volume yield of C1-5 gases at EasyRo2.3% in a closed system is mainly related to the re-cracking of previously formed C2-5 wet gases, not the direct cracking of oil. The stepwise pyrolysis experiments show that the gas from the cracking of residual oil at EasyRo2.3% is characterized by very high dryness index (higher than 92%) and heavy methane carbon isotopes ranging from -28.7‰ to -26.7‰, which is quite different from the gases from the con-tinuous pyrolysis in a closed system. The kinetic modeling of methane carbon isotope fractionation shows that the carbon isotopes of methane within the main stage of gas generation (EasyRo<2.3%) are far lighter than the carbon isotopes of the precursor oils under a geological heating rate of 2℃/Ma. The above observations and results provide some new clues to the accurate recognition and objective re-source evaluation of oil cracking gas in highly mature marine basins.

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

    Science.gov (United States)

    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 (δ13Corg) are relatively constant in host and concretion samples ranging from ­-26.3 to -24.0‰ (VPDB). Carbonate carbon isotope compositions (δ13Ccarb) 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 δ13Ccarb values averaging -4.8‰, whereas upper Holz Shale concretions express an average δ13Ccarb 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 δ13C ~ +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

  9. Hydrogen isotopic compositions of organic compounds in plants reflect the plant's carbon metabolism

    Science.gov (United States)

    Cormier, M. A.; Kahmen, A.; Werner, R. A.

    2015-12-01

    The main factors controlling δ2H of plant organic compounds are generally assumed to be the plant's source water and the evaporative deuterium enrichment of leaf water. Hydrogen isotope analyses of plant compounds from sediments or tree rings are therefore mainly applied to assess hydrological conditions at different spatial and temporal scales. However, the biochemical hydrogen isotope fractionation occurring during biosynthesis of plant organic compounds (ɛbio) also accounts for a large part of the variability observed in the δ2H values. Nevertheless, only few studies have directly addressed the physiological basis of this variability and even fewer studies have thus explored possible applications of hydrogen isotope variability in plant organic compounds for plant physiological research. Here we show two datasets indicating that the plant's carbon metabolism can have a substantial influence on δ2H values of n-alkanes and cellulose. First, we performed a controlled experiment where we forced plants into heterotrophic and autotrophic C-metabolism by growing them under four different light treatments. Second, we assessed the δ2H values of different parasitic heterotrophic plants and their autotrophic host plants. Our two datasets show a systematic shift in ɛbio of up to 80 ‰ depending on the plant's carbon metabolism (heterotrophic or autotrophic). Differences in n-alkane and cellulose δ2H values in plants with autotrophic vs. heterotrophic metabolisms can be explained by different NADPH pools that are used by the plants to build their compounds either with assimilates that originate directly from photosynthesis or from stored carbohydrates. Our results have significant implications for the calibration and interpretation of geological records. More importantly, as the δ2H values reflect the plant's carbon metabolism involved during the tissue formation, our findings highlight the potential of δ2H values as new tool for studying plant and ecosystem carbon

  10. Carbon and oxygen isotope study of carbonates from highly shocked clasts of the polymict breccia of the Haughton Crater (Canada)

    Science.gov (United States)

    Agrinier, P.; Martinez, I.; Javoy, M.; Schaerer, U.

    1992-01-01

    It is known that the release of volatiles on impact is an important controlling factor in cratering processes in carbonate terranes and in the mobility of chemical elements. In order to assess the nature and the role of carbon- and oxygen-bearing volatiles during impact-induced metamorphism of sedimentary rocks, the C-13/C-12 and O-18/O-16 ratios and carbonate contents were determined for 30 shocked clasts from the Haughton Crater polymict breccia as well as for some unshocked carbonates from the sedimentary cover adjacent to the crater. Shock-induced CO2 loss during decarbonation of calcite is known to be a function of peak pressure and ambient partial pressure of the volatile species. In our clast samples, shocked from 20 to 60 GPa, we expect about 20 to 100 percent CO2 loss and preferential depletion in C-13 and O-18 in the residual carbonate. Rayleigh model (progressive loss of CO2) and batch model (single-step loss of CO2) curves for this depletion are shown. The magnitudes of the C-13 and O-18 depletions increase with the increase of the CO2 loss. In addition, the isotopic depletions should be correlated with an enrichment in CaO and MgO in the residual solid.

  11. Carbon isotopes in eclogite and apatite separate from Huangzhen and Shima in SE Dabie

    Institute of Scientific and Technical Information of China (English)

    李一良; 郑永飞; 龚冰; 傅斌

    2000-01-01

    The carbon isotope compositions of high- and ultrahigh-pressure eclogite and apatite separate from Huangzhen and Shima in SE Dabie Mountains were analyzed by EA-MS online technique. The δ13C values of the eclogites cover a wide range of -30.7‰ - +1.5‰, whereasthose of apatites only have a small range of -28.1‰- -21.0‰. Some of the eclogites with thehigh δ13C values suffered retrogressive alteration by CO2-bearing fluids. The low δ13C values of the apatites indicate that the eclogites contain surficial carbon of organic origin. It is concluded that protoliths of the eclogites were exposed to the surface of the Earth, and that the carbon-bearing fluid was depleted in 13C during the eclogite-facies metamorphism.

  12. Application of carbon isotope for discriminating sources of soil CO2 in karst area, Guizhou

    Institute of Scientific and Technical Information of China (English)

    黎廷宇; 王世杰

    2001-01-01

    Using carbon isotope of soil CO2 this paper discussed the sources of soil CO2 in karst area, Guizhou Province, China. Oxidation-decomposition of organic matter, respiration of plant root and activity of microbe are thought to be the major sources of soil CO2. However, in karst area, the contribution of dissolution of underlying carbonate rock to soil CO2 should be considered as in acidic environment. Atmospheric CO2 is the major composition of soil CO2 in surface layer of soil profiles and its proportion in soil CO2 decreases with increase of soil depth. CO2 produced by dissolution of carbonate rock contributes 34%-46% to soil CO2 below the depth of 10cm in the studied soil profiles covered by grass.

  13. Volcanism, Mass Extinction, and Carbon Isotope Fluctuations in the Middle Permian of China

    Science.gov (United States)

    Wignall, Paul B.; Sun, Yadong; Bond, David P. G.; Izon, Gareth; Newton, Robert J.; Védrine, Stéphanie; Widdowson, Mike; Ali, Jason R.; Lai, Xulong; Jiang, Haishui; Cope, Helen; Bottrell, Simon H.

    2009-05-01

    The 260-million-year-old Emeishan volcanic province of southwest China overlies and is interbedded with Middle Permian carbonates that contain a record of the Guadalupian mass extinction. Sections in the region thus provide an opportunity to directly monitor the relative timing of extinction and volcanism within the same locations. These show that the onset of volcanism was marked by both large phreatomagmatic eruptions and extinctions amongst fusulinacean foraminifers and calcareous algae. The temporal coincidence of these two phenomena supports the idea of a cause-and-effect relationship. The crisis predates the onset of a major negative carbon isotope excursion that points to subsequent severe disturbance of the ocean-atmosphere carbon cycle.

  14. Carbon isotopes in eclogite and apatite separate from Huangzhen and Shima in SE Dabie

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The carbon isotope compositions of high- and ultrahigh-pressure eclogite and apatite separate from Huangzhen and Shima in SE Dabie Mountains were analyzed by EA-MS online technique. The δ13C values of the eclogites cover a wide range of -30.7‰ - +1.5‰, whereas those of apatites only have a small range of -28.1‰--21.0‰. Some of the eclogites with the high δ13C values suffered retrogressive alteration by CO2-bearing fluids. The low δ13C values of the apatites indicate that the eclogites contain surficial carbon of organic origin. It is concluded that protoliths of the eclogites were exposed to the surface of the Earth, and that the carbon-bearing fluid was depleted in 13C during the eclogite-facies metamorphism.

  15. CO{sub 2}-recycling by plants: how reliable is the carbon isotope estimation?

    Energy Technology Data Exchange (ETDEWEB)

    Siegwolf, R.T.W.; Saurer, M. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Koerner, C. [Basel Univ., Basel (Switzerland)

    1997-06-01

    In the study of plant carbon relations, the amount of the respiratory losses from the soil was estimated, determining the gradient of the stable isotope {sup 13}C with increasing plant canopy height. According to the literature 8-26% of the CO{sub 2} released in the forests by soil and plant respiratory processes are reassimilated (recycled) by photosynthesis during the day. Our own measurements however, which we conducted in grass land showed diverging results from no indicating of carbon recycling, to a considerable {delta}{sup 13}C gradient suggesting a high carbon recycling rate. The role of other factors, such as air humidity and irradiation which influence the {delta}{sup 13}C in a canopy as well, are discussed. (author) 3 figs., 4 refs.

  16. Mineralogy and stable isotope compositions of carbonate and sulphide minerals of carbonate crusts associated with gas hydrate-forming cold vents from the NE Pacific

    Energy Technology Data Exchange (ETDEWEB)

    Conly, A.G. [Lakehead Univ., Thunder Bay, ON (Canada). Dept. of Geology; Scott, S.D. [Toronto Univ., ON (Canada). Dept. of Geology; Riedel, M. [Natural Resources Canada, Sidney, BC (Canada). Geological Survey of Canada, Pacific Geoscience Centre

    2005-07-01

    In 2001, the ROPOS submersible sampled 21 specimens of carbonate crusts from 2 gas hydrate fields located offshore Vancouver Island on the northeast Pacific continental margin. The mineralogy and stable isotopic composition of carbonate and sulphide minerals were used to evaluate petrogenesis and the relationship to associated gas hydrate occurrences. The crusts form the upper surface of carbonate and pelagic mud mounds within the gas hydrate fields. The crusts are made up of micritic carbonate with a highly variable morphology that includes blocky, fissile, nodular and mudcemented brecciated forms. The crusts include micritic calcite and dolomite/ferroan dolomite, with up to 30 per cent detrital and authigenic silicates. The finely disseminated sulphide minerals include pyrite and trace amounts of sphalerite. Bulk-rock chemical compositions are mainly homogeneous. Any variations reflect the calcite:dolomite and carbonate:silicate ratios. The {delta}13 C values for bulk carbonate (calcite and dolomite) were presented. No definitive correlation between {delta}13 C value and carbonate mineralogy was noted, but calcite-dominant samples were found to be more depleted. The {delta}34 S values for sulphide were also presented. The carbon isotopic composition of the carbonate is associated with the balance of inorganic and organic carbon species. Bacterial sulphate reduction and/or bacterial fermentation and carbonate reduction processes responsible for the production of methane were found to control the {delta}13 C of the carbon dioxide reservoir in gas hydrate environments. It was shown that methane was the carbon source involved in bacterial sulphate reduction and that the isotopic composition of the CO{sub 2} reservoir may be controlled by fractionation during bacterial carbonate reduction. The range in sulphur isotopes correlates with the bacterial sulphate reduction under partially closed conditions, where the rate of diffusion of sulphate is less than the rate of

  17. Springtime carbon episodes at Gosan background site revealed by total carbon, stable carbon isotopic composition, and thermal characteristics of carbonaceous particles

    Science.gov (United States)

    Jung, J.; Kawamura, K.

    2011-05-01

    In order to investigate the carbon episodes at Gosan background super-site (33.17° N, 126.10° E) in East Asia during spring of 2007 and 2008, total suspended particles (TSP) were collected and analyzed for particulate organic carbon, elemental carbon, total carbon (TC), total nitrogen (TN), and stable carbon isotopic composition (δ13C) of TC. The carbon episodes at the Gosan site were categorized as long-range transported anthropogenic pollutant (LTP) from Asian continent, Asian dust (AD) accompanying with LTP, and local pollen episodes. The stable carbon isotopic composition of TC (δ13CTC) was found to be lowest during the pollen episodes (range: -26.2 ‰ to -23.5 ‰, avg.: -25.2 ± 0.9 ‰), followed by the LTP episodes (range: -23.5 ‰ to -23.0 ‰, avg.: -23.3 ± 0.3 ‰) and the AD episodes (range: -23.3 to -20.4 %, avg.: -21.8 ± 2.0 ‰). The δ13CTC of the airborne pollens (-28.0 ‰) collected at the Gosan site showed value similar to that of tangerine fruit (-28.1 ‰) produced from Jeju Island. Based on the carbon isotope mass balance equation and the TN and TC regression approach, we found that ∼40-45 % of TC in the TSP samples during the pollen episodes was attributed to airborne pollens from Japanese cedar trees planted around tangerine farms in Jeju Island. The δ13C of citric acid in the airborne pollens (-26.3 ‰) collected at the Gosan site was similar to that in tangerine fruit (-27.4 ‰). The negative correlation between the citric acid-carbon/TC ratios and δ13CTC were obtained during the pollen episodes. These results suggest that citric acid emitted from tangerine fruit may be adsorbed on the airborne pollens and then transported to the Gosan site. Based on the thermal evolution pattern of organic aerosols during the carbon episodes, we found that organic aerosols originated from East China are more volatile on heating and are more likely to form pyrolized organic carbon than the pollen-enriched organic aerosols and organic

  18. Stable carbon isotopic composition of soil organic matter in the karst areas of Southwest China

    Institute of Scientific and Technical Information of China (English)

    ZHU Shufa; LIU Congqiang

    2008-01-01

    This study dealt with the distribution characteristics of soil organic carbon (SOC) and the variation of stable carbon isotopic composition (δ13C values) with depth in six soil profiles, including two soil types and three vegetation forms in the karst areas of Southwest China. The δ13C values of plant-dominant species, leaf litter and soils were measured using the sealed-tube high-temperature combustion method. Soil organic carbon contents of the limestone soil profiles are all above 11.4 g/kg, with the highest value of 71.1 g/kg in the surface soil. However, the contents vary between 2.9 g/kg and 46.0 g/kg in three yellow soil profiles. The difference between the maximum and minimum δ13C values of soil organic matter (SOM) changes from 2.2‰ to 2.9‰ for the three yellow soil profiles. But it changes from 0.8‰ to 1.6‰ for the limestone soil profiles. The contrast research indicated that there existed significant difference in vertical patterns of organic carbon and δ13C values of SOM between yellow soil and limestone soil. This difference may reflect site-specific factors, such as soil type, vegetation form, soil pH value, and clay content, etc., which control the contents of different organic components comprising SOM and soil carbon turnover rates in the profiles. The vertical variation patterns of stable carbon isotope in SOM have a distinct regional character in the karst areas.

  19. Compound specific isotopic fractionation patterns suggest different carbon metabolisms among Chloroflexus-like bacteria in hot spring microbial mats

    NARCIS (Netherlands)

    Sinninghe Damsté, J.S.; Meer, M.T.J. van der; Schouten, S.; Leeuw, J.W. de; Ward, D.M.

    2003-01-01

    Stable carbon isotope fractionations between dissolved inorganic carbon and lipid biomarkers suggest photoautotrophy by Chloroflexus-like organisms in sulfidic and nonsulfidic Yellowstone hot springs. Where co-occurring, cyanobacteria appear to cross-feed Chloroflexus-like organisms supporting photo

  20. Compound-specific carbon isotopes from Earth's largest flood basalt eruptions directly linked to the end-Triassic mass extinction.

    Science.gov (United States)

    Whiteside, Jessica H; Olsen, Paul E; Eglinton, Timothy; Brookfield, Michael E; Sambrotto, Raymond N

    2010-04-13

    A leading hypothesis explaining Phanerozoic mass extinctions and associated carbon isotopic anomalies is the emission of greenhouse, other gases, and aerosols caused by eruptions of continental flood basalt provinces. However, the necessary serial relationship between these eruptions, isotopic excursions, and extinctions has never been tested in geological sections preserving all three records. The end-Triassic extinction (ETE) at 201.4 Ma is among the largest of these extinctions and is tied to a large negative carbon isotope excursion, reflecting perturbations of the carbon cycle including a transient increase in CO(2). The cause of the ETE has been inferred to be the eruption of the giant Central Atlantic magmatic province (CAMP). Here, we show that carbon isotopes of leaf wax derived lipids (n-alkanes), wood, and total organic carbon from two orbitally paced lacustrine sections interbedded with the CAMP in eastern North America show similar excursions to those seen in the mostly marine St. Audrie's Bay section in England. Based on these results, the ETE began synchronously in marine and terrestrial environments slightly before the oldest basalts in eastern North America but simultaneous with the eruption of the oldest flows in Morocco, a CO(2) super greenhouse, and marine biocalcification crisis. Because the temporal relationship between CAMP eruptions, mass extinction, and the carbon isotopic excursions are shown in the same place, this is the strongest case for a volcanic cause of a mass extinction to date.

  1. Stratigraphical and biological significance of negative carbon isotopic anomalies in the basal Cambrian series of Guizhou Province

    Institute of Scientific and Technical Information of China (English)

    YANG Ruidong; WANG Shijie; OUYANG Ziyuan; ZHU Lijun; JIANG Lijun; ZHANG Weihua; GAO Hui

    2005-01-01

    The early Early Cambrian strata within the bounds of Guizhou Province are almost predominated by black shale deposition. Recently, however, the authors have found a section consisting of a set of mudstones interbedded with limestones at the basement of the Cambrian at Yingping, Fuquan County, Guizhou Province, which provides favorable conditions for the study of marine geochemical characteristics of the early Early Cambrian. The characteristics of intense negative carbon isotopic anomalies near the Precambrian/Cambrian boundary at Yingping, Fuquan County, Guizhou Province, can be correlated with those of global carbon isotopic anomalies at the same time on a global scale, corresponding to the intense negative carbon isotopic anomalies near the Neoproterozoic/Cambrian boundaries at the bottom of the Xiaowaitoushan Member, Huize, Yunnan Province, at the top of the Tsagaan Oloom Formation of Mongolia and at the top of the Salarmy Gol Formation of Siberia, as well as those observed in southwestern United States, Iran, Amman, Poland, Newfoundland, the Great Britain, Canada, etc. Negative carbon isotopic anomalies can be used as the important basis for the division of the Precambrian/Cambrian boundaries. There have been found 8 m-thick black shales and cherts below the intense negative carbon isotopic anomalies in this profile. In the black shales there have been found large amounts of fossils such as Bradorida, gernus Archotuba, indicating that during the period of sedimentation of black shales under anaerobic conditions there would be large quantities of organic species living in the sea. But in the section of grayish-green mudstones interbedded with limestones with intense negative carbon isotopic anomalies almost no organic fossil has been fo