Sample records for abundance carbon isotope

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

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

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

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

    NASA Technical Reports Server (NTRS)

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

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

  5. Natural-abundance stable carbon isotopes of small-subunit ribosomal RNA (SSU rRNA) from Guaymas Basin (Mexico)

    NASA Astrophysics Data System (ADS)

    MacGregor, B. J.; Mendlovitz, H.; Albert, D.; Teske, A. P.

    2012-12-01

    Small-subunit ribosomal RNA (SSU rRNA) is a phylogenetically informative molecule found in all species. Because it is poorly preserved in most environments, it is a useful marker for active microbial populations. We are using the natural-abundance stable carbon isotopic composition of specific microbial groups to help identify the carbon substrates contributing to microbial biomass in a variety of marine environments. At Guaymas Basin, hydrothermal fluids interact with abundant sedimentary organic carbon to produce natural gas and petroleum. Where this reaches the sediment surface, it can support dense patches of seafloor life, including Beggiatoa mats. We report here on the stable carbon isotopic composition of SSU rRNA from a Beggiatoa mat transect, a cold background site, a warm site with high oil concentration, and a second Beggiatoa mat. The central part of the transect mat overlay the steepest temperature gradient, and was visually dominated by orange Beggiatoa. This was fringed by white Beggiatoa mat and bare, but still warm, sediment. Methane concentrations were saturating beneath the orange and white mats and at the oily site, lower beneath bare sediment, and below detection at the background site. Our initial hypotheses were that rRNA isotopic composition would be strongly influenced by methane supply, and that archaeal rRNA might be lighter than bacterial due to contributions from methanogens and anaerobic methane oxidizers. We used biotin-labeled oligonucleotides to capture Bacterial and Archaeal SSU rRNA for isotopic determination. Background-site rRNA was isotopically heaviest, and bacterial RNA from below 2 cm at the oily site was lightest, consistent with control by methane. Within the transect mat, however, the pattern was more complicated; at some sediment depths, rRNA from the mat periphery was isotopically lightest. Part of this may be due to the spatially and temporally variable paths followed by hydrothermal fluid, which can include horizontal

  6. Organic chemistry of Murchison meteorite: Carbon isotopic fractionation

    NASA Technical Reports Server (NTRS)

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

    1986-01-01

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

  7. Carbon isotope geochemistry and geobiology

    NASA Technical Reports Server (NTRS)

    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.

  8. Synthetic isotope mixtures for the calibration of isotope amount ratio measurements of carbon

    NASA Astrophysics Data System (ADS)

    Russe, K.; Valkiers, S.; Taylor, P. D. P.

    2004-07-01

    Synthetic isotope mixtures for the calibration of carbon isotope amount ratio measurements have been prepared by mixing carbon tetrafluoride highly enriched in 13C with carbon tetrafluoride depleted in 13C. Mixing procedures based on volumetry and gravimetry are described. The mixtures served as primary measurement standards for the calibration of isotope amount ratio measurements of the Isotopic Reference Materials PEF1, NBS22 and USGS24. Thus SI-traceable measurements of absolute carbon isotope amount ratios have been performed for the first time without any hypothesis needed for a correction of oxygen isotope abundances, such as is the case for measurements on carbon dioxide. As a result, "absolute" carbon isotope amount ratios determined via carbon tetrafluoride have smaller uncertainties than those published for carbon dioxide. From the measurements of the Reference Materials concerned, the absolute carbon isotope amount ratio of Vienna Pee Dee Belemnite (VPDB)--the hypothetical material upon which the scale for relative carbon isotope ratio measurements is based--was calculated to be R13(VPDB) = (11 101 +/- 16) × 10-6.

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

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

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

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

    USGS Publications Warehouse

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

    2002-01-01

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

  11. Carbon isotopic fractionation in heterotrophic microbial metabolism

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

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

  12. Carbon Isotope Chemistry in Molecular Clouds

    NASA Technical Reports Server (NTRS)

    Robertson, Amy N.; Willacy, Karen

    2012-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

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

  14. Raman scattering method and apparatus for measuring isotope ratios and isotopic abundances

    DOEpatents

    Harney, Robert C.; Bloom, Stewart D.

    1978-01-01

    Raman scattering is used to measure isotope ratios and/or isotopic abundances. A beam of quasi-monochromatic photons is directed onto the sample to be analyzed, and the resulting Raman-scattered photons are detected and counted for each isotopic species of interest. These photon counts are treated mathematically to yield the desired isotope ratios or isotopic abundances.

  15. Following Carbon Isotopes from Methane to Molecules

    NASA Astrophysics Data System (ADS)

    Freeman, K. H.

    2017-12-01

    Continuous-flow methods introduced by Hayes (Matthews and Hayes, 1978; Freeman et al., 1990; Hayes et al., 1990) for compound-specific isotope analyses (CSIA) transformed how we study the origins and fates of organic compounds. This analytical revolution launched several decades of research in which researchers connect individual molecular structures to diverse environmental and climate processes affecting their isotopic profiles. Among the first applications, and one of the more dramatic isotopically, was tracing the flow of natural methane into cellular carbon and cellular biochemical constituents. Microbial oxidation of methane can be tracked by strongly 13C-depleted organic carbon in early Earth sedimentary environments, in marine and lake-derived biomarkers in oils, and in modern organisms and their environments. These signatures constrain microbial carbon cycling and inform our understanding of ocean redox. The measurement of molecular isotopes has jumped forward once again, and it is now possible to determine isotope abundances at specific positions within increasingly complex organic structures. In addition, recent analytical developments have lowered sample sensitivity limits of CSIA to picomole levels. These new tools have opened new ways to measure methane carbon in the natural environment and within biochemical pathways. This talk will highlight how molecular isotope methods enable us to follow the fate of methane carbon in complex environments and along diverse metabolic pathways, from trace fluids to specific carbon positions within microbial biomarkers.

  16. Isotope-abundance variations and atomic weights of selected elements: 2016 (IUPAC Technical Report)

    USGS Publications Warehouse

    Coplen, Tyler B.; Shrestha, Yesha

    2016-01-01

    There are 63 chemical elements that have two or more isotopes that are used to determine their standard atomic weights. The isotopic abundances and atomic weights of these elements can vary in normal materials due to physical and chemical fractionation processes (not due to radioactive decay). These variations are well known for 12 elements (hydrogen, lithium, boron, carbon, nitrogen, oxygen, magnesium, silicon, sulfur, chlorine, bromine, and thallium), and the standard atomic weight of each of these elements is given by IUPAC as an interval with lower and upper bounds. Graphical plots of selected materials and compounds of each of these elements have been published previously. Herein and at the URL http://dx.doi.org/10.5066/F7GF0RN2, we provide isotopic abundances, isotope-delta values, and atomic weights for each of the upper and lower bounds of these materials and compounds.

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

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

    The carbon isotope geochemistry of carbonates and organic carbon in the late Proterozoic Damara Supergroup of Namibia, including the Nama, Witvlei, and Gariep groups on the Kalahari Craton and the Mulden and Otavi groups on the Congo Craton, has been investigated as an extension of previous studies of secular variations in the isotopic composition of late Proterozoic seawater. Subsamples of microspar and dolomicrospar were determined, through petrographic and cathodoluminescence examination, to represent the "least-altered" portions of the rock. Carbon-isotopic abundances in these phases are nearly equal to those in total carbonate, suggesting that 13C abundances of late Proterozoic fine-grained carbonates have not been significantly altered by meteoric diagenesis, although 18O abundances often differ significantly. Reduced and variable carbon-isotopic differences between carbonates and organic carbon in these sediments indicate that isotopic compositions of organic carbon have been altered significantly by thermal and deformational processes, likely associated with the Pan-African Orogeny. Distinctive stratigraphic patterns of secular variation, similar to those noted in other, widely separated late Proterozoic basins, are found in carbon-isotopic compositions of carbonates from the Nama and Otavi groups. For example, in Nama Group carbonates delta 13C values rise dramatically from -4 to +5% within a short stratigraphic interval. This excursion suggests correlation with similar excursions noted in Ediacaran-aged successions of Siberia, India, and China. Enrichment of 13C (delta 13C> +5%) in Otavi Group carbonates reflects those in Upper Riphean successions of the Akademikerbreen Group, Svalbard, its correlatives in East Greenland, and the Shaler Group, northwest Canada. The widespread distribution of successions with comparable isotopic signatures supports hypotheses that variations in delta 13C reflect global changes in the isotopic composition of late

  18. [Humus composition and stable carbon isotope natural abundance in paddy soil under long-term fertilization].

    PubMed

    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 < 0.01). The organic carbon content in 10-30 cm soil layer under chemical fertilizations and in 20-40 cm soil layer under organic fertilizations was relatively stable. Soil delta 13C increased gradually with soil depth, its variation range being from -24% per thousand to -28 per thousand, and had a significantly negative linear correlation with soil organic carbon content (P < 0.05). In 0-20 cm soil layer, the delta 13C in treatments organic manure (M), M + NP, M + NPK, M + straw (R) + N, and R + N decreased significantly; while in 30-50 cm soil layer, the delta 13C in all organic fertilization treatments except R + N increased significantly. Tightly combined 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).

  19. High Relative Abundance of Biofuel Sourced Ethanol in Precipitation in the US and Brazil Determined Using Compound Specific Stable Carbon Isotopes

    NASA Astrophysics Data System (ADS)

    Shimizu, M. S.; Felix, J. D. D.; Casas, M.; Avery, G. B., Jr.; Kieber, R. J.; Mead, R. N.; Willey, J. D.; Lane, C.

    2017-12-01

    Ethanol biofuel production and consumption have increased exponentially over the last two decades to help reduce greenhouse gas emissions. Currently, 85% of global ethanol production and consumption occurs in the US and Brazil. Increasing biofuel ethanol usage in these two countries enhances emissions of uncombusted ethanol to the atmosphere contributing to poor air quality. Although measurements of ethanol in the air and the precipitation reveal elevated ethanol concentrations in densely populated cities, other sources such as natural vegetation can contribute to emission to the atmosphere. Previous modeling studies indicated up to 12% of atmospheric ethanol is from anthropogenic emissions. Only one gas phase study in southern Florida attempted to constrain the two sources through direct isotopic measurements. The current study used a stable carbon isotope method to constrain sources of ethanol in rainwater from the US and Brazil. A method was developed using solid phase microextraction (SPME) with subsequent analysis by gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS). Stable carbon isotope signatures (δ13C) of vehicle ethanol emission sources for both the US (-9.8‰) and Brazil (-12.7‰) represented C4 plants as feedstock (corn and sugarcane) for biofuel production. An isotope mixing model using biofuel from vehicles (C4 plants) and biogenic (C3 plants) end-members was implemented to estimate ethanol source apportionment in the rain. We found that stable carbon isotope ratio of ethanol in the rain ranged between -22.6‰ and -12.7‰. Our results suggest that the contribution of biofuel to atmospheric ethanol can be higher than previously estimated. As biofuel usage increasing globally, it is essential to determine the relative abundance of anthropogenic ethanol in other areas of the world.

  20. Methylhopane Biomarker and Carbon Isotopic Evidence for Late Archean Aerobic Ecosystems

    NASA Technical Reports Server (NTRS)

    Eigenbrode, Jennifer L.; Freeman, Katherine H.; Summons, Roger E.

    2007-01-01

    Molecular fossils are particularly valuable in early Earth studies because they provide information about microbial sources and ecology. Here we report on the distribution of 2- methyl and 3-methylhopanes preserved in a 2.72-2.56 billion-year-old section of shallow and deepwater sediments of the Hamersley Province [Eigenbrode et aI., submitted]. These biomarkers are mostly from cyanobacteria and oxygen-respiring methanotrophs, respectively. The relative abundance of 2-methylhopanes increases with carbonate abundance in shallow-water facies indicating cyanobacteria were key microbes in shallow ecosystems and suggesting they supplied both molecular oxygen and fixed carbon. The relative abundance of 3-methylhopane strongly correlates with kerogen-carbon isotopic values, and is more abundant in the samples with 13C-enriched signatures. Thus, molecular data provides evidence for cycling of methane in shallow settings, even though the anoxic deeper environments bear stronger 13C-depletion, which together suggests a more complex methane cycle than previously envisioned. Detailed facies analysis of the Hamersley carbon-isotope record reveals temporal changes suggesting continued oxidation of shallow settings favoring the expansion of aerobic ecosystems and respiring organisms [Eigenbrode et aI., 2006, PNAS, 103: 15759]. Similar analysis of published carbon-isotopic records suggests similar, but diachronous, expansion of oxygenated habitats in shallow then deep waters as anaerobic microbial communities gave way to respiring communities fueled by oxygenic photosynthesis before the post 2.45-Ga atmospheric oxygenation event [Eigenbrode et aI., 2006]. The robust relationships observed provide geochemical support for methanogenesis, aerobic methanotrophy, and oxygenic photosynthesis in the late Archean, as well as major ecological shifts linked to biogeochemical reorganization.

  1. Stable isotope analysis of Dacryoconarid carbonate microfossils: a new tool for Devonian oxygen and carbon isotope stratigraphy.

    PubMed

    Frappier, Amy Benoit; Lindemann, Richard H; Frappier, Brian R

    2015-04-30

    Dacryoconarids are extinct marine zooplankton known from abundant, globally distributed calcite microfossils in the Devonian, but their shell stable isotope composition has not been previously explored. Devonian stable isotope stratigraphy is currently limited to less common invertebrates or bulk rock analyses of uncertain provenance. As with Cenozoic planktonic foraminifera, isotopic analysis of dacryoconarid shells could facilitate higher-resolution, geographically widespread stable isotope records of paleoenvironmental change, including marine hypoxia events, climate changes, and biocrises. We explored the use of Dacryoconarid isotope stratigraphy as a viable method in interpreting paleoenvironments. We applied an established method for determining stable isotope ratios (δ(13) C, δ(18) O values) of small carbonate microfossils to very well-preserved dacryoconarid shells. We analyzed individual calcite shells representing five common genera using a Kiel carbonate device coupled to a MAT 253 isotope ratio mass spectrometer. Calcite shell δ(13) C and δ(18) O values were compared by taxonomic group, rock unit, and locality. Single dacryoconarid calcite shells are suitable for stable isotope analysis using a Kiel-IRMS setup. The dacryoconarid shell δ(13) C values (-4.7 to 2.3‰) and δ(18) O values (-10.3 to -4.8‰) were consistent across taxa, independent of shell size or part, but varied systematically through time. Lower fossil δ(18) O values were associated with warmer water temperature and more variable δ(13) C values were associated with major bioevents. Dacryoconarid δ(13) C and δ(18) O values differed from bulk rock carbonate values. Dacryoconarid individual microfossil δ(13) C and δ(18) O values are highly sensitive to paleoenvironmental changes, thus providing a promising avenue for stable isotope chemostratigraphy to better resolve regional to global paleoceanographic changes throughout the upper Silurian to the upper Devonian. Our results

  2. Measurement of natural carbon isotopic composition of acetone in human urine.

    PubMed

    Yamada, Keita; Ohishi, Kazuki; Gilbert, Alexis; Akasaka, Mai; Yoshida, Naohiro; Yoshimura, Ryoko

    2016-02-01

    The natural carbon isotopic composition of acetone in urine was measured in healthy subjects using gas chromatography-combustion-isotope ratio mass spectrometry combined with headspace solid-phase microextraction (HS-SPME-GC-C-IRMS). Before applying the technique to a urine sample, we optimized the measurement conditions of HS-SPME-GC-C-IRMS using aqueous solutions of commercial acetone reagents. The optimization enabled us to determine the carbon isotopic compositions within ±0.2 ‰ of precision and ±0.3‰ of error using 0.05 or 0.2 mL of aqueous solutions with acetone concentrations of 0.3-121 mg/L. For several days, we monitored the carbon isotopic compositions and concentrations of acetone in urine from three subjects who lived a daily life with no restrictions. We also monitored one subject for 3 days including a fasting period of 24 h. These results suggest that changes in the availability of glucose in the liver are reflected in changes in the carbon isotopic compositions of urine acetone. Results demonstrate that carbon isotopic measurement of metabolites in human biological samples at natural abundance levels has great potential as a tool for detecting metabolic changes caused by changes in physiological states and disease.

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

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

    Formaldehyde (HCHO) is the most abundant carbonyl compound in the atmosphere, and vehicle exhaust emission is one of its important anthropogenic sources. However, there is still uncertainty regarding HCHO flux from vehicle emission as well as from other sources. Herein, automobile source was characterized using HCHO carbon isotopic ratio to assess its contributions to atmospheric flux and demonstrate the complex production/consumption processes during combustion in engine cylinder and subsequent catalytic treatment of exhaust. Vehicle exhausts were sampled under different idling states and HCHO carbon isotopic ratios were measured by gas chromatograph-combustion-isotopic ratio mass spectrometry (GC-C-IRMS). The HCHO directly emitted from stand-alone engines (gasoline and diesel) running at different load was also sampled and measured. The HCHO carbon isotopic ratios were from -30.8 to -25.7‰ for gasoline engine, and from -26.2 to -20.7‰ for diesel engine, respectively. For diesel vehicle without catalytic converter, the HCHO carbon isotopic ratios were -22.1 ± 2.1‰, and for gasoline vehicle with catalytic converter, the ratios were -21.4 ± 0.7‰. Most of the HCHO carbon isotopic ratios were heavier than the fuel isotopic ratios (from -29 to -27‰). For gasoline vehicle, the isotopic fractionation (Δ13C) between HCHO and fuel isotopic ratios was 7.4 ± 0.7‰, which was higher than that of HCHO from stand-alone gasoline engine (Δ13Cmax = 2.7‰), suggesting additional consumption by the catalytic converter. For diesel vehicle without catalytic converter, Δ13C was 5.7 ± 2.0‰, similar to that of stand-alone diesel engine. In general, the carbon isotopic signatures of HCHO emitted from automobiles were not sensitive to idling states or to other vehicle parameters in our study condition. On comparing these HCHO carbon isotopic data with those of past studies, the atmospheric HCHO in a bus station in Guangzhou might mainly come from vehicle emission for

  4. Plant family identity distinguishes patterns of carbon and nitrogen stable isotope abundance and nitrogen concentration in mycoheterotrophic plants associated with ectomycorrhizal fungi.

    PubMed

    Hynson, Nicole A; Schiebold, Julienne M-I; Gebauer, Gerhard

    2016-09-01

    Mycoheterotrophy entails plants meeting all or a portion of their carbon (C) demands via symbiotic interactions with root-inhabiting mycorrhizal fungi. Ecophysiological traits of mycoheterotrophs, such as their C stable isotope abundances, strongly correlate with the degree of species' dependency on fungal C gains relative to C gains via photosynthesis. Less explored is the relationship between plant evolutionary history and mycoheterotrophic plant ecophysiology. We hypothesized that the C and nitrogen (N) stable isotope compositions, and N concentrations of fully and partially mycoheterotrophic species differentiate them from autotrophs, and that plant family identity would be an additional and significant explanatory factor for differences in these traits among species. We focused on mycoheterotrophic species that associate with ectomycorrhizal fungi from plant families Ericaceae and Orchidaceae. Published and unpublished data were compiled on the N concentrations, C and N stable isotope abundances (δ(13)C and δ(15)N) of fully (n = 18) and partially (n = 22) mycoheterotrophic species from each plant family as well as corresponding autotrophic reference species (n = 156). These data were used to calculate site-independent C and N stable isotope enrichment factors (ε). Then we tested for differences in N concentration, (13)C and (15)N enrichment among plant families and trophic strategies. We found that in addition to differentiating partially and fully mycoheterotrophic species from each other and from autotrophs, C and N stable isotope enrichment also differentiates plant species based on familial identity. Differences in N concentrations clustered at the plant family level rather than the degree of dependency on mycoheterotrophy. We posit that differences in stable isotope composition and N concentrations are related to plant family-specific physiological interactions with fungi and their environments. © The Author 2016. Published by Oxford University Press

  5. Plant family identity distinguishes patterns of carbon and nitrogen stable isotope abundance and nitrogen concentration in mycoheterotrophic plants associated with ectomycorrhizal fungi

    PubMed Central

    Hynson, Nicole A.; Schiebold, Julienne M.-I.; Gebauer, Gerhard

    2016-01-01

    Background and Aims Mycoheterotrophy entails plants meeting all or a portion of their carbon (C) demands via symbiotic interactions with root-inhabiting mycorrhizal fungi. Ecophysiological traits of mycoheterotrophs, such as their C stable isotope abundances, strongly correlate with the degree of species’ dependency on fungal C gains relative to C gains via photosynthesis. Less explored is the relationship between plant evolutionary history and mycoheterotrophic plant ecophysiology. We hypothesized that the C and nitrogen (N) stable isotope compositions, and N concentrations of fully and partially mycoheterotrophic species differentiate them from autotrophs, and that plant family identity would be an additional and significant explanatory factor for differences in these traits among species. We focused on mycoheterotrophic species that associate with ectomycorrhizal fungi from plant families Ericaceae and Orchidaceae. Methods Published and unpublished data were compiled on the N concentrations, C and N stable isotope abundances (δ13C and δ15N) of fully (n = 18) and partially (n = 22) mycoheterotrophic species from each plant family as well as corresponding autotrophic reference species (n = 156). These data were used to calculate site-independent C and N stable isotope enrichment factors (ε). Then we tested for differences in N concentration, 13C and 15N enrichment among plant families and trophic strategies. Key Results We found that in addition to differentiating partially and fully mycoheterotrophic species from each other and from autotrophs, C and N stable isotope enrichment also differentiates plant species based on familial identity. Differences in N concentrations clustered at the plant family level rather than the degree of dependency on mycoheterotrophy. Conclusions We posit that differences in stable isotope composition and N concentrations are related to plant family-specific physiological interactions with fungi and their environments. PMID

  6. Reporting of nitrogen-isotope abundances (Technical Report)

    USGS Publications Warehouse

    Coplen, Tyler B.; Krouse, H.R.; Böhlke, John Karl

    1992-01-01

    To eliminate possible confusion in the reporting of nitrogen-isotope analyses, the Commission on Atomic Weights and Isotopic Abundances recommends that the value 272 be employed for the 14N/15N value of N2 in air for calculating atom percent 15N from measured δ15N values.

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

    NASA Astrophysics Data System (ADS)

    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.

  8. Wildfire Activity Across the Triassic-Jurassic Boundary in the Polish Basin: Evidence from New Fossil Charcoal & Carbon-isotope Data

    NASA Astrophysics Data System (ADS)

    Pointer, R.; Belcher, C.; Hesselbo, S. P.; Hodbod, M.; Pieńkowski, G.

    2017-12-01

    New fossil charcoal abundance and carbon-isotope data from two sedimentary cores provide new evidence of extreme environmental conditions in the Polish Basin during the Latest Triassic to Earliest Jurassic. Sedimentary cores from the Polish Basin provide an excellent record of terrestrial environmental conditions across the Triassic-Jurassic Boundary, a time of climatic extremes. Previous work has shown that the marine realm was affected by a large perturbation to the carbon cycle across the Triassic-Jurassic Boundary (manifested by large negative and positive carbon-isotope excursions) and limited records of charcoal abundance and organic geochemistry have indicated important changes in fire regime in the coeval ecosystems. Here we present two new carbon-isotope records generated from fossil plant matter across the Triassic-Jurassic boundary, and present new charcoal records. The charcoal abundance data confirm that there was variation in wildfire activity during the Late Triassic-Early Jurassic in the Polish Basin. Peaks in the number of fossil charcoal fragments present occur in both sedimentary cores, and increases in fossil charcoal abundance are linked to wildfires, signalling a short-lived rise in wildfire activity. Fossil charcoal abundance does not appear to be fully controlled by total organic matter content, depositional environment or bioturbation. We argue that increased wildfire activity is likely caused by an increase in ignition of plant material as a result of an elevated number of lightning strikes. Global warming (caused by a massive input of carbon into the atmosphere, as indicated by carbon-isotope data) can increase storm activity, leading to increased numbers of lightning strikes. Previous Triassic-Jurassic Boundary wildfire studies have found fossil charcoal abundance peaks at other northern hemisphere sites (Denmark & Greenland), and concluded that they represent increases in wildfire activity in the earliest Jurassic. Our new charcoal and

  9. Oxygen and carbon isotopic growth record in a reef coral from the florida keys and a deep-sea coral from blake plateau

    USGS Publications Warehouse

    Emiliani, C.; Harold, Hudson J.; Shinn, E.A.; George, R.Y.

    1978-01-01

    Carbon and oxygen isotope analysis through a 30-year (1944 to 1974) growth of Montastrea annularis from Hen and Chickens Reef (Florida Keys) shows a strong yearly variation in the abundances of both carbon-13 and oxygen-18 and a broad inverse relationship between the two isotopes. Normal annual dense bands are formed during the summer and are characterized by heavy carbon and light oxygen. "Stress bands" are formed during particularly severe winters and are characterized by heavy carbon and heavy oxygen. The isotopic effect of Zooxanthellae metabolism dominates the temperature effect on the oxygen-18/oxygen-16 ratio. The isotopic results on the deep-sea solitary coral Bathypsammia tintinnabulum, where Zooxanthellae are nonexistent, indicates that the abundance of the heavy isotopes carbon-13 and oxygen-18 is inversely related to the growth rate, with both carbon and oxygen approaching equilibrium values with increasing skeletal age.

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

    NASA Astrophysics Data System (ADS)

    Turchyn, Alexandra V.; DePaolo, Donald J.

    2011-11-01

    Pore fluid calcium isotope, calcium concentration and strontium concentration data are used to measure the rates of diagenetic dissolution and precipitation of calcite in deep-sea sediments containing abundant clay and organic material. This type of study of deep-sea sediment diagenesis provides unique information about the ultra-slow chemical reactions that occur in natural marine sediments that affect global geochemical cycles and the preservation of paleo-environmental information in carbonate fossils. For this study, calcium isotope ratios (δ 44/40Ca) of pore fluid calcium from Ocean Drilling Program (ODP) Sites 984 (North Atlantic) and 1082 (off the coast of West Africa) were measured to augment available pore fluid measurements of calcium and strontium concentration. Both study sites have high sedimentation rates and support quantitative sulfate reduction, methanogenesis and anaerobic methane oxidation. The pattern of change of δ 44/40Ca of pore fluid calcium versus depth at Sites 984 and 1082 differs markedly from that of previously studied deep-sea Sites like 590B and 807, which are composed of nearly pure carbonate sediment. In the 984 and 1082 pore fluids, δ 44/40Ca remains elevated near seawater values deep in the sediments, rather than shifting rapidly toward the δ 44/40Ca of carbonate solids. This observation indicates that the rate of calcite dissolution is far lower than at previously studied carbonate-rich sites. The data are fit using a numerical model, as well as more approximate analytical models, to estimate the rates of carbonate dissolution and precipitation and the relationship of these rates to the abundance of clay and organic material. Our models give mutually consistent results and indicate that calcite dissolution rates at Sites 984 and 1082 are roughly two orders of magnitude lower than at previously studied carbonate-rich sites, and the rate correlates with the abundance of clay. Our calculated rates are conservative for these

  11. Martian carbon dioxide: Clues from isotopes in SNC meteorites

    NASA Technical Reports Server (NTRS)

    Karlsson, H. R.; Clayton, R. N.; Mayeda, T. K.; Jull, A. J. T.; Gibson, E. K., Jr.

    1993-01-01

    Attempts to unravel the origin and evolution of the atmosphere and hydrosphere on Mars from isotopic data have been hampered by the impreciseness of the measurements made by the Viking Lander and by Earth-based telescopes. The SNC meteorites which are possibly pieces of the Martian surface offer a unique opportunity to obtain more precise estimates of the planet's volatile inventory and isotopic composition. Recently, we reported results on oxygen isotopes of water extracted by pyrolysis from samples of Shergotty, Zagami, Nakhla, Chassigny, Lafayette, and EETA-79001. Now we describe complementary results on the stable isotopic composition of carbon dioxide extracted simultaneously from those same samples. We will also report on C-14 abundances obtained by accelerator mass spectrometry (AMS) for some of these CO2 samples.

  12. Single Species Dinoflagellate Cyst Carbon Isotope Ecology across the Paleocene-Eocene Thermal Maximum

    NASA Astrophysics Data System (ADS)

    Sluijs, A.; Roij, L. V.; Frieling, J.; Laks, J.; Reichart, G. J.

    2017-12-01

    We present the first ever species-specific records of fossil dinoflagellate cyst stable carbon isotope ratios (δ13C). These records across a Paleocene-Eocene Thermal Maximum section in New Jersey were established using a novel coupled laser ablation - isotope ratio mass spectrometer setup. The overall good correspondence with carbonate δ13C records across the characteristic PETM carbon isotope excursion indicates that the δ13C of dissolved inorganic carbon exerts a major control on dinocysts δ13C. Pronounced and consistent differences between species, however, reflect the differential physiological response to changing seawater carbonate chemistry following PETM carbon injection. Moreover, they reflect different habitats or life cycle processes, notably related to bloom intensity. Intriguingly, decreased inter-specimen variability during the PETM in a species that also drops in abundance suggests a more limited niche, either in time (seasonal) or space. This opens a new approach for ecological and evolutionary reconstructions based on organic microfossils.

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

    NASA Technical Reports Server (NTRS)

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

    2006-01-01

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

  14. Carbon isotopes in mollusk shell carbonates

    NASA Astrophysics Data System (ADS)

    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.

  15. Atmospheric Trace Gas Abundances and Stable Isotope Ratios via IR-LIF

    NASA Technical Reports Server (NTRS)

    Blake, Geoffrey A.

    2004-01-01

    We propose to develop new technologies with support provided by PIDDP that will enable the in situ measurements of abundances and stable isotope ratios in important radiatively and biogenically active gases such as carbon dioxide, carbon monoxide, water, methane, nitrous oxide, and hydrogen sulfide to very high precision (0.1 per mil or better for the isotopic ratios, for example). Such measurements, impossible at present, could provide pivotal new constraints on the global (bio)geochemical budgets of these critical species, and could also be used to examine the dynamics of atmospheric transport on Mars, Titan, and other solar system bodies. We believe the combination of solid state light sources with imaging of the IR laser induced fluorescence (IR-LIF) via newly available detector arrays will make such in situ measurements possible for the first time. Even under ambient terrestrial conditions, the LIF yield from vibrational excitation of species such as water and carbon dioxide should produce emission measures well in excess of ten billion photons/sec from samples volumes of order 1 c.c. These count rates can, in principle, yield detection limits into the sub-ppt range that are required for the in situ isotopic study of atmospheric trace gases. While promising, such technologies are relatively immature, but developing rapidly, and there are a great many uncertainties regarding their applicability to in situ IR-LIF planetary studies. We therefore feel PIDDP support will be critical to developing these new tools, and propose a three-year program to combine microchip near-IR lasers with low background detection axes and state-of-the-art HgCdTe detectors developed for astronomical spectroscopy to investigate the sensitivity of IR-LIF under realistic planetary conditions, to optimize the optical pumping and filtering schemes for important species, and to apply the spectrometer to the non-destructive measurement of stable isotopes in a variety of test samples. These

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

    NASA Technical Reports Server (NTRS)

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

    2009-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Elsila, Jamie

    2009-01-01

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

  18. Stable carbon and sulfur isotopes as records of the early biosphere

    NASA Technical Reports Server (NTRS)

    Desmarais, David J.

    1989-01-01

    The abundance ratios of the stable isotopes of light elements such as carbon and sulfur can differ between various naturally-occurring chemical compounds. If coexisting compounds have achieved mutual chemical and isotopic equilibrium, then the relative isotopic composition can record the conditions at which equilibrium was last maintained. If coexisting chemical compounds indeed formed simultaneously but had not achieved mutual equilibrium, then their relative isotopic compositions often reflect the conditions and mechanisms associated with the kinetically controlled reactions responsible for their production. In the context of Mars, the stable isotopic compositions of various minerals might record not only the earlier environmental conditions of the planet, but also whether or not the chemistry of life ever occurred there. Two major geochemical reservoirs occur in Earth's crust, both for carbon and sulfur. In rocks formed in low temperature sedimentary environments, the oxidized forms of these elements tend to be enriched in the isotope having the larger mass, relative to the reduced forms. In sediments where the organics and sulfides were formed by biological processes, these isotopic contrasts were caused by the processes of biological CO2 fixation and dissimilatory sulfate reduction. Such isotopic contrasts between oxidized and reduced forms of carbon and sulfur are permitted by thermodynamics at ambient temperatures. However, nonbiological chemical reactions associated with the production of organic matter and the reduction of organics and sulfides are extremely slow at ambient temperatures. Thus the synthesis of organics and sulfides under ambient conditions illustrates life's profound role as a chemical catalyst that has altered the chemistry of Earth's crust. Because the stable isotopes of carbon and sulfur can reflect their chemistry, they are useful probes of the Martian surface.

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

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

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

  20. Forward Modeling of Carbonate Proxy Data from Planktonic Foraminifera using Oxygen Isotope Tracers in a Global Ocean Model

    NASA Technical Reports Server (NTRS)

    Schmidt, Gavin A.

    1999-01-01

    The distribution and variation of oxygen isotopes in seawater are calculated using the Goddard Institute for Space Studies global ocean model. Simple ecological models are used to estimate the planktonic foraminiferal abundance as a function of depth, column temperature, season, light intensity, and density stratification. These models are combined to forward model isotopic signals recorded in calcareous ocean sediment. The sensitivity of the results to the changes in foraminiferal ecology, secondary calcification, and dissolution are also examined. Simulated present-day isotopic values for ecology relevant for multiple species compare well with core-top data. Hindcasts of sea surface temperature and salinity are made from time series of the modeled carbonate isotope values as the model climate changes. Paleoclimatic inferences from these carbonate isotope records are strongly affected by erroneous assumptions concerning the covariations of temperature, salinity, and delta (sup 18)O(sub w). Habitat-imposed biases are less important, although errors due to temperature-dependent abundances can be significant.

  1. New Carbonate Standard Reference Materials for Boron Isotope Geochemistry

    NASA Astrophysics Data System (ADS)

    Stewart, J.; Christopher, S. J.; Day, R. D.

    2015-12-01

    The isotopic composition of boron (δ11B) in marine carbonates is well established as a proxy for past ocean pH. Yet, before palaeoceanographic interpretation can be made, rigorous assessment of analytical uncertainty of δ11B data is required; particularly in light of recent interlaboratory comparison studies that reported significant measurement disagreement between laboratories [1]. Well characterised boron standard reference materials (SRMs) in a carbonate matrix are needed to assess the accuracy and precision of carbonate δ11B measurements throughout the entire procedural chemistry; from sample cleaning, to ionic separation of boron from the carbonate matrix, and final δ11B measurement by multi-collector inductively coupled plasma mass spectrometry. To date only two carbonate reference materials exist that have been value-assigned by the boron isotope measurement community [2]; JCp-1 (porites coral) and JCt-1 (Giant Clam) [3]. The National Institute of Standards and Technology (NIST) will supplement these existing standards with new solution based inorganic carbonate boron SRMs that replicate typical foraminiferal and coral B/Ca ratios and δ11B values. These new SRMs will not only ensure quality control of full procedural chemistry between laboratories, but have the added benefits of being both in abundant supply and free from any restrictions associated with shipment of biogenic samples derived from protected species. Here we present in-house δ11B measurements of these new boron carbonate SRM solutions. These preliminary data will feed into an interlaboratory comparison study to establish certified values for these new NIST SRMs. 1. Foster, G.L., et al., Chemical Geology, 2013. 358(0): p. 1-14. 2. Gutjahr, M., et al., Boron Isotope Intercomparison Project (BIIP): Development of a new carbonate standard for stable isotopic analyses. Geophysical Research Abstracts, EGU General Assembly 2014, 2014. 16(EGU2014-5028-1). 3. Inoue, M., et al., Geostandards and

  2. Aerosol carbon isotope composition over Baltic Sea

    NASA Astrophysics Data System (ADS)

    Garbaras, Andrius; Pabedinskas, Algirdas; Masalaite, Agne; Petelski, Tomasz; Gorokhova, Elena; Sapolaite, Justina; Ezerinskis, Zilvinas; Remeikis, Vidmantas

    2017-04-01

    Particulate carbonaceous matter is significant contributor to ambient particulate matter originating from intervening sources which contribution is difficult to quantify due to source diversity, chemical complexity and processes during atmospheric transport. Carbon isotope analysis can be extremely useful in source apportionment of organic matter due to the unique isotopic signatures associated with anthropocentric (fossil fuel), continental (terrestrial plants) and marine sources, and is particularly effective when these sources are mixed (Ceburnis et al., 2011;Ceburnis et al., 2016). We will present the isotope ratio measurement results of aerosol collected during the cruise in the Baltic Sea. Sampling campaign of PM10 and size segregated aerosol particles was performed on the R/V "Oceania" in October 2015. Air mass back trajectories were prevailing both from the continental and marine areas during the sampling period. The total carbon concentration varied from 1 µg/m3 to 8 µg/m3. Two end members (δ13C = -25‰ and δ13C = -28 ‰ ) were established from the total stable carbon isotope analysis in PM10 fraction. δ13C analysis in size segregated aerosol particles revealed δ13C values being highest in the 1 - 2.5 µm range (δ13C = -24.9 ‰ ) during continental transport, while lowest TC δ13C values (δ13C ≈ -27 ‰ ) were detected in the size range D50 <1 µm during stormy weather when air mass trajectory prevailed from the western direction. These measurements revealed that simplified isotope mixing model can not be applied for the aerosol source apportionment (Masalaite et al., 2015) in the perturbed marine environment. Additionally, concentration of bacteria and fungi were measured in size segregated and PM10 aerosol fraction. We were able to relate aerosol source δ13C end members with the abundance of bacteria and fungi over Baltic Sea combining air mass trajectories, stable isotope data, fungi and bacteria concentrations. Ceburnis, D., Garbaras, A

  3. Experimental Assessment of Carbon Isotopes of Light Hydrocarbons under Different Redox Conditions

    NASA Astrophysics Data System (ADS)

    Fu, Q.; Chen, X.

    2017-12-01

    Hydrocarbons can be derived from a variety of carbon sources, by different processes, and under a wide range of physicochemical conditions. Other than bacterial activities facilitating biogenic hydrocarbon formation at low temperatures, decomposition of complex organic matter in sedimentary rocks at elevated temperatures produce thermogenic hydrocarbons, whereas abiogenic hydrocarbons are mainly generated through Fischer-Tropsch type synthesis with mineral catalysts. The carbon isotope has been used extensively to distinguish hydrocarbons of different origins and their formation conditions. For each type of hydrocarbons, however, environmental conditions may change reaction pathways and corresponding isotope fractionations. To better understand the variation of carbon isotopes caused by environmental variables, mineral constraints in particular, a series of laboratory experiments are conducted. In experiments where thermogenic hydrocarbons are formed, oil shale is the source material with different gypsum contents (0, 0.3, 0.5, and 1 wt.%). The abundance of generated light straight chain hydrocarbons decreases with increasing gypsum content, but their carbon isotopes become heavier. For example, the δ13C value of methane increases from -55.1‰ to -41.4‰ with gypsum varying between 0 and 1 wt.%. In similar experiments with the presence of MnO2, carbon isotope values of light alkanes are also higher, but with limited magnitudes (e.g., 3 to 4‰ for methane). In another experiment with dissolved H2 gas of 100 mmol/kg, light alkanes become depleted in 13C than experiments without H2. For example, there is a depletion of 2.7‰ for methane. The variation of carbon isotope values of light alkanes suggests the redox condition, constrained by mineral assemblage, fluid composition, and physical environment, play an important role in isotope fractionation. The pathway of hydrocarbon generation may be different under oxidized or reducing conditions. A set of experiments

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

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    McConnaughey, T.A.

    1986-01-01

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

  5. Bringing organic carbon isotopes and phytoliths to the table as additional constraints on paleoelevation

    NASA Astrophysics Data System (ADS)

    Sheldon, N. D.; Cotton, J. M.; Hren, M. T.; Hyland, E. G.; Smith, S. Y.; Strömberg, C. A. E.

    2015-12-01

    A commonly used tool in paleotectonic and paleoaltimetry studies is the oxygen isotopic composition of authigenic carbonates formed that formed in lakes or soils, with both spatial (e.g., shoreline to mountain top) or temporally resolved records potentially providing constraints. However, in many cases there is a substantial spread in the oxygen isotope data for a given time period, often to the point of allowing for essentially any interpretation of the data depending upon how they have been used by the investigator. One potential way of distinguishing between different potential paleotectonic or paleoaltimetric interpretations is to use carbon isotope and plant microfossil (phytolith) analyses from the same paleosols to screen the oxygen isotope data by looking for evidence of evaporative enrichment. For example, if both inorganic (carbonate) and organic carbon isotopes are measured from the same paleosol, then in it possible to determine if the two isotope record equilibrium conditions or if they record disequilibrium driven by kinetic effects. In the former case, the oxygen isotope results can be considered reliable whereas in the latter case, the oxygen isotope results can be considered unreliable and could be culled from the interpretation. Similarly, because the distribution of C4 plants varies as a function of temperature and elevation, the presence/absence or abundance of C4 plant phytoliths, or of carbon isotope compositions that require a component of C4 vegetation can also be used to constrain paleoelevation by providing a maximum elevation constraint. Worked examples will include the late Miocene-Pliocene of Catamarca, Argentina, where phytoliths and organic carbon isotopes provide a maximum elevation constraint and can be used to demonstrate that oxygen isotopes do not provide a locally useful constraint on paleoelevation, and Eocene-Miocene of southwestern Montana where organic matter and phytoliths can be used to select between different potential

  6. Helium and Carbon Isotope and Relative Abundance Relationships in Lau Basin Basalts: Resolving Mantle Source Composition from Degassing and Contamination Effects

    NASA Astrophysics Data System (ADS)

    Vukajlovich, D. J.; Hilton, D. R.; Castillo, P. R.; Hawkins, J. W.

    2005-12-01

    The Lau Basin has multiple mantle source components including contributions from the Indian and Pacific MORB sources, Tonga-Kermadec Arc and Samoan plume. In order to characterize the volatile systematics of these various sources and to map their spatial distribution, we have sampled basaltic glasses from over 50 dredge sites covering all known spreading centers in the basin as well as many off-axis seamounts. Here, we report He abundance and isotope results obtained by crushing, in addition to CO2 released through stepped heating, from sites at the Mangatolu Triple Junction (MTJ), Rochambeau Bank (RB), Peggy Ridge, and the Northern, Eastern and Central Lau Spreading Centers. High 3He/4He ratios from RB (up to 23 RA, where RA = air 3He/4He) confirm the presence of a plume component in the northwestern Lau Basin (Poreda, EPSL, 1985). Central and Eastern Lau Spreading Center basalts have 3He/4He ratios between 8.3 and 9.4 RA, consistent with a depleted, MORB-like mantle source with little influence from slab or crustal helium. In contrast, the large range in helium isotope ratios of MTJ samples (0.85 to 7.9 RA) and the correlation between low He abundances (~2 - 3 × 10-9 cm3/g) and low helium isotope ratios suggests the volatiles in this region have been severely affected by degassing and additions of radiogenic (crustal) He. CO2 abundances and carbon isotopes for samples from RB vary from 70 to 119 ppm ([CO2]total) with δ13Cvesicle falling between -12.3 to -14.8 ‰ and δ13Cdissolved lying between -9.3 to -10.7 ‰. In the MTJ, low helium concentration samples have δ13C as low as -27.4 ‰ and [CO2]total as low as 7.6ppm; interestingly, this region also has samples with the highest measured values (up to -6.3 ‰ and 132ppm total C). Combining the carbon and helium data, CO2/3He ratios in the MTJ range from arc-like values (~1010) to sediment or crustal values (~1013) showing the superimposition of degassing and/or contamination effects on a predominant slab

  7. What Drives Carbon Isotope Fractionation by the Terrestrial Biosphere?

    NASA Astrophysics Data System (ADS)

    Still, Christopher; Rastogi, Bharat

    2017-11-01

    During photosynthesis, terrestrial plants preferentially assimilate the lighter and much more abundant form of carbon, 12C, which accounts for roughly 99% of naturally occurring forms of this element. This photosynthetic preference for lighter carbon is driven principally by differences in molecular diffusion of carbon dioxide with differing 13C/12C across stomatal pores on leaves, followed by differences in carboxylation rates by the Rubisco enzyme that is central to the process of photosynthesis. As a result of these slight preferences, which work out to about a 2% difference in the fixation rates of 12CO2 versus 13CO2 by C3 vegetation, plant tissues are depleted in the heavier form of carbon (13C) relative to atmospheric CO2. This difference has been exploited in a wide range of scientific applications, as the photosynthetic isotope signature is passed to ecosystem carbon pools and through ecological food webs. What is less appreciated is the signature that terrestrial carbon exchanges leave on atmospheric CO2, as the net uptake of carbon by land plants during their growing season not only draws down the local CO2 concentration, it also leaves behind relatively more CO2 molecules containing 13C. The converse happens outside the growing season, when autotrophic and heterotrophic respiration predominate. During these periods, atmospheric CO2 concentration increases and its corresponding carbon isotope composition becomes relatively depleted in 13C as the products of photosynthesis are respired, along with some small isotope fractionation that happen downstream of the initial photosynthetic assimilation. Similar phenomena were first observed at shorter time scales by the eminent carbon cycle scientist, Charles (Dave) Keeling. Keeling collected samples of air in glass flasks from sites along the Big Sur coast that he later measured for CO2 concentration and carbon isotope composition (δ13C) in his lab (Keeling, 1998). From these samples, Keeling observed increasing

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

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

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

  9. Abundance and isotope systematics of carbon in subglacial basalts, geothermal gases and fluids from Iceland's rift zones

    NASA Astrophysics Data System (ADS)

    Barry, P. H.; Hilton, D. R.; Fueri, E.; Halldorsson, S. A.; Fischer, T. P.; Gronvold, K.

    2010-12-01

    P. H. BARRY1*, D. R. HILTON1, E. FÜRI1, S.A. HALLDÓRSON1, T.P. FISCHER2, K. GRONVOLD3 1 Scripps Institution of Oceanography, UCSD, La Jolla, California 92093, USA (*Correspondence: pbarry@ucsd.edu). 2University of New Mexico, Albuquerque, NM 87131, USA. 3University of Iceland, Askja, Sturlugata 7, IS-101, Reykjavik, Iceland Carbon dioxide (CO2) is the dominant non-aqueous volatile species found in oceanic basalts and geothermal fluids and serves as the carrier gas for trace volatiles such as He and other noble gases. The aim of this study is to identify the superimposed effects of degassing and crustal contamination on the CO2 systematics of the Icelandic hotspot in order to reveal and characterize the carbon abundance and isotopic features of the underlying mantle source. Our approach involves coupling CO2 with He, utilizing the sensitivity of 3He/4He ratios to reveal mantle and crustal inputs. We report new C-isotope (δ13C) and abundance characteristics for a suite of 47 subglacial basalts and 50 geothermal gases and fluids from Iceland. CO2 contents in hyaloclastite glasses are extremely low (10-100 ppm) and likely residual following extensive degassing whereas geothermal fluids are dominated by CO2 (>90 %). C-isotopes range from -27.2 to -3.6 ‰ (vs. PDB) for basalts and from -18.8 to 2.86 ‰ (vs. PDB) for geothermal samples (mean = -4.2 ± 3.6 ‰). CO2/3He ratios range from 108 to 1012 for basalts and from 105 to 1012 for geothermal samples: In both cases, our results extend He-CO2 relationships over a much broader range than reported previously [1]. Taken together, these data suggest that several processes including mixing, degassing, and/or syn- or post-eruptive crustal contamination may act to modify CO2 source characteristics. Equilibrium degassing models are compatible with ~75 % of the basalt data, and preliminary results indicate that initial Icelandic source characteristics are ~500 ppm CO2 and δ13C ~ -5 ‰ (vs. PDB). These values are high

  10. The Carbon Isotope Ratio in Local Molecular Clouds

    NASA Astrophysics Data System (ADS)

    Goto, Miwa; Usuda, Tomonori; Takato, Naruhisa; Masahiko, Hayashi; Sakamoto, Seiichi; Mitchell, George

    We report the carbon isotope ratio in nearby molecular clouds LkHα 101, AFGL 490, and Mon R2 IRS 3. The vibrational transition bands of 12CO ν = 2 ← 0 and 13CO ν = 1 ← 0 were observed with high resolution near-infrared spectroscopy (R = 23,000) to measure the relative abundance of 13CO to 12CO. The isotopic ratios are 12CO/13CO = 1379 (LkHα 101), 8649 (AFGL 490), and 158 (Mon R2 IRS 3), which is twice higher than in the solar neighborhood. The molecular clouds are with high visible extinction (AV = 10 70 mag), well shielded from destructive FUV field. It is questionable that the selective photo-destruction of 13CO plays a major role in biasing isotope ratio. Uncertainty in the Doppler parameters of the unresolved absorption lines, and possible emission filling of fundamental transitions are suspected to account for the high 12CO/13CO ratio. Higher resolution spectroscopy (R ~ 100,000) is the key to go for the accurate measurement of isotope ratio.

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

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Vengosh, A.; Chivas, A.R.; McCulloch, M.T.

    1991-10-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

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

  13. Carbon isotopes in biological carbonates: Respiration and photosynthesis

    USGS Publications Warehouse

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

    1997-01-01

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

  14. Carbon isotopes in biological carbonates: Respiration and photosynthesis

    NASA Astrophysics Data System (ADS)

    McConnaughey, Ted A.; Burdett, Jim; Whelan, Joseph F.; Paull, Charles K.

    1997-02-01

    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 CO 2/O 2 ratios appear to be the major controlling variable. Atmospheric CO 2/O 2 ratios are about thirty times lower than in most natural waters, hence air breathing animals absorb less environmental CO 2 in the course of obtaining 0 2. Tissue CO 2 therefore, does not isotopically equilibrate with environmental CO 2 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 CO 2 in their tissues. Photosynthetic corals calcify mainly during the daytime when photosynthetic CO 2 uptake is several times faster than respiratory CO 2 release. Photosynthesis, therefore, affects skeletal δ13C 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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  16. Abundant carbon in the mantle beneath Hawai`i

    USGS Publications Warehouse

    Anderson, Kyle R.; Poland, Michael

    2017-01-01

    Estimates of carbon concentrations in Earth’s mantle vary over more than an order of magnitude, hindering our ability to understand mantle structure and mineralogy, partial melting, and the carbon cycle. CO2 concentrations in mantle-derived magmas supplying hotspot ocean island volcanoes yield our most direct constraints on mantle carbon, but are extensively modified by degassing during ascent. Here we show that undegassed magmatic and mantle carbon concentrations may be estimated in a Bayesian framework using diverse geologic information at an ocean island volcano. Our CO2 concentration estimates do not rely upon complex degassing models, geochemical tracer elements, assumed magma supply rates, or rare undegassed rock samples. Rather, we couple volcanic CO2 emission rates with probabilistic magma supply rates, which are obtained indirectly from magma storage and eruption rates. We estimate that the CO2content of mantle-derived magma supplying Hawai‘i’s active volcanoes is 0.97−0.19+0.25 wt%—roughly 40% higher than previously believed—and is supplied from a mantle source region with a carbon concentration of 263−62+81 ppm. Our results suggest that mantle plumes and ocean island basalts are carbon-rich. Our data also shed light on helium isotope abundances, CO2/Nb ratios, and may imply higher CO2 emission rates from ocean island volcanoes.

  17. Abundant carbon in the mantle beneath Hawai`i

    NASA Astrophysics Data System (ADS)

    Anderson, Kyle R.; Poland, Michael P.

    2017-09-01

    Estimates of carbon concentrations in Earth’s mantle vary over more than an order of magnitude, hindering our ability to understand mantle structure and mineralogy, partial melting, and the carbon cycle. CO2 concentrations in mantle-derived magmas supplying hotspot ocean island volcanoes yield our most direct constraints on mantle carbon, but are extensively modified by degassing during ascent. Here we show that undegassed magmatic and mantle carbon concentrations may be estimated in a Bayesian framework using diverse geologic information at an ocean island volcano. Our CO2 concentration estimates do not rely upon complex degassing models, geochemical tracer elements, assumed magma supply rates, or rare undegassed rock samples. Rather, we couple volcanic CO2 emission rates with probabilistic magma supply rates, which are obtained indirectly from magma storage and eruption rates. We estimate that the CO2 content of mantle-derived magma supplying Hawai`i’s active volcanoes is 0.97-0.19+0.25 wt%--roughly 40% higher than previously believed--and is supplied from a mantle source region with a carbon concentration of 263-62+81 ppm. Our results suggest that mantle plumes and ocean island basalts are carbon-rich. Our data also shed light on helium isotope abundances, CO2/Nb ratios, and may imply higher CO2 emission rates from ocean island volcanoes.

  18. Variability in the carbon isotope composition of individual amino acids in plant proteins from different sources: 1 Leaves.

    PubMed

    Lynch, Anthony H; Kruger, Nicholas J; Hedges, Robert E M; McCullagh, James S O

    2016-05-01

    The natural carbon isotope composition of individual amino acids from plant leaf proteins has been measured to establish potential sources of variability. The plant leaves studied, taken from a range of plant groups (forbs, trees, grasses, and freshwater aquatic plants), showed no significant influence of either season or environment (water and light availability) on their Δδ(13)C values. Plant groups did, however, differ in carbon isotope composition, although no consistent differences were identified at the species level. A discriminant analysis model was constructed which allowed leaves from (1) nettles, (2) Pooideae, (3) other Poales, (4) trees and (5) freshwater higher plants to be distinguished from each other on the basis of their natural abundance (13)C/(12)C ratios of individual amino acids. Differences in carbon isotope composition are known to be retained, to some extent, in the tissues of their consumers, and hence an understanding of compound-specific variation in (13)C/(12)C fractional abundance in plants has the potential to provide dietary insights of value in archaeological and ecological studies. Copyright © 2016 Elsevier Ltd. All rights reserved.

  19. A Modern Analogue for Proterozoic Inverse Carbon Isotope Signatures

    NASA Astrophysics Data System (ADS)

    Close, H. G.; Diefendorf, A. F.; Freeman, K. H.; Pearson, A.

    2008-12-01

    The carbon isotope distribution preserved in sedimentary lipids changes near the Neoproterozoic-Cambrian boundary. In older samples, n-alkyl lipids contain more 13C than both isoprenoid lipids and kerogen [1]. In younger samples, the opposite prevails. Although extreme heterotrophy has been invoked as a mechanism to explain the enrichment in 13C [2], here we suggest another explanation. The switch may reflect a fundamental transition from an oligotrophic ocean dominated by prokaryotic biomass, to an ocean in which carbon fixation is more intensive and burial is dominated by eukaryotic biomass. An analogue for Proterozoic ordering is found in the modern, oligotrophic Pacific Ocean, where n-alkyl lipids of picoplankton (0.2-0.5 μm particulate matter) contain excess 13C relative to the same lipids found in larger size classes (> 0.5 μm). Picoplanktonic lipids are heavier isotopically (-18 ‰) than both the sterols of eukaryotes (-23 ‰ to -26 ‰) and the total organic matter (-20 ‰; TOM). The 0.2-0.5 μm size class also has a distinct chain-length abundance profile. Although large particles must be the vehicle for total carbon export, paradoxically the lipid component of export production appears to be dominated by the 0.2-0.5 μm source. The picoplanktonic chain lengths and isotopic composition dominate lipids of TOM at 670 meters. When the ratio of prokaryotic to eukaryotic production is high, as in the modern central Pacific Ocean, it appears that exported material has an inverse carbon isotope signature similar to that preserved in Precambrian samples. [1] Logan, G. A. et al., Nature 376:53-56 (1995). [2] Rothman, D. H. et al., PNAS 100:8124-8129 (2003).

  20. The carbon isotopic composition of ecosystem breath

    NASA Astrophysics Data System (ADS)

    Ehleringer, J.

    2008-05-01

    At the global scale, there are repeatable annual fluctuations in the concentration and isotopic composition of atmospheric carbon dioxide, sometimes referred to as the "breathing of the planet". Vegetation components within ecosystems fix carbon dioxide through photosynthesis into stable organic compounds; simultaneously both vegetation and heterotrophic components of the ecosystem release previously fixed carbon as respiration. These two-way fluxes influencing carbon dioxide exchange between the biosphere and the atmosphere impact both the concentration and isotopic composition of carbon dioxide within the convective boundary layer. Over space, the compounding effects of gas exchange activities from ecosystems become reflected in both regional and global changes in the concentration and isotopic composition of atmospheric carbon dioxide. When these two parameters are plotted against each other, there are significant linear relationships between the carbon isotopic composition and inverse concentration of atmospheric carbon dioxide. At the ecosystem scale, these "Keeling plots" intercepts of C3-dominated ecosystems describe the carbon isotope ratio of biospheric gas exchange. Using Farquhar's model, these carbon isotope values can be translated into quantitative measures of the drought-dependent control of photosynthesis by stomata as water availability changes through time. This approach is useful in aggregating the influences of drought across regional landscapes as it provides a quantitative measure of stomatal influence on photosynthetic gas exchange at the ecosystem-to-region scales. Multi-year analyses of the drought-dependent trends across terrestrial ecosystems show a repeated pattern with water stress in all but one C3-ecosystem type. Ecosystems that are dominated by ring-porous trees appear not to exhibit a dynamic stomatal response to water stress and therefore, there is little dependence of the carbon isotope ratio of gas exchange on site water balance

  1. Changing carbon isotope ratio of atmospheric carbon dioxide: implications for food authentication.

    PubMed

    Peck, William H; Tubman, Stephanie C

    2010-02-24

    Carbon isotopes are often used to detect the addition of foreign sugars to foods. This technique takes advantage of the natural difference in carbon isotope ratio between C(3) and C(4) plants. Many foods are derived from C(3) plants, but the low-cost sweeteners corn and sugar cane are C(4) plants. Most adulteration studies do not take into account the secular shift of the carbon isotope ratio of atmospheric carbon dioxide caused by fossil fuel burning, a shift also seen in plant tissues. As a result statistical tests and threshold values that evaluate authenticity of foods based on carbon isotope ratios may need to be corrected for changing atmospheric isotope values. Literature and new data show that the atmospheric trend in carbon isotopes is seen in a 36-year data set of maple syrup analyses (n = 246), demonstrating that published thresholds for cane or corn sugar adulteration in maple syrup (and other foods) have become progressively more lenient over time.

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

    USGS Publications Warehouse

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

    2006-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Boehme, Susan E.

    1993-01-01

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

  4. Site-Specific Carbon Isotopes in Organics

    NASA Astrophysics Data System (ADS)

    Piasecki, A.; Eiler, J. M.

    2012-12-01

    Natural organic molecules exhibit a wide range of internal site-specific isotope variation (i.e., molecules with same isotopic substitution type but different site). Such variations are generally unconstrained by bulk isotopic measurements. If known, site-specific variations might constrain temperatures of equilibrium, mechanisms of formation or consumption reactions, and possibly other details. For example, lipids can exhibit carbon isotope differences of up to 30‰ between adjacent carbon sites as a result of fractionations arising during decarboxylation of pyruvate and other steps in lipid biosynthesis(1). We present a method for site-specific carbon isotope analysis of propane, based on high-resolution, multi-collector gas source mass spectrometry, using a novel prototype instrument - the Thermo MAT 253 Ultra. This machine has an inlet system and electron bombardment ion source resembling those in conventional stable isotope gas source mass spectrometers, and the energy filter, magnet, and detector array resembling those in multi-collector ICPMS and TIMS. The detector array has 7 detector positions, 6 of which are movable, and each of which can collect ions with either a faraday cup (read through amplifiers ranging from 107-1012 ohms) or an SEM. High mass resolving power (up to 27,000, MRP = M/dM definition) is achieved through a narrow entrance slit, adjustable from 250 to 5 μm. Such resolution can cleanly separate isobaric interferences between isotopologues of organic molecules having the same cardinal mass (e.g., 13CH3 and 12CH2D). We use this technology to analyze the isotopologues and fragments of propane, and use such data to solve for the site-specific carbon isotope fractionation. By measuring isotopologues of both the one-carbon (13CH3) and the two-carbon (13C12CH4) fragment ion, we can solve for both bulk δ13C and the difference in δ13C between the terminal and central carbon position. We tested this method by analyzing mixtures between natural

  5. Evaluating microbial carbon sources in Athabasca oil sands tailings ponds using natural abundance stable and radiocarbon isotopes

    NASA Astrophysics Data System (ADS)

    Ahad, J. M.; Pakdel, H.

    2013-12-01

    Natural abundance stable (δ13C) and radiocarbon (Δ14C) isotopes of phospholipid fatty acids (PLFAs) were used to evaluate the carbon sources utilized by the active microbial populations in surface sediments from Athabasca oil sands tailings ponds. The absence of algal-specific PLFAs at three of the four sites investigated, in conjunction with δ13C signatures for PLFAs that were generally within ~3‰ of that reported for oil sands bitumen (~ -30‰), indicated that the microbial communities growing on petroleum constituents were dominated by aerobic heterotrophs. The Δ14C values of PLFAs ranged from -906 to -586‰ and pointed to a significant uptake of fossil carbon (up to ~90% of microbial carbon derived from petroleum), particularly in PLFAs (e.g., cy17:0 and cy19:0) often associated with petroleum hydrocarbon degrading bacteria. The comparatively higher levels of 14C in other, less specific PLFAs (e.g., 16:0) indicated the preferential uptake of younger organic matter by the general microbial population (~50-80% of microbial carbon derived from petroleum). Since the main carbon pools in tailings sediment were essentially 'radiocarbon dead' (i.e., no detectable 14C), the principal source for this modern carbon is considered to be the Athabasca River, which provides the bulk of the water used in the bitumen extraction process. The preferential uptake of the minor amount of young and presumably more biodegradable material present in systems otherwise dominated by recalcitrant petroleum constituents has important implications for remediation strategies. On the one hand, it implies that mining-related organic contaminants could persist in the environment long after tailings pond reclamation has begun. Alternatively, it may be that the young, labile organic matter provided by the Athabasca River plays an important role in stimulating or supporting the microbial utilization of petroleum carbon in oil sands tailings ponds via co-metabolism or priming processes

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

    NASA Technical Reports Server (NTRS)

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

    1983-01-01

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

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

    USDA-ARS?s Scientific Manuscript database

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

  8. Abundance, stable isotopic composition, and export fluxes of DOC, POC, and DIC from the Lower Mississippi River during 2006–2008

    USGS Publications Warehouse

    Cai, Yihua; Guo, Laodong; Wang, Xuri; Aiken, George R.

    2015-01-01

    Sources, abundance, isotopic compositions, and export fluxes of dissolved inorganic carbon (DIC), dissolved and colloidal organic carbon (DOC and COC), and particulate organic carbon (POC), and their response to hydrologic regimes were examined through monthly sampling from the Lower Mississippi River during 2006–2008. DIC was the most abundant carbon species, followed by POC and DOC. Concentration and δ13C of DIC decreased with increasing river discharge, while those of DOC remained fairly stable. COC comprised 61 ± 3% of the bulk DOC with similar δ13C abundances but higher percentages of hydrophobic organic acids than DOC, suggesting its aromatic and diagenetically younger status. POC showed peak concentrations during medium flooding events and at the rising limb of large flooding events. While δ13C-POC increased, δ15N of particulate nitrogen decreased with increasing discharge. Overall, the differences in δ13C between DOC or DIC and POC show an inverse correlation with river discharge. The higher input of soil organic matter and respired CO2 during wet seasons was likely the main driver for the convergence of δ13C between DIC and DOC or POC, whereas enhanced in situ primary production and respiration during dry seasons might be responsible for their isotopic divergence. Carbon export fluxes from the Mississippi River were estimated to be 13.6 Tg C yr−1 for DIC, 1.88 Tg C yr−1 for DOC, and 2.30 Tg C yr−1 for POC during 2006–2008. The discharge-normalized DIC yield decreased during wet seasons, while those of POC and DOC increased and remained constant, respectively, implying variable responses in carbon export to the increasing discharge.

  9. Carbon isotope effects associated with autotrophic acetogenesis

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Lauretta, D. S.

    2004-01-01

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

  11. Stable Carbon Isotope Ratios of Individual Pollen Grains as a Proxy for C3- Versus C4-Grass Abundance in Paleorecords: A Validation Study

    NASA Astrophysics Data System (ADS)

    Nelson, D. M.; Hu, F.; Pearson, A.

    2007-12-01

    C3 and C4 grasses have distinct influences on major biogeochemical processes and unique responses to important environmental controls. Difficulties in distinguishing between these two functional groups of grasses have hindered paleoecological studies of grass-dominated ecosystems. We recently developed a technique to analyze the stable carbon isotope composition of individual grass-pollen grains using a spooling- wire microcombustion device interfaced with an isotope-ratio mass spectrometer (Nelson et al. 2007). This technique holds promise for improving C3 and C4 grass reconstructions. It requires ~90% fewer grains than typical methods and avoids assumptions associated with mixing models. However, our previous work was based on known C3 and C4 grasses from herbarium specimens and field collections and the technique had not been test using geological samples. To test the ability of this technique to reproduce the abundance of C3 and C4 grasses on the landscape, we measured δ13C values of >1500 individual grains of grass pollen isolated from the surface sediments of 10 North American lakes that span a large gradient of C3 and C4 grass abundance. Results indicate a strong positive correlation (r=0.94) between % C4-grass pollen (derived from classifying δ13C values from single grains as C3 and C4) and the literature-reported abundance of C4 grasses on the landscape. However, the measured % C4-grass pollen shows some deviation from the actual abundance at sites with high proportions of C4 grasses. This is likely caused by uncertainty in the magnitude, composition, and variability of the analytical blank associated with these measurements. Correcting for this deviation using regression analysis improves the estimation of the abundance of C4 grasses on the landscape. Comparison of the % C4-grass pollen with C/N and δ13C measurements of total organic matter in the same lake-sediment samples illustrates the distinct advantage of grass-pollen δ13C as a proxy for

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

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

    Amino sugars are quantitatively significant constituents of soil and marine sediment, but their sources and turnover in environmental samples remain poorly understood. The stable carbon isotopic composition of amino sugars can provide information on the lifestyles of their source organisms and can be monitored during incubations with labeled substrates to estimate the turnover rates of microbial populations. However, until now, such investigation has been carried out only with soil samples, partly because of the much lower abundance of amino sugars in marine environments. We therefore optimized a procedure for compound-specific isotopic analysis of amino sugars in marine sediment employing gas chromatography-isotope ratio mass spectrometry. The whole procedure consisted of hydrolysis, neutralization, enrichment, and derivatization of amino sugars. Except for the derivatization step, the protocol introduced negligible isotopic fractionation, and the minimum requirement of amino sugar for isotopic analysis was 20 ng, i.e. equivalent to ~ 8 ng of amino sugar carbon. Our results obtained from δ13C analysis of amino sugars in selected marine sediment samples showed that muramic acid had isotopic imprints from indigenous bacterial activities, whereas glucosamine and galactosamine were mainly derived from organic detritus. The analysis of stable carbon isotopic compositions of amino sugars opens a promising window for the investigation of microbial metabolisms in marine sediments and the deep marine biosphere.

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

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

    Amino sugars are quantitatively significant constituents of soil and marine sediment, but their sources and turnover in environmental samples remain poorly understood. The stable carbon isotopic composition of amino sugars can provide information on the lifestyles of their source organisms and can be monitored during incubations with labeled substrates to estimate the turnover rates of microbial populations. However, until now, such investigation has been carried out only with soil samples, partly because of the much lower abundance of amino sugars in marine environments. We therefore optimized a procedure for compound-specific isotopic analysis of amino sugars in marine sediment, employing gas chromatography-isotope ratio mass spectrometry. The whole procedure consisted of hydrolysis, neutralization, enrichment, and derivatization of amino sugars. Except for the derivatization step, the protocol introduced negligible isotopic fractionation, and the minimum requirement of amino sugar for isotopic analysis was 20 ng, i.e., equivalent to ~8 ng of amino sugar carbon. Compound-specific stable carbon isotopic analysis of amino sugars obtained from marine sediment extracts indicated that glucosamine and galactosamine were mainly derived from organic detritus, whereas muramic acid showed isotopic imprints from indigenous bacterial activities. The δ13C analysis of amino sugars provides a valuable addition to the biomarker-based characterization of microbial metabolism in the deep marine biosphere, which so far has been lipid oriented and biased towards the detection of archaeal signals.

  14. Tracking Movement of Plant Carbon Through Soil to Water by Lignin Phenol Stable Carbon Isotope Composition in a Small Agricultural Watershed

    NASA Astrophysics Data System (ADS)

    Crooker, K.; Filley, T.; Six, J.; Frey, J.

    2005-12-01

    Few studies integrate land cover, soil physical structure, and aquatic physical fractions when investigating the fate of agricultural carbon in watersheds. In crop systems that involve rotations of soy (a C3 plant) and corn (a C4 plant) the large intrinsic differences in stable carbon isotope values and lignin plus cutin chemistry enable tracking of plant carbon movement from soil fractions to DOM and overland flow during precipitation events. In a small (~3Km2) agricultural basin in central Indiana, we studied plant carbon dynamics in a soy/corn agricultural rotation (2004-2005) to determine the relative inputs of these two plants to soil fractions and the resultant contributions to dissolved, colloidal, and particulate organic matter when mobilized. Using bulk isotope values the fraction of carbon derived from corn in macroaggregates (>250 micron), microaggregates (53-250 mm), and silts plus clays (<53 mm) ranged from 39, 49, to 42%, respectively. Unlike bulk analyses, compound specific isotope analysis of lignin in the soil fractions revealed a wide range of relative inputs among the monomers with cinnamyl phenols being almost exclusively (~ 93%) derived from corn. Syringyl phenols ranged from 75-56% corn and vanillyl phenols ranged from 37-40% corn carbon. The relative input among the fractions mirrors closely the comparative plant chemistry abundances between soy and corn. During export of DOM from the land to the stream the relative abundance of plant source varied with discharge (0.05-1.8 m3/sec) as increases in flow increased the relative export of corn-derived C from the fields. Over the full range of flows lignin phenols varied from 0.05 to 82% corn-derived with the greatest relative corn input for cinnamyl and syringyl carbon. The trend with stream discharge indicates a progressive movement of particulate corn residues with overland flow. Ongoing studies look to resolve contributions of algae, bacteria and terrestrial plants to soil fractions and their

  15. Carbon isotopic patterns of amino acids associated with various microbial metabolic pathways and physiological conditions

    NASA Astrophysics Data System (ADS)

    Wang, P. L.; Hsiao, K. T.; Lin, L. H.

    2017-12-01

    Amino acids represent one of the most important categories of biomolecule. Their abundance and isotopic patterns have been broadly used to address issues related to biochemical processes and elemental cycling in natural environments. Previous studies have shown that various carbon assimilative pathways of microorganisms (e.g. autotrophy, heterotrophy and acetotrophy) could be distinguished by carbon isotopic patterns of amino acids. However, the taxonomic and catabolic coverage are limited in previous examination. This study aims to uncover the carbon isotopic patterns of amino acids for microorganisms remaining uncharacterized but bearing biogeochemical and ecological significance in anoxic environments. To fulfill the purpose, two anaerobic strains were isolated from riverine wetland and mud volcano in Taiwan. One strain is a sulfate reducing bacterium (related to Desulfovibrio marrakechensis), which is capable of utilizing either H2 or lactate, and the other is a methanogen (related to Methanolobus profundi), which grows solely with methyl-group compounds. Carbon isotope analyses of amino acids were performed on cells grown in exponential and stationary phase. The isotopic patterns were similar for all examined cultures, showing successive 13C depletion along synthetic pathways. No significant difference was observed for the methanogen and lactate-utilizing sulfate reducer harvested in exponential and stationary phases. In contrast, the H2-utilizing sulfate reducer harvested in stationary phase depleted and enriched 13C in aspartic acid and glycine, respectively when compared with that harvested in exponential phase. Such variations might infer the change of carbon flux during synthesis of these two amino acids in the reverse TCA cycle. In addition, the discriminant function analysis for all available data from culture studies further attests the capability of using carbon isotope patterns of amino acids in identifying microbial metabolisms.

  16. Preservation of carbonate clumped isotopes in sedimentary paleoclimate archives

    NASA Astrophysics Data System (ADS)

    Henkes, G. A.; Passey, B. H.; Grossman, E. L.; Shenton, B.; Perez-Huerta, A.

    2014-12-01

    Carbonate clumped isotope thermometry is increasingly used to reconstruct paleotemperatures of ancient terrestrial environments. One promising application is elucidating paleoelevation from carbonate archives such as paleosols, lacustrine marls, and fossil freshwater shells. Unlike conventional stable isotope approaches (e.g., mineral δ18O or δD), clumped isotope thermometry is independent of the isotopic composition of the precipitating waters and can therefore be used to reconstruct elevation by both the temperature-altitude relationship and the rainfall δ18O-altitude relationship. However, interpretation of clumped isotope data is not without its own complications. Like conventional stable isotopes, clumped isotope paleotemperatures can be effectively reset to warmer values by dissolution/reprecipitation-type diagenesis during sedimentary burial. It is also known that carbonate clumped isotope bonds (i.e., 13C-18O) are susceptible to 'reordering' in the solid mineral lattice at warmer burial temperatures, with laboratory studies of natural carbonates indicating activation of this phenomenon at temperatures as low as 100 °C over geologic timescales. A challenge in applying carbonate clumped isotope thermometry to natural samples is now evaluating terrestrial archives with respect to both types of alteration: 'open-system' alteration and 'closed-system' bond reordering. In this talk we will review our experimental efforts to constrain the kinetics of clumped isotope reordering, with relevance to low-temperature carbonates like fossil shells and early diagenetic minerals, and present new laboratory data that further inform our theoretical framework for the mechanism(s) of 13C-18O bond reordering. Together with traditional analytical and petrographic screening for recrystallization, empirical and laboratory studies of carbonate clumped isotope reordering represent the next steps in evaluating isotopic records of paleoclimate, paleobiology, and paleoelevation

  17. The Importance of CO2 Utilizing Chemolithoautotrophic Microorganisms for Carbon Sequestration and Isotope Signatures of SOM in Tropical Rainforest Soils

    NASA Astrophysics Data System (ADS)

    Nowak, M. E.; Behrendt, T.; Quesada, B.; Yanez Serrano, A. M.; Trumbore, S.

    2015-12-01

    Soil organic matter (SOM) is a major compartment of the tropical carbon cycle with up to 26 % of global carbon stocks stored in tropical soils. Understanding factors and processes driving SOM dynamics under changing climate conditions is crucial for predicting the role of tropical forest ecosystems to act as a carbon sink or source. Soil microorganisms are major drivers of the belowground carbon cycle by releasing CO2 by soil respiration but also by stabilizing and storing SOM, as indicated by recent research. Our investigations focus on chemolithoautotrophic microorganisms, a group that relies on CO2 as their carbon source. Chemolithoautotrophic microorganisms have been shown to be highly abundant in soils, whereas their role in SOM sequestration is still poorly understood. In tropical soils, the activity of chemolithoautotropic microbes might be important for generating and stabilizing carbon, especially in the deeper soil, which is rich in CO2 and reduced energy sources like Fe2+. They further might impact carbon isotope signatures (13C and 14C) of SOM, because of enzymatic fractionation during carboxylation and the use of carbon, which has a distinct isotopic composition than other carbon sources at the same depth. In order to study the activity of chemolithoautotropic microbes and their importance for SOM, we conducted isotope and isotope-labelling studies, gas measurements as well as molecular analyses at soils from the Atto site from 0 to 1 meter depth. These soils are classified as Ferralsols and Alisols and represent the most abundant soil types in the Amazon. With this we will be able to gain knowledge about the function and identity of an important group of microorganisms and their contribution to crucial biogeochemical cycles in the world`s most important ecosystem.

  18. Measurement of isotope abundance variations in nature by gravimetric spiking isotope dilution analysis (GS-IDA).

    PubMed

    Chew, Gina; Walczyk, Thomas

    2013-04-02

    Subtle variations in the isotopic composition of elements carry unique information about physical and chemical processes in nature and are now exploited widely in diverse areas of research. Reliable measurement of natural isotope abundance variations is among the biggest challenges in inorganic mass spectrometry as they are highly sensitive to methodological bias. For decades, double spiking of the sample with a mix of two stable isotopes has been considered the reference technique for measuring such variations both by multicollector-inductively coupled plasma mass spectrometry (MC-ICPMS) and multicollector-thermal ionization mass spectrometry (MC-TIMS). However, this technique can only be applied to elements having at least four stable isotopes. Here we present a novel approach that requires measurement of three isotope signals only and which is more robust than the conventional double spiking technique. This became possible by gravimetric mixing of the sample with an isotopic spike in different proportions and by applying principles of isotope dilution for data analysis (GS-IDA). The potential and principle use of the technique is demonstrated for Mg in human urine using MC-TIMS for isotopic analysis. Mg is an element inaccessible to double spiking methods as it consists of three stable isotopes only and shows great potential for metabolically induced isotope effects waiting to be explored.

  19. Absolute Isotopic Abundance Ratios and the Accuracy of Δ47 Measurements

    NASA Astrophysics Data System (ADS)

    Daeron, M.; Blamart, D.; Peral, M.; Affek, H. P.

    2016-12-01

    Conversion from raw IRMS data to clumped isotope anomalies in CO2 (Δ47) relies on four external parameters: the (13C/12C) ratio of VPDB, the (17O/16O) and (18O/16O) ratios of VSMOW (or VPDB-CO2), and the slope of the triple oxygen isotope line (λ). Here we investigate the influence that these isotopic parameters exert on measured Δ47 values, using real-world data corresponding to 7 months of measurements; simulations based on randomly generated data; precise comparisons between water-equilibrated CO2 samples and between carbonate standards believed to share quasi-identical Δ47 values; reprocessing of two carbonate calibration data sets with different slopes of Δ47 versus T. Using different sets of isotopic parameters generally produces systematic offsets as large as 0.04 ‰ in final Δ47 values. What's more, even using a single set of isotopic parameters can produce intra- and inter-laboratory discrepancies in final Δ47 values, if some of these parameters are inaccurate. Depending on the isotopic compositions of the standards used for conversion to "absolute" values, these errors should correlate strongly with either δ13C or δ18O, or more weakly with both. Based on measurements of samples expected to display identical Δ47 values, such as 25°C water-equilibrated CO2 with different carbon and oxygen isotope compositions, or high-temperature standards ETH-1 and ETH-2, we conclude that the isotopic parameters used so far in most clumped isotope studies produces large, systematic errors controlled by the relative bulk isotopic compositions of samples and standards, which should be one of the key factors responsible for current inter-laboratory discrepancies. By contrast, the isotopic parameters of Brand et al. [2010] appear to yield accurate Δ47 values regardless of bulk isotopic composition. References:Brand, Assonov and Coplen [2010] http://dx.doi.org/10.1351/PAC-REP-09-01-05

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

    Context. An increasing fraction of carbon-enhanced metal-poor (CEMP) stars is found as their iron abundance, [Fe/H], decreases below [Fe/H] =-2.0. The CEMP-s stars have the highest absolute carbon abundances, [C/H], and are thought to owe their enrichment in carbon and the slow neutron-capture (s-process) elements to mass transfer from a former asymptotic giant branch (AGB) binary companion. The most Fe-poor CEMP stars are normally single, exhibit somewhat lower [C/H] than CEMP-s stars, but show no s-process element enhancement (CEMP-no stars). Abundance determinations of CNO offer clues to their formation sites. Aims: Our aim is to use the medium-resolution spectrograph X-Shooter/VLT to determine stellar parameters and abundances for C, N, Sr, and Ba in several classes of CEMP stars in order to further classify and constrain the astrophysical formation sites of these stars. Methods: Atmospheric parameters for our programme stars were estimated from a combination of V-K photometry, model isochrone fits, and estimates from a modified version of the SDSS/SEGUE spectroscopic pipeline. We then used X-Shooter spectra in conjunction with the 1D local thermodynamic equilibrium spectrum synthesis code MOOG, 1D ATLAS9 atmosphere models to derive stellar abundances, and, where possible, isotopic 12C/13C ratios. Results: Abundances (or limits) of C, N, Sr, and Ba are derived for a sample of 27 faint metal-poor stars for which the X-Shooter spectra have sufficient signal-to-noise ratios (S/N). These moderate resolution, low S/N (~10-40) spectra prove sufficient to perform limited chemical tagging and enable assignment of these stars into the CEMP subclasses (CEMP-s and CEMP-no). According to the derived abundances, 17 of our sample stars are CEMP-s and 3 are CEMP-no, while the remaining 7 are carbon-normal. For four CEMP stars, the subclassification remains uncertain, and two of them may be pulsating AGB stars. Conclusions: The derived stellar abundances trace the formation

  1. Linking Carbonic Anhydrase Abundance and Diversity in Soils to Ecological Function

    NASA Astrophysics Data System (ADS)

    Pang, E.; Meredith, L. K.; Welander, P. V.

    2015-12-01

    Carbonic anhydrase (CA) is an ancient enzyme widespread among bacteria, archaea, and eukarya that catalyzes the following reaction: CO2 + H2O ⇌ HCO3- + H+. Its functions are critical for key cellular processes such as concentrating CO2 for autotrophic growth, pH regulation, and pathogen survival in hosts. Currently, there are six known CA classes (α, β, γ, δ, η, ζ) arising from several distinct evolutionary lineages. CA are widespread in sequenced genomes, with many organisms containing multiple classes of CA or multiple CA of the same class. Soils host rich microbial communities with diverse and important ecological functions, but the diversity and abundance of CA in soils has not been explored. CA appears to play an important, but poorly understood, role in some biogeochemical cycles such as those of CO2 and its oxygen isotope composition and also carbonyl sulfide (COS), which are potential tracers in predictive carbon cycle models. Recognizing the prevalence and functional significance of CA in soils, we used a combined bioinformatics and molecular biology approach to address fundamental questions regarding the abundance, diversity, and function of CA in soils. To characterize the abundance and diversity of the different CA classes in soils, we analyzed existing soil metagenomic and metatranscriptomic data from the DOE Joint Genome Institute databases. Out of the six classes of CA, we only found the α, β, and γ classes to be present in soils, with the β class being the most abundant. We also looked at genomes of sequenced soil microorganisms to learn what combination of CA classes they contain, from which we can begin to predict the physiological role of CA. To characterize the functional roles of the different CA classes in soils, we collected soil samples from a variety of biomes with diverse chemical and physical properties and quantified the rate of two CA-mediated processes: soil uptake of COS and acceleration of the oxygen isotope exchange

  2. Uranium isotope fractionation in biogenic carbonates: biological effects

    NASA Astrophysics Data System (ADS)

    Chen, X.; Romaniello, S. J.; Herrmann, A. D.; Anbar, A. D.

    2017-12-01

    Recent laboratory experiments have demonstrated small but potentially significant isotope fractionation ( 0.10 ‰ for 238U/235U) during uranium (U) incorporation into abiotic calcite and aragonite, with heavier U isotopes preferentially enriched in the precipitates [1]. In contrast, measurements of natural biogenic carbonates to date have not been able to resolve significant U isotopic fractionation from seawater although this might be expected given a typical measurement precision of ± 0.10 ‰. Determining whether or not biogenic carbonates display U isotope fractionation similar to abiotic carbonates could have important implications for understanding the mechanisms of U incorporation into various biogenic carbonates. Furthermore, because most marine carbonates are biogenic, the extent of isotopic fractionation, if any, could have important implications for the interpretation of sedimentary carbonates record similar to effects observed for Cr and B isotopes [2, 3]. To resolve this discrepancy, we utilized a higher precision 238U/235U method which uses larger sample sizes to improve measurement precision of natural samples to ± 0.02 ‰ (2 se, N = 6) [4]. Using this method, we have surveyed 238U/235U in primary biogenic skeletal carbonates including scleractinian corals, green and red algae, and mollusks, as well as non-skeletal carbonates such as stromatolites, ooids, and carbonate sands from the Bahamas, Gulf of California, and French Polynesia. New high-precision U isotopes measurements reveal that biogenic skeletal carbonates are typically 0.02 - 0.08 ‰ heavier than modern seawater. Scleractinian corals display values closest to seawater (- 0.37 ‰), while green algae, red algae, mollusks, and echinoderms display variable but larger extents of fractionation up to 0.08 ‰. The direction and magnitude of U isotope fractionation in these biogenic precipitates are generally consistent with results from abiotic coprecipitation experiments, but may be

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

    NASA Astrophysics Data System (ADS)

    Vengosh, Avner; Kolodny, Yehoshua; Starinsky, Abraham; Chivas, Allan R.; McCulloch, Malcolm T.

    1991-10-01

    The abundances and isotopic composition of boron in modern, biogenic calcareous skeletons from the Gulf of Elat, Israel, the Great Barrier Reef, Australia, and in deep-sea sediments have been examined by negative thermal-ionization mass spectrometry. The selected species (Foraminifera, Pteropoda, corals, Gastropoda, and Pelecypoda) yield large variations in boron concentration that range from 1 ppm in gastropod shells to 80 ppm in corals. The boron content of the biogenic skeletons is independent of mineralogical composition and is probably related to biological (vital) effects. The δ11B values of the carbonates range from 14.2 to 32.2%. (relative to NBS SRM 951) and overlap with the δ11B values of modern deep-sea carbonate sediments ( δ11B = 8.9 to 26.2%.). The variations of δ11B may be controlled by isotopic exchange of boron species in which 10B is preferentially partitioned into the tetrahedral species, and coprecipitation of different proportions of trigonal and tetrahedral species in the calcium carbonates. Carbonates with low δ11B values (~ 15%.) may indicate preferential incorporation of tetrahedral species, whereas the higher δ11B values (~30%.) may indicate (1) uptake of both boron species assuming equilibrium with seawater (2) preferential incorporation of B(OH) 4- from in situ high-pH internal fluids of organisms that are isolated from seawater. The B content and δ11B values of deep-sea sediments, Foraminifera tests, and corals are used to estimate the global oceanic sink of elemental boron by calcium carbonate deposition. As a result of enrichment of B in corals, a substantially higher biogenic sink of 6.4 ± 0.9 × 10 10 g/yr is calculated for carbonates. This is only slightly lower than the sink for desorbable B in marine sediments (10 × 10 10 g/yr) and approximately half that of altered oceanic crust (14 × 10 10 g/yr). Thus, carbonates are an important sink for B in the oceans being ~20% of the total sinks. The preferential incorporation of

  4. The puzzle of the CNO isotope ratios in asymptotic giant branch carbon stars

    NASA Astrophysics Data System (ADS)

    Abia, C.; Hedrosa, R. P.; Domínguez, I.; Straniero, O.

    2017-03-01

    Context. The abundance ratios of the main isotopes of carbon, nitrogen and oxygen are modified by the CNO-cycle in the stellar interiors. When the different dredge-up events mix the burning material with the envelope, valuable information on the nucleosynthesis and mixing processes can be extracted by measuring these isotope ratios. Aims: Previous determinations of the oxygen isotopic ratios in asymptotic giant branch (AGB) carbon stars were at odds with the existing theoretical predictions. We aim to redetermine the oxygen ratios in these stars using new spectral analysis tools and further develop discussions on the carbon and nitrogen isotopic ratios in order to elucidate this problem. Methods: Oxygen isotopic ratios were derived from spectra in the K-band in a sample of galactic AGB carbon stars of different spectral types and near solar metallicity. Synthetic spectra calculated in local thermodynamic equillibrium (LTE) with spherical carbon-rich atmosphere models and updated molecular line lists were used. The CNO isotope ratios derived in a homogeneous way, were compared with theoretical predictions for low-mass (1.5-3 M⊙) AGB stars computed with the FUNS code assuming extra mixing both during the RGB and AGB phases. Results: For most of the stars the 16O/17O/18O ratios derived are in good agreement with theoretical predictions confirming that, for AGB stars, are established using the values reached after the first dredge-up (FDU) according to the initial stellar mass. This fact, as far as the oxygen isotopic ratios are concerned, leaves little space for the operation of any extra mixing mechanism during the AGB phase. Nevertheless, for a few stars with large 16O/17O/18O, the operation of such a mechanism might be required, although their observed 12C/13C and 14N/15N ratios would be difficult to reconcile within this scenario. Furthermore, J-type stars tend to have lower 16O/17O ratios than the normal carbon stars, as already indicated in previous studies

  5. Comparison of gas chromatography/isotope ratio mass spectrometry and liquid chromatography/isotope ratio mass spectrometry for carbon stable-isotope analysis of carbohydrates.

    PubMed

    Moerdijk-Poortvliet, Tanja C W; Schierbeek, Henk; Houtekamer, Marco; van Engeland, Tom; Derrien, Delphine; Stal, Lucas J; Boschker, Henricus T S

    2015-07-15

    We compared gas chromatography/isotope ratio mass spectrometry (GC/IRMS) and liquid chromatography/isotope ratio mass spectrometry (LC/IRMS) for the measurement of δ(13)C values in carbohydrates. Contrary to GC/IRMS, no derivatisation is needed for LC/IRMS analysis of carbohydrates. Hence, although LC/IRMS is expected to be more accurate and precise, no direct comparison has been reported. GC/IRMS with the aldonitrile penta-acetate (ANPA) derivatisation method was compared with LC/IRMS without derivatisation. A large number of glucose standards and a variety of natural samples were analysed for five neutral carbohydrates at natural abundance as well as at (13)C-enriched levels. Gas chromatography/chemical ionisation mass spectrometry (GC/CIMS) was applied to check for incomplete derivatisation of the carbohydrate, which would impair the accuracy of the GC/IRMS method. The LC/IRMS technique provided excellent precision (±0.08‰ and ±3.1‰ at natural abundance and enrichment levels, respectively) for the glucose standards and this technique proved to be superior to GC/IRMS (±0.62‰ and ±19.8‰ at natural abundance and enrichment levels, respectively). For GC/IRMS measurements the derivatisation correction and the conversion of carbohydrates into CO2 had a considerable effect on the measured δ(13)C values. However, we did not find any significant differences in the accuracy of the two techniques over the full range of natural δ(13)C abundances and (13)C-labelled glucose. The difference in the performance of GC/IRMS and LC/IRMS diminished when the δ(13)C values were measured in natural samples, because the chromatographic performance and background correction became critical factors, particularly for LC/IRMS. The derivatisation of carbohydrates for the GC/IRMS method was complete. Although both LC/IRMS and GC/IRMS are reliable techniques for compound-specific stable carbon isotope analysis of carbohydrates (provided that derivatisation is complete and the

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

    NASA Astrophysics Data System (ADS)

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

    2008-12-01

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

  7. Carbon-13 Isotopic Abundance and Concentration of Atmospheric Methane for Background Air in the Southern and Northern Hemispheres from 1978 to 1989 (NDP-049)

    DOE Data Explorer

    Stevens, C. M. [Chemical Technology Division, Argonne National Laboratory, Argonne, Illinois (USA)

    2012-01-01

    This data package presents atmospheric CH4 concentration and 13C isotopic abundance data derived from air samples collected over the period 1978-1989 at globally distributed clean-air sites. The data set comprises 201 records, 166 from the Northern Hemisphere and 35 from the Southern Hemisphere. The air samples were collected mostly in rural or marine locations remote from large sources of CH4 and are considered representative of tropospheric background conditions. The air samples were processed by isolation of CH4 from air and conversion to CO2 for isotopic analysis by isotope ratio mass spectrometry. These data represent one of the earliest records of 13C isotopic yy!measurements for atmospheric methane and have been used to refine estimates of CH4 emissions, calculate annual growth rates of emissions from changing sources, and provide evidence for changes in the rate of atmospheric removal of CH4. The data records consist of sample collection date; number of samples combined for analysis; sampling location; analysis date; CH4 concentration; 13C isotopic abundance; and flag codes to indicate outliers, repeated analyses, and other information.

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

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

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

  9. Testing Urey's carbonate-silicate cycle using the calcium isotopic composition of sedimentary carbonates

    NASA Astrophysics Data System (ADS)

    Blättler, Clara L.; Higgins, John A.

    2017-12-01

    Carbonate minerals constitute a major component of the sedimentary geological record and an archive of a fraction of the carbon and calcium cycled through the Earth's surface reservoirs for over three billion years. For calcium, carbonate minerals constitute the ultimate sink for almost all calcium liberated during continental and submarine weathering of silicate minerals. This study presents >500 stable isotope ratios of calcium in Precambrian carbonate sediments, both limestones and dolomites, in an attempt to characterize the isotope mass balance of the sedimentary carbonate reservoir through time. The mean of the dataset is indistinguishable from estimates of the calcium isotope ratio of bulk silicate Earth, consistent with the Urey cycle being the dominant mechanism exchanging calcium among surface reservoirs. The variability in bulk sediment calcium isotope ratios within each geological unit does not reflect changes in the global calcium cycle, but rather highlights the importance of local mineralogical and/or diagenetic effects in the carbonate record. This dataset demonstrates the potential for calcium isotope ratios to help assess these local effects, such as the former presence of aragonite, even in rocks with a history of neomorphism and recrystallization. Additionally, 29 calcium isotope measurements are presented from ODP (Ocean Drilling Program) Site 801 that contribute to the characterization of altered oceanic crust as an additional sink for calcium, and whose distinct isotopic signature places a limit on the importance of this subduction flux over Earth history.

  10. Molecular carbon isotope variations in core samples taken at the Permian-Triassic boundary layers in southern China

    NASA Astrophysics Data System (ADS)

    Wang, Ruiliang; Zhang, Shuichang; Brassell, Simon; Wang, Jiaxue; Lu, Zhengyuan; Ming, Qingzhong; Wang, Xiaomei; Bian, Lizeng

    2012-07-01

    Stable carbon isotope composition (δ13C) of carbonate sediments and the molecular (biomarker) characteristics of a continuous Permian-Triassic (PT) layer in southern China were studied to obtain geochemical signals of global change at the Permian-Triassic boundary (PTB). Carbonate carbon isotope values shifted toward positive before the end of the Permian period and then shifted negative above the PTB into the Triassic period. Molecular carbon isotope values of biomarkers followed the same trend at and below the PTB and remained negative in the Triassic layer. These biomarkers were acyclic isoprenoids, ranging from C15 to C40, steranes (C27 dominates) and terpenoids that were all significantly more abundant in samples from the Permian layer than those from the Triassic layer. The Triassic layer was distinguished by the dominance of higher molecular weight (waxy) n-alkanes. Stable carbon isotope values of individual components, including n-alkanes and acyclic isoprenoids such as phytane, isop-C25, and squalane, are depleted in δ13C by up to 8-10‰ in the Triassic samples as compared to the Permian. Measured molecular and isotopic variations of organic matter in the PT layers support the generally accepted view of Permian oceanic stagnation followed by a massive upwelling of toxic deep waters at the PTB. A series of large-scale (global) outgassing events may be associated with the carbon isotope shift we measured. This is also consistent with the lithological evidence we observed of white thin-clay layers in this region. Our findings, in context with a generally accepted stagnant Permian ocean, followed by massive upwelling of toxic deep waters might be the major causes of the largest global mass extinction event that occurred at the Permian-Triassic boundary.

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

    NASA Technical Reports Server (NTRS)

    Neumann, K.; DesMarais, D. J.

    1998-01-01

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

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

    USGS Publications Warehouse

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

    1984-01-01

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

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

    USGS Publications Warehouse

    Meier, A.L.

    1982-01-01

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

  14. Marine Carbonate Component in the Mantle Beneath the Southeastern Tibetan Plateau: Evidence From Magnesium and Calcium Isotopes

    NASA Astrophysics Data System (ADS)

    Liu, Fang; Li, Xin; Wang, Guiqin; Liu, Yufei; Zhu, Hongli; Kang, Jinting; Huang, Fang; Sun, Weidong; Xia, Xiaoping; Zhang, Zhaofeng

    2017-12-01

    Tracing and identifying recycled carbonates is a key issue to reconstruct the deep carbon cycle. To better understand carbonate subduction and recycling beneath the southeastern Tibetan Plateau, high-K cal-alkaline volcanic rocks including trachy-basalts and trachy-andesites from Tengchong were studied using Mg and Ca isotopes. The low δ26Mg (-0.31 ± 0.03‰ to -0.38 ± 0.03‰) and δ44/40Ca (0.67 ± 0.07‰ to 0.80 ± 0.04‰) values of these volcanic rocks compared to those of the mantle (-0.25 ± 0.07‰ and 0.94 ± 0.05‰, respectively) indicate the incorporation of isotopically light materials into the mantle source, which may be carbonate-bearing sediments with low δ26Mg and δ44/40Ca values. In addition, no correlations of δ26Mg and δ44/40Ca with either SiO2 contents or trace element abundance ratios (e.g., Sm/Yb and Ba/Y) were observed, suggesting that limited Mg and Ca isotopic fractionation occurred during cal-alkaline magmatic differentiation. A binary mixing model using Mg-Ca isotopes shows that 5-8% carbonates dominated primarily by dolostone were recycled back into the mantle. Since Tengchong volcanism is still active and probably related to ongoing plate tectonic movement, we propose that the recycled carbonates are derived from oceanic crust related to the ongoing subduction of the Indian plate.

  15. Gluconeogenesis from labeled carbon: estimating isotope dilution

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kelleher, J.K.

    1986-03-01

    To estimate the rate of gluconeogenesis from steady-state incorporation of labeled 3-carbon precursors into glucose, isotope dilution must be considered so that the rate of labeling of glucose can be quantitatively converted to the rate of gluconeogenesis. An expression for the value of this isotope dilution can be derived using mathematical techniques and a model of the tricarboxylic acid (TCA) cycle. The present investigation employs a more complex model than that used in previous studies. This model includes the following pathways that may affect the correction for isotope dilution: 1) flux of 3-carbon precursor to the oxaloacetate pool via acetyl-CoAmore » and the TCA cycle; 2) flux of 4- or 5-carbon compounds into the TCA cycle; 3) reversible flux between oxaloacetate (OAA) and pyruvate and between OAA and fumarate; 4) incomplete equilibrium between OAA pools; and 5) isotope dilution of 3-carbon tracers between the experimentally measured pool and the precursor for the TCA-cycle OAA pool. Experimental tests are outlined which investigators can use to determine whether these pathways are significant in a specific steady-state system. The study indicated that flux through these five pathways can significantly affect the correction for isotope dilution. To correct for the effects of these pathways an alternative method for calculating isotope dilution is proposed using citrate to relate the specific activities of acetyl-CoA and OAA.« less

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

    NASA Technical Reports Server (NTRS)

    Wiedenbeck, M. E.

    1977-01-01

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

  17. Altitude effect on leaf wax carbon isotopic composition in humid tropical forests

    NASA Astrophysics Data System (ADS)

    Wu, Mong Sin; Feakins, Sarah J.; Martin, Roberta E.; Shenkin, Alexander; Bentley, Lisa Patrick; Blonder, Benjamin; Salinas, Norma; Asner, Gregory P.; Malhi, Yadvinder

    2017-06-01

    The carbon isotopic composition of plant leaf wax biomarkers is commonly used to reconstruct paleoenvironmental conditions. Adding to the limited calibration information available for modern tropical forests, we analyzed plant leaf and leaf wax carbon isotopic compositions in forest canopy trees across a highly biodiverse, 3.3 km elevation gradient on the eastern flank of the Andes Mountains. We sampled the dominant tree species and assessed their relative abundance in each tree community. In total, 405 sunlit canopy leaves were sampled across 129 species and nine forest plots along the elevation profile for bulk leaf and leaf wax n-alkane (C27-C33) concentration and carbon isotopic analyses (δ13C); a subset (76 individuals, 29 species, five forest plots) were additionally analyzed for n-alkanoic acid (C22-C32) concentrations and δ13C. δ13C values display trends of +0.87 ± 0.16‰ km-1 (95% CI, r2 = 0.96, p < 0.01) for bulk leaves and +1.45 ± 0.33‰ km-1 (95% CI, r2 = 0.94, p < 0.01) for C29n-alkane, the dominant chain length. These carbon isotopic gradients are defined in multi-species sample sets and corroborated in a widespread genus and several families, suggesting the biochemical response to environment is robust to taxonomic turnover. We calculate fractionations and compare to adiabatic gradients, environmental variables, leaf wax n-alkane concentrations, and sun/shade position to assess factors influencing foliar chemical response. For the 4 km forested elevation range of the Andes, 4-6‰ higher δ13C values are expected for upland versus lowland C3 plant bulk leaves and their n-alkyl lipids, and we expect this pattern to be a systematic feature of very wet tropical montane environments. This elevation dependency of δ13C values should inform interpretations of sedimentary archives, as 13C-enriched values may derive from C4 grasses, petrogenic inputs or upland C3 plants. Finally, we outline the potential for leaf wax carbon isotopes to trace biomarker

  18. Carbonate clumped isotopes and in situ temperature monitoring for Holocene soils in the San Luis Valley, USA indicate springtime carbonate formation

    NASA Astrophysics Data System (ADS)

    Hudson, A. M.; Paces, J. B.; Ruleman, C.

    2017-12-01

    Pedogenic carbonate horizons are abundant in semi-arid and arid regions worldwide and within the geologic record. They present a widely distributed archive of past environmental conditions, driven by global climate or tectonically-controlled elevation changes. Oxygen and carbon isotopes in calcite-rich nodules and clast rinds are widely-applied indicators of past soil water and CO2 composition linked to changing precipitation and plant communities. The temperature of carbonate formation, however, provides key constraint on past water/CO2 values and elucidate why they may have changed in the past. Clumped isotope thermometry can provide this constraint and additional climate information, given the carbonate forming system is well understood. We present preliminary clumped isotope (Δ47) temperatures for Holocene soil carbonates, constrained by 14C and U-Th disequilibrium dating, compared with two years of in situ soil temperature data to better understand the mechanism and seasonality of carbonate formation in the San Luis Valley region of the southern Rocky Mountains. Five temperature-monitoring sites ranging in elevation (1940-2450 m) and latitude (36.2-37.9°N) were installed in a variety of settings (range front, valley center, and canyon). The resulting records show indistinguishable seasonal temperature variations at >60 cm depth. This suggests Δ47 temperatures should be comparable at sites across the region. Temperatures based on Δ47 measurements of Holocene (>1.8 to 11.0 ka BP) carbonates at these sites yield consistent inter-site temperatures of 10±4°C, which are similar to modern springtime soil temperatures at depth. This seasonality matches previous results of isotopic modeling at sites further south along the Rio Grande corridor. Temperatures during March to May show multiple, abrupt warming and cooling cycles on weekly timescales caused by wetting and drying of the soil during spring precipitation events. This may drive carbonate precipitation

  19. Carbon isotope fractionation during microbial methane oxidation

    NASA Astrophysics Data System (ADS)

    Barker, James F.; Fritz, Peter

    1981-09-01

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

  20. Carbon and sulfur distributions and abundances in lunar fines

    NASA Technical Reports Server (NTRS)

    Gibson, E. K., Jr.; Moore, G. W.

    1973-01-01

    Total sulfur abundances have been determined for 20 Apollo 14, 15, and 16 soil samples and one Apollo 14 breccia. Sulfur concentrations range from 474 to 844 microg S/g. Volatilization experiments on selected samples have been carried out using step-wise heating. Sample residues have been analyzed for their total carbon and sulfur abundances to establish the material balance in lunar fines for these two elements. Volatilization experiments have established that between 31 to 54 microg C/g remains in soils which have been heated at 1100 C for 24 hours under vacuum. The residual carbon is believed to be indigenous lunar carbon whereas all forms of carbon lost from samples below 1100 C is extralunar carbon. Total carbon and sulfur abundances taken from the literature have been used to show the depletion of volatile elements with increasing grade for the Apollo 14 breccias.

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

    NASA Astrophysics Data System (ADS)

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

    2003-12-01

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

  2. Mass transfer and carbon isotope evolution in natural water systems

    USGS Publications Warehouse

    Wigley, T.M.L.; Plummer, Niel; Pearson, F.J.

    1978-01-01

    This paper presents a theoretical treatment of the evolution of the carbon isotopes C13 and C14 in natural waters and in precipitates which derive from such waters. The effects of an arbitrary number of sources (such as dissolution of carbonate minerals and oxidation of organic material) and sinks (such as mineral precipitation, CO2 degassing and production of methane), and of equilibrium fractionation between solid, gas and aqueous phases are considered. The results are expressed as equations relating changes in isotopic composition to changes in conventional carbonate chemistry. One implication of the equations is that the isotopic composition of an aqueous phase may approach a limiting value whenever there are simultaneous inputs and outputs of carbonate. In order to unambiguously interpret isotopic data from carbonate precipitates and identify reactants and products in reacting natural waters, it is essential that isotopic changes are determined chiefly by reactant and product stoichiometry, independent of reaction path. We demonstrate that this is so by means of quantitative examples. The evolution equations are applied to: 1. (1) carbon-14 dating of groundwaters; 2. (2) interpretation of the isotopic composition of carbonate precipitates, carbonate cements and diagenetically altered carbonates; and 3. (3) the identification of chemical reaction stoichiometry. These applications are illustrated by examples which show the variation of ??C13 in solutions and in precipitates formed under a variety of conditions involving incongruent dissolution, CO2 degassing, methane production and mineral precipitation. ?? 1978.

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

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

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

  4. The influence of authigenic clay formation on the mineralogy and stable isotopic record of lacustrine carbonates

    NASA Astrophysics Data System (ADS)

    Bristow, Thomas F.; Kennedy, Martin J.; Morrison, Keith D.; Mrofka, David D.

    2012-08-01

    The mineralogical, compositional and stable isotopic variability of lacustrine carbonates are frequently used as proxies for ancient paleoenvironmental change in continental settings, under the assumption that precipitated carbonates reflect conditions and chemistry of ancient lake waters. In some saline and alkaline lake systems, however, authigenic clay minerals, forming at or near the sediment water interface, are a major sedimentary component. Often these clays are rich in Mg, influencing the geochemical budget of lake waters, and are therefore expected to influence the properties of contemporaneous authigenic carbonate precipitates (which may also contain Mg). This paper documents evidence for a systematic feedback between clay mineral and carbonate authigenesis through multiple precessionally driven, m-scale sedimentary cycles in lacustrine oil-shale deposits of the Eocene Green River Formation from the Uinta Basin (NE Utah). In the studied section, authigenic, Mg-rich, trioctahedral smectite content varies cyclically between 9 and 39 wt.%. The highest concentrations occur in oil-shales and calcareous mudstones deposited during high lake level intervals that favored sedimentary condensation, lengthening the time available for clay diagenesis and reducing dilution by other siliciclastic phases. An inverse relation between dolomite percentage of carbonate and trioctahedral smectite abundance suggests the Mg uptake during clay authigenesis provides a first order control on carbonate mineralogy that better explains carbonate mineralogical trends than the possible alternative controls of (1) variable Mg/Ca ratios in lake water and (2) degree of microbial activity in sediments. We also observe that cyclical change in carbonate mineralogy, believed to be induced by clay authigenesis, also causes isotopic covariation between δ13CPDB and δ18OPDB of bulk sediments because of differences in the equilibrium fractionation factors of dolomite and calcite (˜2‰ and ˜2

  5. Carbon and nitrogen abundances determined from transition layer lines

    NASA Technical Reports Server (NTRS)

    Boehm-Vitense, Erika; Mena-Werth, Jose

    1992-01-01

    The possibility of determining relative carbon, nitrogen, and silicon abundances from the emission-line fluxes in the lower transition layers between stellar chromospheres and coronae is explored. Observations for main-sequence and luminosity class IV stars with presumably solar element abundances show that for the lower transition layers Em = BT sup -gamma. For a given carbon abundance the constants gamma and B in this relation can be determined from the C II and C IV emission-line fluxes. From the N V and S IV lines, the abundances of these elements relative to carbon can be determined from their surface emission-line fluxes. Ratios of N/C abundances determined in this way for some giants and supergiants agree within the limits of errors with those determined from molecular bands. For giants, an increase in the ratio of N/C at B-V of about 0.8 is found, as expected theoretically.

  6. Isotopic measurements (C,N,O) of detonation soot produced from labeled and unlabeled Composition B-3 indicate source of solid carbon residues

    NASA Astrophysics Data System (ADS)

    Podlesak, David; Manner, Virginia; Amato, Ronald; Dattelbaum, Dana; Gusavsen, Richard; Huber, Rachel

    2017-06-01

    Detonation of HE is an exothermic process whereby metastable complex molecules are converted to simple stable molecules such as H2 O, N2, CO, CO2, and solid carbon. The solid carbon contains various allotropes such as detonation nanodiamonds, graphite, and amorphous carbon. It is well known that certain HE formulations such as Composition B (60% RDX, 40% TNT) produce greater amounts of solid carbon than other more oxygen-balanced formulations. To develop a greater understanding of how formulation and environment influence solid carbon formation, we synthesized TNT and RDX with 13 C and 15 N at levels slightly above natural abundance levels. Synthesized RDX and TNT were mixed at a ratio of 60:40 to form Composition B and solid carbon residues were collected from detonations of isotopically-labeled as well as un-labelled Composition B. The raw HE and detonation residues were analyzed isotopically for C, N, O isotopic compositions. We will discuss differences between treatments groups as a function of formulation and environment. LA-UR - 17-21266.

  7. Elemental and isotopic abundances in the solar wind

    NASA Technical Reports Server (NTRS)

    Geiss, J.

    1972-01-01

    The use of collecting foils and lunar material to assay the isotopic composition of the solar wind is reviewed. Arguments are given to show that lunar surface correlated gases are likely to be most useful in studying the history of the solar wind, though the isotopic abundances are thought to give a good approximation to the solar wind composition. The results of the analysis of Surveyor material are also given. The conditions leading to a significant component of the interstellar gas entering the inner solar system are reviewed and suggestions made for experimental searches for this fraction. A critical discussion is given of the different ways in which the basic solar composition could be modified by fractionation taking place between the sun's surface and points of observation such as on the Moon or in interplanetary space. An extended review is made of the relation of isotopic and elemental composition of the interplanetary gas to the dynamic behavior of the solar corona, especially processes leading to fractionation. Lastly, connection is made between the subject of composition, nucleosynthesis and the convective zone of the sun, and processes leading to modification of initial accretion of certain gases on the Earth and Moon.

  8. Natural Isotope Abundance in Metabolites: Techniques and Kinetic Isotope Effect Measurement in Plant, Animal, and Human Tissues.

    PubMed

    Tea, Illa; Tcherkez, Guillaume

    2017-01-01

    The natural isotope abundance in bulk organic matter or tissues is not a sufficient base to investigate physiological properties, biosynthetic mechanisms, and nutrition sources of biological systems. In fact, isotope effects in metabolism lead to a heterogeneous distribution of 2 H, 18 O, 13 C, and 15 N isotopes in metabolites. Therefore, compound-specific isotopic analysis (CSIA) is crucial to biological and medical applications of stable isotopes. Here, we review methods to implement CSIA for 15 N and 13 C from plant, animal, and human samples and discuss technical solutions that have been used for the conversion to CO 2 and N 2 for IRMS analysis, derivatization and isotope effect measurements. It appears that despite the flexibility of instruments used for CSIA, there is no universal method simply because the chemical nature of metabolites of interest varies considerably. Also, CSIA methods are often limited by isotope effects in sample preparation or the addition of atoms from the derivatizing reagents, and this implies that corrections must be made to calculate a proper δ-value. Therefore, CSIA has an enormous potential for biomedical applications, but its utilization requires precautions for its successful application. © 2017 Elsevier Inc. All rights reserved.

  9. Isotopic Ratios of Carbon and Oxygen in Titan’s CO using ALMA

    NASA Astrophysics Data System (ADS)

    Serigano, Joseph; Nixon, C. A.; Cordiner, M. A.; Irwin, P. G. J.; Teanby, N. A.; Charnley, S. B.; Lindberg, J. E.

    2016-04-01

    We report interferometric observations of carbon monoxide (CO) and its isotopologues in Titan’s atmosphere using the Atacama Large Millimeter/submillimeter Array (ALMA). The following transitions were detected: CO (J = 1-0, 2-1, 3-2, 6-5), 13CO (J = 2-1, 3-2, 6-5), C18O (J = 2-1, 3-2), and C17O (J = 3-2). Molecular abundances and the vertical atmospheric temperature profile were derived by modeling the observed emission line profiles using NEMESIS, a line-by-line radiative transfer code. We present the first spectroscopic detection of 17O in the outer solar system with C17O detected at >8σ confidence. The abundance of CO was determined to be 49.6 +/- 1.8 ppm, assumed to be constant with altitude, with isotopic ratios 12C/13C = 89.9 +/- 3.4, 16O/18O = 486 +/- 22, and 16O/17O = 2917 +/- 359. The measurements of 12C/13C and 16O/18O ratios are the most precise values obtained in Titan’s atmospheric CO to date. Our results are in good agreement with previous studies and suggest no significant deviations from standard terrestrial isotopic ratios.

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

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

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

  11. Carbon isotopic composition of individual Precambrian microfossils

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

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

  12. [Distribution characteristics of soil humus fractions stable carbon isotope natural abundance (delta 13C) in paddy field under long-term ridge culture].

    PubMed

    Tang, Xiao-hong; Luo, You-jin; Ren, Zhen-jiang; Lü, Jia-ke; Wei, Chao-fu

    2011-04-01

    A 16-year field experiment was conducted in a ridge culture paddy field in the hilly region of Sichuan Basin, aimed to investigate the distribution characteristics of stable carbon isotope natural abundance (delta 13C) in soil humus fractions. The soil organic carbon (SOC) content in the paddy field under different cultivation modes ranked in the order of wide ridge culture > ridge culture > paddy and upland rotation. In soil humus substances (HS), humin (HU) was the main composition, occupying 21% - 30% of the total SOC. In the extracted soil carbon, humic acid (HA) dominated, occupying 17% - 21% of SOC and 38% - 65% of HS. The delta 13C value of SOC ranged from -27.9 per thousand to -25.6 per thousand, and the difference of the delta 13C value between 0-5 cm and 20-40 cm soil layers was about 1.9 per thousand. The delta 13C value of HA under different cultivation modes was 1 per thousand - 2 per thousand lower than that of SOC, and more approached to the delta 13C value of rapeseed and rice residues. As for fulvic acid (FA), its delta 13C value was about 2 per thousand and 4 per thousand higher than that of SOC and HA, respectively. The delta 13C value of HU in plough layer (0-20 cm) and plow layer (20-40 cm) ranged from -23.7 per thousand - -24.9 per thousand and -22.6 per thousand - -24.2 per thousand, respectively, reflecting the admixture of young and old HS. The delta 13C value in various organic carbon fractions was HU>FA>SOC>rapeseed and rice residues>HA. Long-term rice planting benefited the increase of SOC content, and cultivation mode played an important role in affecting the distribution patterns of soil humus delta 13C in plough layer and plow layer.

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

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

    ;Clumped-isotope; thermometry is an emerging tool to probe the temperature history of surface and subsurface environments based on measurements of the proportion of 13C and 18O isotopes bound to each other within carbonate minerals in 13C18O16O22- groups (heavy isotope ;clumps;). Although most clumped isotope geothermometry implicitly presumes carbonate crystals have attained lattice equilibrium (i.e., thermodynamic equilibrium for a mineral, which is independent of solution chemistry), several factors other than temperature, including dissolved inorganic carbon (DIC) speciation may influence mineral isotopic signatures. Therefore we used a combination of approaches to understand the potential influence of different variables on the clumped isotope (and oxygen isotope) composition of minerals. We conducted witherite precipitation experiments at a single temperature and at varied pH to empirically determine 13C-18O bond ordering (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

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

    PubMed Central

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

    1998-01-01

    The occurrence and abundance of microbial fatty acids have been used for the identification of microorganisms in microbial communities. However, these fatty acids can also be used as indicators of substrate usage. For this, a systematic investigation of the discrimination of the stable carbon isotopes by different microorganisms is necessary. We grew 11 strains representing major bacterial and fungal species with four different isotopically defined carbon sources and determined the isotope ratios of fatty acids of different lipid fractions. A comparison of the differences of δ13C values of palmitic acid (C16:0) with the δ13C values of the substrates revealed that the isotope ratio is independent of the growth stage and that most microorganisms showed enrichment of C16:0 with 13C when growing on glycerol. With the exception of Burkholderia gladioli, all microorganism showed depletion of 13C in C16:0 while incorporating the carbons of glucose, and most of them were enriched with 13C from mannose, with the exception of Pseudomonas fluorescens and the Zygomycotina. Usually, the glycolipid fractions are depleted in 13C compared to the phospholipid fractions. The δ13C pattern was not uniform within the different fatty acids of a given microbial species. Generally, tetradecanoic acid (C14:0) was depleted of 13C compared to palmitic acid (C16:0) while octadecanoic acid (C18:0) was enriched. These results are important for the calibration of a new method in which δ13C values of fatty acids from the environment delineate the use of bacterial substrates in an ecosystem. PMID:9797266

  15. Ratios of carbon isotopes in microbial lipids as an indicator of substrate usage.

    PubMed

    Abraham, W R; Hesse, C; Pelz, O

    1998-11-01

    The occurrence and abundance of microbial fatty acids have been used for the identification of microorganisms in microbial communities. However, these fatty acids can also be used as indicators of substrate usage. For this, a systematic investigation of the discrimination of the stable carbon isotopes by different microorganisms is necessary. We grew 11 strains representing major bacterial and fungal species with four different isotopically defined carbon sources and determined the isotope ratios of fatty acids of different lipid fractions. A comparison of the differences of delta13C values of palmitic acid (C16:0) with the delta13C values of the substrates revealed that the isotope ratio is independent of the growth stage and that most microorganisms showed enrichment of C16:0 with 13C when growing on glycerol. With the exception of Burkholderia gladioli, all microorganism showed depletion of 13C in C16:0 while incorporating the carbons of glucose, and most of them were enriched with 13C from mannose, with the exception of Pseudomonas fluorescens and the Zygomycotina. Usually, the glycolipid fractions are depleted in 13C compared to the phospholipid fractions. The delta13C pattern was not uniform within the different fatty acids of a given microbial species. Generally, tetradecanoic acid (C14:0) was depleted of 13C compared to palmitic acid (C16:0) while octadecanoic acid (C18:0) was enriched. These results are important for the calibration of a new method in which delta13C values of fatty acids from the environment delineate the use of bacterial substrates in an ecosystem.

  16. Isotopic Ratios of Carbon and Oxygen in Titan's CO Using Alma

    NASA Technical Reports Server (NTRS)

    Serigano, Joseph; Nixon, C. A.; Cordiner, M. A.; Irwin, P. G. J.; Teanby, N. A.; Charnley, S. B.; Lindberg, J. E.

    2016-01-01

    We report interferometric observations of carbon monoxide (CO) and its isotopologues in Titan's atmosphere using the Atacama Large Millimeter/submillimeter Array (ALMA). The following transitions were detected: CO (J = 1-0, 2-1, 3-2, 6-5), C-13 O (J = 2-1, 3-2, 6-5), C-18 O (J = 2-1, 3-2), and C-17 O (J = 3-2). Molecular abundances and the vertical atmospheric temperature profile were derived by modeling the observed emission line profiles using NEMESIS, a line-by-line radiative transfer code. We present the first spectroscopic detection of O-17 in the outer solar system with C-17 O detected at greater than 8 sigma confidence. The abundance of CO was determined to be 49.6 +/- 1.8 ppm, assumed to be constant with altitude, with isotopic ratios C-12/C-13 = 89.9 +/- 3.4, O-16/O-18 = 486 +/- 22, and O-16/O-17 = 2917 +/- 359. The measurements of C-12/C-13 and O-16/O-18 ratios are the most precise values obtained in Titan's atmospheric CO to date. Our results are in good agreement with previous studies and suggest no significant deviations from standard terrestrial isotopic ratios.

  17. In Situ Carbon Isotope Analysis by Laser Ablation MC-ICP-MS.

    PubMed

    Chen, Wei; Lu, Jue; Jiang, Shao-Yong; Zhao, Kui-Dong; Duan, Deng-Fei

    2017-12-19

    Carbon isotopes have been widely used in tracing a wide variety of geological and environmental processes. The carbon isotope composition of bulk rocks and minerals was conventionally analyzed by isotope ratio mass spectrometry (IRMS), and, more recently, secondary ionization mass spectrometry (SIMS) has been widely used to determine carbon isotope composition of carbon-bearing solid materials with good spatial resolution. Here, we present a new method that couples a RESOlution S155 193 nm laser ablation system with a Nu Plasma II MC-ICP-MS, with the aim of measuring carbon isotopes in situ in carbonate minerals (i.e., calcite and aragonite). Under routine operating conditions for δ 13 C analysis, instrumental bias generally drifts by 0.8‰-2.0‰ in a typical analytical session of 2-3 h. Using a magmatic calcite as the standard, the carbon isotopic composition was determined for a suite of calcite samples with δ 13 C values in the range of -6.94‰ to 1.48‰. The obtained δ 13 C data are comparable to IRMS values. The combined standard uncertainty for magmatic calcite is <0.3‰ (1s). No significant matrix effects have been identified in calcite with the amplitude of chemical composition variation (i.e., MnO, SrO, MgO, or FeO) up to 2.5 wt %. Two modern corals were investigated using magmatic calcite as the calibration standard, and the average δ 13 C values for both corals are similar to the bulk IRMS values. Moreover, coral exhibits significant heterogeneity in carbon isotope compositions, with differences up to 4.85‰ within an individual coral. This study indicates that LA-MC-ICP-MS can serve as an appropriate method to analyze carbon isotopes of carbonate minerals in situ.

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

    NASA Astrophysics Data System (ADS)

    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., <10%) in shells from aquatic 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

  19. Laser ablation molecular isotopic spectrometry of carbon isotopes

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

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

    DOE PAGES

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

    2014-12-31

    Carbon stable isotopes can be used in characterization and monitoring of CO 2 sequestration sites to track the migration of the CO 2 plume and identify leakage sources, and to evaluate the chemical reactions that take place in the CO 2-water-rock system. However, there are few tools available to incorporate stable isotope information into flow and transport codes used for CO 2 sequestration problems. We present a numerical tool for modeling the transport of stable carbon isotopes in multiphase reactive systems relevant to geologic carbon sequestration. The code is an extension of the reactive transport code TOUGHREACT. The transport modulemore » of TOUGHREACT was modified to include separate isotopic species of CO 2 gas and dissolved inorganic carbon (CO 2, CO 3 2-, HCO 3 -,…). Any process of transport or reaction influencing a given carbon species also influences its isotopic ratio. Isotopic fractionation is thus fully integrated within the dynamic system. The chemical module and database have been expanded to include isotopic exchange and fractionation between the carbon species in both gas and aqueous phases. The performance of the code is verified by modeling ideal systems and comparing with theoretical results. Efforts are also made to fit field data from the Pembina CO 2 injection project in Canada. We show that the exchange of carbon isotopes between dissolved and gaseous carbon species combined with fluid flow and transport, produce isotopic effects that are significantly different from simple two-component mixing. These effects are important for understanding the isotopic variations observed in field demonstrations.« less

  1. Clumped isotope calibration data for lacustrine carbonates: A progress report

    NASA Astrophysics Data System (ADS)

    Tripati, A.

    2015-12-01

    Our capacity to understand Earth's environmental history is highly dependent on the accuracy of reconstructions of past climates. Lake sediments provide important archives of terrestrial climate change, and represent an important tool for reconstructing paleohydrology, paleoclimate, paleoenvironment, and paleoaltimetry. Unfortunately, while multiple methods for constraining marine temperature exist, quantitative terrestrial proxies are scarcer - tree rings, speleothems, and leaf margin analyses have all been used with varying degrees of accuracy. Clumped isotope thermometry has the potential to be a useful instrument for determining terrestrial climates: multiple studies have shown the fraction of 13C—18O bonds in carbonates is inversely related to the temperature at which the rocks formed. We have been measuring the abundance of 13C18O16O in the CO2 produced by the dissolution of carbonate minerals in phosphoric acid in modern lake samples and comparing results to independently known estimates of lake water temperature. Here we discuss an extensive calibration dataset comprised of 132 analyses of 97 samples from 44 localities, including microbialites, tufas, and micrites endogenic carbonates, freshwater gastropods, bivalves, microbialites, and ooids.

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

    USGS Publications Warehouse

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    Recent field studies on major sources of the important greenhouse gas methane (CH4) indicate significant underestimation of methane release from fossil fuel industrial (FFI) and animal husbandry sources, among others. In addition, uncertainties still exist with respect to carbon dioxide (CO2) measurements, especially source fingerprinting. CO2 isotopic analysis provides a valuable in situ measurement approach to fingerprint CH4 and CO2as associated with combustion sources, leakage from geologic reservoirs, or biogenic sources. As a result, these measurements can characterize strong combustion source plumes, such as power plant emissions, and discriminate these emissions from other sources. As part of the COMEX (CO2 and MEthane eXperiment) campaign, a novel CO2 isotopic analyzer was installed and collected data aboard the CIRPAS Twin Otter aircraft. Developing methods to derive CH4 and CO2 budgets from remote sensing data is the goal of the summer 2014 COMEX campaign, which combines hyperspectral imaging (HSI) and non-imaging spectroscopy (NIS) with in situ airborne and surface data. COMEX leverages the synergy between high spatial resolution HSI and moderate spatial resolution NIS. The carbon dioxide isotope analyzer developed by Los Gatos Research (LGR) uses LGR's patented Off-Axis ICOS (Integrated Cavity Output Spectroscopy) technology and incorporates proprietary internal thermal control for high sensitivity and optimal instrument stability. This analyzer measures CO2 concentration as well as 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. Carbonate “clumped” isotope signatures in aragonitic scleractinian and calcitic gorgonian deep-sea corals

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kimball, Justine; Eagle, Robert; Dunbar, Robert

    Here, 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 13C 18O 16O 2 inmore » carbonate minerals, analyzed in CO 2 gas liberated on phosphoric acid digestion of carbonates and reported as Δ 47 values. We analyzed Δ 47 in live-collected aragonitic scleractinian ( Enallopsammia sp.) and high-Mg calcitic gorgonian (Isididae and Coralliidae) deep-sea corals and compared results to published data for other aragonitic scleractinian taxa. Measured Δ 47 values were compared to in situ temperatures, and the relationship between Δ 47 and temperature was determined for each group to investigate taxon-specific effects. We find that aragonitic scleractinian deep-sea corals exhibit higher values than high-Mg calcitic gorgonian corals and the two groups of coral produce statistically different relationships between Δ 47–temperature calibrations. These data are significant in the interpretation of all carbonate clumped isotope calibration data as they show that distinct Δ 47–temperature calibrations can be observed in different materials recovered from the same environment and analyzed using the same instrumentation, phosphoric acid composition, digestion temperature and technique, CO 2 gas purification apparatus, and data handling. There are three possible explanations for the origin of these

  5. Carbonate “clumped” isotope signatures in aragonitic scleractinian and calcitic gorgonian deep-sea corals

    DOE PAGES

    Kimball, Justine; Eagle, Robert; Dunbar, Robert

    2016-12-12

    Here, 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 13C 18O 16O 2 inmore » carbonate minerals, analyzed in CO 2 gas liberated on phosphoric acid digestion of carbonates and reported as Δ 47 values. We analyzed Δ 47 in live-collected aragonitic scleractinian ( Enallopsammia sp.) and high-Mg calcitic gorgonian (Isididae and Coralliidae) deep-sea corals and compared results to published data for other aragonitic scleractinian taxa. Measured Δ 47 values were compared to in situ temperatures, and the relationship between Δ 47 and temperature was determined for each group to investigate taxon-specific effects. We find that aragonitic scleractinian deep-sea corals exhibit higher values than high-Mg calcitic gorgonian corals and the two groups of coral produce statistically different relationships between Δ 47–temperature calibrations. These data are significant in the interpretation of all carbonate clumped isotope calibration data as they show that distinct Δ 47–temperature calibrations can be observed in different materials recovered from the same environment and analyzed using the same instrumentation, phosphoric acid composition, digestion temperature and technique, CO 2 gas purification apparatus, and data handling. There are three possible explanations for the origin of these

  6. Tectonic controls on the long-term carbon isotope mass balance.

    PubMed

    Shields, Graham A; Mills, Benjamin J W

    2017-04-25

    The long-term, steady-state marine carbon isotope record reflects changes to the proportional burial rate of organic carbon relative to total carbon on a global scale. For this reason, times of high δ 13 C are conventionally interpreted to be oxygenation events caused by excess organic burial. Here we show that the carbon isotope mass balance is also significantly affected by tectonic uplift and erosion via changes to the inorganic carbon cycle that are independent of changes to the isotopic composition of carbon input. This view is supported by inverse covariance between δ 13 C and a range of uplift proxies, including seawater 87 Sr/ 86 Sr, which demonstrates how erosional forcing of carbonate weathering outweighs that of organic burial on geological timescales. A model of the long-term carbon cycle shows that increases in δ 13 C need not be associated with increased organic burial and that alternative tectonic drivers (erosion, outgassing) provide testable and plausible explanations for sustained deviations from the long-term δ 13 C mean. Our approach emphasizes the commonly overlooked difference between how net and gross carbon fluxes affect the long-term carbon isotope mass balance, and may lead to reassessment of the role that the δ 13 C record plays in reconstructing the oxygenation of earth's surface environment.

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

    USGS Publications Warehouse

    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 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

  8. METHOD FOR PRODUCING ISOTOPIC METHANES FROM LITHIUM CARBONATE AND LITHIUM HYDRIDE

    DOEpatents

    Frazer, J.W.

    1959-10-27

    A process is descrlbed for the production of methane and for the production of methane containing isotopes of hydrogen and/or carbon. Finely divided lithium hydrlde and litldum carbonate reactants are mixed in intimate contact and subsequently compacted under pressures of from 5000 to 60,000 psl. The compacted lithium hydride and lithium carbenate reactunts are dispised in a gas collecting apparatus. Subsequently, the compact is heated to a temperature in the range 350 to 400 deg C whereupon a solid-solid reaction takes place and gaseous methane is evolved. The evolved methane is contaminated with gaseous hydrogen and a very small amount of CO/sub 2/; however, the desired methane product is separated from sald impurities by well known chemical processes, e.g., condensation in a cold trap. The product methane contalns isotopes of carbon and hydrogen, the Isotopic composition being determined by the carbon isotopes originally present In the lithium carbonate and the hydrogen isotopes originally present in the lithium hydride.

  9. Understanding the Marine Chromium Isotope Record from Modern and Ancient Carbonates

    NASA Astrophysics Data System (ADS)

    Parkinson, I. J.; Bonnand, P.; James, R. H.; Fairchild, I. J.; Dixon, S.

    2011-12-01

    Chromium isotopes may provide a powerful tool for reconstructing the redox state of ancient seawater because Cr isotope fractionation is large (up to 7% in δ53Cr) during the reduction of Cr(VI) to Cr(III) in natural waters [1]. Recent studies have demonstrated that although Cr(VI) is predicted to be the thermodynamically stable form in seawater (as CrO42-), significant amounts (5-20%) of Cr(III) may also be present in surface waters [2]. Therefore the δ53Cr of seawater could vary by up to 2%. Marine carbonates potentially provide a means to extracting information about the Cr isotopic composition of seawater in the geological past and we have developed a high-precision double-spike technique for analysing Cr isotopes in carbonates [3]. The δ53Cr of modern Bahamas Bank carbonates (+0.76%) is broadly consistent with these carbonates recording a seawater Cr signature. Moreover, these pure carbonates contain significant amounts of Cr (1-4 ppm), which indicates that Cr is strongly partitioned into calcium carbonate. Therefore carbonates are likely to provide a faithful record of the δ53Cr composition of seawater. Shallow marine carbonates from the Phanerozoic range in δ53Cr from +0.76 to +1.8%, and some Neoproterozoic carbonates also have heavy Cr isotopic compositions of +0.5 to +1.0 %. Such compositions may reflect changes in the inputs of Cr to the oceans and/or changes in the redox state of the oceans. However, to interpret Cr isotopic compositions in ancient carbonates additionally requires a careful assessment of their trace element contents. This study aims to demonstrate how a combination of redox sensitive trace elements, such as Ce, and Cr isotopes allow an assessment of the marine chromium isotope record. [1] Ellis et al., 2002, Science, 295, 2060-2062. [2] Connolly et al., 2006, Deep Sea Res. Part I, 2006 53, 1975-1988. [3] P. Bonnand, et al., 2011, J. Anal. At. Spectr., 26, 528-535.

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

    NASA Technical Reports Server (NTRS)

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

    1975-01-01

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

  11. Freezing and fractionation: effects of preservation on carbon and nitrogen stable isotope ratios of some limnetic organisms.

    PubMed

    Wolf, J Marshall; Johnson, Brett; Silver, Douglas; Pate, William; Christianson, Kyle

    2016-03-15

    Stable isotopes of carbon and nitrogen have become important natural tracers for studying food-web structure and function. Considerable research has demonstrated that chemical preservatives and fixatives shift the isotopic ratios of aquatic organisms. Much less is known about the effects of freezing as a preservation method although this technique is commonly used. We conducted a controlled experiment to test the effects of freezing (-10 °C) and flash freezing (–79 °C) on the carbon and nitrogen isotope ratios of zooplankton (Cladocera), Mysis diluviana and Rainbow Trout (Oncorhynchus mykiss). Subsamples (~0.5 mg) of dried material were analyzed for percentage carbon, percentage nitrogen, and the relative abundance of stable carbon and nitrogen isotopes (δ13C and δ15N values) using a Carlo Erba NC2500 elemental analyzer interfaced to a ThermoFinnigan MAT Delta Plus isotope ratio mass spectrometer. The effects of freezing were taxon-dependent. Freezing had no effect on the isotopic or elemental values of Rainbow Trout muscle. Effects on the δ13C and δ15N values of zooplankton and Mysis were statistically significant but small relative to typical values of trophic fractionation. The treatment-control offsets had larger absolute values for Mysis (δ13C: ≤0.76 ± 0.41‰, δ15N: ≤0.37 ± 0.16‰) than for zooplankton (δ13C: ≤0.12 ± 0.06‰, δ15N: ≤0.30 ± 0.27‰). The effects of freezing were more variable for the δ13C values of Mysis, and more variable for the δ15N values of zooplankton. Generally, both freezing methods reduced the carbon content of zooplankton and Mysis, but freezing had a negative effect on the %N of zooplankton and a positive effect on the %N of Mysis. The species-dependencies and variability of freezing effects on aquatic organisms suggest that more research is needed to understand the mechanisms responsible for freezing-related fractionation before standardized protocols for freezing as a preservation method can be adopted.

  12. Tectonic controls on the long-term carbon isotope mass balance

    PubMed Central

    Mills, Benjamin J. W.

    2017-01-01

    The long-term, steady-state marine carbon isotope record reflects changes to the proportional burial rate of organic carbon relative to total carbon on a global scale. For this reason, times of high δ13C are conventionally interpreted to be oxygenation events caused by excess organic burial. Here we show that the carbon isotope mass balance is also significantly affected by tectonic uplift and erosion via changes to the inorganic carbon cycle that are independent of changes to the isotopic composition of carbon input. This view is supported by inverse covariance between δ13C and a range of uplift proxies, including seawater 87Sr/86Sr, which demonstrates how erosional forcing of carbonate weathering outweighs that of organic burial on geological timescales. A model of the long-term carbon cycle shows that increases in δ13C need not be associated with increased organic burial and that alternative tectonic drivers (erosion, outgassing) provide testable and plausible explanations for sustained deviations from the long-term δ13C mean. Our approach emphasizes the commonly overlooked difference between how net and gross carbon fluxes affect the long-term carbon isotope mass balance, and may lead to reassessment of the role that the δ13C record plays in reconstructing the oxygenation of earth’s surface environment. PMID:28396434

  13. Carbon and hydrogen isotope fractionation by moderately thermophilic methanogens

    NASA Astrophysics Data System (ADS)

    Valentine, David L.; Chidthaisong, Amnat; Rice, Andrew; Reeburgh, William S.; Tyler, Stanley C.

    2004-04-01

    A series of laboratory studies were conducted to increase understanding of stable carbon (13C/12C) and hydrogen (D/H) isotope fractionation arising from methanogenesis by moderately thermophilic acetate- and hydrogen-consuming methanogens. Studies of the aceticlastic reaction were conducted with two closely related strains of Methanosaeta thermophila. Results demonstrate a carbon isotope fractionation of only 7‰ (α = 1.007) between the methyl position of acetate and the resulting methane. Methane formed by this process is enriched in 13C when compared with other natural sources of methane; the magnitude of this isotope effect raises the possibility that methane produced at elevated temperature by the aceticlastic reaction could be mistaken for thermogenic methane based on carbon isotopic content. Studies of H2/CO2 methanogenesis were conducted with Methanothermobacter marburgensis. The fractionation of carbon isotopes between CO2 and CH4 was found to range from 22 to 58‰ (1.023 ≤ α ≤ 1.064). Greater fractionation was associated with low levels of molecular hydrogen and steady-state metabolism. The fractionation of hydrogen isotopes between source H2O and CH4 was found to range from 127 to 275‰ (1.16 ≤ α ≤ 1.43). Fractionation was dependent on growth phase with greater fractionation associated with later growth stages. The maximum observed fractionation factor was 1.43, independent of the δD-H2 supplied to the culture. Fractionation was positively correlated with temperature and/or metabolic rate. Results demonstrate significant variability in both hydrogen and carbon isotope fractionation during methanogenesis from H2/CO2. The relatively small fractionation associated with deuterium during H2/CO2 methanogenesis provides an explanation for the relatively enriched deuterium content of biogenic natural gas originating from a variety of thermal environments. Results from these experiments are used to develop a hypothesis that differential

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

    NASA Astrophysics Data System (ADS)

    Loyd, S. J.

    2014-12-01

    Carbonate concretions often occur within fine-grained, organic-rich sedimentary rocks. This association reflects the common production of diagenetic minerals through biologic cycling of organic matter. Chemical analysis of carbonate concretions provides the rare opportunity to explore ancient shallow diagenetic environments, which are inherently transient due to progressive burial but are an integral component of the marine carbon cycle. The late Cretaceous Holz Shale (~80 Ma) contains abundant calcite concretions that exhibit textural and geochemical characteristics indicative of relatively shallow formation (i.e., near the sediment-water interface). Sampled concretions contain between 5.4 and 9.8 wt.% total inorganic carbon (TIC), or ~45 and 82 wt.% CaCO3, compared to host shale values which average ~1.5 wt.% TIC. Organic carbon isotope compositions (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

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

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

    Many fields of Earth sciences benefit from the knowledge of mineral formation temperatures. For example, carbonates are extensively used for reconstruction of the Earth's past climatic variations by determining ocean, lake, and soil paleotemperatures. Furthermore, diagenetic minerals and their formation or alteration temperature may provide information about the burial history of important geological units and can have practical applications, for instance, for reconstructing the geochemical and thermal histories of hydrocarbon reservoirs. Carbonate clumped isotope thermometry is a relatively new technique that can provide the formation temperature of carbonate minerals without requiring a priori knowledge of the isotopic composition of the initial solution. It is based on the temperature-dependent abundance of the rare 13C-18O bonds in carbonate minerals, specified as a Δ47 value. The clumped isotope thermometer has been calibrated experimentally from 1 °C to 70 °C. However, higher temperatures that are relevant to geological processes have so far not been directly calibrated in the laboratory. In order to close this calibration gap and to provide a robust basis for the application of clumped isotopes to high-temperature geological processes we precipitated CaCO3 (mainly calcite) in the laboratory between 23 and 250 °C. We used two different precipitation techniques: first, minerals were precipitated from a CaCO3 supersaturated solution at atmospheric pressure (23-91 °C), and, second, from a solution resulting from the mixing of CaCl2 and NaHCO3 in a pressurized reaction vessel at a pressure of up to 80 bar (25-250 °C).

  16. CNO isotopes in red giant stars

    NASA Technical Reports Server (NTRS)

    Wannier, P. G.

    1985-01-01

    Observational data on CNO abundance ratios in red giants and the interstellar medium (ISM) are analyzed for the implications for the production and distribution of CNO nuclides. The data included isotope abundance measurements for the atmospheres and recent ejecta of cool giants, e.g., carbon stars, S-type stars, red supergiants and oxygen-rich giants beginning an ascent of the giant branch. The contribution of intermediate-mass stars to galactic nuclear evolution is discussed after comparing red giant abundances with ISM abundances, particularly the isotopes O-16, -17 and -18. The O-12/O-18 ratios of red giants are distinctly different from those in interstellar molecular clouds. The CNO values also vary widely from the values found in the solar system.

  17. Site-specific equilibrium isotopic fractionation of oxygen, carbon and calcium in apatite

    NASA Astrophysics Data System (ADS)

    Aufort, Julie; Ségalen, Loïc; Gervais, Christel; Paulatto, Lorenzo; Blanchard, Marc; Balan, Etienne

    2017-12-01

    The stable isotope composition of biogenic apatite is an important geochemical marker that can record environmental parameters and is widely used to infer past climates, biomineralization processes, dietary preferences and habitat of vertebrates. In this study, theoretical equilibrium isotopic fractionation of oxygen, carbon and calcium in hydroxyapatite and carbonate-bearing hydroxyapatite is investigated using first-principles methods based on density-functional theory and compared to the theoretical isotopic fractionation properties of calcite, CO2 and H2O. Considering the variability of apatite crystal-chemistry, special attention is given to specific contributions of crystal sites to isotopic fractionation. Significant internal fractionation is calculated for oxygen and carbon isotopes in CO3 between the different structural sites occupied by carbonate groups in apatite (typically 7‰ for both 18O/16O and 13C/12C fractionation at 37 °C). Compared with calcite-water oxygen isotope fractionation, occurrence of A-type substitution in apatite structure, in addition to the main B-type substitution, could explain the larger temperature dependence of oxygen isotope fractionation measured at low temperature between carbonate in apatite and water. Theoretical internal fractionation of oxygen isotopes between carbonate and phosphate in B-type carbonated apatite (∼8‰ at 37 °C) is consistent with experimental values obtained from modern and well-preserved fossil bio-apatites. Concerning calcium, theoretical results suggest a small fractionation between apatite and calcite (-0.17‰ at 37 °C). Internal fractionation reaching 0.8‰ at 37 °C occurs between the two Ca sites in hydroxyapatite. Furthermore, the Ca isotopic fractionation properties of apatite are affected by the occurrence of carbonate groups, which could contribute to the variability observed on natural samples. Owing to the complexity of apatite crystal-chemistry and in light of the theoretical

  18. MYCORRHIZAL VS. SAPROTROPHIC STATUS OF FUNGI: THE ISOTOPIC EVIDENCE

    EPA Science Inventory

    Relative abundance of carbon (C) and nitrogen (N) isotopes in fungal sporocarps may prove useful in unraveling fungal roles in ecosystems. Sporocarps of known mycorrhizal or saprotrophic genera were collected from a single site in Oregon and isotopically compared to foliage, litt...

  19. Magnesium isotope fractionation in bacterial mediated carbonate precipitation experiments

    NASA Astrophysics Data System (ADS)

    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

  20. Insights into Paleogene biogeochemistry from coupled carbon and sulfur isotopes in foraminiferal calcite.

    NASA Astrophysics Data System (ADS)

    Rennie, V.; Paris, G.; Abramovitch, S.; Sessions, A. L.; Adkins, J. F.; Turchyn, A. V.

    2014-12-01

    The Paleogene witnessed large-scale environmental changes, including the beginning of long-term Cenozoic cooling. The carbon isotope composition of foraminiferal calcite suggests a major reorganization of the carbon cycle over the Paleogene, with enhanced organic carbon burial in the Paleocene, and subsequent oxidation of this organic carbon or increased volcanism throughout the Eocene. The sulfur cycle is linked to the carbon cycle via the breakdown of organic carbon during bacterial sulfate reduction. Over geological time, carbon and sulfur isotopic shifts are often coupled due to enhanced pyrite burial being coupled to enhanced organic carbon burial, and enhanced pyrite weathering being coupled to enhanced organic carbon weathering. However, over the Paleogene, carbon and sulfur isotopes are fully decoupled, with the sulfur isotope record showing only one major shift in the early Eocene, after most of the carbon isotope variability is complete. One complication of interpreting the evolution of the sulfur cycle over the Cenozoic, is the fact that the mineral proxies used (typically barite) may not be temporally coincident with those used to reconstruct the carbon cycle (typically carbonate). Furthermore, these minerals are preserved in different locations, and therefore often must be extracted from different sediment cores in different ocean basins, leading to age-model uncertainty when the records are merged. To properly ascertain the phasing between early Cenozoic changes in the carbon cycle and the sulfur cycle, we would ideally measure all isotope records on the same mineral. A new sulfur isotope analytical technique [1] has been optimised for foraminiferal calcite as a proxy for seawater δ34SSO4. The δ34SSO4 in foraminiferal calcite can then be tied to records of carbon isotopes from stratigraphically identical samples, resolving previous age model uncertainties. We present coupled carbon and sulfur isotope records from the same core over the early

  1. Variability in magnesium, carbon and oxygen isotope compositions, and trace element contents of brachiopod shells: implications for paleoceanographic studies

    NASA Astrophysics Data System (ADS)

    Rollion-Bard, Claire; Saulnier, Ségolène; Vigier, Nathalie; Schumacher, Aimryc; Chaussidon, Marc; Lécuyer, Christophe

    2016-04-01

    Magnesium content in the ocean is ≈ 1290 ppm and is one of the most abundant elements. It is involved in the carbon cycle via the dissolution and precipitation of carbonates, especially Mg-rich carbonates as dolomites. The Mg/Ca ratio of the ocean is believed to have changed through time. The causes of these variations, i.e. hydrothermal activity change or enhanced precipitation of dolomite, could be constrained using the magnesium isotope composition (δ26Mg) of carbonates. Brachiopods, as marine environmental proxies, have the advantage to occur worldwide in a depth range from intertidal to abyssal, and have been found in the geological record since the Cambrian. Moreover, as their shell is in low-Mg calcite, they are quite resistant to diagenetic processes. Here we report δ26Mg, δ18O, δ13C values along with trace element contents of one modern brachiopod specimen (Terebratalia transversa) and one fossil specimen (Terebratula scillae, 2.3 Ma). We combined δ26Mg values with oxygen and carbon isotope compositions and trace element contents to look for possible shell geochemical heterogeneities in order to investigate the processes that control the Mg isotope composition of brachiopod shells. We also evaluate the potential of brachiopods as a proxy of past seawater δ26Mg values. The two investigated brachiopod shells present the same range of δ26Mg variation (up to 2 ‰)). This variation cannot be ascribed to changes in environmental parameters, i.e. temperature or pH. As previously observed, the primary layer of calcite shows the largest degree of oxygen and carbon isotope disequilibrium relative to seawater. In contrast, the δ26Mg value of this layer is comparable to that of the secondary calcite layer value. In both T. scillae and T. transversa, negative trends are observable between magnesium isotopic compositions and oxygen and carbon isotopic compositions. These trends, combined to linear relationships between δ26Mg values and REE contents, are best

  2. Stable carbon isotope fractionation by sulfate-reducing bacteria

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

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

  3. Isotopic anomalies from neutron reactions during explosive carbon burning

    NASA Technical Reports Server (NTRS)

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

    1978-01-01

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

  4. Seasonality of Leaf Carbon Isotopic Composition and Leaf Water Isotopic Enrichment in a Mixed Evergreen Forest in Southern California

    NASA Astrophysics Data System (ADS)

    Santiago, L. S.; Sickman, J. O.; Goulden, M.; DeVan, C.; Pasquini, S. C.; Pivovaroff, A. L.

    2011-12-01

    Leaf carbon isotopic composition and leaf water isotopic enrichment reflect physiological processes and are important for linking local and regional scale processes to global patterns. We investigated how seasonality affects the isotopic composition of bulk leaf carbon, leaf sugar carbon, and leaf water hydrogen under a Mediterranean climate. Leaf and stem samples were collected monthly from four tree species (Calocedrus decurrens, Pinus lambertiana, Pinus ponderosa, and Quercus chrysolepis) at the James San Jacinto Mountain Reserve in southern California. Mean monthly bulk leaf carbon isotopic composition varied from -34.5 % in P. ponderosa to -24.7 % in P. lambertiana and became more depleted in 13C from the spring to the summer. Mean monthly leaf sugar varied from -29.3 % in P. ponderosa to -21.8 % in P. lambertiana and was enriched in 13C during the winter, spring and autumn, but depleted during the mid-summer. Leaf water hydrogen isotopic composition was 28.4 to 68.8 % more enriched in deuterium than source water and this enrichment was greater as seasonal drought progressed. These data indicate that leaf carbon and leaf water hydrogen isotopic composition provide sensitive measures that connect plant physiological processes to short-term climatic variability.

  5. Fractionation of carbon (13C/12C) isotopes in glycine decarboxylase reaction.

    PubMed

    Ivlev, A A; Bykova, N V; Igamberdiev, A U

    1996-05-20

    Fractionation of carbon isotopes (13C/12C) by glycine decarboxylase (GDC) was investigated in mitochondrial preparations isolated from photosynthetic tissues of different plants (Pisum, Medicago, Triticum, Hordeum, Spinacia, Brassica, Wolffia). 20 mM glycine was supplied to mitochondria, and the CO2 formed was absorbed and analyzed for isotopic content. CO2 evolved by mitochondria of Pisum was enriched up to 8% in 12C compared to the carboxylic atom of glycine. CO2 evolved by mitochondria of the other plants investigated was enriched by 5-16% in 13C. Carbon isotope effects were sensitive to reaction conditions (pH and the presence of GDC cofactors). Theoretical treatment of the reaction mechanism enabled us to conclude that the value and even the sign of the carbon isotope effect in glycine decarboxylation depend on the contribution of the enzyme-substrate binding step and of the decarboxylation step itself to the overall reaction rate. Therefore, the fractionation of carbon isotopes in GDC reaction was revealed which provides essential isotopic effects in plants in addition to the well-known effect of carbon isotope fractionation by the central photosynthetic enzyme, ribulose-1,5-biphosphate carboxylase.

  6. Empirical High-Temperature Calibration for the Carbonate Clumped Isotopes Paleothermometer

    NASA Astrophysics Data System (ADS)

    Kluge, T.; John, C. M.; Jourdan, A.; Davis, S.; Crawshaw, J.

    2013-12-01

    The clumped isotope paleothermometer is being used in a wide range of applications related to carbonate mineral formation, focusing on temperature and fluid δ18O reconstruction. Whereas the range of typical Earth surface temperatures has been the focus of several studies based on laboratory experiments and biogenic carbonates of known growth temperatures, the clumped isotope-temperature relationship above 70 °C has not been assessed by direct precipitation of carbonates. We investigated the clumped isotope-temperature relationship by precipitating carbonates between 20 and 200°C in the laboratory. The setup consists of a pressurized vessel in which carbonate minerals are precipitated from the mixture of two solutions (CaCl2, NaHCO3). Both solutions are thermally and isotopically equilibrated before injection in the pressure vessel. Minerals precipitated in this setup generally consist of calcite. Samples were reacted with 105% orthophosphoric acid for 10 min at 90°C. The evolved CO2 was continuously collected and subsequently purified with a Porapak trap held at -35°C. Measurements were performed on a MAT 253 using the protocol of Huntington et al. (2009) and Dennis et al. (2011). Clumped isotope values from 20-90°C are consistent with carbonates that were precipitated from a CaCO3 super-saturated solution using the method of McCrea (1950). This demonstrates that the experimental setup does not induce any kinetic fractionation, and can be used for high-temperature carbonate precipitation. The new clumped isotope calibration at high temperature follows the theoretical calculations of Schauble et al. (2006) adjusted for phosphoric acid digestion at 90°C. We gratefully acknowledge funding from Qatar Petroleum, Shell and the Qatar Science and Technology Park.

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

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Thomas, James; Decker, David; Patterson, Gary

    2007-06-25

    Groundwater samples in the Yucca Mountain area were collected for chemical and isotopic analyses and measurements of water temperature, pH, specific conductivity, and alkalinity were obtained at the well or spring at the time of sampling. For this project, groundwater samples were analyzed for major-ion chemistry, deuterium, oxygen-18, and carbon isotopes of dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC). The U.S. Geological Survey (USGS) performed all the fieldwork on this project including measurement of water chemistry field parameters and sample collection. The major ions dissolved in the groundwater, deuterium, oxygen-18, and carbon isotopes of dissolved inorganic carbon (DIC)more » were analyzed by the USGS. All preparation and processing of samples for DOC carbon isotopic analyses and geochemical modeling were performed by the Desert Research Institute (DRI). Analysis of the DOC carbon dioxide gas produced at DRI to obtain carbon-13 and carbon-14 values was conducted at the University of Arizona Accelerator Facility (a NSHE Yucca Mountain project QA qualified contract facility). The major-ion chemistry, deuterium, oxygen-18, and carbon isotopes of DIC were used in geochemical modeling (NETPATH) to determine groundwater sources, flow paths, mixing, and ages. The carbon isotopes of DOC were used to calculate groundwater ages that are independent of DIC model corrected carbon-14 ages. The DIC model corrected carbon-14 calculated ages were used to evaluate groundwater travel times for mixtures of water including water beneath Yucca Mountain. When possible, groundwater travel times were calculated for groundwater flow from beneath Yucca Mountain to down gradient sample sites. DOC carbon-14 groundwater ages were also calculated for groundwaters in the Yucca Mountain area. When possible, groundwater travel times were estimated for groundwater flow from beneath Yucca Mountain to down gradient groundwater sample sites using the DOC calculated

  8. Mercury Abundances and Isotopic Compositions in the Murchison (CM) and Allende (CV)Carbonaceous Chondrites

    NASA Technical Reports Server (NTRS)

    Lauretta, D. S.; Klaue, B.; Blum, J. D.; Buseck, P. R.

    2001-01-01

    The abundance and isotopic composition of Hg was determined in bulk samples of both the Murchison (CM) and Allende (CV) carbonaceous chondrites using single- and multi-collector inductively coupled plasma mass spectrometry (ICP-MS). The bulk abundances of Hg are 294 6 15 ng/g in Murchison and 30.0 6 1.5 ng/g in Allende. These values are within the range of previous measurements of bulk Hg abundances by neutron activation analysis (NAA). Prior studies suggested that both meteorites contain isotopically anomalous Hg, with d l 96/202Hg values for the anomalous, thermal-release components from bulk samples ranging from 2260 %o to 1440 9/00 in Murchison and from 2620 9/00 to 1540 9/00 in Allende (Jovanovic and Reed, 1976a; 1976b; Kumar and Goel, 1992). Our multi-collector ICP-MS measurements suggest that the relative abundances of all seven stable Hg isotopes in both meteorites are identical to terrestrial values within 0.2 to 0.5 9/00m. On-line thermal-release experiments were performed by coupling a programmable oven with the singlecollector ICP-MS. Powdered aliquots of each meteorite were linearly heated from room temperature to 900 C over twenty-five minutes under an Ar atmosphere to measure the isotopic composition of Hg released fiom the meteorites as a h c t i o n of temperature. In separate experiments, the release profiles of S and Se were determined simultaneously with Hg to constrain the Hg distribution within the meteorites and to evaluate the possibility of Se interferences in previous NAA studies. The Hg-release patterns differ between Allende and Murchison. The Hg-release profile for Allende contains two distinct peaks, at 225" and 343"C, whereas the profile for Murchison has only one peak, at 344 C. No isotopically anomalous Hg was detected in the thermal-release experiments at a precision level of 5 to 30 9/00, depending on the isotope ratio. In both meteorites the Hg peak at ;340"C correlates with a peak in the S-release profile. This correlation

  9. Combined simulation of carbon and water isotopes in a global ocean model

    NASA Astrophysics Data System (ADS)

    Paul, André; Krandick, Annegret; Gebbie, Jake; Marchal, Olivier; Dutkiewicz, Stephanie; Losch, Martin; Kurahashi-Nakamura, Takasumi; Tharammal, Thejna

    2013-04-01

    Carbon and water isotopes are included as passive tracers in the MIT general circulation model (MITgcm). The implementation of the carbon isotopes is based on the existing MITgcm carbon cycle component and involves the fractionation processes during photosynthesis and air-sea gas exchange. Special care is given to the use of a real freshwater flux boundary condition in conjunction with the nonlinear free surface of the ocean model. The isotopic content of precipitation and water vapor is obtained from an atmospheric GCM (the NCAR CAM3) and mapped onto the MITgcm grid system, but the kinetic fractionation during evaporation is treated explicitly in the ocean model. In a number of simulations, we test the sensitivity of the carbon isotope distributions to the formulation of fractionation during photosynthesis and compare the results to modern observations of δ13C and Δ14C from GEOSECS, WOCE and CLIVAR. Similarly, we compare the resulting distribution of oxygen isotopes to modern δ18O data from the NASA GISS Global Seawater Oxygen-18 Database. The overall agreement is good, but there are discrepancies in the carbon isotope composition of the surface water and the oxygen isotope composition of the intermediate and deep waters. The combined simulation of carbon and water isotopes in a global ocean model will provide a framework for studying present and past states of ocean circulation such as postulated from deep-sea sediment records.

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

    NASA Technical Reports Server (NTRS)

    Blum, J. D.; Klaue, Bjorn

    2005-01-01

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

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

    NASA Astrophysics Data System (ADS)

    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

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

    DOE Office of Scientific and Technical Information (OSTI.GOV)

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

    1987-03-01

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

  13. Integrated carbon and chlorine isotope modeling: applications to chlorinated aliphatic hydrocarbons dechlorination.

    PubMed

    Jin, Biao; Haderlein, Stefan B; Rolle, Massimo

    2013-02-05

    We propose a self-consistent method to predict the evolution of carbon and chlorine isotope ratios during degradation of chlorinated hydrocarbons. The method treats explicitly the cleavage of isotopically different C-Cl bonds and thus considers, simultaneously, combined carbon-chlorine isotopologues. To illustrate the proposed modeling approach we focus on the reductive dehalogenation of chlorinated ethenes. We compare our method with the currently available approach, in which carbon and chlorine isotopologues are treated separately. The new approach provides an accurate description of dual-isotope effects regardless of the extent of the isotope fractionation and physical characteristics of the experimental system. We successfully applied the new approach to published experimental results on dehalogenation of chlorinated ethenes both in well-mixed systems and in situations where mass-transfer limitations control the overall rate of biodegradation. The advantages of our self-consistent dual isotope modeling approach proved to be most evident when isotope fractionation factors of carbon and chlorine differed significantly and for systems with mass-transfer limitations, where both physical and (bio)chemical transformation processes affect the observed isotopic values.

  14. Fractionation between inorganic and organic carbon during the Lomagundi (2.22 2.1 Ga) carbon isotope excursion

    NASA Astrophysics Data System (ADS)

    Bekker, A.; Holmden, C.; Beukes, N. J.; Kenig, F.; Eglinton, B.; Patterson, W. P.

    2008-07-01

    The Lomagundi (2.22-2.1 Ga) positive carbon isotope excursion in shallow-marine sedimentary carbonates has been associated with the rise in atmospheric oxygen, but subsequent studies have demonstrated that the carbon isotope excursion was preceded by the rise in atmospheric oxygen. The amount of oxygen released to the exosphere during the Lomagundi excursion is constrained by the average global fractionation between inorganic and organic carbon, which is poorly characterized. Because dissolved inorganic and organic carbon reservoirs were arguably larger in the Paleoproterozoic ocean, at a time of lower solar luminosity and lower ocean redox state, decoupling between these two variables might be expected. We determined carbon isotope values of carbonate and organic matter in carbonates and shales of the Silverton Formation, South Africa and in the correlative Sengoma Argillite Formation, near the border in Botswana. These units were deposited between 2.22 and 2.06 Ga along the margin of the Kaapvaal Craton in an open-marine deltaic setting and experienced lower greenschist facies metamorphism. The prodelta to offshore marine shales are overlain by a subtidal carbonate sequence. Carbonates exhibit elevated 13C values ranging from 8.3 to 11.2‰ vs. VPDB consistent with deposition during the Lomagundi positive excursion. The total organic carbon (TOC) contents range from 0.01 to 0.6% and δ13C values range from - 24.8 to - 13.9‰. Thus, the isotopic fractionation between organic and carbonate carbon was on average 30.3 ± 2.8‰ ( n = 32) in the shallow-marine environment. The underlying Sengoma shales have highly variable TOC contents (0.14 to 21.94%) and δ13C values (- 33.7 to - 20.8‰) with an average of - 27.0 ± 3.0‰ ( n = 50). Considering that the shales were also deposited during the Lomagundi excursion, and taking δ13C values of the overlying carbonates as representative of the δ13C value of dissolved inorganic carbon during shale deposition, a carbon

  15. Trace sulfate in mid-Proterozoic carbonates and the sulfur isotope record of biospheric evolution

    NASA Astrophysics Data System (ADS)

    Gellatly, Anne M.; Lyons, Timothy W.

    2005-08-01

    Concentrations of oceanic and atmospheric oxygen have varied over geologic time as a function of sulfur and carbon cycling at or near the Earth's surface. This balance is expressed in the sulfur isotope composition of seawater sulfate. Given the near absence of gypsum in pre-Phanerozoic sediments, trace amounts of carbonate-associated sulfate (CAS) within limestones or dolostones provide the best available constraints on the isotopic composition of sulfate in Precambrian seawater. Although absolute CAS concentrations, which range from those below detection to ˜120 ppm sulfate in this study, may be compromised by diagenesis, the sulfur isotope compositions can be buffered sufficiently to retain primary values. Stratigraphically controlled δ 34S measurements for CAS from three mid-Proterozoic carbonate successions (˜1.2 Ga Mescal Limestone, Apache Group, Arizona, USA; ˜1.45-1.47 Ga Helena and Newland formations, Belt Supergroup, Montana, USA; and ˜1.65 Ga Paradise Creek Formation, McNamara Group, NW Queensland, Australia) show large isotopic variability (+9.1‰ to +18.9‰, -1.1‰ to +27.3‰, and +14.1‰ to +37.3‰, respectively) over stratigraphic intervals of ˜50 to 450 m. This rapid variability, ranging from scattered to highly systematic, and overall low CAS abundances can be linked to sulfate concentrations in the mid-Proterozoic ocean that were substantially lower than those of the Phanerozoic but higher than values inferred for the Archean. Results from the Belt Supergroup specifically corroborate previous arguments for seawater contributions to the basin. Limited sulfate availability that tracks the oxygenation history of the early atmosphere is also consistent with the possibility of extensive deep-ocean sulfate reduction, the scarcity of bedded gypsum, and the stratigraphic δ 34S trends and 34S enrichments commonly observed for iron sulfides of mid-Proterozoic age.

  16. Development of a Field-Deployable Methane Carbon Isotope Analyzer

    NASA Astrophysics Data System (ADS)

    Dong, Feng; Baer, Douglas

    2010-05-01

    Methane is a potent greenhouse gas, whose atmospheric surface mixing ratio has almost doubled compared with preindustrial values. Methane can be produced by biogenic processes, thermogenic processes or biomass, with different isotopic signatures. As a key molecule involved in the radiative forcing in the atmosphere, methane is thus one of the most important molecules linking the biosphere and atmosphere. Therefore precise measurements of mixing ratios and isotopic compositions will help scientists to better understand methane sources and sinks. To date, high precision isotope measurements have been exclusively performed with conventional isotope ratio mass spectrometry, which involves intensive labor and is not readily field deployable. Optical studies using infrared laser spectroscopy have also been reported to measure the isotopic ratios. However, the precision of optical-based analyses, to date, is typically unsatisfactory without pre-concentration procedures. We present characterization of the performance of a portable Methane Carbon Isotope Analyzer (MCIA), based on cavity enhanced laser absorption spectroscopy technique, that provides in-situ measurements of the carbon isotope ratio (13C/12C or del_13C) and methane mixing ratio (CH4). The sample is introduced to the analyzer directly without any requirement for pretreatment or preconcentration. A typical precision of less than 1 per mill (< 0.1%) with a 10-ppm methane sample can be achieved in a measurement time of less than 100 seconds. The MCIA can report carbon isotope ratio and concentration measurements over a very wide range of methane concentrations. Results of laboratory tests and field measurements will be presented.

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

    USGS Publications Warehouse

    Coleman, D.D.; Risatti, J.B.; Schoell, M.

    1981-01-01

    Carbon isotopic analysis of methane has become a popular technique in the exploration for oil and gas because it can be used to differentiate between thermogenic and microbial gas and can sometimes be used for gas-source rock correlations. Methane-oxidizing bacteria, however, can significantly change the carbon isotopic composition of methane; the origin of gas that has been partially oxidized by these bacteria could therefore be misinterpreted. We cultured methane-oxidizing bacteria at two different temperatures and monitored the carbon and hydrogen isotopic compositions of the residual methane. The residual methane was enriched in both 13C and D. For both isotopic species, the enrichment at equivalent levels of conversion was greater at 26??C than at 11.5??C. The change in ??D relative to the change in ??13C was independent of temperature within the range studied. One culture exhibited a change in the fractionation pattern for carbon (but not for hydrogen) midway through the experiment, suggesting that bacterial oxidation of methane may occur via more than one pathway. The change in the ??D value for the residual methane was from 8 to 14 times greater than the change in the ??13C value, indicating that combined carbon and hydrogen isotopic analysis may be an effective way of identifying methane which has been subjected to partial oxidation by bacteria. ?? 1981.

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

    NASA Astrophysics Data System (ADS)

    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

  19. Triple oxygen isotopes in biogenic and sedimentary carbonates

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

    The 17O anomaly (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

  20. Stable carbon isotopic compositions of intact polar lipids reveal complex carbon flow patterns among hydrocarbon degrading microbial communities at the Chapopote asphalt volcano

    NASA Astrophysics Data System (ADS)

    Schubotz, Florence; Lipp, Julius S.; Elvert, Marcus; Hinrichs, Kai-Uwe

    2011-08-01

    Seepage of asphalt forms the basis of a cold seep system at 3000 m water depth at the Chapopote Knoll in the southern Gulf of Mexico. Anaerobic microbial communities are stimulated in the oil-impregnated sediments as evidenced by the presence of intact polar membrane lipids (IPLs) derived from archaea and Bacteria at depths up to 7 m below the seafloor. Detailed investigation of stable carbon isotope composition (δ 13C) of alkyl and acyl moieties derived from a range of IPL precursors with distinct polar head groups resolved the complexity of carbon metabolisms and utilization of diverse carbon sources by uncultured microbial communities. In surface sediments most of the polar lipid-derived fatty acids with phosphatidylethanolamine (PE), phosphatidylglycerol (PG) and diphosphatidylglycerol (DPG) head groups could be tentatively assigned to autotrophic sulfate-reducing bacteria, with a relatively small proportion involved in the anaerobic oxidation of methane. Derivatives of phosphatidyl-( N)-methylethanolamine (PME) were abundant and could be predominantly assigned to heterotrophic oil-degrading bacteria. Archaeal IPLs with phosphate-based hydroxyarchaeols and diglycosidic glyceroldibiphytanylglyceroltetraethers (GDGTs) were assigned to methanotrophic archaea of the ANME-2 and ANME-1 cluster, respectively, whereas δ 13C values of phosphate-based archaeols and mixed phosphate-based and diglycosidic GDGTs point to methanogenic archaea. At a 7 m deep sulfate-methane transition zone that is linked to the upward movement of gas-laden petroleum, a distinct increase in abundance of archaeal IPLs such as phosphate-based hydroxyarchaeols and diglycosidic archaeol and GDGTs is observed; their δ 13C values are consistent with their origin from both methanotrophic and methanogenic archaea. This study reveals previously hidden, highly complex patterns in the carbon-flow of versatile microbial communities involved in the degradation of heavy oil including hydrocarbon gases

  1. Isotopic exchange of carbon-bound hydrogen over geologic timescales

    NASA Astrophysics Data System (ADS)

    Sessions, Alex L.; Sylva, Sean P.; Summons, Roger E.; Hayes, John M.

    2004-04-01

    The increasing popularity of compound-specific hydrogen isotope (D/H) analyses for investigating sedimentary organic matter raises numerous questions about the exchange of carbon-bound hydrogen over geologic timescales. Important questions include the rates of isotopic exchange, methods for diagnosing exchange in ancient samples, and the isotopic consequences of that exchange. This article provides a review of relevant literature data along with new data from several pilot studies to investigate such issues. Published experimental estimates of exchange rates between organic hydrogen and water indicate that at warm temperatures (50-100°C) exchange likely occurs on timescales of 104 to 108 yr. Incubation experiments using organic compounds and D-enriched water, combined with compound-specific D/H analyses, provide a new and highly sensitive method for measuring exchange at low temperatures. Comparison of δD values for isoprenoid and n-alkyl carbon skeletons in sedimentary organic matter provides no evidence for exchange in young (<1 Ma), cool sediments, but strong evidence for exchange in ancient (>350 Ma) rocks. Specific rates of exchange are probably influenced by the nature and abundance of organic matter, pore-water chemistry, the presence of catalytic mineral surfaces, and perhaps even enzymatic activity. Estimates of equilibrium fractionation factors between organic H and water indicate that typical lipids will be depleted in D relative to water by ∼75 to 140‰ at equilibrium (30°C). Thus large differences in δD between organic molecules and water cannot be unambiguously interpreted as evidence against hydrogen exchange. A better approach may be to use changes in stereochemistry as a proxy for hydrogen exchange. For example, estimated rates of H exchange in pristane are similar to predicted rates for stereochemical inversion in steranes and hopanes. The isotopic consequences of this exchange remain in question. Incubations of cholestene with D2O indicate

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    Variation in the isotopic composition of water is one of the major contributors to uncertainty in the realization of the triple point of water (TPW). Although the dependence of the TPW on the isotopic composition of the water has been known for years, there is still a lack of a detailed and accurate experimental determination of the values for the correction constants. This paper is the first of two articles (Part I and Part II) that address quantification of isotope abundance effects on the triple point temperature of water. In this paper, we describe our experimental assessment of the 2H isotope effect. We manufactured five triple point cells with prepared water mixtures with a range of 2H isotopic abundances encompassing widely the natural abundance range, while the 18O and 17O isotopic abundance were kept approximately constant and the 18O  -  17O ratio was close to the Meijer-Li relationship for natural waters. The selected range of 2H isotopic abundances led to cells that realised TPW temperatures between approximately  -140 μK to  +2500 μK with respect to the TPW temperature as realized by VSMOW (Vienna Standard Mean Ocean Water). Our experiment led to determination of the value for the δ2H correction parameter of A2H  =  673 μK / (‰ deviation of δ2H from VSMOW) with a combined uncertainty of 4 μK (k  =  1, or 1σ).

  3. Fluorine Abundances in AGB Carbon Stars: New Results?

    NASA Astrophysics Data System (ADS)

    Abia, C.; de Laverny, P.; Recio-Blanco, A.; Domínguez, I.; Cristallo, S.; Straniero, O.

    2009-09-01

    A recent reanalysis of the fluorine abundance in three Galactic Asymptotic Giant Branch (AGB) carbon stars (TX Psc, AQ Sgr and R Scl) by Abia et al. (2009) results in estimates of fluorine abundances systematically lower by ~0.8 dex on average, with respect to the sole previous estimates by Jorissen, Smith & Lambert (1992). The new F abundances are in better agreement with the predictions of full-network stellar models of low-mass (<3 Msolar) AGB stars.

  4. Carbon chain abundance in the diffuse interstellar medium

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

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

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

    NASA Astrophysics Data System (ADS)

    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

  6. Carbon cycling in terrestrial environments: Chapter 17

    USGS Publications Warehouse

    Wang, Yang; Huntington, Thomas G.; Osher, Laurie J.; Wassenaar, Leonard I; Trumbore, Susan E.; Amundson, Ronald; Harden, Jennifer W.; McKnight, Diane M.; Schiff, Sherry L.; Aiken, George R.; Lyons, W. Berry; Aravena, Ramon O.; Baron, Jill S.

    1998-01-01

    This chapter reviews a number of applications of isotopic techniques for the investigation of carbon cycling processes. Carbon dioxide (C02) is an important greenhouse gas. Its concentration in the atmosphere has increased from an estimated 270 ppm at the beginning of the industrial revolution to ∼ 360 ppm at present. Climatic conditions and atmospheric C02 concentration also influence isotopic discrimination during photosynthesis. Natural and anthropogenically induced variations in the carbon isotopic abundance can be exploited to investigate carbon transformations between pools on various time scales. It also discusses one of the isotopes of carbon, the 14C, that is produced in the atmosphere by interactions of cosmic-ray produced neutrons with stable isotopes of nitrogen (N), oxygen (O), and carbon (C), and has a natural abundance in the atmosphere of ∼1 atom 14 C per 1012 atoms 12C. The most important factor affecting the measured 14C ages of soil organic matter is the rate of organic carbon cycling in soils. Differences in the dynamics of soil carbon among different soils or soil horizons will result in different soil organic 14C signatures. As a result, the deviation of the measured 14C age from the true age could differ significantly among different soils or soil horizons.

  7. Observations of Carbon Isotopic Fractionation in Interstellar Formaldehyde

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

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

  8. Using stable isotopes of carbon to investigate the seasonal variation of carbon transfer in a northwestern Arkansas cave

    USGS Publications Warehouse

    Knierim, Katherine J.; Pollock, Erik; Hays, Phillip D.; Khojasteh, Jam

    2015-01-01

    Stable-isotope analyses are valuable in karst settings, where characterizing biogeochemical cycling of carbon along groundwater flow paths is critical for understanding and protecting sensitive cave and karst water resources. This study quantified the seasonal changes in concentration and isotopic composition (δ13C) of aqueous and gaseous carbon species—dissolved inorganic carbon (DIC) and gaseous carbon dioxide (CO2)—to characterize sources and transfer of these species along a karst flow path, with emphasis on a cave environment. Gas and water samples were collected from the soil and a cave in northwestern Arkansas approximately once a month for one year to characterize carbon cycling along a conceptual groundwater flow path. In the soil, as the DIC concentration increased, the isotopic composition of the DIC became relatively lighter, indicating an organic carbon source for a component of the DIC and corroborating soil DIC as a proxy for soil respiration. In the cave, a positive correlation between DIC and surface temperature was due to increased soil respiration as the organic carbon signal from the soil was transferred to the cave environment via the aqueous phase. CO2 concentration was lowest in the cave during colder months and increased exponentially with increasing surface temperature, presumably due to higher rates of soil respiration during warmer periods and changing ventilation patterns between the surface and cave atmosphere. Isotopic disequilibrium between CO2 and DIC in the cave was greatest when CO2 concentration was changing during November/ December and March/April, presumably due to the rapid addition or removal of gaseous CO2. The isotopic disequilibrium between DIC and CO2 provided evidence that cave CO2 was a mixture of carbon from several sources, which was mostly constrained by mixture between atmospheric CO2 and soil CO2. The concentration and isotopic composition of gaseous and aqueous carbon species were controlled by month

  9. Widespread kelp-derived carbon in pelagic and benthic nearshore fishes suggested by stable isotope analysis

    NASA Astrophysics Data System (ADS)

    von Biela, Vanessa R.; Newsome, Seth D.; Bodkin, James L.; Kruse, Gordon H.; Zimmerman, Christian E.

    2016-11-01

    Kelp forests provide habitat for diverse and abundant fish assemblages, but the extent to which kelp provides a source of energy to fish and other predators is unclear. To examine the use of kelp-derived energy by fishes we estimated the contribution of kelp- and phytoplankton-derived carbon using carbon (δ13C) and nitrogen (δ15N) isotopes measured in muscle tissue. Benthic-foraging kelp greenling (Hexagrammos decagrammus) and pelagic-foraging black rockfish (Sebastes melanops) were collected at eight sites spanning ∼35 to 60°N from the California Current (upwelling) to Alaska Coastal Current (downwelling) in the northeast Pacific Ocean. Muscle δ13C values were expected to be higher for fish tissue primarily derived from kelp, a benthic macroalgae, and lower for tissue primarily derived from phytoplankton, pelagic microalgae. Muscle δ13C values were higher in benthic-feeding kelp greenling than in pelagic-feeding black rockfish at seven of eight sites, indicating more kelp-derived carbon in greenling as expected. Estimates of kelp carbon contributions ranged from 36 to 89% in kelp greenling and 32 to 65% in black rockfish using carbon isotope mixing models. Isotopic evidence suggests that these two nearshore fishes routinely derive energy from kelp and phytoplankton, across coastal upwelling and downwelling systems. Thus, the foraging mode of nearshore predators has a small influence on their ultimate energy source as energy produced by benthic macroalgae and pelagic microalgae were incorporated in fish tissue regardless of feeding mode and suggest strong and widespread benthic-pelagic coupling. Widespread kelp contributions to benthic- and pelagic-feeding fishes suggests that kelp energy provides a benefit to nearshore fishes and highlights the potential for kelp and fish production to be linked.

  10. Stable isotopes of carbon and nitrogen in the study of avian and mammalian trophic ecology

    Treesearch

    Jeffrey F. Kelly

    2000-01-01

    Differential fractionation of stable isotopes of carbon during photosynthesis causes C4 plants and C3 plants to have distinct carbon-isotope signatures. In addition, marine C3 plants have stable-isotope ratios of carbon that are intermediate between C4 and terrestrial C3 plants. The direct incorporation of the carbon-isotope ratio (13C/12C) of plants into consumers...

  11. Mercury (Hg) in meteorites: Variations in abundance, thermal release profile, mass-dependent and mass-independent isotopic fractionation

    NASA Astrophysics Data System (ADS)

    Meier, Matthias M. M.; Cloquet, Christophe; Marty, Bernard

    2016-06-01

    We have measured the concentration, isotopic composition and thermal release profiles of Mercury (Hg) in a suite of meteorites, including both chondrites and achondrites. We find large variations in Hg concentration between different meteorites (ca. 10 ppb to 14,000 ppb), with the highest concentration orders of magnitude above the expected bulk solar system silicates value. From the presence of several different Hg carrier phases in thermal release profiles (150-650 °C), we argue that these variations are unlikely to be mainly due to terrestrial contamination. The Hg abundance of meteorites shows no correlation with petrographic type, or mass-dependent fractionation of Hg isotopes. Most carbonaceous chondrites show mass-independent enrichments in the odd-numbered isotopes 199Hg and 201Hg. We show that the enrichments are not nucleosynthetic, as we do not find corresponding nucleosynthetic deficits of 196Hg. Instead, they can partially be explained by Hg evaporation and redeposition during heating of asteroids from primordial radionuclides and late-stage impact heating. Non-carbonaceous chondrites, most achondrites and the Earth do not show these enrichments in vapor-phase Hg. All meteorites studied here have however isotopically light Hg (δ202Hg = ∼-7 to -1) relative to the Earth's average crustal values, which could suggest that the Earth has lost a significant fraction of its primordial Hg. However, the late accretion of carbonaceous chondritic material on the order of ∼2%, which has been suggested to account for the water, carbon, nitrogen and noble gas inventories of the Earth, can also contribute most or all of the Earth's current Hg budget. In this case, the isotopically heavy Hg of the Earth's crust would have to be the result of isotopic fractionation between surface and deep-Earth reservoirs.

  12. A New Method for Evaluating the Carbon Isotope Characteristics of Carbonate Formed Under Cryogenic Conditions Analogous to Mars

    NASA Technical Reports Server (NTRS)

    Niles, P. B.; Socki, R. A.; Hredzak, P. L.

    2007-01-01

    The two upcoming robotic missions to Mars, Phoenix and MSL, will both have the capability of measuring the carbon isotopic composition of CO2 in the martian atmosphere, as well as possible CO2 trapped in carbonate minerals in the Martian soil. Results from orbital and landed missions now clearly indicate that no large scale deposits of carbonate materials exist at the surface. However, some results from orbital remote sensing have been interpreted to indicate that carbonate minerals are present as fine particles interspersed at low concentrations (approx. 2%) in the martian dust. One likely mechanism for the production of these carbonates is during the freezing of transient water near the surface. Large deposits of near surface ice and photographic evidence for flowing water on the surface suggest that transient melting and refreezing of H2O is an active process on Mars. Any exposure of these fluids to the CO2 rich atmosphere should al-low the production of HCO3- solutions. Carbonates are likely precipitates from these solutions during freezing as extensive CO2 degassing, driven by the fluid s decreasing volume, drives CO2 out. This rapid CO2 degassing increases the pH of the solution and drives carbonate precipitation. It has been shown in previous studies that this rapid CO2 degassing also results in a kinetic isotopic fractionation where the CO2 gas has a much lighter isotopic composition causing a large isotope enrichment of C-13 in the precipitated carbonate. This kinetic isotope enrichment may be very common in the current martian environment, and may be a very important factor in understanding the very high deltaC-13 values of carbonates found in the martian meteorites. However, while previous studies have succeeded in generally quantifying the magnitude of this effect, detailed studies of the consistency of this effect, and the freezing rates needed to produce it are needed to understand any carbon isotope analyses from carbonate minerals in the martian

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

    NASA Astrophysics Data System (ADS)

    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

  14. Evolution of Sulfur Isotopes and Oceanic Oxygenation Recorded in a Neoproterozoic Cap Carbonate From the Chaidam Block, China

    NASA Astrophysics Data System (ADS)

    Shen, B.; Xiao, S.; Kaufman, A.; Zhou, C.

    2006-12-01

    Neoproterozoic successions in the Chaidam Block, northwestern China, include the Hongtiegou Formation, which consists of a 20-meter thick, reddish diamictite with widespread dropstones and outsized clasts. The age of the Hongtiegou diamictite is unknown, but recent biostratigraphic correlations support a Neoproterozoic assignment. The glacial deposit is immediately overlain by a 5-meter thick carbonate of the basal Zhoujieshan Formation, which we interpret as a classic post-glacial cap carbonate. However, carbon isotope compositions of samples from this unit are near zero or slightly positive (up to ~ 2‰), which contrasts with the strongly negative (ca. -5‰) values recorded in the basal portions of most other post-glacial Neoproterozoic caps. Trace sulfate concentrations in samples of the carbonate are notably high, with an average of 366 ± 266 ppm. In the lower 2.5 meters of the Zhoujieshan cap (stage I) sulfur isotope compositions of both carbonate associated sulfate (CAS) and sulfides isolated from the same sample are indistinguishable from each other, and rise in concert by over 10% to values around +22‰. Above this level (stage II), 34S abundances of sulfides continue to increase to a peak of +27‰, but CAS values fall back to ~15‰. As a result isotopic differences between sulfides and sulfates are near zero in stage I and around 10% in stage II. The evolution of both systems in the lower half of the deposit suggests that seawater sulfate must have evolved to progressively heavier 34S compositions, and that sulfate in pore waters ¨C where sulfate reducing bacteria were active ¨C was quantitatively reduced to pyrite. This might result from the progressive distillation of sulfate from seawater by an enhanced rain of carbonate, in addition to bacterial reduction of sulfate, in the glacial aftermath. The anomalous isotope systematics of stage II are difficult to model, but might signal a new source and higher abundances of oceanic sulfate, based on

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

    NASA Technical Reports Server (NTRS)

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

    1972-01-01

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

  16. Experimental high temperature carbon isotope fractionation involving graphite

    NASA Astrophysics Data System (ADS)

    Kueter, N.; Schmidt, M. W.; Lilley, M. D.; Bernasconi, S. M.

    2016-12-01

    Graphite/carbonate carbon isotope fractionation was mainly investigated at 400- 800°C and is based on empirical calibrations, theoretical calculations and few experiments [1,2]. Own work on COH-fluid/graphite isotope fractionation shows that in experiments up to 1000oC a fluid phase is always enriched in 13C compared to coexisting graphitic carbon. The eventual kinetic isotope effect in these experiments is best displayed by the graphitic carbon being at least 3 ‰ lighter than methane. Only few experiments done in the graphite/carbonate pair dealt with higher temperatures reaching 1400°C, indicating a fractionation of up to 2 ‰ at temperatures of the Earth's mantle [2-4]. To better understand carbon isotope fractionation in crustal systems and still overcome kinetic effects, we study the graphite/carbonatite pair with piston cylinder experiments in the Na2CO3-CaCO3-CaO-COH system. Tartaric acid (C4H6O6) supplies reduced carbon, time series are performed at 10 kbar, 1300-1800°C. Initial experiments at 1300°C produce well-ordered, micron-sized graphite flakes growing attached to the capsule walls while the Na-Ca-carbonatite-melt quenches to dendritic textures. No gaseous phase was observed. Conditions well above the liquidus of the Na2CO3-CaCO3-binary lead to dissolution of the H2O from tartaric acid decomposition in the melt, any CO2-component is bound by the excess CaO to CaCO3melt while in the relatively oxidizing capsule environment any CH4-component reacts with CO2 to carbon and H2O. The graphite and the carbonatite quench are measured for their δ13C composition using a GasBench II (carbonate-dissolution in phosphoric acid) and TC/EA (residual graphite combusted in oxygen atmosphere) system coupled to a Thermo Fischer IRMS. Our results expand from the graphite-carbonate system to graphite-fluid system when adding available fluid-carbonate fractionation factors, but are also directly applicable to diamond synthesis as graphite is often found as a

  17. Carbon isotope effect during abiogenic oxidation of methane

    NASA Astrophysics Data System (ADS)

    Kiyosu, Yasuhiro; Roy Krouse, H.

    1989-11-01

    The oxidation of methane during flow over CuO and Fe 2O 3 has been examined in the temperature range of 400-650°C. The reaction rate and carbon isotope fractionation are dependent upon the choice of oxide and temperature. The activation energy is lower for hematite (8.0 kcal mole -1) than for cupric oxide (16.6 kcal mole -1). The measured ratios of the isotopic rate constants α =k 12/k 13 were found to have temperature dependences given by: 10 3(α - 1) =2.93 × 10 6/T 2 + 8.11 (cupric oxide) 10 3(α - 1) =7.44 × 10 6/T 2 + 6.56 (hematite) Abiogenic oxidation of methane is probably a significant mechanism for fractionating carbon isotopes in nature.

  18. Does burial diagenesis reset pristine isotopic compositions in paleosol carbonates?

    NASA Astrophysics Data System (ADS)

    Bera, M. K.; Sarkar, A.; Tandon, S. K.; Samanta, A.; Sanyal, P.

    2010-11-01

    Sedimentological study of early Oligocene continental carbonates from the fluvial Dagshai Formation of the Himalayan foreland basin, India resulted in the recognition of four different types namely, soil, palustrine, pedogenically modified palustrine and groundwater carbonates. Stable oxygen and carbon isotopic ( δ18O and δ13C) analyses of fabric selective carbonate microsamples show that although the pristine isotopic compositions are largely altered during deep-burial diagenesis, complete isotopic homogenization does not occur. δ18O and δ13C analyses of ~ 200 calcrete and palustrine carbonates from different stratigraphic horizons and comparison with δ18O of more robust bioapatite (fossil vertebrate tooth) phase show that dense micrites (~ > 70% carbonate) invariably preserve the pristine δ18O value (mean) of ~ - 9.8‰, while altered carbonates show much lower δ18O value ~ - 13.8‰. Such inhomogeneity causes large intra-sample and intra-soil profile variability as high as > 5‰, suggesting that soils behave like a closed system where diagenetic overprinting occurs in local domains. A simple fluid-rock interaction model suggests active participation of clay minerals to enhance the effect of fluid-rock ratio in local domains during diagenesis. This places an upper limit of 70% micrite concentration above which the effect of diagenetic alteration is minimal. Careful sampling of dense micritic part of the soil carbonate nodules, therefore, does provide pristine isotopic composition and it is inappropriate, as proposed recently, to reject the paleoclimatic potential of all paleosol carbonates affected by burial diagenesis. Based on pristine δ13C value of - 8.8 ± 0.2‰ in soil carbonates an atmospheric CO 2 concentration between ~ 764 and ~ 306 ppmv is estimated for the early Oligocene (~ 31 Ma) Dagshai time. These data show excellent agreement between two independent proxy records (viz. soil carbonate and marine alkenone) and support early Oligocene

  19. Calibrated sulfur isotope abundance ratios of three IAEA sulfur isotope reference materials and V-CDT with a reassessment of the atomic weight of sulfur

    NASA Astrophysics Data System (ADS)

    Ding, T.; Valkiers, S.; Kipphardt, H.; De Bièvre, P.; Taylor, P. D. P.; Gonfiantini, R.; Krouse, R.

    2001-08-01

    Calibrated values have been obtained for sulfur isotope abundance ratios of sulfur isotope reference materials distributed by the IAEA (Vienna). For the calibration of the measurements, a set of synthetic isotope mixtures were prepared gravimetrically from high purity Ag2S materials enriched in32S, 33S, and 34S. All materials were converted into SF6 gas and subsequently, their sulfur isotope ratios were measured on the SF5+ species using a special gas source mass spectrometer equipped with a molecular flow inlet system (IRMM's Avogadro II amount comparator). Values for the 32S/34S abundance ratios are 22.650 4(20), 22.142 4(20), and 23.393 3(17) for IAEA-S-1, IAEA-S-2, and IAEA-S-3, respectively. The calculated 32S/34S abundance ratio for V-CDT is 22.643 6(20), which is very close to the calibrated ratio obtained by Ding et al. (1999). In this way, the zero point of the VCDT scale is anchored firmly to the international system of units SI. The 32S/33S abundance ratios are 126.942(47), 125.473(55), 129.072(32), and 126.948(47) for IAEA-S-1, IAEA-S-2, IAEA-S-3, and V-CDT, respectively. In this way, the linearity of the V-CDT scale is improved over this range. The values of the sulfur molar mass for IAEA-S-1 and V-CDT were calculated to be 32.063 877(56) and 32.063 911(56), respectively, the values with the smallest combined uncertainty ever reported for the sulfur molar masses (atomic weights).

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    shore of the lake immediately after removal from the lake) under various conditions (with labeled and unlabeled substrate, in the presence and absence of daylight, with and without undermat sediment) performed as both constant labeling and pulse-chase experiments. We incubated mat sections in lake water (from equivalent depth to the collected mat) spiked either with 13C-labeled or natural abundance organic (acetate or glucose) or inorganic (bicarbonate) substrates. For those conditions in which inorganic carbon was added, we measured the DOC of the water in each condition to measure conversion from DIC to DOC and vice versa for consumption/conversion of DOC to DIC. By comparing the GasBench DIC/DOC results of these various conditions over the course of the experiments, we assessed carbon flow into and out of the mat around a daily cycle. The assessments were made using the δ13C values and data of the lake water samples from the IRMS in conjunction with bulk mat isotope values. Our data show significant interactions between DIC and DOC pools and allow us to estimate the daily balance between carbon fixation and remineralization mediated by the microbial mat.

  1. Petrography and stable isotope geochemistry of Oligocene-Miocene continental carbonates in south Texas: Implications for paleoclimate and paleoenvironment near sea-level

    NASA Astrophysics Data System (ADS)

    Godfrey, Conan; Fan, Majie; Jesmok, Greg; Upadhyay, Deepshikha; Tripati, Aradhna

    2018-05-01

    Cenozoic sedimentary rocks in the southern Texas Gulf Coastal Plains contain abundant continental carbonates that are useful for reconstructing terrestrial paleoclimate and paleoenvironment in a region near sea-level. Our field observations and thin section characterizations of the Oligocene and Miocene continental carbonates in south Texas identified three types of pedogenic carbonates, including rhizoliths, carbonate nodules, and platy horizons, and two types of groundwater carbonates, including carbonate-cemented beds and carbonate concretions, with distinctive macromorphologic and micromorphologic features. Based on preservations of authigenic microfabrics and variations of carbon and oxygen isotopic compositions, we suggest these carbonates experienced minimal diagenesis, and their stable isotopic compositions reflect paleoclimate and paleoenvironment in south Texas. Our Oligocene and Miocene carbonate clumped isotope temperatures (T(Δ47)) are 23-28 °C, slightly less than or comparable to the range of modern mean annual and mean warm season air temperature (21-27 °C) in the study area. These T(Δ47) values do not show any dependency on carbonate-type, or trends through time suggesting that groundwater carbonates were formed at shallow depths. These data could indicate that air temperature in south Texas was relatively stable since the early Oligocene. The reconstructed paleo-surface water δ18O values are similar to modern surface water which could indicate that meteoric water δ18O values also remained stable since the early Oligocene. Mean pedogenic carbonate δ13C values increased - 4.6‰ during the late Miocene, most likely reflecting an expansion of C4 grassland in south Texas. This study provides the first mid- and late Cenozoic continental records of paleoclimate and paleoecology in a low-latitude, near sea-level region.

  2. Radiocarbon and stable-isotope geochemistry of organic and inorganic carbon in Lake Superior

    NASA Astrophysics Data System (ADS)

    Zigah, Prosper K.; Minor, Elizabeth C.; Werne, Josef P.

    2012-03-01

    We present a lake-wide investigation of Lake Superior carbon and organic matter biogeochemistry using radiocarbon, stable isotope, and carbon concentrations. Dissolved inorganic carbon (DIC) abundance in the lake was 121-122 Tg C, with offshore concentration andδ13C values being laterally homogenous and tightly coupled to the physical and thermal regime and biochemical processes. Offshore Δ14C of DIC (50-65‰) exhibited lateral homogeneity and was more 14C enriched than co-occurring atmospheric CO2 (˜38‰); nearshore Δ14C of DIC (36-38‰) was similar to atmospheric CO2. Dissolved organic carbon (DOC) abundance was 14.2-16.4 Tg C. DOC's concentration and δ13C were homogenous in June (mixed lake), but varied laterally during August (stratification) possibly due to spatial differences in lake productivity. Throughout sampling, DOC had modern radiocarbon values (14-58‰) indicating a semilabile nature with a turnover time of ≤60 years. Lake particulate organic carbon (POC, 0.9-1.3 Tg C) was consistently 13C depleted relative to DOC. The δ15N of epilimnetic particulate organic nitrogen shifted to more negative values during stratification possibly indicating greater use of nitrate (rather than ammonium) by phytoplankton in August. POC's radiocarbon was spatially heterogeneous (Δ14C range: 58‰ to -303‰), and generally 14C depleted relative to DOC and DIC. POC 14C depletion could not be accounted for by black carbon in the lake but, because of its spatial and temporal distribution, is attributed to sediment resuspension. The presence of old POC within the epilimnion of the open lake indicates possible benthic-pelagic coupling in the lake's organic carbon cycle; the ultimate fate of this old POC bears further investigation.

  3. Carbon and hydrogen isotope fractionation during aerobic biodegradation of quinoline and 3-methylquinoline.

    PubMed

    Cui, Mingchao; Zhang, Wenbing; Fang, Jun; Liang, Qianqiong; Liu, Dongxuan

    2017-08-01

    Compound-specific isotope analysis has been used extensively to investigate the biodegradation of various organic pollutants. To date, little isotope fractionation information is available for the biodegradation of quinolinic compounds. In this study, we report on the carbon and hydrogen isotope fractionation during quinoline and 3-methylquinoline aerobic microbial degradation by a Comamonas sp. strain Q10. Degradation of quinoline and 3-methylquinoline was accompanied by isotope fractionation. Large hydrogen and small carbon isotope fractionation was observed for quinoline while minor carbon and hydrogen isotope fractionation effects occurred for 3-methylquinoline. Bulk carbon and hydrogen enrichment factors (ε bulk ) for quinoline biodegradation were -1.2 ± 0.1 and -38 ± 1‰, respectively, while -0.7 ± 0.1 and -5 ± 1‰ for 3-methylquinoline, respectively. This reveals a potential advantage for employing quinoline as the model compound and hydrogen isotope analysis for assessing aerobic biodegradation of quinolinic compounds. The apparent kinetic isotope effects (AKIE C ) values of carbon were 1.008 ± 0.0005 for quinoline and 1.0048 ± 0.0005 for 3-methylquinoline while AKIE H values of hydrogen of 1.264 ± 0.011 for quinoline and 1.0356 ± 0.0103 for 3-methylquinoline were obtained. The combined evaluation of carbon and hydrogen isotope fractionation yields Λ values (Λ = Δδ 2 H/Δδ 13 C ≈ εH bulk /εC bulk ) of 29 ± 2 for quinoline and 8 ± 2 for 3-methylquinoline. The results indicate that the substrate specificity may have a significant influence on the isotope fractionation for the biodegradation of quinolinic compounds. The substrate-specific isotope enrichment factors would be important for assessing the behavior and fate of quinolinic compounds in the environment.

  4. Stable carbon isotopes and levoglucosan for PM2.5 elemental carbon source apportionments in the largest city of Northwest China

    NASA Astrophysics Data System (ADS)

    Zhao, Zhuzi; Cao, Junji; Zhang, Ting; Shen, Zhenxing; Ni, Haiyan; Tian, Jie; Wang, Qiyuan; Liu, Suixin; Zhou, Jiamao; Gu, Jian; Shen, Ganzhou

    2018-07-01

    Stable carbon isotopes provide information on aerosol sources, but no extensive long-term studies of these isotopes have been conducted in China, and they have mainly been used for qualitative rather than quantitative purposes. Here, 24 h PM2.5 samples (n = 58) were collected from July 2008 to June 2009 at Xi'an, China. The concentrations of organic and elemental carbon (OC and EC), water-soluble OC, and the stable carbon isotope abundances of OC and EC were determined. In spring, summer, autumn and winter, the mean stable carbon isotope in OC (δ13COC) were -26.4 ± 0.6, -25.8 ± 0.7, -25.0 ± 0.6 and -24.4 ± 0.8‰, respectively, and the corresponding δ13CEC values were -25.5 ± 0.4, -25.5 ± 0.8, -25.2 ± 0.7 and -23.7 ± 0.6‰. Large δ13CEC and δ13COC values in winter can be linked to the burning coal for residential heating. Less biomass is burned during spring and summer than winter or fall (manifested in the levels of levoglucosan, i.e., 178, 85, 370, 935 ng m-3 in spring, summer, autumn, and winter), and the more negative δ13COC in the warmer months can be explained by the formation of secondary organic aerosols. A levoglucosan tracer method combined with an isotope mass balance analysis indicated that biomass burning accounted for 1.6-29.0% of the EC, and the mean value in winter (14.9 ± 7.5%) was 7 times higher than summer (2.1 ± 0.4%), with intermediate values of 6.1 ± 5.6 and 4.5 ± 2.4% in autumn and spring. Coal combustion accounted for 45.9 ± 23.1% of the EC overall, and the percentages were 63.0, 37.2, 36.7, and 33.7% in winter, autumn, summer and spring respectively. Motor vehicles accounted for 46.6 ± 26.5% of the annual EC, and these contributed over half (56.7-61.8%) of the EC in all seasons except winter. Correlations between motor vehicle-EC and coal combustion-EC with established source indicators (B(ghi)P and As) support the source apportionment results. This paper describes a simple and accurate method for apportioning the

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

    NASA Astrophysics Data System (ADS)

    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. Carbon Abundances in Starburst Galaxies of the Local Universe

    NASA Astrophysics Data System (ADS)

    Peña-Guerrero, María A.; Leitherer, Claus; de Mink, Selma; Wofford, Aida; Kewley, Lisa

    2017-10-01

    The cosmological origin of carbon, the fourth most abundant element in the universe, is not well known and a matter of heavy debate. We investigate the behavior of C/O to O/H in order to constrain the production mechanism of carbon. We measured emission-line intensities in the spectral range from 1600 to 10000 Å on Space Telescope Imaging Spectrograph (STIS) long-slit spectra of 18 starburst galaxies in the local universe. We determined chemical abundances through traditional nebular analysis, and we used a Markov Chain Monte Carlo method to determine where our carbon and oxygen abundances lie in the parameter space. We conclude that our C and O abundance measurements are sensible. We analyzed the behavior of our sample in the [C/O] versus [O/H] diagram with respect to other objects such as DLAs, neutral ISM measurements, and disk and halo stars, finding that each type of object seems to be located in a specific region of the diagram. Our sample shows a steeper C/O versus O/H slope with respect to other samples, suggesting that massive stars contribute more to the production of C than N at higher metallicities, only for objects where massive stars are numerous; otherwise, intermediate-mass stars dominate the C and N production.

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

    PubMed

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

    2013-07-19

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

  8. Autotrophic and heterotrophic acquisition of carbon and nitrogen by a mixotrophic chrysophyte established through stable isotope analysis.

    PubMed

    Terrado, Ramon; Pasulka, Alexis L; Lie, Alle A-Y; Orphan, Victoria J; Heidelberg, Karla B; Caron, David A

    2017-09-01

    Collectively, phagotrophic algae (mixotrophs) form a functional continuum of nutritional modes between autotrophy and heterotrophy, but the specific physiological benefits of mixotrophic nutrition differ among taxa. Ochromonas spp. are ubiquitous chrysophytes that exhibit high nutritional flexibility, although most species generally fall towards the heterotrophic end of the mixotrophy spectrum. We assessed the sources of carbon and nitrogen in Ochromonas sp. strain BG-1 growing mixotrophically via short-term stable isotope probing. An axenic culture was grown in the presence of either heat-killed bacteria enriched with 15 N and 13 C, or unlabeled heat-killed bacteria and labeled inorganic substrates ( 13 C-bicarbonate and 15 N-ammonium). The alga exhibited high growth rates (up to 2 divisions per day) only until heat-killed bacteria were depleted. NanoSIMS and bulk IRMS isotope analyses revealed that Ochromonas obtained 84-99% of its carbon and 88-95% of its nitrogen from consumed bacteria. The chrysophyte assimilated inorganic 13 C-carbon and 15 N-nitrogen when bacterial abundances were very low, but autotrophic (photosynthetic) activity was insufficient to support net population growth of the alga. Our use of nanoSIMS represents its first application towards the study of a mixotrophic alga, enabling a better understanding and quantitative assessment of carbon and nutrient acquisition by this species.

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

    NASA Astrophysics Data System (ADS)

    Price, Gregory; Grimes, Stephen

    2015-04-01

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

  10. The influence of kinetics on the oxygen isotope composition of calcium carbonate

    NASA Astrophysics Data System (ADS)

    Watkins, James M.; Nielsen, Laura C.; Ryerson, Frederick J.; DePaolo, Donald J.

    2013-08-01

    Paleotemperature reconstructions rely on knowledge of the equilibrium separation of oxygen isotopes between aqueous solution and calcium carbonate. Although oxygen isotope separation is expected on theoretical grounds, the temperature-dependence remains uncertain because other factors, such as slow exchange of isotopes between dissolved CO2-species and water, can obscure the temperature signal. This is problematic for crystal growth experiments on laboratory timescales and for interpreting the oxygen isotope composition of crystals formed in natural settings. We present results from experiments in which inorganic calcite is precipitated in the presence of 0.25 μM dissolved bovine carbonic anhydrase (CA). The presence of dissolved CA accelerates oxygen isotope equilibration between the dissolved carbon species CO2, H2CO3, HCO3-, CO32- and water, thereby eliminating this source of isotopic disequilibrium during calcite growth. The experimental results allow us to isolate, for the first time, kinetic oxygen isotope effects occurring at the calcite-water interface. We present a framework of ion-by-ion growth of calcite that reconciles our new measurements with measurements of natural cave calcites that are the best candidate for having precipitated under near-equilibrium conditions. Our findings suggest that isotopic equilibrium between calcite and water is unlikely to have been established in laboratory experiments or in many natural settings. The use of CA in carbonate precipitation experiments offers new opportunities to refine oxygen isotope-based geothermometers and to interrogate environmental variables other than temperature that influence calcite growth rates.

  11. Carbon and nitrogen abundances in red giant stars in the globular cluster 47 Tucanae

    NASA Technical Reports Server (NTRS)

    Dickens, R. J.; Bell, R. A.; Gustafsson, B.

    1979-01-01

    The effects of changes in temperature, gravity, overall metal abundance, and carbon and nitrogen abundances have been investigated for model stellar spectra and colors representing globular-cluster giants of moderate metal deficiency. The results are presented in the form of spectral atlases and theoretical color-color diagrams. Using these results, approximate abundances of carbon and nitrogen have been derived for some red giant stars in 47 Tuc, from intermediate- and low-dispersion spectra and from intermediate- and narrow-band photometry. In all the normal giants studied, nitrogen is overabundant by up to about a factor of 5 (the precise value depends on the adopted carbon abundance), with different enhancements for different giants. The observational material is not sufficient to distinguish between a normal carbon abundance and a slight carbon depletion for the giant-branch stars, but carbon appears to be somewhat depleted in stars on the asymptotic giant branch. A most probable value of M/H = -0.8 for the overall cluster metal abundance is suggested from analysis of Stromgren photometry of red horizontal-branch stars.

  12. Radiocarbon and stable carbon isotope compositions of chemically fractionated soil organic matter in a temperate-zone forest.

    PubMed

    Koarashi, Jun; Iida, Takao; Asano, Tomohiro

    2005-01-01

    To better understand the role of soil organic matter in terrestrial carbon cycle, carbon isotope compositions in soil samples from a temperate-zone forest were measured for bulk, acid-insoluble and base-insoluble organic matter fractions separated by a chemical fractionation method. The measurements also made it possible to estimate indirectly radiocarbon ((14)C) abundances of acid- and base-soluble organic matter fractions, through a mass balance of carbon among the fractions. The depth profiles of (14)C abundances showed that (1) bomb-derived (14)C has penetrated the first 16cm mineral soil at least; (2) Delta(14)C values of acid-soluble organic matter fraction are considerably higher than those of other fractions; and (3) a significant amount of the bomb-derived (14)C has been preserved as the base-soluble organic matter around litter-mineral soil boundary. In contrast, no or little bomb-derived (14)C was observed for the base-insoluble fraction in all sampling depths, indicating that this recalcitrant fraction, accounting for approximately 15% of total carbon in this temperate-zone forest soil, plays a role as a long-term sink in the carbon cycle. These results suggest that bulk soil organic matter cannot provide a representative indicator as a source or a sink of carbon in soil, particularly on annual to decadal timescales.

  13. CO2-dependent carbon isotope fractionation in the dinoflagellate Alexandrium tamarense

    NASA Astrophysics Data System (ADS)

    Wilkes, Elise B.; Carter, Susan J.; Pearson, Ann

    2017-09-01

    The carbon isotopic composition of marine sedimentary organic matter is used to resolve long-term histories of pCO2 based on studies indicating a CO2-dependence of photosynthetic carbon isotope fractionation (εP). It recently was proposed that the δ13C values of dinoflagellates, as recorded in fossil dinocysts, might be used as a proxy for pCO2. However, significant questions remain regarding carbon isotope fractionation in dinoflagellates and how such fractionation may impact sedimentary records throughout the Phanerozoic. Here we investigate εP as a function of CO2 concentration and growth rate in the dinoflagellate Alexandrium tamarense. Experiments were conducted in nitrate-limited chemostat cultures. Values of εP were measured on cells having growth rates (μ) of 0.14-0.35 d-1 and aqueous carbon dioxide concentrations of 10.2-63 μmol kg-1 and were found to correlate linearly with μ/[CO2(aq)] (r2 = 0.94) in accord with prior, analogous chemostat investigations with eukaryotic phytoplankton. A maximum fractionation (εf) value of 27‰ was characterized from the intercept of the experiments, representing the first value of εf determined for an algal species employing Form II RubisCO-a structurally and catalytically distinct form of the carbon-fixing enzyme. This value is larger than theoretical predictions for Form II RubisCO and not significantly different from the ∼25‰ εf values observed for taxa employing Form ID RubisCO. We also measured the carbon isotope contents of dinosterol, hexadecanoic acid, and phytol from each experiment, finding that each class of biomarker exhibits different isotopic behavior. The apparent CO2-dependence of εP values in our experiments strengthens the proposal to use dinocyst δ13C values as a pCO2 proxy. Moreover, the similarity between the εf value for A. tamarense and the consensus value of ∼25‰ indicates that the CO2-sensitivity of carbon isotope fractionation saturates at similar CO2 levels across all three

  14. ICL-based TDLAS sensor for real-time breath gas analysis of carbon monoxide isotopes.

    PubMed

    Ghorbani, Ramin; Schmidt, Florian M

    2017-05-29

    We present a compact sensor for carbon monoxide (CO) in air and exhaled breath based on a room temperature interband cascade laser (ICL) operating at 4.69 µm, a low-volume circular multipass cell and wavelength modulation absorption spectroscopy. A fringe-limited (1σ) sensitivity of 6.5 × 10 -8 cm -1 Hz -1/2 and a detection limit of 9 ± 5 ppbv at 0.07 s acquisition time are achieved, which constitutes a 25-fold improvement compared to direct absorption spectroscopy. Integration over 10 s increases the precision to 0.6 ppbv. The setup also allows measuring the stable isotope 13 CO in breath. We demonstrate quantification of indoor air CO and real-time detection of CO expirograms from healthy non-smokers and a healthy smoker before and after smoking. Isotope ratio analysis indicates depletion of 13 CO in breath compared to natural abundance.

  15. Speleothems as proxy for the carbon isotope composition of atmospheric CO2

    NASA Astrophysics Data System (ADS)

    Baskaran, M.; Krishnamurthy, R. V.

    1993-12-01

    We have measured the stable isotope ratios of carbon in a suite of recent cave deposits (less than 200 years) from the San Saba County, Texas, USA. The methodology for dating these deposits using excess Pb-210 was recently established (Baskaran and Iliffe, 1993). The carbon isotope ratios of these samples, spanning the time period approximately 1800-1990 AD, reflect the carbon isotope ratio of atmospheric CO2 for the same period. The pathways by which the delta C-13 of atmospheric CO2 is imprinted on these speleothems can be explained using a model developed by Cerling (1984). The results suggest that the carbon isotope ratios of speleothems can be used to develop long-term, high-resolution chronologies of the delta C-13 of atmospheric CO2 and, by implication, the concentration of the atmospheric CO2.

  16. A carbon isotope challenge to the snowball Earth.

    PubMed

    Sansjofre, P; Ader, M; Trindade, R I F; Elie, M; Lyons, J; Cartigny, P; Nogueira, A C R

    2011-10-05

    The snowball Earth hypothesis postulates that the planet was entirely covered by ice for millions of years in the Neoproterozoic era, in a self-enhanced glaciation caused by the high albedo of the ice-covered planet. In a hard-snowball picture, the subsequent rapid unfreezing resulted from an ultra-greenhouse event attributed to the buildup of volcanic carbon dioxide (CO(2)) during glaciation. High partial pressures of atmospheric CO(2) (pCO2; from 20,000 to 90,000 p.p.m.v.) in the aftermath of the Marinoan glaciation (∼635 Myr ago) have been inferred from both boron and triple oxygen isotopes. These pCO2 values are 50 to 225 times higher than present-day levels. Here, we re-evaluate these estimates using paired carbon isotopic data for carbonate layers that cap Neoproterozoic glacial deposits and are considered to record post-glacial sea level rise. The new data reported here for Brazilian cap carbonates, together with previous ones for time-equivalent units, provide estimates lower than 3,200 p.p.m.v.--and possibly as low as the current value of ∼400 p.p.m.v. Our new constraint, and our re-interpretation of the boron and triple oxygen isotope data, provide a completely different picture of the late Neoproterozoic environment, with low atmospheric concentrations of carbon dioxide and oxygen that are inconsistent with a hard-snowball Earth.

  17. BOREAS TE-5 Leaf Carbon Isotope Data

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

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

  18. Discrimination factors of carbon and nitrogen stable isotopes in meerkat feces

    PubMed Central

    2017-01-01

    Stable isotope analysis of feces can provide a non-invasive method for tracking the dietary habits of nearly any mammalian species. While fecal samples are often collected for macroscopic and genetic study, stable isotope analysis can also be applied to expand the knowledge of species-specific dietary ecology. It is somewhat unclear how digestion changes the isotope ratios of animals’ diets, so more controlled diet studies are needed. To date, most diet-to-feces controlled stable isotope experiments have been performed on herbivores, so in this study I analyzed the carbon and nitrogen stable isotope ratios in the diet and feces of the meerkat (Suricata suricatta), a small omnivorous mammal. The carbon trophic discrimination factor between diet and feces (Δ13Cfeces) is calculated to be 0.1 ± 1.5‰, which is not significantly different from zero, and in turn, not different than the dietary input. On the other hand, the nitrogen trophic discrimination factor (Δ15Nfeces) is 1.5 ± 1.1‰, which is significantly different from zero, meaning it is different than the average dietary input. Based on data generated in this experiment and a review of the published literature, carbon isotopes of feces characterize diet, while nitrogen isotope ratios of feces are consistently higher than dietary inputs, meaning a discrimination factor needs to be taken into account. The carbon and nitrogen stable isotope values of feces are an excellent snapshot of diet that can be used in concert with other analytical methods to better understand ecology, diets, and habitat use of mammals. PMID:28626611

  19. Isotopic Abundances as Tracers of the Processes of Lunar Formation

    NASA Astrophysics Data System (ADS)

    Pahlevan, K.

    2011-12-01

    Ever since Apollo, isotopic abundances have been used as tracers to study lunar formation, in particular, to study the sources of the lunar material. In the last decade, however, a number of isotopic similarities have been observed between the lunar samples and the Earth's mantle such that these two reservoirs are now known to be indistinguishable from one another to high precision for a variety of isotopic tracers. This occurs against the backdrop of a Solar System that exhibits widespread heterogeneity with respect to these tracers, a situation that strongly argues that the source of the lunar material is the silicate Earth. To reconcile this observation with the fact that the Moon is thought to result from the collision of two isotopically distinct planetary bodies, a scenario has emerged in which the material from the Moon-forming impactor and the proto-Earth are homogenized in the aftermath of the giant impact. This takes place via turbulent mixing in the time after the giant impact but before lunar accretion while the Earth-Moon system exists in the form of a continuous, high-temperature fluid. Importantly, this high-temperature phase of the evolution occurs in the presence of at least two phases (liquid + vapor) making possible chemical and isotopic fractionation. While equilibrium isotopic fractionation tends to zero at high temperatures, and the post giant impact environment experiences some of the highest temperatures encountered in the Earth sciences, there are several factors that nevertheless make equilibrium isotope effects important probes of this early evolution. (1) Because the vaporization of silicates involves decomposition reactions, the bonding environment for elements in the liquid is often very different from that in the vapor. This difference makes the magnitude of isotopic fractionation intrinsically large, even at the relevant temperatures. (2) Since the isotopic composition of a silicate liquid and co-existing vapor are distinctly

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

    PubMed

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

    2016-02-23

    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 δ(18)O and δ(13)C 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 δ(18)O and δ(13)C 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 δ(13)C(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 δ(13)C(DIC) values is proposed which fits well with the observed chlorophyll abundance as a function of latitude.

  1. Carbonic Anhydrase, Calcification Dynamics and Stable Isotope Vital Effects: Deep Sea Corals and Beyond

    NASA Astrophysics Data System (ADS)

    Chen, S.; Gagnon, A. C.; Adkins, J. F.

    2017-12-01

    The stable isotope compositions of biogenic carbonates have been used for paleoceanographic and paleoclimatic reconstructions for decades, and produced some of the most iconic records in the field. However, we still lack a fully mechanistic understanding of the stable isotope proxies, especially the biological overprint on the environmental signals termed "vital effects". A ubiquitous feature of stable isotope vital effects in marine calcifying organisms is a strong correlation between δ18O and δ13C in a range of values that are depleted from equilibrium. Two mechanisms have been proposed to explain this correlation, one based on kinetic isotope effects during CO2(aq)-HCO3- inter-conversion, the other based on equilibrium isotope exchange during pH dependent speciation of the dissolved inorganic carbon pool. Neither mechanism explains all the stable isotope features observed in biogenic carbonates. Here we present a fully kinetic model of biomineralization and its isotope effects using deep sea corals as a test organism. A key component of our model is the consideration of the enzyme carbonic anhydrase in catalyzing the CO2(aq)-HCO3- inter-conversion reactions in the extracellular calcifying fluid (ECF). We find that the amount of carbonic anhydrase not only modulates the carbonate chemistry of the calcifying fluid, but also helps explain the slope of the δ18O-δ13C correlation. With this model, we are not only able to fit deep sea coral data, but also explain the stable isotope vital effects of other calcifying organisms. This fully kinetic model of stable isotope vital effects and the underlying calcification dynamics may also help us better understand mechanisms of other paleoceanographic tracers in biogenic carbonates, including boron isotopes and trace metal proxies.

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

    NASA Astrophysics Data System (ADS)

    Shah, S. R.; Joye, S. B.; Brandes, J. A.; McNichol, A. P.

    2013-05-01

    Orca Basin, an intraslope basin on the Texas-Louisiana continental slope, hosts a hypersaline, anoxic brine in its lowermost 200 m in which limited microbial activity has been reported. This brine contains a large reservoir of reduced and aged carbon, and appears to be stable at decadal time scales: concentrations and isotopic composition of dissolved inorganic (DIC) and organic carbon (DOC) are similar to measurements made in the 1970s. 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 remineralization as its source, radiocarbon and box model results point to the brine interface as the major source region for DIC, allowing for only limited oxidation of methane diffusing upwards from sediments. This conclusion is consistent with previous studies that identify the seawater-brine interface as the focus of microbial activity associated with Orca Basin brine. 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 to the brine as well as DIC.

  3. Organic and inorganic components of aerosols over the central Himalayas: winter and summer variations in stable carbon and nitrogen isotopic composition.

    PubMed

    Hegde, Prashant; Kawamura, Kimitaka; Joshi, H; Naja, M

    2016-04-01

    The aerosol samples were collected from a high elevation mountain site, Nainital, in India (1958 m asl) during September 2006 to June 2007 and were analyzed for water-soluble inorganic species, total carbon, nitrogen, and their isotopic composition (δ(13)C and δ(15)N, respectively). The chemical and isotopic composition of aerosols revealed significant anthropogenic influence over this remote free-troposphere site. The amount of total carbon and nitrogen and their isotopic composition suggest a considerable contribution of biomass burning to the aerosols during winter. On the other hand, fossil fuel combustion sources are found to be dominant during summer. The carbon aerosol in winter is characterized by greater isotope ratios (av. -24.0‰), mostly originated from biomass burning of C4 plants. On the contrary, the aerosols in summer showed smaller δ(13)C values (-26.0‰), indicating that they are originated from vascular plants (mostly of C3 plants). The secondary ions (i.e., SO4 (2-), NH4 (+), and NO3 (-)) were abundant due to the atmospheric reactions during long-range transport in both seasons. The water-soluble organic and inorganic compositions revealed that they are aged in winter but comparatively fresh in summer. This study validates that the pollutants generated from far distant sources could reach high altitudes over the Himalayan region under favorable meteorological conditions.

  4. Carbon Abundances in Starburst Galaxies of the Local Universe

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Peña-Guerrero, María A.; Leitherer, Claus; Mink, Selma de

    The cosmological origin of carbon, the fourth most abundant element in the universe, is not well known and a matter of heavy debate. We investigate the behavior of C/O to O/H in order to constrain the production mechanism of carbon. We measured emission-line intensities in the spectral range from 1600 to 10000 Å on Space Telescope Imaging Spectrograph (STIS) long-slit spectra of 18 starburst galaxies in the local universe. We determined chemical abundances through traditional nebular analysis, and we used a Markov Chain Monte Carlo method to determine where our carbon and oxygen abundances lie in the parameter space. Wemore » conclude that our C and O abundance measurements are sensible. We analyzed the behavior of our sample in the [C/O] versus [O/H] diagram with respect to other objects such as DLAs, neutral ISM measurements, and disk and halo stars, finding that each type of object seems to be located in a specific region of the diagram. Our sample shows a steeper C/O versus O/H slope with respect to other samples, suggesting that massive stars contribute more to the production of C than N at higher metallicities, only for objects where massive stars are numerous; otherwise, intermediate-mass stars dominate the C and N production.« less

  5. Resetting of Mg isotopes between calcite and dolomite during burial metamorphism: Outlook of Mg isotopes as geothermometer and seawater proxy

    NASA Astrophysics Data System (ADS)

    Hu, Zhongya; Hu, Wenxuan; Wang, Xiaomin; Lu, Yizhou; Wang, Lichao; Liao, Zhiwei; Li, Weiqiang

    2017-07-01

    studies of carbonate rocks with thermal history. By contrast, Mg isotopes of dolomite are less prone to post-depositional resetting due to a number of properties including high Mg abundance and high thermodynamic stability, and Mg isotopes in dolomite may be a more robust recorder for original carbonate precipitates.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

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

  8. Modeling whole-tree carbon assimilation rate using observed transpiration rates and needle sugar carbon isotope ratios.

    PubMed

    Hu, Jia; Moore, David J P; Riveros-Iregui, Diego A; Burns, Sean P; Monson, Russell K

    2010-03-01

    *Understanding controls over plant-atmosphere CO(2) exchange is important for quantifying carbon budgets across a range of spatial and temporal scales. In this study, we used a simple approach to estimate whole-tree CO(2) assimilation rate (A(Tree)) in a subalpine forest ecosystem. *We analysed the carbon isotope ratio (delta(13)C) of extracted needle sugars and combined it with the daytime leaf-to-air vapor pressure deficit to estimate tree water-use efficiency (WUE). The estimated WUE was then combined with observations of tree transpiration rate (E) using sap flow techniques to estimate A(Tree). Estimates of A(Tree) for the three dominant tree species in the forest were combined with species distribution and tree size to estimate and gross primary productivity (GPP) using an ecosystem process model. *A sensitivity analysis showed that estimates of A(Tree) were more sensitive to dynamics in E than delta(13)C. At the ecosystem scale, the abundance of lodgepole pine trees influenced seasonal dynamics in GPP considerably more than Engelmann spruce and subalpine fir because of its greater sensitivity of E to seasonal climate variation. *The results provide the framework for a nondestructive method for estimating whole-tree carbon assimilation rate and ecosystem GPP over daily-to weekly time scales.

  9. Carbon isotopic evidence for photosynthesis in Early Cambrian oceans

    NASA Astrophysics Data System (ADS)

    Surge, Donna M.; Savarese, Michael; Dodd, J. Robert; Lohmann, Kyger C.

    1997-06-01

    Were the first metazoan reefs ecologically similar to modern tropical reefs, enabling them to persist under oligotrophic conditions? We tested the hypothesis of ecological similarity by employing a geochemical approach. Petrography, cathodoluminescence, trace elements, and stable isotope analyses of primary precipitates of the Lower Cambrian Ajax Limestone, South Australia, indicate preservation of original C isotopic composition. All primary carbonate components exhibit C isotopic values similar to the composition of inorganically precipitated fibrous marine cements, suggesting that archaeocyaths and the calcimicrobe Epiphyton precipitated skeletal carbonate in equilibrium with ambient seawater in the absence of vital effects. Such data do not support the contention that archaeocyaths possessed photosymbionts. However, a +0.55‰ shift in δ13C occurs in reefs developed under shallower-water conditions relative to deeper reefs. This shift suggests the stratification of primary production in Early Cambrian oceans. The pattern is similar to that seen in the modern ocean, whereby significant photosynthesis modulates the C isotopic composition of the photic zone.

  10. Organic carbon isotope constraints on the dissolved organic carbon (DOC) reservoir at the Cryogenian-Ediacaran transition

    NASA Astrophysics Data System (ADS)

    Jiang, Ganqing; Wang, Xinqiang; Shi, Xiaoying; Zhang, Shihong; Xiao, Shuhai; Dong, Jin

    2010-10-01

    Prominent negative carbonate carbon isotope (δ 13C carb) anomalies from some Ediacaran successions are accompanied by invariant or decoupled organic carbon isotope (δ 13C org) values and have been interpreted as resulting from the remineralization of a large dissolved organic carbon (DOC) reservoir capable of buffering carbon isotopes of organic matter. This inferred oceanic DOC reservoir was thought to have initiated with the onset of Cryogenian glaciations (ca. 720 Ma) and lasted for millions of years until the late Ediacaran Period (< 560 Ma). Carbon isotope analyses of the basal Doushantuo Formation (ca. 635 Ma) in south China reveal that (1) the cap carbonate has δ 13C org around -26‰ (VPDB) and relatively low Δδ 13C (22 ± 2‰) and (2) the overlying organic-rich black shale and shaly dolostone have more negative δ 13C org (-28‰ to -35‰) and higher Δδ 13C (28‰-30‰). Both δ 13C carb and δ 13C org show a + 6‰ shift within a 4-m-thick interval overlying the Doushantuo cap carbonate. The δ 13C org values of the cap carbonate are associated with low TOC (mostly < 0.1%); their paleoceanographic significance requires further tests in other Ediacaran basins. The co-varying positive shift in δ 13C carb and δ 13C org following cap carbonate deposition is best interpreted as resulting from a rapid increase in organic carbon burial, which may have resulted in the rise of oxygen and heralded the first appearance of animals a few meters above the Doushantuo cap carbonate. The data suggest that a large oceanic DOC reservoir did not exist in the early Ediacaran ocean. Excess oceanic DOC required to explain the Ediacaran Shuram and upper Doushantuo δ 13C excursions, if it existed, had to be developed during the Ediacaran Period after cap carbonate deposition.

  11. Changes in carbon sources fueling benthic secondary production over depth and time: coupling Chironomidae stable carbon isotopes to larval abundance.

    PubMed

    Frossard, Victor; Verneaux, Valérie; Millet, Laurent; Magny, Michel; Perga, Marie-Elodie

    2015-06-01

    Stable C isotope ratio (δ(13)C) values of chironomid remains (head capsules; HC) were used to infer changes in benthic C sources over the last 150 years for two French sub-Alpine lakes. The HCs were retrieved from a series of sediment cores from different depths. The HC δ(13)C values started to decrease with the onset of eutrophication. The HC δ(13)C temporal patterns varied among depths, which revealed spatial differences in the contribution of methanotrophic bacteria to the benthic secondary production. The estimates of the methane (CH4)-derived C contribution to chironomid biomass ranged from a few percent prior to the 1930s to up to 30 % in recent times. The chironomid fluxes increased concomitantly with changes in HC δ(13)C values before a drastic decrease due to the development of hypoxic conditions. The hypoxia reinforced the implication for CH4-derived C transfer to chironomid production. In Lake Annecy, the HC δ(13)C values were negatively correlated to total organic C (TOC) content in the sediment (Corg), whereas no relationship was found in Lake Bourget. In Lake Bourget, chironomid abundances reached their maximum with TOC contents between 1 and 1.5 % Corg, which could constitute a threshold for change in chironomid abundance and consequently for the integration of CH4-derived C into the lake food webs. Our results indicated that the CH4-derived C contribution to the benthic food webs occurred at different depths in these two large, deep lakes (deep waters and sublittoral zone), and that the trophic transfer of this C was promoted in sublittoral zones where O2 gradients were dynamic.

  12. Growth factor controls on the distribution and carbon isotope composition of n-alkanes in leaf wax

    NASA Astrophysics Data System (ADS)

    Jia, C.; Xie, S.; Huang, X.

    2012-12-01

    Cuticular wax plays pivotal physiological and ecological roles in the interactions between plants and the environments in which they grow. Plant-derived long-chain alkanes are more resistant to decay than other biochemical polymers. n-Alkane distributions (Carbon Preference Index (CPI) values and Average Chain Length (ACL) values) and carbon isotopic values are used widely in palaeoenvironmental reconstruction. However, there is little information available on how growth stages of the plant might influence the abundance of n-alkanes in the natural environment. In this study, we analyzed n-alkane distributions and carbon isotope data from two tree species (Cinnamomum camphora (L.) Presl. and Liquidambar formosana Hance) collected monthly from 2009 to 2011 in Nanwang Shan, Wuhan, Hubei Province. CPI values for n-alkanes from C. camphora remained stable in autumn and winter but fluctuated dramatically during spring and autumn each year. Positive correlations between CPI values and the relative content of (C27+C29) were observed in both sun and shade leaves of C. camphora from April to July. In L. formosana, CPI values decreased gradually from April to December. A similar trend was observed in all three years suggesting that growth stages rather than temperature or relative humidity affected the CPI values on a seasonal timescale. In the samples of L. formosana ACL values were negatively correlated with CPI values in the growing season (from April to July) and positively correlated with CPI values in the other seasons. The δ13C values of C29 and C31 n-alkanes displayed more negative carbon isotopic values in autumn and winter compared with leaves sampled at the start of the growing season from both trees. The δ13C values of C29 and C31 n-alkanes of L. formosana decreased from April to December. These results demonstrate the importance of elucidating the growing factors that influence the distribution and δ13C values of alkanes in modern leaves prior to using CPI

  13. A balloon measurement of the isotopic composition of galactic cosmic ray boron, carbon and nitrogen. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Zumberge, J. F.

    1981-01-01

    The isotopic compositions of galactic cosmic ray boron, carbon, and nitrogen were measured at energies near 300 MeV amu, using a balloon-borne instrument at an atmospheric depth of approximately 5 g/sq cm. The calibrations of the detectors comprising the instrument are described. The saturation properties of the cesium iodide scintillators used for measurement of particle energy are studied in the context of analyzing the data for mass. The achieved rms mass resolution varies from approximately 0.3 amu at boron to approximately 0.5 amu at nitrogen, consistent with a theoretical analysis of the contributing factors. Corrected for detector interactions and the effects of the residual atmosphere the results are B-10/B=0.33 (+0.17, -0.11), C-13/C=0.06 (+0.13, -0.11), and N-15/N=0.42 (+0.19, -0.17). A model of galactic propagation and solar modulation is described. Assuming a cosmic ray source composition of solar-like isotopic abundances, the model predicts abundances near Earth consistent with the measurements.

  14. Carbon, Hydrogen, and Oxygen Isotope Ratios of Cellulose from Plants Having Intermediary Photosynthetic Modes 1

    PubMed Central

    Sternberg, Leonel O'Reilly; Deniro, Michael J.; Ting, Irwin P.

    1984-01-01

    Carbon and hydrogen isotope ratios of cellulose nitrate and oxygen isotope ratios of cellulose from species of greenhouse plants having different photosynthetic modes were determined. When hydrogen isotope ratios are plotted against carbon isotope ratios, four clusters of points are discernible, each representing different photosynthetic modes: C3 plants, C4 plants, CAM plants, and C3 plants that can shift to CAM or show the phenomenon referred to as CAM-cycling. The combination of oxygen and carbon isotope ratios does not distinguish among the different photosynthetic modes. Analysis of the carbon and hydrogen isotope ratios of cellulose nitrate should prove useful for screening different photosynthetic modes in field specimens that grew near one another. This method will be particularly useful for detection of plants which show CAM-cycling. PMID:16663360

  15. The Antarctic environment and its effect upon the total carbon and sulfur abundances in recovered meteorites

    NASA Technical Reports Server (NTRS)

    Gibson, E. K., Jr.; Andrawes, F. F.

    1980-01-01

    Total carbon and sulfur abundances have been measured for 25 meteorites recovered from the Allan Hills area of Antarctica. The majority (greater than 67%) of the meteorites analyzed do not contain enriched carbon abundances resulting from weathering processes. The presence of secondary carbonates in samples which give no apparent evidence of weathering was noted during pyrolysis experiments, despite the 'normal' total carbon abundances. In selected cases, the surfaces of weathered samples may contain up to a factor of two greater carbon content than the interior. Variations in carbon abundances may reflect the degree of weathering and the amount of secondary minerals present. One of the surprises of this study is that the majority of the Antarctic meteorites studied do not exhibit total carbon and sulfur abundances outside the ranges previously observed for falls.

  16. Temporal variability in arctic fox diet as reflected in stable-carbon isotopes; the importance of sea ice.

    PubMed

    Roth, James D

    2002-09-01

    Consumption of marine foods by terrestrial predators can lead to increased predator densities, potentially impacting their terrestrial resources. For arctic foxes (Alopex lagopus), access to such marine foods in winter depends on sea ice, which is threatened by global climate change. To quantify the importance of marine foods (seal carrion and seal pups) and document temporal variation in arctic fox diet I measured the ratios of the stable isotopes of carbon ((13)C/(12)C) in hair of arctic foxes near Cape Churchill, Manitoba, from 1994 to 1997. These hair samples were compared to the stable carbon isotope ratios of several prey species. Isotopic differences between seasonally dimorphic pelage types indicated a diet with a greater marine content in winter when sea ice provided access to seal carrion. Annual variation in arctic fox diet in both summer and winter was correlated with lemming abundance. Marine food sources became much more important in winters with low lemming populations, accounting for nearly half of the winter protein intake following a lemming decline. Potential alternative summer foods with isotopic signatures differing from lemmings included goose eggs and caribou, but these were unavailable in winter. Reliance on marine food sources in winter during periods of low lemming density demonstrates the importance of the sea ice as a potential habitat for this arctic fox population and suggests that a continued decline in sea ice extent will disrupt an important link between the marine and terrestrial ecosystems.

  17. Palaeo-equatorial temperatures and carbon-cycle evolution at the Triassic- Jurassic boundary: A stable isotope perspective from shallow-water carbonates from the UAE

    NASA Astrophysics Data System (ADS)

    Honig, M. R.; John, C. M.

    2013-12-01

    The Triassic-Jurassic boundary was marked by global changes including carbon-cycle perturbations and the opening of the Atlantic Ocean. These changes were accompanied by one of the major extinction events of the Phanerozoic. The carbon-cycle perturbations have been recorded in carbon isotope curves from bulk carbonates, organic carbon and fossil wood in several Tethyan locations and have been used for chemostratigraphic purposes. Here we present data from shallow-marine carbonates deposited on a homoclinal Middle Eastern carbonate ramp (United Arab Emirates). Our site was located at the equator throughout the Late Triassic and the Early Jurassic, and this study provides the first constraints of environmental changes at the low-latitudes for the Triassic-Jurassic boundary. Shallow-marine carbonate depositional systems are extremely sensitive to palaeoenvironmental changes and their usefulness for chemostratigraphy is being debated. However, the palaeogeographic location of the studied carbonate ramp gives us a unique insight into a tropical carbonate factory at a time of severe global change. Stable isotope measurements (carbon and oxygen) are being carried out on micrite, ooids and shell material along the Triassic-Jurassic boundary. The stable isotope results on micrite show a prominent negative shift in carbon isotope values of approximately 2 ‰ just below the inferred position of the Triassic-Jurassic boundary. A similar isotopic trend is also observed across the Tethys but with a range of amplitudes (from ~2 ‰ to ~4 ‰). These results seem to indicate that the neritic carbonates from our studied section can be used for chemostratigraphic purposes, and the amplitudes of the carbon isotope shifts provide critical constraints on the magnitude of carbon-cycle perturbations at low latitudes across the Triassic-Jurassic boundary. Seawater temperatures across the Triassic-Jurassic boundary will be constrained using the clumped isotope palaeo-thermometer applied

  18. A Carbonate Li Isotope Record Through Earth's History

    NASA Astrophysics Data System (ADS)

    Asael, D.; Kalderon-Asael, B.; Planavsky, N.

    2016-12-01

    Lithium (Li) isotopes emerge as a powerful geochemical proxy for tracking continental weathering through time. Extensive work on Li fractionation in modern systems has brought to a profound understanding of the modern Li budget as well as to a consensus that marine carbonates faithfully record seawater Li isotope signature. As such record is essential in order to track global-scale changes in weathering processes and intensity through Earth's history, we have generated Li isotope data from marine carbonates from over 40 units, ranging in age from 3.0 Ga to modern. Preliminary results provide evidence for strongly inhibited weathering-mediated clay formation prior to the Paleozoic, which we attribute to the pre-Paleozoic lack of land plants. The initial rise in the Li isotope values is observed during the Ordovician, which is followed by a subsequent drop to background values and then begins the generally increasing trend that is already well reported. These findings are open for interpretation but they still support the view that the emergence of land plants dramatically changed the process of weathering and it seems that biomass has a potentially significant role in mineral breakdown in soils. Li isotopes provide a novel perspective on weathering and the impact on the Earth system of the rise of land plants - one of the most significant transitions in Earth's history.

  19. Autotrophic and heterotrophic acquisition of carbon and nitrogen by a mixotrophic chrysophyte established through stable isotope analysis

    PubMed Central

    Terrado, Ramon; Pasulka, Alexis L; Lie, Alle A-Y; Orphan, Victoria J; Heidelberg, Karla B; Caron, David A

    2017-01-01

    Collectively, phagotrophic algae (mixotrophs) form a functional continuum of nutritional modes between autotrophy and heterotrophy, but the specific physiological benefits of mixotrophic nutrition differ among taxa. Ochromonas spp. are ubiquitous chrysophytes that exhibit high nutritional flexibility, although most species generally fall towards the heterotrophic end of the mixotrophy spectrum. We assessed the sources of carbon and nitrogen in Ochromonas sp. strain BG-1 growing mixotrophically via short-term stable isotope probing. An axenic culture was grown in the presence of either heat-killed bacteria enriched with 15N and 13C, or unlabeled heat-killed bacteria and labeled inorganic substrates (13C-bicarbonate and 15N-ammonium). The alga exhibited high growth rates (up to 2 divisions per day) only until heat-killed bacteria were depleted. NanoSIMS and bulk IRMS isotope analyses revealed that Ochromonas obtained 84–99% of its carbon and 88–95% of its nitrogen from consumed bacteria. The chrysophyte assimilated inorganic 13C-carbon and 15N-nitrogen when bacterial abundances were very low, but autotrophic (photosynthetic) activity was insufficient to support net population growth of the alga. Our use of nanoSIMS represents its first application towards the study of a mixotrophic alga, enabling a better understanding and quantitative assessment of carbon and nutrient acquisition by this species. PMID:28524870

  20. Dissolution of barite for the analysis of strontium isotopes and other chemical and isotopic variations using aqueous sodium carbonate

    USGS Publications Warehouse

    Breit, G.N.; Simmons, E.C.; Goldhaber, M.B.

    1985-01-01

    A simple procedure for preparing barite samples for chemical and isotopic analysis is described. Sulfate ion, in barite, in the presence of high concentrations of aqueous sodium carbonate, is replaced by carbonate. This replacement forms insoluble carbonates with the cations commonly in barite: Ba, Sr, Ca and Pb. Sulfate is released into the solution by the carbonate replacement and is separated by filtration. The aqueous sulfate can then be reprecipitated for analysis of the sulfur and oxygen isotopes. The cations in the carbonate phase can be dissolved by acidifying the solid residue. Sr can be separated from the solution for Sr isotope analysis by ion-exchange chromatography. The sodium carbonate used contains amounts of Sr which will affect almost all barite 87Sr 86Sr ratios by less than 0.00001 at 1.95?? of the mean. The procedure is preferred over other techniques used for preparing barite samples for the determination of 87Sr 86Sr ratios because it is simple, rapid and enables simultaneous determination of many compositional parameters on the same material. ?? 1985.

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

    USGS Publications Warehouse

    Miller, L.G.; Kalin, Robert M.; McCauley, S.E.; Hamilton, John T.G.; Harper, D.B.; Millet, D.B.; Oremland, R.S.; Goldstein, Allen H.

    2001-01-01

    The largest biological fractionations of stable carbon isotopes observed in nature occur during production of methane by methanogenic archaea. These fractionations result in substantial (as much as ???70???) shifts in ??13C relative to the initial substrate. We now report that a stable carbon isotopic fractionation of comparable magnitude (up to 70???) occurs during oxidation of methyl halides by methylotrophic bacteria. We have demonstrated biological fractionation with whole Cells of three methylotrophs (strain IMB-1, strain CC495, and strain MB2) and, to a lesser extent, with the purified cobalamin-dependent methyltransferase enzyme obtained from strain CC495. Thus, the genetic similarities recently reported between methylotrophs, and methanogens with respect to their pathways for C1-unit metabolism are also reflected in the carbon isotopic fractionations achieved by these organisms. We found that only part of the observed fractionation of carbon isotopes could be accounted for by the activity of the corrinoid methyltransferase enzyme, suggesting fractionation by enzymes further along the degradation pathway. These observations are of potential biogeochemical significance in the application of stable carbon isotope ratios to constrain the tropospheric budgets for the ozone-depleting halocarbons, methyl bromide and methyl chloride.

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

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

    The Earth's surface has undergone major transitions in its redox state over the past three billion years, which have affected the mobility and distribution of many elements. Here we use Se isotopic and abundance measurements of marine and non-marine mudrocks to reconstruct the evolution of the biogeochemical Se cycle from ∼3.2 Gyr onwards. The six stable isotopes of Se are predominantly fractionated during redox reactions under suboxic conditions, which makes Se a potentially valuable new tool for identifying intermediate stages from an anoxic to a fully oxygenated world. δ82/78Se shows small fractionations of mostly less than 2‰ throughout Earth's history and all are mass-dependent within error. In the Archean, especially after 2.7 Gyr, we find an isotopic enrichment in marine (+0.37 ± 0.27‰) relative to non-marine samples (-0.28 ± 0.67‰), paired with increasing Se abundances. Student t-tests show that these trends are statistically significant. Although we cannot completely rule out the possibility of volcanic Se addition, these trends may indicate the onset of oxidative weathering on land, followed by non-quantitative reduction of Se oxyanions during fluvial transport. The Paleoproterozoic Great Oxidation Event (GOE) is not reflected in the marine δ82/78Se record. However, we find a major inflection in the secular δ82/78Se trend during the Neoproterozoic, from a Precambrian mean of +0.42 ± 0.45‰ to a Phanerozoic mean of -0.19 ± 0.59‰. This drop probably reflects the oxygenation of the deep ocean at this time, stabilizing Se oxyanions throughout the water column. Since then, reduction of Se oxyanions has likely been restricted to anoxic basins and diagenetic environments in sediments. In light of recent Cr isotope data, it is likely that oxidative weathering before the Neoproterozoic produced Se oxyanions in the intermediate redox state SeIV, whereas the fully oxidized species SeVI became more abundant after the Neoproterozoic rise of

  3. 13C and 15N natural isotope abundance reflects breast cancer cell metabolism

    NASA Astrophysics Data System (ADS)

    Tea, Illa; Martineau, Estelle; Antheaume, Ingrid; Lalande, Julie; Mauve, Caroline; Gilard, Francoise; Barillé-Nion, Sophie; Blackburn, Anneke C.; Tcherkez, Guillaume

    2016-09-01

    Breast cancer is the most common cancer in women worldwide. Despite the information provided by anatomopathological assessment and molecular markers (such as receptor expression ER, PR, HER2), breast cancer therapies and prognostics depend on the metabolic properties of tumor cells. However, metabolomics have not provided a robust and congruent biomarker yet, likely because individual metabolite contents are insufficient to encapsulate all of the alterations in metabolic fluxes. Here, we took advantage of natural 13C and 15N isotope abundance to show there are isotopic differences between healthy and cancer biopsy tissues or between healthy and malignant cultured cell lines. Isotope mass balance further suggests that these differences are mostly related to lipid metabolism, anaplerosis and urea cycle, three pathways known to be impacted in malignant cells. Our results demonstrate that the isotope signature is a good descriptor of metabolism since it integrates modifications in C partitioning and N excretion altogether. Our present study is thus a starting point to possible clinical applications such as patient screening and biopsy characterization in every cancer that is associated with metabolic changes.

  4. Cretaceous shales from the western interior of North America: sulfur/carbon ratios and sulfur-isotope composition.

    USGS Publications Warehouse

    Gautier, D.L.

    1986-01-01

    Sulphur/carbon ratios in cores of selected Cretaceous marine shales average 0.67, a value greater than that observed in recent marine sediments and much higher than global values calculated for the Cretaceous. This may be ascribed to generally low levels of bioturbation and enhanced efficiency of sulphate reduction due to low oxygen levels in Cretaceous seaways. Isotopic compositions of pyrite sulphur vary systematically with level of oxygenation of the depositional environment and therefore with organic carbon abundance and type of organic matter. Samples with >4% organic carbon are extremely depleted in 34S (mean delta 34S -31per mille) and contain hydrogen-rich organic matter. Samples containing <1.5% organic carbon display relatively 'heavy' but wide-ranging delta 34S values (-34.6 to +16.8per mille) and contain hydrogen-poor organic matter. Samples with intermediate amounts of organic carbon have average delta 34S of -25.9per mille and contain both types of organic matter. Relations between the nature of these shales, and their sedimentation rate and depositional environment are discussed.-L.C.H.

  5. Carbonate Mineral Formation on Mars: Clues from Stable Isotope Variation Seen in Cryogenic Laboratory Studies of Carbonate Salts

    NASA Technical Reports Server (NTRS)

    Socki, Richard; Niles, Paul B.; Sun, Tao; Fu, Qi; Romanek, Christopher S.; Gibson, Everett K.

    2013-01-01

    The geologic history of water on the planet Mars is intimately connected to the formation of carbonate minerals through atmospheric CO2 and its control of the climate history of Mars. Carbonate mineral formation under modern martian atmospheric conditions could be a critical factor in controlling the martian climate in a means similar to the rock weathering cycle on Earth. The combination of evidence for liquid water on the martian surface and cold surface conditions suggest fluid freezing could be very common on the surface of Mars. Cryogenic calcite forms readily when a rise in pH occurs as a result of carbon dioxide degassing quickly from freezing Ca-bicarbonate-rich water solutions. This is a process that has been observed in some terrestrial settings such as arctic permafrost cave deposits, lakebeds of the Dry Valleys of Antarctica, and in aufeis (river icings) from rivers of N.E. Alaska. We report here the results of a series of laboratory experiments that were conducted to simulate potential cryogenic carbonate formation on the planet Mars. These results indicate that carbonates grown under martian conditions (controlled atmospheric pressure and temperature) show enrichments from starting bicarbonate fluids in both carbon and oxygen isotopes beyond equilibrium values with average delta13C(DIC-CARB) values of 20.5%0 which exceed the expected equilibrium fractionation factor of [10(sup 3) ln alpha = 13%0] at 0 degC. Oxygen isotopes showed a smaller enrichment with delta18O(H2O-CARB) values of 35.5%0, slightly exceeding the equilibrium fractionation factor of [10(sup 3) ln alpha = 34%0 ] at 0degC. Large kinetic carbon isotope effects during carbonate precipitation could substantially affect the carbon isotope evolution of CO2 on Mars allowing for more efficient removal of 13C from the Noachian atmosphere enriched by atmospheric loss. This mechanism would be consistent with the observations of large carbon isotope variations in martian materials despite the

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

    PubMed

    Shen, Xiaoli; Xu, Zemin; Zhang, Xichang; Yang, Fangxing

    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 2mg/kg lambda-cyhalothrin and 84 and 154 days in non-sterile and sterile soils spiked with 10mg/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 2mg/kg lambda-cyhalothrin, and to -27.5‰ with 10mg/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. Copyright © 2015 Elsevier B.V. All rights reserved.

  7. Could a secular increase in organic burial explain the rise of oxygen? Insights from a geological carbon cycle model constrained by the carbon isotope record

    NASA Astrophysics Data System (ADS)

    Krissansen-Totton, J.; Kipp, M.; Catling, D. C.

    2017-12-01

    The stable isotopes of carbon in marine sedimentary rock provide a window into the evolution of the Earth system. Conventionally, a relatively constant carbon isotope ratio in marine sedimentary rocks has been interpreted as implying constant organic carbon burial relative to total carbon burial. Because organic carbon burial corresponds to net oxygen production from photosynthesis, it follows that secular changes in the oxygen source flux cannot explain the dramatic rise of oxygen over Earth history. Instead, secular declines in oxygen sink fluxes are often invoked as causes for the rise of oxygen. However, constant fractional organic burial is difficult to reconcile with tentative evidence for low phosphate concentrations in the Archean ocean, which would imply lower marine productivity and—all else being equal—less organic carbon burial than today. The conventional interpretation of the carbon isotope record rests on the untested assumption that the isotopic ratio of carbon inputs into the ocean reflect mantle isotopic values throughout Earth history. In practice, differing rates of carbonate and organic weathering will allow for changes in isotopic inputs, as suggested by [1] and [2]. However, these inputs can not vary freely because large changes in isotopic inputs would induce secular trends in carbon reservoirs, which are not observed in the isotope record. We apply a geological carbon cycle model to all Earth history, tracking carbon isotopes in crustal, mantle, and ocean reservoirs. Our model is constrained by the carbon isotope record such that we can determine the extent to which large changes in organic burial are permitted. We find both constant organic burial and 3-5 fold increases in organic burial since 4.0 Ga can be reconciled with the carbon isotope record. Changes in the oxygen source flux thus need to be reconsidered as a possible contributor to Earth's oxygenation. [1] L. A. Derry, Organic carbon cycling and the lithosphere, in Treatise on

  8. Triple oxygen isotope composition of tropospheric carbon dioxide and terrestrial carbonates

    NASA Astrophysics Data System (ADS)

    Hofmann, M. E.; Horváth, B.; Pack, A.

    2011-12-01

    The triple oxygen isotope composition of tropospheric CO2 is a potential new tracer in urban air studies and for biosphere-atmosphere interactions [1]. In this study, we are analyzing CO2 from different provenances in order to trace the influx of anthropogenic CO2 to urban air and to test predictions on the stratosphere-troposphere exchange flux. Since July 2010, we are monitoring the triple oxygen isotope composition of CO2 in urban air in a two-week interval. For this purpose, carbon dioxide was extracted from ~450L of ambient air on the campus of the University of Göttingen using a Russian Doll type cryogenic trap [2]. The CO2 was analyzed by CO2-CeO2 equilibration at 685°C and subsequent IR laser fluorination of CeO2 and CF-irmMS [3]. All triple oxygen isotope data are reported as Δ17OTFL values relative to the terrestrial fractionation line (TFL) with a slope βTFL=0.5251 and an intercept γTFL=-0.014%. On average, the Δ17OTFL value of ambient CO2 was -0.11±0.05% (SD) with a seasonal cycle of 0.04±0.01%. Lower Δ17O values were observed during wintertime. In order to test the potential of Δ17O as a tracer for anthropogenic CO2, we analyzed CO2 from different combustion processes. Our results showed that the Δ17O anomaly of tropospheric O2 [4] is passed on fully, or partially to the combustion CO2 [5]. We estimate that elevated anthropogenic emission during wintertime could be responsible for a decrease in Δ17O of urban air CO2 of -0.02±0.01%. In order to predict the triple oxygen isotope composition of tropospheric CO2 on a global scale, we revised the box model calculation from Hoag et al. [1]. For the exponent β for CO2-water equilibrium, we assume that βCO2-water=0.522±0.001 [6]. Furthermore, we took into account that the Δ17OTFL value of CO2 released from soils is affected by kinetic fractionation. Thus, we obtained a Δ17OTFL value for global tropospheric CO2 of -0.13%. The model calculation agrees well with the Δ17OTFL value determined for

  9. Potassium isotope abundances in Australasian tektites and microtektites.

    NASA Astrophysics Data System (ADS)

    Herzog, G. F.; O'D. Alexander, C. M.; Berger, E. L.; Delaney, J. S.; Glass, B. P.

    2008-10-01

    We report electron microprobe determinations of the elemental compositions of 11 Australasian layered tektites and 28 Australasian microtektites; and ion microprobe determinations of the 41K/39K ratios of all 11 tektites and 13 of the microtektites. The elemental compositions agree well with literature values, although the average potassium concentrations measured here for microtektites, 1.1 1.6 wt%, are lower than published average values, 1.9 2.9 wt%. The potassium isotope abundances of the Australasian layered tektites vary little. The average value of δ41K, 0.02 ± 0.12‰ (1σ mean), is indistinguishable from the terrestrial value (= 0 by definition) as represented by our standard, thereby confirming four earlier tektite analyses of Humayun and Koeberl (2004). In agreement with those authors, we conclude that evaporation has significantly altered neither the isotopic nor the elemental composition of Australasian layered tektites for elements less volatile than potassium. Although the average 41K/39K ratio of the microtektites, 1.1 ± 1.7‰ (1σ mean), is also statistically indistinguishable from the value for the standard, the individual ratios vary over a very large range, from -10.6 ± 1.4‰ to +13.8 ± 1.5‰ and at least three of them are significantly different from zero. We interpret these larger variations in terms of the evaporation of isotopically light potassium; condensation of potassium in the vapor plume; partial or complete stirring and quenching of the melts; and the possible uptake of potassium from seawater. That the average 41K/39K ratio of the microtektites equals the terrestrial value suggests that the microtektite-forming system was compositionally closed with respect to potassium and less volatile elements. The possibility remains open that 41K/39K ratios of microtektites vary systematically with location in the strewn field.

  10. Improvement of 2,4-dinitrophenylhydrazine derivatization method for carbon isotope analysis of atmospheric acetone.

    PubMed

    Wen, Sheng; Yu, Yingxin; Guo, Songjun; Feng, Yanli; Sheng, Guoying; Wang, Xinming; Bi, Xinhui; Fu, Jiamo; Jia, Wanglu

    2006-01-01

    Through simulation experiments of atmospheric sampling, a method via 2,4-dinitrophenylhydrazine (DNPH) derivatization was developed to measure the carbon isotopic composition of atmospheric acetone. Using acetone and a DNPH reagent of known carbon isotopic compositions, the simulation experiments were performed to show that no carbon isotope fractionation occurred during the processes: the differences between the predicted and measured data of acetone-DNPH derivatives were all less than 0.5 per thousand. The results permitted the calculation of the carbon isotopic compositions of atmospheric acetone using a mass balance equation. In this method, the atmospheric acetone was collected by a DNPH-coated silica cartridge, washed out as acetone-DNPH derivatives, and then analyzed by gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS). Using this method, the first available delta13C data of atmospheric acetone are presented. Copyright 2006 John Wiley & Sons, Ltd.

  11. Relationships between tree height and carbon isotope discrimination

    Treesearch

    Nate G. McDowell; Barbara J. Bond; Lee T. Dickman; Michael G. Ryan; David Whitehead

    2011-01-01

    Understanding how tree size impacts leaf- and crown-level gas exchange is essential to predicting forest yields and carbon and water budgets. The stable carbon isotope ratio of organic matter has been used to examine the relationship of gas exchange to tree size for a host of species because it carries a temporally integrated signature of foliar photosynthesis and...

  12. Monsoon Variability In The Western Arabian Sea During Last 10,000 Years BP: A Planktic Foraminiferal Abundances And It's Stable Isotope Records

    NASA Astrophysics Data System (ADS)

    Singh, A. K.; Tiwari, M.; Sinha, D. K.; Ramesh, R.

    2007-12-01

    : The western Arabian Sea responds to the southwest monsoon winds by upwelling colder and nutrient rich waters from the deeper layers, causing a reduction in the sea surface temperature and enhanced biological productivity. A number of paleoclimatic studies have been carried out in this region to elucidate past monsoon variability (Sirocco et al., 1993; Gupta et al, 2003; Tiwari, 2005; Saher et.al.; 2007). Globigerina bulloides, a planktic foraminiferal species normally inhabiting surface ocean waters in temperate latitudes ( Be and Tolderlund , 1977) also becomes abundant at tropical latitudes upwelling occurs, and in these cases its abundance can exceed considerably. The conspicuous fluctuation in the abundance of Gg.bulloides during upwelling and non upwelling intervals is established through several studies ( Thiede and Junger, 1980, Gupta et al, 2003) This robust relation has been used as a proxy for wind velocity at several different times in the past in the Arabian Sea (Anderson et.al., 2002). A significant result from some of these centennially resolved Holocene records is declining abundance of Globigerina bulloides which is paralleled by reduced insolation record and this has been inferred as declining strength of Asian Monsoon. We are presenting here the data from the core SS4018 from near the Gulf of Aden, Western Arabian Sea taken at a water depth of 2830 m, precisely dated by the radiocarbon method using Accelerator Mass Spectrometry on planktonic foraminiferal separates. We have carried out the planktic foraminiferal census counts for each sample to know the relative abundance of key species. In addition to this, we have also employed multi- proxy approach such as oxygen and carbon isotopes of planktic foraminiferal tests, TOC, CaCO3 (%) to strengthen our interpretation and also to understand the relationships amongst the proxies themselves. Abundance of the key planktic foraminiferal species and other proxy records reveal at least 3 major climatic

  13. Carbon isotopes of dissolved inorganic carbon reflect utilization of different carbon sources by microbial communities in two limestone aquifer assemblages

    NASA Astrophysics Data System (ADS)

    Nowak, Martin E.; Schwab, Valérie F.; Lazar, Cassandre S.; Behrendt, Thomas; Kohlhepp, Bernd; Totsche, Kai Uwe; Küsel, Kirsten; Trumbore, Susan E.

    2017-08-01

    Isotopes of dissolved inorganic carbon (DIC) are used to indicate both transit times and biogeochemical evolution of groundwaters. These signals can be complicated in carbonate aquifers, as both abiotic (i.e., carbonate equilibria) and biotic factors influence the δ13C and 14C of DIC. We applied a novel graphical method for tracking changes in the δ13C and 14C of DIC in two distinct aquifer complexes identified in the Hainich Critical Zone Exploratory (CZE), a platform to study how water transport links surface and shallow groundwaters in limestone and marlstone rocks in central Germany. For more quantitative estimates of contributions of different biotic and abiotic carbon sources to the DIC pool, we used the NETPATH geochemical modeling program, which accounts for changes in dissolved ions in addition to C isotopes. Although water residence times in the Hainich CZE aquifers based on hydrogeology are relatively short (years or less), DIC isotopes in the shallow, mostly anoxic, aquifer assemblage (HTU) were depleted in 14C compared to a deeper, oxic, aquifer complex (HTL). Carbon isotopes and chemical changes in the deeper HTL wells could be explained by interaction of recharge waters equilibrated with post-bomb 14C sources with carbonates. However, oxygen depletion and δ13C and 14C values of DIC below those expected from the processes of carbonate equilibrium alone indicate considerably different biogeochemical evolution of waters in the upper aquifer assemblage (HTU wells). Changes in 14C and 13C in the upper aquifer complexes result from a number of biotic and abiotic processes, including oxidation of 14C-depleted OM derived from recycled microbial carbon and sedimentary organic matter as well as water-rock interactions. The microbial pathways inferred from DIC isotope shifts and changes in water chemistry in the HTU wells were supported by comparison with in situ microbial community structure based on 16S rRNA analyses. Our findings demonstrate the large

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

    NASA Technical Reports Server (NTRS)

    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.

  15. Grasland Stable Isotope Flux Measurements: Three Isotopomers of Carbon Dioxide Measured by QCL Spectroscopy

    NASA Astrophysics Data System (ADS)

    Zeeman, M. J.; Tuzson, B.; Eugster, W.; Werner, R. A.; Buchmann, N.; Emmenegger, L.

    2007-12-01

    To improve our understanding of greenhouse gas dynamics of managed ecosystems such as grasslands, we not only need to investigate the effects of management (e.g., grass cuts) and weather events (e.g., rainy days) on carbon dioxide fluxes, but also need to increase the time resolution of our measurements. Thus, for the first time, we assessed respiration and assimilation fluxes with high time resolution (5Hz) stable isotope measurements at an intensively managed farmland in Switzerland (Chamau, 400m ASL). Two different methods were used to quantify fluxes of carbon dioxide and associated fluxes of stable carbon isotopes: (1) the flux gradient method, and (2) the eddy covariance method. During a week long intensive measurement campaign, we (1) measured mixing ratios of carbon dioxide isotopomers (12C16O2, 12C16O18O, 13C16O2) with a Quantum Cascade Laser (QCL, Aerodyne Inc.) spectroscope and (2) collected air samples for isotope analyses (13C/12C) and (18O/16O) of carbon dioxide by Isotope Ratio Mass Spectrometry (IRMS, Finnigan) every two hours, concurrently along a height profile (z = 0.05; 0.10; 0.31; 2.15m). In the following week, the QCL setup was used for closed-path eddy covariance flux measurement of the carbon dioxide isotopomers, with the air inlet located next to an open-path Infra Red Gas Analyzers (IRGA, LiCor 7500) used simultaneously for carbon dioxide measurements. During this second week, an area of grass inside the footprint was cut and harvested after several days. The first results of in-field continuous QCL measurements of carbon dioxide mixing ratios and their stable isotopic ratios show good agreement with IRGA measurements and isotope analysis of flask samples by IRMS. Thus, QCL spectroscopy is a very promising tool for stable isotope flux investigations.

  16. Spatially-resolved isotopic study of carbon trapped in ∼3.43 Ga Strelley Pool Formation stromatolites

    NASA Astrophysics Data System (ADS)

    Flannery, David T.; Allwood, Abigail C.; Summons, Roger E.; Williford, Kenneth H.; Abbey, William; Matys, Emily D.; Ferralis, Nicola

    2018-02-01

    The large isotopic fractionation of carbon associated with enzymatic carbon assimilation allows evidence for life's antiquity, and potentially the early operation of several extant metabolic pathways, to be derived from the stable carbon isotope record of sedimentary rocks. Earth's organic carbon isotope record extends to the Late Eoarchean-Early Paleoarchean: the age of the oldest known sedimentary rocks. However, complementary inorganic carbon reservoirs are poorly represented in the oldest units, and commonly reported bulk organic carbon isotope measurements do not capture the micro-scale isotopic heterogeneities that are increasingly reported from younger rocks. Here, we investigated the isotopic composition of the oldest paired occurrences of sedimentary carbonate and organic matter, which are preserved as dolomite and kerogen within textural biosignatures of the ∼3.43 Ga Strelley Pool Formation. We targeted least-altered carbonate phases in situ using microsampling techniques guided by non-destructive elemental mapping. Organic carbon isotope values were measured by spatially-resolved bulk analyses, and in situ using secondary ion mass spectrometry to target microscale domains of organic material trapped within inorganic carbon matrixes. Total observed fractionation of 13C ranges from -29 to -45‰. Our data are consistent with studies of younger Archean rocks that host biogenic stromatolites and organic-inorganic carbon pairs showing greater fractionation than expected for Rubisco fixation alone. We conclude that organic matter was fixed and/or remobilized by at least one metabolism in addition to the CBB cycle, possibly by the Wood-Ljungdahl pathway or methanogenesis-methanotrophy, in a shallow-water marine environment during the Paleoarchean.

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

    PubMed Central

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

    2016-01-01

    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. PMID:26903274

  18. Sediment Tracking Using Carbon and Nitrogen Stable Isotopes

    NASA Astrophysics Data System (ADS)

    Fox, J. F.; Papanicolaou, A.

    2002-12-01

    As landscapes are stripped of valuable, nutrient rich topsoils and streams are clouded with habitat degrading fine sediment, it becomes increasingly important to identify and mitigate erosive surfaces. Particle tracking using vegetative derived carbon (C) and nitrogen (N) isotopic signatures and carbon/nitrogen (C/N) atomic ratios offer a promising technique to identify such problematic sources. Consultants and researchers successfully use C, N, and other stable isotopes of water for hydrologic purposes, such as quantifying groundwater vs. surface water contribution to a hydrograph. Recently, C and N isotopes and C/N atomic ratios of sediment were used to determine sediment mass balance within estuarine environments. The current research investigates C and N isotopes and C/N atomic ratios of source sediment for two primary purposes: (1) to establish a blueprint methodology for estimating sediment source and erosion rates within a watershed using this isotopic technology coupled with mineralogy fingerprinting techniques, radionuclide transport monitoring, and erosion-transport models, and (2) to complete field studies of upland erosion processes, such as, solifluction, mass wasting, creep, fluvial erosion, and vegetative induced erosion. Upland and floodplain sediment profiles and riverine suspended sediment were sampled on two occasions, May 2002 and August 2002, in the upper Palouse River watershed of northern Idaho. Over 300 samples were obtained from deep intermountain valley (i.e. forest) and rolling crop field (i.e. agriculture) locations. Preliminary sample treatment was completed at the Washington State University Water Quality Laboratory where samples were dried, removed of organic constituents, and prepared for isotopic analysis. C and N isotope and C/N atomic ratio analyses was performed at the University of Idaho Natural Resources Stable Isotope Laboratory using a Costech 4010 Elemental Combustion System connected with a continuous flow inlet system to

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

    DOE PAGES

    Jahn, A.; Lindsay, K.; Giraud, X.; ...

    2015-08-05

    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, themore » 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. Lastly, at the same time, the carbon isotopes reveal biases in the physical model, for example, too sluggish ventilation of the deep Pacific Ocean.« less

  20. Analysis of dissolved organic carbon concentration and 13C isotopic signature by TOC-IRMS - assessment of analytical performance

    NASA Astrophysics Data System (ADS)

    Kirkels, Frédérique; Cerli, Chiara; Federherr, Eugen; Kalbitz, Karsten

    2013-04-01

    samples did not affect the precision of the analysis of natural abundance and labeled samples. Natural DOM, derived from different soils and assessed at various concentrations, was measured with similar good analytical performance, and also tested for the effect of freezing and re-dissolving. We found good performance of TOC-IRMS in comparison with other systems capable of determining C concentration and isotopic signatures. We recognize the advantages of this system providing: - High sample throughput, short measurement time (15 minutes), flexible sample volume - Easy maintenance, handling, rapid sample preparation (no pretreatment) This preliminary assessment highlights wide-ranging opportunities for further research on concentrations and isotopic signatures by TOC-IRMS to elucidate the role of dissolved carbon in terrestrial and aquatic systems.

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

    NASA Astrophysics Data System (ADS)

    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

  2. Boron isotope fractionation in magma via crustal carbonate dissolution

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed

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

    2016-08-04

    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.

  4. Calibration strategies for the determination of stable carbon absolute isotope ratios in a glycine candidate reference material by elemental analyser-isotope ratio mass spectrometry.

    PubMed

    Dunn, Philip J H; Malinovsky, Dmitry; Goenaga-Infante, Heidi

    2015-04-01

    We report a methodology for the determination of the stable carbon absolute isotope ratio of a glycine candidate reference material with natural carbon isotopic composition using EA-IRMS. For the first time, stable carbon absolute isotope ratios have been reported using continuous flow rather than dual inlet isotope ratio mass spectrometry. Also for the first time, a calibration strategy based on the use of synthetic mixtures gravimetrically prepared from well characterised, highly (13)C-enriched and (13)C-depleted glycines was developed for EA-IRMS calibration and generation of absolute carbon isotope ratio values traceable to the SI through calibration standards of known purity. A second calibration strategy based on converting the more typically determined delta values on the Vienna PeeDee Belemnite (VPDB) scale using literature values for the absolute carbon isotope ratio of VPDB itself was used for comparison. Both calibration approaches provided results consistent with those previously reported for the same natural glycine using MC-ICP-MS; absolute carbon ratios of 10,649 × 10(-6) with an expanded uncertainty (k = 2) of 24 × 10(-6) and 10,646 × 10(-6) with an expanded uncertainty (k = 2) of 88 × 10(-6) were obtained, respectively. The absolute carbon isotope ratio of the VPDB standard was found to be 11,115 × 10(-6) with an expanded uncertainty (k = 2) of 27 × 10(-6), which is in excellent agreement with previously published values.

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

    NASA Astrophysics Data System (ADS)

    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.

  6. Fractionation of carbon isotopes by phytoplankton and estimates of ancient CO2 levels

    NASA Technical Reports Server (NTRS)

    Freeman, K. H.; Hayes, J. M.

    1992-01-01

    Reports of the 13C content of marine particulate organic carbon are compiled and on the basis of GEOSECS data and temperatures, concentrations, and isotopic compositions of dissolved CO2 in the waters in which the related phytoplankton grew are estimated. In this way, the fractionation of carbon isotopes during photosynthetic fixation of CO2 is found to be significantly correlated with concentrations of dissolved CO2. Because ancient carbon isotopic fractionations have been determined from analyses of sedimentary porphyrins [Popp et al., 1989], the relationship between isotopic fractionation and concentrations of dissolved CO2 developed here can be employed to estimate concentrations of CO2 dissolved in ancient oceans and, in turn, partial pressures of CO2 in ancient atmospheres. The calculations take into account the temperature dependence of chemical and isotopic equilibria in the dissolved-inorganic-carbon system and of air-sea equilibria. Paleoenvironmental temperatures for each sample are estimated from reconstructions of paleogeography, latitudinal temperature gradients, and secular changes in low-latitude sea surface temperature. It is estimated that atmospheric partial pressures of CO2 were over 1000 micro atm 160 - 100 Ma ago, then declined to values near 300 micro atm during the next 100 Ma. Analysis of a high-resolution record of carbon isotopic fractionation at the Cenomanian-Turonian boundary suggests that the partial pressure of CO2 in the atmosphere was drawn down from values near 840 micro atm to values near 700 micro atm during the anoxic event.

  7. Nature of POC transport in a mangrove ecosystem: A carbon stable isotopic study

    NASA Astrophysics Data System (ADS)

    Rezende, C. E.; Lacerda, L. D.; Ovall, A. R. C.; Silva, C. A. R.; Martinelli, L. A.

    1990-06-01

    The isotopic composition of particulate organic carbon (POC) was studied during five tidal cycles in a mangrove creek of Sepetiba Bay, Rio de Janeiro, Brazil. The results show that a mixture of organic carbon from mangrove and marine origins is always present in the creek. Mean mangrove contribution to the POC varied from 16% to 100% and was dependent on tidal amplitude. The results suggest that oceanic carbon can be an important component of carbon balance in mangrove ecosystems. Therefore, earlier carbon balance studies from mangroves which did not include measurements of carbon isotopic composition should be interpreted with care.

  8. Ar39 Detection at the 10-16 Isotopic Abundance Level with Atom Trap Trace Analysis

    NASA Astrophysics Data System (ADS)

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

    2011-03-01

    Atom trap trace analysis, a laser-based atom counting method, has been applied to analyze atmospheric Ar39 (half-life=269yr), a cosmogenic isotope with an isotopic abundance of 8×10-16. In addition to the superior selectivity demonstrated in this work, the counting rate and efficiency of atom trap trace analysis have been improved by 2 orders of magnitude over prior results. The significant applications of this new analytical capability lie in radioisotope dating of ice and water samples and in the development of dark matter detectors.

  9. The Oxygen Isotopic Composition of MIL 090001: A CR2 Chondrite with Abundant Refractory Inclusions

    NASA Technical Reports Server (NTRS)

    Keller, Lindsay P.; McKeegan, K. D.; Sharp, Z. D.

    2012-01-01

    MIL 090001 is a large (>6 kg) carbonaceous chondrite that was classified as a member of the CV reduced subgroup (CVred) that was recovered during the 2009-2010 ANSMET field season [1]. Based on the abundance of refractory inclusions and the extent of aqueous alteration, Keller [2] suggested a CV2 classification. Here we report additional mineralogical and petrographic data for MIL 090001, its whole-rock oxygen isotopic composition and ion microprobe analyses of individual phases. The whole rock oxygen isotopic analyses show that MIL 090001 should be classified as a CR chondrite.

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

    NASA Technical Reports Server (NTRS)

    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.

  11. Early Triassic fluctuations of the global carbon cycle: New evidence from paired carbon isotopes in the western USA basin

    NASA Astrophysics Data System (ADS)

    Caravaca, Gwénaël; Thomazo, Christophe; Vennin, Emmanuelle; Olivier, Nicolas; Cocquerez, Théophile; Escarguel, Gilles; Fara, Emmanuel; Jenks, James F.; Bylund, Kevin G.; Stephen, Daniel A.; Brayard, Arnaud

    2017-07-01

    In the aftermath of the catastrophic end-Permian mass extinction, the Early Triassic records recurrent perturbations in the carbon isotope signal, most notably during the Smithian and through the Smithian/Spathian Boundary (SSB; 1.5 myr after the Permian/Triassic boundary), which show some of the largest excursions of the Phanerozoic. The late Smithian also corresponds to major biotic turnovers and environmental changes, such as temperature fluctuations, that deeply impacted the recovery after the end-Permian mass extinction. Here we document the paired carbon isotope signal along with an analysis of the trace and major elements at the long-known Hot Springs section (southeastern Idaho, USA). This section records Early Triassic sediments from the Griesbachian-Dienerian up to the lower Spathian. We show that the organic and carbonate δ13C variations mirror the signals identified at a global scale. Particularly, the middle Smithian-SSB event represented by a negative-positive isotopic couplet is well identified and is not of diagenetic origin. We also document a positive excursion potentially corresponding to the Dienerian/Smithian Boundary. Observed Smithian-Spathian excursions are recorded similarly in both the organic and carbonate reservoirs, but the organic matter signal systematically shows unexpectedly dampened variations compared to its carbonate counterpart. Additionally, we show that variations in the net isotopic effect (i.e., Δ13C) probably resulted from a complex set of forcing parameters including either a mixing between terrestrial and marine organic matter depending on the evolution of the depositional setting, or variations in the biological fractionation. We establish that the Δ13C signal cannot be directly related to CO2-driven temperature variations at Hot Springs. Even though the carbon isotope signal mirrors the Early Triassic variations known at the global scale, the Hot Springs signal probably also reflects local influences on the carbon

  12. Stable carbon isotope analyses of nanogram quantities of particulate organic carbon (pollen) with laser ablation nano combustion gas chromatography/isotope ratio mass spectrometry

    PubMed Central

    Sluijs, Appy; Laks, Jelmer J.; Reichart, Gert‐Jan

    2016-01-01

    Rationale Analyses of stable carbon isotope ratios (δ 13C values) of organic and inorganic matter remains have been instrumental for much of our understanding of present and past environmental and biological processes. Until recently, the analytical window of such analyses has been limited to samples containing at least several μg of carbon. Methods Here we present a setup combining laser ablation, nano combustion gas chromatography and isotope ratio mass spectrometry (LA/nC/GC/IRMS). A deep UV (193 nm) laser is used for optimal fragmentation of organic matter with minimum fractionation effects and an exceptionally small ablation chamber and combustion oven are used to reduce the minimum sample mass requirement compared with previous studies. Results Analyses of the international IAEA CH‐7 polyethylene standard show optimal accuracy, and precision better than 0.5‰, when measuring at least 42 ng C. Application to untreated modern Eucalyptus globulus (C3 plant) and Zea mays (C4 plant) pollen grains shows a ~ 16‰ offset between these species. Within each single Z. mays pollen grain, replicate analyses show almost identical δ 13C values. Conclusions Isotopic offsets between individual pollen grains exceed analytical uncertainties, therefore probably reflecting interspecimen variability of ~0.5–0.9‰. These promising results set the stage for investigating both δ 13C values and natural carbon isotopic variability between single specimens of a single population of all kinds of organic particles yielding tens of nanograms of carbon. © 2016 The Authors. Rapid Communications in Mass Spectrometry Published by John Wiley & Sons Ltd. PMID:27766694

  13. Basal area growth, carbon isotope discrimination, and intrinsic ...

    EPA Pesticide Factsheets

    Many hectares of intensively managed Douglas-fir (Pseudotsuga menziesii Mirb. Franco) stands in western North America are fertilized with nitrogen to increase growth rates. Understanding the mechanisms of response facilitates prioritization of stands for treatment. The objective of this study was to test the hypothesis that the short-term basal area growth response to a single application of 224 kg N ha-1 as urea was associated with reduced stable carbon isotope discrimination (∆13C) and increased intrinsic water use efficiency (iWUE) in a 20-yr-old plantation of Douglas-fir in the Oregon Coast Range, USA. Increment cores were measured to estimate earlywood, latewood, and total basal area increment over a time series from 1997 to 2015. Stable carbon isotope discrimination and iWUE were estimated using earlywood and latewood stable carbon isotope concentrations in tree-ring holocellulose starting seven years before fertilization in early 2009 and ending seven years after treatment. A highly significant interaction effect between fertilization treatment and year was found for total basal area growth and earlywood basal area increment. Fertilized trees showed significant total basal area growth and earlywood basal area increment in the first (2009) and second (2010) growing seasons after fertilization in 2009. A marginally significant fertilization effect was found for latewood basal area increment only in the first growing season after treatment. A significant i

  14. Environmental isotope investigation of groundwater flow in the Honey Lake Basin, California and Nevada

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Rose, T.P.; Davisson, M.L.; Hudson, G.B.

    The hydrology of Honey Lake Basin was studied using environmental isotope measurements of approximately 130 water samples collected during 1995 and 1996. The principal analytical methods included hydrogen, oxygen and carbon stable isotope ratio measurements, radiocarbon and tritium dating, and measurements of dissolved noble gas abundances.

  15. Geochemically distinct carbon isotope distributions in Allochromatium vinosum DSM 180T grown photoautotrophically and photoheterotrophically.

    PubMed

    Tang, T; Mohr, W; Sattin, S R; Rogers, D R; Girguis, P R; Pearson, A

    2017-03-01

    Anoxygenic, photosynthetic bacteria are common at redox boundaries. They are of interest in microbial ecology and geosciences through their role in linking the carbon, sulfur, and iron cycles, yet much remains unknown about how their flexible carbon metabolism-permitting either autotrophic or heterotrophic growth-is recorded in the bulk sedimentary and lipid biomarker records. Here, we investigated patterns of carbon isotope fractionation in a model photosynthetic sulfur-oxidizing bacterium, Allochromatium vinosum DSM180 T . In one treatment, A. vinosum was grown with CO 2 as the sole carbon source, while in a second treatment, it was grown on acetate. Different intracellular isotope patterns were observed for fatty acids, phytol, individual amino acids, intact proteins, and total RNA between the two experiments. Photoautotrophic CO 2 fixation yielded typical isotopic ordering for the lipid biomarkers: δ 13 C values of phytol > n-alkyl lipids. In contrast, growth on acetate greatly suppressed intracellular isotopic heterogeneity across all molecular classes, except for a marked 13 C-depletion in phytol. This caused isotopic "inversion" in the lipids (δ 13 C values of phytol < n-alkyl lipids). The finding suggests that inverse δ 13 C patterns of n-alkanes and pristane/phytane in the geologic record may be at least in part a signal for photoheterotrophy. In both experimental scenarios, the relative isotope distributions could be predicted from an isotope flux-balance model, demonstrating that microbial carbon metabolisms can be interrogated by combining compound-specific stable isotope analysis with metabolic modeling. Isotopic differences among molecular classes may be a means of fingerprinting microbial carbon metabolism, both in the modern environment and the geologic record. © 2017 John Wiley & Sons Ltd.

  16. Determining the Local Abundance of Martian Methane and its 13-C/l2-C and D/H Isotopic Ratios for Comparison with Related Gas and Soil Analysis on the 2011 Mars Science Laboratory (MSL) Mission

    NASA Technical Reports Server (NTRS)

    Webster, Christopher R.; Mahaffy, Paul R.

    2011-01-01

    Understanding the origin of Martian methane will require numerous complementary measurements from both in situ and remote sensing investigations and laboratory work to correlate planetary surface geophysics with atmospheric dynamics and chemistry. Three instruments (Quadrupole Mass Spectrometer (QMS), Gas Chromatograph (GC) and Tunable Laser Spectrometer (TLS)) with sophisticated sample handling and processing capability make up the Sample Analysis at Mars (SAM) analytical chemistry suite on NASA s 2011 Mars Science Laboratory (MSL) Mission. Leveraging off the SAM sample and gas processing capability that includes methane enrichment, TLS has unprecedented sensitivity for measuring absolute methane (parts-per-trillion), water, and carbon dioxide abundances in both the Martian atmosphere and evolved from heated soil samples. In concert with a wide variety of associated trace gases (e.g. SO2, H2S, NH3, higher hydrocarbons, organics, etc.) and other isotope ratios measured by SAM, TLS will focus on determining the absolute abundances of methane, water and carbon dioxide, and their isotope ratios: 13C/12C and D/H in methane; 13C/12C and 18O/17O/16O in carbon dioxide; and 18O/17O/16O and D/H in water. Measurements near the MSL landing site will be correlated with satellite (Mars Express, Mars 2016) and ground-based observations.

  17. Carbon kinetic isotope effect in the reaction of CH4 with HO

    NASA Technical Reports Server (NTRS)

    Davidson, J. A.; Cantrell, C. A.; Tyler, S. C.; Shetter, R. E.; Cicerone, R. J.

    1987-01-01

    The carbon kinetic isotope effect in the CH4 + HO reaction is measured experimentally and the use of carbon isotope ratios to diagnose atmospheric methane is examined. The chemical, photolysis, and analytical experimental conditions and procedures are described. It is determined that the CH4 + HO reaction has a carbon kinetic isotope effect of 1.010 + or 0.007 for k(12)k(13) (rate constants ratio) at 297 + or - 3 K. This value is compared with the data of Rust and Stevens (1980). Causes for the poor correlation between the data at high methane conversions are discussed. It is supposed that the difference between the k(12) and k(13) values is due to a difference in the activation energy of the two reactions.

  18. Methane seep carbonates yield clumped isotope signatures out of equilibrium with formation temperatures

    DOE PAGES

    Loyd, S. J.; Sample, J.; Tripati, R. E.; ...

    2016-07-22

    Here, methane cold seep systems typically exhibit extensive buildups of authigenic carbonate minerals, resulting from local increases in alkalinity driven by methane oxidation. Here, we demonstrate that modern seep authigenic carbonates exhibit anomalously low clumped isotope values (Δ47), as much as ~0.2‰ lower than expected values. In modern seeps, this range of disequilibrium translates into apparent temperatures that are always warmer than ambient temperatures, by up to 50 °C. We examine various mechanisms that may induce disequilibrium behaviour in modern seep carbonates, and suggest that the observed values result from several factors including kinetic isotopic effects during methane oxidation, mixingmore » of inorganic carbon pools, pH effects and rapid precipitation. Ancient seep carbonates studied here also exhibit potential disequilibrium signals. Ultimately, these findings indicate the predominance of disequilibrium clumped isotope behaviour in modern cold seep carbonates that must be considered when characterizing environmental conditions in both modern and ancient cold seep settings.« less

  19. Stable carbon isotopes: possible clues to early life on Mars.

    PubMed

    Schidlowski, M

    1992-01-01

    Organic and inorganic carbon in terrestrial near-surface environments are characterized by a marked difference in their 13C/12C ratios which can be traced back in the Earth's sedimentary record over almost 4 billion years. There is no doubt that the bias in favour of 12C displayed by biogenic matter derives, for the most part, from the isotope-selecting properties of the carbon-fixing enzyme (ribulose-1,5-bisphosphate carboxylase) that is operative in the principal photosynthetic pathway and promotes most of the carbon transfer from the non-living to the living realm. Postulating a universality of biological principles in analogy to the proven universality of the laws of physics and chemistry, we may expect enzymatic reactions in exobiological systems to be beset with B similar kinetic fractionation effects. Hence, the retrieval from the oldest Martian sediments of isotopic fractionations between reduced and oxidized (carbonate) carbon may substantially constrain current conjectures on the possible existence of former life on Mars.

  20. Detection of oxygen isotopic anomaly in terrestrial atmospheric carbonates and its implications to Mars.

    PubMed

    Shaheen, R; Abramian, A; Horn, J; Dominguez, G; Sullivan, R; Thiemens, Mark H

    2010-11-23

    The debate of life on Mars centers around the source of the globular, micrometer-sized mineral carbonates in the ALH84001 meteorite; consequently, the identification of Martian processes that form carbonates is critical. This paper reports a previously undescribed carbonate formation process that occurs on Earth and, likely, on Mars. We identified micrometer-sized carbonates in terrestrial aerosols that possess excess (17)O (0.4-3.9‰). The unique O-isotopic composition mechanistically describes the atmospheric heterogeneous chemical reaction on aerosol surfaces. Concomitant laboratory experiments define the transfer of ozone isotopic anomaly to carbonates via hydrogen peroxide formation when O(3) reacts with surface adsorbed water. This previously unidentified chemical reaction scenario provides an explanation for production of the isotopically anomalous carbonates found in the SNC (shergottites, nakhlaites, chassignites) Martian meteorites and terrestrial atmospheric carbonates. The anomalous hydrogen peroxide formed on the aerosol surfaces may transfer its O-isotopic signature to the water reservoir, thus producing mass independently fractionated secondary mineral evaporites. The formation of peroxide via heterogeneous chemistry on aerosol surfaces also reveals a previously undescribed oxidative process of utility in understanding ozone and oxygen chemistry, both on Mars and Earth.

  1. Detection of oxygen isotopic anomaly in terrestrial atmospheric carbonates and its implications to Mars

    PubMed Central

    Shaheen, R.; Abramian, A.; Horn, J.; Dominguez, G.; Sullivan, R.; Thiemens, Mark H.

    2010-01-01

    The debate of life on Mars centers around the source of the globular, micrometer-sized mineral carbonates in the ALH84001 meteorite; consequently, the identification of Martian processes that form carbonates is critical. This paper reports a previously undescribed carbonate formation process that occurs on Earth and, likely, on Mars. We identified micrometer-sized carbonates in terrestrial aerosols that possess excess 17O (0.4–3.9‰). The unique O-isotopic composition mechanistically describes the atmospheric heterogeneous chemical reaction on aerosol surfaces. Concomitant laboratory experiments define the transfer of ozone isotopic anomaly to carbonates via hydrogen peroxide formation when O3 reacts with surface adsorbed water. This previously unidentified chemical reaction scenario provides an explanation for production of the isotopically anomalous carbonates found in the SNC (shergottites, nakhlaites, chassignites) Martian meteorites and terrestrial atmospheric carbonates. The anomalous hydrogen peroxide formed on the aerosol surfaces may transfer its O-isotopic signature to the water reservoir, thus producing mass independently fractionated secondary mineral evaporites. The formation of peroxide via heterogeneous chemistry on aerosol surfaces also reveals a previously undescribed oxidative process of utility in understanding ozone and oxygen chemistry, both on Mars and Earth. PMID:21059939

  2. The Paleocene Eocene carbon isotope excursion in higher plant organic matter: Differential fractionation of angiosperms and conifers in the Arctic

    NASA Astrophysics Data System (ADS)

    Schouten, Stefan; Woltering, Martijn; Rijpstra, W. Irene C.; Sluijs, Appy; Brinkhuis, Henk; Sinninghe Damsté, Jaap S.

    2007-06-01

    A study of upper Paleocene-lower Eocene (P-E) sediments deposited on the Lomonosov Ridge in the central Arctic Ocean reveals relatively high abundances of terrestrial biomarkers. These include dehydroabietane and simonellite derived from conifers (gymnosperms) and a tetra-aromatic triterpenoid derived from angiosperms. The relative percentage of the angiosperm biomarker of the summed angiosperm + conifer biomarkers was increased at the end of the Paleocene-Eocene thermal maximum (PETM), different when observed with pollen counts which showed a relative decrease in angiosperm pollen. Stable carbon isotopic analysis of these biomarkers shows that the negative carbon isotope excursion (CIE) during the PETM amounts to 3‰ for both conifer biomarkers, dehydroabietane and simonellite, comparable to the magnitude of the CIE inferred from marine carbonates, but significantly lower than the 4.5‰ of the terrestrial C 29n-alkane [M. Pagani, N. Pedentchouk, M. Huber, A. Sluijs, S. Schouten, H. Brinkhuis, J.S. Sinninghe Damsté, G.R. Dickens, and the IODP Expedition 302 Expedition Scientists (2006), Arctic's hydrology during global warming at the Paleocene-Eocene thermal maximum. Nature, 442, 671-675.], which is a compound sourced by both conifers and angiosperms. Conspicuously, the angiosperm-sourced aromatic triterpane shows a much larger CIE of 6‰ and suggests that angiosperms increased in their carbon isotopic fractionation during the PETM. Our results thus indicate that the 4.5‰ C 29n-alkane CIE reported previously represents the average CIE of conifers and angiosperms at this site and suggest that the large and variable CIE observed in terrestrial records may be partly explained by the variable contributions of conifers and angiosperms. The differential response in isotopic fractionation of angiosperms and conifers points to different physiological responses of these vegetation types to the rise in temperature, humidity, and greenhouse gases during the PETM.

  3. Carbon and nitrogen isotope systematics in diamond: Different sensitivities to isotopic fractionation or a decoupled origin?

    NASA Astrophysics Data System (ADS)

    Hogberg, K.; Stachel, T.; Stern, R. A.

    2016-11-01

    Using stable isotope data obtained on multiple aliquots of diamonds from worldwide sources, it has been argued that carbon and nitrogen in diamond are decoupled. Here we re-investigate the carbon-nitrogen relationship based on the most comprehensive microbeam data set to date of stable isotopes and nitrogen concentrations in diamonds (n = 94) from a single locality. Our diamond samples, derived from two kimberlites in the Chidliak Field (NE Canada), show large variability in δ13C (- 28.4 ‰ to - 1.1‰, mode at - 5.8‰), δ15N (- 5.8 to + 18.8‰, mode at - 3.0‰) and nitrogen contents ([N]; 3800 to less than 1 at.ppm). In combination, cathodoluminescence imaging and microbeam analyses reveal that the diamonds grew from multiple fluid pulses, with at least one major hiatus documented in some samples that was associated with a resorption event and an abrupt change from low δ13C and [N] to mantle-like δ13C and high [N]. Overall, δ13C appears to be uncorrelated to δ15N and [N] on both the inter- and intra-diamond levels. Co-variations of δ15N-log[N], however, result in at least two parallel, negatively correlated linear arrays, which are also present on the level of the individual diamonds falling on these two trends. These arrays emerge from the two principal data clusters, are characterized by slightly negative and slightly positive δ15N (about - 3 and + 2‰, respectively) and variable but overall high [N]. Using published values for the diamond-fluid nitrogen isotope fractionation factor and nitrogen partition coefficient, these trends are perfectly reproduced by a Rayleigh fractionation model. Overall, three key elements are identified in the formation of the diamond suite studied: (1.) a low δ13C and low [N] component that possibly is directly associated with an eclogitic diamond substrate or introduced during an early stage fluid event. (2.) Repeated influx of a variably nitrogen-rich mantle fluid (mildly negative δ13C and δ15N). (3.) In waning

  4. Contribution of deep sourced carbon from hydrocarbon seeps to sedimentary organic carbon: Evidence from Δ14C and δ13C isotopes

    NASA Astrophysics Data System (ADS)

    Feng, D.; Peckmann, J.; Peng, Y.; Liang, Q.; Roberts, H. H.; Chen, D.

    2017-12-01

    Sulfate-driven anaerobic oxidation of methane (AOM) limits the release of methane from marine sediments and promotes the formation of carbonates close to the seafloor along continental margins. It has been established that hydrocarbon seeps are a source of dissolved inorganic and organic carbon to marine environments. However, questions remain about the contribution of deep sourced carbon from hydrocarbon seeps to the sedimentary organic carbon pool. For a number of hydrocarbon seeps from the South China Sea and the Gulf of Mexico, the portion of modern carbon was determined based on natural radiocarbon abundances (Δ14C) and stable carbon isotope (δ13Corganic carbon) compositions of the non-carbonate fractions extracted from authigenic carbonates. Samples from both areas show a mixing trend between ideal planktonic organic carbon (δ13C = -22‰ VPDB and 90% modern carbon) and the ambient methane. The δ13Corganic carbon values of non-carbonate fractions from three ancient seep deposits (northern Italy, Miocene; western Washington State, USA, Eocene to Oligocene) confirm that the proxy can be used to constrain the record of sulfate-driven AOM through most of Earth history by measuring the δ13C values of organic carbon. This study reveals the potential of using δ13C values of organic carbon to discern seep and non-seep environments. This new approach is particularly promising when authigenic carbonate is not present in ancient sedimentary environments. Acknowledgments: The authors thank BOEM and NOAA for their years' support of the deep-sea dives. Funding was provided by the NSF of China (Grants: 41422602 and 41373085).

  5. Apportioning carbon sources of authigenic carbonate of extremely 13C-depleted foraminifera from the western North Pacific sediments: Implication from the coupled 13C and 14C isotopic mass balance approach

    NASA Astrophysics Data System (ADS)

    Uchida, M.; Ohkushi, K.; Ahagon, N.; Kimoto, K.; Inagaki, F.; Shibata, Y.

    2005-12-01

    Recently, Uchida et al. (G-cubed, 2004) and Ohkushi et al. (G-cubed, 2005) interprete /delta 13C variations of planktonic and benthic foraminifera found in Last Glacial sediments in off Shimokita Peninsula and Tokachi as evidence for periodic releases of methane, arising from the dissociation of methane hydrate, and its subsequent oxidation in bottom- and/or surface-water environments. According to recent observations of anomalous bottom-simulating reflections, northwest Pacific marginal sediments around Japan main islands bear large abundances of methane hydrate. In this study, analyzed piston cores (42° 21.42' N, 144° 13.36' E) at a water depth 1066-m was retrieved from the off Tokachi continental slope in the Oyashio current region, where recently is found to bear immense amounts of methane hydrate. The piston core covered past 22 ka with high-resolution. Here we showed that carbon isotope signals indicated that planktonic and benthic foraminifera in several glacial sediment layers in the core were highly depleted in13 C; both the planktonic and benthic foraminiferal /delta 13C values ranged from about -10/permil to -2/permil. Most foraminiferal tests in these horizons were brown as a result of postdepositional alteration. Foraminiferal oxygen isotopes fluctuated abnormally in the glacial sediment layers, showing small (about 0.5/permil) positive shifts relative to normal glacial values. We attributed the positive shifts to authigenic carbonate formation in the foraminiferal tests. In order to decipher the relation between foraminifera carbon isotopic signal and methane release from the seafloor, we have apportioned carbon sources (methane from methane hydrate or not) of foraminiferal carbon isotopic anomalies using dual mass balance isotopic model (14C/ 12C and 13C/ 12C). It has been suggested that sulfate-dependent anaerobic methane oxidation (AOM) dominates carbon oxidation and attendant authigenic carbonate precipitation to foraminifera. To this assumption

  6. Relative and accurate measurement of protein abundance using 15N stable isotope labeling in Arabidopsis (SILIA).

    PubMed

    Guo, Guangyu; Li, Ning

    2011-07-01

    In the quantitative proteomic studies, numerous in vitro and in vivo peptide labeling strategies have been successfully applied to measure differentially regulated protein and peptide abundance. These approaches have been proven to be versatile and repeatable in biological discoveries. (15)N metabolic labeling is one of these widely adopted and economical methods. However, due to the differential incorporation rates of (15)N or (14)N, the labeling results produce imperfectly matched isotopic envelopes between the heavy and light nitrogen-labeled peptides. In the present study, we have modified the solid Arabidopsis growth medium to standardize the (15)N supply, which led to a uniform incorporation of (15)N into the whole plant protein complement. The incorporation rate (97.43±0.11%) of (15)N into (15)N-coded peptides was determined by correlating the intensities of peptide ions with the labeling efficiencies according to Gaussian distribution. The resulting actual incorporation rate (97.44%) and natural abundance of (15)N/(14)N-coded peptides are used to re-calculate the intensities of isotopic envelopes of differentially labeled peptides, respectively. A modified (15)N/(14)N stable isotope labeling strategy, SILIA, is assessed and the results demonstrate that this approach is able to differentiate the fold change in protein abundance down to 10%. The machine dynamic range limitation and purification step will make the precursor ion ratio deriving from the actual ratio fold change. It is suggested that the differentially mixed (15)N-coded and (14)N-coded plant protein samples that are used to establish the protein abundance standard curve should be prepared following a similar protein isolation protocol used to isolate the proteins to be quantitated. Crown Copyright © 2011. Published by Elsevier Ltd. All rights reserved.

  7. Kinetic Fractionation of Stable Isotopes in Carbonates on Mars: Terrestrial Analogs

    NASA Technical Reports Server (NTRS)

    Socki, Richard A.; Gibson, Everett K., Jr.; Golden, D. C.; Ming, Douglas W.; McKay, Gordon A.

    2003-01-01

    An ancient Martian hydrosphere consisting of an alkali-rich ocean would likely produce solid carbonate minerals through the processes of evaporation and/or freezing. We postulate that both (or either) of these kinetically-driven processes would produce carbonate minerals whose stable isotopic compositions are highly fractionated (enriched) with respect to the source carbon. Various scenarios have been proposed for carbonate formation on Mars, including high temperature formation, hydrothermal alteration, precipitation from evaporating brines, and cryogenic formation. 13C and 18O -fractionated carbonates have previously been shown to form kinetically under some of these conditions, ie.: 1) alteration by hydrothermal processes, 2) low temperature precipitation (sedimentary) from evaporating bicarbonate (brine) solutions, and 3) precipitation during the process of cryogenic freezing of bicarbonate-rich fluids. Here we examine several terrestrial field settings within the context of kinetically controlled carbonate precipitation where stable isotope enrichments have been observed.

  8. Biodegradation of Chlorofluorocarbons in a Groundwater Plume using Compound Specific Carbon Isotope Analysis

    NASA Astrophysics Data System (ADS)

    Phillips, E.; Manna, J.; Horst, A.; Gilevska, T.; Sherwood Lollar, B.; Mack, E. E.; Seger, E.; Lutz, E. J.; Norcoss, S.; Morgan, S. E.; West, K. A.; Dworatzek, S.; Webb, J.

    2017-12-01

    Compound specific isotope analysis (CSIA) measures isotope ratios of organic hydrocarbons to monitor intrinsic bioremediation processes that can transform contaminants in field settings. The fraction of original contaminant remaining can be determined using the measured isotope ratio of the contaminant by an experimentally determined fractionation factor. In this study, two separate biotransformation experiments were performed in the Stable Isotope Laboratory at the University of Toronto using CSIA. In these two experiments, a mixed culture derived from a contaminated site was amended with trichlorotrifluoroethane (CFC-113), or trichlorofluoromethane (CFC-11), respectively. The concentrations and carbon isotope ratios of CFC-113, or CFC-11 were analyzed to calculate the fractionation factor for the transformation of each compound. Subsequently, groundwater samples from 9 wells at a historically contaminated site were collected and analyzed. The experimentally determined fractionation factors were then used to evaluate the extent of transformation that had occurred at the field site. In the laboratory studies, significant carbon isotope fractionation was observed for both CFC-113 and CFC-11 as biotransformation proceeded. This significant fractionation is beneficial when evaluating biotransformation at field sites as it can be clearly differentiated from the effects of other physical processes such as transport, or volatilization. Although there was significant variation in the carbon isotope values of CFC-113 between different well locations at the field site, these variations may be due to differences in source carbon isotope signatures. For CFC-11, much more significant isotopic variation was observed within the same well and between wells, showing trends consistent with in situ biotransformation. Results from this study demonstrate that CSIA can be successfully applied to evaluate the extent of transformation of chlorofluorocarbons (CFCs) at contaminated field

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

    NASA Astrophysics Data System (ADS)

    Brookman, Tom H.; Ambrose, Stanley H.

    2012-09-01

    Serial sampling of tooth enamel growth increments for carbon and oxygen isotopic analyses of Macropus (kangaroo) teeth was performed to assess the potential for reconstructing paleoseasonality. The carbon isotope composition of tooth enamel apatite carbonate reflects the proportional intake of C3 and C4 vegetation. The oxygen isotopic composition of enamel reflects that of ingested and metabolic water. Tooth enamel forms sequentially from the tip of the crown to the base, so dietary and environmental changes during the tooth's formation can be detected. 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.

  10. CNO isotopes in red giant stars

    NASA Technical Reports Server (NTRS)

    Wannier, P. G.

    1985-01-01

    The production and distribution of the CNO nuclides is discussed in light of observed abundance ratios in red giants and in the interstellar medium. Isotope abundances have been measured in the atmospheres and in the recent ejecta of cool giants, including carbon stars, S-type stars and red supergiants as well as in oxygen-rich giants making their first ascent of the giant branch. Several of the observations suggest revision of currently accepted nuclear cross-sections and of the mixing processes operating in giant envelopes. By comparing red giant abundances with high-quality observations of the interstellar medium, conclusions are reached about the contribution of intermediate-mass stars to galactic nuclear evolution. The three oxygen isotopes, O-16, -17 and -18, are particularly valuable for such comparison because they reflect three different stages of stellar nucleosynthesis. One remarkable result comes from observations of O-17/O-18 in several classes of red giant stars. The observed range of values for red giants excludes the entire range of values seen in interstellar molecular clouds. Furthermore, both the observations of stars and interstellar clouds exclude the isotopic ratio found in the solar system.

  11. Report on carbon and nitrogen abundance studies

    NASA Technical Reports Server (NTRS)

    Boehm-Vitense, Erika

    1991-01-01

    The aim of the proposal was to determine the nitrogen to carbon abundance ratios from transition layer lines in stars with different T(sub eff) and luminosities. The equations which give the surface emission line fluxes and the measured ratio of the NV to CIV emission line fluxes are presented and explained. The abundance results are compared with those of photospheric abundance studies for stars in common with the photospheric investigations. The results show that the analyses are at least as accurate as the photospheric determinations. These studies can be extended to F and early G stars for which photospheric abundance determinations for giants are hard to do because molecular bands become too weak. The abundance determination in the context of stellar evolution is addressed. The N/C abundance ratio increases steeply at the point of evolution for which the convection zone reaches deepest. Looking at the evolution of the rotation velocities v sin i, a steep decrease in v sin i is related to the increasing depth of the convection zone. It is concluded that the decrease in v sin i for T(sub eff) less than or approximately = 5800 K is most probably due to the rearrangement of the angular momentum in the stars due to deep convective mixing. It appears that the convection zone is rotating with nearly depth independent angular momentum. Other research results and ongoing projects are discussed.

  12. Boron isotope fractionation in magma via crustal carbonate dissolution

    PubMed Central

    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 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. PMID:27488228

  13. In situ analysis of carbon isotopes in North American diamonds

    NASA Astrophysics Data System (ADS)

    van Rythoven, A. D.; Hauri, E. H.; Wang, J.; McCandless, T.; Shirey, S. B.; Schulze, D. J.

    2010-12-01

    Diamonds from three North American kimberlite occurrences were investigated with cathodoluminescence (CL) and secondary ion mass spectrometry (SIMS) to determine their growth history and carbon isotope composition. Diamonds analyzed include fourteen from Lynx (Quebec), twelve from Kelsey Lake (Colorado) and eleven from A154 South (Diavik mine, Northwest Territories). Growth histories for the diamonds vary from simple to highly complex based on their CL images and depending on the individual stone. Deformation laminae are evident in CL images of the Lynx diamonds that typically are brownish in color. Two to five points per diamond were analyzed by SIMS for carbon isotope composition. Sample heterogeneity is minimal in terms of δ13C (vs. PDB) values. Points within single diamond had a maximum range of approximately 1 ‰. The results for the A154 South (-6.4 to -3 ‰) and Kelsey Lake (-11.2 to -2.6 ‰) stones were in accordance with earlier reported values. The Lynx kimberlite stones have anomalously high ratios and range from -3.5 to +0.2 ‰ (average: -1.4 ‰). No previous carbon isotope analyses on diamonds from Lynx or any other eastern Superior craton occurrence have been published. The diamonds possess carbon isotope ratios higher than those for the only other reported analyses of Superior craton diamonds at Wawa, Ontario (-5.5 to -1.1 ‰). In global terms, the only published analyses of diamonds that consistently contain even higher values are those from New South Wales (Australia). However, these diamonds are alluvial and contain eclogitic and/or exotic mineral inclusions. The Lynx diamonds are entirely peridotitic and from a primary deposit. The unusually low (i.e. >-5‰) δ13C values of the Lynx (and Wawa) diamonds may indicate a different carbon reservoir for the Superior craton mantle as compared to other cratons.

  14. Precise and traceable carbon isotope ratio measurements by multicollector ICP-MS: what next?

    PubMed

    Santamaria-Fernandez, Rebeca

    2010-06-01

    This article reviews recent developments in the use of multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) to provide high-precision carbon isotope ratio measurements. MC-ICP-MS could become an alternative method to isotope ratio mass spectrometry (IRMS) for rapid carbon isotope ratio determinations in organic compounds and characterisation and certification of isotopic reference materials. In this overview, the advantages, drawbacks and potential of the method for future applications are critically discussed. Furthermore, suggestions for future improvements in terms of precision and sensitivity are made. No doubt, this is an exciting analytical challenge and, as such, hurdles will need to be cleared.

  15. Assessment of marine-derived nutrients in the Copper River Delta, Alaska, using natural abundance of the stable isotopes of nitrogen, sulfur, and carbon

    USGS Publications Warehouse

    Kline, Thomas C.; Woody, Carol Ann; Bishop, Mary Anne; Powers, Sean P.; Knudsen, E. Eric

    2007-01-01

    We performed nitrogen, sulfur, and carbon stable isotope analysis (SIA) on maturing and juvenile anadromous sockeye and coho salmon, and periphyton in two Copper River delta watersheds of Alaska to trace salmonderived nutrients during 2003–2004. Maturing salmon were isotopically enriched relative to alternate freshwater N, S, and C sources as expected, with differences consistent with species trophic level differences, and minor system, sex, and year-to-year differences, enabling use of SIA to trace these salmon-derived nutrients. Periphyton naturally colonized, incubated, and collected using Wildco Periphtyon Samplers in and near spawning sites was 34S- and 15N-enriched, as expected, and at all freshwater sites was 13C-depleted. At nonspawning and coho-only sites, periphyton 34S and 15N was generally low. However, 34S was low enough at some sites to be suggestive of sulfate reduction, complicating the use of S isotopes. Juvenile salmon SIA ranged in values consistent with using production derived from re-mineralization as well as direct utilization, but only by a minority fraction of coho salmon. Dependency on salmon-derived nutrients ranged from relatively high to relatively low, suggesting a space-limited system. No one particular isotope was found to be superior for determining the relative importance of salmon-derived nutrients.

  16. Carbon isotope fractionation of 1,1,1-trichloroethane during base-catalyzed persulfate treatment.

    PubMed

    Marchesi, Massimo; Thomson, Neil R; Aravena, Ramon; Sra, Kanwartej S; Otero, Neus; Soler, Albert

    2013-09-15

    The extent of carbon isotope fractionation during degradation of 1,1,1-trichloroethane (1,1,1-TCA) by a base-catalyzed persulfate (S₂O₈(2-)) treatment system was investigated. Significant destruction of 1,1,1-TCA was observed at a pH of ∼12. An increase in the NaOH:S₂O₈(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:S₂O₈(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:S₂O₈(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. Copyright © 2013 Elsevier B.V. All rights reserved.

  17. Carbon isotope fractionation between Fe-carbide and diamond; a light C isotope reservoir in the deep Earth and Core?

    NASA Astrophysics Data System (ADS)

    Mikhail, S.; Jones, A. P.; Hunt, S. A.; Guillermier, C.; Dobson, D. P.; Tomlinson, E.; Dan, H.; Milledge, H.; Franchi, I.; Wood, I.; Beard, A.; Verchovsky, S.

    2010-12-01

    The largest accessible reservoir for terrestrial carbon is the mantle; however the core may yield even more. Carbon is commonly proposed as the light element (or one of) to make up the observed density deficit in the earth’s metallic core (NAKAJIMA et al., 2009). The potential isotopic effects of carbon incorporation into the core have not yet been investigated. In-situ ion probe (nanoSIMS) mapping and imaging of carbon isotope variations across rare sub-mm-scale Fe-rich carbide inclusions in mantle diamond (from Jagersfontein, South Africa) show the carbide to be significantly depleted in 13C relative to their diamond host. Distinctive textures suggest metallic liquid precipitates similar in geometry to (giant) nitrogen platelets, controlled by the octahedral symmetry of diamond, which we interpret as syngenic formation. The difference in δ13C values between the two natural phases for diamond-Fe carbide, gives an isotopic fractionation factor (ΔC) which agrees well with HPHT multi-anvil experiments (5-9 GPa and >1400°C). Our measured ΔC between Fe-carbide and diamond may only have local significance, but the measured isotopic values represent characterization of the highest PT carbide known (i.e. > minimum depth of the diamond stability field ≈ 150 km). The direction and magnitude of ΔC agrees with observations of the ΔC between cohenite-graphite in iron meteorites (DEINES and WICKMAN, 1975) and both agree with HPHT experiments, thus suggesting that carbon in the deep Earth, and particularly in the core, may be similarly fractionated (i.e. depleted in the 13C). Since metallic liquid drained from the silicate mantle to form the core during the early Earth, we can use our values as a proxy to constrain evolution of deep carbon reservoirs such as the core and bulk silicate Earth. For example, we can test the suggestion of Grady et al (2004) that the upper mantle value of δ13C ≈ -5 ‰ may not be representative of the bulk Earth, since solar system

  18. Are recycled carbonates essential to explain light Mg isotopes in magmatic rocks? Insights from Late Cenozoic mantle-derived magmas in Iran

    NASA Astrophysics Data System (ADS)

    Pang, K. N.; Teng, F. Z.; Sun, Y.; Chung, S. L.; Zarrinkoub, M. H.

    2016-12-01

    Mantle-derived magmas at continental collision zones represent probes into the mantle that might have been variably metasomatized prior to collision. To address how and to what extent mantle metasomatism occurred, particularly for the role of recycled carbonates, we conducted a Mg isotopic study of two suites of Late Cenozoic mantle-derived magmas in Iran, part of the Arabia-Eurasia collision zone preceded by the long-lasting Tethyan subduction. The Qal'eh Hasan Ali high-Mg ultrapotassic rocks, low-degree partial melts from the metasomatized lithospheric mantle, have mantle-like δ26Mg (-0.23 to -0.28 ‰) despite high CaO/Al2O3 and Zr/Hf, low Ti/Eu and Hf/Sm, and presence of carbonate globules in devitrified glass indicative of carbonate or carbonatite involvement in their genesis. The absence of light Mg isotopic composition of these rocks indicates that either the recycled carbonates were in the form of calcitic rather than dolomitic melts, or the amount of Mg from the carbonatite was too little to appear in these rocks. The Lut-Sistan alkali basalts, sodic magmas suggested to have derived from low-degree melting of the asthenosphere followed by variable differentiation, display a range of δ26Mg from -0.17 to -0.26 ‰ with three outlying data at -0.37‰, -0.39‰ and -0.56 ‰. The samples with light Mg isotopes do not show greater influence by carbonate or carbonatite in terms of the elemental indices noted above. Instead, they are characterized by lower light and middle REE abundances and slightly lower initial 143Nd/144Nd than the majority of samples. The covariations can be explained by minor incorporation of lower crustal garnet during magma ascent through local thickened crust in the collision zone. We propose that thickened crust where garnet pyroxenites exist is capable of imparting a light Mg isotopic signature to mantle-derived magmas, and that such signature is not unique to the involvement of carbonate or carbonatite in the mantle source.

  19. Isotopic abundances of Hg in mercury stars inferred from the Hg II line at 3984 A

    NASA Technical Reports Server (NTRS)

    White, R. E.; Vaughan, A. H., Jr.; Preston, G. W.; Swings, J. P.

    1976-01-01

    Wavelengths of the Hg II absorption feature at 3984 A in 30 Hg stars are distributed uniformly from the value for the terrestrial mix to a value that corresponds to nearly pure Hg-204. The wavelengths are correlated loosely with effective temperatures inferred from Q(UBV). Relative isotopic abundances derived from partially resolved profiles of the 3984-A line in iota CrB, chi Lup, and HR 4072 suggest that mass-dependent fractionation has occurred in all three stars. It is supposed that such fractionation occurs in all Hg stars, and a scheme whereby isotopic compositions can be inferred from a comparison of stellar wavelengths and equivalent widths with those calculated for a family of fractionated isotopic mixes. Theoretical profiles calculated for the derived isotopic composition agree well with high-resolution interferometric profiles obtained for three of the stars.

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

    USGS Publications Warehouse

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

    2004-01-01

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

  1. Determination of Natural 14C Abundances in Dissolved Organic Carbon in Organic-Rich Marine Sediment Porewaters by Thermal Sulfate Reduction

    NASA Astrophysics Data System (ADS)

    Johnson, L.; Komada, T.

    2010-12-01

    The abundances of natural 14C in dissolved organic carbon (DOC) in the marine environment hold clues regarding the processes that influence the biogeochemical cycling of this large carbon reservoir. At present, UV irradiation is the widely accepted method for oxidizing seawater DOC for determination of their 14C abundances. This technique yields precise and accurate values with low blanks, but it requires a dedicated vacuum line, and hence can be difficult to implement. As an alternative technique that can be conducted on a standard preparatory vacuum line, we modified and tested a thermal sulfate reduction method that was previously developed to determine δ13C values of marine DOC (Fry B. et al., 1996. Analysis of marine DOC using a dry combustion method. Mar. Chem., 54: 191-201.) to determine the 14C abundances of DOC in marine sediment porewaters. In this method, the sample is dried in a 100 ml round-bottom Pyrex flask in the presence of excess oxidant (K2SO4) and acid (H3PO4), and combusted at 550 deg.C. The combustion products are cryogenically processed to collect and quantify CO2 using standard procedures. Materials we have oxidized to date range from 6-24 ml in volume, and 95-1500 μgC in size. The oxidation efficiency of this method was tested by processing known amounts of reagent-grade dextrose and sucrose (as examples of labile organic matter), tannic acid and humic acid (as examples of complex natural organic matter), and porewater DOC extracted from organic-rich nearshore sediments. The carbon yields for all of these materials averaged 99±4% (n=18). The 14C abundances of standard materials IAEA C-6 and IAEA C-5 processed by this method using >1mgC aliquots were within error of certified values. The size and the isotopic value of the blank were determined by a standard dilution technique using IAEA C-6 and IAEA C-5 that ranged in size from 150 to 1500 μgC (n=4 and 2, respectively). This yielded a blank size of 6.7±0.7 μgC, and a blank isotopic

  2. Does Short-term Litter Input Manipulation Affect Soil Respiration and the Carbon-isotopic Signature of Soil Respired CO2

    NASA Astrophysics Data System (ADS)

    Cheng, X.; Wu, J.

    2016-12-01

    Global change greatly alters the quality and quantity of plant litter inputs to soils, and further impacts soil organic matter (SOM) dynamics and soil respiration. However, the process-based understanding of how soil respiration may change with future shift in litter input is not fully understood. The Detritus Input and Removal Treatment (DIRT) experiment was conducted in coniferous forest (Platycladus orientalis (Linn.) Franco) ecosystem of central China to investigate the impact of above- and belowground litter input on soil respiration and the carbon-isotopic signature of soil respired CO2. Short-term (1-2 years) litter input manipulation significantly affected soil respiration, based on annual flux values, soil respiration was 31.9%, 20.5% and 37.2% lower in no litter (NL), no root (NR) and no input (NRNL), respectively, compared to control (CK). Whereas double litter (DL) treatment increased soil respiration by 9.1% compared to CK. The recalcitrance index of carbon (RIC) and the relative abundance of fungi increased under litter removal or root exclusion treatment (NL, NR and NRNL) compared to CK. Basal soil respiration was positively related to liable C and microbial biomass and negatively related to RIC and fungi to bacteria (F: B) ratio. The carbon-isotopic signature of soil respired CO2 enriched under litter removal and no input treatment, and slightly depleted under litter addition treatment compared to CK. Our results suggest that short-term litter input manipulation can affect the soil respiration by altering substrate availability and microbial community structure, and also impact the carbon-isotopic signature of soil respired CO2 possibly duo to change in the component of soil respiration and soil microclimate.

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

    DOE Office of Scientific and Technical Information (OSTI.GOV)

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

    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)more » 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

  4. Surface ocean carbon isotope anomalies on glacial terminations: An alternative view

    NASA Astrophysics Data System (ADS)

    Lund, D. C.; Cote, M.; Schmittner, A.

    2016-12-01

    Late Pleistocene glacial terminations are characterized by surface ocean carbon isotope minima on a global scale. During the last deglaciation (i.e. Termination 1), planktonic foraminiferal δ13C anomalies occurred in the Atlantic, Indian, Pacific, and Southern Oceans. Despite the apparently ubiquitous nature of δ13C anomalies on glacial terminations, their cause remains a matter of ongoing debate. The prevailing view is that isotopically light carbon from the abyss was upwelled in the Southern Ocean, resulting in outgassing of 13C-depleted carbon to the atmosphere and its advection to lower latitudes via mode and intermediate waters (Spero and Lea, 2002). Alternatively, carbon isotope minima may be driven by weakening of the biological pump related to circulation-driven changes in the oceanic preformed nutrient budget (Schmittner and Lund, 2015). Here we assess the deep upwelling and biological pump hypotheses using a new compilation of 70 globally-distributed planktonic δ13C records from the published literature. We find that 1) the mean deglacial δ13C anomaly is similar in all ocean basins, 2) the eastern tropical Pacific yields smaller mean δ13C anomalies than the western tropical Pacific, and 3) δ13C anomalies in the Southern Ocean decrease with increasing latitude. Our results are generally inconsistent with the deep upwelling hypothesis, which predicts that the δ13C signal should be largest in the Southern Ocean and upwelling regions. Instead, the spatial pattern in δ13C anomalies supports the biological pump hypothesis, which predicts that reduced export of light carbon from the euphotic zone triggers negative carbon isotope anomalies in the surface ocean and positive anomalies at intermediate depths. Upwelling of relatively 13C-enriched intermediate waters tends to moderate carbon isotope minima in upwelling regions. Our results suggest that the initial rise in atmospheric CO2 during Termination 1 was likely due to weakening of the biological pump

  5. Carbon isotope equilibration during sulphate-limited anaerobic oxidation of methane

    NASA Astrophysics Data System (ADS)

    Yoshinaga, Marcos Y.; Holler, Thomas; Goldhammer, Tobias; Wegener, Gunter; Pohlman, John W.; Brunner, Benjamin; Kuypers, Marcel M. M.; Hinrichs, Kai-Uwe; Elvert, Marcus

    2014-03-01

    Collectively, marine sediments comprise the largest reservoir of methane on Earth. The flux of methane from the sea bed to the overlying water column is mitigated by the sulphate-dependent anaerobic oxidation of methane by marine microbes within a discrete sedimentary horizon termed the sulphate-methane transition zone. According to conventional isotope systematics, the biological consumption of methane leaves a residue of methane enriched in 13C (refs , , ). However, in many instances the methane within sulphate-methane transition zones is depleted in 13C, consistent with the production of methane, and interpreted as evidence for the intertwined anaerobic oxidation and production of methane. Here, we report results from experiments in which we incubated cultures of microbial methane consumers with methane and low levels of sulphate, and monitored the stable isotope composition of the methane and dissolved inorganic carbon pools over time. Residual methane became progressively enriched in 13C at sulphate concentrations above 0.5 mM, and progressively depleted in 13C below this threshold. We attribute the shift to 13C depletion during the anaerobic oxidation of methane at low sulphate concentrations to the microbially mediated carbon isotope equilibration between methane and carbon dioxide. We suggest that this isotopic effect could help to explain the 13C-depletion of methane in subseafloor sulphate-methane transition zones.

  6. Carbonate "Clumped" Isotope Determination of Seawater Temperature During the End-Triassic Extinction Event

    NASA Astrophysics Data System (ADS)

    Gammariello, R. T., Jr.; Petryshyn, V. A.; Ibarra, Y.; Greene, S. E.; Corsetti, F. A.; Bottjer, D. J.; Tripati, A.

    2014-12-01

    Stromatolites are laminated sedimentary structures that are commonly thought to be created by cyanobacteria, either through the trapping and binding of sediment, or through metabolically-induced precipitation. However, stromatolite formation is poorly understood. In general, stromatolite abundance was higher in the Proterozoic than the Phanerozoic, but notable increases in stromatolite abundance occur in association with Phanerozoic mass extinction events. Here, we focus on stromatolites from the latest Triassic Cotham Marble (United Kingdom) that are associated with the extinction interval. The end-Triassic mass extinction is coincident with large-scale volcanism in the Central Atlantic Magmatic Province (CAMP) and the associated breakup of Pangea. Some hypothesize that CAMP-associated increases in atmospheric CO2 led to a rise in global temperatures and ocean acidification that caused or enhanced the extinction. In order to quantify the role of climate change with respect to the end-Triassic mass extinction, we applied the carbonate "clumped" isotope paleothermometer to the well-preserved Cotham Marble stromatolites. The stromatolites were deposited in the shallow Tethys Sea, and today occur in several localities across the southwestern UK. The stromatolites alternate on the cm scale between laminated and dendrolitic microstructures and each was microdrilled for clumped isotope analysis. The two microstructures display different temperatures of formation, where the dendrolitic portions apparently grew under cooler conditions than laminated layers, and younger layers grew in cooler conditions than older layers. Our results suggest that temperature fluctuated and potentially trended towards amelioration of the warm temperatures during the deposition of the Cotham Marble.

  7. [A review of water and carbon flux partitioning and coupling in SPAC using stable isotope techniques].

    PubMed

    Xu, Xiao Wu; Yu, Xin Xiao; Jia, Guo Dong; Li, Han Zhi; Lu, Wei Wei; Liu, Zi Qiang

    2017-07-18

    Soil-vegetation-atmosphere continuum (SPAC) is one of the important research objects in the field of terrestrial hydrology, ecology and global change. The process of water and carbon cycling, and their coupling mechanism are frontier issues. With characteristics of tracing, integration and indication, stable isotope techniques contribute to the estimation of the relationship between carbon sequestration and water consumption in ecosystems. In this review, based on a brief introduction of stable isotope principles and techniques, the applications of stable isotope techniques to water and carbon exchange in SPAC using optical stable isotope techniques were mainly explained, including: partitioning of net carbon exchange into photosynthesis and respiration; partitioning of evapotranspiration into transpiration and evaporation; coupling of water and carbon cycle at the ecosystem scale. Advanced techniques and methods provided long-term and high frequency measurements for isotope signals at the ecosystem scale, but the issues about the precision and accuracy for measurements, partitioning of ecosystem respiration, adaptability for models under non-steady state, scaling up, coupling mechanism of water and carbon cycles, were challenging. The main existing research findings, limitations and future research prospects were discussed, which might help new research and technology development in the field of stable isotope ecology.

  8. Applications of Cavity Ring-Down Spectroscopy (CRDS) to Analysis of Carbon Stable Isotope Composition of Groundwater

    NASA Astrophysics Data System (ADS)

    Jeong, T.; Woo, N. C.; Choi, H.

    2014-12-01

    Carbon Capture and Storage (CCS) has been considered as an effective strategy to reduce atmospheric carbon dioxide (CO2) concentration. However, unintended leakage of CO2 leakage from storage sites could occur through highly permeable conduits such as fractures in low-K formations during the injection and storage of SCCO2 (supercritical phase CO2). Therefore, prediction and detection of CO2 leakage and relevant analysis of carbon isotope are crucial to assure environmental and public safety. Until recently, Isotope Ratio Mass Spectrometry (IRMS) has been utilized to measure the stable isotope ratio of water. However, IRMS is time-consuming operation due to complicated pretreatment, and thus not a practical methodology under field conditions. Carbon Isotope Analyzer (CCIA), which is a kind of Cavity Ring-Down Spectroscopy (CRDS) and has a wide measurement range from 300 to 25000 ppmv, can facilitate the rate of measurements up to 1 Hz by using continuous flow method so that it can be readily applied to field. In this study, carbon stable isotope ratio of groundwater will be analyzed using CCIA. Then, the CCIA results will be compared with IRMS to validate its accuracy and stability. This research will provide an appropriate method for analyzing carbon stable isotope in groundwater, using a continuous flow mode.

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

    NASA Astrophysics Data System (ADS)

    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

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

    EPA Science Inventory


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

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

    EPA Science Inventory

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

  12. Specific activity and isotope abundances of strontium in purified strontium-82

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Fitzsimmons, J. M.; Medvedev, D. G.; Mausner, L. F.

    2015-11-12

    A linear accelerator was used to irradiate a rubidium chloride target with protons to produce strontium-82 (Sr-82), and the Sr-82 was purified by ion exchange chromatography. The amount of strontium associated with the purified Sr-82 was determined by either: ICP-OES or method B which consisted of a summation of strontium quantified by gamma spectroscopy and ICP-MS. The summation method agreed within 10% to the ICP-OES for the total mass of strontium and the subsequent specific activities were determined to be 0.25–0.52 TBq mg -1. Method B was used to determine the isotope abundances by weight% of the purified Sr-82, andmore » the abundances were: Sr-82 (10–20.7%), Sr-83 (0–0.05%), Sr-84 (35–48.5%), Sr-85 (16–25%), Sr-86 (12.5–23%), Sr-87 (0%), and Sr-88 (0–10%). The purified strontium contained mass amounts of Sr-82, Sr-84, Sr-85, Sr-86, and Sr-88 in abundances not associated with natural abundance, and 90% of the strontium was produced by the proton irradiation. A comparison of ICP-OES and method B for the analysis of Sr-82 indicated analysis by ICP-OES would be easier to determine total mass of strontium and comply with regulatory requirements. An ICP-OES analytical method for Sr-82 analysis was established and validated according to regulatory guidelines.« less

  13. Testing the ``Wildfire Hypothesis:'' Terrestrial Organic Carbon Burning as the Cause of the Paleocene-Eocene Boundary Carbon Isotope Excursion

    NASA Astrophysics Data System (ADS)

    Moore, E. A.; Kurtz, A. C.

    2005-12-01

    The 3‰ negative carbon isotope excursion (CIE) at the Paleocene-Eocene boundary has generally been attributed to dissociation of seafloor methane hydrates. We are testing the alternative hypothesis that the carbon cycle perturbation resulted from wildfires affecting the extensive peatlands and coal swamps formed in the Paleocene. Accounting for the CIE with terrestrial organic carbon rather than methane requires a significantly larger net release of fossil carbon to the ocean-atmosphere, which may be more consistent with the extreme global warming and ocean acidification characteristic of the Paleocene-Eocene Thermal Maximum (PETM). While other researchers have noted evidence of fires at the Paleocene-Eocene boundary in individual locations, the research presented here is designed to test the "wildfire hypothesis" for the Paleocene-Eocene boundary by examining marine sediments for evidence of a global increase in wildfire activity. Such fires would produce massive amounts of soot, widely distributed by wind and well preserved in marine sediments as refractory black carbon. We expect that global wildfires occurring at the Paleocene-Eocene boundary would produce a peak in black carbon abundance at the PETM horizon. We are using the method of Gelinas et al. (2001) to produce high-resolution concentration profiles of black carbon across the Paleocene-Eocene boundary using seafloor sediments from ODP cores, beginning with the Bass River core from ODP leg 174AX and site 1209 from ODP leg 198. This method involves the chemical and thermal extraction of non-refractory carbon followed by combustion of the residual black carbon and measurement as CO2. Measurement of the δ 13C of the black carbon will put additional constraints on the source of the organic material combusted, and will allow us to determine if this organic material was formed prior to or during the CIE.

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

    EPA Science Inventory

    Stable isotopes are used widely as a tool for determining sources of carbon (C) fluxes in ecosystem C studies. Environmental factors that change over time, such as moisture, can create dynamic changes in the isotopic composition of C assimilated by plants, and offers a unique opp...

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

    NASA Astrophysics Data System (ADS)

    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.

  16. Carbon and nitrogen isotope variations in tree-rings as records of perturbations in regional carbon and nitrogen cycles.

    PubMed

    Bukata, Andrew R; Kyser, T Kurtis

    2007-02-15

    Increasing anthropogenic pollution from urban centers and fossil fuel combustion can impact the carbon and nitrogen cycles in forests. To assess the impact of twentieth century anthropogenic pollution on forested system carbon and nitrogen cycles, variations in the carbon and nitrogen isotopic compositions of tree-rings were measured. Individual annual growth rings in trees from six sites across Ontario and one in New Brunswick, Canada were used to develop site chronologies of tree-ring delta 15N and delta 13C values. Tree-ring 615N values were approximately 0.5% per hundred higher and correlated with contemporaneous foliar samples from the same tree, but not with delta 15N values of soil samples. Temporal trends in carbon and nitrogen isotopic compositions of these tree-rings are consistent with increasing anthropogenic influence on both the carbon and nitrogen cycles since 1945. Tree-ring delta 13C values and delta 15N values are correlated at both remote and urban-proximal sites, with delta 15N values decreasing since 1945 and converging on 1% per hundred at urban-proximal sites and decreasing but not converging on a single delta 15N value in remote sites. These results indicate that temporal trends in tree-ring nitrogen and carbon isotopic compositions record the regional extent of pollution.

  17. A Test of Carbon and Oxygen Stable Isotope Ratio Process Models in Tree Rings.

    NASA Astrophysics Data System (ADS)

    Roden, J. S.; Farquhar, G. D.

    2008-12-01

    Stable isotopes ratios of carbon and oxygen in tree ring cellulose have been used to infer environmental change. Process-based models have been developed to clarify the potential of historic tree ring records for meaningful paleoclimatic reconstructions. However, isotopic variation can be influenced by multiple environmental factors making simplistic interpretations problematic. Recently, the dual isotope approach, where the variation in one stable isotope ratio (e.g. oxygen) is used to constrain the interpretation of variation in another (e.g. carbon), has been shown to have the potential to de-convolute isotopic analysis. However, this approach requires further testing to determine its applicability for paleo-reconstructions using tree-ring time series. We present a study where the information needed to parameterize mechanistic models for both carbon and oxygen stable isotope ratios were collected in controlled environment chambers for two species (Pinus radiata and Eucalyptus globulus). The seedlings were exposed to treatments designed to modify leaf temperature, transpiration rates, stomatal conductance and photosynthetic capacity. Both species were grown for over 100 days under two humidity regimes that differed by 20%. Stomatal conductance was significantly different between species and for seedlings under drought conditions but not between other treatments or humidity regimes. The treatments produced large differences in transpiration rate and photosynthesis. Treatments that effected photosynthetic rates but not stomatal conductance influenced carbon isotope discrimination more than those that influenced primarily conductance. The various treatments produced a range in oxygen isotope ratios of 7 ‰. Process models predicted greater oxygen isotope enrichment in tree ring cellulose than observed. The oxygen isotope ratios of bulk leaf water were reasonably well predicted by current steady-state models. However, the fractional difference between models that

  18. Experimental Determination of Carbon Isotope Fractionation in C-O-H-Fluids and the Carbonate-melt - Graphite System at High Temperatures

    NASA Astrophysics Data System (ADS)

    Kueter, N.; Schmidt, M. W.; Lilley, M. D.; Bernasconi, S. M.

    2017-12-01

    The understanding of deep-earth carbon fluxes depends greatly on the investigation of carbon isotope systematics in C-O-H-fluids and carbon minerals, such as graphite and diamond (C0). The isotope fractionation factors between the different C-phases and species (in e.g. a fluid) thus govern the observed isotope fractionation patterns. C-isotope fractionation factors relevant for high temperatures are mainly derived from theoretical calculations [e.g. 1,2,3] and, with few exceptions, lack experimental determinations [e.g. 4]. Hundreds of own experiments aimed at equilibrating elemental carbon (C0, graphite/diamond) with C-O-H-fluids demonstrate that kinetics reigns as no system would be closed for H on time scales and temperatures allowing for graphite to equilibrate. To overcome this problem, we performed two studies to determine the C-isotope fractionation in 1) the CO2-CO-CH4 system and 2) the carbonate-melt - graphite system. Equilibrium C-isotope fractionation factors were obtained for CO2 - CO and CH4 - CO pairs (600 - 1200°C) and graphite - Na2CO3/CaCO3melt (900 - 1500°C). Combined with the already available fractionation data for the CaCO3-CO2 pair (400-950°C) from Chacko et al. [4], we determined experimentally based C-isotope fractionation factors for C0 - CH4 and CO2 - C0 pairs by 1) Δ13CCO2-graphite = Δ13CCO2-carbonate + Δ13CCarbonate-graphite and 2) Δ13Cgraphite-CH4 = Δ13CCO2-CH4 - Δ13CCO2-graphite . Current calculated fractionation factors relevant for mantle temperatures (1100 - 1500°C) suggest C-isotope partitioning in the CO2 - C0 pair on the order of 4.2 to 2.4‰, about 2‰ less than predicted by theoretically derived factors [3]. In contrast, our calculations suggest fractionation of about 1.4 to 1.1‰ for the C0 - CH4 pair, about 1‰ higher than expected by theory [3]. [1] Richet et al. (1977) Ann. Rev. Earth Planet. Sci.; [2] Polyakov & Kharlashina (1995) GCA; [3] Bottinga (1969) GCA; [4] Chacko et al. (2001) Rev Mineral Geochem

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

    NASA Technical Reports Server (NTRS)

    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.

  20. [Quantitative estimation source of urban atmospheric CO2 by carbon isotope composition].

    PubMed

    Liu, Wei; Wei, Nan-Nan; Wang, Guang-Hua; Yao, Jian; Zeng, You-Shi; Fan, Xue-Bo; Geng, Yan-Hong; Li, Yan

    2012-04-01

    To effectively reduce urban carbon emissions and verify the effectiveness of currently project for urban carbon emission reduction, quantitative estimation sources of urban atmospheric CO2 correctly is necessary. Since little fractionation of carbon isotope exists in the transportation from pollution sources to the receptor, the carbon isotope composition can be used for source apportionment. In the present study, a method was established to quantitatively estimate the source of urban atmospheric CO2 by the carbon isotope composition. Both diurnal and height variations of concentrations of CO2 derived from biomass, vehicle exhaust and coal burning were further determined for atmospheric CO2 in Jiading district of Shanghai. Biomass-derived CO2 accounts for the largest portion of atmospheric CO2. The concentrations of CO2 derived from the coal burning are larger in the night-time (00:00, 04:00 and 20:00) than in the daytime (08:00, 12:00 and 16:00), and increase with the increase of height. Those derived from the vehicle exhaust decrease with the height increase. The diurnal and height variations of sources reflect the emission and transport characteristics of atmospheric CO2 in Jiading district of Shanghai.

  1. Stable carbon isotopes and lipid biomarkers provide new insight into the formation of calcite and siderite concretions in organic-matter rich deposits

    NASA Astrophysics Data System (ADS)

    Baumann, Lydia; Birgel, Daniel; Wagreich, Michael; Peckmann, Jörn

    2015-04-01

    Carbonate concretions from two distinct settings have been studied for their petrography, stable carbon and oxygen isotopes, and lipid biomarker content. Carbonate concretions are in large part products of microbial degradation of organic matter, as for example by sulfate-reducing bacteria, iron-reducing bacteria, and methanogenic archaea. For these prokaryotes certain lipid biomarkers such as hopanoids, terminally-branched fatty acids (bacteria) and isoprenoids (archaea) are characteristic. Two different types of concretions were studied: a) Upper Miocene septarian calcite concretions of the southern Vienna Basin embedded in brackish sediments represented by partly bituminous calcareous sands, silts and clays; b) Paleocene-Eocene siderite concretions enclosed in marine, sandy to silty turbidites with varying carbonate contents and marl layers from the Upper Gosau Subgroup in northern Styria. Calcite concretions consist of abundant calcite microspar (80-90 vol.%), as well as detrital minerals and iron oxyhydroxides. The septarian cracks show beginning cementation with dog-tooth calcite to varying degrees. Framboidal pyrite occurs in some of the calcite concretions, pointing to bacterial sulfate reduction. Siderite concretions consist of even finer carbonate crystals, mainly siderite (40-70 vol.%) but also abundant ferroan calcite, accompanied by iron oxyhydroxides and detrital minerals. The δ13C values of the calcite concretions (-6.8 to -4.1o ) most likely reflect a combination of bacterial organic matter oxidation and input of marine biodetrital carbonate. The δ18O values range from -8.9 to -7.8o agreeing with a formation within a meteoric environment. The surrounding host sediment shows about 1-2o higher δ13C and δ18O values. The siderite δ13C values (-11.1 to -7.5o ) point to microbial respiration of organic carbon and the δ18O values (-3.5 to +2.2o ) agree with a marine depositional environment. In contrast to the calcite concretions, the stable isotope

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

    EPA Science Inventory

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

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

    USGS Publications Warehouse

    Hassan, Afifa Afifi

    1982-01-01

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

  4. Stable Carbon Isotopic Signatures of Abiotic Organics from Hydrothermal Synthesis Experiments

    NASA Technical Reports Server (NTRS)

    Stern, Jennifer C.; Summers, David P.; Kubo, Mike; Yassar, Saima

    2006-01-01

    Stable carbon isotopes can be powerful biogeochemical markers in the study of life's origins. Biogenic carbon fixation produces organics that are depleted in C-13 by about -20 to -30%0. Less attention has been paid to the isotopic signatures of abiotic processes. The possibility of abiotic processes producing organics with morphologies and isotopic signatures in the biogenic range has been at the center of recent debate over the Earth's earliest microfossils. The abiotic synthesis of organic compounds in hydrothermal environments is one possible source of endogenous organic matter to the prebiotic earth. Simulated hydrothermal settings have been shown to synthesize, among other things, single chain amphiphiles and simple lipids from a mix of CO, CO2, and H2. A key characteristic of these amphiphilic molecules is the ability to self-assemble in aqueous phases into more organized structures called vesicles, which form a selectively permeable boundary and serve the function of containing and concentrating other organic molecules. The ability to form cell like structures also makes these compounds more likely to be mistaken for biogenic. Hydrothermal simulation experiments were conducted from oxalic or formic acid in water at 175 C for 72 hr. The molecular and isotopic composition of the products of these reactions were determined and compared to biogenic fractionations . Preliminary results indicate isotopic fractionation during abiotic hydrocarbon synthesis in hydrothermal environments is on par with biological carbon fixation.

  5. Carbonate petrography, kerogen distribution, and carbon and oxygen isotope variations in an early Proterozoic transition from limestone to iron-formation deposition, Transvaal Supergroup, South Africa

    NASA Technical Reports Server (NTRS)

    Beukes, N. J.; Klein, C.; Kaufman, A. J.; Hayes, J. M.

    1990-01-01

    sparites are most depleted in 13C. Carbonates in oxide-rich iron-formations are more depleted in 13C than those in siderite-rich iron-formation whereas the kerogens in oxide banded iron-formations (BIF) are more enriched. This implies that the siderite-rich iron-formations were not derived from oxide-rich iron-formation through reduction of ferric iron by organic matter. Organic matter oxidation by ferric iron did, however, decrease the abundance of kerogen in oxide-rich iron-formation and led to the formation of isotopically very light sparry carbonates. Siderite and calcmicrosparite both represent recrystallized primary micritic precipitates but differ in their 13C composition, with the siderites depleted in 13C by 4.6 per mil on average relative to calcmicrosparite. This means that the siderites were precipitated from water with dissolved inorganic carbon depleted in 13C by about 9 per mil relative to that from which the limestones precipitated. This implies an ocean system stratified with regard to total carbonate, with the deeper water, from which siderite-rich iron-formation formed, depleted in 13C. Iron-formations were deposited in areas of very low organic matter supply. Depletion of 13C may, therefore, derive not from degradation of organic matter but from hydrothermal activity, a conclusion which is supported by 18O composition of the carbonate minerals and trace element and rare earth element (REE) compositions of the iron-formations.

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

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

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

  7. The linkage between nutrient supply, intracellular enzyme abundances and bacterial growth: New evidences from the central carbon metabolism of Corynebacterium glutamicum.

    PubMed

    Noack, Stephan; Voges, Raphael; Gätgens, Jochem; Wiechert, Wolfgang

    2017-09-20

    Corynebacterium glutamicum serves as important production host for small molecular compounds that are derived from precursor molecules of the central carbon metabolism. It is therefore a well-studied model organism of industrial biotechnology. However, a deeper understanding of the regulatory principles underlying the synthesis of central metabolic enzymes under different environmental conditions as well as its impact on cell growth is still missing. We studied enzyme abundances in C. glutamicum in response to growth on: (i) one limiting carbon source by sampling chemostat and fed-batch cultivations and (ii) changing carbon sources provided in excess by sampling batch cultivations. The targeted quantification of 20 central metabolic enzymes by isotope dilution mass spectrometry revealed that cells maintain stable enzyme concentrations when grown on d-glucose as single carbon and energy source and, most importantly, independent of its availability. By contrast, switching from d-glucose to d-fructose, d-mannose, d-arabitol, acetate, l-lactate or l-glutamate results in highly specific enzyme regulation patterns that can partly be explained by the activity of known transcriptional regulators. Based on these experimental results we propose a simple framework for modeling cell population growth as a nested function of nutrient supply and intracellular enzyme abundances. In summary, our study extends the basis for the formulation of predictive mechanistic models of bacterial growth, applicable in industrial bioprocess development. Copyright © 2017 Elsevier B.V. All rights reserved.

  8. Lipid Correction for Carbon Stable Isotope Analysis of Deep-sea Fishes

    EPA Science Inventory

    Lipid extraction is used prior to stable isotope analysis of fish tissues to remove variability in the carbon stable isotope ratio (d13C) caused by varying lipid content among samples. Our objective was to evaluate an application of a mass balance correction for the effect of lip...

  9. Methane flux and carbon isotope composition correlate to shifting plant and microbial communities along a permafrost thaw gradient

    NASA Astrophysics Data System (ADS)

    McCalley, C. K.; Mondav, R.; Chanton, J.; Crill, P. M.; Hodgkins, S. B.; Kim, E.; Rich, V. I.; Wehr, R.; Woodcroft, B. J.; Tyson, G. W.; Saleska, S. R.

    2012-12-01

    Methane flux from high latitude wetlands is a critical component of the global carbon budget and is highly sensitive to climate change, with observed and predicted increases as permafrost thaws. Microorganisms mediate wetland methane cycling, but connections between ecosystem-scale flux and underlying microbial dynamics are poorly understood. To address this gap we used isotopic (laser absorption spectrometry) and molecular (16S rRNA gene amplicon sequencing) techniques in a high latitude (68° N) wetland to investigate the relationship between microbial community composition and methane emissions across a permafrost thaw gradient. The transition from permafrost dominated, well drained palsas, through intermediate thaw sites dominated by Sphagnum spp., to wet sites with no underlying permafrost dominated by Eriophorum angustifolium is associated with substantial increases in methane emission. Across this thaw progression the carbon isotopic composition of emitted methane increased from -79.5 ‰ in the intermediate-thawing site to -66.4 ‰ in the thawed site, indicating a relative shift from CO2-reductive towards acetoclastic methanogenesis. Increases in methane flux under thaw were correlated with increasing abundance of methane-producing archaeal clades and increases in methane isotopic composition were associated with shifts in the archaeal community. While CO2 reducing methanogens were found throughout thawing and thawed sites, methanogens of the Methanosarcina (the order of Archaea that contains all known acetoclastic methanogens) were most associated with the fully thawed site. These results directly link microbial community composition to ecosystem scale changes in the magnitude and isotopic composition of methane emissions under permafrost thaw. If isotopic shifts of this magnitude are characteristic of methane dynamics under permafrost loss they should also become detectable in global atmospheric methane observations, providing a global scale tracer of

  10. Carbon Monoxide Isotopes: On the Trail of Galactic Chemical Evolution

    NASA Technical Reports Server (NTRS)

    Langer, W.

    1995-01-01

    From the early days of the discovery of radio emission from carbon monoxide it was realized that it offered unusual potential for under- standing the chemical evolution of the Galaxy and external galaxies through measurements of molecular isotopes. These results bear on stellar nucleosynthesis, star formation, and gases in the interstellar medium. Progress in isotopic radio measurements will be reviewed.

  11. Assessing the statistical robustness of inter- and intra-basinal carbon isotope chemostratigraphic correlation

    NASA Astrophysics Data System (ADS)

    Hay, C.; Creveling, J. R.; Huybers, P. J.

    2016-12-01

    Excursions in the stable carbon isotopic composition of carbonate rocks (δ13Ccarb) can facilitate correlation of Precambrian and Phanerozoic sedimentary successions at a higher temporal resolution than radiometric and biostratigraphic frameworks typically afford. Within the bounds of litho- and biostratigraphic constraints, stratigraphers often correlate isotopic patterns between distant stratigraphic sections through visual alignment of local maxima and minima of isotopic values. The reproducibility of this method can prove challenging and, thus, evaluating the statistical robustness of intrabasinal composite carbon isotope curves, and global correlations to these reference curves, remains difficult. To assess the reproducibility of stratigraphic alignment of δ13Ccarb data, and correlations between carbon isotope excursions, we employ a numerical dynamic time warping methodology that stretches and squeezes the time axis of a record to obtain an optimal correlation (in a least-squares sense) between time-uncertain series of data. In particular, we assess various alignments between series of Early Cambrian δ13Ccarb data with respect to plausible matches. We first show that an alignment of these records obtained visually, and published previously, is broadly reproducible using dynamic time warping. Alternative alignments with similar goodness of fits are also obtainable, and their stratigraphic plausibility are discussed. This approach should be generalizable to an algorithm for the purposes of developing a library of plausible alignments between multiple time-uncertain stratigraphic records.

  12. Experimental Study of Abiotic Organic Synthesis at High Temperature and Pressure Conditions: Carbon Isotope and Mineral Surface Characterizations

    NASA Astrophysics Data System (ADS)

    Fu, Q.; Socki, R. A.; Niles, P. B.

    2010-12-01

    Abiotic organic synthesis processes have been proposed as potential mechanisms for methane generation in subseafloor hydrothermal systems on Earth, and on other planets. To better understand the detailed reaction pathways and carbon isotope fractionations in this process under a wide range of physical and chemical conditions, hydrothermal experiments at high temperature (750 °C) and pressure (0.55 GPa) were performed using piston cylinder apparatus. Formic acid was used as the source of CO2 and H2, and magnetite was the mineral catalyst. The chemical and carbon isotopic compositions of dissolved organic products were determined by GC-C-MS-IRMS, while organic intermediaries on the mineral catalyst were characterized by Pyrolysis-GC-MS. Among experimental products, dissolved CO2 was the dominant carbon species with a relative abundance of 88 mol%. Dissolved CH4 and C2H6 were also identified with a mole ratio of CH4 over C2H6 of 15:1. No dissolved CO was detected in the experiment, which might be attributable to the loss of H2 through the Au capsule used in the experiments at high temperature and pressure conditions and corresponding conversion of CO to CO2 by the water-gas shift reaction. Carbon isotope results showed that the δ13C values of CH4 and C2H6 were -50.3‰ and -39.3‰ (V-PDB), respectively. CO2 derived from decarboxylation of formic acid had a δ13C value of -19.2‰, which was 3.2‰ heavier than its source, formic acid. The δ13C difference between CO2 and CH4 was 31.1‰, which was higher than the value of 9.4‰ calculated from theoretical isotopic equilibrium predictions at experimental conditions, suggesting the presence of a kinetic isotope effect. This number was also higher than the values (4.6 to 27.1‰) observed in similar experiments previously performed at 400 °C and 50 MPa with longer reaction times. CH4 is 11.0‰ less enriched in 13C than C2H6. Alcohols were observed as carbon compounds on magnetite surfaces by Pyrolysis-GC-MS, which

  13. Experimental Study of Abiotic Organic Synthesis at High Temperature and Pressure Conditions: Carbon Isotope and Mineral Surface Characterizations

    NASA Technical Reports Server (NTRS)

    Fu, Qi; Socki, R. A.; Niles, P. B.

    2010-01-01

    Abiotic organic synthesis processes have been proposed as potential mechanisms for methane generation in subseafloor hydrothermal systems on Earth, and on other planets. To better understand the detailed reaction pathways and carbon isotope fractionations in this process under a wide range of physical and chemical conditions, hydrothermal experiments at high temperature (750 C) and pressure (0.55 GPa) were performed using piston cylinder apparatus. Formic acid was used as the source of CO2 and H2, and magnetite was the mineral catalyst. The chemical and carbon isotopic compositions of dissolved organic products were determined by GC-C-MS-IRMS, while organic intermediaries on the mineral catalyst were characterized by Pyrolysis-GC-MS. Among experimental products, dissolved CO2 was the dominant carbon species with a relative abundance of 88 mol%. Dissolved CH4 and C2H6 were also identified with a mole ratio of CH4 over C2H6 of 15:1. No dissolved CO was detected in the experiment, which might be attributable to the loss of H2 through the Au capsule used in the experiments at high temperature and pressure conditions and corresponding conversion of CO to CO2 by the water-gas shift reaction. Carbon isotope results showed that the 13C values of CH4 and C2H6 were -50.3% and -39.3% (V-PDB), respectively. CO2 derived from decarboxylation of formic acid had a (sigma)C-13 value of -19.2%, which was 3.2% heavier than its source, formic acid. The (sigma)C-13 difference between CO2 and CH4 was 31.1%, which was higher than the value of 9.4% calculated from theoretical isotopic equilibrium predictions at experimental conditions, suggesting the presence of a kinetic isotope effect. This number was also higher than the values (4.6 to 27.1%) observed in similar experiments previously performed at 400 C and 50 MPa with longer reaction times. CH4 is 11.0% less enriched in C-13 than C2H6. Alcohols were observed as carbon compounds on magnetite surfaces by Pyrolysis-GC-MS, which confirms

  14. Dual-Carbon sources fuel the OCS deep-reef Community, a stable isotope investigation

    USGS Publications Warehouse

    Sulak, Kenneth J.; Berg, J.; Randall, Michael T.; Dennis, George D.; Brooks, R.A.

    2008-01-01

    The hypothesis that phytoplankton is the sole carbon source for the OCS deep-reef community (>60 m) was tested. Trophic structure for NE Gulf of Mexico deep reefs was analyzed via carbon and nitrogen stable isotopes. Carbon signatures for 114 entities (carbon sources, sediment, fishes, and invertebrates) supported surface phytoplankton as the primary fuel for the deep reef. However, a second carbon source, the macroalga Sargassum, with its epiphytic macroalgal associate, Cladophora liniformis, was also identified. Macroalgal carbon signatures were detected among 23 consumer entities. Most notably, macroalgae contributed 45 % of total carbon to the 13C isotopic spectrum of the particulate-feeding reef-crest gorgonian Nicella. The discontinuous spatial distribution of some sessile deep-reef invertebrates utilizing pelagic macroalgal carbon may be trophically tied to the contagious distribution of Sargassum biomass along major ocean surface features.

  15. The clumped isotope geothermometer in soil and paleosol carbonate

    NASA Astrophysics Data System (ADS)

    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

  16. Stable carbon and nitrogen isotope enrichment in primate tissues

    PubMed Central

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

    2010-01-01

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

  17. Helium-carbon isotopic composition of thermal waters from Tunisia

    NASA Astrophysics Data System (ADS)

    Fourré, E.; Aiuppa, A.; di Napoli, R.; Parello, F.; Gaubi, E.; Jean-Baptiste, P.; Allard, P.; Calabrese, S.; Ben Mammou, A.

    2010-12-01

    Tunisia has numerous thermo-mineral springs. Previous studies have shown that their chemical composition and occurrence are strongly influenced by the regional geology, however little work has been conducted to date to investigate the isotopic composition of volatiles associated with these geothermal manifestations. Here, we report the results of an extensive survey of both natural hot springs and production wells across Tunisia aimed at investigating the spatial distribution of the 3He/4He ratio and associated carbon isotopic compositions. With respect to helium isotopes, not unexpectedly, the lowest 3He/4He values (0.01-0.02 Ra) are associated with the old groundwaters of the “Continental Intercalaire” aquifer of the stable Saharan Platform. The 3He/4He values are equal to the crustal production ratio, with no detectable amount of mantle-derived 3He, in agreement with previous studies of helium isotopes in sedimentary basin, which conclude that tectonically-stable regions are essentially impermeable to mantle volatiles. The low 3He/4He domain extends to the entire Atlasic domain of central Tunisia. This Atlasic domain also displays the highest helium concentrations : along the Gafsa Fault, helium concentrations of 1777 and 4723 x 10-8 cm3STP/g (the highest value of our data set) are observed in the production wells of Sidi Ahmed Zarrouk. This emphasizes the role of deep tectonic features in channelling and transporting deep crustal volatiles to shallow levels. The eastern margin of Tunisia displays higher 3He/4He values indicative of a substantial mantle volatile input. The highest value is recorded in the carbo-gaseous mineral water of Ain Garci (2.4 Ra). This northeastern part of the African plate commonly referred to as the Pelagian block extends from Tunisia to Sicily and is characterized by strong extensional tectonics (Pantelleria rift zone) and present-day magmatic activity. This lithospheric stretching and decompressional mantle melts production in

  18. Petro-structural, geochemical and carbon and oxygen isotopic study on carbonates crosscuting the Oman Ophiolite peridotites: evidence of polygenic CO2 trapping

    NASA Astrophysics Data System (ADS)

    Noël, J.; Godard, M.; Martinez, I.; Oliot, E.; Williams, M. J.; Rodriguez, O.; Chaduteau, C.; Gouze, P.

    2017-12-01

    Carbon trapping in ophiolitic peridotites contributes to the global carbon cycle between solid Earth and its outer envelopes (through subduction and/or modern alteration). To investigate this process, we performed petro-structural (microtomography, EBSD, EPMA) and geochemical studies (LA-ICP-MS, carbon and oxygen isotopes on bulk and minerals using SHRIMP) of harzburgites cored in the Oman Ophiolite. Studied harzburgites are highly serpentinized (> 90 %) and crosscut by 3 generations of carbonates (> 20 Vol%) with compositions from calcite to dolomite (Mg/Ca = 0-0.85). Type 1 carbonates are fine penetrative veinlets and mesh core after olivine. They have low REE (e.g., Yb = 0.08-0.23 x CI-chondrite) and negative Ce anomalies. They have δ13CPDB = -15.2 to 1.10‰ and δ18OSMOW = 17.5 to 33.7‰, suggesting precipitation temperatures up to 110°C. Type 2 carbonates are pluri-mm veins bounded by cm-thick serpentinized vein selvages, oriented dominantly parallel to mantle foliation. Dynamic recrystallization is observed, indicating polygenetic formation: well crystallized calcite with REE abundances similar to Type 1 carbonates are locally replaced by small dolomite and calcite grains with higher REE (e.g., Yb = 0.35-1.0 x CI-chondrite) and positive Gd anomaly. Type 2 carbonates have δ13CPDB = -12.6 to -4.1‰ and δ18OSMOW = 25.0 to 32.7‰, suggesting precipitation temperatures from 10 to 60°C. Type 3 carbonates are late pluri-mm to cm veins reactivating Type 2 veins. They consist of small grains of dolomite and calcite with REE abundances similar to recrystallized Type 2 carbonates. Type 3 carbonates have δ13CPDB = -8.3 to -5.8‰ and δ18OSMOW = 28.8 to 32.7‰, suggesting precipitation temperatures <35°C. δ13C data indicate an evolution of fluid composition precipitating carbonates from seawater- and sediment-derived fluids to meteoric water. Carbonate formation starts during oceanic lithospheric cooling and occurs as a penetrative process at the expense of

  19. Growth versus metabolic tissue replacement in mouse tissues determined by stable carbon and nitrogen isotope analysis

    NASA Astrophysics Data System (ADS)

    Macavoy, S. E.; Jamil, T.; Macko, S. A.; Arneson, L. S.

    2003-12-01

    Stable isotope analysis is becoming an extensively used tool in animal ecology. The isotopes most commonly used for analysis in terrestrial systems are those of carbon and nitrogen, due to differential carbon fractionation in C3 and C4 plants, and the approximately 3‰ enrichment in 15N per trophic level. Although isotope signatures in animal tissues presumably reflect the local food web, analysis is often complicated by differential nutrient routing and fractionation by tissues, and by the possibility that large organisms are not in isotopic equilibrium with the foods available in their immediate environment. Additionally, the rate at which organisms incorporate the isotope signature of a food through both growth and metabolic tissue replacement is largely unknown. In this study we have assessed the rate of carbon and nitrogen isotopic turnover in liver, muscle and blood in mice following a diet change. By determining growth rates, we were able to determine the proportion of tissue turnover caused by growth versus that caused by metabolic tissue replacement. Growth was found to account for approximately 10% of observed tissue turnover in sexually mature mice (Mus musculus). Blood carbon was found to have the shortest half-life (16.9 days), followed by muscle (24.7 days). Liver carbon turnover was not as well described by the exponential decay equations as other tissues. However, substantial liver carbon turnover was observed by the 28th day after diet switch. Surprisingly, these tissues primarily reflect the carbon signature of the protein, rather than carbohydrate, source in their diet. The nitrogen signature in all tissues was enriched by 3 - 5‰ over their dietary protein source, depending on tissue type, and the isotopic turnover rates were comparable to those observed in carbon.

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

    NASA Astrophysics Data System (ADS)

    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

  1. C isotope fractionation during heterotrophic activity driven carbonate precipitation

    NASA Astrophysics Data System (ADS)

    Balci, Nurgul; Demirel, Cansu

    2016-04-01

    Stable carbon isotopic fractionation during carbonate precipitation induced by environmentally enriched heterotrophic halophilic microorganims was experimentally investigated under various salinity (% 4.5, %8, %15) conditions at 30 °C. Halophilic heterotrophic microorganims were enriched from a hypersaline Lake Acigöl located in SW Turkey (Balci et al.,2015) and later used for the precipitation experiments (solid and liquid medium). The carbonate precipitates had relatively high δ13C values (-4.3 to -16.9 ‰) compared to the δ13C values of the organic compounds that ranged from -27.5 to -25.4 ‰. At salinity of 4.5 % δ13C values of carbonate ranged from -4.9 ‰ to -10.9 ‰ with a 13C-enrichment factor of +20 to +16 ‰ higher than the δ13C values of the associated DOC (-27.5) . At salinity 8 % δ13C values of carbonate ranged from -16.3 ‰ to -11.7 ‰ with a 13C-enrichment factor of+11.3 to+15.9 ‰ higher than the δ13C values of the associated DOC. The respected values for 15 % salinity ranged from -12.3 ‰ to -9.7 ‰ with a 13C-enrichment factor of +15.2 to+16.8 ‰ higher than the δ13C values of the associated DOC. The carbonate precipitates produced in the solid medium are more enriched in 13C relative to liquid culture experiments. These results suggest that the carbon in the solid was derived from both the bacterial oxidation of organic compounds in the medium and from the atmospheric CO2. A solid medium used in the experiments may have suppressed convective and advective mass transport favouring diffusion-controlled system. This determination suggests that the rate and equilibration of CO2 exchange with the atmosphere is the major control on C isotope composition of carbonate minerals precipitated in the experiments. Key words: Lake Acıgöl, halophilic bacteria, carbonate biomineralization, C isotopes References Nurgul Balci, Meryem Menekşe, Nevin Gül Karagüler, M. Şeref Sönmez,Patrick Meister 2015.Reproducing authigenic carbonate

  2. New carbon-isotope evidence from the Polish Basin for a major carbon-cycle perturbation at the Triassic-Jurassic Boundary

    NASA Astrophysics Data System (ADS)

    Pointer, Robyn; Hesselbo, Stephen; Littler, Kate; Pieńkowski, Grzegorz; Hodbod, Marta

    2016-04-01

    Carbon-isotope analysis of fossil plant material from a Polish core provides new evidence of a perturbation to the atmospheric carbon-cycle at the Triassic-Jurassic boundary (~201 Ma). The Triassic-Jurassic boundary was a time of extreme climate change which also coincided with the end-Triassic mass extinction. The new data will allow us to identify climatic changes in the Polish Basin across the Triassic-Jurassic boundary and evaluate these changes on a broader scale by comparison to data from other sites located around the world. The Niekłan borehole core, located in the southern Polish Basin, provides a ~200 metre-long terrestrial record spanning the Rhaetian and Hettangian, including the Triassic-Jurassic boundary (~208-199 Ma). The Niekłan core consists of interbedded fluvial and lacustrine sediments containing preserved plant material and thus provides an excellent opportunity to study both terrestrial palaeoenvironmental changes in the Polish Basin and perturbations in the carbon-cycle more broadly. Carbon-isotope analysis of macrofossil plant material and microscopic woody phytoclasts from the Niekłan core reveals a negative carbon-isotope excursion (CIE) of ~-3‰ at the end of the Rhaetian, before a gradual return to more positive values thereafter. The negative CIE suggests an injection of isotopically-light carbon into the atmosphere occurred just before the Triassic-Jurassic boundary. Likely sources of this carbon include volcanogenic gases, methane released from gas hydrates, or a combination of the two. The negative CIE seen in plant material at Niekłan is also recorded in a variety of geological materials from contemporaneous sites world-wide. These time-equivalent, but geographically separated, records indicate that the negative CIE recorded in the Niekłan plant material is the result of a regional or global carbon-cycle perturbation and is not merely a local signal. Future work will focus on using a range of palaeoenvironmental proxies in

  3. Martian Cryogenic Carbonate Formation: Stable Isotope Variations Observed in Laboratory Studies

    NASA Technical Reports Server (NTRS)

    Socki, Richard A.; Niles, Paul B.; Sun, Tao; Fu, Qi; Romanek, Christopher S.; Gibson, Everett K. Jr.

    2014-01-01

    The history of water on Mars is tied to the formation of carbonates through atmospheric CO2 and its control of the climate history of the planet. Carbonate mineral formation under modern martian atmospheric conditions could be a critical factor in controlling the martian climate in a means similar to the rock weathering cycle on Earth. The combination of evidence for liquid water on the martian surface and cold surface conditions suggest fluid freezing could be very common on the surface of Mars. Cryogenic calcite forms easily from freezing solutions when carbon dioxide degasses quickly from Ca-bicarbonate-rich water, a process that has been observed in some terrestrial settings such as arctic permafrost cave deposits, lake beds of the Dry Valleys of Antarctica, and in aufeis (river icings) from rivers of N.E. Alaska. A series of laboratory experiments were conducted that simulated cryogenic carbonate formation on Mars in order to understand their isotopic systematics. The results indicate that carbonates grown under martian conditions show variable enrichments from starting bicarbonate fluids in both carbon and oxygen isotopes beyond equilibrium values.

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

    USGS Publications Warehouse

    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

  5. Investigating controls on boron isotope ratios in shallow marine carbonates

    NASA Astrophysics Data System (ADS)

    Zhang, Shuang; Henehan, Michael J.; Hull, Pincelli M.; Reid, R. Pamela; Hardisty, Dalton S.; Hood, Ashleigh v. S.; Planavsky, Noah J.

    2017-01-01

    The boron isotope-pH proxy has been widely used to reconstruct past ocean pH values. In both planktic foraminifera and corals, species-specific calibrations are required in order to reconstruct absolute values of pH, due to the prevalence of so-called vital effects - physiological modification of the primary environmental signals by the calcifying organisms. Shallow marine abiotic carbonate (e.g. ooids and cements) could conceivably avoid any such calibration requirement, and therefore provide a potentially useful archive for reconstructions in deep (pre-Cenozoic) time. However, shallow marine abiotic carbonates could also be affected by local shifts in pH caused by microbial photosynthesis and respiration, something that has up to now not been fully tested. In this study, we present boron isotope measurements from shallow modern marine carbonates, from the Bahama Bank and Belize to investigate the potential of using shallow water carbonates as pH archives, and to explore the role of microbial processes in driving nominally 'abiogenic' carbonate deposition. For Bahama bank samples, our boron-based pH estimates derived from a range of carbonate types (i.e. ooids, peloids, hardground cements, carbonate mud, stromatolitic micrite and calcified filament micrite) are higher than the estimated modern mean-annual seawater pH values for this region. Furthermore, the majority (73%) of our marine carbonate-based pH estimates fall out of the range of the estimated pre-industrial seawater pH values for this region. In shallow sediment cores, we did not observe a correlation between measured pore water pH and boron-derived pH estimates, suggesting boron isotope variability is a depositional rather than early diagenetic signal. For Belize reef cements, conversely, the pH estimates are lower than likely in situ seawater pH at the time of cement formation. This study indicates the potential for complications when using shallow marine non-skeletal carbonates as marine pH archives

  6. Cellulose and Lignin Carbon Isotope Signatures in Sphagnum Moss Reveal Complementary Environmental Properties

    NASA Astrophysics Data System (ADS)

    Loisel, J.; Nichols, J. E.; Kaiser, K.; Beilman, D. W.; Yu, Z.

    2016-12-01

    The carbon isotope signature (δ13C) of Sphagnum moss is increasingly used as a proxy for past surface wetness in peatlands. However, conflicting interpretations of these carbon isotope records have recently been published. While the water film hypothesis suggests that the presence of a thick (thin) water film around hollow (hummock) mosses leads to less (more) negative δ13C values, the carbon source hypothesis poses that a significant (insignificant) amount of CH4 assimilation by hollow (hummock) mosses leads to more (less) negative δ13C values. To evaluate these competing mechanisms and their impact on moss δ13C, we gathered 30 moss samples from 6 peatlands in southern Patagonia. Samples were collected along a strong hydrological gradient, from very dry hummocks (80 cm above water table depth) to submerged hollows (5 cm below water surface). These peat bogs have the advantage of being colonized by a single cosmopolitan moss species, Sphagnum magellanicum, limiting potential biases introduced by species-specific carbon discrimination. We measured δ13C from stem cellulose and leaf waxes on the same samples to quantify compound-specific carbon signatures. We found that stem cellulose and leaf-wax lipids were both strongly negatively correlated with moss water content, suggesting a primary role of water film thickness on carbon assimilation. In addition, isotopic fractionation during wax synthesis was greater than for cellulose. This offset decreases as conditions get drier, due to (i) a more effective carbon assimilation, or (ii) CH4 uptake through symbiosis with methanotrophic bacteria within the leaves of wet mosses. Biochemical analysis (carbohydrates, amino acids, hydrophenols, cutin acids) of surface moss are currently being conducted to characterize moss carbon allocation under different hydrological conditions. Overall, this modern calibration work should be of use for interpreting carbon isotope records from peatlands.

  7. Carbon isotope records reveal synchronicity between carbon cycle perturbation and the "Carnian Pluvial Event" in the Tethys realm (Late Triassic)

    NASA Astrophysics Data System (ADS)

    Dal Corso, Jacopo; Gianolla, Piero; Newton, Robert J.; Franceschi, Marco; Roghi, Guido; Caggiati, Marcello; Raucsik, Béla; Budai, Tamás; Haas, János; Preto, Nereo

    2015-04-01

    In the early Late Triassic a period of increased rainfall, named the Carnian Pluvial Event (CPE), is evidenced by major lithological changes in continental and marine successions worldwide. The environmental change seems to be closely associated with a negative carbon isotope excursion that was identified in a stratigraphic succession of the Dolomites (Italy) but the temporal relationship between these phenomena is still not well defined. Here we present organic-carbon isotope data from Carnian deep-water stratigraphic sections in Austria and Hungary, and carbonate petrography of samples from a marginal marine section in Italy. A negative 2-4‰ δ13C shift is recorded by bulk organic matter in the studied sections and is coincident with a similar feature highlighted in higher plant and marine algal biomarker carbon-isotope records from the Dolomites (Italy), thus testifying to a global change in the isotopic composition of the reservoirs of the exchangeable carbon. Our new observations verify that sedimentological changes related to the CPE coincide with the carbon cycle perturbation and therefore occurred synchronously within the western Tethys. Consistent with modern observations, our results show that the injection of 13C-depleted CO2 into the Carnian atmosphere-ocean system may have been directly responsible for the increase in rainfall by intensifying the Pangaean mega-monsoon activity. The consequent increased continental weathering and erosion led to the transfer of large amounts of siliciclastics into the basins that were rapidly filled up, while the increased nutrient flux triggered the local development of anoxia. The new carbonate petrography data show that these changes also coincided with the demise of platform microbial carbonate factories and their replacement with metazoan driven carbonate deposition. This had the effect of considerably decreasing carbonate deposition in shallow water environments.

  8. Theoretical isotopic fractionation between structural boron in carbonates and aqueous boric acid and borate ion

    NASA Astrophysics Data System (ADS)

    Balan, Etienne; Noireaux, Johanna; Mavromatis, Vasileios; Saldi, Giuseppe D.; Montouillout, Valérie; Blanchard, Marc; Pietrucci, Fabio; Gervais, Christel; Rustad, James R.; Schott, Jacques; Gaillardet, Jérôme

    2018-02-01

    The 11B/10B ratio in calcite and aragonite is an important proxy of oceanic water pH. However, the physico-chemical mechanisms underpinning this approach are still poorly known. In the present study, we theoretically determine the equilibrium isotopic fractionation properties of structural boron species in calcium carbonates, BO33-, BO2(OH)2- and B(OH)4- anions substituted for carbonate groups, as well as those of B(OH)4- and B(OH)3 species in vacuum. Significant variability of equilibrium isotopic fractionation properties is observed among these structural species which is related to their contrasted coordination state, Bsbnd O bond lengths and atomic-scale environment. The isotopic composition of structural boron does not only depend on its coordination number but also on its medium range environment, i.e. farther than its first coordination shell. The isotopic fractionation between aqueous species and their counterparts in vacuum are assessed using previous investigations based on similar quantum-mechanical modeling approaches. At 300 K, the equilibrium isotope composition of structural trigonal species is 7-15‰ lighter than that of aqueous boric acid molecules, whereas substituted tetrahedral borate ions are heavier than their aqueous counterparts by 10-13‰. Although significant uncertainties are known to affect the theoretical prediction of fractionation factors between solids and solutions, the usually assumed lack of isotopic fractionation during borate incorporation in carbonates is challenged by these theoretical results. The present theoretical equilibrium fractionation factors between structural boron and aqueous species differ from those inferred from experiments which may indicate that isotopic equilibrium, unlike chemical equilibrium, was not reached in most experiments. Further research into the isotopic fractionation processes at the interface between calcium carbonates and aqueous solution as well as long duration experiments aimed at

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

    NASA Astrophysics Data System (ADS)

    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.

  10. Carbon and oxygen isotope ratios of ecosystem respiration along an Oregon conifer transect: preliminary observations based on small-flask sampling.

    PubMed

    Ehleringer, J. R.; Cook, C. S.

    1998-01-01

    Isotope ratio analyses of atmospheric CO(2) at natural abundance have significant potential for contributing to our understanding of photosynthetic and respiration processes in forest ecosystems. Recent advances in isotope ratio mass spectrometry allow for rapid, on-line analysis of small volumes of CO(2) in air, and open new research opportunities at the ecophysiological, whole-organism, and atmospheric levels. Among the immediate applications are the carbon and oxygen isotope ratio analyses of carbon dioxide in atmospheric air. Routine analysis of carbon dioxide in air volumes of approximately 50-300 &mgr;l is accomplished by linking a commercially available, trace gas condenser and gas chromatograph to an isotope ratio mass spectrometer operated in continuous-flow mode. Samples collected in the field are stored in either gas-tight syringes or 100-ml flasks. The small sample volume required makes it possible to subsample the air in flasks for CO(2) and then to sample the remaining air volume for the analysis of the isotopic composition of either methane or nitrous oxide. Reliable delta(13)C and delta(18)O values can be obtained from samples collected and stored for 1-3 days. Longer-term storage, on the order of weeks, is possible for delta(13)C measurements without drift in the isotope ratio signal, and should also be possible for delta(18)O measurements. When linked with an infrared gas analyzer, pump and flask sampling system, it is feasible to sample CO(2) extensively in remote forest locations. The air-sampling system was used to measure the isotope ratios of atmospheric CO(2) and to conduct a regression analysis of the relationship between these two parameters. From the regression, we calculated the delta(13)C of ecosystem respiration of four coniferous ecosystems along a precipitation gradient in central Oregon. The ecosystems along the coast-to-interior Oregon (OTTER) gradient are dominated by spruce-hemlock forests at the wet, coastal sites (> 200 cm

  11. Carbonate stable isotope constraints on sources of arsenic contamination in Neogene tufas and travertines of Attica, Greece

    NASA Astrophysics Data System (ADS)

    Kampouroglou, Evdokia E.; Tsikos, Harilaos; Economou-Eliopoulos, Maria

    2017-11-01

    We presented new C and O isotope data of rockforming calcite in terrestrial carbonate deposits from Neogene basins of Attica (Greece), coupled with standard mineralogical and bulk geochemical results. Whereas both isotope datasets [δ18O from -8.99 to -3.20‰(VPDB); δ13C from -8.17 to +1.40‰(VPDB)] could be interpreted in principle as indicative of a meteoric origin, the clear lack of a statistical correlation between them suggests diverse sources for the isotopic variation of the two elements. On the basis of broad correlations between lower carbon isotope data with increasing Fe and bulk organic carbon, we interpreted the light carbon isotope signatures and As enrichments as both derived mainly from a depositional process involving increased supply of metals and organic carbon to the original basins. Periodically augmented biological production and aerobic cycling of organic matter in the ambient lake waters, would have led to the precipitation of isotopically light calcite in concert with elevated fluxes of As-bearing iron oxy-hydroxide and organic matter to the initial terrestrial carbonate sediment. The terrestrial carbonate deposits of Attica therefore represented effective secondary storage reservoirs of elevated As from the adjacent mineralized hinterland; hence these and similar deposits in the region ought to be regarded as key geological candidates for anomalous supply of As to local soils, groundwater and related human activities.

  12. CARBON ABUNDANCES FOR RED GIANTS IN THE DRACO DWARF SPHEROIDAL GALAXY

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Shetrone, Matthew D.; Stanford, Laura M.; Smith, Graeme H.

    2013-05-15

    Measurements of [C/Fe], [Ca/H], and [Fe/H] have been derived from Keck I LRISb spectra of 35 giants in the Draco dwarf spheroidal galaxy. The iron abundances are derived by a spectrum synthesis modeling of the wavelength region from 4850 to 5375 A, while calcium and carbon abundances are obtained by fitting the Ca II H and K lines and the CH G band, respectively. A range in metallicity of -2.9 {<=} [Fe/H] {<=} -1.6 is found within the giants sampled, with a good correlation between [Fe/H] and [Ca/H]. The great majority of stars in the sample would be classified asmore » having weak absorption in the {lambda}3883 CN band, with only a small scatter in band strengths at a given luminosity on the red giant branch. In this sense the behavior of CN among the Draco giants is consistent with the predominantly weak CN bands found among red giants in globular clusters of metallicity [Fe/H] < -1.8. Over half of the giants in the Draco sample have [Fe/H] > -2.25, and among these there is a trend for the [C/Fe] abundance to decrease with increasing luminosity on the red giant branch. This is a phenomenon that is also seen among both field and globular cluster giants of the Galactic halo, where it has been interpreted as a consequence of deep mixing of material between the base of the convective envelope and the outer limits of the hydrogen-burning shell. However, among the six Draco giants observed that turn out to have metallicities -2.65 < [Fe/H] < -2.25 there is no such trend seen in the carbon abundance. This may be due to small sample statistics or primordial inhomogeneities in carbon abundance among the most metal-poor Draco stars. We identify a potential carbon-rich extremely metal-poor star in our sample. This candidate will require follow-up observations for confirmation.« less

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

    USGS Publications Warehouse

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

    1981-01-01

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

  14. Isotopic Measurements of Organic Sulfonates From The Murchison Meteorite

    NASA Technical Reports Server (NTRS)

    Cooper, G. W.; Chang, S.; DeVincenzi, Donald L. (Technical Monitor)

    1995-01-01

    Organic sulfonates and phosphonates have been extracted from the Murchison meteorite for stable isotope measurements. Preliminary stable isotope measurements of individual alkyl sulfonates, R-SO3H (R=C(sub n)H(sub 2n+l)), are shown. These compounds were found in aqueous extracts of Murchison. Both groups show trends similar to other homologous series of organic compounds indigenous to Murchison. Molecular abundances decrease with increasing carbon number, and all possible isomers at each carbon number (through C-4) are present. Carbon isotope measurements of the sulfonates show a decrease in the C-13/C-12 ratio with increasing carbon number. The overall objectives of this project are to obtain dime element carbon, hydrogen, and sulfur - intramolecular isotopic analyses of individual sulfonates, and isotopic measurement of carbon and hydrogen of the phosphonates as a group. The Murchison meteorite is the best characterized carbonaceous chondrite with respect to organic chemistry. The finding of organic sulfonates and phosphonates in Murchison is of interest because they are the first well-characterized series of sulfur and phosphorus containing organic compounds found in meteorites. Also, meteorites, comets, and interplanetary dust particles may have been involved in chemical evolution on the early Earth. Because of the critical role of organic phosphorus and sulfur in all living systems, it is particularly interesting to see examples of abiotic syntheses of these classes of compounds. The study of the isotopic composition of the sulfonates and phosphonates can yield insight into their possible interstellar origin as well as their mechanisms of synthesis in the early solar system. Previous isotopic analyses of other classes of organic compounds indigenous to meteorites, e.g., amino acids, carboxylic acids, and hydrocarbons indicate the possibility that interstellar molecules were incorporated into meteorite parent bodies. In these compounds the ratios of heavy to

  15. Siderophile and chalcophile element abundances in oceanic basalts, Pb isotope evolution and growth of the earth's core

    NASA Technical Reports Server (NTRS)

    Newsom, H. E.; White, W. M.; Jochum, K. P.; Hofmann, A. W.

    1986-01-01

    The hypothesis that the mantle Pb isotope ratios reflect continued extraction of Pb into the earth's core over geologic time is evaluated by studying the depeletion of chalcophile and siderophile elements in the mantle. Oceanic basalt samples are analyzed in order to determine the Pb, Sr, and Nd isotropic compositions and the abundances of siderophile and chalcophile elements and incompatible lithophile elements. The data reveal that there is no systematic variation of siderophile or chalcophile element abundances relative to abundances of lithophile elements and the Pb/Ce ratio of the mantle is constant. It is suggested that the crust formation involves nonmagmatic and magmatic processes.

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

    NASA Astrophysics Data System (ADS)

    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.

  17. Patterns in Stable Isotope Values of Nitrogen and Carbon in ...

    EPA Pesticide Factsheets

    Stable isotope measurements of nitrogen and carbon (15N, 13ddC) are often used to characterize estuarine, nearshore, and open ocean ecosystems. Reliable information about the spatial distribution of base-level stable isotope values, often represented by primary producers, is critical to interpreting values in these ecosystems. While base-level isotope data are generally readily available for estuaries, nearshore coastal waters, and the open ocean, the continental shelf is less studied. To address this, and as a first step toward developing a surrogate for base-level isotopic signature in this region, we collected surface and deep water samples from the United States’ eastern continental shelf in the Western Atlantic Ocean, from the Gulf of Maine to Cape Hatteras, periodically between 2000 and 2013. During the study, particulate matter 15dN values ranged from 0.8 to 17.4‰, and 13dC values from −26.4 to −15.6‰over the region. We used spatial autocorrelation analysis and random forest modeling to examine the spatial trends and potential environmental drivers of the stable isotope values. We observed general trends toward lower values for both nitrogen and carbon isotopes at the seaward edge of the shelf. Conversely, higher 15dN and 13dC values were observed on the landward edge of the shelf, in particular in the southern portion of the sampling area. Across all sites, the magnitude of the difference between the 15dN of subsurface and surface particulate m

  18. Carbon Isotope Fractionation Effects During Degradation of Methyl Halides in Agricultural Soils

    NASA Astrophysics Data System (ADS)

    Miller, L. G.; Baesman, S. M.; Oremland, R. S.; Bill, M.; Goldstein, A. H.

    2001-12-01

    Fumigation of agricultural soils prior to planting row crops constitutes the largest anthropogenic source of methyl bromide (MeBr) to the atmosphere. Typically, more than 60% of the MeBr added is lost to the atmosphere during the 5-6 day fumigation period. The remainder is oxidized by bacteria or otherwise degraded in the soil. In experiments using washed cells of methylotrophic bacteria isolated from agricultural soil (strain IMB-1), oxidation of MeBr, methyl chloride (MeCl) and methyl iodide to CO2 resulted in large (up to 70‰ ) fractionation of stable carbon isotopes (Miller, et al. 2001). By contrast, fractionation measured in field soils using both in situ techniques and bottle incubations with MeBr was less than 35‰ . This discrepancy was initially attributed to the large transportation losses that occur without isotopic fractionation during field fumigation. However, this rationale cannot explain why bottle incubations with soil resulted in lower fractionation factors than incubations with bacterial cultures. We conducted additional laboratory bottle experiments to examine the biological and chemical controls of carbon isotope fractionation during degradation of MeBr and MeCl by soils and bacteria. Soils were collected from a strawberry field in Santa Cruz County, California within two weeks of the start of each experiment. The rate of removal of methyl halides from the headspace was greatest during incubations at soil moisture contents around 8%. Increasing the amount of soil and hence native bacteria in each bottle minimized the lag in uptake by up to several days. No lag was observed during incubations of soils with added IMB-1. Stable isotope fractionation factors were similar for degradation by live soil and live soil with added IMB-1. Heat-killed controls of cell cultures showed little uptake (<10% over 5 days) and no isotope fractionation. Heat-killed soil controls, by contrast, demonstrated significant loss of MeBr (20-30%) with isotope

  19. Correlating carbon and oxygen isotope events in early to middle Miocene shallow marine carbonates in the Mediterranean region using orbitally tuned chemostratigraphy and lithostratigraphy

    PubMed Central

    Piller, Werner E.; Reuter, Markus; Harzhauser, Mathias

    2015-01-01

    Abstract During the Miocene prominent oxygen isotope events (Mi‐events) reflect major changes in glaciation, while carbonate isotope maxima (CM‐events) reflect changes in organic carbon burial, particularly during the Monterey carbon isotope excursion. However, despite their importance to the global climate history they have never been recorded in shallow marine carbonate successions. The Decontra section on the Maiella Platform (central Apennines, Italy), however, allows to resolve them for the first time in such a setting during the early to middle Miocene. The present study improves the stratigraphic resolution of parts of the Decontra section via orbital tuning of high‐resolution gamma ray (GR) and magnetic susceptibility data to the 405 kyr eccentricity metronome. The tuning allows, within the established biostratigraphic, sequence stratigraphic, and isotope stratigraphic frameworks, a precise correlation of the Decontra section with pelagic records of the Mediterranean region, as well as the global paleoclimatic record and the global sea level curve. Spectral series analyses of GR data further indicate that the 405 kyr orbital cycle is particularly well preserved during the Monterey Event. Since GR is a direct proxy for authigenic uranium precipitation during increased burial of organic carbon in the Decontra section, it follows the same long‐term orbital pacing as observed in the carbon isotope records. The 405 kyr GR beat is thus correlated with the carbon isotope maxima observed during the Monterey Event. Finally, the Mi‐events can now be recognized in the δ18O record and coincide with plankton‐rich, siliceous, or phosphatic horizons in the lithology of the section. PMID:27546980

  20. Correlating carbon and oxygen isotope events in early to middle Miocene shallow marine carbonates in the Mediterranean region using orbitally tuned chemostratigraphy and lithostratigraphy

    NASA Astrophysics Data System (ADS)

    Auer, Gerald; Piller, Werner E.; Reuter, Markus; Harzhauser, Mathias

    2015-04-01

    During the Miocene prominent oxygen isotope events (Mi-events) reflect major changes in glaciation, while carbonate isotope maxima (CM-events) reflect changes in organic carbon burial, particularly during the Monterey carbon isotope excursion. However, despite their importance to the global climate history they have never been recorded in shallow marine carbonate successions. The Decontra section on the Maiella Platform (central Apennines, Italy), however, allows to resolve them for the first time in such a setting during the early to middle Miocene. The present study improves the stratigraphic resolution of parts of the Decontra section via orbital tuning of high-resolution gamma ray (GR) and magnetic susceptibility data to the 405 kyr eccentricity metronome. The tuning allows, within the established biostratigraphic, sequence stratigraphic, and isotope stratigraphic frameworks, a precise correlation of the Decontra section with pelagic records of the Mediterranean region, as well as the global paleoclimatic record and the global sea level curve. Spectral series analyses of GR data further indicate that the 405 kyr orbital cycle is particularly well preserved during the Monterey Event. Since GR is a direct proxy for authigenic uranium precipitation during increased burial of organic carbon in the Decontra section, it follows the same long-term orbital pacing as observed in the carbon isotope records. The 405 kyr GR beat is thus correlated with the carbon isotope maxima observed during the Monterey Event. Finally, the Mi-events can now be recognized in the δ18O record and coincide with plankton-rich, siliceous, or phosphatic horizons in the lithology of the section.

  1. USE OF THE COMPOSITION AND STABLE CARBON ISOTOPE RATIO OF MICROBIAL FATTY ACIDS TO STUDY CARBON CYCLING

    EPA Science Inventory

    We use measurements of the concentration and stable carbon isotopic ratio (Gamma 13C) of individual microbial phospholipid fatty acids (PLFAS) in soils and sediments as indicators of live microbial biomass levels and microbial carbon source. For studies of soil organic matter (SO...

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

    EPA Science Inventory

    We use measurements of the concentration and stable carbon isotopic ratio (D 13C) of individual microbial phospholipid fatty acids (PLFAs) in soils as indicators of live microbial biomass levels and microbial carbon source. We found that intensive sugar cane cultivation leads to ...

  3. Characteristics of Martian Crustal Materials and Implications for Magmatic Assimilation: Preliminary Re-Os Isotope and Highly Siderophile Element Abundance Data for Nakhlites and Tissint

    NASA Astrophysics Data System (ADS)

    Mari, N.; Riches, A. J. V.; Hallis, L. J.; Lee, M. R.

    2017-07-01

    This project, for the first time, aims to integrate nakhlite Os-isotope compositions and HSE abundance data with S-isotope compositions for sample fractions for which textural information is constrained prior to destructive analyses.

  4. Relationships between carbon isotope evolution and variation of microbes during the Permian-Triassic transition at Meishan Section, South China

    NASA Astrophysics Data System (ADS)

    Luo, Genming; Huang, Junhuang; Xie, Shucheng; Wignall, Paul B.; Tang, Xinyan; Huang, Xianyu; Yin, Hongfu

    2010-06-01

    This paper investigates kerogen carbon isotopes, the difference between carbonate and kerogen carbon isotopes (Δ13Ccarb-kero = δ 13Ccarb - δ 13Ckero) and the difference between carbonate and n-C19 alkane compound-specific carbon isotopes (Δ13Ccarb- n-C19 = δ 13Ccarb - δ 13C n-C19) during the Permian-Triassic transition at Meishan, South China. The results show that kerogen carbon isotopes underwent both gradual and sharp shifts in beds 23-25 and 26-29, respectively. The differences between carbonate and organic carbon isotopes, both the Δ13Ccarb-kero and Δ13Ccarb- n-C19, which are mainly affected by CO2-fixing enzyme and pCO2, oscillated frequently during the Permian-Triassic transition. Both the variations of Δ13Ccarb- n-C19 and Δ13Ccarb-kero coupled with the alternation between cyanobacteria and green sulfur bacteria indicated by biomarkers. The episodic low values of Δ13Ccarb- n-C19 corresponded to episodic blooms of green sulfur bacteria, while the episodic high values of Δ13Ccarb- n-C19 corresponded to episodic blooms of cyanobacteria. The relationships between the variation of carbon isotopes and biota show that the microbes which flourished after the extinction of macroorganism affected the carbon isotope fractionation greatly. Combining the carbon isotope compositions and the pattern of size variation of the conodont Neogondolella, this paper supposes that anoxia of the photic zone at bed 24 was episodic and it would be caused by the degradation of terrigenous organic matters by sulfate reducing bacteria in the upper water column. Considered together with results from previous research, the high resolution variation of the biogeochemistry presents the sequence of the important geo-events during the Permian-Triassic crisis.

  5. The stable carbon isotope biogeochemistry of acetate and other dissolved carbon species in deep subseafloor sediments at the northern Cascadia Margin

    USGS Publications Warehouse

    Heuer, Verena B.; Pohlman, John W.; Torres, Marta E.; Elvert, Marcus; Hinrichs, Kai-Uwe

    2009-01-01

    Ocean drilling has revealed the existence of vast microbial populations in the deep subseafloor, but to date little is known about their metabolic activities. To better understand the biogeochemical processes in the deep biosphere, we investigate the stable carbon isotope chemistry of acetate and other carbon-bearing metabolites in sediment pore-waters. Acetate is a key metabolite in the cycling of carbon in anoxic sediments. Its stable carbon isotopic composition provides information on the metabolic processes dominating acetate turnover in situ. This study reports our findings for a methane-rich site at the northern Cascadia Margin (NE Pacific) where Expedition 311 of the Integrated Ocean Drilling Program (IODP) sampled the upper 190 m of sediment. At Site U1329, δ13C values of acetate span a wide range from −46.0‰ to −11.0‰ vs. VPDB and change systematically with sediment depth. In contrast, δ13C values of both the bulk dissolved organic carbon (DOC) (−21.6 ± 1.3‰ vs. VPDB) and the low-molecular-weight compound lactate (−20.9 ± 1.8‰ vs. VPDB) show little variability. These species are interpreted to represent the carbon isotopic composition of fermentation products. Relative to DOC, acetate is up to 23.1‰ depleted and up to 9.1‰ enriched in 13C. Broadly, 13C-depletions of acetate relative to DOC indicate flux of carbon from acetogenesis into the acetate pool while 13C-enrichments of pore-water acetate relative to DOC suggest consumption of acetate by acetoclastic methanogenesis. Isotopic relationships between acetate and lactate or DOC provide new information on the carbon flow and the presence and activity of specific functional microbial communities in distinct biogeochemical horizons of the sediment. In particular, they suggest that acetogenic CO2-reduction can coexist with methanogenic CO2-reduction, a notion contrary to the hypothesis that hydrogen levels are controlled by the thermodynamically most favorable electron

  6. Soil moisture effects on the carbon isotopic composition of soil respiration

    EPA Science Inventory

    The carbon isotopic composition ( 13C) of recently assimilated plant carbon is known to depend on water-stress, caused either by low soil moisture or by low atmospheric humidity. Air humidity has also been shown to correlate with the 13C of soil respiration, which suggests indir...

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

    DOE PAGES

    Garcia del Real, Pablo; Maher, Kate; Kluge, Tobias; ...

    2016-08-19

    Here, magnesium carbonate minerals produced by reaction of H 2O–CO 2 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 deposition of ore-grade, massive-vein cryptocrystalline magnesite; formation of hydrous magnesium carbonates in weathering environments; and 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 CO 2 into magnesium carbonates in these settings is difficult because the fluids are usually notmore » preserved.« less

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

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Garcia del Real, Pablo; Maher, Kate; Kluge, Tobias

    Here, magnesium carbonate minerals produced by reaction of H 2O–CO 2 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 deposition of ore-grade, massive-vein cryptocrystalline magnesite; formation of hydrous magnesium carbonates in weathering environments; and 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 CO 2 into magnesium carbonates in these settings is difficult because the fluids are usually notmore » preserved.« less

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

    ERIC Educational Resources Information Center

    O'Malley, Rebecca M.

    1982-01-01

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

  10. BIODEGRADATION OF FLUORANTHENE AS MONITORED USING STABLE CARBON ISOTOPES

    EPA Science Inventory

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

  11. Biogeochemical Cycling of Methane in the Proterozoic and Its Role in the Carbon Isotope Budget

    NASA Astrophysics Data System (ADS)

    Schrag, D. P.; Laakso, T.

    2016-12-01

    Various studies have proposed that the biogeochemical cycle of methane has played an important role throughout Earth history, both in contributing to greenhouse stability of climate in the Archean and producing carbon isotope variations and climate fluctuations in the Proterozoic and Phanerozoic. Using a simple box model that couples the geochemical cycles on carbon, oxygen, hydrogen, iron, and sulfur, combined with recent studies of methane cycling in anoxic environments, we reexamine the role of methane in both the Archean and Proterozoic, focusing on methane's role in the carbon isotope budget. We find that methane plays a much more modest role at all times of relative anoxia in the deep ocean, which requires an alternative explanation for the carbon isotope record, in particular the "boring billion" during the Mesoproterozoic. In particular, the high burial efficiency driven by lower oxygen levels drives primary production to much lower levels than has been previously described, resulting in relatively little organic matter available for methanogenesis. In addition, the anoxia in deep water results in a reduced role for methanotrophy at these times, and therefore a change in the mechanisms for production of authigenic carbonate, which may have played a significant role in the carbon isotope budget.

  12. The effects of atmospheric [CO2] on carbon isotope fractionation and magnesium incorporation into biogenic marine calcite

    NASA Technical Reports Server (NTRS)

    Vieira, Veronica

    1997-01-01

    The influences of atmospheric carbon dioxide on the fractionation of carbon isotopes and the magnesium incorporation into biogenic marine calcite were investigated using samples of the calcareous alga Amphiroa and benthic foraminifer Sorites grown in the Biosphere 2 Ocean system under variable atmospheric CO2 concentrations (approximately 500 to 1200 ppm). Carbon isotope fractionation was studied in both the organic matter and the skeletal carbonate. Magnesium analysis was to be performed on the carbonate removed during decalcification. These data have not been collected due to technical problems. Carbon isotope data from Amphiroa yields a linear relation between [CO2] and Delta(sup 13)C(sub Corg)values suggesting that the fractionation of carbon isotopes during photosynthesis is positively correlated with atmospheric [CO2]. [CO2] and Delta(sup 13)C(sub Corg) values for Sorites produce a relation that is best described by a hyperbolic function where Delta(sup 13)C(sub Corg) values increase between 300 and 700 ppm and decrease from 700 to 1200 ppm. Further investigation of this relation and Sorites physiology is needed.

  13. Oxygen and carbon isotope compositions of carbonates in a prominent lithologically mixed unit in the central South Norwegian Caledonides

    NASA Astrophysics Data System (ADS)

    Jakob, Johannes; Boulvais, Philippe; Andersen, Torgeir B.

    2018-06-01

    A prominent pre-Scandian lithologically mixed unit in the central South Norwegian Caledonides contains more than 100 partly carbonated and hydrated metaperidotite bodies and locally fossiliferous detrital serpentinites. The lateral consistency of this mixed unit was not fully appreciated in the past. Therefore, parts of the mixed unit along strike were interpreted to belong to several different tectonostratigraphic levels. Here, we present new carbonate stable isotope data that suggest that the carbonates of the mixed unit between Bergen and Otta (re-)equilibrated at unit-wide similar peak metamorphic conditions. The isotope compositions are characteristic for this unit and indicate that it represented one single tectonic unit during the Scandian Orogeny. The carbonates in the mélange are characterized by a narrow range of δ18O (SMOW) values between + 11 and + 15.5‰ and three groups of δ13C (PDB) values: (I) + 1.6 to + 0.3‰, (II) - 1.8 to - 3.9‰, and (III) - 6 to - 8.6‰. Carbonates of group III probably were affected by decarbonation or by a fluid containing organic carbon, whereas carbonates of group I and II overlap with δ13C values typical for Ediacaran-Silurian marine carbonates and may have retained their initial δ13C imprint. We suggest that the δ18O values (re-)equilibrated with unit-wide released metamorphic fluids during Scandian metamorphism. An outcrop-scale homogenisation of the δ13C values reflects the local carbon isotope signature of the released metamorphic fluids that circulated channelized through the mélange unit.

  14. Oxygen and carbon isotope compositions of carbonates in a prominent lithologically mixed unit in the central South Norwegian Caledonides

    NASA Astrophysics Data System (ADS)

    Jakob, Johannes; Boulvais, Philippe; Andersen, Torgeir B.

    2017-11-01

    A prominent pre-Scandian lithologically mixed unit in the central South Norwegian Caledonides contains more than 100 partly carbonated and hydrated metaperidotite bodies and locally fossiliferous detrital serpentinites. The lateral consistency of this mixed unit was not fully appreciated in the past. Therefore, parts of the mixed unit along strike were interpreted to belong to several different tectonostratigraphic levels. Here, we present new carbonate stable isotope data that suggest that the carbonates of the mixed unit between Bergen and Otta (re-)equilibrated at unit-wide similar peak metamorphic conditions. The isotope compositions are characteristic for this unit and indicate that it represented one single tectonic unit during the Scandian Orogeny. The carbonates in the mélange are characterized by a narrow range of δ18O (SMOW) values between + 11 and + 15.5‰ and three groups of δ13C (PDB) values: (I) + 1.6 to + 0.3‰, (II) - 1.8 to - 3.9‰, and (III) - 6 to - 8.6‰. Carbonates of group III probably were affected by decarbonation or by a fluid containing organic carbon, whereas carbonates of group I and II overlap with δ13C values typical for Ediacaran-Silurian marine carbonates and may have retained their initial δ13C imprint. We suggest that the δ18O values (re-)equilibrated with unit-wide released metamorphic fluids during Scandian metamorphism. An outcrop-scale homogenisation of the δ13C values reflects the local carbon isotope signature of the released metamorphic fluids that circulated channelized through the mélange unit.

  15. A reconstruction of atmospheric carbon dioxide and its stable carbon isotopic composition from the penultimate glacial maximum to the last glacial inception

    NASA Astrophysics Data System (ADS)

    Schneider, R.; Schmitt, J.; Köhler, P.; Joos, F.; Fischer, H.

    2013-11-01

    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 new record of δ13Catm before, during and after the Marine Isotope Stage 5.5 (155 000 to 105 000 yr BP). The dataset is archived on the data repository PANGEA® (www.pangea.de) under 10.1594/PANGAEA.817041. 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 a 0.4‰ shift to heavier values 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 MIS5.5 (120 000 yr BP). Based on our isotopic data this lag can be explained by terrestrial carbon release and carbonate compensation.

  16. Elemental and isotopic (C, O, Sr, Nd) compositions of Late Paleozoic carbonated eclogite and marble from the SW Tianshan UHP belt, NW China: Implications for deep carbon cycle

    NASA Astrophysics Data System (ADS)

    Zhu, Jianjiang; Zhang, Lifei; Lü, Zeng; Bader, Thomas

    2018-03-01

    Subduction zones are important for understanding of the global carbon cycle from the surface to deep part of the mantle. The processes involved the metamorphism of carbonate-bearing rocks largely control the fate of carbon and contribute to local carbon isotopic heterogeneities of the mantle. In this study, we present petrological and geochemical results for marbles and carbonated eclogites in the Southwestern Tianshan UHP belt, NW China. Marbles are interlayered with coesite-bearing pelitic schists, and have Sr-Nd isotopic values (εNd (T=320Ma) = -3.7 to -8.9, 87Sr/86Sr (i) = 0.7084-0.7089), typical of marine carbonates. The marbles have dispersed low δ18OVSMOW values (ranging from 14 to 29‰) and unaffected carbon isotope (δ13CVPDB = -0.2-3.6‰), possibly due to infiltration of external H2O-rich fluids. Recycling of these marbles into mantle may play a key role in the carbon budget and contributed to the mantle carbon isotope heterogeneity. The carbonated eclogites have high Sr isotopic compositions (87Sr/86Sr (i) = 0.7077-0.7082) and positive εNd (T = 320 Ma) values (from 7.6 to 8.2), indicative of strong seafloor alteration of their protolith. The carbonates in the carbonated eclogites are mainly dolomite (Fe# = 12-43, Fe# = Fe2+/(Fe2+ + Mg)) that were added into oceanic basalts during seafloor alteration and experienced calcite - dolomite - magnesite transformation during the subduction metamorphic process. The uniformly low δ18O values (∼11.44‰) of carbonates in the carbontaed eclogites can be explained by closed-system equilibrium between carbonate and silicate minerals. The low δ13C values (from -3.3 to -7.7‰) of the carbonated eclogites most likely reflect contribution from organic carbon. Recycling of these carbonated eclogites with C isotope similar to typical mantle reservoirs into mantle may have little effect on the mantle carbon isotope heterogeneity.

  17. Carnivore specific bone bioapatite and collagen carbon isotope fractionations: Case studies of modern and fossil grey wolf populations

    NASA Astrophysics Data System (ADS)

    Fox-Dobbs, K.; Wheatley, P. V.; Koch, P. L.

    2006-12-01

    Stable isotope analyses of modern and fossil biogenic tissues are routinely used to reconstruct present and past vertebrate foodwebs. Accurate isotopic dietary reconstructions require a consumer and tissue specific understanding of how isotopes are sorted, or fractionated, between trophic levels. In this project we address the need for carnivore specific isotope variables derived from populations that are ecologically well- characterized. Specifically, we investigate the trophic difference in carbon isotope values between mammalian carnivore (wolf) bone bioapatite and herbivore (prey) bone bioapatite. We also compare bone bioapatite and collagen carbon isotope values collected from the same individuals. We analyzed bone specimens from two modern North American grey wolf (Canis lupus) populations (Isle Royale National Park, Michigan and Yellowstone National Park, Wyoming), and the ungulate herbivores that are their primary prey (moose and elk, respectively). Because the diets of both wolf populations are essentially restricted to a single prey species, there were no confounding effects due to carnivore diet variability. We measured a trophic difference of approximately -1.3 permil between carnivore (lower value) and herbivore (higher value) bone bioapatite carbon isotope values, and an average inter-tissue difference of 5.1 permil between carnivore bone collagen (lower value) and bioapatite (higher value) carbon isotope values. Both of these isotopic differences differ from previous estimates derived from a suite of African carnivores; our carnivore-herbivore bone bioapatite carbon isotope spacing is smaller (-1.3 vs. -4.0 permil), and our carnivore collagen-bioapatite carbon difference is larger (5.1 vs. 3.0 permil). These discrepancies likely result from comparing values measured from a single hypercarnivore (wolf) to average values calculated from several carnivore species, some of which are insectivorous or partly omnivorous. The trophic and inter

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

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ismail, Atef; Cheong, Lee Yen; Yahya, Noorhana

    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 themore » blocking effect plays a significant role in the shell model configurations.« less

  19. Stable isotopes of pedogenic carbonates from the Somma-Vesuvius area, southern Italy, over the past 18 kyr: palaeoclimatic implications

    NASA Astrophysics Data System (ADS)

    Zanchetta, G.; di Vito, M.; Fallick, A. E.; Sulpizio, R.

    2000-12-01

    Stable isotopes were measured in the carbonate and organic matter of palaeosols in the Somma-Vesuvius area, southern Italy in order to test whether they are suitable proxy records for climatic and ecological changes in this area during the past 18000 yr. The ages of the soils span from ca. 18 to ca. 3 kyr BP. Surprisingly, the Last Glacial to Holocene climate transition was not accompanied by significant change in 18O of pedogenic carbonate. This could be explained by changes in evaporation rate and in isotope fractionation between water and precipitated carbonate with temperature, which counterbalanced the expected change in isotope composition of meteoric water. Because of the rise in temperature and humidity and the progressive increase in tree cover during the Holocene, the Holocene soil carbonates closely reflect the isotopic composition of meteoric water. A cooling of about 2°C after the Avellino eruption (3.8 ka) accounts for a sudden decrease of about 1 in 18O of pedogenic carbonate recorded after this eruption. The 13C values of organic matter and pedogenic carbonate covary, indicating an effective isotope equilibrium between the organic matter, as the source of CO2, and the pedogenic carbonate. Carbon isotopes suggest prevailing C3 vegetation and negligible mixing with volcanogenic or atmospheric CO2.

  20. Influences on the stable oxygen and carbon isotopes in gerbillid rodent teeth in semi-arid and arid environments: Implications for past climate and environmental reconstruction

    NASA Astrophysics Data System (ADS)

    Jeffrey, Amy; Denys, Christiane; Stoetzel, Emmanuelle; Lee-Thorp, Julia A.

    2015-10-01

    The stable isotope composition of small mammal tissues has the potential to provide detailed information about terrestrial palaeoclimate and environments, because their remains are abundant in palaeontological and archaeological sites, and they have restricted home ranges. Applications to the Quaternary record, however, have been sparse and limited by an acute lack of understanding of small mammal isotope ecology, particularly in arid and semi-arid environments. Here we document the oxygen and carbon isotope composition of Gerbillinae (gerbil) tooth apatite across a rainfall gradient in northwestern Africa, in order to test the relative influences of the 18O/16O in precipitation or moisture availability on gerbil teeth values, the sensitivity of tooth apatite 13C/12C to plant responses to moisture availability, and the influence of developmental period on the isotopic composition of gerbil molars and incisors. The results show that the isotopic composition of molars and incisors from the same individuals differs consistent with the different temporal periods reflected by the teeth; molar teeth are permanently rooted and form around the time of birth, whereas incisors grow continuously. The results indicate that tooth choice is an important consideration for applications as proxy Quaternary records, but also highlights a new potential means to distinguish seasonal contexts. The oxygen isotope composition of gerbil tooth apatite is strongly correlated with mean annual precipitation (MAP) below 600 mm, but above 600 mm the teeth reflect the oxygen isotope composition of local meteoric water instead. Predictably, the carbon isotope composition of the gerbil teeth reflected C3 and C4 dietary inputs, however arid and mesic sites could not be distinguished because of the high variability displayed in the carbon isotope composition of the teeth due to the microhabitat and short temporal period reflected by the gerbil. We show that the oxygen isotope composition of small

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

    PubMed

    Porowska, Dorota

    2015-05-01

    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(13)CDIC) 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(13)CDIC 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 CO2 (P CO2) was generally above the atmospheric, hence atmospheric CO2 as a source of carbon in DIC pool was negligible in the aquifer. P CO2 values in the aquifer in Otwock were always one to two orders of magnitude above the atmospheric P CO2, and thus CO2 escaped directly into the vadose zone. Copyright © 2015 Elsevier Ltd. All rights reserved.

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

    NASA Astrophysics Data System (ADS)

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

    2012-11-01

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

  3. Degradation of Perchloroethene by zero-valent iron evaluated by carbon isotope fractionation

    NASA Astrophysics Data System (ADS)

    Leitner, Simon; Watzinger, Andrea; Reichenauer, Thomas G.

    2014-05-01

    Perchloroethene (PCE) is a widely spread groundwater contaminant in formally used industrial sites. Zero valent iron (ZVI) is used for in situ chemical reduction (ISCR) of PCE contaminants in the groundwater. A key factor in the application of in situ remediation technologies is a proper monitoring of contaminant reduction. The measurement of the stable isotope ratio is a promising method that is already used for quantifying microbial degradation of chlorinated contaminants. The carbon isotope ratio of PCE, measured by - isotope ratio mass spectrometry coupled to a gas chromatograph via a combustion interface (GC-C-IRMS), increases during degradation of PCE and can be directly related to the degree of degradation. It can be used to directly quantify chemical degradation and thus serves as a useful monitoring tool for groundwater remediation. An experiment to determine the carbon isotopic fractionation factor was performed as a lab experiment using Nanofer Star (NANOIRON). Two different PCE concentrations (c1: 220mgL-1, c2: 110mgL-1) mixed with 0.5 g of ZVI were sealed under deoxygenated conditions in 250 ml glas bottles locked with mininert caps. The bottles were incubated on a shaker for 865 h. Samples were taken weekly to measure the change in the carbon isotopic ratio of PCE as well as its concentration. Results showed a strong increase in the carbon isotope ratio (δ-value) of PCE (start: -27 o end: -4 ), which indicates a significant dechlorination process of PCE. Beside PCE also one degradation product (Trichloroethylene - TCE) was measured. TCE was further dechlorinated as indicated by the δ-value change of TCE from -26 o to -4 oȦn unexpected intermediate value of -45 o for TCE was observed in the experiment. This fluctuation could be induced by the time depending concentration due to degradation and conversation processes. Furthermore, it seems that the progress of the δ-value is affected by the starting concentration of PCE (δ-value of c1 < c2) as

  4. Do chlorophyllous orchids heterotrophically use mycorrhizal fungal carbon?

    PubMed

    Selosse, Marc-André; Martos, Florent

    2014-11-01

    The roots of orchids associate with mycorrhizal fungi, the rhizoctonias, which are considered to exchange mineral nutrients against plant carbon. The recent discovery that rhizoctonias grow endophytically in non-orchid plants raises the possibility that they provide carbon to orchids, explaining why some orchids differ in isotopic abundances from autotrophic plants.

  5. Carbon-13 natural abundance signatures of long-chain fatty acids to determinate sediment origin: A case study in northeast Austria

    NASA Astrophysics Data System (ADS)

    Mabit, Lionel; Gibbs, Max; Meusburger, Katrin; Toloza, Arsenio; Resch, Christian; Klik, Andreas; Swales, Andrew; Alewell, Christine

    2016-04-01

    - Several recently published information from scientific research have highlighted that compound-specific stable isotope (CSSI) signatures of fatty acids (FAs) based on the measurement of carbon-13 natural abundance signatures showed great promises to identify sediment origin. The authors have used this innovative isotopic approach to investigate the sources of sediment in a three hectares Austrian sub-watershed (i.e. Mistelbach). Through a previous study using the Cs-137 technique, Mabit et al. (Geoderma, 2009) reported a local maximum sedimentation rate reaching 20 to 50 t/ha/yr in the lowest part of this watershed. However, this study did not identify the sources. Subsequently, the deposited sediment at its outlet (i.e. the sediment mixture) and representative soil samples from the four main agricultural fields - expected to be the source soils - of the site were investigated. The bulk delta carbon-13 of the samples and two long-chain FAs (i.e. C22:0 and C24:0) allowed the best statistical discrimination. Using two different mixing models (i.e. IsoSource and CSSIAR v1.00) and the organic carbon content of the soil sources and sediment mixture, the contribution of each source has been established. Results suggested that the grassed waterway contributed to at least 50% of the sediment deposited at the watershed outlet. This study, that will require further validation, highlights that CSSI and Cs-137 techniques are complementary as fingerprints and tracers for establishing land sediment redistribution and could provide meaningful information for optimized decision-making by land managers.

  6. Isotopic analysis of groundwater and carbonate system in the Surdulica geothermal aquifer

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hadzisehovic, M; Miljevic, N.; Sipka, V.

    1993-01-01

    The authors present here results of their investigation of the isotopic chemical composition of groundwater and carbonates in the Surdulica geothermal aquifer, Serbia. They considered the effects of carbonate dissolution and measured [sup 13]C, [sup 14]C, D, [sup 18]O, [sup 3]H, field pH, temperature, Na[sup +], CA [sup 2+], Mg[sup 2+], HCO[sub 3] and other aqueous species from 30 springs and boreholes. Geothermal waters are supersaturated with calcite. Carbon isotope compositions vary with carbonate mineral dissolution. The [delta]D and [delta][sup 18]O of groundwater samples fit the meteoric water line, and indicate that groundwater is recharged mainly from higher altitudes andmore » the cold season. Different groundwater residence times point out two mechanisms for their formation: fissure flow for young waters and standard diffusion processes for old ones.« less

  7. Effect of thermal decarbonation on the stable isotope composition of carbonates

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Durakiewicz, T.; Sharp, Z. D.; Papike, J. J.

    2001-01-01

    The unusual texture and stable isotope variability of carbonates in AH84001 have been used as evidence for early life on Mars (Romanek et al., 1994; McKay et al., 1996). Oxygen and carbon isotope variability is most commonly attributed to low-temperature processes, including Rayleigh-like fractionation associated with biological activity. Another possible explanation for the isotopic variability in meteoritic samples is thermal decarbonation. In this report, different carbonates were heated in a He-stream until decomposition temperatures were reached. The oxygen and carbon isotope ratios ({delta}{sup 18}O and {delta}{sup 13}C values) of the resulting gas were measured on a continuous flow isotope ratiomore » mass spectrometer. The aim of this work is to evaluate the possibility that large isotopic variations can be generated on a small scale abiogenically, by the process of thermal decarbonation. Oxygen isotope fractionations of >4{per_thousand} have been measured during decarbonation of calcite at high temperatures (McCrea, 1950), and in excess of 6{per_thousand} for dolomite decarbonated between 500 and 600 C (Sharma and Clayton, 1965). Isotopic fractionations of this magnitude, coupled with Rayleigh-like distillation behavior could result in very large isotopic variations on a small scale. To test the idea, calcite, dolomite and siderite were heated in a quartz tube in a He-stream in excess of 1 atmosphere. Simultaneous determinations of {delta}{sup 13}C and {Delta}{sup 18}O values were obtained on 250 {micro}l aliquots of the CO{sub 2}-bearing He gas using an automated 6-way switching valve system (Finnigan MAT GasBench II) and a Finnigan MAT Delta Plus mass spectrometer. It was found that decarbonation of calcite in a He atmosphere begins at 720 C, but the rate significantly increases at temperatures of 820 C. After an initial light {delta}{sup 18}O value of -14.1{per_thousand} at 720 C associated with very early decarbonation, {delta}{sup 18}0 values

  8. Reconstruction of limnology and microbialite formation conditions from carbonate clumped isotope thermometry.

    PubMed

    Petryshyn, V A; Lim, D; Laval, B L; Brady, A; Slater, G; Tripati, A K

    2015-01-01

    Quantitative tools for deciphering the environment of microbialite formation are relatively limited. For example, the oxygen isotope carbonate-water geothermometer requires assumptions about the isotopic composition of the water of formation. We explored the utility of using 'clumped' isotope thermometry as a tool to study the temperatures of microbialite formation. We studied microbialites recovered from water depths of 10-55 m in Pavilion Lake, and 10-25 m in Kelly Lake, spanning the thermocline in both lakes. We determined the temperature of carbonate growth and the (18)O/(16)O ratio of the waters that microbialites grew in. Results were then compared to current limnological data from the lakes to reconstruct the history of microbialite formation. Modern microbialites collected at shallow depths (11.7 m) in both lakes yield clumped isotope-based temperatures of formation that are within error of summer water temperatures, suggesting that clumped isotope analyses may be used to reconstruct past climates and to probe the environments in which microbialites formed. The deepest microbialites (21.7-55 m) were recovered from below the present-day thermoclines in both lakes and yield radioisotope ages indicating they primarily formed earlier in the Holocene. During this time, pollen data and our reconstructed water (18)O/(16)O ratios indicate a period of aridity, with lower lake levels. At present, there is a close association between both photosynthetic and heterotrophic communities, and carbonate precipitation/microbialite formation, with biosignatures of photosynthetic influences on carbonate detected in microbialites from the photic zone and above the thermocline (i.e., depths of generally <20 m). Given the deeper microbialites are receiving <1% of photosynthetically active radiation (PAR), it is likely these microbialites primarily formed when lower lake levels resulted in microbialites being located higher in the photic zone, in warm surface waters. © 2014 John

  9. The synthesis of a tritium, carbon-14, and stable isotope-labeled cathepsin C inhibitors.

    PubMed

    Allen, Paul; Bragg, Ryan A; Caffrey, Moya; Ericsson, Cecilia; Hickey, Michael J; Kingston, Lee P; Elmore, Charles S

    2017-02-01

    As part of a medicinal chemistry program aimed at developing a highly potent and selective cathepsin C inhibitor, tritium, carbon-14, and stable isotope-labeled materials were required. The synthesis of tritium-labeled methanesulfonate 5 was achieved via catalytic tritiolysis of a chloro precursor, albeit at a low radiochemical purity of 67%. Tritium-labeled AZD5248 was prepared via a 3-stage synthesis, utilizing amide-directed hydrogen isotope exchange. Carbon-14 and stable isotope-labeled AZD5248 were successfully prepared through modifications of the medicinal chemistry synthetic route, enabling the use of available labeled intermediates. Copyright © 2016 John Wiley & Sons, Ltd.

  10. Compiled records of carbon isotopes in atmospheric CO2 for historical simulations in CMIP6

    NASA Astrophysics Data System (ADS)

    Graven, Heather; Allison, Colin E.; Etheridge, David M.; Hammer, Samuel; Keeling, Ralph F.; Levin, Ingeborg; Meijer, Harro A. J.; Rubino, Mauro; Tans, Pieter P.; Trudinger, Cathy M.; Vaughn, Bruce H.; White, James W. C.

    2017-12-01

    The isotopic composition of carbon (Δ14C and δ13C) in atmospheric CO2 and in oceanic and terrestrial carbon reservoirs is influenced by anthropogenic emissions and by natural carbon exchanges, which can respond to and drive changes in climate. Simulations of 14C and 13C in the ocean and terrestrial components of Earth system models (ESMs) present opportunities for model evaluation and for investigation of carbon cycling, including anthropogenic CO2 emissions and uptake. The use of carbon isotopes in novel evaluation of the ESMs' component ocean and terrestrial biosphere models and in new analyses of historical changes may improve predictions of future changes in the carbon cycle and climate system. We compile existing data to produce records of Δ14C and δ13C in atmospheric CO2 for the historical period 1850-2015. The primary motivation for this compilation is to provide the atmospheric boundary condition for historical simulations in the Coupled Model Intercomparison Project 6 (CMIP6) for models simulating carbon isotopes in the ocean or terrestrial biosphere. The data may also be useful for other carbon cycle modelling activities.

  11. Stable Isotope Values of Nitrogen and Carbon in Particulate ...

    EPA Pesticide Factsheets

    Data set from “Patterns in stable isotope values of nitrogen and carbon in particulate matter from the Northwest Atlantic Continental Shelf, from the Gulf of Maine to Cape Hatteras” by Oczkowski et al. These are the data upon which all results and conclusion are made. Publishing the data allow for use by wider audience. Stable isotope dynamics on the shelf can inform both nearshore and open ocean research efforts, providing an important link along the marine continuum. To our knowledge, this data set is unique in its spatial coverage and variables measured.

  12. Carbon isotope composition of low molecular weight hydrocarbons and monocarboxylic acids from Murchison meteorite

    NASA Technical Reports Server (NTRS)

    Yuen, G.; Blair, N.; Des Marais, D. J.; Chang, S.

    1984-01-01

    Carbon isotopic compositions have been measured for individual hydrocarbons and monocarboxylic acids from the Murchison meteorite, a C2 carbonaceous chondrite which fell in Australia in 1969. With few exceptions, notably benzene, the volatile products are substantially isotopically heavier than their terrestrial counterparts, signifying their extraterrestrial origin. For both classes of compounds, the ratio of C-13 to C-12 decreases with increasing carbon number in a roughly parallel manner, and each carboxylic acid exhibits a higher isotopic ratio than the hydrocarbon containing the same number of carbon atoms. These trends are consistent with the kinetically controlled synthesis of higher homologues from lower ones. The results suggest the possibility that the production mechanisms for hydrocarbons and carboxylic acids may be similar, and impose constraints on the identity of the reactant species.

  13. Carbon and oxygen isotopic composition of coal and carbon dioxide derived from laboratory coal combustion: A preliminary study

    USGS Publications Warehouse

    Warwick, Peter D.; Ruppert, Leslie F.

    2016-01-01

    The concentration of carbon dioxide (CO2) in the atmosphere has dramatically increased from the start of the industrial revolution in the mid-1700s to present levels exceeding 400 ppm. Carbon dioxide derived from fossil fuel combustion is a greenhouse gas and a major contributor to on-going climate change. Carbon and oxygen stable isotope geochemistry is a useful tool to help model and predict the contributions of anthropogenic sources of CO2 in the global carbon cycle. Surprisingly few studies have addressed the carbon and oxygen isotopic composition of CO2 derived from coal combustion. The goal of this study is to document the relationships between the carbon and oxygen isotope signatures of coal and signatures of the CO2 produced from laboratory coal combustion in atmospheric conditions.Six coal samples were selected that represent various geologic ages (Carboniferous to Tertiary) and coal ranks (lignite to bituminous). Duplicate splits of the six coal samples were ignited and partially combusted in the laboratory at atmospheric conditions. The resulting coal-combustion gases were collected and the molecular composition of the collected gases and isotopic analyses of δ13C of CO2, δ13C of CH4, and δ18O of CO2 were analysed by a commercial laboratory. Splits (~ 1 g) of the un-combusted dried ground coal samples were analyzed for δ13C and δ18O by the U.S. Geological Survey Reston Stable Isotope Laboratory.The major findings of this preliminary work indicate that the isotopic signatures of δ13C (relative to the Vienna Pee Dee Belemnite scale, VPDB) of CO2 resulting from coal combustion are similar to the δ13CVPDB signature of the bulk coal (− 28.46 to − 23.86 ‰) and are not similar to atmospheric δ13CVPDB of CO2 (~ − 8 ‰, see http://www.esrl.noaa.gov/gmd/outreach/isotopes/c13tellsus.html). The δ18O values of bulk coal are strongly correlated to the coal dry ash yields and appear to have little or no influence on the δ18O values of CO2

  14. Surface area dependence of calcium isotopic reequilibration in carbonates: Implications for isotopic signatures in the weathering zone

    NASA Astrophysics Data System (ADS)

    Fernandez, N. M.; Druhan, J. L.; Potrel, A.; Jacobson, A. D.

    2016-12-01

    The concept of dynamic equilibrium carries the implicit assumption of continued isotopic exchange between a mineral and the surrounding fluid. While this effect has received much attention in the marine paleoproxy literature, it has been relatively overlooked in application to the terrestrial environment. In weathering systems, a potential consequence is that rapid reequilibration may alter or erase isotopic signatures generated during secondary mineral formation. The extent and timescale over which isotopic signatures are reset in these hydrologic systems is unknown. Using reactive transport modeling, we show isotopic reequilibration under conditions reflecting terrestrial hydrologic settings to be significant and dependent on the reactive surface area of the solid. In particular, we suggest that the non-traditional stable isotopes commonly used in application to carbonates (e.g., Ca, Mg, Sr) are sensitive to these effects due to their rapid reaction rates. We aim to characterize the dependence of Ca isotopic reequilibration on surface area during calcite precipitation via batch experiments conducted at ambient temperature over 48-hour time periods. Calcite precipitation was performed in a closed batch reactor utilizing a controlled free-drift method. The batch reactors contained mixed supersaturated solutions of CaCl2 and NaHCO3 at an initial pH of 8.54. Precipitation was initiated by seed inoculation of calcite crystals with two distinct, pre-constrained surface areas. All experiments achieved the same final state of chemical equilibrium, but as expected, the fastest approach to equilibrium occurred for experiments employing calcite seeds with the highest surface area. This implies that differences in equilibrated Ca isotope ratios (δ44/40Ca) should reflect differences in surface area. This prediction is upheld by models of the experiments, indicating a measureable difference in δ44Ca during calcite precipitation where the higher surface area corresponds to

  15. Isotopes as Tracers of the Hawaiian Coffee-Producing Regions

    PubMed Central

    2011-01-01

    Green coffee bean isotopes have been used to trace the effects of different climatic and geological characteristics associated with the Hawaii islands. Isotope ratio mass spectrometry (IRMS) and inductively coupled plasma mass spectrometry ((MC)-ICP-SFMS and ICP-QMS) were applied to determine the isotopic composition of carbon (δ13C), nitrogen (δ15N), sulfur (δ34S), and oxygen (δ18O), the isotope abundance of strontium (87Sr/86Sr), and the concentrations of 30 different elements in 47 green coffees. The coffees were produced in five Hawaii regions: Hawaii, Kauai, Maui, Molokai, and Oahu. Results indicate that coffee plant seed isotopes reflect interactions between the coffee plant and the local environment. Accordingly, the obtained analytical fingerprinting could be used to discriminate between the different Hawaii regions studied. PMID:21838232

  16. Uranium Isotopes in Calcium Carbonate: A Possible Proxy for Paleo-pH and Carbonate Ion Concentration?

    NASA Astrophysics Data System (ADS)

    Chen, X.; Romaniello, S. J.; Herrmann, A. D.; Wasylenki, L. E.; Anbar, A. D.

    2015-12-01

    Natural variations of 238U/235U in marine carbonates are being explored as a paleoredox proxy. However, in order for this proxy to be robust, it is important to understand how pH and alkalinity affect the fractionation of 238U/235U during coprecipitation with calcite and aragonite. Recent work suggests that the U/Ca ratio of foraminiferal calcite may vary with seawater [CO32-] concentration due to changes in U speciation[1]. Here we explore analogous isotopic consequences in inorganic laboratory co-precipitation experiments. Uranium coprecipitation experiments with calcite and aragonite were performed at pH 8.5 ± 0.1 and 7.5 ± 0.1 using a constant addition method [2]. Dissolved U in the remaining solution was periodically collected throughout the experiments. Samples were purified with UTEVA resin and 238U/235U was determined using a 233U-236U double-spike and MC-ICP-MS, attaining a precision of ± 0.10 ‰ [3]. Small but resolvable U isotope fractionation was observed in aragonite experiments at pH ~8.5, preferentially enriching heavier U isotopes in the solid phase. 238U/235U of the dissolved U in these experiments can be fit by Rayleigh fractionation curves with fractionation factors of 1.00002 - 1.00009. In contrast, no resolvable U isotope fractionation was detected in an aragonite experiment at pH ~7.5 or in calcite experiments at either pH. Equilibrium isotope fractionation among dissolved U species is the most likely mechanism driving these isotope effects. Our quantitative model of this process assumes that charged U species are preferentially incorporated into CaCO3 relative to the neutral U species Ca2UO2(CO3)3(aq), which we hypothesize to have a lighter equilibrium U isotope composition than the charged U species. According to this model, the magnitude of U isotope fractionation should scale with the fraction of the neutral U species in the solution, in agreement with our experimental results. These findings suggest that U isotope variations in

  17. Springtime carbon emission episodes at the Gosan background site revealed by total carbon, stable carbon isotopic composition, and thermal characteristics of carbonaceous particles

    NASA Astrophysics Data System (ADS)

    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.

  18. Isotopic evidence of early hominin diets

    NASA Astrophysics Data System (ADS)

    Sponheimer, Matt; Alemseged, Zeresenay; Cerling, Thure E.; Grine, Frederick E.; Kimbel, William H.; Leakey, Meave G.; Lee-Thorp, Julia A.; Kyalo Manthi, Fredrick; Reed, Kaye E.; Wood, Bernard A.; Wynn, Jonathan G.

    2013-06-01

    Carbon isotope studies of early hominins from southern Africa showed that their diets differed markedly from the diets of extant apes. Only recently, however, has a major influx of isotopic data from eastern Africa allowed for broad taxonomic, temporal, and regional comparisons among hominins. Before 4 Ma, hominins had diets that were dominated by C3 resources and were, in that sense, similar to extant chimpanzees. By about 3.5 Ma, multiple hominin taxa began incorporating 13C-enriched [C4 or crassulacean acid metabolism (CAM)] foods in their diets and had highly variable carbon isotope compositions which are atypical for African mammals. By about 2.5 Ma, Paranthropus in eastern Africa diverged toward C4/CAM specialization and occupied an isotopic niche unknown in catarrhine primates, except in the fossil relations of grass-eating geladas (Theropithecus gelada). At the same time, other taxa (e.g., Australopithecus africanus) continued to have highly mixed and varied C3/C4 diets. Overall, there is a trend toward greater consumption of 13C-enriched foods in early hominins over time, although this trend varies by region. Hominin carbon isotope ratios also increase with postcanine tooth area and mandibular cross-sectional area, which could indicate that these foods played a role in the evolution of australopith masticatory robusticity. The 13C-enriched resources that hominins ate remain unknown and must await additional integration of existing paleodietary proxy data and new research on the distribution, abundance, nutrition, and mechanical properties of C4 (and CAM) plants.

  19. Isotopic evidence of early hominin diets

    PubMed Central

    Sponheimer, Matt; Alemseged, Zeresenay; Cerling, Thure E.; Grine, Frederick E.; Kimbel, William H.; Leakey, Meave G.; Lee-Thorp, Julia A.; Manthi, Fredrick Kyalo; Reed, Kaye E.; Wood, Bernard A.; Wynn, Jonathan G.

    2013-01-01

    Carbon isotope studies of early hominins from southern Africa showed that their diets differed markedly from the diets of extant apes. Only recently, however, has a major influx of isotopic data from eastern Africa allowed for broad taxonomic, temporal, and regional comparisons among hominins. Before 4 Ma, hominins had diets that were dominated by C3 resources and were, in that sense, similar to extant chimpanzees. By about 3.5 Ma, multiple hominin taxa began incorporating 13C-enriched [C4 or crassulacean acid metabolism (CAM)] foods in their diets and had highly variable carbon isotope compositions which are atypical for African mammals. By about 2.5 Ma, Paranthropus in eastern Africa diverged toward C4/CAM specialization and occupied an isotopic niche unknown in catarrhine primates, except in the fossil relations of grass-eating geladas (Theropithecus gelada). At the same time, other taxa (e.g., Australopithecus africanus) continued to have highly mixed and varied C3/C4 diets. Overall, there is a trend toward greater consumption of 13C-enriched foods in early hominins over time, although this trend varies by region. Hominin carbon isotope ratios also increase with postcanine tooth area and mandibular cross-sectional area, which could indicate that these foods played a role in the evolution of australopith masticatory robusticity. The 13C-enriched resources that hominins ate remain unknown and must await additional integration of existing paleodietary proxy data and new research on the distribution, abundance, nutrition, and mechanical properties of C4 (and CAM) plants.

  20. The carbon and oxygen isotope records of reef-dwelling foraminifers subjected to five varied pCO2 seawater

    NASA Astrophysics Data System (ADS)

    Hikami, M.; Ishimura, T.; Suzuki, A.; Nojiri, Y.; Kawahata, H.

    2013-12-01

    Ocean acidification (OA) in response to rising atmospheric pCO2 is generally expected to reduce rates of calcification by reef calcifying organisms, with potentially severe implications for coral reef ecosystems. Reef dwelling foraminifera is one of the most important primary and carbonate producers in coral reef environments. Their shells are composed of high-Mg calcite and they are host to algal endosymbionts. In our previous culture experiment with two algal reef dwelling foraminifers, Amphisorus kudakajimensis and Calcarina gaudichaudii in the seawater of five different pCO2 conditions, net calcification of A. kudakajimensis was reduced under higher pCO2, whereas net calcification of C. gaudichaudii showed continued increasing trend with pCO2. These contrasting responses between the two species are possibly due to differences in calcification mechanisms and to links between calcification by the foraminifers and photosynthesis by the algal endosymbionts. But the factors affecting these calcification mechanisms are poorly understood. In this study, to get a better understanding of the effect of OA on their calcification, we cultured three reef dwelling foraminifers: Amphisorus hemprichii, belong to imperforate species, Baculogypsina sphaerulata, and C. gaudichaudii belong to perforate species, in the seawater of five different pCO2 conditions and we address the response of carbon and oxygen isotopes of the carbonate shells of foraminifers. The oxygen isotope ratio of cultured foraminiferal tests under five varied pCO2 seawater indicated no significant correlation to pCO2 values. On the other hand, the carbon isotope ratio of foraminiferal tests indicated heavy trend with rising pCO2 in all species. Alteration of carbonate chemistry result from ocean acidification may be effect strongly on carbon isotope composition relate to metabolic system (i.e. photosynthesis and respiration). In perforate species, both of oxygen and carbon isotope ratio were lighter than that

  1. Stable carbon and nitrogen isotopes in vertical peat profiles of natural and drained boreal peatlands

    NASA Astrophysics Data System (ADS)

    Nykänen, Hannu; Mpamah, Promise; Rissanen, Antti; Pitkänen, Aki; Turunen, Jukka; Simola, Heikki

    2015-04-01

    Peatlands form a significant carbon pool in the global carbon cycle. Change in peat hydrology, due to global warming is projected to change microbiological processes and peat carbon pool. We tested if bulk stable carbon and nitrogen isotopes serve as indicators of severe long term drying in peatlands drained for forestry. Depth profile analysis of peat, for their carbon and nitrogen content as well as their carbon and nitrogen stable isotopic signatures, were conducted for peatlands in southern and eastern Finland, having ombrotrophic and minerotrophic natural and corresponding drained pairs or separate drained sites. The selection of sites allowed us to compare changes due to different fertility and changes due to long term artificial drying. Drainage lasting over 40 years has led to changes in hydrology, vegetation, nutrient mineralization and respiration. Furthermore, increased nutrient uptake and possible recycling of peat nitrogen and carbon trough vegetation back to the peat surface, also possibly has an effect on the stable isotopic composition of peat carbon and nitrogen. We think that drainage induced changes somehow correspond to those caused by changed hydrology due to climate change. We will present data from these measurements and discuss their implications for carbon and nitrogen flows in peatlands.

  2. Strong Coupling of Shoot Assimilation and Soil Respiration during Drought and Recovery Periods in Beech As Indicated by Natural Abundance δ13C Measurements.

    PubMed

    Blessing, Carola H; Barthel, Matti; Gentsch, Lydia; Buchmann, Nina

    2016-01-01

    Drought down-regulates above- and belowground carbon fluxes, however, the resilience of trees to drought will also depend on the speed and magnitude of recovery of these above- and belowground fluxes after re-wetting. Carbon isotope composition of above- and belowground carbon fluxes at natural abundance provides a methodological approach to study the coupling between photosynthesis and soil respiration (SR) under conditions (such as drought) that influence photosynthetic carbon isotope discrimination. In turn, the direct supply of root respiration with recent photoassimilates will impact on the carbon isotope composition of soil-respired CO 2 . We independently measured shoot and soil CO 2 fluxes of beech saplings ( Fagus sylvatica L.) and their respective δ 13 C continuously with laser spectroscopy at natural abundance. We quantified the speed of recovery of drought stressed trees after re-watering and traced photosynthetic carbon isotope signal in the carbon isotope composition of soil-respired CO 2 . Stomatal conductance responded strongly to the moderate drought (-65%), induced by reduced soil moisture content as well as increased vapor pressure deficit. Simultaneously, carbon isotope discrimination decreased by 8‰, which in turn caused a significant increase in δ 13 C of recent metabolites (1.5-2.5‰) and in δ 13 C of SR (1-1.5‰). Generally, shoot and soil CO 2 fluxes and their δ 13 C were in alignment during drought and subsequent stress release, clearly demonstrating a permanent dependence of root respiration on recently fixed photoassimilates, rather than on older reserves. After re-watering, the drought signal persisted longer in δ 13 C of the water soluble fraction that integrates multiple metabolites (soluble sugars, amino acids, organic acids) than in the neutral fraction which represents most recently assimilated sugars or in the δ 13 C of SR. Nevertheless, full recovery of all aboveground physiological variables was reached within 4 days

  3. Partitioning Ecosystem Respiration Using Stable Carbon Isotopes in a Mixed C3 Annual Grassland

    NASA Astrophysics Data System (ADS)

    Tu, K. P.

    2001-12-01

    -third being heterotrophic. Belowground respiration, comprised of both autotrophic (root) and heterotrophic (microbial) components, accounted for nearly two-thirds of total ecosystem respiration. Root and microbial respiration each contributed to nearly half of total belowground respiration (53% and 47%, respectively). Similarly, plant respiration was divided nearly equally between that from roots (52%) and leaves (48%). Partitioning using natural abundance stable carbon isotope ratios was made possible because of the relatively large differences in δ 13C values among the various sources in this entirely C3 system. To our knowledge, such large isotopic differences in respired CO2 among different plant tissues and belowground components have not been documented before. Further research is needed to determine how such differences may arise and to establish if similar differences exist in other ecosystems or at different times of the growing season. Our results also imply that interpretation of above-canopy Keeling plot intercepts may be complicated by both multiple (and isotopically distinct) sources and by isotopic fractionation that occurs either during the respiration process itself or during the transfer of carbon compounds prior to respiration.

  4. Application of carbon isotope stratigraphy to late miocene shallow marine sediments, new zealand.

    PubMed

    Loutit, T S; Kennett, J P

    1979-06-15

    A distinct (0.5 per mil) carbon-13/carbon-12 isotopic shift in the light direction has been identified in a shallow marine sedimentary sequence of Late Miocene age at Blind River, New Zealand, and correlated with a similar shift in Late Miocene Deep Sea Drilling Project sequences throughout the Indo-Pacific. A dated piston core provides an age for the shift of 6.2 +/- 0.1 million years. Correlations based on the carbon isotopic change require a revision of the previously established magnetostratigraphy at Blind River. The carbon shift at Blind River occurs between 6.2 and 6.3 +/- 0.1 million years before present. A new chronology provides an age for the evolutionary first appearance datum of Globorotalia conomiozea at 6.1 +/- 0.1 million years, the beginning of a distinct latest Miocene cooling event associated with the Kapitean stage at 6.2 +/- 0.1 million years, and the beginning of a distinct shallowing of water depths at 6.1 +/- 0.1 million years. The Miocene-Pliocene boundary as recognized in New Zealand is now dated at 5.3 +/- 0.1 million years. Extension of carbon isotope stratigraphy to other shallow Late Miocene sequences should provide an important datum for international correlation of Late Miocene shallow and deep marine sequences.

  5. Carbon isotope ratios of human tooth enamel record the evidence of terrestrial resource consumption during the Jomon period, Japan.

    PubMed

    Kusaka, Soichiro; Uno, Kevin T; Nakano, Takanori; Nakatsukasa, Masato; Cerling, Thure E

    2015-08-17

    Archaeological remains strongly suggest that the Holocene Japanese hunter-gatherers, the Jomon people, utilized terrestrial plants as their primary food source. However, carbon and nitrogen isotope analysis of bone collagen indicates that they primarily exploited marine resources. We hypothesize that this inconsistency stems from the route of protein synthesis and the different proportions of protein-derived carbon in tooth enamel versus bone collagen. Carbon isotope ratios from bone collagen reflect that of dietary protein and may provide a biased signal of diet, whereas isotope ratios from tooth enamel reflect the integrated diet from all macronutrients (carbohydrates, lipids, and proteins). In order to evaluate the differences in inferred diet between the archaeological evidence and bone collagen isotope data, this study investigated carbon isotopes in Jomon tooth enamel from four coastal sites of the Middle to Late-Final Jomon period (5,000-2,300 years BP). Carbon isotope ratios of human teeth are as depleted as coeval terrestrial mammals, suggesting that C 3 plants and terrestrial mammals were major dietary resources for the Jomon people. Dietary dependence on marine resources calculated from enamel was significantly lower than that calculated from bone collagen. The discrepancy in isotopic ratios between enamel and collagen and the nitrogen isotope ratio in collagen shows a negative correlation on individual and population levels, suggesting diets with variable proportions of terrestrial and marine resources. This study highlights the usefulness of coupling tooth enamel and bone collagen in carbon isotopic studies to reconstruct prehistoric human diet. Am J Phys Anthropol, 2015. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.

  6. Cerium anomaly across the mid-Tournaisian carbon isotope excursion (TICE)

    NASA Astrophysics Data System (ADS)

    Jiang, G.; Morales, D. C.; Maharjan, D. K.

    2015-12-01

    The Early Mississippian (ca. 359-345 Ma) represents one of the most important greenhouse-icehouse climate transitions in Earth history. Closely associated with this critical transition is a prominent positive carbon isotope excursion (δ13C ≥ +5‰) that has been documented from numerous stratigraphic successions across the globe. This δ13C excursion, informally referred to as the TICE (mid-Tournaisian carbon isotope excursion) event, has been interpreted as resulting from enhanced organic carbon burial, with anticipated outcomes including the lowering of atmospheric CO2 and global cooling, the growth of continental ice sheets and sea-level fall, and the increase of ocean oxygenation and ocean redox changes. The casual relationship between these events has been addressed from various perspectives but not yet clearly demonstrated. To document the potential redox change associated with the perturbation of the carbon cycle, we have analyzed rare earth elements (REE) and trace elements across the TICE in two sections across a shallow-to-deep water transect in the southern Great Basin (Utah and Nevada), USA. In both sections, the REE data show a significant positive cerium (Ce) anomaly (Ce/Ce* = Ce/(0.5La+0.5Pr)). Prior to the positive δ13C shift, most Ce/Ce* values are around 0.3 (between 0.2 and 0.4). Across the δ13C peak, Ce/Ce* values increase up to 0.87, followed by a decrease back to 0.2~0.3 after the δ13C excursion (Figure 1). The positive Ce anomaly is best interpreted as recording expansion of oxygen minimum zone and anoxia resulted from increased primary production. This is consistent with a significant increase of nitrogen isotopes (δ15N) across the δ13C peak. Integration of the carbon, nitrogen, and REE data demonstrates a responsive earth systems change linked to the perturbation of the Early Mississippian carbon cycle.

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

    NASA Astrophysics Data System (ADS)

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

    2013-11-01

    Isotopic Ratio Mass Spectrometry (IRMS) is an effective toll to be used for drug product authentication. The isotopic composition could be used to assist in the differentiation between batches of drugs and assist in the identification of counterfeit materials on the market. Only two factors affect the isotopic ratios in pharmaceutical components: the isotopic composition of the raw materials and the synthetic processes performed upon them. Counterfeiting of pharmaceutical drugs threatens consumer confidence in drug products companies' economical well-being. In this preliminary study, the analyzed samples consist in two types of commercially available analgesics, which were purchases from Romanian pharmacies. Differences in 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.

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

    NASA Astrophysics Data System (ADS)

    Nowak-Lovato, K.

    2014-12-01

    Seepage from enhanced oil recovery, carbon storage, and natural gas sites can emit trace gases such as carbon dioxide, methane, and hydrogen sulfide. Trace gas emission at these locations demonstrate unique light stable isotope signatures that provide information to enable source identification of the material. Light stable isotope detection through surface monitoring, offers the ability to distinguish between trace gases emitted from sources such as, biological (fertilizers and wastes), mineral (coal or seams), or liquid organic systems (oil and gas reservoirs). To make light stable isotope measurements, we employ the ultra-sensitive technique, frequency modulation spectroscopy (FMS). FMS is an absorption technique with sensitivity enhancements approximately 100-1000x more than standard absorption spectroscopy with the advantage of providing stable isotope signature information. We have developed an integrated in situ (point source) system that measures carbon dioxide, methane and hydrogen sulfide with isotopic resolution and enhanced sensitivity. The in situ instrument involves the continuous collection of air and records the stable isotope ratio for the gas being detected. We have included in-line flask collection points to obtain gas samples for validation of isotopic concentrations using our in-house isotope ratio mass spectroscopy (IRMS). We present calibration curves for each species addressed above to demonstrate the sensitivity and accuracy of the system. We also show field deployment data demonstrating the capabilities of the system in making live dynamic measurements from an active source.

  9. Enantioselective carbon stable isotope fractionation of hexachlorocyclohexane during aerobic biodegradation by Sphingobium spp.

    PubMed

    Bashir, Safdar; Fischer, Anko; Nijenhuis, Ivonne; Richnow, Hans-Hermann

    2013-10-15

    Carbon isotope fractionation was investigated for the biotransformation of γ- and α- hexachlorocyclohexane (HCH) as well as enantiomers of α-HCH using two aerobic bacterial strains: Sphingobium indicum strain B90A and Sphingobium japonicum strain UT26. Carbon isotope enrichment factors (ε(c)) for γ-HCH (ε(c) = -1.5 ± 0.1 ‰ and -1.7 ± 0.2 ‰) and α-HCH (ε(c) = -1.0 ± 0.2 ‰ and -1.6 ± 0.3 ‰) were similar for both aerobic strains, but lower in comparison with previously reported values for anaerobic γ- and α-HCH degradation. Isotope fractionation of α-HCH enantiomers was higher for (+) α-HCH (ε(c) = -2.4 ± 0.8 ‰ and -3.3 ± 0.8 ‰) in comparison to (-) α-HCH (ε(c) = -0.7 ± 0.2 ‰ and -1.0 ± 0.6 ‰). The microbial fractionation between the α-HCH enantiomers was quantified by the Rayleigh equation and enantiomeric fractionation factors (ε(e)) for S. indicum strain B90A and S. japonicum strain UT26 were -42 ± 16% and -22 ± 6%, respectively. The extent and range of isomer and enantiomeric carbon isotope fractionation of HCHs with Sphingobium spp. suggests that aerobic biodegradation of HCHs can be monitored in situ by compound-specific stable isotope analysis (CSIA) and enantiomer-specific isotope analysis (ESIA). In addition, enantiomeric fractionation has the potential as a complementary approach to CSIA and ESIA for assessing the biodegradation of α-HCH at contaminated field sites.

  10. Evaluating Uranium Isotopes in Carbonates and Implications for Reconstructing Marine Paleoredox Conditions

    NASA Astrophysics Data System (ADS)

    Aharony, Ofer; Gubser, Steven S.; Maldacena, Juan; Ooguri, Hirosi; Oz, Yaron

    2016-12-01

    Uranium isotope ratios (238U/235U, reported as δ238U) have emerged as a promising proxy for marine redox conditions. This proxy relies on isotopic fractionation that occurs during reduction of soluble U(VI) to insoluble U(IV), wherein 238U is preferentially reduced and incorporated via authigenic processes into anoxic sediments, leaving the residual seawater U and resulting carbonates 238U-depleted. Because carbonates are generally well preserved in the rock record, they are useful archives of seawater chemistry throughout Earth history, including δ238U. In principle, the long residence time of U in the ocean permits quantitative inferences of global paleoredox conditions using carbonate δ238U records. To assess the performance of the proxy, we compile all published δ238U measurements from carbonate rocks and sediments, which span the Cryogenian through the modern. The potential for δ238U to serve as a quantitative, global paleoredox proxy is supported by reproducible trends across depositional environments and paleogeographic regions in the Cryogenian non-glacial interlude and across the Permian-Triassic and Triassic-Jurassic boundaries, although carbonates deposited in deeper waters (>200 m) may be subject to local effects. Using a box model, we highlight the key levers associated with seawater δ238U and the timescales of such variability. Like all sedimentary archives, carbonate rocks are prone to diagenetic alteration and additional controls that cause δ238U in carbonates to deviate from global seawater values. Specifically, the U isotopic composition of carbonate sediments can be influenced by diagenesis, carbonate mineralogy, dolomitization, detrital input, local organic matter deposition, and pore water chemistry. We evaluate indicators of these factors in the context of a diagenetic model to assess the sensitivity of carbonate δ238U to local syndepositional or post-depositional processes. These results improve the framework for interpreting

  11. Isotopic Compositions of the Elements, 2001

    NASA Astrophysics Data System (ADS)

    Böhlke, J. K.; de Laeter, J. R.; De Bièvre, P.; Hidaka, H.; Peiser, H. S.; Rosman, K. J. R.; Taylor, P. D. P.

    2005-03-01

    The Commission on Atomic Weights and Isotopic Abundances of the International Union of Pure and Applied Chemistry completed its last review of the isotopic compositions of the elements as determined by isotope-ratio mass spectrometry in 2001. That review involved a critical evaluation of the published literature, element by element, and forms the basis of the table of the isotopic compositions of the elements (TICE) presented here. For each element, TICE includes evaluated data from the "best measurement" of the isotope abundances in a single sample, along with a set of representative isotope abundances and uncertainties that accommodate known variations in normal terrestrial materials. The representative isotope abundances and uncertainties generally are consistent with the standard atomic weight of the element Ar(E) and its uncertainty U[Ar(E)] recommended by CAWIA in 2001.

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

    NASA Technical Reports Server (NTRS)

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

    2015-01-01

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

  13. A Method to Determine 18O Kinetic Isotope Effects in the Hydrolysis of Nucleotide Triphosphates

    PubMed Central

    Du, Xinlin; Ferguson, Kurt; Sprang, Stephen R.

    2007-01-01

    A method to determine 18O kinetic isotope effects (KIE) in the hydrolysis of GTP is described that is generally applicable to reactions involving other nucleotide triphosphates. Internal competition, wherein the substrate of the reaction is a mixture of 18O-labeled and unlabeled nucleotides, is employed and the change in relative abundance of the two species in the course of the reaction is used to calculate KIE. The nucleotide labeled with 18O at sites of mechanistic interest also contains 13C at all carbon positions, while the 16O-nucleotide is depleted of 13C. The relative abundance of the labeled and unlabeled substrates or products is reflected in the carbon isotope ratio (13C/12C) in GTP or GDP, which is determined by use of a liquid chromatography-coupled isotope ratio mass spectrometer (LC-coupled IRMS). The LC is coupled to the IRMS by an Isolink™ interface (ThermoFinnigan). Carbon isotope ratios can be determined with accuracy and precision greater than 0.04%, and are consistent over an order of magnitude in sample amount. KIE values for Ras/NF1333-catalyzed hydrolysis of [β18O3,13C]GTP were determined by change in the isotope ratio of GTP or GDP or the ratio of the isotope ratio of GDP to that of GTP. KIE values computed in the three ways agree within 0.1%, although the method using the ratio of isotope ratios of GDP and GTP gives superior precision (< 0.1%). A single KIE measurement can be conducted in 25 minutes with less than 5 μg nucleotide reaction product. PMID:17963711

  14. 13C-18O isotope signatures and ‘clumped isotope’ thermometry in foraminifera and coccoliths

    NASA Astrophysics Data System (ADS)

    Tripati, Aradhna K.; Eagle, Robert A.; Thiagarajan, Nivedita; Gagnon, Alexander C.; Bauch, Henning; Halloran, Paul R.; Eiler, John M.

    2010-10-01

    Accurate constraints on past ocean temperatures and compositions are critical for documenting climate change and resolving its causes. Most proxies for temperature are not thermodynamically based, appear to be subject to biological processes, require regional calibrations, and/or are influenced by fluid composition. As a result, their interpretation becomes uncertain when they are applied in settings not necessarily resembling those in which they were empirically calibrated. Independent proxies for past temperature could provide an important means of testing and/or expanding on existing reconstructions. Here we report measurements of abundances of stable isotopologues of calcitic and aragonitic benthic and planktic foraminifera and coccoliths, relate those abundances to independently estimated growth temperatures, and discuss the possible scope of equilibrium and kinetic isotope effects. The proportions of 13C- 18O bonds in these samples exhibits a temperature dependence that is generally similar to that previously been reported for inorganic calcite and other biologically precipitated carbonate-containing minerals (apatite from fish, reptile, and mammal teeth; calcitic brachiopods and molluscs; aragonitic coral and mollusks). Most species that exhibit non-equilibrium 18O/ 16O (δ 18O) and 13C/ 12C (δ 13C) ratios are characterized by 13C- 18O bond abundances that are similar to inorganic calcite and are generally indistinguishable from apparent equilibrium, with possible exceptions among benthic foraminiferal samples from the Arctic Ocean where temperatures are near-freezing. Observed isotope ratios in biogenic carbonates can be explained if carbonate minerals generally preserve a state of ordering that reflects the extent of isotopic equilibration of the dissolved inorganic carbon species.

  15. A Carbon Source Apportionment Shift in Mexico City Atmospheric Particles During 2003-2004 as Determined with Stable Carbon Isotopes

    NASA Astrophysics Data System (ADS)

    Lopez-Veneroni, D. G.; Vega, E.

    2013-05-01

    The stable carbon isotope composition of atmospheric particles (PM2.5) was measured at La Merced (MER), a commercial site in the eastern sector, and at Xalostoc (XAL) an industrial site in the NE sector of Mexico City, during three sampling periods in autumn 2003, and spring and autumn 2004. At each site and sampling campaign particle samples were collected daily with minivol samplers during two week periods. Ancillary data included organic and elemental carbon, trace elements and ionic species. This data base was complement with air quality data from the RAMA (Automatic Atmospheric Monitoring Network). In general, particle concentrations, ionic species and some air quality species showed higher concentrations in autumn and lowest values in spring. Moreover, the concentrations of these chemical species were highest at XAL compared to MER. The stable carbon isotope composition of PM2.5 during autumn 2003 and spring 2004 had and average value of -26.04 (± 1.54) ‰ vs. PDB. Differences in the isotopic composition between the two sites were non significant. The average δ13C during these seasons were 1 ‰ lighter relative to data collected previously at these sites during 2000 and 2001, and is consistent with a predominant source of hydrocarbon combustion. In autumn 2004, however, average δ13C at XAL and MER increased to -22.8 (± 0.9) and -20.6 (± 3.1) ‰, respectively. Organic carbon concentrations during this period increased concomitantly at these sites. The shift in the isotopic composition in ambient particles suggests a predominance of soil-derived carbon during this period. The possible causes and implications of this are discussed.

  16. PRODUCTION AND TRANSPORT OF CARBON DIOXIDE IN A CONTAMINATED VADOSE ZONE: A STABLE AND RADIOACTIVE CARBON ISOTOPE STUDY

    EPA Science Inventory

    Analyses of soil gas compositions and stable and radioactive carbon isotopes in the vadose zone above an alluvial aquifer were conducted at an organic solvent disposal site in southeast Phoenix, AZ. The study investigated the source and movement of carbon dioxide above a plume of...

  17. Soil moisture effects on the carbon isotope composition of soil respiration

    Treesearch

    Claire L. Phillips; Nick Nickerson; David Risk; Zachary E. Kayler; Chris Andersen; Alan Mix; Barbara J. Bond

    2010-01-01

    The carbon isotopic composition (δ13C) of recently assimilated plant carbon is known to depend on water-stress, caused either by low soil moisture or by low atmospheric humidity. Air humidity has also been shown to correlate with the δ13C of soil respiration, which suggests indirectly that recently fixed photosynthates...

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

    EPA Science Inventory

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

  19. Accurate experimental determination of the isotope effects on the triple point temperature of water. II. Combined dependence on the 18O and 17O abundances

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    This paper is the second of two articles on the quantification of isotope effects on the triple point temperature of water. In this second article, we address the combined effects of 18O and 17O isotopes. We manufactured five triple point cells with waters with 18O and 17O abundances exceeding widely the natural abundance range while maintaining their natural 18O/17O relationship. The 2H isotopic abundance was kept close to that of VSMOW (Vienna Standard Mean Ocean Water). These cells realized triple point temperatures ranging between  -220 μK to 1420 μK with respect to the temperature realized by a triple point cell filled with VSMOW. Our experiment allowed us to determine an accurate and reliable value for the newly defined combined 18, 17O correction parameter of AO  =  630 μK with a combined uncertainty of 10 μK. To apply this correction, only the 18O abundance of the TPW needs to be known (and the water needs to be of natural origin). Using the results of our two articles, we recommend a correction equation along with the coefficient values for isotopic compositions differing from that of VSMOW and compare the effect of this new equation on a number of triple point cells from the literature and from our own institute. Using our correction equation, the uncertainty in the isotope correction for triple point cell waters used around the world will be  <1 μK.

  20. Carbon and Hydrogen Isotope Fractionation in Lipid Biosynthesis of Piezophilic Bacteria - Implications for Studying Microbial Metabolism and Carbon Cycle in Deep Biosphere

    NASA Astrophysics Data System (ADS)

    Fang, J.; Dasgupta, S.; Zhang, L.; Li, J.; Kato, C.; Bartlett, D.

    2012-12-01

    Piezophiles are pressure-loving microorganisms, which reproduce preferentially or exclusively at pressures greater than atmospheric pressure. In this study, we examined stable carbon and hydrogen isotope fractionation in fatty acid biosynthesis of a piezophilic bacterium Moritella japonica DSK1. The bacterium was grown to stationary phase at hydrstatic pressures of 0.1, 10, 20, and 50 MPa (mega-passcal) in media prepared using sterilized natural seawater supplied with glucose as the sole carbon source. Bacterial cell biomass and individual fatty acids exhibited consistent pressure-dependent carbon and hydrogen isotope fractionations relative to substrates. Average carbon isotope fractionation (delta(FA-glucose)) at high pressures was much higher than that for surface bacteria: -15.7, -15.3, and -18.3‰ at 10, 20, and 50 MPa, respectively. For deltaD, fatty acids are more depleted in D relative to glucose than to water. Monounsaturated fatty acids are more depleted in D than corresponding saturated fatty acids by as much as 36‰. Polyunsaturated fatty acids are most depleted in D. For example, DHA (22:6omega3) has the most negative hydrogen isotope ratio (-170.91‰) (delta(FA-glucose) = -199, delta(FA-water) = -176). The observed isotope effects can be ascribed to the kinetics of enzymatic reactions that are affected by hydrostatic pressure and to operating of two independent lipid biosynthetic pathways of the piezophilic bacteria. Given that most of the biosphere lives under high pressures, our results have important important implications for studying microbial metabolism and carbon cycle in the deep biosphere.

  1. Large Carbonate Associated Sulfate isotopic variability between brachiopods, micrite, and other sedimentary components in Late Ordovician strata

    NASA Astrophysics Data System (ADS)

    Present, Theodore M.; Paris, Guillaume; Burke, Andrea; Fischer, Woodward W.; Adkins, Jess F.

    2015-12-01

    Carbonate Associated Sulfate (CAS) is trace sulfate incorporated into carbonate minerals during their precipitation. Its sulfur isotopic composition is often assumed to track that of seawater sulfate and inform global carbon and oxygen budgets through Earth's history. However, many CAS sulfur isotope records based on bulk-rock samples are noisy. To determine the source of bulk-rock CAS variability, we extracted CAS from different internal sedimentary components micro-drilled from well-preserved Late Ordovician and early Silurian-age limestones from Anticosti Island, Quebec, Canada. Mixtures of these components, whose sulfur isotopic compositions vary by nearly 25‰, can explain the bulk-rock CAS range. Large isotopic variability of sedimentary micrite CAS (34S-depleted from seawater by up to 15‰) is consistent with pore fluid sulfide oxidation during early diagenesis. Specimens recrystallized during burial diagenesis have CAS 34S-enriched by up to 9‰ from Hirnantian seawater, consistent with microbial sulfate reduction in a confined aquifer. In contrast to the other variable components, brachiopods with well-preserved secondary-layer fibrous calcite-a phase independently known to be the best-preserved sedimentary component in these strata-have a more homogeneous isotopic composition. These specimens indicate that seawater sulfate remained close to about 25‰ (V-CDT) through Hirnantian (end-Ordovician) events, including glaciation, mass extinction, carbon isotope excursion, and pyrite-sulfur isotope excursion. The textural relationships between our samples and their CAS isotope ratios highlight the role of diagenetic biogeochemical processes in setting the isotopic composition of CAS.

  2. Serum carbon isotope values change in adults in response to changes in sugar-sweetened beverage intake.

    PubMed

    Fakhouri, Tala H I; Jahren, A Hope; Appel, Lawrence J; Chen, Liwei; Alavi, Reza; Anderson, Cheryl A M

    2014-06-01

    Serum carbon isotope values [13C-to-12C serum carbon isotope ratio (δ(13)C)], which reflect consumption of corn- and cane-based foods, differ between persons consuming high and low amounts of sugar-sweetened beverages (SSBs). In this study, we determined whether serum δ(13)C changes in response to change in SSB intake during an 18-mo behavioral intervention trial. Data were from a subset of 144 participants from the PREMIER trial, a completed behavioral intervention (Maryland, 1998-2004). SSB intake was assessed using 2 24-h dietary recall interviews. Blinded serum samples were assayed for δ(13)C by natural abundance stable isotope mass spectroscopy. Multiple linear regression models with generalized estimating equations and robust variance estimation were used. At baseline, mean SSB intake was 13.8 ± 14.2 fl oz/d, and mean δ(13)C serum value was -19.3 ± 0.6 units per mil (designated ‰). A reduction of 12 oz (355 mL)/d SSB (equivalent to 1 can of soda per day) was associated with 0.17‰ (95% CI: 0.08‰, 0.25‰ P < 0.0001) reduction in serum δ(13)C values over 18 mo (equivalent to a 1% reduction in δ(13)C from baseline). After adjusting for potential confounders, a reduction of 12 oz/d SSB (equivalent to 1 can of soda per day), over an 18-mo period, was associated with 0.12‰ (95% CI: 0.01‰, 0.22‰ P = 0.025) reduction in serum δ(13)C. These findings suggest that serum δ(13)C can be used as a measure of dietary changes in SSB intake. © 2014 American Society for Nutrition.

  3. GasBench/isotope ratio mass spectrometry: a carbon isotope approach to detect exogenous CO(2) in sparkling drinks.

    PubMed

    Cabañero, Ana I; San-Hipólito, Tamar; Rupérez, Mercedes

    2007-01-01

    A new procedure for the determination of carbon dioxide (CO(2)) (13)C/(12)C isotope ratios, using direct injection into a GasBench/isotope ratio mass spectrometry (GasBench/IRMS) system, has been developed to improve isotopic methods devoted to the study of the authenticity of sparkling drinks. Thirty-nine commercial sparkling drink samples from various origins were analyzed. Values of delta(13)C(cava) ranged from -20.30 per thousand to -23.63 per thousand, when C3 sugar addition was performed for a second alcoholic fermentation. Values of delta(13)C(water) ranged from -5.59 per thousand to -6.87 per thousand in the case of naturally carbonated water or water fortified with gas from the spring, and delta(13)C(water) ranged from -29.36 per thousand to -42.09 per thousand when industrial CO(2) was added. It has been demonstrated that the addition of C4 sugar to semi-sparkling wine (aguja) and industrial CO(2) addition to sparkling wine (cava) or water can be detected. The new procedure has advantages over existing methods in terms of analysis time and sample treatment. In addition, it is the first isotopic method developed that allows (13)C/(12)C determination directly from a liquid sample without previous CO(2) extraction. No significant isotopic fractionation was observed nor any influence by secondary compounds present in the liquid phase. Copyright (c) 2007 John Wiley & Sons, Ltd.

  4. A history of violence: Insights into post-accretionary heating in carbonaceous chondrites from volatile element abundances, Zn isotopes and water contents

    NASA Astrophysics Data System (ADS)

    Mahan, Brandon; Moynier, Frédéric; Beck, Pierre; Pringle, Emily A.; Siebert, Julien

    2018-01-01

    Carbonaceous chondrites (CCs) may have been the carriers of water, volatile and moderately volatile elements to Earth. Investigating the abundances of these elements, their relative volatility, and isotopes of state-change tracer elements such as Zn, and linking these observations to water contents, provide vital information on the processes that govern the abundances and isotopic signatures of these species in CCs and other planetary bodies. Here we report Zn isotopic data for 28 CCs (20 CM, 6 CR, 1 C2-ung, and 1 CV3), as well as trace element data for Zn, In, Sn, Tl, Pb, and Bi in 16 samples (8 CM, 6 CR, 1 C2-ung, and 1 CV3), that display a range of elemental abundances from case-normative to intensely depleted. We use these data, water content data from literature and Zn isotopes to investigate volatile depletions and to discern between closed and open system heating. Trace element data have been used to construct relative volatility scales among the elements for the CM and CR chondrites. From least volatile to most, the scale in CM chondrites is Pb-Sn-Bi-In-Zn-Tl, and for CR chondrites it is Tl-Zn-Sn-Pb-Bi-In. These observations suggest that heated CM and CR chondrites underwent volatile loss under different conditions to one another and to that of the solar nebula, e.g. differing oxygen fugacities. Furthermore, the most water and volatile depleted samples are highly enriched in the heavy isotopes of Zn. Taken together, these lines of evidence strongly indicate that heated CM and CR chondrites incurred open system heating, stripping them of water and volatiles concomitantly, during post-accretionary shock impact(s).

  5. Carbon isotope fractionation by sulfate-reducing bacteria using different pathways for the oxidation of acetate.

    PubMed

    Goevert, Dennis; Conrad, Ralf

    2008-11-01

    Acetate is a key intermediate in the anaerobic degradation of organic matter. In anoxic environments, available acetate is a competitive substrate for sulfate-reducing bacteria (SRB) and methane-producing archaea. Little is known about the fractionation of carbon isotopes by sulfate reducers. Therefore, we determined carbon isotope compositions in cultures of three acetate-utilizing SRB, Desulfobacter postgatei, Desulfobacter hydrogenophilus, and Desulfobacca acetoxidans. We found that these species showed strong differences in their isotope enrichment factors (epsilon) of acetate. During the consumption of acetate and sulfate, acetate was enriched in 13C by 19.3% per hundred in Desulfobacca acetoxidans. By contrast, both D. postgatei and D. hydrogenophilus showed a slight depletion of 13C resulting in epsilon(ac)-values of 1.8 and 1.5% per hundred, respectively. We suggest that the different isotope fractionation is due to the different metabolic pathways for acetate oxidation. The strongly fractionating Desulfobacca acetoxidans uses the acetyl-CoA/carbon monoxide dehydrogenase pathway, which is also used by acetoclastic methanogens that show a similar fractionation of acetate (epsilon(ac) = -21 to -27% per hundred). In contrast, Desulfobacter spp. oxidize acetate to CO2 via the tricarboxylic acid (TCA) cycle and apparently did not discriminate against 13C. Our results suggestthat carbon isotope fractionation in environments with sulfate reduction will strongly depend on the composition of the sulfate-reducing bacterial community oxidizing acetate.

  6. Simulation of dual carbon-bromine stable isotope fractionation during 1,2-dibromoethane degradation.

    PubMed

    Jin, Biao; Nijenhuis, Ivonne; Rolle, Massimo

    2018-06-01

    We performed a model-based investigation to simultaneously predict the evolution of concentration, as well as stable carbon and bromine isotope fractionation during 1,2-dibromoethane (EDB, ethylene dibromide) transformation in a closed system. The modelling approach considers bond-cleavage mechanisms during different reactions and allows evaluating dual carbon-bromine isotopic signals for chemical and biotic reactions, including aerobic and anaerobic biological transformation, dibromoelimination by Zn(0) and alkaline hydrolysis. The proposed model allowed us to accurately simulate the evolution of concentrations and isotope data observed in a previous laboratory study and to successfully identify different reaction pathways. Furthermore, we illustrated the model capabilities in degradation scenarios involving complex reaction systems. Specifically, we examined (i) the case of sequential multistep transformation of EDB and the isotopic evolution of the parent compound, the intermediate and the reaction product and (ii) the case of parallel competing abiotic pathways of EDB transformation in alkaline solution.

  7. Correlation between isotopic and meteorological parameters in Italian wines: a local-scale approach.

    PubMed

    Aghemo, Costanza; Albertino, Andrea; Gobetto, Roberto; Spanna, Federico

    2011-08-30

    Since the beginning of the 1980s deuterium nuclear magnetic resonance and carbon-13 mass spectrometry have proved to be reliable techniques for detecting adulteration and for classifying natural products by their geographic origin. Scientific literature has so far mainly focused on data acquired at regional level where isotopic parameters are correlated to climatic mean data relative to large territories. Nebbiolo and Barbera wine samples of various vintages and from different areas within the Piedmont region (northern Italy) were analysed using SNIF-NMR and GC-C-IRMS and a large set of meteorological parameters were recorded by means of weather stations placed in fields where the grapes were grown. Correlations between isotopic ((2)H and (13)C) data and several climatic parameters at a local level (mean temperature, total rainfall, mean humidity and thermal sums) were attempted and some linear correlations were found. Mean temperature and total rainfall were found to be correlated to isotopic ((2)H and (13)C) abundance in linear direct and inverse proportions respectively. Lower or no correlations between deuterium and carbon-13 abundances and other meteorological parameters such as mean humidity and thermal sums were found. Moreover, wines produced from different grape varieties in the same grape field showed significantly different isotopic values. Copyright © 2011 Society of Chemical Industry.

  8. Carbon and nitrogen abundances in F- and G-type stars

    NASA Technical Reports Server (NTRS)

    Clegg, R. E. S.

    1977-01-01

    Carbon and nitrogen abundances have been obtained for a sample of 11-F- and G-type dwarfs covering a range in Fe/H abundance ratio from -0.8 to +0.3. Model atmospheres, which included the effects of convection and line blanketing, were used to calculate synthetic spectra of the CH, CN, and NH molecular bands. Effective oscillator strengths for the bands studied were found by matching synthetic spectra calculated from a model solar atmosphere with the observed solar bands. Many of the metal-poor stars, and particularly the high-velocity stars, were found to have substantial nitrogen over-deficiencies, suggesting that N is manufactured mostly in a secondary manner. The carbon-to-iron ratios were similar to the solar ratio, although there may be slight C over-deficiencies in metal-poor stars. However, the variation in C/Fe is not as marked as that found recently by Hearnshaw (1974). A comprehensive discussion of the theoretical errors is given, and some applications to Galactic evolution are noted.

  9. Hydrogen and carbon isotope fractionation during degradation of chloromethane by methylotrophic bacteria

    PubMed Central

    Nadalig, Thierry; Greule, Markus; Bringel, Françoise; Vuilleumier, Stéphane; Keppler, Frank

    2013-01-01

    Chloromethane (CH3Cl) is a widely studied volatile halocarbon involved in the destruction of ozone in the stratosphere. Nevertheless, its global budget still remains debated. Stable isotope analysis is a powerful tool to constrain fluxes of chloromethane between various environmental compartments which involve a multiplicity of sources and sinks, and both biotic and abiotic processes. In this study, we measured hydrogen and carbon isotope fractionation of the remaining untransformed chloromethane following its degradation by methylotrophic bacterial strains Methylobacterium extorquens CM4 and Hyphomicrobium sp. MC1, which belong to different genera but both use the cmu pathway, the only pathway for bacterial degradation of chloromethane characterized so far. Hydrogen isotope fractionation for degradation of chloromethane was determined for the first time, and yielded enrichment factors (ε) of −29‰ and −27‰ for strains CM4 and MC1, respectively. In agreement with previous studies, enrichment in 13C of untransformed CH3Cl was also observed, and similar isotope enrichment factors (ε) of −41‰ and −38‰ were obtained for degradation of chloromethane by strains CM4 and MC1, respectively. These combined hydrogen and carbon isotopic data for bacterial degradation of chloromethane will contribute to refine models of the global atmospheric budget of chloromethane. PMID:24019296

  10. Toward estimation of origin of methane at ancient seeps — Carbon isotopes of seep carbonates, lipid biomarkers, and adsorbed gas

    NASA Astrophysics Data System (ADS)

    Miyajima, Yusuke; Watanabe, Yumiko; Ijiri, Akira; Goto, Akiko; Jenkins, Robert; Hasegawa, Takashi; Sakai, Saburo; Matsumoto, Ryo

    2017-04-01

    Methane is generated mainly by microbial or thermal degradation of organic matter, and the origin of methane can be estimated based on its stable carbon isotopic signature. Seafloor seepages of methane-charged fluids have been a major source of methane to the ocean, and knowing the origin of methane at the methane seeps can provide valuable insights into the subsurface fluid circulation and biogeochemical processes. Methane seeps in the geological past are archived as authigenic methane-derived carbonate rocks, which precipitate via an alkalinity increase facilitated by microbially mediated anaerobic oxidation of methane. Here we attempted to estimate origins of methane at ancient seeps, based on several proxies preserved within the seep carbonates. We examined methane-seep carbonate rocks in the Japan Sea region, collected from lower Miocene to middle Pleistocene sediments at 11 sites on land, and also carbonate nodules collected from the seafloor off Joetsu, where thermogenic methane is seeping. Carbon isotopic compositions of the carbonates and lipid biomarkers of methane-oxidizing archaea within them were analyzed. In order to directly know original isotopic signatures of methane, we also attempted to extract adsorbed methane through acid dissolution of the powdered carbonates. Early-diagenetic carbonate phases show various δ13C values between -64.7 and -4.7‰ vs. VPDB, suggesting either biogenic or thermogenic, or both origins of methane. A lipid biomarker pentamethylicosane (PMI) extracted from the ancient carbonates has δ13C values mostly lower than -100‰ , whereas that from the modern methane-derived carbonate nodule has a higher value (-80‰ ). The δ13C values of the seeping methane (-36‰ ) and PMI in the modern Joetsu seep carbonate shows an offset of -44‰ . If this carbon isotope offset was similar at the ancient seeps, the δ13C values of PMI indicate that methane at ancient seeps in the Japan Sea region was biogenic in origin, with δ13C

  11. Carbon-isotopic analysis of individual pollen grains from C 3 and C 4 grasses using a spooling-wire microcombustion interface

    NASA Astrophysics Data System (ADS)

    Nelson, David M.; Hu, Feng Sheng; Mikucki, Jill A.; Tian, Jian; Pearson, Ann

    2007-08-01

    Pollen grains from grasses using the C 3 and C 4 photosynthetic pathways have distinct ranges of δ 13C values that may be used to estimate their relative abundance in paleorecords. We evaluated a spooling-wire microcombustion device interfaced with an isotope-ratio mass spectrometer (SWiM-IRMS) for δ 13C analysis of individual grass-pollen grains. Pollen from four C 3 and four C 4 grass species was isolated through micromanipulation and analyzed as single grains suspended in water. A carbon yield greater than the 2 σ range of the carbon content of blanks containing only water was used to distinguish samples containing pollen ("pollen present") from those not containing pollen. This criterion resulted in the exclusion of ˜45% of the 946 samples applied to the wire. The average δ 13C values (±1 σ) of the remaining samples were -26.9‰ (±6.3‰) and -11.5‰ (±9.6‰) for C 3 grasses and C 4 grasses, respectively, after blank-correcting the δ 13C data. These results suggest that the SWiM-IRMS system can be used to distinguish C 3 from C 4 grass pollen. The high variability in measured δ 13C values is likely caused by a combination of factors. These include natural isotopic variability among individual pollen grains; the relatively poor precision that can be obtained when determining δ 13C values of such small samples; and the uncertainty in the magnitude, isotopic composition, and stability of the analytical blank. Nonetheless, high percentages of individual pollen grains were correctly classified as being of either C 3 or C 4 origin. On average, 90% (range = 78-100%) of pollen grains from C 3 grasses had δ 13C values more negative than the cutoff threshold of -19.2‰; while 84% (range = 77-90%) of pollen grains from C 4 grasses had δ 13C values more positive than -19.2‰. Compared with analysis using an elemental analyzer interfaced with an IRMS (EA-IRMS), the number of pollen grains required for δ 13C-based evaluation of C 3/C 4 grass composition

  12. Multiple Controls on the Paleoenvironment of the Early Cambrian Marine Black Shales in the Sichuan Basin, SW China: Geochemical and Organic Carbon Isotopic Evidence

    NASA Astrophysics Data System (ADS)

    Wang, S.; Zhang, G.; Dong, D.; Wang, Y.

    2016-12-01

    In order to understand the paleoenvironment of the Early Cambrian black shale deposition in the western part of the Yangtze Block, geochemical and organic carbon isotopic studies have been performed on two wells that have drilled through the Qiongzhusi Formation in the central and southeastern parts of Sichuan Basin. It shows that the lowest part of the Qiongzhusi Formation has high TOC abundance, while the middle and upper parts display relative low TOC content. Redox-sensitive element (Mo) and trace elemental redox indices (e.g., Ni/Co, V/Cr, U/Th and V/(V+Ni)) suggest that the high-TOC layers were deposited under anoxic conditions, whereas the low-TOC layers under relatively dysoxic/oxic conditions. The relationship of the enrichment factors of Mo and U further shows a transition from suboxic low-TOC layers to euxinic high-TOC layers. On the basis of the Mo-TOC relationship, the Qiongzhusi Formation black shales were deposited in a basin under moderately restricted conditions. Organic carbon isotopes display temporal variations in the Qiongzhusi Formation, with a positive excursion of δ13Corg values in the lower part and a continuous positive shift in the middle and upper parts. All these geochemical and isotopic criteria indicate a paleoenvironmental change from bottom anoxic to middle and upper dysoxic/oxic conditions for the Qiongzhusi Formation black shales. The correlation of organic carbon isotopic data for the Lower Cambrian black shales in different regions of the Yangtze Block shows consistent positive excursion of δ13Corg values in the lower part for each section. This excursion can be ascribed to the widespread Early Cambrian transgression in the Yangtze Block, under which black shales were deposited.

  13. Modelling the 13C and 12C isotopes of inorganic and organic carbon in the Baltic Sea

    NASA Astrophysics Data System (ADS)

    Gustafsson, Erik; Mörth, Carl-Magnus; Humborg, Christoph; Gustafsson, Bo G.

    2015-08-01

    In this study, 12C and 13C contents of all carbon containing state variables (dissolved inorganic and organic carbon, detrital carbon, and the carbon content of autotrophs and heterotrophs) have for the first time been explicitly included in a coupled physical-biogeochemical Baltic Sea model. Different processes in the carbon cycling have distinct fractionation values, resulting in specific isotopic fingerprints. Thus, in addition to simulating concentrations of different tracers, our new model formulation improves the possibility to constrain the rates of processes such as CO2 assimilation, mineralization, and air-sea exchange. We demonstrate that phytoplankton production and respiration, and the related air-sea CO2 fluxes, are to a large degree controlling the isotopic composition of organic and inorganic carbon in the system. The isotopic composition is further, but to a lesser extent, influenced by river loads and deep water inflows as well as transformation of terrestrial organic carbon within the system. Changes in the isotopic composition over the 20th century have been dominated by two processes - the preferential release of 12C to the atmosphere in association with fossil fuel burning, and the eutrophication of the Baltic Sea related to increased nutrient loads under the second half of the century.

  14. RAPID AND PRECISE METHOD FOR MEASURING STABLE CARBON ISOTOPE RATIOS OF DISSOLVED INORGANIC CARBON

    EPA Science Inventory

    We describe a method for rapid preparation, concentration and stable isotopic analysis of dissolved inorganic carbon (d13C-DIC). Liberation of CO2 was accomplished by placing 100 ?l phosphoric acid and 0.9 ml water in an evacuated 1.7-ml gas chromatography (GC) injection vial. Fo...

  15. 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

    NASA Astrophysics Data System (ADS)

    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

  16. Constraining the cause of the end-Guadalupian extinction with coupled records of carbon and calcium isotopes

    NASA Astrophysics Data System (ADS)

    Jost, A. B.; Mundil, R.; He, B.; Brown, S. T.; Altiner, D.; Sun, Y.; DePaolo, D. J.; Payne, J.

    2013-12-01

    A negative δ13C excursion in carbonate sediments from Guadalupian (Middle Permian) and Lopingian (Late Permian) stratigraphic sections has been interpreted to result from a large carbon cycle disturbance during end-Guadalupian extinction event (ca. 260 Ma). However, the carbon isotope data alone are insufficient to uniquely determine the type and magnitude of perturbations to the global carbon cycle. The carbon and calcium cycles are coupled via CaCO3 burial, so changes in calcium isotopes can be used to constrain the cause of a carbon isotope excursion. In this study, we present coupled carbon and calcium isotope records from three Guadalupian-Lopingian (G/L) sections in China and Turkey. Isotope records among our studied sections are inconsistent in both their δ13C and δ44/40Ca records. Similar inconsistencies in δ13C among sections occur across previously published datasets. Sections with large (>3‰) changes in δ13C either show evidence for diagenetic alteration or do not show δ13C and δ44/40Ca changes consistent with severe volcanic degassing from Emeishan or methane clathrate destabilization. We conclude that the large isotopic changes are more likely the result of local burial conditions or diagenetic effects, rather than a large carbon cycle disturbance. Perturbations to the global carbon and calcium cycles appear to have been much smaller across the G/L transition than across the subsequent Permian-Triassic boundary. This finding is consistent with recent paleobiological data showing that the end-Guadalupian extinction was much less severe than previously believed, and was indistinguishable in magnitude from background intervals. However, selective extinction of marine animals with passive respiratory physiology indicates that the G/L extinction cannot simply be due to background extinction or sampling failure, and that it was triggered by some environmental event. Therefore, any environmental event must have been small enough to not generate large

  17. Precision and long-term stability of clumped-isotope analysis of CO2 using a small-sector isotope ratio mass spectrometer.

    PubMed

    Yoshida, Naohiro; Vasilev, Mikhail; Ghosh, Prosenjit; Abe, Osamu; Yamada, Keita; Morimoto, Maki

    2013-01-15

    The ratio of the measured abundance of (13)C-(18)O bonding CO(2) to its stochastic abundance, prescribed by the δ(13)C and δ(18)O values from a carbonate mineral, is sensitive to its growth temperature. Recently, clumped-isotope thermometry, which uses this ratio, has been adopted as a new tool to elucidate paleotemperatures quantitatively. Clumped isotopes in CO(2) were measured with a small-sector isotope ratio mass spectrometer. CO(2) samples digested from several kinds of calcium carbonates by phosphoric acid at 25 °C were purified using both cryogenic and gas-chromatographic separations, and their isotopic composition (δ(13)C, δ(18)O, Δ(47), Δ(48) and Δ(49) values) were then determined using a dual-inlet Delta XP mass spectrometer. The internal precisions of the single gas Δ(47) measurements were 0.005 and 0.02‰ (1 SE) for the optimum and the routine analytical conditions, respectively, which are comparable with those obtained using a MAT 253 mass spectrometer. The long-term variations in the Δ(47) values for the in-house working standard and the heated CO(2) gases since 2007 were close to the routine, single gas uncertainty while showing seasonal-like periodicities with a decreasing trend. Unlike the MAT 253, the Delta XP did not show any significant relationship between the Δ(47) and δ(47) values. The Delta XP gave results that were approximately as precise as those of the MAT 253 for clumped-isotope analysis. The temporal stability of the Delta XP seemed to be lower, although an advantage of the Delta XP was that no dependency of δ(47) on Δ(47) was found. Copyright © 2012 John Wiley & Sons, Ltd.

  18. Carbon isotopic composition of assimilated and respired CO2 in Southeastern US pine forests

    NASA Astrophysics Data System (ADS)

    Mortazavi, B.; Conte, M. H.; Chanton, J.; Martin, T.; Teklemerian, T.; Cropper, W.; Weber, J.

    2010-12-01

    We measured the 13C of assimilated carbon [foliage organic matter (δCOM), leaf soluble carbohydrates ((δCSC), and leaf waxes ((δCW)] and respiratory carbon [foliage (δCF), soil (δCS) and ecosystem respired CO2 (δCR)] over a two-year period at two sites in central Florida that are typical of Southeastern US coastal plain pine ecosystems. Our objective was to determine how climatic variables, operating by affecting plant physiology and photosynthetic discrimination (Δ), influence the isotopic composition of assimilated carbon pools and of ecosystem respired CO2. The first site was a naturally regenerated 32 m tall stand of mature longleaf pine (Pinus palustris Mill.) with mature slash pine (Pinus elliottii) subdominants, while the second was a planted, mid-rotation 13 m tall stand of slash pine (Pinus elliottii var. elliottii Engelm.). δCOM, δCSC, δCW, and δCF of P. palustris were 13C enriched by about 2‰ relative to that of P. elliottii in the mid-rotation plantation. Despite this enrichment, mean δCR of the P. palustris stand was similar to that at the P. elliottii plantation, reflecting additional respiratory inputs from the more isotopically depleted P. elliottii subdominant and understory. In both P. palustris and P. elliottii, a small decrease was observed in δCOM over the two year study, but not in δCSC, δCF, δCS or δCR. Intriguingly, a significant 2‰ decrease was also observed in the very long chain needlewaxes (C32-36 n-alkanoic acids), but not the more abundant C24-28 waxes. As the carbon in waxes is supplied by internal storage reserves, our data suggest there may be distinct carbon source pathways for waxes of differing chain lengths. The long-term decrease in the 13C of foliar carbon and waxes also suggests recovery from severe drought conditions prior to our study. δCF and δCR were consistently 13C enriched relative to assimilated C and were insensitive to variations in vapor pressure deficit (D). The small variability in δCA and

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

    NASA Astrophysics Data System (ADS)

    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. The origin of Neoproterozoic Cap Carbonates: a view from Mg and Sr Isotopes

    NASA Astrophysics Data System (ADS)

    Liu, C.; Raub, T. D.; Evans, D. A.; Wang, Z.

    2010-12-01

    Neoproterozoic cap carbonates are suggested to document Earth’s transition from a ‘snowball earth’ to an ‘extreme greenhouse’ environment. Geochemistry of these rocks is essential for its paleo-environment reconstruction, and Mg and Sr isotopes can help to understand its origin and constrain geochemical evolution of the contemporary ocean. In this study, we studied Mg and Sr isotope composition of 18 cap dolostone samples from Nuccaleena formation carbonate and one from the the mixed siliciclastic transition at its base at Elatina Creek in Adelaide Geosyncline of South Australia. We established a step-leaching procedure using ammonium acetate, various concentrations of acetic acid, and HCl on four of these cap carbonate samples to untangle the isotopic signatures of its various constituent phases. 87Sr/86Sr values of the leachates in each sample decrease continuously as leaching process proceeds and sometimes rebound as silicates are dissolved. The lowest leachate 87Sr/86Sr values, down to 0.7084, are lower than the reported dolostone(~0.7096) but still higher than those of limestones overlying the dolostone in other basins(~0.7079), indicating an input of increasing level of weathering to the ocean over the course of cap-carbonate precipitation. In contrast, δ26MgDSM3 variation with progressing leaching steps exhibits a wave pattern (variation up to 0.4~0.5‰) during the leaching processes, due to different chemical affinity of Mg in various mineral phases. More importantly, Mg isotope composition of the portion that is associated with stratigraphically low, minimum Sr isotope composition is similar to those of contemporary corals (or inorganic aragonite precipitation), but up to ca. 0.6 per mil lower than stratigraphically-higher values, suggesting a warmer weather and/or more significant silicate weathering than contemporary Earth’s climate, and a transition from physical weathering to chemical weather during deglaciation.

  1. Carbon isotope ratios of selected volatiles in Citrus sinensis and in orange-flavoured food.

    PubMed

    Schipilliti, Luisa; Bonaccorsi, Ivana; Cotroneo, Antonella; Dugo, Paola; Mondello, Luigi

    2015-11-01

    Twenty genuine samples of industrially cold-pressed sweet orange essential oils, were analysed by gas chromatography-combustion-isotope ratio mass spectrometry to determine the values of the carbon isotope ratios (δ(13)C(VPDB)) of selected volatiles and assess the corresponding range of authenticity. Successively, four commercial orange-flavoured products were analysed under identical conditions to evaluate the authenticity of the orange flavour. The samples were extracted by solid-phase microextraction under optimised conditions. The evaluation was performed by using an internal standard procedure to neglect the contribution due to the original environment to the isotopic abundance of (13)C. The composition of the volatile fraction of the essential oils and of the flavoured products was determined by gas chromatography coupled to mass spectrometry with linear retention indices, and by gas chromatography with a flame ionisation detector. The δ(13)C(VPDB) values of seven secondary metabolites determined here were successfully used to characterise genuine orange essential oil. These values were used to evaluate the quality of orange-flavoured products, revealing the presence of compounds of different origin, not compatible with the values of genuine orange secondary metabolites. This study provides the range of authenticity of δ(13)C(VPDB) of seven different secondary metabolites in sweet orange genuine essential oil, useful for evaluating the genuineness of orange flavour. In accord with a previous study on different essential oils, the values determined here can be successfully applied for the evaluation of a large number of flavoured food stuffs and correlated with their origins. © 2014 Society of Chemical Industry.

  2. Late Triassic tropical climate of Pangea: Carbon isotopic and other insights into the rise of dinosaurs

    NASA Astrophysics Data System (ADS)

    Whiteside, J. H.; Lindström, S.; Irmis, R. B.; Glasspool, I.; Schaller, M. F.; Dunlavey, M.; Nesbitt, S. J.; Smith, N. D.; Turner, A. H.

    2015-12-01

    The rarity and species-poor nature of early dinosaurs and their relatives at low paleolatitudes persisted for 30 million years after their origin and 10-15 million years after they became abundant and speciose at higher latitudes. New environmental reconstructions from stable carbon isotope ratios of preserved organic matter (δ13Corg), atmospheric pCO2 data based on the δ13C of soil carbonate, palynological, and wildfire data from charcoal from early dinosaur-bearing strata at low paleolatitudes in western North America show that variations in δ13Corg and palynomorph ecotypes are tightly correlated, displaying large and high-frequency excursions. These variations occurred within an environment characterized by elevated and increasing atmospheric pCO2, pervasive wildfires, and rapidly fluctuating extreme climatic conditions. Whereas pseudosuchian archosaur-dominated communities were able to persist in these same regions until the end-Triassic, the large-bodied, fast-growing tachymetabolic dinosaurian herbivores were not. We hypothesize that the greater resources required by the herbivores made it difficult from them to adapt to the unstable conditions at low paleolatitudes in the Late Triassic.

  3. Quinone-based stable isotope probing for assessment of 13C substrate-utilizing bacteria

    NASA Astrophysics Data System (ADS)

    Kunihiro, Tadao; Katayama, Arata; Demachi, Toyoko; Veuger, Bart; Boschker, Henricus T. S.; van Oevelen, Dick

    2015-04-01

    13C abundance in the quinone. In this study, we verified carbon stable isotope of quinone compared with bulk carbon stable isotope of bacterial culture. Results indicated a good correlation between carbon stable isotope of quinone compared with bulk carbon stable isotope. However, our measurement conditions for detection of quinone isotope-ions incurred underestimation of 13C abundance in the quinone. The quinone-SIP technique needs further optimization for measurement conditions of LC-MS/MS.

  4. Authigenic carbonates from methane seeps of the Congo deep-sea fan

    NASA Astrophysics Data System (ADS)

    Pierre, Catherine; Fouquet, Yves

    2007-06-01

    Submersible investigations with the ROV Victor 6000 of some pockmark structures on the seafloor of the Congo deep-sea fan have shown that they are active venting sites of methane-rich fluids, associated with abundant fauna and carbonate crusts. Moreover, methane hydrates have been observed both outcropping and deep in the sediments in the centre of the “Regab” giant pockmark. Authigenic carbonates, mostly calcite sometimes mixed with aragonite, are cementing the sedimentary matrix components and fauna; diatoms are abundant but only as moulds, indicating that biogenic silica dissolution occurred in situ synchronous with carbonate precipitation. The occurrence of diagenetic barite and pyrite in some carbonate crusts demonstrates that they can be formed either within the sulphate/methane transition zone or deeper in sulphate-depleted sediments. The oxygen isotopic compositions of the diagenetic carbonates (3.17 6.01‰ V-PDB) indicate that precipitation occurred with bottom seawater mixed with a variable contribution of water from gas hydrate decomposition. The very low carbon isotopic compositions of the diagenetic carbonates (-57.1 to -27.75‰ V-PDB) demonstrate that carbon derives mostly from the microbial oxidation of methane.

  5. Isotopic compositions of the elements, 2001

    USGS Publications Warehouse

    Böhlke, J.K.; De Laeter, J. R.; De Bievre, P.; Hidaka, H.; Peiser, H.S.; Rosman, K.J.R.; Taylor, P.D.P.

    2005-01-01

    The Commission on Atomic Weights and Isotopic Abundances of the International Union of Pure and Applied Chemistry completed its last review of the isotopic compositions of the elements as determined by isotope-ratio mass spectrometry in 2001. That review involved a critical evaluation of the published literature, element by element, and forms the basis of the table of the isotopic compositions of the elements (TICE) presented here. For each element, TICE includes evaluated data from the “best measurement” of the isotope abundances in a single sample, along with a set of representative isotope abundances and uncertainties that accommodate known variations in normal terrestrial materials. The representative isotope abundances and uncertainties generally are consistent with the standard atomic weight of the element Ar(E)">Ar(E)Ar(E) and its uncertainty U[Ar(E)]">U[Ar(E)]U[Ar(E)] recommended by CAWIA in 2001.

  6. Carbon isotope and abundance systematics of Icelandic geothermal gases, fluids and subglacial basalts with implications for mantle plume-related CO2 fluxes

    NASA Astrophysics Data System (ADS)

    Barry, P. H.; Hilton, D. R.; Füri, E.; Halldórsson, S. A.; Grönvold, K.

    2014-06-01

    We report new carbon dioxide (CO2) abundance and isotope data for 71 geothermal gases and fluids from both high-temperature (HT > 150 °C at 1 km depth) and low-temperature (LT < 150 °C at 1 km depth) geothermal systems located within neovolcanic zones and older segments of the Icelandic crust, respectively. These data are supplemented by CO2 data obtained by stepped heating of 47 subglacial basaltic glasses collected from the neovolcanic zones. The sample suite has been characterized previously for He-Ne (geothermal) and He-Ne-Ar (basalt) systematics (Füri et al., 2010), allowing elemental ratios to be calculated for individual samples. Geothermal fluids are characterized by a wide range in carbon isotope ratios (δ13C), from -18.8‰ to +4.6‰ (vs. VPDB), and CO2/3He values that span eight orders of magnitude, from 1 × 104 to 2 × 1012. Extreme geothermal values suggest that original source compositions have been extensively modified by hydrothermal processes such as degassing and/or calcite precipitation. Basaltic glasses are also characterized by a wide range in δ13C values, from -27.2‰ to -3.6‰, whereas CO2/3He values span a narrower range, from 1 × 108 to 1 × 1012. The combination of both low δ13C values and low CO2 contents in basalts indicates that magmas are extensively and variably degassed. Using an equilibrium degassing model, we estimate that pre-eruptive basaltic melts beneath Iceland contain ∼531 ± 64 ppm CO2 with δ13C values of -2.5 ± 1.1‰, in good agreement with estimates from olivine-hosted melt inclusions (Metrich et al., 1991) and depleted MORB mantle (DMM) CO2 source estimates (Marty, 2012). In addition, pre-eruptive CO2 compositions are estimated for individual segments of the Icelandic axial rift zones, and show a marked decrease from north to south (Northern Rift Zone = 550 ± 66 ppm; Eastern Rift Zone = 371 ± 45 ppm; Western Rift Zone = 206 ± 24 ppm). Notably, these results are model dependent, and selection of a lower

  7. A large column analog experiment of stable isotope variations during reactive transport: II. Carbon mass balance, microbial community structure and predation

    NASA Astrophysics Data System (ADS)

    Druhan, Jennifer L.; Bill, Markus; Lim, HsiaoChien; Wu, Cindy; Conrad, Mark E.; Williams, Kenneth H.; DePaolo, Donald J.; Brodie, Eoin L.

    2014-01-01

    Here we report a combined analysis of carbon mass balance based on isotopic labeling and microbiological characterization during organic carbon stimulated bioreduction of a subsurface sediment in a large laboratory column experimental system. This combination of approaches allows quantification of both the cycling of carbon through multiple redox pathways and the associated spatial and temporal evolution of bacterial communities in response to this nutrient source. Carbon isotope mass balance facilitated by the use of 13C-labeled acetate as the electron donor showed evidence for a net loss of sediment organic carbon over the course of the amendment experiment. Furthermore, these data clearly demonstrated a source of isotopically labeled inorganic carbon that was not attributable to primary metabolism by acetate-oxidizing microorganisms. Fluid samples collected weekly over the duration of the 43-day amendment at <20 cm intervals along the flow path were analyzed for microbial composition by pyrosequencing of ribosomal RNA genes. The microbial community composition was transient, with distinct occurrences of Azoarcus, Geobacter and multiple sulfate reducing species over the course of the experiment. In combination with DNA sequencing data, the anomalous carbon cycling process is shown to occur exclusively during the period of predominant Geobacter species growth. Pyrosequencing indicated, and targeted cloning and sequencing confirmed the presence of several bacteriovorous protozoa, including species of the Breviata, Planococcus and Euplotes genera. Cloning and qPCR analysis demonstrated that Euplotes species were most abundant and displayed a growth trajectory that closely followed that of the Geobacter population. These results suggest a previously undocumented secondary turnover of biomass carbon related to protozoan grazing that was not sufficiently prevalent to be observed in bulk concentrations of carbon species in the system, but was clearly identified in the

  8. The Precambrian Biogeochemical Carbon Isotopic Record: Contributions of Thermal Versus Biological Processes

    NASA Technical Reports Server (NTRS)

    DesMarais, David J.; DeVincenzi, Donald L. (Technical Monitor)

    2000-01-01

    Superplumes offer a new approach for understanding global C cycles. Isotopes help to discern the impacts of geological, environmental and biological processes ujpun the evolution of these cycles. For example, C-13/C-12 values of coeval sedimentary organics and carbonates give global estimates of the fraction of C buried as organics (Forg), which today lies near 0.2. Before Oxygenic photosynthesis arose, our biosphere obtained reducing power for biosynthesis solely from thermal volatiles and rock alteration. Thus Forg was dominated by the mantle redox state, which has remained remarkably constant for greater than Gy. Recent data confirm that the long-term change in Forg had been small, indicating that the mantle redox buffer remains important even today. Oxygenic photosynthesis enabled life to obtain additional reducing power by splitting the water molecule. Accordingly, biological organic production rose above the level constrained by the mantle-derived flux of reduced species. For example, today, chemoautotrophs harvesting energy from hydrothermal emanations can synthesize at most between 0.2 x 10(exp 12) and 2x 10(exp 12) mol C yr-1 of organic C globally. In contrast, global photosynthetic productivity is estimated at 9000 x 10(exp 12) mol C yr-1. Occasionally photosynthetic productivity did contribute to dramatically -elevated Forg values (to 0.4 or more) as evidenced by very high carbonate C-13/C-12. The interplay between biological, tectonic and other environmental factors is illustrated by the mid-Archean to mid-Proterozoic isotopic record. The relatively constant C-13/C-12 values of Archean carbonates support the view that photosynthetically-driven Forg increases were not yet possible. In contrast, major excursions in C-13/C-12, and thus also in Forg, during the early Proterozoic confirmed the global importance of oxygenic photosynthesis by that time. Remarkably, the superplume event at 1.9 Ga did not trigger another major Forg increase, despite the

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

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    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

    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.more » 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.« less

  10. Springtime carbon episodes at Gosan background site revealed by total carbon, stable carbon isotopic composition, and thermal characteristics of carbonaceous particles

    NASA Astrophysics Data System (ADS)

    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

  11. Carbon isotopic fractionation in lipids from methanotrophic bacteria: relevance for interpretation of the geochemical record of biomarkers

    NASA Technical Reports Server (NTRS)

    Summons, R. E.; Jahnke, L. L.; Roksandic, Z.

    1994-01-01

    Experiments with cultured aerobic methane oxidising bacteria confirm that their biomarker lipids will be significantly depleted in 13C compared to the substrate. The methanotrophic bacteria Methylococcus capsulatus and Methylomonas methanica, grown on methane and using the RuMP cycle for carbon assimilation, show maximum 13C fractionation of approximately 30% in the resultant biomass. In M. capsulatus, the maximum fractionation is observed in the earliest part of the exponential growth stage and decreases to approximately 16% as cells approach stationary phase. This change may be associated with a shift from the particulate form to the soluble form of the methane monooxygenase enzyme. Less than maximum fractionation is observed when cells are grown with reduced methane availability. Biomass of M. capsulatus grown on methanol was depleted by 9% compared to the substrate. Additional strong 13C fractionation takes place during polyisoprenoid biosynthesis in methanotrophs. The delta 13C values of individual hopanoid and steroid biomarkers produced by these organisms were as much as l0% more negative than total biomass. In individual cultures, squalene was 13C-enriched by as much as 14% compared to the triterpane skeleton of bacteriohopaneaminopentol. Much of the isotopic dispersion in lipid metabolites could be attributed to shifts in their relative abundances, combined with an overall reduction in fractionation during the growth cycle. In cells grown on methanol, where there was no apparent effect of growth stage on overall fractionation there were still significant isotopic differences between closely related lipids including a 5.3% difference between the hopane and 3 beta-methylhopane skeletons. Hopane and sterane polyisoprenoids were also 13C-depleted compared to fatty acids. These observations have significant implications for the interpretation of specific compound isotopic signatures now being measured for hydrocarbons and other lipids present in sediments and

  12. Preliminary Earth System Modeling (cGENIE) of Paired Organic and Inorganic Carbon Isotope Records to Investigate Carbon Cycle Behavior During the Triassic-Jurassic Transition

    NASA Astrophysics Data System (ADS)

    Yager, J. A.; Stellmann, J. L.; West, A. J.; Corsetti, F. A.; Berelson, W.; Bottjer, D. J.; Rosas, S.

    2016-12-01

    The stable C isotope composition of marine carbonate and organic C yields information regarding major changes in global carbon cycling over geologic time. Excursions from baseline C isotope compositions during the Late Triassic and early Jurassic coincide with the end-Triassic mass extinction. Much remains to be understood about the global extent of these excursions, and about their causes. Here, we use observations from a record from Northern Peru (Levanto) to generate hypotheses concerning C cycle changes, focusing on comparison to other sections spanning the Triassic-Jurassic boundary. Our observations include a decoupling between organic and inorganic C isotopes in some records, broad similarities in the pattern of excursions between sections, and a potential offset between the major ocean basins (Tethys and Panthalassa) in both inorganic and organic C isotope records. We are currently adapting a spatially resolved Earth System Model (cGENIE) for this time period with the goal of using this model to explore possible mechanistic causes of these observations, aiming to tie the C isotope records to changes in global carbon cycle dynamics at the time.

  13. Impact of surface processes and climate variability on clumped isotope thermometry of soil carbonates, southern Central Andes, Argentina (Invited)

    NASA Astrophysics Data System (ADS)

    Huntington, K. W.; Peters, N.; Roe, G.; Hoke, G. D.; Eiler, J.

    2010-12-01

    Soil carbonates archive a potentially rich record of past climate, but rates of pedogenic carbonate formation, erosion, and deposition impact how the isotopic composition and formation temperature of carbonate-bearing paleosols reflect the local environmental conditions under which they form. We investigate these processes using conventional stable isotope (δ18O and δ13C) and clumped isotope thermometry data for Quaternary pedogenic carbonates from the southern Central Andes at ~33°S, Argentina. The study area spans over 2 km of relief in the Río Mendoza and Río de las Cuevas valleys, accessing a range of mean annual temperature conditions and vegetative cover and exhibiting large seasonal variations in temperature, precipitation, and soil moisture. Variations in soil conditions influence carbonate precipitation and dissolution reactions and the rate and depth of pedogenic carbonate formation. Because soil temperature varies predictably as a function of depth in the soil and seasonal and secular variations in air temperature, clumped isotope thermometry of samples collected in soil pits offers a direct way to estimate the seasonality of pedogenic carbonate formation and potential biases in the long-term climate record. We explore potential complications due to the effects of radiative solar heating on the relationship between air and soil temperatures by examining clumped isotope thermometry results in the context of site-to-site variations in vegetative cover. Temperature estimates from clumped isotope thermometry of pedogenic carbonate collected 5-110 cm below geomorphically stable soil surfaces from 1200-3400 m a.s.l. are compared to temperature profiles predicted by simple rule-based models of soil carbonate formation. The models use climate reanalysis daily diagnostic data (soil temperature, soil moisture, and latent heat flux as a proxy for evaporation) and weather station data as input to assess how varying rates of pedogenic carbonate formation

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

    Treesearch

    Daniel H. Doctor; Carol Kendall; Stephen D. Sebestyen; James B. Shanley; Nobuhito Ohte; Elizabeth W. Boyer

    2008-01-01

    The stable isotopic composition of dissolved inorganic carbon (δ13C-DIC) was investigated as a potential tracer of streamflow generation processes at the Sleepers River Research Watershed, Vermont, USA. Downstream sampling showed δ13C-DIC increased between 3-5% from the stream source to the outlet weir...

  15. Field-based stable isotope analysis of carbon dioxide by mid-infrared laser spectroscopy for carbon capture and storage monitoring.

    PubMed

    van Geldern, Robert; Nowak, Martin E; Zimmer, Martin; Szizybalski, Alexandra; Myrttinen, Anssi; Barth, Johannes A C; Jost, Hans-Jürg

    2014-12-16

    A newly developed isotope ratio laser spectrometer for CO2 analyses has been tested during a tracer experiment at the Ketzin pilot site (northern Germany) for CO2 storage. For the experiment, 500 tons of CO2 from a natural CO2 reservoir was injected in supercritical state into the reservoir. The carbon stable isotope value (δ(13)C) of injected CO2 was significantly different from background values. In order to observe the breakthrough of the isotope tracer continuously, the new instruments were connected to a stainless steel riser tube that was installed in an observation well. The laser instrument is based on tunable laser direct absorption in the mid-infrared. The instrument recorded a continuous 10 day carbon stable isotope data set with 30 min resolution directly on-site in a field-based laboratory container during a tracer experiment. To test the instruments performance and accuracy the monitoring campaign was accompanied by daily CO2 sampling for laboratory analyses with isotope ratio mass spectrometry (IRMS). The carbon stable isotope ratios measured by conventional IRMS technique and by the new mid-infrared laser spectrometer agree remarkably well within analytical precision. This proves the capability of the new mid-infrared direct absorption technique to measure high precision and accurate real-time stable isotope data directly in the field. The laser spectroscopy data revealed for the first time a prior to this experiment unknown, intensive dynamic with fast changing δ(13)C values. The arrival pattern of the tracer suggest that the observed fluctuations were probably caused by migration along separate and distinct preferential flow paths between injection well and observation well. The short-term variances as observed in this study might have been missed during previous works that applied laboratory-based IRMS analysis. The new technique could contribute to a better tracing of the migration of the underground CO2 plume and help to ensure the long

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

    NASA Astrophysics Data System (ADS)

    Dannoura, M.; Bosc, A.; Chipeaux, C.; Sartore, M.; Lambrot, C.; Trichet, P.; Bakker, M.; Loustau, D.; Epron, D.

    2010-12-01

    Carbon allocation belowground competes with aboveground growth and biomass production. In the other hand, it contributes to resource acquisition such as nutrient, water and carbon sequestration in soil. Thus, a better characterization of carbon flow from plant to soil and its residence time within each compartment is an important issue for understanding and modeling forest ecosystem carbon budget. 13C pulse labeling of whole crown was conducted at 4 seasons to study the fate of assimilated carbon by photosynthesis into the root on 12 year old Pinus pinaster planted in the INRA domain of Pierroton. Maritime pine is the most widely planted species in South-West Europe. Stem, root and soil CO2 effluxes and their isotope composition were measured continuously by tunable diode laser absorption spectroscopy with a trace gas analyzer (TGA 100A; Campbell Scientific) coupled to flow-through chambers. 13CO2 recovery and peak were observed in respiration of each compartment after labeling. It appeared sequentially from top of stem to bottom, and to coarse root. The maximum velocity of carbon transfer was calculated as the difference in time lag of recovery between two positions on the trunk or on the root. It ranged between 0.08-0.2 m h-1 in stem and between 0.04-0.12 m h-1 in coarse root. This velocity was higher in warmer season, and the difference between time lag of recovery and peak increased after first frost. Photosynthates arrived underground 1.5 to 5 days after labeling, at similar time in soil CO2 effluxes and coarse root respiration. 0.08-1.4 g of carbon was respired per tree during first 20 days following labeling. It presented 0.6 -10% of 13C used for labeling and it is strongly related to seasons. The isotope signal was detected in fine root organs and microbial biomass by periodical core sampling. The peak was observed 6 days after labeling in early summer while it was delayed more than 10 days in autumn and winter with less amount of carbon allocated

  17. Silylated Derivatives Retain Carbon and Alter Expected 13C-Tracer Enrichments Using Continuous Flow-Combustion-Isotope Ratio Mass Spectrometry

    PubMed Central

    Shinebarger, Steven R.; Haisch, Michael; Matthews, Dwight E.

    2008-01-01

    Continuous-flow inlets from oxidation reactors are commonly used systems for biological sample introduction into isotope ratio mass spectrometers (IRMS) to measure 13C enrichment above natural abundance. Because the samples must be volatile enough to pass through a gas chromatograph, silylated derivatization reactions are commonly used to modify biological molecules to add the necessary volatility. Addition of a t-butyldimethylsilyl (TBDMS) group is a common derivatization approach. However, we have found that samples do not produce the expected increment in measured 13C abundance as the TBDMS derivatives. We have made measurements of 13C enrichment of leucine and glutamate standards of known 13C enrichment using derivatives without silicon (N-acetyl n-propyl ester), with silicon (TBDMS), and an intermediate case. The measurements of 13C in amino acids derivatized without silicon were as expected. The 13C enrichment measurements using the TBDMS derivative were higher than expected, but could be corrected to produce the expected 13C enrichment measurement by IRMS if one carbon was removed per silicon. We postulate that the silicon in the derivative forms silicon carbide compounds in the heated cupric oxide reactor, rather than forming silicon dioxide. Doing so reduces the amount of CO2 formed from the carbon in the sample. Silylated derivatives retain carbon with the silicon and must be used carefully and with correction factors to measure 13C enrichments by continuous-flow IRMS. PMID:12510745

  18. Tracking Urban Air Deterioration in San Francisco: Carbon and Nitrogen Isotope Study of Weedy Plants.

    NASA Astrophysics Data System (ADS)

    Colman, A. S.; Wessells, A.; Swaine, M. E.; Fogel, M. L.

    2003-12-01

    Stable isotopes of carbon and nitrogen have long been used as indicators of ecosystem structure and nutrient cycling in natural and anthropogenically disturbed terrestrial ecosytems. However, relatively few of these studies have targeted urban environments, where nitrogen and CO2 emissions dramatically impact atmospheric composition. Here we present the results of carbon and nitrogen isotope analyses of herbaceous plants growing in and around San Francisco. These plants were collected mainly as part of a public outreach walking tour of San Francisco ("The Weed Walk - Concrete Jungle") sponsored by the San Francisco Exploratorium. In all cases, the plants were sampled in areas with negligible forest canopy. A consortium of species was collected at each of several distinct sites to examine the localized and regional impact of automobile traffic and proximity to the ocean on isotopic compositions of carbon and nitrogen. δ 13C measurements trend towards relatively light values in the range of --26 to --36 permil. In comparison, the leaves from similar types of herbaceous species in relatively unpolluted and unforested environments typically have δ 13C values in the range of --22 to --28 permil. The observed light carbon isotopic compositions potentially reflect input of isotopically light CO2 emissions from fossil fuel burning, boosting atmospheric CO2 concentrations to >10 % above background. δ 15N values range from +4 to +9 permil. This is substantially offset from the --4 to +1 permil values that typify vegetation in regions where nitrogen oxides from fossil fuel combustion dominate the nitrogen inputs. The nitrogen isotope compositions might suggest nitrogen contributions from a marine source (typically +6 permil).

  19. Evaluation of carbon isotope flux partitioning theory under simplified and controlled environmental conditions

    USDA-ARS?s Scientific Manuscript database

    Separation of the photosynthetic (Fp) and respiratory (Fr) fluxes of net CO2 exchange (Fn)remains a necessary step toward understanding the biological and physical controls on carbon cycling between the soil, biomass, and atmosphere. Despite recent advancements in stable carbon isotope partitioning ...

  20. Isotopic composition of Murchison organic compounds: Intramolecular carbon isotope fractionation of acetic acid. Simulation studies of cosmochemical organic syntheses

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

    Recently, in our laboratories, samples of Murchison acetic acid were decarboxylated successfully and the carbon isotopic composition was measured for the methane released by this procedure. These analyses showed significant differences in C-13/C-12 ratios for the methyl and carboxyl carbons of the acetic acid molecule, strongly suggesting that more than one carbon source may be involved in the synthesis of the Murchison organic compounds. On the basis of this finding, laboratory model systems simulating cosmochemical synthesis are being studied, especially those processes capable of involving two or more starting carbon sources.

  1. Oxygen isotope fractionation in divalent metal carbonates

    USGS Publications Warehouse

    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.

  2. Rate-dependent carbon and nitrogen kinetic isotope fractionation in hydrolysis of isoproturon.

    PubMed

    Penning, Holger; Cramer, Christopher J; Elsner, Martin

    2008-11-01

    Stable isotope fractionation permits quantifying contaminant degradation in the field when the transformation reaction is associated with a consistent isotope enrichment factor epsilon. When interpreted in conjunction with dual isotope plots, isotope fractionation is also particularly useful for elucidating reaction mechanisms. To assess the consistency of epsilon and dual isotope slopes in a two-step reaction, we investigated the abiotic hydrolysis of the herbicide isoproturon (3-(4-isopropylphenyl)-1,1-dimethylurea) using a fragmentation method that allows measuring isotope ratios in different parts of the molecule. Carbon and nitrogen position-specific isotope fractionation, as well as slopes in dual isotope plots, varied linearly with rate constants k(obs) depending on the presence of buffers that mediate the initial zwitterion formation. The correlation can be explained by two consecutive reaction steps (zwitterion formation followed by dimethylamine elimination) each of which has a different kinetic isotope effect and may be rate-limiting. Intrinsic isotope effects for both steps, extracted from our kinetic data using a novel theoretical treatment, agree well with values computed from density functional calculations. Our study therefore demonstrates that more variable isotope fractionation may be observed in simple chemical reactions than commonly thought, but that consistent epsilon or dual isotope slopes may nonetheless be encountered in certain molecular fragments.

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

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    HOLDEN,N.E.

    2007-07-23

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

  4. Physical and Biological Carbon Isotope Fractionation in Methane During Gas-Push-Pull-Tests

    NASA Astrophysics Data System (ADS)

    Gonzalez-Gil, G.; Schroth, M. H.; Gomez, K.; Zeyer, J.

    2005-12-01

    Stable isotope analyses have become a common tool to assess microbially-mediated processes in subsurface environments. We investigated if stable carbon isotope analysis can be used as a tool to complement gas push-pull tests (GPPTs), a novel technique that was recently developed and tested for the in-situ quantification of CH4 oxidation in soils. During a GPPT a gas mixture containing CH4, O2 and nonreactive tracer gases is injected into the soil, where CH4 is oxidized by indigenous microorganisms. Thereafter, a blend of injected gas mixture and soil air is extracted from the same location, and CH4 oxidation is quantified from an analysis of extracted CH4 and tracer gases. To assess the magnitude of physical isotope fractionation due to molecular diffusion during GPPTs, we conducted laboratory experiments in the absence of microbial activity in a 1m-high, 1m-diameter tank filled with dry sand. During the GPPTs' extraction phase, the isotopic composition of methane was analyzed. Results indicated strong carbon isotope fractionation (>20 per mil) during GPPTs. To assess the combined effect of physical and biological isotope fractionation, numerical simulations of GPPTs were conducted in which microbial CH4 isotope fractionation was simulated using first-order rate constants and microbial kinetic isotope fractionation factors previously reported for methane oxidation in landfill environments. Results of these simulations indicated that for small CH4 oxidation rates, overall isotope fractionation in CH4 is dominated by physical fractionation. Conversely, for high CH4 oxidation rates, overall fractionation is dominated by biological fractionation. Thus, CH4 isotope fractionation data alone from a single GPPT cannot be used to assess microbial CH4 oxidation. However, biological fractionation may be quantified if physical fractionation due to diffusion is known. This can be achieved by conducting two sequential GPPTs, with microbial activity being inhibited in the second

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

    NASA Astrophysics Data System (ADS)

    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.

    2011-04-01

    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. The last 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

  6. Serum Carbon Isotope Values Change in Adults in Response to Changes in Sugar-Sweetened Beverage Intake12

    PubMed Central

    Fakhouri, Tala H. I.; Jahren, A. Hope; Appel, Lawrence J.; Chen, Liwei; Alavi, Reza; Anderson, Cheryl A. M.

    2014-01-01

    Serum carbon isotope values [13C-to-12C serum carbon isotope ratio (δ13C)], which reflect consumption of corn- and cane-based foods, differ between persons consuming high and low amounts of sugar-sweetened beverages (SSBs). In this study, we determined whether serum δ13C changes in response to change in SSB intake during an 18-mo behavioral intervention trial. Data were from a subset of 144 participants from the PREMIER trial, a completed behavioral intervention (Maryland, 1998–2004). SSB intake was assessed using 2 24-h dietary recall interviews. Blinded serum samples were assayed for δ13C by natural abundance stable isotope mass spectroscopy. Multiple linear regression models with generalized estimating equations and robust variance estimation were used. At baseline, mean SSB intake was 13.8 ± 14.2 fl oz/d, and mean δ13C serum value was −19.3 ± 0.6 units per mil (designated ‰). A reduction of 12 oz (355 mL)/d SSB (equivalent to 1 can of soda per day) was associated with 0.17‰ (95% CI: 0.08‰, 0.25‰ P < 0.0001) reduction in serum δ13C values over 18 mo (equivalent to a 1% reduction in δ13C from baseline). After adjusting for potential confounders, a reduction of 12 oz/d SSB (equivalent to 1 can of soda per day), over an 18-mo period, was associated with 0.12‰ (95% CI: 0.01‰, 0.22‰ P = 0.025) reduction in serum δ13C. These findings suggest that serum δ13C can be used as a measure of dietary changes in SSB intake. PMID:24717368

  7. Stable Carbon Isotopes in Treerings; Revisiting the Paleocloud Proxy.

    NASA Astrophysics Data System (ADS)

    Gagen, M.; Zorita, E.; Dorado Liñán, I.; Loader, N.; McCarroll, D.; Robertson, I.; Young, G.

    2017-12-01

    The long term relationship between cloud cover and temperature is one of the most important climate feedbacks contributing to determining the value of climate sensitivity. Climate models still reveal a large spread in the simulation of changes in cloud cover under future warming scenarios and clarity might be aided by a picture of the past variability of cloudiness. Stable carbon isotope ratios from tree ring records have been successfully piloted as a palaeocloud proxy in geographical areas traditionally producing strong dendroclimatological reconstructions (high northern latitudes in the Northern Hemisphere) and with some notable successes elsewhere too. An expansion of tree-ring based palaeocloud reconstructions might help to estimate past variations of cloud cover in periods colder or warmer than the 20th century, providing a way to test model test this specific aspect. Calibration with measured instrumental sunshine and cloud data reveals stable carbon isotope ratios from tree rings as an indicator of incoming short wave solar radiation (SWR) in non-moisture stressed sites, but the statistical identification of the SWR signal is hampered by its interannual co-variability with air temperature during the growing season. Here we present a spatio-temporal statistical analysis of a multivariate stable carbon isotope tree ring data set over Europe to assess its usefulness to reconstruct past solar radiation changes. The interannual co-variability of the tree ring records stronger covariation with SWR than with air temperature. The resulting spatial patterns of interannual co-variability are strongly linked to atmospheric circulation in a physically consistent manner. However, the multidecadal variations in the proxy records show a less physically coherent picture. We explore whether atmospheric corrections applied to the proxy series are contributing to differences in the multi decadal signal and investigate whether multidecadal variations in soil moisture perturb

  8. Carbon Isotopes of Alkanes in Hydrothermal Abiotic Organic Synthesis Processes at High Temperatures and Pressures: An Experimental Study

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

    Observation of methane in the Martian atmosphere has been reported by different detection techniques [1-4]. With more evidence showing extensive water-rock interaction in Martian history [5-7], abiotic formation by Fischer-Tropsch Type (FTT) synthesis during serpentization reactions may be one possible process responsible for methane generation on Mars [8, 9]. While the experimental studies performed to date leave little doubt that chemical reactions exist for the abiotic synthesis of organic compounds by mineral surface-catalyzed reactions [10-12], little is known about the reaction pathways by which CO2 and/or CO are reduced under hydrothermal conditions. Carbon and hydrogen isotope measurements of alkanes have been used as an effective tool to constrain the origin and reaction pathways of hydrocarbon formation. Alkanes generated by thermal breakdown of high molecular weight organic compounds have carbon and hydrogen isotopic signatures completely distinct from those formed abiotically [13-15]. Recent experimental studies, however, showed that different abiogenic hydrocarbon formation processes (e.g., polymerization vs. depolymerization) may have different carbon and hydrogen isotopic patterns [16]. Results from previous experiments studying decomposition of higher molecular weight organic compounds (lignite) also suggested that pressure could be a crucial factor affecting fractionation of carbon isotopes [17]. Under high pressure conditions, no experimental data are available describing fractionation of carbon isotope during mineral catalyzed FTT synthesis. Thus, hydrothermal experiments present an excellent opportunity to provide the requisite carbon isotope data. Such data can also be used to identify reaction pathways of abiotic organic synthesis under experimental conditions.

  9. A New and Improved Carbon Dioxide Isotope Analyzer for Understanding Soil-Plant-Atmosphere Interactions

    NASA Astrophysics Data System (ADS)

    Huang, Y. W.; Berman, E. S.; Owano, T. G.; Verfaillie, J. G.; Oikawa, P. Y.; Baldocchi, D. D.; Still, C. J.; Gardner, A.; Baer, D. S.; Rastogi, B.

    2015-12-01

    Stable CO2 isotopes provide information on biogeochemical processes that occur at the soil-plant-atmosphere interface. While δ13C measurement can provide information on the sources of the CO2, be it photosynthesis, natural gas combustion, other fossil fuel sources, landfills or other sources, δ18O, and δ17O are thought to be determined by the hydrological cycling of the CO2. Though researchers have called for analytical tools for CO2 isotope measurements that are reliable and field-deployable, developing such instrument remains a challenge. 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 new and improved analyzer measures CO2 concentration as well as δ13C, δ18O, and δ17O from CO2 at natural abundance (150-2500 ppm). The laboratory precision is ±200 ppb (1σ) in CO2 at 1 s, with a long-term (2 min) precision of ±20 ppb. The 1-second precision for both δ13C and δ18O is 0.7 ‰, and for δ17O is 1.8 ‰. The long-term (2 min) precision for both δ13C and δ18O is 0.08 ‰, and for δ17O is 0.18 ‰. The instrument has improved precision, stability and user interface over previous LGR CO2 isotope instruments and can be easily programmed for periodic referencing and sampling from different sources when coupled with LGR's multiport inlet unit (MIU). We have deployed two of these instruments at two different field sites, one at Twitchell Island in Sacramento County, CA to monitor the CO2 isotopic fluxes from an alfalfa field from 6/29/2015-7/13/2015, and the other at the Wind River Experimental Forest in Washington to monitor primarily the oxygen isotopes of CO2 within the canopy from 8/4/2015 through mid-November 2015. Methodology, laboratory development and testing and field performance are presented.

  10. Determining Carbon and Oxygen Stable Isotope Systematics in Brines at Elevated p/T Conditions to Enhance Monitoring of CO2 Induced Processes in Carbon Storage Reservoirs

    NASA Astrophysics Data System (ADS)

    Becker, V.; Myrttinen, A.; Mayer, B.; Barth, J. A.

    2012-12-01

    Stable carbon isotope ratios (δ13C) are a powerful tool for inferring carbon sources and mixing ratios of injected and baseline CO2 in storage reservoirs. Furthermore, CO2 releasing and consuming processes can be deduced if the isotopic compositions of end-members are known. At low CO2 pressures (pCO2), oxygen isotope ratios (δ18O) of CO2 usually assume the δ18O of the water plus a temperature-dependent isotope fractionation factor. However, at very high CO2 pressures as they occur in CO2 storage reservoirs, the δ18O of the injected CO2 may in fact change the δ18O of the reservoir brine. Hence, changing δ18O of brine constitutes an additional tracer for reservoir-internal carbon dynamics and allows the determination of the amount of free phase CO2 present in the reservoir (Johnson et al. 2011). Further systematic research to quantify carbon and oxygen isotope fractionation between the involved inorganic carbon species (CO2, H2CO3, HCO3-, CO32-, carbonate minerals) and kinetic and equilibrium isotope effects during gas-water-rock interactions is necessary because p/T conditions and salinities in CO2 storage reservoirs may exceed the boundary conditions of typical environmental isotope applications, thereby limiting the accuracy of stable isotope monitoring approaches in deep saline formations (Becker et al. 2011). In doing so, it is crucial to compare isotopic patterns observed in laboratory experiments with artificial brines to similar experiments with original fluids from representative field sites to account for reactions of dissolved inorganic carbon (DIC) with minor brine components. In the CO2ISO-LABEL project, funded by the German Ministry for Education and Research, multiple series of laboratory experiments are conducted to determine the influence of pressure, temperature and brine composition on the δ13C of DIC and the δ18O of brines in water-CO2-rock reactions with special focus placed on kinetics and stable oxygen and carbon isotope fractionation

  11. The Mean Life Squared Relationship for Abundances of Extinct Radioactivities

    NASA Technical Reports Server (NTRS)

    Lodders, K.; Cameron, A. G. W.

    2004-01-01

    We discovered that the abundances of now extinct radioactivities (relative to stable reference isotopes) in meteorites vary as a function of their mean lifetimes squared. This relationship applies to chondrites, achondrites, and irons but to calcium-aluminum inclusions (CAIs). Certain meteorites contain excesses in isotopic abundances from the decay of radioactive isotopes with half-lives much less than the age of the solar system. These short-lived radioactivities are now extinct, but they were alive when meteorites assembled in the early solar system. The origin of these radioactivities and the processes which control their abundances in the solar nebula are still not well understood. Some clues may come from our finding that the meteoritic abundances of now extinct radioactivities (relative to stable reference isotopes) vary as a function of their mean lifetimes squared. This relationship applies to chondrites, achondrites, and irons, but not to CAIs. This points to at least two different processes establishing the abundances of short-lived isotopes found in the meteoritic record.

  12. Modeling the effects of diagenesis on carbonate clumped-isotope values in deep- and shallow-water settings

    NASA Astrophysics Data System (ADS)

    Stolper, Daniel A.; Eiler, John M.; Higgins, John A.

    2018-04-01

    The measurement of multiply isotopically substituted ('clumped isotope') carbonate groups provides a way to reconstruct past mineral formation temperatures. However, dissolution-reprecipitation (i.e., recrystallization) reactions, which commonly occur during sedimentary burial, can alter a sample's clumped-isotope composition such that it partially or wholly reflects deeper burial temperatures. Here we derive a quantitative model of diagenesis to explore how diagenesis alters carbonate clumped-isotope values. We apply the model to a new dataset from deep-sea sediments taken from Ocean Drilling Project site 807 in the equatorial Pacific. This dataset is used to ground truth the model. We demonstrate that the use of the model with accompanying carbonate clumped-isotope and carbonate δ18O values provides new constraints on both the diagenetic history of deep-sea settings as well as past equatorial sea-surface temperatures. Specifically, the combination of the diagenetic model and data support previous work that indicates equatorial sea-surface temperatures were warmer in the Paleogene as compared to today. We then explore whether the model is applicable to shallow-water settings commonly preserved in the rock record. Using a previously published dataset from the Bahamas, we demonstrate that the model captures the main trends of the data as a function of burial depth and thus appears applicable to a range of depositional settings.

  13. Quantitative Determination of Isotope Ratios from Experimental Isotopic Distributions

    PubMed Central

    Kaur, Parminder; O’Connor, Peter B.

    2008-01-01

    Isotope variability due to natural processes provides important information for studying a variety of complex natural phenomena from the origins of a particular sample to the traces of biochemical reaction mechanisms. These measurements require high-precision determination of isotope ratios of a particular element involved. Isotope Ratio Mass Spectrometers (IRMS) are widely employed tools for such a high-precision analysis, which have some limitations. This work aims at overcoming the limitations inherent to IRMS by estimating the elemental isotopic abundance from the experimental isotopic distribution. In particular, a computational method has been derived which allows the calculation of 13C/12C ratios from the whole isotopic distributions, given certain caveats, and these calculations are applied to several cases to demonstrate their utility. The limitations of the method in terms of the required number of ions and S/N ratio are discussed. For high-precision estimates of the isotope ratios, this method requires very precise measurement of the experimental isotopic distribution abundances, free from any artifacts introduced by noise, sample heterogeneity, or other experimental sources. PMID:17263354

  14. Effects of elemental composition on the incorporation of dietary nitrogen and carbon isotopic signatures in an omnivorous songbird

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Pearson, Scott, F.; Levey, Douglas, J.; Greenberg, Catheryn, H.

    2003-02-28

    Pearson, S.F., D.J. Levey, C.H. Greenberg, and C.M. del Rio. 2003. Effects of elemental composition on the incorporation of dietary nitrogen and carbon isotopic signatures in an omnivorous songbird. Oecologia. 135:516-523. The use of stable isotopes to infer diet requires quantifying the relationship between diet and tissues and, in particular, knowing of how quickly isotopes turnover in different tissues and how isotopic concentrations of different food components change (discriminate) when incorporated into consumer tissues. We used feeding trials with wild-caught yellow-rumped warblers (Dendroica coronata) to determine d15N and d13C turnover rates for blood, d15N and d13C diet-tissue discrimination factors, andmore » diet-tissue relationships for blood and feathers. After 3 weeks on a common diet, 36 warblers were assigned to one of four diets differing in the relative proportion of fruit and insects. Plasma half-life estimates ranged from 0.4 to 0.7 days for d13C and from 0.5 to 1.7 days for d15N. Half-life did not differ among diets. Whole blood half-life for d13C ranged from 3.9 to 6.1 days. Yellow-rumped warbler tissues were enriched relative to diet by 1.7.3.6% for nitrogen isotopes and by 1.2 to 4.3% for carbon isotopes, depending on tissue and diet. Consistent with previous studies, feathers were the most enriched and whole blood and plasma were the least enriched or, in the case of carbon, slightly depleted relative to diet. In general, tissues were more enriched relative to diet for birds with high percentages of insects. For all tissues, carbon and nitrogen isotope discrimination factors increased with carbon and nitrogen concentrations of diets. The isotopic signature of plasma increased linearly with the sum of the isotopic signature of the diet and the discrimination factor. Because the isotopic signature of tissues depends on both elemental concentration and isotopic signature of the diet, attempts to reconstruct diet from stable isotope

  15. [Seasonality and contribution to acid rain of the carbon abundance in rainwater].

    PubMed

    Xu, Tao; Song, Zhi-guang; Liu, Jun-feng; Wang, Cui-ping

    2008-02-01

    This paper reports the results from a study of the carbon abundance in rainwater of Guangzhou city, China. The determination of TOC, DOC, POC and PEC helps to study the seasonality of carbon abundance and its contribution to the acid rain. The results display the fact that the average contents of TOC, DOC, POC and PEC are 7.10 mg/L, 3.58 mg/L, 3.60 mg/L and 0.72 mg/L, respectively. These results confirm the deep effect of the organic pollutant to the rain. The seasonality exists in the carbon abundance of rainwater. The contents of TOC and DOC are up to the maximum in spring and the minimum in summer; the contribution of POC to TOC in summer is obviously higher than that in other seasons; and the relative content of POC is clearly higher in dry season than that in wet season. The seasonality reflects the more emission of the total pollutant in spring and the solid particle pollutant in summer than those in other seasons. Moreover, the emission of the organic pollutant from the mobile vehicles is more obvious in dry season than that in wet season. The contents of TOC and DOC have the negative correlation to the pH values, which confirms the contribution effect of the organic pollutant, such as vehicle emission, to the acid rain.

  16. Triple Oxygen and Clumped Isotopes in Synthetic and Natural Carbonates: Implications for Paleoclimate and Paleohydrology Studies

    NASA Astrophysics Data System (ADS)

    Laskar, A. H.; Rangarajan, R.; Liang, M. C.

    2016-12-01

    Conventional oxygen isotope (δ18O) has widely been used for paleoclimate studies. However, multiple influencing factors such as temperature, precipitation and kinetic effects during carbonate precipitation complicate the interpretation of δ18O data sometimes. Triple oxygen isotope (Δ17O) in carbonates could be sensitive to kinetic effect occur during its precipitation in water. Carbonates may also record the Δ17O signature of the parent waters, providing a basis in the natural carbonates for identifying kinetic processes such as rapid degassing at lower relative humidity inside a cave during speleothem deposition. Clumped isotopes (Δ47) in carbonates give the formation temperatures of the carbonates if precipitated under isotopic equilibrium. The first goal of the study is to explore the applicability of Δ17O for paleohydrolocial studies. The second is to reconstruct paleotemperature with suitable natural carbonates using Δ47values. This is a rare paleoclimate study utilizing two sophisticated new tools. CO2 produced from carbonates by acid digestion was used for both Δ47 and Δ17O analysis. Purified CO2 samples were directly introduced into the Mass spectrometer (MAT 253) for clumped isotope analysis [1] and CO2-O2 exchange method in presence of platinum for Δ17O analysis [2,3]. We measured Δ47 and Δ17O values in synthetic carbonates precipitated at different temperatures (10-90 oC) and Δ17O values in the water from which the carbonate precipitated. We observed consistent Δ47 values in the carbonates while Δ17O were found to vary. Probably a proper slope (between δ18O and δ17O) selection for carbonates would give consistent results. We also measured Δ47 and Δ17O in modern and well dated speleothems from Chinese and Indian caves to study the paleohydrology and paleotemperature. Δ47 and Δ17O were also measured in modern natural carbonate depositions such as corals, foraminifer and marbles to explore their potentials for paleoclimate studies

  17. Hyperfine Induced Transitions as Diagnostics of Low Density Plasmas and Isotopic Abundance ratios.

    NASA Astrophysics Data System (ADS)

    Brage, T.; Judge, P. G.; Aboussaid, A.; Godefroid, M. R.; Jonsson, P.; Leckrone, D. S.

    1996-05-01

    We propose a new diagnostics of isotope abundance ratios and electron densities for low density plasmas, in the form of J = 0 -> J(') = 0 radiative transitions. These are usually viewed as being allowed only through two-photon decay, but they may also be induced by the hyperfine (HPF) interaction in atomic ions. This predicts a companion line to the E1] and M2 lines in the UV0.01 multiplet of ions isoelectronic to beryllium (e.g. C III, N IV, O V and Fe XXII) or magnesium (e.g. Si II, Ca IX, Fe XV and Ni XVII). As an example the companion line to the well known lambda lambda 1906.7,1908.7 lines in C III will be at 1909.597 Angstroms, but only present in the (13) C isotope (which has nuclear spin different from zero). We present new and accurate decay rates for the nsnp (3P^oJ) -> ns(2) (1S_{J('}=0)) transitions in ions of the Be (n=2) and Mg (n=3) isoelectronic sequences. We show that the HPF induced decay rates for the J = 0 -> J(') = 0 transitions are many orders of magnitude larger than those for the competing two-photon processes and, when present, are typically one or two orders of magnitude smaller than the decay rates of the magnetic quadrupole ( J = 2-> J(') = 0) transitions for these ions. We show that several of these HPF-induced transitions are of potential astrophysical interest, in ions of C, N, Na, Mg, Al, Si, K, Cr, Fe and Ni. We highlight those cases that may be of particular diagnostic value for determining isotopic abundance ratios and/or electron densities from UV or EUV emission line data. We present our atomic data in the form of scaling laws so that, given the isotopic nuclear spin and magnetic moment, a simple expression yields estimates for HPF induced decay rates. We examine some UV solar and nebular data in the light of these new results and suggest possible cases for future study. We could not find evidence for the existence of HPF induced lines in the spectra we examined, but we demonstrate that existing data have come close to providing

  18. Paradox of the peak-PCIM (Paleocene Carbon Isotope Maxima; ~57.8Ma) and Abrupt Global Warming

    NASA Astrophysics Data System (ADS)

    Harper, D. T.; Hoenisch, B.; Zachos, J. C.

    2015-12-01

    The Paleocene Carbon Isotope Maxima (PCIM; ~57.8Ma) represents a major transition in global δ13C during the late Paleocene, when the long-term positive trend in δ13C reversed from positive to negative. The peak-PCIM (~57.7Ma) has been tightly resolved in new high-resolution, astronomically-tuned benthic isotope records from IODP Sites 1209 (Pacific) and 1262 (Atlantic), which show the final phase of δ13C enrichment as abrupt (~1‰ in <100kyrs) and coinciding with a 0.5‰ decline in benthic δ18O indicative of 2-3ºC of bottom water warming, effectively marking the onset of a gradual 8Myr long warming trend [Littler et al., EPSL 2014]. Typically, during the Paleogene on orbital time scales, warming is observed during intervals of δ13C depletion, consistent with release of isotopically light carbon to the atmosphere. This event, which has the appearance of a bifurcation in the long-term coupling of climate system and the carbon cycle, poses an interesting paradox as any rapid carbon release to the atmosphere should, in theory, create a negative excursion because all of the major carbon sources are isotopically light, whether volcanic outgassing, weathering/oxidation of organic carbon, or methane release [Dunkley-Jones et al., Phil. Trans. R. Soc. A 2010]. If global, there are several testable mechanisms that may explain the shift including increase in burial flux of light carbon, a reduction in heavy carbon burial flux, or a large-scale circulation change perhaps associated with the transition of a major oceanic gateway. Using trace metal (B/Ca and Mg/Ca) and stable isotope (δ11B, δ18O, and δ13C) geochemistry, here we establish the nature of the peak-PCIM at sites from 3 different ocean basins (IODP Sites 690, 1209, and 1262) and begin to test several of the possible mechanisms for change. Mg/Ca in mixed-layer planktonic foraminifera show 2-3°C of sea surface warming coinciding with, and abrupt as, the benthic carbon isotope enrichment at all sites. Bottom

  19. Textural and isotopic evidence for Ca-Mg carbonate pedogenesis

    NASA Astrophysics Data System (ADS)

    Diaz-Hernandez, J. L.; Sánchez-Navas, A.; Delgado, A.; Yepes, J.; Garcia-Casco, A.

    2018-02-01

    Models for evaluating the terrestrial carbon cycle must take into account not only soil organic carbon, represented by a mixture of plant and animal remains, but also soil inorganic carbon, contained in minerals, mainly in calcite and dolomite. Thick soil caliches derived from weathering of mafic and ultramafic rocks must be considered as sinks for carbon storage in soils. The formation of calcite and dolomite from pedogenic alteration of volcanic tephras under an aridic moisture regime is studied in an unusually thick 3-m soil profile on Gran Canaria island (Canary Islands, Spain). The biological activity of the pedogenic environment (soil respiration) releases CO2 incorporated as dissolved inorganic carbon (DIC) in waters. It drives the formation of low-magnesian calcite and calcian dolomite over basaltic substrates, with a δ13C negative signature (-8 to -6‰ vs. V-PDB). Precipitation of authigenic carbonates in the soil is accompanied by the formation of Mg-rich clay minerals and quartz after the weathering of basalts. Mineralogical, textural, compositional, and isotopic variations throughout the soil profile studied indicate that dolomite formed at greater depths and earlier than the calcite. The isotopic signatures of the surficial calcite and deeper dolomite crusts are primary and resulted from the dissolution-precipitation cycles that led to the formation of both types of caliches under different physicochemical conditions. Dolomite formed within a clay-rich matrix through diffusive transport of reactants. It is precipitated from water with more negative δ18O values (-1.5 to -3.5‰ vs. V-SMOW) in the subsoil compared to those of water in equilibrium with surficial calcite. Thus, calcite precipitated after dolomite, and directly from percolating solutions in equilibrium with vadose water enriched in δ18O (-0.5 to +1.5‰) due to the evaporation processes. The accumulation of inorganic carbon reaches 586.1 kg m-2 in the soil studied, which means that the

  20. A Computational Framework for High-Throughput Isotopic Natural Abundance Correction of Omics-Level Ultra-High Resolution FT-MS Datasets

    PubMed Central

    Carreer, William J.; Flight, Robert M.; Moseley, Hunter N. B.

    2013-01-01

    New metabolomics applications of ultra-high resolution and accuracy mass spectrometry can provide thousands of detectable isotopologues, with the number of potentially detectable isotopologues increasing exponentially with the number of stable isotopes used in newer isotope tracing methods like stable isotope-resolved metabolomics (SIRM) experiments. This huge increase in usable data requires software capable of correcting the large number of isotopologue peaks resulting from SIRM experiments in a timely manner. We describe the design of a new algorithm and software system capable of handling these high volumes of data, while including quality control methods for maintaining data quality. We validate this new algorithm against a previous single isotope correction algorithm in a two-step cross-validation. Next, we demonstrate the algorithm and correct for the effects of natural abundance for both 13C and 15N isotopes on a set of raw isotopologue intensities of UDP-N-acetyl-D-glucosamine derived from a 13C/15N-tracing experiment. Finally, we demonstrate the algorithm on a full omics-level dataset. PMID:24404440

  1. Geochemistry of carbon and sulfur in the 2.7 Ga stromatolitic carbonate and shale (ABDP#10 core) from Meentheena, Western Australia

    NASA Astrophysics Data System (ADS)

    Tomiuka, T.; Yamaguchi, K. E.

    2014-12-01

    Earth's surface environments about 2.7 Ga ago likely experienced drastic changes such as rapid continental growth, negative excursion of organic carbon isotopes, and positive excursion of mass-independently fractionated sulfur isotopes. Discovery of biomarkers indicating cyanobacteria, although questionable, was also claimed. The coeval shallow ocean could have contained appreciable amount of molecular O2 produced by cyanobacteria, but it has been unknown whether deep sea was oxygenated by ocean circulation. In order to unravel the shallow water environment, we obtained modern-weathering-free 2.7 Ga drilcore samples of stromatolitic carbonate and shale by Archean Biosphere Drilling Project (ABDP#10 core) in Meentheena, NE Western Australia. The purpose of this study is to extract information regarding the surface ocean chemistry by abundance (of various species) and corresponding stable isotope compositions of carbon and sulfur. Based on mass balance calculation, we obtained a much reduced fraction of organic carbon to total carbon (forg) to be 0.11 (c.f., Phanerozoic average is 0.2), suggesting that aerobic and/or anaerobic decomposition of organic matter was vigorous. The very low δ13Corg values suggest carbon recycling involving methanogenesis by methanogen (e.g., 2CH2O → CH4 + CO2) accompanied by large isotope fractionation. Generated CH4 was oxidized by methylotroph to CO2, which was reused to form organic matter by biochemical processes such as photosynthesis. Either O2 or SO42- was required to facilitate CH4 oxidation, suggesting availability of oxidized species in the 2.7 Ga shallow sea environment. Abundance of Spy with near zero δ34Spy values suggest syndepositional and/or diagenetic formation of bacteriogenic pyrite utilizing sulfate formed by oxidation of mantle-derived sulfur (δ34S ≈ 0‰). A plot of Spy vs. Corg abundance shows a trend falling between a Phanerozoic normal marine trend (Spy/Corg = 0.36) and a freshwater trend (Spy << Corg

  2. Magnesium isotope fractionation in biogenic and abiogenic carbonates: implications for paleoenvironmental proxies

    NASA Astrophysics Data System (ADS)

    Saenger, Casey; Wang, Zhengrong

    2014-04-01

    Geochemical variations in marine biogenic carbonates that are preserved in the geological record serve as proxies of past environmental change. However, interpreting most proxies is complicated by biologically-mediated vital effects, highlighting the need to develop new tools for reconstructing paleoenvironmental change. Recently, magnesium (Mg) isotope variability in carbonates has been explored extensively to determine its utility as a paleoenvironmental proxy. We review the results of these works, which have yielded valuable information on the factors affecting Mg isotope fractionation between carbonates and solution (Δ26Mgcarb-sol) in biogenic and abiogenic carbonate minerals. Strong evidence exists for a mineralogical control on Δ26Mgcarb-sol, with the negative offset from 0‰ following the sequence aragonite < dolomite < magnesite < calcite. Abiogenic carbonates precipitated from solutions with relatively high Mg/Ca ratios (>˜3 mol/mol) and saturation states (Ω >˜3) that are similar to seawater suggest that Δ26Mgcarb-sol has a temperature dependence of ˜0.01‰ °C-1 and is insensitive to precipitation rate. In contrast, a significant precipitation rate dependence is observed in calcites precipitated from solutions with relatively low Mg/Ca ratios (<˜3 mol/mol) and saturation states (Ω <˜3). This difference likely reflects varying mineral growth mechanisms and we discuss the degree to which Δ26Mgcarb-sol may be affected by factors such as fluid inclusions, amorphous calcium carbonate precursors, ion attachment/detachment kinetics, surface entrapment and Mg speciation. High-Mg calcite organisms, which likely precipitate from relatively unmodified seawater, also exhibit a temperature dependence of ˜0.01‰ °C-1, albeit sometimes with a systematic offset toward smaller fractionations. In contrast, strong vital effects in low-Mg calcite organisms, which exclude Mg from their calcifying fluids, lead to Δ26Mgcarb-sol values that exhibit no clear

  3. Study on strontium isotope abundance-ratio measurements by using a 13-MeV proton beam

    NASA Astrophysics Data System (ADS)

    Jeong, Cheol-Ki; Jang, Han; Lee, Goung-Jin

    2016-09-01

    The Rb-Sr dating method is used in dating Paleozoic and Precambrian rocks. This method measures the 87Rb and the 87Sr concentrations by using thermal ionization mass spectrometry (TIMS) [J. Hefne et al., Inter. J. Phys. Sci. 3(1), 28 (2008)]. In addition, it calculates the initial 87Sr/86Sr ratio to increase the reliability of Rb-Sr dating. In this study, the 87Sr/86Sr ratio was measured by using a 13-MeV proton accelerator. Proton kinetic energies are in the range of tens of megaelectronvolts, and protons have large absorption cross-sections for ( p, n) reactions with most substances. After absorbing a proton with such a high kinetic energy, an element is converted into a nuclide with its atomic number increased by one via nuclear transmutation. These nuclides usually have short half-lives and return to the original state through radioactive decay. When a strontium sample is irradiated with protons, nuclear transmutation occurs; thus, the strontium isotope present in the sample changes to a yttrium isotope, which is an activated radioisotope. Based on this, the 87Sr/86Sr ratio was calculated by analyzing the gamma-rays emitted by each yttrium isotope. The KIRAMS-13 cyclotron at the Cyclotron Center of Chosun University, where 13-MeV protons can be extracted, was utilized in our experiment. The 87Sr/86Sr isotope ratio was computed for samples irradiated with these protons, and the result was similar to the isotope ratio for the Standard Reference Material, i.e., 98.2 ± 3.4%. As part of the analysis, proton activation analyses were performed using 13-MeV protons, and the experimental results of this research suggest a possible approach for measuring the strontium-isotope abundance ratio of samples.

  4. Carbon Stable Isotope Fractionation of Sulfamethoxazole during Biodegradation by Microbacterium sp. Strain BR1 and upon Direct Photolysis.

    PubMed

    Birkigt, Jan; Gilevska, Tetyana; Ricken, Benjamin; Richnow, Hans-Hermann; Vione, Davide; Corvini, Philippe F-X; Nijenhuis, Ivonne; Cichocka, Danuta

    2015-05-19

    Carbon isotope fractionation of sulfamethoxazole (SMX) during biodegradation by Microbacterium sp. strain BR1 (ipso-hydroxylation) and upon direct photolysis was investigated. Carbon isotope signatures (δ(13)C) of SMX were measured by LC-IRMS (liquid chromatography coupled to isotope ratio mass spectrometry). A new LC-IRMS method for the SMX metabolite, 3-amino-5-methylisoxazole (3A5MI), was established. Carbon isotope enrichment factors for SMX (ε(C)) were -0.6 ± 0.1‰ for biodegradation and -2.0 ± 0.1‰ and -3.0 ± 0.2‰ for direct photolysis, at pH 7.4 and pH 5, respectively. The corresponding apparent kinetic isotope effects (AKIE) for ipso-hydroxylation were 1.006 ± 0.001; these fall in the same range as AKIE in previously studied hydroxylation reactions. The differences in SMX and 3A5MI fractionation upon biotic and abiotic degradation suggest that compound specific stable isotope analysis (CSIA) is a suitable method to distinguish SMX reaction pathways. In addition, the study revealed that the extent of isotope fractionation during SMX photolytic cleavage is pH-dependent.

  5. Evaluating North Sea carbon sources using radiogenic (224Ra and 228Ra) and stable carbon isotope (DI13C) tracers

    NASA Astrophysics Data System (ADS)

    Burt, William; Thomas, Helmuth; Hagens, Mathilde; Brenner, Heiko; Paetsch, Johannes; Clargo, Nikki

    2015-04-01

    In the North Sea, much uncertainty still exists regarding the role of boundary fluxes (e.g. benthic input from sediments or lateral inputs from the coastline) in the overall biogeochemical cycling of the system. The stable carbon isotope signature of dissolved inorganic carbon (δ13C-DIC) is a common tool for following transformations of carbon in the water column and identifying carbon sources and sinks. Here, analyses of the first basin-wide observations of δ13C-DIC reveal that a balance between biological production and respiration, as well as a freshwater input near the European continental coast, predominantly control surface distributions in the North Sea. A strong relationship between the biological component of DIC (DICbio) and δ13C-DIC is then used to quantify the metabolic DIC flux associated with changes in the carbon isotopic signature. Correlations are also found between δ13C-DIC and naturally-occurring Radium isotopes (224Ra and 228Ra), which have well-identified sources from the seafloor and coastal boundaries. The relationship between δ13C-DIC and the longer-lived 228Ra isotope (half-life = 5.8 years) is used to derive a metabolic DIC flux from the European continental coastline. 228Ra is also shown to be a highly effective tracer of North Sea total alkalinity (TA) compared to the more conventional use of salinity as a tracer. Coastal alkalinity inputs are calculated using relationships with 228Ra, and ratios of DIC and TA suggest denitrification as the main metabolic pathway for the formation of these coastal inputs. Finally, coastal TA inputs are translated into inputs of protons to quantify their impact on the buffering capacity of the Southern North Sea.

  6. Rates of carbonate soil evolution from carbon, U- and Th-series isotope studies: Example of the Astian sands (SE France)

    NASA Astrophysics Data System (ADS)

    Barbecot, Florent; Ghaleb, Bassam; Hillaire-Marcel, Claude

    2015-04-01

    In carbonate rich soils, C-isotopes (14C, 13C) and carbonate mass budget may inform on centennial to millennial time scale dissolution/precipitation processes and weathering rates, whereas disequilibria between in the U- and Th-decay series provide tools to document high- (228Ra-228Th-210Pb) to low- (234U, 230Th, 231Pa, 226Ra) geochemical processes rate, covering annual to ~ 1Ma time scales, governing both carbonate and silicate soil fractions. Because lithology constitutes a boundary condition, we intend to illustrate the behavior of such isotopes in soils developed over Astian sands formation (up to ~ 30% carbonate) from the Béziers area (SE France). A >20 m thick unsaturated zone was sampled firstly along a naturally exposed section, then in a cored sequence. Geochemical and mineralogical analyses, including stable isotopes and 14C-measurements, were complemented with 228U, 234U, 230Th, 226Ra, 210Pb and 228Th, 232Th measurements. Whereas the upper 7 m depict geochemical and isotopic features forced by dissolution/precipitation processes leading to variable radioactive disequilibria, but overall deficits in more soluble elements of the decay series, the lower part of the sequence shows strong excesses in 234U and 230Th over parent isotopes (i.e., 238U and 234U, respectively). These features might have been interpreted as the result of successive phases of U-loss and gains. However, 226Ra and 230Th are in near-equilibrium, thus leading to conclude at a more likely slow enrichment process in both 234Th(234U) and 230Th, which we link to dissolved U-decay during groundwater recharge events. In addition, 210Pb deficits (vs parent 226Ra) are observed down to 12 m along the natural outcropping section and below the top-soil 210Pb-excess in the cored sequence, due to gaseous 222Rn-diffusion over the cliff outcrop. Based on C-isotope and chemical analysis, reaction rates at 14C-time scale are distinct from those estimates at the short- or long-lived U-series isotopes

  7. Using Oxygen and Carbon Isotopic Signatures in Order to Infer Climatic and Dietary Information in Roman Edessa, Greece

    NASA Astrophysics Data System (ADS)

    Michael, Dimitra-Ermioni; Dotsika, Elissavet

    2017-12-01

    Even though many isotopic studies have been conducted on ancient populations from Greece for the purpose of dietary reconstruction; mostly through carbon and nitrogen isotopic signals of bone collagen, less attention has been given to the utility of apatite signatures (oxygen and carbon) as dietary and palaeoenvironmental tools. Moreover, until recently the isotopic signal of tooth enamel for both the purposes of environmental and dietary reconstructions has been rarely assessed in ancient Greek societies. Therefore, the present study aims to provide with novel isotopic information regarding Edessa; a town in Northern Greece, during the Roman period. The current study primarily aims to explore the possible differentiation between the present climatic conditions in Edessa in relation to those occurring at the Roman period. Secondly, this study aims to reveal the significant utility of enamel isotopic signatures (carbon and oxygen) in palaeoenvironmental and palaeodietary studies regarding ancient human remains. The isotopic analyses have been conducted at the Stable Isotope and Radiocarbon Unit of INN, NCSR “Demokritos”. The population of Roman Edessa (2nd-4th c. AD) consists of 22 individuals, providing with 19 bone samples and 16 enamel ones. The mean enamel oxygen value is at -7.7 ±1.1 %0, the bone apatite mean oxygen value at -9.2 ±1.9 %0, and finally the mean carbon enamel value is at -11.7 ±1.2 %0. Oxygen values probably indicate that Edessa had a cooler climate during the Roman times in relation to present conditions, even though more research should be carried out in order to be more certain. In addition, the possible existence of non-local individuals has been revealed through the oxygen teeth enamel-bone apatite spacing. Finally, the carbon enamel signature has pointed out possible differentiations between the adult and the juvenile diet. Based on Edessa’s findings, the stated study strongly encourages the enamel oxygen and carbon isotopic signals

  8. The relation between isotopic composition of argon and carbon in natural gases

    NASA Technical Reports Server (NTRS)

    Gavrilov, Y. Y.; Zhurov, Y. A.; Teplinskiy, G. I.

    1977-01-01

    The methods and results of determination of the argon and carbon isotope compositions of hydrocarbon gases of Mezozoic complexes of Western Siberia are presented. Based on the Ar-36, Ar-40, C-12, C-13 content of the various deposits and on the presumed mechanisms of entry of these isotopes into the deposits, it is concluded that formation of natural gas in some deposits included vertical migration from a lower complex.

  9. Carbon isotope exchange in the system CO 2-CH 4 at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Horita, Juske

    2001-06-01

    Carbon isotope exchange was investigated for the system CO 2-CH 4 at 150 to 600°C in the presence of several potential catalysts by use of isotopically normal or 13C-enriched gases. Silica gel, graphite, molecular sieve Linde 4A, magnetite, and hematite oxidized small amounts of CH 4 in starting CO 2-CH 4 mixtures to CO and CO 2 but failed to enhance the net rate of carbon isotope exchange between CO 2 and CH 4, even after 169 to 1833 h at 400 to 500°C. In contrast, several commercial transition-metal catalysts (Ni, Pd, Rh, and Pt) promoted reactions significantly toward chemical and isotopic equilibrium. With the Ni catalyst, the attainment of carbon isotopic equilibrium between CO 2 and CH 4 was demonstrated for the first time at temperatures from 200 to 600°C by complete isotopic reversal from opposite directions. The experimentally determined carbon isotope fractionation factors between CO 2 and CH 4 (10 3lnα) were similar to, but slightly greater than (0.7-1.1‰, 0.89‰ on average), those of statistical-mechanical calculations by Richet et al. (1977). The experimental results can be described by the following equation between 200 and 600°C only: 10 3lnα(CO 2-CH 4) = 26.70 - 49.137(10 3/T) + 40.828(10 6/T 2) - 7.512(10 9/T 3) (T = 473.15-873.15 K, 1σ = ±0.14‰, n = 44). Alternatively, an equation generated by fitting Richet et al. (1977) data in the temperature range from 0 to 1300°C can be modified by adding +0.89‰ to its constant; 10 3lnα(CO 2-CH 4) = 0.16 + 11.754(10 6/T 2) - 2.3655(10 9/T 3) + 0.2054(10 12/T 4) (T = 273-1573 K, 1σ = ±0.21‰, n = 44). This and other recent experimental studies in the literature demonstrate that transition metals, which are widespread in many natural materials, can catalyze reactions among natural gases at relatively low temperatures (≤200°C). The role of natural catalysts, "geocatalysts," in the abiogenic formation of methane, hydrocarbons, and simple organic compounds has important implications, ranging

  10. Automated determination of the stable carbon isotopic composition (δ13C) of total dissolved inorganic carbon (DIC) and total nonpurgeable dissolved organic carbon (DOC) in aqueous samples: RSIL lab codes 1851 and 1852

    USGS Publications Warehouse

    Révész, Kinga M.; Doctor, Daniel H.

    2014-01-01

    The purposes of the Reston Stable Isotope Laboratory (RSIL) lab codes 1851 and 1852 are to determine the total carbon mass and the ratio of the stable isotopes of carbon (δ13C) for total dissolved inorganic carbon (DIC, lab code 1851) and total nonpurgeable dissolved organic carbon (DOC, lab code 1852) in aqueous samples. The analysis procedure is automated according to a method that utilizes a total carbon analyzer as a peripheral sample preparation device for analysis of carbon dioxide (CO2) gas by a continuous-flow isotope ratio mass spectrometer (CF-IRMS). The carbon analyzer produces CO2 and determines the carbon mass in parts per million (ppm) of DIC and DOC in each sample separately, and the CF-IRMS determines the carbon isotope ratio of the produced CO2. This configuration provides a fully automated analysis of total carbon mass and δ13C with no operator intervention, additional sample preparation, or other manual analysis. To determine the DIC, the carbon analyzer transfers a specified sample volume to a heated (70 °C) reaction vessel with a preprogrammed volume of 10% phosphoric acid (H3PO4), which allows the carbonate and bicarbonate species in the sample to dissociate to CO2. The CO2 from the reacted sample is subsequently purged with a flow of helium gas that sweeps the CO2 through an infrared CO2 detector and quantifies the CO2. The CO2 is then carried through a high-temperature (650 °C) scrubber reactor, a series of water traps, and ultimately to the inlet of the mass spectrometer. For the analysis of total dissolved organic carbon, the carbon analyzer performs a second step on the sample in the heated reaction vessel during which a preprogrammed volume of sodium persulfate (Na2S2O8) is added, and the hydroxyl radicals oxidize the organics to CO2. Samples containing 2 ppm to 30,000 ppm of carbon are analyzed. The precision of the carbon isotope analysis is within 0.3 per mill for DIC, and within 0.5 per mill for DOC.

  11. Isotopically Light Organic Carbon in Phanerozoic Black Shales: Diagenetic, Source, or Environmental Signal?

    NASA Astrophysics Data System (ADS)

    Meyers, P. A.

    2011-12-01

    A curious depletion of 13C in the organic matter of marine black shales has been widely recognized ever since the advent of carbon isotope measurements half a century ago. Paleozoic and Mesozoic black shales commonly have del13C values between -29 and -26 permil, whereas modern marine organic matter has values between -22 and -18 permil. The black shale values mimic those of continental organic matter, yet sedimentary settings and Rock-Eval results indicate that the organic matter is marine in origin. This presentation will overview and discuss hypotheses to explain the isotopically light values of the black shales. First, the preferential removal of isotopically heavier organic matter components such as carbohydrates by diagenesis will be examined and shown to be wanting. Second, the possible oxidation of isotopically light methane released from clathrates that would have altered the DIC pool available to phytoplankton will be considered and also be found unlikely. A third possibility - that greater concentrations of CO2 in the greenhouse atmospheres that corresponded with deposition of many black shales allowed greater discrimination against 13C during photosynthesis - will be evaluated from del13C values of bulk carbon and of algal and land-plant biomarker molecules. Finally, the possibility that stronger stratification of the surface ocean may have magnified photic zone recycling of organic matter and reincorporation of its isotopically light carbon into fresh biomass will be considered. Although the fourth possibility is contrary to the conditions of vertical mixing of nutrients that exist in modern upwelling systems and that are responsible for their high productivity, it is consistent with the strongly stratified conditions that accompanied the high productivity that produced the Pliocene-Pleistocene sapropels of the Mediterranean Sea. Because the sapropels and most Phanerozic black shales share del15N values near 0 permil, nitrogen fixation evidently was

  12. Calcium and Oxygen Isotopic Composition of Calcium Carbonates

    NASA Astrophysics Data System (ADS)

    Niedermayr, Andrea; Eisenhauer, Anton; Böhm, Florian; Kisakürek, Basak; Balzer, Isabelle; Immenhauser, Adrian; Jürgen Köhler, Stephan; Dietzel, Martin

    2016-04-01

    Different isotopic systems are influenced in multiple ways corresponding to the crystal structure, dehydration, deprotonation, adsorption, desorption, isotope exchange and diffusion processes. In this study we investigated the structural and kinetic effects on fractionation of stable Ca- and O-isotopes during CaCO3 precipitation. Calcite, aragonite and vaterite were precipitated using the CO2 diffusion technique[1]at a constant pH of 8.3, but various temperatures (6, 10, 25 and 40° C) and precipitation rates R (101.5 to 105 μmol h-1 m-2). The calcium isotopic fractionation between solution and vaterite is lower (Δ44/40Ca= -0.10 to -0.55 ‰) compared to calcite (-0.69 to -2.04 ‰) and aragonite (-0.91 to -1.55 ‰). In contrast the fractionation of oxygen isotopes is highest for vaterite (32.1 ‰), followed by aragonite (29.2 ‰) and calcite (27.6 ‰) at 25° C and equilibrium. The enrichment of 18O vs. 16O in all polymorphs decreases with increasing precipitation rate by around -0.7 ‰ per log(R). The calcium isotopic fractionation between calcite/ vaterite and aqueous Ca2+ increases with increasing precipitation rate by ˜0.45 ‰ per log(R) and ˜0.1 ‰ per log(R) at 25° C and 40° C, respectively. In contrast the fractionation of Ca-isotopes between aragonite and aqueous Ca2+ decreases with increasing precipitation rates. The large enrichment of 18O vs. 16O isotopes in carbonates is related to the strong bond of oxygen to the small and highly charged C4+-ion. In contrast equilibrium isotopic fractionation between solution and calcite or vaterite is nearly zero as the Ca-O bond length is similar for calcite, vaterite and the hydrated Ca. Aragonite incorporates preferentially the lighter 40Ca isotope as it has very large Ca-O bonds in comparison to the hydrated Ca. At the crystal surface the lighter 40Ca isotopes are preferentially incorporated as dehydration and diffusion of lighter isotopes are faster. Consequently, the surface becomes enriched in 40

  13. A new record of the Paleocene Carbon Isotope Maximum from the Mississippi Embayment

    NASA Astrophysics Data System (ADS)

    Platt, B. F.; Gerweck, E. D.

    2017-12-01

    The Paleocene-Eocene interval is well known as a time of climatic transitions, especially hyperthermals associated with disturbances in the carbon cycle that are used as proxies for impacts of projected anthropogenic global climate change. A recent roadcut in Benton County, Mississippi exposes a disconformity between the Paleocene Naheola Formation and the Eocene Meridian Sand. The disconformity is developed on a thick, kaolinitic paleosol, which we interpret as a mature Oxisol that supported tropical rainforest vegetation (as evidenced by associated well preserved leaf fossils). The nature of the paleosol at the disconformity led us to hypothesize that the strata might contain evidence of the Paleocene Eocene Thermal Maximum (PETM). We sampled two Mississippi Mineral Resources Institute (MMRI) cores from the equivalent stratigraphic interval from Benton and Tippah Counties, Mississippi, for bulk organic carbon stable isotopes at 25-cm intervals. Results showed no evidence of the negative excursion characteristic of the PETM. Instead, we found a gradual upsection enrichment that we interpret as the positive trend characteristic of the lower Paleocene Carbon Isotope Maximum (PCIM). This is reasonable based on published biostratigraphy and absolute ages from elsewhere in the Naheola Formation. Further analyses will be performed to determine whether the PCIM trend continues throughout the remainder of the core. The identification of the PCIM in Mississippi Embayment (ME) sediments is important because stable carbon isotope data may be useful for improving chronostratigraphy in the ME. Also, the PCIM is associated with a gradual warming trend as indicated by previously published stable oxygen isotopes from benthic foraminifera. Studying successive ME paleosols throughout the PCIM may yield information about the impacts of gradual atmospheric warming on soils and associated terrestrial systems.

  14. VizieR Online Data Catalog: Carbon-enhanced metal-poor (CEMP) star abundances (Yoon+, 2016)

    NASA Astrophysics Data System (ADS)

    Yoon, J.; Beers, T. C.; Placco, V. M.; Rasmussen, K. C.; Carollo, D.; He, S.; Hansen, T. T.; Roederer, I. U.; Zeanah, J.

    2017-03-01

    We have endeavored to compile a list that is as complete as possible of carbon-enhanced metal-poor (CEMP); CEMP-s (and CEMP-r/s) and CEMP-no stars having [Fe/H]<-1.0 and [C/Fe]>=+0.7 with available high-resolution spectroscopic abundance information. We have only considered stars with claimed detections or lower limits for carbon, along with several critical elemental-abundance ratios, such as [Ba/Fe] and [Eu/Fe]. The great majority of our sample comes from the literature compilation of Placco+ (2014, J/ApJ/797/21). See section 2 for further details. (2 data files).

  15. Seasonal variations in the stable carbon isotopic signature of biogenic methane in a coastal sediment

    NASA Technical Reports Server (NTRS)

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

    1986-01-01

    Systematic seasonal variations in the stable carbon isotopic signature of methane gas occur in the anoxic sediments of Cape Lookout Bight, a lagoonal basin on North Carolina's Outer Banks. Values for the carbon isotope ratio of methane range from -57.3 per mil during summer to -68.5 per mil during winter in gas bubbles with an average methane content of 95 percent. The variations are hypothesized to result from changes in the pathways of microbial methane production and cycling of key substrates including acetate and hydrogen. The use of stable isotopic signatures to investigate the global methane cycle through mass balance calculations, involving various sediment and soil biogenic sources, appears to require seasonally averaged data from individual sites.

  16. A carbon and nitrogen isotope study of carbonaceous vein material in ureilite meteorites

    NASA Technical Reports Server (NTRS)

    Russell, S. S.; Arden, J. W.; Franchi, I. A.; Pillinger, C. T.

    1993-01-01

    The ureilite meteorite group is known to be rich in carbon in the form of graphite/diamond veins that are associated with planetary type noble gases. This paper reports preliminary data from a systematic study of the carbon and nitrogen isotopic composition of this carbonaceous vein material. A previous study focused on the whole rock signatures and reported that the carbon inventory appeared to be dominated by the graphitic/diamond intergrowths, whereas the nitrogen was clearly composed of several distinct components including one that was isotopically light, possibly associated with the carbonaceous material. Recent studies have demonstrated that diamonds in the solar system formed in many different environments. C and N measurements from ureilitic diamond made in a similar way would be a useful addition to this overall study. The methods used for isolating diamonds of possible presolar origin from primitive meteorites are equally applicable to the processing of carbon bearing components in the ureilite group so that their stable isotopic composition can be determined. Herein we discuss conjoint C and N stepped combustion measurements made on crushed whole rock ureilite samples that have been treated with 1M HCl/9M HF to dissolve silicate and free metal. In addition, two samples have been further treated with oxidizing acids to leave a diamond rich residue.

  17. Shear heating and solid state diffusion: Constraints from clumped isotope thermometry in carbonate faults

    NASA Astrophysics Data System (ADS)

    Siman-Tov, S.; Affek, H. P.; Matthews, A.; Aharonov, E.; Reches, Z.

    2015-12-01

    Natural faults are expected to heat rapidly during seismic slip and to cool quite quickly after the event. Here we examine clumped isotope thermometry for its ability to identify short duration elevated temperature events along frictionally heated carbonate faults. This method is based on measured Δ47 values that indicate the relative atomic order of oxygen and carbon stable isotopes in the calcite lattice, which is affected by heat and thus can serve as a thermometer. We examine three types of calcite rock samples: (1) samples that were rapidly heated and then cooled in static laboratory experiments, simulating the temperature cycle experienced by fault rock during earthquake slip; (2) limestone samples that were experimentally sheared to simulate earthquake slip events; and (3) samples taken from principle slip zones of natural carbonate faults that likely experienced earthquake slip. Experimental results show that Δ47 values decrease rapidly (in the course of seconds) and systematically both with increasing temperature and shear velocity. On the other hand, carbonate shear zone from natural faults do not show such Δ47 reduction. We propose that the experimental Δ47 response is controlled by the presence of high-stressed nano-grains within the fault zone that can reduce the activation energy for diffusion by up to 60%, and thus lead to an increased rate of solid-state diffusion in the experiments. However, the lowering of activation energy is a double-edged sword in terms of clumped isotopes: In laboratory experiments, it allows for rapid disordering so that isotopic signal appears after very short heating, but in natural faults it also leads to relatively fast isotopic re-ordering after the cessation of frictional heating, thus erasing the high temperature signature in Δ47 values within relatively short geological times (<1 Ma).

  18. Stable hydrogen and carbon isotope ratios of extractable hydrocarbons in the Murchison meteorite

    NASA Technical Reports Server (NTRS)

    Krishnamurthy, R. V.; Epstein, S.; Pizzarello, S.; Cronin, J. R.; Yuen, G. U.

    1991-01-01

    A fairly fool-proof method to ensure that the compounds isolated from meteorites are truly part of the meteorites and not an artifact introduced by exposure to the terrestrial environment, storage, or handling is presented. The stable carbon and hydrogen isotope ratios in several of the chemical compounds extracted from the Murchison meteorite were measured. The results obtained by studying the amino acids in this meteorite gave very unusual hydrogen and carbon isotope ratios. The technique was extended to the different classes of hydrocarbons and the hydrocarbons were isolated using a variety of separation techniques. The results and methods used in this investigation are described in this two page paper.

  19. The carbon-isotopic composition of Proterozoic carbonates: Riphean successions from northwestern Siberia (Anabar Massif, Turukhansk Uplift)

    NASA Technical Reports Server (NTRS)

    Knoll, A. H.; Kaufman, A. J.; Semikhatov, M. A.

    1995-01-01

    Thick carbonate-dominated successions in northwestern Siberia document secular variations in the C-isotopic composition of seawater through Mesoproterozoic and early Neoproterozoic (Early to early Late Riphean) time. Mesoproterozoic dolomites of the Billyakh Group, Anabar Massif, have delta 13C values that fall between 0 and -1.9 permil versus PDB, with values in the upper part of the succession (Yusmastakh Formation) consistently higher than those of the lower (Ust'-Il'ya and Kotuikan formations). Consistent with available biostratigraphic and radiometric data, delta 13C values for Billyakh carbonates compare closely with those characterizing early Mesoproterozoic carbonates (about 1600-1200 Ma) worldwide. In contrast, late Mesoproterozoic to early Neoproterozoic limestones and dolomites in the Turukhansk Uplift exhibit moderate levels of secular variation. Only the lowermost carbonates in the Turukhansk succession (Linok Formation) have delta 13C values that approximate Billyakh values. Higher in the Turukhansk succession, delta 13C values vary from -2.7 to +4.6 permil (with outliers as low as -5.0 permil interpreted as diagentically altered). Again, consistent with paleontological and radiometric data, these values compare well with isotopic values from 1200 to 850 Ma successions elsewhere. Five sections measured in different parts of the Turukhansk basin show nearly identical patterns of variation, confirming that carbonate delta 13C correlates primarily with time and not facies. The Siberian sections illustrate the potential of integrated biostratigraphic and chemostratigraphic data in the intra- and interbasinal correlation of Mesoproterozoic and early Neoproterozoic rocks.

  20. Chemical changes and carbon isotope variations in a cross-section of a large Miocene gymnospermous log

    USGS Publications Warehouse

    Bates, A.L.; Spiker, E. C.

    1992-01-01

    The cross-sectional radius of a 3-m (diam.) brown coal gymnospermous log of Miocene age, previously analyzed for carbohydrate and lignin methoxyl content by solid-state 13C nuclear magnetic resonance spectroscopy, was examined using stable carbon isotopic ratios in order to determine if the isotopic composition could be related to chemical changes or to radial position. This study found a possible relationship between ??13C-values and radial position; however, these changes cannot be linked to carbohydrate content and are probably attributable to changing growth conditions during the lifetime of the tree. An apparent linear relationship between the changes in carbohydrate content after sodium para-periodate treatment and corresponding changes in the ??13C-values indicates constant isotopic fractionation between lignin and carbohydrates along the cross-sectional radius. This result indicates that diagenesis has not produced any significant change in the lignin-carbohydrate carbon isotopic fractionation or, alternatively, that diagenesis has erased any fractionation pattern that once existed. A sample of fresh wood from another gymnospermous species was analyzed by the same methods and found to have lignin-carbohydrate carbon isotopic fractionation significantly different from that of the Miocene log section samples, suggesting that differences may be species-related or that the complex mixture of carbohydrates in the fresh wood was isotopically different from that of the degraded wood, and the whole Miocene log was uniformly altered. ?? 1992.

  1. The application of carbon isotope discrimination of charred wheat grains to reconstruct Late Holocene climate change and identify water management strategy in northwest China

    NASA Astrophysics Data System (ADS)

    Wang, W.; An, C.; Duan, F.; Zhao, Y.; Cao, Z.

    2017-12-01

    The AMS 14C dating and corresponding carbon stable isotope datum of charred wheat grains from archaeological sites in northwest China especially Hexi Corridor and Xinjiang have been collected widely to study its potential roles in reconstructing past climate change and identifying water management strategies through comparison with integrated regional humidity index, carbon isotope data of wheat grown under modern irrigation environment from study area and Mediterranean charred wheat carbon isotope data. The results suggest (1) carbon isotope discrimination values of charred wheat both in Hexi corridor and Xinjiang could respond well to regional moisture change, and there are also good positive correlation relationship between them (2) in contrast to consistent relationship between decreased carbon isotope discrimination values of charred wheat and dry climate condition, increased carbon isotope discrimination values does not represent wetter regional climate completely and may also reveal effects of human irrigation activities. The higher carbon isotope discrimination value of charred wheat which occurred in the Hexi Corridor from 4000 to 3850 a BP, 2100 a BP and 550 a BP and in Tianshan area of Xinjiang from 3730 a BP could be likely to be related with human activities (3) the carbon isotope discrimination value of charred wheat may have a certain limit which is generally not beyond 19‰. And this upper limit could influence its availability in reflecting abrupt change of precipitation/humidity especially rapid wetter trend. We conclude that carbon isotope analysis of charred wheat grains could be a good tool for reconstructing past climate change and identifying ancient irrigation practices.

  2. EasyDelta: A spreadsheet for kinetic modeling of the stable carbon isotope composition of natural gases

    NASA Astrophysics Data System (ADS)

    Zou, Yan-Rong; Wang, Lianyuan; Shuai, Yanhua; Peng, Ping'an

    2005-08-01

    A new kinetic model and an Excel © spreadsheet program for modeling the stable carbon isotope composition of natural gases is provided in this paper. The model and spreadsheet could be used to describe and predict the variances in stable carbon isotope of natural gases under both experimental and geological conditions with heating temperature or geological time. It is a user-friendly convenient tool for the modeling of isotope variation with time under experimental and geological conditions. The spreadsheet, based on experimental data, requires the input of the kinetic parameters of gaseous hydrocarbons generation. Some assumptions are made in this model: the conventional (non-isotope species) kinetic parameters represent the light isotope species; the initial isotopic value is the same for all parallel chemical reaction of gaseous hydrocarbons generation for simplicity, the re-exponential factor ratio, 13A/ 12A, is a constant, and both heavy and light isotope species have similar activation energy distribution. These assumptions are common in modeling of isotope ratios. The spreadsheet is used for searching the best kinetic parameters of the heavy isotope species to reach the minimum errors compared with experimental data, and then extrapolating isotopic changes to the thermal history of sedimentary basins. A short calculation example on the variation in δ13C values of methane is provided in this paper to show application to geological conditions.

  3. Radium isotope quartet in groundwater as a proxy for identification of aquifer rocks and mechanisms of water-rock interactions: examples from the Negev, Israel

    NASA Astrophysics Data System (ADS)

    Vengosh, A.; Pery, N.; Paytan, A.; Haquin, G.; Elhanani, S.; Pankratov, I.

    2006-05-01

    Many aquifer systems are composed of multiple rock types. Previous attempts to evaluate the specific aquifer rocks that control the groundwater chemistry and possible flow paths within these multiple lithological systems have used major ion chemistry and isotopic tracers (e.g., strontium isotopes). Here we propose an additional isotopic proxy that is based on the distribution of radium isotopes in groundwater. Radium has four radioactive isotopes that are part of the decay chains of uranium-238, thorium-232, and uranium-235. The abundance of radium isotope quartet (226Ra-half life 1600 y; 228Ra-5.6 y; 224Ra-3.6 d; 223Ra-11.4 d) in groundwater reflects the Th/U ratios in the rocks. Investigation of groundwater from the Negev, Israel, enabled us to discriminate between groundwaters flowing in the Lower Cretaceous Nubian Sandstone and the Upper Cretaceous Judea Group carbonate aquifers. Groundwater flowing in the sandstone aquifer has distinguishably high 228Ra/226Ra and 224Ra/223Ra ratios due to the high Th/U ratio in sandstone. In contrast, the predominance of uranium in carbonate rocks results in low 228Ra/226Ra and 224Ra/223Ra ratios in the associated groundwater. We show that the radium activity in groundwater in the two-aquifer systems is correlated with temperature, dissolved oxygen, and salinity. The increase of radium activity is also associated with changes in the isotopic ratios; 228Ra/226Ra ratios increase and decrease in the sandstone and carbonate aquifers, respectively. Given that the dissolution of radium isotopes depends on their decay constants, the use of the four radium isotopes with different decay constants enabled us to distinguish between dissolution (higher abundance of the long-lived isotopes) and recoil (predominance of the short-lived isotopes) processes. In spite of these isotopic fractionations, the radium isotopic discrimination between carbonate and sandstone aquifers is significant.

  4. Simulation of carbon isotope discrimination of the terrestrial biosphere

    NASA Astrophysics Data System (ADS)

    Suits, N. S.; Denning, A. S.; Berry, J. A.; Still, C. J.; Kaduk, J.; Miller, J. B.; Baker, I. T.

    2005-03-01

    We introduce a multistage model of carbon isotope discrimination during C3 photosynthesis and global maps of C3/C4 plant ratios to an ecophysiological model of the terrestrial biosphere (SiB2) in order to predict the carbon isotope ratios of terrestrial plant carbon globally at a 1° resolution. The model is driven by observed meteorology from the European Centre for Medium-Range Weather Forecasts (ECMWF), constrained by satellite-derived Normalized Difference Vegetation Index (NDVI) and run for the years 1983-1993. Modeled mean annual C3 discrimination during this period is 19.2‰; total mean annual discrimination by the terrestrial biosphere (C3 and C4 plants) is 15.9‰. We test simulation results in three ways. First, we compare the modeled response of C3 discrimination to changes in physiological stress, including daily variations in vapor pressure deficit (vpd) and monthly variations in precipitation, to observed changes in discrimination inferred from Keeling plot intercepts. Second, we compare mean δ13C ratios from selected biomes (Broadleaf, Temperate Broadleaf, Temperate Conifer, and Boreal) to the observed values from Keeling plots at these biomes. Third, we compare simulated zonal δ13C ratios in the Northern Hemisphere (20°N to 60°N) to values predicted from high-frequency variations in measured atmospheric CO2 and δ13C from terrestrially dominated sites within the NOAA-Globalview flask network. The modeled response to changes in vapor pressure deficit compares favorably to observations. Simulated discrimination in tropical forests of the Amazon basin is less sensitive to changes in monthly precipitation than is suggested by some observations. Mean model δ13C ratios for Broadleaf, Temperate Broadleaf, Temperate Conifer, and Boreal biomes compare well with the few measurements available; however, there is more variability in observations than in the simulation, and modeled δ13C values for tropical forests are heavy relative to observations

  5. Factors controlling shell carbon isotopic composition of land snail Acusta despecta sieboldiana estimated from laboratory culturing experiment

    NASA Astrophysics Data System (ADS)

    Zhang, N.; Yamada, K.; Suzuki, N.; Yoshida, N.

    2014-10-01

    The carbon isotopic composition (δ13C) of land snail shell carbonate derives from three potential sources: diet, atmospheric CO2, and ingested carbonate (limestone). However, their relative contributions remain unclear. Under various environmental conditions, we cultured one land snail subspecies, Acusta despecta sieboldiana, collected from Yokohama, Japan, and confirmed that all of these sources affect shell carbonate δ13C values. Herein, we consider the influences of metabolic rates and temperature on the carbon isotopic composition of the shell carbonate. Based on results obtained from previous works and this study, a simple but credible framework is presented to illustrate how each source and environmental parameter affects shell carbonate δ13C values. According to this framework and some reasonable assumptions, we estimated the contributions of different carbon sources for each snail individual: for cabbage-fed (C3 plant) groups, the contributions of diet, atmospheric CO2, and ingested limestone vary in the ranges of 66-80, 16-24, and 0-13%, respectively. For corn-fed (C4 plant) groups, because of the possible food stress (less ability to consume C4 plants), the values vary in the ranges of 56-64, 18-20, and 16-26%, respectively. Moreover, according to the literature and our observations, the subspecies we cultured in this study show preferences towards different plant species for food. Therefore, we suggest that the potential food preference should be considered adequately for some species in paleoenvironment studies. Finally, we inferred that only the isotopic exchange of the calcite-HCO3--aragonite equilibrium during egg laying and hatching of our cultured snails controls carbon isotope fractionation.

  6. Factors controlling shell carbon isotopic composition of land snail Acusta despecta sieboldiana estimated from lab culturing experiment

    NASA Astrophysics Data System (ADS)

    Zhang, N.; Yamada, K.; Suzuki, N.; Yoshida, N.

    2014-05-01

    The carbon isotopic composition (δ13C) of land snail shell carbonate derives from three potential sources: diet, atmospheric CO2, and ingested carbonate (limestone). However, their relative contributions remain unclear. Under various environmental conditions, we cultured one land snail species, Acusta despecta sieboldiana collected from Yokohama, Japan, and confirmed that all of these sources affect shell carbonate δ13C values. Herein, we consider the influences of metabolic rates and temperature on the carbon isotopic composition of the shell carbonate. Based on previous works and on results obtained in this study, a simple but credible framework is presented for discussion of how each source and environmental parameter can affect shell carbonate δ13C values. According to this framework and some reasonable assumptions, we have estimated the contributions of different carbon sources for each snail individual: for cabbage (C3 plant) fed groups, the contributions of diet, atmospheric CO2 and ingested limestone respectively vary as 66-80%, 16-24%, and 0-13%. For corn (C4 plant) fed groups, because of the possible food stress (lower consumption ability of C4 plant), the values vary respectively as 56-64%, 18-20%, and 16-26%. Moreover, we present new evidence that snails have discrimination to choose C3 and C4 plants as food. Therefore, we suggest that food preferences must be considered adequately when applying δ13C in paleo-environment studies. Finally, we inferred that, during egg laying and hatching of our cultured snails, carbon isotope fractionation is controlled only by the isotopic exchange of the calcite-HCO3--aragonite equilibrium.

  7. Mid-IR enhanced laser ablation molecular isotopic spectrometry

    NASA Astrophysics Data System (ADS)

    Brown, Staci; Ford, Alan; Akpovo, Codjo A.; Johnson, Lewis

    2016-08-01

    A double-pulsed laser-induced breakdown spectroscopy (DP-LIBS) technique utilizing wavelengths in the mid-infrared (MIR) for the second pulse, referred to as double-pulse LAMIS (DP-LAMIS), was examined for its effect on detection limits compared to single-pulse laser ablation molecular isotopic spectrometry (LAMIS). A MIR carbon dioxide (CO2) laser pulse at 10.6 μm was employed to enhance spectral emissions from nanosecond-laser-induced plasma via mid-IR reheating and in turn, improve the determination of the relative abundance of isotopes in a sample. This technique was demonstrated on a collection of 10BO and 11BO molecular spectra created from enriched boric acid (H3BO3) isotopologues in varying concentrations. Effects on the overall ability of both LAMIS and DP-LAMIS to detect the relative abundance of boron isotopes in a starting sample were considered. Least-squares fitting to theoretical models was used to deduce plasma parameters and understand reproducibility of results. Furthermore, some optimization for conditions of the enhanced emission was achieved, along with a comparison of the overall emission intensity, plasma density, and plasma temperature generated by the two techniques.

  8. Isotope Biogeochemistry of Sulfur in a Cold-Water Carbonate Mound (IODP Site 1317)

    NASA Astrophysics Data System (ADS)

    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. The Origin of Carbon-bearing Volatiles in Surprise Valley Hot Springs in the Great Basin: Carbon Isotope and Water Chemistry Characterizations

    NASA Technical Reports Server (NTRS)

    Fu, Qi; Socki, Richard A.; Niles, Paul B.; Romanek, Christopher; Datta, Saugata; Darnell, Mike; Bissada, Adry K.

    2013-01-01

    There are numerous hydrothermal fields within the Great Basin of North America, some of which have been exploited for geothermal resources. With methane and other carbon-bearing compounds being observed, in some cases with high concentrations, however, their origins and formation conditions remain unknown. Thus, studying hydrothermal springs in this area provides us an opportunity to expand our knowledge of subsurface (bio)chemical processes that generate organic compounds in hydrothermal systems, and aid in future development and exploration of potential energy resources as well. While isotope measurement has long been used for recognition of their origins, there are several secondary processes that may generate variations in isotopic compositions: oxidation, re-equilibration of methane and other alkanes with CO2, mixing with compounds of other sources, etc. Therefore, in addition to isotopic analysis, other evidence, including water chemistry and rock compositions, are necessary to identify volatile compounds of different sources. Surprise Valley Hot Springs (SVHS, 41 deg 32'N, 120 deg 5'W), located in a typical basin and range province valley in northeastern California, is a terrestrial hydrothermal spring system of the Great Basin. Previous geophysical studies indicated the presence of clay-rich volcanic and sedimentary rocks of Tertiary age beneath the lava flows in late Tertiary and Quaternary. Water and gas samples were collected for a variety of chemical and isotope composition analyses, including in-situ pH, alkalinity, conductivity, oxidation reduction potential (ORP), major and trace elements, and C and H isotope measurements. Fluids issuing from SVHS can be classified as Na-(Cl)-SO4 type, with the major cation and anion being Na+ and SO4(2-), respectively. Thermodynamic calculation using ORP and major element data indicated that sulfate is the most dominant sulfur species, which is consistent with anion analysis results. Aquifer temperatures at depth

  10. Carbon Monoxide Stable Isotopes: Extraction Technique Development and Urban Atmospheric Analysis

    NASA Astrophysics Data System (ADS)

    Vimont, Isaac Josef

    We have developed an extraction system to analyze isotopes of carbon monoxide (CO). We then analyzed CO isotopes for two years at Indianapolis, IN, USA. These measurements were done at three towers, one of which measured incoming, background air into the city. We quantitatively removed the background signal and determined the urban CO mole fraction and isotopic enhancements. During the winter months, we constrained the isotopic signature and concluded that the majority of CO produced during the winter was produced by fossil fuel combustion. We found that the Indianapolis fossil fuel signature differed from that of studies done in Europe. Further, we performed a limited traffic study to look at CO isotopes from traffic. While this was not conclusive, it did support our hypothesis that a larger fraction of the Indianapolis vehicle fleet may have malfunctioning catalytic systems, which biases the isotopic results, particularly for delta18O. We used the wintertime fossil fuel isotopic signature to help constrain the summertime budget. It was hypothesized that a second source of CO was significant during the summer months. Oxidation of biogenically produced volatile organic compounds (BVOC's) was one possible source. Oxidized BVOC's were consistent with the changes between our winter and summer isotopic source signatures. We then used the isotopic signatures to determine that between zero and sixty percent of the summertime CO budget was produced from oxidized VOC's. This provided the first direct evidence of a larger percentage of urban CO being produced by oxidized VOC's.

  11. Tracing the source of sedimentary organic carbon in the Loess Plateau of China: An integrated elemental ratio, stable carbon signatures, and radioactive isotopes approach.

    PubMed

    Liu, Chun; Dong, Yuting; Li, Zhongwu; Chang, Xiaofeng; Nie, Xiaodong; Liu, Lin; Xiao, Haibing; Bashir, Hassan

    2017-02-01

    Soil erosion, which will induce the redistribution of soil and associated soil organic carbon (SOC) on the Earth's surface, is of critically importance for biogeochemical cycling of essential elements and terrestrial carbon sequestration. Despite the importance of soil erosion, surprisingly few studies have evaluated the sources of eroded carbon (C). This study used natural abundance levels of the stable isotope signature ( 13 C) and radioactive isotopes ( 137 Cs and 210 Pb ex ), along with elements ratio (C/N) based on a two end member mixing model to qualitatively and quantitatively identify the sources of sedimentary OC retained by check dam in the Qiaozigou small watershed in the Loess Plateau, China. Sediment profiles (0-200 cm) captured at natural depositional area of the basin was compared to possible source materials, which included: superficial Loess mineral soils (0-20 cm) from three land use types [i.e., grassland (Medicago sativa), forestland (Robinia pseudoacacia.), shrubland (Prunus sibirica), and gully land (Loess parent material.)]. The results demonstrated that SOC in sediments showed significantly negative correlation with pH (P < 0.01), and positive correlation with soil water content (SWC) (P < 0.05). The sedimentary OC was not derived from grasslands or gullies. Forestland and shrubland were two main sources of eroded organic carbon within the surface sediment (0-60 cm deep), except for that in the 20-40 cm soil layer. Radionuclides analyses also implied that the surface sediments retained by check-dams mainly originated from soils of forestland and shrubland. Results of the two end-member mixing model demonstrated that more than 50% SOC (mean probability estimate (MPE) 50.13% via 13 C and 60.53% via C/N) in surface sediment (0-20 cm deep) derived from forestland, whereas subsurface sedimentary SOC (20-200 cm) mainly resulted from shrubland (MPE > 50%). Although uncertainties on the sources of SOC in deep soils exist, the soil

  12. A revised inoceramid biozonation for the Upper Cretaceous based on high-resolution carbon isotope stratigraphy in northwestern Hokkaido, Japan

    NASA Astrophysics Data System (ADS)

    Hayakawa, Tatsuya; Hirano, Hiromichi

    2013-06-01

    Hayakawa, T., Hirano, H. 2013. A revised inoceramid biozonation for the Upper Cretaceous based on high-resolution carbon isotope stratigraphy in northwestern Hokkaido, Japan. Acta Geologica Polonica, 63 (2), 239-263. Warszawa. Biostratigraphic correlations of inoceramid bivalves between the North Pacific and Euramerican provinces have been difficult because the inoceramid biostratigraphy of the Japanese strata has been based on endemic species of the northwest Pacific. In this study, carbon stable isotope fluctuations of terrestrial organic matter are assembled for the Upper Cretaceous Yezo Group in the Haboro and Obira areas, Hokkaido, Japan, in order to revise the chronology of the inoceramid biozonation in Japan. The carbon isotope curves are correlated with those of marine carbonates in English and German sections with the aid of age-diagnostic taxa. According to the correlations of the carbon isotope curves, 11 isotope events are recognised in the sections studied. As a result of these correlations, the chronology of the inoceramid biozones of the Northwest Pacific has been considerably revised. The revised inoceramid biozones suggest that the timing of the origination and extinction of the inoceramids in the North Pacific biotic province is different from the stage/substage boundaries defined by inoceramids, as used in Europe and North America.

  13. A Multi-proxy Approach to Using Cave Sediment Carbon Isotopes for Late Holocene Paleoenvironmental Reconstruction in Florida

    NASA Astrophysics Data System (ADS)

    Polk, J. S.; van Beynen, P.

    2007-12-01

    Carbon isotopes from cave sediments collected from Jennings Cave in Marion County, Florida were analyzed using a multi-proxy approach. Fulvic acids (FAs), humic acids (HAs), black carbon, phytoliths, and bulk organic matter were extracted from the sediments for carbon isotope analysis to determine periods of vegetation change caused by climatic influences during the Late Holocene (~\\ 2,800 years BP). The carbon isotope record ranges from -35‰ to -14‰, exhibiting variability of ~\\ -21‰, within the different proxies, which indicates changes between C3 and C4 vegetation. This likely indicates changes between a sub-tropical forested environment and more arid, grassy plains conditions. These changes in plant assemblages were in response to changes in available water resources, with increased temperatures and evapotranspiration leading to arid conditions and a shift toward less C3 vegetation (increased C4 vegetation) during the MWP. The cave sediment fulvic acid cabon isotopes record agrees well with ä13C values from a speleothem collected nearby that covers the same time period. Prolonged migration of the NAO and ITCZ affects precipitation in Florida and likely caused vegetation changes during these climatic shifts.

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

    PubMed Central

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

    2016-01-01

    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. PMID:27151563

  15. Methane transport mechanisms and isotopic fractionation in emergent macrophytes of an Alaskan tundra lake

    NASA Technical Reports Server (NTRS)

    Chanton, Jeffrey P.; Martens, Christopher S.; Kelley, Cheryl A.; Crill, Patrick M.; Showers, William J.

    1992-01-01

    The stable carbon isotopic composition of methane associated with and emitted by the two dominant emergent macrophytes abundant in the many Alaskan tundra lakes, Carex rostrata and Arctophila fulva, is determined. The carbon isotopic composition of the methane was -58.6 +/- 0.5 (n=2) for Arctophila and -66.6 +/- 2.5 (n=6) for Carex. The methane emitted by these species is depleted in C-13 by 12 per mil for Arctophila and 18 per mil for Carex relative to methane withdrawn from plant stems 1-2 cm below the waterline. The results suggest more rapid transport of (C-12)H4 relative to (C-13)H4 through plants to the atmosphere. Plant stem methane concentrations ranged from 0.2 to 4.0 percent in Arctophila, with an isotopic composition of -46.1 +/- 4.3 percent (n=8). Carex stem methane concentrations ranged from 150 to 1200 ppm, with an isotopic composition of -48.3 +/- 1.4 per mil (n=3).

  16. Carbon and Oxygen Isotope Measurements of Ordinary Chondrite (OC) Meteorites from Antarctica Indicate Distinct Carbonate Species Using a Stepped Acid Extraction Procedure

    NASA Technical Reports Server (NTRS)

    Evans, Michael E.

    2015-01-01

    The purpose of this study is to characterize the stable isotope values of terrestrial, secondary carbonate minerals from five Ordinary Chondrite (OC) meteorites collected in Antarctica. These samples were identified and requested from NASA based upon their size, alteration history, and collection proximity to known Martian meteorites. They are also assumed to be carbonate-free before falling to Earth. This research addresses two questions involving Mars carbonates: 1) characterize terrestrial, secondary carbonate isotope values to apply to Martian meteorites for isolating in-situ carbonates, and 2) increase understanding of carbonates formed in cold and arid environments with Antarctica as an analog for Mars. Two samples from each meteorite, each approximately 0.5 grams, were crushed and dissolved in pure phosphoric acid for 3 sequential reactions: a) R times 0 for 1 hour at 30 degrees Centigrade (fine calcite extraction), b) R times 1 for 18 hours at 30 degrees Centigrade (course calcite extraction), and c) R times 2 for 3 hours at 150 degrees Centigrade (siderite and/or magnesite extraction). CO (sub 2) 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 foot 2 millimeter stainless column, and then analyzed on a Thermo MAT 253 Isotope Ratio Mass Spectrometer (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 error bands. Two distinct species of carbonates are found: 1) calcite, and 2) non-calcite carbonate (future testing will attempt to differentiate siderite from magnesite). Preliminary results indicate the terrestrial carbonates are formed at approximately sigma (sup 13) C equal to plus 5 per mille, which is consistent with atmospheric CO (sub 2) sigma (sup 13) C equal to minus 7 per mille and fractionation of plus

  17. Equilibrium carbon and hydrogen isotope fractionation in iron

    NASA Astrophysics Data System (ADS)

    Schauble, E. A.

    2009-12-01

    Recent theoretical and experimental studies (e.g., [1-3]) have suggested that Si- and Fe-isotopic signatures can be used to characterize the compositions and conditions of segregation of metallic cores in planetary interiors. This study expands the theoretical framework to include carbon and hydrogen, which may also be alloying elements. Hydrogen (D/H) and carbon (13C/12C) fractionations in iron-rich metallic melts are estimated by modeling analogous iron-rich crystals, i.e., dhcp-FeH and η-Fe2C. C- and H-atoms in these crystals are completely coordinated by iron. The driving energy for equilibrium fractionation is assumed to come from the reduction of vibrational frequencies when heavy isotopes are substituted for light ones; vibrations are assumed to be harmonic. This treatment is crude at high temperature, and for the relatively anharmonic vibrations typical of hydrogen-bearing substances, but may provide a reasonably accurate, semi-quantitative approximation of real fractionation behavior. Vibrational frequencies of all crystals are modeled with density functional theory, using gradient-corrected functionals and ultrasoft pseudopotentials. For both carbon and hydrogen, the models suggest that the metal phase will be strongly depleted in heavy isotopes. At 2000 K, 1 atm, η-Fe2C will have 3‰ lower 13C/12C than coexisting diamond. Combining this result with previous high-temperature theoretical and experimental studies (e.g., [4]), metal-graphite fractionation is expected to be very similar, while metal-CO2 fractionation will be almost twice as large, ca. -5‰. Deuterium/hydrogen fractionations are expected to be an order of magnitude larger, with 50-70‰ lower D/H in dhcp-FeH than in coexisting H2 gas at 2000 K, and approximately 100‰ lower D/H than water vapor. These fractionations are much larger than those inferred for silicon and iron, as expected given the differences in atomic mass. References: 1. Georg et al. (2007) Nature 447:1102; 2. Rustad & Yin

  18. The origin of decoupled carbonate and organic carbon isotope signatures in the early Cambrian (ca. 542-520 Ma) Yangtze platform

    NASA Astrophysics Data System (ADS)

    Jiang, Ganqing; Wang, Xinqiang; Shi, Xiaoying; Xiao, Shuhai; Zhang, Shihong; Dong, Jin

    2012-02-01

    The early Cambrian (ca. 542-520 Ma) strata in South China record two prominent negative carbonate carbon isotope (δ13Ccarb) excursions of early Nemakit-Daldynian (N-D) and early Tommotian ages. Across each of these excursions, carbonate and organic carbon isotopes (δ13Ccarb and δ13Corg) are strongly decoupled. Regional correlation across a shelf-to-basin transect shows lateral heterogeneity of δ13Corg during the early-middle N-D but more homogenized δ13Corg values across the basin during the late N-D and Tommotian. The temporal and lateral variations in δ13Corg suggest that decoupled δ13Ccarb and δ13Corg across the N-D δ13Ccarb excursion were possibly caused by diagenetic alteration of organic matter and/or amplification of detrital organic carbon isotope signature in low-TOC carbonates. In contrast, decoupled δ13Ccarb and δ13Corg of the upper N-D and Tommotian were likely resulted from chemoautotrophic-methanotrophic biomass contribution to TOC in organic-rich black shale and carbonates. The decoupled δ13Ccarb-δ13Corg pattern from the lower N-D strata (ca. 542 Ma) shows striking similarities with those from the basal (ca. 635 Ma) and upper (ca. 551 Ma) Doushantuo Formation. In all three cases, decoupled δ13Ccarb-δ13Corg are seen in organic-poor carbonates (TOC ≤ 0.1‰) and coupled δ13Ccarb-δ13Corg occur in organic-rich black shale and carbonates at the end of the negative δ13Ccarb excursion. These similarities suggest that the shift from decoupled to coupled δ13Ccarb-δ13Corg has no causal link with the terminal oxidation of a large oceanic DOC reservoir. Given the pervasive anoxia/euxinia in Ediacaran-early Cambrian oceans, local DOC-rich environments may have been common, but a large oceanic DOC reservoir capable of buffering the δ13C of marine organic matter requires independent evidence.

  19. Stable carbon and hydrogen isotope fractionation of dissolved organic groundwater pollutants by equilibrium sorption.

    PubMed

    Höhener, Patrick; Yu, Xianjing

    2012-03-15

    Linear free energy relationships (LFERs) were established which relate equilibrium vapor-liquid isotope effects to stable carbon and hydrogen isotope enrichment factors for equilibrium sorption to geosorbents. The LFERs were established for normal, cyclic or branched alkanes, monoaromatic hydrocarbons, and chloroethenes. These LFERs predict that isotopic light compounds sorb more strongly than their heavy counterparts. Defining fractionation as in classical literature by "heavy divided by light", carbon enrichment factors for equilibrium sorption were derived which ranged from -0.13±0.04‰ (benzene) to -0.52±0.19‰ (trichloroethene at 5-15 °C). Hydrogen enrichment factors for sorption of 14 different compounds were between -2.4 and -9.2‰. For perdeuterated hydrocarbons the predicted enrichment factors ranged from -19±5.4‰ (benzene) to -64±30‰ (cyclohexane). Equilibrium sorption experiments with a soil and activated carbon as sorbents were performed in the laboratory for perdeuterocyclohexane and perdeuterotoluene. The measured D/H enrichments agreed with the LFER prediction for both compounds and both sorbents within the uncertainty estimate of the prediction. The results of this work suggest that equilibrium sorption does create only very small isotope shifts for (13)C in groundwater pollutants in aquifers. It is also suggested that deuterium shifts are expected to be higher, especially for strongly sorbing pollutants. Copyright © 2011 Elsevier B.V. All rights reserved.

  20. Cryogenic Carbonate Formation on Mars: Clues from Stable Isotope Variations Seen in Experimental Studies

    NASA Technical Reports Server (NTRS)

    Socki, Richard A.; Niles, Paul B.; Fu, Qi; Gibson, Everett K., Jr.

    2010-01-01

    Discoveries of large deposits of sedimentary materials on the planet Mars by landers and orbiters have confirmed the widely held hypothesis that water has played a crucial role in the development of the martian surface. Recent studies have indicated that both water ice and liquid water may have been present and in the case of water ice perhaps is still present on or near the surface of Mars. However, there remains much controversy about the prevailing atmospheric conditions and climate of Mars during its history and whether liquid water existed on the martian surface simply during discrete geological events or whether this water was present over relatively much longer geologic time periods. The recent identification of Ca-rich carbonate by the Phoenix lander as well as its measurement of the isotopic composition of atmospheric CO2 has shown the importance of understanding the carbonates on Mars as an important sink of atmospheric carbon. This work compliments that of our past experiments where we produced cryogenic calcite in open containers, as analogs for terrestrial aufeis formation, and as a means for evaluating the fractionation of C-13 in CO2 during bicarbonate freezing [13]. Unlike our previous experiments in which carbonates were grown in ambient laboratory condition in open containers (atmospheric pressure and composition), this work attempts to quantify the amount of delta C-13 enrichment possible in both fluids and secondary carbonates formed from freezing of bicarbonate fluids under martian-like atmospheric conditions. Morphologic textures of produced carbonates in these experiments are also examined under SEM in order to identify the effect that the cryogenic freezing process has on the mineral's mineralogy. Understanding the role of kinetic isotope fractionation during formation of carbonates under martian-like conditions will aid in our ability to quantify the isotopic composition of the carbonate sink furthering our ability to model the climate