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Sample records for 13c depleted co2

  1. Diurnal variation of the delta 13C of pine needle respired CO2 evolved in darkness.

    PubMed

    Prater, James L; Mortazavi, Behzad; Chanton, Jeffrey P

    2006-02-01

    The delta 13C of pine needle CO2 evolved in darkness (delta 13Cr) for slash pine trees (Pinus elliottii) was determined by placing recently collected pine needles in darkness and collecting respired CO2 over a short time period (<15 min). Delta 13Cr measurements were made over several 24 h periods to test the hypothesis that significant variation in delta 13Cr would be observed during a diurnal cycle. The delta 13Cr measurements from the 24 h time series trials showed a consistent midday 13C-enrichment (5-10 per thousand) relative to bulk biomass. The delta 13Cr values became more 13C-depleted at night and following shading, and approached bulk-biomass delta 13C values by dawn. The effect of night-time respired 13C-enriched CO2 on the delta 13C value of the remaining assimilate is shown to be minimal (13C depleted by 0.22 per thousand) under field conditions for P. elliottii needles.

  2. The paper trail of the 13C of atmospheric CO2 since the industrial revolution period

    NASA Astrophysics Data System (ADS)

    Yakir, Dan

    2011-07-01

    The 13C concentration in atmospheric CO2 has been declining over the past 150 years as large quantities of 13C-depleted CO2 from fossil fuel burning are added to the atmosphere. Deforestation and other land use changes have also contributed to the trend. Looking at the 13C variations in the atmosphere and in annual growth rings of trees allows us to estimate CO2 uptake by land plants and the ocean, and assess the response of plants to climate. Here I show that the effects of the declining 13C trend in atmospheric CO2 are recorded in the isotopic composition of paper used in the printing industry, which provides a well-organized archive and integrated material derived from trees' cellulose. 13C analyses of paper from two European and two American publications showed, on average, a - 1.65 ± 1.00‰ trend between 1880 and 2000, compared with - 1.45 and - 1.57‰ for air and tree-ring analyses, respectively. The greater decrease in plant-derived 13C in the paper we tested than in the air is consistent with predicted global-scale increases in plant intrinsic water-use efficiency over the 20th century. Distinct deviations from the atmospheric trend were observed in both European and American publications immediately following the World War II period.

  3. Estimation of continuous anthropogenic CO2 using CO2, CO, δ13C(CO2) and Δ14C(CO2)

    NASA Astrophysics Data System (ADS)

    Vardag, S. N.; Gerbig, C.; Janssens-Maenhout, G.; Levin, I.

    2015-07-01

    We investigate different methods for estimating anthropogenic CO2 using modelled continuous atmospheric concentrations of CO2 alone, as well as CO2 in combination with the surrogate tracers CO, δ13C(CO2) and Δ14C(CO2). These methods are applied at three hypothetical stations representing rural, urban and polluted conditions. We find that independent of the tracer used, an observation-based estimate of continuous anthropogenic CO2 is not feasible at rural measurement sites due to the low signal to noise ratio of anthropogenic CO2 estimates at such settings. At urban and polluted sites, potential future continuous Δ14C(CO2) measurements with a precision of 5 ‰ or better are most promising for anthropogenic CO2 determination (precision ca. 10-20%), but the insensitivity against CO2 contributions from biofuel emissions may reduce its accuracy in the future. Other tracers, such as δ13C(CO2) and CO could provide an accurate and already available alternative if all CO2 sources in the catchment area are well characterized with respect to their isotopic signature and CO to anthropogenic CO2 ratio. We suggest a strategy for calibrating these source characteristics on an annual basis using precise Δ14C(CO2) measurements on grab samples. The precision of anthropogenic CO2 determination using δ13C(CO2) is largely determined by the measurement precision of δ13C(CO2) and CO2. The precision when using the CO-method is mainly limited by the variation of natural CO sources and CO sinks. At present, continuous anthropogenic CO2 could be determined using the tracers δ13C(CO2) and/or CO with a precision of about 30 %, a mean bias of about 10 % and without significant diurnal discrepancies. This allows significant improvement, validation and bias reduction of highly resolved emission inventories using atmospheric observation and regional modelling.

  4. The 13C/12C isotopic signal of day-respired CO2 in variegated leaves of Pelargonium × hortorum.

    PubMed

    Tcherkez, Guillaume; Mauve, Caroline; Lamothe, Marlene; Le Bras, Camille; Grapin, Agnes

    2011-02-01

    In leaves, although it is accepted that CO(2) evolved by dark respiration after illumination is naturally (13) C-enriched compared to organic matter or substrate sucrose, much uncertainty remains on whether day respiration produces (13) C-depleted or (13) C-enriched CO(2). Here, we applied equations described previously for mesocosm CO(2) exchange to investigate the carbon isotope composition of CO(2) respired by autotrophic and heterotrophic tissues of Pelargonium × hortorum leaves, taking advantage of leaf variegation. Day-respired CO(2) was slightly (13) C-depleted compared to organic matter both under 21% O(2) and 2% O(2). Furthermore, most, if not all CO(2) molecules evolved in the light came from carbon atoms that had been fixed previously before the experiments, in both variegated and green leaves. We conclude that the usual definition of day respiratory fractionation, that assumes carbon fixed by current net photosynthesis is the respiratory substrate, is not valid in Pelargonium leaves under our conditions. In variegated leaves, total organic matter was slightly (13) C-depleted in white areas and so were most primary metabolites. This small isotopic difference between white and green areas probably came from the small contribution of photosynthetic CO(2) refixation and the specific nitrogen metabolism in white leaf areas. PMID:20955224

  5. The 13C/12C isotopic signal of day-respired CO2 in variegated leaves of Pelargonium × hortorum.

    PubMed

    Tcherkez, Guillaume; Mauve, Caroline; Lamothe, Marlene; Le Bras, Camille; Grapin, Agnes

    2011-02-01

    In leaves, although it is accepted that CO(2) evolved by dark respiration after illumination is naturally (13) C-enriched compared to organic matter or substrate sucrose, much uncertainty remains on whether day respiration produces (13) C-depleted or (13) C-enriched CO(2). Here, we applied equations described previously for mesocosm CO(2) exchange to investigate the carbon isotope composition of CO(2) respired by autotrophic and heterotrophic tissues of Pelargonium × hortorum leaves, taking advantage of leaf variegation. Day-respired CO(2) was slightly (13) C-depleted compared to organic matter both under 21% O(2) and 2% O(2). Furthermore, most, if not all CO(2) molecules evolved in the light came from carbon atoms that had been fixed previously before the experiments, in both variegated and green leaves. We conclude that the usual definition of day respiratory fractionation, that assumes carbon fixed by current net photosynthesis is the respiratory substrate, is not valid in Pelargonium leaves under our conditions. In variegated leaves, total organic matter was slightly (13) C-depleted in white areas and so were most primary metabolites. This small isotopic difference between white and green areas probably came from the small contribution of photosynthetic CO(2) refixation and the specific nitrogen metabolism in white leaf areas.

  6. Leaf and twig delta13C during growth in relation to biochemical composition and respired CO2.

    PubMed

    Eglin, Thomas; Fresneau, Chantal; Lelarge-Trouverie, Caroline; Francois, Christophe; Damesin, Claire

    2009-06-01

    In deciduous trees, the delta(13)C values of leaves are known to diverge during growth from those of woody organs. The main purpose of this study is to determine whether the divergence in delta(13)C between leaves and current-year twigs of Fagus sylvatica (L.) is influenced by changes (i) in the relative contents of organic matter fractions and (ii) in the delta(13)C of respired CO(2). The delta(13)C values of bulk matter, extractive-free matter, lignin, holocellulose, starch, soluble sugars, water-soluble fraction and respired CO(2), as well as their relative contents in bulk matter were determined. The delta(13)C values of biochemical fractions and respired CO(2) showed very similar temporal variations for both leaves and twigs. Variations in bulk matter delta(13)C during growth were, therefore, poorly explained by changes in biochemical composition or in respiratory fractionation and were attributed to the transition from (13)C-enriched reserves (mainly starch) to (13)C-depleted new photoassimilates. The divergence between leaves and twigs was related to higher values of soluble sugar delta(13)C in twigs. However, the difference between lignin and holocellulose delta(13)C varied during growth. This phenomenon was attributed to the delay between holocellulose and lignin deposition. These results may have implications for analysis of organic matter delta(13)C in trees and forest ecosystems.

  7. Changes and their possible causes in δ13C of dark-respired CO2 and its putative bulk and soluble sources during maize ontogeny.

    PubMed

    Ghashghaie, Jaleh; Badeck, Franz W; Girardin, Cyril; Huignard, Christophe; Aydinlis, Zackarie; Fonteny, Charlotte; Priault, Pierrick; Fresneau, Chantal; Lamothe-Sibold, Marlène; Streb, Peter; Terwilliger, Valery J

    2016-04-01

    The issues of whether, where, and to what extent carbon isotopic fractionations occur during respiration affect interpretations of plant functions that are important to many disciplines across the natural sciences. Studies of carbon isotopic fractionation during dark respiration in C3 plants have repeatedly shown respired CO2 to be (13)C enriched relative to its bulk leaf sources and (13)C depleted relative to its bulk root sources. Furthermore, two studies showed respired CO2 to become progressively (13)C enriched during leaf ontogeny and (13)C depleted during root ontogeny in C3 legumes. As such data on C4 plants are scarce and contradictory, we investigated apparent respiratory fractionations of carbon and their possible causes in different organs of maize plants during early ontogeny. As in the C3 plants, leaf-respired CO2 was (13)C enriched whereas root-respired CO2 was (13)C depleted relative to their putative sources. In contrast to the findings for C3 plants, however, not only root- but also leaf-respired CO2 became more (13)C depleted during ontogeny. Leaf-respired CO2 was highly (13)C enriched just after light-dark transition but the enrichment rapidly decreased over time in darkness. We conclude that (i) although carbon isotopic fractionations in C4 maize and leguminous C3 crop roots are similar, increasing phosphoenolpyruvate-carboxylase activity during maize ontogeny could have produced the contrast between the progressive (13)C depletion of maize leaf-respired CO2 and (13)C enrichment of C3 leaf-respired CO2 over time, and (ii) in both maize and C3 leaves, highly (13)C enriched leaf-respired CO2 at light-to-dark transition and its rapid decrease during darkness, together with the observed decrease in leaf malate content, may be the result of a transient effect of light-enhanced dark respiration. PMID:26970389

  8. 13C/12C ratios in CO2 extracted from Antarctic ice

    NASA Astrophysics Data System (ADS)

    Friedli, H.; Moor, E.; Oeschger, H.; Siegenthaler, U.; Stauffer, B.

    Air is extracted from bubbles of polar ice samples by a dry extraction method, and the 13C/12C ratio is measured on CO2 separated from the air. Ice samples of typically 700 g are crushed at ca. -20°C, the evolving air is trapped cryogenically, and CO2 is frozen out from this air for mass-spectrometric isotope analysis. First δ13C and δ 18O results of CO2 from Antarctic ice cores are presented, and δ13C is discussed in relation to atmospheric CO2 variations. δ13C of 400 to 800 year old ice is ca. 1.1 %o higher than the 1980 atmospheric value, which agrees well with model-based estimations. The measurement of three ca. 50,000 yr old samples yielded astonishingly low values, but contamination cannot be excluded.

  9. [Monitoring Atmospheric CO2 and delta(13)C (CO2) Background Levels at Shangdianzi Station in Beijing, China].

    PubMed

    Xia, Ling-ju; Zhou, Ling-xi; Liu, Li-xin; Zhang, Gen

    2016-04-15

    The study presented time series of atmospheric CO2 concentrations from flask sampling at SDZ regional station in Beijing during 2007 and 2013, together with delta(13)CO2) values during 2009 and 2013. The "representative data" of CO2 and delta(13)C (CO2) were selected from the complete data for further analysis. Annual CO2 concentrations increased from 385.6 x 10(-6) in 2007 to 398.1 x 10(-6) in 2013, with an average growth rate of 2.0 x 10(-6) a(-1), while the delta(13)C values decreased from -8.38% per hundred in 2009 to -8.52% per hundred in 2013, with a mean growth rate of -0.03% per hundred x a(-1). The absolute increase of CO2 from 2007 to 2008 reached the lowest level during 2007 and 2013, possibly due to relatively less carbon emissions during the 2008 Olympic Games period. The peak-to-peak amplitudes of atmospheric CO2 and delta(13)C seasonal variations were 23. 9 x 10 -6 and 1. 03%o, respectively. The isotopic signatures of CO2 sources/sinks were also discussed in this study. The delta8 value for heating season I (Jan. 01-Mar. 14) was -21.30% per hundred, while -25.39% per hundred for heating season 11 (Nov. 15-Dec.31) , and for vegetative season (Mar. 15-Nov. 14) the delta(bio) value was estimated to be -21.28% per hundred, likely suggesting the significant impact of fossil fuel and corn straw combustions during winter heating season and biological activities during vegetative season. PMID:27548943

  10. [Monitoring Atmospheric CO2 and delta(13)C (CO2) Background Levels at Shangdianzi Station in Beijing, China].

    PubMed

    Xia, Ling-ju; Zhou, Ling-xi; Liu, Li-xin; Zhang, Gen

    2016-04-15

    The study presented time series of atmospheric CO2 concentrations from flask sampling at SDZ regional station in Beijing during 2007 and 2013, together with delta(13)CO2) values during 2009 and 2013. The "representative data" of CO2 and delta(13)C (CO2) were selected from the complete data for further analysis. Annual CO2 concentrations increased from 385.6 x 10(-6) in 2007 to 398.1 x 10(-6) in 2013, with an average growth rate of 2.0 x 10(-6) a(-1), while the delta(13)C values decreased from -8.38% per hundred in 2009 to -8.52% per hundred in 2013, with a mean growth rate of -0.03% per hundred x a(-1). The absolute increase of CO2 from 2007 to 2008 reached the lowest level during 2007 and 2013, possibly due to relatively less carbon emissions during the 2008 Olympic Games period. The peak-to-peak amplitudes of atmospheric CO2 and delta(13)C seasonal variations were 23. 9 x 10 -6 and 1. 03%o, respectively. The isotopic signatures of CO2 sources/sinks were also discussed in this study. The delta8 value for heating season I (Jan. 01-Mar. 14) was -21.30% per hundred, while -25.39% per hundred for heating season 11 (Nov. 15-Dec.31) , and for vegetative season (Mar. 15-Nov. 14) the delta(bio) value was estimated to be -21.28% per hundred, likely suggesting the significant impact of fossil fuel and corn straw combustions during winter heating season and biological activities during vegetative season.

  11. First airborne samples of a volcanic plume for δ13C of CO2 determinations

    NASA Astrophysics Data System (ADS)

    Fischer, Tobias P.; Lopez, Taryn M.

    2016-04-01

    Volcanic degassing is one of the main natural sources of CO2 to the atmosphere. Carbon isotopes of volcanic gases enable the determination of CO2 sources including mantle, organic or carbonate sediments, and atmosphere. Until recently, this work required sample collection from vents followed by laboratory analyses. Isotope ratio infrared analyzers now enable rapid analyses of plume δ13C-CO2, in situ and in real time. Here we report the first analyses of δ13C-CO2 from airborne samples. These data combined with plume samples from the vent area enable extrapolation to the volcanic source δ13C. We performed our experiment at the previously unsampled and remote Kanaga Volcano in the Western Aleutians. We find a δ13C source composition of -4.4‰, suggesting that CO2 from Kanaga is primarily sourced from the upper mantle with minimal contributions from subducted components. Our method is widely applicable to volcanoes where remote location or activity level precludes sampling using traditional methods.

  12. Late Ordovician land plant spore 13C fractionation records atmospheric CO2 and climate change

    NASA Astrophysics Data System (ADS)

    Beerling, D. J.; Nelson, D. M.; Pearson, A.; Wellman, C.

    2008-12-01

    Molecular systematics and spore wall ultrastructure studies indicate that late Ordovician diad and triad fossil spores were likely produced by plants most closely related to liverworts. Here, we report the first δ13C estimates of Ordovician fossil land plant spores, which were obtained using a spooling wire micro-combustion device interfaced with an isotope-ratio mass spectrometer (Sessions et al., 2005, Analytical Chemistry, 77, 6519). The spores all originate from Saudi Arabia on the west of Gondwana and date to before (Cardadoc, ca. 460 Ma), during (443Ma) and after (Llandovery, ca. 440Ma) the Hirnantian glaciation. We use these numbers along with marine carbonate δ13C records to estimate atmospheric CO2 by implementing a theoretical model that captures the strong CO2-dependency of 13C fractionation in non-vascular land plants (Fletcher et al., 2008, Nature Geoscience, 1, 43). Although provisional at this stage, reconstructed CO2 changes are consistent with the Kump et al. (2008) (Paleo. Paleo. Paleo. 152, 173) 'weathering hypothesis' whereby pre-Hirnantian cooling is caused by relatively low CO2 (ca. 700ppm) related to enhanced weathering of young basaltic rocks during the early phase of the Taconic uplift, with background values subsequently rising to around double this value by the earliest Silurian. Further analyses will better constrain atmospheric CO2 change during the late Ordovician climatic perturbation and address controversial hypotheses concerning the causes and timing of the Earth system transition into an icehouse state.

  13. Delta13C values of grasses as a novel indicator of pollution by fossil-fuel-derived greenhouse gas CO2 in urban areas.

    PubMed

    Lichtfouse, Eric; Lichtfouse, Michel; Jaffrézic, Anne

    2003-01-01

    A novel fossil fuel pollution indicator based on the 13C/12C isotopic composition of plants has been designed. This bioindicator is a promising tool for future mapping of the sequestration of fossil fuel CO2 into urban vegetation. Theoretically, plants growing in fossil-fuel-CO2-contaminated areas, such as major cities, industrial centers, and highway borders, should assimilate a mixture of global atmospheric CO2 of delta13C value of -8.02 per thousand and of fossil fuel CO2 of average delta13C value of -27.28 per thousand. This isotopic difference should, thus, be recorded in plant carbon. Indeed, this study reveals that grasses growing near a major highway in Paris, France, have strikingly depleted delta13C values, averaging at -35.08 per thousand, versus rural grasses that show an average delta13C value of -30.59 per thousand. A simple mixing model was used to calculate the contributions of fossil-fuel-derived CO2 to the plant tissue. Calculation based on contaminated and noncontaminated isotopic end members shows that urban grasses assimilate up to 29.1% of fossil-fuel-CO2-derived carbon in their tissues. The 13C isotopic composition of grasses thus represents a promising new tool for the study of the impact of fossil fuel CO2 in major cities.

  14. Testing a new Method of Estimating the δ13C of Photosynthate in Trees: Stem CO2 Equilibration}

    NASA Astrophysics Data System (ADS)

    Ubierna Lopez, N.; Kavanagh, K.; Marshall, J. D.

    2006-12-01

    Modeling and prediction of forest responses to climate change often deal with the difficulty of estimating gas- exchange responses to rising CO2 concentrations and temperatures. This difficulty can be overcome with stable carbon isotopes, which provide a tool to study the coupling of the carbon and water cycles. Recently, considerable research has concentrated on trying to identify processes occurring after photosynthesis that modify the isotopic composition of a given plant tissue, which has led to questions about which plant tissue will best reflect environmental variations and photosynthetic discrimination. Here, we propose a new method that uses CO2 collected from inside the stem. A simple collection apparatus consisting of a stainless steel tube is inserted into the tree. The gas from the stem diffuses and equilibrates with the headspace. Gas samples are subsequently collected by replacing the gas inside the tubing with acidified water. This technique minimizes any change in pressure inside the system or any atmospheric contamination from outside the system. We compared the measured δ13C of stem CO2 to known leaf values in four conifer species at Mica Creek Experimental Watershed, in northern Idaho, USA. In addition, δ13C of soil respiration, δ13C leaf bulk material, δ13C phloem contents, and photosynthetic gas- exchange data were collected. We collected stem CO2 samples weekly through August 2006 during a long drought period. Mean monthly temperature was 16°C, cumulative precipitation in July and August was 33 mm, and mean maximum VPD was 4.1 kPa during this month. The most depleted species was Larix occidentalis, with δ13C = -26.97 ‰ (SE = 0.30), following by the shade-tolerant Abies grandis, with δ13C = -26.33 ‰ (SE = 0.23). In comparison, Pseudotsuga menziesii, with δ13C = -24.88 ‰ (SE =0.48) and Thuja plicata with δ13C = - 23.79 ‰ (SE = 0.30) were more enriched. These δ13C values are consistent with previous measurements of leaf bulk

  15. Using Headspace Equilibration to Measure the d13C of Soil-Respired CO2

    NASA Astrophysics Data System (ADS)

    Robertson, M. A.; Powers, E.; Marshall, J.

    2007-12-01

    Soil respiration is an important component of the global carbon cycle and can account for as much as 70% of ecosystem respiration. Soil gas flux measurements have been combined with stable isotope analysis to examine ecosystem properties and processes such as water-use efficiency and the role of above ground weather in controlling soil respiration. However, current methods of measuring the δ13C of soil-respired CO2 are either inherently inaccurate or time-consuming and tedious. An alternative method of obtaining this value offers a potential solution to these problems. In this method, plastic chambers are fitted with rubber septa to allow for sample collection, then inverted and partially buried in soil. The chamber headspace is allowed to come to equilibrium with soil air. In this study we tested the viability of this method by examining whether frequent resampling of respiration chambers affected δ13C measurements, whether headspace CO2 concentration and δ13C values approached equilibrium asymptotically, and whether simulated and actual diel temperature cycles affected estimates of δ13C. All experiments were conducted on respiration chambers inverted in potting soil and placed in a Conviron growth chamber, with the exception of one field test that was conducted on respiration chambers installed in a Northern Idaho experimental forest. Samples were collected with a syringe and stored in glass vials for analysis by a ratioing mass spectrometer. We found that resampling respiration chambers as frequently as every 10 minutes had no significant effect on final δ13C values, that both chamber CO2 concentrations and δ13C values exhibited an asymptotic approach to equilibrium, and that the equilibrium value was offset from the initial flux by the amount we expected, approximately 4 ‰. However, we also found that diel temperature variation affected both headspace CO2 concentration and δ13C in the lab and in the field. We concluded that if this method is used in

  16. Vehicle emissions of greenhouse gases and related tracers from a tunnel study: CO : CO2, N2O : CO2, CH4 : CO2, O2 : CO2 ratios, and the stable isotopes 13C and 18O in CO2 and CO

    NASA Astrophysics Data System (ADS)

    Popa, M. E.; Vollmer, M. K.; Jordan, A.; Brand, W. A.; Pathirana, S. L.; Rothe, M.; Röckmann, T.

    2014-02-01

    Measurements of CO2, CO, N2O and CH4 mole fractions, O2 / N2 ratios and the stable isotopes 13C and 18O in CO2 and CO have been performed in air samples from the Islisberg highway tunnel (Switzerland). The molar CO : CO2 ratios, with an average of (4.15 ± 0.34) ppb:ppm, are lower than reported in previous studies, pointing to a reduction in CO emissions from traffic. The 13C in CO2 reflects the isotopic composition of the fuel. 18O in CO2 is slightly depleted compared to the 18O in atmospheric O2, and shows significant variability. In contrast, the δ13C values of CO show that significant fractionation takes place during CO destruction in the catalytic converter. 13C in CO is enriched by 3‰ compared to the 13C in the fuel burnt, while the 18O content is similar to that of atmospheric O2. We compute a fractionation constant of (-2.7 ± 0.7)‰ for 13C during CO destruction. The N2O : CO2 average ratio of (1.8 ± 0.2) × 10-2 ppb:ppm is significantly lower than in past studies, showing a reduction in N2O emissions likely related to improvements in the catalytic converter technology. We also observed small CH4 emissions, with an average CH4 : CO2 ratio of (4.6 ± 0.2) × 10-2 ppb:ppm. The O2 : CO2 ratios of (-1.47 ± 0.01) ppm:ppm are very close to the expected, theoretically calculated values of O2 depletion per CO2 enhancement.

  17. Depletion of 13C in Cretaceous marine organic matter: Source, diagenetic, or environmental sigal?

    USGS Publications Warehouse

    Dean, W.E.; Arthur, M.A.; Claypool, G.E.

    1986-01-01

    not produce a significant shift in ?? 13C in Miocene to Holocene sediments, and therefore probably did not produce the isotopically light Cretaceous OC. This means that Cretaceous marine plankton must have had ?? 13C values that were about 5??? lighter than modern marine plankton, and at least several per mil lighter than Cretaceous terrestrial vegetation. The reason for these lighter values, however, is not obvious. It has been proposed that concentrations of CO2 were higher during the middle Cretaceous, and this more available CO2 may be responsible for the lighter ?? 13C values of Cretaceous marine organic matter. ?? 1986.

  18. Improved CRDS δ13C Stability Through New Calibration Application For CO2 And CH4

    NASA Astrophysics Data System (ADS)

    Rella, Chris; Arata, Caleb; Saad, Nabil; Leggett, Graham; Miles, Natasha; Richardson, Scott; Davis, Ken

    2015-04-01

    Stable carbon isotope ratio measurements of CO2 and CH4 provide valuable insight into global and regional sources and sinks of the two most important greenhouse gases. Methodologies based on Cavity Ring-Down Spectroscopy (CRDS) have been developed and are capable of delivering δ13C measurements with a precision better than 0.12 permil for CO2 and 0.4 permil for CH4 (1 hour window, 5 minute average). Here we present a method to further improve this measurement stability. We have developed a two-point calibration method which corrects for δ13C drift due to a dependence on carbon species concentration. This method calibrates for both carbon species concentration as well as δ13C. In addition, we further demonstrate that this added stability is especially valuable when using carbon isotope data in linear regression models such as Keeling plots, where even small amounts of error can be magnified to give inconclusive results. Furthermore, we show how this method is used to validate multiple instruments simultaneously and can be used to create the standard samples needed for field calibrations.

  19. 13C fractionation of dinoflagellates - a new proxy for past CO2 levels?

    NASA Astrophysics Data System (ADS)

    Hoins, M.; Van de Waal, D. B.; Eberlein, T.; Reichart, G.; Sluijs, A.; Rost, B.

    2012-12-01

    Reliable reconstructions of atmospheric CO2 levels prior to ~1 million years ago are required to quantify climate sensitivity as well as ocean acidification in response to past carbon cycle perturbations. Despite recent progress, however, uncertainties in reconstructed values especially from the Paleogene and older, are still very large. We aim to develop a new proxy for CO2 concentrations based on the carbon isotopic fractionation of autotrophic marine dinoflagellates. Dinoflagellates feature RubisCO (type II) with the lowest CO2 affinity of all eukaryote phytoplankton, which makes this group inherently sensitive to changes in carbonate chemistry. Along with growth and carbon production also the 13C versus 12C incorporation, i.e., the 13C fractionation (ɛp), will likely be affected. Hence, the carbon isotopic composition of dinoflagellates may ultimately reflect the prevailing atmospheric CO2 concentrations. Crucially, microfossils of dinoflagellates, i.e. organic dinoflagellate cysts, have been recovered from ocean sediments as old as the Triassic (i.e. ~215 Ma BP). We performed dilute batch experiments with four dinoflagellate species: Alexandrium tamarense, Scrippsiella trochoidea, Gonyaulax spinifera and Protoceratium reticulatum. Cells were grown at various CO2 concentrations representing the Last Glacial Maximum (180 ppm), present day (380 ppm), and future projections (and estimates for distant past levels; 950 ppm and 1400 ppm). Consistent with expectations, ɛp increased with CO2 concentration in all four species (with a slope of up to 0.19 ‰ μM-1), while growth and carbon production (μc) had little effect. ɛp in relation to CO2 varied between species and strains, but the relation of ɛp to μc/CO2 was more consistent. First results of underlying processes affecting ɛp, including carbon acquisition and leakage, will be discussed. Considering that the cysts of P. reticulatum (Operculodinium centrocarpum) and G. spinifera (Spiniferites sp.) are

  20. 13C Tracking after 13CO2 Supply Revealed Diurnal Patterns of Wood Formation in Aspen.

    PubMed

    Mahboubi, Amir; Linden, Pernilla; Hedenström, Mattias; Moritz, Thomas; Niittylä, Totte

    2015-06-01

    Wood of trees is formed from carbon assimilated in the photosynthetic tissues. Determining the temporal dynamics of carbon assimilation, subsequent transport into developing wood, and incorporation to cell walls would further our understanding of wood formation in particular and tree growth in general. To investigate these questions, we designed a (13)CO2 labeling system to study carbon transport and incorporation to developing wood of hybrid aspen (Populus tremula × tremuloides). Tracking of (13)C incorporation to wood over a time course using nuclear magnetic resonance spectroscopy revealed diurnal patterns in wood cell wall biosynthesis. The dark period had a differential effect on (13)C incorporation to lignin and cell wall carbohydrates. No (13)C was incorporated into aromatic amino acids of cell wall proteins in the dark, suggesting that cell wall protein biosynthesis ceased during the night. The results show previously unrecognized temporal patterns in wood cell wall biosynthesis, suggest diurnal cycle as a possible cue in the regulation of carbon incorporation to wood, and establish a unique (13)C labeling method for the analysis of wood formation and secondary growth in trees.

  1. Estimation of continuous anthropogenic CO2: model-based evaluation of CO2, CO, δ13C(CO2) and Δ14C(CO2) tracer methods

    NASA Astrophysics Data System (ADS)

    Vardag, S. N.; Gerbig, C.; Janssens-Maenhout, G.; Levin, I.

    2015-11-01

    We investigate different methods for estimating anthropogenic CO2 using modeled continuous atmospheric concentrations of CO2 alone, as well as CO2 in combination with the surrogate tracers CO, δ13C(CO2) and Δ14C(CO2). These methods are applied at three hypothetical stations representing rural, urban and polluted conditions. We find that, independent of the tracer used, an observation-based estimate of continuous anthropogenic CO2 is not yet feasible at rural measurement sites due to the low signal-to-noise ratio of anthropogenic CO2 estimates at such settings. The tracers δ13C(CO2) and CO provide an accurate possibility to determine anthropogenic CO2 continuously, only if all CO2 sources in the catchment area are well characterized or calibrated with respect to their isotopic signature and CO to anthropogenic CO2 ratio. We test different calibration strategies for the mean isotopic signature and CO to CO2 ratio using precise Δ14C(CO2) measurements on monthly integrated as well as on grab samples. For δ13C(CO2), a calibration with annually averaged 14C(CO2) grab samples is most promising, since integrated sampling introduces large biases into anthropogenic CO2 estimates. For CO, these biases are smaller. The precision of continuous anthropogenic CO2 determination using δ13C(CO2) depends on measurement precision of δ13C(CO2) and CO2, while the CO method is mainly limited by the variation in natural CO sources and sinks. At present, continuous anthropogenic CO2 could be determined using the tracers δ13C(CO2) and/or CO with a precision of about 30 %, a mean bias of about 10 % and without significant diurnal discrepancies. Hypothetical future measurements of continuous Δ14C(CO2) with a precision of 5 ‰ are promising for anthropogenic CO2 determination (precision ca. 10-20 %) but are not yet available. The investigated tracer-based approaches open the door to improving, validating and reducing biases of highly resolved emission inventories using atmospheric

  2. Effects of Ontogeny on δ13C of Plant- and Soil-Respired CO2 and on Respiratory Carbon Fractionation in C3 Herbaceous Species.

    PubMed

    Salmon, Yann; Buchmann, Nina; Barnard, Romain L

    2016-01-01

    Knowledge gaps regarding potential ontogeny and plant species identity effects on carbon isotope fractionation might lead to misinterpretations of carbon isotope composition (δ13C) of respired CO2, a widely-used integrator of environmental conditions. In monospecific mesocosms grown under controlled conditions, the δ13C of C pools and fluxes and leaf ecophysiological parameters of seven herbaceous species belonging to three functional groups (crops, forage grasses and legumes) were investigated at three ontogenetic stages of their vegetative cycle (young foliage, maximum growth rate, early senescence). Ontogeny-related changes in δ13C of leaf- and soil-respired CO2 and 13C/12C fractionation in respiration (ΔR) were species-dependent and up to 7‰, a magnitude similar to that commonly measured in response to environmental factors. At plant and soil levels, changes in δ13C of respired CO2 and ΔR with ontogeny were related to changes in plant physiological status, likely through ontogeny-driven changes in the C sink to source strength ratio in the aboveground plant compartment. Our data further showed that lower ΔR values (i.e. respired CO2 relatively less depleted in 13C) were observed with decreasing net assimilation. Our findings highlight the importance of accounting for ontogenetic stage and plant community composition in ecological studies using stable carbon isotopes.

  3. Effects of Ontogeny on δ13C of Plant- and Soil-Respired CO2 and on Respiratory Carbon Fractionation in C3 Herbaceous Species

    PubMed Central

    Salmon, Yann; Buchmann, Nina; Barnard, Romain L.

    2016-01-01

    Knowledge gaps regarding potential ontogeny and plant species identity effects on carbon isotope fractionation might lead to misinterpretations of carbon isotope composition (δ13C) of respired CO2, a widely-used integrator of environmental conditions. In monospecific mesocosms grown under controlled conditions, the δ13C of C pools and fluxes and leaf ecophysiological parameters of seven herbaceous species belonging to three functional groups (crops, forage grasses and legumes) were investigated at three ontogenetic stages of their vegetative cycle (young foliage, maximum growth rate, early senescence). Ontogeny-related changes in δ13C of leaf- and soil-respired CO2 and 13C/12C fractionation in respiration (ΔR) were species-dependent and up to 7‰, a magnitude similar to that commonly measured in response to environmental factors. At plant and soil levels, changes in δ13C of respired CO2 and ΔR with ontogeny were related to changes in plant physiological status, likely through ontogeny-driven changes in the C sink to source strength ratio in the aboveground plant compartment. Our data further showed that lower ΔR values (i.e. respired CO2 relatively less depleted in 13C) were observed with decreasing net assimilation. Our findings highlight the importance of accounting for ontogenetic stage and plant community composition in ecological studies using stable carbon isotopes. PMID:27010947

  4. Mechanisms linking metabolism of Helicobacter pylori to (18)O and (13)C-isotopes of human breath CO2.

    PubMed

    Som, Suman; De, Anulekha; Banik, Gourab Dutta; Maity, Abhijit; Ghosh, Chiranjit; Pal, Mithun; Daschakraborty, Sunil B; Chaudhuri, Sujit; Jana, Subhra; Pradhan, Manik

    2015-06-03

    The gastric pathogen Helicobacter pylori utilize glucose during metabolism, but the underlying mechanisms linking to oxygen-18 ((18)O) and carbon-13 ((13)C)-isotopic fractionations of breath CO2 during glucose metabolism are poorly understood. Using the excretion dynamics of (18)O/(16)O and (13)C/(12)C-isotope ratios of breath CO2, we found that individuals with Helicobacter pylori infections exhibited significantly higher isotopic enrichments of (18)O in breath CO2 during the 2h-glucose metabolism regardless of the isotopic nature of the substrate, while no significant enrichments of (18)O in breath CO2 were manifested in individuals without the infections. In contrast, the (13)C-isotopic enrichments of breath CO2 were significantly higher in individuals with Helicobacter pylori compared to individuals without infections in response to (13)C-enriched glucose uptake, whereas a distinguishable change of breath (13)C/(12)C-isotope ratios was also evident when Helicobacter pylori utilize natural glucose. Moreover, monitoring the (18)O and (13)C-isotopic exchange in breath CO2 successfully diagnosed the eradications of Helicobacter pylori infections following a standard therapy. Our findings suggest that breath (12)C(18)O(16)O and (13)C(16)O(16)O can be used as potential molecular biomarkers to distinctively track the pathogenesis of Helicobacter pylori and also for eradication purposes and thus may open new perspectives into the pathogen's physiology along with isotope-specific non-invasive diagnosis of the infection.

  5. The post-Paleozoic chronology and mechanism of 13C depletion in primary marine organic matter

    NASA Technical Reports Server (NTRS)

    Popp, B. N.; Takigiku, R.; Hayes, J. M.; Louda, J. W.; Baker, E. W.

    1989-01-01

    Carbon-isotopic compositions of geoporphyrins have been measured from marine sediments of Mesozoic and Cenozoic age in order to elucidate the timing and extent of depletion of 13C in marine primary producers. These results indicate that the difference in isotopic composition of coeval marine carbonates and marine primary photosynthate was approximately 5 to 7 permil greater during the Mesozoic and early Cenozoic than at present. In contrast to the isotopic record of marine primary producers, isotopic compositions of terrestrial organic materials have remained approximately constant for this same interval of time. This difference in the isotopic records of marine and terrestrial organic matter is considered in terms of the mechanisms controlling the isotopic fractionation associated with photosynthetic fixation of carbon. We show that the decreased isotopic fractionation between marine carbonates and organic matter from the Early to mid-Cenozoic may record variations in the abundance of atmospheric CO2.

  6. A revised atmospheric δ13C-CO2 record covering the last 1000 years from Law Dome, Antarctica

    NASA Astrophysics Data System (ADS)

    Rubino, M.; Etheridge, D. M.; Trudinger, C. M.; Allison, C.; Battle, M. O.; Bender, M. L.; Langenfelds, R.; Steele, P.; Curran, M.; Blunier, T.; Jenk, T. M.; Francey, R.

    2012-12-01

    We present a revised and expanded record of atmospheric δ13C-CO2 extracted from ice cores sampled at Law Dome (East Antarctica) and firn air sampled at Law Dome and at South Pole covering the last 1000 years. We have performed new measurements of 13C of CO2 extracted from ice, incorporated the results from new firn sampling campaigns in Antarctica and merged them with a revised version of the previous δ13C-CO2 measurements [Francey et al., 1999]. Our new measurements from Law Dome ice increase the temporal sampling density over the last 200 years and show good agreement with the results from South Pole firn, providing evidence that our new record reliably extend the Cape Grim δ13C-CO2 record back in time. We also show the preliminary measurements aimed at covering the preindustrial period with higher sample density, including the 10 ppm CO2 decrease observed in ice from Law Dome at the beginning of 1600 AD [Etheridge et al., 1996, MacFarling Meure et al., 2006]. Having higher sample density for both CO2 and δ13C-CO2 in that period allows us to infer sources and sinks of CO2 with higher confidence. Corresponding author: Mauro Rubino, mauro.rubino@csiro.au, +61(0)392394634 References Etheridge, D. et al. (1996), ISSN: 01480227. MacFarling Meure, C. et al. (2006), DOI: 10.1029/2006GL026152. Francey, R. J. et al. (1999), ISSN: 02806509.

  7. Evaluating the Influence of Solar Radiation, Coral Extension Rate and Anthropogenic CO2 on Skeletal δ13C in a Network of Fiji and Tonga Porites Corals

    NASA Astrophysics Data System (ADS)

    Dassie, E. P.; Lemley, G. M.; Linsley, B. K.; Howe, S. S.

    2011-12-01

    While stable oxygen isotope signatures in coral reefs have proven to be reliable recorders of temperature and salinity, it is difficult to interpret their skeletal 13C/12C signatures. Various studies have suggested that coral skeletal δ13C is primarily controlled by complex physiological mechanisms. However, it has also been proposed that δ13C variations in coral skeletons are related to more apparent factors such as solar radiation, skeletal extension rate, and the anthropogenic addition of 13C-depleted CO2 into the atmosphere and surface ocean ("Suess Effect"). We will present time-series variations of δ13C in six coral cores from Fiji and Tonga (South Pacific Ocean). On seasonal timescales, increases in solar radiation are correlated to increases in skeletal δ13C and visa-versa. Annually averaged data shows a correlation between increased coral δ13C and reduced coral extension rate, while a decrease in δ13C is associated with an increased extension rate. In the most recent portion of four of the coral δ13C records (from around 1900 to the core top), the value progressively decreases - a trend that is not present in either the skeletal extension rate or solar radiation data. We conclude that this decreasing δ13C trend is a consequence of the Suess Effect, as reported in other coral δ13C records. However, two of the six corals do not show this decreasing trend, which may be a result of their residence in especially shallow water (sub-tidal environments). The onset of the Suess effect in the four corals may help constrain the timing of the uptake of anthropogenic carbon by the western South Pacific Ocean. Although all factors controlling δ13C variation in corals are not completely understood, this study works towards an understanding of their relative contribution to δ13C variation.

  8. 13C-DEPLETED MICROBIAL LIPIDS INDICATE SEASONAL METHANOTROPHIC ACTIVITY IN SHALLOW ESTUARINE SEDIMENTS

    EPA Science Inventory

    Compound specific isotope analysis was combined with phospholipid fatty acid (PLFA) analysis to identify methanotrophic activity in members of the sedimentary microbial community in the Altamaha and Savannah River estuaries in Georgia. 13C-depleted PLFAs indicate methane utilizat...

  9. Controls on 13C of ecosystem respired CO2 in Southeastern US forests

    NASA Astrophysics Data System (ADS)

    Mortazavi, B.; Chanton, J.; Smith, M.

    2006-12-01

    Pine-dominated southeastern United States forests constitute the largest documented carbon sink among North American or European forests. The extent of large-scale (hundreds of kilometers) spatial variability in the isotopic composition of ecosystem respired CO2 in this region is unresolved. We determined the δ13C of ecosystem (δCr), soil (δCs), and foliage (δCf) respired CO2 over a 2 year period (i) in a rotation-aged pine plantation and a (ii) 80 year old naturally regenerated pine forest in Florida, and contrasted our results with those from similar investigations in a pine plantation and naturally regenerated hardwood forest in North Carolina. We related δCr, δCf, and δCs to environmental factors using a time lag of 5 days. This time lag was based on metabolic pool turnover times determined with a year-long slash pine labeling experiment. Despite large variability in aboveground meteorological conditions, the isotopic composition of ecosystem respired carbon remained relatively constant. The isotopic composition of foliage soluble carbohydrates exhibited the same order of variability as δCr. Soil and stem water δ 18O profiles at both Florida sites indicate that the plants' primary water uptake zone is below the surficial layer of highly variable moisture content. This suggests that the plants are less responsive to variability in aboveground meteorological conditions due to reliable access to groundwater. In contrast, the forests studied in North Carolina derive water primarily from the variable surficial zone, and exhibited a time-lagged response to aboveground conditions. These results highlight that successful regional-scale generalizations of δCr based on local measurements must account for spatial variability in plant physiological responses to meteorological conditions and surface soil water conditions.

  10. Mechanisms linking metabolism of Helicobacter pylori to 18O and 13C-isotopes of human breath CO2

    PubMed Central

    Som, Suman; De, Anulekha; Banik, Gourab Dutta; Maity, Abhijit; Ghosh, Chiranjit; Pal, Mithun; Daschakraborty, Sunil B.; Chaudhuri, Sujit; Jana, Subhra; Pradhan, Manik

    2015-01-01

    The gastric pathogen Helicobacter pylori utilize glucose during metabolism, but the underlying mechanisms linking to oxygen-18 (18O) and carbon-13 (13C)-isotopic fractionations of breath CO2 during glucose metabolism are poorly understood. Using the excretion dynamics of 18O/16O and 13C/12C-isotope ratios of breath CO2, we found that individuals with Helicobacter pylori infections exhibited significantly higher isotopic enrichments of 18O in breath CO2 during the 2h-glucose metabolism regardless of the isotopic nature of the substrate, while no significant enrichments of 18O in breath CO2 were manifested in individuals without the infections. In contrast, the 13C-isotopic enrichments of breath CO2 were significantly higher in individuals with Helicobacter pylori compared to individuals without infections in response to 13C-enriched glucose uptake, whereas a distinguishable change of breath 13C/12C-isotope ratios was also evident when Helicobacter pylori utilize natural glucose. Moreover, monitoring the 18O and 13C-isotopic exchange in breath CO2 successfully diagnosed the eradications of Helicobacter pylori infections following a standard therapy. Our findings suggest that breath 12C18O16O and 13C16O16O can be used as potential molecular biomarkers to distinctively track the pathogenesis of Helicobacter pylori and also for eradication purposes and thus may open new perspectives into the pathogen’s physiology along with isotope-specific non-invasive diagnosis of the infection. PMID:26039789

  11. LASER BIOLOGY AND MEDICINE: Laser analysis of the 13C/12C isotope ratio in CO2 in exhaled air

    NASA Astrophysics Data System (ADS)

    Stepanov, E. V.

    2002-11-01

    Tunable diode lasers (TDLs) are applied to the diagnostics of gastroenterological diseases using respiratory tests and preparations enriched with the stable 13C isotope. This method of the analysis of the 13C/12C isotope ratio in CO2 in exhaled air is based on the selective measurement of the resonance absorption at the vibrational — rotational structure of 12CO2 and 13CO2. The CO2 transmission spectra in the region of 4.35 μm were measured with a PbEuSe double-heterostructure TDL. The accuracy of carbon isotope ratio measurements in CO2 of exhaled air performed with the TDL was ~0.5%. The data of clinical tests of the developed laser-based analyser are presented.

  12. Bacteria and fungi respond differently to multifactorial climate change in a temperate heathland, traced with 13C-glycine and FACE CO2.

    PubMed

    Andresen, Louise C; Dungait, Jennifer A J; Bol, Roland; Selsted, Merete B; Ambus, Per; Michelsen, Anders

    2014-01-01

    It is vital to understand responses of soil microorganisms to predicted climate changes, as these directly control soil carbon (C) dynamics. The rate of turnover of soil organic carbon is mediated by soil microorganisms whose activity may be affected by climate change. After one year of multifactorial climate change treatments, at an undisturbed temperate heathland, soil microbial community dynamics were investigated by injection of a very small concentration (5.12 µg C g(-1) soil) of (13)C-labeled glycine ((13)C2, 99 atom %) to soils in situ. Plots were treated with elevated temperature (+1°C, T), summer drought (D) and elevated atmospheric carbon dioxide (510 ppm [CO2]), as well as combined treatments (TD, TCO2, DCO2 and TDCO2). The (13)C enrichment of respired CO2 and of phospholipid fatty acids (PLFAs) was determined after 24 h. (13)C-glycine incorporation into the biomarker PLFAs for specific microbial groups (Gram positive bacteria, Gram negative bacteria, actinobacteria and fungi) was quantified using gas chromatography-combustion-stable isotope ratio mass spectrometry (GC-C-IRMS). Gram positive bacteria opportunistically utilized the freshly added glycine substrate, i.e. incorporated (13)C in all treatments, whereas fungi had minor or no glycine derived (13)C-enrichment, hence slowly reacting to a new substrate. The effects of elevated CO2 did suggest increased direct incorporation of glycine in microbial biomass, in particular in G(+) bacteria, in an ecosystem subjected to elevated CO2. Warming decreased the concentration of PLFAs in general. The FACE CO2 was (13)C-depleted (δ(13)C = 12.2‰) compared to ambient (δ(13)C = ∼-8‰), and this enabled observation of the integrated longer term responses of soil microorganisms to the FACE over one year. All together, the bacterial (and not fungal) utilization of glycine indicates substrate preference and resource partitioning in the microbial community, and therefore suggests a diversified response pattern

  13. Correction for the 17O interference in δ(13C) measurements when analyzing CO2 with stable isotope mass spectrometry

    USGS Publications Warehouse

    Coplen, Tyler B.; Brand, Willi A.; Assonov, Sergey S.

    2010-01-01

    Measurements of δ(13C) determined on CO2 with an isotope-ratio mass spectrometer (IRMS) must be corrected for the amount of 17O in the CO2. For data consistency, this must be done using identical methods by different laboratories. This report aims at unifying data treatment for CO2 IRMS by proposing (i) a unified set of numerical values, and (ii) a unified correction algorithm, based on a simple, linear approximation formula. Because the oxygen of natural CO2 is derived mostly from the global water pool, it is recommended that a value of 0.528 be employed for the factor λ, which relates differences in 17O and 18O abundances. With the currently accepted N(13C)/N(12C) of 0.011 180(28) in VPDB (Vienna Peedee belemnite) reevaluation of data yields a value of 0.000 393(1) for the oxygen isotope ratio N(17O)/N(16O) of the evolved CO2. The ratio of these quantities, a ratio of isotope ratios, is essential for the 17O abundance correction: [N(17O)/N(16O)]/[N(13C)/N(12C)] = 0.035 16(8). The equation [δ(13C) ≈ 45δVPDB-CO2 + 2 17R/13R (45δVPDB-CO2 – λ46δVPDB-CO2)] closely approximates δ(13C) values with less than 0.010 ‰ deviation for normal oxygen-bearing materials and no more than 0.026 ‰ in extreme cases. Other materials containing oxygen of non-mass-dependent isotope composition require a more specific data treatment. A similar linear approximation is also suggested for δ(18O). The linear approximations are easy to implement in a data spreadsheet, and also help in generating a simplified uncertainty budget.

  14. Real-time measurements of CO2 and δ13C in volcanic gases emitted in atmosphere from Mt. Etna (Italy)

    NASA Astrophysics Data System (ADS)

    Jost, H. J. H.; Rizzo, A. L.; Ancellin, M. A.; Caracausi, A.; Martelli, M.; Liotta, M.

    2014-12-01

    We present new data of real-time measurements of concentration and isotope (δ13C) composition of CO2in fumarolic and plume gases emitted from Mt. Etna volcano, performed by using a Delta Ray tunable diode laser. The first two campaigns of measurements were carried out on 11 July and on 5-6 September 2013, while a third campaign was performed in mid-July 2014. Data acquired along the route Catania-Etna, while car was moving, showed an excess of 13C-depleted CO2 when passing through inhabited centers due to atmospheric pollution produced by the cars exhaust. A similar behavior was observed when accidentally measuring car exhaust of our car. Differently, volcanic gases displayed a 13C-enrichment of CO2 if compared to air. With the assumption of a two components mixing, a simple linear regression was applied to the data in order to obtain the volcanogenic δ13C of CO2. Fumaroles of Torre del Filosofo (2,900 m a.s.l.) displayed a δ13C between -3.2±0.03‰ and -3.7±0.05‰, comparable to IRMS measurements of discrete samples collected in the same date and in previous investigations. Diluted plume gases were collected at more than 1 km from the craters and showed δ13C=-2.2±0.2‰, accordingly with collected crater fumaroles. Data collected in 2014 campaign are under processing, but preliminary results confirm a less negative signature of δ13C of CO2emitted from Central Craters if compared to Torre del Filosofo fumaroles, with some interesting variations over time that need to be compared with other simultaneously acquired parameters. Considering the huge amount of data that may be acquired in a very short time by Delta Ray, we demonstrate that the addition to the atmospheric CO2 content of ~100 ppm of CO2 from an unknown source is enough to allow a mathematical calculation of the end-member with an uncertainty generally < 0.15‰. This is feasible with the assumption of a binary mixing. We thus infer that these measurements performed at Mt. Etna, if performed

  15. Characterization of a Mixture of CO2 Adsorption Products in Hyperbranched Aminosilica Adsorbents by (13)C Solid-State NMR.

    PubMed

    Moore, Jeremy K; Sakwa-Novak, Miles A; Chaikittisilp, Watcharop; Mehta, Anil K; Conradi, Mark S; Jones, Christopher W; Hayes, Sophia E

    2015-11-17

    Hyperbranched amine polymers (HAS) grown from the mesoporous silica SBA-15 (hereafter "SBA-15-HAS") exhibit large capacities for CO2 adsorption. We have used static in situ and magic-angle spinning (MAS) ex situ (13)C nuclear magnetic resonance (NMR) to examine the adsorption of CO2 by SBA-15-HAS. (13)C NMR distinguishes the signal of gas-phase (13)CO2 from that of the chemisorbed species. HAS polymers possess primary, secondary, and tertiary amines, leading to multiple chemisorption reaction outcomes, including carbamate (RnNCOO(-)), carbamic acid (RnNCOOH), and bicarbonate (HCO3(-)) moieties. Carbamates and bicarbonate fall within a small (13)C chemical shift range (162-166 ppm), and a mixture was observed including carbamic acid and carbamate, the former disappearing upon evacuation of the sample. By examining the (13)C-(14)N dipolar coupling through low-field (B0 = 3 T) (13)C{(1)H} cross-polarization MAS NMR, carbamate is confirmed through splitting of the (13)C resonance. A third species that is either bicarbonate or a second carbamate is evident from bimodal T2 decay times of the ∼163 ppm peak, indicating the presence of two species comprising that single resonance. The mixture of products suggests that (1) the presence of amines and water leads to bicarbonate being present and/or (2) the multiple types of amine sites in HAS permit formation of chemically distinct carbamates.

  16. Are δ13C values of n-alkanes affected by atmospheric CO2 concentrations? Results from a free-air CO2 enrichment (FACE) experiment.

    NASA Astrophysics Data System (ADS)

    Sandquist, D. R.; Williams, D. G.; Shuman, B. N.; Kim, S.; Chen, J.; Macdonald, C.

    2015-12-01

    Compound-specific carbon isotope (δ13C) analyses of leaf waxes (i.e., n-alkanes) can be linked to large-scale shifts in vegetation, such as dominant taxa, functional types, life-forms and photosynthetic pathways that are usually coupled with environmental changes in climate. However using these δ13C values to interpret finer-scale ecosystem properties, including climate attributes such as CO2 concentrations, is difficult owing to uncertainty in the magnitude of internal biosynthetic fractionations that determine the δ13C of waxes relative to that of bulk leaf material. We investigated the composition, abundance and δ13C of n-alkanes in the aboveground biomass of a C4 grass and a C3 grass exposed to experimentally controlled CO2 at ambient [490ppm] and elevated [630ppm] levels within natural grassland in Wyoming. The δ13C values of bulk tissues were predictably different based on the C3 and C4 photosynthetic pathways, but the difference between bulk tissue and n-alkanes (ɛlipid), for both C29 and C31, was consistently greater in the C4 grass. The magnitudes of these ɛlipid values were large (- 7‰ to -15‰) relative to those found in most other studies. CO2 concentration of the growing environment also had a significant effect on n-alkane δ13C values, with consistently higher values of ~ 2‰ under elevated CO2 found in both species and in both a wet and a dry year. These results underscore the importance of recognizing potential abiotic effects on leaf wax δ13C values, in addition to the biotic drivers their variation, when interpreting climate from leaf-wax biomarkers of terrestrial ecosystems.

  17. The 13C-mixed triglyceride breath test in healthy adults: determinants of the 13CO2 response.

    PubMed

    Kalivianakis, M; Verkade, H J; Stellaard, F; van der Were, M; Elzinga, H; Vonk, R J

    1997-05-01

    Defects in lipolysis due to pancreatic insufficiency can be diagnosed by the mixed triglyceride (MTG) 13CO2 breath test. However, the effects of various test conditions on the 13CO2 response have only been partially elucidated. In healthy adults, we performed the 13CO2 mixed triglyceride breath test and we compared (a) the inter- and intra-individual variation in the 13CO2 response; (b) the effect of two different test meals; (c) the effect of an additional meal during the test; and (d) the effect of physical exercise during the test. Upon repeating the test in the same individual (test meal cream), repeatability coefficients were large, with respect to either time to maximum 13C excretion rate (3.8 h). maximum 13C excretion rate (4.9% 13C dose h-1) or cumulative recovery of 13C over the 9-h study period (22.7% 13C dose). The cumulative 13C expiration over 9 h obtained with the test meal composed of cream was quantitatively similar to that obtained with bread and butter: 42.2 +/- 8.4% and 47.7 +/- 6.3% respectively. Fasting for 9 h during the test resulted in similar 13C expiration rates and cumulative 13C expiration (43.4% +/- 7.2%) when compared with consumption of an additional meal 3 h after the start of the test (38.3 +/- 5.3%). The 13CO2 response increased in five out of seven subjects, but decreased in the other two, when moderate exercise was performed (bicycle ergometer, 50 W for 5 h). We conclude that the repeatability of the MTG test in healthy adults is low. The present results indicate that a solid and a liquid test meal, containing a similar amount of fats, give similar cumulative 13CO2 responses, and that stringent prolonged fasting during the test is unnecessary. Standardization of physical activity seems preferable, since the unequivocal effects of moderate exercise on the 13CO2 response were observed in the individuals studied. PMID:9179552

  18. Extreme (13)C depletion of carbonates formed during oxidation of biogenic methane in fractured granite.

    PubMed

    Drake, Henrik; Åström, Mats E; Heim, Christine; Broman, Curt; Åström, Jan; Whitehouse, Martin; Ivarsson, Magnus; Siljeström, Sandra; Sjövall, Peter

    2015-01-01

    Precipitation of exceptionally 13C-depleted authigenic carbonate is a result of, and thus a tracer for, sulphate-dependent anaerobic methane oxidation, particularly in marine sediments. Although these carbonates typically are less depleted in 13C than in the source methane, because of incorporation of C also from other sources, they are far more depleted in 13C13C as light as -69‰ V-PDB) than in carbonates formed where no methane is involved. Here we show that oxidation of biogenic methane in carbon-poor deep groundwater in fractured granitoid rocks has resulted in fracture-wall precipitation of the most extremely 13C-depleted carbonates ever reported, δ13C down to -125‰ V-PDB. A microbial consortium of sulphate reducers and methane oxidizers has been involved, as revealed by biomarker signatures in the carbonates and S-isotope compositions of co-genetic sulphide. Methane formed at shallow depths has been oxidized at several hundred metres depth at the transition to a deep-seated sulphate-rich saline water. This process is so far an unrecognized terrestrial sink of methane. PMID:25948095

  19. Extreme (13)C depletion of carbonates formed during oxidation of biogenic methane in fractured granite.

    PubMed

    Drake, Henrik; Åström, Mats E; Heim, Christine; Broman, Curt; Åström, Jan; Whitehouse, Martin; Ivarsson, Magnus; Siljeström, Sandra; Sjövall, Peter

    2015-05-07

    Precipitation of exceptionally 13C-depleted authigenic carbonate is a result of, and thus a tracer for, sulphate-dependent anaerobic methane oxidation, particularly in marine sediments. Although these carbonates typically are less depleted in 13C than in the source methane, because of incorporation of C also from other sources, they are far more depleted in 13C13C as light as -69‰ V-PDB) than in carbonates formed where no methane is involved. Here we show that oxidation of biogenic methane in carbon-poor deep groundwater in fractured granitoid rocks has resulted in fracture-wall precipitation of the most extremely 13C-depleted carbonates ever reported, δ13C down to -125‰ V-PDB. A microbial consortium of sulphate reducers and methane oxidizers has been involved, as revealed by biomarker signatures in the carbonates and S-isotope compositions of co-genetic sulphide. Methane formed at shallow depths has been oxidized at several hundred metres depth at the transition to a deep-seated sulphate-rich saline water. This process is so far an unrecognized terrestrial sink of methane.

  20. Extreme 13C depletion of carbonates formed during oxidation of biogenic methane in fractured granite

    PubMed Central

    Drake, Henrik; Åström, Mats E.; Heim, Christine; Broman, Curt; Åström, Jan; Whitehouse, Martin; Ivarsson, Magnus; Siljeström, Sandra; Sjövall, Peter

    2015-01-01

    Precipitation of exceptionally 13C-depleted authigenic carbonate is a result of, and thus a tracer for, sulphate-dependent anaerobic methane oxidation, particularly in marine sediments. Although these carbonates typically are less depleted in 13C than in the source methane, because of incorporation of C also from other sources, they are far more depleted in 13C13C as light as −69‰ V-PDB) than in carbonates formed where no methane is involved. Here we show that oxidation of biogenic methane in carbon-poor deep groundwater in fractured granitoid rocks has resulted in fracture-wall precipitation of the most extremely 13C-depleted carbonates ever reported, δ13C down to −125‰ V-PDB. A microbial consortium of sulphate reducers and methane oxidizers has been involved, as revealed by biomarker signatures in the carbonates and S-isotope compositions of co-genetic sulphide. Methane formed at shallow depths has been oxidized at several hundred metres depth at the transition to a deep-seated sulphate-rich saline water. This process is so far an unrecognized terrestrial sink of methane. PMID:25948095

  1. Assimilation of xylem-transported 13C-labelled CO2 in leaves and branches of sycamore (Platanus occidentalis L.).

    PubMed

    McGuire, M A; Marshall, J D; Teskey, R O

    2009-01-01

    Previous reports have shown that CO(2) dissolved in xylem sap in tree stems can move upward in the transpiration stream. To determine the fate of this dissolved CO(2), the internal transport of respired CO(2) at high concentration from the bole of the tree was simulated by allowing detached young branches of sycamore (Platanus occidentalis L.) to transpire water enriched with a known quantity of (13)CO(2) in sunlight. Simultaneously, leaf net photosynthesis and CO(2) efflux from woody tissue were measured. Branch and leaf tissues were subsequently analysed for (13)C content to determine the quantity of transported (13)CO(2) label that was fixed. Treatment branches assimilated an average of 35% (SE=2.4) of the (13)CO(2) label taken up in the treatment water. The majority was fixed in the woody tissue of the branches, with smaller amounts fixed in the leaves and petioles. Overall, the fixation of internally transported (13)CO(2) label by woody tissues averaged 6% of the assimilation of CO(2) from the atmosphere by the leaves. Woody tissue assimilation rates calculated from measurements of (13)C differed from rates calculated from measurements of CO(2) efflux in the lower branch but not in the upper branch. The results of this study showed unequivocally that CO(2) transported in xylem sap can be fixed in photosynthetic cells in the leaves and branches of sycamore trees and provided evidence that recycling of xylem-transported CO(2) may be an important means by which trees reduce the carbon cost of respiration.

  2. The 13C Suess effect in scleractinian corals mirror changes in the anthropogenic CO2 inventory of the surface oceans

    NASA Astrophysics Data System (ADS)

    Swart, Peter K.; Greer, Lisa; Rosenheim, Brad E.; Moses, Chris S.; Waite, Amanda J.; Winter, A.; Dodge, Richard E.; Helmle, Kevin

    2010-03-01

    New δ13C data are presented from 10 coral skeletons collected from Florida and elsewhere in the Caribbean (Dominica, Dominican Republic, Puerto Rico, and Belize). These corals range from 96 to 200 years in age and were collected between 1976 and 2002. The change in the δ13C of the skeletons from these corals between 1900 and 1990 has been compared with 27 other published coral records from the Atlantic, Pacific, and Indian Oceans. The new data presented here make possible, for the first time, a global comparison of rates of change in the δ13C value of coral skeletons. Of these records, 64% show a statistically significant (p < 0.05) decrease in δ13C towards the modern day (23 out of 37). This decrease is attributable to the addition of anthropogenically derived CO2 (13C Suess effect) to the atmosphere. Between 1900 and 1990, the average rate of change of the δ13C in all the coral skeletons living under open oceanic conditions is approximately -0.01‰ yr-1. In the Atlantic Ocean the magnitude of the decrease since 1960,-0.019 yr-1 ±0.015‰, is essentially the same as the decrease in the δ13C of atmospheric CO2 and the δ13C of the oceanic dissolved inorganic carbon (-0.023 to -0.029‰ yr-1), while in the Pacific and Indian Oceans the rate is more variable and significantly reduced (-0.007‰ yr-1 ±0.013). These data strongly support the notion that (i) the δ13C of the atmosphere controls ambient δ13C of the dissolved inorganic carbon which in turn is reflected in the coral skeletons, (ii) the rate of decline in the coral skeletons is higher in oceans with a greater anthropogenic CO2 inventory in the surface oceans, (iii) the rate of δ13C decline is accelerating. Superimposed on these secular variations are controls on the δ13C in the skeleton governed by growth rate, insolation, and local water masses.

  3. Fate of xylem-transported 11C- and 13C-labeled CO2 in leaves of poplar.

    PubMed

    Bloemen, Jasper; Bauweraerts, Ingvar; De Vos, Filip; Vanhove, Christian; Vandenberghe, Stefaan; Boeckx, Pascal; Steppe, Kathy

    2015-04-01

    In recent studies, assimilation of xylem-transported CO2 has gained considerable attention as a means of recycling respired CO2 in trees. However, we still lack a clear and detailed picture on the magnitude of xylem-transported CO2 assimilation, in particular within leaf tissues. To this end, detached poplar leaves (Populus × canadensis Moench 'Robusta') were allowed to take up a dissolved (13)CO2 label serving as a proxy of xylem-transported CO2 entering the leaf from the branch. The uptake rate of the (13)C was manipulated by altering the vapor pressure deficit (VPD) (0.84, 1.29 and 1.83 kPa). Highest tissue enrichments were observed under the highest VPD. Among tissues, highest enrichment was observed in the petiole and the veins, regardless of the VPD treatment. Analysis of non-labeled leaves showed that some (13)C diffused from the labeled leaves and was fixed in the mesophyll of the non-labeled leaves. However, (13)C leaf tissue enrichment analysis with elemental analysis coupled to isotope ratio mass spectrometry was limited in spatial resolution at the leaf tissue level. Therefore, (11)C-based CO2 labeling combined with positron autoradiography was used and showed a more detailed spatial distribution within a single tissue, in particular in secondary veins. Therefore, in addition to (13)C, (11) C-based autoradiography can be used to study the fate of xylem-transported CO2 at leaf level, allowing the acquisition of data at a yet unprecedented resolution.

  4. Variation in the leaf δ(13)C is correlated with salinity tolerance under elevated CO(2) concentration.

    PubMed

    del Amor, Francisco M

    2013-02-15

    Increasing atmospheric CO(2) concentration is expected to impact agricultural systems through a direct effect on leaf gas exchange and also due to effects on the global availability of good-quality water as a result of climate warming. Thus, the planning of land use for agriculture requires new tools to identify the capability of current cultivars to adapt to growth restrictions under new ambient conditions. We hypothesized that salinity stress may produce a specific pattern of carbon isotopic composition (δ(13)C) in tomato (Solanum lycopersicum L.) at elevated CO(2) concentration ([CO(2)]) that could be used in the breeding of salinity tolerance in a near-future climate scenario. Five commercial tomato cultivars were evaluated at elevated (800 μmol mol(-1)) or standard (400 μmol mol(-1)) [CO(2)], being irrigated with a nutrient solution containing 0, 60 or 120 mM NaCl. The biomass enhanced ratio, leaf net CO(2) assimilation and stomatal conductance, leaf NO(3)(-) and Cl(-) concentrations and leaf free amino acid profile were analyzed in relation to the pattern of δ(13)C, under different saline stress conditions. The results indicate that at high [CO(2)]: (i) salinity tolerance was enhanced, but the response was strongly cultivar dependent, (ii) leaf NO(3)(-) concentration was increased whilst Cl(-) and proline concentrations decreased, and (iii) leaf δ(13)C was highly correlated with plant dry matter accumulation and with leaf proline concentration, leaf gas exchange and ion concentrations. This study shows that δ(13)C is a useful tool for the determination of the salinity tolerance of tomato at high [CO(2)], as an integrative parameter of the stress period, and was validated by traditional physiological plant stress traits.

  5. Bacteria and Fungi Respond Differently to Multifactorial Climate Change in a Temperate Heathland, Traced with 13C-Glycine and FACE CO2

    PubMed Central

    Andresen, Louise C.; Dungait, Jennifer A. J.; Bol, Roland; Selsted, Merete B.; Ambus, Per; Michelsen, Anders

    2014-01-01

    It is vital to understand responses of soil microorganisms to predicted climate changes, as these directly control soil carbon (C) dynamics. The rate of turnover of soil organic carbon is mediated by soil microorganisms whose activity may be affected by climate change. After one year of multifactorial climate change treatments, at an undisturbed temperate heathland, soil microbial community dynamics were investigated by injection of a very small concentration (5.12 µg C g−1 soil) of 13C-labeled glycine (13C2, 99 atom %) to soils in situ. Plots were treated with elevated temperature (+1°C, T), summer drought (D) and elevated atmospheric carbon dioxide (510 ppm [CO2]), as well as combined treatments (TD, TCO2, DCO2 and TDCO2). The 13C enrichment of respired CO2 and of phospholipid fatty acids (PLFAs) was determined after 24 h. 13C-glycine incorporation into the biomarker PLFAs for specific microbial groups (Gram positive bacteria, Gram negative bacteria, actinobacteria and fungi) was quantified using gas chromatography-combustion-stable isotope ratio mass spectrometry (GC-C-IRMS). Gram positive bacteria opportunistically utilized the freshly added glycine substrate, i.e. incorporated 13C in all treatments, whereas fungi had minor or no glycine derived 13C-enrichment, hence slowly reacting to a new substrate. The effects of elevated CO2 did suggest increased direct incorporation of glycine in microbial biomass, in particular in G+ bacteria, in an ecosystem subjected to elevated CO2. Warming decreased the concentration of PLFAs in general. The FACE CO2 was 13C-depleted (δ13C = 12.2‰) compared to ambient (δ13C = ∼−8‰), and this enabled observation of the integrated longer term responses of soil microorganisms to the FACE over one year. All together, the bacterial (and not fungal) utilization of glycine indicates substrate preference and resource partitioning in the microbial community, and therefore suggests a diversified response pattern to future

  6. Monitoring CO2 concentration and δ13C in an underground cavity using a commercial isotope ratio infrared spectrometer

    NASA Astrophysics Data System (ADS)

    Guillon, Sophie; Agrinier, Pierre; Pili, Éric

    2015-04-01

    CO2 stable carbon isotopes are very attractive in environmental research to investigate both natural and anthropogenic carbon sources. Laser-based isotope ratio infrared spectrometers (IRIS) allow in situ continuous monitoring of CO2 isotopes, and therefore they have a potential for unprecedented understanding of carbon sources and dynamics with a high temporal resolution. Here we present the performance assessment of a commercial IRIS analyzer, including the measurement setup and the data processing scheme that we used. Even if the analyzer performs 1-Hz measurements, an integration time of the order of 1 h is commonly needed to obtain acceptable precision for δ13C. The main sources of uncertainty on δ13C come from the concentration dependence and from the temporal instability of the analyzer. The method is applied to the in situ monitoring of the CO2 carbon isotopes in an underground cavity (Roselend Natural Laboratory, France) during several months. On a weekly timescale, the temporal variability of CO2 is dominated by transient contamination by human breath. Discarding these anthropogenic contaminations, CO2 and δ13C backgrounds do not show diurnal or seasonal fluctuations. A CO2 flux released into the tunnel by the surrounding rocks is measured. The carbon isotope composition of this CO2, identified with a Keeling plot, is consistent with a main production by microbial respiration and a minor production from weathering of carbonate minerals. The presented instrument and application study are relevant to cave monitoring, whether to understand CO2 dynamics in visited and/or painted caves for preservation purposes or to understand paleoclimate recording in speleothems.

  7. Rapid detection and characterization of surface CO2 leakage through the real-time measurement of δ13C signatures in CO2 flux from the ground

    NASA Astrophysics Data System (ADS)

    Krevor, S.; Perrin, J.; Esposito, A.; Rella, C.; Benson, S. M.

    2009-12-01

    A portable stable carbon isotope ratio analyzer for carbon dioxide, based on wavelength scanned cavity ringdown spectroscopy, has been used to detect and characterize an intentional leakage of CO2 from an underground pipeline at the ZERT experimental facility in Bozeman, Montana. Rapid (~1 hour) walking surveys of the entire 100m x 100m site were collected using this mobile, real-time instrument. The resulting concentration and 13C isotopic abundance maps were processed using simple yet powerful analysis techniques, permitting not only the identification of specific leakage locations, but providing the ability to distinguish petrogenic sources of CO2 from biogenic sources. At the site an approximately 100-meter horizontal well has been drilled below an alfalfa field at a depth between 1-3 meters below the surface. The well has perforations along the central 70 meters of the well. The overlying strata are highly permeable sand, silt, and topsoil. The flora consists generally of long grasses and was cut to a height of less than 6 inches before the start of the experiment. For 30 days starting July 15, 2009, CO2 was injected at a rate of 0.2 tonnes per day. The injection rate is designed to simulate leakage from a mature storage reservoir at an annual rate of between .001 and .01%. The isotopic composition of the gas from the tank is at δ13C signature of approximately -52‰, far more negative than either atmospheric (approx. -8‰) or CO2 from soil respiration (approx. -26‰) at the site. The CO2 isotopic and concentration measurements were taken with a Picarro WS-CRDS analyzer with 1/8” tubing connected to a sampling inlet. Simultaneous with CO2 concentrations (including 13C), position data was logged using a GPS receiver. Datapoints are taken around every second. The analyzer was powered using batteries and housed in a conventional garden cart. The surveys consisted of traverses of the site along the length of the pipeline and extending out 100 meters on either

  8. Does sedimentary organic delta 13C record variations in quaternary ocean [CO2(aq)]?

    NASA Technical Reports Server (NTRS)

    Rau, G. H.; Froelich, P. N.; Takahashi, T.; Des Marais, D. J.

    1991-01-01

    Ocean surface water [CO2(aq)] variations based on glacial/interglacial changes in sediment delta 13Corg are shown to compare favorably with reconstructions based on ice core [CO2]. In particular, an approximate 80 microatmospheres increase in atmospheric pCO2 during the last glacial-interglacial transition is calculated to correspond to a 3-4 micromolar increase in ocean surface water [CO2(aq)] at atmospheric equilibrium. A widespread marine delta 13Corg decrease of 1-2% accompanied this event and was not preceded by an equivalent isotopic change in surface water total dissolved inorganic carbon. These observations support the hypothesis that [CO2(aq)] influences photosynthetic isotope fractionation between marine inorganic and organic carbon pools, and therefore that plankton/sediment delta 13Corg may serve as a proxy for surface water [CO2(aq)].

  9. A 13C labelling study on carbon fluxes in Arctic plankton communities under elevated CO2 levels

    NASA Astrophysics Data System (ADS)

    de Kluijver, A.; Soetaert, K.; Czerny, J.; Schulz, K. G.; Boxhammer, T.; Riebesell, U.; Middelburg, J. J.

    2013-03-01

    The effect of CO2 on carbon fluxes (production, consumption, and export) in Arctic plankton communities was investigated during the 2010 EPOCA (European project on Ocean Acidification) mesocosm study off Ny Ålesund, Svalbard. 13C labelled bicarbonate was added to nine mesocosms with a range in pCO2 (185 to 1420 μatm) to follow the transfer of carbon from dissolved inorganic carbon (DIC) into phytoplankton, bacterial and zooplankton consumers, and export. A nutrient-phytoplankton-zooplankton-detritus model amended with 13C dynamics was constructed and fitted to the data to quantify uptake rates and carbon fluxes in the plankton community. The plankton community structure was characteristic for a post-bloom situation and retention food web and showed high bacterial production (∼31% of primary production), high abundance of mixotrophic phytoplankton, low mesozooplankton grazing (∼6% of primary production) and low export (∼7% of primary production). Zooplankton grazing and export of detritus were sensitive to CO2: grazing decreased and export increased with increasing pCO2. Nutrient addition halfway through the experiment increased the export, but not the production rates. Although mixotrophs showed initially higher production rates with increasing CO2, the overall production of POC (particulate organic carbon) after nutrient addition decreased with increasing CO2. Interestingly, and contrary to the low nutrient situation, much more material settled down in the sediment traps at low CO2. The observed CO2 related effects potentially alter future organic carbon flows and export, with possible consequences for the efficiency of the biological pump.

  10. Evaluation of 4 years of continuous δ13C(CO2) data using a moving Keeling plot method

    NASA Astrophysics Data System (ADS)

    Vardag, Sanam Noreen; Hammer, Samuel; Levin, Ingeborg

    2016-07-01

    Different carbon dioxide (CO2) emitters can be distinguished by their carbon isotope ratios. Therefore measurements of atmospheric δ13C(CO2) and CO2 concentration contain information on the CO2 source mix in the catchment area of an atmospheric measurement site. This information may be illustratively presented as the mean isotopic source signature. Recently an increasing number of continuous measurements of δ13C(CO2) and CO2 have become available, opening the door to the quantification of CO2 shares from different sources at high temporal resolution. Here, we present a method to compute the CO2 source signature (δS) continuously and evaluate our result using model data from the Stochastic Time-Inverted Lagrangian Transport model. Only when we restrict the analysis to situations which fulfill the basic assumptions of the Keeling plot method does our approach provide correct results with minimal biases in δS. On average, this bias is 0.2 ‰ with an interquartile range of about 1.2 ‰ for hourly model data. As a consequence of applying the required strict filter criteria, 85 % of the data points - mainly daytime values - need to be discarded. Applying the method to a 4-year dataset of CO2 and δ13C(CO2) measured in Heidelberg, Germany, yields a distinct seasonal cycle of δS. Disentangling this seasonal source signature into shares of source components is, however, only possible if the isotopic end members of these sources - i.e., the biosphere, δbio, and the fuel mix, δF - are known. From the mean source signature record in 2012, δbio could be reliably estimated only for summer to (-25.0 ± 1.0) ‰ and δF only for winter to (-32.5 ± 2.5) ‰. As the isotopic end members δbio and δF were shown to change over the season, no year-round estimation of the fossil fuel or biosphere share is possible from the measured mean source signature record without additional information from emission inventories or other tracer measurements.

  11. Time Series of CO2 Mixing Ratios, Delta-13C, and Delta-18O in Air in Pasadena, CA

    NASA Astrophysics Data System (ADS)

    Newman, S.; Stolper, E.

    2008-12-01

    Flask air samples have been collected mid-afternoon every 1-2 days since October 1998 on the Caltech campus in Pasadena, CA, located ~14 km northeast of Los Angeles. The samples were analyzed by manometry for CO2 mixing ratio and by dual inlet mass spectrometry for δ13C and δ18O. Preliminary time series analyses of all three parameters reveal periodicities at 1 and 0.5 year and 7 days. For comparison, time series of CO2 mixing ratios, δ13C, and δ18O for the Mauna Loa observatory only show periodicities of approximately 1 and 0.5 years (although the record for Mauna Loa cannot show a periodicity at 1 week given the sampling frequency). Seasonal plant growth patterns can explain the 0.5 and 1 year signals. The 7-day cycle in Pasadena could well be due to emissions from burning of fossil fuels, especially gasoline during the workweek. More detailed investigation of seasonal patterns in the Pasadena time series reveals that the seasonal variation amplitudes for δ13C and δ18O are twice as large for Pasadena air as for clean Hawaiian air, and the δ13C pattern is inverted in Pasadena relative to that at Mauna Loa. There is no well-defined seasonal variation in CO2 mixing ratio in Pasadena, in contrast to the well-known Mauna Loa pattern. The seasonal variations in Pasadena reflect the superposition of local contributions of CO2 in Pasadena on global temporal variations, as reflected at clean air sites such as Mauna Loa. The local contributions are significant: e.g., the total CO2 concentration in Pasadena is ~30 ppm higher than at Mauna Loa. The Pasadena pattern reflects burning of fossil fuels that introduces light CO2 into the atmosphere preferentially during the hot summer months when there is more demand for electricity for air conditioning. Thus, CO2 mixing ratios do not decrease during the summer in the urban Los Angeles basin, but rather, the local anthropogenic contribution overwhelms the seasonal pattern observed in clean air.

  12. Using Atmospheric δ13C of CO2 observations to link the water and carbon cycles with climate

    NASA Astrophysics Data System (ADS)

    Alden, C. B.; Miller, J. B.; White, J. W.; Yadav, V.; Michalak, A. M.; Andrews, A. E.; Huang, L.

    2013-12-01

    The ratio of stable carbon isotopes, 13C:12C in atmospheric CO2 (expressed as δ13C) offers unique insights into atmosphere-land CO2 fluxes and the modulating effects of stomatal conductance on this exchange. Photosynthesis discriminates against 13CO2 during uptake. The magnitude of this fractionation is strongly dependent upon ambient CO2 concentrations and water availability, as well as on the mix of C3 and C4 vegetation types. C3 and C4 plants have very different discrimination because of carboxylation pathways, and C3 stomatal conductance varies with water availability because stomata close to reduce transpiration when plants are water stressed. Further, plant stomata respond to ambient CO2 concentrations in order to optimize leaf internal [CO2] while reducing transpirative water loss. Atmospheric δ13C therefore carries information about local and upwind drought conditions and the consequent likelihood of ground-to-atmosphere water transfer via transpiration, and the balance of latent and sensible heat fluxes, as well as about local and upwind distributions of C3 and C4 vegetation and variability therein. δ13C offers a unique lens through which to identify key thresholds and relationships between climate anomalies/change and the modulating climate impacts of plant biosphere response. By unraveling this relationship at local to continental scales, we stand to gain crucial understanding of the drivers of land CO2 uptake variability as well as knowledge of how to predict future climate impacts on the carbon cycle and vice versa. We use a two-step Bayesian inversion model to optimize 1x1 degree and 3-hourly (interpreted at regional and weekly to monthly scales) fields of δ13C of assimilated biomass over North America for the year 2010, using influence functions generated with FLEXPART, driven by National Centers for Environmental Prediction Global Forecast System meteorology. Prior fluxes and fossil fuel, ocean and fire fluxes are from CarbonTracker 2011, and

  13. Using regional-scale atmospheric δ13C of CO2 as an indicator of ecosystem health and function

    NASA Astrophysics Data System (ADS)

    Alden, C. B.; Miller, J. B.; White, J. W.; Yadav, V.; Michalak, A. M.

    2012-12-01

    Year to year terrestrial CO2 uptake and release is highly variable and is a result of, among other factors, weather and climate variability. One of the key ecosystem parameters that links surface-atmosphere fluxes of energy, water and carbon is stomatal conductance. By measuring and analyzing atmospheric patterns of CO2 and its 13C content over North America, we can begin to identify regional scale changes in stomatal conductance, because conductance is closely related to plant isotopic discrimination. Furthermore, 13C is a useful tracer of the differential responses of C3 and C4 plants to climate and weather anomalies, because C3 and C4 plants have very different isotopic discrimination. Both aspects of the terrestrial carbon cycle are of great interest to those seeking to understand the potential effects of global climate change on cropland and forest productivity, natural CO2 sinks, continental runoff, and continental water and energy exchange with the atmosphere. Our findings may be particularly important for parameterization of process-based models, in light of recent results suggesting that stomatal conductance models driven by vapor pressure deficit (Leuning Model) better predict atmospheric δ13C than do models driven by relative humidity (Ball-Berry Model). For the first time, spatial and temporal density of δ13C of CO2 atmospheric observations may be high enough to allow for regional inversions of δ13CO2 to optimize prior estimates of plant discrimination (and disequilibrium flux -- an isoflux resulting from the combination of a finite residence time of carbon in terrestrial biosphere pools and a changing atmospheric signature due to human burning of fossil fuels with a plant-derived δ13C signature). We perform a Bayesian synthesis inversion for 1) CO2 fluxes and 2) δ13CO2 isofluxes, over the North American region: 145-25°W longitude and 10-80°N latitude. Inversion resolution, in order to avoid aggregation errors, is 1°x1° and 3-hourly, but

  14. Atmospheric CO2 level affects plants' carbon use efficiency: insights from a 13C labeling experiment on sunflower stands

    NASA Astrophysics Data System (ADS)

    Gong, Xiaoying; Schäufele, Rudi; Schnyder, Hans

    2015-04-01

    The increase of atmospheric CO2 concentration has been shown to stimulate plant photosynthesis and (to a lesser extent) growth, thereby acting as a possible sink for the additional atmospheric CO2. However, this effect is dependent on the efficiency with which plants convert atmospheric carbon into biomass carbon, since a considerable proportion of assimilated carbon is returned to the atmosphere via plant respiration. As a core parameter for carbon cycling, carbon use efficiency of plants (CUE, the ratio of net primary production to gross primary production) quantifies the proportion of assimilated carbon that is incorporated into plant biomass. CUE has rarely been assessed based on measurements of complete carbon balance, due to methodological difficulties in measuring respiration rate of plants in light. Moreover, foliar respiration is known to be inhibited in light, thus foliar respiration rate is generally lower in light than in dark. However, this phenomenon, termed as inhibition of respiration in light (IRL), has rarely been assessed at the stand-scale and been incorporated into the calculation of CUE. Therefore, how CUE responses to atmospheric CO2 levels is still not clear. We studied CUE of sunflower stands grown at sub-ambient CO2 level (200 μmol mol-1) and elevated CO2 level (1000 μmol mol-1) using mesocosm-scale gas exchange facilities which enabled continuous measurements of 13CO2/12CO2 exchange. Appling steady-state 13C labeling, fluxes of respiration and photosynthesis in light were separated, and tracer kinetic in respiration was analyzed. This study provides the first data on CUE at a mesocosm-level including respiration in light in different CO2 environments. We found that CUE of sunflower was lower at an elevated CO2 level than at a sub-ambient CO2 level; and the ignorance of IRL lead to erroneous estimations of CUE. Variation in CUE at atmospheric CO2 levels was attributed to several mechanisms. In this study, CO2 enrichment i) affected the

  15. REAL TIME CONTINUOUS MEASUREMENTS OF [CO2] AND δ13C AT MULTIPLE LOCATIONS USING CAVITY ENHANCED LASER ABSORPTION

    NASA Astrophysics Data System (ADS)

    McAlexander, W. I.; Rau, G. H.; Dobeck, L.; Spangler, L.

    2009-12-01

    A commercial instrument (Los Gatos Research, model 908-0003) utilizing Cavity Enhanced Laser Absorption Spectroscopy was deployed in 2009 at the ZERT carbon release site (Bozeman, MT) for real time measurement of above-ground CO2 concentration and isotope ratio (δ13C). An automated switching system sampled 13 different locations in the field, as well as two known references, over an 8 day period. Real-time Keeling plots were constructed showing distinct signatures of soil (-27.0 ‰) and fossil (-56.0 ‰) sources compared to background air (-8.2 ‰). Instrument performance gave 0.2 ‰ precision with only 100 seconds of averaging per inlet. Sequential sampling of the various inlets gave a temporal and physical mapping of the CO2 release plume that is difficult to obtain using more conventional techniques. The figures show the nature and quality of the data from one of the locations. Details concerning instrument performance, systematics, calibration, and data processing will be discussed. Fig1: Time chart of CO2 concentration and isotope ratio δ13C from one of 13 sample inlet locations at ZERT release field, July, 2009. Fig2: Keeling plot of data from Fig1 illustrating the two source mixing of soil (-27 ‰) and fossil (-56 ‰) CO2 with background air.

  16. Mineral nutrition and elevated [CO(2)] interact to modify δ(13)C, an index of gas exchange, in Norway spruce.

    PubMed

    Marshall, John D; Linder, Sune

    2013-11-01

    The effects of the past century's increase in atmospheric CO2 concentration ([CO2]) have been recorded in the stable carbon isotope composition (δ(13)C) of the annual growth rings of trees. The isotope record frequently shows increases in photosynthetic CO2 uptake relative to stomatal conductance, which estimates the CO2 concentration gradient across the stomata (ca - ci). This variable, which is one control over the net photosynthetic rate, has been suggested as a homeostatic gas-exchange set point that is easy to estimate from δ(13)C and [CO2]. However, in high-latitude conifer forests, the literature is mixed; some studies show increases in (ca - ci) and others show homeostasis. Here we present leaf and tree-ring δ(13)C data from a controlled experiment that tested factorial combinations of elevated [CO2] (365 and 700 ∝mol mol(-1)) and fertilization on mature Norway spruce (Picea abies (L.) Karst.) trees in northern Sweden. We found first that the leaf carbon pool was contaminated by the current photosynthate in the older leaf cohorts. This is the reverse of the common observation that older photosynthate reserves can be used to produce new tissue; here the older tissue contains recent photosynthate. We found that the tree-ring data lack such contamination and in any case they better integrate over the canopy and the growing season than do leaves. In the second and third years of treatment, elevated [CO2] alone increased (ca - ci) by 38%; when combined with fertilization, it increased (ca - ci) by 60%. The results of this study support the idea that annual rings provide a clearer isotopic signal than do foliage age-classes. The tree-ring data show that inferred (ca - ci) depends not only on [CO2], but also on mineral-nutrient status. The differences in (ca - ci) are sufficiently large to account for the treatment-induced increase in wood-volume production in these stands.

  17. Peatland CO2 emissions: Using 13C to quantify responses to land use change

    NASA Astrophysics Data System (ADS)

    Snell, Helen; Robinson, David; Midwood, Andrew J.

    2013-04-01

    Soil is the largest terrestrial carbon reservoir and annually soils emit about 98 billion tonnes of CO2which is derived from plant root and rhizosphere respiration (autotrophically fuelled by photosynthesis) and microbial degradation of soil organic carbon (heterotrophic respiration). These two processes are intrinsically linked by complex physical and biochemical interactions. In order to meet its GHG reductions targets the Scottish Government plans to increase woodland cover from 17 to 25% by the second half of this century which will inevitably lead to significant tree planting on peatland soils. Tree roots and associated mycorrhiza will alter physical and biological conditions in the soil which may affect the heterotrophic contribution to CO2 emissions and consequently the long term landscape-scale carbon balance since the difference between net primary productivity and heterotrophic respiration defines the terrestrial CO2 sink. Significant uncertainties surround the response of peatlands to tree planting and predicted climate changes. At a field site in eastern Scotland we used natural abundance stable isotopes of carbon to partition soil CO2 efflux into its heterotrophic and autotrophic components to determine whether young Scots pine plantations affect heterotrophic respiration rates in peatland soil. Rate and isotopic composition of soil CO2 efflux was measured in plantation areas and in unforested heather moorland; soil and roots were then excavated and separately incubated to establish the isotopic end members of a simple linear mixing model. Isotopic composition of soil efflux varies temporally and spatially across the site; young Scots pine trees do not increase the heterotrophic flux from soil and therefore do not lead to a net loss of soil carbon from these landscapes.

  18. Effect of photosynthesis on the abundance of 18O13C16O in atmospheric CO2

    NASA Astrophysics Data System (ADS)

    Hofmann, Magdalena E. G.; Pons, Thijs L.; Ziegler, Martin; Lourens, Lucas J.; Röckmann, Thomas

    2016-04-01

    The abundance of the isotopologue 18O13C16O (Δ47) in atmospheric air is a promising new tracer for the atmospheric carbon cycle (Eiler and Schauble, 2004; Affek and Eiler, 2006; Affek et al., 2007). The large gross fluxes in CO2 between the atmosphere and biosphere are supposed to play a major role in controlling its abundance. Eiler and Schauble (2004) set up a box model describing the effect of air-leaf interaction on the abundance of 18O13C16O in atmospheric air. The main assumption is that the exchange between CO2 and water within the mesophyll cells will imprint a Δ47 value on the back-diffusing CO2 that reflects the leaf temperature. Additionally, kinetic effects due to CO2 diffusion into and out of the stomata are thought to play a role. We investigated the effect of photosynthesis on the residual CO2 under controlled conditions using a leaf chamber set-up to quantitatively test the model assumptions suggested by Eiler and Schauble (2004). We studied the effect of photosynthesis on the residual CO2 using two C3 and one C4 plant species: (i) sunflower (Helianthus annuus), a C3 species with a high leaf conductance for CO2 diffusion, (ii) ivy (Hedera hibernica), a C3 species with a low conductance, and (iii), maize (Zea mays), a species with the C4 photosynthetic pathway. We also investigated the effect of different light intensities (photosynthetic photon flux density of 200, 700 and 1800 μmol m2s-1), and thus, photosynthetic rate in sunflower and maize. A leaf was mounted in a cuvette with a transparent window and an adjustable light source. The air inside was thoroughly mixed, making the composition of the outgoing air equal to the air inside. A gas-mixing unit was attached at the entrance of the cuvette that mixed air with a high concentration of scrambled CO2 with a Δ47 value of 0 to 0.1‰ with CO2 free air to set the CO2 concentration of ingoing air at 500 ppm. The flow rate through the cuvette was adjusted to the photosynthetic activity of the leaf

  19. Effect of photosynthesis on the abundance of 18O13C16O in atmospheric CO2

    NASA Astrophysics Data System (ADS)

    Hofmann, Magdalena E. G.; Pons, Thijs L.; Ziegler, Martin; Lourens, Lucas J.; Röckmann, Thomas

    2016-04-01

    The abundance of the isotopologue 18O13C16O (Δ47) in atmospheric air is a promising new tracer for the atmospheric carbon cycle (Eiler and Schauble, 2004; Affek and Eiler, 2006; Affek et al., 2007). The large gross fluxes in CO2 between the atmosphere and biosphere are supposed to play a major role in controlling its abundance. Eiler and Schauble (2004) set up a box model describing the effect of air-leaf interaction on the abundance of 18O13C16O in atmospheric air. The main assumption is that the exchange between CO2 and water within the mesophyll cells will imprint a Δ47 value on the back-diffusing CO2 that reflects the leaf temperature. Additionally, kinetic effects due to CO2 diffusion into and out of the stomata are thought to play a role. We investigated the effect of photosynthesis on the residual CO2 under controlled conditions using a leaf chamber set-up to quantitatively test the model assumptions suggested by Eiler and Schauble (2004). We studied the effect of photosynthesis on the residual CO2 using two C3 and one C4 plant species: (i) sunflower (Helianthus annuus), a C3 species with a high leaf conductance for CO2 diffusion, (ii) ivy (Hedera hibernica), a C3 species with a low conductance, and (iii), maize (Zea mays), a species with the C4 photosynthetic pathway. We also investigated the effect of different light intensities (photosynthetic photon flux density of 200, 700 and 1800 μmol m2s‑1), and thus, photosynthetic rate in sunflower and maize. A leaf was mounted in a cuvette with a transparent window and an adjustable light source. The air inside was thoroughly mixed, making the composition of the outgoing air equal to the air inside. A gas-mixing unit was attached at the entrance of the cuvette that mixed air with a high concentration of scrambled CO2 with a Δ47 value of 0 to 0.1‰ with CO2 free air to set the CO2 concentration of ingoing air at 500 ppm. The flow rate through the cuvette was adjusted to the photosynthetic activity of the

  20. Spatial and Temporal Variability of pCO2, 13C-CO2, and [O2] in the Tidal Amazon River.

    NASA Astrophysics Data System (ADS)

    Gagne-Maynard, W.

    2015-12-01

    River systems play an important role in both transporting and altering organic carbon fixed in terrestrial systems. However, there is a key gap in our understanding of riverine fluxes due to the lack of systematic measurements made in the lower, tidally-influenced reaches of large river systems. For example, the traditional end-member for the Amazon River is located at Óbidos, which is 900km from the mouth of the river. Below this point, tides produce semi-diurnal fluxes to and from floodplains and channels, resulting in complete flow reversal without salinity intrusion. The lower Amazon remains a critical study area because (1) outgassing rates in tropical rivers are extremely high, typically exceeding temperate counterparts and (2) the Amazon's discharge represents a significant proportion of global freshwater input to the ocean(~20%). Furthermore, a lack of measurements in this area due to sampling difficulties means that the processes governing biogeochemical dynamics in this region remain unconstrained. In this study, we implemented a continuous, in-situ equilibrator system for the real-time measurement of pCO2, 13C-CO2, and [O2]. Measurements were collected along various river transects, at floodplain margins and river confluences, and during transit up and down the river. Cruises were planned to coincide with various stages of the hydrograph, with measurements collected at high water, low water and falling water. High-resolution measurements showed both temporal changes in pCO2 and 13C-CO2, and also allowed us to identify "hotspots" of increased pCO2. Within the lower river, several of these hotspots coincided with river confluences and floodplain margins. Measurements over the course of tidal cycles revealed little change in dissolved gas measurements within the mainstem. This approach shows the importance of considering spatial variability in large, dynamic systems influenced by tidal fluxes.

  1. Carbon cycling in floodplain ecosystems: excess pCO2, extreme δ13C, and snail shell proxies

    NASA Astrophysics Data System (ADS)

    Gray, D. P.; Horton, T. W.

    2010-12-01

    Braided river floodplains typically possess high vertical hydrological/hydrogeological connectivity. This surface-subsurface exchange is highly important in the overall function and structure of these complex 4-dimensional systems, including the ecosystems they support. Spring-fed streams on the floodplain are often hotspots of benthic invertebrate diversity and productivity. Here, δ13C values of both dissolved inorganic carbon (DIC) and food-web components from five braided fluvial floodplain spring-fed streams in New Zealand, are used to assess the source of carbon in spring-fed food-webs. Partial pressures of CO2 in spring water ranged from 2-7 times atmospheric pressure, but rapidly approached equilibrium with the atmosphere downstream commensurate with an increase in DIC δ13C. Survey results demonstrate that both out-gassing and photosynthetic draw-down by aquatic plants controlled the net flux of CO2. The gradient in DIC δ13C was transmitted through three trophic levels of spring food-webs. These findings suggest highly productive spring-fed ecosystems are ‘fertilized’ by excess carbon dioxide dissolved in subsurface source waters. Furthermore, the stable carbon isotope composition of gastropod shells and soft tissue can serve as proxies for groundwater derived carbon in spring-fed braided fluvial ecosystems.

  2. Glacial Water Mass Geometry and the Distribution of δ 13C of Σ CO2 in the Western Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Curry, W. B.; Oppo, D. W.

    2004-12-01

    Oxygen and carbon isotopic data were produced on the benthic foraminiferal taxa Cibicidoides and Planulina from twenty five piston cores, gravity cores and multi-cores from the Brazil margin. The cores span water depths from about 400 m to 3000 m and intersect the major water masses in this region. The Holocene and glacial bathymetric profiles of benthic foraminifera δ 13C show significant differences. The Holocene bathymetric profile along the Brazil margin shows the presence of North Atlantic Deep Water as a local maximum in δ 13C centered at about 2500 m, intersecting the northward flowing water masses Antarctic Intermediate Water/Circum-polar Deep Water and Antarctic Bottom Water. The glacial bathymetric profile of δ 13C of Σ CO2 requires the presence of three distinct water masses in the glacial Atlantic Ocean: a shallow ( ˜1000 m), southern-source water mass with an end-member δ 13C value of about 0.3-0.5 ‰ VPDB, a mid-depth ( ˜1500 m), northern-source water mass with an end-member value of about 1.5 ‰ , and a deep (>2000 m), southern-source water with an end-member value of <-0.2 ‰ and perhaps as low as the -0.9 ‰ values observed in the South Atlantic sector of the Southern Ocean [Ninnemann and Charles, 2002]. The origins of the water masses are supported by the meridional gradients in benthic foraminiferal δ 18O: at similar depths in the water column, the southern water masses are colder, less salty and have a higher benthic foraminiferal δ 18O value than the water mass originating in the north. Although there is evidence for significant aging and mixing of the water mass along its trajectory, the mid-depth northern-source water mass crossed the equator and could still be identified as a unique water mass as far south as 30° S. In contrast, the shallow, southern-source water mass did not exert a significant influence in the northern subtropical Atlantic. These new data fill a critical gap in the South Atlantic Ocean and provide the

  3. 13C Tracking after 13CO2 Supply Revealed Diurnal Patterns of Wood Formation in Aspen1

    PubMed Central

    Mahboubi, Amir; Linden, Pernilla; Moritz, Thomas

    2015-01-01

    Wood of trees is formed from carbon assimilated in the photosynthetic tissues. Determining the temporal dynamics of carbon assimilation, subsequent transport into developing wood, and incorporation to cell walls would further our understanding of wood formation in particular and tree growth in general. To investigate these questions, we designed a 13CO2 labeling system to study carbon transport and incorporation to developing wood of hybrid aspen (Populus tremula × tremuloides). Tracking of 13C incorporation to wood over a time course using nuclear magnetic resonance spectroscopy revealed diurnal patterns in wood cell wall biosynthesis. The dark period had a differential effect on 13C incorporation to lignin and cell wall carbohydrates. No 13C was incorporated into aromatic amino acids of cell wall proteins in the dark, suggesting that cell wall protein biosynthesis ceased during the night. The results show previously unrecognized temporal patterns in wood cell wall biosynthesis, suggest diurnal cycle as a possible cue in the regulation of carbon incorporation to wood, and establish a unique 13C labeling method for the analysis of wood formation and secondary growth in trees. PMID:25931520

  4. Implications of CO2 pooling on δ13C of ecosystem respiration and leaves in Amazonian forest

    NASA Astrophysics Data System (ADS)

    de Araújo, A. C.; Ometto, J. P. H. B.; Dolman, A. J.; Kruijt, B.; Waterloo, M. J.; Ehleringer, J. R.

    2007-11-01

    The carbon isotope of a leaf (δ13Cleaf) is generally more negative in riparian zones than in areas with low soil moisture content or rainfall input. In Central Amazonia, the small-scale topography is composed of plateaus and valleys, with plateaus generally being drier than the valley edges in the dry season. The nocturnal accumulation of CO2 is higher in the valleys than on the plateaus in the dry season. The CO2 stored in the valleys takes longer to be released than that on the plateaus, and sometimes the atmospheric CO2 concentration (ca) does not drop to the same level as on the plateaus at any time during the day. Samples of sunlit leaves and atmospheric air were collected along a topographical gradient to test whether the δ13Cleaf of sunlit leaves and the carbon isotope ratio of ecosystem respired CO2 (δ13CR) may be more negative in the valley than those on the plateau. The δ13Cleaf was significantly more negative in the valley than on the plateau. Factors considered to be driving the observed variability in δ13Cleaf were: leaf nitrogen concentration, leaf mass per unit area (LMA), soil moisture availability, more negative carbon isotope ratio of atmospheric CO2 (δ13Ca) in the valleys during daytime hours, and leaf discrimination (Δleaf). The observed pattern of δ13Cleaf suggests that water-use efficiency (WUE) may be higher on the plateaus than in the valleys. The ;13CR was more negative in the valleys than on the plateaus on some nights, whereas in others it was not. It is likely that lateral drainage of CO2 enriched in 13C from upslope areas might have happened when the nights were less stable. Biotic factors such as soil CO2 efflux (Rsoil) and the responses of plants to environmental variables such as vapor pressure deficit (D) may also play a role.

  5. A 13C labelling study on carbon fluxes in Arctic plankton communities under elevated CO2 levels

    NASA Astrophysics Data System (ADS)

    de Kluijver, A.; Soetaert, K.; Czerny, J.; Schulz, K. G.; Boxhammer, T.; Riebesell, U.; Middelburg, J. J.

    2012-07-01

    The effect of CO2 on carbon fluxes in Arctic plankton communities was investigated during the 2010 EPOCA mesocosm study in Ny Ålesund, Svalbard. Nine mesocosms were set up with initial pCO2 levels ranging from 185 to 1420 μatm for 5 weeks. 13C labelled bicarbonate was added at the start of the experiment to follow the transfer of carbon from dissolved inorganic carbon (DIC) into phytoplankton, bacteria, total particulate organic carbon (POC), zooplankton, and settling particles. Polar lipid derived fatty acids (PLFA) were used to trace carbon dynamics of phytoplankton and bacteria and allowed distinction of two groups of phytoplankton: phyto I (autotrophs) and phyto II (mixotrophs). Nutrients were added on day 13. A nutrient-phytoplankton-zooplankton-detritus model amended with 13C dynamics was constructed and fitted to the data to quantify uptake rates and carbon fluxes in the plankton community during the phase prior to nutrient addition (phase 1, days 0-12). During the first 12 days, a phytoplankton bloom developed that was characterized by high growth rates (0.87 days-1) for phyto I and lower growth rates (0.18 days-1) for phyto II. A large part of the carbon fixed by phytoplankton (~31%) was transferred to bacteria, while mesozooplankton grazed only ~6% of the production. After 6 days, the bloom collapsed and part of the organic matter subsequently settled into the sediment traps. The sedimentation losses of detritus in phase 1 were low (0.008 days-1) and overall export was only ~7% of production. Zooplankton grazing and detritus sinking losses prior to nutrient addition were sensitive to CO2: grazing decreased with increasing CO2, while sinking increased. Phytoplankton production increased again after nutrient addition on day 13. Although phyto II showed initially higher growth rates with increasing CO2 (days 14-22), the overall production of POC after nutrient addition (phase 2, days 14-29) decreased with increasing CO2. Significant sedimentation occurred

  6. Imprint of CO2 emission in atmosphere and biosphere on the basis of 14C and 13C measurements

    NASA Astrophysics Data System (ADS)

    Pazdur, Anna; Gabryś, Alicja; Kuc, Tadeusz; Pawełczyk, Sławomira; Piotrowska, Natalia; Rakowski, Andrzej; Różański, Kazimierz; Sensuła, Barbara

    2015-04-01

    As is shown in the IPCC (Intergovernmental Panel on Climate Change) report, the observed climate changes are caused, among others, by human activity. Mainly emission of CO2 to the atmosphere coming from the burning of fossil fuels, can have dire consequences for life on Earth and development of humankind. The report uses, among others, data obtained from isotopic measurements in the biosphere. Measurements of 14C and 13C concentration in modern atmospheric carbon dioxide and biosphere allow the determination of the decrease of the concentration of this isotope. Furthermore, the magnitude of emission to the atmosphere of carbon dioxide not containing the isotope 14C can be estimated on this basis. Such emission stems from fossil fuel combustion - petroleum, natural gas and black coal. A sensitive bioindicator of the emission are annual tree rings. The measurements of 14C concentration in tree ring material using AMS allow to see its seasonal changes. Trees, treated as an archive of changes in conjunction with information about the isotopic composition of carbon can be used for monitoring of environment as sensitive bioindicators on local, as well as on the global scale. Regular investigations of isotopic composition of carbon in trees have been carried out in the GADAM Centre for the urban areas of both Poland and worldwide. This method can be applied in the study of the emission of CO2 to the atmosphere and its spatial and temporal distribution connected with the production of energy by power plants based on fossil fuel combustion for the area of southern Poland. Modelling of CO2 emission using both 14C and 13C carbon isotopes measured in pine tree rings on the background of climatic changes will be presented. The national ecological policy in the era of global warming requires the manufacturers of energy to get involved in the development of methods suitable for monitoring the state of the environment. Hence, the interest in the area of monitoring the fossil fuel

  7. In situ measurement of magnesium carbonate formation from CO2 using static high-pressure and -temperature 13C NMR.

    PubMed

    Surface, J Andrew; Skemer, Philip; Hayes, Sophia E; Conradi, Mark S

    2013-01-01

    We explore a new in situ NMR spectroscopy method that possesses the ability to monitor the chemical evolution of supercritical CO(2) in relevant conditions for geological CO(2) sequestration. As a model, we use the fast reaction of the mineral brucite, Mg(OH)(2), with supercritical CO(2) (88 bar) in aqueous conditions at 80 °C. The in situ conversion of CO(2) into metastable and stable carbonates is observed throughout the reaction. After more than 58 h of reaction, the sample was depressurized and analyzed using in situ Raman spectroscopy, where the laser was focused on the undisturbed products through the glass reaction tube. Postreaction, ex situ analysis was performed on the extracted and dried products using Raman spectroscopy, powder X-ray diffraction, and magic-angle spinning (1)H-decoupled (13)C NMR. These separate methods of analysis confirmed a spatial dependence of products, possibly caused by a gradient of reactant availability, pH, and/or a reaction mechanism that involves first forming hydroxy-hydrated (basic, hydrated) carbonates that convert to the end-product, anhydrous magnesite. This carbonation reaction illustrates the importance of static (unmixed) reaction systems at sequestration-like conditions. PMID:22676479

  8. Extreme 13C depletion of CCl2F2 in firn air samples from NEEM, Greenland

    NASA Astrophysics Data System (ADS)

    Zuiderweg, A.; Holzinger, R.; Martinerie, P.; Schneider, R.; Kaiser, J.; Witrant, E.; Etheridge, D.; Rubino, M.; Petrenko, V.; Blunier, T.; Röckmann, T.

    2012-07-01

    A series of 12 high volume air samples collected from the S2 firn core during the North Greenland Eemian Ice Drilling (NEEM) 2009 campaign have been measured for mixing ratio and stable carbon isotope composition of the chlorofluorocarbon CFC-12 (CCl2F2). While the mixing ratio measurements compare favorably to other firn air studies, the isotope results show extreme 13C depletion at the deepest measurable depth (65 m), to values lower than δ13C = -80‰ vs. VPDB (the international stable carbon isotope scale), compared to present day surface tropospheric measurements near -40‰. Firn air modeling was used to interpret these measurements. Reconstructed atmospheric time series indicate even larger depletions (to -120‰) near 1950 AD, with subsequent rapid enrichment of the atmospheric reservoir of the compound to the present day value. Mass-balance calculations show that this change must have been caused by a large change in the isotopic composition of anthropogenic CFC-12 emissions, probably due to technological changes in the CFC production process over the last 80 yr. Propagating the mass-balance calculations into the future demonstrates that as emissions decrease to zero, isotopic fractionation by the stratospheric sinks will lead to continued 13C enrichment in atmospheric CFC-12.

  9. A new set-up for simultaneous high-precision measurements of CO2, δ13C-CO2 and δ18O-CO2 on small ice core samples

    NASA Astrophysics Data System (ADS)

    Jenk, Theo Manuel; Rubino, Mauro; Etheridge, David; Ciobanu, Viorela Gabriela; Blunier, Thomas

    2016-08-01

    Palaeoatmospheric records of carbon dioxide and its stable carbon isotope composition (δ13C) obtained from polar ice cores provide important constraints on the natural variability of the carbon cycle. However, the measurements are both analytically challenging and time-consuming; thus only data exist from a limited number of sampling sites and time periods. Additional analytical resources with high analytical precision and throughput are thus desirable to extend the existing datasets. Moreover, consistent measurements derived by independent laboratories and a variety of analytical systems help to further increase confidence in the global CO2 palaeo-reconstructions. Here, we describe our new set-up for simultaneous measurements of atmospheric CO2 mixing ratios and atmospheric δ13C and δ18O-CO2 in air extracted from ice core samples. The centrepiece of the system is a newly designed needle cracker for the mechanical release of air entrapped in ice core samples of 8-13 g operated at -45 °C. The small sample size allows for high resolution and replicate sampling schemes. In our method, CO2 is cryogenically and chromatographically separated from the bulk air and its isotopic composition subsequently determined by continuous flow isotope ratio mass spectrometry (IRMS). In combination with thermal conductivity measurement of the bulk air, the CO2 mixing ratio is calculated. The analytical precision determined from standard air sample measurements over ice is ±1.9 ppm for CO2 and ±0.09 ‰ for δ13C. In a laboratory intercomparison study with CSIRO (Aspendale, Australia), good agreement between CO2 and δ13C results is found for Law Dome ice core samples. Replicate analysis of these samples resulted in a pooled standard deviation of 2.0 ppm for CO2 and 0.11 ‰ for δ13C. These numbers are good, though they are rather conservative estimates of the overall analytical precision achieved for single ice sample measurements. Facilitated by the small sample requirement

  10. Extreme 13C depletion of CCl2F2 in firn air samples from NEEM, Greenland

    NASA Astrophysics Data System (ADS)

    Zuiderweg, A.; Holzinger, R.; Martinerie, P.; Schneider, R.; Kaiser, J.; Witrant, E.; Etheridge, D.; Petrenko, V.; Blunier, T.; Röckmann, T.

    2013-01-01

    A series of 12 high volume air samples collected from the S2 firn core during the North Greenland Eemian Ice Drilling (NEEM) 2009 campaign have been measured for mixing ratio and stable carbon isotope composition of the chlorofluorocarbon CFC-12 (CCl2F2). While the mixing ratio measurements compare favorably to other firn air studies, the isotope results show extreme 13C depletion at the deepest measurable depth (65 m), to values lower than δ13C = -80‰ vs. VPDB (the international stable carbon isotope scale), compared to present day surface tropospheric measurements near -40‰. Firn air modeling was used to interpret these measurements. Reconstructed atmospheric time series indicate even larger depletions (to -120‰) near 1950 AD, with subsequent rapid enrichment of the atmospheric reservoir of the compound to the present day value. Mass-balance calculations show that this change is likely to have been caused by a large change in the isotopic composition of anthropogenic CFC-12 emissions, probably due to technological advances in the CFC production process over the last 80 yr, though direct evidence is lacking.

  11. Temporal variability in (13)C of respired CO(2) in a pine and a hardwood forest subject to similar climatic conditions.

    PubMed

    Mortazavi, Behzad; Chanton, Jeffrey P; Prater, James L; Oishi, A Christopher; Oren, Ram; Katul, Gabriel

    2005-01-01

    Temporal variability in the (13)C of foliage (delta(13)C(F)), soil (delta(13)C(S)) and ecosystem (delta(13)C(R)) respired CO(2) was contrasted between a 17.2-m tall evenly aged loblolly pine forest and a 35-m tall unevenly aged mature second growth mixed broadleaf deciduous forest in North Carolina, USA, over a 2-year period. The two forests are located at the Duke Forest within a kilometer of each other and are subject to identical climate and have similar soil types. The delta(13)C(F), collected just prior to dawn, was primarily controlled by the time-lagged vapor pressure deficit (VPD) in both stands; it was used for calculating the ratio of intercellular to ambient CO(2) ( Ci/ Ca). A remarkable similarity was observed in the relationship between Ci/ Ca and time-lagged VPD in these two forests despite large differences in hydraulic characteristics. This similarity emerged as a result of physiological adjustments that compensated for differences in plant hydraulic characteristics, as predicted by a recently proposed equilibrium hypothesis, and has implications to ecophysiological models. We found that in the broadleaf forest, the delta(13)C of forest floor CO(2) efflux dominated the delta(13)C(R), while in the younger pine forest, the delta(13)C of foliage respired CO(2) dominated delta(13)C(R). This dependence resulted in a more variable delta(13)C(R) in the pine forest when compared to the broadleaf forest due to the larger photosynthetic contribution. Given the sensitivity of the atmospheric inversion models to delta(13)C(R), the results demonstrate that these models could be improved by accounting for stand characteristics, in addition to previously recognized effects of moisture availability, when estimating delta(13)C(R).

  12. SOIL RESPIRED D13C SIGNATURES REFLECT ROOT EXUDATE OR ROOT TURNOVER SIGNATURES IN AN ELEVATED CO2 AND OZONE MESOCOSM EXPERIMENT

    EPA Science Inventory

    Bulk tissue and root and soil respired d13C signatures were measured throughout the soil profile in a Ponderosa Pine mesocosm experiment exposed to ambient and elevated CO2 concentrations. For the ambient treatment, root (0-1mm, 1-2mm, and >2mm) and soil d13C signatures were ?24...

  13. Calibration of δ13C and δ18O measurements in CO2 using Off-axis Integrated Cavity Output Spectrometer (ICOS)

    NASA Astrophysics Data System (ADS)

    Joseph, Jobin; Külls, Christoph

    2014-05-01

    The δ13C and δ18O of CO2 has enormous potential as tracers to study and quantify the interaction between the water and carbon cycles. Isotope ratio mass spectrometry (IRMS) being the conventional method for stable isotopic measurements, has many limitations making it impossible for deploying them in remote areas for online or in-situ sampling. New laser based absorption spectroscopy approaches like Cavity Ring Down Spectroscopy (CRDS) and Integrated Cavity Output Spectroscopy (ICOS) have been developed for online measurements of stable isotopes at an expense of considerably less power requirement but with precision comparable to IRMS. In this research project, we introduce a new calibration system for an Off- Axis ICOS (Los Gatos Research CCIA-36d) for a wide range of varying concentrations of CO2 (800ppm - 25,000ppm), a typical CO2 flux range at the plant-soil continuum. The calibration compensates for the concentration dependency of δ13C and δ18O measurements, and was performed using various CO2 standards with known CO2 concentration and δC13 and δO18 values. A mathematical model was developed after the calibration procedure as a correction factor for the concentration dependency of δ13C and δ18O measurements. Temperature dependency of δ13C and δ18O measurements were investigated and no significant influence was found. Simultaneous calibration of δ13C and δ18O is achieved using this calibration system with an overall accuracy of (~ 0.75±0.24 ‰ for δ13C, ~ 0.81 ±0.26‰ for δ18O). This calibration procedure is found to be appropriate for making Off-Axis ICOS suitable for measuring CO2 concentration and δ13C and δ18O measurements at atmosphere-plant-soil continuum.

  14. [Responses of tissue carbon and delta 13C in epilithic mosses to the variations of anthropogenic CO2 and atmospheric nitrogen deposition in city area].

    PubMed

    Liu, Xue-yan; Xiao, Hua-yun; Liu, Cong-qiang; Li, You-yi; Xiao, Hong-wei

    2009-01-01

    We investigated the carbon (C) and nitrogen (N) concentrations and isotopic signatures (delta 13C and delta15 N) in epilithic mosses collected from urban sites to rural sites along four directions at Guiyang area. Mosses C (34.47%-52.76%) decreased significantly with distance from urban to rural area and strongly correlated with tissue N (0.85%-2.97%), showing atmospheric N deposition has positive effect on C assimilation of epilithic mosses, higher atmospheric N/NHx deposition at urban area has improved the photosynthesis and C fixation of mosses near urban, which also caused greater 13C discrimination for urban mosses. Mosses delta 13C signatures (-30.69% per hundred - -26.96% per hundred) got less negative with distance from urban to rural area, which was also related to the anthropogenic CO2 emissions in the city, and these 12C-enriched CO2 sources would lead to more negative mosses delta 13C through enhancing the atmospheric CO2 concentration in urban area. Moreover, according to the characteristics of mosses C and delta 13C variations with distance, it is estimated that the influences of urban anthropogenic CO2 sources on plants was mainly within 20 km from city center. This study mainly focused on the factors regulating tissue C and delta 13C of mosses in city area and the interaction between C and N in mosses, the responses of mosses C and delta 13C to urban CO2 emission and atmospheric N deposition have been revealed, which could provide new geochemical evidences for the control of city atmospheric pollution and the protection of ecosystems around city.

  15. Rate and δ13C values of CO2 produced during short-term online incubation experiments indicate two different processes with distinct carbon sources

    NASA Astrophysics Data System (ADS)

    Osuna, R.; Breecker, D. O.; Sharp, Z. D.

    2009-12-01

    The decomposition of organic matter in soils is a fundamental process influencing the carbon cycle. The rate of microbial oxidation of organic matter is known to increase with temperature, suggesting that many soils may turn from sinks to sources of CO2 as global temperature warms. In this study, we introduce a new, online soil incubation technique that can be used to determine the rate and carbon isotope composition (δ13C) of CO2 respired during the decomposition of organic matter. Air-dried and sieved soil samples are mechanically mixed and are rewetted and preincubated in capped 50 mL tubes. Aliquots of the soils (2 - 200 mg) taken from the storage tubes are loaded into septum-capped Labco Exetainer® vials which are themselves loaded into a thermostated sample tray maintained at a constant temperature. The vials are then flushed with synthetic CO2-free air and the soils are preincubated again for several days. The incubation experiment begins when the vials are flushed a second time with synthetic air. At the end of the incubation, all of the CO2 that was produced is flushed from the vial, cryofocused in a liquid nitrogen trap and then carried into the source of a mass spectrometer in a He stream. The CO2 from each vial is sampled automatically and directed into the mass spectrometer using a Thermo Electron Gasbench II. The number of moles and the δ13C value of CO2 produced during the incubation are determined from voltages measured by the mass spectrometer. The technique allows for rapid sample analysis and short incubation times (hours to days). Incubation of multiple aliquots of the same soil mixture allows trends to be examined. Several patterns have emerged from incubations carried out to date. An initial pulse of CO2 is emitted from the soils during the first minutes of incubation. This pulse of CO2 is emitted from dry soils (i.e. never rewetted), sterilized soils, and from soils incubated in high purity He instead of synthetic air, indicating that the

  16. Atmospheric CO2 and its δ13C measurements from flask sampling at Lin'an regional background station in China

    NASA Astrophysics Data System (ADS)

    Xia, Lingjun; Zhou, Lingxi; Tans, Pieter P.; Liu, Lixin; Zhang, Gen; Wang, Hongyang; Luan, Tian

    2015-09-01

    This study presents CO2 concentrations of air flask samples obtained at a regional background station Lin'an (LAN) in China from January 2009 to December 2013, as well as their stable isotope ratios (δ13C) from January 2011 to December 2013. Background data is selected to represent background characteristics of atmospheric CO2 and δ13C over Yangzte River Delta. The annual mean background CO2 concentrations vary from 395.0 ppm in 2009 to 407.6 ppm in 2013, with a growth rate of 2.8 ± 0.1 ppm yr-1 over the study period, which is higher than the global average level. The annual mean values of δ13C vary from -8.55‰ in 2011 to -8.73‰ in 2013, with a growth rate of -0.029 ± 0.010‰ yr-1. Seasonal cycles of CO2 concentrations and δ13C are observed to be obvious at LAN. The minimum and maximum values of mean seasonal CO2 cycle appear in August and January, respectively, with the peak-to-peak amplitude of 19.4 ppm. The sign of δ13C seasonal cycle is opposite to that of CO2, and the peak-to-peak amplitude is 0.85‰. The isotopic signature of CO2 sources/sinks (δs) is also discussed in this paper. The estimated δs values for heating season (December-February) is -25.4‰ and for vegetative season is -21.3‰ (March-November) suggest the significant impact of fossil fuel combustions during winter heating season and biological activities during vegetative season.

  17. Estimation of Insulin Resistance in Mexican Adults by the [(13)C]Glucose Breath Test Corrected for Endogenous Total CO(2) Production.

    PubMed

    Ibarra-Pastrana, Erika; Candia Plata, Maria Del Carmen; Alvarez, Gerardo; Valencia, Mauro E

    2012-01-01

    Objective. To evaluate the efficacy of the [(13)C]glucose breath test for measuring insulin resistance in Mexican adults with different glycemic states. Research Design and Methods. Fifty-eight adults underwent a [(13)C]glucose breath test with simultaneous measurement of total CO(2) production by indirect calorimetry, at baseline and 90 minutes after the ingestion of 15 g of dextrose and 25 mg of [(13)C]glucose. HOMA was used as a marker of insulin resistance. Results. We found an inverse correlation between HOMA and the breath test δ(13)CO(2) (‰), r = -0.41 (P = 0.001). After adjusting for total CO(2) production, correlations between HOMA and fasting glucose were less strong but remained significant. An ROC curve was constructed using δ(13)CO(2) (‰) and HOMA values; the cut-off point was 9.99‰ δ(13)CO(2), corresponding to a sensitivity of 80.0 (95% CI: 51.9, 95.7) and a specificity of 67.4 (95% CI: 51.5, 80.9). Conclusions. The [(13)C]glucose breath test is a simple noninvasive procedure but was not sufficiently robust for an accurate diagnosis of insulin resistance. Our findings suggest that the test might be helpful in identifying individuals who are not IR, which in turn may contribute to improved diabetes prevention.

  18. Uncertainties and Challenges in Long-term d13C Measurements of Atmospheric CO2 at Canadian Baseline Stations: Can Human induced CO2 Detected & Quantified at Regional Scale?

    NASA Astrophysics Data System (ADS)

    Huang, L.; Chivulescu, A.; Ernst, D.

    2009-04-01

    Detecting and quantifying human induced Greenhouse Gases (GHGs) and air pollutants in ambient air are important to air quality and climate change research, particularly for addressing the issue of the continued increase of atmospheric CO2. Isotope compositions are widely used as tracers in source identifications and attributions for atmospheric CO2. Due to a long life-time (~ 200 years) of CO2 and its exchanges in various processes with natural systems, the signal of human-induced CO2 and its carbon isotopic compositions in the atmosphere is small. It is very challenging to quantify annual change rates and attribute those changes into human-induced and natural portions within an accepted range of uncertainty at global/regional scales. Thus, the requirements for the precision and accuracy in CO2 and related tracers measurements, including δ13C & δ18O in CO2, are very rigid (by WMO measurement community). To conduct attribution studies, the annual mean changes in both CO2 and δ13C have to be determined precisely. It is known that the average annual global change rate of δ13C is very small, ~ 0.028 permil in δ13C per year. To identify the small change accurately, it is required that the annual changes of isotope standards are much less than 0.028 permil. To anchor individual isotopic measurements of flask-air CO2 to the primary VPDB scale (i.e. traceability), various forms of lab-standards can be used, such as pure CO2, air CO2 and CO2 derived from pure carbonates. Usually, more than one level (e.g. primary, secondary and etc.) and more than one form of standards are used in individual labs. However, it is very challenging to ensure that the uncertainties of those standards over one year are less than 0.028 permil (i.e. the stability of the standard is within ~ 0.02 permil) since ensuring that a lower level standard is stable/ or not drifting within ~ 0.02 permil requires a higher level standard with a better stability than 0.02 permil. Ultimately, it is

  19. Evaluating mechanisms of nutrient depletion and 13C enrichment in the intermediate-depth Atlantic during the last ice age

    NASA Astrophysics Data System (ADS)

    Sigman, Daniel M.; Lehman, Scott J.; Oppo, Delia W.

    2003-09-01

    Using an ocean box model, we have studied the effect of altered circulation on the oceanic distributions of phosphate (PO4-3) and the 13C/12C and 14C/12C of dissolved inorganic carbon to evaluate competing hypotheses for the cause of observed nutrient depletion and 13C enrichment at intermediate depths of the Atlantic during the last ice age. Because of "nutrient trapping" and limited air-sea carbon isotopic equilibration, the simple imposition of an intense meridional overturning cell in the Atlantic fails to simultaneously lower nutrient concentrations and raise 13C/12C to observed glacial levels. Export of intermediate water out of the Atlantic causes a basin-to-basin nutrient transfer, thus providing a more efficient mechanism of intermediate-depth Atlantic nutrient depletion and improved carbon isotopic equilibration at low temperatures (i.e., 13C enrichment). Although this export adds nutrients to the intermediate depths of the Pacific and Indian Oceans, the simulated glacial intermediate-depth Indo-Pacific is nevertheless moderately depleted in PO4-3 relative to the model's interglacial control, in agreement with consensus paleoceanographic evidence. This Indo-Pacific PO4-3 depletion results from our use of a "glacial base case" in which nutrient-rich Antarctic Intermediate Water formation is absent as part of the elimination of the modern North-Atlantic-Deep-Water-based "conveyor" circulation.

  20. Terrestrial carbon cycle responses to drought and climate stress: New insights using atmospheric observations of CO2 and delta13C

    NASA Astrophysics Data System (ADS)

    Alden, Caroline B.

    Atmospheric concentrations of carbon dioxide (CO2) continue to rise well into the second decade of the new millennium, in spite of broad-scale human understanding of the impacts of fossil fuel emissions on the earth's climate. Natural sinks for CO2 that are relevant on human time scales---the world's oceans and land biosphere---appear to have kept pace with emissions. The continuously increasing strength of the land biosphere sink for CO2 is surpassing expectations given our understanding of the CO2 fertilization and warming effects on the balance between photosynthesis and respiration, especially in the face of ongoing forest degradation. The climate and carbon cycle links between the atmosphere and land biosphere are not well understood, especially at regional (100 km to 10,000 km) scales. The climate modulating effects of changing plant stomatal conductance in response to temperature and water availability is a key area of uncertainty. Further, the differential response to climate change of C3 and C4 plant functional types is not well known at regional scales. This work outlines the development of a novel application of atmospheric observations of delta13C of CO2 to investigate the links between climate and water and carbon cycling and the integrated responses of C3 and C4 ecosystems to climate variables. A two-step Bayesian batch inversion for 3-hourly, 1x1º CO2 fluxes (step one), and for 3-hourly 1x1º delta13C of recently assimilated carbon (step two) is created here for the first time, and is used to investigate links between regional climate indicators and changes in delta13C of the biosphere. Results show that predictable responses of regional-scale, integrated plant discrimination to temperature, precipitation and relative humidity anomalies can be recovered from atmospheric signals. Model development, synthetic data simulations to test sensitivity, and results for the year 2010 are presented here. This dissertation also includes two other applications

  1. Two episodes of 13C-depletion in organic carbon in the latest Permian: Evidence from the terrestrial sequences in northern Xinjiang, China

    NASA Astrophysics Data System (ADS)

    Cao, Changqun; Wang, Wei; Liu, Lujun; Shen, Shuzhong; Summons, Roger E.

    2008-06-01

    New analyses reveal two intervals of distinctly lower δ13C values in the terrestrial organic matter of Permian-Triassic sequences in northern Xinjiang, China. The younger negative δ13C org spike can be correlated to the conspicuous and sharp δ13C drops both in carbonate carbon and organic carbon near the Permian-Triassic event boundary (PTEB) in the marine section at Meishan. The geochemical correlation criteria are accompanied by a magnetic susceptibility pulse and higher abundances of distinctive, chain-like organic fossil remains of Reduviasporonites. The older negative δ13C org spike originates within a latest Permian regression. Significant changes in organic geochemical proxies are recorded in the equivalent interval of the marine section at Meishan. These include relatively higher concentrations of total organic carbon, isorenieratane, C 14-C 30 aryl isoprenoids and lower ratios of pristane/phytane that, together, indicate the onset of anoxic, euxinic and restricted environments within the photic zone. The massive and widespread oxidation of buried organic matter that induced these euxinic conditions in the ocean would also result in increased concentrations of 13C-depleted atmospheric CO 2. The latest Permian environmental stress marked by the older negative δ13C org episode can be correlated with the distinct changeover of ostracod assemblages and the occurrences of morphological abnormalities of pollen grains. These observations imply that biogeochemical disturbance was manifested on the land at the end of the Permian and that terrestrial organisms responded to it before the main extinction of the marine fauna.

  2. Methanogenic calcite, 13C-depleted bivalve shells, and gas hydrate from a mud volcano offshore southern California

    USGS Publications Warehouse

    Hein, J.R.; Normark, W.R.; McIntyre, B.R.; Lorenson, T.D.; Powell, C.L.

    2006-01-01

    Methane and hydrogen sulfide vent from a cold seep above a shallowly buried methane hydrate in a mud volcano located 24 km offshore southern California in?? 800 m of water. Bivalves, authigenic calcite, and methane hydrate were recovered in a 2.1 m piston core. Aragonite shells of two bivalve species are unusually depleted in 13C (to -91??? ??13C), the most 13C-depleted shells of marine macrofauna yet discovered. Carbon isotopes for both living and dead specimens indicate that they used, in part, carbon derived from anaerobically oxidized methane to construct their shells. The ??13C values are highly variable, but most are within the range -12??? to -91???. This variability may be diagnostic for identifying cold-seep-hydrate systems in the geologic record. Authigenic calcite is abundant in the cores down to ???1.5 m subbottom, the top of the methane hydrate. The calcite is depleted in 13C (??13C = -46??? to -58???), indicating that carbon produced by anaerobically oxidized methane is the main source of the calcite. Methane sources include a geologic hydrocarbon reservoir from Miocene source rocks, and biogenic and thermogenic degradation of organic matter in basin sediments. Oxygen isotopes indicate that most calcite formed out of isotopic equilibrium with ambient bottom water, under the influence of gas hydrate dissociation and strong methane flux. High metal content in the mud volcano sediment indicates leaching of basement rocks by fluid circulating along an underlying fault, which also allows for a high flux of fossil methane. ?? 2006 Geological Society of America.

  3. Conversion of a Continuous Flow Cavity Ring-Down Spectrometer to Measure 13C in CO2 Using Static Analyses of Small Volume Grab Samples (Invited)

    NASA Astrophysics Data System (ADS)

    Rahn, T.; Jordanova, K.; Berryman, E.; van Pelt, A. D.; Marshall, J. D.

    2010-12-01

    Laser-based analyses of concentration and isotopic content allow unprecedented temporal resolution for a number of important atmospheric constituents. Perhaps overlooked is the potential for these tools to also provide analyses in a more traditional "mass spectrometric" mode that is readily deployable in a field setting. Certain sampling regimes (e.g. soil profiles) are not appropriate for continuous sampling due to their slow change and disturbance of gradients caused by frequent/continuous sampling. We have modified the inlet and plumbing system of a commercial continuous flow cavity ring-down spectrometer in a manner that allows for 13C analyses of CO2 from syringe samples at volumes as small as 25 ml of air with ambient concentrations of CO2. The method employs an external high vacuum pump and a series of programmable micro-valves that allow for evacuation of the long-pass ring-down cell followed by controlled filling, via syringe, of the cavity to optimal sampling pressure and subsequent static analysis of CO2 concentration and 13C /13C ratios. The set-up is field deployable with modest power requirements and allows for near real time analysis in a variety of sampling environments and on-the-fly determination of sampling protocol. In its current configuration, the system provides precision of 1% for CO2 concentration and 0.3 permil for δ13C in replicate analyses of reference air. We have deployed the system to a field laboratory in central New Mexico near a controlled tree mortality research site where post-mortality ecosystem CO2 evolution is being studied. Results from the first field season will be presented and discussed.

  4. In Situ 13C NMR at Elevated-Pressures and -Temperatures Investigating the Conversion of CO2 to Magnesium and Calcium Carbonate Minerals

    NASA Astrophysics Data System (ADS)

    Surface, J. A.; Conradi, M. S.; Skemer, P. A.; Hayes, S. E.

    2013-12-01

    We have constructed specialized NMR hardware to conduct in situ elevated-pressure, elevated-temperature 13C NMR studies of unmixed heterogeneous mixtures of solids, liquids, gases, and supercritical fluids. Specifically, our aim is to monitor CO2 uptake in both ultramafic rocks and in more porous geological materials to understand the mechanisms of chemisorption as a function of temperature, pressure and pH. In this in situ NMR probe, we are able to simulate processes at geologically relevant fluid pressures and temperatures, monitoring the kinetics of CO2 conversion to carbonates. The in situ NMR experiments consist of heterogeneous mixtures of rock, salty brine solution, and moderate pressure CO2 gas at elevated temperatures. The purpose of studying these reactions is to determine efficacy of carbonate formation in various geological reservoirs. Via 13C NMR, we have spectroscopically characterized and quantified the conversion of CO2 to magnesium carbonate and calcium carbonate minerals. When CO2 reacts with the calcium or magnesium in a mineral or rock sample, the 13C chemical shift, linewidth, lineshape, and relaxation times change dramatically. This change can be monitored in situ and provide instantaneous and continuous characterization that maps the chemistry that is taking place. For example, on the pathway to MgCO3 formation, there are a number of phases of Mg(OH)x(H2O)y(CO3)z that are apparent via NMR spectroscopy. We will demonstrate that NMR can be used for quantitative characterization of multiple metastable mineral phases in pure forms and in mixtures. Results are confirmed via powder XRD and Raman spectroscopy of aquo- hydro- carbonato- magnesium species and calcium carbonate species. We also have monitored the 13C spectroscopy to analyze the phase of CO2 (liquid, supercritical, or gas) and its conversion into other forms, such as bicarbonate and carbonate species, providing a "window" into the in situ pH of the reacting system. Reference: 'In Situ

  5. How well do we know VPDB? Variability of delta13C and delta18O in CO2 generated from NBS19-calcite.

    PubMed

    Brand, Willi A; Huang, Lin; Mukai, Hitoshi; Chivulescu, Alina; Richter, Jürgen M; Rothe, Michael

    2009-03-01

    In order to generate a local daughter scale from the material defining the international delta13C and delta18O stable isotope ratio scales (NBS19-calcite),1,2 the carbon and oxygen must be liberated to the gas phase, usually as CO2, using acid digestion of the calcite with H3PO4. It is during this conversion step that systematic errors can occur, giving rise to commonly observed discrepancies in isotopic measurements between different stable isotope laboratories. Scale consistency is of particular importance for air-CO2 isotope records where very small differences in isotopic composition have to be reliably compared between different laboratories and quantified over long time periods.3 The information is vital for estimating carbon budgets on regional and global scales and for understanding their variability under the conditions of climate change. Starting from this requirement a number of CO2 preparations from NBS19 were made at Environment Canada (EC) and analyzed in our laboratories together with Narcis II, a set of well-characterized CO2 samples in sealed tubes available from the National Institute for Environmental Studies (NIES).4,5 Narcis II is very homogeneous in delta13C and delta18O with the isotopic composition close to NBS19-CO2. Among our laboratories the results for delta13C agreed to within +/-0.004 per thousand. The same level of agreement in delta13C was obtained when CO2 was generated from NBS19-calcite using different experimental procedures and conditions in the other two laboratories. For delta18O, the corresponding data were +/-0.011 per thousand when using NBS19-CO2 produced at EC, but discrepancies were enhanced by almost one order of magnitude when NBS19-CO2 was prepared by the other laboratories using slightly different reaction conditions (range=0.13 per thousand).In a second series of experiments, larger amounts of CO2 prepared from NBS19 at the Max-Planck-Institut für Biogeochemie (MPI-BGC) were analyzed together with Narcis II and

  6. The Werkendam natural CO2 accumulation: An analogue for CO2 storage in depleted oil reservoirs

    NASA Astrophysics Data System (ADS)

    Bertier, Pieter; Busch, Andreas; Hangx, Suzanne; Kampman, Niko; Nover, Georg; Stanjek, Helge; Weniger, Philipp

    2015-04-01

    The Werkendam natural CO2 accumulation is hosted in the Röt (Early Triassic) sandstone of the West Netherlands Basin, at a depth of 2.8 km, about 20 km south-east of Rotterdam (NL). This reservoir, in a fault-bound structure, was oil-filled prior to charging with magmatic CO2 in the early Cretaceous. It therefore offers a unique opportunity to study long-term CO2-water-rock interactions in the presence of oil. This contribution will present the results of a detailed mineralogical and geochemical characterisation of core sections from the Werkendam CO2 reservoir and an adjacent, stratigraphically equivalent aquifer. X-ray diffraction combined with X-ray fluorescence spectrometry revealed that the reservoir samples contain substantially more feldspar and more barite and siderite than those from the aquifer, while the latter have higher hematite contents. These differences are attributed to the effects hydrocarbons and related fluids on diagenesis in the closed system of the CO2 reservoir versus the open-system of the aquifer. Petrophysical analyses yielded overall higher and more anisotropic permeability for the reservoir samples, while the porosity is overall not significantly different from that of their aquifer equivalents. The differences are most pronounced in coarse-grained sandstones. These have low anhydrite contents and contain traces of calcite, while all other analyzed samples contain abundant anhydrite, dolomite/ankerite and siderite, but no calcite. Detailed petrography revealed mm-sized zones of excessive primary porosity. These are attributed to CO2-induced dissolution of precompactional, grain-replacive anhydrite cement. Diagenetic dolomite/ankerite crystals are covered by anhedral, epitaxial ankerite, separated from the crystals by bitumen coats. Since these carbonates were oil-wet before CO2-charging, the overgrowths are interpreted to have grown after CO2-charging. Their anhedral habit suggests growth in a 2-phase water-CO2 system. Isotopic

  7. Photosynthetic fractionation of 13C and concentrations of dissolved CO2 in the central equatorial Pacific during the last 255,000 years

    NASA Technical Reports Server (NTRS)

    Jasper, J. P.; Hayes, J. M.; Mix, A. C.; Prahl, F. G.

    1994-01-01

    Carbon isotopically based estimates of CO2 levels have been generated from a record of the photosynthetic fractionation of 13C [is equivalent to epsilon(p)] in a central equatorial Pacific sediment core that spans the last approximately 255 ka. Contents of 13C in phytoplanktonic biomass were determined by analysis of C37 alkadienones. These compounds are exclusive products of Prymnesiophyte algae which at present grow most abundantly at depths of 70-90 m in the central equatorial Pacific. A record of the isotopic composition of dissolved CO2 was constructed from isotopic analyses of the planktonic foraminifera Neogloboquadrina dutertrei, which calcifies at 70-90 m in the same region. Values of epsilon(p), derived by comparison of the organic and inorganic delta values, were transformed to yield concentrations of dissolved CO2 [is equivalent to c(e)] based on a new, site-specific calibration of the relationship between epsilon(p) and c(e). The calibration was based on reassessment of existing epsilon(p) versus c(e) data, which support a physiologically based model in which epsilon(p) is inversely related to c(e). Values of PCO2, the partial pressure of CO2 that would be in equilibrium with the estimated concentrations of dissolved CO2, were calculated using Henry's law and the temperature determined from the alkenone-unsaturation index U(K/37). Uncertainties in these values arise mainly from uncertainties about the appropriateness (particularly over time) of the site-specific relationship between epsilon(p) and 1/c(e). These are discussed in detail and it is concluded that the observed record of epsilon(p) most probably reflects significant variations in delta pCO2, the ocean-atmosphere disequilibrium, which appears to have ranged from approximately 110 microatmospheres during glacial intervals (ocean > atmosphere) to approximately 60 microatmospheres during interglacials. Fluxes of CO2 to the atmosphere would thus have been significantly larger during glacial

  8. Real-time measurements of CH4 and CO2 flux and del13C from a proglacial wetland in southwestern Greenland.

    NASA Astrophysics Data System (ADS)

    Stern, J. C.; White, J. R.; Pratt, L. M.; Thompson, H. A.

    2015-12-01

    Arctic permafrost environments represent a large repository of stored carbon that may be mobilized as global temperatures increase, providing a substrate for microbial CH4 production. Proglacial wetlands and lakes are important targets of study to better understand how rapidly changing landscapes affected by climate warming adapt their carbon cycling. Recent advances in portable laser spectrometry have enabled rapid in situ measurements of not only greenhouse gas fluxes, but also del13C compositions of these gases. Here we use a Picarro CH4 and CO2 isotope analyzer to continuously measure CH4 and CO2 flux in situ for comparison to static closed chamber measurements where samples are collected at discrete time intervals and returned to the laboratory for analysis. Real-time, in situ analysis also allowed simple light/dark experiments to be performed on chambers containing different vegetation. In addition, this instrument can be used to measure concentration and del13C of both dissolved CH4 and CO­­2 in lake waters when appropriate gas stripped methods are used. We present data for CH4 and CO2 flux and del13C of emitted and dissolved gases from permafrost-affected wetlands and lakes associated with proglacial landscapes in southwestern Greenland near the Russell Glacier.

  9. Metabolic Fate of the Carboxyl Groups of Malate and Pyruvate and their Influence on δ13C of Leaf-Respired CO2 during Light Enhanced Dark Respiration

    PubMed Central

    Lehmann, Marco M.; Wegener, Frederik; Barthel, Matti; Maurino, Veronica G.; Siegwolf, Rolf T. W.; Buchmann, Nina; Werner, Christiane; Werner, Roland A.

    2016-01-01

    The enhanced CO2 release of illuminated leaves transferred into darkness, termed “light enhanced dark respiration (LEDR)”, is often associated with an increase in the carbon isotope ratio of the respired CO2 (δ13CLEDR). The latter has been hypothesized to result from different respiratory substrates and decarboxylation reactions in various metabolic pathways, which are poorly understood so far. To provide a better insight into the underlying metabolic processes of δ13CLEDR, we fed position-specific 13C-labeled malate and pyruvate via the xylem stream to leaves of species with high and low δ13CLEDR values (Halimium halimifolium and Oxalis triangularis, respectively). During respective label application, we determined label-derived leaf 13CO2 respiration using laser spectroscopy and the 13C allocation to metabolic fractions during light–dark transitions. Our results clearly show that both carboxyl groups (C-1 and C-4 position) of malate similarly influence respiration and metabolic fractions in both species, indicating possible isotope randomization of the carboxyl groups of malate by the fumarase reaction. While C-2 position of pyruvate was only weakly respired, the species-specific difference in natural δ13CLEDR patterns were best reflected by the 13CO2 respiration patterns of the C-1 position of pyruvate. Furthermore, 13C label from malate and pyruvate were mainly allocated to amino and organic acid fractions in both species and only little to sugar and lipid fractions. In summary, our results suggest that respiration of both carboxyl groups of malate (via fumarase) by tricarboxylic acid cycle reactions or by NAD-malic enzyme influences δ13CLEDR. The latter supplies the pyruvate dehydrogenase reaction, which in turn determines natural δ13CLEDR pattern by releasing the C-1 position of pyruvate. PMID:27375626

  10. Metabolic Fate of the Carboxyl Groups of Malate and Pyruvate and their Influence on δ(13)C of Leaf-Respired CO2 during Light Enhanced Dark Respiration.

    PubMed

    Lehmann, Marco M; Wegener, Frederik; Barthel, Matti; Maurino, Veronica G; Siegwolf, Rolf T W; Buchmann, Nina; Werner, Christiane; Werner, Roland A

    2016-01-01

    The enhanced CO2 release of illuminated leaves transferred into darkness, termed "light enhanced dark respiration (LEDR)", is often associated with an increase in the carbon isotope ratio of the respired CO2 (δ(13)CLEDR). The latter has been hypothesized to result from different respiratory substrates and decarboxylation reactions in various metabolic pathways, which are poorly understood so far. To provide a better insight into the underlying metabolic processes of δ(13)CLEDR, we fed position-specific (13)C-labeled malate and pyruvate via the xylem stream to leaves of species with high and low δ(13)CLEDR values (Halimium halimifolium and Oxalis triangularis, respectively). During respective label application, we determined label-derived leaf (13)CO2 respiration using laser spectroscopy and the (13)C allocation to metabolic fractions during light-dark transitions. Our results clearly show that both carboxyl groups (C-1 and C-4 position) of malate similarly influence respiration and metabolic fractions in both species, indicating possible isotope randomization of the carboxyl groups of malate by the fumarase reaction. While C-2 position of pyruvate was only weakly respired, the species-specific difference in natural δ(13)CLEDR patterns were best reflected by the (13)CO2 respiration patterns of the C-1 position of pyruvate. Furthermore, (13)C label from malate and pyruvate were mainly allocated to amino and organic acid fractions in both species and only little to sugar and lipid fractions. In summary, our results suggest that respiration of both carboxyl groups of malate (via fumarase) by tricarboxylic acid cycle reactions or by NAD-malic enzyme influences δ(13)CLEDR. The latter supplies the pyruvate dehydrogenase reaction, which in turn determines natural δ(13)CLEDR pattern by releasing the C-1 position of pyruvate. PMID:27375626

  11. Concentrations and δ13C values of atmospheric CO2 from oceanic atmosphere through time: polluted and non-polluted areas

    NASA Astrophysics Data System (ADS)

    Longinelli, Antonio; Lenaz, Renzo; Ori, Carlo; Selmo, Enrico

    2005-11-01

    CO2 is one of the primary agents of global climate changes. The increase of atmospheric CO2 concentration is essentially related to human-induced emissions and, particularly, to the burning of fossil fuel whose δ13C values are quite negative. Consequently, an increase of the CO2 concentration in the atmosphere should be paralleled by a decrease of its δ13C. Continuous and/or spot measurements of CO2 concentrations were repeatedly carried out during the last decade and in the same period of the year along hemispheric courses from Italy to Antarctica on a vessel of the Italian National Research Program in Antarctica. During these expeditions, discrete air samples were also collected in 4-l Pyrex flasks in order to carry out precise carbon isotope analyses on atmospheric CO2 from different areas, including theoretically 'clean' open ocean areas, with the main purpose of comparing these open ocean results with the results obtained by the National Oceanic and Atmospheric Administration/World Meteorological Organization (NOAA/WMO) at land-based stations. According to the data obtained for these two variables, a relatively large atmospheric pollution is apparent in the Mediterranean area where the CO2 concentration has reached the value of 384 ppmv while quite negative δ13C values have been measured only occasionally. In this area, southerly winds probably help to reduce the effect of atmospheric pollution even though, despite a large variability of CO2 concentrations, these values are consistently higher than those measured in open ocean areas by a few ppmv to about 10 ppmv. A marked, though non-continuous, pollution is apparent in the area of the Bab-el-Mandeb strait where δ13C values considerably more negative than in the Central and Southern Red Sea were measured. The concentration of atmospheric CO2 over the Central Indian Ocean increased from about 361 ppmv at the end of 1996 to about 373 ppmv at the end of 2003 (mean growth rate of about 1.7 ppmv yr

  12. In Situ 13C and 23Na Magic Angle Spinning NMR Investigation of Supercritical CO2 Incorporation in Smectite-Natural Organic Matter Composites

    SciTech Connect

    Bowers, Geoffrey M.; Hoyt, David W.; Burton, Sarah D.; Ferguson, Brennan O.; Varga, Tamas; Kirkpatrick, Robert J.

    2014-01-29

    This paper presents an in situ NMR study of clay-natural organic polymer systems (a hectoritehumic acid [HA] composite) under CO2 storage reservoir conditions (90 bars CO2 pressure, 50°C). The 13C and 23Na NMR data show that supercritical CO2 interacts more strongly with the composite than with the base clay and does not react to form other C-containing species over several days at elevated CO2. With and without organic matter, the data suggest that CO2 enters the interlayer space of Na-hectorite equilibrated at 43% relative humidity. The presence of supercritical CO2 also leads to increased 23Na signal intensity, reduced line width at half height, increased basal width, more rapid 23Na T1 relaxation rates, and a shift to more positive resonance frequencies. Larger changes are observed for the hectorite-HA composite than for the base clay. In light of recently reported MD simulations of other polymer-Na-smectite composites, we interpret the observed changes as an increase in the rate of Na+ site hopping in the presence of supercritical CO2, the presence of potential new Na+ sorption sites when the humic acid is present, and perhaps an accompanying increase in the number of Na+ ions actively involved in site hopping. The results suggest that the presence of organic material either in clay interlayers or on external particle surfaces can significantly affect the behavior of supercritical CO2 and the mobility of metal ions in reservoir rocks.

  13. Evidence for CO2 Ice Formation and CO2 Gas Depletion in the South Polar Winter Atmosphere of Mars from Mars Climate Sounder Measurements

    NASA Astrophysics Data System (ADS)

    Kleinboehl, A.; Patel, P.; Schofield, J. T.; Kass, D. M.; Hayne, P. O.; McCleese, D. J.

    2016-09-01

    New 2D retrievals from MCS data show south polar winter atmospheric temperatures below the CO2 frost point, consistent with CO2 gas removal through condensation. Limb emission features suggest CO2 ice occurrence correlated with CO2 gas depletion.

  14. Description and Preliminary Results From an On-Line Method of Analysis of δ 13C and δ 18O of CO2

    NASA Astrophysics Data System (ADS)

    Pierce, D. L.; Bissell, S.; Giles, L.; Wright, A.; van Haren, J.; Yakir, D.; Berry, J. A.; Lin, G.

    2003-12-01

    At the Biosphere 2 Center in Oracle, Arizona we have developed a continuous flow analysis method to measure in "real-time" the concentration, 13C/12C, and 18O/16O of CO2 in air. CO2 isotope analysis in air samples is crucial for the partitions of the net ecosystem flux into its net assimilation and respiration components. Previous analysis techniques depend on having many glass flasks and transporting the flask samples to the lab for analysis. Our technique transports gas using 1/4 inch tubing from various sampling points in Biosphere 2 Center to an on-site laboratory, which houses the on-line discrimination stable isotope mass spectrometer (O.L.D.S.I.M.S.). OLDSIMS is a system designed to combine a Licor 6262 gas analyzer (Lincoln, NE) for instant CO2 concentration values, a SIRA (Stable Isotope Ratio Analyzer, VG-Micromass, UK), and a Process Control computer for peripheral system control and coordination with the SIRA. The stable isotope and concentration analysis of one sample as well as a know reference gas currently takes OLDSIMS 12.4 minutes to run. Results from a diurnal run of a standard CO2 tank are: [CO2] = 998.7 +/- 0.45 ppm, δ 13C = -3.34 +/- 0.098 ‰ , δ 18O = -11.75 +/- 0.108 ‰ vs PDB. During our presentation we will show this and other data collected at the Biosphere 2 Center tropical rainforest biome to demonstrate the capabilities of this "real-time" technique.

  15. The 'Nuts and Bolts' of 13C NMR Spectroscopy at Elevated-Pressures and -Temperatures for Monitoring In Situ CO2 Conversion to Metal Carbonates

    NASA Astrophysics Data System (ADS)

    Moore, J. K.; Surface, J. A.; Skemer, P. A.; Conradi, M. S.; Hayes, S. E.

    2013-12-01

    We will present details of newly-constructed specialized NMR designed to conduct in situ elevated-pressure, elevated-temperature 13C NMR studies on unmixed slurries of minerals in the presence of CO2 or other gases. This static probe is capable of achieving 300 bar, 300C conditions, and it is designed to spectroscopically examine 13C signals in mixtures of solids, liquids, gases, and supercritical fluids. Ultimately, our aim is to monitor CO2 uptake in both ultramafic rocks and in more porous geological materials to understand the mechanisms of chemisorption as a function of temperature, pressure and pH. We will give details of the hardware setup, and we will show a variety of static in situ NMR, as well as ex situ 'magic-angle spinning' NMR to show the analyses that are possible of minerals in pure form and in mixtures. In addition, specific NMR pulse sequences, techniques, and modeling will be described in detail. In this in situ NMR probe, we are able to simulate processes at geologically relevant fluid pressures and temperatures, monitoring the kinetics of CO2 conversion to carbonates. The in situ NMR experiments consist of heterogeneous mixtures of rock, salty brine solution, and moderate pressure CO2 gas at elevated temperatures. The purpose of studying these reactions is to determine conditions that affect the efficacy of carbonate formation in various targeted geological reservoirs (i.e., peroditite, or others). Via 13C NMR, we have spectroscopically characterized and quantified the conversion of CO2 to magnesium carbonate and calcium carbonate minerals, including metastable intermediates (such as hydromagnesite, or dypingite in the case of magnesium carbonate species, or vaterite in the case of calcium carbonate species). Such species are distinguishable from a combination of the 13C isotropic chemical shift, the static 13C lineshape, and changes in spin-lattice (T1) relaxation times. We will demonstrate that NMR can be used for quantitative

  16. Chemical structures of coal lithotypes before and after CO2 adsorption as investigated by advanced solid-state 13C nuclear magnetic resonance spectroscopy

    USGS Publications Warehouse

    Cao, X.; Mastalerz, Maria; Chappell, M.A.; Miller, L.F.; Li, Y.; Mao, J.

    2011-01-01

    Four lithotypes (vitrain, bright clarain, clarain, and fusain) of a high volatile bituminous Springfield Coal from the Illinois Basin were characterized using advanced solid-state 13C nuclear magnetic resonance (NMR) spectroscopy. The NMR techniques included quantitative direct polarization/magic angle spinning (DP/MAS), cross polarization/total sideband suppression (CP/TOSS), dipolar dephasing, CHn selection, and recoupled C-H long-range dipolar dephasing techniques. The lithotypes that experienced high-pressure CO2 adsorption isotherm analysis were also analyzed to determine possible changes in coal structure as a result of CO2 saturation at high pressure and subsequent evacuation. The main carbon functionalities present in original vitrain, bright clarain, clarain and fusain were aromatic carbons (65.9%-86.1%), nonpolar alkyl groups (9.0%-28.9%), and aromatic C-O carbons (4.1%-9.5%). Among these lithotypes, aromaticity increased in the order of clarain, bright clarain, vitrain, and fusain, whereas the fraction of alkyl carbons decreased in the same order. Fusain was distinct from other three lithotypes in respect to its highest aromatic composition (86.1%) and remarkably small fraction of alkyl carbons (11.0%). The aromatic cluster size in fusain was larger than that in bright clarain. The lithotypes studied responded differently to high pressure CO2 saturation. After exposure to high pressure CO2, vitrain and fusain showed a decrease in aromaticity but an increase in the fraction of alkyl carbons, whereas bright clarain and clarain displayed an increase in aromaticity but a decrease in the fraction of alkyl carbons. Aromatic fused-rings were larger for bright clarain but smaller for fusain in the post-CO2 adsorption samples compared to the original lithotypes. These observations suggested chemical CO2-coal interactions at high pressure and the selectivity of lithotypes in response to CO2 adsorption. ?? 2011 Elsevier B.V.

  17. CO2 concentrations and delta13C (CO2) values in monthly sets of air samples from downtown Parma and the Parma and Taro river valleys, Emilia-Romagna, Italy.

    PubMed

    Longinelli, Antonio; Selmo, Enricomaria

    2006-09-01

    Monthly sets of discrete air samples were collected from September 2004 to June 2005 in the town of Parma, along North-South and East-West runs (8 plus 8 samples), using four-litre Pyrex flasks. The CO2 concentrations and delta13C values were determined on these samples with the aim of evaluating quantitatively the contribution of domestic heating to the winter atmospheric CO2 pollution in downtown Parma by comparing autumn and spring atmospheric values with winter values. After separation of CO2 from the other air gases in the laboratory, the CO2 concentrations were calculated from the intensity of the 12C16O2+ ion beam in the mass spectrometer, after calibration with artificial air samples whose CO2 concentration was very carefully determined by the Monte Cimone Observatory (Sestola, Modena, Italy). The reproducibility of these measurements was of approximately +/-0.4 % and, consequently, the most probable error is not higher than+/-2-3 ppmv and does not affect the magnitude of the gradients between different samples. The standard deviation of delta13C measurements ranges from+/-0.02 to +/-0.04 per thousand (1sigma). The results suggest that the contribution of domestic heating to atmospheric CO2 pollution is almost negligible in the case of ground level atmosphere, where the main CO2 pollution is essentially related to the heavy car traffic. This is probably because of the fact that the gases from the domestic heating systems are discharged tens of metres above ground level at a relatively high temperature so that they rise quickly to the upper atmospheric layers and are then displaced by air masses dynamics. Monthly sets of discrete air samples were also collected from October 2004 to June 2005 along North-South runs from the town of Parma to the Apennine ridge following the Parma and the Taro river valleys (8 samples and 7 samples per set, respectively) and measured using the same technique. The aim of this study was the comparison between the town samples

  18. Identification of /sup 13/C depleted mantle carbon in diamonds from the Roberts Victor Kimberlite, South Africa

    SciTech Connect

    Deines, P.

    1985-01-01

    The Roberts Victor Kimberlite is known for the abundance of eclogite xenoliths, some of which show an unusual depletion in /sup 18/O. The question whether the observed oxygen isotope variations can be related to carbon isotopic composition variations has been investigated. Peridotite-suite diamons (X = -5.4 per thousand vs. PDB, s = +/-0.9 per thousand, n = 65) and sulfide containing diamonds (X = -4.9, s = +/-0.9, n = 20) do not differ in their /sup 13/C content. For these samples, delta/sup 13/C is not related to diamond shape, color, minerals occluded, or the inclusion chemistry. Eclogite suite diamonds (11) can be subdivided into two groups, GI and GII, based on delta/sup 13/C : GI = (X = -15.4, s = +/-0.4, n = 8); GII = (X = -5.9, s = +/-0.4, n = 3). The composition of the gt and cpx inclusions of the two groups is distinct; e.g. cpx of GI is significantly depleted in SiO/sub 2/, MgO, and CaO, and significantly enriched in Al/sub 2/O/sub 3/, FeO and MnO, compared to cpx of GII. Comparison of the chemical composition of the inclusions in E-type diamonds with those of eclogite xenoliths showing /sup 18/O depletion suggests that /sup 13/C and /sup 18/O depletion are not likely to be related. Evaluation of compositional trends of gt and cpx in eclogite xenoliths indicates that GI and GII are not related by a single fractionation event, but represent products from different reservoirs. Equilibration conditions deduced from coexisting gt and cpx demonstrate that GI diamonds come from larger depths than eclogite xenoliths and by inference GII diamonds. The high FeO and MnO content of a gt inclusion in cpx of an eclogite xenolith is used to argue for the existence of two separate events responsible for the formation of GI and GII diamonds.

  19. Monitoring the bio-stimulation of hydrocarbon-contaminated soils by measurements of soil electrical properties, and CO2 content and its 13C/12C isotopic signature

    NASA Astrophysics Data System (ADS)

    Noel, C.; Gourry, J.; Ignatiadis, I.; Colombano, S.; Dictor, M.; Guimbaud, C.; Chartier, M.; Dumestre, A.; Dehez, S.; Naudet, V.

    2013-12-01

    Hydrocarbon contaminated soils represent an environmental issue as it impacts on ecosystems and aquifers. Where significant subsurface heterogeneity exists, conventional intrusive investigations and groundwater sampling can be insufficient to obtain a robust monitoring of hydrocarbon contaminants, as the information they provide is restricted to vertical profiles at discrete locations, with no information between sampling points. In order to obtain wider information in space volume on subsurface modifications, complementary methods can be used like geophysics. Among geophysical methods, geoelectrical techniques such as electrical resistivity (ER) and induced polarization (IP) seem the more promising, especially to study the effects of biodegradation processes. Laboratory and field geoelectrical experiments to characterize soils contaminated by oil products have shown that mature hydrocarbon-contaminated soils are characterized by enhanced electrical conductivity although hydrocarbons are electrically resistive. This high bulk conductivity is due to bacterial impacts on geological media, resulting in changes in the chemical and physical properties and thus, to the geophysical properties of the ground. Moreover, microbial activity induced CO2 production and isotopic deviation of carbon. Indeed, produced CO2 will reflect the pollutant isotopic signature. Thus, the ratio δ13C(CO2) will come closer to δ13C(hydrocarbon). BIOPHY, project supported by the French National Research Agency (ANR), proposes to use electrical methods and gas analyses to develop an operational and non-destructive method for monitoring in situ biodegradation of hydrocarbons in order to optimize soil treatment. Demonstration field is located in the South of Paris (France), where liquid fuels (gasoline and diesel) leaked from some tanks in 1997. In order to stimulate biodegradation, a trench has been dug to supply oxygen to the water table and thus stimulate aerobic metabolic bioprocesses. ER and

  20. Prominent bacterial heterotrophy and sources of 13C-depleted fatty acids to the interior Canada Basin

    NASA Astrophysics Data System (ADS)

    Shah, S. R.; Griffith, D. R.; Galy, V.; McNichol, A. P.; Eglinton, T. I.

    2013-11-01

    In recent decades, the Canada Basin of the Arctic Ocean has experienced rapidly decreasing summer sea ice coverage and freshening of surface waters. It is unclear how these changes translate to deeper waters, particularly as our baseline understanding of organic carbon cycling in the deep basin is quite limited. In this study, we describe full-depth profiles of the abundance, distribution and carbon isotopic composition of fatty acids from suspended particulate matter at a seasonally ice-free station and a semi-permanently ice-covered station. Fatty acids, along with suspended particulate organic carbon (POC), are more concentrated and 13C-enriched under ice cover than in ice-free waters. But this influence, apparent at 50 m depth, does not propagate downward below 150 m depth, likely due to the weak biological pump in the central Canada Basin. Branched fatty acids have δ13C values that are similar to suspended POC at all depths and are more 13C-enriched than even-numbered saturated fatty acids at depths above 3000 m. These are likely to be produced in situ by heterotrophic bacteria incorporating organic carbon that is isotopically similar to total suspended POC. Below surface waters, there is also the suggestion of a source of saturated even-numbered fatty acids which could represent contributions from laterally advected organic carbon and/or from chemoautotrophic bacteria. At 3000 m depth and below, a greater relative abundance of long-chain (C20-24), branched and unsaturated fatty acids is consistent with a stronger influence of re-suspended sedimentary organic carbon. At these deep depths, two individual fatty acids (C12 and iso-C17) are significantly depleted in 13C, allowing for the possibility that methane oxidizing bacteria contribute fatty acids, either directly to suspended particulate matter or to shallow sediments that are subsequently mobilized and incorporated into suspended particulate matter within the deep basin.

  1. Glacial water mass geometry and the distribution of δ13C of ΣCO2 in the western Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Curry, W. B.; Oppo, D. W.

    2005-03-01

    Oxygen and carbon isotopic data were produced on the benthic foraminiferal taxa Cibicidoides and Planulina from 25 new piston cores, gravity cores, and multicores from the Brazil margin. The cores span water depths from about 400 to 3000 m and intersect the major water masses in this region. These new data fill a critical gap in the South Atlantic Ocean and provide the motivation for updating the classic glacial western Atlantic δ13C transect of Duplessy et al. (1988). The distribution of δ13C of ΣCO2 requires the presence of three distinct water masses in the glacial Atlantic Ocean: a shallow (˜1000 m), southern source water mass with an end-member δ13C value of about 0.3-0.5‰ VPDB, a middepth (˜1500 m), northern source water mass with an end-member value of about 1.5‰, and a deep (>2000 m), southern source water with an end-member value of less than -0.2‰, and perhaps as low as the -0.9‰ values observed in the South Atlantic sector of the Southern Ocean (Ninnemann and Charles, 2002). The origins of the water masses are supported by the meridional gradients in benthic foraminiferal δ18O. A revised glacial section of deep water δ13C documents the positions and gradients among these end-member intermediate and deep water masses. The large property gradients in the presence of strong vertical mixing can only be maintained by a vigorous overturning circulation.

  2. Adaptation of continuous-flow cavity ring-down spectroscopy for batch analysis of δ13C of CO2 and comparison with isotope ratio mass spectrometry.

    PubMed

    Berryman, E M; Marshall, J D; Rahn, T; Cook, S P; Litvak, M

    2011-08-30

    Measurements of δ(13)C in CO(2) have traditionally relied on samples stored in sealed vessels and subsequently analyzed using magnetic sector isotope ratio mass spectrometry (IRMS), an accurate but expensive and high-maintenance analytical method. Recent developments in optical spectroscopy have yielded instruments that can measure δ(13)CO(2) in continuous streams of air with precision and accuracy approaching those of IRMS, but at a fraction of the cost. However, continuous sampling is unsuited for certain applications, creating a need for conversion of these instruments for batch operation. Here, we present a flask (syringe) adaptor that allows the collection and storage of small aliquots (20-30 mL air) for injection into the cavity ring-down spectroscopy (CRDS) instrument. We demonstrate that the adaptor's precision is similar to that of traditional IRMS (standard deviation of 0.3‰ for 385 ppm CO(2) standard gas). In addition, the concentration precision (±0.3% of sample concentration) was higher for CRDS than for IRMS (±7% of sample concentration). Using the adaptor in conjunction with CRDS, we sampled soil chambers and found that soil-respired δ(13)C varied between two different locations in a piñon-juniper woodland. In a second experiment, we found no significant discrimination between the respiration of a small beetle (~5 mm) and its diet. Our work shows that the CRDS system is flexible enough to be used for the analysis of batch samples as well as for continuous sampling. This flexibility broadens the range of applications for which CRDS has the potential to replace magnetic sector IRMS.

  3. Safe storage and effective monitoring of CO2 in depleted gas fields.

    PubMed

    Jenkins, Charles R; Cook, Peter J; Ennis-King, Jonathan; Undershultz, James; Boreham, Chris; Dance, Tess; de Caritat, Patrice; Etheridge, David M; Freifeld, Barry M; Hortle, Allison; Kirste, Dirk; Paterson, Lincoln; Pevzner, Roman; Schacht, Ulrike; Sharma, Sandeep; Stalker, Linda; Urosevic, Milovan

    2012-01-10

    Carbon capture and storage (CCS) is vital to reduce CO(2) emissions to the atmosphere, potentially providing 20% of the needed reductions in global emissions. Research and demonstration projects are important to increase scientific understanding of CCS, and making processes and results widely available helps to reduce public concerns, which may otherwise block this technology. The Otway Project has provided verification of the underlying science of CO(2) storage in a depleted gas field, and shows that the support of all stakeholders can be earned and retained. Quantitative verification of long-term storage has been demonstrated. A direct measurement of storage efficiency has been made, confirming that CO(2) storage in depleted gas fields can be safe and effective, and that these structures could store globally significant amounts of CO(2).

  4. Prominent bacterial heterotrophy and sources of 13C-depleted fatty acids to the interior Canada Basin

    NASA Astrophysics Data System (ADS)

    Shah, S. R.; Griffith, D. R.; Galy, V.; McNichol, A. P.; Eglinton, T. I.

    2013-04-01

    In recent decades, the Canada Basin of the Arctic Ocean has experienced rapidly decreasing summer sea ice coverage and freshening of surface waters. It is unclear how these changes translate to depth, particularly as our baseline understanding of organic carbon cycling in the deep basin is limited. In this study, we describe full-depth profiles of the abundance, distribution and carbon isotopic composition of fatty acids from suspended particulate matter at a seasonally ice-free station and a semi-permanently ice-covered station. Fatty acids, along with suspended particulate organic carbon (POC), are more concentrated under ice cover than in ice-free waters. But this influence, apparent at 50 m depth, does not propagate downward below 150 m depth, likely due to the weak biological pump in the central Canada Basin. Branched fatty acids have δ13C values that are similar to suspended POC at all depths and are 13C-enriched compared to even-numbered saturated fatty acids at depths above 3000 m. These are likely to be produced in situ by heterotrophic bacteria incorporating organic carbon that is isotopically similar to total suspended POC. A source of saturated even-numbered fatty acids is also suggested below surface waters which could represent contributions from laterally advected organic carbon or from chemoautotrophic bacteria. At 3000 m depth and below, a greater relative abundance of long-chain (C20-24), branched and unsaturated fatty acids is consistent with a stronger influence of re-suspended sedimentary organic carbon on benthic particulate matter. At these deep depths, two individual fatty acids (C12 and iso-C17) are significantly depleted in 13C, allowing for the possibility that methane oxidizing bacteria contribute fatty acids, either directly to suspended particulate matter or to shallow sediments that are subsequently mobilized and incorporated into suspended particulate matter within the deep basin.

  5. Understanding the role of soil erosion on co2-c loss using (13)c isotopic signatures in abandoned Mediterranean agricultural land.

    PubMed

    Novara, Agata; Keesstra, Saskia; Cerdà, Artemio; Pereira, Paulo; Gristina, Luciano

    2016-04-15

    Understanding soil water erosion processes is essential to evaluate the redistribution of soil organic carbon (SOC) within a landscape and is fundamental to assess the role of soil erosion in the global carbon (C) budget. The main aim of this study was to estimate the C redistribution and losses using (13)C natural abundance. Carbon losses in soil sediment, dissolved organic carbon (DOC) and CO2 emission were determined. Four bounded parallel plots were installed on a 10% slope. In the upper part of the plots, C3soil was replaced with C4soil. The SOC and δ(13)C were measured after 145.2mm rainfall in the upper (2m far from C4strip), middle (4m far from C4strip) lower (6m far from C4strip) trams of the plot and in the sediments collected in the Gerlach collector at the lower part of the plot. A laboratory incubation experiment was performed to evaluate the CO2 emission rate of soils in each area. OC was mainly lost in the sediments as 2.08g(-)(2) of C was lost after 145.2mm rainfall. DOC losses were only 5.61% of off-site OC loss. Three months after the beginning of the experiment, 15.90% of SOC in the upper tram of the plot had a C4 origin. The C4-SOC content decreased along the 6m length of the plot, and in the sediments collected by the Gerlach collector. CO2 emission rate was high in the upper plot tram due to the high SOC content. The discrimination of CO2 in C3 and C4 portion permitted to increase our level of understanding on the stability of SOC and its resilience to decomposition. The transport of sediments along the plot increased SOC mineralization by 43%. Our study underlined the impact of rainfall in C losses in soil and water in abandoned Mediterranean agriculture fields and the consequent implications on the C balance.

  6. Understanding the role of soil erosion on co2-c loss using (13)c isotopic signatures in abandoned Mediterranean agricultural land.

    PubMed

    Novara, Agata; Keesstra, Saskia; Cerdà, Artemio; Pereira, Paulo; Gristina, Luciano

    2016-04-15

    Understanding soil water erosion processes is essential to evaluate the redistribution of soil organic carbon (SOC) within a landscape and is fundamental to assess the role of soil erosion in the global carbon (C) budget. The main aim of this study was to estimate the C redistribution and losses using (13)C natural abundance. Carbon losses in soil sediment, dissolved organic carbon (DOC) and CO2 emission were determined. Four bounded parallel plots were installed on a 10% slope. In the upper part of the plots, C3soil was replaced with C4soil. The SOC and δ(13)C were measured after 145.2mm rainfall in the upper (2m far from C4strip), middle (4m far from C4strip) lower (6m far from C4strip) trams of the plot and in the sediments collected in the Gerlach collector at the lower part of the plot. A laboratory incubation experiment was performed to evaluate the CO2 emission rate of soils in each area. OC was mainly lost in the sediments as 2.08g(-)(2) of C was lost after 145.2mm rainfall. DOC losses were only 5.61% of off-site OC loss. Three months after the beginning of the experiment, 15.90% of SOC in the upper tram of the plot had a C4 origin. The C4-SOC content decreased along the 6m length of the plot, and in the sediments collected by the Gerlach collector. CO2 emission rate was high in the upper plot tram due to the high SOC content. The discrimination of CO2 in C3 and C4 portion permitted to increase our level of understanding on the stability of SOC and its resilience to decomposition. The transport of sediments along the plot increased SOC mineralization by 43%. Our study underlined the impact of rainfall in C losses in soil and water in abandoned Mediterranean agriculture fields and the consequent implications on the C balance. PMID:26820936

  7. Interpretation of speleothem calcite δ13C variations: Evidence from monitoring soil CO2, drip water, and modern speleothem calcite in central Texas

    NASA Astrophysics Data System (ADS)

    Meyer, Kyle W.; Feng, Weimin; Breecker, Daniel O.; Banner, Jay L.; Guilfoyle, Amber

    2014-10-01

    We studied the sources and transport of carbon in two active karst systems in central Texas, Inner Space Cavern (IS) and Natural Bridge North and South Caverns (NB), to provide new insights into the interpretation of speleothem (cave calcite deposit) carbon isotope compositions. We have determined the δ13C values of soil CO2 (δ13Cs) in grassland and savanna above these caves with δ13C values of cave drip water (δ13CHCO3-) and modern speleothem calcite grown on artificial substrates (δ13Ccc). We compare δ13CHCO3- values from direct drip sites, where water was sampled immediately upon discharging from the cave ceiling, to values from indirect sites, where water was sampled after flowing along a prolonged path within the cave that allowed for longer CO2 degassing and have found that direct drip sites yield consistently lower δ13CHCO3- values. The δ13CHCO3- values of direct drip water below savanna (-10.6 ± 0.5‰ and -12.6 ± 0.2‰, in NB and IS, respectively) are indistinguishable from (IS) or similar to (NB) calculated δ13CHCO3- values in equilibrium with measured soil CO2 beneath trees (-13.5‰ to -11.3‰ for juniper trees above NB, and -13.6‰ to -12.6‰ for mixed oak and elm trees above IS, respectively). At IS, the δ13CHCO3- values of direct drip water are higher below grassland (-9.7 ± 0.3‰) than below savanna (12.6 ± 0.2‰). These results suggest that the δ13CHCO3- values of drip waters that initially enter the caves are controlled by deep-rooted plants, where present, and are minimally influenced by host-rock dissolution and/or prior calcite precipitation (PCP). The δ13CHCO3- values of indirect drip water vary seasonally with relatively low values during the summer (-10.8 ± 0.8‰ and -9.2 ± 0.4‰ under juniper savanna at NB and under grassland at IS, respectively) that are similar to the direct drip δ13CHCO3- values (-10.6 ± 0.5‰ and -9.7 ± 0.3‰ under savanna at NB and under grassland at IS, respectively). The relatively high

  8. Continuous high-resolution measurements of dissolved CH4, CO2 and δ13C-CO2 in surface water during the SWERUS-C3 expedition in the East Siberian Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Geibel, Marc Christoph; Magnus Mörth, Carl; Humborg, Christoph; Semiletov, Igor

    2015-04-01

    The carbon budget in the Arctic is still unknown. Especially the fate of CH4 from subsea permafrost on the East Siberian Arctic Shelf (ESAS) is unclear. In July-September 2014 the joined SWERUS-C3 expedition on board the Swedish icebreaker ODEN was undertaken. Among its goals was to get a better insight into the fate of carbon in the Arctic, to document possible CH4 release from subsea permafrost and deep sea and to understand mechanisms and magnitudes of CH4 release to the atmosphere. During the first leg of the expedition the in situ concentration of dissolved CH4, CO2 as well as the δ13C signature of CO2 were determined. Measurements were made continuously with a Water Equilibration Gas Analyzer System (WEGAS) that was specifically developed at Stockholm University for the determination of gases dissolved in water. The aim of this study was to quantify the concentration of dissolved CO2 and CH4 in the surface water of the East Siberian Arctic Ocean (ESAO) as well as the contribution of terrestrial organic matter respiration to the dissolved inorganic carbon (DIC). Combined with continuous high-precision atmospheric measurements that were performed during the SWERUS-C3 expedition, the WEGAS dataset will allow to calculate accurate high-resolution CH4 fluxes and thus give a better insight into the current outgassing of CH4 to the atmosphere. Together with measurements of δ13C of inorganic carbon that was sampled during the expedition, the isotopic composition of the dissolved organic carbon pool will allow to quantify the of terrestrial carbon contribution to total respiration in the ESAO.

  9. Role of Geomechanics in Assessing the Feasibility of CO2 Sequestration in Depleted Hydrocarbon Sandstone Reservoirs

    NASA Astrophysics Data System (ADS)

    Fang, Zhi; Khaksar, Abbas

    2013-05-01

    Carbon dioxide (CO2) sequestration in depleted sandstone hydrocarbon reservoirs could be complicated by a number of geomechanical problems associated with well drilling, completions, and CO2 injection. The initial production of hydrocarbons (gas or oil) and the resulting pressure depletion as well as associated reduction in horizontal stresses (e.g., fracture gradient) narrow the operational drilling mud weight window, which could exacerbate wellbore instabilities while infill drilling. Well completions (casing, liners, etc.) may experience solids flowback to the injector wells when injection is interrupted due to CO2 supply or during required system maintenance. CO2 injection alters the pressure and temperature in the near wellbore region, which could cause fault reactivation or thermal fracturing. In addition, the injection pressure may exceed the maximum sustainable storage pressure, and cause fracturing and fault reactivation within the reservoirs or bounding formations. A systematic approach has been developed for geomechanical assessments for CO2 storage in depleted reservoirs. The approach requires a robust field geomechanical model with its components derived from drilling and production data as well as from wireline logs of historical wells. This approach is described in detail in this paper together with a recent study on a depleted gas field in the North Sea considered for CO2 sequestration. The particular case study shows that there is a limitation on maximum allowable well inclinations, 45° if aligning with the maximum horizontal stress direction and 65° if aligning with the minimum horizontal stress direction, beyond which wellbore failure would become critical while drilling. Evaluation of sanding risks indicates no sand control installations would be needed for injector wells. Fracturing and faulting assessments confirm that the fracturing pressure of caprock is significantly higher than the planned CO2 injection and storage pressures for an ideal

  10. Metal Carbonation of Forsterite in Supercritical CO2 and H2O Using Solid State 29Si, 13C NMR Spectroscop

    SciTech Connect

    Kwak, Ja Hun; Hu, Jian Z.; Hoyt, David W.; Sears, Jesse A.; Wang, Chong M.; Rosso, Kevin M.; Felmy, Andrew R.

    2010-03-11

    Ex situ solid state NMR was used for the first time to study fundamental mineral carbonation processes and reaction extent relevant to geologic carbon sequestration (GCS) using a model silicate mineral forsterite (Mg2SiO4)+supercriticalCO2 with and without H2O. Run conditions were 80 C and 96 atm. 29Si NMR clearly shows that in the absence of CO2, the role of H2O is to hydrolyze surface Mg-O-Si bonds to produce dissolved Mg2+, and mono- and oligomeric hydroxylated silica species. Surface hydrolysis products contain only Q0 (Si(OH)4) and Q1(Si(OH)3OSi) species. An equilibrium between Q0, Q1 and Mg2+ with a saturated concentration equivalent to less than 3.2% of the Mg2SiO4 conversion is obtained at a reaction time of up to 7 days. Using scCO2 without H2O, no reaction is observed within 7 days. Using both scCO2 and H2O, the surface reaction products for silica are mainly Q3 (SiOH(OSi)3) species accompanied by a lesser amount of Q2 (Si(OH)2(OSi)2) and Q4 (Si(OSi)4). However, no Q0 and Q1 were detected, indicating the carbonic acid formation/deprotonation and magnesite (MgCO3) precipitation reactions are faster than the forsterite hydrolysis process. Thus it can be concluded that the Mg2SiO4 hydrolysis process is the rate limiting step of the overall mineral carbonation process. 29Si NMR combined with XRD, TEM, SAED and EDX further reveal that the reaction is a surface reaction with the Mg2SiO4 crystallite in the core and with condensed Q2-Q4 species forming amorphous surface layers. 13C MAS NMR identified a possible reaction intermediate as (MgCO3)4-Mg(OH)2-5H2O. However, at long reaction times only crystallite magnesite MgCO3 products are observed.

  11. Simulations of Arctic ozone depletion with current and doubled levels of CO2

    NASA Technical Reports Server (NTRS)

    Butchart, Neal; Austin, John; Shine, Keith P.

    1994-01-01

    Results from idealized 3-D simulations of a dynamical-radiative-photochemical model of the stratosphere are presented for the Northern Hemisphere winter and spring. For a simulation of a quiescent winter, it is found that with current levels of CO2 only modest polar ozone depletion occurs, consistent with observations. For a second simulation with the same planetary wave amplitudes in the upper troposphere but with doubled CO2, the model predicts a northern hemisphere ozone hole comparable to that observed in Antarctica with almost complete ozone destruction at 20 km. Reasons for the marked difference between the simulations are identified.

  12. Interdisciplinary Investigation of CO2 Sequestration in Depleted Shale Gas Formations

    SciTech Connect

    Zoback, Mark D.; Kovscek, Anthony R.; Wilcox, Jennifer

    2013-09-30

    This project investigates the feasibility of geologic sequestration of CO2 in depleted shale gas reservoirs from an interdisciplinary viewpoint. It is anticipated that over the next two decades, tens of thousands of wells will be drilled in the 23 states in which organic-rich shale gas deposits are found. This research investigates the feasibility of using these formations for sequestration. If feasible, the number of sites where CO2 can be sequestered increases dramatically. The research embraces a broad array of length scales ranging from the ~10 nanometer scale of the pores in the shale formations to reservoir scale through a series of integrated laboratory and theoretical studies.

  13. Partitioning of Organic Compounds into Supercritical CO2 in Depleted Oil Reservoirs - A Review

    NASA Astrophysics Data System (ADS)

    Burant, A.; Lowry, G. V.; Karamalidis, A.

    2012-12-01

    Depleted oil reservoirs, with enhanced oil recovery, will be one of the first adopters of carbon capture and storage (CCS), which is a promising mitigation strategy for global climate change. The large scale implementation of CCS mandates better understanding of the risks associated with CO2 injection, especially in regards to potential leakage of the stored CO2. Organics, in the residual oil and dissolved in the brine, can partition into supercritical CO2 (sc-CO2) and move with that phase if it leaks. This review presents an overview of the thermodynamic models and trends in experimental partitioning data needed to understand what compounds may be expected to move with the sc-CO2. There are two main types of thermodynamic models used for predicting the solubility of organic compounds in sc-CO2, equations of state and quantitative structure activity relationships. Both can predict the partitioning behavior of one compound in sc-CO2, however only equations of state can predict solubility in multicomponent systems. In addition, equations of state have been developed to determine the effect of electrolytes on the partitioning behavior of organics dissolved in brines. There are three main trends in the partitioning behavior of organics in sc-CO2: Pure phase solubility follows trends in vapor pressure; compounds with higher volatility have higher solubility in sc-CO2. Second, the partitioning from water to sc-CO2 follows trends in Henry's constants, which follow the relative solubility of a compound in both the sc-CO2 and aqueous phases. Thirdly, the solubility of a compound can be enhanced by the presence of another; highly volatile compounds enhance the solubility of compounds with lower volatility. Finally, the review presents the gaps in experimental research that can be used to improve the modeling of the partitioning behavior of organics in sc-CO2, specifically in regards to co-solvency effects and the effects of electrolytes on the partitioning of dissolved

  14. CLEAN - Large-Scale CO2 Storage for Enhanced Gas Recovery in a depleted German Gasfield

    NASA Astrophysics Data System (ADS)

    Kühn, Michael; Baltrusch, Steffi; Dahmke, Andreas; Förster, Andrea; Großmann, Jochen; Meyer, Robert; Reinicke, Kurt

    2010-05-01

    The joint research project CLEAN is a German research and development (R&D) alliance of 16 partners from science and industry. The main theme of this pilot project is to enhance gas recovery (EGR) by injection of CO2 into an almost depleted natural gas field. The research focus is on the assessment of all processes associated with the injection. At the same time, the CO2 long-term storage safety of Europe's second largest onshore gas field is analysed and evaluated. The CLEAN study site is located in Saxony-Anhalt (Germany) and is part of the natural gas field Altmark owned by GDF SUEZ E&P Deutschland GmbH. Here, the test field Altensalzwedel, which covers an area of 14 km2, represents a structurally and hydraulically enclosed substructure. The structure is characterized in detail by 12 existing deep wells. Fluviatile silt- and sandstones from Upper Rotliegend built the reservoir in around 3,500 metres depth. The caprock above the reservoir consists of massive Zechstein formations with significant deposits of evaporites. These salt layers with average thickness of several hundred metres represent a natural seal of the reservoir. At present the reservoir temperature is about 125 °C and reservoir pressures decreased from initially 425 bar to pressures between 30 and 50 bar, due to the gas production. For the substructure of Altensalzwedel it is assessed that the natural gas reservoir is depleted by 90 %. In the course of the pilot project CLEAN, less than 100,000 tonnes of CO2 will be injected for the EGR measures. An enhanced R&D program is performed to control existing wells, to advance the monitoring, and to improve the process modelling as a solid basis for a decent risk assessment, which is prerequisite for a future large-scale EGR project associated with the injection and storage of CO2. Within this field, some fundamental scientific, ecological and economical questions will be addressed and answered: Which technology is the most efficient and safe one to

  15. 13C isotopic fractionation during biodegradation of agricultural wastes.

    PubMed

    Chalk, Phillip M; Inácio, Caio T; Urquiaga, Segundo; Chen, Deli

    2015-01-01

    Significant differences in δ(13)C signatures occur within and between plant tissues and their constituent biochemical entities, and also within and between heterotrophic bacteria and fungi and their metabolic products. Furthermore, (13)C isotopic fractionation occurs during the biodegradation of organic molecules as seen in the substrate, respired CO(2) and the microbial biomass, which could be related to substrate composition and/or microbial metabolism. The (13)C isotopic fractionation observed during the decomposition of a single defined C substrate appears to be due to the intra-molecular heterogeneity in (13)C in the substrate and to (13)C isotopic fractionation during microbial metabolism. Very limited data suggest that the latter may be quantitatively more important than the former. Studies with defined fungi in culture media have highlighted the complexities associated with the interpretation of the observed patterns of (13)C isotopic fractionation when a single defined C source is added to the culture medium which itself contains one or more C sources. Techniques involving (13)C enrichment or paired treatments involving an equivalent C(3)- and C(4)-derived substrate have been devised to overcome the problem of background C in the culture medium and (13)C isotopic fractionation during metabolism. Studies with complex substrates have shown an initial (13)C depletion phase in respired CO(2) followed by a (13)C enrichment phase which may or may not be followed by another (13)C depletion phase. Basic studies involving an integrated approach are required to gain a new insight into (13)C isotopic fractionation during organic residue decomposition, by simultaneous measurements of δ(13)C in all C moieties. New analytical tools to measure real-time changes in δ(13)CO(2) and the intra-molecular δ(13)C distribution within plant biochemical entities offer new opportunities for unravelling the complex interactions between substrate and microbial metabolism with

  16. Canopy structure and atmospheric flows in relation to the δ13C of respired CO2 in a subalpine coniferous forest

    USGS Publications Warehouse

    Schaeffer, Sean M.; Anderson, Dean E.; Burns, Sean P.; Monson, Russell K.; Sun, Jielun; Bowling, David R.

    2008-01-01

    Stable isotopes provide insight into ecosystem carbon cycling, plant physiological processes, atmospheric boundary-layer dynamics, and are useful for the integration of processes over multiple scales. Of particular interest is the carbon isotope content (δ13C) of nocturnal ecosystem-respired CO2 (δR). Recent advances in technology have made it possible to continuously examine the variation in δR within a forest canopy over relatively long time-scales (months–years). We used tunable diode laser spectroscopy to examine δR at within- and below-canopy spatial locations in a Colorado subalpine forest (the Niwot Ridge AmeriFlux site). We found a systematic pattern of increased δR within the forest canopy (δR-c) compared to that near the ground (δR-g). Values of δR-c were weakly correlated with the previous day's mean maximum daytime vapor pressure deficit (VPD). Conversely, there was a negative but still weak correlation between δR-g and time-lagged (0–5 days) daily mean soil moisture. The topography and presence of sustained nightly drainage flows at the Niwot Ridge forest site suggests that, on nights with stable atmospheric conditions, there is little mixing of air near the ground with that in the canopy. Atmospheric stability was assessed using thresholds of friction velocity, stability above the canopy, and bulk Richardson number within the canopy. When we selectively calculated δR-g and δR-c by removing time periods when ground and canopy air were well mixed, we found stronger correlations between δR-c and VPD, and δR-g and soil moisture. This suggests that there may be fundamental differences in the environmental controls on δR at sub-canopy spatial scales. These results may help explain the wide variance observed in the correlation of δR with different environmental parameters in other studies.

  17. Carbon isotope analysis in urea at high 13C-abundances using the 13/12CO2-breath test device FANci2.

    PubMed

    Schmidt, G

    2002-09-01

    The increasing application of 13C-labelled urea in medicine requires simple and reasonable methods for measuring highly enriched C in urea. The combination: ultimate organic analysis--mass spectrometry so far prescribed is complicated and expensive. For medical diagnosis, however, isotope selective nondispersive infrared spectrometers (NDIRS) have been available for many years. One of these tools is FANci2 which is very reasonable and easily to be operated. By means of such devices also urea highly enriched in 13C can be analysed, provided that the samples are first diluted with a defined amount of urea of natural isotopic composition and then transformed into carbon dioxide by means of urease. The relative abundance of 13C in this carbon dioxide, measured by nondispersive infrared spectrometry, is then a measure of the 13C abundance in the initial urea sample. Comparison of results of such measurements with those attained by mass spectrometry proves that this procedure is feasible and yields precis results.

  18. Combined δ11B, δ13C, and δ18O analyses of coccolithophore calcite constrains the response of coccolith vesicle carbonate chemistry to CO2-induced ocean acidification

    NASA Astrophysics Data System (ADS)

    Liu, Yi-Wei; Tripati, Robert; Aciego, Sarah; Gilmore, Rosaleen; Ries, Justin

    2016-04-01

    Coccolithophorid algae play a central role in the biological carbon pump, oceanic carbon sequestration, and in marine food webs. It is therefore important to understand the potential impacts of CO2-induced ocean acidification on these organisms. Differences in the regulation of carbonate chemistry, pH, and carbon sources of the intracellular compartments where coccolith formation occurs may underlie the diverse calcification and growth responses to acidified seawater observed in prior experiments. Here we measured stable isotopes of boron (δ11B), carbon (δ13C) and oxygen (δ18O) within coccolith calcite, and δ13C of algal tissue to constrain carbonate system parameters in two strains of Pleurochrysis carterae (P. carterae). The two strains were cultured under variable pCO2, with water temperature, salinity, dissolved inorganic carbon (DIC), and alkalinity monitored. Notably, PIC, POC, and PIC/POC ratio did not vary across treatments, indicating that P. carterae is able to calcify and photosynthesize at relatively constant rates irrespective of pCO2 treatment. The δ11B data indicate that mean pH at the site of coccolith formation did not vary significantly in response to elevated CO2. These results suggest that P. carterae regulates calcifying vesicle pH, even amidst changes in external seawater pH. Furthermore, δ13C and δ18O data suggest that P. carterae may utilize carbon from a single internal DIC pool for both calcification and photosynthesis, and that a greater proportion of dissolved CO2 relative to HCO3- enters the internal DIC pool under acidified conditions. These results suggest that P. carterae is able to calcifyand photosynthesize at relatively constant rates across pCO2 treatments by maintaining pH homeostasis at their site of calcification and utilizing a greater proportion of aqueous CO2.

  19. Combined δ11B, δ13C, and δ18O analyses of coccolithophore calcite constrains the response of coccolith vesicle carbonate chemistry to CO2-induced ocean acidification

    NASA Astrophysics Data System (ADS)

    Liu, Yi-Wei; Tripati, Robert; Aciego, Sarah; Gilmore, Rosaleen; Ries, Justin

    2016-04-01

    Coccolithophorid algae play a central role in the biological carbon pump, oceanic carbon sequestration, and in marine food webs. It is therefore important to understand the potential impacts of CO2-induced ocean acidification on these organisms. Differences in the regulation of carbonate chemistry, pH, and carbon sources of the intracellular compartments where coccolith formation occurs may underlie the diverse calcification and growth responses to acidified seawater observed in prior experiments. Here we measured stable isotopes of boron (δ11B), carbon (δ13C) and oxygen (δ18O) within coccolith calcite, and δ13C of algal tissue to constrain carbonate system parameters in two strains of Pleurochrysis carterae (P. carterae). The two strains were cultured under variable pCO2, with water temperature, salinity, dissolved inorganic carbon (DIC), and alkalinity monitored. Notably, PIC, POC, and PIC/POC ratio did not vary across treatments, indicating that P. carterae is able to calcify and photosynthesize at relatively constant rates irrespective of pCO2 treatment. The δ11B data indicate that mean pH at the site of coccolith formation did not vary significantly in response to elevated CO2. These results suggest that P. carterae regulates calcifying vesicle pH, even amidst changes in external seawater pH. Furthermore, δ13C and δ18O data suggest that P. carterae may utilize carbon from a single internal DIC pool for both calcification and photosynthesis, and that a greater proportion of dissolved CO2 relative to HCO3‑ enters the internal DIC pool under acidified conditions. These results suggest that P. carterae is able to calcifyand photosynthesize at relatively constant rates across pCO2 treatments by maintaining pH homeostasis at their site of calcification and utilizing a greater proportion of aqueous CO2.

  20. Chemical-mechanical coupling observed for depleted oil reservoirs subjected to long-term CO2-exposure - A case study of the Werkendam natural CO2 analogue field

    NASA Astrophysics Data System (ADS)

    Hangx, Suzanne; Bakker, Elisenda; Bertier, Pieter; Nover, Georg; Busch, Andreas

    2015-10-01

    Geological storage of CO2 is one of the most promising technologies to rapidly reduce anthropogenic emissions of carbon dioxide. In order to ensure storage integrity, it is important to understand the effect of long-term CO2/brine/rock interactions on the mechanical behaviour of a storage complex. As most of these reactions are too slow to reproduce on laboratory timescales, we studied a natural CO2 analogue reservoir (the Röt Fringe Sandstone, Werkendam field, the Netherlands; 125-135 Ma of CO2-exposure) and its unreacted counterpart. We focused on CO2-induced mineralogical and porosity-permeability changes, and their effect on mechanical behaviour of both intact rock and simulated fault gouge. Overall, CO2-exposure did not lead to drastic mineralogical changes. The CO2-exposed material shows a stronger dependence of permeability on porosity, which is attributed to differences in diagenesis (closed-system diagenesis and hydrocarbon emplacement) taking place before CO2 charging. The limited extent of reaction was in part the result of bitumen coatings protecting specific mineral phases from reaction. In local, mm-sized zones displaying significant anhydrite cement dissolution, enhanced porosity was observed. For most of the reservoir the long-term mechanical behaviour after CO2-exposure could be described by the behaviour of the unreacted sandstone, while these more 'porous' zones had a lower rock strength. In addition, CO2-exposure did not affect the fault friction behaviour, and slip is expected to result in stable sliding. Simple stress path calculations predict that reservoir failure due to depletion and injection is unlikely, even for the 'porous' zones, nor will fault reactivation occur for realistic injection scenarios.

  1. 13C-Depleted carbon microparticles in >3700-Ma sea-floor sedimentary rocks from west greenland

    PubMed

    Rosing

    1999-01-29

    Turbiditic and pelagic sedimentary rocks from the Isua supracrustal belt in west Greenland [more than 3700 million years ago (Ma)] contain reduced carbon that is likely biogenic. The carbon is present as 2- to 5-micrometer graphite globules and has an isotopic composition of delta13C that is about -19 per mil (Pee Dee belemnite standard). These data and the mode of occurrence indicate that the reduced carbon represents biogenic detritus, which was perhaps derived from planktonic organisms.

  2. Coexisting goethite and gibbsite from a high-paleolatitude (55°N) Late Paleocene laterite: Concentration and 13C/ 12C ratios of occluded CO 2 and associated organic matter

    NASA Astrophysics Data System (ADS)

    Tabor, Neil J.; Yapp, Crayton J.

    2005-12-01

    A Late Paleocene (˜60 Ma BP) lateritic soil from Northern Ireland (the Antrim paleosol, herein referred to as Nire) contains coexisting goethite, gibbsite, phyllosilicate, and hematite. The Fe(III) oxides exhibit pisolitic and Liesegang-type morphologies that are mutually exclusive in hand specimens. X-ray diffraction (XRD) measurements of Al substituted for Fe in goethite indicate two populations: (1) low-Al, Liesegang-type goethites (˜0 mol% Al) and (2) high-Al, pisolitic goethites (˜9 to ˜24 mol% Al). Selective dissolution and incremental vacuum dehydration-decarbonation were used to determine the concentration and δ 13C values of CO 2 occluded in the respective structures of the goethites and gibbsites in this complex mixture of Nire lateritic minerals. The Fe(CO 3)OH component in the high-Al goethites appears to retain a proxy carbon isotopic record of vadose zone CO 2 in the ancient soil. The δ 13C values of CO 2 occluded in coexisting goethites and gibbsites indicate that these minerals did not form in equilibrium with the same environmental CO 2. The measured mole fractions (X) of Fe(CO 3)OH in the high-Al goethites range from 0.0059 (±0.0005) to 0.0077 (±0.0006) and correspond to soil CO 2 concentrations of ˜28,000 to ˜37,000 ppmV. The average values of X and δ 13C for the four high-Al goethites are 0.0067 ± 0.0007 and -20.1 ± 0.5‰, respectively. The δ 13C value of the organic matter undergoing oxidation in this midlatitude (˜55°N) Late Paleocene soil appears to have been ˜ -28.2‰. Taken together, these data indicate an atmospheric CO 2 concentration of ˜2400 ppmV (± ˜1200 ppmV) at ˜60 Ma BP. The inferred high concentration of atmospheric CO 2 would have been coincident with the warm global climate of the Late Paleocene and is consistent with the idea that CO 2 plays an important role in climate variation.

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

    SciTech Connect

    Powers, Heath H; Mcdowell, Nate; Hanson, David; Hunt, John

    2009-01-01

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

  4. On the suitability of partially clathrated ice for analysis of concentration and δ 13C of palaeo-atmospheric CO 2

    NASA Astrophysics Data System (ADS)

    Schaefer, Hinrich; Lourantou, Anna; Chappellaz, Jérôme; Lüthi, Dieter; Bereiter, Bernhard; Barnola, Jean-Marc

    2011-07-01

    The stable carbon isotopic signature of carbon dioxide (δ 13CO 2) measured in the air occlusions of polar ice provides important constraints on the carbon cycle in past climates. In order to exploit this information for previous glacial periods, one must use deep, clathrated ice, where the occluded air is preserved not in bubbles but in the form of air hydrates. Therefore, it must be established whether the original atmospheric δ 13CO 2 signature can be reconstructed from clathrated ice. We present a comparative study using coeval bubbly ice from Berkner Island and ice from the bubble-clathrate transformation zone (BCTZ) of EPICA Dome C (EDC). In the EDC samples the gas is partitioned into clathrates and remaining bubbles as shown by erroneously low and scattered CO 2 concentration values, presenting a worst-case test for δ 13CO 2 reconstructions. Even so, the reconstructed atmospheric δ 13CO 2 values show only slightly larger scatter. The difference to data from coeval bubbly ice is statistically significant. However, the 0.16‰ magnitude of the offset is small for practical purposes, especially in light of uncertainty from non-uniform corrections for diffusion related fractionation that could contribute to the discrepancy. Our results are promising for palaeo-atmospheric studies of δ 13CO 2 using a ball mill dry extraction technique below the BCTZ of ice cores, where gas is not subject to fractionation into microfractures and between clathrate and bubble reservoirs.

  5. An experimental evaluation of the use of C3 δ13C plant tissue as a proxy for the paleoatmospheric δ13CO2 signature of air

    NASA Astrophysics Data System (ADS)

    Lomax, B. H.; Knight, C. A.; Lake, J. A.

    2012-09-01

    Previous work suggests that the relationship between the carbon isotope composition of air (δ13Ca) and plant leaf tissue (δ13Cp) can be used to track changes in the carbon isotope composition of paleo-atmospheric CO2. Here we test this assertion in a series of experiments using the model plant Arabidopsis thaliana grown under a range of atmospheric CO2 concentrations relevant to geologic time (380, 760, 1000, 1500, 2000 and 3000 ppm). Nested within these CO2 experiments water availability was controlled (giving two sets of experimental plants; low and high water treatment at each CO2 concentration) to manipulate stomatal opening, a key process governing carbon fixation and isotope discrimination. Results show a highly significant relationship between δ13Ca and δ13Cp under both experimental water treatments. To test the utility of δ13Cp to predict δ13Ca we compare calculated δ13Ca to measured values of δ13Ca. These data show that although there is a significant relationship between calculated and measured δ13Ca, there is disparity between the two values of δ13Ca and a large difference between calculated values under different water treatments even when grown in a common CO2 concentration. These results demonstrate that environmental factors that alter stomatal opening can severely impact on the use and reliability of δ13Cp to predict δ13Ca and as such, results should be interpreted with caution.

  6. Identification of biomass utilizing bacteria in a carbon-depleted glacier forefield soil by the use of 13C DNA stable isotope probing.

    PubMed

    Zumsteg, Anita; Schmutz, Stefan; Frey, Beat

    2013-06-01

    As Alpine glaciers are retreating rapidly, bare soils with low organic C and N contents are becoming exposed. Carbon availability is a key factor regulating microbial diversity and ecosystem functioning in these soils. The aim of this study was to investigate how bacterial activity, community structure and composition are influenced by organic carbon availability. Bare soils were supplied with (13)C-labelled fungal (Penicillium sp.) and green algal (Chlorella sp.) biomass and the CO2 evolution and its δ(13)C signature were monitored up to 60 days. These organisms have previously been isolated near the glacier terminus. DNA stable isotope probing followed by T-RFLP profiling and sequencing of 16S rRNA genes was employed to identify consumers able to assimilate carbon from these biomass amendments. Higher respiration and higher bacterial activity indicated a more efficient utilization of algal cells than fungal cells. Flavobacterium sp. predominantly incorporated fungal-derived C, whereas the algal-derived C was mainly incorporated by Acidobacteria and Proteobacteria. This study emphasizes the important role of both fungal and algal biomass in increasing the carbon pool in recently deglaciated bare soils, as only 20% of the added C was respired as CO2, and the rest, we presume, remained in the soil.

  7. Short-term natural δ13C variations in pools and fluxes in a beech forest: the transfer of isotopic signal from recent photosynthates to soil respired CO2

    NASA Astrophysics Data System (ADS)

    Gavrichkova, O.; Proietti, S.; Moscatello, S.; Portarena, S.; Battistelli, A.; Matteucci, G.; Brugnoli, E.

    2011-03-01

    The fate of photosynthetic products within the plant-soil continuum determines how long the reduced carbon resides within the ecosystem and when it returns back to the atmosphere in the form of respiratory CO2. We have tested the possibility of measuring natural variation in δ13C to disentangle potential times needed to transfer carbohydrates produced by photosynthesis down to roots and, in general, to belowground up to its further release in the form of soil respiration into the atmosphere in a beech (Fagus sylvatica) forest. For these purposes we have measured the variation in stable carbon and oxygen isotope compositions in plant material and in soil respired CO2 every three hours for three consequent days. Possible steps and different signs of post-photosynthetic fractionation during carbon translocation were also identified. A 12 h-periodicity was observed for variation in δ13C in soluble sugars in the top crown leaves and it can be explained by starch day/night dynamics in synthesis and breakdown and by stomatal limitations under elevated vapour pressure deficits. Photosynthetic products were transported down the trunk and mixed with older carbon pools, therefore causing the dampening of the δ13C signal variation. The strongest periodicity of 24 h was found in δ13C in soil respiration indicating changes in root contribution to the total CO2 efflux. Nevertheless, it was possible to identify the speed of carbon translocation through the plant-soil continuum. A period of 24 h was needed to transfer the C assimilated by photosynthesis from the top crown leaves to the tree trunk at breast height and additional 3 h for further respiration of that C by roots and soil microorganisms and its to subsequent diffusion back to the atmosphere.

  8. Short communication: Using diurnal patterns of (13)C enrichment of CO2 to evaluate the effects of nitrate and docosahexaenoic acid on fiber degradation in the rumen of lactating dairy cows.

    PubMed

    Klop, G; Bannink, A; Dieho, K; Gerrits, W J J; Dijkstra, J

    2016-09-01

    Nitrate decreases enteric CH4 production in ruminants, but may also negatively affect fiber degradation. In this experiment, 28 lactating Holstein dairy cows were grouped into 7 blocks. Within blocks, cows were randomly assigned to 1 of 4 isonitrogenous treatments in a 2×2 factorial arrangement: control (CON); NO3 [21g of nitrate/kg of dry matter (DM)]; DHA [3g of docosahexaenoic acid (DHA)/kg of DM]; or NO3+DHA (21g of nitrate/kg of DM and 3g of DHA/kg of DM). Cows were fed a total mixed ration consisting of 21% grass silage, 49% corn silage, and 30% concentrates on a DM basis. Based on the difference in natural (13)C enrichment and neutral detergent fiber and starch content between grass silage and corn silage, we investigated whether a negative effect on rumen fiber degradation could be detected by evaluating diurnal patterns of (13)C enrichment of exhaled carbon dioxide. A significant nitrate × DHA interaction was found for neutral detergent fiber digestibility, which was reduced on the NO3 treatment to an average of 55%, as compared with 61, 64, and 65% on treatments CON, DHA, and NO3+DHA, respectively. Feeding nitrate, but not DHA, resulted in a pronounced increase in (13)C enrichment of CO2 in the first 3 to 4 h after feeding only. Results support the hypothesis that effects of a feed additive on the rate of fiber degradation in the rumen can be detected by evaluating diurnal patterns of (13)C enrichment of CO2. To be able to detect this, the main ration components have to differ considerably in fiber and nonfiber carbohydrate content as well as in natural (13)C enrichment. PMID:27344384

  9. Depleted deep South China Sea δ13C paleoceanographic events in response to tectonic evolution in Taiwan-Luzon Strait since Middle Miocene

    NASA Astrophysics Data System (ADS)

    Chen, Wen-Huang; Huang, Chi-Yue; Lin, Yen-Jun; Zhao, Quanhong; Yan, Yi; Chen, Duofu; Zhang, Xinchang; Lan, Qing; Yu, Mengming

    2015-12-01

    The most distinctive feature of the deep South China Sea (SCS) paleoceanography is the occurrence of long-term depleted deep-sea benthic foraminiferal δ13C values. They are lower than the global and the Pacific composite records in the last 16 Ma, especially at 13.2, 10.5, 6.5, 3.0 and 1.2-0.4 Ma. This distinct deep SCS paleoceanograhic history coincides with the subduction-collision history in the Taiwan region where waters of the West Pacific (WP) and the SCS exchange. The depleted deep-sea benthic foraminiferal δ13C events indicate that the SCS deep basin became progressively a stagnant environment in the last 16 Ma due to either closure of the connection with the WP bottom water or temporary reduction of the WP deep water flowing into the deep SCS. Both the Taiwan accretionary prism and the Luzon arc became the main tectono-morphological barriers for the WP bottom water flowing into the SCS deep basin when eastward subduction of the SCS oceanic lithosphere beneath the Philippine Sea Plate started from the Middle Miocene (18-16 Ma). This began a long-term trend of depleted SCS deep-sea benthic δ13C values in the last 16 Ma. The oblique arc-continent collision since ~6.5 Ma uplifted the Taiwan accretionary prism rapidly above sea level and further isolated the SCS from the open Pacific. The collision simultaneously causes backthrusting deformations in the North Luzon Trough forearc basin and sequentially closes interarc water gates between volcanic islands from north to south. The Loho and the Taitung interarc water gates in the advanced collision zone were closed at ~3.0 Ma and ~1.2 Ma, coinciding with the very low SCS deep-sea benthic δ13C events at 3.0 and 1.2-0.4 Ma, respectively. The Taitung Canyon between the Lutao and Lanyu volcanic islands in the incipient collision zone is semi-closed presently. These closure events also lead to the result that the WP deep water intrudes westward into the SCS principally through the Bashi Channel between the Lanyu

  10. Depleted δ13C Values in Salt Dome Cap Rock Organic Matter and Implications for Microbial Metabolism and Fixation

    NASA Astrophysics Data System (ADS)

    Loyd, S. J.; Lu, L.; Caesar, K. H.; Kyle, R.

    2015-12-01

    Salt domes occur throughout the Gulf Coast Region USA and are often associated with trapped hydrocarbons. These salt domes can be capped by sulfate and carbonate minerals that result from complex digenetic interactions in the subsurface. The specific natures of these interactions are poorly understood, in particular the role of microbes in facilitating mineralization and element cycling. Carbon isotope compositions of cap rock calcites (δ13Ccarb) are highly variable and range from near neutral to less than -40‰ (VPDB) indicative of methane-sourced carbon. These low values and the common coexistence of elemental sulfur and metal sulfides have spurred hypotheses invoking microbial sulfate reduction as driving carbonate mineral authigenesis. Here, we present new organic carbon isotope (δ13Corg) data that, similar to δ13Ccarb, exhibit depletions below -30 to -25‰. These δ13Corg values are lower than local liquid hydrocarbons and "normal" marine organic matter reflecting either microbial fixation of methane-sourced carbon or microbial fractionation from liquid hydrocarbon sources. The combined carbon isotope data (δ13Ccarb and δ13Corg) indicate that methane likely plays an important role in microbial cycling in salt domes. The δ13Corg values are similar to those of anaerobic oxidation of methane (AOM) related communities from methane-sulfate controlled marine sediments. Ultimately, salt dome environments may share some important characteristics with AOM systems.

  11. CLEAN - Large-Scale CO2 Storage for Enhanced Gas Recovery in a depleted German Gasfield

    NASA Astrophysics Data System (ADS)

    Kuehn, M.; Förster, A.; Grossmann, J.; Meyer, R.; Pilz, P.; Reinicke, K.; Schaefer, D.; Tesmer, M.; Wendel, H.

    2011-12-01

    ) baseline stress conditions, (10) monitoring set-up comprising reservoir, cap rock and shallow aquifer compartments as well as the unsaturated zone and ground surface, (11) implementation of monitoring for the purpose of determining natural variations for the parameters, and (12) assessment of various methods with regard to temporal and spatial scales for the parameters recorded. The joint research project developed technologies and methods to be used for a CO2 based EGR within the Altmark. Furthermore, this work is a major step forward understanding the behavior of CO2 injected into a depleted gas field. The findings support the definition of national and international standards, the development of best practice guidelines and built up expertise for this new technology. Acknowledgement: CLEAN is part of the geoscientific R&D program "GEOTECHNOLOGIEN" funded by the German Federal Ministry of Education and Research (BMBF) and GDF SUEZ.

  12. δ 13C of ecosystem-respired CO2 along a gradient of C3 woody-plant encroachment into C4 grassland

    NASA Astrophysics Data System (ADS)

    Sun, W.; Scott, R. L.; Resco, V.; Cable, J. M.; Huxman, T. E.; Williams, D. G.

    2006-12-01

    Woody plant encroachment into grassland has the potential to affect net primary production, in part by changing the sensitivities of photosynthesis and respiration to precipitation. Encroachment of mesquite (Prosopis) into floodplain sacaton (Sporobolus) grassland along the San Pedro River in southeastern Arizona has altered the magnitude and seasonal pattern of net ecosystem carbon exchange and ecosystem respiration. We hypothesized that because mesquite accesses ground water in these floodplain environments, its advancement and dominance in former grassland reduces the sensitivities of photosynthesis and autotrophic respiration to inputs of growing season precipitation. The observed elevated rates of ecosystem respiration following rainfall inputs are likely to result from microbial decomposition of labile organic matter derived from the highly productive mesquite trees. We used the Keeling plot method to monitor carbon-13 composition of nocturnal ecosystem-respired CO2 (δ 13CR) during the growing seasons of 2005 and 2006 at three sites spanning a gradient of mesquite invasion: C4 sacaton grassland, mixed mesquite/grass shrubland and C3 mesquite woodland. δ 13CR in the C4 grassland increased from -18.8‰ during the dry premonsoon period to -16.7‰ after the onset of summer rains, whereas δ 13CR in the mixed shrub/grass and woodland ecosystems declined from -20.9‰ to - 24‰ and from -20.8‰ to -24.7‰, respectively, following the onset of summer rains. The δ 13CR of respired CO2 was collected separately from soil, roots, leaves and surface litter to evaluate the contribution of each of these components to ecosystem respiration. Partitioning of ecosystem respiration using these isotope end-members and responses to short-term (days) changes in shallow (0-5cm) soil moisture content suggest that in former grassland now occupied by mesquite woodland, rainfall inputs primarily stimulate microbial decomposition and have little effect on autotrophic respiration

  13. Late-Quaternary variation in C3 and C4 grass abundance in southeastern Australia as inferred from δ13C analysis: Assessing the roles of climate, pCO2, and fire

    NASA Astrophysics Data System (ADS)

    Nelson, David M.; Urban, Michael A.; Kershaw, A. Peter; Hu, Feng Sheng

    2016-05-01

    Climate, atmospheric pCO2, and fire all may exert major influences on the relative abundance of C3 and C4 grasses in the present-day vegetation. However, the relative role of these factors in driving variation in C3 and C4 grass abundances in the paleorecord is uncertain, and C4 abundance is often interpreted narrowly as a proxy indicator of aridity or pCO2. We measured δ13C values of individual grains of grass (Poaceae) pollen in the sediments of two sites in southeastern Australia to assess changes in the proportions of C3 and C4 grasses during the past 25,000 years. These data were compared with shifts in pCO2, temperature, moisture balance, and fire to assess how these factors were related to long-term variation of C4 grass abundance during the late Quaternary. At Caledonia Fen, a high-elevation site in the Snowy Mountains, C4 grass abundance decreased from an average of 66% during the glacial period to 11% during the Holocene, primarily in response to increased pCO2 and temperature. In contrast, this pattern did not exist in low-elevation savannah woodlands around Tower Hill Northwest Crater, where C4 grass abundance instead varied in response to shifts in regional aridity. Fire did not appear to have strongly influenced the proportions of C3 and C4 grasses on the landscape at millennial timescales at either site. These patterns are similar to those of a recent study in East Africa, suggesting that elevation-related climatic differences influence how the abundance of C3 and C4 grasses responds to shifts in climate and pCO2. These results caution against using C4 plant abundance as a proxy indicator of either climate or pCO2 without an adequate understanding of key controlling factors.

  14. Short-term natural δ13C and δ18O variations in pools and fluxes in a beech forest: the transfer of isotopic signal from recent photosynthates to soil respired CO2

    NASA Astrophysics Data System (ADS)

    Gavrichkova, O.; Proietti, S.; Moscatello, S.; Portarena, S.; Battistelli, A.; Matteucci, G.; Brugnoli, E.

    2011-10-01

    The fate of photosynthetic products within the plant-soil continuum determines how long the reduced carbon resides within the ecosystem and when it returns back to the atmosphere in the form of respiratory CO2. We have tested the possibility of measuring natural variation in δ13C and δ18O to disentangle the potential times needed to transfer carbohydrates produced by photosynthesis down to trunk, roots and, in general, to belowground up to its further release in the form of soil respiration into the atmosphere in a beech (Fagus sylvatica) forest. We have measured the variation in stable carbon and oxygen isotope compositions in plant material and in soil respired CO2 every three hours for three consecutive days. Possible steps and different signs of post-photosynthetic fractionation during carbon translocation were also identified. A 12 h-periodicity was observed for variation in δ13C in soluble sugars in the top crown leaves and it can be explained by starch day/night dynamics in synthesis and breakdown and by stomatal limitations under elevated vapour pressure deficits. Photosynthetic products were transported down the trunk and mixed with older carbon pools, therefore causing the dampening of the δ13C signal variation. The strongest periodicity of 24 h was found in δ13C in soil respiration indicating changes in root contribution to the total CO2 efflux. Other non-biological causes like diffusion fractionation and advection induced by gas withdrawn from the measurement chamber complicate data interpretation on this step of C transfer path. Nevertheless, it was possible to identify the speed of carbohydrates' translocation from the point of assimilation to the trunk breast height because leaf-imprinted enrichment of δ18O in soluble sugars was less modified along the downward transport and was well related to environmental parameters potentially linked to stomatal conductance. The speed of carbohydrates translocation from the site of assimilation to the trunk

  15. Implications of high-precision measurements of 13C-18O bond ordering in CO2 for thermometry in modern bivalved mollusc shells

    NASA Astrophysics Data System (ADS)

    Petrizzo, Daniel A.; Young, Edward D.; Runnegar, Bruce N.

    2014-10-01

    We report a temperature calibration for Δ47 from bivalve carbonate that lies within error of theoretical predictions (Schauble et al., 2006; Guo et al., 2009). The temperature sensitivity of this calibration is lower than several different earlier calibrations determined using either inorganic calcite, corals, foraminiferans and coccoliths, or brachiopods and bivalved molluscs, but it agrees with more recent Δ47-temperature relationships determined from measurements of clumped-isotopes in mollusc and brachiopod shells. We demonstrate that mollusc shell temperature calibrations originating from different laboratories that have not been corrected for instrument backgrounds may differ by as much as ∼0.07‰ in Δ47 over the ∼0 to 30 °C temperature range even where dΔ47/dT agree. Because recent calibrations for Δ47 vs. T from several different laboratories agree for bivalved mollusc shells, yet differ from an early calibration for bivalved molluscs, we suggest it is unlikely that temperature-Δ47 variability is attributable to phylum-specific vital effects, and instead conclude that differences in calibration slope between phyla and/or inorganic calcite are more easily explained by variability in measurements made in different laboratories. Discrepancies in both calibration slopes and/or intercepts indicate that Δ47 values measured in natural materials may be more significantly influenced by instrument-specific effects, as well as effects from sample preparation and handling and purification of CO2 than current techniques are able to correct for, and therefore, temperatures obtained by comparing measurements of Δ47 to independently determined calcite calibrations may err by a far greater amount than acknowledged in previous studies.

  16. Reactive transport modeling of the long-term effects of CO2 storage in the P18 depleted gas field

    NASA Astrophysics Data System (ADS)

    Tambach, T. J.; Koenen, M.; Wasch, L. J.; Loeve, D.; Maas, J. G.

    2012-04-01

    Depleted gas fields are an import CO2 storage sink for The Netherlands, with a total storage capacity of more than 3 Gtonne. The CO2 sources are located at relatively short distances from potential storage reservoirs and an infrastructure for (cross-border) gas transport over large distances already exists. Several depleted gas fields in the subsurface of the Netherlands have yet been evaluated as potential locations for CO2 storage (for example the K12-B field). The P18 gas field is located in the offshore of The Netherlands and is currently evaluated as potential CO2 storage reservoir. The aim of this study is to predict the long-term effects of CO2 injection into the P18 field using reactive transport modeling (TOUGHREACT). The storage reservoir is described using the mineralogy and petrophysical characteristics of three geological layers in a radial (R,Z) reservoir model with top depth of 3456 m, a thickness of 98 m, and 3300 grid cells. The initial reservoir temperature was defined as 90 degrees C with an initial (depletion) pressure of 20.0 bars. Capillary pressure curves are based on empirical relations. The CO2 is injected uniformly distributed over the model height, at a constant rate of 35 kg/s (1.1 Mton/year), and a temperature of 40 degrees C for 30 years. The well is then shut-in with a reservoir pressure of approximately 375 bar. The simulations are continued up to 10,000 years for computing the long-term effects in the reservoir. The results show that the near-well area is dried out during injection, leading to salt precipitation and reduced permeability during injection. Condensation of the evaporated water occurs outside the near-well area. Water imbibition is modelled after shut in of the well, leading to rewetting of the near-well area and redissolution of the salt. Most geochemical reactions need water to occur, including well-cement minerals, and therefore predictions of water flow after well shut-ins are important to take into account

  17. Utilizing continuous measurements of delta^{13}C_r, delta18O_r, and net ecosystem exchange of CO_2 and H_2O to understand the effects of inter-annual variability in drought on ecosystem functioning

    NASA Astrophysics Data System (ADS)

    Osuna, J. L.; McDowell, N. G.; Shim, J. H.; Rahn, T.; Pockman, W.

    2011-12-01

    In the semi-arid Southwestern US, seasonal drought has strengthened in recent years due to both a decrease in winter precipitation and delayed onset of the summer monsoon. A process-based understanding of ecosystem response to increased drought stress is vital to predicting the long-term stability of semi-arid biomes. To understand the processes responsible for inter-annual and seasonal variability in net ecosystem carbon and water fluxes, we compared nearly continuous measurements of ecosystem scale respiration (R_e) from an eddy covariance system with the stable carbon and oxygen isotope signals in ecosystem respired CO_2 (delta^{13}C_r and delta^{18}O_r) measured continuously by a tunable diode laser spectrometer (TDL) sampling at various canopy heights at the same site. The study site, at Los Alamos National Laboratory, converted from pitilde{n}on juniper woodland to juniper woodland after over 90% of pitilde{n}ons died in 2002-2003 following multiple years of enhanced drought leaving a high necromass at the site. We analyzed the relationships between the Bowen ratio, delta^{18}O_r, daily and annual accumulated NEE, and delta^{13}C_r to understand the (de)coupling between the response of transpiration and respiration under varying degrees of drought stress. Additionally, we explored the variability in the lag and intensity of ecosystem response to precipitation pulses depending on antecedent conditions. The response of delta^{18}O_r was more consistent across years and seasons whereas variability in the contribution of autotrophic versus heterotrophic respiration appeared to cause differing responses of delta^{13}C_r to drought stress and precipitation pulses. This result was supported by the diurnal CO_2 and H_2O fluxes indicating nearly immediate transpirational water loss initiated by most precipitation pulses. Annual accumulated precipitation (versus pulse size) was a better indicator of delta^{13}C_ r response (i.e. relative contributions of autotrophic

  18. Differences in CH4 oxidation and pathways of production between rice cultivars deduced from measurements of CH4 flux and δ13C of CH4 and CO2

    NASA Astrophysics Data System (ADS)

    Bilek, Rebecca S.; Tyler, Stanley C.; Sass, Ronald L.; Fisher, Frank M.

    We report measurements of CH4 flux and δ13C and δD values of emitted CH4 and sediment CH4 and CO2 during the 1995 rice growing season in Beaumont, Texas. Four rice plant cultivars, Lemont, Mars, Cypress, and Della, and an unplanted plot were studied to provide possible explanations for the differences in CH4 emissions between cultivars. Using the measured isotope values, along with data of CH4 and CO2 concentrations and other ecosystem data, we determined differences between cultivars in the processes of oxidation and production throughout the growing season. For instance, rhizospheric CH4 oxidation increased as the season progressed in both Mars and Lemont cultivars. Late in the season, however, 71+/-10% of CH4 produced in the Mars plot was oxidized compared to only 39+/-10% in the Lemont plot. The contribution of acetate fermentation to methanogenesis at specific times during the season was calculated using measured isotopic values and assuming identical isotopic fractionation factors in methanogenic pathways for the cultivars. In these calculations a range of values for the contribution to CH4 production from acetate fermentation and CO2 reduction with H2 was estimated by considering different fractionation factors for the methanogenic CO2 reduction pathway and the possibility of a 10% contribution to CH4 production from acetate produced by homoacetogenesis. In general, a steady increase in the CH4 portion produced by acetate fermentation was noted in the Lemont cultivar, while an increase followed by a decrease near the end of the season was observed for the Mars cultivar.

  19. The impact of pCO2 and climate on D/H and 13C/12C fractionation of higher-plant biomarkers: Implications for paleoclimate and paleoelevation reconstruction during global warm periods

    NASA Astrophysics Data System (ADS)

    Hren, M. T.; Tipple, B. J.; Pagani, M.

    2012-12-01

    Stable hydrogen isotope compositions (D/H) of plant biomarkers record the hydrogen isotopic composition of leaf water at the time of plant growth. However, the magnitude of the apparent hydrogen isotope fractionation between biomarkers and precipitation can vary due to soil- or leaf-water evaporation or differing water-use strategies. As a result, climate-induced changes in soil- or leaf-water evaporation rates and/or changes in plant assemblages during periods of global warming and high atmospheric CO2 could impact apparent carbon and hydrogen isotope fractionations. We measured hydrogen and carbon isotope ratios of long-carbon chain n-alkanes from modern and ~50 million year old fossil leaves preserved in paleo-Sierra Nevada riverine sediments to determine how climate and ecosystem differences during a period of extremely high pCO2 impact the magnitude and variability of D/H and 13C/12C ratios of leaf-waxes across a topographic gradient. δDalkanes (nC27 to nC31) of individual fossil and modern leaves decrease systematically across the topographic gradient and follow the change in the D/H of precipitation due to orographic lifting and continuous rainout. Using estimated values of Eocene δDprecip at the Pacific margin (-43 to -61‰), apparent fractionations (ɛalkane - precip) for Eocene angiosperm trees are similar to that seen for modern, humid environments (~ -106 to -124‰ ±10‰ 1σ), and more negative than observed in modern sun-exposed leaves in the Sierra Nevada (-96 to -102‰) or soils (-87 to -92‰). Single site variability in leaf-wax δD from individual fossil angiosperms can exceed 20‰, but is considerably smaller than observed for modern, mixed angiosperm/gymnosperm forests of the seasonally dry Sierra Nevada range. δ13Calkane values show little or no systematic variation across the range. However, carbon isotope discrimination in ancient and modern leaves is similar, suggesting strong climatic and weak pCO2 controls on D/H and 13C/12C

  20. Estimating the CO2 sequestration potential of depleted and fractured shale formations using CH4 production rates

    NASA Astrophysics Data System (ADS)

    Clarens, A. F.; Tao, Z.

    2013-12-01

    Oil and gas production from hydraulically fractured shale formations is an abundant new source of domestically available energy for the United States. It will also result in significant CO2 emissions with important climate implications. Several studies have suggested that fractured shale formations could be used to permanently store CO2 once they are depleted of hydrocarbons. Many of the largest shale formations being developed in the United States have temperature and pressure profiles that are similar to those of saline aquifers being widely studied for geologic carbon sequestration. Here a modeling framework was developed that can be used to estimate the sequestration capacity for a shale formation based on historical CH4 production. The model is applied to those portions of the Marcellus formation found in Pennsylvania because reliable data on well production is readily available for this state. Production data from over 300 wells was compiled and used to estimate historical production and to extrapolate projected production. In shales, much of the CO2 would be sorbed to the pore and fracture surface and so this model considers sorption kinetics as well as total sorption capacity. The results suggest that shale formations could represent a significant repository for geologic carbon sequestration. The Marcellus shale in Pennsylvania alone could store between 10.4 and 18.4 Gigatonnes of CO2 between now and 2030. This would be over 50% of total annual US CO2 emissions from stationary sources. The mass transfer and sorption kinetics results indicate that CO2 injection proceeds several times faster than CH4 production. Model estimates were most sensitive to the permeability of the formation and assumptions about the ultimate ratio of adsorbed CH4 to CO2. CH4 production is a useful basis for calculating sequestration capacity because gas mass transfer out of the formation will be impacted by the same factors (e.g., temperature, pressure, and moisture content

  1. Coupling aboveground and belowground activities using short term fluctuations in 13C composition of soil respiration

    NASA Astrophysics Data System (ADS)

    Epron, D.; Parent, F.; Grossiord, C.; Plain, C.; Longdoz, B.; Granier, A.

    2011-12-01

    changes in partitioning between the respiration sources. This was particularly clear for eucalypt trees planted on a C4 soil in coastal Congo where soil CO2 efflux were less 13C depleted between 11am and 3pm when the xylem sap flux was maximum. This last result outlines that not only canopy photosynthesis but also canopy transpiration may affect the isotopic composition of soil CO2 efflux and should be considered in mechanistic models that account for the dynamics of soil CO2 efflux and its partitioning.

  2. Isotopic disequilibrium during uptake of atmospheric CO2 into mine process waters: implications for CO2 sequestration.

    PubMed

    Wilson, Siobhan A; Barker, Shaun L L; Dipple, Gregory M; Atudorei, Viorel

    2010-12-15

    Dypingite, a hydrated Mg-carbonate mineral, was precipitated from high-pH, high salinity solutions to investigate controls on carbon fixation and to identify the isotopic characteristics of mineral sequestration in mine tailings. δ(13)C values of dissolved inorganic carbon content and synthetic dypingite are significantly more negative than those predicted for equilibrium exchange of CO(2) gas between the atmosphere and solution. The measured δ(13)C of aqueous carbonate species is consistent with a kinetic fractionation that results from a slow diffusion of atmospheric CO(2) into solution. During dypingite precipitation, dissolved inorganic carbon concentrations decrease and δ(13)C values become more negative, indicating that the rate of CO(2) uptake into solution was outpaced by the rate of carbon fixation within the precipitate. This implies that CO(2) gas uptake is rate-limiting to CO(2) fixation. δ(13)C of carbonate mineral precipitates in mine tailings and of DIC in mine process waters display similar (13)C-depletions that are inconsistent with equilibrium fractionation. Thus, the rate of carbon fixation in mine tailings may also be limited by supply of CO(2). Carbon sequestration could be accelerated by increasing the partial pressure of CO(2) in tailings ponds or by using chemicals that enhance the uptake of gaseous CO(2) into aqueous solution.

  3. Students' Understanding of the Greenhouse Effect, the Societal Consequences of Reducing CO2 Emissions and the Problem of Ozone Layer Depletion.

    ERIC Educational Resources Information Center

    Andersson, Bjorn; Wallin, Anita

    2000-01-01

    Contributes to the growing body of knowledge about students' conceptions and views of environmental and natural resource issues. Questions 9th and 12th grade Swedish students' understandings of the greenhouse effect, reduction of CO2 emissions, and the depletion of the ozone layer. Observes five models of the greenhouse effect that appear among…

  4. The use of tracers to assess leakage from the sequestration of CO2 in a depleted oil reservoir, New Mexico, USA

    SciTech Connect

    Wells, A.W.; Diehl, J.R.; Bromhal, G.S.; Strazisar, B.R.; Wilson, T.H.; White, C.M.

    2007-05-01

    Geological sequestration of CO2 in depleted oil reservoirs is a potentially useful strategy for greenhouse gas management and can be combined with enhanced oil recovery. Development of methods to estimate CO2 leakage rates is essential to assure that storage objectives are being met at sequestration facilities. Perfluorocarbon tracers (PFTs) were added as three 12 h slugs at about one week intervals during the injection of 2090 tons of CO2 into the West Pearl Queen (WPQ) depleted oil formation, sequestration pilot study site located in SE New Mexico. The CO2 was injected into the Permian Queen Formation. Leakage was monitored in soil–gas using a matrix of 40 capillary adsorbent tubes (CATs) left in the soil for periods ranging from days to months. The tracers, perfluoro-1,2-dimethylcyclohexane (PDCH), perfluorotrimethylcyclohexane (PTCH) and perfluorodimethylcyclobutane (PDCB), were analyzed using thermal desorption, and gas chromatography with electron capture detection. Monitoring was designed to look for immediate leakage, such as at the injection well bore and at nearby wells, and to develop the technology to estimate overall CO2 leak rates based on the use of PFTs. Tracers were detected in soil–gas at the monitoring sites 50 m from the injection well within days of injection. Tracers continued to escape over the following years. Leakage appears to have emanated from the vicinity of the injection well in a radial pattern to about 100 m and in directional patterns to 300 m. Leakage rates were estimated for the 3 tracers from each of the 4 sets of CATs in place following the start of CO2 injection. Leakage was fairly uniform during this period. As a first approximation, the CO2 leak rate was estimated at about 0.0085% of the total CO2 sequestered per annum.

  5. Radiocarbon-depleted CO2 evidence for fuel biodegradation at the Naval Air Station North Island (USA) fuel farm site.

    PubMed

    Boyd, Thomas J; Pound, Michael J; Lohr, Daniel; Coffin, Richard B

    2013-05-01

    Dissolved CO(2) radiocarbon and stable carbon isotope ratios were measured in groundwater from a fuel contaminated site at the North Island Naval Air Station in San Diego, CA (USA). A background groundwater sampling well and 16 wells in the underground fuel contamination zone were evaluated. For each sample, a two end-member isotopic mixing model was used to determine the fraction of CO(2) derived from fossil fuel. The CO(2) fraction from fossil sources ranged from 8 to 93% at the fuel contaminated site, while stable carbon isotope values ranged from -14 to +5‰VPDB. Wells associated with highest historical and contemporary fuel contamination showed the highest fraction of CO(2) derived from petroleum (fossil) sources. Stable carbon isotope ratios indicated sub-regions on-site with recycled CO(2) (δ(13)CO(2) as high as +5‰VPDB) - most likely resulting from methanogenesis. Ancillary measurements (pH and cations) were used to determine that no fossil CaCO(3), for instance limestone, biased the analytical conclusions. Radiocarbon analysis is verified as a viable and definitive technique for confirming fossil hydrocarbon conversion to CO(2) (complete oxidation) at hydrocarbon-contaminated groundwater sites. The technique should also be very useful for assessing the efficacy of engineered remediation efforts and by using CO(2) production rates, contaminant mass conversion over time and per unit volume.

  6. CH4 production via CO2 reduction in a temperate bog - A source of (C-13)-depleted CH4

    NASA Technical Reports Server (NTRS)

    Lansdown, J. M.; Quay, P. D.; King, S. L.

    1992-01-01

    The paper reports measurements, taken over two annual cycles, of the flux and delta(C-13) of CH4 released from an acidic peat bog located in the foothills of the Cascade Range in Washington state, U.S. Measurements of the rate of aceticlastic methanogenesis and CO2 reduction in peat soil, using (C-14)-labeled acetate and sodium bicarbonate, show that acetate was not an important CH4 precursor and that CO2 reduction could account for all of the CH4 production. The in situ kinetic isotope effect for CO2 reduction, calculated using the delta-(C-13) of soil water CO2 and CH4 flux, was 0.932 +/- 0.007.

  7. CH4 production via CO2 reduction in a temperate bog - A source of (C-13)-depleted CH4

    NASA Astrophysics Data System (ADS)

    Lansdown, J. M.; Quay, P. D.; King, S. L.

    1992-09-01

    The paper reports measurements, taken over two annual cycles, of the flux and delta(C-13) of CH4 released from an acidic peat bog located in the foothills of the Cascade Range in Washington state, U.S. Measurements of the rate of aceticlastic methanogenesis and CO2 reduction in peat soil, using (C-14)-labeled acetate and sodium bicarbonate, show that acetate was not an important CH4 precursor and that CO2 reduction could account for all of the CH4 production. The in situ kinetic isotope effect for CO2 reduction, calculated using the delta-(C-13) of soil water CO2 and CH4 flux, was 0.932 +/- 0.007.

  8. Hidden shift of the ionome of plants exposed to elevated CO2 depletes minerals at the base of human nutrition

    PubMed Central

    Loladze, Irakli

    2014-01-01

    Mineral malnutrition stemming from undiversified plant-based diets is a top global challenge. In C3 plants (e.g., rice, wheat), elevated concentrations of atmospheric carbon dioxide (eCO2) reduce protein and nitrogen concentrations, and can increase the total non-structural carbohydrates (TNC; mainly starch, sugars). However, contradictory findings have obscured the effect of eCO2 on the ionome—the mineral and trace-element composition—of plants. Consequently, CO2-induced shifts in plant quality have been ignored in the estimation of the impact of global change on humans. This study shows that eCO2 reduces the overall mineral concentrations (−8%, 95% confidence interval: −9.1 to −6.9, p<0.00001) and increases TNC:minerals > carbon:minerals in C3 plants. The meta-analysis of 7761 observations, including 2264 observations at state of the art FACE centers, covers 130 species/cultivars. The attained statistical power reveals that the shift is systemic and global. Its potential to exacerbate the prevalence of ‘hidden hunger’ and obesity is discussed. DOI: http://dx.doi.org/10.7554/eLife.02245.001 PMID:24867639

  9. Carbon fluxes to the soil in a mature temperate forest assessed by 13C isotope tracing.

    PubMed

    Steinmann, Katharina; Siegwolf, Rolf T W; Saurer, Matthias; Körner, Christian

    2004-11-01

    Photosynthetic carbon uptake and respiratory C release from soil are major components of the global carbon balance. The use of 13C depleted CO2)(delta13C = -30 per thousand) in a free air CO2 enrichment experiment in a mature deciduous forest permitted us to trace the carbon transfer from tree crowns to the rhizosphere of 100-120 years old trees. During the first season of CO2 enrichment the CO2 released from soil originated substantially from concurrent assimilation. The small contribution of recent carbon in fine roots suggests a much slower fine root turnover than is often assumed. 13C abundance in soil air correlated best with temperature data taken from 4 to 10 days before air sampling time and is thus rapidly available for root and rhizosphere respiration. The spatial variability of delta13C in soil air showed relationships to above ground tree types such as conifers versus broad-leaved trees. Considering the complexity and strong overlap of roots from different individuals in a forest, this finding opens an exciting new possibility of associating respiration with different species. What might be seen as signal noise does in fact contain valuable information on the spatial heterogeneity of tree-soil interaction.

  10. Keeling plots for hummingbirds: a method to estimate carbon isotope ratios of respired CO(2) in small vertebrates.

    PubMed

    Carleton, Scott A; Wolf, Blair O; del Rio, Carlos Martinez

    2004-09-01

    The carbon isotope composition of an animal's breath reveals the composition of the nutrients that it catabolizes for energy. Here we describe the use of Keeling plots, a method widely applied in ecosystem ecology, to measure the delta(13)C of respired CO(2) of small vertebrates. We measured the delta(13)C of Rufous Hummingbirds ( Selasphorus rufus) in the laboratory and of Mourning ( Zenaida macroura) and White-winged ( Z. asiatica) Doves in the field. In the laboratory, when hummingbirds were fed a sucrose based C3 diet, the delta(13)C of respired CO(2) was not significantly different from that of their diet (delta(13)C(C3 diet)). The delta(13)C of respired CO(2) for C3 fasted birds was slightly, albeit significantly, depleted in delta(13)C relative to delta(13)C(C3 diet). Six hours after birds were shifted to a sucrose based C4 diet, the isotopic composition of their breath revealed that birds were catabolizing a mixture of nutrients derived from both the C3 and the C4 diet. In the field, the delta(13)C of respired CO(2) from Mourning and White-winged Doves reflected that of their diets: the CAM saguaro cactus ( Carnegeia gigantea) and C3 seeds, respectively. Keeling plots are an easy, effective and inexpensive method to measure delta(13)C of respired CO(2) in the lab and the field. PMID:15309607

  11. Keeling plots for hummingbirds: a method to estimate carbon isotope ratios of respired CO(2) in small vertebrates.

    PubMed

    Carleton, Scott A; Wolf, Blair O; del Rio, Carlos Martinez

    2004-09-01

    The carbon isotope composition of an animal's breath reveals the composition of the nutrients that it catabolizes for energy. Here we describe the use of Keeling plots, a method widely applied in ecosystem ecology, to measure the delta(13)C of respired CO(2) of small vertebrates. We measured the delta(13)C of Rufous Hummingbirds ( Selasphorus rufus) in the laboratory and of Mourning ( Zenaida macroura) and White-winged ( Z. asiatica) Doves in the field. In the laboratory, when hummingbirds were fed a sucrose based C3 diet, the delta(13)C of respired CO(2) was not significantly different from that of their diet (delta(13)C(C3 diet)). The delta(13)C of respired CO(2) for C3 fasted birds was slightly, albeit significantly, depleted in delta(13)C relative to delta(13)C(C3 diet). Six hours after birds were shifted to a sucrose based C4 diet, the isotopic composition of their breath revealed that birds were catabolizing a mixture of nutrients derived from both the C3 and the C4 diet. In the field, the delta(13)C of respired CO(2) from Mourning and White-winged Doves reflected that of their diets: the CAM saguaro cactus ( Carnegeia gigantea) and C3 seeds, respectively. Keeling plots are an easy, effective and inexpensive method to measure delta(13)C of respired CO(2) in the lab and the field.

  12. Deployment of a carbon isotope ratiometer for the monitoring of CO2 sequestration leakage.

    PubMed

    McAlexander, Ian; Rau, Greg H; Liem, Jimmy; Owano, Thomas; Fellers, Ray; Baer, Douglas; Gupta, Manish

    2011-08-15

    In an effort to monitor leakage from underground CO(2) storage, a field-deployable analyzer capable of rapidly measuring the CO(2) mixing ratio and δ(13)C values (±0.05 ppm(v) ± 0.2‰, 60 s) was deployed to distinguish between biogenic and fossil CO(2) sources. The analyzer was interfaced with a multiport inlet unit to allow autonomous sampling from multiple locations. The instrument and inlet interface were deployed at the Zero Emissions Research and Technology (ZERT) site (Bozeman, Montana, July 14-22, 2009) during a controlled, subsurface release of CO(2) depleted in (13)C. A biogenic diurnal cycle was observed far from the release, and the associated Keeling plot suggested a CO(2) source (δ(13)C = -27.0 ± 0.5‰) consistent with local C(3) vegetation. Inlets near the leak showed large CO(2) mixing ratios (388/>40 000 ppm(v)) whose predominant source was the release CO(2) (inferred δ(13)C = -58.2 ± 0.7‰). Measurements 3 m from the source showed diurnal CO(2) cycles (382-2400 ppm(v)) influenced by leaked CO(2), possibly due to diel air mixing. Finally, the data from all of the sampling inlets was combined to spatially localize the leak position. PMID:21740048

  13. Scaling-up13C separation by infrared multiphoton dissociation of the CHClF2/Br2 system

    NASA Astrophysics Data System (ADS)

    Chen, G. C.; Wu, B.; Liu, J. L.; Jing, Y.; Chu, M. X.; Xue, L. L.; Ma, P. H.

    1995-06-01

    13C separation at a laboratory scaled-up level by the13C-selective InfraRed MultiPhoton Dissociation (IRMPD) of CHClF2 in the presence of Br2 has been investigated in a flow reactor. With a complete scaled-up system including a flow reactor, an industrially reliable TEA CO2 laser with longer pulse duration and a product-separation set-up for13C separation, it has been attempted to optimize the parameters suitable for large-scale production of the carbon isotope. The optimization of13C separation parameters, such as laser fluence, laser frequency and the partial pressure of CHClF2 and Br2 was tested under static conditions. By irradiation with longer pulses, a lower optimum pressure for a high13C-production rate was determined. Furthermore, the separation process was scaled in the flow system to examine the13C-production rates,13C atomic fractions in the CBr2F2 products and13C depletions in the CHClF2 reactants at different flow rates and laser repetition frequencies. The data obtained from the flow tests demonstrated a 40 mg/h production rate for CBr2F2 at 65%13C by using a 40 W (4 J, 10 Hz) laser beam focused with a lens of 120 cm focal length. If the reliable TEA CO2 laser is operated with 100 W (10 J, 10 Hz) output, the production rate of CBr2F2 for13C at 60% of 200 mg/h can be attained. The measurements of the spatial profile of the focused laser beam imply a 2 g/h production rate for the 60%13C product for an incident power of 200 W (20 J, 10 Hz).

  14. The imprint of anthropogenic CO2 emissions on Atlantic bluefin tuna otoliths

    NASA Astrophysics Data System (ADS)

    Fraile, Igaratza; Arrizabalaga, Haritz; Groeneveld, Jeroen; Kölling, Martin; Santos, Miguel Neves; Macías, David; Addis, Piero; Dettman, David L.; Karakulak, Saadet; Deguara, Simeon; Rooker, Jay R.

    2016-06-01

    Otoliths of Atlantic bluefin tuna (Thunnus thynnus) collected from the Mediterranean Sea and North Atlantic Ocean were analyzed to evaluate changes in the seawater isotopic composition over time. We report an annual otolith δ13C record that documents the magnitude of the δ13C depletion in the Mediterranean Sea between 1989 and 2010. Atlantic bluefin tuna in our sample (n = 632) ranged from 1 to 22 years, and otolith material corresponding to the first year of life (back-calculated birth year) was used to reconstruct seawater isotopic composition. Otolith δ18O remained relatively stable between 1989 and 2010, whereas a statistically significant decrease in δ13C was detected across the time interval investigated, with a rate of decline of 0.05‰ yr- 1 (- 0.94‰ depletion throughout the recorded period). The depletion in otolith δ13C over time was associated with the oceanic uptake of anthropogenically derived CO2.

  15. Carbon isotopic composition of bacterial methane in a soil incubation experiment: Contributions of acetate and CO 2/H 2

    NASA Astrophysics Data System (ADS)

    Sugimoto, Atsuko; Wada, Eitaro

    1993-08-01

    Anaerobic incubations of paddy soil collected from Konosu, Japan, were carried out for 10 weeks to clarify the general principles that govern the variation of carbon isotopic composition of bacterial methane from freshwater areas. The concentrations and isotopic compositions of CH 4, CO 2, and acetate produced in the incubated system were measured. The δ13C value of biogenic CH 4 was highly variable ranging from -60 to -33%., corresponding to changes in its formation pathways: acetate fermentation and CO 2/H 2reduction. Acetate accumulated only during the first week. After it became depleted, acetate production completely limited CH 4 production. The δ13C value of the methyl carbon of acetate, which was accumulated with addition of inhibitor for methanogenesis, ranged from -43 to -30%.. The δ13C value of methane from acetate was estimated to be -43 to -30%., after acetate depletion. The δ13C value of CH 4 from CO 2/H 2 reduction was estimated to be -77 to -60%.. An enrichment in 13C of CO 2 localized around the site of methanogenesis was suggested. CO 2 produced in situ during methanogenesis (e.g., CO 2 from carboxyl group of acetate) was possibly utilized as well. Using the above δ13C values of two endmembers of CH 4, the change of acetate contribution for CH 4 production was calculated: less than 12% until week 1, 65 to 100% at weeks 1 to 3, 16 to 28% at weeks 3 to 5, and 35 to 40% after week 5. Variability of CH 4δ13C resulted from the difference in contribution of each biological process. Also, the δ13C value of CH 4 was a useful indicator for assessing the contribution of each process to methane production in sulfate depleted freshwater areas.

  16. Latitudinal variations in plankton delta C-13 - Implications for CO2 and productivity in past oceans

    NASA Technical Reports Server (NTRS)

    Rau, Greg H.; Takahashi, Taro; Des Marais, David J.

    1989-01-01

    Low C-13/C-12 in present-day Antarctic plankton has been ascribed to high CO2 availability. It is reported here, however, that this high-latitude C-13 depletion develops at CO2 partial pressures that are often below that of the present atmosphere and usually below that of equatorial upwelling systems. Nevertheless, because of much lower water temperatures and hence greater CO2 solubility at high latitude, the preceding pCO2 measurements translate into Antarctic surface-water CO2 (aq) concentrations that are as much as 2.5 times higher than in equatorial waters. It is calculated that an oceanic pCO2 level greater than 800 micro-atm is a warmer low-latitude Cretaceous ocean would have been required to produce the plankton C-13 depletion preserved in Cretaceous sediments.

  17. On the use of phloem sap δ13C to estimate canopy carbon discrimination

    NASA Astrophysics Data System (ADS)

    Rascher, Katherine; Máguas, Cristina; Werner, Christiane

    2010-05-01

    Although the carbon stable isotope composition (d13C) of bulk leaf material is a good integrative parameter of photosynthetic discrimination and can be used as a reliable ecological index of plant functioning; it is not a good tracer of short-term changes in photosynthetic discrimination. In contrast, d13C of phloem sap is potentially useful as an indicator of short-term changes in canopy photosynthetic discrimination. However, recent research indicates that d13C signatures may be substantially altered by metabolic processes downstream of initial leaf-level carbon fixation (e.g. post-photosynthetic fractionation). Accordingly, before phloem sap d13C can be used as a proxy for canopy level carbon discrimination an understanding of factors influencing the degree and magnitude of post-photosynthetic fractionation and how these vary between species is of paramount importance. In this study, we measured the d13C signature along the basipetal transport pathway in two co-occurring tree species in the field - an understory invasive exotic legume, Acacia longifolia, and a native pine, Pinus pinaster. We measured d13C of bulk leaf and leaf water soluble organic matter (WSOM), phloem sap sampled at two points along the plant axis and leaf and root dark respiration. In general, species differences in photosynthetic discrimination resulted in more enriched d13C values in the water-conserving P. pinaster relative to the water-spending A. longifolia. Post-photosynthetic fractionation led to differences in d13C of carbon pools along the plant axis with progressively more depleted d13C from the canopy to the trunk (~6.5 per mil depletion in A. longifolia and ~0.8per mil depletion in P. pinaster). Leaf and root respiration, d13C, were consistently enriched relative to putative substrates. We hypothesize that the pronounced enrichment of leaf respired CO2 relative to leaf WSOM may have left behind relatively depleted carbon to be loaded into the phloem resulting in d13C depletion

  18. Carbon Isotope Composition of Caribbean Sea Surface Waters: Response to the Uptake of Anthropogenic CO2

    NASA Astrophysics Data System (ADS)

    Black, D. E.; Thunell, R.; Wejnert, K. E.; Astor, Y.

    2011-12-01

    The burning of fossil fuels and deforestation have significantly increased atmospheric CO2 levels, from ~280 ppm prior to the industrial revolution to the present value of ~390 ppm. Suess (1955) was the first to show that the carbon isotopic composition of the atmosphere is changing in response to the anthropogenic input of radiocarbon-dead, 13C depleted CO2 from fossil fuel combustion. While biological processes may be the primary mechanism controlling the δ13C of marine carbon, air-sea gas exchange should allow for the transfer of the so-called 13C Suess effect (Keeling, 1979) from the atmosphere to the surface ocean. The first measurements of the δ13C of dissolved inorganic carbon of ocean surface waters were made in 1970 (Kroopnick, 1974) and serve as a baseline for assessing how the carbon isotopic composition of the oceans have changed in response to the invasion of fossil fuel CO2 over the last 40 years. However, in order to gain a longer and more complete picture of the marine δ13C Suess effect, we must rely on indirect measures of changes in surface water δ13C, most notably those preserved in carbonate secreting marine organisms. The Cariaco Basin is one of the rare locations where one can directly compare sediment records with modern instrumental data. Here we report a high resolution planktonic foraminiferal δ13C record from the basin for the last 300 years that clearly resolves the timing and magnitude of the marine 13C Suess effect associated with the oceanic uptake of anthropogenically derived CO2. Cariaco Basin sediment trap and upper-most box core sediment δ13C match both the trend and magnitude of observed δ13C changes in atmospheric CO2 over the last 15 years. The longer sediment record suggests the marine Suess effect to be -0.75 % from pre-industrial values, with most of the change occurring since 1950, coincident with the rapid rise in atmospheric CO2 noted in ice core and instrumental data. If the current anthropogenic CO2 emission

  19. 13C18O in Earth's Atmosphere: a New Proxy for Constraining CO Budget

    NASA Astrophysics Data System (ADS)

    Guo, W.; Eiler, J. M.

    2005-12-01

    Despite its low average mixing ratio (70-100 ppbv), carbon monoxide plays an important role in atmospheric chemistry. It is the major sink of OH radicals, and thus strongly influences the oxidizing capacity of the atmosphere, and the lifetimes of many other atmospheric trace gases (e.g., methane, NHMCs and HCFCs). At present, the budget of atmospheric CO is constrained by its mixing ratio, δ13C, δ18O, δ17O values, inventory analysis and inverse modeling. However, the major sources of CO (CH4-oxidation, NMHC-oxidation, biomass burning, anthropogenic emissions and the ocean) vary in flux and isotopic composition, and some overlap one another in isotopic composition. Therefore, its atmospheric budget cannot be rigorously defined by inversion of the existing isotopic and concentration records. Here we introduce measurements of the abundance anomaly of the 13C18O isotopologue of carbon monoxide as an additional constraint on its atmospheric budget. We define the 13C18O anomaly as the deviation of its actual abundance from its expected statistical abundance,Δ13C18O=(([13C18O]actual/[12C16O]actual)/([13C18O]stati stical /[12C16O]statistical)-1)×1000. Abundances of 13C18O are measured by quantitatively oxidizing CO to CO2 over the Schutze reagent, and then measuring mass 47 (mainly 13C18O16O) in the product CO2, which is proportional to the abundance of 13C18O in the starting CO. External precision of Δ13C18O for repeated measurements of pure CO averages 0.03‰(one standard deviation). We expect Δ13C18O in atmospheric carbon monoxide to be sensitive to: mixing between CO of different isotopic compositions, thermodynamic fractionations, diffusion, and kinetic isotope effects accompanying chemical reactions. We have investigated the thermodynamic fractionation of Δ13C18O by performing measurements on carbon monoxide samples catalytically equilibrated at high temperatures (300-1000°C). Measured Δ13C18O values, ranging from ~0.08‰ to ~0.47‰, vary as a function

  20. Liquid CO2 venting on the seafloor: Yonaguni Knoll IV hydrothermal system, Okinawa Trough

    NASA Astrophysics Data System (ADS)

    Konno, Uta; Tsunogai, Urumu; Nakagawa, Fumiko; Nakaseama, Miwako; Ishibashi, Jun-ichiro; Nunoura, Takuro; Nakamura, Ko-ichi

    2006-08-01

    We determined the chemical and isotopic compositions of the liquid CO2 found on Yonaguni IV knoll hydrothermal site, as well as those in hydrothermal fluid venting from the surrounding chimneys. The δ13C of both CO2 and CH4 in the liquid CO2 almost coincide with those in the hydrothermal fluid, suggesting that the liquid CO2 must be derived from the hydrothermal fluid. While showing homogeneous δ13C, the hydrothermal fluids exhibit wide variation in gas contents. Active phase separation must be taking place within the conduits. Besides, H2-depletion in the liquid CO2 suggests formation of solid CO2-hydrate must also precede the venting of liquid CO2. In conclusion, liquid CO2 must be produced through following subseafloor processes: phase separation of hydrothermal fluid due to boiling, formation of solid CO2-hydrate due to cooling of vapor phase, and melting of the solid CO2-hydrate to liquid CO2 due to a temperature increase within the sedimentary layer.

  1. Seasonal variability of soil CO2 flux and its carbon isotope composition in Krakow urban area, Southern Poland.

    PubMed

    Jasek, Alina; Zimnoch, Miroslaw; Gorczyca, Zbigniew; Smula, Ewa; Rozanski, Kazimierz

    2014-06-01

    As urban atmosphere is depleted of (13)CO2, its imprint should be detectable in the local vegetation and therefore in its CO2 respiratory emissions. This work was aimed at characterising strength and isotope signature of CO2 fluxes from soil in urban areas with varying distances from anthropogenic CO2 emissions. The soil CO2 flux and its δ(13)C isotope signature were measured using a chamber method on a monthly basis from July 2009 to May 2012 within the metropolitan area of Krakow, Southern Poland, at two locations representing different levels of anthropogenic influence: a lawn adjacent to a busy street (A) and an urban meadow (B). The small-scale spatial variability of the soil CO2 flux was also investigated at site B. Site B revealed significantly higher summer CO2 fluxes (by approximately 46 %) than site A, but no significant differences were found between their δ(13)CO2 signatures.

  2. Terrestrial biosphere changes over the last 120 kyr and their impact on ocean δ 13C

    NASA Astrophysics Data System (ADS)

    Hoogakker, B. A. A.; Smith, R. S.; Singarayer, J. S.; Marchant, R.; Prentice, I. C.; Allen, J. R. M.; Anderson, R. S.; Bhagwat, S. A.; Behling, H.; Borisova, O.; Bush, M.; Correa-Metrio, A.; de Vernal, A.; Finch, J. M.; Fréchette, B.; Lozano-Garcia, S.; Gosling, W. D.; Granoszewski, W.; Grimm, E. C.; Grüger, E.; Hanselman, J.; Harrison, S. P.; Hill, T. R.; Huntley, B.; Jiménez-Moreno, G.; Kershaw, P.; Ledru, M.-P.; Magri, D.; McKenzie, M.; Müller, U.; Nakagawa, T.; Novenko, E.; Penny, D.; Sadori, L.; Scott, L.; Stevenson, J.; Valdes, P. J.; Vandergoes, M.; Velichko, A.; Whitlock, C.; Tzedakis, C.

    2015-03-01

    A new global synthesis and biomization of long (>40 kyr) pollen-data records is presented, and used with simulations from the HadCM3 and FAMOUS climate models to analyse the dynamics of the global terrestrial biosphere and carbon storage over the last glacial-interglacial cycle. Global modelled (BIOME4) biome distributions over time generally agree well with those inferred from pollen data. The two climate models show good agreement in global net primary productivity (NPP). NPP is strongly influenced by atmospheric carbon dioxide (CO2) concentrations through CO2 fertilization. The combined effects of modelled changes in vegetation and (via a simple model) soil carbon result in a global terrestrial carbon storage at the Last Glacial Maximum that is 210-470 Pg C less than in pre-industrial time. Without the contribution from exposed glacial continental shelves the reduction would be larger, 330-960 Pg C. Other intervals of low terrestrial carbon storage include stadial intervals at 108 and 85 ka BP, and between 60 and 65 ka BP during Marine Isotope Stage 4. Terrestrial carbon storage, determined by the balance of global NPP and decomposition, influences the stable carbon isotope composition (δ13C) of seawater because terrestrial organic carbon is depleted in 13C. Using a simple carbon-isotope mass balance equation we find agreement in trends between modelled ocean δ13C based on modelled land carbon storage, and palaeo-archives of ocean δ13C, confirming that terrestrial carbon storage variations may be important drivers of ocean δ13C changes.

  3. Design and Implementation of a CO2 Flood Utilizing Advanced Reservoir Characterization and Horizontal Injection Wells In a Shallow Shelf Carbonate Approaching Waterflood Depletion, Class II

    SciTech Connect

    Czirr, K.L.; Gaddis, M.P.; Moshell, M.K.

    2002-02-21

    The principle objective of this project is to demonstrate the economic viability and widespread applicability of an innovative reservoir management and carbon dioxide (CO2) flood project development approach for improving CO2 flood project economics in shallow shelf carbonate (SSC) reservoirs.

  4. A high resolution δ13C record in a modern Porites lobata coral: Insights into controls on skeletal δ13C

    NASA Astrophysics Data System (ADS)

    Allison, Nicola; Finch, Adrian A.; EIMF

    2012-05-01

    δ13C was determined at a high spatial resolution by secondary ion mass spectrometry (SIMS) across a 1 year section of a modern Porites lobata coral skeleton from Hawaii. Skeletal δ13C is dominated by large oscillations of 5-7‰ that typically cover skeletal distances equivalent to periods of ˜14-40 days. These variations do not reflect seawater temperature and it is unlikely that they reflect variations in the δ13C of local seawater. We observe no correlation between skeletal δ13C and the pH of the calcification fluid (estimated from previous measurements of skeletal δ11B). We conclude that either the proportion of skeletal carbon derived from metabolic CO2 is not reflected by estimated ECF pH (as the [CO2] in the overlying coral tissue varies) and/or the δ13C composition of the metabolic CO2 is highly variable. We also observe no correlation between skeletal δ13C and previous δ18O SIMS measurements. Variations in skeletal δ13C and δ18O do not have a common timing, providing no evidence that skeletal δ13C and δ18O vary in response to a single factor. This suggests that skeletal δ13C is principally driven by variations in the δ13C composition of metabolic CO2 rather than by the abundance of metabolic CO2, which would also affect skeletal δ18O. The δ13C composition of metabolic CO2 reflects the processes of photosynthesis, heterotrophic feeding and respiration in the overlying coral tissue. Corals catabolise stored lipid reserves to meet energetic demands when photosynthesis conditions are sub-optimal. Variations in the amounts and types of reserves utilised could induce changes in the δ13C composition of metabolic CO2 and the resultant skeleton which are temporally offset from skeletal δ18O records.

  5. Design and Implementation of a CO2 Flood Utilizing Advanced Reservoir Characterization and Horizontal Injection Wells In a Shallow Shelf Carbonate Approaching Waterflood Depletion, Class II

    SciTech Connect

    Wier, Don R. Chimanhusky, John S.; Czirr, Kirk L.; Hallenbeck, Larry; Gerard, Matthew G.; Dollens, Kim B.; Owen, Rex; Gaddis, Maurice; Moshell, M.K.

    2002-11-18

    The purpose of this project was to economically design an optimum carbon dioxide (CO2) flood for a mature waterflood nearing its economic abandonment. The original project utilized advanced reservoir characterization and CO2 horizontal injection wells as the primary methods to redevelop the South Cowden Unit (SCU). The development plans; project implementation and reservoir management techniques were to be transferred to the public domain to assist in preventing premature abandonment of similar fields.

  6. Optoacoustic 13C-breath test analyzer

    NASA Astrophysics Data System (ADS)

    Harde, Hermann; Helmrich, Günther; Wolff, Marcus

    2010-02-01

    The composition and concentration of exhaled volatile gases reflects the physical ability of a patient. Therefore, a breath analysis allows to recognize an infectious disease in an organ or even to identify a tumor. One of the most prominent breath tests is the 13C-urea-breath test, applied to ascertain the presence of the bacterium helicobacter pylori in the stomach wall as an indication of a gastric ulcer. In this contribution we present a new optical analyzer that employs a compact and simple set-up based on photoacoustic spectroscopy. It consists of two identical photoacoustic cells containing two breath samples, one taken before and one after capturing an isotope-marked substrate, where the most common isotope 12C is replaced to a large extent by 13C. The analyzer measures simultaneously the relative CO2 isotopologue concentrations in both samples by exciting the molecules on specially selected absorption lines with a semiconductor laser operating at a wavelength of 2.744 μm. For a reliable diagnosis changes of the 13CO2 concentration of 1% in the exhaled breath have to be detected at a concentration level of this isotope in the breath of about 500 ppm.

  7. Stable isotope ratios of atmospheric CO_{2} and CH_{4} over Siberia measured at ZOTTO

    NASA Astrophysics Data System (ADS)

    Timokhina, Anastasiya; Prokushkin, Anatily; Lavric, Jost; Heimann, Martin

    2016-04-01

    The boreal and arctic zones of Siberia housing the large amounts of carbon stored in the living biomass of forests and wetlands, as well as in soils and specifically permafrost, play a crucial role in earth's global carbon cycle. The long-term studies of greenhouse gases (GHG) concentrations are important instruments to analyze the response of these systems to climate warming. In parallel to GHG observations, the measurements of their stable isotopic composition can provide useful information for distinguishing contribution of individual GHG source to their atmospheric variations, since each source has its own isotopic signature. In this study we report first results of laboratory analyses of the CO2 and CH4 concentrations, the stable isotope ratio of δ13C-CO2, δ18O-CO2, δ13C-CH4, δD-CH4 measured in one-liter glass flasks which were obtained from 301 height of ZOTTO (Zotino Tall Tower Observatory, near 60° N, 90° E, about 20 km west of the Yenisei River) during 2008 - 2013 and 2010 - 2013 for stable isotope composition of CO2 and CH4. The magnitudes of δ13C-CO2 and δ18O-CO2 in a seasonal cycle are -1.4±0.1‰ (-7.6 - -9.0‰) and -2.2±0.2‰ (-0.1 - -2.3‰), respectively. The δ13C-CO2 seasonal pattern opposes the CO2 concentrations, with a gradual enrichment in heavy isotope occurring during May - July, reflecting its discrimination in photosynthesis, and further depletion in August - September as photosynthetic activity decreases comparatively to ecosystem respiration. Relationship between the CO2 concentrations and respective δ13C-CO2 (Keeling plot) reveals isotopic source signature for growing season (May - September) -27.3±1.4‰ and -30.4±2.5‰ for winter (January - March). The behavior of δ18O-CO2 associated with both high photosynthetic rate in the June (enrichment of atmospheric CO2 by 18O as consequence of CO2 equilibrium with "heavy" leaf water) and respiratory activity of forest floor in June - October (depletion of respired CO2 by 18O

  8. Clumped isotope disequilibrium during rapid CO2 uptake and carbonate precipitation in subaerial alkaline springs associated with ongoing serpentinization

    NASA Astrophysics Data System (ADS)

    Falk, E. S.; Guo, W.; Kelemen, P. B.

    2014-12-01

    Ongoing serpentinization in tectonically exposed ultramafic bodies is manifested at the surface in alkaline springs (pH >11). Where these high-pH waters come in contact with CO2 at the surface, rapid calcite precipitation forms extensive travertines. We study natural travertine samples from Oman and synthetic witherite (BaCO3) from high-pH experiments to identify disequilibrium signals in δ18O, δ13C and clumped isotopes (measured as Δ47) that characterize rapid uptake of atmospheric CO2 and carbonate precipitation from high pH fluids. Kinetic effects preclude the use of clumped or oxygen isotopes for carbonate thermometry in these environments, but trends in δ18O, δ13C and Δ47 could help identify extinct alkaline systems or distinguish CO2 sources. Oman travertines formed at peridotite-hosted alkaline springs have long been known to exhibit a large range of kinetically depleted δ18O and δ13C values. We find fresh carbonate precipitated at these alkaline springs also exhibit large enrichments in Δ47 that covary with the depletions in δ18O and δ13C, thought to arise during hydroxylation of CO2 in high-pH fluids. Witherite precipitated during rapid CO2 uptake and carbonate precipitation in high pH experiments also exhibits disequilibrium values in δ18O, δ13C and Δ47, with the Δ47 of carbonate precipitates strongly affected by the Δ47 the reactant CO2. δ18O, δ13C and Δ47 trends could serve as a marker for carbonates formed in subaerial alkaline environments and track carbon sources in these systems. For example, the δ18O-δ13C slope in carbonates from Martian meteorites is similar to that observed in carbonates from terrestrial alkaline springs, so if corresponding enrichments in Δ47 could be identified in Martian carbonates, it could suggest that alkaline springs were present on the surface of Mars. Clumped isotope signals could also help distinguish carbon sources: kinetic enrichments in Δ47 would be absent or diminished in high-pH carbonates

  9. Influence of pCO2 on carbon allocation in nodulated Medicago sativa L.

    NASA Astrophysics Data System (ADS)

    Pereyra, Gabriela; Hartmann, Henrik; Ziegler, Waldemar; Michalzik, Beate; Gonzalez-Meler, Miquel; Trumbore, Susan

    2016-04-01

    Atmospheric CO2 concentrations (pCO_2) have been related to changes in plant carbon (C) availability and photosynthetic capacity, yet there is no clear consensus as to the effect of pCO2 on the plant C balance and on nitrogen fixation in symbiotic systems. We investigated how different pCO2 (Pleistocene: 170 ppm, ambient: 400 ppm and projected future: 700 ppm) influence C allocation in nodulated Medicago sativa L. We labeled 17 week old plants with depleted 13C (-34.7±1.2‰) and traced the label over a 9-day period, to assess the redistribution of newly assimilated C across different sinks, including nodules. We analyzed N concentrations in plant tissues and found no significant differences in leaves and roots across treatments. However, growth and C fixation rates increased with pCO_2, and differences were greatest between 170 ppm and 700 ppm. Across pCO2 treatments we observed a 13C-enrichment in roots compared to leaves. We further observed the highest 13C depletion of non-structural carbohydrates (NSCs) and respired CO2 in tissues of plants grown at 700 ppm, especially in leaves and nodules. Our preliminary results suggest that sink organs like roots and nodules are fed with newly-assimilated NSCs from leaves to support respiration, and especially in 170 ppm plants represented a major respiratory loss of newly assimilated C (≈ 35{%} of the total plant respiration). Our results suggest that although plant metabolic processes like photosynthesis and respiration are affected by changes in pCO_2, nitrogen acquisition in such a symbiotic system is not.

  10. Factors Controlling Diffusive CO2 Transport and Production in the Cedarburg Bog, Saukville, Wisconsin: Field Observations

    NASA Astrophysics Data System (ADS)

    Joynt, E.; Han, W. S.; Gulbranson, E. L.; Graham, J. P.

    2015-12-01

    Wetland ecosystems are vital components of the carbon cycle containing an estimated 20-30% of the global soil carbon store. The Cedarburg Bog of southeastern Wisconsin boasts a myriad of wetland habitats including the southernmost string bog found in North America. The behavior of carbon dioxide (CO2) in these systems is the response of multiple interdependent variables that are, collectively, not well understood. Modeling this behavior in future climate scenarios requires detailed representation of such relationships within highly diverse environments. In 2014 a LI-COR 8100A automated soil gas flux system was installed in a hollow of the Cedarburg Bog string bog and collectively measured diffusive CO2 concentration and flux. Supplemental groundwater data, soil temperature, and weather data (temperature, pressure, precipitation, etc.) were also included to elucidate correlations between soil CO2 flux/CO2 concentration and external forces. In 2015 field data were complemented with soil moisture data and depth profile sampling of pore water chemistry and stable carbon isotopes from peat and gaseous media in order to discern the source and evolution of CO2 at depth. Preliminary LI-COR data analysis reveals distinct diurnal and seasonal trends; CO2 concentration builds overnight while flux increases during the day, both peaking in mid-summer. Flux events average 405 mg CO2/m2 per hour but reach over 31,800 mg CO2/m2 per hour in a single event and in several instances negative flux events are observed. Correlation significance also yields a wide array of strengths among variables. Initial δ13C data from gaseous CO2 infer, on average, a more positive δ13C signature in the atmosphere compared to the surface and shallow subsurface. Temporal trends of these parameters are similar to one another, becoming depleted in δ13C through time. Further interpretation of data trends will utilize the HYDRUS-1D model to quantify relationships under changing environmental conditions.

  11. Atmospheric pCO2 Reconstructed across the Early Eocene Hyperthermals

    NASA Astrophysics Data System (ADS)

    Cui, Y.; Schubert, B.

    2015-12-01

    Negative carbon isotope excursions (CIEs) are commonly associated with extreme global warming. The Early Eocene is punctuated by five such CIEs, the Paleocene-Eocene thermal maximum (PETM, ca. 55.8 Ma), H1 (ca. 53.6 Ma), H2 (ca. 53.5 Ma), I1 (ca. 53.3 Ma), and I2 (ca. 53.2 Ma), each characterized by global warming. The negative CIEs are recognized in both marine and terrestrial substrates, but the terrestrial substrates exhibit a larger absolute magnitude CIE than the marine substrates. Here we reconcile the difference in CIE magnitude between the terrestrial and marine substrates for each of these events by accounting for the additional carbon isotope fractionation by C3 land plants in response to increased atmospheric pCO2. Our analysis yields background and peak pCO2 values for each of the events. Assuming a common mechanism for each event, we calculate that background pCO2 was not static across the Early Eocene, with the highest background pCO2 immediately prior to I2, the last of the five CIEs. Background pCO2 is dependent on the source used in our analysis with values ranging from 300 to 720 ppmv provided an injection of 13C-depleted carbon with δ13C value of -60‰ (e.g. biogenic methane). The peak pCO2 during each event scales according to the magnitude of CIE, and is therefore greatest during the PETM and smallest during H2. Both background and peak pCO2 are higher if we assume a mechanism of permafrost thawing (δ13C = -25‰). Our reconstruction of pCO2 across these events is consistent with trends in the δ18O value of deep-sea benthic foraminifera, suggesting a strong link between pCO2 and temperature during the Early Eocene.

  12. Detection of inflammatory cell function using 13C magnetic resonance spectroscopy of hyperpolarized [6-13C]-arginine

    PubMed Central

    Najac, Chloé; Chaumeil, Myriam M.; Kohanbash, Gary; Guglielmetti, Caroline; Gordon, Jeremy W.; Okada, Hideho; Ronen, Sabrina M.

    2016-01-01

    Myeloid-derived suppressor cells (MDSCs) are highly prevalent inflammatory cells that play a key role in tumor development and are considered therapeutic targets. MDSCs promote tumor growth by blocking T-cell-mediated anti-tumoral immune response through depletion of arginine that is essential for T-cell proliferation. To deplete arginine, MDSCs express high levels of arginase, which catalyzes the breakdown of arginine into urea and ornithine. Here, we developed a new hyperpolarized 13C probe, [6-13C]-arginine, to image arginase activity. We show that [6-13C]-arginine can be hyperpolarized, and hyperpolarized [13C]-urea production from [6-13C]-arginine is linearly correlated with arginase concentration in vitro. Furthermore we show that we can detect a statistically significant increase in hyperpolarized [13C]-urea production in MDSCs when compared to control bone marrow cells. This increase was associated with an increase in intracellular arginase concentration detected using a spectrophotometric assay. Hyperpolarized [6-13C]-arginine could therefore serve to image tumoral MDSC function and more broadly M2-like macrophages. PMID:27507680

  13. Carbon and Oxygen Stable Isotope Measurements of Martian Atmospheric CO2 by the Phoenix Lander

    NASA Technical Reports Server (NTRS)

    Niles, Paul B.; Boynton, W. V.; Hoffman, J. H.; Ming, D. W.; Hamara, D.

    2010-01-01

    Precise stable isotope measurements of the CO2 in the martian atmosphere have the potential to provide important constraints for our understanding of the history of volatiles, the carbon cycle, current atmospheric processes, and the degree of water/rock interaction on Mars [1]. The isotopic composition of the martian atmosphere has been measured using a number of different methods (Table 1), however a precise value (<1%) has yet to be achieved. Given the elevated Delta(sup 13)C values measured in carbonates in martian meteorites [2-4] it has been proposed that the martian atmosphere was enriched in 13C [8]. This was supported by measurements of trapped CO2 gas in EETA 79001[2] which showed elevated Delta(sup 13)C values (Table 1). More recently, Earth-based spectroscopic measurements of the martian atmosphere have measured the martian CO2 to be depleted in C-13 relative to CO2 in the terrestrial atmosphere[ 7, 9-11]. The Thermal and Evolved Gas Analyzer (TEGA) instrument on the Mars Phoenix Lander [12] included a magnetic-sector mass spectrometer (EGA) [13] which had the goal of measuring the isotopic composition of martian atmospheric CO2 to within 0.5%. The mass spectrometer is a miniature instrument intended to measure both the martian atmosphere as well as gases evolved from heating martian soils.

  14. Anomalous 13C enrichment in modern marine organic carbon

    USGS Publications Warehouse

    Arthur, M.A.; Dean, W.E.; Claypool, G.E.

    1985-01-01

    Marine organic carbon is heavier isotopically (13C enriched) than most land-plant or terrestrial organic C1. Accordingly, ??13C values of organic C in modern marine sediments are routinely interpreted in terms of the relative proportions of marine and terrestrial sources of the preserved organic matter2,3. When independent geochemical techniques are used to evaluate the source of organic matter in Cretaceous or older rocks, those rocks containing mostly marine organic C are found typically to have lighter (more-negative) ??13C values than rocks containing mostly terrestrial organic C. Here we conclude that marine photosynthesis in mid-Cretaceous and earlier oceans generally resulted in a greater fractionation of C isotopes and produced organic C having lighter ??13C values. Modern marine photosynthesis may be occurring under unusual geological conditions (higher oceanic primary production rates, lower PCO2) that limit dissolved CO2 availability and minimize carbon isotope fractionation4. ?? 1985 Nature Publishing Group.

  15. The impact of elevated CO2 concentrations on soil microbial community, soil organic matter storage and nutrient cycling at a natural CO2 vent in NW Bohemia

    NASA Astrophysics Data System (ADS)

    Nowak, Martin; Beulig, Felix; von Fischer, Joe; Muhr, Jan; Kuesel, Kirsten; Trumbore, Susan

    2014-05-01

    Natural CO2 vents or 'mofettes' are diffusive or advective exhalations of geogenic CO2 from soils. These structures occur at several places worldwide and in most cases they are linked to volcanic activity. Characteristic for mofette soils are high CO2 concentrations of up to more than 90% as well as a lack of oxygen, low pH values and reducing conditions. Mofette soils usually are considered to be sites of carbon accumulation, which is not only due to the absence of oxygen, but might also result from lower plant litter quality due to CO2 fertilization of CO2 influenced plants and reduced availability of N and P for the decomposer community. Furthermore, fermentation processes and the formation of reduced elements by anoxic decomposition might fuel chemo-lithoautotrophic or mixotrophic microbial CO2 uptake, a process which might have important ecological functions by closing internal element cycles, formation of trace gasses as well as by re-cycling and storing of carbon. Several studies of microbial community structure revealed a shift towards CO2 utilizing prokaryotes in moffete soils compared to a reference site. Here, we use combined stable and radiocarbon isotope data from mofette soils in NW Bohemia to quantify the contribution of geogenic CO2 to soil organic carbon formation within mofette soils, either resulting from plant litter or from microbial CO2 uptake. This is possible because the geogenic CO2 has a distinct isotopic signature (δ13C = -2 o Δ14C = -1000 ) that is very different from the isotopic signature of atmospheric CO2. First results show that mofette soils have a high Corg content (20 to 40 %) compared to a reference site (2 to 20 %) and soil organic matter is enriched in 13C as well as depleted in 14C. This indicates that geogenic CO2 is re-fixed and stored as SOM. In order to quantify microbial contribution to CO2 fixation and SOM storage, microbial CO2 uptake rates were determined by incubating mofette soils with 13CO2 labelled gas. The

  16. Liquid CO2 venting on the seafloor: Yonaguni Knoll IV hydrothermal system, Okinawa Trough

    NASA Astrophysics Data System (ADS)

    Konno, U.; Tsunogai, U.; Nakagawa, F.; Nakaseama, M.; Ishibashi, J.; Nunoura, T.; Nakamura, K.

    2006-12-01

    In 2000, an active hydrothermal site, venting high-temperature fluid up to 300 oC, was discovered by Shinkai 6500 on the top of Yonaguni Knoll IV during YK 00-06 cruise in Okinawa Trough. During the subsequent subseafloor survey using Shinkai 6500 in 2003 (YK03-05), vents of liquid CO2 droplets were found at the site. Similar liquid CO2 droplets had previously been found at the active hydrothermal sites at JADE hydrothermal field, Okinawa Trough, during the extensive seafloor survey using submersibles in 1989 [Sakai et al., 1990]. Besides, similar liquid CO2 venting has also been recognized in NW Eifuku hydrothermal site on Izu-Bonin- Mariana arc. It thus appears that liquid CO2 venting might be usual phenomenon in some submarine arc volcanoes. The detailed relation between seafloor venting liquid CO2 and the surrounding high-temperature hydrothermal fluid, however, was not clarified in their studies. Furthermore, no definite evidence was obtained for the presence of CO2-hydrate in the subsurface. In this study, in order to discuss the subseafloor processes responsible for producing liquid CO2 at the Yonaguni Knoll IV site, as well as the possibility of the occurrence of solid CO2-hydrate within the sediments, we determined the chemical and isotopic compositions of the liquid CO2 found on the site, as well as those in hydrothermal fluid venting from the surrounding chimneys. In consequence, the ^13C of both CO2 and CH4 in the liquid CO2 almost coincide with those in the hydrothermal fluid, suggesting that the liquid CO2 must be derived from the hydrothermal fluid. While showing homogeneous ^13C, the hydrothermal fluids exhibit wide variation in gas contents. Active phase separation must be taking place within the conduits. Besides, H2-depletion in the liquid CO2 suggests formation of solid CO2-hydrate must also precede the venting of liquid CO2. In conclusion, liquid CO2 must be produced through following subseafloor processes: phase separation of hydrothermal

  17. H2S interference on CO2 isotopic measurements using a Picarro G1101-i cavity ring-down spectrometer

    NASA Astrophysics Data System (ADS)

    Malowany, K.; Stix, J.; Van Pelt, A.; Lucic, G.

    2015-06-01

    Cavity ring-down spectrometers (CRDS) have the capacity to make isotopic measurements of CO2 where concentrations range from atmospheric (~ 400 ppm) to 6000 ppm. Following field trials, it has come to light that the spectrographic lines used for CO2 have an interference with elevated (higher than ambient) amounts of hydrogen sulfide (H2S), which causes significant depletions in the δ13C measurement by the CRDS. In order to deploy this instrument in environments with elevated H2S concentrations (i.e., active volcanoes), we require a robust method for eliminating this interference. Controlled experiments using a Picarro G1101-i optical spectrometer were done to characterize the H2S interference at varying CO2 and H2S concentrations. The addition of H2S to a CO2 standard gas reveals an increase in the 12CO2 concentration and a more significant decrease in the 13CO2 concentration, resulting in a depleted δ13C value. Reacting gas samples containing H2S with copper prior to analysis can eliminate this effect. However, experiments also revealed that the addition of H2S to CO2 results in the formation of carbonyl sulfide (OCS) and carbon disulfide (CS2), causing a decrease in the overall CO2 concentration without affecting the δ13C value. It is important for future work with CRDS, particularly in volcanic regions where H2S is abundant, to be aware of the H2S interference on the CO2 spectroscopic lines and to remove all H2S prior to analysis. We suggest employing a scrub composed of copper to remove H2S from all gas samples that have concentrations in excess of 1 ppb.

  18. Sequestering CO2 in the Built Environment

    NASA Astrophysics Data System (ADS)

    Constantz, B. R.

    2009-12-01

    Calera’s Carbonate Mineralization by Aqueous Precipitation (CMAP) technology with beneficial reuse has been called, “game-changing” by Carl Pope, Director of the Sierra Club. Calera offers a solution to the scale of the carbon problem. By capturing carbon into the built environment through carbonate mineralization, Calera provides a sound and cost-effective alternative to Geologic Sequestration and Terrestrial Sequestration. The CMAP technology permanently converts carbon dioxide into a mineral form that can be stored above ground, or used as a building material. The process produces a suite of carbonate-containing minerals of various polymorphic forms. Calera product can be substituted into blends with ordinary Portland cements and used as aggregate to produce concrete with reduced carbon, carbon neutral, or carbon negative footprints. For each ton of product produced, approximately half a ton of carbon dioxide can be sequestered using the Calera process. Coal and natural gas are composed of predominately istopically light carbon, as the carbon in the fuel is plant-derived. Thus, power plant CO2 emissions have relatively low δ13C values.The carbon species throughout the CMAP process are identified through measuring the inorganic carbon content, δ13C values of the dissolved carbonate species, and the product carbonate minerals. Measuring δ13C allows for tracking the flue gas CO2 throughout the capture process. Initial analysis of the capture of propane flue gas (δ13C ˜ -25 ‰) with seawater (δ13C ˜ -10 ‰) and industrial brucite tailings from a retired magnesium oxide plant in Moss Landing, CA (δ13C ˜ -7 ‰ from residual calcite) produced carbonate mineral products with a δ13C value of ˜ -20 ‰. This isotopically light carbon, transformed from flue gas to stable carbonate minerals, can be transferred and tracked through the capture process, and finally to the built environment. CMAP provides an economical solution to global warming by producing

  19. Indian Monsoon controlling the effect of anthropogenic emission on the seasonal variation of air-CO2 over Bangalore, India

    NASA Astrophysics Data System (ADS)

    Guha, T.; Ghosh, P.

    2012-12-01

    this study we registered large variation in mixing ratio and δ13C of CO2 in a diurnal scale; with higher mixing ratio observed during the morning time compared to the afternoon time and corresponding signature of lower δ13C values are recorded. Using this large range of diurnal variation in Keeling's approach, the average δ13C value of the source CO2 was determined. The average δ13C value of source CO2 is found to be -24.8‰ with an observed range from -24.3‰ to -25.9‰. The average value closely matches with Permian coal δ13C value indicating fossil fuel as major source. The other possible sources are biomass burning and car exhaust having similar δ13C values as well. The proportional contribution of fossil fuel combustion and productivity is mainly affecting the seasonal variation. During the dry seasons the excess contribution of biomass burning together with contribution from fossil fuel produces excess depletion in δ13C values as observed in April-May. During SWM the increase in biosphere productivity causes preferential uptake of 12C during photosynthesis and drives enrichment of δ13C values in air CO2. The role of Indian monsoon controlling the regional atmospheric CO2 variability is presented here.

  20. Understanding of δ13C behavior and its significance in the Furong Cave system through a 10-year cave monitoring study

    NASA Astrophysics Data System (ADS)

    Li, J.; Li, H. C.; Li, T.; Li, X.; Yuan, N.; Zhang, T.

    2015-12-01

    The debate about how speleothem δ13C to reflect paleoclimate and paleovegetation changes calls for understanding of δ13C behavior in a cave system. We have conducted a monitoring study in Furong Cave, Chongqing, China since 2005 involving multiple sites in the overlying soil and inside the cave. The measured proxies include pCO2 of the atmosphere, soil and cave air; dripping rate, pH, electronic conductivity, Ca2+, HCO3-, d13CDIC of the dripwaters; and deposition rate, d13C of seasonally selected carbonate deposits. The many observations from this study are: (1) Soil pCO2 is close to the atmospheric pCO2 in winter and reaches >10000 ppm during the summer due to high productivity under warm and wet climates. (2) The pCO2 in cave air is slightly higher than Soil pCO2 and atmospheric pCO2 in winter (400~900 ppm), but elevates up to ~2000 ppm around October due to seepage of soil CO2 into the cave. The cave air pCO2 exhibits double peaks following the seasonal rainfall (1st peak in April-June controlled by Indian monsoon and 2nd peak in July-September influenced by the North Western Pacific monsoon). The cave air pCO2 has about 2-3 month lag to the soil pCO2. (3) Under the influence of soil CO2 and rainfall, the d13CDIC of drpiwaters are depleted in the summer and enriched during the winter. During 2009-2011, southwestern China experienced extremely drought due to summer monsoon failure. The d13CDIC of dripwater in Furong Cave was strongly enriched because of low soil CO2 productivity, less transportation of soil CO2 into the cave, and high CO2 ratio from bedrock input. Dripping rate does not affect the d13CDIC significantly. (4) The d13C of speleothems is controlled by the open/closed system of the seepage pathway on the first order. Monitoring site MP1 owns a relatively open system shown by fast dripping rates, low Ca and HCO3- contents, and low carbonate deposition rate. The d13C of modern deposits from this site not only shows the seasonal variation following

  1. Degradation pathways of dissolved carbon in landfill leachate traced with compound-specific (13)C analysis of DOC.

    PubMed

    Mohammadzadeh, Hossein; Clark, Ian

    2008-09-01

    thousand) indicates that CO(2)-reducing bacteria must be the primary consumers of H(2), which has resulted in enriched (13)C(DIC) (10 per thousand) and depleted (13)C(CH4) (-58 per thousand). PMID:18763184

  2. Assessing the stable carbon isotopic composition of intercellular CO2 in a CAM plant using gas chromatography-combustion-isotope ratio mass spectrometry.

    PubMed

    Nogués, Salvador; Aranjuelo, Iker; Pardo, Antoni; Azcón-Bieto, Joaquim

    2008-04-01

    Most of the literature focused on internal CO(2) (Ci) determinations in plants has used indirect methods based on gas-exchange estimations. We have developed a new method based on the capture of internal air gas samples and their analysis by gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS). This method provided a direct measure of intercellular CO(2) concentrations combined with stable carbon isotopic composition in O. ficus-indica plants. Plants were grown at both ambient and elevated CO(2) concentration. During the day period, when the stomata are closed, the Ci was high and was very (13)C-enriched in both ambient and elevated CO(2)-grown plants, reflecting Rubisco's fractionation (this plant enzyme has been shown to discriminate by 29 per thousand, in vitro, against (13)CO(2)). Other enzyme fractionations involved in C metabolism in plants, such as carbonic anhydrase, could also be playing an important role in the diurnal delta(13)C enrichment of the Ci. During the night, when stomata are open, Ci concentrations were higher in elevated (and the corresponding delta(13)C values were more (13)C-depleted) than in ambient CO(2)-grown plants.

  3. Study of the diet effect on δ 13C of shell carbonate of the land snail Helix aspersa in experimental conditions

    NASA Astrophysics Data System (ADS)

    Metref, S.; Rousseau, D.-D.; Bentaleb, I.; Labonne, M.; Vianey-Liaud, M.

    2003-06-01

    This study aims to demonstrate the influence of the metabolic CO 2 derived from the diet and of the atmospheric CO 2 on the shell carbonate δ 13C of the pulmonate snail Helix aspersa maxima raised under controlled conditions. Adult snails were analyzed and compared with three hatching and 1-day old young snails stemming from the same breeding. One day after, the 2-day old individuals were raised during 1 month. Three groups of gastropods were fed with fresh lettuce (C 3 plant, δ 13C=-27.49‰), three groups with corn (C 4 plant, δ 13C=-11.7‰), and three groups ate alternately both (C 3+C 4). The difference between the average δ 13C values of the adult snails on the one hand and the hatched and 1-day old snails on the other hand indicates a depletion of 2.47‰. Therefore, the isotopic parents-offspring signal is not preserved. The depleted ingested albumen by the snail embryo in the egg during the building of the shell could explain this depletion. The C 3 diet experiment gave the expected isotopic composition difference between the diet (lettuce) and the shells (average Δ 13C shell-lettuce=13.75‰±0.52). This result shows a clear diet effect on the isotopic composition of the snail shells. For the C 4 experiment, the difference in carbon isotope composition between the corn and the shell (Δ 13C shell-corn) yielded an average value of 4.89‰±0.87. The main result is that Δ 13C is not constant and appears to depend on the type of ingested food. Several hypotheses can arise from this study to explain the different fractionations: (a) differences in the quality of the two diets, (b) differences in turnover rate for C 3 and C 4 feeders. The groups regularly fed with mixed diet yielded δ 13C values showing a preferential use of C 3 food for most values. The C 3-C 4 mixed dietary alternation probably led snails to use mainly the lettuce instead of the corn powder.

  4. Numerical modeling of self-limiting and self-enhancing caprock alteration induced by CO2 storage in a depleted gas reservoir

    SciTech Connect

    Xu, Tianfu; Gherardi, Fabrizio; Xu, Tianfu; Pruess, Karsten

    2007-09-07

    This paper presents numerical simulations of reactive transport which may be induced in the caprock of an on-shore depleted gas reservoir by the geological sequestration of carbon dioxide. The objective is to verify that CO{sub 2} geological disposal activities currently being planned for the study area are safe and do not induce any undesired environmental impact. In our model, fluid flow and mineral alteration are induced in the caprock by penetration of high CO{sub 2} concentrations from the underlying reservoir, where it was assumed that large amounts of CO{sub 2} have already been injected at depth. The main focus is on the potential effect of precipitation and dissolution processes on the sealing efficiency of caprock formations. Concerns that some leakage may occur in the investigated system arise because the seal is made up of potentially highly-reactive rocks, consisting of carbonate-rich shales (calcite+dolomite averaging up to more than 30% of solid volume fraction). Batch simulations and multi-dimensional 1D and 2D modeling have been used to investigate multicomponent geochemical processes. Numerical simulations account for fracture-matrix interactions, gas phase participation in multiphase fluid flow and geochemical reactions, and kinetics of fluid-rock interactions. The geochemical processes and parameters to which the occurrence of high CO{sub 2} concentrations are most sensitive are investigated by conceptualizing different mass transport mechanisms (i.e. diffusion and mixed advection+diffusion). The most relevant mineralogical transformations occurring in the caprock are described, and the feedback of these geochemical processes on physical properties such as porosity is examined to evaluate how the sealing capacity of the caprock could evolve in time. The simulations demonstrate that the occurrence of some gas leakage from the reservoir may have a strong influence on the geochemical evolution of the caprock. In fact, when a free CO{sub 2

  5. Extraction and carbon isotope analysis of CO 2 from scapolite in deep crustal granulites and xenoliths

    NASA Astrophysics Data System (ADS)

    Moecher, David P.; Valley, John W.; Essene, Eric J.

    1994-01-01

    Carbon isotope compositions of scapolite from granulite facies gneisses and lower crustal xenoliths document the composition and constrain the source of carbon in scapolite from the lower crust. CO 2 is extracted from scapolite without fractionating carbon isotopes by reaction with phosphoric acid at 25 or 75°C. Thus, partial yields of CO 2 from scapolite are sufficient for accurate carbon isotopic analysis. Isotopic compositions of coexisting scapolite and calcite in high-grade calc-silicate gneisses and marbles, and consideration of the crystal chemical environment of CO 3 in the scapolite structure, indicate little fractionation of 13C /12C between scapolite and calcite (0.1 ± 1.2%.) at equilibrium conditions of 650-800°C. The carbon isotope composition of CO 2 extracted from scapolite in twenty-nine samples of regional granulite facies gneisses, amphibolites, calc-silicate gneisses, and crustal xenoliths yield values of δ 13C that range from -10 to -1%. (PDB). High-grade marbles and graphitic paragneisses are precluded as major sources of carbon for scapolite in the high grade rocks analyzed in this study, as the former are isotopically enriched, and the latter isotopically depleted in 13C /12C relative to the range of isotopic compositions determined here. The δ 13C values for mafic granulites and amphibolites in granulite terranes composed of supracrustal sequences (-10.1 to -4.0%.) may reflect the isotopic composition of diagenetic carbonate present in their basaltic protoliths. The values of δ 13C for scapolite in mafic xenoliths and some granulite facies orthogneisses (-8.2 to -1.2%.) are consistent with crystallization of the scapolite from a mafic melt or derivation of CO 2 from mafic melts emplaced in the lower crust or upper mantle. The values of δ 13C for scapolites from calc-silicate gneisses and calc-silicate xenoliths (-10.0 to -2.9%.) may result from depletion of 13C /12C as a result of decarbonation of calcite-bearing protoliths during

  6. Diagenetic mineralization in Pennsylvanian coals from Indiana, USA: 13C/12C and 18O/16O implications for cleat origin and coalbed methane generation

    USGS Publications Warehouse

    Solano-Acosta, W.; Schimmelmann, A.; Mastalerz, Maria; Arango, I.

    2008-01-01

    Cleats and fractures in southwestern Indiana coal seams are often filled with authigenic kaolinite and/or calcite. Carbon- and oxygen-stable isotope ratios of kaolinite, calcite, and coalbed CO2 were evaluated in combination with measured values and published estimates of ??18O of coalbed paleowaters that had been present at the time of mineralization. ??18Omineral and ??18Owater values jointly constrain the paleotemperature of mineralization. The isotopic evidence and the thermal and tectonic history of this part of the Illinois Basin led to the conclusion that maximum burial and heat-sterilization of coal seams approximately 272??Ma ago was followed by advective heat redistribution and concurrent precipitation of kaolinite in cleats at a burial depth of < 1600??m at ??? 78 ?? 5????C. Post-Paleozoic uplift, the development of a second generation of cleats, and subsequent precipitation of calcite occurred at shallower burial depth between ??? 500 to ??? 1300??m at a lower temperature of 43 ?? 6????C. The available paleowater in coalbeds was likely ocean water and/or tropical meteoric water with a ??18Owater ??? - 1.25??? versus VSMOW. Inoculation of coalbeds with methanogenic CO2-reducing microbes occurred at an even later time, because modern microbially influenced 13C-enriched coalbed CO2 (i.e., the isotopically fractionated residue of microbial CO2 reduction) is out of isotopic equilibrium with 13C-depleted calcite in cleats. ?? 2007 Elsevier B.V. All rights reserved.

  7. Methanogenesis produces strong 13C enrichment in stromatolites of Lagoa Salgada, Brazil: a modern analogue for Palaeo-/Neoproterozoic stromatolites?

    PubMed

    Birgel, D; Meister, P; Lundberg, R; Horath, T D; Bontognali, T R R; Bahniuk, A M; de Rezende, C E; Vasconcelos, C; McKenzie, J A

    2015-05-01

    Holocene stromatolites characterized by unusually positive inorganic δ(13) CPDB values (i.e. up to +16‰) are present in Lagoa Salgada, a seasonally brackish to hypersaline lagoon near Rio de Janeiro (Brazil). Such positive values cannot be explained by phototrophic fixation of CO2 alone, and they suggest that methanogenesis was a dominating process during the growth of the stromatolites. Indeed, up to 5 mm methane was measured in the porewater. The archaeal membrane lipid archaeol showing δ(13) C values between -15 and 0‰ suggests that archaea are present and producing methane in the modern lagoon sediment. Moreover, (13) C-depleted hopanoids diplopterol and 3β-methylated C32 17β(H),21β(H)-hopanoic acid (both -40‰) are preserved in lagoon sediments and are most likely derived from aerobic methanotrophic bacteria thriving in the methane-enriched water column. Loss of isotopically light methane through the water column would explain the residual (13) C-enriched pool of dissolved inorganic carbon from where the carbonate constituting the stromatolites precipitated. The predominance of methanogenic archaea in the lagoon is most likely a result of sulphate limitation, suppressing the activity of sulphate-reducing bacteria under brackish conditions in a seasonally humid tropical environment. Indeed, sulphate-reduction activity is very low in the modern sediments. In absence of an efficient carbonate-inducing metabolic process, we propose that stromatolite formation in Lagoa Salgada was abiotically induced, while the (13) C-enriched organic and inorganic carbon pools are due to methanogenesis. Unusually, (13) C-enriched stromatolitic deposits also appear in the geological record of prolonged periods in the Palaeo- and Neoproterozoic. Lagoa Salgada represents a possible modern analogue to conditions that may have been widespread in the Proterozoic, at times when low sulphate concentrations in sea water allowed methanogens to prevail over sulphate

  8. Nitrogen control of 13C enrichment in heterotrophic organs relative to leaves in a landscape-building desert plant species

    NASA Astrophysics Data System (ADS)

    Zhang, J.; Gu, L.; Bao, F.; Cao, Y.; Hao, Y.; He, J.; Li, J.; Li, Y.; Ren, Y.; Wang, F.; Wu, R.; Yao, B.; Zhao, Y.; Lin, G.; Wu, B.; Lu, Q.; Meng, P.

    2015-01-01

    A longstanding puzzle in isotope studies of C3 plant species is that heterotrophic plant organs (e.g., stems, roots, seeds, and fruits) tend to be enriched in 13C compared to the autotrophic organ (leaves) that provides them with photosynthate. Our inability to explain this puzzle suggests key deficiencies in understanding post-photosynthetic metabolic processes. It also limits the effectiveness of applications of stable carbon isotope analyses in a variety of scientific disciplines ranging from plant physiology to global carbon cycle studies. To gain insight into this puzzle, we excavated whole plant architectures of Nitraria tangutorum Bobrov, a C3 species that has an exceptional capability of fixing sands and building sand dunes, in two deserts in northwestern China. We systematically and simultaneously measured carbon isotope ratios and nitrogen and phosphorous contents of different parts of the excavated plants. We also determined the seasonal variations in leaf carbon isotope ratios on nearby intact plants of N. tangutorum. We found, for the first time, that higher nitrogen contents in heterotrophic organs were significantly correlated with increased heterotrophic 13C enrichment compared to leaves. However, phosphorous contents had no effect on the enrichment. In addition, new leaves had carbon isotope ratios similar to roots but were progressively depleted in 13C as they matured. We concluded that a nitrogen-mediated process, hypothesized to be the refixation of respiratory CO2 by phosphoenolpyruvate (PEP) carboxylase, was responsible for the differences in 13C enrichment among different heterotrophic organs, while processes such as fractionating foliar metabolism and preferentially loading into phloem of 13C-enriched sugars may contribute to the overall autotrophic-heterotrophic difference in carbon isotope compositions.

  9. 13C-1H dipolar-driven 13C-13C recoupling without 13C rf irradiation in nuclear magnetic resonance of rotating solids

    NASA Astrophysics Data System (ADS)

    Takegoshi, K.; Nakamura, Shinji; Terao, Takehiko

    2003-02-01

    Two recently proposed 13C-13C recoupling methods under magic angle spinning (MAS), resonant interference recoupling (RIR), and 13C-1H dipolar-assisted rotational resonance (DARR), are examined on a common theoretical foundation using the average Hamiltonian theory. In both methods, a rf field is applied on not 13C but 1H to recouple the 13C-1H dipolar interactions, and spectral overlap necessary to conserve energy for 13C-13C polarization transfer is achieved by the 13C-1H dipolar line broadening. While DARR employs time-independent 13C-1H interactions recoupled by suitable rf irradiation to 1H spins, RIR uses time-dependent 13C-1H interactions modulated appropriately by 1H rf irradiation. There are two distinct cases where 13C-1H line broadening realizes 13C-13C spectral overlap. For a pair of a carbonyl or aromatic carbon and an aliphatic carbon, spectral overlap can be achieved between one of the spinning sidebands of the former 13C resonance and the 13C-1H dipolar powder pattern of the latter. On the other hand for a pair of spins with a small chemical shift difference, the two center bands are overlapped with each other due to 13C-1H dipolar broadening. For the former, we show that both RIR and DARR occur in the first order, while for the latter, DARR recoupling is appreciable for time-independent 13C-1H interactions. We refer to the former DARR as the first-order DARR recoupling and the latter as the second-order DARR. Experimentally, we examined the following 13C-1H recoupling methods for DARR: 1H CW irradiation fulfilling a rotary-resonance condition or a modulatory-resonance condition, and 1H π pulses applied synchronously to MAS. For RIR, the FSLG-m2m¯m sequence is applied to 1H. Several one-dimensional DARR and RIR experiments were done for N-acetyl[1,2-13C, 15N] DL-valine, and [2,3-13C] L-alanine. It was found that the polarization transfer rate for RIR is larger than that for DARR except for fast spinning, while the rate for DARR is less sensitive to

  10. Microbial community in a sediment-hosted CO2 lake of the southern Okinawa Trough hydrothermal system.

    PubMed

    Inagaki, Fumio; Kuypers, Marcel M M; Tsunogai, Urumu; Ishibashi, Jun-Ichiro; Nakamura, Ko-Ichi; Treude, Tina; Ohkubo, Satoru; Nakaseama, Miwako; Gena, Kaul; Chiba, Hitoshi; Hirayama, Hisako; Nunoura, Takuro; Takai, Ken; Jørgensen, Bo B; Horikoshi, Koki; Boetius, Antje

    2006-09-19

    Increasing levels of CO2 in the atmosphere are expected to cause climatic change with negative effects on the earth's ecosystems and human society. Consequently, a variety of CO2 disposal options are discussed, including injection into the deep ocean. Because the dissolution of CO2 in seawater will decrease ambient pH considerably, negative consequences for deep-water ecosystems have been predicted. Hence, ecosystems associated with natural CO2 reservoirs in the deep sea, and the dynamics of gaseous, liquid, and solid CO2 in such environments, are of great interest to science and society. We report here a biogeochemical and microbiological characterization of a microbial community inhabiting deep-sea sediments overlying a natural CO2 lake at the Yonaguni Knoll IV hydrothermal field, southern Okinawa Trough. We found high abundances (>10(9) cm(-3)) of microbial cells in sediment pavements above the CO2 lake, decreasing to strikingly low cell numbers (10(7) cm(-3)) at the liquid CO2/CO2-hydrate interface. The key groups in these sediments were as follows: (i) the anaerobic methanotrophic archaea ANME-2c and the Eel-2 group of Deltaproteobacteria and (ii) sulfur-metabolizing chemolithotrophs within the Gamma- and Epsilonproteobacteria. The detection of functional genes related to one-carbon assimilation and the presence of highly 13C-depleted archaeal and bacterial lipid biomarkers suggest that microorganisms assimilating CO2 and/or CH4 dominate the liquid CO2 and CO2-hydrate-bearing sediments. Clearly, the Yonaguni Knoll is an exceptional natural laboratory for the study of consequences of CO2 disposal as well as of natural CO2 reservoirs as potential microbial habitats on early Earth and other celestial bodies.

  11. H2S interference on CO2 isotopic measurements using a Picarro G1101-i cavity ring-down spectrometer

    NASA Astrophysics Data System (ADS)

    Malowany, K.; Stix, J.; Van Pelt, A.; Lucic, G.

    2015-10-01

    Cavity ring-down spectrometers (CRDSs) have the capacity to make isotopic measurements of CO2 where concentrations range from atmospheric (~ 400 ppm) to 6000 ppm. Following field trials, it has come to light that the spectrographic lines used for CO2 have an interference with elevated (higher than ambient) amounts of hydrogen sulfide (H2S), which causes significant depletions in the δ13C measurement by the CRDSs. In order to deploy this instrument in environments with elevated H2S concentrations (i.e., active volcanoes), we require a robust method for eliminating this interference. Controlled experiments using a Picarro G1101-i optical spectrometer were done to characterize the H2S interference at varying CO2 and H2S concentrations. The addition of H2S to a CO2 standard gas reveals an increase in the 12CO2 concentration and a more significant decrease in the 13CO2 concentration, resulting in a depleted δ13C value. Reacting gas samples containing H2S with copper prior to analysis can eliminate this effect. Models post-dating the G1101-i carbon isotope analyzer have maintained the same spectral lines for CO2 and are likely to have a similar H2S response at elevated H2S concentrations. It is important for future work with CRDS, particularly in volcanic regions where H2S is abundant, to be aware of the H2S interference on the CO2 spectroscopic lines and to remove all H2S prior to analysis. We suggest employing a scrub composed of copper to remove H2S from all gas samples that have concentrations in excess of 1 ppb.

  12. Calculation of the 13C NMR shieldings of the C0 2 complexes of aluminosilicates

    NASA Astrophysics Data System (ADS)

    Tossell, J. A.

    1995-04-01

    13C NMR shieldings have been calculated using the random-phase-approximation, localized-orbital local-origins version of ab initio coupled Hartree-Fuck perturbation theory for CO 2 and and for several complexes formed by the reaction of CO 2 with molecular models for aluminosilicate glasses, H 3TOT'H3 3-n, T,T' = Si,Al. Two isomeric forms of the CO 2-aluminosilicate complexes have been considered: (1) "CO 2-like" complexes, in which the CO 2 group is bound through carbon to a bridging oxygen and (2) "CO 3-like" complexes, in which two oxygens of a central CO 3 group form bridging bonds to the two TH 3 groups. The CO 2-like isomer of CO 2-H 3SiOSiH 3 is quite weakly bonded and its 13C isotropic NMR shielding is almost identical to that in free CO 2. As Si is progressively replaced by Al in the - H terminated aluminosilicate model, the CO 2-like isomers show increasing distortion from the free CO 2 geometry and their 13C NMR shieldings decrease uniformly. The calculated 13C shielding value for H 3AlO(CO 2)AlH 3-2 is only about 6 ppm larger than that calculated for point charge stabilized CO 3-2. However, for a geometry of H 3SiO(CO 2) AlH 3-1, in which the bridging oxygen to C bond length has been artificially increased to that found in the - OH terminated cluster (OH) 3SiO(CO 2)Al(OH) 3-1, the calculated 13C shielding is almost identical to that for free CO 2. The CO 3-like isomers of the CO 2-aluminosili-cate complexes show carbonate like geometries and 13C NMR shieldings about 4-9 ppm larger than those of carbonate for all T,T' pairs. For the Si,Si tetrahedral atom pair the CO 2-like isomer is more stable energetically, while for the Si,Al and Al,Al cases the CO 3-like isomer is more stable. Addition of Na + ions to the CO 3-2 or H 3AlO(CO 2)AlH 3-2 complexes reduces the 13C NMR shieldings by about 10 ppm. Complexation with either Na + or CO 2 also reduces the 29Si NMR shieldings of the aluminosilicate models, while the changes in 27Al shielding with Na + or CO 2

  13. Linking carbon isotope signatures of nighttime leaf-respiratory and daytime assimilatory CO2 fluxes observed with laser spectrometry under field conditions

    NASA Astrophysics Data System (ADS)

    Gentsch, Lydia; Ogée, Jérôme; Wingate, Lisa; Sturm, Patrick; Siegwolf, Rolf; Werner, Roland A.; Buchmann, Nina; Knohl, Alexander

    2015-04-01

    The 13C/12C ratio (δ13C) of atmospheric CO2 is a valuable tool for constraining the impact of the terrestrial biosphere on atmospheric CO2 dynamics. Alterations of the 13C signal of terrestrial net CO2 fluxes are generally attributed to variations in photosynthetic 13C discrimination. Yet, over the past decade, evidence has emerged that plant metabolism and respiration modify the initial δ13C signature of recent photosynthetic assimilates. Such postphotosynthetic δ13C modifications were reported for all plant organs, but leaf respiratory metabolism may play a central role as it impacts carbon turnover in other plant tissues. Leaf-respired CO2 is frequently 13C enriched with respect to leaf organic matter. Mechanisms potentially explaining this enrichment include the differential use of carbon sources, metabolite fragmentation or the expression of kinetic isotope effects of respiratory enzymes. For global and ecosystem-scale applications of δ13C, it is now important to study, under field conditions, the variability of δ13C in leaf-respired CO2 (δ13CRES) and the deviation of the latter from δ13C of recent assimilates (δ13CAS). Here, we present 74 days of hourly δ13C measurements for daytime assimilatory and nighttime respiratory CO2 fluxes on leafy branches of three mature Fagus sylvatica trees in a temperate forest. Measurements were conducted with a laser spectrometer (QCLAS-ISO, Aerodyne Research Inc.) measuring CO2 isotopologue mixing ratios in ambient and sampling air from photosynthetic gas exchange chambers. We used daytime measurements of photosynthetic 13C discrimination for diurnally flux-weighted estimates of δ13CAS, and found that flux-weighted δ13CRES roughly tracked previous-day shifts in δ13CAS. Deviations between flux-weighted δ13CAS and δ13CRES were further robustly predicted by previous-day assimilation, with δ13CRES displaying 13C enrichment on low and 13C depletion on high assimilation days. On the hourly timescale, δ13CRES either

  14. Stable isotope monitoring of ionic trapping of CO2 in deep brines

    NASA Astrophysics Data System (ADS)

    Myrttinen, A.; Barth, J. A. C.; Becker, V.; Blum, P.; Grathwohl, P.

    2009-04-01

    CO2 injection into a depleted gas-reservoir is used as a combined method for Enhanced Gas Recovery (EGR) and CO2 storage. In order to safeguard this process, monitoring the degree of dissolution and potential further precipitation and mineral interactions are a necessity. Here a method is introduced, in which stable isotope and geochemical data can be used as a monitoring technique to quantify ionic trapping of injected CO2. Isotope and geochemical data of dissolved inorganic carbon (DIC) can be used to distinguish between already present and to be injected inorganic carbon. Injected CO2, for instance, is formed during combustion of former plant material and is expected to have a different isotope ratio (δ13C value) than the baseline data of the aquifer. This is because combusted CO2 originates from organic material, such as coal and oil with a predominant C3 plant signature. Mixing the injected CO2 with groundwater is therefore expected to change the isotope, as well as the geochemical composition of the groundwater. Mass balance calculations with stable isotope ratios can serve to quantify ionic trapping of CO2 as DIC in groundwater. However, depending on the composition of the aquifer, weathering of carbonate or silicates may occur. Enhanced weathering processes due to CO2 injection can also further influence the isotopic composition. Such interactions between dissolved CO2 and minerals depend on the temperature and pressure regimes applied. Field data, as well as laboratory experiments are planned to quantify isotope ratios of dissolved inorganic carbon as well as oxygen isotope ratios of the water. These are indicative of geochemical processes before, during and after EGR. The isotope method should therefore provide a new tool to quantify the efficiency of ionic trapping under various temperatures and pressures. Keywords: Enhanced Gas Recovery, monitoring of CO2 dissolution, stable isotopes

  15. Soil respiration under mature deciduous forest trees after 7 years of CO2 enrichment

    NASA Astrophysics Data System (ADS)

    Bader, Martin; Körner, Christian

    2010-05-01

    The anthropogenic rise in atmospheric CO2 is expected to impact carbon fluxes not only at ecosystem level but also at the global scale by altering carbon cycle processes in soils. At the Swiss Canopy Crane (SCC), we examined how 7 years of free air CO2 enrichment (FACE) affected soil CO2 dynamics in a c. 100-year-old mixed deciduous forest. The use of 13C-depleted CO2 for canopy enrichment allowed us to trace the flow of recently fixed carbon (C). In the seventh year of growth at ~550 ppm CO2, soil respiratory CO2 consisted of 39% labelled C. During the growing season, soil air CO2 concentration was significantly enhanced under CO2-exposed trees. However, elevated CO2 failed to stimulate cumulative soil respiration (Rs) over the growing season. We found periodic reductions as well as increases in instantaneous rates of Rs in response to elevated CO2, depending on soil temperature and soil volumetric water content (VWC; significant 3-way interaction). During wet periods, soil water savings under CO2-enriched trees led to excessive VWC (>45%) that suppressed Rs. Elevated CO2 stimulated Rs only when VWC was ≤40% and concurrent soil temperature was high (>15 °C). Seasonal Q10 estimates of Rs were significantly lower under elevated (Q10 = 3.30) compared to ambient CO2 (Q10 = 3.97). However, this effect disappeared when 3 consecutive sampling dates of extremely high VWC were disregarded. This suggests that elevated CO2 affected Q10 mainly indirectly through changes in VWC. Fine root respiration did not differ significantly between treatments but soil microbial biomass (Cmic) increased by 14% under elevated CO2 (marginally significant). Our findings do not indicate enhanced soil C emissions in such stands under future atmospheric CO2. It remains to be shown whether C losses via leaching of dissolved organic or inorganic C (DOC, DIC) help to balance the carbon budget in this forest.

  16. New guidelines for δ13C measurements

    USGS Publications Warehouse

    Coplen, Tyler B.; Brand, Willi A.; Gehre, Matthias; Groning, Manfred; Meijer, Harro A. J.; Toman, Blaza; Verkouteren, R. Michael

    2006-01-01

    Consistency of δ13C measurements can be improved 39−47% by anchoring the δ13C scale with two isotopic reference materials differing substantially in 13C/12C. It is recommended thatδ13C values of both organic and inorganic materials be measured and expressed relative to VPDB (Vienna Peedee belemnite) on a scale normalized by assigning consensus values of −46.6‰ to L-SVEC lithium carbonate and +1.95‰ to NBS 19 calcium carbonate. Uncertainties of other reference material values on this scale are improved by factors up to two or more, and the values of some have been notably shifted:  the δ13C of NBS 22 oil is −30.03%.

  17. A Large Metabolic Carbon Ccontribution to the δ13C Record in Marine Aragonitic Bivalve Shells

    NASA Astrophysics Data System (ADS)

    Gillikin, D. P.; Lorrain, A.; Dehairs, F.

    2006-12-01

    The stable carbon isotopic signature archived in bivalve shells was originally thought to record the δ13C of seawater dissolved inorganic carbon (δ13C-DIC). However, more recent studies have shown that the incorporation of isotopically light metabolic carbon (M) significantly affects the δ13C signal recorded in biogenic carbonates. To assess the M contribution to Mercenaria mercenaria shells collected in North Carolina, USA, we sampled seawater δ13C-DIC, tissue, hemolymph and shell δ13C. We found up to a 4‰ decrease through ontogeny in shell δ13C in a 23 year old individual. There was no correlation between shell height or age and tissue δ13C. Thus, the ontogenic decrease observed in the shell δ13C could not be attributed to changes in food sources as the animal ages leading to more negative metabolic CO2, since this would require a negative relationship between tissue δ13C and shell height. Hemolymph δ13C, on the other hand, did exhibit a negative relationship with height, but the δ13C values were more positive than expected, indicating that hemolymph may not be a good proxy of extrapallial fluid δ13C. Nevertheless, the hemolymph data indicate that respired CO2 does influence the δ13C of internal fluids and that the amount of respired CO2 is related to the age of the bivalve. The percent metabolic C incorporated into the shell (%M) was significantly higher (up to 37%) than has been found in other bivalve shells, which usually contain less than 10 %M. Attempts to use shell biometrics to predict %M could not explain more than ~60% of the observed variability. Moreover, there were large differences in the %M between different sites. Thus, the metabolic effect on shell δ13C cannot easily be accounted for to allow reliable δ13C-DIC reconstructions. However, there does seem to be a common effect of size, as all sites had indistinguishable slopes between the %M and shell height (+0.19% per mm of shell height).

  18. Preliminary studies of a canine 13C-aminopyrine demethylation blood test.

    PubMed Central

    Moeller, E M; Steiner, J M; Williams, D A; Klein, P D

    2001-01-01

    The objectives of this study were to determine whether a 13C-aminopyrine demethylation blood test is technically feasible in clinically healthy dogs, whether oral administration of 13C-aminopyrine causes a detectable increase in percent dose/min (PCD) of 13C administered as 13C-aminopyrine and recovered in gas extracted from blood, and whether gas extraction efficiency has an impact on PCD. A dose of 2 mg/kg body weight of 13C-aminopyrine dissolved in deionized water was administered orally to 6 clinically healthy dogs. Blood samples were taken from each dog 0, 30, 60, and 120 min after administration of the 13C-aminopyrine. Carbon dioxide was extracted from blood samples by addition of acid and analyzed by fractional mass spectrometry. None of the 6 dogs showed any side effects after 13C-aminopyrine administration. All 6 dogs showed a measurable increase of the PCD in gas samples extracted from blood samples at 30 min, 60 min, and 120 min after 13C-aminopyrine administration. Coefficients of variation between the triplicate samples were statistically significantly higher for the %CO2, a measure of extraction efficiency, than for PCD values (P < 0.0001). The 13C-aminopyrine demethylation blood test described here is technically feasible. Oral administration of 13C-aminopyrine did not lead to gross side effects in the 6 dogs. Clinically healthy dogs show a measurable increase of PCD in gas extracted from blood samples after oral administration of 13C-aminopyrine. Efficiency of CO2 extraction from blood samples does not have an impact on PCD determined from these blood samples. This test may prove useful to evaluate hepatic function in dogs. PMID:11227194

  19. Nitrogen control of 13C enrichment in heterotrophic organs relative to leaves in a landscape-building desert plant species

    DOE PAGES

    Zhang, J.; Gu, L.; Bao, F.; Cao, Y.; Hao, Y.; He, J.; Li, J.; Li, Y.; Ren, Y.; Wang, F.; et al

    2014-09-10

    A longstanding puzzle in isotope studies of C3 plant species is that heterotrophic plant organs (e.g., stems, roots, seeds, and fruits) tend to be enriched in 13C compared to the autotrophic organ (leaves) that provides them with photosynthate. Our inability to explain this puzzle suggests key deficiencies in understanding post-photosynthetic metabolic processes. It also limits the effectiveness of applications of stable carbon isotope analyses in a variety of scientific disciplines ranging from plant physiology to global carbon cycle studies. To gain insight into this puzzle, we excavated whole plant architectures of Nitraria tangutorum Bobrov, a C3 species that has anmore » exceptional capability of fixing sands and building sand dunes, in two deserts in northwestern China. We systematically and simultaneously measured carbon isotope ratios and nitrogen and phosphorous contents of different parts of the excavated plants. We also determined the seasonal variations in leaf carbon isotope ratios on nearby intact plants of N. tangutorum. We found, for the first time, that higher nitrogen contents in heterotrophic organs were significantly correlated with increased heterotrophic 13C enrichment compared to leaves. However, phosphorous contents had no effect on the enrichment. In addition, new leaves had carbon isotope ratios similar to roots but were progressively depleted in 13C as they matured. We concluded that a nitrogen-mediated process, probably the refixation of respiratory CO2 by phosphoenolpyruvate (PEP) carboxylase, was responsible for the differences in 13C enrichment among different heterotrophic organs while processes within leaves or during phloem loading may contribute to the overall autotrophic – heterotrophic difference in carbon isotope compositions.« less

  20. Isorenieratane record in black shales from the Paris Basin, France: Constraints on recycling of respired CO2 as a mechanism for negative carbon isotope shifts during the Toarcian oceanic anoxic event

    NASA Astrophysics Data System (ADS)

    van Breugel, Yvonne; Baas, Marianne; Schouten, Stefan; Mattioli, Emanuela; Sinninghe Damsté, Jaap S.

    2006-12-01

    The prominent negative stable carbon isotope excursion in both carbonate and organic carbon recorded in organic-rich sediments deposited during the Toarcian oceanic anoxic event (OAE) has commonly been explained by recycling of 13C-depleted CO2 (the so-called Küspert model). More recently, the massive release of 13C-depleted methane or other forms of 13C-depleted carbon was also proposed to account for the observed negative δ13C excursions in organic carbon of terrigenous as well as of marine origin. The occurrence of diagenetic products of the carotenoid isorenieratene (isorenieratane and other aryl isoprenoids) in Toarcian black shales has been regarded as supporting evidence for the Küspert hypothesis as they point to strong stratification of the epicontinental seas. A section of a drill core straddling the Toarcian of the Paris Basin (Cirfontaine-en-Ornois) contained intact isorenieratane, providing evidence that photosynthetic green sulphur bacteria were present at the time of deposition, even prior to the OAE. However, the isorenieratane abundances are very low in the section where the negative δ13C excursion in organic carbon and phytane, a chemical fossil derived from chlorophyll, occurs. The abundance of the isorenieratene derivatives increases, once the δ13C records have shifted to more positive values. The δ13C of isorenieratane (generally circa -13.1 ± 0.5 ‰) indicates that the respired CO2 contribution at the chemocline was low and is thus not likely to be the main cause of the prominent up to 7‰ negative δ13C shift recorded in Toarcian organic carbon records.

  1. Evolution of the stable carbon isotope composition of atmospheric CO2 over the last glacial cycle

    NASA Astrophysics Data System (ADS)

    Eggleston, S.; Schmitt, J.; Bereiter, B.; Schneider, R.; Fischer, H.

    2016-03-01

    We present new δ13C measurements of atmospheric CO2 covering the last glacial/interglacial cycle, complementing previous records covering Terminations I and II. Most prominent in the new record is a significant depletion in δ13C(atm) of 0.5‰ occurring during marine isotope stage (MIS) 4, followed by an enrichment of the same magnitude at the beginning of MIS 3. Such a significant excursion in the record is otherwise only observed at glacial terminations, suggesting that similar processes were at play, such as changing sea surface temperatures, changes in marine biological export in the Southern Ocean (SO) due to variations in aeolian iron fluxes, changes in the Atlantic meridional overturning circulation, upwelling of deep water in the SO, and long-term trends in terrestrial carbon storage. Based on previous modeling studies, we propose constraints on some of these processes during specific time intervals. The decrease in δ13C(atm) at the end of MIS 4 starting approximately 64 kyr B.P. was accompanied by increasing [CO2]. This period is also marked by a decrease in aeolian iron flux to the SO, followed by an increase in SO upwelling during Heinrich event 6, indicating that it is likely that a large amount of δ13C-depleted carbon was transferred to the deep oceans previously, i.e., at the onset of MIS 4. Apart from the upwelling event at the end of MIS 4 (and potentially smaller events during Heinrich events in MIS 3), upwelling of deep water in the SO remained reduced until the last glacial termination, whereupon a second pulse of isotopically light carbon was released into the atmosphere.

  2. Temporal δ13C records from bottlenose dolphins (Tursiops truncatus) reflect variation in foraging location and global carbon cycling

    NASA Astrophysics Data System (ADS)

    Rossman, S. L.; Barros, N. B.; Ostrom, P. H.; Gandhi, H.; Wells, R. S.

    2010-12-01

    first year of life. Given the age of bottlenose dolphins from SB (ca. 60 years), our isotopic data provide a record beginning in 1944. While carbon isotope values show a striking decline over time, the data must be corrected for the Suess effect. The Suess effect results from burning of 13C depleted hydrocarbons which causes a decrease in the δ13C of atmospheric CO2 that subsequent depresses isotope values in food webs. To account for the Suess effect, δ13C values are adjusted by 0.15‰ per decade. Suess corrected δ13C values do not show a temporal linear trend however the average isotope value prior to 1960 is significantly higher than that after 1960 (-10.1 vs -11.66, p=0.038). While documented declines in seagrass abundance prior to 1980 may influence our data, the decline in δ13C of atmospheric CO2 is likely an important factor that controls the isotopic composition of dolphin tissues. Our results suggest that isotope-based estimates of foraging should account for the Suess effect, and that dolphins act as environmental sentinels whose δ13C values records perturbations in global carbon cycling.

  3. Large and unexpected enrichment in stratospheric 16O13C18O and its meridional variation.

    PubMed

    Yeung, Laurence Y; Affek, Hagit P; Hoag, Katherine J; Guo, Weifu; Wiegel, Aaron A; Atlas, Elliot L; Schauffler, Sue M; Okumura, Mitchio; Boering, Kristie A; Eiler, John M

    2009-07-14

    The stratospheric CO(2) oxygen isotope budget is thought to be governed primarily by the O((1)D)+CO(2) isotope exchange reaction. However, there is increasing evidence that other important physical processes may be occurring that standard isotopic tools have been unable to identify. Measuring the distribution of the exceedingly rare CO(2) isotopologue (16)O(13)C(18)O, in concert with (18)O and (17)O abundances, provides sensitivities to these additional processes and, thus, is a valuable test of current models. We identify a large and unexpected meridional variation in stratospheric (16)O(13)C(18)O, observed as proportions in the polar vortex that are higher than in any naturally derived CO(2) sample to date. We show, through photochemical experiments, that lower (16)O(13)C(18)O proportions observed in the midlatitudes are determined primarily by the O((1)D)+CO(2) isotope exchange reaction, which promotes a stochastic isotopologue distribution. In contrast, higher (16)O(13)C(18)O proportions in the polar vortex show correlations with long-lived stratospheric tracer and bulk isotope abundances opposite to those observed at midlatitudes and, thus, opposite to those easily explained by O((1)D)+CO(2). We believe the most plausible explanation for this meridional variation is either an unrecognized isotopic fractionation associated with the mesospheric photochemistry of CO(2) or temperature-dependent isotopic exchange on polar stratospheric clouds. Unraveling the ultimate source of stratospheric (16)O(13)C(18)O enrichments may impose additional isotopic constraints on biosphere-atmosphere carbon exchange, biosphere productivity, and their respective responses to climate change.

  4. In vivo13C spectroscopy in the rat brain using hyperpolarized [1- 13C]pyruvate and [2- 13C]pyruvate

    NASA Astrophysics Data System (ADS)

    Marjańska, Małgorzata; Iltis, Isabelle; Shestov, Alexander A.; Deelchand, Dinesh K.; Nelson, Christopher; Uğurbil, Kâmil; Henry, Pierre-Gilles

    2010-10-01

    The low sensitivity of 13C spectroscopy can be enhanced using dynamic nuclear polarization. Detection of hyperpolarized [1- 13C]pyruvate and its metabolic products has been reported in kidney, liver, and muscle. In this work, the feasibility of measuring 13C signals of hyperpolarized 13C metabolic products in the rat brain in vivo following the injection of hyperpolarized [1- 13C]pyruvate and [2- 13C]pyruvate is investigated. Injection of [2- 13C]pyruvate led to the detection of [2- 13C]lactate, but no other downstream metabolites such as TCA cycle intermediates were detected. Injection of [1- 13C]pyruvate enabled the detection of both [1- 13C]lactate and [ 13C]bicarbonate. A metabolic model was used to fit the hyperpolarized 13C time courses obtained during infusion of [1- 13C]pyruvate and to determine the values of VPDH and VLDH.

  5. CO2-Neutral Fuels

    NASA Astrophysics Data System (ADS)

    Goede, Adelbert; van de Sanden, Richard

    2016-06-01

    Mimicking the biogeochemical cycle of System Earth, synthetic hydrocarbon fuels are produced from recycled CO2 and H2O powered by renewable energy. Recapturing CO2 after use closes the carbon cycle, rendering the fuel cycle CO2 neutral. Non-equilibrium molecular CO2 vibrations are key to high energy efficiency.

  6. Does the Shuram δ13C excursion record Ediacaran oxygenation?

    NASA Astrophysics Data System (ADS)

    Husson, J. M.; Maloof, A. C.; Schoene, B.; Higgins, J. A.

    2013-12-01

    The most negative carbon isotope excursion in Earth history is found in carbonate rocks of the Ediacaran Period (635-542 Ma). Known colloquially as the the 'Shuram' excursion, workers have long noted its tantalizing, broad concordance with the rise of abundant macro-scale fossils in the rock record, variously interpreted as animals, giant protists, macro-algae and lichen, and known as the 'Ediacaran Biota.' Thus, the Shuram excursion has been interpreted by many in the context of a dramatically changing redox state of the Ediacaran oceans - e.g., a result of methane cycling in a low O2 atmosphere, the final destruction of a large pool of recalcitrant dissolved organic carbon (DOC), and the step-wise oxidation of the Ediacaran oceans. More recently, diagenetic interpretations of the Shuram excursion - e.g. sedimentary in-growth of very δ13C depleted authigenic carbonates, meteoric alteration of Ediacaran carbonates, late-stage burial diagenesis - have challenged the various Ediacaran redox models. A rigorous geologic context is required to discriminate between these explanatory models, and determine whether the Shuram excursion can be used to evaluate terminal Neoproterozoic oxygenation. Here, we present chemo-stratigraphic data (δ13C, δ18O, δ44/42Ca and redox sensitive trace element abundances) from 12 measured sections of the Ediacaran-aged Wonoka Formation (Fm.) of South Australia that require a syn-depositional age for the extraordinary range of δ13C values (-12 to +4‰) observed in the formation. In some locations, the Wonoka Fm. is ~700 meters (m) of mixed shelf limestones and siliclastics that record the full 16 ‰ δ13C excursion in a remarkably consistent fashion across 100s of square kilometers of basin area. Fabric-altering diagenesis, where present, occurs at the sub-meter vertical scale, only results in sub-permil offsets in δ13C and cannot be used to explain the full δ13C excursion. In other places, the Wonoka Fm. is host to deep (1 km

  7. Is late Quaternary climate change governed by self-sustained oscillations in atmospheric CO2?

    NASA Astrophysics Data System (ADS)

    Wallmann, Klaus

    2014-05-01

    A simple earth system model is developed to simulate global carbon and phosphorus cycling over the late Quaternary. It is focused on the geological cycling of C and P via continental weathering, volcanic and metamorphic degassing, hydrothermal processes and burial at the seabed. A simple ocean model is embedded in this geological model where the global ocean is represented by surface water, thermocline and deep water boxes. Concentrations of dissolved phosphorus, dissolved inorganic carbon, and total alkalinity are calculated for each box. The partial pressure of CO2 in the atmosphere (pCO2A) is determined by exchange processes with the surface ocean and the continents. It serves as key prognostic model variable and is assumed to govern surface temperatures and global sea-level. The model is formulated as autonomous system, in which the governing equations have no explicit time-dependence. For certain parameter values, the model does not converge towards a steady-state but develops stable self-sustained oscillations. These free oscillations feature pCO2A minima and maxima consistent with the ice-core record when vertical mixing in the ocean is allowed to vary in response to pCO2A-controlled temperature change. A stable 100-kyr cycle with a rapid transition from glacial to interglacial conditions is obtained when additional non-linear equations are applied to calculate deep ocean mixing, iron fertilization and the depth of organic matter degradation as function of pCO2A-controlled surface temperature. The δ13C value of carbon in the ocean/atmosphere system calculated in these model runs is consistent with the benthic δ13C record. However, the simulated 13C depletion in the glacial ocean is not driven by the decline in terrestrial carbon stocks but by sea-level change controlling the rates of organic carbon burial and weathering at continental margins. The pCO2A- and δ13C oscillations develop without any form of external Milankovitch forcing. They are induced and

  8. Leaf Wax δ13C Varies with Elevation in the Peruvian Andes and Western Amazonia

    NASA Astrophysics Data System (ADS)

    Wu, M. S.; Feakins, S. J.; Ponton, C.; Peters, T.; West, A. J.; Galy, V.; Bentley, L. P.; Salinas, N.; Shenkin, A.; Martin, R.; Asner, G. P.; Malhi, Y.

    2015-12-01

    Plant leaf wax carbon isotopic composition (δ13Cwax) reflects the net isotopic effects associated with diffusion into the leaf, fixation of carbon by Rubisco and biosynthesis of individual leaf wax biochemicals. As declining pCO2 with elevation affects the first two fractionations, we expect to find an isotopic gradient in δ13Cwax, if the fractionation of leaf wax biosynthesis is constant. To test this, we report δ13Cwax values from 500 samples of leaves collected by tree-climbers from the upper canopy from 9 forest-inventory plots spanning a 3.5km elevation transect in the Peruvian Andes and western Amazonia during the CHAMBASA field campaign. These samples provide a unique opportunity to study the relationship between δ13Cwax and pCO2 in diverse species across this remote tropical montane forest and lowland rainforest. The very wet climate throughout (2-5 m rainfall per year) minimizes fractionation effects due to stomatal restrictions (i.e. water use efficiency) that may be an important factor elsewhere. Preliminary results show δ13Cwax values on average increase with elevation by ~1.5‰/km, a trend consistent with bulk plant δ13C in previous studies. The mean epsilon between bulk and C29 n-alkane is -7.3±2.2‰. Inter-sample differences are large on the order of 10‰. Shaded leaves and understory leaves are found to be depleted relative to sunlit leaves, presumably due to a lower photosynthetic rate and use of respired CO2 in the understory. C29 n-alkanes are on average ~2.5‰ more depleted than C30 n-alkanoic acids, indicating fractionation during selective decarboxylation. We further compare results from plants with soil and river sediments to provide insights into how leaf wax signals are archived in soils and exported from the landscape. We find a ~1.4‰/km gradient in forest soils similar to plants. We observe a ~2‰ offset between C29 n-alkane in plant leaves and in soils across the elevation profile, which is likely a signal of degradation

  9. 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

  10. The effect of atmospheric CO2 concentration on carbon isotope fractionation in C3 land plants

    NASA Astrophysics Data System (ADS)

    Schubert, Brian A.; Jahren, A. Hope

    2012-11-01

    in C3 plants at elevated pCO2. The values for Δδ13Cp we determined in our ambient pCO2 chambers are consistent with the Δδ13Cp values measured in large modern datasets of plants growing within the Earth’s wettest environments, suggesting that it may be possible to reconstruct changes in paleo-pCO2 level from plants that grew in consistently wet environments, if δ13CCO2 value and initial pCO2 level can be independently quantified. Several implications arise for the reconstruction of water availability and water-use efficiency in both ancient and recent plant Δδ13Cp values across periods of changing pCO2 level. For example, the change in Δδ13Cp implied by our relationship for the rise in pCO2 concentration observed since 1980 is of the same magnitude (= ∼0.7‰) as the isotopic correction for changes in δ13CCO2 required by the input of 13C-depleted carbon to the atmosphere. For these reasons, only the portion of the terrestrial isotopic excursion that persists after accounting for changes in pCO2 concentration should be used for the interpretation of a change in paleo-environmental conditions.

  11. The Late Pleistocene history of surface water δ13C in the Sulu Sea: Possible relationship to Pacific Deepwater δ13C changes

    NASA Astrophysics Data System (ADS)

    Linsley, Braddock K.; Dunbar, Robert B.

    1994-04-01

    A reconstruction of late Pleistocene surface water carbon isotopic (δ13C) variability is presented from Ocean Drilling Program (ODP) site 769 in the Sulu Sea in the western tropical Pacific. The Sulu Sea is a shallowly silled back arc basin with a maximum sill depth of 420 m. Site 769 was drilled on a bathymetric high in 3643 m of water and has average late Pleistocene sedimentation rates of 8.5 cm/kyr. The oxygen isotope record (δ18O) of Globigerinoides ruber at site 769 shows a strong correlation with the SPECMAP stacked δ18O record, attesting to the continuity of sediment archive at the site. Surface δ13C displays consistent glacial-interglacial variability which averages ˜0.9‰ and has varied from 0.75 to 1.1‰ over the last 800 kyr. Comparison to surface water δ13C records in the South China Sea and western tropical Pacific suggests that the glacial-interglacial surface δ13C variability is regional in scale. Planktonic δ13C data from ODP site 677 in the eastern Pacific is also coherent with the site 769. Additionally, we have found that the site 769 surface δ13C record is coherent at periods of 100 and 41 kyr with deepwater δ13C records from the Pacific. The highest correlation occurs with the deep eastern Pacific, where benthic δ13C data from cores RC13-110 and ODP site 677 closely match the Sulu Sea surface water record. We evaluate several possible controls of surface water δ13C in the Sulu Sea that may explain the coherent timing with Pacific deepwater δ13C records. These include variations in terrestrial organic matter flux to the basin, the upwelling of subsurface water and productivity changes, and the influx of western Pacific intermediate water to the Sulu Sea. Our preferred explanation involves a region of upper intermediate water upwelling in the far western Pacific which has been shown to outgas CO2 from subsurface waters into surface waters. Upwelling also occurs in the area of Panama Basin site 677. These equatorial upwelling zones

  12. Fourier Transform Microwave Spectra of CO{2}-ETHYLENE Sulfide, CO{2}-ETHYLENE Oxide and CO{2}-PROPYLENE Oxide Complexes

    NASA Astrophysics Data System (ADS)

    Orita, Yukari; Kawashima, Yoshiyuki; Hirota, Eizi

    2010-06-01

    We have previously examined the difference in roles of O and S in structure and dynamics of the CO-ethylene oxide (EO) and CO-ethylene sulfide (ES) complexes. We have extended the investigation to CO{2}-EO and CO{2}-ES for comparison. We have also observed the CO{2}-propylene oxide (PO) complex, which is an important intermediate in the reaction of PO with CO{2} leading to polycarbonate. Both a-type and b-type transitions were observed for the CO{2}-EO and CO{2}-ES, but no c-type transitions were observed at all. We also detected the {34}S and {13}C isotopic species in natural abundance and the species containing {18}OCO and C{18}O% {2}, which were synthesized by burning paper in an {18}O{2} and{% 16}O{2} mixture. By analyzing the observed spectra we concluded the CO{2} moiety of CO{2}-EO and CO{2}-ES located in a plane % prependicular to the three-membered ring and bisecting the COC or CSC angle of EO or ES, respectively, as in the case of CO-EO and CO-ES complexes. An % ab initio MO calculation at the level of MP2/6-311G(d, p) yielded an optimized structure in good agreement with the experimental result. We have derived from the observed spectra the distance, the stretching force constant, and the binding energy of the bonds between the constituents of the CO{2}-EO and CO{2}-ES complexes and have found that the distances of the two complexes were shorter by 0.2Å than those in CO-EO and CO-ES, respectively, and that the intermolecular bonds were two times stronger in the CO{2} complexes than in the corresponding CO complexes. We have concluded from the observed spectra that the CO{2} moiety in CO{2}-PO is located on the PO three-membered ring plane opposite to the methyl group. The constituents in CO{2}-PO were more weakly bound than those in CO{2}-EO and CO{2}-ES. S. Sato, Y. Kawashima, Y. Tatamitani, and E. Hirota, 63rd International Symposium on Molecular Spectroscopy, WF05 (2008).

  13. Tracing CO2 fluxes and plant volatile organic compound emissions by stable isotopes

    NASA Astrophysics Data System (ADS)

    Werner, Christiane; Wegener, Frederik; Jardine, Kolby

    2014-05-01

    CO2 in the light. Simultaneously, naturally 13C depleted C-2 and C-3 carbon atoms of the acetyl-moiety are emitted as a variety of VOCs. Moreover, during light-dark transitions leaf emission bursts of the oxygenated metabolite acetaldehyde were observed as part of the PDH bypass pathway in the cytosol2. This may be a new piece of evidence for the origin of 13C-enriched δ13CO2 which is released during Light-Enhanced Dark Respiration (LEDR). Our study provides the first evidence that the isotopic signature of respired CO2 is closely linked to carbon partitioning between anabolic and catabolic pathways and plants strategies of carbon investment into secondary compound synthesis. Werner C. & Gessler A. (2011) Diel variations in the carbon isotope composition of respired CO2 and associated carbon sources: a review of dynamics and mechanisms. Biogeosciences 8, 2437-2459 Jardine K, Wegener F, Abrell L, vonHaren J, Werner C (2014) Phytogenic biosynthesis and emission of methyl acetate. PCE 37, 414-424.

  14. Effect of petroleum products on the decomposition of soil organic matter as assessed by 13C natural abundance

    NASA Astrophysics Data System (ADS)

    Stelmach, Wioleta; Szarlip, Paweł; Trembaczowski, Andrzej; Bieganowski, Andrzej

    2016-04-01

    Petroleum products are common contaminants in soils due to human activities. They are toxic for microorganisms and threat their functions, including decomposition of soil organic matter (SOM). The direct estimation of altered SOM decomposition - based on the CO2 emission - is impossible after oil contamination, because oil decomposition also contributes to the CO2 release. We used the natural differences in the isotopic signature (δ13C) of SOM and of oil products to partition the total CO2 for both sources and to analyze the suppression of SOM decomposition. The dynamics of 13C fractionation during the mineralization of gasoline and diesel was measured during 42 days. The 13C fractionation varied between -8.8‰ and +3.6‰ within the first 10 days, and stabilized thereafter at about -5.3‰ for gasoline and +3.2‰ for diesel. These 13C fractionations and δ13C values of CO2 emitted from the soil were used for correct partitioning of the total CO2. Contamination with gasoline reduced the CO2 efflux from SOM decomposition by a factor of 25 (from 151 to 6 mg C-CO2 kg-1 soil during 42 days). The negative effect of diesel was much lower: the CO2 efflux from SOM was decreased by less than a factor of 2. The strong effect of gasoline versus diesel reflects the lower absorption of gasoline to mineral particles and the development of a thin film on water surfaces, leading to toxicity for microorganisms. We conclude that the small differences of 13C of SOM and of organic pollutants can be used to partition CO2 fluxes and analyze pollutant effects on SOM decomposition.

  15. Effect of petroleum products on the decomposition of soil organic matter as assessed by 13C natural abundance

    NASA Astrophysics Data System (ADS)

    Stelmach, Wioleta; Szarlip, Paweł; Trembaczowski, Andrzej; Bieganowski, Andrzej

    2016-04-01

    Petroleum products are common contaminants in soils due to human activities. They are toxic for microorganisms and threat their functions, including decomposition of soil organic matter (SOM). The direct estimation of altered SOM decomposition - based on the CO2 emission - is impossible after oil contamination, because oil decomposition also contributes to the CO2 release. We used the natural differences in the isotopic signature (δ13C) of SOM and of oil products to partition the total CO2 for both sources and to analyze the suppression of SOM decomposition. The dynamics of 13C fractionation during the mineralization of gasoline and diesel was measured during 42 days. The 13C fractionation varied between -8.8‰ and +3.6‰ within the first 10 days, and stabilized thereafter at about -5.3‰ for gasoline and +3.2‰ for diesel. These 13C fractionations and δ13C values of CO2 emitted from the soil were used for correct partitioning of the total CO2. Contamination with gasoline reduced the CO2 efflux from SOM decomposition by a factor of 25 (from 151 to 6 mg C-CO2 kg‑1 soil during 42 days). The negative effect of diesel was much lower: the CO2 efflux from SOM was decreased by less than a factor of 2. The strong effect of gasoline versus diesel reflects the lower absorption of gasoline to mineral particles and the development of a thin film on water surfaces, leading to toxicity for microorganisms. We conclude that the small differences of 13C of SOM and of organic pollutants can be used to partition CO2 fluxes and analyze pollutant effects on SOM decomposition.

  16. Determination of the δ13C of dissolved inorganic carbon in water; RSIL lab code 1710

    USGS Publications Warehouse

    Singleton, Glenda L.; Revesz, Kinga; Coplen, Tyler B.

    2012-01-01

    The purpose of the Reston Stable Isotope Laboratory (RSIL) lab code 1710 is to present a method to determine the δ13C of dissolved inorganic carbon (DIC) of water. The DIC of water is precipitated using ammoniacal strontium chloride (SrCl2) solution to form strontium carbonate (SrCO3). The δ13C is analyzed by reacting SrCO3 with 100-percent phosphoric acid (H3PO4) to liberate carbon quantitatively as carbon dioxide (CO2), which is collected, purified by vacuum sublimation, and analyzed by dual inlet isotope-ratio mass spectrometry (DI-IRMS). The DI-IRMS is a DuPont double-focusing mass spectrometer. One ion beam passes through a slit in a forward collector and is collected in the rear collector. The other measurable ion beams are collected in the front collector. By changing the ion-accelerating voltage under computer control, the instrument is capable of measuring mass/charge (m/z) 45 or 46 in the rear collector and m/z 44 and 46 or 44 and 45, respectively, in the front collector. The ion beams from these m/z values are as follows: m/z 44 = CO2 = 12C16O16O, m/z 45 = CO2 = 13C16O16O primarily, and m/z 46 = CO2 = 12C16O18O primarily. The data acquisition and control software calculates δ13C values.

  17. Trends in stomatal density and 13C/12C ratios of Pinus flexilis needles during last glacial-interglacial cycle

    USGS Publications Warehouse

    Van De Water, Peter K.; Leavitt, Steven W.; Betancourt, J.L.

    1994-01-01

    Measurements of stomatal density and ?? 13C of limber pine (Pinus flexilis) needles (leaves) preserved in pack rat middens from the Great Basin reveal shifts in plant physiology and leaf morphology during the last 30,000 years. Sites were selected so as to offset glacial to Holocene climatic differences and thus to isolate the effects of changing atmospheric CO2 levels. Stomatal density decreased ~17 percent and ?? 13C decreased ~1.5 per mil during deglaciation from 15,000 to 12,000 years ago, concomitant with a 30 percent increase in atmospheric CO2. Water-use efficiency increased ~15 percent during deglaciation, if temperature and humidity were held constant and the proxy values for CO2 and ?? 13C of past atmospheres are accurate. The ??13C variations may help constrain hypotheses about the redistribution of carbon between the atmosphere and biosphere during the last glacial-interglacial cycle.

  18. CO2 -Responsive polymers.

    PubMed

    Lin, Shaojian; Theato, Patrick

    2013-07-25

    This Review focuses on the recent progress in the area of CO2 -responsive polymers and provides detailed descriptions of these existing examples. CO2 -responsive polymers can be categorized into three types based on their CO2 -responsive groups: amidine, amine, and carboxyl groups. Compared with traditional temperature, pH, or light stimuli-responsive polymers, CO2 -responsive polymers provide the advantage to use CO2 as a "green" trigger as well as to capture CO2 directly from air. In addition, the current challenges of CO2 -responsive polymers are discussed and the different solution methods are compared. Noteworthy, CO2 -responsive polymers are considered to have a prosperous future in various scientific areas.

  19. Trimethylamine and Organic Matter Additions Reverse Substrate Limitation Effects on the δ13C Values of Methane Produced in Hypersaline Microbial Mats

    PubMed Central

    Nicholson, Brooke E.; Beaudoin, Claire S.; Detweiler, Angela M.; Bebout, Brad M.

    2014-01-01

    Methane production has been observed in a number of hypersaline environments, and it is generally thought that this methane is produced through the use of noncompetitive substrates, such as the methylamines, dimethylsulfide and methanol. Stable isotope measurements of the produced methane have also suggested that the methanogens are operating under conditions of substrate limitation. Here, substrate limitation in gypsum-hosted endoevaporite and soft-mat hypersaline environments was investigated by the addition of trimethylamine, a noncompetitive substrate for methanogenesis, and dried microbial mat, a source of natural organic matter. The δ13C values of the methane produced after amendments were compared to those in unamended control vials. At all hypersaline sites investigated, the δ13C values of the methane produced in the amended vials were statistically lower (by 10 to 71‰) than the unamended controls, supporting the hypothesis of substrate limitation at these sites. When substrates were added to the incubation vials, the methanogens within the vials fractionated carbon isotopes to a greater degree, resulting in the production of more 13C-depleted methane. Trimethylamine-amended samples produced lower methane δ13C values than the mat-amended samples. This difference in the δ13C values between the two types of amendments could be due to differences in isotope fractionation associated with the dominant methane production pathway (or substrate used) within the vials, with trimethylamine being the main substrate used in the trimethylamine-amended vials. It is hypothesized that increased natural organic matter in the mat-amended vials would increase fermentation rates, leading to higher H2 concentrations and increased CO2/H2 methanogenesis. PMID:25239903

  20. CO2 laser modeling

    NASA Technical Reports Server (NTRS)

    Johnson, Barry

    1992-01-01

    The topics covered include the following: (1) CO2 laser kinetics modeling; (2) gas lifetimes in pulsed CO2 lasers; (3) frequency chirp and laser pulse spectral analysis; (4) LAWS A' Design Study; and (5) discharge circuit components for LAWS. The appendices include LAWS Memos, computer modeling of pulsed CO2 lasers for lidar applications, discharge circuit considerations for pulsed CO2 lidars, and presentation made at the Code RC Review.

  1. Feasibility of Multianimal Hyperpolarized 13C MRS

    PubMed Central

    Ramirez, Marc S.; Lee, Jaehyuk; Walker, Christopher M.; Chen, Yunyun; Kingsley, Charles V.; De La Cerda, Jorge; Maldonado, Kiersten L.; Lai, Stephen Y.; Bankson, James A.

    2014-01-01

    Purpose There is great potential for real-time investigation of metabolism with MRS and hyperpolarized (HP) 13C agents. Unfortunately, HP technology has high associated costs and efficiency limitations that may constrain in vivo studies involving many animals. To improve the throughput of preclinical investigations, we evaluate the feasibility of performing HP MRS on multiple animals simultaneously. Methods Simulations helped assess the viability of a dual-coil strategy for spatially-localized multivolume MRS.A dual-mouse system was assembled and characterized based on bench- and scanner-based experiments. Enzyme phantoms mixed with HP [1-13C] pyruvate emulated real-time metabolism and offered a controlled mechanism for evaluating system performance. Finally, a normal mouse and a mouse bearing a subcutaneous xenograft of colon cancer were simultaneously scanned in vivo using an agent containing HP [1-13C] pyruvate. Results Geometric separation/rotation, active decoupling, and use of low input impedance preamplifiers permitted an encode-by-channel approach for spatially-localized MRS. A pre-calibrated shim allowed straightforward metabolite differentiation in enzyme phantom and in vivo experiments at 7 T, with performance similar to conventional acquisitions. Conclusion The initial feasibility of multi-animal HP 13C MRS was established. Throughput scales with the number of simultaneously-scanned animals, demonstrating the potential for significant improvements in study efficiency. PMID:24903532

  2. Microbial Community in a Sediment-Hosted CO2 Lake of the Southern Okinawa Trough Hydrothermal Field

    NASA Astrophysics Data System (ADS)

    Inagaki, F.; Kuypers, M. M.; Tsunogai, U.; Ishibashi, J.; Nakamura, K.; Treude, T.; Ohkubo, S.; Nakaseama, M.; Gena, K.; Chiba, H.; Hirayama, H.; Nunoura, T.; Takai, K.; Jorgensen, B. B.; Horikoshi, K.; Boetius, A.

    2006-12-01

    One-carbon assimilating (micro-)organisms play an important role for global carbon cycling; however, the increasing level of anthropogenic CO2 in the atmosphere has exceeded the capacity of natural biological feedback, hence as greenhouse gasses it is expected to cause climacteric change with negative effects on the earth's ecosystems and human society. To reduce CO2 emissions into the atmosphere, a variety of options have been discussed, including a disposal of CO2 into the deep ocean. However, the impact of CO2 disposal on deep-sea ecosystems as well as of the consequent microbiological feedback remains largely unknown. At the Yonaguni Knoll IV hydrothermal field, southern Okinawa Trough, we observed a natural liquid CO2 lake in sediments overlying elemental sulfur and CO2 hydrates at a water depth of 1380m. The liquid CO2 droplets were composed of 85% CO2 and 14% methane with hydrogen below the detection limit. We found high abundances (>109 cm-3) of microbial cells in sediment pavements above the CO2 lake, decreasing to strikingly low cell numbers (10&^{7} cm-3) at the liquid CO2/CO2-hydrate interface. Molecular ecological study based on the sequences of 16S rRNA genes showed that the key groups in these sediments were: (i) the anaerobic methanotrophic archaea ANME-2c and the Eel-2 group of Deltaproteobacteria, and (ii) sulfur-metabolizing chemolithotrophs within the Gamma- and Epsilonproteobacteria. The detection of functional genes (mcrA, cbbL) related to one- carbon assimilation as well as the presence of highly 13C-depleted archaeal and bacterial lipid biomarkers suggest that microorganisms assimilating CO2 and/or methane dominate the liquid CO2 and CO2-hydrate-bearing sediments. We propose that the Yonaguni Knoll is an exceptional natural laboratory for the study of consequences of CO2 disposal as well as of natural CO2 reservoirs as potential microbial habitats on early Earth and other celestial bodies.

  3. Synthesis Of [2h, 13c] And [2h3, 13c]Methyl Aryl Sulfides

    DOEpatents

    Martinez, Rodolfo A.; Alvarez, Marc A.; Silks, III, Louis A.; Unkefer, Clifford J.

    2004-03-30

    The present invention is directed to labeled compounds, [.sup.2 H.sub.1, .sup.13 C], [.sup.2 H.sub.2, .sup.13 C] and [.sup.2 H.sub.3, .sup.13 C]methyl aryl sulfides wherein the .sup.13 C methyl group attached to the sulfur of the sulfide includes exactly one, two or three deuterium atoms and the aryl group is selected from the group consisting of 1-naphthyl, substituted 1-naphthyl, 2-naphthyl, substituted 2-naphthyl, and phenyl groups with the structure ##STR1## wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4, and R.sub.5 are each independently, hydrogen, a C.sub.1 -C.sub.4 lower alkyl, a halogen, an amino group from the group consisting of NH.sub.2, NHR and NRR' where R and R' are each a C.sub.1 -C.sub.4 lower alkyl, a phenyl, or an alkoxy group. The present invention is also directed to processes of preparing [.sup.2 H.sub.1, .sup.13 C], [.sup.2 H.sub.2,.sup.13 C] and [.sup.2 H.sub.3, .sup.13 C]methyl aryl sulfides wherein the .sup.13 C methyl group attached to the sulfur of the sulfide includes exactly one, two or three deuterium atoms. The present invention is also directed to the labeled compounds of [.sup.2 H.sub.1, .sup.13 C]methyl iodide and [.sup.2 H.sub.2, .sup.13 C]methyl iodide.

  4. Natural (13) C distribution in oil palm (Elaeis guineensis Jacq.) and consequences for allocation pattern.

    PubMed

    Lamade, Emmanuelle; Tcherkez, Guillaume; Darlan, Nuzul Hijri; Rodrigues, Rosario Lobato; Fresneau, Chantal; Mauve, Caroline; Lamothe-Sibold, Marlène; Sketriené, Diana; Ghashghaie, Jaleh

    2016-01-01

    Oil palm has now become one of the most important crops, palm oil representing nearly 25% of global plant oil consumption. Many studies have thus addressed oil palm ecophysiology and photosynthesis-based models of carbon allocation have been used. However, there is a lack of experimental data on carbon fixation and redistribution within palm trees, and important C-sinks have not been fully characterized yet. Here, we carried out extensive measurement of natural (13) C-abundance (δ(13) C) in oil palm tissues, including fruits at different maturation stages. We find a (13) C-enrichment in heterotrophic organs compared to mature leaves, with roots being the most (13) C-enriched. The δ(13) C in fruits decreased during maturation, reflecting the accumulation in (13) C-depleted lipids. We further used observed δ(13) C values to compute plausible carbon fluxes using a steady-state model of (13) C-distribution including metabolic isotope effects ((12) v/(13) v). The results suggest that fruits represent a major respiratory loss (≈39% of total tree respiration) and that sink organs such as fruits are fed by sucrose from leaves. That is, glucose appears to be a quantitatively important compound in palm tissues, but computations indicate that it is involved in dynamic starch metabolism rather that C-exchange between organs. PMID:26228944

  5. Natural (13) C distribution in oil palm (Elaeis guineensis Jacq.) and consequences for allocation pattern.

    PubMed

    Lamade, Emmanuelle; Tcherkez, Guillaume; Darlan, Nuzul Hijri; Rodrigues, Rosario Lobato; Fresneau, Chantal; Mauve, Caroline; Lamothe-Sibold, Marlène; Sketriené, Diana; Ghashghaie, Jaleh

    2016-01-01

    Oil palm has now become one of the most important crops, palm oil representing nearly 25% of global plant oil consumption. Many studies have thus addressed oil palm ecophysiology and photosynthesis-based models of carbon allocation have been used. However, there is a lack of experimental data on carbon fixation and redistribution within palm trees, and important C-sinks have not been fully characterized yet. Here, we carried out extensive measurement of natural (13) C-abundance (δ(13) C) in oil palm tissues, including fruits at different maturation stages. We find a (13) C-enrichment in heterotrophic organs compared to mature leaves, with roots being the most (13) C-enriched. The δ(13) C in fruits decreased during maturation, reflecting the accumulation in (13) C-depleted lipids. We further used observed δ(13) C values to compute plausible carbon fluxes using a steady-state model of (13) C-distribution including metabolic isotope effects ((12) v/(13) v). The results suggest that fruits represent a major respiratory loss (≈39% of total tree respiration) and that sink organs such as fruits are fed by sucrose from leaves. That is, glucose appears to be a quantitatively important compound in palm tissues, but computations indicate that it is involved in dynamic starch metabolism rather that C-exchange between organs.

  6. Life cycle investigation of CO2 recovery and sequestration.

    PubMed

    Khoo, Hsien H; Tan, Reginald B H

    2006-06-15

    The Life Cycle Assessment of four CO2 recoverytechnologies, combined with nine CO2 sequestration systems, serves to expand the debate of CO2 mitigation methods beyond a single issue-prevention of global warming-to a wider range of environmental concerns: resource depletion, acidic and toxic gases, wastes, etc, so that the overall, and unexpected, environmental impacts may be revealed.

  7. Life cycle investigation of CO2 recovery and sequestration.

    PubMed

    Khoo, Hsien H; Tan, Reginald B H

    2006-06-15

    The Life Cycle Assessment of four CO2 recoverytechnologies, combined with nine CO2 sequestration systems, serves to expand the debate of CO2 mitigation methods beyond a single issue-prevention of global warming-to a wider range of environmental concerns: resource depletion, acidic and toxic gases, wastes, etc, so that the overall, and unexpected, environmental impacts may be revealed. PMID:16830576

  8. Testing the limits of the diffusion-production-equilibrium model of soil CO2: The effect of rapid carbonate precipitation on the pedogenic carbonate proxy

    NASA Astrophysics Data System (ADS)

    Wynn, J. G.; Chelladurai, J. L.

    2009-12-01

    A large body of terrestrial paleoenvironmental proxy research hinges on the well-established diffusion-production-equilibrium model of soil CO2. Although soil CO2 is the linchpin between the isotopic composition of pedogenic carbonate and the terrestrial biomass, it is not preserved directly in paleosols, and the model makes important boundary condition assumptions on processes that control its isotopic composition. The standard model assumes two-end member diffusional mixing between soil-respired CO2 and atmospheric CO2, and equilibrium precipitation of soil CaCO3 in an open system. We modified the boundary conditions of the standard model to specifically account for the flux and stable isotope fractionation of CO2 into the CaCO3 reservoir under partially closed-system conditions. Model calculations show that diversion of a relatively small fraction of the CO2 flux into CaCO3 results in a large change in the isotopic composition of soil CO2 and hence of CaCO3 at the sites of pedogenic carbonate accumulation. We also incubated two types of biomass (derived from C3 and C4 photosynthesis) in synthetic profiles with controlled conditions designed to test this modified model hypothesis. While soil CO2 from the surface horizons validated two-end member mixing, the δ13C values of CO2 from developing carbonate horizons was consistently 13C-depleted by several per mil compared to model predictions. This negative offset from the standard model mixing diagram (a Keeling Plot) is only consistent with the positive fractionation factor for carbonate precipitation in partially-closed system conditions. We also consider the conditions under which terrestrial paleoenvironmental proxy studies may be compromised by inappropriate boundary condition assumptions, in an effort to provide more robust model validation and application to terrestrial proxy data.

  9. Glacial CO2 Cycles: A Composite Scenario

    NASA Astrophysics Data System (ADS)

    Broecker, W. S.

    2015-12-01

    There are three main contributors to the glacial drawdown of atmospheric CO2 content: starvation of the supply of carbon to the ocean-atmosphere reservoir, excess CO2 storage in the deep sea, and surface-ocean cooling. In this talk, I explore a scenario in which all three play significant roles. Key to this scenario is the assumption that deep ocean storage is related to the extent of nutrient stratification of the deep Atlantic. The stronger this stratification, the larger the storage of respiration CO2. Further, it is my contention that the link between Milankovitch insolation cycles and climate is reorganizations of the ocean's thermohaline circulation leading to changes in the deep ocean's CO2 storage. If this is the case, the deep Atlantic d13C record kept in benthic foraminifera shells tells us that deep ocean CO2 storage follows Northern Hemisphere summer insolation cycles and thus lacks the downward ramp so prominent in the records of sea level, benthic 18O and CO2. Rather, the ramp is created by the damping of planetary CO2 emissions during glacial time intervals. As it is premature to present a specific scenario, I provide an example as to how these three contributors might be combined. As their magnitudes and shapes remain largely unconstrained, the intent of this exercise is to provoke creative thinking.

  10. Anaerobic Methane Oxidation in Soils - revealed using 13C-labelled methane tracers

    NASA Astrophysics Data System (ADS)

    Riekie, G. J.; Baggs, E. M.; Killham, K. S.; Smith, J. U.

    2008-12-01

    In marine sediments, anaerobic methane oxidation is a significant biogeochemical process limiting methane flux from ocean to atmosphere. To date, evidence for anaerobic methane oxidation in terrestrial environments has proved elusive, and its significance is uncertain. In this study, an isotope dilution method specifically designed to detect the process of anaerobic methane oxidation in methanogenic wetland soils is applied. Methane emissions of soils from three contrasting permanently waterlogged sites in Scotland are investigated in strictly anoxic microcosms to which 13C- labelled methane is added, and changes in the concentration and 12C/13C isotope ratios of methane and carbon dioxide are subsequently measured and used to calculate separate the separate components of the methane flux. The method used takes into account the 13C-methane associated with methanogenesis, and the amount of methane dissolved in the soil. The calculations make no prior assumptions about the kinetics of methane production or oxidation. The results indicate that methane oxidation can take place in anoxic soil environments. The clearest evidence for anaerobic methane oxidation is provided by soils from a minerotrophic fen site (pH 6.0) in Bin Forest underlain by ultra-basic and serpentine till. In the fresh soil anoxic microcosms, net consumption methane was observed, and the amount of headspace 13C-CO2 increased at a greater rate than the 12+13C-CO2, further proof of methane oxidation. A net increase in methane was measured in microcosms of soil from Murder Moss, an alkaline site, pH 6.5, with a strong calcareous influence. However, the 13C-CH4 data provided evidence of methane oxidation, both in the disappearance of C- CH4 and appearance of smaller quantities of 13C-CO2. The least alkaline (pH 5.5) microcosms, of Gateside Farm soil - a granitic till - exhibited net methanogenesis and the changes in 13C-CH4 and 13C-CO2 here followed the pattern expected if no methane is consumed

  11. Modelling urban δ13C variations in the Greater Toronto Area

    NASA Astrophysics Data System (ADS)

    Pugliese, S.; Vogel, F. R.; Murphy, J. G.; Worthy, D. E. J.; Zhang, J.; Zheng, Q.; Moran, M. D.

    2015-12-01

    Even in urbanized regions, carbon dioxide (CO2) emissions are derived from a variety of biogenic and anthropogenic sources and are influenced by atmospheric transport across borders. As policies are introduced to reduce the emission of CO2, there is a need for independent verification of emissions reporting. In this work, we aim to use carbon isotope (13CO2 and 12CO2) simulations in combination with atmospheric measurements to distinguish between CO2 sources in the Greater Toronto Area (GTA), Canada. This is being done by developing an urban δ13C framework based on existing CO2 emission data and forward modelling using a chemistry transport model, CHIMERE. The framework is designed to use region specific δ13C signatures of the dominant CO2 sources together with a CO2 inventory at a fine spatial and temporal resolution; the product is compared against highly accurate 13CO2 and 12CO2 ambient data. The strength of this framework is its potential to estimate both locally produced and regionally transported CO­2. Locally, anthropogenic CO­2 in urban areas is often derived from natural gas combustion (for heating) and gasoline/diesel combustion (for transportation); the isotopic signatures of these processes are significantly different (approximately d13CVPDB = -40 ‰ and -26 ‰ respectively) and can be used to infer their relative contributions. Furthermore, the contribution of transported CO2 can also be estimated as nearby regions often rely on other sources of heating (e.g. coal combustion), which has a very different signature (approximately d13CVPDB = -23 ‰). We present an analysis of the GTA in contrast to Paris, France where atmospheric observations are also available and 13CO2 has been studied. Utilizing our δ13C framework and differences in sectoral isotopic signatures, we quantify the relative contribution of CO2 sources on the overall measured concentration and assess the ability of this framework as a tool for tracing the evolution of sector

  12. CO2 Accounting and Risk Analysis for CO2 Sequestration at Enhanced Oil Recovery Sites.

    PubMed

    Dai, Zhenxue; Viswanathan, Hari; Middleton, Richard; Pan, Feng; Ampomah, William; Yang, Changbing; Jia, Wei; Xiao, Ting; Lee, Si-Yong; McPherson, Brian; Balch, Robert; Grigg, Reid; White, Mark

    2016-07-19

    Using CO2 in enhanced oil recovery (CO2-EOR) is a promising technology for emissions management because CO2-EOR can dramatically reduce sequestration costs in the absence of emissions policies that include incentives for carbon capture and storage. This study develops a multiscale statistical framework to perform CO2 accounting and risk analysis in an EOR environment at the Farnsworth Unit (FWU), Texas. A set of geostatistical-based Monte Carlo simulations of CO2-oil/gas-water flow and transport in the Morrow formation are conducted for global sensitivity and statistical analysis of the major risk metrics: CO2/water injection/production rates, cumulative net CO2 storage, cumulative oil/gas productions, and CO2 breakthrough time. The median and confidence intervals are estimated for quantifying uncertainty ranges of the risk metrics. A response-surface-based economic model has been derived to calculate the CO2-EOR profitability for the FWU site with a current oil price, which suggests that approximately 31% of the 1000 realizations can be profitable. If government carbon-tax credits are available, or the oil price goes up or CO2 capture and operating expenses reduce, more realizations would be profitable. The results from this study provide valuable insights for understanding CO2 storage potential and the corresponding environmental and economic risks of commercial-scale CO2-sequestration in depleted reservoirs.

  13. CO2 Accounting and Risk Analysis for CO2 Sequestration at Enhanced Oil Recovery Sites.

    PubMed

    Dai, Zhenxue; Viswanathan, Hari; Middleton, Richard; Pan, Feng; Ampomah, William; Yang, Changbing; Jia, Wei; Xiao, Ting; Lee, Si-Yong; McPherson, Brian; Balch, Robert; Grigg, Reid; White, Mark

    2016-07-19

    Using CO2 in enhanced oil recovery (CO2-EOR) is a promising technology for emissions management because CO2-EOR can dramatically reduce sequestration costs in the absence of emissions policies that include incentives for carbon capture and storage. This study develops a multiscale statistical framework to perform CO2 accounting and risk analysis in an EOR environment at the Farnsworth Unit (FWU), Texas. A set of geostatistical-based Monte Carlo simulations of CO2-oil/gas-water flow and transport in the Morrow formation are conducted for global sensitivity and statistical analysis of the major risk metrics: CO2/water injection/production rates, cumulative net CO2 storage, cumulative oil/gas productions, and CO2 breakthrough time. The median and confidence intervals are estimated for quantifying uncertainty ranges of the risk metrics. A response-surface-based economic model has been derived to calculate the CO2-EOR profitability for the FWU site with a current oil price, which suggests that approximately 31% of the 1000 realizations can be profitable. If government carbon-tax credits are available, or the oil price goes up or CO2 capture and operating expenses reduce, more realizations would be profitable. The results from this study provide valuable insights for understanding CO2 storage potential and the corresponding environmental and economic risks of commercial-scale CO2-sequestration in depleted reservoirs. PMID:27362472

  14. {sup 13}C-{sup 1}H and {sup 13}C-{sup 13}C spin couplings in [2`-{sup 13}C]2`-deoxyribonucleosides: Correlations with molecular structure

    SciTech Connect

    Bandyopadhyay, T.; Stripe, W.A.; Carmichael, I.; Serianni, A.S.; Wu, J.

    1997-02-19

    2`-Deoxyribonucleosides (2`-deoxyadenosine (1), 2`-depoxycytidine (2), thymidine (3)) singly enriched with {sup 13}C at C2` have been prepared and used to obtain one-, two-, and three-bond {sup 13}C-{sup 1}H and {sup 13}C-{sup 13}C spin-coupling constants involving C2`. Spin couplings in 1-3 involving C1` and C2`are also compared to corresponding values in ribonucleosides in order to assess the effects of nucleoside structure and conformation on J values within the furanose ring. {sup 1}J{sub C2`,H2`R} and {sup 1}J{sub C2`,H2`S} in 1-3 and {sup 1}J{sub C2`,H2`} in ribonucleosides depend on C-H bond orientation: {sup 1}J{sub C1`,H1`} in 1-3 and in ribonucleosides exhibits a similar dependence. The latter couplings appear to be essentially unaffected by N-glycoside torsion. {sup 1}J{sub CC} values depend on the number and distribution of electronegative substituents on the C-C fragment. A modified projection curve is proposed to aid in the interpretation of {sup 2}J{sub C2`,H1`} values; the presence of N substitution at C1` caused a shift to more negative couplings relative to the O-substituted analog. In contrast, {sup 2}J{sub C1`,H2`} is essentially unaffected by the same change in the electronegative substituent at C1`. {sup 2}J{sub CC} values within the furanose ring are determined buy two coupling pathways; in one case (i.e., {sup 2}J{sub C1`,C3`}), the observed coupling is shown to be the algebraic sum of the two couplings arising from each pathway. 41 refs., 4 figs., 2 tabs.

  15. Assessment of liver function in dogs using the 13C-galactose breath test.

    PubMed

    Silva, S; Wyse, C A; Goodfellow, M R; Yam, P S; Preston, T; Papasouliotis, K; Hall, E J

    2010-08-01

    The aim of this study was to evaluate the application of the 13C-galactose breath test (13C-GBT) in assessing canine liver function by applying it to a group of healthy dogs, and to a group with clinicopathological evidence of liver dysfunction. Breath samples were collected 30 min before ingestion of 13C-galactose, and then at regular intervals thereafter for 6 h. The proportion of 13CO2/12CO2 in the breath samples was measured by isotope-ratio mass spectrometry. There was no significant difference in recovery of 13CO2 in the diseased group, compared to the healthy controls, but there was considerable inter-subject variation in both groups, possibly due to differences in the rate of gastric emptying, which could preclude detection of alterations in hepatic metabolism of galactose. The results of this study do not support the application of the 13C-GBT for assessment of canine liver function. PMID:19546016

  16. Use of Isotope Ratio Determination (13C/12C) to Assess the Production Method of Sparkling Wine.

    PubMed

    Rossier, Joël S; Maury, Valérie; Gaillard, Laetitia; Pfammatter, Elmar

    2016-01-01

    The production of a sparkling wine can be performed with different methods taking from a few weeks to several years, which often justifies a difference in added value for the consumer. This paper presents the use of isotope ratio δ(13)C measurements combined with physico-chemical analyses for the determination of mislabelling of sparkling wines produced by 'ancestral', 'traditional', 'closed tank' or 'gasification' methods. This work shows that the isotope composition of CO(2) compared with that of the corresponding dried residue of wine (DRW) can assess whether carbonate CO(2) in a sparkling wine originates from alcohol fermentation or from artificial gas addition. Isotopic ratios expressed as δ(13)C(CO2) and δ(13)C(DRW) measurements have been obtained for each wine by gasbench isotopic ratio mass spectroscopy and cavity ring down infrared spectroscopy, respectively. When the difference between δ(13)C(CO2) and δ(13)C(DRW) is negative, the presence of artificial CO(2) can be undoubtedly inferred, which would exclude the production methods 'ancestral' or 'traditional' for instance. Other parameters such as alcohol content, sugar and acid distributions are also important to complete the analytical panel to aid fraud tracking.

  17. The delta 13C record of Devonian to Permian carbonates

    NASA Astrophysics Data System (ADS)

    Buggisch, W.

    2003-04-01

    A δ13Ccarb curve will be presented for samples spanning the time interval from the Silurian/Devonian to the Permian/Triassic boundary. Reliable data are usually based on analyses of brachiopod shells. Because of the huge reservoir of carbon in carbonates, also whole rock samples are suitable for stable carbon isotope analyses if they are not altered by meteoric water or by incorporation of re-oxidized organic carbon during diagenesis. There are several possibilities to test the quality of the data: (1) comparison of the δ13C record of whole rock samples with samples from brachiopod shells, (2) with the organic record, (3) analyses of the same time interval in different sections. If the same pattern of isotope data is observed in separa-ted palaeogeographic settings, it is probably caused by a change in the global carbon reservoir. Reliable δ13C data will be presented for the Devonian, Mississippian and Middle to Late Permian. During Pennsylvanian and Early Permian most carbonates were affected by meteoric diagenesis due to the large glacio-eustatic sea level changes of the Permo-Carboniferous glaciation. Long term variations (mean values for 10 Ma) are known from literature. Devonian δ13C values are about 0 to 2 ppm (V-PDB) they increase up to 5 to 6 ppm during the Mississippian - Pennsylvanian transition and drop sharply at the Permian Triassic boundary. The Devonian - Carboniferous trend is probably at least partly due to the evolution of land plants. Short term variations in the range of 0.1 to 1 Ma modify the long term trend significantly. Large positive excursions of δ13C up to 5 or 6 ppm are known from the Silurian - Devonian boundary and during the Middle Tournaisian of Laurentia and Europe. Many positive excursions of a magnitude of 2 to 3 ppm are observed, some are verified worldwide as for instance at the Frasnian - Famennian boundary which coincides with one of the largest extinction events in earth history. Short time variations in the isotopic

  18. Methanogenesis produces strong 13C-enrichment in stromatolites of Lagoa Salgada, Brazil: A modern analogue for Palaeo-/Neoproterozoic stromatolites?

    NASA Astrophysics Data System (ADS)

    Meister, Patrick; Birgel, Daniel; Lundberg, Rebecca; Horat, Thomas; Bontognali, Tomaso; Bahniuk Rumbelsperger, Anelize; Rezende, Carlos; Vásconcelos, Crisógono; McKenzie, Judith A.

    2015-04-01

    Holocene stromatolites characterized by unusually positive inorganic carbon isotope values (δ13C up to +16 ‰ relative to the Vienna Peedee Belemnite Standard; VPDB) are present in Lagoa Salgada, a seasonally brackish to hypersaline lagoon near Rio de Janeiro (Brazil). Such positive values cannot be explained by phototrophic fixation of CO2 alone. Instead, strong carbon isotope fractionation is commonly observed during methanogenesis, where isotopically light C is preferentially incorporated into methane and the residual inorganic carbon is 13C-enriched. We suggest that methanogenesis was the dominating process of organic carbon mineralization during the growth of the stromatolites. Indeed, the presence of dissolved methane in porewater (up to 5 mM) and the archaeal membrane lipid archaeol showing relatively high δ13C values (-15 to 0 ‰ VPDB) indicates that methanogenic archaea are present and active in the modern lagoon sediment. Moreover, 13C-depleted hopanoids diplopterol and 3-methylated bishomohopanoic acid (both -40‰ VPDB) are preserved in lagoon sediments and are most likely derived from aerobic methanotrophic bacteria thriving in the methane-enriched water column. Loss of isotopically light methane through the water column to the atmosphere would explain the residual 13C-enriched pool of dissolved inorganic carbon from where the carbonate constituting the stromatolites precipitated. The predominance of methanogenic archaea in the lagoon is most likely a result of sulphate limitation suppressing the activity of sulphate-reducing bacteria under brackish conditions in a seasonally humid tropical and arid environment. Also in the modern sediments, sulphate reduction activity is very low. Under dominating methanogenic conditions and in absence of an efficient carbonate-inducing metabolic process, we propose that stromatolite formation in Lagoa Salgada was abiotically induced while the 13C-enriched organic and inorganic carbon pools are due to

  19. Positive feedback between increasing atmospheric CO2 and ecosystem productivity

    NASA Astrophysics Data System (ADS)

    Gelfand, I.; Hamilton, S. K.; Robertson, G. P.

    2009-12-01

    Increasing atmospheric CO2 will likely affect both the hydrologic cycle and ecosystem productivity. Current assumptions that increasing CO2 will lead to increased ecosystem productivity and plant water use efficiency (WUE) are driving optimistic predictions of higher crop yields as well as greater availability of freshwater resources due to a decrease in evapotranspiration. The plant physiological response that drives these effects is believed to be an increase in carbon uptake either by (a) stronger CO2 gradient between the stomata and the atmosphere, or by (b) reduced CO2 limitation of enzymatic carboxylation within the leaf. The (a) scenario will lead to increased water use efficiency (WUE) in plants. However, evidence for increased WUE is mostly based on modeling studies, and experiments producing a short duration or step-wise increase in CO2 concentration (e.g. free-air CO2 enrichment). We hypothesize that the increase in atmospheric CO2 concentration is having a positive effect on ecosystem productivity and WUE. To investigate this hypothesis, we analyzed meteorological, ANPP, and soil CO2 flux datasets together with carbon isotopic ratio (13C/12C) of archived plant samples from the long term ecological research (LTER) program at Kellogg Biological Station. The datasets were collected between 1989 and 2007 (corresponding to an increase in atmospheric CO2 concentration of ~33 ppmv at Mauna Loa). Wheat (Triticum aestivum) samples taken from 1989 and 2007 show a significant decrease in the C isotope discrimination factor (Δ) over time. Stomatal conductance is directly related to Δ, and thus Δ is inversely related to plant intrinsic WUE (iWUE). Historical changes in the 13C/12C ratio (δ13C) in samples of a perennial forb, Canada goldenrod (Solidago canadensis), taken from adjacent successional fields, indicate changes in Δ upon uptake of CO2 as well. These temporal trends in Δ suggest a positive feedback between the increasing CO2 concentration in the

  20. 13C Incorporation into Signature Fatty Acids as an Assay for Carbon Allocation in Arbuscular Mycorrhiza

    PubMed Central

    Olsson, Pål Axel; van Aarle, Ingrid M.; Gavito, Mayra E.; Bengtson, Per; Bengtsson, Göran

    2005-01-01

    The ubiquitous arbuscular mycorrhizal fungi consume significant amounts of plant assimilated C, but this C flow has been difficult to quantify. The neutral lipid fatty acid 16:1ω5 is a quantitative signature for most arbuscular mycorrhizal fungi in roots and soil. We measured carbon transfer from four plant species to the arbuscular mycorrhizal fungus Glomus intraradices by estimating 13C enrichment of 16:1ω5 and compared it with 13C enrichment of total root and mycelial C. Carbon allocation to mycelia was detected within 1 day in monoxenic arbuscular mycorrhizal root cultures labeled with [13C]glucose. The 13C enrichment of neutral lipid fatty acid 16:1ω5 extracted from roots increased from 0.14% 1 day after labeling to 2.2% 7 days after labeling. The colonized roots usually were more enriched for 13C in the arbuscular mycorrhizal fungal neutral lipid fatty acid 16:1ω5 than for the root specific neutral lipid fatty acid 18:2ω6,9. We labeled plant assimilates by using 13CO2 in whole-plant experiments. The extraradical mycelium often was more enriched for 13C than was the intraradical mycelium, suggesting rapid translocation of carbon to and more active growth by the extraradical mycelium. Since there was a good correlation between 13C enrichment in neutral lipid fatty acid 16:1ω5 and total 13C in extraradical mycelia in different systems (r2 = 0.94), we propose that the total amount of labeled C in intraradical and extraradical mycelium can be calculated from the 13C enrichment of 16:1ω5. The method described enables evaluation of C flow from plants to arbuscular mycorrhizal fungi to be made without extraction, purification and identification of fungal mycelia. PMID:15870350

  1. *d13C composition of primary producers and role of detritus in a freshwater coastal ecosystem

    USGS Publications Warehouse

    Keough, J.R.; Hagley, C.A.; Sierszen, M.

    1998-01-01

    Stable-isotope ratio signatures of primary producers in a coastal wetland and in adjacent offshore waters of western Lake Superior indicated that phytoplankton are the primary source of carbon for the grazing food web of this ecosystem. This study outlines the possible roles of other autotrophs in this regard. Isotopic signatures of macrophytes reflected their life-form-associated constraints on diffusion of inorganic carbon. Data indicated that differences between wetland and lake phytoplankton may be explained by the isotopic signatures of their dissolved inorganic carbon (DIC) sources. Results of an in situ experiment showed that respiration associated with macrophyte decomposition is capable of enriching surrounding water with significant amounts of *d13C-depleted DIC and lowering the net *d13C ratio of DIC in water in low-turbulence situations. The *d13C ratio for wetland phytoplankton may be depleted relative to pelagic algae because the fixed carbon is derived from decomposing detritus.

  2. Noble gas and carbon isotopic evidence for CO2-driven silicate dissolution in a recent natural CO2 field

    NASA Astrophysics Data System (ADS)

    Dubacq, Benoît; Bickle, Mike J.; Wigley, Max; Kampman, Niko; Ballentine, Chris J.; Sherwood Lollar, Barbara

    2012-08-01

    Secure storage of anthropogenic carbon dioxide (CO2) in geological reservoirs requires predicting gas-water-rock interactions over millennial timescales. Noble gases and carbon isotope measurements can be used to shed light on the nature of competing dissolution-precipitation processes over different timescales, from the fast dissolution of gaseous CO2 in groundwater to more sluggish reactions involving dissolution and precipitation of newly formed minerals in the reservoir. Here we study a compilation of gas analyses including noble gases and δ13C of CO2 from nine different natural CO2 reservoirs. Amongst these reservoirs, the Bravo Dome CO2 field (New Mexico, USA) shows distinct geochemical trends which are explained by degassing of noble gases from groundwater altering the composition of the gas phase. This groundwater degassing is synchronous with the dissolution of CO2 in groundwater. Progressive creation of alkalinity via CO2-promoted mineral dissolution is required to explain the observed positive correlation between CO2/3He and δ13C of the gas phase, a unique feature of Bravo Dome. The differences between Bravo Dome and other natural CO2 reservoirs are likely explained by the more recent filling of Bravo Dome, reflecting CO2-water-rock interactions over thousands of years rather than over millions of years in older reservoirs.

  3. Halloysite Nanotubes Capturing Isotope Selective Atmospheric CO2

    NASA Astrophysics Data System (ADS)

    Jana, Subhra; Das, Sankar; Ghosh, Chiranjit; Maity, Abhijit; Pradhan, Manik

    2015-03-01

    With the aim to capture and subsequent selective trapping of CO2, a nanocomposite has been developed through selective modification of the outer surface of the halloysite nanotubes (HNTs) with an organosilane to make the nanocomposite a novel solid-phase adsorbent to adsorb CO2 from the atmosphere at standard ambient temperature and pressure. The preferential adsorption of three major abundant isotopes of CO2 (12C16O2, 13C16O2, and 12C16O18O) from the ambient air by amine functionalized HNTs has been explored using an optical cavity-enhanced integrated cavity output spectroscopy. CO2 adsorption/desorption cycling measurements demonstrate that the adsorbent can be regenerated at relatively low temperature and thus, recycled repeatedly to capture atmospheric CO2. The amine grafted halloysite shows excellent stability even in oxidative environments and has high efficacy of CO2 capture, introducing a new route to the adsorption of isotope selective atmospheric CO2.

  4. Temperature-mediated changes in microbial carbon use efficiency and 13C discrimination

    NASA Astrophysics Data System (ADS)

    Lehmeier, Christoph A.; Ballantyne, Ford, IV; Min, Kyungjin; Billings, Sharon A.

    2016-06-01

    Understanding how carbon dioxide (CO2) flux from ecosystems feeds back to climate warming depends in part on our ability to quantify the efficiency with which microorganisms convert organic carbon (C) into either biomass or CO2. Quantifying ecosystem-level respiratory CO2 losses often also requires assumptions about stable C isotope fractionations associated with the microbial transformation of organic substrates. However, the diversity of organic substrates' δ13C and the challenges of measuring microbial C use efficiency (CUE) in their natural environment fundamentally limit our ability to project ecosystem C budgets in a warming climate. Here, we quantify the effect of temperature on C fluxes during metabolic transformations of cellobiose, a common microbial substrate, by a cosmopolitan microorganism growing at a constant rate. Biomass C specific respiration rate increased by 250 % between 13 and 26.5 °C, decreasing CUE from 77 to 56 %. Biomass C specific respiration rate was positively correlated with an increase in respiratory 13C discrimination from 4.4 to 6.7 ‰ across the same temperature range. This first demonstration of a direct link between temperature, microbial CUE, and associated isotope fluxes provides a critical step towards understanding δ13C of respired CO2 at multiple scales, and towards a framework for predicting future ecosystem C fluxes.

  5. Decarboxylation of [1-(13)C]leucine by hydroxyl radicals.

    PubMed

    Guitton, J; Tinardon, F; Lamrini, R; Lacan, P; Desage, M; Francina, A

    1998-08-01

    The decarboxylation of [1-13C]leucine by hydroxyl radicals was studied by using gas chromatography-isotope ratio mass spectrometry (GC-IRMS) to follow the production of 13CO2. A Fenton reaction between a (Fe2+)-porphyrin and hydrogen peroxide under aerobic conditions yielded hydroxyl radicals. The decarboxylation rates (VLeu) measured by GC-IRMS were dependent on [1-13C]leucine, porphyrin and hydrogen peroxide concentrations. The 13CO2 production was also dependent on bicarbonate or carbon dioxide added in the reaction medium. Bicarbonate facilitated 13CO2 production, whereas carbon dioxide decreased 13CO2 production. Proton effects on some decarboxylation intermediates could explain bicarbonate or carbon dioxide effects. No effect on the decarboxylation rates was observed in the presence of the classical hydroxyl radicals scavengers dimethyl sulfoxide, mannitol, and uric acid. By contrast, a competitive effect with a strong decrease of the decarboxylation rates was observed in the presence of various amino acids: unlabeled leucine, valine, phenylalanine, cysteine, lysine, and histidine. Two reaction products, methyl-4 oxo-2 pentanoate and methyl-3 butanoate were identified by gas chromatography-mass spectrometry in comparison with standards. The present results suggest that [1-13C]leucine can participate to the coordination sphere of (Fe2+)-porphyrin, with a caged process of the hydroxyl radicals which cannot get out of the coordination sphere. PMID:9680180

  6. Deglacial change in terrestrial carbon storage estimated by benthic δ13C

    NASA Astrophysics Data System (ADS)

    Peterson, C. D.; Lisiecki, L. E.

    2012-12-01

    Terrestrial carbon storage is dramatically decreased during glacial periods due to cold temperatures, increased aridity, and the presence of large ice sheets on land. Most of the carbon released by the terrestrial biosphere is stored in the glacial ocean, where the isotopic signature of terrestrial carbon (δ13C terrestrial carbon = -25‰) is observed as a 0.32-0.7‰ depletion in benthic foraminiferal δ13C. The wide range in estimated δ13C change is due to different subsets of benthic δ13C data and different methods of weighting the mean δ13C by volume. We estimate the glacial-interglacial δ13C change of marine DIC using benthic Cibicides spp. δ13C records from 356 core sites (five to eight times as many as previous studies). We divide the ocean into 9 regions to generate linear regressions of regional δ13C versus depth (0.5-5 km) for the late Holocene (0-6 ka) and LGM (18-21 ka) and estimate a mean δ13C decrease of 0.53 +/-0.06‰ (2σ), equivalent to 715-885 Pg C. Our estimate is in good agreement with a vegetation reconstruction estimate of ~750-1050 Pg C [Crowley, 1995] and a recent model estimate of ~670 Pg C [Kohler, 2010] and is ~66% larger than the previous whole ocean δ13C estimate of 0.32‰ [Duplessy et al., 1988]. To evaluate the uncertainty of our estimate, we used a bootstrapping approach (100,000 iterations) to generate realistic error estimates for our different regional line-fits of δ13C vs. depth for both the LGM and Holocene time slices. We propagated the bootstrapped linear regressions through all of our calculations to estimate a 95% confidence interval for global δ13C change (+/-0.06‰) and the uncertainty contribution from each region. The largest sources of uncertainty in our estimate are the South Pacific (35% of variance) and Indian Ocean (36% of variance) because they are the regions with the largest volumes and sparsest δ13C data. Additionally, we note that mean benthic δ13C change could in part reflect glacial

  7. Variation in woody plant delta(13)C along a topoedaphic gradient in a subtropical savanna parkland.

    PubMed

    Bai, Edith; Boutton, Thomas W; Liu, Feng; Wu, X Ben; Archer, Steven R

    2008-06-01

    delta(13)C values of C(3) plants are indicators of plant carbon-water relations that integrate plant responses to environmental conditions. However, few studies have quantified spatial variation in plant delta(13)C at the landscape scale. We determined variation in leaf delta(13)C, leaf nitrogen per leaf area (N(area)), and specific leaf area (SLA) in April and August 2005 for all individuals of three common woody species within a 308 x 12-m belt transect spanning an upland-lowland topoedaphic gradient in a subtropical savanna in southern Texas. Clay content, available soil moisture, and soil total N were all negatively correlated with elevation. The delta(13)C values of Prosopis glandulosa (deciduous N(2)-fixing tree legume), Condalia hookeri (evergreen shrub), and Zanthoxylum fagara (evergreen shrub) leaves increased 1-4 per thousand with decreasing elevation, with the delta(13)C value of P. glandulosa leaves being 1-3 per thousand higher than those of the two shrub species. Contrary to theory and results from previous studies, delta(13)C values were highest where soil water was most available, suggesting that some other variable was overriding or interacting with water availability. Leaf N(area) was positively correlated with leaf delta(13)C of all species (p < 0.01) and appeared to exert the strongest control over delta(13)C along this topoedaphic gradient. Since leaf N(area) is positively related to photosynthetic capacity, plants with high leaf N(area) are likely to have low p (I)/p (a) ratios and therefore higher delta(13)C values, assuming stomatal conductance is constant. Specific leaf area was not correlated significantly with leaf delta(13)C. Following a progressive growing season drought in July/August, leaf delta(13)C decreased. The lower delta(13)C in August may reflect the accumulation of (13)C-depleted epicuticular leaf wax. We suggest control of leaf delta(13)C along this topoedaphic gradient is mediated by leaf N(area) rather than by stomatal

  8. Investigating 14CO2 chamber methodologies

    NASA Astrophysics Data System (ADS)

    Egan, J. E.; Phillips, C. L.; Nickerson, N. R.; Risk, D. A.

    2012-12-01

    The radiogenic isotope of carbon (14C) is an exceptionally useful tool in studying soil respired CO2, providing information about soil turnover rates, depths of production and the biological sources of production through partitioning. Unfortunately, little work has been done to thoroughly investigate the possibility of inherent biases in the current measurement techniques for 14CO2, caused by disturbances to the soil's natural diffusive regime, because of high costs and sampling logistics. Our aim in this study is to investigate the degree of bias present in the current sampling methodologies using a numerical model and laboratory calibration device. Four chamber techniques were tested numerically with varying fraction modern of production, δ13C of production, collar lengths, flux rates and diffusivities. Two of the chambers were then tested on the lab calibration device. One of these chambers, Iso-FD, has recently been tested for its use as a 13CO2 chamber and it does not induce gas transport fractionation biases present in other 13CO2 sampling methodologies. We then implemented it in the field to test its application as a 14CO2 chamber because of its excellent performance as a 13CO2chamber. Presented here are the results from the numerical modeling experiment, the laboratory calibration experiment and preliminary field results from the Iso-FD chamber.

  9. CO2 blood test

    MedlinePlus

    Bicarbonate test; HCO3-; Carbon dioxide test; TCO2; Total CO2; CO2 test - serum ... Many medicines can interfere with blood test results. Your health care provider will tell you if you need to stop taking any medicines before you have this test. DO ...

  10. Stable Carbon Isotopes (δ 13C) in Coral Skeletons: Experimental Approach and Applications for Paleoceanography

    NASA Astrophysics Data System (ADS)

    Grottoli, A. G.

    2004-12-01

    Scleractinian corals obtain fixed carbon via photosynthesis by their endosymbiotic algae (zooxanthellae) and via hetertrophy (injestion of zooplankton, δ 13C ≈ -17 to -22‰ ). Carbon dioxide (CO2) used for photosynthesis is obtained from seawater (δ 13C ≈ 0%) or from respired CO2 within the coral host. The δ 13C of the carbon used in the formation of the underlying coral skeleton is fractionated as a result of both of these metabolic processes. Here I have pooled evidence from several field and tank experiments on the effect of photosynthesis and heterotrophy of coral skeletal δ 13C. In the experiments, decreases in light levels due to shading or depth resulted in a significant decrease in skeletal δ 13C in all species studied (Pavona gigantea, Pavona clavus, Porites compressa). Decreases in photosynthesis in bleached corals also resulted in a decrease in skeletal δ 13C compared to non-bleached corals growing under the same conditions and at the same location. Skeletal δ 13C also decreased at higher than normal light levels most likely due to photoinhibition. Thus, decreases in photosynthesis due to reduced light levels, due to bleaching-induced decreases in chlorophyll a concentrations, or due to photodamage-induced decreases in functional cholorphyll a, results in significant δ 13C decreases. Comprehensive interpretation of all of the data showed that changes in photosynthesis itself can drive the changes in δ 13C. In field experiments, the addition of natural concentrations of zooplankton to the diet resulted in decreases in skeletal δ 13C. Such a decrease was more pronounced with depth and in P. gigantea compared to P. clavus. In situ feeding experiments have since confirmed these findings. However under tank conditions with unaturally high feeding rates, enhanced nitrogen supply in the diet can disrupt the coral-algal symbiosis, stimlate zooxanthellae growth and photosynthesis, and cause an incrase in skeletal δ 13C. It is proposed that under

  11. Soil carbon and nitrogen cycling and storage throughout the soil profile in a sweetgum plantation after 11 years of CO2-enrichment

    SciTech Connect

    Iversen, Colleen M; Keller, Dr. Jason K.; Garten Jr, Charles T; Norby, Richard J

    2012-01-01

    Increased partitioning of carbon (C) to fine roots under elevated [CO2], especially deep in the soil profile, could alter soil C and nitrogen (N) cycling in forests. After more than 11 years of free-Air CO2 enrichment in a Liquidambar styraciflua L. (sweetgum) plantation in Oak Ridge, TN, USA, greater inputs of fine roots resulted in the incorporation of new C (i.e., C with a depleted 13C) into root-derived particulate organic matter (POM) pools to 90-cm depth. Even though production in the sweetgum stand was limited by soil N availability, soil C and N content increased over time, and were greater throughout the soil profile under elevated [CO2] at the conclusion of the experiment. However, greater C inputs under elevated [CO2] did not result in increased net N immobilization or C mineralization rates in long-term laboratory incubations, and did not appear to prime the decomposition of older SOM. The 13CO2 of the C mineralized from the incubated soil closely tracked the 13C of the labile POM pool in the elevated [CO2] treatment, especially in shallower soil, and did not indicate the decomposition of older (i.e., pre-experiment) SOM. While potential C mineralization rates were positively and linearly related to total soil organic matter (SOM) C content in the top 30 cm of soil, this relationship did not hold in deeper soil. Taken together with an increased mean residence time of C in deeper soil pools, these findings indicate that C inputs from relatively deep roots under elevated [CO2] may have increased potential for long-term storage. Expanded representation of biogeochemical cycling throughout the soil profile may improve model projections of future forest responses to rising atmospheric [CO2].

  12. Co2 geological sequestration

    SciTech Connect

    Xu, Tianfu

    2004-11-18

    Human activities are increasingly altering the Earth's climate. A particular concern is that atmospheric concentrations of carbon dioxide (CO{sub 2}) may be rising fast because of increased industrialization. CO{sub 2} is a so-called ''greenhouse gas'' that traps infrared radiation and may contribute to global warming. Scientists project that greenhouse gases such as CO{sub 2} will make the arctic warmer, which would melt glaciers and raise sea levels. Evidence suggests that climate change may already have begun to affect ecosystems and wildlife around the world. Some animal species are moving from one habitat to another to adapt to warmer temperatures. Future warming is likely to exceed the ability of many species to migrate or adjust. Human production of CO{sub 2} from fossil fuels (such as at coal-fired power plants) is not likely to slow down soon. It is urgent to find somewhere besides the atmosphere to put these increased levels of CO{sub 2}. Sequestration in the ocean and in soils and forests are possibilities, but another option, sequestration in geological formations, may also be an important solution. Such formations could include depleted oil and gas reservoirs, unmineable coal seams, and deep saline aquifers. In many cases, injection of CO2 into a geological formation can enhance the recovery of hydrocarbons, providing value-added byproducts that can offset the cost of CO{sub 2} capture and sequestration. Before CO{sub 2} gas can be sequestered from power plants and other point sources, it must be captured. CO{sub 2} is also routinely separated and captured as a by-product from industrial processes such as synthetic ammonia production, H{sub 2} production, and limestone calcination. Then CO{sub 2} must be compressed into liquid form and transported to the geological sequestration site. Many power plants and other large emitters of CO{sub 2} are located near geological formations that are amenable to CO{sub 2} sequestration.

  13. Chlorophyll a specific Δ14C, δ13C and δ15N values in stream periphyton: implications for aquatic food web studies

    NASA Astrophysics Data System (ADS)

    Ishikawa, N. F.; Yamane, M.; Suga, H.; Ogawa, N. O.; Yokoyama, Y.; Ohkouchi, N.

    2015-07-01

    We determined the isotopic composition of chlorophyll a in periphytic algae attached to a streambed substrate (periphyton). The samples were collected from a stream flowing on limestone bedrock in the Seri River, central Japan. Stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) and natural radiocarbon abundances (Δ14C) were measured in chlorophyll a (δ13Cchl, δ15Nchl and Δ14Cchl) and bulk (δ13Cbulk, δ15Nbulk and Δ14Cbulk) for periphyton, pure aquatic primary producer (Cladophora sp.) and terrestrial primary producer (Quercus glauca). Periphyton δ13Cbulk and δ13Cchl values did not necessarily correspond to δ13Cbulk for an algal-grazing specialist (Mayfly larva, Epeorus latifolium), suggesting that periphyton δ13C values do not faithfully trace carbon transfer between primary producers and primary consumers. Periphyton Δ14Cchl values (-258 ‰ in April and -190 ‰ in October) were slightly lower than Δ14Cbulk values (-228 ‰ in April and -179 ‰ in October), but were close to the Δ14C value for dissolved inorganic carbon (DIC) (-217 ± 31 ‰), which is a mixture of weathered carbonates (Δ14C = -1000 ‰) and dissolved atmospheric CO2 (Δ14C approximately +30 ‰ in 2013). Δ14Cchl values were also close to Δ14Cbulk for E. latifolium (-215 ‰ in April and -199 ‰ in October) and Cladophora sp. (-210 ‰), whereas the Δ14Cbulk value for Q. glauca (+27 ‰) was closer to Δ14C for atmospheric CO2. Although the bulk isotopic composition of periphyton is recognised as a surrogate for the photosynthetic algal community, natural periphyton is a mixture of aquatic and terrestrial organic materials. Our results indicate that the bulk periphyton matrix at the study site consists of 89 to 95 % algal carbon (derived from 14C-depleted DIC) and 5 to 11 % terrestrial organic carbon (derived from 14C-enriched atmospheric CO2).

  14. Outsourcing CO2 Emissions

    NASA Astrophysics Data System (ADS)

    Davis, S. J.; Caldeira, K. G.

    2009-12-01

    CO2 emissions from the burning of fossil fuels are the primary cause of global warming. Much attention has been focused on the CO2 directly emitted by each country, but relatively little attention has been paid to the amount of emissions associated with consumption of goods and services in each country. This consumption-based emissions inventory differs from the production-based inventory because of imports and exports of goods and services that, either directly or indirectly, involved CO2 emissions. Using the latest available data and reasonable assumptions regarding trans-shipment of embodied carbon through third-party countries, we developed a global consumption-based CO2 emissions inventory and have calculated associated consumption-based energy and carbon intensities. We find that, in 2004, 24% of CO2 emissions are effectively outsourced to other countries, with much of the developed world outsourcing CO2 emissions to emerging markets, principally China. Some wealthy countries, including Switzerland and Sweden, outsource over half of their consumption-based emissions, with many northern Europeans outsourcing more than three tons of emissions per person per year. The United States is both a big importer and exporter of emissions embodied in trade, outsourcing >2.6 tons of CO2 per person and at the same time as >2.0 tons of CO2 per person are outsourced to the United States. These large flows indicate that CO2 emissions embodied in trade must be taken into consideration when considering responsibility for increasing atmospheric greenhouse gas concentrations.

  15. Multi-year estimates of plant and ecosystem 13C discrimination at AmeriFlux sites

    NASA Astrophysics Data System (ADS)

    Dang, X.; Lai, C.; Hollinger, D. Y.; Bush, S.; Randerson, J. T.; Law, B. E.; Schauer, A. J.; Ehleringer, J.

    2011-12-01

    We estimated plant and ecosystem 13C discrimination continuously at 8 AmeriFlux sites (Howland Forest, Harvard Forest, Wind River Forest, Rannells Prairie, Freeman Ranch, Chestnut Ridge, Metolius, and Marys River fir) over 8 years (2002-2009). We used an observation-based approach from weekly measurements of eddy covariance CO2 fluxes and their 13C/12C ratios to estimate photosynthetic 13C discrimination (△A) and respiration (δ13CR) on seasonal and interannual time scales. The coordinated, systematic flask sampling across the AmeriFlux subnetwork were used for cross-site synthesis of monthly flux estimates [Dang et al. Combining tower mixing ratio and community model data to estimate regional-scale net ecosystem carbon exchange by boundary layer inversion over 4 flux towers in the U.S.A., Journal of Geophysical Research-Biogeosciences, in press]. Here, we evaluated environmental factors that also influenced temporal variability in △A and δ13CR from daily to interannual time scales, comparing atmospheric 13C/12C measurements, leaf and needle organic matter, and tree ring cellulose. Across these major biomes that dominate the continent, we show differential ecophysiological responses to environmental stresses, among which water availability appeared to be a dominant factor. Our decadal measurement period provided robust estimates of atmospheric 13C discrimination by terrestrial ecosystems, but also suggest regions where enhanced monitoring efforts are required (e.g., 13C/12C emission from fire and urban metabolism; increased temporal resolution of 13C measurements in stress-sensitive ecosystems) to make atmospheric 13C/12C measurements an effective constraint for continental-scale assessments of the terrestrial carbon cycle.

  16. A method for simultaneous echo planar imaging of hyperpolarized 13C pyruvate and 13C lactate

    NASA Astrophysics Data System (ADS)

    Reed, Galen D.; Larson, Peder E. Z.; von Morze, Cornelius; Bok, Robert; Lustig, Michael; Kerr, Adam B.; Pauly, John M.; Kurhanewicz, John; Vigneron, Daniel B.

    2012-04-01

    A rapid echo planar imaging sequence for dynamic imaging of [1-13C] lactate and [1-13C] pyruvate simultaneously was developed. Frequency-based separation of these metabolites was achieved by spatial shifting in the phase-encoded direction with the appropriate choice of echo spacing. Suppression of the pyruvate-hydrate and alanine resonances is achieved through an optimized spectral-spatial RF waveform. Signal sampling efficiency as a function of pyruvate and lactate excitation angle was simulated using two site exchange models. Dynamic imaging is demonstrated in a transgenic mouse model, and phantom validations of the RF pulse frequency selectivity were performed.

  17. Tracing solid waste leachate in groundwater using δ13 C from dissolved inorganic carbon.

    PubMed

    Haarstad, Ketil; Mæhlum, Trond

    2013-01-01

    Tracers can be used to monitor emissions of leachate from landfills in order to detect hydrological pathways and to evaluate environmental pollution. We investigated the stable carbon isotope ratio (δ(13)CCO (2)) in dissolved inorganic carbon and tritium ((3)H) in water, in addition to the tracers of pollution commonly found in relatively high concentrations in leachate, such as chloride (Cl), organic matter (COD), nitrogen (total and NH(4)-N), iron (Fe), electrical conductivity (EC) and pH. The sampling was performed at seven landfills in the south-eastern part of Norway during a period of 5 years. The objective was to evaluate the potential for tracing leachate in the environment with emphasis on groundwater pollution. By measuring the δ(13)CCO (2) in leachates, groundwaters and surface waters, the influence of leachate can be identified. The value of δ(13)CCO (2) varied from-5.5 to 25.9 ‰ in leachate, from-25.4 to 14.7 ‰ in groundwater and from-19.7 to-13.1 ‰ in creeks. A comparison of the carbon isotope ratio with COD, EC and the concentrations of total and NH (4)-N, Cl and Fe showed that δ(13)CCO (2) is a good tracer for leachate due to higher sensitivity compared to other parameters. The mean concentrations of all the studied parameters were higher in the leachate samples; however, only the carbon isotope ratio showed significant differences between all the groups with strong and middle pollution and samples with low pollution, showing that it can be used as a convenient tracer for leachate in groundwater and surface water. The carbon isotope ratio showed strong correlation between nitrogen, EC and bicarbonate, but not with pH. Tritium was only sporadically found in measureable concentrations and is not considered as a suitable tracer at the sampled locations.

  18. Extraordinary 13C enrichment of diether lipids at the Lost City Hydrothermal Field indicates a carbon-limited ecosystem

    NASA Astrophysics Data System (ADS)

    Bradley, Alexander S.; Hayes, John M.; Summons, Roger E.

    2009-01-01

    Active and inactive carbonate chimneys from the Lost City Hydrothermal Field contain up to 0.6% organic carbon with diverse lipid assemblages. The δ 13C values of total organic carbon range from -21.5‰ vs. VPDB at an extinct carbonate chimney to -2.8‰ at a 70 °C, actively venting carbonate chimney. Samples collected at locations with total organic carbon with δ 13C > -15‰ also contained high abundances of isoprenoidal and nonisoprenoidal diether lipids. Samples with TOC more depleted in 13C lacked or contained lower amounts of these diethers. Isoprenoidal diethers, including sn-2 hydroxyarchaeol, sn-3 hydroxyarchaeol, and putative dihydroxyarchaeol, are likely to derive from methanogenic archaea. These compounds have δ 13C values ranging from -2.9 to +6.7‰ vs. VPDB. Nonisoprenoidal diethers and monoethers are presumably derived from bacteria, and have structures similar to those produced by sulfate-reducing bacteria in culture and at cold seeps. In samples that also contained abundant hydroxyarchaeols, these diethers have δ 13C values between -11.8 and +3.6‰. In samples without abundant hydroxyarchaeols, the nonisoprenoidal diethers were typically more depleted in 13C, with δ 13C as low as -28.7‰ in chimneys and -45‰ in fissures. The diethers at Lost City are probably derived from hydrogen-consuming methanogens and bacteria. High hydrogen concentrations favor methanogenesis over methanotrophy and allow the concurrent growth of methanogens and sulfate-reducing bacteria. The unusual enrichment of 13C in lipids can be attributed to nearly complete consumption of bioavailable carbon in vent fluids. Under carbon-limited conditions, the isotope effects that usually lead to 13C-depletion in organic material cannot be expressed. Consequently, metabolic products such as lipids and methane have δ 13C values typical of abiotic carbon.

  19. Effects of temperature and substrate stoichiometry on microbial specific respiration rate, carbon use efficiency, and 13C fractionation

    NASA Astrophysics Data System (ADS)

    Min, K.; Lehmeier, C.; Sellers, M.; Chen, Y.; Ballantyne, F.; Billings, S. A.

    2013-12-01

    Microbial activity contributes up to 60% of soil respiration. However, uncertainty in microbial respiration with rising temperature has previously prevented better predictions of the amount and the source of carbon (C) respired from soil. Three key variables of microbial C economies are of particular interest for estimating microbially mediated C release with temperature: (1) specific respiration rate (SRR), which is microbial CO2 release per microbial biomass-C, (2) carbon use efficiency (CUE), which determines how much organic C consumed by microbes is transformed into biomass, and (3) changes in the δ13C of respired CO2 with temperature, which suggests the form of organic C mineralized and helps to partition soil respiration in plant- and microbe-derived CO2. However, it is difficult to obtain these variables in intact soils, due to confounding factors that influence the amount and δ13C of respired CO2. Here we present an experimental approach that allows us to grow an isolated microbial population on well-characterized organic substrates and directly measure SRR, CUE and δ13C of respired CO2. We explored the effect of temperature on those variables, and how it changes with C:N of the substrate provided. This is important given various substrates available for microbial decay, and the potential for changing microbial CUE with substrate C:N. This approach thus can help constrain potential microbial C loss with warming as soil organic substrates with varying C:N are decomposed. We hypothesized that (1) increased SRR and declined CUE with warming would be more evident at higher C:N, (2) apparent 13C fractionation between biomass and respired CO2 would decrease with temperature due to C limitation, and (3) this fractionation would be higher for high C:N. Pseudomonas fluorescens (a ubiquitous Gram-negative bacterium) was grown at 0.13 h-1 in a chemostat from 13 to 26.5°C. The concentration of cellobiose, the sole C source with constant δ13C, was adjusted to have

  20. Quantitative identification of metastable magnesium carbonate minerals by solid-state 13C NMR spectroscopy.

    PubMed

    Moore, Jeremy K; Surface, J Andrew; Brenner, Allison; Wang, Louis S; Skemer, Philip; Conradi, Mark S; Hayes, Sophia E

    2015-01-01

    In the conversion of CO2 to mineral carbonates for the permanent geosequestration of CO2, there are multiple magnesium carbonate phases that are potential reaction products. Solid-state (13)C NMR is demonstrated as an effective tool for distinguishing magnesium carbonate phases and quantitatively characterizing magnesium carbonate mixtures. Several of these mineral phases include magnesite, hydromagnesite, dypingite, and nesquehonite, which differ in composition by the number of waters of hydration or the number of crystallographic hydroxyl groups. These carbonates often form in mixtures with nearly overlapping (13)C NMR resonances which makes their identification and analysis difficult. In this study, these phases have been investigated with solid-state (13)C NMR spectroscopy, including both static and magic-angle spinning (MAS) experiments. Static spectra yield chemical shift anisotropy (CSA) lineshapes that are indicative of the site-symmetry variations of the carbon environments. MAS spectra yield isotropic chemical shifts for each crystallographically inequivalent carbon and spin-lattice relaxation times, T1, yield characteristic information that assist in species discrimination. These detailed parameters, and the combination of static and MAS analyses, can aid investigations of mixed carbonates by (13)C NMR.

  1. How secure is subsurface CO2 storage? Controls on leakage in natural CO2 reservoirs

    NASA Astrophysics Data System (ADS)

    Miocic, Johannes; Gilfillan, Stuart; McDermott, Christopher; Haszeldine, Stuart

    2014-05-01

    Carbon Capture and Storage (CCS) is the only industrial scale technology available to directly reduce carbon dioxide (CO2) emissions from fossil fuelled power plants and large industrial point sources to the atmosphere. The technology includes the capture of CO2 at the source and transport to subsurface storage sites, such as depleted hydrocarbon reservoirs or saline aquifers, where it is injected and stored for long periods of time. To have an impact on the greenhouse gas emissions it is crucial that there is no or only a very low amount of leakage of CO2 from the storage sites to shallow aquifers or the surface. CO2 occurs naturally in reservoirs in the subsurface and has often been stored for millions of years without any leakage incidents. However, in some cases CO2 migrates from the reservoir to the surface. Both leaking and non-leaking natural CO2 reservoirs offer insights into the long-term behaviour of CO2 in the subsurface and on the mechanisms that lead to either leakage or retention of CO2. Here we present the results of a study on leakage mechanisms of natural CO2 reservoirs worldwide. We compiled a global dataset of 49 well described natural CO2 reservoirs of which six are leaking CO2 to the surface, 40 retain CO2 in the subsurface and for three reservoirs the evidence is inconclusive. Likelihood of leakage of CO2 from a reservoir to the surface is governed by the state of CO2 (supercritical vs. gaseous) and the pressure in the reservoir and the direct overburden. Reservoirs with gaseous CO2 is more prone to leak CO2 than reservoirs with dense supercritical CO2. If the reservoir pressure is close to or higher than the least principal stress leakage is likely to occur while reservoirs with pressures close to hydrostatic pressure and below 1200 m depth do not leak. Additionally, a positive pressure gradient from the reservoir into the caprock averts leakage of CO2 into the caprock. Leakage of CO2 occurs in all cases along a fault zone, indicating that

  2. Synthesis Of 2h- And 13c-Substituted Dithanes

    DOEpatents

    Martinez, Rodolfo A.; Alvarez, Marc A.; Silks, III, Louis A.; Unkefer, Clifford J.

    2004-05-04

    The present invention is directed to labeled compounds, [2-.sup.13 C]dithane wherein the .sup.13 C atom is directly bonded to one or two deuterium atoms. The present invention is also directed to processes of preparing [2-.sup.13 C]dithane wherein the .sup.13 C atom is directly bonded to one or two deuterium atoms. The present invention is also directed to labeled compounds, e.g., [.sup.2 H.sub.1-2, .sup.13 C]methanol (arylthio)-, acetates wherein the .sup.13 C atom is directly bonded to exactly one or two deuterium atoms.

  3. Synthesis of 2H- and 13C-substituted dithanes

    DOEpatents

    Martinez, Rodolfo A.; Alvarez, Marc A.; Silks, III, Louis A.; Unkefer, Clifford J.

    2003-01-01

    The present invention is directed to labeled compounds, [2-.sup.13 C]dithiane wherein the .sup.13 C atom is directly bonded to one or two deuterium atoms. The present invention is also directed to processes of preparing [2-.sup.13 C]dithiane wherein the .sup.13 C atom is directly bonded to one or two deuterium atoms. The present invention is also directed to labeled compounds, e.g., [.sup.2 H.sub.1-2, .sup.13 C]methanol (arylthio)-, acetates wherein the .sup.13 C atom is directly bonded to exactly one or two deuterium atoms.

  4. Application of a nanoEA-IRMS system for δ13C measurement of biomineral-bound organics in samples of diatom opal with nanomolar quantities of C

    NASA Astrophysics Data System (ADS)

    Méndez-Vicente, Ana; María Mejía-Ramírez, Luz; Stoll, Heather

    2013-04-01

    We describe the isotopic measurement of δ13C in very small samples of diatom opal (nanomolar quantities of C) both from fossil sediments and cultures. We use a nano-EA system composed of a combustion elemental analyzer (EA3000 series, Eurovector), with standard 18 mm diameter quartz oxidation-reduction reactors and an ash removal device that aids in removal of uncombusted opal and ensures a long reactor lifetime. This is coupled to a custom designed trapping and cromatography system (Nano-CF, Nu Instruments Ltd.) which cryogenically removes CO2 generated by sample combustion and introduces the gas into a low-flow helium carrier stream to the mass spectrometer (Nu Perspective IRMS instrument, Nu Instruments Ltd.). This technique allows for an important reduction in the minimum sample requirements for analysis compared to a typical EA, however the need to reduce the contribution of the blank to the measured values becomes all the more critical. Blank from the capsules can be minimized through specific protocols including cleaning with solvents and reducing the size of the capsule by cutting it to a smaller size, attaining blanks as low as 13.75±2.15 nmol C. Under these conditions we can accurately measure both standards and diatom reference materials in the range of 100 to 330 nmol C, with a precision of 2σ < 1 ‰. The measured δ13C is independent of sample size in this range for standards or samples with δ13C < -11 ‰, which is the compositional range expected for natural diatom samples. Furthermore, no memory effect is observed in samples with an isotopic δ13C value differing by > 10 ‰ analysed in sequence. Applied to measure biomineral-bound organics in cleaned diatom samples from sediments, the low sample size requirements of this technique allows us to analyse multiple size fractions within one sample, and explore isotopic fractionation patterns between them. We have analysed samples from sediments of both centric and pennate diatoms typically in the

  5. Calculation of total meal d13C from individual food d13C.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Variations in the isotopic signature of carbon in biological samples can be used to distinguish dietary patterns and monitor shifts in metabolism. But for these variations to have meaning, the isotopic signature of the diet must be known. We sought to determine if knowledge of the 13C isotopic abund...

  6. In vivo dynamic turnover of cerebral 13C isotopomers from [U- 13C]glucose

    NASA Astrophysics Data System (ADS)

    Xu, Su; Shen, Jun

    2006-10-01

    An INEPT-based 13C MRS method and a cost-effective and widely available 11.7 Tesla 89-mm bore vertical magnet were used to detect dynamic 13C isotopomer turnover from intravenously infused [U- 13C]glucose in a 211 μL voxel located in the adult rat brain. The INEPT-based 1H → 13C polarization transfer method is mostly adiabatic and therefore minimizes signal loss due to B 1 inhomogeneity of the surface coils used. High quality and reproducible data were acquired as a result of combined use of outer volume suppression, ISIS, and the single-shot three-dimensional localization scheme built in the INEPT pulse sequence. Isotopomer patterns of both glutamate C4 at 34.00 ppm and glutamine C4 at 31.38 ppm are dominated first by a doublet originated from labeling at C4 and C5 but not at C3 (with 1JC4C5 = 51 Hz) and then by a quartet originated from labeling at C3, C4, and C5 (with 1JC3C4 = 35 Hz). A lag in the transition of glutamine C4 pattern from doublet-dominance to quartet dominance as compared to glutamate C4 was observed, which provides an independent verification of the precursor-product relationship between neuronal glutamate and glial glutamine and a significant intercompartmental cerebral glutamate-glutamine cycle between neurons and glial cells.

  7. sup 13 C and sup 18 O isotopic disequilibrium in biological carbonates: I. Patterns

    SciTech Connect

    McConnaughey, T. )

    1989-01-01

    Biological carbonates frequently precipitate out of {sup 18}O and {sup 13}C equilibrium with ambient waters. Two patterns of isotopic disequilibrium are particularly common. Kinetic disequilibria, so designated because they apparently result from kinetic isotope effects during CO{sub 2} hydration and hydroxylation, involve simultaneous depletions of {sup 18}O and {sup 13}C as large as 4{per thousand} and 10 to 15{per thousand}, respectively. Rapid skeletogenesis favors strong kinetic effects, and approximately linear correlations between skeletal {delta}{sup 18}O and {delta}{sup 13}C are common in carbonates showing mainly the kinetic pattern. Metabolic effects involve additional positive or negative modulation of skeletal {delta}{sup 13}C, reflecting changes in the {delta}{sup 13}C of dissolved inorganic carbon, caused mainly by photosynthesis and respiration. Kinetic isotope disequilibria tend to be fairly consistent in rapidly growing parts of photosynthetic corals, and time dependent isotopic variations therefore reflect changes in environmental conditions. {delta}{sup 18}O variations from Galapagos corals yields meaningful clues regarding seawater temperature, while {delta}{sup 13}C variations reflect changes in photosynthesis, modulated by cloudiness.

  8. Dipolar-coupling-mediated total correlation spectroscopy in solid-state 13C NMR: Selection of individual 13C- 13C dipolar interactions

    NASA Astrophysics Data System (ADS)

    Spano, Justin; Wi, Sungsool

    2010-06-01

    Herein is described a useful approach in solid-state NMR, for selecting homonuclear 13C- 13C spin pairs in a multiple- 13C homonuclear dipolar coupled spin system. This method builds upon the zero-quantum (ZQ) dipolar recoupling method introduced by Levitt and coworkers (Marin-Montesinos et al., 2006 [30]) by extending the originally introduced one-dimensional (1D) experiment into a two-dimensional (2D) method with selective irradiation scheme, while moving the 13C- 13C mixing scheme from the transverse to the longitudinal mode, together with a dramatic improvement in the proton decoupling efficiency. Selective spin-pair recoupling experiments incorporating Gaussian and cosine-modulated Gaussian pulses for inverting specific spins were performed, demonstrating the ability to detect informative, simplified/individualized, long-range 13C- 13C homonuclear dipolar coupling interactions more accurately by removing less informative, stronger, short-range 13C- 13C interactions from 2D correlation spectra. The capability of this new approach was demonstrated experimentally on uniformly 13C-labeled Glutamine and a tripeptide sample, GAL.

  9. Photolytic production of CO2 on Iapetus

    NASA Astrophysics Data System (ADS)

    Palmer, Eric; Brown, R. H.

    2008-09-01

    Carbon Dioxide has been detected on the surface of Iapetus by Cassini's VIMS instrument at the 4.26 micron band. This CO2 is concentrated on the equatorial leading side, where we also see an abundance of dark material. The residence time of free CO2 on the surface of Iapetus is very short, thus the CO2 is unlikely to be in the form of frost; it is more likely that the CO2 is tightly bound in the form of complexed molecules. We explore the possibility of photolytically generating CO2 from a mixture of the carbon rich material and water ice that matches the expected composition of the dark material on Iapetus' surface. An ice regolith was created with flash frozen water that was crushed into sub-millimeter shards and mixed with amorphous 13C. The regolith was placed in a vacuum chamber with a surface area of 10 cm2 and a thickness of 2 cm and exposed to UV light from a deuterium lamp with peaks of flux centered around 121 and 160 nm. Temperatures were varied between 60 and 130K at a pressure of 10-8 torr. Both CO and CO2 were produced by photolytic reactions and detected by a mass spectrometer. Applying these results to Iapetus, Jeans escape calculations show that CO2 generated by photolysis will remain gravitationally bound to Iapetus for between 100 and 200 years, ballistically scattering across the surface until it is sequestered in a polar cold trap or escapes to space. The average particle will interact with the surface more than 1000 times before escaping unless interactions with surface grains causes it to become complexed, such as adsorption. We are continuing to evaluate the photochemistry for this simulated Iapetus surface using a Nicolet IR spectrometer to identify all the products generated and estimate the associated production rate.

  10. Acetate and Bicarbonate Assimilation and Metabolite Formation in Chlamydomonas reinhardtii: A 13C-NMR Study

    PubMed Central

    Singh, Himanshu; Shukla, Manish R.; Chary, Kandala V. R.; Rao, Basuthkar J.

    2014-01-01

    Cellular metabolite analyses by 13C-NMR showed that C. reinhardtii cells assimilate acetate at a faster rate in heterotrophy than in mixotrophy. While heterotrophic cells produced bicarbonate and CO2aq, mixotrophy cells produced bicarbonate alone as predominant metabolite. Experiments with singly 13C-labelled acetate (13CH3-COOH or CH3-13COOH) supported that both the 13C nuclei give rise to bicarbonate and CO2aq. The observed metabolite(s) upon further incubation led to the production of starch and triacylglycerol (TAG) in mixotrophy, whereas in heterotrophy the TAG production was minimal with substantial accumulation of glycerol and starch. Prolonged incubation up to eight days, without the addition of fresh acetate, led to an increased TAG production at the expense of bicarbonate, akin to that of nitrogen-starvation. However, such TAG production was substantially high in mixotrophy as compared to that in heterotrophy. Addition of mitochondrial un-coupler blocked the formation of bicarbonate and CO2aq in heterotrophic cells, even though acetate uptake ensued. Addition of PSII-inhibitor to mixotrophic cells resulted in partial conversion of bicarbonate into CO2aq, which were found to be in equilibrium. In an independent experiment, we have monitored assimilation of bicarbonate via photoautotrophy and found that the cells indeed produce starch and TAG at a much faster rate as compared to that in mixotrophy and heterotrophy. Further, we noticed that the accumulation of starch is relatively more as compared to TAG. Based on these observations, we suggest that acetate assimilation in C. reinhardtii does not directly lead to TAG formation but via bicarbonate/CO2aq pathways. Photoautotrophic mode is found to be the best growth condition for the production of starch and TAG and starch in C. reinhardtii. PMID:25207648

  11. Measurement of 13C and 15N isotope labeling by gas chromatography/combustion/isotope ratio mass spectrometry to study amino acid fluxes in a plant-microbe symbiotic association.

    PubMed

    Molero, Gemma; Aranjuelo, Iker; Teixidor, Pilar; Araus, José Luis; Nogués, Salvador

    2011-03-15

    We have developed a method based on a double labeling with stable isotopes and gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) analyses to study amino acid exchange in a symbiotic plant-microbe association. Isotopic precision was studied for 21 standards including 15 amino acid derivatives, three N-protected amino acid methyl esters, three amines and one international standard. High correlations were observed between the δ(13)C and δ(15)N values obtained by GC/C/IRMS and those obtained by an elemental analyzer (EA) coupled to an isotope ratio mass spectrometer (R(2) = 0.9868 and 0.9992, respectively). The mean precision measured was 0.04‰ for δ(13)C and 0.28‰ for δ(15)N (n = 15). This method was applied in vivo to the symbiotic relationship between alfalfa (Medicago sativa L.) and N(2)-fixing bacteria. Plants were simultaneously labeled over 10 days with (13)C-depleted CO(2) ((12)CO(2)), which was assimilated through photosynthesis by leaves, and (15)N(2) fixed via nodules. Subsequently, the C and N isotope compositions (i.e. δ(13)C and δ(15)N) of free amino acids were analyzed in leaves and nodules by GC/C/IRMS. The method revealed the pattern of C and N exchange between leaves and nodules, highlighting that γ-aminobutanoic acid and glycine may represent an important form of C transport from leaves to the nodules. The results confirmed the validity, reliability and accuracy of the method for assessing C and N fluxes between plants and symbiotic bacteria and support the use of this technique in a broad range of metabolic and fluxomic studies.

  12. Testing the root-priming of soil organic matter decomposition using the isotopic signature of fossil fuel CO2

    NASA Astrophysics Data System (ADS)

    Bradley, Robert; Paterson, Eric; Chapman, Steve; Thornton, Barry; Sim, Allan

    2013-04-01

    Plant roots provide various forms of soil labile carbon (i.e., rhizodeposition), which stimulate the growth of heterotrophic bacteria in the rhizosphere. This, in turn, provides a food source for phagotrophic protozoa and other bacterivores, whose carbon:nutrient ratios are generally higher than those of their food source. In order to maintain their stoichiometric composition, bacterivores release their extra nutrients into the rhizosphere, where they may be absorbed by plant roots. Thus, rhizodeposition should reduce carbon limitation, but increase nutrient demand, of the soil microbial biomass. We hypothesized that this shift towards nutrient deficiency would stimulate the production of microbial enzymes that depolymerise soil organic matter into microbial available forms. In other words, roots should stimulate the decomposition of soil organic matter. We report on experiment where we tested such a "root-priming" effect using 3 contrasting plant species (Achillea millefolium, Lolium perenne, Trifolium repens). An agricultural soil, with a delta-13C value of approximately -14 ‰ , was transferred into 30 pots and planted with seeds of each species. A ring was inserted in the middle of each pot, and no seeds were planted within the ring. Plants were grown in a growth chamber designed to deliver 13C-depleted air. The resulting plant biomass had a delta-13C value of approximately -52 ‰ . On 7 occasions during the growth trial, pots were sampled for the flux and delta-13C value of soil CO2. Using similar data from control pots without plants, we compared the expected vs. observed contributions of CO2 from roots and soil organic matter. Results from this study revealed a negative root-priming effect for all three species. We discuss the experimental conditions that could have led to this observation, as well as the novelty and potential of our experimental protocol.

  13. Evaluation of a [13C]-Dextromethorphan Breath Test to Assess CYP2D6 Phenotype

    PubMed Central

    Leeder, J. Steven; Pearce, Robin E.; Gaedigk, Andrea; Modak, Anil; Rosen, David I.

    2016-01-01

    A [13C]-dextromethorphan ([13C]-DM) breath test was evaluated to assess its feasibility as a rapid, phenotyping assay for CYP2D6 activity. [13C]-DM (0.5 mg/kg) was administered orally with water or potassium bicarbonate-sodium bicarbonate to 30 adult Caucasian volunteers (n = 1 each): CYP2D6 poor metabolizers (2 null alleles; PM-0) and extensive metabolizers with 1 (EM-1) or 2 functional alleles (EM-2). CYP2D6 phenotype was determined by 13CO2 enrichment measured by infrared spectrometry (delta-over-baseline [DOB] value) in expired breath samples collected before and up to 240 minutes after [13C]-DM ingestion and by 4-hour urinary metabolite ratio. The PM-0 group was readily distinguishable from either EM group by both the breath test and urinary metabolite ratio. Using a single point determination of phenotype at 40 minutes and defining PMs as subjects with a DOB ≤ 0.5, the sensitivity of the method was 100%; specificity was 95% with 95% accuracy and resulted in the misclassification of 1 EM-1 individual as a PM. Modification of the initial protocol (timing of potassium bicarbonate-sodium bicarbonate administration relative to dose) yielded comparable results, but there was a tendency toward increased DOB values. Although further development is required, these studies suggest that the [13C]-DM breath test offers promise as a rapid, minimally invasive phenotyping assay for CYP2D6 activity. PMID:18728242

  14. Use of the Biphasic 13C-Sucrose/Glucose Breath Test to Assess Sucrose Maldigestion in Adults with Functional Bowel Disorders

    PubMed Central

    Balesh, Albert M.; Shelby, Harold T.

    2016-01-01

    Sucrase insufficiency has been observed in children with of functional bowel disorders (FBD) and symptoms of dietary carbohydrate intolerance may be indistinguishable from those of FBD. A two-phase 13C-sucrose/13C-glucose breath test (13C-S/GBT) was used to assess sucrase activity because disaccharidase assays are seldom performed in adults. When 13C-sucrose is hydrolyzed to liberate monosaccharides, oxidation to 13CO2 is a proportional indicator of sucrase activity. Subsequently, 13C-glucose oxidation rate was determined after a secondary substrate ingestion (superdose) to adjust for individual habitus effects (Phase II). 13CO2 enrichment recovery ratio from 13C-sucrose and secondary 13C-glucose loads reflect the individualized sucrase activity [Coefficient of Glucose Oxidation for Sucrose (CGO-S)]. To determine if sucrase insufficiency could be a factor in FBD, 13C-S/GBT was validated using subjects with known sucrase gene mutation status by comparing 13CO2-breath enrichment with plasma 13C-glucose enrichment. 13C-S/GBT was used to assess sucrose digestion in FBD patients and asymptomatic controls. 13CO2-breath enrichment correlated with the appearance of 13C-sucrose-derived glucose in plasma (r2 = 0.80). Mean, control group CGO-S-enrichment outcomes were 1.01 at 60′, 0.92 at 75′, and 0.96 at mean 60′–75′ with normal CGO-S defined as >0.85 (95% C.I.). In contrast, FBD patients demonstrated lower CGO-S values of 0.77 at 60′, 0.77 at 75′, and 0.76 at mean 60′–75′ (Chi Square: 6.55; p < 0.01), which points to sucrose maldigestion as a cause of FBD. PMID:27579322

  15. Use of the Biphasic (13)C-Sucrose/Glucose Breath Test to Assess Sucrose Maldigestion in Adults with Functional Bowel Disorders.

    PubMed

    Opekun, Antone R; Balesh, Albert M; Shelby, Harold T

    2016-01-01

    Sucrase insufficiency has been observed in children with of functional bowel disorders (FBD) and symptoms of dietary carbohydrate intolerance may be indistinguishable from those of FBD. A two-phase (13)C-sucrose/(13)C-glucose breath test ((13)C-S/GBT) was used to assess sucrase activity because disaccharidase assays are seldom performed in adults. When (13)C-sucrose is hydrolyzed to liberate monosaccharides, oxidation to (13)CO2 is a proportional indicator of sucrase activity. Subsequently, (13)C-glucose oxidation rate was determined after a secondary substrate ingestion (superdose) to adjust for individual habitus effects (Phase II). (13)CO2 enrichment recovery ratio from (13)C-sucrose and secondary (13)C-glucose loads reflect the individualized sucrase activity [Coefficient of Glucose Oxidation for Sucrose (CGO-S)]. To determine if sucrase insufficiency could be a factor in FBD, (13)C-S/GBT was validated using subjects with known sucrase gene mutation status by comparing (13)CO2-breath enrichment with plasma (13)C-glucose enrichment. (13)C-S/GBT was used to assess sucrose digestion in FBD patients and asymptomatic controls. (13)CO2-breath enrichment correlated with the appearance of (13)C-sucrose-derived glucose in plasma (r (2) = 0.80). Mean, control group CGO-S-enrichment outcomes were 1.01 at 60', 0.92 at 75', and 0.96 at mean 60'-75' with normal CGO-S defined as >0.85 (95% C.I.). In contrast, FBD patients demonstrated lower CGO-S values of 0.77 at 60', 0.77 at 75', and 0.76 at mean 60'-75' (Chi Square: 6.55; p < 0.01), which points to sucrose maldigestion as a cause of FBD. PMID:27579322

  16. Fossil bryophytes as recorders of ancient CO2 levels: Experimental evidence and a Cretaceous case study

    NASA Astrophysics Data System (ADS)

    Fletcher, Benjamin J.; Beerling, David J.; Brentnall, Stuart J.; Royer, Dana L.

    2005-09-01

    Biological and geochemical CO2 proxies provide critical constraints on understanding the role of atmospheric CO2 in driving climate change during Earth history. As no single existing CO2 proxy is without its limitations, there is a clear need for new approaches to reconstructing past CO2 concentrations. Here we develop a new pre-Quaternary CO2 proxy based on the stable carbon isotope composition (δ13C) of astomatous land plants. In a series of CO2-controlled laboratory experiments, we show that the carbon isotope discrimination (Δ13C) of a range of bryophyte (liverwort and moss) species increases with atmospheric CO2 across the range 375 to 6000 ppm. Separate experiments establish that variations in growth temperature, water content and substrate type have minor impacts on the Δ13C of liverworts but not mosses, indicating the greater potential of liverworts to faithfully record past variations in CO2. A mechanistic model for calculating past CO2 concentrations from bryophyte Δ13C (White et al., 1994) is extended and calibrated using our experimental results. The potential for fossil liverworts to record past CO2 changes is investigated by analyzing the δ13C of specimens collected from Alexander Island, Antarctica dating to the "greenhouse" world of the mid-Cretaceous. Our analysis and isotopic model yield mid-Cretaceous CO2 concentrations of 1000-1400 ppm, in general agreement with independent proxy data and long-term carbon cycle models. The exceptionally long evolutionary history of bryophytes offers the possibility of reconstructing CO2 concentrations back to the mid-Ordovician, pre-dating all currently used quantitative CO2 proxies.

  17. Geochemical constraints for coexisting CO"2 gas hydrate and calcite: implications for sheet cracks, stromatactis, zebra and tepee-like structures [rapid communication

    NASA Astrophysics Data System (ADS)

    DiFilippo, Erica L.; Hammond, Douglas E.; Corsetti, Frank A.

    2003-08-01

    The Ordovician Meiklejohn Peak mud-mound in western Nevada contains sedimentary structures (e.g., stromatactis and "zebra-rock") that resemble features found in modern methane hydrate deposits. However, the δ13C of the mud-mound carbonates (-1 to 1‰ PDB) does not suggest interaction with δ13C-depleted methane. Consequently, Krause (Sedimentary Geology 145 (2001) 189) proposed that the Meiklejohn structures might have been produced by the formation and dissociation of CO 2 gas hydrate rather than methane gas hydrate. Structures in Neoproterozoic cap carbonates, sheet cracks and tepee-like structures have also been suggested to represent gas hydrate interaction with carbonate sediments (Geology 29 (2001) 443), but, similarly, δ13C values do not suggest direct interaction with methane. The objective of this contribution is to see if the presence of CO 2 gas hydrate is plausible for either setting. To test the feasibility of CO 2 gas hydrate involvement in the formation of these structures, necessary concentrations of TCO 2 were calculated based on required phase equilibria using the quadruple points Q1 (-1.73 °C, 10.2 atm) and Q2 (10.2 °C, 44.5 atm) from the phase diagram for CO 2 gas hydrate (Miller, S.L., 1974. The Nature and Occurrence of Clathrate Hydrates. In: Kaplan, I.R. (Ed.), Natural Gases in Marine Sediments. Plenum, New York, NY, pp. 151-178). A limit for Ca +2 was established based on the lack of evidence for gypsum formation in this environment and the assumption that sulfate was up to 100% of its present oceanic value; the calculated TCO 2 concentration, however, is relatively insensitive to the concentration of SO 4-2 used. The lowest permissible value of pCO 2 and TCO 2 were found at Q1, where TCO 2 must be at least 300 times the present value. These conditions are implausible for the formation of the Meiklejohn Peak mud-mound. Although some models for Neoproterozoic "Snowball Earth" require highly elevated atmospheric CO 2, these models predict

  18. Assessing the use of delta(13)C natural abundance in separation of root and microbial respiration in a Danish beech (Fagus sylvatica L.) forest.

    PubMed

    Formánek, Pavel; Ambus, Per

    2004-01-01

    Our understanding of forest biosphere-atmosphere interactions is fundamental for predicting forest ecosystem responses to climatic changes. Currently, however, our knowledge is incomplete partly due to inability to separate the major components of soil CO(2) effluxes, viz. root respiration, microbial decomposition of soil organic matter and microbial decomposition of litter material. In this study we examined whether the delta(13)C characteristics of solid organic matter and respired CO(2) from different soil-C components and root respiration in a Danish beech forest were useful to provide information on the root respiration contribution to total CO(2) effluxes. The delta(13)C isotopic analyses of CO(2) were performed using a FinniganMAT Delta(PLUS) isotope-ratio mass spectrometer coupled in continuous flow mode to a trace gas preparation-concentration unit (PreCon). Gas samples in 2-mL crimp seal vials were analysed in a fully automatic mode with an experimental standard error +/-0.11 per thousand. We observed that the CO(2) derived from root-free mineral soil horizons (A, B(W)) was more enriched in (13)C (delta(13)C range -21.6 to -21.2 per thousand ) compared with CO(2) derived from root-free humus layers (delta(13)C range -23.6 to -23.4 per thousand ). The CO(2) evolved from root respiration in isolated young beech plants revealed a value intermediate between those for the soil humus and mineral horizons, delta(13)C(root) = -22.2 per thousand, but was associated with great variability (SE +/- 1.0 per thousand ) due to plant-specific differences. delta(13)C of CO(2) from in situ below-ground respiration averaged -22.8 per thousand, intermediate between the values for the humus layer and root respiration, but variability was great (SE +/- 0.4 per thousand ) due to pronounced spatial patterns. Overall, we were unable to statistically separate the CO(2) of root respiration vs. soil organic matter decomposition based solely on delta(13)C signatures, yet the trend in

  19. Late Quaternary Biomass Changes from 13C Measurements in a Highland Peatbog from Equatorial Africa (Burundi)

    NASA Astrophysics Data System (ADS)

    Aucour, Anne-Marie; Hillaire-Marcel, Claude; Bonnefille, Raymonde

    1994-03-01

    Stable carbon isotope ratios of total organic matter were measured in two cores collected from the Kashiru peatbog in Burundi, Equatorial Africa. The record, which spans at least the last 40,000 yr, documents the C 3-C 4 biomass balance in the organic sediment. Among the major modern peat formers, most plants are C 3 species and are characterized by δ 13C values of -25.5 ± 2.3% (vs PDB). The C 4 plants, which are characterized by higher δ 13C values (-11.3 ± 0.7%) belong to the Gramineae ( Miscanthidium sp.) and Cyperaceae families ( Cyperus latifolius, C. papyrus, Pycreus nigricans). In the fossil record, δ 13C values of total organic matter vary between -28 and -15% in response to the relative fluxes of C 3 and C 4 plants. Before 30,000 yr B.P., low δ 13C values (-23.5 ± 1.1%) match high arboreal pollen contents. From 30,000 to 15,000 yr B.P., higher δ 13C values (-17.6 ± 1.1%) correspond to a significant increase in percentages of grass pollen. During this episode, a short and sharp shift toward lighter carbon isotopic compositions at 21,000 yr B.P. is synchronous with higher input of arboreal pollen. From 15,000 to 12,000 yr B.P., the 13C content decreases (δ 13C = -22.9 ± 1.4%). This shift, which cannot be explained by an increase in the arboreal vegetation, could be explained by the spreading of C 3 Gramineae or C 3 Cyperaceae. The interval from 12,000 to 7000 yr B.P. is poorly documented in these cores due to much lower organic matter accumulation. Low δ 13C values (δ 13C = -25.2 ± 1.3%) are observed from 7000 to 5000 yr B.P., when the pollen data show development of C 3 mountain forest. The Late Holocene is characterized by a mixed C 3-C 4 organic matter accumulation (δ 13C = -20.9 ± 1.6%). This study depicts a change in the dominant photosynthetic pathway among the herbaceous components, notably at the glacial-interglacial transition, when C 3 plants were favored by increased water supply and/or higher atmospheric CO 2 concentration.

  20. Chlorophyll a-specific Δ14C, δ13C and δ15N values in stream periphyton: implications for aquatic food web studies

    NASA Astrophysics Data System (ADS)

    Ishikawa, N. F.; Yamane, M.; Suga, H.; Ogawa, N. O.; Yokoyama, Y.; Ohkouchi, N.

    2015-11-01

    Periphytic algae attached to a streambed substrate (periphyton) are an important primary producer in stream ecosystems. We determined the isotopic composition of chlorophyll a in periphyton collected from a stream flowing on limestone bedrock in the Seri River, central Japan. Stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) and natural radiocarbon abundances (Δ14C) were measured in chlorophyll a (δ13Cchl, δ15Nchl and Δ14Cchl) and bulk (δ13Cbulk, δ15Nbulk and Δ14Cbulk) for periphyton, a pure aquatic primary producer (Cladophora sp.) and a terrestrial primary producer (Quercus glauca). Periphyton δ13Cbulk and δ13Cchl values did not necessarily correspond to δ13Cbulk for an algal-grazing specialist (Epeorus latifolium). Periphyton Δ14Cchl values (-258 ‰ in April and -190 ‰ in October) were slightly lower than Δ14Cbulk values (-228 ‰ in April and -179 ‰ in October) but were close to the Δ14C value for dissolved inorganic carbon (DIC; -217 ± 31 ‰), which is a mixture of weathered carbonates (Δ14C = -1000 ‰), CO2 derived from aquatic and terrestrial organic matters (variable Δ14C) and dissolved atmospheric CO2 (Δ14C approximately +30 ‰ in 2013). Δ14Cchl values were also close to Δ14Cbulk for E. latifolium (-215 ‰ in April and -199 ‰ in October) and Cladophora sp. (-210 ‰), whereas the Δ14Cbulk value for Q. glauca (+27 ‰) was closer to Δ14C for atmospheric CO2. Although the bulk isotopic composition of periphyton is recognised as a surrogate for the photosynthetic algal community, natural periphyton is a mixture of aquatic and terrestrial organic materials. Our results indicate that the bulk periphyton matrix at the study site consists of 89 to 95 % algal carbon (derived from 14C-depleted DIC) and 5 to 11 % terrestrial organic carbon (derived from 14C-enriched atmospheric CO2).

  1. CO2-neutral fuels

    NASA Astrophysics Data System (ADS)

    Goede, A. P. H.

    2015-08-01

    The need for storage of renewable energy (RE) generated by photovoltaic, concentrated solar and wind arises from the fact that supply and demand are ill-matched both geographically and temporarily. This already causes problems of overcapacity and grid congestion in countries where the fraction of RE exceeds the 20% level. A system approach is needed, which focusses not only on the energy source, but includes conversion, storage, transport, distribution, use and, last but not least, the recycling of waste. Furthermore, there is a need for more flexibility in the energy system, rather than relying on electrification, integration with other energy systems, for example the gas network, would yield a system less vulnerable to failure and better adapted to requirements. For example, long-term large-scale storage of electrical energy is limited by capacity, yet needed to cover weekly to seasonal demand. This limitation can be overcome by coupling the electricity net to the gas system, considering the fact that the Dutch gas network alone has a storage capacity of 552 TWh, sufficient to cover the entire EU energy demand for over a month. This lecture explores energy storage in chemicals bonds. The focus is on chemicals other than hydrogen, taking advantage of the higher volumetric energy density of hydrocarbons, in this case methane, which has an approximate 3.5 times higher volumetric energy density. More importantly, it allows the ready use of existing gas infrastructure for energy storage, transport and distribution. Intermittent wind electricity generated is converted into synthetic methane, the Power to Gas (P2G) scheme, by splitting feedstock CO2 and H2O into synthesis gas, a mixture of CO and H2. Syngas plays a central role in the synthesis of a range of hydrocarbon products, including methane, diesel and dimethyl ether. The splitting is accomplished by innovative means; plasmolysis and high-temperature solid oxygen electrolysis. A CO2-neutral fuel cycle is

  2. Response of δ13C in plant and soil respiration to a water pulse

    NASA Astrophysics Data System (ADS)

    Salmon, Y.; Buchmann, N.; Barnard, R. L.

    2011-05-01

    Stable carbon isotopes have been used to assess the coupling between changes in environmental conditions and the response of soil or ecosystem respiration, usually by studying the time-lagged response of δ13C of respired CO2 (δ13CR) to changes in photosynthetic carbon isotope discrimination (Δi). However, the lack of a systematic response of δ13CR to environmental changes in field studies stresses the need to better understand the mechanisms to this response. We experimentally created a wide range of carbon allocation and respiration conditions in Fagus sylvatica mesocosms, by growing saplings under different temperatures and girdling combinations. After a period of drought, a water pulse was applied and the short-term responses of δ13C in soil CO2 efflux (δ13CRsoil) and δ13C in aboveground plant respiration (δ13CRabove) were measured, as well as leaf gas exchange rates and soil microbial biomass δ13C responses. Both δ13CRsoil and δ 13CRabove values of all the trees decreased immediately after the water pulse. These responses were not driven by changes in Δi, but rather by a fast release of C stored in roots and shoots. Changes in δ13CRsoil associated with the water pulse were significantly positively correlated with changes in stomatal conductance, showing a strong impact of the plant component on δ13CRsoil. However, three days after the water pulse in girdled trees, changes in δ13CRsoil were related to changes in microbial biomass δ13C, suggesting that changes in the carbon source respired by soil microorganisms also contributed to the response of δ13CRsoil. Our study shows that improving our mechanistic understanding of the responses of δ13CR to changes in environmental conditions requires the understanding of not only the plant's physiological responses, but also the responses of soil microorganisms and of plant-microbial interactions.

  3. Microbial metabolism in soil at low temperatures: Mechanisms unraveled by position-specific 13C labeling

    NASA Astrophysics Data System (ADS)

    Bore, Ezekiel

    2016-04-01

    Microbial transformation of organic substances in soil is the most important process of the C cycle. Most of the current studies base their information about transformation of organic substances on incubation studies under laboratory conditions and thus, we have a profound knowledge on SOM transformations at ambient temperatures. However, metabolic pathway activities at low temperature are not well understood, despite the fact that the processes are relevant for many soils globally and seasonally. To analyze microbial metabolism at low soil temperatures, isotopomeres of position-specifically 13C labeled glucose were incubated at three temperature; 5, -5 -20 oC. Soils were sampled after 1, 3 and 10 days and additionally after 30 days for samples at -20 °C. The 13C from individual molecule position was quantifed in respired CO2, bulk soil, extractable organic C and extractable microbial biomass by chloroform fumigation extraction (CFE) and cell membranes of microbial communities classified by 13C phospholipid fatty acid (PLFA) analysis. 13CO2 released showed a dominance of the flux from C-1 position at 5 °C. Consequently, at 5 °C, pentose phosphate pathway activity is a dominant metabolic pathway of glucose metabolization. In contrast to -5 °C and -20 oC, metabolic behaviors completely switched towards a preferential respiration of the glucose C-4 position. With decreasing temperature, microorganism strongly shifted towards metabolization of glucose via glycolysis which indicates a switch to cellular maintenance. High recoveries of 13C in extractable microbial biomass at -5 °C indicates optimal growth condition for the microorganisms. PLFA analysis showed high incorporation of 13C into Gram negative bacteria at 5 °C but decreased with temperature. Gram positive bacteria out-competed Gram negatives with decreasing temperature. This study revealed a remarkable microbial activity at temperatures below 0 °C, differing significantly from that at ambient

  4. Correlation of 13C /12C and 34S /32S secular variations

    NASA Astrophysics Data System (ADS)

    Veizer, Ján; Holser, William T.; Wilgus, Cheryl K.

    1980-04-01

    Statistical evaluation of 3056 δ13C measurements in carbonate rocks and fossils shows that they record a 2‰ 13C depletion from the late Proterozoic to the early Paleozoic, a 2.5‰ enrichment to the Permian, and a 1.5‰ depletion to the Cenozoic. These variations, not controlled primarily by facies or alteration phenomena, correlate negatively with the δ34S sulfate secular trend, as confirmed by collation of 1083 δ34S measurements. The correlation suggests that the biologically mediated redox fluxes of the C and S cycles have been approximately balanced through this long span of geological time, generally levelling available oxygen. Such a redox system is consistent with the controlling mechanism proposed by GARRELS and PERRY (1974). Consequently, the sedimentary reservoirs of C organic as well as S bacteriological'have varied through geological time.

  5. High-Resolution Isotopic Monitoring of Cave Air CO2

    NASA Astrophysics Data System (ADS)

    Töchterle, Paul; Dublyansky, Yuri; Mandic, Magda; Stöbener, Nils; Jost, Hj; Spötl, Christoph

    2016-04-01

    This study aims at characterising the ventilation patterns in Spannagel Cave, a high-alpine cave system in the Zillertal Alps, Austria. A Thermo Scientific Delta Ray Isotope Ratio Infrared Spectrometer was installed in a chamber ca. 100 m behind the cave entrance to monitor pCO2 and δ13C and δ18O of CO2 at high temporal resolution (up to 1 s). The air temperature was independently monitored inside and outside the cave. This study aims at characterising the ventilation patterns in Spannagel Cave, a high-alpine cave system in the Zillertal Alps, Austria. A Thermo Scientific Delta Ray Isotope Ratio Infrared Spectrometer was installed in a chamber ca. 100 m behind the cave entrance to monitor pCO2 and δ13C and δ18O of CO2 at high temporal resolution (up to 1s). The air temperature was independently monitored inside and outside the cave. The data show two distinct patterns in terms of CO2 concentration and its isotopic composition, which are closely coupled with the temperature difference between the cave interior and the outside atmosphere. This gradient controls the direction of air flow in the cave on a seasonal to synoptic timescale (chimney-type ventilation). The summer circulation is characterised by CO2 closely resembling atmospheric values (pCO2 = 399 ± 12 ppm, δ13C = -8.5 ± 0.7 permil, δ18O = 8.1 ± 2.5 permil). The winter circulation mode features generally higher CO2 concentrations and lower isotopic compositions (pCO2 = 409 ± 14 ppm, δ13C = -10.1 ± 0.7 permil, δ18O = 2.3 ± 1.5 permil). The high temporal resolution of stable isotope data allows tracking cave air ventilation changes, including transient and short-lived ones. Moreover, the data make it possible to address concomitant geochemical processes, such as the input of atmospheric CO2 and the degassing of CO2 from seepage water. These processes would not be possible to quantify without the new generation of laser-based isotope ratio instruments represented by the Delta Ray.

  6. Investigating the Multiple Food Sources and N Chemistry of Invasive Earthworms at the Rhinelander, WI, Free Air CO2 Enrichment (FACE) Experiment

    NASA Astrophysics Data System (ADS)

    Top, S. M.; Filley, T. R.

    2013-12-01

    Rising levels of atmospheric CO2 can directly and indirectly alter biogeochemical cycling in forest ecosystems through changes to plant productivity, tissue chemistry, and associated feedbacks to microbial and faunal communities. At the Rhinelander free air CO2 enrichment site (FACE), Rhinelander WI, we examined the consumption and movement of plant tissue and soil by invasive earthworm species using a multi-proxy stable isotope and amino acid chemistry analysis of plant and soil, as well as fecal matter extracted from invasive earthworms present at the site. Using an isotopic mixing model that exploits the 13C-depleted CO2 source and a previous 15N labeling in the FACE experiment, we determined potential sources to the earthworm fecal matter and the movement of amino compounds. For epigeic, surface dwelling earthworms, the stable isotope modeling showed the largest contribution to the C and N in fecal matter was from leaf litter (up to 80%) which was depleted in amino acid C under elevated CO2 conditions. Fecal matter from the endogeic, mineral soil dwelling earthworms was primarily derived from 0-5 cm soil (up to 56%) and fine root tissue (up to 70%). Additionally, amino acid C in this group of earthworms had a proportionately greater relative concentration compared to the epigeic species and the 0-5cm soil. Here we demonstrate that earthworms are incorporating multiple sources (leaf litter, root, and soil) into their fecal matter, which then get deposited throughout the soil profile, where nutrients could become available for plant use.

  7. Study on CO2 global recycling system.

    PubMed

    Takeuchi, M; Sakamoto, Y; Niwa, S

    2001-09-28

    In order to assist in finding ways to mitigate CO2 emission and to slow the depletion of fossil fuels we have established and evaluated a representative system, which consists of three technologies developed in our laboratory. These technologies were in CO2 recovery, hydrogen production and methanol synthesis and in addition we established the necessary supporting systems. Analysis of outline designs of the large scale renewable energy power generation system and this system and energy input for building plant, energy input for running plant has been conducted based on a case using this system for a 1000-MW coal fired power plant, followed by an evaluation of the material balance and energy balance. The results are as follows. Energy efficiency is 34%, the CO2 reduction rate is 41%, the balance ratio of the energy and CO2 of the system is 2.2 and 1.8, respectively, on the assumption that the primary renewable energy is solar thermal power generation, the stationary CO2 emission source is a coal-fired power plant and the generation efficiency of the methanol power plant is 60%. By adopting the system, 3.7 million tons of CO2 can be recovered, approximately 2.7 million tons of methanol can be produced, and 15.4 billion kWh of electricity can be generated per year. Compared to generating all electrical power using only coal, approximately 2.6 million tons of coal per year can be saved and approximately 2.15 million tons of CO2 emission can be reduced. Therefore, it is clearly revealed that this system would be effective to reduce CO2 emissions and to utilize renewable energy.

  8. Carbon isotope discrimination during litter decomposition can be explained by selective use of substrate with differing δ13C

    NASA Astrophysics Data System (ADS)

    Ngao, J.; Cotrufo, M. F.

    2011-01-01

    Temporal dynamics of C isotopic composition (δ13C) of CO2 and leaf litter was monitored during a litter decomposition experiment using Arbutus unedo L., as a slow decomposing model substrate. This allowed us (1) to quantify isotopic discrimination variation during litter decomposition, and (2) to test whether selective substrate use or kinetic fractionation could explain the observed isotopic discrimination. Total cumulative CO2-C loss (CL) comprised 27% of initial litter C. Temporal evolution of CL was simulated following a three-C-pool model. Isotopic composition of respired CO2 (δRL) was higher with respect to that of the bulk litter. The isotopic discrimination Δ(L/R) varied from -2‰ to 0‰ and it is mostly attributed to the variations of δRL. A three-pool model, with the three pools differing in their δ13C, described well the dynamic of Δ(L/R), in the intermediate stage of the process. This suggests that the observed isotopic discrimination between respired CO2 and bulk litter is in good agreement with the hypothesis of successive consumption of C compounds differing in δ13C during decomposition. However, to explain also 13C-CO2 dynamics at the beginning and end of the incubation the model had to be modified, with discrimination factors ranging from -1‰ to -4.6‰ attributed to the labile and the recalcitrance pool, respectively. We propose that this discrimination is also the result of further selective use of specific substrates within the two pools, likely being both the labile and recalcitrant pool of composite nature. In fact, the 2‰ 13C enrichment of the α-cellulose observed by the end of the experiment, and potentially attributable to kinetic fractionation, could not explain the measured Δ(L/R) dynamics.

  9. Combined Effects of Ocean Acidification and Light or Nitrogen Availabilities on 13C Fractionation in Marine Dinoflagellates.

    PubMed

    Hoins, Mirja; Eberlein, Tim; Groβmann, Christian H; Brandenburg, Karen; Reichart, Gert-Jan; Rost, Björn; Sluijs, Appy; Van de Waal, Dedmer B

    2016-01-01

    Along with increasing oceanic CO2 concentrations, enhanced stratification constrains phytoplankton to shallower upper mixed layers with altered light regimes and nutrient concentrations. Here, we investigate the effects of elevated pCO2 in combination with light or nitrogen-limitation on 13C fractionation (εp) in four dinoflagellate species. We cultured Gonyaulax spinifera and Protoceratium reticulatum in dilute batches under low-light ('LL') and high-light ('HL') conditions, and grew Alexandrium fundyense and Scrippsiella trochoidea in nitrogen-limited continuous cultures ('LN') and nitrogen-replete batches ('HN'). The observed CO2-dependency of εp remained unaffected by the availability of light for both G. spinifera and P. reticulatum, though at HL εp was consistently lower by about 2.7‰ over the tested CO2 range for P. reticulatum. This may reflect increased uptake of (13C-enriched) bicarbonate fueled by increased ATP production under HL conditions. The observed CO2-dependency of εp disappeared under LN conditions in both A. fundyense and S. trochoidea. The generally higher εp under LN may be associated with lower organic carbon production rates and/or higher ATP:NADPH ratios. CO2-dependent εp under non-limiting conditions has been observed in several dinoflagellate species, showing potential for a new CO2-proxy. Our results however demonstrate that light- and nitrogen-limitation also affect εp, thereby illustrating the need to carefully consider prevailing environmental conditions. PMID:27153107

  10. Combined Effects of Ocean Acidification and Light or Nitrogen Availabilities on 13C Fractionation in Marine Dinoflagellates

    PubMed Central

    Hoins, Mirja; Eberlein, Tim; Groβmann, Christian H.; Brandenburg, Karen; Reichart, Gert-Jan; Rost, Björn; Sluijs, Appy; Van de Waal, Dedmer B.

    2016-01-01

    Along with increasing oceanic CO2 concentrations, enhanced stratification constrains phytoplankton to shallower upper mixed layers with altered light regimes and nutrient concentrations. Here, we investigate the effects of elevated pCO2 in combination with light or nitrogen-limitation on 13C fractionation (εp) in four dinoflagellate species. We cultured Gonyaulax spinifera and Protoceratium reticulatum in dilute batches under low-light (‘LL’) and high-light (‘HL’) conditions, and grew Alexandrium fundyense and Scrippsiella trochoidea in nitrogen-limited continuous cultures (‘LN’) and nitrogen-replete batches (‘HN’). The observed CO2-dependency of εp remained unaffected by the availability of light for both G. spinifera and P. reticulatum, though at HL εp was consistently lower by about 2.7‰ over the tested CO2 range for P. reticulatum. This may reflect increased uptake of (13C-enriched) bicarbonate fueled by increased ATP production under HL conditions. The observed CO2-dependency of εp disappeared under LN conditions in both A. fundyense and S. trochoidea. The generally higher εp under LN may be associated with lower organic carbon production rates and/or higher ATP:NADPH ratios. CO2-dependent εp under non-limiting conditions has been observed in several dinoflagellate species, showing potential for a new CO2-proxy. Our results however demonstrate that light- and nitrogen-limitation also affect εp, thereby illustrating the need to carefully consider prevailing environmental conditions. PMID:27153107

  11. Interpreting terrestrial organic carbon isotope records across natural and anthropogenic pCO2 change

    NASA Astrophysics Data System (ADS)

    Schubert, B.; Jahren, H.

    2014-12-01

    Changes in the net carbon isotope fractionation (Δδ13C) measured in organic carbon from terrestrial substrates results from changes in climate, plant community shifts, and pCO2 level, but separating out these effects in the geologic record can be difficult. Here we present a compilation of 614 Δδ13C measurements on bulk terrestrial organic matter (TOM) and fossil leaves from 23 distinct records within 19 published studies that span the last 30,000 years up to the industrial revolution. To this dataset we add 2735 Δδ13C measurements made on tree ring tissue from 51 records that extend from 1950 to 2010. These records together span the ~80 ppm rise in pCO2 from the Late Glacial to through the Holocene (190-270 ppm; fossil leaves and TOM), and the ~70 ppm rise observed across the last 60 years (310-380 ppm; tree-ring tissue). We find a 2.0‰ relative increase in Δδ13C value across Termination 1 (18,000-11,500 years BP) and a 1.0‰ increase in Δδ13C value recorded in tree rings between 1950 and 2010. We use our recently developed relationship between pCO2 and Δδ13C to show that both increases in Δδ13C value exactly match, in trend and absolute magnitude, the increase in Δδ13C value we predict from our equations in response to rising pCO2 levels. These results have significance for the interpretation of terrestrial organic isotope records spanning both natural and anthropogenic pCO2 changes; we contend that environmental reconstructions based on long-term terrestrial Δδ13C records cannot be accurately interpreted until the isotope data are adjusted for known changes in pCO2 concentration.

  12. Fish tissue lipid-C:N relationships for correcting ä13C values and estimating lipid content in aquatic food web studies

    EPA Science Inventory

    Normalizing 13C values of animal tissue for lipid content is necessary to accurately interpret food web relationships from stable isotope analysis. This is because lipids are 13C-depleted relative to proteins and carbohydrates, and because lipid content varies among speci...

  13. sup 13 C-enriched ribonucleosides: Synthesis and application of sup 13 C- sup 1 H and sup 13 C- sup 13 C spin-coupling constants to assess furanose and N-glycoside bond conformations

    SciTech Connect

    Kline, P.C.; Serianni, A.S. )

    1990-09-26

    Adenosine (1), cytidine (2), guanosine (3), and uridine (4) have been prepared chemically with {sup 13}C enrichment (99 atom %) at C1{prime} and C2{prime} of the ribose ring. Reliable synthetic protocols have been developed to permit access to millimole quantities of labeled ribonucleosides required for structural studies of stable isotopically labeled oligonucleotides and for in vivo metabolism studies. High-resolution {sup 1}H and {sup 13}C NMR spectra of the enriched ribonucleosides have been obtained, and {sup 13}C-{sup 13}C and {sup 13}C-{sup 1}H spin-coupling constants have been measured for pathways within the {beta}-D-ribofuranose ring and across the N-glycoside bond. Related couplings were determined in methyl {alpha}- and {beta}-D-riboruanosides (5,6), and in two conformationally constrained nucleosides, 2,2{prime}-anhydro-(1-{beta}-D-arabinofuranosyl)uracil (7) and 2{prime},3{prime}-O-isopropylidene-2,5{prime}-O-cyclouridine (8). The latter data were used to construct a crude Karplus curve for the {sup 13}C-C-N-{sup 13}C coupling pathway across the N-glycoside bond in 1-4. {sup 1}H-{sup 1}H, {sup 13}C-{sup 1}H, and {sup 13}C-{sup 13}C coupling data are used to evaluate current models describing the conformational dynamics of 1-4 in aqueous solution.

  14. Synthesis Of [2h, 13c]M [2h2m 13c], And [2h3,, 13c] Methyl Aryl Sulfones And Sulfoxides

    DOEpatents

    Martinez, Rodolfo A.; Alvarez, Marc A.; Silks, III, Louis A.; Unkefer, Clifford J.; Schmidt, Jurgen G.

    2004-07-20

    The present invention is directed to labeled compounds, [.sup.2 H.sub.1, .sup.13 C], [.sup.2 H.sub.2, .sup.13 C] and [.sup.2 H.sub.3, .sup.13 C]methyl aryl sulfones and [.sup.2 H.sub.1, .sup.13 C], [.sup.2 H.sub.2, .sup.13 C] and [.sup.2 H.sub.3, .sup.13 C]methyl aryl sulfoxides, wherein the .sup.13 C methyl group attached to the sulfur of the sulfone or sulfoxide includes exactly one, two or three deuterium atoms and the aryl group is selected from the group consisting of 1-naphthyl, substituted 1-naphthyl, 2-naphthyl, substituted 2-naphthyl, and phenyl groups with the structure: ##STR1## wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4 and R.sub.5 are each independently, hydrogen, a C.sub.1 -C.sub.4 lower alkyl, a halogen, an amino group from the group consisting of NH.sub.2, NHR and NRR' where R and R' are each a C.sub.1 -C.sub.4 lower alkyl, a phenyl, or an alkoxy group. The present invention is also directed to processes of preparing methyl aryl sulfones and methyl aryl sulfoxides.

  15. What is the main driver of atmospheric CO2 dynamic: ocean or permafrost?

    NASA Astrophysics Data System (ADS)

    Zimov, S. A.; Zimov, N.

    2010-12-01

    Majority have assumed that during the Last Deglaciation (LD) ocean was a strong source of carbon (C) transporting hundreds of gigatons of C into the terrestrial and atmospheric storages. Increase in the δ13C of foraminifera shells during the LD by 0.3-0.4 per mil considered as an evidence of such a source. However terrestrial and oceanic branches of the biological carbon cycle have very similar carbon isotopic signatures and carbon storage capacities. So the same δ13C increase could be caused by an oceanic bio-productivity increase and the increase of C in bottom sediments (Brovkin et al. 2002). Additionally it has been shown experimentally that at 90 ppmv increase in atmospheric CO2, due to changes in the concentration of carbonate ions in sea water, would cause the δ13C of foraminifera shells to increase by at least 0.25-0.5 per mil (Spero et al. 1997). At all stable parameters to equilibrate for 90 ppm CO2 increase in the atmosphere ocean inorganic C reservoir should have increased by 1800 Gt C (Sigman et al. 2000). Therefore it is very hard to find a mechanism which would allow ocean in LD to release carbon instead of absorbing it, and such a mechanism haven’t been found so far. Methane (CH4) produced by steppe-tundra biome (ST) soil thawing has a unique isotopic signal depleted in all isotopes. Inclusion of this source into a model of the atmospheric methane isotope budget allowed us to reconstruct the dynamics of methane’s main sources. Results indicated that thawing of ST soils during the deglaciation, were the largest methane source and resulted in 255 Gt C emitted in the form of CH4 to the atmosphere (Zimov, see AGU 2010). When soil turns anaerobic only minor portion of soil C converts into CH4. Bigger portion of ST didn’t turn anaerobic at all and all decomposing C was turned into CO2. Besides that part of the soil CH4 flux was consumed by methanotrophs. Therefore C storage in ST soils were many times higher then CH4 emission into the atmosphere

  16. The 13C/2H-glucose test for determination of small intestinal lactase activity.

    PubMed

    Vonk, R J; Stellaard, F; Priebe, M G; Koetse, H A; Hagedoorn, R E; De Bruijn, S; Elzinga, H; Lenoir-Wijnkoop, I; Antoine, J M

    2001-03-01

    To diagnose hypolactasia, determination of lactase enzyme activity in small intestinal biopsy material is considered to be the golden standard. Because of its strongly invasive character and the sampling problems, alternative methods have been looked for. We analysed the 13C-glucose response in serum after consumption of 25 g of naturally enriched 13C-lactose. As an internal standard, 0.5 g of 2H-glucose was added and the 2H-glucose response in serum was measured simultaneously. The studies were performed in healthy volunteers with a background of genetically determined lactase nonpersistence (n = 12; low lactase activity) and lactase persistence (n = 27; high lactase activity). The results were compared with those of the lactose hydrogen breath test, the lactose 13CO2 breath test and the previously described 13C-lactose digestion test. After consumption of 13C-lactose and 2H-glucose, the mean ratio 13C-glucose/2H-glucose concentration in serum at 45-75 min was 0.26 +/- 0.09 in the low lactase activity group and 0.93 +/- 0.17 in the high lactase activity group (P < 0.01). Threshold of the ratio between digesters and maldigesters was calculated as 0.46. Accuracy of the new test was superior to all other tests. We conclude that the 13C/2H-glucose test has the potential of determining the small intestinal lactase activity in vivo and of estimating the amount of lactose which is digested in the small intestine. PMID:11264650

  17. The 13C/2H-glucose test for determination of small intestinal lactase activity.

    PubMed

    Vonk, R J; Stellaard, F; Priebe, M G; Koetse, H A; Hagedoorn, R E; De Bruijn, S; Elzinga, H; Lenoir-Wijnkoop, I; Antoine, J M

    2001-03-01

    To diagnose hypolactasia, determination of lactase enzyme activity in small intestinal biopsy material is considered to be the golden standard. Because of its strongly invasive character and the sampling problems, alternative methods have been looked for. We analysed the 13C-glucose response in serum after consumption of 25 g of naturally enriched 13C-lactose. As an internal standard, 0.5 g of 2H-glucose was added and the 2H-glucose response in serum was measured simultaneously. The studies were performed in healthy volunteers with a background of genetically determined lactase nonpersistence (n = 12; low lactase activity) and lactase persistence (n = 27; high lactase activity). The results were compared with those of the lactose hydrogen breath test, the lactose 13CO2 breath test and the previously described 13C-lactose digestion test. After consumption of 13C-lactose and 2H-glucose, the mean ratio 13C-glucose/2H-glucose concentration in serum at 45-75 min was 0.26 +/- 0.09 in the low lactase activity group and 0.93 +/- 0.17 in the high lactase activity group (P < 0.01). Threshold of the ratio between digesters and maldigesters was calculated as 0.46. Accuracy of the new test was superior to all other tests. We conclude that the 13C/2H-glucose test has the potential of determining the small intestinal lactase activity in vivo and of estimating the amount of lactose which is digested in the small intestine.

  18. 13C labelled cholesteryl octanoate breath test for assessing pancreatic exocrine insufficiency

    PubMed Central

    Ventrucci, M; Cipolla, A; Ubalducci, G; Roda, A; Roda, E

    1998-01-01

    Background—A non-invasive test for assessment of fat digestion has been developed based on the intraluminal hydrolysis of cholesteryl-[1-13C]octanoate by pancreatic esterase. 
Aims—To determine the diagnostic performance of this breath test in the assessment of exocrine pancreatic function. 
Methods—The test was performed in 20 healthy controls, 22 patients with chronic pancreatic disease (CPD), four with biliopancreatic diversion (BPD), and 32 with non-pancreatic digestive diseases (NPD); results were compared with those of other tubeless tests (faecal chymotrypsin and fluorescein dilaurate test). 
Results—Hourly recoveries of 13CO2 were significantly lower in CPD when compared with healthy controls or NPD. In patients with CPD with mild to moderate insufficiency, the curve of 13CO2 recovery was similar to that of healthy controls, while in those with severe insufficiency it was flat. In three patients with CPD with severe steatorrhoea, a repeat test after pancreatic enzyme supplementation showed a significant rise in 13CO2 recovery. The four BPD patients had low and delayed 13CO2 recovery. Only eight of the 32 patients with NPD had abnormal breath test results. There was a significant correlation between the results of the breath test and those of faecal chymotrypsin, the fluorescein dilaurate test, and faecal fat measurements. For the diagnosis of pancreatic disease using the three hour cumulative 13CO2 recovery test, the sensitivity was 68.2% and specificity 75.0%; values were similar to those of the other two tubeless pancreatic function tests. In seven healthy controls, nine patients with CPD, and nine with NPD a second breath test was performed using Na-[1-13C]octanoate and a pancreatic function index was calculated as the ratio of 13C recovery obtained in the two tests: at three hours this index was abnormal in eight patients with CPD and in three with NPD. 
Conclusion—The cholesteryl-[1-13C]octanoate breath test can be useful for the

  19. Precise and traceable (13)C/(12)C isotope amount ratios by multicollector ICPMS.

    PubMed

    Santamaria-Fernandez, Rebeca; Carter, David; Hearn, Ruth

    2008-08-01

    A new method for the measurement of SI traceable carbon isotope amount ratios using a multicollector inductively coupled mass spectrometer (MC-ICPMS) is reported for the first time. Carbon (13)C/(12)C isotope amount ratios have been measured for four reference materials with carbon isotope amount ratios ranging from 0.010659 (delta(13)C(VPDB) = -46.6 per thousand) to 0.011601 (delta(13)C(VPDB) = +37 per thousand). Internal normalization by measuring boron (11)B/(10)B isotope amount ratios has been used to correct for the effects of instrumental mass bias. Absolute (13)C/(12)C ratios have been measured and corrected for instrumental mass bias and full uncertainty budgets have been calculated using the Kragten approach. Corrected (13)C/(12)C ratios for NIST RM8545 (Lithium Carbonate LSVEC), NIST RM8573 (L-Glutamic Acid USGS40), NIST RM8542 (IAEA-CH6 Sucrose) and NIST RM8574 (L-Glutamic Acid USGS41) differed from reference values by 0.06-0.20%. Excellent linear correlation (R = 0.9997) was obtained between corrected carbon isotope amount ratios and expected carbon isotope amount ratios of the four chosen NIST RMs. The method has proved to be linear within this range (from (13)C/(12)C = 0.010659 to (13)C/(12)C =0.011601), and therefore, it is suitable for the measurement of carbon isotope amount ratios within the natural range of variation of organic carbon compounds, carbonates, elemental carbon, carbon monoxide, and carbon dioxide. In addition, a CO2 gas sample previously characterized in-house by conventional dual inlet isotope ratio mass spectrometry has been analyzed and excellent agreement has been found between the carbon isotope amount ratio value measured by MC-ICPMS and the IRMS measurements. Absolute values for carbon isotope amount ratios traceable to the SI are given for each NIST RM, and the combined uncertainty budget (including instrumental error and each parameter contributing to Russell expression for mass bias correction) has been found to be < 0

  20. A Proof of Concept Study to Detect Urease Producing Bacteria in Lungs Using Aerosolized 13C-Urea

    PubMed Central

    Timmins, Graham; Davies, Lea; Heynekamp, Theresa; Harkins, Michelle; Sharp, Zachary D.; Kelly, H. William

    2016-01-01

    This is a “proof of concept” study to determine whether inhalation of 13C-urea can be safely used to detect the presence of urease producing bacteria in the airways of patients with cystic fibrosis (CF) by detecting 13CO2 in breath. This was a prospective, 2-part, open label, single-center, single-arm, single-administration, dose-escalation investigational device exemption trial. First, the safety of 20 and 50 mg inhaled 13C-urea was evaluated in 6 healthy adult participants. Then, 3 adult CF participants colonized with Pseudomonas aeruginosa were enrolled for each dose of inhaled 13C-urea. The safety of inhaled 13C-urea was assessed by spirometry and physical examination. 13C-urea was administered using a jet nebulizer, followed by serial spirometry (10 min and 30 min post inhalation) and collection of exhaled breath at 5, 10, and 15 min post inhalation. There was no clinical significant change in any of the spirometry values compared to baseline in healthy participants and CF patients. Mean of 13CO2/12CO2 delta over baseline (DOB) values in CF participants at 5, 10, and 15 min post inhalation was as follows: 20 mg dose 4‰ (2.2‰–4.9‰), 1‰ (1.0‰–1.4‰), and 1‰ (0.4‰–1.5‰); 50 mg dose: 10‰ (6.2‰–14.5‰), 3‰ (2.1‰–4.3‰), and 1.5‰ (0.6‰–2.3‰). Inhaled 13C-urea for detection of urease producing bacteria was safe, and preliminary data suggest that 13CO2/12CO2 DOB values may be higher in CF patients with P. aeruginosa at 5–10 min after inhalation of 13C-urea. A future direction is to investigate use of inhaled 13C-urea in young children who have difficulty producing sputum for culturing. PMID:27458537

  1. Characterization of Acetate and Pyruvate Metabolism in Suspension Cultures of Zea mays by 13C NMR Spectroscopy

    PubMed Central

    Ashworth, Dennis J.; Lee, Rino Y.; Adams, Douglas O.

    1987-01-01

    Carbon-13 nuclear magnetic resonance (NMR) spectroscopy has been applied to the direct observation of acetate and pyruvate metabolism in suspension cultures of Zea mays (var Black Mexican Sweet). Growth of the corn cells in the presence of 2 millimolar [2-13C]acetate resulted in a rapid uptake of the substrate from the medium and initial labeling (0-4 hours) of primarily the intracellular glutamate and malate pools. Further metabolism of these intermediates resulted in labeling of glutamine, aspartate, and alanine. With [1-13C]acetate as the substrate very little incorporation into intermediary metabolites was observed in the 13C NMR spectra due to loss of the label as 13CO2. Uptake of [3-13C]pyruvate by the cells was considerably slower than with [2-13C]acetate; however, the labelling patterns were similar with the exception of increased [3-13C] alanine generation with pyruvate as the substrate. Growth of the cells for up to 96 hours with 2 millimolar [3-13C]pyruvate ultimately resulted in labeling of valine, leucine, isoleucine, threonine, and the polyamine putrescine. PMID:16665721

  2. Stable carbon isotope analysis in a South Texas cave: Investigating sources of CO2 production

    NASA Astrophysics Data System (ADS)

    Thompson, Reece

    Studies of interactions between modern local climate, cave atmosphere, and ?13C ratios are needed to determine sources of CO2 in caves, and the cycles of seasonal variations that alter karst geochemistry. A seasonal study, focusing on the analysis of stable isotopes collected from a modern cave system, was conducted in Robber Baron Cave (RBC) in order to identify sources of CO2 in its atmosphere. Determining what conditions affect cave morphology and the transfer path of carbon through a cave system is necessary in order to assess the role of caves in the carbon cycle and correctly interpret past ecological changes. This study investigates the extent that stable isotopic values of carbon in CO2 are affected by CO2 sourced from soils, bedrock, atmospheric air, and vegetation, and how ?13C signals are transmitted in a modern cave system. This study also measures how ventilation affects CO2 concentration and ?13C on seasonal scales. In-cave air grab samples were collected monthly at various transects located in RBC in order to measure CO2 composition in addition to factors such as temperature, and barometric pressure. Soil gas and limestone bedrock were also collected and tested for ?13C composition. Air samples were analyzed using an Ambient Air-Model G2101-I Picarro Cavity Ring-Down Spectroscopy Analyzer for both the concentration and ?13C isotopic value of CO2. These values were then compared to isotopic values of known sources of CO2 in order to determine possible sources of CO2 that result in high CO2 concentrations found in RBC. The background stable isotopic value of carbon from CO2 measured in RBC is -19.1‰ VPDB.

  3. Strength and limits using 13C phospholipid fatty acid analysis in soil ecology

    NASA Astrophysics Data System (ADS)

    Watzinger, Andrea

    2016-04-01

    This presentation on microbial phospholipid biomarkers, their isotope analysis and their ability to reveal soil functions summarizes experiences gained by the author for more than 10 years. The amount and composition of phospholipid fatty acids (PLFAs) measured in environmental samples strongly depend on the methodology. To achieve comparable results the extraction, separation and methylation method must be kept constant. PLFAs patterns are sensitive to microbial community shifts even though the taxonomic resolution of PLFAs is low. The possibility to easily link lipid biomarkers with stable isotope techniques is identified as a major advantage when addressing soil functions. Measurement of PLFA isotopic ratios is sensitive and enables detecting isotopic fractionation. The difference between the carbon isotopic ratio of single PLFAs and their substrate (δ13C) can vary between -6 and +11‰. This difference derives from the fractionation during biosynthesis and from substrate inhomogeneity. Consequently, natural abundance studies are restricted to quantifying substrate uptake of the total microbial biomass. In contrast, artificial labelling enables quantifying carbon uptake into single PLFAs, but labelling success depends on homogeneous and undisturbed label application. Current developments in microbial ecology (e.g. 13C and 15N proteomics) and isotope techniques (online monitoring of CO2 isotope ratios) will likely improve soil functional interpretations in the future. 13C PLFA analysis will continue to contribute because it is affordable, sensitive and allows frequent sampling combined with the use of small amounts of 13C label.

  4. /sup 13/C nuclear magnetic resonance studies of cardiac metabolism

    SciTech Connect

    Seeholzer, S.H.

    1985-01-01

    The last decade has witnessed the increasing use of Nuclear Magnetic Resonance (NMR) techniques for following the metabolic fate of compounds specifically labeled with /sup 13/C. The goals of the present study are: (1) to develop reliable quantitative procedures for measuring the /sup 13/C enrichment of specific carbon sites in compounds enriched by the metabolism of /sup 13/C-labeled substrates in rat heart, and (2) to use these quantitative measurements of fractional /sup 13/C enrichment within the context of a mathematical flux model describing the carbon flow through the TCA cycle and ancillary pathways, as a means for obtaining unknown flux parameters. Rat hearts have been perfused in vitro with various combinations of glucose, acetate, pyruvate, and propionate to achieve steady state flux conditions, followed by perfusion with the same substrates labeled with /sup 13/C in specific carbon sites. The hearts were frozen at different times after addition of /sup 13/C-labeled substrates and neutralized perchloric acid extracts were used to obtain high resolution proton-decoupled /sup 13/C NMR spectra at 90.55 MHz. The fractional /sup 13/C enrichment (F.E.) of individual carbon sites in different metabolites was calculated from the area of the resolved resonances after correction for saturation and nuclear Overhauser effects. These F.E. measurements by /sup 13/C NMR were validated by the analysis of /sup 13/C-/sup 1/H scalar coupling patterns observed in /sup 1/H NMR spectra of the extracted metabolites. The results obtained from perfusion of hearts glucose plus either (2-/sup 13/C) acetate or (3-/sup 13/C) pyruvate are similar to those obtained by previous investigators using /sup 14/C-labeled substrates.

  5. Effects of eustatic sea-level change, ocean dynamics, and iron fertilization on atmospheric pCO2 and seawater composition over the last 130 000 years

    NASA Astrophysics Data System (ADS)

    Wallmann, K.; Schneider, B.; Sarnthein, M.

    2015-06-01

    We developed and employed an earth system model to explore the forcings of atmospheric pCO2 change and the chemical and isotopic evolution of seawater over the last glacial cycle. Concentrations of dissolved phosphorus, reactive nitrogen, molecular oxygen, dissolved inorganic carbon (DIC), total alkalinity (TA), 13C-DIC and 14C-DIC were calculated for 24 ocean boxes. The bi-directional water fluxes between these model boxes were derived from a 3-D circulation field of the modern ocean (Opa 8.2, NEMO) and tuned such that tracer distributions calculated by the box model were consistent with observational data from the modern ocean. To model the last 130 kyr, we employed records of past changes in sea-level, ocean circulation, and dust deposition. According to the model, about half of the glacial pCO2 drawdown may be attributed to marine regressions. The glacial sea-level low-stands implied steepened ocean margins, a reduced burial of particulate organic carbon, phosphorus, and neritic carbonate at the margin seafloor, a decline in benthic denitrification, and enhanced weathering of emerged shelf sediments. In turn, they led to a distinct rise in the standing stocks of DIC, TA, and nutrients in the global ocean, promoted the glacial sequestration of atmospheric CO2 in the ocean, and added 13C- and 14C-depleted DIC to the ocean as recorded in benthic foraminifera signals. The other half of the glacial drop in pCO2 was linked to reduced deep ocean dynamics, a shoaling of Atlantic meridional overturning circulation, and a rise in iron fertilization. The increased transit time of deep waters in the glacial ocean led to significant 14C depletions with respect to the atmosphere. The deglacial rapid and stepwise rise in atmospheric pCO2 was induced by upwelling both in the Southern Ocean and subarctic North Pacific and promoted by a drop in dust-borne iron discharge to the Southern Ocean. The deglacial sea-level rise led to a gradual decline in nutrient, DIC, and TA stocks

  6. Unraveling carbohydrate transport mechanisms in young beech trees (Fagus sylvatica f. purpurea) by 13CO2 efflux measurements from stem and soil

    NASA Astrophysics Data System (ADS)

    Thoms, Ronny; Muhr, Jan; Keitel, Claudia; Kayler, Zachary; Gavrichkova, Olga; Köhler, Michael; Gessler, Arthur; Gleixner, Gerd

    2016-04-01

    Transport mechanisms of soluble carbohydrates and diurnal CO2 efflux from tree stems and surrounding soil are well studied. However, the effect of transport carbohydrates on respiration and their interaction with storage processes is largely unknown. Therefore, we performed a set of 13CO2 pulse labeling experiments on young trees of European beech (Fagus sylvatica f. purpurea). We labeled the whole tree crowns in a closed transparent plastic chamber with 99% 13CO2 for 30 min. In one experiment, only a single branch was labeled and removed 36 hours after labeling. In all experiments, we continuously measured the 13CO2 efflux from stem, branch and soil and sampled leaf and stem material every 3 h for 2 days, followed by a daily sampling of leaves in the successive 5 days. The compound specific δ 13C value of extracted soluble carbohydrates from leaf and stem material was measured by high-performance liquid chromatography linked with an isotope ratio mass spectrometer (HPLC-IRMS). The 13CO2 signal from soil respiration occurred only few hours after labeling indicating a very high transport rate of carbohydrates from leaf to roots and to the rhizosphere. The label was continuously depleted within the next 5 days. In contrast, we observed a remarkable oscillating pattern of 13CO2 efflux from the stem with maximum 13CO2 enrichment at noon and minima at night time. This oscillation suggests that enriched carbohydrates are respired during the day, whereas in the night the enriched sugars are not respired. The observed oscillation in stem 13CO2 enrichment remained unchanged even when only single branches were labelled and cut right afterwards. Thus, storage and conversion of carbohydrates only occurred within the stem. The δ13C patterns of extracted soluble carbohydrates showed, that a transformation of transitory starch to carbohydrates and vice versa was no driver of the oscillating 13CO2 efflux from the stem. Carbohydrates might have been transported in the phloem to

  7. Interaction between rhizosphere microorganisms and plant roots: 13C fluxes in the rhizosphere after pulse labeling

    NASA Astrophysics Data System (ADS)

    Yevdokimov, I. V.; Ruser, R.; Buegger, F.; Marx, M.; Munch, J. C.

    2007-07-01

    The input dynamics of labeled C into pools of soil organic matter and CO2 fluxes from soil were studied in a pot experiment with the pulse labeling of oats and corn under a 13CO2 atmosphere, and the contribution of the root and microbial respiration to the emission of CO2 from the soil was determined from the fluxes of labeled C in the microbial biomass and the evolved carbon dioxide. A considerable amount of 13C (up to 96% of the total amount of the label found in the rhizosphere soil) was incorporated into the biomass of the rhizosphere microorganisms. The diurnal fluctuations of the labeled C pools in the microbial biomass, dissolved organic carbon, and CO2 released in the rhizosphere of oats and corn were related to the day/night changes, i.e., to the on and off periods of the photosynthetic activity of the plants. The average contribution of the corn root respiration (70% of the total CO2 emission from the soil surface) was higher than that of the oats roots (44%), which was related to the lower incorporation of rhizodeposit carbon into the microbial biomass in the soil under the corn plants than in the soil under the oats plants.

  8. CO2 Exsolution from CO2 Saturated Water: Core-Scale Experiments and Focus on Impacts of Pressure Variations.

    PubMed

    Xu, Ruina; Li, Rong; Ma, Jin; Jiang, Peixue

    2015-12-15

    For CO2 sequestration and utilization in the shallow reservoirs, reservoir pressure changes are due to the injection rate changing, a leakage event, and brine withdrawal for reservoir pressure balance. The amounts of exsolved CO2 which are influenced by the pressure reduction and the subsequent secondary imbibition process have a significant effect on the stability and capacity of CO2 sequestration and utilization. In this study, exsolution behavior of the CO2 has been studied experimentally using a core flooding system in combination with NMR/MRI equipment. Three series of pressure variation profiles, including depletion followed by imbibitions without or with repressurization and repetitive depletion and repressurization/imbibition cycles, were designed to investigate the exsolution responses for these complex pressure variation profiles. We found that the exsolved CO2 phase preferentially occupies the larger pores and exhibits a uniform spatial distribution. The mobility of CO2 is low during the imbibition process, and the residual trapping ratio is extraordinarily high. During the cyclic pressure variation process, the first cycle has the largest contribution to the amount of exsolved CO2. The low CO2 mobility implies a certain degree of self-sealing during a possible reservoir depletion. PMID:26509211

  9. CO2 Exsolution from CO2 Saturated Water: Core-Scale Experiments and Focus on Impacts of Pressure Variations.

    PubMed

    Xu, Ruina; Li, Rong; Ma, Jin; Jiang, Peixue

    2015-12-15

    For CO2 sequestration and utilization in the shallow reservoirs, reservoir pressure changes are due to the injection rate changing, a leakage event, and brine withdrawal for reservoir pressure balance. The amounts of exsolved CO2 which are influenced by the pressure reduction and the subsequent secondary imbibition process have a significant effect on the stability and capacity of CO2 sequestration and utilization. In this study, exsolution behavior of the CO2 has been studied experimentally using a core flooding system in combination with NMR/MRI equipment. Three series of pressure variation profiles, including depletion followed by imbibitions without or with repressurization and repetitive depletion and repressurization/imbibition cycles, were designed to investigate the exsolution responses for these complex pressure variation profiles. We found that the exsolved CO2 phase preferentially occupies the larger pores and exhibits a uniform spatial distribution. The mobility of CO2 is low during the imbibition process, and the residual trapping ratio is extraordinarily high. During the cyclic pressure variation process, the first cycle has the largest contribution to the amount of exsolved CO2. The low CO2 mobility implies a certain degree of self-sealing during a possible reservoir depletion.

  10. Determination of 15N/14N and 13C/12C in Solid and Aqueous Cyanides

    USGS Publications Warehouse

    Johnson, C.A.

    1996-01-01

    The stable isotopic compositions of nitrogen and carbon in cyanide compounds can be determined by combusting aliquots in sealed tubes to form N2 gas and CO2 gas and analyzing the gases by mass spectrometry. Free cyanide (CN-aq + HCNaq) in simple solutions can also be analyzed by first precipitating the cyanide as copper(II) ferrocyanide and then combusting the precipitate. Reproducibility is ??0.5??? or better for both ??15N and ??13C. If empirical corrections are made on the basis of carbon yields, the reproducibility of ??13C can be improved to ??0.2???. The analytical methods described herein are sufficiently accurate and precise to apply stable isotope techniques to problems of cyanide degradation in natural waters and industrial process solutions.

  11. Malate as a key carbon source of leaf dark-respired CO2 across different environmental conditions in potato plants

    PubMed Central

    Lehmann, Marco M.; Rinne, Katja T.; Blessing, Carola; Siegwolf, Rolf T. W.; Buchmann, Nina; Werner, Roland A.

    2015-01-01

    Dissimilation of carbon sources during plant respiration in support of metabolic processes results in the continuous release of CO2. The carbon isotopic composition of leaf dark-respired CO2 (i.e. δ 13 C R) shows daily enrichments up to 14.8‰ under different environmental conditions. However, the reasons for this 13C enrichment in leaf dark-respired CO2 are not fully understood, since daily changes in δ13C of putative leaf respiratory carbon sources (δ 13 C RS) are not yet clear. Thus, we exposed potato plants (Solanum tuberosum) to different temperature and soil moisture treatments. We determined δ 13 C R with an in-tube incubation technique and δ 13 C RS with compound-specific isotope analysis during a daily cycle. The highest δ 13 C RS values were found in the organic acid malate under different environmental conditions, showing less negative values compared to δ 13 C R (up to 5.2‰) and compared to δ 13 C RS of soluble carbohydrates, citrate and starch (up to 8.8‰). Moreover, linear relationships between δ 13 C R and δ 13 C RS among different putative carbon sources were strongest for malate during daytime (r2=0.69, P≤0.001) and nighttime (r2=0.36, P≤0.001) under all environmental conditions. A multiple linear regression analysis revealed δ 13 C RS of malate as the most important carbon source influencing δ 13 C R. Thus, our results strongly indicate malate as a key carbon source of 13C enriched dark-respired CO2 in potato plants, probably driven by an anapleurotic flux replenishing intermediates of the Krebs cycle. PMID:26139821

  12. Malate as a key carbon source of leaf dark-respired CO2 across different environmental conditions in potato plants.

    PubMed

    Lehmann, Marco M; Rinne, Katja T; Blessing, Carola; Siegwolf, Rolf T W; Buchmann, Nina; Werner, Roland A

    2015-09-01

    Dissimilation of carbon sources during plant respiration in support of metabolic processes results in the continuous release of CO2. The carbon isotopic composition of leaf dark-respired CO2 (i.e. δ (13) C R ) shows daily enrichments up to 14.8‰ under different environmental conditions. However, the reasons for this (13)C enrichment in leaf dark-respired CO2 are not fully understood, since daily changes in δ(13)C of putative leaf respiratory carbon sources (δ (13) C RS ) are not yet clear. Thus, we exposed potato plants (Solanum tuberosum) to different temperature and soil moisture treatments. We determined δ (13) C R with an in-tube incubation technique and δ (13) C RS with compound-specific isotope analysis during a daily cycle. The highest δ (13) C RS values were found in the organic acid malate under different environmental conditions, showing less negative values compared to δ (13) C R (up to 5.2‰) and compared to δ (13) C RS of soluble carbohydrates, citrate and starch (up to 8.8‰). Moreover, linear relationships between δ (13) C R and δ (13) C RS among different putative carbon sources were strongest for malate during daytime (r(2)=0.69, P≤0.001) and nighttime (r(2)=0.36, P≤0.001) under all environmental conditions. A multiple linear regression analysis revealed δ (13) C RS of malate as the most important carbon source influencing δ (13) C R . Thus, our results strongly indicate malate as a key carbon source of (13)C enriched dark-respired CO2 in potato plants, probably driven by an anapleurotic flux replenishing intermediates of the Krebs cycle.

  13. CO2 laser preionisation

    NASA Technical Reports Server (NTRS)

    Spiers, Gary D.

    1991-01-01

    The final report for work done during the reporting period of January 25, 1990 to January 24, 1991 is presented. A literature survey was conducted to identify the required parameters for effective preionization in TEA CO2 lasers and the methods and techniques for characterizing preionizers are reviewed. A numerical model of the LP-140 cavity was used to determine the cause of the transverse mode stability improvement obtained when the cavity was lengthened. The measurement of the voltage and current discharge pulses on the LP-140 were obtained and their subsequent analysis resulted in an explanation for the low efficiency of the laser. An assortment of items relating to the development of high-voltage power supplies is also provided. A program for analyzing the frequency chirp data files obtained with the HP time and frequency analyzer is included. A program to calculate the theoretical LIMP chirp is also included and a comparison between experiment and theory is made. A program for calculating the CO2 linewidth and its dependence on gas composition and pressure is presented. The program also calculates the number of axial modes under the FWHM of the line for a given resonator length. A graphical plot of the results is plotted.

  14. Diurnal and Seasonal Variation in the Carbon Isotope Composition of Leaf- and Root- respired CO2 in C3 and C4 Species

    NASA Astrophysics Data System (ADS)

    Sun, W.; Resco, V.; Chen, S.; Williams, D. G.

    2008-12-01

    The carbon isotope signature of leaf (δ13Cl) and root (δ13Cr) dark- respired CO2 records and integrates short-term metabolic changes. Plants with C3 and C4 photosynthetic metabolism are expected to differ in diurnal and seasonal patterns in δ13Cl and δ13Cr because of differences in photorespiration, isotopic fractionation at metabolic branch points and allocation patterns. A thorough understanding of the environmental and metabolic controls on δ13Cl and δ13Cr is necessary to interpret the δ13C of ecosystem respired CO2 and partition the CO2 efflux into autotrophic and heterotrophic respiration sources. We measured δ13Cl in two C3 tree species (Prosopis velutina and Celtis reticulata), a C3 herb (Viguiera dentata) and a C4 grass (Sporobolus wrightii), and δ13Cr in P. velutina and S. wrightii in a semiarid savanna in southeastern Arizona, USA. δ13Cl during the dry pre-monsoon period was relatively enriched in 13C during daytime periods and became depleted in 13C at night relative to daytime values for all species with the exception of S. wrightii, the C4 grass. δ13Cl in S. wrightii was strongly influenced by seasonal differences in water availability with a larger diurnal amplitude in δ13Cl (8.2 +/- 0.6‰) during the wet monsoon period compared to that in the dry pre-monsoon period (4.4 +/- 0.4‰). The δ13C values of starch and lipid fractions remained constant over diurnal periods within the pre-monsoon and monsoon seasons. For C3 species, δ13Cl and δ13C of the cumulative, flux-weighted photosynthate pool estimated from gas exchange were strongly positively correlated, suggesting that progressive 13C-enrichment of leaf-respired CO2 during the daytime period resulted from changes in the δ13C signature of respiratory substrates associated with short-term changes in photosynthetic 13C discrimination. Rapid decreases in δ13Cl following the daytime period was likely caused by decreases in the ratio of PDH:acetyl-CoA oxidation rather than by a shift in

  15. CO2 storage capacity estimation: Methodology and gaps

    USGS Publications Warehouse

    Bachu, S.; Bonijoly, D.; Bradshaw, J.; Burruss, R.; Holloway, S.; Christensen, N.P.; Mathiassen, O.M.

    2007-01-01

    Implementation of CO2 capture and geological storage (CCGS) technology at the scale needed to achieve a significant and meaningful reduction in CO2 emissions requires knowledge of the available CO2 storage capacity. CO2 storage capacity assessments may be conducted at various scales-in decreasing order of size and increasing order of resolution: country, basin, regional, local and site-specific. Estimation of the CO2 storage capacity in depleted oil and gas reservoirs is straightforward and is based on recoverable reserves, reservoir properties and in situ CO2 characteristics. In the case of CO2-EOR, the CO2 storage capacity can be roughly evaluated on the basis of worldwide field experience or more accurately through numerical simulations. Determination of the theoretical CO2 storage capacity in coal beds is based on coal thickness and CO2 adsorption isotherms, and recovery and completion factors. Evaluation of the CO2 storage capacity in deep saline aquifers is very complex because four trapping mechanisms that act at different rates are involved and, at times, all mechanisms may be operating simultaneously. The level of detail and resolution required in the data make reliable and accurate estimation of CO2 storage capacity in deep saline aquifers practical only at the local and site-specific scales. This paper follows a previous one on issues and development of standards for CO2 storage capacity estimation, and provides a clear set of definitions and methodologies for the assessment of CO2 storage capacity in geological media. Notwithstanding the defined methodologies suggested for estimating CO2 storage capacity, major challenges lie ahead because of lack of data, particularly for coal beds and deep saline aquifers, lack of knowledge about the coefficients that reduce storage capacity from theoretical to effective and to practical, and lack of knowledge about the interplay between various trapping mechanisms at work in deep saline aquifers. ?? 2007 Elsevier Ltd

  16. Functional groups identified by solid state 13C NMR spectroscopy

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Animal manure is generally high in organic matter intensity so it is well suitable for 13C nuclear magnetic resonance (NMR) analysis. Solid-state 13C NMR techniques used in characterizing organic matter and its components include, but are not limited to, cross-polarization /magic angle spinning (CP...

  17. Diethers enriched in 13C suggest carbon-limitation at the Lost City Hydrothermal Field

    NASA Astrophysics Data System (ADS)

    Bradley, A. S.; Hayes, J. M.; Summons, R. E.

    2004-12-01

    Active and inactive carbonate vent structures from the Lost City Hydrothermal Field (LCHF) contain up to 0.6% organic carbon including diverse lipids. Values of δ 13C for total organic carbon (TOC) range from -18.7‰ vs. VPDB at the active, high-temperature vent known as "The Beehive" (90° C), to -3.1‰ at Marker 7 (active, 70° C). Samples with relatively high levels of 13C also contained high amounts of isoprenoidal and nonisoprenoidal diethers. Samples more depleted in 13C lacked or contained low amounts of these diethers. The correlation between high 13C and abundant diethers is supported by compound-specific isotopic analyses. Archaeal and bacterial diethers are enriched in 13C relative to photosynthetically derived marine carbon. The biomarkers sn-2 hydroxyarchaeol, sn-3 hydroxyarchaeol, and dihydroxyarchaeol - considered diagnostic for methane-cycling archaea - had δ values ranging from -8.5 to +4.8‰ . Phylogenetic data confirms the presence at these vents of a single group of methanogens, related to the Methanosarcinales (Schrenk et al., 2004). Diethers with non-isoprenoidal alkyl chains are also present, are of presumed bacterial origin, and may indicated the presence of sulfate-reducing bacteria. Values of δ for these compounds range from -7.3 to +1.0‰ . At the Beehive vent, diether lipids are absent and the TOC is depleted in 13C. Coexistence of isotopically similar hydroxyarchaeols and nonisoprenoidal glycerol diethers is typical of marine, cold-seep environments at which concentrations of H2 are low and methane is oxidized anaerobically. At the LCHF, however, concentrations of H2 in pore waters reach 15 mM (Proskurowski et al., 2003). This H2, produced by serpentinization reactions, drives production (rather than oxidation) of methane. Simultaneously, sulfate-reducing bacteria can flourish as carbon-fixing autotrophs. Under such conditions, carbon may be the limiting substrate, its nearly complete consumption accounting for the enrichment of

  18. Non-CO2 greenhouse gases and climate change.

    PubMed

    Montzka, S A; Dlugokencky, E J; Butler, J H

    2011-08-03

    Earth's climate is warming as a result of anthropogenic emissions of greenhouse gases, particularly carbon dioxide (CO(2)) from fossil fuel combustion. Anthropogenic emissions of non-CO(2) greenhouse gases, such as methane, nitrous oxide and ozone-depleting substances (largely from sources other than fossil fuels), also contribute significantly to warming. Some non-CO(2) greenhouse gases have much shorter lifetimes than CO(2), so reducing their emissions offers an additional opportunity to lessen future climate change. Although it is clear that sustainably reducing the warming influence of greenhouse gases will be possible only with substantial cuts in emissions of CO(2), reducing non-CO(2) greenhouse gas emissions would be a relatively quick way of contributing to this goal.

  19. Determining CO2 storage potential during miscible CO2 enhanced oil recovery: Noble gas and stable isotope tracers

    USGS Publications Warehouse

    Shelton, Jenna L.; McIntosh, Jennifer C.; Hunt, Andrew; Beebe, Thomas L; Parker, Andrew D; Warwick, Peter; Drake, Ronald; McCray, John E.

    2016-01-01

    Rising atmospheric carbon dioxide (CO2) concentrations are fueling anthropogenic climate change. Geologic sequestration of anthropogenic CO2 in depleted oil reservoirs is one option for reducing CO2 emissions to the atmosphere while enhancing oil recovery. In order to evaluate the feasibility of using enhanced oil recovery (EOR) sites in the United States for permanent CO2 storage, an active multi-stage miscible CO2flooding project in the Permian Basin (North Ward Estes Field, near Wickett, Texas) was investigated. In addition, two major natural CO2 reservoirs in the southeastern Paradox Basin (McElmo Dome and Doe Canyon) were also investigated as they provide CO2 for EOR operations in the Permian Basin. Produced gas and water were collected from three different CO2 flooding phases (with different start dates) within the North Ward Estes Field to evaluate possible CO2 storage mechanisms and amounts of total CO2retention. McElmo Dome and Doe Canyon were sampled for produced gas to determine the noble gas and stable isotope signature of the original injected EOR gas and to confirm the source of this naturally-occurring CO2. As expected, the natural CO2produced from McElmo Dome and Doe Canyon is a mix of mantle and crustal sources. When comparing CO2 injection and production rates for the CO2 floods in the North Ward Estes Field, it appears that CO2 retention in the reservoir decreased over the course of the three injections, retaining 39%, 49% and 61% of the injected CO2 for the 2008, 2010, and 2013 projects, respectively, characteristic of maturing CO2 miscible flood projects. Noble gas isotopic composition of the injected and produced gas for the flood projects suggest no active fractionation, while δ13CCO2 values suggest no active CO2dissolution into formation water, or mineralization. CO2 volumes capable of dissolving in residual formation fluids were also estimated along with the potential to store pure-phase supercritical CO2. Using a combination

  20. CO2 Laser Market

    NASA Astrophysics Data System (ADS)

    Simonsson, Samuel

    1989-03-01

    It gives me a great deal of pleasure to introduce our final speaker of this morning's session for two reasons: First of all, his company has been very much in the news not only in our own community but in the pages of Wall Street Journal and in the world economic press. And, secondly, we would like to welcome him to our shores. He is a temporary resident of the United States, for a few months, forsaking his home in Germany to come here and help with the start up of a new company which we believe, probably, ranks #1 as the world supplier of CO2 lasers now, through the combination of former Spectra Physics Industrial Laser Division and Rofin-Sinar GMBH. Samuel Simonsson is the Chairman of the Board of Rofin-Sinar, Inc., here in the U.S. and managing director of Rofin-Sinar GMBH. It is a pleasure to welcome him.

  1. Taphonomy of deciduous leaves and changes in the d13C signal after deposition in fresh water settings

    NASA Astrophysics Data System (ADS)

    Reimann, Simon; Roth-Nebelsick, Anita; Nebelsick, James; Grein, Michaela

    2016-04-01

    Carbon isotopic signals from fossil plant material are an important source of information for palaeoecology and palaeoclimatology. Usually, the 13C isotope is depleted in plant material, compared to the atmospheric 13C content, because 13C is discriminated against 12C during the process of photosynthesis. The degree of 13C discrimination depends on the photosynthetic pathway (C3, C4 and CAM) and is substantially affected by environmental factors (for example, water stress). Various plant material components, however, differ also with respect to their 13C content. It is generally assumed that the d13C signal found in fossil plants reflects that of the living plant to a sufficient degree. Obtaining information on possible alterations during the taphonomic process is, however, desirable. In this study, changes in d13C of deciduous leaves are monitored, from the living leaf still attached to the tree to leaves deposited in fresh water setting for one or more years, thus focusing on early stages of taphonomy. The considered taxa are species from Quercus (oak) and Fagus (beech). Deposited leaves from three fresh water environments in Southwestern Germany were studied: active stream in a forest, still water pond in a forest, and a waterlogged moor environment. Additionally to the isotope measurements, the degree of leaf tissue degradation and colonization with degrading organisms were observed with Scanning Electron Microscopy.

  2. Hydrogen coupled CO2 fixation in legume cropping systems

    NASA Astrophysics Data System (ADS)

    Philpott, T.; Cen, Y.; Layzell, D. B.; Kyser, K.; Scott, N. A.

    2009-05-01

    Electron flow from oxidation of excess H2 released by root nodules was shown to contribute to microbial CO2 fixation in soybean crops. This discovery has important implications for carbon storage in soils used to grow legumes; however, further research is needed to understand the fate and turnover time of this H2-coupled CO2 fixation. Isotopic labeling of soil through incubation with 13CO2 was used to elucidate movement of sequestered carbon into soil carbon pools. Measurement of isotopic shifts was determined using Isotope Ratio Mass Spectrometry. Preliminary experiments have confirmed CO2 uptake through an isotopic shift (Δ13C -20.4 to -14.5 ‰) in 24 hour incubated soils labeled with 13CO2 (1% v/v, 99.5 Atom%) under elevated H2 concentration (6000 ppm). Other incubation experiments have confirmed the biotic nature of observed CO2 uptake by comparing isotopic shifts in oven dried and autoclaved soils to moist soil. Under an elevated H2 atmosphere, no significant isotopic shift was observed in dry and autoclaved soils whereas moist soil showed an isotopic shift of Δ13C -21.9 to 11.4 ‰ over 48 hours. Future experiments will involve longer incubations (7 days) and will be aimed at determining isotopic shifts within soil carbon pools. Samples will be incubated and fractionated into microbial biomass, light fraction carbon, and acid stable carbon and subsequent isotopic analysis will be carried out. This will help determine the distribution of H2- coupled fixed CO2 within soil carbon pools and the turnover time of sequestered carbon. This and further research may lead to modification of greenhouse gas coefficients for leguminous crops that includes a CO2 fixation component.

  3. Whole-core analysis by sup 13 C NMR

    SciTech Connect

    Vinegar, H.J.; Tutunjian, P.N. ); Edelstein, W.A.; Roemer, P.B. )

    1991-06-01

    This paper reports on a whole-core nuclear magnetic resonance (NMR) system that was used to obtain natural abundance {sup 13}C spectra. The system enables rapid, nondestructive measurements of bulk volume of movable oil, aliphatic/aromatic ratio, oil viscosity, and organic vs. carbonate carbon. {sup 13}C NMR can be used in cores where the {sup 1}H NMR spectrum is too broad to resolve oil and water resonances separately. A 5 1/4-in. {sup 13}C/{sup 1}H NMR coil was installed on a General Electric (GE) CSI-2T NMR imager/spectrometer. With a 4-in.-OD whole core, good {sup 13}C signal/noise ratio (SNR) is obtained within minutes, while {sup 1}H spectra are obtained in seconds. NMR measurements have been made of the {sup 13}C and {sup 1}H density of crude oils with a wide range of API gravities. For light- and medium-gravity oils, the {sup 13}C and {sup 1}H signal per unit volume is constant within about 3.5%. For heavy crudes, the {sup 13}C and {sup 1}H density measured by NMR is reduced by the shortening of spin-spin relaxation time. {sup 13}C and {sup 1}H NMR spin-lattice relaxation times were measured on a suite of Cannon viscosity standards, crude oils (4 to 60{degrees} API), and alkanes (C{sub 5} through C{sub 16}) with viscosities at 77{degrees}F ranging from 0.5 cp to 2.5 {times} 10{sup 7} cp. The {sup 13}C and {sup 1}H relaxation times show a similar correlation with viscosity from which oil viscosity can be estimated accurately for viscosities up to 100 cp. The {sup 13}C surface relaxation rate for oils on water-wet rocks is very low. Nonproton decoupled {sup 13}C NMR is shown to be insensitive to kerogen; thus, {sup 13}C NMR measures only the movable hydrocarbon content of the cores. In carbonates, the {sup 13}C spectrum also contains a carbonate powder pattern useful in quantifying inorganic carbon and distinguishing organic from carbonate carbon.

  4. NMR structure analysis of uniformly 13C-labeled carbohydrates.

    PubMed

    Fontana, Carolina; Kovacs, Helena; Widmalm, Göran

    2014-06-01

    In this study, a set of nuclear magnetic resonance experiments, some of them commonly used in the study of (13)C-labeled proteins and/or nucleic acids, is applied for the structure determination of uniformly (13)C-enriched carbohydrates. Two model substances were employed: one compound of low molecular weight [(UL-(13)C)-sucrose, 342 Da] and one compound of medium molecular weight ((13)C-enriched O-antigenic polysaccharide isolated from Escherichia coli O142, ~10 kDa). The first step in this approach involves the assignment of the carbon resonances in each monosaccharide spin system using the anomeric carbon signal as the starting point. The (13)C resonances are traced using (13)C-(13)C correlations from homonuclear experiments, such as (H)CC-CT-COSY, (H)CC-NOESY, CC-CT-TOCSY and/or virtually decoupled (H)CC-TOCSY. Based on the assignment of the (13)C resonances, the (1)H chemical shifts are derived in a straightforward manner using one-bond (1)H-(13)C correlations from heteronuclear experiments (HC-CT-HSQC). In order to avoid the (1) J CC splitting of the (13)C resonances and to improve the resolution, either constant-time (CT) in the indirect dimension or virtual decoupling in the direct dimension were used. The monosaccharide sequence and linkage positions in oligosaccharides were determined using either (13)C or (1)H detected experiments, namely CC-CT-COSY, band-selective (H)CC-TOCSY, HC-CT-HSQC-NOESY or long-range HC-CT-HSQC. However, due to the short T2 relaxation time associated with larger polysaccharides, the sequential information in the O-antigen polysaccharide from E. coli O142 could only be elucidated using the (1)H-detected experiments. Exchanging protons of hydroxyl groups and N-acetyl amides in the (13)C-enriched polysaccharide were assigned by using HC-H2BC spectra. The assignment of the N-acetyl groups with (15)N at natural abundance was completed by using HN-SOFAST-HMQC, HNCA, HNCO and (13)C-detected (H)CACO spectra.

  5. NMR structure analysis of uniformly 13C-labeled carbohydrates.

    PubMed

    Fontana, Carolina; Kovacs, Helena; Widmalm, Göran

    2014-06-01

    In this study, a set of nuclear magnetic resonance experiments, some of them commonly used in the study of (13)C-labeled proteins and/or nucleic acids, is applied for the structure determination of uniformly (13)C-enriched carbohydrates. Two model substances were employed: one compound of low molecular weight [(UL-(13)C)-sucrose, 342 Da] and one compound of medium molecular weight ((13)C-enriched O-antigenic polysaccharide isolated from Escherichia coli O142, ~10 kDa). The first step in this approach involves the assignment of the carbon resonances in each monosaccharide spin system using the anomeric carbon signal as the starting point. The (13)C resonances are traced using (13)C-(13)C correlations from homonuclear experiments, such as (H)CC-CT-COSY, (H)CC-NOESY, CC-CT-TOCSY and/or virtually decoupled (H)CC-TOCSY. Based on the assignment of the (13)C resonances, the (1)H chemical shifts are derived in a straightforward manner using one-bond (1)H-(13)C correlations from heteronuclear experiments (HC-CT-HSQC). In order to avoid the (1) J CC splitting of the (13)C resonances and to improve the resolution, either constant-time (CT) in the indirect dimension or virtual decoupling in the direct dimension were used. The monosaccharide sequence and linkage positions in oligosaccharides were determined using either (13)C or (1)H detected experiments, namely CC-CT-COSY, band-selective (H)CC-TOCSY, HC-CT-HSQC-NOESY or long-range HC-CT-HSQC. However, due to the short T2 relaxation time associated with larger polysaccharides, the sequential information in the O-antigen polysaccharide from E. coli O142 could only be elucidated using the (1)H-detected experiments. Exchanging protons of hydroxyl groups and N-acetyl amides in the (13)C-enriched polysaccharide were assigned by using HC-H2BC spectra. The assignment of the N-acetyl groups with (15)N at natural abundance was completed by using HN-SOFAST-HMQC, HNCA, HNCO and (13)C-detected (H)CACO spectra. PMID:24771296

  6. Canopy CO2 enrichment permits tracing the fate of recently assimilated carbon in a mature deciduous forest.

    PubMed

    Keel, Sonja G; Siegwolf, Rolf T W; Körner, Christian

    2006-01-01

    How rapidly newly assimilated carbon (C) is invested into recalcitrant structures of forests, and how closely C pools and fluxes are tied to photosynthesis, is largely unknown. A crane and a purpose-built free-air CO2 enrichment (FACE) system permitted us to label the canopy of a mature deciduous forest with 13C-depleted CO2 for 4 yr and continuously trace the flow of recent C through the forest without disturbance. Potted C4 grasses in the canopy ('isometers') served as a reference for the C-isotope input signal. After four growing seasons, leaves were completely labelled, while newly formed wood (tree rings) still contained 9% old C. Distinct labels were found in fine roots (38%) and sporocarps of mycorrhizal fungi (62%). Soil particles attached to fine roots contained 9% new C, whereas no measurable signal was detected in bulk soil. Soil-air CO2 consisted of 35% new C, indicating that considerable amounts of assimilates were rapidly returned back to the atmosphere. These data illustrate a relatively slow dilution of old mobile C pools in trees, but a pronounced allocation of very recent assimilates to C pools of short residence times.

  7. Emerging Patterns In The Isotopic Composition Of Soil CO2 Concentrations, Soil CO2 Production, And Soil-Atmosphere CO2 Exchange At The Watershed Scale: On The Intersection Between Hydrology And Biology In The Critical Zone

    NASA Astrophysics Data System (ADS)

    Riveros-Iregui, D. A.; Liang, L.; Lorenzo, T. M.

    2014-12-01

    Stable isotopes are commonly used to understand how physical and biological processes mediate the exchange of carbon between terrestrial ecosystems and the atmosphere. Numerous studies have described fundamental relationships between environmental variables, the carbon isotopic composition (δ13C) of recently assimilated sugars in plants, litter, soil carbon, or recently respired CO2. However, studies that examine the spatial variability of the 13C content of forest soils at the landscape scale are lacking. We report on measurements of the carbon isotopic composition of soil CO2 concentrations (δ13CC), soil CO2 production (δ13CP), and soil-atmosphere CO2 exchange (δ13CD) across a subalpine forest of the northern Rocky Mountains of Montana over two growing seasons. We evaluate the variability of these measurements across different landscape positions. Our analysis demonstrates that soil moisture and the lateral redistribution of soil water are strong predictors of the spatial variability of δ13CC, δ13CP, and δ13CD at the watershed scale. We suggest that there are concomitant yet independent effects of soil water on physical (i.e., soil gas diffusivity) and biological (i.e., photosynthetic activity) processes that mediate the 13C composition of forest soils. We show systematic spatial variability in the δ13C of forest soils at the landscape scale that can be useful to accurately predict and model land-atmosphere CO2 exchange over complex terrain.

  8. Study of Urban environmental quality through Isotopes δ13C

    NASA Astrophysics Data System (ADS)

    González-Sosa, E.; Mastachi-Loza, C.; Becerril-Piña, R.; Ramos-Salinas, N. M.

    2012-04-01

    Usually, trees with similar pH values on their bark develop epiphytes of similar species, the acidity to be a factor for growth. The aim of the study was evaluate the air quality through isotope δ13C in order to define the levels of environmental quality in the city of Queretaro, Mexico. In this work were collected at least 4 epiphytes positioned in trees of the species Prosopis Laevigata at 25 sites of Queretaro City. The samples were analyzed for trace elements with an inductively coupled plasma atomic emission spectroscopy (ICP). The collecting took place during dry period, in May and early rain June 2011 period, and on four sectors to identify the spatial distribution of pollution, using isotopic analysis of concentration of δ 13C. According with the results there are significant differences among the species in each of the sampled areas. The 5 February Avenue presented greater diversity and richness of δ13C, followed by those who were surveyed in the proximity of the UAQ and finally in the middle-east area. An average value of δ13C-17.92%, followed by those surveyed in the vicinity of the UAQ that correspond to sector I and II with an concentration of δ13C-17.55% and δ13C-17.22%, and finally the samples collected in trees scattered in the East-Sector II and IV with a value of δ13C-17.02% and δ13C-15.62%, respectively. Also were observed differences between the dry and wet period. It is likely that these results of δ 13C in moist period reflect the drag of the isotopes due to rain events that could mark a trend in the dilution of this element, however there is a trend in terms of abundance and composition of finding more impact in those species sampled in dry period, in May and early June 2011.

  9. C-13/C-12 ratio in methane from the flooded Amazon forest

    NASA Technical Reports Server (NTRS)

    Tyler, Stanley C.; Blake, Donald R.; Rowland, F. Sherwood

    1987-01-01

    The C1-C4 hydrocarbon concentrations and the C-13/C-12 ratio in CH4 detected in air samples collected in the Amazon region (3.5 deg S latitude and 5.9 deg W longitude) are analyzed. It is observed that the CH4 concentrations of each sample are enhanced over the background concentration for remote locations, and the C-13/C-12 ratio in this biogenic methane is depleted in C-13 relative to atmospheric CH4. It is concluded, from the C2-C4 hydrocarbon data, that minor yields of C2-C4 hyrocarbons are released coincident with CH4; however, the minor yields do not contribute to the regionally enhanced concentrations of hydrocarbons found in Amazonia and the global atmosphere release of C2-C4 compounds.

  10. delta13C and water-use efficiency in Australian grasstrees and South African conifers over the last century.

    PubMed

    Swanborough, Perry W; Lamont, Byron B; February, Edmund C

    2003-07-01

    Annual or biannual time courses of plant delta13C (delta13C(p)) over the last century (70-100 years) were recorded for leafbases of four grasstrees (Xanthorrhoea preissii) at four sites in mediterranean Australia and wood of four conifers (Widdringtonia cedarbergensis) at two sites in mediterranean South Africa. There was a strong downward trend of 2-5.5(per thousand ) from 1935 to 1940 to the present in the eight plants. Trends were more variable from 1900 to 1940 with plants at two sites of each species showing an upward trend of 1-2.5 per thousand. Accepting that delta13C of the air (delta13C(a)) fell by almost 2 per thousand over the last century, the ratio of leaf intercellular CO2 to atmospheric CO2 (c(i)/c(a)) rose in five plants and remained unchanged in three over that period. Changes in c(i)/c(a) rather than delta13C(a) were more closely correlated with changes in delta13C(p) and accounted for 6.7-71.8% (22.6 c(i)/c(a)) and 28.2-93.3% (delta13C(a)) of the variation in delta13C(p). We doubt that possible changing patterns of rainfall, water availability, temperature, shade, air pollution or clearing for agriculture have contributed to the overall trend for c(i)/c(a) to rise over time. Instead, we provide evidence (concentrations of Fe and Mn in the grasstree leafbases) that decreasing photosynthetic capacity associated with falling nutrient availability due to the reduced occurrence of fire may have contributed to rising c(i)/c(a). Intrinsic water-use efficiency (W(i)) as a function of (c(a)-c(i)) usually increased linearly over the period, with the two exceptions explained by their marked increase in c(i)/c(a). We conclude that grasstrees may provide equivalent delta13C(p )and W(i) data to long-lived conifers and that their interpretation requires a consideration of the causes of variation in both c(i)/c(a )and delta13C(a). PMID:12728309

  11. Ar + CO2 and He + CO2 Plasmas in ASTRAL

    NASA Astrophysics Data System (ADS)

    Boivin, R. F.; Gardner, A.; Munoz, J.; Kamar, O.; Loch, S.

    2007-11-01

    Spectroscopy study of the ASTRAL helicon plasma source running Ar + CO2 and He + CO2 gas mixes is presented. ASTRAL produces plasmas with the following parameters: ne = 10^10 - 10^13 cm-3, Te = 2 - 10 eV and Ti = 0.03 - 0.5 eV, B-field <= 1.3 kGauss, rf power <= 2 kWatt. A 0.33 m scanning monochromator is used for this study. Using Ar + CO2 gas mixes, very different plasmas are observed as the concentration of CO2 is changed. At low CO2 concentration, the bluish plasma is essentially atomic and argon transitions dominate the spectra. Weak C I and O I lines are present in the 750 - 1000 nm range. At higher CO2 concentration, the plasma becomes essentially molecular and is characterized by intense, white plasma columns. Here, spectra are filled with molecular bands (CO2, CO2^+, CO and CO^+). Limited molecular dissociative excitation processes associated with the production of C I and O I emission are also observed. On the other hand, He + CO2 plasmas are different. Here, rf matches are only possible at low CO2 concentration. Under these conditions, the spectra are characterized by strong C I and O I transitions with little or no molecular bands. Strong dissociative processes observed in these plasmas can be link to the high Te associated with He plasmas. An analysis of the spectra with possible scientific and industrial applications will be presented.

  12. A field and laboratory method for monitoring the concentration and isotopic composition of soil CO2.

    PubMed

    Breecker, Dan; Sharp, Zachary D

    2008-01-01

    The stable isotope composition of nmol size gas samples can be determined accurately and precisely using continuous flow isotope ratio mass spectrometry (IRMS). We have developed a technique that exploits this capability in order to measure delta13C and delta18O values and, simultaneously, the concentration of CO2 in sub-mL volume soil air samples. A sampling strategy designed for monitoring CO2 profiles at particular locations of interest is also described. This combined field and laboratory technique provides several advantages over those previously reported: (1) the small sample size required allows soil air to be sampled at a high spatial resolution, (2) the field setup minimizes sampling times and does not require powered equipment, (3) the analytical method avoids the introduction of air (including O2) into the mass spectrometer thereby extending filament life, and (4) pCO2, delta13C and delta18O are determined simultaneously. The reproducibility of measurements of CO2 in synthetic tank air using this technique is: +/-0.08 per thousand (delta13C), +/-0.10 per thousand (delta18O), and +/-0.7% (pCO2) at 5550 ppm. The reproducibility for CO2 in soil air is estimated as: +/-0.06 per thousand (delta13C), +/-0.06 per thousand (delta18O), and +/-1.6% (pCO2). Monitoring soil CO2 using this technique is applicable to studies concerning soil respiration and ecosystem gas exchange, the effect of elevated atmospheric CO2 (e.g. free air carbon dioxide enrichment) on soil processes, soil water budgets including partitioning evaporation from transpiration, pedogenesis and weathering, diffuse solid-earth degassing, and the calibration of speleothem and pedogenic carbonate delta13C values as paleoenvironmental proxies.

  13. Seasonal variations in bulk tissue, fatty acid and monosaccharide delta(13)C values of leaves from mesotrophic grassland plant communities under different grazing managements.

    PubMed

    Dungait, Jennifer A J; Docherty, Gordon; Straker, Vanessa; Evershed, Richard P

    2010-03-01

    Leaves of 26 grass, herb, shrub and tree species were collected from mesotrophic grasslands to assess natural variability in bulk, fatty acid and monosaccharide delta(13)C values under different grazing management (cattle- or deer-grazed) on three sample dates (May, July and October) such that interspecific and spatiotemporal variations in whole leaf tissues and compound-specific delta(13)C values could be determined. The total mean leaf bulk delta(13)C value for plants was -28.9 per thousand with a range of values spanning 7.5 per thousand. Significant interspecific variation between bulk leaf delta(13)C values was only determined in October (P=<0.001) when delta(13)C values of the leaf tissues from both sites was on average 1.5 per thousand depleted compared to during July and May. Samples from May were significantly different between fields (P=0.03) indicating an effect from deer- or cattle-grazing in young leaves. The average individual monosaccharide delta(13)C value was 0.8 per thousand higher compared with whole leaf tissues. Monosaccharides were the most abundant components of leaf biomass, i.e. arabinose, xylose, mannose, galactose and glucose, and therefore, fluctuations in their individual delta(13)C values had a major influence on bulk delta(13)C values. An average depletion of ca. 1 per thousand in the bulk delta(13)C values of leaves from the deer-grazed field compared to the cattle-grazed field could be explained by a general depletion of 1.1 per thousand in glucose delta(13)C values, as glucose constituted >50% total leaf monosaccharides. In October, delta(13)C values of all monosaccharides varied between species, with significant variation in delta(13)C values of mannose and glucose in July, and mannose in May. This provided an explanation for the noted variability in the tissue bulk delta(13)C values observed in October 1999. The fatty acids C(16:0), C(18:2) and C(18:3) were highly abundant in all plant species. Fatty acid delta(13)C values were

  14. Intercomparison of two cavity ring-down spectroscopy analyzers for atmospheric 13CO2 / 12CO2 measurement

    NASA Astrophysics Data System (ADS)

    Pang, Jiaping; Wen, Xuefa; Sun, Xiaomin; Huang, Kuan

    2016-08-01

    Isotope ratio infrared spectroscopy (IRIS) permits continuous in situ measurement of CO2 isotopic composition under ambient conditions. Previous studies have mainly focused on single IRIS instrument performance; few studies have considered the comparability among different IRIS instruments. In this study, we carried out laboratory and ambient measurements using two Picarro CO2δ13C analyzers (G1101-i and G2201-i (newer version)) and evaluated their performance and comparability. The best precision was 0.08-0.15 ‰ for G1101-i and 0.01-0.04 ‰ for G2201-i. The dependence of δ13C on CO2 concentration was 0.46 ‰ per 100 ppm and 0.09 ‰ per 100 ppm, the instrument drift ranged from 0.92-1.09 ‰ and 0.19-0.37 ‰, and the sensitivity of δ13C to the water vapor mixing ratio was 1.01 ‰ / % H2O and 0.09 ‰ / % H2O for G1101-i and G2201-i, respectively. The accuracy after correction by the two-point mixing ratio gain and offset calibration method ranged from -0.04-0.09 ‰ for G1101-i and -0.13-0.03 ‰ for G2201-i. The sensitivity of δ13C to the water vapor mixing ratio improved from 1.01 ‰ / % H2O before the upgrade of G1101-i (G1101-i-original) to 0.15 ‰ / % H2O after the upgrade of G1101-i (G1101-i-upgraded). Atmospheric δ13C measured by G1101-i and G2201-i captured the rapid changes in atmospheric δ13C signals on hourly to diurnal cycle scales, with a difference of 0.07 ± 0.24 ‰ between G1101-i-original and G2201-i and 0.05 ± 0.30 ‰ between G1101-i-upgraded and G2201-i. A significant linear correlation was observed between the δ13C difference of G1101-i-original and G2201-i and the water vapor concentration, but there was no significant correlation between the δ13C difference of G1101-i-upgraded and G2201-i and the water vapor concentration. The difference in the Keeling intercept values decreased from 1.24 ‰ between G1101-i-original and G2201-i to 0.36 ‰ between G1101-i-upgraded and G2201-i, which indicates the importance of consistency

  15. Highly isotopically depleted isoprenoids: Molecular markers for ancient methane venting

    NASA Astrophysics Data System (ADS)

    Thiel, Volker; Peckmann, Jörn; Seifert, Richard; Wehrung, Patrick; Reitner, Joachim; Michaelis, Walter

    1999-12-01

    We propose that organic compounds found in a Miocene limestone from Marmorito (Northern Italy) are source markers for organic matter present in ancient methane vent systems (cold seeps). The limestone contains high concentrations of the tail-to-tail linked, acyclic C 20 isoprenoid 2,6,11,15-tetramethylhexadecane (crocetane), a C 25 homolog 2,6,10,15,19-pentamethylicosane (PME), and a distinctive glycerol ether lipid containing 3,7,11,15-tetramethylhexadecyl (phytanyl-) moieties. The chemical structures of these biomarkers indicate a common origin from archaea. Their extremely 13C-depleted isotope compositions (δ 13C ≈ -108 to -115.6‰ PDB) suggest that the respective archaea have directly or indirectly introduced isotopically depleted, methane-derived carbon into their biomass. We postulate that a second major cluster of biomarkers showing heavier isotope values (δ 13C ≈ -88‰) is derived from sulfate-reducing bacteria (SRB). The observed biomarkers sustain the idea that methanogenic bacteria, in a syntrophic community with SRB, are responsible for the anaerobic oxidation of methane in marine sediments. Marmorito may thus represent a conceivable ancient scenario for methane consumption performed by a defined, two-membered bacterial consortium: (1) archaea that perform reversed methanogenesis by oxidizing methane and producing CO 2 and H 2; and (2) SRB that consume the resulting H 2. Furthermore, the respective organic molecules are, unlike other compounds, tightly bound to the crystalline carbonate phase. The Marmorito carbonates can thus be regarded as "cold seep microbialites" rather than mere "authigenic" carbonates.

  16. Using Position-Specific 13C and 14C Labeling and 13C-PLFA Analysis to Assess Microbial Transformations of Free Versus Sorbed Alanine

    NASA Astrophysics Data System (ADS)

    Apostel, C.; Herschbach, J.; Bore, E. K.; Kuzyakov, Y.; Dippold, M. A.

    2015-12-01

    Sorption of charged or partially charged low molecular weight organic substances (LMWOS) to soil mineral surfaces delays microbial uptake and therefore mineralization of LMWOS to CO2, as well as all other biochemical transformations. We used position-specific labeling, a tool of isotope applications novel to soil sciences, to compare the transformation mechanisms of sorbed and non-sorbed alanine in soil. Alanine as an amino acid links C- and N-cycles in soil and therefore is a model substance for the pool of LMWOS. To assess transformations of sorbed alanine, we added position-specific and uniformly 13C and 14C labeled alanine tracer to soil that had previously been sterilized by γ-radiation. The labeled soil was added to non-sterilized soil from the same site and incubated. Soil labeled with the same tracers without previous sorption was prepared and incubated as well. We captured the respired CO2 and determined its 14C-activity at increasing time intervals. The incorporation of 14C into microbial biomass was determined by chloroform fumigation extraction (CFE), and utilization of individual C positions by distinct microbial groups was evaluated by 13C-phospholipid fatty acid analysis (PLFA). A dual peak in the respired CO2 revealed two sorption mechanisms. To compare the fate of individual C atoms independent of their concentration and pool size in soil, we applied the divergence index (DI). The DI reveals the convergent or divergent behavior of C from individual molecule positions during microbial utilization. Alanine C-1 position was mainly oxidized to CO2, while its C-2 and C-3 were preferentially incorporated in microbial biomass and PLFA. This indicates that sorption by the COOH group does not protect this group from preferential oxidation. Microbial metabolism was determinative for the preferential oxidation of individual molecule positions. The use of position-specific labeling revealed mechanisms and kinetics of microbial utilization of sorbed and non

  17. Monitoring of near surface CO2

    NASA Astrophysics Data System (ADS)

    Faber, E.; Möller, I.; Teschner, M.; Poggenburg, J.; Spickenbom, K.; Schulz, H. J.

    2009-04-01

    Monitoring of near surface CO2 ECKHARD FABER1, INGO MÖLLER1, MANFRED TESCHNER1, JÜRGEN POGGENBURG1, KAI SPICKENBOM1, HANS-MARTIN SCHULZ1,2 1Bundesanstalt für Geowissenschaften und Rohstoffe (BGR), Stilleweg 2, D-30655 Hannover, e.faber@bgr.de 2present adress: GeoForschungsZentrum Potsdam (GFZ), Telegrafenberg, D-14473 Potsdam Underground gas storage and sequestration of carbon dioxide is one of the methods to reduce the input of antropogenic CO2 into the atmosphere and its greenhouse effect. Storage of CO2 is planned in depleted reservoirs, in aquifers and in salt caverns. Storage sites must have very small leakage rates to safely store the CO2 for centuries. Thus, a careful investigation and site selection is crucial. However, any leakage of CO2 to the surface is potentially dangerous for humans and environment. Therefore, instruments and systems for the detection of any CO2 escaping the storage sites and reaching the atmosphere have to be developed. Systems to monitor gases in deep wells, groundwater and surface sediments for leaking CO2 are developed, tested and are contnuously improved. Our group is mainly analysing CO2 in shallow (down to 3 m) soil samples using automatically operating monitoring systems. The systems are equipped with sensors to measure CO2 (and other gases) concentrations and other environmental parameters (atmospheric pressure, ambient and soil temperatures, etc.). Data are measured in short intervals (minute to subminute), are stored locally and are transferred by telemetrical systems into the BGR laboratory (Weinlich et al., 2006). In addition to soil gases monitoring systems technical equipment is available for continuous underwater gas flow measurements. Several of those monitoring systems are installed in different areas like Czech Republic, Austria, Italy and Germany. To detect any leaking gas from a sequestration site after CO2 injection, the naturally existing CO2 concentration (before injection) must be known. Thus, the natural

  18. Halloysite Nanotubes Capturing Isotope Selective Atmospheric CO2

    PubMed Central

    Jana, Subhra; Das, Sankar; Ghosh, Chiranjit; Maity, Abhijit; Pradhan, Manik

    2015-01-01

    With the aim to capture and subsequent selective trapping of CO2, a nanocomposite has been developed through selective modification of the outer surface of the halloysite nanotubes (HNTs) with an organosilane to make the nanocomposite a novel solid-phase adsorbent to adsorb CO2 from the atmosphere at standard ambient temperature and pressure. The preferential adsorption of three major abundant isotopes of CO2 (12C16O2, 13C16O2, and 12C16O18O) from the ambient air by amine functionalized HNTs has been explored using an optical cavity-enhanced integrated cavity output spectroscopy. CO2 adsorption/desorption cycling measurements demonstrate that the adsorbent can be regenerated at relatively low temperature and thus, recycled repeatedly to capture atmospheric CO2. The amine grafted halloysite shows excellent stability even in oxidative environments and has high efficacy of CO2 capture, introducing a new route to the adsorption of isotope selective atmospheric CO2. PMID:25736700

  19. Delta Ray Road Trip: Measuring δ13C, δ18O and concentration of CO2 across Canada

    NASA Astrophysics Data System (ADS)

    Jost, Hansjurg; Stow, Peter; Mandic, Luka

    2016-04-01

    The Delta Ray Road Trip was conceived to demonstrate that there is now an instrument capable of being taken to the sample collection point and in fact taken to the samples along an 8000 km route across Canada. The concept was to drive a Thermo Scientific Delta Ray Isotope Ratio Infrared Spectrometer from coast to coast across the 2nd largest country in the world. This route took the Delta Ray from a coastal environment, through forests, arable farm land, urban and industrial centres, across prairies and over mountains. The vehicle was a standard RV with as few modifications as possible. Along the way there were stops at most of the major universities in Canada as well as the AGU-GAC-MAC conference in Montreal, where indoor measurements were performed. Date was uploaded in quasi realtime to a website. We will present data acquired during the trip and discuss the lessons learned.

  20. 13C-Breath Tests for Sucrose Digestion in Congenital Sucrase Isomaltase Deficient and Sacrosidase Supplemented Patients

    PubMed Central

    Robayo-Torres, Claudia C.; Opekun, Antone R.; Quezada-Calvillo, Roberto; Xavier, Villa; Smith, E. O’Brian; Navarrete, Marilyn; Baker, S. Susan; Nichols, Buford L

    2008-01-01

    Congenital sucrase-isomaltase deficiency (CSID) is characterized by absence or deficiency of the mucosal sucrase-isomaltase enzyme. Specific diagnosis requires upper gastrointestinal biopsy with evidence of low to absent sucrase enzyme activity and normal histology. The hydrogen breath test (BT) is useful but is not specific for confirmation of CSID. We investigated a more specific 13C-sucrose labeled BT. Objectives were to determine if CSID can be detected with the 13C-sucrose BT without duodenal biopsy sucrase assay and if the 13C-sucrose BT can document restoration of sucrose digestion by CSID patients after oral supplementation with sacrosidase (Sucraid®). Methods Ten CSID patients were diagnosed by low biopsy sucrase activity. Ten controls were children who underwent endoscopy and biopsy because of dyspepsia or chronic diarrhea with normal mucosal enzymes activity and histology. Uniformly-labeled 13C-glucose and 13C-sucrose loads were orally administered. 13CO2 breath enrichments were assayed using an infrared spectrophotometer. In CSID patients the 13C-sucrose load was repeated adding Sucraid®. Sucrose digestion and oxidation were calculated as a mean % coefficient of glucose oxidation (% CGO) averaged between 30 and 90 minutes. Results Classification of patients by 13C-sucrose BT % CGO agreed with biopsy sucrase activity. The breath test also documented the return to normal of sucrose digestion and oxidation after supplementation of CSID patients with Sucraid®. Conclusion 13C-sucrose BT is an accurate and specific non-invasive confirmatory test for CSID and for enzyme replacement management. PMID:19330928

  1. Biosynthetic uniform 13C,15N-labelling of zervamicin IIB. Complete 13C and 15N NMR assignment.

    PubMed

    Ovchinnikova, Tatyana V; Shenkarev, Zakhar O; Yakimenko, Zoya A; Svishcheva, Natalia V; Tagaev, Andrey A; Skladnev, Dmitry A; Arseniev, Alexander S

    2003-01-01

    Zervamicin IIB is a member of the alpha-aminoisobutyric acid containing peptaibol antibiotics. A new procedure for the biosynthetic preparation of the uniformly 13C- and 15N-enriched peptaibol is described This compound was isolated from the biomass of the fungus-producer Emericellopsis salmosynnemata strain 336 IMI 58330 obtained upon cultivation in the totally 13C, 15N-labelled complete medium. To prepare such a medium the autolysed biomass and the exopolysaccharides of the obligate methylotrophic bacterium Methylobacillus flagellatus KT were used. This microorganism was grown in totally 13C, 15N-labelled minimal medium containing 13C-methanol and 15N-ammonium chloride as the only carbon and nitrogen sources. Preliminary NMR spectroscopic analysis indicated a high extent of isotope incorporation (> 90%) and led to the complete 13C- and 15N-NMR assignment including the stereospecific assignment of Aib residues methyl groups. The observed pattern of the structurally important secondary chemical shifts of 1H(alpha), 13C=O and 13C(alpha) agrees well with the previously determined structure of zervamicin IIB in methanol solution. PMID:14658801

  2. Diploptene δ13C values from contemporary thermokarst lake sediments show complex spatial variation

    NASA Astrophysics Data System (ADS)

    Davies, Kimberley L.; Pancost, Richard D.; Edwards, Mary E.; Anthony, Katey M. Walter; Langdon, Peter G.; Chaves Torres, Lidia

    2016-05-01

    Cryospheric changes in northern high latitudes are linked to significant greenhouse gas flux to the atmosphere, for example, methane that originates from organic matter decomposition in thermokarst lakes. The set of pathways that link methane production in sediments, via oxidation in the lake system, to the flux of residual methane to the atmosphere is complex and exhibits temporal and spatial variation. The isotopic signal of bacterial biomarkers (hopanoids, e.g. diploptene) in sediments has been used to identify contemporary ocean-floor methane seeps and, in the geological record, periods of enhanced methane production (e.g. the PETM). The biomarker approach could potentially be used to assess temporal changes in lake emissions through the Holocene via the sedimentary biomarker record. However, there are no data on the consistency of the signal of isotopic depletion in relation to source or on the amount of noise (unexplained variation) in biomarker values from modern lake sediments. We assessed methane oxidation as represented by the isotopic signal of biomarkers from methane oxidising bacteria (MOB) in multiple surface sediment samples in three distinct areas known to emit varying levels of methane in two shallow Alaskan thermokarst lakes. Diploptene was present and had δ13C values lower than -38 ‰ in all sediments analysed, suggesting methane oxidation was widespread. However, there was considerable variation in δ13C values within each area. The most 13C-depleted diploptene was found in an area of high methane ebullition in Ace Lake (diploptene δ13C values between -68.2 and -50.1 ‰). In contrast, significantly higher diploptene δ13C values (between -42.9 and -38.8 ‰) were found in an area of methane ebullition in Smith Lake. δ13C values of diploptene between -56.8 and -46.9 ‰ were found in the centre of Smith Lake, where ebullition rates are low but diffusive methane efflux occurs. The small-scale heterogeneity of the samples may reflect patchy

  3. Methanogenic capabilities of ANME-archaea deduced from (13) C-labelling approaches.

    PubMed

    Bertram, Sebastian; Blumenberg, Martin; Michaelis, Walter; Siegert, Michael; Krüger, Martin; Seifert, Richard

    2013-08-01

    Anaerobic methanotrophic archaea (ANME) are ubiquitous in marine sediments where sulfate dependent anaerobic oxidation of methane (AOM) occurs. Despite considerable progress in the understanding of AOM, physiological details are still widely unresolved. We investigated two distinct microbial mat samples from the Black Sea that were dominated by either ANME-1 or ANME-2. The (13) C lipid stable isotope probing (SIP) method using labelled substances, namely methane, bicarbonate, acetate, and methanol, was applied, and the substrate-dependent methanogenic capabilities were tested. Our data provide strong evidence for a versatile physiology of both, ANME-1 and ANME-2. Considerable methane production rates (MPRs) from CO2 -reduction were observed, particularly from ANME-2 dominated samples and in the presence of methane, which supports the hypothesis of a co-occurrence of methanotrophy and methanogenesis in the AOM systems (AOM/MPR up to 2:1). The experiments also revealed strong methylotrophic capabilities through (13) C-assimilation from labelled methanol, which was independent of the presence of methane. Additionally, high MPRs from methanol were detected in both of the mat samples. As demonstrated by the (13) C-uptake into lipids, ANME-1 was found to thrive also under methane free conditions. Finally, C35 -isoprenoid hydrocarbons were identified as new lipid biomarkers for ANME-1, most likely functioning as a hydrogen sink during methanogenesis.

  4. Structure of B sub 13 C sub 2

    SciTech Connect

    Bylander, D.M.; Kleinman, L. )

    1991-01-15

    By comparing calculated lattice constants with x-ray data as well as by comparison of calculated free energies, we find that the correct structure of B{sub 13}C{sub 2} is B{sub 12}(CBC) rather than B{sub 11}C(BBC), as had been suggested. We also show that B{sub 12}C{sub 3} is stable against 13B{sub 12}C{sub 3}{r arrow}12B{sub 13}C{sub 2}+15C as is B{sub 13}C{sub 2} against 3B{sub 13}C{sub 2}{r arrow}2B{sub 12}C{sub 3}+15B.

  5. Dihydroflavanonols from Cedrus deodara, A (13)C NMR study.

    PubMed

    Agrawal, P K; Agarwal, S K; Rastogi, R P; Osterdahal, B G

    1981-09-01

    High resolution (13)C NMR study of taxifolin, cedeodarin, cedrin and their methyl ethers allowed unambiguous placement of the Me in 5,7-dihydroxyflavanonol nucleus, besides providing other valuable information on the substitution pattern in the molecule.

  6. Method for tracing simulated CO2 leak in terrestrial environment with a 13CO2 tracer

    NASA Astrophysics Data System (ADS)

    Moni, Christophe; Rasse, Daniel

    2013-04-01

    Facilities for the geological storage of carbon dioxide (CO2) as part of carbon capture and storage (CCS) schemes will be designed to prevent any leakage from the defined 'storage complex'. However, developing regulations and guidance throughout the world (e.g. the EC Directive and the USEPA Vulnerability Evaluation Framework) recognize the importance of assessing the potential for environmental impacts from CO2 storage. RISCS, a European (FP7) project, aims to improve understanding of those impacts that could plausibly occur in the hypothetical case that unexpected leakage occurs. As part of the RISCS project the potential impacts that an unexpected CO2 leaks might have on a cropland ecosystems was investigated. A CO2 exposure field experiment based on CO2 injection at 85 cm depth under an oats culture was designed. To facilitate the characterization of the simulated leaking zone the gas used for injection was produced from natural gas and had a δ13C of -46‰. The aim of the present communication is to depict how the injected gas was traced within the soil-vegetation-atmosphere continuum using 13CO2 continuous cavity ring-down spectrometry (CRDS). Four subsurface experimental injection plots (6m x 3m) were set up. In order to test the effects of different intensity of leakage, the field experiment was designed as to create a longitudinal CO2 gradient for each plot. For this purpose gas supply pipes were inserted at one extremity of each plot at the base of a 45 cm thick layer of sand buried 40 cm below the surface under the clayey plough layer of Norwegian moraine soils. Soil CO2 concentration and isotopic signature were punctually recorded: 1) in the soil at 20 cm depth at 6 positions distributed on the central transect, 2) at the surface following a (50x50 cm) grid sampling pattern, and 3) in the canopy atmosphere at 10, 20, 30 cm along three longitudinal transects (seven sampling point per transect). Soil CO2 fluxes and isotopic signature were finally

  7. Pulsed polarization transfer for 13C NMR in solids

    NASA Astrophysics Data System (ADS)

    Bax, Ad; Szeverenyi, Nikolaus M.; Maciel, Gary E.

    A new pulsed polarization transfer experiment method is described for the polarization of 13C spins in a solid by magnetization transfer from protons. The method is directly analogous to the INEPT sequence for liquids introduced by Freeman and Morris. As polarization is transferred in PPT between individual 1H 13C pairs, rather than between spin reservoirs, different opportunities exist for structurally selective experiments. Results on p-diethoxybenzene and coronene are presented.

  8. Abundance anomaly of the 13C species of CCH

    NASA Astrophysics Data System (ADS)

    Sakai, N.; Saruwatari, O.; Sakai, T.; Takano, S.; Yamamoto, S.

    2010-03-01

    Aims: We have observed the N = 1-0 lines of CCH and its 13C isotopic species toward a cold dark cloud, TMC-1 and a star-forming region, L1527, to investigate the 13C abundances and formation pathways of CCH. Methods: The observations have been carried out with the IRAM 30 m telescope. Results: We have successfully detected the lines of 13CCH and C13CH toward the both sources and found a significant intensity difference between the two 13C isotopic species. The [C13CH] /[13CCH] abundance ratios are 1.6 ± 0.4 (3σ) and 1.6 ± 0.1 (3σ) for TMC-1 and L1527, respectively. The abundance difference between C13CH and 13CCH means that the two carbon atoms of CCH are not equivalent in the formation pathway. On the other hand, the [CCH]/[C13CH] and [CCH]/[13CCH] ratios are evaluated to be larger than 170 and 250 toward TMC-1, and to be larger than 80 and 135 toward L1527, respectively. Therefore, both of the 13C species are significantly diluted in comparison with the interstellar 12C/13C ratio of 60. The dilution is discussed in terms of a behavior of 13C in molecular clouds.

  9. Localized in vivo13C NMR spectroscopy of the brain

    PubMed Central

    Gruetter, Rolf; Adriany, Gregor; Choi, In-Young; Henry, Pierre-Gilles; Lei, Hongxia; Öz, Gülin

    2006-01-01

    Localized 13C NMR spectroscopy provides a new investigative tool for studying cerebral metabolism. The application of 13C NMR spectroscopy to living intact humans and animals presents the investigator with a number of unique challenges. This review provides in the first part a tutorial insight into the ingredients required for achieving a successful implementation of localized 13C NMR spectroscopy. The difficulties in establishing 13C NMR are the need for decoupling of the one-bond 13C–1H heteronuclear J coupling, the large chemical shift range, the low sensitivity and the need for localization of the signals. The methodological consequences of these technical problems are discussed, particularly with respect to (a) RF front-end considerations, (b) localization methods, (c) the low sensitivity, and (d) quantification methods. Lastly, some achievements of in vivo localized 13C NMR spectroscopy of the brain are reviewed, such as: (a) the measurement of brain glutamine synthesis and the feasibility of quantifying glutamatergic action in the brain; (b) the demonstration of significant anaplerotic fluxes in the brain; (c) the demonstration of a highly regulated malate-aspartate shuttle in brain energy metabolism and isotope flux; (d) quantification of neuronal and glial energy metabolism; and (e) brain glycogen metabolism in hypoglycemia in rats and humans. We conclude that the unique and novel insights provided by 13C NMR spectroscopy have opened many new research areas that are likely to improve the understanding of brain carbohydrate metabolism in health and disease. PMID:14679498

  10. Harding Iceland spar: a new delta 18O-delta 13C carbonate standard for hydrothermal minerals.

    USGS Publications Warehouse

    Landis, G.P.

    1983-01-01

    An isotopically homogenous calcite, Iceland spar from the Iceberg claim, near the Harding pegmatite of N New Mexico, has delta 18O +11.78 + or - 0.07per mille (=+22.15per mille for CO2) and delta 13C -4.80 + or - 0.02per mille and has been prepared in quantities suitable for use as a working standard in MS.-R.A.H.

  11. 13C-tryptophan breath test detects increased catabolic turnover of tryptophan along the kynurenine pathway in patients with major depressive disorder

    PubMed Central

    Teraishi, Toshiya; Hori, Hiroaki; Sasayama, Daimei; Matsuo, Junko; Ogawa, Shintaro; Ota, Miho; Hattori, Kotaro; Kajiwara, Masahiro; Higuchi, Teruhiko; Kunugi, Hiroshi

    2015-01-01

    Altered tryptophan–kynurenine (KYN) metabolism has been implicated in major depressive disorder (MDD). The l-[1-13C]tryptophan breath test (13C-TBT) is a noninvasive, stable-isotope tracer method in which exhaled 13CO2 is attributable to tryptophan catabolism via the KYN pathway. We included 18 patients with MDD (DSM-IV) and 24 age- and sex-matched controls. 13C-tryptophan (150 mg) was orally administered and the 13CO2/12CO2 ratio in the breath was monitored for 180 min. The cumulative recovery rate during the 180-min test (CRR0–180; %), area under the Δ13CO2-time curve (AUC; %*min), and the maximal Δ13CO2 (Cmax; %) were significantly higher in patients with MDD than in the controls (p = 0.004, p = 0.008, and p = 0.002, respectively). Plasma tryptophan concentrations correlated negatively with Cmax in both the patients and controls (p = 0.020 and p = 0.034, respectively). Our results suggest that the 13C-TBT could be a novel biomarker for detecting a subgroup of MDD with increased tryptophan–KYN metabolism. PMID:26524975

  12. Global patterns in leaf 13C discrimination and implications for studies of past and future climate.

    PubMed

    Diefendorf, Aaron F; Mueller, Kevin E; Wing, Scott L; Koch, Paul L; Freeman, Katherine H

    2010-03-30

    Fractionation of carbon isotopes by plants during CO(2) uptake and fixation (Delta(leaf)) varies with environmental conditions, but quantitative patterns of Delta(leaf) across environmental gradients at the global scale are lacking. This impedes interpretation of variability in ancient terrestrial organic matter, which encodes climatic and ecological signals. To address this problem, we converted 3,310 published leaf delta(13)C values into mean Delta(leaf) values for 334 woody plant species at 105 locations (yielding 570 species-site combinations) representing a wide range of environmental conditions. Our analyses reveal a strong positive correlation between Delta(leaf) and mean annual precipitation (MAP; R(2) = 0.55), mirroring global trends in gross primary production and indicating stomatal constraints on leaf gas-exchange, mediated by water supply, are the dominant control of Delta(leaf) at large spatial scales. Independent of MAP, we show a lesser, negative effect of altitude on Delta(leaf) and minor effects of temperature and latitude. After accounting for these factors, mean Delta(leaf) of evergreen gymnosperms is lower (by 1-2.7 per thousand) than for other woody plant functional types (PFT), likely due to greater leaf-level water-use efficiency. Together, environmental and PFT effects contribute to differences in mean Delta(leaf) of up to 6 per thousand between biomes. Coupling geologic indicators of ancient precipitation and PFT (or biome) with modern Delta(leaf) patterns has potential to yield more robust reconstructions of atmospheric delta(13)C values, leading to better constraints on past greenhouse-gas perturbations. Accordingly, we estimate a 4.6 per thousand decline in the delta(13)C of atmospheric CO(2) at the onset of the Paleocene-Eocene Thermal Maximum, an abrupt global warming event approximately 55.8 Ma. PMID:20231481

  13. 13C-18O bonding (Δ47) in deep-sea corals: a calibration study

    NASA Astrophysics Data System (ADS)

    Kimball, J. B.; Tripati, A.; Dunbar, R. B.; Eagle, R.

    2013-12-01

    Deep-sea corals are a potentially valuable archive of temperature in intermediate and deep waters, regions for which a paucity of temperature data exists. These archives could give valuable insight into the natural variability of areas of the ocean that play an active role in large-scale climate dynamics. Due to significant 'vital effects' (i.e., non-equilibrium mineral compositions) in δ18O, however, deep-sea coral have been challenging to develop as a paleotemperature proxy. Clumped-isotope paleothermometry is a new method that may circumvent some of the known complications with δ18O paleotemperature analysis in deep-sea coral. This geothermometer is based on the ordering of heavy 13C-18O ';clumps' in carbonate minerals. Initial calibration studies have shown that the method is independent from the solution chemistry of the precipitating fluids as well as 'vital effects' in deep-sea corals and other types of carbonates. Some kinetic effects have been observed in tropical corals and speleothems. Here we report new data in order to further develop clumped isotopes as a paleothermometer in deep-sea corals as well as to investigate taxon-specific effects. 13C-18O bond ordering was analyzed in live-collected scleractinian (Enallopsammia sp.) and gorgonian (Isididae and Coralliidae) deep-sea corals. We determined mass 47 anomalies in samples (Δ47), which refers to the parts per thousand excess of 13C-18O-16O in CO2 produced on acid digestion of a sample, relative to the amount predicted to be present if isotopes were randomly distributed amongst all CO2 isotopologues. Measured Δ47 values were compared to in situ temperatures and the relationship between Δ47 and temperature was determined for each group to investigate taxon-specific effects.

  14. Seasonal and interannual variations of atmospheric CO2 and climate

    USGS Publications Warehouse

    Dettinger, M.D.; Ghil, M.

    1998-01-01

    Interannual variations of atmospheric CO2 concentrations at Mauna Loa are almost masked by the seasonal cycle and a strong trend; at the South Pole, the seasonal cycle is small and is almost lost in the trend and interannual variations. Singular-spectrum analysis (SSA) issued here to isolate and reconstruct interannual signals at both sites and to visualize recent decadal changes in the amplitude and phase of the seasonal cycle. Analysis of the Mauna Loa CO2 series illustrates a hastening of the CO2 seasonal cycle, a close temporal relation between Northern Hemisphere (NH) mean temperature trends and the amplitude of the seasonal CO2 cycle, and tentative ties between the latter and seasonality changes in temperature over the NH continents. Variations of the seasonal CO2 cycle at the South Pole differ from those at Mauna Loa: it is phase changes of the seasonal cycle at the South Pole, rather than amplitude changes, that parallel hemispheric and global temperature trends. The seasonal CO2 cycles exhibit earlier occurrences of the seasons by 7 days at Mauna Loa and 18 days at the South Pole. Interannual CO2 variations are shared at the two locations, appear to respond to tropical processes, and can be decomposed mostly into two periodicities, around (3 years)-1 and (4 years)-1, respectively. Joint SSA analyses of CO2 concentrations and tropical climate indices isolate a shared mode with a quasi-triennial (QT) period in which the CO2 and sea-surface temperature (SST) participation are in phase opposition. The other shared mode has a quasi-quadrennial (QQ) period and CO2 variations are in phase with the corresponding tropical SST variations throughout the tropics. Together these interannual modes exhibit a mean lag between tropical SSTs and CO2 variations of about 6-8 months, with SST leading. Analysis of the QT and QQ signals in global gridded SSTs, joint SSA of CO2 and ??13C isotopic ratios, and SSA of CO2 and NH-land temperatures indicate that the QT variations in

  15. Is CO2 ice permanent?

    NASA Technical Reports Server (NTRS)

    Lindner, Bernhard Lee

    1992-01-01

    Carbon dioxide ice has been inferred to exist at the south pole in summertime, but Earth based measurements in 1969 of water vapor in the Martian atmosphere suggest that all CO2 ice sublined from the southern polar cap and exposed underlying water ice. This implies that the observed summertime CO2 ice is of recent origin. It appears possible to construct an energy balance model that maintains seasonal CO2 ice at the south pole year round and still reasonably simulates the polar cap regression and atmospheric pressure data. This implies that the CO2 ice observed in the summertime south polar cap could be seasonal in origin, and that minor changes in climate could cause CO2 ice to completely vanish, as would appear to have happened in 1969. However, further research remains before it is certain whether the CO2 ice observed in the summertime south polar cap is seasonal or is part of a permanent reservoir.

  16. India Co2 Emissions

    NASA Astrophysics Data System (ADS)

    Sharan, S.; Diffenbaugh, N. S.

    2010-12-01

    created a balance in between the “developed” and developing countries. If India was producing the same amounts of emissions per capita as the it would have a total of 20 billion metric tons of CO2 emissions annually.

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

    NASA Astrophysics Data System (ADS)

    Guillon, S.; Pili, E.; Agrinier, P.

    2012-05-01

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

  18. Impact of oceanic circulation changes on atmospheric δ13CO2

    NASA Astrophysics Data System (ADS)

    Menviel, L.; Mouchet, A.; Meissner, K. J.; Joos, F.; England, M. H.

    2015-12-01

    δ13CO2 measured in Antarctic ice cores provides constraints on oceanic and terrestrial carbon cycle processes linked with millennial-scale and glacial/interglacial changes in atmospheric CO2. However, the interpretation of δ13CO2 is not straightforward. Using two Earth system models of intermediate complexity we perform a set of sensitivity experiments in which the formation rates of North Atlantic Deep Water (NADW), North Pacific Deep Water (NPDW), Antarctic Bottom Water (AABW) and Antarctic Intermediate Water (AAIW) are varied. We study the impact of these circulation changes on atmospheric δ13CO2 as well as on the oceanic δ13C distribution. In general, we find that the formation rates of AABW, NADW, NPDW and AAIW are negatively correlated with changes in δ13CO2: namely strong oceanic ventilation decreases atmospheric δ13CO2. However, since large scale ocean circulation reorganizations also impact nutrient utilization and the Earth's climate the relationship between atmospheric δ13CO2 levels and ocean ventilation rate is not unequivocal. In both models atmospheric δ13CO2 is very sensitive to changes in AABW formation rates: increased AABW formation enhances the upwelling of low δ13C waters to the surface and decreases atmospheric δ13CO2. By contrast, the impact of NADW changes on atmospheric δ13CO2 is less robust and might be model dependent.

  19. Measuring DNA synthesis rates with [1-13C]glycine.

    PubMed

    Chen, P; Abramson, F P

    1998-05-01

    We have devised and evaluated a stable-isotopic method for measuring DNA synthesis rates. The probe is [1-13C]-glycine that is incorporated into purines via de novo biosynthesis. The human hepatoma cell line HEP G2 was grown in medium containing [1-13C]glycine, the cells were harvested at various times, and the DNA was extracted. Following hydrolysis to the nucleosides, a reversed-phase HPLC separation was used to provide separate peaks for deoxythymidine (dT), deoxyadenosine (dA), and deoxyguanosine (dG). The HPLC effluent was continuously fed into a chemical reaction interface and an isotope ratio mass spectrometer (HPLC/CRI/IRMS). The isotope ratio of the CO2 produced in the CRI was used to monitor for enrichment. The cells were grown continuously for 5 days in labeled medium and also in a 1-day pulse labeling experiment where the washout of label was observed for the subsequent 9 days. As predicted from the role of glycine in de novo purine biosynthesis, the isotope ratio of the pyrimidine dT did not change. However, for the two purines, dA and dG, the characteristic log growth behavior of the cells was observed in their 13C/12C ratios and good agreement in the doubling time was obtained for each type of experiment. Parallel experiments that measured the HEP G2 doubling time in culture using tritiated thymidine incorporation and direct cell counts were carried out compare to our new method with established ones. We believe that the use of [1-13C]-glycine and the HPLC/CRI/IRMS is a highly sensitive and selective approach that forms the basis of a method that can measure DNA synthesis rates using a nonradioactive, nontoxic tracer. PMID:9599574

  20. On the status of IAEA delta-13C stable isotope reference materials.

    NASA Astrophysics Data System (ADS)

    Assonov, Sergey; Groening, Manfred; Fajgelj, Ales

    2016-04-01

    For practical reasons all isotope measurements are performed on relative scales realized through the use of international, scale-defining primary standards. In fact these standards were materials (artefacts, similar to prototypes of meter and kg) selected based on their properties. The VPDB delta-13C scale is realised via two highest-level reference materials NBS19 and LSVEC, the first defining the scale and the second aimed to normalise lab-to-lab calibrations. These two reference materials (RMs) have been maintained and distributed by IAEA and NIST. The priority task is to maintain these primary RMs at the required uncertainty level, thus ensuring the long-term scale consistency. The second task is to introduce replacements when needed (currently for exhausted NBS19, work in progress). The next is to produce a family of lower level RMs (secondary, tertiary) addressing needs of various applications (with different delta values, in different physical-chemical forms) and their needs for the uncertainty; these RMs should be traceable to the highest level RMs. Presently three is a need for a range of RMs addressing existing and newly emerging analytical techniques (e.g. optical isotopic analysers) in form of calibrated CO2 gases with different delta-13C values. All that implies creating a family of delta-13C stable isotope reference materials. Presently IAEA works on replacement for NBS19 and planning new RMs. Besides, we found that LSVEC (introduced as second anchor for the VPDB scale in 2006) demonstrate a considerable scatter of its delta-13C value which implies a potential bias of the property value and increased value uncertainty which may conflict with uncertainty requirements for atmospheric monitoring. That is not compatible with the status of LSVEC, and therefore it should be replaced as soon as possible. The presentation will give an overview of the current status, the strategic plan of developments and the near future steps.

  1. CO2 interaction with geomaterials.

    SciTech Connect

    Guthrie, George D.; Al-Saidi, Wissam A.; Jordan, Kenneth D.; Voora, Vamsee, K.; Romanov, Vyacheslav N.; Lopano, Christina L; Myshakin, Eugene M.; Hur, Tae Bong; Warzinski, Robert P.; Lynn, Ronald J.; Howard, Bret H.; Cygan, Randall Timothy

    2010-09-01

    This work compares the sorption and swelling processes associated with CO2-coal and CO2-clay interactions. We investigated the mechanisms of interaction related to CO2 adsortion in micropores, intercalation into sub-micropores, dissolution in solid matrix, the role of water, and the associated changes in reservoir permeability, for applications in CO2 sequestration and enhanced coal bed methane recovery. The structural changes caused by CO2 have been investigated. A high-pressure micro-dilatometer was equipped to investigate the effect of CO2 pressure on the thermoplastic properties of coal. Using an identical dilatometer, Rashid Khan (1985) performed experiments with CO2 that revealed a dramatic reduction in the softening temperature of coal when exposed to high-pressure CO2. A set of experiments was designed for -20+45-mesh samples of Argonne Premium Pocahontas No.3 coal, which is similar in proximate and ultimate analysis to the Lower Kittanning seam coal that Khan used in his experiments. No dramatic decrease in coal softening temperature has been observed in high-pressure CO2 that would corroborate the prior work of Khan. Thus, conventional polymer (or 'geopolymer') theories may not be directly applicable to CO2 interaction with coals. Clays are similar to coals in that they represent abundant geomaterials with well-developed microporous structure. We evaluated the CO2 sequestration potential of clays relative to coals and investigated the factors that affect the sorption capacity, rates, and permanence of CO2 trapping. For the geomaterials comparison studies, we used source clay samples from The Clay Minerals Society. Preliminary results showed that expandable clays have CO2 sorption capacities comparable to those of coal. We analyzed sorption isotherms, XRD, DRIFTS (infrared reflectance spectra at non-ambient conditions), and TGA-MS (thermal gravimetric analysis) data to compare the effects of various factors on CO2 trapping. In montmorillonite, CO2

  2. Soil respiration vs. soil CO2 efflux: the role of CO2 storage flux in soil respiration models

    NASA Astrophysics Data System (ADS)

    Maier, Martin; Helmer, Schack-Kirchner; Ernst, Hildebrand

    2010-05-01

    Most studies implicitly consider soil surface efflux of CO2 to be the instantaneous soil respiration, thereby neglecting possible changes in the amount of CO2 stored in the soil pore-space. For the widely used chamber-based and micro-meteorological measurements, filling or depletion of this CO2 pool can result in either an under- or overestimation of the soil respiration. Soil temperature and moisture are the major abiotic factors controlling soil respiration, and are used as explanatory variables by most models. However, these two factors also influence soil gas transport, and thus, the amount of stored CO2. This effect can add undesired noise to soil respiration models or even interfere with the model parameters. To examine the effect of CO2 storage flux, we monitored both the soil CO2 efflux and the CO2 storage in the soil pore-space of a deep and well-aerated riparian soil. Measurements were carried out from March 2009 to March 2010 using an automated chamber system and CO2 concentration measurements at various depths (0.05 to 2.1 m) in the soil profile. First results show that the integration of the storage flux can lead to a significant divergence of soil respiration and soil CO2 efflux, potentially affecting respiration models. It will be discussed whether the integration of the storage flux either changes the overall parameter estimation or is only relevant to improve the understanding of particular meteorological situations.

  3. Can subterranean cave systems affect soil CO2 fluxes?

    NASA Astrophysics Data System (ADS)

    Krajnc, Bor; Ferlan, Mitja; Ogrinc, Nives

    2015-04-01

    Main factors affecting soil CO2 fluxes in most ecosystems are soil temperature and soil moisture. Nevertheless occasionally high soil CO2 fluxes were observed at carst areas, which could result from ventilation of subterranean cavities (Ferlan et al., 2011). The aim of this work was to determine the influence of cave ventilation to soil CO2 fluxes. Research was done in a dead-end passage of Postojna cave (Pisani rov) and on the surface area above the passage (Velika Jeršanova dolina) in south-western Slovenia. Inside the cave we measured CO2 concentrations, its carbon (13C) stable isotope composition, 222Rn activity concentrations, temperatures and air pressure. At the surface we had chosen two sampling plots; test plot above the cave and control. At both plots we measured soil CO2 fluxes with automatic chambers, CO2 concentrations, temperatures and carbon stable isotope composition of soil air at three different depths (0.2 m, 0.5 m and 0.8 m) and different meteorological parameters such as: air temperature, air pressure, wind speed an precipitation. To detect the cave influence, we compared two surface CO2 flux measurements with air temperatures and changes of CO2 concentrations in the cave atmosphere. Our results on CO2 concentrations in the gallery of the cave indicated that the ventilation of this particular gallery also depends on outside air temperatures. Outside temperature increased and corresponded to higher CO2 concentrations, whereas at lower temperatures (T < 9 oC) cave started to ventilate and exhaled CO2 reach air through unknown fissures and cracks. At the control plot the soil CO2 fluxes were in a good correlation with soil temperatures (r = 0.789, p =0.01), where greater soil temperatures correspond to greater soil CO2 fluxes. Soil CO2 fluxes at the plot above the cave did not show statistically significant correlations with soil temperatures or soil moisture indicating that other factors possibly cave ventilation could influence it. References

  4. Fossil chironomid d13C as a new proxy for past methanogenic contribution to benthic food-webs in lakes?

    NASA Astrophysics Data System (ADS)

    van Hardenbroek, M.; Heiri, O. M.; Grey, J.; Bodelier, P. L. E.; Lotter, A. F.

    2009-04-01

    Lake sediments are an important source of atmospheric methane. Methanogenic archaea in lake sediments produce 13C-depleted methane that is partly released to the water column and the atmosphere. Another part is utilized by methane oxidizing bacteria (MOB) that are an important food source for deposit-feeding chironomid larvae (Diptera: Chironomidae). If methane-derived carbon is a significant component of the chironomid diet this will lead to strongly negative d13C in the tissue and exoskeleton of chironomid larvae. Chironomid cuticles, especially the strongly sclerotized head capsules, are well preserved as fossils in lake sediments. If the relationship between modern methane fluxes in lakes and chironomid d13C can be established this would therefore provide an approach for estimating past methane fluxes based on d13C of fossil chironomid remains. Using culturing experiments we show that the stable carbon isotope signature of MOB and other food sources can be traced in chironomid muscle tissue as well as in the fossilizing exoskeleton. In addition we measured d13C in chironomid larval head capsules and other invertebrate remains from a range of surface and downcore sediment samples. Small intra-specific variability (-27.1 ± 0.08 permille) was measured in replicate samples of chironomid head capsules of Corynocera ambigua (n=7). d13C of chironomid head capsules from a several different taxa ranged from -28.0 to -25.8 permille, but in some instances we observed d13C values as low as -36.9 to -31.5 permille, suggesting that carbon from MOB can be successfully traced in fossil and subfossil chironomid remains. Our results demonstrate that the stable carbon isotope signature of MOB is incorporated into chironomid head capsules. Future research will focus on quantifying the relationship between methane fluxes, MOB, and head capsule d13C in order to reconstruct past methane fluxes based on the lake sediment record.

  5. Interactive effects of elevated CO2 and nitrogen deposition on fatty acid molecular and isotope composition of above- and belowground tree biomass and forest soil fractions.

    PubMed

    Griepentrog, Marco; Eglinton, Timothy I; Hagedorn, Frank; Schmidt, Michael W I; Wiesenberg, Guido L B

    2015-01-01

    Atmospheric carbon dioxide (CO2) and reactive nitrogen (N) concentrations have been increasing due to human activities and impact the global carbon (C) cycle by affecting plant photosynthesis and decomposition processes in soil. Large amounts of C are stored in plants and soils, but the mechanisms behind the stabilization of plant- and microbial-derived organic matter (OM) in soils are still under debate and it is not clear how N deposition affects soil OM dynamics. Here, we studied the effects of 4 years of elevated (13C-depleted) CO2 and N deposition in forest ecosystems established in open-top chambers on composition and turnover of fatty acids (FAs) in plants and soils. FAs served as biomarkers for plant- and microbial-derived OM in soil density fractions. We analyzed above- and belowground plant biomass of beech and spruce trees as well as soil density fractions for the total organic C and FA molecular and isotope (δ13C) composition. FAs did not accumulate relative to total organic C in fine mineral fractions, showing that FAs are not effectively stabilized by association with soil minerals. The δ13C values of FAs in plant biomass increased under high N deposition. However, the N effect was only apparent under elevated CO2 suggesting a N limitation of the system. In soil fractions, only isotope compositions of short-chain FAs (C16+18) were affected. Fractions of 'new' (experimental-derived) FAs were calculated using isotope depletion in elevated CO2 plots and decreased from free light to fine mineral fractions. 'New' FAs were higher in short-chain compared to long-chain FAs (C20-30), indicating a faster turnover of short-chain compared to long-chain FAs. Increased N deposition did not significantly affect the quantity of 'new' FAs in soil fractions, but showed a tendency of increased amounts of 'old' (pre-experimental) C suggesting that decomposition of 'old' C is retarded by high N inputs.

  6. Transport and imaging of brute-force (13)C hyperpolarization.

    PubMed

    Hirsch, Matthew L; Smith, Bryce A; Mattingly, Mark; Goloshevsky, Artem G; Rosay, Melanie; Kempf, James G

    2015-12-01

    We demonstrate transport of hyperpolarized frozen 1-(13)C pyruvic acid from its site of production to a nearby facility, where a time series of (13)C images was acquired from the aqueous dissolution product. Transportability is tied to the hyperpolarization (HP) method we employ, which omits radical electron species used in other approaches that would otherwise relax away the HP before reaching the imaging center. In particular, we attained (13)C HP by 'brute-force', i.e., using only low temperature and high-field (e.g., T<∼2K and B∼14T) to pre-polarize protons to a large Boltzmann value (∼0.4% (1)H polarization). After polarizing the neat, frozen sample, ejection quickly (<1s) passed it through a low field (B<100G) to establish the (1)H pre-polarization spin temperature on (13)C via the process known as low-field thermal mixing (yielding ∼0.1% (13)C polarization). By avoiding polarization agents (a.k.a. relaxation agents) that are needed to hyperpolarize by the competing method of dissolution dynamic nuclear polarization (d-DNP), the (13)C relaxation time was sufficient to transport the sample for ∼10min before finally dissolving in warm water and obtaining a (13)C image of the hyperpolarized, dilute, aqueous product (∼0.01% (13)C polarization, a >100-fold gain over thermal signals in the 1T scanner). An annealing step, prior to polarizing the sample, was also key for increasing T1∼30-fold during transport. In that time, HP was maintained using only modest cryogenics and field (T∼60K and B=1.3T), for T1((13)C) near 5min. Much greater time and distance (with much smaller losses) may be covered using more-complete annealing and only slight improvements on transport conditions (e.g., yielding T1∼5h at 30K, 2T), whereas even intercity transfer is possible (T1>20h) at reasonable conditions of 6K and 2T. Finally, it is possible to increase the overall enhancement near d-DNP levels (i.e., 10(2)-fold more) by polarizing below 100mK, where nanoparticle

  7. Transport and imaging of brute-force 13C hyperpolarization

    NASA Astrophysics Data System (ADS)

    Hirsch, Matthew L.; Smith, Bryce A.; Mattingly, Mark; Goloshevsky, Artem G.; Rosay, Melanie; Kempf, James G.

    2015-12-01

    We demonstrate transport of hyperpolarized frozen 1-13C pyruvic acid from its site of production to a nearby facility, where a time series of 13C images was acquired from the aqueous dissolution product. Transportability is tied to the hyperpolarization (HP) method we employ, which omits radical electron species used in other approaches that would otherwise relax away the HP before reaching the imaging center. In particular, we attained 13C HP by 'brute-force', i.e., using only low temperature and high-field (e.g., T < ∼2 K and B ∼ 14 T) to pre-polarize protons to a large Boltzmann value (∼0.4% 1H polarization). After polarizing the neat, frozen sample, ejection quickly (<1 s) passed it through a low field (B < 100 G) to establish the 1H pre-polarization spin temperature on 13C via the process known as low-field thermal mixing (yielding ∼0.1% 13C polarization). By avoiding polarization agents (a.k.a. relaxation agents) that are needed to hyperpolarize by the competing method of dissolution dynamic nuclear polarization (d-DNP), the 13C relaxation time was sufficient to transport the sample for ∼10 min before finally dissolving in warm water and obtaining a 13C image of the hyperpolarized, dilute, aqueous product (∼0.01% 13C polarization, a >100-fold gain over thermal signals in the 1 T scanner). An annealing step, prior to polarizing the sample, was also key for increasing T1 ∼ 30-fold during transport. In that time, HP was maintained using only modest cryogenics and field (T ∼ 60 K and B = 1.3 T), for T1(13C) near 5 min. Much greater time and distance (with much smaller losses) may be covered using more-complete annealing and only slight improvements on transport conditions (e.g., yielding T1 ∼ 5 h at 30 K, 2 T), whereas even intercity transfer is possible (T1 > 20 h) at reasonable conditions of 6 K and 2 T. Finally, it is possible to increase the overall enhancement near d-DNP levels (i.e., 102-fold more) by polarizing below 100 mK, where

  8. A 13C-NMR study of azacryptand complexes.

    PubMed

    Wild, Aljoscha A C; Fennell, Kevin; Morgan, Grace G; Hewage, Chandralal M; Malthouse, J Paul G

    2014-09-28

    An azacryptand has been solubilised in aqueous media containing 50% (v/v) dimethyl sulphoxide. (13)C-NMR has been used to determine how the azacryptand is affected by zinc binding at pH 10. Using (13)C-NMR and (13)C-enriched bicarbonate we have been able to observe the formation of 4 different carbamate derivatives of the azacryptand at pH 10. The azacryptand was shown to solubilise zinc or cadmium at alkaline pHs. Two moles of zinc are bound per mole of azacryptand and this complex binds 1 mole of carbonate. By replacing the zinc with cadmium-113 we have shown that the (13)C-NMR signal of the (13)C-enriched carbon of the bound carbonate is split into two triplets at 2.2 °C. This shows that two cadmium complexes are formed and in each of these complexes the carbonate group is bound by two magnetically equivalent metal ions. It also demonstrates that these cadmium complexes are not in fast exchange. From temperature studies we show that in the zinc complexes both complexes are in fast exchange with each other but are in slow exchange with free bicarbonate. HOESY is used to determine the position of the carbonate carbon in the complex. The solution and crystal structures of the zinc-carbonate-azacryptand complexes are compared. PMID:25091182

  9. 13C-based metabolic flux analysis: fundamentals and practice.

    PubMed

    Yang, Tae Hoon

    2013-01-01

    Isotope-based metabolic flux analysis is one of the emerging technologies applied to system level metabolic phenotype characterization in metabolic engineering. Among the developed approaches, (13)C-based metabolic flux analysis has been established as a standard tool and has been widely applied to quantitative pathway characterization of diverse biological systems. To implement (13)C-based metabolic flux analysis in practice, comprehending the underlying mathematical and computational modeling fundamentals is of importance along with carefully conducted experiments and analytical measurements. Such knowledge is also crucial when designing (13)C-labeling experiments and properly acquiring key data sets essential for in vivo flux analysis implementation. In this regard, the modeling fundamentals of (13)C-labeling systems and analytical data processing are the main topics we will deal with in this chapter. Along with this, the relevant numerical optimization techniques are addressed to help implementation of the entire computational procedures aiming at (13)C-based metabolic flux analysis in vivo.

  10. A scientific workflow framework for (13)C metabolic flux analysis.

    PubMed

    Dalman, Tolga; Wiechert, Wolfgang; Nöh, Katharina

    2016-08-20

    Metabolic flux analysis (MFA) with (13)C labeling data is a high-precision technique to quantify intracellular reaction rates (fluxes). One of the major challenges of (13)C MFA is the interactivity of the computational workflow according to which the fluxes are determined from the input data (metabolic network model, labeling data, and physiological rates). Here, the workflow assembly is inevitably determined by the scientist who has to consider interacting biological, experimental, and computational aspects. Decision-making is context dependent and requires expertise, rendering an automated evaluation process hardly possible. Here, we present a scientific workflow framework (SWF) for creating, executing, and controlling on demand (13)C MFA workflows. (13)C MFA-specific tools and libraries, such as the high-performance simulation toolbox 13CFLUX2, are wrapped as web services and thereby integrated into a service-oriented architecture. Besides workflow steering, the SWF features transparent provenance collection and enables full flexibility for ad hoc scripting solutions. To handle compute-intensive tasks, cloud computing is supported. We demonstrate how the challenges posed by (13)C MFA workflows can be solved with our approach on the basis of two proof-of-concept use cases.

  11. Synthesis and applications of {sup 13}C glycerol

    SciTech Connect

    Stocking, E.; Khalsa, O.; Martinez, R.A.; Silks, L.A. III

    1994-12-01

    Due in part to the use of labeled glycerol for the {sup 13}C enrichment of biomolecules, we are currently developing new synthetic routes to various isotopomers of glycerol. Judging from our experience, traditional methods of glycerol synthesis are not easily adapted for isotopic enrichment and/or have poor overall yields (12 to 15%). Furthermore, the use of glycerol for enrichment can be prohibitively expensive and its availability is limited by the level of demand. We are presently developing a short de novo synthesis of glycerol from carbon dioxide ({approximately}53% overall yield for four steps) and are examining the feasibility of synthesizing site-specific {sup 13}C-labeled glycerol and dihydroxyacetone (DHA) from labeled methanol and carbon dioxide. One application of {sup 13}C glycerol we have examined is enzymatic conversion of glycerol to glyceraldehyde-3-monophosphate or dihydroxyacetone monophosphate (DHAP) with yields ranging from 25 to 50% (as determined by NMR spectroscopy). We are also pursuing the chemical conversion of {sup 13}C-labeled DHA to DHAP. We are especially interested in {sup 13}C-labeled DHAP because we are investigating its use as a chemo-enzymatic precursor for both labeled 2-deoxyribose and 2-deoxyribonucleic acids.

  12. A scientific workflow framework for (13)C metabolic flux analysis.

    PubMed

    Dalman, Tolga; Wiechert, Wolfgang; Nöh, Katharina

    2016-08-20

    Metabolic flux analysis (MFA) with (13)C labeling data is a high-precision technique to quantify intracellular reaction rates (fluxes). One of the major challenges of (13)C MFA is the interactivity of the computational workflow according to which the fluxes are determined from the input data (metabolic network model, labeling data, and physiological rates). Here, the workflow assembly is inevitably determined by the scientist who has to consider interacting biological, experimental, and computational aspects. Decision-making is context dependent and requires expertise, rendering an automated evaluation process hardly possible. Here, we present a scientific workflow framework (SWF) for creating, executing, and controlling on demand (13)C MFA workflows. (13)C MFA-specific tools and libraries, such as the high-performance simulation toolbox 13CFLUX2, are wrapped as web services and thereby integrated into a service-oriented architecture. Besides workflow steering, the SWF features transparent provenance collection and enables full flexibility for ad hoc scripting solutions. To handle compute-intensive tasks, cloud computing is supported. We demonstrate how the challenges posed by (13)C MFA workflows can be solved with our approach on the basis of two proof-of-concept use cases. PMID:26721184

  13. Tracing source, mixing and uptaking processes of carbon in an epikarst spring-pond system in southeastern Guizhou of China by carbon isotopes (13C-14C)

    NASA Astrophysics Data System (ADS)

    Zhao, M.; Chen, B.; Liu, Z.; Li, H. C.; Yang, R.

    2015-12-01

    δ13C and Δ14C of dissolved inorganic carbon (DIC), particulate organic carbon (POC) and aquatic plants from a karst spring and two spring-fed ponds in Laqiao, Maolan County, Guizhou Province in January, July and October of 2013 were measured to understand the roles of aquatic photosynthesis through DIC uptake in karst surface waters. The mean Δ14C and δ13C values of DIC for the spring pool, midstream and downstream ponds are -60.6±26.3‰ and -13.53±1.97‰, -62.8±62.9‰ and -11.72±2.72‰, and -54.2±56.5‰ and -9.40±2.03‰, respectively. Both Δ14C and δ13C show seasonal variations, with lower Δ14C values but heavier δ13C values in dry season and vice versa in summer rainy season. This observation indicates that (1) the main carbon source of the spring DIC is from limestone bedrock dissolution and soil CO2 with higher contribution in summer due to higher productivity; and (2) 13C and 14C have different behaviors during DIC uptake by aquatic plants and during CO2 exchange between DIC and the atmospheric CO2. Biological uptake of CO2 will not affect the Δ14C of DIC, but lead to δ13CDIC enrichment. CO2 exchange between DIC and the atmospheric CO2 should elevate both the Δ14C and δ13C of DIC. In Laqiao spring-pond system, it seems that the effect of biological uptake on the Δ14C and δ13C of DIC is much stronger than that of CO2 exchange with the atmosphere. The mean Δ14C values of POC from the spring pool, midstream and downstream ponds are -308.1 ±64.3‰, -164.4±84.4‰ and -195.1±108.5‰, respectively, indicating mixture of aquatic algae and detrital particle (clay and dust). More aquatic algae were formed in the stream ponds especially in the summer. SEM results of the POC samples support this conclusion. Furthermore, the Δ14C values of the submerged aquatic plants range from -200.0‰ to -51.3 ‰ and were similar to those of the DIC, indicating that the aquatic plants used DIC for photosynthesis. The Δ14C value of an emergent plant

  14. Convergent Cenozoic CO2 history

    NASA Astrophysics Data System (ADS)

    Royer, D. L.; Beerling, D. J.

    2011-12-01

    The quality and quantity of Cenozoic CO2 records have increased significantly in the last decade. Gains in quality have come primarily from a fuller accounting of confounding factors; examples include soil respiration rates in the pedogenic carbonate method, alkalinity and seawater δ11B in the boron method, and cell size in the alkenone phytoplankton method. Previously, variability across Cenozoic CO2 estimates in a given time period sometimes exceeded an order of magnitude, but through these improvements variability has been reduced to a factor of two or less. Further improvements in the record can probably be facilitated by more robust quantification of statistical error, generation of CO2 estimates at single locations from multiple methods, and cross-calibration with Pleistocene ice-core CO2 records (Beerling & Royer, 2011, Nature Geoscience 4: 418-420). An improved Cenozoic CO2 record offers opportunities for better understanding Earth system processes. We provide one example related to climate sensitivity. We find a significant relationship between CO2 radiative forcing and global temperature during the Cenozoic, even after accounting for forcings related to solar evolution and paleogeographic changes. Although the calculations are based on simple assumptions and should be taken as provisional, the mean Cenozoic climate sensitivity (3 °C or higher per CO2 doubling) is similar to or higher than calculations for the present-day (~3 °C per CO2 doubling).

  15. Leaves: Elevated CO2 levels

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Burning fossil fuels and land use changes such as deforestation and urbanization have led to a dramatic rise in the concentration of carbon dioxide (CO2) in the atmosphere since the onset of the Industrial Revolution. The highly dilute CO2 from the atmosphere enters plant leaves where it is concentr...

  16. Assessing microbial utilization of free versus sorbed Alanine by using position-specific 13C labeling and 13C-PLFA analysis

    NASA Astrophysics Data System (ADS)

    Herschbach, Jennifer; Apostel, Carolin; Spielvogel, Sandra; Kuzyakov, Yakov; Dippold, Michaela

    2016-04-01

    Microbial utilization is a key transformation process of soil organic matter (SOM). Sorption of low molecular weight organic substances (LMWOS) to soil mineral surfaces blocks or delays microbial uptake and therefore mineralization of LMWOS to CO2, as well as all other biochemical transformations. We used position-specific labeling, a tool of isotope applications novel to soil science, combined with 13C-phospholipid fatty acid (PLFA) analysis, to assess microbial utilization of sorbed and non-sorbed Alanine in soil. Alanine has various functional groups enabling different sorption mechanisms via its positive charge (e.g. to clay minerals by cation exchange), as well as via its negative charge (e.g. to iron oxides by ligand exchange). To assess changes in the transformation pathways caused by sorption, we added uniformly and position-specifically 13C and 14C labeled Alanine to the Ap of a loamy Luvisol in a short-term (10 days) incubation experiment. To allow for sorption of the tracer solution to an aliquot of this soil, microbial activity was minimized in this subsample by sterilizing the soil by γ-radiation. After shaking, the remaining solutions were filtered and the non-sorbed Alanine was removed with Millipore water and then added to non-sterilized soil. For the free Alanine treatment, solutions with Alanine of similar amount and isotopic composition were prepared, added to the soil and incubated as well. The respired CO2 was trapped in NaOH and its 14C-activity was determined at increasing times intervals. Microbial utilization of Alanine's individual C positions was evaluated in distinct microbial groups classified by 13C-PLFA analysis. Sorption to soil minerals delayed respiration to CO2 and reduced initial respiration rate by 80%. Irrespective of sorption, the highest amount was respired from the carboxylic position (C-1), whereas the amino-bound (C-2) and the methylic position (C-3) were preferentially incorporated into PLFA of microorganisms due to the

  17. Carbon Release from Melting Arctic Permafrost on the North Slope, AK: 12CO2 and 13CO2 Concentrations and Fluxes, and Their Relationship to Methane and Methane Isotope Concentrations Measured in August 2013

    NASA Astrophysics Data System (ADS)

    Munster, J. B.; Sayres, D. S.; Healy, C. E.; Dumas, E. J.; Dobosy, R.; Kochendorfer, J.; Heuer, M.; Meyers, T. P.; Baker, B.; Anderson, J. G.

    2014-12-01

    One of the most important uncertainties in climate change is the positive feedback mechanism associated with the melting Arctic. As the Arctic permafrost destabilizes, labile carbon stored in the permafrost is subject to respiration and methanogenesis, producing greenhouse gases CO2 and CH4. Understanding the timing and rate of this release is paramount to our long-term understanding of the global climate structure, yet the remote location of the North Slope logistically precludes widespread tower measurements, necessitating airborne measurements. Presented are 12C and 13C CO2 concentration flux measurements taken via an aircraft at a height of 10-30m during mid to late August 2013 from the north slope of Alaska. The data show different regimes for CO2 vs δ-13C over regions within a roughly 100km box, indicating heterogenous landscape with differing dominant biological processes. The data are compared to CH4 measurements that were taken simultaneously, showing highly varying concentrations of CH4 with several different archetypical relationships to the total CO2 regimes. The relationship between CO2, δ-13C CO2, and CH4 concentrations provide further insight into the biological processes occurring in the melting Arctic permafrost. The data show that the dominant uptake and emission processes change by time of day and location. While the CO2 and isotopologue data alone indicates whether a region is dominant in respiration or photosynthesis, combining the data with CH4 measurements provides insight into the provenance of the CH4 as well as methanogenic biological pathways active on the North Slope, while mass balance between CH4, CO2 or δ-13C CO2 determines whether the methane signature is from methanogenesis, natural hydrocarbon seeps, or methane flaring. The data show few if any cases for which increases in methane concentrations are accompanied by a deviation in CO2 or δ-13C CO2 that would indicate incomplete methane flaring or natural seeps.

  18. CO2 Sequestration short course

    SciTech Connect

    DePaolo, Donald J.; Cole, David R; Navrotsky, Alexandra; Bourg, Ian C

    2014-12-08

    Given the public’s interest and concern over the impact of atmospheric greenhouse gases (GHGs) on global warming and related climate change patterns, the course is a timely discussion of the underlying geochemical and mineralogical processes associated with gas-water-mineral-interactions encountered during geological sequestration of CO2. The geochemical and mineralogical processes encountered in the subsurface during storage of CO2 will play an important role in facilitating the isolation of anthropogenic CO2 in the subsurface for thousands of years, thus moderating rapid increases in concentrations of atmospheric CO2 and mitigating global warming. Successful implementation of a variety of geological sequestration scenarios will be dependent on our ability to accurately predict, monitor and verify the behavior of CO2 in the subsurface. The course was proposed to and accepted by the Mineralogical Society of America (MSA) and The Geochemical Society (GS).

  19. Disequilibrium of 13CO2 fluxes between photosynthesis and respiration in North American temperate forest biomes

    NASA Astrophysics Data System (ADS)

    Lai, C.; Ehleringer, J.; Schauer, A.; Tans, P.; Hollinger, D.; Paw U, K.; Wofsy, S.

    2003-12-01

    We report the first weekly dataset of seasonal and interannual variability in δ 13C of CO2 fluxes from dominant forest ecosystems in the US. We observed large variations in the δ 13C of respired biosphere-atmosphere fluxes (δ 13CR) across 3 temperate coniferous